STM32F75xxx And STM32F74xxx Advanced Arm® Based 32 Bit MCUs STM32F7[45]xxx Reference Manual

User Manual:

Open the PDF directly: View PDF .
Page Count: 1709

Download
Open PDF In Browser	View PDF

RM0385
Reference manual
STM32F75xxx and STM32F74xxx advanced Arm®-based
32-bit MCUs
Introduction
This reference manual targets application developers. It provides complete information on
how to use the STM32F75xxx and STM32F74xxx microcontroller memory and peripherals.
The STM32F75xxx and STM32F74xxx is a family of microcontrollers with different memory
sizes, packages and peripherals.
For ordering information, mechanical and electrical device characteristics refer to the
datasheets.
For information on the Arm® Cortex®-M7 with FPU core, refer to the Cortex®-M7 with FPU
technical reference manual.

Related documents
Available from STMicroelectronics web site www.st.com:
• STM32F75xxx and STM32F74xxx datasheets
• STM32F7 Series Cortex®-M7 processor programming manual (PM0253)

March 2018

RM0385 Rev 7

1/1709
www.st.com

1

Contents

RM0385

Contents
1

2

Documentation conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
1.1

List of abbreviations for registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

1.2

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

1.3

Peripheral availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

System and memory overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2.1

2.2

3

2/1709

System architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2.1.1

Multi AHB BusMatrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

2.1.2

AHB/APB bridges (APB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

2.1.3

CPU AXIM bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

2.1.4

ITCM bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

2.1.5

DTCM bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

2.1.6

CPU AHBS bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

2.1.7

AHB peripheral bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

2.1.8

DMA memory bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

2.1.9

DMA peripheral bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

2.1.10

Ethernet DMA bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

2.1.11

USB OTG HS DMA bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

2.1.12

LCD-TFT controller DMA bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

2.1.13

DMA2D bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Memory organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
2.2.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

2.2.2

Memory map and register boundary addresses . . . . . . . . . . . . . . . . . . 69

2.3

Embedded SRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2.4

Flash memory overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2.5

Boot configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Embedded Flash memory (FLASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

3.2

Flash main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

3.3

Flash functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.3.1

Flash memory organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

3.3.2

Read access latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

RM0385 Rev 7

RM0385

Contents

3.4

3.5

4

3.3.3

Flash program and erase operations . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

3.3.4

Unlocking the Flash control register . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

3.3.5

Program/erase parallelism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

3.3.6

Flash erase sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

3.3.7

Flash programming sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

3.3.8

Flash Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

FLASH Option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.4.1

Option bytes description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

3.4.2

Option bytes programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

FLASH memory protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
3.5.1

Read protection (RDP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

3.5.2

Write protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

3.6

One-time programmable bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

3.7

FLASH registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
3.7.1

Flash access control register (FLASH_ACR) . . . . . . . . . . . . . . . . . . . . 91

3.7.2

Flash key register (FLASH_KEYR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

3.7.3

Flash option key register (FLASH_OPTKEYR) . . . . . . . . . . . . . . . . . . . 92

3.7.4

Flash status register (FLASH_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

3.7.5

Flash control register (FLASH_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

3.7.6

Flash option control register (FLASH_OPTCR) . . . . . . . . . . . . . . . . . . . 95

3.7.7

Flash option control register (FLASH_OPTCR1) . . . . . . . . . . . . . . . . . . 96

3.7.8

Flash interface register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Power controller (PWR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.1

4.2

4.3

Power supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
4.1.1

Independent A/D converter supply and reference voltage . . . . . . . . . . 100

4.1.2

Independent USB transceivers supply . . . . . . . . . . . . . . . . . . . . . . . . . 101

4.1.3

Battery backup domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

4.1.4

Voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Power supply supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
4.2.1

Power-on reset (POR)/power-down reset (PDR) . . . . . . . . . . . . . . . . . 107

4.2.2

Brownout reset (BOR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

4.2.3

Programmable voltage detector (PVD) . . . . . . . . . . . . . . . . . . . . . . . . 108

Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
4.3.1

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

4.3.2

Run mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

RM0385 Rev 7

3/1709
43

Contents

RM0385

4.4

4.5

5

Low-power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

4.3.4

Sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

4.3.5

Stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

4.3.6

Standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

4.3.7

Programming the RTC alternate functions to wake up the device from
the Stop and Standby modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Power control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
4.4.1

PWR power control register (PWR_CR1) . . . . . . . . . . . . . . . . . . . . . . 123

4.4.2

PWR power control/status register (PWR_CSR1) . . . . . . . . . . . . . . . . 125

4.4.3

PWR power control/status register 2 (PWR_CR2) . . . . . . . . . . . . . . . 127

4.4.4

PWR power control register 2 (PWR_CSR2) . . . . . . . . . . . . . . . . . . . 129

PWR register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

Reset and clock control (RCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
5.1

5.2

5.3

4/1709

4.3.3

Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
5.1.1

System reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

5.1.2

Power reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

5.1.3

Backup domain reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
5.2.1

HSE clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

5.2.2

HSI clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

5.2.3

PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

5.2.4

LSE clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

5.2.5

LSI clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

5.2.6

System clock (SYSCLK) selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

5.2.7

Clock security system (CSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

5.2.8

RTC/AWU clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

5.2.9

Watchdog clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

5.2.10

Clock-out capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

5.2.11

Internal/external clock measurement using TIM5/TIM11 . . . . . . . . . . . 141

5.2.12

Peripheral clock enable register (RCC_AHBxENR,
RCC_APBxENRy) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

RCC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
5.3.1

RCC clock control register (RCC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . 143

5.3.2

RCC PLL configuration register (RCC_PLLCFGR) . . . . . . . . . . . . . . . 146

5.3.3

RCC clock configuration register (RCC_CFGR) . . . . . . . . . . . . . . . . . 148

5.3.4

RCC clock interrupt register (RCC_CIR) . . . . . . . . . . . . . . . . . . . . . . . 150

RM0385 Rev 7

RM0385

6

Contents
5.3.5

RCC AHB1 peripheral reset register (RCC_AHB1RSTR) . . . . . . . . . . 153

5.3.6

RCC AHB2 peripheral reset register (RCC_AHB2RSTR) . . . . . . . . . . 156

5.3.7

RCC AHB3 peripheral reset register (RCC_AHB3RSTR) . . . . . . . . . . 157

5.3.8

RCC APB1 peripheral reset register (RCC_APB1RSTR) . . . . . . . . . . 157

5.3.9

RCC APB2 peripheral reset register (RCC_APB2RSTR) . . . . . . . . . . 161

5.3.10

RCC AHB1 peripheral clock register (RCC_AHB1ENR) . . . . . . . . . . . 163

5.3.11

RCC AHB2 peripheral clock enable register (RCC_AHB2ENR) . . . . . 165

5.3.12

RCC AHB3 peripheral clock enable register (RCC_AHB3ENR) . . . . . 166

5.3.13

RCC APB1 peripheral clock enable register (RCC_APB1ENR) . . . . . 166

5.3.14

RCC APB2 peripheral clock enable register (RCC_APB2ENR) . . . . . 170

5.3.15

RCC AHB1 peripheral clock enable in low-power mode register
(RCC_AHB1LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

5.3.16

RCC AHB2 peripheral clock enable in low-power mode register
(RCC_AHB2LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

5.3.17

RCC AHB3 peripheral clock enable in low-power mode register
(RCC_AHB3LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

5.3.18

RCC APB1 peripheral clock enable in low-power mode register
(RCC_APB1LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

5.3.19

RCC APB2 peripheral clock enabled in low-power mode register
(RCC_APB2LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

5.3.20

RCC backup domain control register (RCC_BDCR) . . . . . . . . . . . . . . 183

5.3.21

RCC clock control & status register (RCC_CSR) . . . . . . . . . . . . . . . . 184

5.3.22

RCC spread spectrum clock generation register (RCC_SSCGR) . . . . 186

5.3.23

RCC PLLI2S configuration register (RCC_PLLI2SCFGR) . . . . . . . . . 187

5.3.24

RCC PLLSAI configuration register (RCC_PLLSAICFGR) . . . . . . . . . 190

5.3.25

RCC dedicated clocks configuration register (RCC_DKCFGR1) . . . . 191

5.3.26

RCC dedicated clocks configuration register (DCKCFGR2) . . . . . . . . 193

5.3.27

RCC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

General-purpose I/Os (GPIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
6.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

6.2

GPIO main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

6.3

GPIO functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
6.3.1

General-purpose I/O (GPIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

6.3.2

I/O pin alternate function multiplexer and mapping . . . . . . . . . . . . . . . 202

6.3.3

I/O port control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

6.3.4

I/O port data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

6.3.5

I/O data bitwise handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

RM0385 Rev 7

5/1709
43

Contents

RM0385

6.4

7

6/1709

6.3.6

GPIO locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

6.3.7

I/O alternate function input/output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

6.3.8

External interrupt/wakeup lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

6.3.9

Input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

6.3.10

Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

6.3.11

Alternate function configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

6.3.12

Analog configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

6.3.13

Using the HSE or LSE oscillator pins as GPIOs . . . . . . . . . . . . . . . . . 207

6.3.14

Using the GPIO pins in the backup supply domain . . . . . . . . . . . . . . . 207

GPIO registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
6.4.1

GPIO port mode register (GPIOx_MODER) (x =A..K) . . . . . . . . . . . . . 208

6.4.2

GPIO port output type register (GPIOx_OTYPER) (x = A..K) . . . . . . . 208

6.4.3

GPIO port output speed register (GPIOx_OSPEEDR)
(x = A..K) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

6.4.4

GPIO port pull-up/pull-down register (GPIOx_PUPDR)
(x = A..K) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

6.4.5

GPIO port input data register (GPIOx_IDR) (x = A..K) . . . . . . . . . . . . . 210

6.4.6

GPIO port output data register (GPIOx_ODR) (x = A..K) . . . . . . . . . . . 210

6.4.7

GPIO port bit set/reset register (GPIOx_BSRR) (x = A..K) . . . . . . . . . 210

6.4.8

GPIO port configuration lock register (GPIOx_LCKR)
(x = A..K) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

6.4.9

GPIO alternate function low register (GPIOx_AFRL)
(x = A..K) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

6.4.10

GPIO alternate function high register (GPIOx_AFRH)
(x = A..J) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

6.4.11

GPIO register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

System configuration controller (SYSCFG) . . . . . . . . . . . . . . . . . . . . 216
7.1

I/O compensation cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

7.2

SYSCFG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
7.2.1

SYSCFG memory remap register (SYSCFG_MEMRMP) . . . . . . . . . . 216

7.2.2

SYSCFG peripheral mode configuration register (SYSCFG_PMC) . . 217

7.2.3

SYSCFG external interrupt configuration register 1
(SYSCFG_EXTICR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

7.2.4

SYSCFG external interrupt configuration register 2
(SYSCFG_EXTICR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

7.2.5

SYSCFG external interrupt configuration register 3
(SYSCFG_EXTICR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

RM0385 Rev 7

RM0385

8

Contents
7.2.6

SYSCFG external interrupt configuration register 4
(SYSCFG_EXTICR4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

7.2.7

Compensation cell control register (SYSCFG_CMPCR) . . . . . . . . . . . 220

7.2.8

SYSCFG register maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

Direct memory access controller (DMA) . . . . . . . . . . . . . . . . . . . . . . . 222
8.1

DMA introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

8.2

DMA main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

8.3

DMA functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
8.3.1

DMA block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

8.3.2

DMA overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

8.3.3

DMA transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

8.3.4

Channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

8.3.5

Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

8.3.6

DMA streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

8.3.7

Source, destination and transfer modes . . . . . . . . . . . . . . . . . . . . . . . 227

8.3.8

Pointer incrementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

8.3.9

Circular mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

8.3.10

Double-buffer mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

8.3.11

Programmable data width, packing/unpacking, endianness . . . . . . . . 232

8.3.12

Single and burst transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

8.3.13

FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

8.3.14

DMA transfer completion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

8.3.15

DMA transfer suspension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

8.3.16

Flow controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

8.3.17

Summary of the possible DMA configurations . . . . . . . . . . . . . . . . . . . 239

8.3.18

Stream configuration procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

8.3.19

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

8.4

DMA interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

8.5

DMA registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
8.5.1

DMA low interrupt status register (DMA_LISR) . . . . . . . . . . . . . . . . . . 243

8.5.2

DMA high interrupt status register (DMA_HISR) . . . . . . . . . . . . . . . . . 244

8.5.3

DMA low interrupt flag clear register (DMA_LIFCR) . . . . . . . . . . . . . . 245

8.5.4

DMA high interrupt flag clear register (DMA_HIFCR) . . . . . . . . . . . . . 245

8.5.5

DMA stream x configuration register (DMA_SxCR) . . . . . . . . . . . . . . . 246

8.5.6

DMA stream x number of data register (DMA_SxNDTR) . . . . . . . . . . 249

8.5.7

DMA stream x peripheral address register (DMA_SxPAR) . . . . . . . . . 250

RM0385 Rev 7

7/1709
43

Contents

9

8/1709

RM0385
8.5.8

DMA stream x memory 0 address register (DMA_SxM0AR) . . . . . . . . 250

8.5.9

DMA stream x memory 1 address register (DMA_SxM1AR) . . . . . . . . 250

8.5.10

DMA stream x FIFO control register (DMA_SxFCR) . . . . . . . . . . . . . . 251

8.5.11

DMA register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

Chrom-ART Accelerator™ controller (DMA2D) . . . . . . . . . . . . . . . . . 257
9.1

DMA2D introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

9.2

DMA2D main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

9.3

DMA2D functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
9.3.1

General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

9.3.2

DMA2D control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

9.3.3

DMA2D foreground and background FIFOs . . . . . . . . . . . . . . . . . . . . 259

9.3.4

DMA2D foreground and background pixel format converter (PFC) . . . 260

9.3.5

DMA2D foreground and background CLUT interface . . . . . . . . . . . . . 262

9.3.6

DMA2D blender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

9.3.7

DMA2D output PFC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

9.3.8

DMA2D output FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

9.3.9

DMA2D AHB master port timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

9.3.10

DMA2D transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

9.3.11

DMA2D configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

9.3.12

DMA2D transfer control (start, suspend, abort and completion) . . . . . 268

9.3.13

Watermark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

9.3.14

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

9.3.15

AHB dead time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

9.4

DMA2D interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

9.5

DMA2D registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
9.5.1

DMA2D control register (DMA2D_CR) . . . . . . . . . . . . . . . . . . . . . . . . 270

9.5.2

DMA2D Interrupt Status Register (DMA2D_ISR) . . . . . . . . . . . . . . . . 272

9.5.3

DMA2D interrupt flag clear register (DMA2D_IFCR) . . . . . . . . . . . . . . 273

9.5.4

DMA2D foreground memory address register (DMA2D_FGMAR) . . . 274

9.5.5

DMA2D foreground offset register (DMA2D_FGOR) . . . . . . . . . . . . . . 274

9.5.6

DMA2D background memory address register (DMA2D_BGMAR) . . 274

9.5.7

DMA2D background offset register (DMA2D_BGOR) . . . . . . . . . . . . . 275

9.5.8

DMA2D foreground PFC control register (DMA2D_FGPFCCR) . . . . . 276

9.5.9

DMA2D foreground color register (DMA2D_FGCOLR) . . . . . . . . . . . . 278

9.5.10

DMA2D background PFC control register (DMA2D_BGPFCCR) . . . . 279

9.5.11

DMA2D background color register (DMA2D_BGCOLR) . . . . . . . . . . . 281
RM0385 Rev 7

RM0385

10

Contents

12

DMA2D foreground CLUT memory address register
(DMA2D_FGCMAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

9.5.13

DMA2D background CLUT memory address register
(DMA2D_BGCMAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282

9.5.14

DMA2D output PFC control register (DMA2D_OPFCCR) . . . . . . . . . . 282

9.5.15

DMA2D output color register (DMA2D_OCOLR) . . . . . . . . . . . . . . . . . 283

9.5.16

DMA2D output memory address register (DMA2D_OMAR) . . . . . . . . 284

9.5.17

DMA2D output offset register (DMA2D_OOR) . . . . . . . . . . . . . . . . . . 285

9.5.18

DMA2D number of line register (DMA2D_NLR) . . . . . . . . . . . . . . . . . 285

9.5.19

DMA2D line watermark register (DMA2D_LWR) . . . . . . . . . . . . . . . . . 286

9.5.20

DMA2D AHB master timer configuration register (DMA2D_AMTCR) . 286

9.5.21

DMA2D register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

Nested vectored interrupt controller (NVIC) . . . . . . . . . . . . . . . . . . . . 289
10.1

11

9.5.12

NVIC features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
10.1.1

SysTick calibration value register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

10.1.2

Interrupt and exception vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

Extended interrupts and events controller (EXTI) . . . . . . . . . . . . . . . 294
11.1

EXTI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

11.2

EXTI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

11.3

Wakeup event management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

11.4

Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

11.5

Hardware interrupt selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

11.6

Hardware event selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

11.7

Software interrupt/event selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

11.8

External interrupt/event line mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

11.9

EXTI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
11.9.1

Interrupt mask register (EXTI_IMR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

11.9.2

Event mask register (EXTI_EMR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

11.9.3

Rising trigger selection register (EXTI_RTSR) . . . . . . . . . . . . . . . . . . 298

11.9.4

Falling trigger selection register (EXTI_FTSR) . . . . . . . . . . . . . . . . . . 298

11.9.5

Software interrupt event register (EXTI_SWIER) . . . . . . . . . . . . . . . . 299

11.9.6

Pending register (EXTI_PR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

11.9.7

EXTI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

Cyclic redundancy check calculation unit (CRC) . . . . . . . . . . . . . . . . 301
RM0385 Rev 7

9/1709
43

Contents

RM0385

12.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

12.2

CRC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

12.3

CRC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

12.4

13

12.3.1

CRC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

12.3.2

CRC internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

12.3.3

CRC operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

CRC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
12.4.1

Data register (CRC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304

12.4.2

Independent data register (CRC_IDR) . . . . . . . . . . . . . . . . . . . . . . . . 304

12.4.3

Control register (CRC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

12.4.4

Initial CRC value (CRC_INIT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

12.4.5

CRC polynomial (CRC_POL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

12.4.6

CRC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

Flexible memory controller (FMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
13.1

FMC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307

13.2

FMC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

13.3

AHB interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
13.3.1

13.4

13.5

13.6

10/1709

Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . 309

External device address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .311
13.4.1

NOR/PSRAM address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

13.4.2

NAND Flash memory address mapping . . . . . . . . . . . . . . . . . . . . . . . 312

13.4.3

SDRAM address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

NOR Flash/PSRAM controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
13.5.1

External memory interface signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318

13.5.2

Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . 319

13.5.3

General timing rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

13.5.4

NOR Flash/PSRAM controller asynchronous transactions . . . . . . . . . 321

13.5.5

Synchronous transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

13.5.6

NOR/PSRAM controller registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

NAND Flash controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
13.6.1

External memory interface signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352

13.6.2

NAND Flash supported memories and transactions . . . . . . . . . . . . . . 354

13.6.3

Timing diagrams for NAND Flash memory . . . . . . . . . . . . . . . . . . . . . 354

13.6.4

NAND Flash operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355

13.6.5

NAND Flash prewait functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356

RM0385 Rev 7

RM0385

Contents

13.7

13.8

14

13.6.6

Computation of the error correction code (ECC)
in NAND Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357

13.6.7

NAND Flash controller registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358

SDRAM controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
13.7.1

SDRAM controller main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364

13.7.2

SDRAM External memory interface signals . . . . . . . . . . . . . . . . . . . . . 364

13.7.3

SDRAM controller functional description . . . . . . . . . . . . . . . . . . . . . . . 365

13.7.4

Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

13.7.5

SDRAM controller registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

FMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382

Quad-SPI interface (QUADSPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384
14.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384

14.2

QUADSPI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384

14.3

QUADSPI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384
14.3.1

QUADSPI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384

14.3.2

QUADSPI pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385

14.3.3

QUADSPI command sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386

14.3.4

QUADSPI signal interface protocol modes . . . . . . . . . . . . . . . . . . . . . 388

14.3.5

QUADSPI indirect mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390

14.3.6

QUADSPI status flag polling mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 392

14.3.7

QUADSPI memory-mapped mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 392

14.3.8

QUADSPI Flash memory configuration . . . . . . . . . . . . . . . . . . . . . . . . 393

14.3.9

QUADSPI delayed data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393

14.3.10 QUADSPI configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393
14.3.11 QUADSPI usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394
14.3.12 Sending the instruction only once . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
14.3.13 QUADSPI error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
14.3.14 QUADSPI busy bit and abort functionality . . . . . . . . . . . . . . . . . . . . . . 397
14.3.15 nCS behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

14.4

QUADSPI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399

14.5

QUADSPI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400
14.5.1

QUADSPI control register (QUADSPI_CR) . . . . . . . . . . . . . . . . . . . . . 400

14.5.2

QUADSPI device configuration register (QUADSPI_DCR) . . . . . . . . . 403

14.5.3

QUADSPI status register (QUADSPI_SR) . . . . . . . . . . . . . . . . . . . . . 404

14.5.4

QUADSPI flag clear register (QUADSPI_FCR) . . . . . . . . . . . . . . . . . . 405

14.5.5

QUADSPI data length register (QUADSPI_DLR) . . . . . . . . . . . . . . . . 405
RM0385 Rev 7

11/1709
43

Contents

RM0385
14.5.6

QUADSPI communication configuration register (QUADSPI_CCR) . . 406

14.5.7

QUADSPI address register (QUADSPI_AR) . . . . . . . . . . . . . . . . . . . . 408

14.5.8

QUADSPI alternate bytes registers (QUADSPI_ABR) . . . . . . . . . . . . 409

14.5.9

QUADSPI data register (QUADSPI_DR) . . . . . . . . . . . . . . . . . . . . . . . 409

14.5.10 QUADSPI polling status mask register (QUADSPI _PSMKR) . . . . . . . 410
14.5.11 QUADSPI polling status match register (QUADSPI _PSMAR) . . . . . . 410
14.5.12 QUADSPI polling interval register (QUADSPI _PIR) . . . . . . . . . . . . . . 411
14.5.13 QUADSPI low-power timeout register (QUADSPI_LPTR) . . . . . . . . . . 411
14.5.14 QUADSPI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412

15

Analog-to-digital converter (ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413
15.1

ADC introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413

15.2

ADC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413

15.3

ADC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413
15.3.1

ADC on-off control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415

15.3.2

ADC1/2 and ADC3 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416

15.3.3

ADC clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419

15.3.4

Channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419

15.3.5

Single conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420

15.3.6

Continuous conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420

15.3.7

Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420

15.3.8

Analog watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421

15.3.9

Scan mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422

15.3.10 Injected channel management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
15.3.11 Discontinuous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

15.4

Data alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424

15.5

Channel-wise programmable sampling time . . . . . . . . . . . . . . . . . . . . . 425

15.6

Conversion on external trigger and trigger polarity . . . . . . . . . . . . . . . . 426

15.7

Fast conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

15.8

Data management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428

15.9

12/1709

15.8.1

Using the DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428

15.8.2

Managing a sequence of conversions without using the DMA . . . . . . 428

15.8.3

Conversions without DMA and without overrun detection . . . . . . . . . . 429

Multi ADC mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
15.9.1

Injected simultaneous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432

15.9.2

Regular simultaneous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433

RM0385 Rev 7

RM0385

Contents
15.9.3

Interleaved mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

15.9.4

Alternate trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436

15.9.5

Combined regular/injected simultaneous mode . . . . . . . . . . . . . . . . . . 438

15.9.6

Combined regular simultaneous + alternate trigger mode . . . . . . . . . . 438

15.10 Temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
15.11 Battery charge monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
15.12 ADC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442
15.13 ADC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443
15.13.1 ADC status register (ADC_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443
15.13.2 ADC control register 1 (ADC_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 444
15.13.3 ADC control register 2 (ADC_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
15.13.4 ADC sample time register 1 (ADC_SMPR1) . . . . . . . . . . . . . . . . . . . . 448
15.13.5 ADC sample time register 2 (ADC_SMPR2) . . . . . . . . . . . . . . . . . . . . 449
15.13.6 ADC injected channel data offset register x (ADC_JOFRx) (x=1..4) . . 449
15.13.7 ADC watchdog higher threshold register (ADC_HTR) . . . . . . . . . . . . . 449
15.13.8 ADC watchdog lower threshold register (ADC_LTR) . . . . . . . . . . . . . . 450
15.13.9 ADC regular sequence register 1 (ADC_SQR1) . . . . . . . . . . . . . . . . . 450
15.13.10 ADC regular sequence register 2 (ADC_SQR2) . . . . . . . . . . . . . . . . . 451
15.13.11 ADC regular sequence register 3 (ADC_SQR3) . . . . . . . . . . . . . . . . . 452
15.13.12 ADC injected sequence register (ADC_JSQR) . . . . . . . . . . . . . . . . . . 453
15.13.13 ADC injected data register x (ADC_JDRx) (x= 1..4) . . . . . . . . . . . . . . 453
15.13.14 ADC regular data register (ADC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . 454
15.13.15 ADC Common status register (ADC_CSR) . . . . . . . . . . . . . . . . . . . . . 454
15.13.16 ADC common control register (ADC_CCR) . . . . . . . . . . . . . . . . . . . . . 455
15.13.17 ADC common regular data register for dual and triple modes
(ADC_CDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458
15.13.18 ADC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458

16

Digital-to-analog converter (DAC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461
16.1

DAC introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461

16.2

DAC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461

16.3

DAC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462
16.3.1

DAC channel enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462

16.3.2

DAC output buffer enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

16.3.3

DAC data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

16.3.4

DAC conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

16.3.5

DAC output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465
RM0385 Rev 7

13/1709
43

Contents

RM0385

16.4

16.3.6

DAC trigger selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465

16.3.7

DMA request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

16.3.8

Noise generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

16.3.9

Triangle-wave generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

Dual DAC channel conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468
16.4.1

Independent trigger without wave generation . . . . . . . . . . . . . . . . . . . 469

16.4.2

Independent trigger with single LFSR generation . . . . . . . . . . . . . . . . 469

16.4.3

Independent trigger with different LFSR generation . . . . . . . . . . . . . . 469

16.4.4

Independent trigger with single triangle generation . . . . . . . . . . . . . . . 470

16.4.5

Independent trigger with different triangle generation . . . . . . . . . . . . . 470

16.4.6

Simultaneous software start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470

16.4.7

Simultaneous trigger without wave generation . . . . . . . . . . . . . . . . . . 471

16.4.8

Simultaneous trigger with single LFSR generation . . . . . . . . . . . . . . . 471

16.4.9

Simultaneous trigger with different LFSR generation . . . . . . . . . . . . . 471

16.4.10 Simultaneous trigger with single triangle generation . . . . . . . . . . . . . . 472
16.4.11 Simultaneous trigger with different triangle generation . . . . . . . . . . . . 472

16.5

DAC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
16.5.1

DAC control register (DAC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473

16.5.2

DAC software trigger register (DAC_SWTRIGR) . . . . . . . . . . . . . . . . 476

16.5.3

DAC channel1 12-bit right-aligned data holding register
(DAC_DHR12R1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476

16.5.4

DAC channel1 12-bit left aligned data holding register
(DAC_DHR12L1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477

16.5.5

DAC channel1 8-bit right aligned data holding register
(DAC_DHR8R1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477

16.5.6

DAC channel2 12-bit right aligned data holding register
(DAC_DHR12R2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478

16.5.7

DAC channel2 12-bit left aligned data holding register
(DAC_DHR12L2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478

16.5.8

DAC channel2 8-bit right-aligned data holding register
(DAC_DHR8R2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478

16.5.9

Dual DAC 12-bit right-aligned data holding register
(DAC_DHR12RD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479

16.5.10 DUAL DAC 12-bit left aligned data holding register
(DAC_DHR12LD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479
16.5.11 DUAL DAC 8-bit right aligned data holding register
(DAC_DHR8RD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480
16.5.12 DAC channel1 data output register (DAC_DOR1) . . . . . . . . . . . . . . . . 480
16.5.13 DAC channel2 data output register (DAC_DOR2) . . . . . . . . . . . . . . . . 480

14/1709

RM0385 Rev 7

RM0385

Contents
16.5.14 DAC status register (DAC_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481
16.5.15 DAC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482

17

Digital camera interface (DCMI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483
17.1

DCMI introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483

17.2

DCMI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483

17.3

DCMI clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483

17.4

DCMI functional overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483

17.5

17.4.1

DCMI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484

17.4.2

DMA interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484

17.4.3

DCMI physical interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484

17.4.4

Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

17.4.5

Capture modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489

17.4.6

Crop feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490

17.4.7

JPEG format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491

17.4.8

FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491

Data format description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492
17.5.1

Data formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

17.5.2

Monochrome format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

17.5.3

RGB format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493

17.5.4

YCbCr format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493

17.5.5

YCbCr format - Y only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493

17.5.6

Half resolution image extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

17.6

DCMI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

17.7

DCMI register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494
17.7.1

DCMI control register (DCMI_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

17.7.2

DCMI status register (DCMI_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498

17.7.3

DCMI raw interrupt status register (DCMI_RIS) . . . . . . . . . . . . . . . . . 499

17.7.4

DCMI interrupt enable register (DCMI_IER) . . . . . . . . . . . . . . . . . . . . 500

17.7.5

DCMI masked interrupt status register (DCMI_MIS) . . . . . . . . . . . . . . 501

17.7.6

DCMI interrupt clear register (DCMI_ICR) . . . . . . . . . . . . . . . . . . . . . . 502

17.7.7

DCMI embedded synchronization code register (DCMI_ESCR) . . . . . 503

17.7.8

DCMI embedded synchronization unmask register (DCMI_ESUR) . . 504

17.7.9

DCMI crop window start (DCMI_CWSTRT) . . . . . . . . . . . . . . . . . . . . . 505

17.7.10 DCMI crop window size (DCMI_CWSIZE) . . . . . . . . . . . . . . . . . . . . . . 505
17.7.11 DCMI data register (DCMI_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506

RM0385 Rev 7

15/1709
43

Contents

RM0385
17.7.12 DCMI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507

18

LCD-TFT display controller (LTDC) . . . . . . . . . . . . . . . . . . . . . . . . . . 508
18.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508

18.2

LTDC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508

18.3

LTDC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509

18.4

18.3.1

LTDC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509

18.3.2

LTDC pins and external signal interface . . . . . . . . . . . . . . . . . . . . . . . 509

18.3.3

LTDC reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510

LTDC programmable parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .511
18.4.1

LTDC global configuration parameters . . . . . . . . . . . . . . . . . . . . . . . . 511

18.4.2

Layer programmable parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514

18.5

LTDC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518

18.6

LTDC programming procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519

18.7

LTDC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521
18.7.1

LTDC synchronization size configuration register (LTDC_SSCR) . . . . 521

18.7.2

LTDC back porch configuration register (LTDC_BPCR) . . . . . . . . . . . 521

18.7.3

LTDC active width configuration register (LTDC_AWCR) . . . . . . . . . . 522

18.7.4

LTDC total width configuration register (LTDC_TWCR) . . . . . . . . . . . . 523

18.7.5

LTDC global control register (LTDC_GCR) . . . . . . . . . . . . . . . . . . . . . 523

18.7.6

LTDC shadow reload configuration register (LTDC_SRCR) . . . . . . . . 525

18.7.7

LTDC background color configuration register (LTDC_BCCR) . . . . . . 525

18.7.8

LTDC interrupt enable register (LTDC_IER) . . . . . . . . . . . . . . . . . . . . 526

18.7.9

LTDC interrupt status register (LTDC_ISR) . . . . . . . . . . . . . . . . . . . . . 527

18.7.10 LTDC Interrupt Clear Register (LTDC_ICR) . . . . . . . . . . . . . . . . . . . . . 527
18.7.11 LTDC line interrupt position configuration register (LTDC_LIPCR) . . . 528
18.7.12 LTDC current position status register (LTDC_CPSR) . . . . . . . . . . . . . 528
18.7.13 LTDC current display status register (LTDC_CDSR) . . . . . . . . . . . . . . 529
18.7.14 LTDC layer x control register (LTDC_LxCR) . . . . . . . . . . . . . . . . . . . . 530
18.7.15 LTDC layer x window horizontal position configuration register
(LTDC_LxWHPCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531
18.7.16 LTDC layer x window vertical position configuration register
(LTDC_LxWVPCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532
18.7.17 LTDC layer x color keying configuration register
(LTDC_LxCKCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533
18.7.18 LTDC layer x pixel format configuration register
(LTDC_LxPFCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533

16/1709

RM0385 Rev 7

RM0385

Contents
18.7.19 LTDC layer x constant alpha configuration register
(LTDC_LxCACR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534
18.7.20 LTDC layer x default color configuration register
(LTDC_LxDCCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535
18.7.21 LTDC layer x blending factors configuration register
(LTDC_LxBFCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 536
18.7.22 LTDC layer x color frame buffer address register
(LTDC_LxCFBAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537
18.7.23 LTDC layer x color frame buffer length register
(LTDC_LxCFBLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537
18.7.24 LTDC layer x color frame buffer line number register
(LTDC_LxCFBLNR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538
18.7.25 LTDC layer x CLUT write register (LTDC_LxCLUTWR) . . . . . . . . . . . 539
18.7.26 LTDC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540

19

True random number generator (RNG) . . . . . . . . . . . . . . . . . . . . . . . . 543
19.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543

19.2

RNG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543

19.3

RNG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
19.3.1

RNG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544

19.3.2

RNG internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544

19.3.3

Random number generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545

19.3.4

RNG initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547

19.3.5

RNG operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547

19.3.6

RNG clocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

19.3.7

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

19.4

RNG low-power usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549

19.5

RNG interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549

19.6

RNG processing time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549

19.7

Entropy source validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

19.8

19.7.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

19.7.2

Validation conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

19.7.3

Data collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

RNG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
19.8.1

RNG control register (RNG_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551

19.8.2

RNG status register (RNG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552

19.8.3

RNG data register (RNG_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553

19.8.4

RNG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554

RM0385 Rev 7

17/1709
43

Contents

20

RM0385

Cryptographic processor (CRYP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555
20.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555

20.2

CRYP main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555

20.3

CRYP functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557
20.3.1

CRYP block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

20.3.2

CRYP internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

20.3.3

CRYP DES/TDES cryptographic core . . . . . . . . . . . . . . . . . . . . . . . . . 558

20.3.4

CRYP AES cryptographic core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

20.3.5

CRYP procedure to perform a cipher operation . . . . . . . . . . . . . . . . . . 565

20.3.6

CRYP busy state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568

20.3.7

Preparing the CRYP AES key for decryption . . . . . . . . . . . . . . . . . . . . 569

20.3.8

CRYP stealing and data padding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

20.3.9

CRYP suspend/resume operations . . . . . . . . . . . . . . . . . . . . . . . . . . . 571

20.3.10 CRYP DES/TDES basic chaining modes (ECB, CBC) . . . . . . . . . . . . 572
20.3.11 CRYP AES basic chaining modes (ECB, CBC) . . . . . . . . . . . . . . . . . . 577
20.3.12 CRYP AES counter mode (AES-CTR) . . . . . . . . . . . . . . . . . . . . . . . . . 582
20.3.13 CRYP AES Galois/counter mode (GCM) . . . . . . . . . . . . . . . . . . . . . . . 586
20.3.14 CRYP AES Galois message authentication code (GMAC) . . . . . . . . . 591
20.3.15 CRYP AES Counter with CBC-MAC (CCM) . . . . . . . . . . . . . . . . . . . . 592
20.3.16 CRYP data registers and data swapping . . . . . . . . . . . . . . . . . . . . . . . 598
20.3.17 CRYP key registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602
20.3.18 CRYP initialization vector registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
20.3.19 CRYP DMA interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
20.3.20 CRYP error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606

18/1709

20.4

CRYP interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606

20.5

CRYP processing time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608

20.6

CRYP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
20.6.1

CRYP control register (CRYP_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 609

20.6.2

CRYP status register (CRYP_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611

20.6.3

CRYP data input register (CRYP_DIN) . . . . . . . . . . . . . . . . . . . . . . . . 611

20.6.4

CRYP data output register (CRYP_DOUT) . . . . . . . . . . . . . . . . . . . . . 612

20.6.5

CRYP DMA control register (CRYP_DMACR) . . . . . . . . . . . . . . . . . . . 613

20.6.6

CRYP interrupt mask set/clear register (CRYP_IMSCR) . . . . . . . . . . . 613

20.6.7

CRYP raw interrupt status register (CRYP_RISR) . . . . . . . . . . . . . . . 614

20.6.8

CRYP masked interrupt status register (CRYP_MISR) . . . . . . . . . . . . 614

20.6.9

CRYP key register 0L (CRYP_K0LR) . . . . . . . . . . . . . . . . . . . . . . . . . 615

RM0385 Rev 7

RM0385

Contents
20.6.10 CRYP key register 0R (CRYP_K0RR) . . . . . . . . . . . . . . . . . . . . . . . . . 616
20.6.11 CRYP key register 1L (CRYP_K1LR) . . . . . . . . . . . . . . . . . . . . . . . . . 616
20.6.12 CRYP key register 1R (CRYP_K1RR) . . . . . . . . . . . . . . . . . . . . . . . . . 616
20.6.13 CRYP key register 2L (CRYP_K2LR) . . . . . . . . . . . . . . . . . . . . . . . . . 617
20.6.14 CRYP key register 2R (CRYP_K2RR) . . . . . . . . . . . . . . . . . . . . . . . . . 617
20.6.15 CRYP key register 3L (CRYP_K3LR) . . . . . . . . . . . . . . . . . . . . . . . . . 618
20.6.16 CRYP key register 3R (CRYP_K3RR) . . . . . . . . . . . . . . . . . . . . . . . . . 618
20.6.17 CRYP initialization vector register 0L (CRYP_IV0LR) . . . . . . . . . . . . . 618
20.6.18 CRYP initialization vector register 0R (CRYP_IV0RR) . . . . . . . . . . . . 619
20.6.19 CRYP initialization vector register 1L (CRYP_IV1LR) . . . . . . . . . . . . . 619
20.6.20 CRYP initialization vector register 1R (CRYP_IV1RR) . . . . . . . . . . . . 619
20.6.21 CRYP register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621

21

Hash processor (HASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623
21.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623

21.2

HASH main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623

21.3

HASH functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624
21.3.1

HASH block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624

21.3.2

HASH internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624

21.3.3

About secure hash algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625

21.3.4

Message data feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625

21.3.5

Message digest computing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627

21.3.6

Message padding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628

21.3.7

HMAC operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629

21.3.8

Context swapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631

21.3.9

HASH DMA interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633

21.3.10 HASH error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633

21.4

HASH interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633

21.5

HASH processing time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634

21.6

HASH registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635
21.6.1

HASH control register (HASH_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 635

21.6.2

HASH data input register (HASH_DIN) . . . . . . . . . . . . . . . . . . . . . . . . 638

21.6.3

HASH start register (HASH_STR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639

21.6.4

HASH digest registers (HASH_HR0..7) . . . . . . . . . . . . . . . . . . . . . . . . 640

21.6.5

HASH interrupt enable register (HASH_IMR) . . . . . . . . . . . . . . . . . . . 642

21.6.6

HASH status register (HASH_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643

RM0385 Rev 7

19/1709
43

Contents

22

RM0385
21.6.7

HASH context swap registers (HASH_CSRx) . . . . . . . . . . . . . . . . . . . 644

21.6.8

HASH register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645

Advanced-control timers (TIM1/TIM8) . . . . . . . . . . . . . . . . . . . . . . . . . 646
22.1

TIM1/TIM8 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646

22.2

TIM1/TIM8 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646

22.3

TIM1/TIM8 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648
22.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648

22.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650

22.3.3

Repetition counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661

22.3.4

External trigger input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663

22.3.5

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664

22.3.6

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668

22.3.7

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670

22.3.8

PWM input mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671

22.3.9

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672

22.3.10 Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673
22.3.11 PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674
22.3.12 Asymmetric PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 677
22.3.13 Combined PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 678
22.3.14 Combined 3-phase PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 679
22.3.15 Complementary outputs and dead-time insertion . . . . . . . . . . . . . . . . 680
22.3.16 Using the break function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 682
22.3.17 Clearing the OCxREF signal on an external event . . . . . . . . . . . . . . . 688
22.3.18 6-step PWM generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 690
22.3.19 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 691
22.3.20 Retriggerable one pulse mode (OPM) . . . . . . . . . . . . . . . . . . . . . . . . . 692
22.3.21 Encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693
22.3.22 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695
22.3.23 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696
22.3.24 Interfacing with Hall sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696
22.3.25 Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 699
22.3.26 ADC synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703
22.3.27 DMA burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703
22.3.28 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704

22.4

TIM1/TIM8 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705
22.4.1

20/1709

TIM1/TIM8 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . . 705
RM0385 Rev 7

RM0385

Contents
22.4.2

TIM1/TIM8 control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . . 706

22.4.3

TIM1/TIM8 slave mode control register (TIMx_SMCR) . . . . . . . . . . . . 709

22.4.4

TIM1/TIM8 DMA/interrupt enable register (TIMx_DIER) . . . . . . . . . . . 711

22.4.5

TIM1/TIM8 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . 713

22.4.6

TIM1/TIM8 event generation register (TIMx_EGR) . . . . . . . . . . . . . . . 715

22.4.7

TIM1/TIM8 capture/compare mode register 1 (TIMx_CCMR1) . . . . . . 716

22.4.8

TIM1/TIM8 capture/compare mode register 2 (TIMx_CCMR2) . . . . . . 720

22.4.9

TIM1/TIM8 capture/compare enable register (TIMx_CCER) . . . . . . . . 722

22.4.10 TIM1/TIM8 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726
22.4.11 TIM1/TIM8 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726
22.4.12 TIM1/TIM8 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . 726
22.4.13 TIM1/TIM8 repetition counter register (TIMx_RCR) . . . . . . . . . . . . . . 727
22.4.14 TIM1/TIM8 capture/compare register 1 (TIMx_CCR1) . . . . . . . . . . . . 727
22.4.15 TIM1/TIM8 capture/compare register 2 (TIMx_CCR2) . . . . . . . . . . . . 728
22.4.16 TIM1/TIM8 capture/compare register 3 (TIMx_CCR3) . . . . . . . . . . . . 728
22.4.17 TIM1/TIM8 capture/compare register 4 (TIMx_CCR4) . . . . . . . . . . . . 729
22.4.18 TIM1/TIM8 break and dead-time register (TIMx_BDTR) . . . . . . . . . . . 729
22.4.19 TIM1/TIM8 DMA control register (TIMx_DCR) . . . . . . . . . . . . . . . . . . . 732
22.4.20 TIM1/TIM8 DMA address for full transfer (TIMx_DMAR) . . . . . . . . . . . 733
22.4.21 TIM1/TIM8 capture/compare mode register 3 (TIMx_CCMR3) . . . . . . 734
22.4.22 TIM1/TIM8 capture/compare register 5 (TIMx_CCR5) . . . . . . . . . . . . 735
22.4.23 TIM1/TIM8 capture/compare register 6 (TIMx_CCR6) . . . . . . . . . . . . 736
22.4.24 TIM1 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737
22.4.25 TIM8 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 739

23

General-purpose timers (TIM2/TIM3/TIM4/TIM5) . . . . . . . . . . . . . . . . . 741
23.1

TIM2/TIM3/TIM4/TIM5 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741

23.2

TIM2/TIM3/TIM4/TIM5 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . 741

23.3

TIM2/TIM3/TIM4/TIM5 functional description . . . . . . . . . . . . . . . . . . . . . 743
23.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743

23.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745

23.3.3

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755

23.3.4

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759

23.3.5

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761

23.3.6

PWM input mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762

23.3.7

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763

23.3.8

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764

RM0385 Rev 7

21/1709
43

Contents

RM0385
23.3.9

PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765

23.3.10 Asymmetric PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768
23.3.11 Combined PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 769
23.3.12 Clearing the OCxREF signal on an external event . . . . . . . . . . . . . . . 770
23.3.13 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 772
23.3.14 Retriggerable one pulse mode (OPM) . . . . . . . . . . . . . . . . . . . . . . . . . 773
23.3.15 Encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774
23.3.16 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 776
23.3.17 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 776
23.3.18 Timers and external trigger synchronization . . . . . . . . . . . . . . . . . . . . 777
23.3.19 Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780
23.3.20 DMA burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 784
23.3.21 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 785

23.4

TIM2/TIM3/TIM4/TIM5 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 786
23.4.1

TIMx control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . 786

23.4.2

TIMx control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . 787

23.4.3

TIMx slave mode control register (TIMx_SMCR) . . . . . . . . . . . . . . . . . 789

23.4.4

TIMx DMA/Interrupt enable register (TIMx_DIER) . . . . . . . . . . . . . . . . 792

23.4.5

TIMx status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793

23.4.6

TIMx event generation register (TIMx_EGR) . . . . . . . . . . . . . . . . . . . . 794

23.4.7

TIMx capture/compare mode register 1 (TIMx_CCMR1) . . . . . . . . . . . 795

23.4.8

TIMx capture/compare mode register 2 (TIMx_CCMR2) . . . . . . . . . . . 799

23.4.9

TIMx capture/compare enable register (TIMx_CCER) . . . . . . . . . . . . 801

23.4.10 TIMx counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 802
23.4.11 TIMx prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
23.4.12 TIMx auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . . . . . . 803
23.4.13 TIMx capture/compare register 1 (TIMx_CCR1) . . . . . . . . . . . . . . . . . 803
23.4.14 TIMx capture/compare register 2 (TIMx_CCR2) . . . . . . . . . . . . . . . . . 804
23.4.15 TIMx capture/compare register 3 (TIMx_CCR3) . . . . . . . . . . . . . . . . . 804
23.4.16 TIMx capture/compare register 4 (TIMx_CCR4) . . . . . . . . . . . . . . . . . 805
23.4.17 TIMx DMA control register (TIMx_DCR) . . . . . . . . . . . . . . . . . . . . . . . 806
23.4.18 TIMx DMA address for full transfer (TIMx_DMAR) . . . . . . . . . . . . . . . 806
23.4.19 TIM2 option register (TIM2_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807
23.4.20 TIM5 option register (TIM5_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807
23.4.21 TIMx register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808

24

22/1709

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14) . . 811

RM0385 Rev 7

RM0385

Contents

24.1

TIM9/TIM10/TIM11/TIM12/TIM13/TIM14 introduction . . . . . . . . . . . . . . .811

24.2

TIM9/TIM10/TIM11/TIM12/TIM13/TIM14 main features . . . . . . . . . . . . . .811

24.3

24.2.1

TIM9/TIM12 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 811

24.2.2

TIM10/TIM11/TIM13/TIM14 main features . . . . . . . . . . . . . . . . . . . . . . 812

TIM9/TIM10/TIM11/TIM12/TIM13/TIM14 functional description . . . . . . . 814
24.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 814

24.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816

24.3.3

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819

24.3.4

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 821

24.3.5

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 823

24.3.6

PWM input mode (only for TIM9/TIM12) . . . . . . . . . . . . . . . . . . . . . . . 824

24.3.7

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825

24.3.8

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825

24.3.9

PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826

24.3.10 Combined PWM mode (TIM9/TIM12 only) . . . . . . . . . . . . . . . . . . . . . 827
24.3.11 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829
24.3.12 Retriggerable one pulse mode (OPM) (TIM12 only) . . . . . . . . . . . . . . 830
24.3.13 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831
24.3.14 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831
24.3.15 TIM9/TIM12 external trigger synchronization . . . . . . . . . . . . . . . . . . . 832
24.3.16 Slave mode – combined reset + trigger mode . . . . . . . . . . . . . . . . . . . 834
24.3.17 Timer synchronization (TIM9/TIM12) . . . . . . . . . . . . . . . . . . . . . . . . . . 835
24.3.18 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835

24.4

TIM9/TIM12 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835
24.4.1

TIM9/TIM12 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . 835

24.4.2

TIM9/TIM12 slave mode control register (TIMx_SMCR) . . . . . . . . . . . 836

24.4.3

TIM9/TIM12 Interrupt enable register (TIMx_DIER) . . . . . . . . . . . . . . 838

24.4.4

TIM9/TIM12 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . 838

24.4.5

TIM9/TIM12 event generation register (TIMx_EGR) . . . . . . . . . . . . . . 839

24.4.6

TIM9/TIM12 capture/compare mode register 1 (TIMx_CCMR1) . . . . . 840

24.4.7

TIM9/TIM12 capture/compare enable register (TIMx_CCER) . . . . . . . 844

24.4.8

TIM9/TIM12 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845

24.4.9

TIM9/TIM12 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 845

24.4.10 TIM9/TIM12 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . 846
24.4.11 TIM9/TIM12 capture/compare register 1 (TIMx_CCR1) . . . . . . . . . . . 846
24.4.12 TIM9/TIM12 capture/compare register 2 (TIMx_CCR2) . . . . . . . . . . . 846
24.4.13 TIM9/TIM12 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848
RM0385 Rev 7

23/1709
43

Contents

RM0385

24.5

TIM10/TIM11/TIM13/TIM14 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 850
24.5.1

TIM10/TIM11/TIM13/TIM14 control register 1 (TIMx_CR1) . . . . . . . . . 850

24.5.2

TIM10/TIM11/TIM13/TIM14 Interrupt enable register (TIMx_DIER) . . 851

24.5.3

TIM10/TIM11/TIM13/TIM14 status register (TIMx_SR) . . . . . . . . . . . . 851

24.5.4

TIM10/TIM11/TIM13/TIM14 event generation register (TIMx_EGR) . . 852

24.5.5

TIM10/TIM11/TIM13/TIM14 capture/compare mode register 1
(TIMx_CCMR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853

24.5.6

TIM10/TIM11/TIM13/TIM14 capture/compare enable register
(TIMx_CCER) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855

24.5.7

TIM10/TIM11/TIM13/TIM14 counter (TIMx_CNT) . . . . . . . . . . . . . . . . 856

24.5.8

TIM10/TIM11/TIM13/TIM14 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . 857

24.5.9

TIM10/TIM11/TIM13/TIM14 auto-reload register (TIMx_ARR) . . . . . . 857

24.5.10 TIM10/TIM11/TIM13/TIM14 capture/compare register 1
(TIMx_CCR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857
24.5.11 TIM11 option register 1 (TIM11_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . 858
24.5.12 TIM10/TIM11/TIM13/TIM14 register map . . . . . . . . . . . . . . . . . . . . . . 858

25

Basic timers (TIM6/TIM7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860
25.1

TIM6/TIM7 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860

25.2

TIM6/TIM7 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860

25.3

TIM6/TIM7 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 861

25.4

26
24/1709

25.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 861

25.3.2

Counting mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863

25.3.3

UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866

25.3.4

Clock source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866

25.3.5

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 867

TIM6/TIM7 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 867
25.4.1

TIM6/TIM7 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . . 867

25.4.2

TIM6/TIM7 control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . . 869

25.4.3

TIM6/TIM7 DMA/Interrupt enable register (TIMx_DIER) . . . . . . . . . . . 869

25.4.4

TIM6/TIM7 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . 870

25.4.5

TIM6/TIM7 event generation register (TIMx_EGR) . . . . . . . . . . . . . . . 870

25.4.6

TIM6/TIM7 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 870

25.4.7

TIM6/TIM7 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 871

25.4.8

TIM6/TIM7 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . 871

25.4.9

TIM6/TIM7 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 872

Low-power timer (LPTIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873
RM0385 Rev 7

RM0385

Contents

26.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873

26.2

LPTIM main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873

26.3

LPTIM implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873

26.4

LPTIM functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874
26.4.1

LPTIM block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874

26.4.2

LPTIM trigger mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874

26.4.3

LPTIM reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 875

26.4.4

Glitch filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 875

26.4.5

Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876

26.4.6

Trigger multiplexer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876

26.4.7

Operating mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 877

26.4.8

Timeout function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 879

26.4.9

Waveform generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 879

26.4.10 Register update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880
26.4.11 Counter mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 881
26.4.12 Timer enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 881
26.4.13 Encoder mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 882

27

26.5

LPTIM interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883

26.6

LPTIM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 884
26.6.1

LPTIM interrupt and status register (LPTIM_ISR) . . . . . . . . . . . . . . . . 884

26.6.2

LPTIM interrupt clear register (LPTIM_ICR) . . . . . . . . . . . . . . . . . . . . 885

26.6.3

LPTIM interrupt enable register (LPTIM_IER) . . . . . . . . . . . . . . . . . . . 886

26.6.4

LPTIM configuration register (LPTIM_CFGR) . . . . . . . . . . . . . . . . . . . 887

26.6.5

LPTIM control register (LPTIM_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . 889

26.6.6

LPTIM compare register (LPTIM_CMP) . . . . . . . . . . . . . . . . . . . . . . . 890

26.6.7

LPTIM autoreload register (LPTIM_ARR) . . . . . . . . . . . . . . . . . . . . . . 891

26.6.8

LPTIM counter register (LPTIM_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . 891

26.6.9

LPTIM register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 892

Independent watchdog (IWDG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893
27.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893

27.2

IWDG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893

27.3

IWDG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893
27.3.1

IWDG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893

27.3.2

Window option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894

27.3.3

Hardware watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895

RM0385 Rev 7

25/1709
43

Contents

RM0385

27.4

28

26/1709

Low-power freeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895

27.3.5

Behavior in Stop and Standby modes . . . . . . . . . . . . . . . . . . . . . . . . . 895

27.3.6

Register access protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895

27.3.7

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895

IWDG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896
27.4.1

Key register (IWDG_KR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896

27.4.2

Prescaler register (IWDG_PR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 897

27.4.3

Reload register (IWDG_RLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 898

27.4.4

Status register (IWDG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899

27.4.5

Window register (IWDG_WINR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900

27.4.6

IWDG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901

System window watchdog (WWDG) . . . . . . . . . . . . . . . . . . . . . . . . . . 902
28.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902

28.2

WWDG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902

28.3

WWDG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902

28.4

29

27.3.4

28.3.1

Enabling the watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903

28.3.2

Controlling the downcounter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903

28.3.3

Advanced watchdog interrupt feature . . . . . . . . . . . . . . . . . . . . . . . . . 903

28.3.4

How to program the watchdog timeout . . . . . . . . . . . . . . . . . . . . . . . . 904

28.3.5

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905

WWDG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
28.4.1

Control register (WWDG_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906

28.4.2

Configuration register (WWDG_CFR) . . . . . . . . . . . . . . . . . . . . . . . . . 906

28.4.3

Status register (WWDG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907

28.4.4

WWDG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908

Real-time clock (RTC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909
29.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909

29.2

RTC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910

29.3

RTC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .911
29.3.1

RTC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911

29.3.2

GPIOs controlled by the RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912

29.3.3

Clock and prescalers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914

29.3.4

Real-time clock and calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915

29.3.5

Programmable alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915

RM0385 Rev 7

RM0385

Contents
29.3.6

Periodic auto-wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 916

29.3.7

RTC initialization and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 917

29.3.8

Reading the calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 918

29.3.9

Resetting the RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 919

29.3.10 RTC synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 920
29.3.11 RTC reference clock detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 920
29.3.12 RTC smooth digital calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 921
29.3.13 Time-stamp function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923
29.3.14 Tamper detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 924
29.3.15 Calibration clock output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 926
29.3.16 Alarm output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 926

29.4

RTC low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927

29.5

RTC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927

29.6

RTC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 928
29.6.1

RTC time register (RTC_TR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 928

29.6.2

RTC date register (RTC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 929

29.6.3

RTC control register (RTC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 930

29.6.4

RTC initialization and status register (RTC_ISR) . . . . . . . . . . . . . . . . . 933

29.6.5

RTC prescaler register (RTC_PRER) . . . . . . . . . . . . . . . . . . . . . . . . . 936

29.6.6

RTC wakeup timer register (RTC_WUTR) . . . . . . . . . . . . . . . . . . . . . . 937

29.6.7

RTC alarm A register (RTC_ALRMAR) . . . . . . . . . . . . . . . . . . . . . . . . 938

29.6.8

RTC alarm B register (RTC_ALRMBR) . . . . . . . . . . . . . . . . . . . . . . . . 939

29.6.9

RTC write protection register (RTC_WPR) . . . . . . . . . . . . . . . . . . . . . 940

29.6.10 RTC sub second register (RTC_SSR) . . . . . . . . . . . . . . . . . . . . . . . . . 940
29.6.11 RTC shift control register (RTC_SHIFTR) . . . . . . . . . . . . . . . . . . . . . . 941
29.6.12 RTC timestamp time register (RTC_TSTR) . . . . . . . . . . . . . . . . . . . . . 942
29.6.13 RTC timestamp date register (RTC_TSDR) . . . . . . . . . . . . . . . . . . . . 943
29.6.14 RTC time-stamp sub second register (RTC_TSSSR) . . . . . . . . . . . . . 944
29.6.15 RTC calibration register (RTC_CALR) . . . . . . . . . . . . . . . . . . . . . . . . . 945
29.6.16 RTC tamper configuration register (RTC_TAMPCR) . . . . . . . . . . . . . . 946
29.6.17 RTC alarm A sub second register (RTC_ALRMASSR) . . . . . . . . . . . . 949
29.6.18 RTC alarm B sub second register (RTC_ALRMBSSR) . . . . . . . . . . . . 950
29.6.19 RTC option register (RTC_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 951
29.6.20 RTC backup registers (RTC_BKPxR) . . . . . . . . . . . . . . . . . . . . . . . . . 951
29.6.21 RTC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952

30

Inter-integrated circuit (I2C) interface . . . . . . . . . . . . . . . . . . . . . . . . . 954
RM0385 Rev 7

27/1709
43

Contents

RM0385

30.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954

30.2

I2C main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954

30.3

I2C implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955

30.4

I2C functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955
30.4.1

I2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 956

30.4.2

I2C clock requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 957

30.4.3

Mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 957

30.4.4

I2C initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958

30.4.5

Software reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 962

30.4.6

Data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 963

30.4.7

I2C slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 965

30.4.8

I2C master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 974

30.4.9

I2C_TIMINGR register configuration examples . . . . . . . . . . . . . . . . . . 986

30.4.10 SMBus specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 987
30.4.11 SMBus initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990
30.4.12 SMBus: I2C_TIMEOUTR register configuration examples . . . . . . . . . 992
30.4.13 SMBus slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992
30.4.14 Error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 999
30.4.15 DMA requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1001
30.4.16 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1002

30.5

I2C low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1002

30.6

I2C interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003

30.7

I2C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1004
30.7.1

Control register 1 (I2C_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1004

30.7.2

Control register 2 (I2C_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1007

30.7.3

Own address 1 register (I2C_OAR1) . . . . . . . . . . . . . . . . . . . . . . . . . 1010

30.7.4

Own address 2 register (I2C_OAR2) . . . . . . . . . . . . . . . . . . . . . . . . . 1011

30.7.5

Timing register (I2C_TIMINGR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012

30.7.6

Timeout register (I2C_TIMEOUTR) . . . . . . . . . . . . . . . . . . . . . . . . . . 1013

30.7.7

Interrupt and status register (I2C_ISR) . . . . . . . . . . . . . . . . . . . . . . . 1014

30.7.8

Interrupt clear register (I2C_ICR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016

30.7.9

PEC register (I2C_PECR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017

30.7.10 Receive data register (I2C_RXDR) . . . . . . . . . . . . . . . . . . . . . . . . . . 1018
30.7.11 Transmit data register (I2C_TXDR) . . . . . . . . . . . . . . . . . . . . . . . . . . 1018
30.7.12 I2C register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1019

28/1709

RM0385 Rev 7

RM0385

31

Contents

Universal synchronous asynchronous receiver
transmitter (USART) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1021
31.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1021

31.2

USART main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1021

31.3

USART extended features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1022

31.4

USART implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023

31.5

USART functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023
31.5.1

USART character description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1026

31.5.2

USART transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1028

31.5.3

USART receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1030

31.5.4

USART baud rate generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036

31.5.5

Tolerance of the USART receiver to clock deviation . . . . . . . . . . . . . 1039

31.5.6

USART auto baud rate detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1040

31.5.7

Multiprocessor communication using USART . . . . . . . . . . . . . . . . . . 1041

31.5.8

Modbus communication using USART . . . . . . . . . . . . . . . . . . . . . . . 1043

31.5.9

USART parity control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1044

31.5.10 USART LIN (local interconnection network) mode . . . . . . . . . . . . . . 1045
31.5.11 USART synchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047
31.5.12 USART Single-wire Half-duplex communication . . . . . . . . . . . . . . . . 1050
31.5.13 USART Smartcard mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1050
31.5.14 USART IrDA SIR ENDEC block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1055
31.5.15 USART continuous communication in DMA mode . . . . . . . . . . . . . . . 1057
31.5.16 RS232 hardware flow control and RS485 driver enable
using USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1059

31.6

USART low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1061

31.7

USART interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1062

31.8

USART registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1064
31.8.1

Control register 1 (USART_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1064

31.8.2

Control register 2 (USART_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1067

31.8.3

Control register 3 (USART_CR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1070

31.8.4

Baud rate register (USART_BRR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1073

31.8.5

Guard time and prescaler register (USART_GTPR) . . . . . . . . . . . . . 1074

31.8.6

Receiver timeout register (USART_RTOR) . . . . . . . . . . . . . . . . . . . . 1075

31.8.7

Request register (USART_RQR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1076

31.8.8

Interrupt and status register (USART_ISR) . . . . . . . . . . . . . . . . . . . . 1077

31.8.9

Interrupt flag clear register (USART_ICR) . . . . . . . . . . . . . . . . . . . . . 1081

RM0385 Rev 7

29/1709
43

Contents

RM0385
31.8.10 Receive data register (USART_RDR) . . . . . . . . . . . . . . . . . . . . . . . . 1082
31.8.11 Transmit data register (USART_TDR) . . . . . . . . . . . . . . . . . . . . . . . . 1083
31.8.12 USART register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1083

32

Serial peripheral interface / inter-IC sound (SPI/I2S) . . . . . . . . . . . . 1085
32.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1085

32.2

SPI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1085

32.3

I2S main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086

32.4

SPI/I2S implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086

32.5

SPI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087
32.5.1

General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087

32.5.2

Communications between one master and one slave . . . . . . . . . . . . 1088

32.5.3

Standard multi-slave communication . . . . . . . . . . . . . . . . . . . . . . . . . 1090

32.5.4

Multi-master communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091

32.5.5

Slave select (NSS) pin management . . . . . . . . . . . . . . . . . . . . . . . . . 1092

32.5.6

Communication formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1093

32.5.7

Configuration of SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095

32.5.8

Procedure for enabling SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096

32.5.9

Data transmission and reception procedures . . . . . . . . . . . . . . . . . . 1096

32.5.10 SPI status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1106
32.5.11 SPI error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1107
32.5.12 NSS pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1108
32.5.13 TI mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1108
32.5.14 CRC calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1109

32.6

SPI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1111

32.7

I2S functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1112
32.7.1

I2S general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1112

32.7.2

I2S full duplex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1113

32.7.3

Supported audio protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1114

32.7.4

Start-up description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1121

32.7.5

Clock generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1123

32.7.6

I2S master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1126

32.7.7

I2S slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1128

32.7.8

I2S status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1129

32.7.9

I2S error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1130

32.7.10 DMA features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1131

30/1709

RM0385 Rev 7

RM0385

Contents

32.8

I2S interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1131

32.9

SPI and I2S registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1132
32.9.1

SPI control register 1 (SPIx_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1132

32.9.2

SPI control register 2 (SPIx_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1134

32.9.3

SPI status register (SPIx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1137

32.9.4

SPI data register (SPIx_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1138

32.9.5

SPI CRC polynomial register (SPIx_CRCPR) . . . . . . . . . . . . . . . . . . 1138

32.9.6

SPI Rx CRC register (SPIx_RXCRCR) . . . . . . . . . . . . . . . . . . . . . . . 1140

32.9.7

SPI Tx CRC register (SPIx_TXCRCR) . . . . . . . . . . . . . . . . . . . . . . . 1140

32.9.8

SPIx_I2S configuration register (SPIx_I2SCFGR) . . . . . . . . . . . . . . . 1141

32.9.9

SPIx_I2S prescaler register (SPIx_I2SPR) . . . . . . . . . . . . . . . . . . . . 1143

32.9.10 SPI/I2S register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1144

33

Serial audio interface (SAI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1145
33.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1145

33.2

SAI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1146

33.3

SAI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1147
33.3.1

SAI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1147

33.3.2

SAI pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1148

33.3.3

Main SAI modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1148

33.3.4

SAI synchronization mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1149

33.3.5

Audio data size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1150

33.3.6

Frame synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1151

33.3.7

Slot configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1154

33.3.8

SAI clock generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1156

33.3.9

Internal FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1158

33.3.10 AC’97 link controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1160
33.3.11 SPDIF output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1162
33.3.12 Specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1165
33.3.13 Error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1169
33.3.14 Disabling the SAI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1172
33.3.15 SAI DMA interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1172

33.4

SAI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1173

33.5

SAI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1174
33.5.1

Global configuration register (SAI_GCR) . . . . . . . . . . . . . . . . . . . . . . 1174

33.5.2

Configuration register 1 (SAI_ACR1 / SAI_BCR1) . . . . . . . . . . . . . . 1174

RM0385 Rev 7

31/1709
43

Contents

RM0385
33.5.3

Configuration register 2 (SAI_ACR2 / SAI_BCR2) . . . . . . . . . . . . . . 1177

33.5.4

Frame configuration register (SAI_AFRCR / SAI_BFRCR) . . . . . . . . 1179

33.5.5

Slot register (SAI_ASLOTR / SAI_BSLOTR) . . . . . . . . . . . . . . . . . . . 1181

33.5.6

Interrupt mask register 2 (SAI_AIM / SAI_BIM) . . . . . . . . . . . . . . . . . 1182

33.5.7

Status register (SAI_ASR / SAI_BSR) . . . . . . . . . . . . . . . . . . . . . . . . 1183

33.5.8

Clear flag register (SAI_ACLRFR / SAI_BCLRFR) . . . . . . . . . . . . . . 1185

33.5.9

Data register (SAI_ADR / SAI_BDR) . . . . . . . . . . . . . . . . . . . . . . . . . 1186

33.5.10 SAI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1188

34

SPDIF receiver interface (SPDIFRX) . . . . . . . . . . . . . . . . . . . . . . . . . 1189
34.1

SPDIFRX interface introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1189

34.2

SPDIFRX main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1189

34.3

SPDIFRX functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1189
34.3.1

S/PDIF protocol (IEC-60958) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1190

34.3.2

SPDIFRX decoder (SPDIFRX_DC) . . . . . . . . . . . . . . . . . . . . . . . . . . 1192

34.3.3

SPDIFRX tolerance to clock deviation . . . . . . . . . . . . . . . . . . . . . . . . 1196

34.3.4

SPDIFRX synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1196

34.3.5

SPDIFRX handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1198

34.3.6

Data reception management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1200

34.3.7

Dedicated control flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1202

34.3.8

Reception errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1202

34.3.9

Clocking strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1205

34.3.10 DMA Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1205
34.3.11 Interrupt Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1206
34.3.12 Register protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1207

34.4

34.5

32/1709

Programming procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1207
34.4.1

Initialization phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1208

34.4.2

Handling of interrupts coming from SPDIFRX . . . . . . . . . . . . . . . . . . 1209

34.4.3

Handling of interrupts coming from DMA . . . . . . . . . . . . . . . . . . . . . . 1209

SPDIFRX interface registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1210
34.5.1

Control register (SPDIFRX_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1210

34.5.2

Interrupt mask register (SPDIFRX_IMR) . . . . . . . . . . . . . . . . . . . . . . 1212

34.5.3

Status register (SPDIFRX_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1213

34.5.4

Interrupt flag clear register (SPDIFRX_IFCR) . . . . . . . . . . . . . . . . . . 1215

34.5.5

Data input register (SPDIFRX_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . 1216

34.5.6

Data input register (SPDIFRX_FMT1_DR) . . . . . . . . . . . . . . . . . . . . 1217

34.5.7

Data input register (SPDIFRX_FMT2_DR) . . . . . . . . . . . . . . . . . . . . 1218
RM0385 Rev 7

RM0385

Contents
34.5.8

Channel status register (SPDIFRX_CSR) . . . . . . . . . . . . . . . . . . . . . 1219

34.5.9

Debug information register (SPDIFRX_DIR) . . . . . . . . . . . . . . . . . . . 1219

34.5.10 SPDIFRX interface register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1221

35

SD/SDIO/MMC card host interface (SDMMC) . . . . . . . . . . . . . . . . . . 1222
35.1

SDMMC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1222

35.2

SDMMC bus topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1222

35.3

SDMMC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1224

35.4

35.3.1

SDMMC adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1226

35.3.2

SDMMC APB2 interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1237

Card functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1238
35.4.1

Card identification mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1238

35.4.2

Card reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1239

35.4.3

Operating voltage range validation . . . . . . . . . . . . . . . . . . . . . . . . . . 1239

35.4.4

Card identification process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1239

35.4.5

Block write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1240

35.4.6

Block read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1241

35.4.7

Stream access, stream write and stream read
(MultiMediaCard only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1241

35.4.8

Erase: group erase and sector erase . . . . . . . . . . . . . . . . . . . . . . . . 1243

35.4.9

Wide bus selection or deselection . . . . . . . . . . . . . . . . . . . . . . . . . . . 1243

35.4.10 Protection management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1243
35.4.11 Card status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1247
35.4.12 SD status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1250
35.4.13 SD I/O mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1254
35.4.14 Commands and responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1255

35.5

35.6

Response formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1258
35.5.1

R1 (normal response command) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1259

35.5.2

R1b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1259

35.5.3

R2 (CID, CSD register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1259

35.5.4

R3 (OCR register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260

35.5.5

R4 (Fast I/O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260

35.5.6

R4b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260

35.5.7

R5 (interrupt request) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1261

35.5.8

R6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1261

SDIO I/O card-specific operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1262
35.6.1

SDIO I/O read wait operation by SDMMC_D2 signalling . . . . . . . . . . 1262

RM0385 Rev 7

33/1709
43

Contents

RM0385
35.6.2

SDIO read wait operation by stopping SDMMC_CK . . . . . . . . . . . . . 1263

35.6.3

SDIO suspend/resume operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263

35.6.4

SDIO interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263

35.7

HW flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263

35.8

SDMMC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1264
35.8.1

SDMMC power control register (SDMMC_POWER) . . . . . . . . . . . . . 1264

35.8.2

SDMMC clock control register (SDMMC_CLKCR) . . . . . . . . . . . . . . 1264

35.8.3

SDMMC argument register (SDMMC_ARG) . . . . . . . . . . . . . . . . . . . 1266

35.8.4

SDMMC command register (SDMMC_CMD) . . . . . . . . . . . . . . . . . . 1266

35.8.5

SDMMC command response register (SDMMC_RESPCMD) . . . . . . 1267

35.8.6

SDMMC response 1..4 register (SDMMC_RESPx) . . . . . . . . . . . . . . 1267

35.8.7

SDMMC data timer register (SDMMC_DTIMER) . . . . . . . . . . . . . . . 1268

35.8.8

SDMMC data length register (SDMMC_DLEN) . . . . . . . . . . . . . . . . . 1269

35.8.9

SDMMC data control register (SDMMC_DCTRL) . . . . . . . . . . . . . . . 1269

35.8.10 SDMMC data counter register (SDMMC_DCOUNT) . . . . . . . . . . . . . 1272
35.8.11 SDMMC status register (SDMMC_STA) . . . . . . . . . . . . . . . . . . . . . . 1272
35.8.12 SDMMC interrupt clear register (SDMMC_ICR) . . . . . . . . . . . . . . . . 1273
35.8.13 SDMMC mask register (SDMMC_MASK) . . . . . . . . . . . . . . . . . . . . . 1275
35.8.14 SDMMC FIFO counter register (SDMMC_FIFOCNT) . . . . . . . . . . . . 1277
35.8.15 SDMMC data FIFO register (SDMMC_FIFO) . . . . . . . . . . . . . . . . . . 1278
35.8.16 SDMMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1279

36

Controller area network (bxCAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1281
36.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1281

36.2

bxCAN main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1281

36.3

bxCAN general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1282

36.4

36.5

36.3.1

CAN 2.0B active core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1282

36.3.2

Control, status and configuration registers . . . . . . . . . . . . . . . . . . . . 1282

36.3.3

Tx mailboxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1282

36.3.4

Acceptance filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1283

bxCAN operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1284
36.4.1

Initialization mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1284

36.4.2

Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1284

36.4.3

Sleep mode (low-power) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1285

Test mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286
36.5.1

34/1709

Silent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286

RM0385 Rev 7

RM0385

37

Contents
36.5.2

Loop back mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286

36.5.3

Loop back combined with silent mode . . . . . . . . . . . . . . . . . . . . . . . . 1287

36.6

Behavior in debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1287

36.7

bxCAN functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1287
36.7.1

Transmission handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1287

36.7.2

Time triggered communication mode . . . . . . . . . . . . . . . . . . . . . . . . . 1289

36.7.3

Reception handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1289

36.7.4

Identifier filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1291

36.7.5

Message storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1295

36.7.6

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297

36.7.7

Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297

36.8

bxCAN interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1300

36.9

CAN registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1301
36.9.1

Register access protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1301

36.9.2

CAN control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1301

36.9.3

CAN mailbox registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1311

36.9.4

CAN filter registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1318

36.9.5

bxCAN register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1322

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS) . . . . . . . 1326
37.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1326

37.2

OTG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327
37.2.1

General features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1328

37.2.2

Host-mode features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1329

37.2.3

Peripheral-mode features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1329

37.3

OTG implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1330

37.4

OTG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1331

37.5

37.4.1

OTG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1331

37.4.2

USB OTG pin and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . 1332

37.4.3

OTG core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1333

37.4.4

Full-speed OTG PHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1333

37.4.5

Embedded full speed OTG PHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1334

37.4.6

High-speed OTG PHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1335

OTG dual role device (DRD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1335
37.5.1

ID line detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1335

37.5.2

HNP dual role device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1336

RM0385 Rev 7

35/1709
43

Contents

RM0385
37.5.3

37.6

37.7

37.8

37.9

SRP dual role device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1336

USB peripheral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1336
37.6.1

SRP-capable peripheral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1337

37.6.2

Peripheral states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1337

37.6.3

Peripheral endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1338

USB host . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1340
37.7.1

SRP-capable host . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1341

37.7.2

USB host states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1341

37.7.3

Host channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1343

37.7.4

Host scheduler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1344

SOF trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1345
37.8.1

Host SOFs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1345

37.8.2

Peripheral SOFs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1345

OTG low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1346

37.10 Dynamic update of the OTG_HFIR register . . . . . . . . . . . . . . . . . . . . . 1347
37.11 USB data FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1347
37.11.1 Peripheral FIFO architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1348
37.11.2 Host FIFO architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1349
37.11.3 FIFO RAM allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1350

37.12 OTG_FS system performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1352
37.13 OTG_FS/OTG_HS interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1352
37.14 OTG_FS/OTG_HS control and status registers . . . . . . . . . . . . . . . . . . 1354
37.14.1 CSR memory map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1354

37.15 OTG_FS/OTG_HS registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1360
37.15.1 OTG control and status register (OTG_GOTGCTL) . . . . . . . . . . . . . 1360
37.15.2 OTG interrupt register (OTG_GOTGINT) . . . . . . . . . . . . . . . . . . . . . 1363
37.15.3 OTG AHB configuration register (OTG_GAHBCFG) . . . . . . . . . . . . . 1365
37.15.4 OTG USB configuration register (OTG_GUSBCFG) . . . . . . . . . . . . . 1367
37.15.5 OTG reset register (OTG_GRSTCTL) . . . . . . . . . . . . . . . . . . . . . . . . 1370
37.15.6 OTG core interrupt register (OTG_GINTSTS) . . . . . . . . . . . . . . . . . . 1373
37.15.7 OTG interrupt mask register (OTG_GINTMSK) . . . . . . . . . . . . . . . . . 1378
37.15.8 OTG receive status debug read/OTG status read and
pop registers (OTG_GRXSTSR/OTG_GRXSTSP) . . . . . . . . . . . . . . 1381
37.15.9 OTG receive FIFO size register (OTG_GRXFSIZ) . . . . . . . . . . . . . . 1384
37.15.10 OTG host non-periodic transmit FIFO size register
(OTG_HNPTXFSIZ)/Endpoint 0 Transmit FIFO size
(OTG_DIEPTXF0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1384

36/1709

RM0385 Rev 7

RM0385

Contents
37.15.11 OTG non-periodic transmit FIFO/queue status register
(OTG_HNPTXSTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1385
37.15.12 OTG general core configuration register (OTG_GCCFG) . . . . . . . . . 1386
37.15.13 OTG core ID register (OTG_CID) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1387
37.15.14 OTG core LPM configuration register (OTG_GLPMCFG) . . . . . . . . . 1387
37.15.15 OTG host periodic transmit FIFO size register
(OTG_HPTXFSIZ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1392
37.15.16 OTG device IN endpoint transmit FIFO size register
(OTG_DIEPTXFx) (x = 1..5[FS] /8[HS], where x is the
FIFO number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1392
37.15.17 Host-mode registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1393
37.15.18 OTG host configuration register (OTG_HCFG) . . . . . . . . . . . . . . . . . 1393
37.15.19 OTG host frame interval register (OTG_HFIR) . . . . . . . . . . . . . . . . . 1394
37.15.20 OTG host frame number/frame time remaining register
(OTG_HFNUM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395
37.15.21 OTG_Host periodic transmit FIFO/queue status register
(OTG_HPTXSTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395
37.15.22 OTG host all channels interrupt register (OTG_HAINT) . . . . . . . . . . 1396
37.15.23 OTG host all channels interrupt mask register
(OTG_HAINTMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1397
37.15.24 OTG host port control and status register (OTG_HPRT) . . . . . . . . . . 1398
37.15.25 OTG host channel x characteristics register (OTG_HCCHARx)
(x = 0..15[HS] / 11[FS], where x = Channel number) . . . . . . . . . . . . . 1400
37.15.26 OTG host channel x split control register (OTG_HCSPLTx)
(x = 0..15, where x = Channel number) . . . . . . . . . . . . . . . . . . . . . . . 1401
37.15.27 OTG host channel x interrupt register (OTG_HCINTx)
(x = 0..15[HS] / 11[FS], where x = Channel number) . . . . . . . . . . . . . 1402
37.15.28 OTG host channel x interrupt mask register (OTG_HCINTMSKx)
(x = 0..15[HS] / 11[FS], where x = Channel number) . . . . . . . . . . . . . 1404
37.15.29 OTG host channel x transfer size register (OTG_HCTSIZx)
(x = 0..15[HS] / 11[FS], where x = Channel number) . . . . . . . . . . . . . 1405
37.15.30 OTG host channel x DMA address register (OTG_HCDMAx)
(x = 0..15, where x = Channel number) . . . . . . . . . . . . . . . . . . . . . . . 1406
37.15.31 Device-mode registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1406
37.15.32 OTG device configuration register (OTG_DCFG) . . . . . . . . . . . . . . . 1407
37.15.33 OTG device control register (OTG_DCTL) . . . . . . . . . . . . . . . . . . . . 1409
37.15.34 OTG device status register (OTG_DSTS) . . . . . . . . . . . . . . . . . . . . . 1411
37.15.35 OTG device IN endpoint common interrupt mask register
(OTG_DIEPMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1412
37.15.36 OTG device OUT endpoint common interrupt mask register
(OTG_DOEPMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1413

RM0385 Rev 7

37/1709
43

Contents

RM0385
37.15.37 OTG device all endpoints interrupt register (OTG_DAINT) . . . . . . . . 1415
37.15.38 OTG all endpoints interrupt mask register
(OTG_DAINTMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1415
37.15.39 OTG device VBUS discharge time register
(OTG_DVBUSDIS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1416
37.15.40 OTG device VBUS pulsing time register
(OTG_DVBUSPULSE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1416
37.15.41 OTG device threshold control register (OTG_DTHRCTL) . . . . . . . . . 1417
37.15.42 OTG device IN endpoint FIFO empty interrupt mask register
(OTG_DIEPEMPMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1418
37.15.43 OTG device each endpoint interrupt register (OTG_DEACHINT) . . . 1419
37.15.44 OTG device each endpoint interrupt mask register
(OTG_DEACHINTMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1419
37.15.45 OTG device each IN endpoint-1 interrupt mask register
(OTG_HS_DIEPEACHMSK1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1420
37.15.46 OTG device each OUT endpoint-1 interrupt mask register
(OTG_HS_DOEPEACHMSK1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1421
37.15.47 OTG device control IN endpoint 0 control register
(OTG_DIEPCTL0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1422
37.15.48 OTG device IN endpoint x control register (OTG_DIEPCTLx)
(x = 1..5[FS] / 0..8[HS], where x = endpoint number) . . . . . . . . . . . . 1424
37.15.49 OTG device IN endpoint x interrupt register (OTG_DIEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint number) . . . . . . . . . . . . . . . 1426
37.15.50 OTG device IN endpoint 0 transfer size register
(OTG_DIEPTSIZ0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1428
37.15.51 OTG device IN endpoint x DMA address register (OTG_DIEPDMAx)
(x = 0..8, where x = endpoint number) . . . . . . . . . . . . . . . . . . . . . . . . 1429
37.15.52 OTG device IN endpoint transmit FIFO status register
(OTG_DTXFSTSx) (x = 0..5[FS] /8[HS], where
x = endpoint number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1429
37.15.53 OTG device IN endpoint x transfer size register (OTG_DIEPTSIZx)
(x = 1..5[FS] /8[HS], where x = endpoint number) . . . . . . . . . . . . . . . 1430
37.15.54 OTG device control OUT endpoint 0 control register
(OTG_DOEPCTL0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1431
37.15.55 OTG device OUT endpoint x interrupt register (OTG_DOEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint number) . . . . . . . . . . . . . . . 1432
37.15.56 OTG device OUT endpoint 0 transfer size register
(OTG_DOEPTSIZ0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1434
37.15.57 OTG device OUT endpoint x DMA address register (OTG_DOEPDMAx)
(x = 0..8, where x = endpoint number) . . . . . . . . . . . . . . . . . . . . . . . . 1435
37.15.58 OTG device OUT endpoint x control register (OTG_DOEPCTLx)
(x = 1..5[FS] /8[HS], where x = endpoint number) . . . . . . . . . . . . . . . 1436

38/1709

RM0385 Rev 7

RM0385

Contents
37.15.59 OTG device OUT endpoint x transfer size register
(OTG_DOEPTSIZx) (x = 1..5[FS] /8[HS],
where x = Endpoint number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1438
37.15.60 OTG power and clock gating control register (OTG_PCGCCTL) . . . 1439
37.15.61 OTG_FS/OTG_HS register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1440

37.16 OTG_FS/OTG_HS programming model . . . . . . . . . . . . . . . . . . . . . . . 1453
37.16.1 Core initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453
37.16.2 Host initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453
37.16.3 Device initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454
37.16.4 DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455
37.16.5 Host programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455
37.16.6 Device programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1488
37.16.7 Worst case response time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1506
37.16.8 OTG programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1508

38

Ethernet (ETH): media access control (MAC) with
DMA controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1515
38.1

Ethernet introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1515

38.2

Ethernet main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1515
38.2.1

MAC core features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1516

38.2.2

DMA features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1517

38.2.3

PTP features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1517

38.3

Ethernet pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1518

38.4

Ethernet functional description: SMI, MII and RMII . . . . . . . . . . . . . . . 1519

38.5

38.4.1

Station management interface: SMI . . . . . . . . . . . . . . . . . . . . . . . . . 1519

38.4.2

Media-independent interface: MII . . . . . . . . . . . . . . . . . . . . . . . . . . . 1523

38.4.3

Reduced media-independent interface: RMII . . . . . . . . . . . . . . . . . . 1525

38.4.4

MII/RMII selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1526

Ethernet functional description: MAC 802.3 . . . . . . . . . . . . . . . . . . . . . 1527
38.5.1

MAC 802.3 frame format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1527

38.5.2

MAC frame transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1531

38.5.3

MAC frame reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1538

38.5.4

MAC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1544

38.5.5

MAC filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1544

38.5.6

MAC loopback mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1547

38.5.7

MAC management counters: MMC . . . . . . . . . . . . . . . . . . . . . . . . . . 1547

38.5.8

Power management: PMT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1548

RM0385 Rev 7

39/1709
43

Contents

RM0385
38.5.9

38.6

39

Ethernet functional description: DMA controller operation . . . . . . . . . . 1557
38.6.1

Initialization of a transfer using DMA . . . . . . . . . . . . . . . . . . . . . . . . . 1558

38.6.2

Host bus burst access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1558

38.6.3

Host data buffer alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1559

38.6.4

Buffer size calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1559

38.6.5

DMA arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1560

38.6.6

Error response to DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1560

38.6.7

Tx DMA configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1560

38.6.8

Rx DMA configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1572

38.6.9

DMA interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1583

38.7

Ethernet interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1584

38.8

Ethernet register descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1585
38.8.1

MAC register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1585

38.8.2

MMC register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1605

38.8.3

IEEE 1588 time stamp registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1610

38.8.4

DMA register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1618

38.8.5

Ethernet register maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1632

HDMI-CEC controller (HDMI-CEC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1636
39.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1636

39.2

HDMI-CEC controller main features . . . . . . . . . . . . . . . . . . . . . . . . . . . 1636

39.3

HDMI-CEC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1637

39.4

39.3.1

HDMI-CEC pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1637

39.3.2

HDMI-CEC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1637

39.3.3

Message description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1637

39.3.4

Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1638

Arbitration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1639
39.4.1

39.5

40/1709

Precision time protocol (IEEE1588 PTP) . . . . . . . . . . . . . . . . . . . . . . 1551

SFT option bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1640

Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1641
39.5.1

Bit error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1641

39.5.2

Message error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1641

39.5.3

Bit Rising Error (BRE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1641

39.5.4

Short Bit Period Error (SBPE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1642

39.5.5

Long Bit Period Error (LBPE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1642

39.5.6

Transmission Error Detection (TXERR) . . . . . . . . . . . . . . . . . . . . . . . 1644

RM0385 Rev 7

RM0385

40

Contents

39.6

HDMI-CEC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1645

39.7

HDMI-CEC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1646
39.7.1

CEC control register (CEC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1646

39.7.2

CEC configuration register (CEC_CFGR) . . . . . . . . . . . . . . . . . . . . . 1647

39.7.3

CEC Tx data register (CEC_TXDR) . . . . . . . . . . . . . . . . . . . . . . . . . . 1650

39.7.4

CEC Rx data register (CEC_RXDR) . . . . . . . . . . . . . . . . . . . . . . . . . 1650

39.7.5

CEC Interrupt and Status Register (CEC_ISR) . . . . . . . . . . . . . . . . . 1650

39.7.6

CEC interrupt enable register (CEC_IER) . . . . . . . . . . . . . . . . . . . . . 1652

39.7.7

HDMI-CEC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1654

Debug support (DBG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1655
40.1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1655

40.2

Reference Arm® documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1656

40.3

SWJ debug port (serial wire and JTAG) . . . . . . . . . . . . . . . . . . . . . . . . 1656
40.3.1

40.4

Mechanism to select the JTAG-DP or the SW-DP . . . . . . . . . . . . . . . 1657

Pinout and debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1657
40.4.1

SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1658

40.4.2

Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1658

40.4.3

Internal pull-up and pull-down on JTAG pins . . . . . . . . . . . . . . . . . . . 1659

40.4.4

Using serial wire and releasing the unused debug pins as GPIOs . . 1660

40.5

STM32F75xxx and STM32F74xxx JTAG Debug Port connection . . . . 1660

40.6

ID codes and locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1662
40.6.1

MCU device ID code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1662

40.6.2

Boundary scan Debug Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1662

40.6.3

Cortex®-M7 with FPU Debug Port . . . . . . . . . . . . . . . . . . . . . . . . . . . 1662

40.6.4

Cortex®-M7 with FPU JEDEC-106 ID code . . . . . . . . . . . . . . . . . . . . 1663

40.7

JTAG debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1663

40.8

SW debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1665

40.9

40.8.1

SW protocol introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1665

40.8.2

SW protocol sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1665

40.8.3

SW-DP state machine (reset, idle states, ID code) . . . . . . . . . . . . . . 1666

40.8.4

DP and AP read/write accesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1667

40.8.5

SW-DP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1667

40.8.6

SW-AP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1668

AHB-AP (AHB access port) - valid for both JTAG-DP
and SW-DP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1669

RM0385 Rev 7

41/1709
43

Contents

RM0385

40.10 Core debug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1670
40.11 Capability of the debugger host to connect under system reset . . . . . 1671
40.12 FPB (Flash patch breakpoint) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1671
40.13 DWT (data watchpoint trigger) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1672
40.14 ITM (instrumentation trace macrocell) . . . . . . . . . . . . . . . . . . . . . . . . . 1672
40.14.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1672
40.14.2 Time stamp packets, synchronization and overflow packets . . . . . . . 1672

40.15 ETM (Embedded trace macrocell) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1674
40.15.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1674
40.15.2 Signal protocol, packet types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1674
40.15.3 Main ETM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1675
40.15.4 Configuration example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1675

40.16 MCU debug component (DBGMCU) . . . . . . . . . . . . . . . . . . . . . . . . . . 1675
40.16.1 Debug support for low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . 1675
40.16.2 Debug support for timers, watchdog, bxCAN and I2C . . . . . . . . . . . . 1676
40.16.3 Debug MCU configuration register . . . . . . . . . . . . . . . . . . . . . . . . . . 1676
40.16.4 DBGMCU_CR register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1677
40.16.5 Debug MCU APB1 freeze register (DBGMCU_APB1_FZ) . . . . . . . . 1678
40.16.6 Debug MCU APB2 Freeze register (DBGMCU_APB2_FZ) . . . . . . . . 1680

40.17 Pelican TPIU (trace port interface unit) . . . . . . . . . . . . . . . . . . . . . . . . 1681
40.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1681
40.17.2 TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1682
40.17.3 TPIU formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1684
40.17.4 TPIU frame synchronization packets . . . . . . . . . . . . . . . . . . . . . . . . . 1684
40.17.5 Transmission of the synchronization frame packet . . . . . . . . . . . . . . 1684
40.17.6 Synchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1685
40.17.7 Asynchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1685
40.17.8 TRACECLKIN connection inside the
STM32F75xxx and STM32F74xxx . . . . . . . . . . . . . . . . . . . . . . . . . . 1685
40.17.9 TPIU registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1686
40.17.10 Example of configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1686

40.18 DBG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1687

41

42/1709

Device electronic signature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1688
41.1

Unique device ID register (96 bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1688

41.2

Flash size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1689

RM0385 Rev 7

RM0385

Contents

41.3

42

Package data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1690

Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1691

RM0385 Rev 7

43/1709
43

List of tables

RM0385

List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Table 22.
Table 23.
Table 24.
Table 25.
Table 26.
Table 27.
Table 28.
Table 29.
Table 30.
Table 31.
Table 32.
Table 33.
Table 34.
Table 35.
Table 36.
Table 37.
Table 38.
Table 39.
Table 40.
Table 41.
Table 42.
Table 43.
Table 44.
Table 45.
Table 46.
Table 47.
Table 48.

44/1709

STM32F75xxx and STM32F74xxx register boundary addresses . . . . . . . . . . . . . . . . . . . . 70
Boot modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Flash memory organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Number of wait states according to CPU clock (HCLK) frequency . . . . . . . . . . . . . . . . . . . 78
Program/erase parallelism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Flash interrupt request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Option byte organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Access versus read protection level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
OTP area organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Flash register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Voltage regulator configuration mode versus device operating mode . . . . . . . . . . . . . . . 105
Low-power mode summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Features over all modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Sleep-now entry and exit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Sleep-on-exit entry and exit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Stop operating modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Stop mode entry and exit (STM32F75xxx and STM32F74xxx) . . . . . . . . . . . . . . . . . . . . 118
Standby mode entry and exit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
PWR - register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
RCC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
Port bit configuration table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
GPIO register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
SYSCFG register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
DMA1 request mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
DMA2 request mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
Source and destination address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
Source and destination address registers in double-buffer mode (DBM = 1) . . . . . . . . . . 232
Packing/unpacking and endian behavior (bit PINC = MINC = 1) . . . . . . . . . . . . . . . . . . . 233
Restriction on NDT versus PSIZE and MSIZE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
FIFO threshold configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
Possible DMA configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
DMA interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
DMA register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Supported color mode in input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
Data order in memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
Alpha mode configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
Supported CLUT color mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
CLUT data order in system memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
Supported color mode in output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
Data order in memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
DMA2D interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
DMA2D register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
STM32F75xxx and STM32F74xxx vector table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
External interrupt/event controller register map and reset values. . . . . . . . . . . . . . . . . . . 300
CRC internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
CRC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
NOR/PSRAM bank selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
NOR/PSRAM External memory address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

RM0385 Rev 7

RM0385
Table 49.
Table 50.
Table 51.
Table 52.
Table 53.
Table 54.
Table 55.
Table 56.
Table 57.
Table 58.
Table 59.
Table 60.
Table 61.
Table 62.
Table 63.
Table 64.
Table 65.
Table 66.
Table 67.
Table 68.
Table 69.
Table 70.
Table 71.
Table 72.
Table 73.
Table 74.
Table 75.
Table 76.
Table 77.
Table 78.
Table 79.
Table 80.
Table 81.
Table 82.
Table 83.
Table 84.
Table 85.
Table 86.
Table 87.
Table 88.
Table 89.
Table 90.
Table 91.
Table 92.
Table 93.
Table 94.
Table 95.
Table 96.
Table 97.
Table 98.
Table 99.
Table 100.

List of tables
NAND memory mapping and timing registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
NAND bank selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
SDRAM bank selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
SDRAM address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
SDRAM address mapping with 8-bit data bus width. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
SDRAM address mapping with 16-bit data bus width. . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
SDRAM address mapping with 32-bit data bus width. . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
Programmable NOR/PSRAM access parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Non-multiplexed I/O NOR Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
16-bit multiplexed I/O NOR Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
Non-multiplexed I/Os PSRAM/SRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
16-Bit multiplexed I/O PSRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
NOR Flash/PSRAM: example of supported memories and transactions . . . . . . . . . . . . . 320
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
Programmable NAND Flash access parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
8-bit NAND Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
16-bit NAND Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
ECC result relevant bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
SDRAM signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
FMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
QUADSPI pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385
QUADSPI interrupt requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399
QUADSPI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
ADC pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
Analog watchdog channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
Configuring the trigger polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426
External trigger for regular channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426
External trigger for injected channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427
ADC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442
ADC global register map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458
ADC register map and reset values for each ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458
ADC register map and reset values (common ADC registers) . . . . . . . . . . . . . . . . . . . . . 460

RM0385 Rev 7

45/1709
50

List of tables
Table 101.
Table 102.
Table 103.
Table 104.
Table 105.
Table 106.
Table 107.
Table 108.
Table 109.
Table 110.
Table 111.
Table 112.
Table 113.
Table 114.
Table 115.
Table 116.
Table 117.
Table 118.
Table 119.
Table 120.
Table 121.
Table 122.
Table 123.
Table 124.
Table 125.
Table 126.
Table 127.
Table 128.
Table 129.
Table 130.
Table 131.
Table 132.
Table 133.
Table 134.
Table 135.
Table 136.
Table 137.
Table 138.
Table 139.
Table 140.
Table 141.
Table 142.
Table 143.
Table 144.
Table 145.
Table 146.
Table 147.
Table 148.
Table 149.

46/1709

RM0385

DAC pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462
External triggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465
DAC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
DCMI external signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
Positioning of captured data bytes in 32-bit words (8-bit width) . . . . . . . . . . . . . . . . . . . . 486
Positioning of captured data bytes in 32-bit words (10-bit width) . . . . . . . . . . . . . . . . . . . 486
Positioning of captured data bytes in 32-bit words (12-bit width) . . . . . . . . . . . . . . . . . . . 486
Positioning of captured data bytes in 32-bit words (14-bit width) . . . . . . . . . . . . . . . . . . . 487
Data storage in monochrome progressive video format . . . . . . . . . . . . . . . . . . . . . . . . . . 492
Data storage in RGB progressive video format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493
Data storage in YCbCr progressive video format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493
Data storage in YCbCr progressive video format - Y extraction mode . . . . . . . . . . . . . . . 494
DCMI interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494
DCMI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507
LTDC pins and signal interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509
Clock domain for each register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510
Pixel data mapping versus color format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515
LTDC interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519
LTDC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
RNG internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
RNG interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549
RNG register map and reset map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554
CRYP internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557
Counter mode initialization vector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584
GCM last block definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587
GCM mode IV registers initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587
CCM mode IV registers initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594
DES/TDES data swapping feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600
AES data swapping feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602
Key registers CRYP_KxR/LR endianness (TDES K1/2/3 and
AES 128/192/256-bit keys) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602
Initialization vector registers CRYP_IVxR endianness . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
Cryptographic processor configuration for
memory-to-peripheral DMA transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
Cryptographic processor configuration for
peripheral to memory DMA transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605
CRYP interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607
Processing time (in clock cycle) for ECB, CBC and CTR per 128-bit block . . . . . . . . . . . 608
Processing time (in clock cycle) for GCM and CCM per 128-bit block . . . . . . . . . . . . . . . 608
CRYP register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621
HASH internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625
Hash processor outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628
HASH interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634
Processing time (in clock cycle) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634
HASH register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645
Behavior of timer outputs versus BRK/BRK2 inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 687
Counting direction versus encoder signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694
TIMx internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 711
Output control bits for complementary OCx and OCxN channels with break feature . . . . 725
TIM1 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737
TIM8 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 739
Counting direction versus encoder signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775

RM0385 Rev 7

RM0385
Table 150.
Table 151.
Table 152.
Table 153.
Table 154.
Table 155.
Table 156.
Table 157.
Table 158.
Table 159.
Table 160.
Table 161.
Table 162.
Table 163.
Table 164.
Table 165.
Table 166.
Table 167.
Table 168.
Table 169.
Table 170.
Table 171.
Table 172.
Table 173.
Table 174.
Table 175.
Table 176.
Table 177.
Table 178.
Table 179.
Table 180.
Table 181.
Table 182.
Table 183.
Table 184.
Table 185.
Table 186.
Table 187.
Table 188.
Table 189.
Table 190.
Table 191.
Table 192.
Table 193.
Table 194.
Table 195.
Table 196.
Table 197.

List of tables
TIMx internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 792
Output control bit for standard OCx channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 802
TIM2/TIM3/TIM4/TIM5 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . 808
TIMx internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837
Output control bit for standard OCx channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845
TIM9/TIM12 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848
Output control bit for standard OCx channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856
TIM10/TIM11/TIM13/TIM14 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . 858
TIM6/TIM7 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 872
STM32F75xxx and STM32F74xxx LPTIM features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873
LPTIM1 external trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874
Prescaler division ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876
Encoder counting scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 882
Interrupt events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883
LPTIM register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 892
IWDG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901
WWDG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908
RTC pin PC13 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
RTC pin PI8 configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 913
RTC pin PC2 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914
RTC functions over modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914
Effect of low-power modes on RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927
Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 928
RTC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952
STM32F75xxx and STM32F74xxx I2C implementation . . . . . . . . . . . . . . . . . . . . . . . . . . 955
Comparison of analog vs. digital filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958
I2C-SMBUS specification data setup and hold times . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961
I2C configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 965
I2C-SMBUS specification clock timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976
Examples of timing settings for fI2CCLK = 8 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986
Examples of timings settings for fI2CCLK = 16 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986
Examples of timings settings for fI2CCLK = 48 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . 987
SMBus timeout specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989
SMBUS with PEC configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 991
Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tTIMEOUT = 25 ms) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992
Examples of TIMEOUTB settings for various I2CCLK frequencies . . . . . . . . . . . . . . . . . 992
Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tIDLE = 50 µs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992
Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1002
I2C Interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003
I2C register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1019
STM32F75xxx and STM32F74xxx USART features . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023
Noise detection from sampled data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1035
Error calculation for programmed baud rates at fCK = 216 MHz
in both cases of oversampling by 8 (OVER8 = 1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1038
Error calculation for programmed baud rates at fCK = 216 MHz
in both cases of oversampling by 16 (OVER8 = 0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1038
Tolerance of the USART receiver when BRR [3:0] = 0000. . . . . . . . . . . . . . . . . . . . . . . 1039
Tolerance of the USART receiver when BRR [3:0] is different from 0000 . . . . . . . . . . . 1039
Frame formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1044
Effect of low-power modes on the USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1061

RM0385 Rev 7

47/1709
50

List of tables
Table 198.
Table 199.
Table 200.
Table 201.
Table 202.
Table 203.
Table 204.
Table 205.
Table 206.
Table 207.
Table 208.
Table 209.
Table 210.
Table 211.
Table 212.
Table 213.
Table 214.
Table 215.
Table 216.
Table 217.
Table 218.
Table 219.
Table 220.
Table 221.
Table 222.
Table 223.
Table 224.
Table 225.
Table 226.
Table 227.
Table 228.
Table 229.
Table 230.
Table 231.
Table 232.
Table 233.
Table 234.
Table 235.
Table 236.
Table 237.
Table 238.
Table 239.
Table 240.
Table 241.
Table 242.
Table 243.
Table 244.
Table 245.
Table 246.
Table 247.
Table 248.
Table 249.

48/1709

RM0385

USART interrupt requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1062
USART register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1083
STM32F75xxx and STM32F74xxx SPI implementation . . . . . . . . . . . . . . . . . . . . . . . . . 1086
SPI interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1111
Audio-frequency precision using standard 8 MHz HSE . . . . . . . . . . . . . . . . . . . . . . . . . 1125
I2S interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1131
SPI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1144
SAI internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1148
SAI input/output pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1148
External synchronization selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1150
Example of possible audio frequency sampling range . . . . . . . . . . . . . . . . . . . . . . . . . . 1157
SOPD pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1163
Parity bit calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1163
Audio sampling frequency versus symbol rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1164
SAI interrupt sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1173
SAI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1188
Transition sequence for preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1195
Minimum SPDIFRX_CLK frequency versus audio sampling rate . . . . . . . . . . . . . . . . . . 1205
Bit field property versus SPDIFRX state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1207
SPDIFRX interface register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1221
SDMMC I/O definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1225
Command format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1230
Short response format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1231
Long response format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1231
Command path status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1231
Data token format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1234
DPSM flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1235
Transmit FIFO status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236
Receive FIFO status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236
Card status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1247
SD status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1250
Speed class code field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1251
Performance move field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1252
AU_SIZE field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1252
Maximum AU size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1252
Erase size field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1253
Erase timeout field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1253
Erase offset field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1253
Block-oriented write commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1256
Block-oriented write protection commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1257
Erase commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1257
I/O mode commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1257
Lock card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1258
Application-specific commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1258
R1 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1259
R2 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1259
R3 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260
R4 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260
R4b response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260
R5 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1261
R6 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1262
Response type and SDMMC_RESPx registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268

RM0385 Rev 7

RM0385
Table 250.
Table 251.
Table 252.
Table 253.
Table 254.
Table 255.
Table 256.
Table 257.
Table 258.
Table 259.
Table 260.
Table 261.
Table 262.
Table 263.
Table 264.
Table 265.
Table 266.
Table 267.
Table 268.
Table 269.
Table 270.
Table 271.
Table 272.
Table 273.
Table 274.
Table 275.
Table 276.
Table 277.
Table 278.
Table 279.
Table 280.
Table 281.
Table 282.
Table 283.
Table 284.
Table 285.
Table 286.
Table 287.
Table 288.
Table 289.
Table 290.
Table 291.
Table 292.
Table 293.
Table 294.
Table 295.
Table 296.
Table 297.
Table 298.
Table 299.
Table 300.

List of tables
SDMMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1279
Transmit mailbox mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1296
Receive mailbox mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1296
bxCAN register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1322
OTG_HS speeds supported . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327
OTG_FS speeds supported . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327
OTG implementation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1330
OTG_FS input/output pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1332
OTG_HS input/output pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1332
OTG_FS/OTG_HS input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1333
Compatibility of STM32 low power modes with the OTG . . . . . . . . . . . . . . . . . . . . . . . . 1346
Core global control and status registers (CSRs). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1354
Host-mode control and status registers (CSRs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1355
Device-mode control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1357
Data FIFO (DFIFO) access register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1359
Power and clock gating control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 1360
TRDT values (FS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1370
TRDT values (HS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1370
Minimum duration for soft disconnect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1410
OTG_FS/OTG_HS register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1440
Alternate function mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1518
Management frame format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1520
Clock range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1522
TX interface signal encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1524
RX interface signal encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1524
Frame statuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1540
Destination address filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1546
Source address filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1547
Receive descriptor 0 - encoding for bits 7, 5 and 0 (normal descriptor
format only, EDFE=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1578
Time stamp snapshot dependency on registers bits . . . . . . . . . . . . . . . . . . . . . . . . . . . 1612
Ethernet register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1632
HDMI pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1637
Error handling timing parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1643
TXERR timing parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1644
HDMI-CEC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1645
HDMI-CEC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1654
SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1658
Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1658
JTAG debug port data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1663
32-bit debug port registers addressed through the shifted value A[3:2] . . . . . . . . . . . . . 1665
Packet request (8-bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1666
ACK response (3 bits). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1666
DATA transfer (33 bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1666
SW-DP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1667
Cortex®-M7 with FPU AHB-AP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1669
Core debug registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1670
Main ITM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1673
Asynchronous TRACE pin assignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1682
Synchronous TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1682
Flexible TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1683
Important TPIU registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1686

RM0385 Rev 7

49/1709
50

List of tables

RM0385

Table 301. DBG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1687
Table 302. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1691

50/1709

RM0385 Rev 7

RM0385

List of figures

List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Figure 31.
Figure 32.
Figure 33.
Figure 34.
Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.
Figure 41.
Figure 42.
Figure 43.
Figure 44.
Figure 45.
Figure 46.
Figure 47.

System architecture for STM32F75xxx and STM32F74xxx devices . . . . . . . . . . . . . . . . . 64
Memory map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Flash memory interface connection inside system architecture
(STM32F75xxx and STM32F74xxx) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
RDP levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Power supply overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
VDDUSB connected to VDD power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
VDDUSB connected to external independent power supply . . . . . . . . . . . . . . . . . . . . . . 102
Backup domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Power-on reset/power-down reset waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
BOR thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
PVD thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Simplified diagram of the reset circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Clock tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
HSE/ LSE clock sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Frequency measurement with TIM5 in Input capture mode . . . . . . . . . . . . . . . . . . . . . . . 142
Frequency measurement with TIM11 in Input capture mode . . . . . . . . . . . . . . . . . . . . . . 143
Basic structure of an I/O port bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
Basic structure of a 5-Volt tolerant I/O port bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
Input floating/pull up/pull down configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
Alternate function configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
High impedance-analog configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
DMA block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
Channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
Peripheral-to-memory mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
Memory-to-peripheral mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
Memory-to-memory mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
FIFO structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
DMA2D block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
External interrupt/event controller block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
External interrupt/event GPIO mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
CRC calculation unit block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
FMC block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
FMC memory banks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
Mode1 read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
Mode1 write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
ModeA read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
ModeA write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
Mode2 and mode B read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
Mode2 write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
ModeB write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
ModeC read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
ModeC write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
ModeD read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
ModeD write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
Muxed read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
Muxed write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

RM0385 Rev 7

51/1709
61

List of figures
Figure 48.
Figure 49.
Figure 50.
Figure 51.
Figure 52.
Figure 53.
Figure 54.
Figure 55.
Figure 56.
Figure 57.
Figure 58.
Figure 59.
Figure 60.
Figure 61.
Figure 62.
Figure 63.
Figure 64.
Figure 65.
Figure 66.
Figure 67.
Figure 68.
Figure 69.
Figure 70.
Figure 71.
Figure 72.
Figure 73.
Figure 74.
Figure 75.
Figure 76.
Figure 77.
Figure 78.
Figure 79.
Figure 80.
Figure 81.
Figure 82.
Figure 83.
Figure 84.
Figure 85.
Figure 86.
Figure 87.
Figure 88.
Figure 89.
Figure 90.
Figure 91.
Figure 92.
Figure 93.
Figure 94.
Figure 95.
Figure 96.
Figure 97.
Figure 98.
Figure 99.

52/1709

RM0385

Asynchronous wait during a read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
Asynchronous wait during a write access waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
Wait configuration waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
Synchronous multiplexed read mode waveforms - NOR, PSRAM (CRAM) . . . . . . . . . . . 341
Synchronous multiplexed write mode waveforms - PSRAM (CRAM). . . . . . . . . . . . . . . . 343
NAND Flash controller waveforms for common memory access . . . . . . . . . . . . . . . . . . . 355
Access to non ‘CE don’t care’ NAND-Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
Burst write SDRAM access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
Burst read SDRAM access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
Logic diagram of Read access with RBURST bit set (CAS=1, RPIPE=0) . . . . . . . . . . . . 368
Read access crossing row boundary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
Write access crossing row boundary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
Self-refresh mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
Power-down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
QUADSPI block diagram when dual-flash mode is disabled . . . . . . . . . . . . . . . . . . . . . . 384
QUADSPI block diagram when dual-flash mode is enabled . . . . . . . . . . . . . . . . . . . . . . 385
An example of a read command in quad mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386
An example of a DDR command in quad mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
nCS when CKMODE = 0 (T = CLK period). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
nCS when CKMODE = 1 in SDR mode (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . 397
nCS when CKMODE = 1 in DDR mode (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . 398
nCS when CKMODE = 1 with an abort (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . . 398
Single ADC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414
ADC1 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416
ADC2 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417
ADC3 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
Analog watchdog’s guarded area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
Injected conversion latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423
Right alignment of 12-bit data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425
Left alignment of 12-bit data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425
Left alignment of 6-bit data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425
Multi ADC block diagram(1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430
Injected simultaneous mode on 4 channels: dual ADC mode . . . . . . . . . . . . . . . . . . . . . 433
Injected simultaneous mode on 4 channels: triple ADC mode . . . . . . . . . . . . . . . . . . . . . 433
Regular simultaneous mode on 16 channels: dual ADC mode . . . . . . . . . . . . . . . . . . . . 434
Regular simultaneous mode on 16 channels: triple ADC mode . . . . . . . . . . . . . . . . . . . . 434
Interleaved mode on 1 channel in continuous conversion mode: dual ADC mode. . . . . . 435
Interleaved mode on 1 channel in continuous conversion mode: triple ADC mode . . . . . 436
Alternate trigger: injected group of each ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437
Alternate trigger: 4 injected channels (each ADC) in discontinuous mode . . . . . . . . . . . . 437
Alternate trigger: injected group of each ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
Alternate + regular simultaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
Case of trigger occurring during injected conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
Temperature sensor and VREFINT channel block diagram . . . . . . . . . . . . . . . . . . . . . . 440
DAC channel block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462
DAC output buffer connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463
Data registers in single DAC channel mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464
Data registers in dual DAC channel mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464
Timing diagram for conversion with trigger disabled TEN = 0 . . . . . . . . . . . . . . . . . . . . . 465
DAC LFSR register calculation algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467
DAC conversion (SW trigger enabled) with LFSR wave generation. . . . . . . . . . . . . . . . . 467

RM0385 Rev 7

RM0385
Figure 100.
Figure 101.
Figure 102.
Figure 103.
Figure 104.
Figure 105.
Figure 106.
Figure 107.
Figure 108.
Figure 109.
Figure 110.
Figure 111.
Figure 112.
Figure 113.
Figure 114.
Figure 115.
Figure 116.
Figure 117.
Figure 118.
Figure 119.
Figure 120.
Figure 121.
Figure 122.
Figure 123.
Figure 124.
Figure 125.
Figure 126.
Figure 127.
Figure 128.
Figure 129.
Figure 130.
Figure 131.
Figure 132.
Figure 133.
Figure 134.
Figure 135.
Figure 136.
Figure 137.
Figure 138.
Figure 139.
Figure 140.
Figure 141.
Figure 142.
Figure 143.
Figure 144.
Figure 145.
Figure 146.
Figure 147.
Figure 148.
Figure 149.
Figure 150.
Figure 151.

List of figures
DAC triangle wave generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468
DAC conversion (SW trigger enabled) with triangle wave generation . . . . . . . . . . . . . . . 468
DCMI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484
Top-level block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484
DCMI signal waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487
Frame capture waveforms in snapshot mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489
Frame capture waveforms in continuous grab mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490
Coordinates and size of the window after cropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490
Data capture waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491
Pixel raster scan order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492
LTDC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509
LCD-TFT synchronous timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
Layer window programmable parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515
Blending two layers with background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517
Interrupt events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519
RNG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
Entropy source model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545
CRYP block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557
AES-ECB mode overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560
AES-CBC mode overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561
AES-CTR mode overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562
AES-GCM mode overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563
AES-GMAC mode overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563
AES-CCM mode overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564
STM32 cryptolib DES/TDES flowcharts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565
STM32 cryptolib AES flowchart examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566
Example of suspend mode management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571
DES/TDES-ECB mode encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572
DES/TDES-ECB mode decryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573
DES/TDES-CBC mode encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574
DES/TDES-CBC mode decryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575
AES-ECB mode encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577
AES-ECB mode decryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 578
AES-CBC mode encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579
AES-CBC mode decryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 580
Message construction for the Counter mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582
AES-CTR mode encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583
AES-CTR mode decryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584
Message construction for the Galois/counter mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586
Message construction for the Galois Message Authentication Code mode . . . . . . . . . . . 591
Message construction for the Counter with CBC-MAC mode. . . . . . . . . . . . . . . . . . . . . . 592
64-bit block construction according to the data type (IN FIFO). . . . . . . . . . . . . . . . . . . . . 599
128-bit block construction according to the data type. . . . . . . . . . . . . . . . . . . . . . . . . . . . 601
CRYP interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606
HASH block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624
Message data swapping feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626
HASH save/restore mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631
HASH interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633
Advanced-control timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 649
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 649

RM0385 Rev 7

53/1709
61

List of figures
Figure 152.
Figure 153.
Figure 154.
Figure 155.
Figure 156.
Figure 157.
Figure 158.
Figure 159.
Figure 160.
Figure 161.
Figure 162.
Figure 163.
Figure 164.
Figure 165.
Figure 166.
Figure 167.
Figure 168.
Figure 169.
Figure 170.
Figure 171.
Figure 172.
Figure 173.
Figure 174.
Figure 175.
Figure 176.
Figure 177.
Figure 178.
Figure 179.
Figure 180.
Figure 181.
Figure 182.
Figure 183.
Figure 184.
Figure 185.
Figure 186.
Figure 187.
Figure 188.
Figure 189.
Figure 190.
Figure 191.
Figure 192.
Figure 193.
Figure 194.
Figure 195.
Figure 196.
Figure 197.
Figure 198.
Figure 199.
Figure 200.
Figure 201.
Figure 202.
Figure 203.

54/1709

RM0385

Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652
Counter timing diagram, update event when ARPE=0 (TIMx_ARR not preloaded) . . . . . 653
Counter timing diagram, update event when ARPE=1 (TIMx_ARR preloaded) . . . . . . . . 653
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 656
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 656
Counter timing diagram, update event when repetition counter is not used . . . . . . . . . . . 657
Counter timing diagram, internal clock divided by 1, TIMx_ARR = 0x6 . . . . . . . . . . . . . . 658
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659
Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36 . . . . . . . . . . . . . . 659
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660
Counter timing diagram, update event with ARPE=1 (counter underflow) . . . . . . . . . . . . 660
Counter timing diagram, Update event with ARPE=1 (counter overflow) . . . . . . . . . . . . . 661
Update rate examples depending on mode and TIMx_RCR register settings . . . . . . . . . 662
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 664
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666
Control circuit in external clock mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 668
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669
Output stage of capture/compare channel (channel 1, idem ch. 2 and 3) . . . . . . . . . . . . 669
Output stage of capture/compare channel (channel 4). . . . . . . . . . . . . . . . . . . . . . . . . . . 670
Output stage of capture/compare channel (channel 5, idem ch. 6) . . . . . . . . . . . . . . . . . 670
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672
Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 675
Center-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676
Generation of 2 phase-shifted PWM signals with 50% duty cycle . . . . . . . . . . . . . . . . . . 678
Combined PWM mode on channel 1 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 679
3-phase combined PWM signals with multiple trigger pulses per period . . . . . . . . . . . . . 680
Complementary output with dead-time insertion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681
Dead-time waveforms with delay greater than the negative pulse . . . . . . . . . . . . . . . . . . 681
Dead-time waveforms with delay greater than the positive pulse. . . . . . . . . . . . . . . . . . . 682
Break and Break2 circuitry overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684
Various output behavior in response to a break event on BRK (OSSI = 1) . . . . . . . . . . . 686
PWM output state following BRK and BRK2 pins assertion (OSSI=1) . . . . . . . . . . . . . . . 687
PWM output state following BRK assertion (OSSI=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . 688
Clearing TIMx OCxREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 689
6-step generation, COM example (OSSR=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 690
Example of one pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 691
Retriggerable one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693
Example of counter operation in encoder interface mode. . . . . . . . . . . . . . . . . . . . . . . . . 694
Example of encoder interface mode with TI1FP1 polarity inverted. . . . . . . . . . . . . . . . . . 695
Measuring time interval between edges on 3 signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696
Example of Hall sensor interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 699

RM0385 Rev 7

RM0385
Figure 204.
Figure 205.
Figure 206.
Figure 207.
Figure 208.
Figure 209.
Figure 210.
Figure 211.
Figure 212.
Figure 213.
Figure 214.
Figure 215.
Figure 216.
Figure 217.
Figure 218.
Figure 219.
Figure 220.
Figure 221.
Figure 222.
Figure 223.
Figure 224.
Figure 225.
Figure 226.
Figure 227.
Figure 228.
Figure 229.
Figure 230.
Figure 231.
Figure 232.
Figure 233.
Figure 234.
Figure 235.
Figure 236.
Figure 237.
Figure 238.
Figure 239.
Figure 240.
Figure 241.
Figure 242.
Figure 243.
Figure 244.
Figure 245.
Figure 246.
Figure 247.
Figure 248.
Figure 249.
Figure 250.
Figure 251.
Figure 252.
Figure 253.
Figure 254.

List of figures
Control circuit in Gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701
Control circuit in external clock mode 2 + trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . 702
General-purpose timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 742
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 744
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 744
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 747
Counter timing diagram, Update event when ARPE=0 (TIMx_ARR not preloaded). . . . . 747
Counter timing diagram, Update event when ARPE=1 (TIMx_ARR preloaded). . . . . . . . 748
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 749
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 749
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 750
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 750
Counter timing diagram, Update event when repetition counter
is not used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 751
Counter timing diagram, internal clock divided by 1, TIMx_ARR=0x6 . . . . . . . . . . . . . . . 752
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 753
Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36 . . . . . . . . . . . . . . 753
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 754
Counter timing diagram, Update event with ARPE=1 (counter underflow). . . . . . . . . . . . 754
Counter timing diagram, Update event with ARPE=1 (counter overflow) . . . . . . . . . . . . . 755
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 756
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 756
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758
Control circuit in external clock mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 760
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760
Output stage of capture/compare channel (channel 1). . . . . . . . . . . . . . . . . . . . . . . . . . . 761
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763
Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766
Center-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767
Generation of 2 phase-shifted PWM signals with 50% duty cycle . . . . . . . . . . . . . . . . . . 768
Combined PWM mode on channels 1 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770
Clearing TIMx OCxREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 771
Example of one-pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 772
Retriggerable one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774
Example of counter operation in encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . 775
Example of encoder interface mode with TI1FP1 polarity inverted . . . . . . . . . . . . . . . . . 776
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777
Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 778
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 779
Control circuit in external clock mode 2 + trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . 780
Master/Slave timer example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780
Gating TIM with OC1REF of TIM3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 781
Gating TIM with Enable of TIM3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782
Triggering TIM with update of TIM3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 783
Triggering TIM with Enable of TIM3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 783

RM0385 Rev 7

55/1709
61

List of figures
Figure 255.
Figure 256.
Figure 257.
Figure 258.
Figure 259.
Figure 260.
Figure 261.
Figure 262.
Figure 263.
Figure 264.
Figure 265.
Figure 266.
Figure 267.
Figure 268.
Figure 269.
Figure 270.
Figure 271.
Figure 272.
Figure 273.
Figure 274.
Figure 275.
Figure 276.
Figure 277.
Figure 278.
Figure 279.
Figure 280.
Figure 281.
Figure 282.
Figure 283.
Figure 284.
Figure 285.
Figure 286.
Figure 287.
Figure 288.
Figure 289.
Figure 290.
Figure 291.
Figure 292.
Figure 293.
Figure 294.
Figure 295.
Figure 296.
Figure 297.
Figure 298.
Figure 299.
Figure 300.
Figure 301.

56/1709

RM0385

Triggering TIM3 and TIM2 with TIM3 TI1 input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 784
General-purpose timer block diagram (TIM9/TIM12) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 812
General-purpose timer block diagram (TIM10/TIM11/TIM13/TIM14) . . . . . . . . . . . . . . . . 813
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 815
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 815
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 818
Counter timing diagram, update event when ARPE=0 (TIMx_ARR not
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 818
Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 820
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 821
Capture/compare channel (example: channel 1 input stage . . . . . . . . . . . . . . . . . . . . . . 822
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 822
Output stage of capture/compare channel (channel 1). . . . . . . . . . . . . . . . . . . . . . . . . . . 823
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825
Output compare mode, toggle on OC1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 827
Combined PWM mode on channel 1 and 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 828
Example of one pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829
Retriggerable one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831
Measuring time interval between edges on 2 signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832
Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834
Basic timer block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 862
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 862
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 864
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 864
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865
Counter timing diagram, update event when ARPE = 0 (TIMx_ARR not
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865
Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 867
Low-power timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874
Glitch filter timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876
LPTIM output waveform, single counting mode configuration . . . . . . . . . . . . . . . . . . . . . 877
LPTIM output waveform, Single counting mode configuration
and Set-once mode activated (WAVE bit is set) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 878
LPTIM output waveform, Continuous counting mode configuration . . . . . . . . . . . . . . . . . 878
Waveform generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880
Encoder mode counting sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883
Independent watchdog block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893
Watchdog block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
Window watchdog timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904

RM0385 Rev 7

RM0385
Figure 302.
Figure 303.
Figure 304.
Figure 305.
Figure 306.
Figure 307.
Figure 308.
Figure 309.
Figure 310.
Figure 311.
Figure 312.
Figure 313.
Figure 314.
Figure 315.
Figure 316.
Figure 317.
Figure 318.
Figure 319.
Figure 320.
Figure 321.
Figure 322.
Figure 323.
Figure 324.
Figure 325.
Figure 326.
Figure 327.
Figure 328.
Figure 329.
Figure 330.
Figure 331.
Figure 332.
Figure 333.
Figure 334.
Figure 335.
Figure 336.
Figure 337.
Figure 338.
Figure 339.
Figure 340.
Figure 341.
Figure 342.
Figure 343.
Figure 344.
Figure 345.
Figure 346.
Figure 347.
Figure 348.
Figure 349.
Figure 350.
Figure 351.
Figure 352.
Figure 353.

List of figures
RTC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911
I2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 956
I2C bus protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958
Setup and hold timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959
I2C initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 962
Data reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 963
Data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 964
Slave initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 967
Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=0. . . . . . . . . . . . . 969
Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=1. . . . . . . . . . . . . 970
Transfer bus diagrams for I2C slave transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 971
Transfer sequence flowchart for slave receiver with NOSTRETCH=0 . . . . . . . . . . . . . . 972
Transfer sequence flowchart for slave receiver with NOSTRETCH=1 . . . . . . . . . . . . . . 973
Transfer bus diagrams for I2C slave receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 973
Master clock generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 975
Master initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 977
10-bit address read access with HEAD10R=0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 977
10-bit address read access with HEAD10R=1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 978
Transfer sequence flowchart for I2C master transmitter for N≤255 bytes . . . . . . . . . . . . 979
Transfer sequence flowchart for I2C master transmitter for N>255 bytes . . . . . . . . . . . . 980
Transfer bus diagrams for I2C master transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981
Transfer sequence flowchart for I2C master receiver for N≤255 bytes. . . . . . . . . . . . . . . 983
Transfer sequence flowchart for I2C master receiver for N >255 bytes . . . . . . . . . . . . . . 984
Transfer bus diagrams for I2C master receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985
Timeout intervals for tLOW:SEXT, tLOW:MEXT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989
Transfer sequence flowchart for SMBus slave transmitter N bytes + PEC. . . . . . . . . . . . 993
Transfer bus diagrams for SMBus slave transmitter (SBC=1) . . . . . . . . . . . . . . . . . . . . . 994
Transfer sequence flowchart for SMBus slave receiver N Bytes + PEC . . . . . . . . . . . . . 995
Bus transfer diagrams for SMBus slave receiver (SBC=1). . . . . . . . . . . . . . . . . . . . . . . . 996
Bus transfer diagrams for SMBus master transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 997
Bus transfer diagrams for SMBus master receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 999
I2C interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003
USART block diagram
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1025
Word length programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1027
Configurable stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1029
TC/TXE behavior when transmitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1030
Start bit detection when oversampling by 16 or 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1031
Data sampling when oversampling by 16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1034
Data sampling when oversampling by 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1035
Mute mode using Idle line detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1042
Mute mode using address mark detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1043
Break detection in LIN mode (11-bit break length - LBDL bit is set) . . . . . . . . . . . . . . . . 1046
Break detection in LIN mode vs. Framing error detection. . . . . . . . . . . . . . . . . . . . . . . . 1047
USART example of synchronous transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1048
USART data clock timing diagram (M bits = 00). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1048
USART data clock timing diagram (M bits = 01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1049
RX data setup/hold time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1049
ISO 7816-3 asynchronous protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1051
Parity error detection using the 1.5 stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1052
IrDA SIR ENDEC- block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1056
IrDA data modulation (3/16) -Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1057
Transmission using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1058

RM0385 Rev 7

57/1709
61

List of figures
Figure 354.
Figure 355.
Figure 356.
Figure 357.
Figure 358.
Figure 359.
Figure 360.
Figure 361.
Figure 362.
Figure 363.
Figure 364.
Figure 365.
Figure 366.
Figure 367.
Figure 368.
Figure 369.
Figure 370.
Figure 371.
Figure 372.
Figure 373.
Figure 374.
Figure 375.
Figure 376.
Figure 377.
Figure 378.
Figure 379.
Figure 380.
Figure 381.
Figure 382.
Figure 383.
Figure 384.
Figure 385.
Figure 386.
Figure 387.
Figure 388.
Figure 389.
Figure 390.
Figure 391.
Figure 392.
Figure 393.
Figure 394.
Figure 395.
Figure 396.
Figure 397.
Figure 398.
Figure 399.
Figure 400.
Figure 401.
Figure 402.
Figure 403.
Figure 404.

58/1709

RM0385

Reception using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1059
Hardware flow control between 2 USARTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1059
RS232 RTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1060
RS232 CTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1061
USART interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1063
SPI block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087
Full-duplex single master/ single slave application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088
Half-duplex single master/ single slave application . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089
Simplex single master/single slave application (master in transmit-only/
slave in receive-only mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1090
Master and three independent slaves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091
Multi-master application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1092
Hardware/software slave select management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1093
Data clock timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1094
Data alignment when data length is not equal to 8-bit or 16-bit . . . . . . . . . . . . . . . . . . . 1095
Packing data in FIFO for transmission and reception . . . . . . . . . . . . . . . . . . . . . . . . . . 1099
Master full-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1102
Slave full-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1103
Master full-duplex communication with CRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1104
Master full-duplex communication in packed mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1105
NSSP pulse generation in Motorola SPI master mode . . . . . . . . . . . . . . . . . . . . . . . . . . 1108
TI mode transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1109
I2S block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1112
Full-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1114
I2S Philips protocol waveforms (16/32-bit full accuracy). . . . . . . . . . . . . . . . . . . . . . . . . 1115
I2S Philips standard waveforms (24-bit frame) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1115
Transmitting 0x8EAA33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1116
Receiving 0x8EAA33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1116
I2S Philips standard (16-bit extended to 32-bit packet frame) . . . . . . . . . . . . . . . . . . . . 1116
Example of 16-bit data frame extended to 32-bit channel frame . . . . . . . . . . . . . . . . . . 1116
MSB Justified 16-bit or 32-bit full-accuracy length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1117
MSB justified 24-bit frame length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1117
MSB justified 16-bit extended to 32-bit packet frame . . . . . . . . . . . . . . . . . . . . . . . . . . . 1118
LSB justified 16-bit or 32-bit full-accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1118
LSB justified 24-bit frame length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1118
Operations required to transmit 0x3478AE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1119
Operations required to receive 0x3478AE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1119
LSB justified 16-bit extended to 32-bit packet frame . . . . . . . . . . . . . . . . . . . . . . . . . . . 1119
Example of 16-bit data frame extended to 32-bit channel frame . . . . . . . . . . . . . . . . . . 1120
PCM standard waveforms (16-bit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1120
PCM standard waveforms (16-bit extended to 32-bit packet frame). . . . . . . . . . . . . . . . 1121
Start sequence in master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1122
Audio sampling frequency definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1123
I2S clock generator architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1123
SAI functional block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1147
Audio frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1151
FS role is start of frame + channel side identification (FSDEF = TRIS = 1) . . . . . . . . . . 1153
FS role is start of frame (FSDEF = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1154
Slot size configuration with FBOFF = 0 in SAI_xSLOTR . . . . . . . . . . . . . . . . . . . . . . . . 1155
First bit offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1155
Audio block clock generator overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1156
AC’97 audio frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1160

RM0385 Rev 7

RM0385

List of figures

Figure 405. Example of typical AC’97 configuration on devices featuring at least
2 embedded SAIs (three external AC’97 decoders) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1161
Figure 406. SPDIF format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1162
Figure 407. SAI_xDR register ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1163
Figure 408. Data companding hardware in an audio block in the SAI . . . . . . . . . . . . . . . . . . . . . . . . 1166
Figure 409. Tristate strategy on SD output line on an inactive slot . . . . . . . . . . . . . . . . . . . . . . . . . . 1168
Figure 410. Tristate on output data line in a protocol like I2S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1169
Figure 411. Overrun detection error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1170
Figure 412. FIFO underrun event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1170
Figure 413. SPDIFRX block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1190
Figure 414. S/PDIF Sub-Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1190
Figure 415. S/PDIF block format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1191
Figure 416. S/PDIF Preambles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1191
Figure 417. Channel coding example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1192
Figure 418. SPDIFRX decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1193
Figure 419. Noise filtering and edge detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1193
Figure 420. Thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1195
Figure 421. Synchronization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1197
Figure 422. Synchronization process scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1198
Figure 423. SPDIFRX States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1199
Figure 424. SPDIFRX_DR register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1201
Figure 425. Channel/user data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1202
Figure 426. S/PDIF overrun error when RXSTEO = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1204
Figure 427. S/PDIF overrun error when RXSTEO = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1205
Figure 428. SPDIFRX interface interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1206
Figure 429. “No response” and “no data” operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1223
Figure 430. (Multiple) block read operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1223
Figure 431. (Multiple) block write operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1223
Figure 432. Sequential read operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1224
Figure 433. Sequential write operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1224
Figure 434. SDMMC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1224
Figure 435. SDMMC adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1226
Figure 436. Control unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1227
Figure 437. SDMMC_CK clock dephasing (BYPASS = 0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1228
Figure 438. SDMMC adapter command path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1228
Figure 439. Command path state machine (SDMMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229
Figure 440. SDMMC command transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1230
Figure 441. Data path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1232
Figure 442. Data path state machine (DPSM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1233
Figure 443. CAN network topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1282
Figure 444. Dual-CAN block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1283
Figure 445. bxCAN operating modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1285
Figure 446. bxCAN in silent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286
Figure 447. bxCAN in loop back mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286
Figure 448. bxCAN in combined mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1287
Figure 449. Transmit mailbox states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1289
Figure 450. Receive FIFO states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1290
Figure 451. Filter bank scale configuration - register organization . . . . . . . . . . . . . . . . . . . . . . . . . . 1293
Figure 452. Example of filter numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1294
Figure 453. Filtering mechanism - example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1295
Figure 454. CAN error state diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1296
Figure 455. Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1298

RM0385 Rev 7

59/1709
61

List of figures
Figure 456.
Figure 457.
Figure 458.
Figure 459.
Figure 460.
Figure 461.
Figure 462.
Figure 463.
Figure 464.
Figure 465.
Figure 466.
Figure 467.
Figure 468.
Figure 469.
Figure 470.
Figure 471.
Figure 472.
Figure 473.
Figure 474.
Figure 475.
Figure 476.
Figure 477.
Figure 478.
Figure 479.
Figure 480.
Figure 481.
Figure 482.
Figure 483.
Figure 484.
Figure 485.
Figure 486.
Figure 487.
Figure 488.
Figure 489.
Figure 490.
Figure 491.
Figure 492.
Figure 493.
Figure 494.
Figure 495.
Figure 496.
Figure 497.
Figure 498.
Figure 499.
Figure 500.
Figure 501.
Figure 502.
Figure 503.
Figure 504.
Figure 505.
Figure 506.
Figure 507.

60/1709

RM0385

CAN frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1299
Event flags and interrupt generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1300
CAN mailbox registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1312
OTG full-speed block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1331
OTG high-speed block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1332
OTG_FS A-B device connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1335
USB_FS peripheral-only connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1337
USB_FS host-only connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1341
SOF connectivity (SOF trigger output to TIM and ITR1 connection) . . . . . . . . . . . . . . . 1345
Updating OTG_HFIR dynamically (RLDCTRL = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1347
Device-mode FIFO address mapping and AHB FIFO access mapping . . . . . . . . . . . . . 1348
Host-mode FIFO address mapping and AHB FIFO access mapping . . . . . . . . . . . . . . . 1349
Interrupt hierarchy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353
Transmit FIFO write task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1457
Receive FIFO read task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1458
Normal bulk/control OUT/SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1460
Bulk/control IN transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1464
Normal interrupt OUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1467
Normal interrupt IN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1472
Isochronous OUT transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1474
Isochronous IN transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1477
Normal bulk/control OUT/SETUP transactions - DMA . . . . . . . . . . . . . . . . . . . . . . . . . . 1479
Normal bulk/control IN transaction - DMA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1481
Normal interrupt OUT transactions - DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1482
Normal interrupt IN transactions - DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1483
Normal isochronous OUT transaction - DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1484
Normal isochronous IN transactions - DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1485
Receive FIFO packet read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1491
Processing a SETUP packet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1493
Bulk OUT transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1499
TRDT max timing case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1508
A-device SRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1509
B-device SRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1510
A-device HNP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1511
B-device HNP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1513
ETH block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1519
SMI interface signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1520
MDIO timing and frame structure - Write cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1521
MDIO timing and frame structure - Read cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1522
Media independent interface signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1523
MII clock sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1525
Reduced media-independent interface signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1525
RMII clock sources- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1526
Clock scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1526
Address field format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1528
MAC frame format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1530
Tagged MAC frame format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1530
Transmission bit order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1537
Transmission with no collision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1537
Transmission with collision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1538
Frame transmission in MMI and RMII modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1538
Receive bit order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1542

RM0385 Rev 7

RM0385

List of figures

Figure 508.
Figure 509.
Figure 510.
Figure 511.
Figure 512.
Figure 513.
Figure 514.
Figure 515.
Figure 516.
Figure 517.
Figure 518.
Figure 519.
Figure 520.
Figure 521.
Figure 522.
Figure 523.
Figure 524.
Figure 525.
Figure 526.
Figure 527.
Figure 528.
Figure 529.
Figure 530.
Figure 531.
Figure 532.
Figure 533.
Figure 534.
Figure 535.
Figure 536.
Figure 537.

Reception with no error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1543
Reception with errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1543
Reception with false carrier indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1543
MAC core interrupt masking scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1544
Wakeup frame filter register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1549
Networked time synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1552
System time update using the Fine correction method. . . . . . . . . . . . . . . . . . . . . . . . . . 1554
PTP trigger output to TIM2 ITR1 connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1556
PPS output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1557
Descriptor ring and chain structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1558
TxDMA operation in default mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1562
TxDMA operation in OSF mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1564
Normal transmit descriptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1565
Enhanced transmit descriptor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1571
Receive DMA operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1573
Normal Rx DMA descriptor structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1575
Enhanced receive descriptor field format with IEEE1588 time stamp enabled. . . . . . . . 1581
Interrupt scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1584
Ethernet MAC remote wakeup frame filter register (ETH_MACRWUFFR). . . . . . . . . . . 1595
HDMI-CEC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1637
Message structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1638
Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1638
Bit timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1639
Signal free time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1639
Arbitration phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1640
SFT of three nominal bit periods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1640
Error bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1641
Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1642
TXERR detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1644
Block diagram of STM32 MCU and Cortex®-M7 with FPU -level
debug support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1655
Figure 538. SWJ debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1657
Figure 539. JTAG Debug Port connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1661
Figure 540. TPIU block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1681

RM0385 Rev 7

61/1709
61

Documentation conventions

RM0385

1

Documentation conventions

1.1

List of abbreviations for registers
The following abbreviations(a) are used in register descriptions:

read/write (rw)

Software can read and write to this bit.

read-only (r)

Software can only read this bit.

write-only (w)

Software can only write to this bit. Reading this bit returns the reset value.

read/clear write0 (rc_w0)

Software can read as well as clear this bit by writing 0. Writing 1 has no
effect on the bit value.

read/clear write1 (rc_w1)

Software can read as well as clear this bit by writing 1. Writing 0 has no
effect on the bit value.

read/clear write (rc_w)

Software can read as well as clear this bit by writing to the register. The
value written to this bit is not important.

read/clear by read (rc_r)

Software can read this bit. Reading this bit automatically clears it to 0.
Writing this bit has no effect on the bit value.

read/set by read (rs_r)

Software can read this bit. Reading this bit automatically sets it to 1.
Writing this bit has no effect on the bit value.

read/set (rs)

Software can read as well as set this bit. Writing 0 has no effect on the bit
value.

read/write once (rwo)

Software can only write once to this bit and can also read it at any time.
Only a reset can return the bit to its reset value.

toggle (t)

The software can toggle this bit by writing 1. Writing 0 has no effect.

read-only write trigger (rt_w1) Software can read this bit. Writing 1 triggers an event but has no effect on
the bit value.
Reserved (Res.)

Reserved bit, must be kept at reset value.

a. This is an exhaustive list of all abbreviations applicable to STM microcontrollers, some of them may not be
used in the current document.

62/1709

RM0385 Rev 7

RM0385

1.2

Documentation conventions

Glossary
This section gives a brief definition of acronyms and abbreviations used in this document:
•

The CPU core integrates two debug ports:
–

JTAG debug port (JTAG-DP) provides a 5-pin standard interface based on the
Joint Test Action Group (JTAG) protocol.

–

SWD debug port (SWD-DP) provides a 2-pin (clock and data) interface based on
the Serial Wire Debug (SWD) protocol.
For both the JTAG and SWD protocols, refer to the Cortex®-M7 Technical
Reference Manual.

1.3

•

Word: data of 32-bit length.

•

Half-word: data of 16-bit length.

•

Byte: data of 8-bit length.

•

Double word: data of 64-bit length.

•

IAP (in-application programming): IAP is the ability to re-program the Flash memory
of a microcontroller while the user program is running.

•

ICP (in-circuit programming): ICP is the ability to program the Flash memory of a
microcontroller using the JTAG protocol, the SWD protocol or the bootloader while the
device is mounted on the user application board.

•

Option bytes: product configuration bits stored in the Flash memory.

•

AHB: advanced high-performance bus.

•

AHBS: AHB Slave bus.

•

AXIM: AXI master bus.

•

ITCM: Instruction Tighly Coupled Memory.

•

DTCM: Data Tighly Coupled Memory.

•

CPU: refers to the Cortex®-M7 core.

Peripheral availability
For peripheral availability and number across all sales types, refer to the particular device
datasheet.

RM0385 Rev 7

63/1709
63

System and memory overview

RM0385

2

System and memory overview

2.1

System architecture
The main system architecture is based on 2 sub-systems:
•

•

An AXI to multi AHB bridge converting AXI4 protocol to AHB-Lite protocol:
–

1x AXI to 64-bit AHB bridge connected to the embedded flash

–

3x AXI to 32bit AHB bridge connected to AHB bus matrix

A multi-AHB Bus-Matrix

AHBS

Chrom-ART
Accelerator
(DMA2D)
DMA2D

LCD-TFT_M

USB_HS_M

DMA_P2

ETHERNET_M

AHBP

AXIM

4KB
I/D Cache

GP
MAC
USB OTG LCD-TFT
DMA2 Ethernet
HS
DMA_MEM2

DMA_PI

ARM Cortex-M7

GP
DMA1
DMA_MEM1

ITCM

DTCM

Figure 1. System architecture for STM32F75xxx and STM32F74xxx devices

DTCM RAM
64KB
ITCM RAM
16KB

AXI to
multi-AHB

ART

ITCM

64-bit AHB

FLASH
1MB

64-bit BuS Matrix
SRAM1
240KB
SRAM2
16KB
AHB
Periph1
AHB
periph2
FMC external
MemCtl

APB1

APB2

Quad-SPI

32-bit Bus Matrix - S
MS34163V1

64/1709

RM0385 Rev 7

RM0385

System and memory overview
The multi-AHB Bus-Matrix interconnects all the masters and slaves and it consists on:
–

32-bit multi-AHB Bus-Matrix

–

64-bit multi-AHB Bus-Matrix: It interconnects the 64-bit AHB bus from CPU
through the AXI to AHB bridge and the 32-bit AHB bus from GP DMAs and
peripheral DMAs upsized to 64-bit to the internal flash.

The multi AHB bus matrix interconnects:
•

•

2.1.1

12 bus masters:
–

3x32-bit AHB bus Cortex®-M7 AXI Master bus 64-bits, splitted 4 masters through
the AXI to AHB bridge.

–

1x64-bit AHB bus connected to the embedded flash

–

Cortex® -M7 AHB Peripherals bus

–

DMA1 memory bus

–

DMA2 memory bus

–

DMA2 peripheral bus

–

Ethernet DMA bus

–

USB OTG HS DMA bus

–

LCD Controller DMA-bus

–

Chrom-Art Accelerator™ (DMA2D) memory bus

Eight bus slaves:
–

the embedded Flash on AHB bus (for Flash read/write access, for code execution
and data access)

–

Cortex®-M7 AHBS slave interface for DMAs data transfer on DTCM RAM only.

–

Main internal SRAM1 (240 KB)

–

Auxiliary internal SRAM2 (16 KB)

–

AHB1peripherals including AHB to APB bridges and APB peripherals

–

AHB2 peripherals including AHB to APB bridges and APB peripherals

–

FMC

–

Quad SPI

Multi AHB BusMatrix
The multi AHB BusMatrix manages the access arbitration between masters. The arbitration
uses a round-robin algorithm.
It provides access from a master to a slave, enabling concurrent access and efficient
operation even when several high-speed peripherals work simultaneously.
The DTCM and ITCM RAMs (tightly coupled memories) are not part of the bus matrix.
The Data TCM RAM is accessible by the GP-DMAs and peripherals DMAs through specific
AHB slave bus of the CPU.
The instruction TCM RAM is reserved only for CPU. it is accessed at CPU clock speed with
0 wait states. The architecture is shown in Figure 1.

2.1.2

AHB/APB bridges (APB)
The two AHB/APB bridges, APB1 and APB2, provide full synchronous connections between
the AHB and the two APB buses, allowing flexible selection of the peripheral frequency.

RM0385 Rev 7

65/1709
67

System and memory overview

RM0385

Refer to the device datasheets for more details on APB1 and APB2 maximum frequencies,
and to Table 1 for the address mapping of AHB and APB peripherals.
After each device reset, all peripheral clocks are disabled (except for the SRAM, DTCM,
ITCM RAM and Flash memory interface). Before using a peripheral its clock has to be
enabled in the RCC_AHBxENR or RCC_APBxENR register.
Note:

When a 16- or an 8-bit access is performed on an APB register, the access is transformed
into a 32-bit access: the bridge duplicates the 16- or 8-bit data to feed the 32-bit vector.

2.1.3

CPU AXIM bus
This bus connects the Instruction and data bus of the Cortex®-M7 with FPU core to the
multi-AHB Bus-Matrix through AXI to AHB bridge. There are 4 AXI bus accesses:

2.1.4

–

CPU AXI bus access 1: The target of this AXI bus is the external memory FMC
containing code or data. For the NAND Bank mapped at address 0x8000 0000 to
0x8FFF FFFF, the MPU memory attribute for this space must be reconfigured by
software to Device.

–

CPU AXI bus access 2: The target of this AXI bus is the external memory Quad
SPI containing code or data.

–

CPU AXI bus access 3: The target of this AXI bus is the internal SRAMs (SRAM1
and SRAM2) containing code or data.

–

CPU AXI bus access 4: The target of this AXI bus is the embedded Flash mapped
on AXI interface containing code or data.

ITCM bus
This bus is used by the Cortex®-M7 for instruction fetches and data access on the
embedded flash mapped on ITCM interface and instruction fetches only on ITCM RAM.

2.1.5

DTCM bus
This bus is used by the Cortex®-M7 for data access on the DTCM RAM. It can be also used
for instruction fetches.

2.1.6

CPU AHBS bus
This bus connects the AHB Slave bus of the Cortex®-M7 to the BusMatrix. This bus is used
by DMAs and Peripherals DMAs for Data transfer on DTCM RAM only.
The ITCM bus is not accessible on AHBS. So the DMA data transfer to/from ITCM RAM is
not supported. For DMA transfer to/from Flash on ITCM interface, all the transfers are
forced through AHB bus

2.1.7

AHB peripheral bus
This bus connects the AHB Peripheral bus of the Cortex®-M7 to the BusMatrix. This bus is
used by the core to perform all data accesses to peripherals.
The target of this bus is the AHB1 peripherals including the APB peripherals and the AHB2
peripherals.

66/1709

RM0385 Rev 7

RM0385

2.1.8

System and memory overview

DMA memory bus
This bus connects the DMA memory bus master interface to the BusMatrix. It is used by the
DMA to perform transfer to/from memories. The targets of this bus are data memories:
internal SRAM1, SRAM2 and DTCM (through the AHBS bus of Cortex®-M7) internal Flash
memory and external memories through the FMC or Quad SPI.

2.1.9

DMA peripheral bus
This bus connects the DMA peripheral master bus interface to the BusMatrix. This bus is
used by the DMA to access AHB peripherals or to perform memory-to-memory transfers.
The targets of this bus are the AHB and APB peripherals plus data memories: internal
SRAM1, SRAM2 and DTCM (through the AHBS bus of Cortex®-M7) internal Flash memory
and external memories through the FMC or Quad SPI.

2.1.10

Ethernet DMA bus
This bus connects the Ethernet DMA master interface to the BusMatrix. This bus is used by
the Ethernet DMA to load/store data to a memory. The targets of this bus are data
memories: internal SRAM1, SRAM2 and DTCM (through the AHBS bus of Cortex®-M7)
internal Flash memory, and external memories through the FMC or Quad SPI.

2.1.11

USB OTG HS DMA bus
This bus connects the USB OTG HS DMA master interface to the BusMatrix. This bus is
used by the USB OTG DMA to load/store data to a memory. The targets of this bus are data
memories: internal SRAM1, SRAM2 and DTCM (through the AHBS bus of Cortex®-M7),
internal Flash memory, and external memories through the FMC or Quad SPI.

2.1.12

LCD-TFT controller DMA bus
This bus connects the LCD controller DMA master interface to the BusMatrix. It is used by
the LCD-TFT DMA to load data from a memory. The targets of this bus are data memories:
internal SRAM1, SRAM2 and DTCM (through the AHBS bus of Cortex®-M7), external
memories through FMC or Quad SPI, and internal Flash memory.

2.1.13

DMA2D bus
This bus connect the DMA2D master interface to the BusMatrix. This bus is used by the
DMA2D graphic Accelerator to load/store data to a memory. The targets of this bus are data
memories: internal SRAM1, SRAM2 and DTCM (through the AHBS bus of Cortex®-M7),
external memories through FMC or Quad SPI, and internal Flash memory.

RM0385 Rev 7

67/1709
67

RM0385

2.2

Memory organization

2.2.1

Introduction
Program memory, data memory, registers and I/O ports are organized within the same linear
4-Gbyte address space.
The bytes are coded in memory in Little Endian format. The lowest numbered byte in a word
is considered the word’s least significant byte and the highest numbered byte the most
significant.
The addressable memory space is divided into 8 main blocks, of 512 Mbytes each.

68/1709

RM0385 Rev 7

RM0385

2.2.2

Memory map and register boundary addresses
Figure 2. Memory map
Reserved

0xE010 0000 - 0xFFFF FFFF

Cortex-M7 internal
peripherals

0xE000 0000 - 0xE00F FFFF

AHB3

0x6000 0000 - 0xDFFF FFFF

Reserved

0x5006 0C00 - 0x5FFF FFFF
0x5006 0BFF

AHB2
0xFFFF FFFF

512-Mbyte
Block 7
Cortex-M7
Internal
peripherals

Reserved

0x5000 0000
0x4008 0000 - 0x4FFF FFFF
0x4007 FFFF

0xE000 0000
0xDFFF FFFF
512-Mbyte
Block 6
FMC
0xD000 0000
0xCFFF FFFF

AHB1
512-Mbyte
Block 5
FMC

0xC000 0000
0x9FFF FFFF

0x8000 0000
0x7FFF FFFF

512-Mbyte
Block 4
Quad SPI and
FMC bank 3

0x4002 0000
Reserved

0x4001 6C00 - 0x4001 FFFF
0x4001 6BFF

512-Mbyte
Block 3
FMC bank 1 to
bank 2

0x6000 0000
0x5FFF FFFF
APB2
512-Mbyte
Block 2
Peripherals
0x4000 0000
0x3FFF FFFF
512-Mbyte
Block 1
SRAM
0x2000 0000
0x1FFF FFFF
512-Mbyte
Block 0
0x0000 0000

Reserved

0x2005 0000 - 0x3FFF FFFF

SRAM2 (16 KB)

0x2004 C000 - 0x2004 FFFF

SRAM1 (240 KB)

0x2001 0000 - 0x2004 BFFF

DTCM (64 KB)

0x2000 0000 - 0x2000 FFFF

Reserved

0x1FFF 0020 - 0x1FFF FFFF

Option Bytes

0x1FFF 0000 - 0x1FFF 001F

Reserved

0x0820 0000 - 0x1FFE FFFF

Reserved

0x4001 0000
0x4000 8000 - 0x4000 FFFF
0x4000 7FFF

APB1

Flash memory on AXIM interface 0x0800 0000 - 0x080F FFFF
Reserved

0x0030 0000 - 0x07FF FFFF

Flash memory on ITCM interface 0x0020 0000 - 0x002F FFFF
Reserved

0x0011 0000 - 0x001F FFFF

System memory

0x0010 0000 - 0x0010 EDBF

Reserved

0x0000 4000 - 0x000F FFFF

ITCM RAM

0x0000 0000 - 0x0000 3FFF

0x4000 0000

MS34165V2

RM0385 Rev 7

69/1709
75

RM0385
All the memory map areas that are not allocated to on-chip memories and peripherals are
considered “Reserved”. For the detailed mapping of available memory and register areas,
refer to the following table.
The following table gives the boundary addresses of the peripherals available in the
devices.
Table 1. STM32F75xxx and STM32F74xxx register boundary addresses
Boundary address

Peripheral

Bus

Register map

0xA000 1000 - 0xA0001FFF

QuadSPI Control
Register

AHB3

0xA000 0000 - 0xA000 0FFF

FMC control register

0x5006 0800 - 0x5006 0BFF

RNG

Section 19.8.4: RNG register map on page 554

0x5006 0400 - 0x5006 07FF

HASH

Section 21.6.8: HASH register map on page 645

0x5006 0000 - 0x5006 03FF

CRYP

0x5005 0000 - 0x5005 03FF

DCMI

Section 17.7.12: DCMI register map on page 507

0x5000 0000 - 0x5003 FFFF

USB OTG FS

Section 37.15.61: OTG_FS/OTG_HS register map
on page 1440

0x4004 0000 - 0x4007 FFFF

USB OTG HS

Section 37.15.61: OTG_FS/OTG_HS register map
on page 1440

Section 14.5.14: QUADSPI register map on
page 412
Section 13.8: FMC register map on page 382

AHB2

Section 20.6.21: CRYP register map on page 621

0x4002 B000 - 0x4002 BBFF Chrom-ART (DMA2D)

Section 9.5.21: DMA2D register map on page 287

0x4002 8000 - 0x4002 93FF

ETHERNET MAC

Section 38.8.5: Ethernet register maps on
page 1632

0x4002 6400 - 0x4002 67FF

DMA2

0x4002 6000 - 0x4002 63FF

DMA1

0x4002 4000 - 0x4002 4FFF

BKPSRAM

0x4002 3C00 - 0x4002 3FFF

Flash interface
register

0x4002 3800 - 0x4002 3BFF

RCC

0x4002 3000 - 0x4002 33FF

CRC

0x4002 2800 - 0x4002 2BFF

GPIOK

0x4002 2400 - 0x4002 27FF

GPIOJ

0x4002 2000 - 0x4002 23FF

GPIOI

0x4002 1C00 - 0x4002 1FFF

GPIOH

0x4002 1800 - 0x4002 1BFF

GPIOG

0x4002 1400 - 0x4002 17FF

GPIOF

0x4002 1000 - 0x4002 13FF

GPIOE

0x4002 0C00 - 0x4002 0FFF

GPIOD

0x4002 0800 - 0x4002 0BFF

GPIOC

0x4002 0400 - 0x4002 07FF

GPIOB

0x4002 0000 - 0x4002 03FF

GPIOA

70/1709

Section 8.5.11: DMA register map on page 253
Section 5.3.27: RCC register map on page 196
Section 3.7.8: Flash interface register map
Section 5.3.27: RCC register map on page 196
AHB1

Section 12.4.6: CRC register map on page 306
Section : on page 213

Section : on page 213

RM0385 Rev 7

RM0385
Table 1. STM32F75xxx and STM32F74xxx register boundary addresses (continued)
Boundary address

Peripheral

Bus

Register map

0x4001 6800 - 0x4001 6BFF

LCD-TFT

Section 18.7.26: LTDC register map on page 540

0x4001 5C00 - 0x4001 5FFF

SAI2

Section 33.5.10: SAI register map on page 1188

0x4001 5800 - 0x4001 5BFF

SAI1

Section 33.5.10: SAI register map on page 1188

0x4001 5400 - 0x4001 57FF

SPI6

0x4001 5000 - 0x4001 53FF

SPI5

Section 32.9.10: SPI/I2S register map on
page 1144

0x4001 4800 - 0x4001 4BFF

TIM11

0x4001 4400 - 0x4001 47FF

TIM10

0x4001 4000 - 0x4001 43FF

TIM9

Section 24.4.13: TIM9/TIM12 register map on
page 848

0x4001 3C00 - 0x4001 3FFF

EXTI

Section 11.9.7: EXTI register map on page 300

0x4001 3800 - 0x4001 3BFF

SYSCFG

0x4001 3400 - 0x4001 37FF

SPI4

Section 32.9.10: SPI/I2S register map on
page 1144

0x4001 3000 - 0x4001 33FF

SPI1

Section 32.9.10: SPI/I2S register map on
page 1144

0x4001 2C00 - 0x4001 2FFF

SDMMC1

Section 35.8.16: SDMMC register map on
page 1279

0x4001 2000 - 0x4001 23FF

ADC1 - ADC2 - ADC3

0x4001 1400 - 0x4001 17FF

USART6

0x4001 1000 - 0x4001 13FF

USART1

0x4001 0400 - 0x4001 07FF

TIM8

0x4001 0000 - 0x4001 03FF

TIM1

Section 24.5.12: TIM10/TIM11/TIM13/TIM14
register map on page 858

APB2

Section 7.2.8: SYSCFG register maps on
page 221

Section 15.13.18: ADC register map on page 458
Section 31.8.12: USART register map on
page 1083
Section 22.4.24: TIM1 register map on page 737

RM0385 Rev 7

71/1709
75

RM0385
Table 1. STM32F75xxx and STM32F74xxx register boundary addresses (continued)
Boundary address

Peripheral

Bus

Register map

0x4000 7C00 - 0x4000 7FFF

UART8

0x4000 7800 - 0x4000 7BFF

UART7

0x4000 7400 - 0x4000 77FF

DAC

Section 16.5.15: DAC register map on page 482

0x4000 7000 - 0x4000 73FF

PWR

Section 4.4.4: PWR power control register 2
(PWR_CSR2) on page 129

0x4000 6C00 - 0x4000 6FFF

HDMI-CEC

Section 39.7.7: HDMI-CEC register map on
page 1654

0x4000 6800 - 0x4000 6BFF

CAN2

0x4000 6400 - 0x4000 67FF

CAN1

0x4000 6000 - 0x4000 63FF

I2C4

0x4000 5C00 - 0x4000 5FFF

I2C3

0x4000 5800 - 0x4000 5BFF

I2C2

0x4000 5400 - 0x4000 57FF

I2C1

0x4000 5000 - 0x4000 53FF

UART5

0x4000 4C00 - 0x4000 4FFF

UART4

0x4000 4800 - 0x4000 4BFF

USART3

0x4000 4400 - 0x4000 47FF

USART2

0x4000 4000 - 0x4000 43FF

SPDIFRX

0x4000 3C00 - 0x4000 3FFF

SPI3 / I2S3

0x4000 3800 - 0x4000 3BFF

SPI2 / I2S2

0x4000 3000 - 0x4000 33FF

IWDG

0x4000 2C00 - 0x4000 2FFF

WWDG

Section 31.8.12: USART register map on
page 1083

Section 36.9.5: bxCAN register map on page 1322
Section 30.7.12: I2C register map on page 1019

Section 30.7.12: I2C register map on page 1019

Section 31.8.12: USART register map on
page 1083

APB1

Section 34.5.10: SPDIFRX interface register map
on page 1221
Section 32.9.10: SPI/I2S register map on
page 1144
Section 27.4.6: IWDG register map on page 901
Section 28.4.4: WWDG register map on page 908

0x4000 2800 - 0x4000 2BFF RTC & BKP Registers

Section 29.6.21: RTC register map on page 952

0x4000 2400 - 0x4000 27FF

LPTIM1

Section 26.6.9: LPTIM register map on page 892

0x4000 2000 - 0x4000 23FF

TIM14

0x4000 1C00 - 0x4000 1FFF

TIM13

0x4000 1800 - 0x4000 1BFF

TIM12

0x4000 1400 - 0x4000 17FF

TIM7

0x4000 1000 - 0x4000 13FF

TIM6

0x4000 0C00 - 0x4000 0FFF

TIM5

0x4000 0800 - 0x4000 0BFF

TIM4

0x4000 0400 - 0x4000 07FF

TIM3

0x4000 0000 - 0x4000 03FF

TIM2

72/1709

Section 24.5.12: TIM10/TIM11/TIM13/TIM14
register map on page 858
Section 24.4.13: TIM9/TIM12 register map on
page 848
Section 25.4.9: TIM6/TIM7 register map on
page 872

Section 23.4.21: TIMx register map on page 808

RM0385 Rev 7

RM0385

2.3

Embedded SRAM
The STM32F75xxx and STM32F74xxx feature:
•

System SRAM up to 320 Kbytes including Data TCM RAM 64 Kbytes

•

Instruction RAM (ITCM-RAM) 16 Kbytes.

•

4 Kbytes of backup SRAM (see section 5.1.2: Battery backup domain)

The embedded SRAM is divided into up to four blocks:
•

•

System SRAM:
–

SRAM1 mapped at address 0x2001 0000 and accessible by all AHB masters from
AHB bus Matrix.

–

SRAM2 mapped at address 0x2004 C000 and accessible by all AHB masters from
AHB bus Matrix.

–

DTCM-RAM on TCM interface (Tightly Coupled Memory interface) mapped at
address 0x2000 0000 and accessible by all AHB masters from AHB bus Matrix but
through a specific AHB slave bus of the CPU.

Instruction SRAM:
–

Instruction RAM (ITCM-RAM) mapped at address 0x0000 0000 and accessible
only by CPU.

The SRAM1 and SRAM2 can be accessed as bytes, half-words (16 bits) or full words (32
bits). While DTCM and ITCM RAMs can be accessed as bytes, half-words (16 bits), full
words (32 bits) or double words (64 bits). These memories can be addressed at maximum
system clock frequency without wait state.
The AHB masters support concurrent SRAM accesses (from the Ethernet or the USB OTG
HS): for instance, the Ethernet MAC can read/write from/to SRAM2 while the CPU is
reading/writing from/to SRAM1.

2.4

Flash memory overview
The Flash memory interface manages CPU AXI and TCM accesses to the Flash memory. It
implements the erase and program Flash memory operations and the read and write
protection mechanisms. It accelerates code execution with ART on TCM interface or L1Cache on AXIM interface.
The Flash memory is organized as follows:
•

A main memory block divided into sectors.

•

An information block:
–

System memory from which the device boots in System memory boot mode

–

1024 OTP (one-time programmable) bytes for user data.

–

Option bytes to configure read and write protection, BOR level, software/hardware
watchdog, boot memory base address and reset when the device is in Standby or
Stop mode.

Refer to Section 3: Embedded Flash memory (FLASH) for more details.

RM0385 Rev 7

73/1709
75

RM0385

2.5

Boot configuration
In the STM32F75xxx and STM32F74xxx, two different boot areas can be selected through
the BOOT pin and the boot base address programmed in the BOOT_ADD0 and
BOOT_ADD1 option bytes as shown in the Table 2.
Table 2. Boot modes
Boot mode selection
Boot area

BOOT

Boot address option
bytes

0

BOOT_ADD0[15:0]

Boot address defined by user option byte BOOT_ADD0[15:0]
ST programmed value: Flash on ITCM at 0x0020 0000

1

BOOT_ADD1[15:0]

Boot address defined by user option byte BOOT_ADD1[15:0]
ST programmed value: System bootloader at 0x0010 0000

The values on the BOOT pin are latched on the 4th rising edge of SYSCLK after reset
release. It is up to the user to set the BOOT pin after reset.
The BOOT pin is also resampled when the device exits the Standby mode. Consequently,
they must be kept in the required Boot mode configuration when the device is in the Standby
mode.
After startup delay, the selection of the boot area is done before releasing the processor
reset.
The BOOT_ADD0 and BOOT_ADD1 address option bytes allows to program any boot
memory address from 0x0000 0000 to 0x3FFF FFFF which includes:
•

All Flash address space mapped on ITCM or AXIM interface

•

All RAM address space: ITCM, DTCM RAMs and SRAMs mapped on AXIM interface

•

The System memory bootloader

The BOOT_ADD0 / BOOT_ADD1 option bytes can be modified after reset in order to boot
from any other boot address after next reset.
If the programmed boot memory address is out of the memory mapped area or a reserved
area, the default boot fetch address is programmed as follows:
–

Boot address 0: ITCM-FLASH at 0x0020 0000

–

Boot address 1: ITCM-RAM at 0x0000 0000

When flash level 2 protection is enabled, only boot from Flash (on ITCM or AXIM interface)
or system bootloader will be available. If the already programmed boot address in the
BOOT_ADD0 and/or BOOT_ADD1 option bytes is out of the memory range or RAM
address (on ITCM or AXIM) the default fetch will be forced from Flash on ITCM interface at
address 0x00200000.

Embedded bootloader
The embedded bootloader code is located in the system memory. It is programmed by ST
during production. For full information, refer to the application note (AN2606) STM32
microcontroller system memory boot mode.

74/1709

RM0385 Rev 7

RM0385
By default, when the boot from system bootloader is selected, the code is executed from
TCM interface. It could be executed from AXIM interface by reprogramming the
BOOT_ADDx address option bytes to 0x1FF0 0000.

RM0385 Rev 7

75/1709
75

Embedded Flash memory (FLASH)

RM0385

3

Embedded Flash memory (FLASH)

3.1

Introduction
The Flash memory interface manages Cortex®-M7 AXI and TCM accesses to the Flash
memory. It implements the erase and program Flash memory operations and the read and
write protection mechanisms.
The Flash memory interface accelerates code execution with a system of instruction
prefetch and cache lines on ITCM interface (ART Accelerator™).

3.2

Flash main features
•

Flash memory read operations

•

Flash memory program/erase operations

•

Read / write protections

•

64 cache lines of 256 bits on ITCM interface (ART Accelerator™)

•

Prefetch on TCM instruction code

Figure 3 shows the Flash memory interface connection inside the system architecture.

ITCM

Figure 3. Flash memory interface connection inside system architecture
(STM32F75xxx and STM32F74xxx)

Chrom-ART
Accelerator
(DMA2D)
DMA2D

LCD-TFT_M

USB_HS_M

ETHERNET_M

DMA_P2

GP
MAC
USB OTG LCD-TFT
DMA2 Ethernet
HS
DMA_MEM2

DMA_PI

AHBP

4KB
I/D Cache

AXIM

GP
DMA1
DMA_MEM1

ARM Cortex-M7

AXI to
multi-AHB

ITCM Bus (64bits)

ART

Flash interface

AHB 64-bit
data bus

Flash bus
256 bits Flash
memory

Flash register
On AHB1

Bus Matrix - S
MSv35952V1

76/1709

RM0385 Rev 7

RM0385

Embedded Flash memory (FLASH)

3.3

Flash functional description

3.3.1

Flash memory organization
The Flash memory has the following main features:
•

Capacity up to 1 Mbyte

•

256 bits wide data read

•

Byte, half-word, word and double word write

•

Sector and mass erase

The Flash memory is organized as follows:
•

A main memory block divided into 4 sectors of 32 Kbytes, 1 sector of 128 Kbytes, and 3
sectors of 256 Kbytes

•

Information blocks containing:
–

System memory from which the device boots in System memory boot mode

–

1024 OTP (one-time programmable) for user data

–

The OTP area contains 16 additional bytes used to lock the corresponding OTP
data block.

–

Option bytes to configure read and write protection, BOR level, software/hardware
watchdog, boot memory base address and reset when the device is in Standby or
Stop mode.

The embedded flash has three main interfaces:
•

•

•

64-bits ITCM interface:
–

It is connected to the ITCM bus of Cortex-M7 and used for instruction execution
and data read access.

–

Write accesses are not supported on ITCM interface

–

Supports a unified 64 cache lines of 256 bits (ART accelerator)

64-bits AHB interface:
–

It is connected to the AXI bus of Cortex-M7 through the AHB bus matrix and used
for code execution, read and write accesses.

–

DMAs and peripherals DMAs data transfer on Flash are done through the AHB
interface whatever the addressed flash interface TCM or AHB.

32-bits AHB register interface:
–

It is used for control and status register accesses.

The main memory and information block organization are shown in Table 3.

RM0385 Rev 7

77/1709
98

Embedded Flash memory (FLASH)

RM0385

Table 3. Flash memory organization
Block

Main memory
block

Name

Bloc base address on AXIM
interface

Block base address
on ICTM interface

Sector
size

Sector 0

0x0800 0000 - 0x0800 7FFF

0x0020 0000 - 0x0020 7FFF

32 KB

Sector 1

0x0800 8000 - 0x0800 FFFF

0x0020 8000 - 0x0020 FFFF

32 KB

Sector 2

0x0801 0000 - 0x0801 7FFF

0x0021 0000 - 0x0021 7FFF

32 KB

Sector 3

0x0801 8000 - 0x0801 FFFF

0x0021 8000 - 0x0021 FFFF

32 KB

Sector 4

0x0802 0000 - 0x0803 FFFF

0x0022 0000 - 0x0023 FFFF

128 KB

Sector 5

0x0804 0000 - 0x0807 FFFF

0x0024 0000 - 0x0027 FFFF

256 KB

Sector 6

0x0808 0000 - 0x080B FFFF 0x0028 0000 - 0x002B FFFF

256 KB

Sector 7

0x080C 0000 - 0x080F FFFF

256 KB

System memory
Information block

3.3.2

0x002C 0000 - 0x02F FFFF

0x1FF0 0000 - 0x1FF0 EDBF 0x0010 0000 - 0x0010 EDBF 60 Kbytes

OTP

0x1FF0 F000 - 0x1FF0 F41F

Option bytes

0x1FFF 0000 - 0x1FFF 001F

0x0010 F000 - 0x0010 F41F 1024 bytes
-

32 bytes

Read access latency
To correctly read data from Flash memory, the number of wait states (LATENCY) must be
correctly programmed in the Flash access control register (FLASH_ACR) according to the
frequency of the CPU clock (HCLK) and the supply voltage of the device.
The correspondence between wait states and CPU clock frequency is given in Table 13 and
Table 4.

Note:

- when VOS[1:0] = '0x01', the maximum value of fHCLK is 144 MHz.
- when VOS[1:0] = '0x10', the maximum value of fHCLK is 168 MHz. It can be extended to
180 MHz by activating the over-drive mode.
- when VOS[1:0] = '0x11, the maximum value of fHCLK is 180 MHz. It can be extended to
216 MHz by activating the over-drive mode.
- The over-drive mode is not available when VDD ranges from 1.8 to 2.1 V.
Refer to Section 4.1.4: Voltage regulator for details on how to activate the over-drive mode.
Table 4. Number of wait states according to CPU clock (HCLK) frequency
HCLK (MHz)

Wait states (WS)
Voltage range

Voltage range

Voltage range

Voltage range

2.7 V - 3.6 V

2.4 V - 2.7 V

2.1 V - 2.4 V

1.8 V - 2.1 V

0 WS (1 CPU cycle)

0 < HCLK ≤ 30

0 < HCLK ≤ 24

0 < HCLK ≤ 22

0 < HCLK ≤ 20

1 WS (2 CPU cycles)

30 < HCLK ≤ 60

24 < HCLK ≤ 48

22 1, 1->2, 0->2)
there is no mass erase.
•

Level 2: debug/chip read disabled
The read protection Level 2 is activated by writing 0xCC to the RDP option byte. When
the read protection Level 2 is set:
–

All protections provided by Level 1 are active.

–

Booting from RAM is no more allowed.

–

Booting system memory bootloader is possible and all the commands are not
accessible except Get, GetID and GetVersion. Refer to AN2606.

–

JTAG, SWV (serial-wire viewer), ETM, and boundary scan are disabled.

–

User option bytes can no longer be changed.

–

When booting from Flash memory, accesses (read, erase and program) to Flash
memory and backup SRAM from user code are allowed.

Memory read protection Level 2 is an irreversible operation. When Level 2 is activated,
the level of protection cannot be decreased to Level 0 or Level 1.

88/1709

RM0385 Rev 7

RM0385

Embedded Flash memory (FLASH)

Note:

The JTAG port is permanently disabled when Level 2 is active (acting as a JTAG fuse). As a
consequence, boundary scan cannot be performed. STMicroelectronics is not able to
perform analysis on defective parts on which the Level 2 protection has been set.

Note:

If the read protection is set while the debugger is still connected through JTAG/SWD, apply
a POR (power-on reset).
Table 8. Access versus read protection level

Memory area

Protection
Level

Debug features, Boot from RAM or
from System memory bootloader
Read

Main Flash Memory
and Backup SRAM
Option Bytes

OTP

Level 1

Write

Erase

Booting from Flash memory
Read

Write

NO(1)

NO

Erase

YES

Level 2

NO

YES

Level 1

YES

YES

Level 2

NO

NO

Level 1

NO

NA

YES

NA

Level 2

NO

NA

YES

NA

1. The main Flash memory and backup SRAM are only erased when the RDP changes from level 1 to 0. The OTP area
remains unchanged.

Figure 4 shows how to go from one RDP level to another.
Figure 4. RDP levels
RDP /= AAh & /= CCh
Others options modified

Level 1
RDP /= AAh
RDP /= CCh
default

Write options
including
RDP = CCh

Write optionsincluding
RDP /= CCh & /= AAh

L ev e l 2
RDP = CCh

Write options
including
RDP = AAh

L ev e l 0
Write options
including
RDP = CCh

Options write (RDP level increase) includes
- Options erase
- New options program
Options write (RDP level decrease) includes
- Mass erase
- Options erase
- New options program

RDP = AA h

RDP = AAh
Others option(s) modified
Options write (RDP level identical) includes
- Options erase
- New options program
ai16045

RM0385 Rev 7

89/1709
98

Embedded Flash memory (FLASH)

3.5.2

RM0385

Write protections
Up to 8 user sectors in Flash memory can be protected against unwanted write operations
due to loss of program counter contexts. When the non-write protection nWRPi bit (0 ≤ i ≤ 7)
in the FLASH_OPTCR or FLASH_OPTCR1 registers is low, the corresponding sector
cannot be erased or programmed. Consequently, a mass erase cannot be performed if one
of the sectors is write-protected.
If an erase/program operation to a write-protected part of the Flash memory is attempted
(sector protected by write protection bit, OTP part locked or part of the Flash memory that
can never be written like the ICP), the write protection error flag (WRPERR) is set in the
FLASH_SR register.

Note:

When the memory read protection level is selected (RDP level = 1), it is not possible to
program or erase Flash memory sector i if the CPU debug features are connected (JTAG or
single wire) or boot code is being executed from RAM, even if nWRPi = 1.

Write protection error flag
If an erase/program operation to a write protected area of the Flash memory is performed,
the Write Protection Error flag (WRPERR) is set in the FLASH_SR register.
If an erase operation is requested, the WRPERR bit is set when:
•

A sector erase is requested and the Sector Number SNB field is not valid

•

A mass erase is requested while at least one of the user sector is write protected by
option bit (MER and nWRi = 0 with 0 ≤ i ≤ 7 bits in the FLASH_OPTCR register

•

A sector erase is requested on a write protected sector. (SER = 1, SNB = i and
nWRPi = 0 with 0 ≤ i ≤ 7 bits in the FLASH_OPTCR register)

•

The Flash memory is readout protected and an intrusion is detected.

If a program operation is requested, the WRPERR bit is set when:

3.6

•

A write operation is performed on system memory or on the reserved part of the user
specific sector.

•

A write operation is performed to the information block

•

A write operation is performed on a sector write protected by option bit.

•

A write operation is requested on an OTP area which is already locked

•

The Flash memory is read protected and an intrusion is detected.

One-time programmable bytes
Table 9 shows the organization of the one-time programmable (OTP) part of the OTP area.
Table 9. OTP area organization

OTP
[255:224] [223:193] [192:161] [160:128]
Block
0

1

90/1709

[127:96]

[95:64]

[63:32]

[31:0]

Address
byte 0

OTP0

OTP0

OTP0

OTP0

OTP0

OTP0

OTP0

OTP0

0x1FF0 F000

OTP0

OTP0

OTP0

OTP0

OTP0

OTP0

OTP0

OTP0

0x1FF0 F020

OTP1

OTP1

OTP1

OTP1

OTP1

OTP1

OTP1

OTP1

0x1FF0 F040

OTP1

OTP1

OTP1

OTP1

OTP1

OTP1

OTP1

OTP1

0x1FF0 F060

RM0385 Rev 7

RM0385

Embedded Flash memory (FLASH)
Table 9. OTP area organization (continued)

OTP
[255:224] [223:193] [192:161] [160:128]
Block
14

15
Lock
block

[127:96]

[95:64]

[63:32]

[31:0]

Address
byte 0

-

-

-

-

-

-

-

-

-

OPT14

OPT14

OPT14

OPT14

OPT14

OPT14

OPT14

OPT14

0x1FF0 F380

OPT14

OPT14

OPT14

OPT14

OPT14

OPT14

OPT14

OPT14

0x1FF0 F3A0

OPT15

OPT15

OPT15

OPT15

OPT15

OPT15

OPT15

OPT15

0x1FF0 F3C0

OPT15

OPT15

OPT15

OPT15

OPT15

OPT15

OPT15

OPT15

0x1FF0 F3E0

reserved

reserved

reserved

reserved

LOCK15... LOCK11... LOCK7... LOCK3...
0x1FF0 F400
LOCKB12 LOCKB8 LOCKB4 LOCKB0

The OTP area is divided into 16 OTP data blocks of 64 bytes and one lock OTP block of 16
bytes. The OTP data and lock blocks cannot be erased. The lock block contains 16 bytes
LOCKBi (0 ≤ i ≤ 15) to lock the corresponding OTP data block (blocks 0 to 15). Each OTP
data block can be programmed until the value 0x00 is programmed in the corresponding
OTP lock byte. The lock bytes must only contain 0x00 and 0xFF values, otherwise the OTP
bytes might not be taken into account correctly.

3.7

FLASH registers

3.7.1

Flash access control register (FLASH_ACR)
The Flash access control register is used to enable/disable the acceleration features and
control the Flash memory access time according to CPU frequency.
Address offset: 0x00
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

9

8

3

2

1

0

15

14

13

12

11

10

Res.

Res.

Res.

Res.

ARTRST

Res.

rw

ARTEN PRFTEN
rw

7

6

5

4

Res.

Res.

Res.

Res.

rw

LATENCY[3:0]
rw

rw

rw

rw

Bits 31:12 Reserved, must be kept cleared.
Bit 11 ARTRST: ART Accelerator reset
0: ART Accelerator is not reset
1: ART Accelerator is reset
Bit 10 Reserved, must be kept cleared.

RM0385 Rev 7

91/1709
98

Embedded Flash memory (FLASH)

RM0385

Bit 9 ARTEN: ART Accelerator Enable
0: ART Accelerator is disabled
1: ART Accelerator is enabled
Bit 8 PRFTEN: Prefetch enable
0: Prefetch is disabled
1: Prefetch is enabled
Bits 7:4 Reserved, must be kept cleared.
Bits 3:0 LATENCY[3:0]: Latency
These bits represent the ratio of the CPU clock period to the Flash memory access time.
0000: Zero wait state
0001: One wait state
0010: Two wait states
1110: Fourteen wait states
1111: Fifteen wait states

3.7.2

Flash key register (FLASH_KEYR)
The Flash key register is used to allow access to the Flash control register and so, to allow
program and erase operations.
Address offset: 0x04
Reset value: 0x0000 0000
Access: no wait state, word access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

KEY[31:16]
w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

w

w

w

w

w

w

w

KEY[15:0]
w

w

w

w

w

w

w

w

w

Bits 31:0 FKEYR[31:0]: FPEC key
The following values must be programmed consecutively to unlock the FLASH_CR register
and allow programming/erasing it:
a) KEY1 = 0x45670123
b) KEY2 = 0xCDEF89AB

3.7.3

Flash option key register (FLASH_OPTKEYR)
The Flash option key register is used to allow program and erase operations in the
information block.
Address offset: 0x08
Reset value: 0x0000 0000
Access: no wait state, word access

92/1709

RM0385 Rev 7

RM0385

Embedded Flash memory (FLASH)

31

30

29

28

27

26

25

24

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

23

22

21

20

19

18

17

16

w

w

w

w

w

w

w

w

7

6

5

4

3

2

1

0

w

w

w

w

w

w

w

OPTKEYR[31:16]

OPTKEYR[15:0]
w

w

w

w

w

w

w

w

w

Bits 31:0 OPTKEYR[31:0]: Option byte key
The following values must be programmed consecutively to unlock the FLASH_OPTCR
register and allow programming it:
a) OPTKEY1 = 0x08192A3B
b) OPTKEY2 = 0x4C5D6E7F

3.7.4

Flash status register (FLASH_SR)
The Flash status register gives information on ongoing program and erase operations.
Address offset: 0x0C
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BSY

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OPERR

EOP

rc_w1

rc_w1

r

ERSERR PGPERR PGAERR WRPERR
rc_w1

rc_w1

rc_w1

rc_w1

Bits 31:17 Reserved, must be kept cleared.
Bit 16 BSY: Busy
This bit indicates that a Flash memory operation is in progress. It is set at the beginning of a
Flash memory operation and cleared when the operation finishes or an error occurs.
0: no Flash memory operation ongoing
1: Flash memory operation ongoing
Bits 15:8 Reserved, must be kept cleared.
Bit 7 ERSERR: Erase Sequence Error
Set by hardware when a write access to the Flash memory is performed by the code while
the control register has not been correctly configured.
Cleared by writing 1.
Bit 6 PGPERR: Programming parallelism error
Set by hardware when the size of the access (byte, half-word, word, double word) during the
program sequence does not correspond to the parallelism configuration PSIZE (x8, x16,
x32, x64).
Cleared by writing 1.
Bit 5 PGAERR: Programming alignment error
Set by hardware when the data to program cannot be contained in the same 128-bit Flash
memory row.
Cleared by writing 1.

RM0385 Rev 7

93/1709
98

Embedded Flash memory (FLASH)

RM0385

Bit 4 WRPERR: Write protection error
Set by hardware when an address to be erased/programmed belongs to a write-protected
part of the Flash memory.
Cleared by writing 1.
Bits 3:2 Reserved, must be kept cleared.
Bit 1 OPERR: Operation error
Set by hardware when a flash operation (programming / erase /read) request is detected and
can not be run because of parallelism, alignment, or write protection error. This bit is set only
if error interrupts are enabled (ERRIE = 1).
Bit 0 EOP: End of operation
Set by hardware when one or more Flash memory operations (program/erase) has/have
completed successfully. It is set only if the end of operation interrupts are enabled (EOPIE =
1).
Cleared by writing a 1.

3.7.5

Flash control register (FLASH_CR)
The Flash control register is used to configure and start Flash memory operations.
Address offset: 0x10
Reset value: 0x8000 0000
Access: no wait state when no Flash memory operation is ongoing, word, half-word and
byte access.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

LOCK

Res.

Res.

Res.

Res.

Res.

ERRIE

EOPIE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

STRT

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

MER

SER

PG

rw

rw

rw

rw

rw

rs

PSIZE[1:0]
rw

rs

Res.

rw

SNB[3:0]
rw

rw

Bit 31 LOCK: Lock
Write to 1 only. When it is set, this bit indicates that the FLASH_CR register is locked. It is
cleared by hardware after detecting the unlock sequence.
In the event of an unsuccessful unlock operation, this bit remains set until the next reset.
Bits 30:26 Reserved, must be kept cleared.
Bit 25 ERRIE: Error interrupt enable
This bit enables the interrupt generation when the OPERR bit in the FLASH_SR register is
set to 1.
0: Error interrupt generation disabled
1: Error interrupt generation enabled
Bit 24 EOPIE: End of operation interrupt enable
This bit enables the interrupt generation when the EOP bit in the FLASH_SR register goes
to 1.
0: Interrupt generation disabled
1: Interrupt generation enabled
Bits 23:17 Reserved, must be kept cleared.

94/1709

RM0385 Rev 7

RM0385

Embedded Flash memory (FLASH)

Bit 16 STRT: Start
This bit triggers an erase operation when set. It is set only by software and cleared when the
BSY bit is cleared.
Bits 15:10 Reserved, must be kept cleared.
Bits 9:8 PSIZE: Program size
These bits select the program parallelism.
00 program x8
01 program x16
10 program x32
11 program x64
Bit 7 Reserved, must be kept cleared.
Bits 6:3 SNB[3:0]: Sector number
These bits select the sector to erase.
0000 sector 0
0001 sector 1
...
0111 sector 7
Others not allowed
Bit 2 MER: Mass Erase
Erase activated for all user sectors.
Bit 1 SER: Sector Erase
Sector Erase activated.
Bit 0 PG: Programming
Flash programming activated.

3.7.6

Flash option control register (FLASH_OPTCR)
The FLASH_OPTCR register is used to modify the user option bytes.
Address offset: 0x14
Reset value: 0xC0FFAAFD. The option bytes are loaded with values from Flash memory at
reset release.
Access: no wait state when no Flash memory operation is ongoing, word, half-word and
byte access.

31

30

IWDG_ IWDG_
STOP STDBY
rw

rw

15

14

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

9

8

rw

rw

rw

rw

22

rw

rw

rw

21

20

19

18

17

16

nWRP[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

nRST_ nRST_
STDBY STOP

RDP[7:0]
rw

23

rw

RM0385 Rev 7

rw

IWDG_ WWDG
SW
_SW
rw

rw

BOR_LEV[1:0]
rw

rw

OPTST OPTLO
RT
CK
rs

rs

95/1709
98

Embedded Flash memory (FLASH)

RM0385

Bit 31 IWDG_STOP: Independent watchdog counter freeze in Stop mode
0: Freeze IWDG counter in STOP mode.
1: IWDG counter active in STOP mode.
Bit 30 IWDG_STDBY: Independent watchdog counter freeze in standby mode
0: Freeze IWDG counter in standby mode.
1: IWDG counter active in standby mode.
Bits 29:24 Reserved, must be kept cleared.
Bits 23:16 nWRP[7:0]: Not write protect
These bits contain the value of the write-protection option bytes for sectors 0 to 7 after reset.
They can be written to program a new write-protect into Flash memory.
0: Write protection active on sector i
1: Write protection not active on sector i
Bits 15:8 RDP[7:0]: Read protect
These bits contain the value of the read-protection option level after reset. They can be
written to program a new read protection value into Flash memory.
0xAA: Level 0, read protection not active
0xCC: Level 2, chip read protection active
Others: Level 1, read protection of memories active
Bits 7:4 USER: User option bytes
These bits contain the value of the user option byte after reset. They can be written to
program a new user option byte value into Flash memory.
Bit 7: nRST_STDBY
Bit 6: nRST_STOP
Bit 5: IWDG_SW
Bit 4: WWDG_SW
Bits 3:2 BOR_LEV[1:0]: BOR reset Level
These bits contain the supply level threshold that activates/releases the reset. They can be
written to program a new BOR level. By default, BOR is off. When the supply voltage (VDD)
drops below the selected BOR level, a device reset is generated.
00: BOR Level 3 (VBOR3), brownout threshold level 3
01: BOR Level 2 (VBOR2), brownout threshold level 2
10: BOR Level 1 (VBOR1), brownout threshold level 1
11: BOR off, POR/PDR reset threshold level is applied
Note: For full details on BOR characteristics, refer to the “Electrical characteristics” section of
the product datasheet.
Bit 1 OPTSTRT: Option start
This bit triggers a user option operation when set. It is set only by software and cleared when
the BSY bit is cleared.
Bit 0 OPTLOCK: Option lock
Write to 1 only. When this bit is set, it indicates that the FLASH_OPTCR register is locked.
This bit is cleared by hardware after detecting the unlock sequence.
In the event of an unsuccessful unlock operation, this bit remains set until the next reset.

Note:

When modifying the IWDG_SW, IWDG_STOP or IWDG_STDBY option byte, a system
reset is required to make the change effective.

3.7.7

Flash option control register (FLASH_OPTCR1)
The FLASH_OPTCR1 register is used to modify the user option bytes.

96/1709

RM0385 Rev 7

RM0385

Embedded Flash memory (FLASH)
Address offset: 0x18
Reset value: 0x0040 0080 (ITCM-FLASH). The option bytes are loaded with values from
Flash memory at reset release.
Access: no wait state when no Flash memory operation is ongoing, word, half-word and
byte access.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

6

5

4

3

2

1

0

BOOT_ADD1[15:0]
rw
15

14

13

12

11

10

9

8

7

BOOT_ADD0[15:0]
rw

Bits 31:16 BOOT_ADD1[15:0]: Boot base address when Boot pin =1
BOOT_ADD1[15:0] correspond to address [29:14],
The boot memory address can be programmed to any address in the range 0x0000 0000 to
0x2004 FFFF with a granularity of 16KB.
Example:
BOOT_ADD1 = 0x0000: Boot from ITCM RAM (0x0000 0000)
BOOT_ADD1 = 0x0040: Boot from System memory bootloader (0x0010 0000)
BOOT_ADD1 = 0x0080: Boot from Flash on ITCM interface (0x0020 0000)
BOOT_ADD1 = 0x2000: Boot from Flash on AXIM interface (0x0800 0000)
BOOT_ADD1 = 0x8000: Boot from DTCM RAM (0x2000 0000)
BOOT_ADD1 = 0x8004: Boot from SRAM1 (0x2001 0000)
BOOT_ADD1 = 0x8013: Boot from SRAM2 (0x2004 C000)
Bits 15:0 BOOT_ADD0[15:0]: Boot base address when Boot pin =0
BOOT_ADD0[15:0] correspond to address [29:14],
The boot base address can be programmed to any address in the range 0x0000 0000 to
0x2004 FFFF with a granularity of 16KB.
Example:
BOOT_ADD0 = 0x0000: Boot from ITCM RAM (0x0000 0000)
BOOT_ADD0 = 0x0040: Boot from System memory bootloader (0x0010 0000)
BOOT_ADD0 = 0x0080: Boot from Flash on ITCM interface (0x0020 0000)
BOOT_ADD0 = 0x2000: Boot from Flash on AXIM interface (0x0800 0000)
BOOT_ADD0 = 0x8000: Boot from DTCM RAM (0x2000 0000)
BOOT_ADD0 = 0x8004: Boot from SRAM1 (0x2001 0000)
BOOT_ADD0 = 0x8013: Boot from SRAM2 (0x2004 C000)

RM0385 Rev 7

97/1709
98

Embedded Flash memory (FLASH)

3.7.8

RM0385

Flash interface register map

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

FLASH_SR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BSY

Res.

Res.

Res.

Res.

Res.

Res.

Res.

nWRP[7:0]

0

0

0

0

0

0

0

0

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

0

0

0

1

0

RDP[7:0]

1

1

1

0

1

0

1

0

BOOT_ADD1[15:0]
0

0

0

PSIZE[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EOPIE
Res.

Res.

ERRIE

Res.

Res.

0

1

FLASH_
OPTCR1
Reset value

Res.

Res.
Res.

Res.

Res.
Res.

Res.

Res.

LOCK
IWDG_STOP

IWDG_STDBY
1

0

0

0

1

0

SNB[3:0]

0

0

0

1

1

EOP

0

Reset value

0

0

0

PG

0

FLASH_OPTCR

0

0

0

0

0

OPTLOCK

0

0

0

OPERR

0

0

0

SER

0

1

0

MER

0

Reset value

0

OPTSTRT

0

0x14

0

OPTKEYR[15:0]

0

FLASH_CR

Res.

PRFTEN

0

OPTKEYR[31:16]

Reset value

98/1709

0

Reset value

0x10

0

Res.

0

BOR_LEV[1:0]

0

Res.

0

WRPERR

0

WWDG_SW

0

KEY[15:0]

PGAERR

0

0

IWDG_SW

0

0

PGPERR

0

0

nRST_STOP

0

0

Res.

0

LATENCY[3:0]

ERSERR

0

FLASH_
OPTKEYR

0x0C

0x18

Res.

KEY[31:16]

Res.

0x08

0

Res.

Reset value

0

nRST_STDBY

FLASH_KEYR

STRT

0x04

0

ARTEN

Res.

Reset value

ARTRST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FLASH_ACR
0x00

Res.

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 10. Flash register map and reset values

1

1

1

1

0

1

0

0

0

0

0

BOOT_ADD0[15:0]
0

0

0

0

RM0385 Rev 7

0

0

0

0

0

0

0

0

0

1

0

0

RM0385

Power controller (PWR)

4

Power controller (PWR)

4.1

Power supplies
The device requires a 1.8 to 3.6 V operating voltage supply (VDD). An embedded linear
voltage regulator is used to supply the internal 1.2 V digital power.
The real-time clock (RTC), the RTC backup registers, and the backup SRAM (BKP SRAM)
can be powered from the VBAT voltage when the main VDD supply is powered off.

Note:

Depending on the operating power supply range, some peripheral may be used with limited
functionality and performance. For more details refer to section "General operating
conditions" in STM32F75xxx and STM32F74xxx datasheets.

RM0385 Rev 7

99/1709
131

Power controller (PWR)

RM0385
Figure 5. Power supply overview
VBAT

Backup circuitry
(OSC32K,RTC,
Wakeup logic
Backup registers,
backup RAM)

OUT

GP I/Os
IN

2 × 2.2 μF
VDD

IO
Logic
Kernel logic
(CPU,
digital
& RAM)

VCAP_1
VCAP_2

VDD
1/2/...14/20

19 × 100 nF
+ 1 × 4.7 μF

Level shifter

Power switch

VBAT =
1.65 to 3.6V

Voltage
regulator

VSS

1/2/...14/20

Flash memory

BYPASS_REG
VDDUSB

VDDUSB

100 nF
+ 1 μF
PDR_ON
VDD

Reset
controller

VDDA
VREF

100 nF
+ 1 μF

OTG FS
PHY

100 nF
+ 1 μF

VREF+
VREF-

ADC

Analog:
RCs, PLL,
...

VSSA
MSv35942V1

1. VDDA and VSSA must be connected to VDD and VSS, respectively.

4.1.1

Independent A/D converter supply and reference voltage
To improve conversion accuracy, the ADC has an independent power supply which can be
separately filtered and shielded from noise on the PCB.
•

The ADC voltage supply input is available on a separate VDDA pin.

•

An isolated supply ground connection is provided on pin VSSA.

To ensure a better accuracy of low voltage inputs, the user can connect a separate external
reference voltage ADC input on VREF. The voltage on VREF ranges from 1.8 V to VDDA.

100/1709

RM0385 Rev 7

RM0385

4.1.2

Power controller (PWR)

Independent USB transceivers supply
The VDDUSB is an independent USB power supply for full speed transceivers (USB OTG FS
and USB OTG HS in FS mode). It can be connected either to VDD or an external
independent power supply (3.0 to 3.6V) for USB transceivers (refer Figure 6 and Figure 7).
For example, when the device is powered at 1.8V, an independent power supply 3.3V can
be connected to VDDUSB. When the VDDUSB is connected to a separated power supply, it is
independent from VDD or VDDA but it must be the last supply to be provided and the first to
disappear. The following conditions VDDUSB must be respected:
•

During power-on phase (VDD < VDD_MIN), VDDUSB should be always lower than VDD

•

During power-down phase (VDD < VDD_MIN), VDDUSB should be always lower than VDD

•

VDDUSB rising and falling time rate specifications must be respected

•

In operating mode phase, VDDUSB could be lower or higher than VDD:
–

If USB (USB OTG_HS/OTG_FS) is used, the associated GPIOs powered by
VDDUSB are operating between VDDUSB_MIN and VDDUSB_MAX.

–

The VDDUSB supplies both USB transceiver (USB OTG_HS and USB OTG_FS). If
only one USB transceiver is used in the application, the GPIOs associated to the
other USB transceiver are still supplied at by VDDUSB.

–

If USB (USB OTG_HS/OTG_FS) is not used, the associated GPIOs powered by
VDDUSB are operating between VDD_MIN and VDD_MAX.
Figure 6. VDDUSB connected to VDD power supply

VDD

VDD_MAX

VDD= VDDA = VDDUSB
VDD_MIN

Power-on

Operating mode

Power-down

time

MS37591V1

RM0385 Rev 7

101/1709
131

Power controller (PWR)

RM0385

Figure 7. VDDUSB connected to external independent power supply
VDDUSB_MAX
USB functional area
VDDUSB
VDDUSB_MIN
USB non
functional
area

VDD = VDDA

Power-on

Operating mode

USB non
functional
area

VDD_MIN

time

Power-down

MS37590V1

4.1.3

Battery backup domain
Backup domain description
To retain the content of the RTC backup registers, backup SRAM, and supply the RTC when
VDD is turned off, VBAT pin can be connected to an optional standby voltage supplied by a
battery or by another source.
To allow the RTC to operate even when the main digital supply (VDD) is turned off, the VBAT
pin powers the following blocks:
•

The RTC

•

The LSE oscillator

•

The backup SRAM when the low-power backup regulator is enabled

•

PC13 to PC15 I/Os, plus PI8 I/O (when available)

The switch to the VBAT supply is controlled by the power-down reset embedded in the Reset
block.

Warning:

102/1709

During tRSTTEMPO (temporization at VDD startup) or after a PDR
is detected, the power switch between VBAT and VDD remains
connected to VBAT.
During the startup phase, if VDD is established in less than
tRSTTEMPO (Refer to the datasheet for the value of tRSTTEMPO)
and VDD > VBAT + 0.6 V, a current may be injected into VBAT
through an internal diode connected between VDD and the
power switch (VBAT).
If the power supply/battery connected to the VBAT pin cannot
support this current injection, it is strongly recommended to

RM0385 Rev 7

RM0385

Power controller (PWR)
connect an external low-drop diode between this power
supply and the VBAT pin.

If no external battery is used in the application, it is recommended to connect the VBAT pin to
VDD with a 100 nF external decoupling ceramic capacitor in parallel.
When the backup domain is supplied by VDD (analog switch connected to VDD), the
following functions are available:

Note:

•

PC14 and PC15 can be used as either GPIO or LSE pins

•

PC13 and PI8 can be used as a GPIO pin (refer to Table 147: RTC pin PC13
configuration and Table 148: RTC pin PI8 configuration for more details about these
pins configuration)

Due to the fact that the switch only sinks a limited amount of current (3 mA), the use of
GPIOs PI8 and PC13 to PC15 are restricted: the speed has to be limited to 2 MHz with a
maximum load of 30 pF and these I/Os must not be used as a current source (e.g. to drive
an LED).
When the backup domain is supplied by VBAT (analog switch connected to VBAT because
VDD is not present), the following functions are available:
•

PC14 and PC15 can be used as LSE pins only

•

PC13 can be used as tamper pin (TAMP1)

•

PI8 can be used as tamper pin (TAMP2)

Backup domain access
After reset, the backup domain (RTC registers, RTC backup register and backup SRAM) is
protected against possible unwanted write accesses. To enable access to the backup
domain, proceed as follows:
•

Access to the RTC and RTC backup registers

1.

Enable the power interface clock by setting the PWREN bits in the RCC_APB1ENR
register (see Section 5.3.13)

2.

Set the DBP bit in the PWR power control register (PWR_CR1) to enable access to the
backup domain

3.

Select the RTC clock source: see Section 5.2.8: RTC/AWU clock

4.

Enable the RTC clock by programming the RTCEN [15] bit in the RCC backup domain
control register (RCC_BDCR)

•

Access to the backup SRAM

1.

Enable the power interface clock by setting the PWREN bits in the RCC_APB1ENR
register (see Section 5.3.13)

2.

Set the DBP bit in the PWR power control register (PWR_CR1) to enable access to the
backup domain

3.

Enable the backup SRAM clock by setting BKPSRAMEN bit in the RCC AHB1
peripheral clock register (RCC_AHB1ENR).

RTC and RTC backup registers
The real-time clock (RTC) is an independent BCD timer/counter. The RTC provides a timeof-day clock/calendar, two programmable alarm interrupts, and a periodic programmable
wakeup flag with interrupt capability. The RTC contains 32 backup data registers (128 bytes)

RM0385 Rev 7

103/1709
131

Power controller (PWR)

RM0385

which are reset when a tamper detection event occurs. For more details refer to Section 29:
Real-time clock (RTC).

Backup SRAM
The backup domain includes 4 Kbytes of backup SRAM addressed in 32-bit, 16-bit or 8-bit
mode. Its content is retained even in Standby or VBAT mode when the low-power backup
regulator is enabled. It can be considered as an internal EEPROM when VBAT is always
present.
When the backup domain is supplied by VDD (analog switch connected to VDD), the backup
SRAM is powered from VDD which replaces the VBAT power supply to save battery life.
When the backup domain is supplied by VBAT (analog switch connected to VBAT because
VDD is not present), the backup SRAM is powered by a dedicated low-power regulator. This
regulator can be ON or OFF depending whether the application needs the backup SRAM
function in Standby and VBAT modes or not. The power-down of this regulator is controlled
by a dedicated bit, the BRE control bit of the PWR_CSR1 register (see Section 4.4.2: PWR
power control/status register (PWR_CSR1)).
The backup SRAM is not mass erased by an tamper event. It is read protected to prevent
confidential data, such as cryptographic private key, from being accessed. The backup
SRAM can be erased only through the Flash interface when a protection level change from
level 1 to level 0 is requested. Refer to the description of Read protection (RDP) option byte.
Figure 8. Backup domain

Power switch
Voltage regulator
3.3 -> 1.2 V

LP voltage regulator
3.3 -> 1.2 V

1.2 V domain

Backup SRAM
interface

Backup SRAM
1.2 V
RTC

LSE 32.768 Hz

Backup domain

MS30430V1

4.1.4

Voltage regulator
An embedded linear voltage regulator supplies all the digital circuitries except for the backup
domain and the Standby circuitry. The regulator output voltage is around 1.2 V.
This voltage regulator requires two external capacitors to be connected to two dedicated
pins, VCAP_1 and VCAP_2 available in all packages. Specific pins must be connected either to
VSS or VDD to activate or deactivate the voltage regulator. These pins depend on the
package.

104/1709

RM0385 Rev 7

RM0385

Power controller (PWR)
When activated by software, the voltage regulator is always enabled after Reset. It works in
three different modes depending on the application modes (Run, Stop, or Standby mode).
•

In Run mode, the main regulator supplies full power to the 1.2 V domain (core,
memories and digital peripherals). In this mode, the regulator output voltage (around
1.2 V) can be scaled by software to different voltage values (scale 1, scale 2, and scale
3 can be configured through VOS[1:0] bits of the PWR_CR1 register). The scale can
be modified only when the PLL is OFF and the HSI or HSE clock source is selected as
system clock source. The new value programmed is active only when the PLL is ON.
When the PLL is OFF, the voltage scale 3 is automatically selected.
The voltage scaling allows optimizing the power consumption when the device is
clocked below the maximum system frequency. After exit from Stop mode, the voltage
scale 3 is automatically selected.(see Section 4.4.1: PWR power control register
(PWR_CR1).
2 operating modes are available:

•

–

Normal mode: The CPU and core logic operate at maximum frequency at a given
voltage scaling (scale 1, scale 2 or scale 3)

–

Over-drive mode: This mode allows the CPU and the core logic to operate at a
higher frequency than the normal mode for the voltage scaling scale 1 and scale
2.

In Stop mode: the main regulator or low-power regulator supplies a low-power voltage
to the 1.2V domain, thus preserving the content of registers and internal SRAM.
The voltage regulator can be put either in main regulator mode (MR) or in low-power
mode (LPR). Both modes can be configured by software as follows:
–

–

•
Note:

Normal mode: the 1.2 V domain is preserved in nominal leakage mode. It is the
default mode when the main regulator (MR) or the low-power regulator (LPR) is
enabled.
Under-drive mode: the 1.2 V domain is preserved in reduced leakage mode. This
mode is only available with the main regulator or the low-power regulator mode
(see Table 11).

In Standby mode: the regulator is powered down. The content of the registers and
SRAM are lost except for the Standby circuitry and the backup domain.

Over-drive and under-drive mode are not available when the regulator is bypassed.
For more details, refer to the voltage regulator section in the datasheets.
Table 11. Voltage regulator configuration mode versus device operating mode(1)
Voltage regulator
configuration

Run mode

Sleep mode

Stop mode

Standby mode

Normal mode

MR

MR

MR or LPR

-

MR

MR

-

-

Under-drive mode

-

-

MR or LPR

-

Power-down mode

-

-

-

Yes

Over-drive

mode(2)

1. ‘-’ means that the corresponding configuration is not available.
2. The over-drive mode is not available when VDD = 1.8 to 2.1 V.

RM0385 Rev 7

105/1709
131

Power controller (PWR)

RM0385

Entering Over-drive mode
It is recommended to enter Over-drive mode when the application is not running critical
tasks and when the system clock source is either HSI or HSE. To optimize the configuration
time, enable the Over-drive mode during the PLL lock phase.
To enter Over-drive mode, follow the sequence below:

Note:

1.

Select HSI or HSE as system clock.

2.

Configure RCC_PLLCFGR register and set PLLON bit of RCC_CR register.

3.

Set ODEN bit of PWR_CR1 register to enable the Over-drive mode and wait for the
ODRDY flag to be set in the PWR_CSR1 register.

4.

Set the ODSW bit in the PWR_CR1 register to switch the voltage regulator from
Normal mode to Over-drive mode. The System will be stalled during the switch but the
PLL clock system will be still running during locking phase.

5.

Wait for the ODSWRDY flag in the PWR_CSR1 to be set.

6.

Select the required Flash latency as well as AHB and APB prescalers.

7.

Wait for PLL lock.

8.

Switch the system clock to the PLL.

9.

Enable the peripherals that are not generated by the System PLL (I2S clock, LCD-TFT
clock, SAI1 clock, USB_48MHz clock....).

The PLLI2S and PLLSAI can be configured at the same time as the system PLL.
During the Over-drive switch activation, no peripheral clocks should be enabled. The
peripheral clocks must be enabled once the Over-drive mode is activated.
Entering Stop mode disables the Over-drive mode, as well as the PLL. The application
software has to configure again the Over-drive mode and the PLL after exiting from Stop
mode.

Exiting from Over-drive mode
It is recommended to exit from Over-drive mode when the application is not running critical
tasks and when the system clock source is either HSI or HSE.There are two sequences that
allow exiting from over-drive mode:
•

By resetting simultaneously the ODEN and ODSW bits bit in the PWR_CR1 register
(sequence 1)

•

By resetting first the ODSW bit to switch the voltage regulator to Normal mode and then
resetting the ODEN bit to disable the Over-drive mode (sequence 2).

Example of sequence 1:

106/1709

1.

Select HSI or HSE as system clock source.

2.

Disable the peripheral clocks that are not generated by the System PLL (I2S clock,
LCD-TFT clock, SAI1 clock, USB_48MHz clock,....)

3.

Reset simultaneously the ODEN and the ODSW bits in the PWR_CR1 register to
switch back the voltage regulator to Normal mode and disable the Over-drive mode.

4.

Wait for the ODWRDY flag of PWR_CSR1 to be reset.

RM0385 Rev 7

RM0385

Power controller (PWR)
Example of sequence 2:
1.

Select HSI or HSE as system clock source.

2.

Disable the peripheral clocks that are not generated by the System PLL (I2S clock,
LCD-TFT clock, SAI1 clock, USB_48MHz clock,....).

3.

Reset the ODSW bit in the PWR_CR1 register to switch back the voltage regulator to
Normal mode. The system clock is stalled during voltage switching.

4.

Wait for the ODWRDY flag of PWR_CSR1 to be reset.

5.

Reset the ODEN bit in the PWR_CR1 register to disable the Over-drive mode.

Note:

During step 3, the ODEN bit remains set and the Over-drive mode is still enabled but not
active (ODSW bit is reset). If the ODEN bit is reset instead, the Over-drive mode is disabled
and the voltage regulator is switched back to the initial voltage.

4.2

Power supply supervisor

4.2.1

Power-on reset (POR)/power-down reset (PDR)
The device has an integrated POR/PDR circuitry that allows proper operation starting
from 1.8 V.
The device remains in Reset mode when VDD/VDDA is below a specified threshold,
VPOR/PDR, without the need for an external reset circuit. For more details concerning the
power on/power-down reset threshold, refer to the electrical characteristics of the
datasheet.
Figure 9. Power-on reset/power-down reset waveform
VDD/VDDA

PDR
40 mV
hysteresis

PDR

Temporization
tRSTTEMPO

Reset
MS30431V1

RM0385 Rev 7

107/1709
131

Power controller (PWR)

4.2.2

RM0385

Brownout reset (BOR)
During power on, the Brownout reset (BOR) keeps the device under reset until the supply
voltage reaches the specified VBOR threshold.
VBOR is configured through device option bytes. By default, BOR is off. 3 programmable
VBOR threshold levels can be selected:

Note:

•

BOR Level 3 (VBOR3). Brownout threshold level 3.

•

BOR Level 2 (VBOR2). Brownout threshold level 2.

•

BOR Level 1 (VBOR1). Brownout threshold level 1.

For full details about BOR characteristics, refer to the "Electrical characteristics" section in
the device datasheet.
When the supply voltage (VDD) drops below the selected VBOR threshold, a device reset is
generated.
The BOR can be disabled by programming the device option bytes. In this case, the
power-on and power-down is then monitored by the POR/ PDR (see Section 4.2.1: Poweron reset (POR)/power-down reset (PDR)).
The BOR threshold hysteresis is ~100 mV (between the rising and the falling edge of the
supply voltage).
Figure 10. BOR thresholds
VDD/VDDA

BOR threshold

100 mV
hysteresis

Reset

MS30433V1

4.2.3

Programmable voltage detector (PVD)
The user can use the PVD to monitor the VDD power supply by comparing it to a threshold
selected by the PLS[2:0] bits in the PWR power control register (PWR_CR1).
The PVD is enabled by setting the PVDE bit.
A PVDO flag is available, in the PWR power control/status register (PWR_CSR1), to
indicate if VDD is higher or lower than the PVD threshold. This event is internally connected

108/1709

RM0385 Rev 7

RM0385

Power controller (PWR)
to the EXTI line16 and can generate an interrupt if enabled through the EXTI registers. The
PVD output interrupt can be generated when VDD drops below the PVD threshold and/or
when VDD rises above the PVD threshold depending on EXTI line16 rising/falling edge
configuration. As an example the service routine could perform emergency shutdown tasks.
Figure 11. PVD thresholds
VDD

PVD threshold

100 mV
hysteresis

PVD output

MS30432V2

4.3

Low-power modes
By default, the microcontroller is in Run mode after a system or a power-on reset. In Run
mode the CPU is clocked by HCLK and the program code is executed. Several low-power
modes are available to save power when the CPU does not need to be kept running, for
example when waiting for an external event. It is up to the user to select the mode that gives
the best compromise between low-power consumption, short startup time and available
wakeup sources.
The devices feature three low-power modes:
•

Sleep mode (Cortex®-M7 core stopped, peripherals kept running)

•

Stop mode (all clocks are stopped)

•

Standby mode (1.2 V domain powered off)

In addition, the power consumption in Run mode can be reduce by one of the following
means:
•

Slowing down the system clocks

•

Gating the clocks to the APBx and AHBx peripherals when they are unused.

Entering low-power mode
Low-power modes are entered by the MCU by executing the WFI (Wait For Interrupt), or
WFE (Wait for Event) instructions, or when the SLEEPONEXIT bit in the Cortex®-M7
System Control register is set on Return from ISR.

RM0385 Rev 7

109/1709
131

Power controller (PWR)

RM0385

Entering Low-power mode through WFI or WFE will be executed only if no interrupt is
pending or no event is pending.

Exiting low-power mode
The MCU exits from Sleep and Stop modes low-power mode depending on the way the lowpower mode was entered:
•
If the WFI instruction or Return from ISR was used to enter the low-power mode, any
peripheral interrupt acknowledged by the NVIC can wake up the device.
•

If the WFE instruction is used to enter the low-power mode, the MCU exits the lowpower mode as soon as an event occurs. The wakeup event can be generated either
by:
–

NVIC IRQ interrupt:
When SEVONPEND = 0 in the Cortex®-M7 System Control register: by enabling
an interrupt in the peripheral control register and in the NVIC. When the MCU
resumes from WFE, the peripheral interrupt pending bit and the NVIC peripheral
IRQ channel pending bit (in the NVIC interrupt clear pending register) have to be
cleared. Only NVIC interrupts with sufficient priority will wakeup and interrupt the
MCU.
When SEVONPEND = 1 in the Cortex®-M7 System Control register: by enabling
an interrupt in the peripheral control register and optionally in the NVIC. When the
MCU resumes from WFE, the peripheral interrupt pending bit and when enabled
the NVIC peripheral IRQ channel pending bit (in the NVIC interrupt clear pending
register) have to be cleared. All NVIC interrupts will wakeup the MCU, even the
disabled ones.Only enabled NVIC interrupts with sufficient priority will wakeup and
interrupt the MCU.

–

Event
This is done by configuring a EXTI line in event mode. When the CPU resumes
from WFE, it is not necessary to clear the EXTI peripheral interrupt pending bit or
the NVIC IRQ channel pending bit as the pending bits corresponding to the event
line is not set. It may be necessary to clear the interrupt flag in the peripheral.

The MCU exits from Standby low-power mode through an external reset (NRST pin), an
IWDG reset, a rising edge on one of the enabled WKUPx pins or a RTC event occurs (see
Figure 284: RTC block diagram).
After waking up from Standby mode, program execution restarts in the same way as after a
Reset (boot pin sampling, option bytes loading, reset vector is fetched, etc.).
Only enabled NVIC interrupts with sufficient priority will wakeup and interrupt the MCU.
Table 12. Low-power mode summary
Mode name

Entry

Wakeup

Sleep
(Sleep now
or Sleep-onexit)

WFI

Any interrupt

WFE

Wakeup event

110/1709

Effect on 1.2 V
domain clocks

Effect on
VDD
domain
clocks

Voltage regulator

CPU CLK OFF
no effect on other
clocks or analog
clock sources

None

ON

RM0385 Rev 7

RM0385

Power controller (PWR)
Table 12. Low-power mode summary (continued)

Mode name

Any EXTI line (configured
in the EXTI registers,
internal and external lines)

WKUP pin rising or falling
edge, RTC alarm (Alarm A
PDDS bit +
or Alarm B), RTC Wakeup
SLEEPDEEP bit event, RTC tamper events,
+ WFI or WFE
RTC time stamp event,
external reset in NRST
pin, IWDG reset

HSI and
HSE
oscillators
OFF

All 1.2 V domain
clocks OFF

Voltage regulator

Main regulator or
Low-power
regulator (depends
on PWR power
control register
(PWR_CR1))

OFF

Table 13. Features over all modes (1)
Standby

CPU

Y

-

-

-

-

-

-

Flash access

Y

Y

-

-

-

-

-

DTCM RAM

Y

Y

Y

-

-

-

-

ITCM RAM

Y

Y

Y

-

-

-

-

SRAM1

Y

Y

Y

-

-

-

-

SRAM2

Y

Y

Y

-

-

-

-

FMC

O

O

-

-

-

-

-

QUADSPI

O

O

-

-

-

-

-

Backup Registers

Y

Y

Y

-

Y

-

Y

Backup RAM

Y

Y

Y

-

Y

-

Y

Brown-out reset (BOR)

Y

Y

Y

Y

Y

Y

-

Programmable Voltage
Detector (PVD)

O

O

O

O

-

-

-

High Speed Internal (HSI)

O

O

(2)

-

-

-

-

High Speed External (HSE)

O

O

-

-

-

-

-

Low Speed Internal (LSI)

O

O

O

-

O

-

-

Low Speed External (LSE)

O

O

O

-

O

-

O

RTC

O

O

O

O

O

O

O

RM0385 Rev 7

VBAT

-

Peripheral

Wakeup

-

Wakeup

Stop
Sleep

Standby

SLEEPDEEP bit
+ WFI or WFE

Wakeup

Run

Stop

Entry

Effect on
VDD
domain
clocks

Effect on 1.2 V
domain clocks

111/1709
131

Power controller (PWR)

RM0385
Table 13. Features over all modes (continued)(1)

Number of RTC tamper pins

3

3

3

3

3

3

2

CRC calculation unit

O

O

-

-

-

-

-

GPIOs

Y

Y

Y

Y

-

6 pins

2
tamper

DMA

O

O

-

-

-

-

-

Chrom-Art Accelerator
(DMA2D)

O

O

-

-

-

-

-

LCD-TFT

O

O

-

-

-

-

-

DCMI

O

O

-

-

-

-

-

USARTx (x=1..8)

O

O

-

-

-

-

-

I2Cx (x=1,2,3,4)

O

O

-

-

-

-

-

SPIx (x=1..6)

O

O

-

-

-

-

-

SAIx (x=1,2)

O

O

-

-

-

-

-

SPDIFRX

O

O

-

-

-

-

-

ADCx (x=1,2,3)

O

O

-

-

-

-

-

DACx (x=1,2)

O

O

-

-

-

-

-

Temperature sensor

O

O

-

-

-

-

-

Timers (TIMx)

O

O

-

-

-

-

-

Low-power timer 1 (LPTIM1)

O

O

O

O

-

-

-

Independent watchdog (IWDG)

O

O

O

O

O

O

-

Window watchdog (WWDG)

O

O

-

-

-

-

-

Systick timer

O

O

-

-

-

-

-

Random number generator
(RNG)

O

O

-

-

-

-

-

Cryptographic processor
(CRYP)

O

O

-

-

-

-

-

Hash processor (HASH)

O

O

-

-

-

-

-

SDMMC

O

O

-

-

-

-

-

CANx ( x=1,2)

O

O

-

-

-

-

-

USB OTG FS

O

O

-

O

-

-

-

USB OTG HS

O

O

-

O

-

-

-

Ethernet

O

O

-

O

-

-

-

HDMI-CEC

O

O

-

-

-

-

-

RM0385 Rev 7

VBAT

Wakeup

-

Wakeup

Sleep

-

Peripheral

112/1709

Standby

Run

Stop

RM0385

Power controller (PWR)

1. Legend: Y = Yes (Enable). O = Optional (Disable by default. Can be enabled by software). - = Not
available. Wakeup highlighted in gray.
2. Some peripherals with wakeup from Stop capability can request HSI to be enabled. In this case, HSI is
woken up by the peripheral, and only feeds the peripheral which requested it. HSI is automatically put off
when the peripheral does not need it anymore.

4.3.1

Debug mode
By default, the debug connection is lost when the devices enters in Stop or Standby mode
while the debug features are used. This is due to the fact that the Cortex®-M7 core is no
longer clocked.
However, by setting some configuration bits in the DBGMCU_CR register, the software can
be debugged even when using the low-power modes extensively. For more details, refer to
Section 40.16.1: Debug support for low-power modes.

4.3.2

Run mode
Slowing down system clocks
In Run mode the speed of the system clocks (SYSCLK, HCLK, PCLK1, PCLK2) can be
reduced by programming the prescaler registers. These prescalers can also be used to slow
down peripherals before entering Sleep mode.
For more details refer to Section 5.3.3: RCC clock configuration register (RCC_CFGR).

Peripheral clock gating
In Run mode, the HCLKx and PCLKx for individual peripherals and memories can be
stopped at any time to reduce power consumption.
To further reduce power consumption in Sleep mode the peripheral clocks can be disabled
prior to executing the WFI or WFE instructions.
Peripheral clock gating is controlled by the AHB1 peripheral clock enable register
(RCC_AHB1ENR), AHB2 peripheral clock enable register (RCC_AHB2ENR), AHB3
peripheral clock enable register (RCC_AHB3ENR) (see Section 5.3.10: RCC AHB1
peripheral clock register (RCC_AHB1ENR), Section 5.3.11: RCC AHB2 peripheral clock
enable register (RCC_AHB2ENR), and Section 5.3.12: RCC AHB3 peripheral clock enable
register (RCC_AHB3ENR).
Disabling the peripherals clocks in Sleep mode can be performed automatically by resetting
the corresponding bit in RCC_AHBxLPENR and RCC_APBxLPENR registers.

4.3.3

Low-power mode
Entering low-power mode
Low-power modes are entered by the MCU executing the WFI (Wait For Interrupt), or WFE
(Wait For Event) instructions, or when the SLEEPONEXIT bit in the Cortex®-M7 System
Control register is set on Return from ISR.

RM0385 Rev 7

113/1709
131

Power controller (PWR)

RM0385

Exiting low-power mode
From Sleep and Stop modes the MCU exits low-power mode depending on the way the
mode was entered:
•

If the WFI instruction or Return from ISR was used to enter the low-power mode, any
peripheral interrupt acknowledged by the NVIC can wake up the device

•

If the WFE instruction was used to enter the low-power mode, the MCU exits the mode
as soon as an event occurs. The wakeup event can by generated either by:
–

NVIC IRQ interrupt
- When SEVEONPEND=0 in the Cortex®-M7 System Control register.
By enabling an interrupt in the peripheral control register and in the NVIC. When
the MCU resumes from WFE, the peripheral interrupt pending bit and the NVIC
peripheral IRQ channel pending bit (in the NVIC interrupt clear pending register)
have to be cleared.
Only NVIC interrupts with sufficient priority will wakeup and interrupt the MCU.
- When SEVEONPEND=1 in the Cortex®-M7 System Control register.
By enabling an interrupt in the peripheral control register and optionally in the
NVIC. When the MCU resumes from WFE, the peripheral interrupt pending bit and
(when enabled) the NVIC peripheral IRQ channel pending bit (in the NVIC
interrupt clear pending register) have to be cleared.
All NVIC interrupts will wakeup the MCU, even the disabled ones.
Only enabled NVIC interrupts with sufficient priority will wakeup and interrupt the
MCU.
- Event
Configuring a EXTI line in event mode. When the CPU resumes from WFE, it is
not necessary to clear the EXTI peripheral interrupt pending bit or the NVIC IRQ
channel pending bit as the pending bits corresponding to the event line is not set.
It may be necessary to clear the interrupt flag in the peripheral.

From Standby mode the MCU exits Low-power mode through an external reset (NRST pin),
an IWDG reset, a rising edge on one of the enabled WKUPx pins or a RTC event (see
Figure 284: RTC block diagram).

4.3.4

Sleep mode
I/O states in Sleep mode
In Sleep mode, all I/O pins keep the same state as in Run mode.
Entering Sleep mode
The Sleep mode is entered by executing the WFI (Wait For Interrupt) or WFE (Wait for
Event) instructions. Two options are available to select the Sleep mode entry mechanism,
depending on the SLEEPONEXIT bit in the Cortex®-M7 System Control register:
•

Sleep-now: if the SLEEPONEXIT bit is cleared, the MCU enters Sleep mode as soon
as WFI or WFE instruction is executed.

•

Sleep-on-exit: if the SLEEPONEXIT bit is set, the MCU enters Sleep mode as soon as
it exits the lowest priority ISR.

Refer to Table 14 and Table 15 for details on how to enter Sleep mode.

114/1709

RM0385 Rev 7

RM0385

Power controller (PWR)

Exiting Sleep mode
If the WFI instruction is used to enter Sleep mode, any peripheral interrupt acknowledged by
the nested vectored interrupt controller (NVIC) can wake up the device from Sleep mode.
If the WFE instruction is used to enter Sleep mode, the MCU exits Sleep mode as soon as
an event occurs. The wakeup event can be generated either by:
•

Enabling an interrupt in the peripheral control register but not in the NVIC, and enabling
the SEVONPEND bit in the Cortex®-M7 System Control register. When the MCU
resumes from WFE, the peripheral interrupt pending bit and the peripheral NVIC IRQ
channel pending bit (in the NVIC interrupt clear pending register) have to be cleared.

•

Or configuring an external or internal EXTI line in event mode. When the CPU resumes
from WFE, it is not necessary to clear the peripheral interrupt pending bit or the NVIC
IRQ channel pending bit as the pending bit corresponding to the event line is not set.

This mode offers the lowest wakeup time as no time is wasted in interrupt entry/exit.
Refer to Table 14 and Table 15 for more details on how to exit Sleep mode.
Table 14. Sleep-now entry and exit
Sleep-now mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP = 0, and
– No interrupt (for WFI) or event (for WFE) is pending.
Refer to the Cortex®-M7 System Control register.

Mode entry

On Return from ISR while:
– SLEEPDEEP = 0 and
– SLEEPONEXIT = 1,
– No interrupt is pending.
Refer to the Cortex®-M7 System Control register.

Mode exit

If WFI or Return from ISR was used for entry:
Interrupt: Refer to Table 43: STM32F75xxx and STM32F74xxx vector
table
If WFE was used for entry and SEVONPEND = 0
Wakeup event: Refer to Section 11.3: Wakeup event management
If WFE was used for entry and SEVONPEND = 1
Interrupt even when disabled in NVIC: refer to Table 43: STM32F75xxx
and STM32F74xxx vector table and Wakeup event (see Section 11.3:
Wakeup event management).

Wakeup latency

None

RM0385 Rev 7

115/1709
131

Power controller (PWR)

RM0385
Table 15. Sleep-on-exit entry and exit

Sleep-on-exit

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP = 0, and
– No interrupt (for WFI) or event (for WFE) is pending.
Refer to the Cortex®-M7 System Control register.

4.3.5

Mode entry

On Return from ISR while:
– SLEEPDEEP = 0, and
– SLEEPONEXIT = 1, and
– No interrupt is pending.
Refer to the Cortex®-M7 System Control register.

Mode exit

Interrupt: refer to Table 43: STM32F75xxx and STM32F74xxx vector table

Wakeup latency

None

Stop mode
The Stop mode is based on the Cortex®-M7 deepsleep mode combined with peripheral
clock gating. The voltage regulator can be configured either in normal or low-power mode.
In Stop mode, all clocks in the 1.2 V domain are stopped, the PLLs, the HSI and the HSE
RC oscillators are disabled. Internal SRAM and register contents are preserved.
In Stop mode, the power consumption can be further reduced by using additional settings in
the PWR_CR1 register. However this will induce an additional startup delay when waking up
from Stop mode (see Table 16).
Table 16. Stop operating modes
UDEN[1:0]
bits

MRUDS
bit

LPUDS
bit

STOP MR
(Main Regulator)

-

0

-

0

0

HSI RC startup time

STOP MR- FPD

-

0

-

0

1

HSI RC startup time +
Flash wakeup time from powerdown mode

STOP LP

-

0

0

1

0

HSI RC startup time +
regulator wakeup time from LP
mode

1

HSI RC startup time +
Flash wakeup time from powerdown mode +
regulator wakeup time from LP
mode

Voltage Regulator Mode

Normal
mode

STOP LP-FPD

116/1709

-

-

0

RM0385 Rev 7

LPDS FPDS
bit
bit

1

Wakeup latency

RM0385

Power controller (PWR)
Table 16. Stop operating modes (continued)

Voltage Regulator Mode

STOP UMRFPD

UDEN[1:0]
bits

3

MRUDS
bit

1

LPUDS
bit

-

LPDS FPDS
bit
bit

0

-

HSI RC startup time +
Flash wakeup time from powerdown mode +
Main regulator wakeup time from
under-drive mode + Core logic to
nominal mode

-

HSI RC startup time +
Flash wakeup time from powerdown mode +
regulator wakeup time from LP
under-drive mode + Core logic to
nominal mode

Underdrive
Mode
STOP ULP-FPD

3

-

1

1

Wakeup latency

I/O states in Stop mode
In stop mode, all I/Os pins keep the same state as in the run mode

Entering Stop mode
The Stop mode is entered according to Entering low-power mode, when the SLEEPDEEP
bit in Cortex®-M7 System Control register is set.
Refer to Table 17 for details on how to enter the Stop mode.
When the microcontroller enters in Stop mode, the voltage scale 3 is automatically selected.
To further reduce power consumption in Stop mode, the internal voltage regulator can be put
in low-power or low voltage mode. This is configured by the LPDS, MRUDS, LPUDS and
UDEN bits of the PWR power control register (PWR_CR1).
If Flash memory programming is ongoing, the Stop mode entry is delayed until the memory
access is finished.
If an access to the APB domain is ongoing, The Stop mode entry is delayed until the APB
access is finished.
If the Over-drive mode was enabled before entering Stop mode, it is automatically disabled
during when the Stop mode is activated.
In Stop mode, the following features can be selected by programming individual control bits:
•

Independent watchdog (IWDG): the IWDG is started by writing to its Key register or by
hardware option. Once started it cannot be stopped except by a Reset. See
Section 27.3 in Section 27: Independent watchdog (IWDG).

•

Real-time clock (RTC): this is configured by the RTCEN bit in the RCC backup domain
control register (RCC_BDCR)

•

Internal RC oscillator (LSI RC): this is configured by the LSION bit in the RCC clock
control & status register (RCC_CSR).

•

External 32.768 kHz oscillator (LSE OSC): this is configured by the LSEON bit in the
RCC backup domain control register (RCC_BDCR).

RM0385 Rev 7

117/1709
131

Power controller (PWR)

RM0385

The ADC or DAC can also consume power during the Stop mode, unless they are disabled
before entering it. To disable them, the ADON bit in the ADC_CR2 register and the ENx bit
in the DAC_CR register must both be written to 0.
Note:

Before entering Stop mode, it is recommended to enable the clock security system (CSS)
feature to prevent external oscillator (HSE) failure from impacting the internal MCU
behavior.

Exiting Stop mode
Refer to Table 17 for more details on how to exit Stop mode.
When exiting Stop mode by issuing an interrupt or a wakeup event, the HSI RC oscillator is
selected as system clock.
If the Under-drive mode was enabled, it is automatically disabled after exiting Stop mode.
When the voltage regulator operates in low-power mode, an additional startup delay is
incurred when waking up from Stop mode. By keeping the internal regulator ON during Stop
mode, the consumption is higher although the startup time is reduced.
When the voltage regulator operates in Under-drive mode, an additional startup delay is
induced when waking up from Stop mode.
Table 17. Stop mode entry and exit (STM32F75xxx and STM32F74xxx)
Stop mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– No interrupt (for WFI) or event (for WFE) is pending.
– SLEEPDEEP bit is set in Cortex®-M7 System Control register,
– PDDS bit is cleared in Power Control register (PWR_CR1),
– Select the voltage regulator mode by configuring LPDS, MRUDS, LPUDS
and UDEN bits in PWR_CR (see Table 16: Stop operating modes).

Mode entry

On Return from ISR while:
– No interrupt is pending,
– SLEEPDEEP bit is set in Cortex®-M7 System Control register, and
– SLEEPONEXIT = 1, and
– PDDS is cleared in Power Control register (PWR_CR1).
Note: To enter Stop mode, all EXTI Line pending bits (in Pending register
(EXTI_PR)), all peripheral interrupts pending bits, the RTC Alarm
(Alarm A and Alarm B), RTC wakeup, RTC tamper, and RTC time
stamp flags, must be reset. Otherwise, the Stop mode entry
procedure is ignored and program execution continues.

118/1709

RM0385 Rev 7

RM0385

Power controller (PWR)
Table 17. Stop mode entry and exit (STM32F75xxx and STM32F74xxx) (continued)
Stop mode

4.3.6

Description

Mode exit

If WFI or Return from ISR was used for entry:
All EXTI lines configured in Interrupt mode (the corresponding EXTI
Interrupt vector must be enabled in the NVIC). The interrupt source can
be external interrupts or peripherals with wakeup capability. Refer to
Table 43: STM32F75xxx and STM32F74xxx vector table on page 289.
If WFE was used for entry and SEVONPEND = 0:
All EXTI Lines configured in event mode. Refer to Section 11.3: Wakeup
event management on page 295
If WFE was used for entry and SEVONPEND = 1:
– Any EXTI lines configured in Interrupt mode (even if the corresponding
EXTI Interrupt vector is disabled in the NVIC). The interrupt source can
be external interrupts or peripherals with wakeup capability. Refer to
Table 43: STM32F75xxx and STM32F74xxx vector table on page 289.
– Wakeup event: refer to Section 11.3: Wakeup event management on
page 295.

Wakeup latency

Refer to Table 16: Stop operating modes

Standby mode
The Standby mode allows to achieve the lowest power consumption. It is based on the
Cortex®-M7 deepsleep mode, with the voltage regulator disabled. The 1.2 V domain is
consequently powered off. The PLLs, the HSI oscillator and the HSE oscillator are also
switched off. SRAM and register contents are lost except for registers in the backup domain
(RTC registers, RTC backup register and backup SRAM), and Standby circuitry (see
Figure 5).

Entering Standby mode
The Standby mode is entered according to Entering low-power mode, when the
SLEEPDEEP bit in the Cortex®-M7 System Control register is set.
Refer to Table 18 for more details on how to enter Standby mode.
In Standby mode, the following features can be selected by programming individual control
bits:
•

Independent watchdog (IWDG): the IWDG is started by writing to its Key register or by
hardware option. Once started it cannot be stopped except by a reset. See
Section 27.3 in Section 27: Independent watchdog (IWDG).

•

Real-time clock (RTC): this is configured by the RTCEN bit in the backup domain
control register (RCC_BDCR)

•

Internal RC oscillator (LSI RC): this is configured by the LSION bit in the Control/status
register (RCC_CSR).

•

External 32.768 kHz oscillator (LSE OSC): this is configured by the LSEON bit in the
backup domain control register (RCC_BDCR)

Exiting Standby mode
The microcontroller exits Standby mode when an external Reset (NRST pin), an IWDG
Reset, a rising or falling edge on WKUP pin, an RTC alarm, a tamper event, or a time stamp

RM0385 Rev 7

119/1709
131

Power controller (PWR)

RM0385

event is detected. All registers are reset after wakeup from Standby except for PWR power
control/status register (PWR_CSR1).
After waking up from Standby mode, program execution restarts in the same way as after a
Reset (boot pin sampling, vector reset is fetched, etc.). The SBF status flag in the PWR
power control/status register (PWR_CSR1) indicates that the MCU was in Standby mode.
Refer to Table 18 for more details on how to exit Standby mode.
Table 18. Standby mode entry and exit
Standby mode

Mode entry

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP is set in Cortex®-M7 System Control register,
– PDDS bit is set in Power Control register (PWR_CR1),
– No interrupt (for WFI) or event (for WFE) is pending,
– WUIF bit is cleared in Power Control and Status register (PWR_CSR1),
– the RTC flag corresponding to the chosen wakeup source (RTC Alarm A,
RTC Alarm B, RTC wakeup, Tamper or Timestamp flags) is cleared.
– EIWUP bit is set in Power Control register (PWR_CSR1).
On return from ISR while:
– SLEEPDEEP bit is set in Cortex®-M7 System Control register, and
– SLEEPONEXIT = 1, and
– PDDS bit is set in Power Control register (PWR_CR1), and
– No interrupt is pending,
– WUIF bit is cleared in Power Control and Status register (PWR_CSR1),
– The RTC flag corresponding to the chosen wakeup source (RTC Alarm
A, RTC Alarm B, RTC wakeup, Tamper or Timestamp flags) is cleared.

Mode exit

WKUP pin rising or falling edge, RTC alarm (Alarm A and Alarm B), RTC
wakeup, tamper event, time stamp event, external reset in NRST pin,
IWDG reset.

Wakeup latency

Reset phase.

I/O states in Standby mode
In Standby mode, all I/O pins are high impedance except for:

4.3.7

•

Reset pad (still available)

•

PC13 if configured for tamper, time stamp, RTC Alarm out, or RTC clock calibration out

•

WKUP pins (PA0/PA2/PC1/PC13/PI8/PI11), if enabled

Programming the RTC alternate functions to wake up the device from
the Stop and Standby modes
The MCU can be woken up from a low-power mode by an RTC alternate function.
The RTC alternate functions are the RTC alarms (Alarm A and Alarm B), RTC wakeup, RTC
tamper event detection and RTC time stamp event detection.
These RTC alternate functions can wake up the system from the Stop and Standby lowpower modes.

120/1709

RM0385 Rev 7

RM0385

Power controller (PWR)
The system can also wake up from low-power modes without depending on an external
interrupt (Auto-wakeup mode), by using the RTC alarm or the RTC wakeup events.
The RTC provides a programmable time base for waking up from the Stop or Standby mode
at regular intervals.
For this purpose, two of the three alternate RTC clock sources can be selected by
programming the RTCSEL[1:0] bits in the RCC backup domain control register
(RCC_BDCR):
•

Low-power 32.768 kHz external crystal oscillator (LSE OSC)
This clock source provides a precise time base with a very low-power consumption
(additional consumption of less than 1 µA under typical conditions)

•

Low-power internal RC oscillator (LSI RC)
This clock source has the advantage of saving the cost of the 32.768 kHz crystal. This
internal RC oscillator is designed to use minimum power.

RTC alternate functions to wake up the device from the Stop mode
•

•

•

To wake up the device from the Stop mode with an RTC alarm event, it is necessary to:
a)

Configure the EXTI Line 17 to be sensitive to rising edges (Interrupt or Event
modes)

b)

Enable the RTC Alarm Interrupt in the RTC_CR register

c)

Configure the RTC to generate the RTC alarm

To wake up the device from the Stop mode with an RTC tamper or time stamp event, it
is necessary to:
a)

Configure the EXTI Line 21 to be sensitive to rising edges (Interrupt or Event
modes)

b)

Enable the RTC time stamp Interrupt in the RTC_CR register or the RTC tamper
interrupt in the RTC_TAFCR register

c)

Configure the RTC to detect the tamper or time stamp event

To wake up the device from the Stop mode with an RTC wakeup event, it is necessary
to:
a)

Configure the EXTI Line 22 to be sensitive to rising edges (Interrupt or Event
modes)

b)

Enable the RTC wakeup interrupt in the RTC_CR register

c)

Configure the RTC to generate the RTC Wakeup event

RM0385 Rev 7

121/1709
131

Power controller (PWR)

RM0385

RTC alternate functions to wake up the device from the Standby mode
•

•

•

To wake up the device from the Standby mode with an RTC alarm event, it is necessary
to:
a)

Enable the RTC alarm interrupt in the RTC_CR register

b)

Configure the RTC to generate the RTC alarm

c)

Enable the RTC internal wakeup event from standby by setting the EIWUP bit in
the PWR_CSR1 register

To wake up the device from the Standby mode with an RTC tamper or time stamp
event, it is necessary to:
a)

Enable the RTC time stamp interrupt in the RTC_CR register or the RTC tamper
interrupt in the RTC_TAFCR register

b)

Configure the RTC to detect the tamper or time stamp event

c)

Enable the RTC internal wakeup event from standby by setting the EIWUP bit in
the PWR_CSR1 register

To wake up the device from the Standby mode with an RTC wakeup event, it is
necessary to:
a)

Enable the RTC wakeup interrupt in the RTC_CR register

b)

Configure the RTC to generate the RTC wakeup event

c)

Enable the RTC internal wakeup event from standby by setting the EIWUP bit in
the PWR_CSR1 register

Safe RTC alternate function wakeup flag clearing sequence
To avoid bouncing on the pins onto which the RTC alternate functions are mapped, and exit
correctly from the Stop and Standby modes, it is recommended to follow the sequence
below before entering the Standby mode:
•

•

•

•

122/1709

When using RTC alarm to wake up the device from the low-power modes:
a)

Disable the RTC alarm interrupt (ALRAIE or ALRBIE bits in the RTC_CR register)

b)

Clear the RTC alarm (ALRAF/ALRBF) flag

c)

Enable the RTC alarm interrupt

d)

Re-enter the low-power mode

When using RTC wakeup to wake up the device from the low-power modes:
a)

Disable the RTC Wakeup interrupt (WUTIE bit in the RTC_CR register)

b)

Enable the RTC Wakeup interrupt

c)

Re-enter the low-power mode

When using RTC tamper to wake up the device from the low-power modes:
a)

Disable the RTC tamper interrupt (TAMPIE bit in the RTC_TAFCR register)

b)

Clear the Tamper (TAMP1F/TSF) flag

c)

Enable the RTC tamper interrupt

d)

Re-enter the low-power mode

When using RTC time stamp to wake up the device from the low-power modes:
a)

Disable the RTC time stamp interrupt (TSIE bit in RTC_CR)

b)

Clear the RTC time stamp (TSF) flag

c)

Enable the RTC TimeStamp interrupt

d)

Re-enter the low-power mode
RM0385 Rev 7

RM0385

Power controller (PWR)

4.4

Power control registers

4.4.1

PWR power control register (PWR_CR1)
Address offset: 0x00
Reset value: 0x0000 C000 (reset by wakeup from Standby mode)

31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
Res.

25

24

Res.

Res.

23
Res.

22
Res.

21
Res.

20
Res.

19

UDEN[1:0]
rw

15

14

VOS[1:0]
rw

rw

13

12

ADCDC1 Res.
rw

11

10

9

8

MRUDS

LPUDS

FPDS

DBP

rw

rw

rw

rw

7

6

5

PLS[2:0]
rw

rw

rw

18

rw

17

16

ODSWE
ODEN
N
rw

rw

4

3

2

1

0

PVDE

CSBF

Res.

PDDS

LPDS

rw

rc_w1

rw

rw

Bits 31:20 Reserved, must be kept at reset value.
Bits 19:18 UDEN[1:0]: Under-drive enable in stop mode
These bits are set by software. They allow to achieve a lower power consumption in Stop
mode but with a longer wakeup time.
When set, the digital area has less leakage consumption when the device enters Stop mode.
00: Under-drive disable
01: Reserved
10: Reserved
11:Under-drive enable
Bit 17 ODSWEN: Over-drive switching enabled.
This bit is set by software. It is cleared automatically by hardware after exiting from Stop
mode or when the ODEN bit is reset. When set, It is used to switch to Over-drive mode.
To set or reset the ODSWEN bit, the HSI or HSE must be selected as system clock.
The ODSWEN bit must only be set when the ODRDY flag is set to switch to Over-drive
mode.
0: Over-drive switching disabled
1: Over-drive switching enabled
Note: On any over-drive switch (enabled or disabled), the system clock will be stalled during
the internal voltage set up.
Bit 16 ODEN: Over-drive enable
This bit is set by software. It is cleared automatically by hardware after exiting from Stop
mode. It is used to enabled the Over-drive mode in order to reach a higher frequency.
To set or reset the ODEN bit, the HSI or HSE must be selected as system clock. When the
ODEN bit is set, the application must first wait for the Over-drive ready flag (ODRDY) to be
set before setting the ODSWEN bit.
0: Over-drive disabled
1: Over-drive enabled

RM0385 Rev 7

123/1709
131

Power controller (PWR)

RM0385

Bits 15:14 VOS[1:0]: Regulator voltage scaling output selection
These bits control the main internal voltage regulator output voltage to achieve a trade-off
between performance and power consumption when the device does not operate at the
maximum frequency (refer to the STM32F75xxx and STM32F74xxx datasheets for more
details).
These bits can be modified only when the PLL is OFF. The new value programmed is active
only when the PLL is ON. When the PLL is OFF, the voltage scale 3 is automatically
selected.
00: Reserved (Scale 3 mode selected)
01: Scale 3 mode
10: Scale 2 mode
11: Scale 1 mode (reset value)
Bit 13 ADCDC1:
0: No effect.
1: Refer to AN4073 for details on how to use this bit.
Note: This bit can only be set when operating at supply voltage range 2.7 to 3.6V.
Bit 12 Reserved, must be kept at reset value.
Bit 11 MRUDS: Main regulator in deepsleep under-drive mode
This bit is set and cleared by software.
0: Main regulator ON when the device is in Stop mode
1: Main Regulator in under-drive mode and Flash memory in power-down when the device is
in Stop under-drive mode.
Bit 10 LPUDS: Low-power regulator in deepsleep under-drive mode
This bit is set and cleared by software.
0: Low-power regulator ON if LPDS bit is set when the device is in Stop mode
1: Low-power regulator in under-drive mode if LPDS bit is set and Flash memory in powerdown when the device is in Stop under-drive mode.
Bit 9 FPDS: Flash power-down in Stop mode
When set, the Flash memory enters power-down mode when the device enters Stop mode.
This allows to achieve a lower consumption in stop mode but a longer restart time.
0: Flash memory not in power-down when the device is in Stop mode
1: Flash memory in power-down when the device is in Stop mode
Bit 8 DBP: Disable backup domain write protection
In reset state, the RCC_BDCR register, the RTC registers (including the backup registers),
and the BRE bit of the PWR_CSR1 register, are protected against parasitic write access. This
bit must be set to enable write access to these registers.
0: Access to RTC and RTC Backup registers and backup SRAM disabled
1: Access to RTC and RTC Backup registers and backup SRAM enabled

124/1709

RM0385 Rev 7

RM0385

Power controller (PWR)

Bits 7:5 PLS[2:0]: PVD level selection
These bits are written by software to select the voltage threshold detected by the Power
Voltage Detector
000: 2.0 V
001: 2.1 V
010: 2.3 V
011: 2.5 V
100: 2.6 V
101: 2.7 V
110: 2.8 V
111: 2.9 V
Note: Refer to the electrical characteristics of the datasheet for more details.
Bit 4 PVDE: Power voltage detector enable
This bit is set and cleared by software.
0: PVD disabled
1: PVD enabled
Bit 3 CSBF: Clear standby flag
This bit is always read as 0.
0: No effect
1: Clear the SDF Standby Flag (write)
Bit 2 Reserved, must be kept at reset value
Bit 1 PDDS: Power-down deepsleep
This bit is set and cleared by software. It works together with the LPDS bit.
0: Enter Stop mode when the CPU enters deepsleep. The regulator status depends on the
LPDS bit.
1: Enter Standby mode when the CPU enters deepsleep.
Bit 0 LPDS: Low-power deepsleep
This bit is set and cleared by software. It works together with the PDDS bit.
0:Main voltage regulator ON during Stop mode
1: Low-power voltage regulator ON during Stop mode

4.4.2

PWR power control/status register (PWR_CSR1)
Address offset: 0x04
Reset value: 0x0000 0000 (not reset by wakeup from Standby mode)
Additional APB cycles are needed to read this register versus a standard APB read.

31

30

29

28

27

26

25

24

23

22

21

20

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rc_w1

rc_w1

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

VOS
RDY

Res.

Res.

Res.

Res.

BRE

EIWUP

Res.

Res.

Res.

Res.

BRR

PVDO

SBF

WUIF

rw

rw

r

r

r

r

r

RM0385 Rev 7

19

18

UDRDY[1:0]

17

16

ODSWRDY ODRDY

125/1709
131

Power controller (PWR)

RM0385

Bits 31:20 Reserved, must be kept at reset value.
Bits 19:18 UDRDY[1:0]: Under-drive ready flag
These bits are set by hardware when MCU enters stop Under-drive mode and exits. When
the Under-drive mode is enabled, these bits are not set as long as the MCU has not entered
stop mode yet. they are cleared by programming them to 1.
00: Under-drive is disabled
01: Reserved
10: Reserved
11:Under-drive mode is activated in Stop mode.
Bit 17 ODSWRDY: Over-drive mode switching ready
0: Over-drive mode is not active.
1: Over-drive mode is active on digital area on 1.2 V domain
Bit 16 ODRDY: Over-drive mode ready
0: Over-drive mode not ready.
1: Over-drive mode ready
Bit 14 VOSRDY: Regulator voltage scaling output selection ready bit
0: Not ready
1: Ready
Bits 13:10 Reserved, must be kept at reset value.
Bit 9 BRE: Backup regulator enable
When set, the Backup regulator (used to maintain backup SRAM content in Standby and
VBAT modes) is enabled. If BRE is reset, the backup regulator is switched off. The backup
SRAM can still be used but its content will be lost in the Standby and VBAT modes. Once set,
the application must wait that the Backup Regulator Ready flag (BRR) is set to indicate that
the data written into the RAM will be maintained in the Standby and VBAT modes.
0: Backup regulator disabled
1: Backup regulator enabled
Note: This bit is not reset when the device wakes up from Standby mode, by a system reset,
or by a power reset.
Bit 8 EIWUP: Enable internal wakeup
This bit must be set when RTC events (Alarm A or Alarm B, RTC Tamper, RTC TimeStamp
or RTC Wakeup time) are used to wake up the system from Standby mode.
This bit is always read as 0.
0: Disable internal wakeup sources (RTC events) during Standby mode
1: Enable internal wakeup sources (RTC events) during Standby mode
Bits 7:4 Reserved, must be kept at reset value.
Bit 3 BRR: Backup regulator ready
Set by hardware to indicate that the Backup Regulator is ready.
0: Backup Regulator not ready
1: Backup Regulator ready
Note: This bit is not reset when the device wakes up from Standby mode or by a system reset
or power reset.

126/1709

RM0385 Rev 7

RM0385

Power controller (PWR)

Bit 2 PVDO: PVD output
This bit is set and cleared by hardware. It is valid only if PVD is enabled by the PVDE bit.
0: VDD is higher than the PVD threshold selected with the PLS[2:0] bits.
1: VDD is lower than the PVD threshold selected with the PLS[2:0] bits.
Note: The PVD is stopped by Standby mode. For this reason, this bit is equal to 0 after
Standby or reset until the PVDE bit is set.
Bit 1 SBF: Standby flag
This bit is set by hardware and cleared only by a POR/PDR (power-on reset/power-down
reset) or by setting the CSBF bit in the PWR power control register (PWR_CR1)
0: Device has not been in Standby mode
1: Device has been in Standby mode
Bit 0 WUIF: Wakeup internal flag
This bit is set when a wakeup is detected on the internal wakeup line in standby mode. It is
cleared when all internal wakeup sources are cleared.
0: No wakeup internal event occurred
1: A wakeup event was detected from the RTC alarm (Alarm A or Alarm B), RTC Tamper
event, RTC TimeStamp event or RTC Wakeup

4.4.3

PWR power control/status register 2 (PWR_CR2)
Address offset: 0x08
Reset value: 0x0000 0000 (not reset by wakeup from Standby mode)

31

30

Res. Res.

15

14

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

9

8

23

22

Res. Res.

7

6

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

5

4

3

2

1

0

Res. Res. WUPP6 WUPP5 WUPP4 WUPP3 WUPP2 WUPP1 Res. Res. CWUPF6 CWUPF5 CWUPF4 CWUPF3 CWUPF2 CWUPF1
rw

rw

rw

rw

rw

rw

r

r

r

r

r

r

Bits 31:14 Reserved, always read as 0.
Bit 13 WUPP6: Wakeup pin polarity bit for PI11
These bits define the polarity used for event detection on external wake-up pin PI11.
0: Detection on rising edge
1: Detection on falling edge
Bit 12 WUPP5: Wakeup pin polarity bit for PI8
These bits define the polarity used for event detection on external wake-up pin PI8.
0: Detection on rising edge
1: Detection on falling edge
Bit 11 WUPP4: Wakeup pin polarity bit for PC13
These bits define the polarity used for event detection on external wake-up pin PC13.
0: Detection on rising edge
1: Detection on falling edge
Bit 10 WUPP3: Wakeup pin polarity bit for PC1
These bits define the polarity used for event detection on external wake-up pin PC1.
0: Detection on rising edge
1: Detection on falling edge

RM0385 Rev 7

127/1709
131

Power controller (PWR)

RM0385

Bit 9 WUPP2: Wakeup pin polarity bit for PA2
These bits define the polarity used for event detection on external wake-up pin PA2.
0: Detection on rising edge
1: Detection on falling edge
Bit 8 WUPP1: Wakeup pin polarity bit for PA0
These bits define the polarity used for event detection on external wake-up pin PA0.
0: Detection on rising edge
1: Detection on falling edge
Bits 7:6 Reserved, always read as 0
Bit 5 CWUPF6: Clear Wakeup Pin flag for PI11
These bits are always read as 0
0: No effect
1: Clear the WUPF Wakeup Pin flag after 2 System clock cycles.
Bit 4 CWUPF5: Clear Wakeup Pin flag for PI8
These bits are always read as 0
0: No effect
1: Clear the WUPF Wakeup Pin flag after 2 System clock cycles.
Bit 3 CWUPF4: Clear Wakeup Pin flag for PC13
These bits are always read as 0
0: No effect
1: Clear the WUPF Wakeup Pin flag after 2 System clock cycles.
Bit 2 CWUPF3: Clear Wakeup Pin flag for PC1
These bits are always read as 0
0: No effect
1: Clear the WUPF Wakeup Pin flag after 2 System clock cycles.
Bit 1 CWUPF2: Clear Wakeup Pin flag for PA2
These bits are always read as 0
0: No effect
1: Clear the WUPF Wakeup Pin flag after 2 System clock cycles.
Bit 0 CWUPF1: Clear Wakeup Pin flag for PA0
These bits are always read as 0
0: No effect
1: Clear the WUPF Wakeup Pin flag after 2 System clock cycles.

128/1709

RM0385 Rev 7

RM0385

Power controller (PWR)

4.4.4

PWR power control register 2 (PWR_CSR2)
Address offset: 0x0C
Reset value: 0x0000 0000 (reset by wakeup from Standby mode, except wakeup flags
which are reset by RESET pin)
Additional APB cycles are needed to read this register versus a standard APB read.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

WUPF2

WUPF1

r

r

EWUP6 EWUP5 EWUP4 EWUP3 EWUP2 EWUP1
rw

rw

rw

rw

rw

Res.

rw

Res. WUPF6 WUPF5 WUPF4 WUPF3
r

r

r

r

Bits 31:14 Reserved, always read as 0.
Bit 13 EWUP6: Enable Wakeup pin for PI11
This bit is set and cleared by software.
0: An event on WKUP pin PI11 does not wake-up the device from Standby mode.
1: A rising or falling edge on WKUP pin PI11 wakes-up the system from Standby mode.
Bit 12 EWUP5: Enable Wakeup pin for PI8
This bit is set and cleared by software.
0: An event on WKUP pin PI8 does not wake-up the device from Standby mode.
1: A rising or falling edge on WKUP pin PI8 wakes-up the system from Standby mode.
Bit 11 EWUP4: Enable Wakeup pin for PC13
This bit is set and cleared by software.
0: An event on WKUP pin PC13 does not wake-up the device from Standby mode.
1: A rising or falling edge on WKUP pin PC13 wakes-up the system from Standby mode.
Bit 10 EWUP3: Enable Wakeup pin for PC1
This bit is set and cleared by software.
0: An event on WKUP pin PC1 does not wake-up the device from Standby mode.
1: A rising or falling edge on WKUP pin PC1 wakes-up the system from Standby mode.
Bit 9 EWUP2: Enable Wakeup pin for PA2
This bit is set and cleared by software.
0: An event on WKUP pin PA2 does not wake-up the device from Standby mode.
1: A rising or falling edge on WKUP pin PA2 wakes-up the system from Standby mode.
Bit 8 EWUP1: Enable Wakeup pin for PA0
This bit is set and cleared by software.
0: An event on WKUP pin PA0 does not wake-up the device from Standby mode.
1: A rising or falling edge on WKUP pin PA0 wakes-up the system from Standby mode.
Bits 7:6 Reserved, always read as 0

RM0385 Rev 7

129/1709
131

Power controller (PWR)

RM0385

Bit 5 WUPF6: Wakeup Pin flag for PI11
This bit is set by hardware and cleared only by a Reset pin or by setting the CWUPF6 bit in
the PWR power control register 2 (PWR_CR2).
0: No Wakeup event occured
1: A wakeup event is detected on WKUP PI11
Note: An additional wakeup event is detected if WKUP pin is enabled (by setting the EWUP6
bit) when WKUP pin PI11 level is already high.
Bit 4 WUPF5: Wakeup Pin flag for PI8
This bit is set by hardware and cleared only by a Reset pin or by setting the CWUPF5 bit in
the PWR power control register 2 (PWR_CR2).
0: No Wakeup event occured
1: A wakeup event is detected on WKUP PI8
Note: An additional wakeup event is detected if WKUP pin is enabled (by setting the EWUP5
bit) when WKUP pin PI8 level is already high.
Bit 3 WUPF4: Wakeup Pin flag for PC13
This bit is set by hardware and cleared only by a Reset pin or by setting the CWUPF4 bit in
the PWR power control register 2 (PWR_CR2).
0: No Wakeup event occured
1: A wakeup event is detected on WKUP PC13
Note: An additional wakeup event is detected if WKUP pin is enabled (by setting the EWUP4
bit) when WKUP pin PC13 level is already high.
Bit 2 WUPF3: Wakeup Pin flag for PC1
This bit is set by hardware and cleared only by a Reset pin or by setting the CWUPF3 bit in
the PWR power control register 2 (PWR_CR2).
0: No Wakeup event occured
1: A wakeup event is detected on WKUP PC1
Note: An additional wakeup event is detected if WKUP pin is enabled (by setting the EWUP3
bit) when WKUP pin PC1 level is already high.
Bit 1 WUPF2: Wakeup Pin flag for PA2
This bit is set by hardware and cleared only by a Reset pin or by setting the CWUPF2 bit in
the PWR power control register 2 (PWR_CR2).
0: No Wakeup event occured
1: A wakeup event is detected on WKUP PA2
Note: An additional wakeup event is detected if WKUP pin is enabled (by setting the EWUP2
bit) when WKUP pin PA2 level is already high.
Bit 0 WUPF1: Wakeup Pin flag for PA0
This bit is set by hardware and cleared only by a Reset pin or by setting the CWUPF1 bit in
the PWR power control register 2 (PWR_CR2).
0: No Wakeup event occured
1: A wakeup event is detected on WKUP PA0
Note: An additional wakeup event is detected if WKUP pin is enabled (by setting the EWUP1
bit) when WKUP pin PA0 level is already high.

130/1709

RM0385 Rev 7

0x00C
PWR_CSR2

RM0385 Rev 7
WUPP4
WUPP3
WUPP2
WUPP1

0
0
0
0
0

EWUP4
EWUP3
EWUP2
EWUP1

0
0
0
0
0
0

CWUPF5
CWUPF4
CWUPF3
CWUPF2
CWUPF1

0
0
0
0
0
0

WUPF5
WUPF4
WUPF3
WUPF2
WUPF1

Res.

LPUDS
FPDS
DBP
0
0
0

Res.

Res.
Res.
Res.

SBF
WUIF

PDDS
LPDS

Res.

CSBF
0
PVDO

0
BRR

PVDE

PLS[2:0]

Res.

EIWUP

MRUDS

0

Res.

Res.

ADCDC1

0

0
CWUPF6

Res.

1

0

Res.

VOSRDY

1
BRE

0

WUPF6

0
Res.

1

VOS[1:0]

ODEN
1

Res.

UDEN[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

WUPP5

Res.

1

Res.

WUPP6

Res.
0

EWUP5

Res.

Reset value

EWUP6

Reset value
Res.

0

Res.

ODRDY

0

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

PWR_CR1
Res.

Register

ODSWEN

ODSWRDY

0

Res.

1

Res.

UDRDY[1:0]

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PWR_CR2

Res.

0x008
PWR_CSR1

Res.

0x004

Res.

0x000

Res.

Offset

Res.

4.5

Res.

RM0385
Power controller (PWR)

PWR register map

The following table summarizes the PWR registers.
Table 19. PWR - register map and reset values

0
0

0
0
0
0

0
0
0
0
0
0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

131/1709

131

Reset and clock control (RCC)

RM0385

5

Reset and clock control (RCC)

5.1

Reset
There are three types of reset, defined as system Reset, power Reset and backup domain
Reset.

5.1.1

System reset
A system reset sets all registers to their reset values except the reset flags in the clock
controller CSR register and the registers in the Backup domain (see Figure 12).
A system reset is generated when one of the following events occurs:
1.

A low level on the NRST pin (external reset)

2.

Window watchdog end of count condition (WWDG reset)

3.

Independent watchdog end of count condition (IWDG reset)

4.

A software reset (SW reset) (see Software reset)

5.

Low-power management reset (see Low-power management reset)

Software reset
The reset source can be identified by checking the reset flags in the RCC clock control &
status register (RCC_CSR).
The SYSRESETREQ bit in Cortex®-M7 Application Interrupt and Reset Control Register
must be set to force a software reset on the device. Refer to the Cortex®-M7 technical
reference manual for more details.

Low-power management reset
There are two ways of generating a low-power management reset:
1.

Reset generated when entering the Standby mode:
This type of reset is enabled by resetting the nRST_STDBY bit in the user option bytes.
In this case, whenever a Standby mode entry sequence is successfully executed, the
device is reset instead of entering the Standby mode.

2.

Reset when entering the Stop mode:
This type of reset is enabled by resetting the nRST_STOP bit in the user option bytes.
In this case, whenever a Stop mode entry sequence is successfully executed, the
device is reset instead of entering the Stop mode.

5.1.2

Power reset
A power reset is generated when one of the following events occurs:
1.

Power-on/power-down reset (POR/PDR reset) or brownout (BOR) reset

2.

When exiting the Standby mode

A power reset sets all registers to their reset values except the Backup domain (see
Figure 12)
These sources act on the NRST pin and it is always kept low during the delay phase. The
RESET service routine vector is fixed at address 0x0000_0004 in the memory map.

132/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)
The system reset signal provided to the device is output on the NRST pin. The pulse
generator guarantees a minimum reset pulse duration of 20 µs for each internal reset
source. In case of an external reset, the reset pulse is generated while the NRST pin is
asserted low.
Figure 12. Simplified diagram of the reset circuit
VDD/VDDA

RPU
External
reset

System reset

Filter

NRST
Pulse
generator
(min 20 μs)

WWDG reset
IWDG reset
Power reset
Software reset
Low-power management reset
ai16095c

The Backup domain has two specific resets that affect only the Backup domain (see
Figure 12).

5.1.3

Backup domain reset
The backup domain reset sets all RTC registers and the RCC_BDCR register to their reset
values. The BKPSRAM is not affected by this reset. The only way of resetting the
BKPSRAM is through the Flash interface by requesting a protection level change from 1 to
0.
A backup domain reset is generated when one of the following events occurs:

5.2

1.

Software reset, triggered by setting the BDRST bit in the RCC backup domain control
register (RCC_BDCR).

2.

VDD or VBAT power on, if both supplies have previously been powered off.

Clocks
Three different clock sources can be used to drive the system clock (SYSCLK):
•

HSI oscillator clock

•

HSE oscillator clock

•

Main PLL (PLL) clock

The devices have the two following secondary clock sources:
•

32 kHz low-speed internal RC (LSI RC) which drives the independent watchdog and,
optionally, the RTC used for Auto-wakeup from the Stop/Standby mode.

•

32.768 kHz low-speed external crystal (LSE crystal) which optionally drives the RTC
clock (RTCCLK)

Each clock source can be switched on or off independently when it is not used, to optimize
power consumption.

RM0385 Rev 7

133/1709
198

Reset and clock control (RCC)

RM0385
Figure 13. Clock tree
Peripheral
clock enable

LSI

LPTimer clock
Peripheral
clock enable

LSE
HSI
SYSCLK
PCLKx

USART clocks
Peripheral
clock enable
I2C clocks

LSI

LSI RC
32 kHz
OSC32_IN
OSC32_OUT
MCO2

RTCSEL[1:0]

LSE OSC
32.768 kHz

RTCCLK
PLL48CLK

SYSCLK
PLLI2S

HSE_RTC

Peripheral
clock enable

Clock enable
216 MHz max.

HSI
/8

SW
HSI
HSE

SYSCLK
216 MHz
max

HSE

4-26 MHz
HSE OSC

HCLK
to AHB bus, core,
memory and DMA
to Cortex System timer
FCLK Cortex
free-running clock

AHB
PRESC
/1,2,..512

PLLCLK

OSC_IN

HDMI-CEC clock
Ethernet PTP clock

/488

OSC_OUT

To RTC
SDMMC clock

Peripheral
clock enable

/1 to 5

16 MHz
HSI RC

IWDGCLK
To Independent watchdog

LSE

/2 to 31

LSE
MCO1

RTC
enable

LSE

/1 to 5

Watchdog
enable

Peripheral
clock enable
APBx
PRESC
/1,2,4,8,16

APBx peripheral clocks
Peripheral
clock enable

if (APBx presc =
1x1 else x2

APBx timer clocks

/M
VCO
xN

PLL

VCO
xN

PLLI2S

Peripheral
clock enable

/P

PLLQ

/Q

PLL48CLK
Peripheral
clock enable

SPDIF-Rx Clock

/P

I2SSRC

/Q

SAI1 clock

DIV
Peripheral
clock enable

PLLSAIP

SAI2 clock

/P

PLLSAIQ
xN

I2S Clock
Peripheral
clock enable

Ext. clock
PLLI2SQ

PLLSAI

/Q
/R

PLLLSAIR

DIV
DIV

LTDC Clock

LCD-TFT clock

MACTXCLK
MII_RMII_SEL in SYSCFG_PMC to Ethernet MAC

/2,20

Peripheral
clock enable

ETH_MII_RX_CLK_MII

USB2.0 PHY
24 to 60 MHz

Peripheral
clock enable
Peripheral
clock enable

ETH_MII_TX_CLK_MII
PHY Ethernet
25 to 50 MHz

Peripheral
clock enable

PLLI2SR

/R

I2S_CKIN

VCO

USB & RNG Clock

/R

Peripheral
clock enable
Peripheral
clock enable

OTG_HS_ULPI_CK

MACRXCLK

MACRMIICLK
USBHS
ULPI clock
MSv35914V2

1. For full details about the internal and external clock source characteristics, refer to the Electrical characteristics section in
the device datasheet.
2. When TIMPRE bit of the RCC_DKCFGR1 register is reset, if APBx prescaler is 1, then TIMxCLK = PCLKx, otherwise
TIMxCLK = 2x PCLKx.
3. When TIMPRE bit in the RCC_DCKCFGR1 register is set, if APBx prescaler is 1,2 or 4, then TIMxCLK = HCLK, otherwise
TIMxCLK = 4x PCLKx.

134/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)
The clock controller provides a high degree of flexibility to the application in the choice of the
external crystal or the oscillator to run the core and peripherals at the highest frequency
All peripheral clocks are derived from their bus clock (HCLK,PLCK1, PCLK2) except for:
•

•

•

•

The 48MHz clock, used for USB OTG FS, SDMMC and RNG. This clock is derived
from one of the following sources:
–

main PLL VCO (PLLQ Clock)

–

PLLSAI VCO (PLLSAI clock)

The U(S)ARTs clocks which are derived from one of the following sources:
–

System clock (SYSCLK)

–

HSI clock

–

LSE clock

–

APB1 or APB2 clock (PCLK1 or PCLK2 depending on which APB is mapped the
U(S)ART)

The I2Cs clocks which are derived from one of the following sources:
–

System clock (SYSCLK)

–

HSI clock

–

APB1 clock (PCLK1)

I2S clock
To achieve high-quality audio performance, the I2S clock can be derived either from a
specific PLL (PLLI2S) or from an external clock mapped on the I2S_CKIN pin. For
more information about I2S clock frequency and precision, refer to Section 32.7.5:
Clock generator.

•

•

The SAI1 and SAI2 clocks which are derived from one of the following sources:
–

PLLSAI VCO (PLLSAIQ)

–

PLLI2S VCO ( PLLI2SQ)

–

External clock mapped on the I2S_CKIN pin.

LTDC clock
The LTDC clock is generated from a specific PLL (PLLSAI).

•

The low-power timer (LPTIM1) clock which is derived from one of the following
sources:
–

LSI clock

–

LSE clock

–

HSI clock

–

APB1 clock (PCLK1)

–

External clock mapped on LPTIM1_IN1

•

The USB OTG HS (60 MHz) clock which is provided from the external PHY

•

The Ethernet MAC clocks (TX, RX and RMII) which are provided from the external
PHY. For further information on the Ethernet configuration, refer to Section 38.4.4:
MII/RMII selection in the Ethernet peripheral description. When the Ethernet is used,
the AHB clock frequency must be at least 25 MHz.

•

SPDIFRX clock: which is generated from PLLI2SP VCO.

•

The HDMI-CEC clock which is derived from one of the following sources:
–

LSE clock

–

HSI clock divided by 488
RM0385 Rev 7

135/1709
198

Reset and clock control (RCC)
•

RM0385

The RTC clock which is derived from one of the following sources:
–

LSE clock

–

LSI clock

–

HSE clock divided by 32

•

The IWDG clock which is always the LSI clock.

•

The timer clock frequencies are automatically set by hardware. There are two cases
depending on the value of TIMPRE bit in RCC_CFGR register:
–

If TIMPRE bit in RCC_DKCFGR1 register is reset:
If the APB prescaler is configured to a division factor of 1, the timer clock
frequencies (TIMxCLK) are set to PCLKx. Otherwise, the timer clock frequencies
are twice the frequency of the APB domain to which the timers are connected:
TIMxCLK = 2xPCLKx.

–

If TIMPRE bit in RCC_DKCFGR1 register is set:
If the APB prescaler is configured to a division factor of 1, 2 or 4, the timer clock
frequencies (TIMxCLK) are set to HCLK. Otherwise, the timer clock frequencies is
four times the frequency of the APB domain to which the timers are connected:
TIMxCLK = 4xPCLKx.

The RCC feeds the external clock of the Cortex System Timer (SysTick) with the AHB clock
(HCLK) divided by 8. The SysTick can work either with this clock or with the Cortex clock
(HCLK), configurable in the SysTick control and status register.
FCLK acts as Cortex®-M7 free-running clock. For more details, refer to the Cortex®-M7
technical reference manual.

5.2.1

HSE clock
The high speed external clock signal (HSE) can be generated from two possible clock
sources:
•

HSE external crystal/ceramic resonator

•

HSE external user clock

The resonator and the load capacitors have to be placed as close as possible to the
oscillator pins in order to minimize output distortion and startup stabilization time. The
loading capacitance values must be adjusted according to the selected oscillator.

136/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)
Figure 14. HSE/ LSE clock sources
-

Hardware configuration

OSC_OUT

External clock
(HI-Z)
External clock
source
MSv42094V1

OSC_IN

OSC_OUT

Crystal/ceramic
resonators

CL1

Load
capacitors

CL2
MSv42081V1

External source (HSE bypass)
In this mode, an external clock source must be provided. This mode is selected by setting
the HSEBYP and HSEON bits in the RCC clock control register (RCC_CR). The external
clock signal (square, sinus or triangle) with ~50% duty cycle has to drive the OSC_IN pin
while the OSC_OUT pin should be left HI-Z. See Figure 14.

External crystal/ceramic resonator (HSE crystal)
The HSE has the advantage of producing a very accurate rate on the main clock.
The associated hardware configuration is shown in Figure 14. Refer to the electrical
characteristics section of the datasheet for more details.
The HSERDY flag in the RCC clock control register (RCC_CR) indicates if the high-speed
external oscillator is stable or not. At startup, the clock is not released until this bit is set by
hardware. An interrupt can be generated if enabled in the RCC clock interrupt register
(RCC_CIR).
The HSE Crystal can be switched on and off using the HSEON bit in the RCC clock control
register (RCC_CR).

5.2.2

HSI clock
The HSI clock signal is generated from an internal 16 MHz RC oscillator and can be used
directly as a system clock, or used as PLL input.
The HSI RC oscillator has the advantage of providing a clock source at low cost (no external
components). It also has a faster startup time than the HSE crystal oscillator however, even
RM0385 Rev 7

137/1709
198

Reset and clock control (RCC)

RM0385

with calibration the frequency is less accurate than an external crystal oscillator or ceramic
resonator.

Calibration
RC oscillator frequencies can vary from one chip to another due to manufacturing process
variations, this is why each device is factory calibrated by ST for 1% accuracy at TA= 25 °C.
After reset, the factory calibration value is loaded in the HSICAL[7:0] bits in the RCC clock
control register (RCC_CR).
If the application is subject to voltage or temperature variations this may affect the RC
oscillator speed. The HSI frequency can be trimmed in the application using the
HSITRIM[4:0] bits in the RCC clock control register (RCC_CR).
The HSIRDY flag in the RCC clock control register (RCC_CR) indicates if the HSI RC is
stable or not. At startup, the HSI RC output clock is not released until this bit is set by
hardware.
The HSI RC can be switched on and off using the HSION bit in the RCC clock control
register (RCC_CR).
The HSI signal can also be used as a backup source (Auxiliary clock) if the HSE crystal
oscillator fails. Refer to Section 5.2.7: Clock security system (CSS) on page 139.

5.2.3

PLL
The devices feature three PLLs:
•

A main PLL (PLL) clocked by the HSE or HSI oscillator and featuring two different
output clocks:
–

The first output is used to generate the high speed system clock (up to 216 MHz)

–

The second output is used to generate 48MHz clock for the USB OTG FS,
SDMMC and RNG.

•

PLLI2S is used to generate an accurate clock to achieve high-quality audio
performance on the I2S, SAIs and SPDIFRX interfaces.

•

PLLSAI is used to generate clock for SAIs intefraces, LCD-TFT clock and the 48MHz
(PLLSAI48CLK) that can be seleced for the USB OTG FS, SDMMC and RNG.

Since the main-PLL configuration parameters cannot be changed once PLL is enabled, it is
recommended to configure PLL before enabling it (selection of the HSI or HSE oscillator as
PLL clock source, and configuration of division factors M, N, P, and Q).
The PLLI2S and PLLSAI use the same input clock as PLL (PLLM[5:0] and PLLSRC bits are
common to both PLLs). However, the PLLI2S and PLLSAI have dedicated enable/disable
and division factors (N and R) configuration bits. Once the PLLI2S and PLLSAI are enabled,
the configuration parameters cannot be changed.
The three PLLs are disabled by hardware when entering Stop and Standby modes, or when
an HSE failure occurs when HSE or PLL (clocked by HSE) are used as system clock. RCC
PLL configuration register (RCC_PLLCFGR),RCC clock configuration register
(RCC_CFGR), and RCC dedicated clocks configuration register (RCC_DKCFGR1) can be
used to configure PLL, PLLI2S, and PLLSAI.

138/1709

RM0385 Rev 7

RM0385

5.2.4

Reset and clock control (RCC)

LSE clock
The LSE clock is generated from a 32.768 kHz low-speed external crystal or ceramic
resonator. It has the advantage providing a low-power but highly accurate clock source to
the real-time clock peripheral (RTC) for clock/calendar or other timing functions.
The LSE oscillator is switched on and off using the LSEON bit in RCC backup domain
control register (RCC_BDCR).
The LSERDY flag in the RCC backup domain control register (RCC_BDCR) indicates if the
LSE crystal is stable or not. At startup, the LSE crystal output clock signal is not released
until this bit is set by hardware. An interrupt can be generated if enabled in the RCC clock
interrupt register (RCC_CIR).

External source (LSE bypass)
In this mode, an external clock source must be provided. It must have a frequency up to
1 MHz. This mode is selected by setting the LSEBYP and LSEON bits in the RCC backup
domain control register (RCC_BDCR). The external clock signal (square, sinus or triangle)
with ~50% duty cycle has to drive the OSC32_IN pin while the OSC32_OUT pin should be
left HI-Z. See Figure 14.

5.2.5

LSI clock
The LSI RC acts as an low-power clock source that can be kept running in Stop and
Standby mode for the independent watchdog (IWDG) and Auto-wakeup unit (AWU). The
clock frequency is around 32 kHz. For more details, refer to the electrical characteristics
section of the datasheets.
The LSI RC can be switched on and off using the LSION bit in the RCC clock control &
status register (RCC_CSR).
The LSIRDY flag in the RCC clock control & status register (RCC_CSR) indicates if the lowspeed internal oscillator is stable or not. At startup, the clock is not released until this bit is
set by hardware. An interrupt can be generated if enabled in the RCC clock interrupt register
(RCC_CIR).

5.2.6

System clock (SYSCLK) selection
After a system reset, the HSI oscillator is selected as the system clock. When a clock source
is used directly or through PLL as the system clock, it is not possible to stop it.
A switch from one clock source to another occurs only if the target clock source is ready
(clock stable after startup delay or PLL locked). If a clock source that is not yet ready is
selected, the switch occurs when the clock source is ready. Status bits in the RCC clock
control register (RCC_CR) indicate which clock(s) is (are) ready and which clock is currently
used as the system clock.

5.2.7

Clock security system (CSS)
The clock security system can be activated by software. In this case, the clock detector is
enabled after the HSE oscillator startup delay, and disabled when this oscillator is stopped.
If a failure is detected on the HSE clock, this oscillator is automatically disabled, a clock
failure event is sent to the break inputs of advanced-control timers TIM1 and TIM8, and an
interrupt is generated to inform the software about the failure (clock security system

RM0385 Rev 7

139/1709
198

Reset and clock control (RCC)

RM0385

interrupt CSSI), allowing the MCU to perform rescue operations. The CSSI is linked to the
Cortex®-M7 NMI (non-maskable interrupt) exception vector.
Note:

When the CSS is enabled, if the HSE clock happens to fail, the CSS generates an interrupt,
which causes the automatic generation of an NMI. The NMI is executed indefinitely unless
the CSS interrupt pending bit is cleared. As a consequence, the application has to clear the
CSS interrupt in the NMI ISR by setting the CSSC bit in the Clock interrupt register
(RCC_CIR).
If the HSE oscillator is used directly or indirectly as the system clock (indirectly meaning that
it is directly used as PLL input clock, and that PLL clock is the system clock) and a failure is
detected, then the system clock switches to the HSI oscillator and the HSE oscillator is
disabled.
If the HSE oscillator clock was the clock source of PLL used as the system clock when the
failure occurred, PLL is also disabled. In this case, if the PLLI2S or PLLSAI was enabled, it
is also disabled when the HSE fails.

5.2.8

RTC/AWU clock
Once the RTCCLK clock source has been selected, the only possible way of modifying the
selection is to reset the power domain.
The RTCCLK clock source can be either the HSE 1 MHz (HSE divided by a programmable
prescaler), the LSE or the LSI clock. This is selected by programming the RTCSEL[1:0] bits
in the RCC backup domain control register (RCC_BDCR) and the RTCPRE[4:0] bits in RCC
clock configuration register (RCC_CFGR). This selection cannot be modified without
resetting the Backup domain.
If the LSE is selected as the RTC clock, the RTC will work normally if the backup or the
system supply disappears. If the LSI is selected as the AWU clock, the AWU state is not
guaranteed if the system supply disappears. If the HSE oscillator divided by a value
between 2 and 31 is used as the RTC clock, the RTC state is not guaranteed if the backup
or the system supply disappears.
The LSE clock is in the Backup domain, whereas the HSE and LSI clocks are not. As a
consequence:
•

•

If LSE is selected as the RTC clock:
–

The RTC continues to work even if the VDD supply is switched off, provided the
VBAT supply is maintained.

–

The RTC remains clocked and functional under system reset.

If LSI is selected as the Auto-wakeup unit (AWU) clock:
–

•

If the HSE clock is used as the RTC clock:
–

Note:

140/1709

The AWU state is not guaranteed if the VDD supply is powered off. Refer to
Section 5.2.5: LSI clock on page 139 for more details on LSI calibration.
The RTC state is not guaranteed if the VDD supply is powered off or if the internal
voltage regulator is powered off (removing power from the 1.2 V domain) and also
when entering in Stop mode

To read the RTC calendar register when the APB1 clock frequency is less than seven times
the RTC clock frequency (fAPB1 < 7xfRTCLCK), the software must read the calendar time and
date registers twice. The data are correct if the second read access to RTC_TR gives the
same result than the first one. Otherwise a third read access must be performed.

RM0385 Rev 7

RM0385

5.2.9

Reset and clock control (RCC)

Watchdog clock
If the independent watchdog (IWDG) is started by either hardware option or software
access, the LSI oscillator is forced ON and cannot be disabled. After the LSI oscillator
temporization, the clock is provided to the IWDG.

5.2.10

Clock-out capability
Two microcontroller clock output (MCO) pins are available:
•

MCO1
The user can output four different clock sources onto the MCO1 pin (PA8) using the
configurable prescaler (from 1 to 5):
–

HSI clock

–

LSE clock

–

HSE clock

–

PLL clock

The desired clock source is selected using the MCO1PRE[2:0] and MCO1[1:0] bits in
the RCC clock configuration register (RCC_CFGR).
•

MCO2
The user can output four different clock sources onto the MCO2 pin (PC9) using the
configurable prescaler (from 1 to 5):
–

HSE clock

–

PLL clock

–

System clock (SYSCLK)

–

PLLI2S clock

The desired clock source is selected using the MCO2PRE[2:0] and MCO2 bits in the
RCC clock configuration register (RCC_CFGR).
For the different MCO pins, the corresponding GPIO port has to be programmed in alternate
function mode.

5.2.11

Internal/external clock measurement using TIM5/TIM11
It is possible to indirectly measure the frequencies of all on-board clock source generators
by means of the input capture of TIM5 channel4 and TIM11 channel1 as shown in Figure 15
and Figure 15.

Internal/external clock measurement using TIM5 channel4
TIM5 has an input multiplexer which allows choosing whether the input capture is triggered
by the I/O or by an internal clock. This selection is performed through the TI4_RMP [1:0] bits
in the TIM5_OR register.
The primary purpose of having the LSE connected to the channel4 input capture is to be
able to precisely measure the HSI (this requires to have the HSI used as the system clock
source). The number of HSI clock counts between consecutive edges of the LSE signal
provides a measurement of the internal clock period. Taking advantage of the high precision
of LSE crystals (typically a few tens of ppm) we can determine the internal clock frequency
with the same resolution, and trim the source to compensate for manufacturing-process
and/or temperature- and voltage-related frequency deviations.

RM0385 Rev 7

141/1709
198

Reset and clock control (RCC)

RM0385

The HSI oscillator has dedicated, user-accessible calibration bits for this purpose.
The basic concept consists in providing a relative measurement (e.g. HSI/LSE ratio): the
precision is therefore tightly linked to the ratio between the two clock sources. The greater
the ratio, the better the measurement.
It is also possible to measure the LSI frequency: this is useful for applications that do not
have a crystal. The ultra-low-power LSI oscillator has a large manufacturing process
deviation: by measuring it versus the HSI clock source, it is possible to determine its
frequency with the precision of the HSI. The measured value can be used to have more
accurate RTC time base timeouts (when LSI is used as the RTC clock source) and/or an
IWDG timeout with an acceptable accuracy.
Use the following procedure to measure the LSI frequency:
1.

Enable the TIM5 timer and configure channel4 in Input capture mode.

2.

This bit is set the TI4_RMP bits in the TIM5_OR register to 0x01 to connect the LSI
clock internally to TIM5 channel4 input capture for calibration purposes.

3.

Measure the LSI clock frequency using the TIM5 capture/compare 4 event or interrupt.

4.

Use the measured LSI frequency to update the prescaler of the RTC depending on the
desired time base and/or to compute the IWDG timeout.
Figure 15. Frequency measurement with TIM5 in Input capture mode
TIM5

TI4_RMP[1:0]
GPIO
RTC_WakeUp_IT
LSE
LSI

TI4

ai17741V2

Internal/external clock measurement using TIM11 channel1
TIM11 has an input multiplexer which allows choosing whether the input capture is triggered
by the I/O or by an internal clock. This selection is performed through TI1_RMP [1:0] bits in
the TIM11_OR register. The HSE_RTC clock (HSE divided by a programmable prescaler) is
connected to channel 1 input capture to have a rough indication of the external crystal
frequency. This requires that the HSI is the system clock source. This can be useful for
instance to ensure compliance with the IEC 60730/IEC 61335 standards which require to be
able to determine harmonic or subharmonic frequencies (–50/+100% deviations).

142/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)
Figure 16. Frequency measurement with TIM11 in Input capture mode
TIM11

TI1_RMP[1:0]
GPIO
TI1
HSE_RTC(1 MHz)
MS40454V1

5.2.12

Peripheral clock enable register (RCC_AHBxENR,
RCC_APBxENRy)
Each peripheral clock can be enabled by the xxxxEN bit of the RCC_AHBxENR or
RCC_APBxENRy registers.
When the peripheral clock is not active, the peripheral registers read or write accesses are
not supported.The peripheral enable bit has a synchronization mechanism to create a glitch
free clock for the peripheral.
After the enable bit is set, there is a 2 peripheral clock cycles delay before the clock being
active.

Caution:

Just after enabling the clock for a peripheral, software must wait for a 2 peripheral clock
cycles delay before accessing the peripheral registers.

5.3

RCC registers
Refer to Section 1.1: List of abbreviations for registers for a list of abbreviations used in
register descriptions.

5.3.1

RCC clock control register (RCC_CR)
Address offset: 0x00
Reset value: 0x0000 XX83 where X is undefined.
Access: no wait state, word, half-word and byte access

31

30

Res.

Res.

15

14

29

28

27

26

25

PLLSAI PLLSAI PLLI2S PLLI2S PLLRD
RDY
ON
RDY
ON
Y

24

23

22

21

20

19

18

17

16

PLLON

Res.

Res.

Res.

Res.

CSS
ON

HSE
BYP

HSE
RDY

HSE
ON

rw

rw

r

rw

3

2

1

0

Res.

HSI
RDY

HSION

r

rw

r

rw

r

rw

r

rw

13

12

11

10

9

8

7

6

HSICAL[7:0]
r

r

r

r

r

5

4

HSITRIM[4:0]
r

r

r

rw

RM0385 Rev 7

rw

rw

rw

rw

143/1709
198

Reset and clock control (RCC)

RM0385

Bits 31:28 Reserved, must be kept at reset value.
Bit 29 PLLSAIRDY: PLLSAI clock ready flag
Set by hardware to indicate that the PLLSAI is locked.
0: PLLSAI unlocked
1: PLLSAI locked
Bit 28 PLLSAION: PLLSAI enable
Set and cleared by software to enable PLLSAI.
Cleared by hardware when entering Stop or Standby mode.
0: PLLSAI OFF
1: PLLSAI ON
Bit 27 PLLI2SRDY: PLLI2S clock ready flag
Set by hardware to indicate that the PLLI2S is locked.
0: PLLI2S unlocked
1: PLLI2S locked
Bit 26 PLLI2SON: PLLI2S enable
Set and cleared by software to enable PLLI2S.
Cleared by hardware when entering Stop or Standby mode.
0: PLLI2S OFF
1: PLLI2S ON
Bit 25 PLLRDY: Main PLL (PLL) clock ready flag
Set by hardware to indicate that PLL is locked.
0: PLL unlocked
1: PLL locked
Bit 24 PLLON: Main PLL (PLL) enable
Set and cleared by software to enable PLL.
Cleared by hardware when entering Stop or Standby mode. This bit cannot be reset if PLL
clock is used as the system clock.
0: PLL OFF
1: PLL ON
Bits 23:20 Reserved, must be kept at reset value.
Bit 19 CSSON: Clock security system enable
Set and cleared by software to enable the clock security system. When CSSON is set, the
clock detector is enabled by hardware when the HSE oscillator is ready, and disabled by
hardware if an oscillator failure is detected.
0: Clock security system OFF (Clock detector OFF)
1: Clock security system ON (Clock detector ON if HSE oscillator is stable, OFF if not)
Bit 18 HSEBYP: HSE clock bypass
Set and cleared by software to bypass the oscillator with an external clock. The external
clock must be enabled with the HSEON bit, to be used by the device.
The HSEBYP bit can be written only if the HSE oscillator is disabled.
0: HSE oscillator not bypassed
1: HSE oscillator bypassed with an external clock
Bit 17 HSERDY: HSE clock ready flag
Set by hardware to indicate that the HSE oscillator is stable. After the HSEON bit is cleared,
HSERDY goes low after 6 HSE oscillator clock cycles.
0: HSE oscillator not ready
1: HSE oscillator ready

144/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 16 HSEON: HSE clock enable
Set and cleared by software.
Cleared by hardware to stop the HSE oscillator when entering Stop or Standby mode. This
bit cannot be reset if the HSE oscillator is used directly or indirectly as the system clock.
0: HSE oscillator OFF
1: HSE oscillator ON
Bits 15:8 HSICAL[7:0]: Internal high-speed clock calibration
These bits are initialized automatically at startup.
Bits 7:3 HSITRIM[4:0]: Internal high-speed clock trimming
These bits provide an additional user-programmable trimming value that is added to the
HSICAL[7:0] bits. It can be programmed to adjust to variations in voltage and temperature
that influence the frequency of the internal HSI RC.
Bit 2 Reserved, must be kept at reset value.
Bit 1 HSIRDY: Internal high-speed clock ready flag
Set by hardware to indicate that the HSI oscillator is stable. After the HSION bit is cleared,
HSIRDY goes low after 6 HSI clock cycles.
0: HSI oscillator not ready
1: HSI oscillator ready
Bit 0 HSION: Internal high-speed clock enable
Set and cleared by software.
Set by hardware to force the HSI oscillator ON when leaving the Stop or Standby mode or in
case of a failure of the HSE oscillator used directly or indirectly as the system clock. This bit
cannot be cleared if the HSI is used directly or indirectly as the system clock.
0: HSI oscillator OFF
1: HSI oscillator ON

RM0385 Rev 7

145/1709
198

Reset and clock control (RCC)

5.3.2

RM0385

RCC PLL configuration register (RCC_PLLCFGR)
Address offset: 0x04
Reset value: 0x2400 3010
Access: no wait state, word, half-word and byte access.
This register is used to configure the PLL clock outputs according to the formulas:

31
Res.

30
Res.

•

f(VCO clock) = f(PLL clock input) × (PLLN / PLLM)

•

f(PLL general clock output) = f(VCO clock) / PLLP

•

f(USB OTG FS, SDMMC, RNG clock output) = f(VCO clock) / PLLQ
29
Res.

28

27

Res.

14

13

12

25

24

PLLQ[3:0]
rw

15

26

11

Res.

rw

rw

rw

10

9

8

23

22

21

20

19

18

Res.

PLLSR
C

Res.

Res.

Res.

Res.

rw
7

6

5

4

PLLN[8:0]
rw

rw

rw

rw

rw

3

2

17

16

PLLP[1:0]
rw

rw

1

0

rw

rw

PLLM[5:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 PLLQ[3:0]: Main PLL (PLL) division factor for USB OTG FS, SDMMC and random number
generator clocks
Set and cleared by software to control the frequency of USB OTG FS clock, the random
number generator clock and the SDMMC clock. These bits should be written only if PLL is
disabled.
Caution: The USB OTG FS requires a 48 MHz clock to work correctly. The SDMMC and the
random number generator need a frequency lower than or equal to 48 MHz to work
correctly.
USB OTG FS clock frequency = VCO frequency / PLLQ with 2 ≤ PLLQ ≤ 15
0000: PLLQ = 0, wrong configuration
0001: PLLQ = 1, wrong configuration
0010: PLLQ = 2
0011: PLLQ = 3
0100: PLLQ = 4
...
1111: PLLQ = 15
Bit 23 Reserved, must be kept at reset value.
Bit 22 PLLSRC: Main PLL(PLL) and audio PLL (PLLI2S) entry clock source
Set and cleared by software to select PLL and PLLI2S clock source. This bit can be written
only when PLL and PLLI2S are disabled.
0: HSI clock selected as PLL and PLLI2S clock entry
1: HSE oscillator clock selected as PLL and PLLI2S clock entry
Bits 21:18 Reserved, must be kept at reset value.

146/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bits 17:16 PLLP[1:0]: Main PLL (PLL) division factor for main system clock
Set and cleared by software to control the frequency of the general PLL output clock. These
bits can be written only if PLL is disabled.
Caution: The software has to set these bits correctly not to exceed 216 MHz on this domain.
PLL output clock frequency = VCO frequency / PLLP with PLLP = 2, 4, 6, or 8
00: PLLP = 2
01: PLLP = 4
10: PLLP = 6
11: PLLP = 8
Bits 14:6 PLLN[8:0]: Main PLL (PLL) multiplication factor for VCO
Set and cleared by software to control the multiplication factor of the VCO. These bits can
be written only when PLL is disabled. Only half-word and word accesses are allowed to
write these bits.
Caution: The software has to set these bits correctly to ensure that the VCO output
frequency is between 100 and 432 MHz.
VCO output frequency = VCO input frequency × PLLN with 50 ≤ PLLN ≤ 432
000000000: PLLN = 0, wrong configuration
000000001: PLLN = 1, wrong configuration
...
000110010: PLLN = 50
...
001100011: PLLN = 99
001100100: PLLN = 100
...
110110000: PLLN = 432
110110001: PLLN = 433, wrong configuration
...
111111111: PLLN = 511, wrong configuration
Note: Between 50 and 99, multiplication factors are possible for VCO input frequency higher
than 1 MHz. However care must be taken to fulfill the minimum VCO output frequency
as specified above.
Bits 5:0 PLLM[5:0]: Division factor for the main PLLs (PLL, PLLI2S and PLLSAI) input clock
Set and cleared by software to divide the PLL and PLLI2S input clock before the VCO.
These bits can be written only when the PLL and PLLI2S are disabled.
Caution: The software has to set these bits correctly to ensure that the VCO input frequency
ranges from 1 to 2 MHz. It is recommended to select a frequency of 2 MHz to limit
PLL jitter.
VCO input frequency = PLL input clock frequency / PLLM with 2 ≤ PLLM ≤ 63
000000: PLLM = 0, wrong configuration
000001: PLLM = 1, wrong configuration
000010: PLLM = 2
000011: PLLM = 3
000100: PLLM = 4
...
111110: PLLM = 62
111111: PLLM = 63

RM0385 Rev 7

147/1709
198

Reset and clock control (RCC)

5.3.3

RM0385

RCC clock configuration register (RCC_CFGR)
Address offset: 0x08
Reset value: 0x0000 0000
Access: 0 ≤ wait state ≤ 2, word, half-word and byte access
1 or 2 wait states inserted only if the access occurs during a clock source switch.

31

30

29

MCO2

14

26

rw

25

24

23

22

I2SSC
R

MCO1 PRE[2:0]

rw

rw

rw

rw

rw

rw

rw

rw

12

11

10

9

8

7

6

Res.

Res.

rw

rw

rw

rw

PPRE1[2:0]
rw

rw

21

20

19

MCO1

13

PPRE2[2:0]
rw

27

MCO2 PRE[2:0]

rw
15

28

18

17

16

RTCPRE[4:0]

5

rw

rw

rw

rw

rw

4

3

2

1

0

SWS1

SWS0

SW1

SW0

r

r

rw

rw

HPRE[3:0]
rw

rw

Bits 31:30 MCO2[1:0]: Microcontroller clock output 2
Set and cleared by software. Clock source selection may generate glitches on MCO2. It is
highly recommended to configure these bits only after reset before enabling the external
oscillators and the PLLs.
00: System clock (SYSCLK) selected
01: PLLI2S clock selected
10: HSE oscillator clock selected
11: PLL clock selected
Bits 27:29 MCO2PRE: MCO2 prescaler
Set and cleared by software to configure the prescaler of the MCO2. Modification of this
prescaler may generate glitches on MCO2. It is highly recommended to change this
prescaler only after reset before enabling the external oscillators and the PLLs.
0xx: no division
100: division by 2
101: division by 3
110: division by 4
111: division by 5
Bits 24:26 MCO1PRE: MCO1 prescaler
Set and cleared by software to configure the prescaler of the MCO1. Modification of this
prescaler may generate glitches on MCO1. It is highly recommended to change this
prescaler only after reset before enabling the external oscillators and the PLL.
0xx: no division
100: division by 2
101: division by 3
110: division by 4
111: division by 5
Bit 23 I2SSRC: I2S clock selection
Set and cleared by software. This bit allows to select the I2S clock source between the
PLLI2S clock and the external clock. It is highly recommended to change this bit only after
reset and before enabling the I2S module.
0: PLLI2S clock used as I2S clock source
1: External clock mapped on the I2S_CKIN pin used as I2S clock source

148/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bits 22:21 MCO1: Microcontroller clock output 1
Set and cleared by software. Clock source selection may generate glitches on MCO1. It is
highly recommended to configure these bits only after reset before enabling the external
oscillators and PLL.
00: HSI clock selected
01: LSE oscillator selected
10: HSE oscillator clock selected
11: PLL clock selected
Bits 20:16 RTCPRE: HSE division factor for RTC clock
Set and cleared by software to divide the HSE clock input clock to generate a 1 MHz clock
for RTC.
Caution: The software has to set these bits correctly to ensure that the clock supplied to the
RTC is 1 MHz. These bits must be configured if needed before selecting the RTC
clock source.
00000: no clock
00001: no clock
00010: HSE/2
00011: HSE/3
00100: HSE/4
...
11110: HSE/30
11111: HSE/31
Bits 15:13 PPRE2: APB high-speed prescaler (APB2)
Set and cleared by software to control APB high-speed clock division factor.
Caution: The software has to set these bits correctly not to exceed 108 MHz on this domain.
The clocks are divided with the new prescaler factor from 1 to 16 AHB cycles after
PPRE2 write.
0xx: AHB clock not divided
100: AHB clock divided by 2
101: AHB clock divided by 4
110: AHB clock divided by 8
111: AHB clock divided by 16
Bits 12:10 PPRE1: APB Low-speed prescaler (APB1)
Set and cleared by software to control APB low-speed clock division factor.
Caution: The software has to set these bits correctly not to exceed 54 MHz on this domain.
The clocks are divided with the new prescaler factor from 1 to 16 AHB cycles after
PPRE1 write.
0xx: AHB clock not divided
100: AHB clock divided by 2
101: AHB clock divided by 4
110: AHB clock divided by 8
111: AHB clock divided by 16
Bits 9:8 Reserved, must be kept at reset value.

RM0385 Rev 7

149/1709
198

Reset and clock control (RCC)

RM0385

Bits 7:4 HPRE: AHB prescaler
Set and cleared by software to control AHB clock division factor.
Caution: The clocks are divided with the new prescaler factor from 1 to 16 AHB cycles after
HPRE write.
Caution: The AHB clock frequency must be at least 25 MHz when the Ethernet is used.
0xxx: system clock not divided
1000: system clock divided by 2
1001: system clock divided by 4
1010: system clock divided by 8
1011: system clock divided by 16
1100: system clock divided by 64
1101: system clock divided by 128
1110: system clock divided by 256
1111: system clock divided by 512
Bits 3:2 SWS: System clock switch status
Set and cleared by hardware to indicate which clock source is used as the system clock.
00: HSI oscillator used as the system clock
01: HSE oscillator used as the system clock
10: PLL used as the system clock
11: not applicable
Bits 1:0 SW: System clock switch
Set and cleared by software to select the system clock source.
Set by hardware to force the HSI selection when leaving the Stop or Standby mode or in
case of failure of the HSE oscillator used directly or indirectly as the system clock.
00: HSI oscillator selected as system clock
01: HSE oscillator selected as system clock
10: PLL selected as system clock
11: not allowed

5.3.4

RCC clock interrupt register (RCC_CIR)
Address offset: 0x0C
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
Res.

25
Res.

24
Res.

23

w
15

14

13

Res.

PLLSAI
RDYIE

PLLI2S
RDYIE

rw

rw

150/1709

12

11

10

PLL
HSE
HSI
RDYIE RDYIE RDYIE
rw

rw

rw

22

21

PLLSAI PLLI2S
CSSC
RDYC RDYC

9

8

LSE
RDYIE

LSI
RDYIE

7
CSSF

rw

rw

r

RM0385 Rev 7

w

w

6

5

PLLSAI PLLI2S
RDYF
RDYF
r

r

20

19

18

17

16

PLL
RDYC

HSE
RDYC

HSI
RDYC

LSE
RDYC

LSI
RDYC

w

w

w

w

w

4

3

2

1

0

PLL
RDYF

HSE
RDYF

HSI
RDYF

LSE
RDYF

LSI
RDYF

r

r

r

r

r

RM0385

Reset and clock control (RCC)

Bits 31:24 Reserved, must be kept at reset value.
Bit 23 CSSC: Clock security system interrupt clear
This bit is set by software to clear the CSSF flag.
0: No effect
1: Clear CSSF flag
Bit 22 PLLSAIRDYC: PLLSAI Ready Interrupt Clear
This bit is set by software to clear PLLSAIRDYF flag. It is reset by hardware when the
PLLSAIRDYF is cleared.
0: PLLSAIRDYF not cleared
1: PLLSAIRDYF cleared
Bit 21 PLLI2SRDYC: PLLI2S ready interrupt clear
This bit is set by software to clear the PLLI2SRDYF flag.
0: No effect
1: PLLI2SRDYF cleared
Bit 20 PLLRDYC: Main PLL(PLL) ready interrupt clear
This bit is set by software to clear the PLLRDYF flag.
0: No effect
1: PLLRDYF cleared
Bit 19 HSERDYC: HSE ready interrupt clear
This bit is set by software to clear the HSERDYF flag.
0: No effect
1: HSERDYF cleared
Bit 18 HSIRDYC: HSI ready interrupt clear
This bit is set software to clear the HSIRDYF flag.
0: No effect
1: HSIRDYF cleared
Bit 17 LSERDYC: LSE ready interrupt clear
This bit is set by software to clear the LSERDYF flag.
0: No effect
1: LSERDYF cleared
Bit 16 LSIRDYC: LSI ready interrupt clear
This bit is set by software to clear the LSIRDYF flag.
0: No effect
1: LSIRDYF cleared
Bit 15 Reserved, must be kept at reset value.
Bit 14 PLLSAIRDYIE: PLLSAI Ready Interrupt Enable
This bit is set and reset by software to enable/disable interrupt caused by PLLSAI lock.
0: PLLSAI lock interrupt disabled
1: PLLSAI lock interrupt enabled
Bit 13 PLLI2SRDYIE: PLLI2S ready interrupt enable
This bit is set and cleared by software to enable/disable interrupt caused by PLLI2S lock.
0: PLLI2S lock interrupt disabled
1: PLLI2S lock interrupt enabled

RM0385 Rev 7

151/1709
198

Reset and clock control (RCC)

RM0385

Bit 12 PLLRDYIE: Main PLL (PLL) ready interrupt enable
This bit is set and cleared by software to enable/disable interrupt caused by PLL lock.
0: PLL lock interrupt disabled
1: PLL lock interrupt enabled
Bit 11 HSERDYIE: HSE ready interrupt enable
This bit is set and cleared by software to enable/disable interrupt caused by the HSE
oscillator stabilization.
0: HSE ready interrupt disabled
1: HSE ready interrupt enabled
Bit 10 HSIRDYIE: HSI ready interrupt enable
This bit is set and cleared by software to enable/disable interrupt caused by the HSI
oscillator stabilization.
0: HSI ready interrupt disabled
1: HSI ready interrupt enabled
Bit 9 LSERDYIE: LSE ready interrupt enable
This bit is set and cleared by software to enable/disable interrupt caused by the LSE
oscillator stabilization.
0: LSE ready interrupt disabled
1: LSE ready interrupt enabled
Bit 8 LSIRDYIE: LSI ready interrupt enable
This bit is set and cleared by software to enable/disable interrupt caused by LSI oscillator
stabilization.
0: LSI ready interrupt disabled
1: LSI ready interrupt enabled
Bit 7 CSSF: Clock security system interrupt flag
This bit is set by hardware when a failure is detected in the HSE oscillator.
It is cleared by software by setting the CSSC bit.
0: No clock security interrupt caused by HSE clock failure
1: Clock security interrupt caused by HSE clock failure
Bit 6 PLLSAIRDYF: PLLSAI Ready Interrupt flag
This bit is set by hardware when the PLLSAI is locked and PLLSAIRDYDIE is set.
It is cleared by software by setting the PLLSAIRDYC bit.
0: No clock ready interrupt caused by PLLSAI lock
1: Clock ready interrupt caused by PLLSAI lock
Bit 5 PLLI2SRDYF: PLLI2S ready interrupt flag
This bit is set by hardware when the PLLI2S is locked and PLLI2SRDYDIE is set.
It is cleared by software by setting the PLLRI2SDYC bit.
0: No clock ready interrupt caused by PLLI2S lock
1: Clock ready interrupt caused by PLLI2S lock
Bit 4 PLLRDYF: Main PLL (PLL) ready interrupt flag
This bit is set by hardware when PLL is locked and PLLRDYDIE is set.
It is cleared by software setting the PLLRDYC bit.
0: No clock ready interrupt caused by PLL lock
1: Clock ready interrupt caused by PLL lock

152/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 3 HSERDYF: HSE ready interrupt flag
This bit is set by hardware when External High Speed clock becomes stable and
HSERDYDIE is set.
It is cleared by software by setting the HSERDYC bit.
0: No clock ready interrupt caused by the HSE oscillator
1: Clock ready interrupt caused by the HSE oscillator
Bit 2 HSIRDYF: HSI ready interrupt flag
This bit is set by hardware when the Internal High Speed clock becomes stable and
HSIRDYDIE is set.
It is cleared by software by setting the HSIRDYC bit.
0: No clock ready interrupt caused by the HSI oscillator
1: Clock ready interrupt caused by the HSI oscillator
Bit 1 LSERDYF: LSE ready interrupt flag
This bit is set by hardware when the External low-speed clock becomes stable and
LSERDYDIE is set.
It is cleared by software by setting the LSERDYC bit.
0: No clock ready interrupt caused by the LSE oscillator
1: Clock ready interrupt caused by the LSE oscillator
Bit 0 LSIRDYF: LSI ready interrupt flag
This bit is set by hardware when the internal low-speed clock becomes stable and
LSIRDYDIE is set.
It is cleared by software by setting the LSIRDYC bit.
0: No clock ready interrupt caused by the LSI oscillator
1: Clock ready interrupt caused by the LSI oscillator

5.3.5

RCC AHB1 peripheral reset register (RCC_AHB1RSTR)
Address offset: 0x10
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.

31
Res.

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

OTGH
S
RST

Res.

Res.

Res.

ETHMAC
RST

Res.

DMA2D
RST

DMA2
RST

DMA1
RST

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

7

6

5

4

3

2

1

rw
15
Res.

14
Res.

rw

13

12

Res.

CRCR
ST
rw

11

10

9

8

Res.

GPIOK
RST

GPIOJ
RST

GPIOI
RST

rw

rw

rw

0

GPIOH GPIOGG GPIOF GPIOE GPIOD GPIOC GPIOB
RST
RST
RST
RST
RST
RST
RST
rw

rw

rw

rw

rw

rw

rw

GPIOA
RST
rw

Bits 31:30 Reserved, must be kept at reset value.
Bit 29 OTGHSRST: USB OTG HS module reset
This bit is set and cleared by software.
0: does not reset the USB OTG HS module
1: resets the USB OTG HS module
Bits 28:26 Reserved, must be kept at reset value.

RM0385 Rev 7

153/1709
198

Reset and clock control (RCC)

RM0385

Bit 25 ETHMACRST: Ethernet MAC reset
This bit is set and cleared by software.
0: does not reset Ethernet MAC
1: resets Ethernet MAC
Bit 24 Reserved, must be kept at reset value.
Bit 23 DMA2DRST: DMA2D reset
This bit is set and reset by software.
0: does not reset DMA2D
1: resets DMA2D
Bit 22 DMA2RST: DMA2 reset
This bit is set and cleared by software.
0: does not reset DMA2
1: resets DMA2
Bit 21 DMA1RST: DMA2 reset
This bit is set and cleared by software.
0: does not reset DMA2
1: resets DMA2
Bits 20:13 Reserved, must be kept at reset value.
Bit 12 CRCRST: CRC reset
This bit is set and cleared by software.
0: does not reset CRC
1: resets CRC
Bit 11 Reserved, must be kept at reset value.
Bit 10 GPIOKRST: IO port K reset
This bit is set and cleared by software.
0: does not reset IO port K
1: resets IO port K
Bit 9 GPIOJRST: IO port J reset
This bit is set and cleared by software.
0: does not reset IO port J
1: resets IO port J
Bit 8 GPIOIRST: IO port I reset
This bit is set and cleared by software.
0: does not reset IO port I
1: resets IO port I
Bit 7 GPIOHRST: IO port H reset
This bit is set and cleared by software.
0: does not reset IO port H
1: resets IO port H
Bit 6 GPIOGRST: IO port G reset
This bit is set and cleared by software.
0: does not reset IO port G
1: resets IO port G

154/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 5 GPIOFRST: IO port F reset
This bit is set and cleared by software.
0: does not reset IO port F
1: resets IO port F
Bit 4 GPIOERST: IO port E reset
This bit is set and cleared by software.
0: does not reset IO port E
1: resets IO port E
Bit 3 GPIODRST: IO port D reset
This bit is set and cleared by software.
0: does not reset IO port D
1: resets IO port D
Bit 2 GPIOCRST: IO port C reset
This bit is set and cleared by software.
0: does not reset IO port C
1: resets IO port C
Bit 1 GPIOBRST: IO port B reset
This bit is set and cleared by software.
0: does not reset IO port B
1:resets IO port B
Bit 0 GPIOARST: IO port A reset
This bit is set and cleared by software.
0: does not reset IO port A
1: resets IO port A

RM0385 Rev 7

155/1709
198

Reset and clock control (RCC)

5.3.6

RM0385

RCC AHB2 peripheral reset register (RCC_AHB2RSTR)
Address offset: 0x14
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

OTGFS
RST

RNG
RST

HASH
RST

CRYP
RST

Res.

DCMI
RST

rw

rw

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 OTGFSRST: USB OTG FS module reset
Set and cleared by software.
0: does not reset the USB OTG FS module
1: resets the USB OTG FS module
Bit 6 RNGRST: Random number generator module reset
Set and cleared by software.
0: does not reset the random number generator module
1: resets the random number generator module
Bit 5 HASHRST: Hash module reset
Set and cleared by software.
0: does not reset the HASH module
1: resets the HASH module
Bit 4 CRYPRST: Cryptographic module reset
Set and cleared by software.
0: does not reset the cryptographic module
1: resets the cryptographic module
Bits 3:1 Reserved, must be kept at reset value.
Bit 0 DCMIRST: Camera interface reset
Set and cleared by software.
0: does not reset the Camera interface
1: resets the Camera interface

156/1709

RM0385 Rev 7

Res.

Res.

rw

RM0385

Reset and clock control (RCC)

5.3.7

RCC AHB3 peripheral reset register (RCC_AHB3RSTR)
Address offset: 0x18
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

QSPIRST FMCRST
rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 QSPIRST: Quad SPI memory controller reset
Set and cleared by software.
0: does not reset the QUADSPI memory controller
1: resets the QUADSPI memory controller
Bit 0 FMCRST: Flexible memory controller module reset
Set and cleared by software.
0: does not reset the FMC module
1: resets the FMC module

5.3.8

RCC APB1 peripheral reset register (RCC_APB1RSTR)
Address offset: 0x20
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

UART8R UART7R
PWR
CAN2
DACRST
CECRST
ST
ST
RST
RST
rw

rw

rw

rw

15

14

13

12

11

10

SPI3
RST

SPI2
RST

Res.

Res.

WWDG
RST

Res.

rw

rw

rw

25

24

CAN1
I2C4RST
RST

23

22

21

I2C3
RST

I2C2
RST

I2C1
RST

20

19

18

17

16

UART5 UART4 UART3 UART2 SPDIFR
RST
RST
RST
RST
XRST

rw

rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

0

TIM13
RST

TIM12
RST

TIM7
RST

TIM6
RST

TIM5
RST

TIM4
RST

TIM3
RST

TIM2
RST

rw

rw

rw

rw

rw

rw

rw

rw

LPTIM1 TIM14
RST
RST
rw

rw

RM0385 Rev 7

157/1709
198

Reset and clock control (RCC)

RM0385

Bit 31 UART8RST: UART8 reset
Set and cleared by software.
0: does not reset UART8
1: resets UART8
Bit 30 UART7RST: UART7 reset
Set and cleared by software.
0: does not reset UART7
1: resets UART7
Bit 29 DACRST: DAC reset
Set and cleared by software.
0: does not reset the DAC interface
1: resets the DAC interface
Bit 28 PWRRST: Power interface reset
Set and cleared by software.
0: does not reset the power interface
1: resets the power interface
Bit 27 CECRST: HDMI-CEC reset
Set and cleared by software.
0: does not reset HDMI-CEC
1: resets HDMI-CEC
Bit 26 CAN2RST: CAN2 reset
Set and cleared by software.
0: does not reset CAN2
1: resets CAN2
Bit 25 CAN1RST: CAN1 reset
Set and cleared by software.
0: does not reset CAN1
1: resets CAN1
Bit 24 I2C4RST: I2C4 reset
Set and cleared by software.
0: does not reset I2C4
1: resets I2C4
Bit 23 I2C3RST: I2C3 reset
Set and cleared by software.
0: does not reset I2C3
1: resets I2C3
Bit 22 I2C2RST: I2C2 reset
Set and cleared by software.
0: does not reset I2C2
1: resets I2C2
Bit 21 I2C1RST: I2C1 reset
Set and cleared by software.
0: does not reset I2C1
1: resets I2C1

158/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 20 UART5RST: UART5 reset
Set and cleared by software.
0: does not reset UART5
1: resets UART5
Bit 19 UART4RST: USART4 reset
Set and cleared by software.
0: does not reset UART4
1: resets UART4
Bit 18 USART3RST: USART3 reset
Set and cleared by software.
0: does not reset USART3
1: resets USART3
Bit 17 USART2RST: USART2 reset
Set and cleared by software.
0: does not reset USART2
1: resets USART2
Bit 16 SPDIFRXRST: SPDIFRX reset
Set and cleared by software.
0: does not reset SPDIFRX
1: resets SPDIFRX
Bit 15 SPI3RST: SPI3 reset
Set and cleared by software.
0: does not reset SPI3
1: resets SPI3
Bit 14 SPI2RST: SPI2 reset
Set and cleared by software.
0: does not reset SPI2
1: resets SPI2
Bits 13:12 Reserved, must be kept at reset value.
Bit 11 WWDGRST: Window watchdog reset
Set and cleared by software.
0: does not reset the window watchdog
1: resets the window watchdog
Bit 10 Reserved, must be kept at reset value.
Bit 9 LPTIM1RST: Low-power timer 1 reset
Set and cleared by software.
0: does not reset LPTMI1
1: resets LPTMI1
Bit 8 TIM14RST: TIM14 reset
Set and cleared by software.
0: does not reset TIM14
1: resets TIM14
Bit 7 TIM13RST: TIM13 reset
Set and cleared by software.
0: does not reset TIM13
1: resets TIM13

RM0385 Rev 7

159/1709
198

Reset and clock control (RCC)

RM0385

Bit 6 TIM12RST: TIM12 reset
Set and cleared by software.
0: does not reset TIM12
1: resets TIM12
Bit 5 TIM7RST: TIM7 reset
Set and cleared by software.
0: does not reset TIM7
1: resets TIM7
Bit 4 TIM6RST: TIM6 reset
Set and cleared by software.
0: does not reset TIM6
1: resets TIM6
Bit 3 TIM5RST: TIM5 reset
Set and cleared by software.
0: does not reset TIM5
1: resets TIM5
Bit 2 TIM4RST: TIM4 reset
Set and cleared by software.
0: does not reset TIM4
1: resets TIM4
Bit 1 TIM3RST: TIM3 reset
Set and cleared by software.
0: does not reset TIM3
1: resets TIM3
Bit 0 TIM2RST: TIM2 reset
Set and cleared by software.
0: does not reset TIM2
1: resets TIM2

160/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

5.3.9

RCC APB2 peripheral reset register (RCC_APB2RSTR)
Address offset: 0x24
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

Res.

Res.

Res.

Res.

Res.

LTDC
RST

15

14

13

12

11

10

Res.

SYSCFG
RST

SPI4
RST

SPI1
RST

SDMMC1
RST

rw

rw

rw

rw

25

24

23

22

21

20

Res.

Res.

SAI2
RST

SAI1
RST

SPI6
RST

SPI5
RST

rw

rw

rw

rw

9

8

7

6

5

4

Res.

ADC
RST

rw

Res.

Res.

rw

Res.

USART6 USART1
RST
RST
rw

rw

19

18

17

16

Res.

TIM11
RST

TIM10
RST

TIM9
RST

rw

rw

rw

2

1

0

Res.

TIM8
RST

TIM1
RST

rw

rw

3
Res.

Bits 31:27 Reserved, must be kept at reset value.
Bit 26 LTDCRST: LTDC reset
This bit is set and reset by software.
0: does not reset LCD-TFT
1: resets LCD-TFT
Bits 27:24 Reserved, must be kept at reset value.
Bit 23 SAI2RST: SAI2 reset
This bit is set and cleared by software.
0: does not reset SAI2
1: resets SAI2
Bit 22 SAI1RST: SAI1 reset
This bit is set and reset by software.
0: does not reset SAI1
1: resets SAI1
Bit 21 SPI6RST: SPI6 reset
This bit is set and cleared by software.
0: does not reset SPI6
1: resets SPI6
Bit 20 SPI5RST: SPI5 reset
This bit is set and cleared by software.
0: does not reset SPI5
1: resets SPI5
Bit 19 Reserved, must be kept at reset value.
Bit 18 TIM11RST: TIM11 reset
This bit is set and cleared by software.
0: does not reset TIM11
1: resets TIM14
Bit 17 TIM10RST: TIM10 reset
This bit is set and cleared by software.
0: does not reset TIM10
1: resets TIM10

RM0385 Rev 7

161/1709
198

Reset and clock control (RCC)

RM0385

Bit 16 TIM9RST: TIM9 reset
This bit is set and cleared by software.
0: does not reset TIM9
1: resets TIM9
Bit 15 Reserved, must be kept at reset value.
Bit 14 SYSCFGRST: System configuration controller reset
This bit is set and cleared by software.
0: does not reset the System configuration controller
1: resets the System configuration controller
Bit 13 SPI4RST: SPI4 reset
This bit is set and cleared by software.
0: does not reset SPI4
1: resets SPI4
Bit 12 SPI1RST: SPI1 reset
This bit is set and cleared by software.
0: does not reset SPI1
1: resets SPI1
Bit 11 SDMMC1RST: SDMMC1 reset
This bit is set and cleared by software.
0: does not reset the SDMMC1 module
1: resets the SDMMC1 module
Bits 10:9 Reserved, must be kept at reset value.
Bit 8 ADCRST: ADC interface reset (common to all ADCs)
This bit is set and cleared by software.
0: does not reset the ADC interface
1: resets the ADC interface
Bits 7:6 Reserved, must be kept at reset value.
Bit 5 USART6RST: USART6 reset
This bit is set and cleared by software.
0: does not reset USART6
1: resets USART6
Bit 4

USART1RST: USART1 reset
This bit is set and cleared by software.
0: does not reset USART1
1: resets USART1

Bits 3:2 Reserved, must be kept at reset value.
Bit 1 TIM8RST: TIM8 reset
This bit is set and cleared by software.
0: does not reset TIM8
1: resets TIM8
Bit 0 TIM1RST: TIM1 reset
This bit is set and cleared by software.
0: does not reset TIM1
1: resets TIM1

162/1709

RM0385 Rev 7

RM0385

5.3.10

Reset and clock control (RCC)

RCC AHB1 peripheral clock register (RCC_AHB1ENR)
Address offset: 0x30
Reset value: 0x0010 0000
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

ETHM ETHM
OTGHS OTGHS
Res.
ACPTP ACRX
ULPIEN
EN
EN
EN

15
Res.

26

25

24

23

22

21

20

19

18

17

16

ETHM
ACTX
EN

ETHMA
CEN

Res.

DMA2D
EN

DMA2
EN

DMA1
EN

DTCMRA
MEN

Res.

BKPSR
AMEN

Res.

Res.

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

14

13

12

11

10

9

8

7

6

5

4

Res.

CRC
EN

Res.

GPIOK
EN

GPIOJ
EN

GPIOI
EN

GPIOH
EN

GPIOG
EN

GPIOF
EN

GPIOE
EN

rw

rw

rw

rw

rw

rw

rw

Res.

rw

rw
3

2

GPIOD GPIOC GPIO GPIO
EN
EN
BEN AEN
rw

rw

rw

rw

Bit 31 Reserved, must be kept at reset value.
Bit 30 OTGHSULPIEN: USB OTG HSULPI clock enable
This bit is set and cleared by software.
0: USB OTG HS ULPI clock disabled
1: USB OTG HS ULPI clock enabled
Bit 29 OTGHSEN: USB OTG HS clock enable
This bit is set and cleared by software.
0: USB OTG HS clock disabled
1: USB OTG HS clock enabled
Bit 28 ETHMACPTPEN: Ethernet PTP clock enable
This bit is set and cleared by software.
0: Ethernet PTP clock disabled
1: Ethernet PTP clock enabled
Bit 27 ETHMACRXEN: Ethernet Reception clock enable
This bit is set and cleared by software.
0: Ethernet Reception clock disabled
1: Ethernet Reception clock enabled
Bit 26 ETHMACTXEN: Ethernet Transmission clock enable
This bit is set and cleared by software.
0: Ethernet Transmission clock disabled
1: Ethernet Transmission clock enabled
Bit 25 ETHMACEN: Ethernet MAC clock enable
This bit is set and cleared by software.
0: Ethernet MAC clock disabled
1: Ethernet MAC clock enabled
Bit 24 Reserved, must be kept at reset value.
Bit 23 DMA2DEN: DMA2D clock enable
This bit is set and cleared by software.
0: DMA2D clock disabled
1: DMA2D clock enabled

RM0385 Rev 7

163/1709
198

Reset and clock control (RCC)

RM0385

Bit 22 DMA2EN: DMA2 clock enable
This bit is set and cleared by software.
0: DMA2 clock disabled
1: DMA2 clock enabled
Bit 21 DMA1EN: DMA1 clock enable
This bit is set and cleared by software.
0: DMA1 clock disabled
1: DMA1 clock enabled
Bit 20 DTCMRAMEN: DTCM data RAM clock enable
This bit is set and cleared by software.
0: DTCM RAM clock disabled
1: DTCM RAM clock enabled
Bit 19 Reserved, must be kept at reset value.
Bit 18 BKPSRAMEN: Backup SRAM interface clock enable
This bit is set and cleared by software.
0: Backup SRAM interface clock disabled
1: Backup SRAM interface clock enabled
Bits 17:13 Reserved, must be kept at reset value.
Bit 12 CRCEN: CRC clock enable
This bit is set and cleared by software.
0: CRC clock disabled
1: CRC clock enabled
Bit 11 Reserved, must be kept at reset value.
Bit 10 GPIOKEN: IO port K clock enable
This bit is set and cleared by software.
0: IO port K clock disabled
1: IO port K clock enabled
Bit 9 GPIOJEN: IO port J clock enable
This bit is set and cleared by software.
0: IO port J clock disabled
1: IO port J clock enabled
Bit 8 GPIOIEN: IO port I clock enable
This bit is set and cleared by software.
0: IO port I clock disabled
1: IO port I clock enabled
Bit 7 GPIOHEN: IO port H clock enable
This bit is set and cleared by software.
0: IO port H clock disabled
1: IO port H clock enabled
Bit 6 GPIOGEN: IO port G clock enable
This bit is set and cleared by software.
0: IO port G clock disabled
1: IO port G clock enabled

164/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 5 GPIOFEN: IO port F clock enable
This bit is set and cleared by software.
0: IO port F clock disabled
1: IO port F clock enabled
Bit 4 GPIOEEN: IO port E clock enable
This bit is set and cleared by software.
0: IO port E clock disabled
1: IO port E clock enabled
Bit 3 GPIODEN: IO port D clock enable
This bit is set and cleared by software.
0: IO port D clock disabled
1: IO port D clock enabled
Bit 2 GPIOCEN: IO port C clock enable
This bit is set and cleared by software.
0: IO port C clock disabled
1: IO port C clock enabled
Bit 1 GPIOBEN: IO port B clock enable
This bit is set and cleared by software.
0: IO port B clock disabled
1: IO port B clock enabled
Bit 0 GPIOAEN: IO port A clock enable
This bit is set and cleared by software.
0: IO port A clock disabled
1: IO port A clock enabled

5.3.11

RCC AHB2 peripheral clock enable register (RCC_AHB2ENR)
Address offset: 0x34
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

OTGFS
EN

RNG
EN

HASH
EN

CRYP
EN

Res.

DCMI
EN

rw

rw

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 OTGFSEN: USB OTG FS clock enable
This bit is set and cleared by software.
0: USB OTG FS clock disabled
1: USB OTG FS clock enabled
Bit 6 RNGEN: Random number generator clock enable
This bit is set and cleared by software.
0: Random number generator clock disabled
1: Random number generator clock enabled

RM0385 Rev 7

165/1709
198

Reset and clock control (RCC)

RM0385

Bit 5 HASHEN: Hash modules clock enable
This bit is set and cleared by software.
0: Hash modules clock disabled
1: Hash modules clock enabled
Bit 4 CRYPEN: Cryptographic modules clock enable
This bit is set and cleared by software.
0: cryptographic module clock disabled
1: cryptographic module clock enabled
Bits 3:1 Reserved, must be kept at reset value.
Bit 0 DCMIEN: Camera interface enable
This bit is set and cleared by software.
0: Camera interface clock disabled
1: Camera interface clock enabled

5.3.12

RCC AHB3 peripheral clock enable register (RCC_AHB3ENR)
Address offset: 0x38
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

QSPIEN

FMCEN

rw

rw

17

16

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 QSPIEN: Quad SPI memory controller clock enable
This bit is set and cleared by software.
0: QUASPI controller clock disabled
1: QUASPI controller clock enabled
Bit 0 FMCEN: Flexible memory controller clock enable
This bit is set and cleared by software.
0: FMC clock disabled
1: FMC clock enabled

5.3.13

RCC APB1 peripheral clock enable register (RCC_APB1ENR)
Address offset: 0x40
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.

31

30

UART8 UART7
EN
EN
rw

166/1709

rw

29

28

27

26

25

DAC
EN

PWR
EN

CEC
EN

CAN2
EN

CAN1
EN

rw

rw

rw

rw

rw

24
I2C4
EN

23

22

21

I2C3
EN

I2C2
EN

I2C1
EN

rw

rw

rw

RM0385 Rev 7

20

19

18

USART USART
UART5 UART4
SPDIFRX
3
2
EN
EN
EN
EN
EN
rw

rw

rw

rw

rw

RM0385

Reset and clock control (RCC)

15

14

13

12

11

10

SPI3
EN

SPI2
EN

Res.

Res.

WWDG
EN

Res.

rw

rw

rw

9

8

LPTIM1 TIM14
EN
EN
rw

rw

7

6

5

4

3

2

1

0

TIM13
EN

TIM12
EN

TIM7
EN

TIM6
EN

TIM5
EN

TIM4
EN

TIM3
EN

TIM2
EN

rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 UART8EN: UART8 clock enable
This bit is set and cleared by software.
0: UART8 clock disabled
1: UART8 clock enabled
Bit 30 UART7EN: UART7 clock enable
This bit is set and cleared by software.
0: UART7 clock disabled
1: UART7 clock enabled
Bit 29 DACEN: DAC interface clock enable
This bit is set and cleared by software.
0: DAC interface clock disabled
1: DAC interface clock enable
Bit 28 PWREN: Power interface clock enable
This bit is set and cleared by software.
0: Power interface clock disabled
1: Power interface clock enable
Bit 27 CECEN: HDMI-CEC clock enable
This bit is set and cleared by software.
0: HDMI-CEC clock disabled
1: HDMI-CEC clock enabled
Bit 26 CAN2EN: CAN 2 clock enable
This bit is set and cleared by software.
0: CAN 2 clock disabled
1: CAN 2 clock enabled
Bit 25 CAN1EN: CAN 1 clock enable
This bit is set and cleared by software.
0: CAN 1 clock disabled
1: CAN 1 clock enabled
Bit 24 I2C4: I2C4 clock enable
This bit is set and cleared by software.
0: I2C4 clock disabled
1: I2C4 clock enabled
Bit 23 I2C3EN: I2C3 clock enable
This bit is set and cleared by software.
0: I2C3 clock disabled
1: I2C3 clock enabled
Bit 22 I2C2EN: I2C2 clock enable
This bit is set and cleared by software.
0: I2C2 clock disabled
1: I2C2 clock enabled

RM0385 Rev 7

167/1709
198

Reset and clock control (RCC)

RM0385

Bit 21 I2C1EN: I2C1 clock enable
This bit is set and cleared by software.
0: I2C1 clock disabled
1: I2C1 clock enabled
Bit 20 UART5EN: UART5 clock enable
This bit is set and cleared by software.
0: UART5 clock disabled
1: UART5 clock enabled
Bit 19 UART4EN: UART4 clock enable
This bit is set and cleared by software.
0: UART4 clock disabled
1: UART4 clock enabled
Bit 18 USART3EN: USART3 clock enable
This bit is set and cleared by software.
0: USART3 clock disabled
1: USART3 clock enabled
Bit 17 USART2EN: USART2 clock enable
This bit is set and cleared by software.
0: USART2 clock disabled
1: USART2 clock enabled
Bit 16 SPDIFRXEN: SPDIFRX clock enable
This bit is set and cleared by software.
0: SPDIFRX clock disabled
1: SPDIFRX clock enable
Bit 15 SPI3EN: SPI3 clock enable
This bit is set and cleared by software.
0: SPI3 clock disabled
1: SPI3 clock enabled
Bit 14 SPI2EN: SPI2 clock enable
This bit is set and cleared by software.
0: SPI2 clock disabled
1: SPI2 clock enabled
Bits 13:12 Reserved, must be kept at reset value.
Bit 11 WWDGEN: Window watchdog clock enable
This bit is set and cleared by software.
0: Window watchdog clock disabled
1: Window watchdog clock enabled
Bit 10 Reserved, must be kept at reset value.
Bit 9 LPTMI1EN: Low-power timer 1 clock enable
This bit is set and cleared by software.
0: LPTIM1 clock disabled
1: LPTIM1 clock enabled
Bit 8 TIM14EN: TIM14 clock enable
This bit is set and cleared by software.
0: TIM14 clock disabled
1: TIM14 clock enabled

168/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 7 TIM13EN: TIM13 clock enable
This bit is set and cleared by software.
0: TIM13 clock disabled
1: TIM13 clock enabled
Bit 6 TIM12EN: TIM12 clock enable
This bit is set and cleared by software.
0: TIM12 clock disabled
1: TIM12 clock enabled
Bit 5 TIM7EN: TIM7 clock enable
This bit is set and cleared by software.
0: TIM7 clock disabled
1: TIM7 clock enabled
Bit 4 TIM6EN: TIM6 clock enable
This bit is set and cleared by software.
0: TIM6 clock disabled
1: TIM6 clock enabled
Bit 3 TIM5EN: TIM5 clock enable
This bit is set and cleared by software.
0: TIM5 clock disabled
1: TIM5 clock enabled
Bit 2 TIM4EN: TIM4 clock enable
This bit is set and cleared by software.
0: TIM4 clock disabled
1: TIM4 clock enabled
Bit 1 TIM3EN: TIM3 clock enable
This bit is set and cleared by software.
0: TIM3 clock disabled
1: TIM3 clock enabled
Bit 0 TIM2EN: TIM2 clock enable
This bit is set and cleared by software.
0: TIM2 clock disabled
1: TIM2 clock enabled

RM0385 Rev 7

169/1709
198

Reset and clock control (RCC)

5.3.14

RM0385

RCC APB2 peripheral clock enable register (RCC_APB2ENR)
Address offset: 0x44
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

Res.

Res.

Res.

Res.

Res.

LTDC
EN

15

14

13

12

11

25

24

Res.

Res.

10

9

8

ADC3
EN

ADC2
EN

ADC1
EN

rw

rw

rw

rw

Res.

SYSCFG SPI4
EN
EN
rw

rw

SPI1 SDMMC1
EN
EN
rw

rw

23

21

20

SAI2EN SAI1EN SPI6EN SPI5EN
rw

rw

rw

rw

7

6

5

4

Res.

Bits 31:27 Reserved, must be kept at reset value.
Bit 26 LTDCEN: LTDC clock enable
This bit is set and cleared by software.
0: LTDC clock disabled
1: LTDC clock enabled
Bits 27: 24 Reserved, must be kept at reset value.
Bit 23 SAI2EN: SAI2 clock enable
This bit is set and cleared by software.
0: SAI2 clock disabled
1: SAI2 clock enabled
Bit 22 SAI1EN: SAI1 clock enable
This bit is set and cleared by software.
0: SAI1 clock disabled
1: SAI1 clock enabled
Bit 21 SPI6EN: SPI6 clock enable
This bit is set and cleared by software.
0: SPI6 clock disabled
1: SPI6 clock enabled
Bit 20 SPI5EN: SPI5 clock enable
This bit is set and cleared by software.
0: SPI5 clock disabled
1: SPI5 clock enabled
Bit 18 TIM11EN: TIM11 clock enable
This bit is set and cleared by software.
0: TIM11 clock disabled
1: TIM11 clock enabled
Bit 17 TIM10EN: TIM10 clock enable
This bit is set and cleared by software.
0: TIM10 clock disabled
1: TIM10 clock enabled

170/1709

22

RM0385 Rev 7

Res.

USART6 USART1
EN
EN
rw

rw

19

18

17

16

Res.

TIM11
EN

TIM10
EN

TIM9
EN

rw

rw

rw

2

1

0

Res.

TIM8
EN

TIM1
EN

rw

rw

3
Res.

RM0385

Reset and clock control (RCC)

Bit 16 TIM9EN: TIM9 clock enable
This bit is set and cleared by software.
0: TIM9 clock disabled
1: TIM9 clock enabled
Bit 15 Reserved, must be kept at reset value.
Bit 14 SYSCFGEN: System configuration controller clock enable
This bit is set and cleared by software.
0: System configuration controller clock disabled
1: System configuration controller clock enabled
Bit 13 SPI4EN: SPI4 clock enable
This bit is set and cleared by software.
0: SPI4 clock disabled
1: SPI4 clock enabled
Bit 12 SPI1EN: SPI1 clock enable
This bit is set and cleared by software.
0: SPI1 clock disabled
1: SPI1 clock enabled
Bit 11 SDMMC1EN: SDMMC1 clock enable
This bit is set and cleared by software.
0: SDMMC1 module clock disabled
1: SDMMC1 module clock enabled
Bit 10 ADC3EN: ADC3 clock enable
This bit is set and cleared by software.
0: ADC3 clock disabled
1: ADC3 clock enabled
Bit 9

ADC2EN: ADC2 clock enable
This bit is set and cleared by software.
0: ADC2 clock disabled
1: ADC2 clock enabled

Bit 8

ADC1EN: ADC1 clock enable
This bit is set and cleared by software.
0: ADC1 clock disabled
1: ADC1 clock enabled

Bits 7:6 Reserved, must be kept at reset value.
Bit 5 USART6EN: USART6 clock enable
This bit is set and cleared by software.
0: USART6 clock disabled
1: USART6 clock enabled
Bit 4 USART1EN: USART1 clock enable
This bit is set and cleared by software.
0: USART1 clock disabled
1: USART1 clock enabled

RM0385 Rev 7

171/1709
198

Reset and clock control (RCC)

RM0385

Bits 3:2 Reserved, must be kept at reset value.
Bit 1 TIM8EN: TIM8 clock enable
This bit is set and cleared by software.
0: TIM8 clock disabled
1: TIM8 clock enabled
Bit 0 TIM1EN: TIM1 clock enable
This bit is set and cleared by software.
0: TIM1 clock disabled
1: TIM1 clock enabled

172/1709

RM0385 Rev 7

RM0385

5.3.15

Reset and clock control (RCC)

RCC AHB1 peripheral clock enable in low-power mode register
(RCC_AHB1LPENR)
Address offset: 0x50
Reset value: 0x7EF7 B7FFh
Access: no wait state, word, half-word and byte access.

31
Res.

30

rw
15
FLITF
LPEN
rw

29

28

27

26

25

24

OTGHS
ETHMA
OTGHS ETHPTP ETHRX ETHTX
C
ULPI
LPEN
LPEN
LPEN
LPEN
LPEN
LPEN
rw

rw

rw
11

10

9

Res.

GPIOK
LPEN

GPIOIJ
LPEN

rw

rw

14

13

12

Res.

AXI
LPEN

CRC
LPEN

rw

rw

rw

Res.

23

22

21

20

DMA2D
LPEN

DMA2
LPEN

rw

rw

rw

rw

7

6

5

4

rw
8

DMA1 DTCM
LPEN LPEN

19
Res.

18

17

16

BKPS
SRAM2 SRAM1
RAM
LPEN LPEN
LPEN

3

rw

rw

rw

2

1

0

GPIOI GPIOH GPIOGG GPIOF GPIOE GPIOD GPIOC GPIOB GPIOA
LPEN LPEN
LPEN
LPEN LPEN LPEN LPEN LPEN LPEN
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 Reserved, must be kept at reset value.
Bit 30 OTGHSULPILPEN: USB OTG HS ULPI clock enable during Sleep mode
This bit is set and cleared by software.
0: USB OTG HS ULPI clock disabled during Sleep mode
1: USB OTG HS ULPI clock enabled during Sleep mode
Bit 29 OTGHSLPEN: USB OTG HS clock enable during Sleep mode
This bit is set and cleared by software.
0: USB OTG HS clock disabled during Sleep mode
1: USB OTG HS clock enabled during Sleep mode
Bit 28 ETHMACPTPLPEN: Ethernet PTP clock enable during Sleep mode
This bit is set and cleared by software.
0: Ethernet PTP clock disabled during Sleep mode
1: Ethernet PTP clock enabled during Sleep mode
Bit 27 ETHMACRXLPEN: Ethernet reception clock enable during Sleep mode
This bit is set and cleared by software.
0: Ethernet reception clock disabled during Sleep mode
1: Ethernet reception clock enabled during Sleep mode
Bit 26 ETHMACTXLPEN: Ethernet transmission clock enable during Sleep mode
This bit is set and cleared by software.
0: Ethernet transmission clock disabled during sleep mode
1: Ethernet transmission clock enabled during sleep mode
Bit 25 ETHMACLPEN: Ethernet MAC clock enable during Sleep mode
This bit is set and cleared by software.
0: Ethernet MAC clock disabled during Sleep mode
1: Ethernet MAC clock enabled during Sleep mode
Bit 24 Reserved, must be kept at reset value.
Bit 23 DMA2DLPEN: DMA2D clock enable during Sleep mode
This bit is set and cleared by software.
0: DMA2D clock disabled during Sleep mode
1: DMA2D clock enabled during Sleep mode

RM0385 Rev 7

173/1709
198

Reset and clock control (RCC)

RM0385

Bit 22 DMA2LPEN: DMA2 clock enable during Sleep mode
This bit is set and cleared by software.
0: DMA2 clock disabled during Sleep mode
1: DMA2 clock enabled during Sleep mode
Bit 21 DMA1LPEN: DMA1 clock enable during Sleep mode
This bit is set and cleared by software.
0: DMA1 clock disabled during Sleep mode
1: DMA1 clock enabled during Sleep mode
Bit 20 DTCMLPEN: DTCM RAM interface clock enable during Sleep mode
This bit is set and cleared by software.
0: DTCM RAM interface clock disabled during Sleep mode
1: DTCM RAM interface clock enabled during Sleep mode
Bit 19 Reserved, must be kept at reset value.
Bit 18 BKPSRAMLPEN: Backup SRAM interface clock enable during Sleep mode
This bit is set and cleared by software.
0: Backup SRAM interface clock disabled during Sleep mode
1: Backup SRAM interface clock enabled during Sleep mode
Bit 17 SRAM2LPEN: SRAM2 interface clock enable during Sleep mode
This bit is set and cleared by software.
0: SRAM2 interface clock disabled during Sleep mode
1: SRAM2 interface clock enabled during Sleep mode
Bit 16 SRAM1LPEN: SRAM1 interface clock enable during Sleep mode
This bit is set and cleared by software.
0: SRAM1 interface clock disabled during Sleep mode
1: SRAM1 interface clock enabled during Sleep mode
Bit 15 FLITFLPEN: Flash interface clock enable during Sleep mode
This bit is set and cleared by software.
0: Flash interface clock disabled during Sleep mode
1: Flash interface clock enabled during Sleep mode
Bit 14 Reserved, must be kept at reset value.
Bit 13 AXILPEN: AXI to AHB bridge clock enable during Sleep mode
This bit is set and cleared by software.
0: AXI to AHB bridge clock disabled during Sleep mode
1: AXI to AHB bridge clock enabled during Sleep mode
Bit 12 CRCLPEN: CRC clock enable during Sleep mode
This bit is set and cleared by software.
0: CRC clock disabled during Sleep mode
1: CRC clock enabled during Sleep mode
Bit 11 Reserved, must be kept at reset value.
Bit 10 GPIOKLPEN: IO port K clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port K clock disabled during Sleep mode
1: IO port K clock enabled during Sleep mode

174/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 9 GPIOJLPEN: IO port J clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port J clock disabled during Sleep mode
1: IO port J clock enabled during Sleep mode
Bit 8 GPIOILPEN: IO port I clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port I clock disabled during Sleep mode
1: IO port I clock enabled during Sleep mode
Bit 7 GPIOHLPEN: IO port H clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port H clock disabled during Sleep mode
1: IO port H clock enabled during Sleep mode
Bit 6 GPIOGLPEN: IO port G clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port G clock disabled during Sleep mode
1: IO port G clock enabled during Sleep mode
Bit 5 GPIOFLPEN: IO port F clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port F clock disabled during Sleep mode
1: IO port F clock enabled during Sleep mode
Bit 4 GPIOELPEN: IO port E clock enable during Sleep mode
Set and cleared by software.
0: IO port E clock disabled during Sleep mode
1: IO port E clock enabled during Sleep mode
Bit 3 GPIODLPEN: IO port D clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port D clock disabled during Sleep mode
1: IO port D clock enabled during Sleep mode
Bit 2 GPIOCLPEN: IO port C clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port C clock disabled during Sleep mode
1: IO port C clock enabled during Sleep mode
Bit 1 GPIOBLPEN: IO port B clock enable during Sleep mode
This bit is set and cleared by software.
0: IO port B clock disabled during Sleep mode
1: IO port B clock enabled during Sleep mode
Bit 0 GPIOALPEN: IO port A clock enable during sleep mode
This bit is set and cleared by software.
0: IO port A clock disabled during Sleep mode
1: IO port A clock enabled during Sleep mode

5.3.16

RCC AHB2 peripheral clock enable in low-power mode register
(RCC_AHB2LPENR)
Address offset: 0x54
Reset value: 0x0000 00F1
Access: no wait state, word, half-word and byte access.

RM0385 Rev 7

175/1709
198

Reset and clock control (RCC)

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

HASH
LPEN

CRYP
LPEN

Res.

DCMI
LPEN

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTGFS RNG
LPEN LPEN
rw

rw

Res.

Res.

rw

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 OTGFSLPEN: USB OTG FS clock enable during Sleep mode
This bit is set and cleared by software.
0: USB OTG FS clock disabled during Sleep mode
1: USB OTG FS clock enabled during Sleep mode
Bit 6 RNGLPEN: Random number generator clock enable during Sleep mode
This bit is set and cleared by software.
0: Random number generator clock disabled during Sleep mode
1: Random number generator clock enabled during Sleep mode
Bit 5 HASHLPEN: Hash modules clock enable during Sleep mode
This bit is set and cleared by software.
0: Hash modules clock disabled during Sleep mode
1: Hash modules clock enabled during Sleep mode
Bit 4 CRYPLPEN: Cryptography modules clock enable during Sleep mode
This bit is set and cleared by software.
0: cryptography modules clock disabled during Sleep mode
1: cryptography modules clock enabled during Sleep mode
Bits 3:1 Reserved, must be kept at reset value.
Bit 0 DCMILPEN: Camera interface enable during Sleep mode
This bit is set and cleared by software.
0: Camera interface clock disabled during Sleep mode
1: Camera interface clock enabled during Sleep mode

5.3.17

RCC AHB3 peripheral clock enable in low-power mode register
(RCC_AHB3LPENR)
Address offset: 0x58
Reset value: 0x0000 0003
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

QSPI
LPEN

FMC
LPEN
rw

176/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bits 31:2Reserved, must be kept at reset value.
Bit 1 QSPILPEN: QUADSPI memory controller clock enable during Sleep mode
This bit is set and cleared by software.
0: QUADSPI controller clock disabled during Sleep mode
1: QUADSPI controller clock enabled during Sleep mode
Bit 0 FMCLPEN: Flexible memory controller module clock enable during Sleep mode
This bit is set and cleared by software.
0: FMC module clock disabled during Sleep mode
1: FMC module clock enabled during Sleep mode

5.3.18

RCC APB1 peripheral clock enable in low-power mode register
(RCC_APB1LPENR)
Address offset: 0x60
Reset value: 0xFFFF CBFFh
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

25

24

23

22

21

DAC
LPEN

PWR
LPEN

CEC
LPEN

CAN2
LPEN

CAN1
LPEN

I2C4
LPEN

I2C3
LPEN

I2C2
LPEN

I2C1
LPEN

rw

rw

rw

rw

rw

rw

rw

rw

13

12

11

7

6

Res.

WWDG
LPEN

UART8 UART7
LPEN LPEN
rw
15

14

SPI3
LPEN

SPI2
LPEN

rw

rw

Res.

rw

10
Res.

9

8

LPTMI1 TIM14
LPEN
LPEN
rw

TIM13 TIM12
LPEN LPEN
rw

rw

20

19

18

17

16

UART5 UART4 USART3 USART2 SPDIFRX
LPEN
LPEN LPEN
LPEN
LPEN
rw

rw

rw

rw

rw

5

4

3

2

1

0

TIM7
LPEN

TIM6
LPEN

TIM5
LPEN

TIM4
LPEN

TIM3
LPEN

TIM2
LPEN

rw

rw

rw

rw

rw

rw

Bit 31 UART8LPEN: UART8 clock enable during Sleep mode
This bit is set and cleared by software.
0: UART8 clock disabled during Sleep mode
1: UART8 clock enabled during Sleep mode
Bit 30 UART7LPEN: UART7 clock enable during Sleep mode
This bit is set and cleared by software.
0: UART7 clock disabled during Sleep mode
1: UART7 clock enabled during Sleep mode
Bit 29 DACLPEN: DAC interface clock enable during Sleep mode
This bit is set and cleared by software.
0: DAC interface clock disabled during Sleep mode
1: DAC interface clock enabled during Sleep mode
Bit 28 PWRLPEN: Power interface clock enable during Sleep mode
This bit is set and cleared by software.
0: Power interface clock disabled during Sleep mode
1: Power interface clock enabled during Sleep mode
Bit 27 CECLPEN: HDMI-CEC clock enable during Sleep mode
This bit is set and cleared by software.
0: HDMI-CEC clock disabled during Sleep mode
1: HDMI-CEC clock enabled during Sleep mode

RM0385 Rev 7

177/1709
198

Reset and clock control (RCC)

RM0385

Bit 26 CAN2LPEN: CAN 2 clock enable during Sleep mode
This bit is set and cleared by software.
0: CAN 2 clock disabled during sleep mode
1: CAN 2 clock enabled during sleep mode
Bit 25 CAN1LPEN: CAN 1 clock enable during Sleep mode
This bit is set and cleared by software.
0: CAN 1 clock disabled during Sleep mode
1: CAN 1 clock enabled during Sleep mode
Bit 24 I2C4LPEN: I2C4 clock enable during Sleep mode
This bit is set and cleared by software.
0: I2C4 clock disabled during Sleep mode
1: I2C4 clock enabled during Sleep mode
Bit 23 I2C3LPEN: I2C3 clock enable during Sleep mode
This bit is set and cleared by software.
0: I2C3 clock disabled during Sleep mode
1: I2C3 clock enabled during Sleep mode
Bit 22 I2C2LPEN: I2C2 clock enable during Sleep mode
This bit is set and cleared by software.
0: I2C2 clock disabled during Sleep mode
1: I2C2 clock enabled during Sleep mode
Bit 21 I2C1LPEN: I2C1 clock enable during Sleep mode
This bit is set and cleared by software.
0: I2C1 clock disabled during Sleep mode
1: I2C1 clock enabled during Sleep mode
Bit 20 UART5LPEN: UART5 clock enable during Sleep mode
This bit is set and cleared by software.
0: UART5 clock disabled during Sleep mode
1: UART5 clock enabled during Sleep mode
Bit 19 UART4LPEN: UART4 clock enable during Sleep mode
This bit is set and cleared by software.
0: UART4 clock disabled during Sleep mode
1: UART4 clock enabled during Sleep mode
Bit 18 USART3LPEN: USART3 clock enable during Sleep mode
This bit is set and cleared by software.
0: USART3 clock disabled during Sleep mode
1: USART3 clock enabled during Sleep mode
Bit 17 USART2LPEN: USART2 clock enable during Sleep mode
This bit is set and cleared by software.
0: USART2 clock disabled during Sleep mode
1: USART2 clock enabled during Sleep mode
Bit 16 SPDIFRXLPEN: SPDIFRX clock enable during Sleep mode
This bit is set and cleared by software.
0: SPDIFRX clock disabled during Sleep mode
1: SPDIFRX clock enabled during Sleep mode

178/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 15 SPI3LPEN: SPI3 clock enable during Sleep mode
This bit is set and cleared by software.
0: SPI3 clock disabled during Sleep mode
1: SPI3 clock enabled during Sleep mode
Bit 14 SPI2LPEN: SPI2 clock enable during Sleep mode
This bit is set and cleared by software.
0: SPI2 clock disabled during Sleep mode
1: SPI2 clock enabled during Sleep mode
Bits 13:12 Reserved, must be kept at reset value.
Bit 11 WWDGLPEN: Window watchdog clock enable during Sleep mode
This bit is set and cleared by software.
0: Window watchdog clock disabled during sleep mode
1: Window watchdog clock enabled during sleep mode
Bit 10 Reserved, must be kept at reset value.
Bit 9 LPTIM1LPEN: low-power timer 1 clock enable during Sleep mode
This bit is set and cleared by software.
0: LPTIM1 clock disabled during Sleep mode
1: LPTIM1 clock enabled during Sleep mode
Bit 8 TIM14LPEN: TIM14 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM14 clock disabled during Sleep mode
1: TIM14 clock enabled during Sleep mode
Bit 7 TIM13LPEN: TIM13 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM13 clock disabled during Sleep mode
1: TIM13 clock enabled during Sleep mode
Bit 6 TIM12LPEN: TIM12 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM12 clock disabled during Sleep mode
1: TIM12 clock enabled during Sleep mode
Bit 5 TIM7LPEN: TIM7 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM7 clock disabled during Sleep mode
1: TIM7 clock enabled during Sleep mode
Bit 4 TIM6LPEN: TIM6 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM6 clock disabled during Sleep mode
1: TIM6 clock enabled during Sleep mode
Bit 3 TIM5LPEN: TIM5 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM5 clock disabled during Sleep mode
1: TIM5 clock enabled during Sleep mode

RM0385 Rev 7

179/1709
198

Reset and clock control (RCC)

RM0385

Bit 2 TIM4LPEN: TIM4 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM4 clock disabled during Sleep mode
1: TIM4 clock enabled during Sleep mode
Bit 1 TIM3LPEN: TIM3 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM3 clock disabled during Sleep mode
1: TIM3 clock enabled during Sleep mode
Bit 0 TIM2LPEN: TIM2 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM2 clock disabled during Sleep mode
1: TIM2 clock enabled during Sleep mode

180/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

5.3.19

RCC APB2 peripheral clock enabled in low-power mode register
(RCC_APB2LPENR)
Address offset: 0x64
Reset value: 0x04F7 7F33h
Access: no wait state, word, half-word and byte access.

31
Res.

30
Res.

29
Res.

28
Res.

27

26

Res.

LTDC
LPEN

25
Res.

24

23

22

21

20

Res.

SAI2
LPEN

SAI1
LPEN

SPI6
LPEN

SPI5
LPEN

rw

rw

rw

rw

7

6

5

4

rw
15

14

13

12

11

10

9

8

Res.

SYSCFG
LPEN

SPI4
LPEN

SPI1
LPEN

SDMMC1
LPEN

ADC3
LPEN

ADC2
LPEN

ADC1
LPEN

rw

rw

rw

rw

rw

rw

rw

Res.

Res.

USART6 USART1
LPEN
LPEN
rw

rw

19

18

17

16

Res.

TIM11
LPEN

TIM10
LPEN

TIM9
LPEN

rw

rw

rw

3
Res.

2

1

0

Res.

TIM8
LPEN

TIM1
LPEN

rw

rw

Bits 31:27 Reserved, must be kept at reset value.
Bit 26 LTDCLPEN: LTDC clock enable during Sleep mode
This bit is set and cleared by software.
0: LTDC clock disabled during Sleep mode
1: LTDC clock enabled during Sleep mode
Bits 25:24 Reserved, must be kept at reset value.
Bit 23 SAI2LPEN: SAI2 clock enable during Sleep mode
This bit is set and cleared by software.
0: SAI2 clock disabled during Sleep mode
1: SAI2 clock enabled during Sleep mode
Bit 22 SAI1LPEN: SAI1 clock enable during Sleep mode
This bit is set and cleared by software.
0: SAI1 clock disabled during Sleep mode
1: SAI1 clock enabled during Sleep mode
Bit 21 SPI6LPEN: SPI6 clock enable during Sleep mode
This bit is set and cleared by software.
0: SPI6 clock disabled during Sleep mode
1: SPI6 clock enabled during Sleep mode
Bit 20 SPI5LPEN: SPI5 clock enable during Sleep mode
This bit is set and cleared by software.
0: SPI5 clock disabled during Sleep mode
1: SPI5 clock enabled during Sleep mode
Bit 19 Reserved, must be kept at reset value.
Bit 18 TIM11LPEN: TIM11 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM11 clock disabled during Sleep mode
1: TIM11 clock enabled during Sleep mode
Bit 17 TIM10LPEN: TIM10 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM10 clock disabled during Sleep mode
1: TIM10 clock enabled during Sleep mode

RM0385 Rev 7

181/1709
198

Reset and clock control (RCC)

RM0385

Bit 16 TIM9LPEN: TIM9 clock enable during sleep mode
This bit is set and cleared by software.
0: TIM9 clock disabled during Sleep mode
1: TIM9 clock enabled during Sleep mode
Bit 15 Reserved, must be kept at reset value.
Bit 14 SYSCFGLPEN: System configuration controller clock enable during Sleep mode
This bit is set and cleared by software.
0: System configuration controller clock disabled during Sleep mode
1: System configuration controller clock enabled during Sleep mode
Bit 13 SPI4LPEN: SPI4 clock enable during Sleep mode
This bit is set and cleared by software.
0: SPI4 clock disabled during Sleep mode
1: SPI4 clock enabled during Sleep mode
Bit 12 SPI1LPEN: SPI1 clock enable during Sleep mode
This bit is set and cleared by software.
0: SPI1 clock disabled during Sleep mode
1: SPI1 clock enabled during Sleep mode
Bit 11 SDMMC1LPEN: SDMMC1 clock enable during Sleep mode
This bit is set and cleared by software.
0: SDMMC1 module clock disabled during Sleep mode
1: SDMMC1 module clock enabled during Sleep mode
Bit 10 ADC3LPEN: ADC 3 clock enable during Sleep mode
This bit is set and cleared by software.
0: ADC 3 clock disabled during Sleep mode
1: ADC 3 clock enabled during Sleep mode
Bit 9 ADC2LPEN: ADC2 clock enable during Sleep mode
This bit is set and cleared by software.
0: ADC2 clock disabled during Sleep mode
1: ADC2 clock enabled during Sleep mode
Bit 8 ADC1LPEN: ADC1 clock enable during Sleep mode
This bit is set and cleared by software.
0: ADC1 clock disabled during Sleep mode
1: ADC1 clock enabled during Sleep mode
Bits 7:6 Reserved, must be kept at reset value.
Bit 5 USART6LPEN: USART6 clock enable during Sleep mode
This bit is set and cleared by software.
0: USART6 clock disabled during Sleep mode
1: USART6 clock enabled during Sleep mode
Bit 4 USART1LPEN: USART1 clock enable during Sleep mode
This bit is set and cleared by software.
0: USART1 clock disabled during Sleep mode
1: USART1 clock enabled during Sleep mode

182/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bits 3:2 Reserved, must be kept at reset value.
Bit 1 TIM8LPEN: TIM8 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM8 clock disabled during Sleep mode
1: TIM8 clock enabled during Sleep mode
Bit 0 TIM1LPEN: TIM1 clock enable during Sleep mode
This bit is set and cleared by software.
0: TIM1 clock disabled during Sleep mode
1: TIM1 clock enabled during Sleep mode

5.3.20

RCC backup domain control register (RCC_BDCR)
Address offset: 0x70
Reset value: 0x0000 0000, reset by Backup domain reset.
Access: 0 ≤ wait state ≤ 3, word, half-word and byte access
Wait states are inserted in case of successive accesses to this register.
The LSEON, LSEBYP, LSEDRV[1:0], RTCSEL and RTCEN bits in the RCC backup domain
control register (RCC_BDCR) are in the Backup domain. As a result, after Reset, these bits
are write-protected and the DBP bit in the PWR power control register (PWR_CR1) has to
be set before these can be modified. Refer to Section 5.1.1: System reset on page 132 for
further information. These bits are only reset after a Backup domain Reset (see
Section 5.1.3: Backup domain reset). Any internal or external Reset will not have any effect
on these bits.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BDRST

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

RTCEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

RTCSEL[1:0]
rw

rw

LSEDRV[1:0]
rw

rw

0

LSEBYP LSERDY LSEON
rw

r

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 BDRST: Backup domain software reset
This bit is set and cleared by software.
0: Reset not activated
1: Resets the entire Backup domain
Note: The BKPSRAM is not affected by this reset, the only way of resetting the BKPSRAM is
through the Flash interface when a protection level change from level 1 to level 0 is
requested.
Bit 15 RTCEN: RTC clock enable
This bit is set and cleared by software.
0: RTC clock disabled
1: RTC clock enabled
Bits 14:10 Reserved, must be kept at reset value.

RM0385 Rev 7

183/1709
198

Reset and clock control (RCC)

RM0385

Bits 9:8 RTCSEL[1:0]: RTC clock source selection
These bits are set by software to select the clock source for the RTC. Once the RTC clock
source has been selected, it cannot be changed anymore unless the Backup domain is
reset. The BDRST bit can be used to reset them.
00: No clock
01: LSE oscillator clock used as the RTC clock
10: LSI oscillator clock used as the RTC clock
11: HSE oscillator clock divided by a programmable prescaler (selection through the
RTCPRE[4:0] bits in the RCC clock configuration register (RCC_CFGR)) used as the RTC
clock
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:3 LSEDRV[1:0]: LSE oscillator drive capability
Set by software to modulate the LSE oscillator’s drive capability.
00: Low driving capability
01: Medium high driving capability
10: Medium low driving capability
11: High driving capability
Bit 2 LSEBYP: External low-speed oscillator bypass
This bit is set and cleared by software to bypass the oscillator. This bit can be written only
when the LSE clock is disabled.
0: LSE oscillator not bypassed
1: LSE oscillator bypassed
Bit 1 LSERDY: External low-speed oscillator ready
This bit is set and cleared by hardware to indicate when the external 32 kHz oscillator is
stable. After the LSEON bit is cleared, LSERDY goes low after 6 external low-speed
oscillator clock cycles.
0: LSE clock not ready
1: LSE clock ready
Bit 0 LSEON: External low-speed oscillator enable
This bit is set and cleared by software.
0: LSE clock OFF
1: LSE clock ON

5.3.21

RCC clock control & status register (RCC_CSR)
Address offset: 0x74
Reset value: 0x0E00 0000, reset by system reset, except reset flags by power reset only.
Access: 0 ≤ wait state ≤ 3, word, half-word and byte access
Wait states are inserted in case of successive accesses to this register.

31

30

LPWR WWDG
RSTF RSTF
r

r

29

28

27

26

25

24

23

22

21

20

19

18

17

16

IWDG
RSTF

SFT
RSTF

POR
RSTF

PIN
RSTF

BOR
RSTF

RMVF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

r

r

r

r

rw
1

0

15

14

13

12

11

10

9

8

7

6

5

4

3

2

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LSIRDY LSION
r

184/1709

RM0385 Rev 7

rw

RM0385

Reset and clock control (RCC)

Bit 31 LPWRRSTF: Low-power reset flag
This bit is set by hardware when a Low-power management reset occurs.
Cleared by writing to the RMVF bit.
0: No Low-power management reset occurred
1: Low-power management reset occurred
For further information on Low-power management reset, refer to Low-power management
reset.
Bit 30 WWDGRSTF: Window watchdog reset flag
This bit is set by hardware when a window watchdog reset occurs.
Cleared by writing to the RMVF bit.
0: No window watchdog reset occurred
1: Window watchdog reset occurred
Bit 29 IWDGRSTF: Independent watchdog reset flag
This bit is set by hardware when an independent watchdog reset from VDD domain occurs.
Cleared by writing to the RMVF bit.
0: No watchdog reset occurred
1: Watchdog reset occurred
Bit 28 SFTRSTF: Software reset flag
This bit is set by hardware when a software reset occurs.
Cleared by writing to the RMVF bit.
0: No software reset occurred
1: Software reset occurred
Bit 27 PORRSTF: POR/PDR reset flag
This bit is set by hardware when a POR/PDR reset occurs.
Cleared by writing to the RMVF bit.
0: No POR/PDR reset occurred
1: POR/PDR reset occurred
Bit 26 PINRSTF: PIN reset flag
This bit is set by hardware when a reset from the NRST pin occurs.
Cleared by writing to the RMVF bit.
0: No reset from NRST pin occurred
1: Reset from NRST pin occurred
Bit 25 BORRSTF: BOR reset flag
Cleared by software by writing the RMVF bit.
This bit is set by hardware when a POR/PDR or BOR reset occurs.
0: No POR/PDR or BOR reset occurred
1: POR/PDR or BOR reset occurred
Bit 24 RMVF: Remove reset flag
This bit is set by software to clear the reset flags.
0: No effect
1: Clear the reset flags

RM0385 Rev 7

185/1709
198

Reset and clock control (RCC)

RM0385

Bits 23:2 Reserved, must be kept at reset value.
Bit 1 LSIRDY: Internal low-speed oscillator ready
This bit is set and cleared by hardware to indicate when the internal RC 40 kHz oscillator is
stable. After the LSION bit is cleared, LSIRDY goes low after 3 LSI clock cycles.
0: LSI RC oscillator not ready
1: LSI RC oscillator ready
Bit 0 LSION: Internal low-speed oscillator enable
This bit is set and cleared by software.
0: LSI RC oscillator OFF
1: LSI RC oscillator ON

5.3.22

RCC spread spectrum clock generation register (RCC_SSCGR)
Address offset: 0x80
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.
The spread spectrum clock generation is available only for the main PLL.
The RCC_SSCGR register must be written either before the main PLL is enabled or after
the main PLL disabled.

Note:

For full details about PLL spread spectrum clock generation (SSCG) characteristics, refer to
the “Electrical characteristics” section in your device datasheet.

31

30

29

28

SSCG
EN

SPR
EAD
SEL

Res.

Res.

13

12

rw

rw

15

14

27

26

25

24

23

rw

21

20

19

18

17

16

INCSTEP
rw

rw

rw

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

INCSTEP
rw

22

MODPER
rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 SSCGEN: Spread spectrum modulation enable
This bit is set and cleared by software.
0: Spread spectrum modulation DISABLE. (To write after clearing CR[24]=PLLON bit)
1: Spread spectrum modulation ENABLE. (To write before setting CR[24]=PLLON bit)
Bit 30 SPREADSEL: Spread Select
This bit is set and cleared by software.
To write before to set CR[24]=PLLON bit.
0: Center spread
1: Down spread

186/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bits 29:28 Reserved, must be kept at reset value.
Bits 27:13 INCSTEP: Incrementation step
These bits are set and cleared by software. To write before setting CR[24]=PLLON bit.
Configuration input for modulation profile amplitude.
Bits 12:0 MODPER: Modulation period
These bits are set and cleared by software. To write before setting CR[24]=PLLON bit.
Configuration input for modulation profile period.

5.3.23

RCC PLLI2S configuration register (RCC_PLLI2SCFGR)
Address offset: 0x84
Reset value: 0x2400 3000
Access: no wait state, word, half-word and byte access.
This register is used to configure the PLLI2S clock outputs according to the formulas:
f(VCO clock) = f(PLLI2S clock input) × (PLLI2SN / PLLM)
f(PLLI2S_P) = f(VCO clock) / PLLI2SP
f(PLLI2S_Q) = f(VCO clock) / PLLI2SQ
f(PLLI2S_R) = f(VCO clock) / PLLI2SR

31

30

Res.

15

29

28

27

PLLI2SR[2:0]

26

25

24

PLLI2SQ[0:3]

rw

rw

rw

rw

14

13

12

11

Res.

rw

rw

rw

10

9

8

23

22

21

20

19

18

Res.

Res.

Res.

Res.

Res.

Res.

rw
7

6

PLLI2SN[8:0]
rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

17

rw

16

PLLI2SP[1:0]
rw

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

rw

187/1709
198

Reset and clock control (RCC)

RM0385

Bit 31 Reserved, must be kept at reset value.
Bits 30:28 PLLI2SR[2:0]: PLLI2S division factor for I2S clocks
These bits are set and cleared by software to control the I2S clock frequency. These bits
should be written only if the PLLI2S is disabled. The factor must be chosen in accordance
with the prescaler values inside the I2S peripherals, to reach 0.3% error when using
standard crystals and 0% error with audio crystals. For more information about I2S clock
frequency and precision, refer to Section 32.7.4: Start-up description in the I2S chapter.
Caution: The I2Ss requires a frequency lower than or equal to 192 MHz to work correctly.
I2S clock frequency = VCO frequency / PLLR with 2 ≤ PLLR ≤ 7
000: PLLR = 0, wrong configuration
001: PLLR = 1, wrong configuration
010: PLLR = 2
...
111: PLLR = 7
Bits 27:24 PLLI2SQ[3:0]: PLLI2S division factor for SAIs clock
These bits are set and cleared by software to control the SAIs clock frequency.
They should be written when the PLLI2S is disabled.
SAI clock frequency = VCO frequency / PLLI2SQ with 2 <= PLLI2SIQ <= 15
0000: PLLI2SQ = 0, wrong configuration
0001: PLLI2SQ = 1, wrong configuration
0010: PLLI2SQ = 2
0011: PLLI2SQ = 3
0100: PLLI2SQ = 4
0101: PLLI2SQ = 5
...
1111: PLLI2SQ = 15
Bits 23:18 Reserved, must be kept at reset value.
Bits 17:16 PLLI2SP[1:0]: PLLI2S division factor for SPDIFRX clock
These bits are set and cleared by software to control the SPDIFRX clock. These
bits can be written only if the PLLI2S is disabled.
The factor must be chosen in accordance with the prescaler values inside the SPDIF to
reach an audio clock close to 44 kHz or 48 kHz according to the SPDIF mode
SPDIF clock frequency = VCO frequency / PLLI2SP with PLLI2S P = 2, 4, 6, or 8
00: PLLI2SP = 2
01: PLLI2SP = 4
10: PLLI2SP = 6
11: PLLI2SP = 8

188/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bit 15 Reserved, must be kept at reset value.
Bits 14:6 PLLI2SN[8:0]: PLLI2S multiplication factor for VCO
These bits are set and cleared by software to control the multiplication factor of the VCO.
These bits can be written only when the PLLI2S is disabled. Only half-word and word
accesses are allowed to write these bits.
Caution: The software has to set these bits correctly to ensure that the VCO output
frequency is between 100 and 432 MHz.
VCO output frequency = VCO input frequency × PLLI2SN with 50 ≤ PLLI2SN ≤ 432
000000000: PLLI2SN = 0, wrong configuration
000000001: PLLI2SN = 1, wrong configuration
...
001100010: PLLI2SN = 50
...
001100011: PLLI2SN = 99
001100100: PLLI2SN = 100
001100101: PLLI2SN = 101
001100110: PLLI2SN = 102
...
110110000: PLLI2SN = 432
110110000: PLLI2SN = 433, wrong configuration
...
111111111: PLLI2SN = 511, wrong configuration
Note: Between 50 and 99, multiplication factors are possible for VCO input frequency higher
than 1 MHz. However care must be taken to fulfill the minimum VCO output frequency
as specified above.
Bits 5:0 Reserved, must be kept at reset value.

RM0385 Rev 7

189/1709
198

Reset and clock control (RCC)

5.3.24

RM0385

RCC PLLSAI configuration register (RCC_PLLSAICFGR)
Address offset: 0x88
Reset value: 0x2400 3000
Access: no wait state, word, half-word and byte access.
This register is used to configure the PLLSAI clock outputs according to the formulas:

31

30

Res.

15

•

f(VCO clock) = f(PLLSAI clock input) × (PLLSAIN / PLLM)

•

f(PLLISAI_P) = f(VCO clock) / PLLSAIP

•

f(PLLISAI_Q) = f(VCO clock) / PLLSAIQ

•

f(PLLISAI_R) = f(VCO clock) / PLLSAIR
29

28

27

PLLSAIR[2:0]

26

25

24

PLLSAIQ[4:0]

23

22

21

20

19

18

Res.

Res.

Res.

Res.

Res.

Res.

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

14

13

12

11

10

9

8

7

6

rw

rw

rw

rw

rw

rw

rw

rw

Res.

PLLSAIN[8:0]
rw

Bit 31 Reserved, must be kept at reset value.
Bits 30:28 PLLSAIR[2:0]: PLLSAI division factor for LCD clock
Set and reset by software to control the LCD clock frequency.
These bits should be written when the PLLSAI is disabled.
LCD clock frequency = VCO frequency / PLLSAIR with 2 ≤ PLLSAIR ≤ 7
000: PLLSAIR = 0, wrong configuration
001: PLLSAIR = 1, wrong configuration
010: PLLSAIR = 2
...
111: PLLSAIR = 7
Bits 27:24 PLLSAIQ[3:0]: PLLSAI division factor for SAI clock
Set and reset by software to control the frequency of SAI clock.
These bits should be written when the PLLSAI is disabled.
SAI1 clock frequency = VCO frequency / PLLSAIQ with 2 ≤ PLLSAIQ ≤ 15
0000: PLLSAIQ = 0, wrong configuration
0001: PLLSAIQ = 1, wrong configuration
...
0010: PLLSAIQ = 2
0011: PLLSAIQ = 3
0100: PLLSAIQ = 4
0101: PLLSAIQ = 5
...
1111: PLLSAIQ = 15
Bits 23:18 Reserved, must be kept at reset value.

190/1709

RM0385 Rev 7

17

16

PLLSAIP[1:0]

RM0385

Reset and clock control (RCC)

Bits 17:16 PLLSAIP[1:0]: PLLSAI division factor for 48MHz clock
Set and reset by software to control the frequency of the PLLSAI output clock
(PLLSAI48CLK). This output can be selected for USB, RNG, SDMMC (48 MHz clock). These
bits should be written only if the PLLSAI is disabled.
Only half-word and word accesses are allowed to write these bits.
PLLSAI48 output clock frequency = VCO frequency / PLLSAIP with PLLSAI P = 2, 4, 6, or 8
00: PLLSAIP = 2
01: PLLSAIP = 4
10: PLLSAIP = 6
11: PLLSAIP = 8
Bit 15 Reserved, must be kept at reset value.
Bits 14:6 PLLSAIN[8:0]: PLLSAI division factor for VCO
Set and reset by software to control the multiplication factor of the VCO.
These bits should be written when the PLLSAI is disabled.
Only half-word and word accesses are allowed to write these bits.
Caution: The software has to set these bits correctly to ensure that the VCO output frequency
is between 100 and 432 MHz.
VCO output frequency = VCO input frequency x PLLSAIN with 50 ≤ PLLSAIN ≤ 432
000000000: PLLSAIN = 0, wrong configuration
000000001: PLLSAIN = 1, wrong configuration
......
001100010: PLLISAIN = 50
...
001100011: PLLISAIN = 99
001100100: PLLISAIN = 100
001100101: PLLISAIN = 101
001100110: PLLISAIN = 102
...
110110000: PLLSAIN = 432
110110000: PLLSAIN = 433, wrong configuration
...
111111111: PLLSAIN = 511, wrong configuration
Note: Between 50 and 99, multiplication factors are possible for VCO input frequency higher
than 1 MHz. However care must be taken to fulfill the minimum VCO output frequency
as specified above.
Bits 5:0 Reserved, must be kept at reset value

5.3.25

RCC dedicated clocks configuration register (RCC_DKCFGR1)
Address offset: 0x8C
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.
This register allows to configure the timer clock prescalers and the PLLSAI and PLLI2S
output clock dividers for SAIs and LTDC peripherals according to the following formula:
f(PLLSAIDIVQ clock output) = f(PLLSAI_Q) / PLLSAIDIVQ
f(PLLSAIDIVR clock output) = f(PLLSAI_R) / PLLSAIDIVR
f(PLLI2SDIVQ clock output) = f(PLLI2S_Q) / PLLI2SDIVQ
RM0385 Rev 7

191/1709
198

Reset and clock control (RCC)

RM0385

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMPRE

15

14

13

Res.

Res.

Res.

12

11

10

9

rw

rw

rw

22

SAI2SEL[1:0]

21

20

SAI1SEL[1:0]

rw

rw

rw

rw

rw

8

7

6

5

4

Res.

Res.

Res.

PLLSAIDIVQ[4:0]
rw

23

rw

19

18

Res.

Res.

3

2

17

16

PLLSAIDIVR[1:0]
rw

rw

1

0

rw

rw

PLLI2SDIVQ[4:0]
rw

rw

rw

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 TIMPRE: Timers clocks prescalers selection
This bit is set and reset by software to control the clock frequency of all the timers connected
to APB1 and APB2 domain.
0: If the APB prescaler (PPRE1, PPRE2 in the RCC_CFGR register) is configured to a
division factor of 1, TIMxCLK = PCLKx. Otherwise, the timer clock frequencies are set to
twice to the frequency of the APB domain to which the timers are connected:
TIMxCLK = 2xPCLKx.
1:If the APB prescaler (PPRE1, PPRE2 in the RCC_CFGR register) is configured to a
division factor of 1, 2 or 4, TIMxCLK = HCLK. Otherwise, the timer clock frequencies are set
to four times to the frequency of the APB domain to which the timers are connected:
TIMxCLK = 4xPCLKx.
Bits 23:22 SAI2SEL[1:0]: SAI2 clock source selection:
These bits are set and cleared by software to control the SAI2 clock frequency.
They should be written when the PLLSAI and PLLI2S are disabled.
00: SAI2 clock frequency = f(PLLSAI_Q) / PLLSAIDIVQ
01: SAI2 clock frequency = f(PLLI2S_Q) / PLLI2SDIVQ
10: SAI2 clock frequency = Alternate function input frequency
11: wrong configuration
Bits 21:20 SAI1SEL[1:0]: SAI1 clock source selection
These bits are set and cleared by software to control the SAI1 clock frequency.
They should be written when the PLLSAI and PLLI2S are disabled.
00: SAI1 clock frequency = f(PLLSAI_Q) / PLLSAIDIVQ
01: SAI1 clock frequency = f(PLLI2S_Q) / PLLI2SDIVQ
10: SAI1 clock frequency = Alternate function input frequency
11: wrong configuration
Bits 19: 18 Reserved, must be kept at reset value.
Bits 17:16 PLLSAIDIVR[1:0]: division factor for LCD_CLK
These bits are set and cleared by software to control the frequency of LCD_CLK.
They should be written only if PLLSAI is disabled.
LCD_CLK frequency = f(PLLSAI_R) / PLLSAIDIVR with 2 ≤ PLLSAIDIVR ≤ 16
00: PLLSAIDIVR = /2
01: PLLSAIDIVR = /4
10: PLLSAIDIVR = /8
11: PLLSAIDIVR = /16
Bits 15: 13 Reserved, must be kept at reset value.

192/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bits 12:8 PLLSAIDIVQ[4:0]: PLLSAI division factor for SAI1 clock
These bits are set and reset by software to control the SAI1 clock frequency.
They should be written only if PLLSAI is disabled.
SAI1 clock frequency = f(PLLSAI_Q) / PLLSAIDIVQ with 1 ≤ PLLSAIDIVQ ≤ 31
00000: PLLSAIDIVQ = /1
00001: PLLSAIDIVQ = /2
00010: PLLSAIDIVQ = /3
00011: PLLSAIDIVQ = /4
00100: PLLSAIDIVQ = /5
...
11111: PLLSAIDIVQ = /32
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:0 PLLI2SDIV[4:0]: PLLI2S division factor for SAI1 clock
These bits are set and reset by software to control the SAI1 clock frequency.
They should be written only if PLLI2S is disabled.
SAI1 clock frequency = f(PLLI2S_Q) / PLLI2SDIVQ with 1 <= PLLI2SDIVQ <= 31
00000: PLLI2SDIVQ = /1
00001: PLLI2SDIVQ = /2
00010: PLLI2SDIVQ = /3
00011: PLLI2SDIVQ = /4
00100: PLLI2SDIVQ = /5
...
11111: PLLI2SDIVQ = /32

5.3.26

RCC dedicated clocks configuration register (DCKCFGR2)
Address: 0x90h
Reset value: 0x0000 0000h
Access: no wait state, word, half-word and byte access
This register allows to select the source clock for the 48MHz, SDMMC, HDMI-CEC,
LPTIM1, UARTs, USARTs and I2Cs clocks.

31

30

29

Res.

Res.

Res.

15

14

13

28

26

SDMM CK48M CECSE
C1SEL
SEL
L

25

24

LPTIM1SEL

23

22

I2C4SEL

21

20

I2C3SEL

19

18

I2C2SEL

17

16

I2C1SEL

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

12

11

10

9

8

7

6

5

4

3

2

1

0

UART8SEL

UART7SEL

rw

rw

rw

27

rw

USART6SEL
rw

rw

UART5SEL

UART4SEL

UART3SEL

UART2SEL

UART1SEL

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

rw

rw

rw

rw

193/1709
198

Reset and clock control (RCC)

RM0385

Bits 31:29 Reserved, must be kept at reset value.
Bit 28 SDMMCSEL: SDMMC clock source selection
Set and reset by software.
0: 48 MHz clock is selected as SDMMC clock
1: System clock is selected as SDMMC clock
Bit 27 CK48MSEL: 48MHz clock source selection
Set and reset by software.
0: 48MHz clock from PLL is selected
1: 48MHz clock from PLLSAI is selected.
Bit 26 CECSEL: HDMI-CEC clock source selection
Set and reset by software.
0: LSE clock is selected as HDMI-CEC clock
1: HSI divided by 488 clock is selected as HDMI-CEC clock
Bits 25:24 LPTIM1SEL: Low-power timer 1 clock source selection
Set and reset by software.
00: APB1 clock (PCLK1) selected as LPTILM1 clock
01: LSI clock is selected as LPTILM1 clock
10: HSI clock is selected as LPTILM1 clock
11: LSE clock is selected as LPTILM1 clock
Bits 23:22 I2C4SEL: I2C4 clock source selection
Set and reset by software.
00: APB1 clock ( PCLK1) is selected as I2C4 clock
01: System clock is selected as I2C4 clock
10: HSI clock is selected as I2C4 clock
11: reserved
Bits 21:20 I2C3SEL: I2C3 clock source selection
Set and reset by software.
00: APB clock is selected as I2C3 clock
01: System clock is selected as I2C3 clock
10: HSI clock is selected as I2C3 clock
11: reserved
Bits 19:18 I2C2SEL: I2C2 clock source selection
Set and reset by software.
00: APB1 clock (PCLK1) is selected as I2C2 clock
01: System clock is selected as I2C2 clock
10: HSI clock is selected as I2C2 clock
11: reserved
Bits 17:16 I2C1SEL: I2C1 clock source selection
Set and reset by software.
00: APB clock (PCLK1) is selected as I2C1 clock
01: System clock is selected as I2C1 clock
10: HSI clock is selected as I2C1 clock
11: reserved

194/1709

RM0385 Rev 7

RM0385

Reset and clock control (RCC)

Bits 15:14 UART8SEL[1:0]: UART 8 clock source selection
Set and reset by software.
00: APB1 clock (PCLK1) is selected as UART 8 clock
01: System clock is selected as UART 8 clock
10: HSI clock is selected as UART 8 clock
11: LSE clock is selected as UART 8 clock
Bits 13:12 UART7SEL[1:0]: UART 7 clock source selection
Set and reset by software.
00: APB1 clock (PCLK1) is selected as UART 7 clock
01: System clock is selected as UART 7 clock
10: HSI clock is selected as UART 7 clock
11: LSE clock is selected as UART 7 clock
Bits 11:10 USART6SEL[1:0]: USART 6 clock source selection
Set and reset by software.
00: APB2 clock(PCLK2) is selected as USART 6 clock
01: System clock is selected as USART 6 clock
10: HSI clock is selected as USART 6 clock
11: LSE clock is selected as USART 6 clock
Bits 9:8 UART5SEL[1:0]: UART 5 clock source selection
Set and reset by software.
00: APB1 clock(PCLK1) is selected as UART 5 clock
01: System clock is selected as UART 5 clock
10: HSI clock is selected as UART 5 clock
11: LSE clock is selected as UART 5 clock
Bits7:6 UART4SEL[1:0]: UART 4 clock source selection
Set and reset by software.
00: APB1 clock (PLCLK1) is selected as UART 4 clock
01: System clock is selected as UART 4 clock
10: HSI clock is selected as UART 4 clock
11: LSE clock is selected as UART 4 clock
Bits5:4 USART3SEL[1:0]: USART 3 clock source selection
Set and reset by software.
00: APB1 clock (PCLK1) is selected as USART 3 clock
01: System clock is selected as USART 3 clock
10: HSI clock is selected as USART 3 clock
11: LSE clock is selected as USART 3 clock
Bits 3:2 USART2SEL[1:0]: USART 2 clock source selection
Set and reset by software.
00: APB1 clock (PCLK1) is selected as USART 2 clock
01: System clock is selected as USART 2 clock
10: HSI clock is selected as USART 2 clock
11: LSE clock is selected as USART 2 clock
Bits 1:0 USART1SEL[1:0]: USART 1 clock source selection
Set and reset by software.
00: APB2 clock (PCLK2) is selected as USART 1 clock
01: System clock is selected as USART 1 clock
10: HSI clock is selected as USART 1 clock
11: LSE clock is selected as USART 1 clock

RM0385 Rev 7

195/1709
198

Reserved

0x30

RCC_
AHB1ENR

0x34

RCC_
AHB2ENR

196/1709

DMA2DEN

DMA2EN

DMA1EN

Res.

Res.

Res.

RM0385 Rev 7

GPIOAEN

GPIOFEN

DCMIEN

GPIOGEN

RNGEN

HASHEN

GPIOBEN

GPIOHEN

OTGFSEN

Res.

GPIOIEN

Res.

GPIOCEN

GPIOJEN

Res.

Res.

GPIOKEN

Res.

GPIOEEN

Res.

Res.

GPIODEN

CRCEN

Res.

Res.

Res. Res.

Res.

Res.

CRYPEN

Res. Res.

Res.

Res.

Res. Res.

Res. Res.

Res. Res.

TIM5RST
TIM4RST
TIM3RST
TIM2RST

Res.
Res.
TIM8RST
TIM1RST

TIM6RST

Res. Res.

Res. Res. USART1RST

TIM12RST Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

GPIOJRST

GPIOKRST

Res.

CRCRST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA1RST

GPIOGRST PLLSAIRDYF

CSSF

LSIRDYIE

LSERDYIE

HSIRDYIE

HSERDYIE

PLLRDYIE

PLLI2SRDYIE

Res.

Res.

Res.

GPIOARST

GPIOBRST

GPIOCRST

GPIODRST

CRYPRST GPIOERST

PLLRDYF

LSIRDYF

LSERDYF

HSIRDYF

HSERDYF

Res.

Res.

Res.
PLL SAION

PLL SAIRDY

Res.

Res.

Res.

Res.

Res.

Res.

PPRE2 2

SW 0

SW 1

SWS 0

SWS 1

HPRE 0

HPRE 1

HPRE 2

HPRE 3

Res.

Res.

HSICAL 0

HSICAL 1

HSICAL 2

HSICAL 3

HSICAL 4

HSICAL 5

HSICAL 6

HSICAL 7

HSEON

HSERDY

HSEBYP

CSSON

Res.

Res.

Res.

Res.

PLL ON

PLL RDY

PLLM 0

PLLM 1

PLLM 2

HSION

HSIRDY

Reserved

PLLM 3 HSITRIM 0

PLLM 4 HSITRIM 1

PLLM 5 HSITRIM 2

PLLN 0 HSITRIM 3

PLLN 1 HSITRIM 4

PLLN 2

PLLN 3

PPRE1 2 PLLN 6
PPRE1 1 PLLN 5
PPRE1 0 PLLN 4

PPRE2 0 PLLN 7

PLLN 8

Res.

RTCPRE 0 PLLP 0

RTCPRE 1 PLLP 1

RTCPRE 2

RTCPRE 3

MCO1 0
RTCPRE 4

MCO1 1 PLLSRC

I2SSRC

MCO1PRE1 PLLQ 1
MCO1PRE0 PLLQ 0

MCO1PRE2 PLLQ 2 PLL I2SON

MCO2PRE0 PLLQ 3 PLL I2SRDY

MCO2PRE1

MCO2PRE2

MCO2 0

PLLSAIRDYIE PPRE2 1

Res.

LSIRDYC

LSERDYC

HSIRDYC

HSERDYC

PLLRDYC

PLLI2SRDYC

HASHRST GPIOFRST PLLI2SRDYF

RNGRST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CSSC
DMA2RST PLLSAIRDYC

DMA2DRST

Res.

ETHMACRST

Res.

Res.

Res.

OTGHSRST

Res.

Res.
GPIOIRST
OTGFSRS GPIOHRST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res. FMCRST DCMIRST

Res. QSPIRST

Res.

Res.

Res.

Res.

TIM13RST Res.

Res.
TIM7RST

TIM14RST Res.

ADCRST

Res.

LPTIM1RST Res.

Res.

Res.

Res.

Res. Res. USART6RST

Res. Res.

Res. Res.

Res. Res.

Res.

Res.

Res.

Res. Res. SDMMC1RST WWDGRST Res.

Res.

SPI1RST

Res.

Res.
Res.

Res.

SPI2RST

SP45RST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res. Res.

Res. Res.

Res. Res. SYSCFGRST

Res. Res.

Res.

Res.

Res.

SPI3RST

SPDIFRXRST Res.

TIM9RST

Res.

Res.
Res.

UART2RST Res.

Res. Res.

UART3RST Res.

Res. Res. TIM10RST

Res.

UART4RST Res.

Res.

BKPSRAMEN Res. Res. TIM11RST

Res. Res.

Res.

Res.

Res.

Res.

UART5RST Res.

I2C1RST

I2C2RST

I2C3RST

I2C4RST

CAN1RST Res.

Res.

Reserved

Res.

Res.

Res.

CAN2RST Res.

CECRST

PWRRST

DACRST

UART7RST Res.

SPI5RST

SPI6RST

SAI1RST

Res.
SAI2RST

Res.

LTDCRST

Res.

Res.

Res.

Res.

Res.

Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

DTCMRAMEN Res. Res.

Res.

Res.

Res.

ETHMACEN

RCC_APB2RS
TR

ETHMACTXEN Res. Res.

0x24

Res.

RCC_APB1RS
TR

Res.

0x20

ETHMACRXEN Res. Res.

Reserved

Res.

0x1C

Res. Res.

RCC_AHB3RS
TR

OTGHSEN

0x18

ETHMACPTPEN Res. Res.

RCC_AHB2RS
TR

Res.

0x14

Res.

RCC_AHB1RS
TR

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

0x10
Res.

RCC_CIR
Res.

0x0C
MCO2 1

RCC_CFGR

Res.

0x08

Res.

RCC_PLLCFG
R

Res.

0x04

Res.

RCC_CR

UART8RST Res.

0x00

Res.

Register
name

Res. Res.

Reserved

Res.

Addr.
offset

OTGHSULPIEN Res. Res.

5.3.27

Res.

0x28

0x2C

Res.

Reset and clock control (RCC)
RM0385

RCC register map
Table 20 gives the register map and reset values.
Table 20. RCC register map and reset values

0x68
Reserved

0x6C

Reserved

0x70

RCC_BDCR

0x74

RCC_CSR

0x78

Reserved

0x7C

Reserved

RM0385 Rev 7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

LSION

Res.

Res. Res.

Res. Res.

Res.

Res. Res.

LSIRDY

Res.

Res. Res.

Res. Res.

Res.

Res. Res.

Res.

Res.

Res. Res.

Res. Res.

Res.

RMVF

Res. Res.

Res.

SPI5LPEN

SPI6LPEN

SAI1LPEN

SAI2LPEN

Res.

Res.

Res.

TIM9LPEN

SPI1LPEN

SPI4LPEN

Res. Res. ADC3LPEN

Res.

Res.

Res. Res.

Res. Res.

Res. Res.

LSERDY

LSEON

Res. Res.

TIM1LPEN

TIM8LPEN

Res.

Res.

Res. Res. USART1LPEN

Res. Res. USART6LPEN

Res. Res.

LSEBYP

LSEDRV[1:0]

Res.

Res.

Res. Res.

RTCSEL 0 Res. Res. ADC1LPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SPI2LPEN

SPI3LPEN

Res.

Res.

Res.

Res.

SPDIFRXLPEN Res.

USART2LPEN Res.

USART3LPEN Res.

UART4LPEN Res.

UART5LPEN Res.

I2C1LPEN

I2C2LPEN

I2C3LPEN

I2C4LPEN

CAN1LPEN Res.

CAN2LPEN Res.

CECLPEN

PWRLPEN

DACLPEN

UART7LPEN Res.

Res.

TIM2LPEN

TIM3LPEN

TIM4LPEN

TIM5LPEN

TIM6LPEN

TIM7LPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CRYPLPEN

HASHLPEN

RNGLPEN

OTGFSLPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res. FMCLPEN DCMILPEN

Res. QSPILPEN

Res.

Res.

Res.

Res.

TIM12LPEN Res.

TIM13LPEN Res.

TIM14LPEN Res.

LPTIM1LPEN Res.

Res.

Res. Res. SDMMC1LPEN WWDGLPEN Res.

Res. Res.

Res. Res.

Res. Res. SYSCFGLPEN

Res. Res.

Res. Res.

Res. Res. TIM10LPEN

Res. Res. TIM11LPEN

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res. LTDCLPEN

Res.

Res.

Res.

Res.

RTCSEL 1 Res. Res. ADC2LPEN

Res.

Res.

Res.

Res.

Res.

RTCEN

BDRST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res. Res. BORRSTF

Res.

RCC_APB2LP
ENR

Res. Res. PINRSTF

0x64

Res. Res.

RCC_APB1LP
ENR

Res.

0x60

Res. Res. PORRSTF

Reserved

Res. Res.

0x5C

Res. Res.

RCC_AHB3LP
ENR

Res.

0x58

Res.

RCC_AHB2LP
ENR

Res. Res. SFTRSTF

0x54

Res. Res. WDGRSTF

RCC_AHB1LP
ENR
Res. Res.
Res.

Res.

Res.

Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res.

SPI5EN

SPI6EN

SAI1EN

SAI2EN

Res.

Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

UART4EN Res. Res.

UART5EN Res. Res.

I2C1EN

I2C2EN

I2C3EN

I2C4EN

CAN1EN Res. Res.

CAN2EN Res. Res.

CECEN

PWREN

DACEN

SPI7EN

GPIOALPEN

GPIOBLPEN

GPIOCLPEN

GPIODLPEN

GPIOELPEN

GPIOFLPEN

GPIOGLPEN

GPIOHLPEN

GPIOILPEN

GPIOJLPEN

GPIOKLPEN

Res.

CRCLPEN

AXILPEN

Res.

FLITFLPEN

SRAM1LPEN

SRAM2LPEN

Res.

TIM9EN

SPI1EN

SPI4EN

Res.

Res.

SPI2EN

SPI3EN

Res. Res.

Res. Res.

Res. Res.

Res. Res.

SPDIFRXEN Res. Res.

Res.

Res.

Res. Res.

Res. Res.

Res. Res.

Res. Res.

TIM1EN

TIM8EN

Res.

Res.

Res. Res. USART1EN

Res. Res. USART6EN

Res. Res.

Res. Res.

Res. Res. ADC1EN

Res. Res. ADC2EN

Res. Res. ADC3EN

Res. Res.

TIM2EN

TIM3EN

TIM4EN

TIM5EN

TIM6EN

TIM7EN

Res. FMCEN

Res. QSPIEN

Res. Res.

Res. Res.

Res. Res.

Res. Res.

TIM12EN Res. Res.

TIM13EN Res. Res.

TIM14EN Res. Res.

LPTIM1EN Res. Res.

Res.

Res. Res. SDMMC1EN WWDGEN Res. Res.

Res. Res.

Res. Res.

Res. Res. SYSCFGEN

Res. Res.

Res. Res.

Res. Res. TIM10EN USART2EN Res. Res.

BKPSRAMLPEN Res. Res. TIM11EN USART3EN Res. Res.

Res.

DTCMLPEN

DMA1LPEN

DMA2LPEN

DMA2DLPEN

Res.

ETHMACLPEN

ETHMACTXLPEN Res. Res. LTDCEN

ETHMACRXLPEN Res. Res.

ETHMACPTPLPEN Res. Res.

OTGHSLPEN

OTGHSULPILPEN Res. Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

0x50
Res. Res.

Reserved
SPI8EN

0x4C
Res.

Reserved

Res. Res.

0x48

Res.

RCC_
APB2ENR

Res.

0x44

Res.

RCC_
APB1ENR

UART8LPEN Res.

0x40

Res.

Reserved

Res. Res.

0x3C

Res. Res.

RCC_
AHB3ENR

Res.

0x38

Res.

Register
name

Res. Res. WWDGRSTF

Addr.
offset

Res. Res. LPWRRSTF

RM0385
Reset and clock control (RCC)

Table 20. RCC register map and reset values (continued)

197/1709

198

198/1709

RM0385 Rev 7

Refer to Section 2.2.2 on page 69 for the register boundary addresses.
UART1SEL

Res.

Res.

Res.

PLLSAIDIVQ[4:0]

UART2SEL

Res.

Res.

Res.

Res.

Res.
Res.
Res.
Res.
Res.
Res.

Res.
Res.
Res.
Res.
Res.
Res.

PLLSAIN[8:0]

Res.

PLLI2SN[8:0]

UART3SEL

Res.

Res.

PLLSAIDIVR[1:0] PLLSAIP[1:0] PLLI2SP[1:0]

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

SAI1SEL[1:0]

Res.

Res.

PLLSAIQ[4:0]

INCSTEP

UART4SEL

UART5SEL

UART6SEL

UART7SEL

UART8SEL

I2C1SEL

I2C2SEL

I2C3SEL

SAI2SEL[1:0]

TIMPRE

Res.

Res.

Res.

PLLI2SR[2:
PLLI2SQ[3:0]
0]

I2C4SEL

LPTIM1SEL

Res.

Res.

CECSEL

Res.

RCC_DCKCF
GR2
Res.

Res.

0x90
CK48MSEL

RCC_DCKCF
GR1
PLLSAIR[2:0]

Res.

0x8C
Res.

RCC_PLLSAI
CFGR

Res.

0x88

Res.

RCC_PLLI2SC
FGR

SDMMC1SEL

0x84

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

RCC_SSCGR
SSCGEN

0x80
SPREADSEL

Register
name

Res.

Addr.
offset

Res.

Reset and clock control (RCC)
RM0385

Table 20. RCC register map and reset values (continued)

MODPER

PLLI2SDIVQ[4:0]

RM0385

General-purpose I/Os (GPIO)

6

General-purpose I/Os (GPIO)

6.1

Introduction
Each general-purpose I/O port has four 32-bit configuration registers (GPIOx_MODER,
GPIOx_OTYPER, GPIOx_OSPEEDR and GPIOx_PUPDR), two 32-bit data registers
(GPIOx_IDR and GPIOx_ODR) and a 32-bit set/reset register (GPIOx_BSRR). In addition
all GPIOs have a 32-bit locking register (GPIOx_LCKR) and two 32-bit alternate function
selection registers (GPIOx_AFRH and GPIOx_AFRL).

6.2

6.3

GPIO main features
•

Output states: push-pull or open drain + pull-up/down

•

Output data from output data register (GPIOx_ODR) or peripheral (alternate function
output)

•

Speed selection for each I/O

•

Input states: floating, pull-up/down, analog

•

Input data to input data register (GPIOx_IDR) or peripheral (alternate function input)

•

Bit set and reset register (GPIOx_ BSRR) for bitwise write access to GPIOx_ODR

•

Locking mechanism (GPIOx_LCKR) provided to freeze the I/O port configurations

•

Analog function

•

Alternate function selection registers

•

Fast toggle capable of changing every two clock cycles

•

Highly flexible pin multiplexing allows the use of I/O pins as GPIOs or as one of several
peripheral functions

GPIO functional description
Subject to the specific hardware characteristics of each I/O port listed in the datasheet, each
port bit of the general-purpose I/O (GPIO) ports can be individually configured by software in
several modes:
•

Input floating

•

Input pull-up

•

Input-pull-down

•

Analog

•

Output open-drain with pull-up or pull-down capability

•

Output push-pull with pull-up or pull-down capability

•

Alternate function push-pull with pull-up or pull-down capability

•

Alternate function open-drain with pull-up or pull-down capability

Each I/O port bit is freely programmable, however the I/O port registers have to be
accessed as 32-bit words, half-words or bytes. The purpose of the GPIOx_BSRR and
GPIOx_BRR registers is to allow atomic read/modify accesses to any of the GPIOx_ODR
registers. In this way, there is no risk of an IRQ occurring between the read and the modify
access.

RM0385 Rev 7

199/1709
215

General-purpose I/Os (GPIO)

RM0385

Figure 17 and Figure 18 shows the basic structures of a standard and a 5-Volt tolerant I/O
port bit, respectively. Table 21 gives the possible port bit configurations.
Figure 17. Basic structure of an I/O port bit
Analog

To on-chip
peripheral

Alternate function input
Input data register

trigger

on/off

Protection
diode

Pull
up

Input driver

I/O pin

Output driver

VDD

on/off

Protection
diode

Pull
down

P-MOS

VSS

Output
control

VSS

N-MOS

Read/write
VSS
From on-chip
peripheral

VDD

VDD

Output data register

Bit set/reset registers

Read

Write

on/off

Push-pull,
open-drain or
disabled

Alternate function output

Analog
ai15938

Figure 18. Basic structure of a 5-Volt tolerant I/O port bit
Analog

To on-chip
peripheral

Input data register

Alternate function input

Read/write
From on-chip
peripheral

Output data register

Write

Bit set/reset registers

Read

on/off
VDD
TTL Schmitt
trigger

on/off

Pull
up

VDD_FT (1)

Protection
diode

Input driver

I/O pin

Output driver

VDD

on/off

P-MOS
Output
control

Pull
down

VSS

Protection
diode
VSS

N-MOS
VSS

Alternate function output

Push-pull,
open-drain or
disabled

Analog
ai15939b

1. VDD_FT is a potential specific to five-volt tolerant I/Os and different from VDD.

200/1709

RM0385 Rev 7

RM0385

General-purpose I/Os (GPIO)
Table 21. Port bit configuration table(1)
MODE(i)
[1:0]

01

10

00

11

OTYPER(i)

OSPEED(i)
[1:0]

PUPD(i)
[1:0]

I/O configuration

0

0

0

GP output

PP

0

0

1

GP output

PP + PU

0

1

0

GP output

PP + PD

1

1

Reserved

0

0

GP output

OD

1

0

1

GP output

OD + PU

1

1

0

GP output

OD + PD

1

1

1

Reserved (GP output OD)

0

0

0

AF

PP

0

0

1

AF

PP + PU

0

1

0

AF

PP + PD

1

1

Reserved

0

0

AF

OD

1

0

1

AF

OD + PU

1

1

0

AF

OD + PD

1

1

1

Reserved

0

SPEED
[1:0]

1

0

SPEED
[1:0]

1

x

x

x

0

0

Input

Floating

x

x

x

0

1

Input

PU

x

x

x

1

0

Input

PD

x

x

x

1

1

Reserved (input floating)

x

x

x

0

0

Input/output

x

x

x

0

1

x

x

x

1

0

x

x

x

1

1

Analog

Reserved

1. GP = general-purpose, PP = push-pull, PU = pull-up, PD = pull-down, OD = open-drain, AF = alternate
function.

RM0385 Rev 7

201/1709
215

General-purpose I/Os (GPIO)

6.3.1

RM0385

General-purpose I/O (GPIO)
During and just after reset, the alternate functions are not active and most of the I/O ports
are configured in input floating mode.
The debug pins are in AF pull-up/pull-down after reset:
•

PA15: JTDI in pull-up

•

PA14: JTCK/SWCLK in pull-down

•

PA13: JTMS/SWDAT in pull-up

•

PB4: NJTRST in pull-up

•

PB3: JTDO in floating state

When the pin is configured as output, the value written to the output data register
(GPIOx_ODR) is output on the I/O pin. It is possible to use the output driver in push-pull
mode or open-drain mode (only the low level is driven, high level is HI-Z).
The input data register (GPIOx_IDR) captures the data present on the I/O pin at every AHB
clock cycle.
All GPIO pins have weak internal pull-up and pull-down resistors, which can be activated or
not depending on the value in the GPIOx_PUPDR register.

6.3.2

I/O pin alternate function multiplexer and mapping
The device I/O pins are connected to on-board peripherals/modules through a multiplexer
that allows only one peripheral alternate function (AF) connected to an I/O pin at a time. In
this way, there can be no conflict between peripherals available on the same I/O pin.
Each I/O pin has a multiplexer with up to sixteen alternate function inputs (AF0 to AF15) that
can be configured through the GPIOx_AFRL (for pin 0 to 7) and GPIOx_AFRH (for pin 8 to
15) registers:
•

After reset the multiplexer selection is alternate function 0 (AF0). The I/Os are
configured in alternate function mode through GPIOx_MODER register.

•

The specific alternate function assignments for each pin are detailed in the device
datasheet.

•

Cortex-M7 with FPU EVENTOUT is mapped on AF15

In addition to this flexible I/O multiplexing architecture, each peripheral has alternate
functions mapped onto different I/O pins to optimize the number of peripherals available in
smaller packages.
To use an I/O in a given configuration, the user has to proceed as follows:

202/1709

•

Debug function: after each device reset these pins are assigned as alternate function
pins immediately usable by the debugger host

•

System function: MCOx pins have to be configured in alternate function mode.

•

GPIO: configure the desired I/O as output, input or analog in the GPIOx_MODER
register.

•

Peripheral alternate function:
–

Connect the I/O to the desired AFx in one of the GPIOx_AFRL or GPIOx_AFRH
register.

–

Select the type, pull-up/pull-down and output speed via the GPIOx_OTYPER,
GPIOx_PUPDR and GPIOx_OSPEEDER registers, respectively.

RM0385 Rev 7

RM0385

General-purpose I/Os (GPIO)
–
•

•

Configure the desired I/O as an alternate function in the GPIOx_MODER register.

Additional functions:
–

For the ADC and DAC, configure the desired I/O in analog mode in the
GPIOx_MODER register and configure the required function in the ADC and DAC
registers.

–

For the additional functions like RTC_OUT, RTC_TS, RTC_TAMPx, WKUPx and
oscillators, configure the required function in the related RTC, PWR and RCC
registers. These functions have priority over the configuration in the standard
GPIO registers. For details about I/O control by the RTC, refer to Section 29.3:
RTC functional description on page 911.

EVENTOUT
–

Configure the I/O pin used to output the core EVENTOUT signal by connecting it
to AF15.

Refer to the “Alternate function mapping” table in the device datasheet for the detailed
mapping of the alternate function I/O pins.

6.3.3

I/O port control registers
Each of the GPIO ports has four 32-bit memory-mapped control registers (GPIOx_MODER,
GPIOx_OTYPER, GPIOx_OSPEEDR, GPIOx_PUPDR) to configure up to 16 I/Os. The
GPIOx_MODER register is used to select the I/O mode (input, output, AF, analog). The
GPIOx_OTYPER and GPIOx_OSPEEDR registers are used to select the output type (pushpull or open-drain) and speed. The GPIOx_PUPDR register is used to select the pullup/pull-down whatever the I/O direction.

6.3.4

I/O port data registers
Each GPIO has two 16-bit memory-mapped data registers: input and output data registers
(GPIOx_IDR and GPIOx_ODR). GPIOx_ODR stores the data to be output, it is read/write
accessible. The data input through the I/O are stored into the input data register
(GPIOx_IDR), a read-only register.
See Section 6.4.5: GPIO port input data register (GPIOx_IDR) (x = A..K) and Section 6.4.6:
GPIO port output data register (GPIOx_ODR) (x = A..K) for the register descriptions.

6.3.5

I/O data bitwise handling
The bit set reset register (GPIOx_BSRR) is a 32-bit register which allows the application to
set and reset each individual bit in the output data register (GPIOx_ODR). The bit set reset
register has twice the size of GPIOx_ODR.
To each bit in GPIOx_ODR, correspond two control bits in GPIOx_BSRR: BS(i) and BR(i).
When written to 1, bit BS(i) sets the corresponding ODR(i) bit. When written to 1, bit BR(i)
resets the ODR(i) corresponding bit.
Writing any bit to 0 in GPIOx_BSRR does not have any effect on the corresponding bit in
GPIOx_ODR. If there is an attempt to both set and reset a bit in GPIOx_BSRR, the set
action takes priority.
Using the GPIOx_BSRR register to change the values of individual bits in GPIOx_ODR is a
“one-shot” effect that does not lock the GPIOx_ODR bits. The GPIOx_ODR bits can always
be accessed directly. The GPIOx_BSRR register provides a way of performing atomic
bitwise handling.
RM0385 Rev 7

203/1709
215

General-purpose I/Os (GPIO)

RM0385

There is no need for the software to disable interrupts when programming the GPIOx_ODR
at bit level: it is possible to modify one or more bits in a single atomic AHB write access.

6.3.6

GPIO locking mechanism
It is possible to freeze the GPIO control registers by applying a specific write sequence to
the GPIOx_LCKR register. The frozen registers are GPIOx_MODER, GPIOx_OTYPER,
GPIOx_OSPEEDR, GPIOx_PUPDR, GPIOx_AFRL and GPIOx_AFRH.
To write the GPIOx_LCKR register, a specific write / read sequence has to be applied. When
the right LOCK sequence is applied to bit 16 in this register, the value of LCKR[15:0] is used
to lock the configuration of the I/Os (during the write sequence the LCKR[15:0] value must
be the same). When the LOCK sequence has been applied to a port bit, the value of the port
bit can no longer be modified until the next MCU reset or peripheral reset. Each
GPIOx_LCKR bit freezes the corresponding bit in the control registers (GPIOx_MODER,
GPIOx_OTYPER, GPIOx_OSPEEDR, GPIOx_PUPDR, GPIOx_AFRL and GPIOx_AFRH.
The LOCK sequence (refer to Section 6.4.8: GPIO port configuration lock register
(GPIOx_LCKR) (x = A..K)) can only be performed using a word (32-bit long) access to the
GPIOx_LCKR register due to the fact that GPIOx_LCKR bit 16 has to be set at the same
time as the [15:0] bits.
For more details refer to LCKR register description in Section 6.4.8: GPIO port configuration
lock register (GPIOx_LCKR) (x = A..K).

6.3.7

I/O alternate function input/output
Two registers are provided to select one of the alternate function inputs/outputs available for
each I/O. With these registers, the user can connect an alternate function to some other pin
as required by the application.
This means that a number of possible peripheral functions are multiplexed on each GPIO
using the GPIOx_AFRL and GPIOx_AFRH alternate function registers. The application can
thus select any one of the possible functions for each I/O. The AF selection signal being
common to the alternate function input and alternate function output, a single channel is
selected for the alternate function input/output of a given I/O.
To know which functions are multiplexed on each GPIO pin, refer to the device datasheet.

6.3.8

External interrupt/wakeup lines
All ports have external interrupt capability. To use external interrupt lines, the port must be
configured in input mode. Refer to Section 11: Extended interrupts and events controller
(EXTI) and to Section 11.3: Wakeup event management.

204/1709

RM0385 Rev 7

RM0385

6.3.9

General-purpose I/Os (GPIO)

Input configuration
When the I/O port is programmed as input:
•

The output buffer is disabled

•

The Schmitt trigger input is activated

•

The pull-up and pull-down resistors are activated depending on the value in the
GPIOx_PUPDR register

•

The data present on the I/O pin are sampled into the input data register every AHB
clock cycle

•

A read access to the input data register provides the I/O state

Figure 19 shows the input configuration of the I/O port bit.

Input data register

Figure 19. Input floating/pull up/pull down configurations

Read/write

Output data register

Write

Bit set/reset registers

Read

on

TTL Schmitt
trigger

VDD VDD
on/off
protection
diode

pull
up

input driver

I/O pin
on/off

output driver
pull
down
VSS

protection
diode

VSS

ai15940b

6.3.10

Output configuration
When the I/O port is programmed as output:
•

The output buffer is enabled:
–

Open drain mode: A “0” in the Output register activates the N-MOS whereas a “1”
in the Output register leaves the port in Hi-Z (the P-MOS is never activated)

–

Push-pull mode: A “0” in the Output register activates the N-MOS whereas a “1” in
the Output register activates the P-MOS

•

The Schmitt trigger input is activated

•

The pull-up and pull-down resistors are activated depending on the value in the
GPIOx_PUPDR register

•

The data present on the I/O pin are sampled into the input data register every AHB
clock cycle

•

A read access to the input data register gets the I/O state

•

A read access to the output data register gets the last written value

Figure 20 shows the output configuration of the I/O port bit.

RM0385 Rev 7

205/1709
215

General-purpose I/Os (GPIO)

RM0385

Input data register

Figure 20. Output configuration

Write

Read/write

on

VDD

VDD

TTL Schmitt
trigger

on/off

Input driver

Output data register

Bit set/reset registers

Read

protection
diode

pull
up

Output driver

I/O pin

VDD

on/off

P-MOS
Output
control

protection
diode

pull
down
VSS

VSS

N-MOS
Push-pull or
VSS
Open-drain

ai15941b

6.3.11

Alternate function configuration
When the I/O port is programmed as alternate function:
•

The output buffer can be configured in open-drain or push-pull mode

•

The output buffer is driven by the signals coming from the peripheral (transmitter
enable and data)

•

The Schmitt trigger input is activated

•

The weak pull-up and pull-down resistors are activated or not depending on the value
in the GPIOx_PUPDR register

•

The data present on the I/O pin are sampled into the input data register every AHB
clock cycle

•

A read access to the input data register gets the I/O state

Figure 21 shows the Alternate function configuration of the I/O port bit.
Figure 21. Alternate function configuration

Input data register

Alternate function input

To on-chip
peripheral

Read/write

VDD VDD
TTL Schmitt
trigger

on/off

I/O pin
Output driver

on/off

VDD
P-MOS

Output
control

protection
diode

Pull
down

VSS

VSS

N-MOS
VSS

From on-chip
peripheral

protection
diode

Pull
up

Input driver
Output data register

Write

Bit set/reset registers

Read

on

push-pull or
open-drain

Alternate function output
ai15942b

206/1709

RM0385 Rev 7

RM0385

6.3.12

General-purpose I/Os (GPIO)

Analog configuration
When the I/O port is programmed as analog configuration:
•

The output buffer is disabled

•

The Schmitt trigger input is deactivated, providing zero consumption for every analog
value of the I/O pin. The output of the Schmitt trigger is forced to a constant value (0).

•

The weak pull-up and pull-down resistors are disabled by hardware

•

Read access to the input data register gets the value “0”

Figure 22 shows the high-impedance, analog-input configuration of the I/O port bits.
Figure 22. High impedance-analog configuration

Input data register

Analog

To on-chip
peripheral

Read/write

From on-chip
peripheral

6.3.13

Output data register

Write

Bit set/reset registers

Read

off
0
VDD

TTL Schmitt
trigger

protection
diode

Input driver

I/O pin
protection
diode
VSS

Analog
ai15943

Using the HSE or LSE oscillator pins as GPIOs
When the HSE or LSE oscillator is switched OFF (default state after reset), the related
oscillator pins can be used as normal GPIOs.
When the HSE or LSE oscillator is switched ON (by setting the HSEON or LSEON bit in the
RCC_CSR register) the oscillator takes control of its associated pins and the GPIO
configuration of these pins has no effect.
When the oscillator is configured in a user external clock mode, only the OSC_IN or
OSC32_IN pin is reserved for clock input and the OSC_OUT or OSC32_OUT pin can still be
used as normal GPIO.

6.3.14

Using the GPIO pins in the backup supply domain
The PC13/PC14/PC15/PI8 GPIO functionality is lost when the core supply domain is
powered off (when the device enters Standby mode). In this case, if their GPIO configuration
is not bypassed by the RTC configuration, these pins are set in an analog input mode.

RM0385 Rev 7

207/1709
215

General-purpose I/Os (GPIO)

6.4

RM0385

GPIO registers
This section gives a detailed description of the GPIO registers.
For a summary of register bits, register address offsets and reset values, refer to Table 22.
The peripheral registers can be written in word, half word or byte mode.

6.4.1

GPIO port mode register (GPIOx_MODER) (x =A..K)
Address offset:0x00
Reset values:

31

30

•

0xA800 0000 for port A

•

0x0000 0280 for port B

•

0x0000 0000 for other ports
29

MODER15[1:0]

28

MODER14[1:0]

27

26

MODER13[1:0]

25

24

MODER12[1:0]

23

22

MODER11[1:0]

21

20

MODER10[1:0]

19

18

MODER9[1:0]

17

16

MODER8[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

MODER7[1:0]
rw

rw

MODER6[1:0]
rw

rw

MODER5[1:0]
rw

rw

MODER4[1:0]
rw

rw

MODER3[1:0]
rw

rw

MODER2[1:0]
rw

rw

MODER1[1:0]
rw

rw

MODER0[1:0]
rw

rw

Bits 2y+1:2y MODERy[1:0]: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O mode.
00: Input mode (reset state)
01: General purpose output mode
10: Alternate function mode
11: Analog mode

6.4.2

GPIO port output type register (GPIOx_OTYPER) (x = A..K)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OT15

OT14

OT13

OT12

OT11

OT10

OT9

OT8

OT7

OT6

OT5

OT4

OT3

OT2

OT1

OT0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 OTy: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O output type.
0: Output push-pull (reset state)
1: Output open-drain

208/1709

RM0385 Rev 7

RM0385

General-purpose I/Os (GPIO)

6.4.3

GPIO port output speed register (GPIOx_OSPEEDR)
(x = A..K)
Address offset: 0x08
Reset value:

31

•

0x0C00 0000 for port A

•

0x0000 00C0 for port B

•

0x0000 0000 for other ports

30

29

OSPEEDR15
[1:0]

28

27

OSPEEDR14
[1:0]

26

25

OSPEEDR13
[1:0]

24

OSPEEDR12
[1:0]

23

22

OSPEEDR11
[1:0]

21

20

OSPEEDR10
[1:0]

19

18

17

16

OSPEEDR9
[1:0]

OSPEEDR8
[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OSPEEDR7
[1:0]

OSPEEDR6
[1:0]

OSPEEDR5
[1:0]

OSPEEDR4
[1:0]

OSPEEDR3
[1:0]

OSPEEDR2
[1:0]

OSPEEDR1
[1:0]

OSPEEDR0
[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 2y+1:2y OSPEEDRy[1:0]: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O output speed.
00: Low speed
01: Medium speed
10: High speed
11: Very high speed
Note: Refer to the product datasheets for the values of OSPEEDRy bits versus VDD range
and external load.

6.4.4

GPIO port pull-up/pull-down register (GPIOx_PUPDR)
(x = A..K)
Address offset: 0x0C
Reset values:

31

30

PUPDR15[1:0]

•

0x6400 0000 for port A

•

0x0000 0100 for port B

•

0x0000 0000 for other ports
29

28

PUPDR14[1:0]

27

26

PUPDR13[1:0]

25

24

PUPDR12[1:0]

23

22

PUPDR11[1:0]

21

20

PUPDR10[1:0]

19

18

PUPDR9[1:0]

17

16

PUPDR8[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PUPDR7[1:0]
rw

rw

PUPDR6[1:0]
rw

rw

PUPDR5[1:0]
rw

rw

PUPDR4[1:0]
rw

rw

PUPDR3[1:0]
rw

RM0385 Rev 7

rw

PUPDR2[1:0]
rw

rw

PUPDR1[1:0]
rw

rw

PUPDR0[1:0]
rw

rw

209/1709
215

General-purpose I/Os (GPIO)

RM0385

Bits 2y+1:2y PUPDRy[1:0]: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O pull-up or pull-down
00: No pull-up, pull-down
01: Pull-up
10: Pull-down
11: Reserved

6.4.5

GPIO port input data register (GPIOx_IDR) (x = A..K)
Address offset: 0x10
Reset value: 0x0000 XXXX

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

IDR15

IDR14

IDR13

IDR12

IDR11

IDR10

IDR9

IDR8

IDR7

IDR6

IDR5

IDR4

IDR3

IDR2

IDR1

IDR0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 IDRy: Port input data bit (y = 0..15)
These bits are read-only. They contain the input value of the corresponding I/O port.

6.4.6

GPIO port output data register (GPIOx_ODR) (x = A..K)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

ODR15 ODR14 ODR13 ODR12 ODR11 ODR10
rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

0

ODR9

ODR8

ODR7

ODR6

ODR5

ODR4

ODR3

ODR2

ODR1

ODR0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 ODRy: Port output data bit (y = 0..15)
These bits can be read and written by software.
Note: For atomic bit set/reset, the ODR bits can be individually set and/or reset by writing to
the GPIOx_BSRR or GPIOx_BRR registers (x = A..F).

6.4.7

GPIO port bit set/reset register (GPIOx_BSRR) (x = A..K)
Address offset: 0x18
Reset value: 0x0000 0000

210/1709

RM0385 Rev 7

RM0385

General-purpose I/Os (GPIO)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

BR15

BR14

BR13

BR12

BR11

BR10

BR9

BR8

BR7

BR6

BR5

BR4

BR3

BR2

BR1

BR0

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

BS15

BS14

BS13

BS12

BS11

BS10

BS9

BS8

BS7

BS6

BS5

BS4

BS3

BS2

BS1

BS0

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:16 BRy: Port x reset bit y (y = 0..15)
These bits are write-only. A read to these bits returns the value 0x0000.
0: No action on the corresponding ODRx bit
1: Resets the corresponding ODRx bit
Note: If both BSx and BRx are set, BSx has priority.
Bits 15:0 BSy: Port x set bit y (y= 0..15)
These bits are write-only. A read to these bits returns the value 0x0000.
0: No action on the corresponding ODRx bit
1: Sets the corresponding ODRx bit

6.4.8

GPIO port configuration lock register (GPIOx_LCKR)
(x = A..K)
This register is used to lock the configuration of the port bits when a correct write sequence
is applied to bit 16 (LCKK). The value of bits [15:0] is used to lock the configuration of the
GPIO. During the write sequence, the value of LCKR[15:0] must not change. When the
LOCK sequence has been applied on a port bit, the value of this port bit can no longer be
modified until the next MCU reset or peripheral reset.

Note:

A specific write sequence is used to write to the GPIOx_LCKR register. Only word access
(32-bit long) is allowed during this locking sequence.
Each lock bit freezes a specific configuration register (control and alternate function
registers).
Address offset: 0x1C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LCKK

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

LCK15

LCK14

LCK13

LCK12

LCK11

LCK10

LCK9

LCK8

LCK7

LCK6

LCK5

LCK4

LCK3

LCK2

LCK1

LCK0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

211/1709
215

General-purpose I/Os (GPIO)

RM0385

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 LCKK: Lock key
This bit can be read any time. It can only be modified using the lock key write sequence.
0: Port configuration lock key not active
1: Port configuration lock key active. The GPIOx_LCKR register is locked until the next MCU
reset or peripheral reset.
LOCK key write sequence:
WR LCKR[16] = ‘1’ + LCKR[15:0]
WR LCKR[16] = ‘0’ + LCKR[15:0]
WR LCKR[16] = ‘1’ + LCKR[15:0]
RD LCKR
RD LCKR[16] = ‘1’ (this read operation is optional but it confirms that the lock is active)
Note: During the LOCK key write sequence, the value of LCK[15:0] must not change.
Any error in the lock sequence aborts the lock.
After the first lock sequence on any bit of the port, any read access on the LCKK bit will
return ‘1’ until the next MCU reset or peripheral reset.
Bits 15:0 LCKy: Port x lock bit y (y= 0..15)
These bits are read/write but can only be written when the LCKK bit is ‘0.
0: Port configuration not locked
1: Port configuration locked

6.4.9

GPIO alternate function low register (GPIOx_AFRL)
(x = A..K)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

rw

rw

15

14

29

28

27

26

rw

rw

rw

rw

13

12

11

10

AFR7[3:0]

rw

rw

24

23

22

rw

rw

rw

rw

9

8

7

6

AFR6[3:0]

AFR3[3:0]
rw

25

rw

rw

rw

20

19

18

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

AFR5[3:0]

AFR2[3:0]
rw

21

rw

rw

rw

AFR0[3:0]
rw

rw

Bits 31:0 AFRy[3:0]: Alternate function selection for port x pin y (y = 0..7)
These bits are written by software to configure alternate function I/Os
AFSELy selection:
0000: AF0
0001: AF1
0010: AF2
0011: AF3
0100: AF4
0101: AF5
0110: AF6
0111: AF7

212/1709

1000: AF8
1001: AF9
1010: AF10
1011: AF11
1100: AF12
1101: AF13
1110: AF14
1111: AF15

RM0385 Rev 7

16

AFR4[3:0]

AFR1[3:0]
rw

17

rw

rw

rw

RM0385

General-purpose I/Os (GPIO)

6.4.10

GPIO alternate function high register (GPIOx_AFRH)
(x = A..J)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

AFR15[3:0]

26

25

24

23

AFR14[3:0]

22

21

20

19

AFR13[3:0]

18

17

16

AFR12[3:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

AFR11[3:0]
rw

rw

rw

AFR10[3:0]
rw

rw

rw

rw

AFR9[3:0]
rw

rw

rw

rw

AFR8[3:0]
rw

rw

rw

rw

rw

Bits 31:0 AFRy[3:0]: Alternate function selection for port x pin y (y = 8..15)
These bits are written by software to configure alternate function I/Os
AFSELy selection:
0000: AF0
0001: AF1
0010: AF2
0011: AF3
0100: AF4
0101: AF5
0110: AF6
0111: AF7

1000: AF8
1001: AF9
1010: AF10
1011: AF11
1100: AF12
1101: AF13
1110: AF14
1111: AF15

RM0385 Rev 7

213/1709
215

0x08
Reset value

GPIOB_OSPEEDR

Reset value

GPIOx_OSPEEDR
(where x = C..K)

Reset value

0x0C

214/1709

GPIOA_PUPDR

Reset value
0

0

0

0
0
0

0
0

0

0

1

1
0
1

0
0

0

0

0

0
1
0

0
0

0

0

1

0
0
0

0
0

0

0

0

0
0
0

0
0

0

0

0

0
0
0

0
0

0

0

0

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

GPIOx_OTYPER
(where x = A..K)

Reset value

0
0

0
0

0

0

0

0

RM0385 Rev 7
0
0

0
0

0

0

0

0
0
0

0
0

0
0

0

0

0

0
0
0

0
0

0
0

0

0

0

0

0
0

0
0

0
0

0

0

0

0

0
0

0
0

0
1

0

0

0

0

0
0

0
0

1
0

0

0

0

0

0
0

0
0

0
0

0

0

0

0

OT1
OT0

MODER0[1:0]

MODER0[1:0]

0

0
0
0
0

0
0

0
0

0

0

0

0

OSPEEDR0[1:0]

MODER1[1:0]

0

OSPEEDR0[1:0]

MODER1[1:0]

0

OSPEEDR0[1:0]

OT2

0

PUPDR0[1:0]

OT3

0

OSPEEDR1[1:0]

MODER2[1:0]

0

OSPEEDR1[1:0]

MODER2[1:0]

0

OSPEEDR1[1:0]

OT4

0

PUPDR1[1:0]

OT5

1

OSPEEDR2[1:0]

MODER3[1:0]

0

OSPEEDR2[1:0]

MODER3[1:0]

0

OSPEEDR2[1:0]

OT6

0

PUPDR2[1:0]

OT7

1

OSPEEDR3[1:0]

MODER4[1:0]

0

OSPEEDR3[1:0]

MODER4[1:0]

0

OSPEEDR3[1:0]

OT8

0

PUPDR3[1:0]

OT9

0

OSPEEDR4[1:0]

0

OSPEEDR4[1:0]

MODER5[1:0]

0

OSPEEDR4[1:0]

MODER5[1:0]

0

PUPDR4[1:0]

OT11
OT10

0

OSPEEDR5[1:0]

MODER6[1:0]

0

OSPEEDR5[1:0]

MODER6[1:0]

0

OSPEEDR5[1:0]

OT12

0

PUPDR5[1:0]

OT13

0

OSPEEDR6[1:0]

0

OSPEEDR6[1:0]

MODER7[1:0]

0

OSPEEDR6[1:0]

MODER7[1:0]

0

PUPDR6[1:0]

OT14

0

OT15

0

OSPEEDR7[1:0]

MODER8[1:0]

0

OSPEEDR7[1:0]

MODER8[1:0]

0

OSPEEDR7[1:0]

0

Res.

0

PUPDR7[1:0]

0

Res.

0

OSPEEDR8[1:0]

MODER9[1:0]

0

OSPEEDR8[1:0]

MODER9[1:0]

0

OSPEEDR8[1:0]

0

Res.

0

PUPDR8[1:0]

0

Res.

0

OSPEEDR9[1:0]

MODER10[1:0]

0

OSPEEDR9[1:0]

MODER10[1:0]

0

OSPEEDR9[1:0]

0

Res.

0

PUPDR9[1:0]

0

Res.

0

OSPEEDR10[1:0]

MODER11[1:0]

0

OSPEEDR10[1:0]

MODER11[1:0]

0

OSPEEDR10[1:0]

0

Res.

0

PUPDR10[1:0]

0

Res.

0

OSPEEDR11[1:0]

MODER12[1:0]

0

OSPEEDR11[1:0]

MODER12[1:0]

0

OSPEEDR11[1:0]

0

Res.

0

PUPDR11[1:0]

0

Res.

0

OSPEEDR12[1:0]

MODER13[1:0]

0

OSPEEDR12[1:0]

MODER13[1:0]

1

OSPEEDR12[1:0]

0

Res.

0

PUPDR12[1:0]

0

Res.

MODER14[1:0]

0

OSPEEDR13[1:0]

MODER14[1:0]

0

OSPEEDR13[1:0]

0

Res.

MODER15[1:0]
1

OSPEEDR13[1:0]

GPIOA_OSPEEDR
0

PUPDR13[1:0]

0

Res.

GPIOx_MODER
(where x = C..K)

OSPEEDR14[1:0]

0x00
0

OSPEEDR14[1:0]

Reset value
1

OSPEEDR14[1:0]

0x08
GPIOB_MODER

MODER15[1:0]

Reset value

PUPDR14[1:0]

0x08
0

Res.

0x04
Reset value

Res.

0x00
MODER0[1:0]

MODER1[1:0]

MODER2[1:0]

MODER3[1:0]

MODER4[1:0]

MODER5[1:0]

MODER6[1:0]

MODER7[1:0]

MODER8[1:0]

MODER9[1:0]

MODER10[1:0]

MODER11[1:0]

MODER12[1:0]

MODER13[1:0]

MODER14[1:0]

MODER15[1:0]

GPIOA_MODER

OSPEEDR15[1:0]

0x00

OSPEEDR15[1:0]

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Offset Register name

OSPEEDR15[1:0]

6.4.11

PUPDR15[1:0]

General-purpose I/Os (GPIO)
RM0385

GPIO register map

The following table gives the GPIO register map and reset values.
Table 22. GPIO register map and reset values

0
0

0
0

0

0

0

0

0

0

RM0385

General-purpose I/Os (GPIO)

0

0

0

0

0x10

Res.

Res.

PUPDR0[1:0]

0

0x14

GPIOx_ODR
(where x = A..K)

0

0

ODR6

ODR5

ODR4

ODR3

ODR2

ODR1

ODR0
BS0

ODR7

BS1

ODR8

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
LCK0

ODR9

0

LCK1

ODR11

ODR10

BS2

ODR12

BS3

ODR13

0

LCK2

ODR14

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

AFR4[3:0]
0

0

LCK3

Res.

0

0

BS4

Res.

0

0

BS5

Res.

0

0

LCK4

Res.

0

0

LCK5

Res.

0

0

BS6

Res.

0

0

BS7

Res.

0

0

LCK6

Res.

0

0

LCK7

Res.

0

0

BS8

Res.

Reset value

0

0

BS9

Res.

Reset value

AFR5[3:0]

0

LCK8

Res.

0x24

GPIOx_AFRH
(where x = A..J)

AFR6[3:0]

0

0

Reset value
AFR7[3:0]

0

LCK9

Res.

0x20

GPIOx_AFRL
(where x = A..K)

0

BS11

0x1C

0

BS10

0

x

LCK11

0

x

LCK10

BR3

0

x

BS12

BR4

0

x

BS13

BR5

0

x

LCK12

BR6

0

x

LCK13

BR7

0

x

BS14

BR8

0

x

BS15

BR9

0

x

LCK14

BR11

BR10

0

x

LCK15

BR12

0

x

BR0

BR13

0

x

BR1

BR14

0

x

Res.

BR15

Reset value
GPIOx_LCKR
(where x = A..K)

x

LCKK

GPIOx_BSRR
(where x = A..I/J/K)

x

BR2

0x18

Res.

Reset value

x
ODR15

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

IDR0

0

IDR1

0

Res.

PUPDR1[1:0]

0

IDR2

1

IDR3

0

Res.

PUPDR2[1:0]

0

IDR4

0

IDR5

0

Res.

PUPDR3[1:0]

0

IDR6

0

IDR7

0

Res.

PUPDR4[1:0]

0

IDR8

0

IDR9

0

Res.

PUPDR5[1:0]

0

IDR11

0

IDR10

0

Res.

PUPDR6[1:0]

0

IDR12

0

IDR13

0
Res.

PUPDR7[1:0]

0

IDR14

0

IDR15

0

Res.

PUPDR8[1:0]

0

Res.

PUPDR9[1:0]

PUPDR10[1:0]

0

Res.

PUPDR11[1:0]

PUPDR12[1:0]

0

Res.

PUPDR13[1:0]

0

Res.

PUPDR14[1:0]

Reset value
GPIOx_IDR
(where x = A..I/J/K)

Res.

GPIOB_PUPDR

Res.

0x0C

PUPDR15[1:0]

Offset Register name

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 22. GPIO register map and reset values (continued)

0

0

0

AFR3[3:0]
0

0

0

0

AFR2[3:0]
0

0

0

0

AFR15[3:0]

AFR14[3:0]

AFR13[3:0]

AFR12[3:0]

AFR11[3:0]

AFR10[3:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

AFR1[3:0]
0

0

0

0

AFR9[3:0]
0

0

0

0

AFR0[3:0]
0

0

0

0

AFR8[3:0]
0

0

0

0

Refer to Section 2.2 for the register boundary addresses.

RM0385 Rev 7

215/1709
215

System configuration controller (SYSCFG)

7

RM0385

System configuration controller (SYSCFG)
The system configuration controller is mainly used to:

7.1

•

Remap the memory areas

•

Select the Ethernet PHY interface

•

Manage the external interrupt line connection to the GPIOs.

I/O compensation cell
By default the I/O compensation cell is not used. However when the I/O output buffer speed
is configured in 50 MHz or 100 MHz mode, it is recommended to use the compensation cell
for slew rate control on I/O tf(IO)out)/tr(IO)out commutation to reduce the I/O noise on power
supply.
When the compensation cell is enabled, a READY flag is set to indicate that the
compensation cell is ready and can be used. The I/O compensation cell can be used only
when the supply voltage ranges from 2.4 to 3.6 V.

7.2

SYSCFG registers

7.2.1

SYSCFG memory remap register (SYSCFG_MEMRMP)
This register is used for specific configurations on memory mapping:
•

1bit is used to indicate which option bytes BOOT_ADD0 or BOOT_ADD1 defines the
boot memory base address.

•

Other bits are used to swap FMC SDRAM Banks with FMC NOR/PSRAM bank

Address offset: 0x00
Reset value: 0x0000 0000
)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MEM_
BOOT

SWP_FMC[1:0]
rw

rw

r

Bits 31:12 Reserved, must be kept at reset value.

216/1709

RM0385 Rev 7

RM0385

System configuration controller (SYSCFG)

Bits 11:10 SWP_FMC[1:0]: FMC memory mapping swap
Set and cleared by software. These bits are used to swap the FMC SDRAM
banks and FMC NOR/PSRAM in order to enable the code execution from
SDRAM Banks without modifying the default MPU attribute
00: No FMC memory mapping swapping
SDRAM bank1 and Bank2 are mapped at 0xC000 0000 and 0xD000 0000
respectively (default mapping)
NOR/RAM is accessible @ 0x60000000 (default mapping)
01: NOR/RAM and SDRAM memory mapping swapped,
SDRAM bank1 and bank2 are mapped at 0x6000 0000 and 0x7000 0000,
respectively
NOR/PSRAM bank is mapped at 0xC000 0000
10: Reserved
11: Reserved
Bits 9:1 Reserved, must be kept at reset value.
Bit 0 MEM_BOOT: Memory boot mapping
This bit indicates which option bytes BOOT_ADD0 or BOOT_ADD1 defines the
boot memory base address.
0: Boot memory base address is defined by BOOT_ADD0 option byte
(Factory Reset value: TCM-FLASH mapped at 0x00200000).
1: Boot memory base address is defined by BOOT_ADD1 option byte
(Factory Reset value: System memory mapped at 0x001 0000).
Note: Refer to section 2.3: Memory map for details about the boot memory base
address selection.

7.2.2

SYSCFG peripheral mode configuration register (SYSCFG_PMC)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

MII_RMII
_SEL

Res.

Res.

Res.

Res.

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ADCxDC2

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bit 23 MII_RMII_SEL: Ethernet PHY interface selection
Set and Cleared by software.These bits control the PHY interface for the
Ethernet MAC.
0: MII interface is selected
1: RMII PHY interface is selected
Note: This configuration must be done while the MAC is under reset and before
enabling the MAC clocks.
Bits 22:19 Reserved, must be kept at reset value.

RM0385 Rev 7

217/1709
221

System configuration controller (SYSCFG)

RM0385

Bits 18:16 ADCxDC2:
0: No effect.
1: Refer to AN4073 on how to use this bit.
Note: These bits can be set only if the following conditions are met:
- ADC clock higher or equal to 30 MHz.
- Only one ADCxDC2 bit must be selected if ADC conversions do not start
at the same time and the sampling times differ.
- These bits must not be set when the ADCDC1 bit is set in PWR_CR
register.
Bits 15:0 Reserved, must be kept at reset value.

7.2.3

SYSCFG external interrupt configuration register 1
(SYSCFG_EXTICR1)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

EXTI3[3:0]
rw

rw

rw

EXTI2[3:0]
rw

rw

rw

rw

EXTI1[3:0]
rw

rw

rw

rw

EXTI0[3:0]
rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 EXTIx[3:0]: EXTI x configuration (x = 0 to 3)
These bits are written by software to select the source input for the EXTIx
external interrupt.
0000: PA[x] pin
0001: PB[x] pin
0010: PC[x] pin
0011: PD[x] pin
0100: PE[x] pin
0101: PF[x] pin
0110: PG[x] pin
0111: PH[x] pin
1000: PI[x] pin
1001:PJ[x] pin
1010:PK[x] pin

7.2.4

SYSCFG external interrupt configuration register 2
(SYSCFG_EXTICR2)
Address offset: 0x0C
Reset value: 0x0000 0000

218/1709

RM0385 Rev 7

rw

RM0385

System configuration controller (SYSCFG)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

EXTI7[3:0]
rw

rw

rw

EXTI6[3:0]
rw

rw

rw

rw

EXTI5[3:0]
rw

rw

rw

rw

EXTI4[3:0]
rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 EXTIx[3:0]: EXTI x configuration (x = 4 to 7)
These bits are written by software to select the source input for the EXTIx
external interrupt.
0000: PA[x] pin
0001: PB[x] pin
0010: PC[x] pin
0011: PD[x] pin
0100: PE[x] pin
0101: PF[x] pin
0110: PG[x] pin
0111: PH[x] pin
1000: PI[x] pin
1001:PJ[x] pin
1010:PK[x] pin

7.2.5

SYSCFG external interrupt configuration register 3
(SYSCFG_EXTICR3)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

EXTI11[3:0]
rw

rw

rw

EXTI10[3:0]
rw

rw

rw

rw

EXTI9[3:0]
rw

rw

rw

rw

EXTI8[3:0]
rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 EXTIx[3:0]: EXTI x configuration (x = 8 to 11)
These bits are written by software to select the source input for the EXTIx external
interrupt.
0000: PA[x] pin
0001: PB[x] pin
0010: PC[x] pin
0011: PD[x] pin
0100: PE[x] pin
0101: PF[x] pin
0110: PG[x] pin
0111: PH[x] pin
1000: PI[x] pin
1001:PJ[x] pin
1010:PK[x] pin
Note: PK[11:8] are not used

RM0385 Rev 7

219/1709
221

System configuration controller (SYSCFG)

7.2.6

RM0385

SYSCFG external interrupt configuration register 4
(SYSCFG_EXTICR4)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

15

EXTI15[3:0]
rw

rw

EXTI14[3:0]

rw

rw

rw

rw

rw

EXTI13[3:0]
rw

rw

rw

rw

EXTI12[3:0]
rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 EXTIx[3:0]: EXTI x configuration (x = 12 to 15)
These bits are written by software to select the source input for the EXTIx external
interrupt.
0000: PA[x] pin
0001: PB[x] pin
0010: PC[x] pin
0011: PD[x] pin
0100: PE[x] pin
0101: PF[x] pin
0110: PG[x] pin
0111: PH[x] pin
1001:PJ[x] pin
1010:PK[x] pin
Note: PK[15:12] are not used

7.2.7

Compensation cell control register (SYSCFG_CMPCR)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

READY

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CMP_PD

r

Bits 31:9 Reserved, must be kept at reset value.
Bit 8 READY: Compensation cell ready flag
0: I/O compensation cell not ready
1: O compensation cell ready
Bits 7:2 Reserved, must be kept at reset value.
Bit 0 CMP_PD: Compensation cell power-down
0: I/O compensation cell power-down mode
1: I/O compensation cell enabled

220/1709

RM0385 Rev 7

rw

RM0385

7.2.8

System configuration controller (SYSCFG)

SYSCFG register maps
The following table gives the SYSCFG register map and the reset values.

0

0

EXTI2[3:0]
0

0

0

0

EXTI6[3:0]
0

0

0

0

EXTI11[3:0]

EXTI10[3:0]

0

0

Res.

MEM_BOOT

Res.

Res.

Res.

Res.

Res.
0

0

0

EXTI9[3:0]

0

Res.

Res.

Res.
0

0

0

EXTI8[3:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
CMP_PD

0

EXTI12[3:0]

Res.

0

EXTI13[3:0]

Res.

0

EXTI14[3:0]

Res.

0

EXTI15[3:0]

Res.

0

EXTI4[3:0]

Res.

0

0

Res.

0

0

READY

0

Res.

Res.

Res.

Res.

Res.
0

0

Res.

0

EXTI5[3:0]

EXTI0[3:0]
0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

EXTI1[3:0]
0

Res.

0

Res.

Res.

Res.
Res.

Res.

SWP_FMC[1:0]

Res.
0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SYSCFG_CMPCR

Res.

0x20

Res.

Reset value

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0x14

Res.

Reset value
SYSCFG_EXTICR4

0

0

Res.

Res.
Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0x10

0

EXTI7[3:0]
0

Res.

Reset value
SYSCFG_EXTICR3

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SYSCFG_EXTICR2

Res.

0x0C

EXTI3[3:0]
0

Res.

Reset value

Res.

ADC1DC2
0

Res.

ADC2DC2
0

Res.

ADC3DC2

Res.

Res.

Res.

0
Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SYSCFG_EXTICR1

Res.

0x08

0
Res.

Reset value

MII_RMII_SEL

Res.

Res.

Res.

Res.

Res.

Res.

SYSCFG_PMC

Res.

0x04

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SYSCFG_
MEMRMP

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

0x00

Res.

Register

Res.

Offset

Res.

Table 23. SYSCFG register map and reset values

Reset value

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

RM0385 Rev 7

221/1709
221

Direct memory access controller (DMA)

RM0385

8

Direct memory access controller (DMA)

8.1

DMA introduction
Direct memory access (DMA) is used in order to provide high-speed data transfer between
peripherals and memory and between memory and memory. Data can be quickly moved by
DMA without any CPU action. This keeps CPU resources free for other operations.
The DMA controller combines a powerful dual AHB master bus architecture with
independent FIFO to optimize the bandwidth of the system, based on a complex bus matrix
architecture.
The two DMA controllers (DMA1 and DMA2) have 16 streams in total (8 for each controller),
each dedicated to managing memory access requests from one or more peripherals.
Each stream can have up to 8 channels (requests) in total.
Each DMA controller has an arbiter for handling the priority between DMA requests.

8.2

DMA main features
The main DMA features are:
•

Dual AHB master bus architecture, one dedicated to memory accesses and one
dedicated to peripheral accesses

•

AHB slave programming interface supporting only 32-bit accesses

•

8 streams for each DMA controller, up to 8 channels (requests) per stream

•

Four-word depth 32 first-in, first-out memory buffers (FIFOs) per stream, that can be
used in FIFO mode or direct mode:

•

222/1709

–

FIFO mode: with threshold level software selectable between 1/4, 1/2 or 3/4 of the
FIFO size

–

Direct mode: each DMA request immediately initiates a transfer from/to the
memory. When it is configured in direct mode (FIFO disabled), to transfer data in
memory-to-peripheral mode, the DMA preloads only one data from the memory to
the internal FIFO to ensure an immediate data transfer as soon as a DMA request
is triggered by a peripheral.

Each stream can be configured to be:
–

a regular channel that supports peripheral-to-memory, memory-to-peripheral and
memory-to-memory transfers

–

a double buffer channel that also supports double buffering on the memory side

•

Priorities between DMA stream requests are software-programmable (4 levels
consisting of very high, high, medium, low) or hardware in case of equality (for
example, request 0 has priority over request 1)

•

Each stream also supports software trigger for memory-to-memory transfers (only
available for the DMA2 controller)

•

Each stream request can be selected among up to 8 possible channel requests. This
selection is software-configurable and allows several peripherals to initiate DMA
requests

•

The number of data items to be transferred can be managed either by the DMA
controller or by the peripheral:

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)
–

DMA flow controller: the number of data items to be transferred is softwareprogrammable from 1 to 65535

–

Peripheral flow controller: the number of data items to be transferred is unknown
and controlled by the source or the destination peripheral that signals the end of
the transfer by hardware

•

Independent source and destination transfer width (byte, half-word, word): when the
data widths of the source and destination are not equal, the DMA automatically
packs/unpacks the necessary transfers to optimize the bandwidth. This feature is only
available in FIFO mode

•

Incrementing or non-incrementing addressing for source and destination

•

Supports incremental burst transfers of 4, 8 or 16 beats. The size of the burst is
software-configurable, usually equal to half the FIFO size of the peripheral

•

Each stream supports circular buffer management

•

5 event flags (DMA half transfer, DMA transfer complete, DMA transfer error, DMA
FIFO error, direct mode error) logically ORed together in a single interrupt request for
each stream

RM0385 Rev 7

223/1709
256

Direct memory access controller (DMA)

RM0385

8.3

DMA functional description

8.3.1

DMA block diagram
Figure 23 shows the block diagram of a DMA.
Figure 23. DMA block diagram

STREAM 7

Peripheral port

FIFO

FIFO

Memory port

STREAM 7

STREAM 6

STREAM 5
FIFO
STREAM 5

STREAM 6

STREAM 4
FIFO

STREAM 3
FIFO
STREAM 3

STREAM 4

STREAM 2

STREAM 1
FIFO

FIFO
STREAM 2

REQ_STR7_CH0
REQ_STR7_CH1

FIFO

Arbiter

STREAM 1

REQ_STR1_CH7

REQ_STREAM0
REQ_STREAM1
REQ_STREAM2
REQ_STREAM3
REQ_STREAM4
REQ_STREAM5
REQ_STREAM6
REQ_STREAM7

STREAM 0

REQ_STR1_CH0
REQ_STR1_CH1

STREAM 0

REQ_STR0_CH7

AHB master

REQ_STR0_CH0
REQ_STR0_CH1

AHB master

DMA controller

REQ_STR7_CH7

Channel
selection

AHB slave
programming
interface

Programming port

ai15945b

8.3.2

DMA overview
The DMA controller performs direct memory transfer: as an AHB master, it can take the
control of the AHB bus matrix to initiate AHB transactions.
It carries out the following transactions:
•

peripheral-to-memory

•

memory-to-peripheral

•

memory-to-memory

The DMA controller provides two AHB master ports: the AHB memory port, intended to be
connected to memories and the AHB peripheral port, intended to be connected to
peripherals. However, to allow memory-to-memory transfers, the AHB peripheral port must
also have access to the memories.
The AHB slave port is used to program the DMA controller (it supports only 32-bit
accesses).

224/1709

RM0385 Rev 7

RM0385
Note:

Direct memory access controller (DMA)
The DMA1 controller AHB peripheral port is not connected to the bus matrix like in the case
of the DMA2 controller, thus only DMA2 streams are able to perform memory-to-memory
transfers.
See Figure 1 for the implementation of the system of two DMA controllers.

8.3.3

DMA transactions
A DMA transaction consists of a sequence of a given number of data transfers. The number
of data items to be transferred and their width (8-bit, 16-bit or 32-bit) are softwareprogrammable.
Each DMA transfer consists of three operations:
•

a loading from the peripheral data register or a location in memory, addressed through
the DMA_SxPAR or DMA_SxM0AR register

•

a storage of the data loaded to the peripheral data register or a location in memory
addressed through the DMA_SxPAR or DMA_SxM0AR register

•

a post-decrement of the DMA_SxNDTR register, containing the number of transactions
that still have to be performed

After an event, the peripheral sends a request signal to the DMA controller. The DMA
controller serves the request depending on the channel priorities. As soon as the DMA
controller accesses the peripheral, an Acknowledge signal is sent to the peripheral by the
DMA controller. The peripheral releases its request as soon as it gets the Acknowledge
signal from the DMA controller. Once the request has been deasserted by the peripheral,
the DMA controller releases the Acknowledge signal. If there are more requests, the
peripheral can initiate the next transaction.

8.3.4

Channel selection
Each stream is associated with a DMA request that can be selected out of 816 possible
channel requests. The selection is controlled by the CHSEL[23:0] bits in the DMA_SxCR
register.
Figure 24. Channel selection
REQ_STRx_CH7
REQ_STRx_CH6
REQ_STRx_CH5
REQ_STREAMx

REQ_STRx_CH4
REQ_STRx_CH3
REQ_STRx_CH2
REQ_STRx_CH1
REQ_STRx_CH0

31
DMA_SxCR

27

25

0

CHSEL[2:0]
ai15947b

RM0385 Rev 7

225/1709
256

Direct memory access controller (DMA)

RM0385

The 8 requests from the peripherals (such as TIM, ADC, SPI, I2C) are independently
connected to each channel and their connection depends on the product implementation.
Table 24 and Table 25 give examples of DMA request mappings.
Table 24. DMA1 request mapping
Peripheral
requests

Stream 0

Stream 1

Stream 2

Stream 3

Stream 4

Stream 5

Stream 6

Stream 7

Channel 0

SPI3_RX

SPDIFRX_DT

SPI3_RX

SPI2_RX

SPI2_TX

SPI3_TX

SPDIFRX_CS

SPI3_TX

Channel 1

I2C1_RX

I2C3_RX

TIM7_UP

-

TIM7_UP

I2C1_RX

I2C1_TX

I2C1_TX

Channel 2

TIM4_CH1

-

I2C4_RX

TIM4_CH2

-

I2C4_RX

TIM4_UP

TIM4_CH3

Channel 3

-

TIM2_UP
TIM2_CH3

I2C3_RX

-

I2C3_TX

TIM2_CH1

TIM2_CH2
TIM2_CH4

TIM2_UP
TIM2_CH4

Channel 4

UART5_RX

USART3_RX

UART4_RX

USART3_TX

UART4_TX

USART2_RX

USART2_TX

UART5_TX

UART7_RX

TIM3_CH1
TIM3_TRIG

TIM3_CH2

UART8_RX

TIM3_CH3

Channel 5

UART8_TX

UART7_TX

TIM3_CH4
TIM3_UP

Channel 6

TIM5_CH3
TIM5_UP

TIM5_CH4
TIM5_TRIG

TIM5_CH1

TIM5_CH4
TIM5_TRIG

TIM5_CH2

-

TIM5_UP

-

TIM6_UP

I2C2_RX

I2C2_RX

USART3_TX

DAC1

DAC2

I2C2_TX

Channel 7

Table 25. DMA2 request mapping
Peripheral
requests

Stream 0

Stream 1

Stream 2

Stream 3

Stream 4

Stream 5

Stream 6

Stream 7

Channel 0

ADC1

SAI1_A

TIM8_CH1
TIM8_CH2
TIM8_CH3

SAI1_A

ADC1

SAI1_B

TIM1_CH1
TIM1_CH2
TIM1_CH3

SAI2_B

Channel 1

-

DCMI

ADC2

ADC2

SAI1_B

SPI6_TX

SPI6_RX

DCMI

Channel 2

ADC3

ADC3

-

SPI5_RX

SPI5_TX

CRYP_OUT

CRYP_IN

HASH_IN

Channel 3

SPI1_RX

-

SPI1_RX

SPI1_TX

SAI2_A

SPI1_TX

SAI2_B

QUADSPI

Channel 4

SPI4_RX

SPI4_TX

USART1_RX

SDMMC1

-

USART1_RX

SDMMC1

USART1_TX

Channel 5

-

USART6_RX

USART6_RX

SPI4_RX

SPI4_TX

-

USART6_TX

USART6_TX

TIM1_UP

TIM1_CH3

-

SPI5_RX

SPI5_TX

TIM8_CH4
TIM8_TRIG
TIM8_COM

Channel 6

TIM1_TRIG

TIM1_CH1

TIM1_CH2

TIM1_CH1

TIM1_CH4
TIM1_TRIG
TIM1_COM

Channel 7

-

TIM8_UP

TIM8_CH1

TIM8_CH2

TIM8_CH3

226/1709

RM0385 Rev 7

RM0385

8.3.5

Direct memory access controller (DMA)

Arbiter
An arbiter manages the 8 DMA stream requests based on their priority for each of the two
AHB master ports (memory and peripheral ports) and launches the peripheral/memory
access sequences.
Priorities are managed in two stages:
•

•

8.3.6

Software: each stream priority can be configured in the DMA_SxCR register. There are
four levels:
–

Very high priority

–

High priority

–

Medium priority

–

Low priority

Hardware: If two requests have the same software priority level, the stream with the
lower number takes priority over the stream with the higher number. For example,
stream 2 takes priority over stream 4.

DMA streams
Each of the 8 DMA controller streams provides a unidirectional transfer link between a
source and a destination.
Each stream can be configured to perform:
•

Regular type transactions: memory-to-peripherals, peripherals-to-memory or memoryto-memory transfers

•

Double-buffer type transactions: double buffer transfers using two memory pointers for
the memory (while the DMA is reading/writing from/to a buffer, the application can
write/read to/from the other buffer).

The amount of data to be transferred (up to 65535) is programmable and related to the
source width of the peripheral that requests the DMA transfer connected to the peripheral
AHB port. The register that contains the amount of data items to be transferred is
decremented after each transaction.

8.3.7

Source, destination and transfer modes
Both source and destination transfers can address peripherals and memories in the entire
4 Gbytes area, at addresses comprised between 0x0000 0000 and 0xFFFF FFFF.
The direction is configured using the DIR[1:0] bits in the DMA_SxCR register and offers
three possibilities: memory-to-peripheral, peripheral-to-memory or memory-to-memory
transfers. Table 26 describes the corresponding source and destination addresses.
Table 26. Source and destination address
Bits DIR[1:0] of the
DMA_SxCR register

Direction

Source address

Destination address

00

Peripheral-to-memory

DMA_SxPAR

DMA_SxM0AR

01

Memory-to-peripheral

DMA_SxM0AR

DMA_SxPAR

10

Memory-to-memory

DMA_SxPAR

DMA_SxM0AR

11

Reserved

-

-

RM0385 Rev 7

227/1709
256

Direct memory access controller (DMA)

RM0385

When the data width (programmed in the PSIZE or MSIZE bits in the DMA_SxCR register)
is a half-word or a word, respectively, the peripheral or memory address written into the
DMA_SxPAR or DMA_SxM0AR/M1AR registers has to be aligned on a word or half-word
address boundary, respectively.

Peripheral-to-memory mode
Figure 25 describes this mode.
When this mode is enabled (by setting the bit EN in the DMA_SxCR register), each time a
peripheral request occurs, the stream initiates a transfer from the source to fill the FIFO.
When the threshold level of the FIFO is reached, the contents of the FIFO are drained and
stored into the destination.
The transfer stops once the DMA_SxNDTR register reaches zero, when the peripheral
requests the end of transfers (in case of a peripheral flow controller) or when the EN bit in
the DMA_SxCR register is cleared by software.
In direct mode (when the DMDIS value in the DMA_SxFCR register is ‘0’), the threshold
level of the FIFO is not used: after each single data transfer from the peripheral to the FIFO,
the corresponding data are immediately drained and stored into the destination.
The stream has access to the AHB source or destination port only if the arbitration of the
corresponding stream is won. This arbitration is performed using the priority defined for
each stream using the PL[1:0] bits in the DMA_SxCR register.
Figure 25. Peripheral-to-memory mode
DMA_SxM0AR

DMA controller

DMA_SxM1AR(1)

AHB memory
port

Memory bus

Memory
destination
REQ_STREAMx

FIFO
level

Arbiter

FIFO

AHB peripheral
port

Peripheral bus

peripheral
source

DMA_SxPAR

Peripheral DMA request

ai15948

1. For double-buffer mode.

Memory-to-peripheral mode
Figure 26 describes this mode.
When this mode is enabled (by setting the EN bit in the DMA_SxCR register), the stream
immediately initiates transfers from the source to entirely fill the FIFO.

228/1709

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)
Each time a peripheral request occurs, the contents of the FIFO are drained and stored into
the destination. When the level of the FIFO is lower than or equal to the predefined
threshold level, the FIFO is fully reloaded with data from the memory.
The transfer stops once the DMA_SxNDTR register reaches zero, when the peripheral
requests the end of transfers (in case of a peripheral flow controller) or when the EN bit in
the DMA_SxCR register is cleared by software.
In direct mode (when the DMDIS value in the DMA_SxFCR register is '0'), the threshold
level of the FIFO is not used. Once the stream is enabled, the DMA preloads the first data to
transfer into an internal FIFO. As soon as the peripheral requests a data transfer, the DMA
transfers the preloaded value into the configured destination. It then reloads again the
empty internal FIFO with the next data to be transfer. The preloaded data size corresponds
to the value of the PSIZE bitfield in the DMA_SxCR register.
The stream has access to the AHB source or destination port only if the arbitration of the
corresponding stream is won. This arbitration is performed using the priority defined for
each stream using the PL[1:0] bits in the DMA_SxCR register.
Figure 26. Memory-to-peripheral mode
DMA_SxM0AR

DMA controller

DMA_SxM1AR(1)

AHB memory
port

Memory bus

Memory
source

REQ_STREAMx

Arbiter

FIFO
level

FIFO

AHB peripheral
port

DMA_SxPAR

Peripheral bus

Peripheral
destination

Peripheral DMA request

ai15949

1. For double-buffer mode.

Memory-to-memory mode
The DMA channels can also work without being triggered by a request from a peripheral.
This is the memory-to-memory mode, described in Figure 27.
When the stream is enabled by setting the Enable bit (EN) in the DMA_SxCR register, the
stream immediately starts to fill the FIFO up to the threshold level. When the threshold level
is reached, the FIFO contents are drained and stored into the destination.
The transfer stops once the DMA_SxNDTR register reaches zero or when the EN bit in the
DMA_SxCR register is cleared by software.

RM0385 Rev 7

229/1709
256

Direct memory access controller (DMA)

RM0385

The stream has access to the AHB source or destination port only if the arbitration of the
corresponding stream is won. This arbitration is performed using the priority defined for
each stream using the PL[1:0] bits in the DMA_SxCR register.
Note:

When memory-to-memory mode is used, the circular and direct modes are not allowed.
Only the DMA2 controller is able to perform memory-to-memory transfers.
Figure 27. Memory-to-memory mode
DMA_SxM0AR

DMA controller

DMA_SxM1AR(1)

AHB memory
port

Memory bus

Memory 2
destination
Arbiter
Stream enable

FIFO
level

FIFO

AHB peripheral
port

DMA_SxPAR

Peripheral bus

Memory 1
source

ai15950

1. For double-buffer mode.

8.3.8

Pointer incrementation
Peripheral and memory pointers can optionally be automatically post-incremented or kept
constant after each transfer depending on the PINC and MINC bits in the DMA_SxCR
register.
Disabling the increment mode is useful when the peripheral source or destination data is
accessed through a single register.
If the increment mode is enabled, the address of the next transfer is the address of the
previous one incremented by 1 (for bytes), 2 (for half-words) or 4 (for words) depending on
the data width programmed in the PSIZE or MSIZE bits in the DMA_SxCR register.
In order to optimize the packing operation, it is possible to fix the increment offset size for
the peripheral address whatever the size of the data transferred on the AHB peripheral port.
The PINCOS bit in the DMA_SxCR register is used to align the increment offset size with
the data size on the peripheral AHB port, or on a 32-bit address (the address is then
incremented by 4). The PINCOS bit has an impact on the AHB peripheral port only.
If the PINCOS bit is set, the address of the following transfer is the address of the previous
one incremented by 4 (automatically aligned on a 32-bit address), whatever the PSIZE
value. The AHB memory port, however, is not impacted by this operation.

230/1709

RM0385 Rev 7

RM0385

8.3.9

Direct memory access controller (DMA)

Circular mode
The circular mode is available to handle circular buffers and continuous data flows (e.g.
ADC scan mode). This feature can be enabled using the CIRC bit in the DMA_SxCR
register.
When the circular mode is activated, the number of data items to be transferred is
automatically reloaded with the initial value programmed during the stream configuration
phase, and the DMA requests continue to be served.

Note:

In the circular mode, it is mandatory to respect the following rule in case of a burst mode
configured for memory:
DMA_SxNDTR = Multiple of ((Mburst beat) × (Msize)/(Psize)), where:
–

(Mburst beat) = 4, 8 or 16 (depending on the MBURST bits in the DMA_SxCR
register)

–

((Msize)/(Psize)) = 1, 2, 4, 1/2 or 1/4 (Msize and Psize represent the MSIZE and
PSIZE bits in the DMA_SxCR register. They are byte dependent)

–

DMA_SxNDTR = Number of data items to transfer on the AHB peripheral port

For example: Mburst beat = 8 (INCR8), MSIZE = ‘00’ (byte) and PSIZE = ‘01’ (half-word), in
this case: DMA_SxNDTR must be a multiple of (8 × 1/2 = 4).
If this formula is not respected, the DMA behavior and data integrity are not guaranteed.
NDTR must also be a multiple of the Peripheral burst size multiplied by the peripheral data
size, otherwise this could result in a bad DMA behavior.

8.3.10

Double-buffer mode
This mode is available for all the DMA1 and DMA2 streams.
The double-buffer mode is enabled by setting the DBM bit in the DMA_SxCR register.
A double-buffer stream works as a regular (single buffer) stream with the difference that it
has two memory pointers. When the double-buffer mode is enabled, the circular mode is
automatically enabled (CIRC bit in DMA_SxCR is not relevant) and at each end of
transaction, the memory pointers are swapped.
In this mode, the DMA controller swaps from one memory target to another at each end of
transaction. This allows the software to process one memory area while the second memory
area is being filled/used by the DMA transfer. The double-buffer stream can work in both
directions (the memory can be either the source or the destination) as described in
Table 27: Source and destination address registers in double-buffer mode (DBM = 1).

Note:

In double-buffer mode, it is possible to update the base address for the AHB memory port
on-the-fly (DMA_SxM0AR or DMA_SxM1AR) when the stream is enabled, by respecting the
following conditions:

•

When the CT bit is ‘0’ in the DMA_SxCR register, the DMA_SxM1AR register can be
written. Attempting to write to this register while CT = '1' sets an error flag (TEIF) and
the stream is automatically disabled.

•

When the CT bit is ‘1’ in the DMA_SxCR register, the DMA_SxM0AR register can be
written. Attempting to write to this register while CT = '0', sets an error flag (TEIF) and
the stream is automatically disabled.

To avoid any error condition, it is advised to change the base address as soon as the TCIF
flag is asserted because, at this point, the targeted memory must have changed from

RM0385 Rev 7

231/1709
256

Direct memory access controller (DMA)

RM0385

memory 0 to 1 (or from 1 to 0) depending on the value of CT in the DMA_SxCR register in
accordance with one of the two above conditions.
For all the other modes (except the double-buffer mode), the memory address registers are
write-protected as soon as the stream is enabled.
Table 27. Source and destination address registers in double-buffer mode (DBM = 1)
Bits DIR[1:0] of the
DMA_SxCR register

Direction

Source address

Destination address

00

Peripheral-to-memory

DMA_SxPAR

DMA_SxM0AR / DMA_SxM1AR

01

Memory-to-peripheral DMA_SxM0AR / DMA_SxM1AR

DMA_SxPAR

Not allowed(1)

10
11

Reserved

-

-

1. When the double-buffer mode is enabled, the circular mode is automatically enabled. Since the memory-to-memory mode
is not compatible with the circular mode, when the double-buffer mode is enabled, it is not allowed to configure the
memory-to-memory mode.

8.3.11

Programmable data width, packing/unpacking, endianness
The number of data items to be transferred has to be programmed into DMA_SxNDTR
(number of data items to transfer bit, NDT) before enabling the stream (except when the
flow controller is the peripheral, PFCTRL bit in DMA_SxCR is set).
When using the internal FIFO, the data widths of the source and destination data are
programmable through the PSIZE and MSIZE bits in the DMA_SxCR register (can be 8-,
16- or 32-bit).
When PSIZE and MSIZE are not equal:
•

The data width of the number of data items to transfer, configured in the DMA_SxNDTR
register is equal to the width of the peripheral bus (configured by the PSIZE bits in the
DMA_SxCR register). For instance, in case of peripheral-to-memory, memory-toperipheral or memory-to-memory transfers and if the PSIZE[1:0] bits are configured for
half-word, the number of bytes to be transferred is equal to 2 × NDT.

•

The DMA controller only copes with little-endian addressing for both source and
destination. This is described in Table 28: Packing/unpacking and endian behavior (bit
PINC = MINC = 1).

This packing/unpacking procedure may present a risk of data corruption when the operation
is interrupted before the data are completely packed/unpacked. So, to ensure data
coherence, the stream may be configured to generate burst transfers: in this case, each
group of transfers belonging to a burst are indivisible (refer to Section 8.3.12: Single and
burst transfers).
In direct mode (DMDIS = 0 in the DMA_SxFCR register), the packing/unpacking of data is
not possible. In this case, it is not allowed to have different source and destination transfer
data widths: both are equal and defined by the PSIZE bits in the DMA_SxCR register.
MSIZE bits are not relevant.

232/1709

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)
Table 28. Packing/unpacking and endian behavior (bit PINC = MINC = 1)

Number AHB
AHB
of data Memory
memory peripheral
items to transfer
port
port
transfer - number
width
width
(NDT)

8

8

4

1
2
-3
4

8

16

2

-3

Peripheral port address / byte lane
Memory port
address / byte
lane

Peripheral
transfer
number

PINCOS = 1

PINCOS = 0

0x0 / B0[7:0]
0x1 / B1[7:0]
0x2 / B2[7:0]
0x3 / B3[7:0]

1
2
3
4

0x0 / B0[7:0]
0x4 / B1[7:0]
0x8 / B2[7:0]
0xC / B3[7:0]

0x0 / B0[7:0]
0x1 / B1[7:0]
0x2 / B2[7:0]
0x3 / B3[7:0]

1
2

1

0x0 / B1|B0[15:0]

0x0 / B1|B0[15:0]

2

0x4 / B3|B2[15:0]

0x2 / B3|B2[15:0]

4

0x0 / B0[7:0]
0x1 / B1[7:0]
0x2 / B2[7:0]
0x3 / B3[7:0]
0x0 / B0[7:0]
0x1 / B1[7:0]
0x2 / B2[7:0]
0x3 / B3[7:0]

1

0x0 /
B3|B2|B1|B0[31:0]

0x0 /
B3|B2|B1|B0[31:0]

1
2
3
4

0x0 / B0[7:0]
0x4 / B1[7:0]
0x8 / B2[7:0]
0xC / B3[7:0]

0x0 / B0[7:0]
0x1 / B1[7:0]
0x2 / B2[7:0]
0x3 / B3[7:0]

8

32

1

1
2
-3
4
1

0x0 / B1|B0[15:0]

16

8

4

-2

0x2 / B3|B2[15:0]
0x0 / B1|B0[15:0]

1

0x0 / B1|B0[15:0]

0x0 / B1|B0[15:0]

16

2

-

1

16

2

0x2 / B1|B0[15:0]

2

0x4 / B3|B2[15:0]

0x2 / B3|B2[15:0]

1

0x0 / B1|B0[15:0]
0x2 / B3|B2[15:0]

1

0x0 /
B3|B2|B1|B0[31:0]

0x0 /
B3|B2|B1|B0[31:0]

1

0x0 / B3|B2|B1|B0[31:0] 1
2
3
4

0x0 / B0[7:0]
0x4 / B1[7:0]
0x8 / B2[7:0]
0xC / B3[7:0]

0x0 / B0[7:0]
0x1 / B1[7:0]
0x2 / B2[7:0]
0x3 / B3[7:0]

1

0x0 /B3|B2|B1|B0[31:0]

1
2

0x0 / B1|B0[15:0]
0x4 / B3|B2[15:0]

0x0 / B1|B0[15:0]
0x2 / B3|B2[15:0]

0x0 /B3|B2|B1|B0 [31:0] 1

0x0 /B3|B2|B1|B0
[31:0]

0x0 /
B3|B2|B1|B0[31:0]

16

32

1

-2

32

8

4

-

32

16

2

-

32

32

1

-1

Note:

Peripheral port may be the source or the destination (it could also be the memory source in
the case of memory-to-memory transfer).
PSIZE, MSIZE and NDT[15:0] have to be configured so as to ensure that the last transfer
will not be incomplete. This can occur when the data width of the peripheral port (PSIZE
bits) is lower than the data width of the memory port (MSIZE bits). This constraint is
summarized in Table 29.
Table 29. Restriction on NDT versus PSIZE and MSIZE
PSIZE[1:0] of DMA_SxCR

MSIZE[1:0] of DMA_SxCR

NDT[15:0] of DMA_SxNDTR

00 (8-bit)

01 (16-bit)

must be a multiple of 2

00 (8-bit)

10 (32-bit)

must be a multiple of 4

01 (16-bit)

10 (32-bit)

must be a multiple of 2

RM0385 Rev 7

233/1709
256

Direct memory access controller (DMA)

8.3.12

RM0385

Single and burst transfers
The DMA controller can generate single transfers or incremental burst transfers of 4, 8 or 16
beats.
The size of the burst is configured by software independently for the two AHB ports by using
the MBURST[1:0] and PBURST[1:0] bits in the DMA_SxCR register.
The burst size indicates the number of beats in the burst, not the number of bytes
transferred.
To ensure data coherence, each group of transfers that form a burst are indivisible: AHB
transfers are locked and the arbiter of the AHB bus matrix does not degrant the DMA master
during the sequence of the burst transfer.
Depending on the single or burst configuration, each DMA request initiates a different
number of transfers on the AHB peripheral port:
•

When the AHB peripheral port is configured for single transfers, each DMA request
generates a data transfer of a byte, half-word or word depending on the PSIZE[1:0] bits
in the DMA_SxCR register

•

When the AHB peripheral port is configured for burst transfers, each DMA request
generates 4,8 or 16 beats of byte, half word or word transfers depending on the
PBURST[1:0] and PSIZE[1:0] bits in the DMA_SxCR register.

The same as above has to be considered for the AHB memory port considering the
MBURST and MSIZE bits.
In direct mode, the stream can only generate single transfers and the MBURST[1:0] and
PBURST[1:0] bits are forced by hardware.
The address pointers (DMA_SxPAR or DMA_SxM0AR registers) must be chosen so as to
ensure that all transfers within a burst block are aligned on the address boundary equal to
the size of the transfer.
The burst configuration has to be selected in order to respect the AHB protocol, where
bursts must not cross the 1 Kbyte address boundary because the minimum address space
that can be allocated to a single slave is 1 Kbyte. This means that the 1 Kbyte address
boundary must not be crossed by a burst block transfer, otherwise an AHB error is
generated, that is not reported by the DMA registers.

8.3.13

FIFO
FIFO structure
The FIFO is used to temporarily store data coming from the source before transmitting them
to the destination.
Each stream has an independent 4-word FIFO and the threshold level is softwareconfigurable between 1/4, 1/2, 3/4 or full.
To enable the use of the FIFO threshold level, the direct mode must be disabled by setting
the DMDIS bit in the DMA_SxFCR register.
The structure of the FIFO differs depending on the source and destination data widths, and
is described in Figure 28: FIFO structure.

234/1709

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)
Figure 28. FIFO structure
4 words
Empty

Source: byte
B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0

1/4

1/2

3/4

Full

byte lane 3

B15

B 11

B7

B3

byte lane 2

B14

B10

B6

B2

byte lane 1

B13

B9

B5

B1

byte lane 0 W3 B12

W2 B8

W1 B4

W0 B0

Destination: word
W3, W2, W1, W0

4 words
Empty
byte lane 3

Source: byte
B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0

1/4

1/2

3/4

B15

B 11

B7

byte lane 2 H7 B14

H5 B10

H3 B6

B13

B9

B5

byte lane 0 H6 B12

H4 B8

H2 B4

byte lane 1

Full
B3

H1

Destination: half-word

B2
H7, H6, H5, H4, H3, H2, H1, H0

B1
H0

B0

4 words
Empty

Source: half-word

1/4

1/2

3/4

Full

byte lane 3
H7

H5

H3

H1

H6

H4

H2

H0

Destination: word

byte lane 2
H7 H6 H5 H4 H3 H2 H1 H0

W3, W2, W1, W0

byte lane 1
byte lane 0 W3

W2

W1

W0

4-words
Empty

Source: half-word
H7 H6 H5 H4 H3 H2 H1 H0

byte lane 3

1/4

1/2

3/4

B15

B 11

B7

byte lane 2 H7 B14

H5 B10

H3 B6

B13

B9

B5

byte lane 0 H6 B12

H4 B8

H2 B4

byte lane 1

Full
B3

H1

Destination: byte

B2
B1

H0

B15 B14 B13 B12 B11 B10 B9 B8
B7 B6 B5 B4 B3 B2 B1 B0

B0

ai15951

FIFO threshold and burst configuration
Caution is required when choosing the FIFO threshold (bits FTH[1:0] of the DMA_SxFCR
register) and the size of the memory burst (MBURST[1:0] of the DMA_SxCR register): The
content pointed by the FIFO threshold must exactly match an integer number of memory
burst transfers. If this is not in the case, a FIFO error (flag FEIFx of the DMA_HISR or
DMA_LISR register) is generated when the stream is enabled, then the stream is
automatically disabled. The allowed and forbidden configurations are described in Table 30.
The forbidden configurations are highlighted in gray in the table.
Table 30. FIFO threshold configurations
MSIZE

Byte

FIFO level

MBURST = INCR4

MBURST = INCR8

1/4

1 burst of 4 beats

Forbidden

1/2

2 bursts of 4 beats

1 burst of 8 beats

3/4

3 bursts of 4 beats

Forbidden

Full

4 bursts of 4 beats

2 bursts of 8 beats

RM0385 Rev 7

MBURST = INCR16

Forbidden

1 burst of 16 beats

235/1709
256

Direct memory access controller (DMA)

RM0385

Table 30. FIFO threshold configurations (continued)
MSIZE

Half-word

FIFO level

MBURST = INCR4

1/4

Forbidden

1/2

1 burst of 4 beats

3/4

Forbidden

Full

2 bursts of 4 beats

MBURST = INCR8

Forbidden

1 burst of 8 beats

1/4
Word

1/2

Forbidden

3/4
Full

MBURST = INCR16

Forbidden

Forbidden

1 burst of 4 beats

In all cases, the burst size multiplied by the data size must not exceed the FIFO size (data
size can be: 1 (byte), 2 (half-word) or 4 (word)).
Incomplete burst transfer at the end of a DMA transfer may happen if one of the following
conditions occurs:
•

For the AHB peripheral port configuration: the total number of data items (set in the
DMA_SxNDTR register) is not a multiple of the burst size multiplied by the data size.

•

For the AHB memory port configuration: the number of remaining data items in the
FIFO to be transferred to the memory is not a multiple of the burst size multiplied by the
data size.

In such cases, the remaining data to be transferred is managed in single mode by the DMA,
even if a burst transaction is requested during the DMA stream configuration.
Note:

When burst transfers are requested on the peripheral AHB port and the FIFO is used
(DMDIS = 1 in the DMA_SxCR register), it is mandatory to respect the following rule to
avoid permanent underrun or overrun conditions, depending on the DMA stream direction:
If (PBURST × PSIZE) = FIFO_SIZE (4 words), FIFO_Threshold = 3/4 is forbidden with
PSIZE = 1, 2 or 4 and PBURST = 4, 8 or 16.
This rule ensures that enough FIFO space at a time is free to serve the request from the
peripheral.

FIFO flush
The FIFO can be flushed when the stream is disabled by resetting the EN bit in the
DMA_SxCR register and when the stream is configured to manage peripheral-to-memory or
memory-to-memory transfers. If some data are still present in the FIFO when the stream is
disabled, the DMA controller continues transferring the remaining data to the destination
(even though stream is effectively disabled). When this flush is completed, the transfer
complete status bit (TCIFx) in the DMA_LISR or DMA_HISR register is set.
The remaining data counter DMA_SxNDTR keeps the value in this case to indicate how
many data items are currently available in the destination memory.
Note that during the FIFO flush operation, if the number of remaining data items in the FIFO
to be transferred to memory (in bytes) is less than the memory data width (for example 2
bytes in FIFO while MSIZE is configured to word), data is sent with the data width set in the
MSIZE bit in the DMA_SxCR register. This means that memory is written with an undesired

236/1709

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)
value. The software may read the DMA_SxNDTR register to determine the memory area
that contains the good data (start address and last address).
If the number of remaining data items in the FIFO is lower than a burst size (if the MBURST
bits in DMA_SxCR register are set to configure the stream to manage burst on the AHB
memory port), single transactions are generated to complete the FIFO flush.

Direct mode
By default, the FIFO operates in direct mode (DMDIS bit in the DMA_SxFCR is reset) and
the FIFO threshold level is not used. This mode is useful when the system requires an
immediate and single transfer to or from the memory after each DMA request.
When the DMA is configured in direct mode (FIFO disabled), to transfer data in memory-toperipheral mode, the DMA preloads one data from the memory to the internal FIFO to
ensure an immediate data transfer as soon as a DMA request is triggered by a peripheral.
To avoid saturating the FIFO, it is recommended to configure the corresponding stream with
a high priority.
This mode is restricted to transfers where:
•

the source and destination transfer widths are equal and both defined by the
PSIZE[1:0] bits in DMA_SxCR (MSIZE[1:0] bits are not relevant)

•

burst transfers are not possible (PBURST[1:0] and MBURST[1:0] bits in DMA_SxCR
are don’t care)

Direct mode must not be used when implementing memory-to-memory transfers.

8.3.14

DMA transfer completion
Different events can generate an end of transfer by setting the TCIFx bit in the DMA_LISR
or DMA_HISR status register:
•

•

Note:

In DMA flow controller mode:
–

The DMA_SxNDTR counter has reached zero in the memory-to-peripheral mode.

–

The stream is disabled before the end of transfer (by clearing the EN bit in the
DMA_SxCR register) and (when transfers are peripheral-to-memory or memoryto-memory) all the remaining data have been flushed from the FIFO into the
memory.

In Peripheral flow controller mode:
–

The last external burst or single request has been generated from the peripheral
and (when the DMA is operating in peripheral-to-memory mode) the remaining
data have been transferred from the FIFO into the memory

–

The stream is disabled by software, and (when the DMA is operating in peripheralto-memory mode) the remaining data have been transferred from the FIFO into
the memory

The transfer completion is dependent on the remaining data in FIFO to be transferred into
memory only in the case of peripheral-to-memory mode. This condition is not applicable in
memory-to-peripheral mode.
If the stream is configured in noncircular mode, after the end of the transfer (that is when the
number of data to be transferred reaches zero), the DMA is stopped (EN bit in DMA_SxCR
register is cleared by Hardware) and no DMA request is served unless the software
reprograms the stream and re-enables it (by setting the EN bit in the DMA_SxCR register).

RM0385 Rev 7

237/1709
256

Direct memory access controller (DMA)

8.3.15

RM0385

DMA transfer suspension
At any time, a DMA transfer can be suspended to be restarted later on or to be definitively
disabled before the end of the DMA transfer.
There are two cases:
•

The stream disables the transfer with no later-on restart from the point where it was
stopped. There is no particular action to do, except to clear the EN bit in the
DMA_SxCR register to disable the stream. The stream may take time to be disabled
(ongoing transfer is completed first). The transfer complete interrupt flag (TCIF in the
DMA_LISR or DMA_HISR register) is set in order to indicate the end of transfer. The
value of the EN bit in DMA_SxCR is now ‘0’ to confirm the stream interruption. The
DMA_SxNDTR register contains the number of remaining data items at the moment
when the stream was stopped so that the software can determine how many data items
have been transferred before the stream was interrupted.

•

The stream suspends the transfer before the number of remaining data items to be
transferred in the DMA_SxNDTR register reaches 0. The aim is to restart the transfer
later by re-enabling the stream. In order to restart from the point where the transfer was
stopped, the software has to read the DMA_SxNDTR register after disabling the stream
by writing the EN bit in DMA_SxCR register (and then checking that it is at ‘0’) to know
the number of data items already collected. Then:
–

The peripheral and/or memory addresses have to be updated in order to adjust
the address pointers

–

The SxNDTR register has to be updated with the remaining number of data items
to be transferred (the value read when the stream was disabled)

–

The stream may then be re-enabled to restart the transfer from the point it was
stopped

Note:

A transfer complete interrupt flag (TCIF in DMA_LISR or DMA_HISR) is set to indicate the
end of transfer due to the stream interruption.

8.3.16

Flow controller
The entity that controls the number of data to be transferred is known as the flow controller.
This flow controller is configured independently for each stream using the PFCTRL bit in the
DMA_SxCR register.
The flow controller can be:
•

The DMA controller: in this case, the number of data items to be transferred is
programmed by software into the DMA_SxNDTR register before the DMA stream is
enabled.

•

The peripheral source or destination: this is the case when the number of data items to
be transferred is unknown. The peripheral indicates by hardware to the DMA controller
when the last data are being transferred. This feature is only supported for peripherals
that are able to signal the end of the transfer, that is: SDMMC1.

When the peripheral flow controller is used for a given stream, the value written into the
DMA_SxNDTR has no effect on the DMA transfer. Actually, whatever the value written, it will
be forced by hardware to 0xFFFF as soon as the stream is enabled, to respect the following
schemes:
•

238/1709

Anticipated stream interruption: EN bit in DMA_SxCR register is reset to 0 by the
software to stop the stream before the last data hardware signal (single or burst) is sent
by the peripheral. In such a case, the stream is switched off and the FIFO flush is
RM0385 Rev 7

RM0385

Direct memory access controller (DMA)
triggered in the case of a peripheral-to-memory DMA transfer. The TCIFx flag of the
corresponding stream is set in the status register to indicate the DMA completion. To
know the number of data items transferred during the DMA transfer, read the
DMA_SxNDTR register and apply the following formula:
–

Note:

Number_of_data_transferred = 0xFFFF – DMA_SxNDTR

•

Normal stream interruption due to the reception of a last data hardware signal: the
stream is automatically interrupted when the peripheral requests the last transfer
(single or burst) and when this transfer is complete. the TCIFx flag of the corresponding
stream is set in the status register to indicate the DMA transfer completion. To know the
number of data items transferred, read the DMA_SxNDTR register and apply the same
formula as above.

•

The DMA_SxNDTR register reaches 0: the TCIFx flag of the corresponding stream is
set in the status register to indicate the forced DMA transfer completion. The stream is
automatically switched off even though the last data hardware signal (single or burst)
has not been yet asserted. The already transferred data is not lost. This means that a
maximum of 65535 data items can be managed by the DMA in a single transaction,
even in peripheral flow control mode.

When configured in memory-to-memory mode, the DMA is always the flow controller and
the PFCTRL bit is forced to 0 by hardware.
The circular mode is forbidden in the peripheral flow controller mode.

8.3.17

Summary of the possible DMA configurations
Table 31 summarizes the different possible DMA configurations. The forbidden
configurations are highlighted in gray in the table.
Table 31. Possible DMA configurations

DMA transfer
mode

Peripheral-tomemory

Memory-toperipheral

Memory-tomemory

Source

Destination

Flow
controller

Circular
mode

DMA

Possible

Peripheral

Forbidden

DMA

Possible

Peripheral

Forbidden

DMA only

Forbidden

AHB
AHB
peripheral port memory port

AHB
memory port

AHB
peripheral port

AHB
AHB
peripheral port memory port

RM0385 Rev 7

Transfer
type

Direct
mode

single

Possible

burst

Forbidden

single

Possible

burst

Forbidden

single

Possible

burst

Forbidden

single

Possible

burst

Forbidden

single
burst

Doublebuffer mode
Possible

Forbidden

Possible

Forbidden

Forbidden Forbidden

239/1709
256

Direct memory access controller (DMA)

8.3.18

RM0385

Stream configuration procedure
The following sequence must be followed to configure a DMA stream x (where x is the
stream number):
1.

If the stream is enabled, disable it by resetting the EN bit in the DMA_SxCR register,
then read this bit in order to confirm that there is no ongoing stream operation. Writing
this bit to 0 is not immediately effective since it is actually written to 0 once all the
current transfers are finished. When the EN bit is read as 0, this means that the stream
is ready to be configured. It is therefore necessary to wait for the EN bit to be cleared
before starting any stream configuration. All the stream dedicated bits set in the status
register (DMA_LISR and DMA_HISR) from the previous data block DMA transfer must
be cleared before the stream can be re-enabled.

2.

Set the peripheral port register address in the DMA_SxPAR register. The data is moved
from/ to this address to/ from the peripheral port after the peripheral event.

3.

Set the memory address in the DMA_SxMA0R register (and in the DMA_SxMA1R
register in the case of a double-buffer mode). The data is written to or read from this
memory after the peripheral event.

4.

Configure the total number of data items to be transferred in the DMA_SxNDTR
register. After each peripheral event or each beat of the burst, this value is
decremented.

5.

Select the DMA channel (request) using CHSEL[2:0] in the DMA_SxCR register.

6.

If the peripheral is intended to be the flow controller and if it supports this feature, set
the PFCTRL bit in the DMA_SxCR register.

7.

Configure the stream priority using the PL[1:0] bits in the DMA_SxCR register.

8.

Configure the FIFO usage (enable or disable, threshold in transmission and reception)

9.

Configure the data transfer direction, peripheral and memory incremented/fixed mode,
single or burst transactions, peripheral and memory data widths, circular mode,
double-buffer mode and interrupts after half and/or full transfer, and/or errors in the
DMA_SxCR register.

10. Activate the stream by setting the EN bit in the DMA_SxCR register.
As soon as the stream is enabled, it can serve any DMA request from the peripheral
connected to the stream.
Once half the data have been transferred on the AHB destination port, the half-transfer flag
(HTIF) is set and an interrupt is generated if the half-transfer interrupt enable bit (HTIE) is
set. At the end of the transfer, the transfer complete flag (TCIF) is set and an interrupt is
generated if the transfer complete interrupt enable bit (TCIE) is set.

Warning:

240/1709

To switch off a peripheral connected to a DMA stream
request, it is mandatory to, first, switch off the DMA stream to
which the peripheral is connected, then to wait for EN bit = 0.
Only then can the peripheral be safely disabled.

RM0385 Rev 7

RM0385

8.3.19

Direct memory access controller (DMA)

Error management
The DMA controller can detect the following errors:
•

•

•

Transfer error: the transfer error interrupt flag (TEIFx) is set when:
–

a bus error occurs during a DMA read or a write access

–

a write access is requested by software on a memory address register in
double-buffer mode whereas the stream is enabled and the current target memory
is the one impacted by the write into the memory address register (refer to
Section 8.3.10: Double-buffer mode)

FIFO error: the FIFO error interrupt flag (FEIFx) is set if:
–

a FIFO underrun condition is detected

–

a FIFO overrun condition is detected (no detection in memory-to-memory mode
because requests and transfers are internally managed by the DMA)

–

the stream is enabled while the FIFO threshold level is not compatible with the
size of the memory burst (refer to Table 30: FIFO threshold configurations)

Direct mode error: the direct mode error interrupt flag (DMEIFx) can only be set in the
peripheral-to-memory mode while operating in direct mode and when the MINC bit in
the DMA_SxCR register is cleared. This flag is set when a DMA request occurs while
the previous data have not yet been fully transferred into the memory (because the
memory bus was not granted). In this case, the flag indicates that 2 data items were be
transferred successively to the same destination address, which could be an issue if
the destination is not able to manage this situation

In direct mode, the FIFO error flag can also be set under the following conditions:
•

In the peripheral-to-memory mode, the FIFO can be saturated (overrun) if the memory
bus is not granted for several peripheral requests.

•

In the memory-to-peripheral mode, an underrun condition may occur if the memory bus
has not been granted before a peripheral request occurs.

If the TEIFx or the FEIFx flag is set due to incompatibility between burst size and FIFO
threshold level, the faulty stream is automatically disabled through a hardware clear of its
EN bit in the corresponding stream configuration register (DMA_SxCR).
If the DMEIFx or the FEIFx flag is set due to an overrun or underrun condition, the faulty
stream is not automatically disabled and it is up to the software to disable or not the stream
by resetting the EN bit in the DMA_SxCR register. This is because there is no data loss
when this kind of errors occur.
When the stream's error interrupt flag (TEIF, FEIF, DMEIF) in the DMA_LISR or DMA_HISR
register is set, an interrupt is generated if the corresponding interrupt enable bit (TEIE,
FEIE, DMIE) in the DMA_SxCR or DMA_SxFCR register is set.
Note:

When a FIFO overrun or underrun condition occurs, the data is not lost because the
peripheral request is not acknowledged by the stream until the overrun or underrun
condition is cleared. If this acknowledge takes too much time, the peripheral itself may
detect an overrun or underrun condition of its internal buffer and data might be lost.

RM0385 Rev 7

241/1709
256

Direct memory access controller (DMA)

8.4

RM0385

DMA interrupts
For each DMA stream, an interrupt can be produced on the following events:
•

Half-transfer reached

•

Transfer complete

•

Transfer error

•

FIFO error (overrun, underrun or FIFO level error)

•

Direct mode error

Separate interrupt enable control bits are available for flexibility as shown in Table 32.
Table 32. DMA interrupt requests
Interrupt event

Event flag

Enable control bit

Half-transfer

HTIF

HTIE

Transfer complete

TCIF

TCIE

Transfer error

TEIF

TEIE

FIFO overrun/underrun

FEIF

FEIE

DMEIF

DMEIE

Direct mode error

Note:

242/1709

Before setting an enable control bit EN = 1, the corresponding event flag must be cleared,
otherwise an interrupt is immediately generated.

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)

8.5

DMA registers
The DMA registers have to be accessed by words (32 bits).

8.5.1

DMA low interrupt status register (DMA_LISR)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

TCIF3

HTIF3

TEIF3

DMEIF3

Res.

FEIF3

TCIF2

HTIF2

TEIF2

DMEIF2

Res.

FEIF2

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

TCIF1

HTIF1

TEIF1

DMEIF1

Res.

FEIF1

TCIF0

HTIF0

TEIF0

DMEIF0

Res.

FEIF0

r

r

r

r

r

r

r

r

r

r

Bits 31:28, 15:12 Reserved, must be kept at reset value.
Bits 27, 21, 11, 5 TCIF[3:0]: stream x transfer complete interrupt flag (x = 3..0)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_LIFCR register.
0: no transfer complete event on stream x
1: a transfer complete event occurred on stream x
Bits 26, 20, 10, 4 HTIF[3:0]: stream x half transfer interrupt flag (x = 3..0)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_LIFCR register.
0: no half transfer event on stream x
1: a half transfer event occurred on stream x
Bits 25, 19, 9, 3 TEIF[3:0]: stream x transfer error interrupt flag (x = 3..0)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_LIFCR register.
0: no transfer error on stream x
1: a transfer error occurred on stream x
Bits 24, 18, 8, 2 DMEIF[3:0]: stream x direct mode error interrupt flag (x = 3..0)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_LIFCR register.
0: No direct mode error on stream x
1: a direct mode error occurred on stream x
Bits 23, 17, 7, 1 Reserved, must be kept at reset value.
Bits 22, 16, 6, 0 FEIF[3:0]: stream x FIFO error interrupt flag (x = 3..0)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_LIFCR register.
0: no FIFO error event on stream x
1: a FIFO error event occurred on stream x

RM0385 Rev 7

243/1709
256

Direct memory access controller (DMA)

8.5.2

RM0385

DMA high interrupt status register (DMA_HISR)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

TCIF7

HTIF7

TEIF7

DMEIF7

Res.

FEIF7

TCIF6

HTIF6

TEIF6

DMEIF6

Res.

FEIF6

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

TCIF5

HTIF5

TEIF5

DMEIF5

Res.

FEIF5

TCIF4

HTIF4

TEIF4

DMEIF4

Res.

FEIF4

r

r

r

r

r

r

r

r

r

r

r

Bits 31:28, 15:12 Reserved, must be kept at reset value.
Bits 27, 21, 11, 5 TCIF[7:4]: stream x transfer complete interrupt flag (x = 7..4)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_HIFCR register.
0: no transfer complete event on stream x
1: atransfer complete event occurred on stream x
Bits 26, 20, 10, 4 HTIF[7:4]: stream x half transfer interrupt flag (x = 7..4)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_HIFCR register.
0: no half transfer event on stream x
1: a half transfer event occurred on stream x
Bits 25, 19, 9, 3 TEIF[7:4]: stream x transfer error interrupt flag (x = 7..4)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_HIFCR register.
0: no transfer error on stream x
1: a transfer error occurred on stream x
Bits 24, 18, 8, 2 DMEIF[7:4]: stream x direct mode error interrupt flag (x = 7..4)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_HIFCR register.
0: no direct mode error on stream x
1: a direct mode error occurred on stream x
Bits 23, 17, 7, 1 Reserved, must be kept at reset value.
Bits 22, 16, 6, 0 FEIF[7:4]: stream x FIFO error interrupt flag (x = 7..4)
This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_HIFCR register.
0: no FIFO error event on stream x
1: a FIFO error event occurred on stream x

244/1709

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)

8.5.3

DMA low interrupt flag clear register (DMA_LIFCR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

Res.

Res.

Res.

Res.

27

15

14

13

12

Res.

Res.

Res.

Res.

26

25

24

CTCIF3 CHTIF3 CTEIF3 CDMEIF3
w

w

w

w

11

10

9

8

CTCIF1 CHTIF1 CTEIF1 CDMEIF1
w

w

w

23

22

21

Res.

CFEIF3

CTCIF2

20

19

18

CHTIF2 CTEIF2 CDMEIF2

w

w

w

w

w

7

6

5

4

3

2

Res.

CFEIF1

CTCIF0

w

w

w

CHTIF0 CTEIF0 CDMEIF0
w

w

17

16

Res.

CFEIF2
w

1

0

Res.

CFEIF0

w

w

Bits 31:28, 15:12 Reserved, must be kept at reset value.
Bits 27, 21, 11, 5 CTCIF[3:0]: stream x clear transfer complete interrupt flag (x = 3..0)
Writing 1 to this bit clears the corresponding TCIFx flag in the DMA_LISR register.
Bits 26, 20, 10, 4 CHTIF[3:0]: stream x clear half transfer interrupt flag (x = 3..0)
Writing 1 to this bit clears the corresponding HTIFx flag in the DMA_LISR register
Bits 25, 19, 9, 3 CTEIF[3:0]: Stream x clear transfer error interrupt flag (x = 3..0)
Writing 1 to this bit clears the corresponding TEIFx flag in the DMA_LISR register.
Bits 24, 18, 8, 2 CDMEIF[3:0]: stream x clear direct mode error interrupt flag (x = 3..0)
Writing 1 to this bit clears the corresponding DMEIFx flag in the DMA_LISR register.
Bits 23, 17, 7, 1 Reserved, must be kept at reset value.
Bits 22, 16, 6, 0 CFEIF[3:0]: stream x clear FIFO error interrupt flag (x = 3..0)
Writing 1 to this bit clears the corresponding CFEIFx flag in the DMA_LISR register.

8.5.4

DMA high interrupt flag clear register (DMA_HIFCR)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res. Res. Res. Res. CTCIF7 CHTIF7 CTEIF7 CDMEIF7

15

14

13

12

w

w

w

w

11

10

9

8

Res. Res. Res. Res. CTCIF5 CHTIF5 CTEIF5 CDMEIF5
w

w

w

23

22

21

20

Res.

CFEIF7

CTCIF6

CHTIF6

w

w

w

7

6

5

4

Res.

CFEIF5

CTCIF4

CHTIF4

w

w

w

w

19

18

CTEIF6 CDMEIF6
w

w

3

2

CTEIF4 CDMEIF4
w

17

16

Res.

CFEIF6
w

1

0

Res.

CFEIF4

w

w

Bits 31:28, 15:12 Reserved, must be kept at reset value.
Bits 27, 21, 11, 5 CTCIF[7:4]: stream x clear transfer complete interrupt flag (x = 7..4)
Writing 1 to this bit clears the corresponding TCIFx flag in the DMA_HISR register.
Bits 26, 20, 10, 4 CHTIF[7:4]: stream x clear half transfer interrupt flag (x = 7..4)
Writing 1 to this bit clears the corresponding HTIFx flag in the DMA_HISR register.
Bits 25, 19, 9, 3 CTEIF[7:4]: stream x clear transfer error interrupt flag (x = 7..4)
Writing 1 to this bit clears the corresponding TEIFx flag in the DMA_HISR register.

RM0385 Rev 7

245/1709
256

Direct memory access controller (DMA)

RM0385

Bits 24, 18, 8, 2 CDMEIF[7:4]: stream x clear direct mode error interrupt flag (x = 7..4)
Writing 1 to this bit clears the corresponding DMEIFx flag in the DMA_HISR register.
Bits 23, 17, 7, 1 Reserved, must be kept at reset value.
Bits 22, 16, 6, 0 CFEIF[7:4]: stream x clear FIFO error interrupt flag (x = 7..4)
Writing 1 to this bit clears the corresponding CFEIFx flag in the DMA_HISR register.

8.5.5

DMA stream x configuration register (DMA_SxCR)
This register is used to configure the concerned stream.
Address offset: 0x10 + 0x18 * x, (x = 0 to 7)
Reset value: 0x0000 0000

31

30

29

28

Res.

Res.

Res.

Res.

27

rw
15
PINCOS
rw

14

13

12

11

MSIZE[1:0]

PSIZE[1:0]

rw

rw

rw

26

25

CHSEL[2:0]

rw

rw

24

23

MBURST [1:0]
rw

22

rw

rw

rw

7

6

10

9

8

MINC

PINC

CIRC

rw

rw

rw

DIR[1:0]
rw

21

PBURST[1:0]

rw

20

19

18

Res.

CT

DBM

rw

rw

rw

17

rw

5

4

3

2

1

0

TCIE

HTIE

TEIE

DMEIE

EN

rw

rw

rw

rw

rw

rw

Bits 27:25 CHSEL[2:0]: channel selection
These bits are set and cleared by software.
000: channel 0 selected
001: channel 1 selected
010: channel 2 selected
011: channel 3 selected
100: channel 4 selected
101: channel 5 selected
110: channel 6 selected
111: channel 7 selected
These bits are protected and can be written only if EN is ‘0’.
Bits 24:23 MBURST[1:0]: memory burst transfer configuration
These bits are set and cleared by software.
00: single transfer
01: INCR4 (incremental burst of 4 beats)
10: INCR8 (incremental burst of 8 beats)
11: INCR16 (incremental burst of 16 beats)
These bits are protected and can be written only if EN is ‘0’.
In direct mode, these bits are forced to 0x0 by hardware as soon as bit EN= '1'.
Bits 22:21 PBURST[1:0]: peripheral burst transfer configuration
These bits are set and cleared by software.
00: single transfer
01: INCR4 (incremental burst of 4 beats)
10: INCR8 (incremental burst of 8 beats)
11: INCR16 (incremental burst of 16 beats)
These bits are protected and can be written only if EN is ‘0’.
In direct mode, these bits are forced to 0x0 by hardware.

246/1709

RM0385 Rev 7

rw

PFCTRL

Bits 31:28 Reserved, must be kept at reset value.

Bit 20 Reserved, must be kept at reset value.

16
PL[1:0]

RM0385

Direct memory access controller (DMA)

Bit 19 CT: current target (only in double-buffer mode)
This bit is set and cleared by hardware. It can also be written by software.
0: current target memory is Memory 0 (addressed by the DMA_SxM0AR pointer)
1: current target memory is Memory 1 (addressed by the DMA_SxM1AR pointer)
This bit can be written only if EN is ‘0’ to indicate the target memory area of the first transfer.
Once the stream is enabled, this bit operates as a status flag indicating which memory area
is the current target.
Bit 18 DBM: double-buffer mode
This bit is set and cleared by software.
0: no buffer switching at the end of transfer
1: memory target switched at the end of the DMA transfer
This bit is protected and can be written only if EN is ‘0’.
Bits 17:16 PL[1:0]: priority level
These bits are set and cleared by software.
00: low
01: medium
10: high
11: very high
These bits are protected and can be written only if EN is ‘0’.
Bit 15 PINCOS: peripheral increment offset size
This bit is set and cleared by software
0: The offset size for the peripheral address calculation is linked to the PSIZE
1: The offset size for the peripheral address calculation is fixed to 4 (32-bit alignment).
This bit has no meaning if bit PINC = '0'.
This bit is protected and can be written only if EN = '0'.
This bit is forced low by hardware when the stream is enabled (bit EN = '1') if the direct mode
is selected or if PBURST are different from “00”.
Bits 14:13 MSIZE[1:0]: memory data size
These bits are set and cleared by software.
00: byte (8-bit)
01: half-word (16-bit)
10: word (32-bit)
11: reserved
These bits are protected and can be written only if EN is ‘0’.
In direct mode, MSIZE is forced by hardware to the same value as PSIZE as soon as
bit EN = '1'.
Bits 12:11 PSIZE[1:0]: peripheral data size
These bits are set and cleared by software.
00: byte (8-bit)
01: half-word (16-bit)
10: word (32-bit)
11: reserved
These bits are protected and can be written only if EN is ‘0’.
Bit 10 MINC: memory increment mode
This bit is set and cleared by software.
0: memory address pointer is fixed
1: memory address pointer is incremented after each data transfer (increment is done
according to MSIZE)
This bit is protected and can be written only if EN is ‘0’.

RM0385 Rev 7

247/1709
256

Direct memory access controller (DMA)

RM0385

Bit 9 PINC: peripheral increment mode
This bit is set and cleared by software.
0: peripheral address pointer is fixed
1: peripheral address pointer is incremented after each data transfer (increment is done
according to PSIZE)
This bit is protected and can be written only if EN is ‘0’.
Bit 8 CIRC: circular mode
This bit is set and cleared by software and can be cleared by hardware.
0: circular mode disabled
1: circular mode enabled
When the peripheral is the flow controller (bit PFCTRL = 1) and the stream is enabled (bit
EN = 1), then this bit is automatically forced by hardware to 0.
It is automatically forced by hardware to 1 if the DBM bit is set, as soon as the stream is
enabled (bit EN ='1').
Bits 7:6 DIR[1:0]: data transfer direction
These bits are set and cleared by software.
00: peripheral-to-memory
01: memory-to-peripheral
10: memory-to-memory
11: reserved
These bits are protected and can be written only if EN is ‘0’.
Bit 5 PFCTRL: peripheral flow controller
This bit is set and cleared by software.
0: DMA is the flow controller
1: The peripheral is the flow controller
This bit is protected and can be written only if EN is ‘0’.
When the memory-to-memory mode is selected (bits DIR[1:0]=10), then this bit is
automatically forced to 0 by hardware.
Bit 4 TCIE: transfer complete interrupt enable
This bit is set and cleared by software.
0: TC interrupt disabled
1: TC interrupt enabled
Bit 3 HTIE: half transfer interrupt enable
This bit is set and cleared by software.
0: HT interrupt disabled
1: HT interrupt enabled
Bit 2 TEIE: transfer error interrupt enable
This bit is set and cleared by software.
0: TE interrupt disabled
1: TE interrupt enabled
Bit 1 DMEIE: direct mode error interrupt enable
This bit is set and cleared by software.
0: DME interrupt disabled
1: DME interrupt enabled

248/1709

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)

Bit 0 EN: stream enable / flag stream ready when read low
This bit is set and cleared by software.
0: stream disabled
1: stream enabled
This bit may be cleared by hardware:
–
on a DMA end of transfer (stream ready to be configured)
–
if a transfer error occurs on the AHB master buses
–
when the FIFO threshold on memory AHB port is not compatible with the size of the
burst
When this bit is read as 0, the software is allowed to program the configuration and FIFO bits
registers. It is forbidden to write these registers when the EN bit is read as 1.
Note: Before setting EN bit to '1' to start a new transfer, the event flags corresponding to the
stream in DMA_LISR or DMA_HISR register must be cleared.

8.5.6

DMA stream x number of data register (DMA_SxNDTR)
Address offset: 0x14 + 0x18 * x, (x = 0 to 7)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

NDT[15:0]
rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 NDT[15:0]: number of data items to transfer (0 up to 65535)
This register can be written only when the stream is disabled. When the stream is enabled,
this register is read-only, indicating the remaining data items to be transmitted. This register
decrements after each DMA transfer.
Once the transfer is completed, this register can either stay at zero (when the stream is in
normal mode) or be reloaded automatically with the previously programmed value in the
following cases:
–
when the stream is configured in circular mode.
–
when the stream is enabled again by setting EN bit to '1'.
If the value of this register is zero, no transaction can be served even if the stream is
enabled.

RM0385 Rev 7

249/1709
256

Direct memory access controller (DMA)

8.5.7

RM0385

DMA stream x peripheral address register (DMA_SxPAR)
Address offset: 0x18 + 0x18 * x, (x = 0 to 7)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PAR[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

PAR[15:0]
rw

Bits 31:0 PAR[31:0]: peripheral address
Base address of the peripheral data register from/to which the data is read/written.
These bits are write-protected and can be written only when bit EN = '0' in the DMA_SxCR
register.

8.5.8

DMA stream x memory 0 address register (DMA_SxM0AR)
Address offset: 0x1C + 0x18 * x, (x = 0 to 7)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

M0A[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

M0A[15:0]
rw

Bits 31:0 M0A[31:0]: memory 0 address
Base address of memory area 0 from/to which the data is read/written.
These bits are write-protected. They can be written only if:
–
the stream is disabled (bit EN= '0' in the DMA_SxCR register) or
–
the stream is enabled (EN=’1’ in DMA_SxCR register) and bit CT = '1' in the
DMA_SxCR register (in double-buffer mode).

8.5.9

DMA stream x memory 1 address register (DMA_SxM1AR)
Address offset: 0x20 + 0x18 * x, (x = 0 to 7)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

M1A[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

M1A[15:0]
rw

250/1709

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

RM0385

Direct memory access controller (DMA)

Bits 31:0 M1A[31:0]: memory 1 address (used in case of double-buffer mode)
Base address of memory area 1 from/to which the data is read/written.
This register is used only for the double-buffer mode.
These bits are write-protected. They can be written only if:
–
the stream is disabled (bit EN= '0' in the DMA_SxCR register) or
–
the stream is enabled (EN=’1’ in DMA_SxCR register) and bit CT = '0' in the
DMA_SxCR register.

8.5.10

DMA stream x FIFO control register (DMA_SxFCR)
Address offset: 0x24 + 0x24 * x, (x = 0 to 7)
Reset value: 0x0000 0021

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

5

4

3

2

1

0

15

14

13

12

11

10

9

8

7

6

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FEIE

Res.

rw

FS[2:0]
r

r

DMDIS
r

rw

FTH[1:0]
rw

rw

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 FEIE: FIFO error interrupt enable
This bit is set and cleared by software.
0: FE interrupt disabled
1: FE interrupt enabled
Bit 6 Reserved, must be kept at reset value.
Bits 5:3 FS[2:0]: FIFO status
These bits are read-only.
000: 0 < fifo_level < 1/4
001: 1/4 ≤ fifo_level < 1/2
010: 1/2 ≤ fifo_level < 3/4
011: 3/4 ≤ fifo_level < full
100: FIFO is empty
101: FIFO is full
others: no meaning
These bits are not relevant in the direct mode (DMDIS bit is zero).
Bit 2 DMDIS: direct mode disable
This bit is set and cleared by software. It can be set by hardware.
0: direct mode enabled
1: direct mode disabled
This bit is protected and can be written only if EN is ‘0’.
This bit is set by hardware if the memory-to-memory mode is selected (DIR bit in
DMA_SxCR are “10”) and the EN bit in the DMA_SxCR register is ‘1’ because the direct
mode is not allowed in the memory-to-memory configuration.

RM0385 Rev 7

251/1709
256

Direct memory access controller (DMA)

RM0385

Bits 1:0 FTH[1:0]: FIFO threshold selection
These bits are set and cleared by software.
00: 1/4 full FIFO
01: 1/2 full FIFO
10: 3/4 full FIFO
11: full FIFO
These bits are not used in the direct mode when the DMIS value is zero.
These bits are protected and can be written only if EN is ‘0’.

252/1709

RM0385 Rev 7

0x0028

0x002C

DMA_S1CR

DMA_S1NDTR

Res.

CT

DBM

0

0

0

0

0

0

0

-

0

0

0

0

Res

Res

Res

Res

Res

Res

Reset value

Res

0
0
0
0
0
0

DMA_S0FCR
Res
FEIE
Res

0
0
0

0
0

DMA_S0M0AR

0

DMA_S0M1AR
0

DMA_S0PAR

0

0

Reset value

RM0385 Rev 7

Reset value

0

0
0

0

0

0

0

0

0

0

0
0

0

0

0
0

0

0

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMEIE
EN

0
TEIE

0
0
0
0

CFEIF4

0
0
0
0
0

FS[2:0]

Res

0
0
0
0
0
0
0
0

FEIF4

0
0
0
0
0
0
0
0

Res

TEIF0
DMEIF0

0
CFEIF0

0
CDMEIF4

HTIF0
DMEIF4

CDMEIF0

0
CTEIF4

TCIF0
TEIF4

CTEIF0

0

HTIE

0
CHTIF4

HTIF4

0
CTCIF4

TCIF4
CHTIF0

0

TCIE

CTCIF0

0

PFCTRL

0
Res

FEIF0

Res.

Res.
FEIF1

0
Res
FEIF5

0
CFEIF5

0
Res
CFEIF1

0
Res

0
DIR[1:0]

TEIF1
DMEIF1

DMEIF5

CDMEIF1

CDMEIF5

0

CIRC

TEIF5

Res.

Res.

Res.

Res.

HTIF1

HTIF5
CTEIF1

CTEIF5

CHTIF1

CHTIF5

Res.
FEIF2

TCIF1

Res

Res

Res

Res

Res

TCIF5

Res

Res

Res

Res

CTCIF1
0

PINC

0

0

MINC

0

CTCIF5

PSIZE[1:0]

Res

Res

Res

Res

0

Res

FEIF6

0

MSIZE[1:0]

PINCOS

Res

0
CFEIF2

CFEIF6

0

FTH[1:0]

0
0
0
PL[1:0]

0

DMDIS

0
0

Res

0

NDT[15:0]

EN

0

Res

0
0

Res

TEIF2
DMEIF2

DMEIF6

CDMEIF2

CDMEIF6

0

DBM

0

DMEIE

0

Res

0
0

Res

HTIF2

0

TEIE

0

Res

0
CTEIF6

0

HTIE

0

Res

0
0

CT

0

TCIE

0

Res

0
0
0

Res

TCIF2
TEIF6

CTEIF2

0
CHTIF6

HTIF6

CHTIF2

0
CTCIF6

TCIF6

CTCIF2

0

Res

0

PFCTRL

0

Res

0
0
PBURST[1:0]

0

DIR[1:0]

0

Res

Res

0

Res.
FEIF3
0

Res
FEIF7

0

Res

0

Res
CFEIF3

0

CFEIF7

0

CIRC

0

Res

0

Res

0

PINC

0

Res

0
0
MBURST[1:0]

0

MINC

0

Res

0

Res

TEIF3
DMEIF3

DMEIF7

CDMEIF3

0

CDMEIF7

HTIF3

TEIF7

TEIF3

HTIF7

CHTIF3

0

CTEIF7

0

CHTIF7

0

PSIZE[1:0]

0

Res

0

Res

0

Res

CHSEL[2:0]

0

MSIZE[1:0]

0

Res

0

Res
0

0

PINCOS

0

Res

0

Res

Res.

Res.

Res.

Res.

TCIF3

Res

Res

Res

Res

TCIF7

CTCIF3

Res

Res

0

CTCIF7

Res

Res

0

0

PL[1:0]

0

Res

0

Res

Res

Res

Res

Res

0

0

PBURST[1:0]

0

Res

0
0

MBURST[1:]

0

Res

0
0

Res

0

Res

0
0
Res

Reset value

Res

0

Res

0
Res

Reset value

CHSEL[2:0]

0
Res

Res

Reset value

Res

0
Res

Reset value

Res

0

Res

Reset value
Res

Reset value

Res

0

Res

0x0024
Reset value

Res

Reset value

Res.

0x0020
DMA_S0NDTR

Res.

0x001C
DMA_S0CR

Res

0x0018
DMA_HIFCR

Res

0x0014
DMA_LIFCR

Res

0x0010
DMA_HISR

Res

0x000C

Res

0x0008

Res

0x0004
DMA_LISR

Res.

0x0000

Res.

19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

31
30
29
28
27
26
25
24
23
22
21
20

Offset Register name

Res

8.5.11

Res

RM0385
Direct memory access controller (DMA)

DMA register map

Table 33 summarizes the DMA registers.
Table 33. DMA register map and reset values

0

0
0
0
0
0
0

NDT[15:0]

PA[31:0]

M0A[31:0]

M1A[31:0]
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0
0

0
0
0
0
0
0

1

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

253/1709

256

Direct memory access controller (DMA)

RM0385

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

M0A[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S1FCR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S2FCR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

FEIE

Res

0

0

0

0

CIRC

0

PSIZE[1:0]

MSIZE[1:0]

PINCOS

PL[1:0]
0

PINC

Res

0

MINC

Res

0

Res

Res

0

Res

Res

DBM

0

Res

0

CT

0

Res

0

Res

0
Res

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]
0
Res

Res

Res

Res

Res

0
Res

Res

Res

Res

Res

0

0

0

0

0

0

FS[2:0]

FTH[1:0]

0

1

0

0

0

0

1

EN

0

DMEIE

0

DMDIS

0

TEIE

0

HTIE

0

TCIE

0

0

0

0

0

0

0

NDT[15:0]
0

DMA_S3PAR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PA[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S3M0AR

254/1709

0

0

0

Reset value

0

0

0

Reset value

0x0064

0

0

0

Reset value

0

0

0

DMA_S3NDTR

0

0

Reset value

DMA_S3CR

0x0060

0

1

M1A[31:0]

Reset value

0x005C

0

0

0

Reset value

0x0058

DIR
[1:0]

PSIZE[1:0]

0

0

M0A[31:0]

DMA_S2M1AR

0x0054

0

Res

0x0050

0

0

PA[31:0]

DMA_S2M0AR
Reset value

0

DIR[1:0]

0x004C

0

0

PFCTRL

Reset value

0

1

NDT[15:0]
0

DMA_S2PAR

0x0048

MSIZE[1:0]

PINCOS

PL[1:0]

Reset value

0

CIRC

Res

0

PINC

Res

0

MINC

Res

0

Res

Res

0

Res

0

DBM

0

Res

0

CT

0

Res

0

Res

0

Res

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]
0

Res

Res

Res

DMA_S2NDTR

Res

0x0044

Res

Reset value

Res

Res

Res

Res

DMA_S2CR

0x0040

0

Res

Reset value

FS[2:0]

FTH[1:0]

0

EN

0

DMDIS

0

TEIE

0

DMEIE

0

HTIE

0

TCIE

0

PFCTRL

Reset value

Res

M1A[31:0]

Res

DMA_S1M1AR

0x003C

0

Res

0

DMA_S1M0AR
Reset value

0x0038

0

Res

Reset value

PA[31:0]

FEIE

DMA_S1PAR

0x0030

0x0034

19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Offset Register name

31
30
29
28
27
26
25
24
23
22
21
20

Table 33. DMA register map and reset values (continued)

0

0

0

M0A[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RM0385 Rev 7

0

0

0

RM0385

Direct memory access controller (DMA)

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S3FCR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S4FCR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

FEIE

Res

0

PSIZE[1:0]
0

0

0

CIRC

0

0

0

0

0

0

1

0

0

0

0

1

0

0

0

0

0

0

NDT[15:0]
0

DMA_S5PAR

MSIZE[1:0]

PINCOS

PL[1:0]
0

PINC

Res

0

MINC

Res

0

Res

Res

0

Res

Res

DBM

0

Res

0

CT

0

Res

0

Res

0
Res

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]
0
Res

Res

Res

Res

Res

0
Res

Res

Res

Res

Res

0

FS[2:0]

FTH[1:0]

0

EN

0

DMEIE

0

DMDIS

0

TEIE

0

HTIE

0
Res

M1A[31:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PA[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S5M0AR

0

0

0

M0A[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S5FCR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

FEIE

Res

Reset value

0

RM0385 Rev 7

FS[2:0]
1

0

0

0

FTH[1:0]

Reset value

Res

M1A[31:0]

Res

DMA_S5M1AR

0

Res

0x009C

0

0

Res

0x0098

0

0

0

Reset value

1

DMDIS

0x0094

0

0

0

Reset value

0

0

0

DMA_S5NDTR

0

0

Reset value

DMA_S5CR

0

0

Res

DMA_S4M1AR

0

Reset value
0x0090

0

1

M0A[31:0]

Reset value

0x008C

0

0

0

Reset value

0x0088

DIR
[1:0]

PSIZE[1:0]

0

Res

0x0084

0

Res

0x0080

0

FS[2:0]

0

PA[31:0]

DMA_S4M0AR
Reset value

0

0

TCIE

0x007C

0

0

PFCTRL

Reset value

0

0

NDT[15:0]
0

DMA_S4PAR

0

DIR[1:0]

0x0078

MSIZE[1:0]

PINCOS

PL[1:0]

Reset value

0

CIRC

Res

0

PINC

Res

0

MINC

Res

0

Res

Res

0

Res

0

DBM

0

Res

0

CT

0

Res

0

Res

0

Res

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]
0

Res

Res

Res

DMA_S4NDTR

Res

0x0074

Res

Reset value

Res

Res

Res

DMA_S4CR

Res

0x0070

0

Res

Reset value

0

FTH[1:0]

0

EN

0

DMDIS

0

TEIE

0

DMEIE

0

HTIE

0

TCIE

0

Res

0

PFCTRL

0

Res

0

FEIE

Reset value

Res

M1A[31:0]

Res

0x006C

DMA_S3M1AR

Res

0x0068

19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Offset Register name

31
30
29
28
27
26
25
24
23
22
21
20

Table 33. DMA register map and reset values (continued)

0

1

255/1709
256

Direct memory access controller (DMA)

RM0385

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S6FCR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

FEIE

Res

0

0

0

0

0

0

DIR[1:0]

CIRC

0

PSIZE[1:0]

MSIZE[1:0]

PINCOS

PL[1:0]
0

PINC

Res

0

MINC

Res

0

Res

Res

0

Res

Res

DBM

0

Res

0

CT

0

Res

Res

0

Res

0

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]
0
Res

Res

Res

Res

Res

0
Res

Res

Res

Res

Res

0

0

0

FS[2:0]

FTH[1:0]

0

1

0

0

0

0

1

EN

0

DMEIE

0

DMDIS

0

TEIE

0

HTIE

0

0

0

0

0

0

0

NDT[15:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PA[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S7M0AR

0

0

0

M0A[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S7FCR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

FEIE

Res

Reset value

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

RM0385 Rev 7

FS[2:0]
1

0

0

0

FTH[1:0]

Reset value

Res

M1A[31:0]

Res

DMA_S7M1AR

256/1709

EN

0

0

DMA_S7PAR

0x00CC

TEIE

0

Res

0x00C8

DMEIE

0

0

Reset value

HTIE

0

DMDIS

0x00C4

0

0

0

Reset value

0

0

0

Reset value
0x00C0

0

0

0

DMA_S7NDTR

0

M1A[31:0]

Reset value

0x00BC

0

0

Reset value

DMA_S7CR

0

0

Reset value

0x00B8

0

TCIE

0

PFCTRL

0

DIR[1:0]

PSIZE[1:0]

PINCOS

PL[1:0]

0

M0A[31:0]

DMA_S6M1AR

0x00B4

0

Res

0x00B0

0

PA[31:0]

DMA_S6M0AR
Reset value

0

TCIE

0x00AC

0

PFCTRL

Reset value

0

NDT[15:0]
0

DMA_S6PAR

0x00A8

MSIZE[1:0]

19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Reset value

0

PINC

Res

0

CIRC

Res

0

MINC

Res

0

Res

Res

0

Res

0

CT

0

DBM

0

Res

0

Res

Res

0

Res

0

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]
0

Res

Res
Res

Res

DMA_S6NDTR

Res

0x00A4

Res

Reset value

Res

Res

Res

DMA_S6CR

0x00A0

Res

Offset Register name

31
30
29
28
27
26
25
24
23
22
21
20

Table 33. DMA register map and reset values (continued)

0

1

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

9

Chrom-ART Accelerator™ controller (DMA2D)

9.1

DMA2D introduction
The Chrom-ART Accelerator™ (DMA2D) is a specialized DMA dedicated to image
manipulation. It can perform the following operations:
•

Filling a part or the whole of a destination image with a specific color

•

Copying a part or the whole of a source image into a part or the whole of a destination
image

•

Copying a part or the whole of a source image into a part or the whole of a destination
image with a pixel format conversion

•

Blending a part and/or two complete source images with different pixel format and copy
the result into a part or the whole of a destination image with a different color format.

All the classical color coding schemes are supported from 4-bit up to 32-bit per pixel with
indexed or direct color mode. The DMA2D has its own dedicated memories for CLUTs (color
look-up tables).

9.2

DMA2D main features
The main DMA2D features are:
•

Single AHB master bus architecture.

•

AHB slave programming interface supporting 8/16/32-bit accesses (except for CLUT
accesses which are 32-bit).

•

User programmable working area size

•

User programmable offset for sources and destination areas

•

User programmable sources and destination addresses on the whole memory space

•

Up to 2 sources with blending operation

•

Alpha value can be modified (source value, fixed value or modulated value)

•

User programmable source and destination color format

•

Up to 11 color formats supported from 4-bit up to 32-bit per pixel with indirect or direct
color coding

•

2 internal memories for CLUT storage in indirect color mode

•

Automatic CLUT loading or CLUT programming via the CPU

•

User programmable CLUT size

•

Internal timer to control AHB bandwidth

•

4 operating modes: register-to-memory, memory-to-memory, memory-to-memory with
pixel format conversion, and memory-to-memory with pixel format conversion and
blending

RM0385 Rev 7

257/1709
288

Chrom-ART Accelerator™ controller (DMA2D)
•

Area filling with a fixed color

•

Copy from an area to another

•

Copy with pixel format conversion between source and destination images

•

Copy from two sources with independent color format and blending

•

Abort and suspend of DMA2D operations

•

Watermark interrupt on a user programmable destination line

•

Interrupt generation on bus error or access conflict

•

Interrupt generation on process completion

9.3

DMA2D functional description

9.3.1

General description

RM0385

The DMA2D controller performs direct memory transfer. As an AHB master, it can take the
control of the AHB bus matrix to initiate AHB transactions.
The DMA2D can operate in the following modes:
•

Register-to-memory

•

Memory-to-memory

•

Memory-to-memory with Pixel Format Conversion

•

Memory-to-memory with Pixel Format Conversion and Blending

The AHB slave port is used to program the DMA2D controller.
The block diagram of the DMA2D is shown in Figure 29: DMA2D block diagram.

258/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)
Figure 29. DMA2D block diagram
AHB MASTER

FG PFC

A mode
8-bit A

Color mode
FG
FIFO

32

A 8

32

RGB

Expander

X

A 32

32

CLUT itf

256x32-bit
RAM

32

Color mode

A
Red
Green

32
Converter
32/24/16

Color
OUT
FIFO

Blue

BG PFC

A mode

Color mode
BG
FIFO

OUT PFC

BLENDER

8-bit A

32

A 8

32

RGB

Expander

X

A 32

CLUT itf

256x32-bit
RAM

AHB SLAVE

MS30439V1

9.3.2

DMA2D control
The DMA2D controller is configured through the DMA2D Control Register (DMA2D_CR)
which allows selecting:
The user application can perform the following operations:

9.3.3

•

Select the operating mode

•

Enable/disable the DMA2D interrupt

•

Start/suspend/abort ongoing data transfers

DMA2D foreground and background FIFOs
The DMA2D foreground (FG) FG FIFO and background (BG) FIFO fetch the input data to
be copied and/or processed.
The FIFOs fetch the pixels according to the color format defined in their respective pixel
format converter (PFC).

RM0385 Rev 7

259/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

RM0385

They are programmed through a set of control registers:
•

DMA2D foreground memory address register (DMA2D_FGMAR)

•

DMA2D foreground offset register (DMA2D_FGOR)

•

DMA2D background memory address register (DMA2D_BGMAR)

•

DMA2D background offset register (DMA2D_BGBOR)

•

DMA2D number of lines register (number of lines and pixel per lines) (DMA2D_NLR)

When the DMA2D operates in register-to-memory mode, none of the FIFOs is activated.
When the DMA2D operates in memory-to-memory mode (no pixel format conversion nor
blending operation), only the FG FIFO is activated and acts as a buffer.
When the DMA2D operates in memory-to-memory operation with pixel format conversion
(no blending operation), the BG FIFO is not activated.

9.3.4

DMA2D foreground and background pixel format converter (PFC)
DMA2D foreground pixel format converter (PFC) and background pixel format converter
perform the pixel format conversion to generate a 32-bit per pixel value. The PFC can also
modify the alpha channel.
The first stage of the converter converts the color format. The original color format of the
foreground pixel and background pixels are configured through the CM[3:0] bits of the
DMA2D_FGPFCCR and DMA2D_BGPFCCR, respectively.
The supported input formats are given in Table 34: Supported color mode in input.
Table 34. Supported color mode in input
CM[3:0]

260/1709

Color mode

0000

ARGB8888

0001

RGB888

0010

RGB565

0011

ARGB1555

0100

ARGB4444

0101

L8

0110

AL44

0111

AL88

1000

L4

1001

A8

1010

A4

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)
The color format are coded as follows:
•

Alpha value field: transparency
0xFF value corresponds to an opaque pixel and 0x00 to a transparent one.

•

R field for Red

•

G field for Green

•

B field for Blue

•

L field: luminance
This field is the index to a CLUT to retrieve the three/four RGB/ARGB components.

If the original format was direct color mode (ARGB/RGB), then the extension to 8-bit per
channel is performed by copying the MSBs into the LSBs. This ensures a perfect linearity of
the conversion.
If the original format is indirect color mode (L/AL), a CLUT is required and each pixel format
converter is associated with a 256 entry 32-bit CLUT.
If the original format does not include an alpha channel, the alpha value is automatically set
to 0xFF (opaque).
For the specific alpha mode A4 and A8, no color information is stored nor indexed. The color
to be used for the image generation is fixed and is defined in the DMA2D_FGCOLR for
foreground pixels and in the DMA2D_BGCOLR register for background pixels.
The order of the fields in the system memory is defined in Table 35: Data order in memory.
Table 35. Data order in memory
Color Mode

@+3

@+2

@+1

@+0

ARGB8888

A0[7:0]

R0[7:0]

G0[7:0]

B0[7:0]

B1[7:0]

R0[7:0]

G0[7:0]

B0[7:0]

G2[7:0]

B2[7:0]

R1[7:0]

G1[7:0]

R3[7:0]

G3[7:0]

B3[7:0]

R2[7:0]

RGB565

R1[4:0]G1[5:3]

G1[2:0]B1[4:0]

R0[4:0]G0[5:3]

G0[2:0]B0[4:0]

ARGB1555

A1[0]R1[4:0]G1[4:3]

G1[2:0]B1[4:0]

A0[0]R0[4:0]G0[4:3]

G0[2:0]B0[4:0]

ARGB4444

A1[3:0]R1[3:0]

G1[3:0]B1[3:0]

A0[3:0]R0[3:0]

G0[3:0]B0[3:0]

L8

L3[7:0]

L2[7:0]

L1[7:0]

L0[7:0]

AL44

A3[3:0]L3[3:0]

A2[3:0]L2[3:0]

A1[3:0]L1[3:0]

A0[3:0]L0[3:0]

AL88

A1[7:0]

L1[7:0]

A0[7:0]

L0[7:0]

L4

L7[3:0]L6[3:0]

L5[3:0]L4[3:0]

L3[3:0]L2[3:0]

L1[3:0]L0[3:0]

A8

A3[7:0]

A2[7:0]

A1[7:0]

A0[7:0]

A4

A7[3:0]A6[3:0]

A5[3:0]A4[3:0]

A3[3:0]A2[3:0]

A1[3:0]A0[3:0]

RGB888

The 24-bit RGB888 aligned on 32-bit is supported through the ARGB8888 mode.
Once the 32-bit value is generated, the alpha channel can be modified according to the
AM[1:0] field of the DMA2D_FGPFCCR/DMA2D_BGPFCCR registers as shown in
Table 36: Alpha mode configuration.

RM0385 Rev 7

261/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

RM0385

The alpha channel can be:
•

kept as it is (no modification),

•

replaced by the ALPHA[7:0] value of DMA2D_FGPFCCR/DMA2D_BGPFCCR,

•

or replaced by the original alpha value multiplied by the ALPHA[7:0] value of
DMA2D_FGPFCCR/DMA2D_BGPFCCR divided by 255.
Table 36. Alpha mode configuration

9.3.5

AM[1:0]

Alpha mode

00

No modification

01

Replaced by value in DMA2D_xxPFCCR

10

Replaced by original value multiplied by the value in DMA2D_xxPFCCR / 255

11

Reserved

DMA2D foreground and background CLUT interface
The CLUT interface manages the CLUT memory access and the automatic loading of the
CLUT.
Three kinds of accesses are possible:
•

CLUT read by the PFC during pixel format conversion operation

•

CLUT accessed through the AHB slave port when the CPU is reading or writing data
into the CLUT

•

CLUT written through the AHB master port when an automatic loading of the CLUT is
performed

The CLUT memory loading can be done in two different ways:
•

Automatic loading
The following sequence should be followed to load the CLUT:
a)

Program the CLUT address into the DMA2D_FGCMAR register (foreground
CLUT) or DMA2D_BGCMAR register (background CLUT)

b)

Program the CLUT size in the CS[7:0] field of the DMA2D_FGPFCCR register
(foreground CLUT) or DMA2D_BGPFCCR register (background CLUT).

c)

Set the START bit of the DMA2D_FGPFCCR register (foreground CLUT) or
DMA2D_BGPFCCR register (background CLUT) to start the transfer. During this
automatic loading process, the CLUT is not accessible by the CPU. If a conflict
occurs, a CLUT access error interrupt is raised assuming CAEIE is set to ‘1’ in
DMA2D_CR.

•

Manual loading
The application has to program the CLUT manually through the DMA2D AHB slave
port to which the local CLUT memory is mapped.The foreground CLUT is located at
address offset 0x0400 and the background CLUT at address offset 0x0800.

The CLUT format can be 24 or 32 bits. It is configured through the CCM bit of the
DMA2D_FGPFCCR register (foreground CLUT) or DMA2D_BGPFCCR register
(background CLUT) as shown in Table 37: Supported CLUT color mode.

262/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)
Table 37. Supported CLUT color mode
CCM

CLUT color mode

0

32-bit ARGB8888

1

24-bit RGB888

The way the CLUT data are organized in the system memory is specified in Table 38: CLUT
data order in system memory.
Table 38. CLUT data order in system memory
CLUT Color Mode
ARGB8888

RGB888

9.3.6

@+3

@+2

@+1

@+0

A0[7:0]

R0[7:0]

G0[7:0]

B0[7:0]

B1[7:0]

R0[7:0]

G0[7:0]

B0[7:0]

G2[7:0]

B2[7:0]

R1[7:0]

G1[7:0]

R3[7:0]

G3[7:0]

B3[7:0]

R2[7:0]

DMA2D blender
The DMA2D blender blends the source pixels by pair to compute the resulting pixel.
The blending is performed according to the following equation:

with αMult =

αFG . αBG
255

αOUT = αFG + αBG - αMult

COUT =

CFG.αFG + CBG.αBG - CBG.αMult
αOUT

with C = R or G or B

Division is rounded to the nearest lower integer

No configuration register is required by the blender. The blender usage depends on the
DMA2D operating mode defined in MODE[1:0] field of the DMA2D_CR register.

9.3.7

DMA2D output PFC
The output PFC performs the pixel format conversion from 32 bits to the output format
defined in the CM[2:0] field of the DMA2D output pixel format converter configuration
register (DMA2D_OPFCCR).
The supported output formats are given in Table 39: Supported color mode in output

RM0385 Rev 7

263/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

RM0385

Table 39. Supported color mode in output
CM[2:0]

9.3.8

Color mode

000

ARGB8888

001

RGB888

010

RGB565

011

ARGB1555

100

ARGB4444

DMA2D output FIFO
The output FIFO programs the pixels according to the color format defined in the output
PFC.
The destination area is defined through a set of control registers:
•

DMA2D output memory address register (DMA2D_OMAR)

•

DMA2D output offset register (DMA2D_OOR)

•

DMA2D number of lines register (number of lines and pixel per lines) (DMA2D_NLR)

If the DMA2D operates in register-to-memory mode, the configured output rectangle is filled
by the color specified in the DMA2D output color register (DMA2D_OCOLR) which contains
a fixed 32-bit, 24-bit or 16-bit value. The format is selected by the CM[2:0] field of the
DMA2D_OPFCCR register.
The data are stored into the memory in the order defined in Table 40: Data order in memory
Table 40. Data order in memory
Color Mode

@+3

@+2

@+1

@+0

ARGB8888

A0[7:0]

R0[7:0]

G0[7:0]

B0[7:0]

B1[7:0]

R0[7:0]

G0[7:0]

B0[7:0]

G2[7:0]

B2[7:0]

R1[7:0]

G1[7:0]

R3[7:0]

G3[7:0]

B3[7:0]

R2[7:0]

RGB565

R1[4:0]G1[5:3]

G1[2:0]B1[4:0]

R0[4:0]G0[5:3]

G0[2:0]B0[4:0]

ARGB1555

A1[0]R1[4:0]G1[4:3]

G1[2:0]B1[4:0]

A0[0]R0[4:0]G0[4:3]

G0[2:0]B0[4:0]

ARGB4444

A1[3:0]R1[3:0]

G1[3:0]B1[3:0]

A0[3:0]R0[3:0]

G0[3:0]B0[3:0]

RGB888

The RGB888 aligned on 32-bit is supported through the ARGB8888 mode.

9.3.9

DMA2D AHB master port timer
An 8-bit timer is embedded into the AHB master port to provide an optional limitation of the
bandwidth on the crossbar.
This timer is clocked by the AHB clock and counts a dead time between two consecutive
accesses. This limits the bandwidth usage.

264/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)
The timer enabling and the dead time value are configured through the AHB master port
timer configuration register (DMA2D_AMPTCR).

9.3.10

DMA2D transactions
DMA2D transactions consist of a sequence of a given number of data transfers. The
number of data and the width can be programmed by software.
Each DMA2D data transfer is composed of up to 4 steps:

9.3.11

1.

Data loading from the memory location pointed by the DMA2D_FGMAR register and
pixel format conversion as defined in DMA2D_FGCR.

2.

Data loading from a memory location pointed by the DMA2D_BGMAR register and
pixel format conversion as defined in DMA2D_BGCR.

3.

Blending of all retrieved pixels according to the alpha channels resulting of the PFC
operation on alpha values.

4.

Pixel format conversion of the resulting pixels according to the DMA2D_OCR register
and programming of the data to the memory location addressed through the
DMA2D_OMAR register.

DMA2D configuration
Both source and destination data transfers can target peripherals and memories in the
whole 4 Gbyte memory area, at addresses ranging between 0x0000 0000 and
0xFFFF FFFF.
The DMA2D can operate in any of the four following modes selected through MODE[1:0]
bits of the DMA2D_CR register:
•

Register-to-memory

•

Memory-to-memory

•

Memory-to-memory with PFC

•

Memory-to-memory with PFC and blending

Register-to-memory
The register-to-memory mode is used to fill a user defined area with a predefined color.
The color format is set in the DMA2D_OPFCCR.
The DMA2D does not perform any data fetching from any source. It just writes the color
defined in the DMA2D_OCOLR register to the area located at the address pointed by the
DMA2D_OMAR and defined in the DMA2D_NLR and DMA2D_OOR.

Memory-to-memory
In memory-to-memory mode, the DMA2D does not perform any graphical data
transformation. The foreground input FIFO acts as a buffer and the data are transferred
from the source memory location defined in DMA2D_FGMAR to the destination memory
location pointed by DMA2D_OMAR.
The color mode programmed in the CM[3:0] bits of the DMA2D_FGPFCCR register defines
the number of bits per pixel for both input and output.

RM0385 Rev 7

265/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

RM0385

The size of the area to be transferred is defined by the DMA2D_NLR and DMA2D_FGOR
registers for the source, and by DMA2D_NLR and DMA2D_OOR registers for the
destination.

Memory-to-memory with PFC
In this mode, the DMA2D performs a pixel format conversion of the source data and stores
them in the destination memory location.
The size of the areas to be transferred are defined by the DMA2D_NLR and DMA2D_FGOR
registers for the source, and by DMA2D_NLR and DMA2D_OOR registers for the
destination.
Data are fetched from the location defined in the DMA2D_FGMAR register and processed
by the foreground PFC. The original pixel format is configured through the
DMA2D_FGPFCCR register.
If the original pixel format is direct color mode, then the color channels are all expanded to 8
bits.
If the pixel format is indirect color mode, the associated CLUT has to be loaded into the
CLUT memory.
The CLUT loading can be done automatically by following the sequence below:
1.

Set the CLUT address into the DMA2D_FGCMAR.

2.

Set the CLUT size in the CS[7:0] bits of the DMA2D_FGPFCCR register.

3.

Set the CLUT format (24 or 32 bits) in the CCM bit of the DMA2D_FGPFCCR register.

4.

Start the CLUT loading by setting the START bit of the DMA2D_FGPFCCR register.

Once the CLUT loading is complete, the CTCIF flag of the DMA2D_IFR register is raised,
and an interrupt is generated if the CTCIE bit is set in DMA2D_CR. The automatic CLUT
loading process can not work in parallel with classical DMA2D transfers.
The CLUT can also be filled by the CPU or by any other master through the APB port. The
access to the CLUT is not possible when a DMA2D transfer is ongoing and uses the CLUT
(indirect color format).
In parallel to the color conversion process, the alpha value can be added or changed
depending on the value programmed in the DMA2D_FGPFCCR register. If the original
image does not have an alpha channel, a default alpha value of 0xFF is automatically added
to obtain a fully opaque pixel. The alpha value can be modified according to the AM[1:0] bits
of the DMA2D_FGPFCCR register:
•

It can be unchanged.

•

It can be replaced by the value defined in the ALPHA[7:0] value of the
DMA2D_FGPFCCR register.

•

It can be replaced by the original value multiplied by the ALPHA[7:0] value of the
DMA2D_FGPFCCR register divided by 255.

The resulting 32-bit data are encoded by the OUT PFC into the format specified by the
CM[2:0] field of the DMA2D_OPFCCR register. The output pixel format cannot be the
indirect mode since no CLUT generation process is supported.
The processed data are written into the destination memory location pointed by
DMA2D_OMAR.

266/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

Memory-to-memory with PFC and blending
In this mode, 2 sources are fetched in the foreground FIFO and background FIFO from the
memory locations defined by DMA2D_FGMAR and DMA2D_BGMAR.
The two pixel format converters have to be configured as described in the memory-tomemory mode. Their configurations can be different as each pixel format converter are
independent and have their own CLUT memory.
Once each pixel has been converted into 32 bits by their respective PFCs, they are blended
according to the equation below:
with αMult =

αFG . αBG
255

αOUT = αFG + αBG - αMult

COUT =

CFG.αFG + CBG.αBG - CBG.αMult
αOUT

with C = R or G or B

Division are rounded to the nearest lower integer

The resulting 32-bit pixel value is encoded by the output PFC according to the specified
output format, and the data are written into the destination memory location pointed by
DMA2D_OMAR.

Configuration error detection
The DMA2D checks that the configuration is correct before any transfer. The configuration
error interrupt flag is set by hardware when a wrong configuration is detected when a new
transfer/automatic loading starts. An interrupt is then generated if the CEIE bit of the
DMA2D_CR is set.
The wrong configurations that can be detected are listed below:
•

Foreground CLUT automatic loading: MA bits of DMA2D_FGCMAR are not aligned
with CCM of DMA2D_FGPFCCR.

•

Background CLUT automatic loading: MA bits of DMA2D_BGCMAR are not aligned
with CCM of DMA2D_BGPFCCR

•

Memory transfer (except in register-to-memory mode): MA bits of DMA2D_FGMAR are
not aligned with CM of DMA2D_FGPFCCR

•

Memory transfer (except in register-to-memory mode): CM bits of DMA2D_FGPFCCR
are invalid

•

Memory transfer (except in register-to-memory mode): PL bits of DMA2D_NLR are odd
while CM of DMA2D_FGPFCCR is A4 or L4

•

Memory transfer (except in register-to-memory mode): LO bits of DMA2D_FGOR are
odd while CM of DMA2D_FGPFCCR is A4 or L4

•

Memory transfer (only in blending mode): MA bits of DMA2D_BGMAR are not aligned
with the CM of DMA2D_BGPFCCR

•

Memory transfer: (only in blending mode) CM bits of DMA2D_BGPFCCR are invalid

•

Memory transfer (only in blending mode): PL bits of DMA2D_NLR odd while CM of
DMA2D_BGPFCCR is A4 or L4

RM0385 Rev 7

267/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

9.3.12

RM0385

•

Memory transfer (only in blending mode): LO bits of DMA2D_BGOR are odd while CM
of DMA2D_BGPFCCR is A4 or L4

•

Memory transfer (except in memory to memory mode): MA bits of DMA2D_OMAR are
not aligned with CM bits of DMA2D_OPFCCR.

•

Memory transfer (except in memory to memory mode): CM bits of DMA2D_OPFCCR
are invalid

•

Memory transfer: NL bits of DMA2D_NLR = 0

•

Memory transfer: PL bits of DMA2D_NLR = 0

DMA2D transfer control (start, suspend, abort and completion)
Once the DMA2D is configured, the transfer can be launched by setting the START bit of the
DMA2D_CR register. Once the transfer is completed, the START bit is automatically reset
and the TCIF flag of the DMA2D_ISR register is raised. An interrupt can be generated if the
TCIE bit of the DMA2D_CR is set.
The user application can suspend the DMA2D at any time by setting the SUSP bit of the
DMA2D_CR register. The transaction can then be aborted by setting the ABORT bit of the
DMA2D_CR register or can be restarted by resetting the SUSP bit of the DMA2D_CR
register.
The user application can abort at any time an ongoing transaction by setting the ABORT bit
of the DMA2D_CR register. In this case, the TCIF flag is not raised.
Automatic CLUT transfers can also be aborted or suspended by using the ABORT or the
SUSP bit of the DMA2D_CR register.

9.3.13

Watermark
A watermark can be programmed to generate an interrupt when the last pixel of a given line
has been written to the destination memory area.
The line number is defined in the LW[15:0] field of the DMA2D_LWR register.
When the last pixel of this line has been transferred, the TWIF flag of the DMA2D_ISR
register is raised and an interrupt is generated if the TWIE bit of the DMA2D_CR is set.

9.3.14

Error management
Two kind of errors can be triggered:
•

AHB master port errors signaled by the TEIF flag of the DMA2D_ISR register.

•

Conflicts caused by CLUT access (CPU trying to access the CLUT while a CLUT
loading or a DMA2D transfer is ongoing) signalled by the CAEIF flag of the
DMA2D_ISR register.

Both flags are associated to their own interrupt enable flag in the DMA2D_CR register to
generate an interrupt if need be (TEIE and CAEIE).

9.3.15

AHB dead time
To limit the AHB bandwidth usage, a dead time between two consecutive AHB accesses
can be programmed.
This feature can be enabled by setting the EN bit in the DMA2D_AMTCR register.

268/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)
The dead time value is stored in the DT[7:0] field of the DMA2D_AMTCR register. This
value represents the guaranteed minimum number of cycles between two consecutive
transactions on the AHB bus.
The update of the dead time value while the DMA2D is running will be taken into account for
the next AHB transfer.

9.4

DMA2D interrupts
An interrupt can be generated on the following events:
•

Configuration error

•

CLUT transfer complete

•

CLUT access error

•

Transfer watermark reached

•

Transfer complete

•

Transfer error

Separate interrupt enable bits are available for flexibility.
Table 41. DMA2D interrupt requests
Interrupt event

Event flag

Enable control bit

CEIF

CEIE

CLUT transfer complete

CTCIF

CTCIE

CLUT access error

CAEIF

CAEIE

Transfer watermark

TWF

TWIE

Transfer complete

TCIF

TCIE

Transfer error

TEIF

TEIE

Configuration error

RM0385 Rev 7

269/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

RM0385

9.5

DMA2D registers

9.5.1

DMA2D control register (DMA2D_CR)
Address offset: 0x0000
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

CEIE

CTCIE

CAEIE

TWIE

TCIE

TEIE

Res.

Res.

Res.

Res.

Res.

ABORT

SUSP

START

rw

rw

rw

rw

rw

rw

rs

rw

rs

MODE[1:0]

Bits 31:18 Reserved, must be kept at reset value
Bits 17:16 MODE[1:0]: DMA2D mode
These bits are set and cleared by software. They cannot be modified while a transfer is
ongoing.
00: Memory-to-memory (FG fetch only)
01: Memory-to-memory with PFC (FG fetch only with FG PFC active)
10: Memory-to-memory with blending (FG and BG fetch with PFC and blending)
11: Register-to-memory (no FG nor BG, only output stage active)
Bits 15:14 Reserved, must be kept at reset value
Bit 13 CEIE: Configuration Error Interrupt Enable
This bit is set and cleared by software.
0: CE interrupt disable
1: CE interrupt enable
Bit 12 CTCIE: CLUT transfer complete interrupt enable
This bit is set and cleared by software.
0: CTC interrupt disable
1: CTC interrupt enable
Bit 11 CAEIE: CLUT access error interrupt enable
This bit is set and cleared by software.
0: CAE interrupt disable
1: CAE interrupt enable
Bit 10 TWIE: Transfer watermark interrupt enable
This bit is set and cleared by software.
0: TW interrupt disable
1: TW interrupt enable
Bit 9 TCIE: Transfer complete interrupt enable
This bit is set and cleared by software.
0: TC interrupt disable
1: TC interrupt enable

270/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

Bit 8 TEIE: Transfer error interrupt enable
This bit is set and cleared by software.
0: TE interrupt disable
1: TE interrupt enable
Bits 7:3 Reserved, must be kept at reset value
Bit 2 ABORT: Abort
This bit can be used to abort the current transfer. This bit is set by software and is
automatically reset by hardware when the START bit is reset.
0: No transfer abort requested
1: Transfer abort requested
Bit 1 SUSP: Suspend
This bit can be used to suspend the current transfer. This bit is set and reset by
software. It is automatically reset by hardware when the START bit is reset.
0: Transfer not suspended
1: Transfer suspended
Bit 0 START: Start
This bit can be used to launch the DMA2D according to the parameters loaded in the
various configuration registers. This bit is automatically reset by the following events:
–
At the end of the transfer
–
When the data transfer is aborted by the user application by setting the ABORT
bit in DMA2D_CR
–
When a data transfer error occurs
–
When the data transfer has not started due to a configuration error or another
transfer operation already ongoing (automatic CLUT loading).

RM0385 Rev 7

271/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

9.5.2

RM0385

DMA2D Interrupt Status Register (DMA2D_ISR)
Address offset: 0x0004
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CEIF

CTCIF

CAEIF

TWIF

TCIF

TEIF

r

r

r

r

r

r

Bits 31:6 Reserved, must be kept at reset value
Bit 5 CEIF: Configuration error interrupt flag
This bit is set when the START bit of DMA2D_CR, DMA2DFGPFCCR or
DMA2D_BGPFCCR is set and a wrong configuration has been programmed.
Bit 4 CTCIF: CLUT transfer complete interrupt flag
This bit is set when the CLUT copy from a system memory area to the internal DMA2D
memory is complete.
Bit 3 CAEIF: CLUT access error interrupt flag
This bit is set when the CPU accesses the CLUT while the CLUT is being automatically
copied from a system memory to the internal DMA2D.
Bit 2 TWIF: Transfer watermark interrupt flag
This bit is set when the last pixel of the watermarked line has been transferred.
Bit 1 TCIF: Transfer complete interrupt flag
This bit is set when a DMA2D transfer operation is complete (data transfer only).
Bit 0 TEIF: Transfer error interrupt flag
This bit is set when an error occurs during a DMA transfer (data transfer or automatic
CLUT loading).

272/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

9.5.3

DMA2D interrupt flag clear register (DMA2D_IFCR)
Address offset: 0x0008
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CCEIF CCTCIF CAECIF CTWIF

CTCIF

CTEIF

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Bits 31:6 Reserved, must be kept at reset value
Bit 5 CCEIF: Clear configuration error interrupt flag
Programming this bit to 1 clears the CEIF flag in the DMA2D_ISR register
Bit 4 CCTCIF: Clear CLUT transfer complete interrupt flag
Programming this bit to 1 clears the CTCIF flag in the DMA2D_ISR register
Bit 3 CAECIF: Clear CLUT access error interrupt flag
Programming this bit to 1 clears the CAEIF flag in the DMA2D_ISR register
Bit 2 CTWIF: Clear transfer watermark interrupt flag
Programming this bit to 1 clears the TWIF flag in the DMA2D_ISR register
Bit 1 CTCIF: Clear transfer complete interrupt flag
Programming this bit to 1 clears the TCIF flag in the DMA2D_ISR register
Bit 0 CTEIF: Clear Transfer error interrupt flag
Programming this bit to 1 clears the TEIF flag in the DMA2D_ISR register

RM0385 Rev 7

273/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

9.5.4

RM0385

DMA2D foreground memory address register (DMA2D_FGMAR)
Address offset: 0x000C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MA[31: 0]: Memory address
Address of the data used for the foreground image. This register can only be written
when data transfers are disabled. Once the data transfer has started, this register is
read-only.
The address alignment must match the image format selected e.g. a 32-bit per pixel
format must be 32-bit aligned, a 16-bit per pixel format must be 16-bit aligned and a 4bit per pixel format must be 8-bit aligned.

9.5.5

DMA2D foreground offset register (DMA2D_FGOR)
Address offset: 0x0010
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

rw

rw

rw

rw

rw

rw

LO[13:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:14 Reserved, must be kept at reset value
Bits 13:0 LO[13: 0]: Line offset
Line offset used for the foreground expressed in pixel. This value is used to generate
the address. It is added at the end of each line to determine the starting address of the
next line.
These bits can only be written when data transfers are disabled. Once a data transfer
has started, they become read-only.
If the image format is 4-bit per pixel, the line offset must be even.

9.5.6

DMA2D background memory address register (DMA2D_BGMAR)
Address offset: 0x0014
Reset value: 0x0000 0000

274/1709

RM0385 Rev 7

RM0385

31

Chrom-ART Accelerator™ controller (DMA2D)

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31: 0 MA[31: 0]: Memory address
Address of the data used for the background image. This register can only be written
when data transfers are disabled. Once a data transfer has started, this register is readonly.
The address alignment must match the image format selected e.g. a 32-bit per pixel
format must be 32-bit aligned, a 16-bit per pixel format must be 16-bit aligned and a 4bit per pixel format must be 8-bit aligned.

9.5.7

DMA2D background offset register (DMA2D_BGOR)
Address offset: 0x0018
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

rw

rw

rw

rw

rw

rw

LO[13:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:14 Reserved, must be kept at reset value
Bits 13:0 LO[13: 0]: Line offset
Line offset used for the background image (expressed in pixel). This value is used for
the address generation. It is added at the end of each line to determine the starting
address of the next line.
These bits can only be written when data transfers are disabled. Once data transfer has
started, they become read-only.
If the image format is 4-bit per pixel, the line offset must be even.

RM0385 Rev 7

275/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

9.5.8

RM0385

DMA2D foreground PFC control register (DMA2D_FGPFCCR)
Address offset: 0x001C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

ALPHA[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

CS[7:0]
rw

rw

rw

rw

rw

rw

rw

23

22

21

20

19

18

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

Res.

Res.

START

CCM

rs

rw

rw

17

16

AM[1:0]
rw

rw

1

0

rw

rw

CM[3:0]
rw

rw

Bits 31:24 ALPHA[7: 0]: Alpha value
These bits define a fixed alpha channel value which can replace the original alpha value
or be multiplied by the original alpha value according to the alpha mode selected
through the AM[1:0] bits.
These bits can only be written when data transfers are disabled. Once a transfer has
started, they become read-only.
Bits 23:18 Reserved, must be kept at reset value
Bits 17:16 AM[1: 0]: Alpha mode
These bits select the alpha channel value to be used for the foreground image. They
can only be written data the transfer are disabled. Once the transfer has started, they
become read-only.
00: No modification of the foreground image alpha channel value
01: Replace original foreground image alpha channel value by ALPHA[7: 0]
10: Replace original foreground image alpha channel value by ALPHA[7:0] multiplied
with original alpha channel value
other configurations are meaningless
Bits 15:8 CS[7: 0]: CLUT size
These bits define the size of the CLUT used for the foreground image. Once the CLUT
transfer has started, this field is read-only.
The number of CLUT entries is equal to CS[7:0] + 1.
Bits 7:6 Reserved, must be kept at reset value

276/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

Bit 5 START: Start
This bit can be set to start the automatic loading of the CLUT. It is automatically reset:
–
at the end of the transfer
–
when the transfer is aborted by the user application by setting the ABORT bit in
DMA2D_CR
–
when a transfer error occurs
–
when the transfer has not started due to a configuration error or another
transfer operation already ongoing (data transfer or automatic background
CLUT transfer).
Bit 4 CCM: CLUT color mode
This bit defines the color format of the CLUT. It can only be written when the transfer is
disabled. Once the CLUT transfer has started, this bit is read-only.
0: ARGB8888
1: RGB888
others: meaningless
Bits 3:0 CM[3: 0]: Color mode
These bits defines the color format of the foreground image. They can only be written
when data transfers are disabled. Once the transfer has started, they are read-only.
0000: ARGB8888
0001: RGB888
0010: RGB565
0011: ARGB1555
0100: ARGB4444
0101: L8
0110: AL44
0111: AL88
1000: L4
1001: A8
1010: A4
others: meaningless

RM0385 Rev 7

277/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

9.5.9

RM0385

DMA2D foreground color register (DMA2D_FGCOLR)
Address offset: 0x0020
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

23

22

21

rw

rw

rw

rw

19

18

17

16

RED[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

GREEN[7:0]
rw

20

BLUE[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value
Bits 23:16 RED[7: 0]: Red Value
These bits defines the red value for the A4 or A8 mode of the foreground image. They
can only be written when data transfers are disabled. Once the transfer has started,
they are read-only.
Bits 15:8 GREEN[7: 0]: Green Value
These bits defines the green value for the A4 or A8 mode of the foreground image. They
can only be written when data transfers are disabled. Once the transfer has started,
They are read-only.
Bits 7:0 BLUE[7: 0]: Blue Value
These bits defines the blue value for the A4 or A8 mode of the foreground image. They
can only be written when data transfers are disabled. Once the transfer has started,
They are read-only.

278/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

9.5.10

DMA2D background PFC control register (DMA2D_BGPFCCR)
Address offset: 0x0024
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

ALPHA[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

CS[7:0]
rw

rw

rw

rw

rw

rw

rw

23

22

21

20

19

18

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

Res.

Res.

START

CCM

rs

rw

rw

17

16

AM[1:0]
rw

rw

1

0

rw

rw

CM[3:0]
rw

rw

Bits 31:24 ALPHA[7: 0]: Alpha value
These bits define a fixed alpha channel value which can replace the original alpha value
or be multiplied with the original alpha value according to the alpha mode selected with
bits AM[1: 0]. These bits can only be written when data transfers are disabled. Once the
transfer has started, they are read-only.
Bits 23:18 Reserved, must be kept at reset value
Bits 17:16 AM[1: 0]: Alpha mode
These bits define which alpha channel value to be used for the background image.
These bits can only be written when data transfers are disabled. Once the transfer has
started, they are read-only.
00: No modification of the foreground image alpha channel value
01: Replace original background image alpha channel value by ALPHA[7: 0]
10: Replace original background image alpha channel value by ALPHA[7:0] multiplied
with original alpha channel value
others: meaningless
Bits 15:8 CS[7: 0]: CLUT size
These bits define the size of the CLUT used for the BG. Once the CLUT transfer has
started, this field is read-only.
The number of CLUT entries is equal to CS[7:0] + 1.
Bits 7:6 Reserved, must be kept at reset value

RM0385 Rev 7

279/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

RM0385

Bit 5 START: Start
This bit is set to start the automatic loading of the CLUT. This bit is automatically reset:
–
at the end of the transfer
–
when the transfer is aborted by the user application by setting the ABORT bit in
the DMA2D_CR
–
when a transfer error occurs
–
when the transfer has not started due to a configuration error or another
transfer operation already on going (data transfer or automatic foreground
CLUT transfer).
Bit 4 CCM: CLUT Color mode
These bits define the color format of the CLUT. This register can only be written when
the transfer is disabled. Once the CLUT transfer has started, this bit is read-only.
0: ARGB8888
1: RGB888
others: meaningless
Bits 3:0 CM[3: 0]: Color mode
These bits define the color format of the foreground image. These bits can only be
written when data transfers are disabled. Once the transfer has started, they are readonly.
0000: ARGB8888
0001: RGB888
0010: RGB565
0011: ARGB1555
0100: ARGB4444
0101: L8
0110: AL44
0111: AL88
1000: L4
1001: A8
1010: A4
others: meaningless

280/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

9.5.11

DMA2D background color register (DMA2D_BGCOLR)
Address offset: 0x0028
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

23

22

21

rw

rw

rw

rw

19

18

17

16

RED[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

GREEN[7:0]
rw

20

BLUE[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value
Bits 23:16 RED[7: 0]: Red Value
These bits define the red value for the A4 or A8 mode of the background. These bits
can only be written when data transfers are disabled. Once the transfer has started,
they are read-only.
Bits 15:8 GREEN[7: 0]: Green Value
These bits define the green value for the A4 or A8 mode of the background. These bits
can only be written when data transfers are disabled. Once the transfer has started,
they are read-only.
Bits 7:0 BLUE[7: 0]: Blue Value
These bits define the blue value for the A4 or A8 mode of the background. These bits
can only be written when data transfers are disabled. Once the transfer has started,
they are read-only.

9.5.12

DMA2D foreground CLUT memory address register
(DMA2D_FGCMAR)
Address offset: 0x002C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

281/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

RM0385

Bits 31: 0 MA[31: 0]: Memory Address
Address of the data used for the CLUT address dedicated to the foreground image. This
register can only be written when no transfer is ongoing. Once the CLUT transfer has
started, this register is read-only.
If the foreground CLUT format is 32-bit, the address must be 32-bit aligned.

9.5.13

DMA2D background CLUT memory address register
(DMA2D_BGCMAR)
Address offset: 0x0030
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31: 0 MA[31: 0]: Memory address
Address of the data used for the CLUT address dedicated to the background image.
This register can only be written when no transfer is on going. Once the CLUT transfer
has started, this register is read-only.
If the background CLUT format is 32-bit, the address must be 32-bit aligned.

9.5.14

DMA2D output PFC control register (DMA2D_OPFCCR)
Address offset: 0x0034
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CM[2:0]
rw

282/1709

RM0385 Rev 7

rw

rw

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

Bits 31: 3 Reserved, must be kept at reset value
Bits 19:3 Reserved, must be kept at reset value
Bits 2:0 CM[2: 0]: Color mode
These bits define the color format of the output image. These bits can only be written
when data transfers are disabled. Once the transfer has started, they are read-only.
000: ARGB8888
001: RGB888
010: RGB565
011: ARGB1555
100: ARGB4444
others: meaningless

9.5.15

DMA2D output color register (DMA2D_OCOLR)
Address offset: 0x0038
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

ALPHA[7:0]

19

18

17

16

RED[7:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

GREEN[7:0]

BLUE[7:0]

RED[4:0]
A

GREEN[5:0]

RED[4:0]

GREEN[4:0]

ALPHA[3:0]
rw

rw

rw

RED[3:0]
rw

BLUE[4:0]

rw

rw

rw

BLUE[4:0]
GREEN[3:0]

rw

rw

rw

rw

BLUE[3:0]
rw

rw

rw

rw

rw

Bits 31:24 ALPHA[7: 0]: Alpha Channel Value
These bits define the alpha channel of the output color. These bits can only be written
when data transfers are disabled. Once the transfer has started, they are read-only.
Bits 23:16 RED[7: 0]: Red Value
These bits define the red value of the output image. These bits can only be written when
data transfers are disabled. Once the transfer has started, they are read-only.
Bits 15:8 GREEN[7: 0]: Green Value
These bits define the green value of the output image. These bits can only be written
when data transfers are disabled. Once the transfer has started, they are read-only.
Bits 7:0 BLUE[7: 0]: Blue Value
These bits define the blue value of the output image. These bits can only be written
when data transfers are disabled. Once the transfer has started, they are read-only.

RM0385 Rev 7

283/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

9.5.16

RM0385

DMA2D output memory address register (DMA2D_OMAR)
Address offset: 0x003C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31: 0 MA[31: 0]: Memory Address
Address of the data used for the output FIFO. These bits can only be written when data
transfers are disabled. Once the transfer has started, they are read-only.
The address alignment must match the image format selected e.g. a 32-bit per pixel
format must be 32-bit aligned and a 16-bit per pixel format must be 16-bit aligned.

284/1709

RM0385 Rev 7

RM0385

Chrom-ART Accelerator™ controller (DMA2D)

9.5.17

DMA2D output offset register (DMA2D_OOR)
Address offset: 0x0040
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

rw

rw

rw

rw

rw

rw

LO[13:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:14 Reserved, must be kept at reset value
Bits 13:0 LO[13: 0]: Line Offset
Line offset used for the output (expressed in pixels). This value is used for the address
generation. It is added at the end of each line to determine the starting address of the
next line. These bits can only be written when data transfers are disabled. Once the
transfer has started, they are read-only.

9.5.18

DMA2D number of line register (DMA2D_NLR)
Address offset: 0x0044
Reset value: 0x0000 0000

31

30

Res.

Res.

15

14

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PL[13:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

NL[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:30 Reserved, must be kept at reset value
Bits 29:16 PL[13: 0]: Pixel per lines
Number of pixels per lines of the area to be transferred. These bits can only be written
when data transfers are disabled. Once the transfer has started, they are read-only.
If any of the input image format is 4-bit per pixel, pixel per lines must be even.
Bits 15:0 NL[15: 0]: Number of lines
Number of lines of the area to be transferred. These bits can only be written when data
transfers are disabled. Once the transfer has started, they are read-only.

RM0385 Rev 7

285/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

9.5.19

RM0385

DMA2D line watermark register (DMA2D_LWR)
Address offset: 0x0048
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

LW[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value
Bits 15:0 LW[15:0]: Line watermark
These bits allow to configure the line watermark for interrupt generation.
An interrupt is raised when the last pixel of the watermarked line has been transferred.
These bits can only be written when data transfers are disabled. Once the transfer has
started, they are read-only.

9.5.20

DMA2D AHB master timer configuration register (DMA2D_AMTCR)
Address offset: 0x004C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EN

DT[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved
Bits 15:8 DT[7: 0]: Dead Time
Dead time value in the AHB clock cycle inserted between two consecutive accesses on
the AHB master port. These bits represent the minimum guaranteed number of cycles
between two consecutive AHB accesses.
Bits 7:1 Reserved
Bit 0 EN: Enable
Enables the dead time functionality.

286/1709

RM0385 Rev 7

RM0385

9.5.21

Chrom-ART Accelerator™ controller (DMA2D)

DMA2D register map
The following table summarizes the DMA2D registers. Refer to Section 2.2.2 on page 69 for
the DMA2D register base address.

CCEIF

CCTCIF

CAECIF

CTWIF

CTCIF

CTEIF

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA2D_FGOR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

LO[13:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

0

0

0

0

0

0

0

0

DMA2D_BGCOLR

Res.

Res.

Res.

Res.

Res.

ALPHA[7:0]

Res.

DMA2D_BGPFCCR

Reset value

AM[1:0]

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

RED[7:0]

0

0

0

0

0

0

0

0

0

0

0

0

GREEN[7:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CS[7:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

RED[7:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA2D_FGCMAR

0

0

0

0

0

0

0

0

0

0

CM[3:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

GREEN[7:0]

0

CM[3:0]

BLUE[7:0]

CCM

Res.

Reset value

0

START

DMA2D_FGCOLR

0

0

Res.

0

0

Res.

0

0

CS[7:0]

AM[1:0]

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Reset value

Res.

ALPHA[7:0]

Res.

DMA2D_FGPFCCR

Res.

0
Res.

Reset value

LO[13:0]

CCM

0

START

0

Res.

0

Res.

Reset value
DMA2D_BGOR

Reset value

0

MA[31:0]
Res.

DMA2D_BGMAR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

BLUE[7:0]

MA[31:0]
0

0

0

0

0

0

0

0

0

0

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA2D_OPFCCR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MA[31:0]
Res.

DMA2D_BGCMAR
Res.

0x0034

0

Res.

0x0030

0

Res.

0x002C

0

Res.

0x0028

SUSP

TEIF
0

Res.

0x0024

0

Res.

0x0020

0

Res.

0x001C

Reset value

Res.

0x0018

START

TCIF
0

MA[31:0]

Res.

0x0014

Res.

0

Res.

0x0010

ABORT
TWIF

0

Res.

0x000C

Res.

Res.

0

Reset value
DMA2D_FGMAR

0

CAEIF

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA2D_IFCR

0

0

Reset value

0x0008

0
CTCIF

Res.

Res.

TEIE
0

CEIF

TCIE
0

Res.

TWIE
0

Res.

CAEIE
0

Res.

CTCIE
0
Res.

Res.

CEIE
0
Res.

Res.
Res.

0
Res.

MODE[1:0]
0

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA2D_ISR

Res.

0x0004

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA2D_CR

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

0x0000

Register

Res.

Offset

Res.

Table 42. DMA2D register map and reset values

Reset value

CM[2:0]
0

RM0385 Rev 7

0

0

287/1709
288

Chrom-ART Accelerator™ controller (DMA2D)

RM0385

Res. Res. Res.

Res. Res. Res.

Res. Res. Res.

Res. Res. Res.

Res. Res. Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA2D_OOR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

288/1709

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

Res.

RED[7:0][255:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

LW[15:0]

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DT[7:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ALPHA[7:0][255:0]

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

0

GREEN[7:0][255:0]

0
Res.

0

BLUE[7:0][255:0]

Res.

Res.

Res.

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
Res.

DMA2D_BGCLUT

0

Res.

0

Res.

0x08000x0BFF

Reset value

0

Res.

0

Res.

DMA2D_FGCLUT

Res.

0x04000x07FC

Res.

Reserved

0

Res.

0

Reset value

0x0050Ox03FC

0

Res.

0

Res.

Res.

Res.

DMA2D_AMTCR

0

NL[15:0]

0

Reset value

0x004C

0

LO[13:0]

PL[13:0]
0
Res.

Res.

DMA2D_LWR

Res.

Reset value

0x0048

0

Res.

Res.

DMA2D_NLR

Res.

Reset value

0x0044

BLUE[3:0]

0

MA[31:0]
Res.

0x0040

GREEN[3:0]

0

Res.

0x003C

RED[3:0]

0

Res.

DMA2D_OMAR

ALPHA[3:0]

EN

Res. Res. Res.

0

Res.

Res. Res. Res.

0

Res.

Res. Res. Res.

0

BLUE[4:0]

Res.

Res. Res. Res.

0

GREEN[4:0]

Res.

Res. Res. Res.

0

RED[4:0]

BLUE[4:0]

Res.

Res. Res. Res.

0

BLUE[7:0]
GREEN[5:0]

Res.

Res. Res. Res.

A

RED[4:0]

Res.

Res. Res. Res.

Reset value

Res. Res. Res.

0x0038

GREEN[7:0]

Res. Res. Res.

DMA2D_OCOLR

RED[7:0]

Res. Res. Res.

ALPHA[7:0]

Res.

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 42. DMA2D register map and reset values (continued)

RED[7:0][255:0]

GREEN[7:0][255:0]

BLUE[7:0][255:0]

X X X X X X X X X X X X X X X X X X X X X X X X

RM0385 Rev 7

RM0385

Nested vectored interrupt controller (NVIC)

10

Nested vectored interrupt controller (NVIC)

10.1

NVIC features
The nested vector interrupt controller NVIC includes the following features:
•

up to 98 maskable interrupt channels for STM32F75xxx and STM32F74xxx (not
including the 16 interrupt lines of Cortex®-M7 with FPU)

•

16 programmable priority levels (4 bits of interrupt priority are used)

•

low-latency exception and interrupt handling

•

power management control

•

implementation of system control registers

The NVIC and the processor core interface are closely coupled, which enables low latency
interrupt processing and efficient processing of late arriving interrupts.
All interrupts including the core exceptions are managed by the NVIC. For more information
on exceptions and NVIC programming, refer to programming manual PMxxxx.

10.1.1

SysTick calibration value register
The SysTick calibration value is fixed to 18750, which gives a reference time base of 1 ms
with the SysTick clock set to 18.75 MHz (HCLK/8, with HCLK set to 150 MHz).

10.1.2

Interrupt and exception vectors
See Table 43, for the vector table for the STM32F75xxx and STM32F74xxx devices.

Position

Priority

Table 43. STM32F75xxx and STM32F74xxx vector table

Type of
priority

-

-

-

-

-3

-

Acronym

Description

Address

-

Reserved

0x0000 0000

fixed

Reset

Reset

0x0000 0004

-2

fixed

NMI

Non maskable interrupt. The RCC
Clock Security System (CSS) is linked
to the NMI vector.

0x0000 0008

-

-1

fixed

HardFault

All class of fault

0x0000 000C

-

0

settable

MemManage

Memory management

0x0000 0010

-

1

settable

BusFault

Pre-fetch fault, memory access fault

0x0000 0014

-

2

settable

UsageFault

Undefined instruction or illegal state

0x0000 0018

-

-

-

-

Reserved

RM0385 Rev 7

0x0000 001C - 0x0000
002B

289/1709
300

Nested vectored interrupt controller (NVIC)

RM0385

Position

Priority

Table 43. STM32F75xxx and STM32F74xxx vector table (continued)

Type of
priority

-

3

settable

SVCall

System service call via SWI
instruction

0x0000 002C

-

4

settable

Debug Monitor

Debug Monitor

0x0000 0030

-

-

-

-

Reserved

0x0000 0034

-

5

settable

PendSV

Pendable request for system service

0x0000 0038

-

6

settable

SysTick

System tick timer

0x0000 003C

0

7

settable

WWDG

Window Watchdog interrupt

0x0000 0040

1

8

settable

PVD

PVD through EXTI line detection
interrupt

0x0000 0044

2

9

settable

TAMP_STAMP

Tamper and TimeStamp interrupts
through the EXTI line

0x0000 0048

3

10

settable

RTC_WKUP

RTC Wakeup interrupt through the
EXTI line

0x0000 004C

4

11

settable

FLASH

Flash global interrupt

0x0000 0050

5

12

settable

RCC

RCC global interrupt

0x0000 0054

6

13

settable

EXTI0

EXTI Line0 interrupt

0x0000 0058

7

14

settable

EXTI1

EXTI Line1 interrupt

0x0000 005C

8

15

settable

EXTI2

EXTI Line2 interrupt

0x0000 0060

9

16

settable

EXTI3

EXTI Line3 interrupt

0x0000 0064

10

17

settable

EXTI4

EXTI Line4 interrupt

0x0000 0068

11

18

settable

DMA1_Stream0

DMA1 Stream0 global interrupt

0x0000 006C

12

19

settable

DMA1_Stream1

DMA1 Stream1 global interrupt

0x0000 0070

13

20

settable

DMA1_Stream2

DMA1 Stream2 global interrupt

0x0000 0074

14

21

settable

DMA1_Stream3

DMA1 Stream3 global interrupt

0x0000 0078

15

22

settable

DMA1_Stream4

DMA1 Stream4 global interrupt

0x0000 007C

16

23

settable

DMA1_Stream5

DMA1 Stream5 global interrupt

0x0000 0080

17

24

settable

DMA1_Stream6

DMA1 Stream6 global interrupt

0x0000 0084

18

25

settable

ADC

ADC1, ADC2 and ADC3 global
interrupts

0x0000 0088

19

26

settable

CAN1_TX

CAN1 TX interrupts

0x0000 008C

20

27

settable

CAN1_RX0

CAN1 RX0 interrupts

0x0000 0090

21

28

settable

CAN1_RX1

CAN1 RX1 interrupt

0x0000 0094

290/1709

Acronym

Description

RM0385 Rev 7

Address

RM0385

Nested vectored interrupt controller (NVIC)

Position

Priority

Table 43. STM32F75xxx and STM32F74xxx vector table (continued)

Type of
priority

22

29

settable

CAN1_SCE

CAN1 SCE interrupt

0x0000 0098

23

30

settable

EXTI9_5

EXTI Line[9:5] interrupts

0x0000 009C

24

31

settable

TIM1_BRK_TIM9

TIM1 Break interrupt and TIM9 global
interrupt

0x0000 00A0

25

32

settable

TIM1_UP_TIM10

TIM1 Update interrupt and TIM10
global interrupt

0x0000 00A4

26

33

settable

TIM1_TRG_COM_TIM11

TIM1 Trigger and Commutation
interrupts and TIM11 global interrupt

0x0000 00A8

27

34

settable

TIM1_CC

TIM1 Capture Compare interrupt

0x0000 00AC

28

35

settable

TIM2

TIM2 global interrupt

0x0000 00B0

29

36

settable

TIM3

TIM3 global interrupt

0x0000 00B4

30

37

settable

TIM4

TIM4 global interrupt

0x0000 00B8

Acronym

Description

2C1

event interrupt

31

38

settable

I2C1_EV

I

32

39

settable

I2C1_ER

I2C1 error interrupt

33

40

settable

Address

0x0000 00BC
0x0000 00C0

I2C2_EV

I

2C2

event interrupt

0x0000 00C4

error interrupt

0x0000 00C8

34

41

settable

I2C2_ER

I2C2

35

42

settable

SPI1

SPI1 global interrupt

0x0000 00CC

36

43

settable

SPI2

SPI2 global interrupt

0x0000 00D0

37

44

settable

USART1

USART1 global interrupt

0x0000 00D4

38

45

settable

USART2

USART2 global interrupt

0x0000 00D8

39

46

settable

USART3

USART3 global interrupt

0x0000 00DC

40

47

settable

EXTI15_10

EXTI Line[15:10] interrupts

0x0000 00E0

41

48

settable

RTC_Alarm

RTC Alarms (A and B) through EXTI
line interrupt

0x0000 00E4

42

49

settable

OTG_FS_WKUP

USB On-The-Go FS Wakeup through
EXTI line interrupt

0x0000 00E8

43

50

settable

TIM8_BRK_TIM12

TIM8 Break interrupt and TIM12
global interrupt

0x0000 00EC

44

51

settable

TIM8_UP_TIM13

TIM8 Update interrupt and TIM13
global interrupt

0x0000 00F0

45

52

settable

TIM8_TRG_COM_TIM14

TIM8 Trigger and Commutation
interrupts and TIM14 global interrupt

0x0000 00F4

46

53

settable

TIM8_CC

TIM8 Capture Compare interrupt

0x0000 00F8

RM0385 Rev 7

291/1709
300

Nested vectored interrupt controller (NVIC)

RM0385

Position

Priority

Table 43. STM32F75xxx and STM32F74xxx vector table (continued)

Type of
priority

47

54

settable

DMA1_Stream7

DMA1 Stream7 global interrupt

0x0000 00FC

48

55

settable

FSMC

FSMC global interrupt

0x0000 0100

49

56

settable

SDMMC1

SDMMC1 global interrupt

0x0000 0104

50

57

settable

TIM5

TIM5 global interrupt

0x0000 0108

51

58

settable

SPI3

SPI3 global interrupt

0x0000 010C

52

59

settable

UART4

UART4 global interrupt

0x0000 0110

53

60

settable

UART5

UART5 global interrupt

0x0000 0114

54

61

settable

TIM6_DAC

TIM6 global interrupt,
DAC1 and DAC2 underrun error
interrupts

0x0000 0118

55

62

settable

TIM7

TIM7 global interrupt

0x0000 011C

56

63

settable

DMA2_Stream0

DMA2 Stream0 global interrupt

0x0000 0120

57

64

settable

DMA2_Stream1

DMA2 Stream1 global interrupt

0x0000 0124

58

65

settable

DMA2_Stream2

DMA2 Stream2 global interrupt

0x0000 0128

59

66

settable

DMA2_Stream3

DMA2 Stream3 global interrupt

0x0000 012C

60

67

settable

DMA2_Stream4

DMA2 Stream4 global interrupt

0x0000 0130

61

68

settable

ETH

Ethernet global interrupt

0x0000 0134

62

69

settable

ETH_WKUP

Ethernet Wakeup through EXTI line
interrupt

0x0000 0138

63

70

settable

CAN2_TX

CAN2 TX interrupts

0x0000 013C

64

71

settable

CAN2_RX0

CAN2 RX0 interrupts

0x0000 0140

65

72

settable

CAN2_RX1

CAN2 RX1 interrupt

0x0000 0144

66

73

settable

CAN2_SCE

CAN2 SCE interrupt

0x0000 0148

67

74

settable

OTG_FS

USB On The Go FS global interrupt

0x0000 014C

68

75

settable

DMA2_Stream5

DMA2 Stream5 global interrupt

0x0000 0150

69

76

settable

DMA2_Stream6

DMA2 Stream6 global interrupt

0x0000 0154

70

77

settable

DMA2_Stream7

DMA2 Stream7 global interrupt

0x0000 0158

71

78

settable

USART6

USART6 global interrupt

0x0000 015C

Acronym

Description

2C3

event interrupt

Address

0x0000 0160

72

79

settable

I2C3_EV

I

73

80

settable

I2C3_ER

I2C3 error interrupt

0x0000 0164

74

81

settable

OTG_HS_EP1_OUT

USB On The Go HS End Point 1 Out
global interrupt

0x0000 0168

292/1709

RM0385 Rev 7

RM0385

Nested vectored interrupt controller (NVIC)

Position

Priority

Table 43. STM32F75xxx and STM32F74xxx vector table (continued)

Type of
priority

75

82

settable

OTG_HS_EP1_IN

USB On The Go HS End Point 1 In
global interrupt

0x0000 016C

76

83

settable

OTG_HS_WKUP

USB On The Go HS Wakeup through
EXTI interrupt

0x0000 0170

77

84

settable

OTG_HS

USB On The Go HS global interrupt

0x0000 0174

78

85

settable

DCMI

DCMI global interrupt

0x0000 0178

79

86

settable

CRYP

CRYP crypto global interrupt

0x0000 017C

80

87

settable

HASH_RNG

Hash and Rng global interrupt

0x0000 0180

81

88

settable

FPU

FPU global interrupt

0x0000 0184

82

89

settable

UART7

UART7 global interrupt

0x0000 0188

83

90

settable

UART8

UART8 global interrupt

0x0000 018C

84

91

settable

SPI4

SPI4 global interrupt

0x0000 0190

85

92

settable

SPI5

SPI5 global interrupt

0x0000 0194

86

93

settable

SPI6

SPI6 global interrupt

0x0000 0198

87

94

settable

SAI1

SAI1 global interrupt

0x0000 019C

88

95

settable

LCD-TFT

LCD-TFT global interrupt

0x0000 01A0

89

96

settable

LCD-TFT

LCD-TFT global Error interrupt

0x0000 01A4

90

97

settable

DMA2D

DMA2D global interrupt

0x0000 01A8

91

98

settable

SAI2

SAI2 global interrupt

0x0000 01AC

92

99

settable

QuadSPI

QuadSPI global interrupt

0x0000 01B0

93

100

settable

LP Timer1

LP Timer1 global interrupt

0x0000 01B4

94

101

settable

HDMI-CEC

HDMI-CEC global interrupt

0x0000 01B8

95

102

settable

I2C4_EV

I2C4 event interrupt

0x0000 01BC

96

103

settable

I2C4_ER

I2C4 Error interrupt

0x0000 01C0

97

104

settable

SPDIFRX

SPDIFRX global interrupt

0x0000 01C4

Acronym

Description

RM0385 Rev 7

Address

293/1709
300

Extended interrupts and events controller (EXTI)

11

RM0385

Extended interrupts and events controller (EXTI)
The external interrupt/event controller consists of up to 24 edge detectors for generating
event/interrupt requests. Each input line can be independently configured to select the type
(interrupt or event) and the corresponding trigger event (rising or falling or both). Each line
can also masked independently. A pending register maintains the status line of the interrupt
requests.

11.1

EXTI main features
The main features of the EXTI controller are the following:

11.2

•

independent trigger and mask on each interrupt/event line

•

dedicated status bit for each interrupt line

•

generation of up to 24 software event/interrupt requests

•

detection of external signals with a pulse width lower than the APB2 clock period. Refer
to the electrical characteristics section of the STM32F75xxx and STM32F74xxx
datasheets for details on this parameter.

EXTI block diagram
Figure 30 shows the block diagram.
Figure 30. External interrupt/event controller block diagram
AMBA APB bus
PCLK2

Peripheral interface

Pending
request
register

Interrupt
mask
register

Software
interrupt
event
register

Rising
trigger
selection
register

Falling
trigger
selection
register

To NVIC interrupt
controller

Edge detect
circuit

Pulse
generator

Input
line

Event
mask
register
MSv34192V1

294/1709

RM0385 Rev 7

RM0385

11.3

Extended interrupts and events controller (EXTI)

Wakeup event management
The STM32F75xxx and STM32F74xxx devices are able to handle external or internal
events in order to wake up the core (WFE). The wakeup event can be generated either by:
•

enabling an interrupt in the peripheral control register but not in the NVIC, and enabling
the SEVONPEND bit in the Cortex®-M7 System Control register. When the MCU
resumes from WFE, the peripheral interrupt pending bit and the peripheral NVIC IRQ
channel pending bit (in the NVIC interrupt clear pending register) have to be cleared.

•

or configuring an external or internal EXTI line in event mode. When the CPU resumes
from WFE, it is not necessary to clear the peripheral interrupt pending bit or the NVIC
IRQ channel pending bit as the pending bit corresponding to the event line is not set.

To use an external line as a wakeup event, refer to Section 11.4: Functional description.

11.4

Functional description
To generate the interrupt, the interrupt line should be configured and enabled. This is done
by programming the two trigger registers with the desired edge detection and by enabling
the interrupt request by writing a ‘1’ to the corresponding bit in the interrupt mask register.
When the selected edge occurs on the external interrupt line, an interrupt request is
generated. The pending bit corresponding to the interrupt line is also set. This request is
reset by writing a ‘1’ in the pending register.
To generate the event, the event line should be configured and enabled. This is done by
programming the two trigger registers with the desired edge detection and by enabling the
event request by writing a ‘1’ to the corresponding bit in the event mask register. When the
selected edge occurs on the event line, an event pulse is generated. The pending bit
corresponding to the event line is not set.
An interrupt/event request can also be generated by software by writing a ‘1’ in the software
interrupt/event register.

11.5

Hardware interrupt selection
To configure a line as interrupt sources, use the following procedure:

11.6

1.

Configure the corresponding mask bit (EXTI_IMR)

2.

Configure the Trigger selection bits of the interrupt lines (EXTI_RTSR and EXTI_FTSR)

3.

Configure the enable and mask bits that control the NVIC IRQ channel mapped to the
external interrupt controller (EXTI) so that an interrupt coming from one of the 24 lines
can be correctly acknowledged.

Hardware event selection
To configure a line as event sources, use the following procedure:
1.

Configure the corresponding mask bit (EXTI_EMR)

2.

Configure the Trigger selection bits of the event line (EXTI_RTSR and EXTI_FTSR)

RM0385 Rev 7

295/1709
300

Extended interrupts and events controller (EXTI)

11.7

RM0385

Software interrupt/event selection
The line can be configured as software interrupt/event line. The following is the procedure to
generate a software interrupt.

11.8

1.

Configure the corresponding mask bit (EXTI_IMR, EXTI_EMR)

2.

Set the required bit in the software interrupt register (EXTI_SWIER)

External interrupt/event line mapping
Up to 168 GPIOs are connected to the 16 external interrupt/event lines in the following
manner:
Figure 31. External interrupt/event GPIO mapping
EXTI0[3:0] bits in the SYSCFG_EXTICR1 register
PA0
PB0
PC0
PD0
PE0
PF0
PG0
PH0
PI0
PJ0
PK0

EXTI0

EXTI1[3:0] bits in the SYSCFG_EXTICR1 register

PA1
PB1
PC1
PD1
PE1
PF1
PG1
PH1
PI1
PJ1
PK1

EXTI1

EXTI15[3:0] bits in the SYSCFG_EXTICR4 register

PA15
PB15
PC15
PD15
PE15
PF15
PG15
PH15
PJ15

EXTI15

MS30440V1

296/1709

RM0385 Rev 7

RM0385

Extended interrupts and events controller (EXTI)
The eight other EXTI lines are connected as follows:

11.9

•

EXTI line 16 is connected to the PVD output

•

EXTI line 17 is connected to the RTC Alarm event

•

EXTI line 18 is connected to the USB OTG FS Wakeup event

•

EXTI line 19 is connected to the Ethernet Wakeup event

•

EXTI line 20 is connected to the USB OTG HS (configured in FS) Wakeup event

•

EXTI line 21 is connected to the RTC Tamper and TimeStamp events

•

EXTI line 22 is connected to the RTC Wakeup event

•

EXTI line 23 is connected to the LPTIM1 asynchronous event

EXTI registers
Refer to Section 1.1 on page 62 for a list of abbreviations used in register descriptions.

11.9.1

Interrupt mask register (EXTI_IMR)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IM23

IM22

IM21

IM20

IM19

IM18

IM17

IM16

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

IM15

IM14

IM13

IM12

IM11

IM10

IM9

IM8

IM7

IM6

IM5

IM4

IM3

IM2

IM1

IM0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:0 IMx: Interrupt mask on line x
0: Interrupt request from line x is masked
1: Interrupt request from line x is not masked

11.9.2

Event mask register (EXTI_EMR)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EM23

EM22

EM21

EM20

EM19

EM18

EM17

EM16

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

EM15

EM14

EM13

EM12

EM11

EM10

EM9

EM8

EM7

EM6

EM5

EM4

EM3

EM2

EM1

EM0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

297/1709
300

Extended interrupts and events controller (EXTI)

RM0385

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:0 EMx: Event mask on line x
0: Event request from line x is masked
1: Event request from line x is not masked

11.9.3

Rising trigger selection register (EXTI_RTSR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TR23

TR22

TR21

TR20

TR19

TR18

TR17

TR16

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

TR15

TR14

TR13

TR12

TR11

TR10

TR9

TR8

TR7

TR6

TR5

TR4

TR3

TR2

TR1

TR0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:0 TRx: Rising trigger event configuration bit of line x
0: Rising trigger disabled (for Event and Interrupt) for input line
1: Rising trigger enabled (for Event and Interrupt) for input line

Note:

The external wakeup lines are edge triggered, no glitch must be generated on these lines.
If a rising edge occurs on the external interrupt line while writing to the EXTI_RTSR register,
the pending bit is be set.
Rising and falling edge triggers can be set for the same interrupt line. In this configuration,
both generate a trigger condition.

11.9.4

Falling trigger selection register (EXTI_FTSR)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TR23

TR22

TR21

TR20

TR19

TR18

TR17

TR16

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

TR15

TR14

TR13

TR12

TR11

TR10

TR9

TR8

TR7

TR6

TR5

TR4

TR3

TR2

TR1

TR0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:0 TRx: Falling trigger event configuration bit of line x
0: Falling trigger disabled (for Event and Interrupt) for input line
1: Falling trigger enabled (for Event and Interrupt) for input line.

298/1709

RM0385 Rev 7

RM0385

Extended interrupts and events controller (EXTI)

Note:

The external wakeup lines are edge triggered, no glitch must be generated on these lines.
If a falling edge occurs on the external interrupt line while writing to the EXTI_FTSR register,
the pending bit is not set.
Rising and falling edge triggers can be set for the same interrupt line. In this configuration,
both generate a trigger condition.

11.9.5

Software interrupt event register (EXTI_SWIER)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

SWIER SWIER SWIER SWIER SWIER SWIER SWIER
15
14
13
12
11
10
9
rw

rw

rw

rw

rw

rw

rw

23

22

21

20

19

18

17

16

SWIER SWIER SWIER SWIER SWIER SWIER SWIER SWIER
23
22
21
20
19
18
17
16
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

SWIER SWIER SWIER SWIER SWIER SWIER SWIER SWIER SWIER
8
7
6
5
4
3
2
1
0
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:0 SWIERx: Software Interrupt on line x
If interrupt are enabled on line x in the EXTI_IMR register, writing '1' to SWIERx bit when it is
set at '0' sets the corresponding pending bit in the EXTI_PR register, thus resulting in an
interrupt request generation.
This bit is cleared by clearing the corresponding bit in EXTI_PR (by writing a 1 to the bit).

11.9.6

Pending register (EXTI_PR)
Address offset: 0x14
Reset value: undefined

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PR23

PR22

PR21

PR20

PR19

PR18

PR17

PR16

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PR15

PR14

PR13

PR12

PR11

PR10

PR9

PR8

PR7

PR6

PR5

PR4

PR3

PR2

PR1

PR0

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:0 PRx: Pending bit
0: No trigger request occurred
1: selected trigger request occurred
This bit is set when the selected edge event arrives on the external interrupt line.
This bit is cleared by programming it to ‘1’.

RM0385 Rev 7

299/1709
300

Extended interrupts and events controller (EXTI)

11.9.7

RM0385

EXTI register map
Table 44 gives the EXTI register map and the reset values.

Res.

Res.

Res.

Res.

Res.

EXTI_IMR

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

0x00

Register

Res.

Offset

Res.

Table 44. External interrupt/event controller register map and reset values

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_PR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

SWIER[23:0]
0

Res.

Reset value

0x14

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_SWIER

0

TR[23:0]
0

Res.

Reset value

0x10

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_FTSR

0

TR[23:0]
0

Res.

Reset value

0x0C

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_RTSR

0

EM[23:0]
0

Res.

Reset value

0x08

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_EMR

0x04

0
Res.

Reset value

IM[23:0]

0

0

PR[23:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

Refer to Section 2.2.2 on page 69for the register boundary addresses.

300/1709

RM0385 Rev 7

RM0385

Cyclic redundancy check calculation unit (CRC)

12

Cyclic redundancy check calculation unit (CRC)

12.1

Introduction
The CRC (cyclic redundancy check) calculation unit is used to get a CRC code from 8-, 16or 32-bit data word and a generator polynomial.
Among other applications, CRC-based techniques are used to verify data transmission or
storage integrity. In the scope of the functional safety standards, they offer a means of
verifying the Flash memory integrity. The CRC calculation unit helps compute a signature of
the software during runtime, to be compared with a reference signature generated at link
time and stored at a given memory location.

12.2

CRC main features
•

Uses CRC-32 (Ethernet) polynomial: 0x4C11DB7
X32 + X26 + X23 + X22 + X16 + X12 + X11 + X10 +X8 + X7 + X5 + X4 + X2+ X +1

•

Alternatively, uses fully programmable polynomial with programmable size (7, 8, 16, 32
bits)

•

Handles 8-,16-, 32-bit data size

•

Programmable CRC initial value

•

Single input/output 32-bit data register

•

Input buffer to avoid bus stall during calculation

•

CRC computation done in 4 AHB clock cycles (HCLK) for the 32-bit data size

•

General-purpose 8-bit register (can be used for temporary storage)

•

Reversibility option on I/O data

RM0385 Rev 7

301/1709
306

Cyclic redundancy check calculation unit (CRC)

RM0385

12.3

CRC functional description

12.3.1

CRC block diagram
Figure 32. CRC calculation unit block diagram
32-bit AHB bus
32-bit (read access)
Data register (output)

crc_hclk

CRC computation
32-bit (write access)
Data register (input)

MS19882V2

12.3.2

CRC internal signals
Table 45. CRC internal input/output signals

12.3.3

Signal name

Signal type

crc_hclk

Digital input

Description
AHB clock

CRC operation
The CRC calculation unit has a single 32-bit read/write data register (CRC_DR). It is used to
input new data (write access), and holds the result of the previous CRC calculation (read
access).
Each write operation to the data register creates a combination of the previous CRC value
(stored in CRC_DR) and the new one. CRC computation is done on the whole 32-bit data
word or byte by byte depending on the format of the data being written.
The CRC_DR register can be accessed by word, right-aligned half-word and right-aligned
byte. For the other registers only 32-bit access is allowed.
The duration of the computation depends on data width:
•

4 AHB clock cycles for 32-bit

•

2 AHB clock cycles for 16-bit

•

1 AHB clock cycles for 8-bit

An input buffer allows to immediately write a second data without waiting for any wait states
due to the previous CRC calculation.
The data size can be dynamically adjusted to minimize the number of write accesses for a
given number of bytes. For instance, a CRC for 5 bytes can be computed with a word write
followed by a byte write.

302/1709

RM0385 Rev 7

RM0385

Cyclic redundancy check calculation unit (CRC)
The input data can be reversed, to manage the various endianness schemes. The reversing
operation can be performed on 8 bits, 16 bits and 32 bits depending on the REV_IN[1:0] bits
in the CRC_CR register.
For example: input data 0x1A2B3C4D is used for CRC calculation as:
0x58D43CB2 with bit-reversal done by byte
0xD458B23C with bit-reversal done by half-word
0xB23CD458 with bit-reversal done on the full word
The output data can also be reversed by setting the REV_OUT bit in the CRC_CR register.
The operation is done at bit level: for example, output data 0x11223344 is converted into
0x22CC4488.
The CRC calculator can be initialized to a programmable value using the RESET control bit
in the CRC_CR register (the default value is 0xFFFFFFFF).
The initial CRC value can be programmed with the CRC_INIT register. The CRC_DR
register is automatically initialized upon CRC_INIT register write access.
The CRC_IDR register can be used to hold a temporary value related to CRC calculation. It
is not affected by the RESET bit in the CRC_CR register.

Polynomial programmability
The polynomial coefficients are fully programmable through the CRC_POL register, and the
polynomial size can be configured to be 7, 8, 16 or 32 bits by programming the
POLYSIZE[1:0] bits in the CRC_CR register. Even polynomials are not supported.
If the CRC data is less than 32-bit, its value can be read from the least significant bits of the
CRC_DR register.
To obtain a reliable CRC calculation, the change on-fly of the polynomial value or size can
not be performed during a CRC calculation. As a result, if a CRC calculation is ongoing, the
application must either reset it or perform a CRC_DR read before changing the polynomial.
The default polynomial value is the CRC-32 (Ethernet) polynomial: 0x4C11DB7.

RM0385 Rev 7

303/1709
306

Cyclic redundancy check calculation unit (CRC)

12.4

CRC registers

12.4.1

Data register (CRC_DR)

RM0385

Address offset: 0x00
Reset value: 0xFFFF FFFF
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DR[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DR[31:0]: Data register bits
This register is used to write new data to the CRC calculator.
It holds the previous CRC calculation result when it is read.
If the data size is less than 32 bits, the least significant bits are used to write/read the
correct value.

12.4.2

Independent data register (CRC_IDR)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IDR[7:0]
rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 IDR[7:0]: General-purpose 8-bit data register bits
These bits can be used as a temporary storage location for one byte.
This register is not affected by CRC resets generated by the RESET bit in the CRC_CR register

304/1709

RM0385 Rev 7

RM0385

Cyclic redundancy check calculation unit (CRC)

12.4.3

Control register (CRC_CR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

REV_
OUT

Res.

Res.

RESET

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

REV_IN[1:0]
rw

rw

POLYSIZE[1:0]
rw

rw

rs

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 REV_OUT: Reverse output data
This bit controls the reversal of the bit order of the output data.
0: Bit order not affected
1: Bit-reversed output format
Bits 6:5 REV_IN[1:0]: Reverse input data
These bits control the reversal of the bit order of the input data
00: Bit order not affected
01: Bit reversal done by byte
10: Bit reversal done by half-word
11: Bit reversal done by word
Bits 4:3 POLYSIZE[1:0]: Polynomial size
These bits control the size of the polynomial.
00: 32 bit polynomial
01: 16 bit polynomial
10: 8 bit polynomial
11: 7 bit polynomial
Bits 2:1 Reserved, must be kept at reset value.
Bit 0 RESET: RESET bit
This bit is set by software to reset the CRC calculation unit and set the data register to the value
stored in the CRC_INIT register. This bit can only be set, it is automatically cleared by hardware

12.4.4

Initial CRC value (CRC_INIT)
Address offset: 0x10
Reset value: 0xFFFF FFFF

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CRC_INIT[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CRC_INIT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

305/1709
306

Cyclic redundancy check calculation unit (CRC)

RM0385

Bits 31:0 CRC_INIT[31:0]: Programmable initial CRC value
This register is used to write the CRC initial value.

12.4.5

CRC polynomial (CRC_POL)
Address offset: 0x14
Reset value: 0x04C1 1DB7

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

POL[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

POL[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 POL[31:0]: Programmable polynomial
This register is used to write the coefficients of the polynomial to be used for CRC calculation.
If the polynomial size is less than 32 bits, the least significant bits have to be used to program the
correct value.

12.4.6

CRC register map

Offset

Register
name

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 46. CRC register map and reset values

CRC_DR

DR[31:0]
1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

CRC_IDR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

CRC_CR
0x08

Reset value

0x10

CRC_INIT
Reset value

0x14

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

0

CRC_INIT[31:0]
1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

CRC_POL

Polynomial coefficients

Reset value

0x04C11DB7

1

1

1

1

1

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

306/1709

1

IDR[7:0]

REV_OUT

0x04

1

Res.

1

RESET

1

Res.

1

POLYSIZE[1:0]

1

REV_IN[1:0]

Reset value

Res.

0x00

RM0385 Rev 7

1

1

1

RM0385

13

Flexible memory controller (FMC)

Flexible memory controller (FMC)
The Flexible memory controller (FMC) includes three memory controllers:

13.1

•

The NOR/PSRAM memory controller

•

The NAND memory controller

•

The Synchronous DRAM (SDRAM/Mobile LPSDR SDRAM) controller

FMC main features
The FMC functional block makes the interface with: synchronous and asynchronous static
memories, SDRAM memories, and NAND Flash memory. Its main purposes are:
•

to translate AHB transactions into the appropriate external device protocol

•

to meet the access time requirements of the external memory devices

All external memories share the addresses, data and control signals with the controller.
Each external device is accessed by means of a unique Chip Select. The FMC performs
only one access at a time to an external device.
The main features of the FMC controller are the following:
•

Interface with static-memory mapped devices including:
–

Static random access memory (SRAM)

–

NOR Flash memory/OneNAND Flash memory

–

PSRAM (4 memory banks)

–

NAND Flash memory with ECC hardware to check up to 8 Kbytes of data

•

Interface with synchronous DRAM (SDRAM/Mobile LPSDR SDRAM) memories

•

Interface with parallel LCD modules, supporting Intel 8080 and Motorola 6800 modes.

•

Burst mode support for faster access to synchronous devices such as NOR Flash
memory, PSRAM and SDRAM)

•

Programmable continuous clock output for asynchronous and synchronous accesses

•

8-,16- or 32-bit wide data bus

•

Independent Chip Select control for each memory bank

•

Independent configuration for each memory bank

•

Write enable and byte lane select outputs for use with PSRAM, SRAM and SDRAM
devices

•

External asynchronous wait control

•

Write FIFO with 16 x32-bit depth

•

Cacheable Read FIFO with 6 x32-bit depth (6 x14-bit address tag) for SDRAM
controller.

The Write FIFO is common to all memory controllers and consists of:
•

a Write Data FIFO which stores the AHB data to be written to the memory (up to 32
bits) plus one bit for the AHB transfer (burst or not sequential mode)

•

a Write Address FIFO which stores the AHB address (up to 28 bits) plus the AHB data
size (up to 2 bits). When operating in burst mode, only the start address is stored
except when crossing a page boundary (for PSRAM and SDRAM). In this case, the
AHB burst is broken into two FIFO entries.
RM0385 Rev 7

307/1709
383

Flexible memory controller (FMC)

RM0385

The Write FIFO can be disabled by setting the WFDIS bit in the FMC_BCR1 register.
At startup the FMC pins must be configured by the user application. The FMC I/O pins which
are not used by the application can be used for other purposes.
The FMC registers that define the external device type and associated characteristics are
usually set at boot time and do not change until the next reset or power-up. However, the
settings can be changed at any time.

13.2

FMC block diagram
The FMC consists of the following main blocks:
•

The AHB interface (including the FMC configuration registers)

•

The NOR Flash/PSRAM/SRAM controller

•

The SDRAM controller

•

The NAND Flash controller

The block diagram is shown in the figure below.
Figure 33. FMC block diagram
FMC interrupts to NVIC

FMC_NL (or NADV)
FMC_CLK
From clock
controller
HCLK

NOR/PSRAM
memory
controller

Configuration
registers
NAND
memory
controller

SDRAM
controller

NOR/PSRAM
signals

FMC_NBL[3:0]

NOR / PSRAM / SRAM
shared signals

FMC_A[25:0]
FMC_D[31:0]

Shared signals

FMC_NE[4:1]
FMC_NOE
FMC_NWE
FMC_NWAIT

NOR / PSRAM / SRAM
shared signals

FMC_NCE
FMC_INT

NAND signals

FMC_SDCLK
FMC_SDNWE
FMC_SDCKE[1:0]
FMC_SDNE[1:0]
FMC_NRAS
FMC_NCAS

SDRAM signals

MS30443V7

308/1709

RM0385 Rev 7

RM0385

13.3

Flexible memory controller (FMC)

AHB interface
The AHB slave interface allows internal CPUs and other bus master peripherals to access
the external memories.
AHB transactions are translated into the external device protocol. In particular, if the
selected external memory is 16- or 8-bit wide, 32-bit wide transactions on the AHB are split
into consecutive 16- or 8-bit accesses. The FMC Chip Select (FMC_NEx) does not toggle
between the consecutive accesses except in case of access mode D when the extended
mode is enabled.
The FMC generates an AHB error in the following conditions:
•

When reading or writing to an FMC bank (Bank 1 to 4) which is not enabled.

•

When reading or writing to the NOR Flash bank while the FACCEN bit is reset in the
FMC_BCRx register.

•

When writing to a write protected SDRAM bank (WP bit set in the SDRAM_SDCRx
register).

•

When the SDRAM address range is violated (access to reserved address range)

The effect of an AHB error depends on the AHB master which has attempted the R/W
access:
•

If the access has been attempted by the Cortex®-M7 CPU, a hard fault interrupt is
generated.

•

If the access has been performed by a DMA controller, a DMA transfer error is
generated and the corresponding DMA channel is automatically disabled.

The AHB clock (HCLK) is the reference clock for the FMC.

13.3.1

Supported memories and transactions
General transaction rules
The requested AHB transaction data size can be 8-, 16- or 32-bit wide whereas the
accessed external device has a fixed data width. This may lead to inconsistent transfers.

RM0385 Rev 7

309/1709
383

Flexible memory controller (FMC)

RM0385

Therefore, some simple transaction rules must be followed:
•

AHB transaction size and memory data size are equal
There is no issue in this case.

•

AHB transaction size is greater than the memory size:
In this case, the FMC splits the AHB transaction into smaller consecutive memory
accesses to meet the external data width. The FMC Chip Select (FMC_NEx) does not
toggle between the consecutive accesses.

•

AHB transaction size is smaller than the memory size:
The transfer may or not be consistent depending on the type of external device:
–

Accesses to devices that have the byte select feature (SRAM, ROM, PSRAM,
SDRAM)
In this case, the FMC allows read/write transactions and accesses the right data
through its byte lanes NBL[3:0].
Bytes to be written are addressed by NBL[3:0].
All memory bytes are read (NBL[3:0] are driven low during read transaction) and
the useless ones are discarded.

–

Accesses to devices that do not have the byte select feature (NOR and NAND
Flash memories)
This situation occurs when a byte access is requested to a 16-bit wide Flash
memory. Since the device cannot be accessed in byte mode (only 16-bit words
can be read/written from/to the Flash memory), Write transactions and Read
transactions are allowed (the controller reads the entire 16-bit memory word and
uses only the required byte).

Wrap support for NOR Flash/PSRAM and SDRAM
The synchronous memories must be configured in linear burst mode of undefined length as
not all masters can issue a wrap transactions.
If a master generates an AHB wrap transaction:
•

The read is splited into two linear burst transactions.

•

The write is splited into two linear burst transactions if the write fifo is enabled and into
several linear burst transactions if the write fifo is disabled.

Configuration registers
The FMC can be configured through a set of registers. Refer to Section 13.5.6, for a
detailed description of the NOR Flash/PSRAM controller registers. Refer to Section 13.6.7,
for a detailed description of the NAND Flash registers and to Section 13.7.5 for a detailed
description of the SDRAM controller registers.

310/1709

RM0385 Rev 7

RM0385

13.4

Flexible memory controller (FMC)

External device address mapping
From the FMC point of view, the external memory is divided into fixed-size banks of
256 Mbytes each (see Figure 34):
•

Bank 1 used to address up to 4 NOR Flash memory or PSRAM devices. This bank is
split into 4 NOR/PSRAM subbanks with 4 dedicated Chip Selects, as follows:
–

Bank 1 - NOR/PSRAM 1

–

Bank 1 - NOR/PSRAM 2

–

Bank 1 - NOR/PSRAM 3

–

Bank 1 - NOR/PSRAM 4

•

Bank 3 used to address NAND Flash memory devices.The MPU memory attribute for
this space must be reconfigured by software to Device.

•

Bank 4 and 5 used to address SDRAM devices (1 device per bank).

For each bank the type of memory to be used can be configured by the user application
through the Configuration register.
Figure 34. FMC memory banks
Address

Bank

Supported memory type

0x6000 0000

Bank 1
4 x 64 MB

NOR/PSRAM/SRAM

0x6FFF FFFF
0x7000 0000

Bank 2
Reserved
0x7FFF FFFF
0x8000 0000

Bank 3
4 x 64 MB

NAND Flash memory

0x8FFF FFFF
0x9000 0000

Bank 4
Reserved
0x9FFF FFFF
0xC000 0000

SDRAM Bank 1
4 x 64 MB
SDRAM

0xCFFF FFFF
0xD000 0000

SDRAM Bank 2
4 x 64 MB
0xDFFF FFFF
MS30444V3

RM0385 Rev 7

311/1709
383

Flexible memory controller (FMC)

13.4.1

RM0385

NOR/PSRAM address mapping
HADDR[27:26] bits are used to select one of the four memory banks as shown in Table 47.
Table 47. NOR/PSRAM bank selection
HADDR[27:26](1)

Selected bank

00

Bank 1 - NOR/PSRAM 1

01

Bank 1 - NOR/PSRAM 2

10

Bank 1 - NOR/PSRAM 3

11

Bank 1 - NOR/PSRAM 4

1. HADDR are internal AHB address lines that are translated to external memory.

The HADDR[25:0] bits contain the external memory address. Since HADDR is a byte
address whereas the memory is addressed at word level, the address actually issued to the
memory varies according to the memory data width, as shown in the following table.
Table 48. NOR/PSRAM External memory address
Memory width(1)

Data address issued to the memory

Maximum memory capacity (bits)

8-bit

HADDR[25:0]

64 Mbytes x 8 = 512 Mbit

16-bit

HADDR[25:1] >> 1

64 Mbytes/2 x 16 = 512 Mbit

32-bit

HADDR[25:2] >> 2

64 Mbytes/4 x 32 = 512 Mbit

1. In case of a 16-bit external memory width, the FMC will internally use HADDR[25:1] to generate the
address for external memory FMC_A[24:0]. In case of a 32-bit memory width, the FMC will internally use
HADDR[25:2] to generate the external address.
Whatever the external memory width, FMC_A[0] should be connected to external memory address A[0].

13.4.2

NAND Flash memory address mapping
The NAND bank is divided into memory areas as indicated in Table 49.
Table 49. NAND memory mapping and timing registers
Start address

End address

0x8800 0000

0x8BFF FFFF

0x8000 0000

0x83FF FFFF

FMC bank
Bank 3 - NAND Flash

Memory space

Timing register

Attribute

FMC_PATT (0x8C)

Common

FMC_PMEM (0x88)

For NAND Flash memory, the common and attribute memory spaces are subdivided into
three sections (see in Table 50 below) located in the lower 256 Kbytes:

312/1709

•

Data section (first 64 Kbytes in the common/attribute memory space)

•

Command section (second 64 Kbytes in the common / attribute memory space)

•

Address section (next 128 Kbytes in the common / attribute memory space)

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Table 50. NAND bank selection
Section name

HADDR[17:16]

Address range

Address section

1X

0x020000-0x03FFFF

Command section

01

0x010000-0x01FFFF

Data section

00

0x000000-0x0FFFF

The application software uses the 3 sections to access the NAND Flash memory:
•

To sending a command to NAND Flash memory, the software must write the
command value to any memory location in the command section.

•

To specify the NAND Flash address that must be read or written, the software
must write the address value to any memory location in the address section. Since an
address can be 4 or 5 bytes long (depending on the actual memory size), several
consecutive write operations to the address section are required to specify the full
address.

•

To read or write data, the software reads or writes the data from/to any memory
location in the data section.

Since the NAND Flash memory automatically increments addresses, there is no need to
increment the address of the data section to access consecutive memory locations.

13.4.3

SDRAM address mapping
The HADDR[28] bit (internal AHB address line 28) is used to select one of the two memory
banks as indicated in Table 51.
Table 51. SDRAM bank selection
HADDR[28]

Selected bank

Control register

Timing register

0

SDRAM Bank1

FMC_SDCR1

FMC_SDTR1

1

SDRAM Bank2

FMC_SDCR2

FMC_SDTR2

The following table shows SDRAM mapping for a 13-bit row, a 11-bit column and a 4 internal
bank configuration.
Table 52. SDRAM address mapping
Memory width(1)

Internal bank

Row address

Column
address(2)

Maximum
memory capacity
(Mbytes)

8-bit

HADDR[25:24]

HADDR[23:11]

HADDR[10:0]

64 Mbytes:
4 x 8K x 2K

16-bit

HADDR[26:25]

HADDR[24:12]

HADDR[11:1]

128 Mbytes:
4 x 8K x 2K x 2

32-bit

HADDR[27:26]

HADDR[25:13]

HADDR[12:2]

256 Mbytes:
4 x 8K x 2K x 4

1. When interfacing with a 16-bit memory, the FMC internally uses the HADDR[11:1] internal AHB address
lines to generate the external address. Whatever the memory width, FMC_A[0] has to be connected to the
external memory address A[0].

RM0385 Rev 7

313/1709
383

Flexible memory controller (FMC)

RM0385

2. The AutoPrecharge is not supported. FMC_A[10] must be connected to the external memory address
A[10] but it will be always driven ‘low’.

The HADDR[27:0] bits are translated to external SDRAM address depending on the
SDRAM controller configuration:
•

Data size:8, 16 or 32 bits

•

Row size:11, 12 or 13 bits

•

Column size: 8, 9, 10 or 11 bits

•

Number of internal banks: two or four internal banks

The following tables show the SDRAM address mapping versus the SDRAM controller
configuration.
Table 53. SDRAM address mapping with 8-bit data bus width(1)(2)
Row size
configuration

HADDR(AHB Internal Address Lines)
27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Bank
[1:0]

Res.

Bank
[1:0]

Res.

11-bit row size
configuration

Bank
[1:0]

Bank
[1:0]

Res.

Bank
[1:0]

Res.

Row[11:0]
Row[11:0]
Row[11:0]
Row[11:0]

Bank
[1:0]
Bank
[1:0]

Res.
Res.

Row[10:0]

Bank
[1:0]

Res.

Res.

13-bit row size
configuration

Row[10:0]

Bank
[1:0]

Res.

Res.

Row[10:0]

Bank
[1:0]

Res.
Res.

12-bit row size
configuration

Row[10:0]

Bank
[1:0]
Bank
[1:0]

Row[12:0]
Row[12:0]
Row[12:0]
Row[12:0]

Column[7:0]
Column[8:0]
Column[9:0]
Column[10:0]
Column[7:0]
Column[8:0]
Column[9:0]
Column[10:0]
Column[7:0]
Column[8:0]
Column[9:0]
Column[10:0]

1. BANK[1:0] are the Bank Address BA[1:0]. When only 2 internal banks are used, BA1 must always be set to ‘0’.
2. Access to Reserved (Res.) address range generates an AHB error.

314/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Table 54. SDRAM address mapping with 16-bit data bus width(1)(2)

Bank
Row[10:0]
[1:0]
Bank
Res.
Row[10:0]
11-bit row size
[1:0]
Bank
configuration
Res.
Row[10:0]
[1:0]
Bank
Res.
Row[10:0]
[1:0]
Bank
Res.
Row[11:0]
[1:0]
Bank
Res.
Row[11:0]
12-bit row size
[1:0]
Bank
configuration
Res.
Row[11:0]
[1:0]
Bank
Res.
Row[11:0]
[1:0]
Bank
Res.
Row[12:0]
[1:0]
Bank
Res.
Row[12:0]
13-bit row size
[1:0]
Bank
configuration
Res.
Row[12:0]
[1:0]
Re Bank
Row[12:0]
s. [1:0]
Res.

0

10
9
8
7
6
5
4
3
2
1

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

Row size
Configuration

27

HADDR(AHB address Lines)

BM0(3)

Column[7:0]
Column[8:0]

BM0

Column[9:0]

BM0

Column[10:0]

BM0

Column[7:0]

BM0

Column[8:0]

BM0

Column[9:0]

BM0

Column[10:0]

BM0

Column[7:0]

BM0

Column[8:0]

BM0

Column[9:0]

BM0

Column[10:0]

BM0

1. BANK[1:0] are the Bank Address BA[1:0]. When only 2 internal banks are used, BA1 must always be set to ‘0’.
2. Access to Reserved space (Res.) generates an AHB error.
3. BM0: is the byte mask for 16-bit access.

Table 55. SDRAM address mapping with 32-bit data bus width(1)(2)

Bank
[1:0]
Bank
Res.
[1:0]
Bank
Res.
[1:0]
Bank
Res.
[1:0]
Res.

11-bit row size
configuration

Row[10:0]
Row[10:0]
Row[10:0]
Row[10:0]

RM0385 Rev 7

Column[7:0]
Column[8:0]
Column[9:0]
Column[10:0]

0

1

20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2

21

22

23

24

25

26

Row size
configuration

27

HADDR(AHB address Lines)

BM[1:0](3)
BM[1:0]
BM[1:0]
BM[1:0]

315/1709
383

Flexible memory controller (FMC)

RM0385

Table 55. SDRAM address mapping with 32-bit data bus width(1)(2) (continued)

Bank
[1:0]
Bank
Res.
12-bit row size
[1:0]
Bank
configuration
Res.
[1:0]
Bank
Res.
[1:0]
Bank
Res.
[1:0]
Bank
Res.
13-bit row size
[1:0]
configuration Res. Bank
[1:0]
Bank
[1:0]
Res.

Row[11:0]
Row[11:0]
Row[11:0]
Row[11:0]
Row[12:0]
Row[12:0]
Row[12:0]
Row[12:0]

Column[7:0]
Column[8:0]
Column[9:0]
Column[10:0]
Column[7:0]
Column[8:0]
Column[9:0]
Column[10:0]

0

1

20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2

21

22

23

24

25

26

Row size
configuration

27

HADDR(AHB address Lines)

BM[1:0]
BM[1:0]
BM[1:0]
BM[1:0]
BM[1:0
BM[1:0
BM[1:0
BM[1:0

1. BANK[1:0] are the Bank Address BA[1:0]. When only 2 internal banks are used, BA1 must always be set to ‘0’.
2. Access to Reserved space (Res.) generates an AHB error.
3. BM[1:0]: is the byte mask for 32-bit access.

13.5

NOR Flash/PSRAM controller
The FMC generates the appropriate signal timings to drive the following types of memories:
•

•

•

Asynchronous SRAM and ROM
–

8 bits

–

16 bits

–

32 bits

PSRAM (CellularRAM™)
–

Asynchronous mode

–

Burst mode for synchronous accesses

–

Multiplexed or non-multiplexed

NOR Flash memory
–

Asynchronous mode

–

Burst mode for synchronous accesses

–

Multiplexed or non-multiplexed

The FMC outputs a unique Chip Select signal, NE[4:1], per bank. All the other signals
(addresses, data and control) are shared.

316/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
The FMC supports a wide range of devices through a programmable timings among which:
•

Programmable wait states (up to 15)

•

Programmable bus turnaround cycles (up to 15)

•

Programmable output enable and write enable delays (up to 15)

•

Independent read and write timings and protocol to support the widest variety of
memories and timings

•

Programmable continuous clock (FMC_CLK) output.

The FMC Clock (FMC_CLK) is a submultiple of the HCLK clock. It can be delivered to the
selected external device either during synchronous accesses only or during asynchronous
and synchronous accesses depending on the CCKEN bit configuration in the FMC_BCR1
register:
•

If the CCLKEN bit is reset, the FMC generates the clock (CLK) only during
synchronous accesses (Read/write transactions).

•

If the CCLKEN bit is set, the FMC generates a continuous clock during asynchronous
and synchronous accesses. To generate the FMC_CLK continuous clock, Bank 1 must
be configured in synchronous mode (see Section 13.5.6: NOR/PSRAM controller
registers). Since the same clock is used for all synchronous memories, when a
continuous output clock is generated and synchronous accesses are performed, the
AHB data size has to be the same as the memory data width (MWID) otherwise the
FMC_CLK frequency will be changed depending on AHB data transaction (refer to
Section 13.5.5: Synchronous transactions for FMC_CLK divider ratio formula).

The size of each bank is fixed and equal to 64 Mbytes. Each bank is configured through
dedicated registers (see Section 13.5.6: NOR/PSRAM controller registers).
The programmable memory parameters include access times (see Table 56) and support
for wait management (for PSRAM and NOR Flash accessed in burst mode).
Table 56. Programmable NOR/PSRAM access parameters
Parameter

Function

Access mode

Unit

Min.

Max.

Address
setup

Duration of the address
setup phase

Asynchronous

AHB clock cycle
(HCLK)

0

15

Address hold

Duration of the address hold
phase

Asynchronous,
muxed I/Os

AHB clock cycle
(HCLK)

1

15

Data setup

Duration of the data setup
phase

Asynchronous

AHB clock cycle
(HCLK)

1

256

Bust turn

Duration of the bus
turnaround phase

Asynchronous and
AHB clock cycle
synchronous read
(HCLK)
/ write

0

15

Clock divide
ratio

Number of AHB clock cycles
(HCLK) to build one memory
clock cycle (CLK)

Synchronous

AHB clock cycle
(HCLK)

2

16

Data latency

Number of clock cycles to
issue to the memory before
the first data of the burst

Synchronous

Memory clock
cycle (CLK)

2

17

RM0385 Rev 7

317/1709
383

Flexible memory controller (FMC)

13.5.1

RM0385

External memory interface signals
Table 57, Table 58 and Table 59 list the signals that are typically used to interface with NOR
Flash memory, SRAM and PSRAM.

Note:

The prefix “N” identifies the signals that are active low.

NOR Flash memory, non-multiplexed I/Os
Table 57. Non-multiplexed I/O NOR Flash memory
FMC signal name

I/O

Function

CLK

O

Clock (for synchronous access)

A[25:0]

O

Address bus

D[31:0]

I/O

Bidirectional data bus

NE[x]

O

Chip Select, x = 1..4

NOE

O

Output enable

NWE

O

Write enable

NL(=NADV)

O

Latch enable (this signal is called address
valid, NADV, by some NOR Flash devices)

NWAIT

I

NOR Flash wait input signal to the FMC

The maximum capacity is 512 Mbits (26 address lines).

NOR Flash memory, 16-bit multiplexed I/Os
Table 58. 16-bit multiplexed I/O NOR Flash memory
FMC signal name

I/O

Function

CLK

O

Clock (for synchronous access)

A[25:16]

O

Address bus

AD[15:0]

I/O

16-bit multiplexed, bidirectional address/data bus (the 16-bit address
A[15:0] and data D[15:0] are multiplexed on the databus)

NE[x]

O

Chip Select, x = 1..4

NOE

O

Output enable

NWE

O

Write enable

NL(=NADV)

O

Latch enable (this signal is called address valid, NADV, by some NOR
Flash devices)

NWAIT

I

NOR Flash wait input signal to the FMC

The maximum capacity is 512 Mbits.

318/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

PSRAM/SRAM, non-multiplexed I/Os
Table 59. Non-multiplexed I/Os PSRAM/SRAM
FMC signal name

I/O

Function

CLK

O

Clock (only for PSRAM synchronous access)

A[25:0]

O

Address bus

D[31:0]

I/O

Data bidirectional bus

NE[x]

O

Chip Select, x = 1..4 (called NCE by PSRAM (CellularRAM™ i.e. CRAM))

NOE

O

Output enable

NWE

O

Write enable

NL(= NADV)

O

Address valid only for PSRAM input (memory signal name: NADV)

NWAIT

I

PSRAM wait input signal to the FMC

NBL[3:0]

O

Byte lane output. Byte 0 to Byte 3 control (Upper and lower byte enable)

The maximum capacity is 512 Mbits.

PSRAM, 16-bit multiplexed I/Os
Table 60. 16-Bit multiplexed I/O PSRAM
FMC signal name

I/O

Function

CLK

O

Clock (for synchronous access)

A[25:16]

O

Address bus

AD[15:0]

I/O

16-bit multiplexed, bidirectional address/data bus (the 16-bit address
A[15:0] and data D[15:0] are multiplexed on the databus)

NE[x]

O

Chip Select, x = 1..4 (called NCE by PSRAM (CellularRAM™ i.e. CRAM))

NOE

O

Output enable

NWE

O

Write enable

NL(= NADV)

O

Address valid PSRAM input (memory signal name: NADV)

NWAIT

I

PSRAM wait input signal to the FMC

NBL[1:0]

O

Byte lane output. Byte 0 and Byte 1 control (upper and lower byte enable)

The maximum capacity is 512 Mbits (26 address lines).

13.5.2

Supported memories and transactions
Table 61 below shows an example of the supported devices, access modes and
transactions when the memory data bus is 16-bit wide for NOR Flash memory, PSRAM and
SRAM. The transactions not allowed (or not supported) by the FMC are shown in gray in
this example.

RM0385 Rev 7

319/1709
383

Flexible memory controller (FMC)

RM0385

Table 61. NOR Flash/PSRAM: example of supported memories and transactions
Device

NOR Flash
(muxed I/Os
and nonmuxed
I/Os)

PSRAM
(multiplexed
I/Os and nonmultiplexed
I/Os)

SRAM and
ROM

320/1709

Mode

R/W

AHB
data
size

Memory
data size

Allowed/
not
allowed

Comments

Asynchronous

R

8

16

Y

-

Asynchronous

W

8

16

N

-

Asynchronous

R

16

16

Y

-

Asynchronous

W

16

16

Y

-

Asynchronous

R

32

16

Y

Split into 2 FMC accesses

Asynchronous

W

32

16

Y

Split into 2 FMC accesses

Asynchronous
page

R

-

16

N

Mode is not supported

Synchronous

R

8

16

N

-

Synchronous

R

16

16

Y

-

Synchronous

R

32

16

Y

-

Asynchronous

R

8

16

Y

-

Asynchronous

W

8

16

Y

Use of byte lanes NBL[1:0]

Asynchronous

R

16

16

Y

-

Asynchronous

W

16

16

Y

-

Asynchronous

R

32

16

Y

Split into 2 FMC accesses

Asynchronous

W

32

16

Y

Split into 2 FMC accesses

Asynchronous
page

R

-

16

N

Mode is not supported

Synchronous

R

8

16

N

-

Synchronous

R

16

16

Y

-

Synchronous

R

32

16

Y

-

Synchronous

W

8

16

Y

Use of byte lanes NBL[1:0]

Synchronous

W

16/32

16

Y

-

Asynchronous

R

8 / 16

16

Y

-

Asynchronous

W

8 / 16

16

Y

Use of byte lanes NBL[1:0]

Asynchronous

R

32

16

Y

Split into 2 FMC accesses

Asynchronous

W

32

16

Y

Split into 2 FMC accesses
Use of byte lanes NBL[1:0]

RM0385 Rev 7

RM0385

13.5.3

Flexible memory controller (FMC)

General timing rules
Signals synchronization

13.5.4

•

All controller output signals change on the rising edge of the internal clock (HCLK)

•

In synchronous mode (read or write), all output signals change on the rising edge of
HCLK. Whatever the CLKDIV value, all outputs change as follows:
–

NOEL/NWEL/ NEL/NADVL/ NADVH /NBLL/ Address valid outputs change on the
falling edge of FMC_CLK clock.

–

NOEH/ NWEH / NEH/ NOEH/NBLH/ Address invalid outputs change on the rising
edge of FMC_CLK clock.

NOR Flash/PSRAM controller asynchronous transactions
Asynchronous static memories (NOR Flash, PSRAM, SRAM)
•

Signals are synchronized by the internal clock HCLK. This clock is not issued to the
memory

•

The FMC always samples the data before de-asserting the NOE signal. This
guarantees that the memory data hold timing constraint is met (minimum Chip Enable
high to data transition is usually 0 ns)

•

If the extended mode is enabled (EXTMOD bit is set in the FMC_BCRx register), up to
four extended modes (A, B, C and D) are available. It is possible to mix A, B, C and D
modes for read and write operations. For example, read operation can be performed in
mode A and write in mode B.

•

If the extended mode is disabled (EXTMOD bit is reset in the FMC_BCRx register), the
FMC can operate in Mode1 or Mode2 as follows:
–

Mode 1 is the default mode when SRAM/PSRAM memory type is selected (MTYP
= 0x0 or 0x01 in the FMC_BCRx register)

–

Mode 2 is the default mode when NOR memory type is selected (MTYP = 0x10 in
the FMC_BCRx register).

RM0385 Rev 7

321/1709
383

Flexible memory controller (FMC)

RM0385

Mode 1 - SRAM/PSRAM (CRAM)
The next figures show the read and write transactions for the supported modes followed by
the required configuration of FMC_BCRx, and FMC_BTRx/FMC_BWTRx registers.
Figure 35. Mode1 read access waveforms
Memory transaction
A[25:0]

NBL[3:0]

NEx

NOE
NWE

High

data driven
by memory

D[31:0]
ADDSET
HCLK cycles

DATAST
HCLK cycles
MS30452V1

Figure 36. Mode1 write access waveforms

Memory transaction
A[25:0]

NBL[3:0]

NEx

NOE
1HCLK
NWE

D[31:0]

data driven by FMC
ADDSET
HCLK cycles

(DATAST + 1)
HCLK cycles
MS38299V1

322/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
The one HCLK cycle at the end of the write transaction helps guarantee the address and
data hold time after the NWE rising edge. Due to the presence of this HCLK cycle, the
DATAST value must be greater than zero (DATAST > 0).
Table 62. FMC_BCRx bit fields
Bit number

Bit name

Value to set

31:22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19

CBURSTRW

0x0 (no effect in asynchronous mode)

18:16

CPSIZE

0x0 (no effect in asynchronous mode)

15

ASYNCWAIT

14

EXTMOD

0x0

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

Reserved

0x0

9

WAITPOL

Meaningful only if bit 15 is 1

8

BURSTEN

0x0

7

Reserved

0x1

6

FACCEN

Don’t care

5:4

MWID

As needed

3:2

MTYP

As needed, exclude 0x2 (NOR Flash memory)

1

MUXE

0x0

0

MBKEN

0x1

0x000

Set to 1 if the memory supports this feature. Otherwise keep at 0.

Table 63. FMC_BTRx bit fields
Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

Don’t care

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the second access phase (DATAST+1 HCLK cycles for
write accesses, DATAST HCLK cycles for read accesses).

7:4

ADDHLD

Don’t care

3:0

ADDSET

Duration of the first access phase (ADDSET HCLK cycles).
Minimum value for ADDSET is 0.

Time between NEx high to NEx low (BUSTURN HCLK).

RM0385 Rev 7

323/1709
383

Flexible memory controller (FMC)

RM0385

Mode A - SRAM/PSRAM (CRAM) OE toggling
Figure 37. ModeA read access waveforms
Memory transaction
A[25:0]

NBL[3:0]

NEx

NOE
NWE

High

data driven
by memory

D[31:0]
ADDSET
HCLK cycles

DATAST
HCLK cycles
MS30454V1

1. NBL[3:0] are driven low during the read access

Figure 38. ModeA write access waveforms

Memory transaction
A[25:0]

NBL[3:0]

NEx

NOE
1HCLK

NWE

D[31:0]

data driven by FMC
ADDSET

(DATAST + 1)

HCLK cycles

HCLK cycles
MS39900V1

324/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
The differences compared with Mode1 are the toggling of NOE and the independent read
and write timings.
Table 64. FMC_BCRx bit fields
Bit number

Bit name

Value to set

31:22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19

CBURSTRW

0x0 (no effect in asynchronous mode)

18:16

CPSIZE

0x0 (no effect in asynchronous mode)

15

ASYNCWAIT

14

EXTMOD

0x1

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

Reserved

0x0

9

WAITPOL

Meaningful only if bit 15 is 1

8

BURSTEN

0x0

7

Reserved

0x1

6

FACCEN

Don’t care

5:4

MWID

As needed

3:2

MTYP

As needed, exclude 0x2 (NOR Flash memory)

1

MUXEN

0x0

0

MBKEN

0x1

0x000

Set to 1 if the memory supports this feature. Otherwise keep at 0.

Table 65. FMC_BTRx bit fields
Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x0

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the second access phase (DATAST HCLK cycles) for read
accesses.

7:4

ADDHLD

Don’t care

3:0

ADDSET

Duration of the first access phase (ADDSET HCLK cycles) for read
accesses.
Minimum value for ADDSET is 0.

Time between NEx high to NEx low (BUSTURN HCLK).

RM0385 Rev 7

325/1709
383

Flexible memory controller (FMC)

RM0385
Table 66. FMC_BWTRx bit fields

Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x0

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the second access phase (DATAST HCLK cycles) for write
accesses.

7:4

ADDHLD

Don’t care

3:0

ADDSET

Duration of the first access phase (ADDSET HCLK cycles) for write
accesses.
Minimum value for ADDSET is 0.

Time between NEx high to NEx low (BUSTURN HCLK).

Mode 2/B - NOR Flash
Figure 39. Mode2 and mode B read access waveforms
Memory transaction
A[25:0]

NADV

NEx

NOE
NWE

High

data driven
by memory

D[31:0]
ADDSET
HCLK cycles

DATAST
HCLK cycles
MS30456V1

326/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Figure 40. Mode2 write access waveforms

Memory transaction
A[25:0]

NADV

NEx

NOE
1HCLK
NWE

D[31:0]

data driven by FMC
ADDSET
HCLK cycles

(DATAST + 1)
HCLK cycles
MS39901V1

Figure 41. ModeB write access waveforms

Memory transaction
A[25:0]

NADV

NEx

NOE
1HCLK
NWE

D[31:0]

data driven by FMC
ADDSET
HCLK cycles

(DATAST + 1)
HCLK cycles
MS39902V1

The differences with Mode1 are the toggling of NWE and the independent read and write
timings when extended mode is set (Mode B).

RM0385 Rev 7

327/1709
383

Flexible memory controller (FMC)

RM0385
Table 67. FMC_BCRx bit fields

Bit number

Bit name

Value to set

31:22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19

CBURSTRW

0x0 (no effect in asynchronous mode)

18:16

CPSIZE

0x0 (no effect in asynchronous mode)

15

ASYNCWAIT

14

EXTMOD

0x1 for mode B, 0x0 for mode 2

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

Reserved

0x0

9

WAITPOL

Meaningful only if bit 15 is 1

8

BURSTEN

0x0

7

Reserved

0x1

6

FACCEN

0x1

5:4

MWID

As needed

3:2

MTYP

0x2 (NOR Flash memory)

1

MUXEN

0x0

0

MBKEN

0x1

0x000

Set to 1 if the memory supports this feature. Otherwise keep at 0.

Table 68. FMC_BTRx bit fields

328/1709

Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x1 if extended mode is set

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the access second phase (DATAST HCLK cycles) for
read accesses.

7:4

ADDHLD

Don’t care

3:0

ADDSET

Duration of the access first phase (ADDSET HCLK cycles) for read
accesses. Minimum value for ADDSET is 0.

Time between NEx high to NEx low (BUSTURN HCLK).

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Table 69. FMC_BWTRx bit fields

Note:

Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x1 if extended mode is set

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the access second phase (DATAST HCLK cycles) for
write accesses.

7:4

ADDHLD

Don’t care

3:0

ADDSET

Duration of the access first phase (ADDSET HCLK cycles) for write
accesses. Minimum value for ADDSET is 0.

Time between NEx high to NEx low (BUSTURN HCLK).

The FMC_BWTRx register is valid only if the extended mode is set (mode B), otherwise its
content is don’t care.

Mode C - NOR Flash - OE toggling
Figure 42. ModeC read access waveforms
Memory transaction
A[25:0]

NADV

NEx

NOE
NWE

High

data driven
by memory

D[31:0]
ADDSET
HCLK cycles

DATAST
HCLK cycles
MS30459V1

RM0385 Rev 7

329/1709
383

Flexible memory controller (FMC)

RM0385

Figure 43. ModeC write access waveforms

Memory transaction
A[25:0]

NADV

NEx

NOE
1HCLK
NWE

D[31:0]

data driven by FMC
ADDSET

(DATAST + 1)

HCLK cycles

HCLK cycles

MS39903V1

The differences compared with Mode1 are the toggling of NOE and the independent read
and write timings.
Table 70. FMC_BCRx bit fields

330/1709

Bit number

Bit name

Value to set

31:22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19

CBURSTRW

0x0 (no effect in asynchronous mode)

18:16

CPSIZE

0x0 (no effect in asynchronous mode)

15

ASYNCWAIT

14

EXTMOD

0x1

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

Reserved

0x0

9

WAITPOL

Meaningful only if bit 15 is 1

8

BURSTEN

0x0

7

Reserved

0x1

6

FACCEN

0x1

5:4

MWID

0x000

Set to 1 if the memory supports this feature. Otherwise keep at 0.

As needed

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Table 70. FMC_BCRx bit fields (continued)
Bit number

Bit name

Value to set

3:2

MTYP

1

MUXEN

0x0

0

MBKEN

0x1

0x02 (NOR Flash memory)

Table 71. FMC_BTRx bit fields
Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x2

27:24

DATLAT

0x0

23:20

CLKDIV

0x0

19:16

BUSTURN

15:8

DATAST

Duration of the second access phase (DATAST HCLK cycles) for
read accesses.

7:4

ADDHLD

Don’t care

3:0

ADDSET

Duration of the first access phase (ADDSET HCLK cycles) for read
accesses. Minimum value for ADDSET is 0.

Time between NEx high to NEx low (BUSTURN HCLK).

Table 72. FMC_BWTRx bit fields
Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x2

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the second access phase (DATAST HCLK cycles) for
write accesses.

7:4

ADDHLD

Don’t care

3:0

ADDSET

Duration of the first access phase (ADDSET HCLK cycles) for write
accesses. Minimum value for ADDSET is 0.

Time between NEx high to NEx low (BUSTURN HCLK).

RM0385 Rev 7

331/1709
383

Flexible memory controller (FMC)

RM0385

Mode D - asynchronous access with extended address
Figure 44. ModeD read access waveforms
Memory transaction
A[25:0]

NADV

NEx

NOE
NWE

High

data driven
by memory

D[31:0]
ADDSET
HCLK cycles

ADDHLD
HCLK cycles

DATAST
HCLK cycles
MS30461V1

Figure 45. ModeD write access waveforms

Memory transaction
A[25:0]

NADV

NEx

NOE
1HCLK
NWE

D[31:0]

data driven by FMC
ADDSET

ADDHLD

(DATAST + 1)

HCLK cycles

HCLK cycles

HCLK cycles
MS39904V1

The differences with Mode1 are the toggling of NOE that goes on toggling after NADV
changes and the independent read and write timings.
332/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Table 73. FMC_BCRx bit fields
Bit number

Bit name

Value to set

31:22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19

CBURSTRW

0x0 (no effect in asynchronous mode)

18:16

CPSIZE

0x0 (no effect in asynchronous mode)

15

ASYNCWAIT

14

EXTMOD

0x1

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

Reserved

0x0

9

WAITPOL

Meaningful only if bit 15 is 1

8

BURSTEN

0x0

7

Reserved

0x1

6

FACCEN

Set according to memory support

5:4

MWID

As needed

3:2

MTYP

As needed

1

MUXEN

0x0

0

MBKEN

0x1

0x000

Set to 1 if the memory supports this feature. Otherwise keep at 0.

Table 74. FMC_BTRx bit fields
Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x3

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the second access phase (DATAST HCLK cycles) for read
accesses.

7:4

ADDHLD

Duration of the middle phase of the read access (ADDHLD HCLK
cycles)

3:0

ADDSET

Duration of the first access phase (ADDSET HCLK cycles) for read
accesses. Minimum value for ADDSET is 1.

Time between NEx high to NEx low (BUSTURN HCLK).

RM0385 Rev 7

333/1709
383

Flexible memory controller (FMC)

RM0385
Table 75. FMC_BWTRx bit fields

Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x3

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the second access phase (DATAST + 1 HCLK cycles) for
write accesses.

7:4

ADDHLD

Duration of the middle phase of the write access (ADDHLD HCLK
cycles)

3:0

ADDSET

Duration of the first access phase (ADDSET HCLK cycles) for write
accesses. Minimum value for ADDSET is 1.

Time between NEx high to NEx low (BUSTURN HCLK).

Muxed mode - multiplexed asynchronous access to NOR Flash memory
Figure 46. Muxed read access waveforms

334/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Figure 47. Muxed write access waveforms

Memory transaction
A[25:16]

NADV

NEx

NOE
1HCLK
NWE

Lower address

AD[15:0]

data driven by FMC

ADDSET

ADDHLD

(DATAST + 1)

HCLK cycles

HCLK cycles

HCLK cycles
MS39905V2

The difference with ModeD is the drive of the lower address byte(s) on the data bus.
Table 76. FMC_BCRx bit fields
Bit number

Bit name

Value to set

31:22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19

CBURSTRW

0x0 (no effect in asynchronous mode)

18:16

CPSIZE

0x0 (no effect in asynchronous mode)

15

ASYNCWAIT

14

EXTMOD

0x0

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

Reserved

0x0

9

WAITPOL

Meaningful only if bit 15 is 1

8

BURSTEN

0x0

7

Reserved

0x1

6

FACCEN

0x1

5:4

MWID

0x000

Set to 1 if the memory supports this feature. Otherwise keep at 0.

As needed

RM0385 Rev 7

335/1709
383

Flexible memory controller (FMC)

RM0385

Table 76. FMC_BCRx bit fields (continued)
Bit number

Bit name

Value to set

3:2

MTYP

1

MUXEN

0x1

0

MBKEN

0x1

0x2 (NOR Flash memory) or 0x1(PSRAM)

Table 77. FMC_BTRx bit fields
Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x0

27:24

DATLAT

Don’t care

23:20

CLKDIV

Don’t care

19:16

BUSTURN

15:8

DATAST

Duration of the second access phase (DATAST HCLK cycles for read
accesses and DATAST+1 HCLK cycles for write accesses).

7:4

ADDHLD

Duration of the middle phase of the access (ADDHLD HCLK cycles).

3:0

ADDSET

Duration of the first access phase (ADDSET HCLK cycles). Minimum
value for ADDSET is 1.

Time between NEx high to NEx low (BUSTURN HCLK).

WAIT management in asynchronous accesses
If the asynchronous memory asserts the WAIT signal to indicate that it is not yet ready to
accept or to provide data, the ASYNCWAIT bit has to be set in FMC_BCRx register.
If the WAIT signal is active (high or low depending on the WAITPOL bit), the second access
phase (Data setup phase), programmed by the DATAST bits, is extended until WAIT
becomes inactive. Unlike the data setup phase, the first access phases (Address setup and
Address hold phases), programmed by the ADDSET and ADDHLD bits, are not WAIT
sensitive and so they are not prolonged.
The data setup phase must be programmed so that WAIT can be detected 4 HCLK cycles
before the end of the memory transaction. The following cases must be considered:

336/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
1.

The memory asserts the WAIT signal aligned to NOE/NWE which toggles:
DATAST ≥ ( 4 × HCLK ) + max_wait_assertion_time

2.

The memory asserts the WAIT signal aligned to NEx (or NOE/NWE not toggling):
if
max_wait_assertion_time > address_phase + hold_phase
then:

DATAST ≥ ( 4 × HCLK ) + ( max_wait_assertion_time

– address_phase – hold_phase )

otherwise
DATAST ≥ 4 × HCLK
where max_wait_assertion_time is the maximum time taken by the memory to assert
the WAIT signal once NEx/NOE/NWE is low.
Figure 48 and Figure 49 show the number of HCLK clock cycles that are added to the

memory access phase after WAIT is released by the asynchronous memory (independently
of the above cases).
Figure 48. Asynchronous wait during a read access waveforms
Memory transaction

A[25:0]

address phase

data setup phase

NEx

NWAIT

don’t care

don’t care

NOE

data driven by memory

D[15:0]

4HCLK

MS30463V2

1. NWAIT polarity depends on WAITPOL bit setting in FMC_BCRx register.

RM0385 Rev 7

337/1709
383

Flexible memory controller (FMC)

RM0385

Figure 49. Asynchronous wait during a write access waveforms
Memory transaction

A[25:0]
address phase

data setup phase

NEx

NWAIT

don’t care

don’t care
1HCLK

NWE

D[15:0]

data driven by FMC
3HCLK
MSv40168V1

1. NWAIT polarity depends on WAITPOL bit setting in FMC_BCRx register.

13.5.5

Synchronous transactions
The memory clock, FMC_CLK, is a submultiple of HCLK. It depends on the value of
CLKDIV and the MWID/ AHB data size, following the formula given below:
FMC_CLK divider ratio = max (CLKDIV + 1,MWID ( AHB data size ))
If MWID is 16 or 8-bit, the FMC_CLK divider ratio is always defined by the programmed
CLKDIV value.
If MWID is 32-bit, the FMC_CLK divider ratio depends also on AHB data size.
Example:
•

If CLKDIV=1, MWID = 32 bits, AHB data size=8 bits, FMC_CLK=HCLK/4.

•

If CLKDIV=1, MWID = 16 bits, AHB data size=8 bits, FMC_CLK=HCLK/2.

NOR Flash memories specify a minimum time from NADV assertion to CLK high. To meet
this constraint, the FMC does not issue the clock to the memory during the first internal
clock cycle of the synchronous access (before NADV assertion). This guarantees that the
rising edge of the memory clock occurs in the middle of the NADV low pulse.

Data latency versus NOR memory latency
The data latency is the number of cycles to wait before sampling the data. The DATLAT
value must be consistent with the latency value specified in the NOR Flash configuration
register. The FMC does not include the clock cycle when NADV is low in the data latency
count.

338/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

Caution:

Some NOR Flash memories include the NADV Low cycle in the data latency count, so that
the exact relation between the NOR Flash latency and the FMC DATLAT parameter can be
either:
•

NOR Flash latency = (DATLAT + 2) CLK clock cycles

•

or NOR Flash latency = (DATLAT + 3) CLK clock cycles

Some recent memories assert NWAIT during the latency phase. In such cases DATLAT can
be set to its minimum value. As a result, the FMC samples the data and waits long enough
to evaluate if the data are valid. Thus the FMC detects when the memory exits latency and
real data are processed.
Other memories do not assert NWAIT during latency. In this case the latency must be set
correctly for both the FMC and the memory, otherwise invalid data are mistaken for good
data, or valid data are lost in the initial phase of the memory access.

Single-burst transfer
When the selected bank is configured in burst mode for synchronous accesses, if for
example an AHB single-burst transaction is requested on 16-bit memories, the FMC
performs a burst transaction of length 1 (if the AHB transfer is 16 bits), or length 2 (if the
AHB transfer is 32 bits) and de-assert the Chip Select signal when the last data is strobed.
Such transfers are not the most efficient in terms of cycles compared to asynchronous read
operations. Nevertheless, a random asynchronous access would first require to re-program
the memory access mode, which would altogether last longer.

Cross boundary page for CellularRAM™ 1.5
CellularRAM™ 1.5 does not allow burst access to cross the page boundary. The FMC
controller allows to split automatically the burst access when the memory page size is
reached by configuring the CPSIZE bits in the FMC_BCR1 register following the memory
page size.

Wait management
For synchronous NOR Flash memories, NWAIT is evaluated after the programmed latency
period, which corresponds to (DATLAT+2) CLK clock cycles.
If NWAIT is active (low level when WAITPOL = 0, high level when WAITPOL = 1), wait
states are inserted until NWAIT is inactive (high level when WAITPOL = 0, low level when
WAITPOL = 1).
When NWAIT is inactive, the data is considered valid either immediately (bit WAITCFG = 1)
or on the next clock edge (bit WAITCFG = 0).
During wait-state insertion via the NWAIT signal, the controller continues to send clock
pulses to the memory, keeping the Chip Select and output enable signals valid. It does not
consider the data as valid.
In burst mode, there are two timing configurations for the NOR Flash NWAIT signal:
•

The Flash memory asserts the NWAIT signal one data cycle before the wait state
(default after reset).

•

The Flash memory asserts the NWAIT signal during the wait state

The FMC supports both NOR Flash wait state configurations, for each Chip Select, thanks
to the WAITCFG bit in the FMC_BCRx registers (x = 0..3).

RM0385 Rev 7

339/1709
383

Flexible memory controller (FMC)

RM0385
Figure 50. Wait configuration waveforms
Memory transaction = burst of 4 half words

HCLK

CLK
A[25:16]

addr[25:16]

NADV
NWAIT
(WAITCFG = 0)
NWAIT
(WAITCFG = 1)
inserted wait state
A/D[15:0]

addr[15:0]

data

data

data
ai15798c

340/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

Figure 51. Synchronous multiplexed read mode waveforms - NOR, PSRAM (CRAM)
Memory transaction = burst of 4 half words
HCLK

CLK

A[25:16]

addr[25:16]

NEx

NOE

NWE

High

NADV
NWAIT
(WAITCFG=
0)
(DATLAT + 2)
CLK cycles
A/D[15:0]

Addr[15:0]

inserted wait state
data

1 clock 1 clock
cycle
cycle

data

data

data

Data strobes

Data strobes

ai17723f

1. Byte lane outputs (NBL are not shown; for NOR access, they are held high, and, for PSRAM (CRAM)
access, they are held low.

Table 78. FMC_BCRx bit fields
Bit number

Bit name

Value to set

31-22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19

CBURSTRW

18:16

CPSIZE

15

ASYNCWAIT

0x0

14

EXTMOD

0x0

13

WAITEN

To be set to 1 if the memory supports this feature, to be kept at 0
otherwise

12

WREN

No effect on synchronous read

11

WAITCFG

To be set according to memory

10

Reserved

0x0

0x000

No effect on synchronous read
0x0 (no effect in asynchronous mode)

RM0385 Rev 7

341/1709
383

Flexible memory controller (FMC)

RM0385

Table 78. FMC_BCRx bit fields (continued)
Bit number

Bit name

Value to set

9

WAITPOL

To be set according to memory

8

BURSTEN

0x1

7

Reserved

0x1

6

FACCEN

Set according to memory support (NOR Flash memory)

5-4

MWID

As needed

3-2

MTYP

0x1 or 0x2

1

MUXEN

As needed

0

MBKEN

0x1

Table 79. FMC_BTRx bit fields

342/1709

Bit number

Bit name

Value to set

31:30

Reserved

0x0

29:28

ACCMOD

0x0

27-24

DATLAT

Data latency

27-24

DATLAT

Data latency

23-20

CLKDIV

0x0 to get CLK = HCLK (Not supported)
0x1 to get CLK = 2 × HCLK
..

19-16

BUSTURN

15-8

DATAST

Don’t care

7-4

ADDHLD

Don’t care

3-0

ADDSET

Don’t care

Time between NEx high to NEx low (BUSTURN HCLK).

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Figure 52. Synchronous multiplexed write mode waveforms - PSRAM (CRAM)
Memory transaction = burst of 2 half words

HCLK

CLK

A[25:16]

addr[25:16]

NEx
Hi-Z
NOE

NWE

NADV

NWAIT
(WAITCFG = 0)
(DATLAT + 2)
CLK cycles
A/D[15:0]

Addr[15:0]

inserted wait state
data

data

1 clock 1 clock

ai14731f

1. The memory must issue NWAIT signal one cycle in advance, accordingly WAITCFG must be programmed to 0.
2. Byte Lane (NBL) outputs are not shown, they are held low while NEx is active.

Table 80. FMC_BCRx bit fields
Bit number

Bit name

31-22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19
18:16
15

Value to set
0x000

CBURSTRW 0x1
CPSIZE

As needed (0x1 for CRAM 1.5)

ASYNCWAIT 0x0

14

EXTMOD

0x0

13

WAITEN

To be set to 1 if the memory supports this feature, to be kept at 0
otherwise.

RM0385 Rev 7

343/1709
383

Flexible memory controller (FMC)

RM0385

Table 80. FMC_BCRx bit fields (continued)
Bit number

Bit name

Value to set

12

WREN

0x1

11

WAITCFG

0x0

10

Reserved

0x0

9

WAITPOL

to be set according to memory

8

BURSTEN

no effect on synchronous write

7

Reserved

0x1

6

FACCEN

Set according to memory support

5-4

MWID

As needed

3-2

MTYP

0x1

1

MUXEN

As needed

0

MBKEN

0x1

Table 81. FMC_BTRx bit fields

344/1709

Bit number

Bit name

Value to set

31-30

Reserved

0x0

29:28

ACCMOD

0x0

27-24

DATLAT

Data latency

23-20

CLKDIV

0x0 to get CLK = HCLK (not supported)
0x1 to get CLK = 2 × HCLK

19-16

BUSTURN

15-8

DATAST

Don’t care

7-4

ADDHLD

Don’t care

3-0

ADDSET

Don’t care

Time between NEx high to NEx low (BUSTURN HCLK).

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

13.5.6

NOR/PSRAM controller registers
SRAM/NOR-Flash chip-select control registers 1..4 (FMC_BCR1..4)
Address offset: 8 * (x – 1), x = 1...4
Reset value: 0x0000 30DB for Bank1 and 0x0000 30D2 for Bank 2 to 4
This register contains the control information of each memory bank, used for SRAMs,
PSRAM and NOR Flash memories.

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

ASYNC
WAIT

EXT
MOD

WAIT
EN

WREN

WAIT
CFG

Res.

WAIT
POL

BURST
EN

Res.

FACC
EN

rw

rw

rw

rw

rw

rw

rw

rw

21

20

19

WFDIS

CCLK
EN

CBURST
RW

18

rw

rw

rw

rw

rw

5

4

3

2

1

0

MUX
EN

MBK
EN

16

rw

rw

CPSIZE[2:0]

MWID[1:0]

MTYP[1:0]

rw

rw

rw

17

rw

rw

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 WFDIS: Write FIFO Disable
This bit disables the Write FIFO used by the FMC controller.
0: Write FIFO enabled (Default after reset)
1: Write FIFO disabled
Note: The WFDIS bit of the FMC_BCR2..4 registers is don’t care. It is only enabled through the
FMC_BCR1 register.
Bit 20 CCLKEN: Continuous Clock Enable.
This bit enables the FMC_CLK clock output to external memory devices.
0: The FMC_CLK is only generated during the synchronous memory access (read/write
transaction). The FMC_CLK clock ratio is specified by the programmed CLKDIV value in the
FMC_BCRx register (default after reset).
1: The FMC_CLK is generated continuously during asynchronous and synchronous access. The
FMC_CLK clock is activated when the CCLKEN is set.
Note: The CCLKEN bit of the FMC_BCR2..4 registers is don’t care. It is only enabled through the
FMC_BCR1 register. Bank 1 must be configured in synchronous mode to generate the
FMC_CLK continuous clock.
Note: If CCLKEN bit is set, the FMC_CLK clock ratio is specified by CLKDIV value in the
FMC_BTR1 register. CLKDIV in FMC_BWTR1 is don’t care.
Note: If the synchronous mode is used and CCLKEN bit is set, the synchronous memories
connected to other banks than Bank 1 are clocked by the same clock (the CLKDIV value in
the FMC_BTR2..4 and FMC_BWTR2..4 registers for other banks has no effect.)
Bit 19 CBURSTRW: Write burst enable.
For PSRAM (CRAM) operating in burst mode, the bit enables synchronous accesses during write
operations. The enable bit for synchronous read accesses is the BURSTEN bit in the FMC_BCRx
register.
0: Write operations are always performed in asynchronous mode
1: Write operations are performed in synchronous mode.

RM0385 Rev 7

345/1709
383

Flexible memory controller (FMC)

RM0385

Bits 18:16 CPSIZE[2:0]: CRAM page size.
These are used for CellularRAM™ 1.5 which does not allow burst access to cross the address
boundaries between pages. When these bits are configured, the FMC controller splits
automatically the burst access when the memory page size is reached (refer to memory datasheet
for page size).
000: No burst split when crossing page boundary (default after reset)
001: 128 bytes
010: 256 bytes
011: 512 bytes
100: 1024 bytes
Others: reserved
Bit 15 ASYNCWAIT: Wait signal during asynchronous transfers
This bit enables/disables the FMC to use the wait signal even during an asynchronous protocol.
0: NWAIT signal is not taken in to account when running an asynchronous protocol (default after
reset)
1: NWAIT signal is taken in to account when running an asynchronous protocol
Bit 14 EXTMOD: Extended mode enable.
This bit enables the FMC to program the write timings for non multiplexed asynchronous accesses
inside the FMC_BWTR register, thus resulting in different timings for read and write operations.
0: values inside FMC_BWTR register are not taken into account (default after reset)
1: values inside FMC_BWTR register are taken into account
Note: When the extended mode is disabled, the FMC can operate in Mode1 or Mode2 as follows:
–
Mode 1 is the default mode when the SRAM/PSRAM memory type is selected (MTYP
=0x0 or 0x01)
–
Mode 2 is the default mode when the NOR memory type is selected (MTYP = 0x10).
Bit 13 WAITEN: Wait enable bit.
This bit enables/disables wait-state insertion via the NWAIT signal when accessing the memory in
synchronous mode.
0: NWAIT signal is disabled (its level not taken into account, no wait state inserted after the
programmed Flash latency period)
1: NWAIT signal is enabled (its level is taken into account after the programmed latency period to
insert wait states if asserted) (default after reset)
Bit 12 WREN: Write enable bit.
This bit indicates whether write operations are enabled/disabled in the bank by the FMC:
0: Write operations are disabled in the bank by the FMC, an AHB error is reported,
1: Write operations are enabled for the bank by the FMC (default after reset).
Bit 11 WAITCFG: Wait timing configuration.
The NWAIT signal indicates whether the data from the memory are valid or if a wait state must be
inserted when accessing the memory in synchronous mode. This configuration bit determines if
NWAIT is asserted by the memory one clock cycle before the wait state or during the wait state:
0: NWAIT signal is active one data cycle before wait state (default after reset),
1: NWAIT signal is active during wait state (not used for PSRAM).
Bit 10 Reserved, must be kept at reset value.
Bit 9 WAITPOL: Wait signal polarity bit.
Defines the polarity of the wait signal from memory used for either in synchronous or
asynchronous mode:
0: NWAIT active low (default after reset),
1: NWAIT active high.

346/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

Bit 8 BURSTEN: Burst enable bit.
This bit enables/disables synchronous accesses during read operations. It is valid only for
synchronous memories operating in burst mode:
0: Burst mode disabled (default after reset). Read accesses are performed in asynchronous mode.
1: Burst mode enable. Read accesses are performed in synchronous mode.
Bit 7 Reserved, must be kept at reset value.
Bit 6 FACCEN: Flash access enable
Enables NOR Flash memory access operations.
0: Corresponding NOR Flash memory access is disabled
1: Corresponding NOR Flash memory access is enabled (default after reset)
Bits 5:4 MWID[1:0]: Memory data bus width.
Defines the external memory device width, valid for all type of memories.
00: 8 bits
01: 16 bits (default after reset)
10: 32 bits
11: reserved
Bits 3:2 MTYP[1:0]: Memory type.
Defines the type of external memory attached to the corresponding memory bank:
00: SRAM (default after reset for Bank 2...4)
01: PSRAM (CRAM)
10: NOR Flash/OneNAND Flash (default after reset for Bank 1)
11: reserved
Bit 1 MUXEN: Address/data multiplexing enable bit.
When this bit is set, the address and data values are multiplexed on the data bus, valid only with
NOR and PSRAM memories:
0: Address/Data non multiplexed
1: Address/Data multiplexed on databus (default after reset)
Bit 0 MBKEN: Memory bank enable bit.
Enables the memory bank. After reset Bank1 is enabled, all others are disabled. Accessing a
disabled bank causes an ERROR on AHB bus.
0: Corresponding memory bank is disabled
1: Corresponding memory bank is enabled

SRAM/NOR-Flash chip-select timing registers 1..4 (FMC_BTR1..4)
Address offset: 0x04 + 8 * (x – 1), x = 1..4
Reset value: 0x0FFF FFFF
This register contains the control information of each memory bank, used for SRAMs,
PSRAM and NOR Flash memories.If the EXTMOD bit is set in the FMC_BCRx register, then
this register is partitioned for write and read access, that is, 2 registers are available: one to
configure read accesses (this register) and one to configure write accesses (FMC_BWTRx
registers).

RM0385 Rev 7

347/1709
383

Flexible memory controller (FMC)

31

30

Res.

Res.

29

14

27

ACCMOD[1:0]
rw

15

28

13

26

RM0385

25

24

23

DATLAT[3:0]

rw

rw

rw

rw

rw

rw

rw

12

11

10

9

8

7

rw

rw

21

20

19

CLKDIV[3:0]

rw

DATAST[7:0]
rw

22

rw

rw

rw

rw

rw

rw

6

5

4

3

rw

rw

17

16

BUSTURN[3:0]

rw

ADDHLD[3:0]
rw

18

rw

rw

rw

2

1

0

ADDSET[3:0]
rw

rw

rw

rw

rw

Bits 31:30 Reserved, must be kept at reset value.
Bits 29:28 ACCMOD[1:0]: Access mode
Specifies the asynchronous access modes as shown in the timing diagrams. These bits are
taken into account only when the EXTMOD bit in the FMC_BCRx register is 1.
00: access mode A
01: access mode B
10: access mode C
11: access mode D
Bits 27:24 DATLAT[3:0]: (see note below bit descriptions): Data latency for synchronous memory
For synchronous access with read/write burst mode enabled (BURSTEN / CBURSTRW bits
set), defines the number of memory clock cycles (+2) to issue to the memory before
reading/writing the first data:
This timing parameter is not expressed in HCLK periods, but in FMC_CLK periods.
For asynchronous access, this value is don't care.
0000: Data latency of 2 CLK clock cycles for first burst access
1111: Data latency of 17 CLK clock cycles for first burst access (default value after reset)
Bits 23:20 CLKDIV[3:0]: Clock divide ratio (for FMC_CLK signal)
Defines the period of FMC_CLK clock output signal, expressed in number of HCLK cycles:
0000: Reserved
0001: FMC_CLK period = 2 × HCLK periods
0010: FMC_CLK period = 3 × HCLK periods
1111: FMC_CLK period = 16 × HCLK periods (default value after reset)
In asynchronous NOR Flash, SRAM or PSRAM accesses, this value is don’t care.
Note: Refer to Section 13.5.5: Synchronous transactions for FMC_CLK divider ratio formula)

348/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

Bits 19:16 BUSTURN[3:0]: Bus turnaround phase duration
These bits are written by software to add a delay at the end of a write-to-read (and read-towrite) transaction. This delay allows to match the minimum time between consecutive
transactions (tEHEL from NEx high to NEx low) and the maximum time needed by the
memory to free the data bus after a read access (tEHQZ). The programmed bus turnaround
delay is inserted between an asynchronous read (muxed or mode D) or write transaction and
any other asynchronous /synchronous read or write to or from a static bank. The bank can be
the same or different in case of read, in case of write the bank can be different except for
muxed or mode D.
In some cases, whatever the programmed BUSTURN values, the bus turnaround delay is
fixed
as follows:
• The bus turnaround delay is not inserted between two consecutive asynchronous write
transfers to the same static memory bank except for modes muxed and D.
• There is a bus turnaround delay of 1 HCLK clock cycle between:
–Two consecutive asynchronous read transfers to the same static memory bank except for
modes muxed and D.
–An asynchronous read to an asynchronous or synchronous write to any static bank or
dynamic bank except for modes muxed and D.
–An asynchronous (modes 1, 2, A, B or C) read and a read from another static bank.
• There is a bus turnaround delay of 2 HCLK clock cycle between:
–Two consecutive synchronous writes (burst or single) to the same bank.
–A synchronous write (burst or single) access and an asynchronous write or read transfer
to or from static memory bank (the bank can be the same or different for the case of
read.
–Two consecutive synchronous reads (burst or single) followed by any
synchronous/asynchronous read or write from/to another static memory bank.
• There is a bus turnaround delay of 3 HCLK clock cycle between:
–Two consecutive synchronous writes (burst or single) to different static bank.
–A synchronous write (burst or single) access and a synchronous read from the same or a
different bank.
0000: BUSTURN phase duration = 0 HCLK clock cycle added
...
1111: BUSTURN phase duration = 15 x HCLK clock cycles added (default value after reset)
Bits 15:8 DATAST[7:0]: Data-phase duration
These bits are written by software to define the duration of the data phase (refer to Figure 35
to Figure 47), used in asynchronous accesses:
0000 0000: Reserved
0000 0001: DATAST phase duration = 1 × HCLK clock cycles
0000 0010: DATAST phase duration = 2 × HCLK clock cycles
...
1111 1111: DATAST phase duration = 255 × HCLK clock cycles (default value after reset)
For each memory type and access mode data-phase duration, refer to the respective figure
(Figure 35 to Figure 47).
Example: Mode1, write access, DATAST=1: Data-phase duration= DATAST+1 = 2 HCLK
clock cycles.
Note: In synchronous accesses, this value is don’t care.

RM0385 Rev 7

349/1709
383

Flexible memory controller (FMC)

RM0385

Bits 7:4 ADDHLD[3:0]: Address-hold phase duration
These bits are written by software to define the duration of the address hold phase (refer to
Figure 35 to Figure 47), used in mode D or multiplexed accesses:
0000: Reserved
0001: ADDHLD phase duration =1 × HCLK clock cycle
0010: ADDHLD phase duration = 2 × HCLK clock cycle
...
1111: ADDHLD phase duration = 15 × HCLK clock cycles (default value after reset)
For each access mode address-hold phase duration, refer to the respective figure (Figure 35
to Figure 47).
Note: In synchronous accesses, this value is not used, the address hold phase is always 1
memory clock period duration.
Bits 3:0 ADDSET[3:0]: Address setup phase duration
These bits are written by software to define the duration of the address setup phase (refer to
Figure 35 to Figure 47), used in SRAMs, ROMs, asynchronous NOR Flash and PSRAM:
0000: ADDSET phase duration = 0 × HCLK clock cycle
...
1111: ADDSET phase duration = 15 × HCLK clock cycles (default value after reset)
For each access mode address setup phase duration, refer to the respective figure
(Figure 35 to Figure 47).
Note: In synchronous accesses, this value is don’t care.
In Muxed mode or Mode D, the minimum value for ADDSET is 1.

Note:

PSRAMs (CRAMs) have a variable latency due to internal refresh. Therefore these
memories issue the NWAIT signal during the whole latency phase to prolong the latency as
needed.
With PSRAMs (CRAMs) the filled DATLAT must be set to 0, so that the FMC exits its latency
phase soon and starts sampling NWAIT from memory, then starts to read or write when the
memory is ready.
This method can be used also with the latest generation of synchronous Flash memories
that issue the NWAIT signal, unlike older Flash memories (check the datasheet of the
specific Flash memory being used).

SRAM/NOR-Flash write timing registers 1..4 (FMC_BWTR1..4)
Address offset: 0x104 + 8 * (x – 1), x = 1...4
Reset value: 0x0FFF FFFF
This register contains the control information of each memory bank. It is used for SRAMs,
PSRAMs and NOR Flash memories. When the EXTMOD bit is set in the FMC_BCRx
register, then this register is active for write access.
31

30

Res.

Res.

15

14

29

28

ACCMOD[1:0]
rw

rw

13

12

27

26

25

24

23

22

21

20

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

DATAST[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

rw

rw

18

17

16

BUSTURN[3:0]
rw

rw

rw

rw

3

2

1

0

ADDHLD[3:0]

Bits 31:30 Reserved, must be kept at reset value.

350/1709

19

ADDSET[3:0]
rw

rw

rw

rw

rw

RM0385

Flexible memory controller (FMC)

Bits 29:28 ACCMOD[1:0]: Access mode.
Specifies the asynchronous access modes as shown in the next timing diagrams.These bits are
taken into account only when the EXTMOD bit in the FMC_BCRx register is 1.
00: access mode A
01: access mode B
10: access mode C
11: access mode D
Bits 27:20 Reserved, must be kept at reset value.
Bits 19:16 BUSTURN[3:0]: Bus turnaround phase duration
The programmed bus turnaround delay is inserted between an asynchronous write transfer and
any other asynchronous /synchronous read or write transfer to or from a static bank. The bank can
be the same or different in case of read, in case of write the bank can be different expect for muxed
or mode D.
In some cases, whatever the programmed BUSTURN values, the bus turnaround delay is fixed as
follows:
• The bus turnaround delay is not inserted between two consecutive asynchronous write transfers
to the same static memory bank except for modes muxed and D.
• There is a bus turnaround delay of 2 HCLK clock cycle between:
–Two consecutive synchronous writes (burst or single) to the same bank.
–A synchronous write (burst or single) transfer and an asynchronous write or read transfer to or
from static memory bank.
• There is a bus turnaround delay of 3 HCLK clock cycle between:
–Two consecutive synchronous writes (burst or single) to different static bank.
–A synchronous write (burst or single) transfer and a synchronous read from the same or a
different bank.
0000: BUSTURN phase duration = 0 HCLK clock cycle added
...
1111: BUSTURN phase duration = 15 HCLK clock cycles added (default value after reset)
Bits 15:8 DATAST[7:0]: Data-phase duration.
These bits are written by software to define the duration of the data phase (refer to Figure 35 to
Figure 47), used in asynchronous SRAM, PSRAM and NOR Flash memory accesses:
0000 0000: Reserved
0000 0001: DATAST phase duration = 1 × HCLK clock cycles
0000 0010: DATAST phase duration = 2 × HCLK clock cycles
...
1111 1111: DATAST phase duration = 255 × HCLK clock cycles (default value after reset)
Bits 7:4 ADDHLD[3:0]: Address-hold phase duration.
These bits are written by software to define the duration of the address hold phase (refer to
Figure 44 to Figure 47), used in asynchronous multiplexed accesses:
0000: Reserved
0001: ADDHLD phase duration = 1 × HCLK clock cycle
0010: ADDHLD phase duration = 2 × HCLK clock cycle
...
1111: ADDHLD phase duration = 15 × HCLK clock cycles (default value after reset)
Note: In synchronous NOR Flash accesses, this value is not used, the address hold phase is always
1 Flash clock period duration.

RM0385 Rev 7

351/1709
383

Flexible memory controller (FMC)

RM0385

Bits 3:0 ADDSET[3:0]: Address setup phase duration.
These bits are written by software to define the duration of the address setup phase in HCLK
cycles (refer to Figure 35 to Figure 47), used in asynchronous accesses:
0000: ADDSET phase duration = 0 × HCLK clock cycle
...
1111: ADDSET phase duration = 15 × HCLK clock cycles (default value after reset)
Note: In synchronous accesses, this value is not used, the address setup phase is always 1 Flash
clock period duration. In muxed mode, the minimum ADDSET value is 1.

13.6

NAND Flash controller
The FMC generates the appropriate signal timings to drive the following types of device:
•

8- and 16-bit NAND Flash memories

The NAND bank is configured through dedicated registers (Section 13.6.7). The
programmable memory parameters include access timings (shown in Table 82) and ECC
configuration.
Table 82. Programmable NAND Flash access parameters

13.6.1

Parameter

Function

Access mode

Unit

Min. Max.

Memory setup
time

Number of clock cycles (HCLK)
required to set up the address
before the command assertion

Read/Write

AHB clock cycle
(HCLK)

1

255

Memory wait

Minimum duration (in HCLK clock
cycles) of the command assertion

Read/Write

AHB clock cycle
(HCLK)

2

255

Memory hold

Number of clock cycles (HCLK)
during which the address must be
held (as well as the data if a write
access is performed) after the
command de-assertion

Read/Write

AHB clock cycle
(HCLK)

1

254

Memory
databus high-Z

Number of clock cycles (HCLK)
during which the data bus is kept
in high-Z state after a write
access has started

Write

AHB clock cycle
(HCLK)

1

255

External memory interface signals
The following tables list the signals that are typically used to interface NAND Flash memory.

Note:

The prefix “N” identifies the signals which are active low.

8-bit NAND Flash memory
Table 83. 8-bit NAND Flash

352/1709

FMC signal name

I/O

Function

A[17]

O

NAND Flash address latch enable (ALE) signal

A[16]

O

NAND Flash command latch enable (CLE) signal

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Table 83. 8-bit NAND Flash (continued)
FMC signal name

I/O

Function

D[7:0]

I/O

8-bit multiplexed, bidirectional address/data bus

NCE

O

Chip Select

NOE(= NRE)

O

Output enable (memory signal name: read enable, NRE)

NWE

O

Write enable

NWAIT/INT

I

NAND Flash ready/busy input signal to the FMC

Theoretically, there is no capacity limitation as the FMC can manage as many address
cycles as needed.

16-bit NAND Flash memory
Table 84. 16-bit NAND Flash
FMC signal name

I/O

Function

A[17]

O

NAND Flash address latch enable (ALE) signal

A[16]

O

NAND Flash command latch enable (CLE) signal

D[15:0]

I/O

16-bit multiplexed, bidirectional address/data bus

NCE

O

Chip Select

NOE(= NRE)

O

Output enable (memory signal name: read enable, NRE)

NWE

O

Write enable

NWAIT/INT

I

NAND Flash ready/busy input signal to the FMC

Theoretically, there is no capacity limitation as the FMC can manage as many address
cycles as needed.

RM0385 Rev 7

353/1709
383

Flexible memory controller (FMC)

13.6.2

RM0385

NAND Flash supported memories and transactions
Table 85 shows the supported devices, access modes and transactions. Transactions not
allowed (or not supported) by the NAND Flash controller are shown in gray.
Table 85. Supported memories and transactions
Device

NAND 8-bit

NAND 16-bit

13.6.3

AHB
Memory
Allowed/
data size data size not allowed

Mode

R/W

Comments

Asynchronous

R

8

8

Y

-

Asynchronous

W

8

8

Y

-

Asynchronous

R

16

8

Y

Split into 2 FMC accesses

Asynchronous

W

16

8

Y

Split into 2 FMC accesses

Asynchronous

R

32

8

Y

Split into 4 FMC accesses

Asynchronous

W

32

8

Y

Split into 4 FMC accesses

Asynchronous

R

8

16

Y

-

Asynchronous

W

8

16

N

-

Asynchronous

R

16

16

Y

-

Asynchronous

W

16

16

Y

-

Asynchronous

R

32

16

Y

Split into 2 FMC accesses

Asynchronous

W

32

16

Y

Split into 2 FMC accesses

Timing diagrams for NAND Flash memory
The NAND Flash memory bank is managed through a set of registers:
•

Control register: FMC_PCR

•

Interrupt status register: FMC_SR

•

ECC register: FMC_ECCR

•

Timing register for Common memory space: FMC_PMEM

•

Timing register for Attribute memory space: FMC_PATT

Each timing configuration register contains three parameters used to define number of
HCLK cycles for the three phases of any NAND Flash access, plus one parameter that
defines the timing for starting driving the data bus when a write access is performed.
Figure 53 shows the timing parameter definitions for common memory accesses, knowing
that Attribute memory space access timings are similar.

354/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Figure 53. NAND Flash controller waveforms for common memory access
HCLK
A[25:0]
NCEx
High

NREG,
NIOW,
NIOR
NWE,
NOE

MEMxSET
+1

MEMxWAIT + 1

MEMxHOLD

(1)
MEMxHIZ + 1

write_data
read_data

Valid

MS33733V3

1. NOE remains high (inactive) during write accesses. NWE remains high (inactive) during read accesses.
2. For write access, the hold phase delay is (MEMHOLD) HCLK cycles and for read access is
(MEMHOLD + 2) HCLK cycles.

13.6.4

NAND Flash operations
The command latch enable (CLE) and address latch enable (ALE) signals of the NAND
Flash memory device are driven by address signals from the FMC controller. This means
that to send a command or an address to the NAND Flash memory, the CPU has to perform
a write to a specific address in its memory space.
A typical page read operation from the NAND Flash device requires the following steps:
1.

Program and enable the corresponding memory bank by configuring the FMC_PCR
and FMC_PMEM (and for some devices, FMC_PATT, see Section 13.6.5: NAND Flash
prewait functionality) registers according to the characteristics of the NAND Flash
memory (PWID bits for the data bus width of the NAND Flash, PTYP = 1, PWAITEN =
0 or 1 as needed, see Section 13.4.2: NAND Flash memory address mapping for
timing configuration).

2.

The CPU performs a byte write to the common memory space, with data byte equal to
one Flash command byte (for example 0x00 for Samsung NAND Flash devices). The
LE input of the NAND Flash memory is active during the write strobe (low pulse on
NWE), thus the written byte is interpreted as a command by the NAND Flash memory.
Once the command is latched by the memory device, it does not need to be written
again for the following page read operations.

3.

The CPU can send the start address (STARTAD) for a read operation by writing four
bytes (or three for smaller capacity devices), STARTAD[7:0], STARTAD[16:9],
STARTAD[24:17] and finally STARTAD[25] (for 64 Mb x 8 bit NAND Flash memories) in
the common memory or attribute space. The ALE input of the NAND Flash device is
active during the write strobe (low pulse on NWE), thus the written bytes are
interpreted as the start address for read operations. Using the attribute memory space
makes it possible to use a different timing configuration of the FMC, which can be used

RM0385 Rev 7

355/1709
383

Flexible memory controller (FMC)

RM0385

to implement the prewait functionality needed by some NAND Flash memories (see
details in Section 13.6.5: NAND Flash prewait functionality).

13.6.5

4.

The controller waits for the NAND Flash memory to be ready (R/NB signal high), before
starting a new access to the same or another memory bank. While waiting, the
controller holds the NCE signal active (low).

5.

The CPU can then perform byte read operations from the common memory space to
read the NAND Flash page (data field + Spare field) byte by byte.

6.

The next NAND Flash page can be read without any CPU command or address write
operation. This can be done in three different ways:
–

by simply performing the operation described in step 5

–

a new random address can be accessed by restarting the operation at step 3

–

a new command can be sent to the NAND Flash device by restarting at step 2

NAND Flash prewait functionality
Some NAND Flash devices require that, after writing the last part of the address, the
controller waits for the R/NB signal to go low. (see Figure 54).
Figure 54. Access to non ‘CE don’t care’ NAND-Flash

1. CPU wrote byte 0x00 at address 0x7001 0000.
2. CPU wrote byte A7~A0 at address 0x7002 0000.
3. CPU wrote byte A16~A9 at address 0x7002 0000.
4. CPU wrote byte A24~A17 at address 0x7002 0000.
5. CPU wrote byte A25 at address 0x7802 0000: FMC performs a write access using FMC_PATT timing
definition, where ATTHOLD ≥ 7 (providing that (7+1) × HCLK = 112 ns > tWB max). This guarantees that
NCE remains low until R/NB goes low and high again (only requested for NAND Flash memories where
NCE is not don’t care).

356/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
When this functionality is required, it can be ensured by programming the MEMHOLD value
to meet the tWB timing. However any CPU read access to the NAND Flash memory has a
hold delay of (MEMHOLD + 2) HCLK cycles and CPU write access has a hold delay of
(MEMHOLD) HCLK cycles inserted between the rising edge of the NWE signal and the next
access.
To cope with this timing constraint, the attribute memory space can be used by
programming its timing register with an ATTHOLD value that meets the tWB timing, and by
keeping the MEMHOLD value at its minimum value. The CPU must then use the common
memory space for all NAND Flash read and write accesses, except when writing the last
address byte to the NAND Flash device, where the CPU must write to the attribute memory
space.

13.6.6

Computation of the error correction code (ECC)
in NAND Flash memory
The FMC NAND Card controller includes two error correction code computation hardware
blocks, one per memory bank. They reduce the host CPU workload when processing the
ECC by software.
These two ECC blocks are identical and associated with Bank 2 and Bank 3. As a
consequence, no hardware ECC computation is available for memories connected to Bank
4.
The ECC algorithm implemented in the FMC can perform 1-bit error correction and 2-bit
error detection per 256, 512, 1 024, 2 048, 4 096 or 8 192 bytes read or written from/to the
NAND Flash memory. It is based on the Hamming coding algorithm and consists in
calculating the row and column parity.
The ECC modules monitor the NAND Flash data bus and read/write signals (NCE and
NWE) each time the NAND Flash memory bank is active.
The ECC operates as follows:
•

When accessing NAND Flash memory bank 2 or bank 3, the data present on the
D[15:0] bus is latched and used for ECC computation.

•

When accessing any other address in NAND Flash memory, the ECC logic is idle, and
does not perform any operation. As a result, write operations to define commands or
addresses to the NAND Flash memory are not taken into account for ECC
computation.

Once the desired number of bytes has been read/written from/to the NAND Flash memory
by the host CPU, the FMC_ECCR registers must be read to retrieve the computed value.
Once read, they should be cleared by resetting the ECCEN bit to ‘0’. To compute a new data
block, the ECCEN bit must be set to one in the FMC_PCR registers.

RM0385 Rev 7

357/1709
383

Flexible memory controller (FMC)

RM0385

To perform an ECC computation:

13.6.7

1.

Enable the ECCEN bit in the FMC_PCR register.

2.

Write data to the NAND Flash memory page. While the NAND page is written, the ECC
block computes the ECC value.

3.

Read the ECC value available in the FMC_ECCR register and store it in a variable.

4.

Clear the ECCEN bit and then enable it in the FMC_PCR register before reading back
the written data from the NAND page. While the NAND page is read, the ECC block
computes the ECC value.

5.

Read the new ECC value available in the FMC_ECCR register.

6.

If the two ECC values are the same, no correction is required, otherwise there is an
ECC error and the software correction routine returns information on whether the error
can be corrected or not.

NAND Flash controller registers
NAND Flash control registers (FMC_PCR)
Address offset: 0x80
Reset value: 0x0000 0018

31

30

29

28

27

26

25

24

23

22

21

20

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

TAR[2:0]
rw

rw

11

10

9

TCLR[3:0]
rw

rw

rw

rw

8

7

6

Res.

Res.

ECCEN

rw

rw

5

4

PWID[1:0]
rw

rw

19

18

17

ECCPS[2:0]

TAR3

rw

rw

rw

3

2

1

PTYP PBKEN PWAITEN
rw

rw

rw

Bits 31:20 Reserved, must be kept at reset value.
Bits 19:17 ECCPS[2:0]: ECC page size.
Defines the page size for the extended ECC:
000: 256 bytes
001: 512 bytes
010: 1024 bytes
011: 2048 bytes
100: 4096 bytes
101: 8192 bytes
Bits 16:13 TAR[3:0]: ALE to RE delay.
Sets time from ALE low to RE low in number of AHB clock cycles (HCLK).
Time is: t_ar = (TAR + SET + 2) × THCLK where THCLK is the HCLK clock period
0000: 1 HCLK cycle (default)
1111: 16 HCLK cycles
Note: SET is MEMSET or ATTSET according to the addressed space.

358/1709

RM0385 Rev 7

16

rw
0
Res.

RM0385

Flexible memory controller (FMC)

Bits 12:9 TCLR[3:0]: CLE to RE delay.
Sets time from CLE low to RE low in number of AHB clock cycles (HCLK).
Time is t_clr = (TCLR + SET + 2) × THCLK where THCLK is the HCLK clock period
0000: 1 HCLK cycle (default)
1111: 16 HCLK cycles
Note: SET is MEMSET or ATTSET according to the addressed space.
Bits 8:7 Reserved, must be kept at reset value.
Bit 6 ECCEN: ECC computation logic enable bit
0: ECC logic is disabled and reset (default after reset),
1: ECC logic is enabled.
Bits 5:4 PWID[1:0]: Data bus width.
Defines the external memory device width.
00: 8 bits
01: 16 bits (default after reset).
10: reserved.
11: reserved.
Bit 3 PTYP: Memory type.
Defines the type of device attached to the corresponding memory bank:
0: Reserved, must be kept at reset value
1: NAND Flash (default after reset)
Bit 2 PBKEN: NAND Flash memory bank enable bit.
Enables the memory bank. Accessing a disabled memory bank causes an ERROR on AHB
bus
0: Corresponding memory bank is disabled (default after reset)
1: Corresponding memory bank is enabled
Bit 1 PWAITEN: Wait feature enable bit.
Enables the Wait feature for the NAND Flash memory bank:
0: disabled
1: enabled
Bit 0 Reserved, must be kept at reset value.

FIFO status and interrupt register (FMC_SR)
Address offset: 0x84
Reset value: 0x0000 0040
This register contains information about the FIFO status and interrupt. The FMC features a
FIFO that is used when writing to memories to transfer up to 16 words of data from the AHB.
This is used to quickly write to the FIFO and free the AHB for transactions to peripherals
other than the FMC, while the FMC is draining its FIFO into the memory. One of these
register bits indicates the status of the FIFO, for ECC purposes.
The ECC is calculated while the data are written to the memory. To read the correct ECC,
the software must consequently wait until the FIFO is empty.

RM0385 Rev 7

359/1709
383

Flexible memory controller (FMC)

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FEMPT

IFEN

ILEN

IREN

IFS

ILS

IRS

r

rw

rw

rw

rw

rw

rw

Bits 31:7 Reserved, must be kept at reset value.
Bit 6 FEMPT: FIFO empty.
Read-only bit that provides the status of the FIFO
0: FIFO not empty
1: FIFO empty
Bit 5 IFEN: Interrupt falling edge detection enable bit
0: Interrupt falling edge detection request disabled
1: Interrupt falling edge detection request enabled
Bit 4 ILEN: Interrupt high-level detection enable bit
0: Interrupt high-level detection request disabled
1: Interrupt high-level detection request enabled
Bit 3 IREN: Interrupt rising edge detection enable bit
0: Interrupt rising edge detection request disabled
1: Interrupt rising edge detection request enabled
Bit 2 IFS: Interrupt falling edge status
The flag is set by hardware and reset by software.
0: No interrupt falling edge occurred
1: Interrupt falling edge occurred
Note: If this bit is written by software to 1 it will be set.
Bit 1 ILS: Interrupt high-level status
The flag is set by hardware and reset by software.
0: No Interrupt high-level occurred
1: Interrupt high-level occurred
Bit 0 IRS: Interrupt rising edge status
The flag is set by hardware and reset by software.
0: No interrupt rising edge occurred
1: Interrupt rising edge occurred
Note: If this bit is written by software to 1 it will be set.

Common memory space timing register 2..4 (FMC_PMEM)
Address offset: Address: 0x88
Reset value: 0xFCFC FCFC
The FMC_PMEM read/write register contains the timing information for NAND Flash
memory bank. This information is used to access either the common memory space of the
NAND Flash for command, address write access and data read/write access.

360/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

31

30

29

28

rw

rw

rw

rw

15

14

13

12

27

26

25

24

23

22

21

rw

rw

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

5

4

MEMHIZ[7:0]

rw

rw

rw

rw

19

18

17

16

rw

rw

rw

rw

3

2

1

0

rw

rw

rw

MEMHOLD[7:0]

MEMWAIT[7:0]
rw

20

MEMSET[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 MEMHIZ[7:0]: Common memory x data bus Hi-Z time
Defines the number of HCLK clock cycles during which the data bus is kept Hi-Z after the
start of a NAND Flash write access to common memory space on socket. This is only valid
for write transactions:
0000 0000: 1 HCLK cycle
1111 1110: 255 HCLK cycles
1111 1111: reserved.
Bits 23:16 MEMHOLD[7:0]: Common memory hold time
Defines the number of HCLK clock cycles for write access and HCLK (+2) clock cycles for
read access during which the address is held (and data for write accesses) after the
command is deasserted (NWE, NOE), for NAND Flash read or write access to common
memory space on socket x:
0000 0000: reserved.
0000 0001: 1 HCLK cycle for write access / 3 HCLK cycles for read access
1111 1110: 254 HCLK cycles for write access / 256 HCLK cycles for read access
1111 1111: reserved.
Bits 15:8 MEMWAIT[7:0]: Common memory wait time
Defines the minimum number of HCLK (+1) clock cycles to assert the command (NWE,
NOE), for NAND Flash read or write access to common memory space on socket. The
duration of command assertion is extended if the wait signal (NWAIT) is active (low) at the
end of the programmed value of HCLK:
0000 0000: reserved
0000 0001: 2HCLK cycles (+ wait cycle introduced by deasserting NWAIT)
1111 1110: 255 HCLK cycles (+ wait cycle introduced by deasserting NWAIT)
1111 1111: reserved.
Bits 7:0 MEMSET[7:0]: Common memory x setup time
Defines the number of HCLK (+1) clock cycles to set up the address before the command
assertion (NWE, NOE), for NAND Flash read or write access to common memory space on
socket x:
0000 0000: 1 HCLK cycle
1111 1110: 255 HCLK cycles
1111 1111: reserved

Attribute memory space timing registers (FMC_PATT)
Address offset: 0x8C
Reset value: 0xFCFC FCFC
The FMC_PATT read/write register contains the timing information for NAND Flash memory
bank. It is used for 8-bit accesses to the attribute memory space of the NAND Flash for the
last address write access if the timing must differ from that of previous accesses (for
Ready/Busy management, refer to Section 13.6.5: NAND Flash prewait functionality).

RM0385 Rev 7

361/1709
383

Flexible memory controller (FMC)

31

30

29

28

rw

rw

rw

rw

15

14

13

12

27

RM0385

26

25

24

23

22

21

rw

rw

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

5

4

ATTHIZ[7:0]

rw

rw

rw

rw

19

18

17

16

rw

rw

rw

rw

3

2

1

0

rw

rw

rw

ATTHOLD[7:0]

ATTWAIT[7:0]
rw

20

ATTSET[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 ATTHIZ[7:0]: Attribute memory data bus Hi-Z time
Defines the number of HCLK clock cycles during which the data bus is kept in Hi-Z after the
start of a NAND Flash write access to attribute memory space on socket. Only valid for writ
transaction:
0000 0000: 0 HCLK cycle
1111 1110: 255 HCLK cycles
1111 1111: reserved.
Bits 23:16 ATTHOLD[7:0]: Attribute memory hold time
Defines the number of HCLK clock cycles for write access and HCLK (+2) clock cycles for
read access during which the address is held (and data for write access) after the command
deassertion (NWE, NOE), for NAND Flash read or write access to attribute memory space
on socket:
0000 0000: reserved
0000 0001: 1 HCLK cycle for write access / 3 HCLK cycles for read access
1111 1110: 254 HCLK cycles for write access / 256 HCLK cycles for read access
1111 1111: reserved.
Bits 15:8 ATTWAIT[7:0]: Attribute memory wait time
Defines the minimum number of HCLK (+1) clock cycles to assert the command (NWE,
NOE), for NAND Flash read or write access to attribute memory space on socket x. The
duration for command assertion is extended if the wait signal (NWAIT) is active (low) at the
end of the programmed value of HCLK:
0000 0000: reserved
0000 0001: 2 HCLK cycles (+ wait cycle introduced by deassertion of NWAIT)
1111 1110: 255 HCLK cycles (+ wait cycle introduced by deasserting NWAIT)
1111 1111: reserved.
Bits 7:0 ATTSET[7:0]: Attribute memory setup time
Defines the number of HCLK (+1) clock cycles to set up address before the command
assertion (NWE, NOE), for NAND Flash read or write access to attribute memory space on
socket:
0000 0000: 1 HCLK cycle
1111 1110: 255 HCLK cycles
1111 1111: reserved.

362/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

ECC result registers (FMC_ECCR)
Address offset: 0x94
Reset value: 0x0000 0000
This register contain the current error correction code value computed by the ECC
computation modules of the FMC NAND controller. When the CPU reads the data from a
NAND Flash memory page at the correct address (refer to Section 13.6.6: Computation of
the error correction code (ECC) in NAND Flash memory), the data read/written from/to the
NAND Flash memory are processed automatically by the ECC computation module. When
X bytes have been read (according to the ECCPS field in the FMC_PCR registers), the CPU
must read the computed ECC value from the FMC_ECC registers. It then verifies if these
computed parity data are the same as the parity value recorded in the spare area, to
determine whether a page is valid, and, to correct it otherwise. The FMC_ECCR register
should be cleared after being read by setting the ECCEN bit to ‘0’. To compute a new data
block, the ECCEN bit must be set to ’1’.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ECC[31:16]

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

ECC[15:0]

r

r

r

r

r

r

r

r

r

Bits 31:0 ECC[31:0]: ECC result
This field contains the value computed by the ECC computation logic. Table 86 describes
the contents of these bit fields.

Table 86. ECC result relevant bits
ECCPS[2:0]

Page size in bytes

ECC bits

000

256

ECC[21:0]

001

512

ECC[23:0]

010

1024

ECC[25:0]

011

2048

ECC[27:0]

100

4096

ECC[29:0]

101

8192

ECC[31:0]

RM0385 Rev 7

363/1709
383

Flexible memory controller (FMC)

RM0385

13.7

SDRAM controller

13.7.1

SDRAM controller main features
The main features of the SDRAM controller are the following:

13.7.2

•

Two SDRAM banks with independent configuration

•

8-bit, 16-bit, 32-bit data bus width

•

13-bits Address Row, 11-bits Address Column, 4 internal banks: 4x16Mx32bit
(256 MB), 4x16Mx16bit (128 MB), 4x16Mx8bit (64 MB)

•

Word, half-word, byte access

•

SDRAM clock can be HCLK/2 or HCLK/3

•

Automatic row and bank boundary management

•

Multibank ping-pong access

•

Programmable timing parameters

•

Automatic Refresh operation with programmable Refresh rate

•

Self-refresh mode

•

Power-down mode

•

SDRAM power-up initialization by software

•

CAS latency of 1,2,3

•

Cacheable Read FIFO with depth of 6 lines x32-bit (6 x14-bit address tag)

SDRAM External memory interface signals
At startup, the SDRAM I/O pins used to interface the FMC SDRAM controller with the
external SDRAM devices must configured by the user application. The SDRAM controller
I/O pins which are not used by the application, can be used for other purposes.
Table 87. SDRAM signals

364/1709

SDRAM signal

I/O
type

Description

Alternate function

SDCLK

O

SDRAM clock

-

SDCKE[1:0]

O

SDCKE0: SDRAM Bank 1 Clock Enable
SDCKE1: SDRAM Bank 2 Clock Enable

-

SDNE[1:0]

O

SDNE0: SDRAM Bank 1 Chip Enable
SDNE1: SDRAM Bank 2 Chip Enable

-

A[12:0]

O

Address

FMC_A[12:0]

D[31:0]

I/O

Bidirectional data bus

FMC_D[31:0]

BA[1:0]

O

Bank Address

FMC_A[15:14]

NRAS

O

Row Address Strobe

-

NCAS

O

Column Address Strobe

-

SDNWE

O

Write Enable

-

NBL[3:0]

O

Output Byte Mask for write accesses
(memory signal name: DQM[3:0]

FMC_NBL[3:0]

RM0385 Rev 7

RM0385

13.7.3

Flexible memory controller (FMC)

SDRAM controller functional description
All SDRAM controller outputs (signals, address and data) change on the falling edge of the
memory clock (FMC_SDCLK).

SDRAM initialization
The initialization sequence is managed by software. If the two banks are used, the
initialization sequence must be generated simultaneously to Bank 1and Bank 2 by setting
the Target Bank bits CTB1 and CTB2 in the FMC_SDCMR register:
1.

Program the memory device features into the FMC_SDCRx register. The SDRAM
clock frequency, RBURST and RPIPE must be programmed in the FMC_SDCR1
register.

2.

Program the memory device timing into the FMC_SDTRx register. The TRP and TRC
timings must be programmed in the FMC_SDTR1 register.

3.

Set MODE bits to ‘001’ and configure the Target Bank bits (CTB1 and/or CTB2) in the
FMC_SDCMR register to start delivering the clock to the memory (SDCKE is driven
high).

4.

Wait during the prescribed delay period. Typical delay is around 100 μs (refer to the
SDRAM datasheet for the required delay after power-up).

5.

Set MODE bits to ‘010’ and configure the Target Bank bits (CTB1 and/or CTB2) in the
FMC_SDCMR register to issue a “Precharge All” command.

6.

Set MODE bits to ‘011’, and configure the Target Bank bits (CTB1 and/or CTB2) as well
as the number of consecutive Auto-refresh commands (NRFS) in the FMC_SDCMR
register. Refer to the SDRAM datasheet for the number of Auto-refresh commands that
should be issued. Typical number is 8.

7.

Configure the MRD field according to the SDRAM device, set the MODE bits to '100',
and configure the Target Bank bits (CTB1 and/or CTB2) in the FMC_SDCMR register
to issue a "Load Mode Register" command in order to program the SDRAM device.
In particular:
a)

the CAS latency must be selected following configured value in FMC_SDCR1/2
registers

b)

the Burst Length (BL) of 1 must be selected by configuring the M[2:0] bits to 000 in
the mode register. Refer to SDRAM device datasheet.

If the Mode Register is not the same for both SDRAM banks, this step has to be
repeated twice, once for each bank, and the Target Bank bits set accordingly.
8.

Program the refresh rate in the FMC_SDRTR register
The refresh rate corresponds to the delay between refresh cycles. Its value must be
adapted to SDRAM devices.

9.

For mobile SDRAM devices, to program the extended mode register it should be done
once the SDRAM device is initialized: First, a dummy read access should be performed
while BA1=1 and BA=0 (refer to SDRAM address mapping section for BA[1:0] address
mapping) in order to select the extended mode register instead of the load mode
register and then program the needed value.

At this stage the SDRAM device is ready to accept commands. If a system reset occurs
during an ongoing SDRAM access, the data bus might still be driven by the SDRAM device.
Therefor the SDRAM device must be first reinitialized after reset before issuing any new
access by the NOR Flash/PSRAM/SRAM or NAND Flash controller.

RM0385 Rev 7

365/1709
383

Flexible memory controller (FMC)
Note:

RM0385

If two SDRAM devices are connected to the FMC, all the accesses performed at the same
time to both devices by the Command Mode register (Load Mode Register command) are
issued using the timing parameters configured for SDRAM Bank 1 (TMRD andTRAS
timings) in the FMC_SDTR1 register.

SDRAM controller write cycle
The SDRAM controller accepts single and burst write requests and translates them into
single memory accesses. In both cases, the SDRAM controller keeps track of the active row
for each bank to be able to perform consecutive write accesses to different banks (Multibank
ping-pong access).
Before performing any write access, the SDRAM bank write protection must be disabled by
clearing the WP bit in the FMC_SDCRx register.
Figure 55. Burst write SDRAM access waveforms
TRCD = 3

SDNE

SDCLK
A[12:0]

Row n

Cola Colb Colc Cold Cole Colf Cog Colh Coli Colj Colk Coll

NRAS

NCAS
SDNWE

DATA[31:0]

Dna

Dnb Dnc

Dnd Dne Dnf

Dng Dnh Dni

Dnj

Dnk Dnl
MS30448V3

The SDRAM controller always checks the next access.
•

If the next access is in the same row or in another active row, the write operation is
carried out,

•

if the next access targets another row (not active), the SDRAM controller generates a
precharge command, activates the new row and initiates a write command.

SDRAM controller read cycle
The SDRAM controller accepts single and burst read requests and translates them into
single memory accesses. In both cases, the SDRAM controller keeps track of the active row
in each bank to be able to perform consecutive read accesses in different banks (Multibank
ping-pong access).

366/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Figure 56. Burst read SDRAM access
TRCD = 3

CAS latency = 2

SDNE

SDCLK
A[12:0]

Row n

Cola Colb

Colc

Cold Cole Colf

NRAS

NCAS

NWE

Dna

DATA[31:0]

Dnb

Dnc

Dnd

Dne

Dnf
MS30449V3

The FMC SDRAM controller features a Cacheable read FIFO (6 lines x 32 bits). It is used to
store data read in advance during the CAS latency period and the RPIPE delay following the
below formula. The RBURST bit must be set in the FMC_SDCR1 register to anticipate the
next read access.
Number for anticipated data = CAS latency + 1 + (RPIPE delay)/2
Examples:
•

CAS latency = 3, RPIPE delay = 0: Four data (not committed) are stored in the FIFO.

•

CAS latency = 3, RPIPE delay = 2: Five data (not committed) are stored in the FIFO.

The read FIFO features a 14-bit address tag to each line to identify its content: 11 bits for the
column address, 2 bits to select the internal bank and the active row, and 1 bit to select the
SDRAM device
When the end of the row is reached in advance during an AHB burst read, the data read in
advance (not committed) are not stored in the read FIFO. For single read access, data are
correctly stored in the FIFO.
Each time a read request occurs, the SDRAM controller checks:
•

If the address matches one of the address tags, data are directly read from the FIFO
and the corresponding address tag/ line content is cleared and the remaining data in
the FIFO are compacted to avoid empty lines.

•

Otherwise, a new read command is issued to the memory and the FIFO is updated with
new data. If the FIFO is full, the older data are lost.

RM0385 Rev 7

367/1709
383

Flexible memory controller (FMC)

RM0385

Figure 57. Logic diagram of Read access with RBURST bit set (CAS=1, RPIPE=0)
1st Read access: Requested data is not in the FIFO
FMC SDRAM Controller

AXI Master

read request@0x00
Data 1

SDRAM
Device
(CAS = 1)

6 lines FIFO

@0x04 Data 2
@0x08 Data 3
...
...
Add. Tag read FIFO

Data stored in FIFO
in advance during
the CAS latency period

2nd Read access : Requested data was previously stored in the FIFO
Address matches with
one of the address tags

AXI Master

FMC SDRAM Controller
read request@0x04
Data 2

SDRAM
Device
(CAS = 1)

6 lines FIFO

@0x04 Data 2
@0x08 Data 3
...
...
Add. Tag read FIFO

Data read from FIFO

MS30445V2

During a write access or a Precharge command, the read FIFO is flushed and ready to be
filled with new data.
After the first read request, if the current access was not performed to a row boundary, the
SDRAM controller anticipates the next read access during the CAS latency period and the
RPIPE delay (if configured). This is done by incrementing the memory address. The
following condition must be met:
•

368/1709

RBURST control bit should be set to ‘1’ in the FMC_SDCR1 register.

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
The address management depends on the next AHB request:
•

Next AHB request is sequential (AHB Burst)
In this case, the SDRAM controller increments the address.

•

Next AHB request is not sequential
–

If the new read request targets the same row or another active row, the new
address is passed to the memory and the master is stalled for the CAS latency
period, waiting for the new data from memory.

–

If the new read request does not target an active row, the SDRAM controller
generates a Precharge command, activates the new row, and initiates a read
command.

If the RURST is reset, the read FIFO is not used.

Row and bank boundary management
When a read or write access crosses a row boundary, if the next read or write access is
sequential and the current access was performed to a row boundary, the SDRAM controller
executes the following operations:
1.

Precharge of the active row,

2.

Activation of the new row

3.

Start of a read/write command.

At a row boundary, the automatic activation of the next row is supported for all columns and
data bus width configurations.
If necessary, the SDRAM controller inserts additional clock cycles between the following
commands:
•

Between Precharge and Active commands to match TRP parameter (only if the next
access is in a different row in the same bank),

•

Between Active and Read commands to match the TRCD parameter.

These parameters are defined into the FMC_SDTRx register.
Refer to Figure 55 and Figure 56 for read and burst write access crossing a row boundary.

RM0385 Rev 7

369/1709
383

Flexible memory controller (FMC)

RM0385

Figure 58. Read access crossing row boundary
TRP = 3

TRCD = 3 CAS latency = 2

SDNE

SDCLK
Row n
A[12:0]

Col a

Row n +1

Col a Col b

NRAS

NCAS

NWE

Data[31:0]

Dna

Dn+1 a
Precharge

Activate Row

Read Command
MS30446V2

Figure 59. Write access crossing row boundary
TRP = 3

TRCD = 3

SDNE

SDCLK
A[12:0]

Cna

Colb

Row n+1

Cola

Colb

NRAS

NCAS

NWE

Data[31:0]

Dna

Dn+1a

Dnb
Precharge

Activate Row

Dn+1b

Write command
MS30447V2

370/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
If the next access is sequential and the current access crosses a bank boundary, the
SDRAM controller activates the first row in the next bank and initiates a new read/write
command. Two cases are possible:
•

If the current bank is not the last one, the active row in the new bank must be
precharged.At a bank boundary, the automatic activation of the next row is supported
for all rows/columns and data bus width configuration.

•

If the current bank is the last one, the automatic activation of the next row is supported
only when addressing 13-bit rows, 11-bit columns, 4 internal banks and 32-bit data bus
SDRAM devices. Otherwise, the SDRAM address range is violated and an AHB error is
generated.

•

In case of 13-bit row address, 11-bit column address, 4 internal banks and bus width
32-bit SDRAM memories, at boundary bank, the SDRAM controller continues to
read/write from the second SDRAM device (assuming it has been initialized):
a)

The SDRAM controller activates the first row (after precharging the active row, if
there is already an active row in the first internal bank, and initiates a new
read/write command.

b)

If the first row is already activated, the SDRAM controller just initiates a read/write
command.

SDRAM controller refresh cycle
The Auto-refresh command is used to refresh the SDRAM device content. The SDRAM
controller periodically issues auto-refresh commands. An internal counter is loaded with the
COUNT value in the register FMC_SDRTR. This value defines the number of memory clock
cycles between the refresh cycles (refresh rate). When this counter reaches zero, an
internal pulse is generated.
If a memory access is ongoing, the auto-refresh request is delayed. However, if the memory
access and the auto-refresh requests are generated simultaneously, the auto-refresh
request takes precedence.
If the memory access occurs during an auto-refresh operation, the request is buffered and
processed when the auto-refresh is complete.
If a new auto-refresh request occurs while the previous one was not served, the RE
(Refresh Error) bit is set in the Status register. An Interrupt is generated if it has been
enabled (REIE = ‘1’).
If SDRAM lines are not in idle state (not all row are closed), the SDRAM controller generates
a PALL (Precharge ALL) command before the auto-refresh.
If the Auto-refresh command is generated by the FMC_SDCMR Command Mode register
(Mode bits = ‘011’), a PALL command (Mode bits =’ 010’) must be issued first.

13.7.4

Low-power modes
Two low-power modes are available:
•

Self-refresh mode
The auto-refresh cycles are performed by the SDRAM device itself to retain data
without external clocking.

•

Power-down mode
The auto-refresh cycles are performed by the SDRAM controller.

RM0385 Rev 7

371/1709
383

Flexible memory controller (FMC)

RM0385

Self-refresh mode
This mode is selected by setting the MODE bits to ‘101’ and by configuring the Target Bank
bits (CTB1 and/or CTB2) in the FMC_SDCMR register.
The SDRAM clock stops running after a TRAS delay and the internal refresh timer stops
counting only if one of the following conditions is met:
•

A Self-refresh command is issued to both devices

•

One of the devices is not activated (SDRAM bank is not initialized).

Before entering Self-Refresh mode, the SDRAM controller automatically issues a PALL
command.
If the Write data FIFO is not empty, all data are sent to the memory before activating the
Self-refresh mode and the BUSY status flag remains set.
In Self-refresh mode, all SDRAM device inputs become don’t care except for SDCKE which
remains low.
The SDRAM device must remain in Self-refresh mode for a minimum period of time of
TRAS and can remain in Self-refresh mode for an indefinite period beyond that. To
guarantee this minimum period, the BUSY status flag remains high after the Self-refresh
activation during a TRAS delay.
As soon as an SDRAM device is selected, the SDRAM controller generates a sequence of
commands to exit from Self-refresh mode. After the memory access, the selected device
remains in Normal mode.
To exit from Self-refresh, the MODE bits must be set to ‘000’ (Normal mode) and the Target
Bank bits (CTB1 and/or CTB2) must be configured in the FMC_SDCMR register.

372/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)
Figure 60. Self-refresh mode
T0

T1

T2

Tn+1

T0+1

T0+2

SDCLK

tRAS(min)
SDCKE

COMMAND

PRECHARGE

AUTO
REFRESH

NOP

NOP

or COMMAND
INHERIT

AUTO
REFRESH

DOM/
DOML/DOMU

A0- A9
A11, A12

ALL
BANKS

A10

Data[31:0] Hi-Z
tRP
Precharge all
active banks

tXSR
Exit Self-refresh mode
(restart refresh timebase)
CLK stable prior to existing
Self-refresh mode

Enter Self-refresh mode

MS30450V1

Power-down mode
This mode is selected by setting the MODE bits to ‘110’ and by configuring the Target Bank
bits (CTB1 and/or CTB2) in the FMC_SDCMR register.

RM0385 Rev 7

373/1709
383

Flexible memory controller (FMC)

RM0385
Figure 61. Power-down mode

SDCLK

SDCKE

COMMAND

NOP

NOP

ACTIVE

tRCD
All banks idle

Input buffers gated off
tRAS

Enter Power-down

Exit Power-down

tRC

MS30451V1

If the Write data FIFO is not empty, all data are sent to the memory before activating the
Power-down mode.
As soon as an SDRAM device is selected, the SDRAM controller exits from the Power-down
mode. After the memory access, the selected SDRAM device remains in Normal mode.
During Power-down mode, all SDRAM device input and output buffers are deactivated
except for the SDCKE which remains low.
The SDRAM device cannot remain in Power-down mode longer than the refresh period and
cannot perform the Auto-refresh cycles by itself. Therefore, the SDRAM controller carries
out the refresh operation by executing the operations below:
1.

Exit from Power-down mode and drive the SDCKE high

2.

Generate the PALL command only if a row was active during Power-down mode

3.

Generate the auto-refresh command

4.

Drive SDCKE low again to return to Power-down mode.

To exit from Power-down mode, the MODE bits must be set to ‘000’ (Normal mode) and the
Target Bank bits (CTB1 and/or CTB2) must be configured in the FMC_SDCMR register.

13.7.5

SDRAM controller registers
SDRAM Control registers 1,2 (FMC_SDCR1,2)
Address offset: 0x140+ 4* (x – 1), x = 1,2
Reset value: 0x0000 02D0
This register contains the control parameters for each SDRAM memory bank

374/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

6

5

4

3

2

1

Res.

RPIPE[1:0]
rw

rw

RBURST
rw

SDCLK
rw

rw

WP
rw

7
CAS

rw

NB
rw

rw

MWID
rw

NR
rw

rw

0
NC

rw

rw

rw

Bits 31:15 Reserved, must be kept at reset value.
Bits 14:13 RPIPE[1:0]: Read pipe
These bits define the delay, in HCLK clock cycles, for reading data after CAS latency.
00: No HCLK clock cycle delay
01: One HCLK clock cycle delay
10: Two HCLK clock cycle delay
11: reserved.
Note: The corresponding bits in the FMC_SDCR2 register is read only.
Bit 12 RBURST: Burst read
This bit enables burst read mode. The SDRAM controller anticipates the next read commands
during the CAS latency and stores data in the Read FIFO.
0: single read requests are not managed as bursts
1: single read requests are always managed as bursts
Note: The corresponding bit in the FMC_SDCR2 register is don’t care.
Bits 11:10 SDCLK[1:0]: SDRAM clock configuration
These bits define the SDRAM clock period for both SDRAM banks and allow disabling the clock
before changing the frequency. In this case the SDRAM must be re-initialized.
00: SDCLK clock disabled
01: reserved
10: SDCLK period = 2 x HCLK periods
11: SDCLK period = 3 x HCLK periods
Note: The corresponding bits in the FMC_SDCR2 register are don’t care.
Bit 9 WP: Write protection
This bit enables write mode access to the SDRAM bank.
0: Write accesses allowed
1: Write accesses ignored
Bits 8:7 CAS[1:0]: CAS Latency
This bits sets the SDRAM CAS latency in number of memory clock cycles
00: reserved.
01: 1 cycle
10: 2 cycles
11: 3 cycles
Bit 6 NB: Number of internal banks
This bit sets the number of internal banks.
0: Two internal Banks
1: Four internal Banks

RM0385 Rev 7

375/1709
383

Flexible memory controller (FMC)

RM0385

Bits 5:4 MWID[1:0]: Memory data bus width.
These bits define the memory device width.
00: 8 bits
01: 16 bits
10: 32 bits
11: reserved.
Bits 3:2 NR[1:0]: Number of row address bits
These bits define the number of bits of a row address.
00: 11 bit
01: 12 bits
10: 13 bits
11: reserved.
Bits 1:0 NC[1:0]: Number of column address bits
These bits define the number of bits of a column address.
00: 8 bits
01: 9 bits
10: 10 bits
11: 11 bits.

Note:

Before modifying the RBURST or RPIPE settings or disabling the SDCLK clock, the user
must first send a PALL command to make sure ongoing operations are complete.

SDRAM Timing registers 1,2 (FMC_SDTR1,2)
Address offset: 0x148 + 4 * (x – 1), x = 1,2
Reset value: 0x0FFF FFFF
This register contains the timing parameters of each SDRAM bank
31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

27

26

rw

rw

11

10

rw

24

23

22

rw

rw

rw

rw

9

8

7

6

TRCD

TRC
rw

25

rw

rw

rw

20

19

18

rw

rw

rw

rw

5

4

3

2

TRP

TRAS
rw

21

rw

rw

rw

16

rw

rw

1

0

rw

rw

TWR

TXSR
rw

17

TMRD
rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 TRCD[3:0]: Row to column delay
These bits define the delay between the Activate command and a Read/Write command in number
of memory clock cycles.
0000: 1 cycle.
0001: 2 cycles
....
1111: 16 cycles

376/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

Bits 23:20 TRP[3:0]: Row precharge delay
These bits define the delay between a Precharge command and another command in number of
memory clock cycles. The TRP timing is only configured in the FMC_SDTR1 register. If two
SDRAM devices are used, the TRP must be programmed with the timing of the slowest device.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Note: The corresponding bits in the FMC_SDTR2 register are don’t care.
Bits 19:16 TWR[3:0]: Recovery delay
These bits define the delay between a Write and a Precharge command in number of memory clock
cycles.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Note: TWR must be programmed to match the write recovery time (tWR) defined in the SDRAM
datasheet, and to guarantee that:
TWR ≥ TRAS - TRCD and TWR ≥TRC - TRCD - TRP
Example: TRAS= 4 cycles, TRCD= 2 cycles. So, TWR >= 2 cycles. TWR must be
programmed to 0x1.
If two SDRAM devices are used, the FMC_SDTR1 and FMC_SDTR2 must be programmed
with the same TWR timing corresponding to the slowest SDRAM device.
Bits 15:12 TRC[3:0]: Row cycle delay
These bits define the delay between the Refresh command and the Activate command, as well as
the delay between two consecutive Refresh commands. It is expressed in number of memory clock
cycles. The TRC timing is only configured in the FMC_SDTR1 register. If two SDRAM devices are
used, the TRC must be programmed with the timings of the slowest device.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Note: TRC must match the TRC and TRFC (Auto Refresh period) timings defined in the SDRAM
device datasheet.
Note: The corresponding bits in the FMC_SDTR2 register are don’t care.
Bits 11:8 TRAS[3:0]: Self refresh time
These bits define the minimum Self-refresh period in number of memory clock cycles.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Bits 7:4 TXSR[3:0]: Exit Self-refresh delay
These bits define the delay from releasing the Self-refresh command to issuing the Activate
command in number of memory clock cycles.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles
Note: If two SDRAM devices are used, the FMC_SDTR1 and FMC_SDTR2 must be programmed
with the same TXSR timing corresponding to the slowest SDRAM device.

RM0385 Rev 7

377/1709
383

Flexible memory controller (FMC)

RM0385

Bits 3:0 TMRD[3:0]: Load Mode Register to Active
These bits define the delay between a Load Mode Register command and an Active or Refresh
command in number of memory clock cycles.
0000: 1 cycle
0001: 2 cycles
....
1111: 16 cycles

Note:

If two SDRAM devices are connected, all the accesses performed simultaneously to both
devices by the Command Mode register (Load Mode Register command) are issued using
the timing parameters configured for Bank 1 (TMRD and TRAS timings) in the FMC_SDTR1
register.
The TRP and TRC timings are only configured in the FMC_SDTR1 register. If two SDRAM
devices are used, the TRP and TRC timings must be programmed with the timings of the
slowest device.

SDRAM Command Mode register (FMC_SDCMR)
Address offset: 0x150
Reset value: 0x0000 0000
This register contains the command issued when the SDRAM device is accessed. This
register is used to initialize the SDRAM device, and to activate the Self-refresh and the
Power-down modes. As soon as the MODE field is written, the command will be issued only
to one or to both SDRAM banks according to CTB1 and CTB2 command bits. This register
is the same for both SDRAM banks.
31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
rw

rw

15

14

13

12

11

10

9

8

7

6

5

4
CTB1

CTB2

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

MRD
rw

21

20

19

18

17

16

rw

rw

rw

rw

3

2

1

0

MRD

NRFS

MODE
rw

rw

rw

Bits 31:22 Reserved, must be kept at reset value.
Bits 21:9 MRD[12:0]: Mode Register definition
This 13-bit field defines the SDRAM Mode Register content. The Mode Register is programmed
using the Load Mode Register command.
Bits 8:5 NRFS[3:0]: Number of Auto-refresh
These bits define the number of consecutive Auto-refresh commands issued when MODE = ‘011’.
0000: 1 Auto-refresh cycle
0001: 2 Auto-refresh cycles
....
1110: 15 Auto-refresh cycles
1111: 16 Auto-refresh cycles
Bit 4 CTB1: Command Target Bank 1
This bit indicates whether the command will be issued to SDRAM Bank 1 or not.
0: Command not issued to SDRAM Bank 1
1: Command issued to SDRAM Bank 1

378/1709

RM0385 Rev 7

RM0385

Flexible memory controller (FMC)

Bit 3 CTB2: Command Target Bank 2
This bit indicates whether the command will be issued to SDRAM Bank 2 or not.
0: Command not issued to SDRAM Bank 2
1: Command issued to SDRAM Bank 2
Bits 2:0 MODE[2:0]: Command mode
These bits define the command issued to the SDRAM device.
000: Normal Mode
001: Clock Configuration Enable
010: PALL (“All Bank Precharge”) command
011: Auto-refresh command
100: Load Mode Register
101: Self-refresh command
110: Power-down command
111: Reserved
Note: When a command is issued, at least one Command Target Bank bit ( CTB1 or CTB2) must be
set otherwise the command will be ignored.
Note: If two SDRAM banks are used, the Auto-refresh and PALL command must be issued
simultaneously to the two devices with CTB1 and CTB2 bits set otherwise the command will
be ignored.
Note: If only one SDRAM bank is used and a command is issued with it’s associated CTB bit set, the
other CTB bit of the the unused bank must be kept to 0.

SDRAM Refresh Timer register (FMC_SDRTR)
Address offset:0x154
Reset value: 0x0000 0000
This register sets the refresh rate in number of SDCLK clock cycles between the refresh
cycles by configuring the Refresh Timer Count value.
Refresh rate = ( COUNT + 1 ) × SDRAM clock frequency
COUNT = ( SDRAM refresh period ⁄ Number of rows ) – 20

Example
Refresh rate = 64 ms ⁄ ( 8196rows ) = 7.81μs
where 64 ms is the SDRAM refresh period.
7.81μs × 60MHz = 468.6
The refresh rate must be increased by 20 SDRAM clock cycles (as in the above example) to
obtain a safe margin if an internal refresh request occurs when a read request has been
accepted. It corresponds to a COUNT value of ‘0000111000000’ (448).
This 13-bit field is loaded into a timer which is decremented using the SDRAM clock. This
timer generates a refresh pulse when zero is reached. The COUNT value must be set at
least to 41 SDRAM clock cycles.

RM0385 Rev 7

379/1709
383

Flexible memory controller (FMC)

RM0385

As soon as the FMC_SDRTR register is programmed, the timer starts counting. If the value
programmed in the register is ’0’, no refresh is carried out. This register must not be
reprogrammed after the initialization procedure to avoid modifying the refresh rate.
Each time a refresh pulse is generated, this 13-bit COUNT field is reloaded into the counter.
If a memory access is in progress, the Auto-refresh request is delayed. However, if the
memory access and Auto-refresh requests are generated simultaneously, the Auto-refresh
takes precedence. If the memory access occurs during a refresh operation, the request is
buffered to be processed when the refresh is complete.
This register is common to SDRAM bank 1 and bank 2.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

Res.

REIE
rw

COUNT
rw

rw

rw

rw

rw

rw

rw

0
CRE

rw

rw

rw

rw

rw

rw

w

Bits 31: 15 Reserved, must be kept at reset value.
Bit 14 REIE: RES Interrupt Enable
0: Interrupt is disabled
1: An Interrupt is generated if RE = 1
Bits 13:1 COUNT[12:0]: Refresh Timer Count
This 13-bit field defines the refresh rate of the SDRAM device. It is expressed in number of memory
clock cycles. It must be set at least to 41 SDRAM clock cycles (0x29).
Refresh rate = (COUNT + 1) x SDRAM frequency clock
COUNT = (SDRAM refresh period / Number of rows) - 20
Bit 0 CRE: Clear Refresh error flag
This bit is used to clear the Refresh Error Flag (RE) in the Status Register.
0: no effect
1: Refresh Error flag is cleared

Note:

The programmed COUNT value must not be equal to the sum of the following timings:
TWR+TRP+TRC+TRCD+4 memory clock cycles .

SDRAM Status register (FMC_SDSR)
Address offset: 0x158
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

4

3

2

1

15

14

13

12

11

10

9

8

7

6

5

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BUSY
r

Bits 31:5 Reserved, must be kept at reset value.

380/1709

RM0385 Rev 7

MODES2

MODES1

r

r

r

r

0
RE
r

RM0385

Flexible memory controller (FMC)

Bit 5 BUSY: Busy status
This bit defines the status of the SDRAM controller after a Command Mode request
0: SDRAM Controller is ready to accept a new request
1; SDRAM Controller is not ready to accept a new request
Bits 4:3 MODES2[1:0]: Status Mode for Bank 2
This bit defines the Status Mode of SDRAM Bank 2.
00: Normal Mode
01: Self-refresh mode
10: Power-down mode
Bits 2:1 MODES1[1:0]: Status Mode for Bank 1
This bit defines the Status Mode of SDRAM Bank 1.
00: Normal Mode
01: Self-refresh mode
10: Power-down mode
Bit 0 RE: Refresh error flag
0: No refresh error has been detected
1: A refresh error has been detected
An interrupt is generated if REIE = 1 and RE = 1

RM0385 Rev 7

381/1709
383

Flexible memory controller (FMC)

13.8

RM0385

FMC register map

Reset value

382/1709

0

1

CPSIZE
[2:0]

FACCEN

WAITEN

WREN

WAITCFG

WAITPOL

BURSTEN

0

1

1

0

0

0

1

CPSIZE
[2:0]

WAITEN

WREN

WAITCFG

WAITPOL

BURSTEN

FACCEN

0

0

1

1

0

0

0

0

0

0

1

1

1

1

1

1

1

1

1

1

1

1

DATLAT[3:0]

CLKDIV[3:0] BUSTURN[3:0]

1

1

1

1

1

1

1

1

1

1

1

1

DATLAT[3:0]

CLKDIV[3:0] BUSTURN[3:0]

1

1

1

1

1

DATLAT[3:0]

CLKDIV[3:0] BUSTURN[3:0]

1

1

1

1

1

1

1

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

1

Res.

Res.

Res.

Res.

Res.

Res.

1

1

1

1

1

1

1

1

1

1

1

RM0385 Rev 7

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

MWID MTYP
[1:0] [1:0]
0

1

0

MWID MTYP
[1:0] [1:0]

1

0

0

0

1

1

0

0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

ADDHLD[3:0] ADDSET[3:0]

1

1

1

1

1

1

1

1

1

1

ADDHLD[3:0] ADDSET[3:0]

1

1

DATAST[7:0]

1

0

0

ADDHLD[3:0] ADDSET[3:0]

DATAST[7:0]

1

1

1

ADDHLD[3:0] ADDSET[3:0]

DATAST[7:0]

1

Res.

Res.
1

DATAST[7:0]

BUSTURN[3:0]

1

1

1

0

0

ADDHLD[3:0] ADDSET[3:0]

DATAST[7:0]

BUSTURN[3:0]

1

Res.

1

DATAST[7:0]

Res.

EXTMOD

0

0

Res.

ASYNCWAIT

0

0

MBKEN

BURSTEN

0

MUXEN

WAITPOL

0

MBKEN

WAITCFG

1

MWID MTYP
[1:0] [1:0]

MUXEN

WREN

1

1

1

MBKEN

FACCEN

WAITEN

0

Res.

EXTMOD

0

0

Res.

ASYNCWAIT

0

0

1

1

MUXEN

BURSTEN

CPSIZE
[2:0]

0

0

MBKEN

WAITPOL

1

MWID MTYP
[1:0] [1:0]

MUXEN

WREN

WAITCFG

0

Res.

WAITEN

0

FACCEN

EXTMOD

0

Res.

ASYNCWAIT

1

CLKDIV[3:0] BUSTURN[3:0]

0

0

1

Res.

ACCMOD[1:0]
0

0

0

DATLAT[3:0]

Res.

FMC_BWTR2

Res.

0x10C

0

Res.

Reset value

0

ACCMOD[1:0]

FMC_BWTR1

Res.

0x104

0

Res.

Reset value

0

ACCMOD[1:0]

Res.

FMC_BTR4

0x1C

0

Res.

Reset value

0

ACCMOD[1:0]

Res.

FMC_BTR3

0x14

0

Res.

Reset value

0

ACCMOD[1:0]

Res.

FMC_BTR2

0x0C

0

Res.

Reset value

ACCMOD[1:0]

Res.

FMC_BTR1

0x04

0

Res.

Reset value

0

0

EXTMOD

Res.
Res.

CBURSTRW

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FMC_BCR4

Res.

0

Res.

Reset value

CBURSTRW

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FMC_BCR3

0

CPSIZE
[2:0]

ASYNCWAIT

CCLKEN

CBURSTRW
0
CBURSTRW

Res.

WFDIS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.

0x18

0

Reset value

Res.

0x10

Res.

FMC_BCR2

0x08

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FMC_BCR1

0x00

Res.

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 88. FMC register map

1

1

1

1

1

1

1

1

ADDHLD[3:0] ADDSET[3:0]

1

1

1

1

1

1

1

1

1

1

RM0385

Flexible memory controller (FMC)

1

Res.

Res.

0

0

0

0

1

1

1

1

MEMHOLDx[7:0]
0

0

1

1

ATTHIZ[7:0]
1

1

1

1

1

1

1

1

1

1

0

1

0

0

1

1

1

1

1

1

0

0

1

1

1

1

1

1

1

0

0

1

0

0

0

0

1

1

1

1

0

0

1

ATTSET[7:0]
0

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

0

1

1

1

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

0

1

1

1

0

1

0

0

0

0

0

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

MODE[2:0]

COUNT[12:0]

Reset value

0

TMRD[3:0]

0

NRFS[3:0]
0

0

TMRD[3:0]

TXSR[3:0]

Res.

0

1

Res.

0

1

Res.

0

0

TXSR[3:0]

Res.

0

0

Res.

0

1

TRAS[3:0]
1

1

SDCLK
CAS
MWID
WP
NB
NR[1:0] NC
[1:0]
[1:0]
[1:0]

MRD[12:0]

Res.

Res.

Res.

Res.

Res.

Res.

1

0

0
CRE

1

0

0

0

0

Res.

1

1

MODES1[1:0]

1

1

0

Res.

Res.
Res.

1

1

1

TRAS[3:0]

TRC[3:0]

REIE

Res.
Res.

1

Res.

Res.

1

Res.

Res.

1

1

Res.

1

1

TWR[3:0]

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

TRC[3:0]

1

MODES2[1:0]

Res.

Res.

Res.

0

MWID
CAS
SDCLK
NR[1:0] NC
NB
WP
[1:0]
[1:0]
[1:0]

CTB2

RPIPE[
1:0]

CTB1

0

Res.

1

TWR[3:0]

TRP[3:0]

1

Res.

Res.

Res.

Res.

Res.

FMC_SDSR

0

BUSY

0

Reset value

0x158

0

MEMSETx[7:0]

Res.

1

1

Res.

Res.

Res.

Res.

Res.

FMC_SDRTR

0

Res.

0

Res.

1

Res.

Res.

1

TRCD[3:0]

Res.

Res.

Res.

Res.

Res.

1

TRP[3:0]

Reset value
0x154

0

0

RBURST

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

0x150

Reset value
FMC_SDCMR

TRCD[3:0]
1

Res.

0x14C

1

1

0

Reset value
FMC_SDTR2

1

1

RBURST

0

0

Res.

0x148

0

1

Reset value
FMC_SDTR1

PWID
[1:0]

1

1

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

FMC_SDCR2

1

ATTWAIT[7:0]

Reset value

0x144

1

ECCx[31:0]

Res.

FMC_SDCR1

0

ATTHOLD[7:0]

FMC_ECCR
Reset value

MEMWAITx[7:0]

Res.

Reset value

1

Res.

0x140

1

FMC_PATT

Res.

0x94

MEMHIZx[7:0]

Res.

0x8C

1

1

FMC_PMEM
Reset value

1

0

Reset value
0x88

1

Res.

1

PWAITEN

Res.

0

1

ILS

0

1

IRS

0

TCLR[3:0]

1

PTYP

0

1

PBKEN

0

1

Res.

0

1

ADDHLD[3:0] ADDSET[3:0]

Res.

0

Res.

TAR[3:0]

1

1

IFS

1

1

ILEN

1

1

IREN

1

1

IFEN

1

1

Res.

DATAST[7:0]

1

ECCEN

ECCPS
[2:0]

1

Res.

1

1

Res.

1

1

Res.

1

1

FEMPT

1

Res.

1

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

1

ADDHLD[3:0] ADDSET[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.
Res.

1

BUSTURN[3:0]

1

Res.

Res.

Res.

Res.

Res.

FMC_SR

1

DATAST[7:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ACCMOD[1:0]
ACCMOD[1:0]
0

Reset value
0x84

BUSTURN[3:0]

1

Res.

FMC_PCR

Res.

0x80

0
Res.

Reset value

0

Res.

FMC_BWTR4

Res.

0x11C

0

Res.

Reset value

Res.

FMC_BWTR3

Res.

0x114

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 88. FMC register map (continued)

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

RM0385 Rev 7

383/1709
383

Quad-SPI interface (QUADSPI)

RM0385

14

Quad-SPI interface (QUADSPI)

14.1

Introduction
The QUADSPI is a specialized communication interface targeting single, dual or quad SPI
Flash memories. It can operate in any of the three following modes:
•

indirect mode: all the operations are performed using the QUADSPI registers

•

status polling mode: the external Flash memory status register is periodically read and
an interrupt can be generated in case of flag setting

•

memory-mapped mode: the external Flash memory is mapped to the microcontroller
address space and is seen by the system as if it was an internal memory

Both throughput and capacity can be increased two-fold using dual-flash mode, where two
Quad-SPI Flash memories are accessed simultaneously.

14.2

QUADSPI main features
•

Three functional modes: indirect, status-polling, and memory-mapped

•

Dual-flash mode, where 8 bits can be sent/received simultaneously by accessing two
Flash memories in parallel.

•

SDR and DDR support

•

Fully programmable opcode for both indirect and memory mapped mode

•

Fully programmable frame format for both indirect and memory mapped mode

•

Integrated FIFO for reception and transmission

•

8, 16, and 32-bit data accesses are allowed

•

DMA channel for indirect mode operations

•

Interrupt generation on FIFO threshold, timeout, operation complete, and access error

14.3

QUADSPI functional description

14.3.1

QUADSPI block diagram
Figure 62. QUADSPI block diagram when dual-flash mode is disabled
QUADSPI
Registers /
control

Clock
management

AHB
FIFO

Shift register

SPI FLASH
CLK
BK1_IO0/SO
BK1_IO1/SI
BK1_IO2
BK1_IO3
BK1_nCS

CLK
Q0/SI
Q1/SO
Q2/WP
Q3/HOLD
CS
MS35315V1

384/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)
Figure 63. QUADSPI block diagram when dual-flash mode is enabled
QUADSPI
Registers /
control

Clock
management

SPI FLASH 1
CLK
BK1_IO0/SO
BK1_IO1/SI
BK1_IO2
BK1_IO3
BK1_nCS

AHB
FIFO

CLK
Q0/SI
Q1/SO
Q2/WP
Q3/HOLD
CS
SPI FLASH 2

Shift register

CLK
Q0/SI
Q1/SO
Q2/WP
Q3/HOLD
CS

BK2_IO0/SO
BK2_IO1/SI
BK2_IO2
BK2_IO3
BK2_nCS

MS35316V1

14.3.2

QUADSPI pins
Table 89 lists the QUADSPI pins, six for interfacing with a single Flash memory, or 10 to 11
for interfacing with two Flash memories (FLASH 1 and FLASH 2) in dual-flash mode.
Table 89. QUADSPI pins
Signal name

Signal type

Description

CLK

Digital output

Clock to FLASH 1 and FLASH 2

BK1_IO0/SO

Digital input/output

Bidirectional IO in dual/quad modes or serial output
in single mode, for FLASH 1

BK1_IO1/SI

Digital input/output

Bidirectional IO in dual/quad modes or serial input
in single mode, for FLASH 1

BK1_IO2

Digital input/output

Bidirectional IO in quad mode, for FLASH 1

BK1_IO3

Digital input/output

Bidirectional IO in quad mode, for FLASH 1

BK2_IO0/SO

Digital input/output

Bidirectional IO in dual/quad modes or serial output
in single mode, for FLASH 2

BK2_IO1/SI

Digital input/output

Bidirectional IO in dual/quad modes or serial input
in single mode, for FLASH 2

BK2_IO2

Digital input/output

Bidirectional IO in quad mode, for FLASH 2

BK2_IO3

Digital input/output

Bidirectional IO in quad mode, for FLASH 2

BK1_nCS

Digital output

Chip select (active low) for FLASH 1. Can also be
used for FLASH 2 if QUADSPI is always used in
dual-flash mode.

BK2_nCS

Digital output

Chip select (active low) for FLASH 2. Can also be
used for FLASH 1 if QUADSPI is always used in
dual-flash mode.

RM0385 Rev 7

385/1709
412

Quad-SPI interface (QUADSPI)

14.3.3

RM0385

QUADSPI command sequence
The QUADSPI communicates with the Flash memory using commands. Each command
can include 5 phases: instruction, address, alternate byte, dummy, data. Any of these
phases can be configured to be skipped, but at least one of the instruction, address,
alternate byte, or data phase must be present.
nCS falls before the start of each command and rises again after each command finishes.
Figure 64. An example of a read command in quad mode
Instruction

Address

Alt.

Dummy

Data

nCS
SCLK
IO0

7

6

5

4

0

4

0

4

0

4

0

4

0

4

0

IO1

5

1

5

1

5

1

5

1

5

1

5

1

IO2

6

2

6

2

6

2

6

2

6

2

6

2

7

3

7

3

7

3

7

3

7

3

7

3

IO3

4

3

2

1

0

A23-16

A15-8

A7-0

M7-0

Byte 1
IO switch from
output to input

Byte 2

MS35317V1

Instruction phase
During this phase, an 8-bit instruction, configured in INSTRUCTION field of
QUADSPI_CCR[7:0] register, is sent to the Flash memory, specifying the type of operation
to be performed.
Though most Flash memories can receive instructions only one bit at a time from the
IO0/SO signal (single SPI mode), the instruction phase can optionally send 2 bits at a time
(over IO0/IO1 in dual SPI mode) or 4 bits at a time (over IO0/IO1/IO2/IO3 in quad SPI
mode). This can be configured using the IMODE[1:0] field of QUADSPI_CCR[9:8] register.
When IMODE = 00, the instruction phase is skipped, and the command sequence starts
with the address phase, if present.

Address phase
In the address phase, 1-4 bytes are sent to the Flash memory to indicate the address of the
operation. The number of address bytes to be sent is configured in the ADSIZE[1:0] field of
QUADSPI_CCR[13:12] register. In indirect and automatic-polling modes, the address bytes
to be sent are specified in the ADDRESS[31:0] field of QUADSPI_AR register, while in
memory-mapped mode the address is given directly via the AHB (from the Cortex® or from
a DMA).
The address phase can send 1 bit at a time (over SO in single SPI mode), 2 bits at a time
(over IO0/IO1 in dual SPI mode), or 4 bits at a time (over IO0/IO1/IO2/IO3 in quad SPI
mode). This can be configured using the ADMODE[1:0] field of QUADSPI_CCR[11:10]
register.
When ADMODE = 00, the address phase is skipped, and the command sequence proceeds
directly to the next phase, if any.

386/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)

Alternate-bytes phase
In the alternate-bytes phase, 1-4 bytes are sent to the Flash memory, generally to control
the mode of operation. The number of alternate bytes to be sent is configured in the
ABSIZE[1:0] field of QUADSPI_CCR[17:16] register. The bytes to be sent are specified in
the QUADSPI_ABR register.
The alternate-bytes phase can send 1 bit at a time (over SO in single SPI mode), 2 bits at a
time (over IO0/IO1 in dual SPI mode), or 4 bits at a time (over IO0/IO1/IO2/IO3 in quad SPI
mode). This can be configured using the ABMODE[1:0] field of QUADSPI_CCR[15:14]
register.
When ABMODE = 00, the alternate-bytes phase is skipped, and the command sequence
proceeds directly to the next phase, if any.
There may be times when only a single nibble needs to be sent during the alternate-byte
phase rather than a full byte, such as when dual-mode is used and only two cycles are used
for the alternate bytes. In this case, firmware can use quad-mode (ABMODE = 11) and send
a byte with bits 7 and 3 of ALTERNATE set to ‘1’ (keeping the IO3 line high), and bits 6 and
2 set to ‘0’ (keeping the IO2 line low). In this case the upper two bits of the nibble to be sent
are placed in bits 4:3 of ALTERNATE while the lower two bits are placed in bits 1 and 0. For
example, if the nibble 2 (0010) is to be sent over IO0/IO1, then ALTERNATE should be set
to 0x8A (1000_1010).

Dummy-cycles phase
In the dummy-cycles phase, 1-31 cycles are given without any data being sent or received,
in order to allow the Flash memory the time to prepare for the data phase when higher clock
frequencies are used. The number of cycles given during this phase is specified in the
DCYC[4:0] field of QUADSPI_CCR[22:18] register. In both SDR and DDR modes, the
duration is specified as a number of full CLK cycles.
When DCYC is zero, the dummy-cycles phase is skipped, and the command sequence
proceeds directly to the data phase, if present.
The operating mode of the dummy-cycles phase is determined by DMODE.
In order to assure enough “turn-around” time for changing the data signals from output
mode to input mode, there must be at least one dummy cycle when using dual or quad
mode to receive data from the Flash memory.

Data phase
During the data phase, any number of bytes can be sent to, or received from the Flash
memory.
In indirect and automatic-polling modes, the number of bytes to be sent/received is specified
in the QUADSPI_DLR register.
In indirect write mode the data to be sent to the Flash memory must be written to the
QUADSPI_DR register, while in indirect read mode the data received from the Flash
memory is obtained by reading from the QUADSPI_DR register.
In memory-mapped mode, the data which is read is sent back directly over the AHB to the
Cortex or to a DMA.
The data phase can send/receive 1 bit at a time (over SO/SI in single SPI mode), 2 bits at a
time (over IO0/IO1 in dual SPI mode), or 4 bits at a time (over IO0/IO1/IO2/IO3 in quad SPI

RM0385 Rev 7

387/1709
412

Quad-SPI interface (QUADSPI)

RM0385

mode). This can be configured using the ABMODE[1:0] field of QUADSPI_CCR[15:14]
register.
When DMODE = 00, the data phase is skipped, and the command sequence finishes
immediately by raising nCS. This configuration must only be used in only indirect write
mode.

14.3.4

QUADSPI signal interface protocol modes
Single SPI mode
Legacy SPI mode allows just a single bit to be sent/received serially. In this mode, data is
sent to the Flash memory over the SO signal (whose I/O shared with IO0). Data received
from the Flash memory arrives via SI (whose I/O shared with IO1).
The different phases can each be configured separately to use this single bit mode by
setting the IMODE/ADMODE/ABMODE/DMODE fields (in QUADSPI_CCR) to 01.
In each phase which is configured in single mode:
•

IO0 (SO) is in output mode

•

IO1 (SI) is in input mode (high impedance)

•

IO2 is in output mode and forced to ‘0’ (to deactivate the “write protect” function)

•

IO3 is in output mode and forced to ‘1’ (to deactivate the “hold” function)

This is the case even for the dummy phase if DMODE = 01.

Dual SPI mode
In dual SPI mode, two bits are sent/received simultaneously over the IO0/IO1 signals.
The different phases can each be configured separately to use dual SPI mode by setting the
IMODE/ADMODE/ABMODE/DMODE fields of QUADSPI_CCR register to 10.
In each phase which is configured in dual mode:
•

IO0/IO1 are at high-impedance (input) during the data phase for read operations, and
outputs in all other cases

•

IO2 is in output mode and forced to ‘0’

•

IO3 is in output mode and forced to ‘1’

In the dummy phase when DMODE = 01, IO0/IO1 are always high-impedance.

Quad SPI mode
In quad SPI mode, four bits are sent/received simultaneously over the IO0/IO1/IO2/IO3
signals.
The different phases can each be configured separately to use quad SPI mode by setting
the IMODE/ADMODE/ABMODE/DMODE fields of QUADSPI_CCR register to 11.
In each phase which is configured in quad mode, IO0/IO1/IO2/IO3 are all are at highimpedance (input) during the data phase for read operations, and outputs in all other cases.
In the dummy phase when DMODE = 11, IO0/IO1/IO2/IO3 are all high-impedance.
IO2 and IO3 are used only in Quad SPI mode. If none of the phases are configured to use
Quad SPI mode, then the pins corresponding to IO2 and IO3 can be used for other functions
even while QUADSPI is active.

388/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)

SDR mode
By default, the DDRM bit (QUADSPI_CCR[31]) is 0 and the QUADSPI operates in single
data rate (SDR) mode.
In SDR mode, when the QUADSPI is driving the IO0/SO, IO1, IO2, IO3 signals, these
signals transition only with the falling edge of CLK.
When receiving data in SDR mode, the QUADSPI assumes that the Flash memories also
send the data using CLK’s falling edge. By default (when SSHIFT = 0), the signals are
sampled using the following (rising) edge of CLK.

DDR mode
When the DDRM bit (QUADSPI_CCR[31]) is set to 1, the QUADSPI operates in double data
rate (DDR) mode.
In DDR mode, when the QUADSPI is driving the IO0/SO, IO1, IO2, IO3 signals in the
address/alternate-byte/data phases, a bit is sent on each of the falling and rising edges of
CLK.
The instruction phase is not affected by DDRM. The instruction is always sent using CLK’s
falling edge.
When receiving data in DDR mode, the QUADSPI assumes that the Flash memories also
send the data using both rising and falling CLK edges. When DDRM = 1, firmware must
clear SSHIFT bit (bit 4 of QUADSPI_CR). Thus, the signals are sampled one half of a CLK
cycle later (on the following, opposite edge).
Figure 65. An example of a DDR command in quad mode
Instruction

Address

Alt.

Dummy

Data

nCS
SCLK
IO0

4 0 4 0 4 0 4 0

4 0 4 0

IO1

5 4 5 4 5 4 5 4

5 4 5 4

IO2

6 2 6 2 6 2 6 2

6 2 6 2

7

6

5

4

3

2

1

IO3

0

7 3 7 3 7 3 7 3
A23-16A15-8 A7-0 M7-0
IO switch from
output to input

7 3 7 3
Byte1Byte2

MS35318V1

Dual-flash mode
When the DFM bit (bit 6 of QUADSPI_CR) is 1, the QUADSPI is in dual-flash mode, where
two external quad SPI Flash memories (FLASH 1 and FLASH 2) are used in order to
send/receive 8 bits (or 16 bits in DDR mode) every cycle, effectively doubling the throughput
as well as the capacity.
Each of the Flash memories use the same CLK and optionally the same nCS signals, but
each have separate IO0, IO1, IO2, and IO3 signals.
Dual-flash mode can be used in conjunction with single-bit, dual-bit, and quad-bit modes, as
well as with either SDR or DDR mode.

RM0385 Rev 7

389/1709
412

Quad-SPI interface (QUADSPI)

RM0385

The Flash memory size, as specified in FSIZE[4:0] (QUADSPI_DCR[20:16]), should reflect
the total Flash memory capacity, which is double the size of one individual component.
If address X is even, then the byte which the QUADSPI gives for address X is the byte at the
address X/2 of FLASH 1, and the byte which the QUADSPI gives for address X+1 is the
byte at the address X/2 of FLASH 2. In other words, bytes at even addresses are all stored
in FLASH 1 and bytes at odd addresses are all stored in FLASH 2.
When reading the Flash memories status registers in dual-flash mode, twice as many bytes
should be read compared to doing the same read in single-flash mode. This means that if
each Flash memory gives 8 valid bits after the instruction for fetching the status register,
then the QUADSPI must be configured with a data length of 2 bytes (16 bits), and the
QUADSPI will receive one byte from each Flash memory. If each Flash memory gives a
status of 16 bits, then the QUADSPI must be configured to read 4 bytes to get all the status
bits of both Flash memories in dual-flash mode. The least-significant byte of the result (in
the data register) is the least-significant byte of FLASH 1 status register, while the next byte
is the least-significant byte of FLASH 2 status register. Then, the third byte of the data
register is FLASH 1 second byte, while the forth byte is FLASH 2 second byte (in the case
that the Flash memories have 16-bit status registers).
An even number of bytes must always be accessed in dual-flash mode. For this reason, bit
0 of the data length field (QUADSPI_DLR[0]) is stuck at 1 when DRM = 1.
In dual-flash mode, the behavior of FLASH 1 interface signals are basically the same as in
normal mode. FLASH 2 interface signals have exactly the same waveforms as FLASH 1
during the instruction, address, alternate-byte, and dummy-cycles phases. In other words,
each Flash memory always receives the same instruction and the same address. Then,
during the data phase, the BK1_IOx and BK2_IOx buses are both transferring data in
parallel, but the data that are sent to (or received from) FLASH 1 are distinct from those of
FLASH 2.

14.3.5

QUADSPI indirect mode
When in indirect mode, commands are started by writing to QUADSPI registers and data is
transferred by writing or reading the data register, in the same way as for other
communication peripherals.
When FMODE = 00 (QUADSPI_CCR[27:26]), the QUADSPI is in indirect write mode,
where bytes are sent to the Flash memory during the data phase. Data are provided by
writing to the data register (QUADSPI_DR).
When FMODE = 01, the QUADSPI is in indirect read mode, where bytes are received from
the Flash memory during the data phase. Data are recovered by reading QUADSPI_DR.
The number of bytes to be read/written is specified in the data length register
(QUADSPI_DLR). If QUADSPI_DLR = 0xFFFF_FFFF (all 1’s), then the data length is
considered undefined and the QUADSPI simply continues to transfer data until the end of
Flash memory (as defined by FSIZE) is reached. If no bytes are to be transferred, DMODE
(QUADSPI_CCR[25:24]) should be set to 00.
If QUADSPI_DLR = 0xFFFF_FFFF and FSIZE = 0x1F (max value indicating a 4GB Flash
memory), then in this special case the transfers continue indefinitely, stopping only after an
abort request or after the QUADSPI is disabled. After the last memory address is read (at
address 0xFFFF_FFFF), reading continues with address = 0x0000_0000.
When the programmed number of bytes to be transmitted or received is reached, TCF is set
and an interrupt is generated if TCIE = 1. In the case of undefined number of data, the TCF

390/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)
is set when the limit of the external SPI memory is reached according to the Flash memory
size defined in the QUADSPI_CR.

Triggering the start of a command
Essentially, a command starts as soon as firmware gives the last information that is
necessary for this command. Depending on the QUADSPI configuration, there are three
different ways to trigger the start of a command in indirect mode. The commands starts
immediately after:
1.

a write is performed to INSTRUCTION[7:0] (QUADSPI_CCR), if no address is
necessary (when ADMODE = 00) and if no data needs to be provided by the firmware
(when FMODE = 01 or DMODE = 00)

2.

a write is performed to ADDRESS[31:0] (QUADSPI_AR), if an address is necessary
(when ADMODE != 00) and if no data needs to be provided by the firmware (when
FMODE = 01 or DMODE = 00)

3.

a write is performed to DATA[31:0] (QUADSPI_DR), if an address is necessary (when
ADMODE != 00) and if data needs to be provided by the firmware (when FMODE = 00
and DMODE != 00)

Writes to the alternate byte register (QUADSPI_ABR) never trigger the communication start.
If alternate bytes are required, they must be programmed before.
As soon as a command is started, the BUSY bit (bit 5 of QUADSPI_SR) is automatically set.

FIFO and data management
In indirect mode, data go through a 32-byte FIFO which is internal to the QUADSPI.
FLEVEL[5:0] (QUADSPI_SR[13:8]) indicates how many bytes are currently being held in
the FIFO.
In indirect write mode (FMODE = 00), firmware adds data to the FIFO when it writes
QUADSPI_DR. Word writes add 4 bytes to the FIFO, halfword writes add 2 bytes, and byte
writes add only 1 byte. If firmware adds too many bytes to the FIFO (more than is indicated
by DL[31:0]), the extra bytes are flushed from the FIFO at the end of the write operation
(when TCF is set).
Byte/halfword accesses to QUADSPI_DR must be done only to the least significant
byte/halfword of the 32-bit register.
FTHRES[3:0] is used to define a FIFO threshold. When the threshold is reached, the FTF
(FIFO threshold flag) is set. In indirect read mode, FTF is set when the number of valid
bytes to be read from the FIFO is above the threshold. FTF is also set if there are data in the
FIFO after the last byte is read from the Flash memory, regardless of the FTHRES setting.
In indirect write mode, FTF is set when the number of empty bytes in the FIFO is above the
threshold.
If FTIE = 1, there is an interrupt when FTF is set. If DMAEN = 1, a DMA transfer is initiated
when FTF is set. FTF is cleared by HW as soon as the threshold condition is no longer true
(after enough data has been transferred by the CPU or DMA).
In indirect read mode, when the FIFO becomes full, the QUADSPI temporarily stops reading
bytes from the Flash memory to avoid an overrun. Note that the reading of the Flash
memory does not restart until 4 bytes become vacant in the FIFO (when FLEVEL ≤ 28).
Thus, when FTHRES ≥ 29, the application must take care to read enough bytes to assure
that the QUADSPI starts retrieving data from the Flash memory again. Otherwise, the FTF
flag stays at '0' as long as 28 < FLEVEL < FTHRES.

RM0385 Rev 7

391/1709
412

Quad-SPI interface (QUADSPI)

14.3.6

RM0385

QUADSPI status flag polling mode
In automatic-polling mode, the QUADSPI periodically starts a command to read a defined
number of status bytes (up to 4). The received bytes can be masked to isolate some status
bits and an interrupt can be generated when the selected bits have a defined value.
The accesses to the Flash memory begin in the same way as in indirect read mode: if no
address is required (AMODE = 00), accesses begin as soon as the QUADSPI_CCR is
written. Otherwise, if an address is required, the first access begins when QUADSPI_AR is
written. BUSY goes high at this point and stays high even between the periodic accesses.
The contents of MASK[31:0] (QUADSPI_PSMAR) are used to mask the data from the Flash
memory in automatic-polling mode. If the MASK[n] = 0, then bit n of the result is masked
and not considered. If MASK[n] = 1, and the content of bit[n] is the same as MATCH[n]
(QUADSPI_PSMAR), then there is a match for bit n.
If the polling match mode bit (PMM, bit 23 of QUADSPI_CR) is 0, then “AND” match mode is
activated. This means status match flag (SMF) is set only when there is a match on all of the
unmasked bits.
If PMM = 1, then “OR” match mode is activated. This means SMF is set if there is a match
on any of the unmasked bits.
An interrupt is called when SMF is set if SMIE = 1.
If the automatic-polling-mode-stop (APMS) bit is set, operation stops and BUSY goes to 0
as soon as a match is detected. Otherwise, BUSY stays at ‘1’ and the periodic accesses
continue until there is an abort or the QUADSPI is disabled (EN = 0).
The data register (QUADSPI_DR) contains the latest received status bytes (the FIFO is
deactivated). The content of the data register is not affected by the masking used in the
matching logic. The FTF status bit is set as soon as a new reading of the status is complete,
and FTF is cleared as soon as the data is read.

14.3.7

QUADSPI memory-mapped mode
When configured in memory-mapped mode, the external SPI device is seen as an internal
memory.
It is forbidden to access QUADSPI Flash bank area before having properly configured and
enabled the QUADSPI peripheral.
No more than 256MB can addressed even if the Flash memory capacity is larger.
If an access is made to an address outside of the range defined by FSIZE but still within the
256MB range, then a bus error is given. The effect of this error depends on the bus master
that attempted the access:
•

If it is the Cortex® CPU, bus fault exception is generated when enabled (or a hard fault
exception when bus fault is disabled)

•

If it is a DMA, a DMA transfer error is generated and the corresponding DMA channel is
automatically disabled.

Byte, halfword, and word access types are all supported.
Support for execute in place (XIP) operation is implemented, where the QUADSPI
anticipates the next microcontroller access and load in advance the byte at the following
address. If the subsequent access is indeed made at a continuous address, the access will
be completed faster since the value is already prefetched.

392/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)
By default, the QUADSPI never stops its prefetch operation, keeping the previous read
operation active with nCS maintained low, even if no access to the Flash memory occurs for
a long time. Since Flash memories tend to consume more when nCS is held low, the
application might want to activate the timeout counter (TCEN = 1, bit 3 of QUADSPI_CR) so
that nCS is released after a period of TIMEOUT[15:0] (QUADSPI_LPTR) cycles have
elapsed without any access since when the FIFO becomes full with prefetch data.
BUSY goes high as soon as the first memory-mapped access occurs. Because of the
prefetch operations, BUSY does not fall until there is a timeout, there is an abort, or the
peripheral is disabled.

14.3.8

QUADSPI Flash memory configuration
The device configuration register (QUADSPI_DCR) can be used to specify the
characteristics of the external SPI Flash memory.
The FSIZE[4:0] field defines the size of external memory using the following formula:
Number of bytes in Flash memory = 2[FSIZE+1]
FSIZE+1 is effectively the number of address bits required to address the Flash memory.
The Flash memory capacity can be up to 4GB (addressed using 32 bits) in indirect mode,
but the addressable space in memory-mapped mode is limited to 256MB.
If DFM = 1, FSIZE indicates the total capacity of the two Flash memories together.
When the QUADSPI executes two commands, one immediately after the other, it raises the
chip select signal (nCS) high between the two commands for only one CLK cycle by default.
If the Flash memory requires more time between commands, the chip select high time
(CSHT) field can be used to specify the minimum number of CLK cycles (up to 8) that nCS
must remain high.
The clock mode (CKMODE) bit indicates the CLK signal logic level in between commands
(when nCS = 1).

14.3.9

QUADSPI delayed data sampling
By default, the QUADSPI samples the data driven by the Flash memory one half of a CLK
cycle after the Flash memory drives the signal.
In case of external signal delays, it may be beneficial to sample the data later. Using the
SSHIFT bit (bit 4 of QUADSPI_CR), the sampling of the data can be shifted by half of a CLK
cycle.
Clock shifting is not supported in DDR mode: the SSHIFT bit must be clear when DDRM bit
is set.

14.3.10

QUADSPI configuration
The QUADSPI configuration is done in two phases:
•

QUADSPI IP configuration

•

QUADSPI Flash memory configuration

Once configured and enabled, the QUADSPI can be used in one of its three operating
modes: indirect mode, status-polling mode, or memory-mapped mode.
QUADSPI IP configuration

RM0385 Rev 7

393/1709
412

Quad-SPI interface (QUADSPI)

RM0385

The QUADSPI IP is configured using the QUADSPI_CR. The user shall configure the clock
prescaler division factor and the sample shifting settings for the incoming data.
DDR mode can be set through the DDRM bit. Once enabled, the address and the alternate
bytes are sent on both clock edges and the data are sent/received on both clock edges.
Regardless of the DDRM bit setting, instructions are always sent in SDR mode.
The DMA requests are enabled setting the DMAEN bit. In case of interrupt usage, their
respective enable bit can be also set during this phase.
FIFO level for either DMA request generation or interrupt generation is programmed in the
FTHRES bits.
If timeout counter is needed, the TCEN bit can be set and the timeout value programmed in
the QUADSPI_LPTR register.
Dual-flash mode can be activated by setting DFM to 1.

QUADSPI Flash memory configuration
The parameters related to the targeted external Flash memory are configured through the
QUADSPI_DCR register.The user shall program the Flash memory size in the FSIZE bits,
the Chip Select minimum high time in the CSHT bits, and the functional mode (Mode 0 or
Mode 3) in the MODE bit.

14.3.11

QUADSPI usage
The operating mode is selected using FMODE[1:0] (QUADSPI_CCR[27:26]).

Indirect mode procedure
When FMODE is programmed to 00, indirect write mode is selected and data can be sent to
the Flash memory. With FMODE = 01, indirect read mode is selected where data can be
read from the Flash memory.
When the QUADSPI is used in indirect mode, the frames are constructed in the following
way:
1.

394/1709

Specify a number of data bytes to read or write in the QUADSPI_DLR.

2.

Specify the frame format, mode and instruction code in the QUADSPI_CCR.

3.

Specify optional alternate byte to be sent right after the address phase in the
QUADSPI_ABR.

4.

Specify the operating mode in the QUADSPI_CR. If FMODE = 00 (indirect write mode)
and DMAEN = 1, then QUADSPI_AR should be specified before QUADSPI_CR,
because otherwise QUADSPI_DR might be written by the DMA before QUADSPI_AR
is updated (if the DMA controller has already been enabled)

5.

Specify the targeted address in the QUADSPI_AR.

6.

Read/Write the data from/to the FIFO through the QUADSPI_DR.

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)
When writing the control register (QUADSPI_CR) the user specifies the following settings:
•

The enable bit (EN) set to ‘1’

•

The DMA enable bit (DMAEN) for transferring data to/from RAM

•

Timeout counter enable bit (TCEN)

•

Sample shift setting (SSHIFT)

•

FIFO threshold level (FTRHES) to indicate when the FTF flag should be set

•

Interrupt enables

•

Automatic polling mode parameters: match mode and stop mode (valid when
FMODE = 11)

•

Clock prescaler

When writing the communication configuration register (QUADSPI_CCR) the user specifies
the following parameters:
•

The instruction byte through the INSTRUCTION bits

•

The way the instruction has to be sent through the IMODE bits (1/2/4 lines)

•

The way the address has to be sent through the ADMODE bits (None/1/2/4 lines)

•

The address size (8/16/24/32-bit) through the ADSIZE bits

•

The way the alternate bytes have to be sent through the ABMODE (None/1/2/4 lines)

•

The alternate bytes number (1/2/3/4) through the ABSIZE bits

•

The presence or not of dummy bytes through the DBMODE bit

•

The number of dummy bytes through the DCYC bits

•

The way the data have to be sent/received (None/1/2/4 lines) through the DMODE bits

If neither the address register (QUADSPI_AR) nor the data register (QUADSPI_DR) need to
be updated for a particular command, then the command sequence starts as soon as
QUADSPI_CCR is written. This is the case when both ADMODE and DMODE are 00, or if
just ADMODE = 00 when in indirect read mode (FMODE = 01).
When an address is required (ADMODE is not 00) and the data register does not need to be
written (when FMODE = 01 or DMODE = 00), the command sequence starts as soon as the
address is updated with a write to QUADSPI_AR.
In case of data transmission (FMODE = 00 and DMODE! = 00), the communication start is
triggered by a write in the FIFO through QUADSPI_DR.

Status flag polling mode
The status flag polling mode is enabled setting the FMODE field (QUADSPI_CCR[27:26]) to
10. In this mode, the programmed frame will be sent and the data retrieved periodically.
The maximum amount of data read in each frame is 4 bytes. If more data is requested in
QUADSPI_DLR, it will be ignored and only 4 bytes will be read.
The periodicity is specified in the QUADSPI_PISR register.
Once the status data has been retrieved, it can internally be processed i order to:
•

set the status match flag and generate an interrupt if enabled

•

stop automatically the periodic retrieving of the status bytes

The received value can be masked with the value stored in the QUADSPI_PSMKR and
ORed or ANDed with the value stored in the QUADSPI_PSMAR.

RM0385 Rev 7

395/1709
412

Quad-SPI interface (QUADSPI)

RM0385

In case of match, the status match flag is set and an interrupt is generated if enabled, and
the QUADSPI can be automatically stopped if the AMPS bit is set.
In any case, the latest retrieved value is available in the QUADSPI_DR.

Memory-mapped mode
In memory-mapped mode, the external Flash memory is seen as internal memory but with
some latency during accesses. Only read operations are allowed to the external Flash
memory in this mode.
Memory-mapped mode is entered by setting the FMODE to 11 in the QUADSPI_CCR
register.
The programmed instruction and frame is sent when a master is accessing the memory
mapped space.
The FIFO is used as a prefetch buffer to anticipate linear reads. Any access to
QUADSPI_DR in this mode returns zero.
The data length register (QUADSPI_DLR) has no meaning in memory-mapped mode.

14.3.12

Sending the instruction only once
Some Flash memories (e.g. Winbound) might provide a mode where an instruction must be
sent only with the first command sequence, while subsequent commands start directly with
the address. One can take advantage of such a feature using the SIOO bit
(QUADSPI_CCR[28]).
SIOO is valid for all functional modes (indirect, automatic polling, and memory-mapped). If
the SIOO bit is set, the instruction is sent only for the first command following a write to
QUADSPI_CCR. Subsequent command sequences skip the instruction phase, until there is
a write to QUADSPI_CCR.
SIOO has no effect when IMODE = 00 (no instruction).

14.3.13

QUADSPI error management
An error can be generated in the following case:

396/1709

•

In indirect mode or status flag polling mode when a wrong address has been
programmed in the QUADSPI_AR (according to the Flash memory size defined by
FSIZE[4:0] in the QUADSPI_DCR): this will set the TEF and an interrupt is generated if
enabled.

•

Also in indirect mode, if the address plus the data length exceeds the Flash memory
size, TEF will be set as soon as the access is triggered.

•

In memory-mapped mode, when an out of range access is done by a master or when
the QUADSPI is disabled: this will generate a bus error as a response to the faulty bus
master request.

•

When a master is accessing the memory mapped space while the memory mapped
mode is disabled: this will generate a bus error as a response to the faulty bus master
request.

RM0385 Rev 7

RM0385

14.3.14

Quad-SPI interface (QUADSPI)

QUADSPI busy bit and abort functionality
Once the QUADSPI starts an operation with the Flash memory, the BUSY bit is
automatically set in the QUADSPI_SR.
In indirect mode, the BUSY bit is reset once the QUADSPI has completed the requested
command sequence and the FIFO is empty.
In automatic-polling mode, BUSY goes low only after the last periodic access is complete,
due to a match when APMS = 1, or due to an abort.
After the first access in memory-mapped mode, BUSY goes low only on a timeout event or
on an abort.
Any operation can be aborted by setting the ABORT bit in the QUADSPI_CR. Once the
abort is completed, the BUSY bit and the ABORT bit are automatically reset, and the FIFO
is flushed.

Note:

Some Flash memories might misbehave if a write operation to a status registers is aborted.

14.3.15

nCS behavior
By default, nCS is high, deselecting the external Flash memory. nCS falls before an
operation begins and rises as soon as it finishes.
When CKMODE = 0 (“mode0”, where CLK stays low when no operation is in progress) nCS
falls one CLK cycle before an operation first rising CLK edge, and nCS rises one CLK cycle
after the operation final rising CLK edge, as shown in Figure 66.
Figure 66. nCS when CKMODE = 0 (T = CLK period)
T

T

nCS

SCLK
MS35319V1

When CKMODE=1 (“mode3”, where CLK goes high when no operation is in progress) and
DDRM=0 (SDR mode), nCS still falls one CLK cycle before an operation first rising CLK
edge, and nCS rises one CLK cycle after the operation final rising CLK edge, as shown in
Figure 67.
Figure 67. nCS when CKMODE = 1 in SDR mode (T = CLK period)
T

T

nCS

SCLK
MS35320V1

RM0385 Rev 7

397/1709
412

Quad-SPI interface (QUADSPI)

RM0385

When CKMODE = 1 (“mode3”) and DDRM = 1 (DDR mode), nCS falls one CLK cycle
before an operation first rising CLK edge, and nCS rises one CLK cycle after the operation
final active rising CLK edge, as shown in Figure 68. Because DDR operations must finish
with a falling edge, CLK is low when nCS rises, and CLK rises back up one half of a CLK
cycle afterwards.
Figure 68. nCS when CKMODE = 1 in DDR mode (T = CLK period)
T

T

T/2

nCS

SCLK
MS35321V1

When the FIFO stays full in a read operation or if the FIFO stays empty in a write operation,
the operation stalls and CLK stays low until firmware services the FIFO. If an abort occurs
when an operation is stalled, nCS rises just after the abort is requested and then CLK rises
one half of a CLK cycle later, as shown in Figure 69.
Figure 69. nCS when CKMODE = 1 with an abort (T = CLK period)
T

Clock stalled

T/2

nCS

SCLK

Abort
MS35322V1

When not in dual-flash mode (DFM = 0), only FLASH 1 is accessed and thus the BK2_nCS
stays high. In dual-flash mode, BK2_nCS behaves exactly the same as BK1_nCS. Thus, if
there is a FLASH 2 and if the application always stays in dual-flash mode, then FLASH 2
may use BK1_nCS and the pin outputting BK2_nCS can be used for other functions.

398/1709

RM0385 Rev 7

RM0385

14.4

Quad-SPI interface (QUADSPI)

QUADSPI interrupts
An interrupt can be produced on the following events:
•

Timeout

•

Status match

•

FIFO threshold

•

Transfer complete

•

Transfer error

Separate interrupt enable bits are available for flexibility.
Table 90. QUADSPI interrupt requests
Interrupt event

Event flag

Enable control bit

Timeout

TOF

TOIE

Status match

SMF

SMIE

FIFO threshold

FTF

FTIE

Transfer complete

TCF

TCIE

Transfer error

TEF

TEIE

RM0385 Rev 7

399/1709
412

Quad-SPI interface (QUADSPI)

RM0385

14.5

QUADSPI registers

14.5.1

QUADSPI control register (QUADSPI_CR)
Address offset: 0x0000
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

PRESCALER[7:0]

23

22

21

20

19

18

17

16

PMM

APMS

Res.

TOIE

SMIE

FTIE

TCIE

TEIE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

FSEL

DFM

Res.

SSHIFT

TCEN

rw

rw

rw

rw

FTHRES[4:0]
rw

rw

rw

rw

rw

DMAEN ABORT
rw

rw

EN
rw

Bits 31:24 PRESCALER[7:0]: Clock prescaler
This field defines the scaler factor for generating CLK based on the AHB clock
(value+1).
0: FCLK = FAHB, AHB clock used directly as QUADSPI CLK (prescaler bypassed)
1: FCLK = FAHB/2
2: FCLK = FAHB/3
...
255: FCLK = FAHB/256
For odd clock division factors, CLK’s duty cycle is not 50%. The clock signal remains
low one cycle longer than it stays high.
This field can be modified only when BUSY = 0.
Bit 23 PMM: Polling match mode
This bit indicates which method should be used for determining a “match” during
automatic polling mode.
0: AND match mode. SMF is set if all the unmasked bits received from the Flash
memory match the corresponding bits in the match register.
1: OR match mode. SMF is set if any one of the unmasked bits received from the Flash
memory matches its corresponding bit in the match register.
This bit can be modified only when BUSY = 0.
Bit 22 APMS: Automatic poll mode stop
This bit determines if automatic polling is stopped after a match.
0: Automatic polling mode is stopped only by abort or by disabling the QUADSPI.
1: Automatic polling mode stops as soon as there is a match.
This bit can be modified only when BUSY = 0.
Bit 21 Reserved, must be kept at reset value.
Bit 20 TOIE: TimeOut interrupt enable
This bit enables the TimeOut interrupt.
0: Interrupt disable
1: Interrupt enabled
Bit 19 SMIE: Status match interrupt enable
This bit enables the status match interrupt.
0: Interrupt disable
1: Interrupt enabled

400/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)

Bit 18 FTIE: FIFO threshold interrupt enable
This bit enables the FIFO threshold interrupt.
0: Interrupt disabled
1: Interrupt enabled
Bit 17 TCIE: Transfer complete interrupt enable
This bit enables the transfer complete interrupt.
0: Interrupt disabled
1: Interrupt enabled
Bit 16 TEIE: Transfer error interrupt enable
This bit enables the transfer error interrupt.
0: Interrupt disable
1: Interrupt enabled
Bits 15:13 Reserved, must be kept at reset value.
Bits 12:8 FTHRES[4:0] FIFO threshold level
Defines, in indirect mode, the threshold number of bytes in the FIFO that will cause the
FIFO threshold flag (FTF, QUADSPI_SR[2]) to be set.
In indirect write mode (FMODE = 00):
0: FTF is set if there are 1 or more free bytes available to be written to in the FIFO
1: FTF is set if there are 2 or more free bytes available to be written to in the FIFO
...
31: FTF is set if there are 32 free bytes available to be written to in the FIFO
In indirect read mode (FMODE = 01):
0: FTF is set if there are 1 or more valid bytes that can be read from the FIFO
1: FTF is set if there are 2 or more valid bytes that can be read from the FIFO
...
31: FTF is set if there are 32 valid bytes that can be read from the FIFO
If DMAEN = 1, then the DMA controller for the corresponding channel must be disabled
before changing the FTHRES value.
Bit 7 FSEL: Flash memory selection
This bit selects the Flash memory to be addressed in single flash mode (when DFM =
0).
0: FLASH 1 selected
1: FLASH 2 selected
This bit can be modified only when BUSY = 0.
This bit is ignored when DFM = 1.
Bit 6 DFM: Dual-flash mode
This bit activates dual-flash mode, where two external Flash memories are used
simultaneously to double throughput and capacity.
0: Dual-flash mode disabled
1: Dual-flash mode enabled
This bit can be modified only when BUSY = 0.
Bit 5 Reserved, must be kept at reset value.

RM0385 Rev 7

401/1709
412

Quad-SPI interface (QUADSPI)

RM0385

Bit 4 SSHIFT: Sample shift
By default, the QUADSPI samples data 1/2 of a CLK cycle after the data is driven by the
Flash memory. This bit allows the data is to be sampled later in order to account for
external signal delays.
0: No shift
1: 1/2 cycle shift
Firmware must assure that SSHIFT = 0 when in DDR mode (when DDRM = 1).
This field can be modified only when BUSY = 0.
Bit 3 TCEN: Timeout counter enable
This bit is valid only when memory-mapped mode (FMODE = 11) is selected. Activating
this bit causes the chip select (nCS) to be released (and thus reduces consumption) if
there has not been an access after a certain amount of time, where this time is defined
by TIMEOUT[15:0] (QUADSPI_LPTR).
Enable the timeout counter.
By default, the QUADSPI never stops its prefetch operation, keeping the previous read
operation active with nCS maintained low, even if no access to the Flash memory
occurs for a long time. Since Flash memories tend to consume more when nCS is held
low, the application might want to activate the timeout counter (TCEN = 1, bit 3 of
QUADSPI_CR) so that nCS is released after a period of TIMEOUT[15:0]
(QUADSPI_LPTR) cycles have elapsed without an access since when the FIFO
becomes full with prefetch data.
0: Timeout counter is disabled, and thus the chip select (nCS) remains active
indefinitely after an access in memory-mapped mode.
1: Timeout counter is enabled, and thus the chip select is released in memory-mapped
mode after TIMEOUT[15:0] cycles of Flash memory inactivity.
This bit can be modified only when BUSY = 0.
Bit 2 DMAEN: DMA enable
In indirect mode, DMA can be used to input or output data via the QUADSPI_DR
register. DMA transfers are initiated when the FIFO threshold flag, FTF, is set.
0: DMA is disabled for indirect mode
1: DMA is enabled for indirect mode
Bit 1 ABORT: Abort request
This bit aborts the on-going command sequence. It is automatically reset once the abort
is complete.
This bit stops the current transfer.
In polling mode or memory-mapped mode, this bit also reset the APM bit or the DM bit.
0: No abort requested
1: Abort requested
Bit 0 EN: Enable
Enable the QUADSPI.
0: QUADSPI is disabled
1: QUADSPI is enabled

402/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)

14.5.2

QUADSPI device configuration register (QUADSPI_DCR)
Address offset: 0x0004
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

Res.

Res.

Res.

Res.

Res.

CSHT[2:0]
rw

rw

Res.

Res.

rw

Res.

20

19

18

17

16

rw

FSIZE[4:0]
rw

rw

rw

rw

4

3

2

1

0

Res.

CK
MODE

Res.

Res.

Res.

rw

Bits 31:21 Reserved, must be kept at reset value.
Bits 20:16 FSIZE[4:0]: Flash memory size
This field defines the size of external memory using the following formula:
Number of bytes in Flash memory = 2[FSIZE+1]
FSIZE+1 is effectively the number of address bits required to address the Flash
memory. The Flash memory capacity can be up to 4GB (addressed using 32 bits) in
indirect mode, but the addressable space in memory-mapped mode is limited to
256MB.
If DFM = 1, FSIZE indicates the total capacity of the two Flash memories together.
This field can be modified only when BUSY = 0.
Bits 15:11 Reserved, must be kept at reset value.
Bits 10:8 CSHT[2:0]: Chip select high time
CSHT+1 defines the minimum number of CLK cycles which the chip select (nCS) must
remain high between commands issued to the Flash memory.
0: nCS stays high for at least 1 cycle between Flash memory commands
1: nCS stays high for at least 2 cycles between Flash memory commands
...
7: nCS stays high for at least 8 cycles between Flash memory commands
This field can be modified only when BUSY = 0.
Bits 7:1 Reserved, must be kept at reset value.
Bit 0 CKMODE: Mode 0 / mode 3
This bit indicates the level that CLK takes between commands (when nCS = 1).
0: CLK must stay low while nCS is high (chip select released). This is referred to as
mode 0.
1: CLK must stay high while nCS is high (chip select released). This is referred to as
mode 3.
This field can be modified only when BUSY = 0.

RM0385 Rev 7

403/1709
412

Quad-SPI interface (QUADSPI)

14.5.3

RM0385

QUADSPI status register (QUADSPI_SR)
Address offset: 0x0008
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

BUSY

TOF

SMF

FTF

TCF

TEF

r

r

r

r

r

r

FLEVEL[5:0]
r

r

r

r

r

r

Bits 31:14 Reserved, must be kept at reset value.
Bits 13:8 FLEVEL[5:0]: FIFO level
This field gives the number of valid bytes which are being held in the FIFO. FLEVEL = 0
when the FIFO is empty, and 32 when it is full. In memory-mapped mode and in
automatic status polling mode, FLEVEL is zero.
Bits 7:6 Reserved, must be kept at reset value.
Bit 5 BUSY: Busy
This bit is set when an operation is on going. This bit clears automatically when the
operation with the Flash memory is finished and the FIFO is empty.
Bit 4 TOF: Timeout flag
This bit is set when timeout occurs. It is cleared by writing 1 to CTOF.
Bit 3 SMF: Status match flag
This bit is set in automatic polling mode when the unmasked received data matches the
corresponding bits in the match register (QUADSPI_PSMAR). It is cleared by writing 1
to CSMF.
Bit 2 FTF: FIFO threshold flag
In indirect mode, this bit is set when the FIFO threshold has been reached, or if there is
any data left in the FIFO after reads from the Flash memory are complete. It is cleared
automatically as soon as threshold condition is no longer true.
In automatic polling mode this bit is set every time the status register is read, and the bit
is cleared when the data register is read.
Bit 1 TCF: Transfer complete flag
This bit is set in indirect mode when the programmed number of data has been
transferred or in any mode when the transfer has been aborted.It is cleared by writing 1
to CTCF.
Bit 0 TEF: Transfer error flag
This bit is set in indirect mode when an invalid address is being accessed in indirect
mode. It is cleared by writing 1 to CTEF.

404/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)

14.5.4

QUADSPI flag clear register (QUADSPI_FCR)
Address offset: 0x000C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CTOF

CSMF

Res.

CTCF

CTEF

w

w

w

w

Bits 31:5 Reserved, must be kept at reset value.
Bit 4 CTOF: Clear timeout flag
Writing 1 clears the TOF flag in the QUADSPI_SR register
Bit 3 CSMF: Clear status match flag
Writing 1 clears the SMF flag in the QUADSPI_SR register
Bit 2 Reserved, must be kept at reset value.
Bit 1 CTCF: Clear transfer complete flag
Writing 1 clears the TCF flag in the QUADSPI_SR register
Bit 0 CTEF: Clear transfer error flag
Writing 1 clears the TEF flag in the QUADSPI_SR register

14.5.5

QUADSPI data length register (QUADSPI_DLR)
Address offset: 0x0010
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DL[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DL[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

405/1709
412

Quad-SPI interface (QUADSPI)

RM0385

Bits 31:0 DL[31:0]: Data length
Number of data to be retrieved (value+1) in indirect and status-polling modes. A value
no greater than 3 (indicating 4 bytes) should be used for status-polling mode.
All 1s in indirect mode means undefined length, where QUADSPI will continue until the
end of memory, as defined by FSIZE.
0x0000_0000: 1 byte is to be transferred
0x0000_0001: 2 bytes are to be transferred
0x0000_0002: 3 bytes are to be transferred
0x0000_0003: 4 bytes are to be transferred
...
0xFFFF_FFFD: 4,294,967,294 (4G-2) bytes are to be transferred
0xFFFF_FFFE: 4,294,967,295 (4G-1) bytes are to be transferred
0xFFFF_FFFF: undefined length -- all bytes until the end of Flash memory (as defined
by FSIZE) are to be transferred. Continue reading indefinitely if FSIZE = 0x1F.
DL[0] is stuck at ‘1’ in dual-flash mode (DFM = 1) even when ‘0’ is written to this bit, thus
assuring that each access transfers an even number of bytes.
This field has no effect when in memory-mapped mode (FMODE = 10).
This field can be written only when BUSY = 0.

14.5.6

QUADSPI communication configuration register (QUADSPI_CCR)
Address offset: 0x0014
Reset value: 0x0000 0000

31

30

29

28

DDRM

DHHC

Res.

SIOO

13

rw

rw

15

14

ABMODE[1:0]
rw

rw

26

25

24

FMODE[1:0]

DMODE[1:0]

rw

rw

rw

rw

rw

12

11

10

9

8

ADSIZE[1:0]
rw

27

rw

ADMODE[1:0]
rw

rw

23

22

21

Res.

7

rw

19

18

DCYC[4:0]

17

ABSIZE[1:0]

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

INSTRUCTION[7:0]
rw

rw

rw

rw

rw

Bit 31 DDRM: Double data rate mode
This bit sets the DDR mode for the address, alternate byte and data phase:
0: DDR Mode disabled
1: DDR Mode enabled
This field can be written only when BUSY = 0.
Bit 30 DHHC: DDR hold
Delay the data output by 1/4 of the QUADSPI output clock cycle in DDR mode:
0: Delay the data output using analog delay
1: Delay the data output by 1/4 of a QUADSPI output clock cycle.
This feature is only active in DDR mode.
This field can be written only when BUSY = 0.
Bit 29 Reserved, must be kept at reset value.

406/1709

16

rw

IMODE[1:0]
rw

20

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)

Bit 28 SIOO: Send instruction only once mode
See Section 14.3.12: Sending the instruction only once on page 396. This bit has no
effect when IMODE = 00.
0: Send instruction on every transaction
1: Send instruction only for the first command
This field can be written only when BUSY = 0.
Bits 27:26 FMODE[1:0]: Functional mode
This field defines the QUADSPI functional mode of operation.
00: Indirect write mode
01: Indirect read mode
10: Automatic polling mode
11: Memory-mapped mode
If DMAEN = 1 already, then the DMA controller for the corresponding channel must be
disabled before changing the FMODE value.
This field can be written only when BUSY = 0.
Bits 25:24 DMODE[1:0]: Data mode
This field defines the data phase’s mode of operation:
00: No data
01: Data on a single line
10: Data on two lines
11: Data on four lines
This field also determines the dummy phase mode of operation.
This field can be written only when BUSY = 0.
Bit 23 Reserved, must be kept at reset value.
Bits 22:18 DCYC[4:0]: Number of dummy cycles
This field defines the duration of the dummy phase. In both SDR and DDR modes, it
specifies a number of CLK cycles (0-31).
This field can be written only when BUSY = 0.
Bits 17:16 ABSIZE[1:0]: Alternate bytes size
This bit defines alternate bytes size:
00: 8-bit alternate byte
01: 16-bit alternate bytes
10: 24-bit alternate bytes
11: 32-bit alternate bytes
This field can be written only when BUSY = 0.
Bits 15:14 ABMODE[1:0]: Alternate bytes mode
This field defines the alternate-bytes phase mode of operation:
00: No alternate bytes
01: Alternate bytes on a single line
10: Alternate bytes on two lines
11: Alternate bytes on four lines
This field can be written only when BUSY = 0.

RM0385 Rev 7

407/1709
412

Quad-SPI interface (QUADSPI)

RM0385

Bits 13:12 ADSIZE[1:0]: Address size
This bit defines address size:
00: 8-bit address
01: 16-bit address
10: 24-bit address
11: 32-bit address
This field can be written only when BUSY = 0.
Bits 11:10 ADMODE[1:0]: Address mode
This field defines the address phase mode of operation:
00: No address
01: Address on a single line
10: Address on two lines
11: Address on four lines
This field can be written only when BUSY = 0.
Bits 9:8 IMODE[1:0]: Instruction mode
This field defines the instruction phase mode of operation:
00: No instruction
01: Instruction on a single line
10: Instruction on two lines
11: Instruction on four lines
This field can be written only when BUSY = 0.
Bits 7:0 INSTRUCTION[7:0]: Instruction
Instruction to be send to the external SPI device.
This field can be written only when BUSY = 0.

14.5.7

QUADSPI address register (QUADSPI_AR)
Address offset: 0x0018
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ADDRESS[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

ADDRESS[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 ADDRESS[31:0]: Address
Address to be send to the external Flash memory
Writes to this field are ignored when BUSY = 0 or when FMODE = 11 (memory-mapped
mode).
In dual flash mode, ADDRESS[0] is automatically stuck to ‘0’ as the address should
always be even

408/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)

14.5.8

QUADSPI alternate bytes registers (QUADSPI_ABR)
Address offset: 0x001C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ALTERNATE[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

ALTERNATE[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 ALTERNATE[31:0]: Alternate Bytes
Optional data to be send to the external SPI device right after the address.
This field can be written only when BUSY = 0.

14.5.9

QUADSPI data register (QUADSPI_DR)
Address offset: 0x0020
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DATA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DATA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DATA[31:0]: Data
Data to be sent/received to/from the external SPI device.
In indirect write mode, data written to this register is stored on the FIFO before it is sent
to the Flash memory during the data phase. If the FIFO is too full, a write operation is
stalled until the FIFO has enough space to accept the amount of data being written.
In indirect read mode, reading this register gives (via the FIFO) the data which was
received from the Flash memory. If the FIFO does not have as many bytes as requested
by the read operation and if BUSY=1, the read operation is stalled until enough data is
present or until the transfer is complete, whichever happens first.
In automatic polling mode, this register contains the last data read from the Flash
memory (without masking).
Word, halfword, and byte accesses to this register are supported. In indirect write mode,
a byte write adds 1 byte to the FIFO, a halfword write 2, and a word write 4. Similarly, in
indirect read mode, a byte read removes 1 byte from the FIFO, a halfword read 2, and a
word read 4. Accesses in indirect mode must be aligned to the bottom of this register: a
byte read must read DATA[7:0] and a halfword read must read DATA[15:0].

RM0385 Rev 7

409/1709
412

Quad-SPI interface (QUADSPI)

14.5.10

RM0385

QUADSPI polling status mask register (QUADSPI _PSMKR)
Address offset: 0x0024
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MASK[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MASK[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MASK[31:0]: Status mask
Mask to be applied to the status bytes received in polling mode.
For bit n:
0: Bit n of the data received in automatic polling mode is masked and its value is not
considered in the matching logic
1: Bit n of the data received in automatic polling mode is unmasked and its value is
considered in the matching logic
This field can be written only when BUSY = 0.

14.5.11

QUADSPI polling status match register (QUADSPI _PSMAR)
Address offset: 0x0028
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MATCH[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MATCH[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MATCH[31:0]: Status match
Value to be compared with the masked status register to get a match.
This field can be written only when BUSY = 0.

410/1709

RM0385 Rev 7

RM0385

Quad-SPI interface (QUADSPI)

14.5.12

QUADSPI polling interval register (QUADSPI _PIR)
Address offset: 0x002C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

INTERVAL[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 INTERVAL[15:0]: Polling interval
Number of CLK cycles between to read during automatic polling phases.
This field can be written only when BUSY = 0.

14.5.13

QUADSPI low-power timeout register (QUADSPI_LPTR)
Address offset: 0x0030
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

TIMEOUT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 TIMEOUT[15:0]: Timeout period
After each access in memory-mapped mode, the QUADSPI prefetches the subsequent
bytes and holds these bytes in the FIFO. This field indicates how many CLK cycles the
QUADSPI waits after the FIFO becomes full until it raises nCS, putting the Flash
memory in a lower-consumption state.
This field can be written only when BUSY = 0.

RM0385 Rev 7

411/1709
412

Quad-SPI interface (QUADSPI)

14.5.14

RM0385

QUADSPI register map

0

0

0

0

Reset value

0x0020

0

0x0024

DCYC[4:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ABORT

EN

Res.

TEF

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

INSTRUCTION[7:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

QUADSPI_PIR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MATCH[31:0]
0

0

0

0

0

0

0

0

0

TIMEOUT[15:0]
0

0

0

0

Refer to Section 2.2.2 for the register boundary addresses.

RM0385 Rev 7

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

INTERVAL[15:0]
0

Reset value

412/1709

0

MASK[31:0]

Reset value

0x0030

0

DATA[31:0]

Reset value

QUADSPI_
LPTR

CKMODE

TCF

0

ALTERNATE[31:0]

QUADSPI_
PSMAR

0x002C

TCEN

0

ADDRESS[31:0]

QUADSPI_
PSMKR
Reset value

0x0028

0

QUADSPI_DR
Reset value

DMAEN
0

CTEF

0

QUADSPI_ABR
Reset value

Res.
FTF

0

CTCF

0

IMODE[1:0]

0

ADMODE[1:0]

0

ADSIZE[1:0]

0

ABMODE[1:0]

0

QUADSPI_AR

0x0018

0x001C

0

0

ABSIZE[1:0]

0

0

Res.

0

0

DMODE[1:0]

DHHC

Reset value

0

FMODE[1:0]

QUADSPI_CCR

0

Res.

0

SIOO

0

0x0014

Res.

DFM
Res.

Res.

0

DL[31:0]

Reset value

DDRM

QUADSPI_DLR

SSHIFT

0

Reset value
0x0010

Res.

FSEL
Res.

Res.

SMF

0

Res.

0

CSMF

0

TOF

0

0

CTOF

0

0

BUS

0

0

Res.

0

Res.

FLEVEL[6:0]

0

0

0

Res.

Res.

Res.

0

Res.

0

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

QUADSPI_FCR

CSHT

0

Reset value

0x000C

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

FSIZE[4:0]

0

Res.

Res.

Res.

Res.

Res.

Res.

0
Res.

Res.

Res.

0

FTHRES
[4:0]

Res.

Res.

Res.

TEIE

Res.

Res.

Res.

0

Res.

Res.
Res.

QUADSPI_SR

Res.

Reset value

0x0008

0

Res.

QUADSPI_DCR
0x0004

0

Res.

0

FTIE

0

TCIE

0

Res.

0

SMIE

0

Res.

0

Res.

0

Res.

0

TOIE

0

PRESCALER[7:0]

Res.

0

QUADSPI_CR
0x0000

Res.

PMM

APMS

Reset value

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 91. QUADSPI register map and reset values
Register
name

0

0

0

0

0

0

RM0385

Analog-to-digital converter (ADC)

15

Analog-to-digital converter (ADC)

15.1

ADC introduction
The 12-bit ADC is a successive approximation analog-to-digital converter. It has up to 19
multiplexed channels allowing it to measure signals from 16 external sources, two internal
sources, and the VBAT channel. The A/D conversion of the channels can be performed in
single, continuous, scan or discontinuous mode. The result of the ADC is stored into a leftor right-aligned 16-bit data register.
The analog watchdog feature allows the application to detect if the input voltage goes
beyond the user-defined, higher or lower thresholds.

15.2

ADC main features
•

12-bit, 10-bit, 8-bit or 6-bit configurable resolution

•

Interrupt generation at the end of conversion, end of injected conversion, and in case of
analog watchdog or overrun events

•

Single and continuous conversion modes

•

Scan mode for automatic conversion of channel 0 to channel ‘n’

•

Data alignment with in-built data coherency

•

Channel-wise programmable sampling time

•

External trigger option with configurable polarity for both regular and injected
conversions

•

Discontinuous mode

•

Dual/Triple mode (on devices with 2 ADCs or more)

•

Configurable DMA data storage in Dual/Triple ADC mode

•

Configurable delay between conversions in Dual/Triple interleaved mode

•

ADC supply requirements: 2.4 V to 3.6 V at full speed and down to 1.8 V at slower
speed

•

ADC input range: VREF– ≤ VIN ≤ VREF+

•

DMA request generation during regular channel conversion

Figure 70 shows the block diagram of the ADC.
Note:

VREF–, if available (depending on package), must be tied to VSSA.

15.3

ADC functional description
Figure 70 shows a single ADC block diagram and Table 92 gives the ADC pin description.

RM0385 Rev 7

413/1709
460

Analog-to-digital converter (ADC)

RM0385

Figure 70. Single ADC block diagram
Interrupt
enable bits

Flags
DMA overrun
End of conversion
End of injected conversion
Analog watchdog event

OVR

OVRIE

EOC

EOCIE

JEOC

JEOCIE

AWD

AWDIE

ADC Interrupt to NVIC

Analog watchdog
Compare result
Higher threshold (12 bits)

Injected data registers
(4 x 16 bits)

V REF+
V REF-

Regular data register
(16 bits)

V DDA
V SSA

Analog
mux

Address/data bus

Lower threshold (12 bits)

DMA request

ADCx_IN0
ADCx_IN1

GPIO
ports

up to 4
up to 16

ADCx_IN15

ADCCLK

Injected
channels

Analog to digital

Regular
channels

converter

Temp. sensor
V REFINT
V BAT
From ADC prescaler
EXTSEL[3:0] bits

JEXTSEL[3:0] bits
TIM1_TRGO
TIM1_CH4
TIM2_TRGO
TIM2_CH1
TIM3_CH4
TIM4_TRGO
TIM8_CH4
TIM1_TRGO(2)
TIM8_TRGO
TIM8_TRGO(2)
TIM3_CH3
TIM5_TRGO
TIM3_CH1
TIM6_TRGO

EXTEN
[1:0] bits

JEXTEN
[1:0] bits

Start trigger
(injected group)

Start trigger
(regular group)

TIM1_CH1
TIM1_CH2
TIM1_CH3
TIM2_CH2
TIM5_TRGO
TIM4_CH4
TIM3_CH4
TIM8_TRGO
TIM8_TRGO(2)
TIM1_TRGO
TIM1_TRGO(2)
TIM2_TRGO
TIM4_TRGO
TIM6_TRGO

EXTI_11
MS35935V2

414/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)
Table 92. ADC pins
Name

15.3.1

Signal type

Remarks

VREF+

Input, analog reference
positive

The higher/positive reference voltage for the ADC,
1.8 V ≤ VREF+ ≤ VDDA

VDDA

Input, analog supply

Analog power supply equal to VDD and
2.4 V ≤VDDA ≤VDD (3.6 V) for full speed
1.8 V ≤VDDA ≤VDD (3.6 V) for reduced speed

VREF–

Input, analog reference
negative

The lower/negative reference voltage for the ADC,
VREF– = VSSA

VSSA

Input, analog supply
ground

Ground for analog power supply equal to VSS

ADCx_IN[15:0]

Analog input signals

16 analog input channels

ADC on-off control
The ADC is powered on by setting the ADON bit in the ADC_CR2 register. When the ADON
bit is set for the first time, it wakes up the ADC from the Power-down mode.
The conversion starts when either the SWSTART or the JSWSTART bit is set.
The user can stop conversion and put the ADC in power down mode by clearing the ADON
bit. In this mode the ADC consumes almost no power (only a few µA).

RM0385 Rev 7

415/1709
460

Analog-to-digital converter (ADC)

15.3.2

RM0385

ADC1/2 and ADC3 connectivity
ADC1, ADC2 and ADC3 are tightly coupled and share some external channels as described
in Figure 71, Figure 72 and Figure 73.
Figure 71. ADC1 connectivity

ADC1

Channel selection

VIN[0]

ADC123_IN0

VIN[1]

ADC123_IN1

VIN[2]

ADC123_IN2

VIN[3]

ADC123_IN3

VIN[4]

ADC12_IN4

VIN[5]

ADC12_IN5

VIN[6]

ADC12_IN6

VREF+

VIN[7]

ADC12_IN7

VIN[8]

ADC12_IN8

VIN

SAR
ADC1

VIN[9]

ADC12_IN9

VIN[10]

ADC123_IN10

VREF-

VIN[11]

ADC123_IN11

VIN[12]

ADC123_IN12

VIN[13]

ADC123_IN13

VIN[14]

ADC12_IN14

VIN[15]

ADC12_IN15
N.C.
VREFINT
VBAT/4 or VSENSE

VIN[16]
VIN[17]
VIN[18]

MSv35937V1

416/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)
Figure 72. ADC2 connectivity

ADC2

Channel selection

VIN[0]

ADC123_IN0

VIN[1]

ADC123_IN1

VIN[2]

ADC123_IN2

VIN[3]

ADC123_IN3

VIN[4]

ADC12_IN4

VIN[5]

ADC12_IN5

VIN[6]

ADC12_IN6

VREF+

VIN[7]

ADC12_IN7

VIN[8]

ADC12_IN8

VIN

SAR
ADC2

VIN[9]

ADC12_IN9

VIN[10]

ADC123_IN10

VREF-

VIN[11]

ADC123_IN11

VIN[12]

ADC123_IN12

VIN[13]

ADC123_IN13

VIN[14]

ADC12_IN14

VIN[15]

ADC12_IN15
N.C.
N.C.
N.C.

VIN[16]
VIN[17]
VIN[18]

MSv35938V1

RM0385 Rev 7

417/1709
460

Analog-to-digital converter (ADC)

RM0385
Figure 73. ADC3 connectivity

ADC3

Channel selection

VIN[0]

ADC123_IN0

VIN[1]

ADC123_IN1

VIN[2]

ADC123_IN2

VIN[3]

ADC123_IN3

VIN[4]

ADC3_IN4

VIN[5]

ADC3_IN5

VIN[6]

ADC3_IN6

VREF+

VIN[7]

ADC3_IN7

VIN[8]

ADC3_IN8

VIN

SAR
ADC3

VIN[9]

ADC3_IN9

VIN[10]

ADC123_IN10

VREF-

VIN[11]

ADC123_IN11

VIN[12]

ADC123_IN12

VIN[13]

ADC123_IN13

VIN[14]

ADC3_IN14

VIN[15]

ADC3_IN15
N.C.
N.C.
N.C.

VIN[16]
VIN[17]
VIN[18]

MSv35939V1

418/1709

RM0385 Rev 7

RM0385

15.3.3

Analog-to-digital converter (ADC)

ADC clock
The ADC features two clock schemes:
•

Clock for the analog circuitry: ADCCLK, common to all ADCs
This clock is generated from the APB2 clock divided by a programmable prescaler that
allows the ADC to work at fPCLK2/2, /4, /6 or /8. Refer to the datasheets for the
maximum value of ADCCLK.

•

Clock for the digital interface (used for registers read/write access)
This clock is equal to the APB2 clock. The digital interface clock can be
enabled/disabled individually for each ADC through the RCC APB2 peripheral clock
enable register (RCC_APB2ENR).

15.3.4

Channel selection
There are 16 multiplexed channels. It is possible to organize the conversions in two groups:
regular and injected. A group consists of a sequence of conversions that can be done on
any channel and in any order. For instance, it is possible to implement the conversion
sequence in the following order: ADC_IN3, ADC_IN8, ADC_IN2, ADC_IN2, ADC_IN0,
ADC_IN2, ADC_IN2, ADC_IN15.
•

A regular group is composed of up to 16 conversions. The regular channels and their
order in the conversion sequence must be selected in the ADC_SQRx registers. The
total number of conversions in the regular group must be written in the L[3:0] bits in the
ADC_SQR1 register.

•

An injected group is composed of up to 4 conversions. The injected channels and
their order in the conversion sequence must be selected in the ADC_JSQR register.
The total number of conversions in the injected group must be written in the L[1:0] bits
in the ADC_JSQR register.

If the ADC_SQRx or ADC_JSQR registers are modified during a conversion, the current
conversion is reset and a new start pulse is sent to the ADC to convert the newly chosen
group.

Temperature sensor, VREFINT and VBAT internal channels
•

The temperature sensor is internally connected to ADC1_IN18 channel which is shared
with VBAT. Only one conversion, temperature sensor or VBAT, must be selected at a
time. When the temperature sensor and VBAT conversion are set simultaneously, only
the VBAT conversion is performed.
The internal reference voltage VREFINT is connected to ADC1_IN17.

The VBAT channel is connected to ADC1_IN18 channel. It can also be converted as an
injected or regular channel.
Note:

The temperature sensor, VREFINT and the VBAT channel are available only on the master
ADC1 peripheral.

RM0385 Rev 7

419/1709
460

Analog-to-digital converter (ADC)

15.3.5

RM0385

Single conversion mode
In Single conversion mode the ADC does one conversion. This mode is started with the
CONT bit at 0 by either:
•

setting the SWSTART bit in the ADC_CR2 register (for a regular channel only)

•

setting the JSWSTART bit (for an injected channel)

•

external trigger (for a regular or injected channel)

Once the conversion of the selected channel is complete:
•

•

If a regular channel was converted:
–

The converted data are stored into the 16-bit ADC_DR register

–

The EOC (end of conversion) flag is set

–

An interrupt is generated if the EOCIE bit is set

If an injected channel was converted:
–

The converted data are stored into the 16-bit ADC_JDR1 register

–

The JEOC (end of conversion injected) flag is set

–

An interrupt is generated if the JEOCIE bit is set

Then the ADC stops.

15.3.6

Continuous conversion mode
In continuous conversion mode, the ADC starts a new conversion as soon as it finishes one.
This mode is started with the CONT bit at 1 either by external trigger or by setting the
SWSTRT bit in the ADC_CR2 register (for regular channels only).
After each conversion:
•

If a regular group of channels was converted:
–

The last converted data are stored into the 16-bit ADC_DR register

–

The EOC (end of conversion) flag is set

–

An interrupt is generated if the EOCIE bit is set

Note:

Injected channels cannot be converted continuously. The only exception is when an injected
channel is configured to be converted automatically after regular channels in continuous
mode (using JAUTO bit), refer to Auto-injection section).

15.3.7

Timing diagram
As shown in Figure 74, the ADC needs a stabilization time of tSTAB before it starts
converting accurately. After the start of the ADC conversion and after 15 clock cycles, the
EOC flag is set and the 16-bit ADC data register contains the result of the conversion.

420/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)
Figure 74. Timing diagram

ADC_CLK

ADON

SWSTART/
JSWSTART
Start 1st conversion

Start next conversion

ADC conversion

ADC

Next ADC conversion

Conversion time
tSTAB

(total conv. time)

EOC
Software clears the EOC bit
ai16047b

15.3.8

Analog watchdog
The AWD analog watchdog status bit is set if the analog voltage converted by the ADC is
below a lower threshold or above a higher threshold. These thresholds are programmed in
the 12 least significant bits of the ADC_HTR and ADC_LTR 16-bit registers. An interrupt can
be enabled by using the AWDIE bit in the ADC_CR1 register.
The threshold value is independent of the alignment selected by the ALIGN bit in the
ADC_CR2 register. The analog voltage is compared to the lower and higher thresholds
before alignment.
Table 93 shows how the ADC_CR1 register should be configured to enable the analog
watchdog on one or more channels.
Figure 75. Analog watchdog’s guarded area
Analog voltage
Higher threshold

HTR
Guarded area

Lower threshold

LTR
ai16048

Table 93. Analog watchdog channel selection
Channels guarded by the analog
watchdog

ADC_CR1 register control bits (x = don’t care)
AWDSGL bit

AWDEN bit

JAWDEN bit

None

x

0

0

All injected channels

0

0

1

RM0385 Rev 7

421/1709
460

Analog-to-digital converter (ADC)

RM0385

Table 93. Analog watchdog channel selection (continued)
Channels guarded by the analog
watchdog

ADC_CR1 register control bits (x = don’t care)
AWDSGL bit

AWDEN bit

JAWDEN bit

All regular channels

0

1

0

All regular and injected channels

0

1

1

Single(1)

injected channel

1

0

1

regular channel

1

1

0

1

1

1

(1)

Single

Single (1) regular or injected channel
1. Selected by the AWDCH[4:0] bits

15.3.9

Scan mode
This mode is used to scan a group of analog channels.
The Scan mode is selected by setting the SCAN bit in the ADC_CR1 register. Once this bit
has been set, the ADC scans all the channels selected in the ADC_SQRx registers (for
regular channels) or in the ADC_JSQR register (for injected channels). A single conversion
is performed for each channel of the group. After each end of conversion, the next channel
in the group is converted automatically. If the CONT bit is set, regular channel conversion
does not stop at the last selected channel in the group but continues again from the first
selected channel.
If the DMA bit is set, the direct memory access (DMA) controller is used to transfer the data
converted from the regular group of channels (stored in the ADC_DR register) to SRAM
after each regular channel conversion.
The EOC bit is set in the ADC_SR register:
•

At the end of each regular group sequence if the EOCS bit is cleared to 0

•

At the end of each regular channel conversion if the EOCS bit is set to 1

The data converted from an injected channel are always stored into the ADC_JDRx
registers.

15.3.10

Injected channel management
Triggered injection
To use triggered injection, the JAUTO bit must be cleared in the ADC_CR1 register.

422/1709

1.

Start the conversion of a group of regular channels either by external trigger or by
setting the SWSTART bit in the ADC_CR2 register.

2.

If an external injected trigger occurs or if the JSWSTART bit is set during the
conversion of a regular group of channels, the current conversion is reset and the
injected channel sequence switches to Scan-once mode.

3.

Then, the regular conversion of the regular group of channels is resumed from the last
interrupted regular conversion.
If a regular event occurs during an injected conversion, the injected conversion is not
interrupted but the regular sequence is executed at the end of the injected sequence.
Figure 76 shows the corresponding timing diagram.

RM0385 Rev 7

RM0385
Note:

Analog-to-digital converter (ADC)
When using triggered injection, one must ensure that the interval between trigger events is
longer than the injection sequence. For instance, if the sequence length is 30 ADC clock
cycles (that is two conversions with a sampling time of 3 clock periods), the minimum
interval between triggers must be 31 ADC clock cycles.

Auto-injection
If the JAUTO bit is set, then the channels in the injected group are automatically converted
after the regular group of channels. This can be used to convert a sequence of up to 20
conversions programmed in the ADC_SQRx and ADC_JSQR registers.
In this mode, external trigger on injected channels must be disabled.
If the CONT bit is also set in addition to the JAUTO bit, regular channels followed by injected
channels are continuously converted.
Note:

It is not possible to use both the auto-injected and discontinuous modes simultaneously.
Figure 76. Injected conversion latency
ADCCLK

Injection event

Reset ADC

SOC

max latency (1)

ai16049

1. The maximum latency value can be found in the electrical characteristics of the STM32F75xxx and
STM32F74xxx datasheets.

15.3.11

Discontinuous mode
Regular group
This mode is enabled by setting the DISCEN bit in the ADC_CR1 register. It can be used to
convert a short sequence of n conversions (n ≤ 8) that is part of the sequence of
conversions selected in the ADC_SQRx registers. The value of n is specified by writing to
the DISCNUM[2:0] bits in the ADC_CR1 register.
When an external trigger occurs, it starts the next n conversions selected in the ADC_SQRx
registers until all the conversions in the sequence are done. The total sequence length is
defined by the L[3:0] bits in the ADC_SQR1 register.

RM0385 Rev 7

423/1709
460

Analog-to-digital converter (ADC)

RM0385

Example:

Note:

•

n = 3, channels to be converted = 0, 1, 2, 3, 6, 7, 9, 10

•

1st trigger: sequence converted 0, 1, 2. An EOC event is generated at each
conversion.

•

2nd trigger: sequence converted 3, 6, 7. An EOC event is generated at each
conversion

•

3rd trigger: sequence converted 9, 10.An EOC event is generated at each conversion

•

4th trigger: sequence converted 0, 1, 2. An EOC event is generated at each conversion

When a regular group is converted in discontinuous mode, no rollover occurs.
When all subgroups are converted, the next trigger starts the conversion of the first
subgroup. In the example above, the 4th trigger reconverts the channels 0, 1 and 2 in the
1st subgroup.

Injected group
This mode is enabled by setting the JDISCEN bit in the ADC_CR1 register. It can be used to
convert the sequence selected in the ADC_JSQR register, channel by channel, after an
external trigger event.
When an external trigger occurs, it starts the next channel conversions selected in the
ADC_JSQR registers until all the conversions in the sequence are done. The total sequence
length is defined by the JL[1:0] bits in the ADC_JSQR register.
Example:
n = 1, channels to be converted = 1, 2, 3
1st trigger: channel 1 converted
2nd trigger: channel 2 converted
3rd trigger: channel 3 converted and JEOC event generated
4th trigger: channel 1
Note:

When all injected channels are converted, the next trigger starts the conversion of the first
injected channel. In the example above, the 4th trigger reconverts the 1st injected channel
1.
It is not possible to use both the auto-injected and discontinuous modes simultaneously.
Discontinuous mode must not be set for regular and injected groups at the same time.
Discontinuous mode must be enabled only for the conversion of one group.

15.4

Data alignment
The ALIGN bit in the ADC_CR2 register selects the alignment of the data stored after
conversion. Data can be right- or left-aligned as shown in Figure 77 and Figure 78.
The converted data value from the injected group of channels is decreased by the userdefined offset written in the ADC_JOFRx registers so the result can be a negative value.
The SEXT bit represents the extended sign value.
For channels in a regular group, no offset is subtracted so only twelve bits are significant.

424/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)
Figure 77. Right alignment of 12-bit data
Injected group
SEXT SEXT SEXT SEXT

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

Regular group
0

0

0

0

ai16050

Figure 78. Left alignment of 12-bit data
Injected group
SEXT

D11

D10

D9

D8

D8

D7

D7

D6

D5

D4

D3

D2

D5

D4

D3

D2

D1

D1

D0

0

0

0

0

0

0

0

Regular group
D11

D10

D9

D6

D0

ai16051

Special case: when left-aligned, the data are aligned on a half-word basis except when the
resolution is set to 6-bit. in that case, the data are aligned on a byte basis as shown in
Figure 79.
Figure 79. Left alignment of 6-bit data
Injected group
SEXT SEXT SEXT

SEXT

SEXT SEXT SEXT

SEXT SEXT

D5

D4

D3

D3

D2

D2

D1

D0

0

D0

0

0

Regular group
0

0

0

0

0

0

0

0

D5

D4

D1

ai16052

15.5

Channel-wise programmable sampling time
The ADC samples the input voltage for a number of ADCCLK cycles that can be modified
using the SMP[2:0] bits in the ADC_SMPR1 and ADC_SMPR2 registers. Each channel can
be sampled with a different sampling time.
The total conversion time is calculated as follows:
Tconv = Sampling time + 12 cycles
Example:
With ADCCLK = 30 MHz and sampling time = 3 cycles:
Tconv = 3 + 12 = 15 cycles = 0.5 µs with APB2 at 60 MHz

RM0385 Rev 7

425/1709
460

Analog-to-digital converter (ADC)

15.6

RM0385

Conversion on external trigger and trigger polarity
Conversion can be triggered by an external event (e.g. timer capture, EXTI line). If the
EXTEN[1:0] control bits (for a regular conversion) or JEXTEN[1:0] bits (for an injected
conversion) are different from “0b00”, then external events are able to trigger a conversion
with the selected polarity. Table 94 provides the correspondence between the EXTEN[1:0]
and JEXTEN[1:0] values and the trigger polarity.
Table 94. Configuring the trigger polarity
Source

Note:

EXTEN[1:0] / JEXTEN[1:0]

Trigger detection disabled

00

Detection on the rising edge

01

Detection on the falling edge

10

Detection on both the rising and falling edges

11

The polarity of the external trigger can be changed on the fly.
The EXTSEL[3:0] and JEXTSEL[3:0] control bits are used to select which out of 16 possible
events can trigger conversion for the regular and injected groups.
Table 95 gives the possible external trigger for regular conversion.
Table 95. External trigger for regular channels
Source

EXTSEL[3:0]

TIM1_CH1

0000

TIM1_CH2

0001

TIM1_CH3

0010

TIM2_CH2

0011

TIM5_TRGO

0100

TIM4_CH4

0101

TIM3_CH4
TIM8_TRGO

Internal signal from on-chip timers

0110
0111

TIM8_TRGO(2)

1000

TIM1_TRGO

1001

TIM1_TRGO(2)

1010

TIM2_TRGO

1011

TIM4_TRGO

1100

TIM6_TRGO

1101

EXTI line11

426/1709

Type

External pin

RM0385 Rev 7

1111

RM0385

Analog-to-digital converter (ADC)
Table 96 gives the possible external trigger for injected conversion.
Table 96. External trigger for injected channels
Source

Connection type

JEXTSEL[3:0]

TIM1_TRGO

0000

TIM1_CH4

0001

TIM2_TRGO
TIM2_CH1

Internal signal from on-chip timers

0010
0011

TIM3_CH4

0100

TIM4_TRGO

0101

TIM8_CH4

0111

TIM1_TRGO(2)

1000

TIM8_TRGO

1001

TIM8_TRGO(2)
TIM3_CH3

Internal signal from on-chip timers

1010
1011

TIM5_TRGO

1100

TIM3_CH1

1101

TIM6_TRGO

1110

Software source trigger events can be generated by setting SWSTART (for regular
conversion) or JSWSTART (for injected conversion) in ADC_CR2.
A regular group conversion can be interrupted by an injected trigger.
Note:

The trigger selection can be changed on the fly. However, when the selection changes,
there is a time frame of 1 APB clock cycle during which the trigger detection is disabled.
This is to avoid spurious detection during transitions.

15.7

Fast conversion mode
It is possible to perform faster conversion by reducing the ADC resolution. The RES bits are
used to select the number of bits available in the data register. The minimum conversion
time for each resolution is then as follows:
•

12 bits: 3 + 12 = 15 ADCCLK cycles

•

10 bits: 3 + 10 = 13 ADCCLK cycles

•

8 bits: 3 + 8 = 11 ADCCLK cycles

•

6 bits: 3 + 6 = 9 ADCCLK cycles

RM0385 Rev 7

427/1709
460

Analog-to-digital converter (ADC)

15.8

Data management

15.8.1

Using the DMA

RM0385

Since converted regular channel values are stored into a unique data register, it is useful to
use DMA for conversion of more than one regular channel. This avoids the loss of the data
already stored in the ADC_DR register.
When the DMA mode is enabled (DMA bit set to 1 in the ADC_CR2 register), after each
conversion of a regular channel, a DMA request is generated. This allows the transfer of the
converted data from the ADC_DR register to the destination location selected by the
software.
Despite this, if data are lost (overrun), the OVR bit in the ADC_SR register is set and an
interrupt is generated (if the OVRIE enable bit is set). DMA transfers are then disabled and
DMA requests are no longer accepted. In this case, if a DMA request is made, the regular
conversion in progress is aborted and further regular triggers are ignored. It is then
necessary to clear the OVR flag and the DMAEN bit in the used DMA stream, and to reinitialize both the DMA and the ADC to have the wanted converted channel data transferred
to the right memory location. Only then can the conversion be resumed and the data
transfer, enabled again. Injected channel conversions are not impacted by overrun errors.
When OVR = 1 in DMA mode, the DMA requests are blocked after the last valid data have
been transferred, which means that all the data transferred to the RAM can be considered
as valid.
At the end of the last DMA transfer (number of transfers configured in the DMA controller’s
DMA_SxNTR register):
•

No new DMA request is issued to the DMA controller if the DDS bit is cleared to 0 in the
ADC_CR2 register (this avoids generating an overrun error). However the DMA bit is
not cleared by hardware. It must be written to 0, then to 1 to start a new transfer.

•

Requests can continue to be generated if the DDS bit is set to 1. This allows
configuring the DMA in double-buffer circular mode.

To recover the ADC from OVR state when the DMA is used, follow the steps below:

15.8.2

1.

Reinitialize the DMA (adjust destination address and NDTR counter)

2.

Clear the ADC OVR bit in ADC_SR register

3.

Trigger the ADC to start the conversion.

Managing a sequence of conversions without using the DMA
If the conversions are slow enough, the conversion sequence can be handled by the
software. In this case the EOCS bit must be set in the ADC_CR2 register for the EOC status
bit to be set at the end of each conversion, and not only at the end of the sequence. When
EOCS = 1, overrun detection is automatically enabled. Thus, each time a conversion is
complete, EOC is set and the ADC_DR register can be read. The overrun management is
the same as when the DMA is used.
To recover the ADC from OVR state when the EOCS is set, follow the steps below:

428/1709

1.

Clear the ADC OVR bit in ADC_SR register

2.

Trigger the ADC to start the conversion.

RM0385 Rev 7

RM0385

15.8.3

Analog-to-digital converter (ADC)

Conversions without DMA and without overrun detection
It may be useful to let the ADC convert one or more channels without reading the data each
time (if there is an analog watchdog for instance). For that, the DMA must be disabled
(DMA = 0) and the EOC bit must be set at the end of a sequence only (EOCS = 0). In this
configuration, overrun detection is disabled.

15.9

Multi ADC mode
In devices with two ADCs or more, the Dual (with two ADCs) and Triple (with three ADCs)
ADC modes can be used (see Figure 80).
In multi ADC mode, the start of conversion is triggered alternately or simultaneously by the
ADC1 master to the ADC2 and ADC3 slaves, depending on the mode selected by the
MULTI[4:0] bits in the ADC_CCR register.

Note:

In multi ADC mode, when configuring conversion trigger by an external event, the
application must set trigger by the master only and disable trigger by slaves to prevent
spurious triggers that would start unwanted slave conversions.
The four possible modes below are implemented:
•

Injected simultaneous mode

•

Regular simultaneous mode

•

Interleaved mode

•

Alternate trigger mode

It is also possible to use the previous modes combined in the following ways:

Note:

•

Injected simultaneous mode + Regular simultaneous mode

•

Regular simultaneous mode + Alternate trigger mode

In multi ADC mode, the converted data can be read on the multi-mode data register
(ADC_CDR). The status bits can be read in the multi-mode status register (ADC_CSR).

RM0385 Rev 7

429/1709
460

Analog-to-digital converter (ADC)

RM0385
Figure 80. Multi ADC block diagram(1)
Regular data register
(12bits)
bits)
(16
Injected data registers
(4 x 16 bits)

Regular
channels

ADC3(2) (Slave)

Injected
channels

Regular data register
(12
(16bits)
bits)
Injected data registers
(4 x 16 bits)

Regular
channels

internal triggers
Common regular data register
(32 bits)(3)

Dual/Triple
mode control

Address/data bus

ADC2 (Slave)

Injected
channels

Common part

Regular data register
(16 bits)
Injected data registers
(4 x 16 bits)

ADCx_IN0
ADCx_IN1

GPIO
Ports

Regular
channels

ADCx_IN15

Injected
channels

Temp. sensor
VREFINT
VBAT
EXTI_11

ADC1 (Master)
Start trigger mux
(regular group)

Start trigger mux
(injected group)

MS36623V1

1. Although external triggers are present on ADC2 and ADC3 they are not shown in this diagram.
2. In the Dual ADC mode, the ADC3 slave part is not present.
3. In Triple ADC mode, the ADC common data register (ADC_CDR) contains the ADC1, ADC2 and ADC3’s
regular converted data. All 32 register bits are used according to a selected storage order.
In Dual ADC mode, the ADC common data register (ADC_CDR) contains both the ADC1 and ADC2’s
regular converted data. All 32 register bits are used.

430/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)
•

DMA requests in Multi ADC mode:
In Multi ADC mode the DMA may be configured to transfer converted data in three
different modes. In all cases, the DMA streams to use are those connected to the ADC:
–

DMA mode 1: On each DMA request (one data item is available), a half-word
representing an ADC-converted data item is transferred.
In Dual ADC mode, ADC1 data are transferred on the first request, ADC2 data are
transferred on the second request and so on.
In Triple ADC mode, ADC1 data are transferred on the first request, ADC2 data
are transferred on the second request and ADC3 data are transferred on the third
request; the sequence is repeated. So the DMA first transfers ADC1 data followed
by ADC2 data followed by ADC3 data and so on.
DMA mode 1 is used in regular simultaneous triple mode.
Example:
Regular simultaneous triple mode: 3 consecutive DMA requests are generated
(one for each converted data item)
1st request: ADC_CDR[31:0] = ADC1_DR[15:0]
2nd request: ADC_CDR[31:0] = ADC2_DR[15:0]
3rd request: ADC_CDR[31:0] = ADC3_DR[15:0]
4th request: ADC_CDR[31:0] = ADC1_DR[15:0]

–

DMA mode 2: On each DMA request (two data items are available) two halfwords representing two ADC-converted data items are transferred as a word.
In Dual ADC mode, both ADC2 and ADC1 data are transferred on the first request
(ADC2 data take the upper half-word and ADC1 data take the lower half-word) and
so on.
In Triple ADC mode, three DMA requests are generated. On the first request, both
ADC2 and ADC1 data are transferred (ADC2 data take the upper half-word and
ADC1 data take the lower half-word). On the second request, both ADC1 and
ADC3 data are transferred (ADC1 data take the upper half-word and ADC3 data
take the lower half-word).On the third request, both ADC3 and ADC2 data are
transferred (ADC3 data take the upper half-word and ADC2 data take the lower
half-word) and so on.
DMA mode 2 is used in interleaved mode and in regular simultaneous mode (for
Dual ADC mode only).
Example:

a)

Interleaved dual mode: a DMA request is generated each time 2 data items are
available:
1st request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0]
2nd request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0]

b)

Interleaved triple mode: a DMA request is generated each time 2 data items are
available
1st request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0]
2nd request: ADC_CDR[31:0] = ADC1_DR[15:0] | ADC3_DR[15:0]
3rd request: ADC_CDR[31:0] = ADC3_DR[15:0] | ADC2_DR[15:0]
4th request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0]

RM0385 Rev 7

431/1709
460

Analog-to-digital converter (ADC)
–

RM0385

DMA mode 3: This mode is similar to the DMA mode 2. The only differences are
that the on each DMA request (two data items are available) two bytes
representing two ADC converted data items are transferred as a half-word. The
data transfer order is similar to that of the DMA mode 2.
DMA mode 3 is used in interleaved mode in 6-bit and 8-bit resolutions.
Example:

a)

Interleaved dual mode: a DMA request is generated each time 2 data items are
available
1st request: ADC_CDR[15:0] = ADC2_DR[7:0] | ADC1_DR[7:0]
2nd request: ADC_CDR[15:0] = ADC2_DR[7:0] | ADC1_DR[7:0]

b)

Interleaved triple mode: a DMA request is generated each time 2 data items are
available
1st request: ADC_CDR[15:0] = ADC2_DR[7:0] | ADC1_DR[7:0]
2nd request: ADC_CDR[15:0] = ADC1_DR[7:0] | ADC3_DR[15:0]
3rd request: ADC_CDR[15:0] = ADC3_DR[7:0] | ADC2_DR[7:0]
4th request: ADC_CDR[15:0] = ADC2_DR[7:0] | ADC1_DR[7:0]

Overrun detection: If an overrun is detected on one of the concerned ADCs (ADC1 and
ADC2 in dual and triple modes, ADC3 in triple mode only), the DMA requests are no longer
issued to ensure that all the data transferred to the RAM are valid. It may happen that the
EOC bit corresponding to one ADC remains set because the data register of this ADC
contains valid data.

15.9.1

Injected simultaneous mode
This mode converts an injected group of channels. The external trigger source comes from
the injected group multiplexer of ADC1 (selected by the JEXTSEL[3:0] bits in the ADC1_CR2
register). A simultaneous trigger is provided to ADC2 and ADC3.

Note:

Do not convert the same channel on the two/three ADCs (no overlapping sampling times for
the two/three ADCs when converting the same channel).
In simultaneous mode, one must convert sequences with the same length or ensure that the
interval between triggers is longer than the longer of the 2 sequences (Dual ADC mode) /3
sequences (Triple ADC mode). Otherwise, the ADC with the shortest sequence may restart
while the ADC with the longest sequence is completing the previous conversions.
Regular conversions can be performed on one or all ADCs. In that case, they are
independent of each other and are interrupted when an injected event occurs. They are
resumed at the end of the injected conversion group.

432/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)

Dual ADC mode
At the end of conversion event on ADC1 or ADC2:
•

The converted data are stored into the ADC_JDRx registers of each ADC interface.

•

A JEOC interrupt is generated (if enabled on one of the two ADC interfaces) when the
ADC1/ADC2’s injected channels have all been converted.
Figure 81. Injected simultaneous mode on 4 channels: dual ADC mode
ADC1
ADC2

CH0
CH15

CH1
CH14

...

CH2

CH3

CH13

CH12 ...

CH15
CH0
End of conversion on ADC1 and ADC2

Trigger
Sampling
Conversion

ai16054

Triple ADC mode
At the end of conversion event on ADC1, ADC2 or ADC3:
•

The converted data are stored into the ADC_JDRx registers of each ADC interface.

•

A JEOC interrupt is generated (if enabled on one of the three ADC interfaces) when the
ADC1/ADC2/ADC3’s injected channels have all been converted.
Figure 82. Injected simultaneous mode on 4 channels: triple ADC mode
...

ADC1

CH0

CH1

CH2

CH3

ADC2

CH15

CH14

CH13

ADC3

CH10

CH12

CH8

CH12 ...
CH5 ...

CH15
CH0
CH2

End of conversion on ADC1, ADC2 and ADC3

Trigger
Sampling
Conversion

15.9.2

ai16055

Regular simultaneous mode
This mode is performed on a regular group of channels. The external trigger source comes
from the regular group multiplexer of ADC1 (selected by the EXTSEL[3:0] bits in the
ADC1_CR2 register). A simultaneous trigger is provided to ADC2 and ADC3.

Note:

Do not convert the same channel on the two/three ADCs (no overlapping sampling times for
the two/three ADCs when converting the same channel).
In regular simultaneous mode, one must convert sequences with the same length or ensure
that the interval between triggers is longer than the long conversion time of the 2 sequences
(Dual ADC mode) /3 sequences (Triple ADC mode). Otherwise, the ADC with the shortest
sequence may restart while the ADC with the longest sequence is completing the previous
conversions.
Injected conversions must be disabled.

RM0385 Rev 7

433/1709
460

Analog-to-digital converter (ADC)

RM0385

Dual ADC mode
At the end of conversion event on ADC1 or ADC2:
•

A 32-bit DMA transfer request is generated (if DMA[1:0] bits in the ADC_CCR register
are equal to 0b10). This request transfers the ADC2 converted data stored in the upper
half-word of the ADC_CDR 32-bit register to the SRAM and then the ADC1 converted
data stored in the lower half-word of ADC_CCR to the SRAM.

•

An EOC interrupt is generated (if enabled on one of the two ADC interfaces) when the
ADC1/ADC2’s regular channels have all been converted.
Figure 83. Regular simultaneous mode on 16 channels: dual ADC mode
ADC1
ADC2

CH0
CH15

CH1
CH14

...

CH2

CH3

CH13

CH12 ...

CH15
CH0
End of conversion on ADC1 and ADC2

Trigger
Sampling
Conversion

ai16054

Triple ADC mode
At the end of conversion event on ADC1, ADC2 or ADC3:
•

Three 32-bit DMA transfer requests are generated (if DMA[1:0] bits in the ADC_CCR
register are equal to 0b01). Three transfers then take place from the ADC_CDR 32-bit
register to SRAM: first the ADC1 converted data, then the ADC2 converted data and
finally the ADC3 converted data. The process is repeated for each new three
conversions.

•

An EOC interrupt is generated (if enabled on one of the three ADC interfaces) when the
ADC1/ADC2/ADC3’s regular channels are have all been converted.
Figure 84. Regular simultaneous mode on 16 channels: triple ADC mode
ADC1

CH0

CH1

...

CH2

CH3

CH12 ...
CH5 ...

ADC2

CH15

CH14

CH13

ADC3

CH10

CH12

CH8

CH15
CH0
CH2

End of conversion on ADC1, ADC2 and ADC3

Trigger
Sampling
Conversion

15.9.3

ai16055

Interleaved mode
This mode can be started only on a regular group (usually one channel). The external
trigger source comes from the regular channel multiplexer of ADC1.

Dual ADC mode
After an external trigger occurs:

434/1709

•

ADC1 starts immediately

•

ADC2 starts after a delay of several ADC clock cycles

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)
The minimum delay which separates 2 conversions in interleaved mode is configured in the
DELAY bits in the ADC_CCR register. However, an ADC cannot start a conversion if the
complementary ADC is still sampling its input (only one ADC can sample the input signal at
a given time). In this case, the delay becomes the sampling time + 2 ADC clock cycles. For
instance, if DELAY = 5 clock cycles and the sampling takes 15 clock cycles on both ADCs,
then 17 clock cycles will separate conversions on ADC1 and ADC2).
If the CONT bit is set on both ADC1 and ADC2, the selected regular channels of both ADCs
are continuously converted.

Note:

If the conversion sequence is interrupted (for instance when DMA end of transfer occurs),
the multi-ADC sequencer must be reset by configuring it in independent mode first (bits
DUAL[4:0] = 00000) before reprogramming the interleaved mode.
After an EOC interrupt is generated by ADC2 (if enabled through the EOCIE bit) a 32-bit
DMA transfer request is generated (if the DMA[1:0] bits in ADC_CCR are equal to 0b10).
This request first transfers the ADC2 converted data stored in the upper half-word of the
ADC_CDR 32-bit register into SRAM, then the ADC1 converted data stored in the register’s
lower half-word into SRAM.
Figure 85. Interleaved mode on 1 channel in continuous conversion mode: dual ADC
mode
End of conversion on ADC1
...

CH0

ADC1
ADC2
Trigger

Conversion

CH0
...

CH0

Sampling

CH0

End of conversion on ADC2
8 ADCCLK
cycles

ai16056

Triple ADC mode
After an external trigger occurs:
•

ADC1 starts immediately and

•

ADC2 starts after a delay of several ADC clock cycles

•

ADC3 starts after a delay of several ADC clock cycles referred to the ADC2 conversion

The minimum delay which separates 2 conversions in interleaved mode is configured in the
DELAY bits in the ADC_CCR register. However, an ADC cannot start a conversion if the
complementary ADC is still sampling its input (only one ADC can sample the input signal at
a given time). In this case, the delay becomes the sampling time + 2 ADC clock cycles. For
instance, if DELAY = 5 clock cycles and the sampling takes 15 clock cycles on the three
ADCs, then 17 clock cycles will separate the conversions on ADC1, ADC2 and ADC3).
If the CONT bit is set on ADC1, ADC2 and ADC3, the selected regular channels of all ADCs
are continuously converted.
Note:

If the conversion sequence is interrupted (for instance when DMA end of transfer occurs),
the multi-ADC sequencer must be reset by configuring it in independent mode first (bits
DUAL[4:0] = 00000) before reprogramming the interleaved mode.
In this mode a DMA request is generated each time 2 data items are available, (if the
DMA[1:0] bits in the ADC_CCR register are equal to 0b10). The request first transfers the
RM0385 Rev 7

435/1709
460

Analog-to-digital converter (ADC)

RM0385

first converted data stored in the lower half-word of the ADC_CDR 32-bit register to SRAM,
then it transfers the second converted data stored in ADC_CDR’s upper half-word to SRAM.
The sequence is the following:
•

1st request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0]

•

2nd request: ADC_CDR[31:0] = ADC1_DR[15:0] | ADC3_DR[15:0]

•

3rd request: ADC_CDR[31:0] = ADC3_DR[15:0] | ADC2_DR[15:0]

•

4th request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0], ...

Figure 86. Interleaved mode on 1 channel in continuous conversion mode: triple ADC
mode
End of conversion on ADC1
DMA request every 2 conversions
ADC1

CH0

ADC2
ADC3

...

CH0

CH0

CH0

CH0

CH0

CH0

...

CH0

...

CH0

Sampling
Conversion

End of conversion on ADC3

Trigger

End of conversion on ADC2
6 ADCCLK
cycles

15.9.4

ai16058

Alternate trigger mode
This mode can be started only on an injected group. The source of external trigger comes
from the injected group multiplexer of ADC1.

Note:

Regular conversions can be enabled on one or all ADCs. In this case the regular
conversions are independent of each other. A regular conversion is interrupted when the
ADC has to perform an injected conversion. It is resumed when the injected conversion is
finished.
If the conversion sequence is interrupted (for instance when DMA end of transfer occurs),
the multi-ADC sequencer must be reset by configuring it in independent mode first (bits
DUAL[4:0] = 00000) before reprogramming the interleaved mode.
The time interval between 2 trigger events must be greater than or equal to 1 ADC clock
period. The minimum time interval between 2 trigger events that start conversions on the
same ADC is the same as in the single ADC mode.

Dual ADC mode
•

When the 1st trigger occurs, all injected ADC1 channels in the group are converted

•

When the 2nd trigger occurs, all injected ADC2 channels in the group are converted

•

and so on

A JEOC interrupt, if enabled, is generated after all injected ADC1 channels in the group
have been converted.

436/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)
A JEOC interrupt, if enabled, is generated after all injected ADC2 channels in the group
have been converted.
If another external trigger occurs after all injected channels in the group have been
converted then the alternate trigger process restarts by converting the injected ADC1
channels in the group.
Figure 87. Alternate trigger: injected group of each ADC
1st trigger

EOC, JEOC
on ADC1

3rd trigger

(n)th trigger

EOC, JEOC
on ADC1

ADC1

...

ADC2

2nd trigger

EOC, JEOC
on ADC2
4th trigger

EOC, JEOC
on ADC2

Sampling
(n+1)th trigger

Conversion
ai16059

If the injected discontinuous mode is enabled for both ADC1 and ADC2:
•

When the 1st trigger occurs, the first injected ADC1 channel is converted.

•

When the 2nd trigger occurs, the first injected ADC2 channel are converted

•

and so on

A JEOC interrupt, if enabled, is generated after all injected ADC1 channels in the group
have been converted.
A JEOC interrupt, if enabled, is generated after all injected ADC2 channels in the group
have been converted.
If another external trigger occurs after all injected channels in the group have been
converted then the alternate trigger process restarts.
Figure 88. Alternate trigger: 4 injected channels (each ADC) in discontinuous mode
1st trigger

3rd trigger

5th trigger

7th trigger
JEOC on ADC1

Sampling
Conversion

ADC1
ADC2
JEOC on ADC2
2nd trigger

4th trigger

6th trigger

8th trigger

ai16060

Triple ADC mode
•

When the 1st trigger occurs, all injected ADC1 channels in the group are converted.

•

When the 2nd trigger occurs, all injected ADC2 channels in the group are converted.

•

When the 3rd trigger occurs, all injected ADC3 channels in the group are converted.

•

and so on

RM0385 Rev 7

437/1709
460

Analog-to-digital converter (ADC)

RM0385

A JEOC interrupt, if enabled, is generated after all injected ADC1 channels in the group
have been converted.
A JEOC interrupt, if enabled, is generated after all injected ADC2 channels in the group
have been converted.
A JEOC interrupt, if enabled, is generated after all injected ADC3 channels in the group
have been converted.
If another external trigger occurs after all injected channels in the group have been
converted then the alternate trigger process restarts by converting the injected ADC1
channels in the group.
Figure 89. Alternate trigger: injected group of each ADC
1st trigger

4th trigger

EOC, JEOC
on ADC1

EOC, JEOC
on ADC1

ADC1

(n)th trigger

Sampling
Conversion

...

ADC2

2nd trigger
(n+1)th trigger

3rd trigger

(n+2)th trigger

5th trigger
EOC, JEOC
on ADC2

EOC, JEOC
on ADC3
ai16061

15.9.5

Combined regular/injected simultaneous mode
It is possible to interrupt the simultaneous conversion of a regular group to start the
simultaneous conversion of an injected group.

Note:

In combined regular/injected simultaneous mode, one must convert sequences with the
same length or ensure that the interval between triggers is longer than the long conversion
time of the 2 sequences (Dual ADC mode) /3 sequences (Triple ADC mode). Otherwise, the
ADC with the shortest sequence may restart while the ADC with the longest sequence is
completing the previous conversions.

15.9.6

Combined regular simultaneous + alternate trigger mode
It is possible to interrupt the simultaneous conversion of a regular group to start the alternate
trigger conversion of an injected group. Figure 90 shows the behavior of an alternate trigger
interrupting a simultaneous regular conversion.
The injected alternate conversion is immediately started after the injected event. If regular
conversion is already running, in order to ensure synchronization after the injected
conversion, the regular conversion of all (master/slave) ADCs is stopped and resumed
synchronously at the end of the injected conversion.

Note:

438/1709

In combined regular simultaneous + alternate trigger mode, one must convert sequences
with the same length or ensure that the interval between triggers is longer than the long
conversion time of the 2 sequences (Dual ADC mode) /3 sequences (Triple ADC mode).

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)
Otherwise, the ADC with the shortest sequence may restart while the ADC with the longest
sequence is completing the previous conversions.
If the conversion sequence is interrupted (for instance when DMA end of transfer occurs),
the multi-ADC sequencer must be reset by configuring it in independent mode first (bits
DUAL[4:0] = 00000) before reprogramming the interleaved mode.
Figure 90. Alternate + regular simultaneous
1st trigger

CH0

ADC1 reg

CH1

CH2

CH2

CH3

CH3

CH4

CH6

CH7

CH7

CH8

CH0

ADC1 inj
CH3

ADC2 reg

CH5

CH6

CH0

ADC2 inj

synchro not lost
2nd trigger

ai16062

If a trigger occurs during an injected conversion that has interrupted a regular conversion, it
is ignored. Figure 91 shows the behavior in this case (2nd trigger is ignored).
Figure 91. Case of trigger occurring during injected conversion
1st trigger

CH0

ADC1 reg

CH1

3rd trigger

CH2

CH2

CH3

CH3

CH0

ADC1 inj
CH3

ADC2 reg

CH5

CH6

CH4
CH0

CH6

CH7

CH7

CH8

CH0

ADC2 inj

2nd trigger

2nd trigger
ai16063

15.10

Temperature sensor
The temperature sensor can be used to measure the ambient temperature (TA) of the
device.
•

On STM32F75xxx and STM32F74xxx devices, the temperature sensor is internally
connected to the same input channel, ADC1_IN18, as VBAT: ADC1_IN18 is used to
convert the sensor output voltage or VBAT into a digital value. Only one conversion,
temperature sensor or VBAT, must be selected at a time. When the temperature sensor
and the VBAT conversion are set simultaneously, only the VBAT conversion is
performed.

RM0385 Rev 7

439/1709
460

Analog-to-digital converter (ADC)

RM0385

Figure 92 shows the block diagram of the temperature sensor.
When not in use, the sensor can be put in power down mode.
Note:

The TSVREFE bit must be set to enable the conversion of both internal channels: the
ADC1_IN18 (temperature sensor) and the ADC1_IN17 (VREFINT).

Main features
•

Supported temperature range: –40 to 125 °C

•

Precision: ±1.5 °C
Figure 92. Temperature sensor and VREFINT channel block diagram
TSVREFE control bit

V SENSE
ADC1_IN18

converted data
ADC1

Internal
power block

VREFINT

Address/data bus

Temperature
sensor

ADC1_IN17

MS35936V1

1. VSENSE is input to ADC1_IN18.

440/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)

Reading the temperature
To use the sensor:
3.

Select ADC1_IN18 input channel.

4.

Select a sampling time greater than the minimum sampling time specified in the
datasheet.

5.

Set the TSVREFE bit in the ADC_CCR register to wake up the temperature sensor
from power down mode

6.

Start the ADC conversion by setting the SWSTART bit (or by external trigger)

7.

Read the resulting VSENSE data in the ADC data register

8.

Calculate the temperature using the following formula:
Temperature (in °C) = {(VSENSE – V25) / Avg_Slope} + 25
Where:
–

V25 = VSENSE value for 25° C

–

Avg_Slope = average slope of the temperature vs. VSENSE curve (given in mV/°C
or µV/°C)

Refer to the datasheet electrical characteristics section for the actual values of V25 and
Avg_Slope.
Note:

The sensor has a startup time after waking from power down mode before it can output
VSENSE at the correct level. The ADC also has a startup time after power-on, so to minimize
the delay, the ADON and TSVREFE bits should be set at the same time.
The temperature sensor output voltage changes linearly with temperature. The offset of this
linear function depends on each chip due to process variation (up to 45 °C from one chip to
another).
The internal temperature sensor is more suited for applications that detect temperature
variations instead of absolute temperatures. If accurate temperature reading is required, an
external temperature sensor should be used.

15.11

Battery charge monitoring
The VBATE bit in the ADC_CCR register is used to switch to the battery voltage. As the
VBAT voltage could be higher than VDDA, to ensure the correct operation of the ADC, the
VBAT pin is internally connected to a bridge divider.
When the VBATE is set, the bridge is automatically enabled to connect:
•

Note:

VBAT/4 to the ADC1_IN18 input channel

The VBAT and temperature sensor are connected to the same ADC internal channel
(ADC1_IN18). Only one conversion, either temperature sensor or VBAT, must be selected
at a time. When both conversion are enabled simultaneously, only the VBAT conversion is
performed.

RM0385 Rev 7

441/1709
460

Analog-to-digital converter (ADC)

15.12

RM0385

ADC interrupts
An interrupt can be produced on the end of conversion for regular and injected groups,
when the analog watchdog status bit is set and when the overrun status bit is set. Separate
interrupt enable bits are available for flexibility.
Two other flags are present in the ADC_SR register, but there is no interrupt associated with
them:
•

JSTRT (Start of conversion for channels of an injected group)

•

STRT (Start of conversion for channels of a regular group)
Table 97. ADC interrupts
Interrupt event

442/1709

Event flag

Enable control bit

End of conversion of a regular group

EOC

EOCIE

End of conversion of an injected group

JEOC

JEOCIE

Analog watchdog status bit is set

AWD

AWDIE

Overrun

OVR

OVRIE

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)

15.13

ADC registers
Refer to Section 1.1 on page 62 for a list of abbreviations used in register descriptions.
The peripheral registers must be written at word level (32 bits). Read accesses can be done
by bytes (8 bits), half-words (16 bits) or words (32 bits).

15.13.1

ADC status register (ADC_SR)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OVR

STRT

JSTRT

JEOC

EOC

AWD

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

Bits 31:6 Reserved, must be kept at reset value.
Bit 5 OVR: Overrun
This bit is set by hardware when data are lost (either in single mode or in dual/triple mode). It
is cleared by software. Overrun detection is enabled only when DMA = 1 or EOCS = 1.
0: No overrun occurred
1: Overrun has occurred
Bit 4 STRT: Regular channel start flag
This bit is set by hardware when regular channel conversion starts. It is cleared by software.
0: No regular channel conversion started
1: Regular channel conversion has started
Bit 3 JSTRT: Injected channel start flag
This bit is set by hardware when injected group conversion starts. It is cleared by software.
0: No injected group conversion started
1: Injected group conversion has started
Bit 2 JEOC: Injected channel end of conversion
This bit is set by hardware at the end of the conversion of all injected channels in the group.
It is cleared by software.
0: Conversion is not complete
1: Conversion complete
Bit 1 EOC: Regular channel end of conversion
This bit is set by hardware at the end of the conversion of a regular group of channels. It is
cleared by software or by reading the ADC_DR register.
0: Conversion not complete (EOCS=0), or sequence of conversions not complete (EOCS=1)
1: Conversion complete (EOCS=0), or sequence of conversions complete (EOCS=1)
Bit 0 AWD: Analog watchdog flag
This bit is set by hardware when the converted voltage crosses the values programmed in
the ADC_LTR and ADC_HTR registers. It is cleared by software.
0: No analog watchdog event occurred
1: Analog watchdog event occurred

RM0385 Rev 7

443/1709
460

Analog-to-digital converter (ADC)

15.13.2

RM0385

ADC control register 1 (ADC_CR1)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

Res.

Res.

Res.

Res.

Res.

OVRIE
rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

SCAN
rw

DISCNUM[2:0]
rw

rw

rw

25

24
RES

JDISCEN DISCEN JAUTO AWDSGL
rw

rw

rw

rw

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

6

5

4

3

2

1

0

JEOCIE

AWDIE

EOCIE

rw

rw

rw

rw

rw

rw

rw

AWDEN JAWDEN

AWDCH[4:0]
rw

Bits 31:27 Reserved, must be kept at reset value.
Bit 26 OVRIE: Overrun interrupt enable
This bit is set and cleared by software to enable/disable the Overrun interrupt.
0: Overrun interrupt disabled
1: Overrun interrupt enabled. An interrupt is generated when the OVR bit is set.
Bits 25:24 RES[1:0]: Resolution
These bits are written by software to select the resolution of the conversion.
00: 12-bit (minimum 15 ADCCLK cycles)
01: 10-bit (minimum 13 ADCCLK cycles)
10: 8-bit (minimum 11 ADCCLK cycles)
11: 6-bit (minimum 9 ADCCLK cycles)
Bit 23 AWDEN: Analog watchdog enable on regular channels
This bit is set and cleared by software.
0: Analog watchdog disabled on regular channels
1: Analog watchdog enabled on regular channels
Bit 22 JAWDEN: Analog watchdog enable on injected channels
This bit is set and cleared by software.
0: Analog watchdog disabled on injected channels
1: Analog watchdog enabled on injected channels
Bits 21:16 Reserved, must be kept at reset value.
Bits 15:13 DISCNUM[2:0]: Discontinuous mode channel count
These bits are written by software to define the number of regular channels to be converted
in discontinuous mode, after receiving an external trigger.
000: 1 channel
001: 2 channels
...
111: 8 channels
Bit 12 JDISCEN: Discontinuous mode on injected channels
This bit is set and cleared by software to enable/disable discontinuous mode on the injected
channels of a group.
0: Discontinuous mode on injected channels disabled
1: Discontinuous mode on injected channels enabled

444/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)

Bit 11 DISCEN: Discontinuous mode on regular channels
This bit is set and cleared by software to enable/disable Discontinuous mode on regular
channels.
0: Discontinuous mode on regular channels disabled
1: Discontinuous mode on regular channels enabled
Bit 10 JAUTO: Automatic injected group conversion
This bit is set and cleared by software to enable/disable automatic injected group conversion
after regular group conversion.
0: Automatic injected group conversion disabled
1: Automatic injected group conversion enabled
Bit 9 AWDSGL: Enable the watchdog on a single channel in scan mode
This bit is set and cleared by software to enable/disable the analog watchdog on the channel
identified by the AWDCH[4:0] bits.
0: Analog watchdog enabled on all channels
1: Analog watchdog enabled on a single channel
Bit 8 SCAN: Scan mode
This bit is set and cleared by software to enable/disable the Scan mode. In Scan mode, the
inputs selected through the ADC_SQRx or ADC_JSQRx registers are converted.
0: Scan mode disabled
1: Scan mode enabled
Note: An EOC interrupt is generated if the EOCIE bit is set:
–
At the end of each regular group sequence if the EOCS bit is cleared to 0
–
At the end of each regular channel conversion if the EOCS bit is set to 1
Note: A JEOC interrupt is generated only on the end of conversion of the last channel if the
JEOCIE bit is set.
Bit 7 JEOCIE: Interrupt enable for injected channels
This bit is set and cleared by software to enable/disable the end of conversion interrupt for
injected channels.
0: JEOC interrupt disabled
1: JEOC interrupt enabled. An interrupt is generated when the JEOC bit is set.
Bit 6 AWDIE: Analog watchdog interrupt enable
This bit is set and cleared by software to enable/disable the analog watchdog interrupt.
0: Analog watchdog interrupt disabled
1: Analog watchdog interrupt enabled
Bit 5 EOCIE: Interrupt enable for EOC
This bit is set and cleared by software to enable/disable the end of conversion interrupt.
0: EOC interrupt disabled
1: EOC interrupt enabled. An interrupt is generated when the EOC bit is set.
Bits 4:0 AWDCH[4:0]: Analog watchdog channel select bits
These bits are set and cleared by software. They select the input channel to be guarded by
the analog watchdog.
Note: 00000: ADC analog input Channel0
00001: ADC analog input Channel1
...
01111: ADC analog input Channel15
10000: ADC analog input Channel16
10001: ADC analog input Channel17
10010: ADC analog input Channel18
Other values reserved

RM0385 Rev 7

445/1709
460

Analog-to-digital converter (ADC)

15.13.3

RM0385

ADC control register 2 (ADC_CR2)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

Res.

SWSTART

29

28

27

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

DDS

DMA

Res.

Res.

Res.

Res.

Res.

Res.

CONT

ADON

rw

rw

rw

rw

EXTEN

26

25

24

EXTSEL[3:0]

ALIGN EOCS
rw

rw

23

22

Res.

JSWSTART

21

20

19

JEXTEN

18

17

16

JEXTSEL[3:0]

Bit 31 Reserved, must be kept at reset value.
Bit 30 SWSTART: Start conversion of regular channels
This bit is set by software to start conversion and cleared by hardware as soon as the
conversion starts.
0: Reset state
1: Starts conversion of regular channels
Note: This bit can be set only when ADON = 1 otherwise no conversion is launched.
Bits 29:28 EXTEN: External trigger enable for regular channels
These bits are set and cleared by software to select the external trigger polarity and enable
the trigger of a regular group.
00: Trigger detection disabled
01: Trigger detection on the rising edge
10: Trigger detection on the falling edge
11: Trigger detection on both the rising and falling edges
Bits 27:24 EXTSEL[3:0]: External event select for regular group
These bits select the external event used to trigger the start of conversion of a regular group:
0000: Timer 1 CH1
0001: Timer 1 CH2
0010: Timer 1 CH3
0011: Timer 2 CH2
0100: Timer 5 TRGO
0101: Timer 4 CH4
0110: Timer 3 CH4
0111: Timer 8 TRGO
1000: Timer 8 TRGO(2)
1001: Timer 1 TRGO
1010: Timer 1 TRGO(2)
1011: Timer 2 TRGO
1100: Timer 4 TRGO
1101: Timer 6 TRGO
1110: Reserved
1111: EXTI line11
Bit 23 Reserved, must be kept at reset value.

446/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)

Bit 22 JSWSTART: Start conversion of injected channels
This bit is set by software and cleared by hardware as soon as the conversion starts.
0: Reset state
1: Starts conversion of injected channels
This bit can be set only when ADON = 1 otherwise no conversion is launched.
Bits 21:20 JEXTEN: External trigger enable for injected channels
These bits are set and cleared by software to select the external trigger polarity and enable
the trigger of an injected group.
00: Trigger detection disabled
01: Trigger detection on the rising edge
10: Trigger detection on the falling edge
11: Trigger detection on both the rising and falling edges
Bits 19:16 JEXTSEL[3:0]: External event select for injected group
These bits select the external event used to trigger the start of conversion of an injected group.
0000: Timer 1 TRGO
0001: Timer 1 CH4
0010: Timer 2 TRGO
0011: Timer 2 CH1
0100: Timer 3 CH4
0101: Timer4 TRGO
0110: Reserved
0111: Timer 8 CH4
1000: Timer 1 TRGO(2)
1001: Timer 8 TRGO
1010: Timer 8 TRGO(2)
1011: Timer 3 CH3
1100: Timer 5 TRGO
1101: Timer 3 CH1
1110: Timer 6 TRGO
1111: Reserved
Bits 15:12 Reserved, must be kept at reset value.
Bit 11 ALIGN: Data alignment
This bit is set and cleared by software. Refer to Figure 77 and Figure 78.
0: Right alignment
1: Left alignment
Bit 10 EOCS: End of conversion selection
This bit is set and cleared by software.
0: The EOC bit is set at the end of each sequence of regular conversions. Overrun detection
is enabled only if DMA=1.
1: The EOC bit is set at the end of each regular conversion. Overrun detection is enabled.
Bit 9 DDS: DMA disable selection (for single ADC mode)
This bit is set and cleared by software.
0: No new DMA request is issued after the last transfer (as configured in the DMA controller)
1: DMA requests are issued as long as data are converted and DMA=1

RM0385 Rev 7

447/1709
460

Analog-to-digital converter (ADC)

RM0385

Bit 8 DMA: Direct memory access mode (for single ADC mode)
This bit is set and cleared by software. Refer to the DMA controller chapter for more details.
0: DMA mode disabled
1: DMA mode enabled
Bits 7:2 Reserved, must be kept at reset value.
Bit 1 CONT: Continuous conversion
This bit is set and cleared by software. If it is set, conversion takes place continuously until it
is cleared.
0: Single conversion mode
1: Continuous conversion mode
Bit 0 ADON: A/D Converter ON / OFF
This bit is set and cleared by software.
0: Disable ADC conversion and go to power down mode
1: Enable ADC

15.13.4

ADC sample time register 1 (ADC_SMPR1)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

rw

rw

SMP15_0

SMP14[2:0]

rw

rw

rw

26

25

24

23

SMP18[2:0]

22

21

20

SMP17[2:0]

19

18

SMP16[2:0]

17

16

SMP15[2:1]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

SMP13[2:0]
rw

SMP12[2:0]
rw

SMP11[2:0]
rw

SMP10[2:0]
rw

rw

Bits 31: 27 Reserved, must be kept at reset value.
Bits 26:0 SMPx[2:0]: Channel x sampling time selection
These bits are written by software to select the sampling time individually for each channel.
During sampling cycles, the channel selection bits must remain unchanged.
Note: 000: 3 cycles
001: 15 cycles
010: 28 cycles
011: 56 cycles
100: 84 cycles
101: 112 cycles
110: 144 cycles
111: 480 cycles

448/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)

15.13.5

ADC sample time register 2 (ADC_SMPR2)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

Res.

Res.

15

14

SMP5_0

29

28

27

26

SMP9[2:0]

rw

24

23

22

21

20

SMP7[2:0]

19

18

SMP6[2:0]

17

16

SMP5[2:1]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

SMP4[2:0]

rw

25
SMP8[2:0]

rw

SMP3[2:0]
rw

SMP2[2:0]

SMP1[2:0]

rw

SMP0[2:0]

rw

rw

rw

Bits 31:30 Reserved, must be kept at reset value.
Bits 29:0 SMPx[2:0]: Channel x sampling time selection
These bits are written by software to select the sampling time individually for each channel.
During sample cycles, the channel selection bits must remain unchanged.
Note: 000: 3 cycles
001: 15 cycles
010: 28 cycles
011: 56 cycles
100: 84 cycles
101: 112 cycles
110: 144 cycles
111: 480 cycles

15.13.6

ADC injected channel data offset register x (ADC_JOFRx) (x=1..4)
Address offset: 0x14-0x20
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

15

14

13

12

Res.

Res.

Res.

Res.

JOFFSETx[11:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 JOFFSETx[11:0]: Data offset for injected channel x
These bits are written by software to define the offset to be subtracted from the raw
converted data when converting injected channels. The conversion result can be read from
in the ADC_JDRx registers.

15.13.7

ADC watchdog higher threshold register (ADC_HTR)
Address offset: 0x24
Reset value: 0x0000 0FFF

RM0385 Rev 7

449/1709
460

Analog-to-digital converter (ADC)

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

15

14

13

12

Res.

Res.

Res.

Res.

HT[11:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 HT[11:0]: Analog watchdog higher threshold
These bits are written by software to define the higher threshold for the analog watchdog.

Note:

The software can write to these registers when an ADC conversion is ongoing. The
programmed value will be effective when the next conversion is complete. Writing to this
register is performed with a write delay that can create uncertainty on the effective time at
which the new value is programmed.

15.13.8

ADC watchdog lower threshold register (ADC_LTR)
Address offset: 0x28
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

15

14

13

12

Res.

Res.

Res.

Res.

LT[11:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 LT[11:0]: Analog watchdog lower threshold
These bits are written by software to define the lower threshold for the analog watchdog.

Note:

The software can write to these registers when an ADC conversion is ongoing. The
programmed value will be effective when the next conversion is complete. Writing to this
register is performed with a write delay that can create uncertainty on the effective time at
which the new value is programmed.

15.13.9

ADC regular sequence register 1 (ADC_SQR1)
Address offset: 0x2C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

SQ16_0
rw

450/1709

12

11

10

9

8

SQ15[4:0]
rw

rw

rw

23

22

21

20

19

18

rw

rw

rw

rw

rw

rw

7

rw

rw

6

5

4

3

2

1

0

rw

rw

L[3:0]

rw

rw

rw

rw

RM0385 Rev 7

16

SQ16[4:1]

SQ14[4:0]
rw

17

SQ13[4:0]
rw

rw

rw

rw

rw

RM0385

Analog-to-digital converter (ADC)

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:20 L[3:0]: Regular channel sequence length
These bits are written by software to define the total number of conversions in the regular
channel conversion sequence.
0000: 1 conversion
0001: 2 conversions
...
1111: 16 conversions
Bits 19:15 SQ16[4:0]: 16th conversion in regular sequence
These bits are written by software with the channel number (0..18) assigned as the 16th in
the conversion sequence.
Bits 14:10 SQ15[4:0]: 15th conversion in regular sequence
Bits 9:5 SQ14[4:0]: 14th conversion in regular sequence
Bits 4:0 SQ13[4:0]: 13th conversion in regular sequence

15.13.10 ADC regular sequence register 2 (ADC_SQR2)
Address offset: 0x30
Reset value: 0x0000 0000
31

30

Res.

Res.

15

14

29

28

rw

rw

13

12

26

25

24

23

rw

rw

rw

rw

rw

11

10

9

8

7

SQ12[4:0]

SQ10_0
rw

27

rw

rw

21

20

19

18

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

SQ11[4:0]

SQ9[4:0]
rw

22

rw

rw

rw

rw

16

SQ10[4:1]

SQ8[4:0]
rw

17

SQ7[4:0]
rw

rw

rw

rw

rw

Bits 31:30 Reserved, must be kept at reset value.
Bits 29:26 SQ12[4:0]: 12th conversion in regular sequence
These bits are written by software with the channel number (0..18) assigned as the 12th in
the sequence to be converted.
Bits 24:20 SQ11[4:0]: 11th conversion in regular sequence
Bits 19:15 SQ10[4:0]: 10th conversion in regular sequence
Bits 14:10 SQ9[4:0]: 9th conversion in regular sequence
Bits 9:5 SQ8[4:0]: 8th conversion in regular sequence
Bits 4:0 SQ7[4:0]: 7th conversion in regular sequence

RM0385 Rev 7

451/1709
460

Analog-to-digital converter (ADC)

RM0385

15.13.11 ADC regular sequence register 3 (ADC_SQR3)
Address offset: 0x34
Reset value: 0x0000 0000
31

30

Res.

Res.

29

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

27

26

25

24

23

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

SQ6[4:0]

SQ4_0
rw

28

SQ3[4:0]
rw

22

21

20

19

SQ5[4:0]

17

16

SQ4[4:1]

SQ2[4:0]
rw

18

SQ1[4:0]
rw

Bits 31:30 Reserved, must be kept at reset value.
Bits 29:25 SQ6[4:0]: 6th conversion in regular sequence
These bits are written by software with the channel number (0..18) assigned as the 6th in the
sequence to be converted.
Bits 24:20 SQ5[4:0]: 5th conversion in regular sequence
Bits 19:15 SQ4[4:0]: 4th conversion in regular sequence
Bits 14:10 SQ3[4:0]: 3rd conversion in regular sequence
Bits 9:5 SQ2[4:0]: 2nd conversion in regular sequence
Bits 4:0 SQ1[4:0]: 1st conversion in regular sequence

452/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)

15.13.12 ADC injected sequence register (ADC_JSQR)
Address offset: 0x38
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

JSQ4[0]
rw

JSQ3[4:0]
rw

21

20

19

JL[1:0]

17

16

JSQ4[4:1]

JSQ2[4:0]
rw

18

JSQ1[4:0]
rw

Bits 31:22 Reserved, must be kept at reset value.
Bits 21:20 JL[1:0]: Injected sequence length
These bits are written by software to define the total number of conversions in the injected
channel conversion sequence.
00: 1 conversion
01: 2 conversions
10: 3 conversions
11: 4 conversions
Bits 19:15 JSQ4[4:0]: 4th conversion in injected sequence (when JL[1:0]=3, see note below)
These bits are written by software with the channel number (0..18) assigned as the 4th in the
sequence to be converted.
Bits 14:10 JSQ3[4:0]: 3rd conversion in injected sequence (when JL[1:0]=3, see note below)
Bits 9:5 JSQ2[4:0]: 2nd conversion in injected sequence (when JL[1:0]=3, see note below)
Bits 4:0 JSQ1[4:0]: 1st conversion in injected sequence (when JL[1:0]=3, see note below)

Note:

When JL[1:0]=3 (4 injected conversions in the sequencer), the ADC converts the channels
in the following order: JSQ1[4:0], JSQ2[4:0], JSQ3[4:0], and JSQ4[4:0].
When JL=2 (3 injected conversions in the sequencer), the ADC converts the channels in the
following order: JSQ2[4:0], JSQ3[4:0], and JSQ4[4:0].
When JL=1 (2 injected conversions in the sequencer), the ADC converts the channels in
starting from JSQ3[4:0], and then JSQ4[4:0].
When JL=0 (1 injected conversion in the sequencer), the ADC converts only JSQ4[4:0]
channel.

15.13.13 ADC injected data register x (ADC_JDRx) (x= 1..4)
Address offset: 0x3C - 0x48
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

JDATA[15:0]
r

RM0385 Rev 7

453/1709
460

Analog-to-digital converter (ADC)

RM0385

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 JDATA[15:0]: Injected data
These bits are read-only. They contain the conversion result from injected channel x. The
data are left -or right-aligned as shown in Figure 77 and Figure 78.

15.13.14 ADC regular data register (ADC_DR)
Address offset: 0x4C
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

DATA[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 DATA[15:0]: Regular data
These bits are read-only. They contain the conversion result from the regular
channels. The data are left- or right-aligned as shown in Figure 77 and
Figure 78.

15.13.15 ADC Common status register (ADC_CSR)
Address offset: 0x00 (this offset address is relative to ADC1 base address + 0x300)
Reset value: 0x0000 0000
This register provides an image of the status bits of the different ADCs. Nevertheless it is
read-only and does not allow to clear the different status bits. Instead each status bit must
be cleared by writing it to 0 in the corresponding ADC_SR register.
31
Res.

30
Res.

15

14

Res.

Res.

29
Res.

13

28
Res.

12

OVR2 STRT2

27

26

Res.

11

Res.

10

JSTRT
JEOC2
2

25
Res.

24
Res.

9

8

EOC2

AWD2

r

r

23
Res.

22
Res.

7

6

Res.

Res.

21
OVR3

20

19

r

r

16
AWD3

ADC3
r

r

r

r

r

5

4

3

2

1

0

EOC1

AWD1

r

r

OVR1

STRT1 JSTRT1 JEOC 1
ADC1

r

r

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 OVR3: Overrun flag of ADC3
This bit is a copy of the OVR bit in the ADC3_SR register.
Bit 20 STRT3: Regular channel Start flag of ADC3
This bit is a copy of the STRT bit in the ADC3_SR register.

454/1709

17
EOC3

r

ADC2
r

18

STRT3 JSTRT3 JEOC 3

RM0385 Rev 7

r

r

r

RM0385

Analog-to-digital converter (ADC)

Bit 19 JSTRT3: Injected channel Start flag of ADC3
This bit is a copy of the JSTRT bit in the ADC3_SR register.
Bit 18 JEOC3: Injected channel end of conversion of ADC3
This bit is a copy of the JEOC bit in the ADC3_SR register.
Bit 17 EOC3: End of conversion of ADC3
This bit is a copy of the EOC bit in the ADC3_SR register.
Bit 16 AWD3: Analog watchdog flag of ADC3
This bit is a copy of the AWD bit in the ADC3_SR register.
Bits 15:14 Reserved, must be kept at reset value.
Bit 13 OVR2: Overrun flag of ADC2
This bit is a copy of the OVR bit in the ADC2_SR register.
Bit 12 STRT2: Regular channel Start flag of ADC2
This bit is a copy of the STRT bit in the ADC2_SR register.
Bit 11 JSTRT2: Injected channel Start flag of ADC2
This bit is a copy of the JSTRT bit in the ADC2_SR register.
Bit 10 JEOC2: Injected channel end of conversion of ADC2
This bit is a copy of the JEOC bit in the ADC2_SR register.
Bit 9 EOC2: End of conversion of ADC2
This bit is a copy of the EOC bit in the ADC2_SR register.
Bit 8 AWD2: Analog watchdog flag of ADC2
This bit is a copy of the AWD bit in the ADC2_SR register.
Bits 7:6 Reserved, must be kept at reset value.
Bit 5 OVR1: Overrun flag of ADC1
This bit is a copy of the OVR bit in the ADC1_SR register.
Bit 4 STRT1: Regular channel Start flag of ADC1
This bit is a copy of the STRT bit in the ADC1_SR register.
Bit 3 JSTRT1: Injected channel Start flag of ADC1
This bit is a copy of the JSTRT bit in the ADC1_SR register.
Bit 2 JEOC1: Injected channel end of conversion of ADC1
This bit is a copy of the JEOC bit in the ADC1_SR register.
Bit 1 EOC1: End of conversion of ADC1
This bit is a copy of the EOC bit in the ADC1_SR register.
Bit 0 AWD1: Analog watchdog flag of ADC1
This bit is a copy of the AWD bit in the ADC1_SR register.

15.13.16 ADC common control register (ADC_CCR)
Address offset: 0x04 (this offset address is relative to ADC1 base address + 0x300)
Reset value: 0x0000 0000

RM0385 Rev 7

455/1709
460

Analog-to-digital converter (ADC)

RM0385

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

DMA[1:0]
rw

rw

13

12

DDS

Res.

rw

11

10

9

8

DELAY[3:0]
rw

rw

rw

23

22

TSVREFE VBATE

21

20

19

18

Res.

Res.

Res.

Res.

rw

rw

7

6

5

Res.

Res.

Res.

rw

4

3

2

17

16

ADCPRE
rw

rw

1

0

rw

rw

MULTI[4:0]
rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bit 23 TSVREFE: Temperature sensor and VREFINT enable
This bit is set and cleared by software to enable/disable the temperature sensor and the
VREFINT channel.
0: Temperature sensor and VREFINT channel disabled
1: Temperature sensor and VREFINT channel enabled
Note: VBATE must be disabled when TSVREFE is set. If both bits are set, only the VBAT
conversion is performed.
Bit 22 VBATE: VBAT enable
This bit is set and cleared by software to enable/disable the VBAT channel.
0: VBAT channel disabled
1: VBAT channel enabled
Bits 21:18 Reserved, must be kept at reset value.
Bits 17:16 ADCPRE: ADC prescaler
Set and cleared by software to select the frequency of the clock to the ADC. The clock is
common for all the ADCs.
Note: 00: PCLK2 divided by 2
01: PCLK2 divided by 4
10: PCLK2 divided by 6
11: PCLK2 divided by 8
Bits 15:14 DMA: Direct memory access mode for multi ADC mode
This bit-field is set and cleared by software. Refer to the DMA controller section for more
details.
00: DMA mode disabled
01: DMA mode 1 enabled (2 / 3 half-words one by one - 1 then 2 then 3)
10: DMA mode 2 enabled (2 / 3 half-words by pairs - 2&1 then 1&3 then 3&2)
11: DMA mode 3 enabled (2 / 3 bytes by pairs - 2&1 then 1&3 then 3&2)
Bit 13 DDS: DMA disable selection (for multi-ADC mode)
This bit is set and cleared by software.
0: No new DMA request is issued after the last transfer (as configured in the DMA
controller). DMA bits are not cleared by hardware, however they must have been cleared
and set to the wanted mode by software before new DMA requests can be generated.
1: DMA requests are issued as long as data are converted and DMA = 01, 10 or 11.
Bit 12 Reserved, must be kept at reset value.

456/1709

RM0385 Rev 7

RM0385

Analog-to-digital converter (ADC)

Bits 11:8 DELAY: Delay between 2 sampling phases
Set and cleared by software. These bits are used in dual or triple interleaved modes.
0000: 5 * TADCCLK
0001: 6 * TADCCLK
0010: 7 * TADCCLK
...
1111: 20 * TADCCLK
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:0 MULTI[4:0]: Multi ADC mode selection
These bits are written by software to select the operating mode.
– All the ADCs independent:
00000: Independent mode
– 00001 to 01001: Dual mode, ADC1 and ADC2 working together, ADC3 is independent
00001: Combined regular simultaneous + injected simultaneous mode
00010: Combined regular simultaneous + alternate trigger mode
00011: Reserved
00101: Injected simultaneous mode only
00110: Regular simultaneous mode only
00111: interleaved mode only
01001: Alternate trigger mode only
– 10001 to 11001: Triple mode: ADC1, 2 and 3 working together
10001: Combined regular simultaneous + injected simultaneous mode
10010: Combined regular simultaneous + alternate trigger mode
10011: Reserved
10101: Injected simultaneous mode only
10110: Regular simultaneous mode only
10111: interleaved mode only
11001: Alternate trigger mode only
All other combinations are reserved and must not be programmed
Note: In multi mode, a change of channel configuration generates an abort that can cause a
loss of synchronization. It is recommended to disable the multi ADC mode before any
configuration change.

RM0385 Rev 7

457/1709
460

Analog-to-digital converter (ADC)

RM0385

15.13.17 ADC common regular data register for dual and triple modes
(ADC_CDR)
Address offset: 0x08 (this offset address is relative to ADC1 base address + 0x300)
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DATA2[15:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

DATA1[15:0]
r

Bits 31:16 DATA2[15:0]: 2nd data item of a pair of regular conversions
– In dual mode, these bits contain the regular data of ADC2. Refer to Dual ADC mode.
– In triple mode, these bits contain alternatively the regular data of ADC2, ADC1 and ADC3.
Refer to Triple ADC mode.
Bits 15:0 DATA1[15:0]: 1st data item of a pair of regular conversions
– In dual mode, these bits contain the regular data of ADC1. Refer to Dual ADC mode
– In triple mode, these bits contain alternatively the regular data of ADC1, ADC3 and ADC2.
Refer to Triple ADC mode.

15.13.18 ADC register map
The following table summarizes the ADC registers.
Table 98. ADC global register map
Offset

Register

0x000 - 0x04C

ADC1

0x050 - 0x0FC

Reserved

0x100 - 0x14C

ADC2

0x118 - 0x1FC

Reserved

0x200 - 0x24C

ADC3

0x250 - 0x2FC

Reserved

0x300 - 0x308

Common registers

458/1709

RM0385 Rev 7

AWDIE

EOCIE

0

0

0

0

0

0

0

0

STRT

JSTRT

JEOC

EOC

AWD

Res.

JEOCIE

0

SCAN

0

AWD SGL

0

JAUTO

Res.

Res.

Res.

Res.

Res.

0

Res.

0

DISCEN

0

DISC
NUM [2:0]

0
JDISCEN

0

JAWDEN

RES[1:0]

Res.

Res.

OVRIE
0

AWDEN

Reset value

Res.

ADC_CR1

Res.

0x04

Res.

Reset value

OVR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ADC_SR

Res.

0x00

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 99. ADC register map and reset values for each ADC

0

0

0

0

0

AWDCH[4:0]
0

0

0

0

0

RM0385

Analog-to-digital converter (ADC)

0

0

0

0

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ADC_JOFR1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

0

0

0

0

0

Res.

0

Res.

0

Res.

Res.

Res.

Res.

DDS

0

0

0

0

0

0

0

JOFFSET2[11:0]
0

0

0

0

0

0

0

JOFFSET3[11:0]
0

0

0

0

0

0

0

JOFFSET4[11:0]
0

0

0

0

0

0

HT[11:0]
1

1

1

1

1

1

LT[11:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

JDATA[15:0]
0

0

0

0

0

0

0

0

0

JDATA[15:0]
0

0

0

0

0

0

0

0

0

JDATA[15:0]
0

0

0

0

0

0

0

0

0

Regular DATA[15:0]
0

RM0385 Rev 7

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

ADC_DR

0

JDATA[15:0]

0
Res.

Reset value
0x4C

0

JOFFSET1[11:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

0x48

0

0
Res.

Reset value
ADC_JDR4

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

ADC_JDR3

0

0
Res.

Reset value
0x44

0

0
Res.

0x40

0

0

Injected channel sequence JSQx_x bits

Reset value
ADC_JDR2

0

JL[1:0]

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

ADC_JDR1

0

0

Regular channel sequence SQx_x bits

Reset value
0x3C

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.
0

Res.

Res.

0x38

Res.

Reset value
ADC_JSQR

0

Res.

ADC_SQR3

0

0

Regular channel sequence SQx_x bits
0

Res.

Reset value
0x34

0

0

Regular channel sequence SQx_x bits

Res.

0x30

L[3:0]
0

Res.

Reset value
ADC_SQR2

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.
Res.

Res.

Res.

Res.

Res.

Res.

ADC_SQR1

0

0
Res.

Reset value
0x2C

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.
Res.

Res.

Res.

Res.

Res.

0x28

0

1
Res.

Reset value
ADC_LTR

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.
Res.

Res.

Res.

ADC_HTR

0

0
Res.

Reset value
0x24

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.
Res.

0x20

0

0
Res.

Reset value
ADC_JOFR4

0

0
Res.

ADC_JOFR3

0

0

Reset value
0x1C

0

0

0

Sample time bits SMPx_x

Reset value
0x18

0

Sample time bits SMPx_x

ADC_SMPR2

ADC_JOFR2

0

DMA

Res.

Res.

Res.

Res.

JEXTEN[1:0]

JSWSTART

Res.

0

ADON

0

CONT

0

EOCS

0

Res.

0x14

0

ADC_SMPR1

Res.

0x10

0

JEXTSEL
[3:0]

Res.

0x0C

0

EXTSEL [3:0]

ALIGN

Reset value

EXTEN[1:0]

ADC_CR2

Res.

0x08

Register

SWSTART

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 99. ADC register map and reset values for each ADC (continued)

0

0

0

0

0

0

0

0

0

0

459/1709
460

Analog-to-digital converter (ADC)

RM0385

ADC_CDR
Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

JEOC

EOC

AWD

STRT

0

0

0

0

Res.

0

MULTI [4:0]

0

0

0

0

0

0

0

0

0

0

Regular DATA1[15:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

460/1709

0

ADC1

Res.

Res.

Res.

DDS
0

DELAY [3:0]

Regular DATA2[15:0]

0

-

JSTRT

0

Res.

0

OVR

0

Res.

EOC

0

ADC2

DMA[1:0]
0

AWD

0

JEOC

0

ADCPRE[1:0]

Res.

Res.

Res.

VBATE
0

Res.

TSVREFE

Res.

0

STRT

0

JSTRT

0

Res.

0

OVR

EOC

AWD

0

Res.

JEOC

STRT

JSTRT

Res.

OVR

0

ADC3

Res.

Res.

Res.

Res.

Res.

Res.

ADC_CCR

0

-

Reset value
0x08

Res.

Res.

Res.

Reset value

-

0x04

Res.

Res.

Res.

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

ADC_CSR

Res.

0x00

Register

Res.

Offset

Res.

Table 100. ADC register map and reset values (common ADC registers)

RM0385 Rev 7

0

0

0

RM0385

Digital-to-analog converter (DAC)

16

Digital-to-analog converter (DAC)

16.1

DAC introduction
The DAC module is a 12-bit, voltage output digital-to-analog converter. The DAC can be
configured in 8- or 12-bit mode and may be used in conjunction with the DMA controller. In
12-bit mode, the data could be left- or right-aligned. The DAC has two output channels, each
with its own converter. In dual DAC channel mode, conversions could be done
independently or simultaneously when both channels are grouped together for synchronous
update operations. An input reference pin, VREF+ (shared with ADC) is available for better
resolution.

16.2

DAC main features
•

Two DAC converters: one output channel each

•

Left or right data alignment in 12-bit mode

•

Synchronized update capability

•

Noise-wave generation

•

Triangular-wave generation

•

Dual DAC channel for independent or simultaneous conversions

•

DMA capability for each channel

•

DMA underrun error detection

•

External triggers for conversion

•

Input voltage reference, VREF+

Figure 93 shows the block diagram of a DAC channel and Table 101 gives the pin
description.

RM0385 Rev 7

461/1709
482

Digital-to-analog converter (DAC)

RM0385
Figure 93. DAC channel block diagram

DAC control register
TSELx[2:0] bits
Trigger selectorx

SWTR IGx
TIM2_T RGO
TIM4_T RGO
TIM5_TRGO
TIM6_T RGO
TIM7_T RGO
TIM8_TRGO

DMAENx

EXTI_9
DM A req ue stx
DHRx

Control logicx

12-bit

LFSRx

trianglex

TENx
MAMPx[3:0] bits
WAVENx[1:0] bits

12-bit

DORx
12-bit
VDDA
DAC1_ OU T1/2

Digital-to-analog
converterx

VSSA
VR EF+

ai14708d

Table 101. DAC pins
Name

Signal type

Remarks

VREF+

Input, analog reference
positive

The higher/positive reference voltage for the DAC,
1.8 V ≤ VREF+ ≤ VDDA

VDDA

Input, analog supply

Analog power supply

VSSA

Input, analog supply ground

Ground for analog power supply

DAC_OUTx

Analog output signal

DAC channelx analog output

Note:

Once the DAC channelx is enabled, the corresponding GPIO pin (PA4 or PA5) is
automatically connected to the analog converter output (DAC_OUTx). In order to avoid
parasitic consumption, the PA4 or PA5 pin should first be configured to analog (AIN).

16.3

DAC functional description

16.3.1

DAC channel enable
Each DAC channel can be powered on by setting its corresponding ENx bit in the DAC_CR
register. The DAC channel is then enabled after a startup time tWAKEUP.

462/1709

RM0385 Rev 7

RM0385

Digital-to-analog converter (DAC)

Note:

The ENx bit enables the analog DAC Channelx macrocell only. The DAC Channelx digital
interface is enabled even if the ENx bit is reset.

16.3.2

DAC output buffer enable
The DAC integrates two output buffers that can be used to reduce the output impedance,
and to drive external loads directly without having to add an external operational amplifier.
Each DAC channel output buffer can be enabled and disabled using the corresponding
BOFFx bit in the DAC_CR register.
Figure 94. DAC output buffer connection
DAC_CR.BOFF1
VREF+

TSEL1[2:0]

Bypass, when
off

12
8

DAC

CH1

TSEL2[2:0]

DAC1

8

Buffer

PA4

VREF+
12

CH2

DAC

Buffer

Bypass, when
off

PA5

DAC_CR.BOFF2
MSv35941V1

16.3.3

DAC data format
Depending on the selected configuration mode, the data have to be written into the specified
register as described below:
•

Single DAC channelx, there are three possibilities:
–

8-bit right alignment: the software has to load data into the DAC_DHR8Rx [7:0]
bits (stored into the DHRx[11:4] bits)

–

12-bit left alignment: the software has to load data into the DAC_DHR12Lx [15:4]
bits (stored into the DHRx[11:0] bits)

–

12-bit right alignment: the software has to load data into the DAC_DHR12Rx [11:0]
bits (stored into the DHRx[11:0] bits)

Depending on the loaded DAC_DHRyyyx register, the data written by the user is shifted and
stored into the corresponding DHRx (data holding registerx, which are internal non-memorymapped registers). The DHRx register is then loaded into the DORx register either
automatically, by software trigger or by an external event trigger.

RM0385 Rev 7

463/1709
482

Digital-to-analog converter (DAC)

RM0385

Figure 95. Data registers in single DAC channel mode

31

24

15

7

0
8-bit right aligned
12-bit left aligned
12-bit right aligned
ai14710b

•

Dual DAC channels, there are three possibilities:
–

8-bit right alignment: data for DAC channel1 to be loaded into the DAC_DHR8RD
[7:0] bits (stored into the DHR1[11:4] bits) and data for DAC channel2 to be loaded
into the DAC_DHR8RD [15:8] bits (stored into the DHR2[11:4] bits)

–

12-bit left alignment: data for DAC channel1 to be loaded into the DAC_DHR12LD
[15:4] bits (stored into the DHR1[11:0] bits) and data for DAC channel2 to be
loaded into the DAC_DHR12LD [31:20] bits (stored into the DHR2[11:0] bits)

–

12-bit right alignment: data for DAC channel1 to be loaded into the
DAC_DHR12RD [11:0] bits (stored into the DHR1[11:0] bits) and data for DAC
channel2 to be loaded into the DAC_DHR12LD [27:16] bits (stored into the
DHR2[11:0] bits)

Depending on the loaded DAC_DHRyyyD register, the data written by the user is shifted
and stored into DHR1 and DHR2 (data holding registers, which are internal non-memorymapped registers). The DHR1 and DHR2 registers are then loaded into the DOR1 and
DOR2 registers, respectively, either automatically, by software trigger or by an external
event trigger.
Figure 96. Data registers in dual DAC channel mode

31

24

15

7

0
8-bit right aligned
12-bit left aligned
12-bit right aligned
ai14709b

16.3.4

DAC conversion
The DAC_DORx cannot be written directly and any data transfer to the DAC channelx must
be performed by loading the DAC_DHRx register (write to DAC_DHR8Rx, DAC_DHR12Lx,
DAC_DHR12Rx, DAC_DHR8RD, DAC_DHR12LD or DAC_DHR12RD).
Data stored in the DAC_DHRx register are automatically transferred to the DAC_DORx
register after one APB1 clock cycle, if no hardware trigger is selected (TENx bit in DAC_CR
register is reset). However, when a hardware trigger is selected (TENx bit in DAC_CR
register is set) and a trigger occurs, the transfer is performed three APB1 clock cycles later.

464/1709

RM0385 Rev 7

RM0385

Digital-to-analog converter (DAC)
When DAC_DORx is loaded with the DAC_DHRx contents, the analog output voltage
becomes available after a time tSETTLING that depends on the power supply voltage and the
analog output load.
Figure 97. Timing diagram for conversion with trigger disabled TEN = 0
APB1_CLK

DHR

DOR

0x1AC

0x1AC

Output voltage
available on DAC_OUT pin

tSETTLING

16.3.5

ai14711b

DAC output voltage
Digital inputs are converted to output voltages on a linear conversion between 0 and VREF+.
The analog output voltages on each DAC channel pin are determined by the following
equation:
DOR
DACoutput = V REF × -------------4096

16.3.6

DAC trigger selection
If the TENx control bit is set, conversion can then be triggered by an external event (timer
counter, external interrupt line). The TSELx[2:0] control bits determine which out of 8
possible events will trigger conversion as shown in Table 102.
Table 102. External triggers
Source

Type

TSEL[2:0]

Timer 6 TRGO event

000

Timer 8 TRGO event

001

Timer 7 TRGO event
Timer 5 TRGO event

Internal signal from on-chip
timers

010
011

Timer 2 TRGO event

100

Timer 4 TRGO event

101

EXTI line9

External pin

110

SWTRIG

Software control bit

111

Each time a DAC interface detects a rising edge on the selected timer TRGO output, or on
the selected external interrupt line 9, the last data stored into the DAC_DHRx register are
transferred into the DAC_DORx register. The DAC_DORx register is updated three APB1
cycles after the trigger occurs.

RM0385 Rev 7

465/1709
482

Digital-to-analog converter (DAC)

RM0385

If the software trigger is selected, the conversion starts once the SWTRIG bit is set.
SWTRIG is reset by hardware once the DAC_DORx register has been loaded with the
DAC_DHRx register contents.
Note:

TSELx[2:0] bit cannot be changed when the ENx bit is set.
When software trigger is selected, the transfer from the DAC_DHRx register to the
DAC_DORx register takes only one APB1 clock cycle.

16.3.7

DMA request
Each DAC channel has a DMA capability. Two DMA channels are used to service DAC
channel DMA requests.
A DAC DMA request is generated when an external trigger (but not a software trigger)
occurs while the DMAENx bit is set. The value of the DAC_DHRx register is then transferred
into the DAC_DORx register.
In dual mode, if both DMAENx bits are set, two DMA requests are generated. If only one
DMA request is needed, you should set only the corresponding DMAENx bit. In this way, the
application can manage both DAC channels in dual mode by using one DMA request and a
unique DMA channel.

DMA underrun
The DAC DMA request is not queued so that if a second external trigger arrives before the
acknowledgement for the first external trigger is received (first request), then no new
request is issued and the DMA channelx underrun flag DMAUDRx in the DAC_SR register
is set, reporting the error condition. DMA data transfers are then disabled and no further
DMA request is treated. The DAC channelx continues to convert old data.
The software should clear the DMAUDRx flag by writing “1”, clear the DMAEN bit of the
used DMA stream and re-initialize both DMA and DAC channelx to restart the transfer
correctly. The software should modify the DAC trigger conversion frequency or lighten the
DMA workload to avoid a new DMA underrun. Finally, the DAC conversion could be
resumed by enabling both DMA data transfer and conversion trigger.
For each DAC channelx, an interrupt is also generated if its corresponding DMAUDRIEx bit
in the DAC_CR register is enabled.

16.3.8

Noise generation
In order to generate a variable-amplitude pseudonoise, an LFSR (linear feedback shift
register) is available. DAC noise generation is selected by setting WAVEx[1:0] to “01”. The
preloaded value in LFSR is 0xAAA. This register is updated three APB1 clock cycles after
each trigger event, following a specific calculation algorithm.

466/1709

RM0385 Rev 7

RM0385

Digital-to-analog converter (DAC)
Figure 98. DAC LFSR register calculation algorithm

XOR
X6
X 12

11

10

9

8

7

6

X4
5

4

X0

X
3

2

1

0

12
NOR

ai14713c

The LFSR value, that may be masked partially or totally by means of the MAMPx[3:0] bits in
the DAC_CR register, is added up to the DAC_DHRx contents without overflow and this
value is then stored into the DAC_DORx register.
If LFSR is 0x0000, a ‘1 is injected into it (antilock-up mechanism).
It is possible to reset LFSR wave generation by resetting the WAVEx[1:0] bits.
Figure 99. DAC conversion (SW trigger enabled) with LFSR wave generation
APB1_CLK

DHR

0x00

0xAAA

DOR

0xD55

SWTRIG
ai14714b

Note:

The DAC trigger must be enabled for noise generation by setting the TENx bit in the
DAC_CR register.

16.3.9

Triangle-wave generation
It is possible to add a small-amplitude triangular waveform on a DC or slowly varying signal.
DAC triangle-wave generation is selected by setting WAVEx[1:0] to “10”. The amplitude is
configured through the MAMPx[3:0] bits in the DAC_CR register. An internal triangle counter
is incremented three APB1 clock cycles after each trigger event. The value of this counter is
then added to the DAC_DHRx register without overflow and the sum is stored into the
DAC_DORx register. The triangle counter is incremented as long as it is less than the
maximum amplitude defined by the MAMPx[3:0] bits. Once the configured amplitude is
reached, the counter is decremented down to 0, then incremented again and so on.

RM0385 Rev 7

467/1709
482

Digital-to-analog converter (DAC)

RM0385

It is possible to reset triangle wave generation by resetting the WAVEx[1:0] bits.
Figure 100. DAC triangle wave generation

n
tio

en

cr
em
en

em

cr

ta

De

MAMPx[3:0] max amplitude
+ DAC_DHRx base value

In

n
tio
ta

DAC_DHRx base value
0
ai14715c

Figure 101. DAC conversion (SW trigger enabled) with triangle wave generation
APB1_CLK

DHR

DOR

0x00

0xAAA

0xD55

SWTRIG
ai14714b

Note:

The DAC trigger must be enabled for noise generation by setting the TENx bit in the
DAC_CR register.
The MAMPx[3:0] bits must be configured before enabling the DAC, otherwise they cannot
be changed.

16.4

Dual DAC channel conversion
To efficiently use the bus bandwidth in applications that require the two DAC channels at the
same time, three dual registers are implemented: DHR8RD, DHR12RD and DHR12LD. A
unique register access is then required to drive both DAC channels at the same time.
Eleven possible conversion modes are possible using the two DAC channels and these dual
registers. All the conversion modes can nevertheless be obtained using separate DHRx
registers if needed.
All modes are described in the paragraphs below.

468/1709

RM0385 Rev 7

RM0385

16.4.1

Digital-to-analog converter (DAC)

Independent trigger without wave generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure different trigger sources by setting different values in the TSEL1[2:0] and
TSEL2[2:0] bits

•

Load the dual DAC channel data into the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

When a DAC channel1 trigger arrives, the DHR1 register is transferred into DAC_DOR1
(three APB1 clock cycles later).
When a DAC channel2 trigger arrives, the DHR2 register is transferred into DAC_DOR2
(three APB1 clock cycles later).

16.4.2

Independent trigger with single LFSR generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure different trigger sources by setting different values in the TSEL1[2:0] and
TSEL2[2:0] bits

•

Configure the two DAC channel WAVEx[1:0] bits as “01” and the same LFSR mask
value in the MAMPx[3:0] bits

•

Load the dual DAC channel data into the desired DHR register (DHR12RD, DHR12LD
or DHR8RD)

When a DAC channel1 trigger arrives, the LFSR1 counter, with the same mask, is added to
the DHR1 register and the sum is transferred into DAC_DOR1 (three APB1 clock cycles
later). Then the LFSR1 counter is updated.
When a DAC channel2 trigger arrives, the LFSR2 counter, with the same mask, is added to
the DHR2 register and the sum is transferred into DAC_DOR2 (three APB1 clock cycles
later). Then the LFSR2 counter is updated.

16.4.3

Independent trigger with different LFSR generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure different trigger sources by setting different values in the TSEL1[2:0] and
TSEL2[2:0] bits

•

Configure the two DAC channel WAVEx[1:0] bits as “01” and set different LFSR masks
values in the MAMP1[3:0] and MAMP2[3:0] bits

•

Load the dual DAC channel data into the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

When a DAC channel1 trigger arrives, the LFSR1 counter, with the mask configured by
MAMP1[3:0], is added to the DHR1 register and the sum is transferred into DAC_DOR1
(three APB1 clock cycles later). Then the LFSR1 counter is updated.
When a DAC channel2 trigger arrives, the LFSR2 counter, with the mask configured by
MAMP2[3:0], is added to the DHR2 register and the sum is transferred into DAC_DOR2
(three APB1 clock cycles later). Then the LFSR2 counter is updated.

RM0385 Rev 7

469/1709
482

Digital-to-analog converter (DAC)

16.4.4

RM0385

Independent trigger with single triangle generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure different trigger sources by setting different values in the TSEL1[2:0] and
TSEL2[2:0] bits

•

Configure the two DAC channel WAVEx[1:0] bits as “1x” and the same maximum
amplitude value in the MAMPx[3:0] bits

•

Load the dual DAC channel data into the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

When a DAC channel1 trigger arrives, the DAC channel1 triangle counter, with the same
triangle amplitude, is added to the DHR1 register and the sum is transferred into
DAC_DOR1 (three APB1 clock cycles later). The DAC channel1 triangle counter is then
updated.
When a DAC channel2 trigger arrives, the DAC channel2 triangle counter, with the same
triangle amplitude, is added to the DHR2 register and the sum is transferred into
DAC_DOR2 (three APB1 clock cycles later). The DAC channel2 triangle counter is then
updated.

16.4.5

Independent trigger with different triangle generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure different trigger sources by setting different values in the TSEL1[2:0] and
TSEL2[2:0] bits

•

Configure the two DAC channel WAVEx[1:0] bits as “1x” and set different maximum
amplitude values in the MAMP1[3:0] and MAMP2[3:0] bits

•

Load the dual DAC channel data into the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

When a DAC channel1 trigger arrives, the DAC channel1 triangle counter, with a triangle
amplitude configured by MAMP1[3:0], is added to the DHR1 register and the sum is
transferred into DAC_DOR1 (three APB1 clock cycles later). The DAC channel1 triangle
counter is then updated.
When a DAC channel2 trigger arrives, the DAC channel2 triangle counter, with a triangle
amplitude configured by MAMP2[3:0], is added to the DHR2 register and the sum is
transferred into DAC_DOR2 (three APB1 clock cycles later). The DAC channel2 triangle
counter is then updated.

16.4.6

Simultaneous software start
To configure the DAC in this conversion mode, the following sequence is required:
•

Load the dual DAC channel data to the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

In this configuration, one APB1 clock cycle later, the DHR1 and DHR2 registers are
transferred into DAC_DOR1 and DAC_DOR2, respectively.

470/1709

RM0385 Rev 7

RM0385

16.4.7

Digital-to-analog converter (DAC)

Simultaneous trigger without wave generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure the same trigger source for both DAC channels by setting the same value in
the TSEL1[2:0] and TSEL2[2:0] bits

•

Load the dual DAC channel data to the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

When a trigger arrives, the DHR1 and DHR2 registers are transferred into DAC_DOR1 and
DAC_DOR2, respectively (after three APB1 clock cycles).

16.4.8

Simultaneous trigger with single LFSR generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure the same trigger source for both DAC channels by setting the same value in
the TSEL1[2:0] and TSEL2[2:0] bits

•

Configure the two DAC channel WAVEx[1:0] bits as “01” and the same LFSR mask
value in the MAMPx[3:0] bits

•

Load the dual DAC channel data to the desired DHR register (DHR12RD, DHR12LD or
DHR8RD)

When a trigger arrives, the LFSR1 counter, with the same mask, is added to the DHR1
register and the sum is transferred into DAC_DOR1 (three APB1 clock cycles later). The
LFSR1 counter is then updated. At the same time, the LFSR2 counter, with the same mask,
is added to the DHR2 register and the sum is transferred into DAC_DOR2 (three APB1
clock cycles later). The LFSR2 counter is then updated.

16.4.9

Simultaneous trigger with different LFSR generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure the same trigger source for both DAC channels by setting the same value in
the TSEL1[2:0] and TSEL2[2:0] bits

•

Configure the two DAC channel WAVEx[1:0] bits as “01” and set different LFSR mask
values using the MAMP1[3:0] and MAMP2[3:0] bits

•

Load the dual DAC channel data into the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

When a trigger arrives, the LFSR1 counter, with the mask configured by MAMP1[3:0], is
added to the DHR1 register and the sum is transferred into DAC_DOR1 (three APB1 clock
cycles later). The LFSR1 counter is then updated.
At the same time, the LFSR2 counter, with the mask configured by MAMP2[3:0], is added to
the DHR2 register and the sum is transferred into DAC_DOR2 (three APB1 clock cycles
later). The LFSR2 counter is then updated.

RM0385 Rev 7

471/1709
482

Digital-to-analog converter (DAC)

16.4.10

RM0385

Simultaneous trigger with single triangle generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure the same trigger source for both DAC channels by setting the same value in
the TSEL1[2:0] and TSEL2[2:0] bits

•

Configure the two DAC channel WAVEx[1:0] bits as “1x” and the same maximum
amplitude value using the MAMPx[3:0] bits

•

Load the dual DAC channel data into the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

When a trigger arrives, the DAC channel1 triangle counter, with the same triangle
amplitude, is added to the DHR1 register and the sum is transferred into DAC_DOR1 (three
APB1 clock cycles later). The DAC channel1 triangle counter is then updated.
At the same time, the DAC channel2 triangle counter, with the same triangle amplitude, is
added to the DHR2 register and the sum is transferred into DAC_DOR2 (three APB1 clock
cycles later). The DAC channel2 triangle counter is then updated.

16.4.11

Simultaneous trigger with different triangle generation
To configure the DAC in this conversion mode, the following sequence is required:
•

Set the two DAC channel trigger enable bits TEN1 and TEN2

•

Configure the same trigger source for both DAC channels by setting the same value in
the TSEL1[2:0] and TSEL2[2:0] bits

•

Configure the two DAC channel WAVEx[1:0] bits as “1x” and set different maximum
amplitude values in the MAMP1[3:0] and MAMP2[3:0] bits

•

Load the dual DAC channel data into the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

When a trigger arrives, the DAC channel1 triangle counter, with a triangle amplitude
configured by MAMP1[3:0], is added to the DHR1 register and the sum is transferred into
DAC_DOR1 (three APB1 clock cycles later). Then the DAC channel1 triangle counter is
updated.
At the same time, the DAC channel2 triangle counter, with a triangle amplitude configured
by MAMP2[3:0], is added to the DHR2 register and the sum is transferred into DAC_DOR2
(three APB1 clock cycles later). Then the DAC channel2 triangle counter is updated.

472/1709

RM0385 Rev 7

RM0385

Digital-to-analog converter (DAC)

16.5

DAC registers
Refer to Section 1 on page 62 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by words (32 bits).

16.5.1

DAC control register (DAC_CR)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

Res.

Res.

DMAU
DRIE2

DMA
EN2

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

Res.

DMAU
DRIE1

DMA
EN1

rw

rw

Res.

27

26

25

24

MAMP2[3:0]

rw

rw

22

21

WAVE2[1:0]

MAMP1[3:0]
rw

23

rw

rw

19

18

17

16

TEN2

BOFF2

EN2

rw

rw

rw

rw

3

2

1

0

TEN1

BOFF1

EN1

rw

rw

rw

TSEL2[2:0]

WAVE1[1:0]
rw

20

TSEL1[2:0]
rw

rw

rw

Bits 31:30 Reserved, must be kept at reset value.
Bit 29 DMAUDRIE2: DAC channel2 DMA underrun interrupt enable
This bit is set and cleared by software.
0: DAC channel2 DMA underrun interrupt disabled
1: DAC channel2 DMA underrun interrupt enabled
Bit 28 DMAEN2: DAC channel2 DMA enable
This bit is set and cleared by software.
0: DAC channel2 DMA mode disabled
1: DAC channel2 DMA mode enabled
Bits 27:24 MAMP2[3:0]: DAC channel2 mask/amplitude selector
These bits are written by software to select mask in wave generation mode or amplitude in
triangle generation mode.
0000: Unmask bit0 of LFSR/ triangle amplitude equal to 1
0001: Unmask bits[1:0] of LFSR/ triangle amplitude equal to 3
0010: Unmask bits[2:0] of LFSR/ triangle amplitude equal to 7
0011: Unmask bits[3:0] of LFSR/ triangle amplitude equal to 15
0100: Unmask bits[4:0] of LFSR/ triangle amplitude equal to 31
0101: Unmask bits[5:0] of LFSR/ triangle amplitude equal to 63
0110: Unmask bits[6:0] of LFSR/ triangle amplitude equal to 127
0111: Unmask bits[7:0] of LFSR/ triangle amplitude equal to 255
1000: Unmask bits[8:0] of LFSR/ triangle amplitude equal to 511
1001: Unmask bits[9:0] of LFSR/ triangle amplitude equal to 1023
1010: Unmask bits[10:0] of LFSR/ triangle amplitude equal to 2047
≥ 1011: Unmask bits[11:0] of LFSR/ triangle amplitude equal to 4095
Bits 23:22 WAVE2[1:0]: DAC channel2 noise/triangle wave generation enable
These bits are set/reset by software.
00: wave generation disabled
01: Noise wave generation enabled
1x: Triangle wave generation enabled
Note: Only used if bit TEN2 = 1 (DAC channel2 trigger enabled)

RM0385 Rev 7

473/1709
482

Digital-to-analog converter (DAC)

RM0385

Bits 21:19 TSEL2[2:0]: DAC channel2 trigger selection
These bits select the external event used to trigger DAC channel2
000: Timer 6 TRGO event
001: Timer 8 TRGO event
010: Timer 7 TRGO event
011: Timer 5 TRGO event
100: Timer 2 TRGO event
101: Timer 4 TRGO event
110: External line9
111: Software trigger
Note: Only used if bit TEN2 = 1 (DAC channel2 trigger enabled).
Bit 18 TEN2: DAC channel2 trigger enable
This bit is set and cleared by software to enable/disable DAC channel2 trigger
0: DAC channel2 trigger disabled and data written into the DAC_DHRx register are
transferred one APB1 clock cycle later to the DAC_DOR2 register
1: DAC channel2 trigger enabled and data from the DAC_DHRx register are transferred
three APB1 clock cycles later to the DAC_DOR2 register
Note: When software trigger is selected, the transfer from the DAC_DHRx register to the
DAC_DOR2 register takes only one APB1 clock cycle.
Bit 17 BOFF2: DAC channel2 output buffer disable
This bit is set and cleared by software to enable/disable DAC channel2 output buffer.
0: DAC channel2 output buffer enabled
1: DAC channel2 output buffer disabled
Bit 16 EN2: DAC channel2 enable
This bit is set and cleared by software to enable/disable DAC channel2.
0: DAC channel2 disabled
1: DAC channel2 enabled
Bits 15:14 Reserved, must be kept at reset value.
Bit 13 DMAUDRIE1: DAC channel1 DMA Underrun Interrupt enable
This bit is set and cleared by software.
0: DAC channel1 DMA Underrun Interrupt disabled
1: DAC channel1 DMA Underrun Interrupt enabled
Bit 12 DMAEN1: DAC channel1 DMA enable
This bit is set and cleared by software.
0: DAC channel1 DMA mode disabled
1: DAC channel1 DMA mode enabled

474/1709

RM0385 Rev 7

RM0385

Digital-to-analog converter (DAC)

Bits 11:8 MAMP1[3:0]: DAC channel1 mask/amplitude selector
These bits are written by software to select mask in wave generation mode or amplitude in
triangle generation mode.
0000: Unmask bit0 of LFSR/ triangle amplitude equal to 1
0001: Unmask bits[1:0] of LFSR/ triangle amplitude equal to 3
0010: Unmask bits[2:0] of LFSR/ triangle amplitude equal to 7
0011: Unmask bits[3:0] of LFSR/ triangle amplitude equal to 15
0100: Unmask bits[4:0] of LFSR/ triangle amplitude equal to 31
0101: Unmask bits[5:0] of LFSR/ triangle amplitude equal to 63
0110: Unmask bits[6:0] of LFSR/ triangle amplitude equal to 127
0111: Unmask bits[7:0] of LFSR/ triangle amplitude equal to 255
1000: Unmask bits[8:0] of LFSR/ triangle amplitude equal to 511
1001: Unmask bits[9:0] of LFSR/ triangle amplitude equal to 1023
1010: Unmask bits[10:0] of LFSR/ triangle amplitude equal to 2047
≥ 1011: Unmask bits[11:0] of LFSR/ triangle amplitude equal to 4095
Bits 7:6 WAVE1[1:0]: DAC channel1 noise/triangle wave generation enable
These bits are set and cleared by software.
00: wave generation disabled
01: Noise wave generation enabled
1x: Triangle wave generation enabled
Note: Only used if bit TEN1 = 1 (DAC channel1 trigger enabled).
Bits 5:3 TSEL1[2:0]: DAC channel1 trigger selection
These bits select the external event used to trigger DAC channel1.
000: Timer 6 TRGO event
001: Timer 8 TRGO event
010: Timer 7 TRGO event
011: Timer 5 TRGO event
100: Timer 2 TRGO event
101: Timer 4 TRGO event
110: External line9
111: Software trigger
Note: Only used if bit TEN1 = 1 (DAC channel1 trigger enabled).
Bit 2 TEN1: DAC channel1 trigger enable
This bit is set and cleared by software to enable/disable DAC channel1 trigger.
0: DAC channel1 trigger disabled and data written into the DAC_DHRx register are
transferred one APB1 clock cycle later to the DAC_DOR1 register
1: DAC channel1 trigger enabled and data from the DAC_DHRx register are transferred
three APB1 clock cycles later to the DAC_DOR1 register
Note: When software trigger is selected, the transfer from the DAC_DHRx register to the
DAC_DOR1 register takes only one APB1 clock cycle.
Bit 1 BOFF1: DAC channel1 output buffer disable
This bit is set and cleared by software to enable/disable DAC channel1 output buffer.
0: DAC channel1 output buffer enabled
1: DAC channel1 output buffer disabled
Bit 0 EN1: DAC channel1 enable
This bit is set and cleared by software to enable/disable DAC channel1.
0: DAC channel1 disabled
1: DAC channel1 enabled

RM0385 Rev 7

475/1709
482

Digital-to-analog converter (DAC)

16.5.2

RM0385

DAC software trigger register (DAC_SWTRIGR)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

0

15

14

13

12

11

10

9

8

7

6

5

4

3

2

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SWTRIG2 SWTRIG1
w

w

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 SWTRIG2: DAC channel2 software trigger
This bit is set and cleared by software to enable/disable the software trigger.
0: Software trigger disabled
1: Software trigger enabled
Note: This bit is cleared by hardware (one APB1 clock cycle later) once the DAC_DHR2
register value has been loaded into the DAC_DOR2 register.
Bit 0 SWTRIG1: DAC channel1 software trigger
This bit is set and cleared by software to enable/disable the software trigger.
0: Software trigger disabled
1: Software trigger enabled
Note: This bit is cleared by hardware (one APB1 clock cycle later) once the DAC_DHR1
register value has been loaded into the DAC_DOR1 register.

16.5.3

DAC channel1 12-bit right-aligned data holding register
(DAC_DHR12R1)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

DACC1DHR[11:0]
rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 DACC1DHR[11:0]: DAC channel1 12-bit right-aligned data
These bits are written by software which specifies 12-bit data for DAC channel1.

476/1709

RM0385 Rev 7

RM0385

Digital-to-analog converter (DAC)

16.5.4

DAC channel1 12-bit left aligned data holding register
(DAC_DHR12L1)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

DACC1DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

3

2

1

0

Res.

Res.

Res.

Res.

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:4 DACC1DHR[11:0]: DAC channel1 12-bit left-aligned data
These bits are written by software which specifies 12-bit data for DAC channel1.
Bits 3:0 Reserved, must be kept at reset value.

16.5.5

DAC channel1 8-bit right aligned data holding register
(DAC_DHR8R1)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DACC1DHR[7:0]
rw

rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 DACC1DHR[7:0]: DAC channel1 8-bit right-aligned data
These bits are written by software which specifies 8-bit data for DAC channel1.

RM0385 Rev 7

477/1709
482

Digital-to-analog converter (DAC)

16.5.6

RM0385

DAC channel2 12-bit right aligned data holding register
(DAC_DHR12R2)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

15

14

13

12

Res.

Res.

Res.

Res.

DACC2DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 DACC2DHR[11:0]: DAC channel2 12-bit right-aligned data
These bits are written by software which specifies 12-bit data for DAC channel2.

16.5.7

DAC channel2 12-bit left aligned data holding register
(DAC_DHR12L2)
Address offset: 0x18
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

DACC2DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

3

2

1

0

Res.

Res.

Res.

Res.

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:4 DACC2DHR[11:0]: DAC channel2 12-bit left-aligned data
These bits are written by software which specify 12-bit data for DAC channel2.
Bits 3:0 Reserved, must be kept at reset value.

16.5.8

DAC channel2 8-bit right-aligned data holding register
(DAC_DHR8R2)
Address offset: 0x1C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DACC2DHR[7:0]
rw

478/1709

RM0385 Rev 7

rw

rw

rw

rw

RM0385

Digital-to-analog converter (DAC)

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 DACC2DHR[7:0]: DAC channel2 8-bit right-aligned data
These bits are written by software which specifies 8-bit data for DAC channel2.

16.5.9

Dual DAC 12-bit right-aligned data holding register
(DAC_DHR12RD)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

Res.

Res.

Res.

Res.

27

26

25

24

23

22

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

rw

rw

rw

DACC2DHR[11:0]

DACC1DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:16 DACC2DHR[11:0]: DAC channel2 12-bit right-aligned data
These bits are written by software which specifies 12-bit data for DAC channel2.
Bits 15:12 Reserved, must be kept at reset value.
Bits 11:0 DACC1DHR[11:0]: DAC channel1 12-bit right-aligned data
These bits are written by software which specifies 12-bit data for DAC channel1.

16.5.10

DUAL DAC 12-bit left aligned data holding register
(DAC_DHR12LD)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

DACC2DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

DACC1DHR[11:0]
rw

rw

19

18

17

16

Res.

Res.

Res.

Res.

3

2

1

0

Res.

Res.

Res.

Res.

Bits 31:20 DACC2DHR[11:0]: DAC channel2 12-bit left-aligned data
These bits are written by software which specifies 12-bit data for DAC channel2.
Bits 19:16 Reserved, must be kept at reset value.
Bits 15:4 DACC1DHR[11:0]: DAC channel1 12-bit left-aligned data
These bits are written by software which specifies 12-bit data for DAC channel1.
Bits 3:0 Reserved, must be kept at reset value.

RM0385 Rev 7

479/1709
482

Digital-to-analog converter (DAC)

16.5.11

RM0385

DUAL DAC 8-bit right aligned data holding register
(DAC_DHR8RD)
Address offset: 0x28
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

DACC2DHR[7:0]
rw

rw

rw

rw

DACC1DHR[7:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:8 DACC2DHR[7:0]: DAC channel2 8-bit right-aligned data
These bits are written by software which specifies 8-bit data for DAC channel2.
Bits 7:0 DACC1DHR[7:0]: DAC channel1 8-bit right-aligned data
These bits are written by software which specifies 8-bit data for DAC channel1.

16.5.12

DAC channel1 data output register (DAC_DOR1)
Address offset: 0x2C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

15

14

13

12

Res.

Res.

Res.

Res.

DACC1DOR[11:0]
r

r

r

r

r

r

r

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 DACC1DOR[11:0]: DAC channel1 data output
These bits are read-only, they contain data output for DAC channel1.

16.5.13

DAC channel2 data output register (DAC_DOR2)
Address offset: 0x30
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

15

14

13

12

Res.

Res.

Res.

Res.

DACC2DOR[11:0]
r

480/1709

r

r

r

r

RM0385 Rev 7

r

r

RM0385

Digital-to-analog converter (DAC)

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 DACC2DOR[11:0]: DAC channel2 data output
These bits are read-only, they contain data output for DAC channel2.

16.5.14

DAC status register (DAC_SR)
Address offset: 0x34
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

DMAUDR2

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rc_w1
15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

DMAUDR1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rc_w1

Bits 31:30 Reserved, must be kept at reset value.
Bit 29 DMAUDR2: DAC channel2 DMA underrun flag
This bit is set by hardware and cleared by software (by writing it to 1).
0: No DMA underrun error condition occurred for DAC channel2
1: DMA underrun error condition occurred for DAC channel2 (the currently selected trigger is
driving DAC channel2 conversion at a frequency higher than the DMA service capability rate)
Bits 28:14 Reserved, must be kept at reset value.
Bit 13 DMAUDR1: DAC channel1 DMA underrun flag
This bit is set by hardware and cleared by software (by writing it to 1).
0: No DMA underrun error condition occurred for DAC channel1
1: DMA underrun error condition occurred for DAC channel1 (the currently selected trigger is
driving DAC channel1 conversion at a frequency higher than the DMA service capability rate)
Bits 12:0 Reserved, must be kept at reset value.

RM0385 Rev 7

481/1709
482

0x34

DAC_SR

Reset value

482/1709

0

RM0385 Rev 7

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Reset value

Res.

Reset value

Res.

0

Res.

0

Res.

0

Res.

0
0

Res.

Reserved

Res.

0

Res.

0

Res.
Res.

0
0
0
0
0
0

Res.
Res.
Res.
Res.
Res.

Reset value

Res.

Res.

0

Res.
Res.

Res.

Res.

0

0

0

0

0
0

0

0

0

0

0

0

0

0
0
0
0

Res.
Res.
Res.

0

DACC1DHR[11:0]

Reset value

0

Reset value

0

0

0
0
0
0

0

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.
0

DACC2DHR[7:0]
DACC1DHR[7:0]

0
0
0
0

0
0
0
0

0

DACC2DHR[11:0]

DACC2DHR[7:0]

0
0
0
0

0
0
0
0

0
0
0

DACC1DHR[11:0]
Reserved

0
0
0
0

0
0

0
0

0
0

0

0
0
0
0

Res.

0
Res.

0
Res.

0
Res.

0

0

DACC2DHR[11:0]

0
0
0
0

0
0
0
0

Res.

0
Res.

0

Res.

0
Res.

0

Res.

0

Res.

0

Res.

0

Res.

Reset value

Res.

Reset value
0
0

Res.

0
0

Res.

Reset value

Res.

Reset value

Res.

Res.

Res.

Res.

0

Res.

0

Res.

EN2

0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

BOFF1
EN1

0
0
0
0
0
0
0
0
0
0
0
0

0

0

0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

SWTRIG1

Reset value
SWTRIG2

Res.

DMAEN1

0

TEN1

TSEL1[2:0]

WAVE1[2:0]

DMAUDRIE1

Res.

Res.

TSEL2[2:0]

MAMP1[3:0]

Res.

Res.

Res.

0

Res.

Res.

TEN2
BOFF2

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMAEN2

0

WAVE2[2:0]

DMAUDRIE2

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

DACC2DHR[11:0]
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

DMAUDR1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

MAMP2[3:0]

Res.

Res.

Res.

DAC_
DHR8RD

Res.

0

Res.

0

Res.

0
0

Res.

0

Res.

DACC2DHR[11:0]
0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

0x30

DAC_
DOR2
0

Res.

DAC_
DOR1
0

Res.

0x2C
Res.

0x24
DAC_
DHR12LD

Res.

0

Res.

Reset value

Res.

0

Res.

DAC_
DHR12RD

Res.

0x20

Res.

DAC_
DHR8R2

Res.

0x1C

Res.

0x18
DAC_
DHR12L2

Res.

0x14
DAC_
DHR12R2
Res.

DAC_
DHR8R1

Res.

0x10

Res.

DAC_
DHR12L1

Res.

0x0C

Res.

0x08
DAC_
DHR12R1

Res.

DAC_
SWTRIGR

Res.

Reset value

DMAUDR2

0

Res.

0x28
Reset value

Res.

0x04

Res.

DAC_CR

Res.

0x00

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

Offset

Res.

16.5.15

Res.

Digital-to-analog converter (DAC)
RM0385

DAC register map
Table 103 summarizes the DAC registers.
Table 103. DAC register map

0
0

DACC1DHR[11:0]

DACC1DHR[7:0]

DACC1DHR[11:0]
0
0
0
0

0
0
0
0

DACC1DOR[11:0]
0
0
0

0

0

0

DACC2DOR[11:0]

RM0385

Digital camera interface (DCMI)

17

Digital camera interface (DCMI)

17.1

DCMI introduction
The digital camera is a synchronous parallel interface able to receive a high-speed data flow
from an external 8-, 10-, 12- or 14-bit CMOS camera module. It supports different data
formats: YCbCr4:2:2/RGB565 progressive video and compressed data (JPEG).
This interface is for use with black & white cameras, X24 and X5 cameras, and it is
assumed that all preprocessing like resizing is performed in the camera module.

17.2

17.3

DCMI main features
•

8-, 10-, 12- or 14-bit parallel interface

•

Embedded/external line and frame synchronization

•

Continuous or snapshot mode

•

Crop feature

•

Supports the following data formats:
–

8/10/12/14- bit progressive video: either monochrome or raw bayer

–

YCbCr 4:2:2 progressive video

–

RGB 565 progressive video

–

Compressed data: JPEG

DCMI clocks
The digital camera interface uses two clock domains, DCMI_PIXCLK and HCLK. The
signals generated with DCMI_PIXCLK are sampled on the rising edge of HCLK once they
are stable. An enable signal is generated in the HCLK domain, to indicate that data coming
from the camera are stable and can be sampled. The maximum DCMI_PIXCLK period must
be higher than 2.5 HCLK periods.

17.4

DCMI functional overview
The digital camera interface is a synchronous parallel interface that can receive high-speed
(up to 54 Mbytes/s) data flows. It consists of up to 14 data lines (D13-D0) and a pixel clock
line (DCMI_PIXCLK). The pixel clock has a programmable polarity, so that data can be
captured on either the rising or the falling edge of the pixel clock.
The data are packed into a 32-bit data register (DCMI_DR) and then transferred through a
general-purpose DMA channel. The image buffer is managed by the DMA, not by the
camera interface.
The data received from the camera can be organized in lines/frames (raw YUB/RGB/Bayer
modes) or can be a sequence of JPEG images. To enable JPEG image reception, the JPEG
bit (bit 3 of DCMI_CR register) must be set.

RM0385 Rev 7

483/1709
507

Digital camera interface (DCMI)

RM0385

The data flow is synchronized either by hardware using the optional DCMI_HSYNC
(horizontal synchronization) and DCMI_VSYNC (vertical synchronization) signals or by
synchronization codes embedded in the data flow.

17.4.1

DCMI block diagram
Figure 102 shows the DCMI block diagram.
Figure 102. DCMI block diagram

DMA
interface

Control/Status
register

AHB
interface
FIFO/
Data
formatter

Data
extraction

Synchronizer

DCMI_PIXCLK

DCMI_D[0:13], DCMI_HSYNC, DCMI_VSYNC
ai15604b

Figure 103. Top-level block diagram
DCMI_D[0:13]
DCMI_PIXCLK

HCLK

DCMI_HSYNC

External
interface

DCMI_VSYNC
DCMI
Interrupt
controller

DCMI_IT

DMA_REQ

ai15603b

17.4.2

DMA interface
The DMA interface is active when the CAPTURE bit in the DCMI_CR register is set. A DMA
request is generated each time the camera interface receives a complete 32-bit data block
in its register.

17.4.3

DCMI physical interface
The interface is composed of 11/13/15/17 inputs. Only the Slave mode is supported.

484/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)
The camera interface can capture 8-bit, 10-bit, 12-bit or 14-bit data depending on the
EDM[1:0] bits in the DCMI_CR register. If less than 14 bits are used, the unused input pins
must be connected to ground.
Table 104 shows the DCMI pins.
Table 104. DCMI external signals
Signal name
8 bits
10 bits
12 bits
14 bits

DCMI_D[0..7]
DCMI_D[0..9]
DCMI_D[0..11]
DCMI_D[0..13]

Signal type

Signal description

Digital inputs

DCMI data

DCMI_PIXCLK

Digital input

Pixel clock

DCMI_HSYNC

Digital input

Horizontal synchronization / Data valid

DCMI_VSYNC

Digital input

Vertical synchronization

The data are synchronous with DCMI_PIXCLK and change on the rising/falling edge of the
pixel clock depending on the polarity.
The DCMI_HSYNC signal indicates the start/end of a line.
The DCMI_VSYNC signal indicates the start/end of a frame
Figure 104. DCMI signal waveforms
DCMI_PIXCLK

DCMI_DR[0:13]

DCMI_HSYNC

DCMI_VSYNC
ai15606b

1. The capture edge of DCMI_PIXCLK is the falling edge, the active state of DCMI_HSYNC and
DCMI_VSYNC is 1.
2. DCMI_HSYNC and DCMI_VSYNC can change states at the same time.

8-bit data
When EDM[1:0] in DCMI_CR are programmed to “00” the interface captures 8 LSBs at its
input (DCMI_D[0:7]) and stores them as 8-bit data. The DCMI_D[13:8] inputs are ignored. In
this case, to capture a 32-bit word, the camera interface takes four pixel clock cycles.
The first captured data byte is placed in the LSB position in the 32-bit word and the 4th
captured data byte is placed in the MSB position in the 32-bit word. Table 105 gives an
example of the positioning of captured data bytes in two 32-bit words.

RM0385 Rev 7

485/1709
507

Digital camera interface (DCMI)

RM0385

Table 105. Positioning of captured data bytes in 32-bit words (8-bit width)
Byte address

31:24

23:16

15:8

7:0

0

Dn+3[7:0]

Dn+2[7:0]

Dn+1[7:0]

Dn[7:0]

4

Dn+7[7:0]

Dn+6[7:0]

Dn+5[7:0]

Dn+4[7:0]

10-bit data
When EDM[1:0] in DCMI_CR are programmed to “01”, the camera interface captures 10-bit
data at its input DCMI_D[0..9] and stores them as the 10 least significant bits of a 16-bit
word. The remaining most significant bits in the DCMI_DR register (bits 11 to 15) are
cleared to zero. So, in this case, a 32-bit data word is made up every two pixel clock cycles.
The first captured data are placed in the LSB position in the 32-bit word and the 2nd
captured data are placed in the MSB position in the 32-bit word as shown in Table 106.
Table 106. Positioning of captured data bytes in 32-bit words (10-bit width)
Byte address

31:26

25:16

15:10

9:0

0

0

Dn+1[9:0]

0

Dn[9:0]

4

0

Dn+3[9:0]

0

Dn+2[9:0]

12-bit data
When EDM[1:0] in DCMI_CR are programmed to “10”, the camera interface captures the
12-bit data at its input DCMI_D[0..11] and stores them as the 12 least significant bits of a 16bit word. The remaining most significant bits are cleared to zero. So, in this case a 32-bit
data word is made up every two pixel clock cycles.
The first captured data are placed in the LSB position in the 32-bit word and the 2nd
captured data are placed in the MSB position in the 32-bit word as shown in Table 107.
Table 107. Positioning of captured data bytes in 32-bit words (12-bit width)
Byte address

31:28

27:16

15:12

11:0

0

0

Dn+1[11:0]

0

Dn[11:0]

4

0

Dn+3[11:0]

0

Dn+2[11:0]

14-bit data
When EDM[1:0] in DCMI_CR are programmed to “11”, the camera interface captures the
14-bit data at its input DCMI_D[0..13] and stores them as the 14 least significant bits of a 16bit word. The remaining most significant bits are cleared to zero. So, in this case a 32-bit
data word is made up every two pixel clock cycles.
The first captured data are placed in the LSB position in the 32-bit word and the 2nd
captured data are placed in the MSB position in the 32-bit word as shown in Table 108.

486/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)
Table 108. Positioning of captured data bytes in 32-bit words (14-bit width)

17.4.4

Byte address

31:30

29:16

15:14

13:0

0

0

Dn+1[13:0]

0

Dn[13:0]

4

0

Dn+3[13:0]

0

Dn+2[13:0]

Synchronization
The digital camera interface supports embedded or hardware (DCMI_HSYNC and
DCMI_VSYNC) synchronization. When embedded synchronization is used, it is up to the
digital camera module to make sure that the 0x00 and 0xFF values are used ONLY for
synchronization (not in data). Embedded synchronization codes are supported only for the
8-bit parallel data interface width (that is, in the DCMI_CR register, the EDM[1:0] bits should
be cleared to “00”).
For compressed data, the DCMI supports only the hardware synchronization mode. In this
case, DCMI_VSYNC is used as a start/end of the image, and DCMI_HSYNC is used as a
Data Valid signal. Figure 105 shows the corresponding timing diagram.
Figure 105. Timing diagram
Padding data
at the end of the JPEG stream

Beginning of JPEG stream

Programmable
JPEG packet size

JPEG data
End of JPEG stream
DCMI_HSYNC

DCMI_VSYNC

Packet dispatching depends on the image content.
This results in a variable blanking duration.

JPEG packet data
ai15944b

Hardware synchronization mode
In hardware synchronization mode, the two synchronization signals
(DCMI_HSYNC/DCMI_VSYNC) are used.
Depending on the camera module/mode, data may be transmitted during horizontal/vertical
synchronization periods. The DCMI_HSYNC/DCMI_VSYNC signals act like blanking
signals since all the data received during DCMI_HSYNC/DCMI_VSYNC active periods are
ignored.
In order to correctly transfer images into the DMA/RAM buffer, data transfer is synchronized
with the DCMI_VSYNC signal. When the hardware synchronization mode is selected, and

RM0385 Rev 7

487/1709
507

Digital camera interface (DCMI)

RM0385

capture is enabled (CAPTURE bit set in DCMI_CR), data transfer is synchronized with the
deactivation of the DCMI_VSYNC signal (next start of frame).
Transfer can then be continuous, with successive frames transferred by DMA to successive
buffers or the same/circular buffer. To allow the DMA management of successive frames, a
VSIF (Vertical synchronization interrupt flag) is activated at the end of each frame.

Embedded data synchronization mode
In this synchronization mode, the data flow is synchronized using 32-bit codes embedded in
the data flow. These codes use the 0x00/0xFF values that are not used in data anymore.
There are 4 types of codes, all with a 0xFF0000XY format. The embedded synchronization
codes are supported only in 8-bit parallel data width capture (in the DCMI_CR register, the
EDM[1:0] bits should be programmed to “00”). For other data widths, this mode generates
unpredictable results and must not be used.
Note:

Camera modules can have 8 such codes (in interleaved mode). For this reason, the
interleaved mode is not supported by the camera interface (otherwise, every other
half-frame would be discarded).
•

Mode 2
Four embedded codes signal the following events
–

Frame start (FS)

–

Frame end (FE)

–

Line start (LS)

–

Line end (LE)

The XY values in the 0xFF0000XY format of the four codes are programmable (see
Section 17.7.7: DCMI embedded synchronization code register (DCMI_ESCR)).
A 0xFF value programmed as a “frame end” means that all the unused codes are
interpreted as valid frame end codes.
In this mode, once the camera interface has been enabled, the frame capture starts
after the first occurrence of the frame end (FE) code followed by a frame start (FS)
code.
•

Mode 1
An alternative coding is the camera mode 1. This mode is ITU656 compatible.
The codes signal another set of events:
–

SAV (active line) - line start

–

EAV (active line) - line end

–

SAV (blanking) - end of line during interframe blanking period

–

EAV (blanking) - end of line during interframe blanking period

This mode can be supported by programming the following codes:
•

FS ≤ 0xFF

•

FE ≤ 0xFF

•

LS ≤ SAV (active)

•

LE ≤ EAV (active)

An embedded unmask code is also implemented for frame/line start and frame/line end
codes. Using it, it is possible to compare only the selected unmasked bits with the
programmed code. You can therefore select a bit to compare in the embedded code and

488/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)
detect a frame/line start or frame/line end. This means that there can be different codes for
the frame/line start and frame/line end with the unmasked bit position remaining the same.

Example
FS = 0xA5
Unmask code for FS = 0x10
In this case the frame start code is embedded in the bit 4 of the frame start code.

17.4.5

Capture modes
This interface supports two types of capture: snapshot (single frame) and continuous grab.

Snapshot mode (single frame)
In this mode, a single frame is captured (CM = ‘1’ in the DCMI_CR register). After the
CAPTURE bit is set in DCMI_CR, the interface waits for the detection of a start of frame
before sampling the data. The camera interface is automatically disabled (CAPTURE bit
cleared in DCMI_CR) after receiving the first complete frame. An interrupt is generated
(IT_FRAME) if it is enabled.
In case of an overrun, the frame is lost and the CAPTURE bit is cleared.
Figure 106. Frame capture waveforms in snapshot mode

DCMI_HSYNC

DCMI_VSYNC

Frame 1 captured

Frame 2
not captured

ai15832b

1. Here, the active state of DCMI_HSYNC and DCMI_VSYNC is 1.
2. DCMI_HSYNC and DCMI_VSYNC can change states at the same time.

Continuous grab mode
In this mode (CM bit = ‘0’ in DCMI_CR), once the CAPTURE bit has been set in DCMI_CR,
the grabbing process starts on the next DCMI_VSYNC or embedded frame start depending
on the mode. The process continues until the CAPTURE bit is cleared in DCMI_CR. Once
the CAPTURE bit has been cleared, the grabbing process continues until the end of the
current frame.

RM0385 Rev 7

489/1709
507

Digital camera interface (DCMI)

RM0385

Figure 107. Frame capture waveforms in continuous grab mode

DCMI_HSYNC

DCMI_VSYNC

Frame 1 captured

Frame 2 captured

ai15833b

1. Here, the active state of DCMI_HSYNC and DCMI_VSYNC is 1.
2. DCMI_HSYNC and DCMI_VSYNC can change states at the same time.

In continuous grab mode, you can configure the FCRC bits in DCMI_CR to grab all pictures,
every second picture or one out of four pictures to decrease the frame capture rate.
Note:

In the hardware synchronization mode (ESS = ‘0’ in DCMI_CR), the IT_VSYNC interrupt is
generated (if enabled) even when CAPTURE = ‘0’ in DCMI_CR so, to reduce the frame
capture rate even further, the IT_VSYNC interrupt can be used to count the number of
frames between 2 captures in conjunction with the Snapshot mode. This is not allowed by
embedded data synchronization mode.

17.4.6

Crop feature
With the crop feature, the camera interface can select a rectangular window from the
received image. The start (upper left corner) coordinates and size (horizontal dimension in
number of pixel clocks and vertical dimension in number of lines) are specified using two 32bit registers (DCMI_CWSTRT and DCMI_CWSIZE). The size of the window is specified in
number of pixel clocks (horizontal dimension) and in number of lines (vertical dimension).
Figure 108. Coordinates and size of the window after cropping
VST bit in DCMI_CSTRT

VLINE bit in DCMI_CSIZE
HOFFCNT bit in DCMI_CSTRT
CAPCNT bit in DCMI_CSIZE

MS35933V2

These registers specify the coordinates of the starting point of the capture window as a line
number (in the frame, starting from 0) and a number of pixel clocks (on the line, starting from
0), and the size of the window as a line number and a number of pixel clocks. The CAPCNT
value can only be a multiple of 4 (two least significant bits are forced to 0) to allow the
correct transfer of data through the DMA.

490/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)
If the DCMI_VSYNC signal goes active before the number of lines is specified in the
DCMI_CWSIZE register, then the capture stops and an IT_FRAME interrupt is generated
when enabled.
Figure 109. Data capture waveforms
DCMI_HSYNC

DCMI_VSYNC
HOFFCNT
CAPCNT

Data not captured in this phase

Data captured in this phase
MS35934V2

1. Here, the active state of DCMI_HSYNC and DCMI_VSYNC is 1.
2. DCMI_HSYNC and DCMI_VSYNC can change states at the same time.

17.4.7

JPEG format
To allow JPEG image reception, it is necessary to set the JPEG bit in the DCMI_CR register.
JPEG images are not stored as lines and frames, so the DCMI_VSYNC signal is used to
start the capture while DCMI_HSYNC serves as a data enable signal. The number of bytes
in a line may not be a multiple of 4, you should therefore be careful when handling this case
since a DMA request is generated each time a complete 32-bit word has been constructed
from the captured data. When an end of frame is detected and the 32-bit word to be
transferred has not been completely received, the remaining data are padded with ‘0s’ and a
DMA request is generated.
The crop feature and embedded synchronization codes cannot be used in the JPEG format.

17.4.8

FIFO
Input mode
A four-word FIFO is implemented to manage data rate transfers on the AHB. The DCMI
features a simple FIFO controller with a read pointer incremented each time the camera
interface reads from the AHB, and a write pointer incremented each time the camera
interface writes to the FIFO. There is no overrun protection to prevent the data from being
overwritten if the AHB interface does not sustain the data transfer rate.
In case of overrun or errors in the synchronization signals, the FIFO is reset and the DCMI
interface waits for a new start of frame.

RM0385 Rev 7

491/1709
507

Digital camera interface (DCMI)

RM0385

17.5

Data format description

17.5.1

Data formats
Three types of data are supported:
•

8-bit progressive video: either monochrome or raw Bayer format

•

YCbCr 4:2:2 progressive video

•

RGB565 progressive video. A pixel coded in 16 bits (5 bits for blue, 5 bits for red, 6 bits
for green) takes two clock cycles to be transferred.

Compressed data: JPEG
For B&W, YCbCr or RGB data, the maximum input size is 2048 × 2048 pixels. No limit in
JPEG compressed mode.
For monochrome, RGB & YCbCr, the frame buffer is stored in raster mode. 32-bit words are
used. Only the little endian format is supported.
Figure 110. Pixel raster scan order

17.5.2

Monochrome format
Characteristics:
•

Raster format

•

8 bits per pixel

Table 109 shows how the data are stored.
Table 109. Data storage in monochrome progressive video format

492/1709

Byte address

31:24

23:16

15:8

7:0

0

n+3

n+2

n+1

n

4

n+7

n+6

n+5

n+4

RM0385 Rev 7

RM0385

17.5.3

Digital camera interface (DCMI)

RGB format
Characteristics:
•

Raster format

•

RGB

•

Interleaved: one buffer: R, G & B interleaved: BRGBRGBRG, etc.

•

Optimized for display output

The RGB planar format is compatible with standard OS frame buffer display formats.
Only 16 BPP (bits per pixel): RGB565 (2 pixels per 32-bit word) is supported.
The 24 BPP (palletized format) and grayscale formats are not supported. Pixels are stored
in a raster scan order, that is from top to bottom for pixel rows, and from left to right within a
pixel row. Pixel components are R (red), G (green) and B (blue). All components have the
same spatial resolution (4:4:4 format). A frame is stored in a single part, with the
components interleaved on a pixel basis.
Table 110 shows how the data are stored.
Table 110. Data storage in RGB progressive video format

17.5.4

Byte address

31:27

26:21

20:16

15:11

10:5

4:0

0

Red n + 1

Green n + 1

Blue n + 1

Red n

Green n

Blue n

4

Red n + 4

Green n + 3

Blue n + 3

Red n + 2

Green n + 2

Blue n + 2

YCbCr format
Characteristics:
•

Raster format

•

YCbCr 4:2:2

•

Interleaved: one Buffer: Y, Cb & Cr interleaved: CbYCrYCbYCr, etc.

Pixel components are Y (luminance or “luma”), Cb and Cr (chrominance or “chroma” blue
and red). Each component is encoded in 8 bits. Luma and chroma are stored together
(interleaved) as shown in Table 111.
Table 111. Data storage in YCbCr progressive video format

17.5.5

Byte address

31:24

23:16

15:8

7:0

0

Yn+1

Cr n

Yn

Cb n

4

Yn+3

Cr n + 2

Yn+2

Cb n + 2

YCbCr format - Y only
Characteristics:
•

Raster format

•

YCbCr 4:2:2

•

The buffer only contains Y information - monochrome image

Pixel components are Y (luminance or “luma”), Cb and Cr (chrominance or “chroma” blue
and red). In this mode, the chroma information is dropped. Only Luma component of each

RM0385 Rev 7

493/1709
507

Digital camera interface (DCMI)

RM0385

pixel , encoded in 8 bits, is stored as shown in Table 112.
The result is a monochrome image having the same resolution as the original YCbCr data.
Table 112. Data storage in YCbCr progressive video format - Y extraction mode

17.5.6

Byte address

31:24

23:16

15:8

7:0

0

Yn+3

Yn+2

Yn+1

Yn

4

Yn+7

Yn+6

Yn+5

Yn+4

Half resolution image extraction
This is a modification of the previous reception modes, being applicable to monochrome,
RGB or Y extraction modes.
This mode allows to only store a half resolution image. It is selected through OELS and LSM
control bits.

17.6

DCMI interrupts
Five interrupts are generated. All interrupts are maskable by software. The global interrupt
(IT_DCMI) is the OR of all the individual interrupts. Table 113 gives the list of all interrupts.
Table 113. DCMI interrupts
Interrupt name

17.7

Interrupt event

IT_LINE

Indicates the end of line

IT_FRAME

Indicates the end of frame capture

IT_OVR

indicates the overrun of data reception

IT_VSYNC

Indicates the synchronization frame

IT_ERR

Indicates the detection of an error in the embedded synchronization frame
detection

IT_DCMI

Logic OR of the previous interrupts

DCMI register description
All DCMI registers have to be accessed as 32-bit words, otherwise a bus error occurs.

17.7.1

DCMI control register (DCMI_CR)
Address offset: 0x00
Reset value: 0x0000 0000

494/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OELS

LSM

OEBS

rw

rw

rw

rw

4

3

2

1

0

ESS

JPEG

CROP

CM

CAPTURE

rw

rw

rw

rw

rw

15

14

13

12

Res.

ENABLE

Res.

Res.

rw

11

10

9

8

EDM[1:0]

FCRC[1:0]

rw

rw

rw

rw

7

6

5

VSPOL HSPOL PCKPOL
rw

rw

rw

17

16
BSM[1:0]
rw

Bits 31:21 Reserved, must be kept at reset value.
Bit 20 OELS: Odd/Even Line Select (Line Select Start)
This bit works in conjunction with LSM field (LSM = 1)
0: Interface captures first line after the frame start, second one being dropped
1: Interface captures second line from the frame start, first one being dropped
Bit 19 LSM: Line Select mode
0: Interface captures all received lines
1: Interface captures one line out of two.
Bit 18 OEBS: Odd/Even Byte Select (Byte Select Start)
This bit works in conjunction with BSM field (BSM <> 00)
0: Interface captures first data (byte or double byte) from the frame/line start,
second one being dropped
1: Interface captures second data (byte or double byte) from the frame/line start,
first one being dropped
Bits 17:16 BSM[1:0]: Byte Select mode
00: Interface captures all received data
01: Interface captures every other byte from the received data
10: Interface captures one byte out of four
11: Interface captures two bytes out of four
Note: This mode only work for EDM[1:0]=00. For all other EDM values, this bit
field must be programmed to the reset value.
Bit 15 Reserved, must be kept at reset value.
Bit 14 ENABLE: DCMI enable
0: DCMI disabled
1: DCMI enabled
Note: The DCMI configuration registers should be programmed correctly before
enabling this Bit
Bits 13:12 Reserved, must be kept at reset value.
Bits 11:10 EDM[1:0]: Extended data mode
00: Interface captures 8-bit data on every pixel clock
01: Interface captures 10-bit data on every pixel clock
10: Interface captures 12-bit data on every pixel clock
11: Interface captures 14-bit data on every pixel clock
Bits 9:8 FCRC[1:0]: Frame capture rate control
These bits define the frequency of frame capture. They are meaningful only in
Continuous grab mode. They are ignored in snapshot mode.
00: All frames are captured
01: Every alternate frame captured (50% bandwidth reduction)
10: One frame in 4 frames captured (75% bandwidth reduction)
11: reserved

RM0385 Rev 7

495/1709
507

Digital camera interface (DCMI)

RM0385

Bit 7 VSPOL: Vertical synchronization polarity
This bit indicates the level on the DCMI_VSYNC pin when the data are not valid
on the parallel interface.
0: DCMI_VSYNC active low
1: DCMI_VSYNC active high
Bit 6 HSPOL: Horizontal synchronization polarity
This bit indicates the level on the DCMI_HSYNC pin when the data are not valid
on the parallel interface.
0: DCMI_HSYNC active low
1: DCMI_HSYNC active high
Bit 5 PCKPOL: Pixel clock polarity
This bit configures the capture edge of the pixel clock
0: Falling edge active.
1: Rising edge active.
Bit 4 ESS: Embedded synchronization select
0: Hardware synchronization data capture (frame/line start/stop) is synchronized
with the DCMI_HSYNC/DCMI_VSYNC signals.
1: Embedded synchronization data capture is synchronized with synchronization
codes embedded in the data flow.
Note: Valid only for 8-bit parallel data. HSPOL/VSPOL are ignored when the ESS
bit is set.
This bit is disabled in JPEG mode.
Bit 3 JPEG: JPEG format
0: Uncompressed video format
1: This bit is used for JPEG data transfers. The DCMI_HSYNC signal is used as
data enable. The crop and embedded synchronization features (ESS bit) cannot
be used in this mode.
Bit 2 CROP: Crop feature
0: The full image is captured. In this case the total number of bytes in an image
frame should be a multiple of 4
1: Only the data inside the window specified by the crop register will be captured.
If the size of the crop window exceeds the picture size, then only the picture size
is captured.
Bit 1 CM: Capture mode
0: Continuous grab mode - The received data are transferred into the destination
memory through the DMA. The buffer location and mode (linear or circular
buffer) is controlled through the system DMA.
1: Snapshot mode (single frame) - Once activated, the interface waits for the
start of frame and then transfers a single frame through the DMA. At the end of
the frame, the CAPTURE bit is automatically reset.

496/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)

Bit 0 CAPTURE: Capture enable
0: Capture disabled.
1: Capture enabled.
The camera interface waits for the first start of frame, then a DMA request is
generated to transfer the received data into the destination memory.
In snapshot mode, the CAPTURE bit is automatically cleared at the end of the
1st frame received.
In continuous grab mode, if the software clears this bit while a capture is
ongoing, the bit will be effectively cleared after the frame end.
Note: The DMA controller and all DCMI configuration registers should be
programmed correctly before enabling this bit.

RM0385 Rev 7

497/1709
507

Digital camera interface (DCMI)

17.7.2

RM0385

DCMI status register (DCMI_SR)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FNE
r

VSYNC HSYNC
r

r

Bits 31:3 Reserved, must be kept at reset value.
Bit 2 FNE: FIFO not empty
This bit gives the status of the FIFO
1: FIFO contains valid data
0: FIFO empty
Bit 1 VSYNC:
This bit gives the state of the DCMI_VSYNC pin with the correct programmed
polarity.
When embedded synchronization codes are used, the meaning of this bit is the
following:
0: active frame
1: synchronization between frames
In case of embedded synchronization, this bit is meaningful only if the
CAPTURE bit in DCMI_CR is set.
Bit 0 HSYNC:
This bit gives the state of the DCMI_HSYNC pin with the correct programmed
polarity.
When embedded synchronization codes are used, the meaning of this bit is the
following:
0: active line
1: synchronization between lines
In case of embedded synchronization, this bit is meaningful only if the
CAPTURE bit in DCMI_CR is set.

498/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)

17.7.3

DCMI raw interrupt status register (DCMI_RIS)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LINE
_RIS

VSYNC
_RIS

ERR
_RIS

OVR
_RIS

FRAME
_RIS

r

r

r

r

r

DCMI_RIS gives the raw interrupt status and is accessible in read only. When read, this
register returns the status of the corresponding interrupt before masking with the DCMI_IER
register value.
Bits 31:5 Reserved, must be kept at reset value.
Bit 4 LINE_RIS: Line raw interrupt status
This bit gets set when the DCMI_HSYNC signal changes from the inactive state
to the active state. It goes high even if the line is not valid.
In the case of embedded synchronization, this bit is set only if the CAPTURE bit
in DCMI_CR is set.
It is cleared by writing a ‘1’ to the LINE_ISC bit in DCMI_ICR.
Bit 3 VSYNC_RIS: DCMI_VSYNC raw interrupt status
This bit is set when the DCMI_VSYNC signal changes from the inactive state to
the active state.
In the case of embedded synchronization, this bit is set only if the CAPTURE bit
is set in DCMI_CR.
It is cleared by writing a ‘1’ to the VSYNC_ISC bit in DCMI_ICR.
Bit 2 ERR_RIS: Synchronization error raw interrupt status
0: No synchronization error detected
1: Embedded synchronization characters are not received in the correct order.
This bit is valid only in the embedded synchronization mode. It is cleared by
writing a ‘1’ to the ERR_ISC bit in DCMI_ICR.
Note: This bit is available only in embedded synchronization mode.
Bit 1 OVR_RIS:Overrun raw interrupt status
0: No data buffer overrun occurred
1: A data buffer overrun occurred and the data FIFO is corrupted.
This bit is cleared by writing a ‘1’ to the OVR_ISC bit in DCMI_ICR.
Bit 0 FRAME_RIS: Capture complete raw interrupt status
0: No new capture
1: A frame has been captured.
This bit is set when a frame or window has been captured.
In case of a cropped window, this bit is set at the end of line of the last line in the
crop. It is set even if the captured frame is empty (e.g. window cropped outside
the frame).
This bit is cleared by writing a ‘1’ to the FRAME_ISC bit in DCMI_ICR.

RM0385 Rev 7

499/1709
507

Digital camera interface (DCMI)

17.7.4

RM0385

DCMI interrupt enable register (DCMI_IER)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LINE
_IE

VSYNC
_IE

ERR
_IE

OVR
_IE

FRAME
_IE

rw

rw

rw

rw

rw

The DCMI_IER register is used to enable interrupts. When one of the DCMI_IER bits is set,
the corresponding interrupt is enabled. This register is accessible in both read and write.
Bits 31:5 Reserved, must be kept at reset value.
Bit 4 LINE_IE: Line interrupt enable
0: No interrupt generation when the line is received
1: An Interrupt is generated when a line has been completely received
Bit 3 VSYNC_IE: DCMI_VSYNC interrupt enable
0: No interrupt generation
1: An interrupt is generated on each DCMI_VSYNC transition from the inactive to
the active state
The active state of the DCMI_VSYNC signal is defined by the VSPOL bit.
Bit 2 ERR_IE: Synchronization error interrupt enable
0: No interrupt generation
1: An interrupt is generated if the embedded synchronization codes are not
received in the correct order.
Note: This bit is available only in embedded synchronization mode.
Bit 1 OVR_IE: Overrun interrupt enable
0: No interrupt generation
1: An interrupt is generated if the DMA was not able to transfer the last data
before new data (32-bit) are received.
Bit 0 FRAME_IE: Capture complete interrupt enable
0: No interrupt generation
1: An interrupt is generated at the end of each received frame/crop window (in
crop mode).

500/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)

17.7.5

DCMI masked interrupt status register (DCMI_MIS)
This DCMI_MIS register is a read-only register. When read, it returns the current masked
status value (depending on the value in DCMI_IER) of the corresponding interrupt. A bit in
this register is set if the corresponding enable bit in DCMI_IER is set and the corresponding
bit in DCMI_RIS is set.
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

LINE
_MIS

VSYNC
_MIS

ERR
_MIS

OVR
_MIS

FRAME
_MIS

r

r

r

r

r

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Bits 31:5 Reserved, must be kept at reset value.
Bit 4 LINE_MIS: Line masked interrupt status
This bit gives the status of the masked line interrupt
0: No interrupt generation when the line is received
1: An Interrupt is generated when a line has been completely received and the
LINE_IE bit is set in DCMI_IER.
Bit 3 VSYNC_MIS: VSYNC masked interrupt status
This bit gives the status of the masked VSYNC interrupt
0: No interrupt is generated on DCMI_VSYNC transitions
1: An interrupt is generated on each DCMI_VSYNC transition from the inactive
to the active state and the VSYNC_IE bit is set in DCMI_IER.
The active state of the DCMI_VSYNC signal is defined by the VSPOL bit.
Bit 2 ERR_MIS: Synchronization error masked interrupt status
This bit gives the status of the masked synchronization error interrupt
0: No interrupt is generated on a synchronization error
1: An interrupt is generated if the embedded synchronization codes are not
received in the correct order and the ERR_IE bit in DCMI_IER is set.
Note: This bit is available only in embedded synchronization mode.
Bit 1 OVR_MIS: Overrun masked interrupt status
This bit gives the status of the masked overflow interrupt
0: No interrupt is generated on overrun
1: An interrupt is generated if the DMA was not able to transfer the last data
before new data (32-bit) are received and the OVR_IE bit is set in DCMI_IER.
Bit 0 FRAME_MIS: Capture complete masked interrupt status
This bit gives the status of the masked capture complete interrupt
0: No interrupt is generated after a complete capture
1: An interrupt is generated at the end of each received frame/crop window (in
crop mode) and the FRAME_IE bit is set in DCMI_IER.

RM0385 Rev 7

501/1709
507

Digital camera interface (DCMI)

17.7.6

RM0385

DCMI interrupt clear register (DCMI_ICR)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LINE
_ISC

VSYNC
_ISC

ERR
_ISC

OVR
_ISC

FRAME
_ISC

w

w

w

w

w

The DCMI_ICR register is write-only. Writing a ‘1’ into a bit of this register clears the
corresponding bit in the DCMI_RIS and DCMI_MIS registers. Writing a ‘0’ has no effect.
Bits 31:5 Reserved, must be kept at reset value.
Bit 4 LINE_ISC: line interrupt status clear
Writing a ‘1’ into this bit clears LINE_RIS in the DCMI_RIS register
Bit 3 VSYNC_ISC: Vertical Synchronization interrupt status clear
Writing a ‘1’ into this bit clears the VSYNC_RIS bit in DCMI_RIS
Bit 2 ERR_ISC: Synchronization error interrupt status clear
Writing a ‘1’ into this bit clears the ERR_RIS bit in DCMI_RIS
Note: This bit is available only in embedded synchronization mode.
Bit 1 OVR_ISC: Overrun interrupt status clear
Writing a ‘1’ into this bit clears the OVR_RIS bit in DCMI_RIS
Bit 0 FRAME_ISC: Capture complete interrupt status clear
Writing a ‘1’ into this bit clears the FRAME_RIS bit in DCMI_RIS

502/1709

RM0385 Rev 7

RM0385

Digital camera interface (DCMI)

17.7.7

DCMI embedded synchronization code register (DCMI_ESCR)
Address offset: 0x18
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

FEC[7:0]]

20

19

18

17

16

LEC[7:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

LSC[7:0]
rw

FSC[7:0]
rw

Bits 31:24 FEC[7:0]: Frame end delimiter code
This byte specifies the code of the frame end delimiter. The code consists of 4
bytes in the form of 0xFF, 0x00, 0x00, FEC.
If FEC is programmed to 0xFF, all the unused codes (0xFF0000XY) are
interpreted as frame end delimiters.
Bits 23:16 LEC[7:0]: Line end delimiter code
This byte specifies the code of the line end delimiter. The code consists of 4
bytes in the form of 0xFF, 0x00, 0x00, LEC.
Bits 15:8 LSC[7:0]: Line start delimiter code
This byte specifies the code of the line start delimiter. The code consists of 4
bytes in the form of 0xFF, 0x00, 0x00, LSC.
Bits 7:0 FSC[7:0]: Frame start delimiter code
This byte specifies the code of the frame start delimiter. The code consists of 4
bytes in the form of 0xFF, 0x00, 0x00, FSC.
If FSC is programmed to 0xFF, no frame start delimiter is detected. But, the 1st
occurrence of LSC after an FEC code will be interpreted as a start of frame
delimiter.

RM0385 Rev 7

503/1709
507

Digital camera interface (DCMI)

17.7.8

RM0385

DCMI embedded synchronization unmask register (DCMI_ESUR)
Address offset: 0x1C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

FEU[7:0]

20

19

18

17

16

LEU[7:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

LSU[7:0]
rw

FSU[7:0]
rw

Bits 31:24 FEU[7:0]: Frame end delimiter unmask
This byte specifies the mask to be applied to the code of the frame end delimiter.
0: The corresponding bit in the FEC byte in DCMI_ESCR is masked while
comparing the frame end delimiter with the received data.
1: The corresponding bit in the FEC byte in DCMI_ESCR is compared while
comparing the frame end delimiter with the received data
Bits 23:16 LEU[7:0]: Line end delimiter unmask
This byte specifies the mask to be applied to the code of the line end delimiter.
0: The corresponding bit in the LEC byte in DCMI_ESCR is masked while
comparing the line end delimiter with the received data
1: The corresponding bit in the LEC byte in DCMI_ESCR is compared while
comparing the line end delimiter with the received data
Bits 15:8 LSU[7:0]: Line start delimiter unmask
This byte specifies the mask to be applied to the code of the line start delimiter.
0: The corresponding bit in the LSC byte in DCMI_ESCR is masked while
comparing the line start delimiter with the received data
1: The corresponding bit in the LSC byte in DCMI_ESCR is compared while
comparing the line start delimiter with the received data
Bits 7:0 FSU[7:0]: Frame start delimiter unmask
This byte specifies the mask to be applied to the code of the frame start
delimiter.
0: The corresponding bit in the FSC byte in DCMI_ESCR is masked while
comparing the frame start delimiter with the received data
1: The corresponding bit in the FSC byte in DCMI_ESCR is compared while
comparing the frame start delimiter with the received data

504/1709

RM0385 Rev 7

RM0385

17.7.9

Digital camera interface (DCMI)

DCMI crop window start (DCMI_CWSTRT)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

Res.

Res.

Res.

28

27

26

25

24

23

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

Res.

Res.
rw

rw

rw

rw

rw

rw

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

VST[12:0]

HOFFCNT[13:0]
rw

rw

Bits 31:29 Reserved, must be kept at reset value.
Bits 28:16 VST[12:0]: Vertical start line count
The image capture starts with this line number. Previous line data are ignored.
0x0000 => line 1
0x0001 => line 2
0x0002 => line 3
....
Bits 15:14 Reserved, must be kept at reset value.
Bits 13:0 HOFFCNT[13:0]: Horizontal offset count
This value gives the number of pixel clocks to count before starting a capture.

17.7.10

DCMI crop window size (DCMI_CWSIZE)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

Res.

Res.

15

14

Res.

Res.

29

28

27

26

25

24

23

rw

rw

rw

rw

rw

rw

rw

13

12

11

10

9

8

7

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

VLINE[13:0]

CAPCNT[13:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:30 Reserved, must be kept at reset value.
Bits 29:16 VLINE[13:0]: Vertical line count
This value gives the number of lines to be captured from the starting point.
0x0000 => 1 line
0x0001 => 2 lines
0x0002 => 3 lines
....

RM0385 Rev 7

505/1709
507

Digital camera interface (DCMI)

RM0385

Bits 15:14 Reserved, must be kept at reset value.
Bits 13:0 CAPCNT[13:0]: Capture count
This value gives the number of pixel clocks to be captured from the starting
point on the same line. It value should corresponds to word-aligned data for
different widths of parallel interfaces.
0x0000 => 1 pixel
0x0001 => 2 pixels
0x0002 => 3 pixels
....

17.7.11

DCMI data register (DCMI_DR)
Address offset: 0x28
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

Byte3[7:0]

20

19

18

17

16

Byte2[7:0]

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

Byte1[7:0]
r

r

r

r

r

Byte0[7:0]
r

r

r

r

r

r

r

r

Bits 31:24 Byte3[7:0]: Data byte 3
Bits 23:16 Byte2[7:0]: Data byte 2
Bits 15:8 Byte1[7:0]: Data byte 1
Bits 7:0 Byte0[7:0]: Data byte 0

The digital camera Interface packages all the received data in 32-bit format before
requesting a DMA transfer. A 4-word deep FIFO is available to leave enough time for DMA
transfers and avoid DMA overrun conditions.

506/1709

RM0385 Rev 7

0x20

0x24

0x28
DCMI_ESCR

Reset value

DCMI_CWSIZE

Reset value
FEC

0

0
0

Reset value

0
0

DCMI_ESUR

Reset value
0
0
0

DCMI_CWSTRT

Reset value

0

DCMI_DR

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

FEU

0

0

0

Byte3

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0

RM0385 Rev 7
0

0

VST[12:0

VLINE13:0]

0
0

0
0

0
0

0

0

0

LEC

0

LEU

0

0

0

Byte2

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0

0

0

Byte1

0

FRAME_MIS

0
0
0

0

LSC
FSC

0

LSU

0
0

0

FRAME_ISC

ERR_MIS

0

ERR_ISC

0

OVR_ISC

VSYNC_IE
ERR_IE
OVR_IE
FRAME_IE

Reset value
LINE_IE

Res.

Res.

Res.

Res.

Res.

Res.

VSYNC_RIS
ERR_RIS
OVR_RIS
FRAME_RIS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LINE_RIS

Reset value

VSYNC_ISC

OVR_MIS

Res.

Res.

VSYNC_MIS

Reset value
LINE_MIS

Reset value

LINE_ISC

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LSM
OEBS

Res.
Res.
Res.
Res.

Res.

CROP
CM
CAPTURE

0
0
0
0
0
0
0
0

Reset value

0
0
0
0

0
0
0

0

HOFFCNT[13:0]

CAPCNT[13:0]

Byte0
0
0
0
0
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.
Res.
Res.
Res.
Res.
Res.
Res.

HSYNC

ESS
JPEG

0
FNE

PCKPOL

0
VSYNC

VSPOL
HSPOL

0

Res.

Res.

Res.

ENABLE

0

Res.

Res.

Res.

Res.

Res.

OELS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EDM FCRC

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

DCMI_ICR
Res.

DCMI_MIS
0

Res.

0x1C
DCMI_IER
0

BSM

Res.

0x18
DCMI_RIS

Res.

Reset value

Res.

0x14

Res.

0x10
DCMI_SR

Res.

0x0C
DCMI_CR

Res.

0x08

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

0x04

Res.

0x00

Res.

Offset

Res.

17.7.12

Res.

RM0385
Digital camera interface (DCMI)

DCMI register map

Table 114 summarizes the DCMI registers.
Table 114. DCMI register map and reset values

0
0
0

0
0
0
0
0

0
0
0
0
0

FSU

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

507/1709

507

LCD-TFT display controller (LTDC)

18

RM0385

LCD-TFT display controller (LTDC)
This section applies to the whole STM32F756xx and STM32F746xx devices, unless
otherwise specified.

18.1

Introduction
The LCD-TFT (liquid crystal display - thin film transistor) display controller provides a
parallel digital RGB (red, green, blue) and signals for horizontal, vertical synchronization,
pixel clock and data enable as output to interface directly to a variety of LCD and TFT
panels.

18.2

LTDC main features
•

24-bit RGB parallel pixel output; 8 bits-per-pixel (RGB888)

•

2 display layers with dedicated FIFO (64x32-bit)

•

Color look-up table (CLUT) up to 256 color (256x24-bit) per layer

•

Programmable timings for different display panels

•

Programmable background color

•

Programmable polarity for HSYNC, VSYNC and data enable

•

Up to 8 input color formats selectable per layer

•

–

ARGB8888

–

RGB888

–

RGB565

–

ARGB1555

–

ARGB4444

–

L8 (8-bit luminance or CLUT)

–

AL44 (4-bit alpha + 4-bit luminance)

–

AL88 (8-bit alpha + 8-bit luminance)

Pseudo-random dithering output for low bits per channel
–

508/1709

Dither width 2-bits for red, green, blue

•

Flexible blending between two layers using alpha value (per pixel or constant)

•

Color keying (transparency color)

•

Programmable window position and size

•

Supports thin film transistor (TFT) color displays

•

AHB master interface with burst of 16 words

•

Up to 4 programmable interrupt events

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.3

LTDC functional description

18.3.1

LTDC block diagram
The block diagram of the LTDC is shown in Figure 111: LTDC block diagram.
Figure 111. LTDC block diagram

APB2 clock domain

AHB clock domain

Pixel clock domain

Layer1
FIFO

PFC

AHB
interface

LCD_HSYNC
Blending
unit

Layer1
FIFO

Dithering
unit

LCD_VSYNC
LCD_DE
LCD_CLK

PFC

LCD_R[7:0]

LCD-TFT
panel

LCD_G[7:0]
Configuration
and status
registers

LCD_B[7:0]

Timing
generator

Interrupts
MSv19675V1

Layer FIFO: One FIFO 64x32-bit per layer.
PFC: pixel format converter, performing the pixel format conversion from the selected input
pixel format of a layer to words.
AHB interface: for data transfer from memories to the FIFO.
Blending, dithering unit and timings generator: Refer to Section 18.4.1 and Section 18.4.2.

18.3.2

LTDC pins and external signal interface
Table 115 summarizes the LTDC signal interface.
Table 115. LTDC pins and signal interface
LCD-TFT
signals

I/O

LCD_CLK

O

Clock output

LCD_HSYNC

O

Horizontal synchronization

LCD_VSYNC

O

Vertical synchronization

LCD_DE

O

Not data enable

LCD_R[7:0]

O

Data: 8-bit red data

Description

RM0385 Rev 7

509/1709
542

LCD-TFT display controller (LTDC)

RM0385

Table 115. LTDC pins and signal interface (continued)
LCD-TFT
signals

I/O

LCD_G[7:0]

O

Data: 8-bit green data

LCD_B[7:0]

O

Data: 8-bit blue data

Description

The LTDC-TFT controller pins must be configured by the user application. The unused pins
can be used for other purposes.
For LTDC outputs up to 24-bit (RGB888), if less than 8 bpp are used to output for example
RGB565 or RGB666 to interface on 16- or 18-bit displays, the RGB display data lines must
be connected to the MSB of the LCD-TFT controller RGB data lines. As an example, in the
case of an LCD-TFT controller interfacing with a RGB565 16-bit display, the LCD display
R[4:0], G[5:0] and B[4:0] data lines pins must be connected to LCD-TFT controller
LCD_R[7:3], LCD_G[7:2] and LCD_B[7:3].

18.3.3

LTDC reset and clocks
The LCD-TFT controller peripheral uses 3 clock domains:
•

AHB clock domain (HCLK)
This domain contains the LCD-TFT AHB master interface for data transfer from the
memories to the Layer FIFO and the frame buffer configuration register

•

APB2 clock domain (PCLK2):
This domain contains the global configuration registers and the interrupt register.

•

Pixel clock domain (LCD_CLK)
This domain contains the pixel data generation, the layer configuration register as well
as the LCD-TFT interface signal generator. The LCD_CLK output should be configured
following the panel requirements. The LCD_CLK is generated from a specific PLL
output (refer to the reset and clock control section).

Table 116 summarizes the clock domain for each register.
Table 116. Clock domain for each register
LTDC register

Clock domain

LTDC_LxCR
LTDC_LxCFBAR
LTDC_LxCFBLR

HCLK

LTDC_LxCFBLNR
LTDC_SRCR
LTDC_IER
LTDC_ISR

PCLK2

LTDC_ICR

510/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)
Table 116. Clock domain for each register (continued)
LTDC register

Clock domain

LTDC_SSCR
LTDC_BPCR
LTDC_AWCR
LTDC_TWCR
LTDC_GCR
LTDC_BCCR
LTDC_LIPCR
LTDC_CPSR
Pixel clock (LCD_CLK)

LTDC_CDSR
LTDC_LxWHPCR
LTDC_LxWVPCR
LTDC_LxCKCR
LTDC_LxPFCR
LTDC_LxCACR
LTDC_LxDCCR
LTDC_LxBFCR
LTDC_LxCLUTWR

Care must be taken while accessing the LTDC registers, the APB2 bus is stalled during:
•

6 PCKL2 periods + 5 LCD_CLK periods (5 HCLK periods for register on AHB clock
domain) for register write access and update;

•

7 PCKL2 periods + 5 LCD_CLK periods (5 HCLK periods for register on AHB clock
domain) for register read access.

For registers on PCLK2 clock domain, APB2 bus is stalled for 6 PCKL2 periods during the
register write accesses, and for 7 PCKL2 periods during Read accesses.
The LCD controller can be reset by setting the corresponding bit in the RCC_APB2RSTR
register. It resets the three clock domains.

18.4

LTDC programmable parameters
The LCD-TFT controller provides flexible configurable parameters. It can be enabled or
disabled through the LTDC_GCR register.

18.4.1

LTDC global configuration parameters
Synchronous timings
Figure 112 presents the configurable timing parameters generated by the synchronous
timings generator block presented in the block diagram Figure 111. It generates the

RM0385 Rev 7

511/1709
542

LCD-TFT display controller (LTDC)

RM0385

horizontal and vertical synchronization timings panel signals, the pixel clock and the data
enable signals.
Figure 112. LCD-TFT synchronous timings
Total width
HFP

HSYNC
width

HBP
Active width

VSYNC width
VBP

Total height

Data1, Line1

Active display area
Active height

Data(n), Line(n)
VFP

MSv19674V1

Note:

The HBP and HFP are respectively the horizontal back porch and front porch period.
The VBP and the VFP are respectively the vertical back porch and front porch period.
The LCD-TFT programmable synchronous timings are:

512/1709

•

HSYNC and VSYNC width: horizontal and vertical synchronization width, configured by
programming a value of HSYNC width - 1 and VSYNC width - 1 in the LTDC_SSCR
register

•

HBP and VBP: horizontal and vertical synchronization back porch width, configured by
programming the accumulated value HSYNC width + HBP - 1 and the accumulated
value VSYNC width + VBP - 1 in the LTDC_BPCR register.

•

Active width and active height: the active width and active height are configured by
programming the accumulated value HSYNC width + HBP + active width - 1 and the
accumulated value VSYNC width + VBP + active height - 1 in the LTDC_AWCR
register (only up to 1024x768 is supported).

•

Total width: the total width is configured by programming the accumulated value
HSYNC width + HBP + active width + HFP - 1 in the LTDC_TWCR register. The HFP
is the horizontal front porch period.

•

Total height: the total height is configured by programming the accumulated value
VSYNC height + VBP + active height + VFP - 1 in the LTDC_TWCR register. The
VFP is the vertical front porch period.

RM0385 Rev 7

RM0385
Note:

LCD-TFT display controller (LTDC)
When the LTDC is enabled, the timings generated start with X/Y=0/0 position as the first
horizontal synchronization pixel in the vertical synchronization area and following the back
porch, active data display area and the front porch.
When the LTDC is disabled, the timing generator block is reset to X = total width - 1,
Y = total height - 1 and held the last pixel before the vertical synchronization phase and the
FIFO are flushed. Therefore only blanking data is output continuously.

Example of synchronous timings configuration
TFT-LCD timings (must be extracted from panel datasheet):
•

horizontal and vertical synchronization width: 0xA pixels and 0x2 lines

•

horizontal and vertical back porch: 0x14 pixels and 0x2 lines

•

active width and active height: 0x140 pixels, 0xF0 lines (320x240)

•

horizontal front porch: 0xA pixels

•

vertical front porch: 0x4 lines

The programmed values in the LTDC timings registers are:
•

LTDC_SSCR register: to be programmed to 0x00070003. (HSW[11:0] is 0x7 and
VSH[10:0] is 0x3)

•

LTDC_BPCR register: to be programmed to 0x001D0003 (AHBP[11:0] is 0x1D(0xA+
0x13) and AVBP[10:0]A is 0x3(0x2 + 0x1)).

•

LTDC_AWCR register: to be programmed to 0x015D00F3 (AAW[11:0] is 0x15D(0xA
+0x14 +0x13F) and AAH[10:0] is 0xF3(0x2 +0x2 + 0xEF).

•

LTDC_TWCR register: to be programmed to 0x00000167 (TOTALW[11:0] is 0x167(0xA
+0x14 +0x140 + 0x9).

•

LTDC_THCR register: to be programmed to 0x000000F7 (TOTALH[10:0]is 0xF7(0x2
+0x2 + 0xF0 + 3)

Programmable polarity
The horizontal and vertical synchronization, data enable and pixel clock output signals
polarity can be programmed to active high or active low through the LTDC_GCR register.

Background color
A constant background color (RGB888) can programmed through the LTDC_BCCR register.
It is used for blending with the bottom layer.

Dithering
The dithering pseudo-random technique using an LFSR is used to add a small random
value (threshold) to each pixel color channel (R, G or B) value, thus rounding up the MSB in
some cases when displaying a 24-bit data on 18-bit display. Thus the Dithering technique is
used to round data which is different from one frame to the other.
The dithering pseudo-random technique is the same as comparing LSBs against a
threshold value and adding a 1 to the MSB part only, if the LSB part is >= the threshold. The
LSBs are typically dropped once dithering was applied.
The width of the added pseudo-random value is 2 bits for each color channel: 2 bits for red,
2 bits for green and 2 bits for blue.

RM0385 Rev 7

513/1709
542

LCD-TFT display controller (LTDC)

RM0385

Once the LCD-TFT controller is enabled, the LFSR starts running with the first active pixel
and it is kept running even during blanking periods and when dithering is switched off. If the
LTDC is disabled, the LFSR is reset.
The dithering can be switched On and Off on the fly through the LTDC_GCR register.

Reload shadow registers
Some configuration registers are shadowed. The shadow registers values can be reloaded
immediately to the active registers when writing to these registers or at the beginning of the
vertical blanking period following the configuration in the LTDC_SRCR register. If the
immediate reload configuration is selected, the reload should be only activated when all new
registers have been written.
The shadow registers should not be modified again before the reload has been done.
Reading from the shadow registers returns the actual active value. The new written value
can only be read after the reload has taken place.
A register reload interrupt can be generated if enabled in the LTDC_IER register.
The shadowed registers are all the layer1 and layer2 registers except the
LTDC_LxCLUTWR register.

Interrupt generation event
Refer to Section 18.5: LTDC interrupts for interrupt configuration.

18.4.2

Layer programmable parameters
Up to two layers can be enabled, disabled and configured separately. The layer display
order is fixed and it is bottom up. If two layers are enabled, the layer2 is the top displayed
window.

Windowing
Every layer can be positioned and resized and it must be inside the active display area.
The window position and size are configured through the top-left and bottom-right X/Y
positions and the internal timing generator that includes the synchronous, back porch size
and the active data area. Refer to LTDC_LxWHPCR and LTDC_WVPCR registers.
The programmable layer position and size defines the first/last visible pixel of a line and the
first/last visible line in the window. It allows to display either the full image frame or only a
part of the image frame. Refer to Figure 113.
• The first and the last visible pixel in the layer are set by configuring the WHSTPOS[11:0]
and WHSPPOS[11:0] in the LTDC_LxWHPCR register.
• The first and the last visible lines in the layer are set by configuring the WVSTPOS[10:0]
and WVSPPOS[10:0] in the LTDC_LxWVPCR register.

514/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)
Figure 113. Layer window programmable parameters
Active data area

WVSTPOS bits in
LTDC_LxWVPCR

WHSTPOS bits in
LTDC_LxWHPCR

WVSPPOS bits in
LTDC_LxWVPCR

Window

WHSPPOS bits in
LTDC_LxWHPCR
MSv19676V3

Pixel input format
The programmable pixel format is used for the data stored in the frame buffer of a layer.
Up to 8 input pixel formats can be configured for every layer through the LTDC_LxPFCR
register
The pixel data is read from the frame buffer and then transformed to the internal 8888
(ARGB) format as follows: components having a width of less than 8 bits get expanded to 8
bits by bit replication. The selected bit range is concatenated multiple times until it is longer
than 8 bits. Of the resulting vector, the 8 MSB bits are chosen. Example: 5 bits of an
RGB565 red channel become (bit positions): 43210432 (the 3 LSBs are filled with the 3
MSBs of the 5 bits)
Table 117 describes the pixel data mapping depending on the selected format.
Table 117. Pixel data mapping versus color format
ARGB8888
@+3
Ax[7:0]

@+2
Rx[7:0]

@+1
Gx[7:0]

@
Bx[7:0]

@+7
Ax+1[7:0]

@+6
Rx+1[7:0]

@+5
Gx+1[7:0]

@+4
Bx+1[7:0]

RGB888
@+3
Bx+1[7:0]

@+2
Rx[7:0]

@+1
Gx[7:0]

@
Bx[7:0]

@+7
Gx+2[7:0]

@+6
Bx+2[7:0]

@+5
Rx+1[7:0]

@+4
Gx+1[7:0]

RGB565
@+3
Rx+1[4:0] Gx+1[5:3]

@+2
Gx+1[2:0] Bx+1[4:0]

@+1
Rx[4:0] Gx[5:3]

@
Gx[2:0] Bx[4:0]

@+7
Rx+3[4:0] Gx+3[5:3]

@+6
Gx+3[2:0] Bx+3[4:0]

@+5
Rx+2[4:0] Gx+2[5:3]

@+4
Gx+2[2:0] Bx+2[4:0]

ARGB1555

RM0385 Rev 7

515/1709
542

LCD-TFT display controller (LTDC)

RM0385

Table 117. Pixel data mapping versus color format (continued)
@+3
Ax+1[0]Rx+1[4:0]
Gx+1[4:3]

@+2
Gx+1[2:0] Bx+1[4:0]

@+1
Ax[0] Rx[4:0] Gx[4:3]

@
Gx[2:0] Bx[4:0]

@+7
Ax+3[0]Rx+3[4:0]
Gx+3[4:3]

@+6
Gx+3[2:0] Bx+3[4:0]

@+5
Ax+2[0]Rx+2[4:0]Gx+2[4:
3]

@+4
Gx+2[2:0] Bx+2[4:0]

ARGB4444
@+3
Ax+1[3:0]Rx+1[3:0]

@+2
Gx+1[3:0] Bx+1[3:0]

@+1
Ax[3:0] Rx[3:0]

@
Gx[3:0] Bx[3:0]

@+7
Ax+3[3:0]Rx+3[3:0]

@+6
Gx+3[3:0] Bx+3[3:0]

@+5
Ax+2[3:0]Rx+2[3:0]

@+4
Gx+2[3:0] Bx+2[3:0]

L8
@+3
Lx+3[7:0]

@+2
Lx+2[7:0]

@+1
Lx+1[7:0]

@
Lx[7:0]

@+7
Lx+7[7:0]

@+6
Lx+6[7:0]

@+5
Lx+5[7:0]

@+4
Lx+4[7:0]

AL44
@+3
Ax+3[3:0] Lx+3[3:0]

@+2
Ax+2[3:0] Lx+2[3:0]

@+1
Ax+1[3:0] Lx+1[3:0]

@
Ax[3:0] Lx[3:0]

@+7
Ax+7[3:0] Lx+7[3:0]

@+6
Ax+6[3:0] Lx+6[3:0]

@+5
Ax+5[3:0] Lx+5[3:0]

@+4
Ax+4[3:0] Lx+4[3:0]

AL88
@+3
Ax+1[7:0]

@+2
Lx+1[7:0]

@+1
Ax[7:0]

@
Lx[7:0]

@+7
Ax+3[7:0]

@+6
Lx+3[7:0]

@+5
Ax+2[7:0]

@+4
Lx+2[7:0]

Color look-up table (CLUT)
The CLUT can be enabled at run-time for every layer through the LTDC_LxCR register and
it is only useful in case of indexed color when using the L8, AL44 and AL88 input pixel
format.
First, the CLUT has to be loaded with the R, G and B values that replace the original R, G, B
values of that pixel (indexed color). Each color (RGB value) has its own address which is the
position within the CLUT.
The R, G and B values and their own respective address are programmed through the
LTDC_LxCLUTWR register.
• In case of L8 and AL88 input pixel format, the CLUT has to be loaded by 256 colors. The
address of each color is configured in the CLUTADD bits in the LTDC_LxCLUTWR
register.
• In case of AL44 input pixel format, the CLUT has to be only loaded by 16 colors. The
address of each color must be filled by replicating the 4-bit L channel to 8-bit as follows:

516/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)
–
–
–
–
–

L0 (indexed color 0), at address 0x00
L1, at address 0x11
L2, at address 0x22
.....
L15, at address 0xFF

Color frame buffer address
Every layer has a start address for the color frame buffer configured through the
LTDC_LxCFBAR register.
When a layer is enabled, the data is fetched from the color frame buffer.

Color frame buffer length
Every layer has a total line length setting for the color frame buffer in bytes and a number of
lines in the frame buffer configurable in the LTDC_LxCFBLR and LTDC_LxCFBLNR register
respectively.
The line length and the number of lines settings are used to stop the prefetching of data to
the layer FIFO at the end of the frame buffer.
•

If it is set to less bytes than required, a FIFO underrun interrupt is generated if it has
been previously enabled.

•

If it is set to more bytes than actually required, the useless data read from the FIFO is
discarded. The useless data is not displayed.

Color frame buffer pitch
Every layer has a configurable pitch for the color frame buffer, which is the distance between
the start of one line and the beginning of the next line in bytes. It is configured through the
LTDC_LxCFBLR register.

Layer blending
The blending is always active and the two layers can be blended following the blending
factors configured through the LTDC_LxBFCR register.
The blending order is fixed and it is bottom up. If two layers are enabled, first the Layer1 is
blended with the Background color, then the layer2 is blended with the result of blended
color of layer1 and the background. Refer to Figure 114.
Figure 114. Blending two layers with background

Layer2
Layer1

Layer2

BG

Layer1 + BG

Layer2 +
Layer1 + BG
MSv48123V1

RM0385 Rev 7

517/1709
542

LCD-TFT display controller (LTDC)

RM0385

Default color
Every layer can have a default color in the format ARGB which is used outside the defined
layer window or when a layer is disabled.
The default color is configured through the LTDC_LxDCCR register.
The blending is always performed between the two layers even when a layer is disabled. To
avoid displaying the default color when a layer is disabled, keep the blending factors of this
layer in the LTDC_LxBFCR register to their reset value.

Color keying
A color key (RGB) can be configured to be representative for a transparent pixel.
If the color keying is enabled, the current pixels (after format conversion and before CLUT
respectively blending) are compared to the color key. If they match for the programmed
RGB value, all channels (ARGB) of that pixel are set to 0.
The color key value can be configured and used at run-time to replace the pixel RGB value.
The color keying is enabled through the LTDC_LxCKCR register.
The color keying is configured through the LTDC_LxCKCR register. The programmed value
depends on the pixel format as it is compared to current pixel after pixel format conversion
to ARGB888.
Example: if the a mid-yellow color (50% red + 50% green) is used as the transparent color
key:

18.5

•

In RGB565, the mid-yellow color is 0x8400. Set the LTDC_LxCKCR to 0x848200.

•

In ARGB8888, the mid-yellow color is 0x808000, set LTDC_LxCKCR to 0x808000.

•

In all CLUT-based color modes (L8, AL88, AL44), set one of the palette entry to the
mid-yellow color 0x808000 and set the LTDC_LxCKCR to 0x808000.

LTDC interrupts
The LTDC provides four maskable interrupts logically ORed to two interrupt vectors.
The interrupt sources can be enabled or disabled separately through the LTDC_IER
register. Setting the appropriate mask bit to 1 enables the corresponding interrupt.
The two interrupts are generated on the following events:
•

Line interrupt: generated when a programmed line is reached. The line interrupt
position is programmed in the LTDC_LIPCR register

•

Register reload interrupt: generated when the shadow registers reload was performed
during the vertical blanking period

•

FIFO underrun interrupt: generated when a pixel is requested from an empty layer
FIFO

•

Transfer error interrupt: generated when an AHB bus error occurs during data transfer

Those interrupts events are connected to the NVIC controller as described in Figure 115.

518/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)
Figure 115. Interrupt events

Line
LTDC global interrupt

Register reload
FIFO underrun

LTDC global error interrupt

Transfer error

MS19678V1

Table 118. LTDC interrupt requests
Interrupt event

Event flag

Enable control bit

LIF

LIE

Register reload

RRIF

RRIEN

FIFO underrun

FUDERRIF

FUDERRIE

Transfer error

TERRIF

TERRIE

Line

RM0385 Rev 7

519/1709
542

LCD-TFT display controller (LTDC)

18.6

Note:

520/1709

RM0385

LTDC programming procedure
•

Enable the LTDC clock in the RCC register.

•

Configure the required pixel clock following the panel datasheet.

•

Configure the synchronous timings: VSYNC, HSYNC, vertical and horizontal back
porch, active data area and the front porch timings following the panel datasheet as
described in the Section 18.4.1: LTDC global configuration parameters.

•

Configure the synchronous signals and clock polarity in the LTDC_GCR register.

•

If needed, configure the background color in the LTDC_BCCR register.

•

Configure the needed interrupts in the LTDC_IER and LTDC_LIPCR register.

•

Configure the layer1/2 parameters by:
–

programming the layer window horizontal and vertical position in the
LTDC_LxWHPCR and LTDC_WVPCR registers. The layer window must be in the
active data area.

–

programming the pixel input format in the LTDC_LxPFCR register

–

programming the color frame buffer start address in the LTDC_LxCFBAR register

–

programming the line length and pitch of the color frame buffer in the
LTDC_LxCFBLR register

–

programming the number of lines of the color frame buffer in the
LTDC_LxCFBLNR register

–

if needed, loading the CLUT with the RGB values and its address in the
LTDC_LxCLUTWR register

–

If needed, configuring the default color and the blending factors respectively in the
LTDC_LxDCCR and LTDC_LxBFCR registers

•

Enable layer1/2 and if needed the CLUT in the LTDC_LxCR register.

•

If needed, enable dithering and color keying respectively in the LTDC_GCR and
LTDC_LxCKCR registers. They can be also enabled on the fly.

•

Reload the shadow registers to active register through the LTDC_SRCR register.

•

Enable the LCD-TFT controller in the LTDC_GCR register.

•

All layer parameters can be modified on the fly except the CLUT. The new configuration
has to be either reloaded immediately or during vertical blanking period by configuring
the LTDC_SRCR register.

All layer’s registers are shadowed. Once a register is written, it must not be modified again
before the reload has been done. Thus, a new write to the same register overrides the
previous configuration if not yet reloaded.

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.7

LTDC registers

18.7.1

LTDC synchronization size configuration register (LTDC_SSCR)
This register defines the number of horizontal synchronization pixels minus 1 and the
number of vertical synchronization lines minus 1. Refer to Figure 112 and Section 18.4:
LTDC programmable parameters for an example of configuration.
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

Res.

Res.

Res.

Res.

Res.

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

rw

rw

rw

HSW[11:0]

VSH[10:0]
rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:16 HSW[11:0]: horizontal synchronization width (in units of pixel clock period)
These bits define the number of Horizontal Synchronization pixel minus 1.
Bits 15:11 Reserved, must be kept at reset value.
Bits 10:0 VSH[10:0]: vertical synchronization height (in units of horizontal scan line)
These bits define the vertical Synchronization height minus 1. It represents the number of
horizontal synchronization lines.

18.7.2

LTDC back porch configuration register (LTDC_BPCR)
This register defines the accumulated number of horizontal synchronization and back porch
pixels minus 1 (HSYNC width + HBP - 1) and the accumulated number of vertical
synchronization and back porch lines minus 1 (VSYNC height + VBP - 1). Refer to
Figure 112 and Section 18.4: LTDC programmable parameters for an example of
configuration.
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

Res.

Res.

Res.

Res.

Res.

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

rw

rw

rw

AHBP[11:0]

AVBP[10:0]
rw

rw

rw

rw

RM0385 Rev 7

rw

rw

521/1709
542

LCD-TFT display controller (LTDC)

RM0385

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:16 AHBP[11:0]: accumulated horizontal back porch (in units of pixel clock period)
These bits define the accumulated horizontal back porch width that includes the horizontal
synchronization and horizontal back porch pixels minus 1.
The horizontal back porch is the period between horizontal synchronization going inactive
and the start of the active display part of the next scan line.
Bits 15:11 Reserved, must be kept at reset value.
Bits 10:0 AVBP[10:0]: accumulated Vertical back porch (in units of horizontal scan line)
These bits define the accumulated vertical back porch width that includes the vertical
synchronization and vertical back porch lines minus 1.
The vertical back porch is the number of horizontal scan lines at a start of frame to the start of
the first active scan line of the next frame.

18.7.3

LTDC active width configuration register (LTDC_AWCR)
This register defines the accumulated number of horizontal synchronization, back porch and
active pixels minus 1 (HSYNC width + HBP + active width - 1) and the accumulated
number of vertical synchronization, back porch lines and active lines minus 1
(VSYNC height + BVBP + active height - 1). Refer to Figure 112 and Section 18.4: LTDC
programmable parameters for an example of configuration.
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

Res.

Res.

Res.

Res.

Res.

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

rw

rw

rw

AAW[11:0]

AAH[10:0]
rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:16 AAW[11:0]: accumulated active width (in units of pixel clock period)
These bits define the accumulated active width which includes the horizontal
synchronization, horizontal back porch and active pixels minus 1.
The active width is the number of pixels in active display area of the panel scan line.
Refer to device datasheet for maximum active width supported following maximum pixel
clock.
Bits 15:11 Reserved, must be kept at reset value.
Bits 10:0 AAH[10:0]: accumulated active height (in units of horizontal scan line)
These bits define the accumulated height which includes the vertical synchronization, vertical
back porch and the active height lines minus 1. The active height is the number of active
lines in the panel.
Refer to device datasheet for maximum active height supported following maximum pixel
clock.

522/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.7.4

LTDC total width configuration register (LTDC_TWCR)
This register defines the accumulated number of horizontal synchronization, back porch,
active and front porch pixels minus 1 (HSYNC width + HBP + active width + HFP - 1) and
the accumulated number of vertical synchronization, back porch lines, active and front lines
minus 1 (VSYNC height + BVBP + active height + VFP - 1). Refer to Figure 112 and
Section 18.4: LTDC programmable parameters for an example of configuration.
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

Res.

Res.

Res.

Res.

Res.

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

rw

rw

rw

TOTALW[11:0]

TOTALH[10:0]
rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:16 TOTALW[11:0]: total width (in units of pixel clock period)
These bits defines the accumulated total width which includes the horizontal synchronization,
horizontal back porch, active width and horizontal front porch pixels minus 1.
Bits 15:11 Reserved, must be kept at reset value.
Bits 10:0 TOTALH[10:0]: total height (in units of horizontal scan line)
These bits defines the accumulated height which includes the vertical synchronization,
vertical back porch, the active height and vertical front porch height lines minus 1.

18.7.5

LTDC global control register (LTDC_GCR)
This register defines the global configuration of the LCD-TFT controller.
Address offset: 0x18
Reset value: 0x0000 2220

31

30

29

28

HSPOL VSPOL DEPOL PCPOL
rw

rw

rw

rw

15

14

13

12

Res.

DRW[2:0]
r

r

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DEN

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

LTDCEN

rw

Res.
r

DGW[2:0]
r

r

Res.
r

RM0385 Rev 7

DBW[2:0]
r

r

r

rw

523/1709
542

LCD-TFT display controller (LTDC)

RM0385

Bit 31 HSPOL: horizontal synchronization polarity
This bit is set and cleared by software.
0: horizontal synchronization polarity is active low.
1: horizontal synchronization polarity is active high.
Bit 30 VSPOL: vertical synchronization polarity
This bit is set and cleared by software.
0: vertical synchronization is active low.
1: vertical synchronization is active high.
Bit 29 DEPOL: not data enable polarity
This bit is set and cleared by software.
0: not data enable polarity is active low.
1: not data enable polarity is active high.
Bit 28 PCPOL: pixel clock polarity
This bit is set and cleared by software.
0: pixel clock polarity is active low.
1: pixel clock is active high.
Bits 27:17 Reserved, must be kept at reset value.
Bit 16 DEN: dither enable
This bit is set and cleared by software.
0: dither disable
1: dither enable
Bit 15 Reserved, must be kept at reset value.
Bits 14:12 DRW[2:0]: dither red width
These bits return the Dither Red Bits.
Bit 11 Reserved, must be kept at reset value.
Bits 10:8 DGW[2:0]: dither green width
These bits return the dither green bits.
Bit 7 Reserved, must be kept at reset value.
Bits 6:4 DBW[2:0]: dither blue width
These bits return the dither blue bits.
Bits 3:1 Reserved, must be kept at reset value.
Bit 0 LTDCEN: LCD-TFT controller enable
This bit is set and cleared by software.
0: LTDC disable
1: LTDC enable

524/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.7.6

LTDC shadow reload configuration register (LTDC_SRCR)
This register allows to reload either immediately or during the vertical blanking period, the
shadow registers values to the active registers. The shadow registers are all Layer1 and
Layer2 registers except the LTDC_L1CLUTWR and the LTDC_L2CLUTWR.
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

VBR

IMR

rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 VBR: vertical blanking reload
This bit is set by software and cleared only by hardware after reload (it cannot be cleared
through register write once it is set).
0: no effect
1: The shadow registers are reloaded during the vertical blanking period (at the beginning of
the first line after the active display area).
Bit 0 IMR: immediate reload
This bit is set by software and cleared only by hardware after reload.
0: no effect
1: The shadow registers are reloaded immediately.

Note:

The shadow registers read back the active values. Until the reload has been done, the 'old'
value is read.

18.7.7

LTDC background color configuration register (LTDC_BCCR)
This register defines the background color (RGB888).
Address offset: 0x2C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

23

22

21

rw

rw

rw

rw

19

18

17

16

BCRED[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

BCGREEN[7:0]
rw

20

BCBLUE[7:0]
rw

rw

rw

rw

RM0385 Rev 7

rw

rw

rw

rw

525/1709
542

LCD-TFT display controller (LTDC)

RM0385

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:16 BCRED[7:0]: background color red value
These bits configure the background red value.
Bits 15:8 BCGREEN[7:0]: background color green value
These bits configure the background green value.
Bits 7:0 BCBLUE[7:0]: background color blue value
These bits configure the background blue value.

18.7.8

LTDC interrupt enable register (LTDC_IER)
This register determines which status flags generate an interrupt request by setting the
corresponding bit to 1.
Address offset: 0x34
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RRIE

TERRIE

FUIE

LIE

rw

rw

rw

rw

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 RRIE: register reload interrupt enable
This bit is set and cleared by software.
0: register reload interrupt disable
1: register reload interrupt enable
Bit 2 TERRIE: transfer error interrupt enable
This bit is set and cleared by software.
0: transfer error interrupt disable
1: transfer error interrupt enable
Bit 1 FUIE: FIFO underrun interrupt enable
This bit is set and cleared by software.
0: FIFO underrun interrupt disable
1: FIFO underrun Interrupt enable
Bit 0 LIE: line interrupt enable
This bit is set and cleared by software.
0: line interrupt disable
1: line interrupt enable

526/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.7.9

LTDC interrupt status register (LTDC_ISR)
This register returns the interrupt status flag.
Address offset: 0x38
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RRIF

TERRIF

FUIF

LIF

r

r

r

r

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 RRIF: register reload interrupt flag
0: no register reload interrupt generated
1: register reload interrupt generated when a vertical blanking reload occurs (and the first line
after the active area is reached)
Bit 2 TERRIF: transfer error interrupt flag
0: no transfer error interrupt generated
1: transfer error interrupt generated when a bus error occurs
Bit 1 FUIF: FIFO underrun interrupt flag
0: no FIFO underrun interrupt generated.
1: FIFO underrun interrupt generated, if one of the layer FIFOs is empty and pixel data is
read from the FIFO
Bit 0 LIF: line interrupt flag
0: no line interrupt generated
1: line interrupt generated when a programmed line is reached

18.7.10

LTDC Interrupt Clear Register (LTDC_ICR)
Address offset: 0x3C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CFUIF

CLIF

w

w

CRRIF CTERRIF
w

RM0385 Rev 7

w

527/1709
542

LCD-TFT display controller (LTDC)

RM0385

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 CRRIF: clears register reload interrupt flag
0: no effect
1: clears the RRIF flag in the LTDC_ISR register
Bit 2 CTERRIF: clears the transfer error interrupt flag
0: no effect
1: clears the TERRIF flag in the LTDC_ISR register.
Bit 1 CFUIF: clears the FIFO underrun interrupt flag
0: no effect
1: clears the FUDERRIF flag in the LTDC_ISR register.
Bit 0 CLIF: clears the line interrupt flag
0: no effect
1: clears the LIF flag in the LTDC_ISR register.

18.7.11

LTDC line interrupt position configuration register (LTDC_LIPCR)
This register defines the position of the line interrupt. The line value to be programmed
depends on the timings parameters. Refer to Figure 112.
Address offset: 0x40
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

LIPOS[10:0]
rw

rw

rw

rw

rw

rw

Bits 31:11 Reserved, must be kept at reset value.
Bits 10:0 LIPOS[10:0]: line interrupt position
These bits configure the line interrupt position.

18.7.12

LTDC current position status register (LTDC_CPSR)
Address offset: 0x44
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CXPOS[15:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

CYPOS[15:0]
r

528/1709

r

r

r

r

r

r

r

r

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

Bits 31:16 CXPOS[15:0]: current X position
These bits return the current X position.
Bits 15:0 CYPOS[15:0]: current Y position
These bits return the current Y position.

18.7.13

LTDC current display status register (LTDC_CDSR)
This register returns the status of the current display phase which is controlled by the
HSYNC, VSYNC, and horizontal/vertical DE signals.
Example: if the current display phase is the vertical synchronization, the VSYNCS bit is set
(active high). If the current display phase is the horizontal synchronization, the HSYNCS bit
is active high.
Address offset: 0x48
Reset value: 0x0000 000F

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

HDES

VDES

r

r

HSYNCS VSYNCS
r

r

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 HSYNCS: horizontal synchronization display status
0: active low
1: active high
Bit 2 VSYNCS: vertical synchronization display status
0: active low
1: active high
Bit 1 HDES: horizontal data enable display status
0: active low
1: active high
Bit 0 VDES: vertical data enable display status
0: active low
1: active high

Note:

The returned status does not depend on the configured polarity in the LTDC_GCR register,
instead it returns the current active display phase.

RM0385 Rev 7

529/1709
542

LCD-TFT display controller (LTDC)

18.7.14

RM0385

LTDC layer x control register (LTDC_LxCR)
Address offset: 0x84 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CLUTEN

Res.

Res.

COLKEN

LEN

rw

rw

rw

Bits 31:5 Reserved, must be kept at reset value.
Bit 4 CLUTEN: color look-up table enable
This bit is set and cleared by software.
0: color look-up table disable
1: color look-up table enable
The CLUT is only meaningful for L8, AL44 and AL88 pixel format. Refer to Color look-up
table (CLUT)
Bits 3:2 Reserved, must be kept at reset value.
Bit 1 COLKEN: color keying enable
This bit is set and cleared by software.
0: color keying disable
1: color keying enable
Bit 0 LEN: layer enable
This bit is set and cleared by software.
0: layer disable
1: layer enable

530/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.7.15

LTDC layer x window horizontal position configuration register
(LTDC_LxWHPCR)
This register defines the horizontal position (first and last pixel) of the layer 1 or 2 window.
The first visible pixel of a line is the programmed value of AHBP[11:0] bits + 1 in the
LTDC_BPCR register.
The last visible pixel of a line is the programmed value of AAW[10:0] bits in the
LTDC_AWCR register.
Address offset: 0x88 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

Res.

Res.

Res.

Res.

27

26

25

24

23

22

21

20

19

18

17

16

WHSPPOS[11:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

WHSTPOS[11:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:16 WHSPPOS[11:0]: window horizontal stop position
These bits configure the last visible pixel of a line of the layer window.
WHSPPOS[11:0] must be ≥ AHBP[11:0] bits + 1 (programmed in LTDC_BPCR register).
Bits 15:12 Reserved, must be kept at reset value.
Bits 11:0 WHSTPOS[11:0]: window horizontal start position
These bits configure the first visible pixel of a line of the layer window.
WHSTPOS[11:0] must be ≤ AAW[11:0] bits (programmed in LTDC_AWCR register).

Example:
The LTDC_BPCR register is configured to 0x000E0005 (AHBP[11:0] is 0xE) and the
LTDC_AWCR register is configured to 0x028E01E5 (AAW[11:0] is 0x28E). To configure the
horizontal position of a window size of 630x460, with horizontal start offset of 5 pixels in the
active data area:
1.

layer window first pixel, WHSTPOS[11:0], must be programmed to 0x14 (0xE+1+0x5)

2.

layer window last pixel, WHSPPOS[11:0], must be programmed to 0x28A.

RM0385 Rev 7

531/1709
542

LCD-TFT display controller (LTDC)

18.7.16

RM0385

LTDC layer x window vertical position configuration register
(LTDC_LxWVPCR)
This register defines the vertical position (first and last line) of the layer1 or 2 window.
The first visible line of a frame is the programmed value of AVBP[10:0] bits + 1 in the register
LTDC_BPCR register.
The last visible line of a frame is the programmed value of AAH[10:0] bits in the
LTDC_AWCR register.
Address offset: 0x8C + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

27

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

Res.

Res.

Res.

Res.

Res.

26

25

24

23

22

21

20

19

18

17

16

WVSPPOS[10:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

WVSTPOS[10:0]
rw

rw

rw

rw

rw

rw

Bits 31:27 Reserved, must be kept at reset value.
Bits 26:16 WVSPPOS[10:0]: window vertical stop position
These bits configure the last visible line of the layer window.
WVSPPOS[10:0] must be ≥ AVBP[10:0] bits + 1 (programmed in LTDC_BPCR register).
Bits 15:11 Reserved, must be kept at reset value.
Bits 10:0 WVSTPOS[10:0]: window vertical start position
These bits configure the first visible line of the layer window.
WVSTPOS[10:0] must be ≤ AAH[10:0] bits (programmed in LTDC_AWCR register).

Example:
The LTDC_BPCR register is configured to 0x000E0005 (AVBP[10:0] is 0x5) and the
LTDC_AWCR register is configured to 0x028E01E5 (AAH[10:0] is 0x1E5).
To configure the vertical position of a window size of 630x460, with vertical start offset of 8
lines in the active data area:

532/1709

1.

layer window first line: WVSTPOS[10:0] must be programmed to 0xE (0x5 + 1 + 0x8).

2.

layer window last line: WVSTPOS[10:0] must be programmed to 0x1DA.

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.7.17

LTDC layer x color keying configuration register
(LTDC_LxCKCR)
This register defines the color key value (RGB), that is used by the color keying.
Address offset: 0x90 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

23

22

21

rw

rw

rw

rw

19

18

17

16

CKRED[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

CKGREEN[7:0]
rw

20

CKBLUE[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:16 CKRED[7:0]: color key red value
Bits 15:8 CKGREEN[7:0]: color key green value
Bits 7:0 CKBLUE[7:0]: color key blue value

18.7.18

LTDC layer x pixel format configuration register
(LTDC_LxPFCR)
This register defines the pixel format that is used for the stored data in the frame buffer of a
layer. The pixel data is read from the frame buffer and then transformed to the internal
format 8888 (ARGB).
Address offset: 0x94 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PF[2:0]
rw

RM0385 Rev 7

rw

rw

533/1709
542

LCD-TFT display controller (LTDC)

RM0385

Bits 31:3 Reserved, must be kept at reset value.
Bits 2:0 PF[2:0]: pixel format
These bits configure the pixel format
000: ARGB8888
001: RGB888
010: RGB565
011: ARGB1555
100: ARGB4444
101: L8 (8-bit luminance)
110: AL44 (4-bit alpha, 4-bit luminance)
111: AL88 (8-bit alpha, 8-bit luminance)

18.7.19

LTDC layer x constant alpha configuration register
(LTDC_LxCACR)
This register defines the constant alpha value (divided by 255 by hardware), that is used in
the alpha blending. Refer to LTDC_LxBFCR register.
Address offset: 0x98 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 00FF

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

CONSTA[7:0]
rw

rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 CONSTA[7:0]: constant alpha
These bits configure the constant alpha used for blending. The constant alpha is divided by
255 by hardware.
Example: if the programmed constant alpha is 0xFF, the constant alpha value is
255 / 255 = 1.

534/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.7.20

LTDC layer x default color configuration register
(LTDC_LxDCCR)
This register defines the default color of a layer in the format ARGB. The default color is
used outside the defined layer window or when a layer is disabled. The reset value of
0x00000000 defines a transparent black color.
Address offset: 0x9C + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

DCALPHA[7:0]

20

19

18

17

16

DCRED[7:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

DCGREEN[7:0]
rw

rw

rw

rw

rw

DCBLUE[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 DCALPHA[7:0]: default color alpha
These bits configure the default alpha value.
Bits 23:16 DCRED[7:0]: default color red
These bits configure the default red value.
Bits 15:8 DCGREEN[7:0]: default color green
These bits configure the default green value.
Bits 7:0 DCBLUE[7:0]: default color blue
These bits configure the default blue value.

RM0385 Rev 7

535/1709
542

LCD-TFT display controller (LTDC)

18.7.21

RM0385

LTDC layer x blending factors configuration register
(LTDC_LxBFCR)
This register defines the blending factors F1 and F2.
The general blending formula is: BC = BF1 x C + BF2 x Cs
•

BC = blended color

•

BF1 = blend factor 1

•

C = current layer color

•

BF2 = blend factor 2

•

Cs = subjacent layers blended color

Address offset: 0xA0 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0607
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BF1[2:0]
rw

rw

rw

Bits 31:11 Reserved, must be kept at reset value.
Bits 10:8 BF1[2:0]: blending factor 1
These bits select the blending factor F1.
000: reserved
001: reserved
010: reserved
011: reserved
100: constant alpha
101: reserved
110: pixel alpha x constant alpha
111: reserved
Bits 7:3 Reserved, must be kept at reset value.
Bits 2:0 BF2[2:0]: blending factor 2
These bits select the blending factor F2
000: reserved
001: reserved
010: reserved
011: reserved
100: reserved
101: 1 - constant alpha
110: reserved
111: 1 - (pixel alpha x constant alpha)

536/1709

RM0385 Rev 7

BF2[2:0]
rw

rw

rw

RM0385

LCD-TFT display controller (LTDC)

Note:

The constant alpha value, is the programmed value in the LxCACR register divided by 255
by hardware.
Example: Only layer1 is enabled, BF1 configured to constant alpha. BF2 configured to
1 - constant alpha. The constant alpha programmed in the LxCACR register is 240 (0xF0).

Thus, the constant alpha value is 240/255 = 0.94. C: current layer color is 128.
Cs: background color is 48. Layer1 is blended with the background color.
BC = constant alpha x C + (1 - Constant Alpha) x Cs = 0.94 x 128 + (1- 0.94) x 48 = 123.

18.7.22

LTDC layer x color frame buffer address register
(LTDC_LxCFBAR)
This register defines the color frame buffer start address which has to point to the address
where the pixel data of the top left pixel of a layer is stored in the frame buffer.
Address offset: 0xAC + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CFBADD[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CFBADD[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 CFBADD[31:0]: color frame buffer start address
These bits define the color frame buffer start address.

18.7.23

LTDC layer x color frame buffer length register
(LTDC_LxCFBLR)
This register defines the color frame buffer line length and pitch.
Address offset: 0xB0 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

Res.

Res.

Res.

15

14

13

Res.

Res.

Res.

28

27

26

25

24

23

22

21

20

19

18

17

16

CFBP[12:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

CFBLL[12:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:29 Reserved, must be kept at reset value.
Bits 28:16 CFBP[12:0]: color frame buffer pitch in bytes
These bits define the pitch that is the increment from the start of one line of pixels to the start
of the next line in bytes.
Bits 15:13 Reserved, must be kept at reset value.

RM0385 Rev 7

537/1709
542

LCD-TFT display controller (LTDC)

RM0385

Bits 12:0 CFBLL[12:0]: color frame buffer line length
These bits define the length of one line of pixels in bytes + 3.
The line length is computed as follows:
active high width * number of bytes per pixel + 3.

Example:

18.7.24

•

A frame buffer having the format RGB565 (2 bytes per pixel) and a width of 256 pixels
(total number of bytes per line is 256 * 2 = 512), where pitch = line length requires a
value of 0x02000203 to be written into this register.

•

A frame buffer having the format RGB888 (3 bytes per pixel) and a width of 320 pixels
(total number of bytes per line is 320 * 3 = 960), where pitch = line length requires a
value of 0x03C003C3 to be written into this register.

LTDC layer x color frame buffer line number register
(LTDC_LxCFBLNR)
This register defines the number of lines in the color frame buffer.
Address offset: 0xB4 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

CFBLNBR[10:0]
rw

rw

rw

rw

rw

rw

Bits 31:11 Reserved, must be kept at reset value.
Bits 10:0 CFBLNBR[10:0]: frame buffer line number
These bits define the number of lines in the frame buffer that corresponds to the active high
width.

Note:

The number of lines and line length settings define how much data is fetched per frame for
every layer. If it is configured to less bytes than required, a FIFO underrun interrupt will be
generated if enabled.
The start address and pitch settings on the other hand define the correct start of every line in
memory.

538/1709

RM0385 Rev 7

RM0385

LCD-TFT display controller (LTDC)

18.7.25

LTDC layer x CLUT write register (LTDC_LxCLUTWR)
This register defines the CLUT address and the RGB value.
Address offset: 0xC4 + 0x80 * (x - 1), (x = 1 to 2)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

CLUTADD[7:0]

19

18

17

16

RED[7:0]

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

w

w

w

GREEN[7:0]
w

w

w

w

w

BLUE[7:0]
w

w

w

w

w

w

w

w

Bits 31:24 CLUTADD[7:0]: CLUT address
These bits configure the CLUT address (color position within the CLUT) of each RGB value.
Bits 23:16 RED[7:0]: red value
These bits configure the red value.
Bits 15:8 GREEN[7:0]: green value
These bits configure the green value.
Bits 7:0 BLUE[7:0]: blue value
These bits configure the blue value.

Note:

The CLUT write register should only be configured during blanking period or if the layer is
disabled. The CLUT can be enabled or disabled in the LTDC_LxCR register.
The CLUT is only meaningful for L8, AL44 and AL88 pixel format.

RM0385 Rev 7

539/1709
542

LCD-TFT display controller (LTDC)

18.7.26

RM0385

LTDC register map
The following table summarizes the LTDC registers. Refer to the register boundary
addresses table for the LTDC register base address.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DEN

3

2

1

0

4

5

6

11

7

12

Res.
Res.
Res.

Res.
0

8

13

Res.
Res.

Res.
1

9

14

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

TOTALH[10:0]
0

0
Res.

10

15

0

DRW[2:0]

0

0

0

0

DGW[2:0]
0

1

0

0

0

0

0

0

DBW[2:0]

LTDCEN

0

0

0

0

0

1

0

0

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LTDC_LIPCR

Res.

0x0040

Res.

Reset value

0x0044

Reset value

540/1709

CXPOS[15:0]
0

0

0

0

0

0

0

0

0

0

TERRIF

FUIF

LIF

0

0

0

0
CLIF

RRIF

0

0

0

0

0

LIPOS10:0]
0

LTDC_CPSR

0

CFUIF

Reset value

0

CTERRIF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LTDC_ICR

Res.

0x003C

Res.

Reset value

0

CRRIF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LTDC_ISR

Res.

0x0038

Res.

Reset value

LIE

0

FUIE

0

TERRIE

0

RRIE

0

Res.

BCBLUE[7:0]

Res.

BCGREEN[7:0]

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LTDC_IER

Res.

0x0034

Res.

Reset value

BCRED[7:0]

0

Res.

Res.

Res.

Res.

Res.

Res.

LTDC_BCCR

Res.

0x002C

Res.

Reset value

IMR

0

0

Res.

0

0

VBR

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

Res.

Res.

0

Res.

0

0

Res.

0

0

AAH[10:0]

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

Res.

0

Res.

0

0

AVBP[10:0]
0

Res.

0

Res.

16
0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

0

VSH[10:0]
0

Res.

0

Res.

0

Res.

18

19

20

21

22

17
0

Res.

Res.

0

Res.

0

Res.

Res.

0

Res.

LTDC_SRCR

0

Res.

0

Res.

0

23

24

28
PCPOL

0

0

Res.

DEPOL

0

0

TOTALW[11:0]

Res.

VSPOL

0

0

Res.

29

Res.
Res.

HSPOL

Reset value

Res.

0x0024

LTDC_GCR

Res.

Reset value

0x0018

0

Res.

Res.

Res.

LTDC_TWCR

0

AAW[11:0]
0

Res.

Reset value

0x0014

0

Res.

Res.

Res.

LTDC_AWCR

0

AHBP[11:0]
0

Res.

Reset value

0x0010

25

30

Res.
Res.

LTDC_BPCR

Res.

0x000C

HSW[11:0]
0

Res.

Reset value

26

31

LTDC_SSCR

0x0008

27

Register name

Res.

Offset

Res.

Table 119. LTDC register map and reset values

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CYPOS[15:0]
0

0

0

0

0

RM0385 Rev 7

0

0

0

0

0

0

0

0

0

0

0

RM0385

LCD-TFT display controller (LTDC)

3

2

1

0

VSYNCS

0

0

0

0

0

0

HDES

VDES

CLUTEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

LTDC_L1BFCR

0

0

PF[2:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

1

1

0

0

DCBLUE[7:0]
0

0

0

0

0

0

0

BF1[2:0]
1

1

0

0

0

0

0

BF2[2:0]
1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

CFBP[12:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

LTDC_L2CR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CLUTEN

Res.

Res.

COLKEN

LEN

BLUE[7:0]

Res.

GREEN[7:0]

0

Res.

RED[7:0]

0

Res.

CLUTADD[7:0]

0

CFBLNBR[10:0]
0

LTDC_L1CLUTWR

0

CFBLL[12:0]

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.
Res.

0

Res.

Res.
Res.

Res.

0

Res.

LTDC_L1CFBLR

0

Res.

0

Res.

0

Res.

0

Res.

Reset value

Res.

0x0104

0

CFBADD[31:0]

Reset value

0x00C4

0

1

Res.

0

1

Res.

0

1

Res.

0

1

Res.

0

LTDC_L1CFBLNR

0

0

Res.

Reset value

LTDC_L1CFBAR

1

DCGREEN[7:0]

Res.

DCRED[7:0]

Res.

DCALPHA[7:0]

Res.

LTDC_L1DCCR

Reset value

0x00B4

0

CONSTA[7:0]
1

Res.

0x00B0

0

CKBLUE[7:0]

Res.

CKGREEN[7:0]

Reset value

0x00AC

0

WVSTPOS[10:0]
0

CKRED[7:0]

0

Res.

Res.
Res.

0

0

Res.

Res.
Res.

0

0

Res.

0

0

Res.

0

Res.

0

Res.

0x00A0

LEN

0

Res.

0

Res.

0

Res.

0

Reset value

0x009C

0

0
Res.

LTDC_L1CACR

0

WHSTPOS[11:0]

Reset value

0x0098

COLKEN

12
Res.
Res.

Res.

Res.

1

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

LTDC_L1PFCR

0

WVSPPOS[10:0]

Reset value

0x0094

0

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

LTDC_L1CKCR

Res.

Reset value

0x0090

0

Res.

Res.

Res.

LTDC_L1WVPCR

Res.

0x008C

WHSPPOS[11:0]
0

Res.

Reset value

Res.

Res.

Res.

LTDC_L1WHPCR

Res.

0x0088

1

0
Res.

Reset value

1
Res.

13
Res.

4

14
Res.

HSYNCS

15
Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LTDC_L1CR

Res.

Reset value

0x0084

1
Res.

16
Res.

5

17
Res.

Res.

18
Res.

6

19
Res.

Res.

20
Res.

7

21
Res.

Res.

22
Res.

8

23
Res.

Res.

24
Res.

9

25
Res.

Res.

26
Res.

Res.

27
Res.

11

28
Res.

10

29
Res.

Res.

30

LTDC_CDSR

Res.

31

0x0048

Register name

Res.

Offset

Res.

Table 119. LTDC register map and reset values (continued)

0

0

Reset value

0

RM0385 Rev 7

541/1709
542

LCD-TFT display controller (LTDC)

RM0385

0

0

0

4

5

6

7

8

12

9

13

Res.

11

14

Res.

10

15

0

0

0

0

0

0

0

0

0

0

0

0

0

0

WVSTPOS[10:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CKBLUE[7:0]

Res.

CKGREEN[7:0]

0

Res.

CKRED[7:0]

0

0

1

0

2

0

0

Res.

Res.

Res.

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

Res.

16
0

3

0

WHSTPOS[11:0]

Res.

0

Res.

0

Res.

0

Res.

0

Res.

17

18

19

20

21

22
0

WVSPPOS[10:0]

Res.

Res.
Res.

Res.

Res.

Res.

Res.

LTDC_L2PFCR

0

Res.

0

Res.

0

Reset value

0x0114

23

24

25

26

28
Res.
Res.
Res.

Res.

Res.

LTDC_L2CKCR

Res.

Reset value

0x0110

0

Res.

29
Res.
Res.

LTDC_L2WVPCR

Res.

0x010C

WHSPPOS[11:0]
0

Res.

Reset value

27

30

LTDC_L2WHPCR

Res.

31

0x0108

Register name

Res.

Offset

Res.

Table 119. LTDC register map and reset values (continued)

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LTDC_L2CACR

Res.

0x0118

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

LTDC_L2BFCR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

CFBP[12:0]

0

0

0

0

0

0

0

Reset value

0x0144

CLUTADD[7:0]
0

0

0

0

0

0

RED[7:0]

0

0

0

0

0

BF1[2:0]
1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

BF2[2:0]
1

1

1

0

0

0

0

0

0

RM0385 Rev 7

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CFBLNBR[10:0]
0

0

0

0

GREEN[7:0]

Refer to Section 2.2.2 for the register boundary addresses.

542/1709

0

0

LTDC_L2CLUTWR
Reset value

1

CFBLL[12:0]

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.
Res.

0

Res.

Res.
Res.

Res.

LTDC_L2CFBLNR

0

Res.

LTDC_L2CFBLR

0

Res.

0

Res.

0

Res.

0

Res.

Reset value

Reset value

0x0134

0

1

CFBADD[31:0]

Res.

0x0130

LTDC_L2CFBAR

0

Res.

0

0

DCBLUE[7:0]

Res.

0

1

Res.

0

1

Res.

0

1

Res.

Reset value

Reset value

0x012C

1

DCGREEN[7:0]

Res.

DCRED[7:0]

Res.

DCALPHA[7:0]

Res.

0x0120

LTDC_L2DCCR

0

CONSTA[7:0]
1

Res.

0x011C

PF[2:0]
0

Res.

Reset value

0

0

0

0

0

BLUE[7:0]
0

0

0

0

0

0

0

0

RM0385

True random number generator (RNG)

19

True random number generator (RNG)

19.1

Introduction
The RNG is a true random number generator that continuously provides 32-bit entropy
samples, based on an analog noise source. It can be used by the application as a live
entropy source to build a NIST compliant Deterministic Random Bit Generator (DRBG).
The RNG true random number generator has been validated according to the German
AIS-31 standard.

19.2

RNG main features
•

The RNG delivers 32-bit true random numbers, produced by an analog entropy source
post-processed with linear-feedback shift registers (LFSR).

•

It is validated according to the AIS-31 pre-defined class PTG.2 evaluation methodology,
which is part of the German Common Criteria (CC) scheme.

•

It produces one 32-bit random samples every 42 RNG clock cycles (dedicated clock).

•

It allows embedded continuous basic health tests with associated error management
–

Includes too low sampling clock detection and repetition count tests.

•

It can be disabled to reduce power consumption.

•

It has an AMBA AHB slave peripheral, accessible through 32-bit word single accesses
only (else an AHB bus error is generated). Warning! any write not equal to 32 bits might
corrupt the register content.

RM0385 Rev 7

543/1709
554

True random number generator (RNG)

RM0385

19.3

RNG functional description

19.3.1

RNG block diagram
Figure 116 shows the RNG block diagram.

32-bit AHB Bus

Figure 116. RNG block diagram

T-RNGv1
Banked Registers
control

AHB
interface

rng_hclk

data

RNG_DR

status

RNG_SR

AHB clock domain

Alarms

rng_it

RNG_CR

Fault detection
Clock checker

16-bit

Data shift reg
Post-processing logic

16-bit

8-bit LFSR (x2)
rng_clk
2-bit

Sampling &
Normalization (x 2)

RNG clock domain

en_osc

Analog
Analog
noise
noise
source 1 source 2
Analog noise source

MSv42096V1

19.3.2

RNG internal signals
Table 120 describes a list of useful-to-know internal signals available at the RNG level, not
at the STM32 product level (on pads).
Table 120. RNG internal input/output signals

544/1709

Signal name

Signal type

Description

rng_it

Digital output

RNG global interrupt request

rng_hclk

Digital input

AHB clock

rng_clk

Digital input

RNG dedicated clock, asynchronous to rng_hclk

RM0385 Rev 7

RM0385

19.3.3

True random number generator (RNG)

Random number generation
The true random number generator (RNG) delivers truly random data through its AHB
interface at deterministic intervals. The RNG implements the entropy source model pictured
on Figure 117, and provides three main functions to the application:
•

Collects the bitstring output of the entropy source box

•

Obtains samples of the noise source for validation purpose

•

Collects error messages from continuous health tests
Figure 117. Entropy source model

Error
message

Heath
tests

Output

Conditioning
(optional)
Raw data

Post-processing
(optional)
Digitization

Noise Source

Output
(raw data or
digitized noise
source)

Entropy source
MSv42095V1

The main components of the RNG are:
•

A source of physical randomness (analog noise source)

•

A digitization stage for this analog noise source

•

A stage delivering post-processed noise source (raw data)

•

An output buffer for the raw data. If further cryptographic conditioning is required by the
application it will need to be performed by software.

•

An optional output for the digitized noise source (unbuffered, on digital pads)

•

Basic health tests on the digitized noise source

All those components are detailed below.

RM0385 Rev 7

545/1709
554

True random number generator (RNG)

RM0385

Noise source
The noise source is the component that contains the non-deterministic, entropy-providing
activity that is ultimately responsible for the uncertainty associated with the bitstring output
by the entropy source. It is composed of:
•

Two analog noise sources, each based on three XORed free-running ring oscillator
outputs. It is possible to disable those analog oscillators to save power, as described in
Section 19.4: RNG low-power usage.

•

A sampling stage of these outputs clocked by a dedicated clock input (rng_clk),
delivering a 2-bit raw data output.

This noise source sampling is independent to the AHB interface clock frequency
(rng_hclk).
Note:

In Section 19.7: Entropy source validation recommended RNG clock frequencies are given.

Post processing
The sample values obtained from a true random noise source consist of 2-bit bitstrings.
Because this noise source output is biased, the RNG implements a post-processing
component that reduces that bias to a tolerable level.
The RNG post-processing consists of two stages, applied to each noise source bits:
•

The RNG takes half of the bits from the sampled noise source, and half of the bits from
inverted sampled noise source. Thus, if the source generates more ‘1’ than ‘0’ (or the
opposite), it is filtered

•

A linear feedback shift register (LFSR) performs a whitening process, producing 8-bit
strings.

This component is clocked by the RNG clock.
The times required between two random number generations, and between the RNG
initialization and availability of first sample are described in Section 19.6: RNG processing
time.

Output buffer
The RNG_DR data output register can store up to two 16-bit words which have been output
from the post-processing component (LFSR). In order to read back 32-bit random samples it
is required to wait 42 RNG clock cycles.
Whenever a random number is available through the RNG_DR register the DRDY flag
transitions from “0” to “1”. This flag remains high until output buffer becomes empty after
reading one word from the RNG_DR register.
Note:

546/1709

When interrupts are enabled an interrupt is generated when this data ready flag transitions
from “0” to “1”. Interrupt is then cleared automatically by the RNG as explained above.

RM0385 Rev 7

RM0385

True random number generator (RNG)

Health checks
This component ensures that the entire entropy source (with its noise source) starts then
operates as expected, obtaining assurance that failures are caught quickly and with a high
probability and reliability.
The RNG implements the following health check features:
1.

2.

Behavior tests, applied to the entropy source at run-time
–

Repetition count test, flagging an error when:

a)

One of the noise source has provided more than 64 consecutive bits at a constant
value (“0” or “1”)

b)

One of the noise sources has delivered more than 32 consecutive occurrence of
two bits patterns (“01” or “10”)

Vendor specific continuous test
–

Real-time “too slow” sampling clock detector, flagging an error when one RNG
clock cycle is smaller than AHB clock cycle divided by 16.

The CECS and SECS status bits in the RNG_SR register indicate when an error condition is
detected, as detailed in Section 19.3.7: Error management.
Note:

An interrupt can be generated when an error is detected.

19.3.4

RNG initialization
When a hardware reset occurs the following chain of events occurs:
1.

The analog noise source is enabled, and logic starts sampling the analog output after
four RNG clock cycles, filling LFSR shift register and associated 16-bit post-processing
shift register.

2.

The output buffer is refilled automatically according to the RNG usage.

The associated initialization time can be found in Section 19.6: RNG processing time.

19.3.5

RNG operation
Normal operations
To run the RNG using interrupts the following steps are recommended:
1.

Enable the interrupts by setting the IE bit in the RNG_CR register. At the same time
enable the RNG by setting the bit RNGEN=1.

2.

An interrupt is now generated when a random number is ready or when an error
occurs. Therefore at each interrupt, check that:
–

No error occurred. The SEIS and CEIS bits should be set to ‘0’ in the RNG_SR
register.

–

A random number is ready. The DRDY bit must be set to ‘1’ in the RNG_SR
register.

–

If above two conditions are true the content of the RNG_DR register can be read.

RM0385 Rev 7

547/1709
554

True random number generator (RNG)

RM0385

To run the RNG in polling mode following steps are recommended:
1.

Enable the random number generation by setting the RNGEN bit to “1” in the RNG_CR
register.

2.

Read the RNG_SR register and check that:

3.
Note:

–

No error occurred (the SEIS and CEIS bits should be set to ‘0’)

–

A random number is ready (the DRDY bit should be set to ‘1’)

If above conditions are true read the content of the RNG_DR register.

When data is not ready (DRDY=”0”) RNG_DR returns zero.

Low-power operations
If the power consumption is a concern to the application, low-power strategies can be used,
as described in Section 19.4: RNG low-power usage on page 549.

Software post-processing
If a NIST approved DRBG with 128 bits of security strength is required an approved random
generator software must be built around the RNG true random number generator.

19.3.6

RNG clocking
The RNG runs on two different clocks: the AHB bus clock and a dedicated RNG clock.
The AHB clock is used to clock the AHB banked registers and the post-processing
component. The RNG clock is used for noise source sampling. Recommended clock
configurations are detailed in Section 19.7: Entropy source validation.

Caution:

When the CED bit in the RNG_CR register is set to “0”, the RNG clock frequency must be
higher than AHB clock frequency divided by 16, otherwise the clock checker will flag a clock
error (CECS or CEIS in the RNG_SR register) and the RNG will stop producing random
numbers.
See Section 19.3.1: RNG block diagram for details (AHB and RNG clock domains).

19.3.7

Error management
In parallel to random number generation an health check block verifies the correct noise
source behavior and the frequency of the RNG source clock as detailed in this section.
Associated error state is also described.

Clock error detection
When the clock error detection is enabled (CED = 0) and if the RNG clock frequency is too
low, the RNG stops generating random numbers and sets to “1” both the CEIS and CECS
bits to indicate that a clock error occurred. In this case, the application should check that the
RNG clock is configured correctly (see Section 19.3.6: RNG clocking) and then it must clear
the CEIS bit interrupt flag. As soon as the RNG clock operates correctly, the CECS bit will
be automatically cleared.
The RNG operates only when the CECS flag is set to “0”. However note that the clock error
has no impact on the previously generated random numbers, and the RNG_DR register
contents can still be used.

548/1709

RM0385 Rev 7

RM0385

True random number generator (RNG)

Noise source error detection
When a noise source (or seed) error occurs, the RNG stops generating random numbers
and sets to “1” both SEIS and SECS bits to indicate that a seed error occurred. If a value is
available in the RNG_DR register, it must not be used as it may not have enough entropy.
In order to fully recover from a seed error application must clear the SEIS bit by writing it to
“0”, then clear and set the RNGEN bit to reinitialize and restart the RNG.

19.4

RNG low-power usage
If power consumption is a concern, the RNG can be disabled as soon as the DRDY bit is set
to “1” by setting the RNGEN bit to “0” in the RNG_CR register. The 32-bit random value
stored in the RNG_DR register will be still be available. If a new random is needed the
application will need to re-enable the RNG and wait for 42+4 RNG clock cycles.
When disabling the RNG the user deactivates all the analog seed generators, whose power
consumption is given in the datasheet electrical characteristics section.

19.5

RNG interrupts
In the RNG an interrupt can be produced on the following events:
•

Data ready flag

•

Seed error, see Section 19.3.7: Error management

•

Clock error, see Section 19.3.7: Error management

Dedicated interrupt enable control bits are available as shown in Table 121
Table 121. RNG interrupt requests
Interrupt event

Event flag

Enable control bit

Data ready flag

DRDY

IE

Seed error flag

SEIS

IE

Clock error flag

CEIS

IE

The user can enable or disable the above interrupt sources individually by changing the
mask bits or the general interrupt control bit IE in the RNG_CR register. The status of the
individual interrupt sources can be read from the RNG_SR register.
Note:

Interrupts are generated only when RNG is enabled.

19.6

RNG processing time
The RNG can produce one 32-bit random numbers every 42 RNG clock cycles.
After enabling or re-enabling the RNG using the RNGEN bit it takes 46 RNG clock cycles
before random data are available.

RM0385 Rev 7

549/1709
554

True random number generator (RNG)

RM0385

19.7

Entropy source validation

19.7.1

Introduction
In order to assess the amount of entropy available from the RNG, STMicroelectronics has
tested the peripheral against AIS-31 PTG.2 set of tests. The results can be provided on
demand or the customer can reproduce the measurements using the AIS reference
software. The customer could also test the RNG against an older NIST SP800-22 set of
tests.

19.7.2

Validation conditions
STMicroelectronics has validated the RNG true random number generator in the following
conditions:

19.7.3

•

RNG clock rng_clk= 48 MHz (CED bit = ‘0’ in RNG_CR register) and rng_clk= 400kHz
(CED bit=”1” in RNG_CR)

•

AHB clock rng_hclk= 60 MHz

Data collection
If raw data needs to be read instead of pre-processed data the developer is invited to
contact STMicroelectronics to receive the correct procedure to follow.

550/1709

RM0385 Rev 7

RM0385

True random number generator (RNG)

19.8

RNG registers
The RNG is associated with a control register, a data register and a status register.

19.8.1

RNG control register (RNG_CR)
Address offset: 0x000
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CED

Res.

IE

RNGEN

Res.

Res.

rw

rw

rw

Bits 31:6 Reserved, must be kept at reset value
Bit 5 CED: Clock error detection
0: Clock error detection is enable
1: Clock error detection is disable
The clock error detection cannot be enabled nor disabled on-the-fly when the RNG is
enabled, i.e. to enable or disable CED the RNG must be disabled.
Bit 4 Reserved, must be kept at reset value.
Bit 3 IE: Interrupt Enable
0: RNG Interrupt is disabled
1: RNG Interrupt is enabled. An interrupt is pending as soon as DRDY=’1’, SEIS=’1’ or
CEIS=’1’ in the RNG_SR register.
Bit 2 RNGEN: True random number generator enable
0: True random number generator is disabled. Analog noise sources are powered off and
logic clocked by the RNG clock is gated.
1: True random number generator is enabled.
Bits 1:0 Reserved, must be kept at reset value.

RM0385 Rev 7

551/1709
554

True random number generator (RNG)

19.8.2

RM0385

RNG status register (RNG_SR)
Address offset: 0x004
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SEIS

CEIS

Res.

Res.

SECS

CECS

DRDY

rc_w0

rc_w0

r

r

r

Bits 31:7 Reserved, must be kept at reset value.
Bit 6 SEIS: Seed error interrupt status
This bit is set at the same time as SECS. It is cleared by writing it to ‘0’.
0: No faulty sequence detected
1: At least one faulty sequence has been detected. See SECS bit description for details.
An interrupt is pending if IE = ‘1’ in the RNG_CR register.
Bit 5 CEIS: Clock error interrupt status
This bit is set at the same time as CECS. It is cleared by writing it to ‘0’.
0: The RNG clock is correct (fRNGCLK > fHCLK/16)
1: The RNG clock has been detected too slow (fRNGCLK < fHCLK/16)
An interrupt is pending if IE = ‘1’ in the RNG_CR register.
Bits 4:3 Reserved, must be kept at reset value.
Bit 2 SECS: Seed error current status
0: No faulty sequence has currently been detected. If the SEIS bit is set, this means that a
faulty sequence was detected and the situation has been recovered.
1: One of the noise source has provided more than 64 consecutive bits at a constant value
(“0” or “1”), or more than 32 consecutive occurrence of two bits patterns (“01” or “10”)
Bit 1 CECS: Clock error current status
0: The RNG clock is correct (fRNGCLK> fHCLK/16). If the CEIS bit is set, this means that a
slow clock was detected and the situation has been recovered.
1: The RNG clock is too slow (fRNGCLK< fHCLK/16).
Note: CECS bit is valid only if the CED bit in the RNG_CR register is set to “0”.
Bit 0 DRDY: Data Ready
0: The RNG_DR register is not yet valid, no random data is available.
1: The RNG_DR register contains valid random data.
Once the RNG_DR register has been read, this bit returns to ‘0’ until a new random value is
generated.
If IE=’1’ in the RNG_CR register, an interrupt is generated when DRDY=’1’.

552/1709

RM0385 Rev 7

RM0385

True random number generator (RNG)

19.8.3

RNG data register (RNG_DR)
Address offset: 0x008
Reset value: 0x0000 0000
The RNG_DR register is a read-only register that delivers a 32-bit random value when read.
After being read this register delivers a new random value after 42 periods of RNG clock if
the output FIFO is empty.
The content of this register is valid when DRDY=’1’, even if RNGEN=’0’.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

RNDATA[31:16]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

RNDATA[15:0]
r

r

Bits 31:0 RNDATA[31:0]: Random data
32-bit random data which are valid when DRDY=’1’. When DRDY=’0’ RNDATA value is zero.

RM0385 Rev 7

553/1709
554

True random number generator (RNG)

19.8.4

RM0385

RNG register map
Table 122 gives the RNG register map and reset values.

0x000

RNG_CR

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
CED
Res.
IE
RNGEN
Res.
Res.

Offset Register name

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 122. RNG register map and reset map

0x004

0x008

554/1709

0

0 0

RNG_SR

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
SEIS
CEIS
Res.
Res.
SECS
CECS
DRDY

Reset value

Reset value
RNG_DR
Reset value

0 0
0 0 0
RNDATA[31:0]
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

20

Cryptographic processor (CRYP)

20.1

Introduction
The cryptographic processor (CRYP) can be used both to encrypt and decrypt data using
the DES, Triple-DES or AES algorithms. It is a fully compliant implementation of the
following standards:
•

The data encryption standard (DES) and Triple-DES (TDES) as defined by Federal
Information Processing Standards Publication (FIPS PUB 46-3, Oct 1999), and the
American National Standards Institute (ANSI X9.52)

•

The advanced encryption standard (AES) as defined by Federal Information
Processing Standards Publication (FIPS PUB 197, Nov 2001)

Multiple key sizes and chaining modes are supported:
•

DES/TDES chaining modes ECB and CBC, supporting standard 56-bit keys with 8-bit
parity per key

•

AES chaining modes ECB, CBC, CTR, GCM, GMAC, CCM for key sizes of 128, 192 or
256 bits

The CRYP is a 32-bit AHB peripheral. It supports DMA transfers for incoming and outgoing
data (two DMA channels are required). The peripheral also includes input and output FIFOs
(each 8 words deep) for better performance.
The CRYP peripheral provides hardware acceleration to AES and DES cryptographic
algorithms packaged in STM32 cryptographic library.

20.2

CRYP main features
•

•

•

Compliant implementation of the following standards:
–

NIST FIPS publication 46-3, Data Encryption Standard (DES)

–

ANSI X9.52, Triple Data Encryption Algorithm Modes of Operation

–

NIST FIPS publication 197, Advanced Encryption Standard (AES)

AES symmetric block cipher implementation
–

128-bit data block processing

–

Support for 128-, 192- and 256-bit cipher key lengths

–

Encryption and decryption with multiple chaining modes: Electronic Code Book
(ECB), Cipher Block Chaining (CBC), Counter mode (CTR), Galois Counter Mode
(GCM), Galois Message Authentication Code mode (GMAC) and Counter with
CBC-MAC (CCM).

–

14 (respectively 18) clock cycles for processing one 128-bit block of data with a
128-bit (respectively 256-bit) key in AES-ECB mode

–

Integrated key scheduler with its key derivation stage (ECB or CBC decryption
only)

DES/TDES encryption/decryption implementation
–

64-bit data block processing

–

Support for 64-, 128- and 192-bit cipher key lengths (including parity)

–

Encryption and decryption with support of ECB and CBC chaining modes

RM0385 Rev 7

555/1709
622

Cryptographic processor (CRYP)

•

556/1709

RM0385

–

Direct implementation of simple DES algorithms (a single key K1 is used)

–

16 (respectively 64) clock cycles for processing one 64-bit block of data in DES
(respectively TDES) ECB mode

–

Software implementation of ciphertext stealing

Features common to DES/TDES and AES
–

AMBA AHB slave peripheral, accessible through 32-bit word single accesses only
(otherwise an AHB bus error is generated, and write accesses are ignored)

–

256-bit register for storing the cryptographic key (8x 32-bit registers)

–

128-bit registers for storing initialization vectors (4× 32-bit)

–

1x32-bit INPUT buffer associated with an internal IN FIFO of eight 32- bit words,
corresponding to four incoming DES blocks or two AES blocks

–

1x32-bit OUTPUT buffer associated with an internal OUT FIFO of eight 32-bit
words, corresponding to four processed DES blocks or two AES blocks

–

Automatic data flow control supporting direct memory access (DMA) using two
channels (one for incoming data, one for processed data). Single and burst
transfers are supported.

–

Data swapping logic to support 1-, 8-, 16- or 32-bit data

–

Possibility for software to suspend a message if the cryptographic processor
needs to process another message with higher priority (suspend/resume
operation)

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

20.3

CRYP functional description

20.3.1

CRYP block diagram
Figure 118 shows the block diagram of the cryptographic processor.
Figure 118. CRYP block diagram

AHB
interface

CRYP_SR

swapping

status
control

CRYP_DOUT

swapping

data out

CRYP_DIN

8x32-bit
IN FIFO

32-bit AHB2 bus

data in

8x32-bit
OUT FIFO

Banked Registers (main)

CRYP_CR

key

CRYP_Kx

Key

iv

CRYP_IVx

IV

AES
Core
(AEA)
+
DES/
TDES
Core
(DEA)

Banked Registers (IRQ & DMA)

CRYP_IMSCR

cryp_hclk

CRYP_RIS
CRYP_MIS
CRYP_DMACR
cryp_in_dma
cryp_out_dma

DMA
interface

cryp_it

Control Logic

IRQ
interface
MSv41968V2

20.3.2

CRYP internal signals
Table 123 provides a list of useful-to-know internal signals available at cryptographic
processor level and not at STM32 product level (on pads).
Table 123. CRYP internal input/output signals
Signal name

Signal type

Description

cryp_hclk

digital input

AHB bus clock

cryp_it

digital output

Cryptographic processor global interrupt request

cryp_in_dma

digital
input/output

IN FIFO DMA burst request/ acknowledge

cryp_out_dma

digital
input/output

OUT FIFO DMA burst request/ acknowledge (with single
request for DES)

RM0385 Rev 7

557/1709
622

Cryptographic processor (CRYP)

20.3.3

RM0385

CRYP DES/TDES cryptographic core
Overview
The DES/Triple-DES cryptographic core consists of three components:
•

The DES Algorithm (DEA core)

•

Multiple keys (one for the DES algorithm, one to three for the TDES algorithm)

•

The initialization vector, which is used only in CBC mode

The DES/Triple-DES cryptographic core provides two operating modes:
•

ALGODIR=0: Plaintext encryption using the key stored in the CRYP_Kx registers.

•

ALGODIR=1: Ciphertext decryption using the key stored in the CRYP_Kx registers.

The operating mode is selected by programming the ALGODIR bit in the CRYP_CR
register.

Typical data processing
Typical usage of the cryptographic processor in DES modes can be found
inSection 20.3.10: CRYP DES/TDES basic chaining modes (ECB, CBC).
Note:

The outputs of the intermediate DEA stages are never revealed outside the cryptographic
boundary, with the exclusion of the IV registers in CBC mode.

DES keying and chaining modes
The TDES allows three different keying options:

•

Three independent keys
The first option specifies that all the keys are independent, that is, K1, K2 and K3 are
independent. FIPS PUB 46-3 – 1999 (and ANSI X9.52 – 1998) refers to this option as
the Keying Option 1 and, to the TDES as 3-key TDES.

•

Two independent keys
The second option specifies that K1 and K2 are independent and K3 is equal to K1,
that is, K1 and K2 are independent, K3 = K1. FIPS PUB 46-3 – 1999 (and ANSI X9.52
– 1998) refers to this second option as the Keying Option 2 and, to the TDES as 2-key
TDES.

•

Three equal keys
The third option specifies that K1, K2 and K3 are equal, that is:
K1 = K2 = K3
FIPS PUB 46-3 – 1999 (and ANSI X9.52 – 1998) refers to the third option as the
Keying Option 3. This “1-key” TDES is equivalent to single DES.

The following chaining algorithms are supported by the DES hardware and can be selected
through the ALGOMODE bits in the CRYP_CR register:
•

Electronic Code Book (ECB)

•

Cipher Block Chaining (CBC)

These modes are described in details in Section 20.3.10: CRYP DES/TDES basic chaining
modes (ECB, CBC).

558/1709

RM0385 Rev 7

RM0385

20.3.4

Cryptographic processor (CRYP)

CRYP AES cryptographic core
Overview
The AES cryptographic core consists of the following components:
•

The AES Algorithm (AEA core)

•

The Multiplier over a binary Galois field (GF2mul)

•

The key information

•

The initialization vector (IV) or Nonce information

•

Chaining algorithms logic (XOR, feedback/counter, mask)

The AES core works on 128-bit data blocks of (four words) with 128-, 192- or 256-bit key
lengths. Depending on the chaining mode, the peripheral requires zero or one 128-bit
initialization vector (IV).
The cryptographic peripheral features two operating modes:
•

ALGODIR=0: Plaintext encryption using the key stored in the CRYP_Kx registers.

•

ALGODIR=1: Ciphertext decryption using the key stored in the CRYP_Kx registers.
When ECB and CBC chaining modes are selected, an initial key derivation process is
automatically performed by the cryptographic peripheral.

The operating mode is selected by programming the ALGODIR bit in the CRYP_CR
register.

Typical data processing
A description of cryptographic processor typical usage in AES mode can be found in
Section 20.3.11: CRYP AES basic chaining modes (ECB, CBC).
Note:

The outputs of the intermediate AEA stages is never revealed outside the cryptographic
boundary, with the exclusion of the IV registers.

AES chaining modes
The following chaining algorithms are supported by the cryptographic processor and can be
selected through the ALGOMODE bits in the CRYP_CR register:
•

Electronic Code Book (ECB)

•

Cipher Block Chaining (CBC)

•

Counter Mode (CTR)

•

Galois/Counter Mode (GCM)

•

Galois Message Authentication Code mode (GMAC)

•

Counter with CBC-MAC (CCM)

A quick introduction on these chaining modes can be found in the following subsections.
For detailed instructions, refer to Section 20.3.11: CRYP AES basic chaining modes (ECB,
CBC) and onward.

RM0385 Rev 7

559/1709
622

Cryptographic processor (CRYP)

RM0385

AES Electronic CodeBook (ECB)
Figure 119. AES-ECB mode overview

ECB is the simplest operating mode. There are no chaining operations, and no special
initialization stage. The message is divided into blocks and each block is encrypted or
decrypted separately.
Note:

560/1709

For decryption, a special key scheduling is required before processing the first block.

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

AES Cipher block chaining (CBC)
Figure 120. AES-CBC mode overview

CBC operating mode chains the output of each block with the input of the following block. To
make each message unique, an initialization vector is used during the first block processing.
Note:

For decryption,a special key scheduling is required before processing the first block.

RM0385 Rev 7

561/1709
622

Cryptographic processor (CRYP)

RM0385

AES Counter mode (CTR)
Figure 121. AES-CTR mode overview

The CTR mode uses the AES core to generate a key stream; these keys are then XORed
with the plaintext to obtain the ciphertext as specified in NIST Special Publication 800-38A,
Recommendation for Block Cipher Modes of Operation.
Note:

562/1709

Unlike ECB and CBC modes, no key scheduling is required for the CTR decryption, since in
this chaining scheme the AES core is always used in encryption mode for producing the
counter blocks.

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

AES Galois/Counter mode (GCM)
Figure 122. AES-GCM mode overview

In Galois/Counter mode (GCM), the plaintext message is encrypted, while a message
authentication code (MAC) is computed in parallel, thus generating the corresponding
ciphertext and its MAC (also known as authentication tag). It is defined in NIST Special
Publication 800-38D, Recommendation for Block Cipher Modes of Operation Galois/Counter Mode (GCM) and GMAC.
GCM mode is based on AES in counter mode for confidentiality. It uses a multiplier over a
fixed finite field for computing the message authentication code. It requires an initial value
and a particular 128-bit block at the end of the message.

AES Galois Message Authentication Code (GMAC)
Figure 123. AES-GMAC mode overview

RM0385 Rev 7

563/1709
622

Cryptographic processor (CRYP)

RM0385

Galois Message Authentication Code (GMAC) allows authenticating a message and
generating the corresponding message authentication code (MAC). It is defined in NIST
Special Publication 800-38D, Recommendation for Block Cipher Modes of Operation Galois/Counter Mode (GCM) and GMAC.
GMAC is similar to Galois/Counter mode (GCM), except that it is applied on a message
composed only by clear-text authenticated data (i.e. only header, no payload).

AES Counter with CBC-MAC (CCM)
Figure 124. AES-CCM mode overview

In Counter with Cipher Block Chaining-Message Authentication Code (CCM), the plaintext
message is encrypted while a message authentication code (MAC) is computed in parallel,
thus generating the corresponding ciphertext and the corresponding MAC (also known as
tag). It is described by NIST in Special Publication 800-38C, Recommendation for Block
Cipher Modes of Operation - The CCM Mode for Authentication and Confidentiality.
CCM mode is based on AES in counter mode for confidentiality and it uses CBC for
computing the message authentication code. It requires an initial value.
Like GCM CCM chaining mode, AES-CCM mode can be applied on a message composed
only by cleartext authenticated data (i.e. only header, no payload). Note that this way of
using CCM is not called CMAC (it is not similar to GCM/GMAC), and its usage is not
recommended by NIST.

564/1709

RM0385 Rev 7

RM0385

20.3.5

Cryptographic processor (CRYP)

CRYP procedure to perform a cipher operation
Introduction
To understand how the cryptographic peripheral operates, a typical cipher operation is
described below. For the detailed peripheral usage according to the cipher mode, refer to
the specific section, e.g. Section 20.3.11: CRYP AES basic chaining modes (ECB, CBC).
The flowcharts shown in Figure 125 and Figure 126 describe the way STM32 cryptographic
library implements DES (respectively AES) algorithm. The cryptographic processor
accelerates the execution of the following cryptographic algorithms:

Note:

•

AES-128, AES-192, AES-256 bit in the following modes: ECB, CBC, CTR, CCM, GCM

•

DES, TripleDES in the following modes: ECB, CBC

For more details on the cryptographic library, refer to use manual UM1924 “STM32 crypto
library” available from www.st.com.
Figure 125. STM32 cryptolib DES/TDES flowcharts
Encryption

Decryption

Begin

Begin

DES_x encrypt init

DES_x decrypt init

Error status

Error status

success

success

DES_x encrypt
append

AES_x decrypt
append

data to append
Error status

data to append
Error status

success

success

DES_x encrypt
finish

DES_x decrypt
finish

Error status

Error status

success

success

End

End
MSv43713V1

RM0385 Rev 7

565/1709
622

Cryptographic processor (CRYP)

RM0385

Figure 126. STM32 cryptolib AES flowchart examples
Encryption

Authenticated Decryption

Begin

Begin

AES_x encrypt init

AES_x decrypt init

Error status

Error status

success

success

AES_x encrypt
append

AES_x header
append

data to append
Error status

data to append
Error status

success
AES_x decrypt
append
data to append
Error status

success

success

AES_x encrypt
finish/final

AES_x decrypt
finish/final

Error status

Error status

success

success

End

MAC/Tag
comparison
End
MSv43714V1

CRYP initialization
1.

566/1709

Initialize the cryptographic processor. The order of operations is not important except
for AES-ECB and AES-CBC decryption, where the key preparation requires a specific
sequence.
a)

Disable the cryptographic processor by setting to 0 the CRYPEN bit in the
CRYP_CR register.

b)

Configure the key size (128-, 192- or 256-bit, in the AES only) with the KEYSIZE
bits in the CRYP_CR register.

c)

Write the symmetric key into the CRYP_KxL/R registers (2 to 8 registers to be
written depending on the algorithm).

d)

Configure the data type (1-, 8-, 16- or 32-bit), with the DATATYPE bits in the
CRYP_CR register.

e)

In case of decryption in AES-ECB or AES-CBC mode, prepare the key that has
been written. First configure the key preparation mode by setting the ALGOMODE
bits to 0b111 in the CRYP_CR register. Then write the CRYPEN bit to 1: the BUSY

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
bit is set automatically. Wait until BUSY returns to 0 (CRYPEN is automatically
cleared as well): the key is prepared for decryption.

2.

f)

Configure the algorithm and chaining with the ALGOMODE bits in the CRYP_CR
register.

g)

Configure the direction (encryption/decryption) through the ALGODIR bit in the
CRYP_CR register.

h)

When it is required (e.g. CBC or CTR chaining modes), write the initialization
vectors into the CRYP_IVxL/R register.

Flush the IN and OUT FIFOs by writing the FFLUSH bit to 1 in the CRYP_CR register.

Preliminary warning for all cases
If the ECB or CBC mode is selected and data are not a multiple of 64 bits (for DES) or 128
bits (for AES), the second and the last block management is more complex than the
sequences below. Refer to Section 20.3.8: CRYP stealing and data padding for more
details.

Appending data using the CPU in polling mode
1.

Enable the cryptographic processor by setting to 1 the CRYPEN bit in the CRYP_CR
register.

2.

Write data in the IN FIFO (one block or until the FIFO is full).

3.

Repeat the following sequence until the second last block of data has been processed:
a)

Wait until the not-empty-flag OFNE is set to 1, then read the OUT FIFO (one block
or until the FIFO is empty).

b)

Wait until the not-full-flag IFNF is set to 1, then write the IN FIFO (one block or until
the FIFO is full) except if it is the last block.

4.

The BUSY bit is set automatically by the cryptographic processor. At the end of the
processing, the BUSY bit returns to 0 and both FIFOs are empty (IN FIFO empty flag
IFEM=1 and OUT FIFO not empty flag OFNE=0).

5.

If the next processing block is the last block, the CPU must pad (when applicable) the
data with zeroes to obtain a complete block

6.

When the operation is complete, the cryptographic processor can be disabled by
clearing the CRYPEN bit in CRYP_CR register.

Appending data using the CPU in interrupt mode
1.

Enable the interrupts by setting the INIM and OUTIM bits in the CRYP_IMSCR register.

2.

Enable the cryptographic processor by setting to 1 the CRYPEN bit in the CRYP_CR
register.

3.

4.

In the interrupt service routine that manages the input data:
a)

If the last block is being loaded, the CPU must pad (when applicable) the data with
zeroes to have a complete block. Then load the block into the IN FIFO.

b)

If it is not the last block, load the data into the IN FIFO. You can load only one
block (2 words for DES, 4 words for AES), or load data until the FIFO is full.

c)

In all cases, after the last word of data has been written, disable the interrupt by
clearing the INIM interrupt mask.

In the interrupt service routine that manages the input data:

RM0385 Rev 7

567/1709
622

Cryptographic processor (CRYP)

RM0385

a)

Read the output data from the OUT FIFO. You can read only one block (2 words
for DES, 4 words for AES), or read data until the FIFO is empty.

b)

When the last word has been read, INIM and BUSY bits are set to 0 and both
FIFOs are empty (IFEM=1 and OFNE=0). You can disable the interrupt by clearing
the OUTIM bit, and disable the peripheral by clearing the CRYPEN bit.

c)

If you read the last block of cleartext data (i.e. decryption), optionally discard the
data that is not part of message/payload.

Appending data using the DMA
1.

Prepare the last block of data by optionally padding it with zeroes to have a complete
block.

2.

Configure the DMA controller to transfer the input data from the memory and transfer
the output data from the peripheral to the memory, as described in Section 20.3.19:
CRYP DMA interface. The DMA should be configured to set an interrupt on transfer
completion to indicate that the processing is complete.

3.

Enable the cryptographic processor by setting to 1 the CRYPEN bit in CRYP_CR
register, then enable the DMA IN and OUT requests by setting to 1 the DIEN and
DOEN bits in the CRYP_DMACR register.

4.

All the transfers and processing are managed by the DMA and the cryptographic
processor. The DMA interrupt indicates that the processing is complete. Both FIFOs
are normally empty and BUSY flag is set 0.

Caution:

It is important that DMA controller empties the cryptographic processor output FIFO before
filling up the cryptographic processor input FIFO. To achieve this, the DMA controller should
be configured so that the transfer from the cryptographic peripheral to the memory has a
higher priority than the transfer from the memory to the cryptographic peripheral.

20.3.6

CRYP busy state
The cryptographic processor is busy and processing data (BUSY set to 1 in CRYP_SR
register) when all the conditions below are met:
•

CRYPEN = 1 in CRYP_CR register.

•

There are enough data in the input FIFO (at least two words for the DES or TDES
algorithm mode, four words for the AES algorithm mode).

•

There is enough free-space in the output FIFO (at least two word locations for DES,
four for AES).

Write operations to the CRYP_Kx(L/R)R key registers, to the CRYP_IVx(L/R)R initialization
registers, or to bits [9:2] of the CRYP_CR register, are ignored when cryptographic
processor is busy (i.e. the registers are not modified). It is thus not possible to modify the
configuration of the cryptographic processor while it is processing a data block.
It is possible to clear the CRYPEN bit while BUSY bit is set to 1. In this case the ongoing
DES/TDES or AES processing first completes (i.e. the word results are written to the output
FIFO) before the BUSY bit is cleared by hardware.
Note:

If the application needs to suspend a message to process another one with a higher priority,
refer to Section 20.3.9: CRYP suspend/resume operations
When a block is being processed in DES or TDES mode, if the output FIFO becomes full
and the input FIFO contains at least one new block, then the new block is popped off the

568/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
input FIFO and the BUSY bit remains high until there is enough space to store this new
block into the output FIFO.

20.3.7

Preparing the CRYP AES key for decryption
When performing an AES ECB or CBC decryption, the AES key has to be prepared, i.e. a
complete key schedule of encryption is required before performing the decryption. In other
words, the key in the last round of encryption must be used as the first round key for
decryption.
This preparation is not required in any other AES modes than AES ECB or CBC decryption.
If the application software stores somehow the initial key prepared for decryption, the key
scheduling operation can be performed only once for all the data to be decrypted with a
given cipher key.

Note:

The latency of the key preparation operation is 14, 16 or 18 clock cycles depending on the
key size (128-, 192- or 256-bit).
The CRYP key preparation process is performed as follow:
1.

Write the encryption key to K0...K3 key registers.

2.

Program ALGOMODE bits to 0b111 in CRYP_CR. Writing this value when CRYPEN is
et to 1 immediately starts an AES round for key preparation. The BUSY bit in the
CRYP_SR register is set to 1.

3.

When the key processing is complete, the resulting key is copied back into the K0...K3
key registers, and the BUSY bit is cleared.

Note:

As the CRYPEN bitfield is reset by hardware at the end of the key preparation, the
application software must set it again for the next operation.

20.3.8

CRYP stealing and data padding
When using DES or AES algorithm in ECB or CBC modes to manage messages that are
not multiple of the block size (64 bits for DES, 128 bits for AES), use ciphertext stealing
techniques such as those described in NIST Special Publication 800-38A, Recommendation
for Block Cipher Modes of Operation: Three Variants of Ciphertext Stealing for CBC Mode.
Since the cryptographic processor does not implement such techniques, the last two
blocks must be handled in a special way by the application.

Note:

Ciphertext stealing techniques are not documented in this reference manual.
Similarly, when the AES algorithm is used in other modes than ECB or CBC, incomplete
input data blocks (i.e. block shorter than 128 bits) have to be padded with zeroes by the
application prior to encryption (i.e. extra bits should be appended to the trailing end of the
data string). After decryption, the extra bits have to be discarded. The cryptographic
processor does not implement automatic data padding operation to the last block, so the
application should follow the recommendation given in Section 20.3.5: CRYP procedure to
perform a cipher operation to manage messages that are not multiple of 128 bits.

Note:

Padding data are swapped in a similar way as normal data, according to the DATATYPE
field in CRYP_CR register (see Section 20.3.16: CRYP data registers and data swapping for
details).

RM0385 Rev 7

569/1709
622

Cryptographic processor (CRYP)

RM0385

With this version of cryptographic processor, a special workaround is required in order to
properly compute authentication tags while doing a GCM encryption or a CCM decryption
with the last block of payload size inferior to 128 bits. This workaround is described below:
•

•

570/1709

During GCM encryption payload phase and before inserting a last plaintext block
smaller than 128 bits, the application has to follow the below sequence:
a)

Disable the peripheral by setting the CRYPEN bit to 0 in CRYP_CR.

b)

Load CRYP_IV1R register content in a temporary variable. Decrement the value
by 1 and reinsert the result in CRYP_IV1R register.

c)

Change the AES mode to CTR mode by writing the ALGOMODE bitfield to 0b0110
in the CRYP_CR register.

a)

Set the CRYPEN bit to 1 in CRYP_CR to enable again the peripheral.

b)

Pad the last block (smaller than 128 bits) with zeros to have a complete block of
128 bits, then write it into CRYP_DIN register.

c)

Upon encryption completion, read the 128-bit generated ciphertext from the
CRYP_DOUT register and store it as intermediate data.

d)

Change again the AES mode to GCM mode by writing the ALGOMODE bitfield to
0b1000 in the CRYP_CR register.

e)

Select Final phase by writing the GCM_CCMPH bitfield to 0b11 in the CRYP_CR
register.

f)

In the intermediate data, set to 0 the bits corresponding to the padded bits of the
last payload block then insert the resulting data to CRYP_DIN register.

g)

When the operation is complete, read data from CRYP_DOUT. These data have
to be discarded.

h)

Apply the normal Final phase as described in Section 20.3.13: CRYP AES
Galois/counter mode (GCM).

During CCM decryption payload phase and before inserting a last ciphertext block
smaller than 128 bits, the application has to follow the below sequence:
a)

To disable the peripheral, set the CRYPEN bit to 0 in CRYP_CR.

b)

Load CRYP_IV1R in a temporary variable (named here IV1temp).

c)

Load CRYP_CSGCMCCM0R, CRYP_CSGCMCCM1R, CRYP_CSGCMCCM2R,
and CRYP_CSGCMCCM3R registers content from LSB to MSB in 128-bit
temporary variable (named here temp1).

d)

Load in CRYP_IV1R the content previously stored in IV1temp.

e)

Change the AES mode to CTR mode by writing the ALGOMODE bitfield to 0b0110
in the CRYP_CR register.

a)

Set the CRYPEN bit to 1 in CRYP_CR to enable again the peripheral.

b)

Pad the last block (smaller than 128 bits) with zeros to have a complete block of
128 bits, then write it to CRYP_DIN register.

c)

Upon decryption completion, read the 128-bit generated data from DOUT register,
and store them as intermediate data (here named intdata_o).

d)

Save again CRYP_CSGCMCCM0R, CRYP_CSGCMCCM1R,
CRYP_CSGCMCCM2R, and CRYP_CSGCMCCM3R registers content, from LSB
to MSB, in a new 128-bit temporary variable (named here temp2).

e)

Change again the AES mode to CCM mode by writing the ALGOMODE bitfield to
0b1001 in the CRYP_CR register.

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
f)

Select the header phase by writing the GCM_CCMPH bitfield to 0b01 in the
CRYP_CR register.

g)

In the intermediate data (intdata_o which was generated with CTR), set to 0 the
bits corresponding to the padded bits of the last payload block, XOR with temp1,
XOR with temp2, and insert the resulting data into CRYP_DIN register. In other
words:
CRYP_DIN=(intdata_o AND mask) XOR temp1 XOR temp2.

20.3.9

h)

Wait for operation completion.

i)

Apply the normal Final phase as described in Section 20.3.15: CRYP AES
Counter with CBC-MAC (CCM).

CRYP suspend/resume operations
A message can be suspended if another message with a higher priority has to be
processed. When this highest priority message has been sent, the suspended message can
be resumed in both encryption or decryption mode.
Suspend/resume operations do not break the chaining operation and the message
processing can be resumed as soon as cryptographic processor is enabled again to receive
the next data block.
Figure 127 gives an example of suspend.resume operation: message 1 is suspended in
order to send a higher priority message (message 2), which is shorter than message 1 (AES
algorithm).
Figure 127. Example of suspend mode management
Message 2

Message 1
128-bit block 1

128-bit block 2
New higher
priority message
2 to be processed

128-bit block 3

CRYP suspend
sequence
128-bit block 1

128-bit block 2
128-bit block 4

128-bit block 5

CRYP resume
sequence

128-bit block 6
...
MSv43715V1

A detailed description of suspend/resume operations can be found in each AES mode
section.

RM0385 Rev 7

571/1709
622

Cryptographic processor (CRYP)

20.3.10

RM0385

CRYP DES/TDES basic chaining modes (ECB, CBC)
Overview
FIPS PUB 46-3 – 1999 (and ANSI X9.52-1998) provides a thorough explanation of the
processing involved in the four operation modes supplied by the DES computing core:
TDES-ECB encryption, TDES-ECB decryption, TDES-CBC encryption and TDES-CBC
decryption. This section only gives a brief explanation of each mode.

DES/TDES-ECB encryption
Figure 128 illustrates the encryption in DES and TDES Electronic CodeBook (DES/TDESECB) mode. This mode is selected by writing in ALGOMODE to 0b000 and ALGODIR to 0
in CRYP_CR.
Figure 128. DES/TDES-ECB mode encryption
IN FIFO
plaintext P
P, 64 bits
DATATYPE

swapping

64
DEA, encrypt

K1

64
DEA, decrypt

K2

64
K3

DEA, encrypt
O, 64 bits

DATATYPE
swapping
C, 64 bits
OUT FIFO
ciphertext C
ai16069b

1. K: key; C: cipher text; I: input block; O: output block; P: plain text.

A 64-bit plaintext data block (P) is used after bit/byte/half-word as the input block (I). The
input block is processed through the DEA in the encrypt state using K1. The output of this
process is fed back directly to the input of the DEA where the DES is performed in the
decrypt state using K2. The output of this process is fed back directly to the input of the DEA
where the DES is performed in the encrypt state using K3. The resultant 64-bit output block
(O) is used, after bit/byte/half-word swapping, as ciphertext (C) and it is pushed into the
OUT FIFO.
Note:

For more information on data swapping, refer to Section 20.3.16: CRYP data registers and
data swapping.
Detailed DES/TDES encryption sequence can be found in Section 20.3.5: CRYP procedure
to perform a cipher operation.

572/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

DES/TDES-ECB mode decryption
Figure 129 illustrates the decryption in DES and TDES Electronic CodeBook (DES/TDESECB) mode. This mode is selected by writing ALGOMODE to 0b000 and ALGODIR to 1 in
CRYP_CR.
Figure 129. DES/TDES-ECB mode decryption
IN FIFO
ciphertext C
C, 64 bits
DATATYPE

swapping
I, 64 bits

64
DEA, decrypt

K3

64
DEA, encrypt

K2

64
K1

DEA, decrypt
O, 64 bits

DATATYPE
swapping
P, 64 bits
OUT FIFO
plaintext P
MS19021V1

1. K: key; C: cipher text; I: input block; O: output block; P: plain text.

A 64-bit ciphertext block (C) is used, after bit/byte/half-word swapping, as the input block (I).
The keying sequence is reversed compared to that used in the encryption process. The
input block is processed through the DEA in the decrypt state using K3. The output of this
process is fed back directly to the input of the DEA where the DES is performed in the
encrypt state using K2. The new result is directly fed to the input of the DEA where the DES
is performed in the decrypt state using K1. The resultant 64-bit output block (O), after
bit/byte/half-word swapping, produces the plaintext (P).
Note:

For more information on data swapping refer to Section 20.3.16: CRYP data registers and
data swapping.
Detailed DES/TDES encryption sequence can be found in Section 20.3.5: CRYP procedure
to perform a cipher operation.

RM0385 Rev 7

573/1709
622

Cryptographic processor (CRYP)

RM0385

DES/TDES-CBC encryption
Figure 130 illustrates the encryption in DES and TDES Cipher Block Chaining (DES/TDESECB) mode. This mode is selected by writing in ALGOMODE to 0b001 and ALGODIR to 0
in CRYP_CR.
Figure 130. DES/TDES-CBC mode encryption
IN FIFO
plaintext P
P, 64 bits
DATATYPE

AHB2 data write
(before CRYP
is enabled)

swapping

+
I, 64 bits

64

DEA, encrypt

K1
O is written back
into IV at the
same time as it
is pushed into
the OUT FIFO

Ps, 64 bits

64
IV0(L/R)

64
DEA, decrypt

K2

64
K3

DEA, encrypt
O, 64 bits

DATATYPE

swapping
C, 64 bits
OUT FIFO
ciphertext C
ai16070b

K: key; C: cipher text; I: input block; O: output block; Ps: plain text before swapping (when
decoding) or after swapping (when encoding); P: plain text; IV: initialization vectors.
This mode begins by dividing a plaintext message into 64-bit data blocks. In TCBC
encryption, the first input block (I1), obtained after bit/byte/half-word swapping, is formed by
exclusive-ORing the first plaintext data block (P1) with a 64-bit initialization vector IV
(I1 = IV ⊕ P1). The input block is processed through the DEA in the encrypt state using K1.
The output of this process is fed back directly to the input of the DEA, which performs the
DES in the decrypt state using K2. The output of this process is fed directly to the input of
the DEA, which performs the DES in the encrypt state using K3. The resultant 64-bit output
block (O1) is used directly as the ciphertext (C1), that is, C1 = O1.
This first ciphertext block is then exclusive-ORed with the second plaintext data block to
produce the second input block, (I2) = (C1 ⊕ P2). Note that I2 and P2 now refer to the second
block. The second input block is processed through the TDEA to produce the second
ciphertext block.
This encryption process continues to “chain” successive cipher and plaintext blocks
together until the last plaintext block in the message is encrypted.
If the message does not consist of an integral number of data blocks, then the final partial
data block should be encrypted in a manner specified for the application.

574/1709

RM0385 Rev 7

RM0385
Note:

Cryptographic processor (CRYP)
For more information on data swapping refer to Section 20.3.16: CRYP data registers and
data swapping.
Detailed DES/TDES encryption sequence can be found in Section 20.3.5: CRYP procedure
to perform a cipher operation.

DES/TDES-CBC decryption
Figure 130 illustrates the decryption in DES and TDES Cipher Block Chaining (DES/TDESECB) mode. This mode is selected by writing ALGOMODE to 0b001 and ALGODIR to 1 in
CRYP_CR.
Figure 131. DES/TDES-CBC mode decryption
IN FIFO
ciphertext C
C, 64 bits
DATATYPE
swapping
I, 64 bits

64
I is written back
into IV at the
same time as P
is pushed into
the OUT FIFO

DEA, decrypt

K3

64
DEA, encrypt

K2

64
K1
AHB2 data write
(before CRYP
is enabled)

DEA, decrypt
O, 64 bits

64
IV0(L/R)

+
Ps, 64 bits

DATATYPE

swapping
P, 64 bits
OUT FIFO
plaintext P
MS19022V1

1. K: key; C: cipher text; I: input block; O: output block; Ps: plain text before swapping (when decoding) or
after swapping (when encoding); P: plain text; IV: initialization vectors.

In this mode the first ciphertext block (C1) is used directly as the input block (I1). The keying
sequence is reversed compared to that used for the encrypt process. The input block is
processed through the DEA in the decrypt state using K3. The output of this process is fed
directly to the input of the DEA where the DES is processed in the encrypt state using K2.
This resulting value is directly fed to the input of the DEA where the DES is processed in the
decrypt state using K1. The resulting output block is exclusive-ORed with the IV (which must
be the same as that used during encryption) to produce the first plaintext block (P1 = O1
⊕ IV).
The second ciphertext block is then used as the next input block and is processed through
the TDEA. The resulting output block is exclusive-ORed with the first ciphertext block to
produce the second plaintext data block (P2 = O2 ⊕ C1). Note that P2 and O2 refer to the
second block of data.

RM0385 Rev 7

575/1709
622

Cryptographic processor (CRYP)

RM0385

The DES/TDES-CBC decryption process continues in this manner until the last complete
ciphertext block has been decrypted.
Ciphertext representing a partial data block must be decrypted in a manner specified for the
application.
Note:

For more information on data swapping refer to Section 20.3.16: CRYP data registers and
data swapping.
Detailed DES/TDES encryption sequence can be found in Section 20.3.5: CRYP procedure
to perform a cipher operation.

DES/TDES suspend/resume operations in ECB/CBC modes
Before interrupting the current message, the user application must respect the following
steps:

Note:

1.

If DMA is used, stop the DMA transfers to the IN FIFO by clearing to 0 the DIEN bit in
the CRYP_DMACR register.

2.

Wait until both the IN and the OUT FIFOs are empty (IFEM=1 and OFNE=0 in the
CRYP_SR) and the BUSY bit is cleared. Alternatively, as the input FIFO can contain up
to four unprocessed DES blocks, the application could decide for real-time reason to
interrupt the cryptographic processing without waiting for the IN FIFO to be empty. In
this case, the alternative is:
a)

Wait until OUT FIFO is empty (OFNE=0).

b)

Read back the data loaded in the IN FIFO that have not been processed and save
them in the memory until the IN FIFO is empty.

3.

If DMA is used stop the DMA transfers from the OUT FIFO by clearing to 0 the DOEN
bit in the CRYP_DMACR register.

4.

Disable the cryptographic processor by setting the CRYPEN bit to 0 in CRYP_CR, then
save the current configuration (bits [9:2] in the CRYP_CR register). If CBC mode is
selected, save the initialization vector registers, since CRYP_IVx registers have
changed from initial values during the data processing.

Key registers do not need to be saved as the original key value is known by the application.
5.

If DMA is used, save the DMA controller status (such as the pointers to IN and OUT
data transfers, number of remaining bytes).

To resume message processing, the user application must respect the following sequence:

576/1709

1.

If DMA is used, reconfigure the DMA controller to complete the rest of the FIFO IN and
FIFO OUT transfers.

2.

Make sure the cryptographic processor is disabled by reading the CRYPEN bit in
CRYP_CR (it must be 0).

3.

Configure again the cryptographic processor with the initial setting in CRYP_CR, as
well as the key registers using the saved configuration.

4.

If the CBC mode is selected, restore CRYP_IVx registers using the saved
configuration.

5.

Optionally, write the data that were saved during context saving into the IN FIFO.

6.

Enable the cryptographic processor by setting the CRYPEN bit to 1.

7.

If DMA is used, enable again DMA requests for the cryptographic processor, by setting
to 1 the DIEN and DOEN bits in the CRYP_DMACR register.

RM0385 Rev 7

RM0385

20.3.11

Cryptographic processor (CRYP)

CRYP AES basic chaining modes (ECB, CBC)
Overview
FIPS PUB 197 (November 26, 2001) provides a thorough explanation of the processing
involved in the four basic operation modes supplied by the AES computing core: AES-ECB
encryption, AES-ECB decryption, AES-CBC encryption and AES-CBC decryption. This
section only gives a brief explanation of each mode.

AES ECB encryption
Figure 132 illustrates the AES Electronic codebook (AES-ECB) mode encryption. This
mode is selected by writing ALGOMODE to 0b100 and ALGODIR to 0 in CRYP_CR.
Figure 132. AES-ECB mode encryption
IN FIFO
plaintext P
P, 128 bits
DATATYPE

swapping

K 0...3(1)

I, 128 bits

128/192
or 256

AEA, encrypt

DATATYPE

swapping
C, 128 bits

OUT FIFO
ciphertext C
ai16071b

1. K: key; C: cipher text; I: input block; O: output block; P: plain text.
2. If Key size = 128: Key = [K3 K2].
If Key size = 192: Key = [K3 K2 K1]
If Key size = 256: Key = [K3 K2 K1 K0].

In this mode a 128- bit plaintext data block (P) is used after bit/byte/half-word swapping as
the input block (I). The input block is processed through the AEA in the encrypt state using
the 128, 192 or 256-bit key. The resultant 128-bit output block (O) is used after bit/byte/halfword swapping as ciphertext (C). It is then pushed into the OUT FIFO.
For more information on data swapping refer to Section 20.3.16: CRYP data registers and
data swapping.

RM0385 Rev 7

577/1709
622

Cryptographic processor (CRYP)

RM0385

AES ECB decryption
Figure 133 illustrates the AES Electronic codebook (AES-ECB) mode decryption. This
mode is selected by writing in ALGOMODE to 0b100 and ALGODIR to 1 in CRYP_CR.
Figure 133. AES-ECB mode decryption
IN FIFO
ciphertext C
C, 128 bits
DATATYPE

swapping

K 0...3(1)

128/192
or 256

I, 128 bits

AEA, decrypt
O, 128 bits

DATATYPE

swapping
P, 128 bits

OUT FIFO
plaintext P
MS19023V1

1. K: key; C: cipher text; I: input block; O: output block; P: plain text.
2. If Key size = 128 => Key = [K3 K2].
If Key size = 192 => Key = [K3 K2 K1]
If Key size = 256 => Key = [K3 K2 K1 K0].

To perform an AES decryption in ECB mode, the secret key has to be prepared (it is
necessary to execute the complete key schedule for encryption) by collecting the last round
key, and using it as the first round key for the decryption of the ciphertext. This preparation
phase is computed by the AES core. Refer to Section 20.3.7: Preparing the CRYP AES key
for decryption for more details on how to prepare the key.
When the key preparation is complete, the decryption proceed as follow: a 128-bit ciphertext
block (C) is used after bit/byte/half-word swapping as the input block (I). The keying
sequence is reversed compared to that of the encryption process. The resultant 128-bit
output block (O), after bit/byte or half-word swapping, produces the plaintext (P). The AESCBC decryption process continues in this manner until the last complete ciphertext block
has been decrypted.
For more information on data swapping refer to Section 20.3.16: CRYP data registers and
data swapping.

578/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

AES CBC encryption
Figure 134 illustrates the AES Cipher block chaining (AES-CBC) mode encryption. This
mode is selected by writing ALGOMODE to 0b101 and ALGODIR to 0 in CRYP_CR.
Figure 134. AES-CBC mode encryption
IN FIFO
plaintext P
P, 128 bits
DATATYPE
AHB2 data write
(before CRYP
is enabled)

IV=[IV1 IV0](2)
128, 192
or 256

K 0...3(3)

swapping
128

Ps, 128 bits

+
I, 128 bits

AEA, encrypt

O is written
back into IV
at the same time
as it is pushed
into the OUT FIFO

O, 128 bits
DATATYPE

swapping
C, 128 bits
OUT FIFO
ciphertext C
ai16072b

1. K: key; C: cipher text; I: input block; O: output block; Ps: plain text before swapping (when decoding) or
after swapping (when encoding); P: plain text; IV: Initialization vectors.
2. IVx=[IVxR IVxL], R=right, L=left.
3. If Key size = 128 => Key = [K3 K2].
If Key size = 192 => Key = [K3 K2 K1]
If Key size = 256 => Key = [K3 K2 K1 K0].

In this mode the first input block (I1) obtained after bit/byte/half-word swapping is formed by
exclusive-ORing the first plaintext data block (P1) with a 128-bit initialization vector IV (I1 =
IV ⊕ P1). The input block is processed through the AEA in the encrypt state using the 128-,
192- or 256-bit key (K0...K3). The resultant 128-bit output block (O1) is used directly as
ciphertext (C1), that is, C1 = O1. This first ciphertext block is then exclusive-ORed with the
second plaintext data block to produce the second input block, (I2) = (C1 ⊕ P2). Note that I2
and P2 now refer to the second block. The second input block is processed through the AEA
to produce the second ciphertext block. This encryption process continues to “chain”
successive cipher and plaintext blocks together until the last plaintext block in the message
is encrypted.
If the message does not consist of an integral number of data blocks, then the final partial
data block should be encrypted in a manner specified for the application, as explained in
Section 20.3.8: CRYP stealing and data padding.
For more information on data swapping, refer to Section 20.3.16: CRYP data registers and
data swapping.

RM0385 Rev 7

579/1709
622

Cryptographic processor (CRYP)

RM0385

AES CBC decryption
Figure 135 illustrates the AES Cipher block chaining (AES-CBC) mode decryption. This
mode is selected by writing ALGOMODE to 0b101 and ALGODIR to 1 in CRYP_CR.
Figure 135. AES-CBC mode decryption
IN FIFO
ciphertext C
C, 128 bits
DATATYPE

swapping
I, 128 bits

128, 192
or 256

K 0...3(3)

AEA, decrypt

I is written
back into IV
at the same time
as P is pushed
into the OUT FIFO
AHB2 data write
(before CRYP
is enabled)

128

IV=[IV1 IV0](2)
DATATYPE

O, 128 bits

+

Ps, 128 bits

swapping
P, 128 bits

OUT FIFO
plaintext P
MS19024V1

1. K: key; C: cipher text; I: input block; O: output block; Ps: plain text before swapping (when decoding) or
after swapping (when encoding); P: plain text; IV: Initialization vectors.
2. IVx=[IVxR IVxL], R=right, L=left.
3. If Key size = 128 => Key = [K3 K2].
If Key size = 192 => Key = [K3 K2 K1]
If Key size = 256 => Key = [K3 K2 K1 K0].

In CBC mode, like in ECB mode, the secret key must be prepared to perform an AES
decryption. Refer to Section 20.3.7: Preparing the CRYP AES key for decryption for more
details on how to prepare the key.
When the key preparation process is complete, the decryption proceeds as follow: the first
128-bit ciphertext block (C1) is used directly as the input block (I1). The input block is
processed through the AEA in the decrypt state using the 128-, 192- or 256-bit key. The
resulting output block is exclusive-ORed with the 128-bit initialization vector IV (which must
be the same as that used during encryption) to produce the first plaintext block (P1 = O1 ⊕
IV).
The second ciphertext block is then used as the next input block and is processed through
the AEA. The resulting output block is exclusive-ORed with the first ciphertext block to
produce the second plaintext data block (P2 = O2 ⊕ C1). Note that P2 and O2 refer to the
second block of data. The AES-CBC decryption process continues in this manner until the
last complete ciphertext block has been decrypted.

580/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
Ciphertext representing a partial data block must be decrypted in a manner specified for the
application, as explained in Section 20.3.8: CRYP stealing and data padding.
For more information on data swapping, refer to Section 20.3.16: CRYP data registers and
data swapping.

AES suspend/resume operations in ECB/CBC modes
Before interrupting the current message, the user application must respect the following
sequence:

Note:

1.

If DMA is used, stop the DMA transfers to the IN FIFO by clearing to 0 the DIEN bit in
the CRYP_DMACR register.

2.

Wait until both the IN and the OUT FIFOs are empty (IFEM=1 and OFNE=0 in the
CRYP_SR) and the BUSY bit is cleared.

3.

If DMA is used, stop the DMA transfers from the OUT FIFO by clearing to 0 the DOEN
bit in the CRYP_DMACR register.

4.

Disable the CRYP by setting the CRYPEN bit to 0 in CRYP_CR, then save the current
configuration (bits [9:2] in the CRYP_CR register). If ECB mode is not selected, save
the initialization vector registers, because CRYP_IVx registers have changed from
initial values during the data processing.

Key registers do not need to be saved as the original key value is known by the application.
5.

If DMA is used, save the DMA controller status (such as pointers to IN and OUT data
transfers, number of remaining bytes).

To resume message processing, the user application must respect the following sequence:
1.

If DMA is used, reconfigure the DMA controller to complete the rest of the FIFO IN and
FIFO OUT transfers.

2.

Make sure the cryptographic processor is disabled by reading the CRYPEN bit in
CRYP_CR (it must be set to 0).

3.

Configure the cryptographic processor again with the initial setting in CRYP_CR, as
well as the key registers using the saved configuration.

4.

For AES-ECB or AES-CBC decryption, the key must be prepared again, as described
in Section 20.3.7: Preparing the CRYP AES key for decryption.

5.

If ECB mode is not selected, restore CRYP_IVx registers using the saved
configuration.

6.

Enable the cryptographic processor by setting the CRYPEN bit to 1.

7.

If DMA is used, enable again the DMA requests from the cryptographic processor, by
setting DIEN and DOEN bits to 1 in the CRYP_DMACR register.

RM0385 Rev 7

581/1709
622

Cryptographic processor (CRYP)

20.3.12

RM0385

CRYP AES counter mode (AES-CTR)
Overview
The AES counter mode (CTR) uses the AES block as a key stream generator. The
generated keys are then XORed with the plaintext to obtain the ciphertext.
CTR chaining is defined in NIST Special Publication 800-38A, Recommendation for Block
Cipher Modes of Operation. A typical message construction in CTR mode is given in
Figure 136.
Figure 136. Message construction for the Counter mode
16-Bytes boundaries

CTR mode

Encrypted Ciphertext (C)

Pad
ding

decrypt

ICB

4-Bytes boundaries

Nonce

Plaintext (P)

Initialization
vector (IV)

Counter
(0x1)

MSv43716V1

The structure of this message is as below:
•

•

582/1709

A 16-byte Initial Counter Block (ICB), composed of three distinct fields:
–

A nonce: a 32-bit, single-use value (i.e. a new nonce should be assigned to each
new communication).

–

The initialization vector (IV): a 64-bit value that must be unique for each execution
of the mode under a given key.

–

The counter: a 32-bit big-endian integer that is incremented each time a block has
been processed. The initial value of the counter should be set to 1.

The plaintext (P) is both authenticated and encrypted as ciphertext C, with a known
length. This length can be non-multiple of 16 bytes, in which case a plaintext padding is
required.

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

AES CTR processing
Figure 137 (respectively Figure 138) describes the AES-CTR encryption (respectively
decryption) process implemented within this peripheral. This mode is selected by writing in
ALGOMODE bitfield to 0b110 in CRYP_CR.
Figure 137. AES-CTR mode encryption
IN FIFO
plaintext P
P, 128 bits
AHB2 data write
(before CRYP
is enabled)

DATATYPE

swapping
IV0...1(L/R)
Ps, 128 bits

+1

K0...3

I, 128 bits

128, 192
or 256

AEA, encrypt

(I + 1) is written
back into IV
at same time
than C is pushed
in OUT FIFO

O, 128 bits

+
Cs, 128 bit

DATATYPE

swapping
C, 128 bits

OUT FIFO
ciphertext C
ai16073b

1. K: key; C: cipher text; I: input Block; o: output block; Ps: plain text before swapping (when decoding) or
after swapping (when encoding); Cs: cipher text after swapping (when decoding) or before swapping (when
encoding); P: plain text; IV: Initialization vectors.

RM0385 Rev 7

583/1709
622

Cryptographic processor (CRYP)

RM0385
Figure 138. AES-CTR mode decryption
IN FIFO
ciphertext P
C, 128 bits
AHB2 data write
(before CRYP
is enabled)

DATATYPE

swapping
IV0...1(L/R)
Cs, 128 bits

+1

I, 128 bits
128, 192
or 256

K0...3

AEA, encrypt

(I + 1) is written
back into IV
at same time
than P is pushed
in OUT FIFO

O, 128 bits

+
Ps, 128 bits

DATATYPE

swapping
P, 128 bits

OUT FIFO
plaintext C
MS19025V1

1. K: key; C: cipher text; I: input Block; o: output block; Ps: plain text before swapping (when decoding) or
after swapping (when encoding); Cs: cipher text after swapping (when decoding) or before swapping (when
encoding); P: plain text; IV: Initialization vectors.

In CTR mode, the output block is XORed with the subsequent input block before it is input to
the algorithm. Initialization vectors in the peripheral must be initialized as shown on
Table 124.
Table 124. Counter mode initialization vector
CRYP_IV1R[31:0]

CRYP_IV1L[31:0]

CRYP_IV0R[31:0]

CRYP_IV0L[31:0]

nonce

IV[63:32]

IV[31:0]

32-bit counter= 0x1

Unlike in CBC mode, which uses the CRYP_IVx registers only once when processing the
first data block, in CTR mode IV registers are used for processing each data block, and the
peripheral increments the least significant 32 bits (leaving the other most significant 96 bits
unchanged).
CTR decryption does not differ from CTR encryption, since the core always encrypts the
current counter block to produce the key stream that will be XORed with the plaintext or
cipher as input. Thus when ALGOMODE is set to 0b110, ALGODIR is don’t care.
Note:

584/1709

In this mode the key must NOT be prepared for decryption.

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
The following sequence must be used to perform an encryption or a decryption in CTR
chaining mode:
1.

Make sure the cryptographic processor is disabled by clearing the CRYPEN bit in the
CRYP_CR register.

2.

Configure CRYP_CR as follows:
a)

Program ALGOMODE bits to 0b110 to select CTR mode.

b)

Configure the data type (1, 8, 16 or 32 bits) through the DATATYPE bits.

3.

Initialize the key registers (128,192 and 256 bits) in CRYP_KEYRx as well as the
initialization vector (IV) as described in Table 124.

4.

Flush the IN and OUT FIFOs by writing the FFLUSH bit to 1 in the CRYP_CR register.

5.

If it is the last block, optionally pad the data with zeros to have a complete block.

6.

Append data in the cryptographic processor and read the result. The three possible
scenarios are described in Section 20.3.5: CRYP procedure to perform a cipher
operation.

7.

Repeat the previous step until the second last block is processed. For the last block,
execute the two previous steps. For this last block, the driver must discard the data that
is not part of the data when the last block size is less than 16 bytes.

Suspend/resume operations in CTR mode
Like for the CBC mode, it is possible to interrupt a message to send a higher priority
message, and resume the message which was interrupted. Detailed CBC sequence can be
found in Section 20.3.11: CRYP AES basic chaining modes (ECB, CBC).
Note:

Like for CBC mode, IV registers must be reloaded during the resume operation.

RM0385 Rev 7

585/1709
622

Cryptographic processor (CRYP)

20.3.13

RM0385

CRYP AES Galois/counter mode (GCM)
Overview
The AES Galois/counter mode (GCM) allows encrypting and authenticating the plaintext,
and generating the correspondent ciphertext and tag (also known as message
authentication code). To ensure confidentiality, GCM algorithm is based on AES counter
mode. It uses a multiplier over a fixed finite field to generate the tag.
GCM chaining is defined in NIST Special Publication 800-38D, Recommendation for Block
Cipher Modes of Operation - Galois/Counter Mode (GCM) and GMAC. A typical message
construction in GCM mode is given in Figure 139.
Figure 139. Message construction for the Galois/counter mode
[Len(A)]64

Len(A)
16-Bytes boundaries
Additional Authenticated Data
(AAD)

Len(P) = Len(C)
Padding
‘0’

Paddi
ng ‘0’

Plaintext (P)

Last
Block

Counter
(0x1)

authentication

Initialization vector (IV)

Zeroe
d bits

Authenticated & Encrypted Ciphertext (C)
authentication

4-Bytes boundaries

authentication

encry
pt

ICB

[Len(C)]64

AuthTag
(T)
MSv43717V1

The structure of this message is defined as below:
•

Note:

586/1709

A 16-byte Initial Counter Block (ICB), composed of two distinct fields:
–

The initialization vector (IV): a 96-bit value that must be unique for each execution
of the mode under a given key. Note that the GCM standard supports IV that are
shorter than 96-bit, but in this case strict rules apply.

–

The counter: a 32-bit big-endian integer that is incremented each time a block has
been processed. According to NIST specification, the counter value is 0x2 when
processing the first block of payload.

•

The authenticated header A (also knows as Additional Authentication Data) has a
known length Len(A) that can be non-multiple of 16 bytes and cannot exceed 264-1
bits. This part of the message is only authenticated, not encrypted.

•

The plaintext message (P) is both authenticated and encrypted as ciphertext C, with a
known length Len(P) that can be non-multiple of 16 bytes, and cannot exceed 232 -2
blocks of 128-bits.

GCM standard specifies that ciphertext C has same bit length as the plaintext P.
•

When a part of the message (AAD or P) has a length which is non-multiple of 16 bytes,
a special padding scheme is required.

•

The last block is composed of the length of A (on 64 bits) and the length of ciphertext C
(on 64 bits) as shown inTable 125.

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
Table 125. GCM last block definition
Endianness
Input data

Bit[0]

Bit[32]
0x0

Bit[64]

Header length[31:0]

Bit[96]
0x0

Payload length[31:0]

AES GCM processing
This mode is selected by writing ALGOMODE bitfield to 0b110 in CRYP_CR.
The mechanism for the confidentiality of the plaintext in GCM mode is a variation of the
Counter mode, with a particular 32-bit incrementing function that generates the necessary
sequence of counter blocks.
CRYP_IV registers are used for processing each data block. The cryptographic processor
automatically increments the 32 least signification bits of the counter block. The first counter
block (CB1) written by the application is equal to the Initial Counter Block incremented by
one (see Table 126).
Table 126. GCM mode IV registers initialization

Note:

Register

CRYP_IV1R[31:0]

CRYP_IV1L[31:0]

CRYP_IV0R[31:0]

CRYP_IV0L[31:0]

Input data

ICB[127:96]

ICB[95:64]

ICB[63:32]

ICB[31:0]
32-bit counter= 0x2

In this mode the key must NOT be prepared for decryption.
The authentication mechanism in GCM mode is based on a hash function, called GF2mul,
that performs multiplication by a fixed parameter, called the hash subkey (H), within a binary
Galois field.
To process a GCM message, the driver must go through four phases, which are described
in the following subsections.
•

The Init phase: the peripheral prepares the GCM hash subkey (H) and performs the IV
processing

•

The Header phase: the peripheral processes the Additional Authenticated Data (AAD),
with hash computation only.

•

The Payload phase: the peripheral processes the plaintext (P) with hash computation,
keystream encryption and data XORing. It operates in a similar way for ciphertext (C).

•

The Final phase: the peripheral generates the authenticated tag (T) using the data last
block.

RM0385 Rev 7

587/1709
622

Cryptographic processor (CRYP)
1.

RM0385

GCM init phase
During this first step, the GCM hash subkey (H) is calculated and saved internally to be
used for processing all the blocks. It is recommended to follow the sequence below:

2.

a)

Make sure the cryptographic processor is disabled by clearing the CRYPEN bit in
the CRYP_CR register.

b)

Select the GCM chaining mode by programming ALGOMODE bits to 0b01000 in
CRYP_CR.

c)

Configure GCM_CCMPH bits to 0b00 in CRYP_CR to indicate that the init phase
is ongoing.

d)

Initialize the key registers (128, 192 and 256 bits) in CRYP_KEYRx as well as the
initialization vector (IV) as defined in Table 126.

e)

Set CRYPEN bit to 1 to start the calculation of the hash key.

f)

Wait for the CRYPEN bit to be cleared to 0 by the cryptographic processor, before
moving on to the next phase.

GCM header phase
The below sequence shall be performed after the GCM init phase. It must be complete
before jumping to the payload phase. The sequence is identical for encryption and
decryption.

Note:

g)

Set the GCM_CCMPH bits to 0b01 in CRYP_CR to indicate that the header phase
is ongoing.

h)

Set the CRYPEN bit to 1 to start accepting data.

i)

If it is the last block of additional authenticated data, optionally pad the data with
zeros to have a complete block.

j)

Append additional authenticated data in the cryptographic processor. The three
possible scenarios are described in Section 20.3.5: CRYP procedure to perform a
cipher operation.

k)

Repeat the previous step until the second last additional authenticated data block
is processed. For the last block, execute the two previous steps. Once all the
additional authenticated data have been supplied, wait until the BUSY flag is
cleared before moving on to the next phase.

This phase can be skipped if there is no additional authenticated data, i.e. Len(A)=0.
In header and payload phases, CRYPEN bit is not automatically cleared by the
cryptographic processor.

588/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
3.

GCM payload phase (encryption or decryption)
When the payload size is not null, this sequence must be executed after the GCM
header phase. During this phase, the encrypted/decrypted payload is stored in the
CRYP_DOUT register.
l)

Set the CRYPEN bit to 0.

m) Configure GCM_CCMPH to 0b10 in the CRYP_CR register to indicate that the
payload phase is ongoing.

Note:

n)

Select the algorithm direction (0 for encryption, 1 for decryption) through the
ALGODIR bit in CRYP_CR.

o)

Set the CRYPEN bit to 1 to start accepting data.

p)

If it is the last block of cleartext or plaintext, optionally pad the data with zeros to
have a complete block. For encryption, refer to Section 20.3.8: CRYP stealing and
data padding for more details.

q)

Append payload data in the cryptographic processor, and read the result. The
three possible scenarios are described in Section 20.3.5: CRYP procedure to
perform a cipher operation.

r)

Repeat the previous step until the second last plaintext block is encrypted or until
the last block of ciphertext is decrypted. For the last block of plaintext (encryption
only), execute the two previous steps. For the last block, the driver must discard
the bits that are not part of the cleartext or the ciphertext when the last block size
is less than 16 bytes. Once all payload data have been supplied, wait until the
BUSY flag is cleared.

This phase can be skipped if there is no payload data, i.e. Len(C)=0 (see GMAC mode).
4.

GCM final phase
In this last step, the cryptographic processor generates the GCM authentication tag
and stores it in CRYP_DOUT register.

Note:

s)

Configure GCM_CCMPH[1:0] to 0b11 in CRYP_CR to indicate that the Final
phase is ongoing. Set the ALGODIR bit to 0 in the same register.

t)

Write the input to the CRYP_DIN register four times. The input must be composed
of the length in bits of the additional authenticated data (coded on 64 bits)
concatenated with the length in bits of the payload (coded of 64 bits), as show in
Table 125.

In this final phase data have to be swapped according to the DATATYPE programmed in
CRYP_CR register.
u)

Wait until the OFNE flag (FIFO output not empty) is set to 1 in the CRYP_SR
register.

v)

Read the CRYP_DOUT register 4four times: the output corresponds to the
authentication tag.

w)

Disable the cryptographic processor (CRYPEN bit = 0 in CRYP_CR)

x)

If an authenticated decryption is being performed, compare the generated tag with
the expected tag passed with the message.

Suspend/resume operations in GCM mode
Before interrupting the current message in header or payload phase, the user application
must respect the following sequence:

RM0385 Rev 7

589/1709
622

Cryptographic processor (CRYP)

Note:

RM0385

1.

If DMA is used, stop DMA transfers to the IN FIFO by clearing to 0 the DIEN bit in the
CRYP_DMACR register.

2.

Wait until both the IN and the OUT FIFOs are empty (IFEM=1 and OFNE=0 in the
CRYP_SR register) and the BUSY bit is cleared.

3.

If DMA is used, stop DMA transfers from the OUT FIFO by clearing to 0 the DOEN bit
in the CRYP_DMACR register.

4.

Disable the cryptographic processor by setting the CRYPEN bit to 0 in CRYP_CR, then
save the current configuration (bits [9:2], bits [17:16] and bits 19 of the CRYP_CR
register). In addition, save the initialization vector registers, since CRYP_IVx registers
have changed from their initial values during data processing.

Key registers do not need to be saved as original their key value is known by the
application.
5.

Save context swap registers: CRYP_CSGCMCCM0..7 and CRYP_CSGCM0..7

6.

If DMA is used, save the DMA controller status (pointers to IN and OUT data transfers,
number of remaining bytes, etc.).

To resume message processing, the user must respect the following sequence:

Note:

590/1709

1.

If DMA is used, reconfigure the DMA controller to complete the rest of the FIFO IN and
FIFO OUT transfers.

2.

Make sure the cryptographic processor is disabled by reading the CRYPEN bit in
CRYP_CR (it must be 0).

3.

Configure again the cryptographic processor with the initial setting in CRYP_CR, as
well as the key registers using the saved configuration.

4.

Restore context swap registers: CRYP_CSGCMCCM0..7 and CRYP_CSGCM0..7

5.

Restore CRYP_IVx registers using the saved configuration.

6.

Enable the cryptographic processor by setting the CRYPEN bit to 1.

7.

If DMA is used, enable again cryptographic processor DMA requests by setting to 1 the
DIEN and DOEN bits in the CRYP_DMACR register.

In Header phase, DMA OUT FIFO transfer is not used.

RM0385 Rev 7

RM0385

CRYP AES Galois message authentication code (GMAC)
Overview
The Galois message authentication code (GMAC) allows authenticating a plaintext and
generating the corresponding tag information (also known as message authentication
code). It is based on GCM algorithm, as defined in NIST Special Publication 800-38D,
Recommendation for Block Cipher Modes of Operation - Galois/Counter Mode (GCM) and
GMAC.
A typical message construction in GMAC mode is given in Figure 140.
Figure 140. Message construction for the Galois Message Authentication Code mode
[Len(A)]64

064

16-Bytes boundaries
Len(A)

ICB

Authenticated Data

Padding
‘0’

Last
Block

authentication

20.3.14

Cryptographic processor (CRYP)

4-Bytes boundaries

AuthTag
(T)
Initialization vector (IV)

Counter
(0x1)
MSv43718V1

AES GMAC processing
This mode is selected by writing ALGOMODE bitfield to 0b110 in CRYP_CR.
GMAC algorithm corresponds to the GCM algorithm applied on a message composed only
of an header. As a consequence, all steps and settings are the same as in GCM mode,
except that the payload phase (3) is not used.

Suspend/resume operations in GMAC
GMAC is exactly the same as GCM algorithm except that only header phase (2) can be
interrupted.

RM0385 Rev 7

591/1709
622

Cryptographic processor (CRYP)

20.3.15

RM0385

CRYP AES Counter with CBC-MAC (CCM)
Overview
The AES Counter with Cipher Block Chaining-Message Authentication Code (CCM)
algorithm allows encrypting and authenticating the plaintext, and generating the
correspondent ciphertext and tag (also known as message authentication code). To ensure
confidentiality, CCM algorithm is based on AES counter mode. It uses Cipher Block
Chaining technique to generate the message authentication code. This is commonly called
CBC-MAC

Note:

NIST does not approve this CBC-MAC as an authentication mode outside of the context of
the CCM specification.
CCM chaining is specified in NIST Special Publication 800-38C, Recommendation for Block
Cipher Modes of Operation - The CCM Mode for Authentication and Confidentiality. A typical
message construction in CCM mode is given in Figure 141
Figure 141. Message construction for the Counter with CBC-MAC mode
Alen
16-Bytes boundaries
[a]32
[a]16

Associated Data
(A)

Padding
“0”

Tlen

Plaintext (P)

Paddin
g “0”

Enc
(T)

flags

Authenticated & Encrypted Ciphertext (C)
Nonce (N)

Q

decryp &
compare

4-Bytes boundaries

authentication

Encrypt.

B0

Clen
Plen

MAC
(T)

Nlen

MSv43719V1

The structure of this message is as below:
•

Note:

592/1709

One 16-byte first authentication block (called B0 by the standard), composed of three
distinct fields:
–

Q: a bit string representation of the byte length of P (Plen)

–

A nonce (N): single-use value (i.e. a new nonce should be assigned to each new
communication). Size of nonce Nlen + size of Plen shall be equal to 15 bytes.

–

Flags: most significant byte containing four flags for control information, as
specified by the standard. It contains two 3-bit strings to encode the values t (MAC
length expressed in bytes) and q (plaintext length such as Plen<28q bytes). Note
that the counter blocks range associated to q is equal to 28q-4, i.e. if q maximum
value is 8, the counter blocks used in cipher shall be on 60 bits.

The cryptographic peripheral can only manage padded plaintext/ciphertext messages of
length Plen < 236 +1 bytes.

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
•

16-bytes blocks (B) associated to the Associated Data (A).
This part of the message is only authenticated, not encrypted. This section has a
known length, ALen, that can be a non-multiple of 16 bytes (see Figure 141). The
standard also states that, on the MSB bits of the first message block (B1), the
associated data length expressed in bytes (a) must be encoded as defined below:
–
–
–

Note:

If 0 < a < 216-28, then it is encoded as [a]16, i.e. two bytes.

If 216-28 < a < 232, then it is encoded as 0xff || 0xfe || [a]32, i.e. six bytes.

If 232 < a < 264, then it is encoded as 0xff || 0xff || [a]64, i.e. ten bytes.

•

16-byte blocks (B) associated to the plaintext message (P), which is both authenticated
and encrypted as ciphertext C, with a known length of Plen. This length can be a nonmultiple of 16 bytes (see Figure 141) but cannot exceed 232 blocks of 128-bit.

•

The encrypted MAC (T) of length Tlen appended to the ciphertext C of overall length
Clen.

•

When a part of the message (A or P) has a length which is a non-multiple of 16 bytes, a
special padding scheme is required.

CCM chaining mode can also be used with associated data only (i.e. no payload).
As an example, the C.1 section in NIST Special Publication 800-38C gives the following:
N: 10111213 141516 (Nlen= 56 bits or 0x7 bytes)
A: 00010203 04050607 (Alen= 64 bits or 0x8 bytes)
P: 20212223 (Plen= 32 bits i.e. Q= 0x4 bytes)
T: 6084341b (Tlen= 32 bits or t= 4)
B0: 4f101112 13141516 00000000 00000004
B1: 00080001 02030405 06070000 00000000
B2: 20212223 00000000 00000000 00000000
CTR0: 0710111213 141516 00000000 00000000
CTR1: 0710111213 141516 00000000 00000001
The usage of control blocks CTRx is explained in the following section. The generation of
CTR0 from the first block (B0) must be managed by software.

RM0385 Rev 7

593/1709
622

Cryptographic processor (CRYP)

RM0385

AES CCM processing
This mode is selected by writing ALGOMODE bitfield to 0b1001 in CRYP_CR.
The data input to the generation-encryption process are a valid nonce, a valid payload
string, and a valid associated data string, all properly formatted. The CBC chaining
mechanism is applied to the formatted data to generate a MAC, whose length is known.
Counter mode encryption, which requires a sufficiently long sequence of counter blocks as
input, is applied to the payload string and separately to the MAC. The resulting data, called
the ciphertext C, is the output of the generation-encryption process on plaintext P.
CRYP_IV registers are used for processing each data block. The cryptographic processor
automatically increments the CTR counter with a bit length defined by the first block (B0).
The first counter written by application, CTR1, is equal to B0 with the first 5 bits zeroed and
the most significant bits containing P byte length also zeroed, then incremented by one (see
Table 127).
Table 127. CCM mode IV registers initialization
Register

CRYP_IV0L[31:0]

CRYP_IV0R[31:0]

CRYP_IV1L[31:0]

CRYP_IV1R[31:0]

Endianness

IV[0:31]

IV[32:63]

IV[64:95]

IV[96:127]

Input data

B0[31:0], where the 5
most significant bits
are set to 0 (flag bits)

B0[63:32]

B0[95:64]

B0[127:96], where Q length
bits are set to 0, except for
bit 0 that is set to 1

Note:

In this mode, the key must NOT be prepared for decryption.
To process a CCM message, the driver must go through four phases, which are described
below.

594/1709

•

The Init phase: the peripheral processes the first block and prepares the first counter
block.

•

The Header phase: the peripheral processes the Associated data (A), with hash
computation only.

•

The Payload phase: the peripheral processes the plaintext (P), with hash computation,
counter block encryption and data XORing. It operates in a similar way for ciphertext
(C).

•

The Final phase: the peripheral generates the message authentication code (MAC).

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
1.

CCM init phase
In this first step, the first block (B0) of the CCM message is programmed into the
CRYP_DIN register. During this phase, the CRYP_DOUT register does not contain any
output data. It is recommended to follow the sequence below:

Note:

a)

Make sure that the cryptographic processor is disabled by clearing the CRYPEN
bit in the CRYP_CR register.

b)

Select the CCM chaining mode by programming the ALGOMODE bits to 0b01001
in the CRYP_CR register.

c)

Configure the GCM_CCMPH bits to 0b00 in CRYP_CR to indicate that we are in
the init phase.

d)

Initialize the key registers (128, 192 and 256 bits) in CRYP_KEYRx as well as the
initialization vector (IV) with CTR1 information, as defined in Table 127.

e)

Set the CRYPEN bit to 1 in CRYP_CR to start accepting data.

f)

Write the B0 packet into CRYP_DIN register, then wait for the CRYPEN bit to be
cleared to 0 by the cryptographic processor before moving on to the next phase.

In this init phase data have to be swapped according to the DATATYPE programmed in
CRYP_CR register.
2.

CCM header phase
The below sequence shall be performed after the CCM Init phase. It must be complete
before jumping to the payload phase. The sequence is identical for encryption and
decryption. During this phase, the CRYP_DOUT register does not contain any output
data.
g)

Set the GCM_CCMPH bit to 0b01 in CRYP_CR to indicate that the header phase
is ongoing.

h)

Set the CRYPEN bit to 1 to start accepting data.

i)

If it is the last block of associated data, optionally pad the data with zeros to have
a complete block.

j)

Append the associated data in the cryptographic processor. The three possible
scenarios are described in Section 20.3.5: CRYP procedure to perform a cipher
operation.

k)

Repeat the previous step until the second last associated data block is processed.
For the last block, execute the two previous steps. Once all the additional
authenticated data have been supplied, wait until the BUSY flag is cleared.

Note:

This phase can be skipped if there is no associated data (Alen=0).

Note:

The first block of the associated data B1 must be formatted with the associated data length.
This task must be managed by the driver.

RM0385 Rev 7

595/1709
622

Cryptographic processor (CRYP)
3.

RM0385

CCM payload phase (encryption or decryption)
When the payload size is not null, this sequence must be performed after the CCM
header phase. During this phase, the encrypted/decrypted payload is stored in the
CRYP_DOUT register.
l)

Set the CRYPEN bit to 0.

m) Configure GCM_CCMPH bits to 0b10 in CRYP_CR to indicate that the payload
phase is ongoing.
n)

Select the algorithm direction (0 for encryption, 1 for decryption) through the
ALGODIR bit in CRYP_CR.

o)

Set the CRYPEN bit to 1 to start accepting data.

p)

If it is the last block of cleartext, optionally pad the data with zeros to have a
complete block (encryption only). For decryption, refer to Section 20.3.8: CRYP
stealing and data padding for more details.

q)

Append payload data in the cryptographic processor, and read the result. The
three possible scenarios are described in Section 20.3.5: CRYP procedure to
perform a cipher operation.

r)

Repeat the previous step until the second last plaintext block is encrypted or until
the last block of ciphertext is decrypted. For the last block of plaintext (encryption
only), execute the two previous steps. For the last block of ciphertext (decryption
only), the driver must discard the data that is not part of the cleartext when the last
block size is less than 16 bytes. Once all payload data have been supplied, wait
until the BUSY flag is cleared

Note:

This phase can be skipped if there is no payload data, i.e. Plen=0 or Clen=Tlen

Note:

Do not forget to remove LSBTlen(C) encrypted tag information when decrypting ciphertext C.
4.

CCM final phase
In this last step, the cryptographic processor generates the CCM authentication tag and
stores it in the CRYP_DOUT register.

Note:

596/1709

s)

Configure GCM_CCMPH[1:0] bits to 0b11 in CRYP_CR to indicate that the final
phase is ongoing and set the ALGODIR bit to 0 in the same register.

t)

Load in CRYP_DIN, the CTR0 information which is described in Table 127 with
bit[0] set to 0.

In this final phase, data have to be swapped according to the DATATYPE programmed in
CRYP_CR register.
u)

Wait until the OFNE flag (FIFO output not empty) is set to 1 in the CRYP_SR
register.

v)

Read the CRYP_DOUT register four times: the output corresponds to the
encrypted CCM tag.

w)

Disable the cryptographic processor (CRYPEN bit set to 0 in CRYP_CR)

x)

If an authenticated decryption is being performed, compare the generated
encrypted tag with the encrypted tag padded in the ciphertext, i.e. LSBTlen(C)=
MSBTlen(CRYP_DOUT data).

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

Suspend/resume operations in CCM mode
Before interrupting the current message in payload phase, the user application must respect
the following sequence:

Note:

1.

If DMA is used, stop the DMA transfers to the IN FIFO by clearing to 0 the DIEN bit in
the CRYP_DMACR register.

2.

Wait until both the IN and the OUT FIFOs are empty (IFEM=1 and OFNE=0 in the
CRYP_SR register) and the BUSY bit is cleared.

3.

If DMA is used, stop the DMA transfers from the OUT FIFO by clearing to 0 the DOEN
bit in the CRYP_DMACR register.

4.

Disable the cryptographic processor by setting the CRYPEN bit to 0 in CRYP_CR, then
save the current configuration (bits [9:2], bits [17:16] and bits 19 in the CRYP_CR
register). In addition, save the initialization vector registers, since CRYP_IVx registers
have changed from their initial values during the data processing.

Key registers do not need to be saved as their original key value is known by the
application.
5.

Save context swap registers: CRYP_CSGCMCCM0..7

6.

If DMA is used, save the DMA controller status (pointers for IN and OUT data transfers,
number of remaining bytes, etc.).

To resume message processing, the user application must respect the following sequence:

Note:

1.

If DMA is used, reconfigure the DMA controller to complete the rest of the FIFO IN and
FIFO OUT transfers.

2.

Make sure the cryptographic processor is disabled by reading the CRYPEN bit in
CRYP_CR (must be 0).

3.

Configure the cryptographic processor again with the initial setting in CRYP_CR and
key registers using the saved configuration.

4.

Restore context swap registers: CRYP_CSGCMCCM0..7

5.

Restore CRYP_IVx registers using the saved configuration.

6.

Enable the cryptographic processor by setting the CRYPEN bit to 1.

7.

If DMA is used, enable again cryptographic processor DMA requests by setting to 1 the
DIEN and DOEN bits in the CRYP_DMACR register.

In Header phase DMA OUT FIFO transfer is not used.

RM0385 Rev 7

597/1709
622

Cryptographic processor (CRYP)

20.3.16

RM0385

CRYP data registers and data swapping
Introduction
The CRYP_DIN register is the 32-bit wide data input register of the peripheral. It is used to
enter into the input FIFO up to four 64-bit blocks (TDES) or two 128-bit blocks (AES) of
plaintext (when encrypting) or ciphertext (when decrypting), one 32-bit word at a time.
The first word written into the FIFO is the LSB of the input block. The MSB of the input block
is written at the end. CRYP_DIN data endianness can be described as below when
DATATYPE=”00” (no data swapping):
•

In the DES/TDES modes
Bit 1 (leftmost bit) of the data block corresponds to the MSB (bit 31) of the first word
entered into the FIFO, bit 64 (rightmost bit) corresponds to the LSB (bit 0) of the
second word entered into the FIFO.

•

In the AES mode
Bit 0 (leftmost bit) of the data block corresponds to the MSB (bit 31) of the first word
written into the FIFO, bit 127 (rightmost bit) corresponds to the LSB (bit 0) of the 4th
word written into the FIFO.

Similarly CRYP_DOUT register is the 32-bit wide data out register of the peripheral. It is a
read-only register that is used to retrieve from the output FIFO up to four 64-bit blocks
(TDES) or two 128-bit blocks (AES) of plaintext (when encrypting) or ciphertext (when
decrypting), one 32-bit word at a time.
Like for the input data, the LSB of the output block is the first word read from the output
FIFO. The MSB of the output block is read at the end. CRYP_DOUT data endianness can
be described as below when DATATYPE=”00” (no data swapping):
•

In the DES/TDES modes
Bit 1 (leftmost bit) of the data block corresponds to the MSB (bit 31) of the first word
read from the FIFO, bit 64 (rightmost bit) corresponds to the LSB (bit 0) of the second
word read from the FIFO.

•

In the AES mode
Bit 0 (leftmost bit) of the data block corresponds to the MSB (bit 31) of the first word
read from the FIFO, bit 127 (rightmost bit) corresponds to the LSB (bit 0) of the 4th
word read from the FIFO.

598/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

DES/TDES data swapping feature
Depending on the type of data to be processed (e.g. byte swapping when data are ASCII
text stream), a bit, byte, half-word or no swapping operation must be done on the data read
from the input FIFO before entering the little-endian DES processing core. The same
swapping must be performed on the data produced by the little-endian DES processing core
before they are written to the output FIFO.
Figure 142 shows how the DES processing core 64-bit data block M1...64 is constructed
from two consecutive 32-bit words popped into IN FIFO by the driver. This is done according
to the DATATYPE bitfield in the CRYP_CR register.
Note:

The same swapping is performed between the IN FIFO and the CRYP data block, and
between the CRYP data block and the OUT FIFO.
Figure 142. 64-bit block construction according to the data type (IN FIFO)

DATATYPE = 0b00: no swapping
LSB

written first!
Word0

bit31

DATATYPE = 0b01: 16-bit or half-word swapping

System interface
bit0

bit31

written first!
Word0
bit31
bit16 bit15

bit0

M33
M32
DES core interface

M1
LSB

LSB

MSB
Word1

M64
MSB

M1
LSB

bit31..24 bit23..16 bit15..8

M1..8
LSB

System interface

MSB

bit31..24 bit23..16 bit15..8

LSB

bit31

M32
M33
DES core interface

M48

System interface

written first!

Word1

Word2
bit7..0

M17

bit0

MSB
Word1
bit16 bit15

M49

bit0

M64
MSB

DATATYPE = 0b11: bit swapping

DATATYPE = 0b10: 8-bit or byte swapping
LSB written first!
Word1

M16

System interface

bit7..0

M9..16 M17..24 M25..32 M33..40 M41..48 M49..56 M57..64
DES core interface
MSB

MSB

Word2

bit31bit30 bit29

bit2 bit1 bit0 bit31 bit30 bit29

bit2 bit1 bit0

M1 M2 M3
LSB

M30 M31 M32 M33 M34 M35
DES core interface

M62 M63 M64
MSB

MSv43720V1

Note:

The CRYP Key registers (CRYP_Kx(L/R)) and initialization registers (CRYP_IVx(L/R)) are
not sensitive to the swap mode selected. They have a fixed little-endian configuration (refer
to Section 20.3.17 and Section 20.3.18, respectively).
A typical example of data swapping is given in Table 128.

RM0385 Rev 7

599/1709
622

Cryptographic processor (CRYP)

RM0385

Table 128. DES/TDES data swapping feature
DATATYPE in
CRYP_CR

Data block representation (64-bit)
0xABCD7720 6973FE01
Swapping performed
System memory data
(plaintext or cypher)
Address @: 0xABCD7720 (LSB, written first)
Address @+4: 0x6973FE01

0b00

No swapping

TDES block size = 64bit = 2x 32 bit

0xABCD7720 6973FE01

system memory

0xABCD7720
0x6973FE01

@
@+4

Address @: 0x7720ABCD (swapped LSB, written first)
Address @+4: 0xFE016973
0b01

Half-word (16-bit)
swapping

system memory
TDES block size = 64bit = 2x 32 bit

0xABCD 7720 6973 FE01

0x7720 ABCD
0xFE01 6973

@
@+4

Address @: 0x2077CDAB (swapped LSB, written first)
Address @+4: 0x01FE7369
0b10

Byte (8-bit) swapping

system memory
TDES block size = 64bit = 2x 32 bit

0xAB CD 77 20 69 73 FE 01

0b11

Bit swapping

0x 20 77 CD AB
0x 01 FE 73 69

LSB data word: 0xABCD7720
0b1010 1011 1100 1101 0111 0111 0010 0000
MSB data word: 0x6973FE01
0b0110 1001 0111 0011 1111 1110 0000 0001
Address @: 0x04EEB3D5 (swapped LSB, written first)
Address @+4: 0x807FCE96

600/1709

RM0385 Rev 7

@
@+4

RM0385

Cryptographic processor (CRYP)

AES data swapping feature
Depending on the type of data to be processed (e.g. byte swapping when data are ASCII
text stream), a bit, byte, half-word or no swapping operation must be done on data read from
the input FIFO before entering the little-endian AES processing core. The same swapping
must be performed on the data produced by the little-endian AES processing core before
they are written to the output FIFO.
Figure 143 shows how the AES processing core 128-bit data block P0..127 is constructed
from four consecutive 32-bit words written by the driver to the CRYP_DIN register. This is
done according to the DATATYPE bitfield in the CRYP control register (CRYP_CR).
Note:

The same swapping is performed between the CRYP_DIN and the CRYP data block, and
between the CRYP data block and the CRYP_DOUT.
Figure 143. 128-bit block construction according to the data type

DATATYPE “00”: no swapping
LSB

System interface

written first!
Word0

bit31

bit0

bit31

P0

P31

P32

MSB
Word2

Word1
bit0

bit31

P64
P63
AES core interface

LSB

Word3
bit0

bit31

P95

P96

bit0

P12
7
MSB

DATATYPE “01”: 16-bit or half-word swapping

bit31

P
0
LSB

System interface

written first!

LSB

Word0
bit16 bit15

P1
5

P1
6

bit31

bit0

P3
1

Word1
bit16 bit15

P3
2

P4
7

P4
8

bit0

bit31

MSB
Word2
bit16 bit15

bit0

P6
3
AES core interface

bit31

P96

Word3
bit16 bit15

P11
1

P11
2

bit0

P12
7
MSB

DATATYPE “10”: 8-bit or byte swapping
System interface

written first!

LSB
Word0

bit31..24 bit23..16 bit15..8

P0..7
LSB

P8..15

P16..2
3

bit7..0

bit31..24 bit23..16 bit15..8

P24..3
1

MSB
Word2

Word1
bit7..0

bit31..24 bit23..16 bit15..8

AES core interface

Word3
bit7..0

bit31..24 bit23..16 bit15..8

P96..1
03

P112..1
19

bit7..0

P120..1
27
MSB

DATATYPE “11”: bit swapping

P0 P1
LSB

System interface

written first!

LSB
Word0
bit3 bit3 bit2
9
0
1

P2

bit2 bit1 bit0

P29 P30 P31

Word1
bit3 bit3 bit2
9
0
1

P32 P33 P34

Word2
bit2 bit1 bit0

P61 P62 P63
AES core interface

MSB
Word3
bit3 bit3 bit2
9
0
1

P96 P97 P98

bit2 bit1 bit0

P125 P126 P127
MSB
MSv43721V1

RM0385 Rev 7

601/1709
622

Cryptographic processor (CRYP)
Note:

RM0385

The swapping operation concerns only the CRYP_DOUT and CRYP_DIN registers. The
CRYP_KxL/KxR and CRYP_IVxL/IVxR registers are not sensitive to the swap mode
selected.They have a fixed little-endian configuration (refer to Section 20.3.17 and
Section 20.3.18).
Typical examples of data swapping are given in Table 129.
Table 129. AES data swapping feature

DATATYPE
in CRYP_CR

Data block representation (64-bit)
0x4E6F7720 69732074

Swapping performed

System memory data (little-endian)
Address @: 0x4E6F7720 (LSB, written first)
Address @+4: 0x69732074

0b00

No swapping

0b01

Half-word (16-bit) swapping

Address @: 0x77204E6F (swapped LSB, written first)
Address @+4: 0x20746973

0b10

Byte (8-bit) swapping

Address @: 0x20776F4E (swapped LSB, written first)
Address @+4: 0x74207369

0b11

Bit swapping

LSB data word: 0x4E6F7720
0b0100 1110 0110 1111 0111 0111 0010 0000
MSB data word: 0x69732074
0b0110 1001 0111 0011 0010 0000 0111 0100
Address @: 0x4EEF672 (swapped LSB, written first)
Address @+4: 0x2E04CE96

20.3.17

CRYP key registers
The CRYP_Kx registers are used to store the encryption or decryption keys.
They are organized as eight registers in a little-endian configuration, as shown in Table 130.
Table 130. Key registers CRYP_KxR/LR endianness (TDES K1/2/3 and
AES 128/192/256-bit keys)

K0LR[31:0]

K0RR[31:0]

K1LR[31:0]

K1RR[31:0]

K2LR[31:0]

K2RR[31:0]

K3LR[31:0]

K3RR[31:0]

-

-

K1[1:32]

K1[33:64]

K2[1:32]

K2[33:64]

K2[1:32]

K2[33:64]

K0LR[31:0]

K0RR[31:0]

K1LR[31:0]

K1RR[31:0]

K2LR[31:0]

K2RR[31:0]

K3LR[31:0]

K3RR[31:0]

-

-

-

-

k[0:31]

k[32:63]

k[64:95]

k[96:127]

K0LR[31:0]

K0RR[31:0]

K1LR[31:0]

K1RR[31:0]

K2LR[31:0]

K2RR[31:0]

K3LR[31:0]

K3RR[31:0]

-

-

k[0:31]

k[32:63]

k[64:95]

k[96:127]

k[128:159]

k[160:191]

K0LR[31:0]

K0RR[31:0]

K1LR[31:0]

K1RR[31:0]

K2LR[31:0]

K2RR[31:0]

K3LR[31:0]

K3RR[31:0]

k[0:31]

k[32:63]

k[64:95]

k[96:127]

k[128:159]

k[160:191]

k[192:223]

k[224:255]

Note:

602/1709

DES/TDES keys include 8-bit parity information that are not used by the cryptographic
processor. In other words, bits 8, 16, 24, 32, 40, 48, 56 and 64 of each 64-bit key value
Kx[1:64] are not used.

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
Keys are considered as four 64-bit data items. They therefore do not have the same data
format and representation in system memory as plaintext or ciphertext data.
Any write operation to the CRYP_Kx(L/R) registers when the BUSY bit is set to 1 in the
CRYP_SR register is disregarded (i.e. register content not modified). Thus, the software
must check that the BUSY equals 0 before modifying key registers.
Key registers are not affected by the data swapping feature controlled by DATATYPE value
in CRYP_CR register.
Refer to Section 20.6: CRYP registers for a detailed description of CRYP_Kx(L/R) registers.

20.3.18

CRYP initialization vector registers
The CRYP_IVxL/IVxR registers are used to store the initialization vector or the nonce,
depending on the chaining mode selected. When used, these registers are updated by the
core after each computation round of the TDES or AES core.
They are organized as four registers in a little-endian configuration, as shown in Table 131.
Table 131. Initialization vector registers CRYP_IVxR endianness
CRYP_IV1R[31:0]

CRYP_IV1L[31:0]

CRYP_IV0R[31:0]

CRYP_IV0L[31:0]

IV[96:127]

IV[64:95]

IV[32:63]

IV[0:31]

Initialization vector registers are considered as two 64-bit data items. They therefore do not
have the same data format and representation in system memory as plaintext or ciphertext
data.
Any write operation to the CRYP_IV0...1(L/R) registers when the BUSY bit is set to 1 in the
CRYP_SR register is disregarded (i.e. register content not modified). Therefore, the
software must check that the BUSY equals 0 in the CRYP_SR register before modifying
initialization vectors.
Reading the CRYP_IV0...1(L/R) register returns the latest counter value (useful for
managing suspend mode) except for CCM/GCM.
Note:

In DES/TDES mode, only CRYP_IV0x are used.
Initialization vector registers are not affected by the data swapping feature controlled by
DATATYPE value in CRYP_CR register.
Refer to Section 20.6: CRYP registers for a detailed description of CRYP_IVxL/IVxR
registers.

RM0385 Rev 7

603/1709
622

Cryptographic processor (CRYP)

20.3.19

RM0385

CRYP DMA interface
The cryptographic processor provides an interface to connect to the DMA (Direct Memory
Access) controller. The DMA operation is controlled through the CRYP DMA control register
(CRYP_DMACR).

Data input using DMA
DMA can be enabled for writing data into the cryptographic peripheral by setting the DIEN
bit in the CRYP_DMACR register. When this bit is set, the cryptographic processor initiates
a DMA request during the INPUT phase each time it requires a word to be written to the
CRYP_DIN register.
Table 132 shows the recommended configuration to transfer data from memory to
cryptographic processor through the DMA controller.
Table 132. Cryptographic processor configuration for
memory-to-peripheral DMA transfers
DMA channel control
register field

Programming recommendation

Transfer size

Message length, multiple of 128-bit. This 128-bit granularity corresponds to
two blocks for DES, one block for AES.
According to the algorithm and the mode selected, special padding/
ciphertext stealing might be required. Refer to Section 20.3.8: CRYP
stealing and data padding for details.

Source burst size
(memory)

CRYP FIFO_size /2 /transfer_width = 4

Destination burst size
(peripheral)

CRYP FIFO_size /2 /transfer_width = 4
(FIFO_size= 8x32-bit, transfer_width= 32-bit)

DMA FIFO size

CRYP FIFO_size /2 = 16 bytes

Source transfer width
(memory)

32-bit words

Destination transfer
width (peripheral)

32-bit words

Source address
increment (memory)

Yes, after each 32-bit transfer.

Destination address
Fixed address of CRYP_DIN shall be used (no increment).
increment (peripheral)

Data output using DMA
To enable the DMA for reading data from AES peripheral, set the DOEN bit in the
CRYP_DMACR register. When this bit is set, the cryptographic processor initiates a DMA
request during the OUTPUT phase each time it requires a word to be read from the
CRYP_DOUT register.
Table 133 shows the recommended configuration to transfer data from cryptographic
processor to memory through the DMA controller.

604/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
Table 133. Cryptographic processor configuration for
peripheral to memory DMA transfers
DMA channel control
register field

Programming recommendation

Transfer size

Message length, multiple of 128-bit. This 128-bit granularity corresponds to
two blocks for DES, one block for AES.
Depending on the algorithm used, extra bits have to be discarded.

Source burst size
(peripheral)

When DES is used:
Single transfer (burst size=1)
When AES is used:
CRYP FIFO_size /2 /transfer_width = 4
(FIFO_size= 8x32-bit, transfer_width= 32-bit)

Destination burst size
(memory)

CRYP FIFO_size /2 /transfer_width = 4

DMA FIFO size

CRYP FIFO_size /2 = 16 bytes

Source transfer width
(peripheral)

32-bit words

memory transfer width
32-bit words
(memory)
Source address
Fixed address of CRYP_DOUT shall be used (no increment).
increment (peripheral)
Destination address
increment (memory)

Yes, after each 32-bit transfer.

DMA mode
When AES is used, the cryptographic processor manages two DMA transfer requests
through cryp_in_dma and cryp_out_dma internal input/output signals, which are
asserted:
•

for IN FIFO: every time a block has been read from FIFO by CRYP,

•

for OUT FIFO: every time a block has been written into the FIFO by the cryptographic
processor.

When DES is used, the cryptographic processor manages two DMA transfer requests
through cryp_in_dma and cryp_out_dma internal input/output signals, which are
asserted:
•

for IN FIFO: every time two blocks have been read from FIFO by the cryptographic
processor

•

for OUT FIFO: every time a word has been written into the FIFO by the cryptographic
processor (single transfer). Note that a burst transfer is also triggered when two blocks
have been written into the FIFO.

All request signals are de-asserted if the cryptographic peripheral is disabled or the DMA
enable bit is cleared (DIEN bit for the IN FIFO and DOEN bit for the OUT FIFO in the
CRYP_DMACR register).
Caution:

It is important that DMA controller empties the cryptographic peripheral output FIFO before
filling up the CRYP input FIFO. To achieve it, the DMA controller should be configured so

RM0385 Rev 7

605/1709
622

Cryptographic processor (CRYP)

RM0385

that the transfer from the peripheral to the memory has a higher priority than the transfer
from the memory to the peripheral.
For more detailed information on DMA operations, refer to Section 20.3.5: CRYP procedure
to perform a cipher operation.

20.3.20

CRYP error management
No error flags are generated by the cryptographic processor.

20.4

CRYP interrupts
Overview
There are two individual maskable interrupt sources generated by the cryptographic
processor to signal the following events:
•

Input FIFO empty or not full

•

Output FIFO full or not empty

These two sources are combined into a single interrupt signal which is the only interrupt
signal from the CRYP peripheral that drives the NVIC (nested vectored interrupt controller).
The interrupt logic is summarized on Figure 144.
Figure 144. CRYP interrupt mapping diagram
CRYP_CR.CRYPEN
INMIS
CRYP_RISR.INRIS
CRYP_IMSCR.INIM
CRYP_RISR.OUTRIS
CRYP_IMSCR.OUTIM

cryp_it
(IP global interrupt
request signal)
OUTMIS
MSv43722V1

You can enable or disable CRYP interrupt sources individually by changing the mask bits in
the CRYP_IMSCR register. Setting the appropriate mask bit to 1 enables the interrupt.
The status of the individual maskable interrupt sources can be read either from the
CRYP_RISR register, for raw interrupt status, or from the CRYP_MISR register for masked
interrupt status. The status of the individual source of event flags can be read from the
CRYP_SR register.
Table 134 gives a summary of the available features.

606/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)
Table 134. CRYP interrupt requests
Interrupt event
Output FIFO full
Output FIFO not empty
Input FIFO not full
Input FIFO empty

Event flag (interrupt status)

Enable control bit

Event flag (source)

OUTRIS, OUTMIS

OUTIM and
CRYPEN

OFFU

OUTRIS, OUTMIS

INIM and
CRYPEN

OFNE
IFNF
IFEM

Output FIFO service interrupt - OUTMIS
The output FIFO service interrupt is asserted when there is one or more (32-bit word) data
items in the output FIFO. This interrupt is cleared by reading data from the output FIFO until
there is no valid (32-bit) word left (that is when the interrupt follows the state of the output
FIFO not empty flag OFNE).
The output FIFO service interrupt OUTMIS is NOT enabled with the CRYP enable bit.
Consequently, disabling the CRYP will not force the OUTMIS signal low if the output FIFO is
not empty.

Input FIFO service interrupt - INMIS
The input FIFO service interrupt is asserted when there are less than four words in the input
FIFO. It is cleared by performing write operations to the input FIFO until it holds four or more
words.
The input FIFO service interrupt INMIS is enabled with the CRYP enable bit. Consequently,
when CRYP is disabled, the INMIS signal is low even if the input FIFO is empty.

RM0385 Rev 7

607/1709
622

Cryptographic processor (CRYP)

20.5

RM0385

CRYP processing time
The time required to process a 128-bit block for each mode of operation is summarized
below.
Table 135. Processing time (in clock cycle) for ECB, CBC and CTR per 128-bit block
Algorithm / Key size

ECB

CBC

CTR

128b

14

14

14

192b

16

16

16

256b

18

18

18

Table 136. Processing time (in clock cycle) for GCM and CCM per 128-bit block
GCM

CCM

Algorithm / Key size
Init

608/1709

Header Payload

Tag

Total

Init

Header

Payload

Tag

Total

128b

24

10

14

14

62

12

14

25

14

65

192b

28

10

16

16

70

14

16

29

16

75

256b

32

10

18

18

78

16

18

33

18

85

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

20.6

CRYP registers
The cryptographic core is associated with several control and status registers, eight key
registers and four initialization vectors registers.

20.6.1

CRYP control register (CRYP_CR)
Address offset: 0x00
Reset value: 0x0000 0000

31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
Res.

25
Res.

24

23

22

Res.

21

20

19
ALGOM
ODE[3]

Res.

18
Res.

rw
15

14

CRYPEN FFLUSH
rw

w

13

12

11

10

Res.

Res.

Res.

Res.

9

8

KEYSIZE[1:0]
rw

rw

7

6

DATATYPE[1:0]
rw

rw

5

4

3

ALGOMODE[2:0]
rw

rw

rw

17

16

GCM_CCMPH[
1:0]
rw

rw

2

1

0

ALGODIR

Res.

Res.

rw

Bits 31:20 Reserved, must be kept at reset value.
Bit 18 Reserved, must be kept at reset value.
Bits 17:16 GCM_CCMPH[1:0]: GCM or CCM Phase selection
This bitfield has no effect if GCM, GMAC or CCM algorithm is not selected in
ALGOMODE field.
00: Init phase
01: Header phase
10: Payload phase
11: Final phase
Bit 15 CRYPEN: CRYP processor Enable
0: Cryptographic processor peripheral is disabled
1: Cryptographic processor peripheral is enabled
This bit is automatically cleared by hardware when the key preparation process
ends (ALGOMODE= 0b111) or after GCM/GMAC or CCM init phase.
Bit 14 FFLUSH: CRYP FIFO Flush
0: No FIFO flush
1: FIFO flush enabled
When CRYPEN = 0, writing this bit to 1 flushes the IN and OUT FIFOs (i.e. read
and write pointers of the FIFOs are reset). Writing this bit to 0 has no effect.
When CRYPEN = 1, writing this bit to 0 or 1 has no effect.
Reading this bit always returns 0.
FFLUSH bit has to be set only when BUSY=0. If not, the FIFO is flushed, but the
block being processed may be pushed into the output FIFO just after the flush
operation, resulting in a non-empty FIFO condition.
Bits 13:10 Reserved, must be kept at reset value.

RM0385 Rev 7

609/1709
622

Cryptographic processor (CRYP)

RM0385

Bits 9:8 KEYSIZE[1:0]: Key Size selection (AES mode only)
This bitfield defines the bit-length of the key used for the AES cryptographic core.
This bitfield is ‘don’t care’ in the DES or TDES modes.
00: 128-bit key length
01: 192-bit key length
10: 256-bit key length
11: Reserved, do not use this value
Writing KEYSIZE bits while BUSY=1 has no effect. These bits can only be
configured when BUSY=0.
Bits 7:6 DATATYPE[1:0]: Data Type selection
This bitfield defines the format of data written in CRYP_DIN or read from
CRYP_DOUT registers. For more details refer to Section 20.3.16: CRYP data
registers and data swapping).
00: 32-bit data. No swapping for each word. First word pushed into the IN FIFO
(or popped off the OUT FIFO) forms bits 1...32 of the data block, the second
word forms bits 33...64 etc.
01: 16-bit data, or half-word. Each word pushed into the IN FIFO (or popped off
the OUT FIFO) is considered as 2 half-words, which are swapped with each
other.
10: 8-bit data, or bytes. Each word pushed into the IN FIFO (or popped off the
OUT FIFO) is considered as 4 bytes, which are swapped with each other.
11: bit data, or bit-string. Each word pushed into the IN FIFO (or popped off the
OUT FIFO) is considered as 32 bits (1st bit of the string at position 0), which are
swapped with each other.
Writing DATATYPE bits while BUSY=1 has no effect. These bits can only be
configured when BUSY=0.
Bits 19, 5:3 ALGOMODE[3:0]: Algorithm mode
Below definition includes the bit 19:
0000: TDES-ECB (triple-DES Electronic Codebook).
0001: TDES-CBC (triple-DES Cipher Block Chaining).
0010: DES-ECB (simple DES Electronic Codebook).
0011: DES-CBC (simple DES Cipher Block Chaining).
0100: AES-ECB (AES Electronic Codebook).
0101: AES-CBC (AES Cipher Block Chaining).
0110: AES-CTR (AES Counter Mode).
0111: AES key preparation for ECB or CBC decryption.
1000: AES-GCM (Galois Counter Mode) and AES-GMAC (Galois Message
Authentication Code mode).
1001: AES-CCM (Counter with CBC-MAC).
Writing ALGOMODE bits while BUSY=1 has no effect. These bits can only be
configured when BUSY=0.
Bit 2 ALGODIR: Algorithm Direction
0: Encrypt
1: Decrypt
Writing ALGODIR bit while BUSY=1 has no effect. It can only be configured
when BUSY=0.
Bits 1:0 Reserved, must be kept at reset value.

610/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

20.6.2

CRYP status register (CRYP_SR)
Address offset: 0x04
Reset value: 0x0000 0003

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BUSY

OFFU

OFNE

IFNF

IFEM

r

r

r

r

r

Bits 31:5 Reserved, must be kept at reset value.
Bit 4 BUSY: Busy bit
0: The CRYP core is not processing any data. The reason is:
–
either that the CRYP core is disabled (CRYPEN=0 in the CRYP_CR
register) and the last processing has completed,
–
or the CRYP core is waiting for enough data in the input FIFO or enough
free space in the output FIFO (that is in each case at least 2 words in
the DES, 4 words in the AES).
1: The CRYP core is currently processing a block of data or a key preparation is
ongoing (AES ECB or CBC decryption only).
Bit 3 OFFU: Output FIFO full flag
0: Output FIFO is not full
1: Output FIFO is full
Bit 2 OFNE: Output FIFO not empty flag
0: Output FIFO is empty
1: Output FIFO is not empty
Bit 1 IFNF: Input FIFO not full flag
0: Input FIFO is full
1: Input FIFO is not full
Bit 0 IFEM: Input FIFO empty flag
0: Input FIFO is not empty
1: Input FIFO is empty

20.6.3

CRYP data input register (CRYP_DIN)
Address offset: 0x08
Reset value: 0x0000 0000
The CRYP_DIN register is the data input register. It is 32-bit wide. It is used to enter into the
input FIFO up to four 64-bit blocks (TDES) or two 128-bit blocks (AES) of plaintext (when
encrypting) or ciphertext (when decrypting), one 32-bit word at a time.
To fit different data sizes, the data can be swapped after processing by configuring the
DATATYPE bits in the CRYP_CR register. Refer to Section 20.3.16: CRYP data registers
and data swapping for more details.

RM0385 Rev 7

611/1709
622

Cryptographic processor (CRYP)

RM0385

When CRYP_DIN register is written to the data are pushed into the input FIFO.
•

If CRYPEN = 1, when at least two 32-bit words in the DES/TDES mode have been
pushed into the input FIFO (four words in the AES mode), and when at least two words
are free in the output FIFO (four words in the AES mode), the CRYP engine starts an
encrypting or decrypting process.

When CRYP_DIN register is read:

Note:

31

•

If CRYPEN = 0, the FIFO is popped, and then the data present in the Input FIFO are
returned, from the oldest one (first reading) to the newest one (last reading). The IFEM
flag must be checked before each read operation to make sure that the FIFO is not
empty.

•

if CRYPEN = 1, an undefined value is returned.

After the CRYP_DIN register has been read once or several times, the FIFO must be
flushed by setting the FFLUSH bit prior to processing new data.
30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DATAIN[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DATAIN[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DATAIN[31:0]: Data Input
On read FIFO is popped (last written value is returned), and its value is returned
if CRYPEN=0. If CRYPEN=1 DATAIN register returns an undefined value.
On write current register content is pushed inside the FIFO.

20.6.4

CRYP data output register (CRYP_DOUT)
Address offset: 0x0C
Reset value: 0x0000 0000
The CRYP_DOUT register is the data output register. It is read-only and 32-bit wide. It is
used to retrieve from the output FIFO up to four 64-bit blocks (TDES) or two 128-bit blocks
(AES) of plaintext (when encrypting) or ciphertext (when decrypting), one 32-bit word at a
time.
To fit different data sizes, the data can be swapped after processing by configuring the
DATATYPE bits in the CRYP_CR register. Refer to Section 20.3.16: CRYP data registers
and data swapping for more details.
When CRYP_DOUT register is read, the last data entered into the output FIFO (pointed to
by the read pointer) is returned.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DATAOUT[31:16]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

DATAOUT[15:0]

612/1709

r

r

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

Bits 31:0 DATAOUT[31:0]: Data Output
On read returns output FIFO content (pointed to by read pointer), else returns an
undefined value.
On write, no effect.

20.6.5

CRYP DMA control register (CRYP_DMACR)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DOEN

DIEN

rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 DOEN: DMA Output Enable
When this bit is set, DMA requests are automatically generated by the
peripheral during the output data phase.
0: DMA for outgoing data transfer is disabled
1: DMA for outgoing data transfer is enabled
Bit 0 DIEN: DMA Input Enable
When this bit is set, DMA requests are automatically generated by the
peripheral during the input data phase.
0: DMA for incoming data transfer is disabled
1: DMA for incoming data transfer is enabled

20.6.6

CRYP interrupt mask set/clear register (CRYP_IMSCR)
Address offset: 0x14
Reset value: 0x0000 0000
The CRYP_IMSCR register is the interrupt mask set or clear register. It is a read/write
register. When a read operation is performed, this register gives the current value of the
mask applied to the relevant interrupt. Writing 1 to the particular bit sets the mask, thus
enabling the interrupt to be read. Writing 0 to this bit clears the corresponding mask. All the
bits are cleared to 0 when the peripheral is reset.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OUTIM

INIM

rw

rw

RM0385 Rev 7

613/1709
622

Cryptographic processor (CRYP)

RM0385

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 OUTIM: Output FIFO service interrupt mask
0: Output FIFO service interrupt is masked
1: Output FIFO service interrupt is not masked
Bit 0 INIM: Input FIFO service interrupt mask
0: Input FIFO service interrupt is masked
1: Input FIFO service interrupt is not masked

20.6.7

CRYP raw interrupt status register (CRYP_RISR)
Address offset: 0x18
Reset value: 0x0000 0001
The CRYP_RISR register is the raw interrupt status register. It is a read-only register. When
a read operation is performed, this register gives the current raw status of the corresponding
interrupt, i.e. the interrupt information without taking CRYP_IMSCR mask into account.
Write operations have no effect.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OUTRIS

INRIS

r

r

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 OUTRIS: Output FIFO service raw interrupt status
This bit gives the output FIFO interrupt information without taking CRYP_IMSCR
corresponding mask into account.
0: Raw interrupt not pending
1: Raw interrupt pending
Bit 0 INRIS: Input FIFO service raw interrupt status
This bit gives the input FIFO interrupt information without taking CRYP_IMSCR
corresponding mask into account.
0: Raw interrupt not pending
1: Raw interrupt pending

20.6.8

CRYP masked interrupt status register (CRYP_MISR)
Address offset: 0x1C
Reset value: 0x0000 0000
The CRYP_MISR register is the masked interrupt status register. It is a read-only register.
When a read operation is performed, this register gives the current masked status of the
corresponding interrupt, i.e. the interrupt information taking CRYP_IMSCR mask into
account. Write operations have no effect.

614/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OUTMIS

INMIS

r

r

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 OUTMIS: Output FIFO service masked interrupt status
This bit gives the output FIFO interrupt information without taking into account
the corresponding CRYP_IMSCR mask.
0: Interrupt not pending
1: Interrupt pending
Bit 0 INMIS: Input FIFO service masked interrupt status
This bit gives the input FIFO interrupt information without taking into account the
corresponding CRYP_IMSCR mask.
0: Interrupt not pending
1: Interrupt pending when CRYPEN= 1

20.6.9

CRYP key register 0L (CRYP_K0LR)
Address offset: 0x20
Reset value: 0x0000 0000
CRYP key registers contain the cryptographic keys.
•

In DES/TDES mode, the keys are 64-bit binary values (number from left to right, that is
the leftmost bit is bit 1) and named K1, K2 and K3 (K0 is not used). Each key consists
of 56 information bits and 8 parity bits.

•

In AES mode, the key is considered as a single 128, 192 or 256 bits long sequence
K0K1K2...K127/191/255. The AES key is entered into the registers as follows:
–

for AES-128: K0..K127 corresponds to b127..b0 (b255..b128 are not used),

–

for AES-192: K0..K191 corresponds to b191..b0 (b255..b192 are not used),

–

for AES-256: K0..K255 corresponds to b255..b0.

In all cases key bit K0 is the leftmost bit in CRYP inner memory and register bit b0 is the
rightmost bit in corresponding CRYP_KxLR key register.
For more information refer to Section 20.3.17: CRYP key registers.
Note:

Write accesses to these registers are disregarded when the cryptographic processor is busy
(bit BUSY = 1 in the CRYP_SR register)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

K255

K254

K253

K252

K251

K250

K249

K248

K247

K246

K245

K244

K243

K242

K241

K240
w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

K239

K238

K237

K236

K235

K234

K233

K232

K231

K230

K229

K228

K227

K226

K225

K224

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

RM0385 Rev 7

615/1709
622

Cryptographic processor (CRYP)

RM0385

Bits 31:0 K[255:224]: AES key bit x (x= 224 to 255)
Note: This register is not used in DES mode

20.6.10

CRYP key register 0R (CRYP_K0RR)
Address offset: 0x24
Reset value: 0x0000 0000
Refer to Section 20.6.9: CRYP key register 0L (CRYP_K0LR) for details.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

K223

K222

K221

K220

K219

K218

K217

K216

K215

K214

K213

K212

K211

K210

K209

K208
w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

K207

K206

K205

K204

K203

K202

K201

K200

K199

K198

K197

K196

K195

K194

K193

K192

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:0 K[223:192]: AES key bit x (x= 192 to 223)
Note: This register is not used in DES mode

20.6.11

CRYP key register 1L (CRYP_K1LR)
Address offset: 0x28
Reset value: 0x0000 0000
Refer to Section 20.6.9: CRYP key register 0L (CRYP_K0LR) for details.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

K191

K190

K189

K188

K187

K186

K185

K184

K183

K182

K181

K180

K179

K178

K177

K176

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

K175

K174

K173

K172

K171

K170

K169

K168

K167

K166

K165

K164

K163

K162

K161

K160

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:0 K[191:160]: AES key bit x (x= 160 to 191)
In DES mode, K192 corresponds to key K1 bit 1 and K160 corresponds to key
K1 bit 32.

20.6.12

CRYP key register 1R (CRYP_K1RR)
Address offset: 0x2C
Reset value: 0x0000 0000
Refer to Section 20.6.9: CRYP key register 0L (CRYP_K0LR) for details.

616/1709

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

K159

K158

K157

K156

K155

K154

K153

K152

K151

K150

K149

K148

K147

K146

K145

K144

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

K143

K142

K141

K140

K139

K138

K137

K136

K135

K134

K133

K132

K131

K130

K129

K128

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:0 K[159:128]: AES key bit x (x= 128 to 159)
In DES mode K159 corresponds to key K1 bit 33 and K128 corresponds to key
K1 bit 64.

20.6.13

CRYP key register 2L (CRYP_K2LR)
Address offset: 0x30
Reset value: 0x0000 0000
Refer to Section 20.6.9: CRYP key register 0L (CRYP_K0LR) for details.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

K127

K126

K125

K124

K123

K122

K121

K120

K119

K118

K117

K116

K115

K114

K113

K112

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

K111

K110

K109

K108

K107

K106

K105

K104

K103

K102

K101

K100

K99

K98

K97

K96

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:0 K[127:96]: AES key bit x (x= 96 to 127)
In DES mode K127 corresponds to key K2 bit 1 and K96 corresponds to key K2
bit 32.

20.6.14

CRYP key register 2R (CRYP_K2RR)
Address offset: 0x34
Reset value: 0x0000 0000
Refer to Section 20.6.9: CRYP key register 0L (CRYP_K0LR) for details.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

K95

K94

K93

K92

K91

K90

K89

K88

K87

K86

K85

K84

K83

K82

K81

K80

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

K79

K78

K77

K76

K75

K74

K73

K72

K71

K70

K69

K68

K67

K66

K65

K64

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:0 K[95:64]: AES key bit x (x= 64 to 95)
In DES mode K95 corresponds to key K2 bit 33 and K64 corresponds to key K2
bit 64.

RM0385 Rev 7

617/1709
622

Cryptographic processor (CRYP)

20.6.15

RM0385

CRYP key register 3L (CRYP_K3LR)
Address offset: 0x38
Reset value: 0x0000 0000
Refer to Section 20.6.9: CRYP key register 0L (CRYP_K0LR) for details.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

K63

K62

K61

K60

K59

K58

K57

K56

K55

K54

K53

K52

K51

K50

K49

K48
w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

K47

K46

K45

K44

K43

K42

K41

K40

K39

K38

K37

K36

K35

K34

K33

K32

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:0 K[63:32]: AES key bit x (x= 32 to 63)
In DES mode K63 corresponds to key K3 bit 1 and K32 corresponds to key K3
bit 32.

20.6.16

CRYP key register 3R (CRYP_K3RR)
Address offset: 0x3C
Reset value: 0x0000 0000
Refer to Section 20.6.9: CRYP key register 0L (CRYP_K0LR) for details.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

K31

K30

K29

K28

K27

K26

K25

K24

K23

K22

K21

K20

K19

K18

K17

K16
w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

K15

K14

K13

K12

K11

K10

K9

K8

K7

K6

K5

K4

K3

K2

K1

K0

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:0 K[31:0]: AES key bit x (x= 0 to 31)
In DES mode K31 corresponds to key K3 bit 33 and K0 corresponds to key K3
bit 64.

20.6.17

CRYP initialization vector register 0L (CRYP_IV0LR)
Address offset: 0x40
Reset value: 0x0000 0000
The CRYP_IV0...1(L/R)R are the left-word and right-word registers for the initialization
vector (64 bits for DES/TDES and 128 bits for AES). For more information refer to
Section 20.3.18: CRYP initialization vector registers.
IV0 is the leftmost bit whereas IV63 (DES, TDES) or IV127 (AES) are the rightmost bits of
the initialization vector. IV1(L/R)R is used only in the AES. Only CRYP_IV0(L/R) is used in
DES/TDES.

Note:

618/1709

Write access to these registers are disregarded when the cryptographic processor is busy
(bit BUSY = 1 in the CRYP_SR register).

RM0385 Rev 7

RM0385

Cryptographic processor (CRYP)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

IV0

IV1

IV2

IV3

IV4

IV5

IV6

IV7

IV8

IV9

IV10

IV11

IV12

IV13

IV14

IV15

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

IV16

IV17

IV18

IV19

IV20

IV21

IV22

IV23

IV24

IV25

IV26

IV27

IV28

IV29

IV30

IV31

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 IV[0:31]: Initialization vector bit x (x= 0 to 31)

20.6.18

CRYP initialization vector register 0R (CRYP_IV0RR)
Address offset: 0x44
Reset value: 0x0000 0000
Refer to Section 20.6.17: CRYP initialization vector register 0L (CRYP_IV0LR) for details.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

IV32

IV33

IV34

IV35

IV36

IV37

IV38

IV39

IV40

IV41

IV42

IV43

IV44

IV45

IV46

IV47

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

IV48

IV49

IV50

IV51

IV52

IV53

IV54

IV55

IV56

IV57

IV58

IV59

IV60

IV61

IV62

IV63

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 IV[32:63]: Initialization vector bit x (x= 32 to 63)

20.6.19

CRYP initialization vector register 1L (CRYP_IV1LR)
Address offset: 0x48
Reset value: 0x0000 0000
Refer to Section 20.6.17: CRYP initialization vector register 0L (CRYP_IV0LR) for details.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

IV64

IV65

IV66

IV67

IV68

IV69

IV70

IV71

IV72

IV73

IV74

IV75

IV76

IV77

IV78

IV79

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

IV80

IV81

IV82

IV83

IV84

IV85

IV86

IV87

IV88

IV89

IV90

IV91

IV92

IV93

IV94

IV95

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 IV[64:95]: Initialization vector bit x (x= 64 to 95)
Note: This register is not used in DES mode

20.6.20

CRYP initialization vector register 1R (CRYP_IV1RR)
Address offset: 0x4C
Reset value: 0x0000 0000
Refer to Section 20.6.17: CRYP initialization vector register 0L (CRYP_IV0LR) for details.

RM0385 Rev 7

619/1709
622

Cryptographic processor (CRYP)

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

IV96

IV97

IV98

IV99

IV100

IV101

IV102

IV103

IV104

IV105

IV106

IV107

IV108

IV109

IV110

IV111

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

IV112

IV113

IV114

IV115

IV116

IV117

IV118

IV119

IV120

IV121

IV122

IV123

IV124

IV125

IV126

IV127

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 IV[96:127]: Initialization vector bit x (x= 96 to 127)
Note: This register is not used in DES mode

620/1709

RM0385 Rev 7

0x20

0x24

0x38

0x3C

0x40

0x1C
CRYP_MISR

Reset value

Reset value

Reset value

Reset value

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

CRYP_K0LR

CRYP_K0RR
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0
0

CRYP_K3LR

CRYP_K3RR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CRYP_IV0LR

0

RM0385 Rev 7
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0
0

0

0

0

0

0
0
0
0
0
0
0
0

CRYP_DMACR
Res.
Res.
Res.
Res.

Res.

IFEM

Res.

IFNF

Res.

OFNE

Res.

OFFU

Res.

BUSY

0

Reset value

Reset value

Reset value

Reset value
DIEN

0
Res.

0

INIM

0
Res.

0

INRIS

0
Res.

0

INMIS

0
Res.

1
0

Res.

2

3

4

5

6

7

8

9

ALGODIR
Res.

ALGOMODE[2:0]

DATATYPE

KEYSIZE

11
10

Res.
Res.

0

DOEN

0
Res.

12
Res.
Res.

0

OUTIM

Res.

Res.

0
Res.

13
Res.
Res.

0

OUTRIS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0
Res.

14
Res.

15
FFLUSH
Res.

Res.

0

OUTMIS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

16
CRYPEN

17

0

Res.

GCM_CCMPH
0

Res.

18

19

20

0

Res.

Res.

ALGOMODE[3]
Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

CRYP_DIN

Res.

Res.

CRYP_DOUT

Res.

0

Res.

0

Res.

0

Res.

0

Res.

21
Res.

Res.

0

Res.

Res.

0

Res.

24

Res.

22

25

Res.

0

Res.

26

Res.

23

27

Res.

Res.

28

Res.

0

Res.

29

Res.

0

Res.

Res.

Res.

30

Res.

0

Res.

Res.

Res.

0

Res.
0

Res.

Res.

Res.
0

Res.

Res.

0

Res.
0

Res.

Res.

0

Res.
0

Res.

0

Res.
0

Res.

0

Res.

Res.

Reset value

Res.

0

Res.

Res.

31

CRYP_CR

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Register
name

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

CRYP_RISR
0

Res.

0x18
0

Res.

CRYP_IMSCR
0

Res.

0x14
0

Res.

Reset value

Res.

0x10
Reset value

Res.

0x0C

Res.

0x08

Res.

CRYP_SR

Res.

0x04

Res.

0x00
0x00

Res.

Offset

Res.

20.6.21

Res.

RM0385
Cryptographic processor (CRYP)

CRYP register map
Table 137. CRYP register map and reset values

0
0
0
1
1

DATAIN
0
0
0
0
0
0
0
0
0
0
0
0
0
0

DATAOUT

0
0

0
0

0
1

0
0

CRYP_K0LR

CRYP_K0RR

...
...

CRYP_K3LR

CRYP_K3RR

CRYP_IV0LR
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

621/1709

622

Cryptographic processor (CRYP)

RM0385

9

8

7

6

5

4

3

2

1

0

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

11

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CRYP_IV1LR
0

0

0

0

0

0

0

0

0

0

0

0

0

0

CRYP_IV1RR
Reset value

0

CRYP_IV0RR

CRYP_IV1LR
Reset value

10

0x4C

Reset value

12

0x48

CRYP_IV0RR

13

0x44

Register
name

30

Offset

31

Table 137. CRYP register map and reset values (continued)

0

0

0

0

CRYP_IV1RR
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

622/1709

RM0385 Rev 7

RM0385

21

Hash processor (HASH)

Hash processor (HASH)
This section applies to the whole STM32F756xx devices, unless otherwise specified.

21.1

Introduction
The hash processor is a fully compliant implementation of the secure hash algorithm
(SHA-1, SHA-224, SHA-256), the MD5 (message-digest algorithm 5) hash algorithm and
the HMAC (keyed-hash message authentication code) algorithm suitable for a variety of
applications. HMAC is suitable for applications requiring message authentication.
The hash processor computes FIPS (Federal Information Processing Standards) approved
digests of length of 160, 224, 256 bits, for messages of up to (261 – 1) bits. It also computes
128 bits digests for the MD5 algorithm.

21.2

HASH main features
•

•

Suitable for data authentication applications, compliant with:
–

Federal Information Processing Standards Publication FIPS PUB 180-4, Secure
Hash Standard (SHA-1 and SHA-2 family)

–

Internet Engineering Task Force (IETF) Request For Comments RFC 1321 MD5
Message-Digest Algorithm

–

Internet Engineering Task Force (IETF) Request For Comments RFC 2104
HMAC: Keyed-Hashing for Message Authentication, and Federal Information
Processing Standards Publication FIPS PUB 198-1, The Keyed-Hash Message
Authentication Code (HMAC)

Corresponding 32-bit words of the digest from consecutive message blocks are added
to each other to form the digest of the whole message
–

Automatic 32-bit words swapping to comply with the internal little-endian
representation of the input bit-string

–

Word swapping supported: bits, bytes, half-words and 32-bit words

•

Automatic padding to complete the input bit string to fit digest minimum block size of
512 bits (16 × 32 bits)

•

Single 32-bit input register associated to an internal input FIFO of sixteen 32-bit words,
corresponding to one block size

•

Fast computation of SHA-1, SHA-224, SHA-256, and MD5
–

82 (respectively 66) clock cycles for processing one 512-bit block of data using

RM0385 Rev 7

623/1709
645

Hash processor (HASH)

RM0385

SHA-1 (respectively SHA-256) algorithm
–

66 clock cycles for processing one 512-bit block of data using MD5 algorithm

•

AHB slave peripheral, accessible through 32-bit word accesses only (else an AHB
error is generated)

•

8 × 32-bit words (H0 to H7) for output message digest

•

Automatic data flow control with support of direct memory access (DMA) using one
channel. Fixed burst of 4 supported.

•

Interruptible message digest computation, on a per-32-bit word basis
–

Re-loadable digest registers

–

Hashing computation suspend/resume mechanism, including using DMA

21.3

HASH functional description

21.3.1

HASH block diagram
Figure 145 shows the block diagram of the hash processor.

32-bit AHB2 bus

data, key

result

HASH_Hx

status

HASH_SR

control

AHB2
interface

HASH_DIN

start

swapping

Banked Registers (main)

16x32-bit
IN FIFO

Figure 145. HASH block diagram

digest

HASH_CR
+

HASH_STR

Banked Registers (context swapping)

HASH_CSRx
hash_hclk2

HASH
Core
(SHA-1,
SHA-224,
SHA-256,
MD5)

HMAC
logic

Context swap

Banked Registers (IRQ)

CRYP_IMR

hash_in_dma
hash_it

DMA
interface
IRQ
interface

Control Logic

MSv41957V2

21.3.2

HASH internal signals
Table 138 describes a list of useful to know internal signals available at HASH level, not at
product level (on pads).

624/1709

RM0385 Rev 7

RM0385

Hash processor (HASH)
Table 138. HASH internal input/output signals

21.3.3

Signal name

Signal type

hash_hclk2

digital input

hash_it

digital output

hash_in_dma

digital input/output

Description
AHB2 bus clock
Hash processor global interrupt request
DMA burst request/ acknowledge

About secure hash algorithms
The hash processor is a fully compliant implementation of the secure hash algorithm
defined by FIPS PUB 180-4 standard and the IETF RFC1321 publication (MD5).
With each algorithm, the HASH computes a condensed representation of a message or data
file. More specifically, when a message of any length below 264 bits is provided on input, the
SHA-1, SHA-224, SHA-256 and MD5 processing core produces respectively a 160-bit, 224
bit, 256 bit and 128-bit output string called a message digest. The message digest can then
be processed with a digital signature algorithm in order to generate or verify the signature
for the message.
Signing the message digest rather than the message often improves the efficiency of the
process because the message digest is usually much smaller in size than the message. The
verifier of a digital signature has to use the same hash algorithm as the one used by the
creator of the digital signature.
The SHA-2 functions supported by the hash processor are qualified as “secure” because it
is computationally infeasible to find a message that corresponds to a given message digest
(SHA-1 is no more qualified as secure since February 2017), or to find two different
messages that produce the same message digest. Any change to a message in transit will,
with very high probability, result in a different message digest, and the signature will fail to
verify.

21.3.4

Message data feeding
The message (or data file) to be processed by the HASH should be considered as a bit
string. Per FIPS PUB 180-1 and 180-2 standards this message bit string grows from left to
right, with hexadecimal words expressed in “big-endian” convention, so that within each
word, the most significant bit is stored in the left-most bit position. For example message
string “abc” with a bit string representation of “01100001 01100010 01100011” is
represented by a 32-bit word 0x00636261, and 8-bit words 0x61626300.
Data are entered into the HASH one 32-bit word at a time, by writing them into the
HASH_DIN register. The current contents of the HASH_DIN register are transferred to the
16 words input FIFO (IN FIFO) each time the register is written with new data. Hence
HASH_DIN and the input FIFO form a seventeen 32-bit words length FIFO (named the IN
buffer).
In accordance to the kind of data to be processed (e.g. byte swapping when data are ASCII
text stream) there must be a bit, byte, half-word or no swapping operation to be performed
on data from the input FIFO before entering the little-endian hash processing core.
Figure 146 shows how the hash processing core 32-bit data block M0...31 is constructed
from one 32-bit words popped into IN FIFO by the driver, according to the DATATYPE
bitfield in the HASH control register (HASH_CR).

RM0385 Rev 7

625/1709
645

Hash processor (HASH)

RM0385

HASH_DIN data endianness when bit swapping is disabled (DATATYPE=”00”) can be
described as following: the least significant bit of the message has to be at MSB position in
the first word entered into the hash processor, the 32nd bit of the bit string has to be at MSB
position in the second word entered into the hash processor and so on.
Figure 146. Message data swapping feature
DATATYPE “00”: no swapping
written first!

LSB

System interface

Word0
bit31

bit0

bit31

M0

M31

M32

MSB
Word2

Word1
bit0

bit31

M64
M63
HASH core interface

LSB

Word3
bit0

bit31

bit0

M95

M96

M127
MSB

DATATYPE “01”: 16-bit or half-word swapping

bit31

M0
LSB

System interface

written first!

LSB

Word0
bit16 bit15

M15

M16

bit0

bit31

Word1
bit16 bit15

M31

M32

M47

M48

bit0

bit31

MSB
Word2
bit16 bit15

bit0

M63
HASH core interface

bit31

M96

Word3
bit16 bit15

M111

M112

bit0

M127
MSB

DATATYPE “10”: 8-bit or byte swapping
System interface

written first!

LSB
Word0

bit31..24 bit23..16 bit15..8

M0..7
LSB

M8..15

bit7..0

MSB
Word2

Word1
bit31..24 bit23..16 bit15..8

bit7..0

bit31..24 bit23..16 bit15..8

Word3
bit7..0

bit31..24 bit23..16 bit15..8

M96..103

M16..23 M24..31
HASH core interface

bit7..0

M112.119 M120.127

MSB

DATATYPE “11”: bit swapping
LSB
Word0
bit3 bit3 bit2
9
0
1

M0 M1 M2
LSB

System interface

written first!
bit2 bit1 bit0

Word1
bit3 bit3 bit2
9
0
1

M29 M30 M31 M32 M33 M34

Word2
bit2 bit1 bit0

M61 M62 M63
HASH core interface

MSB
Word3
bit3 bit3 bit2
9
0
1

M96 M97 M98

bit2 bit1 bit0

M125 M126 M127

MSB

MSv41984V1

626/1709

RM0385 Rev 7

RM0385

21.3.5

Hash processor (HASH)

Message digest computing
The hash processor sequentially processes 512-bit blocks when computing the message
digest. Thus, each time 16 × 32-bit words (= 512 bits) have been written to the hash
processor by the DMA or the CPU, the HASH automatically starts computing the message
digest. This operation is known as ‘partial digest computation’.
As described in Section 21.3.4: Message data feeding, the message to be processed is
entered into the HASH 32-bit word at a time, writing to the HASH_DIN register to fill the
input FIFO. In order to perform the hash computation on this data below sequence shall be
used by the application.
1.

2.
Caution:

Initialize the hash processor using the HASH_CR register:
–

Select the right algorithm using ALGO field. If needed program the correct
swapping operation on the message input words using DATATYPE bitfield in
HASH_CR.

–

Set MODE=1 and select the key length using LKEY if HMAC mode has been
selected.

–

Update NBLW to define the number of valid bits in last word if it is different from 32
bits. If it is the case automatic padding could be applied by the HASH.

Complete the initialization by setting to 1 the INIT bit in HASH_CR. Also set the bit
DMAE to 1 if data are transferred via DMA.

When programming step 2, it is important to set up before or at the same time the correct
configuration values (ALGO, DATATYPE, HMAC mode, key length, NBLW).
3.

Start filling data by writing to HASH_DIN register, unless data are automatically:
transferred via DMA. Note that the processing of a block can start only once the last
value of the block has entered the IN FIFO. The way the partial or final digest
computation is managed depends on the way data are fed into the processor:
a)

When data are filled by software:

–

The partial digest computation is triggered when the software writes an additional
word to the HASH_DIN register (actually the first word of the next block). Once the
processor is ready again (DINIS=1 in HASH_SR), the software can write new data
to HASH_DIN. This mechanism avoids the introduction of wait states by the
HASH.

–

The final digest computation is triggered when the last block is entered and the
software writes the DCAL bit to 1. If the message length is not an exact multiple of
512 bits, the NBLW field in HASH_STR register must be written prior to writing
DCAL bit (see Section 21.3.6 for details).

b)

When data are filled by DMA as a single DMA transfer (MDMAT bit=”0”):

–

The partial digest computation is triggered automatically each time the FIFO is full.

–

The final digest computation is triggered automatically when the last block has
been transferred to the HASH_DIN register (DCAL bit is set to 1 by hardware). If
the message length is not an exact multiple of 512 bits, the NBLW field in
HASH_STR register must be written prior to enabling the DMA (see
Section 21.3.6 for details).

c)

When data are filled using multiple DMA transfers (MDMAT bit=”1”) :

–

The partial digest computations are triggered as for single DMA transfers.
However the final digest computation is not triggered automatically when the last
block has been transferred to the HASH_DIN register (DCAL bit is not set to 1 by
hardware). It allows the hash processor to receive a new DMA transfer as part of

RM0385 Rev 7

627/1709
645

Hash processor (HASH)

RM0385

this digest computation. To launch the final digest computation, the software must
set MDMAT bit to 0 before the last DMA transfer in order to trigger the final digest
computation as it is done for single DMA transfers (see description before).
4.

Once computed, the digest can be read from the output registers as described in
Table 139.
Table 139. Hash processor outputs
Algorithm

Valid output registers

Most significant bit

Digest size (in bits)

MD5

HASH_H0 to
HASH_H3

HASH_H0[31]

128

SHA-1

HASH_H0 to
HASH_H4

HASH_H0[31]

160

SHA-224

HASH_H0 to
HASH_H6

HASH_H0[31]

224

SHA-256

HASH_H0 to
HASH_H7

HASH_H0[31]

256

For more information about HMAC detailed instructions, refer to Section 21.3.7: HMAC
operation.

21.3.6

Message padding
Overview
When computing a condensed representation of a message, the process of feeding data
into the hash processor (with automatic partial digest computation every 512-bit block) loops
until the last bits of the original message are written to the HASH_DIN register.
As the length (number of bits) of a message can be any integer value, the last word written
to the hash processor may have a valid number of bits between 1 and 32. This number of
valid bits in the last word, NBLW, has to be written to the HASH_STR register, so that
message padding is correctly performed before the final message digest computation.

Padding processing
Detailed padding sequences with DMA is enabled or disabled are described in
Section 21.3.5: Message digest computing.

Padding example
As specified by Federal Information Processing Standards PUB 180-1 and PUB 180-2,
message padding consists in appending a “1” followed by k “0”s, itself followed by a 64-bit
integer that is equal to the length L in bits of the message. These three padding operations
generate a padded message of length L + 1 + k + 64, which by construction is a multiple of
512 bits.
For the hash processor, the “1” is added to the last word written to the HASH_DIN register at
the bit position defined by the NBLW bitfield, and the remaining upper bits are cleared (“0”s).

628/1709

RM0385 Rev 7

RM0385

Hash processor (HASH)
Example from FIPS PUB180-2
Let us assume that the original message is the ASCII binary-coded form of “abc”, of length
L = 24:
byte 0

byte 1

byte 2

byte 3

01100001 01100010 01100011 UUUUUUUU
<-- 1st word written to HASH_DIN -->

NBLW has to be loaded with the value 24: a “1” is appended at bit location 24 in the bit string
(starting counting from left to right in the above bit string), which corresponds to bit 31 in the
HASH_DIN register (little-endian convention):
01100001 01100010 01100011 1UUUUUUU

Since L = 24, the number of bits in the above bit string is 25, and 423 “0” bits are appended,
making now 448 bits.
This gives in hexadecimal (byte words in big-endian format):
61626380
00000000
00000000
00000000

00000000 00000000 00000000
00000000 00000000 00000000
00000000 00000000 00000000
00000000

The message length value, L, in two-word format (that is 00000000 00000018) is appended.
Hence the final padded message in hexadecimal (byte words in big-endian format):
61626380
00000000
00000000
00000000

00000000
00000000
00000000
00000000

00000000
00000000
00000000
00000000

00000000
00000000
00000000
00000018

If the hash processor is programmed to swap byte within HASH_DIN input register
(DATATYPE=10 in HASH_CR), the above message has to be entered by following below
the sequence:
1.

0xUU636261 is written to the HASH_DIN register (where ‘U’ means don’t care).

2.

0x18 is written to the HASH_STR register (the number of valid bits in the last word
written to the HASH_DIN register is 24, as the original message length is 24 bits).

3.

0x10 is written to the HASH_STR register to start the message padding (described
above) and then perform the digest computation.

4.

The hash computing is complete with the message digest available in the HASH_HRx
registers (x = 0...4) for the SHA-1 algorithm. For this FIPS example, the expected value
is as follows:
HASH_H0
HASH_H1
HASH_H2
HASH_H3
HASH_H4

21.3.7

=
=
=
=
=

0xA9993E36
0x4706816A
0xBA3E2571
0x7850C26C
0x9CD0D89D

HMAC operation
Overview
As specified by Internet Engineering Task Force RFC2104, HMAC: keyed-hashing for
message authentication, the HMAC algorithm is used for message authentication by
irreversibly binding the message being processed to a key chosen by the user. The
algorithm consists of two nested hash operations:

RM0385 Rev 7

629/1709
645

Hash processor (HASH)

RM0385

HMAC(message) = Hash((key | pad) XOR [0x5C]n
| Hash((key | pad) XOR [0x36]n | message))

where:
•

[X]n represents a repetition of X n times, where n equal to the size of the underlying
hash function data block that is 512 bits for SHA-1, SHA224, SHA-256, MD5 hash
algorithms (i.e. n=64).

•

pad is a sequence of zeroes needed to extend the key to the length n defined above. If
the key length is greater than n, the application shall first hash the key using Hash()
function and then use the resultant byte string as the actual key to HMAC.

•

| represents the concatenation operator.

HMAC processing
Four different steps are required to compute the HMAC:
1.

2.

The block is initialized by writing the INIT bit to 1 with the MODE bit at 1 and the ALGO
bits set to the value corresponding to the desired algorithm. The LKEY bit must also be
set to 1 if the key being used is longer than 64 bytes. In this case, as required by HMAC
specifications, the hash processor will use the hash of the key instead of the real key.
The key to be used for the inner hash function must be provided to the hash processor:
The key loading operation follows the same mechanism as the message bit string
loading, i.e. write key data into HASH_DIN and complete the transfer by writing to
HASH_STR register.

Note:

Note:

Endianness details can be found in Section 21.3.4: Message data feeding.
3.

Once the last key word has been entered and computation has started, the hash
processor elaborates the inner key material. Once this operation has completed, it is
ready to accept the message bit string as described in Section 21.3.4: Message data
feeding.

4.

After the final hash round, the hash processor returns “ready” to indicate that it is ready
to receive the key to be used for the outer hash function (normally, this key is the same
as the one used for the inner hash function). When the last word of the key is entered
and computation starts, the HMAC result can be found in the HASH_H0...HASH_H7
registers.

The computation latency of the HMAC primitive depends on the lengths of the keys and
message, as described in Section 21.5: HASH processing time.
HMAC example
Below is an example of HMAC SHA-1 algorithm (ALGO=”00” and MODE=”1” in HASH_CR)
as specified by NIST.
Let us assume that the original message is the ASCII binary-coded form of “Sample
message for keylen=blocklen”, of length L = 34 bytes. If the HASH is programmed in
no swapping mode (DATATYPE=00 in HASH_CR), the following data must be loaded
sequentially into HASH_DIN register:
1.

Inner hash key input (lenght=64, i.e. no padding), specified by NIST. As key
lenght=64, LKEY bit is set to 0 in HASH_CR register
00010203 04050607 08090A0B 0C0D0E0F 10111213 14151617
18191A1B 1C1D1E1F 20212223 24252627 28292A2B 2C2D2E2F

630/1709

RM0385 Rev 7

RM0385

Hash processor (HASH)
30313233 34353637 38393A3B 3C3D3E3F

2.

Message input (lenght=34, i.e. padding required). HASH_STR must be set to 0x20 to
start message padding and inner hash computation (see ‘U’ as don’t care)
53616D70 6C65206D 65737361 67652066 6F72206B 65796C65
6E3D626C 6F636B6C 656EUUUU

3.

Outer hash key input (lenght=64, i.e. no padding). A key identical to the inner hash key
is entered here.

4.

Final outer hash computing is then performed by the HASH. The HMAC SHA-1
digest result is available in the HASH_HRx registers (x = 0...4), as shown below:
HASH_H0
HASH_H1
HASH_H2
HASH_H3
HASH_H4

21.3.8

=
=
=
=
=

0x5FD596EE
0x78D5553C
0x8FF4E72D
0x266DFD19
0x2366DA29

Context swapping
Overview
It is possible to interrupt a hash/HMAC operation to perform another processing with a
higher priority. The interrupted process completes later when the higher-priority task has
been processed, as shown in Figure 147.
Figure 147. HASH save/restore mechanism
Message 2

Message 1
512-bit block 1

512-bit block 2
New higher
priority message
2 to be processed

HASH suspend
sequence

512-bit block 1

512-bit block 3

<512-bit block 2
(last block)
512-bit block 4

512-bit block 5

HASH resume
sequence

512-bit block 6
...

MSv41985V1

To do so, the context of the interrupted task must be saved from the HASH registers to
memory, and then be restored from memory to the HASH registers.
The procedures where the data flow is controlled by software or by DMA are described
below.
RM0385 Rev 7

631/1709
645

Hash processor (HASH)

RM0385

Data loaded by software
When the DMA is not used to load the message into the hash processor, the context can be
saved only when no block processing is ongoing. This means that the user application must
wait until DINIS = 1 (last block processed and input FIFO empty) or NBW ≠ 0 (FIFO not full
and no processing ongoing). The detailed procedure is described below.
•

Current context saving
Before interrupting the current message digest calculation, the application must store
the contents of the following registers into memory:

•

–

HASH_IMR

–

HASH_STR

–

HASH_CR

–

HASH_CSR0 to HASH_CSR53

Current context restoring
To resume processing the interrupted message, the application must respect the
following steps:
a)

Write the following registers with the values saved in memory: HASH_IMR,
HASH_STR and HASH_CR.

b)

Initialize the hash processor by setting the INIT bit in the HASH_CR register.

c)

Write the HASH_CSR0 to HASH_CSR53 registers with the values saved in
memory.

d)

Restart the processing from the point where it has been interrupted.

Data loaded by DMA
When the DMA is used to load the message into the hash processor, it is not possible to
predict if a DMA transfer is ongoing. The user application must thus stop DMA transfers,
then wait until the hash processor is ready before interrupting the current message digest
calculation. The detailed procedure is described below.
•

Current context saving
Before interrupting the current message digest calculation using DMA, the application
must respect the following steps:

•

a)

Clear the DMAE bit to disable the DMA interface.

b)

Wait until the current DMA transfer is complete (wait for DMAS = 0 in the
HASH_SR register). Note that the block may or may not have been totally
transferred to the HASH.

c)

Disable the corresponding channel in the DMA controller.

d)

Wait until the hash processor is ready (no block is being processed), that is wait
for DINIS = 1

Current context restoring
To resume processing the interrupted message using DMA, the application must
respect the following steps:

632/1709

a)

Reconfigure the DMA controller so that it proceeds with the transfer of the
message up to the end if it is not interrupted again.

b)

Restart the processing from the point where it was interrupted by setting the
DMAE bit.

RM0385 Rev 7

RM0385
Note:

Hash processor (HASH)
If the context swapping does not involve HMAC operations, the HASH_CSR38 to
HASH_CSR53 registers do not need to be saved and restored.
If the context swapping occurs between two blocks (the last block was completely
processed and the next block has not yet been pushed into the IN FIFO, NBW = 000 in the
HASH_CR register), the HASH_CSR22 to HASH_CSR37 registers do not need to be saved
and restored.

21.3.9

HASH DMA interface
The hash processor provides an interface to connect to the DMA controller. This DMA can
be used to write data to the HASH by setting the DMAE bit in the HASH_CR register. When
this bit is set, the HASH asserts the burst request signal to the DMA controller when there is
enough free words in the FIFO to support a burst of four words.
Once four 32-bit words have been received, the HASH automatically restarts this process,
checks the FIFO size, and asserts a new request if the FIFO status allow a burst reception.
For more information refer to Section 21.3.5: Message digest computing.
Before starting the DMA transfer, the software must program the number of valid bits in the
last word that will be copied into HASH_DIN register. This is done by writing in HASH_STR
register the following value:
NBLW = Len(Message)% 32
where “x%32” gives the remainder of x divided by 32.
DMAS bit in HASH_SR register provides information on the DMA interface activity. This bit
is set with DMAE and cleared when DMAE is cleared to 0 and no DMA transfer is ongoing.

Note:

No interrupt is associated to DMAS bit.

21.3.10

HASH error management
No error flags are generated by the HASH hardware.

21.4

HASH interrupts
Two individual maskable interrupt sources are generated by the hash processor to signal
following events:
•

Digest calculation completion (DCIS)

•

Data input buffer ready (DINIS)

Both interrupt sources are connected to the same global interrupt request signal, as shown
on Figure 148.
Figure 148. HASH interrupt mapping diagram

HASH_SR.DCIS
HASH_IMR.DCIE
HASH_SR.DINIS
HASH_IMR.DINIE

hash_it
(IP global interrupt
request signal)

MSv41986V1

RM0385 Rev 7

633/1709
645

Hash processor (HASH)

RM0385

The above interrupt sources can be enabled or disabled individually by changing the mask
bits in the HASH_IMR register. Setting the appropriate mask bit to 1 enables the interrupt.
The status of the individual interrupt events can be read from the HASH_SR register.
Table 140 gives a summary of the available features.
Table 140. HASH interrupt requests
Interrupt event

21.5

Event flag

Enable control bit

Digest computation completed flag

DCIS

DCIE

Data input buffer ready to get a new block flag

DINIS

DINIE

HASH processing time
Table 141 summarizes the time required to process a 512-bit intermediate block for each
mode of operation.
Table 141. Processing time (in clock cycle)
Mode of operation

FIFO load(1)

Computation phase

Total

MD5

16

50

66

SHA-1

16

66

82

16

50

66

SHA-224
SHA-256

1. The time required to load the 16 words of the block into the processor must be added to this value.

The time required to process the last block of a message (or of a key in HMAC) can be
longer. This time depends on the length of the last block and the size of the key (in HMAC
mode).
Compared to the processing of an intermediate block, it can be increased by the factor
below:

634/1709

•

1 to 2.5 for a hash message

•

~2.5 for an HMAC input-key

•

1 to 2.5 for an HMAC message

•

~2.5 for an HMAC output key in case of a short key

•

3.5 to 5 for an HMAC output key in case of a long key

RM0385 Rev 7

RM0385

Hash processor (HASH)

21.6

HASH registers
The HASH core is associated with several control and status registers and five message
digest registers. All these registers are accessible through 32-bit word accesses only, else
an AHB2 error is generated.

21.6.1

HASH control register (HASH_CR)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ALGO[1]

Res.

LKEY

rw
15

14

Res.

Res.

13

12

11

10

MDMAT DINNE
rw

r

9

8

NBW
r

r

7

6

ALGO[0] MODE
r

r

rw

rw

5

4

DATATYPE
rw

rw

rw

3

2

1

0

DMAE

INIT

Res.

Res.

rw

w

Bits 31:19 Reserved, must be kept at reset value.
Bit 18 ALGO[1]: refer to bit 7 description
Bit 17 Reserved, must be kept at reset value.
Bit 16 LKEY: Long key selection
This bit selects between short key (≤ 64 bytes) or long key (> 64 bytes) in HMAC
mode.
0: Short key (≤ 64 bytes)
1: Long key (> 64 bytes)
Note: This selection is only taken into account when the INIT bit is set and
MODE= 1. Changing this bit during a computation has no effect.
Bit 15 Reserved, must be kept at reset value.
Bit 14 Reserved, must be kept at reset value.
Bit 13 MDMAT: Multiple DMA Transfers
This bit is set when hashing large files when multiple DMA transfers are needed.
0: DCAL is automatically set at the end of a DMA transfer.
1: DCAL is not automatically set at the end of a DMA transfer.
Bit 12 DINNE: DIN not empty
This bit is set when the HASH_DIN register holds valid data (that is after being
written at least once). It is cleared when either the INIT bit (initialization) or the
DCAL bit (completion of the previous message processing) is written to 1.
0: No data are present in the data input buffer
1: The input buffer contains at least one word of data

RM0385 Rev 7

635/1709
645

Hash processor (HASH)

RM0385

Bits 11:8 NBW: Number of words already pushed
This bitfield reflects the number of words in the message that have already been
pushed into the IN FIFO. NBW increments (+1) when a write access is
performed to the HASH_DIN register while DINNE = 1.
It goes to zero when the INIT bit is written to 1 or when a digest calculation starts
(DCAL written to 1 or DMA end of transfer).
If the DMA is not used
0000 and DINNE=0: no word has been pushed into the DIN buffer, i.e. both
HASH_DIN register and IN FIFO are empty.
0000 and DINNE=1: one word has been pushed into the DIN buffer, i.e.
HASH_DIN register contains one word and IN FIFO is empty.
0001: two words have been pushed into the DIN buffer, i.e. HASH_DIN register
and the IN FIFO contain one word each.
...
1111: 16 words have been pushed into the DIN buffer.
If the DMA is used
NBW is the exact number of words that have been pushed into the IN FIFO by
the DMA.
Bits 18, 7 ALGO[1:0]: Algorithm selection
These bits selects the SHA-1, SHA-224, SHA-256 or the MD5 algorithm:
00: SHA-1 algorithm selected
01: MD5 algorithm selected
10: SHA-224 algorithm selected
11: SHA-256 algorithm selected
Note: This selection is only taken into account when the INIT bit is set. Changing
this bit during a computation has no effect.
Bit 6 MODE: Mode selection
This bit selects the HASH or HMAC mode for the selected algorithm:
0: Hash mode selected
1: HMAC mode selected. LKEY must be set if the key being used is longer than
64 bytes.
Note: This selection is only taken into account when the INIT bit is set. Changing
this bit during a computation has no effect.
Bits 5:4 DATATYPE: Data type selection
These bits define the format of the data entered into the HASH_DIN register:
00: 32-bit data. The data written to HASH_DIN are directly used by the hash
processing, without reordering.
01: 16-bit data or half-word. The data written to HASH_DIN are considered as
two half-words, and are swapped before being used by the hash processing.
10: 8-bit data or bytes. The data written to HASH_DIN are considered as four
bytes, and are swapped before being used by the hash processing.
11: bit data or bit-string. The data written to HASH_DIN are considered as 32 bits
(1st bit of the string at position 0), and are swapped before being used by the
hash processing (first bit of the string at position 31).

636/1709

RM0385 Rev 7

RM0385

Hash processor (HASH)

Bit 3 DMAE: DMA enable
0: DMA transfers disabled
1: DMA transfers enabled. A DMA request is sent as soon as the hash core is
ready to receive data.
After this bit is set it is cleared by hardware while the last data of the message is
written to the hash processor.
Setting this bit to 0 while a DMA transfer is on-going is not aborting this current
transfer. Instead, the DMA interface of the HASH remains internally enabled until
the transfer is complete or INIT is written to 1.
Setting INIT bit to 1 does not clear DMAE bit.
Bit 2 INIT: Initialize message digest calculation
Writing this bit to 1 resets the hash processor core, so that the HASH is ready to
compute the message digest of a new message.
Writing this bit to 0 has no effect. Reading this bit always return 0.
Bits 1:0 Reserved, must be kept at reset value.

RM0385 Rev 7

637/1709
645

Hash processor (HASH)

21.6.2

RM0385

HASH data input register (HASH_DIN)
Address offset: 0x04
Reset value: 0x0000 0000
HASH_DIN is the data input register. It is 32-bit wide. This register is used to enter the
message by blocks of 512 bits. When the HASH_DIN register is programmed, the value
presented on the AHB databus is ‘pushed’ into the hash core and the register takes the new
value presented on the AHB databus. To get a correct message format, the DATATYPE bits
must have been previously configured in the HASH_CR register.
When a block of 16 words has been written to the HASH_DIN register, an intermediate
digest calculation is launched:
•

by writing new data into the HASH_DIN register (the first word of the next block) if the
DMA is not used (intermediate digest calculation),

•

automatically if the DMA is used.

When the last block has been written to the HASH_DIN register, the final digest calculation
(including padding) is launched:
•

by writing the DCAL bit to 1 in the HASH_STR register (final digest calculation),

•

automatically if the DMA is used and MDMAT bit is set to 0.

When a digest calculation (intermediate or final) is ongoing and a new write access to the
HASH_DIN register is performed, wait-states are inserted on the AHB2 bus until the hash
calculation completes.
When the HASH_DIN register is read, the last word written to this location is accessed (zero
after reset).
.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DATAIN
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

DATAIN
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DATAIN: Data input
Reading this register returns the current register content.
Writing this register pushes the current register content into the IN FIFO, and the
register takes the new value presented on the AHB databus.

638/1709

RM0385 Rev 7

RM0385

Hash processor (HASH)

21.6.3

HASH start register (HASH_STR)
Address offset: 0x08
Reset value: 0x0000 0000
The HASH_STR register has two functions:
•

It is used to define the number of valid bits in the last word of the message entered in
the hash processor (that is the number of valid least significant bits in the last data
written to the HASH_DIN register)

•

It is used to start the processing of the last block in the message by writing the DCAL
bit to 1

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DCAL

Res.

Res.

Res.
rw

rw

rw

rw

w

NBLW
rw

Bits 31:9 Reserved, must be kept at reset value.
Bit 8 DCAL: Digest calculation
Writing this bit to 1 starts the message padding, using the previously written
value of NBLW, and starts the calculation of the final message digest with all data
words written to the IN FIFO since the INIT bit was last written to 1.
Reading this bit returns 0.
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:0 NBLW: Number of valid bits in the last word
When the last word of the message bit string is written in HASH_DIN register, the
hash processor takes only the valid bits specified as below, after internal data
swapping:
0x00: All 32 bits of the last data written are valid message bits i.e. M[31:0]
0x01: Only one bit of the last data written (after swapping) is valid i.e. M[0]
0x02: Only two bits of the last data written (after swapping) are valid i.e. M[1:0]
0x03: Only three bits of the last data written (after swapping) are valid i.e. M[2:0]
...
0x1F: Only 31 bits of the last data written (after swapping) are valid i.e. M[30:0]
The above mechanism is valid only if DCAL=0. If NBLW bits are written while
DCAL is set to 1, the NBLW bitfield remains unchanged. In other words it is not
possible to configure NBLW and set DCAL at the same time.
Reading NBLW bits returns the last value written to NBLW.

RM0385 Rev 7

639/1709
645

Hash processor (HASH)

21.6.4

RM0385

HASH digest registers (HASH_HR0..7)
These registers contain the message digest result named as follows:
•

HASH_HR0, HASH_HR1, HASH_HR2, HASH_HR3 and HASH_HR4 registers return
the SHA-1 digest result
In this case, the HASH_HR5 to HASH_HR7 register are not used, and they are read as
zero.

•

HASH_HR0, HASH_HR1, HASH_HR2 and HASH_HR3 registers return A, B, C and D
(respectively), as defined by MD5.
In this case, the HASH_HR4 to HASH_HR7 registers are not used, and they are read
as zero.

•

HASH_HR0 to HASH_HR6 registers return the SHA-224 digest result.
In this case, the HASH_HR7 register is not used, and it is read as zero.

•

HASH_HR0 to HASH_HR7 registers return the SHA-256 digest result.

In all cases, the digest most significant bit is stored in HASH_HR0[31] and it is not used.
If a read access to one of these registers is performed while the hash core is calculating an
intermediate digest or a final message digest (that is when the DCAL bit has been written to
1), then the read operation is stalled until the hash calculation completes.
Note:

HASH_HR0, HASH_HR1, HASH_HR2, HASH_HR3 and HASH_HR4 mapping are
duplicated in two memory regions.

HASH_HR0
Address offset: 0x0C and 0x310
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

H0
r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8
H0

r

r

r

r

r

r

r

r

HASH_HR1
Address offset: 0x10 and 0x314
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24
H1

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8
H1

r

640/1709

r

r

r

r

r

r

r

RM0385 Rev 7

RM0385

Hash processor (HASH)

HASH_HR2
Address offset: 0x14 and 0x318
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

23

22

21

20

19

18

17

16

H2

H2
r

r

r

r

r

r

r

HASH_HR3
Address offset: 0x18 and 0x31C
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

23

22

21

20

19

18

17

16

H3

H3
r

r

r

r

r

r

r

HASH_HR4
Address offset: 0x1C and 0x320
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

H4

H4
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

23

22

21

20

19

18

17

16

HASH_HR5
Address offset: 0x324
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

H5

H5
r

r

r

r

r

r

r

r

RM0385 Rev 7

641/1709
645

Hash processor (HASH)

RM0385

HASH_HR6
Address offset: 0x328
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

H6

H6
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

23

22

21

20

19

18

17

16

HASH_HR7
Address offset: 0x32C
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

H7

H7
r

r

r

r

r

r

r

r

Note:

When starting a digest computation for a new bit stream (by writing the INIT bit to 1), these
registers are forced to their reset values.

21.6.5

HASH interrupt enable register (HASH_IMR)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DCIE

DINIE

rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 DCIE: Digest calculation completion interrupt enable
0: Digest calculation completion interrupt disabled
1: Digest calculation completion interrupt enabled.
Bit 0 DINIE: Data input interrupt enable
0: Data input interrupt disabled
1: Data input interrupt enabled

642/1709

RM0385 Rev 7

RM0385

Hash processor (HASH)

21.6.6

HASH status register (HASH_SR)
Address offset: 0x24
Reset value: 0x0000 0001

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BUSY

DMAS

DCIS

DINIS

r

r

rc_w0

rc_w0

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 BUSY: Busy bit
0: No block is currently being processed
1: The hash core is processing a block of data
Bit 2 DMAS: DMA Status
This bit provides information on the DMA interface activity. It is set with DMAE
and cleared when DMAE=0 and no DMA transfer is ongoing. No interrupt is
associated with this bit.
0: DMA interface is disabled (DMAE=0) and no transfer is ongoing
1: DMA interface is enabled (DMAE=1) or a transfer is ongoing
Bit 1 DCIS: Digest calculation completion interrupt status
This bit is set by hardware when a digest becomes ready (the whole message
has been processed). It is cleared by writing it to 0 or by writing the INIT bit to 1
in the HASH_CR register.
0: No digest available in the HASH_HRx registers
1: Digest calculation complete, a digest is available in the HASH_HRx registers.
An interrupt is generated if the DCIE bit is set in the HASH_IMR register.
Bit 0 DINIS: Data input interrupt status
This bit is set by hardware when the input buffer is ready to get a new block (16
locations are free). It is cleared by writing it to 0 or by writing the HASH_DIN
register.
0: Less than 16 locations are free in the input buffer
1: A new block can be entered into the input buffer. An interrupt is generated if
the DINIE bit is set in the HASH_IMR register.

RM0385 Rev 7

643/1709
645

Hash processor (HASH)

21.6.7

RM0385

HASH context swap registers (HASH_CSRx)
These registers contain the complete internal register states of the hash processor. They
are useful when a context swap has to be done because a high-priority task needs to use
the hash processor while it is already used by another task.
When such an event occurs, the HASH_CSRx registers have to be read and the read
values have to be saved in the system memory space. Then the hash processor can be
used by the preemptive task, and when the hash computation is complete, the saved
context can be read from memory and written back into the HASH_CSRx registers.

HASH_CSR0
Address offset: 0x0F8
Reset value: 0x0000 0002
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CS0
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

23

22

21

20

19

18

17

16

CS0

HASH_CSRx (x=1 to 53)
Address offset: 0x0F8 + x * 0x4
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24
CSx

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

CSx

644/1709

RM0385 Rev 7

RM0385

21.6.8

Hash processor (HASH)

HASH register map
Table 142 gives the summary HASH register map and reset values.

0

0

0

0

0

0

0

0

0

0

0

DCAL
Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0xF8
0xFC

0x1CC

0x310
0x314
0x318
0x31C
0x320
0x324
0x328
0x32C

HASH_CSR53
Reset value
HASH_HR0
Reset value
HASH_HR1
Reset value
HASH_HR2
Reset value
HASH_HR3
Reset value
HASH_HR4
Reset value
HASH_HR5
Reset value
HASH_HR6
Reset value
HASH_HR7
Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0 0
...
...

0

0

0

0

0

0

0

0

0

0

0

0 0 0 0
Reserved

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

BUSY

DCIS

DINIS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CSR53
0 0 0
H0
0 0
H1
0 0
H2
0 0
H3
0 0
H4
0 0
H5
0 0
H6
0 0
H7
0 0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CSR0
0 0 0 0
CSR1
0 0 0 0

0
DMAS

Reset value
HASH_CSR0
Reset value
HASH_CSR1
Reset value

Res.

HASH_SR

Res.

0x24

Res.

Reset value

DINIE

0

0

DCIE

0

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

NBLW

Res.

0

Res.

0

H0
0 0
H1
0 0
H2
0 0
H3
0 0
H4
0 0
Res.

0

Res.

0

Res.

HASH_IMR

Res.

0

INIT
Res.

MODE
0

DMAE

ALGO[0]
0

0

Reset value
HASH_HR0
Reset value
HASH_HR1
Reset value
HASH_HR2
Reset value
HASH_HR3
Reset value
HASH_HR4
Reset value

DATATYPE

DINNE

Res.

.MDMAT

Res.

0

0

Res.

0x20

0

0

Res.

0x1C

0

0

Res.

0x18

0

Reset value

Res.

0x14

0

HASH_STR

Res.

0x10

0

NBW

DATAIN

Res.

0x0C

HASH_DIN

Res.

0x08

0

Res.

0x04

0

LKEY
Res.

Res.

Reset value

ALGO[1]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

HASH_CR

Res.

0x00

Res.

Offset Register name

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 142. HASH register map and reset values

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

RM0385 Rev 7

645/1709
645

Advanced-control timers (TIM1/TIM8)

RM0385

22

Advanced-control timers (TIM1/TIM8)

22.1

TIM1/TIM8 introduction
The advanced-control timers (TIM1/TIM8) consist of a 16-bit auto-reload counter driven by a
programmable prescaler.
It may be used for a variety of purposes, including measuring the pulse lengths of input
signals (input capture) or generating output waveforms (output compare, PWM,
complementary PWM with dead-time insertion).
Pulse lengths and waveform periods can be modulated from a few microseconds to several
milliseconds using the timer prescaler and the RCC clock controller prescalers.
The advanced-control (TIM1/TIM8) and general-purpose (TIMy) timers are completely
independent, and do not share any resources. They can be synchronized together as
described in Section 22.3.25: Timer synchronization.

22.2

TIM1/TIM8 main features
TIM1/TIM8 timer features include:

646/1709

•

16-bit up, down, up/down auto-reload counter.

•

16-bit programmable prescaler allowing dividing (also “on the fly”) the counter clock
frequency either by any factor between 1 and 65536.

•

Up to 6 independent channels for:
–

Input Capture (but channels 5 and 6)

–

Output Compare

–

PWM generation (Edge and Center-aligned Mode)

–

One-pulse mode output

•

Complementary outputs with programmable dead-time

•

Synchronization circuit to control the timer with external signals and to interconnect
several timers together.

•

Repetition counter to update the timer registers only after a given number of cycles of
the counter.

•

2 break inputs to put the timer’s output signals in a safe user selectable configuration.

•

Interrupt/DMA generation on the following events:
–

Update: counter overflow/underflow, counter initialization (by software or
internal/external trigger)

–

Trigger event (counter start, stop, initialization or count by internal/external trigger)

–

Input capture

–

Output compare

•

Supports incremental (quadrature) encoder and Hall-sensor circuitry for positioning
purposes

•

Trigger input for external clock or cycle-by-cycle current management

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 149. Advanced-control timer block diagram
Internal clock (CK_INT)

CK_TIM18 from RCC

ETRF
ETRP
Polarity selection &
edgedetector & prescaler

ETR

TIMx_ETR

ITR0
ITR1
ITR2
ITR3

Trigger
controller

TRGO
to other timersto DAC/ADC

Input
filter
TGI

ITR
TRC

TRGI

Slave
controller
mode

Reset, enable, up/down, count

TI1F_ED

Encoder
Interface

TI1FP1
TI2FP2

REP register
U

UI

Auto-reload register

Repetition
counter

Stop, clear or up/down
CK_PSC
XOR
TI1
TIMx_CH1

Input filter &
edge detector

TI1FP1
TI1FP2

CK_CNT
PSC
prescaler
CC1I U
IC1

Prescaler

IC1PS

TRC

+/-

CNT counter
CC1I

Capture/Compare 1 register

CC2I

TIMx_CH2

Input filter &
edge detector

TI2FP1
TI2FP2
TRC

IC2

Prescaler

IC2PS

Capture/Compare 2 register

TIMx_CH3

Input filter &
edge detector

TI3FP3
TI3FP4

IC3

Prescaler

IC3PS

TRC

TIMx_CH4

Input filter &
edge detector

TI4FP3
TI4FP4
TRC

Internal sources

Output
control

OC1
TIMx_CH1N
OC1N
TIMx_CH2

OC2REF
DTG

Output
control

OC2
TIMx_CH2N

CC3I
Capture/Compare 3 register

CC4I
IC4

Prescaler

IC4PS

TIMx_CH3

OC3REF
DTG
CC4I

U
TI4

TIMx_CH1
DTG

OC2N
CC3I U

TI3

DTG registers

OC1REF

CC2I

U
TI2

U

Output
control

OC3
TIMx_CH3N
OC3N

Capture/Compare 4 register

OC4REF

Output OC4
control

Capture/Compare 5 register

OC5REF

Output OC5
control

Capture/Compare 6 register

OC6REF

Output OC6
control

TIMx_CH4

SBIF
BIF

TIMx_BKIN

ETRF
BRK request

Break and Break2 circuitry (1)

B2IF
BRK2 request

TIMx_BKIN2

Notes:
Reg

Preload registers transferred
to active registers on U event
according to control bit
Event
Interrupt & DMA output

MS34408V1

1. See Figure 191: Break and Break2 circuitry overview for details

RM0385 Rev 7

647/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

22.3

TIM1/TIM8 functional description

22.3.1

Time-base unit
The main block of the programmable advanced-control timer is a 16-bit counter with its
related auto-reload register. The counter can count up, down or both up and down. The
counter clock can be divided by a prescaler.
The counter, the auto-reload register and the prescaler register can be written or read by
software. This is true even when the counter is running.
The time-base unit includes:
•

Counter register (TIMx_CNT)

•

Prescaler register (TIMx_PSC)

•

Auto-reload register (TIMx_ARR)

•

Repetition counter register (TIMx_RCR)

The auto-reload register is preloaded. Writing to or reading from the auto-reload register
accesses the preload register. The content of the preload register are transferred into the
shadow register permanently or at each update event (UEV), depending on the auto-reload
preload enable bit (ARPE) in TIMx_CR1 register. The update event is sent when the counter
reaches the overflow (or underflow when downcounting) and if the UDIS bit equals 0 in the
TIMx_CR1 register. It can also be generated by software. The generation of the update
event is described in detailed for each configuration.
The counter is clocked by the prescaler output CK_CNT, which is enabled only when the
counter enable bit (CEN) in TIMx_CR1 register is set (refer also to the slave mode controller
description to get more details on counter enabling).
Note that the counter starts counting 1 clock cycle after setting the CEN bit in the TIMx_CR1
register.

Prescaler description
The prescaler can divide the counter clock frequency by any factor between 1 and 65536. It
is based on a 16-bit counter controlled through a 16-bit register (in the TIMx_PSC register).
It can be changed on the fly as this control register is buffered. The new prescaler ratio is
taken into account at the next update event.
Figure 150 and Figure 151 give some examples of the counter behavior when the prescaler
ratio is changed on the fly:

648/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 150. Counter timing diagram with prescaler division change from 1 to 2

CK_PSC

CEN
Timerclock = CK_CNT

Counter register

F7

F8

F9

FA FB FC

01

00

02

03

Update event (UEV)

Prescaler control register

0

1

Write a new value in TIMx_PSC
Prescaler buffer

0

Prescaler counter

0

1

1

0

0

1

1

0

1

0

MS31076V2

Figure 151. Counter timing diagram with prescaler division change from 1 to 4

CK_PSC
CEN

Timerclock = CK_CNT

Counter register

F7

F8

F9

FA FB FC

00

01

Update event (UEV)

Prescaler control register

0

3

Write a new value in TIMx_PSC
Prescaler buffer

Prescaler counter

0

3

0

0

1

2

3

0

1

2

3
MS31077V2

RM0385 Rev 7

649/1709
740

Advanced-control timers (TIM1/TIM8)

22.3.2

RM0385

Counter modes
Upcounting mode
In upcounting mode, the counter counts from 0 to the auto-reload value (content of the
TIMx_ARR register), then restarts from 0 and generates a counter overflow event.
If the repetition counter is used, the update event (UEV) is generated after upcounting is
repeated for the number of times programmed in the repetition counter register
(TIMx_RCR) + 1. Else the update event is generated at each counter overflow.
Setting the UG bit in the TIMx_EGR register (by software or by using the slave mode
controller) also generates an update event.
The UEV event can be disabled by software by setting the UDIS bit in the TIMx_CR1
register. This is to avoid updating the shadow registers while writing new values in the
preload registers. Then no update event occurs until the UDIS bit has been written to 0.
However, the counter restarts from 0, as well as the counter of the prescaler (but the
prescale rate does not change). In addition, if the URS bit (update request selection) in
TIMx_CR1 register is set, setting the UG bit generates an update event UEV but without
setting the UIF flag (thus no interrupt or DMA request is sent). This is to avoid generating
both update and capture interrupts when clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):
•

The repetition counter is reloaded with the content of TIMx_RCR register,

•

The auto-reload shadow register is updated with the preload value (TIMx_ARR),

•

The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register).

The following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.

650/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 152. Counter timing diagram, internal clock divided by 1

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

32

31

33

34 35 36

00

01

02

03

04

05

06

07

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31078V2

Figure 153. Counter timing diagram, internal clock divided by 2

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0034

0035

0036

0000

0001

0002

0003

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31079V2

RM0385 Rev 7

651/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 154. Counter timing diagram, internal clock divided by 4

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0035

0036

0000

0001

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31080V2

Figure 155. Counter timing diagram, internal clock divided by N

CK_PSC

Timerclock = CK_CNT

Counter register

1F

20

00

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31081V2

652/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 156. Counter timing diagram, update event when ARPE=0 (TIMx_ARR not
preloaded)
CK_PSC

CEN

Timerclock = CK_CNT
Counter register

31

32

33

34

35

36

00

01

02

03

04

05

06

07

Counter overflow

Update event (UEV)

Update interrupt flag (UIF)

Auto-reload preload register

FF

36

Write a new value in TIMx_ARR
MS31082V3

Figure 157. Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded)
CK_PSC

CEN
Timerclock = CK_CNT
Counter register

F0

F1

F2

F3

F4 F5

00

01

02

03

04

05

06

07

Counter overflow
Update event (UEV)

Update interrupt flag
(UIF)
Auto-reload preload
register

F5

36

Auto-reload shadow
register

F5

Write a new value in TIMx_ARR

RM0385 Rev 7

36

MS31083V2

653/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Downcounting mode
In downcounting mode, the counter counts from the auto-reload value (content of the
TIMx_ARR register) down to 0, then restarts from the auto-reload value and generates a
counter underflow event.
If the repetition counter is used, the update event (UEV) is generated after downcounting is
repeated for the number of times programmed in the repetition counter register
(TIMx_RCR) + 1. Else the update event is generated at each counter underflow.
Setting the UG bit in the TIMx_EGR register (by software or by using the slave mode
controller) also generates an update event.
The UEV update event can be disabled by software by setting the UDIS bit in TIMx_CR1
register. This is to avoid updating the shadow registers while writing new values in the
preload registers. Then no update event occurs until UDIS bit has been written to 0.
However, the counter restarts from the current auto-reload value, whereas the counter of the
prescaler restarts from 0 (but the prescale rate doesn’t change).
In addition, if the URS bit (update request selection) in TIMx_CR1 register is set, setting the
UG bit generates an update event UEV but without setting the UIF flag (thus no interrupt or
DMA request is sent). This is to avoid generating both update and capture interrupts when
clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):
•

The repetition counter is reloaded with the content of TIMx_RCR register.

•

The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register).

•

The auto-reload active register is updated with the preload value (content of the
TIMx_ARR register). Note that the auto-reload is updated before the counter is
reloaded, so that the next period is the expected one.

The following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.

654/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 158. Counter timing diagram, internal clock divided by 1

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

04

05

03

02

01 00

36

35

34 33 32

31

30

2F

Counter underflow
(cnt_udf)

Update event (UEV)

Update interrupt flag
(UIF)
MS31184V1

Figure 159. Counter timing diagram, internal clock divided by 2

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0002

0001

0000

0036

0035

0034

0033

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31185V1

RM0385 Rev 7

655/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 160. Counter timing diagram, internal clock divided by 4

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0001

0000

0000

0001

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31186V1

Figure 161. Counter timing diagram, internal clock divided by N

CK_PSC

Timerclock = CK_CNT

Counter register

20

1F

00

36

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31187V1

656/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 162. Counter timing diagram, update event when repetition counter is not used
CK_PSC

CEN

Timerclock = CK_CNT
Counter register

05

04

03

02

01 00

36 35 34

33

32

31 30 2F

Counter underflow

Update event (UEV)
Update interrupt flag
(UIF)
Auto-reload preload
register

FF

36

Write a new value in TIMx_ARR
MS31188V1

Center-aligned mode (up/down counting)
In center-aligned mode, the counter counts from 0 to the auto-reload value (content of the
TIMx_ARR register) – 1, generates a counter overflow event, then counts from the autoreload value down to 1 and generates a counter underflow event. Then it restarts counting
from 0.
Center-aligned mode is active when the CMS bits in TIMx_CR1 register are not equal to
'00'. The Output compare interrupt flag of channels configured in output is set when: the
counter counts down (Center aligned mode 1, CMS = "01"), the counter counts up (Center
aligned mode 2, CMS = "10") the counter counts up and down (Center aligned mode 3,
CMS = "11").
In this mode, the DIR direction bit in the TIMx_CR1 register cannot be written. It is updated
by hardware and gives the current direction of the counter.
The update event can be generated at each counter overflow and at each counter underflow
or by setting the UG bit in the TIMx_EGR register (by software or by using the slave mode
controller) also generates an update event. In this case, the counter restarts counting from
0, as well as the counter of the prescaler.
The UEV update event can be disabled by software by setting the UDIS bit in the TIMx_CR1
register. This is to avoid updating the shadow registers while writing new values in the
preload registers. Then no update event occurs until UDIS bit has been written to 0.
However, the counter continues counting up and down, based on the current auto-reload
value.
In addition, if the URS bit (update request selection) in TIMx_CR1 register is set, setting the
UG bit generates an UEV update event but without setting the UIF flag (thus no interrupt or

RM0385 Rev 7

657/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

DMA request is sent). This is to avoid generating both update and capture interrupts when
clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):
•

The repetition counter is reloaded with the content of TIMx_RCR register

•

The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register)

•

The auto-reload active register is updated with the preload value (content of the
TIMx_ARR register). Note that if the update source is a counter overflow, the autoreload is updated before the counter is reloaded, so that the next period is the expected
one (the counter is loaded with the new value).

The following figures show some examples of the counter behavior for different clock
frequencies.
Figure 163. Counter timing diagram, internal clock divided by 1, TIMx_ARR = 0x6
CK_PSC
CEN

Timerclock = CK_CNT
Counter register

04

03 02

01 00

01

02 03 04 05

06

05 04

03

Counter underflow

Counter overflow

Update event (UEV)
Update interrupt flag (UIF)
MS31189V3

1. Here, center-aligned mode 1 is used (for more details refer to Section 22.4: TIM1/TIM8 registers).

658/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 164. Counter timing diagram, internal clock divided by 2

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0002

0003

0001

0000

0001

0002

0003

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31190V1

Figure 165. Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0034

0035

0036

0035

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)
Note: Here, center_aligned mode 2 or 3 is updated with an UIF on overflow
MS31191V1

RM0385 Rev 7

659/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 166. Counter timing diagram, internal clock divided by N

CK_PSC

Timerclock = CK_CNT

Counter register

1F

20

01

00

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31192V1

Figure 167. Counter timing diagram, update event with ARPE=1 (counter underflow)
CK_PSC

CEN

Timerclock = CK_CNT
Counter register

06

05

04

03

02

01 00

01

02

03

04

05

06

07

Counter underflow
Update event (UEV)
Update interrupt flag
(UIF)
Auto-reload preload
register

FD

36

Write a new value in TIMx_ARR
Auto-reload active
register

FD

36
MS31193V1

660/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 168. Counter timing diagram, Update event with ARPE=1 (counter overflow)
CK_PSC

CEN
Timer clock = CK_CNT
Counter register

F7

F8

F9

FA FB FC 36

35

34

33

32

31

30

2F

Counter overflow
Update event (UEV)

Update interrupt flag
(UIF)
Auto-reload preload
register

FD

36

Write a new value in TIMx_ARR
Auto-reload active
FD
register

36
MS31194V1

22.3.3

Repetition counter
Section 22.3.1: Time-base unit describes how the update event (UEV) is generated with
respect to the counter overflows/underflows. It is actually generated only when the repetition
counter has reached zero. This can be useful when generating PWM signals.
This means that data are transferred from the preload registers to the shadow registers
(TIMx_ARR auto-reload register, TIMx_PSC prescaler register, but also TIMx_CCRx
capture/compare registers in compare mode) every N+1 counter overflows or underflows,
where N is the value in the TIMx_RCR repetition counter register.
The repetition counter is decremented:
•

At each counter overflow in upcounting mode,

•

At each counter underflow in downcounting mode,

•

At each counter overflow and at each counter underflow in center-aligned mode.
Although this limits the maximum number of repetition to 32768 PWM cycles, it makes
it possible to update the duty cycle twice per PWM period. When refreshing compare
registers only once per PWM period in center-aligned mode, maximum resolution is
2xTck, due to the symmetry of the pattern.

The repetition counter is an auto-reload type; the repetition rate is maintained as defined by
the TIMx_RCR register value (refer to Figure 169). When the update event is generated by
software (by setting the UG bit in TIMx_EGR register) or by hardware through the slave
mode controller, it occurs immediately whatever the value of the repetition counter is and the
repetition counter is reloaded with the content of the TIMx_RCR register.

RM0385 Rev 7

661/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

In Center aligned mode, for odd values of RCR, the update event occurs either on the
overflow or on the underflow depending on when the RCR register was written and when
the counter was launched: if the RCR was written before launching the counter, the UEV
occurs on the overflow. If the RCR was written after launching the counter, the UEV occurs
on the underflow.
For example, for RCR = 3, the UEV is generated each 4th overflow or underflow event
depending on when the RCR was written.
Figure 169. Update rate examples depending on mode and TIMx_RCR register settings

Edge-aligned mode

Counter-aligned mode
Upcounting

Counter
TIMx_CNT

TIMx_RCR = 0

TIMx_RCR = 1

TIMx_RCR = 2

TIMx_RCR = 3

TIMx_RCR = 3
and
re-synchronization

UEV

UEV

UEV

UEV

UEV

(by SW)
UEV

Downcounting

(by SW)

(by SW)

Update event: Preload registers transferred to active registers and update interrupt generated
Update Event if the repetition counter underflow occurs when the counter is equal to the auto-reload value.

MSv31195V1

662/1709

RM0385 Rev 7

RM0385

22.3.4

Advanced-control timers (TIM1/TIM8)

External trigger input
The timer features an external trigger input ETR. It can be used as:
•

external clock (external clock mode 2, see Section 22.3.5)

•

trigger for the slave mode (see Section 22.3.25)

•

PWM reset input for cycle-by-cycle current regulation (see Section 22.3.7)

Figure 170 below describes the ETR input conditioning. The input polarity is defined with the
ETP bit in TIMxSMCR register. The trigger can be prescaled with the divider programmed
by the ETPS[1:0] bitfield and digitally filtered with the ETF[3:0] bitfield.
Figure 170. External trigger input block
ETR input

ETR
0
1

Divider
/1, /2, /4, /8

ETP
TIMx_SMCR

ETPS[1:0]
TIMx_SMCR

ETRP
fDTS

RM0385 Rev 7

Filter
downcounter

ETF[3:0]
TIMx_SMCR

To the Output mode controller
To the CK_PSC circuitry
To the Slave mode controller

MS34403V2

663/1709
740

Advanced-control timers (TIM1/TIM8)

22.3.5

RM0385

Clock selection
The counter clock can be provided by the following clock sources:
•

Internal clock (CK_INT)

•

External clock mode1: external input pin

•

External clock mode2: external trigger input ETR

•

Encoder mode

Internal clock source (CK_INT)
If the slave mode controller is disabled (SMS=000), then the CEN, DIR (in the TIMx_CR1
register) and UG bits (in the TIMx_EGR register) are actual control bits and can be changed
only by software (except UG which remains cleared automatically). As soon as the CEN bit
is written to 1, the prescaler is clocked by the internal clock CK_INT.
Figure 171 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.
Figure 171. Control circuit in normal mode, internal clock divided by 1

Internal clock
CEN=CNT_EN

UG

CNT_INIT

Counter clock = CK_CNT = CK_PSC
Counter register

31

32

33

34

35 36

00 01

02

03 04 05

06

07
MS31085V2

External clock source mode 1
This mode is selected when SMS=111 in the TIMx_SMCR register. The counter can count at
each rising or falling edge on a selected input.

664/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 172. TI2 external clock connection example
TIMx_SMCR
TS[2:0]
or TI2F
TI1F
ITRx
TI1_ED
TI1FP1

TI2

Filter

Edge
detector

TI2F_Rising
TI2F_Falling

0
1

TI2FP2
ETRF

or
or

0xx
100

TRGI

101
110
111

ETRF
CK_INT

ICF[3:0]

CC2P

TIMx_CCMR1

TIMx_CCER

(internal clock)

Encoder
mode
External clock
mode 1
External clock
mode 2

CK_PSC

Internal clock
mode

ECE

SMS[2:0]

TIMx_SMCR

MS31196V1

For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:

Note:

1.

Configure channel 2 to detect rising edges on the TI2 input by writing CC2S = ‘01’ in
the TIMx_CCMR1 register.

2.

Configure the input filter duration by writing the IC2F[3:0] bits in the TIMx_CCMR1
register (if no filter is needed, keep IC2F=0000).

3.

Select rising edge polarity by writing CC2P=0 and CC2NP=0 in the TIMx_CCER
register.

4.

Configure the timer in external clock mode 1 by writing SMS=111 in the TIMx_SMCR
register.

5.

Select TI2 as the trigger input source by writing TS=110 in the TIMx_SMCR register.

6.

Enable the counter by writing CEN=1 in the TIMx_CR1 register.

The capture prescaler is not used for triggering, so the user does not need to configure it.
When a rising edge occurs on TI2, the counter counts once and the TIF flag is set.
The delay between the rising edge on TI2 and the actual clock of the counter is due to the
resynchronization circuit on TI2 input.

RM0385 Rev 7

665/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 173. Control circuit in external clock mode 1

TI2
CNT_EN
Counter clock = CK_CNT = CK_PSC
Counter register

34

35

36

TIF

Write TIF=0

MS31087V2

External clock source mode 2
This mode is selected by writing ECE=1 in the TIMx_SMCR register.
The counter can count at each rising or falling edge on the external trigger input ETR.
The Figure 174 gives an overview of the external trigger input block.
Figure 174. External trigger input block

or TI2F
TI1F

ETR

or
or

TRGI
0

ETR pin
1

Divider
/1, /2, /4, /8

ETRP
fDTS

Filter
downcounter

ETRF
CK_INT

ETP

ETPS[1:0]

ETF[3:0]

TIMx_SMCR

TIMx_SMCR

TIMx_SMCR

(internal clock)

Encoder
mode
External clock
mode 1
External clock
mode 2

CK_PSC

Internal clock
mode

ECE

SMS[2:0]

TIMx_SMCR

MS33116V1

For example, to configure the upcounter to count each 2 rising edges on ETR, use the
following procedure:

666/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
1.

As no filter is needed in this example, write ETF[3:0]=0000 in the TIMx_SMCR register.

2.

Set the prescaler by writing ETPS[1:0]=01 in the TIMx_SMCR register

3.

Select rising edge detection on the ETR pin by writing ETP=0 in the TIMx_SMCR
register

4.

Enable external clock mode 2 by writing ECE=1 in the TIMx_SMCR register.

5.

Enable the counter by writing CEN=1 in the TIMx_CR1 register.

The counter counts once each 2 ETR rising edges.
The delay between the rising edge on ETR and the actual clock of the counter is due to the
resynchronization circuit on the ETRP signal.
Figure 175. Control circuit in external clock mode 2

f CK_INT
CNT_EN
ETR

ETRP

ETRF
Counter clock =
CK_INT =CK_PSC
Counter register

34

35

36

MS33111V2

RM0385 Rev 7

667/1709
740

Advanced-control timers (TIM1/TIM8)

22.3.6

RM0385

Capture/compare channels
Each Capture/Compare channel is built around a capture/compare register (including a
shadow register), an input stage for capture (with digital filter, multiplexing, and prescaler,
except for channels 5 and 6) and an output stage (with comparator and output control).
Figure 176 to Figure 179 give an overview of one Capture/Compare channel.
The input stage samples the corresponding TIx input to generate a filtered signal TIxF.
Then, an edge detector with polarity selection generates a signal (TIxFPx) which can be
used as trigger input by the slave mode controller or as the capture command. It is
prescaled before the capture register (ICxPS).
Figure 176. Capture/compare channel (example: channel 1 input stage)

TI1F_ED
To the slave mode controller
TI1
fDTS

TI1F_Rising
Filter
TI1F
downcounter

Edge
detector

TI1F_Falling

0 TI1FP1

01

1
TI2FP1

ICF[3:0]
TIMx_CCMR1

CC1P/CC1NP
TIMx_CCER
TI2F_Rising
0
(from channel 2)
TI2F_Falling
1
(from channel 2)

10

TRC
(from slave mode
controller)

IC1

IC1PS
Divider
/1, /2, /4, /8

11

CC1S[1:0] ICPS[1:0]

CC1E

TIMx_CCMR1

TIMx_CCER

MS33115V1

The output stage generates an intermediate waveform which is then used for reference:
OCxRef (active high). The polarity acts at the end of the chain.

668/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 177. Capture/compare channel 1 main circuit

APB Bus

Read CCR1L

read_in_progress

8
low

Read CCR1H S

high

8

(if 16-bit)

MCU-peripheral interface

Capture/compare preload register

CC1S[0]

R

R
compare_transfer

capture_transfer
CC1S[1]

Input
mode

S write CCR1H

write_in_progress
Output
mode

CC1S[1]
CC1S[0]
OC1PE

Capture/compare shadow register

UEV
Comparator

Capture

IC1PS

write CCR1L

CC1E

CNT>CCR1
Counter

(from time
base unit)

OC1PE

TIM1_CCMR1

CNT=CCR1

CC1G
TIM1_EGR

MS31089V2

Figure 178. Output stage of capture/compare channel (channel 1, idem ch. 2 and 3)

To the master mode
controller
0

ETRF
‘0’
OC1REF
CNT>CCR1 Output
mode
CNT=CCR1
controller

OC1REFC
OC1_DT

Output
selector

Dead-time
generator

x0
01
11

1

Output
enable
circuit

OC1

Output
enable
circuit

OC1N

CC1P
TIM1_CCER

OC1N_DT

(1)

‘0’

OCxREF
OC5REF

11
10
0x

0
1

CC1NE CC1E TIM1_CCER
OC1CE OC1M[3:0]

DTG[7:0]

CC1NE CC1E

CC1NP

MOE OSSI OSSR

TIM1_CCMR1

TIM1_BDTR

TIM1_CCER

TIM1_CCER

TIM1_BDTR

MS35909V1

1. OCxREF, where x is the rank of the complementary channel

RM0385 Rev 7

669/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 179. Output stage of capture/compare channel (channel 4)
To the master
mode controller
ETRF
OC4REFC
OC4REF

‘0’

0

0

1

1

CC4E

CC4P

CNT > CCR4

Output
mode
CNT = CCR4
controller

Output
selector

OC3REF

TIM1_CCER

Output
enable
circuit

TIM1_CCER

CC4E TIM1_CCER
MOE

OC4CE OC4M[3:0]

OC4

TIM1_CCMR2

OSSI TIM1_BDTR

OIS4

TIM1_CR
MS35911V1

Figure 180. Output stage of capture/compare channel (channel 5, idem ch. 6)
To the master
mode controller
ETRF
‘0’
CNT > CCR5

Output
mode
CNT = CCR5
controller

0

0

OC5REF 1

1

CC5E

CC5P

TIM1_CCER

TIM1_CCER

OC5CE OC5M[3:0]

Output
enable
circuit

OC5

(1)

CC5E TIM1_CCER
MOE

OSSI TIM1_BDTR

TIM1_CCMR2
OIS5

TIM1_CR
MS35910V1

1. Not available externally.

The capture/compare block is made of one preload register and one shadow register. Write
and read always access the preload register.
In capture mode, captures are actually done in the shadow register, which is copied into the
preload register.
In compare mode, the content of the preload register is copied into the shadow register
which is compared to the counter.

22.3.7

Input capture mode
In Input capture mode, the Capture/Compare Registers (TIMx_CCRx) are used to latch the
value of the counter after a transition detected by the corresponding ICx signal. When a
capture occurs, the corresponding CCXIF flag (TIMx_SR register) is set and an interrupt or

670/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
a DMA request can be sent if they are enabled. If a capture occurs while the CCxIF flag was
already high, then the over-capture flag CCxOF (TIMx_SR register) is set. CCxIF can be
cleared by software by writing it to ‘0’ or by reading the captured data stored in the
TIMx_CCRx register. CCxOF is cleared when you write it to ‘0’.
The following example shows how to capture the counter value in TIMx_CCR1 when TI1
input rises. To do this, use the following procedure:
1.

Select the active input: TIMx_CCR1 must be linked to the TI1 input, so write the CC1S
bits to 01 in the TIMx_CCMR1 register. As soon as CC1S becomes different from 00,
the channel is configured in input and the TIMx_CCR1 register becomes read-only.

2.

Program the input filter duration you need with respect to the signal you connect to the
timer (when the input is one of the TIx (ICxF bits in the TIMx_CCMRx register). Let’s
imagine that, when toggling, the input signal is not stable during at must 5 internal clock
cycles. We must program a filter duration longer than these 5 clock cycles. We can
validate a transition on TI1 when 8 consecutive samples with the new level have been
detected (sampled at fDTS frequency). Then write IC1F bits to 0011 in the
TIMx_CCMR1 register.

3.

Select the edge of the active transition on the TI1 channel by writing CC1P and CC1NP
bits to 0 in the TIMx_CCER register (rising edge in this case).

4.

Program the input prescaler. In our example, we wish the capture to be performed at
each valid transition, so the prescaler is disabled (write IC1PS bits to ‘00’ in the
TIMx_CCMR1 register).

5.

Enable capture from the counter into the capture register by setting the CC1E bit in the
TIMx_CCER register.

6.

If needed, enable the related interrupt request by setting the CC1IE bit in the
TIMx_DIER register, and/or the DMA request by setting the CC1DE bit in the
TIMx_DIER register.

When an input capture occurs:
•

The TIMx_CCR1 register gets the value of the counter on the active transition.

•

CC1IF flag is set (interrupt flag). CC1OF is also set if at least two consecutive captures
occurred whereas the flag was not cleared.

•

An interrupt is generated depending on the CC1IE bit.

•

A DMA request is generated depending on the CC1DE bit.

In order to handle the overcapture, it is recommended to read the data before the
overcapture flag. This is to avoid missing an overcapture which could happen after reading
the flag and before reading the data.
Note:

IC interrupt and/or DMA requests can be generated by software by setting the
corresponding CCxG bit in the TIMx_EGR register.

22.3.8

PWM input mode
This mode is a particular case of input capture mode. The procedure is the same except:
•

Two ICx signals are mapped on the same TIx input.

•

These 2 ICx signals are active on edges with opposite polarity.

•

One of the two TIxFP signals is selected as trigger input and the slave mode controller
is configured in reset mode.

RM0385 Rev 7

671/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

For example, the user can measure the period (in TIMx_CCR1 register) and the duty cycle
(in TIMx_CCR2 register) of the PWM applied on TI1 using the following procedure
(depending on CK_INT frequency and prescaler value):
1.

Select the active input for TIMx_CCR1: write the CC1S bits to 01 in the TIMx_CCMR1
register (TI1 selected).

2.

Select the active polarity for TI1FP1 (used both for capture in TIMx_CCR1 and counter
clear): write the CC1P and CC1NP bits to ‘0’ (active on rising edge).

3.

Select the active input for TIMx_CCR2: write the CC2S bits to 10 in the TIMx_CCMR1
register (TI1 selected).

4.

Select the active polarity for TI1FP2 (used for capture in TIMx_CCR2): write the CC2P
and CC2NP bits to CC2P/CC2NP=’10’ (active on falling edge).

5.

Select the valid trigger input: write the TS bits to 101 in the TIMx_SMCR register
(TI1FP1 selected).

6.

Configure the slave mode controller in reset mode: write the SMS bits to 0100 in the
TIMx_SMCR register.

7.

Enable the captures: write the CC1E and CC2E bits to ‘1’ in the TIMx_CCER register.
Figure 181. PWM input mode timing

22.3.9

Forced output mode
In output mode (CCxS bits = 00 in the TIMx_CCMRx register), each output compare signal
(OCxREF and then OCx/OCxN) can be forced to active or inactive level directly by software,
independently of any comparison between the output compare register and the counter.
To force an output compare signal (OCXREF/OCx) to its active level, user just needs to
write 0101 in the OCxM bits in the corresponding TIMx_CCMRx register. Thus OCXREF is
forced high (OCxREF is always active high) and OCx get opposite value to CCxP polarity
bit.
For example: CCxP=0 (OCx active high) => OCx is forced to high level.
The OCxREF signal can be forced low by writing the OCxM bits to 0100 in the
TIMx_CCMRx register.

672/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Anyway, the comparison between the TIMx_CCRx shadow register and the counter is still
performed and allows the flag to be set. Interrupt and DMA requests can be sent
accordingly. This is described in the output compare mode section below.

22.3.10

Output compare mode
This function is used to control an output waveform or indicate when a period of time has
elapsed. Channels 1 to 4 can be output, while Channel 5 and 6 are only available inside the
microcontroller (for instance, for compound waveform generation or for ADC triggering).
When a match is found between the capture/compare register and the counter, the output
compare function:
•

Assigns the corresponding output pin to a programmable value defined by the output
compare mode (OCxM bits in the TIMx_CCMRx register) and the output polarity (CCxP
bit in the TIMx_CCER register). The output pin can keep its level (OCXM=0000), be set
active (OCxM=0001), be set inactive (OCxM=0010) or can toggle (OCxM=0011) on
match.

•

Sets a flag in the interrupt status register (CCxIF bit in the TIMx_SR register).

•

Generates an interrupt if the corresponding interrupt mask is set (CCXIE bit in the
TIMx_DIER register).

•

Sends a DMA request if the corresponding enable bit is set (CCxDE bit in the
TIMx_DIER register, CCDS bit in the TIMx_CR2 register for the DMA request
selection).

The TIMx_CCRx registers can be programmed with or without preload registers using the
OCxPE bit in the TIMx_CCMRx register.
In output compare mode, the update event UEV has no effect on OCxREF and OCx output.
The timing resolution is one count of the counter. Output compare mode can also be used to
output a single pulse (in One Pulse mode).

Procedure
1.

Select the counter clock (internal, external, prescaler).

2.

Write the desired data in the TIMx_ARR and TIMx_CCRx registers.

3.

Set the CCxIE bit if an interrupt request is to be generated.

4.

Select the output mode. For example:

5.

–

Write OCxM = 0011 to toggle OCx output pin when CNT matches CCRx

–

Write OCxPE = 0 to disable preload register

–

Write CCxP = 0 to select active high polarity

–

Write CCxE = 1 to enable the output

Enable the counter by setting the CEN bit in the TIMx_CR1 register.

The TIMx_CCRx register can be updated at any time by software to control the output
waveform, provided that the preload register is not enabled (OCxPE=’0’, else TIMx_CCRx
shadow register is updated only at the next update event UEV). An example is given in
Figure 182.

RM0385 Rev 7

673/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 182. Output compare mode, toggle on OC1
Write B201h in the CC1R register

TIM1_CNT

0039

TIM1_CCR1

003B

003A

B200

B201

B201

003A

OC1REF= OC1

Match detected on CCR1
Interrupt generated if enabled
MS31092V1

22.3.11

PWM mode
Pulse Width Modulation mode allows you to generate a signal with a frequency determined
by the value of the TIMx_ARR register and a duty cycle determined by the value of the
TIMx_CCRx register.
The PWM mode can be selected independently on each channel (one PWM per OCx
output) by writing ‘0110’ (PWM mode 1) or ‘0111’ (PWM mode 2) in the OCxM bits in the
TIMx_CCMRx register. You must enable the corresponding preload register by setting the
OCxPE bit in the TIMx_CCMRx register, and eventually the auto-reload preload register (in
upcounting or center-aligned modes) by setting the ARPE bit in the TIMx_CR1 register.
As the preload registers are transferred to the shadow registers only when an update event
occurs, before starting the counter, you have to initialize all the registers by setting the UG
bit in the TIMx_EGR register.
OCx polarity is software programmable using the CCxP bit in the TIMx_CCER register. It
can be programmed as active high or active low. OCx output is enabled by a combination of
the CCxE, CCxNE, MOE, OSSI and OSSR bits (TIMx_CCER and TIMx_BDTR registers).
Refer to the TIMx_CCER register description for more details.
In PWM mode (1 or 2), TIMx_CNT and TIMx_CCRx are always compared to determine
whether TIMx_CCRx ≤ TIMx_CNT or TIMx_CNT ≤ TIMx_CCRx (depending on the direction
of the counter).
The timer is able to generate PWM in edge-aligned mode or center-aligned mode
depending on the CMS bits in the TIMx_CR1 register.

674/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

PWM edge-aligned mode
•

Upcounting configuration
Upcounting is active when the DIR bit in the TIMx_CR1 register is low. Refer to the
Upcounting mode on page 650.
In the following example, we consider PWM mode 1. The reference PWM signal
OCxREF is high as long as TIMx_CNT < TIMx_CCRx else it becomes low. If the
compare value in TIMx_CCRx is greater than the auto-reload value (in TIMx_ARR)
then OCxREF is held at ‘1’. If the compare value is 0 then OCxRef is held at ‘0’.
Figure 183 shows some edge-aligned PWM waveforms in an example where
TIMx_ARR=8.
Figure 183. Edge-aligned PWM waveforms (ARR=8)

0

Counter register

CCRx=4

1

2

3

4

5

6

7

8

0

1

OCXREF
CCxIF

OCXREF
CCRx=8
CCxIF

OCXREF

‘1’

CCRx>8
CCxIF

OCXREF

‘0’

CCRx=0
CCxIF

MS31093V1

•

Downcounting configuration
Downcounting is active when DIR bit in TIMx_CR1 register is high. Refer to the
Downcounting mode on page 654
In PWM mode 1, the reference signal OCxRef is low as long as
TIMx_CNT > TIMx_CCRx else it becomes high. If the compare value in TIMx_CCRx is
greater than the auto-reload value in TIMx_ARR, then OCxREF is held at ‘1’. 0% PWM
is not possible in this mode.

PWM center-aligned mode
Center-aligned mode is active when the CMS bits in TIMx_CR1 register are different from
‘00’ (all the remaining configurations having the same effect on the OCxRef/OCx signals).
The compare flag is set when the counter counts up, when it counts down or both when it
counts up and down depending on the CMS bits configuration. The direction bit (DIR) in the

RM0385 Rev 7

675/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

TIMx_CR1 register is updated by hardware and must not be changed by software. Refer to
the Center-aligned mode (up/down counting) on page 657.
Figure 184 shows some center-aligned PWM waveforms in an example where:
•

TIMx_ARR=8,

•

PWM mode is the PWM mode 1,

•

The flag is set when the counter counts down corresponding to the center-aligned
mode 1 selected for CMS=01 in TIMx_CR1 register.
Figure 184. Center-aligned PWM waveforms (ARR=8)
Counter register

0

1

2

3

4

5

6

7

8

7

6

5

4

3

2

1

0

1

OCxREF
CCRx = 4
CMS=01
CMS=10
CMS=11

CCxIF

OCxREF
CCRx=7

CMS=10 or 11

CCxIF
OCxREF

‘1’

CCRx=8
CMS=01
CMS=10
CMS=11

CCxIF

OCxREF
CCRx>8

‘1’

CMS=01
CMS=10
CMS=11

CCxIF

OCxREF
CCRx=0
CCxIF

‘0’

CMS=01
CMS=10
CMS=11

AI14681b

Hints on using center-aligned mode
•

676/1709

When starting in center-aligned mode, the current up-down configuration is used. It
means that the counter counts up or down depending on the value written in the DIR bit

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
in the TIMx_CR1 register. Moreover, the DIR and CMS bits must not be changed at the
same time by the software.
•

•

22.3.12

Writing to the counter while running in center-aligned mode is not recommended as it
can lead to unexpected results. In particular:
–

The direction is not updated if you write a value in the counter that is greater than
the auto-reload value (TIMx_CNT>TIMx_ARR). For example, if the counter was
counting up, it continues to count up.

–

The direction is updated if you write 0 or write the TIMx_ARR value in the counter
but no Update Event UEV is generated.

The safest way to use center-aligned mode is to generate an update by software
(setting the UG bit in the TIMx_EGR register) just before starting the counter and not to
write the counter while it is running.

Asymmetric PWM mode
Asymmetric mode allows two center-aligned PWM signals to be generated with a
programmable phase shift. While the frequency is determined by the value of the
TIMx_ARR register, the duty cycle and the phase-shift are determined by a pair of
TIMx_CCRx register. One register controls the PWM during up-counting, the second during
down counting, so that PWM is adjusted every half PWM cycle:
–

OC1REFC (or OC2REFC) is controlled by TIMx_CCR1 and TIMx_CCR2

–

OC3REFC (or OC4REFC) is controlled by TIMx_CCR3 and TIMx_CCR4

Asymmetric PWM mode can be selected independently on two channel (one OCx output
per pair of CCR registers) by writing ‘1110’ (Asymmetric PWM mode 1) or ‘1111’
(Asymmetric PWM mode 2) in the OCxM bits in the TIMx_CCMRx register.
Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
When a given channel is used as asymmetric PWM channel, its complementary channel
can also be used. For instance, if an OC1REFC signal is generated on channel 1
(Asymmetric PWM mode 1), it is possible to output either the OC2REF signal on channel 2,
or an OC2REFC signal resulting from asymmetric PWM mode 1.
Figure 185 represents an example of signals that can be generated using Asymmetric PWM
mode (channels 1 to 4 are configured in Asymmetric PWM mode 1). Together with the
deadtime generator, this allows a full-bridge phase-shifted DC to DC converter to be
controlled.

RM0385 Rev 7

677/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 185. Generation of 2 phase-shifted PWM signals with 50% duty cycle
Counter register

0

1

2

3

4

5

6

7

8

7

6

5

4

3

2

1

0

1

OC1REFC
CCR1=0
CCR2=8
OC3REFC
CCR3=3
CCR4=5

MS33117V1

22.3.13

Combined PWM mode
Combined PWM mode allows two edge or center-aligned PWM signals to be generated with
programmable delay and phase shift between respective pulses. While the frequency is
determined by the value of the TIMx_ARR register, the duty cycle and delay are determined
by the two TIMx_CCRx registers. The resulting signals, OCxREFC, are made of an OR or
AND logical combination of two reference PWMs:
–

OC1REFC (or OC2REFC) is controlled by TIMx_CCR1 and TIMx_CCR2

–

OC3REFC (or OC4REFC) is controlled by TIMx_CCR3 and TIMx_CCR4

Combined PWM mode can be selected independently on two channels (one OCx output per
pair of CCR registers) by writing ‘1100’ (Combined PWM mode 1) or ‘1101’ (Combined PWM
mode 2) in the OCxM bits in the TIMx_CCMRx register.
When a given channel is used as combined PWM channel, its complementary channel must
be configured in the opposite PWM mode (for instance, one in Combined PWM mode 1 and
the other in Combined PWM mode 2).
Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
Figure 186 represents an example of signals that can be generated using Asymmetric PWM
mode, obtained with the following configuration:

678/1709

–

Channel 1 is configured in Combined PWM mode 2,

–

Channel 2 is configured in PWM mode 1,

–

Channel 3 is configured in Combined PWM mode 2,

–

Channel 4 is configured in PWM mode 1.

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 186. Combined PWM mode on channel 1 and 3

OC2’
OC1’

OC2
OC1
OC1REF
OC2REF
OC1REF’
OC2REF’

OC1REFC
OC1REFC’

OC1REFC = OC1REF AND OC2REF
OC1REFC’ = OC1REF’ OR OC2REF’

MS31094V1

22.3.14

Combined 3-phase PWM mode
Combined 3-phase PWM mode allows one to three center-aligned PWM signals to be
generated with a single programmable signal ANDed in the middle of the pulses. The
OC5REF signal is used to define the resulting combined signal. The 3-bits GC5C[3:1] in the
TIMx_CCR5 allow selection on which reference signal the OC5REF is combined. The
resulting signals, OCxREFC, are made of an AND logical combination of two reference
PWMs:
–

If GC5C1 is set, OC1REFC is controlled by TIMx_CCR1 and TIMx_CCR5

–

If GC5C2 is set, OC2REFC is controlled by TIMx_CCR2 and TIMx_CCR5

–

If GC5C3 is set, OC3REFC is controlled by TIMx_CCR3 and TIMx_CCR5

Combined 3-phase PWM mode can be selected independently on channels 1 to 3 by setting
at least one of the 3-bits GC5C[3:1].

RM0385 Rev 7

679/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 187. 3-phase combined PWM signals with multiple trigger pulses per period
ARR
OC5
OC6
OC1
OC4
OC2
OC3
Counter
OC5ref
OC1refC

GC5C[3:0]

OC2refC
OC3refC
Preload
Active

xxx

100
001

xxx
100

OC4ref
OC6ref
TRGO2

MS33102V1

The TRGO2 waveform shows how the ADC can be synchronized on given 3-phase PWM
signals. Refer to Section 22.3.26: ADC synchronization for more details.

22.3.15

Complementary outputs and dead-time insertion
The advanced-control timers (TIM1/TIM8) can output two complementary signals and
manage the switching-off and the switching-on instants of the outputs.
This time is generally known as dead-time and you have to adjust it depending on the
devices you have connected to the outputs and their characteristics (intrinsic delays of levelshifters, delays due to power switches...)
You can select the polarity of the outputs (main output OCx or complementary OCxN)
independently for each output. This is done by writing to the CCxP and CCxNP bits in the
TIMx_CCER register.
The complementary signals OCx and OCxN are activated by a combination of several
control bits: the CCxE and CCxNE bits in the TIMx_CCER register and the MOE, OISx,
OISxN, OSSI and OSSR bits in the TIMx_BDTR and TIMx_CR2 registers. Refer to
Table 146: Output control bits for complementary OCx and OCxN channels with break
feature on page 725 for more details. In particular, the dead-time is activated when
switching to the idle state (MOE falling down to 0).

680/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Dead-time insertion is enabled by setting both CCxE and CCxNE bits, and the MOE bit if the
break circuit is present. There is one 10-bit dead-time generator for each channel. From a
reference waveform OCxREF, it generates 2 outputs OCx and OCxN. If OCx and OCxN are
active high:
•

The OCx output signal is the same as the reference signal except for the rising edge,
which is delayed relative to the reference rising edge.

•

The OCxN output signal is the opposite of the reference signal except for the rising
edge, which is delayed relative to the reference falling edge.

If the delay is greater than the width of the active output (OCx or OCxN) then the
corresponding pulse is not generated.
The following figures show the relationships between the output signals of the dead-time
generator and the reference signal OCxREF. (we suppose CCxP=0, CCxNP=0, MOE=1,
CCxE=1 and CCxNE=1 in these examples)
Figure 188. Complementary output with dead-time insertion

OCxREF
OCx
delay
OCxN
delay

MS31095V1

Figure 189. Dead-time waveforms with delay greater than the negative pulse

OCxREF
OCx
delay
OCxN

MS31096V1

RM0385 Rev 7

681/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 190. Dead-time waveforms with delay greater than the positive pulse

OCxREF
OCx
OCxN
delay

MS31097V1

The dead-time delay is the same for each of the channels and is programmable with the
DTG bits in the TIMx_BDTR register. Refer to Section 22.4.18: TIM1/TIM8 break and deadtime register (TIMx_BDTR) for delay calculation.

Re-directing OCxREF to OCx or OCxN
In output mode (forced, output compare or PWM), OCxREF can be re-directed to the OCx
output or to OCxN output by configuring the CCxE and CCxNE bits in the TIMx_CCER
register.
This allows you to send a specific waveform (such as PWM or static active level) on one
output while the complementary remains at its inactive level. Other alternative possibilities
are to have both outputs at inactive level or both outputs active and complementary with
dead-time.
Note:

When only OCxN is enabled (CCxE=0, CCxNE=1), it is not complemented and becomes
active as soon as OCxREF is high. For example, if CCxNP=0 then OCxN=OCxRef. On the
other hand, when both OCx and OCxN are enabled (CCxE=CCxNE=1) OCx becomes
active when OCxREF is high whereas OCxN is complemented and becomes active when
OCxREF is low.

22.3.16

Using the break function
The purpose of the break function is to protect power switches driven by PWM signals
generated with the TIM1 and TIM8 timers. The two break inputs are usually connected to
fault outputs of power stages and 3-phase inverters. When activated, the break circuitry
shuts down the PWM outputs and forces them to a predefined safe state. A number of
internal MCU events can also be selected to trigger an output shut-down.
The break features two channels. A break channel which gathers both system-level fault
(clock failure,...) and application fault (from input pins), and can force the outputs to a
predefined level (either active or inactive) after a deadtime duration. A break2 channel which
only includes application faults and is able to force the outputs to an inactive state.

682/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
The output enable signal and output levels during break are depending on several control
bits:
–

the MOE bit in TIMx_BDTR register allows to enable /disable the outputs by
software and is reset in case of break or break2 event.

–

the OSSI bit in the TIMx_BDTR register defines whether the timer controls the
output in inactive state or releases the control to the GPIO controller (typically to
have it in Hi-Z mode)

–

the OISx and OISxN bits in the TIMx_CR2 register which are setting the output
shut-down level, either active or inactive. The OCx and OCxN outputs cannot be
set both to active level at a given time, whatever the OISx and OISxN values.
Refer to Table 146: Output control bits for complementary OCx and OCxN
channels with break feature on page 725 for more details.

When exiting from reset, the break circuit is disabled and the MOE bit is low. You can enable
the break functions by setting the BKE and BKE2 bits in the TIMx_BDTR register. The break
input polarities can be selected by configuring the BKP and BKP2 bits in the same register.
BKEx and BKPx can be modified at the same time. When the BKEx and BKPx bits are
written, a delay of 1 APB clock cycle is applied before the writing is effective. Consequently,
it is necessary to wait 1 APB clock period to correctly read back the bit after the write
operation.
Because MOE falling edge can be asynchronous, a resynchronization circuit has been
inserted between the actual signal (acting on the outputs) and the synchronous control bit
(accessed in the TIMx_BDTR register). It results in some delays between the asynchronous
and the synchronous signals. In particular, if you write MOE to 1 whereas it was low, you
must insert a delay (dummy instruction) before reading it correctly. This is because you write
the asynchronous signal and read the synchronous signal.
The break (BRK) event can be generated by two sources of events ORed together:
•

An external source connected to one of the BKIN pin (as per selection done in the
AFIO controller)

•

An internal source: clock failure event generated by the CSS detector

The break2 (BRK2) can be generated by an external source connected to one of the BKIN2
pin (as per selection done in the AFIO controller).
Break events can also be generated by software using BG and B2G bits in the TIMx_EGR
register. The software break generation using BG and BG2 is active whatever the BKE and
BKE2 enable bits values.

RM0385 Rev 7

683/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 191. Break and Break2 circuitry overview
System break requests

SBIF flag

CSS

Software break requests: BG
BIF flag
BKE
BKF[3:0]
BKIN inputs
from AF
controller

BKP

BRK request

Filter

Application break requests

Software break requests: BG2
B2IF flag
BK2E
BK2F[3:0]
BKIN2 inputs
from AF
controller

BK2P
BRK2 request

Filter

Application break requests

MSv37533V2

Note:

An asynchronous (clockless) operation is only guaranteed when the programmable filter is
disabled. If it is enabled, a fail safe clock mode (for example by using the internal PLL and/or
the CSS) must be used to guarantee that break events are handled.
When one of the breaks occurs (selected level on one of the break inputs):

684/1709

•

The MOE bit is cleared asynchronously, putting the outputs in inactive state, idle state
or even releasing the control to the GPIO controller (selected by the OSSI bit). This
feature is enabled even if the MCU oscillator is off.

•

Each output channel is driven with the level programmed in the OISx bit in the
TIMx_CR2 register as soon as MOE=0. If OSSI=0, the timer releases the output control
(taken over by the GPIO controller), otherwise the enable output remains high.

•

When complementary outputs are used:
–

The outputs are first put in inactive state (depending on the polarity). This is done
asynchronously so that it works even if no clock is provided to the timer.

–

If the timer clock is still present, then the dead-time generator is reactivated in
order to drive the outputs with the level programmed in the OISx and OISxN bits
after a dead-time. Even in this case, OCx and OCxN cannot be driven to their

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
active level together. Note that because of the resynchronization on MOE, the
dead-time duration is slightly longer than usual (around 2 ck_tim clock cycles).
–

Note:

If OSSI=0, the timer releases the output control (taken over by the GPIO controller
which forces a Hi-Z state), otherwise the enable outputs remain or become high as
soon as one of the CCxE or CCxNE bits is high.

•

The break status flag (SBIF, BIF and B2IF bits in the TIMx_SR register) is set. An
interrupt is generated if the BIE bit in the TIMx_DIER register is set. A DMA request
can be sent if the BDE bit in the TIMx_DIER register is set.

•

If the AOE bit in the TIMx_BDTR register is set, the MOE bit is automatically set again
at the next update event (UEV). As an example, this can be used to perform a
regulation. Otherwise, MOE remains low until the application sets it to ‘1’ again. In this
case, it can be used for security and you can connect the break input to an alarm from
power drivers, thermal sensors or any security components.

The break inputs are active on level. Thus, the MOE cannot be set while the break input is
active (neither automatically nor by software). In the meantime, the status flag BIF and B2IF
cannot be cleared.
In addition to the break input and the output management, a write protection has been
implemented inside the break circuit to safeguard the application. It allows to freeze the
configuration of several parameters (dead-time duration, OCx/OCxN polarities and state
when disabled, OCxM configurations, break enable and polarity). The application can
choose from 3 levels of protection selected by the LOCK bits in the TIMx_BDTR register.
Refer to Section 22.4.18: TIM1/TIM8 break and dead-time register (TIMx_BDTR). The
LOCK bits can be written only once after an MCU reset.
Figure 192 shows an example of behavior of the outputs in response to a break.

RM0385 Rev 7

685/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 192. Various output behavior in response to a break event on BRK (OSSI = 1)
BREAK (MOE

)

OCxREF

OCx
(OCxN not implemented, CCxP=0, OISx=1)

OCx
(OCxN not implemented, CCxP=0, OISx=0)

OCx
(OCxN not implemented, CCxP=1, OISx=1)

OCx
(OCxN not implemented, CCxP=1, OISx=0)

OCx
delay
delay
OCxN
(CCxE=1, CCxP=0, OISx=0, CCxNE=1, CCxNP=0, OISxN=1)

delay

OCx
delay
delay
OCxN
(CCxE=1, CCxP=0, OISx=1, CCxNE=1, CCxNP=1, OISxN=1)

delay

OCx
OCxN
(CCxE=1, CCxP=0, OISx=0, CCxNE=0, CCxNP=0, OISxN=1)

delay

OCx
OCxN
(CCxE=1, CCxP=0, OISx=1, CCxNE=0, CCxNP=0, OISxN=0)

delay

OCx
OCxN
(CCxE=1, CCxP=0, CCxNE=0, CCxNP=0, OISx=OISxN=0 or OISx=OISxN=1)

MS31098V1

686/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
The two break inputs have different behaviors on timer outputs:
–

The BRK input can either disable (inactive state) or force the PWM outputs to a
predefined safe state.

–

BRK2 can only disable (inactive state) the PWM outputs.

The BRK has a higher priority than BRK2 input, as described in Table 143.
Note:

BRK2 must only be used with OSSR = OSSI = 1.
Table 143. Behavior of timer outputs versus BRK/BRK2 inputs
Typical use case
BRK2

Timer outputs
state

Active

Inactive

BRK

OCxN output
(low side switches)

OCx output
(high side switches)

X

– Inactive then
forced output
state (after a
deadtime)
– Outputs disabled
if OSSI = 0
(control taken
over by GPIO
logic)

ON after deadtime
insertion

OFF

Active

Inactive

OFF

OFF

Figure 193 gives an example of OCx and OCxN output behavior in case of active signals on
BRK and BRK2 inputs. In this case, both outputs have active high polarities (CCxP =
CCxNP = 0 in TIMx_CCER register).
Figure 193. PWM output state following BRK and BRK2 pins assertion (OSSI=1)
BRK2

BRK
OCx
Deadtime

Deadtime

I/O state

Active

Inactive

Idle
MS34106V1

RM0385 Rev 7

687/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 194. PWM output state following BRK assertion (OSSI=0)
BRK

I/O state defined by the GPIO controller (HI-Z)

OCx
Deadtime

I/O state defined by the GPIO controller (HI-Z)

I/O state

Active

Inactive

Disabled
MS34107V1

22.3.17

Clearing the OCxREF signal on an external event
The OCxREF signal for a given channel can be driven low by applying a high level to the
ETRF input (OCxCE enable bit of the corresponding TIMx_CCMRx register set to ‘1’). The
OCxREF signal remains low until the next update event, UEV, occurs.
When ETRF is chosen, ETR must be configured as follows:
1.

The External Trigger Prescaler should be kept off: bits ETPS[1:0] of the TIMx_SMCR
register set to ‘00’.

2.

The external clock mode 2 must be disabled: bit ECE of the TIMx_SMCR register set to
‘0’.

3.

The External Trigger Polarity (ETP) and the External Trigger Filter (ETF) can be
configured according to the user needs.

Figure 195 shows the behavior of the OCxREF signal when the ETRF Input becomes High,
for both values of the enable bit OCxCE. In this example, the timer TIMx is programmed in
PWM mode.

688/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 195. Clearing TIMx OCxREF

(CCRx)
Counter (CNT)

ETRF

OCxREF
(OCxCE = ‘0’)
OCxREF
(OCxCE = ‘1’)

ocref_clr_int
becomes high

ocref_clr_int
still high
MS33105V2

Note:

In case of a PWM with a 100% duty cycle (if CCRx>ARR), then OCxREF is enabled again at
the next counter overflow.

RM0385 Rev 7

689/1709
740

Advanced-control timers (TIM1/TIM8)

22.3.18

RM0385

6-step PWM generation
When complementary outputs are used on a channel, preload bits are available on the
OCxM, CCxE and CCxNE bits. The preload bits are transferred to the shadow bits at the
COM commutation event. Thus you can program in advance the configuration for the next
step and change the configuration of all the channels at the same time. COM can be
generated by software by setting the COM bit in the TIMx_EGR register or by hardware (on
TRGI rising edge).
A flag is set when the COM event occurs (COMIF bit in the TIMx_SR register), which can
generate an interrupt (if the COMIE bit is set in the TIMx_DIER register) or a DMA request
(if the COMDE bit is set in the TIMx_DIER register).
The Figure 196 describes the behavior of the OCx and OCxN outputs when a COM event
occurs, in 3 different examples of programmed configurations.
Figure 196. 6-step generation, COM example (OSSR=1)

690/1709

RM0385 Rev 7

RM0385

One-pulse mode
One-pulse mode (OPM) is a particular case of the previous modes. It allows the counter to
be started in response to a stimulus and to generate a pulse with a programmable length
after a programmable delay.
Starting the counter can be controlled through the slave mode controller. Generating the
waveform can be done in output compare mode or PWM mode. You select One-pulse mode
by setting the OPM bit in the TIMx_CR1 register. This makes the counter stop automatically
at the next update event UEV.
A pulse can be correctly generated only if the compare value is different from the counter
initial value. Before starting (when the timer is waiting for the trigger), the configuration must
be:
•

In upcounting: CNT < CCRx ≤ ARR (in particular, 0 < CCRx)

•

In downcounting: CNT > CCRx
Figure 197. Example of one pulse mode.
TI2
OC1REF
OC1

TIM1_ARR
Counter

22.3.19

Advanced-control timers (TIM1/TIM8)

TIM1_CCR1

0
tDELAY

tPULSE

t

MS31099V1

For example you may want to generate a positive pulse on OC1 with a length of tPULSE and
after a delay of tDELAY as soon as a positive edge is detected on the TI2 input pin.
Let’s use TI2FP2 as trigger 1:
1.

Map TI2FP2 to TI2 by writing CC2S=’01’ in the TIMx_CCMR1 register.

2.

TI2FP2 must detect a rising edge, write CC2P=’0’ and CC2NP=’0’ in the TIMx_CCER
register.

3.

Configure TI2FP2 as trigger for the slave mode controller (TRGI) by writing TS=110 in
the TIMx_SMCR register.

4.

TI2FP2 is used to start the counter by writing SMS to ‘110’ in the TIMx_SMCR register
(trigger mode).

RM0385 Rev 7

691/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

The OPM waveform is defined by writing the compare registers (taking into account the
clock frequency and the counter prescaler).
•

The tDELAY is defined by the value written in the TIMx_CCR1 register.

•

The tPULSE is defined by the difference between the auto-reload value and the compare
value (TIMx_ARR - TIMx_CCR1).

•

Let’s say you want to build a waveform with a transition from ‘0’ to ‘1’ when a compare
match occurs and a transition from ‘1’ to ‘0’ when the counter reaches the auto-reload
value. To do this you enable PWM mode 2 by writing OC1M=111 in the TIMx_CCMR1
register. You can optionally enable the preload registers by writing OC1PE=’1’ in the
TIMx_CCMR1 register and ARPE in the TIMx_CR1 register. In this case you have to
write the compare value in the TIMx_CCR1 register, the auto-reload value in the
TIMx_ARR register, generate an update by setting the UG bit and wait for external
trigger event on TI2. CC1P is written to ‘0’ in this example.

In our example, the DIR and CMS bits in the TIMx_CR1 register should be low.
You only want 1 pulse (Single mode), so you write '1 in the OPM bit in the TIMx_CR1
register to stop the counter at the next update event (when the counter rolls over from the
auto-reload value back to 0). When OPM bit in the TIMx_CR1 register is set to '0', so the
Repetitive Mode is selected.
Particular case: OCx fast enable:
In One-pulse mode, the edge detection on TIx input set the CEN bit which enables the
counter. Then the comparison between the counter and the compare value makes the
output toggle. But several clock cycles are needed for these operations and it limits the
minimum delay tDELAY min we can get.
If you want to output a waveform with the minimum delay, you can set the OCxFE bit in the
TIMx_CCMRx register. Then OCxRef (and OCx) are forced in response to the stimulus,
without taking in account the comparison. Its new level is the same as if a compare match
had occurred. OCxFE acts only if the channel is configured in PWM1 or PWM2 mode.

22.3.20

Retriggerable one pulse mode (OPM)
This mode allows the counter to be started in response to a stimulus and to generate a
pulse with a programmable length, but with the following differences with Non-retriggerable
one pulse mode described in Section 22.3.19:
–

The pulse starts as soon as the trigger occurs (no programmable delay)

–

The pulse is extended if a new trigger occurs before the previous one is completed

The timer must be in Slave mode, with the bits SMS[3:0] = ‘1000’ (Combined Reset + trigger
mode) in the TIMx_SMCR register, and the OCxM[3:0] bits set to ‘1000’ or ‘1001’ for
Retrigerrable OPM mode 1 or 2.
If the timer is configured in Up-counting mode, the corresponding CCRx must be set to 0
(the ARR register sets the pulse length). If the timer is configured in Down-counting mode,
CCRx must be above or equal to ARR.
Note:

The OCxM[3:0] and SMS[3:0] bit fields are split into two parts for compatibility reasons, the
most significant bit are not contiguous with the 3 least significant ones.
This mode must not be used with center-aligned PWM modes. It is mandatory to have
CMS[1:0] = 00 in TIMx_CR1.

692/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 198. Retriggerable one pulse mode
TRGI

Counter

Output

MS33106V1

22.3.21

Encoder interface mode
To select Encoder Interface mode write SMS=‘001’ in the TIMx_SMCR register if the
counter is counting on TI2 edges only, SMS=’010’ if it is counting on TI1 edges only and
SMS=’011’ if it is counting on both TI1 and TI2 edges.
Select the TI1 and TI2 polarity by programming the CC1P and CC2P bits in the TIMx_CCER
register. When needed, you can program the input filter as well. CC1NP and CC2NP must
be kept low.
The two inputs TI1 and TI2 are used to interface to an quadrature encoder. Refer to
Table 144. The counter is clocked by each valid transition on TI1FP1 or TI2FP2 (TI1 and TI2
after input filter and polarity selection, TI1FP1=TI1 if not filtered and not inverted,
TI2FP2=TI2 if not filtered and not inverted) assuming that it is enabled (CEN bit in
TIMx_CR1 register written to ‘1’). The sequence of transitions of the two inputs is evaluated
and generates count pulses as well as the direction signal. Depending on the sequence the
counter counts up or down, the DIR bit in the TIMx_CR1 register is modified by hardware
accordingly. The DIR bit is calculated at each transition on any input (TI1 or TI2), whatever
the counter is counting on TI1 only, TI2 only or both TI1 and TI2.
Encoder interface mode acts simply as an external clock with direction selection. This
means that the counter just counts continuously between 0 and the auto-reload value in the
TIMx_ARR register (0 to ARR or ARR down to 0 depending on the direction). So you must
configure TIMx_ARR before starting. In the same way, the capture, compare, repetition
counter, trigger output features continue to work as normal. Encoder mode and External
clock mode 2 are not compatible and must not be selected together.

Note:

The prescaler must be set to zero when encoder mode is enabled
In this mode, the counter is modified automatically following the speed and the direction of
the quadrature encoder and its content, therefore, always represents the encoder’s position.
The count direction correspond to the rotation direction of the connected sensor. The table
summarizes the possible combinations, assuming TI1 and TI2 don’t switch at the same
time.

RM0385 Rev 7

693/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Table 144. Counting direction versus encoder signals

Active edge

Level on
opposite
signal (TI1FP1
for TI2,
TI2FP2 for
TI1)

TI1FP1 signal

TI2FP2 signal

Rising

Falling

Rising

Falling

Counting on
TI1 only

High

Down

Up

No Count

No Count

Low

Up

Down

No Count

No Count

Counting on
TI2 only

High

No Count

No Count

Up

Down

Low

No Count

No Count

Down

Up

Counting on
TI1 and TI2

High

Down

Up

Up

Down

Low

Up

Down

Down

Up

A quadrature encoder can be connected directly to the MCU without external interface logic.
However, comparators are normally be used to convert the encoder’s differential outputs to
digital signals. This greatly increases noise immunity. The third encoder output which
indicate the mechanical zero position, may be connected to an external interrupt input and
trigger a counter reset.
The Figure 199 gives an example of counter operation, showing count signal generation
and direction control. It also shows how input jitter is compensated where both edges are
selected. This might occur if the sensor is positioned near to one of the switching points. For
this example we assume that the configuration is the following:
•

CC1S=’01’ (TIMx_CCMR1 register, TI1FP1 mapped on TI1).

•

CC2S=’01’ (TIMx_CCMR2 register, TI1FP2 mapped on TI2).

•

CC1P=’0’ and CC1NP=’0’ (TIMx_CCER register, TI1FP1 non-inverted, TI1FP1=TI1).

•

CC2P=’0’ and CC2NP=’0’ (TIMx_CCER register, TI1FP2 non-inverted, TI1FP2= TI2).

•

SMS=’011’ (TIMx_SMCR register, both inputs are active on both rising and falling
edges).

•

CEN=’1’ (TIMx_CR1 register, Counter enabled).
Figure 199. Example of counter operation in encoder interface mode.
forward

jitter

backward

jitter

forward

TI1
TI2

Counter

up

down

up

MS33107V1

694/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Figure 200 gives an example of counter behavior when TI1FP1 polarity is inverted (same
configuration as above except CC1P=’1’).
Figure 200. Example of encoder interface mode with TI1FP1 polarity inverted.
forward

jitter

backward

jitter

forward

TI1
TI2

Counter

down

up

down

MS33108V1

The timer, when configured in Encoder Interface mode provides information on the sensor’s
current position. You can obtain dynamic information (speed, acceleration, deceleration) by
measuring the period between two encoder events using a second timer configured in
capture mode. The output of the encoder which indicates the mechanical zero can be used
for this purpose. Depending on the time between two events, the counter can also be read
at regular times. You can do this by latching the counter value into a third input capture
register if available (then the capture signal must be periodic and can be generated by
another timer). when available, it is also possible to read its value through a DMA request.
The IUFREMAP bit in the TIMx_CR1 register forces a continuous copy of the update
interrupt flag (UIF) into the timer counter register’s bit 31 (TIMxCNT[31]). This allows both
the counter value and a potential roll-over condition signaled by the UIFCPY flag to be read
in an atomic way. It eases the calculation of angular speed by avoiding race conditions
caused, for instance, by a processing shared between a background task (counter reading)
and an interrupt (update interrupt).
There is no latency between the UIF and UIFCPY flag assertions.
In 32-bit timer implementations, when the IUFREMAP bit is set, bit 31 of the counter is
overwritten by the UIFCPY flag upon read access (the counter’s most significant bit is only
accessible in write mode).

22.3.22

UIF bit remapping
The IUFREMAP bit in the TIMx_CR1 register forces a continuous copy of the Update
Interrupt Flag UIF into the timer counter register’s bit 31 (TIMxCNT[31]). This allows both
the counter value and a potential roll-over condition signaled by the UIFCPY flag to be read
in an atomic way. In particular cases, it can ease the calculations by avoiding race
conditions, caused for instance by a processing shared between a background task
(counter reading) and an interrupt (Update Interrupt).
There is no latency between the UIF and UIFCPY flags assertion.

RM0385 Rev 7

695/1709
740

Advanced-control timers (TIM1/TIM8)

22.3.23

RM0385

Timer input XOR function
The TI1S bit in the TIMx_CR2 register, allows the input filter of channel 1 to be connected to
the output of an XOR gate, combining the three input pins TIMx_CH1, TIMx_CH2 and
TIMx_CH3.
The XOR output can be used with all the timer input functions such as trigger or input
capture. It is convenient to measure the interval between edges on two input signals, as per
Figure 201 below.
Figure 201. Measuring time interval between edges on 3 signals

TI1
TI2
TI3

XOR

TIMx
Counter

MS33109V1

22.3.24

Interfacing with Hall sensors
This is done using the advanced-control timers (TIM1 or TIM8) to generate PWM signals to
drive the motor and another timer TIMx (TIM2, TIM3, TIM4) referred to as “interfacing timer”
in Figure 202. The “interfacing timer” captures the 3 timer input pins (CC1, CC2, CC3)
connected through a XOR to the TI1 input channel (selected by setting the TI1S bit in the
TIMx_CR2 register).
The slave mode controller is configured in reset mode; the slave input is TI1F_ED. Thus,
each time one of the 3 inputs toggles, the counter restarts counting from 0. This creates a
time base triggered by any change on the Hall inputs.
On the “interfacing timer”, capture/compare channel 1 is configured in capture mode,
capture signal is TRC (See Figure 176: Capture/compare channel (example: channel 1
input stage) on page 668). The captured value, which corresponds to the time elapsed
between 2 changes on the inputs, gives information about motor speed.
The “interfacing timer” can be used in output mode to generate a pulse which changes the
configuration of the channels of the advanced-control timer (TIM1 or TIM8) (by triggering a
COM event). The TIM1 timer is used to generate PWM signals to drive the motor. To do this,
the interfacing timer channel must be programmed so that a positive pulse is generated
after a programmed delay (in output compare or PWM mode). This pulse is sent to the
advanced-control timer (TIM1 or TIM8) through the TRGO output.

696/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Example: you want to change the PWM configuration of your advanced-control timer TIM1
after a programmed delay each time a change occurs on the Hall inputs connected to one of
the TIMx timers.
•

Configure 3 timer inputs ORed to the TI1 input channel by writing the TI1S bit in the
TIMx_CR2 register to ‘1’,

•

Program the time base: write the TIMx_ARR to the max value (the counter must be
cleared by the TI1 change. Set the prescaler to get a maximum counter period longer
than the time between 2 changes on the sensors,

•

Program the channel 1 in capture mode (TRC selected): write the CC1S bits in the
TIMx_CCMR1 register to ‘01’. You can also program the digital filter if needed,

•

Program the channel 2 in PWM 2 mode with the desired delay: write the OC2M bits to
‘111’ and the CC2S bits to ‘00’ in the TIMx_CCMR1 register,

•

Select OC2REF as trigger output on TRGO: write the MMS bits in the TIMx_CR2
register to ‘101’,

In the advanced-control timer TIM1, the right ITR input must be selected as trigger input, the
timer is programmed to generate PWM signals, the capture/compare control signals are
preloaded (CCPC=1 in the TIMx_CR2 register) and the COM event is controlled by the
trigger input (CCUS=1 in the TIMx_CR2 register). The PWM control bits (CCxE, OCxM) are
written after a COM event for the next step (this can be done in an interrupt subroutine
generated by the rising edge of OC2REF).
The Figure 202 describes this example.

RM0385 Rev 7

697/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Figure 202. Example of Hall sensor interface

698/1709

RM0385 Rev 7

RM0385

22.3.25

Advanced-control timers (TIM1/TIM8)

Timer synchronization
The TIMx timers are linked together internally for timer synchronization or chaining. They
can be synchronized in several modes: Reset mode, Gated mode, and Trigger mode.

Slave mode: Reset mode
The counter and its prescaler can be reinitialized in response to an event on a trigger input.
Moreover, if the URS bit from the TIMx_CR1 register is low, an update event UEV is
generated. Then all the preloaded registers (TIMx_ARR, TIMx_CCRx) are updated.
In the following example, the upcounter is cleared in response to a rising edge on TI1 input:
•

Configure the channel 1 to detect rising edges on TI1. Configure the input filter duration
(in this example, we don’t need any filter, so we keep IC1F=0000). The capture
prescaler is not used for triggering, so you don’t need to configure it. The CC1S bits
select the input capture source only, CC1S = 01 in the TIMx_CCMR1 register. Write
CC1P=0 and CC1NP=’0’ in TIMx_CCER register to validate the polarity (and detect
rising edges only).

•

Configure the timer in reset mode by writing SMS=100 in TIMx_SMCR register. Select
TI1 as the input source by writing TS=101 in TIMx_SMCR register.

•

Start the counter by writing CEN=1 in the TIMx_CR1 register.

The counter starts counting on the internal clock, then behaves normally until TI1 rising
edge. When TI1 rises, the counter is cleared and restarts from 0. In the meantime, the
trigger flag is set (TIF bit in the TIMx_SR register) and an interrupt request, or a DMA
request can be sent if enabled (depending on the TIE and TDE bits in TIMx_DIER register).
The following figure shows this behavior when the auto-reload register TIMx_ARR=0x36.
The delay between the rising edge on TI1 and the actual reset of the counter is due to the
resynchronization circuit on TI1 input.
Figure 203. Control circuit in reset mode

TI1

UG
Counter clock = ck_cnt = ck_psc
Counter register

30 31 32 33 34 35 36 00 01 02 03 00 01 02 03

TIF

MS31401V1

RM0385 Rev 7

699/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Slave mode: Gated mode
The counter can be enabled depending on the level of a selected input.
In the following example, the upcounter counts only when TI1 input is low:
•

Configure the channel 1 to detect low levels on TI1. Configure the input filter duration
(in this example, we don’t need any filter, so we keep IC1F=0000). The capture
prescaler is not used for triggering, so you don’t need to configure it. The CC1S bits
select the input capture source only, CC1S=01 in TIMx_CCMR1 register. Write
CC1P=1 and CC1NP=’0’ in TIMx_CCER register to validate the polarity (and detect
low level only).

•

Configure the timer in gated mode by writing SMS=101 in TIMx_SMCR register. Select
TI1 as the input source by writing TS=101 in TIMx_SMCR register.

•

Enable the counter by writing CEN=1 in the TIMx_CR1 register (in gated mode, the
counter doesn’t start if CEN=0, whatever is the trigger input level).

The counter starts counting on the internal clock as long as TI1 is low and stops as soon as
TI1 becomes high. The TIF flag in the TIMx_SR register is set both when the counter starts
or stops.
The delay between the rising edge on TI1 and the actual stop of the counter is due to the
resynchronization circuit on TI1 input.
Figure 204. Control circuit in Gated mode

TI1
cnt_en
Counter clock = ck_cnt = ck_psc

Counter register

30 31 32 33

34

35 36 37 38

TIF

Write TIF=0
MS31402V1

Slave mode: Trigger mode
The counter can start in response to an event on a selected input.
In the following example, the upcounter starts in response to a rising edge on TI2 input:
•

700/1709

Configure the channel 2 to detect rising edges on TI2. Configure the input filter duration
(in this example, we don’t need any filter, so we keep IC2F=0000). The capture
prescaler is not used for triggering, so you don’t need to configure it. The CC2S bits are
configured to select the input capture source only, CC2S=01 in TIMx_CCMR1 register.

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)
Write CC2P=1 and CC2NP=0 in TIMx_CCER register to validate the polarity (and
detect low level only).
•

Configure the timer in trigger mode by writing SMS=110 in TIMx_SMCR register. Select
TI2 as the input source by writing TS=110 in TIMx_SMCR register.

When a rising edge occurs on TI2, the counter starts counting on the internal clock and the
TIF flag is set.
The delay between the rising edge on TI2 and the actual start of the counter is due to the
resynchronization circuit on TI2 input.
Figure 205. Control circuit in trigger mode
TI2
cnt_en
Counter clock = ck_cnt = ck_psc

Counter register

34

35

36 37 38

TIF
MS31403V1

Slave mode: Combined reset + trigger mode
In this case, a rising edge of the selected trigger input (TRGI) reinitializes the counter,
generates an update of the registers, and starts the counter.
This mode is used for one-pulse mode.

Slave mode: external clock mode 2 + trigger mode
The external clock mode 2 can be used in addition to another slave mode (except external
clock mode 1 and encoder mode). In this case, the ETR signal is used as external clock
input, and another input can be selected as trigger input (in reset mode, gated mode or
trigger mode). It is recommended not to select ETR as TRGI through the TS bits of
TIMx_SMCR register.
In the following example, the upcounter is incremented at each rising edge of the ETR
signal as soon as a rising edge of TI1 occurs:

RM0385 Rev 7

701/1709
740

Advanced-control timers (TIM1/TIM8)
1.

2.

3.

RM0385

Configure the external trigger input circuit by programming the TIMx_SMCR register as
follows:
–

ETF = 0000: no filter

–

ETPS=00: prescaler disabled

–

ETP=0: detection of rising edges on ETR and ECE=1 to enable the external clock
mode 2.

Configure the channel 1 as follows, to detect rising edges on TI:
–

IC1F=0000: no filter.

–

The capture prescaler is not used for triggering and does not need to be
configured.

–

CC1S=01in TIMx_CCMR1 register to select only the input capture source

–

CC1P=0 and CC1NP=’0’ in TIMx_CCER register to validate the polarity (and
detect rising edge only).

Configure the timer in trigger mode by writing SMS=110 in TIMx_SMCR register. Select
TI1 as the input source by writing TS=101 in TIMx_SMCR register.

A rising edge on TI1 enables the counter and sets the TIF flag. The counter then counts on
ETR rising edges.
The delay between the rising edge of the ETR signal and the actual reset of the counter is
due to the resynchronization circuit on ETRP input.
Figure 206. Control circuit in external clock mode 2 + trigger mode

TI1

CEN/CNT_EN

ETR

Counter clock = CK_CNT = CK_PSC

Counter register

34

35

36

TIF
MS33110V1

Note:

702/1709

The clock of the slave peripherals (timer, ADC, ...) receiving the TRGO or the TRGO2
signals must be enabled prior to receive events from the master timer, and the clock
frequency (prescaler) must not be changed on-the-fly while triggers are received from the
master timer.

RM0385 Rev 7

RM0385

22.3.26

Advanced-control timers (TIM1/TIM8)

ADC synchronization
The timer can generate an ADC triggering event with various internal signals, such as reset,
enable or compare events. It is also possible to generate a pulse issued by internal edge
detectors, such as:
–

Rising and falling edges of OC4ref

–

Rising edge on OC5ref or falling edge on OC6ref

The triggers are issued on the TRGO2 internal line which is redirected to the ADC. There is
a total of 16 possible events, which can be selected using the MMS2[3:0] bits in the
TIMx_CR2 register.
An example of an application for 3-phase motor drives is given in Figure 187 on page 680.
Note:

The clock of the slave peripherals (timer, ADC, ...) receiving the TRGO or the TRGO2
signals must be enabled prior to receive events from the master timer, and the clock
frequency (prescaler) must not be changed on-the-fly while triggers are received from the
master timer.

Note:

The clock of the ADC must be enabled prior to receive events from the master timer, and
must not be changed on-the-fly while triggers are received from the timer.

22.3.27

DMA burst mode
The TIMx timers have the capability to generate multiple DMA requests upon a single event.
The main purpose is to be able to re-program part of the timer multiple times without
software overhead, but it can also be used to read several registers in a row, at regular
intervals.
The DMA controller destination is unique and must point to the virtual register TIMx_DMAR.
On a given timer event, the timer launches a sequence of DMA requests (burst). Each write
into the TIMx_DMAR register is actually redirected to one of the timer registers.
The DBL[4:0] bits in the TIMx_DCR register set the DMA burst length. The timer recognizes
a burst transfer when a read or a write access is done to the TIMx_DMAR address), i.e. the
number of transfers (either in half-words or in bytes).
The DBA[4:0] bits in the TIMx_DCR registers define the DMA base address for DMA
transfers (when read/write access are done through the TIMx_DMAR address). DBA is
defined as an offset starting from the address of the TIMx_CR1 register:
Example:
00000: TIMx_CR1
00001: TIMx_CR2
00010: TIMx_SMCR
As an example, the timer DMA burst feature is used to update the contents of the CCRx
registers (x = 2, 3, 4) upon an update event, with the DMA transferring half words into the
CCRx registers.

RM0385 Rev 7

703/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

This is done in the following steps:
1.

Configure the corresponding DMA channel as follows:
–

DMA channel peripheral address is the DMAR register address

–

DMA channel memory address is the address of the buffer in the RAM containing
the data to be transferred by DMA into CCRx registers.

–

Number of data to transfer = 3 (See note below).

–

Circular mode disabled.

2.

Configure the DCR register by configuring the DBA and DBL bit fields as follows:
DBL = 3 transfers, DBA = 0xE.

3.

Enable the TIMx update DMA request (set the UDE bit in the DIER register).

4.

Enable TIMx

5.

Enable the DMA channel

This example is for the case where every CCRx register to be updated once. If every CCRx
register is to be updated twice for example, the number of data to transfer should be 6. Let's
take the example of a buffer in the RAM containing data1, data2, data3, data4, data5 and
data6. The data is transferred to the CCRx registers as follows: on the first update DMA
request, data1 is transferred to CCR2, data2 is transferred to CCR3, data3 is transferred to
CCR4 and on the second update DMA request, data4 is transferred to CCR2, data5 is
transferred to CCR3 and data6 is transferred to CCR4.
Note:

A null value can be written to the reserved registers.

22.3.28

Debug mode
When the microcontroller enters debug mode (Cortex®-M7 core halted), the TIMx counter
either continues to work normally or stops, depending on DBG_TIMx_STOP configuration
bit in DBG module.
For safety purposes, when the counter is stopped (DBG_TIMx_STOP = 1), the outputs are
disabled (as if the MOE bit was reset). The outputs can either be forced to an inactive state
(OSSI bit = 1), or have their control taken over by the GPIO controller (OSSI bit = 0),
typically to force a Hi-Z.
For more details, refer to Section 40.16.2: Debug support for timers, watchdog, bxCAN and
I2C.
For safety purposes, when the counter is stopped (DBG_TIMx_STOP = 1), the outputs are
disabled (as if the MOE bit was reset). The outputs can either be forced to an inactive state
(OSSI bit = 1), or have their control taken over by the GPIO controller (OSSI bit = 0) to force
them to Hi-Z.

704/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

22.4

TIM1/TIM8 registers
Refer to for a list of abbreviations used in register descriptions.

22.4.1

TIM1/TIM8 control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15
Res.

14
Res.

13
Res.

12

11

10

Res.

UIFRE
MAP

Res.

rw

9

8

CKD[1:0]
rw

7
ARPE

rw

rw

6

5

CMS[1:0]
rw

rw

4

3

2

1

0

DIR

OPM

URS

UDIS

CEN

rw

rw

rw

rw

rw

Bits 15:12 Reserved, must be kept at reset value.
Bit 11 UIFREMAP: UIF status bit remapping
0: No remapping. UIF status bit is not copied to TIMx_CNT register bit 31.
1: Remapping enabled. UIF status bit is copied to TIMx_CNT register bit 31.
Bit 10 Reserved, must be kept at reset value.
Bits 9:8 CKD[1:0]: Clock division
This bit-field indicates the division ratio between the timer clock (CK_INT) frequency and the
dead-time and sampling clock (tDTS)used by the dead-time generators and the digital filters
(ETR, TIx),
00: tDTS=tCK_INT
01: tDTS=2*tCK_INT
10: tDTS=4*tCK_INT
11: Reserved, do not program this value
Bit 7 ARPE: Auto-reload preload enable
0: TIMx_ARR register is not buffered
1: TIMx_ARR register is buffered
Bits 6:5 CMS[1:0]: Center-aligned mode selection
00: Edge-aligned mode. The counter counts up or down depending on the direction bit
(DIR).
01: Center-aligned mode 1. The counter counts up and down alternatively. Output compare
interrupt flags of channels configured in output (CCxS=00 in TIMx_CCMRx register) are set
only when the counter is counting down.
10: Center-aligned mode 2. The counter counts up and down alternatively. Output compare
interrupt flags of channels configured in output (CCxS=00 in TIMx_CCMRx register) are set
only when the counter is counting up.
11: Center-aligned mode 3. The counter counts up and down alternatively. Output compare
interrupt flags of channels configured in output (CCxS=00 in TIMx_CCMRx register) are set
both when the counter is counting up or down.
Note: It is not allowed to switch from edge-aligned mode to center-aligned mode as long as
the counter is enabled (CEN=1)
Bit 4 DIR: Direction
0: Counter used as upcounter
1: Counter used as downcounter
Note: This bit is read only when the timer is configured in Center-aligned mode or Encoder
mode.

RM0385 Rev 7

705/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bit 3 OPM: One pulse mode
0: Counter is not stopped at update event
1: Counter stops counting at the next update event (clearing the bit CEN)
Bit 2 URS: Update request source
This bit is set and cleared by software to select the UEV event sources.
0: Any of the following events generate an update interrupt or DMA request if enabled.
These events can be:
–
Counter overflow/underflow
–
Setting the UG bit
–
Update generation through the slave mode controller
1: Only counter overflow/underflow generates an update interrupt or DMA request if
enabled.
Bit 1 UDIS: Update disable
This bit is set and cleared by software to enable/disable UEV event generation.
0: UEV enabled. The Update (UEV) event is generated by one of the following events:
–
Counter overflow/underflow
–
Setting the UG bit
–
Update generation through the slave mode controller
Buffered registers are then loaded with their preload values.
1: UEV disabled. The Update event is not generated, shadow registers keep their value
(ARR, PSC, CCRx). However the counter and the prescaler are reinitialized if the UG bit is
set or if a hardware reset is received from the slave mode controller.
Bit 0 CEN: Counter enable
0: Counter disabled
1: Counter enabled
Note: External clock, gated mode and encoder mode can work only if the CEN bit has been
previously set by software. However trigger mode can set the CEN bit automatically by
hardware.

22.4.2

TIM1/TIM8 control register 2 (TIMx_CR2)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

23

21

20

MMS2[3:0]
rw

rw
6

15

14

13

12

11

10

9

8

7

Res.

OIS4

OIS3N

OIS3

OIS2N

OIS2

OIS1N

OIS1

TI1S

rw

rw

rw

rw

rw

rw

rw

rw

706/1709

22

RM0385 Rev 7

rw

rw

5

4

MMS[2:0]
rw

rw

rw

19

18

17

16

Res.

OIS6

Res.

OIS5

rw

rw

3

2

1

0

CCDS

CCUS

Res.

CCPC

rw

rw

rw

RM0385

Advanced-control timers (TIM1/TIM8)

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:20 MMS2[3:0]: Master mode selection 2
These bits allow the information to be sent to ADC for synchronization (TRGO2) to be
selected. The combination is as follows:
0000: Reset - the UG bit from the TIMx_EGR register is used as trigger output (TRGO2). If
the reset is generated by the trigger input (slave mode controller configured in reset mode),
the signal on TRGO2 is delayed compared to the actual reset.
0001: Enable - the Counter Enable signal CNT_EN is used as trigger output (TRGO2). It is
useful to start several timers at the same time or to control a window in which a slave timer is
enabled. The Counter Enable signal is generated by a logic OR between the CEN control bit
and the trigger input when configured in Gated mode. When the Counter Enable signal is
controlled by the trigger input, there is a delay on TRGO2, except if the Master/Slave mode
is selected (see the MSM bit description in TIMx_SMCR register).
0010: Update - the update event is selected as trigger output (TRGO2). For instance, a
master timer can then be used as a prescaler for a slave timer.
0011: Compare pulse - the trigger output sends a positive pulse when the CC1IF flag is to
be set (even if it was already high), as soon as a capture or compare match occurs
(TRGO2).
0100: Compare - OC1REF signal is used as trigger output (TRGO2)
0101: Compare - OC2REF signal is used as trigger output (TRGO2)
0110: Compare - OC3REF signal is used as trigger output (TRGO2)
0111: Compare - OC4REF signal is used as trigger output (TRGO2)
1000: Compare - OC5REF signal is used as trigger output (TRGO2)
1001: Compare - OC6REF signal is used as trigger output (TRGO2)
1010: Compare Pulse - OC4REF rising or falling edges generate pulses on TRGO2
1011: Compare Pulse - OC6REF rising or falling edges generate pulses on TRGO2
1100: Compare Pulse - OC4REF or OC6REF rising edges generate pulses on TRGO2
1101: Compare Pulse - OC4REF rising or OC6REF falling edges generate pulses on
TRGO2
1110: Compare Pulse - OC5REF or OC6REF rising edges generate pulses on TRGO2
1111: Compare Pulse - OC5REF rising or OC6REF falling edges generate pulses on
TRGO2
Note: The clock of the slave timer or ADC must be enabled prior to receive events from the
master timer, and must not be changed on-the-fly while triggers are received from the
master timer.
Bit 19 Reserved, must be kept at reset value.
Bit 18 OIS6: Output Idle state 6 (OC6 output)
Refer to OIS1 bit
Bit 17 Reserved, must be kept at reset value.
Bit 16 OIS5: Output Idle state 5 (OC5 output)
Refer to OIS1 bit
Bit 15 Reserved, must be kept at reset value.
Bit 14 OIS4: Output Idle state 4 (OC4 output)
Refer to OIS1 bit
Bit 13 OIS3N: Output Idle state 3 (OC3N output)
Refer to OIS1N bit
Bit 12 OIS3: Output Idle state 3 (OC3 output)
Refer to OIS1 bit

RM0385 Rev 7

707/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bit 11 OIS2N: Output Idle state 2 (OC2N output)
Refer to OIS1N bit
Bit 10 OIS2: Output Idle state 2 (OC2 output)
Refer to OIS1 bit
Bit 9 OIS1N: Output Idle state 1 (OC1N output)
0: OC1N=0 after a dead-time when MOE=0
1: OC1N=1 after a dead-time when MOE=0
Note: This bit can not be modified as long as LOCK level 1, 2 or 3 has been programmed
(LOCK bits in TIMx_BDTR register).
Bit 8 OIS1: Output Idle state 1 (OC1 output)
0: OC1=0 (after a dead-time if OC1N is implemented) when MOE=0
1: OC1=1 (after a dead-time if OC1N is implemented) when MOE=0
Note: This bit can not be modified as long as LOCK level 1, 2 or 3 has been programmed
(LOCK bits in TIMx_BDTR register).
Bit 7 TI1S: TI1 selection
0: The TIMx_CH1 pin is connected to TI1 input
1: The TIMx_CH1, CH2 and CH3 pins are connected to the TI1 input (XOR combination)
Bits 6:4 MMS[2:0]: Master mode selection
These bits allow to select the information to be sent in master mode to slave timers for
synchronization (TRGO). The combination is as follows:
000: Reset - the UG bit from the TIMx_EGR register is used as trigger output (TRGO). If the
reset is generated by the trigger input (slave mode controller configured in reset mode) then
the signal on TRGO is delayed compared to the actual reset.
001: Enable - the Counter Enable signal CNT_EN is used as trigger output (TRGO). It is
useful to start several timers at the same time or to control a window in which a slave timer is
enable. The Counter Enable signal is generated by a logic OR between CEN control bit and
the trigger input when configured in gated mode. When the Counter Enable signal is
controlled by the trigger input, there is a delay on TRGO, except if the master/slave mode is
selected (see the MSM bit description in TIMx_SMCR register).
010: Update - The update event is selected as trigger output (TRGO). For instance a master
timer can then be used as a prescaler for a slave timer.
011: Compare Pulse - The trigger output send a positive pulse when the CC1IF flag is to be
set (even if it was already high), as soon as a capture or a compare match occurred.
(TRGO).
100: Compare - OC1REF signal is used as trigger output (TRGO)
101: Compare - OC2REF signal is used as trigger output (TRGO)
110: Compare - OC3REF signal is used as trigger output (TRGO)
111: Compare - OC4REF signal is used as trigger output (TRGO)
Note: The clock of the slave timer or ADC must be enabled prior to receive events from the
master timer, and must not be changed on-the-fly while triggers are received from the
master timer.
Bit 3 CCDS: Capture/compare DMA selection
0: CCx DMA request sent when CCx event occurs
1: CCx DMA requests sent when update event occurs

708/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

Bit 2 CCUS: Capture/compare control update selection
0: When capture/compare control bits are preloaded (CCPC=1), they are updated by setting
the COMG bit only
1: When capture/compare control bits are preloaded (CCPC=1), they are updated by setting
the COMG bit or when an rising edge occurs on TRGI
Note: This bit acts only on channels that have a complementary output.
Bit 1 Reserved, must be kept at reset value.
Bit 0 CCPC: Capture/compare preloaded control
0: CCxE, CCxNE and OCxM bits are not preloaded
1: CCxE, CCxNE and OCxM bits are preloaded, after having been written, they are updated
only when a commutation event (COM) occurs (COMG bit set or rising edge detected on
TRGI, depending on the CCUS bit).
Note: This bit acts only on channels that have a complementary output.

22.4.3

TIM1/TIM8 slave mode control register (TIMx_SMCR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SMS[3]

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

ETP

ECE

rw

rw

rw

ETPS[1:0]
rw

rw

ETF[3:0]
rw

rw

rw

MSM
rw

rw

TS[2:0]
rw

rw

Res.
rw

0

SMS[2:0]
rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 SMS[3]: Slave mode selection - bit 3
Refer to SMS description - bits 2:0.
Bit 15 ETP: External trigger polarity
This bit selects whether ETR or ETR is used for trigger operations
0: ETR is non-inverted, active at high level or rising edge.
1: ETR is inverted, active at low level or falling edge.
Bit 14 ECE: External clock enable
This bit enables External clock mode 2.
0: External clock mode 2 disabled
1: External clock mode 2 enabled. The counter is clocked by any active edge on the ETRF
signal.
Note: 1: Setting the ECE bit has the same effect as selecting external clock mode 1 with
TRGI connected to ETRF (SMS=111 and TS=111).
2: It is possible to simultaneously use external clock mode 2 with the following slave
modes: reset mode, gated mode and trigger mode. Nevertheless, TRGI must not be
connected to ETRF in this case (TS bits must not be 111).
3: If external clock mode 1 and external clock mode 2 are enabled at the same time,
the external clock input is ETRF.

RM0385 Rev 7

709/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bits 13:12 ETPS[1:0]: External trigger prescaler
External trigger signal ETRP frequency must be at most 1/4 of TIMxCLK frequency. A
prescaler can be enabled to reduce ETRP frequency. It is useful when inputting fast external
clocks.
00: Prescaler OFF
01: ETRP frequency divided by 2
10: ETRP frequency divided by 4
11: ETRP frequency divided by 8
Bits 11:8 ETF[3:0]: External trigger filter
This bit-field then defines the frequency used to sample ETRP signal and the length of the
digital filter applied to ETRP. The digital filter is made of an event counter in which N
consecutive events are needed to validate a transition on the output:
0000: No filter, sampling is done at fDTS
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Bit 7 MSM: Master/slave mode
0: No action
1: The effect of an event on the trigger input (TRGI) is delayed to allow a perfect
synchronization between the current timer and its slaves (through TRGO). It is useful if we
want to synchronize several timers on a single external event.
Bits 6:4 TS[2:0]: Trigger selection
This bit-field selects the trigger input to be used to synchronize the counter.
000: Internal Trigger 0 (ITR0)
001: Internal Trigger 1 (ITR1)
010: Internal Trigger 2 (ITR2)
011: Internal Trigger 3 (ITR3)
100: TI1 Edge Detector (TI1F_ED)
101: Filtered Timer Input 1 (TI1FP1)
110: Filtered Timer Input 2 (TI2FP2)
111: External Trigger input (ETRF)
See Table 145: TIMx internal trigger connection on page 711 for more details on ITRx
meaning for each Timer.
Note: These bits must be changed only when they are not used (e.g. when SMS=000) to
avoid wrong edge detections at the transition.
Note: The other bit is at position 16 in the same register
Bit 3 Reserved, must be kept at reset value.

710/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

Bits 16, 2, 1, 0 SMS[3:0]: Slave mode selection
When external signals are selected the active edge of the trigger signal (TRGI) is linked to
the polarity selected on the external input (see Input Control register and Control Register
description.
0000: Slave mode disabled - if CEN = ‘1’ then the prescaler is clocked directly by the internal
clock.
0001: Encoder mode 1 - Counter counts up/down on TI1FP1 edge depending on TI2FP2
level.
0010: Encoder mode 2 - Counter counts up/down on TI2FP2 edge depending on TI1FP1
level.
0011: Encoder mode 3 - Counter counts up/down on both TI1FP1 and TI2FP2 edges
depending on the level of the other input.
0100: Reset Mode - Rising edge of the selected trigger input (TRGI) reinitializes the counter
and generates an update of the registers.
0101: Gated Mode - The counter clock is enabled when the trigger input (TRGI) is high. The
counter stops (but is not reset) as soon as the trigger becomes low. Both start and stop of
the counter are controlled.
0110: Trigger Mode - The counter starts at a rising edge of the trigger TRGI (but it is not
reset). Only the start of the counter is controlled.
0111: External Clock Mode 1 - Rising edges of the selected trigger (TRGI) clock the counter.
1000: Combined reset + trigger mode - Rising edge of the selected trigger input (TRGI)
reinitializes the counter, generates an update of the registers and starts the counter.
Codes above 1000: Reserved.
Note: The gated mode must not be used if TI1F_ED is selected as the trigger input (TS=100).
Indeed, TI1F_ED outputs 1 pulse for each transition on TI1F, whereas the gated mode
checks the level of the trigger signal.
Note: The clock of the slave peripherals (timer, ADC, ...) receiving the TRGO or the TRGO2
signals must be enabled prior to receive events from the master timer, and the clock
frequency (prescaler) must not be changed on-the-fly while triggers are received from
the master timer.

Table 145. TIMx internal trigger connection

22.4.4

Slave TIM

ITR0 (TS = 000)

ITR1 (TS = 001)

ITR2 (TS = 010)

ITR3 (TS = 011)

TIM1

TIM5

TIM2

TIM3

TIM4

TIM8

TIM1

TIM2

TIM4

TIM5

TIM1/TIM8 DMA/interrupt enable register (TIMx_DIER)
Address offset: 0x0C
Reset value: 0x0000

15

14

Res.

TDE
rw

13

12

11

10

9

COMDE CC4DE CC3DE CC2DE CC1DE
rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

UDE

BIE

TIE

COMIE

CC4IE

CC3IE

CC2IE

CC1IE

UIE

rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

711/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bit 15 Reserved, must be kept at reset value.
Bit 14 TDE: Trigger DMA request enable
0: Trigger DMA request disabled
1: Trigger DMA request enabled
Bit 13 COMDE: COM DMA request enable
0: COM DMA request disabled
1: COM DMA request enabled
Bit 12 CC4DE: Capture/Compare 4 DMA request enable
0: CC4 DMA request disabled
1: CC4 DMA request enabled
Bit 11 CC3DE: Capture/Compare 3 DMA request enable
0: CC3 DMA request disabled
1: CC3 DMA request enabled
Bit 10 CC2DE: Capture/Compare 2 DMA request enable
0: CC2 DMA request disabled
1: CC2 DMA request enabled
Bit 9 CC1DE: Capture/Compare 1 DMA request enable
0: CC1 DMA request disabled
1: CC1 DMA request enabled
Bit 8 UDE: Update DMA request enable
0: Update DMA request disabled
1: Update DMA request enabled
Bit 7 BIE: Break interrupt enable
0: Break interrupt disabled
1: Break interrupt enabled
Bit 6 TIE: Trigger interrupt enable
0: Trigger interrupt disabled
1: Trigger interrupt enabled
Bit 5 COMIE: COM interrupt enable
0: COM interrupt disabled
1: COM interrupt enabled
Bit 4 CC4IE: Capture/Compare 4 interrupt enable
0: CC4 interrupt disabled
1: CC4 interrupt enabled
Bit 3 CC3IE: Capture/Compare 3 interrupt enable
0: CC3 interrupt disabled
1: CC3 interrupt enabled

712/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

Bit 2 CC2IE: Capture/Compare 2 interrupt enable
0: CC2 interrupt disabled
1: CC2 interrupt enabled
Bit 1 CC1IE: Capture/Compare 1 interrupt enable
0: CC1 interrupt disabled
1: CC1 interrupt enabled
Bit 0 UIE: Update interrupt enable
0: Update interrupt disabled
1: Update interrupt enabled

22.4.5

TIM1/TIM8 status register (TIMx_SR)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CC6IF

CC5IF

rc_w0

rc_w0

15

14

Res.

Res.

13

12

11

10

9

CC4OF CC3OF CC2OF CC1OF
rc_w0

rc_w0

rc_w0

rc_w0

8

7

6

5

4

3

2

1

0

B2IF

BIF

TIF

COMIF

CC4IF

CC3IF

CC2IF

CC1IF

UIF

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

Bits 31:18 Reserved, must be kept at reset value.
Bit 17 CC6IF: Compare 6 interrupt flag
Refer to CC1IF description (Note: Channel 6 can only be configured as output)
Bit 16 CC5IF: Compare 5 interrupt flag
Refer to CC1IF description (Note: Channel 5 can only be configured as output)
Bits 15: Reserved, must be kept at reset value.
Bit 12 CC4OF: Capture/Compare 4 overcapture flag
Refer to CC1OF description
Bit 11 CC3OF: Capture/Compare 3 overcapture flag
Refer to CC1OF description
Bit 10 CC2OF: Capture/Compare 2 overcapture flag
Refer to CC1OF description
Bit 9 CC1OF: Capture/Compare 1 overcapture flag
This flag is set by hardware only when the corresponding channel is configured in input
capture mode. It is cleared by software by writing it to ‘0’.
0: No overcapture has been detected.
1: The counter value has been captured in TIMx_CCR1 register while CC1IF flag was
already set
Bit 8 B2IF: Break 2 interrupt flag
This flag is set by hardware as soon as the break 2 input goes active. It can be cleared by
software if the break 2 input is not active.
0: No break event occurred.
1: An active level has been detected on the break 2 input. An interrupt is generated if BIE=1
in the TIMx_DIER register.

RM0385 Rev 7

713/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bit 7 BIF: Break interrupt flag
This flag is set by hardware as soon as the break input goes active. It can be cleared by
software if the break input is not active.
0: No break event occurred.
1: An active level has been detected on the break input. An interrupt is generated if BIE=1 in
the TIMx_DIER register.
Bit 6 TIF: Trigger interrupt flag
This flag is set by hardware on trigger event (active edge detected on TRGI input when the
slave mode controller is enabled in all modes but gated mode. It is set when the counter
starts or stops when gated mode is selected. It is cleared by software.
0: No trigger event occurred.
1: Trigger interrupt pending.
Bit 5 COMIF: COM interrupt flag
This flag is set by hardware on COM event (when Capture/compare Control bits - CCxE,
CCxNE, OCxM - have been updated). It is cleared by software.
0: No COM event occurred.
1: COM interrupt pending.
Bit 4 CC4IF: Capture/Compare 4 interrupt flag
Refer to CC1IF description
Bit 3 CC3IF: Capture/Compare 3 interrupt flag
Refer to CC1IF description
Bit 2 CC2IF: Capture/Compare 2 interrupt flag
Refer to CC1IF description
Bit 1 CC1IF: Capture/Compare 1 interrupt flag
If channel CC1 is configured as output: This flag is set by hardware when the counter
matches the compare value, with some exception in center-aligned mode (refer to the CMS
bits in the TIMx_CR1 register description). It is cleared by software.
0: No match.
1: The content of the counter TIMx_CNT matches the content of the TIMx_CCR1 register.
When the contents of TIMx_CCR1 are greater than the contents of TIMx_ARR, the CC1IF
bit goes high on the counter overflow (in upcounting and up/down-counting modes) or
underflow (in downcounting mode)
If channel CC1 is configured as input: This bit is set by hardware on a capture. It is
cleared by software or by reading the TIMx_CCR1 register.
0: No input capture occurred
1: The counter value has been captured in TIMx_CCR1 register (An edge has been
detected on IC1 which matches the selected polarity)
Bit 0 UIF: Update interrupt flag
This bit is set by hardware on an update event. It is cleared by software.
0: No update occurred.
1: Update interrupt pending. This bit is set by hardware when the registers are updated:
– At overflow or underflow regarding the repetition counter value (update if repetition
counter = 0) and if the UDIS=0 in the TIMx_CR1 register.
– When CNT is reinitialized by software using the UG bit in TIMx_EGR register, if URS=0
and UDIS=0 in the TIMx_CR1 register.
– When CNT is reinitialized by a trigger event (refer to Section 22.4.3: TIM1/TIM8 slave
mode control register (TIMx_SMCR)), if URS=0 and UDIS=0 in the TIMx_CR1 register.

714/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

22.4.6

TIM1/TIM8 event generation register (TIMx_EGR)
Address offset: 0x14
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

B2G

BG

TG

COMG

CC4G

CC3G

CC2G

CC1G

UG

w

w

w

w

w

w

w

w

w

Bits 15:9 Reserved, must be kept at reset value.
Bit 8 B2G: Break 2 generation
This bit is set by software in order to generate an event, it is automatically cleared by
hardware.
0: No action
1: A break 2 event is generated. MOE bit is cleared and B2IF flag is set. Related interrupt
can occur if enabled.
Bit 7 BG: Break generation
This bit is set by software in order to generate an event, it is automatically cleared by
hardware.
0: No action
1: A break event is generated. MOE bit is cleared and BIF flag is set. Related interrupt or
DMA transfer can occur if enabled.
Bit 6 TG: Trigger generation
This bit is set by software in order to generate an event, it is automatically cleared by
hardware.
0: No action
1: The TIF flag is set in TIMx_SR register. Related interrupt or DMA transfer can occur if
enabled.
Bit 5 COMG: Capture/Compare control update generation
This bit can be set by software, it is automatically cleared by hardware
0: No action
1: When CCPC bit is set, it allows to update CCxE, CCxNE and OCxM bits
Note: This bit acts only on channels having a complementary output.
Bit 4 CC4G: Capture/Compare 4 generation
Refer to CC1G description
Bit 3 CC3G: Capture/Compare 3 generation
Refer to CC1G description
Bit 2 CC2G: Capture/Compare 2 generation
Refer to CC1G description

RM0385 Rev 7

715/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bit 1 CC1G: Capture/Compare 1 generation
This bit is set by software in order to generate an event, it is automatically cleared by
hardware.
0: No action
1: A capture/compare event is generated on channel 1:
If channel CC1 is configured as output:
CC1IF flag is set, Corresponding interrupt or DMA request is sent if enabled.
If channel CC1 is configured as input:
The current value of the counter is captured in TIMx_CCR1 register. The CC1IF flag is set,
the corresponding interrupt or DMA request is sent if enabled. The CC1OF flag is set if the
CC1IF flag was already high.
Bit 0 UG: Update generation
This bit can be set by software, it is automatically cleared by hardware.
0: No action
1: Reinitialize the counter and generates an update of the registers. Note that the prescaler
counter is cleared too (anyway the prescaler ratio is not affected). The counter is cleared if
the center-aligned mode is selected or if DIR=0 (upcounting), else it takes the auto-reload
value (TIMx_ARR) if DIR=1 (downcounting).

22.4.7

TIM1/TIM8 capture/compare mode register 1 (TIMx_CCMR1)
Address offset: 0x18
Reset value: 0x0000 0000
The channels can be used in input (capture mode) or in output (compare mode). The
direction of a channel is defined by configuring the corresponding CCxS bits. All the other
bits of this register have a different function in input and in output mode. For a given bit,
OCxx describes its function when the channel is configured in output, ICxx describes its
function when the channel is configured in input. So you must take care that the same bit
can have a different meaning for the input stage and for the output stage.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC2M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC1M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw
15

14

OC2
CE

13

12

OC2M[2:0]
IC2F[3:0]

rw

rw

rw

11

10

OC2
PE

OC2
FE

9

rw

8

CC2S[1:0]

7

IC2PSC[1:0]
rw

rw

rw

5

4

OC1M[2:0]
IC1F[3:0]

rw

rw

rw

Output compare mode
Bits 31:25 Reserved, must be kept at reset value.
Bit 24 OC2M[3]: Output Compare 2 mode - bit 3
Refer to OC2M description on bits 14:12.
Bits 23:17 Reserved, must be kept at reset value.
Bits16 OC1M[3]: Output Compare 1 mode - bit 3
Refer to OC1M description on bits 6:4

716/1709

6

OC1
CE

RM0385 Rev 7

rw

rw

3

2

OC1
PE

OC1
FE

1

0

CC1S[1:0]

IC1PSC[1:0]
rw

rw

rw

rw

rw

RM0385

Advanced-control timers (TIM1/TIM8)

Bit 15 OC2CE: Output Compare 2 clear enable
Bits 14:12 OC2M[2:0]: Output Compare 2 mode
Bit 11 OC2PE: Output Compare 2 preload enable
Bit 10 OC2FE: Output Compare 2 fast enable
Bits 9:8 CC2S[1:0]: Capture/Compare 2 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC2 channel is configured as output
01: CC2 channel is configured as input, IC2 is mapped on TI2
10: CC2 channel is configured as input, IC2 is mapped on TI1
11: CC2 channel is configured as input, IC2 is mapped on TRC. This mode is working only if
an internal trigger input is selected through the TS bit (TIMx_SMCR register)
Note: CC2S bits are writable only when the channel is OFF (CC2E = ‘0’ in TIMx_CCER).
Bit 7 OC1CE: Output Compare 1 clear enable
0: OC1Ref is not affected by the ETRF input
1: OC1Ref is cleared as soon as a High level is detected on ETRF input

RM0385 Rev 7

717/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bits 6:4 OC1M: Output Compare 1 mode
These bits define the behavior of the output reference signal OC1REF from which OC1 and
OC1N are derived. OC1REF is active high whereas OC1 and OC1N active level depends
on CC1P and CC1NP bits.
0000: Frozen - The comparison between the output compare register TIMx_CCR1 and the
counter TIMx_CNT has no effect on the outputs.(this mode is used to generate a timing
base).
0001: Set channel 1 to active level on match. OC1REF signal is forced high when the
counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).
0010: Set channel 1 to inactive level on match. OC1REF signal is forced low when the
counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).
0011: Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1.
0100: Force inactive level - OC1REF is forced low.
0101: Force active level - OC1REF is forced high.
0110: PWM mode 1 - In upcounting, channel 1 is active as long as TIMx_CNTTIMx_CCR1 else active (OC1REF=’1’).
0111: PWM mode 2 - In upcounting, channel 1 is inactive as long as
TIMx_CNTTIMx_CCR1 else inactive.
1000: Retrigerrable OPM mode 1 - In up-counting mode, the channel is active until a trigger
event is detected (on TRGI signal). Then, a comparison is performed as in PWM mode 1
and the channels becomes active again at the next update. In down-counting mode, the
channel is inactive until a trigger event is detected (on TRGI signal). Then, a comparison is
performed as in PWM mode 1 and the channels becomes inactive again at the next update.
1001: Retrigerrable OPM mode 2 - In up-counting mode, the channel is inactive until a
trigger event is detected (on TRGI signal). Then, a comparison is performed as in PWM
mode 2 and the channels becomes inactive again at the next update. In down-counting
mode, the channel is active until a trigger event is detected (on TRGI signal). Then, a
comparison is performed as in PWM mode 1 and the channels becomes active again at the
next update.
1010: Reserved,
1011: Reserved,
1100: Combined PWM mode 1 - OC1REF has the same behavior as in PWM mode 1.
OC1REFC is the logical OR between OC1REF and OC2REF.
1101: Combined PWM mode 2 - OC1REF has the same behavior as in PWM mode 2.
OC1REFC is the logical AND between OC1REF and OC2REF.
1110: Asymmetric PWM mode 1 - OC1REF has the same behavior as in PWM mode 1.
OC1REFC outputs OC1REF when the counter is counting up, OC2REF when it is counting
down.
1111: Asymmetric PWM mode 2 - OC1REF has the same behavior as in PWM mode 2.
OC1REFC outputs OC1REF when the counter is counting up, OC2REF when it is counting
down.
Note: These bits can not be modified as long as LOCK level 3 has been programmed (LOCK
bits in TIMx_BDTR register) and CC1S=’00’ (the channel is configured in output).
Note: In PWM mode, the OCREF level changes only when the result of the comparison
changes or when the output compare mode switches from “frozen” mode to “PWM”
mode.
Note: On channels having a complementary output, this bit field is preloaded. If the CCPC bit
is set in the TIMx_CR2 register then the OC1M active bits take the new value from the
preloaded bits only when a COM event is generated.

718/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

Bit 3 OC1PE: Output Compare 1 preload enable
0: Preload register on TIMx_CCR1 disabled. TIMx_CCR1 can be written at anytime, the
new value is taken in account immediately.
1: Preload register on TIMx_CCR1 enabled. Read/Write operations access the preload
register. TIMx_CCR1 preload value is loaded in the active register at each update event.
Note: 1: These bits can not be modified as long as LOCK level 3 has been programmed
(LOCK bits in TIMx_BDTR register) and CC1S=’00’ (the channel is configured in
output).
2: The PWM mode can be used without validating the preload register only in one
pulse mode (OPM bit set in TIMx_CR1 register). Else the behavior is not guaranteed.
Bit 2 OC1FE: Output Compare 1 fast enable
This bit is used to accelerate the effect of an event on the trigger in input on the CC output.
0: CC1 behaves normally depending on counter and CCR1 values even when the trigger is
ON. The minimum delay to activate CC1 output when an edge occurs on the trigger input is
5 clock cycles.
1: An active edge on the trigger input acts like a compare match on CC1 output. Then, OC is
set to the compare level independently from the result of the comparison. Delay to sample
the trigger input and to activate CC1 output is reduced to 3 clock cycles. OCFE acts only if
the channel is configured in PWM1 or PWM2 mode.
Bits 1:0 CC1S: Capture/Compare 1 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC1 channel is configured as output
01: CC1 channel is configured as input, IC1 is mapped on TI1
10: CC1 channel is configured as input, IC1 is mapped on TI2
11: CC1 channel is configured as input, IC1 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC1S bits are writable only when the channel is OFF (CC1E = ‘0’ in TIMx_CCER).

Input capture mode
Bits 31:16 Reserved, must be kept at reset value.
Bits 15:12 IC2F: Input capture 2 filter
Bits 11:10 IC2PSC[1:0]: Input capture 2 prescaler
Bits 9:8 CC2S: Capture/Compare 2 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC2 channel is configured as output
01: CC2 channel is configured as input, IC2 is mapped on TI2
10: CC2 channel is configured as input, IC2 is mapped on TI1
11: CC2 channel is configured as input, IC2 is mapped on TRC. This mode is working only if an
internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC2S bits are writable only when the channel is OFF (CC2E = ‘0’ in TIMx_CCER).

RM0385 Rev 7

719/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bits 7:4 IC1F[3:0]: Input capture 1 filter
This bit-field defines the frequency used to sample TI1 input and the length of the digital filter applied
to TI1. The digital filter is made of an event counter in which N consecutive events are needed to
validate a transition on the output:
0000: No filter, sampling is done at fDTS
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Bits 3:2 IC1PSC: Input capture 1 prescaler
This bit-field defines the ratio of the prescaler acting on CC1 input (IC1). The prescaler is reset as
soon as CC1E=’0’ (TIMx_CCER register).
00: no prescaler, capture is done each time an edge is detected on the capture input
01: capture is done once every 2 events
10: capture is done once every 4 events
11: capture is done once every 8 events
Bits 1:0 CC1S: Capture/Compare 1 Selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC1 channel is configured as output
01: CC1 channel is configured as input, IC1 is mapped on TI1
10: CC1 channel is configured as input, IC1 is mapped on TI2
11: CC1 channel is configured as input, IC1 is mapped on TRC. This mode is working only if an
internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC1S bits are writable only when the channel is OFF (CC1E = ‘0’ in TIMx_CCER).

22.4.8

TIM1/TIM8 capture/compare mode register 2 (TIMx_CCMR2)
Address offset: 0x1C
Reset value: 0x0000 0000
Refer to the above CCMR1 register description.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC4M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC3M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

OC3
PE

OC3
FE

rw
15

14

OC4
CE

13

12

OC4M[2:0]
IC4F[3:0]

rw

720/1709

rw

rw

11

10

OC4
PE

OC4
FE

9

8

CC4S[1:0]

rw

OC3
CE.

IC4PSC[1:0]
rw

rw

rw

OC3M[2:0]
IC3F[3:0]

rw

rw

rw

RM0385 Rev 7

rw

rw

0

CC3S[1:0]

IC3PSC[1:0]
rw

rw

rw

rw

rw

RM0385

Advanced-control timers (TIM1/TIM8)

Output compare mode
Bits 31:25 Reserved, must be kept at reset value.
Bit 24 OC4M[3]: Output Compare 4 mode - bit 3
Bits 23:17 Reserved, must be kept at reset value.
Bit 16 OC3M[3]: Output Compare 3 mode - bit 3
Bit 15 OC4CE: Output compare 4 clear enable
Bits 14:12 OC4M: Output compare 4 mode
Bit 11 OC4PE: Output compare 4 preload enable
Bit 10 OC4FE: Output compare 4 fast enable
Bits 9:8 CC4S: Capture/Compare 4 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC4 channel is configured as output
01: CC4 channel is configured as input, IC4 is mapped on TI4
10: CC4 channel is configured as input, IC4 is mapped on TI3
11: CC4 channel is configured as input, IC4 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC4S bits are writable only when the channel is OFF (CC4E = ‘0’ in TIMx_CCER).
Bit 7 OC3CE: Output compare 3 clear enable
Bits 6:4 OC3M: Output compare 3 mode
Bit 3 OC3PE: Output compare 3 preload enable
Bit 2 OC3FE: Output compare 3 fast enable
Bits 1:0 CC3S: Capture/Compare 3 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC3 channel is configured as output
01: CC3 channel is configured as input, IC3 is mapped on TI3
10: CC3 channel is configured as input, IC3 is mapped on TI4
11: CC3 channel is configured as input, IC3 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC3S bits are writable only when the channel is OFF (CC3E = ‘0’ in TIMx_CCER).

Input capture mode
Bits 31:16 Reserved, must be kept at reset value.
Bits 15:12 IC4F: Input capture 4 filter
Bits 11:10 IC4PSC: Input capture 4 prescaler
Bits 9:8 CC4S: Capture/Compare 4 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC4 channel is configured as output
01: CC4 channel is configured as input, IC4 is mapped on TI4
10: CC4 channel is configured as input, IC4 is mapped on TI3
11: CC4 channel is configured as input, IC4 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC4S bits are writable only when the channel is OFF (CC4E = ‘0’ in TIMx_CCER).

RM0385 Rev 7

721/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bits 7:4 IC3F: Input capture 3 filter
Bits 3:2 IC3PSC: Input capture 3 prescaler
Bits 1:0 CC3S: Capture/compare 3 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC3 channel is configured as output
01: CC3 channel is configured as input, IC3 is mapped on TI3
10: CC3 channel is configured as input, IC3 is mapped on TI4
11: CC3 channel is configured as input, IC3 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC3S bits are writable only when the channel is OFF (CC3E = ‘0’ in TIMx_CCER).

22.4.9

TIM1/TIM8 capture/compare enable register (TIMx_CCER)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CC6P

CC6E

Res.

Res.

CC5P

CC5E

rw

rw

rw

rw

5

4

CC2P

CC2E

rw

rw

15

14

13

12

CC4NP

Res.

CC4P

CC4E

rw

rw

rw

11

10

CC3NP CC3NE
rw

rw

9

8

CC3P

CC3E

rw

rw

7

6

CC2NP CC2NE
rw

rw

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 CC6P: Capture/Compare 6 output polarity
Refer to CC1P description
Bit 20 CC6E: Capture/Compare 6 output enable
Refer to CC1E description
Bits 19:18 Reserved, must be kept at reset value.
Bit 17 CC5P: Capture/Compare 5 output polarity
Refer to CC1P description
Bit 16 CC5E: Capture/Compare 5 output enable
Refer to CC1E description
Bit 15 CC4NP: Capture/Compare 4 complementary output polarity
Refer to CC1NP description
Bit 14 Reserved, must be kept at reset value.
Bit 13 CC4P: Capture/Compare 4 output polarity
Refer to CC1P description
Bit 12 CC4E: Capture/Compare 4 output enable
Refer to CC1E description
Bit 11 CC3NP: Capture/Compare 3 complementary output polarity
Refer to CC1NP description
Bit 10 CC3NE: Capture/Compare 3 complementary output enable
Refer to CC1NE description

722/1709

RM0385 Rev 7

3

2

CC1NP CC1NE
rw

rw

1

0

CC1P

CC1E

rw

rw

RM0385

Advanced-control timers (TIM1/TIM8)

Bit 9 CC3P: Capture/Compare 3 output polarity
Refer to CC1P description
Bit 8 CC3E: Capture/Compare 3 output enable
Refer to CC1E description
Bit 7 CC2NP: Capture/Compare 2 complementary output polarity
Refer to CC1NP description
Bit 6 CC2NE: Capture/Compare 2 complementary output enable
Refer to CC1NE description
Bit 5 CC2P: Capture/Compare 2 output polarity
Refer to CC1P description
Bit 4 CC2E: Capture/Compare 2 output enable
Refer to CC1E description
Bit 3 CC1NP: Capture/Compare 1 complementary output polarity
CC1 channel configured as output:
0: OC1N active high.
1: OC1N active low.
CC1 channel configured as input:
This bit is used in conjunction with CC1P to define the polarity of TI1FP1 and TI2FP1. Refer
to CC1P description.
Note: This bit is not writable as soon as LOCK level 2 or 3 has been programmed (LOCK bits
in TIMx_BDTR register) and CC1S=”00” (channel configured as output).
On channels having a complementary output, this bit is preloaded. If the CCPC bit is set in the
TIMx_CR2 register then the CC1NP active bit takes the new value from the preloaded bit only
when a Commutation event is generated.
Bit 2 CC1NE: Capture/Compare 1 complementary output enable
0: Off - OC1N is not active. OC1N level is then function of MOE, OSSI, OSSR, OIS1, OIS1N
and CC1E bits.
1: On - OC1N signal is output on the corresponding output pin depending on MOE, OSSI,
OSSR, OIS1, OIS1N and CC1E bits.
On channels having a complementary output, this bit is preloaded. If the CCPC bit is set in the
TIMx_CR2 register then the CC1NE active bit takes the new value from the preloaded bit only
when a Commutation event is generated.

RM0385 Rev 7

723/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bit 1 CC1P: Capture/Compare 1 output polarity
CC1 channel configured as output:
0: OC1 active high
1: OC1 active low
CC1 channel configured as input: CC1NP/CC1P bits select the active polarity of TI1FP1
and TI2FP1 for trigger or capture operations.
00: non-inverted/rising edge. The circuit is sensitive to TIxFP1 rising edge (capture or trigger
operations in reset, external clock or trigger mode), TIxFP1 is not inverted (trigger operation
in gated mode or encoder mode).
01: inverted/falling edge. The circuit is sensitive to TIxFP1 falling edge (capture or trigger
operations in reset, external clock or trigger mode), TIxFP1 is inverted (trigger operation in
gated mode or encoder mode).
10: reserved, do not use this configuration.
11: non-inverted/both edges/ The circuit is sensitive to both TIxFP1 rising and falling edges
(capture or trigger operations in reset, external clock or trigger mode), TIxFP1 is not inverted
(trigger operation in gated mode). This configuration must not be used in encoder mode.
Note: This bit is not writable as soon as LOCK level 2 or 3 has been programmed (LOCK bits
in TIMx_BDTR register).
On channels having a complementary output, this bit is preloaded. If the CCPC bit is set in the
TIMx_CR2 register then the CC1P active bit takes the new value from the preloaded bit only
when a Commutation event is generated.
Bit 0 CC1E: Capture/Compare 1 output enable
CC1 channel configured as output:
0: Off - OC1 is not active. OC1 level is then function of MOE, OSSI, OSSR, OIS1, OIS1N
and CC1NE bits.
1: On - OC1 signal is output on the corresponding output pin depending on MOE, OSSI,
OSSR, OIS1, OIS1N and CC1NE bits.
CC1 channel configured as input: This bit determines if a capture of the counter value
can actually be done into the input capture/compare register 1 (TIMx_CCR1) or not.
0: Capture disabled.
1: Capture enabled.
On channels having a complementary output, this bit is preloaded. If the CCPC bit is set in the
TIMx_CR2 register then the CC1E active bit takes the new value from the preloaded bit only
when a Commutation event is generated.

724/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

Table 146. Output control bits for complementary OCx and OCxN channels with break feature
Output states(1)

Control bits
MOE bit OSSI bit OSSR bit CCxE bit CCxNE bit

1

0

0

Output disabled (not driven by the timer: Hi-Z)
OCx=0, OCxN=0

0

0

1

Output disabled (not driven
OCxREF + Polarity
by the timer: Hi-Z)
OCxN = OCxREF xor CCxNP
OCx=0

0

1

0

OCxREF + Polarity
OCx=OCxREF xor CCxP

Output Disabled (not driven by
the timer: Hi-Z)
OCxN=0

X

1

1

OCREF + Polarity + deadtime

Complementary to OCREF (not
OCREF) + Polarity + dead-time

1

0

1

Off-State (output enabled
with inactive state)
OCx=CCxP

OCxREF + Polarity
OCxN = OCxREF x or CCxNP

1

1

0

OCxREF + Polarity
OCx=OCxREF xor CCxP

Off-State (output enabled with
inactive state)
OCxN=CCxNP

X

X

0

0

0

1

1

0

1

1

X

1

OCxN output state

X

0

0

OCx output state

X

Output disabled (not driven by the timer anymore). The
output state is defined by the GPIO controller and can be
High, Low or Hi-Z.
Off-State (output enabled with inactive state)
Asynchronously: OCx=CCxP, OCxN=CCxNP (if BRK or
BRK2 is triggered).
Then (this is valid only if BRK is triggered), if the clock is
present: OCx=OISx and OCxN=OISxN after a dead-time,
assuming that OISx and OISxN do not correspond to OCX
and OCxN both in active state (may cause a short circuit
when driving switches in half-bridge configuration).
Note: BRK2 can only be used if OSSI = OSSR = 1.

1. When both outputs of a channel are not used (control taken over by GPIO), the OISx, OISxN, CCxP and CCxNP bits must
be kept cleared.

Note:

The state of the external I/O pins connected to the complementary OCx and OCxN channels
depends on the OCx and OCxN channel state and the GPIO registers.

RM0385 Rev 7

725/1709
740

Advanced-control timers (TIM1/TIM8)

22.4.10

RM0385

TIM1/TIM8 counter (TIMx_CNT)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

UIF
CPY

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

r

CNT[15:0]
rw

Bit 31 UIFCPY: UIF copy
This bit is a read-only copy of the UIF bit of the TIMx_ISR register. If the UIFREMAP bit in
the TIMxCR1 is reset, bit 31 is reserved and read at 0.
Bits 30:16 Reserved, must be kept at reset value.
Bits 15:0 CNT[15:0]: Counter value

22.4.11

TIM1/TIM8 prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

PSC[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 PSC[15:0]: Prescaler value
The counter clock frequency (CK_CNT) is equal to fCK_PSC / (PSC[15:0] + 1).
PSC contains the value to be loaded in the active prescaler register at each update event
(including when the counter is cleared through UG bit of TIMx_EGR register or through
trigger controller when configured in “reset mode”).

22.4.12

TIM1/TIM8 auto-reload register (TIMx_ARR)
Address offset: 0x2C
Reset value: 0xFFFF

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

ARR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 ARR[15:0]: Auto-reload value
ARR is the value to be loaded in the actual auto-reload register.
Refer to the Section 22.3.1: Time-base unit on page 648 for more details about ARR update
and behavior.
The counter is blocked while the auto-reload value is null.

726/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

22.4.13

TIM1/TIM8 repetition counter register (TIMx_RCR)
Address offset: 0x30
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

REP[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 REP[15:0]: Repetition counter value
These bits allow the user to set-up the update rate of the compare registers (i.e. periodic
transfers from preload to active registers) when preload registers are enable, as well as the
update interrupt generation rate, if this interrupt is enable.
Each time the REP_CNT related downcounter reaches zero, an update event is generated
and it restarts counting from REP value. As REP_CNT is reloaded with REP value only at
the repetition update event U_RC, any write to the TIMx_RCR register is not taken in
account until the next repetition update event.
It means in PWM mode (REP+1) corresponds to:
the number of PWM periods in edge-aligned mode
the number of half PWM period in center-aligned mode.

22.4.14

TIM1/TIM8 capture/compare register 1 (TIMx_CCR1)
Address offset: 0x34
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR1[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 CCR1[15:0]: Capture/Compare 1 value
If channel CC1 is configured as output: CCR1 is the value to be loaded in the actual
capture/compare 1 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(bit OC1PE). Else the preload value is copied in the active capture/compare 1 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC1 output.
If channel CC1 is configured as input: CR1 is the counter value transferred by the last
input capture 1 event (IC1). The TIMx_CCR1 register is read-only and cannot be
programmed.

RM0385 Rev 7

727/1709
740

Advanced-control timers (TIM1/TIM8)

22.4.15

RM0385

TIM1/TIM8 capture/compare register 2 (TIMx_CCR2)
Address offset: 0x38
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR2[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 CCR2[15:0]: Capture/Compare 2 value
If channel CC2 is configured as output: CCR2 is the value to be loaded in the actual
capture/compare 2 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(bit OC2PE). Else the preload value is copied in the active capture/compare 2 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC2 output.
If channel CC2 is configured as input: CCR2 is the counter value transferred by the last
input capture 2 event (IC2). The TIMx_CCR2 register is read-only and cannot be
programmed.

22.4.16

TIM1/TIM8 capture/compare register 3 (TIMx_CCR3)
Address offset: 0x3C
Reset value: 0x0000

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR3[15:0]
rw

rw

Bits 15:0 CCR3[15:0]: Capture/Compare value
If channel CC3 is configured as output: CCR3 is the value to be loaded in the actual
capture/compare 3 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2 register
(bit OC3PE). Else the preload value is copied in the active capture/compare 3 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC3 output.
If channel CC3 is configured as input: CCR3 is the counter value transferred by the last
input capture 3 event (IC3). The TIMx_CCR3 register is read-only and cannot be
programmed.

728/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

22.4.17

TIM1/TIM8 capture/compare register 4 (TIMx_CCR4)
Address offset: 0x40
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR4[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 CCR4[15:0]: Capture/Compare value
If channel CC4 is configured as output: CCR4 is the value to be loaded in the actual
capture/compare 4 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2 register
(bit OC4PE). Else the preload value is copied in the active capture/compare 4 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC4 output.
If channel CC4 is configured as input: CCR4 is the counter value transferred by the last
input capture 4 event (IC4). The TIMx_CCR4 register is read-only and cannot be
programmed.

22.4.18

TIM1/TIM8 break and dead-time register (TIMx_BDTR)
Address offset: 0x44
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

BK2P

BK2E

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

15

14

13

12

11

10

MOE

AOE

BKP

BKE

OSSR

OSSI

rw

rw

rw

rw

rw

rw

Note:

23

22

21

LOCK[1:0]
rw

rw

20

19

BK2F[3:0]

18

17

16

BKF[3:0]

DTG[7:0]
rw

rw

rw

rw

rw

As the bits BK2P, BK2E, BK2F[3:0], BKF[3:0], AOE, BKP, BKE, OSSI, OSSR and DTG[7:0]
can be write-locked depending on the LOCK configuration, it can be necessary to configure
all of them during the first write access to the TIMx_BDTR register.
Bits 31:26 Reserved, must be kept at reset value.
Bit 25 BK2P: Break 2 polarity
0: Break input BRK2 is active low
1: Break input BRK2 is active high
Note: This bit cannot be modified as long as LOCK level 1 has been programmed (LOCK bits
in TIMx_BDTR register).
Note: Any write operation to this bit takes a delay of 1 APB clock cycle to become effective.

RM0385 Rev 7

729/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bit 24 BK2E: Break 2 enable
This bit enables the complete break 2 protection (including all sources connected to bk_acth
and BKIN sources, as per Figure 191: Break and Break2 circuitry overview).
0: Break2 function disabled
1: Break2 function enabled
Note: The BRKIN2 must only be used with OSSR = OSSI = 1.
Note: This bit cannot be modified when LOCK level 1 has been programmed (LOCK bits in
TIMx_BDTR register).
Note: Any write operation to this bit takes a delay of 1 APB clock cycle to become effective.
Bits 23:20 BK2F[3:0]: Break 2 filter
This bit-field defines the frequency used to sample BRK2 input and the length of the digital
filter applied to BRK2. The digital filter is made of an event counter in which N consecutive
events are needed to validate a transition on the output:
0000: No filter, BRK2 acts asynchronously
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Note: This bit cannot be modified when LOCK level 1 has been programmed (LOCK bits in
TIMx_BDTR register).
Bits 19:16 BKF[3:0]: Break filter
This bit-field defines the frequency used to sample BRK input and the length of the digital
filter applied to BRK. The digital filter is made of an event counter in which N consecutive
events are needed to validate a transition on the output:
0000: No filter, BRK acts asynchronously
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Note: This bit cannot be modified when LOCK level 1 has been programmed (LOCK bits in
TIMx_BDTR register).

730/1709

RM0385 Rev 7

RM0385

Advanced-control timers (TIM1/TIM8)

Bit 15 MOE: Main output enable
This bit is cleared asynchronously by hardware as soon as one of the break inputs is active
(BRK or BRK2). It is set by software or automatically depending on the AOE bit. It is acting
only on the channels which are configured in output.
0: In response to a break 2 event. OC and OCN outputs are disabled
In response to a break event or if MOE is written to 0: OC and OCN outputs are disabled or
forced to idle state depending on the OSSI bit.
1: OC and OCN outputs are enabled if their respective enable bits are set (CCxE, CCxNE in
TIMx_CCER register).
See OC/OCN enable description for more details (Section 22.4.9: TIM1/TIM8
capture/compare enable register (TIMx_CCER)).
Bit 14 AOE: Automatic output enable
0: MOE can be set only by software
1: MOE can be set by software or automatically at the next update event (if none of the break
inputs BRK and BRK2 is active)
Note: This bit can not be modified as long as LOCK level 1 has been programmed (LOCK bits
in TIMx_BDTR register).
Bit 13 BKP: Break polarity
0: Break input BRK is active low
1: Break input BRK is active high
Note: This bit can not be modified as long as LOCK level 1 has been programmed (LOCK bits
in TIMx_BDTR register).
Note: Any write operation to this bit takes a delay of 1 APB clock cycle to become effective.
Bit 12 BKE: Break enable
This bit enables the complete break protection (including all sources connected to bk_acth
and BKIN sources, as per Figure 191: Break and Break2 circuitry overview).
0: Break function disabled
1: Break function enabled
Note: This bit cannot be modified when LOCK level 1 has been programmed (LOCK bits in
TIMx_BDTR register).
Note: Any write operation to this bit takes a delay of 1 APB clock cycle to become effective.
Bit 11 OSSR: Off-state selection for Run mode
This bit is used when MOE=1 on channels having a complementary output which are
configured as outputs. OSSR is not implemented if no complementary output is implemented
in the timer.
See OC/OCN enable description for more details (Section 22.4.9: TIM1/TIM8
capture/compare enable register (TIMx_CCER)).
0: When inactive, OC/OCN outputs are disabled (the timer releases the output control which
is taken over by the GPIO logic, which forces a Hi-Z state).
1: When inactive, OC/OCN outputs are enabled with their inactive level as soon as CCxE=1
or CCxNE=1 (the output is still controlled by the timer).
Note: This bit can not be modified as soon as the LOCK level 2 has been programmed (LOCK
bits in TIMx_BDTR register).

RM0385 Rev 7

731/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bit 10 OSSI: Off-state selection for Idle mode
This bit is used when MOE=0 due to a break event or by a software write, on channels
configured as outputs.
See OC/OCN enable description for more details (Section 22.4.9: TIM1/TIM8
capture/compare enable register (TIMx_CCER)).
0: When inactive, OC/OCN outputs are disabled (the timer releases the output control which
is taken over by the GPIO logic and which imposes a Hi-Z state).
1: When inactive, OC/OCN outputs are first forced with their inactive level then forced to their
idle level after the deadtime. The timer maintains its control over the output.
Note: This bit can not be modified as soon as the LOCK level 2 has been programmed (LOCK
bits in TIMx_BDTR register).
Bits 9:8 LOCK[1:0]: Lock configuration
These bits offer a write protection against software errors.
00: LOCK OFF - No bit is write protected.
01: LOCK Level 1 = DTG bits in TIMx_BDTR register, OISx and OISxN bits in TIMx_CR2
register and BKE/BKP/AOE bits in TIMx_BDTR register can no longer be written.
10: LOCK Level 2 = LOCK Level 1 + CC Polarity bits (CCxP/CCxNP bits in TIMx_CCER
register, as long as the related channel is configured in output through the CCxS bits) as well
as OSSR and OSSI bits can no longer be written.
11: LOCK Level 3 = LOCK Level 2 + CC Control bits (OCxM and OCxPE bits in
TIMx_CCMRx registers, as long as the related channel is configured in output through the
CCxS bits) can no longer be written.
Note: The LOCK bits can be written only once after the reset. Once the TIMx_BDTR register
has been written, their content is frozen until the next reset.
Bits 7:0 DTG[7:0]: Dead-time generator setup
This bit-field defines the duration of the dead-time inserted between the complementary
outputs. DT correspond to this duration.
DTG[7:5]=0xx => DT=DTG[7:0]x tdtg with tdtg=tDTS.
DTG[7:5]=10x => DT=(64+DTG[5:0])xtdtg with Tdtg=2xtDTS.
DTG[7:5]=110 => DT=(32+DTG[4:0])xtdtg with Tdtg=8xtDTS.
DTG[7:5]=111 => DT=(32+DTG[4:0])xtdtg with Tdtg=16xtDTS.
Example if TDTS=125ns (8MHz), dead-time possible values are:
0 to 15875 ns by 125 ns steps,
16 us to 31750 ns by 250 ns steps,
32 us to 63us by 1 us steps,
64 us to 126 us by 2 us steps
Note: This bit-field can not be modified as long as LOCK level 1, 2 or 3 has been programmed
(LOCK bits in TIMx_BDTR register).

22.4.19

TIM1/TIM8 DMA control register (TIMx_DCR)
Address offset: 0x48
Reset value: 0x0000

15

14

13

Res.

Res.

Res.

12

11

10

9

8

DBL[4:0]
rw

rw

rw

rw

7

6

5

Res.

Res.

Res.

rw

Bits 15:13 Reserved, must be kept at reset value.

732/1709

RM0385 Rev 7

4

3

2

1

0

rw

rw

DBA[4:0]
rw

rw

rw

RM0385

Advanced-control timers (TIM1/TIM8)

Bits 12:8 DBL[4:0]: DMA burst length
This 5-bit vector defines the length of DMA transfers (the timer recognizes a burst transfer
when a read or a write access is done to the TIMx_DMAR address), i.e. the number of
transfers. Transfers can be in half-words or in bytes (see example below).
00000: 1 transfer
00001: 2 transfers
00010: 3 transfers
...
10001: 18 transfers
Example: Let us consider the following transfer: DBL = 7 bytes & DBA = TIM2_CR1.
– If DBL = 7 bytes and DBA = TIM2_CR1 represents the address of the byte to be
transferred, the address of the transfer should be given by the following equation:
(TIMx_CR1 address) + DBA + (DMA index), where DMA index = DBL
In this example, 7 bytes are added to (TIMx_CR1 address) + DBA, which gives us the
address from/to which the data will be copied. In this case, the transfer is done to 7 registers
starting from the following address: (TIMx_CR1 address) + DBA
According to the configuration of the DMA Data Size, several cases may occur:
– If you configure the DMA Data Size in half-words, 16-bit data will be transferred to each of
the 7 registers.
– If you configure the DMA Data Size in bytes, the data will also be transferred to 7 registers:
the first register will contain the first MSB byte, the second register, the first LSB byte and
so on. So with the transfer Timer, you also have to specify the size of data transferred by
DMA.
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:0 DBA[4:0]: DMA base address
This 5-bits vector defines the base-address for DMA transfers (when read/write access are
done through the TIMx_DMAR address). DBA is defined as an offset starting from the
address of the TIMx_CR1 register.
Example:
00000: TIMx_CR1,
00001: TIMx_CR2,
00010: TIMx_SMCR,
...

22.4.20

TIM1/TIM8 DMA address for full transfer (TIMx_DMAR)
Address offset: 0x4C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DMAB[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

DMAB[15:0]
rw

rw

RM0385 Rev 7

733/1709
740

Advanced-control timers (TIM1/TIM8)

RM0385

Bits 31:0 DMAB[31:0]: DMA register for burst accesses
A read or write operation to the DMAR register accesses the register located at the address
(TIMx_CR1 address) + (DBA + DMA index) x 4
where TIMx_CR1 address is the address of the control register 1, DBA is the DMA base
address configured in TIMx_DCR register, DMA index is automatically controlled by the DMA
transfer, and ranges from 0 to DBL (DBL configured in TIMx_DCR).

22.4.21

TIM1/TIM8 capture/compare mode register 3 (TIMx_CCMR3)
Address offset: 0x54
Reset value: 0x0000 0000
Refer to the above CCMR1 register description. Channels 5 and 6 can only be configured in
output.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC6M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC5M[3]

rw
15

14

OC6
CE

13

12

OC6M[2:0]

rw

rw

rw

rw

11

10

OC6
PE

OC6FE

rw

rw

9
Res.

rw

8

7

Res.

OC5
CE
rw

Output compare mode
Bits 31:25 Reserved, must be kept at reset value.
Bits 23:17 Reserved, must be kept at reset value.
Bit 15 OC6CE: Output compare 6 clear enable
Bits 24, 14, 13, 12 OC6M[3:0]: Output compare 6 mode
Bit 11 OC6PE: Output compare 6 preload enable
Bit 10 OC6FE: Output compare 6 fast enable
Bits 9:8 Reserved, must be kept at reset value.
Bit 7 OC5CE: Output compare 5 clear enable
Bits 16, 6, 5, 4 OC5M[3:0]: Output compare 5 mode
Bit 3 OC5PE: Output compare 5 preload enable
Bit 2 OC5FE: Output compare 5 fast enable
Bits 1:0 Reserved, must be kept at reset value.

734/1709

RM0385 Rev 7

6

5

4

OC5M[2:0]
rw

rw

3

2

OC5PE OC5FE
rw

rw

rw

1

0

Res.

Res.

RM0385

Advanced-control timers (TIM1/TIM8)

22.4.22

TIM1/TIM8 capture/compare register 5 (TIMx_CCR5)
Address offset: 0x58
Reset value: 0x0000 0000

31

30

29

GC5C3 GC5C2 GC5C1

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

CCR5[15:0]
rw

rw

Bit 31 GC5C3: Group Channel 5 and Channel 3
Distortion on Channel 3 output:
0: No effect of OC5REF on OC3REFC
1: OC3REFC is the logical AND of OC3REFC and OC5REF
This bit can either have immediate effect or be preloaded and taken into account after an
update event (if preload feature is selected in TIMxCCMR2).
Note: it is also possible to apply this distortion on combined PWM signals.
Bit 30 GC5C2: Group Channel 5 and Channel 2
Distortion on Channel 2 output:
0: No effect of OC5REF on OC2REFC
1: OC2REFC is the logical AND of OC2REFC and OC5REF
This bit can either have immediate effect or be preloaded and taken into account after an
update event (if preload feature is selected in TIMxCCMR1).
Note: it is also possible to apply this distortion on combined PWM signals.
Bit 29 GC5C1: Group Channel 5 and Channel 1
Distortion on Channel 1 output:
0: No effect of OC5REF on OC1REFC5
1: OC1REFC is the logical AND of OC1REFC and OC5REF
This bit can either have immediate effect or be preloaded and taken into account after an
update event (if preload feature is selected in TIMxCCMR1).
Note: it is also possible to apply this distortion on combined PWM signals.
Bits 28:16 Reserved, must be kept at reset value.
Bits 15:0 CCR5[15:0]: Capture/Compare 5 value
CCR5 is the value to be loaded in the actual capture/compare 5 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR3 register
(bit OC5PE). Else the preload value is copied in the active capture/compare 5 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC5 output.

RM0385 Rev 7

735/1709
740

Advanced-control timers (TIM1/TIM8)

22.4.23

RM0385

TIM1/TIM8 capture/compare register 6 (TIMx_CCR6)
Address offset: 0x5C
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR6[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 CCR6[15:0]: Capture/Compare 6 value
CCR6 is the value to be loaded in the actual capture/compare 6 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR3 register
(bit OC6PE). Else the preload value is copied in the active capture/compare 6 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC6 output.

736/1709

RM0385 Rev 7

0x24

TIM1_CNT

Reset value

0

RM0385 Rev 7

0

0

0
0
0

OC4M
[2:0]

0
0

IC4F[3:0]

0

0

CC4IF
CC3IF
CC2IF
CC1IF
UIF

0
0
0
0
0

Res.
Res.

CC3G

0
0

IC2
PSC
[1:0]
CC2
S
[1:0]

0
0

0

0
0

0
0

0

0
0

IC4
PSC
[1:0]

CC4
S
[1:0]
0

0
0

0
0

CC4
S
[1:0]

0

0

CC2G
CC1G
UG

CC3IE
CC2IE
CC1IE
UIE

MSM

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CNT[15:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

OIS1
TI1S

Res.

UIFREMAP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ARPE

DIR
OPM
URS
UDIS
CEN

0
0
0
0
0

CCDS
CCUS
Res.
CCPC

0
0
0

0

TS[2:0]

0
0
0
0

0
0
0
0
0

CC2
S
[1:0]
OC1M
[2:0]

0
0

IC1F[3:0]

0
0

OC3M
[2:0]

0
0

IC3F[3:0]

Res.

OIS2

OIS2N
OIS1N

OIS3

MMS
[2:0]

OC1FE

CC4IE

0

ETF[3:0]

0

0

OC1PE

0

COMIE

0

TIE

0

BIE

0

UDE

0

CC1DE

0

CC2DE

0

CC3DE

OIS3N

0

0

OC3FE

COMIF
0

COM

TIF
0
CC4G

BIF
0
TG

B2IF
0
BG

CC1OF
0

B2G

CC2OF
0

OC1CE

CC3OF

OIS4

0

CMS
[1:0]

OC3PE

IC2F[3:0]
OC2FE

0

0

CC1E

0
0

Res.

0

ETP
S
[1:0]

0

CC1P

0
0
OC2PE

0

CC4DE

0

COMDE

ECE
0

TDE

Res.

0

OC3CE

0
CC4OF

Reset value
0

Res.

Res.

ETP
0

Res.

0

0

CC1NE

0

0

0

CC1NP

0

0

0

CC2E

0
Res.

Res.

OIS5

Res.

OIS6

Res.

0

CC2P

0

CC3E

0
OC2M
[2:0]

OC4FE

0
Res.

Res.

SMS[3]

Reset value
0

Res.

Res.

Res.

Res.

Res.

0

OC4PE

OC2CE

CC5IF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
CKD
[1:0]

CC2NE

0

CC2NP

0

0

CC3P

0

0

CC3NE

Reset value

CC3NP

Reset value

CC4E

OC1M[3]

CC6IF

Res.

Res.

Res.

Res.

0

CC4P

Res.

Res.

Res.

Res.

Res.

0

Res.

OC4CE

0
OC3M[3]

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

CC5E

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

CC5P

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MMS2[3:0]

Res.

CC6E

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

OC2M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

CC6P

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

OC4M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

TIM1_CCER

Res.

0x20

Res.

TIM1_CCMR2
Input Capture
mode

Res.

0x1C

Res.

TIM1_CCMR2
Output
Compare mode

Res.

TIM1_CCMR1
Input Capture
mode
Res.

TIM1_CCMR1
Output
Compare mode

Res.

0x18
TIM1_EGR

Res.

0x14
TIM1_SR

Res.

0x10
TIM1_DIER

Res.

0x0C
TIM1_SMCR

Res.

0x08
TIM1_CR2

Res.

0x04
TIM1_CR1

Res.

0x00

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

Offset

Res.

22.4.24

UIFCP

RM0385
Advanced-control timers (TIM1/TIM8)

TIM1 register map
TIM1 registers are mapped as 16-bit addressable registers as described in the table below:
Table 147. TIM1 register map and reset values

0
0

IC1
PSC
[1:0]
CC1
S
[1:0]

0
0

0

0
0

0

SMS[2:0]
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0
0

CC1
S
[1:0]

0

0

0

0

CC3
S
[1:0]

IC3
PSC
[1:0]

CC3
S
[1:0]
0

737/1709

740

0x5C

738/1709

TIM1_CCR6

Reset value

RM0385 Rev 7
OC5M[3]
OC6CE

0

Res.

Res.

Reset value
0

0
0

0

0
0

0

0

0
0

0

0

0
0
0

0

0

OC6M
[2:0]

0

0

0
0

0

0
0

0
0

0
0

0

0
0

0

0

0

0

0

0

0

DBL[4:0]

0

0

0

0

0

0

0
0

0

0

0

0

0

0

0

0

0

OC5M
[2:0]

0

CCR5[15:0]

0

CCR6[15:0]

0
Res.

Reset value
0
0

0

0

0

Res.

0
0

0

0

0

Res.

Res.

1

OC5FE

0
0

0

0

0

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

OC5PE

0
0

0

0

0

1

0

Res.

0
0

0

0

0

0

0

Res.

BKF[3:0]
0

0

0

0

1

Res.

0
0

0

0

1

0

Res.

Reset value
0

0

0

1

0

OC5CE

0

0

0

OSSI

Reset value
0

0

1

0

Res.

0

0

1

0

OC6FE

0

1

0

BKE

0

0

OSSR

Reset value

BKP

Reset value

AOE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

MOE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

OC6PE

Res.

Res.

Res.
0

Res.

Res.

Res.

Res.

BK2E

0

Res.

Res.

Res.

BK2P

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BK2F[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

OC6M[3]

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0
0

Res.

0
0

Res.

0
0

Res.

Reset value

Res.

Reset value

Res.

TIM1_CCR5
Res.

Reset value

Res.

0x58

Res.

TIM1_CCMR3
Output
Compare mode

Res.

TIM1_DMAR

Res.

0x4C
Res.

TIM1_DCR

Res.

0x48

Res.

TIM1_BDTR

Res.

0x44

GC5C1

TIM1_CCR4

Res.

0x40
Res.

TIM1_CCR3

Res.

0x3C

Res.

TIM1_CCR2

Res.

0x38

Res.

TIM1_CCR1

Res.

0x34

Res.

TIM1_RCR

Res.

TIM1_ARR

Res.

0x54
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIM1_PSC

Res.

0x30

GC5C2

0x2C

GC5C3

0x28

Res.

Offset
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

Advanced-control timers (TIM1/TIM8)
RM0385

Table 147. TIM1 register map and reset values (continued)

PSC[15:0]

ARR[15:0]

REP[15:0]

CCR1[15:0]

CCR2[15:0]

CCR3[15:0]

CCR4[15:0]

LOC
K
[1:0]
DT[7:0]

0

0
0
0
0
0
0

1
1
1
1
1
1

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0

0

0

0
0

DBA[4:0]

DMAB[15:0]
0
0
0
0
0

0
0
0
0
0

0
0
0
0

0

0

0

0

0

0

0

0

0

0

0

0

Refer to Section 2.2.2: Memory map and register boundary addresses for the register
boundary addresses.

0x24

TIM8_CNT

Reset value

0

0

RM0385 Rev 7

0

0

0
0
0

OC4M
[2:0]

0
0

IC4F[3:0]

0

0

0
0

IC2
PSC
[1:0]
CC2
S
[1:0]

0
0

0

0
0

0
0

0

0
0

0

IC4
PSC
[1:0]

CC4
S
[1:0]

0
0

0
0

CC4
S
[1:0]

0

0

UIE

UIF

0
0
0
0
0

UG

CC1IE

CC1IF

0
CC1G

CC2IE

CC2IF

0
CC2G

CC3IE

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CNT[15:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

UIFREMA

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ARPE

DIR
OPM
URS
UDIS
CEN

0
0
0
0
0

CCDS
CCUS
Res.
CCPC

0

TS[2:0]

0
0
0
0

0
0
0
0
0

CC2
S
[1:0]
OC1M
[2:0]

0
0

IC1F[3:0]

0
0

OC3M
[2:0]

0
0

IC3F[3:0]

Res.

TI1S
MMS
[2:0]

OC1FE

CC4IE
CC3IF

0
CC3G

OIS1

OIS2N

0

0

OC1PE

COMIE

0
COM

0

CC4G

CC4IF

TIE

0

TG

ETF[3:0]
MSM

OIS3
OIS2

OIS3N

OIS1N

OIS4

Res.

0

0

OC3FE

IC2F[3:0]

0

CMS
[1:0]

OC3PE

0

0

CC1E

0
0

0

CC1P

0
COMIF

Reset value
TIF

BIE

0

BIF

0

B2IF

0

CC1OF

0

CC2OF

0

Res.

0

Res.

0

CC3OF

0

Res.

0

CC4OF

0

Res.

0

SBIF

0

Res.

UDE

0

0

0

BG

0

0

0

B2G

0

0

0

OC1CE

0

CC1DE

0

CC2DE

0

Res.

OIS5

Res.

OIS6

Res.

0

CC1NE

0

0

0

CC1NP

0
0
OC2FE

0

ETP
S
[1:0]

0

CC2E

0

0

OC3CE

0

0

0

CC2P

0

CC3E

0
OC2M
[2:0]

OC4FE

0

CC3DE

Reset value

OC2PE

0

CC4DE

0

COMDE

ECE
0

TDE

ETP
0

Res.

Res.

0

Res.

Res.

SMS[3]
0

Res.

Res.

Res.

Res.

Res.

Res.

0

CKD
[1:0]

CC2NE

0

CC2NP

0

0

CC3P

Reset value

CC3NE

OC2CE

CC5IF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

OC4PE

Reset value

CC3NP

OC1M[3]

CC6IF

Res.

Res.

Res.

Res.

0

CC4E

Res.

Res.

Res.

Res.

0

CC4P

OC4CE

0
OC3M[3]

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

CC5E

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

CC5P

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MMS2[3:0]

Res.

CC6E

0

Res.

Reset value

CC6P

Res.

Res.

OC2M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

OC4M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

TIM8_CCER

Res.

0x20

Res.

TIM8_CCMR2
Input Capture
mode

Res.

0x1C

Res.

TIM8_CCMR2
Output
Compare mode

Res.

TIM8_CCMR1
Input Capture
mode
Res.

TIM8_CCMR1
Output
Compare mode

Res.

0x18
TIM8_EGR

Res.

0x14
TIM8_SR

Res.

0x10
TIM8_DIER

Res.

0x0C
TIM8_SMCR

Res.

0x08
TIM8_CR2

Res.

0x04
TIM8_CR1

Res.

0x00

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

Offset

Res.

22.4.25

UIFCPY

RM0385
Advanced-control timers (TIM1/TIM8)

TIM8 register map
TIM8 registers are mapped as 16-bit addressable registers as described in the table below:
Table 148. TIM8 register map and reset values

0
0

0
0

IC1
PSC
[1:0]
CC1
S
[1:0]

0
0

0

0
0

0

SMS[2:0]
0
0
0

CC1
S
[1:0]

0

0

0

0

CC3
S
[1:0]

0

IC3
PSC
[1:0]

CC3
S
[1:0]

739/1709

740

0x58

0x5C

740/1709
TIM8_CCR5

Reset value

0

0

0

TIM8_CCR6

Reset value

RM0385 Rev 7
Res.

Res.
OC6CE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC5M[3]

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC6M[3]

Res.

Res.

0
0
0
0

Res.
Res.
Res.
Res.
Res.

BKF[3:0]

Reset value
0

0
0

0

0
0

0

0

0

0
0

Reset value

0

0

0

0

0

0

0

0

OC6M
[2:0]

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0
0
0

0

0
0

0
0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0
0

DBL[4:0]
0
0
0

Res.

0
0

0

0

0

Res.

Reset value
0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

0

0

OSSI

Reset value
0

BKE

Res.

Res.

Res.

0

0

OSSR

Res.

Res.

Res.

Res.

Reset value
0

0

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0
0

1
1

0
0

0
0

0
0

0
0

0
0

0
0

0

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

0

0

0

1

0

0

0

0

0

0

OC5M
[2:0]

0

CCR5[15:0]

0

CCR6[15:0]

0
Res.

0

Res.

Res.

Res.

Res.

0

0

1

0

Res.

0

Res.

Res.

Res.

Res.

Reset value
0

1

0

OC5FE

0

Res.

Res.

Res.

Res.

Res.

0

1

0

OC5PE

BKP

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
1

0

Res.

AOE

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

0

OC5CE

MOE

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
0

Res.

BK2E

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

OC6FE

BK2P

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

OC6PE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0
BK2F[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

TIM8_CCMR3
Output
Compare mode

Res.

TIM8_DMAR

Res.

0x4C

Res.

TIM8_DCR

Res.

TIM8_BDTR

Res.

0x48

GC5C1

0x44
Res.

TIM8_CCR4

Res.

0x40

Res.

TIM8_CCR3

Res.

0x3C

Res.

TIM8_CCR2

Res.

0x38

Res.

TIMx_CCR1

Res.

TIM8_RCR

Res.

0x34

Res.

0x54
TIM8_ARR

Res.

0x30

GC5C2

0x2C

GC5C3

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

TIM8_PSC
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Register
name
Res.

0x28

Res.

Offset

Res.

Advanced-control timers (TIM1/TIM8)
RM0385

Table 148. TIM8 register map and reset values (continued)

PSC[15:0]

ARR[15:0]

REP[15:0]

CCR1[15:0]

CCR2[15:0]

CCR3[15:0]

CCR4[15:0]

LOC
K
[1:0]
DT[7:0]

0
0
0
0
0
0

1
1
1
1
1
1

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

0
0
0

0

0

0
0

DBA[4:0]

DMAB[15:0]
0
0
0
0
0

0
0
0
0
0

0
0
0
0

0

0

0

0

0

0

0

0

0

0

0

0

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

23

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

23.1

TIM2/TIM3/TIM4/TIM5 introduction
The general-purpose timers consist of a 16-bit or 32-bit auto-reload counter driven by a
programmable prescaler.
They may be used for a variety of purposes, including measuring the pulse lengths of input
signals (input capture) or generating output waveforms (output compare and PWM).
Pulse lengths and waveform periods can be modulated from a few microseconds to several
milliseconds using the timer prescaler and the RCC clock controller prescalers.
The timers are completely independent, and do not share any resources. They can be
synchronized together as described in Section 23.3.19: Timer synchronization.

23.2

TIM2/TIM3/TIM4/TIM5 main features
General-purpose TIMx timer features include:
•

16-bit (TIM3, TIM4) or 32-bit (TIM2 and TIM5) up, down, up/down auto-reload counter.

•

16-bit programmable prescaler used to divide (also “on the fly”) the counter clock
frequency by any factor between 1 and 65535.

•

Up to 4 independent channels for:
–

Input capture

–

Output compare

–

PWM generation (Edge- and Center-aligned modes)

–

One-pulse mode output

•

Synchronization circuit to control the timer with external signals and to interconnect
several timers.

•

Interrupt/DMA generation on the following events:
–

Update: counter overflow/underflow, counter initialization (by software or
internal/external trigger)

–

Trigger event (counter start, stop, initialization or count by internal/external trigger)

–

Input capture

–

Output compare

•

Supports incremental (quadrature) encoder and hall-sensor circuitry for positioning
purposes

•

Trigger input for external clock or cycle-by-cycle current management

RM0385 Rev 7

741/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 207. General-purpose timer block diagram

Internal clock (CK_INT)
TIMxCLK from RCC
ETRF
ETR

TIMx_ETR

Trigger
controller
TRGO

Polarity selection & edge ETRP
Input filter
detector & prescaler
ITR0
ITR1
ITR2
ITR3

to other timers
to DAC/ADC
TGI

ITR
TRC

TRGI

Slave
controller Reset, enable, up, count
mode

TI1F_ED

Encoder
interface

TI1FP1
TI2FP2

U

Auto-reload register

Stop, clear or up/down
CK_PSC
XOR
TI1
TIMx_CH1
TI2

TIMx_CH2

Input filter &
edge detector

Input filter &
edge detector

TI1FP1
TI1FP2

IC1

PSC CK_CNT
prescaler
CC1I U
Prescaler

TRC
TI2FP1
TI2FP2
TRC

IC1PS
CC2I

IC2

Prescaler

TI3

TIMx_CH3

TI4

TIMx_CH4

Input filter &
edge detector

Input filter &
edge detector

IC3

Prescaler

TRC
TI4FP3
TI4FP4

CNT counter
CC1I

Capture/Compare 1 register

Capture/Compare 2 register OC2REF

Capture/Compare 3 register

Prescaler

TIMx_CH1

Output OC2
control

TIMx_CH2

OC3REF

Output OC3
control

TIMx_CH3

Output OC4
control

TIMx_CH4

CC4I

U
IC4PS

Output OC1
control

CC3I

U

IC3PS
CC4I

IC4

OC1REF

CC2I

U

IC2PS
CC3I

TI3FP3
TI3FP4

+/-

UI
U

Capture/Compare 4 register OC4REF

TRC
ETRF

Notes:
Reg

Preload registers transferred
to active registers on U event
according to control bit
Event
Interrupt & DMA output

MS19673V1

742/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

23.3

TIM2/TIM3/TIM4/TIM5 functional description

23.3.1

Time-base unit
The main block of the programmable timer is a 16-bit/32-bit counter with its related autoreload register. The counter can count up, down or both up and down but also down or both
up and down. The counter clock can be divided by a prescaler.
The counter, the auto-reload register and the prescaler register can be written or read by
software. This is true even when the counter is running.
The time-base unit includes:
•

Counter Register (TIMx_CNT)

•

Prescaler Register (TIMx_PSC):

•

Auto-Reload Register (TIMx_ARR)

The auto-reload register is preloaded. Writing to or reading from the auto-reload register
accesses the preload register. The content of the preload register are transferred into the
shadow register permanently or at each update event (UEV), depending on the auto-reload
preload enable bit (ARPE) in TIMx_CR1 register. The update event is sent when the counter
reaches the overflow (or underflow when downcounting) and if the UDIS bit equals 0 in the
TIMx_CR1 register. It can also be generated by software. The generation of the update
event is described in detail for each configuration.
The counter is clocked by the prescaler output CK_CNT, which is enabled only when the
counter enable bit (CEN) in TIMx_CR1 register is set (refer also to the slave mode controller
description to get more details on counter enabling).
Note that the actual counter enable signal CNT_EN is set 1 clock cycle after CEN.

Prescaler description
The prescaler can divide the counter clock frequency by any factor between 1 and 65536. It
is based on a 16-bit counter controlled through a 16-bit/32-bit register (in the TIMx_PSC
register). It can be changed on the fly as this control register is buffered. The new prescaler
ratio is taken into account at the next update event.
Figure 208 and Figure 209 give some examples of the counter behavior when the prescaler
ratio is changed on the fly:

RM0385 Rev 7

743/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 208. Counter timing diagram with prescaler division change from 1 to 2

CK_PSC

CEN
Timerclock = CK_CNT

Counter register

F7

F8

F9

FA FB FC

01

00

02

03

Update event (UEV)

Prescaler control register

0

1

Write a new value in TIMx_PSC
Prescaler buffer

0

Prescaler counter

0

1

0

1

0

1

1

0

1

0

MS31076V2

Figure 209. Counter timing diagram with prescaler division change from 1 to 4

CK_PSC
CEN

Timerclock = CK_CNT

Counter register

F7

F8

F9

FA FB FC

00

01

Update event (UEV)

Prescaler control register

0

3

Write a new value in TIMx_PSC
Prescaler buffer

Prescaler counter

0

3

0

0

1

2

3

0

1

2

3
MS31077V2

744/1709

RM0385 Rev 7

RM0385

23.3.2

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

Counter modes
Upcounting mode
In upcounting mode, the counter counts from 0 to the auto-reload value (content of the
TIMx_ARR register), then restarts from 0 and generates a counter overflow event.
An Update event can be generated at each counter overflow or by setting the UG bit in the
TIMx_EGR register (by software or by using the slave mode controller).
The UEV event can be disabled by software by setting the UDIS bit in TIMx_CR1 register.
This is to avoid updating the shadow registers while writing new values in the preload
registers. Then no update event occurs until the UDIS bit has been written to 0. However,
the counter restarts from 0, as well as the counter of the prescaler (but the prescale rate
does not change). In addition, if the URS bit (update request selection) in TIMx_CR1
register is set, setting the UG bit generates an update event UEV but without setting the UIF
flag (thus no interrupt or DMA request is sent). This is to avoid generating both update and
capture interrupts when clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):
•

The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register)

•

The auto-reload shadow register is updated with the preload value (TIMx_ARR)

The following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.
Figure 210. Counter timing diagram, internal clock divided by 1

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

31

32

33

34 35 36

00

01

02

03

04

05

06

07

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31078V2

RM0385 Rev 7

745/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 211. Counter timing diagram, internal clock divided by 2

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0035

0034

0036

0000

0001

0002

0003

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31079V2

Figure 212. Counter timing diagram, internal clock divided by 4

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0035

0036

0000

0001

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31080V2

746/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Figure 213. Counter timing diagram, internal clock divided by N

CK_PSC

Timerclock = CK_CNT

Counter register

1F

00

20

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31081V2

Figure 214. Counter timing diagram, Update event when ARPE=0 (TIMx_ARR not
preloaded)
CK_PSC

CEN

Timerclock = CK_CNT
Counter register

31

32

33

34

35

36

00

01

02

03

04

05

06

07

Counter overflow

Update event (UEV)
Update interrupt flag
(UIF)
Auto-reload preload
register

FF

36

Write a new value in TIMx_ARR
MS31082V2

RM0385 Rev 7

747/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 215. Counter timing diagram, Update event when ARPE=1 (TIMx_ARR
preloaded)
CK_PSC

CEN
Timerclock = CK_CNT
Counter register

F0

F1

F2

F3

F4 F5

00

01

02

03

04

05

06

07

Counter overflow
Update event (UEV)

Update interrupt flag
(UIF)
Auto-reload preload
register

F5

36

Auto-reload shadow
register

F5

Write a new value in TIMx_ARR

36

MS31083V2

Downcounting mode
In downcounting mode, the counter counts from the auto-reload value (content of the
TIMx_ARR register) down to 0, then restarts from the auto-reload value and generates a
counter underflow event.
An Update event can be generate at each counter underflow or by setting the UG bit in the
TIMx_EGR register (by software or by using the slave mode controller)
The UEV update event can be disabled by software by setting the UDIS bit in TIMx_CR1
register. This is to avoid updating the shadow registers while writing new values in the
preload registers. Then no update event occurs until UDIS bit has been written to 0.
However, the counter restarts from the current auto-reload value, whereas the counter of the
prescaler restarts from 0 (but the prescale rate doesn’t change).
In addition, if the URS bit (update request selection) in TIMx_CR1 register is set, setting the
UG bit generates an update event UEV but without setting the UIF flag (thus no interrupt or
DMA request is sent). This is to avoid generating both update and capture interrupts when
clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):

748/1709

•

The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register).

•

The auto-reload active register is updated with the preload value (content of the
TIMx_ARR register). Note that the auto-reload is updated before the counter is
reloaded, so that the next period is the expected one.

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
The following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.
Figure 216. Counter timing diagram, internal clock divided by 1

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

04

05

03

02

01

00

36

35

34

33

32

31

30

2F

Counter underflow
(cnt_udf)

Update event (UEV)

Update interrupt flag
(UIF)
MS31184V1

Figure 217. Counter timing diagram, internal clock divided by 2

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0002

0001

0000

0036

0035

0034

0033

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31185V1

RM0385 Rev 7

749/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 218. Counter timing diagram, internal clock divided by 4

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0001

0000

0000

0001

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31186V1

Figure 219. Counter timing diagram, internal clock divided by N

CK_PSC

Timerclock = CK_CNT

Counter register

20

1F

00

36

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31187V1

750/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Figure 220. Counter timing diagram, Update event when repetition counter
is not used
CK_PSC

CEN

Timerclock = CK_CNT
Counter register

05

04

03

02

01 00

36 35 34

33

32

31 30 2F

Counter underflow

Update event (UEV)
Update interrupt flag
(UIF)
Auto-reload preload
register

FF

36

Write a new value in TIMx_ARR
MS31188V1

Center-aligned mode (up/down counting)
In center-aligned mode, the counter counts from 0 to the auto-reload value (content of the
TIMx_ARR register) – 1, generates a counter overflow event, then counts from the autoreload value down to 1 and generates a counter underflow event. Then it restarts counting
from 0.
Center-aligned mode is active when the CMS bits in TIMx_CR1 register are not equal to
'00'. The Output compare interrupt flag of channels configured in output is set when: the
counter counts down (Center aligned mode 1, CMS = "01"), the counter counts up (Center
aligned mode 2, CMS = "10") the counter counts up and down (Center aligned mode 3,
CMS = "11").
In this mode, the direction bit (DIR from TIMx_CR1 register) cannot be written. It is updated
by hardware and gives the current direction of the counter.
The update event can be generated at each counter overflow and at each counter underflow
or by setting the UG bit in the TIMx_EGR register (by software or by using the slave mode
controller) also generates an update event. In this case, the counter restarts counting from
0, as well as the counter of the prescaler.
The UEV update event can be disabled by software by setting the UDIS bit in TIMx_CR1
register. This is to avoid updating the shadow registers while writing new values in the
preload registers. Then no update event occurs until the UDIS bit has been written to 0.
However, the counter continues counting up and down, based on the current auto-reload
value.
In addition, if the URS bit (update request selection) in TIMx_CR1 register is set, setting the
UG bit generates an update event UEV but without setting the UIF flag (thus no interrupt or

RM0385 Rev 7

751/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

DMA request is sent). This is to avoid generating both update and capture interrupt when
clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):
•

The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register).

•

The auto-reload active register is updated with the preload value (content of the
TIMx_ARR register). Note that if the update source is a counter overflow, the autoreload is updated before the counter is reloaded, so that the next period is the expected
one (the counter is loaded with the new value).

The following figures show some examples of the counter behavior for different clock
frequencies.
Figure 221. Counter timing diagram, internal clock divided by 1, TIMx_ARR=0x6
CK_PSC
CEN

Timerclock = CK_CNT
Counter register

04

03 02

01 00

01

02 03 04 05

06

05 04

03

Counter underflow

Counter overflow

Update event (UEV)
Update interrupt flag (UIF)
MS31189V3

1. Here, center-aligned mode 1 is used (for more details refer to Section 23.4.1: TIMx control register 1
(TIMx_CR1) on page 786).

752/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Figure 222. Counter timing diagram, internal clock divided by 2

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0002

0003

0001

0000

0001

0002

0003

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31190V1

Figure 223. Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0034

0035

0036

0035

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)
Note: Here, center_aligned mode 2 or 3 is updated with an UIF on overflow
MS31191V1

1. Center-aligned mode 2 or 3 is used with an UIF on overflow.

RM0385 Rev 7

753/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 224. Counter timing diagram, internal clock divided by N

CK_PSC

Timerclock = CK_CNT

Counter register

1F

20

01

00

Counter underflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31192V1

Figure 225. Counter timing diagram, Update event with ARPE=1 (counter underflow)
CK_PSC

CEN

Timerclock = CK_CNT
Counter register

06

05

04

03

02

01 00

01

02

03

04

05

06

07

Counter underflow
Update event (UEV)
Update interrupt flag
(UIF)
Auto-reload preload
register

FD

36

Write a new value in TIMx_ARR
Auto-reload active
register

FD

36
MS31193V1

754/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Figure 226. Counter timing diagram, Update event with ARPE=1 (counter overflow)
CK_PSC

CEN
Timer clock = CK_CNT
Counter register

F7

F8

F9

FA FB FC 36

35

34

33

32

31

30

2F

Counter overflow
Update event (UEV)

Update interrupt flag
(UIF)
Auto-reload preload
register

FD

36

Write a new value in TIMx_ARR
Auto-reload active
FD
register

36
MS31194V1

23.3.3

Clock selection
The counter clock can be provided by the following clock sources:
•

Internal clock (CK_INT)

•

External clock mode1: external input pin (TIx)

•

External clock mode2: external trigger input (ETR)

•

Internal trigger inputs (ITRx): using one timer as prescaler for another timer, for
example, you can configure Timer 13 to act as a prescaler for Timer 2. Refer to : Using
one timer as prescaler for another timer on page 781 for more details.

Internal clock source (CK_INT)
If the slave mode controller is disabled (SMS=000 in the TIMx_SMCR register), then the
CEN, DIR (in the TIMx_CR1 register) and UG bits (in the TIMx_EGR register) are actual
control bits and can be changed only by software (except UG which remains cleared
automatically). As soon as the CEN bit is written to 1, the prescaler is clocked by the internal
clock CK_INT.
Figure 227 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.

RM0385 Rev 7

755/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 227. Control circuit in normal mode, internal clock divided by 1

Internal clock
CEN=CNT_EN

UG

CNT_INIT

Counter clock = CK_CNT = CK_PSC
Counter register

32

31

33

34

35 36

00 01

02

03 04 05

06

07
MS31085V2

External clock source mode 1
This mode is selected when SMS=111 in the TIMx_SMCR register. The counter can count at
each rising or falling edge on a selected input.
Figure 228. TI2 external clock connection example
TIMx_SMCR
TS[2:0]
or TI2F
TI1F
ITRx
TI1_ED
TI1FP1
TI2

Filter

Edge
detector

TI2F_Rising
TI2F_Falling

0
1

TI2FP2
ETRF

or
or

0xx
100

TRGI

101
110
111

ETRF
CK_INT

ICF[3:0]

CC2P

TIMx_CCMR1

TIMx_CCER

(internal clock)

Encoder
mode
External clock
mode 1
External clock
mode 2

CK_PSC

Internal clock
mode

ECE

SMS[2:0]

TIMx_SMCR

MS31196V1

For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:
For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:

756/1709

RM0385 Rev 7

RM0385

Note:

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
1.

Configure channel 2 to detect rising edges on the TI2 input by writing CC2S= ‘01 in the
TIMx_CCMR1 register.

2.

Configure the input filter duration by writing the IC2F[3:0] bits in the TIMx_CCMR1
register (if no filter is needed, keep IC2F=0000).

The capture prescaler is not used for triggering, so you don’t need to configure it.
3.

Select rising edge polarity by writing CC2P=0 and CC2NP=0 and CC2NP=0 in the
TIMx_CCER register.

4.

Configure the timer in external clock mode 1 by writing SMS=111 in the TIMx_SMCR
register.

5.

Select TI2 as the input source by writing TS=110 in the TIMx_SMCR register.

6.

Enable the counter by writing CEN=1 in the TIMx_CR1 register.

When a rising edge occurs on TI2, the counter counts once and the TIF flag is set.
The delay between the rising edge on TI2 and the actual clock of the counter is due to the
resynchronization circuit on TI2 input.
Figure 229. Control circuit in external clock mode 1

TI2
CNT_EN
Counter clock = CK_CNT = CK_PSC
Counter register

34

35

36

TIF

Write TIF=0

MS31087V2

External clock source mode 2
This mode is selected by writing ECE=1 in the TIMx_SMCR register.
The counter can count at each rising or falling edge on the external trigger input ETR.
Figure 230 gives an overview of the external trigger input block.

RM0385 Rev 7

757/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 230. External trigger input block

or TI2F
TI1F

ETR

or
or

TRGI
0

ETR pin
1

Divider
/1, /2, /4, /8

ETRP
fDTS

Filter
downcounter

ETRF
CK_INT

ETP

ETPS[1:0]

ETF[3:0]

TIMx_SMCR

TIMx_SMCR

TIMx_SMCR

(internal clock)

Encoder
mode
External clock
mode 1
External clock
mode 2

CK_PSC

Internal clock
mode

ECE

SMS[2:0]

TIMx_SMCR

MS33116V1

For example, to configure the upcounter to count each 2 rising edges on ETR, use the
following procedure:
1.

As no filter is needed in this example, write ETF[3:0]=0000 in the TIMx_SMCR register.

2.

Set the prescaler by writing ETPS[1:0]=01 in the TIMx_SMCR register

3.

Select rising edge detection on the ETR pin by writing ETP=0 in the TIMx_SMCR
register

4.

Enable external clock mode 2 by writing ECE=1 in the TIMx_SMCR register.

5.

Enable the counter by writing CEN=1 in the TIMx_CR1 register.

The counter counts once each 2 ETR rising edges.
The delay between the rising edge on ETR and the actual clock of the counter is due to the
resynchronization circuit on the ETRP signal.

758/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Figure 231. Control circuit in external clock mode 2

f CK_INT
CNT_EN
ETR

ETRP

ETRF
Counter clock =
CK_INT =CK_PSC
Counter register

34

35

36

MS33111V2

23.3.4

Capture/compare channels
Each Capture/Compare channel is built around a capture/compare register (including a
shadow register), a input stage for capture (with digital filter, multiplexing and prescaler) and
an output stage (with comparator and output control).
The following figure gives an overview of one Capture/Compare channel.
The input stage samples the corresponding TIx input to generate a filtered signal TIxF.
Then, an edge detector with polarity selection generates a signal (TIxFPx) which can be
used as trigger input by the slave mode controller or as the capture command. It is
prescaled before the capture register (ICxPS).

RM0385 Rev 7

759/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 232. Capture/compare channel (example: channel 1 input stage)

TI1F_ED
To the slave mode controller
TI1F_Rising

TI1

Filter
TI1F
downcounter

fDTS

Edge
detector

TI1F_Falling

0 TI1FP1

01

1
TI2FP1

CC1P/CC1NP

ICF[3:0]

TRC

TIMx_CCER

TIMx_CCMR1

TI2F_Rising
0
(from channel 2)
TI2F_Falling
1
(from channel 2)

IC1

10

(from slave mode
controller)

IC1PS
Divider
/1, /2, /4, /8

11

CC1S[1:0] ICPS[1:0]

CC1E

TIMx_CCMR1

TIMx_CCER

MS33115V1

The output stage generates an intermediate waveform which is then used for reference:
OCxRef (active high). The polarity acts at the end of the chain.
Figure 233. Capture/compare channel 1 main circuit

APB Bus

Read CCR1L

read_in_progress

CC1S[0]
IC1PS

write_in_progress

Input
mode

S write CCR1H

Capture/compare preload register

R

R
compare_transfer

capture_transfer
CC1S[1]

8
low

Read CCR1H S

high

8

(if 16-bit)

MCU-peripheral interface

Output
mode

CNT>CCR1
Counter

CC1S[0]

UEV
Comparator

CC1E

CC1S[1]

OC1PE

Capture/compare shadow register
Capture

write CCR1L

(from time
base unit)

OC1PE

TIMx_CCMR1

CNT=CCR1

CC1G
TIMx_EGR

MS33144V1

760/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Figure 234. Output stage of capture/compare channel (channel 1)
TIMx_SMCR
OCCS
OCREF_CLR 0

To the master
mode controller

ETRF 1

OC1REFC

ocref_clr_int

OC1REF

‘0’

CNT > CCR1

Output
mode
CNT = CCR1
controller

Output
selector

OC3REF

0

0

1

1

CC1E

CC1P

TIMx_CCER

TIMx_CCER

Output
enable
circuit

CC1E TIMx_CCER
MOE

OC1CE OC1M[3:0]
TIMx_CCMR2

OC1

OSSI TIMx_BDTR

OIS4

TIMx_CR2
MS33145V1

The capture/compare block is made of one preload register and one shadow register. Write
and read always access the preload register.
In capture mode, captures are actually done in the shadow register, which is copied into the
preload register.
In compare mode, the content of the preload register is copied into the shadow register
which is compared to the counter.

23.3.5

Input capture mode
In Input capture mode, the Capture/Compare Registers (TIMx_CCRx) are used to latch the
value of the counter after a transition detected by the corresponding ICx signal. When a
capture occurs, the corresponding CCXIF flag (TIMx_SR register) is set and an interrupt or
a DMA request can be sent if they are enabled. If a capture occurs while the CCxIF flag was
already high, then the over-capture flag CCxOF (TIMx_SR register) is set. CCxIF can be
cleared by software by writing it to 0 or by reading the captured data stored in the
TIMx_CCRx register. CCxOF is cleared when you write it to 0.
The following example shows how to capture the counter value in TIMx_CCR1 when TI1
input rises. To do this, use the following procedure:
1.

Select the active input: TIMx_CCR1 must be linked to the TI1 input, so write the CC1S
bits to 01 in the TIMx_CCMR1 register. As soon as CC1S becomes different from 00,
the channel is configured in input and the TIMx_CCR1 register becomes read-only.

2.

Program the input filter duration you need with respect to the signal you connect to the
timer (when the input is one of the TIx (ICxF bits in the TIMx_CCMRx register). Let’s
imagine that, when toggling, the input signal is not stable during at must 5 internal clock
cycles. We must program a filter duration longer than these 5 clock cycles. We can
validate a transition on TI1 when 8 consecutive samples with the new level have been

RM0385 Rev 7

761/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

detected (sampled at fDTS frequency). Then write IC1F bits to 0011 in the
TIMx_CCMR1 register.
3.

Select the edge of the active transition on the TI1 channel by writing the CC1P and
CC1NP and CC1NP bits to 000 in the TIMx_CCER register (rising edge in this case).

4.

Program the input prescaler. In our example, we wish the capture to be performed at
each valid transition, so the prescaler is disabled (write IC1PS bits to 00 in the
TIMx_CCMR1 register).

5.

Enable capture from the counter into the capture register by setting the CC1E bit in the
TIMx_CCER register.

6.

If needed, enable the related interrupt request by setting the CC1IE bit in the
TIMx_DIER register, and/or the DMA request by setting the CC1DE bit in the
TIMx_DIER register.

When an input capture occurs:
•

The TIMx_CCR1 register gets the value of the counter on the active transition.

•

CC1IF flag is set (interrupt flag). CC1OF is also set if at least two consecutive captures
occurred whereas the flag was not cleared.

•

An interrupt is generated depending on the CC1IE bit.

•

A DMA request is generated depending on the CC1DE bit.

In order to handle the overcapture, it is recommended to read the data before the
overcapture flag. This is to avoid missing an overcapture which could happen after reading
the flag and before reading the data.
Note:

IC interrupt and/or DMA requests can be generated by software by setting the
corresponding CCxG bit in the TIMx_EGR register.

23.3.6

PWM input mode
This mode is a particular case of input capture mode. The procedure is the same except:

762/1709

•

Two ICx signals are mapped on the same TIx input.

•

These 2 ICx signals are active on edges with opposite polarity.

•

One of the two TIxFP signals is selected as trigger input and the slave mode controller
is configured in reset mode.

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
For example, you can measure the period (in TIMx_CCR1 register) and the duty cycle (in
TIMx_CCR2 register) of the PWM applied on TI1 using the following procedure (depending
on CK_INT frequency and prescaler value):
1.

Select the active input for TIMx_CCR1: write the CC1S bits to 01 in the TIMx_CCMR1
register (TI1 selected).

2.

Select the active polarity for TI1FP1 (used both for capture in TIMx_CCR1 and counter
clear): write the CC1P to ‘0’ and the CC1NP bit to ‘0’ (active on rising edge).

3.

Select the active input for TIMx_CCR2: write the CC2S bits to 10 in the TIMx_CCMR1
register (TI1 selected).

4.

Select the active polarity for TI1FP2 (used for capture in TIMx_CCR2): write the CC2P
bit to ‘1’ and the CC2NP bit to ’0’ (active on falling edge).

5.

Select the valid trigger input: write the TS bits to 101 in the TIMx_SMCR register
(TI1FP1 selected).

6.

Configure the slave mode controller in reset mode: write the SMS bits to 100 in the
TIMx_SMCR register.

7.

Enable the captures: write the CC1E and CC2E bits to ‘1 in the TIMx_CCER register.
Figure 235. PWM input mode timing

1. The PWM input mode can be used only with the TIMx_CH1/TIMx_CH2 signals due to the fact that only
TI1FP1 and TI2FP2 are connected to the slave mode controller.

23.3.7

Forced output mode
In output mode (CCxS bits = 00 in the TIMx_CCMRx register), each output compare signal
(OCxREF and then OCx) can be forced to active or inactive level directly by software,
independently of any comparison between the output compare register and the counter.
To force an output compare signal (ocxref/OCx) to its active level, you just need to write 101
in the OCxM bits in the corresponding TIMx_CCMRx register. Thus ocxref is forced high
(OCxREF is always active high) and OCx get opposite value to CCxP polarity bit.
e.g.: CCxP=0 (OCx active high) => OCx is forced to high level.
ocxref signal can be forced low by writing the OCxM bits to 100 in the TIMx_CCMRx
register.

RM0385 Rev 7

763/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Anyway, the comparison between the TIMx_CCRx shadow register and the counter is still
performed and allows the flag to be set. Interrupt and DMA requests can be sent
accordingly. This is described in the Output Compare Mode section.

23.3.8

Output compare mode
This function is used to control an output waveform or indicating when a period of time has
elapsed.
When a match is found between the capture/compare register and the counter, the output
compare function:
•

Assigns the corresponding output pin to a programmable value defined by the output
compare mode (OCxM bits in the TIMx_CCMRx register) and the output polarity (CCxP
bit in the TIMx_CCER register). The output pin can keep its level (OCXM=000), be set
active (OCxM=001), be set inactive (OCxM=010) or can toggle (OCxM=011) on match.

•

Sets a flag in the interrupt status register (CCxIF bit in the TIMx_SR register).

•

Generates an interrupt if the corresponding interrupt mask is set (CCXIE bit in the
TIMx_DIER register).

•

Sends a DMA request if the corresponding enable bit is set (CCxDE bit in the
TIMx_DIER register, CCDS bit in the TIMx_CR2 register for the DMA request
selection).

The TIMx_CCRx registers can be programmed with or without preload registers using the
OCxPE bit in the TIMx_CCMRx register.
In output compare mode, the update event UEV has no effect on ocxref and OCx output.
The timing resolution is one count of the counter. Output compare mode can also be used to
output a single pulse (in One-pulse mode).

Procedure
1.

Select the counter clock (internal, external, prescaler).

2.

Write the desired data in the TIMx_ARR and TIMx_CCRx registers.

3.

Set the CCxIE and/or CCxDE bits if an interrupt and/or a DMA request is to be
generated.

4.

Select the output mode. For example, you must write OCxM=011, OCxPE=0, CCxP=0
and CCxE=1 to toggle OCx output pin when CNT matches CCRx, CCRx preload is not
used, OCx is enabled and active high.

5.

Enable the counter by setting the CEN bit in the TIMx_CR1 register.

The TIMx_CCRx register can be updated at any time by software to control the output
waveform, provided that the preload register is not enabled (OCxPE=0, else TIMx_CCRx
shadow register is updated only at the next update event UEV). An example is given in
Figure 236.

764/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Figure 236. Output compare mode, toggle on OC1
Write B201h in the CC1R register

TIM1_CNT

0039

003B

003A

B201

B201

003A

TIM1_CCR1

B200

OC1REF= OC1

Match detected on CCR1
Interrupt generated if enabled
MS31092V1

23.3.9

PWM mode
Pulse width modulation mode allows you to generate a signal with a frequency determined
by the value of the TIMx_ARR register and a duty cycle determined by the value of the
TIMx_CCRx register.
The PWM mode can be selected independently on each channel (one PWM per OCx
output) by writing 110 (PWM mode 1) or ‘111 (PWM mode 2) in the OCxM bits in the
TIMx_CCMRx register. You must enable the corresponding preload register by setting the
OCxPE bit in the TIMx_CCMRx register, and eventually the auto-reload preload register (in
upcounting or center-aligned modes) by setting the ARPE bit in the TIMx_CR1 register.
As the preload registers are transferred to the shadow registers only when an update event
occurs, before starting the counter, you have to initialize all the registers by setting the UG
bit in the TIMx_EGR register.
OCx polarity is software programmable using the CCxP bit in the TIMx_CCER register. It
can be programmed as active high or active low. OCx output is enabled by the CCxE bit in
the TIMx_CCER register. Refer to the TIMx_CCERx register description for more details.
In PWM mode (1 or 2), TIMx_CNT and TIMx_CCRx are always compared to determine
whether TIMx_CCRx ≤ TIMx_CNT or TIMx_CNT ≤ TIMx_CCRx (depending on the direction
of the counter). However, to comply with the OCREF_CLR functionality (OCREF can be
cleared by an external event through the ETR signal until the next PWM period), the
OCREF signal is asserted only:
•

When the result of the comparison or

•

When the output compare mode (OCxM bits in TIMx_CCMRx register) switches from
the “frozen” configuration (no comparison, OCxM=‘000) to one of the PWM modes
(OCxM=‘110 or ‘111).

This forces the PWM by software while the timer is running.

RM0385 Rev 7

765/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

The timer is able to generate PWM in edge-aligned mode or center-aligned mode
depending on the CMS bits in the TIMx_CR1 register.

PWM edge-aligned mode
Upcounting configuration
Upcounting is active when the DIR bit in the TIMx_CR1 register is low. Refer to Upcounting
mode on page 745.
In the following example, we consider PWM mode 1. The reference PWM signal OCxREF is
high as long as TIMx_CNT 8
CCxIF

OCXREF

‘0’

CCRx=0
CCxIF

MS31093V1

Downcounting configuration
Downcounting is active when DIR bit in TIMx_CR1 register is high. Refer to Downcounting
mode on page 748.
In PWM mode 1, the reference signal ocxref is low as long as TIMx_CNT>TIMx_CCRx else
it becomes high. If the compare value in TIMx_CCRx is greater than the auto-reload value in
TIMx_ARR, then ocxref is held at 100%. PWM is not possible in this mode.

PWM center-aligned mode
Center-aligned mode is active when the CMS bits in TIMx_CR1 register are different from
‘00 (all the remaining configurations having the same effect on the ocxref/OCx signals). The

766/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
compare flag is set when the counter counts up, when it counts down or both when it counts
up and down depending on the CMS bits configuration. The direction bit (DIR) in the
TIMx_CR1 register is updated by hardware and must not be changed by software. Refer to
Center-aligned mode (up/down counting) on page 751.
Figure 238 shows some center-aligned PWM waveforms in an example where:
•

TIMx_ARR=8,

•

PWM mode is the PWM mode 1,

•

The flag is set when the counter counts down corresponding to the center-aligned
mode 1 selected for CMS=01 in TIMx_CR1 register.
Figure 238. Center-aligned PWM waveforms (ARR=8)
Counter register

0

1

2

3

4

5

6

7

8

7

6

5

4

3

2

1

0

1

OCxREF
CCRx = 4
CMS=01
CMS=10
CMS=11

CCxIF

OCxREF
CCRx=7

CMS=10 or 11

CCxIF
OCxREF

‘1’

CCRx=8
CMS=01
CMS=10
CMS=11

CCxIF

OCxREF
CCRx>8

‘1’

CMS=01
CMS=10
CMS=11

CCxIF

OCxREF
CCRx=0
CCxIF

‘0’

CMS=01
CMS=10
CMS=11

AI14681b

Hints on using center-aligned mode:
•

When starting in center-aligned mode, the current up-down configuration is used. It
means that the counter counts up or down depending on the value written in the DIR bit

RM0385 Rev 7

767/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

in the TIMx_CR1 register. Moreover, the DIR and CMS bits must not be changed at the
same time by the software.
•

•

23.3.10

Writing to the counter while running in center-aligned mode is not recommended as it
can lead to unexpected results. In particular:
–

The direction is not updated if you write a value in the counter that is greater than
the auto-reload value (TIMx_CNT>TIMx_ARR). For example, if the counter was
counting up, it continues to count up.

–

The direction is updated if you write 0 or write the TIMx_ARR value in the counter
but no Update Event UEV is generated.

The safest way to use center-aligned mode is to generate an update by software
(setting the UG bit in the TIMx_EGR register) just before starting the counter and not to
write the counter while it is running.

Asymmetric PWM mode
Asymmetric mode allows two center-aligned PWM signals to be generated with a
programmable phase shift. While the frequency is determined by the value of the
TIMx_ARR register, the duty cycle and the phase-shift are determined by a pair of
TIMx_CCRx registers. One register controls the PWM during up-counting, the second
during down counting, so that PWM is adjusted every half PWM cycle:
•

OC1REFC (or OC2REFC) is controlled by TIMx_CCR1 and TIMx_CCR2

•

OC3REFC (or OC4REFC) is controlled by TIMx_CCR3 and TIMx_CCR4

Asymmetric PWM mode can be selected independently on two channels (one OCx output
per pair of CCR registers) by writing ‘1110’ (Asymmetric PWM mode 1) or ‘1111’
(Asymmetric PWM mode 2) in the OCxM bits in the TIMx_CCMRx register.
Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
When a given channel is used as asymmetric PWM channel, its secondary channel can also
be used. For instance, if an OC1REFC signal is generated on channel 1 (Asymmetric PWM
mode 1), it is possible to output either the OC2REF signal on channel 2, or an OC2REFC
signal resulting from asymmetric PWM mode 2.
Figure 239 shows an example of signals that can be generated using Asymmetric PWM
mode (channels 1 to 4 are configured in Asymmetric PWM mode 1).
Figure 239. Generation of 2 phase-shifted PWM signals with 50% duty cycle
Counter register

0

1

2

3

4

5

6

7

8

7

6

5

4

3

2

1

0

1

OC1REFC
CCR1=0
CCR2=8
OC3REFC
CCR3=3
CCR4=5

MS33117V1

768/1709

RM0385 Rev 7

RM0385

23.3.11

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

Combined PWM mode
Combined PWM mode allows two edge or center-aligned PWM signals to be generated with
programmable delay and phase shift between respective pulses. While the frequency is
determined by the value of the TIMx_ARR register, the duty cycle and delay are determined
by the two TIMx_CCRx registers. The resulting signals, OCxREFC, are made of an OR or
AND logical combination of two reference PWMs:
– OC1REFC (or OC2REFC) is controlled by TIMx_CCR1 and TIMx_CCR2
– OC3REFC (or OC4REFC) is controlled by TIMx_CCR3 and TIMx_CCR4
Combined PWM mode can be selected independently on two channels (one OCx output per
pair of CCR registers) by writing ‘1100’ (Combined PWM mode 1) or ‘1101’ (Combined PWM
mode 2) in the OCxM bits in the TIMx_CCMRx register.
When a given channel is used as combined PWM channel, its secondary channel must be
configured in the opposite PWM mode (for instance, one in Combined PWM mode 1 and the
other in Combined PWM mode 2).

Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
Figure 240 shows an example of signals that can be generated using Asymmetric PWM
mode, obtained with the following configuration:
•

Channel 1 is configured in Combined PWM mode 2,

•

Channel 2 is configured in PWM mode 1,

•

Channel 3 is configured in Combined PWM mode 2,

•

Channel 4 is configured in PWM mode 1

RM0385 Rev 7

769/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Figure 240. Combined PWM mode on channels 1 and 3

OC2’
OC1’

OC2
OC1
OC1REF
OC2REF
OC1REF’
OC2REF’

OC1REFC
OC1REFC’

OC1REFC = OC1REF AND OC2REF
OC1REFC’ = OC1REF’ OR OC2REF’

MS31094V1

23.3.12

Clearing the OCxREF signal on an external event
The OCxREF signal of a given channel can be cleared when a high level is applied on the
ocref_clr_int input (OCxCE enable bit in the corresponding TIMx_CCMRx register set to 1).
OCxREF remains low until the next update event (UEV) occurs. This function can only be
used in Output compare and PWM modes. It does not work in Forced mode.
OCREF_CLR_INPUT can be selected between the OCREF_CLR input and ETRF (ETR
after the filter) by configuring the OCCS bit in the TIMx_SMCR register.
The OCxREF signal for a given channel can be reset by applying a high level on the ETRF
input (OCxCE enable bit set to 1 in the corresponding TIMx_CCMRx register). OCxREF
remains low until the next update event (UEV) occurs.
This function can be used only in the output compare and PWM modes. It does not work in
forced mode.
For example, the OCxREF signal can be connected to the output of a comparator to be
used for current handling. In this case, ETR must be configured as follows:

770/1709

1.

The external trigger prescaler should be kept off: bits ETPS[1:0] in the TIMx_SMCR
register are cleared to 00.

2.

The external clock mode 2 must be disabled: bit ECE in the TIM1_SMCR register is
cleared to 0.

3.

The external trigger polarity (ETP) and the external trigger filter (ETF) can be
configured according to the application’s needs.

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Figure 241 shows the behavior of the OCxREF signal when the ETRF input becomes high,
for both values of the OCxCE enable bit. In this example, the timer TIMx is programmed in
PWM mode.
Figure 241. Clearing TIMx OCxREF

(CCRx)
Counter (CNT)

ETRF

OCxREF
(OCxCE = ‘0’)
OCxREF
(OCxCE = ‘1’)

ocref_clr_int
becomes high

ocref_clr_int
still high
MS33105V2

Note:

In case of a PWM with a 100% duty cycle (if CCRx>ARR), OCxREF is enabled again at the
next counter overflow.

RM0385 Rev 7

771/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

23.3.13

RM0385

One-pulse mode
One-pulse mode (OPM) is a particular case of the previous modes. It allows the counter to
be started in response to a stimulus and to generate a pulse with a programmable length
after a programmable delay.
Starting the counter can be controlled through the slave mode controller. Generating the
waveform can be done in output compare mode or PWM mode. You select One-pulse mode
by setting the OPM bit in the TIMx_CR1 register. This makes the counter stop automatically
at the next update event UEV.
A pulse can be correctly generated only if the compare value is different from the counter
initial value. Before starting (when the timer is waiting for the trigger), the configuration must
be:
•

CNTTIMx_CCR1 else active (OC1REF=1).
0111: PWM mode 2 - In upcounting, channel 1 is inactive as long as
TIMx_CNTTIMx_CCR1 else inactive.
1000: Retriggerable OPM mode 1 - In up-counting mode, the channel is active until a trigger
event is detected (on TRGI signal). Then, a comparison is performed as in PWM mode 1
and the channels becomes inactive again at the next update. In down-counting mode, the
channel is inactive until a trigger event is detected (on TRGI signal). Then, a comparison is
performed as in PWM mode 1 and the channels becomes inactive again at the next update.
1001: Retriggerable OPM mode 2 - In up-counting mode, the channel is inactive until a
trigger event is detected (on TRGI signal). Then, a comparison is performed as in PWM
mode 2 and the channels becomes inactive again at the next update. In down-counting
mode, the channel is active until a trigger event is detected (on TRGI signal). Then, a
comparison is performed as in PWM mode 1 and the channels becomes active again at the
next update.
1010: Reserved,
1011: Reserved,
1100: Combined PWM mode 1 - OC1REF has the same behavior as in PWM mode 1.
OC1REFC is the logical OR between OC1REF and OC2REF.
1101: Combined PWM mode 2 - OC1REF has the same behavior as in PWM mode 2.
OC1REFC is the logical AND between OC1REF and OC2REF.
1110: Asymmetric PWM mode 1 - OC1REF has the same behavior as in PWM mode 1.
OC1REFC outputs OC1REF when the counter is counting up, OC2REF when it is counting
down.
1111: Asymmetric PWM mode 2 - OC1REF has the same behavior as in PWM mode 2.
OC1REFC outputs OC1REF when the counter is counting up, OC2REF when it is counting
down.
Note: 1: These bits can not be modified as long as LOCK level 3 has been programmed
(LOCK bits in TIMx_BDTR register) and CC1S=00 (the channel is configured in
output).
2: In PWM mode, the OCREF level changes only when the result of the comparison
changes or when the output compare mode switches from “frozen” mode to “PWM”
mode.

RM0385 Rev 7

797/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Bit 3 OC1PE: Output compare 1 preload enable
0: Preload register on TIMx_CCR1 disabled. TIMx_CCR1 can be written at anytime, the
new value is taken in account immediately.
1: Preload register on TIMx_CCR1 enabled. Read/Write operations access the preload
register. TIMx_CCR1 preload value is loaded in the active register at each update event.
Note: 1: These bits can not be modified as long as LOCK level 3 has been programmed
(LOCK bits in TIMx_BDTR register) and CC1S=00 (the channel is configured in
output).
2: The PWM mode can be used without validating the preload register only in onepulse mode (OPM bit set in TIMx_CR1 register). Else the behavior is not guaranteed.
Bit 2 OC1FE: Output compare 1 fast enable
This bit is used to accelerate the effect of an event on the trigger in input on the CC output.
0: CC1 behaves normally depending on counter and CCR1 values even when the trigger is
ON. The minimum delay to activate CC1 output when an edge occurs on the trigger input is
5 clock cycles.
1: An active edge on the trigger input acts like a compare match on CC1 output. Then, OC
is set to the compare level independently from the result of the comparison. Delay to sample
the trigger input and to activate CC1 output is reduced to 3 clock cycles. OCFE acts only if
the channel is configured in PWM1 or PWM2 mode.
Bits 1:0 CC1S: Capture/Compare 1 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC1 channel is configured as output.
01: CC1 channel is configured as input, IC1 is mapped on TI1.
10: CC1 channel is configured as input, IC1 is mapped on TI2.
11: CC1 channel is configured as input, IC1 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC1S bits are writable only when the channel is OFF (CC1E = 0 in TIMx_CCER).

Input capture mode
Bits 31:16 Reserved, always read as 0.
Bits 15:12 IC2F: Input capture 2 filter
Bits 11:10 IC2PSC[1:0]: Input capture 2 prescaler
Bits 9:8 CC2S: Capture/compare 2 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC2 channel is configured as output.
01: CC2 channel is configured as input, IC2 is mapped on TI2.
10: CC2 channel is configured as input, IC2 is mapped on TI1.
11: CC2 channel is configured as input, IC2 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC2S bits are writable only when the channel is OFF (CC2E = 0 in TIMx_CCER).

798/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

Bits 7:4 IC1F: Input capture 1 filter
This bit-field defines the frequency used to sample TI1 input and the length of the digital filter
applied to TI1. The digital filter is made of an event counter in which N consecutive events
are needed to validate a transition on the output:
0000: No filter, sampling is done at fDTS
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Bits 3:2 IC1PSC: Input capture 1 prescaler
This bit-field defines the ratio of the prescaler acting on CC1 input (IC1). The prescaler is
reset as soon as CC1E=0 (TIMx_CCER register).
00: no prescaler, capture is done each time an edge is detected on the capture input
01: capture is done once every 2 events
10: capture is done once every 4 events
11: capture is done once every 8 events
Bits 1:0 CC1S: Capture/Compare 1 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC1 channel is configured as output
01: CC1 channel is configured as input, IC1 is mapped on TI1
10: CC1 channel is configured as input, IC1 is mapped on TI2
11: CC1 channel is configured as input, IC1 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC1S bits are writable only when the channel is OFF (CC1E = 0 in TIMx_CCER).

23.4.8

TIMx capture/compare mode register 2 (TIMx_CCMR2)
Address offset: 0x1C
Reset value: 0x0000
Refer to the above CCMR1 register description.

31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
Res.

25

24

Res.

OC4M
[3]

23
Res.

22
Res.

21
Res.

20
Res.

19
Res.

18
Res.

17

16

Res.

OC3M
[3]

Res.

Res.

rw
15

14

OC4CE

13

12

OC4M[2:0]

rw

rw

10

OC4PE OC4FE

IC4F[3:0]
rw

11

IC4PSC[1:0]
rw

rw

rw

9

8

CC4S[1:0]
rw

rw

rw
7

6

OC3CE

5

4

OC3M[2:0]

RM0385 Rev 7

rw

rw

2

OC3PE OC3FE

IC3F[3:0]
rw

3

IC3PSC[1:0]
rw

rw

rw

1

0

CC3S[1:0]
rw

rw

799/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Output compare mode
Bits 31:25 Reserved, always read as 0.
Bit 24 OC4M[3]: Output Compare 2 mode - bit 3
Bits 23:17 Reserved, always read as 0.
Bit 16 OC3M[3]: Output Compare 1 mode - bit 3
Bit 15 OC4CE: Output compare 4 clear enable
Bits 14:12 OC4M: Output compare 4 mode
Refer to OC1M description (bits 6:4 in TIMx_CCMR1 register)
Bit 11 OC4PE: Output compare 4 preload enable
Bit 10 OC4FE: Output compare 4 fast enable
Bits 9:8 CC4S: Capture/Compare 4 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC4 channel is configured as output
01: CC4 channel is configured as input, IC4 is mapped on TI4
10: CC4 channel is configured as input, IC4 is mapped on TI3
11: CC4 channel is configured as input, IC4 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC4S bits are writable only when the channel is OFF (CC4E = 0 in TIMx_CCER).
Bit 7 OC3CE: Output compare 3 clear enable
Bits 6:4 OC3M: Output compare 3 mode
Refer to OC1M description (bits 6:4 in TIMx_CCMR1 register)
Bit 3 OC3PE: Output compare 3 preload enable
Bit 2 OC3FE: Output compare 3 fast enable
Bits 1:0 CC3S: Capture/Compare 3 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC3 channel is configured as output
01: CC3 channel is configured as input, IC3 is mapped on TI3
10: CC3 channel is configured as input, IC3 is mapped on TI4
11: CC3 channel is configured as input, IC3 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC3S bits are writable only when the channel is OFF (CC3E = 0 in TIMx_CCER).

Input capture mode
Bits 31:16 Reserved, always read as 0.
Bits 15:12 IC4F: Input capture 4 filter
Bits 11:10 IC4PSC: Input capture 4 prescaler
Bits 9:8 CC4S: Capture/Compare 4 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC4 channel is configured as output
01: CC4 channel is configured as input, IC4 is mapped on TI4
10: CC4 channel is configured as input, IC4 is mapped on TI3
11: CC4 channel is configured as input, IC4 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC4S bits are writable only when the channel is OFF (CC4E = 0 in TIMx_CCER).

800/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

Bits 7:4 IC3F: Input capture 3 filter
Bits 3:2 IC3PSC: Input capture 3 prescaler
Bits 1:0 CC3S: Capture/Compare 3 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC3 channel is configured as output
01: CC3 channel is configured as input, IC3 is mapped on TI3
10: CC3 channel is configured as input, IC3 is mapped on TI4
11: CC3 channel is configured as input, IC3 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC3S bits are writable only when the channel is OFF (CC3E = 0 in TIMx_CCER).

23.4.9

TIMx capture/compare enable register (TIMx_CCER)
Address offset: 0x20
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

CC4NP

Res.

CC4P

CC4E

CC3NP

Res.

CC3P

CC3E

CC2NP

Res.

CC2P

CC2E

CC1NP

Res.

CC1P

CC1E

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 15 CC4NP: Capture/Compare 4 output Polarity.
Refer to CC1NP description
Bit 14 Reserved, must be kept at reset value.
Bit 13 CC4P: Capture/Compare 4 output Polarity.
Refer to CC1P description
Bit 12 CC4E: Capture/Compare 4 output enable.
refer to CC1E description
Bit 11 CC3NP: Capture/Compare 3 output Polarity.
Refer to CC1NP description
Bit 10 Reserved, must be kept at reset value.
Bit 9 CC3P: Capture/Compare 3 output Polarity.
Refer to CC1P description
Bit 8 CC3E: Capture/Compare 3 output enable.
Refer to CC1E description
Bit 7 CC2NP: Capture/Compare 2 output Polarity.
Refer to CC1NP description
Bit 6 Reserved, must be kept at reset value.
Bit 5 CC2P: Capture/Compare 2 output Polarity.
refer to CC1P description
Bit 4 CC2E: Capture/Compare 2 output enable.
Refer to CC1E description
Bit 3 CC1NP: Capture/Compare 1 output Polarity.
CC1 channel configured as output: CC1NP must be kept cleared in this case.
CC1 channel configured as input: This bit is used in conjunction with CC1P to define
TI1FP1/TI2FP1 polarity. refer to CC1P description.

RM0385 Rev 7

801/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Bit 2 Reserved, must be kept at reset value.
Bit 1 CC1P: Capture/Compare 1 output Polarity.
CC1 channel configured as output:
0: OC1 active high
1: OC1 active low
CC1 channel configured as input: CC1NP/CC1P bits select TI1FP1 and TI2FP1 polarity
for trigger or capture operations.
00: noninverted/rising edge
Circuit is sensitive to TIxFP1 rising edge (capture, trigger in reset, external clock or trigger
mode), TIxFP1 is not inverted (trigger in gated mode, encoder mode).
01: inverted/falling edge
Circuit is sensitive to TIxFP1 falling edge (capture, trigger in reset, external clock or trigger
mode), TIxFP1 is inverted (trigger in gated mode, encoder mode).
10: reserved, do not use this configuration.
11: noninverted/both edges
Circuit is sensitive to both TIxFP1 rising and falling edges (capture, trigger in reset, external
clock or trigger mode), TIxFP1 is not inverted (trigger in gated mode). This configuration
must not be used for encoder mode.
Bit 0 CC1E: Capture/Compare 1 output enable.
CC1 channel configured as output:
0: Off - OC1 is not active
1: On - OC1 signal is output on the corresponding output pin
CC1 channel configured as input: This bit determines if a capture of the counter value can
actually be done into the input capture/compare register 1 (TIMx_CCR1) or not.
0: Capture disabled
1: Capture enabled

Table 151. Output control bit for standard OCx channels
CCxE bit

OCx output state

0

Output Disabled (OCx=0, OCx_EN=0)

1

OCx=OCxREF + Polarity, OCx_EN=1

Note:

The state of the external IO pins connected to the standard OCx channels depends on the
OCx channel state and the GPIO and AFIO registers.

23.4.10

TIMx counter (TIMx_CNT)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

CNT[31]
or
UIFCPY

23

22

21

20

19

18

17

16

CNT[30:16]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

CNT[15:0]

802/1709

rw

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

Bit 31 Value depends on IUFREMAP in TIMx_CR1.
If UIFREMAP = 0
CNT[31]: Most significant bit of counter value (on TIM2 and TIM5)
Reserved on other timers
If UIFREMAP = 1
UIFCPY: UIF Copy
This bit is a read-only copy of the UIF bit of the TIMx_ISR register
Bits 30:16 CNT[30:16]: Most significant part counter value (on TIM2 and TIM5)
Bits 15:0 CNT[15:0]: Least significant part of counter value

23.4.11

TIMx prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

PSC[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 PSC[15:0]: Prescaler value
The counter clock frequency CK_CNT is equal to fCK_PSC / (PSC[15:0] + 1).
PSC contains the value to be loaded in the active prescaler register at each update event
(including when the counter is cleared through UG bit of TIMx_EGR register or through
trigger controller when configured in “reset mode”).

23.4.12

TIMx auto-reload register (TIMx_ARR)
Address offset: 0x2C
Reset value: 0xFFFF FFFF

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ARR[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

ARR[15:0]
rw

Bits 31:16 ARR[31:16]: High auto-reload value (on TIM2 and TIM5)
Bits 15:0 ARR[15:0]: Low Auto-reload value
ARR is the value to be loaded in the actual auto-reload register.
Refer to the Section 23.3.1: Time-base unit on page 743 for more details about ARR update
and behavior.
The counter is blocked while the auto-reload value is null.

23.4.13

TIMx capture/compare register 1 (TIMx_CCR1)
Address offset: 0x34
Reset value: 0x0000 0000

RM0385 Rev 7

803/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

25

24

RM0385

31

30

29

28

27

26

23

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR1[31:16] (depending on timers)

CCR1[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 CCR1[31:16]: High Capture/Compare 1 value (on TIM2 and TIM5)
Bits 15:0 CCR1[15:0]: Low Capture/Compare 1 value
If channel CC1 is configured as output:
CCR1 is the value to be loaded in the actual capture/compare 1 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(bit OC1PE). Else the preload value is copied in the active capture/compare 1 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC1 output.
If channel CC1is configured as input:
CCR1 is the counter value transferred by the last input capture 1 event (IC1). The
TIMx_CCR1 register is read-only and cannot be programmed.

23.4.14

TIMx capture/compare register 2 (TIMx_CCR2)
Address offset: 0x38
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CCR2[31:16] (depending on timers)
rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR2[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 CCR2[31:16]: High Capture/Compare 2 value (on TIM2 and TIM5)
Bits 15:0 CCR2[15:0]: Low Capture/Compare 2 value
If channel CC2 is configured as output:
CCR2 is the value to be loaded in the actual capture/compare 2 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(bit OC2PE). Else the preload value is copied in the active capture/compare 2 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC2 output.
If channel CC2 is configured as input:
CCR2 is the counter value transferred by the last input capture 2 event (IC2). The
TIMx_CCR2 register is read-only and cannot be programmed.

23.4.15

TIMx capture/compare register 3 (TIMx_CCR3)
Address offset: 0x3C
Reset value: 0x0000 0000

804/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

31

30

29

28

27

26

25

24

23

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR3[31:16] (depending on timers)

CCR3[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 CCR3[31:16]: High Capture/Compare 3 value (on TIM2 and TIM5)
Bits 15:0 CCR3[15:0]: Low Capture/Compare value
If channel CC3 is configured as output:
CCR3 is the value to be loaded in the actual capture/compare 3 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2 register
(bit OC3PE). Else the preload value is copied in the active capture/compare 3 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC3 output.
If channel CC3is configured as input:
CCR3 is the counter value transferred by the last input capture 3 event (IC3). The
TIMx_CCR3 register is read-only and cannot be programmed.

23.4.16

TIMx capture/compare register 4 (TIMx_CCR4)
Address offset: 0x40
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CCR4[31:16] (depending on timers)
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR4[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 CCR4[31:16]: High Capture/Compare 4 value (on TIM2 and TIM5)
Bits 15:0 CCR4[15:0]: Low Capture/Compare value
1.
if CC4 channel is configured as output (CC4S bits):
CCR4 is the value to be loaded in the actual capture/compare 4 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2
register (bit OC4PE). Else the preload value is copied in the active capture/compare 4
register when an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC4 output.
2.
if CC4 channel is configured as input (CC4S bits in TIMx_CCMR4 register):
CCR4 is the counter value transferred by the last input capture 4 event (IC4). The
TIMx_CCR4 register is read-only and cannot be programmed.

RM0385 Rev 7

805/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

23.4.17

RM0385

TIMx DMA control register (TIMx_DCR)
Address offset: 0x48
Reset value: 0x0000

15

14

13

Res.

Res.

Res.

12

11

10

9

8

DBL[4:0]
rw

rw

rw

rw

7

6

5

Res.

Res.

Res.

rw

4

3

2

1

0

rw

rw

DBA[4:0]
rw

rw

rw

Bits 15:13 Reserved, must be kept at reset value.
Bits 12:8 DBL[4:0]: DMA burst length
This 5-bit vector defines the number of DMA transfers (the timer recognizes a burst transfer
when a read or a write access is done to the TIMx_DMAR address).
00000: 1 transfer,
00001: 2 transfers,
00010: 3 transfers,
...
10001: 18 transfers.
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:0 DBA[4:0]: DMA base address
This 5-bit vector defines the base-address for DMA transfers (when read/write access are
done through the TIMx_DMAR address). DBA is defined as an offset starting from the
address of the TIMx_CR1 register.
Example:
00000: TIMx_CR1
00001: TIMx_CR2
00010: TIMx_SMCR
...
Example: Let us consider the following transfer: DBL = 7 transfers & DBA = TIMx_CR1. In
this case the transfer is done to/from 7 registers starting from the TIMx_CR1 address.

23.4.18

TIMx DMA address for full transfer (TIMx_DMAR)
Address offset: 0x4C
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DMAB[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 DMAB[15:0]: DMA register for burst accesses
A read or write operation to the DMAR register accesses the register located at the address
(TIMx_CR1 address) + (DBA + DMA index) x 4
where TIMx_CR1 address is the address of the control register 1, DBA is the DMA base
address configured in TIMx_DCR register, DMA index is automatically controlled by the
DMA transfer, and ranges from 0 to DBL (DBL configured in TIMx_DCR).

806/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

23.4.19

TIM2 option register (TIM2_OR)
Address offset: 0x50
Reset value: 0x0000

15

14

13

12

Res.

Res.

Res.

Res.

11

10

ITR1_RMP[1:0]
rw

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 15:12 Reserved, must be kept at reset value.
Bits 11:10 ITR1_RMP[1:0]: Internal trigger 1 remap
Set and cleared by software.
00: TIM8_TRGOUT
01: ETH_PTP trigger output is connected to TIM2_ITR1
10: OTG_FS_SOF is connected to the TIM2_ITR1 input
11: OTG_HS_SOF is connected to the TIM2_ITR1 input
Bits 9:0 Reserved, must be kept at reset value.

23.4.20

TIM5 option register (TIM5_OR)
Address offset: 0x50
Reset value: 0x0000

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

TI4_RMP[1:0]
rw

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 15:8 Reserved, must be kept at reset value.
Bits 7:6 TI4_RMP[1:0]: Timer Input 4 remap
Set and cleared by software.
00: TIM5 channel4 is connected to the GPIO: Refer to the alternate function mapping table in
the datasheets.
01: The LSI internal clock is connected to the TIM5_CH4 input for calibration purposes
10: The LSE internal clock is connected to the TIM5_CH4 input for calibration purposes
11: The RTC wakeup interrupt is connected to the TIM5_CH4 input for calibration purposes.
Wakeup interrupt should be enabled.
Bits 5:0 Reserved, must be kept at reset value.

RM0385 Rev 7

807/1709
810

0x20

TIMx_CCER

808/1709

Reset value

RM0385 Rev 7

IC4F[3:0]

0

0

0

0

0
0
0
0

0

0
0
0

OC4M
[2:0]
CC4S
[1:0]

0

0

0

0

0

0

0

Reset value

0
OC1M
[2:0]

0
0

0

0

0

IC4
PSC
[1:0]

CC4S
[1:0]

0

0

0

0

0

0

0

0

0

UG

0

CC1G

UIE

UIF
0

CC2G

CC1IE

CC1IF
0

0
0
0
0
0

OC1FE

0
0
0
0

OCCS
CC2IE

CC2IF
0

CC3G

CC3IE

CC3IF
0

OC1PE

TS[2:0]
SMS[2:0]

0
0
0
0
0
0

Res.
CC4IE
0

Res.
CC4IF
0

Res.

DIR
OPM
URS
UDIS
CEN

0
0
0
0
0

TI1S
MMS[2:0]
CCDS
Res.
Res.
Res.

ARPE

Res.

Res.

UIFREMA

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

CC4G

TIE
0

TIF
0

TG

MSM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0
0
0

0

0
0

0

IC1F[3:0]

0
0

OC3M
[2:0]

0

IC3F[3:0]
IC1
PSC
[1:0]
CC1S
[1:0]

0
0
0

OC3FE

0

CMS
[1:0]

OC3PE

0

Res.

Res.

UDE

0

Res.

CC1OF
Res.

CC2OF

0

Res.

0

Res.

0

CC3OF

0

Res.

0

CC4OF

0

Res.

0

0

Res.

0

IC3
PSC
[1:0]

CC3S
[1:0]

0

0

0

0

0

CC1E

CC2S
[1:0]

0
CC2S
[1:0]
OC1CE

0

CC1DE

0

CC2DE

0

ETF[3:0]

Res.

0
IC2
PSC
[1:0]

0
OC2FE

0

CC3DE

0

CC4DE

0

COMDE

0

Res.

ECE
0

Res.

Reset value

CC1P

0

0

CC1NP

0

0

CC2E

IC2F[3:0]

OC3CE

0
Res.

ETP
0

TDE

SMS[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ETPS
[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

CKD
[1:0]

CC2P

0
0
0

Res.

0
OC2M
[2:0]
OC2PE

0

CC3E

0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

CC2NP

0

OC4FE

OC2CE

0

OC4PE

OC1M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

CC3NP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC2M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

CC3P

0

CC4E

0

0

CC4P

Reset value

Res.

O24CE

Reset value

CC4NP

0

OC3M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC4M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

TIMx_CCMR2
Input Capture
mode

Res.

0x1C

Res.

TIMx_CCMR2
Output
Compare mode
Res.

TIMx_CCMR1
Input Capture
mode

Res.

0x18

Res.

TIMx_CCMR1
Output
Compare mode

Res.

TIMx_EGR

Res.

0x14

Res.

TIMx_SR
Res.

0x10

Res.

TIMx_DIER

Res.

0x0C

Res.

TIMx_SMCR

Res.

0x08

Res.

TIMx_CR2

Res.

0x04

Res.

0x00

Res.

TIMx_CR1

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

Offset

Res.

23.4.21

Res.

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
RM0385

TIMx register map
TIMx registers are mapped as described in the table below:
Table 152. TIM2/TIM3/TIM4/TIM5 register map and reset values

CC1S
[1:0]

0
0
0
0

CC3S
[1:0]

0

0

0
0

0

0

0

0

0

0

RM0385

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

TIMx_CNT

CNT[31] or UIFCPY

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

TIMx_PSC

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0x28

CNT[30:16]
(TIM2 and TIM5 only, reserved on the other timers)

Reset value

1

1

1

1

1

1

1

1

1

1

1

1

1

0

0

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PSC[15:0]
0

0

0

0

0

0

0

0

0

ARR[15:0]
1

1

1

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

0

0

0

0

0

0

0

0

Res.

Res.

0

Res.

0

0

0

0

0

0

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

0

ITR1_RMP[1:0

0

0

RM0385 Rev 7

0

DBA[4:0]

DMAB[15:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIM2_OR

Res.

Reset value

0x50

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_DMAR
0x4C

0
Res.

Reset value

DBL[4:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_DCR
0x48

Res.

Reserved
Res.

0x44

0

Res.

0

0

CCR4[15:0]

Res.

0

0

CCR3[15:0]

CCR4[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_CCR4

0

CCR2[15:0]

CCR3[31:16]
(TIM2 and TIM5 only, reserved on the other timers)
0

0

Res.

0

CCR2[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_CCR3

Reset value

0

CCR1[15:0]

Res.

0

TIMx_CCR2

Reset value

0x40

0

CCR1[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_CCR1

Reset value

0x3C

0

Reserved

Reset value

0x38

0

Res.

0x30

0x34

0

ARR[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_ARR
Reset value

0

0

Res.

0x2C

CNT[15:0]

Res.

0x24

Register
name

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 152. TIM2/TIM3/TIM4/TIM5 register map and reset values (continued)

0

809/1709
810

General-purpose timers (TIM2/TIM3/TIM4/TIM5)

RM0385

Reset value

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

810/1709

RM0385 Rev 7

0

Res.

Res.

Res.

Res.

Res.

Res.

TI4_RMP[1:0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIM5_OR
0x50

Res.

Register
name

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 152. TIM2/TIM3/TIM4/TIM5 register map and reset values (continued)

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

24

General-purpose timers
(TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

24.1

TIM9/TIM10/TIM11/TIM12/TIM13/TIM14 introduction
The TIM9/TIM10/TIM11/TIM12/TIM13/TIM14 general-purpose timers consist in a 16-bit
auto-reload counter driven by a programmable prescaler.
They may be used for a variety of purposes, including measuring the pulse lengths of input
signals (input capture) or generating output waveforms (output compare, PWM).
Pulse lengths and waveform periods can be modulated from a few microseconds to several
milliseconds using the timer prescaler and the RCC clock controller prescalers.
The TIM9/TIM10/TIM11/TIM12/TIM13/TIM14 timers are completely independent, and do not
share any resources. They can be synchronized together as described in Section 24.3.17:
Timer synchronization (TIM9/TIM12).

24.2

TIM9/TIM10/TIM11/TIM12/TIM13/TIM14 main features

24.2.1

TIM9/TIM12 main features
The features of the TIM9/TIM12 general-purpose timers include:
•

16-bit auto-reload upcounter

•

16-bit programmable prescaler used to divide the counter clock frequency by any factor
between 1 and 65536 (can be changed “on the fly”)

•

Up to 2 independent channels for:
–

Input capture

–

Output compare

–

PWM generation (edge-aligned mode)

–

One-pulse mode output

•

Synchronization circuit to control the timer with external signals and to interconnect
several timers together

•

Interrupt generation on the following events:
–

Update: counter overflow, counter initialization (by software or internal trigger)

–

Trigger event (counter start, stop, initialization or count by internal trigger)

–

Input capture

–

Output compare

RM0385 Rev 7

811/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

Figure 256. General-purpose timer block diagram (TIM9/TIM12)
Internal clock (CK_INT)
Trigger
controller
ITR0
ITR1
ITR2
ITR3

TGI

ITR
TRC
TI1F_ED

TRGI

Slave
controller Reset, enable, up, count
mode

TI1FP1
TI2FP2

U

Auto-reload register
Stop, Clear

CK_PSC

TI1

TIMx_CH1

TI2

TIMx_CH2

Input filter &
edge detector

Input filter &
edge detector

TI1FP1
TI1FP2

IC1

PSC CK_CNT
prescaler
CC1I U
Prescaler

TRC

IC1PS
CC2I

TI2FP1
TI2FP2
TRC

IC2

Prescaler

+/-

CNT counter
CC1I

Capture/Compare 1 register

OC1REF

Output
control

OC1
TIMx_CH1

CC2I

U

IC2PS

UI
U

Capture/Compare 2 register OC2REF

Output OC2
control

TIMx_CH2

Notes:
Reg

Preload registers transferred
to active registers on U event
according to control bit
Event
ai17190b

Interrupt

24.2.2

TIM10/TIM11/TIM13/TIM14 main features
The features of general-purpose timers TIM10/TIM11/TIM13/TIM14 include:
•

16-bit auto-reload upcounter

•

16-bit programmable prescaler used to divide the counter clock frequency by any factor
between 1 and 65536 (can be changed “on the fly”)

•

independent channel for:

•

812/1709

–

Input capture

–

Output compare

–

PWM generation (edge-aligned mode)

–

One-pulse mode output

Interrupt generation on the following events:
–

Update: counter overflow, counter initialization (by software)

–

Input capture

–

Output compare

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
Figure 257. General-purpose timer block diagram (TIM10/TIM11/TIM13/TIM14)

Internal clock (CK_INT)

Trigger
Controller

Auto-reload register

U

UI
Stop, clear

CK_PSC

TIMx_CH1

TI1

Input filter &
edge selector

TI1FP1

PSC
prescaler

CK_CNT

+/-

Prescaler

IC1PS

U

CNT counter

C1I

CC1I

U

IC1

Enable
counter

Capture/compare 1 register

OC1REF

Output
control

OC1

TIMx_CH1

Notes:
Reg

Preload registers transferred
to active registers on U event
according to control bit
Event
ai17725d

Interrupt & DMA output

RM0385 Rev 7

813/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

24.3

TIM9/TIM10/TIM11/TIM12/TIM13/TIM14 functional description

24.3.1

Time-base unit
The main block of the timer is a 16-bit up-counter with its related auto-reload register. The
counters counts up.
The counter clock can be divided by a prescaler.
The counter, the auto-reload register and the prescaler register can be written or read by
software. This is true even when the counter is running.
The time-base unit includes:
•

Counter register (TIMx_CNT)

•

Prescaler register (TIMx_PSC)

•

Auto-reload register (TIMx_ARR)

The auto-reload register is preloaded. Writing to or reading from the auto-reload register
accesses the preload register. The content of the preload register are transferred into the
shadow register permanently or at each update event (UEV), depending on the auto-reload
preload enable bit (ARPE) in TIMx_CR1 register. The update event is sent when the counter
reaches the overflow and if the UDIS bit equals 0 in the TIMx_CR1 register. It can also be
generated by software. The generation of the update event is described in details for each
configuration.
The counter is clocked by the prescaler output CK_CNT, which is enabled only when the
counter enable bit (CEN) in TIMx_CR1 register is set (refer also to the slave mode controller
description to get more details on counter enabling).
Note that the counter starts counting 1 clock cycle after setting the CEN bit in the TIMx_CR1
register.

Prescaler description
The prescaler can divide the counter clock frequency by any factor between 1 and 65536. It
is based on a 16-bit counter controlled through a 16-bit register (in the TIMx_PSC register).
It can be changed on the fly as this control register is buffered. The new prescaler ratio is
taken into account at the next update event.
Figure 258 and Figure 259 give some examples of the counter behavior when the prescaler
ratio is changed on the fly.

814/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
Figure 258. Counter timing diagram with prescaler division change from 1 to 2

CK_PSC

CEN
Timerclock = CK_CNT

Counter register

F7

F8

F9

FA FB FC

01

00

02

03

Update event (UEV)

Prescaler control register

0

1

Write a new value in TIMx_PSC
Prescaler buffer

0

Prescaler counter

0

1

0

1

0

1

1

0

1

0

MS31076V2

Figure 259. Counter timing diagram with prescaler division change from 1 to 4

CK_PSC
CEN

Timerclock = CK_CNT

Counter register

F7

F8

F9

FA FB FC

00

01

Update event (UEV)

Prescaler control register

0

3

Write a new value in TIMx_PSC
Prescaler buffer

Prescaler counter

0

3

0

0

1

2

3

0

1

2

3
MS31077V2

RM0385 Rev 7

815/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

24.3.2

RM0385

Counter modes
Upcounting mode
In upcounting mode, the counter counts from 0 to the auto-reload value (content of the
TIMx_ARR register), then restarts from 0 and generates a counter overflow event.
Setting the UG bit in the TIMx_EGR register (by software or by using the slave mode
controller on TIM9/TIM12) also generates an update event.
The UEV event can be disabled by software by setting the UDIS bit in the TIMx_CR1
register. This is to avoid updating the shadow registers while writing new values in the
preload registers. Then no update event occurs until the UDIS bit has been written to 0.
However, the counter restarts from 0, as well as the counter of the prescaler (but the
prescale rate does not change). In addition, if the URS bit (update request selection) in
TIMx_CR1 register is set, setting the UG bit generates an update event UEV but without
setting the UIF flag (thus no interrupt is sent). This is to avoid generating both update and
capture interrupts when clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):
•

The auto-reload shadow register is updated with the preload value (TIMx_ARR),

•

The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register).

The following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.
Figure 260. Counter timing diagram, internal clock divided by 1

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

31

32

33

34 35 36

00

01

02

03

04

05

06

07

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31078V2

816/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
Figure 261. Counter timing diagram, internal clock divided by 2

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0035

0034

0036

0000

0002

0001

0003

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)

MS31079V2

Figure 262. Counter timing diagram, internal clock divided by 4

CK_PSC

CNT_EN

Timerclock = CK_CNT
Counter register

0035

0036

0000

0001

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31080V2

RM0385 Rev 7

817/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

Figure 263. Counter timing diagram, internal clock divided by N

CK_PSC

Timerclock = CK_CNT

Counter register

1F

00

20

Counter overflow

Update event (UEV)

Update interrupt flag
(UIF)
MS31081V2

Figure 264. Counter timing diagram, update event when ARPE=0 (TIMx_ARR not
preloaded)
CK_PSC

CEN

Timerclock = CK_CNT
Counter register

31

32

33

34

35

36

00

01

02

03

04

05

06

07

Counter overflow

Update event (UEV)
Update interrupt flag
(UIF)
Auto-reload preload
register

FF

36

Write a new value in TIMx_ARR
MS31082V2

818/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
Figure 265. Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded)
CK_PSC

CEN
Timerclock = CK_CNT
Counter register

F0

F1

F2

F3

F4 F5

00

01

02

03

04

05

06

07

Counter overflow
Update event (UEV)

Update interrupt flag
(UIF)
Auto-reload preload
register

F5

36

Auto-reload shadow
register

F5

Write a new value in TIMx_ARR

24.3.3

36

MS31083V2

Clock selection
The counter clock can be provided by the following clock sources:
•

Internal clock (CK_INT)

•

External clock mode1 (for TIM9/TIM12): external input pin (TIx)

•

Internal trigger inputs (ITRx) (for TIM9/TIM12): connecting the trigger output from
another timer. For instance, another timer can be configured as a prescaler for TIM12.
Refer to Section : Using one timer as prescaler for another timer for more details.

Internal clock source (CK_INT)
The internal clock source is the default clock source for TIM10/TIM11/TIM13/TIM14.
For TIM9/TIM12, the internal clock source is selected when the slave mode controller is
disabled (SMS=’000’). The CEN bit in the TIMx_CR1 register and the UG bit in the
TIMx_EGR register are then used as control bits and can be changed only by software
(except for UG which remains cleared). As soon as the CEN bit is programmed to 1, the
prescaler is clocked by the internal clock CK_INT.
Figure 266 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.

RM0385 Rev 7

819/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

Figure 266. Control circuit in normal mode, internal clock divided by 1

Internal clock
CEN=CNT_EN

UG

CNT_INIT

r clock = CK_CNT = CK_PSC
Counter register

31

32

33

34

35 36

00 01

02

03 04 05

06

07
MS31085V2

External clock source mode 1 (TIM9/TIM12)
This mode is selected when SMS=’111’ in the TIMx_SMCR register. The counter can count
at each rising or falling edge on a selected input.
Figure 267. TI2 external clock connection example
TIMx_SMCR
TS[2:0]
or TI2F
TI1F
ITRx
TI1_ED
TI1FP1
TI2

Filter

Edge
detector

TI2F_Rising
TI2F_Falling

0

TI2FP2

1

or
or

0xx
100

TRGI

101

CC2P

TIMx_CCMR1

TIMx_CCER

External clock
mode 1

CK_PSC

110
CK_INT

ICF[3:0]

Encoder
mode

(internal clock)

Internal clock
mode

SMS[2:0]
TIMx_SMCR

MS33114V1

For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:

820/1709

RM0385 Rev 7

RM0385

Note:

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
1.

Configure channel 2 to detect rising edges on the TI2 input by writing CC2S = ‘01’ in
the TIMx_CCMR1 register.

2.

Configure the input filter duration by writing the IC2F[3:0] bits in the TIMx_CCMR1
register (if no filter is needed, keep IC2F=’0000’).

3.

Select the rising edge polarity by writing CC2P=’0’ and CC2NP=’0’ in the TIMx_CCER
register.

4.

Configure the timer in external clock mode 1 by writing SMS=’111’ in the TIMx_SMCR
register.

5.

Select TI2 as the trigger input source by writing TS=’110’ in the TIMx_SMCR register.

6.

Enable the counter by writing CEN=’1’ in the TIMx_CR1 register.

The capture prescaler is not used for triggering, so you don’t need to configure it.
When a rising edge occurs on TI2, the counter counts once and the TIF flag is set.
The delay between the rising edge on TI2 and the actual clock of the counter is due to the
resynchronization circuit on TI2 input.
Figure 268. Control circuit in external clock mode 1

TI2
CNT_EN
Counter clock = CK_CNT = CK_PSC
Counter register

34

35

36

TIF

Write TIF=0

MS31087V2

24.3.4

Capture/compare channels
Each Capture/Compare channel is built around a capture/compare register (including a
shadow register), a input stage for capture (with digital filter, multiplexing and prescaler) and
an output stage (with comparator and output control).
Figure 269 to Figure 271 give an overview of one capture/compare channel.
The input stage samples the corresponding TIx input to generate a filtered signal TIxF.
Then, an edge detector with polarity selection generates a signal (TIxFPx) which can be
used as trigger input by the slave mode controller or as the capture command. It is
prescaled before the capture register (ICxPS).

RM0385 Rev 7

821/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

Figure 269. Capture/compare channel (example: channel 1 input stage
TI1F_ED
To the slave mode controller
TI1F_Rising

TI1

Filter
TI1F
downcounter

fDTS

Edge
detector

TI1F_Falling

0 TI1FP1

01

1
TI2FP1

CC1P/CC1NP

ICF[3:0]

TRC

TIMx_CCER

TIMx_CCMR1

TI2F_Rising
0
(from channel 2)
TI2F_Falling
1
(from channel 2)

IC1

10

(from slave mode
controller)

IC1PS
Divider
/1, /2, /4, /8

11

CC1S[1:0] ICPS[1:0]

CC1E

TIMx_CCMR1

TIMx_CCER

MS33115V1

The output stage generates an intermediate waveform which is then used for reference:
OCxRef (active high). The polarity acts at the end of the chain.
Figure 270. Capture/compare channel 1 main circuit

APB Bus

Read CCR1L

read_in_progress

CC1S[0]
IC1PS

write_in_progress

Input
mode

S write CCR1H

Capture/compare preload register

R

R
compare_transfer

capture_transfer
CC1S[1]

8
low

Read CCR1H S

high

8

(if 16-bit)

MCU-peripheral interface

Output
mode

CNT>CCR1
Counter

CC1S[0]

UEV
Comparator

CC1E

CC1S[1]

OC1PE

Capture/compare shadow register
Capture

write CCR1L

(from time
base unit)

OC1PE

TIM1_CCMR1

CNT=CCR1

CC1G
TIM1_EGR

MS31089V2

822/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
Figure 271. Output stage of capture/compare channel (channel 1)
To the master mode
controller
OC1REF

OC1REFC

‘0’
CNT > CCR1
CNT = CCR1

Output
mode
controller

Output
selector

OC2REF

OC1CE

0

0

1

1

Output
enable
circuit

CC1E

CC1P

CC1E

TIM1_CCER

TIM1_CCER

TIM1_CCER

OC1

OC1M[3:0]

TIM1_CCMR2

MSv45743V1

The capture/compare block is made of one preload register and one shadow register. Write
and read always access the preload register.
In capture mode, captures are actually done in the shadow register, which is copied into the
preload register.
In compare mode, the content of the preload register is copied into the shadow register
which is compared to the counter.

24.3.5

Input capture mode
In Input capture mode, the Capture/Compare Registers (TIMx_CCRx) are used to latch the
value of the counter after a transition detected by the corresponding ICx signal. When a
capture occurs, the corresponding CCXIF flag (TIMx_SR register) is set and an interrupt or
a DMA request can be sent if they are enabled. If a capture occurs while the CCxIF flag was
already high, then the over-capture flag CCxOF (TIMx_SR register) is set. CCxIF can be
cleared by software by writing it to ‘0’ or by reading the captured data stored in the
TIMx_CCRx register. CCxOF is cleared when you write it to ‘0’.
The following example shows how to capture the counter value in TIMx_CCR1 when TI1
input rises. To do this, use the following procedure:
1.

Select the active input: TIMx_CCR1 must be linked to the TI1 input, so write the CC1S
bits to ‘01’ in the TIMx_CCMR1 register. As soon as CC1S becomes different from ‘00’,
the channel is configured in input mode and the TIMx_CCR1 register becomes readonly.

2.

Program the input filter duration you need with respect to the signal you connect to the
timer (by programming the ICxF bits in the TIMx_CCMRx register if the input is one of
the TIx inputs). Let’s imagine that, when toggling, the input signal is not stable during at
must 5 internal clock cycles. We must program a filter duration longer than these 5
clock cycles. We can validate a transition on TI1 when 8 consecutive samples with the

RM0385 Rev 7

823/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

new level have been detected (sampled at fDTS frequency). Then write IC1F bits to
‘0011’ in the TIMx_CCMR1 register.
3.

Select the edge of the active transition on the TI1 channel by programming CC1P and
CC1NP bits to ‘00’ in the TIMx_CCER register (rising edge in this case).

4.

Program the input prescaler. In our example, we wish the capture to be performed at
each valid transition, so the prescaler is disabled (write IC1PS bits to ‘00’ in the
TIMx_CCMR1 register).

5.

Enable capture from the counter into the capture register by setting the CC1E bit in the
TIMx_CCER register.

6.

If needed, enable the related interrupt request by setting the CC1IE bit in the
TIMx_DIER register.

When an input capture occurs:
•

The TIMx_CCR1 register gets the value of the counter on the active transition.

•

CC1IF flag is set (interrupt flag). CC1OF is also set if at least two consecutive captures
occurred whereas the flag was not cleared.

•

An interrupt is generated depending on the CC1IE bit.

In order to handle the overcapture, it is recommended to read the data before the
overcapture flag. This is to avoid missing an overcapture which could happen after reading
the flag and before reading the data.
Note:

IC interrupt requests can be generated by software by setting the corresponding CCxG bit in
the TIMx_EGR register.

24.3.6

PWM input mode (only for TIM9/TIM12)
This mode is a particular case of input capture mode. The procedure is the same except:
•

Two ICx signals are mapped on the same TIx input.

•

These 2 ICx signals are active on edges with opposite polarity.

•

One of the two TIxFP signals is selected as trigger input and the slave mode controller
is configured in reset mode.

For example, you can measure the period (in TIMx_CCR1 register) and the duty cycle (in
TIMx_CCR2 register) of the PWM applied on TI1 using the following procedure (depending
on CK_INT frequency and prescaler value):

824/1709

1.

Select the active input for TIMx_CCR1: write the CC1S bits to ‘01’ in the TIMx_CCMR1
register (TI1 selected).

2.

Select the active polarity for TI1FP1 (used both for capture in TIMx_CCR1 and counter
clear): program the CC1P and CC1NP bits to ‘00’ (active on rising edge).

3.

Select the active input for TIMx_CCR2: write the CC2S bits to ‘10’ in the TIMx_CCMR1
register (TI1 selected).

4.

Select the active polarity for TI1FP2 (used for capture in TIMx_CCR2): program the
CC2P and CC2NP bits to ‘11’ (active on falling edge).

5.

Select the valid trigger input: write the TS bits to ‘101’ in the TIMx_SMCR register
(TI1FP1 selected).

6.

Configure the slave mode controller in reset mode: write the SMS bits to ‘100’ in the
TIMx_SMCR register.

7.

Enable the captures: write the CC1E and CC2E bits to ‘1’ in the TIMx_CCER register.

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
Figure 272. PWM input mode timing
TI1

TIMx_CNT

0000

0004

0001

0002

TIMx_CCR1

0004

TIMx_CCR2

0002

IC1 capture
period
measurement

0003

0004

IC2 capture
pulse width
measurment

0000

IC1 capture
period
measurement

ai15413c

1. The PWM input mode can be used only with the TIMx_CH1/TIMx_CH2 signals due to the fact that only
TI1FP1 and TI2FP2 are connected to the slave mode controller.

24.3.7

Forced output mode
In output mode (CCxS bits = ‘00’ in the TIMx_CCMRx register), each output compare signal
(OCxREF and then OCx) can be forced to active or inactive level directly by software,
independently of any comparison between the output compare register and the counter.
To force an output compare signal (OCXREF/OCx) to its active level, you just need to write
‘0101’ in the OCxM bits in the corresponding TIMx_CCMRx register. Thus OCXREF is
forced high (OCxREF is always active high) and OCx get opposite value to CCxP polarity
bit.
For example: CCxP=’0’ (OCx active high) => OCx is forced to high level.
The OCxREF signal can be forced low by writing the OCxM bits to ‘0100’ in the
TIMx_CCMRx register.
Anyway, the comparison between the TIMx_CCRx shadow register and the counter is still
performed and allows the flag to be set. Interrupt requests can be sent accordingly. This is
described in the output compare mode section below.

24.3.8

Output compare mode
This function is used to control an output waveform or indicating when a period of time has
elapsed.
When a match is found between the capture/compare register and the counter, the output
compare function:
1.

Assigns the corresponding output pin to a programmable value defined by the output
compare mode (OCxM bits in the TIMx_CCMRx register) and the output polarity (CCxP
bit in the TIMx_CCER register). The output pin can keep its level (OCxM=’0000’), be
set active (OCxM=’0001’), be set inactive (OCxM=’0010’) or can toggle (OCxM=’0011’)
on match.

2.

Sets a flag in the interrupt status register (CCxIF bit in the TIMx_SR register).

3.

Generates an interrupt if the corresponding interrupt mask is set (CCXIE bit in the
TIMx_DIER register).

RM0385 Rev 7

825/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

The TIMx_CCRx registers can be programmed with or without preload registers using the
OCxPE bit in the TIMx_CCMRx register.
In output compare mode, the update event UEV has no effect on OCxREF and OCx output.
The timing resolution is one count of the counter. Output compare mode can also be used to
output a single pulse (in One-pulse mode).
Procedure:
1.

Select the counter clock (internal, external, prescaler).

2.

Write the desired data in the TIMx_ARR and TIMx_CCRx registers.

3.

Set the CCxIE bit if an interrupt request is to be generated.

4.

Select the output mode. For example:

5.

–

Write OCxM = ‘0011’ to toggle OCx output pin when CNT matches CCRx

–

Write OCxPE = ‘0’ to disable preload register

–

Write CCxP = ‘0’ to select active high polarity

–

Write CCxE = ‘1’ to enable the output

Enable the counter by setting the CEN bit in the TIMx_CR1 register.

The TIMx_CCRx register can be updated at any time by software to control the output
waveform, provided that the preload register is not enabled (OCxPE=’0’, else TIMx_CCRx
shadow register is updated only at the next update event UEV). An example is given in
Figure 273.
Figure 273. Output compare mode, toggle on OC1.
Write B201h in the CC1R register

TIM1_CNT

0039

TIM1_CCR1

003B

003A

B200

B201

B201

003A

OC1REF= OC1

Match detected on CCR1
Interrupt generated if enabled
MS31092V1

24.3.9

PWM mode
Pulse Width Modulation mode allows you to generate a signal with a frequency determined
by the value of the TIMx_ARR register and a duty cycle determined by the value of the
TIMx_CCRx register.
The PWM mode can be selected independently on each channel (one PWM per OCx
output) by writing ‘0110’ (PWM mode 1) or ‘0111’ (PWM mode 2) in the OCxM bits in the

826/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
TIMx_CCMRx register. You must enable the corresponding preload register by setting the
OCxPE bit in the TIMx_CCMRx register, and eventually the auto-reload preload register (in
upcounting or center-aligned modes) by setting the ARPE bit in the TIMx_CR1 register.
As the preload registers are transferred to the shadow registers only when an update event
occurs, before starting the counter, you have to initialize all the registers by setting the UG
bit in the TIMx_EGR register.
The OCx polarity is software programmable using the CCxP bit in the TIMx_CCER register.
It can be programmed as active high or active low. The OCx output is enabled by the CCxE
bit in the TIMx_CCER register. Refer to the TIMx_CCERx register description for more
details.
In PWM mode (1 or 2), TIMx_CNT and TIMx_CCRx are always compared to determine
whether TIMx_CNT ≤ TIMx_CCRx.
The timer is able to generate PWM in edge-aligned mode only since the counter is
upcounting.
In the following example, we consider PWM mode 1. The reference PWM signal OCxREF is
high as long as TIMx_CNT < TIMx_CCRx else it becomes low. If the compare value in
TIMx_CCRx is greater than the auto-reload value (in TIMx_ARR) then OCxREF is held at
‘1’. If the compare value is 0 then OCxRef is held at ‘0’. Figure 274 shows some edgealigned PWM waveforms in an example where TIMx_ARR=8.
Figure 274. Edge-aligned PWM waveforms (ARR=8)

0

Counter register

CCRx=4

1

2

3

4

5

6

7

8

0

1

OCXREF
CCxIF

OCXREF
CCRx=8
CCxIF

OCXREF

‘1’

CCRx>8
CCxIF

OCXREF

‘0’

CCRx=0
CCxIF

MS31093V1

24.3.10

Combined PWM mode (TIM9/TIM12 only)
Combined PWM mode allows two edge or center-aligned PWM signals to be generated with
programmable delay and phase shift between respective pulses. While the frequency is
determined by the value of the TIMx_ARR register, the duty cycle and delay are determined
RM0385 Rev 7

827/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

by the two TIMx_CCRx registers. The resulting signals, OCxREFC, are made of an OR or
AND logical combination of two reference PWMs:
•

OC1REFC (or OC2REFC) is controlled by the TIMx_CCR1 and TIMx_CCR2 registers

Combined PWM mode can be selected independently on two channels (one OCx output per
pair of CCR registers) by writing ‘1100’ (Combined PWM mode 1) or ‘1101’ (Combined PWM
mode 2) in the OCxM bits in the TIMx_CCMRx register.
When a given channel is used as a combined PWM channel, its complementary channel
must be configured in the opposite PWM mode (for instance, one in Combined PWM mode
1 and the other in Combined PWM mode 2).
Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
Figure 275 represents an example of signals that can be generated using combined PWM
mode, obtained with the following configuration:
•

Channel 1 is configured in Combined PWM mode 2,

•

Channel 2 is configured in PWM mode 1,
Figure 275. Combined PWM mode on channel 1 and 2

OC2’
OC1’

OC2
OC1
OC1REF
OC2REF
OC1REF’
OC2REF’

OC1REFC
OC1REFC’

OC1REFC = OC1REF AND OC2REF
OC1REFC’ = OC1REF’ OR OC2REF’

MS31094V1

828/1709

RM0385 Rev 7

RM0385

One-pulse mode
One-pulse mode (OPM) is a particular case of the previous modes. It allows the counter to
be started in response to a stimulus and to generate a pulse with a programmable length
after a programmable delay.
Starting the counter can be controlled through the slave mode controller. Generating the
waveform can be done in output compare mode or PWM mode. You select One-pulse mode
by setting the OPM bit in the TIMx_CR1 register. This makes the counter stop automatically
at the next update event UEV.
A pulse can be correctly generated only if the compare value is different from the counter
initial value. Before starting (when the timer is waiting for the trigger), the configuration must
be as follows:
CNT < CCRx ≤ ARR (in particular, 0 < CCRx)
Figure 276. Example of one pulse mode.
TI2
OC1REF
OC1

TIM1_ARR
Counter

24.3.11

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

TIM1_CCR1

0
tDELAY

tPULSE

t

MS31099V1

For example you may want to generate a positive pulse on OC1 with a length of tPULSE and
after a delay of tDELAY as soon as a positive edge is detected on the TI2 input pin.
Use TI2FP2 as trigger 1:
1.

Map TI2FP2 to TI2 by writing CC2S=’01’ in the TIMx_CCMR1 register.

2.

TI2FP2 must detect a rising edge, write CC2P=’0’ and CC2NP=’0’ in the TIMx_CCER
register.

3.

Configure TI2FP2 as trigger for the slave mode controller (TRGI) by writing TS=’110’ in
the TIMx_SMCR register.

4.

TI2FP2 is used to start the counter by writing SMS to ‘110’ in the TIMx_SMCR register
(trigger mode).

RM0385 Rev 7

829/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

The OPM waveform is defined by writing the compare registers (taking into account the
clock frequency and the counter prescaler).
•

The tDELAY is defined by the value written in the TIMx_CCR1 register.

•

The tPULSE is defined by the difference between the auto-reload value and the compare
value (TIMx_ARR - TIMx_CCR1).

•

Let’s say you want to build a waveform with a transition from ‘0’ to ‘1’ when a compare
match occurs and a transition from ‘1’ to ‘0’ when the counter reaches the auto-reload
value. To do this you enable PWM mode 2 by writing OC1M=’0111’ in the
TIMx_CCMR1 register. You can optionally enable the preload registers by writing
OC1PE=’1’ in the TIMx_CCMR1 register and ARPE in the TIMx_CR1 register. In this
case you have to write the compare value in the TIMx_CCR1 register, the auto-reload
value in the TIMx_ARR register, generate an update by setting the UG bit and wait for
external trigger event on TI2. CC1P is written to ‘0’ in this example.

You only want 1 pulse (Single mode), so you write '1 in the OPM bit in the TIMx_CR1
register to stop the counter at the next update event (when the counter rolls over from the
auto-reload value back to 0). When OPM bit in the TIMx_CR1 register is set to '0', so the
Repetitive Mode is selected.
Particular case: OCx fast enable
In One-pulse mode, the edge detection on TIx input set the CEN bit which enables the
counter. Then the comparison between the counter and the compare value makes the
output toggle. But several clock cycles are needed for these operations and it limits the
minimum delay tDELAY min we can get.
If you want to output a waveform with the minimum delay, you can set the OCxFE bit in the
TIMx_CCMRx register. Then OCxRef (and OCx) are forced in response to the stimulus,
without taking in account the comparison. Its new level is the same as if a compare match
had occurred. OCxFE acts only if the channel is configured in PWM1 or PWM2 mode.

24.3.12

Retriggerable one pulse mode (OPM) (TIM12 only)
This mode allows the counter to be started in response to a stimulus and to generate a
pulse with a programmable length, but with the following differences with non-retriggerable
one pulse mode described in Section 24.3.11: One-pulse mode:
•

The pulse starts as soon as the trigger occurs (no programmable delay)

•

The pulse is extended if a new trigger occurs before the previous one is completed

The timer must be in Slave mode, with the bits SMS[3:0] = ‘1000’ (Combined Reset + trigger
mode) in the TIMx_SMCR register, and the OCxM[3:0] bits set to ‘1000’ or ‘1001’ for
retrigerrable OPM mode 1 or 2.
If the timer is configured in up-counting mode, the corresponding CCRx must be set to 0
(the ARR register sets the pulse length). If the timer is configured in down-counting mode,
CCRx must be above or equal to ARR.
Note:

The OCxM[3:0] and SMS[3:0] bit fields are split into two parts for compatibility reasons, the
most significant bit are not contiguous with the 3 least significant ones.
This mode must not be used with center-aligned PWM modes. It is mandatory to have
CMS[1:0] = 00 in TIMx_CR1.

830/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
Figure 277. Retriggerable one pulse mode
TRGI

Counter

Output

MS33106V1

24.3.13

UIF bit remapping
The IUFREMAP bit in the TIMx_CR1 register forces a continuous copy of the Update
Interrupt Flag UIF into bit 31 of the timer counter register (TIMxCNT[31]). This allows to
atomically read both the counter value and a potential roll-over condition signaled by the
UIFCPY flag. In particular cases, it can ease the calculations by avoiding race conditions
caused for instance by a processing shared between a background task (counter reading)
and an interrupt (Update Interrupt).
There is no latency between the assertions of the UIF and UIFCPY flags.

24.3.14

Timer input XOR function
The TI1S bit in the TIMx_CR2 register, allows the input filter of channel 1 to be connected to
the output of a XOR gate, combining the two input pins TIMx_CH1 and TIMx_CH2.
The XOR output can be used with all the timer input functions such as trigger or input
capture. It is useful for measuring the interval between the edges on two input signals, as
shown in Figure 278.
Figure 278. Measuring time interval between edges on 2 signals
TI1
TI2
TI1 XOR TI2

Counter

MS31400V1

RM0385 Rev 7

831/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

24.3.15

RM0385

TIM9/TIM12 external trigger synchronization
The TIM9/TIM12 timers can be synchronized with an external trigger in several modes:
Reset mode, Gated mode and Trigger mode.

Slave mode: Reset mode
The counter and its prescaler can be reinitialized in response to an event on a trigger input.
Moreover, if the URS bit from the TIMx_CR1 register is low, an update event UEV is
generated. Then all the preloaded registers (TIMx_ARR, TIMx_CCRx) are updated.
In the following example, the upcounter is cleared in response to a rising edge on TI1 input:
1.

Configure the channel 1 to detect rising edges on TI1. Configure the input filter duration
(in this example, we don’t need any filter, so we keep IC1F=’0000’). The capture
prescaler is not used for triggering, so you don’t need to configure it. The CC1S bits
select the input capture source only, CC1S = ‘01’ in the TIMx_CCMR1 register.
Program CC1P and CC1NP to ‘00’ in TIMx_CCER register to validate the polarity (and
detect rising edges only).

2.

Configure the timer in reset mode by writing SMS=’100’ in TIMx_SMCR register. Select
TI1 as the input source by writing TS=’101’ in TIMx_SMCR register.

3.

Start the counter by writing CEN=’1’ in the TIMx_CR1 register.

The counter starts counting on the internal clock, then behaves normally until TI1 rising
edge. When TI1 rises, the counter is cleared and restarts from 0. In the meantime, the
trigger flag is set (TIF bit in the TIMx_SR register) and an interrupt request can be sent if
enabled (depending on the TIE bit in TIMx_DIER register).
The following figure shows this behavior when the auto-reload register TIMx_ARR=0x36.
The delay between the rising edge on TI1 and the actual reset of the counter is due to the
resynchronization circuit on TI1 input.
Figure 279. Control circuit in reset mode
TI1

UG
Counter clock = ck_cnt = ck_psc
Counter register

30 31 32 33 34 35 36 00 01 02 03

00 01 02 03

TIF

MS31401V2

Slave mode: Gated mode
The counter can be enabled depending on the level of a selected input.
In the following example, the upcounter counts only when TI1 input is low:

832/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)
1.

Configure the channel 1 to detect low levels on TI1. Configure the input filter duration
(in this example, we don’t need any filter, so we keep IC1F=’0000’). The capture
prescaler is not used for triggering, so you don’t need to configure it. The CC1S bits
select the input capture source only, CC1S=’01’ in TIMx_CCMR1 register. Program
CC1P=’1’ and CC1NP=’0’ in TIMx_CCER register to validate the polarity (and detect
low level only).

2.

Configure the timer in gated mode by writing SMS=’101’ in TIMx_SMCR register.
Select TI1 as the input source by writing TS=’101’ in TIMx_SMCR register.

3.

Enable the counter by writing CEN=’1’ in the TIMx_CR1 register (in gated mode, the
counter doesn’t start if CEN=’0’, whatever is the trigger input level).

The counter starts counting on the internal clock as long as TI1 is low and stops as soon as
TI1 becomes high. The TIF flag in the TIMx_SR register is set both when the counter starts
or stops.
The delay between the rising edge on TI1 and the actual stop of the counter is due to the
resynchronization circuit on TI1 input.
Figure 280. Control circuit in gated mode

TI1
cnt_en
Counter clock = ck_cnt = ck_psc

Counter register

30 31 32 33

34

35 36 37 38

TIF

Write TIF=0
MS31402V1

Slave mode: Trigger mode
The counter can start in response to an event on a selected input.
In the following example, the upcounter starts in response to a rising edge on TI2 input:
1.

Configure the channel 2 to detect rising edges on TI2. Configure the input filter duration
(in this example, we don’t need any filter, so we keep IC2F=’0000’). The capture
prescaler is not used for triggering, so you don’t need to configure it. The CC2S bits are
configured to select the input capture source only, CC2S=’01’ in TIMx_CCMR1 register.
Program CC2P=’1’ and CC2NP=’0’ in TIMx_CCER register to validate the polarity (and
detect low level only).

2.

Configure the timer in trigger mode by writing SMS=’110’ in TIMx_SMCR register.
Select TI2 as the input source by writing TS=’110’ in TIMx_SMCR register.

When a rising edge occurs on TI2, the counter starts counting on the internal clock and the
TIF flag is set.

RM0385 Rev 7

833/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

The delay between the rising edge on TI2 and the actual start of the counter is due to the
resynchronization circuit on TI2 input.
Figure 281. Control circuit in trigger mode
TI2
cnt_en
Counter clock = ck_cnt = ck_psc

Counter register

34

35

36 37 38

TIF
MS31403V1

24.3.16

Slave mode – combined reset + trigger mode
In this case, a rising edge of the selected trigger input (TRGI) reinitializes the counter,
generates an update of the registers, and starts the counter.
This mode is used for one-pulse mode.

834/1709

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

24.3.17

Timer synchronization (TIM9/TIM12)
The TIM timers are linked together internally for timer synchronization or chaining. Refer to
Section 23.3.19: Timer synchronization for details.

Note:

The clock of the slave timer must be enabled prior to receive events from the master timer,
and must not be changed on-the-fly while triggers are received from the master timer.

24.3.18

Debug mode
When the microcontroller enters debug mode (Cortex®-M7 core halted), the TIMx counter
either continues to work normally or stops, depending on DBG_TIMx_STOP configuration
bit in DBG module. For more details, refer to Section 40.16.2: Debug support for timers,
watchdog, bxCAN and I2C.

24.4

TIM9/TIM12 registers
Refer to Section 1.1 for a list of abbreviations used in register descriptions.
The peripheral registers have to be written by half-words (16 bits) or words (32 bits). Read
accesses can be done by bytes (8 bits), half-words (16 bits) or words (32 bits).

24.4.1

TIM9/TIM12 control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15
Res.

14
Res.

13
Res.

12

11

10

Res.

UIFRE
MAP

Res.

rw

9

8

CKD[1:0]
rw

7

6

5

4

3

2

1

0

ARPE

Res.

Res.

Res.

OPM

URS

UDIS

CEN

rw

rw

rw

rw

rw

rw

Bits 15:12 Reserved, must be kept at reset value.
Bit 11 UIFREMAP: UIF status bit remapping
0: No remapping. UIF status bit is not copied to TIMx_CNT register bit 31.
1: Remapping enabled. UIF status bit is copied to TIMx_CNT register bit 31.
Bit 10 Reserved, must be kept at reset value.
Bits 9:8 CKD[1:0]: Clock division
This bit-field indicates the division ratio between the timer clock (CK_INT) frequency and
sampling clock used by the digital filters (TIx),
00: tDTS = tCK_INT
01: tDTS = 2 × tCK_INT
10: tDTS = 4 × tCK_INT
11: Reserved
Bit 7 ARPE: Auto-reload preload enable
0: TIMx_ARR register is not buffered.
1: TIMx_ARR register is buffered.
Bits 6:4 Reserved, must be kept at reset value.

RM0385 Rev 7

835/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

Bit 3 OPM: One-pulse mode
0: Counter is not stopped on the update event
1: Counter stops counting on the next update event (clearing the CEN bit).
Bit 2 URS: Update request source
This bit is set and cleared by software to select the UEV event sources.
0: Any of the following events generates an update interrupt if enabled. These events can
be:
–
Counter overflow
–
Setting the UG bit
–
Update generation through the slave mode controller
1: Only counter overflow generates an update interrupt if enabled.
Bit 1 UDIS: Update disable
This bit is set and cleared by software to enable/disable update event (UEV) generation.
0: UEV enabled. An UEV is generated by one of the following events:
–
Counter overflow
–
Setting the UG bit
Buffered registers are then loaded with their preload values.
1: UEV disabled. No UEV is generated, shadow registers keep their value (ARR, PSC,
CCRx). The counter and the prescaler are reinitialized if the UG bit is set.
Bit 0 CEN: Counter enable
0: Counter disabled
1: Counter enabled
CEN is cleared automatically in one-pulse mode, when an update event occurs.
Note: External clock and gated mode can work only if the CEN bit has been previously set by
software. However trigger mode can set the CEN bit automatically by hardware.

24.4.2

TIM9/TIM12 slave mode control register (TIMx_SMCR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SMS[3]

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MSM

rw

rw

TS[2:0]
rw

rw

Res.
rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 SMS[3]: Slave mode selection - bit 3
Refer to SMS description - bits 2:0
Bits 15:8 Reserved, must be kept at reset value.
Bit 7 MSM: Master/Slave mode
0: No action
1: The effect of an event on the trigger input (TRGI) is delayed to allow a perfect
synchronization between the current timer and its slaves (through TRGO). It is useful in
order to synchronize several timers on a single external event.

836/1709

RM0385 Rev 7

0

SMS[2:0]
rw

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

Bits 6:4 TS[2:0]: Trigger selection
This bitfield selects the trigger input to be used to synchronize the counter.
000: Internal Trigger 0 (ITR0)
001: Internal Trigger 1 (ITR1)
010: Internal Trigger 2 (ITR2)
011: Internal Trigger 3 (ITR3)
100: TI1 Edge Detector (TI1F_ED)
101: Filtered Timer Input 1 (TI1FP1)
110: Filtered Timer Input 2 (TI2FP2)
111: Reserved.
See Table 153: TIMx internal trigger connection on page 837 for more details on the
meaning of ITRx for each timer.
Note: These bits must be changed only when they are not used (e.g. when SMS=’000’) to
avoid wrong edge detections at the transition.
Bit 3 Reserved, must be kept at reset value.
Bits 16, 2, 1, 0 SMS[3:0]: Slave mode selection
When external signals are selected the active edge of the trigger signal (TRGI) is linked to the
polarity selected on the external input (see Input Control register and Control Register
description.
0000: Slave mode disabled - if CEN = ‘1’ then the prescaler is clocked directly by the internal
clock.
0001: Reserved
0010: Reserved
0011: Reserved
0100: Reset Mode - Rising edge of the selected trigger input (TRGI) reinitializes the counter
and generates an update of the registers.
0101: Gated Mode - The counter clock is enabled when the trigger input (TRGI) is high. The
counter stops (but is not reset) as soon as the trigger becomes low. Both start and stop of
the counter are controlled.
0110: Trigger Mode - The counter starts at a rising edge of the trigger TRGI (but it is not
reset). Only the start of the counter is controlled.
0111: External Clock Mode 1 - Rising edges of the selected trigger (TRGI) clock the counter.
1000: Combined reset + trigger mode - Rising edge of the selected trigger input (TRGI)
reinitializes the counter, generates an update of the registers and starts the counter.
Other codes: reserved.
Note: The gated mode must not be used if TI1F_ED is selected as the trigger input
(TS=’100’). Indeed, TI1F_ED outputs 1 pulse for each transition on TI1F, whereas the
gated mode checks the level of the trigger signal.
Note: The clock of the slave timer must be enabled prior to receive events from the master
timer, and must not be changed on-the-fly while triggers are received from the master
timer.

Table 153. TIMx internal trigger connection
Slave TIM

ITR0 (TS = ‘000’)

ITR1 (TS = ‘001’)

ITR2 (TS = ‘010’)

ITR3 (TS = ‘011’)

TIM9

TIM2

TIM3

TIM10_OC

TIM11_OC

TIM12

TIM4

TIM5

TIM13_OC

TIM14_OC

RM0385 Rev 7

837/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

24.4.3

RM0385

TIM9/TIM12 Interrupt enable register (TIMx_DIER)
Address offset: 0x0C
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIE

Res.

Res.

Res.

CC2IE

CC1IE

UIE

rw

rw

rw

rw

Bits 15:7

Reserved, must be kept at reset value.

Bit 6 TIE: Trigger interrupt enable
0: Trigger interrupt disabled.
1: Trigger interrupt enabled.
Bits 5:3

Reserved, must be kept at reset value.

Bit 2 CC2IE: Capture/Compare 2 interrupt enable
0: CC2 interrupt disabled.
1: CC2 interrupt enabled.
Bit 1 CC1IE: Capture/Compare 1 interrupt enable
0: CC1 interrupt disabled.
1: CC1 interrupt enabled.
Bit 0 UIE: Update interrupt enable
0: Update interrupt disabled.
1: Update interrupt enabled.

24.4.4

TIM9/TIM12 status register (TIMx_SR)
Address offset: 0x10
Reset value: 0x0000

15

14

13

12

11

Res.

Res.

Res.

Res.

Res.

10

rc_w0

Bits 15:11

9

CC2OF CC1OF

8

7

6

5

4

3

2

1

0

Res.

Res.

TIF

Res.

Res.

Res.

CC2IF

CC1IF

UIF

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

Reserved, must be kept at reset value.

Bit 10 CC2OF: Capture/compare 2 overcapture flag
refer to CC1OF description
Bit 9 CC1OF: Capture/Compare 1 overcapture flag
This flag is set by hardware only when the corresponding channel is configured in input
capture mode. It is cleared by software by writing it to ‘0’.
0: No overcapture has been detected.
1: The counter value has been captured in TIMx_CCR1 register while CC1IF flag was
already set
Bits 8:7

838/1709

Reserved, must be kept at reset value.

RM0385 Rev 7

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

Bit 6 TIF: Trigger interrupt flag
This flag is set by hardware on trigger event (active edge detected on TRGI input when the
slave mode controller is enabled in all modes but gated mode. It is set when the counter
starts or stops when gated mode is selected. It is cleared by software.
0: No trigger event occurred.
1: Trigger interrupt pending.
Bits 5:3

Reserved, must be kept at reset value.

Bit 2 CC2IF: Capture/Compare 2 interrupt flag
refer to CC1IF description
Bit 1 CC1IF: Capture/compare 1 interrupt flag
If channel CC1 is configured as output:
This flag is set by hardware when the counter matches the compare value. It is cleared by
software.
0: No match.
1: The content of the counter TIMx_CNT matches the content of the TIMx_CCR1 register.
When the contents of TIMx_CCR1 are greater than the contents of TIMx_ARR, the CC1IF bit
goes high on the counter overflow.
If channel CC1 is configured as input:
This bit is set by hardware on a capture. It is cleared by software or by reading the
TIMx_CCR1 register.
0: No input capture occurred.
1: The counter value has been captured in TIMx_CCR1 register (an edge has been detected
on IC1 which matches the selected polarity).
Bit 0 UIF: Update interrupt flag
This bit is set by hardware on an update event. It is cleared by software.
0: No update occurred.
1: Update interrupt pending. This bit is set by hardware when the registers are updated:
– At overflow and if UDIS=’0’ in the TIMx_CR1 register.
– When CNT is reinitialized by software using the UG bit in TIMx_EGR register, if URS=’0’ and
UDIS=’0’ in the TIMx_CR1 register.
– When CNT is reinitialized by a trigger event (refer to the synchro control register
description), if URS=’0’ and UDIS=’0’ in the TIMx_CR1 register.

24.4.5

TIM9/TIM12 event generation register (TIMx_EGR)
Address offset: 0x14
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TG

Res.

Res.

Res.

CC2G

CC1G

UG

w

w

w

w

Bits 15:7 Reserved, must be kept at reset value.
Bit 6 TG: Trigger generation
This bit is set by software in order to generate an event, it is automatically cleared by
hardware.
0: No action
1: The TIF flag is set in the TIMx_SR register. Related interrupt can occur if enabled
Bits 5:3 Reserved, must be kept at reset value.

RM0385 Rev 7

839/1709
859

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

RM0385

Bit 2 CC2G: Capture/compare 2 generation
refer to CC1G description
Bit 1 CC1G: Capture/compare 1 generation
This bit is set by software to generate an event, it is automatically cleared by hardware.
0: No action
1: A capture/compare event is generated on channel 1:
If channel CC1 is configured as output:
the CC1IF flag is set, the corresponding interrupt is sent if enabled.
If channel CC1 is configured as input:
The current counter value is captured in the TIMx_CCR1 register. The CC1IF flag is set, the
corresponding interrupt is sent if enabled. The CC1OF flag is set if the CC1IF flag was
already high.
Bit 0 UG: Update generation
This bit can be set by software, it is automatically cleared by hardware.
0: No action
1: Re-initializes the counter and generates an update of the registers. The prescaler counter
is also cleared and the prescaler ratio is not affected. The counter is cleared.

24.4.6

TIM9/TIM12 capture/compare mode register 1 (TIMx_CCMR1)
Address offset: 0x18
Reset value: 0x0000
The channels can be used in input (capture mode) or in output (compare mode). The
direction of a channel is defined by configuring the corresponding CCxS bits. All the other
bits in this register have different functions in input and output modes. For a given bit, OCxx
describes its function when the channel is configured in output mode, ICxx describes its
function when the channel is configured in input mode. So you must take care that the same
bit can have different meanings for the input stage and the output stage.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC2M
[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC1M
[3]

Res.

Res.

rw
15

14

Res.

13

12

OC2M[2:0]

rw

rw

10

OC2PE OC2FE

IC2F[3:0]
rw

11

IC2PSC[1:0]
rw

rw

rw

9

8

CC2S[1:0]
rw

rw

rw
7
Res.

rw

Bits 31:25 Reserved, always read as 0
Bit 24 OC2M[3]: Output Compare 2 mode - bit 3
Refer to OC2M description on bits 14:12
Bits 23:17 Reserved, always read as 0
Bit 16 OC1M[3]: Output Compare 1 mode - bit 3
Refer to OC1M description on bits 6:4

840/1709

5

4

OC1M[2:0]

Reserved, must be kept at reset value.

RM0385 Rev 7

rw

rw

3

2

OC1PE OC1FE

IC1F[3:0]

Output compare mode

Bit 15

6

IC1PSC[1:0]
rw

rw

rw

1

0

CC1S[1:0]
rw

rw

RM0385

General-purpose timers (TIM9/TIM10/TIM11/TIM12/TIM13/TIM14)

Bits 14:12 OC2M[2:0]: Output compare 2 mode
Refer to OC1M[3:0] for bit description.
Bit 11 OC2PE: Output compare 2 preload enable
Bit 10 OC2FE: Output compare 2 fast enable
Bits 9:8 CC2S[1:0]: Capture/Compare 2 selection
This bitfield defines the direction of the channel (input/output) as well as the used input.
00: CC2 channel is configured as output
01: CC2 channel is configured as input, IC2 is mapped on TI2
10: CC2 channel is configured as input, IC2 is mapped on TI1
11: CC2 channel is configured as input, IC2 is mapped on TRC. This mode works only if an
internal trigger input is selected through the TS bit (TIMx_SMCR register
Note: The CC2S bits are writable only when the channel is OFF (CC2E = 0 in TIMx_CCER).
Bit 7

Reserved, must be kept at reset value.

Bits 6:4 OC1M[3:0]: Output compare 1 mode (refer to bit 16 for OC1M[3])
These bits define the behavior of the output reference signal OC1REF from which OC1 is
derived. OC1REF is active high whereas the active level of OC1 depends on the CC1P.
0000: Frozen - The comparison between the output compare register TIMx_CCR1 and the
counter TIMx_CNT has no effect on the outputs.(this mode is used to generate a
timing base).
0001: Set channel 1 to active level on match. The OC1REF signal is forced high when the
TIMx_CNT counter matches the capture/compare register 1 (TIMx_CCR1).
0010: Set channel 1 to inactive level on match. The OC1REF signal is forced low when the
TIMx_CNT counter matches the capture/compare register 1 (TIMx_CCR1).
0011: Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1
0100: Force inactive level - OC1REF is forced low
0101: Force active level - OC1REF is forced high
0110: PWM mode 1 - channel 1 is active as long as TIMx_CNT W[6:0]

W[6:0]
CMP

APB bus

Register interface

WWDG_SR

preload
7-bit DownCounter (CNT)
÷ 4096

T6
EWI
EWIF

Logic

= 0x40 ?

readback
T[6:0]

cnt_out

pclk

WDGA

Write to WWDG_CR
T[6:0]

WWDG_CR

wwdg_out_rst

wwdg_it

÷ 2WDGTB
MS47214V1

28.3.1

Enabling the watchdog
When the user option WWDG_SW selects “Software window watchdog”, the watchdog is
always disabled after a reset. It is enabled by setting the WDGA bit in the WWDG_CR
register, then it cannot be disabled again except by a reset.
When the user option WWDG_SW selects “Hardware window watchdog”, the watchdog is
always enabled after a reset, it cannot be disabled.

28.3.2

Controlling the downcounter
This downcounter is free-running, counting down even if the watchdog is disabled. When
the watchdog is enabled, the T6 bit must be set to prevent generating an immediate reset.
The T[5:0] bits contain the number of increments which represents the time delay before the
watchdog produces a reset. The timing varies between a minimum and a maximum value
due to the unknown status of the prescaler when writing to the WWDG_CR register (see
Figure 301). The Configuration register (WWDG_CFR) contains the high limit of the window:
To prevent a reset, the downcounter must be reloaded when its value is lower than the
window register value and greater than 0x3F. Figure 301 describes the window watchdog
process.

Note:

The T6 bit can be used to generate a software reset (the WDGA bit is set and the T6 bit is
cleared).

28.3.3

Advanced watchdog interrupt feature
The Early Wakeup Interrupt (EWI) can be used if specific safety operations or data logging
must be performed before the actual reset is generated. The EWI interrupt is enabled by
setting the EWI bit in the WWDG_CFR register. When the downcounter reaches the value
0x40, an EWI interrupt is generated and the corresponding interrupt service routine (ISR)
can be used to trigger specific actions (such as communications or data logging), before
resetting the device.

RM0385 Rev 7

903/1709
908

System window watchdog (WWDG)

RM0385

In some applications, the EWI interrupt can be used to manage a software system check
and/or system recovery/graceful degradation, without generating a WWDG reset. In this
case, the corresponding interrupt service routine (ISR) should reload the WWDG counter to
avoid the WWDG reset, then trigger the required actions.
The EWI interrupt is cleared by writing '0' to the EWIF bit in the WWDG_SR register.
Note:

When the EWI interrupt cannot be served, e.g. due to a system lock in a higher priority task,
the WWDG reset will eventually be generated.

28.3.4

How to program the watchdog timeout
Use the formula in Figure 301 to calculate the WWDG timeout.

Warning:

When writing to the WWDG_CR register, always write 1 in the
T6 bit to avoid generating an immediate reset.

Figure 301. Window watchdog timing diagram

CNT DownCounter
Refresh not allowed

Refresh allowed

T[6:0]

W[6:0]

0x3F

Time
Tpclk x 4096 x 2

WDGTB

0x41
0x40
0x3F

wwdg_ewit
EWIF = 0
wwdg_rst

T6 bit
MS47266V1

The formula to calculate the timeout value is given by:
WDGTB[1:0]
t WWDG = t PCLK × 4096 × 2
× ( T [ 5:0 ] + 1 )

904/1709

RM0385 Rev 7

( ms )

RM0385

System window watchdog (WWDG)

where:
tWWDG: WWDG timeout
tPCLK: APB clock period measured in ms
4096: value corresponding to internal divider
As an example, lets assume APB frequency is equal to 48 MHz, WDGTB1:0] is set to 3 and
T[5:0] is set to 63:
3
t WWDG = ( 1 ⁄ 48000 ) × 4096 × 2 × ( 63 + 1 ) = 43.69ms
Refer to the datasheet for the minimum and maximum values of the tWWDG.

28.3.5

Debug mode
When the microcontroller enters debug mode (processor halted), the WWDG counter either
continues to work normally or stops, depending on the configuration bit in DBG module. For
more details refer to Section 40.16.2: Debug support for timers, watchdog, bxCAN and I2C.

RM0385 Rev 7

905/1709
908

System window watchdog (WWDG)

28.4

RM0385

WWDG registers
Refer to Section 1.1 on page 62 for a list of abbreviations used in register descriptions.
The peripheral registers can be accessed by half-words (16-bit) or words (32-bit).

28.4.1

Control register (WWDG_CR)
Address offset: 0x000
Reset value: 0x0000 007F

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

6

5

4

3

2

1

0

rw

rw

rw

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WDGA

T[6:0]

rs

rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 WDGA: Activation bit
This bit is set by software and only cleared by hardware after a reset. When WDGA = 1, the
watchdog can generate a reset.
0: Watchdog disabled
1: Watchdog enabled
Bits 6:0 T[6:0]: 7-bit counter (MSB to LSB)
These bits contain the value of the watchdog counter, decremented every
(4096 x 2WDGTB1:0]) PCLK cycles. A reset is produced when it is decremented from 0x40 to
0x3F (T6 becomes cleared).

28.4.2

Configuration register (WWDG_CFR)
Address offset: 0x004
Reset value: 0x0000 007F

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

3

2

1

0

rw

rw

rw

15

14

13

12

11

10

9

Res.

Res.

Res.

Res.

Res.

Res.

EWI
rs

WDGTB[1:0]
rw

rw

W[6:0]
rw

rw

rw

rw

Bits 31:10 Reserved, must be kept at reset value.
Bit 9 EWI: Early wakeup interrupt
When set, an interrupt occurs whenever the counter reaches the value 0x40. This interrupt is
only cleared by hardware after a reset.

906/1709

RM0385 Rev 7

RM0385

System window watchdog (WWDG)

Bits 8:7 WDGTB[1:0]: Timer base
The time base of the prescaler can be modified as follows:
00: CK Counter Clock (PCLK div 4096) div 1
01: CK Counter Clock (PCLK div 4096) div 2
10: CK Counter Clock (PCLK div 4096) div 4
11: CK Counter Clock (PCLK div 4096) div 8
Bits 6:0 W[6:0]: 7-bit window value
These bits contain the window value to be compared with the downcounter.

28.4.3

Status register (WWDG_SR)
Address offset: 0x008
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EWIF
rc_w0

Bits 31:1 Reserved, must be kept at reset value.
Bit 0 EWIF: Early wakeup interrupt flag
This bit is set by hardware when the counter has reached the value 0x40. It must be cleared by
software by writing ‘0’. Writing ‘1’ has no effect. This bit is also set if the interrupt is not enabled.

RM0385 Rev 7

907/1709
908

System window watchdog (WWDG)

28.4.4

RM0385

WWDG register map
The following table gives the WWDG register map and reset values.

0

1

1

1

1

1

Res.

Res.

Res.

Res.

1

1

W[6:0]

Reset value

0

Refer to Section 2.2.2: Memory map and register boundary addresses for the register
boundary addresses.

908/1709

1

Res.

0

1

EWIF

Res.

0

Res.

1

WDGTB0

1

Res.

1

WDGTB1

1

Res.

1

EWI

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WWDG_SR

Res.

0x008

Res.

Reset value

T[6:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WWDG_CFR

Res.

0x004

0
Res.

Reset value

WDGA

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WWDG_CR

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

0x000

Register

Res.

Offset

Res.

Table 166. WWDG register map and reset values

RM0385 Rev 7

RM0385

Real-time clock (RTC)

29

Real-time clock (RTC)

29.1

Introduction
The RTC provides an automatic wakeup to manage all low-power modes.
The real-time clock (RTC) is an independent BCD timer/counter. The RTC provides a timeof-day clock/calendar with programmable alarm interrupts.
The RTC includes also a periodic programmable wakeup flag with interrupt capability.
Two 32-bit registers contain the seconds, minutes, hours (12- or 24-hour format), day (day
of week), date (day of month), month, and year, expressed in binary coded decimal format
(BCD). The sub-seconds value is also available in binary format.
Compensations for 28-, 29- (leap year), 30-, and 31-day months are performed
automatically. Daylight saving time compensation can also be performed.
Additional 32-bit registers contain the programmable alarm subseconds, seconds, minutes,
hours, day, and date.
A digital calibration feature is available to compensate for any deviation in crystal oscillator
accuracy.
After Backup domain reset, all RTC registers are protected against possible parasitic write
accesses.
As long as the supply voltage remains in the operating range, the RTC never stops,
regardless of the device status (Run mode, low-power mode or under reset).

RM0385 Rev 7

909/1709
953

Real-time clock (RTC)

29.2

RM0385

RTC main features
The RTC unit main features are the following (see Figure 302: RTC block diagram):
•

Calendar with subseconds, seconds, minutes, hours (12 or 24 format), day (day of
week), date (day of month), month, and year.

•

Daylight saving compensation programmable by software.

•

Programmable alarm with interrupt function. The alarm can be triggered by any
combination of the calendar fields.

•

Automatic wakeup unit generating a periodic flag that triggers an automatic wakeup
interrupt.

•

Reference clock detection: a more precise second source clock (50 or 60 Hz) can be
used to enhance the calendar precision.

•

Accurate synchronization with an external clock using the subsecond shift feature.

•

Digital calibration circuit (periodic counter correction): 0.95 ppm accuracy, obtained in a
calibration window of several seconds

•

Time-stamp function for event saving

•

Tamper detection event with configurable filter and internal pull-up

•

Maskable interrupts/events:

•

910/1709

–

Alarm A

–

Alarm B

–

Wakeup interrupt

–

Time-stamp

–

Tamper detection

32 backup registers.

RM0385 Rev 7

RM0385

Real-time clock (RTC)

29.3

RTC functional description

29.3.1

RTC block diagram
Figure 302. RTC block diagram

RTC_TAMP3

Backup registers
and RTC tamper
control register

RTC_TAMP2
RTC_TAMP1

TAMPxF

Time stamp
registers

RTC_TS
RTC_REFIN

TSF

LSE (32.768 Hz)
Divided HSE
RTCCLK

LSI

RTC_CALR
Smooth
calibration

RTC_PRER
Asynchronous
7-bit prescaler
(default = 128)

ck_apre
(default 256 Hz

RTC_PRER
Synchronous
15-bit prescaler
(default = 256)

ck_spre
(default 1 Hz)
Calendar
Shadow registers
RTC_TR,
RTC_DR

Shadow register
RTC_SSR
WUCKSEL[1:0]
Prescaler
2, 4, 8, 16

RTC_CALIB
RTC_ALARM

Output
control

RTC_OUT

RTC_WUTR
WUTF

16-bit wakeup
auto reload timer
OSEL[1:0]
Alarm A
RTC_ALRMAR
RTC_ALRMASSR

=

ALRAF

Alarm B
RTC_ALRMBR
RTC_ALRMBSSR

=

ALRBF

MSv48341V1

RM0385 Rev 7

911/1709
953

Real-time clock (RTC)

RM0385

The RTC includes:
•

Two alarms

•

Three tamper events from I/Os
–

One timestamp event from I/O

•

Tamper event detection can generate a timestamp event

•

Timestamp can be generated when a switch to VBAT occurs

•

32 x 32-bit backup registers
–

•

•

29.3.2

Tamper detection erases the backup registers.

•

The backup registers (RTC_BKPxR) are implemented in the RTC domain that
remains powered-on by VBAT when the VDD power is switched off.

Output functions: RTC_OUT which selects one of the following two outputs:
–

RTC_CALIB: 512 Hz or 1Hz clock output (with an LSE frequency of 32.768 kHz).
This output is enabled by setting the COE bit in the RTC_CR register.

–

RTC_ALARM: This output is enabled by configuring the OSEL[1:0] bits in the
RTC_CR register which select the Alarm A, Alarm B or Wakeup outputs.

Input functions:
–

RTC_TS: timestamp event

–

RTC_TAMP1: tamper1 event detection

–

RTC_TAMP2: tamper2 event detection

–

RTC_TAMP3: tamper3 event detection

–

RTC_REFIN: 50 or 60 Hz reference clock input

GPIOs controlled by the RTC
RTC_OUT, RTC_TS and RTC_TAMP1 are mapped on the same pin (PC13). PC13 pin
configuration is controlled by the RTC, whatever the PC13 GPIO configuration, except for
the RTC_ALARM output open-drain mode. The RTC functions mapped on PC13 are
available in all low-power modes and in VBAT mode.
The output mechanism follows the priority order shown in Table 167.
Table 167. RTC pin PC13 configuration(1)

OSEL[1:0]
bits
PC13 Pin
configuration (RTC_ALARM
and function
output
enable)

TSE bit

COE bit
(RTC_CALIB
output
enable)

RTC_ALARM
_TYPE
bit

TAMP1E bit
(RTC_TAMP1
input
enable)

(RTC_TS
input
enable)

TSINSEL bits

RTC_ALARM
output OD

01 or 10 or 11

Don’t care

0

Don’t care

Don’t care

Don’t care

RTC_ALARM
output PP

01 or 10 or 11

Don’t care

1

Don’t care

Don’t care

Don’t care

RTC_CALIB
output PP

00

1

Don’t care

Don’t care

Don’t care

Don’t care

912/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)
Table 167. RTC pin PC13 configuration(1) (continued)

OSEL[1:0]
bits
PC13 Pin
configuration (RTC_ALARM
and function
output
enable)
RTC_TAMP1
input floating

RTC_TS and
RTC_TAMP1
input floating

RTC_TS input
floating
Wakeup pin or
Standard
GPIO

COE bit
(RTC_CALIB
output
enable)

00

0

00

1

01 or 10 or 11

0

00

0

00

1

01 or 10 or 11

0

00

0

00

1

01 or 10 or 11

0

00

0

TSE bit

RTC_ALARM
_TYPE
bit

TAMP1E bit
(RTC_TAMP1
input
enable)

(RTC_TS
input
enable)

TSINSEL bits

Don’t care

1

0

Don’t care

Don’t care

1

1

00

Don’t care

0

1

00

Don’t care

0

0

Don’t care

1. OD: open drain; PP: push-pull.

RTC_TAMP2 and RTC_TS are mapped on the same pin (PI8). PI8 configuration is
controlled by the RTC, whatever the PI8 GPIO configuration. The RTC functions mapped on
PI8 are available in all low-power modes and in VBAT mode.
The output mechanism follows the priority order shown in Table 168.
Table 168. RTC pin PI8 configuration
TAMP2E bit
(RTC_TAMP2
input enable)

TSE bit

TSINSEL bit

(RTC_TS
input enable)

(Timestamp
pin selection)

RTC_TAMP2 input
floating

1

0

Don’t care

RTC_TS and
RTC_TAMP2 input
floating

1

1

01

RTC_TS input floating

0

1

01

Wakeup pin or Standard GPIO

0

0

Don’t care

PI8 pin configuration
and function

RTC_TAMP3 and RTC_TS are mapped on the same pin (PC1). PC1 configuration is
controlled by the RTC, whatever the PC1 GPIO configuration. The RTC functions mapped
on PC1 are available in all low-power modes, but are not available in VBAT mode.

RM0385 Rev 7

913/1709
953

Real-time clock (RTC)

RM0385
Table 169. RTC pin PC2 configuration
TAMP2E bit
(RTC_TAMP3
input enable)

TSE bit

TSINSEL bit

(RTC_TS
input enable)

(Timestamp
pin selection)

RTC_TAMP3 input
floating

1

0

Don’t care

RTC_TS and
RTC_TAMP3 input
floating

1

1

10 or 11

RTC_TS input floating

0

1

01

Wakeup pin or Standard GPIO

0

0

Don’t care

PC2 pin configuration and function

RTC_REFIN is mapped on PB15. PB15 must be configured in alternate function mode to
allow RTC_REFIN function. RTC_REFIN is not available in VBAT and in Standby mode.
The table below summarizes the RTC pins and functions capabilities in all modes.
Table 170. RTC functions over modes
Pin

29.3.3

RTC functions

Functional in all lowpower modes except
Standby modes

Functional in Standby
mode

Functional in
VBAT mode

PC13

RTC_TAMP1
RTC_TS
RTC_OUT

YES

YES

YES

PI8

RTC_TAMP2
RTC_TS

YES

YES

YES

PC1

RTC_TAMP3
RTC_TS

YES

YES

NO

PB15

RTC_REFIN

YES

NO

NO

Clock and prescalers
The RTC clock source (RTCCLK) is selected through the clock controller among the LSE
clock, the LSI oscillator clock, and the HSE clock. For more information on the RTC clock
source configuration, refer to Section 5: Reset and clock control (RCC).
A programmable prescaler stage generates a 1 Hz clock which is used to update the
calendar. To minimize power consumption, the prescaler is split into 2 programmable
prescalers (see Figure 302: RTC block diagram):

Note:

914/1709

•

A 7-bit asynchronous prescaler configured through the PREDIV_A bits of the
RTC_PRER register.

•

A 15-bit synchronous prescaler configured through the PREDIV_S bits of the
RTC_PRER register.

When both prescalers are used, it is recommended to configure the asynchronous prescaler
to a high value to minimize consumption.

RM0385 Rev 7

RM0385

Real-time clock (RTC)
The asynchronous prescaler division factor is set to 128, and the synchronous division
factor to 256, to obtain an internal clock frequency of 1 Hz (ck_spre) with an LSE frequency
of 32.768 kHz.
The minimum division factor is 1 and the maximum division factor is 222.
This corresponds to a maximum input frequency of around 4 MHz.
fck_apre is given by the following formula:
f RTCCLK
f CK_APRE = --------------------------------------PREDIV_A + 1

The ck_apre clock is used to clock the binary RTC_SSR subseconds downcounter. When it
reaches 0, RTC_SSR is reloaded with the content of PREDIV_S.
fck_spre is given by the following formula:
f RTCCLK
f CK_SPRE = ----------------------------------------------------------------------------------------------( PREDIV_S + 1 ) × ( PREDIV_A + 1 )

The ck_spre clock can be used either to update the calendar or as timebase for the 16-bit
wakeup auto-reload timer. To obtain short timeout periods, the 16-bit wakeup auto-reload
timer can also run with the RTCCLK divided by the programmable 4-bit asynchronous
prescaler (see Section 29.3.6: Periodic auto-wakeup for details).

29.3.4

Real-time clock and calendar
The RTC calendar time and date registers are accessed through shadow registers which
are synchronized with PCLK (APB clock). They can also be accessed directly in order to
avoid waiting for the synchronization duration.
•

RTC_SSR for the subseconds

•

RTC_TR for the time

•

RTC_DR for the date

Every two RTCCLK periods, the current calendar value is copied into the shadow registers,
and the RSF bit of RTC_ISR register is set (see Section 29.6.4: RTC initialization and status
register (RTC_ISR)). The copy is not performed in Stop and Standby mode. When exiting
these modes, the shadow registers are updated after up to 2 RTCCLK periods.
When the application reads the calendar registers, it accesses the content of the shadow
registers. It is possible to make a direct access to the calendar registers by setting the
BYPSHAD control bit in the RTC_CR register. By default, this bit is cleared, and the user
accesses the shadow registers.
When reading the RTC_SSR, RTC_TR or RTC_DR registers in BYPSHAD=0 mode, the
frequency of the APB clock (fAPB) must be at least 7 times the frequency of the RTC clock
(fRTCCLK).
The shadow registers are reset by system reset.

29.3.5

Programmable alarms
The RTC unit provides programmable alarm: Alarm A and Alarm B. The description below is
given for Alarm A, but can be translated in the same way for Alarm B.

RM0385 Rev 7

915/1709
953

Real-time clock (RTC)

RM0385

The programmable alarm function is enabled through the ALRAE bit in the RTC_CR
register. The ALRAF is set to 1 if the calendar subseconds, seconds, minutes, hours, date
or day match the values programmed in the alarm registers RTC_ALRMASSR and
RTC_ALRMAR. Each calendar field can be independently selected through the MSKx bits
of the RTC_ALRMAR register, and through the MASKSSx bits of the RTC_ALRMASSR
register. The alarm interrupt is enabled through the ALRAIE bit in the RTC_CR register.
Caution:

If the seconds field is selected (MSK1 bit reset in RTC_ALRMAR), the synchronous
prescaler division factor set in the RTC_PRER register must be at least 3 to ensure correct
behavior.
Alarm A and Alarm B (if enabled by bits OSEL[1:0] in RTC_CR register) can be routed to the
RTC_ALARM output. RTC_ALARM output polarity can be configured through bit POL the
RTC_CR register.

29.3.6

Periodic auto-wakeup
The periodic wakeup flag is generated by a 16-bit programmable auto-reload down-counter.
The wakeup timer range can be extended to 17 bits.
The wakeup function is enabled through the WUTE bit in the RTC_CR register.
The wakeup timer clock input can be:
•

RTC clock (RTCCLK) divided by 2, 4, 8, or 16.
When RTCCLK is LSE(32.768kHz), this allows to configure the wakeup interrupt period
from 122 µs to 32 s, with a resolution down to 61 µs.

•

ck_spre (usually 1 Hz internal clock)
When ck_spre frequency is 1Hz, this allows to achieve a wakeup time from 1 s to
around 36 hours with one-second resolution. This large programmable time range is
divided in 2 parts:
–

from 1s to 18 hours when WUCKSEL [2:1] = 10

–

and from around 18h to 36h when WUCKSEL[2:1] = 11. In this last case 216 is
added to the 16-bit counter current value.When the initialization sequence is
complete (see Programming the wakeup timer on page 918), the timer starts
counting down.When the wakeup function is enabled, the down-counting remains
active in low-power modes. In addition, when it reaches 0, the WUTF flag is set in
the RTC_ISR register, and the wakeup counter is automatically reloaded with its
reload value (RTC_WUTR register value).

The WUTF flag must then be cleared by software.
When the periodic wakeup interrupt is enabled by setting the WUTIE bit in the RTC_CR
register, it can exit the device from low-power modes.
The periodic wakeup flag can be routed to the RTC_ALARM output provided it has been
enabled through bits OSEL[1:0] of RTC_CR register. RTC_ALARM output polarity can be
configured through the POL bit in the RTC_CR register.
System reset, as well as low-power modes (Sleep, Stop and Standby) have no influence on
the wakeup timer.

916/1709

RM0385 Rev 7

RM0385

29.3.7

Real-time clock (RTC)

RTC initialization and configuration
RTC register access
The RTC registers are 32-bit registers. The APB interface introduces 2 wait-states in RTC
register accesses except on read accesses to calendar shadow registers when
BYPSHAD=0.

RTC register write protection
After system reset, the RTC registers are protected against parasitic write access by
clearing the DBP bit in the PWR_CR1 register (refer to the power control section). DBP bit
must be set in order to enable RTC registers write access.
After Backup domain reset, all the RTC registers are write-protected. Writing to the RTC
registers is enabled by writing a key into the Write Protection register, RTC_WPR.
The following steps are required to unlock the write protection on all the RTC registers
except for RTC_TAMPCR, RTC_BKPxR, RTC_OR and RTC_ISR[13:8].
1.

Write ‘0xCA’ into the RTC_WPR register.

2.

Write ‘0x53’ into the RTC_WPR register.

Writing a wrong key reactivates the write protection.
The protection mechanism is not affected by system reset.

Calendar initialization and configuration
To program the initial time and date calendar values, including the time format and the
prescaler configuration, the following sequence is required:
1.

Set INIT bit to 1 in the RTC_ISR register to enter initialization mode. In this mode, the
calendar counter is stopped and its value can be updated.

2.

Poll INITF bit of in the RTC_ISR register. The initialization phase mode is entered when
INITF is set to 1. It takes around 2 RTCCLK clock cycles (due to clock synchronization).

3.

To generate a 1 Hz clock for the calendar counter, program both the prescaler factors in
RTC_PRER register.

4.

Load the initial time and date values in the shadow registers (RTC_TR and RTC_DR),
and configure the time format (12 or 24 hours) through the FMT bit in the RTC_CR
register.

5.

Exit the initialization mode by clearing the INIT bit. The actual calendar counter value is
then automatically loaded and the counting restarts after 4 RTCCLK clock cycles.

When the initialization sequence is complete, the calendar starts counting.
Note:

After a system reset, the application can read the INITS flag in the RTC_ISR register to
check if the calendar has been initialized or not. If this flag equals 0, the calendar has not
been initialized since the year field is set at its Backup domain reset default value (0x00).
To read the calendar after initialization, the software must first check that the RSF flag is set
in the RTC_ISR register.

RM0385 Rev 7

917/1709
953

Real-time clock (RTC)

RM0385

Daylight saving time
The daylight saving time management is performed through bits SUB1H, ADD1H, and BKP
of the RTC_CR register.
Using SUB1H or ADD1H, the software can subtract or add one hour to the calendar in one
single operation without going through the initialization procedure.
In addition, the software can use the BKP bit to memorize this operation.

Programming the alarm
A similar procedure must be followed to program or update the programmable alarms. The
procedure below is given for Alarm A but can be translated in the same way for Alarm B.

Note:

1.

Clear ALRAE in RTC_CR to disable Alarm A.

2.

Program the Alarm A registers (RTC_ALRMASSR/RTC_ALRMAR).

3.

Set ALRAE in the RTC_CR register to enable Alarm A again.

Each change of the RTC_CR register is taken into account after around 2 RTCCLK clock
cycles due to clock synchronization.

Programming the wakeup timer
The following sequence is required to configure or change the wakeup timer auto-reload
value (WUT[15:0] in RTC_WUTR):

29.3.8

1.

Clear WUTE in RTC_CR to disable the wakeup timer.

2.

Poll WUTWF until it is set in RTC_ISR to make sure the access to wakeup auto-reload
counter and to WUCKSEL[2:0] bits is allowed. It takes around 2 RTCCLK clock cycles
(due to clock synchronization).

3.

Program the wakeup auto-reload value WUT[15:0], and the wakeup clock selection
(WUCKSEL[2:0] bits in RTC_CR). Set WUTE in RTC_CR to enable the timer again.
The wakeup timer restarts down-counting. The WUTWF bit is cleared up to 2 RTCCLK
clock cycles after WUTE is cleared, due to clock synchronization.

Reading the calendar
When BYPSHAD control bit is cleared in the RTC_CR register
To read the RTC calendar registers (RTC_SSR, RTC_TR and RTC_DR) properly, the APB
clock frequency (fPCLK) must be equal to or greater than seven times the RTC clock
frequency (fRTCCLK). This ensures a secure behavior of the synchronization mechanism.
If the APB clock frequency is less than seven times the RTC clock frequency, the software
must read the calendar time and date registers twice. If the second read of the RTC_TR
gives the same result as the first read, this ensures that the data is correct. Otherwise a third
read access must be done. In any case the APB clock frequency must never be lower than
the RTC clock frequency.
The RSF bit is set in RTC_ISR register each time the calendar registers are copied into the
RTC_SSR, RTC_TR and RTC_DR shadow registers. The copy is performed every two
RTCCLK cycles. To ensure consistency between the 3 values, reading either RTC_SSR or
RTC_TR locks the values in the higher-order calendar shadow registers until RTC_DR is
read. In case the software makes read accesses to the calendar in a time interval smaller
than 2 RTCCLK periods: RSF must be cleared by software after the first calendar read, and

918/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)
then the software must wait until RSF is set before reading again the RTC_SSR, RTC_TR
and RTC_DR registers.
After waking up from low-power mode (Stop or Standby), RSF must be cleared by software.
The software must then wait until it is set again before reading the RTC_SSR, RTC_TR and
RTC_DR registers.
The RSF bit must be cleared after wakeup and not before entering low-power mode.
After a system reset, the software must wait until RSF is set before reading the RTC_SSR,
RTC_TR and RTC_DR registers. Indeed, a system reset resets the shadow registers to
their default values.
After an initialization (refer to Calendar initialization and configuration on page 917): the
software must wait until RSF is set before reading the RTC_SSR, RTC_TR and RTC_DR
registers.
After synchronization (refer to Section 29.3.10: RTC synchronization): the software must
wait until RSF is set before reading the RTC_SSR, RTC_TR and RTC_DR registers.

When the BYPSHAD control bit is set in the RTC_CR register (bypass shadow
registers)
Reading the calendar registers gives the values from the calendar counters directly, thus
eliminating the need to wait for the RSF bit to be set. This is especially useful after exiting
from low-power modes (STOP or Standby), since the shadow registers are not updated
during these modes.
When the BYPSHAD bit is set to 1, the results of the different registers might not be
coherent with each other if an RTCCLK edge occurs between two read accesses to the
registers. Additionally, the value of one of the registers may be incorrect if an RTCCLK edge
occurs during the read operation. The software must read all the registers twice, and then
compare the results to confirm that the data is coherent and correct. Alternatively, the
software can just compare the two results of the least-significant calendar register.
Note:

While BYPSHAD=1, instructions which read the calendar registers require one extra APB
cycle to complete.

29.3.9

Resetting the RTC
The calendar shadow registers (RTC_SSR, RTC_TR and RTC_DR) and some bits of the
RTC status register (RTC_ISR) are reset to their default values by all available system reset
sources.
On the contrary, the following registers are reset to their default values by a Backup domain
reset and are not affected by a system reset: the RTC current calendar registers, the RTC
control register (RTC_CR), the prescaler register (RTC_PRER), the RTC calibration register
(RTC_CALR), the RTC shift register (RTC_SHIFTR), the RTC timestamp registers
(RTC_TSSSR, RTC_TSTR and RTC_TSDR), the RTC tamper configuration register
(RTC_TAMPCR), the RTC backup registers (RTC_BKPxR), the wakeup timer register
(RTC_WUTR), the Alarm A and Alarm B registers (RTC_ALRMASSR/RTC_ALRMAR and
RTC_ALRMBSSR/RTC_ALRMBR), and the Option register (RTC_OR).
In addition, when it is clocked by the LSE, the RTC keeps on running under system reset if
the reset source is different from the Backup domain reset one (refer to the RTC clock
section of the Reset and clock controller for details on the list of RTC clock sources not
RM0385 Rev 7

919/1709
953

Real-time clock (RTC)

RM0385

affected by system reset). When a Backup domain reset occurs, the RTC is stopped and all
the RTC registers are set to their reset values.

29.3.10

RTC synchronization
The RTC can be synchronized to a remote clock with a high degree of precision. After
reading the sub-second field (RTC_SSR or RTC_TSSSR), a calculation can be made of the
precise offset between the times being maintained by the remote clock and the RTC. The
RTC can then be adjusted to eliminate this offset by “shifting” its clock by a fraction of a
second using RTC_SHIFTR.
RTC_SSR contains the value of the synchronous prescaler counter. This allows one to
calculate the exact time being maintained by the RTC down to a resolution of
1 / (PREDIV_S + 1) seconds. As a consequence, the resolution can be improved by
increasing the synchronous prescaler value (PREDIV_S[14:0]. The maximum resolution
allowed (30.52 μs with a 32768 Hz clock) is obtained with PREDIV_S set to 0x7FFF.
However, increasing PREDIV_S means that PREDIV_A must be decreased in order to
maintain the synchronous prescaler output at 1 Hz. In this way, the frequency of the
asynchronous prescaler output increases, which may increase the RTC dynamic
consumption.
The RTC can be finely adjusted using the RTC shift control register (RTC_SHIFTR). Writing
to RTC_SHIFTR can shift (either delay or advance) the clock by up to a second with a
resolution of 1 / (PREDIV_S + 1) seconds. The shift operation consists of adding the
SUBFS[14:0] value to the synchronous prescaler counter SS[15:0]: this will delay the clock.
If at the same time the ADD1S bit is set, this results in adding one second and at the same
time subtracting a fraction of second, so this will advance the clock.

Caution:

Before initiating a shift operation, the user must check that SS[15] = 0 in order to ensure that
no overflow will occur.
As soon as a shift operation is initiated by a write to the RTC_SHIFTR register, the SHPF
flag is set by hardware to indicate that a shift operation is pending. This bit is cleared by
hardware as soon as the shift operation has completed.

Caution:

This synchronization feature is not compatible with the reference clock detection feature:
firmware must not write to RTC_SHIFTR when REFCKON=1.

29.3.11

RTC reference clock detection
The update of the RTC calendar can be synchronized to a reference clock, RTC_REFIN,
which is usually the mains frequency (50 or 60 Hz). The precision of the RTC_REFIN
reference clock should be higher than the 32.768 kHz LSE clock. When the RTC_REFIN
detection is enabled (REFCKON bit of RTC_CR set to 1), the calendar is still clocked by the
LSE, and RTC_REFIN is used to compensate for the imprecision of the calendar update
frequency (1 Hz).
Each 1 Hz clock edge is compared to the nearest RTC_REFIN clock edge (if one is found
within a given time window). In most cases, the two clock edges are properly aligned. When
the 1 Hz clock becomes misaligned due to the imprecision of the LSE clock, the RTC shifts
the 1 Hz clock a bit so that future 1 Hz clock edges are aligned. Thanks to this mechanism,
the calendar becomes as precise as the reference clock.
The RTC detects if the reference clock source is present by using the 256 Hz clock
(ck_apre) generated from the 32.768 kHz quartz. The detection is performed during a time

920/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)
window around each of the calendar updates (every 1 s). The window equals 7 ck_apre
periods when detecting the first reference clock edge. A smaller window of 3 ck_apre
periods is used for subsequent calendar updates.
Each time the reference clock is detected in the window, the synchronous prescaler which
outputs the ck_spre clock is forced to reload. This has no effect when the reference clock
and the 1 Hz clock are aligned because the prescaler is being reloaded at the same
moment. When the clocks are not aligned, the reload shifts future 1 Hz clock edges a little
for them to be aligned with the reference clock.
If the reference clock halts (no reference clock edge occurred during the 3 ck_apre window),
the calendar is updated continuously based solely on the LSE clock. The RTC then waits for
the reference clock using a large 7 ck_apre period detection window centered on the
ck_spre edge.
When the RTC_REFIN detection is enabled, PREDIV_A and PREDIV_S must be set to their
default values:
•

PREDIV_A = 0x007F

•

PREVID_S = 0x00FF

Note:

RTC_REFIN clock detection is not available in Standby mode.

29.3.12

RTC smooth digital calibration
The RTC frequency can be digitally calibrated with a resolution of about 0.954 ppm with a
range from -487.1 ppm to +488.5 ppm. The correction of the frequency is performed using
series of small adjustments (adding and/or subtracting individual RTCCLK pulses). These
adjustments are fairly well distributed so that the RTC is well calibrated even when observed
over short durations of time.
The smooth digital calibration is performed during a cycle of about 220 RTCCLK pulses, or
32 seconds when the input frequency is 32768 Hz. This cycle is maintained by a 20-bit
counter, cal_cnt[19:0], clocked by RTCCLK.
The smooth calibration register (RTC_CALR) specifies the number of RTCCLK clock cycles
to be masked during the 32-second cycle:
•

Setting the bit CALM[0] to 1 causes exactly one pulse to be masked during the 32-

second cycle.

Note:

•

Setting CALM[1] to 1 causes two additional cycles to be masked

•

Setting CALM[2] to 1 causes four additional cycles to be masked

•

and so on up to CALM[8] set to 1 which causes 256 clocks to be masked.

CALM[8:0] (RTC_CALR) specifies the number of RTCCLK pulses to be masked during the
32-second cycle. Setting the bit CALM[0] to ‘1’ causes exactly one pulse to be masked
during the 32-second cycle at the moment when cal_cnt[19:0] is 0x80000; CALM[1]=1
causes two other cycles to be masked (when cal_cnt is 0x40000 and 0xC0000); CALM[2]=1
causes four other cycles to be masked (cal_cnt = 0x20000/0x60000/0xA0000/ 0xE0000);
and so on up to CALM[8]=1 which causes 256 clocks to be masked (cal_cnt = 0xXX800).
While CALM allows the RTC frequency to be reduced by up to 487.1 ppm with fine
resolution, the bit CALP can be used to increase the frequency by 488.5 ppm. Setting CALP
to ‘1’ effectively inserts an extra RTCCLK pulse every 211 RTCCLK cycles, which means
that 512 clocks are added during every 32-second cycle.

RM0385 Rev 7

921/1709
953

Real-time clock (RTC)

RM0385

Using CALM together with CALP, an offset ranging from -511 to +512 RTCCLK cycles can
be added during the 32-second cycle, which translates to a calibration range of -487.1 ppm
to +488.5 ppm with a resolution of about 0.954 ppm.
The formula to calculate the effective calibrated frequency (FCAL) given the input frequency
(FRTCCLK) is as follows:
FCAL = FRTCCLK x [1 + (CALP x 512 - CALM) / (220 + CALM - CALP x 512)]

Calibration when PREDIV_A<3
The CALP bit can not be set to 1 when the asynchronous prescaler value (PREDIV_A bits in
RTC_PRER register) is less than 3. If CALP was already set to 1 and PREDIV_A bits are
set to a value less than 3, CALP is ignored and the calibration operates as if CALP was
equal to 0.
To perform a calibration with PREDIV_A less than 3, the synchronous prescaler value
(PREDIV_S) should be reduced so that each second is accelerated by 8 RTCCLK clock
cycles, which is equivalent to adding 256 clock cycles every 32 seconds. As a result,
between 255 and 256 clock pulses (corresponding to a calibration range from 243.3 to
244.1 ppm) can effectively be added during each 32-second cycle using only the CALM bits.
With a nominal RTCCLK frequency of 32768 Hz, when PREDIV_A equals 1 (division factor
of 2), PREDIV_S should be set to 16379 rather than 16383 (4 less). The only other
interesting case is when PREDIV_A equals 0, PREDIV_S should be set to 32759 rather
than 32767 (8 less).
If PREDIV_S is reduced in this way, the formula given the effective frequency of the
calibrated input clock is as follows:
FCAL = FRTCCLK x [1 + (256 - CALM) / (220 + CALM - 256)]
In this case, CALM[7:0] equals 0x100 (the midpoint of the CALM range) is the correct
setting if RTCCLK is exactly 32768.00 Hz.

Verifying the RTC calibration
RTC precision is ensured by measuring the precise frequency of RTCCLK and calculating
the correct CALM value and CALP values. An optional 1 Hz output is provided to allow
applications to measure and verify the RTC precision.
Measuring the precise frequency of the RTC over a limited interval can result in a
measurement error of up to 2 RTCCLK clock cycles over the measurement period,
depending on how the digital calibration cycle is aligned with the measurement period.
However, this measurement error can be eliminated if the measurement period is the same
length as the calibration cycle period. In this case, the only error observed is the error due to
the resolution of the digital calibration.
•

By default, the calibration cycle period is 32 seconds.

Using this mode and measuring the accuracy of the 1 Hz output over exactly 32 seconds
guarantees that the measure is within 0.477 ppm (0.5 RTCCLK cycles over 32 seconds, due
to the limitation of the calibration resolution).
•

CALW16 bit of the RTC_CALR register can be set to 1 to force a 16- second calibration
cycle period.

In this case, the RTC precision can be measured during 16 seconds with a maximum error
of 0.954 ppm (0.5 RTCCLK cycles over 16 seconds). However, since the calibration

922/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)
resolution is reduced, the long term RTC precision is also reduced to 0.954 ppm: CALM[0]
bit is stuck at 0 when CALW16 is set to 1.
•

CALW8 bit of the RTC_CALR register can be set to 1 to force a 8- second calibration
cycle period.

In this case, the RTC precision can be measured during 8 seconds with a maximum error of
1.907 ppm (0.5 RTCCLK cycles over 8s). The long term RTC precision is also reduced to
1.907 ppm: CALM[1:0] bits are stuck at 00 when CALW8 is set to 1.

Re-calibration on-the-fly
The calibration register (RTC_CALR) can be updated on-the-fly while RTC_ISR/INITF=0, by
using the follow process:

29.3.13

1.

Poll the RTC_ISR/RECALPF (re-calibration pending flag).

2.

If it is set to 0, write a new value to RTC_CALR, if necessary. RECALPF is then
automatically set to 1

3.

Within three ck_apre cycles after the write operation to RTC_CALR, the new calibration
settings take effect.

Time-stamp function
Time-stamp is enabled by setting the TSE or ITSE bits of RTC_CR register to 1.
When TSE is set:
The calendar is saved in the time-stamp registers (RTC_TSSSR, RTC_TSTR, RTC_TSDR)
when a time-stamp event is detected on the RTC_TS pin.
When ITSE is set:
The calendar is saved in the time-stamp registers (RTC_TSSSR, RTC_TSTR, RTC_TSDR)
when an internal time-stamp event is detected. The internal timestamp event is generated
by the switch to the VBAT supply.
When a time-stamp event occurs, due to internal or external event, the time-stamp flag bit
(TSF) in RTC_ISR register is set. In case the event is internal, the ITSF flag is also set in
RTC_ISR register.
By setting the TSIE bit in the RTC_CR register, an interrupt is generated when a time-stamp
event occurs.
If a new time-stamp event is detected while the time-stamp flag (TSF) is already set, the
time-stamp overflow flag (TSOVF) flag is set and the time-stamp registers (RTC_TSTR and
RTC_TSDR) maintain the results of the previous event.

Note:

TSF is set 2 ck_apre cycles after the time-stamp event occurs due to synchronization
process.
There is no delay in the setting of TSOVF. This means that if two time-stamp events are
close together, TSOVF can be seen as '1' while TSF is still '0'. As a consequence, it is
recommended to poll TSOVF only after TSF has been set.

Caution:

If a time-stamp event occurs immediately after the TSF bit is supposed to be cleared, then
both TSF and TSOVF bits are set.To avoid masking a time-stamp event occurring at the
same moment, the application must not write ‘0’ into TSF bit unless it has already read it to
‘1’.

RM0385 Rev 7

923/1709
953

Real-time clock (RTC)

RM0385

Optionally, a tamper event can cause a time-stamp to be recorded. See the description of
the TAMPTS control bit in Section 29.6.16: RTC tamper configuration register
(RTC_TAMPCR).

29.3.14

Tamper detection
The RTC_TAMPx input events can be configured either for edge detection, or for level
detection with filtering.
The tamper detection can be configured for the following purposes:
•

erase the RTC backup registers (default configuration)

•

generate an interrupt, capable to wakeup from Stop and Standby modes

•

generate a hardware trigger for the low-power timers

RTC backup registers
The backup registers (RTC_BKPxR) are not reset by system reset or when the device
wakes up from Standby mode.
The backup registers are reset when a tamper detection event occurs (see Section 29.6.20:
RTC backup registers (RTC_BKPxR) and Tamper detection initialization on page 924)
except if the TAMPxNOERASE bit is set, or if TAMPxMF is set in the RTC_TAMPCR
register.

Tamper detection initialization
Each input can be enabled by setting the corresponding TAMPxE bits to 1 in the
RTC_TAMPCR register.
Each RTC_TAMPx tamper detection input is associated with a flag TAMPxF in the RTC_ISR
register.
When TAMPxMF is cleared:
The TAMPxF flag is asserted after the tamper event on the pin, with the latency provided
below:
•

3 ck_apre cycles when TAMPFLT differs from 0x0 (Level detection with filtering)

•

3 ck_apre cycles when TAMPTS=1 (Timestamp on tamper event)

•

No latency when TAMPFLT=0x0 (Edge detection) and TAMPTS=0

A new tamper occurring on the same pin during this period and as long as TAMPxF is set
cannot be detected.
When TAMPxMF is set:
A new tamper occurring on the same pin cannot be detected during the latency described
above and 2.5 ck_rtc additional cycles.
By setting the TAMPIE bit in the RTC_TAMPCR register, an interrupt is generated when a
tamper detection event occurs (when TAMPxF is set). Setting TAMPIE is not allowed when
one or more TAMPxMF is set.
When TAMPIE is cleared, each tamper pin event interrupt can be individually enabled by
setting the corresponding TAMPxIE bit in the RTC_TAMPCR register. Setting TAMPxIE is
not allowed when the corresponding TAMPxMF is set.

924/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)

Trigger output generation on tamper event
The tamper event detection can be used as trigger input by the low-power timers.
When TAMPxMF bit in cleared in RTC_TAMPCR register, the TAMPxF flag must be cleared
by software in order to allow a new tamper detection on the same pin.
When TAMPxMF bit is set, the TAMPxF flag is masked, and kept cleared in RTC_ISR
register. This configuration allows to trig automatically the low-power timers in Stop mode,
without requiring the system wakeup to perform the TAMPxF clearing. In this case, the
backup registers are not cleared.

Timestamp on tamper event
With TAMPTS set to ‘1’, any tamper event causes a timestamp to occur. In this case, either
the TSF bit or the TSOVF bit are set in RTC_ISR, in the same manner as if a normal
timestamp event occurs. The affected tamper flag register TAMPxF is set at the same time
that TSF or TSOVF is set.

Edge detection on tamper inputs
If the TAMPFLT bits are “00”, the RTC_TAMPx pins generate tamper detection events when
either a rising edge or a falling edge is observed depending on the corresponding
TAMPxTRG bit. The internal pull-up resistors on the RTC_TAMPx inputs are deactivated
when edge detection is selected.
Caution:

When using the edge detection, it is recommended to check by software the tamper pin
level just after enabling the tamper detection (by reading the GPIO registers), and before
writing sensitive values in the backup registers, to ensure that an active edge did not occur
before enabling the tamper event detection.
When TAMPFLT="00" and TAMPxTRG = 0 (rising edge detection), a tamper event may be
detected by hardware if the tamper input is already at high level before enabling the tamper
detection.
After a tamper event has been detected and cleared, the RTC_TAMPx should be disabled
and then re-enabled (TAMPxE set to 1) before re-programming the backup registers
(RTC_BKPxR). This prevents the application from writing to the backup registers while the
RTC_TAMPx input value still indicates a tamper detection. This is equivalent to a level
detection on the RTC_TAMPx input.

Note:

Tamper detection is still active when VDD power is switched off. To avoid unwanted resetting
of the backup registers, the pin to which the RTC_TAMPx is mapped should be externally
tied to the correct level.

Level detection with filtering on RTC_TAMPx inputs
Level detection with filtering is performed by setting TAMPFLT to a non-zero value. A tamper
detection event is generated when either 2, 4, or 8 (depending on TAMPFLT) consecutive
samples are observed at the level designated by the TAMPxTRG bits.
The RTC_TAMPx inputs are precharged through the I/O internal pull-up resistance before
its state is sampled, unless disabled by setting TAMPPUDIS to 1,The duration of the
precharge is determined by the TAMPPRCH bits, allowing for larger capacitances on the
RTC_TAMPx inputs.
The trade-off between tamper detection latency and power consumption through the pull-up
can be optimized by using TAMPFREQ to determine the frequency of the sampling for level
detection.
RM0385 Rev 7

925/1709
953

Real-time clock (RTC)

RM0385

Note:

Refer to the datasheets for the electrical characteristics of the pull-up resistors.

29.3.15

Calibration clock output
When the COE bit is set to 1 in the RTC_CR register, a reference clock is provided on the
RTC_CALIB device output.
If the COSEL bit in the RTC_CR register is reset and PREDIV_A = 0x7F, the RTC_CALIB
frequency is fRTCCLK/64. This corresponds to a calibration output at 512 Hz for an RTCCLK
frequency at 32.768 kHz. The RTC_CALIB duty cycle is irregular: there is a light jitter on
falling edges. It is therefore recommended to use rising edges.
When COSEL is set and “PREDIV_S+1” is a non-zero multiple of 256 (i.e: PREDIV_S[7:0] =
0xFF), the RTC_CALIB frequency is fRTCCLK/(256 * (PREDIV_A+1)). This corresponds to a
calibration output at 1 Hz for prescaler default values (PREDIV_A = Ox7F, PREDIV_S =
0xFF), with an RTCCLK frequency at 32.768 kHz. The 1 Hz output is affected when a shift
operation is on going and may toggle during the shift operation (SHPF=1).

Note:

When the RTC_CALIB or RTC_ALARM output is selected, the RTC_OUT pin is
automatically configured as output.
When COSEL bit is cleared, the RTC_CALIB output is the output of the 6th stage of the
asynchronous prescaler.
When COSEL bit is set, the RTC_CALIB output is the output of the 8th stage of the
synchronous prescaler.

29.3.16

Alarm output
The OSEL[1:0] control bits in the RTC_CR register are used to activate the alarm output
RTC_ALARM, and to select the function which is output. These functions reflect the
contents of the corresponding flags in the RTC_ISR register.
The polarity of the output is determined by the POL control bit in RTC_CR so that the
opposite of the selected flag bit is output when POL is set to 1.

Alarm output
The RTC_ALARM pin can be configured in output open drain or output push-pull using the
control bit RTC_ALARM_TYPE in the RTC_OR register.
Note:

Once the RTC_ALARM output is enabled, it has priority over RTC_CALIB (COE bit is don't
care and must be kept cleared).
When the RTC_CALIB or RTC_ALARM output is selected, the RTC_OUT pin is
automatically configured as output.

926/1709

RM0385 Rev 7

RM0385

29.4

Real-time clock (RTC)

RTC low-power modes
Table 171. Effect of low-power modes on RTC
Mode

Description

Sleep

No effect
RTC interrupts cause the device to exit the Sleep mode.

Stop

The RTC remains active when the RTC clock source is LSE or LSI. RTC alarm, RTC
tamper event, RTC timestamp event, and RTC Wakeup cause the device to exit the Stop
mode.

The RTC remains active when the RTC clock source is LSE or LSI. RTC alarm, RTC
Standby tamper event, RTC timestamp event, and RTC Wakeup cause the device to exit the
Standby mode.

29.5

RTC interrupts
All RTC interrupts are connected to the EXTI controller. Refer to Section 11: Extended
interrupts and events controller (EXTI).
To enable the RTC Alarm interrupt, the following sequence is required:
1.

Configure and enable the EXTI line corresponding to the RTC Alarm event in interrupt
mode and select the rising edge sensitivity.

2.

Configure and enable the RTC_ALARM IRQ channel in the NVIC.

3.

Configure the RTC to generate RTC alarms.

To enable the RTC Tamper interrupt, the following sequence is required:
1.

Configure and enable the EXTI line corresponding to the RTC Tamper event in interrupt
mode and select the rising edge sensitivity.

2.

Configure and Enable the RTC_TAMP_STAMP IRQ channel in the NVIC.

3.

Configure the RTC to detect the RTC tamper event.

To enable the RTC TimeStamp interrupt, the following sequence is required:
1.

Configure and enable the EXTI line corresponding to the RTC TimeStamp event in
interrupt mode and select the rising edge sensitivity.

2.

Configure and Enable the RTC_TAMP_STAMP IRQ channel in the NVIC.

3.

Configure the RTC to detect the RTC time-stamp event.

To enable the Wakeup timer interrupt, the following sequence is required:
1.

Configure and enable the EXTI line corresponding to the Wakeup timer even in
interrupt mode and select the rising edge sensitivity.

2.

Configure and Enable the RTC_WKUP IRQ channel in the NVIC.

3.

Configure the RTC to detect the RTC Wakeup timer event.

RM0385 Rev 7

927/1709
953

Real-time clock (RTC)

RM0385
Table 172. Interrupt control bits
Interrupt event

Event flag

Enable
control
bit

Exit from
Sleep
mode

Exit from
Stop
mode

Exit from
Standby
mode

Alarm A

ALRAF

ALRAIE

yes

yes(1)

yes(1)

Alarm B

ALRBF

ALRBIE

yes

yes(1)

yes(1)

RTC_TS input (timestamp)

TSF

TSIE

yes

yes(1)

yes(1)

RTC_TAMP1 input detection

TAMP1F

TAMPIE

yes

yes(1)

yes(1)

RTC_TAMP2 input detection

TAMP2F

TAMPIE

yes

yes(1)

yes(1)

RTC_TAMP3 input detection

TAMP3F

TAMPIE

yes

yes(1)

yes(1)

Wakeup timer interrupt

WUTF

WUTIE

yes

yes(1)

yes(1)

1. Wakeup from STOP and Standby modes is possible only when the RTC clock source is LSE or LSI.

29.6

RTC registers
Refer to Section 1.1 on page 62 of the reference manual for a list of abbreviations used in
register descriptions.
The peripheral registers can be accessed by words (32-bit).

29.6.1

RTC time register (RTC_TR)
The RTC_TR is the calendar time shadow register. This register must be written in
initialization mode only. Refer to Calendar initialization and configuration on page 917 and
Reading the calendar on page 918.
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.
Address offset: 0x00
Backup domain reset value: 0x0000 0000
System reset: 0x0000 0000 when BYPSHAD = 0. Not affected when BYPSHAD = 1.

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PM
rw

15

14

Res.

13

12

11

MNT[2:0]
rw

rw

10

9

8

MNU[3:0]
rw

rw

rw

rw

7

rw

Bits 31-23 Reserved, must be kept at reset value
Bit 22 PM: AM/PM notation
0: AM or 24-hour format
1: PM
Bits 21:20 HT[1:0]: Hour tens in BCD format

928/1709

6

Res.

RM0385 Rev 7

21

20

19

18

HT[1:0]

16

HU[3:0]

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

ST[2:0]
rw

17

rw

SU[3:0]
rw

rw

rw

RM0385

Real-time clock (RTC)

Bits 19:16 HU[3:0]: Hour units in BCD format
Bit 15 Reserved, must be kept at reset value.
Bits 14:12 MNT[2:0]: Minute tens in BCD format
Bits 11:8 MNU[3:0]: Minute units in BCD format
Bit 7 Reserved, must be kept at reset value.
Bits 6:4 ST[2:0]: Second tens in BCD format
Bits 3:0 SU[3:0]: Second units in BCD format

29.6.2

RTC date register (RTC_DR)
The RTC_DR is the calendar date shadow register. This register must be written in
initialization mode only. Refer to Calendar initialization and configuration on page 917 and
Reading the calendar on page 918.
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.
Address offset: 0x04
Backup domain reset value: 0x0000 2101
System reset: 0x0000 2101 when BYPSHAD = 0. Not affected when BYPSHAD = 1.

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

WDU[2:0]
rw

rw

12

11

MT
rw

rw

10

9

rw

22

rw

rw

7

6

Res.

Res.

rw

21

20

19

18

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

YT[3:0]

8

MU[3:0]
rw

23

rw

17

16

YU[3:0]

DT[1:0]
rw

rw

DU[3:0]
rw

rw

Bits 31:24 Reserved, must be kept at reset value
Bits 23:20 YT[3:0]: Year tens in BCD format
Bits 19:16 YU[3:0]: Year units in BCD format
Bits 15:13 WDU[2:0]: Week day units
000: forbidden
001: Monday
...
111: Sunday
Bit 12 MT: Month tens in BCD format
Bits 11:8 MU: Month units in BCD format
Bits 7:6 Reserved, must be kept at reset value.
Bits 5:4 DT[1:0]: Date tens in BCD format
Bits 3:0 DU[3:0]: Date units in BCD format

RM0385 Rev 7

929/1709
953

Real-time clock (RTC)

29.6.3

RM0385

RTC control register (RTC_CR)
Address offset: 0x08
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ITSE

COE

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

TSIE

WUTIE ALRBIE ALRAIE

rw

rw

rw

rw

TSE

WUTE

rw

rw

ALRBE ALRAE
rw

Res.

rw

22

21

20

19

18

POL

COSEL

BKP

rw

rw

rw

rw

w

w

5

4

3

2

1

0

OSEL[1:0]

FMT
rw

BYPS
REFCKON TSEDGE
HAD
rw

rw

rw

17

16

SUB1H ADD1H

WUCKSEL[2:0]
rw

rw

rw

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 ITSE: timestamp on internal event enable
0: internal event timestamp disabled
1: internal event timestamp enabled
Bit 23 COE: Calibration output enable
This bit enables the RTC_CALIB output
0: Calibration output disabled
1: Calibration output enabled
Bits 22:21 OSEL[1:0]: Output selection
These bits are used to select the flag to be routed to RTC_ALARM output
00: Output disabled
01: Alarm A output enabled
10: Alarm B output enabled
11: Wakeup output enabled
Bit 20 POL: Output polarity
This bit is used to configure the polarity of RTC_ALARM output
0: The pin is high when ALRAF/ALRBF/WUTF is asserted (depending on OSEL[1:0])
1: The pin is low when ALRAF/ALRBF/WUTF is asserted (depending on OSEL[1:0]).
Bit 19 COSEL: Calibration output selection
When COE=1, this bit selects which signal is output on RTC_CALIB.
0: Calibration output is 512 Hz (with default prescaler setting)
1: Calibration output is 1 Hz (with default prescaler setting)
These frequencies are valid for RTCCLK at 32.768 kHz and prescalers at their default values
(PREDIV_A=127 and PREDIV_S=255). Refer to Section 29.3.15: Calibration clock output
Bit 18 BKP: Backup
This bit can be written by the user to memorize whether the daylight saving time change has
been performed or not.

930/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)

Bit 17 SUB1H: Subtract 1 hour (winter time change)
When this bit is set, 1 hour is subtracted to the calendar time if the current hour is not 0. This
bit is always read as 0.
Setting this bit has no effect when current hour is 0.
0: No effect
1: Subtracts 1 hour to the current time. This can be used for winter time change outside
initialization mode.
Bit 16 ADD1H: Add 1 hour (summer time change)
When this bit is set, 1 hour is added to the calendar time. This bit is always read as 0.
0: No effect
1: Adds 1 hour to the current time. This can be used for summer time change outside
initialization mode.
Bit 15 TSIE: Time-stamp interrupt enable
0: Time-stamp Interrupt disable
1: Time-stamp Interrupt enable
Bit 14 WUTIE: Wakeup timer interrupt enable
0: Wakeup timer interrupt disabled
1: Wakeup timer interrupt enabled
Bit 13 ALRBIE: Alarm B interrupt enable
0: Alarm B Interrupt disable
1: Alarm B Interrupt enable
Bit 12 ALRAIE: Alarm A interrupt enable
0: Alarm A interrupt disabled
1: Alarm A interrupt enabled
Bit 11 TSE: timestamp enable
0: timestamp disable
1: timestamp enable
Bit 10 WUTE: Wakeup timer enable
0: Wakeup timer disabled
1: Wakeup timer enabled
Note: When the wakeup timer is disabled, wait for WUTWF=1 before enabling it again.
Bit 9 ALRBE: Alarm B enable
0: Alarm B disabled
1: Alarm B enabled
Bit 8 ALRAE: Alarm A enable
0: Alarm A disabled
1: Alarm A enabled
Bit 7 Reserved, must be kept at reset value.
Bit 6 FMT: Hour format
0: 24 hour/day format
1: AM/PM hour format

RM0385 Rev 7

931/1709
953

Real-time clock (RTC)

RM0385

Bit 5 BYPSHAD: Bypass the shadow registers
0: Calendar values (when reading from RTC_SSR, RTC_TR, and RTC_DR) are taken from
the shadow registers, which are updated once every two RTCCLK cycles.
1: Calendar values (when reading from RTC_SSR, RTC_TR, and RTC_DR) are taken
directly from the calendar counters.
Note: If the frequency of the APB clock is less than seven times the frequency of RTCCLK,
BYPSHAD must be set to ‘1’.
Bit 4 REFCKON: RTC_REFIN reference clock detection enable (50 or 60 Hz)
0: RTC_REFIN detection disabled
1: RTC_REFIN detection enabled
Note: PREDIV_S must be 0x00FF.
Bit 3 TSEDGE: Time-stamp event active edge
0: RTC_TS input rising edge generates a time-stamp event
1: RTC_TS input falling edge generates a time-stamp event
TSE must be reset when TSEDGE is changed to avoid unwanted TSF setting.
Bits 2:0 WUCKSEL[2:0]: Wakeup clock selection
000: RTC/16 clock is selected
001: RTC/8 clock is selected
010: RTC/4 clock is selected
011: RTC/2 clock is selected
10x: ck_spre (usually 1 Hz) clock is selected
11x: ck_spre (usually 1 Hz) clock is selected and 216 is added to the WUT counter value
(see note below)

Note:

Bits 7, 6 and 4 of this register can be written in initialization mode only (RTC_ISR/INITF = 1).
WUT = Wakeup unit counter value. WUT = (0x0000 to 0xFFFF) + 0x10000 added when
WUCKSEL[2:1 = 11].
Bits 2 to 0 of this register can be written only when RTC_CR WUTE bit = 0 and RTC_ISR
WUTWF bit = 1.
It is recommended not to change the hour during the calendar hour increment as it could
mask the incrementation of the calendar hour.
ADD1H and SUB1H changes are effective in the next second.
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.

Caution:

932/1709

TSE must be reset when TSEDGE is changed to avoid spuriously setting of TSF.

RM0385 Rev 7

RM0385

Real-time clock (RTC)

29.6.4

RTC initialization and status register (RTC_ISR)
This register is write protected (except for RTC_ISR[13:8] bits). The write access procedure
is described in RTC register write protection on page 917.
Address offset: 0x0C
Backup domain reset value: 0x0000 0007
System reset: not affected except INIT, INITF, and RSF bits which are cleared to ‘0’

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ITSF

RECALPF

15

14

13

12

11

10

9

8

7

6

5

4

3

2

INIT

INITF

RSF

INITS

rw

r

rc_w0

r

TAMP3F TAMP2F TAMP1F TSOVF
rc_w0

rc_w0

rc_w0

rc_w0

TSF
rc_w0

WUTF ALRBF ALRAF
rc_w0

rc_w0

rc_w0

SHPF WUTWF
r

r

rc_w0

r

1

0

ALRB
WF

ALRAWF

r

r

Bits 31:18 Reserved, must be kept at reset value
Bit 17 ITSF: Internal tTime-stamp flag
This flag is set by hardware when a time-stamp on the internal event occurs.
This flag is cleared by software by writing 0, and must be cleared together with TSF bit by
writing 0 in both bits.
Bit 16 RECALPF: Recalibration pending Flag
The RECALPF status flag is automatically set to ‘1’ when software writes to the RTC_CALR
register, indicating that the RTC_CALR register is blocked. When the new calibration settings
are taken into account, this bit returns to ‘0’. Refer to Re-calibration on-the-fly.
Bit 15 TAMP3F: RTC_TAMP3 detection flag
This flag is set by hardware when a tamper detection event is detected on the RTC_TAMP3
input.
It is cleared by software writing 0
Bit 14 TAMP2F: RTC_TAMP2 detection flag
This flag is set by hardware when a tamper detection event is detected on the RTC_TAMP2
input.
It is cleared by software writing 0
Bit 13 TAMP1F: RTC_TAMP1 detection flag
This flag is set by hardware when a tamper detection event is detected on the RTC_TAMP1
input.
It is cleared by software writing 0
Bit 12 TSOVF: Time-stamp overflow flag
This flag is set by hardware when a time-stamp event occurs while TSF is already set.
This flag is cleared by software by writing 0. It is recommended to check and then clear
TSOVF only after clearing the TSF bit. Otherwise, an overflow might not be noticed if a timestamp event occurs immediately before the TSF bit is cleared.
Bit 11 TSF: Time-stamp flag
This flag is set by hardware when a time-stamp event occurs.
This flag is cleared by software by writing 0. If ITSF flag is set, TSF must be cleared together
with ITSF by writing 0 in both bits.

RM0385 Rev 7

933/1709
953

Real-time clock (RTC)

RM0385

Bit 10 WUTF: Wakeup timer flag
This flag is set by hardware when the wakeup auto-reload counter reaches 0.
This flag is cleared by software by writing 0.
This flag must be cleared by software at least 1.5 RTCCLK periods before WUTF is set to 1
again.
Bit 9 ALRBF: Alarm B flag
This flag is set by hardware when the time/date registers (RTC_TR and RTC_DR) match the
Alarm B register (RTC_ALRMBR).
This flag is cleared by software by writing 0.
Bit 8 ALRAF: Alarm A flag
This flag is set by hardware when the time/date registers (RTC_TR and RTC_DR) match the
Alarm A register (RTC_ALRMAR).
This flag is cleared by software by writing 0.
Bit 7 INIT: Initialization mode
0: Free running mode
1: Initialization mode used to program time and date register (RTC_TR and RTC_DR), and
prescaler register (RTC_PRER). Counters are stopped and start counting from the new
value when INIT is reset.
Bit 6 INITF: Initialization flag
When this bit is set to 1, the RTC is in initialization state, and the time, date and prescaler
registers can be updated.
0: Calendar registers update is not allowed
1: Calendar registers update is allowed
Bit 5 RSF: Registers synchronization flag
This bit is set by hardware each time the calendar registers are copied into the shadow
registers (RTC_SSRx, RTC_TRx and RTC_DRx). This bit is cleared by hardware in
initialization mode, while a shift operation is pending (SHPF=1), or when in bypass shadow
register mode (BYPSHAD=1). This bit can also be cleared by software.
It is cleared either by software or by hardware in initialization mode.
0: Calendar shadow registers not yet synchronized
1: Calendar shadow registers synchronized
Bit 4 INITS: Initialization status flag
This bit is set by hardware when the calendar year field is different from 0 (Backup domain
reset state).
0: Calendar has not been initialized
1: Calendar has been initialized
Bit 3 SHPF: Shift operation pending
0: No shift operation is pending
1: A shift operation is pending
This flag is set by hardware as soon as a shift operation is initiated by a write to the
RTC_SHIFTR register. It is cleared by hardware when the corresponding shift operation has
been executed. Writing to the SHPF bit has no effect.

934/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)

Bit 2 WUTWF: Wakeup timer write flag
This bit is set by hardware up to 2 RTCCLK cycles after the WUTE bit has been set to 0 in
RTC_CR, and is cleared up to 2 RTCCLK cycles after the WUTE bit has been set to 1. The
wakeup timer values can be changed when WUTE bit is cleared and WUTWF is set.
0: Wakeup timer configuration update not allowed
1: Wakeup timer configuration update allowed
Bit 1 ALRBWF: Alarm B write flag
This bit is set by hardware when Alarm B values can be changed, after the ALRBE bit has
been set to 0 in RTC_CR.
It is cleared by hardware in initialization mode.
0: Alarm B update not allowed
1: Alarm B update allowed
Bit 0 ALRAWF: Alarm A write flag
This bit is set by hardware when Alarm A values can be changed, after the ALRAE bit has
been set to 0 in RTC_CR.
It is cleared by hardware in initialization mode.
0: Alarm A update not allowed
1: Alarm A update allowed

Note:

The bits ALRAF, ALRBF, WUTF and TSF are cleared 2 APB clock cycles after programming
them to 0.

RM0385 Rev 7

935/1709
953

Real-time clock (RTC)

29.6.5

RM0385

RTC prescaler register (RTC_PRER)
This register must be written in initialization mode only. The initialization must be performed
in two separate write accesses. Refer to Calendar initialization and configuration on
page 917.
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.
Address offset: 0x10
Backup domain reset value: 0x007F 00FF
System reset: not affected

31

30

29

28

27

26

25

24

23

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

rw

rw

rw

rw

rw

rw

rw

Res.

22

21

19

18

17

16

PREDIV_A[6:0]
rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

PREDIV_S[14:0]
rw

Bits 31:23 Reserved, must be kept at reset value
Bits 22:16 PREDIV_A[6:0]: Asynchronous prescaler factor
This is the asynchronous division factor:
ck_apre frequency = RTCCLK frequency/(PREDIV_A+1)
Bit 15 Reserved, must be kept at reset value.
Bits 14:0 PREDIV_S[14:0]: Synchronous prescaler factor
This is the synchronous division factor:
ck_spre frequency = ck_apre frequency/(PREDIV_S+1)

936/1709

20

RM0385 Rev 7

RM0385

Real-time clock (RTC)

29.6.6

RTC wakeup timer register (RTC_WUTR)
This register can be written only when WUTWF is set to 1 in RTC_ISR.
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.
Address offset: 0x14
Backup domain reset value: 0x0000 FFFF
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

WUT[15:0]
rw

Bits 31:16 Reserved, must be kept at reset value
Bits 15:0 WUT[15:0]: Wakeup auto-reload value bits
When the wakeup timer is enabled (WUTE set to 1), the WUTF flag is set every (WUT[15:0]
+ 1) ck_wut cycles. The ck_wut period is selected through WUCKSEL[2:0] bits of the
RTC_CR register
When WUCKSEL[2] = 1, the wakeup timer becomes 17-bits and WUCKSEL[1] effectively
becomes WUT[16] the most-significant bit to be reloaded into the timer.
The first assertion of WUTF occurs (WUT+1) ck_wut cycles after WUTE is set. Setting
WUT[15:0] to 0x0000 with WUCKSEL[2:0] =011 (RTCCLK/2) is forbidden.

RM0385 Rev 7

937/1709
953

Real-time clock (RTC)

29.6.7

RM0385

RTC alarm A register (RTC_ALRMAR)
This register can be written only when ALRAWF is set to 1 in RTC_ISR, or in initialization
mode.
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.
Address offset: 0x1C
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

MSK4

WDSEL

29

28

27

DT[1:0]

26

25

24

DU[3:0]

23

22

MSK3

PM

21

20

19

18

HT[1:0]

17

16

HU[3:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

MSK2
rw

MNT[2:0]
rw

rw

MNU[3:0]
rw

rw

rw

rw

MSK1
rw

rw

ST[2:0]
rw

rw

Bit 31 MSK4: Alarm A date mask
0: Alarm A set if the date/day match
1: Date/day don’t care in Alarm A comparison
Bit 30 WDSEL: Week day selection
0: DU[3:0] represents the date units
1: DU[3:0] represents the week day. DT[1:0] is don’t care.
Bits 29:28 DT[1:0]: Date tens in BCD format.
Bits 27:24 DU[3:0]: Date units or day in BCD format.
Bit 23 MSK3: Alarm A hours mask
0: Alarm A set if the hours match
1: Hours don’t care in Alarm A comparison
Bit 22 PM: AM/PM notation
0: AM or 24-hour format
1: PM
Bits 21:20 HT[1:0]: Hour tens in BCD format.
Bits 19:16 HU[3:0]: Hour units in BCD format.
Bit 15 MSK2: Alarm A minutes mask
0: Alarm A set if the minutes match
1: Minutes don’t care in Alarm A comparison
Bits 14:12 MNT[2:0]: Minute tens in BCD format.
Bits 11:8 MNU[3:0]: Minute units in BCD format.
Bit 7 MSK1: Alarm A seconds mask
0: Alarm A set if the seconds match
1: Seconds don’t care in Alarm A comparison
Bits 6:4 ST[2:0]: Second tens in BCD format.
Bits 3:0 SU[3:0]: Second units in BCD format.

938/1709

RM0385 Rev 7

SU[3:0]
rw

rw

rw

RM0385

Real-time clock (RTC)

29.6.8

RTC alarm B register (RTC_ALRMBR)
This register can be written only when ALRBWF is set to 1 in RTC_ISR, or in initialization
mode.
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.
Address offset: 0x20
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

MSK4

WDSEL

29

28

27

DT[1:0]

26

25

24

DU[3:0]

23

22

MSK3

PM

21

20

19

18

HT[1:0]

17

16

HU[3:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

MSK2
rw

MNT[2:0]
rw

rw

MNU[3:0]
rw

rw

rw

rw

MSK1
rw

rw

ST[2:0]
rw

rw

SU[3:0]
rw

rw

rw

Bit 31 MSK4: Alarm B date mask
0: Alarm B set if the date and day match
1: Date and day don’t care in Alarm B comparison
Bit 30 WDSEL: Week day selection
0: DU[3:0] represents the date units
1: DU[3:0] represents the week day. DT[1:0] is don’t care.
Bits 29:28 DT[1:0]: Date tens in BCD format
Bits 27:24 DU[3:0]: Date units or day in BCD format
Bit 23 MSK3: Alarm B hours mask
0: Alarm B set if the hours match
1: Hours don’t care in Alarm B comparison
Bit 22 PM: AM/PM notation
0: AM or 24-hour format
1: PM
Bits 21:20 HT[1:0]: Hour tens in BCD format
Bits 19:16 HU[3:0]: Hour units in BCD format
Bit 15 MSK2: Alarm B minutes mask
0: Alarm B set if the minutes match
1: Minutes don’t care in Alarm B comparison
Bits 14:12 MNT[2:0]: Minute tens in BCD format
Bits 11:8 MNU[3:0]: Minute units in BCD format
Bit 7 MSK1: Alarm B seconds mask
0: Alarm B set if the seconds match
1: Seconds don’t care in Alarm B comparison
Bits 6:4 ST[2:0]: Second tens in BCD format
Bits 3:0 SU[3:0]: Second units in BCD format

RM0385 Rev 7

939/1709
953

Real-time clock (RTC)

29.6.9

RM0385

RTC write protection register (RTC_WPR)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

w

w

w

w

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

KEY
w

w

w

w

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 KEY: Write protection key
This byte is written by software.
Reading this byte always returns 0x00.
Refer to RTC register write protection for a description of how to unlock RTC register write
protection.

29.6.10

RTC sub second register (RTC_SSR)
Address offset: 0x28
Backup domain reset value: 0x0000 0000
System reset: 0x0000 0000 when BYPSHAD = 0. Not affected when BYPSHAD = 1.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

SS[15:0]
r

r

r

r

r

r

r

r

r

Bits31:16 Reserved, must be kept at reset value
Bits 15:0 SS: Sub second value
SS[15:0] is the value in the synchronous prescaler counter. The fraction of a second is given by
the formula below:
Second fraction = (PREDIV_S - SS) / (PREDIV_S + 1)
Note: SS can be larger than PREDIV_S only after a shift operation. In that case, the correct
time/date is one second less than as indicated by RTC_TR/RTC_DR.

940/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)

29.6.11

RTC shift control register (RTC_SHIFTR)
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.
Address offset: 0x2C
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ADD1S

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

w

w

w

w

w

w

w

w
15
Res.

SUBFS[14:0]
w

w

w

w

w

w

w

w

Bit 31 ADD1S: Add one second
0: No effect
1: Add one second to the clock/calendar
This bit is write only and is always read as zero. Writing to this bit has no effect when a shift
operation is pending (when SHPF=1, in RTC_ISR).
This function is intended to be used with SUBFS (see description below) in order to effectively
add a fraction of a second to the clock in an atomic operation.
Bits 30:15 Reserved, must be kept at reset value
Bits 14:0 SUBFS: Subtract a fraction of a second
These bits are write only and is always read as zero. Writing to this bit has no effect when a
shift operation is pending (when SHPF=1, in RTC_ISR).
The value which is written to SUBFS is added to the synchronous prescaler counter. Since this
counter counts down, this operation effectively subtracts from (delays) the clock by:
Delay (seconds) = SUBFS / (PREDIV_S + 1)
A fraction of a second can effectively be added to the clock (advancing the clock) when the
ADD1S function is used in conjunction with SUBFS, effectively advancing the clock by:
Advance (seconds) = (1 - (SUBFS / (PREDIV_S + 1))).
Note: Writing to SUBFS causes RSF to be cleared. Software can then wait until RSF=1 to be
sure that the shadow registers have been updated with the shifted time.

RM0385 Rev 7

941/1709
953

Real-time clock (RTC)

29.6.12

RM0385

RTC timestamp time register (RTC_TSTR)
The content of this register is valid only when TSF is set to 1 in RTC_ISR. It is cleared when
TSF bit is reset.
Address offset: 0x30
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PM
r

15

14

Res.

13

12

11

MNT[2:0]
r

r

10

9

8

MNU[3:0]
r

r

r

r

7

r

Bits 31:23 Reserved, must be kept at reset value
Bit 22 PM: AM/PM notation
0: AM or 24-hour format
1: PM
Bits 21:20 HT[1:0]: Hour tens in BCD format.
Bits 19:16 HU[3:0]: Hour units in BCD format.
Bit 15 Reserved, must be kept at reset value
Bits 14:12 MNT[2:0]: Minute tens in BCD format.
Bits 11:8 MNU[3:0]: Minute units in BCD format.
Bit 7 Reserved, must be kept at reset value
Bits 6:4 ST[2:0]: Second tens in BCD format.
Bits 3:0 SU[3:0]: Second units in BCD format.

942/1709

6

Res.

RM0385 Rev 7

21

20

19

18

HT[1:0]
r

r

r

r

5

4

3

2

ST[2:0]
r

r

17

16

HU[3:0]
r

r

1

0

r

r

SU[3:0]
r

r

r

RM0385

Real-time clock (RTC)

29.6.13

RTC timestamp date register (RTC_TSDR)
The content of this register is valid only when TSF is set to 1 in RTC_ISR. It is cleared when
TSF bit is reset.
Address offset: 0x34
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

r

r

15

WDU[1:0]
r

r

MT
r

r

MU[3:0]
r

r

r

r

DT[1:0]
r

DU[3:0]
r

r

r

Bits 31:16 Reserved, must be kept at reset value
Bits 15:13 WDU[1:0]: Week day units
Bit 12 MT: Month tens in BCD format
Bits 11:8 MU[3:0]: Month units in BCD format
Bits 7:6 Reserved, must be kept at reset value
Bits 5:4 DT[1:0]: Date tens in BCD format
Bits 3:0 DU[3:0]: Date units in BCD format

RM0385 Rev 7

943/1709
953

Real-time clock (RTC)

29.6.14

RM0385

RTC time-stamp sub second register (RTC_TSSSR)
The content of this register is valid only when RTC_ISR/TSF is set. It is cleared when the
RTC_ISR/TSF bit is reset.
Address offset: 0x38
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

SS[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 Reserved, must be kept at reset value
Bits 15:0 SS: Sub second value
SS[15:0] is the value of the synchronous prescaler counter when the timestamp event
occurred.

944/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)

29.6.15

RTC calibration register (RTC_CALR)
This register is write protected. The write access procedure is described in RTC register
write protection on page 917.
Address offset: 0x3C
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

CALP

CALW8

CALW
16

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

CALM[8:0]
rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value
Bit 15 CALP: Increase frequency of RTC by 488.5 ppm
0: No RTCCLK pulses are added.
1: One RTCCLK pulse is effectively inserted every 211 pulses (frequency increased by
488.5 ppm).
This feature is intended to be used in conjunction with CALM, which lowers the frequency of
the calendar with a fine resolution. if the input frequency is 32768 Hz, the number of RTCCLK
pulses added during a 32-second window is calculated as follows: (512 * CALP) - CALM.
Refer to Section 29.3.12: RTC smooth digital calibration.
Bit 14 CALW8: Use an 8-second calibration cycle period
When CALW8 is set to ‘1’, the 8-second calibration cycle period is selected.
Note: CALM[1:0] are stuck at “00” when CALW8=’1’. Refer to Section 29.3.12: RTC smooth
digital calibration.
Bit 13 CALW16: Use a 16-second calibration cycle period
When CALW16 is set to ‘1’, the 16-second calibration cycle period is selected.This bit must
not be set to ‘1’ if CALW8=1.
Note: CALM[0] is stuck at ‘0’ when CALW16=’1’. Refer to Section 29.3.12: RTC smooth
digital calibration.
Bits 12:9 Reserved, must be kept at reset value
Bits 8:0 CALM[8:0]: Calibration minus
The frequency of the calendar is reduced by masking CALM out of 220 RTCCLK pulses (32
seconds if the input frequency is 32768 Hz). This decreases the frequency of the calendar
with a resolution of 0.9537 ppm.
To increase the frequency of the calendar, this feature should be used in conjunction with
CALP. See Section 29.3.12: RTC smooth digital calibration on page 921.

RM0385 Rev 7

945/1709
953

Real-time clock (RTC)

29.6.16

RM0385

RTC tamper configuration register (RTC_TAMPCR)
Address offset: 0x40
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

TAMP
PUDIS
rw

TAMPPRCH
[1:0]
rw

rw

TAMPFLT[1:0]
rw

rw

24

rw

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

TAMPFREQ[2:0]
rw

23

TAMP3
TAMP2
TAMP1
TAMP3
TAMP3 TAMP2
TAMP2 TAMP1
TAMP1
NO
NO
NO
MF
IE
MF
IE
MF
IE
ERASE
ERASE
ERASE

TAMP
TS

rw

rw

TAMP3 TAMP3 TAMP2 TAMP2
TRG
E
TRG
E
rw

rw

rw

rw

TAMPI
E
rw

TAMP1 TAMP1
TRG
E
rw

rw

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 TAMP3MF: Tamper 3 mask flag
0: Tamper 3 event generates a trigger event and TAMP3F must be cleared by software to
allow next tamper event detection.
1: Tamper 3 event generates a trigger event. TAMP3F is masked and internally cleared by
hardware. The backup registers are not erased.
Note: The Tamper 3 interrupt must not be enabled when TAMP3MF is set.
Bit 23 TAMP3NOERASE: Tamper 3 no erase
0: Tamper 3 event erases the backup registers.
1: Tamper 3 event does not erase the backup registers.
Bit 22 TAMP3IE: Tamper 3 interrupt enable
0: Tamper 3 interrupt is disabled if TAMPIE = 0.
1: Tamper 3 interrupt enabled.
Bit 21 TAMP2MF: Tamper 2 mask flag
0: Tamper 2 event generates a trigger event and TAMP2F must be cleared by software to
allow next tamper event detection.
1: Tamper 2 event generates a trigger event. TAMP2F is masked and internally cleared by
hardware. The backup registers are not erased.
Note: The Tamper 2 interrupt must not be enabled when TAMP2MF is set.
Bit 20 TAMP2NOERASE: Tamper 2 no erase
0: Tamper 2 event erases the backup registers.
1: Tamper 2 event does not erase the backup registers.
Bit 19 TAMP2IE: Tamper 2 interrupt enable
0: Tamper 2 interrupt is disabled if TAMPIE = 0.
1: Tamper 2 interrupt enabled.
Bit 18 TAMP1MF: Tamper 1 mask flag
0: Tamper 1 event generates a trigger event and TAMP1F must be cleared by software to
allow next tamper event detection.
1: Tamper 1 event generates a trigger event. TAMP1F is masked and internally cleared by
hardware.The backup registers are not erased.
Note: The Tamper 1 interrupt must not be enabled when TAMP1MF is set.

946/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)

Bit 17 TAMP1NOERASE: Tamper 1 no erase
0: Tamper 1 event erases the backup registers.
1: Tamper 1 event does not erase the backup registers.
Bit 16 TAMP1IE: Tamper 1 interrupt enable
0: Tamper 1 interrupt is disabled if TAMPIE = 0.
1: Tamper 1 interrupt enabled.
Bit 15 TAMPPUDIS: RTC_TAMPx pull-up disable
This bit determines if each of the RTC_TAMPx pins are precharged before each sample.
0: Precharge RTC_TAMPx pins before sampling (enable internal pull-up)
1: Disable precharge of RTC_TAMPx pins.
Bits 14:13 TAMPPRCH[1:0]: RTC_TAMPx precharge duration
These bit determines the duration of time during which the pull-up/is activated before each
sample. TAMPPRCH is valid for each of the RTC_TAMPx inputs.
0x0: 1 RTCCLK cycle
0x1: 2 RTCCLK cycles
0x2: 4 RTCCLK cycles
0x3: 8 RTCCLK cycles
Bits 12:11 TAMPFLT[1:0]: RTC_TAMPx filter count
These bits determines the number of consecutive samples at the specified level (TAMP*TRG)
needed to activate a Tamper event. TAMPFLT is valid for each of the RTC_TAMPx inputs.
0x0: Tamper event is activated on edge of RTC_TAMPx input transitions to the active level
(no internal pull-up on RTC_TAMPx input).
0x1: Tamper event is activated after 2 consecutive samples at the active level.
0x2: Tamper event is activated after 4 consecutive samples at the active level.
0x3: Tamper event is activated after 8 consecutive samples at the active level.
Bits 10:8 TAMPFREQ[2:0]: Tamper sampling frequency
Determines the frequency at which each of the RTC_TAMPx inputs are sampled.
0x0: RTCCLK / 32768 (1 Hz when RTCCLK = 32768 Hz)
0x1: RTCCLK / 16384 (2 Hz when RTCCLK = 32768 Hz)
0x2: RTCCLK / 8192 (4 Hz when RTCCLK = 32768 Hz)
0x3: RTCCLK / 4096 (8 Hz when RTCCLK = 32768 Hz)
0x4: RTCCLK / 2048 (16 Hz when RTCCLK = 32768 Hz)
0x5: RTCCLK / 1024 (32 Hz when RTCCLK = 32768 Hz)
0x6: RTCCLK / 512 (64 Hz when RTCCLK = 32768 Hz)
0x7: RTCCLK / 256 (128 Hz when RTCCLK = 32768 Hz)
Bit 7 TAMPTS: Activate timestamp on tamper detection event
0: Tamper detection event does not cause a timestamp to be saved
1: Save timestamp on tamper detection event
TAMPTS is valid even if TSE=0 in the RTC_CR register.
Bit 6 TAMP3TRG: Active level for RTC_TAMP3 input
if TAMPFLT ≠ 00:
0: RTC_TAMP3 input staying low triggers a tamper detection event.
1: RTC_TAMP3 input staying high triggers a tamper detection event.
if TAMPFLT = 00:
0: RTC_TAMP3 input rising edge triggers a tamper detection event.
1: RTC_TAMP3 input falling edge triggers a tamper detection event.

RM0385 Rev 7

947/1709
953

Real-time clock (RTC)

RM0385

Note: The Tamper 3 falling edge detection is not allowed when switch to VBAT is used,
otherwise a detection would always occurs when entering in Vbat mode.
Bit 5 TAMP3E: RTC_TAMP3 detection enable
0: RTC_TAMP3 input detection disabled
1: RTC_TAMP3 input detection enabled
Bit 4 TAMP2TRG: Active level for RTC_TAMP2 input
if TAMPFLT != 00:
0: RTC_TAMP2 input staying low triggers a tamper detection event.
1: RTC_TAMP2 input staying high triggers a tamper detection event.
if TAMPFLT = 00:
0: RTC_TAMP2 input rising edge triggers a tamper detection event.
1: RTC_TAMP2 input falling edge triggers a tamper detection event.
Bit 3 TAMP2E: RTC_TAMP2 input detection enable
0: RTC_TAMP2 detection disabled
1: RTC_TAMP2 detection enabled
Bit 2 TAMPIE: Tamper interrupt enable
0: Tamper interrupt disabled
1: Tamper interrupt enabled.
Note: This bit enables the interrupt for all tamper pins events, whatever TAMPxIE level. If this
bit is cleared, each tamper event interrupt can be individually enabled by setting
TAMPxIE.
Bit 1 TAMP1TRG: Active level for RTC_TAMP1 input
If TAMPFLT != 00
0: RTC_TAMP1 input staying low triggers a tamper detection event.
1: RTC_TAMP1 input staying high triggers a tamper detection event.
if TAMPFLT = 00:
0: RTC_TAMP1 input rising edge triggers a tamper detection event.
1: RTC_TAMP1 input falling edge triggers a tamper detection event.
Bit 0 TAMP1E: RTC_TAMP1 input detection enable
0: RTC_TAMP1 detection disabled
1: RTC_TAMP1 detection enabled

Caution:

948/1709

When TAMPFLT = 0, TAMPxE must be reset when TAMPxTRG is changed to avoid
spuriously setting TAMPxF.

RM0385 Rev 7

RM0385

Real-time clock (RTC)

29.6.17

RTC alarm A sub second register (RTC_ALRMASSR)
This register can be written only when ALRAE is reset in RTC_CR register, or in initialization
mode.
This register is write protected. The write access procedure is described in RTC register
write protection on page 917
Address offset: 0x44
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

Res.

Res.

Res.

Res.

27

26

25

24

rw

rw

rw

rw

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

MASKSS[3:0]

Res.

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

rw

w

rw

rw

SS[14:0]
rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 MASKSS[3:0]: Mask the most-significant bits starting at this bit
0: No comparison on sub seconds for Alarm A. The alarm is set when the seconds unit is
incremented (assuming that the rest of the fields match).
1: SS[14:1] are don’t care in Alarm A comparison. Only SS[0] is compared.
2: SS[14:2] are don’t care in Alarm A comparison. Only SS[1:0] are compared.
3: SS[14:3] are don’t care in Alarm A comparison. Only SS[2:0] are compared.
...
12: SS[14:12] are don’t care in Alarm A comparison. SS[11:0] are compared.
13: SS[14:13] are don’t care in Alarm A comparison. SS[12:0] are compared.
14: SS[14] is don’t care in Alarm A comparison. SS[13:0] are compared.
15: All 15 SS bits are compared and must match to activate alarm.
The overflow bits of the synchronous counter (bits 15) is never compared. This bit can be
different from 0 only after a shift operation.
Bits23:15 Reserved, must be kept at reset value.
Bits 14:0 SS[14:0]: Sub seconds value
This value is compared with the contents of the synchronous prescaler counter to determine if
Alarm A is to be activated. Only bits 0 up MASKSS-1 are compared.

RM0385 Rev 7

949/1709
953

Real-time clock (RTC)

29.6.18

RM0385

RTC alarm B sub second register (RTC_ALRMBSSR)
This register can be written only when ALRBE is reset in RTC_CR register, or in initialization
mode.
This register is write protected.The write access procedure is described in Section : RTC
register write protection.
Address offset: 0x48
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

Res.

Res.

Res.

Res.

27

26

25

24

rw

rw

rw

rw

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

MASKSS[3:0]

Res.

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

rw

w

rw

rw

SS[14:0]
rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 MASKSS[3:0]: Mask the most-significant bits starting at this bit
0x0: No comparison on sub seconds for Alarm B. The alarm is set when the seconds unit is
incremented (assuming that the rest of the fields match).
0x1: SS[14:1] are don’t care in Alarm B comparison. Only SS[0] is compared.
0x2: SS[14:2] are don’t care in Alarm B comparison. Only SS[1:0] are compared.
0x3: SS[14:3] are don’t care in Alarm B comparison. Only SS[2:0] are compared.
...
0xC: SS[14:12] are don’t care in Alarm B comparison. SS[11:0] are compared.
0xD: SS[14:13] are don’t care in Alarm B comparison. SS[12:0] are compared.
0xE: SS[14] is don’t care in Alarm B comparison. SS[13:0] are compared.
0xF: All 15 SS bits are compared and must match to activate alarm.
The overflow bits of the synchronous counter (bits 15) is never compared. This bit can be
different from 0 only after a shift operation.
Bits 23:15

Reserved, must be kept at reset value.

Bits 14:0 SS[14:0]: Sub seconds value
This value is compared with the contents of the synchronous prescaler counter to determine
if Alarm B is to be activated. Only bits 0 up to MASKSS-1 are compared.

950/1709

RM0385 Rev 7

RM0385

Real-time clock (RTC)

29.6.19

RTC option register (RTC_OR)
Address offset: 0x4C
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

RTC_
ALARM
_TYPE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSINSEL[1:0]

rw

rw

rw

Res.

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 RTC_ALARM_TYPE: RTC_ALARM on PC13 output type
0: RTC_ALARM, when mapped on PC13, is open-drain output
1: RTC_ALARM, when mapped on PC13, is push-pull output
Bits 2:1 TSINSEL[1:0]: TIMESTAMP mapping
00: TIMESTAMP is mapped on PC13
01: TIMESTAMP is mapped on PI8
10: TIMESTAMP is mapped on PC1
11: TIMESTAMP is mapped on PC1
Bit 0 Reserved, must be kept at reset value.

29.6.20

RTC backup registers (RTC_BKPxR)
Address offset: 0x50 to 0xCC
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

BKP[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

w

rw

rw

BKP[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 BKP[31:0]
The application can write or read data to and from these registers.
They are powered-on by VBAT when VDD is switched off, so that they are not reset by
System reset, and their contents remain valid when the device operates in low-power mode.
This register is reset on a tamper detection event, as long as TAMPxF=1.

RM0385 Rev 7

951/1709
953

0x2C

952/1709

RTC_SHIFTR

Reset value

0
0

RTC_WPR
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0
0
0
0

RM0385 Rev 7
1
1
1

Res.
Res.
Res.

Res.

Reset value

0

HU[3:0]

Reset value
0

1

0

0
0

1

0

0

0
0

1

0

0

0
0

1

MNT[2:0]

0

MNT[2:0]

0

0

0

0

PREDIV_A[6:0]

0

1

0

0

0

0

1

0

0

0

0
0
0
0
0

0
0
0
0
0
0
0
0
0

0
0

1
1

MNU[3:0]

0
0

MNU[3:0]

Reset value

0

0

1

1

0

0

0

0

0

SS[15:0]

SUBFS[14:0]
0
0
0
0
0
0
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DT[1:0]

HT[1:0]

PM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
ST[2:0]

0
0

0
0

0

PREDIV_S[14:0]

WUT[15:0]

0
0
0
0
1
1
1

1
1
1
1
1
1

1
1
1
1
1
1

1

1

0

0
0

0

0

0

0

0

0
0
0

ST[2:0]

0

ST[2:0]

0

WUCKSEL[2:0]

0
ALRAWF

0
ALRBWF

0
SHPF

0
WUT WF

0
RSF

TSEDGE

0

BYPSHAD

0

Res.

0

INITS

MU[3:0]
Res.

0

INITF

MT

0

REFCKON

0

ALRAF

WDU[2:0]

0

FMT

ALRAE

0

WUTF

0

Res.

WUTE
ALRBE

0

ALRBF

0

MNU[3:0]

INIT

TSE

COSEL

ALRAIE

POL

0

TSF

1

ALRBIE

0

TSOVF

0

TAMP1F

0

TSIE

0

WUTIE

1

.TAMP2F

0

ADD1H

0

TAMP3F

0

RECALPF

0

BKP

0

SUB1H

0

ITSF

0

Res.

Res.

Res.

YU[3:0]

0

MSK1

1

Res.

Res.
OSEL[1:0]

Res.

0
MNT[2:0]

MSK2

HU[3:0]
MSK2

1

Res.

Reset value

MSK2

HT[1:0]

0
HT[1:0]

1

Res.
0

Res.

0

0
0

HU[3:0]

Res.

0

Res.

1

Res.
0

0

Res.

0

PM

COE

0

Res.

0

PM

Res.

Res.

Res.

Res.

Res.

YT[3:0]

0

Res.

0

Res.

Res.
0

0

Res.

0

MSK3

ITSE

0

Res.

Res.

Res.

0

Res.

0

0

0

Res.

0

0

MSK3

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

DU[3:0]
0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.
0

0

Res.
0

Res.

Res.

Reset value

Res.
0

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

DU[3:0]

Res.

0
0

Res.

0

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

RTC_SSR
Res.

Reset value

Res.

0x28

Res.

0
0

Res.

0
0

Res.

0
0

Res.

0
0

Res.

RTC_WUTR

Res.

0x14

DT[1:0]

Reset value

Res.

RTC_PRER

DT[1:0]

RTC_ALRMBR

Res.

0x10

Res.

RTC_ISR
Res.

0x0C

Res.

RTC_CR

Res.

0x08

Res.

RTC_DR

Res.

0x04

Res.

0

MSK4

RTC_TR

Res.

0

WDSEL

0x00

Res.

MSK4
WDSEL

Reset value

Res.

0x24
RTC_ALRMAR

Res.

0x20

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

Offset

Res.

29.6.21

Res.

0x1C

ADD1S

Real-time clock (RTC)
RM0385

RTC register map
Table 173. RTC register map and reset values

SU[3:0]
0

0

0

0

0

0

0

DU[3:0]
1

SU[3:0]
0

SU[3:0]

0
0
0

KEY

0x50
to 0xCC
0x4C
RTC_ OR

Reset value

Reset value

0

0

0

0

0

0

0

0
0

0

0
0

0

0

MASKSS
[3:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RTC_BKP0R

0

to
RTC_BKP31R

0

RM0385 Rev 7
TAMP2NOERASE
TAMP2IE
TAMP1MF
TAMP1NOERASE
TAMP1IE
TAMPPUDIS

0
0
0
0
0
0
0
0
0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0

0

0

0

0

0

Res.
Res.
Res.
Res.
Res.
Res.
WDU[1:0]

0

0

0

0

0

0

0

0

0
0

0

0

MT
0
0

0

0

0

0

0

0

0

0

0

0

0

MU[3:0]
0

0

0
0
0

0

0

0

0

0

0

0

0

SS[14:0]

SS[14:0]

0
0
0
0
0
0
0
0

0
0
0
0
0
0

0
0
0
0
0
0

0

0

0

0

0

DT[1:0]

0
Res.

0
Res.

0

TAMP1E

0

.TAMPIE

0

TAMP1TRG

0

.TAMP2E

0

TAMP3E

0

TAMP2TRG

0
Res.

0

TAMPTS

0
Res.

0

TAMP3TRG

0
Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

TAMPFREQ[2:0]

0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

TAMPFLT[1:0]

0
CALW16

Reset value
0
CALW8

Reset value

CALP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

TAMPPRCH[1:0]

TAMP3IE
TAMP2MF

TAMP3NOERASE

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

0
0
Res.

MASKSS
[3:0]

0

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
HT[1:0]

PM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MNT[2:0]

Res.

Res.
ST[2:0]

0
0

Reset value
0
0

Res.

Reset value
Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Reset value
Res.

Res.

Res.

Res.

Res.

RTC_TSTR
MNU[3:0]

TSINSEL[1:0]

RTC_
ALRMBSSR
Res.

Register
name

HU[3:0]

RTC_ALARM_TYPE

0x48
RTC_
ALRMASSR
TAMP3MF

Reset value

Res.

0x44
Res.

RTC_TAMPCR

Res.

0x40

Res.

RTC_ CALR

Res.

0x3C
Res.

RTC_TSSSR

Res.
Res.
Res.
Res.
Res.
Res.
Res.

0x38

Res.

RTC_TSDR

Res.

0x34

Res.

0x30

Res.

Offset

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

RM0385
Real-time clock (RTC)

Table 173. RTC register map and reset values (continued)

SU[3:0]

0

0
0
0

0

DU[3:0]

SS[15:0]

0
0
0
0
0
0

0
0
0
0
0
0

CALM[8:0]

0
0
0
0
0
0
0
0

BKP[31:0]

BKP[31:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

953/1709

953

Inter-integrated circuit (I2C) interface

RM0385

30

Inter-integrated circuit (I2C) interface

30.1

Introduction
The I2C (inter-integrated circuit) bus interface handles communications between the
microcontroller and the serial I2C bus. It provides multimaster capability, and controls all I2C
bus-specific sequencing, protocol, arbitration and timing. It supports Standard-mode (Sm),
Fast-mode (Fm) and Fast-mode Plus (Fm+).
It is also SMBus (system management bus) and PMBus (power management bus)
compatible.
DMA can be used to reduce CPU overload.

30.2

I2C main features
•

I2C bus specification rev03 compatibility:
–

Slave and master modes

–

Multimaster capability

–

Standard-mode (up to 100 kHz)

–

Fast-mode (up to 400 kHz)

–

Fast-mode Plus (up to 1 MHz)

–

7-bit and 10-bit addressing mode

–

Multiple 7-bit slave addresses (2 addresses, 1 with configurable mask)

–

All 7-bit addresses acknowledge mode

–

General call

–

Programmable setup and hold times

–

Easy to use event management

–

Optional clock stretching

–

Software reset

•

1-byte buffer with DMA capability

•

Programmable analog and digital noise filters

The following additional features are also available depending on the product
implementation (see Section 30.3: I2C implementation):
•

954/1709

SMBus specification rev 3.0 compatibility:
–

Hardware PEC (Packet Error Checking) generation and verification with ACK
control

–

Command and data acknowledge control

–

Address resolution protocol (ARP) support

–

Host and Device support

–

SMBus alert

–

Timeouts and idle condition detection

•

PMBus rev 1.3 standard compatibility

•

Independent clock: a choice of independent clock sources allowing the I2C
communication speed to be independent from the PCLK reprogramming
RM0385 Rev 7

RM0385

30.3

Inter-integrated circuit (I2C) interface

I2C implementation
This manual describes the full set of features implemented in I2C1, I2C2, I2C3 and I2C4.
I2C1, I2C2, I2C3 and I2C4are identical and implement the full set of features as shown in
the following table.
Table 174. STM32F75xxx and STM32F74xxx I2C implementation
I2C features(1)

I2C1

I2C2

I2C3

I2C4

7-bit addressing mode

X

X

X

X

10-bit addressing mode

X

X

X

X

Standard-mode (up to 100 kbit/s)

X

X

X

X

Fast-mode (up to 400 kbit/s)

X

X

X

X

Fast-mode Plus with 20mA output drive I/Os (up to 1
Mbit/s)

X

X

X

X

Independent clock

X

X

X

X

Wakeup from Stop mode

-

-

-

-

SMBus/PMBus

X

X

X

X

1. X = supported.

30.4

I2C functional description
In addition to receiving and transmitting data, this interface converts it from serial to parallel
format and vice versa. The interrupts are enabled or disabled by software. The interface is
connected to the I2C bus by a data pin (SDA) and by a clock pin (SCL). It can be connected
with a standard (up to 100 kHz), Fast-mode (up to 400 kHz) or Fast-mode Plus (up to
1 MHz) I2C bus.
This interface can also be connected to a SMBus with the data pin (SDA) and clock pin
(SCL).
If SMBus feature is supported: the additional optional SMBus Alert pin (SMBA) is also
available.

RM0385 Rev 7

955/1709
1020

Inter-integrated circuit (I2C) interface

30.4.1

RM0385

I2C block diagram
The block diagram of the I2C interface is shown in Figure 303.
Figure 303. I2C block diagram

I2c_ker_ck

I2CCLK

Data control
Shift register

Digital
noise
filter

Analog
noise
filter

GPIO
logic

I2C_SDA

Digital
noise
filter

Analog
noise
filter

GPIO
logic

I2C_SCL

SMBUS
PEC
generation/
check
Wakeup
on
address
match

Clock control
Master clock
generation
Slave clock
stretching
SMBus
Timeout
check

SMBus Alert
control &
status

I2c_pclk

PCLK

I2C_SMBA

Registers

APB bus
MSv46198V2

The I2C is clocked by an independent clock source which allows to the I2C to operate
independently from the PCLK frequency.
This independent clock source can be selected from the following three clock sources:
•

PCLK1: APB1 clock (default value)

•

HSI: high speed internal oscillator

•

SYSCLK: system clock

Refer to Section 5: Reset and clock control (RCC) for more details.

956/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
For I2C I/Os supporting 20 mA output current drive for Fast-mode Plus operation, the driving
capability is enabled through control bits in the system configuration controller (SYSCFG).
Refer to Section 30.3: I2C implementation.

30.4.2

I2C clock requirements
The I2C kernel is clocked by I2CCLK.
The I2CCLK period tI2CCLK must respect the following conditions:
tI2CCLK < (tLOW - tfilters) / 4 and tI2CCLK < tHIGH
with:
tLOW: SCL low time and tHIGH: SCL high time
tfilters: when enabled, sum of the delays brought by the analog filter and by the digital filter.
Analog filter delay is maximum 260 ns. Digital filter delay is DNF x tI2CCLK.
The PCLK clock period tPCLK must respect the following condition:
tPCLK < 4/3 tSCL
with tSCL: SCL period

Caution:

When the I2C kernel is clocked by PCLK, this clock must respect the conditions for tI2CCLK.

30.4.3

Mode selection
The interface can operate in one of the four following modes:
•

Slave transmitter

•

Slave receiver

•

Master transmitter

•

Master receiver

By default, it operates in slave mode. The interface automatically switches from slave to
master when it generates a START condition, and from master to slave if an arbitration loss
or a STOP generation occurs, allowing multimaster capability.

Communication flow
In Master mode, the I2C interface initiates a data transfer and generates the clock signal. A
serial data transfer always begins with a START condition and ends with a STOP condition.
Both START and STOP conditions are generated in master mode by software.
In Slave mode, the interface is capable of recognizing its own addresses (7 or 10-bit), and
the General Call address. The General Call address detection can be enabled or disabled
by software. The reserved SMBus addresses can also be enabled by software.
Data and addresses are transferred as 8-bit bytes, MSB first. The first byte(s) following the
START condition contain the address (one in 7-bit mode, two in 10-bit mode). The address
is always transmitted in Master mode.
A 9th clock pulse follows the 8 clock cycles of a byte transfer, during which the receiver must
send an acknowledge bit to the transmitter. Refer to the following figure.

RM0385 Rev 7

957/1709
1020

Inter-integrated circuit (I2C) interface

RM0385
Figure 304. I2C bus protocol

SDA
MSB

ACK

SCL
1

2

8

9

Start
condition

Stop
condition
MS19854V1

Acknowledge can be enabled or disabled by software. The I2C interface addresses can be
selected by software.

30.4.4

I2C initialization
Enabling and disabling the peripheral
The I2C peripheral clock must be configured and enabled in the clock controller (refer to
Section 5: Reset and clock control (RCC)).
Then the I2C can be enabled by setting the PE bit in the I2C_CR1 register.
When the I2C is disabled (PE=0), the I2C performs a software reset. Refer to
Section 30.4.5: Software reset for more details.

Noise filters
Before enabling the I2C peripheral by setting the PE bit in I2C_CR1 register, the user must
configure the noise filters, if needed. By default, an analog noise filter is present on the SDA
and SCL inputs. This analog filter is compliant with the I2C specification which requires the
suppression of spikes with a pulse width up to 50 ns in Fast-mode and Fast-mode Plus. The
user can disable this analog filter by setting the ANFOFF bit, and/or select a digital filter by
configuring the DNF[3:0] bit in the I2C_CR1 register.
When the digital filter is enabled, the level of the SCL or the SDA line is internally changed
only if it remains stable for more than DNF x I2CCLK periods. This allows to suppress
spikes with a programmable length of 1 to 15 I2CCLK periods.
Table 175. Comparison of analog vs. digital filters
-

Analog filter

Digital filter

Pulse width of
suppressed spikes

≥ 50 ns

Programmable length from 1 to 15 I2C peripheral
clocks

Available in Stop mode

– Programmable length: extra filtering capability
vs. standard requirements
– Stable length

Variation vs. temperature,
voltage, process

Wakeup from Stop mode on address match is not
available when digital filter is enabled

Benefits

Drawbacks

958/1709

RM0385 Rev 7

RM0385
Caution:

Inter-integrated circuit (I2C) interface
Changing the filter configuration is not allowed when the I2C is enabled.

I2C timings
The timings must be configured in order to guarantee a correct data hold and setup time,
used in master and slave modes. This is done by programming the PRESC[3:0],
SCLDEL[3:0] and SDADEL[3:0] bits in the I2C_TIMINGR register.
The STM32CubeMX tool calculates and provides the I2C_TIMINGR content in the I2C
configuration window
Figure 305. Setup and hold timings
DATA HOLD TIME
SCL falling edge internal
detection

tSYNC1 SDADEL: SCL stretched low by the I2C

SDA output delay
SCL

SDA

tHD;DAT
Data hold time: in case of transmission, the data is sent on SDA output after
the SDADEL delay, if it is already available in I2C_TXDR.
DATA SETUP TIME
SCLDEL
SCL stretched low by the I2C

SCL

SDA

tSU;DAT
SU;STA
Data setup time: in case of transmission, the SCLDEL counter starts
when the data is sent on SDA output.
MSv40108V1
MS49608V1

RM0385 Rev 7

959/1709
1020

Inter-integrated circuit (I2C) interface
•

RM0385

When the SCL falling edge is internally detected, a delay is inserted before sending
SDA output. This delay is tSDADEL = SDADEL x tPRESC + tI2CCLK where tPRESC = (PRESC+1)
x tI2CCLK.
TSDADEL impacts the hold time tHD;DAT.

The total SDA output delay is:
tSYNC1 + {[SDADEL x (PRESC+1) + 1] x tI2CCLK }
tSYNC1 duration depends on these parameters:

–

SCL falling slope

–

When enabled, input delay brought by the analog filter: tAF(min) < tAF < tAF(max) ns.

–

When enabled, input delay brought by the digital filter: tDNF = DNF x tI2CCLK

–

Delay due to SCL synchronization to I2CCLK clock (2 to 3 I2CCLK periods)

In order to bridge the undefined region of the SCL falling edge, the user must program
SDADEL in such a way that:
{tf (max) +tHD;DAT (min) -tAF(min) - [(DNF +3) x tI2CCLK]} / {(PRESC +1) x tI2CCLK } ≤ SDADEL
SDADEL ≤ {tHD;DAT (max) -tAF(max) - [(DNF+4) x tI2CCLK]} / {(PRESC +1) x tI2CCLK }
Note:

tAF(min) / tAF(max) are part of the equation only when the analog filter is enabled. Refer to
device datasheet for tAF values.
The maximum tHD;DAT could be 3.45 µs, 0.9 µs and 0.45 µs for Standard-mode, Fast-mode
and Fast-mode Plus, but must be less than the maximum of tVD;DAT by a transition time.
This maximum must only be met if the device does not stretch the LOW period (tLOW) of the
SCL signal. If the clock stretches the SCL, the data must be valid by the set-up time before
it releases the clock.
The SDA rising edge is usually the worst case, so in this case the previous equation
becomes:
SDADEL ≤ {tVD;DAT (max) -tr (max) -260 ns - [(DNF+4) x tI2CCLK]} / {(PRESC +1) x tI2CCLK }.

Note:

This condition can be violated when NOSTRETCH=0, because the device stretches SCL
low to guarantee the set-up time, according to the SCLDEL value.
Refer to Table 176: I2C-SMBUS specification data setup and hold times for tf, tr, tHD;DAT and
tVD;DAT standard values.
•

After tSDADEL delay, or after sending SDA output in case the slave had to stretch the
clock because the data was not yet written in I2C_TXDR register, SCL line is kept at
low level during the setup time. This setup time is tSCLDEL = (SCLDEL+1) x tPRESC where
tPRESC = (PRESC+1) x tI2CCLK.
tSCLDEL impacts the setup time tSU;DAT .

In order to bridge the undefined region of the SDA transition (rising edge usually worst
case), the user must program SCLDEL in such a way that:
{[tr (max) + tSU;DAT (min)] / [(PRESC+1)] x tI2CCLK]} - 1 <= SCLDEL
Refer to Table 176: I2C-SMBUS specification data setup and hold times for tr and tSU;DAT
standard values.
The SDA and SCL transition time values to be used are the ones in the application. Using
the maximum values from the standard increases the constraints for the SDADEL and
SCLDEL calculation, but ensures the feature whatever the application.

960/1709

RM0385 Rev 7

RM0385
Note:

Inter-integrated circuit (I2C) interface
At every clock pulse, after SCL falling edge detection, the I2C master or slave stretches SCL
low during at least [(SDADEL+SCLDEL+1) x (PRESC+1) + 1] x tI2CCLK, in both transmission
and reception modes. In transmission mode, in case the data is not yet written in I2C_TXDR
when SDADEL counter is finished, the I2C keeps on stretching SCL low until the next data
is written. Then new data MSB is sent on SDA output, and SCLDEL counter starts,
continuing stretching SCL low to guarantee the data setup time.
If NOSTRETCH=1 in slave mode, the SCL is not stretched. Consequently the SDADEL
must be programmed in such a way to guarantee also a sufficient setup time.
Table 176. I2C-SMBUS specification data setup and hold times

Symbol

Parameter

Standard-mode
(Sm)

Fast-mode
(Fm)

Fast-mode Plus
(Fm+)

SMBUS
Unit

Min.

Max

Min.

Max

Min.

Max

Min.

Max

tHD;DAT

Data hold time

0

-

0

-

0

-

0.3

-

tVD;DAT

Data valid time

-

3.45

-

0.9

-

0.45

-

-

tSU;DAT

Data setup time

250

-

100

-

50

-

250

-

µs

tr

Rise time of both SDA
and SCL signals

-

1000

-

300

-

120

-

1000

tf

Fall time of both SDA
and SCL signals

-

300

-

300

-

120

-

300

ns

Additionally, in master mode, the SCL clock high and low levels must be configured by
programming the PRESC[3:0], SCLH[7:0] and SCLL[7:0] bits in the I2C_TIMINGR register.
•

When the SCL falling edge is internally detected, a delay is inserted before releasing
the SCL output. This delay is tSCLL = (SCLL+1) x tPRESC where tPRESC = (PRESC+1) x
tI2CCLK.
tSCLL impacts the SCL low time tLOW .

•

When the SCL rising edge is internally detected, a delay is inserted before forcing the
SCL output to low level. This delay is tSCLH = (SCLH+1) x tPRESC where tPRESC =
(PRESC+1) x tI2CCLK. tSCLH impacts the SCL high time tHIGH .

Refer to I2C master initialization for more details.
Caution:

Changing the timing configuration is not allowed when the I2C is enabled.
The I2C slave NOSTRETCH mode must also be configured before enabling the peripheral.
Refer to I2C slave initialization for more details.

Caution:

Changing the NOSTRETCH configuration is not allowed when the I2C is enabled.

RM0385 Rev 7

961/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Figure 306. I2C initialization flowchart

Initial settings

Clear PE bit in I2C_CR1

Configure ANFOFF and DNF[3:0] in I2C_CR1

Configure PRESC[3:0],
SDADEL[3:0], SCLDEL[3:0], SCLH[7:0],
SCLL[7:0] in I2C_TIMINGR

Configure NOSTRETCH in I2C_CR1

Set PE bit in I2C_CR1

End

MS19847V2

30.4.5

Software reset
A software reset can be performed by clearing the PE bit in the I2C_CR1 register. In that
case I2C lines SCL and SDA are released. Internal states machines are reset and
communication control bits, as well as status bits come back to their reset value. The
configuration registers are not impacted.
Here is the list of impacted register bits:
1.

I2C_CR2 register: START, STOP, NACK

2.

I2C_ISR register: BUSY, TXE, TXIS, RXNE, ADDR, NACKF, TCR, TC, STOPF, BERR,
ARLO, OVR

and in addition when the SMBus feature is supported:
1.

I2C_CR2 register: PECBYTE

2.

I2C_ISR register: PECERR, TIMEOUT, ALERT

PE must be kept low during at least 3 APB clock cycles in order to perform the software
reset. This is ensured by writing the following software sequence: - Write PE=0 - Check
PE=0 - Write PE=1.

962/1709

RM0385 Rev 7

RM0385

30.4.6

Inter-integrated circuit (I2C) interface

Data transfer
The data transfer is managed through transmit and receive data registers and a shift
register.

Reception
The SDA input fills the shift register. After the 8th SCL pulse (when the complete data byte is
received), the shift register is copied into I2C_RXDR register if it is empty (RXNE=0). If
RXNE=1, meaning that the previous received data byte has not yet been read, the SCL line
is stretched low until I2C_RXDR is read. The stretch is inserted between the 8th and 9th
SCL pulse (before the Acknowledge pulse).
Figure 307. Data reception
ACK pulse

ACK pulse

legend:

SCL
Shift register

SCL
stretch
xx

data1

xx

data2

xx

RXNE
rd data0 rd data1

I2C_RXDR

data0

data1

data2

MS19848V1

RM0385 Rev 7

963/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Transmission
If the I2C_TXDR register is not empty (TXE=0), its content is copied into the shift register
after the 9th SCL pulse (the Acknowledge pulse). Then the shift register content is shifted
out on SDA line. If TXE=1, meaning that no data is written yet in I2C_TXDR, SCL line is
stretched low until I2C_TXDR is written. The stretch is done after the 9th SCL pulse.
Figure 308. Data transmission
ACK pulse

ACK pulse
legend:

xx

xx

data2

Shift register

data1

SCL

SCL
stretch
xx

TXE

wr data1

I2C_TXDR

data0

wr data2

data1

data2

MS19849V1

Hardware transfer management
The I2C has a byte counter embedded in hardware in order to manage byte transfer and to
close the communication in various modes such as:
–

NACK, STOP and ReSTART generation in master mode

–

ACK control in slave receiver mode

–

PEC generation/checking when SMBus feature is supported

The byte counter is always used in master mode. By default it is disabled in slave mode, but
it can be enabled by software by setting the SBC (Slave Byte Control) bit in the I2C_CR2
register.
The number of bytes to be transferred is programmed in the NBYTES[7:0] bit field in the
I2C_CR2 register. If the number of bytes to be transferred (NBYTES) is greater than 255, or
if a receiver wants to control the acknowledge value of a received data byte, the reload
mode must be selected by setting the RELOAD bit in the I2C_CR2 register. In this mode,
TCR flag is set when the number of bytes programmed in NBYTES has been transferred,
and an interrupt is generated if TCIE is set. SCL is stretched as long as TCR flag is set. TCR
is cleared by software when NBYTES is written to a non-zero value.
When the NBYTES counter is reloaded with the last number of bytes, RELOAD bit must be
cleared.

964/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
When RELOAD=0 in master mode, the counter can be used in 2 modes:

Caution:

•

Automatic end mode (AUTOEND = ‘1’ in the I2C_CR2 register). In this mode, the
master automatically sends a STOP condition once the number of bytes programmed
in the NBYTES[7:0] bit field has been transferred.

•

Software end mode (AUTOEND = ‘0’ in the I2C_CR2 register). In this mode, software
action is expected once the number of bytes programmed in the NBYTES[7:0] bit field
has been transferred; the TC flag is set and an interrupt is generated if the TCIE bit is
set. The SCL signal is stretched as long as the TC flag is set. The TC flag is cleared by
software when the START or STOP bit is set in the I2C_CR2 register. This mode must
be used when the master wants to send a RESTART condition.

The AUTOEND bit has no effect when the RELOAD bit is set.
Table 177. I2C configuration

30.4.7

Function

SBC bit

RELOAD bit

AUTOEND bit

Master Tx/Rx NBYTES + STOP

x

0

1

Master Tx/Rx + NBYTES + RESTART

x

0

0

Slave Tx/Rx
all received bytes ACKed

0

x

x

Slave Rx with ACK control

1

1

x

I2C slave mode
I2C slave initialization
In order to work in slave mode, the user must enable at least one slave address. Two
registers I2C_OAR1 and I2C_OAR2 are available in order to program the slave own
addresses OA1 and OA2.
•

OA1 can be configured either in 7-bit mode (by default) or in 10-bit addressing mode by
setting the OA1MODE bit in the I2C_OAR1 register.
OA1 is enabled by setting the OA1EN bit in the I2C_OAR1 register.

•

If additional slave addresses are required, the 2nd slave address OA2 can be
configured. Up to 7 OA2 LSB can be masked by configuring the OA2MSK[2:0] bits in
the I2C_OAR2 register. Therefore for OA2MSK configured from 1 to 6, only OA2[7:2],
OA2[7:3], OA2[7:4], OA2[7:5], OA2[7:6] or OA2[7] are compared with the received
address. As soon as OA2MSK is not equal to 0, the address comparator for OA2
excludes the I2C reserved addresses (0000 XXX and 1111 XXX), which are not
acknowledged. If OA2MSK=7, all received 7-bit addresses are acknowledged (except
reserved addresses). OA2 is always a 7-bit address.
These reserved addresses can be acknowledged if they are enabled by the specific
enable bit, if they are programmed in the I2C_OAR1 or I2C_OAR2 register with
OA2MSK=0.
OA2 is enabled by setting the OA2EN bit in the I2C_OAR2 register.

•

The General Call address is enabled by setting the GCEN bit in the I2C_CR1 register.

When the I2C is selected by one of its enabled addresses, the ADDR interrupt status flag is
set, and an interrupt is generated if the ADDRIE bit is set.

RM0385 Rev 7

965/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

By default, the slave uses its clock stretching capability, which means that it stretches the
SCL signal at low level when needed, in order to perform software actions. If the master
does not support clock stretching, the I2C must be configured with NOSTRETCH=1 in the
I2C_CR1 register.
After receiving an ADDR interrupt, if several addresses are enabled the user must read the
ADDCODE[6:0] bits in the I2C_ISR register in order to check which address matched. DIR
flag must also be checked in order to know the transfer direction.

Slave clock stretching (NOSTRETCH = 0)
In default mode, the I2C slave stretches the SCL clock in the following situations:
•

When the ADDR flag is set: the received address matches with one of the enabled
slave addresses. This stretch is released when the ADDR flag is cleared by software
setting the ADDRCF bit.

•

In transmission, if the previous data transmission is completed and no new data is
written in I2C_TXDR register, or if the first data byte is not written when the ADDR flag
is cleared (TXE=1). This stretch is released when the data is written to the I2C_TXDR
register.

•

In reception when the I2C_RXDR register is not read yet and a new data reception is
completed. This stretch is released when I2C_RXDR is read.

•

When TCR = 1 in Slave Byte Control mode, reload mode (SBC=1 and RELOAD=1),
meaning that the last data byte has been transferred. This stretch is released when
then TCR is cleared by writing a non-zero value in the NBYTES[7:0] field.

•

After SCL falling edge detection, the I2C stretches SCL low during
[(SDADEL+SCLDEL+1) x (PRESC+1) + 1] x tI2CCLK.

Slave without clock stretching (NOSTRETCH = 1)
When NOSTRETCH = 1 in the I2C_CR1 register, the I2C slave does not stretch the SCL
signal.

966/1709

•

The SCL clock is not stretched while the ADDR flag is set.

•

In transmission, the data must be written in the I2C_TXDR register before the first SCL
pulse corresponding to its transfer occurs. If not, an underrun occurs, the OVR flag is
set in the I2C_ISR register and an interrupt is generated if the ERRIE bit is set in the
I2C_CR1 register. The OVR flag is also set when the first data transmission starts and
the STOPF bit is still set (has not been cleared). Therefore, if the user clears the
STOPF flag of the previous transfer only after writing the first data to be transmitted in
the next transfer, he ensures that the OVR status is provided, even for the first data to
be transmitted.

•

In reception, the data must be read from the I2C_RXDR register before the 9th SCL
pulse (ACK pulse) of the next data byte occurs. If not an overrun occurs, the OVR flag
is set in the I2C_ISR register and an interrupt is generated if the ERRIE bit is set in the
I2C_CR1 register.

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

Slave Byte Control mode
In order to allow byte ACK control in slave reception mode, Slave Byte Control mode must
be enabled by setting the SBC bit in the I2C_CR1 register. This is required to be compliant
with SMBus standards.
Reload mode must be selected in order to allow byte ACK control in slave reception mode
(RELOAD=1). To get control of each byte, NBYTES must be initialized to 0x1 in the ADDR
interrupt subroutine, and reloaded to 0x1 after each received byte. When the byte is
received, the TCR bit is set, stretching the SCL signal low between the 8th and 9th SCL
pulses. The user can read the data from the I2C_RXDR register, and then decide to
acknowledge it or not by configuring the ACK bit in the I2C_CR2 register. The SCL stretch is
released by programming NBYTES to a non-zero value: the acknowledge or notacknowledge is sent and next byte can be received.
NBYTES can be loaded with a value greater than 0x1, and in this case, the reception flow is
continuous during NBYTES data reception.
Note:

The SBC bit must be configured when the I2C is disabled, or when the slave is not
addressed, or when ADDR=1.
The RELOAD bit value can be changed when ADDR=1, or when TCR=1.

Caution:

Slave Byte Control mode is not compatible with NOSTRETCH mode. Setting SBC when
NOSTRETCH=1 is not allowed.
Figure 309. Slave initialization flowchart
Slave
initialization

Initial settings

Clear {OA1EN, OA2EN} in I2C_OAR1 and I2C_OAR2

Configure {OA1[9:0], OA1MODE, OA1EN,
OA2[6:0], OA2MSK[2:0], OA2EN, GCEN}

Configure SBC in I2C_CR1*

Enable interrupts and/or
DMA in I2C_CR1

End

*SBC must be set to support SMBus features

MS19850V2

RM0385 Rev 7

967/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Slave transmitter
A transmit interrupt status (TXIS) is generated when the I2C_TXDR register becomes
empty. An interrupt is generated if the TXIE bit is set in the I2C_CR1 register.
The TXIS bit is cleared when the I2C_TXDR register is written with the next data byte to be
transmitted.
When a NACK is received, the NACKF bit is set in the I2C_ISR register and an interrupt is
generated if the NACKIE bit is set in the I2C_CR1 register. The slave automatically releases
the SCL and SDA lines in order to let the master perform a STOP or a RESTART condition.
The TXIS bit is not set when a NACK is received.
When a STOP is received and the STOPIE bit is set in the I2C_CR1 register, the STOPF
flag is set in the I2C_ISR register and an interrupt is generated. In most applications, the
SBC bit is usually programmed to ‘0’. In this case, If TXE = 0 when the slave address is
received (ADDR=1), the user can choose either to send the content of the I2C_TXDR
register as the first data byte, or to flush the I2C_TXDR register by setting the TXE bit in
order to program a new data byte.
In Slave Byte Control mode (SBC=1), the number of bytes to be transmitted must be
programmed in NBYTES in the address match interrupt subroutine (ADDR=1). In this case,
the number of TXIS events during the transfer corresponds to the value programmed in
NBYTES.
Caution:

When NOSTRETCH=1, the SCL clock is not stretched while the ADDR flag is set, so the
user cannot flush the I2C_TXDR register content in the ADDR subroutine, in order to
program the first data byte. The first data byte to be sent must be previously programmed in
the I2C_TXDR register:
•

This data can be the data written in the last TXIS event of the previous transmission
message.

•

If this data byte is not the one to be sent, the I2C_TXDR register can be flushed by
setting the TXE bit in order to program a new data byte. The STOPF bit must be
cleared only after these actions, in order to guarantee that they are executed before the
first data transmission starts, following the address acknowledge.
If STOPF is still set when the first data transmission starts, an underrun error will be
generated (the OVR flag is set).
If a TXIS event is needed, (Transmit Interrupt or Transmit DMA request), the user must
set the TXIS bit in addition to the TXE bit, in order to generate a TXIS event.

968/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 310. Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=0
Slave
transmission

Slave initialization

No
I2C_ISR.ADDR
=1?
Yes

SCL
stretched

Read ADDCODE and DIR in I2C_ISR
Optional: Set I2C_ISR.TXE = 1
Set I2C_ICR.ADDRCF

No
I2C_ISR.TXIS
=1?
Yes
Write I2C_TXDR.TXDATA

MS19851V2

RM0385 Rev 7

969/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Figure 311. Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=1
Slave
transmission

Slave initialization

No
No
I2C_ISR.TXIS
=1?

I2C_ISR.STOPF
=1?
Yes

Yes
Write I2C_TXDR.TXDATA

Optional: Set I2C_ISR.TXE = 1
and I2C_ISR.TXIS=1

Set I2C_ICR.STOPCF

MS19852V2

970/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 312. Transfer bus diagrams for I2C slave transmitter
legend:

Example I2C slave transmitter 3 bytes with 1st data flushed,
NOSTRETCH=0:
TXIS TXIS

ADDR

S

Address

A

TXIS

A

data1

reception
data3

A

data2

EV2 EV3

EV1

transmission

TXIS

NA

P

SCL stretch

EV4 EV5

TXE

EV1: ADDR ISR: check ADDCODE and DIR, set TXE, set ADDRCF
EV2: TXIS ISR: wr data1
EV3: TXIS ISR: wr data2
EV4: TXIS ISR: wr data3
EV5: TXIS ISR: wr data4 (not sent)

legend :

Example I2C slave transmitter 3 bytes without 1st data flush,
NOSTRETCH=0:

S

TXIS

TXIS

ADDR

Address

A

EV1

data1

A

transmission

TXIS

data2

A

EV2

reception
data3

EV3

NA

SCL stretch

P

EV4

TXE

EV1: ADDR ISR: check ADDCODE and DIR, set ADDRCF
EV2: TXIS ISR: wr data2
EV3: TXIS ISR: wr data3
EV4: TXIS ISR: wr data4 (not sent)

legend:

Example I2C slave transmitter 3 bytes, NOSTRETCH=1:

transmission
TXIS

S

Address

EV1

TXIS

data1

A

EV2

A

STOPF

TXIS

data2

EV3

A

data3

EV4

reception
SCL stretch

NA P

EV5

TXE

EV1: wr data1
EV2: TXIS ISR: wr data2
EV3: TXIS ISR: wr data3
EV4: TXIS ISR: wr data4 (not sent)
EV5: STOPF ISR: (optional: set TXE and TXIS), set STOPCF
MS19853V1

RM0385 Rev 7

971/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Slave receiver
RXNE is set in I2C_ISR when the I2C_RXDR is full, and generates an interrupt if RXIE is
set in I2C_CR1. RXNE is cleared when I2C_RXDR is read.
When a STOP is received and STOPIE is set in I2C_CR1, STOPF is set in I2C_ISR and an
interrupt is generated.
Figure 313. Transfer sequence flowchart for slave receiver with NOSTRETCH=0
Slave reception

Slave initialization

No
I2C_ISR.ADDR
=1?
Yes
SCL
stretched
Read ADDCODE and DIR in I2C_ISR
Set I2C_ICR.ADDRCF

No
I2C_ISR.RXNE
=1?
Yes
Write I2C_RXDR.RXDATA

MS19855V2

972/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 314. Transfer sequence flowchart for slave receiver with NOSTRETCH=1
Slave reception

Slave initialization

No
No

I2C_ISR.STOPF
=1?

I2C_ISR.RXNE
=1?

Yes

Yes

Set I2C_ICR.STOPCF

Read I2C_RXDR.RXDATA

MS19856V2

Figure 315. Transfer bus diagrams for I2C slave receiver
legend:

Example I2C slave receiver 3 bytes, NOSTRETCH=0:

transmission
ADDR

S

RXNE

Address

A

data1

A

RXNE

RXNE

data2

data3

A

EV1

EV2

EV3

A

reception
SCL stretch

EV4

RXNE
EV1: ADDR ISR: check ADDCODE and DIR, set ADDRCF
EV2: RXNE ISR: rd data1
EV3 : RXNE ISR: rd data2
EV4: RXNE ISR: rd data3

Example I2C slave receiver 3 bytes, NOSTRETCH=1:

legend:
transmission

RXNE
S

Address

A

data 1

RXNE
data 2

A

EV1

RXNE
data 3

A

EV2

A

reception
P

SCL stretch

EV3

RXNE
EV1: RXNE ISR: rd data1
EV2: RXNE ISR: rd data2
EV3: RXNE ISR: rd data3
EV4: STOPF ISR: set STOPCF
MS19857V2

RM0385 Rev 7

973/1709
1020

Inter-integrated circuit (I2C) interface

30.4.8

RM0385

I2C master mode
I2C master initialization
Before enabling the peripheral, the I2C master clock must be configured by setting the
SCLH and SCLL bits in the I2C_TIMINGR register.
The STM32CubeMX tool calculates and provides the I2C_TIMINGR content in the I2C
Configuration window.
A clock synchronization mechanism is implemented in order to support multi-master
environment and slave clock stretching.
In order to allow clock synchronization:
•

The low level of the clock is counted using the SCLL counter, starting from the SCL low
level internal detection.

•

The high level of the clock is counted using the SCLH counter, starting from the SCL
high level internal detection.

The I2C detects its own SCL low level after a tSYNC1 delay depending on the SCL falling
edge, SCL input noise filters (analog + digital) and SCL synchronization to the I2CxCLK
clock. The I2C releases SCL to high level once the SCLL counter reaches the value
programmed in the SCLL[7:0] bits in the I2C_TIMINGR register.
The I2C detects its own SCL high level after a tSYNC2 delay depending on the SCL rising
edge, SCL input noise filters (analog + digital) and SCL synchronization to I2CxCLK clock.
The I2C ties SCL to low level once the SCLH counter is reached reaches the value
programmed in the SCLH[7:0] bits in the I2C_TIMINGR register.
Consequently the master clock period is:
tSCL = tSYNC1 + tSYNC2 + {[(SCLH+1) + (SCLL+1)] x (PRESC+1) x tI2CCLK}
The duration of tSYNC1 depends on these parameters:
–

SCL falling slope

–

When enabled, input delay induced by the analog filter.

–

When enabled, input delay induced by the digital filter: DNF x tI2CCLK

–

Delay due to SCL synchronization with I2CCLK clock (2 to 3 I2CCLK periods)

The duration of tSYNC2 depends on these parameters:

974/1709

–

SCL rising slope

–

When enabled, input delay induced by the analog filter.

–

When enabled, input delay induced by the digital filter: DNF x tI2CCLK

–

Delay due to SCL synchronization with I2CCLK clock (2 to 3 I2CCLK periods)

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 316. Master clock generation
SCL master clock generation

SCL high level detected
SCLH counter starts

tSYNC2

SCLH
tSYNC1

SCLL

SCL

SCL low level detected
SCLL counter starts

SCL released

SCL driven low

SCL master clock synchronization
SCL high level detected
SCLH counter starts

SCL high level detected
SCLH counter starts

SCLH

SCL high level detected
SCLH counter starts

SCLH

SCLL

SCLH

SCLL
SCL driven low by
another device

SCL driven low by
another device

SCL low level detected
SCLL counter starts
SCL low level detected
SCLL counter starts

SCL released
MS19858V1

Caution:

In order to be I2C or SMBus compliant, the master clock must respect the timings given
below:

RM0385 Rev 7

975/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Table 178. I2C-SMBUS specification clock timings
Symbol

fSCL

Parameter

SCL clock frequency

Standardmode (Sm)

Fast-mode Fast-mode
(Fm)
Plus (Fm+)

Min

Max

Min

Max

Min

Max

Min

Max

-

100

-

400

-

1000

-

100

kHz

SMBUS
Unit

tHD:STA

Hold time (repeated) START condition

4.0

-

0.6

-

0.26

-

4.0

-

µs

tSU:STA

Set-up time for a repeated START
condition

4.7

-

0.6

-

0.26

-

4.7

-

µs

tSU:STO

Set-up time for STOP condition

4.0

-

0.6

-

0.26

-

4.0

-

µs

tBUF

Bus free time between a STOP and
START condition

4.7

-

1.3

-

0.5

-

4.7

-

µs

tLOW

Low period of the SCL clock

4.7

-

1.3

-

0.5

-

4.7

-

µs

tHIGH

Period of the SCL clock

4.0

-

0.6

-

0.26

-

4.0

50

µs

tr

Rise time of both SDA and SCL signals

-

1000

-

300

-

120

-

1000

ns

tf

Fall time of both SDA and SCL signals

-

300

-

300

-

120

-

300

ns

Note:

SCLL is also used to generate the tBUF and tSU:STA timings.
SCLH is also used to generate the tHD:STA and tSU:STO timings.
Refer to Section 30.4.9: I2C_TIMINGR register configuration examples for examples of
I2C_TIMINGR settings vs. I2CCLK frequency.

Master communication initialization (address phase)
In order to initiate the communication, the user must program the following parameters for
the addressed slave in the I2C_CR2 register:
•

Addressing mode (7-bit or 10-bit): ADD10

•

Slave address to be sent: SADD[9:0]

•

Transfer direction: RD_WRN

•

In case of 10-bit address read: HEAD10R bit. HEAD10R must be configure to indicate
if the complete address sequence must be sent, or only the header in case of a
direction change.

•

The number of bytes to be transferred: NBYTES[7:0]. If the number of bytes is equal to
or greater than 255 bytes, NBYTES[7:0] must initially be filled with 0xFF.

The user must then set the START bit in I2C_CR2 register. Changing all the above bits is
not allowed when START bit is set.
Then the master automatically sends the START condition followed by the slave address as
soon as it detects that the bus is free (BUSY = 0) and after a delay of tBUF.
In case of an arbitration loss, the master automatically switches back to slave mode and can
acknowledge its own address if it is addressed as a slave.
Note:

976/1709

The START bit is reset by hardware when the slave address has been sent on the bus,
whatever the received acknowledge value. The START bit is also reset by hardware if an
arbitration loss occurs.
In 10-bit addressing mode, when the Slave Address first 7 bits is NACKed by the slave, the

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
master will re-launch automatically the slave address transmission until ACK is received. In
this case ADDRCF must be set if a NACK is received from the slave, in order to stop
sending the slave address.
If the I2C is addressed as a slave (ADDR=1) while the START bit is set, the I2C switches to
slave mode and the START bit is cleared when the ADDRCF bit is set.

Note:

The same procedure is applied for a Repeated Start condition. In this case BUSY=1.
Figure 317. Master initialization flowchart
Master
initialization

Initial settings

Enable interrupts and/or DMA in I2C_CR1

End
MS19859V2

Initialization of a master receiver addressing a 10-bit address slave
•

If the slave address is in 10-bit format, the user can choose to send the complete read
sequence by clearing the HEAD10R bit in the I2C_CR2 register. In this case the master
automatically sends the following complete sequence after the START bit is set:
(Re)Start + Slave address 10-bit header Write + Slave address 2nd byte + REStart +
Slave address 10-bit header Read
Figure 318. 10-bit address read access with HEAD10R=0

S

11110XX

0

Slave address
1st 7 bits

R/W

A1

Slave address
2nd byte

A2

Sr

11110XX

1

Slave address
1st 7 bits

R/W

A3

DATA

A

DATA

A

P

Read

Write

MSv41066V1

RM0385 Rev 7

977/1709
1020

Inter-integrated circuit (I2C) interface
•

RM0385

If the master addresses a 10-bit address slave, transmits data to this slave and then
reads data from the same slave, a master transmission flow must be done first. Then a
repeated start is set with the 10 bit slave address configured with HEAD10R=1. In this
case the master sends this sequence: ReStart + Slave address 10-bit header Read.
Figure 319. 10-bit address read access with HEAD10R=1

S

11110XX

0

Slave address
1st 7 bits

R/W

A

Slave address
2nd byte

A

DATA

A

DATA

A/A

Write

Sr

11110XX

1

Slave address
1st 7 bits

R/W

A

DATA

A

DATA

A

P

Read
MS19823V1

Master transmitter
In the case of a write transfer, the TXIS flag is set after each byte transmission, after the 9th
SCL pulse when an ACK is received.
A TXIS event generates an interrupt if the TXIE bit is set in the I2C_CR1 register. The flag is
cleared when the I2C_TXDR register is written with the next data byte to be transmitted.
The number of TXIS events during the transfer corresponds to the value programmed in
NBYTES[7:0]. If the total number of data bytes to be sent is greater than 255, reload mode
must be selected by setting the RELOAD bit in the I2C_CR2 register. In this case, when
NBYTES data have been transferred, the TCR flag is set and the SCL line is stretched low
until NBYTES[7:0] is written to a non-zero value.
The TXIS flag is not set when a NACK is received.
•

When RELOAD=0 and NBYTES data have been transferred:
–

In automatic end mode (AUTOEND=1), a STOP is automatically sent.

–

In software end mode (AUTOEND=0), the TC flag is set and the SCL line is
stretched low in order to perform software actions:
A RESTART condition can be requested by setting the START bit in the I2C_CR2
register with the proper slave address configuration, and number of bytes to be
transferred. Setting the START bit clears the TC flag and the START condition is
sent on the bus.
A STOP condition can be requested by setting the STOP bit in the I2C_CR2
register. Setting the STOP bit clears the TC flag and the STOP condition is sent on
the bus.

•

978/1709

If a NACK is received: the TXIS flag is not set, and a STOP condition is automatically
sent after the NACK reception. the NACKF flag is set in the I2C_ISR register, and an
interrupt is generated if the NACKIE bit is set.

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 320. Transfer sequence flowchart for I2C master transmitter for N≤255 bytes
Master
transmission

Master initialization

NBYTES = N
AUTOEND = 0 for RESTART; 1 for STOP
Configure slave address
Set I2C_CR2.START

No
I2C_ISR.TXIS
=1?

I2C_ISR.NACKF =
1?

No

Yes

Yes

Write I2C_TXDR

End

NBYTES
transmitted?

No

Yes

I2C_ISR.TC =
1?
No

Yes

Set I2C_CR2.START with
slave addess NBYTES ...

End

MS19860V2

RM0385 Rev 7

979/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Figure 321. Transfer sequence flowchart for I2C master transmitter for N>255 bytes

Master
transmission

Master initialization

NBYTES = 0xFF; N=N-255
RELOAD = 1
Configure slave address
Set I2C_CR2.START

No
No
I2C_ISR.TXIS

I2C_ISR.NACKF

= 1?

= 1?
Yes

Yes

Write I2C_TXDR
End

No

NBYTES
transmitted

?

Yes

Yes
I2C_ISR.TC
= 1?
Set I2C_CR2.START
No

with slave addess
NBYTES

...
I2C_ISR.TCR
= 1?

Yes
IF N< 256
NBYTES = N; N = 0; RELOAD = 0
End

AUTOEND = 0 for RESTART; 1 for STOP
ELSE
NBYTES = 0xFF; N = N-255
RELOAD = 1

MS19861V3

980/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 322. Transfer bus diagrams for I2C master transmitter

Example I2C master transmitter 2 bytes, automatic end mode (STOP)
legend:
transmission

TXIS TXIS

reception
S

Address

A

A

data1

data2

A

P

SCL stretch
INIT

EV1 EV2

TXE
NBYTES xx

2

INIT: program Slave address, program NBYTES = 2, AUTOEND=1, set START
EV1: TXIS ISR: wr data1
EV2: TXIS ISR: wr data2

Example I2C master transmitter 2 bytes, software end mode (RESTART)
TXIS TXIS

legend:

TC

transmission
S Address

INIT

A

data1

A

data2

EV1 EV2

A

ReS

EV3

Address

reception
SCL stretch

TXE

NBYTES

xx

2

INIT: program Slave address, program NBYTES = 2, AUTOEND=0, set START
EV1: TXIS ISR: wr data1
EV2: TXIS ISR: wr data2
EV3: TC ISR: program Slave address, program NBYTES = N, set START

MS19862V1

RM0385 Rev 7

981/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Master receiver
In the case of a read transfer, the RXNE flag is set after each byte reception, after the 8th
SCL pulse. An RXNE event generates an interrupt if the RXIE bit is set in the I2C_CR1
register. The flag is cleared when I2C_RXDR is read.
If the total number of data bytes to be received is greater than 255, reload mode must be
selected by setting the RELOAD bit in the I2C_CR2 register. In this case, when
NBYTES[7:0] data have been transferred, the TCR flag is set and the SCL line is stretched
low until NBYTES[7:0] is written to a non-zero value.
•

When RELOAD=0 and NBYTES[7:0] data have been transferred:
–

In automatic end mode (AUTOEND=1), a NACK and a STOP are automatically
sent after the last received byte.

–

In software end mode (AUTOEND=0), a NACK is automatically sent after the last
received byte, the TC flag is set and the SCL line is stretched low in order to allow
software actions:
A RESTART condition can be requested by setting the START bit in the I2C_CR2
register with the proper slave address configuration, and number of bytes to be
transferred. Setting the START bit clears the TC flag and the START condition,
followed by slave address, are sent on the bus.
A STOP condition can be requested by setting the STOP bit in the I2C_CR2
register. Setting the STOP bit clears the TC flag and the STOP condition is sent on
the bus.

982/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 323. Transfer sequence flowchart for I2C master receiver for N≤255 bytes

Master reception

Master initialization

NBYTES = N
AUTOEND = 0 for RESTART; 1 for STOP
Configure slave address
Set I2C_CR2.START

I2C_ISR.RXNE
=1?

No

Yes
Read I2C_RXDR

NBYTES
received?

No

Yes

I2C_ISR.TC =
1?
No

Yes

Set I2C_CR2.START with
slave addess NBYTES ...

End

MS19863V2

RM0385 Rev 7

983/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Figure 324. Transfer sequence flowchart for I2C master receiver for N >255 bytes
Master reception

Master initialization

NBYTES = 0xFF; N=N-255
RELOAD =1
Configure slave address
Set I2C_CR2.START

I2C_ISR.RXNE
=1?

No

Yes
Read I2C_RXDR

NBYTES
received?

No

Yes
Yes
I2C_ISR.TC =
1?
Set I2C_CR2.START with
slave addess NBYTES ...

No
No
I2C_ISR.TCR
= 1?
Yes
IF N< 256
NBYTES =N; N=0;RELOAD=0
AUTOEND=0 for RESTART; 1 for STOP
ELSE
NBYTES =0xFF;N=N-255
RELOAD=1

End

MS19864V2

984/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 325. Transfer bus diagrams for I2C master receiver

Example I2C master receiver 2 bytes, automatic end mode (STOP)
RXNE

S

Address

A

data1

RXNE

data2

A

NA

legend:
P

transmission
reception

INIT

EV2

EV1

SCL stretch
NBYTES xx

2

INIT: program Slave address, program NBYTES = 2, AUTOEND=1, set START
EV1: RXNE ISR: rd data1
EV2: RXNE ISR: rd data2

Example I2C master receiver 2 bytes, software end mode (RESTART)
RXNE

RXNE

legend:

TC

transmission
S

Address

A

data1

INIT

data2

A

EV1

NA

ReS Address

EV2

reception
SCL stretch

NBYTES
xx

2

N

INIT: program Slave address, program NBYTES = 2, AUTOEND=0, set START
EV1: RXNE ISR: rd data1
EV2: RXNE ISR: read data2
EV3: TC ISR: program Slave address, program NBYTES = N, set START

MS19865V1

RM0385 Rev 7

985/1709
1020

Inter-integrated circuit (I2C) interface

30.4.9

RM0385

I2C_TIMINGR register configuration examples
The tables below provide examples of how to program the I2C_TIMINGR to obtain timings
compliant with the I2C specification. In order to get more accurate configuration values, the
STM32CubeMX tool (I2C Configuration window) should be used.
Table 179. Examples of timing settings for fI2CCLK = 8 MHz
Standard-mode (Sm)

Fast-mode (Fm)

Fast-mode Plus (Fm+)

Parameter
10 kHz

100 kHz

400 kHz

500 kHz

PRESC

1

1

0

0

SCLL

0xC7

0x13

0x9

0x6

tSCLL

200x250 ns = 50 µs

20x250 ns = 5.0 µs

10x125 ns = 1250 ns

7x125 ns = 875 ns

SCLH

0xC3

0xF

0x3

0x3

tSCLH

196x250 ns = 49 µs

16x250 ns = 4.0µs

4x125ns = 500ns

4x125 ns = 500 ns

(1)

tSCL

~100

µs(2)

~10

µs(2)

~2500

ns(3)

~2000 ns(4)

SDADEL

0x2

0x2

0x1

0x0

tSDADEL

2x250 ns = 500 ns

2x250 ns = 500 ns

1x125 ns = 125 ns

0 ns

SCLDEL

0x4

0x4

0x3

0x1

tSCLDEL

5x250 ns = 1250 ns

5x250 ns = 1250 ns

4x125 ns = 500 ns

2x125 ns = 250 ns

1. SCL period tSCL is greater than tSCLL + tSCLH due to SCL internal detection delay. Values provided for tSCL are examples
only.
2. tSYNC1 + tSYNC2 minimum value is 4 x tI2CCLK = 500 ns. Example with tSYNC1 + tSYNC2 = 1000 ns
3.

tSYNC1 + tSYNC2 minimum value is 4 x tI2CCLK = 500 ns. Example with tSYNC1 + tSYNC2 = 750 ns

4.

tSYNC1 + tSYNC2 minimum value is 4 x tI2CCLK = 500 ns. Example with tSYNC1 + tSYNC2 = 655 ns

Table 180. Examples of timings settings for fI2CCLK = 16 MHz
Standard-mode (Sm)

Fast-mode (Fm)

Fast-mode Plus (Fm+)

Parameter
10 kHz

100 kHz

400 kHz

1000 kHz

PRESC

3

3

1

0

SCLL

0xC7

0x13

0x9

0x4

tSCLL

200 x 250 ns = 50 µs

20 x 250 ns = 5.0 µs

10 x 125 ns = 1250 ns

5 x 62.5 ns = 312.5 ns

SCLH

0xC3

0xF

0x3

0x2

tSCLH

196 x 250 ns = 49 µs

16 x 250 ns = 4.0 µs

4 x 125ns = 500 ns

3 x 62.5 ns = 187.5 ns

(1)

tSCL

~100

µs(2)

~10

µs(2)

~2500

ns(3)

~1000 ns(4)

SDADEL

0x2

0x2

0x2

0x0

tSDADEL

2 x 250 ns = 500 ns

2 x 250 ns = 500 ns

2 x 125 ns = 250 ns

0 ns

SCLDEL

0x4

0x4

0x3

0x2

tSCLDEL

5 x 250 ns = 1250 ns

5 x 250 ns = 1250 ns

4 x 125 ns = 500 ns

3 x 62.5 ns = 187.5 ns

1. SCL period tSCL is greater than tSCLL + tSCLH due to SCL internal detection delay. Values provided for tSCL are examples
only.

986/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

2. tSYNC1 + tSYNC2 minimum value is 4 x tI2CCLK = 250 ns. Example with tSYNC1 + tSYNC2 = 1000 ns
3.

tSYNC1 + tSYNC2 minimum value is 4 x tI2CCLK = 250 ns. Example with tSYNC1 + tSYNC2 = 750 ns

4. tSYNC1 + tSYNC2 minimum value is 4 x tI2CCLK = 250 ns. Example with tSYNC1 + tSYNC2 = 500 ns

Table 181. Examples of timings settings for fI2CCLK = 48 MHz
Standard-mode (Sm)

Fast-mode (Fm)

Fast-mode Plus (Fm+)

400 kHz

1000 kHz

Parameter
10 kHz

100 kHz

PRESC

0xB

0xB

5

5

SCLL

0xC7

0x13

0x9

0x3

tSCLL

200 x 250 ns = 50 µs

20 x 250 ns = 5.0 µs

10 x 125 ns = 1250 ns

4 x 125 ns = 500 ns

SCLH

0xC3

0xF

0x3

0x1

tSCLH

196 x 250 ns = 49 µs

16 x 250 ns = 4.0 µs

4 x 125 ns = 500 ns

2 x 125 ns = 250 ns

tSCL(1)

~100 µs(2)

~10 µs(2)

~2500 ns(3)

~875 ns(4)

SDADEL

0x2

0x2

0x3

0x0

tSDADEL

2 x 250 ns = 500 ns

2 x 250 ns = 500 ns

3 x 125 ns = 375 ns

0 ns

SCLDEL

0x4

0x4

0x3

0x1

tSCLDEL

5 x 250 ns = 1250 ns

5 x 250 ns = 1250 ns

4 x 125 ns = 500 ns

2 x 125 ns = 250 ns

1. The SCL period tSCL is greater than tSCLL + tSCLH due to the SCL internal detection delay. Values provided for tSCL are only
examples.
2. tSYNC1 + tSYNC2 minimum value is 4x tI2CCLK = 83.3 ns. Example with tSYNC1 + tSYNC2 = 1000 ns
3. tSYNC1 + tSYNC2 minimum value is 4x tI2CCLK = 83.3 ns. Example with tSYNC1 + tSYNC2 = 750 ns
4. tSYNC1 + tSYNC2 minimum value is 4x tI2CCLK = 83.3 ns. Example with tSYNC1 + tSYNC2 = 250 ns

30.4.10

SMBus specific features
This section is relevant only when SMBus feature is supported. Refer to Section 30.3: I2C
implementation.

Introduction
The System Management Bus (SMBus) is a two-wire interface through which various
devices can communicate with each other and with the rest of the system. It is based on I2C
principles of operation. SMBus provides a control bus for system and power management
related tasks.
This peripheral is compatible with the SMBUS specification (http://smbus.org).
The System Management Bus Specification refers to three types of devices.
•

A slave is a device that receives or responds to a command.

•

A master is a device that issues commands, generates the clocks and terminates the
transfer.

•

A host is a specialized master that provides the main interface to the system’s CPU. A
host must be a master-slave and must support the SMBus host notify protocol. Only
one host is allowed in a system.

This peripheral can be configured as master or slave device, and also as a host.

RM0385 Rev 7

987/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Bus protocols
There are eleven possible command protocols for any given device. A device may use any
or all of the eleven protocols to communicate. The protocols are Quick Command, Send
Byte, Receive Byte, Write Byte, Write Word, Read Byte, Read Word, Process Call, Block
Read, Block Write and Block Write-Block Read Process Call. These protocols should be
implemented by the user software.
For more details of these protocols, refer to SMBus specification (http://smbus.org).

Address resolution protocol (ARP)
SMBus slave address conflicts can be resolved by dynamically assigning a new unique
address to each slave device. In order to provide a mechanism to isolate each device for the
purpose of address assignment each device must implement a unique device identifier
(UDID). This 128-bit number is implemented by software.
This peripheral supports the Address Resolution Protocol (ARP). The SMBus Device
Default Address (0b1100 001) is enabled by setting SMBDEN bit in I2C_CR1 register. The
ARP commands should be implemented by the user software.
Arbitration is also performed in slave mode for ARP support.
For more details of the SMBus Address Resolution Protocol, refer to SMBus specification
(http://smbus.org).

Received Command and Data acknowledge control
A SMBus receiver must be able to NACK each received command or data. In order to allow
the ACK control in slave mode, the Slave Byte Control mode must be enabled by setting
SBC bit in I2C_CR1 register. Refer to Slave Byte Control mode on page 967 for more
details.

Host Notify protocol
This peripheral supports the Host Notify protocol by setting the SMBHEN bit in the I2C_CR1
register. In this case the host will acknowledge the SMBus Host address (0b0001 000).
When this protocol is used, the device acts as a master and the host as a slave.

SMBus alert
The SMBus ALERT optional signal is supported. A slave-only device can signal the host
through the SMBALERT# pin that it wants to talk. The host processes the interrupt and
simultaneously accesses all SMBALERT# devices through the Alert Response Address
(0b0001 100). Only the device(s) which pulled SMBALERT# low will acknowledge the Alert
Response Address.
When configured as a slave device(SMBHEN=0), the SMBA pin is pulled low by setting the
ALERTEN bit in the I2C_CR1 register. The Alert Response Address is enabled at the same
time.
When configured as a host (SMBHEN=1), the ALERT flag is set in the I2C_ISR register
when a falling edge is detected on the SMBA pin and ALERTEN=1. An interrupt is
generated if the ERRIE bit is set in the I2C_CR1 register. When ALERTEN=0, the ALERT
line is considered high even if the external SMBA pin is low.
If the SMBus ALERT pin is not needed, the SMBA pin can be used as a standard GPIO if
ALERTEN=0.
988/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

Packet error checking
A packet error checking mechanism has been introduced in the SMBus specification to
improve reliability and communication robustness. Packet Error Checking is implemented
by appending a Packet Error Code (PEC) at the end of each message transfer. The PEC is
calculated by using the C(x) = x8 + x2 + x + 1 CRC-8 polynomial on all the message bytes
(including addresses and read/write bits).
The peripheral embeds a hardware PEC calculator and allows to send a Not Acknowledge
automatically when the received byte does not match with the hardware calculated PEC.

Timeouts
This peripheral embeds hardware timers in order to be compliant with the 3 timeouts defined
in SMBus specification.
.

Table 182. SMBus timeout specifications
Limits
Symbol
tTIMEOUT

Parameter

Unit

Detect clock low timeout

Min

Max

25

35

ms

tLOW:SEXT(1)

Cumulative clock low extend time (slave device)

-

25

ms

tLOW:MEXT(2)

Cumulative clock low extend time (master device)

-

10

ms

1. tLOW:SEXT is the cumulative time a given slave device is allowed to extend the clock cycles in one message
from the initial START to the STOP. It is possible that, another slave device or the master will also extend
the clock causing the combined clock low extend time to be greater than tLOW:SEXT. Therefore, this
parameter is measured with the slave device as the sole target of a full-speed master.
2. tLOW:MEXT is the cumulative time a master device is allowed to extend its clock cycles within each byte of a
message as defined from START-to-ACK, ACK-to-ACK, or ACK-to-STOP. It is possible that a slave device
or another master will also extend the clock causing the combined clock low time to be greater than
tLOW:MEXT on a given byte. Therefore, this parameter is measured with a full speed slave device as the sole
target of the master.

Figure 326. Timeout intervals for tLOW:SEXT, tLOW:MEXT.
Start

Stop
tLOW:SEXT
ClkAck
tLOW:MEXT

ClkAck
tLOW:MEXT

tLOW:MEXT

SMBCLK

SMBDAT

MS19866V1

RM0385 Rev 7

989/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Bus idle detection
A master can assume that the bus is free if it detects that the clock and data signals have
been high for tIDLE greater than tHIGH,MAX. (refer to Table 176: I2C-SMBUS specification data
setup and hold times)
This timing parameter covers the condition where a master has been dynamically added to
the bus and may not have detected a state transition on the SMBCLK or SMBDAT lines. In
this case, the master must wait long enough to ensure that a transfer is not currently in
progress. The peripheral supports a hardware bus idle detection.

30.4.11

SMBus initialization
This section is relevant only when SMBus feature is supported. Refer to Section 30.3: I2C
implementation.
In addition to I2C initialization, some other specific initialization must be done in order to
perform SMBus communication:

Received Command and Data Acknowledge control (Slave mode)
A SMBus receiver must be able to NACK each received command or data. In order to allow
ACK control in slave mode, the Slave Byte Control mode must be enabled by setting the
SBC bit in the I2C_CR1 register. Refer to Slave Byte Control mode on page 967 for more
details.

Specific address (Slave mode)
The specific SMBus addresses should be enabled if needed. Refer to Bus idle detection on
page 990 for more details.
•

The SMBus Device Default address (0b1100 001) is enabled by setting the SMBDEN
bit in the I2C_CR1 register.

•

The SMBus Host address (0b0001 000) is enabled by setting the SMBHEN bit in the
I2C_CR1 register.

•

The Alert Response Address (0b0001100) is enabled by setting the ALERTEN bit in the
I2C_CR1 register.

Packet error checking
PEC calculation is enabled by setting the PECEN bit in the I2C_CR1 register. Then the PEC
transfer is managed with the help of a hardware byte counter: NBYTES[7:0] in the I2C_CR2
register. The PECEN bit must be configured before enabling the I2C.
The PEC transfer is managed with the hardware byte counter, so the SBC bit must be set
when interfacing the SMBus in slave mode. The PEC is transferred after NBYTES-1 data
have been transferred when the PECBYTE bit is set and the RELOAD bit is cleared. If
RELOAD is set, PECBYTE has no effect.
Caution:

990/1709

Changing the PECEN configuration is not allowed when the I2C is enabled.

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Table 183. SMBUS with PEC configuration
Mode

SBC bit RELOAD bit AUTOEND bit PECBYTE bit

Master Tx/Rx NBYTES + PEC+ STOP

x

0

1

1

Master Tx/Rx NBYTES + PEC + ReSTART

x

0

0

1

Slave Tx/Rx with PEC

1

0

x

1

Timeout detection
The timeout detection is enabled by setting the TIMOUTEN and TEXTEN bits in the
I2C_TIMEOUTR register. The timers must be programmed in such a way that they detect a
timeout before the maximum time given in the SMBus specification.
•

tTIMEOUT check
In order to enable the tTIMEOUT check, the 12-bit TIMEOUTA[11:0] bits must be
programmed with the timer reload value in order to check the tTIMEOUT parameter. The
TIDLE bit must be configured to ‘0’ in order to detect the SCL low level timeout.
Then the timer is enabled by setting the TIMOUTEN in the I2C_TIMEOUTR register.
If SCL is tied low for a time greater than (TIMEOUTA+1) x 2048 x tI2CCLK, the TIMEOUT
flag is set in the I2C_ISR register.
Refer to Table 184: Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tTIMEOUT = 25 ms).

Caution:

Changing the TIMEOUTA[11:0] bits and TIDLE bit configuration is not allowed when the
TIMEOUTEN bit is set.
•

tLOW:SEXT and tLOW:MEXT check
Depending on if the peripheral is configured as a master or as a slave, The 12-bit
TIMEOUTB timer must be configured in order to check tLOW:SEXT for a slave and
tLOW:MEXT for a master. As the standard specifies only a maximum, the user can choose
the same value for the both.
Then the timer is enabled by setting the TEXTEN bit in the I2C_TIMEOUTR register.
If the SMBus peripheral performs a cumulative SCL stretch for a time greater than
(TIMEOUTB+1) x 2048 x tI2CCLK, and in the timeout interval described in Bus idle
detection on page 990 section, the TIMEOUT flag is set in the I2C_ISR register.
Refer to Table 185: Examples of TIMEOUTB settings for various I2CCLK frequencies

Caution:

Changing the TIMEOUTB configuration is not allowed when the TEXTEN bit is set.

Bus Idle detection
In order to enable the tIDLE check, the 12-bit TIMEOUTA[11:0] field must be programmed
with the timer reload value in order to obtain the tIDLE parameter. The TIDLE bit must be
configured to ‘1 in order to detect both SCL and SDA high level timeout.
Then the timer is enabled by setting the TIMOUTEN bit in the I2C_TIMEOUTR register.
If both the SCL and SDA lines remain high for a time greater than (TIMEOUTA+1) x 4 x
tI2CCLK, the TIMEOUT flag is set in the I2C_ISR register.
Refer to Table 186: Examples of TIMEOUTA settings for various I2CCLK frequencies (max
tIDLE = 50 µs)

RM0385 Rev 7

991/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Caution:

Changing the TIMEOUTA and TIDLE configuration is not allowed when the TIMEOUTEN is
set.

30.4.12

SMBus: I2C_TIMEOUTR register configuration examples
This section is relevant only when SMBus feature is supported. Refer to Section 30.3: I2C
implementation.
•

Configuring the maximum duration of tTIMEOUT to 25 ms:
Table 184. Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tTIMEOUT = 25 ms)

•

fI2CCLK

TIMEOUTA[11:0] bits

8 MHz

0x61

0

1

98 x 2048 x 125 ns = 25 ms

16 MHz

0xC3

0

1

196 x 2048 x 62.5 ns = 25 ms

32 MHz

0x186

0

1

391 x 2048 x 31.25 ns = 25 ms

TIDLE bit TIMEOUTEN bit

tTIMEOUT

Configuring the maximum duration of tLOW:SEXT and tLOW:MEXT to 8 ms:
Table 185. Examples of TIMEOUTB settings for various I2CCLK frequencies

•

tLOW:EXT

fI2CCLK

TIMEOUTB[11:0] bits

TEXTEN bit

8 MHz

0x1F

1

32 x 2048 x 125 ns = 8 ms

16 MHz

0x3F

1

64 x 2048 x 62.5 ns = 8 ms

32 MHz

0x7C

1

125 x 2048 x 31.25 ns = 8 ms

Configuring the maximum duration of tIDLE to 50 µs
Table 186. Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tIDLE = 50 µs)

30.4.13

tTIDLE

fI2CCLK

TIMEOUTA[11:0] bits

8 MHz

0x63

1

1

100 x 4 x 125 ns = 50 µs

16 MHz

0xC7

1

1

200 x 4 x 62.5 ns = 50 µs

32 MHz

0x18F

1

1

400 x 4 x 31.25 ns = 50 µs

TIDLE bit TIMEOUTEN bit

SMBus slave mode
This section is relevant only when SMBus feature is supported. Refer to Section 30.3: I2C
implementation.
In addition to I2C slave transfer management (refer to Section 30.4.7: I2C slave mode)
some additional software flowcharts are provided to support SMBus.

SMBus Slave transmitter
When the IP is used in SMBus, SBC must be programmed to ‘1’ in order to allow the PEC
transmission at the end of the programmed number of data bytes. When the PECBYTE bit
is set, the number of bytes programmed in NBYTES[7:0] includes the PEC transmission. In
992/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
that case the total number of TXIS interrupts will be NBYTES-1 and the content of the
I2C_PECR register is automatically transmitted if the master requests an extra byte after the
NBYTES-1 data transfer.

Caution:

The PECBYTE bit has no effect when the RELOAD bit is set.
Figure 327. Transfer sequence flowchart for SMBus slave transmitter N bytes + PEC

SMBus slave
transmission

Slave initialization

No
I2C_ISR.ADDR =
1?
Yes
Read ADDCODE and DIR in I2C_ISR
I2C_CR2.NBYTES = N + 1
PECBYTE=1
Set I2C_ICR.ADDRCF

I2C_ISR.TXIS
=1?

SCL
stretched

No

Yes
Write I2C_TXDR.TXDATA

MS19867V2

RM0385 Rev 7

993/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Figure 328. Transfer bus diagrams for SMBus slave transmitter (SBC=1)
legend:

Example SMBus slave transmitter 2 bytes + PEC,

transmission
TXIS TXIS

ADDR

S

Address

A

EV1
NBYTES

reception

data1

A

data2

A

PEC

NA

P

SCL stretch

EV2 EV3
3

EV1: ADDR ISR: check ADDCODE, program NBYTES=3, set PECBYTE, set ADDRCF
EV2: TXIS ISR: wr data1
EV3: TXIS ISR: wr data2
MS19869V1

SMBus Slave receiver
When the I2C is used in SMBus mode, SBC must be programmed to ‘1’ in order to allow the
PEC checking at the end of the programmed number of data bytes. In order to allow the
ACK control of each byte, the reload mode must be selected (RELOAD=1). Refer to Slave
Byte Control mode on page 967 for more details.
In order to check the PEC byte, the RELOAD bit must be cleared and the PECBYTE bit
must be set. In this case, after NBYTES-1 data have been received, the next received byte
is compared with the internal I2C_PECR register content. A NACK is automatically
generated if the comparison does not match, and an ACK is automatically generated if the
comparison matches, whatever the ACK bit value. Once the PEC byte is received, it is
copied into the I2C_RXDR register like any other data, and the RXNE flag is set.
In the case of a PEC mismatch, the PECERR flag is set and an interrupt is generated if the
ERRIE bit is set in the I2C_CR1 register.
If no ACK software control is needed, the user can program PECBYTE=1 and, in the same
write operation, program NBYTES with the number of bytes to be received in a continuous
flow. After NBYTES-1 are received, the next received byte is checked as being the PEC.
Caution:

994/1709

The PECBYTE bit has no effect when the RELOAD bit is set.

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 329. Transfer sequence flowchart for SMBus slave receiver N Bytes + PEC
SMBus slave
reception

Slave initialization

No
I2C_ISR.ADDR =
1?
Yes
Read ADDCODE and DIR in I2C_ISR
I2C_CR2.NBYTES = 1, RELOAD =1
PECBYTE=1
Set I2C_ICR.ADDRCF

I2C_ISR.RXNE =1?
I2C_ISR.TCR = 1?

SCL
stretched

No

Yes
Read I2C_RXDR.RXDATA
Program I2C_CR2.NACK = 0
I2C_CR2.NBYTES = 1
N=N-1

N = 1?

No

Yes
Read I2C_RXDR.RXDATA
Program RELOAD = 0
NACK = 0 and NBYTES = 1

No
I2C_ISR.RXNE =1?

Yes
Read I2C_RXDR.RXDATA

End
MS19868V2

RM0385 Rev 7

995/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Figure 330. Bus transfer diagrams for SMBus slave receiver (SBC=1)
legend:

Example SMBus slave receiver 2 bytes + PEC

transmission
ADDR

RXNE

S Address

A

data1

A

EV1

RXNE

data2

A

EV2

NBYTES

RXNE

PEC

reception

A

EV3

SCL stretch

P

EV4

3

EV1: ADDR ISR: check ADDCODE and DIR, program NBYTES = 3, PECBYTE=1, RELOAD=0, set ADDRCF
EV2: RXNE ISR: rd data1
EV3: RXNE ISR: rd data2
EV4: RXNE ISR: rd PEC

legend :

Example SMBus slave receiver 2 bytes + PEC, with ACK control
(RELOAD=1/0)
ADDR
S Address

RXNE,TCR
A

data1

EV1
NBYTES

A

RXNE,TCR
data2

EV2

A

transmission

RXNE
PEC

EV3

A

reception
P

SCL stretch

EV4

1

EV1: ADDR ISR: check ADDCODE and DIR, program NBYTES = 1, PECBYTE=1, RELOAD=1, set ADDRCF
EV2: RXNE-TCR ISR: rd data1, program NACK=0 and NBYTES = 1
EV3: RXNE-TCR ISR: rd data2, program NACK=0, NBYTES = 1 and RELOAD=0
EV4: RXNE-TCR ISR: rd PEC
MS19870V1

This section is relevant only when SMBus feature is supported. Refer to Section 30.3: I2C
implementation.
In addition to I2C master transfer management (refer to Section 30.4.8: I2C master mode)
some additional software flowcharts are provided to support SMBus.

SMBus Master transmitter
When the SMBus master wants to transmit the PEC, the PECBYTE bit must be set and the
number of bytes must be programmed in the NBYTES[7:0] field, before setting the START
bit. In this case the total number of TXIS interrupts will be NBYTES-1. So if the PECBYTE
bit is set when NBYTES=0x1, the content of the I2C_PECR register is automatically
transmitted.
If the SMBus master wants to send a STOP condition after the PEC, automatic end mode
should be selected (AUTOEND=1). In this case, the STOP condition automatically follows
the PEC transmission.

996/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
When the SMBus master wants to send a RESTART condition after the PEC, software
mode must be selected (AUTOEND=0). In this case, once NBYTES-1 have been
transmitted, the I2C_PECR register content is transmitted and the TC flag is set after the
PEC transmission, stretching the SCL line low. The RESTART condition must be
programmed in the TC interrupt subroutine.

Caution:

The PECBYTE bit has no effect when the RELOAD bit is set.
Figure 331. Bus transfer diagrams for SMBus master transmitter

Example SMBus master transmitter 2 bytes + PEC, automatic end mode (STOP)
TXIS TXIS
S Address A

legend:

data1

A

data2

A

PEC

A

P

transmission
reception

EV1

INIT

EV2
SCL stretch

TXE

NBYTES xx

3

INIT: program Slave address, program NBYTES = 3, AUTOEND=1, set PECBYTE, set START
EV1: TXIS ISR: wr data1
EV2: TXIS ISR: wr data2

Example SMBus master transmitter 2 bytes + PEC, software end mode (RESTART)

TXIS

legend:

TC

TXIS

transmission
S Address A
INIT

xx

data1

A

data2

A

PEC

A

EV1 EV2

Rstart Address
EV3

reception
SCL stretch

N

3

NBYTES
INIT: program Slave address, program NBYTES = 3, AUTOEND=0, set PECBYTE, set START
EV1: TXIS ISR: wr data1
EV2: TXIS ISR: wr data2
EV3: TC ISR: program Slave address, program NBYTES = N, set START

MS19871V1

RM0385 Rev 7

997/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

SMBus Master receiver
When the SMBus master wants to receive the PEC followed by a STOP at the end of the
transfer, automatic end mode can be selected (AUTOEND=1). The PECBYTE bit must be
set and the slave address must be programmed, before setting the START bit. In this case,
after NBYTES-1 data have been received, the next received byte is automatically checked
versus the I2C_PECR register content. A NACK response is given to the PEC byte, followed
by a STOP condition.
When the SMBus master receiver wants to receive the PEC byte followed by a RESTART
condition at the end of the transfer, software mode must be selected (AUTOEND=0). The
PECBYTE bit must be set and the slave address must be programmed, before setting the
START bit. In this case, after NBYTES-1 data have been received, the next received byte is
automatically checked versus the I2C_PECR register content. The TC flag is set after the
PEC byte reception, stretching the SCL line low. The RESTART condition can be
programmed in the TC interrupt subroutine.
Caution:

998/1709

The PECBYTE bit has no effect when the RELOAD bit is set.

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface
Figure 332. Bus transfer diagrams for SMBus master receiver

Example SMBus master receiver 2 bytes + PEC, automatic end mode (STOP)
RXNE

Address

S

A

data1

A

RXNE

data2

A

RXNE
PEC

NA

legend:
transmission

P

reception
INIT

EV2

EV1

EV3
SCL stretch

NBYTES xx

3

INIT: program Slave address, program NBYTES = 3, AUTOEND=1, set PECBYTE, set START
EV1: RXNE ISR: rd data1
EV2: RXNE ISR: rd data2
EV3: RXNE ISR: rd PEC

Example SMBus master receiver 2 bytes + PEC, software end mode (RESTART)
RXNE

RXNE

legend:

RXNE TC

transmission
S Address A

data1

data2

A
EV1

INIT

A

PEC

EV2

NA
EV3

Restart Address
EV4

reception
SCL stretch

NBYTES
xx

3

N

INIT: program Slave address, program NBYTES = 3, AUTOEND=0, set PECBYTE, set START
EV1: RXNE ISR: rd data1
EV2: RXNE ISR: rd data2
EV3: RXNE ISR: read PEC
EV4: TC ISR: program Slave address, program NBYTES = N, set START
MS19872V1

30.4.14

Error conditions
The following are the error conditions which may cause communication to fail.

Bus error (BERR)
A bus error is detected when a START or a STOP condition is detected and is not located
after a multiple of 9 SCL clock pulses. A START or a STOP condition is detected when a
SDA edge occurs while SCL is high.
The bus error flag is set only if the I2C is involved in the transfer as master or addressed
slave (i.e not during the address phase in slave mode).

RM0385 Rev 7

999/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

In case of a misplaced START or RESTART detection in slave mode, the I2C enters
address recognition state like for a correct START condition.
When a bus error is detected, the BERR flag is set in the I2C_ISR register, and an interrupt
is generated if the ERRIE bit is set in the I2C_CR1 register.

Arbitration lost (ARLO)
An arbitration loss is detected when a high level is sent on the SDA line, but a low level is
sampled on the SCL rising edge.
•

In master mode, arbitration loss is detected during the address phase, data phase and
data acknowledge phase. In this case, the SDA and SCL lines are released, the
START control bit is cleared by hardware and the master switches automatically to
slave mode.

•

In slave mode, arbitration loss is detected during data phase and data acknowledge
phase. In this case, the transfer is stopped, and the SCL and SDA lines are released.

When an arbitration loss is detected, the ARLO flag is set in the I2C_ISR register, and an
interrupt is generated if the ERRIE bit is set in the I2C_CR1 register.

Overrun/underrun error (OVR)
An overrun or underrun error is detected in slave mode when NOSTRETCH=1 and:
•

In reception when a new byte is received and the RXDR register has not been read yet.
The new received byte is lost, and a NACK is automatically sent as a response to the
new byte.

•

In transmission:
–

When STOPF=1 and the first data byte should be sent. The content of the
I2C_TXDR register is sent if TXE=0, 0xFF if not.

–

When a new byte should be sent and the I2C_TXDR register has not been written
yet, 0xFF is sent.

When an overrun or underrun error is detected, the OVR flag is set in the I2C_ISR register,
and an interrupt is generated if the ERRIE bit is set in the I2C_CR1 register.

Packet Error Checking Error (PECERR)
This section is relevant only when the SMBus feature is supported. Refer to Section 30.3:
I2C implementation.
A PEC error is detected when the received PEC byte does not match with the I2C_PECR
register content. A NACK is automatically sent after the wrong PEC reception.
When a PEC error is detected, the PECERR flag is set in the I2C_ISR register, and an
interrupt is generated if the ERRIE bit is set in the I2C_CR1 register.

1000/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

Timeout Error (TIMEOUT)
This section is relevant only when the SMBus feature is supported. Refer to Section 30.3:
I2C implementation.
A timeout error occurs for any of these conditions:
•

TIDLE=0 and SCL remained low for the time defined in the TIMEOUTA[11:0] bits: this is
used to detect a SMBus timeout.

•

TIDLE=1 and both SDA and SCL remained high for the time defined in the TIMEOUTA
[11:0] bits: this is used to detect a bus idle condition.

•

Master cumulative clock low extend time reached the time defined in the
TIMEOUTB[11:0] bits (SMBus tLOW:MEXT parameter)

•

Slave cumulative clock low extend time reached the time defined in TIMEOUTB[11:0]
bits (SMBus tLOW:SEXT parameter)

When a timeout violation is detected in master mode, a STOP condition is automatically
sent.
When a timeout violation is detected in slave mode, SDA and SCL lines are automatically
released.
When a timeout error is detected, the TIMEOUT flag is set in the I2C_ISR register, and an
interrupt is generated if the ERRIE bit is set in the I2C_CR1 register.

Alert (ALERT)
This section is relevant only when the SMBus feature is supported. Refer to Section 30.3:
I2C implementation.
The ALERT flag is set when the I2C interface is configured as a Host (SMBHEN=1), the
alert pin detection is enabled (ALERTEN=1) and a falling edge is detected on the SMBA pin.
An interrupt is generated if the ERRIE bit is set in the I2C_CR1 register.

30.4.15

DMA requests
Transmission using DMA
DMA (Direct Memory Access) can be enabled for transmission by setting the TXDMAEN bit
in the I2C_CR1 register. Data is loaded from an SRAM area configured using the DMA
peripheral (see Section 8: Direct memory access controller (DMA) on page 222) to the
I2C_TXDR register whenever the TXIS bit is set.
Only the data are transferred with DMA.
•

In master mode: the initialization, the slave address, direction, number of bytes and
START bit are programmed by software (the transmitted slave address cannot be
transferred with DMA). When all data are transferred using DMA, the DMA must be

RM0385 Rev 7

1001/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

initialized before setting the START bit. The end of transfer is managed with the
NBYTES counter. Refer to Master transmitter on page 978.
•

•

Note:

In slave mode:
–

With NOSTRETCH=0, when all data are transferred using DMA, the DMA must be
initialized before the address match event, or in ADDR interrupt subroutine, before
clearing ADDR.

–

With NOSTRETCH=1, the DMA must be initialized before the address match
event.

For instances supporting SMBus: the PEC transfer is managed with NBYTES counter.
Refer to SMBus Slave transmitter on page 992 and SMBus Master transmitter on
page 996.

If DMA is used for transmission, the TXIE bit does not need to be enabled.

Reception using DMA
DMA (Direct Memory Access) can be enabled for reception by setting the RXDMAEN bit in
the I2C_CR1 register. Data is loaded from the I2C_RXDR register to an SRAM area
configured using the DMA peripheral (refer to Section 8: Direct memory access controller
(DMA)) whenever the RXNE bit is set. Only the data (including PEC) are transferred with
DMA.
•

In master mode, the initialization, the slave address, direction, number of bytes and
START bit are programmed by software. When all data are transferred using DMA, the
DMA must be initialized before setting the START bit. The end of transfer is managed
with the NBYTES counter.

•

In slave mode with NOSTRETCH=0, when all data are transferred using DMA, the
DMA must be initialized before the address match event, or in the ADDR interrupt
subroutine, before clearing the ADDR flag.

•

If SMBus is supported (see Section 30.3: I2C implementation): the PEC transfer is
managed with the NBYTES counter. Refer to SMBus Slave receiver on page 994 and
SMBus Master receiver on page 998.

Note:

If DMA is used for reception, the RXIE bit does not need to be enabled.

30.4.16

Debug mode
When the microcontroller enters debug mode (core halted), the SMBus timeout either
continues to work normally or stops, depending on the DBG_I2Cx_STOP configuration bits
in the DBG module.

30.5

I2C low-power modes
Table 187. Low-power modes
Mode

Description

Sleep

No effect
I2C interrupts cause the device to exit the Sleep mode.

Stop

The contents of I2C registers are kept.

Standby The I2C peripheral is powered down and must be reinitialized after exiting Standby.

1002/1709

RM0385 Rev 7

RM0385

30.6

Inter-integrated circuit (I2C) interface

I2C interrupts
The table below gives the list of I2C interrupt requests.
Table 188. I2C Interrupt requests
Event flag

Event flag/Interrupt
clearing method

Interrupt enable
control bit

Receive buffer not empty

RXNE

Read I2C_RXDR register

RXIE

Transmit buffer interrupt status

TXIS

Write I2C_TXDR register

TXIE

Stop detection interrupt flag

STOPF

Write STOPCF=1

STOPIE

Transfer Complete Reload

TCR

Write I2C_CR2 with
NBYTES[7:0] ≠ 0

TCIE

Transfer complete

TC

Write START=1 or STOP=1

Address matched

ADDR

Write ADDRCF=1

ADDRIE

NACK reception

NACKF

Write NACKCF=1

NACKIE

Bus error

BERR

Write BERRCF=1

Arbitration loss

ARLO

Write ARLOCF=1

Overrun/Underrun

OVR

Write OVRCF=1

PEC error

PECERR

Write PECERRCF=1

Timeout/tLOW error

TIMEOUT

Write TIMEOUTCF=1

ALERT

Write ALERTCF=1

Interrupt event

SMBus Alert

ERRIE

Depending on the product implementation, all these interrupts events can either share the
same interrupt vector (I2C global interrupt), or be grouped into 2 interrupt vectors (I2C event
interrupt and I2C error interrupt). Refer to Table 43: STM32F75xxx and STM32F74xxx
vector table for details.
Figure 333. I2C interrupt mapping diagram
TCR
TC

TCIE

TXIS
TXIE
RXNE
RXIE

I2C event interrupt

STOPF
STOPIE
ADDR
ADDRIE

I2C global interrupt

NACKF
NACKIE

BERR
OVR
ARLO
TIMEOUT
ALERT
PECERR

ERRIE

I2C error interrupt

MSv41065V1

RM0385 Rev 7

1003/1709
1020

Inter-integrated circuit (I2C) interface

30.7

RM0385

I2C registers
Refer to Section 1.1 on page 62 for a list of abbreviations used in register descriptions.
The peripheral registers are accessed by words (32-bit).

30.7.1

Control register 1 (I2C_CR1)
Address offset: 0x00
Reset value: 0x0000 0000
Access: No wait states, except if a write access occurs while a write access to this register is
ongoing. In this case, wait states are inserted in the second write access until the previous
one is completed. The latency of the second write access can be up to 2 x PCLK1 + 6 x
I2CCLK.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PECEN

ALERT
EN

SMBD
EN

SMBH
EN

GCEN

Res.

NOSTR
ETCH

SBC

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

ERRIE

TCIE

STOP
IE

NACK
IE

ADDR
IE

RXIE

TXIE

PE

rw

rw

rw

rw

rw

rw

rw

rw

15

14

RXDMA TXDMA
EN
EN
rw

rw

13

12

Res.

ANF
OFF
rw

11

10

9

8

DNF
rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bit 23 PECEN: PEC enable
0: PEC calculation disabled
1: PEC calculation enabled
Note: If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 22 ALERTEN: SMBus alert enable
Device mode (SMBHEN=0):
0: Releases SMBA pin high and Alert Response Address Header disabled: 0001100x
followed by NACK.
1: Drives SMBA pin low and Alert Response Address Header enables: 0001100x followed
by ACK.
Host mode (SMBHEN=1):
0: SMBus Alert pin (SMBA) not supported.
1: SMBus Alert pin (SMBA) supported.
Note: When ALERTEN=0, the SMBA pin can be used as a standard GPIO.
If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 21 SMBDEN: SMBus Device Default address enable
0: Device default address disabled. Address 0b1100001x is NACKed.
1: Device default address enabled. Address 0b1100001x is ACKed.
Note: If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.

1004/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

Bit 20 SMBHEN: SMBus Host address enable
0: Host address disabled. Address 0b0001000x is NACKed.
1: Host address enabled. Address 0b0001000x is ACKed.
Note: If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 19 GCEN: General call enable
0: General call disabled. Address 0b00000000 is NACKed.
1: General call enabled. Address 0b00000000 is ACKed.
Bit 18 Reserved, must be kept at reset value.
Bit 17 NOSTRETCH: Clock stretching disable
This bit is used to disable clock stretching in slave mode. It must be kept cleared in master
mode.
0: Clock stretching enabled
1: Clock stretching disabled
Note: This bit can only be programmed when the I2C is disabled (PE = 0).
Bit 16 SBC: Slave byte control
This bit is used to enable hardware byte control in slave mode.
0: Slave byte control disabled
1: Slave byte control enabled
Bit 15 RXDMAEN: DMA reception requests enable
0: DMA mode disabled for reception
1: DMA mode enabled for reception
Bit 14 TXDMAEN: DMA transmission requests enable
0: DMA mode disabled for transmission
1: DMA mode enabled for transmission
Bit 13 Reserved, must be kept at reset value.
Bit 12 ANFOFF: Analog noise filter OFF
0: Analog noise filter enabled
1: Analog noise filter disabled
Note: This bit can only be programmed when the I2C is disabled (PE = 0).
Bits 11:8 DNF[3:0]: Digital noise filter
These bits are used to configure the digital noise filter on SDA and SCL input. The digital filter
will filter spikes with a length of up to DNF[3:0] * tI2CCLK
0000: Digital filter disabled
0001: Digital filter enabled and filtering capability up to 1 tI2CCLK
...

1111: digital filter enabled and filtering capability up to15 tI2CCLK
Note: If the analog filter is also enabled, the digital filter is added to the analog filter.
This filter can only be programmed when the I2C is disabled (PE = 0).

RM0385 Rev 7

1005/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Bit 7 ERRIE: Error interrupts enable
0: Error detection interrupts disabled
1: Error detection interrupts enabled
Note: Any of these errors generate an interrupt:
Arbitration Loss (ARLO)
Bus Error detection (BERR)
Overrun/Underrun (OVR)
Timeout detection (TIMEOUT)
PEC error detection (PECERR)
Alert pin event detection (ALERT)
Bit 6 TCIE: Transfer Complete interrupt enable
0: Transfer Complete interrupt disabled
1: Transfer Complete interrupt enabled
Note: Any of these events will generate an interrupt:
Transfer Complete (TC)
Transfer Complete Reload (TCR)
Bit 5 STOPIE: STOP detection Interrupt enable
0: Stop detection (STOPF) interrupt disabled
1: Stop detection (STOPF) interrupt enabled
Bit 4 NACKIE: Not acknowledge received Interrupt enable
0: Not acknowledge (NACKF) received interrupts disabled
1: Not acknowledge (NACKF) received interrupts enabled
Bit 3 ADDRIE: Address match Interrupt enable (slave only)
0: Address match (ADDR) interrupts disabled
1: Address match (ADDR) interrupts enabled
Bit 2 RXIE: RX Interrupt enable
0: Receive (RXNE) interrupt disabled
1: Receive (RXNE) interrupt enabled
Bit 1 TXIE: TX Interrupt enable
0: Transmit (TXIS) interrupt disabled
1: Transmit (TXIS) interrupt enabled
Bit 0 PE: Peripheral enable
0: Peripheral disable
1: Peripheral enable
Note: When PE=0, the I2C SCL and SDA lines are released. Internal state machines and
status bits are put back to their reset value. When cleared, PE must be kept low for at
least 3 APB clock cycles.

1006/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

30.7.2

Control register 2 (I2C_CR2)
Address offset: 0x04
Reset value: 0x0000 0000
Access: No wait states, except if a write access occurs while a write access to this register is
ongoing. In this case, wait states are inserted in the second write access until the previous
one is completed. The latency of the second write access can be up to 2 x PCLK1 + 6 x
I2CCLK.

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

PEC
BYTE

AUTO
END

RE
LOAD

rs

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

15

14

13

12

11

10

NACK

STOP

START

HEAD
10R

ADD10

RD_
WRN

rs

rs

rs

rw

rw

rw

23

22

21

20

19

18

17

16

rw

rw

rw

rw

3

2

1

0

rw

rw

rw

rw

NBYTES[7:0]

SADD[9:0]
rw

rw

rw

rw

rw

rw

Bits 31:27 Reserved, must be kept at reset value.
Bit 26 PECBYTE: Packet error checking byte
This bit is set by software, and cleared by hardware when the PEC is transferred, or when a
STOP condition or an Address matched is received, also when PE=0.
0: No PEC transfer.
1: PEC transmission/reception is requested
Note: Writing ‘0’ to this bit has no effect.
This bit has no effect when RELOAD is set.
This bit has no effect is slave mode when SBC=0.
If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 25 AUTOEND: Automatic end mode (master mode)
This bit is set and cleared by software.
0: software end mode: TC flag is set when NBYTES data are transferred, stretching SCL low.
1: Automatic end mode: a STOP condition is automatically sent when NBYTES data are
transferred.
Note: This bit has no effect in slave mode or when the RELOAD bit is set.
Bit 24 RELOAD: NBYTES reload mode
This bit is set and cleared by software.
0: The transfer is completed after the NBYTES data transfer (STOP or RESTART will follow).
1: The transfer is not completed after the NBYTES data transfer (NBYTES will be reloaded).
TCR flag is set when NBYTES data are transferred, stretching SCL low.
Bits 23:16 NBYTES[7:0]: Number of bytes
The number of bytes to be transmitted/received is programmed there. This field is don’t care in
slave mode with SBC=0.
Note: Changing these bits when the START bit is set is not allowed.

RM0385 Rev 7

1007/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Bit 15 NACK: NACK generation (slave mode)
The bit is set by software, cleared by hardware when the NACK is sent, or when a STOP
condition or an Address matched is received, or when PE=0.
0: an ACK is sent after current received byte.
1: a NACK is sent after current received byte.
Note: Writing ‘0’ to this bit has no effect.
This bit is used in slave mode only: in master receiver mode, NACK is automatically
generated after last byte preceding STOP or RESTART condition, whatever the NACK
bit value.
When an overrun occurs in slave receiver NOSTRETCH mode, a NACK is
automatically generated whatever the NACK bit value.
When hardware PEC checking is enabled (PECBYTE=1), the PEC acknowledge value
does not depend on the NACK value.
Bit 14 STOP: Stop generation (master mode)
The bit is set by software, cleared by hardware when a Stop condition is detected, or when PE
= 0.
In Master Mode:
0: No Stop generation.
1: Stop generation after current byte transfer.
Note: Writing ‘0’ to this bit has no effect.
Bit 13 START: Start generation
This bit is set by software, and cleared by hardware after the Start followed by the address
sequence is sent, by an arbitration loss, by a timeout error detection, or when PE = 0. It can
also be cleared by software by writing ‘1’ to the ADDRCF bit in the I2C_ICR register.
0: No Start generation.
1: Restart/Start generation:
– If the I2C is already in master mode with AUTOEND = 0, setting this bit generates a
Repeated Start condition when RELOAD=0, after the end of the NBYTES transfer.
– Otherwise setting this bit will generate a START condition once the bus is free.
Note: Writing ‘0’ to this bit has no effect.
The START bit can be set even if the bus is BUSY or I2C is in slave mode.
This bit has no effect when RELOAD is set. In 10-bit addressing mode, if a NACK is
received on the first part of the address, the START bit is not cleared by hardware and
the master will resend the address sequence, unless the START bit is cleared by
software
Bit 12 HEAD10R: 10-bit address header only read direction (master receiver mode)
0: The master sends the complete 10 bit slave address read sequence: Start + 2 bytes 10bit
address in write direction + Restart + 1st 7 bits of the 10 bit address in read direction.
1: The master only sends the 1st 7 bits of the 10 bit address, followed by Read direction.
Note: Changing this bit when the START bit is set is not allowed.
Bit 11 ADD10: 10-bit addressing mode (master mode)
0: The master operates in 7-bit addressing mode,
1: The master operates in 10-bit addressing mode
Note: Changing this bit when the START bit is set is not allowed.
Bit 10 RD_WRN: Transfer direction (master mode)
0: Master requests a write transfer.
1: Master requests a read transfer.
Note: Changing this bit when the START bit is set is not allowed.

1008/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

Bits 9:8 SADD[9:8]: Slave address bit 9:8 (master mode)
In 7-bit addressing mode (ADD10 = 0):
These bits are don’t care
In 10-bit addressing mode (ADD10 = 1):
These bits should be written with bits 9:8 of the slave address to be sent
Note: Changing these bits when the START bit is set is not allowed.
Bits 7:1 SADD[7:1]: Slave address bit 7:1 (master mode)
In 7-bit addressing mode (ADD10 = 0):
These bits should be written with the 7-bit slave address to be sent
In 10-bit addressing mode (ADD10 = 1):
These bits should be written with bits 7:1 of the slave address to be sent.
Note: Changing these bits when the START bit is set is not allowed.
Bit 0 SADD0: Slave address bit 0 (master mode)
In 7-bit addressing mode (ADD10 = 0):
This bit is don’t care
In 10-bit addressing mode (ADD10 = 1):
This bit should be written with bit 0 of the slave address to be sent
Note: Changing these bits when the START bit is set is not allowed.

RM0385 Rev 7

1009/1709
1020

Inter-integrated circuit (I2C) interface

30.7.3

RM0385

Own address 1 register (I2C_OAR1)
Address offset: 0x08
Reset value: 0x0000 0000
Access: No wait states, except if a write access occurs while a write access to this register is
ongoing. In this case, wait states are inserted in the second write access until the previous
one is completed. The latency of the second write access can be up to 2 x PCLK1 + 6 x
I2CCLK.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OA1EN

Res.

Res.

Res.

Res.

OA1
MODE

rw

rw

OA1[9:8]
rw

rw

OA1[7:1]
rw

rw

rw

rw

OA1[0]
rw

Bits 31:16 Reserved, must be kept at reset value.
Bit 15 OA1EN: Own Address 1 enable
0: Own address 1 disabled. The received slave address OA1 is NACKed.
1: Own address 1 enabled. The received slave address OA1 is ACKed.
Bits 14:11 Reserved, must be kept at reset value.
Bit 10 OA1MODE: Own Address 1 10-bit mode
0: Own address 1 is a 7-bit address.
1: Own address 1 is a 10-bit address.
Note: This bit can be written only when OA1EN=0.
Bits 9:8 OA1[9:8]: Interface address
7-bit addressing mode: do not care
10-bit addressing mode: bits 9:8 of address
Note: These bits can be written only when OA1EN=0.
Bits 7:1 OA1[7:1]: Interface address
7-bit addressing mode: 7-bit address
10-bit addressing mode: bits 7:1 of 10-bit address
Note: These bits can be written only when OA1EN=0.
Bit 0 OA1[0]: Interface address
7-bit addressing mode: do not care
10-bit addressing mode: bit 0 of address
Note: This bit can be written only when OA1EN=0.

1010/1709

RM0385 Rev 7

rw

rw

rw

RM0385

Inter-integrated circuit (I2C) interface

30.7.4

Own address 2 register (I2C_OAR2)
Address offset: 0x0C
Reset value: 0x0000 0000
Access: No wait states, except if a write access occurs while a write access to this register is
ongoing. In this case, wait states are inserted in the second write access until the previous
one is completed. The latency of the second write access can be up to 2 x PCLK1 + 6 x
I2CCLK.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OA2EN

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

rw

OA2MSK[2:0]
rw

rw

OA2[7:1]
rw

Res.

Bits 31:16 Reserved, must be kept at reset value.
Bit 15 OA2EN: Own Address 2 enable
0: Own address 2 disabled. The received slave address OA2 is NACKed.
1: Own address 2 enabled. The received slave address OA2 is ACKed.
Bits 14:11 Reserved, must be kept at reset value.
Bits 10:8 OA2MSK[2:0]: Own Address 2 masks
000: No mask
001: OA2[1] is masked and don’t care. Only OA2[7:2] are compared.
010: OA2[2:1] are masked and don’t care. Only OA2[7:3] are compared.
011: OA2[3:1] are masked and don’t care. Only OA2[7:4] are compared.
100: OA2[4:1] are masked and don’t care. Only OA2[7:5] are compared.
101: OA2[5:1] are masked and don’t care. Only OA2[7:6] are compared.
110: OA2[6:1] are masked and don’t care. Only OA2[7] is compared.
111: OA2[7:1] are masked and don’t care. No comparison is done, and all (except reserved)
7-bit received addresses are acknowledged.
Note: These bits can be written only when OA2EN=0.
As soon as OA2MSK is not equal to 0, the reserved I2C addresses (0b0000xxx and
0b1111xxx) are not acknowledged even if the comparison matches.
Bits 7:1 OA2[7:1]: Interface address
7-bit addressing mode: 7-bit address
Note: These bits can be written only when OA2EN=0.
Bit 0 Reserved, must be kept at reset value.

RM0385 Rev 7

1011/1709
1020

Inter-integrated circuit (I2C) interface

30.7.5

RM0385

Timing register (I2C_TIMINGR)
Address offset: 0x10
Reset value: 0x0000 0000
Access: No wait states

31

30

29

28

PRESC[3:0]
rw

rw

rw

rw

15

14

13

12

rw

rw

rw

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

19

SCLDEL[3:0]

SCLH[7:0]
rw

20

18

17

16

SDADEL[3:0]

SCLL[7:0]
rw

Bits 31:28 PRESC[3:0]: Timing prescaler
This field is used to prescale I2CCLK in order to generate the clock period tPRESC used for data
setup and hold counters (refer to I2C timings on page 959) and for SCL high and low level
counters (refer to I2C master initialization on page 974).
tPRESC = (PRESC+1) x tI2CCLK
Bits 27:24 Reserved, must be kept at reset value.
Bits 23:20 SCLDEL[3:0]: Data setup time
This field is used to generate a delay tSCLDEL between SDA edge and SCL rising edge. In
master mode and in slave mode with NOSTRETCH = 0, the SCL line is stretched low during
tSCLDEL.
tSCLDEL = (SCLDEL+1) x tPRESC
Note: tSCLDEL is used to generate tSU:DAT timing.
Bits 19:16 SDADEL[3:0]: Data hold time
This field is used to generate the delay tSDADEL between SCL falling edge and SDA edge. In
master mode and in slave mode with NOSTRETCH = 0, the SCL line is stretched low during
tSDADEL.
tSDADEL= SDADEL x tPRESC
Note: SDADEL is used to generate tHD:DAT timing.
Bits 15:8 SCLH[7:0]: SCL high period (master mode)
This field is used to generate the SCL high period in master mode.
tSCLH = (SCLH+1) x tPRESC
Note: SCLH is also used to generate tSU:STO and tHD:STA timing.
Bits 7:0 SCLL[7:0]: SCL low period (master mode)
This field is used to generate the SCL low period in master mode.
tSCLL = (SCLL+1) x tPRESC
Note: SCLL is also used to generate tBUF and tSU:STA timings.

Note:

This register must be configured when the I2C is disabled (PE = 0).

Note:

The STM32CubeMX tool calculates and provides the I2C_TIMINGR content in the I2C
Configuration window.

1012/1709

RM0385 Rev 7

RM0385

30.7.6

Inter-integrated circuit (I2C) interface

Timeout register (I2C_TIMEOUTR)
Address offset: 0x14
Reset value: 0x0000 0000
Access: No wait states, except if a write access occurs while a write access to this register is
ongoing. In this case, wait states are inserted in the second write access until the previous
one is completed. The latency of the second write access can be up to 2 x PCLK1 + 6 x
I2CCLK.

31

30

29

28

TEXTEN

Res.

Res.

Res.

rw
15

14

13

12

TIMOUTEN

Res.

Res.

TIDLE

rw

rw

27

26

25

24

23

22

21

20

19

18

17

16

TIMEOUTB[11:0]
rw

rw

rw

rw

rw

11

10

9

8

7

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

TIMEOUTA[11:0]
rw

rw

rw

rw

rw

rw

rw

Bit 31 TEXTEN: Extended clock timeout enable
0: Extended clock timeout detection is disabled
1: Extended clock timeout detection is enabled. When a cumulative SCL stretch for more
than tLOW:EXT is done by the I2C interface, a timeout error is detected (TIMEOUT=1).
Bits 30:28 Reserved, must be kept at reset value.
Bits 27:16 TIMEOUTB[11:0]: Bus timeout B
This field is used to configure the cumulative clock extension timeout:
In master mode, the master cumulative clock low extend time (tLOW:MEXT) is detected
In slave mode, the slave cumulative clock low extend time (tLOW:SEXT) is detected
tLOW:EXT= (TIMEOUTB+1) x 2048 x tI2CCLK
Note: These bits can be written only when TEXTEN=0.
Bit 15 TIMOUTEN: Clock timeout enable
0: SCL timeout detection is disabled
1: SCL timeout detection is enabled: when SCL is low for more than tTIMEOUT (TIDLE=0) or
high for more than tIDLE (TIDLE=1), a timeout error is detected (TIMEOUT=1).
Bits 14:13 Reserved, must be kept at reset value.
Bit 12 TIDLE: Idle clock timeout detection
0: TIMEOUTA is used to detect SCL low timeout
1: TIMEOUTA is used to detect both SCL and SDA high timeout (bus idle condition)
Note: This bit can be written only when TIMOUTEN=0.
Bits 11:0 TIMEOUTA[11:0]: Bus Timeout A
This field is used to configure:
– The SCL low timeout condition tTIMEOUT when TIDLE=0
tTIMEOUT= (TIMEOUTA+1) x 2048 x tI2CCLK
– The bus idle condition (both SCL and SDA high) when TIDLE=1
tIDLE= (TIMEOUTA+1) x 4 x tI2CCLK
Note: These bits can be written only when TIMOUTEN=0.

Note:

If the SMBus feature is not supported, this register is reserved and forced by hardware to
“0x00000000”. Refer to Section 30.3: I2C implementation.

RM0385 Rev 7

1013/1709
1020

Inter-integrated circuit (I2C) interface

30.7.7

RM0385

Interrupt and status register (I2C_ISR)
Address offset: 0x18
Reset value: 0x0000 0001
Access: No wait states

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

BUSY

Res.

ALERT

TIME
OUT

PEC
ERR

OVR

ARLO

BERR

TCR

TC

ADDR

RXNE

TXIS

TXE

r

r

r

r

r

r

r

r

r

r

rs

rs

r

23

22

21

20

19

18

17

ADDCODE[6:0]

STOPF NACKF
r

r

16
DIR

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:17 ADDCODE[6:0]: Address match code (Slave mode)
These bits are updated with the received address when an address match event occurs
(ADDR = 1).
In the case of a 10-bit address, ADDCODE provides the 10-bit header followed by the 2 MSBs
of the address.
Bit 16 DIR: Transfer direction (Slave mode)
This flag is updated when an address match event occurs (ADDR=1).
0: Write transfer, slave enters receiver mode.
1: Read transfer, slave enters transmitter mode.
Bit 15 BUSY: Bus busy
This flag indicates that a communication is in progress on the bus. It is set by hardware when a
START condition is detected. It is cleared by hardware when a Stop condition is detected, or
when PE=0.
Bit 14 Reserved, must be kept at reset value.
Bit 13 ALERT: SMBus alert
This flag is set by hardware when SMBHEN=1 (SMBus host configuration), ALERTEN=1 and
a SMBALERT event (falling edge) is detected on SMBA pin. It is cleared by software by setting
the ALERTCF bit.
Note: This bit is cleared by hardware when PE=0.
If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 12 TIMEOUT: Timeout or tLOW detection flag
This flag is set by hardware when a timeout or extended clock timeout occurred. It is cleared
by software by setting the TIMEOUTCF bit.
Note: This bit is cleared by hardware when PE=0.
If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.

1014/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

Bit 11 PECERR: PEC Error in reception
This flag is set by hardware when the received PEC does not match with the PEC register
content. A NACK is automatically sent after the wrong PEC reception. It is cleared by software
by setting the PECCF bit.
Note: This bit is cleared by hardware when PE=0.
If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 10 OVR: Overrun/Underrun (slave mode)
This flag is set by hardware in slave mode with NOSTRETCH=1, when an overrun/underrun
error occurs. It is cleared by software by setting the OVRCF bit.
Note: This bit is cleared by hardware when PE=0.
Bit 9 ARLO: Arbitration lost
This flag is set by hardware in case of arbitration loss. It is cleared by software by setting the
ARLOCF bit.
Note: This bit is cleared by hardware when PE=0.
Bit 8 BERR: Bus error
This flag is set by hardware when a misplaced Start or Stop condition is detected whereas the
peripheral is involved in the transfer. The flag is not set during the address phase in slave
mode. It is cleared by software by setting BERRCF bit.
Note: This bit is cleared by hardware when PE=0.
Bit 7 TCR: Transfer Complete Reload
This flag is set by hardware when RELOAD=1 and NBYTES data have been transferred. It is
cleared by software when NBYTES is written to a non-zero value.
Note: This bit is cleared by hardware when PE=0.
This flag is only for master mode, or for slave mode when the SBC bit is set.
Bit 6 TC: Transfer Complete (master mode)
This flag is set by hardware when RELOAD=0, AUTOEND=0 and NBYTES data have been
transferred. It is cleared by software when START bit or STOP bit is set.
Note: This bit is cleared by hardware when PE=0.
Bit 5 STOPF: Stop detection flag
This flag is set by hardware when a Stop condition is detected on the bus and the peripheral is
involved in this transfer:
– either as a master, provided that the STOP condition is generated by the peripheral.
– or as a slave, provided that the peripheral has been addressed previously during this
transfer.
It is cleared by software by setting the STOPCF bit.
Note: This bit is cleared by hardware when PE=0.
Bit 4 NACKF: Not Acknowledge received flag
This flag is set by hardware when a NACK is received after a byte transmission. It is cleared by
software by setting the NACKCF bit.
Note: This bit is cleared by hardware when PE=0.
Bit 3 ADDR: Address matched (slave mode)
This bit is set by hardware as soon as the received slave address matched with one of the
enabled slave addresses. It is cleared by software by setting ADDRCF bit.
Note: This bit is cleared by hardware when PE=0.

RM0385 Rev 7

1015/1709
1020

Inter-integrated circuit (I2C) interface

RM0385

Bit 2 RXNE: Receive data register not empty (receivers)
This bit is set by hardware when the received data is copied into the I2C_RXDR register, and is
ready to be read. It is cleared when I2C_RXDR is read.
Note: This bit is cleared by hardware when PE=0.
Bit 1 TXIS: Transmit interrupt status (transmitters)
This bit is set by hardware when the I2C_TXDR register is empty and the data to be
transmitted must be written in the I2C_TXDR register. It is cleared when the next data to be
sent is written in the I2C_TXDR register.
This bit can be written to ‘1’ by software when NOSTRETCH=1 only, in order to generate a
TXIS event (interrupt if TXIE=1 or DMA request if TXDMAEN=1).
Note: This bit is cleared by hardware when PE=0.
Bit 0 TXE: Transmit data register empty (transmitters)
This bit is set by hardware when the I2C_TXDR register is empty. It is cleared when the next
data to be sent is written in the I2C_TXDR register.
This bit can be written to ‘1’ by software in order to flush the transmit data register I2C_TXDR.
Note: This bit is set by hardware when PE=0.

30.7.8

Interrupt clear register (I2C_ICR)
Address offset: 0x1C
Reset value: 0x0000 0000
Access: No wait states

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

ARLO
CF

BERR
CF

Res.

Res.

STOP
CF

NACK
CF

ADDR
CF

Res.

Res.

Res.

w

w

w

w

w

ALERT
TIM
PECCF OVRCF
CF
OUTCF
w

w

w

w

Bits 31:14 Reserved, must be kept at reset value.
Bit 13 ALERTCF: Alert flag clear
Writing 1 to this bit clears the ALERT flag in the I2C_ISR register.
Note: If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 12 TIMOUTCF: Timeout detection flag clear
Writing 1 to this bit clears the TIMEOUT flag in the I2C_ISR register.
Note: If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 11 PECCF: PEC Error flag clear
Writing 1 to this bit clears the PECERR flag in the I2C_ISR register.
Note: If the SMBus feature is not supported, this bit is reserved and forced by hardware to ‘0’.
Refer to Section 30.3: I2C implementation.
Bit 10 OVRCF: Overrun/Underrun flag clear
Writing 1 to this bit clears the OVR flag in the I2C_ISR register.

1016/1709

RM0385 Rev 7

RM0385

Inter-integrated circuit (I2C) interface

Bit 9 ARLOCF: Arbitration Lost flag clear
Writing 1 to this bit clears the ARLO flag in the I2C_ISR register.
Bit 8 BERRCF: Bus error flag clear
Writing 1 to this bit clears the BERRF flag in the I2C_ISR register.
Bits 7:6 Reserved, must be kept at reset value.
Bit 5 STOPCF: Stop detection flag clear
Writing 1 to this bit clears the STOPF flag in the I2C_ISR register.
Bit 4 NACKCF: Not Acknowledge flag clear
Writing 1 to this bit clears the NACKF flag in I2C_ISR register.
Bit 3 ADDRCF: Address matched flag clear
Writing 1 to this bit clears the ADDR flag in the I2C_ISR register. Writing 1 to this bit also clears
the START bit in the I2C_CR2 register.
Bits 2:0 Reserved, must be kept at reset value.

30.7.9

PEC register (I2C_PECR)
Address offset: 0x20
Reset value: 0x0000 0000
Access: No wait states

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

r

r

PEC[7:0]
r

r

r

r

r

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 PEC[7:0] Packet error checking register
This field contains the internal PEC when PECEN=1.
The PEC is cleared by hardware when PE=0.

Note:

If the SMBus feature is not supported, this register is reserved and forced by hardware to
“0x00000000”. Refer to Section 30.3: I2C implementation.

RM0385 Rev 7

1017/1709
1020

Inter-integrated circuit (I2C) interface

30.7.10

RM0385

Receive data register (I2C_RXDR)
Address offset: 0x24
Reset value: 0x0000 0000
Access: No wait states

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
r

r

r

r

r

r

r

r

RXDATA[7:0]

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 RXDATA[7:0] 8-bit receive data
Data byte received from the I2C bus.

30.7.11

Transmit data register (I2C_TXDR)
Address offset: 0x28
Reset value: 0x0000 0000
Access: No wait states

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

TXDATA[7:0]

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 TXDATA[7:0] 8-bit transmit data
Data byte to be transmitted to the I2C bus.
Note: These bits can be written only when TXE=1.

1018/1709

RM0385 Rev 7

rw

rw

0x24

I2C_RXDR

Reset value

RM0385 Rev 7
ARLO
BERR
TCR
TC
STOPF
NACKF
ADDR
RXNE
TXIS
TXE

0
0
0
0
0
0
0
0
0
0
0
0
1

Res.

Res.

STOPCF

NACKCF

ADDRCF

0

0

0

PECCF

OVRCF

ARLOCF

BERRCF

0

0

0

0

0

0

Res.

Res.

Res.
Res.
Res.
Res.

ADD10
RD_WRN

Res.
Res.

Res.

0

OA1MODE

STOP
START

Res.

HEAD10R

NACK

Res.
OA1EN

0

0
0

0
0

0

0

0

0

SMBDEN
SMBHEN
GCEN

TXDMAEN
ANFOFF

Res.

SBC
RXDMAEN

NOSTRETCH

Res

ALERTEN

Res.

Res.

Res.

Res.

Res.

PECEN

0

0

0

0

Reset value
0

0

0

0

0

0

0
0

SADD[9:0]

0

0

0

0

0

0

SCLH[7:0]

0

0

0

0

OA1[9:0]

0
0

OA2[7:1]
0
0

0

0

0

0

0

0
0
0

0
0
0
0

0
0
0
0

0
0

0

0

Res.

PE

0

TXIE

NACKIE
ADDRIE

0

RXIE

TCIE

0

STOPIE

ERRIE

0

PEC[7:0]

RXDATA[7:0]

Res.

Res.

0

0

Res.

0

DNF[3:0]

Res.

Res.

0

Res.

Res.

0

0

Res.

OVR

0

Res.

0

Res.

Res.

0

0

Res.

PECERR

0

Res.

0

TIDLE

Res.

Res.

Res.

0

Res.

0

0

Res.

TIMEOUT

0

TIMOUTCF

ADDCODE[6:0]
0

Res.

0
0

Res.

0

Res.

Reset value

Res.
ALERT

0

Res.

0

0

ALERTCF

0

Res.

0

0

Res.

OA2EN

0

Res.

TIMEOUTB[11:0]
TIMOUTEN

0

0

Res.

0

Res.

0

Res.

DIR
BUSY

0

Res.

RELOAD

0
NBYTES[7:0]

Res.

0
Res.

AUTOEND

0

Res.

0
0

0

Res.

0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PECBYTE

0

Res.

Res.

Res.

0

Res.

0

Res.

OA2MS
K [2:0]

Res.

Res.

Res.

Res.

0

Res.

I2C_OAR2
Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

0
0

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

SDADEL[3:
0]

0

Res.

Res.
0

Res.

Reset value
0

Res.

Res.

0

Res.

Res.

0

Res.

Reset value
SCLDEL[3:0
]

0

Res.

0

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

I2C_ISR

Res.

Res.

0

Res.

Res.

Reset value

Res.

I2C_
TIMEOUTR

Res.

0

Res.

0

Res.

Res.

PRESC[3:0]

Res.

I2C_PECR
Res.

Reset value

Res.

0x20

Res.

0x10

Res.

I2C_ICR

Res.

0x1C

Res.

I2C_TIMINGR

Res.

0xC
Reset value

Res.

I2C_OAR1

Res.

0x8

Res.

0

Res.

I2C_CR2

Res.

0

TEXTEN

0x18
Reset value

Res.

0x4

Res.

I2C_CR1

Res.

0x0

Res.

0x14

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

Offset

Res.

30.7.12

Res.

RM0385
Inter-integrated circuit (I2C) interface

I2C register map

The table below provides the I2C register map and reset values.
Table 189. I2C register map and reset values

SCLL[7:0]
0
0
0
0

TIMEOUTA[11:0]

0
0
0
0
0
0
0
0
0
0
0
0
0

0

0

0

0

0

0

1019/1709

1020

Inter-integrated circuit (I2C) interface

RM0385

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

I2C_TXDR
0x28

Res.

Register
name

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 189. I2C register map and reset values (continued)

Reset value

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

1020/1709

TXDATA[7:0]

RM0385 Rev 7

0

0

0

0

0

0

0

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

31

Universal synchronous asynchronous receiver
transmitter (USART)

31.1

Introduction
The universal synchronous asynchronous receiver transmitter (USART) offers a flexible
means of Full-duplex data exchange with external equipment requiring an industry standard
NRZ asynchronous serial data format. The USART offers a very wide range of baud rates
using a programmable baud rate generator.
It supports synchronous one-way communication and Half-duplex Single-wire
communication, as well as multiprocessor communications. It also supports the LIN (Local
Interconnect Network), Smartcard protocol and IrDA (Infrared Data Association) SIR
ENDEC specifications and Modem operations (CTS/RTS).
High speed data communication is possible by using the DMA (direct memory access) for
multibuffer configuration.

31.2

USART main features
•

Full-duplex asynchronous communications

•

NRZ standard format (mark/space)

•

Configurable oversampling method by 16 or 8 to give flexibility between speed and
clock tolerance

•

A common programmable transmit and receive baud rate of up to 27 Mbit/s when
USART clock source is the system clock frequency (Max is 216 MHz) and the
oversampling by 8 is used

•

Dual clock domain allowing:
–

Convenient baud rate programming independent from the PCLK reprogramming

•

Auto baud rate detection

•

Programmable data word length (7, 8 or 9 bits)

•

Programmable data order with MSB-first or LSB-first shifting

•

Configurable stop bits (1 or 2 stop bits)

•

Synchronous mode and clock output for synchronous communications

•

Single-wire Half-duplex communications

•

Continuous communications using DMA

•

Received/transmitted bytes are buffered in reserved SRAM using centralized DMA

•

Separate enable bits for transmitter and receiver

•

Separate signal polarity control for transmission and reception

•

Swappable Tx/Rx pin configuration

•

Hardware flow control for modem and RS-485 transceiver

RM0385 Rev 7

1021/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)
•

Communication control/error detection flags

•

Parity control:
–

Transmits parity bit

–

Checks parity of received data byte

•

Fourteen interrupt sources with flags

•

Multiprocessor communications

RM0385

The USART enters mute mode if the address does not match.
•

31.3

Wakeup from mute mode (by idle line detection or address mark detection)

USART extended features
•

LIN master synchronous break send capability and LIN slave break detection capability
–

•

IrDA SIR encoder decoder supporting 3/16 bit duration for normal mode

•

Smartcard mode

•

1022/1709

13-bit break generation and 10/11-bit break detection when USART is hardware
configured for LIN

–

Supports the T=0 and T=1 asynchronous protocols for smartcards as defined in
the ISO/IEC 7816-3 standard

–

0.5 and 1.5 stop bits for smartcard operation

Support for ModBus communication
–

Timeout feature

–

CR/LF character recognition

RM0385 Rev 7

RM0385

31.4

Universal synchronous asynchronous receiver transmitter (USART)

USART implementation
Table 190. STM32F75xxx and STM32F74xxx USART features
USART1/USART2/
USART3/USART6

UART4/UART5/

Hardware flow control for modem

X

X

Continuous communication using DMA

X

X

Multiprocessor communication

X

X

Synchronous mode

X

-

Smartcard mode

X

-

Single-wire Half-duplex communication

X

X

IrDA SIR ENDEC block

X

X

LIN mode

X

X

Dual clock domain

X

X

Receiver timeout interrupt

X

X

Modbus communication

X

X

Auto baud rate detection

X

X

Driver Enable

X

USART modes/features(1)

X
(2),

USART data length

UART7/UART8

7

8 and 9 bits

1. X = supported.
2. In 7-bit data length mode, Smartcard mode, LIN master mode and Auto baud rate (0x7F and 0x55 frames)
detection are not supported.

31.5

USART functional description
Any USART bidirectional communication requires a minimum of two pins: Receive data In
(RX) and Transmit data Out (TX):
•

RX: Receive data Input.
This is the serial data input. Oversampling techniques are used for data recovery by
discriminating between valid incoming data and noise.

•

TX: Transmit data Output.
When the transmitter is disabled, the output pin returns to its I/O port configuration.
When the transmitter is enabled and nothing is to be transmitted, the TX pin is at high
level. In Single-wire and Smartcard modes, this I/O is used to transmit and receive the
data.

RM0385 Rev 7

1023/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Serial data are transmitted and received through these pins in normal USART mode. The
frames are comprised of:
•

An Idle Line prior to transmission or reception

•

A start bit

•

A data word (7, 8 or 9 bits) least significant bit first

•

0.5, 1, 1.5, 2 stop bits indicating that the frame is complete

•

The USART interface uses a baud rate generator

•

A status register (USART_ISR)

•

Receive and transmit data registers (USART_RDR, USART_TDR)

•

A baud rate register (USART_BRR)

•

A guard-time register (USART_GTPR) in case of Smartcard mode.

Refer to Section 31.8: USART registers on page 1064 for the definitions of each bit.
The following pin is required to interface in synchronous mode and Smartcard mode:
•

CK: Clock output. This pin outputs the transmitter data clock for synchronous
transmission corresponding to SPI master mode (no clock pulses on start bit and stop
bit, and a software option to send a clock pulse on the last data bit). In parallel, data
can be received synchronously on RX. This can be used to control peripherals that
have shift registers. The clock phase and polarity are software programmable. In
Smartcard mode, CK output can provide the clock to the smartcard.

The following pins are required in RS232 Hardware flow control mode:
•

CTS: Clear To Send blocks the data transmission at the end of the current transfer
when high

•

RTS: Request to send indicates that the USART is ready to receive data (when low).

The following pin is required in RS485 Hardware control mode:
•
Note:

1024/1709

DE: Driver Enable activates the transmission mode of the external transceiver.

DE and RTS share the same pin.

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 334. USART block diagram
PWDATA

PRDATA
Write

Read

(CPU or DMA)

TX
RX

IrDA
SIR
ENDEC
block

DR (data register)

(CPU or DMA)

Transmit data register
(TDR)
Transmit shift register

Receive data register
(RDR)
Receive shift register

USART_GTPR register

GT

PSC

USART_CR3 register
USART_CR2 register
RTS/
DE
CTS

CK control

CK

USART_CR2 register
USART_CR1 register

Hardware
flow
controller
Transmit
control

Receiver
control

USART_CR1 register

Receiver
clock

USART_ISR register

USART
interrupt
control
USART_BRR register
TE

Transmitter
clock

/USARTDIV or 2/USARTDIV
(depending on the
oversampling mode)
(Note 1)

BRR[15:0]

RE
fCK

(Note 2)

Transmitter
rate controller

Receiver rate
controller

Conventional baud rate generator
MSv35479V2

1. For details on coding USARTDIV in the USART_BRR register, refer to Section 31.5.4: USART baud rate
generation.
2. fCK can be fLSE, fHSI, fPCLK, fSYS.

RM0385 Rev 7

1025/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

31.5.1

RM0385

USART character description
The word length can be selected as being either 7 or 8 or 9 bits by programming the M[1:0]
bits in the USART_CR1 register (see Figure 335).

Note:

•

7-bit character length: M[1:0] = 10

•

8-bit character length: M[1:0] = 00

•

9-bit character length: M[1:0] = 01

The 7-bit mode is supported only on some USARTs. In addition, not all modes are
supported in 7-bit data length mode. Refer to Section 31.4: USART implementation for
additional information.
By default, the signal (TX or RX) is in low state during the start bit. It is in high state during
the stop bit.
These values can be inverted, separately for each signal, through polarity configuration
control.
An Idle character is interpreted as an entire frame of “1”s (the number of “1”s includes the
number of stop bits).
A Break character is interpreted on receiving “0”s for a frame period. At the end of the
break frame, the transmitter inserts 2 stop bits.
Transmission and reception are driven by a common baud rate generator, the clock for each
is generated when the enable bit is set respectively for the transmitter and receiver.
The details of each block is given below.

1026/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 335. Word length programming
9-bit word length (M = 01 ), 1 Stop bit
Possible
Parity
bit

Data frame
Start
bit

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

Bit7

Clock

Bit8

Stop
bit

Next
Start
bit

**
Start
bit

Idle frame

Stop
bit

Stop
bit

Stop
bit

Stop
bit

Start
bit

Stop
bit

Start
bit

Break frame

Start
bit

8-bit word length (M = 00 ), 1 Stop bit
Possible
Parity
bit

Data frame
Start
bit

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

Bit7

Clock

Stop
bit

Next
Start
bit

**
Start
bit

Idle frame
Break frame

7-bit word length (M = 10 ), 1 Stop bit
Possible
Parity
bit

Data frame
Start
bit

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

Stop
bit

Next
Start
bit

**

Clock

Idle frame
Break frame

Start
bit
Stop
bit

** LBCL bit controls last data clock pulse
MS33194V2

RM0385 Rev 7

1027/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

31.5.2

RM0385

USART transmitter
The transmitter can send data words of either 7, 8 or 9 bits depending on the M bits status.
The Transmit Enable bit (TE) must be set in order to activate the transmitter function. The
data in the transmit shift register is output on the TX pin and the corresponding clock pulses
are output on the CK pin.

Character transmission
During an USART transmission, data shifts out least significant bit first (default
configuration) on the TX pin. In this mode, the USART_TDR register consists of a buffer
(TDR) between the internal bus and the transmit shift register (see Figure 334).
Every character is preceded by a start bit which is a logic level low for one bit period. The
character is terminated by a configurable number of stop bits.
The following stop bits are supported by USART: 0.5, 1, 1.5 and 2 stop bits.
Note:

The TE bit must be set before writing the data to be transmitted to the USART_TDR.
The TE bit should not be reset during transmission of data. Resetting the TE bit during the
transmission will corrupt the data on the TX pin as the baud rate counters will get frozen.
The current data being transmitted will be lost.
An idle frame will be sent after the TE bit is enabled.
Configurable stop bits
The number of stop bits to be transmitted with every character can be programmed in
Control register 2, bits 13,12.
•

1 stop bit: This is the default value of number of stop bits.

•

2 stop bits: This will be supported by normal USART, Single-wire and Modem modes.

•

1.5 stop bits: To be used in Smartcard mode.

•

0.5 stop bit: To be used when receiving data in Smartcard mode.

An idle frame transmission will include the stop bits.
A break transmission will be 10 low bits (when M[1:0] = 00) or 11 low bits (when M[1:0] = 01)
or 9 low bits (when M[1:0] = 10) followed by 2 stop bits (see Figure 336). It is not possible to
transmit long breaks (break of length greater than 9/10/11 low bits).

1028/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 336. Configurable stop bits
8-bit data, 1 Stop bit
Possible
parity bit

Data frame
Start bit

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

CLOCK

Bit7

Stop
bit

Next
start
bit

Next data frame

**
** LBCL bit controls last data clock pulse

8-bit data, 1 1/2 Stop bits
Possible
parity bit

Data frame
Start bit

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

Bit7

1.5
Stop
bits

Next
start
bit

Next data frame

8-bit data, 2 Stop bits
Possible
parity bit

Data frame
Start bit

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

Bit7

2
Stop
bits

Next
start
bit

Next data frame

MSv31887V1

Character transmission procedure
1.

Program the M bits in USART_CR1 to define the word length.

2.

Select the desired baud rate using the USART_BRR register.

3.

Program the number of stop bits in USART_CR2.

4.

Enable the USART by writing the UE bit in USART_CR1 register to 1.

5.

Select DMA enable (DMAT) in USART_CR3 if multibuffer communication is to take
place. Configure the DMA register as explained in multibuffer communication.

6.

Set the TE bit in USART_CR1 to send an idle frame as first transmission.

7.

Write the data to send in the USART_TDR register (this clears the TXE bit). Repeat this
for each data to be transmitted in case of single buffer.

8.

After writing the last data into the USART_TDR register, wait until TC=1. This indicates
that the transmission of the last frame is complete. This is required for instance when
the USART is disabled or enters the Halt mode to avoid corrupting the last
transmission.

Single byte communication
Clearing the TXE bit is always performed by a write to the transmit data register.
The TXE bit is set by hardware and it indicates:
•

The data has been moved from the USART_TDR register to the shift register and the
data transmission has started.

•

The USART_TDR register is empty.

•

The next data can be written in the USART_TDR register without overwriting the
previous data.

This flag generates an interrupt if the TXEIE bit is set.
When a transmission is taking place, a write instruction to the USART_TDR register stores
the data in the TDR register; next, the data is copied in the shift register at the end of the
currently ongoing transmission.

RM0385 Rev 7

1029/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

When no transmission is taking place, a write instruction to the USART_TDR register places
the data in the shift register, the data transmission starts, and the TXE bit is set.
If a frame is transmitted (after the stop bit) and the TXE bit is set, the TC bit goes high. An
interrupt is generated if the TCIE bit is set in the USART_CR1 register.
After writing the last data in the USART_TDR register, it is mandatory to wait for TC=1
before disabling the USART or causing the microcontroller to enter the low-power mode
(see Figure 337: TC/TXE behavior when transmitting).
Figure 337. TC/TXE behavior when transmitting

Break characters
Setting the SBKRQ bit transmits a break character. The break frame length depends on the
M bits (see Figure 335).
If a ‘1’ is written to the SBKRQ bit, a break character is sent on the TX line after completing
the current character transmission. The SBKF bit is set by the write operation and it is reset
by hardware when the break character is completed (during the stop bits after the break
character). The USART inserts a logic 1 signal (STOP) for the duration of 2 bits at the end of
the break frame to guarantee the recognition of the start bit of the next frame.
In the case the application needs to send the break character following all previously
inserted data, including the ones not yet transmitted, the software should wait for the TXE
flag assertion before setting the SBKRQ bit.

Idle characters
Setting the TE bit drives the USART to send an idle frame before the first data frame.

31.5.3

USART receiver
The USART can receive data words of either 7, 8 or 9 bits depending on the M bits in the
USART_CR1 register.

Start bit detection
The start bit detection sequence is the same when oversampling by 16 or by 8.

1030/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
In the USART, the start bit is detected when a specific sequence of samples is recognized.
This sequence is: 1 1 1 0 X 0 X 0X 0X 0 X 0X 0.
Figure 338. Start bit detection when oversampling by 16 or 8

Note:

If the sequence is not complete, the start bit detection aborts and the receiver returns to the
idle state (no flag is set), where it waits for a falling edge.
The start bit is confirmed (RXNE flag set, interrupt generated if RXNEIE=1) if the 3 sampled
bits are at 0 (first sampling on the 3rd, 5th and 7th bits finds the 3 bits at 0 and second
sampling on the 8th, 9th and 10th bits also finds the 3 bits at 0).
The start bit is validated (RXNE flag set, interrupt generated if RXNEIE=1) but the NF noise
flag is set if,
a)

for both samplings, 2 out of the 3 sampled bits are at 0 (sampling on the 3rd, 5th
and 7th bits and sampling on the 8th, 9th and 10th bits)

or
b)

for one of the samplings (sampling on the 3rd, 5th and 7th bits or sampling on the
8th, 9th and 10th bits), 2 out of the 3 bits are found at 0.

If neither conditions a. or b. are met, the start detection aborts and the receiver returns to the
idle state (no flag is set).

RM0385 Rev 7

1031/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Character reception
During an USART reception, data shifts in least significant bit first (default configuration)
through the RX pin. In this mode, the USART_RDR register consists of a buffer (RDR)
between the internal bus and the receive shift register.
Character reception procedure
1.

Program the M bits in USART_CR1 to define the word length.

2.

Select the desired baud rate using the baud rate register USART_BRR

3.

Program the number of stop bits in USART_CR2.

4.

Enable the USART by writing the UE bit in USART_CR1 register to 1.

5.

Select DMA enable (DMAR) in USART_CR3 if multibuffer communication is to take
place. Configure the DMA register as explained in multibuffer communication.

6.

Set the RE bit USART_CR1. This enables the receiver which begins searching for a
start bit.

When a character is received:
•

The RXNE bit is set to indicate that the content of the shift register is transferred to the
RDR. In other words, data has been received and can be read (as well as its
associated error flags).

•

An interrupt is generated if the RXNEIE bit is set.

•

The error flags can be set if a frame error, noise or an overrun error has been detected
during reception. PE flag can also be set with RXNE.

•

In multibuffer, RXNE is set after every byte received and is cleared by the DMA read of
the Receive data Register.

•

In single buffer mode, clearing the RXNE bit is performed by a software read to the
USART_RDR register. The RXNE flag can also be cleared by writing 1 to the RXFRQ
in the USART_RQR register. The RXNE bit must be cleared before the end of the
reception of the next character to avoid an overrun error.

Break character
When a break character is received, the USART handles it as a framing error.

Idle character
When an idle frame is detected, there is the same procedure as for a received data
character plus an interrupt if the IDLEIE bit is set.

1032/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Overrun error
An overrun error occurs when a character is received when RXNE has not been reset. Data
can not be transferred from the shift register to the RDR register until the RXNE bit is
cleared.
The RXNE flag is set after every byte received. An overrun error occurs if RXNE flag is set
when the next data is received or the previous DMA request has not been serviced. When
an overrun error occurs:

Note:

•

The ORE bit is set.

•

The RDR content will not be lost. The previous data is available when a read to
USART_RDR is performed.

•

The shift register will be overwritten. After that point, any data received during overrun
is lost.

•

An interrupt is generated if either the RXNEIE bit is set or EIE bit is set.

•

The ORE bit is reset by setting the ORECF bit in the ICR register.

The ORE bit, when set, indicates that at least 1 data has been lost. There are two
possibilities:
- if RXNE=1, then the last valid data is stored in the receive register RDR and can be read,
- if RXNE=0, then it means that the last valid data has already been read and thus there is
nothing to be read in the RDR. This case can occur when the last valid data is read in the
RDR at the same time as the new (and lost) data is received.

Selecting the clock source and the proper oversampling method
The choice of the clock source is done through the Clock Control system (see Section Reset
and clock control (RCC))). The clock source must be chosen before enabling the USART
(by setting the UE bit).
The clock source frequency is fCK.
When the dual clock domain is supported, the clock source can be one of the following
sources: PCLK (default), LSE, HSI or SYSCLK.
The communication speed range (specially the maximum communication speed) is also
determined by the clock source.
The receiver implements different user-configurable oversampling techniques for data
recovery by discriminating between valid incoming data and noise. This allows a trade-off
between the maximum communication speed and noise/clock inaccuracy immunity.
The oversampling method can be selected by programming the OVER8 bit in the
USART_CR1 register and can be either 16 or 8 times the baud rate clock (Figure 339 and
Figure 340).
Depending on the application:
•

Select oversampling by 8 (OVER8=1) to achieve higher speed (up to fCK/8). In this
case the maximum receiver tolerance to clock deviation is reduced (refer to
Section 31.5.5: Tolerance of the USART receiver to clock deviation on page 1039)

•

Select oversampling by 16 (OVER8=0) to increase the tolerance of the receiver to
clock deviations. In this case, the maximum speed is limited to maximum fCK/16 where
fCK is the clock source frequency.

RM0385 Rev 7

1033/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Programming the ONEBIT bit in the USART_CR3 register selects the method used to
evaluate the logic level. There are two options:
•

The majority vote of the three samples in the center of the received bit. In this case,
when the 3 samples used for the majority vote are not equal, the NF bit is set

•

A single sample in the center of the received bit
Depending on the application:
–

select the three samples’ majority vote method (ONEBIT=0) when operating in a
noisy environment and reject the data when a noise is detected (refer to
Figure 191) because this indicates that a glitch occurred during the sampling.

–

select the single sample method (ONEBIT=1) when the line is noise-free to
increase the receiver’s tolerance to clock deviations (see Section 31.5.5:
Tolerance of the USART receiver to clock deviation on page 1039). In this case
the NF bit will never be set.

When noise is detected in a frame:
•

The NF bit is set at the rising edge of the RXNE bit.

•

The invalid data is transferred from the Shift register to the USART_RDR register.

•

No interrupt is generated in case of single byte communication. However this bit rises
at the same time as the RXNE bit which itself generates an interrupt. In case of
multibuffer communication an interrupt will be issued if the EIE bit is set in the
USART_CR3 register.

The NF bit is reset by setting NFCF bit in ICR register.
Note:

Oversampling by 8 is not available in LIN, Smartcard and IrDA modes. In those modes, the
OVER8 bit is forced to ‘0’ by hardware.
Figure 339. Data sampling when oversampling by 16

RX line
sampled values
Sample clock

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

6/16
7/16

7/16
One bit time

MSv31152V1

1034/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 340. Data sampling when oversampling by 8

RX line
sampled values
Sample
clock (x8)

1

2

3

4

5

6

7

8

2/8
3/8

3/8
One bit time

MSv31153V1

Table 191. Noise detection from sampled data
Sampled value

NE status

Received bit value

000

0

0

001

1

0

010

1

0

011

1

1

100

1

0

101

1

1

110

1

1

111

0

1

Framing error
A framing error is detected when the stop bit is not recognized on reception at the expected
time, following either a de-synchronization or excessive noise.
When the framing error is detected:
•

The FE bit is set by hardware

•

The invalid data is transferred from the Shift register to the USART_RDR register.

•

No interrupt is generated in case of single byte communication. However this bit rises
at the same time as the RXNE bit which itself generates an interrupt. In case of
multibuffer communication an interrupt will be issued if the EIE bit is set in the
USART_CR3 register.

The FE bit is reset by writing 1 to the FECF in the USART_ICR register.

RM0385 Rev 7

1035/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Configurable stop bits during reception
The number of stop bits to be received can be configured through the control bits of Control
Register 2 - it can be either 1 or 2 in normal mode and 0.5 or 1.5 in Smartcard mode.

31.5.4

•

0.5 stop bit (reception in Smartcard mode): No sampling is done for 0.5 stop bit. As
a consequence, no framing error and no break frame can be detected when 0.5 stop bit
is selected.

•

1 stop bit: Sampling for 1 stop Bit is done on the 8th, 9th and 10th samples.

•

1.5 stop bits (Smartcard mode): When transmitting in Smartcard mode, the device
must check that the data is correctly sent. Thus the receiver block must be enabled (RE
=1 in the USART_CR1 register) and the stop bit is checked to test if the smartcard has
detected a parity error. In the event of a parity error, the smartcard forces the data
signal low during the sampling - NACK signal-, which is flagged as a framing error.
Then, the FE flag is set with the RXNE at the end of the 1.5 stop bits. Sampling for 1.5
stop bits is done on the 16th, 17th and 18th samples (1 baud clock period after the
beginning of the stop bit). The 1.5 stop bits can be decomposed into 2 parts: one 0.5
baud clock period during which nothing happens, followed by 1 normal stop bit period
during which sampling occurs halfway through. Refer to Section 31.5.13: USART
Smartcard mode on page 1050 for more details.

•

2 stop bits: Sampling for 2 stop bits is done on the 8th, 9th and 10th samples of the
first stop bit. If a framing error is detected during the first stop bit the framing error flag
will be set. The second stop bit is not checked for framing error. The RXNE flag will be
set at the end of the first stop bit.

USART baud rate generation
The baud rate for the receiver and transmitter (Rx and Tx) are both set to the same value as
programmed in the USART_BRR register.
Equation 1: Baud rate for standard USART (SPI mode included) (OVER8 = 0 or 1)
In case of oversampling by 16, the equation is:
f CK
Tx/Rx baud = -------------------------------USARTDIV

In case of oversampling by 8, the equation is:
2 × f CK
Tx/Rx baud = -------------------------------USARTDIV

Equation 2: Baud rate in Smartcard, LIN and IrDA modes (OVER8 = 0)
In Smartcard, LIN and IrDA modes, only Oversampling by 16 is supported:
f CK
Tx/Rx baud = -------------------------------USARTDIV

1036/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
USARTDIV is an unsigned fixed point number that is coded on the USART_BRR register.

Note:

•

When OVER8 = 0, BRR = USARTDIV.

•

When OVER8 = 1
–

BRR[2:0] = USARTDIV[3:0] shifted 1 bit to the right.

–

BRR[3] must be kept cleared.

–

BRR[15:4] = USARTDIV[15:4]

The baud counters are updated to the new value in the baud registers after a write operation
to USART_BRR. Hence the baud rate register value should not be changed during
communication.
In case of oversampling by 16 or 8, USARTDIV must be greater than or equal to 16d.

How to derive USARTDIV from USART_BRR register values
Example 1
To obtain 9600 baud with fCK = 8 MHz.
•

In case of oversampling by 16:
USARTDIV = 8 000 000/9600
BRR = USARTDIV = 833d = 0341h

•

In case of oversampling by 8:
USARTDIV = 2 * 8 000 000/9600
USARTDIV = 1666,66 (1667d = 683h)
BRR[3:0] = 3h >> 1 = 1h
BRR = 0x681

Example 2
To obtain 921.6 Kbaud with fCK = 48 MHz.
•

In case of oversampling by 16:
USARTDIV = 48 000 000/921 600
BRR = USARTDIV = 52d = 34h

•

In case of oversampling by 8:
USARTDIV = 2 * 48 000 000/921 600
USARTDIV = 104 (104d = 68h)
BRR[3:0] = USARTDIV[3:0] >> 1 = 8h >> 1 = 4h
BRR = 0x64

RM0385 Rev 7

1037/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Table 192. Error calculation for programmed baud rates at fCK = 216 MHz
in both cases of oversampling by 8 (OVER8 = 1)(1)
Desired baud
rate (Bps)

Actual baud rate (Bps)

BRR

Error

9600

9600

AFC4

0.00000000

19200

19200

57E2

0.00000000

38400

38400

2BF1

0.00000000

57600

57600

1D46

0.00000000

115200

115200

EA3

0.00000000

230400

230400

751

0.00000000

460800

461538.461

3A4

0.160256293

921600

923076.923

1D2

0.001602564

13500000

13500000.000

20

0.00000000

27000000

27000000.000

10

0.00000000

1. The lower the CPU clock the lower the accuracy for a particular baud rate. The upper limit of the achievable
baud rate can be fixed with these data.

Table 193. Error calculation for programmed baud rates at fCK = 216 MHz
in both cases of oversampling by 16 (OVER8 = 0)(1)
Desired baud
rate (Bps)

Actual baud rate (Bps)

BRR

Error

9600

9600.000

57E4

0.00000000

19200

19200.000

2BF2

0.00000000

38400

38400.000

15F9

0.00000000

57600

57600.000

EA6

0.00000000

115200

115200.000

753

0.00000000

230400

230522.946

3A9

0.05336179

460800

461538.462

1D4

0.16025641

921600

923076.923

EA

0.16025641

4000000

4000000.000

36

0.00000000

6000000

6000000.000

24

0.00000000

10000000

10285714.286

15

2.85714286

13500000

13500000.000

10

0.00000000

1. The lower the CPU clock the lower the accuracy for a particular baud rate. The upper limit of the achievable
baud rate can be fixed with these data.

1038/1709

RM0385 Rev 7

RM0385

31.5.5

Universal synchronous asynchronous receiver transmitter (USART)

Tolerance of the USART receiver to clock deviation
The asynchronous receiver of the USART works correctly only if the total clock system
deviation is less than the tolerance of the USART receiver. The causes which contribute to
the total deviation are:
•

DTRA: Deviation due to the transmitter error (which also includes the deviation of the
transmitter’s local oscillator)

•

DQUANT: Error due to the baud rate quantization of the receiver

•

DREC: Deviation of the receiver’s local oscillator

•

DTCL: Deviation due to the transmission line (generally due to the transceivers which
can introduce an asymmetry between the low-to-high transition timing and the high-tolow transition timing)
DTRA + DQUANT + DREC + DTCL < USART receiver′ s tolerance

The USART receiver can receive data correctly at up to the maximum tolerated
deviation specified in Table 194 and Table 194 depending on the following choices:
•

9-, 10- or 11-bit character length defined by the M bits in the USART_CR1 register

•

Oversampling by 8 or 16 defined by the OVER8 bit in the USART_CR1 register

•

Bits BRR[3:0] of USART_BRR register are equal to or different from 0000.

•

Use of 1 bit or 3 bits to sample the data, depending on the value of the ONEBIT bit in
the USART_CR3 register.
Table 194. Tolerance of the USART receiver when BRR [3:0] = 0000
OVER8 bit = 0

OVER8 bit = 1

M bits
ONEBIT=0

ONEBIT=1

ONEBIT=0

ONEBIT=1

00

3.75%

4.375%

2.50%

3.75%

01

3.41%

3.97%

2.27%

3.41%

10

4.16%

4.86%

2.77%

4.16%

Table 195. Tolerance of the USART receiver when BRR [3:0] is different from 0000
OVER8 bit = 0

OVER8 bit = 1

M bits

Note:

ONEBIT=0

ONEBIT=1

ONEBIT=0

ONEBIT=1

00

3.33%

3.88%

2%

3%

01

3.03%

3.53%

1.82%

2.73%

10

3.7%

4.31%

2.22%

3.33%

The data specified in Table 194 and Table 195 may slightly differ in the special case when
the received frames contain some Idle frames of exactly 10-bit durations when M bits = 00
(11-bit durations when M bits =01 or 9- bit durations when M bits = 10).

RM0385 Rev 7

1039/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

31.5.6

RM0385

USART auto baud rate detection
The USART is able to detect and automatically set the USART_BRR register value based
on the reception of one character. Automatic baud rate detection is useful under two
circumstances:
•

The communication speed of the system is not known in advance

•

The system is using a relatively low accuracy clock source and this mechanism allows
the correct baud rate to be obtained without measuring the clock deviation.

The clock source frequency must be compatible with the expected communication speed
(when oversampling by 16, the baud rate is between fCK/65535 and fCK/16. when
oversampling by 8, the baud rate is between fCK/65535 and fCK/8).
Before activating the auto baud rate detection, the auto baud rate detection mode must be
chosen. There are various modes based on different character patterns.
They can be chosen through the ABRMOD[1:0] field in the USART_CR2 register. In these
auto baud rate modes, the baud rate is measured several times during the synchronization
data reception and each measurement is compared to the previous one.
These modes are:
•

Mode 0: Any character starting with a bit at 1. In this case the USART measures the
duration of the Start bit (falling edge to rising edge).

•

Mode 1: Any character starting with a 10xx bit pattern. In this case, the USART
measures the duration of the Start and of the 1st data bit. The measurement is done
falling edge to falling edge, ensuring better accuracy in the case of slow signal slopes.

•

Mode 2: A 0x7F character frame (it may be a 0x7F character in LSB first mode or a
0xFE in MSB first mode). In this case, the baud rate is updated first at the end of the
start bit (BRs), then at the end of bit 6 (based on the measurement done from falling
edge to falling edge: BR6). Bit 0 to bit 6 are sampled at BRs while further bits of the
character are sampled at BR6.

•

Mode 3: A 0x55 character frame. In this case, the baud rate is updated first at the end
of the start bit (BRs), then at the end of bit 0 (based on the measurement done from
falling edge to falling edge: BR0), and finally at the end of bit 6 (BR6). Bit 0 is sampled
at BRs, bit 1 to bit 6 are sampled at BR0, and further bits of the character are sampled
at BR6.
In parallel, another check is performed for each intermediate transition of RX line. An
error is generated if the transitions on RX are not sufficiently synchronized with the
receiver (the receiver being based on the baud rate calculated on bit 0).

Prior to activating auto baud rate detection, the USART_BRR register must be initialized by
writing a non-zero baud rate value.
The automatic baud rate detection is activated by setting the ABREN bit in the USART_CR2
register. The USART will then wait for the first character on the RX line. The auto baud rate
operation completion is indicated by the setting of the ABRF flag in the USART_ISR
register. If the line is noisy, the correct baud rate detection cannot be guaranteed. In this
case the BRR value may be corrupted and the ABRE error flag will be set. This also
happens if the communication speed is not compatible with the automatic baud rate
detection range (bit duration not between 16 and 65536 clock periods (oversampling by 16)
and not between 8 and 65536 clock periods (oversampling by 8)).
The RXNE interrupt will signal the end of the operation.

1040/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
At any later time, the auto baud rate detection may be relaunched by resetting the ABRF
flag (by writing a 0).

Note:

If the USART is disabled (UE=0) during an auto baud rate operation, the BRR value may be
corrupted.

31.5.7

Multiprocessor communication using USART
In multiprocessor communication, the following bits are to be kept cleared:
•

LINEN bit in the USART_CR2 register,

•

HDSEL, IREN and SCEN bits in the USART_CR3 register.

It is possible to perform multiprocessor communication with the USART (with several
USARTs connected in a network). For instance one of the USARTs can be the master, its TX
output connected to the RX inputs of the other USARTs. The others are slaves, their
respective TX outputs are logically ANDed together and connected to the RX input of the
master.
In multiprocessor configurations it is often desirable that only the intended message
recipient should actively receive the full message contents, thus reducing redundant USART
service overhead for all non addressed receivers.
The non addressed devices may be placed in mute mode by means of the muting function.
In order to use the mute mode feature, the MME bit must be set in the USART_CR1
register.
In mute mode:
•

None of the reception status bits can be set.

•

All the receive interrupts are inhibited.

•

The RWU bit in USART_ISR register is set to 1. RWU can be controlled automatically
by hardware or by software, through the MMRQ bit in the USART_RQR register, under
certain conditions.

The USART can enter or exit from mute mode using one of two methods, depending on the
WAKE bit in the USART_CR1 register:
•

Idle Line detection if the WAKE bit is reset,

•

Address Mark detection if the WAKE bit is set.

RM0385 Rev 7

1041/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Idle line detection (WAKE=0)
The USART enters mute mode when the MMRQ bit is written to 1 and the RWU is
automatically set.
It wakes up when an Idle frame is detected. Then the RWU bit is cleared by hardware but
the IDLE bit is not set in the USART_ISR register. An example of mute mode behavior using
Idle line detection is given in Figure 341.
Figure 341. Mute mode using Idle line detection

RXNE

Data 1 Data 2 Data 3 Data 4

RX

RWU
MMRQ written to 1

Mute mode

IDLE

RXNE

Data 5 Data 6

Normal mode
Idle frame detected

MSv31154V1

Note:

If the MMRQ is set while the IDLE character has already elapsed, mute mode will not be
entered (RWU is not set).
If the USART is activated while the line is IDLE, the idle state is detected after the duration
of one IDLE frame (not only after the reception of one character frame).

4-bit/7-bit address mark detection (WAKE=1)
In this mode, bytes are recognized as addresses if their MSB is a ‘1’ otherwise they are
considered as data. In an address byte, the address of the targeted receiver is put in the 4
or 7 LSBs. The choice of 7 or 4-bit address detection is done using the ADDM7 bit. This 4bit/7-bit word is compared by the receiver with its own address which is programmed in the
ADD bits in the USART_CR2 register.
Note:

In 7-bit and 9-bit data modes, address detection is done on 6-bit and 8-bit addresses
(ADD[5:0] and ADD[7:0]) respectively.
The USART enters mute mode when an address character is received which does not
match its programmed address. In this case, the RWU bit is set by hardware. The RXNE
flag is not set for this address byte and no interrupt or DMA request is issued when the
USART enters mute mode.
The USART also enters mute mode when the MMRQ bit is written to 1. The RWU bit is also
automatically set in this case.
The USART exits from mute mode when an address character is received which matches
the programmed address. Then the RWU bit is cleared and subsequent bytes are received
normally. The RXNE bit is set for the address character since the RWU bit has been
cleared.
An example of mute mode behavior using address mark detection is given in Figure 342.

1042/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 342. Mute mode using address mark detection
In this example, the current address of the receiver is 1
(programmed in the USART_CR2 register)
RXNE

IDLE

RX

Addr=0 Data 1 Data 2

RWU

IDLE

RXNE

Addr=1 Data 3 Data 4 Addr=2 Data 5

Mute mode

Normal mode
Matching address

MMRQ written to 1
(RXNE was cleared)

RXNE

Mute mode

Non-matching address

Non-matching address
MSv31155V1

31.5.8

Modbus communication using USART
The USART offers basic support for the implementation of Modbus/RTU and Modbus/ASCII
protocols. Modbus/RTU is a half duplex, block transfer protocol. The control part of the
protocol (address recognition, block integrity control and command interpretation) must be
implemented in software.
The USART offers basic support for the end of the block detection, without software
overhead or other resources.

Modbus/RTU
In this mode, the end of one block is recognized by a “silence” (idle line) for more than 2
character times. This function is implemented through the programmable timeout function.
The timeout function and interrupt must be activated, through the RTOEN bit in the
USART_CR2 register and the RTOIE in the USART_CR1 register. The value corresponding
to a timeout of 2 character times (for example 22 x bit duration) must be programmed in the
RTO register. when the receive line is idle for this duration, after the last stop bit is received,
an interrupt is generated, informing the software that the current block reception is
completed.

Modbus/ASCII
In this mode, the end of a block is recognized by a specific (CR/LF) character sequence.
The USART manages this mechanism using the character match function.
By programming the LF ASCII code in the ADD[7:0] field and by activating the character
match interrupt (CMIE=1), the software is informed when a LF has been received and can
check the CR/LF in the DMA buffer.

RM0385 Rev 7

1043/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

31.5.9

RM0385

USART parity control
Parity control (generation of parity bit in transmission and parity checking in reception) can
be enabled by setting the PCE bit in the USART_CR1 register. Depending on the frame
length defined by the M bits, the possible USART frame formats are as listed in Table 196.
Table 196. Frame formats
M bits

PCE bit

USART frame(1)

00

0

| SB | 8-bit data | STB |

00

1

| SB | 7-bit data | PB | STB |

01

0

| SB | 9-bit data | STB |

01

1

| SB | 8-bit data | PB | STB |

10

0

| SB | 7-bit data | STB |

10

1

| SB | 6-bit data | PB | STB |

1. Legends: SB: start bit, STB: stop bit, PB: parity bit. In the data register, the PB is always taking the MSB
position (9th, 8th or 7th, depending on the M bits value).

Even parity
The parity bit is calculated to obtain an even number of “1s” inside the frame of the 6, 7 or 8
LSB bits (depending on M bits values) and the parity bit.
As an example, if data=00110101, and 4 bits are set, then the parity bit will be 0 if even
parity is selected (PS bit in USART_CR1 = 0).

Odd parity
The parity bit is calculated to obtain an odd number of “1s” inside the frame made of the 6, 7
or 8 LSB bits (depending on M bits values) and the parity bit.
As an example, if data=00110101 and 4 bits set, then the parity bit will be 1 if odd parity is
selected (PS bit in USART_CR1 = 1).

Parity checking in reception
If the parity check fails, the PE flag is set in the USART_ISR register and an interrupt is
generated if PEIE is set in the USART_CR1 register. The PE flag is cleared by software
writing 1 to the PECF in the USART_ICR register.

Parity generation in transmission
If the PCE bit is set in USART_CR1, then the MSB bit of the data written in the data register
is transmitted but is changed by the parity bit (even number of “1s” if even parity is selected
(PS=0) or an odd number of “1s” if odd parity is selected (PS=1)).

1044/1709

RM0385 Rev 7

RM0385

31.5.10

Universal synchronous asynchronous receiver transmitter (USART)

USART LIN (local interconnection network) mode
This section is relevant only when LIN mode is supported. Please refer to Section 31.4:
USART implementation on page 1023.
The LIN mode is selected by setting the LINEN bit in the USART_CR2 register. In LIN
mode, the following bits must be kept cleared:
•

STOP[1:0] and CLKEN in the USART_CR2 register,

•

SCEN, HDSEL and IREN in the USART_CR3 register.

LIN transmission
The procedure explained in Section 31.5.2: USART transmitter has to be applied for LIN
Master transmission. It must be the same as for normal USART transmission with the
following differences:
•

Clear the M bits to configure 8-bit word length.

•

Set the LINEN bit to enter LIN mode. In this case, setting the SBKRQ bit sends 13 ‘0’
bits as a break character. Then 2 bits of value ‘1’ are sent to allow the next start
detection.

LIN reception
When LIN mode is enabled, the break detection circuit is activated. The detection is totally
independent from the normal USART receiver. A break can be detected whenever it occurs,
during Idle state or during a frame.
When the receiver is enabled (RE=1 in USART_CR1), the circuit looks at the RX input for a
start signal. The method for detecting start bits is the same when searching break
characters or data. After a start bit has been detected, the circuit samples the next bits
exactly like for the data (on the 8th, 9th and 10th samples). If 10 (when the LBDL = 0 in
USART_CR2) or 11 (when LBDL=1 in USART_CR2) consecutive bits are detected as ‘0,
and are followed by a delimiter character, the LBDF flag is set in USART_ISR. If the LBDIE
bit=1, an interrupt is generated. Before validating the break, the delimiter is checked for as it
signifies that the RX line has returned to a high level.
If a ‘1’ is sampled before the 10 or 11 have occurred, the break detection circuit cancels the
current detection and searches for a start bit again.
If the LIN mode is disabled (LINEN=0), the receiver continues working as normal USART,
without taking into account the break detection.
If the LIN mode is enabled (LINEN=1), as soon as a framing error occurs (i.e. stop bit
detected at ‘0’, which will be the case for any break frame), the receiver stops until the break
detection circuit receives either a ‘1’, if the break word was not complete, or a delimiter
character if a break has been detected.
The behavior of the break detector state machine and the break flag is shown on the
Figure 343: Break detection in LIN mode (11-bit break length - LBDL bit is set) on
page 1046.
Examples of break frames are given on Figure 344: Break detection in LIN mode vs.
Framing error detection on page 1047.

RM0385 Rev 7

1045/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Figure 343. Break detection in LIN mode (11-bit break length - LBDL bit is set)

Case 1: break signal not long enough => break discarded, LBDF is not set
Break frame

RX line
Capture strobe
Break state
machine

Idle

Bit0 Bit1 Bit2 Bit3
0

Read samples

0

0

0

Bit4 Bit5 Bit6
0

0

0

Bit7 Bit8 Bit9 Bit10
0

0

0

Idle

1

Case 2: break signal just long enough => break detected, LBDF is set
Break frame

RX line

Delimiter is immediate
Capture strobe
Break state
machine

Idle

Bit0 Bit1 Bit2 Bit3
0

Read samples

0

0

0

Bit4 Bit5 Bit6
0

0

0

Bit7 Bit8 Bit9 B10
0

0

0

Idle

0

LBDF

Case 3: break signal long enough => break detected, LBDF is set
Break frame

RX line
Capture strobe
Break state
Idle
machine
Read samples

Bit0 Bit1 Bit2 Bit3
0

0

0

0

Bit4 Bit5 Bit6
0

0

0

Bit7 Bit8 Bit9 Bit10 wait delimiter Idle
0

0

0

0

LBDF

MSv31156V1

1046/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 344. Break detection in LIN mode vs. Framing error detection
Case 1: break occurring after an Idle
RX line

data 1

IDLE

BREAK
1 data time

data 2 (0x55)

data 3 (header)

1 data time

RXNE /FE
LBDF

Case 2: break occurring while data is being received
RX line

data 1

data2

BREAK

1 data time

data 2 (0x55)

data 3 (header)

1 data time

RXNE /FE
LBDF
MSv31157V1

31.5.11

USART synchronous mode
The synchronous mode is selected by writing the CLKEN bit in the USART_CR2 register to
1. In synchronous mode, the following bits must be kept cleared:
•

LINEN bit in the USART_CR2 register,

•

SCEN, HDSEL and IREN bits in the USART_CR3 register.

In this mode, the USART can be used to control bidirectional synchronous serial
communications in master mode. The CK pin is the output of the USART transmitter clock.
No clock pulses are sent to the CK pin during start bit and stop bit. Depending on the state
of the LBCL bit in the USART_CR2 register, clock pulses are, or are not, generated during
the last valid data bit (address mark). The CPOL bit in the USART_CR2 register is used to
select the clock polarity, and the CPHA bit in the USART_CR2 register is used to select the
phase of the external clock (see Figure 345, Figure 346 and Figure 347).
During the Idle state, preamble and send break, the external CK clock is not activated.
In synchronous mode the USART transmitter works exactly like in asynchronous mode. But
as CK is synchronized with TX (according to CPOL and CPHA), the data on TX is
synchronous.
In this mode the USART receiver works in a different manner compared to the
asynchronous mode. If RE=1, the data is sampled on CK (rising or falling edge, depending
on CPOL and CPHA), without any oversampling. A setup and a hold time must be
respected (which depends on the baud rate: 1/16 bit duration).

RM0385 Rev 7

1047/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)
Note:

RM0385

The CK pin works in conjunction with the TX pin. Thus, the clock is provided only if the
transmitter is enabled (TE=1) and data is being transmitted (the data register USART_TDR
written). This means that it is not possible to receive synchronous data without transmitting
data.
The LBCL, CPOL and CPHA bits have to be selected when the USART is disabled (UE=0)
to ensure that the clock pulses function correctly.
Figure 345. USART example of synchronous transmission

RX
TX

Data out
Data in
Synchronous device
(e.g. slave SPI)

USART

Clock

CK

MSv31158V2

Figure 346. USART data clock timing diagram (M bits = 00)
Idle or preceding
Start
transmission

Idle or next
Stop transmission

M bits = 00 (8 data bits)

Clock (CPOL=0, CPHA=0)

*

Clock (CPOL=0, CPHA=1)

*
*

Clock (CPOL=1, CPHA=0)
*

Clock (CPOL=1, CPHA=1)
Data on TX
(from master)

0
Start

Data on RX
(from slave)

1

2

3

4

5

6

1

2

3

4

5

6

LSB
0

7
MSB Stop
7
MSB
*

LSB
Capture strobe

*LBCL bit controls last data pulse
MSv34709V2

1048/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 347. USART data clock timing diagram (M bits = 01)
Idle or
preceding Start
transmission

Stop

M bits =01 (9 data bits)

Clock (CPOL=0,
CPHA=0)

Idle or next
transmission

*

Clock (CPOL=0,
CPHA=1)

*

Clock (CPOL=1,
CPHA=0)

*

Clock (CPOL=1,
CPHA=1)

*

Data on TX
(from master)

0

1

2

3

4

5

6

7

Start LSB
Data on RX
(from slave)

0

8
MSB

1

2

3

4

5

6

LSB
Capture
strobe

7

Stop

8
MSB
*

*LBCL bit controls last data pulse
MSv34710V1

Figure 348. RX data setup/hold time

CK
(capture strobe on CK rising
edge in this example)
Data on RX (from slave)

Valid DATA bit

tSETUP

tHOLD

tSETUP=tHOLD 1/16 bit time
MSv31161V2

Note:

The function of CK is different in Smartcard mode. Refer to Section 31.5.13: USART
Smartcard mode for more details.

RM0385 Rev 7

1049/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

31.5.12

RM0385

USART Single-wire Half-duplex communication
Single-wire Half-duplex mode is selected by setting the HDSEL bit in the USART_CR3
register. In this mode, the following bits must be kept cleared:
•

LINEN and CLKEN bits in the USART_CR2 register,

•

SCEN and IREN bits in the USART_CR3 register.

The USART can be configured to follow a Single-wire Half-duplex protocol where the TX
and RX lines are internally connected. The selection between half- and Full-duplex
communication is made with a control bit HDSEL in USART_CR3.
As soon as HDSEL is written to 1:
•

The TX and RX lines are internally connected

•

The RX pin is no longer used

•

The TX pin is always released when no data is transmitted. Thus, it acts as a standard
I/O in idle or in reception. It means that the I/O must be configured so that TX is
configured as alternate function open-drain with an external pull-up.

Apart from this, the communication protocol is similar to normal USART mode. Any conflicts
on the line must be managed by software (by the use of a centralized arbiter, for instance).
In particular, the transmission is never blocked by hardware and continues as soon as data
is written in the data register while the TE bit is set.

31.5.13

USART Smartcard mode
This section is relevant only when Smartcard mode is supported. Please refer to
Section 31.4: USART implementation on page 1023.
Smartcard mode is selected by setting the SCEN bit in the USART_CR3 register. In
Smartcard mode, the following bits must be kept cleared:
•

LINEN bit in the USART_CR2 register,

•

HDSEL and IREN bits in the USART_CR3 register.

Moreover, the CLKEN bit may be set in order to provide a clock to the smartcard.
The smartcard interface is designed to support asynchronous protocol for smartcards as
defined in the ISO 7816-3 standard. Both T=0 (character mode) and T=1 (block mode) are
supported.
The USART should be configured as:
•

8 bits plus parity: where word length is set to 8 bits and PCE=1 in the USART_CR1
register

•

1.5 stop bits: where STOP=11 in the USART_CR2 register. It is also possible to choose
0.5 stop bit for receiving.

In T=0 (character) mode, the parity error is indicated at the end of each character during the
guard time period.
Figure 349 shows examples of what can be seen on the data line with and without parity
error.

1050/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 349. ISO 7816-3 asynchronous protocol
Without Parity error
S

0

1

Guard time
2

3

4

5

6

7

p

Start bit
WithParity error
S

0

Guard time
1

2

3

4

Start bit

5

6

7

p
Line pulled low by receiver
during stop in case of parity error
MSv31162V1

When connected to a smartcard, the TX output of the USART drives a bidirectional line that
is also driven by the smartcard. The TX pin must be configured as open drain.
Smartcard mode implements a single wire half duplex communication protocol.
•

Transmission of data from the transmit shift register is guaranteed to be delayed by a
minimum of 1/2 baud clock. In normal operation a full transmit shift register starts
shifting on the next baud clock edge. In Smartcard mode this transmission is further
delayed by a guaranteed 1/2 baud clock.

•

In transmission, if the smartcard detects a parity error, it signals this condition to the
USART by driving the line low (NACK). This NACK signal (pulling transmit line low for 1
baud clock) causes a framing error on the transmitter side (configured with 1.5 stop
bits). The USART can handle automatic re-sending of data according to the protocol.
The number of retries is programmed in the SCARCNT bit field. If the USART
continues receiving the NACK after the programmed number of retries, it stops
transmitting and signals the error as a framing error. The TXE bit can be set using the
TXFRQ bit in the USART_RQR register.

•

Smartcard auto-retry in transmission: a delay of 2.5 baud periods is inserted between
the NACK detection by the USART and the start bit of the repeated character. The TC
bit is set immediately at the end of reception of the last repeated character (no guardtime). If the software wants to repeat it again, it must insure the minimum 2 baud
periods required by the standard.

•

If a parity error is detected during reception of a frame programmed with a 1.5 stop bits
period, the transmit line is pulled low for a baud clock period after the completion of the
receive frame. This is to indicate to the smartcard that the data transmitted to the
USART has not been correctly received. A parity error is NACKed by the receiver if the
NACK control bit is set, otherwise a NACK is not transmitted (to be used in T=1 mode).
If the received character is erroneous, the RXNE/receive DMA request is not activated.
According to the protocol specification, the smartcard must resend the same character.
If the received character is still erroneous after the maximum number of retries
specified in the SCARCNT bit field, the USART stops transmitting the NACK and
signals the error as a parity error.

•

Smartcard auto-retry in reception: the BUSY flag remains set if the USART NACKs the
card but the card doesn’t repeat the character.

RM0385 Rev 7

1051/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

Note:

RM0385

•

In transmission, the USART inserts the Guard Time (as programmed in the Guard Time
register) between two successive characters. As the Guard Time is measured after the
stop bit of the previous character, the GT[7:0] register must be programmed to the
desired CGT (Character Guard Time, as defined by the 7816-3 specification) minus 12
(the duration of one character).

•

The assertion of the TC flag can be delayed by programming the Guard Time register.
In normal operation, TC is asserted when the transmit shift register is empty and no
further transmit requests are outstanding. In Smartcard mode an empty transmit shift
register triggers the Guard Time counter to count up to the programmed value in the
Guard Time register. TC is forced low during this time. When the Guard Time counter
reaches the programmed value TC is asserted high.

•

The de-assertion of TC flag is unaffected by Smartcard mode.

•

If a framing error is detected on the transmitter end (due to a NACK from the receiver),
the NACK is not detected as a start bit by the receive block of the transmitter.
According to the ISO protocol, the duration of the received NACK can be 1 or 2 baud
clock periods.

•

On the receiver side, if a parity error is detected and a NACK is transmitted the receiver
does not detect the NACK as a start bit.

A break character is not significant in Smartcard mode. A 0x00 data with a framing error is
treated as data and not as a break.
No Idle frame is transmitted when toggling the TE bit. The Idle frame (as defined for the
other configurations) is not defined by the ISO protocol.
Figure 350 details how the NACK signal is sampled by the USART. In this example the
USART is transmitting data and is configured with 1.5 stop bits. The receiver part of the
USART is enabled in order to check the integrity of the data and the NACK signal.
Figure 350. Parity error detection using the 1.5 stop bits
Bit 7

Parity bit

1.5 Stop bit

1 bit time

1.5 bit time

Sampling at

Sampling at

8th, 9th, 10th

8th, 9th, 10th
0.5 bit time

Sampling at

Sampling at

8th, 9th, 10th

8th, 9th, 10th
MSv31163V1

The USART can provide a clock to the smartcard through the CK output. In Smartcard
mode, CK is not associated to the communication but is simply derived from the internal
peripheral input clock through a 5-bit prescaler. The division ratio is configured in the
prescaler register USART_GTPR. CK frequency can be programmed from fCK/2 to fCK/62,
where fCK is the peripheral input clock.

1052/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Block mode (T=1)
In T=1 (block) mode, the parity error transmission is deactivated, by clearing the NACK bit in
the UART_CR3 register.
When requesting a read from the smartcard, in block mode, the software must enable the
receiver Timeout feature by setting the RTOEN bit in the USART_CR2 register and program
the RTO bits field in the RTOR register to the BWT (block wait time) - 11 value. If no answer
is received from the card before the expiration of this period, the RTOF flag will be set and a
timeout interrupt will be generated (if RTOIE bit in the USART_CR1 register is set). If the
first character is received before the expiration of the period, it is signaled by the RXNE
interrupt.
Note:

The RXNE interrupt must be enabled even when using the USART in DMA mode to read
from the smartcard in block mode. In parallel, the DMA must be enabled only after the first
received byte.
After the reception of the first character (RXNE interrupt), the RTO bit fields in the RTOR
register must be programmed to the CWT (character wait time) - 11 value, in order to allow
the automatic check of the maximum wait time between two consecutive characters. This
time is expressed in baudtime units. If the smartcard does not send a new character in less
than the CWT period after the end of the previous character, the USART signals this to the
software through the RTOF flag and interrupt (when RTOIE bit is set).

Note:

The RTO counter starts counting:
- From the end of the stop bit in case STOP = 00.
- From the end of the second stop bit in case of STOP = 10.
- 1 bit duration after the beginning of the STOP bit in case STOP = 11.
- From the beginning of the STOP bit in case STOP = 01.
As in the Smartcard protocol definition, the BWT/CWT values are defined from the
beginning (start bit) of the last character. The RTO register must be programmed to BWT 11 or CWT -11, respectively, taking into account the length of the last character itself.
A block length counter is used to count all the characters received by the USART. This
counter is reset when the USART is transmitting (TXE=0). The length of the block is
communicated by the smartcard in the third byte of the block (prologue field). This value
must be programmed to the BLEN field in the USART_RTOR register. when using DMA
mode, before the start of the block, this register field must be programmed to the minimum
value (0x0). with this value, an interrupt is generated after the 4th received character. The
software must read the LEN field (third byte), its value must be read from the receive buffer.
In interrupt driven receive mode, the length of the block may be checked by software or by
programming the BLEN value. However, before the start of the block, the maximum value of
BLEN (0xFF) may be programmed. The real value will be programmed after the reception of
the third character.
If the block is using the LRC longitudinal redundancy check (1 epilogue byte), the
BLEN=LEN. If the block is using the CRC mechanism (2 epilogue bytes), BLEN=LEN+1
must be programmed. The total block length (including prologue, epilogue and information
fields) equals BLEN+4. The end of the block is signaled to the software through the EOBF
flag and interrupt (when EOBIE bit is set).
In case of an error in the block length, the end of the block is signaled by the RTO interrupt
(Character wait Time overflow).

RM0385 Rev 7

1053/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)
Note:

RM0385

The error checking code (LRC/CRC) must be computed/verified by software.

Direct and inverse convention
The Smartcard protocol defines two conventions: direct and inverse.
The direct convention is defined as: LSB first, logical bit value of 1 corresponds to a H state
of the line and parity is even. In order to use this convention, the following control bits must
be programmed: MSBFIRST=0, DATAINV=0 (default values).
The inverse convention is defined as: MSB first, logical bit value 1 corresponds to an L state
on the signal line and parity is even. In order to use this convention, the following control bits
must be programmed: MSBFIRST=1, DATAINV=1.
Note:

When logical data values are inverted (0=H, 1=L), the parity bit is also inverted in the same
way.
In order to recognize the card convention, the card sends the initial character, TS, as the
first character of the ATR (Answer To Reset) frame. The two possible patterns for the TS
are: LHHL LLL LLH and LHHL HHH LLH.
•

(H) LHHL LLL LLH sets up the inverse convention: state L encodes value 1 and
moment 2 conveys the most significant bit (MSB first). when decoded by inverse
convention, the conveyed byte is equal to '3F'.

•

(H) LHHL HHH LLH sets up the direct convention: state H encodes value 1 and
moment 2 conveys the least significant bit (LSB first). when decoded by direct
convention, the conveyed byte is equal to '3B'.

Character parity is correct when there is an even number of bits set to 1 in the nine
moments 2 to 10.
As the USART does not know which convention is used by the card, it needs to be able to
recognize either pattern and act accordingly. The pattern recognition is not done in
hardware, but through a software sequence. Moreover, supposing that the USART is
configured in direct convention (default) and the card answers with the inverse convention,
TS = LHHL LLL LLH => the USART received character will be ‘03’ and the parity will be odd.
Therefore, two methods are available for TS pattern recognition:
Method 1
The USART is programmed in standard Smartcard mode/direct convention. In this case, the
TS pattern reception generates a parity error interrupt and error signal to the card.
•

The parity error interrupt informs the software that the card didn’t answer correctly in
direct convention. Software then reprograms the USART for inverse convention

•

In response to the error signal, the card retries the same TS character, and it will be
correctly received this time, by the reprogrammed USART

Alternatively, in answer to the parity error interrupt, the software may decide to reprogram
the USART and to also generate a new reset command to the card, then wait again for the
TS.

1054/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Method 2
The USART is programmed in 9-bit/no-parity mode, no bit inversion. In this mode it receives
any of the two TS patterns as:
(H) LHHL LLL LLH = 0x103 -> inverse convention to be chosen
(H) LHHL HHH LLH = 0x13B -> direct convention to be chosen
The software checks the received character against these two patterns and, if any of them
match, then programs the USART accordingly for the next character reception.
If none of the two is recognized, a card reset may be generated in order to restart the
negotiation.

31.5.14

USART IrDA SIR ENDEC block
This section is relevant only when IrDA mode is supported. Please refer to Section 31.4:
USART implementation on page 1023.
IrDA mode is selected by setting the IREN bit in the USART_CR3 register. In IrDA mode,
the following bits must be kept cleared:
•

LINEN, STOP and CLKEN bits in the USART_CR2 register,

•

SCEN and HDSEL bits in the USART_CR3 register.

The IrDA SIR physical layer specifies use of a Return to Zero, Inverted (RZI) modulation
scheme that represents logic 0 as an infrared light pulse (see Figure 351).
The SIR Transmit encoder modulates the Non Return to Zero (NRZ) transmit bit stream
output from USART. The output pulse stream is transmitted to an external output driver and
infrared LED. USART supports only bit rates up to 115.2 Kbps for the SIR ENDEC. In
normal mode the transmitted pulse width is specified as 3/16 of a bit period.
The SIR receive decoder demodulates the return-to-zero bit stream from the infrared
detector and outputs the received NRZ serial bit stream to the USART. The decoder input is
normally high (marking state) in the Idle state. The transmit encoder output has the opposite
polarity to the decoder input. A start bit is detected when the decoder input is low.
•

IrDA is a half duplex communication protocol. If the Transmitter is busy (when the
USART is sending data to the IrDA encoder), any data on the IrDA receive line is
ignored by the IrDA decoder and if the Receiver is busy (when the USART is receiving
decoded data from the IrDA decoder), data on the TX from the USART to IrDA is not
encoded. while receiving data, transmission should be avoided as the data to be
transmitted could be corrupted.

•

A 0 is transmitted as a high pulse and a 1 is transmitted as a 0. The width of the pulse
is specified as 3/16th of the selected bit period in normal mode (see Figure 352).

•

The SIR decoder converts the IrDA compliant receive signal into a bit stream for
USART.

•

The SIR receive logic interprets a high state as a logic one and low pulses as logic
zeros.

•

The transmit encoder output has the opposite polarity to the decoder input. The SIR
output is in low state when Idle.

RM0385 Rev 7

1055/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

•

The IrDA specification requires the acceptance of pulses greater than 1.41 µs. The
acceptable pulse width is programmable. Glitch detection logic on the receiver end
filters out pulses of width less than 2 PSC periods (PSC is the prescaler value
programmed in the USART_GTPR). Pulses of width less than 1 PSC period are always
rejected, but those of width greater than one and less than two periods may be
accepted or rejected, those greater than 2 periods will be accepted as a pulse. The
IrDA encoder/decoder doesn’t work when PSC=0.

•

The receiver can communicate with a low-power transmitter.

•

In IrDA mode, the STOP bits in the USART_CR2 register must be configured to “1 stop
bit”.

IrDA low-power mode
Transmitter
In low-power mode the pulse width is not maintained at 3/16 of the bit period. Instead, the
width of the pulse is 3 times the low-power baud rate which can be a minimum of 1.42 MHz.
Generally, this value is 1.8432 MHz (1.42 MHz < PSC< 2.12 MHz). A low-power mode
programmable divisor divides the system clock to achieve this value.
Receiver
Receiving in low-power mode is similar to receiving in normal mode. For glitch detection the
USART should discard pulses of duration shorter than 1 PSC period. A valid low is accepted
only if its duration is greater than 2 periods of the IrDA low-power Baud clock (PSC value in
the USART_GTPR).
Note:

A pulse of width less than two and greater than one PSC period(s) may or may not be
rejected.
The receiver set up time should be managed by software. The IrDA physical layer
specification specifies a minimum of 10 ms delay between transmission and reception (IrDA
is a half duplex protocol).
Figure 351. IrDA SIR ENDEC- block diagram
SIREN

TX

OR

USART_TX

SIR
Transmit
Encoder

IrDA_OUT

SIR
Receive
DEcoder

IrDA_IN

USART

RX

USART_RX

MSv31164V2

1056/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 352. IrDA data modulation (3/16) -Normal Mode

TX

Start
bit
0

Stop
bit
1

0

1

0

0

1

1

0

1

IrDA_OUT
Bit period

IrDA_IN

RX

0

1

0

3/16

1

0

0

1

1

0

1

MSv31165V1

31.5.15

USART continuous communication in DMA mode
The USART is capable of performing continuous communication using the DMA. The DMA
requests for Rx buffer and Tx buffer are generated independently.

Note:

Please refer to Section 31.4: USART implementation on page 1023 to determine if the DMA
mode is supported. If DMA is not supported, use the USART as explained in Section 31.5.2:
USART transmitter or Section 31.5.3: USART receiver. To perform continuous
communication, the user can clear the TXE/ RXNE flags In the USART_ISR register.

Transmission using DMA
DMA mode can be enabled for transmission by setting DMAT bit in the USART_CR3
register. Data is loaded from a SRAM area configured using the DMA peripheral (refer to
Section 8: Direct memory access controller (DMA) on page 242) to the USART_TDR
register whenever the TXE bit is set. To map a DMA channel for USART transmission, use
the following procedure (x denotes the channel number):
1.

Write the USART_TDR register address in the DMA control register to configure it as
the destination of the transfer. The data is moved to this address from memory after
each TXE event.

2.

Write the memory address in the DMA control register to configure it as the source of
the transfer. The data is loaded into the USART_TDR register from this memory area
after each TXE event.

3.

Configure the total number of bytes to be transferred to the DMA control register.

4.

Configure the channel priority in the DMA register

5.

Configure DMA interrupt generation after half/ full transfer as required by the
application.

6.

Clear the TC flag in the USART_ISR register by setting the TCCF bit in the
USART_ICR register.

7.

Activate the channel in the DMA register.

When the number of data transfers programmed in the DMA Controller is reached, the DMA
controller generates an interrupt on the DMA channel interrupt vector.
In transmission mode, once the DMA has written all the data to be transmitted (the TCIF flag
is set in the DMA_ISR register), the TC flag can be monitored to make sure that the USART

RM0385 Rev 7

1057/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

communication is complete. This is required to avoid corrupting the last transmission before
disabling the USART or entering Stop mode. Software must wait until TC=1. The TC flag
remains cleared during all data transfers and it is set by hardware at the end of transmission
of the last frame.
Figure 353. Transmission using DMA
Idle preamble

Frame 2

Frame 1

Frame 3

TX line
Set by hardware
cleared by DMA read

Set by hardware
cleared by DMA read

TXE flag

Set by hardware

Ignored by the DMA because
the transfer is complete

DMA request
F1

USART_TDR

F2

F3

TC flag

Set by
hardware

DMA writes
USART_TDR
DMA TCIF flag
(transfer
complete)

Set by hardware

Software
configures DMA DMA writes DMA writes DMA writes
F1 into
F2 into
F3 into
to send 3 data
USART_TDR USART_TDR USART_TDR
blocks and
enables USART

Cleared
by
software

The DMA
transfer is
complete
(TCIF=1 in
DMA_ISR)

Software waits until TC=1

ai17192b

Reception using DMA
DMA mode can be enabled for reception by setting the DMAR bit in USART_CR3 register.
Data is loaded from the USART_RDR register to a SRAM area configured using the DMA
peripheral (refer to Section 8: Direct memory access controller (DMA)) whenever a data
byte is received. To map a DMA channel for USART reception, use the following procedure:
1.

Write the USART_RDR register address in the DMA control register to configure it as
the source of the transfer. The data is moved from this address to the memory after
each RXNE event.

2.

Write the memory address in the DMA control register to configure it as the destination
of the transfer. The data is loaded from USART_RDR to this memory area after each
RXNE event.

3.

Configure the total number of bytes to be transferred to the DMA control register.

4.

Configure the channel priority in the DMA control register

5.

Configure interrupt generation after half/ full transfer as required by the application.

6.

Activate the channel in the DMA control register.

When the number of data transfers programmed in the DMA Controller is reached, the DMA
controller generates an interrupt on the DMA channel interrupt vector.

1058/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 354. Reception using DMA
Frame 2

Frame 1

Frame 3

TX line
Set by hardware
cleared by DMA read

RXNE flag
DMA request

F2

F1

USART_TDR

F3

DMA reads
USART_TDR
DMA TCIF flag
(transfer complete)

Software configures the
DMA to receive 3 data
blocks and enables
the USART

Cleared
by
software

Set by hardware

DMA reads F1
from USART_TDR

DMA reads F2
from USART_TDR

The DMA transfer
DMA reads F3
is complete
from USART_TDR (TCIF=1 in
DMA_ISR)
ai17193b

Error flagging and interrupt generation in multibuffer communication
In multibuffer communication if any error occurs during the transaction the error flag is
asserted after the current byte. An interrupt is generated if the interrupt enable flag is set.
For framing error, overrun error and noise flag which are asserted with RXNE in single byte
reception, there is a separate error flag interrupt enable bit (EIE bit in the USART_CR3
register), which, if set, enables an interrupt after the current byte if any of these errors occur.

31.5.16

RS232 hardware flow control and RS485 driver enable
using USART
It is possible to control the serial data flow between 2 devices by using the CTS input and
the RTS output. The Figure 355 shows how to connect 2 devices in this mode:
Figure 355. Hardware flow control between 2 USARTs

USART 2

USART 1
RX

TX
TX circuit

RX circuit
RTS

CTS
RX

TX

RTS

CTS

RX circuit

TX circuit

MSv31169V2

RM0385 Rev 7

1059/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

RS232 RTS and CTS flow control can be enabled independently by writing the RTSE and
CTSE bits respectively to 1 (in the USART_CR3 register).

RS232 RTS flow control
If the RTS flow control is enabled (RTSE=1), then RTS is asserted (tied low) as long as the
USART receiver is ready to receive a new data. When the receive register is full, RTS is deasserted, indicating that the transmission is expected to stop at the end of the current frame.
Figure 356 shows an example of communication with RTS flow control enabled.
Figure 356. RS232 RTS flow control

RX

Start
bit

Data 1

Stop
Start
Idle
bit
bit

Data 2

Stop
bit

RTS

RXNE

RXNE
Data 1 read
Data 2 can now be transmitted

MSv31168V2

RS232 CTS flow control
If the CTS flow control is enabled (CTSE=1), then the transmitter checks the CTS input
before transmitting the next frame. If CTS is asserted (tied low), then the next data is
transmitted (assuming that data is to be transmitted, in other words, if TXE=0), else the
transmission does not occur. when CTS is de-asserted during a transmission, the current
transmission is completed before the transmitter stops.
When CTSE=1, the CTSIF status bit is automatically set by hardware as soon as the CTS
input toggles. It indicates when the receiver becomes ready or not ready for communication.
An interrupt is generated if the CTSIE bit in the USART_CR3 register is set. Figure 357
shows an example of communication with CTS flow control enabled.

1060/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 357. RS232 CTS flow control
CTS

CTS

CTS
Transmit data register
TDR

Data 2

TX

Data 1

empty

Stop Start
bit bit

empty

Data 3

Data 2

Writing data 3 in TDR

Stop
Start
Idle
bit
bit

Data 3

Transmission of Data 3 is
delayed until CTS = 0
MSv31167V2

Note:

For correct behavior, CTS must be asserted at least 3 USART clock source periods before
the end of the current character. In addition it should be noted that the CTSCF flag may not
be set for pulses shorter than 2 x PCLK periods.

RS485 Driver Enable
The driver enable feature is enabled by setting bit DEM in the USART_CR3 control register.
This allows the user to activate the external transceiver control, through the DE (Driver
Enable) signal. The assertion time is the time between the activation of the DE signal and
the beginning of the START bit. It is programmed using the DEAT [4:0] bit fields in the
USART_CR1 control register. The de-assertion time is the time between the end of the last
stop bit, in a transmitted message, and the de-activation of the DE signal. It is programmed
using the DEDT [4:0] bit fields in the USART_CR1 control register. The polarity of the DE
signal can be configured using the DEP bit in the USART_CR3 control register.
In USART, the DEAT and DEDT are expressed in sample time units (1/8 or 1/16 bit duration,
depending on the oversampling rate).

31.6

USART low-power modes
Table 197. Effect of low-power modes on the USART
Mode

Description

Sleep

No effect. USART interrupt causes the device to exit Sleep mode.

Stop

No effect.

Standby

The USART is powered down and must be reinitialized when the device
has exited from Standby mode.

RM0385 Rev 7

1061/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

31.7

RM0385

USART interrupts
Table 198. USART interrupt requests
Interrupt event
Transmit data register empty
CTS interrupt
Transmission Complete
Receive data register not empty (data ready to be read)

Event flag

Enable Control
bit

TXE

TXEIE

CTSIF

CTSIE

TC

TCIE

RXNE

RXNEIE

Overrun error detected

ORE

Idle line detected

IDLE

IDLEIE

PE

PEIE

LBDF

LBDIE

NF or ORE or FE

EIE

Character match

CMF

CMIE

Receiver timeout

RTOF

RTOIE

End of Block

EOBF

EOBIE

Parity error
LIN break
Noise Flag, Overrun error and Framing Error in multibuffer
communication.

The USART interrupt events are connected to the same interrupt vector (see Figure 358).
•

During transmission: Transmission Complete, Clear to Send, Transmit data Register
empty or Framing error (in Smartcard mode) interrupt.

•

During reception: Idle Line detection, Overrun error, Receive data register not empty,
Parity error, LIN break detection, Noise Flag, Framing Error, Character match, etc.

These events generate an interrupt if the corresponding Enable Control Bit is set.

1062/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)
Figure 358. USART interrupt mapping diagram
TC
TCIE
TXE
TXEIE
CTSIF
CTSIE
IDLE
IDLEIE
USART
interrupt

RXNEIE
ORE
RXNEIE
RXNE
PE
PEIE
LBDF
LBDIE
FE
NF
ORE

EIE

CMF
CMIE
RTOF
RTOIE
EOBF
EOBIE

MSv35480V1

RM0385 Rev 7

1063/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

31.8

RM0385

USART registers
Refer to Section 1.1 on page 62 for a list of abbreviations used in register descriptions.

31.8.1

Control register 1 (USART_CR1)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

Res.

Res.

Res.

M1

EOBIE

RTOIE

rw

rw

rw

25

24

23

22

21

20

19

DEAT[4:0]
rw

rw

rw

18

17

16

rw

rw

DEDT[4:0]
rw

15

14

13

12

11

10

9

8

7

6

OVER8

CMIE

MME

M0

WAKE

PCE

PS

PEIE

TXEIE

TCIE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

5

4

RXNEIE IDLEIE
rw

rw

rw

rw

3

2

1

0

TE

RE

Res.

UE

rw

rw

rw

Bits 31:29 Reserved, must be kept at reset value.
Bit 28 M1: Word length
This bit, with bit 12 (M0), determines the word length. It is set or cleared by software.
M[1:0] = 00: 1 Start bit, 8 data bits, n stop bits
M[1:0] = 01: 1 Start bit, 9 data bits, n stop bits
M[1:0] = 10: 1 Start bit, 7 data bits, n stop bits
This bit can only be written when the USART is disabled (UE=0).
Note: Not all modes are supported In 7-bit data length mode. Refer to Section 31.4: USART
implementation for details.
Bit 27 EOBIE: End of Block interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated when the EOBF flag is set in the USART_ISR register.
Note: If the USART does not support Smartcard mode, this bit is reserved and must be kept
at reset value. Please refer to Section 31.4: USART implementation on page 1023.
Bit 26 RTOIE: Receiver timeout interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated when the RTOF bit is set in the USART_ISR register.
Note: If the USART does not support the Receiver timeout feature, this bit is reserved and
must be kept at reset value. Section 31.4: USART implementation on page 1023.
Bits 25:21 DEAT[4:0]: Driver Enable assertion time
This 5-bit value defines the time between the activation of the DE (Driver Enable) signal and
the beginning of the start bit. It is expressed in sample time units (1/8 or 1/16 bit duration,
depending on the oversampling rate).
This bit field can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept at
reset value. Please refer to Section 31.4: USART implementation on page 1023.

1064/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bits 20:16 DEDT[4:0]: Driver Enable de-assertion time
This 5-bit value defines the time between the end of the last stop bit, in a transmitted
message, and the de-activation of the DE (Driver Enable) signal. It is expressed in sample
time units (1/8 or 1/16 bit duration, depending on the oversampling rate).
If the USART_TDR register is written during the DEDT time, the new data is transmitted only
when the DEDT and DEAT times have both elapsed.
This bit field can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept at
reset value. Please refer to Section 31.4: USART implementation on page 1023.
Bit 15 OVER8: Oversampling mode
0: Oversampling by 16
1: Oversampling by 8
This bit can only be written when the USART is disabled (UE=0).
Note: In LIN, IrDA and modes, this bit must be kept at reset value.
Bit 14 CMIE: Character match interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated when the CMF bit is set in the USART_ISR register.
Bit 13 MME: Mute mode enable
This bit activates the mute mode function of the USART. when set, the USART can switch
between the active and mute modes, as defined by the WAKE bit. It is set and cleared by
software.
0: Receiver in active mode permanently
1: Receiver can switch between mute mode and active mode.
Bit 12 M0: Word length
This bit, with bit 28 (M1), determines the word length. It is set or cleared by software. See Bit
28 (M1) description.
This bit can only be written when the USART is disabled (UE=0).
Bit 11 WAKE: Receiver wakeup method
This bit determines the USART wakeup method from Mute mode. It is set or cleared by
software.
0: Idle line
1: Address mark
This bit field can only be written when the USART is disabled (UE=0).
Bit 10 PCE: Parity control enable
This bit selects the hardware parity control (generation and detection). When the parity
control is enabled, the computed parity is inserted at the MSB position (9th bit if M=1; 8th bit
if M=0) and parity is checked on the received data. This bit is set and cleared by software.
Once it is set, PCE is active after the current byte (in reception and in transmission).
0: Parity control disabled
1: Parity control enabled
This bit field can only be written when the USART is disabled (UE=0).
Bit 9 PS: Parity selection
This bit selects the odd or even parity when the parity generation/detection is enabled (PCE
bit set). It is set and cleared by software. The parity will be selected after the current byte.
0: Even parity
1: Odd parity
This bit field can only be written when the USART is disabled (UE=0).

RM0385 Rev 7

1065/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bit 8 PEIE: PE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever PE=1 in the USART_ISR register
Bit 7 TXEIE: interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever TXE=1 in the USART_ISR register
Bit 6 TCIE: Transmission complete interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever TC=1 in the USART_ISR register
Bit 5 RXNEIE: RXNE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever ORE=1 or RXNE=1 in the USART_ISR
register
Bit 4 IDLEIE: IDLE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever IDLE=1 in the USART_ISR register
Bit 3 TE: Transmitter enable
This bit enables the transmitter. It is set and cleared by software.
0: Transmitter is disabled
1: Transmitter is enabled
Note: During transmission, a “0” pulse on the TE bit (“0” followed by “1”) sends a preamble
(idle line) after the current word, except in Smartcard mode. In order to generate an idle
character, the TE must not be immediately written to 1. In order to ensure the required
duration, the software can poll the TEACK bit in the USART_ISR register.
In Smartcard mode, when TE is set there is a 1 bit-time delay before the transmission
starts.
Bit 2 RE: Receiver enable
This bit enables the receiver. It is set and cleared by software.
0: Receiver is disabled
1: Receiver is enabled and begins searching for a start bit
Bit 1 Reserved, must be kept at reset value.
Bit 0 UE: USART enable
When this bit is cleared, the USART prescalers and outputs are stopped immediately, and
current operations are discarded. The configuration of the USART is kept, but all the status
flags, in the USART_ISR are set to their default values. This bit is set and cleared by
software.
0: USART prescaler and outputs disabled, low-power mode
1: USART enabled
Note: In order to go into low-power mode without generating errors on the line, the TE bit
must be reset before and the software must wait for the TC bit in the USART_ISR to be
set before resetting the UE bit.
The DMA requests are also reset when UE = 0 so the DMA channel must be disabled
before resetting the UE bit.

1066/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

31.8.2

Control register 2 (USART_CR2)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

ADD[7:4]

26

25

24

ADD[3:0]

23
RTOEN

22

21

ABRMOD[1:0]

20

19

18

17

MSBFI
DATAINV TXINV
ABREN
RST

16
RXINV

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

SWAP

LINEN

CLKEN

CPOL

CPHA

LBCL

Res.

LBDIE

LBDL

ADDM7

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

rw

rw

STOP[1:0]
rw

rw

Bits 31:28 ADD[7:4]: Address of the USART node
This bit-field gives the address of the USART node or a character code to be recognized.
This is used in multiprocessor communication during Mute mode, for wakeup with 7-bit address
mark detection. The MSB of the character sent by the transmitter should be equal to 1. It may also
be used for character detection during normal reception, Mute mode inactive (for example, end of
block detection in ModBus protocol). In this case, the whole received character (8-bit) is compared
to the ADD[7:0] value and CMF flag is set on match.
This bit field can only be written when reception is disabled (RE = 0) or the USART is disabled
(UE=0)
Bits 27:24 ADD[3:0]: Address of the USART node
This bit-field gives the address of the USART node or a character code to be recognized.
This is used in multiprocessor communication during Mute mode, for wakeup with address mark
detection.
This bit field can only be written when reception is disabled (RE = 0) or the USART is disabled
(UE=0)
Bit 23 RTOEN: Receiver timeout enable
This bit is set and cleared by software.
0: Receiver timeout feature disabled.
1: Receiver timeout feature enabled.
When this feature is enabled, the RTOF flag in the USART_ISR register is set if the RX line is idle
(no reception) for the duration programmed in the RTOR (receiver timeout register).
Note: If the USART does not support the Receiver timeout feature, this bit is reserved and must be
kept at reset value. Please refer to Section 31.4: USART implementation on page 1023.
Bits 22:21 ABRMOD[1:0]: Auto baud rate mode
These bits are set and cleared by software.
00: Measurement of the start bit is used to detect the baud rate.
01: Falling edge to falling edge measurement. (the received frame must start with a single bit = 1 ->
Frame = Start10xxxxxx)
10: 0x7F frame detection.
11: 0x55 frame detection
This bit field can only be written when ABREN = 0 or the USART is disabled (UE=0).
Note: If DATAINV=1 and/or MSBFIRST=1 the patterns must be the same on the line, for example
0xAA for MSBFIRST)
If the USART does not support the auto baud rate feature, this bit is reserved and must be kept
at reset value. Please refer to Section 31.4: USART implementation on page 1023.

RM0385 Rev 7

1067/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bit 20 ABREN: Auto baud rate enable
This bit is set and cleared by software.
0: Auto baud rate detection is disabled.
1: Auto baud rate detection is enabled.
Note: If the USART does not support the auto baud rate feature, this bit is reserved and must be kept
at reset value. Please refer to Section 31.4: USART implementation on page 1023.
Bit 19 MSBFIRST: Most significant bit first
This bit is set and cleared by software.
0: data is transmitted/received with data bit 0 first, following the start bit.
1: data is transmitted/received with the MSB (bit 7/8/9) first, following the start bit.
This bit field can only be written when the USART is disabled (UE=0).
Bit 18 DATAINV: Binary data inversion
This bit is set and cleared by software.
0: Logical data from the data register are send/received in positive/direct logic. (1=H, 0=L)
1: Logical data from the data register are send/received in negative/inverse logic. (1=L, 0=H). The
parity bit is also inverted.
This bit field can only be written when the USART is disabled (UE=0).
Bit 17 TXINV: TX pin active level inversion
This bit is set and cleared by software.
0: TX pin signal works using the standard logic levels (VDD =1/idle, Gnd=0/mark)
1: TX pin signal values are inverted. (VDD =0/mark, Gnd=1/idle).
This allows the use of an external inverter on the TX line.
This bit field can only be written when the USART is disabled (UE=0).
Bit 16 RXINV: RX pin active level inversion
This bit is set and cleared by software.
0: RX pin signal works using the standard logic levels (VDD =1/idle, Gnd=0/mark)
1: RX pin signal values are inverted. (VDD =0/mark, Gnd=1/idle).
This allows the use of an external inverter on the RX line.
This bit field can only be written when the USART is disabled (UE=0).
Bit 15 SWAP: Swap TX/RX pins
This bit is set and cleared by software.
0: TX/RX pins are used as defined in standard pinout
1: The TX and RX pins functions are swapped. This allows to work in the case of a cross-wired
connection to another USART.
This bit field can only be written when the USART is disabled (UE=0).
Bit 14 LINEN: LIN mode enable
This bit is set and cleared by software.
0: LIN mode disabled
1: LIN mode enabled
The LIN mode enables the capability to send LIN synchronous breaks (13 low bits) using the
SBKRQ bit in the USART_RQR register, and to detect LIN Sync breaks.
This bit field can only be written when the USART is disabled (UE=0).
Note: If the USART does not support LIN mode, this bit is reserved and must be kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.

1068/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bits 13:12 STOP[1:0]: STOP bits
These bits are used for programming the stop bits.
00: 1 stop bit
01: 0.5 stop bit
10: 2 stop bits
11: 1.5 stop bits
This bit field can only be written when the USART is disabled (UE=0).
Bit 11 CLKEN: Clock enable
This bit allows the user to enable the CK pin.
0: CK pin disabled
1: CK pin enabled
This bit can only be written when the USART is disabled (UE=0).
Note: If neither synchronous mode nor Smartcard mode is supported, this bit is reserved and must
be kept at reset value. Please refer to Section 31.4: USART implementation on page 1023.
In order to provide correctly the CK clock to the Smartcard when CK is always available When
CLKEN = 1, regardless of the UE bit value, the steps below must be respected:
- UE = 0
- SCEN = 1
- GTPR configuration (If PSC needs to be configured, it is recommended to configure PSC and
GT in a single access to USART_ GTPR register).
- CLKEN= 1
- UE = 1
Bit 10 CPOL: Clock polarity
This bit allows the user to select the polarity of the clock output on the CK pin in synchronous mode.
It works in conjunction with the CPHA bit to produce the desired clock/data relationship
0: Steady low value on CK pin outside transmission window
1: Steady high value on CK pin outside transmission window
This bit can only be written when the USART is disabled (UE=0).
Note: If synchronous mode is not supported, this bit is reserved and must be kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.
Bit 9 CPHA: Clock phase
This bit is used to select the phase of the clock output on the CK pin in synchronous mode. It works
in conjunction with the CPOL bit to produce the desired clock/data relationship (see Figure 346 and
Figure 347)
0: The first clock transition is the first data capture edge
1: The second clock transition is the first data capture edge
This bit can only be written when the USART is disabled (UE=0).
Note: If synchronous mode is not supported, this bit is reserved and must be kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.
Bit 8 LBCL: Last bit clock pulse
This bit is used to select whether the clock pulse associated with the last data bit transmitted (MSB)
has to be output on the CK pin in synchronous mode.
0: The clock pulse of the last data bit is not output to the CK pin
1: The clock pulse of the last data bit is output to the CK pin
Caution: The last bit is the 7th or 8th or 9th data bit transmitted depending on the 7 or 8 or 9 bit
format selected by the M bits in the USART_CR1 register.
This bit can only be written when the USART is disabled (UE=0).
Note: If synchronous mode is not supported, this bit is reserved and must be kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.
Bit 7 Reserved, must be kept at reset value.

RM0385 Rev 7

1069/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bit 6 LBDIE: LIN break detection interrupt enable
Break interrupt mask (break detection using break delimiter).
0: Interrupt is inhibited
1: An interrupt is generated whenever LBDF=1 in the USART_ISR register
Note: If LIN mode is not supported, this bit is reserved and must be kept at reset value. Please refer
to Section 31.4: USART implementation on page 1023.
Bit 5 LBDL: LIN break detection length
This bit is for selection between 11 bit or 10 bit break detection.
0: 10-bit break detection
1: 11-bit break detection
This bit can only be written when the USART is disabled (UE=0).
Note: If LIN mode is not supported, this bit is reserved and must be kept at reset value. Please refer
to Section 31.4: USART implementation on page 1023.
Bit 4 ADDM7:7-bit Address Detection/4-bit Address Detection
This bit is for selection between 4-bit address detection or 7-bit address detection.
0: 4-bit address detection
1: 7-bit address detection (in 8-bit data mode)
This bit can only be written when the USART is disabled (UE=0)
Note: In 7-bit and 9-bit data modes, the address detection is done on 6-bit and 8-bit address
(ADD[5:0] and ADD[7:0]) respectively.
Bits 3:0 Reserved, must be kept at reset value.

Note:

The 3 bits (CPOL, CPHA, LBCL) should not be written while the transmitter is enabled.

31.8.3

Control register 3 (USART_CR3)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

SCARC SCARC SCARC
NT2
NT1
NT0

16
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

CTSIE

CTSE

RTSE

DMAT

DMAR

SCEN

NACK

HDSEL

IRLP

IREN

EIE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

DEP

DEM

DDRE

rw

rw

rw

OVRDI ONEBI
S
T
rw

rw

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 Reserved, must be kept at reset value.
Bit 23 Reserved, must be kept at reset value.
Bits 22:20 Reserved, must be kept at reset value.

1070/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bits 19:17 SCARCNT[2:0]: Smartcard auto-retry count
This bit-field specifies the number of retries in transmit and receive, in Smartcard mode.
In transmission mode, it specifies the number of automatic retransmission retries, before
generating a transmission error (FE bit set).
In reception mode, it specifies the number or erroneous reception trials, before generating a
reception error (RXNE and PE bits set).
This bit field must be programmed only when the USART is disabled (UE=0).
When the USART is enabled (UE=1), this bit field may only be written to 0x0, in order to stop
retransmission.
0x0: retransmission disabled - No automatic retransmission in transmit mode.
0x1 to 0x7: number of automatic retransmission attempts (before signaling error)
Note: If Smartcard mode is not supported, this bit is reserved and must be kept at reset
value. Please refer to Section 31.4: USART implementation on page 1023.
Bit 16 Reserved, must be kept at reset value.
Bit 15 DEP: Driver enable polarity selection
0: DE signal is active high.
1: DE signal is active low.
This bit can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept at
reset value. Please refer to Section 31.4: USART implementation on page 1023.
Bit 14 DEM: Driver enable mode
This bit allows the user to activate the external transceiver control, through the DE signal.
0: DE function is disabled.
1: DE function is enabled. The DE signal is output on the RTS pin.
This bit can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept at
reset value. Section 31.4: USART implementation on page 1023.
Bit 13 DDRE: DMA Disable on Reception Error
0: DMA is not disabled in case of reception error. The corresponding error flag is set but
RXNE is kept 0 preventing from overrun. As a consequence, the DMA request is not
asserted, so the erroneous data is not transferred (no DMA request), but next correct
received data will be transferred (used for Smartcard mode).
1: DMA is disabled following a reception error. The corresponding error flag is set, as well as
RXNE. The DMA request is masked until the error flag is cleared. This means that the
software must first disable the DMA request (DMAR = 0) or clear RXNE before clearing the
error flag.
This bit can only be written when the USART is disabled (UE=0).
Note: The reception errors are: parity error, framing error or noise error.
Bit 12 OVRDIS: Overrun Disable
This bit is used to disable the receive overrun detection.
0: Overrun Error Flag, ORE, is set when received data is not read before receiving new data.
1: Overrun functionality is disabled. If new data is received while the RXNE flag is still set
the ORE flag is not set and the new received data overwrites the previous content of the
USART_RDR register.
This bit can only be written when the USART is disabled (UE=0).
Note: This control bit allows checking the communication flow without reading the data.

RM0385 Rev 7

1071/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bit 11 ONEBIT: One sample bit method enable
This bit allows the user to select the sample method. When the one sample bit method is
selected the noise detection flag (NF) is disabled.
0: Three sample bit method
1: One sample bit method
This bit can only be written when the USART is disabled (UE=0).
Note: ONEBIT feature applies only to data bits, It does not apply to Start bit.
Bit 10 CTSIE: CTS interrupt enable
0: Interrupt is inhibited
1: An interrupt is generated whenever CTSIF=1 in the USART_ISR register
Note: If the hardware flow control feature is not supported, this bit is reserved and must be
kept at reset value. Please refer to Section 31.4: USART implementation on
page 1023.
Bit 9 CTSE: CTS enable
0: CTS hardware flow control disabled
1: CTS mode enabled, data is only transmitted when the CTS input is asserted (tied to 0). If
the CTS input is de-asserted while data is being transmitted, then the transmission is
completed before stopping. If data is written into the data register while CTS is de-asserted,
the transmission is postponed until CTS is asserted.
This bit can only be written when the USART is disabled (UE=0)
Note: If the hardware flow control feature is not supported, this bit is reserved and must be
kept at reset value. Please refer to Section 31.4: USART implementation on
page 1023.
Bit 8 RTSE: RTS enable
0: RTS hardware flow control disabled
1: RTS output enabled, data is only requested when there is space in the receive buffer. The
transmission of data is expected to cease after the current character has been transmitted.
The RTS output is asserted (pulled to 0) when data can be received.
This bit can only be written when the USART is disabled (UE=0).
Note: If the hardware flow control feature is not supported, this bit is reserved and must be
kept at reset value. Please refer to Section 31.4: USART implementation on
page 1023.
Bit 7 DMAT: DMA enable transmitter
This bit is set/reset by software
1: DMA mode is enabled for transmission
0: DMA mode is disabled for transmission
Bit 6 DMAR: DMA enable receiver
This bit is set/reset by software
1: DMA mode is enabled for reception
0: DMA mode is disabled for reception
Bit 5 SCEN: Smartcard mode enable
This bit is used for enabling Smartcard mode.
0: Smartcard Mode disabled
1: Smartcard Mode enabled
This bit field can only be written when the USART is disabled (UE=0).
Note: If the USART does not support Smartcard mode, this bit is reserved and must be kept
at reset value. Please refer to Section 31.4: USART implementation on page 1023.

1072/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bit 4 NACK: Smartcard NACK enable
0: NACK transmission in case of parity error is disabled
1: NACK transmission during parity error is enabled
This bit field can only be written when the USART is disabled (UE=0).
Note: If the USART does not support Smartcard mode, this bit is reserved and must be kept
at reset value. Please refer to Section 31.4: USART implementation on page 1023.
Bit 3 HDSEL: Half-duplex selection
Selection of Single-wire Half-duplex mode
0: Half duplex mode is not selected
1: Half duplex mode is selected
This bit can only be written when the USART is disabled (UE=0).
Bit 2 IRLP: IrDA low-power
This bit is used for selecting between normal and low-power IrDA modes
0: Normal mode
1: Low-power mode
This bit can only be written when the USART is disabled (UE=0).
Note: If IrDA mode is not supported, this bit is reserved and must be kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.
Bit 1 IREN: IrDA mode enable
This bit is set and cleared by software.
0: IrDA disabled
1: IrDA enabled
This bit can only be written when the USART is disabled (UE=0).
Note: If IrDA mode is not supported, this bit is reserved and must be kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.
Bit 0 EIE: Error interrupt enable
Error Interrupt Enable Bit is required to enable interrupt generation in case of a framing
error, overrun error or noise flag (FE=1 or ORE=1 or NF=1 in the USART_ISR register).
0: Interrupt is inhibited
1: An interrupt is generated when FE=1 or ORE=1 or NF=1 in the USART_ISR register.

31.8.4

Baud rate register (USART_BRR)
This register can only be written when the USART is disabled (UE=0). It may be
automatically updated by hardware in auto baud rate detection mode.
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

BRR[15:0]
rw

RM0385 Rev 7

1073/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:4 BRR[15:4]
BRR[15:4] = USARTDIV[15:4]
Bits 3:0 BRR[3:0]
When OVER8 = 0, BRR[3:0] = USARTDIV[3:0].
When OVER8 = 1:
BRR[2:0] = USARTDIV[3:0] shifted 1 bit to the right.
BRR[3] must be kept cleared.

31.8.5

Guard time and prescaler register (USART_GTPR)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

GT[7:0]
rw

rw

1074/1709

rw

rw

rw

PSC[7:0]
rw

rw

rw

rw

RM0385 Rev 7

rw

rw

rw

rw

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:8 GT[7:0]: Guard time value
This bit-field is used to program the Guard time value in terms of number of baud clock
periods.
This is used in Smartcard mode. The Transmission Complete flag is set after this guard time
value.
This bit field can only be written when the USART is disabled (UE=0).
Note: If Smartcard mode is not supported, this bit is reserved and must be kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.
Bits 7:0 PSC[7:0]: Prescaler value
In IrDA Low-power and normal IrDA mode:
PSC[7:0] = IrDA Normal and Low-Power Baud Rate
Used for programming the prescaler for dividing the USART source clock to achieve the lowpower frequency:
The source clock is divided by the value given in the register (8 significant bits):
00000000: Reserved - do not program this value
00000001: divides the source clock by 1
00000010: divides the source clock by 2
...
In Smartcard mode:
PSC[4:0]: Prescaler value
Used for programming the prescaler for dividing the USART source clock to provide the
Smartcard clock.
The value given in the register (5 significant bits) is multiplied by 2 to give the division factor
of the source clock frequency:
00000: Reserved - do not program this value
00001: divides the source clock by 2
00010: divides the source clock by 4
00011: divides the source clock by 6
...
This bit field can only be written when the USART is disabled (UE=0).
Note: Bits [7:5] must be kept at reset value if Smartcard mode is used.
This bit field is reserved and must be kept at reset value when the Smartcard and IrDA
modes are not supported. Please refer to Section 31.4: USART implementation on
page 1023.

31.8.6

Receiver timeout register (USART_RTOR)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

BLEN[7:0]

20

19

18

17

16

RTO[23:16]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

RTO[15:0]
rw

RM0385 Rev 7

1075/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bits 31:24 BLEN[7:0]: Block Length
This bit-field gives the Block length in Smartcard T=1 Reception. Its value equals the number
of information characters + the length of the Epilogue Field (1-LEC/2-CRC) - 1.
Examples:
BLEN = 0 -> 0 information characters + LEC
BLEN = 1 -> 0 information characters + CRC
BLEN = 255 -> 254 information characters + CRC (total 256 characters))
In Smartcard mode, the Block length counter is reset when TXE=0.
This bit-field can be used also in other modes. In this case, the Block length counter is reset
when RE=0 (receiver disabled) and/or when the EOBCF bit is written to 1.
Note: This value can be programmed after the start of the block reception (using the data
from the LEN character in the Prologue Field). It must be programmed only once per
received block.
Bits 23:0 RTO[23:0]: Receiver timeout value
This bit-field gives the Receiver timeout value in terms of number of bit duration.
In standard mode, the RTOF flag is set if, after the last received character, no new start bit is
detected for more than the RTO value.
In Smartcard mode, this value is used to implement the CWT and BWT. See Smartcard
section for more details.
In this case, the timeout measurement is done starting from the Start Bit of the last received
character.
Note: This value must only be programmed once per received character.

Note:

RTOR can be written on the fly. If the new value is lower than or equal to the counter, the
RTOF flag is set.
This register is reserved and forced by hardware to “0x00000000” when the Receiver
timeout feature is not supported. Please refer to Section 31.4: USART implementation on
page 1023.

31.8.7

Request register (USART_RQR)
Address offset: 0x18
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

4

3

2

1

0

15

14

13

12

11

10

9

8

7

6

5

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TXFRQ RXFRQ MMRQ SBKRQ ABRRQ
w

1076/1709

RM0385 Rev 7

w

w

w

w

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bits 31:5 Reserved, must be kept at reset value.
Bit 4 TXFRQ: Transmit data flush request
Writing 1 to this bit sets the TXE flag.
This allows to discard the transmit data. This bit must be used only in Smartcard mode,
when data has not been sent due to errors (NACK) and the FE flag is active in the
USART_ISR register.
If the USART does not support Smartcard mode, this bit is reserved and must be kept at
reset value. Please refer to Section 31.4: USART implementation on page 1023.
Bit 3 RXFRQ: Receive data flush request
Writing 1 to this bit clears the RXNE flag.
This allows to discard the received data without reading it, and avoid an overrun condition.
Bit 2 MMRQ: Mute mode request
Writing 1 to this bit puts the USART in mute mode and sets the RWU flag.
Bit 1 SBKRQ: Send break request
Writing 1 to this bit sets the SBKF flag and request to send a BREAK on the line, as soon as
the transmit machine is available.
Note: In the case the application needs to send the break character following all previously
inserted data, including the ones not yet transmitted, the software should wait for the
TXE flag assertion before setting the SBKRQ bit.
Bit 0 ABRRQ: Auto baud rate request
Writing 1 to this bit resets the ABRF flag in the USART_ISR and request an automatic baud
rate measurement on the next received data frame.
Note: If the USART does not support the auto baud rate feature, this bit is reserved and must
be kept at reset value. Please refer to Section 31.4: USART implementation on
page 1023.

31.8.8

Interrupt and status register (USART_ISR)
Address offset: 0x1C
Reset value: 0x0200 00C0

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TEACK

Res.

RWU

SBKF

CMF

BUSY

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

ABRF

ABRE

Res.

EOBF

RTOF

CTS

CTSIF

LBDF

TXE

TC

RXNE

IDLE

ORE

NF

FE

PE

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

Bits 31:25 Reserved, must be kept at reset value.
Bits 24:22 Reserved, must be kept at reset value.
Bit 21 TEACK: Transmit enable acknowledge flag
This bit is set/reset by hardware, when the Transmit Enable value is taken into account by
the USART.
It can be used when an idle frame request is generated by writing TE=0, followed by TE=1
in the USART_CR1 register, in order to respect the TE=0 minimum period.
Bit 20 Reserved, must be kept at reset value.

RM0385 Rev 7

1077/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bit 19 RWU: Receiver wakeup from Mute mode
This bit indicates if the USART is in mute mode. It is cleared/set by hardware when a
wakeup/mute sequence is recognized. The mute mode control sequence (address or IDLE)
is selected by the WAKE bit in the USART_CR1 register.
When wakeup on IDLE mode is selected, this bit can only be set by software, writing 1 to the
MMRQ bit in the USART_RQR register.
0: Receiver in active mode
1: Receiver in mute mode
Bit 18 SBKF: Send break flag
This bit indicates that a send break character was requested. It is set by software, by writing
1 to the SBKRQ bit in the USART_RQR register. It is automatically reset by hardware during
the stop bit of break transmission.
0: No break character is transmitted
1: Break character will be transmitted
Bit 17 CMF: Character match flag
This bit is set by hardware, when the character defined by ADD[7:0] is received. It is cleared
by software, writing 1 to the CMCF in the USART_ICR register.
An interrupt is generated if CMIE=1in the USART_CR1 register.
0: No Character match detected
1: Character Match detected
Bit 16 BUSY: Busy flag
This bit is set and reset by hardware. It is active when a communication is ongoing on the
RX line (successful start bit detected). It is reset at the end of the reception (successful or
not).
0: USART is idle (no reception)
1: Reception on going
Bit 15 ABRF: Auto baud rate flag
This bit is set by hardware when the automatic baud rate has been set (RXNE will also be
set, generating an interrupt if RXNEIE = 1) or when the auto baud rate operation was
completed without success (ABRE=1) (ABRE, RXNE and FE are also set in this case)
It is cleared by software, in order to request a new auto baud rate detection, by writing 1 to
the ABRRQ in the USART_RQR register.
Note: If the USART does not support the auto baud rate feature, this bit is reserved and kept
at reset value.
Bit 14 ABRE: Auto baud rate error
This bit is set by hardware if the baud rate measurement failed (baud rate out of range or
character comparison failed)
It is cleared by software, by writing 1 to the ABRRQ bit in the USART_CR3 register.
Note: If the USART does not support the auto baud rate feature, this bit is reserved and kept
at reset value.
Bit 13 Reserved, must be kept at reset value.

1078/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bit 12 EOBF: End of block flag
This bit is set by hardware when a complete block has been received (for example T=1
Smartcard mode). The detection is done when the number of received bytes (from the start
of the block, including the prologue) is equal or greater than BLEN + 4.
An interrupt is generated if the EOBIE=1 in the USART_CR2 register.
It is cleared by software, writing 1 to the EOBCF in the USART_ICR register.
0: End of Block not reached
1: End of Block (number of characters) reached
Note: If Smartcard mode is not supported, this bit is reserved and kept at reset value. Please
refer to Section 31.4: USART implementation on page 1023.
Bit 11 RTOF: Receiver timeout
This bit is set by hardware when the timeout value, programmed in the RTOR register has
lapsed, without any communication. It is cleared by software, writing 1 to the RTOCF bit in
the USART_ICR register.
An interrupt is generated if RTOIE=1 in the USART_CR1 register.
In Smartcard mode, the timeout corresponds to the CWT or BWT timings.
0: Timeout value not reached
1: Timeout value reached without any data reception
Note: If a time equal to the value programmed in RTOR register separates 2 characters,
RTOF is not set. If this time exceeds this value + 2 sample times (2/16 or 2/8,
depending on the oversampling method), RTOF flag is set.
The counter counts even if RE = 0 but RTOF is set only when RE = 1. If the timeout has
already elapsed when RE is set, then RTOF will be set.
If the USART does not support the Receiver timeout feature, this bit is reserved and
kept at reset value.
Bit 10 CTS: CTS flag
This bit is set/reset by hardware. It is an inverted copy of the status of the CTS input pin.
0: CTS line set
1: CTS line reset
Note: If the hardware flow control feature is not supported, this bit is reserved and kept at
reset value.
Bit 9 CTSIF: CTS interrupt flag
This bit is set by hardware when the CTS input toggles, if the CTSE bit is set. It is cleared by
software, by writing 1 to the CTSCF bit in the USART_ICR register.
An interrupt is generated if CTSIE=1 in the USART_CR3 register.
0: No change occurred on the CTS status line
1: A change occurred on the CTS status line
Note: If the hardware flow control feature is not supported, this bit is reserved and kept at
reset value.
Bit 8 LBDF: LIN break detection flag
This bit is set by hardware when the LIN break is detected. It is cleared by software, by
writing 1 to the LBDCF in the USART_ICR.
An interrupt is generated if LBDIE = 1 in the USART_CR2 register.
0: LIN Break not detected
1: LIN break detected
Note: If the USART does not support LIN mode, this bit is reserved and kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.

RM0385 Rev 7

1079/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bit 7 TXE: Transmit data register empty
This bit is set by hardware when the content of the USART_TDR register has been
transferred into the shift register. It is cleared by a write to the USART_TDR register.
The TXE flag can also be cleared by writing 1 to the TXFRQ in the USART_RQR register, in
order to discard the data (only in Smartcard T=0 mode, in case of transmission failure).
An interrupt is generated if the TXEIE bit =1 in the USART_CR1 register.
0: data is not transferred to the shift register
1: data is transferred to the shift register)
Note: This bit is used during single buffer transmission.
Bit 6 TC: Transmission complete
This bit is set by hardware if the transmission of a frame containing data is complete and if
TXE is set. An interrupt is generated if TCIE=1 in the USART_CR1 register. It is cleared by
software, writing 1 to the TCCF in the USART_ICR register or by a write to the USART_TDR
register.
An interrupt is generated if TCIE=1 in the USART_CR1 register.
0: Transmission is not complete
1: Transmission is complete
Note: If TE bit is reset and no transmission is on going, the TC bit will be set immediately.
Bit 5 RXNE: Read data register not empty
This bit is set by hardware when the content of the RDR shift register has been transferred
to the USART_RDR register. It is cleared by a read to the USART_RDR register. The RXNE
flag can also be cleared by writing 1 to the RXFRQ in the USART_RQR register.
An interrupt is generated if RXNEIE=1 in the USART_CR1 register.
0: data is not received
1: Received data is ready to be read.
Bit 4 IDLE: Idle line detected
This bit is set by hardware when an Idle Line is detected. An interrupt is generated if
IDLEIE=1 in the USART_CR1 register. It is cleared by software, writing 1 to the IDLECF in
the USART_ICR register.
0: No Idle line is detected
1: Idle line is detected
Note: The IDLE bit will not be set again until the RXNE bit has been set (i.e. a new idle line
occurs).
If mute mode is enabled (MME=1), IDLE is set if the USART is not mute (RWU=0),
whatever the mute mode selected by the WAKE bit. If RWU=1, IDLE is not set.
Bit 3 ORE: Overrun error
This bit is set by hardware when the data currently being received in the shift register is
ready to be transferred into the RDR register while RXNE=1. It is cleared by a software,
writing 1 to the ORECF, in the USART_ICR register.
An interrupt is generated if RXNEIE=1 or EIE = 1 in the USART_CR1 register.
0: No overrun error
1: Overrun error is detected
Note: When this bit is set, the RDR register content is not lost but the shift register is
overwritten. An interrupt is generated if the ORE flag is set during multibuffer
communication if the EIE bit is set.
This bit is permanently forced to 0 (no overrun detection) when the OVRDIS bit is set in
the USART_CR3 register.

1080/1709

RM0385 Rev 7

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bit 2 NF: START bit Noise detection flag
This bit is set by hardware when noise is detected on a received frame. It is cleared by
software, writing 1 to the NFCF bit in the USART_ICR register.
0: No noise is detected
1: Noise is detected
Note: This bit does not generate an interrupt as it appears at the same time as the RXNE bit
which itself generates an interrupt. An interrupt is generated when the NF flag is set
during multibuffer communication if the EIE bit is set.
Note: When the line is noise-free, the NF flag can be disabled by programming the ONEBIT
bit to 1 to increase the USART tolerance to deviations (Refer to Section 31.5.5:
Tolerance of the USART receiver to clock deviation on page 1039).
Bit 1 FE: Framing error
This bit is set by hardware when a de-synchronization, excessive noise or a break character
is detected. It is cleared by software, writing 1 to the FECF bit in the USART_ICR register.
In Smartcard mode, in transmission, this bit is set when the maximum number of transmit
attempts is reached without success (the card NACKs the data frame).
An interrupt is generated if EIE = 1 in the USART_CR1 register.
0: No Framing error is detected
1: Framing error or break character is detected
Bit 0 PE: Parity error
This bit is set by hardware when a parity error occurs in receiver mode. It is cleared by
software, writing 1 to the PECF in the USART_ICR register.
An interrupt is generated if PEIE = 1 in the USART_CR1 register.
0: No parity error
1: Parity error

31.8.9

Interrupt flag clear register (USART_ICR)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CMCF

Res.

rc_w1
15

14

13

Res.

Res.

Res.

12

11

EOBCF RTOCF
rc_w1

rc_w1

10
Res.

9

8

CTSCF LBDCF
rc_w1

7

6

5

Res.

TCCF

Res.

rc_w1

rc_w1

4

3

IDLECF ORECF
rc_w1

rc_w1

2

1

0

NCF

FECF

PECF

rc_w1

rc_w1

rc_w1

Bits 31:20 Reserved, must be kept at reset value.
Bits 19:18 Reserved, must be kept at reset value.
Bit 17 CMCF: Character match clear flag
Writing 1 to this bit clears the CMF flag in the USART_ISR register.
Bits 16:13 Reserved, must be kept at reset value.
Bit 12 EOBCF: End of block clear flag
Writing 1 to this bit clears the EOBF flag in the USART_ISR register.
Note: If the USART does not support Smartcard mode, this bit is reserved and must be kept
at reset value. Please refer to Section 31.4: USART implementation on page 1023.

RM0385 Rev 7

1081/1709
1084

Universal synchronous asynchronous receiver transmitter (USART)

RM0385

Bit 11 RTOCF: Receiver timeout clear flag
Writing 1 to this bit clears the RTOF flag in the USART_ISR register.
Note: If the USART does not support the Receiver timeout feature, this bit is reserved and
must be kept at reset value. Please refer to Section 31.4: USART implementation on
page 1023.
Bit 10 Reserved, must be kept at reset value.
Bit 9 CTSCF: CTS clear flag
Writing 1 to this bit clears the CTSIF flag in the USART_ISR register.
Note: If the hardware flow control feature is not supported, this bit is reserved and must be
kept at reset value. Please refer to Section 31.4: USART implementation on
page 1023.
Bit 8 LBDCF: LIN break detection clear flag
Writing 1 to this bit clears the LBDF flag in the USART_ISR register.
Note: If LIN mode is not supported, this bit is reserved and must be kept at reset value.
Please refer to Section 31.4: USART implementation on page 1023.
Bit 7 Reserved, must be kept at reset value.
Bit 6 TCCF: Transmission complete clear flag
Writing 1 to this bit clears the TC flag in the USART_ISR register.
Bit 5 Reserved, must be kept at reset value.
Bit 4 IDLECF: Idle line detected clear flag
Writing 1 to this bit clears the IDLE flag in the USART_ISR register.
Bit 3 ORECF: Overrun error clear flag
Writing 1 to this bit clears the ORE flag in the USART_ISR register.
Bit 2 NCF: Noise detected clear flag
Writing 1 to this bit clears the NF flag in the USART_ISR register.
Bit 1 FECF: Framing error clear flag
Writing 1 to this bit clears the FE flag in the USART_ISR register.
Bit 0 PECF: Parity error clear flag
Writing 1 to this bit clears the PE flag in the USART_ISR register.

31.8.10

Receive data register (USART_RDR)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

3

2

1

0

r

r

r

r

15

14

13

12

11

10

9

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RDR[8:0]
r

1082/1709

r

RM0385 Rev 7

r

r

r

RM0385

Universal synchronous asynchronous receiver transmitter (USART)

Bits 31:9 Reserved, must be kept at reset value.
Bits 8:0 RDR[8:0]: Receive data value
Contains the received data character.
The RDR register provides the parallel interface between the input shift register and the
internal bus (see Figure 334).
When receiving with the parity enabled, the value read in the MSB bit is the received parity
bit.

31.8.11

Transmit data register (USART_TDR)
Address offset: 0x28
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

15

14

13

12

11

10

9

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TDR[8:0]
rw

rw

rw

rw

rw

Bits 31:9 Reserved, must be kept at reset value.
Bits 8:0 TDR[8:0]: Transmit data value
Contains the data character to be transmitted.
The TDR register provides the parallel interface between the internal bus and the output
shift register (see Figure 334).
When transmitting with the parity enabled (PCE bit set to 1 in the USART_CR1 register),
the value written in the MSB (bit 7 or bit 8 depending on the data length) has no effect
because it is replaced by the parity.
Note: This register must be written only when TXE=1.

31.8.12

USART register map
The table below gives the USART register map and reset values.

RM0385 Rev 7

TE

RE

0

0

Res.

LBDIE

LBDL

ADDM7

Res.

Res.

0

0

0

STOP
[1:0]

0

0

0

0

0

0

0

UE

IDLEIE
0

Res.

TCIE

RXNEIE
0

0

Res.

TXEIE

0

0

Res.

PS

PEIE

0

0

0

LBCL

0

0

PCE

0

0

0

CPOL

MME

0

CPHA

CMIE

0

0

M0

DEDT0

OVER8
SWAP

0

0

WAKE

DEDT1

RXINV

0

0

CLKEN

DEDT2

TXINV

0

0

LINEN

DEDT3
0

DEAT0

0

DEDT4

0

DEAT1
0

DEAT2
0

DEAT3

DATAINV

0

0

0

ADD[3:0]

0

0

MSBFIRST

0

0

ABREN

0

0

ABRMOD0

0

0

0

0x04
Reset value

0

ABRMOD1

ADD[7:4]

0

RTOIE

0

DEAT4

0

RTOEN

USART_CR2

M1

Reset value

EOBIE

Res.

USART_CR1
0x00

Res.

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 199. USART register map and reset values

1083/1709
1084

0x28
USART_TDR

1084/1709

Reset value

RM0385 Rev 7
CTS
CTSIF
LBDF
TXE
TC
RXNE
IDLE
ORE
NF
FE
PE

0
0
1
1
0
0
0
0
0
0

Res.
CTSCF
LBDCF
Res.
TCCF
Res.
IDLECF

0
0
0

RTOCF

0
0

Reset value

Refer to Section 2.2 on page 68 for the register boundary addresses.
0
0
0
0
0
0
0
0

USART_RQR
Res.
Res.

NACK
HDSEL

0
0
0
0

BRR[15:0]

0

EIE

SCEN

0

IRLP

DMAR

CTSE
RTSE

CTSIE

DMAT

ONEBIT

0

IREN

0

GT[7:0]

Reset value
ABRRQ

0
Res.

0

RDR[8:0]

X X X X X X

TDR[8:0]

X X X X X X
PECF

0
Res.

0

MMRQ

0
Res.

0

SBKRQ

0
Res.

0

NCF

0

Res.

DDRE
OVRDIS
0

FECF

0

Res.

0

RXFRQ

0

Res.

Res.
DEP

Res.

SCARCNT2:0]

Res.

Res.

Res.

DEM

Res.
Res.

Res.

Res.

Res.

Res.

Res.

0

ORECF

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

TXFRQ

0

Res.

0

Res.

Res.

0

Res.

0

0

Res.

RTOF

0

Res.

0

Res.

0

0

Res.

0

Res.

BLEN[7:0]
0

Res.
0

Res.
EOBF

0

Res.

0

Res.

0

EOBCF

0

Res.

0

0

Res.

0

Res.

0

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

ABRE

0

Res.

0

Res.

Reset value

Res.

0

Res.

Res.

0

Res.

ABRF

0

Res.

0

Res.

Res.

Reset value

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

CMF
BUSY

0

CMCF

0

Res.

0

Res.

Res.

RWU
SBKF

0

Res.
0

0

Res.

Res.

TEACK

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Reset value

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

USART_RDR

Res.

0x24
Res.

USART_ICR

Res.

0x20

Res.

USART_ISR

Res.

0x1C

Res.

USART_RTOR

Res.

0

Res.

0x18
Reset value

Res.

USART_GTPR

Res.

0x10

Res.

USART_BRR

Res.

0x0C

Res.

USART_CR3

Res.

0x08

Res.

0x14

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register

Res.

Offset

Res.

Universal synchronous asynchronous receiver transmitter (USART)
RM0385

Table 199. USART register map and reset values (continued)

0
0
0

0
0
0
0
0
0

PSC[7:0]

0
0
0
0
0
0
0
0
0
0

RTO[23:0]

0
0
0
0
0

0
0
0
0

X
X
X

X

X

X

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

32

Serial peripheral interface / inter-IC sound (SPI/I2S)

32.1

Introduction
The SPI/I²S interface can be used to communicate with external devices using the SPI
protocol or the I2S audio protocol. SPI or I2S mode is selectable by software. SPI Motorola
mode is selected by default after a device reset.
The serial peripheral interface (SPI) protocol supports half-duplex, full-duplex and simplex
synchronous, serial communication with external devices. The interface can be configured
as master and in this case it provides the communication clock (SCK) to the external slave
device. The interface is also capable of operating in multimaster configuration.
The Inter-IC sound (I2S) protocol is also a synchronous serial communication interface.It
can operate in slave or master mode with half-duplex communication. Full-duplex
operations are possible by combining two I2S blocks. It can address four different audio
standards including the Philips I2S standard, the MSB- and LSB-justified standards and the
PCM standard.

32.2

SPI main features
•

Master or slave operation

•

Full-duplex synchronous transfers on three lines

•

Half-duplex synchronous transfer on two lines (with bidirectional data line)

•

Simplex synchronous transfers on two lines (with unidirectional data line)

•

4-bit to 16-bit data size selection

•

Multimaster mode capability

•

8 master mode baud rate prescalers up to fPCLK/2

•

Slave mode frequency up to fPCLK/2.

•

NSS management by hardware or software for both master and slave: dynamic change
of master/slave operations

•

Programmable clock polarity and phase

•

Programmable data order with MSB-first or LSB-first shifting

•

Dedicated transmission and reception flags with interrupt capability

•

SPI bus busy status flag

•

SPI Motorola support

•

Hardware CRC feature for reliable communication:
–

CRC value can be transmitted as last byte in Tx mode

–

Automatic CRC error checking for last received byte

•

Master mode fault, overrun flags with interrupt capability

•

CRC Error flag

•

Two 32-bit embedded Rx and Tx FIFOs with DMA capability

•

SPI TI mode support

RM0385 Rev 7

1085/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

32.3

32.4

RM0385

I2S main features
•

Half-duplex communication (only transmitter or receiver)

•

Master or slave operations

•

8-bit programmable linear prescaler to reach accurate audio sample frequencies (from
8 kHz to 192 kHz)

•

Data format may be 16-bit, 24-bit or 32-bit

•

Packet frame is fixed to 16-bit (16-bit data frame) or 32-bit (16-bit, 24-bit, 32-bit data
frame) by audio channel

•

Programmable clock polarity (steady state)

•

Underrun flag in slave transmission mode, overrun flag in reception mode (master and
slave) and Frame Error Flag in reception and transmitter mode (slave only)

•

16-bit register for transmission and reception with one data register for both channel
sides

•

Supported I2S protocols:
–

I2S Philips standard

–

MSB-justified standard (left-justified)

–

LSB-justified standard (right-justified)

–

PCM standard (with short and long frame synchronization on 16-bit channel frame
or 16-bit data frame extended to 32-bit channel frame)

•

Data direction is always MSB first

•

DMA capability for transmission and reception (16-bit wide)

•

Master clock can be output to drive an external audio component. Ratio is fixed at
256 × FS (where FS is the audio sampling frequency)

SPI/I2S implementation
This manual describes the SPI/I2S implementation in STM32F75xxx and STM32F74xxx
devices.
Table 200. STM32F75xxx and STM32F74xxx SPI implementation
SPI Features(1)

SPI1

SPI2

SPI3

SPI4

SPI5

SPI6

Hardware CRC calculation

X

X

X

X

X

X

Rx/Tx FIFO

X

X

X

X

X

X

NSS pulse mode

X

X

X

X

X

X

I2S mode

X

X

X

-

-

-

TI mode

X

X

X

X

X

X

1. X = supported.

1086/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

32.5

SPI functional description

32.5.1

General description
The SPI allows synchronous, serial communication between the MCU and external devices.
Application software can manage the communication by polling the status flag or using
dedicated SPI interrupt. The main elements of SPI and their interactions are shown in the
following block diagram Figure 359.
Figure 359. SPI block diagram
Address and data bus
Read
Rx
FIFO
CRC controller
MOSI
MISO

Shift register
RXONLY
CPOL
CPHA
DS[0:3]

Tx
FIFO
Write

BIDIOE

SCK

Baud rate
generator

CRCEN
CRCNEXT
CRCL

Communication
controller

BR[2:0]

Internal NSS
NSS
logic

NSS

MS30117V1

Four I/O pins are dedicated to SPI communication with external devices.
•

MISO: Master In / Slave Out data. In the general case, this pin is used to transmit data
in slave mode and receive data in master mode.

•

MOSI: Master Out / Slave In data. In the general case, this pin is used to transmit data
in master mode and receive data in slave mode.

•

SCK: Serial Clock output pin for SPI masters and input pin for SPI slaves.

•

NSS: Slave select pin. Depending on the SPI and NSS settings, this pin can be used to
either:
–

select an individual slave device for communication

–

synchronize the data frame or

–

detect a conflict between multiple masters

See Section 32.5.5: Slave select (NSS) pin management for details.
The SPI bus allows the communication between one master device and one or more slave
devices. The bus consists of at least two wires - one for the clock signal and the other for
synchronous data transfer. Other signals can be added depending on the data exchange
between SPI nodes and their slave select signal management.

RM0385 Rev 7

1087/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

32.5.2

RM0385

Communications between one master and one slave
The SPI allows the MCU to communicate using different configurations, depending on the
device targeted and the application requirements. These configurations use 2 or 3 wires
(with software NSS management) or 3 or 4 wires (with hardware NSS management).
Communication is always initiated by the master.

Full-duplex communication
By default, the SPI is configured for full-duplex communication. In this configuration, the
shift registers of the master and slave are linked using two unidirectional lines between the
MOSI and the MISO pins. During SPI communication, data is shifted synchronously on the
SCK clock edges provided by the master. The master transmits the data to be sent to the
slave via the MOSI line and receives data from the slave via the MISO line. When the data
frame transfer is complete (all the bits are shifted) the information between the master and
slave is exchanged.
Figure 360. Full-duplex single master/ single slave application

Rx shift register
Tx shift register
SPI clock
generator

MISO

MISO

MOSI

MOSI

SCK

SCK

NSS(1)

NSS (1)

Master

Tx shift register
Rx shift register

Slave
MSv39623V1

1. The NSS pins can be used to provide a hardware control flow between master and slave. Optionally, the
pins can be left unused by the peripheral. Then the flow has to be handled internally for both master and
slave. For more details see Section 32.5.5: Slave select (NSS) pin management.

Half-duplex communication
The SPI can communicate in half-duplex mode by setting the BIDIMODE bit in the
SPIx_CR1 register. In this configuration, one single cross connection line is used to link the
shift registers of the master and slave together. During this communication, the data is
synchronously shifted between the shift registers on the SCK clock edge in the transfer
direction selected reciprocally by both master and slave with the BDIOE bit in their
SPIx_CR1 registers. In this configuration, the master’s MISO pin and the slave’s MOSI pin
are free for other application uses and act as GPIOs.

1088/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 361. Half-duplex single master/ single slave application

(2)

Rx shift register
Tx shift register
SPI clock
generator

MISO

MISO
MOSI

(3)

1kΩ

MOSI

SCK

SCK

NSS (1)

NSS(1)

Master

Tx shift register

(2)

Rx shift register

Slave
MSv39624V1

1. The NSS pins can be used to provide a hardware control flow between master and slave. Optionally, the
pins can be left unused by the peripheral. Then the flow has to be handled internally for both master and
slave. For more details see Section 32.5.5: Slave select (NSS) pin management.
2. In this configuration, the master’s MISO pin and the slave’s MOSI pin can be used as GPIOs.
3. A critical situation can happen when communication direction is changed not synchronously between two
nodes working at bidirectionnal mode and new transmitter accesses the common data line while former
transmitter still keeps an opposite value on the line (the value depends on SPI configuration and
communication data). Both nodes then fight while providing opposite output levels on the common line
temporary till next node changes its direction settings correspondingly, too. It is suggested to insert a serial
resistance between MISO and MOSI pins at this mode to protect the outputs and limit the current blowing
between them at this situation.

Simplex communications
The SPI can communicate in simplex mode by setting the SPI in transmit-only or in receiveonly using the RXONLY bit in the SPIx_CR2 register. In this configuration, only one line is
used for the transfer between the shift registers of the master and slave. The remaining
MISO and MOSI pins pair is not used for communication and can be used as standard
GPIOs.
•

Transmit-only mode (RXONLY=0): The configuration settings are the same as for fullduplex. The application has to ignore the information captured on the unused input pin.
This pin can be used as a standard GPIO.

•

Receive-only mode (RXONLY=1): The application can disable the SPI output function
by setting the RXONLY bit. In slave configuration, the MISO output is disabled and the
pin can be used as a GPIO. The slave continues to receive data from the MOSI pin
while its slave select signal is active (see 32.5.5: Slave select (NSS) pin management).
Received data events appear depending on the data buffer configuration. In the master
configuration, the MOSI output is disabled and the pin can be used as a GPIO. The
clock signal is generated continuously as long as the SPI is enabled. The only way to
stop the clock is to clear the RXONLY bit or the SPE bit and wait until the incoming
pattern from the MISO pin is finished and fills the data buffer structure, depending on its
configuration.

RM0385 Rev 7

1089/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 362. Simplex single master/single slave application (master in transmit-only/
slave in receive-only mode)

Rx shift register
Tx shift register
SPI clock
generator

(2)

MISO

MISO

MOSI

MOSI

SCK

SCK

NSS(1)

NSS(1)

Master

Tx shift register
Rx shift register

Slave
MSv39625V1

1. The NSS pins can be used to provide a hardware control flow between master and slave. Optionally, the
pins can be left unused by the peripheral. Then the flow has to be handled internally for both master and
slave. For more details see Section 32.5.5: Slave select (NSS) pin management.
2. An accidental input information is captured at the input of transmitter Rx shift register. All the events
associated with the transmitter receive flow must be ignored in standard transmit only mode (e.g. OVF
flag).
3. In this configuration, both the MISO pins can be used as GPIOs.

Note:

Any simplex communication can be alternatively replaced by a variant of the half-duplex
communication with a constant setting of the transaction direction (bidirectional mode is
enabled while BDIO bit is not changed).

32.5.3

Standard multi-slave communication
In a configuration with two or more independent slaves, the master uses GPIO pins to
manage the chip select lines for each slave (see Figure 363.). The master must select one
of the slaves individually by pulling low the GPIO connected to the slave NSS input. When
this is done, a standard master and dedicated slave communication is established.

1090/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 363. Master and three independent slaves

NSS (1)
Rx shift register
Tx shift register
SPI clock
generator
Master

MISO

MISO

MOSI

MOSI

SCK

SCK

IO1

NSS

Tx shift register
Rx shift register

Slave 1

IO2
IO3

MISO
MOSI

Tx shift register
Rx shift register

SCK
NSS
Slave 2

MISO
MOSI

Tx shift register
Rx shift register

SCK
NSS
Slave 3
MSv39626V1

1. NSS pin is not used on master side at this configuration. It has to be managed internally (SSM=1, SSI=1) to
prevent any MODF error.
2. As MISO pins of the slaves are connected together, all slaves must have the GPIO configuration of their
MISO pin set as alternate function open-drain (see Section 6.3.7: I/O alternate function input/output on
page 204.

32.5.4

Multi-master communication
Unless SPI bus is not designed for a multi-master capability primarily, the user can use build
in feature which detects a potential conflict between two nodes trying to master the bus at
the same time. For this detection, NSS pin is used configured at hardware input mode.
The connection of more than two SPI nodes working at this mode is impossible as only one
node can apply its output on a common data line at time.
When nodes are non active, both stay at slave mode by default. Once one node wants to
overtake control on the bus, it switches itself into master mode and applies active level on
the slave select input of the other node via dedicated GPIO pin. After the session is

RM0385 Rev 7

1091/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

completed, the active slave select signal is released and the node mastering the bus
temporary returns back to passive slave mode waiting for next session start.
If potentially both nodes raised their mastering request at the same time a bus conflict event
appears (see mode fault MODF event). Then the user can apply some simple arbitration
process (e.g. to postpone next attempt by predefined different time-outs applied at both
nodes).

Figure 364. Multi-master application

Rx (Tx) shift register
Tx (Rx) shift register
SPI clock
generator

Master
(Slave)

MISO

MISO

MOSI

MOSI

SCK

SCK

GPIO

NSS

NSS(1)

GPIO

Rx (Tx) shift register
Tx (Rx) shift register
SPI clock
generator

(1)

Master
(Slave)
MSv39628V1

1. The NSS pin is configured at hardware input mode at both nodes. Its active level enables the MISO line
output control as the passive node is configured as a slave.

32.5.5

Slave select (NSS) pin management
In slave mode, the NSS works as a standard “chip select” input and lets the slave
communicate with the master. In master mode, NSS can be used either as output or input.
As an input it can prevent multimaster bus collision, and as an output it can drive a slave
select signal of a single slave.
Hardware or software slave select management can be set using the SSM bit in the
SPIx_CR1 register:

1092/1709

•

Software NSS management (SSM = 1): in this configuration, slave select information
is driven internally by the SSI bit value in register SPIx_CR1. The external NSS pin is
free for other application uses.

•

Hardware NSS management (SSM = 0): in this case, there are two possible
configurations. The configuration used depends on the NSS output configuration
(SSOE bit in register SPIx_CR1).
–

NSS output enable (SSM=0,SSOE = 1): this configuration is only used when the
MCU is set as master. The NSS pin is managed by the hardware. The NSS signal
is driven low as soon as the SPI is enabled in master mode (SPE=1), and is kept
low until the SPI is disabled (SPE =0). A pulse can be generated between
continuous communications if NSS pulse mode is activated (NSSP=1). The SPI
cannot work in multimaster configuration with this NSS setting.

–

NSS output disable (SSM=0, SSOE = 0): if the microcontroller is acting as the
master on the bus, this configuration allows multimaster capability. If the NSS pin
is pulled low in this mode, the SPI enters master mode fault state and the device is
automatically reconfigured in slave mode. In slave mode, the NSS pin works as a
standard “chip select” input and the slave is selected while NSS line is at low level.

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 365. Hardware/software slave select management
SSI control bit
SSM control bit

1

NSS
Inp.

Master
mode

Slave mode

Vdd

OK

Non active

Vss

Conflict

Active

NSS Input

NSS
pin

0

GPIO
logic

NSS
Output
Control

NSS Output
(used in Master mode and NSS
HW management only)

SSOE control bit
NSS external logic

NSS internal logic

MSv35526V6

32.5.6

Communication formats
During SPI communication, receive and transmit operations are performed simultaneously.
The serial clock (SCK) synchronizes the shifting and sampling of the information on the data
lines. The communication format depends on the clock phase, the clock polarity and the
data frame format. To be able to communicate together, the master and slaves devices must
follow the same communication format.

Clock phase and polarity controls
Four possible timing relationships may be chosen by software, using the CPOL and CPHA
bits in the SPIx_CR1 register. The CPOL (clock polarity) bit controls the idle state value of
the clock when no data is being transferred. This bit affects both master and slave modes. If
CPOL is reset, the SCK pin has a low-level idle state. If CPOL is set, the SCK pin has a
high-level idle state.
If the CPHA bit is set, the second edge on the SCK pin captures the first data bit transacted
(falling edge if the CPOL bit is reset, rising edge if the CPOL bit is set). Data are latched on
each occurrence of this clock transition type. If the CPHA bit is reset, the first edge on the
SCK pin captures the first data bit transacted (falling edge if the CPOL bit is set, rising edge
if the CPOL bit is reset). Data are latched on each occurrence of this clock transition type.
The combination of CPOL (clock polarity) and CPHA (clock phase) bits selects the data
capture clock edge.

RM0385 Rev 7

1093/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 366, shows an SPI full-duplex transfer with the four combinations of the CPHA and
CPOL bits.
Note:

Prior to changing the CPOL/CPHA bits the SPI must be disabled by resetting the SPE bit.
The idle state of SCK must correspond to the polarity selected in the SPIx_CR1 register (by
pulling up SCK if CPOL=1 or pulling down SCK if CPOL=0).
Figure 366. Data clock timing diagram
CPHA =1
CPOL = 1

CPOL = 0

MOSI(1)

MSBit

MISO(1)

MSBit

LSBit

LSBit

NSS (to slave)

Capture strobe

CPHA =0
CPOL = 1

CPOL = 0

MOSI(1)

MISO(1)

LSBit

MSBit

MSBit

LSBit

NSS (to slave)

Capture strobe
ai17154e

1. The order of data bits depends on LSBFIRST bit setting.

Data frame format
The SPI shift register can be set up to shift out MSB-first or LSB-first, depending on the
value of the LSBFIRST bit. The data frame size is chosen by using the DS bits. It can be set
from 4-bit up to 16-bit length and the setting applies for both transmission and reception.
Whatever the selected data frame size, read access to the FIFO must be aligned with the
FRXTH level. When the SPIx_DR register is accessed, data frames are always right-aligned
into either a byte (if the data fits into a byte) or a half-word (see Figure 367). During
communication, only bits within the data frame are clocked and transferred.

1094/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 367. Data alignment when data length is not equal to 8-bit or 16-bit
DS <= 8 bits: data is right-aligned on byte
Example: DS = 5 bit
7

5 4
XXX

7

15

0

15

0
RX

Data frame

14 13
XX

TX

Data frame
5 4

000

DS > 8 bits: data is right-aligned on 16 bit
Example: DS = 14 bit
0
Data frame

14 13
00

TX
0

Data frame

RX
MS19589V2

Note:

The minimum data length is 4 bits. If a data length of less than 4 bits is selected, it is forced
to an 8-bit data frame size.

32.5.7

Configuration of SPI
The configuration procedure is almost the same for master and slave. For specific mode
setups, follow the dedicated sections. When a standard communication is to be initialized,
perform these steps:
1.
2.

3.

Write proper GPIO registers: Configure GPIO for MOSI, MISO and SCK pins.
Write to the SPI_CR1 register:
a)

Configure the serial clock baud rate using the BR[2:0] bits (Note: 4).

b)

Configure the CPOL and CPHA bits combination to define one of the four
relationships between the data transfer and the serial clock (CPHA must be
cleared in NSSP mode). (Note: 2 - except the case when CRC is enabled at TI
mode).

c)

Select simplex or half-duplex mode by configuring RXONLY or BIDIMODE and
BIDIOE (RXONLY and BIDIMODE can't be set at the same time).

d)

Configure the LSBFIRST bit to define the frame format (Note: 2).

e)

Configure the CRCL and CRCEN bits if CRC is needed (while SCK clock signal is
at idle state).

f)

Configure SSM and SSI (Notes: 2 & 3).

g)

Configure the MSTR bit (in multimaster NSS configuration, avoid conflict state on
NSS if master is configured to prevent MODF error).

Write to SPI_CR2 register:
a)

Configure the DS[3:0] bits to select the data length for the transfer.

b)

Configure SSOE (Notes: 1 & 2 & 3).

c)

Set the FRF bit if the TI protocol is required (keep NSSP bit cleared in TI mode).

d)

Set the NSSP bit if the NSS pulse mode between two data units is required (keep
CHPA and TI bits cleared in NSSP mode).

e)

Configure the FRXTH bit. The RXFIFO threshold must be aligned to the read
access size for the SPIx_DR register.

f)

Initialize LDMA_TX and LDMA_RX bits if DMA is used in packed mode.

4.

Write to SPI_CRCPR register: Configure the CRC polynomial if needed.

5.

Write proper DMA registers: Configure DMA streams dedicated for SPI Tx and Rx in
DMA registers if the DMA streams are used.

RM0385 Rev 7

1095/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)
Note:

RM0385

(1) Step is not required in slave mode.
(2) Step is not required in TI mode.
(3) Step is not required in NSSP mode.
(4) The step is not required in slave mode except slave working at TI mode

32.5.8

Procedure for enabling SPI
It is recommended to enable the SPI slave before the master sends the clock. If not,
undesired data transmission might occur. The data register of the slave must already
contain data to be sent before starting communication with the master (either on the first
edge of the communication clock, or before the end of the ongoing communication if the
clock signal is continuous). The SCK signal must be settled at an idle state level
corresponding to the selected polarity before the SPI slave is enabled.
The master at full-duplex (or in any transmit-only mode) starts to communicate when the
SPI is enabled and TXFIFO is not empty, or with the next write to TXFIFO.
In any master receive only mode (RXONLY=1 or BIDIMODE=1 & BIDIOE=0), master starts
to communicate and the clock starts running immediately after SPI is enabled.
For handling DMA, follow the dedicated section.

32.5.9

Data transmission and reception procedures
RXFIFO and TXFIFO
All SPI data transactions pass through the 32-bit embedded FIFOs. This enables the SPI to
work in a continuous flow, and prevents overruns when the data frame size is short. Each
direction has its own FIFO called TXFIFO and RXFIFO. These FIFOs are used in all SPI
modes except for receiver-only mode (slave or master) with CRC calculation enabled (see
Section 32.5.14: CRC calculation).
The handling of FIFOs depends on the data exchange mode (duplex, simplex), data frame
format (number of bits in the frame), access size performed on the FIFO data registers (8-bit
or 16-bit), and whether or not data packing is used when accessing the FIFOs (see
Section 32.5.13: TI mode).
A read access to the SPIx_DR register returns the oldest value stored in RXFIFO that has
not been read yet. A write access to the SPIx_DR stores the written data in the TXFIFO at
the end of a send queue. The read access must be always aligned with the RXFIFO
threshold configured by the FRXTH bit in SPIx_CR2 register. FTLVL[1:0] and FRLVL[1:0]
bits indicate the current occupancy level of both FIFOs.
A read access to the SPIx_DR register must be managed by the RXNE event. This event is
triggered when data is stored in RXFIFO and the threshold (defined by FRXTH bit) is
reached. When RXNE is cleared, RXFIFO is considered to be empty. In a similar way, write
access of a data frame to be transmitted is managed by the TXE event. This event is
triggered when the TXFIFO level is less than or equal to half of its capacity. Otherwise TXE
is cleared and the TXFIFO is considered as full. In this way, RXFIFO can store up to four
data frames, whereas TXFIFO can only store up to three when the data frame format is not
greater than 8 bits. This difference prevents possible corruption of 3x 8-bit data frames
already stored in the TXFIFO when software tries to write more data in 16-bit mode into
TXFIFO. Both TXE and RXNE events can be polled or handled by interrupts. See
Figure 369 through Figure 372.

1096/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Another way to manage the data exchange is to use DMA (see Communication using DMA
(direct memory addressing)).
If the next data is received when the RXFIFO is full, an overrun event occurs (see
description of OVR flag at Section 32.5.10: SPI status flags). An overrun event can be
polled or handled by an interrupt.
The BSY bit being set indicates ongoing transaction of a current data frame. When the clock
signal runs continuously, the BSY flag stays set between data frames at master but
becomes low for a minimum duration of one SPI clock at slave between each data frame
transfer.

Sequence handling
A few data frames can be passed at single sequence to complete a message. When
transmission is enabled, a sequence begins and continues while any data is present in the
TXFIFO of the master. The clock signal is provided continuously by the master until TXFIFO
becomes empty, then it stops waiting for additional data.
In receive-only modes, half-duplex (BIDIMODE=1, BIDIOE=0) or simplex (BIDIMODE=0,
RXONLY=1) the master starts the sequence immediately when both SPI is enabled and
receive-only mode is activated. The clock signal is provided by the master and it does not
stop until either SPI or receive-only mode is disabled by the master. The master receives
data frames continuously up to this moment.
While the master can provide all the transactions in continuous mode (SCK signal is
continuous) it has to respect slave capability to handle data flow and its content at anytime.
When necessary, the master must slow down the communication and provide either a
slower clock or separate frames or data sessions with sufficient delays. Be aware there is no
underflow error signal for master or slave in SPI mode, and data from the slave is always
transacted and processed by the master even if the slave could not prepare it correctly in
time. It is preferable for the slave to use DMA, especially when data frames are shorter and
bus rate is high.
Each sequence must be encased by the NSS pulse in parallel with the multislave system to
select just one of the slaves for communication. In a single slave system it is not necessary
to control the slave with NSS, but it is often better to provide the pulse here too, to
synchronize the slave with the beginning of each data sequence. NSS can be managed by
both software and hardware (see Section 32.5.5: Slave select (NSS) pin management).
When the BSY bit is set it signifies an ongoing data frame transaction. When the dedicated
frame transaction is finished, the RXNE flag is raised. The last bit is just sampled and the
complete data frame is stored in the RXFIFO.

Procedure for disabling the SPI
When SPI is disabled, it is mandatory to follow the disable procedures described in this
paragraph. It is important to do this before the system enters a low-power mode when the
peripheral clock is stopped. Ongoing transactions can be corrupted in this case. In some
modes the disable procedure is the only way to stop continuous communication running.
Master in full-duplex or transmit only mode can finish any transaction when it stops
providing data for transmission. In this case, the clock stops after the last data transaction.
Special care must be taken in packing mode when an odd number of data frames are
transacted to prevent some dummy byte exchange (refer to Data packing section). Before
the SPI is disabled in these modes, the user must follow standard disable procedure. When

RM0385 Rev 7

1097/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

the SPI is disabled at the master transmitter while a frame transaction is ongoing or next
data frame is stored in TXFIFO, the SPI behavior is not guaranteed.
When the master is in any receive only mode, the only way to stop the continuous clock is to
disable the peripheral by SPE=0. This must occur in specific time window within last data
frame transaction just between the sampling time of its first bit and before its last bit transfer
starts (in order to receive a complete number of expected data frames and to prevent any
additional “dummy” data reading after the last valid data frame). Specific procedure must be
followed when disabling SPI in this mode.
Data received but not read remains stored in RXFIFO when the SPI is disabled, and must
be processed the next time the SPI is enabled, before starting a new sequence. To prevent
having unread data, ensure that RXFIFO is empty when disabling the SPI, by using the
correct disabling procedure, or by initializing all the SPI registers with a software reset via
the control of a specific register dedicated to peripheral reset (see the SPIiRST bits in the
RCC_APBiRSTR registers).
Standard disable procedure is based on pulling BSY status together with FTLVL[1:0] to
check if a transmission session is fully completed. This check can be done in specific cases,
too, when it is necessary to identify the end of ongoing transactions, for example:
•

When NSS signal is managed by software and master has to provide proper end of
NSS pulse for slave, or

•

When transactions’ streams from DMA or FIFO are completed while the last data frame
or CRC frame transaction is still ongoing in the peripheral bus.

The correct disable procedure is (except when receive only mode is used):
1.

Wait until FTLVL[1:0] = 00 (no more data to transmit).

2.

Wait until BSY=0 (the last data frame is processed).

3.

Disable the SPI (SPE=0).

4.

Read data until FRLVL[1:0] = 00 (read all the received data).

The correct disable procedure for certain receive only modes is:

Note:

1.

Interrupt the receive flow by disabling SPI (SPE=0) in the specific time window while
the last data frame is ongoing.

2.

Wait until BSY=0 (the last data frame is processed).

3.

Read data until FRLVL[1:0] = 00 (read all the received data).

If packing mode is used and an odd number of data frames with a format less than or equal
to 8 bits (fitting into one byte) has to be received, FRXTH must be set when FRLVL[1:0] =
01, in order to generate the RXNE event to read the last odd data frame and to keep good
FIFO pointer alignment.

Data packing
When the data frame size fits into one byte (less than or equal to 8 bits), data packing is
used automatically when any read or write 16-bit access is performed on the SPIx_DR
register. The double data frame pattern is handled in parallel in this case. At first, the SPI
operates using the pattern stored in the LSB of the accessed word, then with the other half
stored in the MSB. Figure 368 provides an example of data packing mode sequence
handling. Two data frames are sent after the single 16-bit access the SPIx_DR register of
the transmitter. This sequence can generate just one RXNE event in the receiver if the
RXFIFO threshold is set to 16 bits (FRXTH=0). The receiver then has to access both data
frames by a single 16-bit read of SPIx_DR as a response to this single RXNE event. The

1098/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
RxFIFO threshold setting and the following read access must be always kept aligned at the
receiver side, as data can be lost if it is not in line.
A specific problem appears if an odd number of such “fit into one byte” data frames must be
handled. On the transmitter side, writing the last data frame of any odd sequence with an 8bit access to SPIx_DR is enough. The receiver has to change the Rx_FIFO threshold level
for the last data frame received in the odd sequence of frames in order to generate the
RXNE event.
Figure 368. Packing data in FIFO for transmission and reception
NSS
SCK

TXFIFO
SPIx_DR

0x0A

0x04 0x0A

0x04

RXFIFO

MOSI
0x0A

SPI fsm
& shift

16-bit write access to data register
at TxE event:
SPI_DR= 0x40A;

SPIx_DR

0x0A

0x04

SPI fsm
& shift

0x04
0x04 0x0A

16-bit read access from data register
at RxNE event:
unit16_t var;
var= SPI_DR /*var=0x040A*/
MS19590V2

1. In this example: Data size DS[3:0] is 4-bit configured, CPOL=0, CPHA=1 and LSBFIRST =0. The Data
storage is always right aligned while the valid bits are performed on the bus only, the content of LSB byte
goes first on the bus, the unused bits are not taken into account on the transmitter side and padded by
zeros at the receiver side.

Communication using DMA (direct memory addressing)
To operate at its maximum speed and to facilitate the data register read/write process
required to avoid overrun, the SPI features a DMA capability, which implements a simple
request/acknowledge protocol.
A DMA access is requested when the TXE or RXNE enable bit in the SPIx_CR2 register is
set. Separate requests must be issued to the Tx and Rx buffers.
•

In transmission, a DMA request is issued each time TXE is set to 1. The DMA then
writes to the SPIx_DR register.

•

In reception, a DMA request is issued each time RXNE is set to 1. The DMA then reads
the SPIx_DR register.

See Figure 369 through Figure 372.
When the SPI is used only to transmit data, it is possible to enable only the SPI Tx DMA
channel. In this case, the OVR flag is set because the data received is not read. When the
SPI is used only to receive data, it is possible to enable only the SPI Rx DMA channel.
In transmission mode, when the DMA has written all the data to be transmitted (the TCIF
flag is set in the DMA_ISR register), the BSY flag can be monitored to ensure that the SPI
communication is complete. This is required to avoid corrupting the last transmission before
disabling the SPI or entering the Stop mode. The software must first wait until
FTLVL[1:0]=00 and then until BSY=0.

RM0385 Rev 7

1099/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

When starting communication using DMA, to prevent DMA channel management raising
error events, these steps must be followed in order:
1.

Enable DMA Rx buffer in the RXDMAEN bit in the SPI_CR2 register, if DMA Rx is
used.

2.

Enable DMA streams for Tx and Rx in DMA registers, if the streams are used.

3.

Enable DMA Tx buffer in the TXDMAEN bit in the SPI_CR2 register, if DMA Tx is used.

4.

Enable the SPI by setting the SPE bit.

To close communication it is mandatory to follow these steps in order:
1.

Disable DMA streams for Tx and Rx in the DMA registers, if the streams are used.

2.

Disable the SPI by following the SPI disable procedure.

3.

Disable DMA Tx and Rx buffers by clearing the TXDMAEN and RXDMAEN bits in the
SPI_CR2 register, if DMA Tx and/or DMA Rx are used.

Packing with DMA
If the transfers are managed by DMA (TXDMAEN and RXDMAEN set in the SPIx_CR2
register) packing mode is enabled/disabled automatically depending on the PSIZE value
configured for SPI TX and the SPI RX DMA channel. If the DMA channel PSIZE value is
equal to 16-bit and SPI data size is less than or equal to 8-bit, then packing mode is
enabled. The DMA then automatically manages the write operations to the SPIx_DR
register.
If data packing mode is used and the number of data to transfer is not a multiple of two, the
LDMA_TX/LDMA_RX bits must be set. The SPI then considers only one data for the
transmission or reception to serve the last DMA transfer (for more details refer to Data
packing on page 1098.)

1100/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

Communication diagrams
Some typical timing schemes are explained in this section. These schemes are valid no
matter if the SPI events are handled by polling, interrupts or DMA. For simplicity, the
LSBFIRST=0, CPOL=0 and CPHA=1 setting is used as a common assumption here. No
complete configuration of DMA streams is provided.
The following numbered notes are common for Figure 369 on page 1102 through
Figure 372 on page 1105.
1.

The slave starts to control MISO line as NSS is active and SPI is enabled, and is
disconnected from the line when one of them is released. Sufficient time must be
provided for the slave to prepare data dedicated to the master in advance before its
transaction starts.
At the master, the SPI peripheral takes control at MOSI and SCK signals (occasionally
at NSS signal as well) only if SPI is enabled. If SPI is disabled the SPI peripheral is
disconnected from GPIO logic, so the levels at these lines depends on GPIO setting
exclusively.

2.

At the master, BSY stays active between frames if the communication (clock signal) is
continuous. At the slave, BSY signal always goes down for at least one clock cycle
between data frames.

3.

The TXE signal is cleared only if TXFIFO is full.

4.

The DMA arbitration process starts just after the TXDMAEN bit is set. The TXE
interrupt is generated just after the TXEIE is set. As the TXE signal is at an active level,
data transfers to TxFIFO start, until TxFIFO becomes full or the DMA transfer
completes.

5.

If all the data to be sent can fit into TxFIFO, the DMA Tx TCIF flag can be raised even
before communication on the SPI bus starts. This flag always rises before the SPI
transaction is completed.

6.

The CRC value for a package is calculated continuously frame by frame in the
SPIx_TxCRCR and SPIx_RxCRCR registers. The CRC information is processed after
the entire data package has completed, either automatically by DMA (Tx channel must
be set to the number of data frames to be processed) or by SW (the user must handle
CRCNEXT bit during the last data frame processing).
While the CRC value calculated in SPIx_TxCRCR is simply sent out by transmitter,
received CRC information is loaded into RxFIFO and then compared with the
SPIx_RxCRCR register content (CRC error flag can be raised here if any difference).
This is why the user must take care to flush this information from the FIFO, either by
software reading out all the stored content of RxFIFO, or by DMA when the proper
number of data frames is preset for Rx channel (number of data frames + number of
CRC frames) (see the settings at the example assumption).

7.

In data packed mode, TxE and RxNE events are paired and each read/write access to
the FIFO is 16 bits wide until the number of data frames are even. If the TxFIFO is ¾
full FTLVL status stays at FIFO full level. That is why the last odd data frame cannot be
stored before the TxFIFO becomes ½ full. This frame is stored into TxFIFO with an 8bit access either by software or automatically by DMA when LDMA_TX control is set.

8.

To receive the last odd data frame in packed mode, the Rx threshold must be changed
to 8-bit when the last data frame is processed, either by software setting FRXTH=1 or
automatically by a DMA internal signal when LDMA_RX is set.

RM0385 Rev 7

1101/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 369. Master full-duplex communication
NSS

SCK

2

BSY

MOSI

DTx1

MSB

2

DTx2

MSB

MSB

DTx3

SPE

3

TXE

3

Enable Tx/Rx DMA or interrupts
DTx1

FTLVL

00

DTx2

10

DTx3

11

10

DMA or software control at Tx events

10

11

00

4
DRx1

MISO

LSB

DRx2

LSB

DRx3

LSB
1

1
RXNE

DMA or software control at Rx events

FRLVL

00

DMA Tx TICF

DRx1
10

5

00

DRx2
10

DRx3
00

10

00

DMA Rx TICF
MSv19266V2

Assumptions for master full-duplex communication example:
•

Data size > 8 bit

If DMA is used:
•

Number of Tx frames transacted by DMA is set to 3

•

Number of Rx frames transacted by DMA is set to 3

See also : Communication diagrams on page 1101 for details about common assumptions
and notes.

1102/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 370. Slave full-duplex communication
NSS

SCK

BSY

2

MISO

MSB

DTx1

MSB

MSB

DTx2

DTx3
1

1

SPE

3

TXE

3

Enable Tx/Rx DMA or interrupts

4
DTx1

FTLVL

00

DTx3

DTx2

10

10

11

10

11

DRx1

MOSI

DMA or software control at Tx events

LSB

DRx2

00

LSB

DRx3

LSB

RXNE

DMA or software control at Rx events

00

FRLVL

DMA Tx TICF

DRx1
10

5

00

DRx2
10

DRx3
00

10

00

DMA Rx TICF
MSv32123V2

Assumptions for slave full-duplex communication example:
•

Data size > 8 bit

If DMA is used:
•

Number of Tx frames transacted by DMA is set to 3

•

Number of Rx frames transacted by DMA is set to 3

See also : Communication diagrams on page 1101 for details about common assumptions
and notes.

RM0385 Rev 7

1103/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 371. Master full-duplex communication with CRC
NSS
SCK
BSY

2

MOSI

MSB

DTx1

MSB

MSB

DTx2

CRC

SPE
TXE

3
Enable Tx/Rx DMA or interrupts
DTx1

FTLVL

00

DTx2

10

DMA or software control at Tx events

11

10

00

4
DRx1

MISO

LSB

DRx2

LSB

CRC

LSB
1

1

RXNE
DMA or software control at Rx events

FRLVL

00

DMA Tx TICF

5

DRx1
10

00

DRx2
10

DRx3
00

DMA Rx TICF

00

10

6
MSv32124V2

Assumptions for master full-duplex communication with CRC example:
•

Data size = 16 bit

•

CRC enabled

If DMA is used:
•

Number of Tx frames transacted by DMA is set to 2

•

Number of Rx frames transacted by DMA is set to 3

See also : Communication diagrams on page 1101 for details about common assumptions
and notes.

1104/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 372. Master full-duplex communication in packed mode
NSS
SCK
BSY

2
DTx1-2

MOSI

4 3 2 1

5

5

DTx3-4
5

4 3 2 1

4 3 2 1

5

DTx5
4 3 2 1

4 3 2 1

5

SPE
3

3

TXE

Enable Tx/Rx DMA or interrupts
DTx1-2

DTx3-4

DTx5

DMA or software control at Tx events
7

FTLVL

10

00

10

11

10

11

01

00

4
5 4 3 2

MISO

1

5 4 3 2

5 4 3 2

1

5 4 3 2

1

5 4 3 2

DRx3-4

DRx1-2

1

1

1

DRx5

1

RXNE
DMA or software control at Rx events

DRx1-2

DRx3-4

FRTHX=1

DRx5

8

FRLVL

00

DMA Tx TICF

10

01

5

00

01

10

00

01

00

DMA Rx TICF
MSv32125V2

Assumptions for master full-duplex communication in packed mode example:
•

Data size = 5 bit

•

Read/write FIFO is performed mostly by 16-bit access

•

FRXTH=0

If DMA is used:
•

Number of Tx frames to be transacted by DMA is set to 3

•

Number of Rx frames to be transacted by DMA is set to 3

•

PSIZE for both Tx and Rx DMA channel is set to 16-bit

•

LDMA_TX=1 and LDMA_RX=1

See also : Communication diagrams on page 1101 for details about common assumptions
and notes.

RM0385 Rev 7

1105/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

32.5.10

RM0385

SPI status flags
Three status flags are provided for the application to completely monitor the state of the SPI
bus.

Tx buffer empty flag (TXE)
The TXE flag is set when transmission TXFIFO has enough space to store data to send.
TXE flag is linked to the TXFIFO level. The flag goes high and stays high until the TXFIFO
level is lower or equal to 1/2 of the FIFO depth. An interrupt can be generated if the TXEIE
bit in the SPIx_CR2 register is set. The bit is cleared automatically when the TXFIFO level
becomes greater than 1/2.

Rx buffer not empty (RXNE)
The RXNE flag is set depending on the FRXTH bit value in the SPIx_CR2 register:
•

If FRXTH is set, RXNE goes high and stays high until the RXFIFO level is greater or
equal to 1/4 (8-bit).

•

If FRXTH is cleared, RXNE goes high and stays high until the RXFIFO level is greater
than or equal to 1/2 (16-bit).

An interrupt can be generated if the RXNEIE bit in the SPIx_CR2 register is set.
The RXNE is cleared by hardware automatically when the above conditions are no longer
true.

Busy flag (BSY)
The BSY flag is set and cleared by hardware (writing to this flag has no effect).
When BSY is set, it indicates that a data transfer is in progress on the SPI (the SPI bus is
busy).
The BSY flag can be used in certain modes to detect the end of a transfer so that the
software can disable the SPI or its peripheral clock before entering a low-power mode which
does not provide a clock for the peripheral. This avoids corrupting the last transfer.
The BSY flag is also useful for preventing write collisions in a multimaster system.
The BSY flag is cleared under any one of the following conditions:

Note:

1106/1709

•

When the SPI is correctly disabled

•

When a fault is detected in Master mode (MODF bit set to 1)

•

In Master mode, when it finishes a data transmission and no new data is ready to be
sent

•

In Slave mode, when the BSY flag is set to '0' for at least one SPI clock cycle between
each data transfer.

When the next transmission can be handled immediately by the master (e.g. if the master is
in Receive-only mode or its Transmit FIFO is not empty), communication is continuous and
the BSY flag remains set to '1' between transfers on the master side. Although this is not the
case with a slave, it is recommended to use always the TXE and RXNE flags (instead of the
BSY flags) to handle data transmission or reception operations.

RM0385 Rev 7

RM0385

32.5.11

Serial peripheral interface / inter-IC sound (SPI/I2S)

SPI error flags
An SPI interrupt is generated if one of the following error flags is set and interrupt is enabled
by setting the ERRIE bit.

Overrun flag (OVR)
An overrun condition occurs when data is received by a master or slave and the RXFIFO
has not enough space to store this received data. This can happen if the software or the
DMA did not have enough time to read the previously received data (stored in the RXFIFO)
or when space for data storage is limited e.g. the RXFIFO is not available when CRC is
enabled in receive only mode so in this case the reception buffer is limited into a single data
frame buffer (see Section 32.5.14: CRC calculation).
When an overrun condition occurs, the newly received value does not overwrite the
previous one in the RXFIFO. The newly received value is discarded and all data transmitted
subsequently is lost. Clearing the OVR bit is done by a read access to the SPI_DR register
followed by a read access to the SPI_SR register.

Mode fault (MODF)
Mode fault occurs when the master device has its internal NSS signal (NSS pin in NSS
hardware mode, or SSI bit in NSS software mode) pulled low. This automatically sets the
MODF bit. Master mode fault affects the SPI interface in the following ways:
•

The MODF bit is set and an SPI interrupt is generated if the ERRIE bit is set.

•

The SPE bit is cleared. This blocks all output from the device and disables the SPI
interface.

•

The MSTR bit is cleared, thus forcing the device into slave mode.

Use the following software sequence to clear the MODF bit:
1.

Make a read or write access to the SPIx_SR register while the MODF bit is set.

2.

Then write to the SPIx_CR1 register.

To avoid any multiple slave conflicts in a system comprising several MCUs, the NSS pin
must be pulled high during the MODF bit clearing sequence. The SPE and MSTR bits can
be restored to their original state after this clearing sequence. As a security, hardware does
not allow the SPE and MSTR bits to be set while the MODF bit is set. In a slave device the
MODF bit cannot be set except as the result of a previous multimaster conflict.

CRC error (CRCERR)
This flag is used to verify the validity of the value received when the CRCEN bit in the
SPIx_CR1 register is set. The CRCERR flag in the SPIx_SR register is set if the value
received in the shift register does not match the receiver SPIx_RXCRCR value. The flag is
cleared by the software.

TI mode frame format error (FRE)
A TI mode frame format error is detected when an NSS pulse occurs during an ongoing
communication when the SPI is operating in slave mode and configured to conform to the TI
mode protocol. When this error occurs, the FRE flag is set in the SPIx_SR register. The SPI
is not disabled when an error occurs, the NSS pulse is ignored, and the SPI waits for the
next NSS pulse before starting a new transfer. The data may be corrupted since the error
detection may result in the loss of two data bytes.

RM0385 Rev 7

1107/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

The FRE flag is cleared when SPIx_SR register is read. If the ERRIE bit is set, an interrupt
is generated on the NSS error detection. In this case, the SPI should be disabled because
data consistency is no longer guaranteed and communications should be reinitiated by the
master when the slave SPI is enabled again.

32.5.12

NSS pulse mode
This mode is activated by the NSSP bit in the SPIx_CR2 register and it takes effect only if
the SPI interface is configured as Motorola SPI master (FRF=0) with capture on the first
edge (SPIx_CR1 CPHA = 0, CPOL setting is ignored). When activated, an NSS pulse is
generated between two consecutive data frame transfers when NSS stays at high level for
the duration of one clock period at least. This mode allows the slave to latch data. NSSP
pulse mode is designed for applications with a single master-slave pair.
Figure 373 illustrates NSS pin management when NSSP pulse mode is enabled.
Figure 373. NSSP pulse generation in Motorola SPI master mode
Master continuous transfer (CPOL = 1; CPHA = 0; NSSP= 1)
sampling

sampling sampling

sampling

sampling sampling

NSS
output
SCK
output
MOSI
output

MSB

MISO
input Do not care

MSB

LSB
LSB

Do not care
tSCK

tSCK

tSCK

4-bits to 16-bits

MSB

LSB

MSB

LSB

tSCK

Do not care
tSCK

4-bits to 16-bits
MS19838V1

Note:

Similar behavior is encountered when CPOL = 0. In this case the sampling edge is the rising
edge of SCK, and NSS assertion and deassertion refer to this sampling edge.

32.5.13

TI mode
TI protocol in master mode
The SPI interface is compatible with the TI protocol. The FRF bit of the SPIx_CR2 register
can be used to configure the SPI to be compliant with this protocol.
The clock polarity and phase are forced to conform to the TI protocol requirements whatever
the values set in the SPIx_CR1 register. NSS management is also specific to the TI protocol
which makes the configuration of NSS management through the SPIx_CR1 and SPIx_CR2
registers (SSM, SSI, SSOE) impossible in this case.
In slave mode, the SPI baud rate prescaler is used to control the moment when the MISO
pin state changes to HiZ when the current transaction finishes (see Figure 374). Any baud
rate can be used, making it possible to determine this moment with optimal flexibility.
However, the baud rate is generally set to the external master clock baud rate. The delay for
the MISO signal to become HiZ (trelease) depends on internal resynchronization and on the

1108/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
baud rate value set in through the BR[2:0] bits in the SPIx_CR1 register. It is given by the
formula:

t baud_rate
t baud_rate
--------------------- + 4 × t pclk < t release < --------------------- + 6 × t pclk
2
2
If the slave detects a misplaced NSS pulse during a data frame transaction the TIFRE flag is
set.
If the data size is equal to 4-bits or 5-bits, the master in full-duplex mode or transmit-only
mode uses a protocol with one more dummy data bit added after LSB. TI NSS pulse is
generated above this dummy bit clock cycle instead of the LSB in each period.
This feature is not available for Motorola SPI communications (FRF bit set to 0).
Figure 374: TI mode transfer shows the SPI communication waveforms when TI mode is
selected.
Figure 374. TI mode transfer

g

t RELEASE

sa

m

pl

er

in

g
in

gg
tr i

sa

m

pl

er
gg

pl

tri

m
sa

tri

gg

er

in

g

NSS

SCK
MOSI

MISO

Do not care
1 or 0

MSB

LSB

MSB

LSB

MSB

LSB

MSB

LSB

FRAME 1

FRAME 2
MS19835V2

32.5.14

CRC calculation
Two separate CRC calculators are implemented in order to check the reliability of
transmitted and received data. The SPI offers CRC8 or CRC16 calculation independently of
the frame data length, which can be fixed to 8-bit or 16-bit. For all the other data frame
lengths, no CRC is available.

CRC principle
CRC calculation is enabled by setting the CRCEN bit in the SPIx_CR1 register before the
SPI is enabled (SPE = 1). The CRC value is calculated using an odd programmable
polynomial on each bit. The calculation is processed on the sampling clock edge defined by
the CPHA and CPOL bits in the SPIx_CR1 register. The calculated CRC value is checked
automatically at the end of the data block as well as for transfer managed by CPU or by the
DMA. When a mismatch is detected between the CRC calculated internally on the received
data and the CRC sent by the transmitter, a CRCERR flag is set to indicate a data corruption
error. The right procedure for handling the CRC calculation depends on the SPI
configuration and the chosen transfer management.

RM0385 Rev 7

1109/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)
Note:

RM0385

The polynomial value should only be odd. No even values are supported.

CRC transfer managed by CPU
Communication starts and continues normally until the last data frame has to be sent or
received in the SPIx_DR register. Then CRCNEXT bit has to be set in the SPIx_CR1
register to indicate that the CRC frame transaction will follow after the transaction of the
currently processed data frame. The CRCNEXT bit must be set before the end of the last
data frame transaction. CRC calculation is frozen during CRC transaction.
The received CRC is stored in the RXFIFO like a data byte or word. That is why in CRC
mode only, the reception buffer has to be considered as a single 16-bit buffer used to
receive only one data frame at a time.
A CRC-format transaction usually takes one more data frame to communicate at the end of
data sequence. However, when setting an 8-bit data frame checked by 16-bit CRC, two
more frames are necessary to send the complete CRC.
When the last CRC data is received, an automatic check is performed comparing the
received value and the value in the SPIx_RXCRC register. Software has to check the
CRCERR flag in the SPIx_SR register to determine if the data transfers were corrupted or
not. Software clears the CRCERR flag by writing '0' to it.
After the CRC reception, the CRC value is stored in the RXFIFO and must be read in the
SPIx_DR register in order to clear the RXNE flag.

CRC transfer managed by DMA
When SPI communication is enabled with CRC communication and DMA mode, the
transmission and reception of the CRC at the end of communication is automatic (with the
exception of reading CRC data in receive only mode). The CRCNEXT bit does not have to
be handled by the software. The counter for the SPI transmission DMA channel has to be
set to the number of data frames to transmit excluding the CRC frame. On the receiver side,
the received CRC value is handled automatically by DMA at the end of the transaction but
user must take care to flush out received CRC information from RXFIFO as it is always
loaded into it. In full-duplex mode, the counter of the reception DMA channel can be set to
the number of data frames to receive including the CRC, which means, for example, in the
specific case of an 8-bit data frame checked by 16-bit CRC:
DMA_RX = Numb_of_data + 2
In receive only mode, the DMA reception channel counter should contain only the amount of
data transferred, excluding the CRC calculation. Then based on the complete transfer from
DMA, all the CRC values must be read back by software from FIFO as it works as a single
buffer in this mode.
At the end of the data and CRC transfers, the CRCERR flag in the SPIx_SR register is set if
corruption occurred during the transfer.
If packing mode is used, the LDMA_RX bit needs managing if the number of data is odd.

Resetting the SPIx_TXCRC and SPIx_RXCRC values
The SPIx_TXCRC and SPIx_RXCRC values are cleared automatically when new data is
sampled after a CRC phase. This allows the use of DMA circular mode (not available in
receive-only mode) in order to transfer data without any interruption, (several data blocks
covered by intermediate CRC checking phases).

1110/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
If the SPI is disabled during a communication the following sequence must be followed:

Note:

1.

Disable the SPI

2.

Clear the CRCEN bit

3.

Enable the CRCEN bit

4.

Enable the SPI

When the SPI interface is configured as a slave, the NSS internal signal needs to be kept
low during transaction of the CRC phase once the CRCNEXT signal is released. That is why
the CRC calculation can’t be used at NSS Pulse mode when NSS hardware mode should
be applied at slave normally (see more details at the product errata sheet).
At TI mode, despite the fact that clock phase and clock polarity setting is fixed and
independent on SPIx_CR1 register, the corresponding setting CPOL=0 CPHA=1 has to be
kept at the SPIx_CR1 register anyway if CRC is applied. In addition, the CRC calculation
has to be reset between sessions by SPI disable sequence with re-enable the CRCEN bit
described above at both master and slave side, else CRC calculation can be corrupted at
this specific mode.

32.6

SPI interrupts
During SPI communication an interrupts can be generated by the following events:
•

Transmit TXFIFO ready to be loaded

•

Data received in Receive RXFIFO

•

Master mode fault

•

Overrun error

•

TI frame format error

•

CRC protocol error

Interrupts can be enabled and disabled separately.
Table 201. SPI interrupt requests
Interrupt event

Event flag

Enable Control bit

TXE

TXEIE

Data received in RXFIFO

RXNE

RXNEIE

Master Mode fault event

MODF

Transmit TXFIFO ready to be loaded

Overrun error

OVR

TI frame format error

FRE

CRC protocol error

ERRIE

CRCERR

RM0385 Rev 7

1111/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

32.7

I2S functional description

32.7.1

I2S general description

RM0385

The block diagram of the I2S is shown in Figure 375.
Figure 375. I2S block diagram

Address and data bus
Tx buffer

16-bit

BSY OVR MODF

CH
CRC
TxE RxNE FRE
UDR
SIDE
ERR

MOSI/SD
Shift register
MISO

LSB first

Communication
control

16-bit
Rx buffer

NSS/WS

I2SCFG
[1:0]

I2SSTD
[1:0]

CK
POL

DATLEN CH
LEN
[1:0]
I2S
I2SE
MOD

Master control logic
Rx
Bidi Bidi CRC CRC
SSM SSI
mode OE EN Next DFF only

SPI
baud rate generator

LSB
SPE BR2 BR1 BR0 MSTR CPOL CPHA
First

CK
I2S clock generator

I2S_CK
I2SMOD

I2SxCLK

MCK

MCKOE

ODD

I2SDIV[7:0]
MS32126V1

1. MCK is mapped on the MISO pin.

The SPI can function as an audio I2S interface when the I2S capability is enabled (by setting
the I2SMOD bit in the SPIx_I2SCFGR register). This interface mainly uses the same pins,
flags and interrupts as the SPI.

1112/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
The I2S shares three common pins with the SPI:
•

SD: Serial Data (mapped on the MOSI pin) to transmit or receive the two timemultiplexed data channels (in half-duplex mode only).

•

WS: Word Select (mapped on the NSS pin) is the data control signal output in master
mode and input in slave mode.

•

CK: Serial Clock (mapped on the SCK pin) is the serial clock output in master mode
and serial clock input in slave mode.

An additional pin can be used when a master clock output is needed for some external
audio devices:
•

MCK: Master Clock (mapped separately) is used, when the I2S is configured in master
mode (and when the MCKOE bit in the SPIx_I2SPR register is set), to output this
additional clock generated at a preconfigured frequency rate equal to 256 × fS, where
fS is the audio sampling frequency.

The I2S uses its own clock generator to produce the communication clock when it is set in
master mode. This clock generator is also the source of the master clock output. Two
additional registers are available in I2S mode. One is linked to the clock generator
configuration SPIx_I2SPR and the other one is a generic I2S configuration register
SPIx_I2SCFGR (audio standard, slave/master mode, data format, packet frame, clock
polarity, etc.).
The SPIx_CR1 register and all CRC registers are not used in the I2S mode. Likewise, the
SSOE bit in the SPIx_CR2 register and the MODF and CRCERR bits in the SPIx_SR are
not used.
The I2S uses the same SPI register for data transfer (SPIx_DR) in 16-bit wide mode.

32.7.2

I2S full duplex
Figure 376 shows how to perform full-duplex communications using two SPI/I2S instances.
In this case, the WS and CK IOs of both SPI/I2S must be connected together.
For the master full-duplex mode, one of the SPI/I2S block must be programmed in master
(I2SCFG = ‘10’ or ‘11’), and the other SPI/I2S block must be programmed in slave (I2SCFG
= ‘00’ or ‘01’). The MCK can be generated or not, depending on the application needs.
For the slave full-duplex mode, both SPI/I2S blocks must be programmed in slave. One of
them in the slave receiver (I2SCFG = ‘01’), and the other in the slave transmitter (I2SCFG =
‘00’). The master external device then provides the bit clock (CK) and the frame
synchronization (WS).
Note that the full-duplex mode can be used for all the supported standards: I2S Philips,
MSB-justified, LSB-justified and PCM.
For the full-duplex mode, both SPI/I2S instances must use the same standard, with the
same parameters: I2SMOD, I2SSTD, CKPOL, PCMSYNC, DATLEN and CHLEN must
contain the same value on both instances.

RM0385 Rev 7

1113/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 376. Full-duplex communication
MASTER full-duplex configurations

spix_tx_dma

SPI/I2Sx
(MASTER-TX)

STM32

STM32

MCK (O)

MCK (O)

SD (O)

spix_rx_dma

CK (O)
External
slave
device

WS (O)
WS (I)
spix_rx_dma

SPI/I2Sy
(SLAVE-RX)

SPI/I2Sx
(MASTER-RX)

CK (O)
WS (O)
WS (I)

spix_tx_dma

CK (I)

SD (I)

SD (I)

SPI/I2Sy
(SLAVE-TX)

External
slave
device

CK (I)
SD (O)

SLAVE full-duplex configurations
STM32
SD (O)
spix_tx_dma

SPI/I2Sx
(SLAVE-TX)

CK (I)
WS (I)

Optional
Master
Slave

WS (I)
spix_rx_dma

SPI/I2Sy
(SLAVE-RX)

External
master
device

CK (I)
SD (I)

MSv42093V2

32.7.3

Supported audio protocols
The three-line bus has to handle only audio data generally time-multiplexed on two
channels: the right channel and the left channel. However there is only one 16-bit register
for transmission or reception. So, it is up to the software to write into the data register the
appropriate value corresponding to each channel side, or to read the data from the data
register and to identify the corresponding channel by checking the CHSIDE bit in the
SPIx_SR register. Channel left is always sent first followed by the channel right (CHSIDE
has no meaning for the PCM protocol).
Four data and packet frames are available. Data may be sent with a format of:
•

16-bit data packed in a 16-bit frame

•

16-bit data packed in a 32-bit frame

•

24-bit data packed in a 32-bit frame

•

32-bit data packed in a 32-bit frame

When using 16-bit data extended on 32-bit packet, the first 16 bits (MSB) are the significant
bits, the 16-bit LSB is forced to 0 without any need for software action or DMA request (only
one read/write operation).
The 24-bit and 32-bit data frames need two CPU read or write operations to/from the
SPIx_DR register or two DMA operations if the DMA is preferred for the application. For 24bit data frame specifically, the 8 non-significant bits are extended to 32 bits with 0-bits (by
hardware).
For all data formats and communication standards, the most significant bit is always sent
first (MSB first).

1114/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
The I2S interface supports four audio standards, configurable using the I2SSTD[1:0] and
PCMSYNC bits in the SPIx_I2SCFGR register.

I2S Philips standard
For this standard, the WS signal is used to indicate which channel is being transmitted. It is
activated one CK clock cycle before the first bit (MSB) is available.
Figure 377. I2S Philips protocol waveforms (16/32-bit full accuracy)
CK

WS

transmission

reception

Can be 16-bit or 32-bit

SD

MSB

LSB

MSB

Channel left
Channel
right
MS19591V1

Data are latched on the falling edge of CK (for the transmitter) and are read on the rising
edge (for the receiver). The WS signal is also latched on the falling edge of CK.
Figure 378. I2S Philips standard waveforms (24-bit frame)
CK
WS

Transmission

Reception

24-bit data

8-bit remaining 0 forced

SD
MSB

LSB

Channel left 32-bit
Channel right
MS19592V1

This mode needs two write or read operations to/from the SPIx_DR register.
•

In transmission mode:
If 0x8EAA33 has to be sent (24-bit):

RM0385 Rev 7

1115/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 379. Transmitting 0x8EAA33
First write to Data register

Second write to Data register

0x8EAA

0x33XX
Only the 8 MSB are sent
to compare the 24 bits
8 LSBs have no meaning
and can be anything
MS19593V2

•

In reception mode:
If data 0x8EAA33 is received:
Figure 380. Receiving 0x8EAA33
First read to Data register

Second read to Data register

0x8EAA

0x33XX
Only the 8 MSB are sent
to compare the 24 bits
8 LSBs have no meaning
and can be anything
MS19594V1

Figure 381. I2S Philips standard (16-bit extended to 32-bit packet frame)
CK
WS

Transmission

Reception

16-bit data

16-bit remaining 0 forced

SD
MSB

LSB

Channel left 32-bit

Channel right

MS19599V1

When 16-bit data frame extended to 32-bit channel frame is selected during the I2S
configuration phase, only one access to the SPIx_DR register is required. The 16 remaining
bits are forced by hardware to 0x0000 to extend the data to 32-bit format.
If the data to transmit or the received data are 0x76A3 (0x76A30000 extended to 32-bit), the
operation shown in Figure 382 is required.
Figure 382. Example of 16-bit data frame extended to 32-bit channel frame
Only one access to SPIx_DR
0x76A3
MS19595V1

1116/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
For transmission, each time an MSB is written to SPIx_DR, the TXE flag is set and its
interrupt, if allowed, is generated to load the SPIx_DR register with the new value to send.
This takes place even if 0x0000 have not yet been sent because it is done by hardware.
For reception, the RXNE flag is set and its interrupt, if allowed, is generated when the first
16 MSB half-word is received.
In this way, more time is provided between two write or read operations, which prevents
underrun or overrun conditions (depending on the direction of the data transfer).

MSB justified standard
For this standard, the WS signal is generated at the same time as the first data bit, which is
the MSBit.
Figure 383. MSB Justified 16-bit or 32-bit full-accuracy length
CK
Transmission

WS

Reception
16- or 32 bit data

SD
LSB MSB

MSB
Channel left

Channel right
MS30100 V1

Data are latched on the falling edge of CK (for transmitter) and are read on the rising edge
(for the receiver).
Figure 384. MSB justified 24-bit frame length
CK
Transmission

WS

Reception

24 bit data

8-bit remaining
0 forced

SD
MSB

LSB
Channel left 32-bit
Channel right
MS30101V1

RM0385 Rev 7

1117/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 385. MSB justified 16-bit extended to 32-bit packet frame
CK
Transmission

WS

Reception

16-bit data

16-bit remaining
0 forced

SD
MSB

LSB
Channel left 32-bit
Channel right
MS30102V1

LSB justified standard
This standard is similar to the MSB justified standard (no difference for the 16-bit and 32-bit
full-accuracy frame formats).
The sampling of the input and output signals is the same as for the I2S Philips standard.
Figure 386. LSB justified 16-bit or 32-bit full-accuracy
CK
WS
Reception

Transmission
16- or 32-bit data

SD
LSB MSB

MSB
Channel left

Channel right

MS30103V1

Figure 387. LSB justified 24-bit frame length
CK
WS

Reception
Transmission

SD

8-bit data
0 forced

24-bit remaining
MSB

LSB

Channel left 32-bit
Channel right
MS30104V1

•

In transmission mode:
If data 0x3478AE have to be transmitted, two write operations to the SPIx_DR register
are required by software or by DMA. The operations are shown below.

1118/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 388. Operations required to transmit 0x3478AE
First write to Data register
conditioned by TXE=1

Second write to Data register
conditioned by TXE=1

0xXX34

0x78AE

Only the 8 LSB of the
half-word are significant.
A field of 0x00 is forced
instead of the 8 MSBs.

•

MS19596V1

In reception mode:
If data 0x3478AE are received, two successive read operations from the SPIx_DR
register are required on each RXNE event.
Figure 389. Operations required to receive 0x3478AE

First read from Data register
conditioned by RXNE=1

Second read from Data register
conditioned by RXNE=1

0xXX34

0x78AE

Only the 8 LSB of the
half-word are significant.
A field of 0x00 is forced
instead of the 8 MSBs.
MS19597V1

Figure 390. LSB justified 16-bit extended to 32-bit packet frame
CK
Reception

WS
Transmission

SD

16-bit remaining

16-bit data
0 forced
MSB

LSB

Channel left 32-bit
Channel right
MS30105V1

When 16-bit data frame extended to 32-bit channel frame is selected during the I2S
configuration phase, Only one access to the SPIx_DR register is required. The 16 remaining
bits are forced by hardware to 0x0000 to extend the data to 32-bit format. In this case it
corresponds to the half-word MSB.
If the data to transmit or the received data are 0x76A3 (0x0000 76A3 extended to 32-bit),
the operation shown in Figure 391 is required.

RM0385 Rev 7

1119/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 391. Example of 16-bit data frame extended to 32-bit channel frame
Only one access to the SPIx-DR register

0x76A3
MS19598V1

In transmission mode, when a TXE event occurs, the application has to write the data to be
transmitted (in this case 0x76A3). The 0x000 field is transmitted first (extension on 32-bit).
The TXE flag is set again as soon as the effective data (0x76A3) is sent on SD.
In reception mode, RXNE is asserted as soon as the significant half-word is received (and
not the 0x0000 field).
In this way, more time is provided between two write or read operations to prevent underrun
or overrun conditions.

PCM standard
For the PCM standard, there is no need to use channel-side information. The two PCM
modes (short and long frame) are available and configurable using the PCMSYNC bit in
SPIx_I2SCFGR register.
In PCM mode, the output signals (WS, SD) are sampled on the rising edge of CK signal.
The input signals (WS, SD) are captured on the falling edge of CK.
Note that CK and WS are configured as output in MASTER mode.
Figure 392. PCM standard waveforms (16-bit)

CK
WS
short frame
13-bits

WS
long frame

SD

MSB

LSB MSB

MS30106V1

For long frame synchronization, the WS signal assertion time is fixed to 13 bits in master
mode.
For short frame synchronization, the WS synchronization signal is only one cycle long.

1120/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 393. PCM standard waveforms (16-bit extended to 32-bit packet frame)
CK
WS
short frame
Up to 13-bits

WS
long frame
16 bits

SD

MSB

LSB

MS30107V1

Note:

For both modes (master and slave) and for both synchronizations (short and long), the
number of bits between two consecutive pieces of data (and so two synchronization signals)
needs to be specified (DATLEN and CHLEN bits in the SPIx_I2SCFGR register) even in
slave mode.

32.7.4

Start-up description
The Figure 394 shows how the serial interface is handled in MASTER mode, when the
SPI/I2S is enabled (via I2SE bit). It shows as well the effect of CKPOL on the generated
signals.

RM0385 Rev 7

1121/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 394. Start sequence in master mode

Master I2S Philips Standard
WS (O)
CK (O), CKPOL = 0
CK (O), CKPOL = 1
dum

SD (O)

Left sample

Right sample

I2SE

Master I2S MSB or LSB justified
WS (O)
CK (O), CKPOL = 0
CK (O), CKPOL = 1
dum

SD (O)

Left sample

Right sample

I2SE

Master PCM short frame
WS (O)
CK (O), CKPOL = 0
CK (O), CKPOL = 1
SD (O)

dum

Sample1

Sample 2

I2SE

Master PCM long frame
WS (O)
CK (O), CKPOL = 0
CK (O), CKPOL = 1
SD (O)

dum

Sample1

Sample 2

I2SE
dum: not significant data
MSv37520V2

In slave mode, the way the frame synchronization is detected, depends on the value of
ASTRTEN bit.
If ASTRTEN = 0, when the audio interface is enabled (I2SE = 1), then the hardware waits for
the appropriate transition on the incoming WS signal, using the CK signal.

1122/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
The appropriate transition is a falling edge on WS signal when I2S Philips Standard is used,
or a rising edge for other standards. The falling edge is detected by sampling first WS to 1
and then to 0, and vice-versa for the rising edge detection.
If ASTRTEN = 1, the user has to enable the audio interface before the WS becomes active.
This means that the I2SE bit must be set to 1 when WS = 1 for I2S Philips standard, or when
WS = 0 for other standards.

Clock generator
The I2S bit rate determines the data flow on the I2S data line and the I2S clock signal
frequency.
I2S bit rate = number of bits per channel × number of channels × sampling audio frequency
For a 16-bit audio, left and right channel, the I2S bit rate is calculated as follows:
I2S bit rate = 16 × 2 × fS
It will be: I2S bit rate = 32 x 2 x fS if the packet length is 32-bit wide.
Figure 395. Audio sampling frequency definition

16-or 32-bit
right channel

16-or 32-bit left
channel
32- or 64-bits
FS

sampling point

sampling point

FS : audio sampling frequency
MS30108V1

When the master mode is configured, a specific action needs to be taken to properly
program the linear divider in order to communicate with the desired audio frequency.
Figure 396. I2S clock generator architecture

MCK
I²SxCLK

8-bit linear divider
+ reshaping stage

0

Div2

Divider by 4

0
1
1

CK

MCKOE ODD

I²SDIV[7:0]

CHLEN

MCKOE
I²SMOD

32.7.5

MS30109V1

1. Where x can be 2 or 3.

RM0385 Rev 7

1123/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Figure 396 presents the communication clock architecture. The I2SxCLK clock is provided
by the Reset and Clock Controller (RCC) of the product. The I2SxCLK clock can be
asynchronous with respect to the SPI/I2S APB clock.

Warning:
In addition, it is mandatory to keep the I2SxCLK frequency
higher or equal to the APB clock used by the SPI/I2S block. If
this condition is not respected, the SPI/I2S will not work
properly.

The audio sampling frequency may be 192 kHz, 96 kHz, 48 kHz, 44.1 kHz, 32 kHz,
22.05 kHz, 16 kHz, 11.025 kHz or 8 kHz (or any other value within this range).
In order to reach the desired frequency, the linear divider needs to be programmed
according to the formulas below:

For I2S modes:
When the master clock is generated (MCKOE in the SPIx_I2SPR register is set):

Fs =

F I2SxCLK
----------------------------------------------------------------------------------------------------------256 × ( ( 2 × I2SDIV ) + ODD )

When the master clock is disabled (MCKOE bit cleared):

Fs =

F I2SxCLK
-----------------------------------------------------------------------------------------------------------------------------------------------------------------32 × ( CHLEN + 1 ) × ( ( 2 × I2SDIV ) + ODD )

CHLEN = 0 when the channel frame is 16-bit wide and,
CHLEN = 1 when the channel frame is 32-bit wide.

For PCM modes:
When the master clock is generated (MCKOE in the SPIx_I2SPR register is set):

Fs =

F I2SxCLK
----------------------------------------------------------------------------------------------------------128 × ( ( 2 × I2SDIV ) + ODD )

When the master clock is disabled (MCKOE bit cleared):

Fs =

F I2SxCLK
-----------------------------------------------------------------------------------------------------------------------------------------------------------------16 × ( CHLEN + 1 ) × ( ( 2 × I2SDIV ) + ODD )

CHLEN = 0 when the channel frame is 16-bit wide and,
CHLEN = 1 when the channel frame is 32-bit wide.

1124/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
Where FS is the audio sampling frequency, and FI2SxCLKis the frequency of the kernel clock
provided to the SPI/I2S block.

Note:

Note that I2SDIV must be strictly higher than 1.
Table 202provides example precision values for different clock configurations.

Note:

Other configurations are possible that allow optimum clock precision.
Table 202. Audio-frequency precision using standard 8 MHz HSE(1)
SYSCLK
(MHz)

Data
length

I2SDIV

I2SODD

MCLK

48

16

8

0

No

96000

93750

2.3438%

48

32

4

0

No

96000

93750

2.3438%

48

16

15

1

No

48000

48387.0968

0.8065%

48

32

8

0

No

48000

46875

2.3438%

48

16

17

0

No

44100

44117.647

0.0400%

48

32

8

1

No

44100

44117.647

0.0400%

48

16

23

1

No

32000

31914.8936

0.2660%

48

32

11

1

No

32000

32608.696

1.9022%

48

16

34

0

No

22050

22058.8235

0.0400%

48

32

17

0

No

22050

22058.8235

0.0400%

48

16

47

0

No

16000

15957.4468

0.2660%

48

32

23

1

No

16000

15957.447

0.2660%

48

16

68

0

No

11025

11029.4118

0.0400%

48

32

34

0

No

11025

11029.412

0.0400%

48

16

94

0

No

8000

7978.7234

0.2660%

48

32

47

0

No

8000

7978.7234

0.2660%

48

16

2

0

Yes

48000

46875

2.3430%

48

32

2

0

Yes

48000

46875

2.3430%

48

16

2

0

Yes

44100

46875

6.2925%

48

32

2

0

Yes

44100

46875

6.2925%

48

16

3

0

Yes

32000

31250

2.3438%

48

32

3

0

Yes

32000

31250

2.3438%

48

16

4

1

Yes

22050

20833.333

5.5178%

48

32

4

1

Yes

22050

20833.333

5.5178%

48

16

6

0

Yes

16000

15625

2.3438%

48

32

6

0

Yes

16000

15625

2.3438%

48

16

8

1

Yes

11025

11029.4118

0.0400%

48

32

8

1

Yes

11025

11029.4118

0.0400%

RM0385 Rev 7

Target fs
(Hz)

Real fs (kHz)

Error

1125/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Table 202. Audio-frequency precision using standard 8 MHz HSE(1) (continued)
SYSCLK
(MHz)

Data
length

I2SDIV

I2SODD

MCLK

Target fs
(Hz)

48

16

11

1

Yes

8000

8152.17391

1.9022%

48

32

11

1

Yes

8000

8152.17391

1.9022%

Real fs (kHz)

Error

1. This table gives only example values for different clock configurations. Other configurations allowing
optimum clock precision are possible.

32.7.6

I2S master mode
The I2S can be configured in master mode. This means that the serial clock is generated on
the CK pin as well as the Word Select signal WS. Master clock (MCK) may be output or not,
controlled by the MCKOE bit in the SPIx_I2SPR register.

Procedure
1.

Select the I2SDIV[7:0] bits in the SPIx_I2SPR register to define the serial clock baud
rate to reach the proper audio sample frequency. The ODD bit in the SPIx_I2SPR
register also has to be defined.

2.

Select the CKPOL bit to define the steady level for the communication clock. Set the
MCKOE bit in the SPIx_I2SPR register if the master clock MCK needs to be provided
to the external DAC/ADC audio component (the I2SDIV and ODD values should be
computed depending on the state of the MCK output, for more details refer to
Section 32.7.5: Clock generator).

3.

Set the I2SMOD bit in the SPIx_I2SCFGR register to activate the I2S functions and
choose the I2S standard through the I2SSTD[1:0] and PCMSYNC bits, the data length
through the DATLEN[1:0] bits and the number of bits per channel by configuring the
CHLEN bit. Select also the I2S master mode and direction (Transmitter or Receiver)
through the I2SCFG[1:0] bits in the SPIx_I2SCFGR register.

4.

If needed, select all the potential interrupt sources and the DMA capabilities by writing
the SPIx_CR2 register.

5.

The I2SE bit in SPIx_I2SCFGR register must be set.

WS and CK are configured in output mode. MCK is also an output, if the MCKOE bit in
SPIx_I2SPR is set.

Transmission sequence
The transmission sequence begins when a half-word is written into the Tx buffer.
Lets assume the first data written into the Tx buffer corresponds to the left channel data.
When data are transferred from the Tx buffer to the shift register, TXE is set and data
corresponding to the right channel have to be written into the Tx buffer. The CHSIDE flag
indicates which channel is to be transmitted. It has a meaning when the TXE flag is set
because the CHSIDE flag is updated when TXE goes high.
A full frame has to be considered as a left channel data transmission followed by a right
channel data transmission. It is not possible to have a partial frame where only the left
channel is sent.
The data half-word is parallel loaded into the 16-bit shift register during the first bit
transmission, and then shifted out, serially, to the MOSI/SD pin, MSB first. The TXE flag is

1126/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
set after each transfer from the Tx buffer to the shift register and an interrupt is generated if
the TXEIE bit in the SPIx_CR2 register is set.
For more details about the write operations depending on the I2S standard mode selected,
refer to Section 32.7.3: Supported audio protocols).
To ensure a continuous audio data transmission, it is mandatory to write the SPIx_DR
register with the next data to transmit before the end of the current transmission.
To switch off the I2S, by clearing I2SE, it is mandatory to wait for TXE = 1 and BSY = 0.

Reception sequence
The operating mode is the same as for transmission mode except for the point 3 (refer to the
procedure described in Section 32.7.6: I2S master mode), where the configuration should
set the master reception mode through the I2SCFG[1:0] bits.
Whatever the data or channel length, the audio data are received by 16-bit packets. This
means that each time the Rx buffer is full, the RXNE flag is set and an interrupt is generated
if the RXNEIE bit is set in SPIx_CR2 register. Depending on the data and channel length
configuration, the audio value received for a right or left channel may result from one or two
receptions into the Rx buffer.
Clearing the RXNE bit is performed by reading the SPIx_DR register.
CHSIDE is updated after each reception. It is sensitive to the WS signal generated by the
I2S cell.
For more details about the read operations depending on the I2S standard mode selected,
refer to Section 32.7.3: Supported audio protocols.
If data are received while the previously received data have not been read yet, an overrun is
generated and the OVR flag is set. If the ERRIE bit is set in the SPIx_CR2 register, an
interrupt is generated to indicate the error.
To switch off the I2S, specific actions are required to ensure that the I2S completes the
transfer cycle properly without initiating a new data transfer. The sequence depends on the
configuration of the data and channel lengths, and on the audio protocol mode selected. In
the case of:
•

•

•

16-bit data length extended on 32-bit channel length (DATLEN = 00 and CHLEN = 1)
using the LSB justified mode (I2SSTD = 10)
a)

Wait for the second to last RXNE = 1 (n – 1)

b)

Then wait 17 I2S clock cycles (using a software loop)

c)

Disable the I2S (I2SE = 0)

16-bit data length extended on 32-bit channel length (DATLEN = 00 and CHLEN = 1) in
MSB justified, I2S or PCM modes (I2SSTD = 00, I2SSTD = 01 or I2SSTD = 11,
respectively)
a)

Wait for the last RXNE

b)

Then wait 1 I2S clock cycle (using a software loop)

c)

Disable the I2S (I2SE = 0)

For all other combinations of DATLEN and CHLEN, whatever the audio mode selected
through the I2SSTD bits, carry out the following sequence to switch off the I2S:
a)

Wait for the second to last RXNE = 1 (n – 1)

b)

Then wait one I2S clock cycle (using a software loop)

RM0385 Rev 7

1127/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)
c)

RM0385

Disable the I2S (I2SE = 0)

Note:

The BSY flag is kept low during transfers.

32.7.7

I2S slave mode
For the slave configuration, the I2S can be configured in transmission or reception mode.
The operating mode is following mainly the same rules as described for the I2S master
configuration. In slave mode, there is no clock to be generated by the I2S interface. The
clock and WS signals are input from the external master connected to the I2S interface.
There is then no need, for the user, to configure the clock.
The configuration steps to follow are listed below:
1.

Set the I2SMOD bit in the SPIx_I2SCFGR register to select I2S mode and choose the
I2S standard through the I2SSTD[1:0] bits, the data length through the DATLEN[1:0]
bits and the number of bits per channel for the frame configuring the CHLEN bit. Select
also the mode (transmission or reception) for the slave through the I2SCFG[1:0] bits in
SPIx_I2SCFGR register.

2.

If needed, select all the potential interrupt sources and the DMA capabilities by writing
the SPIx_CR2 register.

3.

The I2SE bit in SPIx_I2SCFGR register must be set.

Transmission sequence
The transmission sequence begins when the external master device sends the clock and
when the NSS_WS signal requests the transfer of data. The slave has to be enabled before
the external master starts the communication. The I2S data register has to be loaded before
the master initiates the communication.
For the I2S, MSB justified and LSB justified modes, the first data item to be written into the
data register corresponds to the data for the left channel. When the communication starts,
the data are transferred from the Tx buffer to the shift register. The TXE flag is then set in
order to request the right channel data to be written into the I2S data register.
The CHSIDE flag indicates which channel is to be transmitted. Compared to the master
transmission mode, in slave mode, CHSIDE is sensitive to the WS signal coming from the
external master. This means that the slave needs to be ready to transmit the first data
before the clock is generated by the master. WS assertion corresponds to left channel
transmitted first.
Note:

The I2SE has to be written at least two PCLK cycles before the first clock of the master
comes on the CK line.
The data half-word is parallel-loaded into the 16-bit shift register (from the internal bus)
during the first bit transmission, and then shifted out serially to the MOSI/SD pin MSB first.
The TXE flag is set after each transfer from the Tx buffer to the shift register and an interrupt
is generated if the TXEIE bit in the SPIx_CR2 register is set.
Note that the TXE flag should be checked to be at 1 before attempting to write the Tx buffer.
For more details about the write operations depending on the I2S standard mode selected,
refer to Section 32.7.3: Supported audio protocols.
To secure a continuous audio data transmission, it is mandatory to write the SPIx_DR
register with the next data to transmit before the end of the current transmission. An
underrun flag is set and an interrupt may be generated if the data are not written into the

1128/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)
SPIx_DR register before the first clock edge of the next data communication. This indicates
to the software that the transferred data are wrong. If the ERRIE bit is set into the SPIx_CR2
register, an interrupt is generated when the UDR flag in the SPIx_SR register goes high. In
this case, it is mandatory to switch off the I2S and to restart a data transfer starting from the
left channel.
To switch off the I2S, by clearing the I2SE bit, it is mandatory to wait for TXE = 1 and
BSY = 0.

Reception sequence
The operating mode is the same as for the transmission mode except for the point 1 (refer to
the procedure described in Section 32.7.7: I2S slave mode), where the configuration should
set the master reception mode using the I2SCFG[1:0] bits in the SPIx_I2SCFGR register.
Whatever the data length or the channel length, the audio data are received by 16-bit
packets. This means that each time the RX buffer is full, the RXNE flag in the SPIx_SR
register is set and an interrupt is generated if the RXNEIE bit is set in the SPIx_CR2
register. Depending on the data length and channel length configuration, the audio value
received for a right or left channel may result from one or two receptions into the RX buffer.
The CHSIDE flag is updated each time data are received to be read from the SPIx_DR
register. It is sensitive to the external WS line managed by the external master component.
Clearing the RXNE bit is performed by reading the SPIx_DR register.
For more details about the read operations depending the I2S standard mode selected, refer
to Section 32.7.3: Supported audio protocols.
If data are received while the preceding received data have not yet been read, an overrun is
generated and the OVR flag is set. If the bit ERRIE is set in the SPIx_CR2 register, an
interrupt is generated to indicate the error.
To switch off the I2S in reception mode, I2SE has to be cleared immediately after receiving
the last RXNE = 1.
Note:

The external master components should have the capability of sending/receiving data in 16bit or 32-bit packets via an audio channel.

32.7.8

I2S status flags
Three status flags are provided for the application to fully monitor the state of the I2S bus.

Busy flag (BSY)
The BSY flag is set and cleared by hardware (writing to this flag has no effect). It indicates
the state of the communication layer of the I2S.
When BSY is set, it indicates that the I2S is busy communicating. There is one exception in
master receive mode (I2SCFG = 11) where the BSY flag is kept low during reception.
The BSY flag is useful to detect the end of a transfer if the software needs to disable the I2S.
This avoids corrupting the last transfer. For this, the procedure described below must be
strictly respected.
The BSY flag is set when a transfer starts, except when the I2S is in master receiver mode.

RM0385 Rev 7

1129/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

The BSY flag is cleared:
•

When a transfer completes (except in master transmit mode, in which the
communication is supposed to be continuous)

•

When the I2S is disabled

When communication is continuous:

Note:

•

In master transmit mode, the BSY flag is kept high during all the transfers

•

In slave mode, the BSY flag goes low for one I2S clock cycle between each transfer

Do not use the BSY flag to handle each data transmission or reception. It is better to use the
TXE and RXNE flags instead.

Tx buffer empty flag (TXE)
When set, this flag indicates that the Tx buffer is empty and the next data to be transmitted
can then be loaded into it. The TXE flag is reset when the Tx buffer already contains data to
be transmitted. It is also reset when the I2S is disabled (I2SE bit is reset).

RX buffer not empty (RXNE)
When set, this flag indicates that there are valid received data in the RX Buffer. It is reset
when SPIx_DR register is read.

Channel Side flag (CHSIDE)
In transmission mode, this flag is refreshed when TXE goes high. It indicates the channel
side to which the data to transfer on SD has to belong. In case of an underrun error event in
slave transmission mode, this flag is not reliable and I2S needs to be switched off and
switched on before resuming the communication.
In reception mode, this flag is refreshed when data are received into SPIx_DR. It indicates
from which channel side data have been received. Note that in case of error (like OVR) this
flag becomes meaningless and the I2S should be reset by disabling and then enabling it
(with configuration if it needs changing).
This flag has no meaning in the PCM standard (for both Short and Long frame modes).
When the OVR or UDR flag in the SPIx_SR is set and the ERRIE bit in SPIx_CR2 is also
set, an interrupt is generated. This interrupt can be cleared by reading the SPIx_SR status
register (once the interrupt source has been cleared).

32.7.9

I2S error flags
There are three error flags for the I2S cell.

Underrun flag (UDR)
In slave transmission mode this flag is set when the first clock for data transmission appears
while the software has not yet loaded any value into SPIx_DR. It is available when the
I2SMOD bit in the SPIx_I2SCFGR register is set. An interrupt may be generated if the
ERRIE bit in the SPIx_CR2 register is set.
The UDR bit is cleared by a read operation on the SPIx_SR register.

1130/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

Overrun flag (OVR)
This flag is set when data are received and the previous data have not yet been read from
the SPIx_DR register. As a result, the incoming data are lost. An interrupt may be generated
if the ERRIE bit is set in the SPIx_CR2 register.
In this case, the receive buffer contents are not updated with the newly received data from
the transmitter device. A read operation to the SPIx_DR register returns the previous
correctly received data. All other subsequently transmitted half-words are lost.
Clearing the OVR bit is done by a read operation on the SPIx_DR register followed by a
read access to the SPIx_SR register.

Frame error flag (FRE)
This flag can be set by hardware only if the I2S is configured in Slave mode. It is set if the
external master is changing the WS line while the slave is not expecting this change. If the
synchronization is lost, the following steps are required to recover from this state and
resynchronize the external master device with the I2S slave device:
1.

Disable the I2S.

2.

Re-enable the I2S interface again (Keeping ASTRTEN=0).

Desynchronization between master and slave devices may be due to noisy environment on
the CK communication clock or on the WS frame synchronization line. An error interrupt can
be generated if the ERRIE bit is set. The desynchronization flag (FRE) is cleared by
software when the status register is read.

32.7.10

DMA features
In I2S mode, the DMA works in exactly the same way as it does in SPI mode. There is no
difference except that the CRC feature is not available in I2S mode since there is no data
transfer protection system.

32.8

I2S interrupts
Table 203 provides the list of I2S interrupts.
Table 203. I2S interrupt requests
Interrupt event

Event flag

Enable control bit

Transmit buffer empty flag

TXE

TXEIE

Receive buffer not empty flag

RXNE

RXNEIE

Overrun error

OVR

Underrun error

UDR

Frame error flag

FRE

RM0385 Rev 7

ERRIE

1131/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

SPI and I2S registers

32.9

The peripheral registers can be accessed by half-words (16-bit) or words (32-bit). SPI_DR
in addition by can be accessed by 8-bit access.

32.9.1

SPI control register 1 (SPIx_CR1)
Address offset: 0x00
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

BIDI
MODE

BIDI
OE

CRC
EN

CRC
NEXT

CRCL

RX
ONLY

SSM

SSI

LSB
FIRST

SPE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

5

4

3

BR [2:0]
rw

rw

rw

2

1

0

MSTR

CPOL

CPHA

rw

rw

rw

Bit 15 BIDIMODE: Bidirectional data mode enable. This bit enables half-duplex communication using
common single bidirectional data line. Keep RXONLY bit clear when bidirectional mode is
active.
0: 2-line unidirectional data mode selected
1: 1-line bidirectional data mode selected
Note: This bit is not used in I2S mode.
Bit 14 BIDIOE: Output enable in bidirectional mode
This bit combined with the BIDIMODE bit selects the direction of transfer in bidirectional mode
0: Output disabled (receive-only mode)
1: Output enabled (transmit-only mode)
Note: In master mode, the MOSI pin is used and in slave mode, the MISO pin is used.
This bit is not used in I2S mode.
Bit 13 CRCEN: Hardware CRC calculation enable
0: CRC calculation disabled
1: CRC calculation Enabled
Note: This bit should be written only when SPI is disabled (SPE = ‘0’) for correct operation.
This bit is not used in I2S mode.
Bit 12 CRCNEXT: Transmit CRC next
0: Next transmit value is from Tx buffer
1: Next transmit value is from Tx CRC register
Note: This bit has to be written as soon as the last data is written in the SPIx_DR register.
This bit is not used in I2S mode.
Bit 11 CRCL: CRC length
This bit is set and cleared by software to select the CRC length.
0: 8-bit CRC length
1: 16-bit CRC length
Note: This bit should be written only when SPI is disabled (SPE = ‘0’) for correct operation.
This bit is not used in I2S mode.

1132/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

Bit 10 RXONLY: Receive only mode enabled.
This bit enables simplex communication using a single unidirectional line to receive data
exclusively. Keep BIDIMODE bit clear when receive only mode is active.This bit is also useful
in a multislave system in which this particular slave is not accessed, the output from the
accessed slave is not corrupted.
0: Full-duplex (Transmit and receive)
1: Output disabled (Receive-only mode)
Note: This bit is not used in I2S mode.
Bit 9 SSM: Software slave management
When the SSM bit is set, the NSS pin input is replaced with the value from the SSI bit.
0: Software slave management disabled
1: Software slave management enabled
Note: This bit is not used in I2S mode and SPI TI mode.
Bit 8 SSI: Internal slave select
This bit has an effect only when the SSM bit is set. The value of this bit is forced onto the NSS
pin and the I/O value of the NSS pin is ignored.
Note: This bit is not used in I2S mode and SPI TI mode.
Bit 7 LSBFIRST: Frame format
0: data is transmitted / received with the MSB first
1: data is transmitted / received with the LSB first
Note: 1. This bit should not be changed when communication is ongoing.
2. This bit is not used in I2S mode and SPI TI mode.
Bit 6 SPE: SPI enable
0: Peripheral disabled
1: Peripheral enabled
Note: When disabling the SPI, follow the procedure described in Procedure for disabling the
SPI on page 1097.
This bit is not used in I2S mode.
Bits 5:3 BR[2:0]: Baud rate control
000: fPCLK/2
001: fPCLK/4
010: fPCLK/8
011: fPCLK/16
100: fPCLK/32
101: fPCLK/64
110: fPCLK/128
111: fPCLK/256
Note: These bits should not be changed when communication is ongoing.
This bit is not used in I2S mode.
Bit 2 MSTR: Master selection
0: Slave configuration
1: Master configuration
Note: This bit should not be changed when communication is ongoing.
This bit is not used in I2S mode.

RM0385 Rev 7

1133/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Bit1 CPOL: Clock polarity
0: CK to 0 when idle
1: CK to 1 when idle
Note: This bit should not be changed when communication is ongoing.
This bit is not used in SPI TI mode except the case when CRC is applied at TI mode.
Bit 0 CPHA: Clock phase
0: The first clock transition is the first data capture edge
1: The second clock transition is the first data capture edge
Note: This bit should not be changed when communication is ongoing.
This bit is not used in SPI TI mode except the case when CRC is applied at TI mode.

32.9.2

SPI control register 2 (SPIx_CR2)
Address offset: 0x04
Reset value: 0x0700

15

14

13

12

Res.

LDMA
_TX

LDMA
_RX

FRXT
H

rw

rw

rw

11

10

9

8

DS [3:0]
rw

rw

rw

7

6

5

TXEIE RXNEIE ERRIE
rw

rw

rw

rw

4

3

2

FRF

NSSP

SSOE

rw

rw

rw

1

0

TXDMAEN RXDMAEN
rw

rw

Bit 15 Reserved, must be kept at reset value.
Bit 14 LDMA_TX: Last DMA transfer for transmission
This bit is used in data packing mode, to define if the total number of data to transmit by DMA
is odd or even. It has significance only if the TXDMAEN bit in the SPIx_CR2 register is set and
if packing mode is used (data length =< 8-bit and write access to SPIx_DR is 16-bit wide). It
has to be written when the SPI is disabled (SPE = 0 in the SPIx_CR1 register).
0: Number of data to transfer is even
1: Number of data to transfer is odd
Note: Refer to Procedure for disabling the SPI on page 1097 if the CRCEN bit is set.
This bit is not used in I²S mode.
Bit 13 LDMA_RX: Last DMA transfer for reception
This bit is used in data packing mode, to define if the total number of data to receive by DMA is
odd or even. It has significance only if the RXDMAEN bit in the SPIx_CR2 register is set and if
packing mode is used (data length =< 8-bit and write access to SPIx_DR is 16-bit wide). It has
to be written when the SPI is disabled (SPE = 0 in the SPIx_CR1 register).
0: Number of data to transfer is even
1: Number of data to transfer is odd
Note: Refer to Procedure for disabling the SPI on page 1097 if the CRCEN bit is set.
This bit is not used in I²S mode.
Bit 12 FRXTH: FIFO reception threshold
This bit is used to set the threshold of the RXFIFO that triggers an RXNE event
0: RXNE event is generated if the FIFO level is greater than or equal to 1/2 (16-bit)
1: RXNE event is generated if the FIFO level is greater than or equal to 1/4 (8-bit)
Note: This bit is not used in I²S mode.

1134/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

Bits 11:8 DS [3:0]: Data size
These bits configure the data length for SPI transfers:
0000: Not used
0001: Not used
0010: Not used
0011: 4-bit
0100: 5-bit
0101: 6-bit
0110: 7-bit
0111: 8-bit
1000: 9-bit
1001: 10-bit
1010: 11-bit
1011: 12-bit
1100: 13-bit
1101: 14-bit
1110: 15-bit
1111: 16-bit
If software attempts to write one of the “Not used” values, they are forced to the value “0111”(8bit).
Note: This bit is not used in I²S mode.
Bit 7 TXEIE: Tx buffer empty interrupt enable
0: TXE interrupt masked
1: TXE interrupt not masked. Used to generate an interrupt request when the TXE flag is set.
Bit 6 RXNEIE: RX buffer not empty interrupt enable
0: RXNE interrupt masked
1: RXNE interrupt not masked. Used to generate an interrupt request when the RXNE flag is
set.
Bit 5 ERRIE: Error interrupt enable
This bit controls the generation of an interrupt when an error condition occurs (CRCERR,
OVR, MODF in SPI mode, FRE at TI mode and UDR, OVR, and FRE in I2S mode).
0: Error interrupt is masked
1: Error interrupt is enabled
Bit 4 FRF: Frame format
0: SPI Motorola mode
1 SPI TI mode
Note: This bit must be written only when the SPI is disabled (SPE=0).
This bit is not used in I2S mode.
Bit 3 NSSP: NSS pulse management
This bit is used in master mode only. it allow the SPI to generate an NSS pulse between two
consecutive data when doing continuous transfers. In the case of a single data transfer, it
forces the NSS pin high level after the transfer.
It has no meaning if CPHA = ’1’, or FRF = ’1’.
0: No NSS pulse
1: NSS pulse generated
Note: 1. This bit must be written only when the SPI is disabled (SPE=0).
2. This bit is not used in I2S mode and SPI TI mode.

RM0385 Rev 7

1135/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Bit 2 SSOE: SS output enable
0: SS output is disabled in master mode and the SPI interface can work in multimaster
configuration
1: SS output is enabled in master mode and when the SPI interface is enabled. The SPI
interface cannot work in a multimaster environment.
Note: This bit is not used in I2S mode and SPI TI mode.
Bit 1 TXDMAEN: Tx buffer DMA enable
When this bit is set, a DMA request is generated whenever the TXE flag is set.
0: Tx buffer DMA disabled
1: Tx buffer DMA enabled
Bit 0 RXDMAEN: Rx buffer DMA enable
When this bit is set, a DMA request is generated whenever the RXNE flag is set.
0: Rx buffer DMA disabled
1: Rx buffer DMA enabled

1136/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

32.9.3

SPI status register (SPIx_SR)
Address offset: 0x08
Reset value: 0x0002

15
Res.

14
Res.

13
Res.

12

11

10

9

FTLVL[1:0]

FRLVL[2:0]

r

r

r

r

8

7

6

5

4

3

2

1

0

UDR

CHSIDE

TXE

RXNE

r

r

FRE

BSY

OVR

MODF

CRC
ERR

r

r

r

r

rc_w0

Bits 15:13 Reserved, must be kept at reset value.
Bits 12:11 FTLVL[1:0]: FIFO Transmission Level
These bits are set and cleared by hardware.
00: FIFO empty
01: 1/4 FIFO
10: 1/2 FIFO
11: FIFO full (considered as FULL when the FIFO threshold is greater than 1/2)
Note: These bits are not used in I²S mode.
Bits 10:9 FRLVL[1:0]: FIFO reception level
These bits are set and cleared by hardware.
00: FIFO empty
01: 1/4 FIFO
10: 1/2 FIFO
11: FIFO full
Note: These bits are not used in I²S mode and in SPI receive-only mode while CRC
calculation is enabled.
Bit 8 FRE: Frame format error
This flag is used for SPI in TI slave mode and I2S slave mode. Refer to Section 32.5.11: SPI
error flags and Section 32.7.9: I2S error flags.
This flag is set by hardware and reset when SPIx_SR is read by software.
0: No frame format error
1: A frame format error occurred
Bit 7 BSY: Busy flag
0: SPI (or I2S) not busy
1: SPI (or I2S) is busy in communication or Tx buffer is not empty
This flag is set and cleared by hardware.
Note: The BSY flag must be used with caution: refer to Section 32.5.10: SPI status flags and
Procedure for disabling the SPI on page 1097.
Bit 6 OVR: Overrun flag
0: No overrun occurred
1: Overrun occurred
This flag is set by hardware and reset by a software sequence. Refer to I2S error flags on
page 1130 for the software sequence.
Bit 5 MODF: Mode fault
0: No mode fault occurred
1: Mode fault occurred
This flag is set by hardware and reset by a software sequence. Refer to Section : Mode fault
(MODF) on page 1107 for the software sequence.
Note: This bit is not used in I2S mode.

RM0385 Rev 7

1137/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Bit 4 CRCERR: CRC error flag
0: CRC value received matches the SPIx_RXCRCR value
1: CRC value received does not match the SPIx_RXCRCR value
This flag is set by hardware and cleared by software writing 0.
Note: This bit is not used in I2S mode.
Bit 3 UDR: Underrun flag
0: No underrun occurred
1: Underrun occurred
This flag is set by hardware and reset by a software sequence. Refer to I2S error flags on
page 1130 for the software sequence.
Note: This bit is not used in SPI mode.
Bit 2 CHSIDE: Channel side
0: Channel Left has to be transmitted or has been received
1: Channel Right has to be transmitted or has been received
Note: This bit is not used in SPI mode. It has no significance in PCM mode.
Bit 1 TXE: Transmit buffer empty
0: Tx buffer not empty
1: Tx buffer empty
Bit 0 RXNE: Receive buffer not empty
0: Rx buffer empty
1: Rx buffer not empty

32.9.4

SPI data register (SPIx_DR)
Address offset: 0x0C
Reset value: 0x0000

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DR[15:0]
rw

Bits 15:0 DR[15:0]: Data register
Data received or to be transmitted
The data register serves as an interface between the Rx and Tx FIFOs. When the data
register is read, RxFIFO is accessed while the write to data register accesses TxFIFO (See
Section 32.5.9: Data transmission and reception procedures).
Note: Data is always right-aligned. Unused bits are ignored when writing to the register, and
read as zero when the register is read. The Rx threshold setting must always
correspond with the read access currently used.

32.9.5

SPI CRC polynomial register (SPIx_CRCPR)
Address offset: 0x10
Reset value: 0x0007

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CRCPOLY[15:0]

1138/1709

rw

rw

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

Bits 15:0 CRCPOLY[15:0]: CRC polynomial register
This register contains the polynomial for the CRC calculation.
The CRC polynomial (0007h) is the reset value of this register. Another polynomial can be
configured as required.
Note: The polynomial value should be odd only. No even value is supported.

RM0385 Rev 7

1139/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

32.9.6

RM0385

SPI Rx CRC register (SPIx_RXCRCR)
Address offset: 0x14
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

RxCRC[15:0]
r

r

r

r

r

r

r

r

r

Bits 15:0 RXCRC[15:0]: Rx CRC register
When CRC calculation is enabled, the RxCRC[15:0] bits contain the computed CRC value of
the subsequently received bytes. This register is reset when the CRCEN bit in SPIx_CR1
register is written to 1. The CRC is calculated serially using the polynomial programmed in the
SPIx_CRCPR register.
Only the 8 LSB bits are considered when the CRC frame format is set to be 8-bit length (CRCL
bit in the SPIx_CR1 is cleared). CRC calculation is done based on any CRC8 standard.
The entire 16-bits of this register are considered when a 16-bit CRC frame format is selected
(CRCL bit in the SPIx_CR1 register is set). CRC calculation is done based on any CRC16
standard.
Note: A read to this register when the BSY Flag is set could return an incorrect value.
These bits are not used in I2S mode.

32.9.7

SPI Tx CRC register (SPIx_TXCRCR)
Address offset: 0x18
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

TxCRC[15:0]
r

r

r

r

r

r

r

r

r

Bits 15:0 TxCRC[15:0]: Tx CRC register
When CRC calculation is enabled, the TxCRC[7:0] bits contain the computed CRC value of
the subsequently transmitted bytes. This register is reset when the CRCEN bit of SPIx_CR1 is
written to 1. The CRC is calculated serially using the polynomial programmed in the
SPIx_CRCPR register.
Only the 8 LSB bits are considered when the CRC frame format is set to be 8-bit length
(CRCL bit in the SPIx_CR1 is cleared). CRC calculation is done based on any CRC8
standard.
The entire 16-bits of this register are considered when a 16-bit CRC frame format is selected
(CRCL bit in the SPIx_CR1 register is set). CRC calculation is done based on any CRC16
standard.
Note: A read to this register when the BSY flag is set could return an incorrect value.
These bits are not used in I2S mode.

1140/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

SPIx_I2S configuration register (SPIx_I2SCFGR)

32.9.8

Address offset: 0x1C
Reset value: 0x0000
15

14

13

12

11

10

Res.

Res.

Res.

ASTR
TEN

I2SMOD

I2SE

rw

rw

rw

9

8

I2SCFG
rw

rw

7

6

PCMSYNC

Res.

rw

5

4

I2SSTD
rw

rw

3
CKPOL
rw

2

1

0

DATLEN
rw

CHLEN

rw

rw

Bits 15:13 Reserved: Forced to 0 by hardware
Bit 12 ASTRTEN: Asynchronous start enable.
0: The Asynchronous start is disabled.
When the I2S is enabled in slave mode, the hardware starts the transfer when the I2S clock is
received and an appropriate transition is detected on the WS signal.
1: The Asynchronous start is enabled.
When the I2S is enabled in slave mode, the hardware starts the transfer when the I2S clock is
received and the appropriate level is detected on the WS signal.
Note: The appropriate transition is a falling edge on WS signal when I2S Philips Standard is used,
or a rising edge for other standards.
The appropriate level is a LOW level on WS signal when I2S Philips Standard is used, or a
HIGH level for other standards.
Please refer to Section 32.7.4: Start-up description for additional information.
Bit 11 I2SMOD: I2S mode selection
0: SPI mode is selected
1: I2S mode is selected
Note: This bit should be configured when the SPI is disabled.
Bit 10 I2SE: I2S enable
0: I2S peripheral is disabled
1: I2S peripheral is enabled
Note: This bit is not used in SPI mode.
Bits 9:8 I2SCFG: I2S configuration mode
00: Slave - transmit
01: Slave - receive
10: Master - transmit
11: Master - receive
Note: These bits should be configured when the I2S is disabled.
They are not used in SPI mode.
Bit 7 PCMSYNC: PCM frame synchronization
0: Short frame synchronization
1: Long frame synchronization
Note: This bit has a meaning only if I2SSTD = 11 (PCM standard is used).
It is not used in SPI mode.
Bit 6 Reserved: forced at 0 by hardware

RM0385 Rev 7

1141/1709
1144

Serial peripheral interface / inter-IC sound (SPI/I2S)

RM0385

Bits 5:4 I2SSTD: I2S standard selection
00: I2S Philips standard.
01: MSB justified standard (left justified)
10: LSB justified standard (right justified)
11: PCM standard
For more details on I2S standards, refer to Section 32.7.3 on page 1114
Note: For correct operation, these bits should be configured when the I2S is disabled.
They are not used in SPI mode.
Bit 3 CKPOL: Inactive state clock polarity
0: I2S clock inactive state is low level
1: I2S clock inactive state is high level
Note: For correct operation, this bit should be configured when the I2S is disabled.
It is not used in SPI mode.
The bit CKPOL does not affect the CK edge sensitivity used to receive or transmit the SD and
WS signals.
Bits 2:1 DATLEN: Data length to be transferred
00: 16-bit data length
01: 24-bit data length
10: 32-bit data length
11: Not allowed
Note: For correct operation, these bits should be configured when the I2S is disabled.
They are not used in SPI mode.
Bit 0 CHLEN: Channel length (number of bits per audio channel)
0: 16-bit wide
1: 32-bit wide
The bit write operation has a meaning only if DATLEN = 00 otherwise the channel length is fixed to
32-bit by hardware whatever the value filled in.
Note: For correct operation, this bit should be configured when the I2S is disabled.
It is not used in SPI mode.

1142/1709

RM0385 Rev 7

RM0385

Serial peripheral interface / inter-IC sound (SPI/I2S)

SPIx_I2S prescaler register (SPIx_I2SPR)

32.9.9

Address offset: 0x20
Reset value: 0x0002
15

14

13

12

11

10

9

8

7

6

5

4

3

Res.

Res.

Res.

Res.

Res.

Res.

MCKOE

ODD

I2SDIV[7:0]

rw

rw

rw

2

1

0

Bits 15:10 Reserved: Forced to 0 by hardware
Bit 9 MCKOE: Master clock output enable
0: Master clock output is disabled
1: Master clock output is enabled
Note: This bit should be configured when the I2S is disabled. It is used only when the I2S is in master
mode.
It is not used in SPI mode.
Bit 8 ODD: Odd factor for the prescaler
0: Real divider value is = I2SDIV *2
1: Real divider value is = (I2SDIV * 2)+1
Refer to Section 32.7.4 on page 1121
Note: This bit should be configured when the I2S is disabled. It is used only when the I2S is in master
mode.
It is not used in SPI mode.
Bits 7:0 I2SDIV[7:0]: I2S linear prescaler
I2SDIV [7:0] = 0 or I2SDIV [7:0] = 1 are forbidden values.
Refer to Section 32.7.4 on page 1121
Note: These bits should be configured when the I2S is disabled. They are used only when the I2S is
in master mode.
They are not used in SPI mode.

RM0385 Rev 7

1143/1709
1144

0x20
SPIx_I2SPR

1144/1709

RM0385 Rev 7

Reset value
0
0
0
0

Reset value
1

0
0

0

0

0

0

0

0

RXDMAEN

0
0
0

0

DR[15:0]

0
0

CRCPOLY[15:0]
0
0

RxCRC[15:0]
0
0

TxCRC[15:0]

0
0

0
0
0
0

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.
RXNE

SSOE
TXDMAEN

0

TXE

0
CHSIDE

FRF
NSSP

0

UDR

0
CRCERR

ERRIE

0

OVR

1
MODF

RXNEIE

0

TXEIE

1

BSY
0

0

0

0

BR [2:0]
MSTR
CPOL
CPHA

SSI
LSBFIRST
0

SPE

SSM
0

0
0
0
0
0
0
1
0

0
0
0
0
0
0
0

0
0
0
1
1
1

0
0
0
0
0
0

0
0
0
0
0
0

0

0

0
0

0
0

0

0
0

0
0

0
CHLEN

0

FRE

0

DATLEN

0

0

CKPOL

0

0

I2SSTD

0

DS[3:0]

Res.

0

FRLVL[1:0]

CRCNEXT
0

CRCL

BIDIOE
CRCEN
0

RXONLY

BIDIMODE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

PCMSYNC

FRXTH
0
FTLVL[1:0]

LDMA_TX
LDMA_RX
0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

I2SCFG

0

ODD

0

MCKOE

0

I2SE

0
0

Res.

0
0
0

I2SMOD

0
0

ASTRTEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

Res.

Reset value

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Reset value
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SPIx_I2SCFGR

Res.

0x1C
Res.

SPIx_TXCRCR

Res.

0x18
Res.

SPIx_RXCRCR

Res.

0x14

Res.

SPIx_CRCPR

Res.

0x10

Res.

SPIx_DR
Res.

0x0C

Res.

SPIx_SR

Res.

0x08

Res.

SPIx_CR2

Res.

0x04

Res.

SPIx_CR1

Res.

0x00

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register

Res.

Offset

Res.

32.9.10

Res.

Serial peripheral interface / inter-IC sound (SPI/I2S)
RM0385

SPI/I2S register map
Table 204 shows the SPI/I2S register map and reset values.
Table 204. SPI register map and reset values

0
0
0
0
0
0
0

I2SDIV
0
0
0

0

1

0

RM0385

Serial audio interface (SAI)

33

Serial audio interface (SAI)

33.1

Introduction
The SAI interface (Serial Audio Interface) offers a wide set of audio protocols due to its
flexibility and wide range of configurations. Many stereo or mono audio applications may be
targeted. I2S standards, LSB or MSB-justified, PCM/DSP, TDM, and AC’97 protocols may
be addressed for example. SPDIF output is offered when the audio block is configured as a
transmitter.
To bring this level of flexibility and reconfigurability, the SAI contains two independent audio
sub-blocks. Each block has it own clock generator and I/O line controller.
The SAI can work in master or slave configuration. The audio sub-blocks can be either
receiver or transmitter and can work synchronously or not (with respect to the other one).
The SAI can be connected with other SAIs to work synchronously.

RM0385 Rev 7

1145/1709
1188

Serial audio interface (SAI)

33.2

SAI main features
•

Two independent audio sub-blocks which can be transmitters or receivers with their
respective FIFO.

•

8-word integrated FIFOs for each audio sub-block.

•

Synchronous or asynchronous mode between the audio sub-blocks.

•

Possible synchronization between multiple SAIs.

•

Master or slave configuration independent for both audio sub-blocks.

•

Clock generator for each audio block to target independent audio frequency sampling
when both audio sub-blocks are configured in master mode.

•

Data size configurable: 8-, 10-, 16-, 20-, 24-, 32-bit.

•

Audio protocol: I2S, LSB or MSB-justified, PCM/DSP, TDM, AC’97

•

SPDIF output available if required.

•

Up to 16 slots available with configurable size.

•

Number of bits by frame can be configurable.

•

Frame synchronization active level configurable (offset, bit length, level).

•

First active bit position in the slot is configurable.

•

LSB first or MSB first for data transfer.

•

Mute mode.

•

Stereo/Mono audio frame capability.

•

Communication clock strobing edge configurable (SCK).

•

Error flags with associated interrupts if enabled respectively.

•

•

1146/1709

RM0385

–

Overrun and underrun detection,

–

Anticipated frame synchronization signal detection in slave mode,

–

Late frame synchronization signal detection in slave mode,

–

Codec not ready for the AC’97 mode in reception.

Interruption sources when enabled:
–

Errors,

–

FIFO requests.

2-channel DMA interface.

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

33.3

SAI functional description

33.3.1

SAI block diagram
Figure 397 shows the SAI block diagram while Table 205 and Table 206 list SAI internal and
external signals.
Figure 397. SAI functional block diagram
32-bit APB bus

Audio block A
FIFO ctrl

FIFO
sai_a_
ker_ck

Clock generator
Audio block A

FSM

Configuration
and status
registers

32-bit shift register

sai_pclk
Audio block B
FIFO ctrl

FIFO
sai_b_
ker_ck

Clock generator
Audio block B

Synchro
ctrl out

Configuration
and status
registers

sai_sync_out_sck
sai_sync_out_fs
FS_A
SCK_A
SD_A
MCLK_A
FS_B
SCK_B
SD_B
MCLK_B

FSM
sai_sync_in_sck
32-bit shift register

SAI_BCR1

APB Interface
sai_b_gbl_it sai_b_dma
32-bit APB bus

sai_sync_in_fs

From other SAI Blocks

SAI_ACR1

SAI_GCR

IO Line Management

APB Interface

Synchro
in

SAI

To other SAI Blocks

sai_a_gbl_it sai_a_dma

MSv30031V5

The SAI is mainly composed of two audio sub-blocks with their own clock generator. Each
audio block integrates a 32-bit shift register controlled by their own functional state machine.
Data are stored or read from the dedicated FIFO. FIFO may be accessed by the CPU, or by
DMA in order to leave the CPU free during the communication. Each audio block is
independent. They can be synchronous with each other.
An I/O line controller manages a set of 4 dedicated pins (SD, SCK, FS, MCLK) for a given
audio block in the SAI. Some of these pins can be shared if the two sub-blocks are declared
as synchronous to leave some free to be used as general purpose I/Os. The MCLK pin can
be output, or not, depending on the application, the decoder requirement and whether the
audio block is configured as the master.
If one SAI is configured to operate synchronously with another one, even more I/Os can be
freed (except for pins SD_x).
The functional state machine can be configured to address a wide range of audio protocols.
Some registers are present to set-up the desired protocols (audio frame waveform
generator).

RM0385 Rev 7

1147/1709
1188

Serial audio interface (SAI)

RM0385

The audio sub-block can be a transmitter or receiver, in master or slave mode. The master
mode means the SCK_x bit clock and the frame synchronization signal are generated from
the SAI, whereas in slave mode, they come from another external or internal master. There
is a particular case for which the FS signal direction is not directly linked to the master or
slave mode definition. In AC’97 protocol, it will be an SAI output even if the SAI (link
controller) is set-up to consume the SCK clock (and so to be in Slave mode).
Note:

For ease of reading of this section, the notation SAI_x refers to SAI_A or SAI_B, where ‘x’
represents the SAI A or B sub-block.

33.3.2

SAI pins and internal signals
Table 205. SAI internal input/output signals
Internal signal name Signal type
sai_a_gbl_it/
sai_b_gbl_it
sai_a_dma,
sai_b_dma

Output

Description
Audio block A and B global interrupts.

Input/output Audio block A and B DMA acknowledges and requests.

sai_sync_out_sck,
sai_sync_out_fs

Output

Internal clock and frame synchronization output signals
exchanged with other SAI blocks.

sai_sync_in_sck,
sai_sync_in_fs

Input

Internal clock and frame synchronization input signals
exchanged with other SAI blocks.

sai_a_ker_ck/
sai_b_ker_ck

Input

Audio block A/B kernel clock.

sai_pclk

Input

APB clock.

Table 206. SAI input/output pins
Name
SAI_SCK_A/B
SAI_MCLK_A/B

33.3.3

Signal type

Comments

Input/output Audio block A/B bit clock.
Output

Audio block A/B master clock.

SAI_SD_A/B

Input/output Data line for block A/B.

SAI_FS_A/B

Input/output Frame synchronization line for audio block A/B.

Main SAI modes
Each audio sub-block of the SAI can be configured to be master or slave via MODE bits in
the SAI_xCR1 register of the selected audio block.

Master mode
In master mode, the SAI delivers the timing signals to the external connected device:
•

The bit clock and the frame synchronization are output on pin SCK_x and FS_x,
respectively.

•

If needed, the SAI can also generate a master clock on MCLK_x pin.

Both SCK_x, FS_x and MCLK_x are configured as outputs.

1148/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

Slave mode
The SAI expects to receive timing signals from an external device.
•

If the SAI sub-block is configured in asynchronous mode, then SCK_x and FS_x pins
are configured as inputs.

•

If the SAI sub-block is configured to operate synchronously with another SAI interface
or with the second audio sub-block, the corresponding SCK_x and FS_x pins are left
free to be used as general purpose I/Os.

In slave mode, MCLK_x pin is not used and can be assigned to another function.
It is recommended to enable the slave device before enabling the master.

Configuring and enabling SAI modes
Each audio sub-block can be independently defined as a transmitter or receiver through the
MODE bit in the SAI_xCR1 register of the corresponding audio block. As a result, SAI_SD_x
pin will be respectively configured as an output or an input.
Two master audio blocks in the same SAI can be configured with two different MCLK and
SCK clock frequencies. In this case they have to be configured in asynchronous mode.
Each of the audio blocks in the SAI are enabled by SAIEN bit in the SAI_xCR1 register. As
soon as this bit is active, the transmitter or the receiver is sensitive to the activity on the
clock line, data line and synchronization line in slave mode.
In master TX mode, enabling the audio block immediately generates the bit clock for the
external slaves even if there is no data in the FIFO, However FS signal generation is
conditioned by the presence of data in the FIFO. After the FIFO receives the first data to
transmit, this data is output to external slaves. If there is no data to transmit in the FIFO, 0
values are then sent in the audio frame with an underrun flag generation.
In slave mode, the audio frame starts when the audio block is enabled and when a start of
frame is detected.
In Slave TX mode, no underrun event is possible on the first frame after the audio block is
enabled, because the mandatory operating sequence in this case is:

33.3.4

1.

Write into the SAI_xDR (by software or by DMA).

2.

Wait until the FIFO threshold (FLH) flag is different from 000b (FIFO empty).

3.

Enable the audio block in slave transmitter mode.

SAI synchronization mode
There are two levels of synchronization, either at audio sub-block level or at SAI level.

Internal synchronization
An audio sub-block can be configured to operate synchronously with the second audio subblock in the same SAI. In this case, the bit clock and the frame synchronization signals are
shared to reduce the number of external pins used for the communication. The audio block
configured in synchronous mode sees its own SCK_x, FS_x, and MCLK_x pins released
back as GPIOs while the audio block configured in asynchronous mode is the one for which
FS_x and SCK_x ad MCLK_x I/O pins are relevant (if the audio block is considered as
master).

RM0385 Rev 7

1149/1709
1188

Serial audio interface (SAI)

RM0385

Typically, the audio block in synchronous mode can be used to configure the SAI in full
duplex mode. One of the two audio blocks can be configured as a master and the other as
slave, or both as slaves with one asynchronous block (corresponding SYNCEN[1:0] bits set
to 00 in SAI_xCR1) and one synchronous block (corresponding SYNCEN[1:0] bits set to 01
in the SAI_xCR1).
Note:

Due to internal resynchronization stages, PCLK APB frequency must be higher than twice
the bit rate clock frequency.

External synchronization
The audio sub-blocks can also be configured to operate synchronously with another SAI.
This can be done as follow:

Note:

1.

The SAI, which is configured as the source from which the other SAI is synchronized,
has to define which of its audio sub-block is supposed to provide the FS and SCK
signals to other SAI. This is done by programming SYNCOUT[1:0] bits.

2.

The SAI which shall receive the synchronization signals has to select which SAI will
provide the synchronization by setting the proper value on SYNCIN[1:0] bits. For each
of the two SAI audio sub-blocks, the user must then specify if it operates synchronously
with the other SAI via the SYNCEN bit.

SYNCIN[1:0] and SYNCOUT[1:0] bits are located into the SAI_GCR register, and SYNCEN
bits into SAI_xCR1 register.
If both audio sub-blocks in a given SAI need to be synchronized with another SAI, it is
possible to choose one of the following configurations:
•

Configure each audio block to be synchronous with another SAI block through the
SYNCEN[1:0] bits.

•

Configure one audio block to be synchronous with another SAI through the
SYNCEN[1:0] bits. The other audio block is then configured as synchronous with the
second SAI audio block through SYNCEN[1:0] bits.

The following table shows how to select the proper synchronization signal depending on the
SAI block used. For example SAI2 can select the synchronization from SAI1 by setting SAI2
SYNCIN to 0. If SAI1 wants to select the synchronization coming from SAI2, SAI1 SYNCIN
must be set to 1. Positions noted as ‘Res.’ shall not be used.
Table 207. External synchronization selection
Block instance

33.3.5

SYNCIN= 3

SYNCIN= 2

SYNCIN= 1

SYNCIN= 0

SAI1

Res.

Res.

SAI2 sync

Res.

SAI2

Res.

Res.

Res.

SAI1 sync

Audio data size
The audio frame can target different data sizes by configuring bit DS[2:0] in the SAI_xCR1
register. The data sizes may be 8, 10, 16, 20, 24 or 32 bits. During the transfer, either the
MSB or the LSB of the data are sent first, depending on the configuration of bit LSBFIRST in
the SAI_xCR1 register.

1150/1709

RM0385 Rev 7

RM0385

33.3.6

Serial audio interface (SAI)

Frame synchronization
The FS signal acts as the Frame synchronization signal in the audio frame (start of frame).
The shape of this signal is completely configurable in order to target the different audio
protocols with their own specificities concerning this Frame synchronization behavior. This
reconfigurability is done using register SAI_xFRCR. Figure 398 illustrates this flexibility.
Figure 398. Audio frame
FS Length: up to 256 bits
FS active: up to 128 bits
FS

The falling edge can occur into this area

SCK
SD
(FSOFF = 0)

Slot 0

SD
(FSOFF = 1)

Slot 0

Slot 1

Slot 2

Slot 1

Slot 2

Slot 3

Slot 3

Slot 4

Slot 4

…...

…...

Slot 0

Slot 0

MSv30037V2

In AC’97 mode or in SPDIF mode (bit PRTCFG[1:0] = 10 or PRTCFG[1:0] = 01 in the
SAI_xCR1 register), the frame synchronization shape is forced to match the AC’97 protocol.
The SAI_xFRCR register value is ignored.
Each audio block is independent and consequently each one requires a specific
configuration.

Frame length
•

Master mode
The audio frame length can be configured to up to 256 bit clock cycles, by setting
FRL[7:0] field in the SAI_xFRCR register.
If the frame length is greater than the number of declared slots for the frame, the
remaining bits to transmit will be extended to 0 or the SD line will be released to HI-z
depending the state of bit TRIS in the SAI_xCR2 register (refer to FS signal role). In
reception mode, the remaining bit is ignored.
If bit NODIV is cleared, (FRL+1) must be equal to a power of 2, from 8 to 256, to ensure
that an audio frame contains an integer number of MCLK pulses per bit clock cycle.
If bit NODIV is set, the (FRL+1) field can take any value from 8 to 256. Refer to
Section 33.3.8: SAI clock generator”.

•

Slave mode
The audio frame length is mainly used to specify to the slave the number of bit clock
cycles per audio frame sent by the external master. It is used mainly to detect from the
master any anticipated or late occurrence of the Frame synchronization signal during
an on-going audio frame. In this case an error will be generated. For more details refer
to Section 33.3.13: Error flags.
In slave mode, there are no constraints on the FRL[7:0] configuration in the
SAI_xFRCR register.

The number of bits in the frame is equal to FRL[7:0] + 1.
The minimum number of bits to transfer in an audio frame is 8.

RM0385 Rev 7

1151/1709
1188

Serial audio interface (SAI)

RM0385

Frame synchronization polarity
FSPOL bit in the SAI_xFRCR register sets the active polarity of the FS pin from which a
frame is started. The start of frame is edge sensitive.
In slave mode, the audio block waits for a valid frame to start transmitting or receiving. Start
of frame is synchronized to this signal. It is effective only if the start of frame is not detected
during an ongoing communication and assimilated to an anticipated start of frame (refer to
Section 33.3.13: Error flags).
In master mode, the frame synchronization is sent continuously each time an audio frame is
complete until the SAIEN bit in the SAI_xCR1 register is cleared. If no data are present in
the FIFO at the end of the previous audio frame, an underrun condition will be managed as
described in Section 33.3.13: Error flags), but the audio communication flow will not be
interrupted.

Frame synchronization active level length
The FSALL[6:0] bits of the SAI_xFRCR register allow configuring the length of the active
level of the Frame synchronization signal. The length can be set from 1 to 128 bit clock
cycles.
As an example, the active length can be half of the frame length in I2S, LSB or MSB-justified
modes, or one-bit wide for PCM/DSP or TDM mode.

Frame synchronization offset
Depending on the audio protocol targeted in the application, the Frame synchronization
signal can be asserted when transmitting the last bit or the first bit of the audio frame (this is
the case in I2S standard protocol and in MSB-justified protocol, respectively). FSOFF bit in
the SAI_xFRCR register allows to choose one of the two configurations.

FS signal role
The FS signal can have a different meaning depending on the FS function. FSDEF bit in the
SAI_xFRCR register selects which meaning it will have:
•

0: start of frame, like for instance the PCM/DSP, TDM, AC’97, audio protocols,

•

1: start of frame and channel side identification within the audio frame like for the I2S,
the MSB or LSB-justified protocols.

When the FS signal is considered as a start of frame and channel side identification within
the frame, the number of declared slots must be considered to be half the number for the left
channel and half the number for the right channel. If the number of bit clock cycles on half
audio frame is greater than the number of slots dedicated to a channel side, and TRIS = 0, 0
is sent for transmission for the remaining bit clock cycles in the SAI_xCR2 register.
Otherwise if TRIS = 1, the SD line is released to HI-Z. In reception mode, the remaining bit
clock cycles are not considered until the channel side changes.

1152/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

Figure 399. FS role is start of frame + channel side identification (FSDEF = TRIS = 1)
Number of slots not aligned with the audio frame
Audio frame
Half of frame
FS

sck

slot

Slot 0 ON

Slot 3 ON Slot 4 OFF Slot 5 ON

Slot 1 OFF Slot 2 ON

Number of slots aligned with the audio frame
Audio frame
Half of frame

FS

sck

slot

Slot 0

Slot 1

Slot 2

Slot 3

Slot 4

Slot 5
MS30038V1

1. The frame length should be even.

If FSDEF bit in SAI_xFRCR is kept clear, so FS signal is equivalent to a start of frame, and if
the number of slots defined in NBSLOT[3:0] in SAI_xSLOTR multiplied by the number of bits
by slot configured in SLOTSZ[1:0] in SAI_xSLOTR is less than the frame size (bit FRL[7:0]
in the SAI_xFRCR register), then:
•

if TRIS = 0 in the SAI_xCR2 register, the remaining bit after the last slot will be forced to
0 until the end of frame in case of transmitter,

•

if TRIS = 1, the line will be released to HI-Z during the transfer of these remaining bits.
In reception mode, these bits are discarded.

RM0385 Rev 7

1153/1709
1188

Serial audio interface (SAI)

RM0385
Figure 400. FS role is start of frame (FSDEF = 0)
Audio frame

sck

slot

Slot 0

Slot 1

Slot 2

...

Slot n

Data = 0 after slot n if TRIS = 0
SD output released (HI-Z) after slot n if TRIS = 1
MS30039V1

The FS signal is not used when the audio block in transmitter mode is configured to get the
SPDIF output on the SD line. The corresponding FS I/O will be released and left free for
other purposes.

33.3.7

Slot configuration
The slot is the basic element in the audio frame. The number of slots in the audio frame is
equal to NBSLOT[3:0] + 1.
The maximum number of slots per audio frame is fixed at 16.
For AC’97 protocol or SPDIF (when bit PRTCFG[1:0] = 10 or PRTCFG[1:0] = 01), the
number of slots is automatically set to target the protocol specification, and the value of
NBSLOT[3:0] is ignored.
Each slot can be defined as a valid slot, or not, by setting SLOTEN[15:0] bits of the
SAI_xSLOTR register.
When a invalid slot is transferred, the SD data line is either forced to 0 or released to HI-z
depending on TRIS bit configuration (refer to Output data line management on an inactive
slot) in transmitter mode. In receiver mode, the received value from the end of this slot is
ignored. Consequently, there will be no FIFO access and so no request to read or write the
FIFO linked to this inactive slot status.
The slot size is also configurable as shown in Figure 401. The size of the slots is selected by
setting SLOTSZ[1:0] bits in the SAI_xSLOTR register. The size is applied identically for
each slot in an audio frame.

1154/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)
Figure 401. Slot size configuration with FBOFF = 0 in SAI_xSLOTR
Audio block is receiver

Audio block is transmitter

Slot size = data size

Slot size = data size
slotx

data size

data size

slotx

data size

data size
slotx

00..00

data size

slotx

data size

16-bit
slotx

X..X

16-bit
00..00

data size

slotx

data size

32-bit

XX..XX

32-bit
X: don’t care
MS30033V1

It is possible to choose the position of the first data bit to transfer within the slots. This offset
is configured by FBOFF[4:0] bits in the SAI_xSLOTR register. 0 values will be injected in
transmitter mode from the beginning of the slot until this offset position is reached. In
reception, the bit in the offset phase is ignored. This feature targets the LSB justified
protocol (if the offset is equal to the slot size minus the data size).
Figure 402. First bit offset
Audio block is receiver

Audio block is transmitter

Slot size = data size

Slot size = data size
slotx

slotx

data size

data size
data size

data size

FBOFF

FBOFF

slotx

XX

00

data size

00

slotx

16-bit

data size

00..00

XX

16-bit
FBOFF = SLOT SZ -DS

FBOFF = SLOT SZ -DS
slotx

data size

slotx

XX .. XX

data size

32-bit
X: don’t care

32-bit

MS30034V1

It is mandatory to respect the following conditions to avoid bad SAI behavior:
FBOFF ≤(SLOTSZ - DS),
DS ≤SLOTSZ,
NBSLOT x SLOTSZ ≤FRL (frame length),
The number of slots must be even when bit FSDEF in the SAI_xFRCR register is set.
In AC’97 and SPDIF protocol (bit PRTCFG[1:0] = 10 or PRTCFG[1:0] = 01), the slot size is
automatically set as defined in Section 33.3.10: AC’97 link controller.

RM0385 Rev 7

1155/1709
1188

Serial audio interface (SAI)

33.3.8

RM0385

SAI clock generator
Each audio block has its own clock generator that makes these two blocks completely
independent. There is no difference in terms of functionality between these two clock
generators.
When the audio block is configured as Master, the clock generator provides the
communication clock (the bit clock) and the master clock for external decoders.
When the audio block is defined as slave, the clock generator is OFF.
Figure 403 illustrates the architecture of the audio block clock generator.
Figure 403. Audio block clock generator overview

NODIV
MCKDIV[3:0]

MCLK_x
0
1

sai_x_ker
_ck

Master clock
divider

0

FRL[7:0]
NODIV

NODIV
0
1

Bit clock divider

0
1

SCK_x

MSv30040V2

Note:

If NODIV is set to 1, the MCLK_x signal will be set at 0 level if this pin is configured as the
SAI pin in GPIO peripherals.
The clock source for the clock generator comes from the product clock controller. The
sai_x_ker_ck clock is equivalent to the master clock which can be divided for the external
decoders using bit MCKDIV[3:0]:
MCLK_x = sai_x_ker_ck / (MCKDIV[3:0] * 2), if MCKDIV[3:0] is not equal to 0000.
MCLK_x = sai_x_ker_ck, if MCKDIV[3:0] is equal to 0000.
MCLK_x signal is used only in TDM.
The division must be even in order to keep 50% on the Duty cycle on the MCLK output and
on the SCK_x clock. If bit MCKDIV[3:0] = 0000, division by one is applied to obtain MCLK_x
equal to sai_x_ker_ck.
In the SAI, the single ratio MCLK/FS = 256 is considered. Mostly, three frequency ranges
will be encountered as illustrated in Table 208.

1156/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)
Table 208. Example of possible audio frequency sampling range
Input sai_x_ker_ck
clock frequency

192 kHz x 256

44.1 kHz x 256

sai_x_ker_ck =
MCLK(1)

Most usual audio frequency
sampling achievable

MCKDIV[3:0]

192 kHz

MCKDIV[3:0] = 0000

96 kHz

MCKDIV[3:0] = 0001

48 kHz

MCKDIV[3:0] = 0010

16 kHz

MCKDIV[3:0] = 0110

8 kHz

MCKDIV[3:0] = 1100

44.1 kHz

MCKDIV[3:0] = 0000

22.05 kHz

MCKDIV[3:0] = 0001

11.025 kHz

MCKDIV[3:0] = 0010

MCLK

MCKDIV[3:0] = 0000

1. This may happen when the product clock controller selects an external clock source, instead of PLL clock.

The master clock can be generated externally on an I/O pad for external decoders if the
corresponding audio block is declared as master with bit NODIV = 0 in the SAI_xCR1
register. In slave, the value set in this last bit is ignored since the clock generator is OFF,
and the MCLK_x I/O pin is released for use as a general purpose I/O.
The bit clock is derived from the master clock. The bit clock divider sets the divider factor
between the bit clock (SCK_x) and the master clock (MCLK_x) following the formula:
SCK_x = MCLK x (FRL[7:0] +1) / 256
where:
256 is the fixed ratio between MCLK and the audio frequency sampling.
FRL[7:0] is the number of bit clock cycles- 1 in the audio frame, configured in the
SAI_xFRCR register.
In master mode it is mandatory that (FRL[7:0] +1) is equal to a number with a power of 2
(refer to Section 33.3.6: Frame synchronization) to obtain an even integer number of
MCLK_x pulses by bit clock cycle. The 50% duty cycle is guaranteed on the bit clock
(SCK_x).
The sai_x_ker_ck clock can also be equal to the bit clock frequency. In this case, NODIV bit
in the SAI_xCR1 register should be set and the value inside the MCKDIV divider and the bit
clock divider will be ignored. In this case, the number of bits per frame is fully configurable
without the need to be equal to a power of two.
The bit clock strobing edge on SCK can be configured by bit CKSTR in the SAI_xCR1
register.
Refer to Section 33.3.11: SPDIF output for details on clock generator programming in
SPDIF mode.

RM0385 Rev 7

1157/1709
1188

Serial audio interface (SAI)

33.3.9

RM0385

Internal FIFOs
Each audio block in the SAI has its own FIFO. Depending if the block is defined to be a
transmitter or a receiver, the FIFO can be written or read, respectively. There is therefore
only one FIFO request linked to FREQ bit in the SAI_xSR register.
An interrupt is generated if FREQIE bit is enabled in the SAI_xIM register. This depends on:
•

FIFO threshold setting (FLVL bits in SAI_xCR2)

•

Communication direction (transmitter or receiver). Refer to Interrupt generation in
transmitter mode and Interrupt generation in reception mode.

Interrupt generation in transmitter mode
The interrupt generation depends on the FIFO configuration in transmitter mode:
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO empty
(FTH[2:0] set to 000b), an interrupt is generated (FREQ bit set by hardware to 1 in
SAI_xSR register) if no data are available in SAI_xDR register (FLVL[2:0] bits in SAI_xSR
is less than 001b). This Interrupt (FREQ bit in SAI_xSR register) is cleared by hardware
when the FIFO is no more empty (FLVL[2:0] bits in SAI_xSR are different from 000b) i.e
one or more data are stored in the FIFO.
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO quarter full
(FTH[2:0] set to 001b), an interrupt is generated (FREQ bit set by hardware to 1 in
SAI_xSR register) if less than a quarter of the FIFO contains data (FLVL[2:0] bits in
SAI_xSR are less than 010b). This Interrupt (FREQ bit in SAI_xSR register) is cleared by
hardware when at least a quarter of the FIFO contains data (FLVL[2:0] bits in SAI_xSR
are higher or equal to 010b).
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO half full
(FTH[2:0] set to 010b), an interrupt is generated (FREQ bit set by hardware to 1 in
SAI_xSR register) if less than half of the FIFO contains data (FLVL[2:0] bits in SAI_xSR
are less than 011b). This Interrupt (FREQ bit in SAI_xSR register) is cleared by hardware
when at least half of the FIFO contains data (FLVL[2:0] bits in SAI_xSR are higher or
equal to 011b).
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO three quarter
(FTH[2:0] set to 011b), an interrupt is generated (FREQ bit is set by hardware to 1 in
SAI_xSR register) if less than three quarters of the FIFO contain data (FLVL[2:0] bits in
SAI_xSR are less than 100b). This Interrupt (FREQ bit in SAI_xSR register) is cleared by
hardware when at least three quarters of the FIFO contain data (FLVL[2:0] bits in
SAI_xSR are higher or equal to 100b).
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO full (FTH[2:0]
set to 100b), an interrupt is generated (FREQ bit is set by hardware to 1 in SAI_xSR
register) if the FIFO is not full (FLVL[2:0] bits in SAI_xSR is less than 101b). This Interrupt
(FREQ bit in SAI_xSR register) is cleared by hardware when the FIFO is full (FLVL[2:0]
bits in SAI_xSR is equal to 101b value).

Interrupt generation in reception mode
The interrupt generation depends on the FIFO configuration in reception mode:
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO empty
(FTH[2:0] set to 000b), an interrupt is generated (FREQ bit is set by hardware to 1 in
SAI_xSR register) if at least one data is available in SAI_xDR register(FLVL[2:0] bits in
SAI_xSR is higher or equal to 001b). This Interrupt (FREQ bit in SAI_xSR register) is

1158/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)
cleared by hardware when the FIFO becomes empty (FLVL[2:0] bits in SAI_xSR is equal
to 000b) i.e no data are stored in FIFO.
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO quarter fully
(FTH[2:0] set to 001b), an interrupt is generated (FREQ bit is set by hardware to 1 in
SAI_xSR register) if at least one quarter of the FIFO data locations are available
(FLVL[2:0] bits in SAI_xSR is higher or equal to 010b). This Interrupt (FREQ bit in
SAI_xSR register) is cleared by hardware when less than a quarter of the FIFO data
locations become available (FLVL[2:0] bits in SAI_xSR is less than 010b).
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO half fully
(FTH[2:0] set to 010b value), an interrupt is generated (FREQ bit is set by hardware to 1
in SAI_xSR register) if at least half of the FIFO data locations are available (FLVL[2:0] bits
in SAI_xSR is higher or equal to 011b). This Interrupt (FREQ bit in SAI_xSR register) is
cleared by hardware when less than half of the FIFO data locations become available
(FLVL[2:0] bits in SAI_xSR is less than 011b).
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO three quarter
full(FTH[2:0] set to 011b value), an interrupt is generated (FREQ bit is set by hardware to
1 in SAI_xSR register) if at least three quarters of the FIFO data locations are available
(FLVL[2:0] bits in SAI_xSR is higher or equal to 100b). This Interrupt (FREQ bit in
SAI_xSR register) is cleared by hardware when the FIFO has less than three quarters of
the FIFO data locations avalable(FLVL[2:0] bits in SAI_xSR is less than 100b).
• When the FIFO threshold bits in SAI_xCR2 register are configured as FIFO full(FTH[2:0]
set to 100b), an interrupt is generated (FREQ bit is set by hardware to 1 in SAI_xSR
register) if the FIFO is full (FLVL[2:0] bits in SAI_xSR is equal to 101b). This Interrupt
(FREQ bit in SAI_xSR register) is cleared by hardware when the FIFO is not full
(FLVL[2:0] bits in SAI_xSR is less than 101b).
Like interrupt generation, the SAI can use the DMA if DMAEN bit in the SAI_xCR1 register is
set. The FREQ bit assertion mechanism is the same as the interruption generation
mechanism described above for FREQIE.
Each FIFO is an 8-word FIFO. Each read or write operation from/to the FIFO targets one
word FIFO location whatever the access size. Each FIFO word contains one audio slot.
FIFO pointers are incremented by one word after each access to the SAI_xDR register.
Data should be right aligned when it is written in the SAI_xDR.
Data received will be right aligned in the SAI_xDR.
The FIFO pointers can be reinitialized when the SAI is disabled by setting bit FFLUSH in the
SAI_xCR2 register. If FFLUSH is set when the SAI is enabled the data present in the FIFO
will be lost automatically.

RM0385 Rev 7

1159/1709
1188

Serial audio interface (SAI)

33.3.10

RM0385

AC’97 link controller
The SAI is able to work as an AC’97 link controller. In this protocol:
•

The slot number and the slot size are fixed.

•

The frame synchronization signal is perfectly defined and has a fixed shape.

To select this protocol, set PRTCFG[1:0] bits in the SAI_xCR1 register to 10. When AC’97
mode is selected, only data sizes of 16 or 20 bits can be used, otherwise the SAI behavior is
not guaranteed.
•

NBSLOT[3:0] and SLOTSZ[1:0] bits are consequently ignored.

•

The number of slots is fixed to 13 slots. The first one is 16-bit wide and all the others
are 20-bit wide (data slots).

•

FBOFF[4:0] bits in the SAI_xSLOTR register are ignored.

•

The SAI_xFRCR register is ignored.

•

The MCLK is not used.

The FS signal from the block defined as asynchronous is configured automatically as an
output, since the AC’97 controller link drives the FS signal whatever the master or slave
configuration.
Figure 404 shows an AC’97 audio frame structure.
Figure 404. AC’97 audio frame
FS
1

SDI

Tag

SDO

Tag

2

3

4

5

6

7

8

CMD CMD
PCM
PCM
LINE1
PCM
PCM
PCM
ADDR DATA LFRONT RFRONT DAC CENTER LSURR RSURR

STATUS STATUS PCM PCM
ADDR DATA LEFT RIGHT

LINE1
ADC

PCM
MIC

RSR
VD

RSR
VD

9

10

11

12

PCM
LFE

LINE2
DAC

HSET
DAC

IO
CTRL

RSR
LVD

LINE2
ADC

HSET

IO
STATUS

MS192343V1

Note:

In AC’97 protocol, bit 2 of the tag is reserved (always 0), so bit 2 of the TAG is forced to 0
level whatever the value written in the SAI FIFO.
For more details about tag representation, refer to the AC’97 protocol standard.
One SAI can be used to target an AC’97 point-to-point communication.
Using two SAIs (for devices featuring two embedded SAIs) allows controlling three external
AC’97 decoders as illustrated in Figure 405.
In SAI1, the audio block A must be declared as asynchronous master transmitter whereas
the audio block B is defined to be slave receiver and internally synchronous to the audio
block A.
The SAI2 is configured for audio block A and B both synchronous with the external SAI1 in
slave receiver mode.

1160/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)
Figure 405. Example of typical AC’97 configuration on devices featuring at least
2 embedded SAIs (three external AC’97 decoders)

AC’97 Link Controller
(Bit clock provider)
Audio block A

Primary codec 1

Master
SDA
FIFO
Block B
synchronous with
block A

Transmitter

FSA
SCLKA

Clock
generator

Sdata_out
Sync
Bit_clk
Sdata_in

Slave
SDB
FIFO

Receiver

FSB
SCLKB

Secondary codec 1

Audio block B
Sdata_out
Sync
Bit_clk

SAI1
Audio block A
Slave

Sdata_in
SDA

FIFO
Synchronous with
other SAI clocks

Receiver

FSA
SCLKA
Secondary codec 2

Clock
generator

Slave
SDB
FIFO

Receiver

FSB
SCLKB

Sdata_out
Sync
Bit_clk
Sdata_in

Audio block B
SAI2

MSv31173V1

In receiver mode, the SAI acting as an AC’97 link controller requires no FIFO request and so
no data storage in the FIFO when the Codec ready bit in the slot 0 is decoded low. If bit
CNRDYIE is enabled in the SAI_xIM register, flag CNRDY will be set in the SAI_xSR
register and an interrupt is generated. This flag is dedicated to the AC’97 protocol.

Clock generator programming in AC’97 mode
In AC’97 mode, the frame length is fixed at 256 bits, and its frequency shall be set to
48 kHz. The formulas given in Section 33.3.8: SAI clock generator shall be used with FRL =
255, in order to generate the proper frame rate (FFS_x).

RM0385 Rev 7

1161/1709
1188

Serial audio interface (SAI)

33.3.11

RM0385

SPDIF output
The SPDIF interface is available in transmitter mode only. It supports the audio IEC60958.
To select SPDIF mode, set PRTCFG[1:0] bit to 01 in the SAI_xCR1 register.
For SPDIF protocol:
•

Only SD data line is enabled.

•

FS, SCK, MCLK I/Os pins are left free.

•

MODE[1] bit is forced to 0 to select the master mode in order to enable the clock
generator of the SAI and manage the data rate on the SD line.

•

The data size is forced to 24 bits. The value set in DS[2:0] bits in the SAI_xCR1 register
is ignored.

•

The clock generator must be configured to define the symbol-rate, knowing that the bit
clock should be twice the symbol-rate. The data is coded in Manchester protocol.

•

The SAI_xFRCR and SAI_xSLOTR registers are ignored. The SAI is configured
internally to match the SPDIF protocol requirements as shown in Figure 406.
Figure 406. SPDIF format
Block N+1

Block N
Frame 0

Frame 191

Frame 1

Frame 0

Sub-frame
B Channel A W Channel B M Channel A W Channel B

SOPD

SOPD B,M,W

D0

D1 D2 D3

M Channel A W Channel B B

D20 D21 D22 D23 VP

D4

24-bit data

U

Channel A W Channel B

CS

Status bit

Channel
MS30042V1

A SPDIF block contains 192 frames. Each frame is composed of two 32-bit sub-frames,
generally one for the left channel and one for the right channel. Each sub-frame is
composed of a SOPD pattern (4-bit) to specify if the sub-frame is the start of a block (and so
is identifying a channel A) or if it is identifying a channel A somewhere in the block, or if it is
referring to channel B (see Table 209). The next 28 bits of channel information are
composed of 24 bits data + 4 status bits.

1162/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)
Table 209. SOPD pattern
Preamble coding
SOPD

Description
last bit is 0

last bit is 1

B

11101000

00010111

Channel A data at the start of block

W

11100100

00011011

Channel B data somewhere in the block

M

11100010

00011101

Channel A data

The data stored in SAI_xDR has to be filled as follows:
•

SAI_xDR[26:24] contain the Channel status, User and Validity bits.

•

SAI_xDR[23:0] contain the 24-bit data for the considered channel.

If the data size is 20 bits, then data shall be mapped on SAI_xDR[23:4].
If the data size is 16 bits, then data shall be mapped on SAI_xDR[23:8].
SAI_xDR[23] always represents the MSB.
Figure 407. SAI_xDR register ordering

SAI_xDR[26:0]
0

26
CS U

V D23 D22 D21 D20 D19 D18 D17 D16 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

Data[23:0]

Status
bits

MSv31174V1

Note:

The transfer is performed always with LSB first.
The SAI first sends the adequate preamble for each sub-frame in a block. The SAI_xDR is
then sent on the SD line (manchester coded). The SAI ends the sub-frame by transferring
the Parity bit calculated as described in Table 210.
Table 210. Parity bit calculation
SAI_xDR[26:0]

Parity bit P value transferred

odd number of 0

0

odd number of 1

1

The underrun is the only error flag available in the SAI_xSR register for SPDIF mode since
the SAI can only operate in transmitter mode. As a result, the following sequence should be

RM0385 Rev 7

1163/1709
1188

Serial audio interface (SAI)

RM0385

executed to recover from an underrun error detected via the underrun interrupt or the
underrun status bit:
1.

Disable the DMA stream (via the DMA peripheral) if the DMA is used.

2.

Disable the SAI and check that the peripheral is physically disabled by polling the
SAIEN bit in SAI_xCR1 register.

3.

Clear the COVRUNDR flag in the SAI_xCLRFR register.

4.

Flush the FIFO by setting the FFLUSH bit in SAI_xCR2.
The software needs to point to the address of the future data corresponding to a start of
new block (data for preamble B). If the DMA is used, the DMA source base address
pointer should be updated accordingly.

5.

Enable again the DMA stream (DMA peripheral) if the DMA used to manage data
transfers according to the new source base address.

6.

Enable again the SAI by setting SAIEN bit in SAI_xCR1 register.

Clock generator programming in SPDIF generator mode
For the SPDIF generator, the SAI shall provide a bit clock twice faster as the symbol-rate.
The table hereafter shows usual examples of symbol rates with respect to the audio
sampling rate.
Table 211. Audio sampling frequency versus symbol rates
Audio Sampling Frequencies (FS)

Symbol-rate

44.1 kHz

2.8224 MHz

48 kHz

3.072 MHz

96 kHz

6.144 MHz

192 kHz

12.288 MHz

More generally, the relationship between the audio sampling frequency (FS) and the bit
clock rate (FSCK_X) is given by the formula:
F SCK_x
F S = ----------------------128
And the bit clock rate is obtained as follow:
F SCK_x = F SAI_CK_x

1164/1709

RM0385 Rev 7

RM0385

33.3.12

Serial audio interface (SAI)

Specific features
The SAI interface embeds specific features which can be useful depending on the audio
protocol selected. These functions are accessible through specific bits of the SAI_xCR2
register.

Mute mode
The mute mode can be used when the audio sub-block is a transmitter or a receiver.
Audio sub-block in transmission mode
In transmitter mode, the mute mode can be selected at anytime. The mute mode is active
for entire audio frames. The MUTE bit in the SAI_xCR2 register enables the mute mode
when it is set during an ongoing frame.
The mute mode bit is strobed only at the end of the frame. If it is set at this time, the mute
mode is active at the beginning of the new audio frame and for a complete frame, until the
next end of frame. The bit is then strobed to determine if the next frame will still be a mute
frame.
If the number of slots set through NBSLOT[3:0] bits in the SAI_xSLOTR register is lower
than or equal to 2, it is possible to specify if the value sent in mute mode is 0 or if it is the last
value of each slot. The selection is done via MUTEVAL bit in the SAI_xCR2 register.
If the number of slots set in NBSLOT[3:0] bits in the SAI_xSLOTR register is greater than 2,
MUTEVAL bit in the SAI_xCR2 is meaningless as 0 values are sent on each bit on each
slot.
The FIFO pointers are still incremented in mute mode. This means that data present in the
FIFO and for which the mute mode is requested are discarded.
Audio sub-block in reception mode
In reception mode, it is possible to detect a mute mode sent from the external transmitter
when all the declared and valid slots of the audio frame receive 0 for a given consecutive
number of audio frames (MUTECNT[5:0] bits in the SAI_xCR2 register).
When the number of MUTE frames is detected, the MUTEDET flag in the SAI_xSR register
is set and an interrupt can be generated if MUTEDETIE bit is set in SAI_xCR2.
The mute frame counter is cleared when the audio sub-block is disabled or when a valid slot
receives at least one data in an audio frame. The interrupt is generated just once, when the
counter reaches the value specified in MUTECNT[5:0] bits. The interrupt event is then
reinitialized when the counter is cleared.
Note:

The mute mode is not available for SPDIF audio blocks.

Mono/stereo mode
In transmitter mode, the mono mode can be addressed, without any data preprocessing in
memory, assuming the number of slots is equal to 2 (NBSLOT[3:0] = 0001 in SAI_xSLOTR).
In this case, the access time to and from the FIFO will be reduced by 2 since the data for
slot 0 is duplicated into data slot 1.
To enable the mono mode,
1.

Set MONO bit to 1 in the SAI_xCR1 register.

2.

Set NBSLOT to 1 and SLOTEN to 3 in SAI_xSLOTR.

RM0385 Rev 7

1165/1709
1188

Serial audio interface (SAI)

RM0385

In reception mode, the MONO bit can be set and is meaningful only if the number of slots is
equal to 2 as in transmitter mode. When it is set, only slot 0 data will be stored in the FIFO.
The data belonging to slot 1 will be discarded since, in this case, it is supposed to be the
same as the previous slot. If the data flow in reception mode is a real stereo audio flow with
a distinct and different left and right data, the MONO bit is meaningless. The conversion
from the output stereo file to the equivalent mono file is done by software.

Companding mode
Telecommunication applications can require to process the data to be transmitted or
received using a data companding algorithm.
Depending on the COMP[1:0] bits in the SAI_xCR2 register (used only when TDM mode is
selected), the application software can choose to process or not the data before sending it
on SD serial output line (compression) or to expand the data after the reception on SD serial
input line (expansion) as illustrated in Figure 408. The two companding modes supported
are the µ-Law and the A-Law log which are a part of the CCITT G.711 recommendation.
The companding standard used in the United States and Japan is the µ-Law. It supports 14
bits of dynamic range (COMP[1:0] = 10 in the SAI_xCR2 register).
The European companding standard is A-Law and supports 13 bits of dynamic range
(COMP[1:0] = 11 in the SAI_xCR2 register).
Both µ-Law or A-Law companding standard can be computed based on 1’s complement or
2’s complement representation depending on the CPL bit setting in the SAI_xCR2 register.
In µ-Law and A-Law standards, data are coded as 8 bits with MSB alignment. Companded
data are always 8-bit wide. For this reason, DS[2:0] bits in the SAI_xCR1 register will be
forced to 010 when the SAI audio block is enabled (SAIEN bit = 1 in the SAI_xCR1 register)
and when one of these two companding modes selected through the COMP[1:0] bits.
If no companding processing is required, COMP[1:0] bits should be kept clear.
Figure 408. Data companding hardware in an audio block in the SAI
Receiver mode (bit MODE[0] = 1 in SAI_xCR1)
COMP[1]

FIFO

1

SD

expand
32-bit shift register

0

Transmitter mode (bit MODE[0] = 0 in SAI_xCR1)

0
FIFO
compress

SD
32-bit shift register

1

COMP[1]
MS19244V1

1. Not applicable when AC’97 or SPDIF are selected.

1166/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)
Expansion and compression mode are automatically selected through the SAI_xCR2:
•

If the SAI audio block is configured to be a transmitter, and if the COMP[1] bit is set in
the SAI_xCR2 register, the compression mode will be applied.

•

If the SAI audio block is declared as a receiver, the expansion algorithm will be applied.

Output data line management on an inactive slot
In transmitter mode, it is possible to choose the behavior of the SD line output when an
inactive slot is sent on the data line (via TRIS bit).
•

Either the SAI forces 0 on the SD output line when an inactive slot is transmitted, or

•

The line is released in HI-z state at the end of the last bit of data transferred, to release
the line for other transmitters connected to this node.

It is important to note that the two transmitters cannot attempt to drive the same SD output
pin simultaneously, which could result in a short circuit. To ensure a gap between
transmissions, if the data is lower than 32-bit, the data can be extended to 32-bit by setting
bit SLOTSZ[1:0] = 10 in the SAI_xSLOTR register. The SD output pin will then be tri-stated
at the end of the LSB of the active slot (during the padding to 0 phase to extend the data to
32-bit) if the following slot is declared inactive.
In addition, if the number of slots multiplied by the slot size is lower than the frame length,
the SD output line will be tri-stated when the padding to 0 is done to complete the audio
frame.
Figure 409 illustrates these behaviors.

RM0385 Rev 7

1167/1709
1188

Serial audio interface (SAI)

RM0385

Figure 409. Tristate strategy on SD output line on an inactive slot
Bit TRIS = 1 in the SAI_xCR1 and frame length = number of slots
Audio frame
sck
Slot size = data size
Slot 0 ON

slot
SD (output)

Slot 1 OFF

Slot 2 OFF

Data 0

Slot 3 ON
Data 1

.. ON
..

.. ON
..

Slot n ON
Data m

Slot size > data size
slot

Slot 0 ON

SD (output)
slot

Slot 1 OFF

Slot 2 OFF

Data 1

Data 0
Slot 0 ON

Slot 3 ON

Slot 1 OFF

Slot 2 OFF

SD (output)

Slot 3 ON
Data 0

.. ON
..
.. ON
..

.. ON
..
.. ON
..

Slot n ON
Data m
Slot n ON
Data m

Bit TRIS = 1 in the SAI_xCR1 and frame length > number of slots
Audio frame
sck
Slot size = data size
Slot 0 ON

slot
SD (output)

Slot 1 OFF

Slot 2 OFF

Data 0

.. ON
..

Slot n ON
Data m

Slot size > data size
Slot 0 ON

slot
SD (output)

SD (output)

Slot 2 OFF

.. ON
..

Data 0

Slot 0 ON

slot

Slot 1 OFF

Slot 1 OFF

Slot 2 OFF

.. ON
..

Slot n ON
Data m

.. ON
Data m
MS192345V1

When the selected audio protocol uses the FS signal as a start of frame and a channel side
identification (bit FSDEF = 1 in the SAI_xFRCR register), the tristate mode is managed
according to Figure 410 (where bit TRIS in the SAI_xCR1 register = 1, and FSDEF=1, and
half frame length is higher than number of slots/2, and NBSLOT=6).

1168/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)
Figure 410. Tristate on output data line in a protocol like I2S

sck

Slot size = data size
slot

Slot 0 ON

SD (output)

Slot 1 OFF

Data 0

Slot 2 ON

Slot 3 ON

Data 1

Data 2

Slot 4 OFF

Slot 5 ON
Data 3

Slot size > data size
Slot 0 ON

slot
SD (output)

Slot 1 OFF

Data 0

Slot 0 ON

slot
SD (output)

Data 0

Slot 2 ON
Data 1

Slot 1 OFF

Slot 3 ON

Slot 4 OFF

Data 2

Slot 2 ON

Slot 3 ON

Data 1

Slot 5 ON
Data 3

Slot 4 OFF

Slot 5 ON
Data m
MS192346V1

If the TRIS bit in the SAI_xCR2 register is cleared, all the High impedance states on the SD
output line on Figure 409 and Figure 410 are replaced by a drive with a value of 0.

33.3.13

Error flags
The SAI implements the following error flags:
•

FIFO overrun/underrun

•

Anticipated frame synchronization detection

•

Late frame synchronization detection

•

Codec not ready (AC’97 exclusively)

•

Wrong clock configuration in master mode.

FIFO overrun/underrun (OVRUDR)
The FIFO overrun/underrun bit is called OVRUDR in the SAI_xSR register.
The overrun or underrun errors share the same bit since an audio block can be either
receiver or transmitter and each audio block in a given SAI has its own SAI_xSR register.
Overrun
When the audio block is configured as receiver, an overrun condition may appear if data are
received in an audio frame when the FIFO is full and not able to store the received data. In
this case, the received data are lost, the flag OVRUDR in the SAI_xSR register is set and an
interrupt is generated if OVRUDRIE bit is set in the SAI_xIM register. The slot number, from
which the overrun occurs, is stored internally. No more data will be stored into the FIFO until
it becomes free to store new data. When the FIFO has at least one data free, the SAI audio
block receiver will store new data (from new audio frame) from the slot number which was
stored internally when the overrun condition was detected. This avoids data slot dealignment in the destination memory (refer to Figure 411).

RM0385 Rev 7

1169/1709
1188

Serial audio interface (SAI)

RM0385

The OVRUDR flag is cleared when COVRUDR bit is set in the SAI_xCLRFR register.
Figure 411. Overrun detection error
Example: FIFO overrun on Slot 1
Audio frame

Audio frame

sck
data

Slot 0 ON Slot 1 ON Slot 1 ON Slot 0 ON

Slot 1 ON

... ON

Slot n ON

FIFO full
Data stored again in FIFO

Received data discarded

OVRUDR
COVRUDR = 1
MS192348V2

Underrun
An underrun may occur when the audio block in the SAI is a transmitter and the FIFO is
empty when data need to be transmitted. If an underrun is detected, the slot number for
which the event occurs is stored and MUTE value (00) is sent until the FIFO is ready to
transmit the data corresponding to the slot for which the underrun was detected (refer to
Figure 412). This avoids desynchronization between the memory pointer and the slot in the
audio frame.
The underrun event sets the OVRUDR flag in the SAI_xSR register and an interrupt is
generated if the OVRUDRIE bit is set in the SAI_xIM register. To clear this flag, set
COVRUDR bit in the SAI_xCLRFR register.
The underrun event can occur when the audio sub-block is configured as master or slave.
Figure 412. FIFO underrun event
Example: FIFO underrun on Slot 1
Audio frame

Audio frame

sck
Slot size = data size
data
SD (output)

Slot 0 ON

MUTE

MUTE

MUTE

Slot 1 ON

... ON

Slot 0 ON

FIFO empty

OVRUND
OVRUND=1
MS192347V2

1170/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

Anticipated frame synchronization detection (AFSDET)
The AFSDET flag is used only in slave mode. It is never asserted in master mode. It
indicates that a frame synchronization (FS) has been detected earlier than expected since
the frame length, the frame polarity, the frame offset are defined and known.
Anticipated frame detection sets the AFSDET flag in the SAI_xSR register.
This detection has no effect on the current audio frame which is not sensitive to the
anticipated FS. This means that “parasitic” events on signal FS are flagged without any
perturbation of the current audio frame.
An interrupt is generated if the AFSDETIE bit is set in the SAI_xIM register. To clear the
AFSDET flag, CAFSDET bit must be set in the SAI_xCLRFR register.
To resynchronize with the master after an anticipated frame detection error, four steps are
required:

Note:

1.

Disable the SAI block by resetting SAIEN bit in SAI_xCR1 register. To make sure the
SAI is disabled, read back the SAIEN bit and check it is set to 0.

2.

Flush the FIFO via FFLUS bit in SAI_xCR2 register.

3.

Enable again the SAI peripheral (SAIEN bit set to 1).

4.

The SAI block will wait for the assertion on FS to restart the synchronization with
master.

The SAIEN flag is not asserted in AC’97 mode since the SAI audio block acts as a link
controller and generates the FS signal even when declared as slave.It has no meaning in
SPDIF mode since the FS signal is not used.

Late frame synchronization detection
The LFSDET flag in the SAI_xSR register can be set only when the SAI audio block
operates as a slave. The frame length, the frame polarity and the frame offset configuration
are known in register SAI_xFRCR.
If the external master does not send the FS signal at the expecting time thus generating the
signal too late, the LFSDET flag is set and an interrupt is generated if LFSDETIE bit is set in
the SAI_xIM register.
The LFSDET flag is cleared when CLFSDET bit is set in the SAI_xCLRFR register.
The late frame synchronization detection flag is set when the corresponding error is
detected. The SAI needs to be resynchronized with the master (see sequence described in
Anticipated frame synchronization detection (AFSDET)).
In a noisy environment, glitches on the SCK clock may be wrongly detected by the audio
block state machine and shift the SAI data at a wrong frame position. This event can be
detected by the SAI and reported as a late frame synchronization detection error.
There is no corruption if the external master is not managing the audio data frame transfer in
continuous mode, which should not be the case in most applications. In this case, the
LFSDET flag will be set.
Note:

The LFSDET flag is not asserted in AC’97 mode since the SAI audio block acts as a link
controller and generates the FS signal even when declared as slave.It has no meaning in
SPDIF mode since the signal FS is not used by the protocol.

RM0385 Rev 7

1171/1709
1188

Serial audio interface (SAI)

RM0385

Codec not ready (CNRDY AC’97)
The CNRDY flag in the SAI_xSR register is relevant only if the SAI audio block is configured
to operate in AC’97 mode (PRTCFG[1:0] = 10 in the SAI_xCR1 register). If CNRDYIE bit is
set in the SAI_xIM register, an interrupt is generated when the CNRDY flag is set.
CNRDY is asserted when the Codec is not ready to communicate during the reception of
the TAG 0 (slot0) of the AC’97 audio frame. In this case, no data will be automatically stored
into the FIFO since the Codec is not ready, until the TAG 0 indicates that the Codec is ready.
All the active slots defined in the SAI_xSLOTR register will be captured when the Codec is
ready.
To clear CNRDY flag, CCNRDY bit must be set in the SAI_xCLRFR register.

Wrong clock configuration in master mode (with NODIV = 0)
When the audio block operates as a master (MODE[1] = 0) and NODIV bit is equal to 0, the
WCKCFG flag is set as soon as the SAI is enabled if the following conditions are met:
•

(FRL+1) is not a power of 2, and

•

(FRL+1) is not between 8 and 256.

MODE, NODIV, and SAIEN bits belong to SAI_xCR1 register and FRL to SAI_xFRCR
register.
If WCKCFGIE bit is set, an interrupt is generated when WCKCFG flag is set in the SAI_xSR
register. To clear this flag, set CWCKCFG bit in the SAI_xCLRFR register.
When WCKCFG bit is set, the audio block is automatically disabled, thus performing a
hardware clear of SAIEN bit.

33.3.14

Disabling the SAI
The SAI audio block can be disabled at any moment by clearing SAIEN bit in the SAI_xCR1
register. All the already started frames are automatically completed before the SAI is stops
working. SAIEN bit remains High until the SAI is completely switched-off at the end of the
current audio frame transfer.
If an audio block in the SAI operates synchronously with the other one, the one which is the
master must be disabled first.

33.3.15

SAI DMA interface
To free the CPU and to optimize bus bandwidth, each SAI audio block has an independent
DMA interface to read/write from/to the SAI_xDR register (to access the internal FIFO).
There is one DMA channel per audio sub-block supporting basic DMA request/acknowledge
protocol.
To configure the audio sub-block for DMA transfer, set DMAEN bit in the SAI_xCR1 register.
The DMA request is managed directly by the FIFO controller depending on the FIFO
threshold level (for more details refer to Section 33.3.9: Internal FIFOs). DMA transfer
direction is linked to the SAI audio sub-block configuration:

1172/1709

•

If the audio block operates as a transmitter, the audio block FIFO controller outputs a
DMA request to load the FIFO with data written in the SAI_xDR register.

•

If the audio block is operates as a receiver, the DMA request is related to read
operations from the SAI_xDR register.

RM0385 Rev 7

RM0385

Serial audio interface (SAI)
Follow the sequence below to configure the SAI interface in DMA mode:
1.

Configure SAI and FIFO threshold levels to specify when the DMA request will be
launched.

2.

Configure SAI DMA channel.

3.

Enable the DMA.

4.

Enable the SAI interface.

Note:

Before configuring the SAI block, the SAI DMA channel must be disabled.

33.4

SAI interrupts
The SAI supports 7 interrupt sources as shown in Table 212.
Table 212. SAI interrupt sources

Interrupt
source

Interrupt
group

Audio block mode

Interrupt enable

Interrupt clear

Depends on:

FREQ

FREQ

– FIFO threshold setting (FLVL bits in
SAI_xCR2)
FREQIE in SAI_xIM – Communication direction (transmitter
register
or receiver)

Master or slave
Receiver or transmitter

For more details refer to
Section 33.3.9: Internal FIFOs
OVRUDR

ERROR

Master or slave
Receiver or transmitter

OVRUDRIE in
SAI_xIM register

COVRUDR = 1 in SAI_xCLRFR register

AFSDET

ERROR

Slave
(not used in AC’97 mode
and SPDIF mode)

AFSDETIE in
SAI_xIM register

CAFSDET = 1 in SAI_xCLRFR register

LFSDET

ERROR

Slave
(not used in AC’97 mode
and SPDIF mode)

LFSDETIE in
SAI_xIM register

CLFSDET = 1 in SAI_xCLRFR register

CNRDY

ERROR

Slave
(only in AC’97 mode)

CNRDYIE in
SAI_xIM register

CCNRDY = 1 in SAI_xCLRFR register

MUTEDET

MUTE

Master or slave
Receiver mode only

MUTEDETIE in
SAI_xIM register

CMUTEDET = 1 in SAI_xCLRFR
register

WCKCFG

ERROR

Master with NODIV = 0 in
SAI_xCR1 register

WCKCFGIE in
SAI_xIM register

CWCKCFG = 1 in SAI_xCLRFR register

Follow the sequence below to enable an interrupt:
1.

Disable SAI interrupt.

2.

Configure SAI.

3.

Configure SAI interrupt source.

4.

Enable SAI.

RM0385 Rev 7

1173/1709
1188

Serial audio interface (SAI)

RM0385

33.5

SAI registers

33.5.1

Global configuration register (SAI_GCR)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SYNCOUT[1:0]
rw

rw

SYNCIN[1:0]
rw

rw

Bits 31:6 Reserved, must be kept at reset value.
Bits 5:4 SYNCOUT[1:0]: Synchronization outputs
These bits are set and cleared by software.
00: No synchronization output signals. SYNCOUT[1:0] should be configured as “No synchronization
output signals” when audio block is configured as SPDIF
01: Block A used for further synchronization for others SAI
10: Block B used for further synchronization for others SAI
11: Reserved. These bits must be set when both audio block (A and B) are disabled.
Bits 3:2 Reserved, must be kept at reset value.
Bits 1:0 SYNCIN[1:0]: Synchronization inputs
These bits are set and cleared by software.
Refer to Table 207: External synchronization selection for information on how to program this field.
These bits must be set when both audio blocks (A and B) are disabled.
They are meaningful if one of the two audio blocks is defined to operate in synchronous mode with
an external SAI (SYNCEN[1:0] = 10 in SAI_ACR1 or in SAI_BCR1 registers).

33.5.2

Configuration register 1 (SAI_ACR1 / SAI_BCR1)
Address offset: Block A: 0x004
Address offset: Block B: 0x024
Reset value: 0x0000 0040

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

Res.

Res.

OUTD
MONO
RIV
rw

1174/1709

rw

SYNCEN[1:0]
rw

rw

23

rw

21

20

MCKDIV[3:0]

19

18

NODIV

Res.

rw

rw

rw

rw

rw

7

6

5

4

3

CKSTR LSBFIRST
rw

22

DS[2:0]
rw

rw

RM0385 Rev 7

Res.
rw

2

17

16

DMAEN SAIEN
rw

rw

1

0

PRTCFG[1:0]

MODE[1:0]

rw

rw

rw

rw

RM0385

Serial audio interface (SAI)

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:20 MCKDIV[3:0]: Master clock divider
These bits are set and cleared by software. These bits are meaningless when the audio block
operates in slave mode. They have to be configured when the audio block is disabled.
0000: Divides by 1 the master clock input.
Others: the master clock frequency is calculated accordingly to the following formula:
F sai_x_ker_ck
F SCK_x = -------------------------------------MCKDIV × 2
Bit 19 NODIV: No divider
This bit is set and cleared by software.
0: Master clock generator is enabled
1: No divider used in the clock generator (in this case Master Clock Divider bit has no effect)
Bit 18 Reserved, must be kept at reset value.
Bit 17 DMAEN: DMA enable
This bit is set and cleared by software.
0: DMA disabled
1: DMA enabled
Note: Since the audio block defaults to operate as a transmitter after reset, the MODE[1:0] bits must
be configured before setting DMAEN to avoid a DMA request in receiver mode.
Bit 16 SAIEN: Audio block enable
This bit is set by software.
To switch off the audio block, the application software must program this bit to 0 and poll the bit till it
reads back 0, meaning that the block is completely disabled. Before setting this bit to 1, check that it
is set to 0, otherwise the enable command will not be taken into account.
This bit allows controlling the state of the SAI audio block. If it is disabled when an audio frame
transfer is ongoing, the ongoing transfer completes and the cell is fully disabled at the end of this
audio frame transfer.
0: SAI audio block disabled
1: SAI audio block enabled.
Note: When the SAI block (A or B) is configured in master mode, the clock must be present on the
SAI block input before setting SAIEN bit.
Bits 15:14 Reserved, must be kept at reset value.
Bit 13 OUTDRIV: Output drive
This bit is set and cleared by software.
0: Audio block output driven when SAIEN is set
1: Audio block output driven immediately after the setting of this bit.
Note: This bit has to be set before enabling the audio block and after the audio block configuration.
Bit 12 MONO: Mono mode
This bit is set and cleared by software. It is meaningful only when the number of slots is equal to 2.
When the mono mode is selected, slot 0 data are duplicated on slot 1 when the audio block operates
as a transmitter. In reception mode, the slot1 is discarded and only the data received from slot 0 are
stored. Refer to Section : Mono/stereo mode for more details.
0: Stereo mode
1: Mono mode.

RM0385 Rev 7

1175/1709
1188

Serial audio interface (SAI)

RM0385

Bits 11:10 SYNCEN[1:0]: Synchronization enable
These bits are set and cleared by software. They must be configured when the audio sub-block is
disabled.
00: audio sub-block in asynchronous mode.
01: audio sub-block is synchronous with the other internal audio sub-block. In this case, the audio
sub-block must be configured in slave mode
10: audio sub-block is synchronous with an external SAI embedded peripheral. In this case the
audio sub-block should be configured in Slave mode.
11: Reserved
Note: The audio sub-block should be configured as asynchronous when SPDIF mode is enabled.
Bit 9 CKSTR: Clock strobing edge
This bit is set and cleared by software. It must be configured when the audio block is disabled. This
bit has no meaning in SPDIF audio protocol.
0: Signals generated by the SAI change on SCK rising edge, while signals received by the SAI are
sampled on the SCK falling edge.
1: Signals generated by the SAI change on SCK falling edge, while signals received by the SAI are
sampled on the SCK rising edge.
Bit 8 LSBFIRST: Least significant bit first
This bit is set and cleared by software. It must be configured when the audio block is disabled. This
bit has no meaning in AC’97 audio protocol since AC’97 data are always transferred with the MSB
first. This bit has no meaning in SPDIF audio protocol since in SPDIF data are always transferred
with LSB first.
0: Data are transferred with MSB first
1: Data are transferred with LSB first
Bits 7:5 DS[2:0]: Data size
These bits are set and cleared by software. These bits are ignored when the SPDIF protocols are
selected (bit PRTCFG[1:0]), because the frame and the data size are fixed in such case. When the
companding mode is selected through COMP[1:0] bits, DS[1:0] are ignored since the data size is
fixed to 8 bits by the algorithm.
These bits must be configured when the audio block is disabled.
000: Reserved
001: Reserved
010: 8 bits
011: 10 bits
100: 16 bits
101: 20 bits
110: 24 bits
111: 32 bits

1176/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

Bit 4 Reserved, must be kept at reset value.
Bits 3:2 PRTCFG[1:0]: Protocol configuration
These bits are set and cleared by software. These bits have to be configured when the audio block is
disabled.
00: Free protocol. Free protocol allows to use the powerful configuration of the audio block to
address a specific audio protocol (such as I2S, LSB/MSB justified, TDM, PCM/DSP...) by setting
most of the configuration register bits as well as frame configuration register.
01: SPDIF protocol
10: AC’97 protocol
11: Reserved
Bits 1:0 MODE[1:0]: SAIx audio block mode
These bits are set and cleared by software. They must be configured when SAIx audio block is
disabled.
00: Master transmitter
01: Master receiver
10: Slave transmitter
11: Slave receiver
Note: When the audio block is configured in SPDIF mode, the master transmitter mode is forced
(MODE[1:0] = 00). In Master transmitter mode, the audio block starts generating the FS and the
clocks immediately.

33.5.3

Configuration register 2 (SAI_ACR2 / SAI_BCR2)
Address offset: Block A: 0x008
Address offset: Block B: 0x028
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

COMP[1:0]
rw

rw

CPL
rw

MUTECNT[5:0]
rw

rw

rw

rw

rw

MUTE
VAL

MUTE

TRIS

F
FLUSH

rw

rw

rw

w

rw

RM0385 Rev 7

FTH[2:0]
rw

rw

rw

1177/1709
1188

Serial audio interface (SAI)

RM0385

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:14 COMP[1:0]: Companding mode.
These bits are set and cleared by software. The µ-Law and the A-Law log are a part of the CCITT
G.711 recommendation, the type of complement that will be used depends on CPL bit.
The data expansion or data compression are determined by the state of bit MODE[0].
The data compression is applied if the audio block is configured as a transmitter.
The data expansion is automatically applied when the audio block is configured as a receiver.
Refer to Section : Companding mode for more details.
00: No companding algorithm
01: Reserved.
10: µ-Law algorithm
11: A-Law algorithm
Note: Companding mode is applicable only when TDM is selected.
Bit 13 CPL: Complement bit.
This bit is set and cleared by software.
It defines the type of complement to be used for companding mode
0: 1’s complement representation.
1: 2’s complement representation.
Note: This bit has effect only when the companding mode is µ-Law algorithm or A-Law algorithm.
Bits 12:7 MUTECNT[5:0]: Mute counter.
These bits are set and cleared by software. They are used only in reception mode.
The value set in these bits is compared to the number of consecutive mute frames detected in
reception. When the number of mute frames is equal to this value, the flag MUTEDET will be set and
an interrupt will be generated if bit MUTEDETIE is set.
Refer to Section : Mute mode for more details.
Bit 6 MUTEVAL: Mute value.
This bit is set and cleared by software.It must be written before enabling the audio block: SAIEN.
This bit is meaningful only when the audio block operates as a transmitter, the number of slots is
lower or equal to 2 and the MUTE bit is set.
If more slots are declared, the bit value sent during the transmission in mute mode is equal to 0,
whatever the value of MUTEVAL.
if the number of slot is lower or equal to 2 and MUTEVAL = 1, the MUTE value transmitted for each
slot is the one sent during the previous frame.
Refer to Section : Mute mode for more details.
0: Bit value 0 is sent during the mute mode.
1: Last values are sent during the mute mode.
Note: This bit is meaningless and should not be used for SPDIF audio blocks.
Bit 5 MUTE: Mute.
This bit is set and cleared by software. It is meaningful only when the audio block operates as a
transmitter. The MUTE value is linked to value of MUTEVAL if the number of slots is lower or equal
to 2, or equal to 0 if it is greater than 2.
Refer to Section : Mute mode for more details.
0: No mute mode.
1: Mute mode enabled.
Note: This bit is meaningless and should not be used for SPDIF audio blocks.

1178/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

Bit 4 TRIS: Tristate management on data line.
This bit is set and cleared by software. It is meaningful only if the audio block is configured as a
transmitter. This bit is not used when the audio block is configured in SPDIF mode. It should be
configured when SAI is disabled.
Refer to Section : Output data line management on an inactive slot for more details.
0: SD output line is still driven by the SAI when a slot is inactive.
1: SD output line is released (HI-Z) at the end of the last data bit of the last active slot if the next one
is inactive.
Bit 3 FFLUSH: FIFO flush.
This bit is set by software. It is always read as 0. This bit should be configured when the SAI is
disabled.
0: No FIFO flush.
1: FIFO flush. Programming this bit to 1 triggers the FIFO Flush. All the internal FIFO pointers (read
and write) are cleared. In this case data still present in the FIFO are lost (no more transmission or
received data lost). Before flushing, SAI DMA stream/interruption must be disabled
Bits 2:0 FTH[2:0]: FIFO threshold.
This bit is set and cleared by software.
000: FIFO empty
001: ¼ FIFO
010: ½ FIFO
011: ¾ FIFO
100: FIFO full
101: Reserved
110: Reserved
111: Reserved

33.5.4

Frame configuration register (SAI_AFRCR / SAI_BFRCR)
Address offset: Block A: 0x00C
Address offset: Block B: 0x02C
Reset value: 0x0000 0007

Note:

This register has no meaning in AC’97 and SPDIF audio protocol

31

30

29

28

27

26

25

24

23

22

21

20

19

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

Res.

FSALL[6:0]
rw

rw

rw

rw

rw

18

17

16

FSOFF FSPOL FSDEF

FRL[7:0]
rw

rw

rw

rw

RM0385 Rev 7

rw

rw

1179/1709
1188

Serial audio interface (SAI)

RM0385

Bits 31:19 Reserved, must be kept at reset value.
Bit 18 FSOFF: Frame synchronization offset.
This bit is set and cleared by software. It is meaningless and is not used in AC’97 or SPDIF audio
block configuration. This bit must be configured when the audio block is disabled.
0: FS is asserted on the first bit of the slot 0.
1: FS is asserted one bit before the first bit of the slot 0.
Bit 17 FSPOL: Frame synchronization polarity.
This bit is set and cleared by software. It is used to configure the level of the start of frame on the FS
signal. It is meaningless and is not used in AC’97 or SPDIF audio block configuration.
This bit must be configured when the audio block is disabled.
0: FS is active low (falling edge)
1: FS is active high (rising edge)
Bit 16 FSDEF: Frame synchronization definition.
This bit is set and cleared by software.
0: FS signal is a start frame signal
1: FS signal is a start of frame signal + channel side identification
When the bit is set, the number of slots defined in the SAI_xSLOTR register has to be even. It
means that half of this number of slots will be dedicated to the left channel and the other slots for the
right channel (e.g: this bit has to be set for I2S or MSB/LSB-justified protocols...).
This bit is meaningless and is not used in AC’97 or SPDIF audio block configuration. It must be
configured when the audio block is disabled.
Bit 15 Reserved, must be kept at reset value.
Bits 14:8 FSALL[6:0]: Frame synchronization active level length.
These bits are set and cleared by software. They specify the length in number of bit clock
(SCK) + 1 (FSALL[6:0] + 1) of the active level of the FS signal in the audio frame
These bits are meaningless and are not used in AC’97 or SPDIF audio block configuration.
They must be configured when the audio block is disabled.
Bits 7:0 FRL[7:0]: Frame length.
These bits are set and cleared by software. They define the audio frame length expressed in number
of SCK clock cycles: the number of bits in the frame is equal to FRL[7:0] + 1.
The minimum number of bits to transfer in an audio frame must be equal to 8, otherwise the audio
block will behaves in an unexpected way. This is the case when the data size is 8 bits and only one
slot 0 is defined in NBSLOT[4:0] of SAI_xSLOTR register (NBSLOT[3:0] = 0000).
In master mode, if the master clock (available on MCLK_x pin) is used, the frame length should be
aligned with a number equal to a power of 2, ranging from 8 to 256. When the master clock is not
used (NODIV = 1), it is recommended to program the frame length to an value ranging from 8 to 256.
These bits are meaningless and are not used in AC’97 or SPDIF audio block configuration.

1180/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

33.5.5

Slot register (SAI_ASLOTR / SAI_BSLOTR)
Address offset: Block A: 0x010
Address offset: Block B: 0x030
Reset value: 0x0000 0000

Note:
31

This register has no meaning in AC’97 and SPDIF audio protocol
30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

SLOTEN[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

rw

rw

NBSLOT[3:0]
rw

rw

rw

SLOTSZ[1:0]
rw

rw

rw

Res.

FBOFF[4:0]
rw

rw

rw

Bits 31:16 SLOTEN[15:0]: Slot enable.
These bits are set and cleared by software.
Each SLOTEN bit corresponds to a slot position from 0 to 15 (maximum 16 slots).
0: Inactive slot.
1: Active slot.
The slot must be enabled when the audio block is disabled.
They are ignored in AC’97 or SPDIF mode.
Bits 15:12 Reserved, must be kept at reset value.
Bits 11:8 NBSLOT[3:0]: Number of slots in an audio frame.
These bits are set and cleared by software.
The value set in this bitfield represents the number of slots + 1 in the audio frame (including the
number of inactive slots). The maximum number of slots is 16.
The number of slots should be even if FSDEF bit in the SAI_xFRCR register is set.
The number of slots must be configured when the audio block is disabled.
They are ignored in AC’97 or SPDIF mode.

RM0385 Rev 7

1181/1709
1188

Serial audio interface (SAI)

RM0385

Bits 7:6 SLOTSZ[1:0]: Slot size
This bits is set and cleared by software.
The slot size must be higher or equal to the data size. If this condition is not respected, the behavior
of the SAI will be undetermined.
Refer to Section : Output data line management on an inactive slot for information on how to drive
SD line.
These bits must be set when the audio block is disabled.
They are ignored in AC’97 or SPDIF mode.
00: The slot size is equivalent to the data size (specified in DS[3:0] in the SAI_xCR1 register).
01: 16-bit
10: 32-bit
11: Reserved
Bit 5 Reserved, must be kept at reset value.
Bits 4:0 FBOFF[4:0]: First bit offset
These bits are set and cleared by software.
The value set in this bitfield defines the position of the first data transfer bit in the slot. It represents
an offset value. In transmission mode, the bits outside the data field are forced to 0. In reception
mode, the extra received bits are discarded.
These bits must be set when the audio block is disabled.
They are ignored in AC’97 or SPDIF mode.

33.5.6

Interrupt mask register 2 (SAI_AIM / SAI_BIM)
Address offset: block A: 0x014
Address offset: block B: 0x034
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LFSDET AFSDET CNRDY FREQ WCKCFG MUTEDET OVRUDR
IE
IE
IE
IE
IE
IE
IE
rw

rw

rw

rw

rw

rw

rw

Bits 31:7 Reserved, must be kept at reset value.
Bit 6 LFSDETIE: Late frame synchronization detection interrupt enable.
This bit is set and cleared by software.
0: Interrupt is disabled
1: Interrupt is enabled
When this bit is set, an interrupt will be generated if the LFSDET bit is set in the SAI_xSR register.
This bit is meaningless in AC’97, SPDIF mode or when the audio block operates as a master.
Bit 5 AFSDETIE: Anticipated frame synchronization detection interrupt enable.
This bit is set and cleared by software.
0: Interrupt is disabled
1: Interrupt is enabled
When this bit is set, an interrupt will be generated if the AFSDET bit in the SAI_xSR register is set.
This bit is meaningless in AC’97, SPDIF mode or when the audio block operates as a master.

1182/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

Bit 4 CNRDYIE: Codec not ready interrupt enable (AC’97).
This bit is set and cleared by software.
0: Interrupt is disabled
1: Interrupt is enabled
When the interrupt is enabled, the audio block detects in the slot 0 (tag0) of the AC’97 frame if the
Codec connected to this line is ready or not. If it is not ready, the CNRDY flag in the SAI_xSR
register is set and an interruption i generated.
This bit has a meaning only if the AC’97 mode is selected through PRTCFG[1:0] bits and the audio
block is operates as a receiver.
Bit 3 FREQIE: FIFO request interrupt enable.
This bit is set and cleared by software.
0: Interrupt is disabled
1: Interrupt is enabled
When this bit is set, an interrupt is generated if the FREQ bit in the SAI_xSR register is set.
Since the audio block defaults to operate as a transmitter after reset, the MODE bit must be
configured before setting FREQIE to avoid a parasitic interruption in receiver mode,
Bit 2 WCKCFGIE: Wrong clock configuration interrupt enable.
This bit is set and cleared by software.
0: Interrupt is disabled
1: Interrupt is enabled
This bit is taken into account only if the audio block is configured as a master (MODE[1] = 0) and
NODIV = 0.
It generates an interrupt if the WCKCFG flag in the SAI_xSR register is set.
Note: This bit is used only in TDM mode and is meaningless in other modes.
Bit 1 MUTEDETIE: Mute detection interrupt enable.
This bit is set and cleared by software.
0: Interrupt is disabled
1: Interrupt is enabled
When this bit is set, an interrupt is generated if the MUTEDET bit in the SAI_xSR register is set.
This bit has a meaning only if the audio block is configured in receiver mode.
Bit 0 OVRUDRIE: Overrun/underrun interrupt enable.
This bit is set and cleared by software.
0: Interrupt is disabled
1: Interrupt is enabled
When this bit is set, an interrupt is generated if the OVRUDR bit in the SAI_xSR register is set.

33.5.7

Status register (SAI_ASR / SAI_BSR)
Address offset: block A: 0x018
Address offset: block B: 0x038
Reset value: 0x0000 0008

31

30

29

28

27

26

25

24

23

22

21

20

19

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res. LFSDET AFSDET CNRDY
r

r

RM0385 Rev 7

r

FREQ
r

18

17

16

FLVL[2:0]
r

r

r

2

1

0

WCKCFG MUTEDET OVRUDR
r

r

r

1183/1709
1188

Serial audio interface (SAI)

RM0385

Bits 31:19 Reserved, must be kept at reset value.
Bits 18:16 FLVL[2:0]: FIFO level threshold.
This bit is read only. The FIFO level threshold flag is managed only by hardware and its setting
depends on SAI block configuration (transmitter or receiver mode).
If the SAI block is configured as transmitter:
000: FIFO empty
001: FIFO <= ¼ but not empty
010: ¼ < FIFO <= ½
011: ½ < FIFO <= ¾
100: ¾ < FIFO but not full
101: FIFO full
If SAI block is configured as receiver:
000: FIFO empty
001: FIFO < ¼ but not empty
010: ¼ <= FIFO < ½
011: ½ =< FIFO < ¾
100: ¾ =< FIFO but not full
101: FIFO full
Bits 15:7 Reserved, must be kept at reset value.
Bit 6 LFSDET: Late frame synchronization detection.
This bit is read only.
0: No error.
1: Frame synchronization signal is not present at the right time.
This flag can be set only if the audio block is configured in slave mode.
It is not used in AC’97 or SPDIF mode.
It can generate an interrupt if LFSDETIE bit is set in the SAI_xIM register.
This flag is cleared when the software sets bit CLFSDET in SAI_xCLRFR register
Bit 5 AFSDET: Anticipated frame synchronization detection.
This bit is read only.
0: No error.
1: Frame synchronization signal is detected earlier than expected.
This flag can be set only if the audio block is configured in slave mode.
It is not used in AC’97or SPDIF mode.
It can generate an interrupt if AFSDETIE bit is set in SAI_xIM register.
This flag is cleared when the software sets CAFSDET bit in SAI_xCLRFR register.
Bit 4 CNRDY: Codec not ready.
This bit is read only.
0: External AC’97 Codec is ready
1: External AC’97 Codec is not ready
This bit is used only when the AC’97 audio protocol is selected in the SAI_xCR1 register and
configured in receiver mode.
It can generate an interrupt if CNRDYIE bit is set in SAI_xIM register.
This flag is cleared when the software sets CCNRDY bit in SAI_xCLRFR register.

1184/1709

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

Bit 3 FREQ: FIFO request.
This bit is read only.
0: No FIFO request.
1: FIFO request to read or to write the SAI_xDR.
The request depends on the audio block configuration:
– If the block is configured in transmission mode, the FIFO request is related to a write request
operation in the SAI_xDR.
– If the block configured in reception, the FIFO request related to a read request operation from the
SAI_xDR.
This flag can generate an interrupt if FREQIE bit is set in SAI_xIM register.
Bit 2 WCKCFG: Wrong clock configuration flag.
This bit is read only.
0: Clock configuration is correct
1: Clock configuration does not respect the rule concerning the frame length specification defined in
Section 33.3.6: Frame synchronization (configuration of FRL[7:0] bit in the SAI_xFRCR register)
This bit is used only when the audio block operates in master mode (MODE[1] = 0) and NODIV = 0.
It can generate an interrupt if WCKCFGIE bit is set in SAI_xIM register.
This flag is cleared when the software sets CWCKCFG bit in SAI_xCLRFR register.
Bit 1 MUTEDET: Mute detection.
This bit is read only.
0: No MUTE detection on the SD input line
1: MUTE value detected on the SD input line (0 value) for a specified number of consecutive audio
frame
This flag is set if consecutive 0 values are received in each slot of a given audio frame and for a
consecutive number of audio frames (set in the MUTECNT bit in the SAI_xCR2 register).
It can generate an interrupt if MUTEDETIE bit is set in SAI_xIM register.
This flag is cleared when the software sets bit CMUTEDET in the SAI_xCLRFR register.
Bit 0 OVRUDR: Overrun / underrun.
This bit is read only.
0: No overrun/underrun error.
1: Overrun/underrun error detection.
The overrun and underrun conditions can occur only when the audio block is configured as a
receiver and a transmitter, respectively.
It can generate an interrupt if OVRUDRIE bit is set in SAI_xIM register.
This flag is cleared when the software sets COVRUDR bit in SAI_xCLRFR register.

33.5.8

Clear flag register (SAI_ACLRFR / SAI_BCLRFR)
Address offset: block A: 0x01C
Address offset: block B: 0x03C
Reset value: 0x0000 0000

31
Res.

15
Res.

30

29

28

27

26

Res. Res. Res. Res. Res.

14

13

12

11

10

Res. Res. Res. Res. Res.

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

CLFSDET CAFSDET
w

w

RM0385 Rev 7

CCNRDY
w

Res.

CMUTE COVRUD
CWCKCFG
DET
R
w

w

w

1185/1709
1188

Serial audio interface (SAI)

RM0385

Bits 31:7 Reserved, must be kept at reset value.
Bit 6 CLFSDET: Clear late frame synchronization detection flag.
This bit is write only.
Programming this bit to 1 clears the LFSDET flag in the SAI_xSR register.
This bit is not used in AC’97or SPDIF mode
Reading this bit always returns the value 0.
Bit 5 CAFSDET: Clear anticipated frame synchronization detection flag.
This bit is write only.
Programming this bit to 1 clears the AFSDET flag in the SAI_xSR register.
It is not used in AC’97or SPDIF mode.
Reading this bit always returns the value 0.
Bit 4 CCNRDY: Clear Codec not ready flag.
This bit is write only.
Programming this bit to 1 clears the CNRDY flag in the SAI_xSR register.
This bit is used only when the AC’97 audio protocol is selected in the SAI_xCR1 register.
Reading this bit always returns the value 0.
Bit 3 Reserved, must be kept at reset value.
Bit 2 CWCKCFG: Clear wrong clock configuration flag.
This bit is write only.
Programming this bit to 1 clears the WCKCFG flag in the SAI_xSR register.
This bit is used only when the audio block is set as master (MODE[1] = 0) and NODIV = 0 in the
SAI_xCR1 register.
Reading this bit always returns the value 0.
Bit 1 CMUTEDET: Mute detection flag.
This bit is write only.
Programming this bit to 1 clears the MUTEDET flag in the SAI_xSR register.
Reading this bit always returns the value 0.
Bit 0 COVRUDR: Clear overrun / underrun.
This bit is write only.
Programming this bit to 1 clears the OVRUDR flag in the SAI_xSR register.
Reading this bit always returns the value 0.

33.5.9

Data register (SAI_ADR / SAI_BDR)
Address offset: block A: 0x020
Address offset: block B: 0x040
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DATA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DATA[15:0]
rw

1186/1709

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

RM0385

Serial audio interface (SAI)

Bits 31:0 DATA[31:0]: Data
A write to this register loads the FIFO provided the FIFO is not full.
A read from this register empties the FIFO if the FIFO is not empty.

RM0385 Rev 7

1187/1709
1188

0x001C or
0x003C

0x0020 or
0x0040

1188/1709

SAI_xCLRFR

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

SAI_xDR

0

0

RM0385 Rev 7
0

0

0

0

0

0

0

0

0

0

Refer to Section 2.2 on page 68 for the register boundary addresses.

0

Reset value

0
OVRUDRIE

0

0
0

DATA[31:0]

0

0

0

0

0

0
OVRUDR

TRIS
FFLUS

0
0
0

0
0

0

FTH

MUTE

0

0
0
1
0
0

OVRUDR

MUTEDET

0

MUTEDET

0

MUTEDET

FREQIE
WCKCFG

0

FREQ

FSALL[6:0]

WCKCFG

LSBFIRST

0

MODE[1:0]

PRTCFG[1:0]

Res.

DS[2:0]

CKSTR

1

MUTE VAL

0

Res.

MONO
SYNCEN[1:0]

OUTDRIV

Res.

0

WCKCFG

CNRDYIE

CPL

COMP[1:0]

SAIEN

Res.

Res.

DMAEN

Res.

NODIV

Res.

0

Res.

Res.

MCKDIV[3:0]

Reset value

CNRDY

Reset value

CNRDY

0

AFSDETIE

0

CAFSDET

SLOTSZ[1:0}

0

LFSDET

Res.

MUTECN[5:0]

LFSDET

0

Res.

0

0

Res.

0

Res.

NBSLOT[3:0]

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

FSDEF

0

0

AFSDET

0
0

0

LFSDET

0
0

Res.

SAI_xIM
0

0

Res.

0
0

0

Res.

0

0

Res.

0

Res.

Res.

SLOTEN[15:0]
0

Res.

0

Res.

FSPOL

0

Res.

0

Res.

FSOFF

0
0

Res.

0

Res.

Res.
0
0

Res.

0

Res.

Res.

0

Res.

0

Res.

Res.

Reset value

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Reset value

Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

0

FLVL[2:0]

0

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

SAI_xSLOTR

Res.

Res.

SAI_xSR

Res.

0x0018 or
0x0038
SAI_xFRCR

Res.

0x0014 or
0x0034
SAI_xCR2

Res.

0x0010 or
0x0030
SAI_xCR1

Res.

0x000C or
0x002C

Res.

0x0008 or
0x0028

Res.

0x0004
or
0x0024
0

0

SYNCIN[1:0]

Res.

Res..

SYNCOUT[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SAI_GCR

Res.

0x0000

Res.

Offset
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

33.5.10

Res.

Serial audio interface (SAI)
RM0385

SAI register map
The following table summarizes the SAI registers.
Table 213. SAI register map and reset values

0
0

0
0

FRL[7:0]

0
0
0

1
1
1

FBOFF[4:0]

0
0
0
0
0

0
0
0
0
0
0
0

0

0

0

0

0

0

RM0385

SPDIF receiver interface (SPDIFRX)

34

SPDIF receiver interface (SPDIFRX)

34.1

SPDIFRX interface introduction
The SPDIFRX interface handles S/PDIF audio protocol.

34.2

34.3

SPDIFRX main features
•

Up to 4 inputs available

•

Automatic symbol rate detection

•

Maximum symbol rate: 12.288 MHz

•

Stereo stream from 8 to 192 kHz supported

•

Supports Audio IEC-60958 and IEC-61937, consumer applications

•

SOPDs B, M and W insertion inside S/PDIF flow

•

Parity bit management

•

Communication using DMA for audio samples

•

Communication using DMA for control and user channel information

•

Interrupt capabilities

SPDIFRX functional description
The SPDIFRX peripheral, is designed to receive an S/PDIF flow compliant with IEC-60958
and IEC-61937. These standards support simple stereo streams up to high sample rate,
and compressed multi-channel surround sound, such as those defined by Dolby or DTS.
The receiver provides all the necessary features to detect the symbol rate, and decode the
incoming data. It is possible to use a dedicated path for the user and channel information in
order to ease the interface handling. Figure 413 shows a simplified block diagram.
The SPDIFRX_DC block is responsible of the decoding of the S/PDIF stream received from
SPDIFRX_IN[4:1] inputs. This block re-sample the incoming signal, decode the manchester
stream, recognize frames, sub-frames and blocks elements. It delivers to the REG_IF part,
decoded data, and associated status flags.
This peripheral can be fully controlled via the APB1 bus, and can handle two DMA channels:
•

A DMA channel dedicated to the transfer of audio samples

•

A DMA channel dedicated to the transfer of IEC60958 channel status and user
information

Interrupt services are also available either as an alternative function to the DMA, or for
signaling error or key status of the peripheral.
The SPDIFRX also offers a signal named spdifrx_frame_sync, which toggles every time
that a sub-frame’s preamble is detected. So the duty cycle will be 50%, and the frequency
equal to the frame rate.
This signal can be connected to timer events, in order to compute frequency drift.

RM0385 Rev 7

1189/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385
Figure 413. SPDIFRX block diagram

SPDIFRX

SPDIFRX_CLK

SPDIFRX_DC

SPDIFRX_SR
SPDIFRX_IFCR

SPDIFRX_IN[1]
SPDIFRX_IN[2]
...

SPDIFRX_FE

ctrl ch.

SPDIFRX_CSR

Re-sync & Edge detection

SYNC

SPDIFRX_IMR

SPDIFRX_DEC

SPDIFRX_SEQ

32-bit APB1 bus

SPDIFRX_CR

Biphase and transition decoder

RX_BUF
32 bits

data

SPDIFRX_DR

SPDIF data packing and sequencer

REG_IF

PCLK1

SPDIFRX_IN[n] (1)

SPDIFRX_DIR

SPDIFRX_IRQ

IRQ_IF

DMA_SPDIFRX_DT

spdifrx_frame_sync

DMA_IF

DMA_SPDIFRX_CS

PCLK1 clock domain

SPDIFRX_CLK clock domain

MSv35927V2

1. ‘n’ is fixed to 4.

34.3.1

S/PDIF protocol (IEC-60958)
S/PDIF block
A S/PDIF frame is composed of two sub-frames (see Figure 415). Each sub-frame contains
32 bits (or time slots):
•

Bits 0 to 3 carry one of the synchronization preambles

•

Bits 4 to 27 carry the audio sample word in linear 2's complement representation. The
most significant bit (MSB) is carried by bit 27. When a 20-bit coding range is used, bits
8 to 27 carry the audio sample word with the LSB in bit 8.

•

Bit 28 (validity bit “V”) indicates if the data is valid (for converting it to analog for
example)

•

Bit 29 (user data bit “U”) carries the user data information like the number of tracks of a
Compact Disk.

•

Bit 30 (channel status bit “C”) carries the channel status information like sample rate
and protection against copy.

•

Bit 31 (parity bit “P”) carries a parity bit such that bits 4 to 31 inclusive carry an even
number of ones and an even number of zeroes (even parity).
Figure 414. S/PDIF Sub-Frame Format
0

3
Sync Preamble

4

5

6

7

D0

D1

D2

D3

25

26

27

28

29

30

31

D21

D22

D23

V

U

C

P

LSb

MSb

Synchronization
(type B,M or W)

Audio sample, up to 24 bits

Status bits

28 information bits
MSv35981V1

1190/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
For linear coded audio applications, the first sub-frame (left or “A” channel in stereophonic
operation and primary channel in monophonic operation) normally starts with preamble “M”.
However, the preamble changes to preamble “B” once every 192 frames to identify the start
of the block structure used to organize the channel status and user information. The second
sub-frame (right or “B” channel in stereophonic operation and secondary channel in
monophonic operation) always starts with preamble “W”.
A S/PDIF block contains 192 pairs of sub-frames of 32 bits.
Figure 415. S/PDIF block format
X
M

Y
Ch A

W

Z
Ch B

B

Y
Ch A

W

X
Ch B

M

Y
Ch A

W

X
Ch B

M

Y
Ch A

W

Z
Ch B

B

Y
Ch A

Ch B

W

Sub-frame Sub-frame
Frame 191

Frame 0

Frame 1

Frame 191

Start of block

Frame 0
Start of block

NOTE
For historical reasons preambles "B", "M" and "W" are, for use in professional applications, referred to as "Z", "X" and "Y", respectively.
MSv35923V1

Synchronization preambles
The preambles patterns are inverted or not according to the previous half-bit value. This
previous half-bit value is the level of the line before enabling a transfer for the first “B”
preamble of the first frame. For the others preambles, this previous half-bit value is the
second half-bit of the parity bit of the previous sub-frame. The preambles patterns B, M and
W are described in the Figure 416.
Figure 416. S/PDIF Preambles
0
1 UI

1
2 UI

3 UI

2
4 UI

5 UI

3
6 UI

7 UI

8 UI

Previous half-bit = 0
Preamble “B”
Previous half-bit = 1
Lack of transitions !

Previous half-bit = 0
Preamble “M”
Previous half-bit = 1
Lack of transitions !
Previous half-bit = 0
Preamble “W”
Previous half-bit = 1
Lack of transitions !
Symbol boundary
MSv35982V1

RM0385 Rev 7

1191/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

Coding of information bits
In order to minimize the DC component value on the transmission line, and to facilitate clock
recovery from the data stream, bits 4 to 31 are encoded in biphase-mark.
Each bit to be transmitted is represented by a symbol comprising two consecutive binary
states. The first state of a symbol is always different from the second state of the previous
symbol. The second state of the symbol is identical to the first if the bit to be transmitted is
logical 0. However, it is different if the bit is logical 1. These states are named “UI” (Unit
Interval) in the IEC-60958 specification.
The 24 data bits are transferred LSB first.
Figure 417. Channel coding example
1 UI

2 UI

3 UI

4 UI

5 UI

6 UI

7 UI

8 UI

9 UI

10 UI

11 UI

12 UI

1

2

3

4

5

6

1

0

1

1

0

0

13 UI

14 UI

7

Bit Clock

Source coding

Channel coding
(Biphase-Mark)

BitStream Biphase-Mark
Coded
MSv35921V1

34.3.2

SPDIFRX decoder (SPDIFRX_DC)
Main principle
The technique used by the SPDIFRX in order to decode the S/PDIF stream is based on the
measurement of the time interval between two consecutive edges. Three kinds of time
intervals may be found into an S/PDIF stream:
•

The long time interval, having a duration of 3 x UI, noted TL. It appears only during
preambles.

•

The medium time interval, having a duration of 2 x UI, noted TM. It appears both in
some preambles or into the information field.

•

The short time interval, having a duration of 1 x UI, noted TS. It appears both in some
preambles or into the information field.

The SPDIFRX_DC block is responsible of the decoding of the received S/PDIF stream. It
takes care of the following functions:

1192/1709

•

Resampling and filtering of the incoming signal

•

Estimation of the time-intervals

•

Estimation of the symbol rate and synchronization

•

Decoding of the serial data, and check of integrity

•

Detection of the block, and sub-frame preambles

•

Continuous tracking of the symbol rate

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
Figure 418 gives a detailed view of the SPDIFRX decoder.
Figure 418. SPDIFRX decoder
SPDIFRX_DC

SPDIFRX_SEQ

transition_pulse

SPDIFRX_CLK

transition_width_count

TRCNT
(13 bits)

13

SPDIFRX_DEC

SPDIFRX_IN[1]
...
SPDIFRX_IN[n]

Noise filtering
&
Edge detection

Longest
& shortest
transition
detector

MAX_CNT Transition preamble_info
coder
&
trans_info
MIN_CNT Preamble
detector

data_valid
Biphase
decoder

RX_BUF
Data
Packing

data

data

SYNC

SPDIFRX_FE

ctrl_ch.

WIDTH24
WIDTH40

FINE
SYNC

transition_pulse

MSv35983V2

Noise filtering & rising/falling edge detection
The S/PDIF signal received on the selected SPDIFRX_IN is re-sampled using the
SPDIFRX_CLK clock (acquisition clock). A simple filtering is applied in order cancel spurs.
This is performed by the stage detecting the edge transitions. The edge transitions are
detected as follow:
•

A rising edge is detected when the sequence 0 followed by two 1 is sampled.

•

A falling edge is detected when the sequence 1 followed by two 0 is sampled.

•

After a rising edge, a falling edge sequence is expected.

•

After a falling edge, a rising edge sequence is expected.
Figure 419. Noise filtering and edge detection
S1

S2

Glitch !!

S3

S4

SPDIFRX_IN[n:1]
SPDIFRX_CLK
0 1

1

1 1 1

0 0

0 1

1 1

0

1

1 1

1 1

0 0

0 0

1 1

1 1

0 0

1

1

1 1 1

resampled input
filtered input
transition_pulse
MSv35926V2

Longest and shortest transition detector
The longest and shortest transition detector block detects the maximum (MAX_CNT)
and minimum (MIN_CNT) duration between two transitions. The TRCNT counter is used to
measure the time interval duration. It is clocked by the SPDIFRX_CLK signal. On every
transition pulse, the counter value is stored and the counter is reset to start counting again.
The maximum duration is normally found during the preamble period. This maximum
duration is sent out as MAX_CNT. The minimum duration is sent out as MIN_CNT.

RM0385 Rev 7

1193/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

The search of the longest and shortest transition is stopped when the transition timer
expires. The transition timer is like a watchdog timer that generates a trigger after 70
transitions of the incoming signal. Note that counting 70 transitions insures a delay a bit
longer than a sub-frame.
Note that when the TRCNT overflows due to a too long time interval between two pulses,
the SPDIFRX is stopped and the flag TERR of SPDIFRX_SR register is set to 1.

Transition coder and preamble detector
The transition coder and preamble detector block receives the MAX_CNT and
MIN_CNT. It also receives the current transition width from the TRCNT counter (see
Figure 418). This block encodes the current transition width by comparing the current
transition width with two different thresholds, names THHI and THLO.
•

If the current transition width is less than (THLO - 1), then the data received is half part
of data bit ‘1’, and is coded as TS.

•

If the current transition width is greater than (THLO - 1), and less than THHI, then the
data received is data bit ‘0’, and is coded as TM.

•

If the current transition width is greater than THHI, then the data received is the long
pulse of preambles, and is coded as TL.

•

Else an error code is generated (FERR flag is set).

The thresholds THHI and THLO are elaborated using two different methods.
If the peripheral is doing its initial synchronization (‘coarse synchronization’), then the
thresholds are computed as follow:
•

THLO = MAX_CNT / 2.

•

THHI = MIN_CNT + MAX_CNT / 2.

Once the ‘coarse synchronization’ is completed, then the SPDIFRX uses a more accurate
reference in order to elaborate the thresholds. The SPDIFRX measures the length of 24
symbols (WIDTH24) for defining THLO and the length of 40 symbols (WIDTH40) for THHI.
THHI and THLO are computed as follow:
•

THLO = (WIDTH24) / 32

•

THHI = (WIDTH40) / 32

This second synchronization phase is called the ‘fine synchronization’. Refer to Figure 422
for additional information.
As shown in the figure hereafter, THLO is ideally equal to 1.5 UI, and to THHI 2.5 UI.

1194/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
Figure 420. Thresholds
MAX_CNT
MIN_CNT
1 UI

2 UI

3 UI

SPDIFRX Signal
1.5 UI
2.5 UI

Detection of Short
Transition

Detection of Medium
Transition

THLO

Detection of Long
Transition

THHI
MSv35931V2

The preamble detector checks four consecutive transitions of a specific sequence to
determine if they form the part of preamble. Let us say TRANS0, TRANS1, TRANS2 and
TRANS3 represent four consecutive transitions encoded as mentioned above. Table 214
shows the values of these four transitions to form a preamble. Absence of this pattern
indicates that these transitions form part of the data in the sub frame and bi-phase decoder
will decode them.
Table 214. Transition sequence for preamble
Preamble type

Biphase data
pattern

TRANS3

TRANS2

TRANS1

TRANS0

Preamble B

11101000

TL

TS

TS

TL

Preamble M

11100010

TL

TL

TS

TS

Preamble W

11100100

TL

TM

TS

TM

Bi-phase decoder
The Bi-phase decoder decodes the input bi-phase marked data stream using the transition
information provided by the transition coder and preamble detector block. It first waits for
the preamble detection information. After the preamble detection, it decodes the following
transition information:
•

If the incoming transition information is TM then it is decoded as a ‘0’.

•

Two consecutive TS are decoded as a ‘1’.

•

Any other transition sequence generates an error signal (FERR set to 1).

After decoding 28 data bits this way, this module looks for the following preamble data. If the
new preamble is not what is expected, then this block generates an error signal (FERR set
to 1). Refer to Section 34.3.8: Reception errors, for additional information on error flags.

Data packing
This block is responsible of the decoding of the IEC-60958 frames and blocks. It also
handles the writing into the RX_BUF or into SPDIFRX_CSR register.

RM0385 Rev 7

1195/1709
1221

SPDIF receiver interface (SPDIFRX)

34.3.3

RM0385

SPDIFRX tolerance to clock deviation
The SPDIFRX tolerance to clock deviation depends on the number of sample clock cycles in
one bit slot. The fastest SPDIFRX_CLK is, the more robust the reception will be. The ratio
between SPDIFRX_CLK frequency and the symbol rate must be at least 11.
Two kinds of phenomenon (at least!) can degrade the reception quality:

34.3.4

•

The cycle-to-cycle jitter which reflects the difference of transition length between two
consecutive transitions.

•

The long term jitter which reflects a cumulative effect of the cycle-to-cycle jitter. It can
be seen as a low-frequency symbol modulation.

SPDIFRX synchronization
The synchronization phase starts when setting SPDIFRXEN to 0b01 or 0b11. Figure 421
shows the synchronization process.
If the bit WFA of SPDIFRX_CR register is set to 1, then the peripheral must first detect
activity on the selected SPDIFRX_IN line before starting the synchronization process. The
activity detection is performed by detecting four transitions on the selected SPDIFRX_IN.
The peripheral remains in this state until transitions are not detected. This function can be
particularly helpful because the IP switches in COARSE SYNC mode only if activity is
present on the selected SPDIFRX_IN input, avoiding synchronization errors. See
Section 34.4: Programming procedures for additional information.
The user can still set the SPDIFRX into STATE_IDLE by setting SPDIFRXEN to 0. If the
WFA is set to 0, the peripheral starts the coarse synchronization without checking activity.
The next step consists on doing a first estimate of the thresholds (COARSE SYNC), in order
to perform the fine synchronization (FINE SYNC). Due to disturbances of the SPDIFRX line,
it could happen that the process is not executed first time right. For this purpose, the user
can program the number of allowed re-tries (NBTR) before setting SERR error flag.
When the SPDIFRX has been able to measure properly the duration of 24 and 40
consecutive symbols then the FINE SYNC is completed, the threshold values are updated,
and the flag SYNCD is set to 1. Refer to Section : Transition coder and preamble detector
for additional information.
Two kinds of errors are detected:
•

An overflow of the TRCNT, which generally means that there is no valid S/PDIF stream
in the input line. This overflow is indicated by TERR flag.

•

The number of retries reached the programmed value. This means that strong jitter is
present on the S/PDIF signal. This error is indicated by SERR flag.

When the first FINE SYNC is completed, the reception of channel status (C) and user data
(U) will start when the next “B” preamble is detected (see Figure 425).Then the user can
read IEC-60958 C and U bits through SPDIFRX_CSR register. According to this information
the user can then select the proper settings for DRFMT and RXSTEO. For example if the
user detects that the current audio stream transports encoded data, then he can put
RXSTEO to 0, and DRFMT to 0b10 prior to start data reception. Note that DRFMT and
RXSTEO cannot be modified when SPDIFRXEN = 0b11. Writes to these fields are ignored if
SPDIFRXEN is already 0b11, though these field can be changed with the same write
instruction that causes SPDIFRXEN to become 0b11.
Then the SPDIFRX waits for SPDIFRXEN = 0b11 and the “B” preamble before starting
saving audio samples.

1196/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
Figure 421. Synchronization flowchart
Initial Sync
Process

Wait for 4 transitions if WFA = 1, else skip this step
Parallel flows

Search for Longest/Shortest
pulses for 70 transitions
Compute COARSE thresholds
(THLO, THHI)

COARSE SYNC

Search for preamble for 70
transitions

N

N

preamble
found within 70
trans. ?

TRCNT
overflows ?

FINE SYNC

Y

Decode properly the next 40 symbols
Measurement of 24 and 40 symbols duration (WIDTH24, WIDTH40)

Y
N

Symb.
decoding (1)
OK ?

Y

ATTEMPT ++
Compute FINE thresholds (THLO, THHI)

N

ATTEMPT
== NBTR ?
Y

ERROR: Sync failure !
TERR = 1

Set SYNCD to 1

ERROR: Sync failure !
SERR = 1
Synchronization
done

Sync stopped
· (1) - The decoding is considered OK, when the symbols are properly decoded, and preamble occurs at the expected position
MSv35932V1

Refer to Frame structure and synchronization error for additional information concerning
TRCNT overflow.
The FINE SYNC process is re-triggered every frame in order to update thresholds as shown
in Figure 422 in order to continuously track S/PDIF synchronization.

RM0385 Rev 7

1197/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

Figure 422. Synchronization process scheduling
STATE_SYNC

70
trans.
Frame

SPDIFRX_IN
Synchronization
processes

Frame

STATE_RCV

Frame

Frame

Frame

Frame

Frame

M A1 W B1 M A2 W B2 M A3 W B3 B A4 W B4 M A5 W B5 M A6 W B6 M A5 W B5 M A5 W B5

T
S

COARSE

SPDIFRXEN

FINE

FINE

0b01

FINE

FINE

FINE

FINE

FINE

0b11

SYNCD

Coarse Synchronization process

COARSE

Fine Synchronization process

FINE
T
S

34.3.5

Transition Search (optional phase)

MSv35984V2

SPDIFRX handling
The software can control the state of the SPDIFRX through SPDIFRXEN field. The
SPDIFRX can be into one of the following states:
•

STATE_IDLE:
The peripheral is disabled, the SPDIFRX_CLK domain is reset. The PCLK1 domain is
functional.

•

STATE_SYNC:
The peripheral is synchronized to the stream, thresholds are updated regularly, user
and channel status can be read via interrupt of DMA. The audio samples are not
provided to receive buffer.

•

STATE_RCV:
The peripheral is synchronized to the stream, thresholds are updated regularly, user,
channel status and audio samples can be read via interrupt or DMA channels. When
SPDIFRXEN goes to 0b11, the SPDIFRX waits for “B” preamble before starting saving
audio samples.

•

STOP_STATE:
The peripheral is no longer synchronized, the reception of the user, channel status and
audio samples are stopped. It is expected that the software re-starts the SPDIFRX.

The Figure 423 shows the possible states of the SPDIFRX, and how to transition from one
state to the other. The bits under software control are followed by the mention “(SW)”, the
bits under IP control are followed by the mention “(HW)”.

1198/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
Figure 423. SPDIFRX States
STATE_IDLE

SPDIFRXEN = 0b00 (SW)
SPDIFRXEN = 0b01
(SW)
or
SPDIFRXEN = 0b11
(SW)

SPDIFRXEN = 0b00 (SW)
SPDIFRXEN = 0b00 (SW)

STATE_SYNC
FERR = 1 (HW) or
TERR = 1 (HW) or
SERR = 1 (HW)

STATE_STOP

SPDIFRXEN = 0b11 (SW)
and
sync_done = 1 (HW)

STATE_RCV
FERR = 1 (HW) or
TERR = 1 (HW)

NOTE: sync_done is an internal event informing that the SPDIFRX is properly synchronized

MSv35985V2

When SPDIFRX is in STATE_IDLE:
•

The software can transition to STATE_SYNC by setting SPDIFRXEN to 0b01 or 0b11

When SPDIFRX is in STATE_SYNC:
•

If the synchronization fails or if the received data are not properly decoded with no
chance of recovery without a re-synchronization (FERR or SERR or TERR = 1), the
SPDIFRX goes to STATE_STOP, and waits for software acknowledge.

•

When the synchronization phase is completed, if SPDIFRXEN = 0b01 the peripheral
remains in this state.

•

At any time the software can set SPDIFRXEN to 0, then SPDIFRX returns immediately
to STATE_IDLE. If a DMA transfer is on-going, it will be properly completed.

•

The SPDIFRX goes to STATE_RCV if SPDIFRXEN = 0b11 and if the SYNCD = 1

When SPDIFRX is in STATE_RCV:
•

If the received data are not properly decoded with no chance of recovery without a resynchronization (FERR or SERR or TERR = 1), the SPDIFRX goes to STATE_STOP,
and waits for software acknowledge.

•

At any time the software can set SPDIFRXEN to 0, then SPDIFRX returns immediately
to STATE_IDLE. If a DMA transfer is on-going, it will properly be completed.

When SPDIFRX is in STATE_STOP:
•

The SPDIFRX stops reception and synchronization, and waits for the software to set
the bit SPDIFRXEN to 0, in order to clear the error flags.

RM0385 Rev 7

1199/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

When SPDIFRXEN is set to 0, the IP is disabled, meaning that all the state machines are
reset, and RX_BUF is flushed. Note as well that flags FERR, SERR and TERR are reset.

34.3.6

Data reception management
The SPDIFRX offers a double buffer for the audio sample reception. A 32-bit buffer located
into the SPDIFRX_CLK clock domain (RX_BUF), and the SPDIFRX_DR register. The valid
data contained into the RX_BUF will be immediately transferred into SPDIFRX_DR if
SPDIFRX_DR is empty.
The valid data contained into the RX_BUF will be transferred into SPDIFRX_DR when the
two following conditions are reached:
•

The transition between the parity bit (P) and the next preamble is detected (this
indicated that the word has been completely received).

•

The SPDIFRX_DR is empty.

Having a 2-word buffer gives more flexibility for the latency constraint.
The maximum latency allowed is TSAMPLE - 2TPCLK - 2TSPDIFRX_CLK
Where TSAMPLE is the audio sampling rate of the received stereo audio samples, TPCLK is
the period of PCLK1 clock, and TSPDIFRX_CLK is the period of SPDIFRX_CLK clock.
The SPDIFRX offers the possibility to use either DMA (spdifrx_dma_req/clr_d) or interrupts
for transferring the audio samples into the memory. The recommended option is DMA, refer
to Section 34.3.10: DMA Interface for additional information.
The SPDIFRX offers several way on handling the received data. The user can either have a
separate flow for control information and audio samples, or get them all together.
For each sub-frame, the data reception register SPDIFRX_DR contains the 24 data bits,
and optionally the V, U, C, PE status bits, and the PT (see Mixing data and control flow).
Note that PE bit stands for Parity Error bit, and will be set to 1 when a parity error is detected
in the decoded sub-frame.
The PT field carries the preamble type (B, M or W).
V, U and C are a direct copy of the value received from the S/PDIF interface.
The bit DRFMT allows the selection between 3 audio formats as shown in Figure 424.

1200/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
Figure 424. SPDIFRX_DR register format
Frame 191
IEC60958 block format

M

Ch A

0

3
Sync Preamble

IEC60958 sub-frame

W

Frame 0

Ch B

B

Ch A

W

Frame 1
Ch B

Ch A

M

W

Ch B

4

5

6

7

12

25

26

27

28

29

30

31

S0

S1

S2

S3

S8

S21

S22

S23

V

U

C

P

LSb

MSb

DRFMT = 0b00
31

30

29

0

0

PT[1:0] or 0

28

27

26

25

24

C or 0 U or 0 V or 0 PE or 0

23

0

S23

S0

DR[23:0]

MSb

LSb

DRFMT = 0b01
SPDIFRX_DR

31

S23

DR[23:0]

MSb

8

7

6

S0

0

0

5

4

PT[1:0] or 0

3

2

1

0

C or 0 U or 0 V or 0 PE or 0

LSb

DRFMT = 0b10
31

S23
MSb

16

S8

DRNL2[15:0]

LSb

Ch A

15

S23
MSb

0
DRNL1[15:0]

Ch B

S8
LSb

MSv35925V2

Setting DRFMT to 0b00 or 0b01, offers the possibility to have the data either right or left
aligned into the SPDIFRX_DR register. The status information can be enabled or forced to
zero according to the way the software wants to handle them.
The format given by DRFMT= 0b10 is interesting in non-linear mode, as only 16 bits per
sub-frame are used. By using this format, the data of two consecutive sub-frames are stored
into SPDIFRX_DR, dividing by two the amount of memory footprint. Note that when
RXSTEO = 1, there is no misalignment risks (i.e. data from ChA will be always stored into
SPDIFRX_DR[31:16]). If RXSTEO = 0, then there is a misalignment risk is case of overrun
situation. In that case SPDIFRX_DR[31:16] will always contain the oldest value and
SPDIFRX_DR[15:0] the more recent value (see Figure 426).
In this format the status information cannot be mixed with data, but the user can still get
them through SPDIFRX_CSR register, and use a dedicated DMA channel or interrupt to
transfer them to memory (see Section 34.3.7: Dedicated control flow)

Mixing data and control flow
The user can choose to use this mode in order to get the full flexibility of the handling of the
control flow. The user can select which field shall be kept into the data register
(SPDIFRX_DR).
•

When bit PMSK = 1, the Parity Error information is masked (set to 0), otherwise it is
copied into SPDIFRX_DR.

•

When bit VMSK = 1, the Validity information is masked (set to 0), otherwise it is copied
into SPDIFRX_DR.

•

When bit CUMSK = 1, the Channel Status, and Used data information are masked (set
to 0), otherwise they are copied into SPDIFRX_DR.

•

When bit PTMSK = 1, the Preamble Type is masked (set to 0), otherwise it is copied
into SPDIFRX_DR.

RM0385 Rev 7

1201/1709
1221

SPDIF receiver interface (SPDIFRX)

34.3.7

RM0385

Dedicated control flow
The SPDIFRX offers the possibility to catch both user data and channel status information
via a dedicated DMA channel. This feature allows the SPDIFRX to acquire continuously the
channel status and user information. The acquisition will start at the beginning of a IEC
60958 block. Two fields are available to control this path: CBDMAEN and SPDIFRXEN.
When SPDIFRXEN is set to 0b01 or 0x11, the acquisition is started, after completion of the
synchronization phase. When 8 channel status and 16 user data bits have been received,
they are packed and stored into SPDIFRX_CSR register. A DMA request is triggered if the
bit CBDMAEN is set to 1 (see Figure 425).
If CS[0] corresponds to the first bit of a new block, the bit SOB will be set to 1. Refer to
Section 34.5.8: Channel status register (SPDIFRX_CSR). A bit is available (CHSEL) in
order to select if the user wants to select channel status information (C) from the channel A
or B.
Figure 425. Channel/user data format
Frame 191

SPDIFRX_IN

M A1 W B1

B A2 W B2

Frame 0

Frame 7

M A3 W B3 B A4 W B4

Frame 8

Frame 15

M A5 W B5 M A6 W B6

Frame 16

M A5 W B5 M A5 W B5

0b01 or 0b11

SPDIFRXEN

SYNCD

Start of a new block

spdifrx_dma_req_c
spdifrx_dma_clr_c

Synchronization done

Acquisition of C and U
bits started !!!

Transfer of first
SPDIFRX_CB word with
SOB = 1

Transfer of second
SPDIFRX_CB word with
SOB = 0

SPDIFRX_CSR format
31

25
reserved

24 23

16 15

SOB CS[7:0]

0
USR[15:0]
MSv35924V2

Note:

Once the first start of block is detected (B preamble), the SPDIFRX is checking the
preamble type every 8 frames.

Note:

Overrun error on SPDIFRX_DR register does not affect this path.

34.3.8

Reception errors
Frame structure and synchronization error
The SPDIFRX, detects errors, when one of the following condition occurs:
•

1202/1709

The FERR bit is set to 1 on the following conditions:
–

For each of the 28 information bits, if one symbol transition sequence is not
correct: for example if short pulses are not grouped by pairs.

–

If preambles occur to an unexpected place, or an expected preamble is not
received.

•

The SERR bit is set when the synchronization fails, because the number of re-tries
exceeded the programmed value.

•

The TERR bit is set when the counter used to estimate the width between two
transitions overflows (TRCNT).

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
The overflow occurs when no transition is detected during 8192 periods of
SPDIFRX_CLK clock. It represents at most a time interval of 11.6 frames.
When one of those flags goes to 1, the traffic on selected SPDIFRX_IN is then ignored, an
interrupt is generated if the IFEIE bit of the SPDIFRX_CR register is set.
The normal procedure when one of those errors occur is:
•

Set SPDIFRXEN to 0 in order to clear the error flags

•

Set SPDIFRXEN to 0b01 or 0b11 in order to restart the IP

Refer to Figure 423 for additional information.

Parity error
For each sub-frame, an even number of zeros and ones is expected inside the 28
information bits. If not, the parity error bit PERR is set in the SPDIFRX_SR register and an
interrupt is generated if the parity interrupt enable PERRIE bit is set in the SPDIFRX_CR
register. The reception of the incoming data is not paused, and the SPDIFRX continue to
deliver data to SPDIFRX_DR even if the interrupt is still pending.
The interrupt is acknowledged by clearing the PERR flag through PERRCF bit.
If the software wants to guarantee the coherency between the data read in the
SPDIFRX_DR register and the value of the bit PERR, the bit PMSK must be set to 0.

Overrun error
If both SPDIFRX_DR and RX_BUF are full, while the SPDIFRX_DC needs to write a new
sample in RX_BUF, this new sample is dropped, and an overrun condition is triggered. The
overrun error flag OVR is set in the SPDIFRX_SR register and an interrupt is generated if
the OVRIE bit of the SPDIFRX_CR register is set.
If the RXSTEO bit is set to 0, then as soon as the RX_BUF is empty, the IP will store the
next incoming data, even if the OVR flag is still pending. The main purpose is to reduce as
much as possible the amount of lost samples. Note that the behavior is similar
independently of DRFMT value. See Figure 426.

RM0385 Rev 7

1203/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

Figure 426. S/PDIF overrun error when RXSTEO = 0
DRFMT = 0b0x
Ch B2 cannot be written into the RX_BUF
because it is FULL  Overrun !
SPDIFRX_IN

Ch A3 can be written into the RX_BUF

M Ch A1 W Ch B1 B Ch A2 W Ch B2 M Ch A3 W Ch B3 M Ch A4 W Ch B4 B Ch A5 W Ch B5

Ch A1

Ch B1

Ch A2
Ch B1

Ch A2
Ch B1

Ch A3

Ch B3

Ch A4

Ch A4

Ch B0

Ch B3

RX_BUF and
SPDIFRX_DR content

Ch A3

RX_BUF FULL
Ch B4

Ch A5

Ch A5

Ch B4

Ch A2

Ch A1

Ch B0

Samples stored into
memory

Ch B1

SPDIFRX_DMA_REQ

SPDIFRX_IRQ (OVR)
Acknowledged by SW

DRFMT = 0b10
D6 is available and RX_BUF is FULL  Overrun !

RX_BUF cannot be emptied because SPDIF_RX is FULL
Frame 191
IEC60958 block format

Frame 0

Frame 1

Frame 2

Frame 3

Frame 4

M D0 W D1 B D2 W D3 M D4 W D5 M D6 W D7 M D8 W D9 M D10 W D11
ChA

ChB

ChA

ChB

ChA

ChB

ChA

ChB

ChA

ChB

ChA

ChB

RX_BUF FULL
RXNE
SPDIFRX_DMA_REQ
Acknowledged
by SW

SPDIFRX_IRQ (OVR)

Data read from
SPDIFRX_DR
31

16-15

0

D0 D1
SPDIFRX_DR

31

16-15

0

D2 D3
SPDIFRX_DR

31

16-15

0

D4 D5
SPDIFRX_DR

31

16-15

0

D7 D8
SPDIFRX_DR

31

16-15

0

D9 D10
SPDIFRX_DR

D6 is lost,SPDIFRX[31:16] contains the oldest data
MSv35929V2

If the RXSTEO bit is set to 1, it means that stereo data are transported, then the SPDIFRX
has to avoid misalignment between left and right channels. So the peripheral has to drop a
second sample even if there is room inside the RX_BUF in order to avoid misalignment.
Then the incoming samples can be written normally into the RX_BUF even if the OVR flag is
still pending. Refer to Figure 427.
The OVR flag is cleared by software, by setting the OVRCF bit to 1.

1204/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
Figure 427. S/PDIF overrun error when RXSTEO = 1
Ch B2 cannot be written into the RX_BUF
because it is FULL  Overrun !

SPDIFRX_IN

Ch A3 cannot be written into the RX_BUF even if the
RX_BUF is not FULL in order to avoid misalignments

M Ch A1 W Ch B1 B Ch A2 W Ch B2 M Ch A3 W Ch B3 M Ch A4 W Ch B4 B Ch A5 W Ch B5

Ch B1

Ch A2
Ch B1

Ch A2
Ch B1

-

Ch B3

Ch A4

Ch B4

Ch A5

Ch A5

Ch A1

Ch B4

Ch B0

Ch A4

RX_BUF and
SPDIFRX_DR content

Ch B3

RX_BUF FULL

Ch A2

Ch B1

Ch A1

Samples stored into
memory

Ch B0

SPDIFRX_DMA_REQ

SPDIFRX_IRQ
Acknowledged
by SW
MSv35930V2

34.3.9

Clocking strategy
The SPDIFRX block needs two different clocks:
•

The APB1 clock (PCLK1), which is used for the register interface,

•

The SPDIFRX_CLK which is mainly used by the SPDIFRX_DC part. Those clocks are
not supposed to be phase locked, so all signals crossing those clock domains are resynchronized (SYNC block on Figure 413).

In order to decode properly the incoming S/PDIF stream the SPDIFRX_DC shall re-sample
the received data with a clock at least 11 times higher than the maximum symbol rate, or
704 times higher than the audio sample rate. For example if the user expects to receive a
symbol rate to up to 12.288 MHz, the sample rate shall be at least 135.2 MHz. The clock
used by the SPDIFRX_DC is the SPDIFRX_CLK.
The frequency of the PCLK1 must be at least equal to the symbol rate.
Table 215. Minimum SPDIFRX_CLK frequency versus audio sampling rate

34.3.10

Symbol Rate

Minimum SPDIFRX_CLK frequency

Comments

3.072 MHz

33.8 MHz

For 48 kHz stream

6.144 MHz

67.6 MHz

For 96 kHz stream

12.288 MHz

135.2 MHz

For 192 kHz stream

DMA Interface
The SPDIFRX interface is able to perform communication using the DMA.

Note:

The user should refer to product specifications for availability of the DMA controller.
The SPDIFRX offers two independent DMA channels:
•

A DMA channel dedicated to the data transfer

•

A DMA channel dedicated to the channel status and user data transfer

The DMA mode for the data can be enabled for reception by setting the RXDMAEN bit in the
SPDIFRX_CR register. In this case, as soon as the SPDIFRX_DR is not empty, the

RM0385 Rev 7

1205/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

SPDIFRX interface sends a transfer request to the DMA. The DMA reads the data received
through the SPDIFRX_DR register without CPU intervention.
For the use of DMA for the control data refer to Section 34.3.7: Dedicated control flow.

34.3.11

Interrupt Generation
An interrupt line is shared between:
•

Reception events for data flow (RXNE)

•

Reception event for control flow (CSRNE)

•

Data corruption detection (PERR)

•

Transfer flow interruption (OVR)

•

Frame structure and synchronization errors (SERR, TERR and FERR)

•

Start of new block interrupt (SBD)

•

Synchronization done (SYNCD)
Figure 428. SPDIFRX interface interrupt mapping diagram
SYNCD
SYNCDIE
RXNE
RXNEIE
PERR
PERRIE
OVR

OR

OVRIE

SPDIFRX_IRQ

CSRNE
CSRNEIE
SBD
SBDIE

FERR

OR

SERR

TERR
IFEIE
MSv35928V2

Clearing interrupt source

Note:

1206/1709

•

RXNE is cleared when SPDIFRX_DR register is read

•

CSRNE is cleared when SPDIFRX_CSR register is read

•

FERR is cleared when SPDIFRXEN is set to 0

•

SERR is cleared when SPDIFRXEN is set to 0

•

TERR is cleared when SPDIFRXEN is set to 0

•

Others are cleared through SPDIFRX_IFCR register

The SBD event can only occur when the SPDIFRX is synchronized to the input stream
(SYNCD = 1).

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)
The SBD flag behavior is not guaranteed when the sub-frame which contains the B
preamble is lost due to an overrun.

34.3.12

Register protection
The SPDIFRX block embeds some hardware protection avoid erroneous use of control
registers. The table hereafter shows the bit field properties according to the SPDIFRX state.
Table 216. Bit field property versus SPDIFRX state
SPDIFRXEN
Registers

SPDIFRX_CR

SPDIFRX_IMR

Field

0b00

0b01

0b11

(STATE_IDLE)

(STATE_SYNC)

(STATE_RCV)

INSEL

rw

r

r

WFA

rw

r

r

NBTR

rw

r

r

CHSEL

rw

r

r

CBDMAEN

rw

rw

rw

PTMSK

rw

rw

rw

CUMSK

rw

rw

rw

VMSK

rw

rw

rw

PMSK

rw

rw

rw

DRFMT

rw

rw

r

RXSTEO

rw

rw

r

RXDMAEN

rw

rw

rw

All fields

rw

rw

rw

The table clearly shows that fields such as INSEL must be programmed when the IP is in
STATE_IDLE. In the others IP states, the hardware prevents writing to this field.
Note:

Even if the hardware allows the writing of CBDMAEN and RXDMAEN “on-the-fly”, it is not
recommended to enable the DMA when the IP is already receiving data.

Note:

Note that each of the mask bits (PMSK, VMSK, …) can be changed “on-the-fly” at any IP
state, but any change does not affect data which is already being held in SPDIFRX_DR.

34.4

Programming procedures
The following example illustrates a complete activation sequence of the SPDIFRX block.
The data path and channel status & user information will both use a dedicated DMA
channel. The activation sequence is then split into the following steps:
•

Wait for valid data on the selected SPDIFRX_IN input

•

Synchronize to the S/PDIF stream

•

Read the channel status and user information in order to setup the complete audio path

•

Start data acquisition

RM0385 Rev 7

1207/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

A simple way to check if valid data are available into the SPDIFRX_IN line is to switch the
SPDIFRX into the STATE_SYNC, with bit WFA set to 1. The description hereafter will focus
on detection. It is also possible to implement this function as follow:
•

The software has to check from time to time (i.e. every 100 ms for example) if the
SPDIFRX can find synchronization. This can be done by checking if the bit TERR is
set. When it is set it indicates that no activity as been found.

•

Connect the SPDIFRX_IN input to an external interrupt event block in order to detect
transitions of SPDIFRX_IN line. When activity is detected, then SPDIFRXEN can be
set to 0b01 or 0b11.
For those two implementations, the bit WFA is set to 0.

34.4.1

Initialization phase
•

The initialization function will look like this:

•

Configure the DMA transfer for both audio samples and IEC60958 channel status and
user information (DMA channel selection and activation, priority, number of data to
transfer, circular/no circular mode, DMA interrupts)

•

Configure the destination address:
–

Configure the address of the SPDIFRX_CSR register as source address for
IEC60958 channel status and user information

–

Configure the address of the SPDIFRX_DR register as source address for audio
samples

–

Enable the generation of the SPDIFRX_CLK. Refer to Table 215 in order to define
the minimum clock frequency versus supported audio sampling rate.
Note that the audio sampling rate of the received stream is not known in advance.
This means that the user has to select a SPDIFRX_CLK frequency at least 704
times higher than the maximum audio sampling rate the application is supposed to
handle: for example if the application is able to handle streams to up to 96 kHz,
then FSPDIFRX_CLK shall be at least 704 x 96 kHz = 67.6 MHz

•

Enable interrupt for errors and event signaling (IFEIE = SYNCDIE = OVRIE, PERRIE =
1, others set to 0). Note that SYNCDIE can be set to 0.

•

Configure the SPDIFRX_CR register:

•

–

INSEL shall select the wanted input

–

NBTR = 2, WFA = 1 (16 re-tries allowed, wait for activity before going to
synchronization phase),

–

PTMSK = CUMSK = 1 (Preamble, C and U bits are not mixed with data)

–

VMSK = PMSK = 0 (Parity error and validity bit mixed with data)

–

CHSEL = 0 (channels status will be read from sub-frame A)

–

DRFMT = 0b01 (data aligned to the left)

–

RXSTEO = 1 (expected stereo mode linear)

–

CBDMAEN = RXDMAEN = 1 (enable DMA channels)

–

SPDIFRXEN = 0b01 (switch SPDIFRX to STATE_SYNC)

The CPU can enter in WFI mode

Then the CPU will receive interrupts coming either from DMA or SPDIFRX.

1208/1709

RM0385 Rev 7

RM0385

34.4.2

SPDIF receiver interface (SPDIFRX)

Handling of interrupts coming from SPDIFRX
When an interrupt from the SPDIFRX is received, then the software has to check what is the
source of the interrupt by reading the SPDIFRX_SR register.
•

If SYNCD is set to 1, then it means that the synchronization has been properly
completed. No action has to be performed in our case as the DMA is already
programmed. The software just needs to wait for DMA interrupt in order to read
channel status information.
The SYNCD flag must be cleared by setting SYNCDCF bit of SPDIFRX_IFCR register
to 1.

•

If TERR or SERR or FERR are set to 1, the software has to set SPDIFRXEN to 0, and
re-start from the initialization phase.

•

34.4.3

–

TERR indicates that a time-out occurs either during synchronization phase or
after.

–

SERR indicates that the synchronization fails because the maximum allowed retries have been reached.

–

FERR indicates that the reading of information after synchronization fails
(unexpected preamble, bad data decoding...).

If PERR is set to 1, it means that a parity error has been detected, so one of the
received audio sample or the channel status or user data bits are corrupted. The action
taken here depends on the application: one action could be to drop the current channel
status block as it is not reliable. There is no need to re-start from the initialization
phase, as the synchronization is not lost.
The PERR flag must be cleared by setting PERRCF bit of SPDIFRX_IFCR register
to 1.

Handling of interrupts coming from DMA
If an interrupt is coming from the DMA channel used of the channel status (SPDIFRX_CSR):
If no error occurred (i.e. PERR), the CPU can start the decoding of channel information.
For example bit 1 of the channel status informs the user if the current stream is linear or
not. This information is very important in order to set-up the proper processing chain. In
the same way, bits 24 to 27 of the channel status give the sampling frequency of the
stream incoming stream.
Thanks to that information, the user can then configure the RXSTEO bit and DRFMT
field prior to start the data reception. For example if the current stream is non linear
PCM then RXSTEO is set to 0, and DRFMT is set to 0b10. Then the user can enable
the data reception by setting SPDIFRXEN to 0b11.
The bit SOB, when set to 1 indicates the start of a new block. This information will help
the software to identify the bit 0 of the channel status. Note that if the DMA generates
an interrupt every time 24 values are transferred into the memory, then the first word
will always correspond to the start of a new block.
If an interrupt is coming from the DMA channel used of the audio samples (SPDIFRX_DR):
The process performed here depends of the data type (linear or non-linear), and on the
data format selected.
For example in linear mode, if PE or V bit is set a special processing can be performed
locally in order to avoid spurs on output. In non-linear mode those bits are not important
as data frame have their own checksum.

RM0385 Rev 7

1209/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

34.5

SPDIFRX interface registers

34.5.1

Control register (SPDIFRX_CR)
Address offset: 0x00

29

28

27

26

25

24

23

22

21

20

19

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

CHSEL

CBDMAEN

PTMSK

CUMSK

VMSK

PMSK

RXSTEO

RXDMAEN

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

18

17

16

INSEL[2:0]

SPDIFRXEN[1:0]

DRFMT[1:0]

30
Res.

NBTR[1:0]

31
Res.

WFA

Reset value: 0x0000 0000

rw

Bits 31:19 Reserved, must be kept at reset value.
Bits 18:16 INSEL[2:0]: SPDIFRX input selection(1)
0b000: SPDIFRX_IN1 selected
0b001: SPDIFRX_IN2 selected
0b010: SPDIFRX_IN3 selected
0b011: SPDIFRX_IN4 selected
others reserved
Bit 15 Reserved, must be kept at reset value.
Bit 14 WFA: Wait for activity(1)
This bit is set/reset by software
1: The SPDIFRX waits for activity on SPDIFRX_IN line (4 transitions) before performing the
synchronization
0: The SPDIFRX does not wait for activity on SPDIFRX_IN line before performing the
synchronization
Bits 13:12 NBTR[1:0]: Maximum allowed re-tries during synchronization phase(1)
0b00: No re-try is allowed (only one attempt)
0b01: 3 re-tries allowed
0b10: 15 re-tries allowed
0b11: 63 re-tries allowed
Bit 11 CHSEL: Channel selection(1)
This bit is set/reset by software
1: The control flow will take the channel status from channel B
0: The control flow will take the channel status from channel A
Bit 10 CBDMAEN: Control buffer DMA enable for control flow(1)
This bit is set/reset by software
1: DMA mode is enabled for reception of channel status and used data information.
0: DMA mode is disabled for reception of channel status and used data information.
When this bit is set, the DMA request is made whenever the CSRNE flag is set.

1210/1709

RM0385 Rev 7

rw

RM0385

SPDIF receiver interface (SPDIFRX)

Bit 9 PTMSK: Mask of preamble type bits(1)
This bit is set/reset by software
1: The preamble type bits are not copied into the SPDIFRX_DR, zeros are written instead
0: The preamble type bits are copied into the SPDIFRX_DR
Bit 8 CUMSK: Mask of channel status and user bits(1)
This bit is set/reset by software
1: The channel status and user bits are not copied into the SPDIFRX_DR, zeros are written instead
0: The channel status and user bits are copied into the SPDIFRX_DR
Bit 7 VMSK: Mask of validity bit(1)
This bit is set/reset by software
1: The validity bit is not copied into the SPDIFRX_DR, a zero is written instead
0: The validity bit is copied into the SPDIFRX_DR
Bit 6 PMSK: Mask parity error bit(1)
This bit is set/reset by software
1: The parity error bit is not copied into the SPDIFRX_DR, a zero is written instead
0: The parity error bit is copied into the SPDIFRX_DR
Bits 5:4 DRFMT[1:0]: RX data format(1)
This bit is set/reset by software
0b11: reserved
0b10: Data sample are packed by setting two 16-bit sample into a 32-bit word
0b01: Data samples are aligned in the left (MSB)
0b00: Data samples are aligned in the right (LSB)
Bit 3 RXSTEO: Stereo mode(1)
This bit is set/reset by software
1: The peripheral is in STEREO mode
0: The peripheral is in MONO mode
This bit is used in case of overrun situation in order to handle misalignment
Bit 2 RXDMAEN: Receiver DMA enable for data flow(1)
This bit is set/reset by software
1: DMA mode is enabled for reception.
0: DMA mode is disabled for reception.
When this bit is set, the DMA request is made whenever the RXNE flag is set.
Bits 1:0 SPDIFRXEN[1:0]: Peripheral block enable(1)
This field is modified by software.
It shall be used to change the peripheral phase among the three possible states: STATE_IDLE,
STATE_SYNC and STATE_RCV.
0b00: Disable SPDIFRX (STATE_IDLE).
0b01: Enable SPDIFRX Synchronization only
0b10: Reserved
0b11: Enable SPDIF Receiver
Note: it is not possible to transition from STATE_RCV to STATE_SYNC, the user shall first go the
STATE_IDLE.
it is possible to transition from STATE_IDLE to STATE_RCV: in that case the peripheral
transitions from STATE_IDLE to STATE_SYNC and as soon as the synchronization is
performed goes to STATE_RCV.
1.

Refer to Section 34.3.12: Register protection for additional information on fields properties.

RM0385 Rev 7

1211/1709
1221

SPDIF receiver interface (SPDIFRX)

34.5.2

RM0385

Interrupt mask register (SPDIFRX_IMR)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IFE
IE

SYNCD
IE

SBLK
IE

OVR
IE

rw

rw

rw

rw

PERR CSRNE RXNE
IE
IE
IE
rw

rw

rw

Bits 31:7 Reserved, must be kept at reset value.
Bit 6 IFEIE: Serial Interface Error Interrupt Enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A SPDIFRX interface interrupt is generated whenever SERR=1, TERR=1 or FERR=1 in the
SPDIFRX_SR register.
Bit 5 SYNCDIE: Synchronization Done
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A SPDIFRX interface interrupt is generated whenever SYNCD = 1 in the SPDIFRX_SR register.
Bit 4 SBLKIE: Synchronization Block Detected Interrupt Enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A SPDIFRX interface interrupt is generated whenever SBD = 1 in the SPDIFRX_SR register.
Bit 3 OVRIE: Overrun error Interrupt Enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A SPDIFRX interface interrupt is generated whenever OVR=1 in the SPDIFRX_SR register
Bit 2 PERRIE: Parity error interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A SPDIFRX interface interrupt is generated whenever PERR=1 in the SPDIFRX_SR register
Bit 1 CSRNEIE: Control Buffer Ready Interrupt Enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A SPDIFRX interface interrupt is generated whenever CSRNE = 1 in the SPDIFRX_SR register.
Bit 0 RXNEIE: RXNE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A SPDIFRX interface interrupt is generated whenever RXNE=1 in the SPDIFRX_SR register

1212/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)

34.5.3

Status register (SPDIFRX_SR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

23

22

21

20

19

18

17

16

WIDTH5[14:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TERR

SERR

FERR

SYNCD

SBD

OVR

r

r

r

r

r

r

PERR CSRNE RXNE
r

r

r

Bit 31 Reserved, must be kept at reset value.
Bits 30:16 WIDTH5[14:0]: Duration of 5 symbols counted with SPDIFRX_CLK
This value represents the amount of SPDIFRX_CLK clock periods contained on a length of 5
consecutive symbols. This value can be used to estimate the S/PDIF symbol rate. Its accuracy is
limited by the frequency of SPDIFRX_CLK.
For example if the SPDIFRX_CLK is fixed to 84 MHz, and WIDTH5 = 147d. The estimated sampling
rate of the S/PDIF stream is:
Fs = 5 x FSPDIFRX_CLK / (WIDTH5 x 64) ~ 44.6 kHz, so the closest standard sampling rate is 44.1
kHz.
Note that WIDTH5 is updated by the hardware when SYNCD goes high, and then every frame.
Bits 15:9 Reserved, must be kept at reset value.
Bit 8 TERR: Time-out error
This bit is set by hardware when the counter TRCNT reaches its max value. It indicates that the time
interval between two transitions is too long. It generally indicates that there is no valid signal on
SPDIFRX_IN input.
This flag is cleared by writing SPDIFRXEN to 0
An interrupt is generated if IFEIE=1 in the SPDIFRX_IMR register
0: No sequence error is detected
1: Sequence error is detected
Bit 7 SERR: Synchronization error
This bit is set by hardware when the synchronization fails due to amount of re-tries for NBTR.
This flag is cleared by writing SPDIFRXEN to 0
An interrupt is generated if IFEIE=1 in the SPDIFRX_IMR register.
0: No synchronization error is detected
1: Synchronization error is detected
Bit 6 FERR: Framing error
This bit is set by hardware when an error occurs during data reception: preamble not at the
expected place, short transition not grouped by pairs...
This is set by the hardware only if the synchronization has been completed (SYNCD = 1).
This flag is cleared by writing SPDIFRXEN to 0
An interrupt is generated if IFEIE=1 in the SPDIFRX_IMR register.
0: no Manchester Violation detected
1: Manchester Violation detected

RM0385 Rev 7

1213/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

Bit 5 SYNCD: Synchronization Done
This bit is set by hardware when the initial synchronization phase is properly completed.
This flag is cleared by writing a 1 to its corresponding bit on SPDIFRX_CLR_SR register.
An interrupt is generated if SYNCDIE = 1 in the SPDIFRX_IMR register
0: Synchronization is pending
1: Synchronization is completed
Bit 4 SBD: Synchronization Block Detected
This bit is set by hardware when a “B” preamble is detected
This flag is cleared by writing a 1 to its corresponding bit on SPDIFRX_CLR_SR register.
An interrupt is generated if SBLKIE = 1 in the SPDIFRX_IMR register
0: No “B” preamble detected
1: “B” preamble has been detected
Bit 3 OVR: Overrun error
This bit is set by hardware when a received data is ready to be transferred in the SPDIFRX_DR
register while RXNE = 1 and both SPDIFRX_DR and RX_BUF are full.
This flag is cleared by writing a 1 to its corresponding bit on SPDIFRX_CLR_SR register.
An interrupt is generated if OVRIE=1 in the SPDIFRX_IMR register.
0: No Overrun error
1: Overrun error is detected
Note: When this bit is set, the SPDIFRX_DR register content will not be lost but the last data
received will.
Bit 2 PERR: Parity error
This bit is set by hardware when the data and status bits of the sub-frame received contain an odd
number of 0 and 1.
This flag is cleared by writing a 1 to its corresponding bit on SPDIFRX_CLR_SR register.
An interrupt is generated if PIE = 1 in the SPDIFRX_IMR register.
0: No parity error
1: Parity error
Bit 1 CSRNE: The Control Buffer register is not empty
This bit is set by hardware when a valid control information is ready.
This flag is cleared when reading SPDIFRX_CSR register.
An interrupt is generated if CBRDYIE = 1 in the SPDIFRX_IMR register
0: No control word available on SPDIFRX_CSR register
1: A control word is available on SPDIFRX_CSR register
Bit 0 RXNE: Read data register not empty
This bit is set by hardware when a valid data is available into SPDIFRX_DR register.
This flag is cleared by reading the SPDIFRX_DR register.
An interrupt is generated if RXNEIE=1 in the SPDIFRX_IMR register.
0: Data is not received
1: Received data is ready to be read.

1214/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)

34.5.4

Interrupt flag clear register (SPDIFRX_IFCR)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SYNCD
CF

SBD
CF

OVR
CF

PERR
CF

Res.

Res.

w

w

w

w

Bits 31:6 Reserved, must be kept at reset value.
Bit 5 SYNCDCF: Clears the Synchronization Done flag
Writing 1 in this bit clears the flag SYNCD in the SPDIFRX_SR register.
Reading this bit always returns the value 0.
Bit 4 SBDCF: Clears the Synchronization Block Detected flag
Writing 1 in this bit clears the flag SBD in the SPDIFRX_SR register.
Reading this bit always returns the value 0.
Bit 3 OVRCF: Clears the Overrun error flag
Writing 1 in this bit clears the flag OVR in the SPDIFRX_SR register.
Reading this bit always returns the value 0.
Bit 2 PERRCF: Clears the Parity error flag
Writing 1 in this bit clears the flag PERR in the SPDIFRX_SR register.
Reading this bit always returns the value 0.
Bits 1:0 Reserved, must be kept at reset value.

RM0385 Rev 7

1215/1709
1221

SPDIF receiver interface (SPDIFRX)

34.5.5

RM0385

Data input register (SPDIFRX_DR)
Address offset: 0x10
Reset value: 0x0000 0000
This register can take 3 different formats according to DRFMT. Here is the format when
DRFMT = 0b00:

31

30

Res.

Res.

29

28

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

PT[1:0]

27

26

25

24

C

U

V

PE

23

22

21

20

19

18

17

16

DR[23:16]

DR[15:0]
r

Bits 31:30 Reserved, must be kept at reset value.
Bits 29:28 PT[1:0]: Preamble Type
These bits indicate the preamble received.
00: not used
01: Preamble B received
10: Preamble M received
11: Preamble W received
Note that if PTMSK = 1, this field is forced to zero
Bit 27 C: Channel Status bit
Contains the received channel status bit, if CUMSK = 0, otherwise it is forced to 0
Bit 26 U: User bit
Contains the received user bit, if CUMSK = 0, otherwise it is forced to 0
Bit 25 V: Validity bit
Contains the received validity bit if VMSK = 0, otherwise it is forced to 0
Bit 24 PE: Parity Error bit
Contains a copy of PERR bit if PMSK = 0, otherwise it is forced to 0
Bits 23:0 DR[23:0]: Data value
Contains the 24 received data bits, aligned on D[23]

1216/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)

34.5.6

Data input register (SPDIFRX_FMT1_DR)
Address offset: 0x10
Reset value: 0x0000 0000
This register can take 3 different formats according to DRFMT. Here is the format when
DRFMT = 0b01:

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DR[23:8]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

C

U

V

PE

r

r

r

r

r

r

r

r

r

r

r

DR[7:0]
r

PT[1:0]
r

r

Bits 31:8 DR[23:0]: Data value
Contains the 24 received data bits, aligned on D[23]
Bits 7:6 Reserved, must be kept at reset value.
Bits 5:4 PT[1:0]: Preamble Type
These bits indicate the preamble received.
00: not used
01: Preamble B received
10: Preamble M received
11: Preamble W received
Note that if PTMSK = 1, this field is forced to zero
Bit 3 C: Channel Status bit
Contains the received channel status bit, if CUMSK = 0, otherwise it is forced to 0
Bit 2 U: User bit
Contains the received user bit, if CUMSK = 0, otherwise it is forced to 0
Bit 1 V: Validity bit
Contains the received validity bit if VMSK = 0, otherwise it is forced to 0
Bit 0 PE: Parity Error bit
Contains a copy of PERR bit if PMSK = 0, otherwise it is forced to 0

RM0385 Rev 7

1217/1709
1221

SPDIF receiver interface (SPDIFRX)

34.5.7

RM0385

Data input register (SPDIFRX_FMT2_DR)
Address offset: 0x10
Reset value: 0x0000 0000
This register can take 3 different formats according to DRFMT.
The data format proposed when DRFMT = 0b10, is dedicated to non-linear mode, as only
16 bits are used (bits 23 to 8 from S/PDIF sub-frame).

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DRNL2[15:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

DRNL1[15:0]
r

r

Bits 31:16 DRNL2[15:0]: Data value
This field contains the Channel A
Bits 15:0 DRNL1[15:0]: Data value
This field contains the Channel B

1218/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)

34.5.8

Channel status register (SPDIFRX_CSR)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SOB

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

17

16

CS[7:0]

USR[15:0]
r

r

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 SOB: Start Of Block
This bit indicates if the bit CS[0] corresponds to the first bit of a new block
0: CS[0] is not the first bit of a new block
1: CS[0] is the first bit of a new block
Bits 23:16 CS[7:0]: Channel A status information
Bit CS[0] is the oldest value
Bits 15:0 USR[15:0]: User data information
Bit USR[0] is the oldest value, and comes from channel A, USR[1] comes channel B.
So USR[n] bits come from channel A is n is even, otherwise they come from channel B.

34.5.9

Debug information register (SPDIFRX_DIR)
Address offset: 0x18
Reset value: 0x0000 0000

31

30

29

Res.

Res.

Res.

15

14

13

Res.

Res.

Res.

28

27

26

25

24

23

22

21

20

19

18

TLO[12:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

THI[12:0]
r

Bits 31:29 Reserved, must be kept at reset value.

RM0385 Rev 7

1219/1709
1221

SPDIF receiver interface (SPDIFRX)

RM0385

Bits 28:16 TLO[12:0]: Threshold LOW (TLO = 1.5 x UI / TSPDIFRX_CLK)
This field contains the current threshold LOW estimation. This value can be used to estimate the
sampling rate of the received stream. The accuracy of TLO is limited to a period of the
SPDIFRX_CLK. The sampling rate can be estimated as follow:
Sampling Rate = [2 x TLO x TSPDIFRX_CLK +/- TSPDIFRX_CLK] x 2/3
Note that TLO is updated by the hardware when SYNCD goes high, and then every frame.
Bits 15:13 Reserved, must be kept at reset value.
Bits 12:0 THI[12:0]: Threshold HIGH (THI = 2.5 x UI / TSPDIFRX_CLK)
This field contains the current threshold HIGH estimation. This value can be used to estimate the
sampling rate of the received stream. The accuracy of THI is limited to a period of the
SPDIFRX_CLK. The sampling rate can be estimated as follow:
Sampling Rate = [2 x THI x TSPDIFRX_CLK +/- TSPDIFRX_CLK] x 2/5
Note that THI is updated by the hardware when SYNCD goes high, and then every frame.

1220/1709

RM0385 Rev 7

RM0385

SPDIF receiver interface (SPDIFRX)

34.5.10

SPDIFRX interface register map
Table 217 gives the SPDIFRX interface register map and reset values.

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RXNE

Res.

CSRNE

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

SPDIFRX_
FMT2_DR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

SOB

Res.

Res.

0
Res.

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

C U V

P
E

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

USR[15:0]
0

0

0

TLO[12:0]
0

0

DRNL1[15:0]

CS[7:0]
0

0

Res.

0

0

0

0

0

0
Res.

0

Reset value

0

Res.

0

SPDIFRX_
CSR

SPDIFRX_DIR

0

DRNL2[15:0]

Reset value

0x18

0

DR[23:0]

Res.

0x14

0

0

DR[23:0]

SPDIFRX_
FMT1_DR
Reset value

0x10

0

P
E

0

PT[1:0]

0

PT[1:0]

Reset value

C U V

Res.

0x10

SPDIFRX_DR

Res.

0x10

Res.

Reset value

Res.

Res.

0

Res.

Res.

OVR

Res.

PERR

Res.

0

OVRCF

Res.

0

PERRCF

Res.

SBD

Res.

0

SBDCF

Res.

SYNCD

Res.

0

SYNCDCF

0

0

FERR

0

0

SERR

0

0

Res.

0

0

Res.

0

0

TERR

0

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

Res.
0

Res.

0x0C

SPDIFRX_
IFCR

Res.

Reset value

WIDTH5[14:0]

Res.

SPDIFRX_SR

SPDIFRXEN[1:0]

0

RXNEIE

0

CSRNEIE

RXSTEO

RXDMAEN

0

OVRIE

0

PERRIE

0

Reset value

0x08

DRFMT[1:0]

0

SBLKIE

Res.

PMSK

Res.

0

SYNCDIE

Res.

VMSK

Res.

0

Res.

0

IFEIE

0

Res.

PTMSK

0

Res.

CUMSK

CHSEL

CBDMAEN

0

NBTR[1:0]

0

WFA

Res.
Res.

Res.

0

Res.

INSEL[2:0]
0
Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SPDIFRX_IMR

Res.

Reset value

0x04

0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SPDIFRX_CR
0x00

Res.

Register
name

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 217. SPDIFRX interface register map and reset values

0

0

0

0

0

0

0

THI[12:0]
0

0

0

0

0

0

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

RM0385 Rev 7

1221/1709
1221

SD/SDIO/MMC card host interface (SDMMC)

35

SD/SDIO/MMC card host interface (SDMMC)

35.1

SDMMC main features

RM0385

The SD/SDIO MMC card host interface (SDMMC) provides an interface between the APB2
peripheral bus and MultiMediaCards (MMCs), SD memory cards and SDIO cards.
The MultiMediaCard system specifications are available through the MultiMediaCard
Association website, published by the MMCA technical committee.
SD memory card and SD I/O card system specifications are available through the SD card
Association website.
The SDMMC features include the following:

Note:

•

Full compliance with MultiMediaCard System Specification Version 4.2. Card support
for three different databus modes: 1-bit (default), 4-bit and 8-bit

•

Full compatibility with previous versions of MultiMediaCards (forward compatibility)

•

Full compliance with SD Memory Card Specifications Version 2.0

•

Full compliance with SD I/O Card Specification Version 2.0: card support for two
different databus modes: 1-bit (default) and 4-bit

•

Data transfer up to 50 MHz for the 8 bit mode

•

Data and command output enable signals to control external bidirectional drivers.

1

The SDMMC does not have an SPI-compatible communication mode.

2

The SD memory card protocol is a superset of the MultiMediaCard protocol as defined in the
MultiMediaCard system specification V2.11. Several commands required for SD memory
devices are not supported by either SD I/O-only cards or the I/O portion of combo cards.
Some of these commands have no use in SD I/O devices, such as erase commands, and
thus are not supported in the SDIO protocol. In addition, several commands are different
between SD memory cards and SD I/O cards and thus are not supported in the SDIO
protocol. For details refer to SD I/O card Specification Version 1.0.
The MultiMediaCard/SD bus connects cards to the controller.
The current version of the SDMMC supports only one SD/SDIO/MMC4.2 card at any one
time and a stack of MMC4.1 or previous.

35.2

SDMMC bus topology
Communication over the bus is based on command and data transfers.
The basic transaction on the MultiMediaCard/SD/SD I/O bus is the command/response
transaction. These types of bus transaction transfer their information directly within the
command or response structure. In addition, some operations have a data token.
Data transfers to/from SD/SDIO memory cards are done in data blocks. Data transfers
to/from MMC are done data blocks or streams.

1222/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Figure 429. “No response” and “no data” operations
From host to card(s)

SDMMC_CMD

From host to card

Command

Command

From card to host

Response

SDMMC_D

Operation (no response)

Operation (no data)
ai14734b

Figure 430. (Multiple) block read operation
From host to card From card to host
data from card to host
SDMMC_CMD

Command

Stop command
stops data transfer

Response

SDMMC_D

Command

Data block crc

Data block crc

Response

Data block crc

Block read operation
Data stop operation

Multiple block read operation

ai14735b

Figure 431. (Multiple) block write operation
From host to card From card to host
data from host to card
SDMMC_CMD

SDMMC_D

Command

Stop command
stops data transfer

Response

Command

Data block crc

Busy

Block write operation

Data block crc

Response

Busy

Data stop operation

Multiple block write operation
ai14737b

Note:

The SDMMC will not send any data as long as the Busy signal is asserted (SDMMC_D0
pulled low).

RM0385 Rev 7

1223/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Figure 432. Sequential read operation
From host to
From card to host
card(s)

Stop command
stops data transfer

Data from card to host
SDMMC_CMD

Command

Response

Command

Response

Data stream

SDMMC_D

Data stop operation

Data transfer operation

ai14738b

Figure 433. Sequential write operation
From host to
card(s)
From card to host

Stop command
stops data transfer

Data from host to card
SDMMC_CMD

Command

Response

Command

Response

Data stream

SDMMC_D

Data stop operation

Data transfer operation

ai14739b

35.3

SDMMC functional description
The SDMMC consists of two parts:
•

The SDMMC adapter block provides all functions specific to the MMC/SD/SD I/O card
such as the clock generation unit, command and data transfer.

•

The APB2 interface accesses the SDMMC adapter registers, and generates interrupt
and DMA request signals.
Figure 434. SDMMC block diagram
SDMMC
SDMMC_CK
Interrupts and
DMA request

SDMMC_CMD
APB2
interface

SDMMC
adapter

PCLK2

SDMMCCLK

SDMMC_D[7:0]

APB2 bus

ai15898b

1224/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
By default SDMMC_D0 is used for data transfer. After initialization, the host can change the
databus width.
If a MultiMediaCard is connected to the bus, SDMMC_D0, SDMMC_D[3:0] or
SDMMC_D[7:0] can be used for data transfer. MMC V3.31 or previous, supports only 1 bit of
data so only SDMMC_D0 can be used.
If an SD or SD I/O card is connected to the bus, data transfer can be configured by the host
to use SDMMC_D0 or SDMMC_D[3:0]. All data lines are operating in push-pull mode.
SDMMC_CMD has two operational modes:
•

Open-drain for initialization (only for MMCV3.31 or previous)

•

Push-pull for command transfer (SD/SD I/O card MMC4.2 use push-pull drivers also for
initialization)

SDMMC_CK is the clock to the card: one bit is transferred on both command and data lines
with each clock cycle.
The SDMMC uses two clock signals:
•

SDMMC adapter clock SDMMCCLK = 50 MHz)

•

APB2 bus clock (PCLK2)

PCLK2 and SDMMC_CK clock frequencies must respect the following condition:
Frequenc ( PCLK2 ) > ( ( 3xWidth ) ⁄ 32 ) × Frequency ( SDMMC_CK )

The signals shown in Table 218 are used on the MultiMediaCard/SD/SD I/O card bus.
Table 218. SDMMC I/O definitions
Pin

Direction

Description

SDMMC_CK

Output

MultiMediaCard/SD/SDIO card clock. This pin is the clock from
host to card.

SDMMC_CMD

Bidirectional

MultiMediaCard/SD/SDIO card command. This pin is the
bidirectional command/response signal.

SDMMC_D[7:0]

Bidirectional

MultiMediaCard/SD/SDIO card data. These pins are the
bidirectional databus.

RM0385 Rev 7

1225/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

35.3.1

RM0385

SDMMC adapter
Figure 435 shows a simplified block diagram of an SDMMC adapter.
Figure 435. SDMMC adapter
SDMMC adapter

Adapter
registers
To APB2
interface

FIFO

PCLK2

SDMMC_CK

Command
path

SDMMC_CMD

Data path

SDMMC_D[7:0]

Card bus

Control unit

SDMMCCLK
ai15899b

The SDMMC adapter is a multimedia/secure digital memory card bus master that provides
an interface to a multimedia card stack or to a secure digital memory card. It consists of five
subunits:

Note:

•

Adapter register block

•

Control unit

•

Command path

•

Data path

•

Data FIFO

The adapter registers and FIFO use the APB2 bus clock domain (PCLK2). The control unit,
command path and data path use the SDMMC adapter clock domain (SDMMCCLK).

Adapter register block
The adapter register block contains all system registers. This block also generates the
signals that clear the static flags in the multimedia card. The clear signals are generated
when 1 is written into the corresponding bit location in the SDMMC Clear register.

Control unit
The control unit contains the power management functions and the clock divider for the
memory card clock.
There are three power phases:

1226/1709

•

power-off

•

power-up

•

power-on

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Figure 436. Control unit
Control unit

Power management

Adapter
registers

Clock management

SDMMC_CK

To command and data path
ai14804b

The control unit is illustrated in Figure 436. It consists of a power management subunit and
a clock management subunit.
The power management subunit disables the card bus output signals during the power-off
and power-up phases.
The clock management subunit generates and controls the SDMMC_CK signal. The
SDMMC_CK output can use either the clock divide or the clock bypass mode. The clock
output is inactive:
•

after reset

•

during the power-off or power-up phases

•

if the power saving mode is enabled and the card bus is in the Idle state (eight clock
periods after both the command and data path subunits enter the Idle phase)

The clock management subunit controls SDMMC_CK dephasing. When not in bypass mode
the SDMMC command and data output are generated on the SDMMCCLK falling edge
succeeding the rising edge of SDMMC_CK. (SDMMC_CK rising edge occurs on
SDMMCCLK rising edge) when SDMMC_CLKCR[13] bit is reset (NEGEDGE = 0). When
SDMMC_CLKCR[13] bit is set (NEGEDGE = 1) SDMMC command and data changed on
the SDMMC_CK falling edge.
When SDMMC_CLKCR[10] is set (BYPASS = 1), SDMMC_CK rising edge occurs on
SDMMCCLK rising edge. The data and the command change on SDMMCCLK falling edge
whatever NEGEDGE value.
The data and command responses are latched using SDMMC_CK rising edge.

RM0385 Rev 7

1227/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Figure 437. SDMMC_CK clock dephasing (BYPASS = 0)
SDMMCCLK

SDMMC_CK

CMD / Data
output
NEGEDGE = 0

NEGEDGE = 1

MSv36077V1

Command path
The command path unit sends commands to and receives responses from the cards.
Figure 438. SDMMC adapter command path

To control unit

Status
flag

Control
logic

Command
timer

Adapter registers
SDMMC_CMDin
CMD
Argument
CRC

SDMMC_CMDout

Shift
register

CMD

Response
To APB2 interface
registers

ai15900b

•

Command path state machine (CPSM)
–

1228/1709

When the command register is written to and the enable bit is set, command
transfer starts. When the command has been sent, the command path state
machine (CPSM) sets the status flags and enters the Idle state if a response is not
required. If a response is required, it waits for the response (see Figure 439 on
page 1229). When the response is received, the received CRC code and the
internally generated code are compared, and the appropriate status flags are set.

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Figure 439. Command path state machine (SDMMC)
On reset

CPSM enabled and
pending command

Idle

CPSM disabled

Pend

Response received or
disabled or command
CRC failed

Enabled and
command start
CPSM disabled
or no response

Last data

CPSM disabled or
command timeout

Send

Receive

Response
started

Wait for response
Wait

MS34444V1

When the Wait state is entered, the command timer starts running. If the timeout is reached
before the CPSM moves to the Receive state, the timeout flag is set and the Idle state is
entered.
Note:

The command timeout has a fixed value of 64 SDMMC_CK clock periods.
If the interrupt bit is set in the command register, the timer is disabled and the CPSM waits
for an interrupt request from one of the cards. If a pending bit is set in the command register,
the CPSM enters the Pend state, and waits for a CmdPend signal from the data path
subunit. When CmdPend is detected, the CPSM moves to the Send state. This enables the
data counter to trigger the stop command transmission.

Note:

The CPSM remains in the Idle state for at least eight SDMMC_CK periods to meet the NCC
and NRC timing constraints. NCC is the minimum delay between two host commands, and
NRC is the minimum delay between the host command and the card response.

RM0385 Rev 7

1229/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Figure 440. SDMMC command transfer
at least 8 SDMMC_CK
cycles
SDMMC_CK

Command

Command

Response

State

Idle

Send

Wait

Receive

Idle

Send

SDMMC_CMD

Hi-Z

Controller drives

Hi-Z

Card drives

Hi-Z

Controller drives
ai14807b

•

Command format
–

Command: a command is a token that starts an operation. Command are sent
from the host either to a single card (addressed command) or to all connected
cards (broadcast command are available for MMC V3.31 or previous). Commands
are transferred serially on the CMD line. All commands have a fixed length of 48
bits. The general format for a command token for MultiMediaCards, SD-Memory
cards and SDIO-Cards is shown in Table 219.
The command path operates in a half-duplex mode, so that commands and
responses can either be sent or received. If the CPSM is not in the Send state, the
SDMMC_CMD output is in the Hi-Z state, as shown in Figure 440 on page 1230.
Data on SDMMC_CMD are synchronous with the rising edge of SDMMC_CK.
Table 219 shows the command format.
Table 219. Command format

Bit position

Width

Value

Description

47

1

0

Start bit

46

1

1

Transmission bit

[45:40]

6

-

Command index

[39:8]

32

-

Argument

[7:1]

7

-

CRC7

0

1

1

End bit

–

Response: a response is a token that is sent from an addressed card (or
synchronously from all connected cards for MMC V3.31 or previous), to the host
as an answer to a previously received command. Responses are transferred
serially on the CMD line.

The SDMMC supports two response types. Both use CRC error checking:

Note:

1230/1709

•

48 bit short response

•

136 bit long response

If the response does not contain a CRC (CMD1 response), the device driver must ignore the
CRC failed status.

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Table 220. Short response format
Bit position

Width

Value

Description

47

1

0

Start bit

46

1

0

Transmission bit

[45:40]

6

-

Command index

[39:8]

32

-

Argument

[7:1]

7

-

CRC7(or 1111111)

0

1

1

End bit

Table 221. Long response format
Bit position

Width

Value

Description

135

1

0

Start bit

134

1

0

Transmission bit

[133:128]

6

111111

Reserved

[127:1]

127

-

CID or CSD (including internal CRC7)

0

1

1

End bit

The command register contains the command index (six bits sent to a card) and the
command type. These determine whether the command requires a response, and whether
the response is 48 or 136 bits long (see Section 35.8.4 on page 1266). The command path
implements the status flags shown in Table 222:
Table 222. Command path status flags
Flag

Description

CMDREND

Set if response CRC is OK.

CCRCFAIL

Set if response CRC fails.

CMDSENT

Set when command (that does not require response) is sent

CTIMEOUT

Response timeout.

CMDACT

Command transfer in progress.

The CRC generator calculates the CRC checksum for all bits before the CRC code. This
includes the start bit, transmitter bit, command index, and command argument (or card
status). The CRC checksum is calculated for the first 120 bits of CID or CSD for the long
response format. Note that the start bit, transmitter bit and the six reserved bits are not used
in the CRC calculation.
The CRC checksum is a 7-bit value:
CRC[6:0] = Remainder [(M(x) * x7) / G(x)]
G(x) = x7 + x3 + 1
M(x) = (start bit) * x39 + ... + (last bit before CRC) * x0, or
M(x) = (start bit) * x119 + ... + (last bit before CRC) * x0

RM0385 Rev 7

1231/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Data path
The data path subunit transfers data to and from cards. Figure 441 shows a block diagram
of the data path.
Figure 441. Data path
Data path

To control unit

Status
flag

Control
logic

Data
timer

Data FIFO

SDMMC_Din[7:0]

Transmit
CRC

SDMMC_Dout[7:0]

Shift
register
Receive

ai14808b

The card databus width can be programmed using the clock control register. If the 4-bit wide
bus mode is enabled, data is transferred at four bits per clock cycle over all four data signals
(SDMMC_D[3:0]). If the 8-bit wide bus mode is enabled, data is transferred at eight bits per
clock cycle over all eight data signals (SDMMC_D[7:0]). If the wide bus mode is not
enabled, only one bit per clock cycle is transferred over SDMMC_D0.
Depending on the transfer direction (send or receive), the data path state machine (DPSM)
moves to the Wait_S or Wait_R state when it is enabled:
•

Send: the DPSM moves to the Wait_S state. If there is data in the transmit FIFO, the
DPSM moves to the Send state, and the data path subunit starts sending data to a
card.

•

Receive: the DPSM moves to the Wait_R state and waits for a start bit. When it
receives a start bit, the DPSM moves to the Receive state, and the data path subunit
starts receiving data from a card.

Data path state machine (DPSM)
The DPSM operates at SDMMC_CK frequency. Data on the card bus signals is
synchronous to the rising edge of SDMMC_CK. The DPSM has six states, as shown in
Figure 442: Data path state machine (DPSM).

1232/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Figure 442. Data path state machine (DPSM)
On reset

DPSM disabled

Read Wait

DPSM enabled and
Read Wait Started
and SD I/O mode enabled
Disabled or FIFO underrun or
end of data or CRC fail

Idle
Disabled or CRC fail
or timeout

Enable and not send
ReadWait Stop

Disabled or
end of data
Disabled or
Rx FIFO empty or timeout or
start bit error

Busy
Not busy

Enable and send

Wait_R

Data received and
Read Wait Started and
SD I/O mode enabled

End of packet

Wait_S

End of packet or
end of data or
FIFO overrun
Disabled or CRC fail
Start bit

Data ready

Send

Receive
ai14809b

•

Idle: the data path is inactive, and the SDMMC_D[7:0] outputs are in Hi-Z. When the
data control register is written and the enable bit is set, the DPSM loads the data
counter with a new value and, depending on the data direction bit, moves to either the
Wait_S or the Wait_R state.

•

Wait_R: if the data counter equals zero, the DPSM moves to the Idle state when the
receive FIFO is empty. If the data counter is not zero, the DPSM waits for a start bit on
SDMMC_D. The DPSM moves to the Receive state if it receives a start bit before a
timeout, and loads the data block counter. If it reaches a timeout before it detects a
start bit, it moves to the Idle state and sets the timeout status flag.

•

Receive: serial data received from a card is packed in bytes and written to the data
FIFO. Depending on the transfer mode bit in the data control register, the data transfer
mode can be either block or stream:
–

In block mode, when the data block counter reaches zero, the DPSM waits until it
receives the CRC code. If the received code matches the internally generated
CRC code, the DPSM moves to the Wait_R state. If not, the CRC fail status flag is
set and the DPSM moves to the Idle state.

–

In stream mode, the DPSM receives data while the data counter is not zero. When
the counter is zero, the remaining data in the shift register is written to the data
FIFO, and the DPSM moves to the Wait_R state.

If a FIFO overrun error occurs, the DPSM sets the FIFO error flag and moves to the
Idle state:
•

Wait_S: the DPSM moves to the Idle state if the data counter is zero. If not, it waits until
the data FIFO empty flag is deasserted, and moves to the Send state.

RM0385 Rev 7

1233/1709
1280

SD/SDIO/MMC card host interface (SDMMC)
Note:

RM0385

The DPSM remains in the Wait_S state for at least two clock periods to meet the NWR timing
requirements, where NWR is the number of clock cycles between the reception of the card
response and the start of the data transfer from the host.
•

Send: the DPSM starts sending data to a card. Depending on the transfer mode bit in
the data control register, the data transfer mode can be either block or stream:
–

In block mode, when the data block counter reaches zero, the DPSM sends an
internally generated CRC code and end bit, and moves to the Busy state.

–

In stream mode, the DPSM sends data to a card while the enable bit is high and
the data counter is not zero. It then moves to the Idle state.

If a FIFO underrun error occurs, the DPSM sets the FIFO error flag and moves to the
Idle state.
•

Busy: the DPSM waits for the CRC status flag:
–

If it does not receive a positive CRC status, it moves to the Idle state and sets the
CRC fail status flag.

–

If it receives a positive CRC status, it moves to the Wait_S state if SDMMC_D0 is
not low (the card is not busy).

If a timeout occurs while the DPSM is in the Busy state, it sets the data timeout flag and
moves to the Idle state.
The data timer is enabled when the DPSM is in the Wait_R or Busy state, and
generates the data timeout error:

•

–

When transmitting data, the timeout occurs if the DPSM stays in the Busy state for
longer than the programmed timeout period

–

When receiving data, the timeout occurs if the end of the data is not true, and if the
DPSM stays in the Wait_R state for longer than the programmed timeout period.

Data: data can be transferred from the card to the host or vice versa. Data is
transferred via the data lines. They are stored in a FIFO of 32 words, each word is 32
bits wide.
Table 223. Data token format
Description

1234/1709

Start bit

Data

CRC16

End bit

Block Data

0

-

yes

1

Stream Data

0

-

no

1

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)

DPSM Flags
The status of the data path subunit transfer is reported by several status flags
Table 224. DPSM flags
Flag

Description

DBCKEND

Set to high when data block send/receive CRC check is passed.
In SDIO multibyte transfer mode this flag is set at the end of the transfer (a
multibyte transfer is considered as a single block transfer by the host).

DATAEND

Set to high when SDMMC_DCOUNT register decrements and reaches 0.
DATAEND indicates the end of a transfer on SDMMC data line.

DTIMEOUT

Set to high when data timeout period is reached.
When data timer reaches zero while DPSM is in Wait_R or Busy state, timeout is
set. DTIMEOUT can be set after DATAEND if DPSM remains in busy state for
longer than the programmed period.

DCRCFAIL

Set to high when data block send/receive CRC check fails.

Data FIFO
The data FIFO (first-in-first-out) subunit is a data buffer with a transmit and receive unit.
The FIFO contains a 32-bit wide, 32-word deep data buffer, and transmit and receive logic.
Because the data FIFO operates in the APB2 clock domain (PCLK2), all signals from the
subunits in the SDMMC clock domain (SDMMCCLK) are resynchronized.
Depending on the TXACT and RXACT flags, the FIFO can be disabled, transmit enabled, or
receive enabled. TXACT and RXACT are driven by the data path subunit and are mutually
exclusive:

•

–

The transmit FIFO refers to the transmit logic and data buffer when TXACT is
asserted

–

The receive FIFO refers to the receive logic and data buffer when RXACT is
asserted

Transmit FIFO:
Data can be written to the transmit FIFO through the APB2 interface when the SDMMC
is enabled for transmission.
The transmit FIFO is accessible via 32 sequential addresses. The transmit FIFO
contains a data output register that holds the data word pointed to by the read pointer.
When the data path subunit has loaded its shift register, it increments the read pointer
and drives new data out.
If the transmit FIFO is disabled, all status flags are deasserted. The data path subunit
asserts TXACT when it transmits data.

RM0385 Rev 7

1235/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Table 225. Transmit FIFO status flags
Flag

Description

TXFIFOF

Set to high when all 32 transmit FIFO words contain valid data.

TXFIFOE

Set to high when the transmit FIFO does not contain valid data.

TXFIFOHE

Set to high when 8 or more transmit FIFO words are empty. This flag can be used
as a DMA request.

TXDAVL

Set to high when the transmit FIFO contains valid data. This flag is the inverse of
the TXFIFOE flag.

TXUNDERR

Set to high when an underrun error occurs. This flag is cleared by writing to the
SDMMC Clear register.
Note: In case of TXUNDERR, and DMA is used to fill SDMMC FIFO, user
software should disable DMA stream, and then write DMAEN bit in
SDMMC_DCTRL with ‘0’ (to disable DMA request generation).

•

Receive FIFO
When the data path subunit receives a word of data, it drives the data on the write
databus. The write pointer is incremented after the write operation completes. On the
read side, the contents of the FIFO word pointed to by the current value of the read
pointer is driven onto the read databus. If the receive FIFO is disabled, all status flags
are deasserted, and the read and write pointers are reset. The data path subunit
asserts RXACT when it receives data. Table 226 lists the receive FIFO status flags.
The receive FIFO is accessible via 32 sequential addresses.
Table 226. Receive FIFO status flags
Flag

1236/1709

Description

RXFIFOF

Set to high when all 32 receive FIFO words contain valid data

RXFIFOE

Set to high when the receive FIFO does not contain valid data.

RXFIFOHF

Set to high when 8 or more receive FIFO words contain valid data. This flag can be
used as a DMA request.

RXDAVL

Set to high when the receive FIFO is not empty. This flag is the inverse of the
RXFIFOE flag.

RXOVERR

Set to high when an overrun error occurs. This flag is cleared by writing to the
SDMMC Clear register.
Note: In case of RXOVERR, and DMA is used to read SDMMC FIFO, user
software should disable DMA stream, and then write DMAEN bit in
SDMMC_DCTRL with ‘0’ (to disable DMA request generation).

RM0385 Rev 7

RM0385

35.3.2

SD/SDIO/MMC card host interface (SDMMC)

SDMMC APB2 interface
The APB2 interface generates the interrupt and DMA requests, and accesses the SDMMC
adapter registers and the data FIFO. It consists of a data path, register decoder, and
interrupt/DMA logic.

SDMMC interrupts
The interrupt logic generates an interrupt request signal that is asserted when at least one
of the selected status flags is high. A mask register is provided to allow selection of the
conditions that will generate an interrupt. A status flag generates the interrupt request if a
corresponding mask flag is set.

SDMMC/DMA interface
SDMMC APB interface controls all subunit to perform transfers between the host and card

Example of read procedure using DMA
Send CMD17 (READ_BLOCK) as follows:

Note:

a)

Program the SDMMC data length register (SDMMC data timer register should be
already programmed before the card identification process)

b)

Program DMA channel (refer to DMA configuration for SDMMC controller)

c)

Program the SDMMC data control register: DTEN with ‘1’ (SDMMC card host
enabled to send data); DTDIR with ‘1’ (from card to controller); DTMODE with ‘0’
(block data transfer); DMAEN with ‘1’ (DMA enabled); DBLOCKSIZE with 0x9
(512 bytes). Other fields are don’t care.

d)

Program the SDMMC argument register with the address location of the card from
where data is to be transferred

e)

Program the SDMMC command register: CmdIndex with 17(READ_BLOCK);
WaitResp with ‘1’ (SDMMC card host waits for a response); CPSMEN with ‘1’
(SDMMC card host enabled to send a command). Other fields are at their reset
value.

f)

Wait for SDMMC_STA[6] = CMDREND interrupt, (CMDREND is set if there is no
error on command path).

g)

Wait for SDMMC_STA[10] = DBCKEND, (DBCKEND is set in case of no errors
until the CRC check is passed)

h)

Wait until the FIFO is empty, when FIFO is empty the SDMMC_STA[5] =
RXOVERR value has to be check to guarantee that read succeeded

When FIFO overrun error occurs with last 1-4 bytes, it may happens that RXOVERR flag is
set 2 APB clock cycles after DATAEND flag is set. To guarantee success of read operation
RXOVERR must be cheked after FIFO is empty.

RM0385 Rev 7

1237/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Example of write procedure using DMA
Send CMD24 (WRITE_BLOCK) as follows:
a)

Program the SDMMC data length register (SDMMC data timer register should be
already programmed before the card identification process)

b)

Program DMA channel (refer to DMA configuration for SDMMC controller)

c)

Program the SDMMC argument register with the address location of the card from
where data is to be transferred

d)

Program the SDMMC command register: CmdIndex with 24(WRITE_BLOCK);
WaitResp with ‘1’ (SDMMC card host waits for a response); CPSMEN with ‘1’
(SDMMC card host enabled to send a command). Other fields are at their reset
value.

e)

Wait for SDMMC_STA[6] = CMDREND interrupt, then Program the SDMMC data
control register: DTEN with ‘1’ (SDMMC card host enabled to send data); DTDIR
with ‘0’ (from controller to card); DTMODE with ‘0’ (block data transfer); DMAEN
with ‘1’ (DMA enabled); DBLOCKSIZE with 0x9 (512 bytes). Other fields are don’t
care.

f)

Wait for SDMMC_STA[10] = DBCKEND, (DBCKEND is set in case of no errors)

DMA configuration for SDMMC controller

Note:

a)

Enable DMA2 controller and clear any pending interrupts.

b)

Program the DMA2_Stream3 (or DMA2_Stream6) Channel4 source address
register with the memory location base address and DMA2_Stream3 (or
DMA2_Stream6) Channel4 destination address register with the SDMMC_FIFO
register address.

c)

Program DMA2_Stream3 (or DMA2_Stream6) Channel4 control register (memory
increment, not peripheral increment, peripheral and source width is word size).

d)

Program DMA2_Stream3 (or DMA2_Stream6) Channel4 to select the peripheral
as flow controller (set PFCTRL bit in DMA_S3CR (or DMA_S6CR) configuration
register).

e)

Configure the incremental burst transfer to 4 beats (at least from peripheral side)
in DMA2_Stream3 (or DMA2_Stream6) Channel4.

f)

Enable DMA2_Stream3 (or DMA2_Stream6) Channel4

SDMMC host allows only to use the DMA in peripheral flow controller mode. DMA stream
used to serve SDMMC must be configured in peripheral flow controller mode
SDMMC generates only DMA burst requests to DMA controller. DMA must be configured in
incremental burst mode on peripheral side.

35.4

Card functional description

35.4.1

Card identification mode
While in card identification mode the host resets all cards, validates the operation voltage
range, identifies cards and sets a relative card address (RCA) for each card on the bus. All
data communications in the card identification mode use the command line (CMD) only.

1238/1709

RM0385 Rev 7

RM0385

35.4.2

SD/SDIO/MMC card host interface (SDMMC)

Card reset
The GO_IDLE_STATE command (CMD0) is the software reset command and it puts the
MultiMediaCard and SD memory in the Idle state. The IO_RW_DIRECT command (CMD52)
resets the SD I/O card. After power-up or CMD0, all cards output bus drivers are in the highimpedance state and the cards are initialized with a default relative card address
(RCA=0x0001) and with a default driver stage register setting (lowest speed, highest driving
current capability).

35.4.3

Operating voltage range validation
All cards can communicate with the SDMMC card host using any operating voltage within
the specification range. The supported minimum and maximum VDD values are defined in
the operation conditions register (OCR) on the card.
Cards that store the card identification number (CID) and card specific data (CSD) in the
payload memory are able to communicate this information only under data-transfer VDD
conditions. When the SDMMC card host module and the card have incompatible VDD
ranges, the card is not able to complete the identification cycle and cannot send CSD data.
For this purpose, the special commands, SEND_OP_COND (CMD1), SD_APP_OP_COND
(ACMD41 for SD Memory), and IO_SEND_OP_COND (CMD5 for SD I/O), are designed to
provide a mechanism to identify and reject cards that do not match the VDD range desired
by the SDMMC card host. The SDMMC card host sends the required VDD voltage window
as the operand of these commands. Cards that cannot perform data transfer in the specified
range disconnect from the bus and go to the inactive state.
By using these commands without including the voltage range as the operand, the SDMMC
card host can query each card and determine the common voltage range before placing outof-range cards in the inactive state. This query is used when the SDMMC card host is able
to select a common voltage range or when the user requires notification that cards are not
usable.

35.4.4

Card identification process
The card identification process differs for MultiMediaCards and SD cards. For
MultiMediaCard cards, the identification process starts at clock rate Fod. The SDMMC_CMD
line output drivers are open-drain and allow parallel card operation during this process. The
registration process is accomplished as follows:
1.

The bus is activated.

2.

The SDMMC card host broadcasts SEND_OP_COND (CMD1) to receive operation
conditions.

3.

The response is the wired AND operation of the operation condition registers from all
cards.

4.

Incompatible cards are placed in the inactive state.

5.

The SDMMC card host broadcasts ALL_SEND_CID (CMD2) to all active cards.

6.

The active cards simultaneously send their CID numbers serially. Cards with outgoing
CID bits that do not match the bits on the command line stop transmitting and must wait
for the next identification cycle. One card successfully transmits a full CID to the
SDMMC card host and enters the Identification state.

7.

The SDMMC card host issues SET_RELATIVE_ADDR (CMD3) to that card. This new
address is called the relative card address (RCA); it is shorter than the CID and

RM0385 Rev 7

1239/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

addresses the card. The assigned card changes to the Standby state, it does not react
to further identification cycles, and its output switches from open-drain to push-pull.
8.

The SDMMC card host repeats steps 5 through 7 until it receives a timeout condition.

For the SD card, the identification process starts at clock rate Fod, and the SDMMC_CMD
line output drives are push-pull drivers instead of open-drain. The registration process is
accomplished as follows:
1.

The bus is activated.

2.

The SDMMC card host broadcasts SD_APP_OP_COND (ACMD41).

3.

The cards respond with the contents of their operation condition registers.

4.

The incompatible cards are placed in the inactive state.

5.

The SDMMC card host broadcasts ALL_SEND_CID (CMD2) to all active cards.

6.

The cards send back their unique card identification numbers (CIDs) and enter the
Identification state.

7.

The SDMMC card host issues SET_RELATIVE_ADDR (CMD3) to an active card with
an address. This new address is called the relative card address (RCA); it is shorter
than the CID and addresses the card. The assigned card changes to the Standby state.
The SDMMC card host can reissue this command to change the RCA. The RCA of the
card is the last assigned value.

8.

The SDMMC card host repeats steps 5 through 7 with all active cards.

For the SD I/O card, the registration process is accomplished as follows:

35.4.5

1.

The bus is activated.

2.

The SDMMC card host sends IO_SEND_OP_COND (CMD5).

3.

The cards respond with the contents of their operation condition registers.

4.

The incompatible cards are set to the inactive state.

5.

The SDMMC card host issues SET_RELATIVE_ADDR (CMD3) to an active card with
an address. This new address is called the relative card address (RCA); it is shorter
than the CID and addresses the card. The assigned card changes to the Standby state.
The SDMMC card host can reissue this command to change the RCA. The RCA of the
card is the last assigned value.

Block write
During block write (CMD24 - 27) one or more blocks of data are transferred from the host to
the card with a CRC appended to the end of each block by the host. A card supporting block
write is always able to accept a block of data defined by WRITE_BL_LEN. If the CRC fails,
the card indicates the failure on the SDMMC_D line and the transferred data are discarded
and not written, and all further transmitted blocks (in multiple block write mode) are ignored.
If the host uses partial blocks whose accumulated length is not block aligned and, block
misalignment is not allowed (CSD parameter WRITE_BLK_MISALIGN is not set), the card
will detect the block misalignment error before the beginning of the first misaligned block.
(ADDRESS_ERROR error bit is set in the status register). The write operation will also be
aborted if the host tries to write over a write-protected area. In this case, however, the card
will set the WP_VIOLATION bit.
Programming of the CID and CSD registers does not require a previous block length setting.
The transferred data is also CRC protected. If a part of the CSD or CID register is stored in
ROM, then this unchangeable part must match the corresponding part of the receive buffer.
If this match fails, then the card reports an error and does not change any register contents.

1240/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Some cards may require long and unpredictable times to write a block of data. After
receiving a block of data and completing the CRC check, the card begins writing and holds
the SDMMC_D line low if its write buffer is full and unable to accept new data from a new
WRITE_BLOCK command. The host may poll the status of the card with a SEND_STATUS
command (CMD13) at any time, and the card will respond with its status. The
READY_FOR_DATA status bit indicates whether the card can accept new data or whether
the write process is still in progress. The host may deselect the card by issuing CMD7 (to
select a different card), which will place the card in the Disconnect state and release the
SDMMC_D line(s) without interrupting the write operation. When reselecting the card, it will
reactivate busy indication by pulling SDMMC_D to low if programming is still in progress and
the write buffer is unavailable.

35.4.6

Block read
In Block read mode the basic unit of data transfer is a block whose maximum size is defined
in the CSD (READ_BL_LEN). If READ_BL_PARTIAL is set, smaller blocks whose start and
end addresses are entirely contained within one physical block (as defined by
READ_BL_LEN) may also be transmitted. A CRC is appended to the end of each block,
ensuring data transfer integrity. CMD17 (READ_SINGLE_BLOCK) initiates a block read and
after completing the transfer, the card returns to the Transfer state.
CMD18 (READ_MULTIPLE_BLOCK) starts a transfer of several consecutive blocks.
The host can abort reading at any time, within a multiple block operation, regardless of its
type. Transaction abort is done by sending the stop transmission command.
If the card detects an error (for example, out of range, address misalignment or internal
error) during a multiple block read operation (both types) it stops the data transmission and
remains in the data state. The host must than abort the operation by sending the stop
transmission command. The read error is reported in the response to the stop transmission
command.
If the host sends a stop transmission command after the card transmits the last block of a
multiple block operation with a predefined number of blocks, it is responded to as an illegal
command, since the card is no longer in the data state. If the host uses partial blocks whose
accumulated length is not block-aligned and block misalignment is not allowed, the card
detects a block misalignment error condition at the beginning of the first misaligned block
(ADDRESS_ERROR error bit is set in the status register).

35.4.7

Stream access, stream write and stream read
(MultiMediaCard only)
In stream mode, data is transferred in bytes and no CRC is appended at the end of each
block.

Stream write (MultiMediaCard only)
WRITE_DAT_UNTIL_STOP (CMD20) starts the data transfer from the SDMMC card host to
the card, beginning at the specified address and continuing until the SDMMC card host
issues a stop command. When partial blocks are allowed (CSD parameter
WRITE_BL_PARTIAL is set), the data stream can start and stop at any address within the
card address space, otherwise it can only start and stop at block boundaries. Because the
amount of data to be transferred is not determined in advance, a CRC cannot be used.
When the end of the memory range is reached while sending data and no stop command is
sent by the SDMMC card host, any additional transferred data are discarded.
RM0385 Rev 7

1241/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

The maximum clock frequency for a stream write operation is given by the following
equation fields of the card-specific data register:
8 × 2 writebllen ) ( – NSAC ))
Maximumspeed = MIN (TRANSPEED,(------------------------------------------------------------------------TAAC × R2WFACTOR

•

Maximumspeed = maximum write frequency

•

TRANSPEED = maximum data transfer rate

•

writebllen = maximum write data block length

•

NSAC = data read access time 2 in CLK cycles

•

TAAC = data read access time 1

•

R2WFACTOR = write speed factor

If the host attempts to use a higher frequency, the card may not be able to process the data
and stop programming, set the OVERRUN error bit in the status register, and while ignoring
all further data transfer, wait (in the receive data state) for a stop command. The write
operation is also aborted if the host tries to write over a write-protected area. In this case,
however, the card sets the WP_VIOLATION bit.

Stream read (MultiMediaCard only)
READ_DAT_UNTIL_STOP (CMD11) controls a stream-oriented data transfer.
This command instructs the card to send its data, starting at a specified address, until the
SDMMC card host sends STOP_TRANSMISSION (CMD12). The stop command has an
execution delay due to the serial command transmission and the data transfer stops after
the end bit of the stop command. When the end of the memory range is reached while
sending data and no stop command is sent by the SDMMC card host, any subsequent data
sent are considered undefined.
The maximum clock frequency for a stream read operation is given by the following
equation and uses fields of the card specific data register.
( 8 × 2 readbllen ) ( – NSAC ))
Maximumspeed = MIN (TRANSPEED,-----------------------------------------------------------------------TAAC × R2WFACTOR

•

Maximumspeed = maximum read frequency

•

TRANSPEED = maximum data transfer rate

•

readbllen = maximum read data block length

•

writebllen = maximum write data block length

•

NSAC = data read access time 2 in CLK cycles

•

TAAC = data read access time 1

•

R2WFACTOR = write speed factor

If the host attempts to use a higher frequency, the card is not able to sustain data transfer. If
this happens, the card sets the UNDERRUN error bit in the status register, aborts the
transmission and waits in the data state for a stop command.

1242/1709

RM0385 Rev 7

RM0385

35.4.8

SD/SDIO/MMC card host interface (SDMMC)

Erase: group erase and sector erase
The erasable unit of the MultiMediaCard is the erase group. The erase group is measured in
write blocks, which are the basic writable units of the card. The size of the erase group is a
card-specific parameter and defined in the CSD.
The host can erase a contiguous range of Erase Groups. Starting the erase process is a
three-step sequence.
First the host defines the start address of the range using the ERASE_GROUP_START
(CMD35) command, next it defines the last address of the range using the
ERASE_GROUP_END (CMD36) command and, finally, it starts the erase process by
issuing the ERASE (CMD38) command. The address field in the erase commands is an
Erase Group address in byte units. The card ignores all LSBs below the Erase Group size,
effectively rounding the address down to the Erase Group boundary.
If an erase command is received out of sequence, the card sets the ERASE_SEQ_ERROR
bit in the status register and resets the whole sequence.
If an out-of-sequence (neither of the erase commands, except SEND_STATUS) command
received, the card sets the ERASE_RESET status bit in the status register, resets the erase
sequence and executes the last command.
If the erase range includes write protected blocks, they are left intact and only nonprotected
blocks are erased. The WP_ERASE_SKIP status bit in the status register is set.
The card indicates that an erase is in progress by holding SDMMC_D low. The actual erase
time may be quite long, and the host may issue CMD7 to deselect the card.

35.4.9

Wide bus selection or deselection
Wide bus (4-bit bus width) operation mode is selected or deselected using
SET_BUS_WIDTH (ACMD6). The default bus width after power-up or GO_IDLE_STATE
(CMD0) is 1 bit. SET_BUS_WIDTH (ACMD6) is only valid in a transfer state, which means
that the bus width can be changed only after a card is selected by
SELECT/DESELECT_CARD (CMD7).

35.4.10

Protection management
Three write protection methods for the cards are supported in the SDMMC card host
module:
1.

internal card write protection (card responsibility)

2.

mechanical write protection switch (SDMMC card host module responsibility only)

3.

password-protected card lock operation

Internal card write protection
Card data can be protected against write and erase. By setting the permanent or temporary
write-protect bits in the CSD, the entire card can be permanently write-protected by the
manufacturer or content provider. For cards that support write protection of groups of
sectors by setting the WP_GRP_ENABLE bit in the CSD, portions of the data can be
protected, and the write protection can be changed by the application. The write protection
is in units of WP_GRP_SIZE sectors as specified in the CSD. The SET_WRITE_PROT and
CLR_WRITE_PROT commands control the protection of the addressed group. The
SEND_WRITE_PROT command is similar to a single block read command. The card sends

RM0385 Rev 7

1243/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

a data block containing 32 write protection bits (representing 32 write protect groups starting
at the specified address) followed by 16 CRC bits. The address field in the write protect
commands is a group address in byte units.
The card ignores all LSBs below the group size.

Mechanical write protect switch
A mechanical sliding tab on the side of the card allows the user to set or clear the write
protection on a card. When the sliding tab is positioned with the window open, the card is
write-protected, and when the window is closed, the card contents can be changed. A
matched switch on the socket side indicates to the SDMMC card host module that the card
is write-protected. The SDMMC card host module is responsible for protecting the card. The
position of the write protect switch is unknown to the internal circuitry of the card.

Password protect
The password protection feature enables the SDMMC card host module to lock and unlock
a card with a password. The password is stored in the 128-bit PWD register and its size is
set in the 8-bit PWD_LEN register. These registers are nonvolatile so that a power cycle
does not erase them. Locked cards respond to and execute certain commands. This means
that the SDMMC card host module is allowed to reset, initialize, select, and query for status,
however it is not allowed to access data on the card. When the password is set (as indicated
by a nonzero value of PWD_LEN), the card is locked automatically after power-up. As with
the CSD and CID register write commands, the lock/unlock commands are available in the
transfer state only. In this state, the command does not include an address argument and
the card must be selected before using it. The card lock/unlock commands have the
structure and bus transaction types of a regular single-block write command. The
transferred data block includes all of the required information for the command (the
password setting mode, the PWD itself, and card lock/unlock). The command data block
size is defined by the SDMMC card host module before it sends the card lock/unlock
command, and has the structure shown in Table 240.
The bit settings are as follows:
•

ERASE: setting it forces an erase operation. All other bits must be zero, and only the
command byte is sent

•

LOCK_UNLOCK: setting it locks the card. LOCK_UNLOCK can be set simultaneously
with SET_PWD, however not with CLR_PWD

•

CLR_PWD: setting it clears the password data

•

SET_PWD: setting it saves the password data to memory

•

PWD_LEN: it defines the length of the password in bytes

•

PWD: the password (new or currently used, depending on the command)

The following sections list the command sequences to set/reset a password, lock/unlock the
card, and force an erase.

Setting the password

1244/1709

1.

Select a card (SELECT/DESELECT_CARD, CMD7), if none is already selected.

2.

Define the block length (SET_BLOCKLEN, CMD16) to send, given by the 8-bit card
lock/unlock mode, the 8-bit PWD_LEN, and the number of bytes of the new password.

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
When a password replacement is done, the block size must take into account that both
the old and the new passwords are sent with the command.
3.

Send LOCK/UNLOCK (CMD42) with the appropriate data block size on the data line
including the 16-bit CRC. The data block indicates the mode (SET_PWD = 1), the
length (PWD_LEN), and the password (PWD) itself. When a password replacement is
done, the length value (PWD_LEN) includes the length of both passwords, the old and
the new one, and the PWD field includes the old password (currently used) followed by
the new password.

4.

When the password is matched, the new password and its size are saved into the PWD
and PWD_LEN fields, respectively. When the old password sent does not correspond
(in size and/or content) to the expected password, the LOCK_UNLOCK_FAILED error
bit is set in the card status register, and the password is not changed.

The password length field (PWD_LEN) indicates whether a password is currently set. When
this field is nonzero, there is a password set and the card locks itself after power-up. It is
possible to lock the card immediately in the current power session by setting the
LOCK_UNLOCK bit (while setting the password) or sending an additional command for card
locking.

Resetting the password
1.

Select a card (SELECT/DESELECT_CARD, CMD7), if none is already selected.

2.

Define the block length (SET_BLOCKLEN, CMD16) to send, given by the 8-bit card
lock/unlock mode, the 8-bit PWD_LEN, and the number of bytes in the currently used
password.

3.

Send LOCK/UNLOCK (CMD42) with the appropriate data block size on the data line
including the 16-bit CRC. The data block indicates the mode (CLR_PWD = 1), the
length (PWD_LEN) and the password (PWD) itself. The LOCK_UNLOCK bit is ignored.

4.

When the password is matched, the PWD field is cleared and PWD_LEN is set to 0.
When the password sent does not correspond (in size and/or content) to the expected
password, the LOCK_UNLOCK_FAILED error bit is set in the card status register, and
the password is not changed.

Locking a card
1.

Select a card (SELECT/DESELECT_CARD, CMD7), if none is already selected.

2.

Define the block length (SET_BLOCKLEN, CMD16) to send, given by the 8-bit card
lock/unlock mode (byte 0 in Table 240), the 8-bit PWD_LEN, and the number of bytes
of the current password.

3.

Send LOCK/UNLOCK (CMD42) with the appropriate data block size on the data line
including the 16-bit CRC. The data block indicates the mode (LOCK_UNLOCK = 1), the
length (PWD_LEN), and the password (PWD) itself.

4.

When the password is matched, the card is locked and the CARD_IS_LOCKED status
bit is set in the card status register. When the password sent does not correspond (in
size and/or content) to the expected password, the LOCK_UNLOCK_FAILED error bit
is set in the card status register, and the lock fails.

It is possible to set the password and to lock the card in the same sequence. In this case,
the SDMMC card host module performs all the required steps for setting the password (see
Setting the password on page 1244), however it is necessary to set the LOCK_UNLOCK bit
in Step 3 when the new password command is sent.

RM0385 Rev 7

1245/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

When the password is previously set (PWD_LEN is not 0), the card is locked automatically
after power on reset. An attempt to lock a locked card or to lock a card that does not have a
password fails and the LOCK_UNLOCK_FAILED error bit is set in the card status register.

Unlocking the card
1.

Select a card (SELECT/DESELECT_CARD, CMD7), if none is already selected.

2.

Define the block length (SET_BLOCKLEN, CMD16) to send, given by the 8-bit
cardlock/unlock mode (byte 0 in Table 240), the 8-bit PWD_LEN, and the number of
bytes of the current password.

3.

Send LOCK/UNLOCK (CMD42) with the appropriate data block size on the data line
including the 16-bit CRC. The data block indicates the mode (LOCK_UNLOCK = 0), the
length (PWD_LEN), and the password (PWD) itself.

4.

When the password is matched, the card is unlocked and the CARD_IS_LOCKED
status bit is cleared in the card status register. When the password sent is not correct in
size and/or content and does not correspond to the expected password, the
LOCK_UNLOCK_FAILED error bit is set in the card status register, and the card
remains locked.

The unlocking function is only valid for the current power session. When the PWD field is not
clear, the card is locked automatically on the next power-up.
An attempt to unlock an unlocked card fails and the LOCK_UNLOCK_FAILED error bit is set
in the card status register.

Forcing erase
If the user has forgotten the password (PWD content), it is possible to access the card after
clearing all the data on the card. This forced erase operation erases all card data and all
password data.
1.

Select a card (SELECT/DESELECT_CARD, CMD7), if none is already selected.

2.

Set the block length (SET_BLOCKLEN, CMD16) to 1 byte. Only the 8-bit card
lock/unlock byte (byte 0 in Table 240) is sent.

3.

Send LOCK/UNLOCK (CMD42) with the appropriate data byte on the data line
including the 16-bit CRC. The data block indicates the mode (ERASE = 1). All other bits
must be zero.

4.

When the ERASE bit is the only bit set in the data field, all card contents are erased,
including the PWD and PWD_LEN fields, and the card is no longer locked. When any
other bits are set, the LOCK_UNLOCK_FAILED error bit is set in the card status
register and the card retains all of its data, and remains locked.

An attempt to use a force erase on an unlocked card fails and the LOCK_UNLOCK_FAILED
error bit is set in the card status register.

1246/1709

RM0385 Rev 7

RM0385

35.4.11

SD/SDIO/MMC card host interface (SDMMC)

Card status register
The response format R1 contains a 32-bit field named card status. This field is intended to
transmit the card status information (which may be stored in a local status register) to the
host. If not specified otherwise, the status entries are always related to the previously issued
command.
Table 227 defines the different entries of the status. The type and clear condition fields in
the table are abbreviated as follows:
Type:
•

E: error bit

•

S: status bit

•

R: detected and set for the actual command response

•

X: detected and set during command execution. The SDMMC card host must poll the
card by issuing the status command to read these bits.

Clear condition:
•

A: according to the card current state

•

B: always related to the previous command. Reception of a valid command clears it
(with a delay of one command)

•

C: clear by read
Table 227. Card status

Bits

31

30

29

Identifier

ADDRESS_
OUT_OF_RANGE

ADDRESS_MISALIGN

BLOCK_LEN_ERROR

Type

ERX

-

-

Value

Description

Clear
condition

’0’= no error
’1’= error

The command address argument was out
of the allowed range for this card.
A multiple block or stream read/write
C
operation is (although started in a valid
address) attempting to read or write
beyond the card capacity.

’0’= no error
’1’= error

The commands address argument (in
accordance with the currently set block
length) positions the first data block
misaligned to the card physical blocks.
A multiple block read/write operation
(although started with a valid
address/block-length combination) is
attempting to read or write a data block
which is not aligned with the physical
blocks of the card.

’0’= no error
’1’= error

Either the argument of a
SET_BLOCKLEN command exceeds the
maximum value allowed for the card, or
the previously defined block length is
illegal for the current command (e.g. the C
host issues a write command, the current
block length is smaller than the maximum
allowed value for the card and it is not
allowed to write partial blocks)

RM0385 Rev 7

C

1247/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Table 227. Card status (continued)
Bits

Identifier

Type

Value

Description

Clear
condition

-

’0’= no error
’1’= error

An error in the sequence of erase
commands occurred.

C

ERASE_PARAM

EX

’0’= no error
’1’= error

An invalid selection of erase groups for
erase occurred.

C

26

WP_VIOLATION

EX

’0’= no error
’1’= error

Attempt to program a write-protected
block.

25

CARD_IS_LOCKED

SR

‘0’ = card
unlocked
‘1’ = card locked

When set, signals that the card is locked
by the host

A

24

LOCK_UNLOCK_
FAILED

EX

’0’= no error
’1’= error

Set when a sequence or password error
has been detected in lock/unlock card
command

C

23

COM_CRC_ERROR

ER

’0’= no error
’1’= error

The CRC check of the previous command
B
failed.

22

ILLEGAL_COMMAND

ER

’0’= no error
’1’= error

Command not legal for the card state

B

21

CARD_ECC_FAILED

EX

’0’= success
’1’= failure

Card internal ECC was applied but failed
to correct the data.

C

20

CC_ERROR

ER

’0’= no error
’1’= error

(Undefined by the standard) A card error
occurred, which is not related to the host
command.

C

EX

’0’= no error
’1’= error

(Undefined by the standard) A generic
card error related to the (and detected
during) execution of the last host
command (e.g. read or write failures).

C

Can be either of the following errors:
– The CID register has already been
written and cannot be overwritten
– The read-only section of the CSD does
C
not match the card contents
– An attempt to reverse the copy (set as
original) or permanent WP
(unprotected) bits was made

28

ERASE_SEQ_ERROR

27

19

ERROR

18

Reserved

17

Reserved

16

CID/CSD_OVERWRITE

EX

’0’= no error ‘1’=
error

15

WP_ERASE_SKIP

EX

’0’= not protected Set when only partial address space
’1’= protected
was erased due to existing write

14

CARD_ECC_DISABLED S X

1248/1709

’0’= enabled
’1’= disabled

C

C

The command has been executed without
A
using the internal ECC.

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Table 227. Card status (continued)

Bits

13

Identifier

ERASE_RESET

Type

-

Value

Description

Clear
condition

’0’= cleared
’1’= set

An erase sequence was cleared before
executing because an out of erase
sequence command was received
(commands other than CMD35, CMD36,
CMD38 or CMD13)

The state of the card when receiving the
command. If the command execution
causes a state change, it will be visible to
B
the host in the response on the next
command. The four bits are interpreted as
a binary number between 0 and 15.

C

12:9

CURRENT_STATE

SR

0 = Idle
1 = Ready
2 = Ident
3 = Stby
4 = Tran
5 = Data
6 = Rcv
7 = Prg
8 = Dis
9 = Btst
10-15 = reserved

8

READY_FOR_DATA

SR

’0’= not ready
‘1’ = ready

Corresponds to buffer empty signalling on
the bus

7

SWITCH_ERROR

EX

’0’= no error
’1’= switch error

If set, the card did not switch to the
expected mode as requested by the
SWITCH command

B

6

Reserved

5

APP_CMD

SR

‘0’ = Disabled
‘1’ = Enabled

The card will expect ACMD, or an
indication that the command has been
interpreted as ACMD

C

4

Reserved for SD I/O Card

3

AKE_SEQ_ERROR

ER

’0’= no error
’1’= error

Error in the sequence of the
authentication process

C

2

Reserved for application specific commands

1
0

Reserved for manufacturer test mode

RM0385 Rev 7

1249/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

35.4.12

RM0385

SD status register
The SD status contains status bits that are related to the SD memory card proprietary
features and may be used for future application-specific usage. The size of the SD Status is
one data block of 512 bits. The contents of this register are transmitted to the SDMMC card
host if ACMD13 is sent (CMD55 followed with CMD13). ACMD13 can be sent to a card in
transfer state only (card is selected).
Table 228 defines the different entries of the SD status register. The type and clear condition
fields in the table are abbreviated as follows:
Type:
•

E: error bit

•

S: status bit

•

R: detected and set for the actual command response

•

X: detected and set during command execution. The SDMMC card Host must poll the
card by issuing the status command to read these bits

Clear condition:
•

A: according to the card current state

•

B: always related to the previous command. Reception of a valid command clears it
(with a delay of one command)

•

C: clear by read
Table 228. SD status

Bits

Identifier

Type

Value

Description

Clear
condition

511: 510 DAT_BUS_WIDTH S R

’00’= 1 (default)
‘01’= reserved
‘10’= 4 bit width
‘11’= reserved

Shows the currently defined
databus width that was
defined by
SET_BUS_WIDTH
command

A

509

’0’= Not in the mode
’1’= In Secured Mode

Card is in Secured Mode of
operation (refer to the “SD
Security Specification”).

A

’00xxh’= SD Memory Cards as
defined in Physical Spec Ver1.012.00 (’x’= don’t care). The
following cards are currently
defined:
’0000’= Regular SD RD/WR Card.
’0001’= SD ROM Card

In the future, the 8 LSBs will
be used to define different
variations of an SD memory
card (each bit will define
different SD types). The 8
A
MSBs will be used to define
SD Cards that do not comply
with current SD physical
layer specification.

Size of protected area (See
below)

(See below)

A

Speed Class of the card (See
below)

(See below)

A

SECURED_MODE S R

508: 496 Reserved

495: 480 SD_CARD_TYPE

479: 448

SIZE_OF_PROTE
SR
CT ED_AREA

447: 440 SPEED_CLASS

1250/1709

SR

SR

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Table 228. SD status (continued)

Bits

Identifier

Type

Value

Description

Clear
condition

439: 432

PERFORMANCE_
SR
MOVE

Performance of move indicated by
1 [MB/s] step.
(See below)
(See below)

A

431:428

AU_SIZE

SR

Size of AU
(See below)

(See below)

A

427:424

Reserved

423:408

ERASE_SIZE

SR

Number of AUs to be erased at a
time

(See below)

A

407:402

ERASE_TIMEOUT S R

Timeout value for erasing areas
specified by
UNIT_OF_ERASE_AU

(See below)

A

401:400

ERASE_OFFSET

Fixed offset value added to erase
(See below)
time.

A

399:312

Reserved

311:0

Reserved for Manufacturer

SR

SIZE_OF_PROTECTED_AREA
Setting this field differs between standard- and high-capacity cards. In the case of a
standard-capacity card, the capacity of protected area is calculated as follows:
Protected area = SIZE_OF_PROTECTED_AREA_* MULT * BLOCK_LEN.
SIZE_OF_PROTECTED_AREA is specified by the unit in MULT*BLOCK_LEN.
In the case of a high-capacity card, the capacity of protected area is specified in this field:
Protected area = SIZE_OF_PROTECTED_AREA
SIZE_OF_PROTECTED_AREA is specified by the unit in bytes.

SPEED_CLASS
This 8-bit field indicates the speed class and the value can be calculated by PW/2 (where
PW is the write performance).
Table 229. Speed class code field
SPEED_CLASS

Value definition

00h

Class 0

01h

Class 2

02h

Class 4

03h

Class 6

04h – FFh

Reserved

RM0385 Rev 7

1251/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

PERFORMANCE_MOVE
This 8-bit field indicates Pm (performance move) and the value can be set by 1 [MB/sec]
steps. If the card does not move used RUs (recording units), Pm should be considered as
infinity. Setting the field to FFh means infinity.
Table 230. Performance move field
PERFORMANCE_MOVE

Value definition

00h

Not defined

01h

1 [MB/sec]

02h

02h 2 [MB/sec]

---------

---------

FEh

254 [MB/sec]

FFh

Infinity

AU_SIZE
This 4-bit field indicates the AU size and the value can be selected in the power of 2 base
from 16 KB.
Table 231. AU_SIZE field
AU_SIZE

Value definition

00h

Not defined

01h

16 KB

02h

32 KB

03h

64 KB

04h

128 KB

05h

256 KB

06h

512 KB

07h

1 MB

08h

2 MB

09h

4 MB

Ah – Fh

Reserved

The maximum AU size, which depends on the card capacity, is defined in Table 232. The
card can be set to any AU size between RU size and maximum AU size.
Table 232. Maximum AU size

1252/1709

Capacity

16 MB-64 MB

128 MB-256 MB

512 MB

1 GB-32 GB

Maximum AU Size

512 KB

1 MB

2 MB

4 MB

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)

ERASE_SIZE
This 16-bit field indicates NERASE. When NERASE numbers of AUs are erased, the timeout
value is specified by ERASE_TIMEOUT (Refer to ERASE_TIMEOUT). The host should
determine the proper number of AUs to be erased in one operation so that the host can
show the progress of the erase operation. If this field is set to 0, the erase timeout
calculation is not supported.
Table 233. Erase size field
ERASE_SIZE

Value definition

0000h

Erase timeout calculation is not supported.

0001h

1 AU

0002h

2 AU

0003h

3 AU

---------

---------

FFFFh

65535 AU

ERASE_TIMEOUT
This 6-bit field indicates TERASE and the value indicates the erase timeout from offset when
multiple AUs are being erased as specified by ERASE_SIZE. The range of
ERASE_TIMEOUT can be defined as up to 63 seconds and the card manufacturer can
choose any combination of ERASE_SIZE and ERASE_TIMEOUT depending on the
implementation. Determining ERASE_TIMEOUT determines the ERASE_SIZE.
Table 234. Erase timeout field
ERASE_TIMEOUT

Value definition

00

Erase timeout calculation is not supported.

01

1 [sec]

02

2 [sec]

03

3 [sec]

---------

---------

63

63 [sec]

ERASE_OFFSET
This 2-bit field indicates TOFFSET and one of four values can be selected. This field is
meaningless if the ERASE_SIZE and ERASE_TIMEOUT fields are set to 0.
Table 235. Erase offset field
ERASE_OFFSET

Value definition

0h

0 [sec]

1h

1 [sec]

RM0385 Rev 7

1253/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Table 235. Erase offset field (continued)
ERASE_OFFSET

35.4.13

Value definition

2h

2 [sec]

3h

3 [sec]

SD I/O mode
SD I/O interrupts
To allow the SD I/O card to interrupt the MultiMediaCard/SD module, an interrupt function is
available on a pin on the SD interface. Pin 8, used as SDMMC_D1 when operating in the 4bit SD mode, signals the cards interrupt to the MultiMediaCard/SD module. The use of the
interrupt is optional for each card or function within a card. The SD I/O interrupt is levelsensitive, which means that the interrupt line must be held active (low) until it is either
recognized and acted upon by the MultiMediaCard/SD module or deasserted due to the end
of the interrupt period. After the MultiMediaCard/SD module has serviced the interrupt, the
interrupt status bit is cleared via an I/O write to the appropriate bit in the SD I/O card’s
internal registers. The interrupt output of all SD I/O cards is active low and the application
must provide pull-up resistors externally on all data lines (SDMMC_D[3:0]). The
MultiMediaCard/SD module samples the level of pin 8 (SDMMC_D/IRQ) into the interrupt
detector only during the interrupt period. At all other times, the MultiMediaCard/SD module
ignores this value.
The interrupt period is applicable for both memory and I/O operations. The definition of the
interrupt period for operations with single blocks is different from the definition for multipleblock data transfers.

SD I/O suspend and resume
Within a multifunction SD I/O or a card with both I/O and memory functions, there are
multiple devices (I/O and memory) that share access to the MMC/SD bus. To share access
to the MMC/SD module among multiple devices, SD I/O and combo cards optionally
implement the concept of suspend/resume. When a card supports suspend/resume, the
MMC/SD module can temporarily halt a data transfer operation to one function or memory
(suspend) to free the bus for a higher-priority transfer to a different function or memory. After
this higher-priority transfer is complete, the original transfer is resumed (restarted) where it
left off. Support of suspend/resume is optional on a per-card basis. To perform the
suspend/resume operation on the MMC/SD bus, the MMC/SD module performs the
following steps:
1.

Determines the function currently using the SDMMC_D [3:0] line(s)

2.

Requests the lower-priority or slower transaction to suspend

3.

Waits for the transaction suspension to complete

4.

Begins the higher-priority transaction

5.

Waits for the completion of the higher priority transaction

6.

Restores the suspended transaction

SD I/O ReadWait
The optional ReadWait (RW) operation is defined only for the SD 1-bit and 4-bit modes. The
ReadWait operation allows the MMC/SD module to signal a card that it is reading multiple

1254/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
registers (IO_RW_EXTENDED, CMD53) to temporarily stall the data transfer while allowing
the MMC/SD module to send commands to any function within the SD I/O device. To
determine when a card supports the ReadWait protocol, the MMC/SD module must test
capability bits in the internal card registers. The timing for ReadWait is based on the
interrupt period.

35.4.14

Commands and responses
Application-specific and general commands
The SDMMC card host module system is designed to provide a standard interface for a
variety of applications types. In this environment, there is a need for specific
customer/application features. To implement these features, two types of generic
commands are defined in the standard: application-specific commands (ACMD) and general
commands (GEN_CMD).
When the card receives the APP_CMD (CMD55) command, the card expects the next
command to be an application-specific command. ACMDs have the same structure as
regular MultiMediaCard commands and can have the same CMD number. The card
recognizes it as ACMD because it appears after APP_CMD (CMD55). When the command
immediately following the APP_CMD (CMD55) is not a defined application-specific
command, the standard command is used. For example, when the card has a definition for
SD_STATUS (ACMD13), and receives CMD13 immediately following APP_CMD (CMD55),
this is interpreted as SD_STATUS (ACMD13). However, when the card receives CMD7
immediately following APP_CMD (CMD55) and the card does not have a definition for
ACMD7, this is interpreted as the standard (SELECT/DESELECT_CARD) CMD7.
To use one of the manufacturer-specific ACMDs the SD card Host must perform the
following steps:
1.

Send APP_CMD (CMD55)
The card responds to the MultiMediaCard/SD module, indicating that the APP_CMD bit
is set and an ACMD is now expected.

2.

Send the required ACMD
The card responds to the MultiMediaCard/SD module, indicating that the APP_CMD bit
is set and that the accepted command is interpreted as an ACMD. When a nonACMD
is sent, it is handled by the card as a normal MultiMediaCard command and the
APP_CMD bit in the card status register stays clear.

When an invalid command is sent (neither ACMD nor CMD) it is handled as a standard
MultiMediaCard illegal command error.
The bus transaction for a GEN_CMD is the same as the single-block read or write
commands (WRITE_BLOCK, CMD24 or READ_SINGLE_BLOCK,CMD17). In this case, the
argument denotes the direction of the data transfer rather than the address, and the data
block has vendor-specific format and meaning.
The card must be selected (in transfer state) before sending GEN_CMD (CMD56). The data
block size is defined by SET_BLOCKLEN (CMD16). The response to GEN_CMD (CMD56)
is in R1b format.

RM0385 Rev 7

1255/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Command types
Both application-specific and general commands are divided into the four following types:
•

broadcast command (BC): sent to all cards; no responses returned.

•

broadcast command with response (BCR): sent to all cards; responses received
from all cards simultaneously.

•

addressed (point-to-point) command (AC): sent to the card that is selected; does
not include a data transfer on the SDMMC_D line(s).

•

addressed (point-to-point) data transfer command (ADTC): sent to the card that is
selected; includes a data transfer on the SDMMC_D line(s).

Command formats
See Table 219 on page 1230 for command formats.

Commands for the MultiMediaCard/SD module
Table 236. Block-oriented write commands
CMD
index

Type

Argument

Response
format

Abbreviation

Description

CMD23 ac

[31:16] set to 0
[15:0] number R1
of blocks

SET_BLOCK_COUNT

Defines the number of blocks which
are going to be transferred in the
multiple-block read or write command
that follows.

CMD24 adtc

[31:0] data
address

R1

WRITE_BLOCK

Writes a block of the size selected by
the SET_BLOCKLEN command.

CMD25 adtc

[31:0] data
address

R1

Continuously writes blocks of data
until a STOP_TRANSMISSION
WRITE_MULTIPLE_BLOCK
follows or the requested number of
blocks has been received.

CMD26 adtc

[31:0] stuff bits R1

PROGRAM_CID

Programming of the card identification
register. This command must be
issued only once per card. The card
contains hardware to prevent this
operation after the first programming.
Normally this command is reserved
for manufacturer.

CMD27 adtc

[31:0] stuff bits R1

PROGRAM_CSD

Programming of the programmable
bits of the CSD.

1256/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Table 237. Block-oriented write protection commands

CMD
index

Type

Argument

Response
format

Abbreviation

Description

CMD28 ac

[31:0] data
address

R1b

SET_WRITE_PROT

If the card has write protection features,
this command sets the write protection bit
of the addressed group. The properties of
write protection are coded in the cardspecific data (WP_GRP_SIZE).

CMD29 ac

[31:0] data
address

R1b

CLR_WRITE_PROT

If the card provides write protection
features, this command clears the write
protection bit of the addressed group.

CMD30 adtc

[31:0] write
protect data
address

SEND_WRITE_PROT

If the card provides write protection
features, this command asks the card to
send the status of the write protection
bits.

R1

CMD31 Reserved

Table 238. Erase commands
CMD
index

Type

Argument

Response
format

Abbreviation

Description

CMD32
Reserved. These command indexes cannot be used in order to maintain backward compatibility with older
...
versions of the MultiMediaCard.
CMD34
CMD35 ac

[31:0] data address R1

Sets the address of the first erase
ERASE_GROUP_START group within a range to be selected
for erase.

CMD36 ac

[31:0] data address R1

ERASE_GROUP_END

CMD37

Sets the address of the last erase
group within a continuous range to be
selected for erase.

Reserved. This command index cannot be used in order to maintain backward compatibility with older
versions of the MultiMediaCards

CMD38 ac

[31:0] stuff bits

R1

Erases all previously selected write
blocks.

ERASE

Table 239. I/O mode commands
CMD
index

Type

CMD39 ac

Argument

[31:16] RCA
[15:15] register
write flag
[14:8] register
address
[7:0] register data

Response
format

R4

Abbreviation

FAST_IO

RM0385 Rev 7

Description
Used to write and read 8-bit (register) data
fields. The command addresses a card and a
register and provides the data for writing if
the write flag is set. The R4 response
contains data read from the addressed
register. This command accesses
application-dependent registers that are not
defined in the MultiMediaCard standard.

1257/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Table 239. I/O mode commands (continued)
CMD
index

Type

CMD40 bcr

Argument
[31:0] stuff bits

Response
format
R5

Abbreviation

Description

GO_IRQ_STATE Places the system in the interrupt mode.

CMD41 Reserved

Table 240. Lock card
CMD
index

Type

CMD42 adtc

Response
format

Argument

[31:0] stuff bits

R1b

Abbreviation

LOCK_UNLOCK

Description
Sets/resets the password or locks/unlocks
the card. The size of the data block is set
by the SET_BLOCK_LEN command.

CMD43
...
Reserved
CMD54

Table 241. Application-specific commands
CMD
index
CMD55

Type

ac

Argument
[31:16] RCA
[15:0] stuff bits

Response
format
R1

[31:1] stuff bits
[0]: RD/WR

CMD56

adtc

CMD57
...
CMD59

Reserved.

CMD60
...
CMD63

Reserved for manufacturer.

35.5

Abbreviation

APP_CMD

-

-

Description
Indicates to the card that the next command
bits is an application specific command rather
than a standard command
Used either to transfer a data block to the card
or to get a data block from the card for general
purpose/application-specific commands. The
size of the data block shall be set by the
SET_BLOCK_LEN command.

Response formats
All responses are sent via the SDMMC command line SDMMC_CMD. The response
transmission always starts with the left bit of the bit string corresponding to the response
code word. The code length depends on the response type.
A response always starts with a start bit (always 0), followed by the bit indicating the
direction of transmission (card = 0). A value denoted by x in the tables below indicates a
variable entry. All responses, except for the R3 response type, are protected by a CRC.
Every command code word is terminated by the end bit (always 1).
There are five types of responses. Their formats are defined as follows:

1258/1709

RM0385 Rev 7

RM0385

35.5.1

SD/SDIO/MMC card host interface (SDMMC)

R1 (normal response command)
Code length = 48 bits. The 45:40 bits indicate the index of the command to be responded to,
this value being interpreted as a binary-coded number (between 0 and 63). The status of the
card is coded in 32 bits.
Table 242. R1 response
Bit position

35.5.2

Width (bits

Value

Description

47

1

0

Start bit

46

1

0

Transmission bit

[45:40]

6

X

Command index

[39:8]

32

X

Card status

[7:1]

7

X

CRC7

0

1

1

End bit

R1b
It is identical to R1 with an optional busy signal transmitted on the data line. The card may
become busy after receiving these commands based on its state prior to the command
reception.

35.5.3

R2 (CID, CSD register)
Code length = 136 bits. The contents of the CID register are sent as a response to the
CMD2 and CMD10 commands. The contents of the CSD register are sent as a response to
CMD9. Only the bits [127...1] of the CID and CSD are transferred, the reserved bit [0] of
these registers is replaced by the end bit of the response. The card indicates that an erase
is in progress by holding SDMMC_D0 low. The actual erase time may be quite long, and the
host may issue CMD7 to deselect the card.
Table 243. R2 response
Bit position

Width (bits

Value

Description

135

1

0

Start bit

134

1

0

Transmission bit

[133:128]

6

‘111111’

Command index

[127:1]

127

X

Card status

0

1

1

End bit

RM0385 Rev 7

1259/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

35.5.4

RM0385

R3 (OCR register)
Code length: 48 bits. The contents of the OCR register are sent as a response to CMD1.
The level coding is as follows: restricted voltage windows = low, card busy = low.
Table 244. R3 response
Bit position

35.5.5

Width (bits

Value

Description

47

1

0

Start bit

46

1

0

Transmission bit

[45:40]

6

‘111111’

Reserved

[39:8]

32

X

OCR register

[7:1]

7

‘1111111’

Reserved

0

1

1

End bit

R4 (Fast I/O)
Code length: 48 bits. The argument field contains the RCA of the addressed card, the
register address to be read out or written to, and its content.
Table 245. R4 response
Bit position

Value

Description

47

1

0

Start bit

46

1

0

Transmission bit

[45:40]

6

‘100111’

CMD39

[31:16]

16

X

RCA

[15:8]

8

X

register address

[7:0]

8

X

read register contents

[7:1]

7

X

CRC7

0

1

1

End bit

[39:8] Argument field

35.5.6

Width (bits

R4b
For SD I/O only: an SDIO card receiving the CMD5 will respond with a unique SDIO
response R4. The format is:
Table 246. R4b response
Bit position

1260/1709

Width (bits

Value

Description

47

1

0

Start bit

46

1

0

Transmission bit

[45:40]

6

X

Reserved

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)
Table 246. R4b response (continued)
Bit position

Width (bits

Value

Description

39

16

X

Card is ready

[38:36]

3

X

Number of I/O functions

35

1

X

Present memory

[34:32]

3

X

Stuff bits

[31:8]

24

X

I/O ORC

[7:1]

7

X

Reserved

0

1

1

End bit

[39:8] Argument field

Once an SD I/O card has received a CMD5, the I/O portion of that card is enabled to
respond normally to all further commands. This I/O enable of the function within the I/O card
will remain set until a reset, power cycle or CMD52 with write to I/O reset is received by the
card. Note that an SD memory-only card may respond to a CMD5. The proper response for
a memory-only card would be Present memory = 1 and Number of I/O functions = 0. A
memory-only card built to meet the SD Memory Card specification version 1.0 would detect
the CMD5 as an illegal command and not respond. The I/O aware host will send CMD5. If
the card responds with response R4, the host determines the card’s configuration based on
the data contained within the R4 response.

35.5.7

R5 (interrupt request)
Only for MultiMediaCard. Code length: 48 bits. If the response is generated by the host, the
RCA field in the argument will be 0x0.
Table 247. R5 response
Bit position

Width (bits

Value

47

1

0

Start bit

46

1

0

Transmission bit

[45:40]

6

‘101000’

CMD40

[31:16]

16

X

RCA [31:16] of winning
card or of the host

[15:0]

16

X

Not defined. May be used
for IRQ data

[7:1]

7

X

CRC7

0

1

1

End bit

[39:8] Argument field

35.5.8

Description

R6
Only for SD I/O. The normal response to CMD3 by a memory device. It is shown in
Table 248.

RM0385 Rev 7

1261/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Table 248. R6 response
Bit position

Width (bits)

Value

Description

47

1

0

Start bit

46

1

0

Transmission bit

[45:40]

6

‘101000’

CMD40

[31:16]

16

X

RCA [31:16] of winning card or of the host

[15:0]

16

X

Not defined. May be used for IRQ data

[7:1]

7

X

CRC7

0

1

1

End bit

[39:8] Argument
field

The card [23:8] status bits are changed when CMD3 is sent to an I/O-only card. In this case,
the 16 bits of response are the SD I/O-only values:

35.6

•

Bit [15] COM_CRC_ERROR

•

Bit [14] ILLEGAL_COMMAND

•

Bit [13] ERROR

•

Bits [12:0] Reserved

SDIO I/O card-specific operations
The following features are SD I/O-specific operations:
•

SDIO read wait operation by SDMMC_D2 signalling

•

SDIO read wait operation by stopping the clock

•

SDIO suspend/resume operation (write and read suspend)

•

SDIO interrupts

The SDMMC supports these operations only if the SDMMC_DCTRL[11] bit is set, except for
read suspend that does not need specific hardware implementation.

35.6.1

SDIO I/O read wait operation by SDMMC_D2 signalling
It is possible to start the readwait interval before the first block is received: when the data
path is enabled (SDMMC_DCTRL[0] bit set), the SDIO-specific operation is enabled
(SDMMC_DCTRL[11] bit set), read wait starts (SDMMC_DCTRL[10] =0 and
SDMMC_DCTRL[8] =1) and data direction is from card to SDMMC (SDMMC_DCTRL[1] =
1), the DPSM directly moves from Idle to Readwait. In Readwait the DPSM drives
SDMMC_D2 to 0 after 2 SDMMC_CK clock cycles. In this state, when you set the RWSTOP
bit (SDMMC_DCTRL[9]), the DPSM remains in Wait for two more SDMMC_CK clock cycles
to drive SDMMC_D2 to 1 for one clock cycle (in accordance with SDIO specification). The
DPSM then starts waiting again until it receives data from the card. The DPSM will not start
a readwait interval while receiving a block even if read wait start is set: the readwait interval
will start after the CRC is received. The RWSTOP bit has to be cleared to start a new read
wait operation. During the readwait interval, the SDMMC can detect SDIO interrupts on
SDMMC_D1.

1262/1709

RM0385 Rev 7

RM0385

35.6.2

SD/SDIO/MMC card host interface (SDMMC)

SDIO read wait operation by stopping SDMMC_CK
If the SDIO card does not support the previous read wait method, the SDMMC can perform
a read wait by stopping SDMMC_CK (SDMMC_DCTRL is set just like in the method
presented in Section 35.6.1, but SDMMC_DCTRL[10] =1): DSPM stops the clock two
SDMMC_CK cycles after the end bit of the current received block and starts the clock again
after the read wait start bit is set.
As SDMMC_CK is stopped, any command can be issued to the card. During a read/wait
interval, the SDMMC can detect SDIO interrupts on SDMMC_D1.

35.6.3

SDIO suspend/resume operation
While sending data to the card, the SDMMC can suspend the write operation. the
SDMMC_CMD[11] bit is set and indicates to the CPSM that the current command is a
suspend command. The CPSM analyzes the response and when the ACK is received from
the card (suspend accepted), it acknowledges the DPSM that goes Idle after receiving the
CRC token of the current block.
The hardware does not save the number of the remaining block to be sent to complete the
suspended operation (resume).
The write operation can be suspended by software, just by disabling the DPSM
(SDMMC_DCTRL[0] =0) when the ACK of the suspend command is received from the card.
The DPSM enters then the Idle state.
To suspend a read: the DPSM waits in the Wait_r state as the function to be suspended
sends a complete packet just before stopping the data transaction. The application
continues reading RxFIFO until the FIF0 is empty, and the DPSM goes Idle automatically.

35.6.4

SDIO interrupts
SDIO interrupts are detected on the SDMMC_D1 line once the SDMMC_DCTRL[11] bit is
set.
When SDIO interrupt is detected, SDMMC_STA[22] (SDIOIT) bit is set. This static bit can be
cleared with clear bit SDMMC_ICR[22] (SDIOITC). An interrupt can be generated when
SDIOIT status bit is set. Separated interrupt enable SDMMC_MASK[22] bit (SDIOITE) is
available to enable and disable interrupt request.
When SD card interrupt occurs (SDMMC_STA[22] bit set), host software follows below
steps to handle it.
1.

Disable SDIOIT interrupt signaling by clearing SDIOITE bit (SDMMC_MASK[22] = ‘0’),

2.

Serve card interrupt request, and clear the source of interrupt on the SD card,

3.

Clear SDIOIT bit by writing ‘1’ to SDIOITC bit (SDMMC_ICR[22] = ‘1’),

4.

Enable SDIOIT interrupt signaling by writing ‘1’ to SDIOITE bit (SDMMC_MASK[22] =
‘1’).

Steps 2 to 4 can be executed out of the SDIO interrupt service routine.

35.7

HW flow control
The HW flow control functionality is used to avoid FIFO underrun (TX mode) and overrun
(RX mode) errors.

RM0385 Rev 7

1263/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

The behavior is to stop SDMMC_CK and freeze SDMMC state machines. The data transfer
is stalled while the FIFO is unable to transmit or receive data. Only state machines clocked
by SDMMCCLK are frozen, the APB2 interface is still alive. The FIFO can thus be filled or
emptied even if flow control is activated.
To enable HW flow control, the SDMMC_CLKCR[14] register bit must be set to 1. After reset
Flow Control is disabled.

35.8

SDMMC registers
The device communicates to the system via 32-bit-wide control registers accessible via
APB2.

35.8.1

SDMMC power control register (SDMMC_POWER)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

0

15

14

13

12

11

10

9

8

7

6

5

4

3

2

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PWRCTRL
rw

rw

Bits 31:2 Reserved, must be kept at reset value.
[1:0] PWRCTRL: Power supply control bits.
These bits are used to define the current functional state of the card clock:
00: Power-off: the clock to card is stopped.
01: Reserved
10: Reserved power-up
11: Power-on: the card is clocked.

Note:

At least seven PCLK2 clock periods are needed between two write accesses to this register.

Note:

After a data write, data cannot be written to this register for three SDMMCCLK clock periods
plus two PCLK2 clock periods.

35.8.2

SDMMC clock control register (SDMMC_CLKCR)
Address offset: 0x04
Reset value: 0x0000 0000
The SDMMC_CLKCR register controls the SDMMC_CK output clock.

1264/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

15

14

13

Res.

HWFC
_EN

NEGE
DGE

rw

rw

WID
BUS
rw

BYPAS PWRS
CLKEN
S
AV
rw

rw

rw

rw

CLKDIV
rw

rw

rw

rw

rw

Bits 31:15 Reserved, must be kept at reset value.
Bit 14 HWFC_EN: HW Flow Control enable
0b: HW Flow Control is disabled
1b: HW Flow Control is enabled
When HW Flow Control is enabled, the meaning of the TXFIFOE and RXFIFOF interrupt
signals, see SDMMC Status register definition in Section 35.8.11.
Bit 13 NEGEDGE: SDMMC_CK dephasing selection bit
0b: Command and Data changed on the SDMMCCLK falling edge succeeding the rising
edge of SDMMC_CK. (SDMMC_CK rising edge occurs on SDMMCCLK rising edge).
1b: Command and Data changed on the SDMMC_CK falling edge.
When BYPASS is active, the data and the command change on SDMMCCLK falling edge
whatever NEGEDGE value.
Bits 12:11 WIDBUS: Wide bus mode enable bit
00: Default bus mode: SDMMC_D0 used
01: 4-wide bus mode: SDMMC_D[3:0] used
10: 8-wide bus mode: SDMMC_D[7:0] used
Bit 10 BYPASS: Clock divider bypass enable bit
0: Disable bypass: SDMMCCLK is divided according to the CLKDIV value before driving the
SDMMC_CK output signal.
1: Enable bypass: SDMMCCLK directly drives the SDMMC_CK output signal.
Bit 9 PWRSAV: Power saving configuration bit
For power saving, the SDMMC_CK clock output can be disabled when the bus is idle by
setting PWRSAV:
0: SDMMC_CK clock is always enabled
1: SDMMC_CK is only enabled when the bus is active
Bit 8 CLKEN: Clock enable bit
0: SDMMC_CK is disabled
1: SDMMC_CK is enabled
Bits 7:0 CLKDIV: Clock divide factor
This field defines the divide factor between the input clock (SDMMCCLK) and the output
clock (SDMMC_CK): SDMMC_CK frequency = SDMMCCLK / [CLKDIV + 2].

Note:

1

While the SD/SDIO card or MultiMediaCard is in identification mode, the SDMMC_CK
frequency must be less than 400 kHz.

2

The clock frequency can be changed to the maximum card bus frequency when relative
card addresses are assigned to all cards.

3

After a data write, data cannot be written to this register for three SDMMCCLK clock periods
plus two PCLK2 clock periods. SDMMC_CK can also be stopped during the read wait
interval for SD I/O cards: in this case the SDMMC_CLKCR register does not control
SDMMC_CK.
RM0385 Rev 7

1265/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

35.8.3

RM0385

SDMMC argument register (SDMMC_ARG)
Address offset: 0x08
Reset value: 0x0000 0000
The SDMMC_ARG register contains a 32-bit command argument, which is sent to a card as
part of a command message.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CMDARG[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CMDARG[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 CMDARG: Command argument
Command argument sent to a card as part of a command message. If a command contains
an argument, it must be loaded into this register before writing a command to the command
register.

35.8.4

SDMMC command register (SDMMC_CMD)
Address offset: 0x0C
Reset value: 0x0000 0000
The SDMMC_CMD register contains the command index and command type bits. The
command index is sent to a card as part of a command message. The command type bits
control the command path state machine (CPSM).

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

SDIO
Suspend

CPSM
EN

WAIT
PEND

WAIT
INT

rw

rw

rw

rw

rw

rw

Res.

Res.

Res.

WAITRESP
rw

rw

CMDINDEX
rw

rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bit 11 SDIOSuspend: SD I/O suspend command
If this bit is set, the command to be sent is a suspend command (to be used only with SDIO
card).
Bit 10 CPSMEN: Command path state machine (CPSM) Enable bit
If this bit is set, the CPSM is enabled.
Bit 9 WAITPEND: CPSM Waits for ends of data transfer (CmdPend internal signal).
If this bit is set, the CPSM waits for the end of data transfer before it starts sending a
command. This feature is available only with Stream data transfer mode
SDMMC_DCTRL[2] = 1.

1266/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)

Bit 8 WAITINT: CPSM waits for interrupt request
If this bit is set, the CPSM disables command timeout and waits for an interrupt request.
Bits 7:6 WAITRESP: Wait for response bits
They are used to configure whether the CPSM is to wait for a response, and if yes, which
kind of response.
00: No response, expect CMDSENT flag
01: Short response, expect CMDREND or CCRCFAIL flag
10: No response, expect CMDSENT flag
11: Long response, expect CMDREND or CCRCFAIL flag
Bits 5:0 CMDINDEX: Command index
The command index is sent to the card as part of a command message.

Note:

1

After a data write, data cannot be written to this register for three SDMMCCLK clock periods
plus two PCLK2 clock periods.

2

MultiMediaCards can send two kinds of response: short responses, 48 bits long, or long
responses,136 bits long. SD card and SD I/O card can send only short responses, the
argument can vary according to the type of response: the software will distinguish the type
of response according to the sent command.

35.8.5

SDMMC command response register (SDMMC_RESPCMD)
Address offset: 0x10
Reset value: 0x0000 0000
The SDMMC_RESPCMD register contains the command index field of the last command
response received. If the command response transmission does not contain the command
index field (long or OCR response), the RESPCMD field is unknown, although it must
contain 111111b (the value of the reserved field from the response).

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

5

4

3

2

1

0

r

r

15

14

13

12

11

10

9

8

7

6

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RESPCMD
r

r

r

r

Bits 31:6 Reserved, must be kept at reset value.
Bits 5:0 RESPCMD: Response command index
Read-only bit field. Contains the command index of the last command response received.

35.8.6

SDMMC response 1..4 register (SDMMC_RESPx)
Address offset: (0x10 + (4 × x)); x = 1..4
Reset value: 0x0000 0000
The SDMMC_RESP1/2/3/4 registers contain the status of a card, which is part of the
received response.

RM0385 Rev 7

1267/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

CARDSTATUSx[31:16]

CARDSTATUSx[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:0 CARDSTATUSx: see Table 249.

The Card Status size is 32 or 127 bits, depending on the response type.
Table 249. Response type and SDMMC_RESPx registers
Register

Short response

Long response

SDMMC_RESP1

Card Status[31:0]

Card Status [127:96]

SDMMC_RESP2

Unused

Card Status [95:64]

SDMMC_RESP3

Unused

Card Status [63:32]

SDMMC_RESP4

Unused

Card Status [31:1]0b

The most significant bit of the card status is received first. The SDMMC_RESP4 register
LSB is always 0b.

35.8.7

SDMMC data timer register (SDMMC_DTIMER)
Address offset: 0x24
Reset value: 0x0000 0000
The SDMMC_DTIMER register contains the data timeout period, in card bus clock periods.
A counter loads the value from the SDMMC_DTIMER register, and starts decrementing
when the data path state machine (DPSM) enters the Wait_R or Busy state. If the timer
reaches 0 while the DPSM is in either of these states, the timeout status flag is set.

31

30

29

28

27

26

25

24

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DATATIME[31:16]

DATATIME[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DATATIME: Data timeout period
Data timeout period expressed in card bus clock periods.

Note:

1268/1709

A data transfer must be written to the data timer register and the data length register before
being written to the data control register.

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)

35.8.8

SDMMC data length register (SDMMC_DLEN)
Address offset: 0x28
Reset value: 0x0000 0000
The SDMMC_DLEN register contains the number of data bytes to be transferred. The value
is loaded into the data counter when data transfer starts.

31

30

29

28

27

26

25

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

24

23

22

21

20

19

18

17

16

DATALENGTH[24:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DATALENGTH[15:0]
rw

rw

Bits 31:25 Reserved, must be kept at reset value.
Bits 24:0 DATALENGTH: Data length value
Number of data bytes to be transferred.

Note:

For a block data transfer, the value in the data length register must be a multiple of the block
size (see SDMMC_DCTRL). Before being written to the data control register a timeout must
be written to the data timer register and the data length register.
In case of IO_RW_EXTENDED (CMD53):
- If the Stream or SDIO multibyte data transfer is selected the value in the data length
register must be between 1 and 512.
- If the Block data transfer is selected the value in the data length register must be between
1*Data block size and 512*Data block size.

35.8.9

SDMMC data control register (SDMMC_DCTRL)
Address offset: 0x2C
Reset value: 0x0000 0000
The SDMMC_DCTRL register control the data path state machine (DPSM).

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

SDIO
EN

RW
MOD

RW
STOP

RW
START

DMA
EN

DT
MODE

DTDIR

DTEN

rw

rw

rw

rw

rw

rw

rw

rw

DBLOCKSIZE
rw

RM0385 Rev 7

rw

rw

rw

1269/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Bits 31:12 Reserved, must be kept at reset value.
Bit 11 SDIOEN: SD I/O enable functions
If this bit is set, the DPSM performs an SD I/O-card-specific operation.
Bit 10 RWMOD: Read wait mode
0: Read Wait control stopping SDMMC_D2
1: Read Wait control using SDMMC_CK
Bit 9 RWSTOP: Read wait stop
0: Read wait in progress if RWSTART bit is set
1: Enable for read wait stop if RWSTART bit is set
Bit 8 RWSTART: Read wait start
If this bit is set, read wait operation starts.
Bits 7:4 DBLOCKSIZE: Data block size
Define the data block length when the block data transfer mode is selected:
0000: (0 decimal) lock length = 20 = 1 byte
0001: (1 decimal) lock length = 21 = 2 bytes
0010: (2 decimal) lock length = 22 = 4 bytes
0011: (3 decimal) lock length = 23 = 8 bytes
0100: (4 decimal) lock length = 24 = 16 bytes
0101: (5 decimal) lock length = 25 = 32 bytes
0110: (6 decimal) lock length = 26 = 64 bytes
0111: (7 decimal) lock length = 27 = 128 bytes
1000: (8 decimal) lock length = 28 = 256 bytes
1001: (9 decimal) lock length = 29 = 512 bytes
1010: (10 decimal) lock length = 210 = 1024 bytes
1011: (11 decimal) lock length = 211 = 2048 bytes
1100: (12 decimal) lock length = 212 = 4096 bytes
1101: (13 decimal) lock length = 213 = 8192 bytes
1110: (14 decimal) lock length = 214 = 16384 bytes
1111: (15 decimal) reserved
Bit 3 DMAEN: DMA enable bit
0: DMA disabled.
1: DMA enabled.
Bit 2 DTMODE: Data transfer mode selection 1: Stream or SDIO multibyte data transfer.
0: Block data transfer
1: Stream or SDIO multibyte data transfer
Bit 1 DTDIR: Data transfer direction selection
0: From controller to card.
1: From card to controller.
[0] DTEN: Data transfer enabled bit
Data transfer starts if 1b is written to the DTEN bit. Depending on the direction bit, DTDIR,
the DPSM moves to the Wait_S, Wait_R state or Readwait if RW Start is set immediately at
the beginning of the transfer. It is not necessary to clear the enable bit after the end of a data
transfer but the SDMMC_DCTRL must be updated to enable a new data transfer

1270/1709

RM0385 Rev 7

RM0385
Note:

SD/SDIO/MMC card host interface (SDMMC)
After a data write, data cannot be written to this register for three SDMMCCLK (48 MHz)
clock periods plus two PCLK2 clock periods.
The meaning of the DTMODE bit changes according to the value of the SDIOEN bit. When
SDIOEN=0 and DTMODE=1, the MultiMediaCard stream mode is enabled, and when
SDIOEN=1 and DTMODE=1, the peripheral enables an SDIO multibyte transfer.

RM0385 Rev 7

1271/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

35.8.10

RM0385

SDMMC data counter register (SDMMC_DCOUNT)
Address offset: 0x30
Reset value: 0x0000 0000
The SDMMC_DCOUNT register loads the value from the data length register (see
SDMMC_DLEN) when the DPSM moves from the Idle state to the Wait_R or Wait_S state.
As data is transferred, the counter decrements the value until it reaches 0. The DPSM then
moves to the Idle state and the data status end flag, DATAEND, is set.

31

30

29

28

27

26

25

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

r

r

r

r

r

r

r

24

23

22

21

20

19

18

17

16

DATACOUNT[24:16]
r

r

r

r

r

r

r

r

r

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

DATACOUNT[15:0]
r

r

Bits 31:25 Reserved, must be kept at reset value.
Bits 24:0 DATACOUNT: Data count value
When this bit is read, the number of remaining data bytes to be transferred is returned. Write
has no effect.

Note:

This register should be read only when the data transfer is complete.

35.8.11

SDMMC status register (SDMMC_STA)
Address offset: 0x34
Reset value: 0x0000 0000
The SDMMC_STA register is a read-only register. It contains two types of flag:
•

Static flags (bits [23:22,10:0]): these bits remain asserted until they are cleared by
writing to the SDMMC Interrupt Clear register (see SDMMC_ICR)

•

Dynamic flags (bits [21:11]): these bits change state depending on the state of the
underlying logic (for example, FIFO full and empty flags are asserted and deasserted
as data while written to the FIFO)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SDIOIT

RXD
AVL

TXD
AVL

RX
FIFOE

TX
FIFOE

RX
FIFOF

TX
FIFOF

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

RX
FIFO
HF

TX
FIFO
HE

CMD
ACT

DBCK
END

Res.

DATA
END

CMDS
ENT

DCRC
FAIL

CCRC
FAIL

r

r

r

r

r

r

r

r

RXACT TXACT
r

r

Bits 31:23 Reserved, must be kept at reset value.
Bit 22 SDIOIT: SDIO interrupt received
Bit 21 RXDAVL: Data available in receive FIFO

1272/1709

RM0385 Rev 7

CMDR
RX
TXUND DTIME CTIME
END OVERR ERR
OUT
OUT
r

r

r

r

r

RM0385

SD/SDIO/MMC card host interface (SDMMC)

Bit 20 TXDAVL: Data available in transmit FIFO
Bit 19 RXFIFOE: Receive FIFO empty
Bit 18 TXFIFOE: Transmit FIFO empty
When HW Flow Control is enabled, TXFIFOE signals becomes activated when the FIFO
contains 2 words.
Bit 17 RXFIFOF: Receive FIFO full
When HW Flow Control is enabled, RXFIFOF signals becomes activated 2 words before the
FIFO is full.
Bit 16 TXFIFOF: Transmit FIFO full
Bit 15 RXFIFOHF: Receive FIFO half full: there are at least 8 words in the FIFO
Bit 14 TXFIFOHE: Transmit FIFO half empty: at least 8 words can be written into the FIFO
Bit 13 RXACT: Data receive in progress
Bit 12 TXACT: Data transmit in progress
Bit 11 CMDACT: Command transfer in progress
Bit 10 DBCKEND: Data block sent/received (CRC check passed)
Bit 9 Reserved, must be kept at reset value.
Bit 8 DATAEND: Data end (data counter, SDIDCOUNT, is zero)
Bit 7 CMDSENT: Command sent (no response required)
Bit 6 CMDREND: Command response received (CRC check passed)
Bit 5 RXOVERR: Received FIFO overrun error
Note: If DMA is used to read SDMMC FIFO (DMAEN bit is set in SDMMC_DCTRL register),
user software should disable DMA stream, and then write with ‘0’ (to disable DMA
request generation).
Bit 4 TXUNDERR: Transmit FIFO underrun error
Note: If DMA is used to fill SDMMC FIFO (DMAEN bit is set in SDMMC_DCTRL register),
user software should disable DMA stream, and then write DMAEN with ‘0’ (to disable
DMA request generation).
Bit 3 DTIMEOUT: Data timeout
Bit 2 CTIMEOUT: Command response timeout
The Command TimeOut period has a fixed value of 64 SDMMC_CK clock periods.
Bit 1 DCRCFAIL: Data block sent/received (CRC check failed)
Bit 0 CCRCFAIL: Command response received (CRC check failed)

35.8.12

SDMMC interrupt clear register (SDMMC_ICR)
Address offset: 0x38
Reset value: 0x0000 0000
The SDMMC_ICR register is a write-only register. Writing a bit with 1b clears the
corresponding bit in the SDMMC_STA Status register.

RM0385 Rev 7

1273/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SDIO
ITC

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

5

4

3

2

1

0

DCRC
FAILC

CCRC
FAILC

rw

rw

rw

Res.

Res.

Res.

Res.

Res.

DBCK
ENDC
rw

Res.

6

CMD
DATA
CMD
REND
ENDC SENTC
C
rw

rw

rw

Bits 31:23 Reserved, must be kept at reset value.
Bit 22 SDIOITC: SDIOIT flag clear bit
Set by software to clear the SDIOIT flag.
0: SDIOIT not cleared
1: SDIOIT cleared
Bits 21:11 Reserved, must be kept at reset value.
Bit 10 DBCKENDC: DBCKEND flag clear bit
Set by software to clear the DBCKEND flag.
0: DBCKEND not cleared
1: DBCKEND cleared
Bit 9 Reserved, must be kept at reset value.
Bit 8 DATAENDC: DATAEND flag clear bit
Set by software to clear the DATAEND flag.
0: DATAEND not cleared
1: DATAEND cleared
Bit 7 CMDSENTC: CMDSENT flag clear bit
Set by software to clear the CMDSENT flag.
0: CMDSENT not cleared
1: CMDSENT cleared
Bit 6 CMDRENDC: CMDREND flag clear bit
Set by software to clear the CMDREND flag.
0: CMDREND not cleared
1: CMDREND cleared
Bit 5 RXOVERRC: RXOVERR flag clear bit
Set by software to clear the RXOVERR flag.
0: RXOVERR not cleared
1: RXOVERR cleared
Bit 4 TXUNDERRC: TXUNDERR flag clear bit
Set by software to clear TXUNDERR flag.
0: TXUNDERR not cleared
1: TXUNDERR cleared
Bit 3 DTIMEOUTC: DTIMEOUT flag clear bit
Set by software to clear the DTIMEOUT flag.
0: DTIMEOUT not cleared
1: DTIMEOUT cleared

1274/1709

RM0385 Rev 7

RX
TX
DTIME CTIME
OVERR UNDERR
OUTC OUTC
C
C
rw

rw

rw

rw

RM0385

SD/SDIO/MMC card host interface (SDMMC)

Bit 2 CTIMEOUTC: CTIMEOUT flag clear bit
Set by software to clear the CTIMEOUT flag.
0: CTIMEOUT not cleared
1: CTIMEOUT cleared
Bit 1 DCRCFAILC: DCRCFAIL flag clear bit
Set by software to clear the DCRCFAIL flag.
0: DCRCFAIL not cleared
1: DCRCFAIL cleared
Bit 0 CCRCFAILC: CCRCFAIL flag clear bit
Set by software to clear the CCRCFAIL flag.
0: CCRCFAIL not cleared
1: CCRCFAIL cleared

35.8.13

SDMMC mask register (SDMMC_MASK)
Address offset: 0x3C
Reset value: 0x0000 0000
The interrupt mask register determines which status flags generate an interrupt request by
setting the corresponding bit to 1b.

31

30

29

28

27

26

25

24

23

22

20

19

18

17

16

TX
FIFO
EIE

RX
FIFO
FIE

TX
FIFO
FIE

SDIO
ITIE

RXD
AVLIE

TXD
AVLIE

RX
FIFO
EIE

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

RX
FIFO
HFIE

TX
FIFO
HEIE

RX
ACTIE

TX
ACTIE

CMD
ACTIE

DBCK
ENDIE

DATA
ENDIE

CMD
SENT
IE

CMD
REND
IE

rw

rw

rw

rw

rw

rw

rw

rw

rw

Res.

21

RX
TX
DTIME CTIME DCRC
OVERR UNDERR
OUTIE OUTIE FAILIE
IE
IE
rw

rw

rw

rw

rw

CCRC
FAILIE
rw

Bits 31:23 Reserved, must be kept at reset value.
Bit 22 SDIOITIE: SDIO mode interrupt received interrupt enable
Set and cleared by software to enable/disable the interrupt generated when receiving the
SDIO mode interrupt.
0: SDIO Mode Interrupt Received interrupt disabled
1: SDIO Mode Interrupt Received interrupt enabled
Bit 21 RXDAVLIE: Data available in Rx FIFO interrupt enable
Set and cleared by software to enable/disable the interrupt generated by the presence of
data available in Rx FIFO.
0: Data available in Rx FIFO interrupt disabled
1: Data available in Rx FIFO interrupt enabled
Bit 20 TXDAVLIE: Data available in Tx FIFO interrupt enable
Set and cleared by software to enable/disable the interrupt generated by the presence of
data available in Tx FIFO.
0: Data available in Tx FIFO interrupt disabled
1: Data available in Tx FIFO interrupt enabled

RM0385 Rev 7

1275/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

Bit 19 RXFIFOEIE: Rx FIFO empty interrupt enable
Set and cleared by software to enable/disable interrupt caused by Rx FIFO empty.
0: Rx FIFO empty interrupt disabled
1: Rx FIFO empty interrupt enabled
Bit 18 TXFIFOEIE: Tx FIFO empty interrupt enable
Set and cleared by software to enable/disable interrupt caused by Tx FIFO empty.
0: Tx FIFO empty interrupt disabled
1: Tx FIFO empty interrupt enabled
Bit 17 RXFIFOFIE: Rx FIFO full interrupt enable
Set and cleared by software to enable/disable interrupt caused by Rx FIFO full.
0: Rx FIFO full interrupt disabled
1: Rx FIFO full interrupt enabled
Bit 16 TXFIFOFIE: Tx FIFO full interrupt enable
Set and cleared by software to enable/disable interrupt caused by Tx FIFO full.
0: Tx FIFO full interrupt disabled
1: Tx FIFO full interrupt enabled
Bit 15 RXFIFOHFIE: Rx FIFO half full interrupt enable
Set and cleared by software to enable/disable interrupt caused by Rx FIFO half full.
0: Rx FIFO half full interrupt disabled
1: Rx FIFO half full interrupt enabled
Bit 14 TXFIFOHEIE: Tx FIFO half empty interrupt enable
Set and cleared by software to enable/disable interrupt caused by Tx FIFO half empty.
0: Tx FIFO half empty interrupt disabled
1: Tx FIFO half empty interrupt enabled
Bit 13 RXACTIE: Data receive acting interrupt enable
Set and cleared by software to enable/disable interrupt caused by data being received (data
receive acting).
0: Data receive acting interrupt disabled
1: Data receive acting interrupt enabled
Bit 12 TXACTIE: Data transmit acting interrupt enable
Set and cleared by software to enable/disable interrupt caused by data being transferred
(data transmit acting).
0: Data transmit acting interrupt disabled
1: Data transmit acting interrupt enabled
Bit 11 CMDACTIE: Command acting interrupt enable
Set and cleared by software to enable/disable interrupt caused by a command being
transferred (command acting).
0: Command acting interrupt disabled
1: Command acting interrupt enabled
Bit 10 DBCKENDIE: Data block end interrupt enable
Set and cleared by software to enable/disable interrupt caused by data block end.
0: Data block end interrupt disabled
1: Data block end interrupt enabled
Bit 9 Reserved, must be kept at reset value.

1276/1709

RM0385 Rev 7

RM0385

SD/SDIO/MMC card host interface (SDMMC)

Bit 8 DATAENDIE: Data end interrupt enable
Set and cleared by software to enable/disable interrupt caused by data end.
0: Data end interrupt disabled
1: Data end interrupt enabled
Bit 7 CMDSENTIE: Command sent interrupt enable
Set and cleared by software to enable/disable interrupt caused by sending command.
0: Command sent interrupt disabled
1: Command sent interrupt enabled
Bit 6 CMDRENDIE: Command response received interrupt enable
Set and cleared by software to enable/disable interrupt caused by receiving command
response.
0: Command response received interrupt disabled
1: command Response Received interrupt enabled
Bit 5 RXOVERRIE: Rx FIFO overrun error interrupt enable
Set and cleared by software to enable/disable interrupt caused by Rx FIFO overrun error.
0: Rx FIFO overrun error interrupt disabled
1: Rx FIFO overrun error interrupt enabled
Bit 4 TXUNDERRIE: Tx FIFO underrun error interrupt enable
Set and cleared by software to enable/disable interrupt caused by Tx FIFO underrun error.
0: Tx FIFO underrun error interrupt disabled
1: Tx FIFO underrun error interrupt enabled
Bit 3 DTIMEOUTIE: Data timeout interrupt enable
Set and cleared by software to enable/disable interrupt caused by data timeout.
0: Data timeout interrupt disabled
1: Data timeout interrupt enabled
Bit 2 CTIMEOUTIE: Command timeout interrupt enable
Set and cleared by software to enable/disable interrupt caused by command timeout.
0: Command timeout interrupt disabled
1: Command timeout interrupt enabled
Bit 1 DCRCFAILIE: Data CRC fail interrupt enable
Set and cleared by software to enable/disable interrupt caused by data CRC failure.
0: Data CRC fail interrupt disabled
1: Data CRC fail interrupt enabled
Bit 0 CCRCFAILIE: Command CRC fail interrupt enable
Set and cleared by software to enable/disable interrupt caused by command CRC failure.
0: Command CRC fail interrupt disabled
1: Command CRC fail interrupt enabled

35.8.14

SDMMC FIFO counter register (SDMMC_FIFOCNT)
Address offset: 0x48
Reset value: 0x0000 0000
The SDMMC_FIFOCNT register contains the remaining number of words to be written to or
read from the FIFO. The FIFO counter loads the value from the data length register (see
SDMMC_DLEN) when the data transfer enable bit, DTEN, is set in the data control register
(SDMMC_DCTRL register) and the DPSM is at the Idle state. If the data length is not wordaligned (multiple of 4), the remaining 1 to 3 bytes are regarded as a word.

RM0385 Rev 7

1277/1709
1280

SD/SDIO/MMC card host interface (SDMMC)

RM0385

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

23

22

21

20

r

r

r

r

7

6

5

r

r

19

18

17

16

r

r

r

r

4

3

2

1

0

r

r

r

r

r

FIFOCOUNT[23:16]

FIFOCOUNT[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:0 FIFOCOUNT: Remaining number of words to be written to or read from the FIFO.

35.8.15

SDMMC data FIFO register (SDMMC_FIFO)
Address offset: 0x80
Reset value: 0x0000 0000
The receive and transmit FIFOs can be read or written as 32-bit wide registers. The FIFOs
contain 32 entries on 32 sequential addresses. This allows the CPU to use its load and store
multiple operands to read from/write to the FIFO.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

FIF0Data[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

FIF0Data[15:0]
rw

rw

bits 31:0 FIFOData: Receive and transmit FIFO data
The FIFO data occupies 32 entries of 32-bit words, from address:
SDMMC base + 0x080 to SDMMC base + 0xFC.

1278/1709

RM0385 Rev 7

RM0385

35.8.16

SD/SDIO/MMC card host interface (SDMMC)

SDMMC register map
The following table summarizes the SDMMC registers.

PWRSAV

CLKEN

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

SDMMC_CMD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SDMMC_
RESPCMD

Res.

0x10

Res.

Reset value

0

0

0

0

0

WAITRESP

CMDINDEX

0

Res.

0

Res.

0

WAITINT

0

Res.

0

WAITPEND

0

Res.

0

CPSMEN

0

Res.

0

SDIOSuspend

0

Res.

0

Res.

CMDARG

Reset value

0x0C

CLKDIV

BYPASS

0

WIDBUS

0

Res.

SDMMC_ARG

0

Res.

0x08

Reset value
SDMMC_
RESP1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DTEN

0

0

0

0

0

0

0

0

0

CARDSTATUS2
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CARDSTATUS3
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CARDSTATUS4
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

SDMMC_
DTIMER

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RWSTOP

RWSTART

DATALENGTH

RWMOD

Res.
Res.

0

SDIOEN

Res.
Res.

0

Res.

Res.
Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

SDMMC_
DLEN

Res.

DATATIME

Reset value

SDMMC_
DCTRL

0

DTDIR

0

Reset value

0x2C

0

DTMODE

0

Res.

0x28

0

SDMMC_
RESP4
Reset value

0x24

0

Res.

0x20

0

SDMMC_
RESP3
Reset value

0

DMAEN

Reset value
0x1C

0

SDMMC_
RESP2

Res.

0x18

0

0

0

0

0

Reset value

RM0385 Rev 7

DBLOCKSIZE

Reset value

RESPCMD

CARDSTATUS1

Res.

0x14

0

NEGEDGE

Reset value

0
HWFC_EN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SDMMC_
CLKCR

Res.

Reset value

0x04

PWRCTRL

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SDMMC_
POWER

Res.

0x00

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 250. SDMMC register map

1279/1709
1280

0x80

0x48
SDMMC_
FIFOCNT

Reset value

1280/1709
0
0
0
0
0
0
0

Reset value

0
0
0
0

SDMMC_FIFO
FIF0Data

0
0
0
0
0
0
0

0
0
0
0
0
0
0

RM0385 Rev 7
RXACTIE
TXACTIE
CMDACTIE
DBCKENDIE

0
0

0

0
0
0
0
0
0
0

0

0
0

0
0

0

Res.
Res.
Res.
Res.
DBCKENDC
DATAENDC
CMDSENTC
CMDRENDC
RXOVERRC
TXUNDERRC
DTIMEOUTC
CTIMEOUTC
DCRCFAILC
CCRCFAILC

0
CCRCFAILIE

0

DCRCFAILIE

0

CTIMEOUTIE

0

DTIMEOUTIE

0

RXOVERRIE

0

TXUNDERRIE

0

CMDSENTIE

DBCKEND

0

CMDRENDIE

TXACT
CMDACT

0

0

CCRCFAIL

0

DCRCFAIL

0

CTIMEOUT

0

DTIMEOUT

0

RXOVERR

0
TXUNDERR

0

CMDSENT

0
CMDREND

0

DATAEND

0

Res.

RXACT

0

DATAENDIE

TXFIFOHE

0

Res.

TXFIFOF
RXFIFOHF

Res.
0

Res.

0

Res.

0

TXFIFOE

0

RXFIFOF

0

Res.

0

Res.

0

TXDAVL

0

RXFIFOE

0

Res.

0

RXDAVL

0

Res.

0

Res.

0

Res.

TXFIFOHEIE

0

TXFIFOFIE

0

RXFIFOHFIE

TXFIFOEIE

0
RXFIFOFIE

RXFIFOEIE

Reset value
TXDAVLIE

Reset value

RXDAVLIE

0

SDIOIT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

SDIOITC

Reset value

SDIOITIE

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

SDMMC_
MASK

Res.

0x3C

Res.

SDMMC_ICR

Res.

0x38
Res.

SDMMC_STA

Res.

0x34

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SDMMC_
DCOUNT

Res.

0x30

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register

Res.

Offset

Res.

SD/SDIO/MMC card host interface (SDMMC)
RM0385

Table 250. SDMMC register map (continued)

DATACOUNT

0
0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0

FIFOCOUNT
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0
0

Refer to Section 2.2.2: Memory map and register boundary addresses for the register
boundary addresses.

RM0385

Controller area network (bxCAN)

36

Controller area network (bxCAN)

36.1

Introduction
The Basic Extended CAN peripheral, named bxCAN, interfaces the CAN network. It
supports the CAN protocols version 2.0A and B. It has been designed to manage a high
number of incoming messages efficiently with a minimum CPU load. It also meets the
priority requirements for transmit messages.
For safety-critical applications, the CAN controller provides all hardware functions for
supporting the CAN Time Triggered Communication option.

36.2

bxCAN main features
•

Supports CAN protocol version 2.0 A, B Active

•

Bit rates up to 1 Mbit/s

•

Supports the Time Triggered Communication option

Transmission
•

Three transmit mailboxes

•

Configurable transmit priority

•

Time Stamp on SOF transmission

Reception
•

Two receive FIFOs with three stages

•

Scalable filter banks:
–

28 filter banks shared between CAN1 and CAN2 for dual CAN

•

Identifier list feature

•

Configurable FIFO overrun

•

Time Stamp on SOF reception

Time-triggered communication option
•

Disable automatic retransmission mode

•

16-bit free running timer

•

Time Stamp sent in last two data bytes

Management
•

Maskable interrupts

•

Software-efficient mailbox mapping at a unique address space

Dual CAN peripheral configuration
•

CAN1: Master bxCAN for managing the communication between a Slave bxCAN and
the 512-byte SRAM memory

•

CAN2: Slave bxCAN, with no direct access to the SRAM memory.

•

The two bxCAN cells share the 512-byte SRAM memory (see Figure 444: Dual-CAN
block diagram)

RM0385 Rev 7

1281/1709
1325

Controller area network (bxCAN)

36.3

RM0385

bxCAN general description
In today CAN applications, the number of nodes in a network is increasing and often several
networks are linked together via gateways. Typically the number of messages in the system
(to be handled by each node) has significantly increased. In addition to the application
messages, Network Management and Diagnostic messages have been introduced.
•

An enhanced filtering mechanism is required to handle each type of message.

Furthermore, application tasks require more CPU time, therefore real-time constraints
caused by message reception have to be reduced.
•

A receive FIFO scheme allows the CPU to be dedicated to application tasks for a long
time period without losing messages.

The standard HLP (Higher Layer Protocol) based on standard CAN drivers requires an
efficient interface to the CAN controller.

MCU
Application

CAN
Controller
CAN
Rx

CAN node n

CAN node 2

CAN node 1

Figure 443. CAN network topology

CAN
Tx

CAN
Transceiver
CAN
High

CAN
Low

CAN Bus

MS30392V1

36.3.1

CAN 2.0B active core
The bxCAN module handles the transmission and the reception of CAN messages fully
autonomously. Standard identifiers (11-bit) and extended identifiers (29-bit) are fully
supported by hardware.

36.3.2

Control, status and configuration registers
The application uses these registers to:

36.3.3

•

Configure CAN parameters, e.g. baud rate

•

Request transmissions

•

Handle receptions

•

Manage interrupts

•

Get diagnostic information

Tx mailboxes
Three transmit mailboxes are provided to the software for setting up messages. The
transmission Scheduler decides which mailbox has to be transmitted first.

1282/1709

RM0385 Rev 7

RM0385

Acceptance filters
The bxCAN provides up to 28 scalable/configurable identifier filter banks in dual CAN
configuration, for selecting the incoming messages, that the software needs and discarding
the others.

Receive FIFO
Two receive FIFOs are used by hardware to store the incoming messages. Three complete
messages can be stored in each FIFO. The FIFOs are managed completely by hardware.
Figure 444. Dual-CAN block diagram
CAN1 (Master) with 512 bytes SRAM
Master
Tx Mailboxes
2
Mailbox 0

Master
Receive FIFO 0

Master
Receive FIFO 1
2

2

1
Mailbox 0

Master Control

1

Mailbox 0

1

Master Status
Tx Status

Control/Status/Configuration

Rx FIFO 0 Status

Transmission
Scheduler

Rx FIFO 1 Status
Acceptance Filters

Interrupt Enable
CAN 2.0B Active Core

Error Status

Memory
Access
Controller

Bit Timing

Filter

1

0

Master Filters
(0 to 27)

Filter Master

2

3

..

27

.. 26

Slave Filters
(0 to 27)

Filter Mode
Transmission
Scheduler

Filter Scale

Slave
Receive FIFO 0

Slave
Tx Mailboxes

Filter FIFOAssign

Mailbox 0

Slave
Receive FIFO 1
2

2

Filter Activation

1

Mailbox 0

1

2
Mailbox 0

1

CAN2 (Slave)

Control/Status/Configuration

36.3.4

Controller area network (bxCAN)

Master Control
Master Status
Tx Status
Rx FIFO 0 Status
Rx FIFO 1 Status

CAN 2.0B Active Core
Note: CAN2 start filter bank number n is configurable by writing
CAN2SB[5:0] bits in the CAN_FMR register

Interrupt Enable
Error Status
Bit Timing

ai16094b

RM0385 Rev 7

1283/1709
1325

Controller area network (bxCAN)

36.4

RM0385

bxCAN operating modes
bxCAN has three main operating modes: initialization, normal and Sleep. After a
hardware reset, bxCAN is in Sleep mode to reduce power consumption and an internal pullup is active on CANTX. The software requests bxCAN to enter initialization or Sleep mode
by setting the INRQ or SLEEP bits in the CAN_MCR register. Once the mode has been
entered, bxCAN confirms it by setting the INAK or SLAK bits in the CAN_MSR register and
the internal pull-up is disabled. When neither INAK nor SLAK are set, bxCAN is in normal
mode. Before entering normal mode bxCAN always has to synchronize on the CAN bus.
To synchronize, bxCAN waits until the CAN bus is idle, this means 11 consecutive recessive
bits have been monitored on CANRX.

36.4.1

Initialization mode
The software initialization can be done while the hardware is in Initialization mode. To enter
this mode the software sets the INRQ bit in the CAN_MCR register and waits until the
hardware has confirmed the request by setting the INAK bit in the CAN_MSR register.
To leave Initialization mode, the software clears the INQR bit. bxCAN has left Initialization
mode once the INAK bit has been cleared by hardware.
While in Initialization Mode, all message transfers to and from the CAN bus are stopped and
the status of the CAN bus output CANTX is recessive (high).
Entering Initialization Mode does not change any of the configuration registers.
To initialize the CAN Controller, software has to set up the Bit Timing (CAN_BTR) and CAN
options (CAN_MCR) registers.
To initialize the registers associated with the CAN filter banks (mode, scale, FIFO
assignment, activation and filter values), software has to set the FINIT bit (CAN_FMR). Filter
initialization also can be done outside the initialization mode.

Note:

When FINIT=1, CAN reception is deactivated.
The filter values also can be modified by deactivating the associated filter activation bits (in
the CAN_FA1R register).
If a filter bank is not used, it is recommended to leave it non active (leave the corresponding
FACT bit cleared).

36.4.2

Normal mode
Once the initialization is complete, the software must request the hardware to enter Normal
mode to be able to synchronize on the CAN bus and start reception and transmission.
The request to enter Normal mode is issued by clearing the INRQ bit in the CAN_MCR
register. The bxCAN enters Normal mode and is ready to take part in bus activities when it
has synchronized with the data transfer on the CAN bus. This is done by waiting for the
occurrence of a sequence of 11 consecutive recessive bits (Bus Idle state). The switch to
Normal mode is confirmed by the hardware by clearing the INAK bit in the CAN_MSR
register.
The initialization of the filter values is independent from Initialization Mode but must be done
while the filter is not active (corresponding FACTx bit cleared). The filter scale and mode
configuration must be configured before entering Normal Mode.

1284/1709

RM0385 Rev 7

RM0385

36.4.3

Controller area network (bxCAN)

Sleep mode (low-power)
To reduce power consumption, bxCAN has a low-power mode called Sleep mode. This
mode is entered on software request by setting the SLEEP bit in the CAN_MCR register. In
this mode, the bxCAN clock is stopped, however software can still access the bxCAN
mailboxes.
If software requests entry to initialization mode by setting the INRQ bit while bxCAN is in
Sleep mode, it must also clear the SLEEP bit.
bxCAN can be woken up (exit Sleep mode) either by software clearing the SLEEP bit or on
detection of CAN bus activity.
On CAN bus activity detection, hardware automatically performs the wakeup sequence by
clearing the SLEEP bit if the AWUM bit in the CAN_MCR register is set. If the AWUM bit is
cleared, software has to clear the SLEEP bit when a wakeup interrupt occurs, in order to exit
from Sleep mode.

Note:

If the wakeup interrupt is enabled (WKUIE bit set in CAN_IER register) a wakeup interrupt
will be generated on detection of CAN bus activity, even if the bxCAN automatically
performs the wakeup sequence.
After the SLEEP bit has been cleared, Sleep mode is exited once bxCAN has synchronized
with the CAN bus, refer to Figure 445: bxCAN operating modes. The Sleep mode is exited
once the SLAK bit has been cleared by hardware.
Figure 445. bxCAN operating modes
Reset

Sleep
SLAK = 1
INAK = 0

SL

Q

EE

R

.IN

C

YN

.S
EP

EE

K

.
EP

Q

.A

C

R

K

Q

.A

LE

C

S

Normal

R

P.
IN

AC

E
SL

P.
IN

SL

K

INRQ.ACK

SLAK = 0
INAK = 0

INRQ.SYNC.SLEEP

Initialization
SLAK = 0
INAK = 1
ai15902

1. ACK = The wait state during which hardware confirms a request by setting the INAK or SLAK bits in the
CAN_MSR register
2. SYNC = The state during which bxCAN waits until the CAN bus is idle, meaning 11 consecutive recessive
bits have been monitored on CANRX

RM0385 Rev 7

1285/1709
1325

Controller area network (bxCAN)

36.5

RM0385

Test mode
Test mode can be selected by the SILM and LBKM bits in the CAN_BTR register. These bits
must be configured while bxCAN is in Initialization mode. Once test mode has been
selected, the INRQ bit in the CAN_MCR register must be reset to enter Normal mode.

36.5.1

Silent mode
The bxCAN can be put in Silent mode by setting the SILM bit in the CAN_BTR register.
In Silent mode, the bxCAN is able to receive valid data frames and valid remote frames, but
it sends only recessive bits on the CAN bus and it cannot start a transmission. If the bxCAN
has to send a dominant bit (ACK bit, overload flag, active error flag), the bit is rerouted
internally so that the CAN Core monitors this dominant bit, although the CAN bus may
remain in recessive state. Silent mode can be used to analyze the traffic on a CAN bus
without affecting it by the transmission of dominant bits (Acknowledge Bits, Error Frames).
Figure 446. bxCAN in silent mode
bxCAN
Tx

Rx

=1

CANTX CANRX
MS30393V2

36.5.2

Loop back mode
The bxCAN can be set in Loop Back Mode by setting the LBKM bit in the CAN_BTR
register. In Loop Back Mode, the bxCAN treats its own transmitted messages as received
messages and stores them (if they pass acceptance filtering) in a Receive mailbox.
Figure 447. bxCAN in loop back mode
bxCAN
Tx

Rx

CANTX CANRX
MS30394V2

1286/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)
This mode is provided for self-test functions. To be independent of external events, the CAN
Core ignores acknowledge errors (no dominant bit sampled in the acknowledge slot of a
data / remote frame) in Loop Back Mode. In this mode, the bxCAN performs an internal
feedback from its Tx output to its Rx input. The actual value of the CANRX input pin is
disregarded by the bxCAN. The transmitted messages can be monitored on the CANTX pin.

36.5.3

Loop back combined with silent mode
It is also possible to combine Loop Back mode and Silent mode by setting the LBKM and
SILM bits in the CAN_BTR register. This mode can be used for a “Hot Selftest”, meaning the
bxCAN can be tested like in Loop Back mode but without affecting a running CAN system
connected to the CANTX and CANRX pins. In this mode, the CANRX pin is disconnected
from the bxCAN and the CANTX pin is held recessive.
Figure 448. bxCAN in combined mode
bxCAN
Tx

Rx

=1

CANTX CANRX
MS30395V2

36.6

Behavior in debug mode
When the microcontroller enters the debug mode (Cortex®-M7 core halted), the bxCAN
continues to work normally or stops, depending on:
•

the DBG_CAN1_STOP bit for CAN1 or the DBG_CAN2_STOP bit for CAN2 in the
DBG module for the dual mode.

•

the DBF bit in CAN_MCR. For more details, refer to Section 36.9.2: CAN control and
status registers.

36.7

bxCAN functional description

36.7.1

Transmission handling
In order to transmit a message, the application must select one empty transmit mailbox, set
up the identifier, the data length code (DLC) and the data before requesting the transmission
by setting the corresponding TXRQ bit in the CAN_TIxR register. Once the mailbox has left
empty state, the software no longer has write access to the mailbox registers. Immediately
after the TXRQ bit has been set, the mailbox enters pending state and waits to become the
highest priority mailbox, see Transmit Priority. As soon as the mailbox has the highest
priority it will be scheduled for transmission. The transmission of the message of the

RM0385 Rev 7

1287/1709
1325

Controller area network (bxCAN)

RM0385

scheduled mailbox will start (enter transmit state) when the CAN bus becomes idle. Once
the mailbox has been successfully transmitted, it will become empty again. The hardware
indicates a successful transmission by setting the RQCP and TXOK bits in the CAN_TSR
register.
If the transmission fails, the cause is indicated by the ALST bit in the CAN_TSR register in
case of an Arbitration Lost, and/or the TERR bit, in case of transmission error detection.

Transmit priority
By identifier
When more than one transmit mailbox is pending, the transmission order is given by the
identifier of the message stored in the mailbox. The message with the lowest identifier value
has the highest priority according to the arbitration of the CAN protocol. If the identifier
values are equal, the lower mailbox number will be scheduled first.
By transmit request order
The transmit mailboxes can be configured as a transmit FIFO by setting the TXFP bit in the
CAN_MCR register. In this mode the priority order is given by the transmit request order.
This mode is very useful for segmented transmission.

Abort
A transmission request can be aborted by the user setting the ABRQ bit in the CAN_TSR
register. In pending or scheduled state, the mailbox is aborted immediately. An abort
request while the mailbox is in transmit state can have two results. If the mailbox is
transmitted successfully the mailbox becomes empty with the TXOK bit set in the
CAN_TSR register. If the transmission fails, the mailbox becomes scheduled, the
transmission is aborted and becomes empty with TXOK cleared. In all cases the mailbox
will become empty again at least at the end of the current transmission.

Non automatic retransmission mode
This mode has been implemented in order to fulfill the requirement of the Time Triggered
Communication option of the CAN standard. To configure the hardware in this mode the
NART bit in the CAN_MCR register must be set.
In this mode, each transmission is started only once. If the first attempt fails, due to an
arbitration loss or an error, the hardware will not automatically restart the message
transmission.
At the end of the first transmission attempt, the hardware considers the request as
completed and sets the RQCP bit in the CAN_TSR register. The result of the transmission is
indicated in the CAN_TSR register by the TXOK, ALST and TERR bits.

1288/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)
Figure 449. Transmit mailbox states
EMPTY
RQCP=X
TXOK=X
TME = 1

TXRQ=1

PENDING
ABRQ=1

RQCP=0
TXOK=0
TME = 0

Mailbox does not
have highest priority

EMPTY

ABRQ=1

RQCP=1
TXOK=0
TME = 1

CAN Bus = IDLE

Transmit failed * NART

TRANSMIT
RQCP=0
TXOK=0
TME = 0

EMPTY
RQCP=1
TXOK=1
TME = 1

Mailbox has
highest priority

SCHEDULED
RQCP=0
TXOK=0
TME = 0

Transmit failed * NART

Transmit succeeded

MS30396V2

36.7.2

Time triggered communication mode
In this mode, the internal counter of the CAN hardware is activated and used to generate the
Time Stamp value stored in the CAN_RDTxR/CAN_TDTxR registers, respectively (for Rx
and Tx mailboxes). The internal counter is incremented each CAN bit time (refer to
Section 36.7.7: Bit timing). The internal counter is captured on the sample point of the Start
Of Frame bit in both reception and transmission.

36.7.3

Reception handling
For the reception of CAN messages, three mailboxes organized as a FIFO are provided. In
order to save CPU load, simplify the software and guarantee data consistency, the FIFO is
managed completely by hardware. The application accesses the messages stored in the
FIFO through the FIFO output mailbox.

Valid message
A received message is considered as valid when it has been received correctly according to
the CAN protocol (no error until the last but one bit of the EOF field) and It passed through
the identifier filtering successfully, see Section 36.7.4: Identifier filtering.

RM0385 Rev 7

1289/1709
1325

Controller area network (bxCAN)

RM0385
Figure 450. Receive FIFO states

EMPTY

Valid Message

FMP=0x00
FOVR=0

Received

Release
Mailbox

PENDING_1
FMP=0x01
FOVR=0

Release
Mailbox
RFOM=1

Valid Message
Received

PENDING_2
FMP=0x10
FOVR=0

Release
Mailbox
RFOM=1

Valid Message
Received

PENDING_3
FMP=0x11
FOVR=0

Valid Message
Received

Release
Mailbox
RFOM=1

OVERRUN
FMP=0x11
FOVR=1

Valid Message
Received
MS30397V2

FIFO management
Starting from the empty state, the first valid message received is stored in the FIFO which
becomes pending_1. The hardware signals the event setting the FMP[1:0] bits in the
CAN_RFR register to the value 01b. The message is available in the FIFO output mailbox.
The software reads out the mailbox content and releases it by setting the RFOM bit in the
CAN_RFR register. The FIFO becomes empty again. If a new valid message has been
received in the meantime, the FIFO stays in pending_1 state and the new message is
available in the output mailbox.
If the application does not release the mailbox, the next valid message will be stored in the
FIFO which enters pending_2 state (FMP[1:0] = 10b). The storage process is repeated for
the next valid message putting the FIFO into pending_3 state (FMP[1:0] = 11b). At this
point, the software must release the output mailbox by setting the RFOM bit, so that a
mailbox is free to store the next valid message. Otherwise the next valid message received
will cause a loss of message.
Refer also to Section 36.7.5: Message storage

1290/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

Overrun
Once the FIFO is in pending_3 state (i.e. the three mailboxes are full) the next valid
message reception will lead to an overrun and a message will be lost. The hardware
signals the overrun condition by setting the FOVR bit in the CAN_RFR register. Which
message is lost depends on the configuration of the FIFO:
•

If the FIFO lock function is disabled (RFLM bit in the CAN_MCR register cleared) the
last message stored in the FIFO will be overwritten by the new incoming message. In
this case the latest messages will be always available to the application.

•

If the FIFO lock function is enabled (RFLM bit in the CAN_MCR register set) the most
recent message will be discarded and the software will have the three oldest messages
in the FIFO available.

Reception related interrupts
Once a message has been stored in the FIFO, the FMP[1:0] bits are updated and an
interrupt request is generated if the FMPIE bit in the CAN_IER register is set.
When the FIFO becomes full (i.e. a third message is stored) the FULL bit in the CAN_RFR
register is set and an interrupt is generated if the FFIE bit in the CAN_IER register is set.
On overrun condition, the FOVR bit is set and an interrupt is generated if the FOVIE bit in
the CAN_IER register is set.

36.7.4

Identifier filtering
In the CAN protocol the identifier of a message is not associated with the address of a node
but related to the content of the message. Consequently a transmitter broadcasts its
message to all receivers. On message reception a receiver node decides - depending on
the identifier value - whether the software needs the message or not. If the message is
needed, it is copied into the SRAM. If not, the message must be discarded without
intervention by the software.
To fulfill this requirement the bxCAN Controller provides 28 configurable and scalable filter
banks (27-0) to the application, in order to receive only the messages the software needs.
This hardware filtering saves CPU resources which would be otherwise needed to perform
filtering by software. Each filter bank x consists of two 32-bit registers, CAN_FxR0 and
CAN_FxR1.

Scalable width
To optimize and adapt the filters to the application needs, each filter bank can be scaled
independently. Depending on the filter scale a filter bank provides:
•

One 32-bit filter for the STDID[10:0], EXTID[17:0], IDE and RTR bits.

•

Two 16-bit filters for the STDID[10:0], RTR, IDE and EXTID[17:15] bits.

Refer to Figure 451.
Furthermore, the filters can be configured in mask mode or in identifier list mode.

Mask mode
In mask mode the identifier registers are associated with mask registers specifying which
bits of the identifier are handled as “must match” or as “don’t care”.

RM0385 Rev 7

1291/1709
1325

Controller area network (bxCAN)

RM0385

Identifier list mode
In identifier list mode, the mask registers are used as identifier registers. Thus instead of
defining an identifier and a mask, two identifiers are specified, doubling the number of single
identifiers. All bits of the incoming identifier must match the bits specified in the filter
registers.

Filter bank scale and mode configuration
The filter banks are configured by means of the corresponding CAN_FMR register. To
configure a filter bank it must be deactivated by clearing the FACT bit in the CAN_FAR
register. The filter scale is configured by means of the corresponding FSCx bit in the
CAN_FS1R register, refer to Figure 451. The identifier list or identifier mask mode for the
corresponding Mask/Identifier registers is configured by means of the FBMx bits in the
CAN_FMR register.
To filter a group of identifiers, configure the Mask/Identifier registers in mask mode.
To select single identifiers, configure the Mask/Identifier registers in identifier list mode.
Filters not used by the application should be left deactivated.
Each filter within a filter bank is numbered (called the Filter Number) from 0 to a maximum
dependent on the mode and the scale of each of the filter banks.
Concerning the filter configuration, refer to Figure 451.

1292/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)
Figure 451. Filter bank scale configuration - register organization
Filter
Num.

FBMx = 0

ID

CAN_FxR1[31:24]

CAN_FxR1[23:16]

CAN_FxR1[15:8]

CAN_FxR1[7:0]

Mask

CAN_FxR2[31:24]

CAN_FxR2[23:16]

CAN_FxR2[15:8]

CAN_FxR2[7:0]

Mapping STD ID
Mapping Ext ID

STID[10:3]
EXTID[28:21]

n

STID[2:0]
EXID[20:13]

EXID[12:5]

EXID[4:0]

IDE RTR

0

Two 32-Bit Filters - Identifier List

FBMx = 1

FSCx = 1

One 32-Bit Filter - Identifier Mask

ID

CAN_FxR1[31:24]

CAN_FxR1[23:16]

CAN_FxR1[15:8]

CAN_FxR1[7:0]

n

ID

CAN_FxR2[31:24]

CAN_FxR2[23:16]

CAN_FxR2[15:8]

CAN_FxR2[7:0]

n+1

Mapping STD ID
Mapping Ext ID

STID[10:3]
EXTID[28:21]

STID[2:0]
EXID[20:13]

EXID[12:5]

EXID[4:0]

IDE RTR

0

FBMx = 0

Two 16-Bit Filters - Identifier Mask
ID

CAN_FxR1[15:8]

CAN_FxR1[7:0]

Mask

CAN_FxR1[31:24]

CAN_FxR1[23:16]

ID

CAN_FxR2[15:8]

CAN_FxR2[7:0]

Mask

CAN_FxR2[31:24]

CAN_FxR2[23:16]

FSCx = 0

Mapping

STID[10:3]

n

n+1

STID[2:0] RTR IDE EXID[17:15]

FBMx = 1

Four 16-Bit Filters - Identifier List
ID

CAN_FxR1[15:8]

CAN_FxR1[7:0]

ID

CAN_FxR1[31:24]

CAN_FxR1[23:16]

n
n+1

ID

CAN_FxR2[15:8]

CAN_FxR2[7:0]

n+2

ID

CAN_FxR2[31:24]

CAN_FxR2[23:16]

n+3

STID[10:3]

STID[2:0] RTR IDE EXID[17:15]

x = filter bank number
ID=Identifier

Filter Bank Mode

Filter Bank Scale
1
Config. Bits

2

Mapping

1 These bits are located in the CAN_FS1R register
2 These bits are located in the CAN_FM1R register

MSv30398V4

Filter match index
Once a message has been received in the FIFO it is available to the application. Typically,
application data is copied into SRAM locations. To copy the data to the right location the
application has to identify the data by means of the identifier. To avoid this, and to ease the
access to the SRAM locations, the CAN controller provides a Filter Match Index.
This index is stored in the mailbox together with the message according to the filter priority
rules. Thus each received message has its associated filter match index.
The Filter Match index can be used in two ways:
•

Compare the Filter Match index with a list of expected values.

•

Use the Filter Match Index as an index on an array to access the data destination
location.

For non masked filters, the software no longer has to compare the identifier.
If the filter is masked the software reduces the comparison to the masked bits only.

RM0385 Rev 7

1293/1709
1325

Controller area network (bxCAN)

RM0385

The index value of the filter number does not take into account the activation state of the
filter banks. In addition, two independent numbering schemes are used, one for each FIFO.
Refer to Figure 452 for an example.
Figure 452. Example of filter numbering
Filter
Bank

FIFO0

Filter
Num.

Filter
Bank

FIFO1

Filter
Num.

0

ID List (32-bit)

0
1

2

ID Mask (16-bit)

0
1

1

ID Mask (32-bit)

2

4

ID List (32-bit)

2
3

3

ID List (16-bit)

3
4
5
6

7

Deactivated
ID Mask (16-bit)

4
5

5

Deactivated
ID List (32-bit)

7
8

8

ID Mask (16-bit)

6
7

6

ID Mask (16-bit)

9
10

10

Deactivated
ID List (16-bit)

8
9
10
11

9

ID List (32-bit)

11
12

11

ID List (32-bit)

12
13

13

ID Mask (32-bit)

13

12

ID Mask (32-bit)

14

ID=Identifier
MS30399V2

Filter priority rules
Depending on the filter combination it may occur that an identifier passes successfully
through several filters. In this case the filter match value stored in the receive mailbox is
chosen according to the following priority rules:

1294/1709

•

A 32-bit filter takes priority over a 16-bit filter.

•

For filters of equal scale, priority is given to the Identifier List mode over the Identifier
Mask mode

•

For filters of equal scale and mode, priority is given by the filter number (the lower the
number, the higher the priority).

RM0385 Rev 7

RM0385

Controller area network (bxCAN)
Figure 453. Filtering mechanism - example
Example of 3 filter banks in 32-bit unidentified mode and
the remaining in 32-bit identifier mask mode
Message Received
Identifier

Ctrl

Data

Filter bank
Num

Receive FIFO

3

1

4

Identifier & Mask

2

Identifier List

0

Identifier
Identifier
Identifier

0
1
4

Identifier

5

Identifier
Mask

2

Identifier #4 Match

Identifier
3
Mask
No Match
Found

Message
Stored

FMI

Filter number stored in the
Filter Match Index field
within the CAN_RDTxR
register

Message Discarded
MS31000V2

The example above shows the filtering principle of the bxCAN. On reception of a message,
the identifier is compared first with the filters configured in identifier list mode. If there is a
match, the message is stored in the associated FIFO and the index of the matching filter is
stored in the Filter Match Index. As shown in the example, the identifier matches with
Identifier #2 thus the message content and FMI 2 is stored in the FIFO.
If there is no match, the incoming identifier is then compared with the filters configured in
mask mode.
If the identifier does not match any of the identifiers configured in the filters, the message is
discarded by hardware without disturbing the software.

36.7.5

Message storage
The interface between the software and the hardware for the CAN messages is
implemented by means of mailboxes. A mailbox contains all information related to a
message; identifier, data, control, status and time stamp information.

Transmit mailbox
The software sets up the message to be transmitted in an empty transmit mailbox. The
status of the transmission is indicated by hardware in the CAN_TSR register.

RM0385 Rev 7

1295/1709
1325

Controller area network (bxCAN)

RM0385
Table 251. Transmit mailbox mapping

Offset to transmit mailbox base address

Register name

0

CAN_TIxR

4

CAN_TDTxR

8

CAN_TDLxR

12

CAN_TDHxR

Receive mailbox
When a message has been received, it is available to the software in the FIFO output
mailbox. Once the software has handled the message (e.g. read it) the software must
release the FIFO output mailbox by means of the RFOM bit in the CAN_RFR register to
make the next incoming message available. The filter match index is stored in the MFMI
field of the CAN_RDTxR register. The 16-bit time stamp value is stored in the TIME[15:0]
field of CAN_RDTxR.
Table 252. Receive mailbox mapping
Offset to receive mailbox base
address (bytes)

Register name

0

CAN_RIxR

4

CAN_RDTxR

8

CAN_RDLxR

12

CAN_RDHxR

Figure 454. CAN error state diagram
When TEC or REC > 127

ERROR PASSIVE

ERROR ACTIVE

When TEC and REC < 128
When 128*11 recessive bits occur:

When TEC > 255
BUS OFF
ai15903

1296/1709

RM0385 Rev 7

RM0385

36.7.6

Controller area network (bxCAN)

Error management
The error management as described in the CAN protocol is handled entirely by hardware
using a Transmit Error Counter (TEC value, in CAN_ESR register) and a Receive Error
Counter (REC value, in the CAN_ESR register), which get incremented or decremented
according to the error condition. For detailed information about TEC and REC management,
refer to the CAN standard.
Both of them may be read by software to determine the stability of the network.
Furthermore, the CAN hardware provides detailed information on the current error status in
CAN_ESR register. By means of the CAN_IER register (ERRIE bit, etc.), the software can
configure the interrupt generation on error detection in a very flexible way.

Bus-Off recovery
The Bus-Off state is reached when TEC is greater than 255, this state is indicated by BOFF
bit in CAN_ESR register. In Bus-Off state, the bxCAN is no longer able to transmit and
receive messages.
Depending on the ABOM bit in the CAN_MCR register bxCAN will recover from Bus-Off
(become error active again) either automatically or on software request. But in both cases
the bxCAN has to wait at least for the recovery sequence specified in the CAN standard
(128 occurrences of 11 consecutive recessive bits monitored on CANRX).
If ABOM is set, the bxCAN will start the recovering sequence automatically after it has
entered Bus-Off state.
If ABOM is cleared, the software must initiate the recovering sequence by requesting
bxCAN to enter and to leave initialization mode.
Note:

In initialization mode, bxCAN does not monitor the CANRX signal, therefore it cannot
complete the recovery sequence. To recover, bxCAN must be in normal mode.

36.7.7

Bit timing
The bit timing logic monitors the serial bus-line and performs sampling and adjustment of
the sample point by synchronizing on the start-bit edge and resynchronizing on the following
edges.
Its operation may be explained simply by splitting nominal bit time into three segments as
follows:
•

Synchronization segment (SYNC_SEG): a bit change is expected to occur within this
time segment. It has a fixed length of one time quantum (1 x tq).

•

Bit segment 1 (BS1): defines the location of the sample point. It includes the
PROP_SEG and PHASE_SEG1 of the CAN standard. Its duration is programmable
between 1 and 16 time quanta but may be automatically lengthened to compensate for
positive phase drifts due to differences in the frequency of the various nodes of the
network.

•

Bit segment 2 (BS2): defines the location of the transmit point. It represents the
PHASE_SEG2 of the CAN standard. Its duration is programmable between 1 and 8
time quanta but may also be automatically shortened to compensate for negative
phase drifts.

The resynchronization Jump Width (SJW) defines an upper bound to the amount of
lengthening or shortening of the bit segments. It is programmable between 1 and 4 time
quanta.

RM0385 Rev 7

1297/1709
1325

Controller area network (bxCAN)

RM0385

A valid edge is defined as the first transition in a bit time from dominant to recessive bus
level provided the controller itself does not send a recessive bit.
If a valid edge is detected in BS1 instead of SYNC_SEG, BS1 is extended by up to SJW so
that the sample point is delayed.
Conversely, if a valid edge is detected in BS2 instead of SYNC_SEG, BS2 is shortened by
up to SJW so that the transmit point is moved earlier.
As a safeguard against programming errors, the configuration of the Bit Timing Register
(CAN_BTR) is only possible while the device is in Standby mode.
Note:

For a detailed description of the CAN bit timing and resynchronization mechanism, refer to
the ISO 11898 standard.
Figure 455. Bit timing
NOMINAL BIT TIME
SYNC_SEG

BIT SEGMENT 1 (BS1)

tBS1

1 x tq

1
Baud Rate = ------------------------------------------NominalBitTime
NominalBitTime

BIT SEGMENT 2 (BS2)

tBS2

SAMPLE POINT

TRANSMIT POINT

= 1 X t q + t BS 1 + t BS 2

with:
tBS1 = tq x (TS1[3:0] + 1),
tBS2 = tq x (TS2[2:0] + 1),
tq = (BRP[9:0] + 1) x tPCLK
where tq refers to the Time quantum
tPCLK = time period of the APB clock,
BRP[9:0], TS1[3:0] and TS2[2:0] are defined in the CAN_BTR Register.

MS31001V2

1298/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)
Figure 456. CAN frames
Inter-Frame Space
or Overload Frame

Data Frame (Standard Identifier)

Inter-Frame Space
Arbitration Field
32

6

ID

DLC

ACK Field
2

CRC Field
16

8 *N

ACK

Inter-Frame Space

Inter-Frame Space
or Overload Frame

Data Frame (Extended Identifier)
64 + 8 *N

Arbitration Field

Arbitration Field

32

Ctrl Field Data Field
8 *N

32

Arbitration Field
32

16

6
DLC

ID

Flag Echo
6

ACK
ACK Field
2

CRC

End of Frame or
Error Delimiter or
Overload Delimiter

6

6

EOF
ACK

Data Frame or
Remote Frame

Bus Idle

Inter-Frame Space
or Error Frame

Overload Frame

Overload Overload
Echo
Flag

7

Error
Delimiter
8

Inter-Frame Space

Suspend
Intermission
Transmission
3
8

EOF

Inter-Frame Space
or Overload Frame

Error Frame

Error
Flag
6

7

Inter-Frame Space
or Overload Frame

RTR
IDE
r0

SOF

CRC

RTR
r1
r0

SRR
IDE

Remote Frame
44
CRC Field
Ctrl Field

Inter-Frame Space

Data Frame or
Remote Frame

CRC Field ACK Field
2
16

DLC

SOF

ID

Any Frame

7
EOF

CRC

RTR
IDE
r0

SOF

44 + 8 *N
Data Field

Ctrl Field

Overload
Delimiter

Notes:
0 <= N <= 8
SOF = Start Of Frame
ID = Identifier
RTR = Remote Transmission Request
IDE = Identifier Extension Bit
r0 = Reserved Bit
DLC = Data Length Code
CRC = Cyclic Redundancy Code
Error flag: 6 dominant bits if node is error
active, else 6 recessive bits.
Suspend transmission: applies to error
passive nodes only.
EOF = End of Frame
ACK = Acknowledge bit
Ctrl = Control

8
ai15154b

RM0385 Rev 7

1299/1709
1325

Controller area network (bxCAN)

36.8

RM0385

bxCAN interrupts
Four interrupt vectors are dedicated to bxCAN. Each interrupt source can be independently
enabled or disabled by means of the CAN Interrupt Enable Register (CAN_IER).
Figure 457. Event flags and interrupt generation
CAN_IER

CAN_TSR

RQCP0
RQCP1
RQCP2

+

TRANSMIT
INTERRUPT

TMEIE

&

FMPIE0

&

FMP0

FIFO 0
INTERRUPT

CAN_RF0R

FFIE0

&

FOVIE0

&

FMPIE1

&

FULL0

FOVR0

FMP1

+

FIFO 1
INTERRUPT

CAN_RF1R

FFIE1

&

FOVIE1

&

FULL1

FOVR1

+

ERRIE
EWGIE

&

EPVIE

&

EWGF

CAN_ESR

EPVF
BOFIE
BOFF
LECIE
1 LEC 6

&

ERRI

CAN_MSR

STATUS CHANGE
ERROR
INTERRUPT

&
+

WKUIE

&

SLKIE

&

WKUI

CAN_MSR

&

+

SLAKI

MS31002V2

1300/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)
•

•

•

•

36.9

The transmit interrupt can be generated by the following events:
–

Transmit mailbox 0 becomes empty, RQCP0 bit in the CAN_TSR register set.

–

Transmit mailbox 1 becomes empty, RQCP1 bit in the CAN_TSR register set.

–

Transmit mailbox 2 becomes empty, RQCP2 bit in the CAN_TSR register set.

The FIFO 0 interrupt can be generated by the following events:
–

Reception of a new message, FMP0 bits in the CAN_RF0R register are not ‘00’.

–

FIFO0 full condition, FULL0 bit in the CAN_RF0R register set.

–

FIFO0 overrun condition, FOVR0 bit in the CAN_RF0R register set.

The FIFO 1 interrupt can be generated by the following events:
–

Reception of a new message, FMP1 bits in the CAN_RF1R register are not ‘00’.

–

FIFO1 full condition, FULL1 bit in the CAN_RF1R register set.

–

FIFO1 overrun condition, FOVR1 bit in the CAN_RF1R register set.

The error and status change interrupt can be generated by the following events:
–

Error condition, for more details on error conditions refer to the CAN Error Status
register (CAN_ESR).

–

Wakeup condition, SOF monitored on the CAN Rx signal.

–

Entry into Sleep mode.

CAN registers
The peripheral registers have to be accessed by words (32 bits).

36.9.1

Register access protection
Erroneous access to certain configuration registers can cause the hardware to temporarily
disturb the whole CAN network. Therefore the CAN_BTR register can be modified by
software only while the CAN hardware is in initialization mode.
Although the transmission of incorrect data will not cause problems at the CAN network
level, it can severely disturb the application. A transmit mailbox can be only modified by
software while it is in empty state, refer to Figure 449: Transmit mailbox states.
The filter values can be modified either deactivating the associated filter banks or by setting
the FINIT bit. Moreover, the modification of the filter configuration (scale, mode and FIFO
assignment) in CAN_FMxR, CAN_FSxR and CAN_FFAR registers can only be done when
the filter initialization mode is set (FINIT=1) in the CAN_FMR register.

36.9.2

CAN control and status registers
Refer to Section 1.1 for a list of abbreviations used in register descriptions.

CAN master control register (CAN_MCR)
Address offset: 0x00
Reset value: 0x0001 0002

RM0385 Rev 7

1301/1709
1325

Controller area network (bxCAN)

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DBF
rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

RESET

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TTCM

ABOM

AWUM

NART

RFLM

TXFP

SLEEP

INRQ

rw

rw

rw

rw

rw

rw

rw

rw

rs

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 DBF: Debug freeze
0: CAN working during debug
1: CAN reception/transmission frozen during debug. Reception FIFOs can still be
accessed/controlled normally.
Bit 15 RESET: bxCAN software master reset
0: Normal operation.
1: Force a master reset of the bxCAN -> Sleep mode activated after reset (FMP bits and
CAN_MCR register are initialized to the reset values). This bit is automatically reset to 0.
Bits 14:8 Reserved, must be kept at reset value.
Bit 7 TTCM: Time triggered communication mode
0: Time Triggered Communication mode disabled.
1: Time Triggered Communication mode enabled
Note: For more information on Time Triggered Communication mode, refer to Section 36.7.2:
Time triggered communication mode.
Bit 6 ABOM: Automatic bus-off management
This bit controls the behavior of the CAN hardware on leaving the Bus-Off state.
0: The Bus-Off state is left on software request, once 128 occurrences of 11 recessive bits
have been monitored and the software has first set and cleared the INRQ bit of the
CAN_MCR register.
1: The Bus-Off state is left automatically by hardware once 128 occurrences of 11 recessive
bits have been monitored.
For detailed information on the Bus-Off state refer to Section 36.7.6: Error management.
Bit 5 AWUM: Automatic wakeup mode
This bit controls the behavior of the CAN hardware on message reception during Sleep
mode.
0: The Sleep mode is left on software request by clearing the SLEEP bit of the CAN_MCR
register.
1: The Sleep mode is left automatically by hardware on CAN message detection.
The SLEEP bit of the CAN_MCR register and the SLAK bit of the CAN_MSR register are
cleared by hardware.
Bit 4 NART: No automatic retransmission
0: The CAN hardware will automatically retransmit the message until it has been
successfully transmitted according to the CAN standard.
1: A message will be transmitted only once, independently of the transmission result
(successful, error or arbitration lost).

1302/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

Bit 3 RFLM: Receive FIFO locked mode
0: Receive FIFO not locked on overrun. Once a receive FIFO is full the next incoming
message will overwrite the previous one.
1: Receive FIFO locked against overrun. Once a receive FIFO is full the next incoming
message will be discarded.
Bit 2 TXFP: Transmit FIFO priority
This bit controls the transmission order when several mailboxes are pending at the same
time.
0: Priority driven by the identifier of the message
1: Priority driven by the request order (chronologically)
Bit 1 SLEEP: Sleep mode request
This bit is set by software to request the CAN hardware to enter the Sleep mode. Sleep
mode will be entered as soon as the current CAN activity (transmission or reception of a
CAN frame) has been completed.
This bit is cleared by software to exit Sleep mode.
This bit is cleared by hardware when the AWUM bit is set and a SOF bit is detected on the
CAN Rx signal.
This bit is set after reset - CAN starts in Sleep mode.
Bit 0 INRQ: Initialization request
The software clears this bit to switch the hardware into normal mode. Once 11 consecutive
recessive bits have been monitored on the Rx signal the CAN hardware is synchronized and
ready for transmission and reception. Hardware signals this event by clearing the INAK bit in
the CAN_MSR register.
Software sets this bit to request the CAN hardware to enter initialization mode. Once
software has set the INRQ bit, the CAN hardware waits until the current CAN activity
(transmission or reception) is completed before entering the initialization mode. Hardware
signals this event by setting the INAK bit in the CAN_MSR register.

CAN master status register (CAN_MSR)
Address offset: 0x04
Reset value: 0x0000 0C02

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

RX

SAMP

RXM

TXM

Res.

Res.

Res.

SLAKI

WKUI

ERRI

SLAK

INAK

r

r

r

r

rc_w1

rc_w1

rc_w1

r

r

Bits 31:12 Reserved, must be kept at reset value.
Bit 11 RX: CAN Rx signal
Monitors the actual value of the CAN_RX Pin.
Bit 10 SAMP: Last sample point
The value of RX on the last sample point (current received bit value).
Bit 9 RXM: Receive mode
The CAN hardware is currently receiver.

RM0385 Rev 7

1303/1709
1325

Controller area network (bxCAN)

RM0385

Bit 8 TXM: Transmit mode
The CAN hardware is currently transmitter.
Bits 7:5 Reserved, must be kept at reset value.
Bit 4 SLAKI: Sleep acknowledge interrupt
When SLKIE=1, this bit is set by hardware to signal that the bxCAN has entered Sleep
Mode. When set, this bit generates a status change interrupt if the SLKIE bit in the
CAN_IER register is set.
This bit is cleared by software or by hardware, when SLAK is cleared.
Note: When SLKIE=0, no polling on SLAKI is possible. In this case the SLAK bit can be
polled.
Bit 3 WKUI: Wakeup interrupt
This bit is set by hardware to signal that a SOF bit has been detected while the CAN
hardware was in Sleep mode. Setting this bit generates a status change interrupt if the
WKUIE bit in the CAN_IER register is set.
This bit is cleared by software.
Bit 2 ERRI: Error interrupt
This bit is set by hardware when a bit of the CAN_ESR has been set on error detection and
the corresponding interrupt in the CAN_IER is enabled. Setting this bit generates a status
change interrupt if the ERRIE bit in the CAN_IER register is set.
This bit is cleared by software.
Bit 1 SLAK: Sleep acknowledge
This bit is set by hardware and indicates to the software that the CAN hardware is now in
Sleep mode. This bit acknowledges the Sleep mode request from the software (set SLEEP
bit in CAN_MCR register).
This bit is cleared by hardware when the CAN hardware has left Sleep mode (to be
synchronized on the CAN bus). To be synchronized the hardware has to monitor a
sequence of 11 consecutive recessive bits on the CAN RX signal.
Note: The process of leaving Sleep mode is triggered when the SLEEP bit in the CAN_MCR
register is cleared. Refer to the AWUM bit of the CAN_MCR register description for
detailed information for clearing SLEEP bit
Bit 0 INAK: Initialization acknowledge
This bit is set by hardware and indicates to the software that the CAN hardware is now in
initialization mode. This bit acknowledges the initialization request from the software (set
INRQ bit in CAN_MCR register).
This bit is cleared by hardware when the CAN hardware has left the initialization mode (to
be synchronized on the CAN bus). To be synchronized the hardware has to monitor a
sequence of 11 consecutive recessive bits on the CAN RX signal.

CAN transmit status register (CAN_TSR)
Address offset: 0x08
Reset value: 0x1C00 0000
31

30

29

28

27

26

LOW2

LOW1

LOW0

TME2

TME1

TME0

25

24

CODE[1:0]

23

22

21

20

19

18

17

16

ABRQ2

Res.

Res.

Res.

TERR2

ALST2

TXOK2

RQCP2

rc_w1

rc_w1

rc_w1

rc_w1

6

5

4

3

2

1

0

Res.

Res.

Res.

TERR0

ALST0

TXOK0

RQCP0

rc_w1

rc_w1

rc_w1

rc_w1

r

r

r

r

r

r

r

r

rs

15

14

13

12

11

10

9

8

7

ABRQ1

Res.

Res.

Res.

TERR1

ALST1

TXOK1

rc_w1

rc_w1

rc_w1

rs

1304/1709

RQCP1 ABRQ0
rc_w1

rs

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

Bit 31 LOW2: Lowest priority flag for mailbox 2
This bit is set by hardware when more than one mailbox are pending for transmission and
mailbox 2 has the lowest priority.
Bit 30 LOW1: Lowest priority flag for mailbox 1
This bit is set by hardware when more than one mailbox are pending for transmission and
mailbox 1 has the lowest priority.
Bit 29 LOW0: Lowest priority flag for mailbox 0
This bit is set by hardware when more than one mailbox are pending for transmission and
mailbox 0 has the lowest priority.
Note: The LOW[2:0] bits are set to zero when only one mailbox is pending.
Bit 28 TME2: Transmit mailbox 2 empty
This bit is set by hardware when no transmit request is pending for mailbox 2.
Bit 27 TME1: Transmit mailbox 1 empty
This bit is set by hardware when no transmit request is pending for mailbox 1.
Bit 26 TME0: Transmit mailbox 0 empty
This bit is set by hardware when no transmit request is pending for mailbox 0.
Bits 25:24 CODE[1:0]: Mailbox code
In case at least one transmit mailbox is free, the code value is equal to the number of the
next transmit mailbox free.
In case all transmit mailboxes are pending, the code value is equal to the number of the
transmit mailbox with the lowest priority.
Bit 23 ABRQ2: Abort request for mailbox 2
Set by software to abort the transmission request for the corresponding mailbox.
Cleared by hardware when the mailbox becomes empty.
Setting this bit has no effect when the mailbox is not pending for transmission.
Bits 22:20 Reserved, must be kept at reset value.
Bit 19 TERR2: Transmission error of mailbox 2
This bit is set when the previous TX failed due to an error.
Bit 18 ALST2: Arbitration lost for mailbox 2
This bit is set when the previous TX failed due to an arbitration lost.
Bit 17 TXOK2: Transmission OK of mailbox 2
The hardware updates this bit after each transmission attempt.
0: The previous transmission failed
1: The previous transmission was successful
This bit is set by hardware when the transmission request on mailbox 2 has been completed
successfully. Refer to Figure 449.
Bit 16 RQCP2: Request completed mailbox2
Set by hardware when the last request (transmit or abort) has been performed.
Cleared by software writing a “1” or by hardware on transmission request (TXRQ2 set in
CAN_TMID2R register).
Clearing this bit clears all the status bits (TXOK2, ALST2 and TERR2) for Mailbox 2.
Bit 15 ABRQ1: Abort request for mailbox 1
Set by software to abort the transmission request for the corresponding mailbox.
Cleared by hardware when the mailbox becomes empty.
Setting this bit has no effect when the mailbox is not pending for transmission.
Bits 14:12 Reserved, must be kept at reset value.

RM0385 Rev 7

1305/1709
1325

Controller area network (bxCAN)

RM0385

Bit 11 TERR1: Transmission error of mailbox1
This bit is set when the previous TX failed due to an error.
Bit 10 ALST1: Arbitration lost for mailbox1
This bit is set when the previous TX failed due to an arbitration lost.
Bit 9 TXOK1: Transmission OK of mailbox1
The hardware updates this bit after each transmission attempt.
0: The previous transmission failed
1: The previous transmission was successful
This bit is set by hardware when the transmission request on mailbox 1 has been completed
successfully. Refer to Figure 449
Bit 8 RQCP1: Request completed mailbox1
Set by hardware when the last request (transmit or abort) has been performed.
Cleared by software writing a “1” or by hardware on transmission request (TXRQ1 set in
CAN_TI1R register).
Clearing this bit clears all the status bits (TXOK1, ALST1 and TERR1) for Mailbox 1.
Bit 7 ABRQ0: Abort request for mailbox0
Set by software to abort the transmission request for the corresponding mailbox.
Cleared by hardware when the mailbox becomes empty.
Setting this bit has no effect when the mailbox is not pending for transmission.
Bits 6:4 Reserved, must be kept at reset value.
Bit 3 TERR0: Transmission error of mailbox0
This bit is set when the previous TX failed due to an error.
Bit 2 ALST0: Arbitration lost for mailbox0
This bit is set when the previous TX failed due to an arbitration lost.
Bit 1 TXOK0: Transmission OK of mailbox0
The hardware updates this bit after each transmission attempt.
0: The previous transmission failed
1: The previous transmission was successful
This bit is set by hardware when the transmission request on mailbox 1 has been completed
successfully. Refer to Figure 449
Bit 0 RQCP0: Request completed mailbox0
Set by hardware when the last request (transmit or abort) has been performed.
Cleared by software writing a “1” or by hardware on transmission request (TXRQ0 set in
CAN_TI0R register).
Clearing this bit clears all the status bits (TXOK0, ALST0 and TERR0) for Mailbox 0.

CAN receive FIFO 0 register (CAN_RF0R)
Address offset: 0x0C
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FULL0

Res.

RFOM0 FOVR0
rs

1306/1709

RM0385 Rev 7

rc_w1

rc_w1

FMP0[1:0]
r

r

RM0385

Controller area network (bxCAN)

Bits 31:6 Reserved, must be kept at reset value.
Bit 5 RFOM0: Release FIFO 0 output mailbox
Set by software to release the output mailbox of the FIFO. The output mailbox can only be
released when at least one message is pending in the FIFO. Setting this bit when the FIFO
is empty has no effect. If at least two messages are pending in the FIFO, the software has to
release the output mailbox to access the next message.
Cleared by hardware when the output mailbox has been released.
Bit 4 FOVR0: FIFO 0 overrun
This bit is set by hardware when a new message has been received and passed the filter
while the FIFO was full.
This bit is cleared by software.
Bit 3 FULL0: FIFO 0 full
Set by hardware when three messages are stored in the FIFO.
This bit is cleared by software.
Bit 2 Reserved, must be kept at reset value.
Bits 1:0 FMP0[1:0]: FIFO 0 message pending
These bits indicate how many messages are pending in the receive FIFO.
FMP is increased each time the hardware stores a new message in to the FIFO. FMP is
decreased each time the software releases the output mailbox by setting the RFOM0 bit.

CAN receive FIFO 1 register (CAN_RF1R)
Address offset: 0x10
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FULL1

Res.

RFOM1 FOVR1
rs

rc_w1

rc_w1

FMP1[1:0]
r

r

Bits 31:6 Reserved, must be kept at reset value.
Bit 5 RFOM1: Release FIFO 1 output mailbox
Set by software to release the output mailbox of the FIFO. The output mailbox can only be
released when at least one message is pending in the FIFO. Setting this bit when the FIFO
is empty has no effect. If at least two messages are pending in the FIFO, the software has to
release the output mailbox to access the next message.
Cleared by hardware when the output mailbox has been released.
Bit 4 FOVR1: FIFO 1 overrun
This bit is set by hardware when a new message has been received and passed the filter
while the FIFO was full.
This bit is cleared by software.

RM0385 Rev 7

1307/1709
1325

Controller area network (bxCAN)

RM0385

Bit 3 FULL1: FIFO 1 full
Set by hardware when three messages are stored in the FIFO.
This bit is cleared by software.
Bit 2 Reserved, must be kept at reset value.
Bits 1:0 FMP1[1:0]: FIFO 1 message pending
These bits indicate how many messages are pending in the receive FIFO1.
FMP1 is increased each time the hardware stores a new message in to the FIFO1. FMP is
decreased each time the software releases the output mailbox by setting the RFOM1 bit.

CAN interrupt enable register (CAN_IER)
Address offset: 0x14
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SLKIE

WKUIE

rw

rw

15
ERRIE

14
Res.

rw

13
Res.

12

11

10

9

8

Res.

LEC
IE

BOF
IE

EPV
IE

EWG
IE

rw

rw

rw

rw

7

6

5

4

3

2

1

0

Res.

FOV
IE1

FF
IE1

FMP
IE1

FOV
IE0

FF
IE0

FMP
IE0

TME
IE

rw

rw

rw

rw

rw

rw

rw

Bits 31:18 Reserved, must be kept at reset value.
Bit 17 SLKIE: Sleep interrupt enable
0: No interrupt when SLAKI bit is set.
1: Interrupt generated when SLAKI bit is set.
Bit 16 WKUIE: Wakeup interrupt enable
0: No interrupt when WKUI is set.
1: Interrupt generated when WKUI bit is set.
Bit 15 ERRIE: Error interrupt enable
0: No interrupt will be generated when an error condition is pending in the CAN_ESR.
1: An interrupt will be generation when an error condition is pending in the CAN_ESR.
Bits 14:12 Reserved, must be kept at reset value.
Bit 11 LECIE: Last error code interrupt enable
0: ERRI bit will not be set when the error code in LEC[2:0] is set by hardware on error
detection.
1: ERRI bit will be set when the error code in LEC[2:0] is set by hardware on error detection.
Bit 10 BOFIE: Bus-off interrupt enable
0: ERRI bit will not be set when BOFF is set.
1: ERRI bit will be set when BOFF is set.
Bit 9 EPVIE: Error passive interrupt enable
0: ERRI bit will not be set when EPVF is set.
1: ERRI bit will be set when EPVF is set.

1308/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

Bit 8 EWGIE: Error warning interrupt enable
0: ERRI bit will not be set when EWGF is set.
1: ERRI bit will be set when EWGF is set.
Bit 7 Reserved, must be kept at reset value.
Bit 6 FOVIE1: FIFO overrun interrupt enable
0: No interrupt when FOVR is set.
1: Interrupt generation when FOVR is set.
Bit 5 FFIE1: FIFO full interrupt enable
0: No interrupt when FULL bit is set.
1: Interrupt generated when FULL bit is set.
Bit 4 FMPIE1: FIFO message pending interrupt enable
0: No interrupt generated when state of FMP[1:0] bits are not 00b.
1: Interrupt generated when state of FMP[1:0] bits are not 00b.
Bit 3 FOVIE0: FIFO overrun interrupt enable
0: No interrupt when FOVR bit is set.
1: Interrupt generated when FOVR bit is set.
Bit 2 FFIE0: FIFO full interrupt enable
0: No interrupt when FULL bit is set.
1: Interrupt generated when FULL bit is set.
Bit 1 FMPIE0: FIFO message pending interrupt enable
0: No interrupt generated when state of FMP[1:0] bits are not 00b.
1: Interrupt generated when state of FMP[1:0] bits are not 00b.
Bit 0 TMEIE: Transmit mailbox empty interrupt enable
0: No interrupt when RQCPx bit is set.
1: Interrupt generated when RQCPx bit is set.
Note: Refer to Section 36.8: bxCAN interrupts.

CAN error status register (CAN_ESR)
Address offset: 0x18
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

REC[7:0]
r

r

r

r

r

20

19

18

17

16

r

r

r

TEC[7:0]
r

r

r

r

r
6

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

5

4

LEC[2:0]
rw

RM0385 Rev 7

r

rw

rw

r
3

2

1

0

Res.

BOFF

EPVF

EWGF

r

r

r

1309/1709
1325

Controller area network (bxCAN)

RM0385

Bits 31:24 REC[7:0]: Receive error counter
The implementing part of the fault confinement mechanism of the CAN protocol. In case of
an error during reception, this counter is incremented by 1 or by 8 depending on the error
condition as defined by the CAN standard. After every successful reception the counter is
decremented by 1 or reset to 120 if its value was higher than 128. When the counter value
exceeds 127, the CAN controller enters the error passive state.
Bits 23:16 TEC[7:0]: Least significant byte of the 9-bit transmit error counter
The implementing part of the fault confinement mechanism of the CAN protocol.
Bits 15:7 Reserved, must be kept at reset value.
Bits 6:4 LEC[2:0]: Last error code
This field is set by hardware and holds a code which indicates the error condition of the last
error detected on the CAN bus. If a message has been transferred (reception or
transmission) without error, this field will be cleared to ‘0’.
The LEC[2:0] bits can be set to value 0b111 by software. They are updated by hardware to
indicate the current communication status.
000: No Error
001: Stuff Error
010: Form Error
011: Acknowledgment Error
100: Bit recessive Error
101: Bit dominant Error
110: CRC Error
111: Set by software
Bit 3 Reserved, must be kept at reset value.
Bit 2 BOFF: Bus-off flag
This bit is set by hardware when it enters the bus-off state. The bus-off state is entered on
TEC overflow, greater than 255, refer to Section 36.7.6 on page 1297.
Bit 1 EPVF: Error passive flag
This bit is set by hardware when the Error Passive limit has been reached (Receive Error
Counter or Transmit Error Counter>127).
Bit 0 EWGF: Error warning flag
This bit is set by hardware when the warning limit has been reached
(Receive Error Counter or Transmit Error Counter≥96).

CAN bit timing register (CAN_BTR)
Address offset: 0x1C
Reset value: 0x0123 0000
This register can only be accessed by the software when the CAN hardware is in
initialization mode.
31

30

29

28

27

26

SILM

LBKM

Res.

Res.

Res.

Res.

rw

rw

15

14

13

12

11

10

Res.

Res.

Res.

Res.

Res.

Res.

25

SJW[1:0]
rw

rw

9

8

23

22

Res.

7

21

20

19

18

TS2[2:0]

17

16

TS1[3:0]

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

rw

BRP[9:0]
rw

1310/1709

24

rw

rw

RM0385 Rev 7

rw

rw

rw

RM0385

Controller area network (bxCAN)

Bit 31 SILM: Silent mode (debug)
0: Normal operation
1: Silent Mode
Bit 30 LBKM: Loop back mode (debug)
0: Loop Back Mode disabled
1: Loop Back Mode enabled
Bits 29:26 Reserved, must be kept at reset value.
Bits 25:24 SJW[1:0]: Resynchronization jump width
These bits define the maximum number of time quanta the CAN hardware is allowed to
lengthen or shorten a bit to perform the resynchronization.
tRJW = tq x (SJW[1:0] + 1)
Bit 23 Reserved, must be kept at reset value.
Bits 22:20 TS2[2:0]: Time segment 2
These bits define the number of time quanta in Time Segment 2.
tBS2 = tq x (TS2[2:0] + 1)
Bits 19:16 TS1[3:0]: Time segment 1
These bits define the number of time quanta in Time Segment 1
tBS1 = tq x (TS1[3:0] + 1)
For more information on bit timing, refer to Section 36.7.7: Bit timing on page 1297.
Bits 15:10 Reserved, must be kept at reset value.
Bits 9:0 BRP[9:0]: Baud rate prescaler
These bits define the length of a time quanta.
tq = (BRP[9:0]+1) x tPCLK

36.9.3

CAN mailbox registers
This chapter describes the registers of the transmit and receive mailboxes. Refer to
Section 36.7.5: Message storage on page 1295 for detailed register mapping.
Transmit and receive mailboxes have the same registers except:
•

The FMI field in the CAN_RDTxR register.

•

A receive mailbox is always write protected.

•

A transmit mailbox is write-enabled only while empty, corresponding TME bit in the
CAN_TSR register set.

There are 3 TX Mailboxes and 2 RX Mailboxes. Each RX Mailbox allows access to a 3 level
depth FIFO, the access being offered only to the oldest received message in the FIFO.
Each mailbox consist of 4 registers.

RM0385 Rev 7

1311/1709
1325

Controller area network (bxCAN)

RM0385
Figure 458. CAN mailbox registers

CAN_RI0R

CAN_RI1R

CAN_TI0R

CAN_TI1R

CAN_TI2R

CAN_RDT0R

CAN_RDT1R

CAN_TDT0R

CAN_TDT1R

CAN_TDT2R

CAN_RL0R

CAN_RL1R

CAN_TDL0R

CAN_TDL1R

CAN_TDL2R

CAN_RH0R

CAN_RH1R

CAN_TDH0R

CAN_TDH1R

CAN_TDH2R

FIFO1

FIFO0

Three Tx Mailboxes
MS31003V2

CAN TX mailbox identifier register (CAN_TIxR) (x = 0..2)
Address offsets: 0x180, 0x190, 0x1A0
Reset value: 0xXXXX XXXX (except bit 0, TXRQ = 0)
All TX registers are write protected when the mailbox is pending transmission (TMEx reset).
This register also implements the TX request control (bit 0) - reset value 0.
31

30

29

28

27

26

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

25

24

23

22

21

20

19

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

STID[10:0]/EXID[28:18]

rw

rw

rw

rw

rw

rw

17

16

rw

rw

rw

2

1

0

IDE

RTR

TXRQ

rw

rw

rw

EXID[17:13]

EXID[12:0]
rw

18

rw

rw

rw

rw

rw

rw

Bits 31:21 STID[10:0]/EXID[28:18]: Standard identifier or extended identifier
The standard identifier or the MSBs of the extended identifier (depending on the IDE bit
value).
Bit 20:3 EXID[17:0]: Extended identifier
The LSBs of the extended identifier.
Bit 2 IDE: Identifier extension
This bit defines the identifier type of message in the mailbox.
0: Standard identifier.
1: Extended identifier.
Bit 1 RTR: Remote transmission request
0: Data frame
1: Remote frame
Bit 0 TXRQ: Transmit mailbox request
Set by software to request the transmission for the corresponding mailbox.
Cleared by hardware when the mailbox becomes empty.

1312/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

CAN mailbox data length control and time stamp register
(CAN_TDTxR) (x = 0..2)
All bits of this register are write protected when the mailbox is not in empty state.
Address offsets: 0x184, 0x194, 0x1A4
Reset value: 0xXXXX XXXX
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

TIME[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
rw

rw

DLC[3:0]
rw

rw

Bits 31:16 TIME[15:0]: Message time stamp
This field contains the 16-bit timer value captured at the SOF transmission.
Bits 15:9 Reserved, must be kept at reset value.
Bit 8 TGT: Transmit global time
This bit is active only when the hardware is in the Time Trigger Communication mode,
TTCM bit of the CAN_MCR register is set.
0: Time stamp TIME[15:0] is not sent.
1: Time stamp TIME[15:0] value is sent in the last two data bytes of the 8-byte message:
TIME[7:0] in data byte 7 and TIME[15:8] in data byte 6, replacing the data written in
CAN_TDHxR[31:16] register (DATA6[7:0] and DATA7[7:0]). DLC must be programmed as 8
in order these two bytes to be sent over the CAN bus.
Bits 7:4 Reserved, must be kept at reset value.
Bits 3:0 DLC[3:0]: Data length code
This field defines the number of data bytes a data frame contains or a remote frame request.
A message can contain from 0 to 8 data bytes, depending on the value in the DLC field.

RM0385 Rev 7

1313/1709
1325

Controller area network (bxCAN)

RM0385

CAN mailbox data low register (CAN_TDLxR) (x = 0..2)
All bits of this register are write protected when the mailbox is not in empty state.
Address offsets: 0x188, 0x198, 0x1A8
Reset value: 0xXXXX XXXX
31

30

29

28

27

26

25

24

23

22

21

DATA3[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

DATA1[7:0]
rw

rw

rw

rw

19

18

17

16

DATA2[7:0]

rw

rw

20

rw

rw

rw

rw

rw

4

3

2

1

0

rw

rw

rw

18

17

16

DATA0[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:24 DATA3[7:0]: Data byte 3
Data byte 3 of the message.
Bits 23:16 DATA2[7:0]: Data byte 2
Data byte 2 of the message.
Bits 15:8 DATA1[7:0]: Data byte 1

Data byte 1 of the message.
Bits 7:0 DATA0[7:0]: Data byte 0
Data byte 0 of the message.
A message can contain from 0 to 8 data bytes and starts with byte 0.

CAN mailbox data high register (CAN_TDHxR) (x = 0..2)
All bits of this register are write protected when the mailbox is not in empty state.
Address offsets: 0x18C, 0x19C, 0x1AC
Reset value: 0xXXXX XXXX
31

30

29

28

27

26

25

24

23

22

21

DATA7[7:0]

20

19

DATA6[7:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

DATA5[7:0]

1314/1709

rw

DATA4[7:0]

RM0385 Rev 7

rw

RM0385

Controller area network (bxCAN)

Bits 31:24 DATA7[7:0]: Data byte 7
Data byte 7 of the message.
Note: If TGT of this message and TTCM are active, DATA7 and DATA6 will be replaced by
the TIME stamp value.
Bits 23:16 DATA6[7:0]: Data byte 6
Data byte 6 of the message.
Bits 15:8 DATA5[7:0]: Data byte 5

Data byte 5 of the message.
Bits 7:0 DATA4[7:0]: Data byte 4
Data byte 4 of the message.

CAN receive FIFO mailbox identifier register (CAN_RIxR) (x = 0..1)
Address offsets: 0x1B0, 0x1C0
Reset value: 0xXXXX XXXX
All RX registers are write protected.

31

30

29

28

27

26

25

24

23

22

21

20

19

STID[10:0]/EXID[28:18]
r

r

r

r

r

r

15

14

13

12

11

10

r

r

r

r

r

r

r

r

r

r

r

r

9

8

7

6

5

4

3

r

17

16

r

r

EXID[17:13]

EXID[12:0]
r

18

r

r

r

r

r

r

r
2

1

0

IDE

RTR

Res

r

r

Bits 31:21 STID[10:0]/EXID[28:18]: Standard identifier or extended identifier
The standard identifier or the MSBs of the extended identifier (depending on the IDE bit
value).
Bits 20:3 EXID[17:0]: Extended identifier
The LSBs of the extended identifier.
Bit 2 IDE: Identifier extension
This bit defines the identifier type of message in the mailbox.
0: Standard identifier.
1: Extended identifier.
Bit 1 RTR: Remote transmission request
0: Data frame
1: Remote frame
Bit 0 Reserved, must be kept at reset value.

RM0385 Rev 7

1315/1709
1325

Controller area network (bxCAN)

RM0385

CAN receive FIFO mailbox data length control and time stamp register
(CAN_RDTxR) (x = 0..1)
Address offsets: 0x1B4, 0x1C4
Reset value: 0xXXXX XXXX
All RX registers are write protected.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

TIME[15:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

r

r

r

r

r

r

r

r

r

FMI[7:0]
r

DLC[3:0]
r

r

Bits 31:16 TIME[15:0]: Message time stamp
This field contains the 16-bit timer value captured at the SOF detection.
Bits 15:8 FMI[7:0]: Filter match index
This register contains the index of the filter the message stored in the mailbox passed
through. For more details on identifier filtering refer to Section 36.7.4: Identifier filtering on
page 1291 - Filter Match Index paragraph.
Bits 7:4 Reserved, must be kept at reset value.
Bits 3:0 DLC[3:0]: Data length code
This field defines the number of data bytes a data frame contains (0 to 8). It is 0 in the case
of a remote frame request.

1316/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

CAN receive FIFO mailbox data low register (CAN_RDLxR) (x = 0..1)
All bits of this register are write protected when the mailbox is not in empty state.
Address offsets: 0x1B8, 0x1C8
Reset value: 0xXXXX XXXX
All RX registers are write protected.
31

30

29

28

27

26

25

24

23

22

21

DATA3[7:0]
r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

DATA1[7:0]
r

r

r

r

19

18

17

16

DATA2[7:0]

r

r

20

r

r

r

r

r

4

3

2

1

0

r

r

r

18

17

16

DATA0[7:0]
r

r

r

r

r

r

r

r

Bits 31:24 DATA3[7:0]: Data Byte 3
Data byte 3 of the message.
Bits 23:16 DATA2[7:0]: Data Byte 2
Data byte 2 of the message.
Bits 15:8 DATA1[7:0]: Data Byte 1

Data byte 1 of the message.
Bits 7:0 DATA0[7:0]: Data Byte 0
Data byte 0 of the message.
A message can contain from 0 to 8 data bytes and starts with byte 0.

CAN receive FIFO mailbox data high register (CAN_RDHxR) (x = 0..1)
Address offsets: 0x1BC, 0x1CC
Reset value: 0xXXXX XXXX
All RX registers are write protected.
31

30

29

28

27

26

25

24

23

22

21

DATA7[7:0]

20

19

DATA6[7:0]

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

DATA5[7:0]
r

r

DATA4[7:0]
r

r

Bits 31:24 DATA7[7:0]: Data Byte 7
Data byte 3 of the message.

RM0385 Rev 7

1317/1709
1325

Controller area network (bxCAN)

RM0385

Bits 23:16 DATA6[7:0]: Data Byte 6
Data byte 2 of the message.
Bits 15:8 DATA5[7:0]: Data Byte 5

Data byte 1 of the message.
Bits 7:0 DATA4[7:0]: Data Byte 4
Data byte 0 of the message.

36.9.4

CAN filter registers
CAN filter master register (CAN_FMR)
Address offset: 0x200
Reset value: 0x2A1C 0E01
All bits of this register are set and cleared by software.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

Res.

Res.

CANSB[5:0]
rw

Bits 31:14
Bits 13:8

Bits 7:1
Bit 0

rw

rw

rw

rw

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FINIT

rw

rw

Reserved, must be kept at reset value.
CANSB[5:0]: CAN start bank
These bits are set and cleared by software. When both CAN are used, they define the start
bank of each CAN interface:
000001 = 1 filter assigned to CAN1 and 27 assigned to CAN2
011011 = 27 filters assigned to CAN1 and 1 filter assigned to CAN2
–
to assign all filters to one CAN set CANSB value to zero and deactivate the non
used CAN
–
to use CAN1 only: stop the clock on CAN2 and/or set the CAN_MCR.INRQ on
CAN2
–
to use CAN2 only: set the CAN_MCR.INRQ on CAN1 or deactivate the interupt
register CAN_IER on CAN1
Reserved, must be kept at reset value.
FINIT: Filter initialization mode
Initialization mode for filter banks
0: Active filters mode.
1: Initialization mode for the filters.

CAN filter mode register (CAN_FM1R)
Address offset: 0x204
Reset value: 0x0000 0000
This register can be written only when the filter initialization mode is set (FINIT=1) in the
CAN_FMR register.

1318/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

27

26

rw

rw

Note:

rw

24

23

22

21

20

19

18

17

16

FBM27 FBM26 FBM25 FBM24 FBM23 FBM22 FBM21 FBM20 FBM19 FBM18 FBM17 FBM16
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

5

4

3

2

1

0

FBM9

FBM8

FBM7

FBM6

FBM5

FBM4

FBM3

FBM2

FBM1

FBM0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

FBM15 FBM14 FBM13 FBM12 FBM11 FBM10
rw

25

rw

rw

rw

Refer to Figure 451: Filter bank scale configuration - register organization on page 1293.
Bits 31: Reserved, must be kept at reset value.
Bits 27:0 FBMx: Filter mode
Mode of the registers of Filter x.
0: Two 32-bit registers of filter bank x are in Identifier Mask mode.
1: Two 32-bit registers of filter bank x are in Identifier List mode.

CAN filter scale register (CAN_FS1R)
Address offset: 0x20C
Reset value: 0x0000 0000
This register can be written only when the filter initialization mode is set (FINIT=1) in the
CAN_FMR register.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

FSC27

FSC26

FSC25

FSC24

FSC23

FSC22

FSC21

FSC20

FSC19

FSC18

FSC17

FSC16

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

FSC15

FSC14

FSC13

FSC12

FSC11

FSC10

FSC9

FSC8

FSC7

FSC6

FSC5

FSC4

FSC3

FSC2

FSC1

FSC0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:0 FSCx: Filter scale configuration
These bits define the scale configuration of Filters 27-0.
0: Dual 16-bit scale configuration
1: Single 32-bit scale configuration

Note:

Refer to Figure 451: Filter bank scale configuration - register organization on page 1293.

CAN filter FIFO assignment register (CAN_FFA1R)
Address offset: 0x214
Reset value: 0x0000 0000
This register can be written only when the filter initialization mode is set (FINIT=1) in the
CAN_FMR register.

RM0385 Rev 7

1319/1709
1325

Controller area network (bxCAN)

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

FFA27

FFA26

FFA25

FFA24

FFA23

FFA22

FFA21

FFA20

FFA19

FFA18

FFA17

FFA16

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

FFA15

FFA14

FFA13

FFA12

FFA11

FFA10

FFA9

FFA8

FFA7

FFA6

FFA5

FFA4

FFA3

FFA2

FFA1

FFA0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:0 FFAx: Filter FIFO assignment for filter x
The message passing through this filter will be stored in the specified FIFO.
0: Filter assigned to FIFO 0
1: Filter assigned to FIFO 1

CAN filter activation register (CAN_FA1R)
Address offset: 0x21C
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

FACT2
7

FACT2
6

FACT2
5

FACT2
4

FACT2
3

FACT2
2

FACT2
1

FACT2
0

FACT1
9

FACT1
8

FACT1
7

FACT1
6

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

FACT1
5

FACT1
4

FACT1
3

FACT1
2

FACT1
1

FACT1
0

FACT9

FACT8

FACT7

FACT6

FACT5

FACT4

FACT3

FACT2

FACT1

FACT0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:0 FACTx: Filter active
The software sets this bit to activate Filter x. To modify the Filter x registers (CAN_FxR[0:7]),
the FACTx bit must be cleared or the FINIT bit of the CAN_FMR register must be set.
0: Filter x is not active
1: Filter x is active

1320/1709

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

Filter bank i register x (CAN_FiRx) (i = 0..27, x = 1, 2)
Address offsets: 0x240 to 0x31C
Reset value: 0xXXXX XXXX
There are 28 filter banks, i= 0 to 27. Each filter bank i is composed of two 32-bit registers,
CAN_FiR[2:1].
This register can only be modified when the FACTx bit of the CAN_FAxR register is cleared
or when the FINIT bit of the CAN_FMR register is set.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

FB31

FB30

FB29

FB28

FB27

FB26

FB25

FB24

FB23

FB22

FB21

FB20

FB19

FB18

FB17

FB16

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

FB15

FB14

FB13

FB12

FB11

FB10

FB9

FB8

FB7

FB6

FB5

FB4

FB3

FB2

FB1

FB0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

In all configurations:
Bits 31:0 FB[31:0]: Filter bits
Identifier
Each bit of the register specifies the level of the corresponding bit of the expected identifier.
0: Dominant bit is expected
1: Recessive bit is expected
Mask
Each bit of the register specifies whether the bit of the associated identifier register must
match with the corresponding bit of the expected identifier or not.
0: Do not care, the bit is not used for the comparison
1: Must match, the bit of the incoming identifier must have the same level has specified in
the corresponding identifier register of the filter.

Note:

Depending on the scale and mode configuration of the filter the function of each register can
differ. For the filter mapping, functions description and mask registers association, refer to
Section 36.7.4: Identifier filtering on page 1291.
A Mask/Identifier register in mask mode has the same bit mapping as in identifier list
mode.
For the register mapping/addresses of the filter banks refer to Table 253 on page 1322.

RM0385 Rev 7

1321/1709
1325

0x180

1322/1709
0
0

CAN_BTR

Res.

Reset value

0

0

-

CAN_TI0R

Reset value

x

x

x

x

x

x

0

Res.

x

x

x

1

0

0

0

1

1

Res.

Res.

Res.

x

x

x

x

x

x

RM0385 Rev 7

STID[10:0]/EXID[28:18]

x

x

x

x

x

x
0
TMEIE

0
0
0

0
EWGF

0

EPVF

0
BOFF

FMP1[1:0]

Res.

RQCP0

INRQ

INAK
0

0

0
0
0
FMP0[1:0]

TXFP
SLEEP

ERRI
1

ALST0

SLAK

NART
RFLM

WKUI

0

SLAKI

1

Res.

0

0
TXOK0

FULL0

ABOM
AWUM
0

Res.

Res.

Res.

0

Res.

TXM

Res.

0

0

Res.

FOVR0

Res.

RXM

Res.

TTCM

SAMP

Res.

Res.

Res.

0

Res.

RX

Res.

Res.

Res.

DBF
RESET

Res.

0

0
TERR0

RFOM0
0
Res.

0
FFIE0

FULL1

0
FMPIE0

FOVR1

0

FOVIE0

0

FMPIE1

0

Res.

Res.

Res.

Res.

Res.

ABRQ0

Res.

0

0

0

0

x

x

x

x

x

x

x

Res.

0

0

TXRQ

0

Res.

Res.

Reset value

Res.

0

Res.

Reset value
RFOM1

RQCP1
0

FFIE1

TXOK1
0

FOVIE1

ALST1
0

LEC[2:0]

Res.

Res.

TERR1

Res.

Res.

0

Res.

Res.

Res.
0

Res.

0

Res.

EWGIE

0

Res.

Res.

ABRQ1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

IDE

0

Res.

EPVIE

0

Res.

Res.

RQCP2

Res.
Res.

TXOK2

Res.

Res.

ALST2

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

BOFIE

0

Res.

Res.

Res.

Res.

Res.

TERR2

Res.

Res.

Res.

Res.

Res.

Res.

ABRQ2

Res.

1

Res.

LECIE

Res.
0

Res.

Res.

Res.

Res.

CODE[1:0]

Res.

Res.

Res.

Res.

Res.

1

RTR

0

Res.

x

0

Res.

EXID[17:0]

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0
Res.

Res.

0

Res.

Res.

Reset value

Res.

TS1[3:0]
Res.

Res.

Res.

TME[2:0]

0

Res.

ERRIE

Res.

TEC[7:0]
WKUIE

0
Res.

Res.

Res.

0

Res.

0
Res.

Res.

Res.

0

Res.

0
0

Res.

TS2[2:0]
0

0

Res.

0

Res.

0x018
SLKIE

Reset value
1

Res.

0
Res.

Res.

Res.

Res.

Reset value

Res.

0

Res.

REC[7:0]
Res.

CAN_RF0R

Res.

0

Res.

0

Res.

0

Res.

1

Res.

1

Res.

Res.

1

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

CAN_ESR

Res.

CAN_IER

SJW[1:0]

0

Res.

0x014

Res.

CAN_RF1R

Res.

0x010

Res.

CAN_TSR
LOW[2:0]

0x008

Res.

0

Res.

0x00C
Reset value

Res.

CAN_MSR

Res.

0x004

Res.

CAN_MCR

Res.

0x000

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register

Res.
0

Res.

0x0200x17F
0

Res.

0x01C
0

SILM

Reset value

LBKM

Offset

Res.

36.9.5

Res.

Controller area network (bxCAN)
RM0385

bxCAN register map
Refer to Section 2.2.2 on page 69 for the register boundary addresses. The registers from
offset 0x200 to 0x31C are present only in CAN1.
Table 253. bxCAN register map and reset values

0
0

0
0

0
0
0

BRP[9:0]

x

x

0

RM0385

Controller area network (bxCAN)

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

0x1A8

x

x

x

x

x

x

x

0x1AC

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

DATA7[7:0]
x

x

CAN_RI0R

x

x

x

x

x

x

Res.

Res.

Res.

Res.

x

x

x

x

x

- - - -

- - - - - - -

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

- - - -

- - - - - - -

x

x

x

x

x

x

x

x

x

x

x

x

x

STID[10:0]/EXID[28:18]

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

RM0385 Rev 7

x

x

x

x

x

x

x

x

x

x

x

0

x

x

x

x

x

x

x

x

x

x

0

x

x

x

x

x

x

x

x

x

x

x

-

x

DATA4[7:0]
x

x

x

x

x

x

x

x

x

x

x

x

x

x

EXID[17:0]
x

x

DLC[3:0]

0x1B0
Reset value

x

DATA0[7:0]

DATA5[7:0]
x

x

x

DLC[3:0]

x

x

x

x

DATA4[7:0]

DATA1[7:0]
x

x

DATA0[7:0]

x

DATA6[7:0]
x

Res.

x

DATA2[7:0]
x

Res.

x

EXID[17:0]

DATA3[7:0]

CAN_TDH2R
Reset value

x

DATA5[7:0]

TIME[15:0]

CAN_TDL2R
Reset value

x

DATA1[7:0]

0x1A4
Reset value

x

x

Res.

x

x

Res.

CAN_TDT2R

x

x

Res.

x

x

Res.

x

x

TGT

x

x

Res.

x

x

Res.

x

x

x

x

STID[10:0]/EXID[28:18]
x

x

x

DATA6[7:0]
x

x

x

DATA2[7:0]
x

x

Res.

x

DATA7[7:0]

CAN_TI2R
Reset value

x

x

x

DATA4[7:0]

Res.

0x1A0

x

x

EXID[17:0]

DATA3[7:0]

CAN_TDH1R
Reset value

x

x

Res.

0x19C

x

Res.

DATA5[7:0]

TIME[15:0]
x

x

Res.

x

x

Res.

x

x

Res.

x

x

TGT

x

x

Res.

x

x

Res.

x

x

Res.

x

x

x

DATA0[7:0]

Res.

x

- - - -

Res.

x

CAN_TDL1R
Reset value

x

STID[10:0]/EXID[28:18]

CAN_TDT1R

0x198

x

DATA6[7:0]
x

x

DATA1[7:0]

0x194
Reset value

- - - - - - -

DATA2[7:0]

DATA7[7:0]
x

x

TXRQ

x

x

TXRQ

x

x

Res.

x

x

IDE

x

x

RTR

x

IDE

x

RTR

x

TGT

x

Res.

x

IDE

x

CAN_TI1R
Reset value

x

Res.

0x190

x

DATA3[7:0]

CAN_TDH0R
Reset value

x

DLC[3:0]

RTR

CAN_TDL0R
Reset value

0x18C

x

Res.

0x188

x

Res.

Reset value

Res.

TIME[15:0]

Res.

Res.

CAN_TDT0R
0x184

Res.

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 253. bxCAN register map and reset values (continued)

1323/1709
1325

Controller area network (bxCAN)

RM0385

x

x

x

x

x

x

x

x

x

x

x

x

CAN_RI1R

x

x

x

x

x

x

x

x

x

x

DATA2[7:0]
x

x

x

x

x

DATA7[7:0]
x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

- - - -

DATA1[7:0]
x

x

x

x

DATA6[7:0]
x

x

x

x

x

x

x

x

x

STID[10:0]/EXID[28:18]

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

CAN_RDT1R

x

x

x

x

x

x

x

x

x

x

x

x

TIME[15:0]

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

FMI[7:0]

0x1C4

CAN_RDL1R
Reset value

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

DATA4[7:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

DATA0[7:0]

DATA5[7:0]
x

x

Res.

x

x

x

Res.

x

- - - -

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

DATA1[7:0]

DATA6[7:0]
x

x

Res.

x

x

Res.

x

x

DLC[3:0]

Res.

x

x

-

Res.

x

x

x

Res.

Res.

Res.

x

x

DATA2[7:0]

DATA7[7:0]
x

x

x

Res.

-

x

x

Res.

0x208

-

x

x

Res.

0x1D00x1FF

x

DATA3[7:0]

CAN_RDH1R
Reset value

x

x

Res.

0x1CC

x

x

Res.

0x1C8

x

Res.

Reset value

x

DATA4[7:0]

EXID[17:0]
x

x

x

0x1C0
Reset value

x

DATA0[7:0]

DATA5[7:0]
x

x

Res.

x

IDE

x

Res.

x

DATA3[7:0]

CAN_RDH0R
Reset value

x

Res.

CAN_RDL0R
Reset value

0x1BC

x

Res.

0x1B8

x

Res.

Reset value

DLC[3:0]

RTR

FMI[7:0]

Res.

TIME[15:0]

Res.

CAN_RDT0R
0x1B4

Res.

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 253. bxCAN register map and reset values (continued)

0

0

0

0

0

0

-

1324/1709

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0
Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

0

0

0

0

0

Res.

Res.

FFA[27:0]

Res.

Res.
Res.

0

Res.

Res.
Res.

Res.

Res.

0

Res.

Res.

-

Res.

0x218

Res.

Reset value

0

Res.

Res.

CAN_FFA1R
0x214

0
Res.

-

Res.

0x210

Res.

Reset value

FSC[27:0]

Res.

CAN_FS1R
0x20C

RM0385 Rev 7

RM0385

Controller area network (bxCAN)

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

FB[31:0]
x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

FB[31:0]
x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

FB[31:0]
x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x
.
.
.
.

CAN_F27R1

FB[31:0]
x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

CAN_F27R2
Reset value

0

Res.

0x31C

x

.
.
.
.

Reset value

0

Res.

Res.
Res.

0x318

0

Res.

Res.
Res.

.
.
.
.

x

CAN_F1R2
Reset value

0

Res.

Res.
Res.

0x24C

x

CAN_F1R1
Reset value

0

Res.

Res.
Res.

0x248

0

FB[31:0]

CAN_F0R2
Reset value

0

Res.

Res.
Res.

0x244

0

Res.

Res.
Res.

Reset value

0

Res.

Res.
Res.

CAN_F0R1

0

Res.

Res.
Res.

0x240

0

Res.

Res.

-

0

Res.

Res.

0x2240x23F

0

Res.

-

0

Res.

0x220

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Reset value

FACT[27:0]

Res.

Res.

CAN_FA1R
0x21C

Res.

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 253. bxCAN register map and reset values (continued)

x

x

FB[31:0]
x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

RM0385 Rev 7

x

x

1325/1709
1325

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37

USB on-the-go full-speed/high-speed
(OTG_FS/OTG_HS)

37.1

Introduction

RM0385

Portions Copyright (c) Synopsys, Inc. All rights reserved. Used with permission.
This section presents the architecture and the programming model of the
OTG_FS/OTG_HS controller.
The following acronyms are used throughout the section:
FS

Full-speed

LS

Low-speed

HS

High-speed

MAC

Media access controller

OTG

On-the-go

PFC

Packet FIFO controller

PHY

Physical layer

USB

Universal serial bus

UTMI

USB 2.0 Transceiver Macrocell interface (UTMI)

ULPI

UTMI+ Low Pin Interface

LPM

Link power management

HNP

Host negotiation protocol

SRP

Session request protocol

References are made to the following documents:
•

USB On-The-Go Supplement, Revision 2.0

•

Universal Serial Bus Revision 2.0 Specification

•

USB 2.0 Link Power Management Addendum Engineering Change Notice to the USB
2.0 specification, July 16, 2007

•

Errata for USB 2.0 ECN: Link Power Management (LPM) - 7/2007

The USB OTG is a dual-role device (DRD) controller that supports both device and host
functions and is fully compliant with the On-The-Go Supplement to the USB 2.0
Specification. It can also be configured as a host-only or device-only controller, fully
compliant with the USB 2.0 Specification. OTG_HS supports the speeds defined in the
Table 254: OTG_HS speeds supported below.OTG_FS supports the speeds defined in the
Table 255: OTG_FS speeds supported below.The USB OTG supports both HNP and SRP.
The only external device required is a charge pump for VBUS in OTG mode.

1326/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Table 254. OTG_HS speeds supported
-

HS (480 Mb/s)

FS (12 Mb/s)

LS (1.5 Mb/s)

Host mode

X

X

X

Device mode

X

X

-

Table 255. OTG_FS speeds supported
-

37.2

HS (480 Mb/s)

FS (12 Mb/s)

LS (1.5 Mb/s)

Host mode

-

X

X

Device mode

-

X

-

OTG main features
The main features can be divided into three categories: general, host-mode and devicemode features.

RM0385 Rev 7

1327/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.2.1

RM0385

General features
The OTG_FS/OTG_HS interface general features are the following:
•

It is USB-IF certified to the Universal Serial Bus Specification Rev 2.0

•

OTG_HS supports the following PHY interfaces:

•

•

•

An on-chip full-speed PHY

–

An ULPI interface for external high-speed PHY

It includes full support (PHY) for the optional On-The-Go (OTG) protocol detailed in the
On-The-Go Supplement Rev 2.0 specification
–

Integrated support for A-B device identification (ID line)

–

Integrated support for host Negotiation protocol (HNP) and session request
protocol (SRP)

–

It allows host to turn VBUS off to conserve battery power in OTG applications

–

It supports OTG monitoring of VBUS levels with internal comparators

–

It supports dynamic host-peripheral switch of role

It is software-configurable to operate as:
–

SRP capable USB FS/HS Peripheral (B-device)

–

SRP capable USB FS/HS/LS host (A-device)

–

USB On-The-Go Full-Speed Dual Role device

It supports FS/HS SOF and LS Keep-alives with
–

SOF pulse PAD connectivity

–

SOF pulse internal connection to timer (TIMx)

–

Configurable framing period

–

Configurable end of frame interrupt

•

OTG_HS embeds an internal DMA with shareholding support and software selectable
AHB burst type in DMA mode.

•

It includes power saving features such as system stop during USB suspend, switch-off
of clock domains internal to the digital core, PHY and DFIFO power management.

•

It features a dedicated RAM of 1.25[FS] / 4[HS] Kbytes with advanced FIFO control:

•

1328/1709

–

–

Configurable partitioning of RAM space into different FIFOs for flexible and
efficient use of RAM

–

Each FIFO can hold multiple packets

–

Dynamic memory allocation

–

Configurable FIFO sizes that are not powers of 2 to allow the use of contiguous
memory locations

It guarantees max USB bandwidth for up to one frame (1 ms) without system
intervention.

RM0385 Rev 7

RM0385

37.2.2

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Host-mode features
The OTG_FS/OTG_HS interface main features and requirements in host-mode are the
following:
•

External charge pump for VBUS voltage generation.

•

Up to 12[FS] / 16[HS] host channels (pipes): each channel is dynamically
reconfigurable to allocate any type of USB transfer.

•

Built-in hardware scheduler holding:

•

37.2.3

–

Up to 12[FS] / 16[HS] interrupt plus isochronous transfer requests in the periodic
hardware queue

–

Up to 12[FS] / 16[HS] control plus bulk transfer requests in the non-periodic
hardware queue

Management of a shared Rx FIFO, a periodic Tx FIFO and a nonperiodic Tx FIFO for
efficient usage of the USB data RAM.

Peripheral-mode features
The OTG_FS/OTG_HS interface main features in peripheral-mode are the following:
•

1 bidirectional control endpoint0

•

5[FS] / 8[HS] IN endpoints (EPs) configurable to support bulk, interrupt or isochronous
transfers

•

5[FS] / 8[HS] OUT endpoints configurable to support bulk, interrupt or isochronous
transfers

•

Management of a shared Rx FIFO and a Tx-OUT FIFO for efficient usage of the USB
data RAM

•

Management of up to 6[FS] / 9[HS] dedicated Tx-IN FIFOs (one for each active IN EP)
to put less load on the application

•

Support for the soft disconnect feature.

RM0385 Rev 7

1329/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.3

RM0385

OTG implementation
Table 256. OTG implementation(1)
USB features

OTG_FS

OTG_HS

Device bidirectional endpoints (including EP0)

6

9

Host mode channels

12

16

1.2 KB

4 KB

Size of dedicated SRAM
USB 2.0 link power management (LPM) support

X

OTG revision supported

2.0

Attach detection protocol (ADP) support

-

Battery charging detection (BCD) support

-

1. “X” = supported, “-” = not supported

1330/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.4

OTG functional description

37.4.1

OTG block diagram
Figure 459. OTG full-speed block diagram

AHB peripheral

Cortex core

USB Interrupt

DP
DM
USB2.0
OTG FS
core

Power
and
clock control

UTMIFS

OTG FS
PHY

ID
VBUS
Universal serial bus

USB suspend
SOF

USB clock at 48 MHz
USB clock
domain

RAM bus

System clock
domain

1.25 Kbyte
USB data
FIFOs
MS19928V4

RM0385 Rev 7

1331/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Figure 460. OTG high-speed block diagram

OTG FS PHY
transceiver

OTG_HS_DP
OTG_HS_DM

serial

Peripheral 1

AHB (application bus)

Memory

OTG_HS_ID

OTG_HS
(USB OTG HS core)

CPU

OTG detections

AHB
master
interface

OTG_HS_VBUS

EXTI

Interrupt: async wakeup
Interrupt: EP1 out

NVIC

Interrupt: EP1 in

AHB
slave
interface

Interrupt: global

ULPI_CK;
ULPI_DIR;
ULPI_STP;
ULPI_NXT;
ULPI_D0-7
USB2.0 (D+/D-)
ULPI PHY
(external
component)

ULPI interface (12 pins)

Data FIFO
RAM interface

Peripheral 2

OTG_HS_SOF

Data FIFO
Single-port RAM
(SPRAM)
MSv43325V1

37.4.2

USB OTG pin and internal signals
Table 257. OTG_FS input/output pins
Signal name

Signal type

Description

OTG_FS_DP

Digital input/output USB OTG D+ line

OTG_FS_DM

Digital input/output USB OTG D- line

OTG_FS_ID

Digital input

USB OTG ID

OTG_FS_VBUS

Analog input

USB OTG VBUS

OTG_FS_SOF

Digital output

USB OTG Start Of Frame (visibility)

Table 258. OTG_HS input/output pins
Signal name

1332/1709

Signal type

Description

OTG_HS_DP

Digital input/output USB OTG D+ line

OTG_HS_DM

Digital input/output USB OTG D- line

OTG_HS_ID

Digital input

USB OTG ID

OTG_HS_VBUS

Analog input

USB OTG VBUS

OTG_HS_SOF

Digital output

USB OTG Start Of Frame (visibility)

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Table 258. OTG_HS input/output pins (continued)
Signal name

Signal type

Description

OTG_HS_ULPI_CK

Digital input

USB OTG ULPI clock

OTG_HS_ULPI_DIR

Digital input

USB OTG ULPI data bus direction control

OTG_HS_ULPI_STP

Digital output

USB OTG ULPI data stream stop

OTG_HS_ULPI_NXT

Digital input

USB OTG ULPI next data stream request

OTG_HS_ULPI_D[0..7]

Digital input/output USB OTG ULPI 8-bit bi-directional data bus

Table 259. OTG_FS/OTG_HS input/output signals
Signal name

37.4.3

Signal type

Description

usb_sof

Digital output

USB OTG start-of-frame event for on chip peripherals

usb_wkup

Digital output

USB OTG wakeup event output

usb_gbl_it

Digital output

USB OTG global interrupt

usb_ep1_in_it

Digital output

USB OTG endpoint 1 in interrupt

usb_ep1_out_it

Digital output

USB OTG endpoint 1 out interrupt

OTG core
The USB OTG receives the 48 MHz clock from the reset and clock controller (RCC). The
USB clock is used for driving the 48 MHz domain at full-speed (12 Mbit/s) and must be
enabled prior to configuring the OTG core.
The CPU reads and writes from/to the OTG core registers through the AHB peripheral bus.
It is informed of USB events through the single USB OTG interrupt line described in
Section 37.13: OTG_FS/OTG_HS interrupts.
The CPU submits data over the USB by writing 32-bit words to dedicated OTG locations
(push registers). The data are then automatically stored into Tx-data FIFOs configured
within the USB data RAM. There is one Tx FIFO push register for each in-endpoint
(peripheral mode) or out-channel (host mode).
The CPU receives the data from the USB by reading 32-bit words from dedicated OTG
addresses (pop registers). The data are then automatically retrieved from a shared Rx FIFO
configured within the 1.25[FS] / 4[HS]-Kbyte USB data RAM. There is one Rx FIFO pop
register for each out-endpoint or in-channel.
The USB protocol layer is driven by the serial interface engine (SIE) and serialized over the
USB by the transceiver module within the on-chip physical layer (PHY) or external HS PHY.

37.4.4

Full-speed OTG PHY(a)
The embedded full-speed OTG PHY is controlled by the OTG FS core and conveys USB
control & data signals through the full-speed subset of the UTMI+ Bus (UTMIFS). It provides

a. The content of this section applies only to USB OTG FS.

RM0385 Rev 7

1333/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

the physical support to USB connectivity.
The full-speed OTG PHY includes the following components:
•

FS/LS transceiver module used by both host and device. It directly drives transmission
and reception on the single-ended USB lines.

•

Integrated ID pull-up resistor used to sample the ID line for A/B device identification.

•

DP/DM integrated pull-up and pull-down resistors controlled by the OTG_FS core
depending on the current role of the device. As a peripheral, it enables the DP pull-up
resistor to signal full-speed peripheral connections as soon as VBUS is sensed to be at
a valid level (B-session valid). In host mode, pull-down resistors are enabled on both
DP/DM. Pull-up and pull-down resistors are dynamically switched when the role of the
device is changed via the host negotiation protocol (HNP).

•

Pull-up/pull-down resistor ECN circuit. The DP pull-up consists of two resistors
controlled separately from the OTG_FS as per the resistor Engineering Change Notice
applied to USB Rev2.0. The dynamic trimming of the DP pull-up strength allows for
better noise rejection and Tx/Rx signal quality.

•

VBUS sensing comparators with hysteresis used to detect VBUS valid, A-B session valid
and session-end voltage thresholds. They are used to drive the session request
protocol (SRP), detect valid startup and end-of-session conditions, and constantly
monitor the VBUS supply during USB operations.

•

VBUS pulsing method circuit used to charge/discharge VBUS through resistors during
the SRP (weak drive).

Caution:

To guarantee a correct operation for the USB OTG FS peripheral, the AHB frequency should
be higher than 14.2 MHz.

37.4.5

Embedded full speed OTG PHY(a)
The full-speed OTG PHY includes the following components:
•

FS/LS transceiver module used by both host and device. It directly drives transmission
and reception on the single-ended USB lines.

•

integrated ID pull-up resistor used to sample the ID line for A/B device identification.

•

DP/DM integrated pull-up and pull-down resistors controlled by the OTG_HS core
depending on the current role of the device. As a peripheral, it enables the DP pull-up
resistor to signal full-speed peripheral connections as soon as VBUS is sensed to be at
a valid level (B-session valid). In host mode, pull-down resistors are enabled on both
DP/DM. Pull-up and pull-down resistors are dynamically switched when the peripheral
role is changed via the host negotiation protocol (HNP).

•

Pull-up/pull-down resistor ECN circuit. The DP pull-up consists of 2 resistors controlled
separately from the OTG_HS as per the resistor Engineering Change Notice applied to
USB Rev2.0. The dynamic trimming of the DP pull-up strength allows to achieve a
better noise rejection and Tx/Rx signal quality.

•

VBUS sensing comparators with hysteresis used to detect VBUS valid, A-B session valid
and session-end voltage thresholds. They are used to drive the session request
protocol (SRP), detect valid startup and end-of-session conditions, and constantly
monitor the VBUS supply during USB operations.

a. The content of this section applies only to USB OTG HS.

1334/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
To guarantee a correct operation for the USB OTG_HS peripheral, the AHB frequency
should be higher than 30 MHz.

37.4.6

High-speed OTG PHY(a)
The USB OTG_HS core includes an ULPI interface to connect an external HS PHY.

37.5

OTG dual role device (DRD)
Figure 461. OTG_FS A-B device connection
VDD
5 V to VDD
Voltage
regulator
VDD

GPIO + IRQ

STMPS2141STR
Current-limited 5 V Pwr
Overcurrent power distribution
switch(2)

VBUS
DM
OSC_IN

DP
ID

OSC_OUT

VSS

USBmicro-AB connector

GPIO

EN

MSv36917V1

1. External voltage regulator only needed when building a VBUS powered device.
2. STMPS2141STR needed only if the application has to support a VBUS powered device. A basic power
switch can be used if 5 V are available on the application board.

37.5.1

ID line detection
The host or peripheral (the default) role is assumed depending on the ID input pin. The ID
line status is determined on plugging in the USB cable, depending on whether a MicroA or
MicroB plug is connected to the micro-AB receptacle.
•

If the B-side of the USB cable is connected with a floating ID wire, the integrated pullup resistor detects a high ID level and the default peripheral role is confirmed. In this
configuration the OTG_FS/OTG_HS complies with the standard FSM described in
section 4.2.4: ID pin of the On-the-Go specification Rev2.0, supplement to the USB2.0.

•

If the A-side of the USB cable is connected with a grounded ID, the OTG_FS/OTG_HS
issues an ID line status change interrupt (CIDSCHG bit in OTG_GINTSTS) for host
software initialization, and automatically switches to the host role. In this configuration
the OTG_FS/OTG_HS complies with the standard FSM described by section 4.2.4: ID
pin of the On-the-Go specification Rev2.0, supplement to the USB2.0.

a. The content of this section applies only to USB OTG HS.

RM0385 Rev 7

1335/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.5.2

RM0385

HNP dual role device
The HNP capable bit in the Global USB configuration register (HNPCAP bit in OTG_
GUSBCFG) enables the OTG_FS/OTG_HS core to dynamically change its role from A-host
to A-peripheral and vice-versa, or from B-Peripheral to B-host and vice-versa according to
the host negotiation protocol (HNP). The current device status can be read by the combined
values of the connector ID status bit in the Global OTG control and status register (CIDSTS
bit in OTG_GOTGCTL) and the current mode of operation bit in the global interrupt and
status register (CMOD bit in OTG_GINTSTS).
The HNP program model is described in detail in Section 37.16: OTG_FS/OTG_HS
programming model.

37.5.3

SRP dual role device
The SRP capable bit in the global USB configuration register (SRPCAP bit in
OTG_GUSBCFG) enables the OTG_FS/OTG_HS core to switch off the generation of VBUS
for the A-device to save power. Note that the A-device is always in charge of driving VBUS
regardless of the host or peripheral role of the OTG_FS/OTG_HS.
The SRP A/B-device program model is described in detail in Section 37.16:
OTG_FS/OTG_HS programming model.

37.6

USB peripheral
This section gives the functional description of the OTG_FS/OTG_HS in the USB peripheral
mode. The OTG_FS/OTG_HS works as an USB peripheral in the following circumstances:
•

OTG B-Peripheral
–

•

–
•

1336/1709

If the ID line is present, functional and connected to the B-side of the USB cable,
and the HNP-capable bit in the Global USB Configuration register (HNPCAP bit in
OTG_GUSBCFG) is cleared.

Peripheral only (see Figure 462: USB_FS peripheral-only connection)
–

Note:

OTG A-device state after the HNP switches the OTG_FS/OTG_HS to its
peripheral role

B-device
–

•

OTG B-device default state if B-side of USB cable is plugged in

OTG A-Peripheral

The force device mode bit (FDMOD) in the Section 37.15.4: OTG USB
configuration register (OTG_GUSBCFG) is set to 1, forcing the OTG_FS/OTG_HS
core to work as an USB peripheral-only. In this case, the ID line is ignored even if
it is present on the USB connector.

To build a bus-powered device implementation in case of the B-device or peripheral-only
configuration, an external regulator has to be added, that generates the necessary powersupply from VBUS.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 462. USB_FS peripheral-only connection
VDD
5 V to VDD
Voltage
regulator
VDD
GPIO
GPIO + IRQ

EN

STMPS2141STR
Current-limited 5 V Pwr
Overcurrent power distribution
switch(1)

DM
OSC_IN

DP

OSC_OUT

VSS

USB micro connector

VBUS

MSv36916V2

1. Use a regulator to build a bus-powered device.

37.6.1

SRP-capable peripheral
The SRP capable bit in the Global USB configuration register (SRPCAP bit in
OTG_GUSBCFG) enables the OTG_FS/OTG_HS to support the session request protocol
(SRP). In this way, it allows the remote A-device to save power by switching off VBUS while
the USB session is suspended.
The SRP peripheral mode program model is described in detail in the B-device session
request protocol section.

37.6.2

Peripheral states
Powered state
The VBUS input detects the B-session valid voltage by which the USB peripheral is allowed
to enter the powered state (see USB2.0 section 9.1). The OTG_FS/OTG_HS then
automatically connects the DP pull-up resistor to signal full-speed device connection to the
host and generates the session request interrupt (SRQINT bit in OTG_GINTSTS) to notify
the powered state.
The VBUS input also ensures that valid VBUS levels are supplied by the host during USB
operations. If a drop in VBUS below B-session valid happens to be detected (for instance
because of a power disturbance or if the host port has been switched off), the
OTG_FS/OTG_HS automatically disconnects and the session end detected (SEDET bit in
OTG_GOTGINT) interrupt is generated to notify that the OTG_FS/OTG_HS has exited the
powered state.
In the powered state, the OTG_FS/OTG_HS expects to receive some reset signaling from
the host. No other USB operation is possible. When a reset signaling is received the reset
detected interrupt (USBRST in OTG_GINTSTS) is generated. When the reset signaling is
complete, the enumeration done interrupt (ENUMDNE bit in OTG_GINTSTS) is generated
and the OTG_FS/OTG_HS enters the Default state.

RM0385 Rev 7

1337/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Soft disconnect
The powered state can be exited by software with the soft disconnect feature. The DP pullup resistor is removed by setting the soft disconnect bit in the device control register (SDIS
bit in OTG_DCTL), causing a device disconnect detection interrupt on the host side even
though the USB cable was not really removed from the host port.

Default state
In the Default state the OTG_FS/OTG_HS expects to receive a SET_ADDRESS command
from the host. No other USB operation is possible. When a valid SET_ADDRESS command
is decoded on the USB, the application writes the corresponding number into the device
address field in the device configuration register (DAD bit in OTG_DCFG). The
OTG_FS/OTG_HS then enters the address state and is ready to answer host transactions
at the configured USB address.

Suspended state
The OTG_FS/OTG_HS peripheral constantly monitors the USB activity. After counting 3 ms
of USB idleness, the early suspend interrupt (ESUSP bit in OTG_GINTSTS) is issued, and
confirmed 3 ms later, if appropriate, by the suspend interrupt (USBSUSP bit in
OTG_GINTSTS). The device suspend bit is then automatically set in the device status
register (SUSPSTS bit in OTG_DSTS) and the OTG_FS/OTG_HS enters the suspended
state.
The suspended state may optionally be exited by the device itself. In this case the
application sets the remote wakeup signaling bit in the device control register (RWUSIG bit
in OTG_DCTL) and clears it after 1 to 15 ms.
When a resume signaling is detected from the host, the resume interrupt (WKUPINT bit in
OTG_GINTSTS) is generated and the device suspend bit is automatically cleared.

37.6.3

Peripheral endpoints
The OTG_FS/OTG_HS core instantiates the following USB endpoints:
•

•

1338/1709

Control endpoint 0:
–

Bidirectional and handles control messages only

–

Separate set of registers to handle in and out transactions

–

Proper control (OTG_DIEPCTL0/OTG_DOEPCTL0), transfer configuration
(OTG_DIEPTSIZ0/OTG_DOEPTSIZ0), and status-interrupt
(OTG_DIEPINT0/)OTG_DOEPINT0) registers. The available set of bits inside the
control and transfer size registers slightly differs from that of other endpoints

5[FS] / 8[HS] IN endpoints
–

Each of them can be configured to support the isochronous, bulk or interrupt
transfer type

–

Each of them has proper control (OTG_DIEPCTLx), transfer configuration
(OTG_DIEPTSIZx), and status-interrupt (OTG_DIEPINTx) registers

–

The device IN endpoints common interrupt mask register (OTG_DIEPMSK) is
available to enable/disable a single kind of endpoint interrupt source on all of the
IN endpoints (EP0 included)

–

Support for incomplete isochronous IN transfer interrupt (IISOIXFR bit in
OTG_GINTSTS), asserted when there is at least one isochronous IN endpoint on

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
which the transfer is not completed in the current frame. This interrupt is asserted
along with the end of periodic frame interrupt (OTG_GINTSTS/EOPF).
•

5[FS] / 8[HS] OUT endpoints
–

Each of them can be configured to support the isochronous, bulk or interrupt
transfer type

–

Each of them has a proper control (OTG_DOEPCTLx), transfer configuration
(OTG_DOEPTSIZx) and status-interrupt (OTG_DOEPINTx) register

–

Device OUT endpoints common interrupt mask register (OTG_DOEPMSK) is
available to enable/disable a single kind of endpoint interrupt source on all of the
OUT endpoints (EP0 included)

–

Support for incomplete isochronous OUT transfer interrupt (INCOMPISOOUT bit
in OTG_GINTSTS), asserted when there is at least one isochronous OUT
endpoint on which the transfer is not completed in the current frame. This interrupt
is asserted along with the end of periodic frame interrupt (OTG_GINTSTS/EOPF).

Endpoint control
•

The following endpoint controls are available to the application through the device
endpoint-x IN/OUT control register (OTG_DIEPCTLx/OTG_DOEPCTLx):
–

Endpoint enable/disable

–

Endpoint activate in current configuration

–

Program USB transfer type (isochronous, bulk, interrupt)

–

Program supported packet size

–

Program Tx FIFO number associated with the IN endpoint

–

Program the expected or transmitted data0/data1 PID (bulk/interrupt only)

–

Program the even/odd frame during which the transaction is received or
transmitted (isochronous only)

–

Optionally program the NAK bit to always negative-acknowledge the host
regardless of the FIFO status

–

Optionally program the STALL bit to always stall host tokens to that endpoint

–

Optionally program the SNOOP mode for OUT endpoint not to check the CRC
field of received data

Endpoint transfer
The device endpoint-x transfer size registers (OTG_DIEPTSIZx/OTG_DOEPTSIZx) allow
the application to program the transfer size parameters and read the transfer status.
Programming must be done before setting the endpoint enable bit in the endpoint control
register. Once the endpoint is enabled, these fields are read-only as the OTG_FS/OTG_HS
core updates them with the current transfer status.
The following transfer parameters can be programmed:
•

Transfer size in bytes

•

Number of packets that constitute the overall transfer size

Endpoint status/interrupt
The device endpoint-x interrupt registers (OTG_DIEPINTx/OTG_DOPEPINTx) indicate the
status of an endpoint with respect to USB- and AHB-related events. The application must
read these registers when the OUT endpoint interrupt bit or the IN endpoint interrupt bit in

RM0385 Rev 7

1339/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

the core interrupt register (OEPINT bit in OTG_GINTSTS or IEPINT bit in OTG_GINTSTS,
respectively) is set. Before the application can read these registers, it must first read the
device all endpoints interrupt (OTG_DAINT) register to get the exact endpoint number for
the device endpoint-x interrupt register. The application must clear the appropriate bit in this
register to clear the corresponding bits in the OTG_DAINT and OTG_GINTSTS registers
The peripheral core provides the following status checks and interrupt generation:

37.7

•

Transfer completed interrupt, indicating that data transfer was completed on both the
application (AHB) and USB sides

•

Setup stage has been done (control-out only)

•

Associated transmit FIFO is half or completely empty (in endpoints)

•

NAK acknowledge has been transmitted to the host (isochronous-in only)

•

IN token received when Tx FIFO was empty (bulk-in/interrupt-in only)

•

Out token received when endpoint was not yet enabled

•

Babble error condition has been detected

•

Endpoint disable by application is effective

•

Endpoint NAK by application is effective (isochronous-in only)

•

More than 3 back-to-back setup packets were received (control-out only)

•

Timeout condition detected (control-in only)

•

Isochronous out packet has been dropped, without generating an interrupt

USB host
This section gives the functional description of the OTG_FS/OTG_HS in the USB host
mode. The OTG_FS/OTG_HS works as a USB host in the following circumstances:
•

OTG A-host
–

•

OTG B-host
–

•

1340/1709

If the ID line is present, functional and connected to the A-side of the USB cable,
and the HNP-capable bit is cleared in the Global USB Configuration register
(HNPCAP bit in OTG_GUSBCFG). Integrated pull-down resistors are
automatically set on the DP/DM lines.

Host only
–

Note:

OTG B-device after HNP switching to the host role

A-device
–

•

OTG A-device default state when the A-side of the USB cable is plugged in

The force host mode bit (FHMOD) in the OTG USB configuration register
(OTG_GUSBCFG) forces the OTG_FS/OTG_HS core to work as a USB host-only.
In this case, the ID line is ignored even if present on the USB connector.
Integrated pull-down resistors are automatically set on the DP/DM lines.

On-chip 5 V VBUS generation is not supported. For this reason, a charge pump or, if 5 V are
available on the application board, a basic power switch must be added externally to drive
the 5 V VBUS line. The external charge pump can be driven by any GPIO output. This is
required for the OTG A-host, A-device and host-only configurations.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 463. USB_FS host-only connection
VDD
5V

GPIO + IRQ

EN

STMPS2141STR
5 V Pwr
Current-limited
Overcurrent power distribution
switch(2)
VBUS
DM

OSC_IN

DP
VSS

OSC_OUT

USB Std-A connector

GPIO

MSv36915V2

1. VDD range is between 2 V and 3.6 V.

37.7.1

SRP-capable host
SRP support is available through the SRP capable bit in the global USB configuration
register (SRPCAP bit in OTG_GUSBCFG). With the SRP feature enabled, the host can
save power by switching off the VBUS power while the USB session is suspended.
The SRP host mode program model is described in detail in the A-device session request
protocol) section.

37.7.2

USB host states
Host port power
On-chip 5 V VBUS generation is not supported. For this reason, a charge pump or, if 5 V are
available on the application board, a basic power switch, must be added externally to drive
the 5 V VBUS line. The external charge pump can be driven by any GPIO output or via an
I2C interface connected to an external PMIC (power management IC). When the application
decides to power on VBUS, it must also set the port power bit in the host port control and
status register (PPWR bit in OTG_HPRT).

VBUS valid
When HNP or SRP is enabled the VBUS sensing pin should be connected to VBUS. The
VBUS input ensures that valid VBUS levels are supplied by the charge pump during USB
operations. Any unforeseen VBUS voltage drop below the VBUS valid threshold (4.4 V) leads
to an OTG interrupt triggered by the session end detected bit (SEDET bit in
OTG_GOTGINT). The application is then required to remove the VBUS power and clear the
port power bit.
When HNP and SRP are both disabled, the VBUS sensing pin does not need to be
connected to VBUS.
The charge pump overcurrent flag can also be used to prevent electrical damage. Connect
the overcurrent flag output from the charge pump to any GPIO input and configure it to
generate a port interrupt on the active level. The overcurrent ISR must promptly disable the
VBUS generation and clear the port power bit.

RM0385 Rev 7

1341/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Host detection of a peripheral connection
If SRP or HNP are enabled, even if USB peripherals or B-devices can be attached at any
time, the OTG_FS/OTG_HS will not detect any bus connection until VBUS is no longer
sensed at a valid level (5 V). When VBUS is at a valid level and a remote B-device is
attached, the OTG_FS/OTG_HS core issues a host port interrupt triggered by the device
connected bit in the host port control and status register (PCDET bit in OTG_HPRT).
When HNP and SRP are both disabled, USB peripherals or B-device are detected as soon
as they are connected. The OTG_FS/OTG_HS core issues a host port interrupt triggered by
the device connected bit in the host port control and status (PCDET bit in OTG_HPRT).

Host detection of peripheral a disconnection
The peripheral disconnection event triggers the disconnect detected interrupt (DISCINT bit
in OTG_GINTSTS).

Host enumeration
After detecting a peripheral connection the host must start the enumeration process by
sending USB reset and configuration commands to the new peripheral.
Before starting to drive a USB reset, the application waits for the OTG interrupt triggered by
the debounce done bit (DBCDNE bit in OTG_GOTGINT), which indicates that the bus is
stable again after the electrical debounce caused by the attachment of a pull-up resistor on
DP (FS) or DM (LS).
The application drives a USB reset signaling (single-ended zero) over the USB by keeping
the port reset bit set in the host port control and status register (PRST bit in OTG_HPRT) for
a minimum of 10 ms and a maximum of 20 ms. The application takes care of the timing
count and then of clearing the port reset bit.
Once the USB reset sequence has completed, the host port interrupt is triggered by the port
enable/disable change bit (PENCHNG bit in OTG_HPRT). This informs the application that
the speed of the enumerated peripheral can be read from the port speed field in the host
port control and status register (PSPD bit in OTG_HPRT) and that the host is starting to
drive SOFs (FS) or Keep alives (LS). The host is now ready to complete the peripheral
enumeration by sending peripheral configuration commands.

Host suspend
The application decides to suspend the USB activity by setting the port suspend bit in the
host port control and status register (PSUSP bit in OTG_HPRT). The OTG_FS/OTG_HS
core stops sending SOFs and enters the suspended state.
The suspended state can be optionally exited on the remote device’s initiative (remote
wakeup). In this case the remote wakeup interrupt (WKUPINT bit in OTG_GINTSTS) is
generated upon detection of a remote wakeup signaling, the port resume bit in the host port
control and status register (PRES bit in OTG_HPRT) self-sets, and resume signaling is
automatically driven over the USB. The application must time the resume window and then
clear the port resume bit to exit the suspended state and restart the SOF.
If the suspended state is exited on the host initiative, the application must set the port
resume bit to start resume signaling on the host port, time the resume window and finally
clear the port resume bit.

1342/1709

RM0385 Rev 7

RM0385

37.7.3

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Host channels
The OTG_FS/OTG_HS core instantiates 12[FS] / 16[HS] host channels. Each host channel
supports an USB host transfer (USB pipe). The host is not able to support more than 12[FS]
/ 16[HS] transfer requests at the same time. If more than 12[FS] / 16[HS] transfer requests
are pending from the application, the host controller driver (HCD) must re-allocate channels
when they become available from previous duty, that is, after receiving the transfer
completed and channel halted interrupts.
Each host channel can be configured to support in/out and any type of periodic/nonperiodic
transaction. Each host channel makes us of proper control (OTG_HCCHARx), transfer
configuration (OTG_HCTSIZx) and status/interrupt (OTG_HCINTx) registers with
associated mask (OTG_HCINTMSKx) registers.

Host channel control
•

The following host channel controls are available to the application through the host
channel-x characteristics register (OTG_HCCHARx):
–

Channel enable/disable

–

Program the HS/FS/LS speed of target USB peripheral

–

Program the address of target USB peripheral

–

Program the endpoint number of target USB peripheral

–

Program the transfer IN/OUT direction

–

Program the USB transfer type (control, bulk, interrupt, isochronous)

–

Program the maximum packet size (MPS)

–

Program the periodic transfer to be executed during odd/even frames

Host channel transfer
The host channel transfer size registers (OTG_HCTSIZx) allow the application to program
the transfer size parameters, and read the transfer status. Programming must be done
before setting the channel enable bit in the host channel characteristics register. Once the
endpoint is enabled the packet count field is read-only as the OTG_FS/OTG_HS core
updates it according to the current transfer status.
•

The following transfer parameters can be programmed:
–

transfer size in bytes

–

number of packets making up the overall transfer size

–

initial data PID

Host channel status/interrupt
The host channel-x interrupt register (OTG_HCINTx) indicates the status of an endpoint
with respect to USB- and AHB-related events. The application must read these register
when the host channels interrupt bit in the core interrupt register (HCINT bit in
OTG_GINTSTS) is set. Before the application can read these registers, it must first read the
host all channels interrupt (OTG_HAINT) register to get the exact channel number for the
host channel-x interrupt register. The application must clear the appropriate bit in this
register to clear the corresponding bits in the OTG_HAINT and OTG_GINTSTS registers.

RM0385 Rev 7

1343/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

The mask bits for each interrupt source of each channel are also available in the
OTG_HCINTMSKx register.
•

37.7.4

The host core provides the following status checks and interrupt generation:
–

Transfer completed interrupt, indicating that the data transfer is complete on both
the application (AHB) and USB sides

–

Channel has stopped due to transfer completed, USB transaction error or disable
command from the application

–

Associated transmit FIFO is half or completely empty (IN endpoints)

–

ACK response received

–

NAK response received

–

STALL response received

–

USB transaction error due to CRC failure, timeout, bit stuff error, false EOP

–

Babble error

–

frame overrun

–

data toggle error

Host scheduler
The host core features a built-in hardware scheduler which is able to autonomously re-order
and manage the USB transaction requests posted by the application. At the beginning of
each frame the host executes the periodic (isochronous and interrupt) transactions first,
followed by the nonperiodic (control and bulk) transactions to achieve the higher level of
priority granted to the isochronous and interrupt transfer types by the USB specification.
The host processes the USB transactions through request queues (one for periodic and one
for nonperiodic). Each request queue can hold up to 8 entries. Each entry represents a
pending transaction request from the application, and holds the IN or OUT channel number
along with other information to perform a transaction on the USB. The order in which the
requests are written to the queue determines the sequence of the transactions on the USB
interface.
At the beginning of each frame, the host processes the periodic request queue first, followed
by the nonperiodic request queue. The host issues an incomplete periodic transfer interrupt
(IPXFR bit in OTG_GINTSTS) if an isochronous or interrupt transaction scheduled for the
current frame is still pending at the end of the current frame. The OTG_FS/OTG_HS core is
fully responsible for the management of the periodic and nonperiodic request queues.The
periodic transmit FIFO and queue status register (OTG_HPTXSTS) and nonperiodic
transmit FIFO and queue status register (OTG_HNPTXSTS) are read-only registers which
can be used by the application to read the status of each request queue. They contain:
•

The number of free entries currently available in the periodic (nonperiodic) request
queue (8 max)

•

Free space currently available in the periodic (nonperiodic) Tx FIFO (out-transactions)

•

IN/OUT token, host channel number and other status information.

As request queues can hold a maximum of 8 entries each, the application can push to
schedule host transactions in advance with respect to the moment they physically reach the
SB for a maximum of 8 pending periodic transactions plus 8 pending non-periodic
transactions.
To post a transaction request to the host scheduler (queue) the application must check that
there is at least 1 entry available in the periodic (nonperiodic) request queue by reading the

1344/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
PTXQSAV bits in the OTG_HNPTXSTS register or NPTQXSAV bits in the
OTG_HNPTXSTS register.

37.8

SOF trigger
Figure 464. SOF connectivity (SOF trigger output to TIM and ITR1 connection)

SOF pulse output, to
external audio control
VBUS
ITR1

SOF pulse

DD+

TIM

SOFgen

ID

USB micro-AB connector

STM32

VSS

MSv36914V1

The OTG_FS/OTG_HS core provides means to monitor, track and configure SOF framing in
the host and peripheral, as well as an SOF pulse output connectivity feature.
Such utilities are especially useful for adaptive audio clock generation techniques, where
the audio peripheral needs to synchronize to the isochronous stream provided by the PC, or
the host needs to trim its framing rate according to the requirements of the audio peripheral.

37.8.1

Host SOFs
In host mode the number of PHY clocks occurring between the generation of two
consecutive SOF (HS/FS) or Keep-alive (LS) tokens is programmable in the host frame
interval register (HFIR), thus providing application control over the SOF framing period. An
interrupt is generated at any start of frame (SOF bit in OTG_GINTSTS). The current frame
number and the time remaining until the next SOF are tracked in the host frame number
register (HFNUM).
A SOF pulse signal, is generated at any SOF starting token and with a width of 20 HCLK
cycles. The SOF pulse is also internally connected to the input trigger of the timer, so that
the input capture feature, the output compare feature and the timer can be triggered by the
SOF pulse.

37.8.2

Peripheral SOFs
In device mode, the start of frame interrupt is generated each time an SOF token is received
on the USB (SOF bit in OTG_GINTSTS). The corresponding frame number can be read
from the device status register (FNSOF bit in OTG_DSTS). A SOF pulse signal with a width
of 20 HCLK cycles is also generated.The SOF pulse signal is also internally connected to
the TIM input trigger, so that the input capture feature, the output compare feature and the
timer can be triggered by the SOF pulse.

RM0385 Rev 7

1345/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

The end of periodic frame interrupt (OTG_GINTSTS/EOPF) is used to notify the application
when 80%, 85%, 90% or 95% of the time frame interval elapsed depending on the periodic
frame interval field in the device configuration register (PFIVL bit in OTG_DCFG). This
feature can be used to determine if all of the isochronous traffic for that frame is complete.

37.9

OTG low-power modes
Table 260 below defines the STM32 low power modes and their compatibility with the OTG.
Table 260. Compatibility of STM32 low power modes with the OTG

Mode

Description

USB compatibility

Run

MCU fully active

Required when USB not in
suspend state.

Sleep

USB suspend exit causes the device to exit Sleep mode. Peripheral
registers content is kept.

Available while USB is in
suspend state.

Stop

USB suspend exit causes the device to exit Stop mode. Peripheral
registers content is kept(1).

Available while USB is in
suspend state.

Standby

Powered-down. The peripheral must be reinitialized after exiting
Standby mode.

Not compatible with USB
applications.

1. Within Stop mode there are different possible settings. Some restrictions may also exist, please refer to Section 4: Power
controller (PWR) to understand which (if any) restrictions apply when using OTG.

The following bits and procedures reduce power consumption.
The power consumption of the OTG PHY is controlled by two or three bits in the general
core configuration register, depending on OTG revision supported.
•

PHY power down (OTG_GCCFG/PWRDWN)
It switches on/off the full-speed transceiver module of the PHY. It must be preliminarily
set to allow any USB operation

•

VBUS detection enable (OTG_GCCFG/VBDEN)
It switches on/off the VBUS sensing comparators associated with OTG operations

Power reduction techniques are available while in the USB suspended state, when the USB
session is not yet valid or the device is disconnected.
•

Stop PHY clock (STPPCLK bit in OTG_PCGCCTL)
When setting the stop PHY clock bit in the clock gating control register, most of the
48 MHz clock domain internal to the OTG full-speed core is switched off by clock
gating. The dynamic power consumption due to the USB clock switching activity is cut
even if the 48 MHz clock input is kept running by the application
Most of the transceiver is also disabled, and only the part in charge of detecting the
asynchronous resume or remote wakeup event is kept alive.

•

Gate HCLK (GATEHCLK bit in OTG_PCGCCTL)
When setting the Gate HCLK bit in the clock gating control register, most of the system
clock domain internal to the OTG_FS/OTG_HS core is switched off by clock gating.
Only the register read and write interface is kept alive. The dynamic power

1346/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
consumption due to the USB clock switching activity is cut even if the system clock is
kept running by the application for other purposes.
•

USB system stop
When the OTG_FS/OTG_HS is in the USB suspended state, the application may
decide to drastically reduce the overall power consumption by a complete shut down of
all the clock sources in the system. USB System Stop is activated by first setting the
Stop PHY clock bit and then configuring the system deep sleep mode in the power
control system module (PWR).
The OTG_FS/OTG_HS core automatically reactivates both system and USB clocks by
asynchronous detection of remote wakeup (as an host) or resume (as a device)
signaling on the USB.

To save dynamic power, the USB data FIFO is clocked only when accessed by the
OTG_FS/OTG_HS core.

37.10

Dynamic update of the OTG_HFIR register
The USB core embeds a dynamic trimming capability of micro-SOF[HS] / SOF[FS] framing
period in host mode allowing to synchronize an external device with the micro-SOF[HS] /
SOF[FS] frames.
When the OTG_HFIR register is changed within a current micro-SOF[HS] / SOF[FS] frame,
the SOF period correction is applied in the next frame as described in Figure 465.
For a dynamic update, it is required to set RLDCTRL=0.
Figure 465. Updating OTG_HFIR dynamically (RLDCTRL = 0)
SOF reload

OTG_HFIR write

...

1
0
450
449

...

450

1
0
400
399

1
0
400
399

Frame timer

400

...

1
0
450
449

OTG_HFIR value

...

ai18440b

37.11

USB data FIFOs
The USB system features 1.25[FS] / 4[HS] Kbytes of dedicated RAM with a sophisticated
FIFO control mechanism. The packet FIFO controller module in the OTG_FS/OTG_HS core
organizes RAM space into Tx FIFOs into which the application pushes the data to be
temporarily stored before the USB transmission, and into a single Rx FIFO where the data
received from the USB are temporarily stored before retrieval (popped) by the application.
The number of instructed FIFOs and how these are organized inside the RAM depends on

RM0385 Rev 7

1347/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

the device’s role. In peripheral mode an additional Tx FIFO is instructed for each active IN
endpoint. Any FIFO size is software configured to better meet the application requirements.

37.11.1

Peripheral FIFO architecture
Figure 466. Device-mode FIFO address mapping and AHB FIFO access mapping
Single data
FIFO
IN endpoint Tx FIFO #x
DFIFO push access
from AHB

Dedicated Tx
FIFO #x control
(optional)
MAC pop

IN endpoint Tx FIFO #1
DFIFO push access
from AHB

.
.
.

Tx FIFO #x
packet

OTG_DIEPTXFx[31:16]
OTG_DIEPTXFx[15:0]

.
.
.

Dedicated Tx
FIFO #1 control
(optional)

Tx FIFO #1
packet

.
.
.
OTG_DIEPTXF1[31:16]
OTG_DIEPTXF1[15:0]

MAC pop
IN endpoint Tx FIFO #0
DFIFO push access
from AHB

Dedicated Tx
FIFO #0 control
(optional)

Tx FIFO #0
packet

OTG_DIEPTXF0[31:16]
OTG_DIEPTXF0[15:0]

MAC pop

Any OUT endpoint
DFIFO pop access
from AHB

Dedicated Tx
FIFO #1 control
(optional)

MAC push

Rx packets

OTG_GRXFSIZ[15:0]

A1=0 (Rx start address fixed
to 0)
MSv36929V1

Peripheral Rx FIFO
The OTG peripheral uses a single receive FIFO that receives the data directed to all OUT
endpoints. Received packets are stacked back-to-back until free space is available in the Rx
FIFO. The status of the received packet (which contains the OUT endpoint destination
number, the byte count, the data PID and the validity of the received data) is also stored by
the core on top of the data payload. When no more space is available, host transactions are
NACKed and an interrupt is received on the addressed endpoint. The size of the receive
FIFO is configured in the receive FIFO size register (OTG_GRXFSIZ).
The single receive FIFO architecture makes it more efficient for the USB peripheral to fill in
the receive RAM buffer:
•

All OUT endpoints share the same RAM buffer (shared FIFO)

•

The OTG_FS/OTG_HS core can fill in the receive FIFO up to the limit for any host
sequence of OUT tokens

The application keeps receiving the Rx FIFO non-empty interrupt (RXFLVL bit in
OTG_GINTSTS) as long as there is at least one packet available for download. It reads the
packet information from the receive status read and pop register (OTG_GRXSTSP) and
finally pops data off the receive FIFO by reading from the endpoint-related pop address.

1348/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Peripheral Tx FIFOs
The core has a dedicated FIFO for each IN endpoint. The application configures FIFO sizes
by writing the endpoint 0 transmit FIFO size register (OTG_DIEPTXF0) for IN endpoint0 and
the device IN endpoint transmit FIFOx registers (OTG_DIEPTXFx) for IN endpoint-x.

37.11.2

Host FIFO architecture
Figure 467. Host-mode FIFO address mapping and AHB FIFO access mapping
Single data
FIFO

Any periodic channel
DFIFO push access
from AHB

Periodic Tx
packets
Periodic Tx FIFO
control (optional)

OTG_HPTXFSIZ[31:16]

OTG_HPTXFSIZ[15:0]

MAC pop
Any non-periodic
channel DFIFO push
access from AHB

Non-periodic
Tx packets
Non-periodic Tx
FIFO control

OTG_HNPTXFSIZ[31:16]

OTG_HNPTXFSIZ[15:0]

MAC pop
Rx packets
Any channel DFIFO pop
access from AHB

OTG_GRXFSIZ[15:0]

Rx FIFO control
Rx start address fixed to 0
A1=0

MAC push

MSv36930V1

Host Rx FIFO
The host uses one receiver FIFO for all periodic and nonperiodic transactions. The FIFO is
used as a receive buffer to hold the received data (payload of the received packet) from the
USB until it is transferred to the system memory. Packets received from any remote IN
endpoint are stacked back-to-back until free space is available. The status of each received
packet with the host channel destination, byte count, data PID and validity of the received
data are also stored into the FIFO. The size of the receive FIFO is configured in the receive
FIFO size register (OTG_GRXFSIZ).
The single receive FIFO architecture makes it highly efficient for the USB host to fill in the
receive data buffer:
•

All IN configured host channels share the same RAM buffer (shared FIFO)

•

The OTG_FS/OTG_HS core can fill in the receive FIFO up to the limit for any sequence
of IN tokens driven by the host software

The application receives the Rx FIFO not-empty interrupt as long as there is at least one
packet available for download. It reads the packet information from the receive status read
and pop register and finally pops the data off the receive FIFO.

RM0385 Rev 7

1349/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Host Tx FIFOs
The host uses one transmit FIFO for all non-periodic (control and bulk) OUT transactions
and one transmit FIFO for all periodic (isochronous and interrupt) OUT transactions. FIFOs
are used as transmit buffers to hold the data (payload of the transmit packet) to be
transmitted over the USB. The size of the periodic (nonperiodic) Tx FIFO is configured in the
host periodic (nonperiodic) transmit FIFO size OTG_HPTXFSIZ / OTG_HNPTXFSIZ)
register.
The two Tx FIFO implementation derives from the higher priority granted to the periodic type
of traffic over the USB frame. At the beginning of each frame, the built-in host scheduler
processes the periodic request queue first, followed by the nonperiodic request queue.
The two transmit FIFO architecture provides the USB host with separate optimization for
periodic and nonperiodic transmit data buffer management:
•

All host channels configured to support periodic (nonperiodic) transactions in the OUT
direction share the same RAM buffer (shared FIFOs)

•

The OTG_FS/OTG_HS core can fill in the periodic (nonperiodic) transmit FIFO up to
the limit for any sequence of OUT tokens driven by the host software

The OTG_FS/OTG_HS core issues the periodic Tx FIFO empty interrupt (PTXFE bit in
OTG_GINTSTS) as long as the periodic Tx FIFO is half or completely empty, depending on
the value of the periodic Tx FIFO empty level bit in the AHB configuration register
(PTXFELVL bit in OTG_GAHBCFG). The application can push the transmission data in
advance as long as free space is available in both the periodic Tx FIFO and the periodic
request queue. The host periodic transmit FIFO and queue status register
(OTG_HPTXSTS) can be read to know how much space is available in both.
OTG_FS/OTG_HS core issues the non periodic Tx FIFO empty interrupt (NPTXFE bit in
OTG_GINTSTS) as long as the nonperiodic Tx FIFO is half or completely empty depending
on the non periodic Tx FIFO empty level bit in the AHB configuration register (TXFELVL bit
in OTG_GAHBCFG). The application can push the transmission data as long as free space
is available in both the nonperiodic Tx FIFO and nonperiodic request queue. The host
nonperiodic transmit FIFO and queue status register (OTG_HNPTXSTS) can be read to
know how much space is available in both.

37.11.3

FIFO RAM allocation
Device mode
Receive FIFO RAM allocation: the application should allocate RAM for SETUP packets:

1350/1709

•

10 locations must be reserved in the receive FIFO to receive SETUP packets on
control endpoint. The core does not use these locations, which are reserved for SETUP
packets, to write any other data.

•

One location is to be allocated for Global OUT NAK.

•

Status information is written to the FIFO along with each received packet. Therefore, a
minimum space of (largest packet size / 4) + 1 must be allocated to receive packets. If
multiple isochronous endpoints are enabled, then at least two (largest packet size / 4) +
1 spaces must be allocated to receive back-to-back packets. Typically, two (largest
packet size / 4) + 1 spaces are recommended so that when the previous packet is
being transferred to the CPU, the USB can receive the subsequent packet.

•

Along with the last packet for each endpoint, transfer complete status information is
also pushed to the FIFO. One location for each OUT endpoint is recommended.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Device RxFIFO =
(5 * number of control endpoints + 8) + ((largest USB packet used / 4) + 1 for status
information) + (2 * number of OUT endpoints) + 1 for Global NAK
Example: The MPS is 1,024 bytes for a periodic USB packet and 512 bytes for a nonperiodic USB packet. There are three OUT endpoints, three IN endpoints, one control
endpoint, and three host channels.
Device RxFIFO = (5 * 1 + 8) + ((1,024 / 4) +1) + (2 * 4) + 1 = 279
Transmit FIFO RAM allocation: the minimum RAM space required for each IN endpoint
Transmit FIFO is the maximum packet size for that particular IN endpoint.

Note:

More space allocated in the transmit IN endpoint FIFO results in better performance on the
USB.

Host mode
Receive FIFO RAM allocation:
Status information is written to the FIFO along with each received packet. Therefore, a
minimum space of (largest packet size / 4) + 1 must be allocated to receive packets. If
multiple isochronous channels are enabled, then at least two (largest packet size / 4) + 1
spaces must be allocated to receive back-to-back packets. Typically, two (largest packet
size / 4) + 1 spaces are recommended so that when the previous packet is being transferred
to the CPU, the USB can receive the subsequent packet.
Along with the last packet in the host channel, transfer complete status information is also
pushed to the FIFO. So one location must be allocated for this.
Host RxFIFO = (largest USB packet used / 4) + 1 for status information + 1 transfer
complete
Example: Host RxFIFO = ((1,024 / 4) + 1) + 1 = 258
Transmit FIFO RAM allocation:
The minimum amount of RAM required for the host Non-periodic Transmit FIFO is the
largest maximum packet size among all supported non-periodic OUT channels.
Typically, two largest packet sizes worth of space is recommended, so that when the current
packet is under transfer to the USB, the CPU can get the next packet.
Non-Periodic TxFIFO = largest non-periodic USB packet used / 4
Example: Non-Periodic TxFIFO = (512 / 4) = 128
The minimum amount of RAM required for host periodic Transmit FIFO is the largest
maximum packet size out of all the supported periodic OUT channels. If there is at least one
isochronous OUT endpoint, then the space must be at least two times the maximum packet
size of that channel.
Host Periodic TxFIFO = largest periodic USB packet used / 4
Example: Host Periodic TxFIFO = (1,024 / 4) = 256
Note:

More space allocated in the Transmit Non-periodic FIFO results in better performance on
the USB.

RM0385 Rev 7

1351/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.12

RM0385

OTG_FS system performance
Best USB and system performance is achieved owing to the large RAM buffers, the highly
configurable FIFO sizes, the quick 32-bit FIFO access through AHB push/pop registers and,
especially, the advanced FIFO control mechanism. Indeed, this mechanism allows the
OTG_FS to fill in the available RAM space at best regardless of the current USB sequence.
With these features:
•

•

The application gains good margins to calibrate its intervention in order to optimize the
CPU bandwidth usage:
–

It can accumulate large amounts of transmission data in advance compared to
when they are effectively sent over the USB

–

It benefits of a large time margin to download data from the single receive FIFO

The USB core is able to maintain its full operating rate, that is to provide maximum fullspeed bandwidth with a great margin of autonomy versus application intervention:
–

It has a large reserve of transmission data at its disposal to autonomously manage
the sending of data over the USB

–

It has a lot of empty space available in the receive buffer to autonomously fill it in
with the data coming from the USB

As the OTG_FS core is able to fill in the 1.25-Kbyte RAM buffer very efficiently, and as
1.25-Kbyte of transmit/receive data is more than enough to cover a full speed frame, the
USB system is able to withstand the maximum full-speed data rate for up to one USB frame
(1 ms) without any CPU intervention.

37.13

OTG_FS/OTG_HS interrupts
When the OTG_FS/OTG_HS controller is operating in one mode, either device or host, the
application must not access registers from the other mode. If an illegal access occurs, a
mode mismatch interrupt is generated and reflected in the core interrupt register (MMIS bit
in the OTG_GINTSTS register). When the core switches from one mode to the other, the
registers in the new mode of operation must be reprogrammed as they would be after a
power-on reset.
Figure 468 shows the interrupt hierarchy.

1352/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 468. Interrupt hierarchy
Wakeup interrupt
OTG_FS_WKUP / OTG_HS_WKUP

(1)

AND

Global interrupt
OTG_FS / OTG_HS

OR

OTG_AHBCFG
AHB configuration register

AND

OT

OE

GI
NT

PIN
IEP P
IN
T

HC
IN
T
HP
RT
IN
T

Global interrupt mask (bit 0)

OTG_GINTSTS
Core register interrupt
31:26

25 24

23:20

19 18

17:3

2

1:0

OTG_GINTMSK
Core interrupt mask register

OTG_GOTGINT
OTG interrupt register

EP1_OUT interrupt OTG_HS_EP1_OUT
EP1_IN interrupt OTG_HS_EP1_IN
(15 + #EP):16
OUT endpoints

(#EP-1):0
IN endpoints

17
EP1OUT

1
EP1IN

OTG_DAINTMSK
Device all endpoints interrupt mask
register

OTG_DEACHINTMSK
Device each endpoint interrupt mask
register

OTG_DAINT
Device all endpoints interrupt register

OTG_DEACHINT
Device each endpoint interrupt register

OTG_DIEPMSK/
OTG_DOEPMSK
Device IN/OUT endpoints common
interrupt mask register

OTG_DIEPEACHMSK1/
OTG_DOEPEACHMSK1
Device each IN/OUT endpoint interrupt
mask registers

x=0

...

OTG_DIEPINTx/
OTG_DOEPINTx
Device IN/OUT endpoint interrupt
registers

x = #HC-1

HS only

OTG_HPRT
Host port control and status register

OTG_HAINTMSK
Host all channels interrupt mask register
OTG_HAINT
Host all channels interrupt register
x=0

...

OTG_HCTINTMSKx
Host channels interrupt mask registers

x = #HC-1

OTG_HCTINTx
Host channels interrupt registers

MSv47471V2

1. OTG_FS_WKUP / OTG_HS_WKUP become active (high state) when resume condition occurs during L1 SLEEP or L2
SUSPEND states.

RM0385 Rev 7

1353/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.14

RM0385

OTG_FS/OTG_HS control and status registers
By reading from and writing to the control and status registers (CSRs) through the AHB
slave interface, the application controls the OTG_FS/OTG_HS controller. These registers
are 32 bits wide, and the addresses are 32-bit block aligned. The OTG_FS/OTG_HS
registers must be accessed by words (32 bits).
CSRs are classified as follows:
•

Core global registers

•

Host-mode registers

•

Host global registers

•

Host port CSRs

•

Host channel-specific registers

•

Device-mode registers

•

Device global registers

•

Device endpoint-specific registers

•

Power and clock-gating registers

•

Data FIFO (DFIFO) access registers

Only the core global, power and clock-gating, data FIFO access, and host port control and
status registers can be accessed in both host and device modes. When the
OTG_FS/OTG_HS controller is operating in one mode, either device or host, the application
must not access registers from the other mode. If an illegal access occurs, a mode
mismatch interrupt is generated and reflected in the core interrupt register (MMIS bit in the
OTG_GINTSTS register). When the core switches from one mode to the other, the registers
in the new mode of operation must be reprogrammed as they would be after a power-on
reset.

37.14.1

CSR memory map
The host and device mode registers occupy different addresses. All registers are
implemented in the AHB clock domain.

Global CSR map
These registers are available in both host and device modes.
Table 261. Core global control and status registers (CSRs)
Acronym

Address
offset

Register name

OTG_GOTGCTL

0x000

Section 37.15.1: OTG control and status register (OTG_GOTGCTL)

OTG_GOTGINT

0x004

Section 37.15.2: OTG interrupt register (OTG_GOTGINT)

OTG_GAHBCFG

0x008

Section 37.15.3: OTG AHB configuration register (OTG_GAHBCFG)

OTG_GUSBCFG

0x00C

Section 37.15.4: OTG USB configuration register (OTG_GUSBCFG)

OTG_GRSTCTL

0x010

Section 37.15.5: OTG reset register (OTG_GRSTCTL)

OTG_GINTSTS

0x014

Section 37.15.6: OTG core interrupt register (OTG_GINTSTS)

OTG_GINTMSK

0x018

Section 37.15.7: OTG interrupt mask register (OTG_GINTMSK)

1354/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Table 261. Core global control and status registers (CSRs) (continued)

Acronym

Address
offset

Register name

OTG_GRXSTSR

0x01C

OTG_GRXSTSP

0x020

Section 37.15.8: OTG receive status debug read/OTG status read and pop
registers (OTG_GRXSTSR/OTG_GRXSTSP)

OTG_GRXFSIZ

0x024

Section 37.15.9: OTG receive FIFO size register (OTG_GRXFSIZ)

OTG_HNPTXFSIZ/
OTG_DIEPTXF0(1)

0x028

Section 37.15.10: OTG host non-periodic transmit FIFO size register
(OTG_HNPTXFSIZ)/Endpoint 0 Transmit FIFO size (OTG_DIEPTXF0)

OTG_HNPTXSTS

0x02C

Section 37.15.11: OTG non-periodic transmit FIFO/queue status register
(OTG_HNPTXSTS)

OTG_GCCFG

0x038

Section 37.15.12: OTG general core configuration register (OTG_GCCFG)

OTG_CID

0x03C

Section 37.15.13: OTG core ID register (OTG_CID)

OTG_GLPMCFG

0x54

Section 37.15.14: OTG core LPM configuration register (OTG_GLPMCFG)

OTG_HPTXFSIZ

0x100

Section 37.15.15: OTG host periodic transmit FIFO size register
(OTG_HPTXFSIZ)

OTG_DIEPTXFx

0x104
0x108
...
0x114

Section 37.15.16: OTG device IN endpoint transmit FIFO size register
(OTG_DIEPTXFx) (x = 1..5[FS] /8[HS], where x is the FIFO number) for
USB_OTG FS

OTG_DIEPTXFx

0x104
0x108
...
0x120

Section 37.15.16: OTG device IN endpoint transmit FIFO size register
(OTG_DIEPTXFx) (x = 1..5[FS] /8[HS], where x is the FIFO number) for
USB_OTG HS

1. The general rule is to use OTG_HNPTXFSIZ for host mode and OTG_DIEPTXF0 for device mode.

Host-mode CSR map
These registers must be programmed every time the core changes to host mode.
Table 262. Host-mode control and status registers (CSRs)
Acronym

Offset
address

Register name

OTG_HCFG

0x400

Section 37.15.18: OTG host configuration register (OTG_HCFG)

OTG_HFIR

0x404

Section 37.15.19: OTG host frame interval register (OTG_HFIR)

OTG_HFNUM

0x408

Section 37.15.20: OTG host frame number/frame time remaining register
(OTG_HFNUM)

OTG_HPTXSTS

0x410

Section 37.15.21: OTG_Host periodic transmit FIFO/queue status register
(OTG_HPTXSTS)

OTG_HAINT

0x414

Section 37.15.22: OTG host all channels interrupt register (OTG_HAINT)

OTG_HAINTMSK

0x418

Section 37.15.23: OTG host all channels interrupt mask register
(OTG_HAINTMSK)

RM0385 Rev 7

1355/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Table 262. Host-mode control and status registers (CSRs) (continued)
Acronym

Offset
address

Register name

OTG_HPRT

0x440

Section 37.15.24: OTG host port control and status register (OTG_HPRT)

OTG_HCCHARx

0x500
0x520
...
0x660

Section 37.15.25: OTG host channel x characteristics register
(OTG_HCCHARx) (x = 0..15[HS] / 11[FS], where x = Channel number) for
USB_OTG FS

OTG_HCCHARx

0x500
0x520
...
0x6E0

Section 37.15.25: OTG host channel x characteristics register
(OTG_HCCHARx) (x = 0..15[HS] / 11[FS], where x = Channel number) for
USB_OTG HS

OTG_HCSPLTx

0x504
0x524
....
0x6E4

Section 37.15.26: OTG host channel x split control register
(OTG_HCSPLTx) (x = 0..15, where x = Channel number)

OTG_HCINTx

0x508
0x528
....
0x668

Section 37.15.27: OTG host channel x interrupt register (OTG_HCINTx)
(x = 0..15[HS] / 11[FS], where x = Channel number) for USB_OTG FS

OTG_HCINTx

0x508
0x528
....
0x6E8

Section 37.15.27: OTG host channel x interrupt register (OTG_HCINTx)
(x = 0..15[HS] / 11[FS], where x = Channel number) for USB_OTG HS

OTG_HCINTMSKx

0x50C
0x52C
....
0x66C

Section 37.15.28: OTG host channel x interrupt mask register
(OTG_HCINTMSKx) (x = 0..15[HS] / 11[FS], where x = Channel number)
for USB_OTG FS

OTG_HCINTMSKx

0x50C
0x52C
....
0x6EC

Section 37.15.28: OTG host channel x interrupt mask register
(OTG_HCINTMSKx) (x = 0..15[HS] / 11[FS], where x = Channel number)
for USB_OTG HS

OTG_HCTSIZx

0x510
0x530
....
0x670

Section 37.15.29: OTG host channel x transfer size register
(OTG_HCTSIZx) (x = 0..15[HS] / 11[FS], where x = Channel number) for
USB_OTG FS

OTG_HCTSIZx

0x510
0x530
....
0x6F0

Section 37.15.29: OTG host channel x transfer size register
(OTG_HCTSIZx) (x = 0..15[HS] / 11[FS], where x = Channel number) for
USB_OTG HS

OTG_HCDMAx

0x514
0x534
....
0x6F4

Section 37.15.30: OTG host channel x DMA address register
(OTG_HCDMAx) (x = 0..15, where x = Channel number)

1356/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Device-mode CSR map
These registers must be programmed every time the core changes to device mode.
Table 263. Device-mode control and status registers
Acronym

Offset
address

Register name

OTG_DCFG

0x800

Section 37.15.32: OTG device configuration register (OTG_DCFG)

OTG_DCTL

0x804

Section 37.15.33: OTG device control register (OTG_DCTL)

OTG_DSTS

0x808

Section 37.15.34: OTG device status register (OTG_DSTS)

OTG_DIEPMSK

0x810

Section 37.15.35: OTG device IN endpoint common interrupt mask
register (OTG_DIEPMSK)

OTG_DOEPMSK

0x814

Section 37.15.36: OTG device OUT endpoint common interrupt mask
register (OTG_DOEPMSK)

OTG_DAINT

0x818

Section 37.15.37: OTG device all endpoints interrupt register
(OTG_DAINT)

OTG_DAINTMSK

0x81C

Section 37.15.38: OTG all endpoints interrupt mask register
(OTG_DAINTMSK)

OTG_DVBUSDIS

0x828

Section 37.15.39: OTG device VBUS discharge time register
(OTG_DVBUSDIS)

OTG_DVBUSPULSE

0x82C

Section 37.15.40: OTG device VBUS pulsing time register
(OTG_DVBUSPULSE)

OTG_DTHRCTL

0x830

Section 37.15.41: OTG device threshold control register
(OTG_DTHRCTL)

OTG_DIEPEMPMSK

0x834

Section 37.15.42: OTG device IN endpoint FIFO empty interrupt mask
register (OTG_DIEPEMPMSK)

OTG_DEACHINT

0x838

Section 37.15.43: OTG device each endpoint interrupt register
(OTG_DEACHINT)

OTG_DEACHINTMSK

0x83C

Section 37.15.44: OTG device each endpoint interrupt mask register
(OTG_DEACHINTMSK)

OTG_HS_DIEPEACHM
SK1

0x844

Section 37.15.45: OTG device each IN endpoint-1 interrupt mask
register (OTG_HS_DIEPEACHMSK1)

OTG_HS_DOEPEACHM
0x884
SK1

Section 37.15.46: OTG device each OUT endpoint-1 interrupt mask
register (OTG_HS_DOEPEACHMSK1)

OTG_DIEPCTL0

0x900

Section 37.15.47: OTG device control IN endpoint 0 control register
(OTG_DIEPCTL0) for USB_OTG FS

OTG_DIEPCTLx

0x920
0x940
...
0x9A0

Section 37.15.48: OTG device IN endpoint x control register
(OTG_DIEPCTLx) (x = 1..5[FS] / 0..8[HS], where x = endpoint number)
for USB_OTG FS

RM0385 Rev 7

1357/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Table 263. Device-mode control and status registers (continued)
Acronym

Offset
address

Register name

OTG_DIEPCTLx

0x900
0x920
...
0xA00

Section 37.15.48: OTG device IN endpoint x control register
(OTG_DIEPCTLx) (x = 1..5[FS] / 0..8[HS], where x = endpoint number)
for USB_OTG HS

OTG_DIEPINTx

0x908
0x928
....
0x988

Section 37.15.49: OTG device IN endpoint x interrupt register
(OTG_DIEPINTx) (x = 0..5[FS] /8[HS], where x = Endpoint number) for
USB_OTG FS

OTG_DIEPINTx

0x908
0x928
...
0x9E8

Section 37.15.49: OTG device IN endpoint x interrupt register
(OTG_DIEPINTx) (x = 0..5[FS] /8[HS], where x = Endpoint number) for
USB_OTG HS

OTG_DIEPTSIZ0

0x910

Section 37.15.50: OTG device IN endpoint 0 transfer size register
(OTG_DIEPTSIZ0)

OTG_DIEPDMAx

0x914
0x934
...
0x9F4

Section 37.15.51: OTG device IN endpoint x DMA address register
(OTG_DIEPDMAx) (x = 0..8, where x = endpoint number)

OTG_DTXFSTSx

0x918
0x938
....
0x998

Section 37.15.52: OTG device IN endpoint transmit FIFO status register
(OTG_DTXFSTSx) (x = 0..5[FS] /8[HS], where x = endpoint number) for
USB_OTG FS

OTG_DTXFSTSx

0x918
0x938
.....
0x9F8

Section 37.15.52: OTG device IN endpoint transmit FIFO status register
(OTG_DTXFSTSx) (x = 0..5[FS] /8[HS], where x = endpoint number) for
USB_OTG HS

OTG_DIEPTSIZx

0x930
0x950
...
0x9B0

Section 37.15.53: OTG device IN endpoint x transfer size register
(OTG_DIEPTSIZx) (x = 1..5[FS] /8[HS], where x = endpoint number) for
USB_OTG FS

OTG_DIEPTSIZx

0x930
0x950
...
0x9F0

Section 37.15.53: OTG device IN endpoint x transfer size register
(OTG_DIEPTSIZx) (x = 1..5[FS] /8[HS], where x = endpoint number) for
USB_OTG HS

OTG_DOEPCTL0

0xB00

Section 37.15.54: OTG device control OUT endpoint 0 control register
(OTG_DOEPCTL0)

OTG_DOEPINTx

0xB08
0xB28
...
0xBA8

Section 37.15.55: OTG device OUT endpoint x interrupt register
(OTG_DOEPINTx) (x = 0..5[FS] /8[HS], where x = Endpoint number)
for USB_OTG FS

1358/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Table 263. Device-mode control and status registers (continued)

Acronym

Offset
address

Register name

OTG_DOEPINTx

0xB08
0XB28
...
0xC08

Section 37.15.55: OTG device OUT endpoint x interrupt register
(OTG_DOEPINTx) (x = 0..5[FS] /8[HS], where x = Endpoint number)
for USB_OTG HS

OTG_DOEPTSIZ0

0xB10

Section 37.15.56: OTG device OUT endpoint 0 transfer size register
(OTG_DOEPTSIZ0)

OTG_DOEPDMAx

0xB14
0xB34
...
0xC14

Section 37.15.57: OTG device OUT endpoint x DMA address register
(OTG_DOEPDMAx) (x = 0..8, where x = endpoint number)

OTG_DOEPCTLx

0xB20
0xB40
...
0xBA0

Section 37.15.58: OTG device OUT endpoint x control register
(OTG_DOEPCTLx) (x = 1..5[FS] /8[HS], where x = endpoint number)
for USB_OTG FS

OTG_DOEPCTLx

0xB20
0xB40
...
0xC00

Section 37.15.58: OTG device OUT endpoint x control register
(OTG_DOEPCTLx) (x = 1..5[FS] /8[HS], where x = endpoint number)
for USB_OTG HS

OTG_DOEPTSIZx

0xB30
0xB50
...
0xBB0

Section 37.15.59: OTG device OUT endpoint x transfer size register
(OTG_DOEPTSIZx) (x = 1..5[FS] /8[HS], where x = Endpoint number)
for USB_OTG FS

OTG_DOEPTSIZx

0xB30
0xB50
..
0xBF0

Section 37.15.59: OTG device OUT endpoint x transfer size register
(OTG_DOEPTSIZx) (x = 1..5[FS] /8[HS], where x = Endpoint number)
for USB_OTG HS

Data FIFO (DFIFO) access register map
These registers, available in both host and device modes, are used to read or write the FIFO
space for a specific endpoint or a channel, in a given direction. If a host channel is of type
IN, the FIFO can only be read on the channel. Similarly, if a host channel is of type OUT, the
FIFO can only be written on the channel.
Table 264. Data FIFO (DFIFO) access register map
FIFO access register section

Offset address

Access

Device IN endpoint 0/Host OUT Channel 0: DFIFO write access
Device OUT endpoint 0/Host IN Channel 0: DFIFO read access

0x1000–0x1FFC

w
r

Device IN endpoint 1/Host OUT Channel 1: DFIFO write access
Device OUT endpoint 1/Host IN Channel 1: DFIFO read access

0x2000–0x2FFC

w
r

RM0385 Rev 7

1359/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Table 264. Data FIFO (DFIFO) access register map (continued)
FIFO access register section

Offset address

...

Access

...

...

Device IN endpoint x(1)/Host OUT Channel x(1): DFIFO write access
0xX000–0xXFFC
Device OUT endpoint x(1)/Host IN Channel x(1): DFIFO read access

w
r

1. Where x is 5[FS] / 8[HS]in device mode and 11[FS] / 15[HS]in host mode.

Power and clock gating CSR map
There is a single register for power and clock gating. It is available in both host and device
modes.
Table 265. Power and clock gating control and status registers
Acronym

Offset address

OTG_PCGCCTL

37.15

0xE00–0xE04

Register name
Section 37.15.60: OTG power and clock gating control
register (OTG_PCGCCTL)

OTG_FS/OTG_HS registers
These registers are available in both host and device modes, and do not need to be
reprogrammed when switching between these modes.
Bit values in the register descriptions are expressed in binary unless otherwise specified.

37.15.1

OTG control and status register (OTG_GOTGCTL)
Address offset: 0x000
Reset value: 0x0001 0000
The OTG_GOTGCTL register controls the behavior and reflects the status of the OTG
function of the core.

31

30

29

28

27

26

25

24

23

22

21

20
OTG
VER

19

18

17

16

DBCT

CID
STS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CUR
MOD
r

rw

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

EHEN

HNP
RQ

HNG
SCS

SRQ

SRQ
SCS

rw

r

rw

r

rw

1360/1709

DHNP HSHNP
EN
EN
rw

rw

BSVLD ASVLD

BVALO BVALO AVALO AVALO VBVAL VBVAL
VAL
EN
VAL
EN
OVAL
OEN
rw

RM0385 Rev 7

rw

rw

rw

rw

rw

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 CURMOD: Current mode of operation
Indicates the current mode (host or device).
0: Device mode
1: Host mode
Bit 20 OTGVER: OTG version
Selects the OTG revision.
0:OTG Version 1.3. OTG1.3 is obsolete for new product development.
1:OTG Version 2.0. In this version the core supports only data line pulsing for SRP.
Bit 19 BSVLD: B-session valid
Indicates the device mode transceiver status.
0: B-session is not valid.
1: B-session is valid.
In OTG mode, the user can use this bit to determine if the device is connected or
disconnected.
Note: Only accessible in device mode.
Bit 18 ASVLD: A-session valid
Indicates the host mode transceiver status.
0: A-session is not valid
1: A-session is valid
Note: Only accessible in host mode.
Bit 17 DBCT: Long/short debounce time
Indicates the debounce time of a detected connection.
0: Long debounce time, used for physical connections (100 ms + 2.5 µs)
1: Short debounce time, used for soft connections (2.5 µs)
Note: Only accessible in host mode.
Bit 16 CIDSTS: Connector ID status
Indicates the connector ID status on a connect event.
0: The OTG_FS/OTG_HS controller is in A-device mode
1: The OTG_FS/OTG_HS controller is in B-device mode
Note: Accessible in both device and host modes.
Bits 15:13 Reserved, must be kept at reset value.
Bit 12 EHEN: Embedded host enable
It is used to select between OTG A device state machine and embedded host state machine.
0: OTG A device state machine is selected
1: Embedded host state machine is selected
Bit 11 DHNPEN: Device HNP enabled
The application sets this bit when it successfully receives a SetFeature.SetHNPEnable
command from the connected USB host.
0: HNP is not enabled in the application
1: HNP is enabled in the application
Note: Only accessible in device mode.

RM0385 Rev 7

1361/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 10 HSHNPEN: host set HNP enable
The application sets this bit when it has successfully enabled HNP (using the
SetFeature.SetHNPEnable command) on the connected device.
0: Host Set HNP is not enabled
1: Host Set HNP is enabled
Note: Only accessible in host mode.
Bit 9 HNPRQ: HNP request
The application sets this bit to initiate an HNP request to the connected USB host. The
application can clear this bit by writing a 0 when the host negotiation success status change
bit in the OTG_GOTGINT register (HNSSCHG bit in OTG_GOTGINT) is set. The core clears
this bit when the HNSSCHG bit is cleared.
0: No HNP request
1: HNP request
Note: Only accessible in device mode.
Bit 8 HNGSCS: Host negotiation success
The core sets this bit when host negotiation is successful. The core clears this bit when the
HNP request (HNPRQ) bit in this register is set.
0: Host negotiation failure
1: Host negotiation success
Note: Only accessible in device mode.
Bit 7 BVALOVAL: B-peripheral session valid override value.
This bit is used to set override value for Bvalid signal when BVALOEN bit is set.
0: Bvalid value is '0' when BVALOEN = 1
1: Bvalid value is '1' when BVALOEN = 1
Note: Only accessible in device mode.
Bit 6 BVALOEN: B-peripheral session valid override enable.
This bit is used to enable/disable the software to override the Bvalid signal using the
BVALOVAL bit.
0:Override is disabled and Bvalid signal from the respective PHY selected is used internally
by the core
1:Internally Bvalid received from the PHY is overridden with BVALOVAL bit value
Note: Only accessible in device mode.
Bit 5 AVALOVAL: A-peripheral session valid override value.
This bit is used to set override value for Avalid signal when AVALOEN bit is set.
0: Avalid value is '0' when AVALOEN = 1
1: Avalid value is '1' when AVALOEN = 1
Note: Only accessible in host mode.
Bit 4 AVALOEN: A-peripheral session valid override enable.
This bit is used to enable/disable the software to override the Avalid signal using the
AVALOVAL bit.
0:Override is disabled and Avalid signal from the respective PHY selected is used internally
by the core
1:Internally Avalid received from the PHY is overridden with AVALOVAL bit value
Note: Only accessible in host mode.

1362/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 3 VBVALOVAL: VBUS valid override value.
This bit is used to set override value for vbusvalid signal when VBVALOEN bit is set.
0: vbusvalid value is '0' when VBVALOEN = 1
1: vbusvalid value is '1' when VBVALOEN = 1
Note: Only accessible in host mode.
Bit 2 VBVALOEN: VBUS valid override enable.
This bit is used to enable/disable the software to override the vbusvalid signal using the
VBVALOVAL bit.
0: Override is disabled and vbusvalid signal from the respective PHY selected is used
internally by the core
1: Internally vbusvalid received from the PHY is overridden with VBVALOVAL bit value
Note: Only accessible in host mode.
Bit 1 SRQ: Session request
The application sets this bit to initiate a session request on the USB. The application can
clear this bit by writing a 0 when the host negotiation success status change bit in the
OTG_GOTGINT register (HNSSCHG bit in OTG_GOTGINT) is set. The core clears this bit
when the HNSSCHG bit is cleared.
If the user uses the USB 1.1 full-speed serial transceiver interface to initiate the session
request, the application must wait until VBUS discharges to 0.2 V, after the B-session valid bit
in this register (BSVLD bit in OTG_GOTGCTL) is cleared.
0: No session request
1: Session request
Note: Only accessible in device mode.
Bit 0 SRQSCS: Session request success
The core sets this bit when a session request initiation is successful.
0: Session request failure
1: Session request success
Note: Only accessible in device mode.

37.15.2

OTG interrupt register (OTG_GOTGINT)
Address offset: 0x04
Reset value: 0x0000 0000
The application reads this register whenever there is an OTG interrupt and clears the bits in
this register to clear the OTG interrupt.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ID
CHNG

DBC
DNE

ADTO
CHG

HNG
DET

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rc_w1

rc_w1

rc_w1

rc_w1

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

HNSS
CHG

SRSS
CHG

Res.

Res.

Res.

Res.

Res.

SEDET

Res.

Res.

rc_w1

rc_w1

Res.

Res.

Res.

Res.

Res.

RM0385 Rev 7

rc_w1

1363/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits 31:21 Reserved, must be kept at reset value.
Bit 20 IDCHNG:
This bit when set indicates that there is a change in the value of the ID input pin.
Bit 19 DBCDNE: Debounce done
The core sets this bit when the debounce is completed after the device connect. The
application can start driving USB reset after seeing this interrupt. This bit is only valid when
the HNP Capable or SRP Capable bit is set in the OTG_GUSBCFG register (HNPCAP bit or
SRPCAP bit in OTG_GUSBCFG, respectively).
Note: Only accessible in host mode.
Bit 18 ADTOCHG: A-device timeout change
The core sets this bit to indicate that the A-device has timed out while waiting for the B-device
to connect.
Note: Accessible in both device and host modes.
Bit 17 HNGDET: Host negotiation detected
The core sets this bit when it detects a host negotiation request on the USB.
Note: Accessible in both device and host modes.
Bits 16:10 Reserved, must be kept at reset value.
Bit 9 HNSSCHG: Host negotiation success status change
The core sets this bit on the success or failure of a USB host negotiation request. The
application must read the host negotiation success bit of the OTG_GOTGCTL register
(HNGSCS bit in OTG_GOTGCTL) to check for success or failure.
Note: Accessible in both device and host modes.
Bits 7:3 Reserved, must be kept at reset value.
Bit 8 SRSSCHG: Session request success status change
The core sets this bit on the success or failure of a session request. The application must
read the session request success bit in the OTG_GOTGCTL register (SRQSCS bit in
OTG_GOTGCTL) to check for success or failure.
Note: Accessible in both device and host modes.
Bit 2 SEDET: Session end detected
The core sets this bit to indicate that the level of the voltage on VBUS is no longer valid for a
B-Peripheral session when VBUS < 0.8 V.
Note: Accessible in both device and host modes.
Bits 1:0 Reserved, must be kept at reset value.

1364/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.3

OTG AHB configuration register (OTG_GAHBCFG)
Address offset: 0x008
Reset value: 0x0000 0000
This register can be used to configure the core after power-on or a change in mode. This
register mainly contains AHB system-related configuration parameters. Do not change this
register after the initial programming. The application must program this register before
starting any transactions on either the AHB or the USB.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

PTXFE
LVL

TXFE
LVL

Res.

GINT
MSK

rw

rw

Res.

Res.

Note:

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Configuration register for USB OTG FS

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

Res.

PTXFE
LVL

TXFE
LVL

rw

rw

Res.

Note:

Res.

Res.

Res.

Res.

Res.

Res.

DMAEN
rw

HBSTLEN[3:0]
rw

rw

rw

0
GINT
MSK

rw

rw

Configuration register for USB OTG HS

RM0385 Rev 7

1365/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits 31:9 Reserved, must be kept at reset value.
Bit 8 PTXFELVL: Periodic Tx FIFO empty level
Indicates when the periodic Tx FIFO empty interrupt bit in the OTG_GINTSTS register
(PTXFE bit in OTG_GINTSTS) is triggered.
0: PTXFE (in OTG_GINTSTS) interrupt indicates that the Periodic Tx FIFO is half empty
1: PTXFE (in OTG_GINTSTS) interrupt indicates that the Periodic Tx FIFO is completely
empty
Note: Only accessible in host mode.
Bit 7 TXFELVL: Tx FIFO empty level
In device mode, this bit indicates when IN endpoint Transmit FIFO empty interrupt (TXFE in
OTG_DIEPINTx) is triggered:
0:The TXFE (in OTG_DIEPINTx) interrupt indicates that the IN endpoint Tx FIFO is half
empty
1:The TXFE (in OTG_DIEPINTx) interrupt indicates that the IN endpoint Tx FIFO is
completely empty
In host mode, this bit indicates when the nonperiodic Tx FIFO empty interrupt (NPTXFE bit in
OTG_GINTSTS) is triggered:
0:The NPTXFE (in OTG_GINTSTS) interrupt indicates that the nonperiodic Tx FIFO is half
empty
1:The NPTXFE (in OTG_GINTSTS) interrupt indicates that the nonperiodic Tx FIFO is
completely empty
Bits 6:1 Reserved, must be kept at reset value for USB OTG FS.
Bit 6 Reserved, must be kept at reset value for USB OTG HS.
Bit 5 DMAEN: DMA enabled for USB OTG HS
0: The core operates in slave mode
1: The core operates in DMA mode
Bits 4:1 HBSTLEN[3:0]: Burst length/type for USB OTG HS
0000 Single: Bus transactions use single 32 bit accesses (not recommended)
0001 INCR: Bus transactions use unspecified length accesses (not recommended, uses the
INCR AHB bus command)
0011 INCR4: Bus transactions target 4x 32 bit accesses
0101 INCR8: Bus transactions target 8x 32 bit accesses
0111 INCR16: Bus transactions based on 16x 32 bit accesses
Others: Reserved
Bit 0 GINTMSK: Global interrupt mask
The application uses this bit to mask or unmask the interrupt line assertion to itself.
Irrespective of this bit’s setting, the interrupt status registers are updated by the core.
0: Mask the interrupt assertion to the application.
1: Unmask the interrupt assertion to the application.
Note: Accessible in both device and host modes.

1366/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.4

OTG USB configuration register (OTG_GUSBCFG)
Address offset: 0x00C
Reset value: 0x0000 1440 for USB OTG FS
Reset value: 0x0000 1400 for USB OTG HS
This register can be used to configure the core after power-on or a changing to host mode
or device mode. It contains USB and USB-PHY related configuration parameters. The
application must program this register before starting any transactions on either the AHB or
the USB. Do not make changes to this register after the initial programming.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

FD
MOD

FH
MOD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

14

13

12

11

10

7

6

5

4

3

2

1

0

Res.

PHY
SEL

Res.

Res.

Res.

15
Res.

Res.

Note:
30

29

Res.

FD
MOD

FH
MOD

rw

rw

15

14

13

PHYL
PC

Res.

Note:

8

TRDT

SRP
CAP

rw

rw

rw

TOCAL

r

rw

Configuration register for USB OTG FS

31

rw

9
HNP
CAP

28

27

26

25
ULPI
IPD

PTCI

PCCI

rw

rw

rw

rw

rw

9

8

7

6

5

HNP
CAP

SRP
CAP

Res.

PHY
SEL

Res.

rw

rw

Res.

Res.

Res.

12

11

10

TRDT[3:0]
rw

rw

rw

rw

24

23

22

21

20

19

18

17

16

ULPI
CSM

ULPI
AR

ULPI
FSL

Res.

rw

rw

rw

rw

4

3

2

1

Res.

Res.

ULPIE ULPIE
TSDPS
VBUSI VBUSD

rw

0

TOCAL[2:0]
rw

rw

rw

Configuration register for USB OTG HS
Bit 31 Reserved, must be kept at reset value.
Bit 30 FDMOD: Force device mode
Writing a 1 to this bit, forces the core to device mode irrespective of the OTG_ID input pin.
0: Normal mode
1: Force device mode
After setting the force bit, the application must wait at least 25 ms before the change takes
effect.
Note: Accessible in both device and host modes.
Bit 29 FHMOD: Force host mode
Writing a 1 to this bit, forces the core to host mode irrespective of the OTG_ID input pin.
0: Normal mode
1: Force host mode
After setting the force bit, the application must wait at least 25 ms before the change takes
effect.
Note: Accessible in both device and host modes.
Bits 28:26 Reserved, must be kept at reset value.

RM0385 Rev 7

1367/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 25 ULPIIPD: ULPI interface protect disable for USB OTG HS
This bit controls the circuitry built in the PHY to protect the ULPI interface when the link tristates stp and data. Any pull-up or pull-down resistors employed by this feature can be
disabled. Refer to the ULPI specification for more details.
0: Enables the interface protection circuit
1: Disables the interface protection circuit
Bit 24 PTCI: Indicator pass through for USB OTG HS
This bit controls whether the complement output is qualified with the internal VBUS valid
comparator before being used in the VBUS state in the RX CMD. Refer to the ULPI
specification for more details.
0: Complement Output signal is qualified with the Internal VBUS valid comparator
1: Complement Output signal is not qualified with the Internal VBUS valid comparator
Bit 23 PCCI: Indicator complement for USB OTG HS
This bit controls the PHY to invert the ExternalVbusIndicator input signal, and generate the
complement output. Refer to the ULPI specification for more details.
0: PHY does not invert the ExternalVbusIndicator signal
1: PHY inverts ExternalVbusIndicator signal
Bit 22 TSDPS: TermSel DLine pulsing selection for USB OTG HS
This bit selects utmi_termselect to drive the data line pulse during SRP (session request
protocol).
0: Data line pulsing using utmi_txvalid (default)
1: Data line pulsing using utmi_termsel
Bit 21 ULPIEVBUSI: ULPI external VBUS indicator for USB OTG HS
This bit indicates to the ULPI PHY to use an external VBUS overcurrent indicator.
0: PHY uses an internal VBUS valid comparator
1: PHY uses an external VBUS valid comparator
Bit 20 ULPIEVBUSD: ULPI External VBUS Drive for USB OTG HS
This bit selects between internal or external supply to drive 5 V on VBUS, in the ULPI PHY.
0: PHY drives VBUS using internal charge pump (default)
1: PHY drives VBUS using external supply.
Bit 19 ULPICSM: ULPI clock SuspendM for USB OTG HS
This bit sets the ClockSuspendM bit in the interface control register on the ULPI PHY. This bit
applies only in the serial and carkit modes.
0: PHY powers down the internal clock during suspend
1: PHY does not power down the internal clock
Bit 18 ULPIAR: ULPI Auto-resume for USB OTG HS
This bit sets the AutoResume bit in the interface control register on the ULPI PHY.
0: PHY does not use AutoResume feature
1: PHY uses AutoResume feature
Bit 17 ULPIFSLS: ULPI FS/LS select for USB OTG HS
The application uses this bit to select the FS/LS serial interface for the ULPI PHY. This bit is
valid only when the FS serial transceiver is selected on the ULPI PHY.
0: ULPI interface
1: ULPI FS/LS serial interface
Bit 16 Reserved, must be kept at reset value.

1368/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 15 PHYLPC: PHY Low-power clock select for USB OTG HS
This bit selects either 480 MHz or 48 MHz (low-power) PHY mode. In FS and LS modes, the
PHY can usually operate on a 48 MHz clock to save power.
0: 480 MHz internal PLL clock
1: 48 MHz external clock
In 480 MHz mode, the UTMI interface operates at either 60 or 30 MHz, depending on
whether the 8- or 16-bit data width is selected. In 48 MHz mode, the UTMI interface operates
at 48 MHz in FS and LS modes.
Bit 14 Reserved, must be kept at reset value.
Bits 13:10 TRDT[3:0]: USB turnaround time
These bits allows to set the turnaround time in PHY clocks. They must be configured
according to Table 266: TRDT values (FS) or Table 267: TRDT values (HS), depending on
the application AHB frequency. Higher TRDT values allow stretching the USB response time
to IN tokens in order to compensate for longer AHB read access latency to the data FIFO.
Note: Only accessible in device mode.
Bit 9 HNPCAP: HNP-capable
The application uses this bit to control the OTG_FS/OTG_HS controller’s HNP capabilities.
0: HNP capability is not enabled.
1: HNP capability is enabled.
Note: Accessible in both device and host modes.
Bit 8 SRPCAP: SRP-capable
The application uses this bit to control the OTG_FS/OTG_HS controller’s SRP capabilities. If
the core operates as a non-SRP-capable
B-device, it cannot request the connected A-device (host) to activate VBUS and start a
session.
0: SRP capability is not enabled.
1: SRP capability is enabled.
Note: Accessible in both device and host modes.
Bit 7 Reserved, must be kept at reset value.
Bit 6 PHYSEL: Full Speed serial transceiver select for USB OTG FS
This bit is always 1 with read-only access.
Bit 6 PHYSEL: Full speed serial transceiver select for USB OTG HS
0: USB 2.0 external ULPI high-speed PHY.
1: USB 1.1 full-speed serial transceiver.
Bit 5 Reserved, must be kept at reset value.
Bit 4 Reserved, must be kept at reset value.
Bit 3 Reserved, must be kept at reset value.
Bits 2:0 TOCAL[2:0]: FS timeout calibration
The number of PHY clocks that the application programs in this field is added to the fullspeed interpacket timeout duration in the core to account for any additional delays
introduced by the PHY. This can be required, because the delay introduced by the PHY in
generating the line state condition can vary from one PHY to another.
The USB standard timeout value for full-speed operation is 16 to 18 (inclusive) bit times. The
application must program this field based on the speed of enumeration. The number of bit
times added per PHY clock is 0.25 bit times.

RM0385 Rev 7

1369/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Table 266. TRDT values (FS)
AHB frequency range (MHz)
TRDT minimum value
Min

Max

14.2

15

0xF

15

16

0xE

16

17.2

0xD

17.2

18.5

0xC

18.5

20

0xB

20

21.8

0xA

21.8

24

0x9

24

27.5

0x8

27.5

32

0x7

32

-

0x6

Table 267. TRDT values (HS)
AHB frequency range (MHz)
TRDT minimum value

37.15.5

Min

Max

30

-

0x9

OTG reset register (OTG_GRSTCTL)
Address offset: 0x10
Reset value: 0x8000 0000
The application uses this register to reset various hardware features inside the core.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

AHB
IDL

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r
15
Res.

r
14
Res.

Note:

1370/1709

13
Res.

12
Res.

11
Res.

10

9

8

7

5

4

3

TXFNUM

TXF
FLSH

RXF
FLSH

Res.

rw

rs

rs

Configuration register for USB OTG FS

RM0385 Rev 7

6

2

1

0

FCRST PSRST CSRST
rs

rs

r

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

AHB
IDL

DMAR
EQ

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

9

8

7

6

1

0

r

r

15

14

Res.

Res.

Res.

Res.

Res.

TXFNUM[4:0]
rw

Note:

rw

rw

rw

rw

5

4

3

2

TXF
FLSH

RXF
FLSH

Res.

Res.

rs

rs

PSRST CSRST
rs

rs

Configuration register for USB OTG HS
Bit 31 AHBIDL: AHB master idle
Indicates that the AHB master state machine is in the Idle condition.
Note: Accessible in both device and host modes.
Bits 30:11 Reserved, must be kept at reset value for USB OTG FS.
Bit 30 DMAREQ: DMA request signal enabled for USB OTG HS
This bit indicates that the DMA request is in progress. Used for debug.
Bits 29:11 Reserved, must be kept at reset value for USB OTG HS.
Bits 10:6 TXFNUM[4:0]: Tx FIFO number
This is the FIFO number that must be flushed using the Tx FIFO Flush bit. This field must not
be changed until the core clears the Tx FIFO Flush bit.
00000:
–
Non-periodic Tx FIFO flush in host mode
–
Tx FIFO 0 flush in device mode
00001:
–
Periodic Tx FIFO flush in host mode
–
Tx FIFO 1 flush in device mode
00010: Tx FIFO 2 flush in device mode
...
01111: Tx FIFO 15 flush in device mode
10000: Flush all the transmit FIFOs in device or host mode.
Note: Accessible in both device and host modes.
Bit 5 TXFFLSH: Tx FIFO flush
This bit selectively flushes a single or all transmit FIFOs, but cannot do so if the core is in the
midst of a transaction.
The application must write this bit only after checking that the core is neither writing to the Tx
FIFO nor reading from the Tx FIFO. Verify using these registers:
Read—NAK Effective interrupt ensures the core is not reading from the FIFO
Write—AHBIDL bit in OTG_GRSTCTL ensures the core is not writing anything to the FIFO.
Flushing is normally recommended when FIFOs are reconfigured. FIFO flushing is also
recommended during device endpoint disable. The application must wait until the core clears
this bit before performing any operations. This bit takes eight clocks to clear, using the slower
clock of phy_clk or hclk.
Note: Accessible in both device and host modes.

RM0385 Rev 7

1371/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 4 RXFFLSH: Rx FIFO flush
The application can flush the entire Rx FIFO using this bit, but must first ensure that the core
is not in the middle of a transaction.
The application must only write to this bit after checking that the core is neither reading from
the Rx FIFO nor writing to the Rx FIFO.
The application must wait until the bit is cleared before performing any other operations. This
bit requires 8 clocks (slowest of PHY or AHB clock) to clear.
Note: Accessible in both device and host modes.
Bit 3 Reserved, must be kept at reset value.
Bit 2 FCRST: Host frame counter reset for USB OTG FS
The application writes this bit to reset the frame number counter inside the core. When the
frame counter is reset, the subsequent SOF sent out by the core has a frame number of 0.
When application writes '1' to the bit, it might not be able to read back the value as it will get
cleared by the core in a few clock cycles.
Note: Only accessible in host mode.
Bit 2 Reserved, must be kept at reset value for USB OTG HS.
Bit 1 PSRST: Partial soft reset
Resets the internal state machines but keeps the enumeration info. Could be used to recover
some specific PHY errors.
Note: Accessible in both device and host modes.
Bit 0 CSRST: Core soft reset
Resets the HCLK and PHY clock domains as follows:
Clears the interrupts and all the CSR register bits except for the following bits:
– GATEHCLK bit in OTG_PCGCCTL
– STPPCLK bit in OTG_PCGCCTL
– FSLSPCS bits in OTG_HCFG
– DSPD bit in OTG_DCFG
– SDIS bit in OTG_DCTL
– OTG_GCCFG register
All module state machines (except for the AHB slave unit) are reset to the Idle state, and all
the transmit FIFOs and the receive FIFO are flushed.
Any transactions on the AHB Master are terminated as soon as possible, after completing the
last data phase of an AHB transfer. Any transactions on the USB are terminated immediately.
The application can write to this bit any time it wants to reset the core. This is a self-clearing
bit and the core clears this bit after all the necessary logic is reset in the core, which can take
several clocks, depending on the current state of the core. Once this bit has been cleared,
the software must wait at least 3 PHY clocks before accessing the PHY domain
(synchronization delay). The software must also check that bit 31 in this register is set to 1
(AHB Master is Idle) before starting any operation.
Typically, the software reset is used during software development and also when the user
dynamically changes the PHY selection bits in the above listed USB configuration registers.
When you change the PHY, the corresponding clock for the PHY is selected and used in the
PHY domain. Once a new clock is selected, the PHY domain has to be reset for proper
operation.
Note: Accessible in both device and host modes.

1372/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.6

OTG core interrupt register (OTG_GINTSTS)
Address offset: 0x014
Reset value: 0x1400 0020
This register interrupts the application for system-level events in the current mode (device
mode or host mode).
Some of the bits in this register are valid only in host mode, while others are valid in device
mode only. This register also indicates the current mode. To clear the interrupt status bits of
the rc_w1 type, the application must write 1 into the bit.
The FIFO status interrupts are read-only; once software reads from or writes to the FIFO
while servicing these interrupts, FIFO interrupt conditions are cleared automatically.
The application must clear the OTG_GINTSTS register at initialization before unmasking
the interrupt bit to avoid any interrupts generated prior to initialization.

31

30

29

28

27

26

25

WKUP
INT

SRQ
INT

DISC
INT

CIDS
CHG

LPM
INT

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

r

15

14

13

12

11

10

EOPF

ISOO
DRP

ENUM
DNE

USB
RST

USB
SUSP

ESUSP

Res.

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Note:
31

24

23

22

21

20

19

18

17

16

Res.

IPXFR/
IN
COMP
ISO
OUT

IISOI
XFR

OEP
INT

IEPINT

Res.

Res.

HPRT
INT

RST
DET

r

r

rc_w1

rc_w1

rc_w1

r

r

9

8

7

6

5

4

3

2

1

0

Res.

GO
NAK
EFF

GI
NAK
EFF

NPTXF
E

RXF
LVL

SOF

OTG
INT

MMIS

CMOD

r

r

r

r

rc_w1

r

rc_w1

r

23

22

21

PTXFE HCINT

Configuration register for USB OTG FS
30

29

28

27

26

25

24

19

18

17

16

IISOI
XFR

OEP
INT

IEPINT

Res.

Res.

WKUP
INT

SRQ
INT

DISC
INT

CIDS
CHG

rc_w1

rc_w1

rc_w1

rc_w1

r

r

r

rc_w1

rc_w1

rc_w1

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

EOPF

ISOO
DRP

ENUM
DNE

USB
RST

USB
SUSP

ESUSP

Res.

Res.

GO
NAK
EFF

GI
NAK
EFF

NPTXF
E

RXF
LVL

SOF

OTG
INT

MMIS

CMOD

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

r

r

r

r

rc_w1

r

rc_w1

r

Note:

Res.

PTXFE HCINT

HPRT
INT

20

IPXFR/
IN
DATAF
COMP
SUSP
ISO
OUT

Res.

Configuration register for USB OTG HS

RM0385 Rev 7

1373/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 31 WKUPINT: Resume/remote wakeup detected interrupt
Wakeup interrupt during suspend(L2) or LPM(L1) state.
– During suspend(L2):
In device mode, this interrupt is asserted when a resume is detected on the USB. In host
mode, this interrupt is asserted when a remote wakeup is detected on the USB.
– During LPM(L1):
This interrupt is asserted for either host initiated resume or device initiated remote wakeup
on USB.
Note: Accessible in both device and host modes.
Bit 30 SRQINT: Session request/new session detected interrupt
In host mode, this interrupt is asserted when a session request is detected from the device.
In device mode, this interrupt is asserted when VBUS is in the valid range for a B-peripheral
device. Accessible in both device and host modes.
Bit 29 DISCINT: Disconnect detected interrupt
Asserted when a device disconnect is detected.
Note: Only accessible in host mode.
Bit 28 CIDSCHG: Connector ID status change
The core sets this bit when there is a change in connector ID status.
Note: Accessible in both device and host modes.
Bit 27 LPMINT: LPM interrupt
In device mode, this interrupt is asserted when the device receives an LPM transaction and
responds with a non-ERRORed response.
In host mode, this interrupt is asserted when the device responds to an LPM transaction with
a non-ERRORed response or when the host core has completed LPM transactions for the
programmed number of times (RETRYCNT bit in OTG_GLPMCFG).
This field is valid only if the LPMEN bit in OTG_GLPMCFG is set to 1.
Bit 27 Reserved, must be kept at reset value for USB OTG FS.
Bit 26 PTXFE: Periodic Tx FIFO empty
Asserted when the periodic transmit FIFO is either half or completely empty and there is
space for at least one entry to be written in the periodic request queue. The half or
completely empty status is determined by the periodic Tx FIFO empty level bit in the
OTG_GAHBCFG register (PTXFELVL bit in OTG_GAHBCFG).
Note: Only accessible in host mode.
Bit 25 HCINT: Host channels interrupt
The core sets this bit to indicate that an interrupt is pending on one of the channels of the
core (in host mode). The application must read the OTG_HAINT register to determine the
exact number of the channel on which the interrupt occurred, and then read the
corresponding OTG_HCINTx register to determine the exact cause of the interrupt. The
application must clear the appropriate status bit in the OTG_HCINTx register to clear this bit.
Note: Only accessible in host mode.
Bit 24 HPRTINT: Host port interrupt
The core sets this bit to indicate a change in port status of one of the OTG_FS/OTG_HS
controller ports in host mode. The application must read the OTG_HPRT register to
determine the exact event that caused this interrupt. The application must clear the
appropriate status bit in the OTG_HPRT register to clear this bit.
Note: Only accessible in host mode.

1374/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 23 RSTDET: Reset detected interrupt
In device mode, this interrupt is asserted when a reset is detected on the USB in partial
power-down mode when the device is in suspend.
Note: Only accessible in device mode.
Bit 23 Reserved, must be kept at reset value for USB OTG HS.
Bit 22 Reserved, must be kept at reset value for USB OTG FS.
Bit 22 DATAFSUSP: Data fetch suspended for USB OTG HS
This interrupt is valid only in DMA mode. This interrupt indicates that the core has stopped
fetching data for IN endpoints due to the unavailability of TxFIFO space or request queue
space. This interrupt is used by the application for an endpoint mismatch algorithm. For
example, after detecting an endpoint mismatch, the application:
–
Sets a global nonperiodic IN NAK handshake
–
Disables IN endpoints
–
Flushes the FIFO
–
Determines the token sequence from the IN token sequence learning queue
–
Re-enables the endpoints
Clears the global nonperiodic IN NAK handshake If the global nonperiodic IN NAK is
cleared, the core has not yet fetched data for the IN endpoint, and the IN token is received:
the core generates an “IN token received when FIFO empty” interrupt. The OTG then sends
a NAK response to the host. To avoid this scenario, the application can check the FetSusp
interrupt in OTG_GINTSTS, which ensures that the FIFO is full before clearing a global NAK
handshake. Alternatively, the application can mask the “IN token received when FIFO
empty” interrupt when clearing a global IN NAK handshake.
Bit 21 IPXFR: Incomplete periodic transfer
In host mode, the core sets this interrupt bit when there are incomplete periodic transactions
still pending, which are scheduled for the current frame.
INCOMPISOOUT: Incomplete isochronous OUT transfer
In device mode, the core sets this interrupt to indicate that there is at least one isochronous
OUT endpoint on which the transfer is not completed in the current frame. This interrupt is
asserted along with the End of periodic frame interrupt (EOPF) bit in this register.
Bit 20 IISOIXFR: Incomplete isochronous IN transfer
The core sets this interrupt to indicate that there is at least one isochronous IN endpoint on
which the transfer is not completed in the current frame. This interrupt is asserted along with
the End of periodic frame interrupt (EOPF) bit in this register.
Note: Only accessible in device mode.
Bit 19 OEPINT: OUT endpoint interrupt
The core sets this bit to indicate that an interrupt is pending on one of the OUT endpoints of
the core (in device mode). The application must read the OTG_DAINT register to determine
the exact number of the OUT endpoint on which the interrupt occurred, and then read the
corresponding OTG_DOEPINTx register to determine the exact cause of the interrupt. The
application must clear the appropriate status bit in the corresponding OTG_DOEPINTx
register to clear this bit.
Note: Only accessible in device mode.

RM0385 Rev 7

1375/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 18 IEPINT: IN endpoint interrupt
The core sets this bit to indicate that an interrupt is pending on one of the IN endpoints of the
core (in device mode). The application must read the OTG_DAINT register to determine the
exact number of the IN endpoint on which the interrupt occurred, and then read the
corresponding OTG_DIEPINTx register to determine the exact cause of the interrupt. The
application must clear the appropriate status bit in the corresponding OTG_DIEPINTx
register to clear this bit.
Note: Only accessible in device mode.
Bits 17:16 Reserved, must be kept at reset value.
Bit 15 EOPF: End of periodic frame interrupt
Indicates that the period specified in the periodic frame interval field of the OTG_DCFG
register (PFIVL bit in OTG_DCFG) has been reached in the current frame.
Note: Only accessible in device mode.
Bit 14 ISOODRP: Isochronous OUT packet dropped interrupt
The core sets this bit when it fails to write an isochronous OUT packet into the Rx FIFO
because the Rx FIFO does not have enough space to accommodate a maximum size
packet for the isochronous OUT endpoint.
Note: Only accessible in device mode.
Bit 13 ENUMDNE: Enumeration done
The core sets this bit to indicate that speed enumeration is complete. The application must
read the OTG_DSTS register to obtain the enumerated speed.
Note: Only accessible in device mode.
Bit 12 USBRST: USB reset
The core sets this bit to indicate that a reset is detected on the USB.
Note: Only accessible in device mode.
Bit 11 USBSUSP: USB suspend
The core sets this bit to indicate that a suspend was detected on the USB. The core enters
the suspended state when there is no activity on the data lines for an extended period of
time.
Note: Only accessible in device mode.
Bit 10 ESUSP: Early suspend
The core sets this bit to indicate that an Idle state has been detected on the USB for 3 ms.
Note: Only accessible in device mode.
Bits 9:8 Reserved, must be kept at reset value.
Bit 7 GONAKEFF: Global OUT NAK effective
Indicates that the Set global OUT NAK bit in the OTG_DCTL register (SGONAK bit in
OTG_DCTL), set by the application, has taken effect in the core. This bit can be cleared by
writing the Clear global OUT NAK bit in the OTG_DCTL register (CGONAK bit in
OTG_DCTL).
Note: Only accessible in device mode.

1376/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 6 GINAKEFF: Global IN non-periodic NAK effective
Indicates that the Set global non-periodic IN NAK bit in the OTG_DCTL register (SGINAK bit
in OTG_DCTL), set by the application, has taken effect in the core. That is, the core has
sampled the Global IN NAK bit set by the application. This bit can be cleared by clearing the
Clear global non-periodic IN NAK bit in the OTG_DCTL register (CGINAK bit in
OTG_DCTL).
This interrupt does not necessarily mean that a NAK handshake is sent out on the USB. The
STALL bit takes precedence over the NAK bit.
Note: Only accessible in device mode.
Bit 5 NPTXFE: Non-periodic Tx FIFO empty
This interrupt is asserted when the non-periodic Tx FIFO is either half or completely empty,
and there is space for at least one entry to be written to the non-periodic transmit request
queue. The half or completely empty status is determined by the non-periodic Tx FIFO
empty level bit in the OTG_GAHBCFG register (TXFELVL bit in OTG_GAHBCFG).
Note: Accessible in host mode only.
Bit 4 RXFLVL: Rx FIFO non-empty
Indicates that there is at least one packet pending to be read from the Rx FIFO.
Note: Accessible in both host and device modes.
Bit 3 SOF: Start of frame
In host mode, the core sets this bit to indicate that an SOF (FS), or Keep-Alive (LS) is
transmitted on the USB. The application must write a 1 to this bit to clear the interrupt.
In device mode, in the core sets this bit to indicate that an SOF token has been received on
the USB. The application can read the OTG_DSTS register to get the current frame number.
This interrupt is seen only when the core is operating in FS.
Note: This register may return '1' if read immediately after power on reset. If the register bit
reads '1' immediately after power on reset it does not indicate that an SOF has been
sent (in case of host mode) or SOF has been received (in case of device mode). The
read value of this interrupt is valid only after a valid connection between host and
device is established. If the bit is set after power on reset the application can clear the
bit.
Note: Accessible in both host and device modes.
Bit 2 OTGINT: OTG interrupt
The core sets this bit to indicate an OTG protocol event. The application must read the OTG
interrupt status (OTG_GOTGINT) register to determine the exact event that caused this
interrupt. The application must clear the appropriate status bit in the OTG_GOTGINT
register to clear this bit.
Note: Accessible in both host and device modes.
Bit 1 MMIS: Mode mismatch interrupt
The core sets this bit when the application is trying to access:
– A host mode register, when the core is operating in device mode
– A device mode register, when the core is operating in host mode
The register access is completed on the AHB with an OKAY response, but is ignored by the
core internally and does not affect the operation of the core.
Note: Accessible in both host and device modes.
Bit 0 CMOD: Current mode of operation
Indicates the current mode.
0: Device mode
1: Host mode
Note: Accessible in both host and device modes.

RM0385 Rev 7

1377/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.7

RM0385

OTG interrupt mask register (OTG_GINTMSK)
Address offset: 0x018
Reset value: 0x0000 0000
This register works with the core interrupt register to interrupt the application. When an
interrupt bit is masked, the interrupt associated with that bit is not generated. However, the
core interrupt (OTG_GINTSTS) register bit corresponding to that interrupt is still set.

31
WUIM

30
SRQIM

29

28

DISCIN CIDSC
T
HGM

27

26

LPMIN PTXFE
TM
M

25

24

23

HCIM

PRTIM

RSTDE
TM

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

EOPF
M

ISOOD
RPM

Res.

Res.

rw

rw

Note:
31
WUIM

ENUM USBRS USBSU ESUSP
DNEM
T
SPM
M
rw

rw

rw

rw

22

21

20

Res.

IPXFR
M/IISO
OXFR
M

IISOIX
FRM

rw

rw

rw

rw

5

4

3

2

6

GONA GINAK NPTXF RXFLV
KEFFM EFFM
EM
LM
rw

rw

23

19

18

OEPIN
IEPINT
T

SOFM

17

16

Res.

Res.

1

0

OTGIN
MMISM
T

Res.

rw

rw

rw

rw

rw

22

21

20

19

18

17

16

IISOIX
FRM

Res.

Res.

1

0

Configuration register for USB OTG FS
30
SRQIM

29

28

DISCIN CIDSC
T
HGM

27

26

LPMIN PTXFE
TM
M

25
HCIM

24
PRTIM

RSTDE
TM

FSUS
PM

IPXFR
M/IISO
OXFR
M

OEPIN
IEPINT
T

rw

rw

rw

rw

rw

rw

rw

r

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

EOPF
M

ISOOD
RPM

Res.

Res.

rw

rw

Note:

ENUM USBRS USBSU ESUSP
DNEM
T
SPM
M
rw

rw

rw

rw

GONA GINAK NPTXF RXFLV
KEFFM EFFM
EM
LM
rw

rw

rw

rw

Configuration register for USB OTG HS
Bit 31 WUIM: Resume/remote wakeup detected interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both host and device modes.
Bit 30 SRQIM: Session request/new session detected interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both host and device modes.
Bit 29 DISCINT: Disconnect detected interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in host mode.
Bit 28 CIDSCHGM: Connector ID status change mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both host and device modes.

1378/1709

RM0385 Rev 7

SOFM
rw

OTGIN
MMISM
T
rw

rw

Res.

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 27 LPMINTM: LPM interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both host and device modes.
Bit 26 PTXFEM: Periodic Tx FIFO empty mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in host mode.
Bit 25 HCIM: Host channels interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in host mode.
Bit 24 PRTIM: Host port interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in host mode.
Bit 23 RSTDETM: Reset detected interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 22 Reserved, must be kept at reset value for USB OTG FS.
Bit 22 FSUSPM: Data fetch suspended mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Only accessible in peripheral mode.
Bit 21 IPXFRM: Incomplete periodic transfer mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in host mode.
IISOOXFRM: Incomplete isochronous OUT transfer mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 20 IISOIXFRM: Incomplete isochronous IN transfer mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 19 OEPINT: OUT endpoints interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 18 IEPINT: IN endpoints interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.

RM0385 Rev 7

1379/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bits 17:16 Reserved, must be kept at reset value.
Bit 15 EOPFM: End of periodic frame interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 14 ISOODRPM: Isochronous OUT packet dropped interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 13 ENUMDNEM: Enumeration done mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 12 USBRST: USB reset mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 11 USBSUSPM: USB suspend mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 10 ESUSPM: Early suspend mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bits 9:8 Reserved, must be kept at reset value.
Bit 7 GONAKEFFM: Global OUT NAK effective mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 6 GINAKEFFM: Global non-periodic IN NAK effective mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in device mode.
Bit 5 NPTXFEM: Non-periodic Tx FIFO empty mask
0: Masked interrupt
1: Unmasked interrupt
Note: Only accessible in host mode.
Bit 4 RXFLVLM: Receive FIFO non-empty mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both device and host modes.

1380/1709

RM0385 Rev 7

RM0385

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 3 SOFM: Start of frame mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both device and host modes.
Bit 2 OTGINT: OTG interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both device and host modes.
Bit 1 MMISM: Mode mismatch interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both device and host modes.
Bit 0 Reserved, must be kept at reset value.

37.15.8

OTG receive status debug read/OTG status read and
pop registers (OTG_GRXSTSR/OTG_GRXSTSP)
Address offset for read: 0x01C
Address offset for pop: 0x020
Reset value: 0x0000 0000
A read to the receive status debug read register returns the contents of the top of the
receive FIFO. A read to the receive status read and pop register additionally pops the top
data entry out of the Rx FIFO.
The receive status contents must be interpreted differently in host and device modes. The
core ignores the receive status pop/read when the receive FIFO is empty and returns a
value of 0x0000 0000. The application must only pop the receive status FIFO when the
receive FIFO non-empty bit of the core interrupt register (RXFLVL bit in OTG_GINTSTS) is
asserted.

Host mode:
31

30

29

28

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

DPID
r

9

8

7

6

5

20

19

r

r

r

r

r

17

PKTSTS[3:0]

16
DPID

r

r

r

r

r

4

3

2

1

0

BCNT[10:0]
r

18

CHNUM[3:0]
r

r

RM0385 Rev 7

r

r

r

r

r

r

r

1381/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bits 31:21 Reserved, must be kept at reset value.
Bits 20:17 PKTSTS[3:0]: Packet status
Indicates the status of the received packet
0010: IN data packet received
0011: IN transfer completed (triggers an interrupt)
0101: Data toggle error (triggers an interrupt)
0111: Channel halted (triggers an interrupt)
Others: Reserved
Bits 16:15 DPID: Data PID
Indicates the data PID of the received packet
00: DATA0
10: DATA1
01: DATA2
11: MDATA
Bits 14:4 BCNT[10:0]: Byte count
Indicates the byte count of the received IN data packet.
Bits 3:0 CHNUM[3:0]: Channel number
Indicates the channel number to which the current received packet belongs.

1382/1709

RM0385 Rev 7

RM0385

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Device mode:
31

30

29

28

27

26

25

Res.

Res.

10

9

Res.

Res.

Res.

Res.

STSPH
ST

15

14

13

12

11

24

r

22

21

20

FRMNUM[3:0]

r

DPID[0]

23

19

r

r

r

r

r

17

PKTSTS[3:0]

16
DPID[1]

r

r

r

r

r

r

r

r

r

8

7

6

5

4

3

2

1

0

BCNT[10:0]
r

18

EPNUM[3:0]
r

r

r

r

r

r

r

r

r

Bits 31:28 Reserved, must be kept at reset value.
Bit 27 STSPHST: Status phase start
Indicates the start of the status phase for a control write transfer. This bit is set along with
the OUT transfer completed PKTSTS pattern.
Bits 26:25 Reserved, must be kept at reset value.
Bits 24:21 FRMNUM[3:0]: Frame number
This is the least significant 4 bits of the frame number in which the packet is received on the
USB. This field is supported only when isochronous OUT endpoints are supported.
Bits 20:17 PKTSTS[3:0]: Packet status
Indicates the status of the received packet
0001: Global OUT NAK (triggers an interrupt)
0010: OUT data packet received
0011: OUT transfer completed (triggers an interrupt)
0100: SETUP transaction completed (triggers an interrupt)
0110: SETUP data packet received
Others: Reserved
Bits 16:15 DPID[1:0]: Data PID
Indicates the data PID of the received OUT data packet
00: DATA0
10: DATA1
01: DATA2
11: MDATA
Bits 14:4 BCNT[10:0]: Byte count
Indicates the byte count of the received data packet.
Bits 3:0 EPNUM[3:0]: Endpoint number
Indicates the endpoint number to which the current received packet belongs.

RM0385 Rev 7

1383/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.9

RM0385

OTG receive FIFO size register (OTG_GRXFSIZ)
Address offset: 0x024
Reset value: 0x0000 0200 for USB OTG FS
Reset value: 0x0000 0400 for USB OTG HS
The application can program the RAM size that must be allocated to the Rx FIFO.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

RXFD[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 RXFD[15:0]: Rx FIFO depth
This value is in terms of 32-bit words.
Minimum value is 16
Maximum value is 1024
Programmed values must respect the available FIFO memory allocation and must not
exceed the power-on value.

37.15.10 OTG host non-periodic transmit FIFO size register
(OTG_HNPTXFSIZ)/Endpoint 0 Transmit FIFO size
(OTG_DIEPTXF0)
Address offset: 0x028
Reset value: 0x0200 0200
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

NPTXFD/TX0FD[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

NPTXFSA/TX0FSA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Host mode
Bits 31:16 NPTXFD[15:0]: Non-periodic Tx FIFO depth
This value is in terms of 32-bit words.
Minimum value is 16
Programmed values must respect the available FIFO memory allocation and must not
exceed the power-on value.
Bits 15:0 NPTXFSA[15:0]: Non-periodic transmit RAM start address
This field configures the memory start address for non-periodic transmit FIFO RAM.

1384/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Device mode
Bits 31:16 TX0FD: Endpoint 0 Tx FIFO depth
This value is in terms of 32-bit words.
Minimum value is 16
Programmed values must respect the available FIFO memory allocation and must not
exceed the power-on value.
Bits 15:0 TX0FSA: Endpoint 0 transmit RAM start address
This field configures the memory start address for the endpoint 0 transmit FIFO RAM.

37.15.11 OTG non-periodic transmit FIFO/queue status register
(OTG_HNPTXSTS)
Address offset: 0x02C
Reset value: 0x0008 0200 for USB OTG FS
Reset value: 0x0008 0400 for USB OTG HS
Note:

In device mode, this register is not valid.
This read-only register contains the free space information for the non-periodic Tx FIFO and
the non-periodic transmit request queue.

31

30

29

28

Res.

15

27

26

25

24

23

22

21

NPTXQTOP[6:0]

20

19

18

17

16

NPTQXSAV[7:0]

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

NPTXFSAV[15:0]
r

r

r

r

r

r

r

r

r

RM0385 Rev 7

1385/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 31 Reserved, must be kept at reset value.
Bits 30:24 NPTXQTOP[6:0]: Top of the non-periodic transmit request queue
Entry in the non-periodic Tx request queue that is currently being processed by the MAC.
Bits 30:27: Channel/endpoint number
Bits 26:25:
00: IN/OUT token
01: Zero-length transmit packet (device IN/host OUT)
11: Channel halt command
Bit 24: Terminate (last entry for selected channel/endpoint)
Bits 23:16 NPTQXSAV[7:0]: Non-periodic transmit request queue space available
Indicates the amount of free space available in the non-periodic transmit request queue.
This queue holds both IN and OUT requests.
0: Non-periodic transmit request queue is full
1: 1 location available
2: locations available
n: n locations available (0 ≤ n ≤ 8)
Others: Reserved
Bits 15:0 NPTXFSAV[15:0]: Non-periodic Tx FIFO space available
Indicates the amount of free space available in the non-periodic Tx FIFO.
Values are in terms of 32-bit words.
0: Non-periodic Tx FIFO is full
1: 1 word available
2: 2 words available
n: n words available (where 0 ≤ n ≤ 512)
Others: Reserved

37.15.12 OTG general core configuration register (OTG_GCCFG)
Address offset: 0x038
Reset value: 0x0000 XXXX
31

30

29

28

27

26

25

24

23

22

21
VBDEN

20

19

18

Res.

Res.

DCD
EN

17

16

Res.

PWR
DWN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DCDET

rw

rw

rw

r

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 VBDEN: USB VBUS detection enable
Enables VBUS sensing comparators to detect VBUS valid levels on the VBUS PAD for USB
host and device operation. If HNP and/or SRP support is enabled, VBUS comparators are
automatically enabled independently of VBDEN value.
0 = VBUS detection disabled
1 = VBUS detection enabled
Bits 20:19 Reserved, must be kept at reset value.

1386/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 18 DCDEN: Data contact detection (DCD) mode enable
This bit is set by the software to put the BCD into DCD mode. Only one detection mode
(DCD, PD, SD or OFF) should be selected to work correctly.
Bit 17 Reserved, must be kept at reset value.
Bit 16 PWRDWN: Power down control
Used to activate the transceiver in transmission/reception. When reset, the transceiver is
kept in power-down. 0 = USB FS transceiver disabled
1 = USB FS transceiver enabled
Bits 15:4 Reserved, must be kept at reset value.
Bits 3:1 Reserved, must be kept at reset value.
Bit 0 DCDET: Data contact detection (DCD) status
This bit gives the result of DCD.
0: data lines contact not detected
1: data lines contact detected

37.15.13 OTG core ID register (OTG_CID)
Address offset: 0x03C
Reset value: 0x0000 2000 for USB OTG FS
Reset value: 0x0000 2100 for USB OTG HS
This is a register containing the Product ID as reset value.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PRODUCT_ID[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

18

17

16

PRODUCT_ID[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 PRODUCT_ID[31:0]: Product ID field
Application-programmable ID field.

37.15.14 OTG core LPM configuration register (OTG_GLPMCFG)
Address offset: 0x54
Reset value: 0x0000 0000
31

30

29

28

Res.

Res.

Res.

EN
BESL
rw

r

r

r

rs

rw

rw

rw

rw

rw

rw

rw

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

L1SS
EN

REM
WAKE

LPM
ACK

LPM
EN

rw

rw/r

rw

rw

SLP
STS
r

LPMRSP[1:0]
r

r

27

25

LPMRCNTSTS[2:0]

L1DS
EN
rw

26

24
SND
LPM

BESLTHRS[3:0]
rw

rw

rw

23

rw

22

21

20

LPMRCNT[2:0]

RM0385 Rev 7

19

L1RSM
OK

LPMCHIDX[3:0]

BESL[3:0]
rw/r

rw/r

rw/r

rw/r

1387/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits 31:29 Reserved, must be kept at reset value.
Bit 28 ENBESL: Enable best effort service latency
This bit enables the BESL feature as defined in the LPM errata:
0:The core works as described in the following document:
USB 2.0 Link Power Management Addendum Engineering Change Notice to the USB 2.0
specification, July 16, 2007
1:The core works as described in the LPM Errata:
Errata for USB 2.0 ECN: Link Power Management (LPM) - 7/2007
Note: Only the updated behavior (described in LPM Errata) is considered in this document
and so the ENBESL bit should be set to '1' by application SW.
Bits 27:25 LPMRCNTSTS[2:0]: LPM retry count status
Number of LPM host retries still remaining to be transmitted for the current LPM sequence.
Note: Accessible only in host mode.
Bit 24 SNDLPM: Send LPM transaction
When the application software sets this bit, an LPM transaction containing two tokens, EXT
and LPM is sent. The hardware clears this bit once a valid response (STALL, NYET, or
ACK) is received from the device or the core has finished transmitting the programmed
number of LPM retries.
Note: This bit must be set only when the host is connected to a local port.
Note: Accessible only in host mode.
Bits 23:21 LPMRCNT:[2:0] LPM retry count
When the device gives an ERROR response, this is the number of additional LPM retries
that the host performs until a valid device response (STALL, NYET, or ACK) is received.
Note: Accessible only in host mode.
Bits 20:17 LPMCHIDX[3:0]: LPM Channel Index
The channel number on which the LPM transaction has to be applied while sending an LPM
transaction to the local device. Based on the LPM channel index, the core automatically
inserts the device address and endpoint number programmed in the corresponding channel
into the LPM transaction.
Note: Accessible only in host mode.
Bit 16 L1RSMOK: Sleep state resume OK
Indicates that the device or host can start resume from Sleep state. This bit is valid in LPM
sleep (L1) state. It is set in sleep mode after a delay of 50 μs (TL1Residency).
This bit is reset when SLPSTS is 0.
1: The application or host can start resume from Sleep state
0: The application or host cannot start resume from Sleep state

1388/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 15 SLPSTS: Port sleep status
Device mode:
This bit is set as long as a Sleep condition is present on the USB bus. The core enters the
Sleep state when an ACK response is sent to an LPM transaction and the TL1TokenRetry
timer has expired. To stop the PHY clock, the application must set the STPPCLK bit in
OTG_PCGCCTL, which asserts the PHY suspend input signal.
The application must rely on SLPSTS and not ACK in LPMRSP to confirm transition into
sleep.
The core comes out of sleep:
– When there is any activity on the USB linestate
– When the application writes to the RWUSIG bit in OTG_DCTL or when the application
resets or soft-disconnects the device.
Host mode:
The host transitions to Sleep (L1) state as a side-effect of a successful LPM transaction by
the core to the local port with ACK response from the device. The read value of this bit
reflects the current Sleep status of the port.
The core clears this bit after:
– The core detects a remote L1 wakeup signal,
– The application sets the PRST bit or the PRES bit in the OTG_HPRT register, or
– The application sets the L1Resume/ remote wakeup detected interrupt bit or disconnect
detected interrupt bit in the core interrupt register (WKUPINT or DISCINT bit in
OTG_GINTSTS, respectively).
0: Core not in L1
1: Core in L1
Bits 14:13 LPMRST[1:0]: LPM response
Device mode:
The response of the core to LPM transaction received is reflected in these two bits.
Host mode:
Handshake response received from local device for LPM transaction
11: ACK
10: NYET
01: STALL
00: ERROR (No handshake response)
Bit 12 L1DSEN: L1 deep sleep enable
Enables suspending the PHY in L1 Sleep mode. For maximum power saving during L1
Sleep mode, this bit should be set to '1' by application SW in all the cases.

RM0385 Rev 7

1389/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits11:8 BESLTHRS[3:0]: BESL threshold
Device mode:
The core puts the PHY into deep low power mode in L1 when BESL value is greater than or
equal to the value defined in this field BESL_Thres[3:0].
Host mode:
The core puts the PHY into deep low power mode in L1. BESLTHRS[3:0] specifies the time
for which resume signaling is to be reflected by host (TL1HubDrvResume2) on the USB bus
when it detects device initiated resume.
BESLTHRS must not be programmed with a value greater than 1100b in host mode,
because this exceeds maximum TL1HubDrvResume2.
Thres[3:0] host mode resume signaling time (μs):
0000: 75
0001: 100
0010: 150
0011: 250
0100: 350
0101: 450
0110: 950
All other values: reserved
Bit 7 L1SSEN: L1 Shallow Sleep enable
Enables suspending the PHY in L1 Sleep mode. For maximum power saving during L1
Sleep mode, this bit should be set to '1' by application SW in all the cases.
Bit 6 REMWAKE: bRemoteWake value
Host mode:
The value of remote wake up to be sent in the wIndex field of LPM transaction.
Device mode (read-only):
This field is updated with the received LPM token bRemoteWake bmAttribute when an ACK,
NYET, or STALL response is sent to an LPM transaction.

1390/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bits 5:2 BESL[3:0]: Best effort service latency
Host mode:
The value of BESL to be sent in an LPM transaction. This value is also used to initiate
resume for a duration TL1HubDrvResume1 for host initiated resume.
Device mode (read-only):
This field is updated with the received LPM token BESL bmAttribute when an ACK, NYET,
or STALL response is sent to an LPM transaction.
BESL[3:0]TBESL (μs)
0000: 125
0001: 150
0010: 200
0011: 300
0100: 400
0101: 500
0110: 1000
0111: 2000
1000: 3000
1001: 4000
1010: 5000
1011: 6000
1100: 7000
1101: 8000
1110: 9000
1111: 10000
Bit 1 LPMACK: LPM token acknowledge enable
Handshake response to LPM token preprogrammed by device application software.
1: ACK
Even though ACK is preprogrammed, the core device responds with ACK only on
successful LPM transaction. The LPM transaction is successful if:
– No PID/CRC5 errors in either EXT token or LPM token (else ERROR)
– Valid bLinkState = 0001B (L1) received in LPM transaction (else STALL)
– No data pending in transmit queue (else NYET).
0: NYET
The preprogrammed software bit is over-ridden for response to LPM token when:
– The received bLinkState is not L1 (STALL response), or
– An error is detected in either of the LPM token packets because of corruption (ERROR
response).
Note: Accessible only in device mode.
Bit 0 LPMEN: LPM support enable
The application uses this bit to control the OTG_FS/OTG_HS core LPM capabilities.
If the core operates as a non-LPM-capable host, it cannot request the connected device or
hub to activate LPM mode.
If the core operates as a non-LPM-capable device, it cannot respond to any LPM
transactions.
0: LPM capability is not enabled
1: LPM capability is enabled

RM0385 Rev 7

1391/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

37.15.15 OTG host periodic transmit FIFO size register
(OTG_HPTXFSIZ)
Address offset: 0x100
Reset value: 0x0200 0400
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PTXFSIZ[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

PTXSA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 PTXFSIZ[15:0]: Host periodic Tx FIFO depth
This value is in terms of 32-bit words.
Minimum value is 16
Bits 15:0 PTXSA[15:0]: Host periodic Tx FIFO start address
This field configures the memory start address for periodic transmit FIFO RAM.

37.15.16 OTG device IN endpoint transmit FIFO size register
(OTG_DIEPTXFx) (x = 1..5[FS] /8[HS], where x is the
FIFO number)
Address offset: 0x104 + (x – 1) * 0x04
Reset value: 0x0200 0200 + (x * 0x200)
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

INEPTXFD[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

INEPTXSA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 INEPTXFD[15:0]: IN endpoint Tx FIFO depth
This value is in terms of 32-bit words.
Minimum value is 16
Bits 15:0 INEPTXSA[15:0]: IN endpoint FIFOx transmit RAM start address
This field contains the memory start address for IN endpoint transmit FIFOx. The address
must be aligned with a 32-bit memory location.

1392/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.17 Host-mode registers
Bit values in the register descriptions are expressed in binary unless otherwise specified.
Host-mode registers affect the operation of the core in the host mode. Host mode registers
must not be accessed in device mode, as the results are undefined. Host mode registers
can be categorized as follows:

37.15.18 OTG host configuration register (OTG_HCFG)
Address offset: 0x400
Reset value: 0x0000 0000
This register configures the core after power-on. Do not make changes to this register after
initializing the host.
31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

Res.

Res.

Res.

Res.

Res.

Res.

Res.

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

FSLSS

Res.

r

FSLSPCS[1:0]
rw

rw

Bits 31:3 Reserved, must be kept at reset value.
Bit 2 FSLSS: FS- and LS-only support
The application uses this bit to control the core’s enumeration speed. Using this bit, the
application can make the core enumerate as an FS host, even if the connected device
supports HS traffic. Do not make changes to this field after initial programming.
1: FS/LS-only, even if the connected device can support HS (read-only).
Bits 1:0 FSLSPCS[1:0]: FS/LS PHY clock select
When the core is in FS host mode
01: PHY clock is running at 48 MHz
Others: Reserved
When the core is in LS host mode
00: Reserved
01: Select 48 MHz PHY clock frequency
10: Select 6 MHz PHY clock frequency
11: Reserved
Note: The FSLSPCS must be set on a connection event according to the speed of the
connected device (after changing this bit, a software reset must be performed).

RM0385 Rev 7

1393/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

37.15.19 OTG host frame interval register (OTG_HFIR)
Address offset: 0x404
Reset value: 0x0000 EA60
This register stores the frame interval information for the current speed to which the
OTG_FS/OTG_HS controller has enumerated.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16
RLD
CTRL

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

FRIVL[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 RLDCTRL: Reload control
This bit allows dynamic reloading of the HFIR register during run time.
0: The HFIR can be dynamically reloaded during run time.
1: The HFIR cannot be reloaded dynamically
This bit needs to be programmed during initial configuration and its value must not be
changed during run time.
Caution: RLDCTRL = 1 is not recommended.
Bits 15:0 FRIVL[15:0]: Frame interval for USB OTG FS
The value that the application programs to this field, specifies the interval between two
consecutive SOFs (FS) or Keep-Alive tokens (LS). This field contains the number of PHY
clocks that constitute the required frame interval. The application can write a value to this
register only after the port enable bit of the host port control and status register (PENA bit in
OTG_HPRT) has been set. If no value is programmed, the core calculates the value based
on the PHY clock specified in the FS/LS PHY clock select field of the host configuration
register (FSLSPCS in OTG_HCFG). Do not change the value of this field after the initial
configuration, unless the RLDCTRL bit is set. In such case, the FRIVL is reloaded with each
SOF event.
– Frame interval = 1 ms × (FRIVL - 1)
Bits 15:0 FRIVL[15:0]: Frame interval for USB OTG HS
The value that the application programs to this field, specifies the interval between two
consecutive micro-SOFs (HS) or Keep-Alive tokens (LS). This field contains the number of
PHY clocks that constitute the required frame interval. The application can write a value to
this register only after the port enable bit of the host port control and status register (PENA
bit in OTG_HPRT) has been set. If no value is programmed, the core calculates the value
based on the PHY clock specified in the FS/LS PHY clock select field of the host
configuration register (FSLSPCS in OTG_HCFG). Do not change the value of this field after
the initial configuration, unless the RLDCTRL bit is set. In such case, the FRIVL is reloaded
with each SOF event.
– Frame interval = 125 μs × (FRIVL - 1)
in high speed operation (PHYSEL = 0)
– Frame interval = 1 ms × (FRIVL - 1)
in low/full speed operation (PHYSEL = 1)

1394/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.20 OTG host frame number/frame time remaining register
(OTG_HFNUM)
Address offset: 0x408
Reset value: 0x0000 3FFF
This register indicates the current frame number. It also indicates the time remaining (in
terms of the number of PHY clocks) in the current frame.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

FTREM[15:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

FRNUM[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 FTREM[15:0]: Frame time remaining
Indicates the amount of time remaining in the current frame, in terms of PHY clocks. This
field decrements on each PHY clock. When it reaches zero, this field is reloaded with the
value in the Frame interval register and a new SOF is transmitted on the USB.
Bits 15:0 FRNUM[15:0]: Frame number
This field increments when a new SOF is transmitted on the USB, and is cleared to 0 when
it reaches 0x3FFF.

37.15.21 OTG_Host periodic transmit FIFO/queue status register
(OTG_HPTXSTS)
Address offset: 0x410
Reset value: 0x0008 0100
This read-only register contains the free space information for the periodic Tx FIFO and the
periodic transmit request queue.
31

30

29

28

27

26

25

24

23

22

21

PTXQTOP[7:0]

20

19

18

17

16

PTXQSAV[7:0]

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

PTXFSAVL[15:0]
r

r

r

r

r

r

r

r

r

RM0385 Rev 7

1395/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits 31:24 PTXQTOP[7:0]: Top of the periodic transmit request queue
This indicates the entry in the periodic Tx request queue that is currently being processed by
the MAC.
This register is used for debugging.
Bit 31: Odd/Even frame
0: send in even frame
1: send in odd frame
Bits 30:27: Channel/endpoint number
Bits 26:25: Type
00: IN/OUT
01: Zero-length packet
11: Disable channel command
Bit 24: Terminate (last entry for the selected channel/endpoint)
Bits 23:16 PTXQSAV[7:0]: Periodic transmit request queue space available
Indicates the number of free locations available to be written in the periodic transmit request
queue. This queue holds both IN and OUT requests.
00: Periodic transmit request queue is full
01: 1 location available
10: 2 locations available
bxn: n locations available (0 ≤ n ≤ 8)
Others: Reserved
Bits 15:0 PTXFSAVL[15:0]: Periodic transmit data FIFO space available
Indicates the number of free locations available to be written to in the periodic Tx FIFO.
Values are in terms of 32-bit words
0000: Periodic Tx FIFO is full
0001: 1 word available
0010: 2 words available
bxn: n words available (where 0 ≤ n ≤ PTXFD)
Others: Reserved

37.15.22 OTG host all channels interrupt register (OTG_HAINT)
Address offset: 0x414
Reset value: 0x0000 0000
When a significant event occurs on a channel, the host all channels interrupt register
interrupts the application using the host channels interrupt bit of the core interrupt register
(HCINT bit in OTG_GINTSTS). This is shown in Figure 468. There is one interrupt bit per
channel, up to a maximum of 16 bits. Bits in this register are set and cleared when the
application sets and clears bits in the corresponding host channel-x interrupt register.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

HAINT[15:0]
r

r

1396/1709

r

r

r

r

r

r

r

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 HAINT[15:0]: Channel interrupts
One bit per channel: Bit 0 for Channel 0, bit 15 for Channel 15

37.15.23 OTG host all channels interrupt mask register
(OTG_HAINTMSK)
Address offset: 0x418
Reset value: 0x0000 0000
The host all channel interrupt mask register works with the host all channel interrupt register
to interrupt the application when an event occurs on a channel. There is one interrupt mask
bit per channel, up to a maximum of 16 bits.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

HAINTM[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 HAINTM[15:0]: Channel interrupt mask
0: Masked interrupt
1: Unmasked interrupt
One bit per channel: Bit 0 for channel 0, bit 15 for channel 15

RM0385 Rev 7

1397/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

37.15.24 OTG host port control and status register (OTG_HPRT)
Address offset: 0x440
Reset value: 0x0000 0000
This register is available only in host mode. Currently, the OTG host supports only one port.
A single register holds USB port-related information such as USB reset, enable, suspend,
resume, connect status, and test mode for each port. It is shown in Figure 468. The rc_w1
bits in this register can trigger an interrupt to the application through the host port interrupt
bit of the core interrupt register (HPRTINT bit in OTG_GINTSTS). On a port interrupt, the
application must read this register and clear the bit that caused the interrupt. For the rc_w1
bits, the application must write a 1 to the bit to clear the interrupt.
31
Res.

15

30

29

Res.

Res.

14

13

PTCTL[2:0]
rw

rw

28
Res.

12
PPWR

rw

rw

27
Res.

11

26
Res.

10

PLSTS[1:0]
r

r

25
Res.

9
Res.

24
Res.

23
Res.

8

7

22
Res.

21
Res.

20
Res.

19
Res.

18

PSPD[1:0]
r

rw

1

0

5

4

3

2

POCA

PEN
CHNG

PENA

r

rc_w1

rc_w1

PRST

PSUSP

PRES

rw

rs

rw

rc_w1

16
PTCTL
[3]

r
6

POC
CHNG

17

PCDET PCSTS
rc_w1

r

Bits 31:19 Reserved, must be kept at reset value.
Bits 18:17 PSPD[1:0]: Port speed
Indicates the speed of the device attached to this port.
01: Full speed
10: Low speed
11: Reserved
00: High speed
Bits 16:13 PTCTL[3:0]: Port test control
The application writes a nonzero value to this field to put the port into a Test mode, and the
corresponding pattern is signaled on the port.
0000: Test mode disabled
0001: Test_J mode
0010: Test_K mode
0011: Test_SE0_NAK mode
0100: Test_Packet mode
0101: Test_Force_Enable
Others: Reserved
Bit 12 PPWR: Port power
The application uses this field to control power to this port, and the core clears this bit on an
overcurrent condition.
0: Power off
1: Power on
Bits 11:10 PLSTS[1:0]: Port line status
Indicates the current logic level USB data lines
Bit 10: Logic level of OTG_DP
Bit 11: Logic level of OTG_DM
Bit 9 Reserved, must be kept at reset value.

1398/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 8 PRST: Port reset
When the application sets this bit, a reset sequence is started on this port. The application
must time the reset period and clear this bit after the reset sequence is complete.
0: Port not in reset
1: Port in reset
The application must leave this bit set for a minimum duration of at least 10 ms to start a
reset on the port. The application can leave it set for another 10 ms in addition to the
required minimum duration, before clearing the bit, even though there is no maximum limit
set by the USB standard.
High speed: 50 ms
Full speed/Low speed: 10 ms
Bit 7 PSUSP: Port suspend
The application sets this bit to put this port in suspend mode. The core only stops sending
SOFs when this is set. To stop the PHY clock, the application must set the port clock stop
bit, which asserts the suspend input pin of the PHY.
The read value of this bit reflects the current suspend status of the port. This bit is cleared
by the core after a remote wakeup signal is detected or the application sets the port reset bit
or port resume bit in this register or the resume/remote wakeup detected interrupt bit or
disconnect detected interrupt bit in the core interrupt register (WKUPINT or DISCINT in
OTG_GINTSTS, respectively).
0: Port not in suspend mode
1: Port in suspend mode
Bit 6 PRES: Port resume
The application sets this bit to drive resume signaling on the port. The core continues to
drive the resume signal until the application clears this bit.
If the core detects a USB remote wakeup sequence, as indicated by the port resume/remote
wakeup detected interrupt bit of the core interrupt register (WKUPINT bit in
OTG_GINTSTS), the core starts driving resume signaling without application intervention
and clears this bit when it detects a disconnect condition. The read value of this bit indicates
whether the core is currently driving resume signaling.
0: No resume driven
1: Resume driven
When LPM is enabled and the core is in L1 state, the behavior of this bit is as follow:
1. The application sets this bit to drive resume signaling on the port.
2. The core continues to drive the resume signal until a predetermined time specified in
BESLTHRS[3:0] field of OTG_GLPMCFG register.
3. If the core detects a USB remote wakeup sequence, as indicated by the port
L1Resume/Remote L1Wakeup detected interrupt bit of the core interrupt register
(WKUPINT in OTG_GINTSTS), the core starts driving resume signaling without application
intervention and clears this bit at the end of resume.This bit can be set or cleared by both
the core and the application. This bit is cleared by the core even if there is no device
connected to the host.
Bit 5 POCCHNG: Port overcurrent change
The core sets this bit when the status of the port overcurrent active bit (bit 4) in this register
changes.
Bit 4 POCA: Port overcurrent active
Indicates the overcurrent condition of the port.
0: No overcurrent condition
1: Overcurrent condition
Bit 3 PENCHNG: Port enable/disable change
The core sets this bit when the status of the port enable bit 2 in this register changes.

RM0385 Rev 7

1399/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 2 PENA: Port enable
A port is enabled only by the core after a reset sequence, and is disabled by an overcurrent
condition, a disconnect condition, or by the application clearing this bit. The application
cannot set this bit by a register write. It can only clear it to disable the port. This bit does not
trigger any interrupt to the application.
0: Port disabled
1: Port enabled
Bit 1 PCDET: Port connect detected
The core sets this bit when a device connection is detected to trigger an interrupt to the
application using the host port interrupt bit in the core interrupt register (HPRTINT bit in
OTG_GINTSTS). The application must write a 1 to this bit to clear the interrupt.
Bit 0 PCSTS: Port connect status
0: No device is attached to the port
1: A device is attached to the port

37.15.25 OTG host channel x characteristics register (OTG_HCCHARx)
(x = 0..15[HS] / 11[FS], where x = Channel number)
Address offset: 0x500 + (x * 0x20)
Reset value: 0x0000 0000
31

30

CHENA CHDIS

29

28

27

26

ODD
FRM

25

24

23

22

DAD[6:0]

21

20

19

18

MCNT[1:0]

EPTYP[1:0]

17

16

LSDEV

Res.

rs

rs

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

EPDIR
rw

EPNUM[3:0]
rw

rw

rw

MPSIZ[10:0]
rw

rw

rw

rw

rw

rw

rw

Bit 31 CHENA: Channel enable
This field is set by the application and cleared by the OTG host.
0: Channel disabled
1: Channel enabled
Bit 30 CHDIS: Channel disable
The application sets this bit to stop transmitting/receiving data on a channel, even before
the transfer for that channel is complete. The application must wait for the Channel disabled
interrupt before treating the channel as disabled.
Bit 29 ODDFRM: Odd frame
This field is set (reset) by the application to indicate that the OTG host must perform a
transfer in an odd frame. This field is applicable for only periodic (isochronous and interrupt)
transactions.
0: Even frame
1: Odd frame
Bits 28:22 DAD[6:0]: Device address
This field selects the specific device serving as the data source or sink.

1400/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bits 21:20 MCNT[1:0]: Multicount
This field indicates to the host the number of transactions that must be executed per frame
for this periodic endpoint. For non-periodic transfers, this field is not used
00: Reserved. This field yields undefined results
01: 1 transaction
10: 2 transactions per frame to be issued for this endpoint
11: 3 transactions per frame to be issued for this endpoint
Note: This field must be set to at least 01.
Bits 19:18 EPTYP[1:0]: Endpoint type
Indicates the transfer type selected.
00: Control
01: Isochronous
10: Bulk
11: Interrupt
Bit 17 LSDEV: Low-speed device
This field is set by the application to indicate that this channel is communicating to a lowspeed device.
Bit 16 Reserved, must be kept at reset value.
Bit 15 EPDIR: Endpoint direction
Indicates whether the transaction is IN or OUT.
0: OUT
1: IN
Bits 14:11 EPNUM[3:0]: Endpoint number
Indicates the endpoint number on the device serving as the data source or sink.
Bits 10:0 MPSIZ[10:0]: Maximum packet size
Indicates the maximum packet size of the associated endpoint.

37.15.26 OTG host channel x split control register (OTG_HCSPLTx)
(x = 0..15, where x = Channel number)
Address offset: 0x504 + (x * 0x20)
Reset value: 0x0000 0000
Note:
31
SPLIT
EN

Configuration register applies only to USB OTG HS.
30
Res.

29
Res.

28
Res.

27

26

Res.

Res.

25
Res.

24
Res.

23
Res.

22
Res.

21
Res.

20

19

Res.

Res.

18
Res.

17

16

Res.

COMP
LSPLT

rw

rw
15

14

13

12

11

XACTPOS[1:0]
rw

rw

10

9

8

7

6

5

4

HUBADDR[6:0]
rw

rw

rw

rw

3

2

1

0

rw

rw

rw

PRTADDR[6:0]
rw

rw

rw

RM0385 Rev 7

rw

rw

rw

rw

1401/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 31 SPLITEN: Split enable
The application sets this bit to indicate that this channel is enabled to perform split
transactions.
Bits 30:17

Reserved, must be kept at reset value.

Bit 16 COMPLSPLT: Do complete split
The application sets this bit to request the OTG host to perform a complete split transaction.
Bits 15:14 XACTPOS[1:0]: Transaction position
This field is used to determine whether to send all, first, middle, or last payloads with each
OUT transaction.
11: All. This is the entire data payload of this transaction (which is less than or equal to 188
bytes)
10: Begin. This is the first data payload of this transaction (which is larger than 188 bytes)
00: Mid. This is the middle payload of this transaction (which is larger than 188 bytes)
01: End. This is the last payload of this transaction (which is larger than 188 bytes)
Bits 13:7 HUBADDR[6:0]: Hub address
This field holds the device address of the transaction translator’s hub.
Bits 6:0 PRTADDR[6:0]: Port address
This field is the port number of the recipient transaction translator.

37.15.27 OTG host channel x interrupt register (OTG_HCINTx)
(x = 0..15[HS] / 11[FS], where x = Channel number)
Address offset: 0x508 + (x * 0x20)
Reset value: 0x0000 0000
This register indicates the status of a channel with respect to USB- and AHB-related events.
It is shown in Figure 468. The application must read this register when the host channels
interrupt bit in the core interrupt register (HCINT bit in OTG_GINTSTS) is set. Before the
application can read this register, it must first read the host all channels interrupt
(OTG_HAINT) register to get the exact channel number for the host channel-x interrupt
register. The application must clear the appropriate bit in this register to clear the
corresponding bits in the OTG_HAINT and OTG_GINTSTS registers.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

DTERR

FRM
OR

Res.

ACK

NAK

STALL

Res.

CHH

XFRC

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Res.

Res.

Note:

1402/1709

Res.

Res.

Res.

BBERR TXERR
rc_w1

rc_w1

Configuration register for USB OTG FS.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

DTERR

FRM
OR

CHH

XFRC

rc_w1

rc_w1

rc_w1

rc_w1

Res.

Note:

Res.

Res.

Res.

Res.

BBERR TXERR
rc_w1

rc_w1

NYET

ACK

NAK

STALL

AHB
ERR

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Configuration register for USB OTG HS.
Bits 31:11 Reserved, must be kept at reset value.
Bit 10 DTERR: Data toggle error.
Bit 9 FRMOR: Frame overrun.
Bit 8 BBERR: Babble error.
Bit 7 TXERR: Transaction error.
Indicates one of the following errors occurred on the USB.
CRC check failure
Timeout
Bit stuff error
False EOP
Bit 6 Reserved, must be kept at reset value for USB OTG FS.
Bit 6 NYET: Not yet ready response received interrupt for USB OTG HS.
Bit 5 ACK: ACK response received/transmitted interrupt.
Bit 4 NAK: NAK response received interrupt.
Bit 3 STALL: STALL response received interrupt.
Bit 2 Reserved, must be kept at reset value for USB OTG FS.
Bit 2 AHBERR: AHB error for USB OTG HS
This error is generated only in Internal DMA mode when an AHB error occurs during an AHB
read/write operation. The application can read the corresponding DMA channel address
register to get the error address.
Bit 1 CHH: Channel halted.
Indicates the transfer completed abnormally either because of any USB transaction error or
in response to disable request by the application.
Bit 0 XFRC: Transfer completed.
Transfer completed normally without any errors.

RM0385 Rev 7

1403/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

37.15.28 OTG host channel x interrupt mask register (OTG_HCINTMSKx)
(x = 0..15[HS] / 11[FS], where x = Channel number)
Address offset: 0x50C + (x * 0x20)
Reset value: 0x0000 0000
This register reflects the mask for each channel status described in the previous section.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

DTERR
M

FRM
ORM

Res.

ACKM

NAKM

STALL
M

Res.

CHHM

XFRC
M

rw

rw

rw

rw

rw

rw

rw

Note:

BBERR TXERR
M
M
rw

rw

Configuration register for USB OTG FS

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

DTERR
M

FRM
ORM

AHB
ERRM

CHHM

XFRC
M

rw

rw

rw

rw

rw

Res.

Res.

Note:

Res.

Res.

BBERR TXERR
M
M
rw

rw

NYET

ACKM

NAKM

STALL
M

rw

rw

rw

rw

Configuration register for USB OTG HS
Bits 31:11 Reserved, must be kept at reset value.
Bit 10 DTERRM: Data toggle error mask.
0: Masked interrupt
1: Unmasked interrupt
Bit 9 FRMORM: Frame overrun mask.
0: Masked interrupt
1: Unmasked interrupt
Bit 8 BBERRM: Babble error mask.
0: Masked interrupt
1: Unmasked interrupt
Bit 7 TXERRM: Transaction error mask.
0: Masked interrupt
1: Unmasked interrupt
Bit 6 Reserved, must be kept at reset value for USB OTG FS.
Bit 6 NYET: response received interrupt mask for USB OTG HS.
0: Masked interrupt
1: Unmasked interrupt

1404/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 5 ACKM: ACK response received/transmitted interrupt mask.
0: Masked interrupt
1: Unmasked interrupt
Bit 4 NAKM: NAK response received interrupt mask.
0: Masked interrupt
1: Unmasked interrupt
Bit 3 STALLM: STALL response received interrupt mask.
0: Masked interrupt
1: Unmasked interrupt
Bit 2 AHBERRM: AHB error for USB OTG HS.
0: Masked interrupt
1: Unmasked interrupt
Bit 2 Reserved, must be kept at reset value for USB OTG FS.
Bit 1 CHHM: Channel halted mask
0: Masked interrupt
1: Unmasked interrupt
Bit 0 XFRCM: Transfer completed mask
0: Masked interrupt
1: Unmasked interrupt

37.15.29 OTG host channel x transfer size register (OTG_HCTSIZx)
(x = 0..15[HS] / 11[FS], where x = Channel number)
Address offset: 0x510 + (x * 0x20)
Reset value: 0x0000 0000
31
Res.

15

30

29

28

27

26

25

DPID[1:0]

24

23

22

21

20

19

18

PKTCNT[9:0]

17

16

XFRSIZ[18:16]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

XFRSIZ[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

1405/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 31 Reserved, must be kept at reset value.
Bits 30:29 DPID[1:0]: Data PID
The application programs this field with the type of PID to use for the initial transaction. The
host maintains this field for the rest of the transfer.
00: DATA0
01: DATA2
10: DATA1
11: SETUP (control) / reserved[FS]MDATA[HS] (non-control)
Bits 28:19 PKTCNT[9:0]: Packet count
This field is programmed by the application with the expected number of packets to be
transmitted (OUT) or received (IN).
The host decrements this count on every successful transmission or reception of an OUT/IN
packet. Once this count reaches zero, the application is interrupted to indicate normal
completion.
Bits 18:0 XFRSIZ[18:0]: Transfer size
For an OUT, this field is the number of data bytes the host sends during the transfer.
For an IN, this field is the buffer size that the application has reserved for the transfer. The
application is expected to program this field as an integer multiple of the maximum packet
size for IN transactions (periodic and non-periodic).

37.15.30 OTG host channel x DMA address register (OTG_HCDMAx)
(x = 0..15, where x = Channel number)
Address offset: 0x514 + (x * 0x20)
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DMAADDR[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DMAADDR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DMAADDR[31:0]: DMA address
This field holds the start address in the external memory from which the data for the endpoint
must be fetched or to which it must be stored. This register is incremented on every AHB
transaction.

37.15.31 Device-mode registers
These registers must be programmed every time the core changes to device mode

1406/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.32 OTG device configuration register (OTG_DCFG)
Address offset: 0x800
Reset value: 0x0220 0000
This register configures the core in device mode after power-on or after certain control
commands or enumeration. Do not make changes to this register after initial programming.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

ERRAT
IM

Res.

Res.

Res.

NZLSO
HSK

rw

PFIVL[1:0]
rw

Note:

rw

DAD[6:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

Res.

NZLSO
HSK

Configuration register for USB OTG FS

31

30

29

28

27

26

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

ERRAT
IM

XCVR
DLY

rw

rw

Note:

rw

DSPD[1:0]

Res.

25

24

PERSCHIVL[1:0]
rw

rw

9

8

PFIVL[1:0]
rw

rw

DAD[6:0]
rw

rw

rw

rw

rw

rw

rw

rw

DSPD[1:0]
rw

rw

Configuration register for USB OTG HS
Bits 31:16 Reserved, must be kept at reset value for USB OTG FS.
Bits 31:26 Reserved, must be kept at reset value for USB OTG HS.
Bits 25:24 PERSCHIVL[1:0]: Periodic schedule interval for USB OTG HS
This field specifies the amount of time the Internal DMA engine must allocate for fetching
periodic IN endpoint data. Based on the number of periodic endpoints, this value must be
specified as 25, 50 or 75% of the (micro) frame.

–

When any periodic endpoints are active, the internal DMA engine allocates
the specified amount of time in fetching periodic IN endpoint data

–

When no periodic endpoint is active, then the internal DMA engine services
nonperiodic endpoints, ignoring this field

–

After the specified time within a (micro) frame, the DMA switches to
fetching nonperiodic endpoints

00: 25% of (micro)frame
01: 50% of (micro)frame
10: 75% of (micro)frame
11: Reserved
Bits 23:16 Reserved, must be kept at reset value for USB OTG HS.
Bit 15 ERRATIM: Erratic error interrupt mask
1: Mask early suspend interrupt on erratic error
0: Early suspend interrupt is generated on erratic error

RM0385 Rev 7

1407/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 14 XCVRDLY: Transceiver delay
Enables or disables delay in ULPI timing during device chirp.
0: Disable delay (use default timing)
1: Enable delay to default timing, necessary for some ULPI PHYs
Bit 13 Reserved, must be kept at reset value.
Bits 12:11 PFIVL[1:0]: Periodic frame interval
Indicates the time within a frame at which the application must be notified using the end of
periodic frame interrupt. This can be used to determine if all the isochronous traffic for that
frame is complete.
00: 80% of the frame interval
01: 85% of the frame interval
10: 90% of the frame interval
11: 95% of the frame interval
Bits 10:4 DAD[6:0]: Device address
The application must program this field after every SetAddress control command.
Bit 3 Reserved, must be kept at reset value.
Bit 2 NZLSOHSK: Non-zero-length status OUT handshake
The application can use this field to select the handshake the core sends on receiving a
nonzero-length data packet during the OUT transaction of a control transfer’s status stage.
1:Send a STALL handshake on a nonzero-length status OUT transaction and do not send
the received OUT packet to the application.
0:Send the received OUT packet to the application (zero-length or nonzero-length) and send
a handshake based on the NAK and STALL bits for the endpoint in the device endpoint
control register.
Bits 1:0 DSPD[1:0]: Device speed
Indicates the speed at which the application requires the core to enumerate, or the
maximum speed the application can support. However, the actual bus speed is determined
only after the chirp sequence is completed, and is based on the speed of the USB host to
which the core is connected.
00: Reserved
01: Reserved
10: Reserved
11: Full speed (USB 1.1 transceiver clock is 48 MHz)
Bits 1:0 DSPD[1:0]: Device speed
Indicates the speed at which the application requires the core to enumerate, or the
maximum speed the application can support. However, the actual bus speed is determined
only after the chirp sequence is completed, and is based on the speed of the USB host to
which the core is connected.
00: High speed
01: Full speed using HS
10: Reserved
11: Full speed using internal FS PHY

1408/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.33 OTG device control register (OTG_DCTL)
Address offset: 0x804
Reset value: 0x0000 0002
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DS
BESL
RJCT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

PO
PRG
DNE

CGO
NAK

SGO
NAK

CGI
NAK

SGI
NAK

GON
STS

GIN
STS

SDIS

RWU
SIG

rw

w

w

w

w

r

r

rw

rw

rw

TCTL[2:0]
rw

rw

rw

Bits 31:19 Reserved, must be kept at reset value.
Bit 18 DSBESLRJCT: Deep sleep BESL reject
Core rejects LPM request with BESL value greater than BESL threshold programmed.
NYET response is sent for LPM tokens with BESL value greater than BESL threshold. By
default, the deep sleep BESL reject feature is disabled.
Bits 17:12 Reserved, must be kept at reset value.
Bit 11 POPRGDNE: Power-on programming done
The application uses this bit to indicate that register programming is completed after a
wakeup from power down mode.
Bit 10 CGONAK: Clear global OUT NAK
Writing 1 to this field clears the Global OUT NAK.
Bit 9 SGONAK: Set global OUT NAK
Writing 1 to this field sets the Global OUT NAK.
The application uses this bit to send a NAK handshake on all OUT endpoints.
The application must set the this bit only after making sure that the Global OUT NAK
effective bit in the core interrupt register (GONAKEFF bit in OTG_GINTSTS) is cleared.
Bit 8 CGINAK: Clear global IN NAK
Writing 1 to this field clears the Global IN NAK.
Bit 7 SGINAK: Set global IN NAK
Writing 1 to this field sets the Global non-periodic IN NAK.The application uses this bit to
send a NAK handshake on all non-periodic IN endpoints.
The application must set this bit only after making sure that the Global IN NAK effective bit
in the core interrupt register (GINAKEFF bit in OTG_GINTSTS) is cleared.
Bits 6:4 TCTL[2:0]: Test control
000: Test mode disabled
001: Test_J mode
010: Test_K mode
011: Test_SE0_NAK mode
100: Test_Packet mode
101: Test_Force_Enable
Others: Reserved

RM0385 Rev 7

1409/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 3 GONSTS: Global OUT NAK status
0:A handshake is sent based on the FIFO status and the NAK and STALL bit settings.
1:No data is written to the Rx FIFO, irrespective of space availability. Sends a NAK
handshake on all packets, except on SETUP transactions. All isochronous OUT packets are
dropped.
Bit 2 GINSTS: Global IN NAK status
0:A handshake is sent out based on the data availability in the transmit FIFO.
1:A NAK handshake is sent out on all non-periodic IN endpoints, irrespective of the data
availability in the transmit FIFO.
Bit 1 SDIS: Soft disconnect
The application uses this bit to signal the USB OTG core to perform a soft disconnect. As
long as this bit is set, the host does not see that the device is connected, and the device
does not receive signals on the USB. The core stays in the disconnected state until the
application clears this bit.
0:Normal operation. When this bit is cleared after a soft disconnect, the core generates a
device connect event to the USB host. When the device is reconnected, the USB host
restarts device enumeration.
1:The core generates a device disconnect event to the USB host.
Bit 0 RWUSIG: Remote wakeup signaling
When the application sets this bit, the core initiates remote signaling to wake up the USB
host. The application must set this bit to instruct the core to exit the suspend state. As
specified in the USB 2.0 specification, the application must clear this bit 1 ms to 15 ms after
setting it.
If LPM is enabled and the core is in the L1 (sleep) state, when the application sets this bit,
the core initiates L1 remote signaling to wake up the USB host. The application must set
this bit to instruct the core to exit the sleep state. As specified in the LPM specification, the
hardware automatically clears this bit 50 µs (TL1DevDrvResume) after being set by the
application. The application must not set this bit when bRemoteWake from the previous
LPM transaction is zero (refer to REMWAKE bit in GLPMCFG register).

Table 268 contains the minimum duration (according to device state) for which the Soft
disconnect (SDIS) bit must be set for the USB host to detect a device disconnect. To
accommodate clock jitter, it is recommended that the application add some extra delay to
the specified minimum duration.
Table 268. Minimum duration for soft disconnect
Operating speed

1410/1709

Device state

Minimum duration

Full speed

Suspended

1 ms + 2.5 µs

Full speed

Idle

2.5 µs

Full speed

Not Idle or suspended (Performing transactions)

2.5 µs

High speed

Not Idle or suspended (Performing transactions)

125 µs

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.34 OTG device status register (OTG_DSTS)
Address offset: 0x808
Reset value: 0x0000 0010
This register indicates the status of the core with respect to USB-related events. It must be
read on interrupts from the device all interrupts (OTG_DAINT) register.
31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

r

r

r

r

r

21

20

19

18

17

16

r

FNSOF[13:8]

r

r

r

r

r

r

r

7

6

5

4

3

2

1

Res.
r

22

DEVLNSTS[1:0]

8

FNSOF[7:0]
r

23

Res.

r

Res.

Res.

EERR
r

ENUMSPD[1:0]
r

0
SUSP
STS

r

r

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:22 DEVLNSTS[1:0]: Device line status
Indicates the current logic level USB data lines.
Bit [23]: Logic level of D+
Bit [22]: Logic level of DBits 21:8 FNSOF[13:0]: Frame number of the received SOF
Bits 7:4 Reserved, must be kept at reset value.
Bit 3 EERR: Erratic error
The core sets this bit to report any erratic errors.
Due to erratic errors, the OTG_FS/OTG_HS controller goes into suspended state and an
interrupt is generated to the application with Early suspend bit of the OTG_GINTSTS register
(ESUSP bit in OTG_GINTSTS). If the early suspend is asserted due to an erratic error, the
application can only perform a soft disconnect recover.
Bits 2:1 ENUMSPD[1:0]: Enumerated speed
Indicates the speed at which the OTG_FS/OTG_HS controller has come up after speed
detection through a chirp sequence.
01: Reserved
10: Reserved
11: Full speed (PHY clock is running at 48 MHz)
Others: reserved
Bit 0 SUSPSTS: Suspend status
In device mode, this bit is set as long as a suspend condition is detected on the USB. The
core enters the suspended state when there is no activity on the USB data lines for a period
of 3 ms. The core comes out of the suspend:
– When there is an activity on the USB data lines
– When the application writes to the remote wakeup signaling bit in the OTG_DCTL register
(RWUSIG bit in OTG_DCTL).

RM0385 Rev 7

1411/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

37.15.35 OTG device IN endpoint common interrupt mask register
(OTG_DIEPMSK)
Address offset: 0x810
Reset value: 0x0000 0000
This register works with each of the OTG_DIEPINTx registers for all endpoints to generate
an interrupt per IN endpoint. The IN endpoint interrupt for a specific status in the
OTG_DIEPINTx register can be masked by writing to the corresponding bit in this register.
Status bits are masked by default.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

NAKM

Res.

Res.

Res.

Res.

TXFU
RM

Res.

INEPN
EM

TOM

Res.

EPDM

XFRC
M

rw

rw

rw

Note:

rw

INEPN ITTXFE
MM
MSK

rw

rw

rw

rw

Configuration register for USB OTG FS

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

TXFU
RM

Res.

INEPN
EM

TOM

AHB
ERRM

EPDM

XFRC
M

rw

rw

rw

rw

Res.

Res.

NAKM

Res.

Res.

Res.

rw

Note:

rw

rw

INEPN ITTXFE
MM
MSK
rw

Configuration register for USB OTG HS
Bits 31:14 Reserved, must be kept at reset value.
Bit 13 NAKM: NAK interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bits 12:10 Reserved, must be kept at reset value.
Bit 9 Reserved, must be kept at reset value.
Bit 8 TXFURM: FIFO underrun mask
0: Masked interrupt
1: Unmasked interrupt
Bit 7 Reserved, must be kept at reset value.
Bit 6 INEPNEM: IN endpoint NAK effective mask
0: Masked interrupt
1: Unmasked interrupt
Bit 5 INEPNMM: IN token received with EP mismatch mask
0: Masked interrupt
1: Unmasked interrupt

1412/1709

RM0385 Rev 7

rw

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 4 ITTXFEMSK: IN token received when Tx FIFO empty mask
0: Masked interrupt
1: Unmasked interrupt
Bit 3 TOM: Timeout condition mask (Non-isochronous endpoints)
0: Masked interrupt
1: Unmasked interrupt
Bit 2 AHBERRM: AHB error mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Bit 1 EPDM: Endpoint disabled interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bit 0 XFRCM: Transfer completed interrupt mask
0: Masked interrupt
1: Unmasked interrupt

37.15.36 OTG device OUT endpoint common interrupt mask register
(OTG_DOEPMSK)
Address offset: 0x814
Reset value: 0x0000 0000
This register works with each of the OTG_DOEPINTx registers for all endpoints to generate
an interrupt per OUT endpoint. The OUT endpoint interrupt for a specific status in the
OTG_DOEPINTx register can be masked by writing into the corresponding bit in this
register. Status bits are masked by default.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

OUT
PKT
ERRM

Res.

STS
PHSR
XM

Res.

EPDM

XFRC
M

rw

rw

Res.

NYET
MSK

NAK
MSK

BERR
M

rw

rw

rw

Note:

Res.

Res.

Res.

rw

OTEPD STUPM
M

rw

rw

rw

Configuration register for USB OTG FS

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

OUT
PKT
ERRM

EPDM

XFRC
M

rw

rw

Res.

Note:

NYET
MSK

NAK
MSK

BERR
M

rw

rw

rw

Res.

Res.

Res.

rw

STS
B2B
PHSR
STUPM
XM
rw

rw

AHB
OTEPD STUPM
ERRM
M
rw

rw

rw

Configuration register for USB OTG HS

RM0385 Rev 7

1413/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits 31:15 Reserved, must be kept at reset value.
Bit 14 NYETMSK: NYET interrupt mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Bit 13 NAKMSK: NAK interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bit 12 BERRM: Babble error interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bits 11:10 Reserved, must be kept at reset value.
Bit 9 Reserved, must be kept at reset value.
Bit 8 OUTPKTERRM: Out packet error mask
0: Masked interrupt
1: Unmasked interrupt
Bit 7 Reserved, must be kept at reset value.
Bit 6 B2BSTUPM: Back-to-back SETUP packets received mask for USB OTG HS
Applies to control OUT endpoints only.
0: Masked interrupt
1: Unmasked interrupt
Bit 5 STSPHSRXM: Status phase received for control write mask
0: Masked interrupt
1: Unmasked interrupt
Bit 4 OTEPDM: OUT token received when endpoint disabled mask. Applies to control OUT
endpoints only.
0: Masked interrupt
1: Unmasked interrupt
Bit 3 STUPM: STUPM: SETUP phase done mask. Applies to control endpoints only.
0: Masked interrupt
1: Unmasked interrupt
Bit 2 AHBERRM: AHB error mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Bit 1 EPDM: Endpoint disabled interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bit 0 XFRCM: Transfer completed interrupt mask
0: Masked interrupt
1: Unmasked interrupt

1414/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.37 OTG device all endpoints interrupt register (OTG_DAINT)
Address offset: 0x818
Reset value: 0x0000 0000
When a significant event occurs on an endpoint, a OTG_DAINT register interrupts the
application using the device OUT endpoints interrupt bit or device IN endpoints interrupt bit
of the OTG_GINTSTS register (OEPINT or IEPINT in OTG_GINTSTS, respectively). There
is one interrupt bit per endpoint, up to a maximum of 16 bits for OUT endpoints and 16 bits
for IN endpoints. For a bidirectional endpoint, the corresponding IN and OUT interrupt bits
are used. Bits in this register are set and cleared when the application sets and clears bits in
the corresponding device endpoint-x interrupt register (OTG_DIEPINTx/OTG_DOEPINTx).
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

OEPINT[15:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

IEPINT[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 OEPINT[15:0]: OUT endpoint interrupt bits
One bit per OUT endpoint:
Bit 16 for OUT endpoint 0, bit 19 for OUT endpoint 3.
Bits 15:0 IEPINT[15:0]: IN endpoint interrupt bits
One bit per IN endpoint:
Bit 0 for IN endpoint 0, bit 3 for endpoint 3.

37.15.38 OTG all endpoints interrupt mask register
(OTG_DAINTMSK)
Address offset: 0x81C
Reset value: 0x0000 0000
The OTG_DAINTMSK register works with the device endpoint interrupt register to interrupt
the application when an event occurs on a device endpoint. However, the OTG_DAINT
register bit corresponding to that interrupt is still set.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

OEPM[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

IEPM[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

1415/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits 31:16 OEPM[15:0]: OUT EP interrupt mask bits
One per OUT endpoint:
Bit 16 for OUT EP 0, bit 19 for OUT EP 3
0: Masked interrupt
1: Unmasked interrupt
Bits 15:0 IEPM[15:0]: IN EP interrupt mask bits
One bit per IN endpoint:
Bit 0 for IN EP 0, bit 3 for IN EP 3
0: Masked interrupt
1: Unmasked interrupt

37.15.39 OTG device VBUS discharge time register
(OTG_DVBUSDIS)
Address offset: 0x0828
Reset value: 0x0000 17D7
This register specifies the VBUS discharge time after VBUS pulsing during SRP.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

VBUSDT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 VBUSDT[15:0]: Device VBUS discharge time
Specifies the VBUS discharge time after VBUS pulsing during SRP. This value equals:
VBUS discharge time in PHY clocks / 1 024
Depending on your VBUS load, this value may need adjusting.

37.15.40 OTG device VBUS pulsing time register
(OTG_DVBUSPULSE)
Address offset: 0x082C
Reset value: 0x0000 05B8
This register specifies the VBUS pulsing time during SRP.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DVBUSP[15:0]
rw

rw

1416/1709

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 DVBUSP[15:0]: Device VBUS pulsing time. This feature is only relevant to OTG1.3.
Specifies the VBUS pulsing time during SRP. This value equals:
VBUS pulsing time in PHY clocks / 1 024

37.15.41 OTG device threshold control register (OTG_DTHRCTL)
Address offset: 0x0830
Reset value: 0x0000 0000
Note:
31

Configuration register applies only to USB OTG HS
30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

27
ARPEN

26

Res.

Res.

Res.

Res.

24

23

22

Res.

rw
11

25

10

21

20

19

18

16
RXTH
REN

RXTHRLEN[8:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

0

ISOT
HREN

NONIS
OTH
REN

rw

rw

Res.

TXTHRLEN[8:0]
rw

17

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bit 27 ARPEN: Arbiter parking enable
This bit controls internal DMA arbiter parking for IN endpoints. When thresholding is enabled
and this bit is set to one, then the arbiter parks on the IN endpoint for which there is a token
received on the USB. This is done to avoid getting into underrun conditions. By default
parking is enabled.
Bit 26

Reserved, must be kept at reset value.

Bits 25:17 RXTHRLEN[8:0]: Receive threshold length
This field specifies the receive thresholding size in 32-bit words. This field also specifies the
amount of data received on the USB before the core can start transmitting on the AHB. The
threshold length has to be at least eight 32-bit words. The recommended value for
RXTHRLEN is to be the same as the programmed AHB burst length (HBSTLEN bit in
OTG_GAHBCFG).
Bit 16 RXTHREN: Receive threshold enable
When this bit is set, the core enables thresholding in the receive direction.
Bits 15:11

Reserved, must be kept at reset value.

RM0385 Rev 7

1417/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits 10:2 TXTHRLEN[8:0]: Transmit threshold length
This field specifies the transmit thresholding size in 32-bit words. This field specifies the
amount of data in bytes to be in the corresponding endpoint transmit FIFO, before the core
can start transmitting on the USB. The threshold length has to be at least eight 32-bit words.
This field controls both isochronous and nonisochronous IN endpoint thresholds. The
recommended value for TXTHRLEN is to be the same as the programmed AHB burst length
(HBSTLEN bit in OTG_GAHBCFG).
Bit 1 ISOTHREN: ISO IN endpoint threshold enable
When this bit is set, the core enables thresholding for isochronous IN endpoints.
Bit 0 NONISOTHREN: Nonisochronous IN endpoints threshold enable
When this bit is set, the core enables thresholding for nonisochronous IN endpoints.

37.15.42 OTG device IN endpoint FIFO empty interrupt mask register
(OTG_DIEPEMPMSK)
Address offset: 0x834
Reset value: 0x0000 0000
This register is used to control the IN endpoint FIFO empty interrupt generation
(TXFE_OTG_DIEPINTx).
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

INEPTXFEM[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 INEPTXFEM[15:0]: IN EP Tx FIFO empty interrupt mask bits
These bits act as mask bits for OTG_DIEPINTx.
TXFE interrupt one bit per IN endpoint:
Bit 0 for IN endpoint 0, bit 3 for IN endpoint 3
0: Masked interrupt
1: Unmasked interrupt

1418/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.43 OTG device each endpoint interrupt register (OTG_DEACHINT)
Address offset: 0x0838
Reset value: 0x0000 0000
Note:
31

Configuration register applies only to USB OTG HS.
30

29

28

27

26

25

24

23

22

21

20

19

18

17

16
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OEP1
INT

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IEP1
INT

Res.

r

r

Bits 31:18 Reserved, must be kept at reset value.
Bit 17 OEP1INT: OUT endpoint 1 interrupt bit
Bits 16:2 Reserved, must be kept at reset value.
Bit 1 IEP1INT: IN endpoint 1interrupt bit
Bit 0 Reserved, must be kept at reset value.

37.15.44 OTG device each endpoint interrupt mask register
(OTG_DEACHINTMSK)
Address offset: 0x083C
Reset value: 0x0000 0000
There is one interrupt bit for endpoint 1 IN and one interrupt bit for endpoint 1 OUT.
31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
Res.

25
Res.

24
Res.

23
Res.

22
Res.

21
Res.

20
Res.

19
Res.

18

17

16

Res.

OEP1
INTM

Res.

rw
15
Res.

14
Res.

13
Res.

12
Res.

11
Res.

10
Res.

9
Res.

8
Res.

7
Res.

6
Res.

5
Res.

4
Res.

3
Res.

2

1

0

Res.

IEP1I
NTM

Res.

rw

Bits 31:18 Reserved, must be kept at reset value.
Bit 17 OEP1INTM: OUT endpoint 1 interrupt mask bit
Bits 16:2 Reserved, must be kept at reset value.
Bit 1 IEP1INTM: IN endpoint 1 interrupt mask bit
Bit 0 Reserved, must be kept at reset value.

Note:

Configuration register applies only to USB OTG HS

RM0385 Rev 7

1419/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

37.15.45 OTG device each IN endpoint-1 interrupt mask register
(OTG_HS_DIEPEACHMSK1)
Address offset: 0x844
Reset value: 0x0000 0000
This register works with the OTG_DIEPINT1 register to generate a dedicated interrupt
OTG_HS_EP1_IN for endpoint #1. The IN endpoint interrupt for a specific status in the
OTG_DOEPINT1 register can be masked by writing into the corresponding bit in this
register. Status bits are masked by default.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

NAKM

Res.

Res.

Res.

Res.

TXFU
RM

Res.

INEPN
EM

Res.

ITTXFE
MSK

TOM

AHB
ERRM

EPDM

XFRC
M

rw

rw

rw

rw

rw

rw

Note:

rw

rw

Configuration register applies only to USB OTG HS
Bits 31:14 Reserved, must be kept at reset value.
Bit 13 NAKM: NAK interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bits 12:10 Reserved, must be kept at reset value.
Bit 9 Reserved, must be kept at reset value.
Bit 8 TXFURM: FIFO underrun mask
0: Masked interrupt
1: Unmasked interrupt
Bit 7 Reserved, must be kept at reset value.
Bit 6 INEPNEM: IN endpoint NAK effective mask
0: Masked interrupt
1: Unmasked interrupt
Bit 5 Reserved, must be kept at reset value.
Bit 4 ITTXFEMSK: IN token received when Tx FIFO empty mask
0: Masked interrupt
1: Unmasked interrupt
Bit 3 TOM: Timeout condition mask (Non-isochronous endpoints)
0: Masked interrupt
1: Unmasked interrupt

1420/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 2 AHBERRM: AHB error mask
0: Masked interrupt
1: Unmasked interrupt
Bit 1 EPDM: Endpoint disabled interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bit 0 XFRCM: Transfer completed interrupt mask
0: Masked interrupt
1: Unmasked interrupt

37.15.46 OTG device each OUT endpoint-1 interrupt mask register
(OTG_HS_DOEPEACHMSK1)
Address offset: 0x884
Reset value: 0x0000 0000
This register works with the OTG_DOEPINT1 register to generate a dedicated interrupt
OTG_HS_EP1_OUT for endpoint #1. The OUT endpoint interrupt for a specific status in the
OTG_DOEPINT1 register can be masked by writing into the corresponding bit in this
register. Status bits are masked by default.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

NYET
MSK

NAK
MSK

BERR
M

Res.

Res.

Res.

OUT
PKT
ERRM

Res.

B2B
STUPM

Res.

EPDM

XFRC
M

rw

rw

rw

rw

rw

Note:

rw

rw

OTEPD
AHB
STUPM
M
ERRM
rw

rw

rw

Configuration register applies only to USB OTG HS
Bits 31:15 Reserved, must be kept at reset value.
Bit 14 NYETMSK: NYET interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bit 13 NAKMSK: NAK interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bit 12 BERRM: Babble error interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bits 11:10 Reserved, must be kept at reset value.
Bit 9 Reserved, must be kept at reset value.
Bit 8 OUTPKTERRM: Out packet error mask
0: Masked interrupt
1: Unmasked interrupt

RM0385 Rev 7

1421/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 7 Reserved, must be kept at reset value.
Bit 6 B2BSTUPM: Back-to-back SETUP packets received mask
Applies to control OUT endpoints only.
0: Masked interrupt
1: Unmasked interrupt
Bit 5 Reserved, must be kept at reset value.
Bit 4 OTEPDM: OUT token received when endpoint disabled mask
Applies to control OUT endpoints only.
0: Masked interrupt
1: Unmasked interrupt
Bit 3 STUPM: STUPM: SETUP phase done mask
Applies to control endpoints only.
0: Masked interrupt
1: Unmasked interrupt
Bit 2 AHBERRM: AHB error mask
0: Masked interrupt
1: Unmasked interrupt
Bit 1 EPDM: Endpoint disabled interrupt mask
0: Masked interrupt
1: Unmasked interrupt
Bit 0 XFRCM: Transfer completed interrupt mask
0: Masked interrupt
1: Unmasked interrupt

37.15.47 OTG device control IN endpoint 0 control register
(OTG_DIEPCTL0)
Address offset: 0x900
Reset value: 0x0000 0000
This section describes the OTG_DIEPCTL0 register for USB_OTG FS. Nonzero control
endpoints use registers for endpoints 1–3.
31

30

EPENA EPDIS

29
Res.

28
Res.

27

26

25

24

23

22

TXFNUM[3:0]

21

SNAK

CNAK

STALL

w

w

rw

rw

rw

rw

rs

rs

rs

15

14

13

12

11

10

9

8

7

6

5

USBA
EP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

1422/1709

20

19

Res.

18

EPTYP

17

16

NAK
STS

Res.

r

r

r

4

3

2

1

Res.

Res.

Res.

MPSIZ[1:0]
rw

RM0385 Rev 7

0

rw

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 31 EPENA: Endpoint enable
The application sets this bit to start transmitting data on the endpoint 0.
The core clears this bit before setting any of the following interrupts on this endpoint:
– Endpoint disabled
– Transfer completed
Bit 30 EPDIS: Endpoint disable
The application sets this bit to stop transmitting data on an endpoint, even before the
transfer for that endpoint is complete. The application must wait for the endpoint disabled
interrupt before treating the endpoint as disabled. The core clears this bit before setting the
endpoint disabled interrupt. The application must set this bit only if endpoint enable is
already set for this endpoint.
Bits 29:28 Reserved, must be kept at reset value.
Bit 27 SNAK: Set NAK
A write to this bit sets the NAK bit for the endpoint.
Using this bit, the application can control the transmission of NAK handshakes on an
endpoint. The core can also set this bit for an endpoint after a SETUP packet is received on
that endpoint.
Bit 26 CNAK: Clear NAK
A write to this bit clears the NAK bit for the endpoint.
Bits 25:22 TXFNUM[3:0]: Tx FIFO number
This value is set to the FIFO number that is assigned to IN endpoint 0.
Bit 21 STALL: STALL handshake
The application can only set this bit, and the core clears it when a SETUP token is received
for this endpoint. If a NAK bit, a Global IN NAK or Global OUT NAK is set along with this bit,
the STALL bit takes priority.
Bit 20 Reserved, must be kept at reset value.
Bits 19:18 EPTYP: Endpoint type
Hardcoded to ‘00’ for control.
Bit 17 NAKSTS: NAK status
Indicates the following:
0: The core is transmitting non-NAK handshakes based on the FIFO status
1: The core is transmitting NAK handshakes on this endpoint.
When this bit is set, either by the application or core, the core stops transmitting data, even
if there are data available in the Tx FIFO. Irrespective of this bit’s setting, the core always
responds to SETUP data packets with an ACK handshake.
Bit 16 Reserved, must be kept at reset value.

RM0385 Rev 7

1423/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 15 USBAEP: USB active endpoint
This bit is always set to 1, indicating that control endpoint 0 is always active in all
configurations and interfaces.
Bits 14:2 Reserved, must be kept at reset value.
Bits 1:0 MPSIZ[1:0]: Maximum packet size
The application must program this field with the maximum packet size for the current logical
endpoint.
00: 64 bytes
01: 32 bytes
10: 16 bytes
11: 8 bytes

Note:

Configuration register applies only to USB OTG FS

37.15.48 OTG device IN endpoint x control register (OTG_DIEPCTLx)
(x = 1..5[FS] / 0..8[HS], where x = endpoint number)
Address offset: 0x900 + (x * 0x20)
Reset value: 0x0000 0000
The application uses this register to control the behavior of each logical endpoint other than
endpoint 0.
31

30

EPENA EPDIS

29

28

27

26

SODD
FRM

SD0
PID/
SEVN
FRM

SNAK

CNAK

25

24

23

22

TXFNUM[3:0]

21

20

STALL

Res.

rs

rs

w

w

w

w

rw

rw

rw

rw

rw/rs

15

14

13

12

11

10

9

8

7

6

5

USBA
EP

Res.

Res.

Res.

Res.

rw

19

18

EPTYP[1:0]

17

16

NAK
STS

EO
NUM/
DPID

rw

rw

r

r

4

3

2

1

0

rw

rw

rw

rw

rw

MPSIZ[10:0]
rw

rw

rw

rw

rw

rw

Bit 31 EPENA: Endpoint enable
The application sets this bit to start transmitting data on an endpoint.
The core clears this bit before setting any of the following interrupts on this endpoint:
– SETUP phase done
– Endpoint disabled
– Transfer completed
Bit 30 EPDIS: Endpoint disable
The application sets this bit to stop transmitting/receiving data on an endpoint, even before
the transfer for that endpoint is complete. The application must wait for the endpoint
disabled interrupt before treating the endpoint as disabled. The core clears this bit before
setting the endpoint disabled interrupt. The application must set this bit only if endpoint
enable is already set for this endpoint.
Bit 29 SODDFRM: Set odd frame
Applies to isochronous IN and OUT endpoints only.
Writing to this field sets the Even/Odd frame (EONUM) field to odd frame.

1424/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 28 SD0PID: Set DATA0 PID
Applies to interrupt/bulk IN endpoints only.
Writing to this field sets the endpoint data PID (DPID) field in this register to DATA0.
SEVNFRM: Set even frame
Applies to isochronous IN endpoints only.
Writing to this field sets the Even/Odd frame (EONUM) field to even frame.
Bit 27 SNAK: Set NAK
A write to this bit sets the NAK bit for the endpoint.
Using this bit, the application can control the transmission of NAK handshakes on an
endpoint. The core can also set this bit for OUT endpoints on a transfer completed interrupt,
or after a SETUP is received on the endpoint.
Bit 26 CNAK: Clear NAK
A write to this bit clears the NAK bit for the endpoint.
Bits 25:22 TXFNUM: Tx FIFO number
These bits specify the FIFO number associated with this endpoint. Each active IN endpoint
must be programmed to a separate FIFO number.
This field is valid only for IN endpoints.
Bit 21 STALL: STALL handshake
Applies to non-control, non-isochronous IN endpoints only (access type is rw).
The application sets this bit to stall all tokens from the USB host to this endpoint. If a NAK
bit, Global IN NAK, or Global OUT NAK is set along with this bit, the STALL bit takes priority.
Only the application can clear this bit, never the core.
Applies to control endpoints only (access type is rs).
The application can only set this bit, and the core clears it, when a SETUP token is received
for this endpoint. If a NAK bit, Global IN NAK, or Global OUT NAK is set along with this bit,
the STALL bit takes priority. Irrespective of this bit’s setting, the core always responds to
SETUP data packets with an ACK handshake.
Bit 20 Reserved, must be kept at reset value.
Bits 19:18 EPTYP[1:0]: Endpoint type
This is the transfer type supported by this logical endpoint.
00: Control
01: Isochronous
10: Bulk
11: Interrupt
Bit 17 NAKSTS: NAK status
It indicates the following:
0: The core is transmitting non-NAK handshakes based on the FIFO status.
1: The core is transmitting NAK handshakes on this endpoint.
When either the application or the core sets this bit:
For non-isochronous IN endpoints: The core stops transmitting any data on an IN endpoint,
even if there are data available in the Tx FIFO.
For isochronous IN endpoints: The core sends out a zero-length data packet, even if there
are data available in the Tx FIFO.
Irrespective of this bit’s setting, the core always responds to SETUP data packets with an
ACK handshake.

RM0385 Rev 7

1425/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 16 EONUM: Even/odd frame
Applies to isochronous IN endpoints only.
Indicates the frame number in which the core transmits/receives isochronous data for this
endpoint. The application must program the even/odd frame number in which it intends to
transmit/receive isochronous data for this endpoint using the SEVNFRM and SODDFRM
fields in this register.
0: Even frame
1: Odd frame
DPID: Endpoint data PID
Applies to interrupt/bulk IN endpoints only.
Contains the PID of the packet to be received or transmitted on this endpoint. The
application must program the PID of the first packet to be received or transmitted on this
endpoint, after the endpoint is activated. The application uses the SD0PID register field to
program either DATA0 or DATA1 PID.
0: DATA0
1: DATA1
Bit 15 USBAEP: USB active endpoint
Indicates whether this endpoint is active in the current configuration and interface. The core
clears this bit for all endpoints (other than EP 0) after detecting a USB reset. After receiving
the SetConfiguration and SetInterface commands, the application must program endpoint
registers accordingly and set this bit.
Bits 14:11 Reserved, must be kept at reset value.
Bits 10:0 MPSIZ[10:0]: Maximum packet size
The application must program this field with the maximum packet size for the current logical
endpoint. This value is in bytes.

37.15.49 OTG device IN endpoint x interrupt register (OTG_DIEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint number)
Address offset: 0x908 + (x * 0x20)
Reset value: 0x0000 0080
This register indicates the status of an endpoint with respect to USB- and AHB-related
events. It is shown in Figure 468. The application must read this register when the IN
endpoints interrupt bit of the core interrupt register (IEPINT in OTG_GINTSTS) is set.
Before the application can read this register, it must first read the device all endpoints
interrupt (OTG_DAINT) register to get the exact endpoint number for the device endpoint-x
interrupt register. The application must clear the appropriate bit in this register to clear the
corresponding bits in the OTG_DAINT and OTG_GINTSTS registers.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

TXFIF
OUD
RN

TXFE

IN
EPNE

IN
ITTXFE
EPNM

TOC

Res.

EP
DISD

XFRC

rc_w1

r

r

rc_w1

rc_w1

rc_w1

rc_w1

Res.

Res.

NAK
rc_w1

Note:

1426/1709

Res.

PKTD
RPSTS
rc_w1

Res.

Configuration register for USB OTG FS

RM0385 Rev 7

rc_w1

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

TXFIF
OUD
RN

TXFE

IN
EPNE

IN
ITTXFE
EPNM

TOC

AHB
ERR

EP
DISD

XFRC

rc_w1

r

r

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Res.

Res.

NAK
rc_w1

Note:

Res.

PKTD
RPSTS
rc_w1

Res.

rc_w1

Configuration register for USB OTG HS
Bits 31:14 Reserved, must be kept at reset value.
Bit 13 NAK: NAK input
The core generates this interrupt when a NAK is transmitted or received by the device. In
case of isochronous IN endpoints the interrupt gets generated when a zero length packet is
transmitted due to unavailability of data in the Tx FIFO.
Bit 12 Reserved, must be kept at reset value.
Bit 11 PKTDRPSTS: Packet dropped status
This bit indicates to the application that an ISOC OUT packet has been dropped. This bit
does not have an associated mask bit and does not generate an interrupt.
Bit 10 Reserved, must be kept at reset value.
Bit 9 Reserved, must be kept at reset value.
Bit 8 TXFIFOUDRN: Transmit Fifo Underrun (TxfifoUndrn)
The core generates this interrupt when it detects a transmit FIFO underrun condition for this
endpoint. Dependency: This interrupt is valid only when Thresholding is enabled
Bit 7 TXFE: Transmit FIFO empty
This interrupt is asserted when the Tx FIFO for this endpoint is either half or completely
empty. The half or completely empty status is determined by the Tx FIFO Empty Level bit in
the OTG_GAHBCFG register (TXFELVL bit in OTG_GAHBCFG).
Bit 6 INEPNE: IN endpoint NAK effective
This bit can be cleared when the application clears the IN endpoint NAK by writing to the
CNAK bit in OTG_DIEPCTLx.
This interrupt indicates that the core has sampled the NAK bit set (either by the application
or by the core). The interrupt indicates that the IN endpoint NAK bit set by the application
has taken effect in the core.
This interrupt does not guarantee that a NAK handshake is sent on the USB. A STALL bit
takes priority over a NAK bit.
Bit 5 INEPNM: IN token received with EP mismatch
Indicates that the data in the top of the non-periodic TxFIFO belongs to an endpoint other
than the one for which the IN token was received. This interrupt is asserted on the endpoint
for which the IN token was received.
Bit 4 ITTXFE: IN token received when Tx FIFO is empty
Indicates that an IN token was received when the associated Tx FIFO (periodic/nonperiodic) was empty. This interrupt is asserted on the endpoint for which the IN token was
received.

RM0385 Rev 7

1427/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 3 TOC: Timeout condition
Indicates that the core has detected a timeout condition on the USB for the last IN token on
this endpoint.
Bit 2 AHBERR: AHB error for USB OTG HS
This is generated only in internal DMA mode when there is an AHB error during an AHB
read/write. The application can read the corresponding endpoint DMA address register to
get the error address.
Bit 1 EPDISD: Endpoint disabled interrupt
This bit indicates that the endpoint is disabled per the application’s request.
Bit 0 XFRC: Transfer completed interrupt
This field indicates that the programmed transfer is complete on the AHB as well as on the
USB, for this endpoint.

37.15.50 OTG device IN endpoint 0 transfer size register
(OTG_DIEPTSIZ0)
Address offset: 0x910
Reset value: 0x0000 0000
The application must modify this register before enabling endpoint 0. Once endpoint 0 is
enabled using the endpoint enable bit in the device control endpoint 0 control registers
(EPENA in OTG_DIEPCTL0), the core modifies this register. The application can only read
this register once the core has cleared the endpoint enable bit.
Nonzero endpoints use the registers for endpoints 1–3.
31

30

29

28

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

20

19

PKTCNT[1:0]
rw

rw

4

3

18

17

16

Res.

Res.

Res.

2

1

0

rw

rw

rw

XFRSIZ[6:0]
rw

rw

rw

rw

Bits 31:21 Reserved, must be kept at reset value.
Bits 20:19 PKTCNT[1:0]: Packet count
Indicates the total number of USB packets that constitute the transfer size amount of data for
endpoint 0.
This field is decremented every time a packet (maximum size or short packet) is read from
the Tx FIFO.
Bits 18:7 Reserved, must be kept at reset value.
Bits 6:0 XFRSIZ[6:0]: Transfer size
Indicates the transfer size in bytes for endpoint 0. The core interrupts the application only
after it has exhausted the transfer size amount of data. The transfer size can be set to the
maximum packet size of the endpoint, to be interrupted at the end of each packet.
The core decrements this field every time a packet from the external memory is written to
the Tx FIFO.

1428/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.51 OTG device IN endpoint x DMA address register (OTG_DIEPDMAx)
(x = 0..8, where x = endpoint number)
Address offset: 0x914 + (x * 0x20)
Reset value: 0x0000 0000
Note:
31

Configuration register applies only to USB OTG HS
30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DMAADDR[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DMAADDR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DMAADDR[31:0]: DMA Address
This field holds the start address in the external memory from which the data for the
endpoint must be fetched. This register is incremented on every AHB transaction.

37.15.52 OTG device IN endpoint transmit FIFO status register
(OTG_DTXFSTSx) (x = 0..5[FS] /8[HS], where
x = endpoint number)
Address offset for IN endpoints: 0x918 + (x * 0x20) This read-only register contains the free
space information for the device IN endpoint Tx FIFO.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

INEPTFSAV[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 INEPTFSAV[15:0]: IN endpoint Tx FIFO space available
Indicates the amount of free space available in the endpoint Tx FIFO.
Values are in terms of 32-bit words:
0x0: Endpoint Tx FIFO is full
0x1: 1 word available
0x2: 2 words available
0xn: n words available
Others: Reserved

RM0385 Rev 7

1429/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

37.15.53 OTG device IN endpoint x transfer size register (OTG_DIEPTSIZx)
(x = 1..5[FS] /8[HS], where x = endpoint number)
Address offset: 0x910 + (x * 0x20)
Reset value: 0x0000 0000
The application must modify this register before enabling the endpoint. Once the endpoint is
enabled using the endpoint enable bit in the OTG_DIEPCTLx registers (EPENA bit in
OTG_DIEPCTLx), the core modifies this register. The application can only read this register
once the core has cleared the endpoint enable bit.
31
Res.

15

30

29

28

27

26

25

MCNT[1:0]

24

23

22

21

20

19

18

PKTCNT[9:0]

17

16

XFRSIZ[18:16]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

XFRSIZ[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 Reserved, must be kept at reset value.
Bits 30:29 MCNT[1:0]: Multi count
For periodic IN endpoints, this field indicates the number of packets that must be transmitted
per frame on the USB. The core uses this field to calculate the data PID for isochronous IN
endpoints.
01: 1 packet
10: 2 packets
11: 3 packets
Bits 28:19 PKTCNT[9:0]: Packet count
Indicates the total number of USB packets that constitute the transfer size amount of data for
this endpoint.
This field is decremented every time a packet (maximum size or short packet) is read from
the Tx FIFO.
Bits 18:0 XFRSIZ[18:0]: Transfer size
This field contains the transfer size in bytes for the current endpoint. The core only interrupts
the application after it has exhausted the transfer size amount of data. The transfer size can
be set to the maximum packet size of the endpoint, to be interrupted at the end of each
packet.
The core decrements this field every time a packet from the external memory is written to the
Tx FIFO.

1430/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.15.54 OTG device control OUT endpoint 0 control register
(OTG_DOEPCTL0)
Address offset: 0xB00
Reset value: 0x0000 8000
This section describes the OTG_DOEPCTL0 register. Nonzero control endpoints use
registers for endpoints 1–3.
31

30

EPENA EPDIS

29
Res.

28
Res.

27

26

SNAK

CNAK

w

w

25
Res.

24
Res.

23
Res.

22
Res.

21

20

19

18

EPTYP[1:0]

17

16

NAK
STS

Res.

STALL

SNPM

rs

rw

r

r

r
1

w

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

USBA
EP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

0

MPSIZ[1:0]
r

r

Bit 31 EPENA: Endpoint enable
The application sets this bit to start transmitting data on endpoint 0.
The core clears this bit before setting any of the following interrupts on this endpoint:
– SETUP phase done
– Endpoint disabled
– Transfer completed
Bit 30 EPDIS: Endpoint disable
The application cannot disable control OUT endpoint 0.
Bits 29:28 Reserved, must be kept at reset value.
Bit 27 SNAK: Set NAK
A write to this bit sets the NAK bit for the endpoint.
Using this bit, the application can control the transmission of NAK handshakes on an
endpoint. The core can also set this bit on a transfer completed interrupt, or after a SETUP
is received on the endpoint.
Bit 26 CNAK: Clear NAK
A write to this bit clears the NAK bit for the endpoint.
Bits 25:22 Reserved, must be kept at reset value.
Bit 21 STALL: STALL handshake
The application can only set this bit, and the core clears it, when a SETUP token is received
for this endpoint. If a NAK bit or Global OUT NAK is set along with this bit, the STALL bit
takes priority. Irrespective of this bit’s setting, the core always responds to SETUP data
packets with an ACK handshake.
Bit 20 SNPM: Snoop mode
This bit configures the endpoint to Snoop mode. In Snoop mode, the core does not check
the correctness of OUT packets before transferring them to application memory.
Bits 19:18 EPTYP[1:0]: Endpoint type
Hardcoded to 2’b00 for control.

RM0385 Rev 7

1431/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 17 NAKSTS: NAK status
Indicates the following:
0: The core is transmitting non-NAK handshakes based on the FIFO status.
1: The core is transmitting NAK handshakes on this endpoint.
When either the application or the core sets this bit, the core stops receiving data, even if
there is space in the Rx FIFO to accommodate the incoming packet. Irrespective of this bit’s
setting, the core always responds to SETUP data packets with an ACK handshake.
Bit 16 Reserved, must be kept at reset value.
Bit 15 USBAEP: USB active endpoint
This bit is always set to 1, indicating that a control endpoint 0 is always active in all
configurations and interfaces.
Bits 14:2 Reserved, must be kept at reset value.
Bits 1:0 MPSIZ[1:0]: Maximum packet size
The maximum packet size for control OUT endpoint 0 is the same as what is programmed in
control IN endpoint 0.
00: 64 bytes
01: 32 bytes
10: 16 bytes
11: 8 bytes

37.15.55 OTG device OUT endpoint x interrupt register (OTG_DOEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint number)
Address offset: 0xB08 + (x * 0x20)
Reset value: 0x0000 0080
This register indicates the status of an endpoint with respect to USB- and AHB-related
events. It is shown in Figure 468. The application must read this register when the OUT
endpoints interrupt bit of the OTG_GINTSTS register (OEPINT bit in OTG_GINTSTS) is set.
Before the application can read this register, it must first read the OTG_DAINT register to
get the exact endpoint number for the OTG_DOEPINTx register. The application must clear
the appropriate bit in this register to clear the corresponding bits in the OTG_DAINT and
OTG_GINTSTS registers.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

OUT
PKT
ERR

Res.

Res.

STSPH
SRX

OTEP
DIS

STUP

Res.

EP
DISD

XFRC

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Res.

NYET

NAK

BERR

rc_w1

rc_w1

rc_w1

Note:

1432/1709

Res.

Res.

rc_w1

Configuration register for USB OTG FS.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

OUT
PKT
ERR

Res.

B2B
STUP

STSPH
SRX

OTEP
DIS

STUP

AHB
ERR

EP
DISD

XFRC

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

STPK
TRX

NYET

NAK

BERR

rc_w1

rc_w1

rc_w1

rc_w1

Note:

Res.

Res.

rc_w1

Configuration register for USB OTG HS.
Bits 31:16 Reserved, must be kept at reset value.
Bit 15 STPKTRX: Setup packet received.
Applicable for control OUT endpoints in only in the Buffer DMA Mode. Set by the OTG_HS,
this bit indicates that this buffer holds 8 bytes of setup data. There is only one setup packet
per buffer. On receiving a setup packet, the OTG_HS closes the buffer and disables the
corresponding endpoint after SETUP_COMPLETE status is seen in the Rx FIFO. OTG_HS
puts a SETUP_COMPLETE status into the Rx FIFO when it sees the first IN or OUT token
after the SETUP packet for that particular endpoint. The application must then re-enable the
endpoint to receive any OUT data for the control transfer and reprogram the buffer start
address. Because of the above behavior, OTG_HS can receive any number of back to back
setup packets and one buffer for every setup packet is used.
Bit 14 NYET: NYET interrupt
This interrupt is generated when a NYET response is transmitted for a non isochronous
OUT endpoint.
Bit 13 NAK: NAK input
The core generates this interrupt when a NAK is transmitted or received by the device. In
case of isochronous IN endpoints the interrupt gets generated when a zero length packet is
transmitted due to unavailability of data in the Tx FIFO.
Bit 12 BERR: Babble error interrupt
The core generates this interrupt when babble is received for the endpoint.
Bits 11:10 Reserved, must be kept at reset value.
Bit 9 Reserved, must be kept at reset value.
Bit 8 OUTPKTERR: OUT packet error
This interrupt is asserted when the core detects an overflow or a CRC error for an OUT
packet. This interrupt is valid only when thresholding is enabled.
Bit 7 Reserved, must be kept at reset value.
Bit 6 B2BSTUP: Back-to-back SETUP packets received for USB OTG HS
Applies to control OUT endpoint only.
This bit indicates that the core has received more than three back-to-back SETUP packets
for this particular endpoint.
Bit 5 STSPHSRX: Status phase received for control write
This interrupt is valid only for control OUT endpoints. This interrupt is generated only after
OTG_FS/OTG_HS has transferred all the data that the host has sent during the data phase
of a control write transfer, to the system memory buffer. The interrupt indicates to the
application that the host has switched from data phase to the status phase of a control write
transfer. The application can use this interrupt to ACK or STALL the status phase, after it has
decoded the data phase.

RM0385 Rev 7

1433/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 4 OTEPDIS: OUT token received when endpoint disabled
Applies only to control OUT endpoints.
Indicates that an OUT token was received when the endpoint was not yet enabled. This
interrupt is asserted on the endpoint for which the OUT token was received.
Bit 3 STUP: SETUP phase done
Applies to control OUT endpoint only.
Indicates that the SETUP phase for the control endpoint is complete and no more back-toback SETUP packets were received for the current control transfer. On this interrupt, the
application can decode the received SETUP data packet.
Bit 2 AHBERR: AHB error for USB OTG HS
This is generated only in internal DMA mode when there is an AHB error during an AHB
read/write. The application can read the corresponding endpoint DMA address register to
get the error address.
Bit 1 EPDISD: Endpoint disabled interrupt
This bit indicates that the endpoint is disabled per the application’s request.
Bit 0 XFRC: Transfer completed interrupt
This field indicates that the programmed transfer is complete on the AHB as well as on the
USB, for this endpoint.

37.15.56 OTG device OUT endpoint 0 transfer size register
(OTG_DOEPTSIZ0)
Address offset: 0xB10
Reset value: 0x0000 0000
The application must modify this register before enabling endpoint 0. Once endpoint 0 is
enabled using the endpoint enable bit in the OTG_DOEPCTL0 registers (EPENA bit in
OTG_DOEPCTL0), the core modifies this register. The application can only read this
register once the core has cleared the endpoint enable bit.

31
Res.

30

29

STUPCNT[1:0]

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PKTCNT

Nonzero endpoints use the registers for endpoints 1–5[FS] /8[HS].

Res.

Res.

Res.

2

1

0

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

6

RM0385 Rev 7

4

3
XFRSIZ[6:0]

rw

1434/1709

5

rw

rw

rw

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 31 Reserved, must be kept at reset value.
Bits 30:29 STUPCNT[1:0]: SETUP packet count
This field specifies the number of back-to-back SETUP data packets the endpoint can
receive.
01: 1 packet
10: 2 packets
11: 3 packets
Bits 28:20 Reserved, must be kept at reset value.
Bit 19 PKTCNT: Packet count
This field is decremented to zero after a packet is written into the Rx FIFO.
Bits 18:7 Reserved, must be kept at reset value.
Bits 6:0 XFRSIZ[6:0]: Transfer size
Indicates the transfer size in bytes for endpoint 0. The core interrupts the application only
after it has exhausted the transfer size amount of data. The transfer size can be set to the
maximum packet size of the endpoint, to be interrupted at the end of each packet.
The core decrements this field every time a packet is read from the Rx FIFO and written to
the external memory.

37.15.57 OTG device OUT endpoint x DMA address register (OTG_DOEPDMAx)
(x = 0..8, where x = endpoint number)
Address offset: 0xB14 + (x * 0x20)
Reset value: 0x0000 0000
Note:
31

Configuration register applies only to USB OTG HS
30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DMAADDR[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DMAADDR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DMAADDR[31:0]: DMA Address
This field holds the start address in the external memory from which the data for the
endpoint must be fetched. This register is incremented on every AHB transaction.

RM0385 Rev 7

1435/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

37.15.58 OTG device OUT endpoint x control register (OTG_DOEPCTLx)
(x = 1..5[FS] /8[HS], where x = endpoint number)
Address offset for OUT endpoints: 0xB00 + (x * 0x20)
Reset value: 0x0000 0000
The application uses this register to control the behavior of each logical endpoint other than
endpoint 0.
31

30

EPENA EPDIS

29

28

27

26

25

24

23

22

21

20

SD1
PID/
SODD
FRM

SD0
PID/
SEVN
FRM

SNAK

CNAK

Res.

Res.

Res.

Res.

STALL

SNPM

rw/rs

rw

rw

5

4

rw

rs

rs

w

w

w

w

15

14

13

12

11

10

USBA
EP

Res.

Res.

Res.

Res.

rw

9

8

7

6

19

18

17

16

NAK
STS

EO
NUM/
DPID

rw

r

r

3

2

1

0

rw

rw

rw

rw

EPTYP[1:0]

MPSIZ[10:0]
rw

rw

rw

rw

rw

rw

Bit 31 EPENA: Endpoint enable
Applies to IN and OUT endpoints.
The application sets this bit to start transmitting data on an endpoint.
The core clears this bit before setting any of the following interrupts on this endpoint:
– SETUP phase done
– Endpoint disabled
– Transfer completed
Bit 30 EPDIS: Endpoint disable
The application sets this bit to stop transmitting/receiving data on an endpoint, even before
the transfer for that endpoint is complete. The application must wait for the endpoint
disabled interrupt before treating the endpoint as disabled. The core clears this bit before
setting the endpoint disabled interrupt. The application must set this bit only if endpoint
enable is already set for this endpoint.
Bit 29 SD1PID: Set DATA1 PID
Applies to interrupt/bulk IN and OUT endpoints only. Writing to this field sets the endpoint
data PID (DPID) field in this register to DATA1.
SODDFRM: Set odd frame
Applies to isochronous IN and OUT endpoints only. Writing to this field sets the Even/Odd
frame (EONUM) field to odd frame.
Bit 28 SD0PID: Set DATA0 PID
Applies to interrupt/bulk OUT endpoints only.
Writing to this field sets the endpoint data PID (DPID) field in this register to DATA0.
SEVNFRM: Set even frame
Applies to isochronous OUT endpoints only.
Writing to this field sets the Even/Odd frame (EONUM) field to even frame.
Bit 27 SNAK: Set NAK
A write to this bit sets the NAK bit for the endpoint.
Using this bit, the application can control the transmission of NAK handshakes on an
endpoint. The core can also set this bit for OUT endpoints on a transfer completed interrupt,
or after a SETUP is received on the endpoint.

1436/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 26 CNAK: Clear NAK
A write to this bit clears the NAK bit for the endpoint.
Bits 25:22 Reserved, must be kept at reset value.
Bit 21 STALL: STALL handshake
Applies to non-control, non-isochronous OUT endpoints only (access type is rw).
The application sets this bit to stall all tokens from the USB host to this endpoint. If a NAK
bit, Global IN NAK, or Global OUT NAK is set along with this bit, the STALL bit takes
priority. Only the application can clear this bit, never the core.
Applies to control endpoints only (access type is rs).
The application can only set this bit, and the core clears it, when a SETUP token is received
for this endpoint. If a NAK bit, Global IN NAK, or Global OUT NAK is set along with this bit,
the STALL bit takes priority. Irrespective of this bit’s setting, the core always responds to
SETUP data packets with an ACK handshake.
Bit 20 SNPM: Snoop mode
This bit configures the endpoint to Snoop mode. In Snoop mode, the core does not check
the correctness of OUT packets before transferring them to application memory.
Bits 19:18 EPTYP[1:0]: Endpoint type
This is the transfer type supported by this logical endpoint.
00: Control
01: Isochronous
10: Bulk
11: Interrupt
Bit 17 NAKSTS: NAK status
Indicates the following:
0: The core is transmitting non-NAK handshakes based on the FIFO status.
1: The core is transmitting NAK handshakes on this endpoint.
When either the application or the core sets this bit:
The core stops receiving any data on an OUT endpoint, even if there is space in the Rx
FIFO to accommodate the incoming packet.
Irrespective of this bit’s setting, the core always responds to SETUP data packets with an
ACK handshake.
Bit 16 EONUM: Even/odd frame
Applies to isochronous IN and OUT endpoints only.
Indicates the frame number in which the core transmits/receives isochronous data for this
endpoint. The application must program the even/odd frame number in which it intends to
transmit/receive isochronous data for this endpoint using the SEVNFRM and SODDFRM
fields in this register.
0: Even frame
1: Odd frame
DPID: Endpoint data PID
Applies to interrupt/bulk OUT endpoints only.
Contains the PID of the packet to be received or transmitted on this endpoint. The
application must program the PID of the first packet to be received or transmitted on this
endpoint, after the endpoint is activated. The application uses the SD0PID register field to
program either DATA0 or DATA1 PID.
0: DATA0
1: DATA1

RM0385 Rev 7

1437/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bit 15 USBAEP: USB active endpoint
Indicates whether this endpoint is active in the current configuration and interface. The core
clears this bit for all endpoints (other than EP 0) after detecting a USB reset. After receiving
the SetConfiguration and SetInterface commands, the application must program endpoint
registers accordingly and set this bit.
Bits 14:11 Reserved, must be kept at reset value.
Bits 10:0 MPSIZ[10:0]: Maximum packet size
The application must program this field with the maximum packet size for the current logical
endpoint. This value is in bytes.

37.15.59 OTG device OUT endpoint x transfer size register
(OTG_DOEPTSIZx) (x = 1..5[FS] /8[HS],
where x = Endpoint number)
Address offset: 0xB10 + (x * 0x20)
Reset value: 0x0000 0000
The application must modify this register before enabling the endpoint. Once the endpoint is
enabled using endpoint enable bit of the OTG_DOEPCTLx registers (EPENA bit in
OTG_DOEPCTLx), the core modifies this register. The application can only read this
register once the core has cleared the endpoint enable bit.
31
Res.

15

30

29

28

27

26

25

RXDPID/
STUPCNT[1:0]

24

23

22

21

20

19

18

PKTCNT[9:0]

17

16

XFRSIZ

r/rw

r/rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

XFRSIZ
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 Reserved, must be kept at reset value.
Bits 30:29 RXDPID[1:0]: Received data PID
Applies to isochronous OUT endpoints only.
This is the data PID received in the last packet for this endpoint.
00: DATA0
01: DATA2
10: DATA1
11: MDATA

1438/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

STUPCNT[1:0]: SETUP packet count
Applies to control OUT endpoints only.
This field specifies the number of back-to-back SETUP data packets the endpoint can
receive.
01: 1 packet
10: 2 packets
11: 3 packets
Bits 28:19 PKTCNT[9:0]: Packet count
Indicates the total number of USB packets that constitute the transfer size amount of data for
this endpoint.
This field is decremented every time a packet (maximum size or short packet) is written to
the Rx FIFO.
Bits 18:0 XFRSIZ: Transfer size
This field contains the transfer size in bytes for the current endpoint. The core only interrupts
the application after it has exhausted the transfer size amount of data. The transfer size can
be set to the maximum packet size of the endpoint, to be interrupted at the end of each
packet.
The core decrements this field every time a packet is read from the Rx FIFO and written to
the external memory.

37.15.60 OTG power and clock gating control register (OTG_PCGCCTL)
Address offset: 0xE00
Reset value: 0x200B 8000
This register is available in host and device modes.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

SUSP

PHY
SLEEP

ENL1
GTG

PHY
SUSP

Res.

GATE
HCLK

STPP
CLK

r

r

rw

r

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 SUSP: Deep Sleep
This bit indicates that the PHY is in Deep Sleep when in L1 state.
Bit 6 PHYSLEEP: PHY in Sleep
This bit indicates that the PHY is in the Sleep state.
Bit 5 ENL1GTG: Enable sleep clock gating
When this bit is set, core internal clock gating is enabled in Sleep state if the core cannot
assert utmi_l1_suspend_n. When this bit is not set, the PHY clock is not gated in Sleep
state.
Bit 4 PHYSUSP: PHY suspended
Indicates that the PHY has been suspended. This bit is updated once the PHY is suspended
after the application has set the STPPCLK bit.

RM0385 Rev 7

1439/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Bits 3:2 Reserved, must be kept at reset value.
Bit 1 GATEHCLK: Gate HCLK
The application sets this bit to gate HCLK to modules other than the AHB Slave and Master
and wakeup logic when the USB is suspended or the session is not valid. The application
clears this bit when the USB is resumed or a new session starts.
Bit 0 STPPCLK: Stop PHY clock
The application sets this bit to stop the PHY clock when the USB is suspended, the session
is not valid, or the device is disconnected. The application clears this bit when the USB is
resumed or a new session starts.

37.15.61 OTG_FS/OTG_HS register map
The table below gives the USB OTG register map and reset values.

VBVALOEN

SRQ

SRQSCS

0

0

0

Res.

1440/1709

RM0385 Rev 7

0

0

Res.

Res.

Res.

Res.

Res.

SEDET

1

0

1

Res.

Res.

Res.

Res.

Res.
1

0

Res.

Res.

0

Res.

0

TOCAL

0

Res.

0

GINTMSK

DMAEN

0

Res.

TXFELVL

Res.

0

Res.

0

PHYSEL
1

HBSTLEN

0

Res.

ULPIFSL
0

0

Res.

ULPIAR
0

0

PHYSEL

ULPICSM
0

TRDT

HNPCA

ULPIEVBUSD
0

1

0

SRPCAP

ULPIEVBUSI
0

0

0

0

SRPCAP

TSDPS
0

Res.

PCCI
0

PHYLPC

PTCI
0

Res.

ULPIIPD
0

1

0

HNPCAP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

0

Res.

FHMOD

0

Reset value

TRDT

0

Res.

OTG_
GUSBCFG

Res.

FHMOD
0

Res.

0

Res.

FDMOD

0x00C

Reset value

OTG_
GUSBCFG

Res.

0x00C

FDMOD

Reset value

0

TXFELVL

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
GAHBCFG

Res.

0x008

Res.

Reset value

0

PTXFELVL

0

PTXFELVL

0

Res.

-

Res.

AVALOEN

VBVALOVA
0

GINTMSK

BVALOEN

AVALOVAL

0

Res.

BVALOVAL

0

Res.

HNPRQ

HNGSCS

0

SRSSCHG

0

HNSSCHG

0

Res.

DHNPEN

HSHNPEN

0

Res.

0

Res.

Res.

EHEN

0

Res.

Res.

Res.

0

Res.

Res.
Res.

Res.

0

Res.

0

Res.

0

Res.

DBCT

CIDSTS
Res.

0

Res.

ASVLD

HNGDET

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
GAHBCFG

Res.

0x008

Res.

Reset value

Res.

BSVLD

1

ADTOCHG

0

Res.

OTGVER

0

IDCHNG

0
DBCDNE

0

Res.

0

Res.

Res.

CURMOD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
GOTGINT

Res.

0x004

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
GOTGCTL

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

0x000

Register
name

Res.

Offset

Res.

Table 269. OTG_FS/OTG_HS register map and reset values

0

0

TOCAL

0

0

0

0

OTG_
GINTSTS
DISCINT
CIDSCHG
Res.

Res.

Reset value
0
0
0
1

OTG_
GINTMSK
DISCINT
CIDSCHGM

Reset value
0
0
0
0

OTG_
GINTMSK

DISCINT

CIDSCHGM

LPMINTM

PTXFEM
HCIM
PRTIM

RSTDETM

Reset value

0

0

0

0

0

0

0

0

0
0
0
0
0
0

0
0

0

0

0

0

0

RM0385 Rev 7
ENUMDNEM
USBRST
USBSUSPM
ESUSPM

0
0
0
0

ENUMDNEM

USBRST

USBSUSPM

ESUSPM

0

0

0

0

0

0
MMISM

0
0
0
0
0
0

SOFM
MMISM

NPTXFE
RXFLVL
SOF
OTGINT
MMIS
CMOD

SOF
OTGINT
MMIS
CMOD

Res.

Res.

0
0

PSRST
CSRST
0

PSRST

0
CSRST

FCRST
0

Res.

Res.

TXFFLSH
RXFFLSH

0

Res.

TXFFLSH
RXFFLSH
0

RXFLVL

0

NPTXFE

0

GINAKEFF

0

Res.

TXFNUM

0

GONAKEFF

0

0

0

0

0

0

0

0

Res.

SOFM
OTGINT

0

OTGINT

GINAKEFF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TXFNUM

Res.

RXFLVLM

0

RXFLVLM

0

NPTXFEM

0

GINAKEFFM

0

NPTXFEM

0

GINAKEFFM

0
GONAKEFF

0

Res.

0

Res.

ESUSP

0

0

GONAKEFFM

ESUSP

USBSUSP

Res.

Res.

Res.

1
0

GONAKEFFM

USBSUSP

USBRST

0

Res.

USBRST

ENUMDNE

0

0

Res.

ENUMDNE

ISOODRP

Res.

Res.

AHBIDL

Reset value
0

Res.

ISOODRP

EOPF

Res.
0

Res.

ISOODRPM

0

ISOODRPM

EOPF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

OTG_
GRSTCTL
Res.

Register
name

0

Res.

EOPFM

Res.
0

EOPFM

Res.

IEPINT

0

Res.

OEPINT

0

Res.

IISOIXFR

0

Res.

IPXFR/INCOMPISOOUT

0

Res.

IEPINT

IEPINT

0

IEPINT

OEPINT

OEPINT

0

OEPINT

IISOIXFR

IISOIXFRM

0

IISOIXFRM

0
IPXFR/INCOMPISOOUT

0
IPXFRM/IISOOXFRM

0

IPXFRM/IISOOXFRM

0
DATAFSUSP

0

Res.

0

FSUSPM

1
Res.

RSTDET

0

RSTDETM

HPRTINT

0

HPRTINT

1

PRTIM

HCINT

0

HCINT

1

HCIM

PTXFE

0

PTXFE

0

PTXFEM

LPMINT

0

LPMINTM

DISCINT
CIDSCHG

Reset value
Res.

AHBIDL
DMAREQ

OTG_
GINTSTS
SRQINT

0x018
0

WKUPINT

0x018
1

SRQINT

0x014
Reset value

WKUPINT

0x014
OTG_
GRSTCTL

WUIM

0x010

SRQIM

0x010

WUIM

Offset

SRQIM

RM0385
USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

0
0

0
0
1
0
0
0
0
0

0
0
1
0
0
0
0
0

1441/1709

1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

0

0

0

0

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

Res.

Res.

Res.

Res.

Res.

0

0

0

0

1442/1709

0

0

0

0

0

0

0

0

0

0

BCNT
0

0

0

0

0

0

0

0

0

0

0

0

0

0

CHNUM
0

0

0

0

0

0

BCNT

0

0

EPNUM

0

0

0

EPNUM

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RXFD
0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

Res.

VBDEN

Res.

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

1

Res.

0

Res.

0

NPTXFSAV

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

1

Res.

0

0

0

X

PRODUCT_ID (for USB OTG FS)
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

BESLTHRS

LPMR
CNTSTS

0

0

0

0

0

0

LPM
RCNT

0

0

0

0

0

0

0

LPMCHIDX

0

0

0

0

0

0

0

0

0

1

0

LPM
RSP

0

0

0

0

0

0

0

PTXFSIZ
0

0

0

0

0

0

1

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

BESL

PTXSA
0

0

0

0

0

0

0

0

0

0

0

0

1

INEPTXFD
0

0

LPMEN

0

LPMACK

0

0

0

REMWAKE

0

0

L1DSEN

0

SLPSTS

0

L1RSMOK

0

SNDLPM

0

Res.

PRODUCT_ID (for USB OTG HS)

OTG_
DIEPTXF1
Reset value

0

0

L1SSEN

0x104

0

0

Res.

0

OTG_
HPTXFSIZ
Reset value

0

Res.

0

Reset value

0x100

0

Res.

0

ENBESL

OTG_
GLPMCFG

0

Res.

0

Res.

0x054

0

BCNT

NPTQXSAV

OTG_CID
Reset value

0

0

Res.

0x03C

0

Res.

NPTXQTOP

0

PWRDWN

0

OTG_CID
Reset value

0

0

Res.

0

Reset value
0x03C

0

0

Res.

0

0

DCDEN

0

Res.

Res.

Reset value

0

Res.

0

OTG_
HNPTXSTS

OTG_
GCCFG

0

CHNUM

NPTXFSA/TX0FSA

Res.

Reset value

0x038

0

NPTXFD/TX0FD

Res.

0x02C

0

0

Res.

0x028

0

DPID

Res.

PKTSTS

0

Reset value
OTG_
HNPTXFSIZ/
OTG_
DIEPTXF0

0

DPID

Res.

FRMNUM

0

0

BCNT

DPID

PKTSTS
0

0

Res.

Res.

0

Res.

Res.
Res.

Res.

Res.

Res.

0x024

Res.

OTG_
GRXFSIZ

0
Res.

Reset value

STSPHST

Res.

Res.

Res.

OTG_
GRXSTSP
(Device mode)

0

0

Res.

Reset value
0x020

0

PKTSTS

Res.

Res.

FRMNUM

0

DPID

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

OTG_
GRXSTSP
(host mode)

0
Res.

Reset value

STSPHST

Res.

Res.

OTG_
GRXSTSR
(Device mode)

Res.

0x01C

0

Res.

Reset value

PKTSTS

DCDET

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

OTG_
GRXSTSR
(host mode)

Offset

Res.

Register
name

Res.

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

0

0

0

0

INEPTXSA
0

0

0

0

0

RM0385 Rev 7

0

0

0

0

0

0

1

0

0

0

0

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

0

0

0

0

0

0

0

0

0

0

0

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

0

.
.
.
.
INEPTXFD
0

0

0

0

0

0

1

0

0

INEPTXSA

0

0

0

0

0

0

0

0

0

0

0

1

1

0

0

0

0

.
.
.
.

0

0

0

0

0

0

1

1

0

0

0

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

1

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

INEPTXSA

Res.

INEPTXFD

Res.

OTG_
HCFG

0

Res.

0x400

0

Res.

Reset value

1

INEPTXSA

Res.

OTG_
DIEPTXF7

0

Res.

0x120

0

Res.

.
.
.
.

0

Res.

Reset value
.
.
.
.

0

Res.

OTG_
DIEPTXF5

0

Res.

0x114

0

Res.

.
.
.
.

Res.

Reset value
.
.
.
.

INEPTXFD

FSLSS

OTG_
DIEPTXF2

Res.

0x108

Register
name

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

Reset value

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

Res.

EPDIR

EPTYP

MCNT

ODDFRM

0

0
LSDEV

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CHDIS

1

1

1

1

0

RM0385 Rev 7

0

0

0

0

1

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.
CHENA

DAD

0

1

0

0

PTCTL

PSPD

0

0

0

0

1

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

HAINTM
0

0

0

HAINT
0

0

0

PTXFSAVL

0

0

0

PTXQSAV

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

EPNUM

0

0

0

PCSTS

0

0

Reset value

1

PCDET

0

PTXQTOP

OTG_
HCCHAR0

1

PENA

0

0

PENCHNG

0

0

POCCHNG

0

Reset value

0x500

0

PRES

0

OTG_
HAINT

OTG_
HPRT

1

PSUSP

0

Reset value

0x440

0

PRST

0

Reset value

OTG_
HAINTMSK

1

Res.

OTG_
HPTXSTS

0

Reset value

0x418

1

PLSTS

0

0

FRNUM

Res.

0x414

1

FTREM
0

0

POCA

OTG_
HFNUM
Reset value

0x410

0

0

FRIVL

PPWR

0x408

RLDCTR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
HFIR

Res.

0x404

Res.

Reset value

FSLS
PCS

0

0

0

0

0

0

0

0

0

MPSIZ

0

0

0

0

0

0

0

0

1443/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

OTG_
HCTSIZ1
Reset value

0x534

1444/1709

DPID

0

0

0

XFRCM

STALLM

0

Res.

NAKM

0

CHHM

ACKM

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

EPDIR

EPNUM

0

0

0

XAC
TPOS

MPSIZ

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

0

0

0

STALLM

0

0
NAKM

0

0
ACKM

0
Res.NYE

0

TXERRM

0

BBERRM

Res.

Res.

Res.

Res.

Res.

Res.

0

XFRC

0

CHH

0

STALL

0

NAK

0

ACK

0

TXERR

0

BBERR

0

FRMOR

0

FRMORM

0

DTERR

0

DTERRM

0

Res.

PRTADDR

Res.

HUBADDR

0

0

0

0

0

0

0

XFRCM

Res.

0
COMPLSPLT

0

0

Res.

0

PKTCNT

0

0

XFRSIZ
0

0

0

0

0

OTG_
HCDMA1
Reset value

0

0

Reset value

0x530

0

CHHM

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
HCINTMSK1

0

0

Reset value

0x52C

0

0

Res.

0

Res.

0

0
LSDEV

0

EPTYP

0

Res.

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

0

Res.

0

Res.

0

MCNT

0

Res.

Res.

0

Res.

OTG_
HCINT1

0

Res.

0

0

Res.

Reset value

0

Res.

OTG_
HCSPLT1

0

Res.

0

Res.

ODDFRM

0

0

DAD

Res.

CHDIS

0

0

Res.

CHENA

Reset value

0

Res.

OTG_
HCCHAR1

Res.

0

Res.

0

Res.

0

SPLITEN

0x528

Reset value

Res.

0x524

0

0

DMAADDR

Res.

0x520

0

XFRSIZ

OTG_
HCDMA0

0x514

0

0
XFRC

Res.

PKTCNT

0

0

Res.

Reset value

DPID

Res.

0x510

Res.

OTG_
HCTSIZ0

Res.

Reset value

0

Res.NYE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
HCINTMSK0

Res.

0x50C

Res.

Reset value

0
Res.

0

CHH

0
NAK

0

STALL

0

ACK

0
TXERR

0
BBERR

0

TXERRM

Res.

0

FRMOR

Res.

0

BBERRM

0

FRMORM

0

Res.

0

DTERR

0

PRTADDR

DTERRM

0

Res.

HUBADDR

Res.

Res.

COMPLSPLT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

XAC
TPOS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
HCINT0

Res.

0
Res.

Reset value

Res.

SPLITEN

0x508

OTG_
HCSPLT0

Res.

0x504

Res.

Register
name

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMAADDR
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RM0385 Rev 7

0

0

0

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

0

0

0

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

XFRCM

0

STALLM

0

NAKM

Res.

Res.

Res.

Res.

Res.

0

XFRC

0

CHH

0
NAK

0

STALL

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
XFRC

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

.
.
.
.
LSDEV

Res.

EPDIR

0

-

0

Res.

COMPLSPLT

RM0385 Rev 7

0

0

0

XAC
TPOS

MPSIZ

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

DTERR

FRMOR

BBERR

TXERR

Res.

ACK

NAK

STALL

PRTADDR

Res.

HUBADDR

0

Res.

Reset value

EPNUM

Res.

Res.

EPTYP
Res.

Res.

0

Res.

0

Res.

MCNT
Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

OTG_
HCINT15

0

Res.

0

0

Res.

Reset value

0

Res.

OTG_
HCSPLT15

0

Res.

0

Res.

ODDFRM

0

Res.

0

Res.

CHDIS

Reset value

DAD

Res.

OTG_
HCCHAR15

CHENA

0x6E8

0

0

XFRSIZ

.
.
.
.

SPLITEN

0x6E4

0

0

DMAADDR

Res.

0x6E0

0

0

ACK

0

ACKM

Res.

0

TXERR

Res.

0

Res.NYE

Res.

0

BBERR

Res.

0

TXERRM

0

0

PRTADDR

FRMOR

0

0

Res.

Reset value
.
.
.
.

0

0

BBERRM

0

PKTCNT

OTG_
HCDMA11

Res.

0x674

0

0

CHH

Res.

Reset value

DPID

Res.

0x670

0

FRMORM

0

Reset value
OTG_
HCTSIZ11

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
HCINTMSK11

0

HUBADDR

Reset value

0x66C

0

Res.

XAC
TPOS

0

Res.

0

CHHM

0

DTERR

0

MPSIZ

DTERRM

Res.

EPDIR

LSDEV
Res.
Res.

0
COMPLSPLT

0

EPNUM

Res.

EPTYP
Res.

0

Res.

Res.

0

Res.

MCNT
Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

OTG_
HCINT11

0

Res.

0

0

Res.

Reset value

0

Res.

OTG_
HCSPLT11

Res.

0

DAD

Res.

0

Res.

0x668

0

Res.

0x664

Reset value

Res.

0x660

OTG_
HCCHAR11

ODDFRM

.
.
.
.
CHDIS

.
.
.
.
CHENA

.
.
.
.

SPLITEN

Register
name

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

0

0

0

0

0

0

0

1445/1709
1514

1446/1709

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

OTG_
DVBUSDIS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0x828

Reset value

Res.

0x81C

Res.

0x818

Res.

0x814
OTG_
DOEPMSK

Reset value

0

0

0

0

0

0

OTG_
DAINT

OTG_
DAINTMSK

0

0

0

0

0

0

0

0

0

Reset value

RM0385 Rev 7

Reset value

0

0

0

0

Reset value

0

0

0
0

0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0

Res.
NZLSOHSK

0
0
0
0
0
0
0
0
0

0
0
0

0

0

0

0

0

1

Res.

0

OEPINT

0

0

0

0

0

1

0

OEPM

0

1

0

0

1

1
INEPNEM
INEPNMM
ITTXFEMSK
TOM
AHBERRM
EPDM
XFRCM

0
0
0
0
0
0
0

Res.

0

B2BSTUPM

Res.

GINSTS
SDIS
RWUSIG

0
0
0
0
0
1
0

Res.
Res.
Res.
EERR

TXERRM
Res.NYE
ACKM
NAKM
STALLM

0
0
0
0
0

0
0

0

0

DSPD

BBERRM
0

CHHM
XFRCM

Res.

FRMORM
0

SUSPSTS

DAD

DTERRM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

ENUMSPD

GONSTS

0

TCTL

SGINAK

0

Res.

0

CGINAK

0

XFRCM

FNSOF

EPDM

0

0

AHBERRM

0

0

STUPM

0

0

OTEPDM

0

SGONAK

0

Res.

0

PFIVL

0

TXFURM

0

Res.

Res.

0

Res.

0

Res.

OTG_
DCFG
Res.

PKTCNT

OUTPKTERRM

0

0

CGONAK

0

Res.

0

Res.

Reset value

Res.

0

Res.

0

Res.

DMAADDR

0

POPRGDNE

0

Res.

0
XCVRDLY

0

Res.

0

Res.

0

Res.

0

NAKM

DEV
LN
STS

BERRM

0

Res.

0
ERRATIM

0

Res.

Reset value
0

NAKMSK

0

Res.

Res.

0

Res.

0

NYETMSK

0

Res.

Res.

DSBESLRJCT

0

Res.

OTG_
HCDMA15
0

Res.

0

Res.

Reset value
0

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

Res.

Reset value

Res.

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

Res.
DPID

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

Res.

Res.

Res.

Res.

0

Res.

OTG_
DIEPMSK
Res.

OTG_
DSTS
0

Res.

OTG_
DCTL
0

Res.

0x810

Res.

0x808

Res.

0x804
Res.

Reset value

Res.

0x800

Res.

0x6F4
OTG_
HCTSIZ15

Res.

0x6F0

Res.

OTG_
HCINTMSK15

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

0x6EC

Res.

Offset

Res.

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
RM0385

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

0
0

XFRSIZ

0
0
0

0
0
0
0

0
0
0
0
0

IEPINT

IEPM

VBUSDT

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

1

0

1

1

1

0x900

0x900
OTG_
DIEPCTL0

Reset value
0
0

OTG_
DIEPCTL0

Reset value

0

0

0
SNAK
CNAK

0
0

SNAK

CNAK

0

0

0

0

0

0

TXFNUM

0

0

0

0

RM0385 Rev 7

0

0

0
0

0

0

0

0

0
0

0

0
AHBERRM
EPDM
XFRCM

0
0
0
0

Res.

ITTXFEMSK
TOM

0

AHBERRM
EPDM
XFRCM

0

0

1

0

0

Res.

Res.
Res.

0
0
0

0
0
0

0

ISOTHREN

0

0
NONISOTHREN

0

Res.

1

Res.

0

Res.

INEPTXFEM

1

IEP1INT

0

IEP1INTM

0

Res.

Res.

Res.

0

Res.

TXTHRLEN

MPSIZ

STUPM

0

Res.

0
OTEPDM

Res.

1

Res.

Res.

0

Res.

0

Res.

Res.

0

Res.

0

0

Res.

INEPNEM

-

B2BSTUPM

Res.

0

Res.

0

1

Res.

Res.

0

Res.

Res.

Res.

1

Res.

0
TXFURM

0

Res.

0

OUTPKTERRM

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

0

Res.

0

1

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

Res.

RXTHREN

0

Res.

Res.

Res.

Res.

0

Res.

Res.

0

Res.

BERRM

0

Res.

Res.
NAKM

Res.

Res.

Res.

0

Res.

NAKMSK

Res.

Res.

OEP1INT

Res.

Res.

Res.

Res.

ARPEN

Res.

Res.

Res.

Res.

0

Res.

NYETMSK

0

Res.

Reset value

Res.

Reset value

Res.

0
Res.

Res.

OEP1INTM

Res.

Res.

Res.

Reset value

USBAEP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RXTHRLEN

Res.

NAKSTS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

USBAEP

0
EPTYP

Res.

Res.

Res.

Res.

Reset value

EONUM/DPID

0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

NAKSTS

0

EPTYP

0
STALL

TXFNUM

Res.

0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

STALL

Res.

OTG_HS_
DOEPEACH
MSK1

Res.

OTG_HS_
DIEPEACH
MSK1
Res.

OTG_DEACHI
NTMSK

SD0PID/SEVNFRM

0x884

SODDFRM/SD1PID

0x844
OTG_
DEACHINT

Res.

0x83C
OTG_DIE
PEMPMSK

Res.

0x838
OTG_
DTHRCTL

Res.

0x834

EPDIS

0x830

EPENA

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

OTG_DVB
USPULSE
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Register
name

Res.

0x82C

EPDIS

Offset

EPENA

RM0385
USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

DVBUSP

0
0

0

0

0
0
0
0
0

MPSIZ
0
0

0

0

1447/1709

1514

0x940

.
.
.
.

1448/1709

Reset value

0

0

CNAK

OTG_
DIEPCTL2

SNAK

0
0
0
0
0

Res.
Res.
Res.
Res.

0
0
0
0

OTG_
DIEPINT1

0

0

0

0
TXFNUM

0

0

0

0

0

Res.
Res.
Res.

Reset value

0

0

.
.
.
.

RM0385 Rev 7
0

Reset value

0

0

0

.
.
.
.
0
0
0

0

0
0
0

PKTCNT

0

0
0
0
0
0

0

0

0

0

1

0
0
0
0
0
0
0
0
0
0
0

0
XFRSIZ

0

INEPTFSAV

1

MPSIZ

0
XFRC

0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0

EPDISD

0

0

AHBERR

Res.

0

TOC

Res.

0

ITTXFE

Res.

0

INEPNM

Reset value
0

TXFE

OTG_
DTXFSTS0
0

INEPNE

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0
1
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0

0
0
0
0
0
0

0

0

0

0

0

0

0

ITTXFE
TOC
AHBERR

0
0
0
0
0

0

0

0

0

0

0

0

0

0

0

XFRC

INEPNM

1

EPDISD

TXFE
Res.

INEPNE

TXFIFOUDRN

Res.

Res.

PKTDRPSTS

Res.

NAK

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

TXFIFOUDRN

0

Res.

0

Res.

0

Res.

0

Res.

0

PKTDRPSTS

0

Res.

0

Res.

0

Res.

Res.

Res.

Reset value

NAK

0

Res.

USBAEP

0

Res.

0

Res.

EONUM/DPID

0

Res.

0

Res.

NAKSTS

0

Res.

EPTYP

0

Res.

Res.

STALL

0

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

CNAK

0

USBAEP

0

Res.

SNAK

0

Res.

0

Res.

OTG_
DIEPDMA

EONUM/DPID

0

Res.

SD0PID/SEVNFRM

0
TXFNUM

PKT
CNT

NAKSTS

0

Res.

SODDFRM/SD1PID

Reset value

Res.

Reset value

Res.

0

EPTYP

0

Res.

EPDIS

Reset value

Res.

0

Res.

MCNT

STALL

OTG_
DTXFSTS1
0

Res.

Reset value

SODDFRM

0x938
OTG_
DIEPTSIZ1

SD0PID/SEVNFRM

0x930
EPENA

0x928
OTG_
DIEPCTL1

Res.

0x920

Res.

0x918
OTG_
DIEPTSIZ0

Res.

0x914
OTG_
DIEPINT0

Res.

0x910

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

0x908

EPDIS

Offset

EPENA

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
RM0385

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

0
0

XFRSIZ

DMAADDR

INEPTFSAV

0
0
0
0
0
0
0

0
0
0
0
0
0
0

0
0
0
0
0
0

MPSIZ

0x9E8

OTG_
DIEPINT7

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

NAK

Res.

PKTDRPSTS

Res.

0
0
Res.

.
.
.
.

0
0
0
0

Res.
Res.
Res.
Res.

0
0

USBAEP

.
.
.
.
0

NAKSTS

Reset value

EONUM/DPID

EPTY
P

Reset value

RM0385 Rev 7
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

.
.
.
.

.
.
.
.

Reset value

0

0

0
0
0

PKTCNT

0

.
.
.
.

0

0

0

0
0

0

.
.
.
.
INEPTFSAV

1

0

0

0

XFRC

0

EPDISD

0

TOC

0

AHBERR

0

ITTXFE

0

INEPNM

0

TXFE

0

INEPNE

0

Res.

0

TXFIFOUDRN

Res.

PKTDRPSTS

Res.

Res.

Res.

Res.

Res.

USBAEP
0

NAK

NAKSTS
EONUM/DPID

EPTYP

Res.

STALL

0

Res.

.
.
.
.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

XFRC

0

Res.

0

0

EPDISD

0

Res.

0
STALL

TXFNUM

0

AHBERR

0

Res.

0

0

TOC

0

Res.

0

0

ITTXFE

0

Res.

0

0

INEPNM

0

Res.

0
0

TXFE

0

Res.

0
0

INEPNE

0

Res.

SNAK
CNAK

0

Res.

SODDFRM

0

SD0PID/SEVNFRM

EPDIS

0
0

Res.

Res.

Res.

Res.

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
EPENA

Reset value
0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
DIEPCTL5

0

Res.

0

Res.

0
SNAK

0
CNAK

Reset value
SODDFRM

OTG_
DIEPCTL7
SD0PID/SEVNFRM

Res.

Register
name

TXFNUM

TXFIFOUDRN

0

Res.

Reset value

Res.

0x9B0

OTG_
DIEPTSIZ5

Res.

.
.
.
.

Res.

0x9E0

Res.

.
.
.
.
OTG_
DTXFSTS5

MCNT

0x9B8
OTG_
DIEPINT5

Res.

.
.
.
.

EPDIS

0x9A8

EPENA

.
.
.
.

Res.

0x9A0

Res.

Offset

Res.

RM0385
USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

MPSIZ

1
0
0
0
0
0
0
0

0
0
0
0
0
0
0

0

MPSIZ

0
0
0
0
0
0
0
0

.
.
.
.
XFRSIZ

0

1

0

0

0

0

0

0

0

1449/1709

1514

0xB30

OTG_
DOEPTSIZ1

Reset value

1450/1709
0

OTG_
DOEPINT1

Res.

0

0

0

0

0
0
0
0
0

0

0

0

0

0
NAKSTS
EONUM/DPID
USBAEP

0
0
0
0
0
0

Res.

Res.

Res.

STPKTRX

NYET

NAK

BERR

Reset value
0

Res.

0

SNPM

0

Res.

0

STALL

0

0

0

0

0

0

0

0

0

RM0385 Rev 7

0

0

0

0

0

0

PKTCNT

0
0

0
0

0
0

0
0

0
0
0
0
0
0
0
0
0
0
0

0

XFRSIZ

0

XFRC

0
Res.

Res.

Res.

STSPHSRX
OTEPDIS
STUP
AHBERR
EPDISD
XFRC

Res.

OUTPKTERR

Res.

Res.

B2BSTUP

0

EPDISD

0

0
0
1
0
0
0
0
0
0
0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0

1

MPSIZ

0

Res.

0

AHBERR

0

0

STUP

0

0

OTEPDIS

0

0

STSPHSRX

0

0

Res.

0

Res.

0

B2BSTUP

BERR

0

Res.

0

Res.

Res.

0

Res.

NAK

0

Res.

0

USBAEP

Res.

Res.

Res.

0

Res.

NYET

0

Res.

Reset value
STPKTRX

Res.

NAKSTS

Reset value
0

Res.

Res.
Res.

Res.

Res.

.
.
.
.

Res.

Res.

0

0

OUTPKTERR

0

Res.

EP
TYP

0

Res.

0

Res.

OTG_
DOEPDMA0
0

Res.

0

0

Res.

0

EPTYP

0

Res.

Res.

0

Res.

0
Res.

SNPM

0

Res.

Res.

Res.

0

PKTCNT

STALL

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

PKTCNT

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

0

0

Res.

0

0

Res.

0
Res.

CNAK

0

Res.

Res.

Res.

0

Res.

Res.

SNAK

Res.
0

Res.

Res.

Res.

Res.
MCNT

Res.

0
0

Res.

STUP
CNT

0

Res.

OTG_
DOEPINT0
Res.

0

Res.

EPDIS

0
0

Res.

EPENA
0

Res.

Reset value
0

CNAK

OTG_
DOEPCTL1
0

SNAK

0

Res.

Reset value

SODDFRM

OTG_
DOEPTSIZ0

SD0PID/SEVNFRM

0

Res.

0xB28
Reset value

Res.

0xB20
Reset value

Res.

0xB08
OTG_
DOEPCTL0

Res.

0x9F8
OTG_
DTXFSTS7

Res.

Reset value

EPDIS

0xB14

EPENA

0xB10

Res.

0xB00

Res.

.
.
.
.

Res.

0x9F0
OTG_
DIEPTSIZ7

RXDPID/
STUPCNT

Offset
Register
name
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
RM0385

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

.
.
.
.
.
.
.
.
.
.
.
.
XFRSIZ

.
.
.
.
INEPTFSAV

0
0
0
0
0
0

0
0

0
0

0
0
0
0
0
0
0

XFRSIZ

DMAADDR
0
0
0
0
0
0
0

0
0
0
0
0
0
0

MPSIZ

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

NAK

BERR

Res.

Res.

0

0

0

0

XFRC

0

0

EPDISD

0

0

0

-

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

XFRSIZ

0

0

0

0

0

0

0

0

0

0

0

0

Res.

0

0

STUP

NYET

0

0

AHBERR

STPKTRX

0

0

OTEPDIS

Res.

0

0

STSPHSRX

Res.

0

MPSIZ

0

Res.

0

0

0

0

Res.

RXDPID/
STUPCNT
0

0

0

0

0

0

0

0

BERR

Res.

Res.

0

0

0

0

0

0

XFRC

NAK

PKTCNT

0

EPDISD

NYET

-

0

AHBERR

STPKTRX

0

0

STUP

Res.

0

0

OTEPDIS

Res.

0

0

STSPHSRX

Res.

0

0

Res.

0

B2BSTUP

0

Res.

USBAEP

0

MPSIZ

OUTPKTERR

NAKSTS

EONUM/DPID

0

EPTYP

SNPM

Res.

0

Res.

Res.

0

Res.

Res.

STALL

Res.

0

Res.

OTG_
DOEPINT8

Res.

0

Res.

0

Res.

0

Res.

0

Res.

SNAK

CNAK

0

Res.

SODDFRM

SD0PID/SEVNFRM

0

Res.

EPDIS

Reset value

Res.

EPENA

.
.
.
.

OTG_
DOEPCTL8

0

0

0

0

0

0

0

XFRSIZ

0

0

0

0

0

OTG_
DOEPDMA8
Reset value

0

Res.

0

Res.

Res.

RXDPID/
STUPCNT
0

Reset value

0xC14

0

B2BSTUP

0

.
.
.
.

OTG_
DOEPTSIZ8

0

Res.

USBAEP

0

Reset value

0xC10

0

OUTPKTERR

NAKSTS

EONUM/DPID

0

EPTYP

Res.

0

Res.

Res.

SNPM

Res.

0

Res.

Res.

0

PKTCNT

Res.

0xC08

0

Res.

OTG_
DOEPINT5

Res.

0

Res.

0xC00

0

STALL

0

Reset value
.
.
.
.

0

Res.

0

Res.

SNAK

CNAK

0

Res.

SODDFRM

SD0PID/SEVNFRM

0

Res.

EPDIS

0

Res.

EPENA

Reset value

Res.

OTG_
DOEPCTL5

OTG_
DOEPTSIZ5

0

.
.
.
.

Reset value

0xBB0

0

Res.

0

Res.

0

Res.

0xBA8

0

Res.

0xBA0

0

.
.
.
.

Res.

Reset value
.
.
.
.

Res.

DMAADDR

Res.

OTG_
DOEPDMA1

Res.

0xB34

Register
name

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMAADDR
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RM0385 Rev 7

0

0

0

1451/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

1452/1709

RM0385 Rev 7

STPPCLK

0

Res.

0

GATEHCLK

ENL1GTG

PHYSUSP

0

Reset value

Res.

PHYSLEEP

Res.

SUSP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
PCGCCTL

Res.

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

0xE00

Register
name

Res.

Offset

Res.

Table 269. OTG_FS/OTG_HS register map and reset values (continued)

0

0

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.16

OTG_FS/OTG_HS programming model

37.16.1

Core initialization
The application must perform the core initialization sequence. If the cable is connected
during power-up, the current mode of operation bit in the OTG_GINTSTS (CMOD bit in
OTG_GINTSTS) reflects the mode. The OTG_FS/OTG_HS controller enters host mode
when an “A” plug is connected or device mode when a “B” plug is connected.
This section explains the initialization of the OTG_FS/OTG_HS controller after power-on.
The application must follow the initialization sequence irrespective of host or device mode
operation. All core global registers are initialized according to the core’s configuration:
1.

2.

3.

Program the following fields in the OTG_GAHBCFG register:
–

Global interrupt mask bit GINTMSK = 1

–

Rx FIFO non-empty (RXFLVL bit in OTG_GINTSTS)

–

Periodic Tx FIFO empty level

Program the following fields in the OTG_GUSBCFG register:
–

HNP capable bit

–

SRP capable bit

–

OTG_FS/OTG_HS timeout calibration field

–

USB turnaround time field

The software must unmask the following bits in the OTG_GINTMSK register:
OTG interrupt mask
Mode mismatch interrupt mask

4.

37.16.2

The software can read the CMOD bit in OTG_GINTSTS to determine whether the
OTG_FS/OTG_HS controller is operating in host or device mode.

Host initialization
To initialize the core as host, the application must perform the following steps:

RM0385 Rev 7

1453/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

Program the HPRTINT in the OTG_GINTMSK register to unmask

2.

Program the OTG_HCFG register to select full-speed host

3.

Program the PPWR bit in OTG_HPRT to 1. This drives VBUS on the USB.

4.

Wait for the PCDET interrupt in OTG_HPRT0. This indicates that a device is
connecting to the port.

5.

Program the PRST bit in OTG_HPRT to 1. This starts the reset process.

6.

Wait at least 10 ms for the reset process to complete.

7.

Program the PRST bit in OTG_HPRT to 0.

8.

Wait for the PENCHNG interrupt in OTG_HPRT.

9.

Read the PSPD bit in OTG_HPRT to get the enumerated speed.

RM0385

10. Program the HFIR register with a value corresponding to the selected PHY clock 1
11. Program the FSLSPCS field in the OTG_HCFG register following the speed of the
device detected in step 9. If FSLSPCS has been changed a port reset must be
performed.
12. Program the OTG_GRXFSIZ register to select the size of the receive FIFO.
13. Program the OTG_HNPTXFSIZ register to select the size and the start address of the
Non-periodic transmit FIFO for non-periodic transactions.
14. Program the OTG_HPTXFSIZ register to select the size and start address of the
periodic transmit FIFO for periodic transactions.
To communicate with devices, the system software must initialize and enable at least one
channel.

37.16.3

Device initialization
The application must perform the following steps to initialize the core as a device on powerup or after a mode change from host to device.
1.

2.

3.

Program the following fields in the OTG_DCFG register:
–

Device speed

–

Non-zero-length status OUT handshake

Program the OTG_GINTMSK register to unmask the following interrupts:
–

USB reset

–

Enumeration done

–

Early suspend

–

USB suspend

–

SOF

Wait for the USBRST interrupt in OTG_GINTSTS. It indicates that a reset has been
detected on the USB that lasts for about 10 ms on receiving this interrupt.

Wait for the ENUMDNE interrupt in OTG_GINTSTS. This interrupt indicates the end of reset
on the USB. On receiving this interrupt, the application must read the OTG_DSTS register
to determine the enumeration speed and perform the steps listed in Endpoint initialization on
enumeration completion on page 1488.
At this point, the device is ready to accept SOF packets and perform control transfers on
control endpoint 0.

1454/1709

RM0385 Rev 7

RM0385

37.16.4

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

DMA mode
The OTG host uses the AHB master interface to fetch the transmit packet data (AHB to
USB) and receive the data update (USB to AHB). The AHB master uses the programmed
DMA address (OTG_HCDMAx register in host mode and
OTG_DIEPDMAx/OTG_DOEPDMAx register in peripheral mode) to access the data
buffers.

37.16.5

Host programming model
Channel initialization
The application must initialize one or more channels before it can communicate with
connected devices. To initialize and enable a channel, the application must perform the
following steps:
1.
2.

Program the OTG_GINTMSK register to unmask the following:
Channel interrupt
–

Non-periodic transmit FIFO empty for OUT transactions (applicable when
operating in pipelined transaction-level with the packet count field programmed
with more than one).

–

Non-periodic transmit FIFO half-empty for OUT transactions (applicable when
operating in pipelined transaction-level with the packet count field programmed
with more than one).

3.

Program the OTG_HAINTMSK register to unmask the selected channels’ interrupts.

4.

Program the OTG_HCINTMSK register to unmask the transaction-related interrupts of
interest given in the host channel interrupt register.

5.

Program the selected channel’s OTG_HCTSIZx register with the total transfer size, in
bytes, and the expected number of packets, including short packets. The application
must program the PID field with the initial data PID (to be used on the first OUT
transaction or to be expected from the first IN transaction).

6.

Program the OTG_HCCHARx register of the selected channel with the device’s
endpoint characteristics, such as type, speed, direction, and so forth. (The channel can
be enabled by setting the channel enable bit to 1 only when the application is ready to
transmit or receive any packet).

7.

Program the selected channels in the OTG_HCSPLTx register(s) with the hub and port
addresses (split transactions only).

8.

Program the selected channels in the OTG_HCDMAx register(s) with the buffer start
address (DMA transactions only).

Halting a channel
The application can disable any channel by programming the OTG_HCCHARx register with
the CHDIS and CHENA bits set to 1. This enables the OTG_FS/OTG_HS host to flush the
posted requests (if any) and generates a channel halted interrupt. The application must wait
for the CHH interrupt in OTG_HCINTx before reallocating the channel for other transactions.
The OTG_FS/OTG_HS host does not interrupt the transaction that has already been started
on the USB.
To disable a channel in DMA mode operation, the application does not need to check for
space in the request queue. The OTG_HS host checks for space to write the disable

RM0385 Rev 7

1455/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

request on the disabled channel’s turn during arbitration. Meanwhile, all posted requests are
dropped from the request queue when the CHDIS bit in OTG_HCCHARx is set to 1.
Before disabling a channel, the application must ensure that there is at least one free space
available in the non-periodic request queue (when disabling a non-periodic channel) or the
periodic request queue (when disabling a periodic channel). The application can simply
flush the posted requests when the request queue is full (before disabling the channel), by
programming the OTG_HCCHARx register with the CHDIS bit set to 1, and the CHENA bit
cleared to 0.
The application is expected to disable a channel on any of the following conditions:
1.

When an STALL, TXERR, BBERR or DTERR interrupt in OTG_HCINTx is received for
an IN or OUT channel. The application must be able to receive other interrupts
(DTERR, Nak, data, TXERR) for the same channel before receiving the halt.

2.

When an XFRC interrupt in OTG_HCINTx is received during a non periodic IN transfer
or high-bandwidth interrupt IN transfer

3.

When a DISCINT (disconnect device) interrupt in OTG_GINTSTS is received. (The
application is expected to disable all enabled channels).

4.

When the application aborts a transfer before normal completion.

Ping protocol
When the OTG_HS host operates in high speed, the application must initiate the ping
protocol when communicating with high-speed bulk or control (data and status stage) OUT
endpoints.The application must initiate the ping protocol when it receives a
NAK/NYET/TXERR interrupt. When the OTG_HS host receives one of the above
responses, it does not continue any transaction for a specific endpoint, drops all posted or
fetched OUT requests (from the request queue), and flushes the corresponding data (from
the transmit FIFO).This is valid in slave mode only. In Slave mode, the application can send
a ping token either by setting the DOPING bit in OTG_HCTSIZx before enabling the channel
or by just writing the OTG_HCTSIZx register with the DOPING bit set when the channel is
already enabled. This enables the OTG_HS host to write a ping request entry to the request
queue. The application must wait for the response to the ping token (a NAK, ACK, or
TXERR interrupt) before continuing the transaction or sending another ping token. The
application can continue the data transaction only after receiving an ACK from the OUT
endpoint for the requested ping. In DMA mode operation, the application does not need to
set the DOPING bit in OTG_HCTSIZx for a NAK/NYET response in case of bulk/control
OUT. The OTG_HS host automatically sets the DOPING bit in OTG_HCTSIZx, and issues
the ping tokens for bulk/control OUT. The OTG_HS host continues sending ping tokens until
it receives an ACK, and then switches automatically to the data transaction.

Operational model
The application must initialize a channel before communicating to the connected device.
This section explains the sequence of operation to be performed for different types of USB
transactions.
•

Writing the transmit FIFO
The OTG_FS/OTG_HS host automatically writes an entry (OUT request) to the
periodic/non-periodic request queue, along with the last 32-bit word write of a packet.
The application must ensure that at least one free space is available in the
periodic/non-periodic request queue before starting to write to the transmit FIFO. The
application must always write to the transmit FIFO in 32-bit words. If the packet size is
non-32-bit word aligned, the application must use padding. The OTG_FS/OTG_HS

1456/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
host determines the actual packet size based on the programmed maximum packet
size and transfer size.
Figure 469. Transmit FIFO write task
Start
Read OTG_HPTXSTS /OTG_HNPTXSTS
registers for available FIFO and queue
spaces

Wait for NPTXFE/PTXFE interrupt in
OTG_GINTSTS

No

1 MPS
or LPS FIFO space
available?
Yes

Yes

Write 1 packet
data to transmit
FIFO

More
packets to
send?
No
MPS: Maximum packet size
LPS: Last packet size

•

Done
ai15673c

Reading the receive FIFO
The application must ignore all packet statuses other than IN data packet (bx0010).

RM0385 Rev 7

1457/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Figure 470. Receive FIFO read task

•

Bulk and control OUT/SETUP transactions
A typical bulk or control OUT/SETUP pipelined transaction-level operation is shown in
Figure 471. See channel 1 (ch_1). Two bulk OUT packets are transmitted. A control
SETUP transaction operates in the same way but has only one packet. The
assumptions are:

•

–

The application is attempting to send two maximum-packet-size packets (transfer
size = 1, 024 bytes).

–

The non-periodic transmit FIFO can hold two packets (1 KB for HS/128 bytes for
FS).

–

The non-periodic request queue depth = 4.

Normal bulk and control OUT/SETUP operations
The sequence of operations in (channel 1) is as follows:

1458/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

Initialize channel 1

2.

Write the first packet for channel 1

3.

Along with the last word write, the core writes an entry to the non-periodic request
queue

4.

As soon as the non-periodic queue becomes non-empty, the core attempts to send an
OUT token in the current frame

5.

Write the second (last) packet for channel 1

6.

The core generates the XFRC interrupt as soon as the last transaction is completed
successfully

7.

In response to the XFRC interrupt, de-allocate the channel for other transfers

8.

Handling non-ACK responses

RM0385 Rev 7

1459/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Figure 471. Normal bulk/control OUT/SETUP
Application

1
init_reg(ch_2)

set_ch_en
(ch_2)

1

set_ch_en
(ch_2)

Host

USB

Device

init_reg(ch_1)

write_tx_fifo
(ch_1)

2
2

AHB

1
MPS

4

3

Non-Periodic Request
Queue
Assume that this queue
can hold 4 entries.

ch_1
write_tx_fifo
(ch_1)

5

1
MPS

ch_2
_
ch_1
ch_2

OU T

D AT A0
MPS

3
ACK
set_ch_en
(ch_2)

IN

4

D AT A0

5
RxFLvl interruptt
1
MPS

read_rx_sts
read_rx_fifo

ch_1
ch_2

set_ch_en
(ch_2)

ch_2

ACK
O UT

D AT A1
MPS

ch_2

7

ACK

XferCompl interrupt

6
IN

De-allocate
(ch_1)

D AT A1
RxFLvl interruptt
1
MPS

read_rx_stsre
ad_rx_fifo

RxFLvl interruptt
read_rx_sts

Disable
(ch_2)

7

6
8

ACK

ch_2

XferCompl interruptt

9
RxFLvl interruptt

read_rx_sts

De-allocate
(ch_2)

11

ChHltd interruptt

10
12

13
MSv36018V1

1. The grayed elements are not relevant in the context of this figure.

1460/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
The channel-specific interrupt service routine for bulk and control OUT/SETUP
transactions is shown in the following code samples.
•

Interrupt service routine for bulk/control OUT/SETUP and bulk/control IN
transactions
a)

Bulk/control OUT/SETUP

Unmask (NAK/TXERR/STALL/XFRC)
if (XFRC)
{
Reset Error Count
Mask ACK
De-allocate Channel
}
else if (STALL)
{
Transfer Done = 1
Unmask CHH
Disable Channel
}
else if (NAK or TXERR )
{
Rewind Buffer Pointers
Unmask CHH
Disable Channel
if (TXERR)
{
Increment Error Count
Unmask ACK
}
else
{
Reset Error Count
}
}
else if (CHH)
{
Mask CHH
if (Transfer Done or (Error_count == 3))
{
De-allocate Channel
}
else
{
Re-initialize Channel
}
}

RM0385 Rev 7

1461/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

else if (ACK)
{
Reset Error Count
Mask ACK
}

The application is expected to write the data packets into the transmit FIFO when the
space is available in the transmit FIFO and the request queue. The application can
make use of the NPTXFE interrupt in OTG_GINTSTS to find the transmit FIFO space.
b)

Bulk/control IN

Unmask (TXERR/XFRC/BBERR/STALL/DTERR)
if (XFRC)
{
Reset Error Count
Unmask CHH
Disable Channel
Reset Error Count
Mask ACK
}
else if (TXERR or BBERR or STALL)
{
Unmask CHH
Disable Channel
if (TXERR)
{
Increment Error Count
Unmask ACK
}
}
else if (CHH)
{
Mask CHH
if (Transfer Done or (Error_count == 3))
{
De-allocate Channel
}
else
{
Re-initialize Channel
}
}
else if (ACK)
{
Reset Error Count
Mask ACK
}

1462/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
else if (DTERR)
{
Reset Error Count
}

The application is expected to write the requests as and when the request queue space is
available and until the XFRC interrupt is received.
•

Bulk and control IN transactions
A typical bulk or control IN pipelined transaction-level operation is shown in Figure 472.
See channel 2 (ch_2). The assumptions are:
–

The application is attempting to receive two maximum-packet-size packets
(transfer size = 1 024 bytes).

–

The receive FIFO can contain at least one maximum-packet-size packet and two
status words per packet (72 bytes for FS/520 bytes for HS).

–

The non-periodic request queue depth = 4.

RM0385 Rev 7

1463/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Figure 472. Bulk/control IN transactions
Application

1
init_reg(ch_2)

set_ch_en
(ch_2)

1

set_ch_en
(ch_2)

Host

USB

Device

init_reg(ch_1)

write_tx_fifo
(ch_1)

2
2

AHB

1
MPS

4

3

Non-Periodic Request
Queue
Assume that this queue
can hold 4 entries.

ch_1
ch
c
1
write_tx_fifo
(ch_1)

5

1
MPS

ch_2
ch_1
ch_2

OU T

D AT A0
MPS

3
ACK
set_ch_en
(ch_2)

IN

4

D AT A0

5
RxFLvl interrupt
1
MPS

read_rx_sts
read_rx_fifo

ch_1
ch_2

set_ch_en
(ch_2)

ch_2

ACK
O UT

D AT A1
MPS

ch_2

7

K
ACK

r pt
XferC
r ompl interru

6
IN

De-allocate
(ch_1)

D AT A1
RxFLvl interrupt
1
MPS

read_rx_stsre
ad_rx_fifo

RxFLvl interrupt
read_rx_sts

Disable
(ch_2)

7

6
8

ACK

ch_2

XferCompl interrupt

9
RxFLvl interrupt

read_rx_sts

De-allocate
(ch_2)

11

ChHltd interrupt

10
12

13
ai15675b

1. The grayed elements are not relevant in the context of this figure.

1464/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
The sequence of operations is as follows:
1.

Initialize channel 2.

2.

Set the CHENA bit in OTG_HCCHAR2 to write an IN request to the non-periodic
request queue.

3.

The core attempts to send an IN token after completing the current OUT transaction.

4.

The core generates an RXFLVL interrupt as soon as the received packet is written to
the receive FIFO.

5.

In response to the RXFLVL interrupt, mask the RXFLVL interrupt and read the received
packet status to determine the number of bytes received, then read the receive FIFO
accordingly. Following this, unmask the RXFLVL interrupt.

6.

The core generates the RXFLVL interrupt for the transfer completion status entry in the
receive FIFO.

7.

The application must read and ignore the receive packet status when the receive
packet status is not an IN data packet (PKTSTS in OTG_GRXSTSR ≠ 0b0010).

8.

The core generates the XFRC interrupt as soon as the receive packet status is read.

9.

In response to the XFRC interrupt, disable the channel and stop writing the
OTG_HCCHAR2 register for further requests. The core writes a channel disable
request to the non-periodic request queue as soon as the OTG_HCCHAR2 register is
written.

10. The core generates the RXFLVL interrupt as soon as the halt status is written to the
receive FIFO.
11. Read and ignore the receive packet status.
12. The core generates a CHH interrupt as soon as the halt status is popped from the
receive FIFO.
13. In response to the CHH interrupt, de-allocate the channel for other transfers.
14. Handling non-ACK responses
•

Control transactions
Setup, data, and status stages of a control transfer must be performed as three
separate transfers. setup-, data- or status-stage OUT transactions are performed
similarly to the bulk OUT transactions explained previously. Data- or status-stage IN
transactions are performed similarly to the bulk IN transactions explained previously.
For all three stages, the application is expected to set the EPTYP field in
OTG_HCCHAR1 to control. During the setup stage, the application is expected to set
the PID field in OTG_HCTSIZ1 to SETUP.

•

Interrupt OUT transactions
A typical interrupt OUT operation is shown in Figure 473. The assumptions are:
–

The application is attempting to send one packet in every frame (up to 1 maximum
packet size), starting with the odd frame (transfer size = 1 024 bytes)

–

The periodic transmit FIFO can hold one packet (1 KB)

–

Periodic request queue depth = 4

The sequence of operations is as follows:

RM0385 Rev 7

1465/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

1466/1709

RM0385

1.

Initialize and enable channel 1. The application must set the ODDFRM bit in
OTG_HCCHAR1.

2.

Write the first packet for channel 1.

3.

Along with the last word write of each packet, the OTG_FS/OTG_HS host writes an
entry to the periodic request queue.

4.

The OTG_FS/OTG_HS host attempts to send an OUT token in the next (odd) frame.

5.

The OTG_FS/OTG_HS host generates an XFRC interrupt as soon as the last packet is
transmitted successfully.

6.

In response to the XFRC interrupt, reinitialize the channel for the next transfer.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 473. Normal interrupt OUT
Application

1

AHB

Host

USB

init_reg(ch_1)

init_reg(ch_2)

1

write_tx_fifo
(ch_1)

2

set_ch_en
(ch_2)

Device

Periodic Request Queue
Assume that this queue
can hold 4 entries.

3

1
MPS

4

ch_1

2

ch_2
_

3
OU T

Odd
(micro)

D ATA0
M PS

frame

5
6

AC K

XferCompl interrupt

4

init_reg(ch_1)
write_tx_fifo
(ch_1)

IN

5

1
MPS

D ATA0

RxFLvl interrupt

ACK

read_rx_sts
read_rx_fifo

1
MPS

6

RxFLvl interrupt
read_rx_sts

7

init_reg(ch_2)

XferCompl interrupt

8

ch_1
ch 2
ch_2

9

set_ch_en
(ch_2)
Even

OU T

frame

XferCompl interrupt
D ATA1
MPS

init_reg(ch_1)

write_tx_fifo
(ch_1)

(micro)

1
MPS

ACK
IN

D ATA1

MSv36020V1

1. The grayed elements are not relevant in the context of this figure.

•

Interrupt service routine for interrupt OUT/IN transactions
a)

Interrupt OUT

Unmask (NAK/TXERR/STALL/XFRC/FRMOR)

RM0385 Rev 7

1467/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
if (XFRC)
{
Reset Error Count
Mask ACK
De-allocate Channel
}
else
if (STALL or FRMOR)
{
Mask ACK
Unmask CHH
Disable Channel
if (STALL)
{
Transfer Done = 1
}
}
else
if (NAK or TXERR)
{
Rewind Buffer Pointers
Reset Error Count
Mask ACK
Unmask CHH
Disable Channel
}
else
if (CHH)
{
Mask CHH
if (Transfer Done or (Error_count == 3))
{
De-allocate Channel
}
else
{
Re-initialize Channel (in next b_interval - 1 Frame)
}
}
else
if (ACK)
{
Reset Error Count
Mask ACK
}

1468/1709

RM0385 Rev 7

RM0385

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
The application uses the NPTXFE interrupt in OTG_GINTSTS to find the
transmit FIFO space.
Interrupt IN
Unmask (NAK/TXERR/XFRC/BBERR/STALL/FRMOR/DTERR)
if (XFRC)
{
Reset Error Count
Mask ACK
if (OTG_HCTSIZx.PKTCNT == 0)
{
De-allocate Channel
}
else
{
Transfer Done = 1
Unmask CHH
Disable Channel
}
}
else
if (STALL or FRMOR or NAK or DTERR or BBERR)
{
Mask ACK
Unmask CHH
Disable Channel
if (STALL or BBERR)
{
Reset Error Count
Transfer Done = 1
}
else
if (!FRMOR)
{
Reset Error Count
}
}
else
if (TXERR)
{
Increment Error Count
Unmask ACK
Unmask CHH
Disable Channel
}
else

RM0385 Rev 7

1469/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

if (CHH)
{
Mask CHH
if (Transfer Done or (Error_count == 3))
{
De-allocate Channel
}
else
Re-initialize Channel (in next b_interval - 1 /Frame)
}
}
else
if (ACK)
{
Reset Error Count
Mask ACK
}

•

Interrupt IN transactions
The assumptions are:

•

–

The application is attempting to receive one packet (up to 1 maximum packet size)
in every frame, starting with odd (transfer size = 1 024 bytes).

–

The receive FIFO can hold at least one maximum-packet-size packet and two
status words per packet (1 031 bytes).

–

Periodic request queue depth = 4.

Normal interrupt IN operation
The sequence of operations is as follows:

1470/1709

1.

Initialize channel 2. The application must set the ODDFRM bit in OTG_HCCHAR2.

2.

Set the CHENA bit in OTG_HCCHAR2 to write an IN request to the periodic request
queue.

3.

The OTG_FS/OTG_HS host writes an IN request to the periodic request queue for
each OTG_HCCHAR2 register write with the CHENA bit set.

4.

The OTG_FS/OTG_HS host attempts to send an IN token in the next (odd) frame.

5.

As soon as the IN packet is received and written to the receive FIFO, the
OTG_FS/OTG_HS host generates an RXFLVL interrupt.

6.

In response to the RXFLVL interrupt, read the received packet status to determine the
number of bytes received, then read the receive FIFO accordingly. The application
must mask the RXFLVL interrupt before reading the receive FIFO, and unmask after
reading the entire packet.

7.

The core generates the RXFLVL interrupt for the transfer completion status entry in the
receive FIFO. The application must read and ignore the receive packet status when the
receive packet status is not an IN data packet (PKTSTS in GRXSTSR ≠ 0b0010).

8.

The core generates an XFRC interrupt as soon as the receive packet status is read.

9.

In response to the XFRC interrupt, read the PKTCNT field in OTG_HCTSIZ2. If the
PKTCNT bit in OTG_HCTSIZ2 is not equal to 0, disable the channel before re-

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
initializing the channel for the next transfer, if any). If PKTCNT bit in OTG_HCTSIZ2 =
0, reinitialize the channel for the next transfer. This time, the application must reset the
ODDFRM bit in OTG_HCCHAR2.

RM0385 Rev 7

1471/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Figure 474. Normal interrupt IN
Application

1

AHB

Host

USB

init_reg(ch_1)

init_reg(ch_2)

1

write_tx_fifo
(ch_1)

2

set_ch_en
(ch_2)

Device

Periodic Request Queue
Assume that this queue
can hold 4 entries.

3

1
MPS

4

ch 1
ch_1

2

ch_2

3
OU T

Odd
(micro)

D ATA0
M PS

frame

5
6

AC K

Xfer Com pl i nterr upt

4

init_reg(ch_1)
write_tx_fifo
(ch_1)

IN

5

1
MPS

D ATA0

RxFLvl interrupt

ACK

read_rx_sts
read_rx_fifo

1
MPS

6

RxFLvl interrupt
read_rx_sts

7

init_reg(ch_2)

XferCompl interrupt

8

ch 1
ch_1
ch_2

9

set_ch_en
(ch_2)
Even

OU T

frame

Xfferr Compl interrr upt
D ATA1
MPS

init_reg(ch_1)

write_tx_fifo
(ch_1)

(micro)

1
MPS

ACK
IN

D ATA1

ai15676b

1. The grayed elements are not relevant in the context of this figure.

•

Isochronous OUT transactions
A typical isochronous OUT operation is shown in Figure 474. The assumptions are:
–

1472/1709

The application is attempting to send one packet every frame (up to 1 maximum

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
packet size), starting with an odd frame. (transfer size = 1 024 bytes).
–

The periodic transmit FIFO can hold one packet (1 KB).

–

Periodic request queue depth = 4.

The sequence of operations is as follows:
1.

Initialize and enable channel 1. The application must set the ODDFRM bit in
OTG_HCCHAR1.

2.

Write the first packet for channel 1.

3.

Along with the last word write of each packet, the OTG_FS/OTG_HS host writes an
entry to the periodic request queue.

4.

The OTG_FS/OTG_HS host attempts to send the OUT token in the next frame (odd).

5.

The OTG_FS/OTG_HS host generates the XFRC interrupt as soon as the last packet
is transmitted successfully.

6.

In response to the XFRC interrupt, reinitialize the channel for the next transfer.

7.

Handling non-ACK responses

RM0385 Rev 7

1473/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Figure 475. Isochronous OUT transactions
Application

1

AHB

USB

Host

init_reg(ch_1)
Periodic Request
Queue
Assume that this queue
can hold 4 entries.

init_reg(ch_2)

1

write_tx_fifo
(ch_1)

2

set_ch_en
(ch_2)

Device

3

1
MPS

4

ch_1

2

ch_2

3
OUT

Odd
(micro)
frame

D A T A0
MPS

5
6

XferCompl interrupt
init_reg(ch_1)
write_tx_fifo
(ch_1)

4
1
MPS

5

IN

D A T A0

RxFLvl interrupt
1
MPS

6

read_rx_sts
read_rx_fifo

RxFLvl interrupt
read_rx_sts

7
XferCompl interrupt

init_reg(ch_2)

8

ch_1
ch 2
ch_2

9

set_ch_en
(ch_2)
Even
OUT

(micro)
frame

D A T A0
MPS

XferCompl interrupt
init_reg(ch_1)
IN

write_tx_fifo
(ch_1)

1
MPS

DA TA
0

MSv36022V1

1. The grayed elements are not relevant in the context of this figure.

•

Interrupt service routine for isochronous OUT/IN transactions
Code sample: isochronous OUT

Unmask (FRMOR/XFRC)
if (XFRC)
1474/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
{
De-allocate Channel
}
else
if (FRMOR)
{
Unmask CHH
Disable Channel
}
else
if (CHH)
{
Mask CHH
De-allocate Channel
}
Code sample: Isochronous IN
Unmask (TXERR/XFRC/FRMOR/BBERR)
if (XFRC or FRMOR)
{
if (XFRC and (OTG_HCTSIZx.PKTCNT == 0))
{
Reset Error Count
De-allocate Channel
}
else
{
Unmask CHH
Disable Channel
}
}
else
if (TXERR or BBERR)
{
Increment Error Count
Unmask CHH
Disable Channel
}
else
if (CHH)
{
Mask CHH
if (Transfer Done or (Error_count == 3))
{
De-allocate Channel
}

RM0385 Rev 7

1475/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

else
{
Re-initialize Channel
}
}

•

Isochronous IN transactions
The assumptions are:
–

The application is attempting to receive one packet (up to 1 maximum packet size)
in every frame starting with the next odd frame (transfer size = 1 024 bytes).

–

The receive FIFO can hold at least one maximum-packet-size packet and two
status word per packet (1 031 bytes).

–

Periodic request queue depth = 4.

The sequence of operations is as follows:

1476/1709

1.

Initialize channel 2. The application must set the ODDFRM bit in OTG_HCCHAR2.

2.

Set the CHENA bit in OTG_HCCHAR2 to write an IN request to the periodic request
queue.

3.

The OTG_FS/OTG_HS host writes an IN request to the periodic request queue for
each OTG_HCCHAR2 register write with the CHENA bit set.

4.

The OTG_FS/OTG_HS host attempts to send an IN token in the next odd frame.

5.

As soon as the IN packet is received and written to the receive FIFO, the
OTG_FS/OTG_HS host generates an RXFLVL interrupt.

6.

In response to the RXFLVL interrupt, read the received packet status to determine the
number of bytes received, then read the receive FIFO accordingly. The application
must mask the RXFLVL interrupt before reading the receive FIFO, and unmask it after
reading the entire packet.

7.

The core generates an RXFLVL interrupt for the transfer completion status entry in the
receive FIFO. This time, the application must read and ignore the receive packet status
when the receive packet status is not an IN data packet (PKTSTS bit in
OTG_GRXSTSR ≠ 0b0010).

8.

The core generates an XFRC interrupt as soon as the receive packet status is read.

9.

In response to the XFRC interrupt, read the PKTCNT field in OTG_HCTSIZ2. If
PKTCNT ≠ 0 in OTG_HCTSIZ2, disable the channel before re-initializing the channel
for the next transfer, if any. If PKTCNT = 0 in OTG_HCTSIZ2, reinitialize the channel
for the next transfer. This time, the application must reset the ODDFRM bit in
OTG_HCCHAR2.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 476. Isochronous IN transactions
Application

1

AHB

USB

Host

init_reg(ch_1)
Periodic Request
Queue
Assume that this queue
can hold 4 entries.

init_reg(ch_2)

1

write_tx_fifo
(ch_1)

2

set_ch_en
(ch_2)

Device

3

1
MPS

4

ch 1
ch_1

2

ch_2

3
Odd

OUT

(micro)
frame

DATA0
MPS

5
6

XferCompl interrupt
init_reg(ch_1)
write_tx_fifo
(ch_1)

4
1
MPS

5

IN

DATA0

RxFLvl interrupt
1
MPS

6

read_rx_sts
read_rx_fifo

RxFLvl interrupt
read_rx_sts

7
XferCompl interrupt

init_reg(ch_2)

8

ch 1
ch_1
ch_2

9

set_ch_en
(ch_2)
Even
OUT

(micro)
frame

DATA0
MPS

XferCompl interrupt
init_reg(ch_1)
IN

write_tx_fifo
(ch_1)

1
MPS
DATA0

MSv36021V1

1. The grayed elements are not relevant in the context of this figure.

•

Selecting the queue depth
Choose the periodic and non-periodic request queue depths carefully to match the
number of periodic/non-periodic endpoints accessed.
The non-periodic request queue depth affects the performance of non-periodic
RM0385 Rev 7

1477/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

transfers. The deeper the queue (along with sufficient FIFO size), the more often the
core is able to pipeline non-periodic transfers. If the queue size is small, the core is
able to put in new requests only when the queue space is freed up.
The core’s periodic request queue depth is critical to perform periodic transfers as
scheduled. Select the periodic queue depth, based on the number of periodic transfers
scheduled in a microframe. If the periodic request queue depth is smaller than the
periodic transfers scheduled in a microframe, a frame overrun condition occurs.
•

Handling babble conditions
OTG_FS/OTG_HS controller handles two cases of babble: packet babble and port
babble. Packet babble occurs if the device sends more data than the maximum packet
size for the channel. Port babble occurs if the core continues to receive data from the
device at EOF2 (the end of frame 2, which is very close to SOF).
When OTG_FS/OTG_HS controller detects a packet babble, it stops writing data into
the Rx buffer and waits for the end of packet (EOP). When it detects an EOP, it flushes
already written data in the Rx buffer and generates a Babble interrupt to the
application.
When OTG_FS/OTG_HS controller detects a port babble, it flushes the Rx FIFO and
disables the port. The core then generates a port disabled interrupt (HPRTINT in
OTG_GINTSTS, PENCHNG in OTG_HPRT). On receiving this interrupt, the
application must determine that this is not due to an overcurrent condition (another
cause of the port disabled interrupt) by checking POCA in OTG_HPRT, then perform a
soft reset. The core does not send any more tokens after it has detected a port babble
condition.

Note:

The following paragraphs, ranging from here to the beginning of Section 37.16, and
covering DMA configurations, apply only to USB OTG HS.
•

Bulk and control OUT/SETUP transactions in DMA mode
The sequence of operations is as follows:

1478/1709

1.

Initialize and enable channel 1 as explained in Section : Channel initialization.

2.

The OTG_HS host starts fetching the first packet as soon as the channel is enabled.
For internal DMA mode, the OTG_HS host uses the programmed DMA address to
fetch the packet.

3.

After fetching the last 32-bit word of the second (last) packet, the OTG_HS host masks
channel 1 internally for further arbitration.

4.

The OTG_HS host generates a CHH interrupt as soon as the last packet is sent.

5.

In response to the CHH interrupt, de-allocate the channel for other transfers.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 477. Normal bulk/control OUT/SETUP transactions - DMA
Application

1

Host

AHB

USB

Device

init_reg(ch_1)

2

init_reg(ch_2)

Non-Periodic
Request Queue
Assume that this queue
can hold 4 entries.

1
1
MPS

ch_1

1
MPS

2

ch_2
OUT

ch_1

D ATA0
MPS

ch_2

3

AC K
IN

D ATA0

3
AC K

1
MPS

ch_1
OUT

ch_2

D ATA1
MPS

ch_2

5
ch_2

5

AC K

C hHltd interrupt

4
IN

De-allocate
(ch_1)

D ATA1

4
1
MPS

AC K

ch_2

6
7
ChHltd interrupt
De-allocate
(ch_2)

MSv36927V1

•

NAK and NYET handling with internal DMA:

1.

The OTG_HS host sends a bulk OUT transaction.

2.

The device responds with NAK or NYET.

3.

If the application has unmasked NAK or NYET, the core generates the corresponding
interrupt(s) to the application. The application is not required to service these interrupts,
since the core takes care of rewinding the buffer pointers and re-initializing the Channel
without application intervention.

4.

The core automatically issues a ping token.

5.

When the device returns an ACK, the core continues with the transfer. Optionally, the
application can utilize these interrupts, in which case the NAK or NYET interrupt is
masked by the application.

RM0385 Rev 7

1479/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

The core does not generate a separate interrupt when NAK or NYET is received by the
host functionality.
•

Bulk and control IN transactions in DMA mode
The sequence of operations is as follows:

1480/1709

1.

Initialize and enable the used channel (channel x) as explained in Section : Channel
initialization.

2.

The OTG_HS host writes an IN request to the request queue as soon as the channel
receives the grant from the arbiter (arbitration is performed in a round-robin fashion).

3.

The OTG_HS host starts writing the received data to the system memory as soon as
the last byte is received with no errors.

4.

When the last packet is received, the OTG_HS host sets an internal flag to remove any
extra IN requests from the request queue.

5.

The OTG_HS host flushes the extra requests.

6.

The final request to disable channel x is written to the request queue. At this point,
channel 2 is internally masked for further arbitration.

7.

The OTG_HS host generates the CHH interrupt as soon as the disable request comes
to the top of the queue.

8.

In response to the CHH interrupt, de-allocate the channel for other transfers.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 478. Normal bulk/control IN transaction - DMA

Application

1

Host

AHB

USB

Device

init_reg(ch_1)

2

init_reg(ch_2)

1

Non-Periodic
Request Queue
Assume that this queue
can hold 4 entries.

1
MPS
ch_1
h 1

1
MPS

2

ch_2
OUT

ch_1

0
DATA0
MPS

ch_2

3

AC K
IN

DATA0
0
3
AC K

1
MPS

ch_1
OUT

ch_2

D ATA1
MPS

ch_2

5
ch_2

5

AC K

C hHltd interruptt

4
IN

De

D ATA1

4
1
MPS

AC K

ch_2

6
7
ChHltd interrupt
De-allocate
(ch_2)

8

MSv36928V1

•

Interrupt OUT transactions in DMA mode

1.

Initialize and enable channel x as explained in Section : Channel initialization.

2.

The OTG_HS host starts fetching the first packet as soon the channel is enabled and
writes the OUT request along with the last 32-bit word fetch. In high-bandwidth
transfers, the OTG_HS host continues fetching the next packet (up to the value
specified in the MC field) before switching to the next channel.

3.

The OTG_HS host attempts to send the OUT token at the beginning of the next odd
frame/micro-frame.

RM0385 Rev 7

1481/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

4.

After successfully transmitting the packet, the OTG_HS host generates a CHH
interrupt.

5.

In response to the CHH interrupt, reinitialize the channel for the next transfer.
Figure 479. Normal interrupt OUT transactions - DMA mode
Application

1

Host

AHB

USB

Device

init_reg(ch_1)
Periodic Request
Queue
Assume that this
queue can hold
4 entries.

init_reg(ch_2)

1

2

1
MPS

3

ch_1
ch_2
_

2
O UT

DATA0
MP S

Odd
(micro)
frame

4
5

A CK

C hH ltd interrupt

init_reg(ch_1)

3

IN

1
MPS
DATA0

AC K

1
MPS

ChHltd interrupt

4

ch_1
ch 2
ch_2

init_reg(ch_2)

5

OUT

Even
(micro)
frame

D ATA1
MP S

C hH ltd interrupt

init_reg(ch_1)

AC K
IN

1
MPS

DATA1

MSv36924V1

•

Interrupt IN transactions in DMA mode
The sequence of operations (channelx) is as follows:

1482/1709

1.

Initialize and enable channel x as explained in Section : Channel initialization.

2.

The OTG_HS host writes an IN request to the request queue as soon as the channel x
gets the grant from the arbiter (round-robin with fairness). In high-bandwidth transfers,
the OTG_HS host writes consecutive writes up to MC times.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
3.

The OTG_HS host attempts to send an IN token at the beginning of the next (odd)
frame/micro-frame.

4.

As soon the packet is received and written to the receive FIFO, the OTG_HS host
generates a CHH interrupt.

5.

In response to the CHH interrupt, reinitialize the channel for the next transfer.
Figure 480. Normal interrupt IN transactions - DMA mode
Application

1

AHB

USB

Host

Device

init_reg(ch_1)
Periodic Request
Queue
Assume that this
queue can hold
4 entries.

init_reg(ch_2)

1

2

1
MPS

3

ch_1
h 1
ch_2

2
O UT

DATA0
MP S

Odd
(micro)
frame

4
5
A CK

C h H ltd interruptt

init

3

IN

1
MPS
DATA0

AC K

1
MPS

ChHltd interrupt

4

ch_1
ch
1
ch_2

init_reg(ch_2)

5

OUT

Even
(micro)
frame

D A TA 1
MP S

C h H ltd inte rruptt

init

AC K
IN

1
MPS

DATA1

MSv36925V1

•

Isochronous OUT transactions in DMA mode

1.

Initialize and enable channel x as explained in Section : Channel initialization.

2.

The OTG_HS host starts fetching the first packet as soon as the channel is enabled,
and writes the OUT request along with the last 32-bit word fetch. In high-bandwidth

RM0385 Rev 7

1483/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

transfers, the OTG_HS host continues fetching the next packet (up to the value
specified in the MC field) before switching to the next channel.
3.

The OTG_HS host attempts to send an OUT token at the beginning of the next (odd)
frame/micro-frame.

4.

After successfully transmitting the packet, the OTG_HS host generates a CHH
interrupt.

5.

In response to the CHH interrupt, reinitialize the channel for the next transfer.
Figure 481. Normal isochronous OUT transaction - DMA mode

Application
1

Host

AHB

USB

Device

init_reg(ch_1)
Periodic Request
Queue
Assume that this
queue can hold
4 entries.

init_reg(ch_2)

1

2

1
MPS

3

ch_1
ch_2

2
OUT

DATA0
MPS

4

Odd
(micro)
frame

5
C hHltd interrupt

init_reg(ch_1)

3

IN

1
MPS

DATA0

1
MPS

ChHltd interrupt

4

ch_1
ch_2

init_reg(ch_2)

OUT

Even
(micro)
frame

DATA0
MPS
C hH ltd interrupt

init_reg(ch_1)
IN

1
MPS

DATA0

MSv36923V1

•

Isochronous IN transactions in DMA mode
The sequence of operations ((channel x) is as follows:

1484/1709

1.

Initialize and enable channel x as explained in Section : Channel initialization.

2.

The OTG_HS host writes an IN request to the request queue as soon as the channel x
gets the grant from the arbiter (round-robin with fairness). In high-bandwidth transfers,
the OTG_HS host performs consecutive write operations up to MC times.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
3.

The OTG_HS host attempts to send an IN token at the beginning of the next (odd)
frame/micro-frame.

4.

As soon the packet is received and written to the receive FIFO, the OTG_HS host
generates a CHH interrupt.

5.

In response to the CHH interrupt, reinitialize the channel for the next transfer.
Figure 482. Normal isochronous IN transactions - DMA mode

Application
1

Host

AHB

USB

Device

init_reg(ch_1)
Periodic Request
Queue
Assume that this
queue can hold
4 entries.

init_reg(ch_2)

1

2

1
MPS

3

ch_1
h 1
ch_2

2
OUT

Odd
(micro)
frame

DATA0
MPS

4
5
C hHltd interrupt

init_r

3

IN

1
MPS

DATA0

1
MPS

ChHltdInterrupt

4

ch_1
ch
1
ch_2

init_reg(ch_2)

5

OUT

Even
(micro)
frame

DATA0
MPS
C hH ltd interrupt

init_reg(ch_1)
IN

1
MPS
DATA0

MS36922V1

•

Bulk and control OUT/SETUP split transactions in DMA mode
The sequence of operations in (channel x) is as follows:

1.

Initialize and enable channel x for start split as explained in Section : Channel
initialization.

2.

The OTG_HS host starts fetching the first packet as soon the channel is enabled and
writes the OUT request along with the last 32-bit word fetch.

3.

After successfully transmitting start split, the OTG_HS host generates the CHH
interrupt.

4.

In response to the CHH interrupt, set the COMPLSPLT bit in OTG_HCSPLT1 to send
the complete split.

RM0385 Rev 7

1485/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

5.

After successfully transmitting complete split, the OTG_HS host generates the CHH
interrupt.

6.

In response to the CHH interrupt, de-allocate the channel.

•

Bulk/control IN split transactions in DMA mode
The sequence of operations (channel x) is as follows:

1.

Initialize and enable channel x as explained in Section : Channel initialization.

2.

The OTG_HS host writes the start split request to the nonperiodic request after getting
the grant from the arbiter. The OTG_HS host masks the channel x internally for the
arbitration after writing the request.

3.

As soon as the IN token is transmitted, the OTG_HS host generates the CHH interrupt.

4.

In response to the CHH interrupt, set the COMPLSPLT bit in OTG_HCSPLT2 and reenable the channel to send the complete split token. This unmasks channel x for
arbitration.

5.

The OTG_HS host writes the complete split request to the nonperiodic request after
receiving the grant from the arbiter.

6.

The OTG_HS host starts writing the packet to the system memory after receiving the
packet successfully.

7.

As soon as the received packet is written to the system memory, the OTG_HS host
generates a CHH interrupt.

8.

In response to the CHH interrupt, de-allocate the channel.

•

Interrupt OUT split transactions in DMA mode
The sequence of operations in (channel x) is as follows:

1.

Initialize and enable channel 1 for start split as explained in Section : Channel
initialization. The application must set the ODDFRM bit in OTG_HCCHAR1.

2.

The OTG_HS host starts reading the packet.

3.

The OTG_HS host attempts to send the start split transaction.

4.

After successfully transmitting the start split, the OTG_HS host generates the CHH
interrupt.

5.

In response to the CHH interrupt, set the COMPLSPLT bit in OTG_HCSPLT1 to send
the complete split.

6.

After successfully completing the complete split transaction, the OTG_HS host
generates the CHH interrupt.

7.

In response to CHH interrupt, de-allocate the channel.

•

Interrupt IN split transactions in DMA mode
The sequence of operations in (channel x) is as follows:

1486/1709

1.

Initialize and enable channel x for start split as explained in Section : Channel
initialization.

2.

The OTG_HS host writes an IN request to the request queue as soon as channel x
receives the grant from the arbiter.

3.

The OTG_HS host attempts to send the start split IN token at the beginning of the next
odd micro-frame.

4.

The OTG_HS host generates the CHH interrupt after successfully transmitting the start
split IN token.

5.

In response to the CHH interrupt, set the COMPLSPLT bit in OTG_HCSPLT2 to send
the complete split.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
6.

As soon as the packet is received successfully, the OTG_HS host starts writing the
data to the system memory.

7.

The OTG_HS host generates the CHH interrupt after transferring the received data to
the system memory.

8.

In response to the CHH interrupt, de-allocate or reinitialize the channel for the next start
split.

•

Isochronous OUT split transactions in DMA mode
The sequence of operations (channel x) is as follows:

1.

Initialize and enable channel x for start split (begin) as explained in Section : Channel
initialization. The application must set the ODDFRM bit in OTG_HCCHAR1. Program
the MPS field.

2.

The OTG_HS host starts reading the packet.

3.

After successfully transmitting the start split (begin), the OTG_HS host generates the
CHH interrupt.

4.

In response to the CHH interrupt, reinitialize the registers to send the start split (end).

5.

After successfully transmitting the start split (end), the OTG_HS host generates a CHH
interrupt.

6.

In response to the CHH interrupt, de-allocate the channel.

•

Isochronous IN split transactions in DMA mode
The sequence of operations (channel x) is as follows:

1.

Initialize and enable channel x for start split as explained in Section : Channel
initialization.

2.

The OTG_HS host writes an IN request to the request queue as soon as channel x
receives the grant from the arbiter.

3.

The OTG_HS host attempts to send the start split IN token at the beginning of the next
odd micro-frame.

4.

The OTG_HS host generates the CHH interrupt after successfully transmitting the start
split IN token.

5.

In response to the CHH interrupt, set the COMPLSPLT bit in OTG_HCSPLT2 to send
the complete split.

6.

As soon as the packet is received successfully, the OTG_HS host starts writing the
data to the system memory.
The OTG_HS host generates the CHH interrupt after transferring the received data to
the system memory. In response to the CHH interrupt, de-allocate the channel or
reinitialize the channel for the next start split.

RM0385 Rev 7

1487/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

37.16.6

RM0385

Device programming model
Endpoint initialization on USB reset
1.

Set the NAK bit for all OUT endpoints
–

2.

3.

4.

Unmask the following interrupt bits
–

INEP0 = 1 in OTG_DAINTMSK (control 0 IN endpoint)

–

OUTEP0 = 1 in OTG_DAINTMSK (control 0 OUT endpoint)

–

STUPM = 1 in OTG_DOEPMSK

–

XFRCM = 1 in OTG_DOEPMSK

–

XFRCM = 1 in OTG_DIEPMSK

–

TOM = 1 in OTG_DIEPMSK

Set up the data FIFO RAM for each of the FIFOs
–

Program the OTG_GRXFSIZ register, to be able to receive control OUT data and
setup data. If thresholding is not enabled, at a minimum, this must be equal to 1
max packet size of control endpoint 0 + 2 words (for the status of the control OUT
data packet) + 10 words (for setup packets).

–

Program the OTG_DIEPTXF0 register (depending on the FIFO number chosen) to
be able to transmit control IN data. At a minimum, this must be equal to 1 max
packet size of control endpoint 0.

Program the following fields in the endpoint-specific registers for control OUT endpoint
0 to receive a SETUP packet
–

5.

SNAK = 1 in OTG_DOEPCTLx (for all OUT endpoints)

STUPCNT = 3 in OTG_DOEPTSIZ0 (to receive up to 3 back-to-back SETUP
packets)

For USB OTG_HS in DMA mode, the OTG_DOEPDMA0 register should have a valid
memory address to store any SETUP packets received.

At this point, all initialization required to receive SETUP packets is done.

Endpoint initialization on enumeration completion
1.

On the Enumeration Done interrupt (ENUMDNE in OTG_GINTSTS), read the
OTG_DSTS register to determine the enumeration speed.

2.

Program the MPSIZ field in OTG_DIEPCTL0 to set the maximum packet size. This
step configures control endpoint 0. The maximum packet size for a control endpoint
depends on the enumeration speed.

3.

For USB OTG_HS in DMA mode, program the OTG_DOEPCTL0 register to enable
control OUT endpoint 0, to receive a SETUP packet.

At this point, the device is ready to receive SOF packets and is configured to perform control
transfers on control endpoint 0.

Endpoint initialization on SetAddress command
This section describes what the application must do when it receives a SetAddress
command in a SETUP packet.

1488/1709

1.

Program the OTG_DCFG register with the device address received in the SetAddress
command

2.

Program the core to send out a status IN packet

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Endpoint initialization on SetConfiguration/SetInterface command
This section describes what the application must do when it receives a SetConfiguration or
SetInterface command in a SETUP packet.
1.

When a SetConfiguration command is received, the application must program the
endpoint registers to configure them with the characteristics of the valid endpoints in
the new configuration.

2.

When a SetInterface command is received, the application must program the endpoint
registers of the endpoints affected by this command.

3.

Some endpoints that were active in the prior configuration or alternate setting are not
valid in the new configuration or alternate setting. These invalid endpoints must be
deactivated.

4.

Unmask the interrupt for each active endpoint and mask the interrupts for all inactive
endpoints in the OTG_DAINTMSK register.

5.

Set up the data FIFO RAM for each FIFO.

6.

After all required endpoints are configured; the application must program the core to
send a status IN packet.

At this point, the device core is configured to receive and transmit any type of data packet.

Endpoint activation
This section describes the steps required to activate a device endpoint or to configure an
existing device endpoint to a new type.
1.

2.

Program the characteristics of the required endpoint into the following fields of the
OTG_DIEPCTLx register (for IN or bidirectional endpoints) or the OTG_DOEPCTLx
register (for OUT or bidirectional endpoints).
–

Maximum packet size

–

USB active endpoint = 1

–

Endpoint start data toggle (for interrupt and bulk endpoints)

–

Endpoint type

–

Tx FIFO number

Once the endpoint is activated, the core starts decoding the tokens addressed to that
endpoint and sends out a valid handshake for each valid token received for the
endpoint.

Endpoint deactivation
This section describes the steps required to deactivate an existing endpoint.

Note:

1.

In the endpoint to be deactivated, clear the USB active endpoint bit in the
OTG_DIEPCTLx register (for IN or bidirectional endpoints) or the OTG_DOEPCTLx
register (for OUT or bidirectional endpoints).

2.

Once the endpoint is deactivated, the core ignores tokens addressed to that endpoint,
which results in a timeout on the USB.

The application must meet the following conditions to set up the device core to handle
traffic:
NPTXFEM and RXFLVLM in the OTG_GINTMSK register must be cleared.

RM0385 Rev 7

1489/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Operational model
SETUP and OUT data transfers:
This section describes the internal data flow and application-level operations during data
OUT transfers and SETUP transactions.
•

Packet read

This section describes how to read packets (OUT data and SETUP packets) from the
receive FIFO.
1.

On catching an RXFLVL interrupt (OTG_GINTSTS register), the application must read
the receive status pop register (OTG_GRXSTSP).

2.

The application can mask the RXFLVL interrupt (in OTG_GINTSTS) by writing to
RXFLVLM = 0 (in OTG_GINTMSK), until it has read the packet from the receive FIFO.

3.

If the received packet’s byte count is not 0, the byte count amount of data is popped
from the receive data FIFO and stored in memory. If the received packet byte count is
0, no data is popped from the receive data FIFO.

4.

The receive status readout of the packet of FIFO indicates one of the following:
a)

Global OUT NAK pattern:
PKTSTS = Global OUT NAK, BCNT = 0x000, EPNUM = (0x0),
DPID = (0b00).
These data indicate that the global OUT NAK bit has taken effect.

b)

SETUP packet pattern:
PKTSTS = SETUP, BCNT = 0x008, EPNUM = Control EP Num,
DPID = DATA0. These data indicate that a SETUP packet for the specified
endpoint is now available for reading from the receive FIFO.

c)

Setup stage done pattern:
PKTSTS = Setup Stage Done, BCNT = 0x0, EPNUM = Control EP Num,
DPID = (0b00).
These data indicate that the setup stage for the specified endpoint has completed
and the data stage has started. After this entry is popped from the receive FIFO,
the core asserts a setup interrupt on the specified control OUT endpoint.

d)

Data OUT packet pattern:
PKTSTS = DataOUT, BCNT = size of the received data OUT packet (0 ≤ BCNT
≤ 1 024), EPNUM = EPNUM on which the packet was received, DPID = Actual
Data PID.

e)

Data transfer completed pattern:
PKTSTS = Data OUT transfer done, BCNT = 0x0, EPNUM = OUT EP Num on
which the data transfer is complete, DPID = (0b00).
These data indicate that an OUT data transfer for the specified OUT endpoint has
completed. After this entry is popped from the receive FIFO, the core asserts a
transfer completed interrupt on the specified OUT endpoint.

5.

After the data payload is popped from the receive FIFO, the RXFLVL interrupt
(OTG_GINTSTS) must be unmasked.

6.

Steps 1–5 are repeated every time the application detects assertion of the interrupt line
due to RXFLVL in OTG_GINTSTS. Reading an empty receive FIFO can result in
undefined core behavior.

Figure 483 provides a flowchart of the above procedure.

1490/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 483. Receive FIFO packet read

wait until RXFLVL in
OTG_GINTSTSG

rd_data = rd_reg
(OTG_GRXSTSP);

Y

rd_data.BCNT
=0

rcv_out_pkt()

N
Packet
stored in
memory

mem[0:word_cnt _1] =
rd_rxfifo(rd_data.EPNUM,
word_cnt)

word_cnt =
BCNT[11:2] +
(BCNT[1] | BCNT[1])

ai15677b

SETUP transactions
This section describes how the core handles SETUP packets and the application’s
sequence for handling SETUP transactions.
•

Application requirements

1.

To receive a SETUP packet, the STUPCNT field (OTG_DOEPTSIZx) in a control OUT
endpoint must be programmed to a non-zero value. When the application programs the
STUPCNT field to a non-zero value, the core receives SETUP packets and writes them
to the receive FIFO, irrespective of the NAK status and EPENA bit setting in
OTG_DOEPCTLx. The STUPCNT field is decremented every time the control endpoint
receives a SETUP packet. If the STUPCNT field is not programmed to a proper value
before receiving a SETUP packet, the core still receives the SETUP packet and
decrements the STUPCNT field, but the application may not be able to determine the
correct number of SETUP packets received in the setup stage of a control transfer.
–

2.

STUPCNT = 3 in OTG_DOEPTSIZx

The application must always allocate some extra space in the receive data FIFO, to be
able to receive up to three SETUP packets on a control endpoint.
–

The space to be reserved is 10 words. Three words are required for the first
SETUP packet, 1 word is required for the setup stage done word and 6 words are
required to store two extra SETUP packets among all control endpoints.

–

3 words per SETUP packet are required to store 8 bytes of SETUP data and 4
bytes of SETUP status (setup packet pattern). The core reserves this space in the

RM0385 Rev 7

1491/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

receive data FIFO to write SETUP data only, and never uses this space for data
packets.
3.

The application must read the 2 words of the SETUP packet from the receive FIFO.

4.

The application must read and discard the setup stage done word from the receive
FIFO.

•

Internal data flow

1.

When a SETUP packet is received, the core writes the received data to the receive
FIFO, without checking for available space in the receive FIFO and irrespective of the
endpoint’s NAK and STALL bit settings.
–

2.

For every SETUP packet received on the USB, 3 words of data are written to the
receive FIFO, and the STUPCNT field is decremented by 1.
–

The first word contains control information used internally by the core

–

The second word contains the first 4 bytes of the SETUP command

–

The third word contains the last 4 bytes of the SETUP command

3.

When the setup stage changes to a data IN/OUT stage, the core writes an entry (setup
stage done word) to the receive FIFO, indicating the completion of the setup stage.

4.

On the AHB side, SETUP packets are emptied by the application.

5.

When the application pops the setup stage done word from the receive FIFO, the core
interrupts the application with an STUP interrupt (OTG_DOEPINTx), indicating it can
process the received SETUP packet.

6.

The core clears the endpoint enable bit for control OUT endpoints.

•

Application programming sequence

1.

Program the OTG_DOEPTSIZx register.
–

STUPCNT = 3

2.

Wait for the RXFLVL interrupt (OTG_GINTSTS) and empty the data packets from the
receive FIFO.

3.

Assertion of the STUP interrupt (OTG_DOEPINTx) marks a successful completion of
the SETUP data transfer.
–

1492/1709

The core internally sets the IN NAK and OUT NAK bits for the control IN/OUT
endpoints on which the SETUP packet was received.

On this interrupt, the application must read the OTG_DOEPTSIZx register to
determine the number of SETUP packets received and process the last received
SETUP packet.

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 484. Processing a SETUP packet

Wait for STP in OTG_DOEPINTx

rem_supcnt=
rd_reg(OTG_DOEPTSIZx)

setup_cmd[31:0 = mem[4 – 2 * rem_supcnt]
setup_cmd[63:32] = mem[5 – 2 * rem_supcnt]

Find setup cmd type

ctrl_rd/wr/2 stage

Read

Write

2-stage
setup_np_in_pkt
Data IN phase

setup_np_in_pkt
Status IN phase

rcv_out_pkt
Data OUT phase
MSv37035V1

•

Handling more than three back-to-back SETUP packets

Per the USB 2.0 specification, normally, during a SETUP packet error, a host does not send
more than three back-to-back SETUP packets to the same endpoint. However, the USB 2.0
specification does not limit the number of back-to-back SETUP packets a host can send to
the same endpoint. When this condition occurs, the OTG_FS/OTG_HS controller generates
an interrupt (B2BSTUP in OTG_DOEPINTx).
•

Setting the global OUT NAK

Internal data flow:
1.

When the application sets the Global OUT NAK (SGONAK bit in OTG_DCTL), the core
stops writing data, except SETUP packets, to the receive FIFO. Irrespective of the
space availability in the receive FIFO, non-isochronous OUT tokens receive a NAK
handshake response, and the core ignores isochronous OUT data packets

2.

The core writes the Global OUT NAK pattern to the receive FIFO. The application must
reserve enough receive FIFO space to write this data pattern.

3.

When the application pops the Global OUT NAK pattern word from the receive FIFO,
the core sets the GONAKEFF interrupt (OTG_GINTSTS).

4.

Once the application detects this interrupt, it can assume that the core is in Global OUT
NAK mode. The application can clear this interrupt by clearing the SGONAK bit in
OTG_DCTL.

Application programming sequence:

RM0385 Rev 7

1493/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

RM0385

To stop receiving any kind of data in the receive FIFO, the application must set the
Global OUT NAK bit by programming the following field:
–

SGONAK = 1 in OTG_DCTL

2.

Wait for the assertion of the GONAKEFF interrupt in OTG_GINTSTS. When asserted,
this interrupt indicates that the core has stopped receiving any type of data except
SETUP packets.

3.

The application can receive valid OUT packets after it has set SGONAK in OTG_DCTL
and before the core asserts the GONAKEFF interrupt (OTG_GINTSTS).

4.

The application can temporarily mask this interrupt by writing to the GONAKEFFM bit in
the OTG_GINTMSK register.
–

5.

Whenever the application is ready to exit the Global OUT NAK mode, it must clear the
SGONAK bit in OTG_DCTL. This also clears the GONAKEFF interrupt
(OTG_GINTSTS).
–

6.

CGONAK = 1 in OTG_DCTL

If the application has masked this interrupt earlier, it must be unmasked as follows:
–

•

GONAKEFFM = 0 in the OTG_GINTMSK register

GONAKEFFM = 1 in OTG_GINTMSK

Disabling an OUT endpoint

The application must use this sequence to disable an OUT endpoint that it has enabled.
Application programming sequence:
1.

Before disabling any OUT endpoint, the application must enable Global OUT NAK
mode in the core.
–

SGONAK = 1 in OTG_DCTL

2.

Wait for the GONAKEFF interrupt (OTG_GINTSTS)

3.

Disable the required OUT endpoint by programming the following fields:

4.

5.

–

EPDIS = 1 in OTG_DOEPCTLx

–

SNAK = 1 in OTG_DOEPCTLx

Wait for the EPDISD interrupt (OTG_DOEPINTx), which indicates that the OUT
endpoint is completely disabled. When the EPDISD interrupt is asserted, the core also
clears the following bits:
–

EPDIS = 0 in OTG_DOEPCTLx

–

EPENA = 0 in OTG_DOEPCTLx

The application must clear the Global OUT NAK bit to start receiving data from other
non-disabled OUT endpoints.
–

•

SGONAK = 0 in OTG_DCTL

Generic non-isochronous OUT data transfers

This section describes a regular non-isochronous OUT data transfer (control, bulk, or
interrupt).
Application requirements:

1494/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

Before setting up an OUT transfer, the application must allocate a buffer in the memory
to accommodate all data to be received as part of the OUT transfer.

2.

For OUT transfers, the transfer size field in the endpoint’s transfer size register must be
a multiple of the maximum packet size of the endpoint, adjusted to the word boundary.

3.

–

transfer size[EPNUM] = n × (MPSIZ[EPNUM] + 4 – (MPSIZ[EPNUM] mod 4))

–

packet count[EPNUM] = n

–

n>0

On any OUT endpoint interrupt, the application must read the endpoint’s transfer size
register to calculate the size of the payload in the memory. The received payload size
can be less than the programmed transfer size.
–

Payload size in memory = application programmed initial transfer size – core
updated final transfer size

–

Number of USB packets in which this payload was received = application
programmed initial packet count – core updated final packet count

Internal data flow:
1.

The application must set the transfer size and packet count fields in the endpointspecific registers, clear the NAK bit, and enable the endpoint to receive the data.

2.

Once the NAK bit is cleared, the core starts receiving data and writes it to the receive
FIFO, as long as there is space in the receive FIFO. For every data packet received on
the USB, the data packet and its status are written to the receive FIFO. Every packet
(maximum packet size or short packet) written to the receive FIFO decrements the
packet count field for that endpoint by 1.
–

OUT data packets received with bad data CRC are flushed from the receive FIFO
automatically.

–

After sending an ACK for the packet on the USB, the core discards nonisochronous OUT data packets that the host, which cannot detect the ACK, resends. The application does not detect multiple back-to-back data OUT packets
on the same endpoint with the same data PID. In this case the packet count is not
decremented.

–

If there is no space in the receive FIFO, isochronous or non-isochronous data
packets are ignored and not written to the receive FIFO. Additionally, nonisochronous OUT tokens receive a NAK handshake reply.

–

In all the above three cases, the packet count is not decremented because no data
are written to the receive FIFO.

3.

When the packet count becomes 0 or when a short packet is received on the endpoint,
the NAK bit for that endpoint is set. Once the NAK bit is set, the isochronous or nonisochronous data packets are ignored and not written to the receive FIFO, and nonisochronous OUT tokens receive a NAK handshake reply.

4.

After the data are written to the receive FIFO, the application reads the data from the
receive FIFO and writes it to external memory, one packet at a time per endpoint.

5.

At the end of every packet write on the AHB to external memory, the transfer size for
the endpoint is decremented by the size of the written packet.

6.

The OUT data transfer completed pattern for an OUT endpoint is written to the receive
FIFO on one of the following conditions:
–

The transfer size is 0 and the packet count is 0

–

The last OUT data packet written to the receive FIFO is a short packet
(0 ≤ packet size < maximum packet size)

RM0385 Rev 7

1495/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
7.

RM0385

When either the application pops this entry (OUT data transfer completed), a transfer
completed interrupt is generated for the endpoint and the endpoint enable is cleared.

Application programming sequence:
1.

Program the OTG_DOEPTSIZx register for the transfer size and the corresponding
packet count.

2.

Program the OTG_DOEPCTLx register with the endpoint characteristics, and set the
EPENA and CNAK bits.

3.

–

EPENA = 1 in OTG_DOEPCTLx

–

CNAK = 1 in OTG_DOEPCTLx

Wait for the RXFLVL interrupt (in OTG_GINTSTS) and empty the data packets from the
receive FIFO.
–

This step can be repeated many times, depending on the transfer size.

4.

Asserting the XFRC interrupt (OTG_DOEPINTx) marks a successful completion of the
non-isochronous OUT data transfer.

5.

Read the OTG_DOEPTSIZx register to determine the size of the received data
payload.

•

Generic isochronous OUT data transfer

This section describes a regular isochronous OUT data transfer.
Application requirements:
1.

All the application requirements for non-isochronous OUT data transfers also apply to
isochronous OUT data transfers.

2.

For isochronous OUT data transfers, the transfer size and packet count fields must
always be set to the number of maximum-packet-size packets that can be received in a
single frame and no more. Isochronous OUT data transfers cannot span more than 1
frame.

3.

The application must read all isochronous OUT data packets from the receive FIFO
(data and status) before the end of the periodic frame (EOPF interrupt in
OTG_GINTSTS).

4.

To receive data in the following frame, an isochronous OUT endpoint must be enabled
after the EOPF (OTG_GINTSTS) and before the SOF (OTG_GINTSTS).

Internal data flow:
1.

The internal data flow for isochronous OUT endpoints is the same as that for nonisochronous OUT endpoints, but for a few differences.

2.

When an isochronous OUT endpoint is enabled by setting the endpoint enable and
clearing the NAK bits, the Even/Odd frame bit must also be set appropriately. The core
receives data on an isochronous OUT endpoint in a particular frame only if the
following condition is met:
–

3.

EONUM (in OTG_DOEPCTLx) = FNSOF[0] (in OTG_DSTS)

When the application completely reads an isochronous OUT data packet (data and
status) from the receive FIFO, the core updates the RXDPID field in OTG_DOEPTSIZx
with the data PID of the last isochronous OUT data packet read from the receive FIFO.

Application programming sequence:

1496/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

Program the OTG_DOEPTSIZx register for the transfer size and the corresponding
packet count

2.

Program the OTG_DOEPCTLx register with the endpoint characteristics and set the
endpoint enable, ClearNAK, and Even/Odd frame bits.

3.

–

EPENA = 1

–

CNAK = 1

–

EONUM = (0: Even/1: Odd)

Wait for the RXFLVL interrupt (in OTG_GINTSTS) and empty the data packets from the
receive FIFO
–

This step can be repeated many times, depending on the transfer size.

4.

The assertion of the XFRC interrupt (in OTG_DOEPINTx) marks the completion of the
isochronous OUT data transfer. This interrupt does not necessarily mean that the data
in memory are good.

5.

This interrupt cannot always be detected for isochronous OUT transfers. Instead, the
application can detect the INCOMPISOOUT interrupt in OTG_GINTSTS.

6.

Read the OTG_DOEPTSIZx register to determine the size of the received transfer and
to determine the validity of the data received in the frame. The application must treat
the data received in memory as valid only if one of the following conditions is met:
–

RXDPID = DATA0 (in OTG_DOEPTSIZx) and the number of USB packets in
which this payload was received = 1

–

RXDPID = DATA1 (in OTG_DOEPTSIZx) and the number of USB packets in
which this payload was received = 2

–

RXDPID = D2 (in OTG_DOEPTSIZx) and the number of USB packets in which
this payload was received = 3[HS]
The number of USB packets in which this payload was received =
Application programmed initial packet count – core updated final packet count

The application can discard invalid data packets.
•

Incomplete isochronous OUT data transfers

This section describes the application programming sequence when isochronous OUT data
packets are dropped inside the core.
Internal data flow:
1.

2.

For isochronous OUT endpoints, the XFRC interrupt (in OTG_DOEPINTx) may not
always be asserted. If the core drops isochronous OUT data packets, the application
could fail to detect the XFRC interrupt (OTG_DOEPINTx) under the following
circumstances:
–

When the receive FIFO cannot accommodate the complete ISO OUT data packet,
the core drops the received ISO OUT data

–

When the isochronous OUT data packet is received with CRC errors

–

When the isochronous OUT token received by the core is corrupted

–

When the application is very slow in reading the data from the receive FIFO

When the core detects an end of periodic frame before transfer completion to all
isochronous OUT endpoints, it asserts the incomplete isochronous OUT data interrupt
(INCOMPISOOUT in OTG_GINTSTS), indicating that an XFRC interrupt (in
OTG_DOEPINTx) is not asserted on at least one of the isochronous OUT endpoints. At

RM0385 Rev 7

1497/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

this point, the endpoint with the incomplete transfer remains enabled, but no active
transfers remain in progress on this endpoint on the USB.
Application programming sequence:
1.

Asserting the INCOMPISOOUT interrupt (OTG_GINTSTS) indicates that in the current
frame, at least one isochronous OUT endpoint has an incomplete transfer.

2.

If this occurs because isochronous OUT data is not completely emptied from the
endpoint, the application must ensure that the application empties all isochronous OUT
data (data and status) from the receive FIFO before proceeding.
–

3.

When all data are emptied from the receive FIFO, the application can detect the
XFRC interrupt (OTG_DOEPINTx). In this case, the application must re-enable
the endpoint to receive isochronous OUT data in the next frame.

When it receives an INCOMPISOOUT interrupt (in OTG_GINTSTS), the application
must read the control registers of all isochronous OUT endpoints (OTG_DOEPCTLx) to
determine which endpoints had an incomplete transfer in the current microframe. An
endpoint transfer is incomplete if both the following conditions are met:
–

EONUM bit (in OTG_DOEPCTLx) = FNSOF[0] (in OTG_DSTS)

–

EPENA = 1 (in OTG_DOEPCTLx)

4.

The previous step must be performed before the SOF interrupt (in OTG_GINTSTS) is
detected, to ensure that the current frame number is not changed.

5.

For isochronous OUT endpoints with incomplete transfers, the application must discard
the data in the memory and disable the endpoint by setting the EPDIS bit in
OTG_DOEPCTLx.

6.

Wait for the EPDISD interrupt (in OTG_DOEPINTx) and enable the endpoint to receive
new data in the next frame.
–

•

Because the core can take some time to disable the endpoint, the application may
not be able to receive the data in the next frame after receiving bad isochronous
data.

Stalling a non-isochronous OUT endpoint

This section describes how the application can stall a non-isochronous endpoint.
1.
2.

Put the core in the Global OUT NAK mode.
Disable the required endpoint
–

When disabling the endpoint, instead of setting the SNAK bit in OTG_DOEPCTL,
set STALL = 1 (in OTG_DOEPCTL).
The STALL bit always takes precedence over the NAK bit.

3.

When the application is ready to end the STALL handshake for the endpoint, the
STALL bit (in OTG_DOEPCTLx) must be cleared.

4.

If the application is setting or clearing a STALL for an endpoint due to a
SetFeature.Endpoint Halt or ClearFeature.Endpoint Halt command, the STALL bit must
be set or cleared before the application sets up the status stage transfer on the control
endpoint.

Examples
This section describes and depicts some fundamental transfer types and scenarios.
•

1498/1709

Bulk OUT transaction

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 485 depicts the reception of a single Bulk OUT data packet from the USB to the AHB
and describes the events involved in the process.
Figure 485. Bulk OUT transaction
Host

USB

Device

Application
init _out_ep
1

2

XFRSIZ = 64 bytes
PKTCNT = 1

Wr_reg(OTG_DOEPTSIZx)

EPENA = 1
CN AK = 1

O UT

Wr_reg(OTG_DOEPCTLx)

3
64 bytes
4

6

xact_1
AC K

RXFLVL iintr

OTG_DO

5

EPCTLx

PKTCN

, NAK=1

XFRSIZ
=0
r
OU T
NA K

idle until intr

T0

7

rcv_out _pkt()

XF
int r RC

8

On new xfer
or RxFIFO
not em pty

idle until intr

MS36931V1

After a SetConfiguration/SetInterface command, the application initializes all OUT endpoints
by setting CNAK = 1 and EPENA = 1 (in OTG_DOEPCTLx), and setting a suitable
XFRSIZ and PKTCNT in the OTG_DOEPTSIZx register.
1.

host attempts to send data (OUT token) to an endpoint.

2.

When the core receives the OUT token on the USB, it stores the packet in the Rx FIFO
because space is available there.

3.

After writing the complete packet in the Rx FIFO, the core then asserts the RXFLVL
interrupt (in OTG_GINTSTS).

4.

On receiving the PKTCNT number of USB packets, the core internally sets the NAK bit
for this endpoint to prevent it from receiving any more packets.

5.

The application processes the interrupt and reads the data from the Rx FIFO.

6.

When the application has read all the data (equivalent to XFRSIZ), the core generates
an XFRC interrupt (in OTG_DOEPINTx).

7.

The application processes the interrupt and uses the setting of the XFRC interrupt bit
(in OTG_DOEPINTx) to determine that the intended transfer is complete.

IN data transfers
•

Packet write

This section describes how the application writes data packets to the endpoint FIFO when
dedicated transmit FIFOs are enabled.

RM0385 Rev 7

1499/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

2.

RM0385

The application can either choose the polling or the interrupt mode.
–

In polling mode, the application monitors the status of the endpoint transmit data
FIFO by reading the OTG_DTXFSTSx register, to determine if there is enough
space in the data FIFO.

–

In interrupt mode, the application waits for the TXFE interrupt (in OTG_DIEPINTx)
and then reads the OTG_DTXFSTSx register, to determine if there is enough
space in the data FIFO.

–

To write a single non-zero length data packet, there must be space to write the
entire packet in the data FIFO.

–

To write zero length packet, the application must not look at the FIFO space.

Using one of the above mentioned methods, when the application determines that
there is enough space to write a transmit packet, the application must first write into the
endpoint control register, before writing the data into the data FIFO. Typically, the
application, must do a read modify write on the OTG_DIEPCTLx register to avoid
modifying the contents of the register, except for setting the endpoint enable bit.

The application can write multiple packets for the same endpoint into the transmit FIFO, if
space is available. For periodic IN endpoints, the application must write packets only for one
microframe. It can write packets for the next periodic transaction only after getting transfer
complete for the previous transaction.
•

Setting IN endpoint NAK

Internal data flow:
1.

When the application sets the IN NAK for a particular endpoint, the core stops
transmitting data on the endpoint, irrespective of data availability in the endpoint’s
transmit FIFO.

2.

Non-isochronous IN tokens receive a NAK handshake reply
–

Isochronous IN tokens receive a zero-data-length packet reply

3.

The core asserts the INEPNE (IN endpoint NAK effective) interrupt in OTG_DIEPINTx
in response to the SNAK bit in OTG_DIEPCTLx.

4.

Once this interrupt is seen by the application, the application can assume that the
endpoint is in IN NAK mode. This interrupt can be cleared by the application by setting
the CNAK bit in OTG_DIEPCTLx.

Application programming sequence:
1.

To stop transmitting any data on a particular IN endpoint, the application must set the
IN NAK bit. To set this bit, the following field must be programmed.
–

2.

Wait for assertion of the INEPNE interrupt in OTG_DIEPINTx. This interrupt indicates
that the core has stopped transmitting data on the endpoint.

3.

The core can transmit valid IN data on the endpoint after the application has set the
NAK bit, but before the assertion of the NAK Effective interrupt.

4.

The application can mask this interrupt temporarily by writing to the INEPNEM bit in
OTG_DIEPMSK.
–

5.

1500/1709

SNAK = 1 in OTG_DIEPCTLx

INEPNEM = 0 in OTG_DIEPMSK

To exit endpoint NAK mode, the application must clear the NAK status bit (NAKSTS) in
OTG_DIEPCTLx. This also clears the INEPNE interrupt (in OTG_DIEPINTx).

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
–
6.

If the application masked this interrupt earlier, it must be unmasked as follows:
–

•

CNAK = 1 in OTG_DIEPCTLx
INEPNEM = 1 in OTG_DIEPMSK

IN endpoint disable

Use the following sequence to disable a specific IN endpoint that has been previously
enabled.
Application programming sequence:
1.
2.

The application must stop writing data on the AHB for the IN endpoint to be disabled.
The application must set the endpoint in NAK mode.
–

SNAK = 1 in OTG_DIEPCTLx

3.

Wait for the INEPNE interrupt in OTG_DIEPINTx.

4.

Set the following bits in the OTG_DIEPCTLx register for the endpoint that must be
disabled.

5.

–

EPDIS = 1 in OTG_DIEPCTLx

–

SNAK = 1 in OTG_DIEPCTLx

Assertion of the EPDISD interrupt in OTG_DIEPINTx indicates that the core has
completely disabled the specified endpoint. Along with the assertion of the interrupt, the
core also clears the following bits:
–

EPENA = 0 in OTG_DIEPCTLx

–

EPDIS = 0 in OTG_DIEPCTLx

6.

The application must read the OTG_DIEPTSIZx register for the periodic IN EP, to
calculate how much data on the endpoint were transmitted on the USB.

7.

The application must flush the data in the endpoint transmit FIFO, by setting the
following fields in the OTG_GRSTCTL register:
–

TXFNUM (in OTG_GRSTCTL) = Endpoint transmit FIFO number

–

TXFFLSH in (OTG_GRSTCTL) = 1

The application must poll the OTG_GRSTCTL register, until the TXFFLSH bit is cleared by
the core, which indicates the end of flush operation. To transmit new data on this endpoint,
the application can re-enable the endpoint at a later point.
•

Generic non-periodic IN data transfers

Application requirements:
1.

Before setting up an IN transfer, the application must ensure that all data to be
transmitted as part of the IN transfer are part of a single buffer.

2.

For IN transfers, the transfer size field in the endpoint transfer size register denotes a
payload that constitutes multiple maximum-packet-size packets and a single short
packet. This short packet is transmitted at the end of the transfer.
–

To transmit a few maximum-packet-size packets and a short packet at the end of
the transfer:
Transfer size[EPNUM] = x × MPSIZ[EPNUM] + sp
If (sp > 0), then packet count[EPNUM] = x + 1.
Otherwise, packet count[EPNUM] = x

–

To transmit a single zero-length data packet:

RM0385 Rev 7

1501/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Transfer size[EPNUM] = 0
Packet count[EPNUM] = 1
–

To transmit a few maximum-packet-size packets and a zero-length data packet at
the end of the transfer, the application must split the transfer into two parts. The
first sends maximum-packet-size data packets and the second sends the zerolength data packet alone.
First transfer: transfer size[EPNUM] = x × MPSIZ[epnum]; packet count = n;
Second transfer: transfer size[EPNUM] = 0; packet count = 1;

3.

Once an endpoint is enabled for data transfers, the core updates the transfer size
register. At the end of the IN transfer, the application must read the transfer size
register to determine how much data posted in the transmit FIFO have already been
sent on the USB.

4.

Data fetched into transmit FIFO = Application-programmed initial transfer size – coreupdated final transfer size
–

Data transmitted on USB = (application-programmed initial packet count – core
updated final packet count) × MPSIZ[EPNUM]

–

Data yet to be transmitted on USB = (Application-programmed initial transfer size
– data transmitted on USB)

Internal data flow:
1.

The application must set the transfer size and packet count fields in the endpointspecific registers and enable the endpoint to transmit the data.

2.

The application must also write the required data to the transmit FIFO for the endpoint.

3.

Every time a packet is written into the transmit FIFO by the application, the transfer size
for that endpoint is decremented by the packet size. The data is fetched from the
memory by the application, until the transfer size for the endpoint becomes 0. After
writing the data into the FIFO, the “number of packets in FIFO” count is incremented
(this is a 3-bit count, internally maintained by the core for each IN endpoint transmit
FIFO. The maximum number of packets maintained by the core at any time in an IN
endpoint FIFO is eight). For zero-length packets, a separate flag is set for each FIFO,
without any data in the FIFO.

4.

Once the data are written to the transmit FIFO, the core reads them out upon receiving
an IN token. For every non-isochronous IN data packet transmitted with an ACK
handshake, the packet count for the endpoint is decremented by one, until the packet
count is zero. The packet count is not decremented on a timeout.

5.

For zero length packets (indicated by an internal zero length flag), the core sends out a
zero-length packet for the IN token and decrements the packet count field.

6.

If there are no data in the FIFO for a received IN token and the packet count field for
that endpoint is zero, the core generates an “IN token received when Tx FIFO is empty”
(ITTXFE) interrupt for the endpoint, provided that the endpoint NAK bit is not set. The
core responds with a NAK handshake for non-isochronous endpoints on the USB.

7.

The core internally rewinds the FIFO pointers and no timeout interrupt is generated.

8.

When the transfer size is 0 and the packet count is 0, the transfer complete (XFRC)
interrupt for the endpoint is generated and the endpoint enable is cleared.

Application programming sequence:

1502/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

Program the OTG_DIEPTSIZx register with the transfer size and corresponding packet
count.

2.

Program the OTG_DIEPCTLx register with the endpoint characteristics and set the
CNAK and EPENA (endpoint enable) bits.

3.

When transmitting non-zero length data packet, the application must poll the
OTG_DTXFSTSx register (where x is the FIFO number associated with that endpoint)
to determine whether there is enough space in the data FIFO. The application can
optionally use TXFE (in OTG_DIEPINTx) before writing the data.

•

Generic periodic IN data transfers

This section describes a typical periodic IN data transfer.
Application requirements:
1.

Application requirements 1, 2, 3, and 4 of Generic non-periodic IN data transfers on
page 1501 also apply to periodic IN data transfers, except for a slight modification of
requirement 2.
–

The application can only transmit multiples of maximum-packet-size data packets
or multiples of maximum-packet-size packets, plus a short packet at the end. To
transmit a few maximum-packet-size packets and a short packet at the end of the
transfer, the following conditions must be met:
transfer size[EPNUM] = x × MPSIZ[EPNUM] + sp
(where x is an integer ≥ 0, and 0 ≤ sp < MPSIZ[EPNUM])
If (sp > 0), packet count[EPNUM] = x + 1
Otherwise, packet count[EPNUM] = x;
MCNT[EPNUM] = packet count[EPNUM]

–

The application cannot transmit a zero-length data packet at the end of a transfer.
It can transmit a single zero-length data packet by itself. To transmit a single zerolength data packet:

–

transfer size[EPNUM] = 0
packet count[EPNUM] = 1
MCNT[EPNUM] = packet count[EPNUM]

2.

3.

The application can only schedule data transfers one frame at a time.
–

(MCNT – 1) × MPSIZ ≤ XFERSIZ ≤ MCNT × MPSIZ

–

PKTCNT = MCNT (in OTG_DIEPTSIZx)

–

If XFERSIZ < MCNT × MPSIZ, the last data packet of the transfer is a short
packet.

–

Note that: MCNT is in OTG_DIEPTSIZx, MPSIZ is in OTG_DIEPCTLx, PKTCNT
is in OTG_DIEPTSIZx and XFERSIZ is in OTG_DIEPTSIZx

The complete data to be transmitted in the frame must be written into the transmit FIFO
by the application, before the IN token is received. Even when 1 word of the data to be
transmitted per frame is missing in the transmit FIFO when the IN token is received, the
core behaves as when the FIFO is empty. When the transmit FIFO is empty:
–

A zero data length packet would be transmitted on the USB for isochronous IN
endpoints

–

A NAK handshake would be transmitted on the USB for interrupt IN endpoints

Internal data flow:

RM0385 Rev 7

1503/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

1.

The application must set the transfer size and packet count fields in the endpointspecific registers and enable the endpoint to transmit the data.

2.

The application must also write the required data to the associated transmit FIFO for
the endpoint.

3.

Every time the application writes a packet to the transmit FIFO, the transfer size for that
endpoint is decremented by the packet size. The data are fetched from application
memory until the transfer size for the endpoint becomes 0.

4.

When an IN token is received for a periodic endpoint, the core transmits the data in the
FIFO, if available. If the complete data payload (complete packet, in dedicated FIFO
mode) for the frame is not present in the FIFO, then the core generates an IN token
received when Tx FIFO empty interrupt for the endpoint.

5.

6.

–

A zero-length data packet is transmitted on the USB for isochronous IN endpoints

–

A NAK handshake is transmitted on the USB for interrupt IN endpoints

The packet count for the endpoint is decremented by 1 under the following conditions:
–

For isochronous endpoints, when a zero- or non-zero-length data packet is
transmitted

–

For interrupt endpoints, when an ACK handshake is transmitted

–

When the transfer size and packet count are both 0, the transfer completed
interrupt for the endpoint is generated and the endpoint enable is cleared.

At the “Periodic frame Interval” (controlled by PFIVL in OTG_DCFG), when the core
finds non-empty any of the isochronous IN endpoint FIFOs scheduled for the current
frame non-empty, the core generates an IISOIXFR interrupt in OTG_GINTSTS.

Application programming sequence:
1.

Program the OTG_DIEPCTLx register with the endpoint characteristics and set the
CNAK and EPENA bits.

2.

Write the data to be transmitted in the next frame to the transmit FIFO.

3.

Asserting the ITTXFE interrupt (in OTG_DIEPINTx) indicates that the application has
not yet written all data to be transmitted to the transmit FIFO.

4.

If the interrupt endpoint is already enabled when this interrupt is detected, ignore the
interrupt. If it is not enabled, enable the endpoint so that the data can be transmitted on
the next IN token attempt.

5.

Asserting the XFRC interrupt (in OTG_DIEPINTx) with no ITTXFE interrupt in
OTG_DIEPINTx indicates the successful completion of an isochronous IN transfer. A
read to the OTG_DIEPTSIZx register must give transfer size = 0 and packet count = 0,
indicating all data were transmitted on the USB.

6.

Asserting the XFRC interrupt (in OTG_DIEPINTx), with or without the ITTXFE interrupt
(in OTG_DIEPINTx), indicates the successful completion of an interrupt IN transfer. A
read to the OTG_DIEPTSIZx register must give transfer size = 0 and packet count = 0,
indicating all data were transmitted on the USB.

7.

Asserting the incomplete isochronous IN transfer (IISOIXFR) interrupt in
OTG_GINTSTS with none of the aforementioned interrupts indicates the core did not
receive at least 1 periodic IN token in the current frame.

•

Incomplete isochronous IN data transfers

This section describes what the application must do on an incomplete isochronous IN data
transfer.

1504/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Internal data flow:
1.

An isochronous IN transfer is treated as incomplete in one of the following conditions:
a)

The core receives a corrupted isochronous IN token on at least one isochronous
IN endpoint. In this case, the application detects an incomplete isochronous IN
transfer interrupt (IISOIXFR in OTG_GINTSTS).

b)

The application is slow to write the complete data payload to the transmit FIFO
and an IN token is received before the complete data payload is written to the
FIFO. In this case, the application detects an IN token received when Tx FIFO
empty interrupt in OTG_DIEPINTx. The application can ignore this interrupt, as it
eventually results in an incomplete isochronous IN transfer interrupt (IISOIXFR in
OTG_GINTSTS) at the end of periodic frame.
The core transmits a zero-length data packet on the USB in response to the
received IN token.

2.

The application must stop writing the data payload to the transmit FIFO as soon as
possible.

3.

The application must set the NAK bit and the disable bit for the endpoint.

4.

The core disables the endpoint, clears the disable bit, and asserts the endpoint disable
interrupt for the endpoint.

Application programming sequence:
1.

The application can ignore the IN token received when Tx FIFO empty interrupt in
OTG_DIEPINTx on any isochronous IN endpoint, as it eventually results in an
incomplete isochronous IN transfer interrupt (in OTG_GINTSTS).

2.

Assertion of the incomplete isochronous IN transfer interrupt (in OTG_GINTSTS)
indicates an incomplete isochronous IN transfer on at least one of the isochronous IN
endpoints.

3.

The application must read the endpoint control register for all isochronous IN endpoints
to detect endpoints with incomplete IN data transfers.

4.

The application must stop writing data to the Periodic Transmit FIFOs associated with
these endpoints on the AHB.

5.

Program the following fields in the OTG_DIEPCTLx register to disable the endpoint:

6.

–

SNAK = 1 in OTG_DIEPCTLx

–

EPDIS = 1 in OTG_DIEPCTLx

The assertion of the endpoint disabled interrupt in OTG_DIEPINTx indicates that the
core has disabled the endpoint.
–

•

At this point, the application must flush the data in the associated transmit FIFO or
overwrite the existing data in the FIFO by enabling the endpoint for a new transfer
in the next microframe. To flush the data, the application must use the
OTG_GRSTCTL register.

Stalling non-isochronous IN endpoints

This section describes how the application can stall a non-isochronous endpoint.
Application programming sequence:

RM0385 Rev 7

1505/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

Disable the IN endpoint to be stalled. Set the STALL bit as well.

2.

EPDIS = 1 in OTG_DIEPCTLx, when the endpoint is already enabled
–

STALL = 1 in OTG_DIEPCTLx

–

The STALL bit always takes precedence over the NAK bit

RM0385

3.

Assertion of the endpoint disabled interrupt (in OTG_DIEPINTx) indicates to the
application that the core has disabled the specified endpoint.

4.

The application must flush the non-periodic or periodic transmit FIFO, depending on
the endpoint type. In case of a non-periodic endpoint, the application must re-enable
the other non-periodic endpoints that do not need to be stalled, to transmit data.

5.

Whenever the application is ready to end the STALL handshake for the endpoint, the
STALL bit must be cleared in OTG_DIEPCTLx.

6.

If the application sets or clears a STALL bit for an endpoint due to a
SetFeature.Endpoint Halt command or ClearFeature.Endpoint Halt command, the
STALL bit must be set or cleared before the application sets up the status stage
transfer on the control endpoint.

Special case: stalling the control OUT endpoint
The core must stall IN/OUT tokens if, during the data stage of a control transfer, the host
sends more IN/OUT tokens than are specified in the SETUP packet. In this case, the
application must enable the ITTXFE interrupt in OTG_DIEPINTx and the OTEPDIS interrupt
in OTG_DOEPINTx during the data stage of the control transfer, after the core has
transferred the amount of data specified in the SETUP packet. Then, when the application
receives this interrupt, it must set the STALL bit in the corresponding endpoint control
register, and clear this interrupt.

37.16.7

Worst case response time
When the OTG_FS/OTG_HS controller acts as a device, there is a worst case response
time for any tokens that follow an isochronous OUT. This worst case response time depends
on the AHB clock frequency.
The core registers are in the AHB domain, and the core does not accept another token
before updating these register values. The worst case is for any token following an
isochronous OUT, because for an isochronous transaction, there is no handshake and the
next token could come sooner. This worst case value is 7 PHY clocks when the AHB clock
is the same as the PHY clock. When the AHB clock is faster, this value is smaller.
If this worst case condition occurs, the core responds to bulk/interrupt tokens with a NAK
and drops isochronous and SETUP tokens. The host interprets this as a timeout condition
for SETUP and retries the SETUP packet. For isochronous transfers, the Incomplete
isochronous IN transfer interrupt (IISOIXFR) and Incomplete isochronous OUT transfer
interrupt (IISOOXFR) inform the application that isochronous IN/OUT packets were
dropped.

Choosing the value of TRDT in OTG_GUSBCFG
The value in TRDT (OTG_GUSBCFG) is the time it takes for the MAC, in terms of PHY
clocks after it has received an IN token, to get the FIFO status, and thus the first data from
the PFC block. This time involves the synchronization delay between the PHY and AHB
clocks. The worst case delay for this is when the AHB clock is the same as the PHY clock.
In this case, the delay is 5 clocks.

1506/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Once the MAC receives an IN token, this information (token received) is synchronized to the
AHB clock by the PFC (the PFC runs on the AHB clock). The PFC then reads the data from
the SPRAM and writes them into the dual clock source buffer. The MAC then reads the data
out of the source buffer (4 deep).
If the AHB is running at a higher frequency than the PHY, the application can use a smaller
value for TRDT (in OTG_GUSBCFG).
Figure 486 has the following signals:
•

tkn_rcvd: Token received information from MAC to PFC

•

dynced_tkn_rcvd: Doubled sync tkn_rcvd, from PCLK to HCLK domain

•

spr_read: Read to SPRAM

•

spr_addr: Address to SPRAM

•

spr_rdata: Read data from SPRAM

•

srcbuf_push: Push to the source buffer

•

srcbuf_rdata: Read data from the source buffer. Data seen by MAC

To calculate the value of TRDT, refer to Table 266: TRDT values (FS) or Table 267: TRDT
values (HS).

RM0385 Rev 7

1507/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Figure 486. TRDT max timing case

37.16.8

OTG programming model
The OTG_FS/OTG_HS controller is an OTG device supporting HNP and SRP. When the
core is connected to an “A” plug, it is referred to as an A-device. When the core is connected
to a “B” plug it is referred to as a B-device. In host mode, the OTG_FS/OTG_HS controller
turns off VBUS to conserve power. SRP is a method by which the B-device signals the Adevice to turn on VBUS power. A device must perform both data-line pulsing and VBUS
pulsing, but a host can detect either data-line pulsing or VBUS pulsing for SRP. HNP is a
method by which the B-device negotiates and switches to host role. In Negotiated mode
after HNP, the B-device suspends the bus and reverts to the device role.

A-device session request protocol
The application must set the SRP-capable bit in the core USB configuration register. This
enables the OTG_FS/OTG_HS controller to detect SRP as an A-device.

1508/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 487. A-device SRP
Suspend

6
1

DRV_VBUS

5

2
VBUS_VALID

VBUS pulsing

A_VALID

3

D+

D-

4
Data line pulsing

7
Connect

Low
ai15681c

1. DRV_VBUS = VBUS drive signal to the PHY
VBUS_VALID = VBUS valid signal from PHY
A_VALID = A-peripheral VBUS level signal to PHY
D+ = Data plus line
D- = Data minus line

The following points refer and describe the signal numeration shown in the Figure 487:
1.

To save power, the application suspends and turns off port power when the bus is idle
by writing the port suspend and port power bits in the host port control and status
register.

2.

PHY indicates port power off by deasserting the VBUS_VALID signal.

3.

The device must detect SE0 for at least 2 ms to start SRP when VBUS power is off.

4.

To initiate SRP, the device turns on its data line pull-up resistor for 5 to 10 ms. The
OTG_FS/OTG_HS controller detects data-line pulsing.

5.

The device drives VBUS above the A-device session valid (2.0 V minimum) for VBUS
pulsing.
The OTG_FS/OTG_HS controller interrupts the application on detecting SRP. The
session request detected bit is set in Global interrupt status register (SRQINT set in
OTG_GINTSTS).

6.

The application must service the session request detected interrupt and turn on the
port power bit by writing the port power bit in the host port control and status register.
The PHY indicates port power-on by asserting the VBUS_VALID signal.

7.

When the USB is powered, the device connects, completing the SRP process.

B-device session request protocol
The application must set the SRP-capable bit in the core USB configuration register. This
enables the OTG_FS/OTG_HS controller to initiate SRP as a B-device. SRP is a means by
which the OTG_FS/OTG_HS controller can request a new session from the host.

RM0385 Rev 7

1509/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

Figure 488. B-device SRP
6

Suspend
1

VBUS_VALID

2

B_VALID

3
DISCHRG_VBUS
4
SESS_END
5

8
Data line pulsing

Connect

DP

DM

Low
7
VBUS pulsing

CHRG_VBUS

ai15682c

1. VBUS_VALID = VBUS valid signal from PHY
B_VALID = B-peripheral valid session to PHY
DISCHRG_VBUS = discharge signal to PHY
SESS_END = session end signal to PHY
CHRG_VBUS = charge VBUS signal to PHY
DP = Data plus line
DM = Data minus line

The following points refer and describe the signal numeration shown in the Figure 488:

1510/1709

1.

To save power, the host suspends and turns off port power when the bus is idle.
The OTG_FS/OTG_HS controller sets the early suspend bit in the core interrupt
register after 3 ms of bus idleness. Following this, the OTG_FS/OTG_HS controller
sets the USB suspend bit in the core interrupt register.
The OTG_FS/OTG_HS controller informs the PHY to discharge VBUS.

2.

The PHY indicates the session’s end to the device. This is the initial condition for SRP.
The OTG_FS/OTG_HS controller requires 2 ms of SE0 before initiating SRP.
For a USB 1.1 full-speed serial transceiver, the application must wait until VBUS
discharges to 0.2 V after BSVLD (in OTG_GOTGCTL) is deasserted. This discharge
time can be obtained from the transceiver vendor and varies from one transceiver to
another.

3.

The OTG_FS/OTG_HS core informs the PHY to speed up VBUS discharge.

4.

The application initiates SRP by writing the session request bit in the OTG control and
status register. The OTG_FS/OTG_HS controller perform data-line pulsing followed by
VBUS pulsing.

5.

The host detects SRP from either the data-line or VBUS pulsing, and turns on VBUS.
The PHY indicates VBUS power-on to the device.

6.

The OTG_FS/OTG_HS controller performs VBUS pulsing.
The host starts a new session by turning on VBUS, indicating SRP success. The
OTG_FS/OTG_HS controller interrupts the application by setting the session request

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
success status change bit in the OTG interrupt status register. The application reads
the session request success bit in the OTG control and status register.
7.

When the USB is powered, the OTG_FS/OTG_HS controller connects, completing the
SRP process.

A-device host negotiation protocol
HNP switches the USB host role from the A-device to the B-device. The application must set
the HNP-capable bit in the core USB configuration register to enable the OTG_FS/OTG_HS
controller to perform HNP as an A-device.
Figure 489. A-device HNP

1. DPPULLDOWN = signal from core to PHY to enable/disable the pull-down on the DP line inside the PHY.
DMPULLDOWN = signal from core to PHY to enable/disable the pull-down on the DM line inside the PHY.

The following points refer and describe the signal numeration shown in the Figure 489:
1.

The OTG_FS/OTG_HS controller sends the B-device a SetFeature b_hnp_enable
descriptor to enable HNP support. The B-device’s ACK response indicates that the Bdevice supports HNP. The application must set host Set HNP enable bit in the OTG

RM0385 Rev 7

1511/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

control and status register to indicate to the OTG_FS/OTG_HS controller that the Bdevice supports HNP.
2.

When it has finished using the bus, the application suspends by writing the port
suspend bit in the host port control and status register.

3.

When the B-device observes a USB suspend, it disconnects, indicating the initial
condition for HNP. The B-device initiates HNP only when it must switch to the host role;
otherwise, the bus continues to be suspended.
The OTG_FS/OTG_HS controller sets the host negotiation detected interrupt in the
OTG interrupt status register, indicating the start of HNP.
The OTG_FS/OTG_HS controller deasserts the DM pull down and DM pull down in the
PHY to indicate a device role. The PHY enables the OTG_DP pull-up resistor to
indicate a connect for B-device.
The application must read the current mode bit in the OTG control and status register
to determine device mode operation.

4.

The B-device detects the connection, issues a USB reset, and enumerates the
OTG_FS/OTG_HS controller for data traffic.

5.

The B-device continues the host role, initiating traffic, and suspends the bus when
done.
The OTG_FS/OTG_HS controller sets the early suspend bit in the core interrupt
register after 3 ms of bus idleness. Following this, the OTG_FS/OTG_HS controller
sets the USB suspend bit in the core interrupt register.

6.

In Negotiated mode, the OTG_FS/OTG_HS controller detects the suspend,
disconnects, and switches back to the host role. The OTG_FS/OTG_HS controller
asserts the DM pull down and DM pull down in the PHY to indicate its assumption of
the host role.

7.

The OTG_FS/OTG_HS controller sets the connector ID status change interrupt in the
OTG interrupt status register. The application must read the connector ID status in the
OTG control and status register to determine the OTG_FS/OTG_HS controller
operation as an A-device. This indicates the completion of HNP to the application. The
application must read the Current mode bit in the OTG control and status register to
determine host mode operation.

8.

The B-device connects, completing the HNP process.

B-device host negotiation protocol
HNP switches the USB host role from B-device to A-device. The application must set the
HNP-capable bit in the core USB configuration register to enable the OTG_FS/OTG_HS
controller to perform HNP as a B-device.

1512/1709

RM0385 Rev 7

RM0385

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 490. B-device HNP

1. DPPULLDOWN = signal from core to PHY to enable/disable the pull-down on the DP line inside the PHY.
DMPULLDOWN = signal from core to PHY to enable/disable the pull-down on the DM line inside the PHY.

The following points refer and describe the signal numeration shown in the Figure 490:
1.

The A-device sends the SetFeature b_hnp_enable descriptor to enable HNP support.
The OTG_FS/OTG_HS controller’s ACK response indicates that it supports HNP. The
application must set the device HNP enable bit in the OTG control and status register
to indicate HNP support.
The application sets the HNP request bit in the OTG control and status register to
indicate to the OTG_FS/OTG_HS controller to initiate HNP.

2.

When it has finished using the bus, the A-device suspends by writing the port suspend
bit in the host port control and status register.
The OTG_FS/OTG_HS controller sets the Early suspend bit in the core interrupt
register after 3 ms of bus idleness. Following this, the OTG_FS/OTG_HS controller
sets the USB suspend bit in the core interrupt register.
The OTG_FS/OTG_HS controller disconnects and the A-device detects SE0 on the
bus, indicating HNP. The OTG_FS/OTG_HS controller asserts the DP pull down and
DM pull down in the PHY to indicate its assumption of the host role.
The A-device responds by activating its OTG_DP pull-up resistor within 3 ms of
detecting SE0. The OTG_FS/OTG_HS controller detects this as a connect.
The OTG_FS/OTG_HS controller sets the host negotiation success status change
interrupt in the OTG interrupt status register, indicating the HNP status. The application
must read the host negotiation success bit in the OTG control and status register to

RM0385 Rev 7

1513/1709
1514

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0385

determine host negotiation success. The application must read the current Mode bit in
the core interrupt register (OTG_GINTSTS) to determine host mode operation.

1514/1709

3.

The application sets the reset bit (PRST in OTG_HPRT) and the OTG_FS/OTG_HS
controller issues a USB reset and enumerates the A-device for data traffic.

4.

The OTG_FS/OTG_HS controller continues the host role of initiating traffic, and when
done, suspends the bus by writing the port suspend bit in the host port control and
status register.

5.

In Negotiated mode, when the A-device detects a suspend, it disconnects and switches
back to the host role. The OTG_FS/OTG_HS controller deasserts the DP pull down
and DM pull down in the PHY to indicate the assumption of the device role.

6.

The application must read the current mode bit in the core interrupt (OTG_GINTSTS)
register to determine the host mode operation.

7.

The OTG_FS/OTG_HS controller connects, completing the HNP process.

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

38

Ethernet (ETH): media access control (MAC) with
DMA controller

38.1

Ethernet introduction
Portions Copyright (c) 2004, 2005 Synopsys, Inc. All rights reserved. Used with permission.
The Ethernet peripheral enables the STM32F75xxx and STM32F74xxx to transmit and
receive data over Ethernet in compliance with the IEEE 802.3-2002 standard.
The Ethernet provides a configurable, flexible peripheral to meet the needs of various
applications and customers. It supports two industry standard interfaces to the external
physical layer (PHY): the default media independent interface (MII) defined in the IEEE
802.3 specifications and the reduced media independent interface (RMII). It can be used in
number of applications such as switches, network interface cards, etc.
The Ethernet is compliant with the following standards:

38.2

•

IEEE 802.3-2002 for Ethernet MAC

•

IEEE 1588-2008 standard for precision networked clock synchronization

•

AMBA 2.0 for AHB Master/Slave ports

•

RMII specification from RMII consortium

Ethernet main features
The Ethernet (ETH) peripheral includes the following features, listed by category:

RM0385 Rev 7

1515/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

38.2.1

MAC core features
•

Supports 10/100 Mbit/s data transfer rates with external PHY interfaces

•

IEEE 802.3-compliant MII interface to communicate with an external Fast Ethernet
PHY

•

Supports both full-duplex and half-duplex operations
–

1516/1709

RM0385

Supports CSMA/CD Protocol for half-duplex operation

–

Supports IEEE 802.3x flow control for full-duplex operation

–

Optional forwarding of received pause control frames to the user application in fullduplex operation

–

Back-pressure support for half-duplex operation

–

Automatic transmission of zero-quanta pause frame on deassertion of flow control
input in full-duplex operation

•

Preamble and start-of-frame data (SFD) insertion in Transmit, and deletion in Receive
paths

•

Automatic CRC and pad generation controllable on a per-frame basis

•

Options for automatic pad/CRC stripping on receive frames

•

Programmable frame length to support Standard frames with sizes up to 16 KB

•

Programmable interframe gap (40-96 bit times in steps of 8)

•

Supports a variety of flexible address filtering modes:
–

Up to four 48-bit perfect (DA) address filters with masks for each byte

–

Up to three 48-bit SA address comparison check with masks for each byte

–

64-bit Hash filter (optional) for multicast and unicast (DA) addresses

–

Option to pass all multicast addressed frames

–

Promiscuous mode support to pass all frames without any filtering for network
monitoring

–

Passes all incoming packets (as per filter) with a status report

•

Separate 32-bit status returned for transmission and reception packets

•

Supports IEEE 802.1Q VLAN tag detection for reception frames

•

Separate transmission, reception, and control interfaces to the Application

•

Supports mandatory network statistics with RMON/MIB counters (RFC2819/RFC2665)

•

MDIO interface for PHY device configuration and management

•

Detection of LAN wakeup frames and AMD Magic Packet™ frames

•

Receive feature for checksum off-load for received IPv4 and TCP packets
encapsulated by the Ethernet frame

•

Enhanced receive feature for checking IPv4 header checksum and TCP, UDP, or ICMP
checksum encapsulated in IPv4 or IPv6 datagrams

•

Support Ethernet frame time stamping as described in IEEE 1588-2008. Sixty-four-bit
time stamps are given in each frame’s transmit or receive status

•

Two sets of FIFOs: a 2-KB Transmit FIFO with programmable threshold capability, and
a 2-KB Receive FIFO with a configurable threshold (default of 64 bytes)

•

Receive Status vectors inserted into the Receive FIFO after the EOF transfer enables
multiple-frame storage in the Receive FIFO without requiring another FIFO to store
those frames’ Receive Status

•

Option to filter all error frames on reception and not forward them to the application in
RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Store-and-Forward mode

38.2.2

38.2.3

•

Option to forward under-sized good frames

•

Supports statistics by generating pulses for frames dropped or corrupted (due to
overflow) in the Receive FIFO

•

Supports Store and Forward mechanism for transmission to the MAC core

•

Automatic generation of PAUSE frame control or back pressure signal to the MAC core
based on Receive FIFO-fill (threshold configurable) level

•

Handles automatic retransmission of Collision frames for transmission

•

Discards frames on late collision, excessive collisions, excessive deferral and underrun
conditions

•

Software control to flush Tx FIFO

•

Calculates and inserts IPv4 header checksum and TCP, UDP, or ICMP checksum in
frames transmitted in Store-and-Forward mode

•

Supports internal loopback on the MII for debugging

DMA features
•

Supports all AHB burst types in the AHB Slave Interface

•

Software can select the type of AHB burst (fixed or indefinite burst) in the AHB Master
interface.

•

Option to select address-aligned bursts from AHB master port

•

Optimization for packet-oriented DMA transfers with frame delimiters

•

Byte-aligned addressing for data buffer support

•

Dual-buffer (ring) or linked-list (chained) descriptor chaining

•

Descriptor architecture, allowing large blocks of data transfer with minimum CPU
intervention;

•

each descriptor can transfer up to 8 KB of data

•

Comprehensive status reporting for normal operation and transfers with errors

•

Individual programmable burst size for Transmit and Receive DMA Engines for optimal
host bus utilization

•

Programmable interrupt options for different operational conditions

•

Per-frame Transmit/Receive complete interrupt control

•

Round-robin or fixed-priority arbitration between Receive and Transmit engines

•

Start/Stop modes

•

Current Tx/Rx Buffer pointer as status registers

•

Current Tx/Rx Descriptor pointer as status registers

PTP features
•

Received and transmitted frames time stamping

•

Coarse and fine correction methods

•

Trigger interrupt when system time becomes greater than target time

•

Pulse per second output (product alternate function output)

RM0385 Rev 7

1517/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

38.3

RM0385

Ethernet pins
Table 270 shows the MAC signals and the corresponding MII/RMII signal mapping. All MAC
signals are mapped onto AF11, some signals are mapped onto different I/O pins, and
should be configured in Alternate function mode (for more details, refer to Section 6.3.2: I/O
pin alternate function multiplexer and mapping and the corresponding datasheet).
Table 270. Alternate function mapping
AF11
ETH
ETH_MII_CRS
ETH_MII _RX_CLK / ETH_RMII _REF_CLK
ETH _MDIO
ETH _MII_COL
ETH_MII _RX_DV / ETH_RMII _CRS_DV
ETH _MII_RXD2
ETH _MII_RXD3
ETH _PPS_OUT
ETH _MII_TXD3
ETH_ MII_RX_ER
ETH _MII_TX_EN / ETH _RMII_TX_EN
ETH _MII_TXD0 / ETH _RMII_TXD0
ETH _MII_TXD1 / ETH _RMII_TXD1
ETH _MDC
ETH _MII_TXD2
ETH _MII_TX_CLK
ETH_MII_RXD0 / ETH_RMII_RXD0
ETH _MII_RXD1/ ETH _RMII_RXD1
ETH_MII_TXD3
ETH_PPS_OUT
ETH _MII_TX_EN / ETH _RMII_TX_EN
ETH _MII_TXD0 / ETH _RMII_TXD0
ETH _MII_TXD1 / ETH _RMII_TXD1
ETH _MII_CRS
ETH _MII_COL
ETH _MII_RXD2
ETH _MII_RXD3
ETH _MII_RX_ER

1518/1709

RM0385 Rev 7

RM0385

38.4

Ethernet (ETH): media access control (MAC) with DMA controller

Ethernet functional description: SMI, MII and RMII
The Ethernet peripheral consists of a MAC 802.3 (media access control) with a dedicated
DMA controller. It supports both default media-independent interface (MII) and reduced
media-independent interface (RMII) through one selection bit (refer to SYSCFG_PMC
register).
The DMA controller interfaces with the Core and memories through the AHB Master and
Slave interfaces. The AHB Master Interface controls data transfers while the AHB Slave
interface accesses Control and Status Registers (CSR) space.
The Transmit FIFO (Tx FIFO) buffers data read from system memory by the DMA before
transmission by the MAC Core. Similarly, the Receive FIFO (Rx FIFO) stores the Ethernet
frames received from the line until they are transferred to system memory by the DMA.
The Ethernet peripheral also includes an SMI to communicate with external PHY. A set of
configuration registers permit the user to select the desired mode and features for the MAC
and the DMA controller.

Note:

The AHB clock frequency must be at least 25 MHz when the Ethernet is used.

Bus matrix

AHB Slave interface

Figure 491. ETH block diagram

DMA
control &
status
registers

Operation
mode
register

Media access
control
MAC 802.3

Interface
Select

MAC
control
registers

2 Kbyte
RX FIFO
Ethernet
DMA

RMII

2 Kbyte
TX FIFO

Checksum
PTP
offload
IEEE1588
PMT

MMC

MII

External PHY

MDC
MDIO

ai15620c

1. For AHB connections refer to Figure 1: System architecture.

38.4.1

Station management interface: SMI
The station management interface (SMI) allows the application to access any PHY registers
through a 2-wire clock and data lines. The interface supports accessing up to 32 PHYs.
The application can select one of the 32 PHYs and one of the 32 registers within any PHY
and send control data or receive status information. Only one register in one PHY can be
addressed at any given time.
Both the MDC clock line and the MDIO data line are implemented as alternate function I/O
in the microcontroller:
•

MDC: a periodic clock that provides the timing reference for the data transfer at the
maximum frequency of 2.5 MHz. The minimum high and low times for MDC must be

RM0385 Rev 7

1519/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

160 ns each, and the minimum period for MDC must be 400 ns. In idle state the SMI
management interface drives the MDC clock signal low.
•

MDIO: data input/output bitstream to transfer status information to/from the PHY device
synchronously with the MDC clock signal

STM32 MCU

802.3 MAC

Figure 492. SMI interface signals

MDC

External
PHY

MDIO

ai15621b

SMI frame format
The frame structure related to a read or write operation is shown in Table 271, the order of
bit transmission must be from left to right.
Table 271. Management frame format
Management frame fields
-

Preamble
(32 bits)

Start

Operation

PADDR

RADDR

TA

Data (16 bits)

Idle

Read

1... 1

01

10

ppppp

rrrrr

Z0

ddddddddddddddd

Z

Write

1... 1

01

01

ppppp

rrrrr

10

ddddddddddddddd

Z

The management frame consists of eight fields:

1520/1709

•

Preamble: each transaction (read or write) can be initiated with the preamble field that
corresponds to 32 contiguous logic one bits on the MDIO line with 32 corresponding
cycles on MDC. This field is used to establish synchronization with the PHY device.

•

Start: the start of frame is defined by a <01> pattern to verify transitions on the line
from the default logic one state to zero and back to one.

•

Operation: defines the type of transaction (read or write) in progress.

•

PADDR: the PHY address is 5 bits, allowing 32 unique PHY addresses. The MSB bit of
the address is the first transmitted and received.

•

RADDR: the register address is 5 bits, allowing 32 individual registers to be addressed
within the selected PHY device. The MSB bit of the address is the first transmitted and
received.

•

TA: the turn-around field defines a 2-bit pattern between the RADDR and DATA fields
to avoid contention during a read transaction. For a read transaction the MAC controller
drives high-impedance on the MDIO line for the 2 bits of TA. The PHY device must
drive a high-impedance state on the first bit of TA, a zero bit on the second one.

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
For a write transaction, the MAC controller drives a <10> pattern during the TA field.
The PHY device must drive a high-impedance state for the 2 bits of TA.
•

Data: the data field is 16-bit. The first bit transmitted and received must be bit 15 of the
ETH_MIID register.

•

Idle: the MDIO line is driven in high-impedance state. All three-state drivers must be
disabled and the PHY’s pull-up resistor keeps the line at logic one.

SMI write operation
When the application sets the MII Write and Busy bits (in Ethernet MAC MII address register
(ETH_MACMIIAR)), the SMI initiates a write operation into the PHY registers by transferring
the PHY address, the register address in PHY, and the write data (in Ethernet MAC MII data
register (ETH_MACMIIDR). The application should not change the MII Address register
contents or the MII Data register while the transaction is ongoing. Write operations to the MII
Address register or the MII Data Register during this period are ignored (the Busy bit is
high), and the transaction is completed without any error. After the Write operation has
completed, the SMI indicates this by resetting the Busy bit.
Figure 493 shows the frame format for the write operation.
Figure 493. MDIO timing and frame structure - Write cycle

MDC

MDIO

32 1's

0 1

0 1

Start
OP
Preamble of
code
frame

A4 A3 A2 A1 A0 R4 R3

R2 R1 R0

Register address Turn
around

PHY address

D15 D14

D1 D0

data

Data to PHY
ai15626

SMI read operation
When the user sets the MII Busy bit in the Ethernet MAC MII address register
(ETH_MACMIIAR) with the MII Write bit at 0, the SMI initiates a read operation in the PHY
registers by transferring the PHY address and the register address in PHY. The application
should not change the MII Address register contents or the MII Data register while the
transaction is ongoing. Write operations to the MII Address register or MII Data Register
during this period are ignored (the Busy bit is high) and the transaction is completed without
any error. After the read operation has completed, the SMI resets the Busy bit and then
updates the MII Data register with the data read from the PHY.
Figure 494 shows the frame format for the read operation.

RM0385 Rev 7

1521/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Figure 494. MDIO timing and frame structure - Read cycle

MDC

MDIO

32 1's

0 1 1

0

Start
OP
Preamble of
code
frame

A4 A3 A2 A1 A0 R4 R3

PHY address

R2 R1 R0

Register address Turn
around

Data to PHY

D15 D14

D1 D0

data

Data from PHY
ai15627

SMI clock selection
The MAC initiates the Management Write/Read operation. The SMI clock is a divided clock
whose source is the application clock (AHB clock). The divide factor depends on the clock
range setting in the MII Address register.
Table 272 shows how to set the clock ranges.
Table 272. Clock range

1522/1709

Selection

HCLK clock

MDC clock

000

60-100 MHz

AHB clock / 42

001

100-150 MHz

AHB clock / 62

010

20-35 MHz

AHB clock / 16

011

35-60 MHz

AHB clock / 26

100

150-216 MHz

AHB clock / 102

101, 110, 111

Reserved

-

RM0385 Rev 7

RM0385

Media-independent interface: MII
The media-independent interface (MII) defines the interconnection between the MAC
sublayer and the PHY for data transfer at 10 Mbit/s and 100 Mbit/s.
Figure 495. Media independent interface signals
TX_CLK
TXD[3:0]
TX_EN

STM32 MCU

802.3 MAC

38.4.2

Ethernet (ETH): media access control (MAC) with DMA controller

RX_CLK
RXD[3:0]
RX_ER
RX_DV

External
PHY

CRS
COL
MDC
MDIO
ai15622c

•

MII_TX_CLK: continuous clock that provides the timing reference for the TX data
transfer. The nominal frequency is: 2.5 MHz at 10 Mbit/s speed; 25 MHz at 100 Mbit/s
speed.

•

MII_RX_CLK: continuous clock that provides the timing reference for the RX data
transfer. The nominal frequency is: 2.5 MHz at 10 Mbit/s speed; 25 MHz at 100 Mbit/s
speed.

•

MII_TX_EN: transmission enable indicates that the MAC is presenting nibbles on the
MII for transmission. It must be asserted synchronously (MII_TX_CLK) with the first
nibble of the preamble and must remain asserted while all nibbles to be transmitted are
presented to the MII.

•

MII_TXD[3:0]: transmit data is a bundle of 4 data signals driven synchronously by the
MAC sublayer and qualified (valid data) on the assertion of the MII_TX_EN signal.
MII_TXD[0] is the least significant bit, MII_TXD[3] is the most significant bit. While
MII_TX_EN is deasserted the transmit data must have no effect upon the PHY.

•

MII_CRS: carrier sense is asserted by the PHY when either the transmit or receive
medium is non idle. It shall be deasserted by the PHY when both the transmit and
receive media are idle. The PHY must ensure that the MII_CS signal remains asserted
throughout the duration of a collision condition. This signal is not required to transition
synchronously with respect to the TX and RX clocks. In full duplex mode the state of
this signal is don’t care for the MAC sublayer.

•

MII_COL: collision detection must be asserted by the PHY upon detection of a collision
on the medium and must remain asserted while the collision condition persists. This
signal is not required to transition synchronously with respect to the TX and RX clocks.
In full duplex mode the state of this signal is don’t care for the MAC sublayer.

•

MII_RXD[3:0]: reception data is a bundle of 4 data signals driven synchronously by the
PHY and qualified (valid data) on the assertion of the MII_RX_DV signal. MII_RXD[0] is
the least significant bit, MII_RXD[3] is the most significant bit. While MII_RX_EN is

RM0385 Rev 7

1523/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

deasserted and MII_RX_ER is asserted, a specific MII_RXD[3:0] value is used to
transfer specific information from the PHY (see Table 274).
•

MII_RX_DV: receive data valid indicates that the PHY is presenting recovered and
decoded nibbles on the MII for reception. It must be asserted synchronously
(MII_RX_CLK) with the first recovered nibble of the frame and must remain asserted
through the final recovered nibble. It must be deasserted prior to the first clock cycle
that follows the final nibble. In order to receive the frame correctly, the MII_RX_DV
signal must encompass the frame, starting no later than the SFD field.

•

MII_RX_ER: receive error must be asserted for one or more clock periods
(MII_RX_CLK) to indicate to the MAC sublayer that an error was detected somewhere
in the frame. This error condition must be qualified by MII_RX_DV assertion as
described in Table 274.
Table 273. TX interface signal encoding
MII_TX_EN

MII_TXD[3:0]

Description

0

0000 through 1111

Normal inter-frame

1

0000 through 1111

Normal data transmission

Table 274. RX interface signal encoding
MII_RX_DV

MII_RX_ERR

MII_RXD[3:0]

Description

0

0

0000 through 1111

Normal inter-frame

0

1

0000

Normal inter-frame

0

1

0001 through 1101

0

1

1110

False carrier indication

0

1

1111

Reserved

1

0

0000 through 1111

Normal data reception

1

1

0000 through 1111

Data reception with errors

Reserved

MII clock sources
To generate both TX_CLK and RX_CLK clock signals, the external PHY must be clocked
with an external 25 MHz as shown in Figure 496. Instead of using an external 25 MHz
quartz to provide this clock, the STM32F75xxx and STM32F74xxx microcontrollers can
output this signal on its MCO pin. In this case, the PLL multiplier has to be configured so as
to get the desired frequency on the MCO pin, from the 25 MHz external quartz.

1524/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

25 MHz

802.3 MAC

Figure 496. MII clock sources

STM32
MCU

TX _CLK

External
PHY

RX _CLK

HSE
MCO

For 10/100 Mbit/s

25 MHz

ai15623b

Reduced media-independent interface: RMII
The reduced media-independent interface (RMII) specification reduces the pin count
between the microcontroller Ethernet peripheral and the external Ethernet in 10/100 Mbit/s.
According to the IEEE 802.3u standard, an MII contains 16 pins for data and control. The
RMII specification is dedicated to reduce the pin count to 7 pins (a 62.5% decrease in pin
count).
The RMII is instantiated between the MAC and the PHY. This helps translation of the MAC’s
MII into the RMII. The RMII block has the following characteristics:
•

It supports 10-Mbit/s and 100-Mbit/s operating rates

•

The clock reference must be doubled to 50 MHz

•

The same clock reference must be sourced externally to both MAC and external
Ethernet PHY

•

It provides independent 2-bit wide (dibit) transmit and receive data paths
Figure 497. Reduced media-independent interface signals

TXD[1:0]
TX_EN

STM32
MCU

802.3 MAC

38.4.3

RXD[1:0]
CRS_
DV

External
PHY

MDC
MDIO
REF_ CLK
Clock source

ai15624b

RM0385 Rev 7

1525/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

RMII clock sources
Either clock the PHY from an external 50 MHz clock or use a PHY with an embedded PLL to
generate the 50 MHz frequency.

802.3 MAC

Figure 498. RMII clock sources-

STM32
MCU
25 MHz

External
PHY

PLL
REF_CLK

50 MHz

For 10/100 Mbit/s
MS19930V1

38.4.4

MII/RMII selection
The mode, MII or RMII, is selected using the configuration bit 23, MII_RMII_SEL, in the
SYSCFG_PMC register. The application has to set the MII/RMII mode while the Ethernet
controller is under reset or before enabling the clocks.

MII/RMII internal clock scheme
The clock scheme required to support both the MII and RMII, as well as 10 and 100 Mbit/s
operations is described in Figure 499.
Figure 499. Clock scheme
MAC
MII_TX_CLK as AF
(25 MHz or 2.5 MHz)

MII_RX_CLK as AF
(25 MHz or 2.5 MHz)
RMII_REF_CK as AF
(50 MHz)

GPIO and AF
controller

25 MHz or 2.5 MHz

50 MHz Sync. divider
/2 for 100 Mb/s
/20 for 10 Mb/s
GPIO and AF
controller

25 MHz or 2.5 MHz

0
1

25 MHz
or 2.5 MHz

MACTXCLK

TX

MACRXCLK

RX

0 MII
1 RMII(1)
0
1

25 MHz
or 2.5 MHz

AHB

RMII
HCLK
HCLK
must be greater
than 25 MHz

ai15650

1. The MII/RMII selection is controlled through bit 23, MII_RMII_SEL, in the SYSCFG_PMC register.

To save a pin, the two input clock signals, RMII_REF_CK and MII_RX_CLK, are multiplexed
on the same GPIO pin.

1526/1709

RM0385 Rev 7

RM0385

38.5

Ethernet (ETH): media access control (MAC) with DMA controller

Ethernet functional description: MAC 802.3
The IEEE 802.3 International Standard for local area networks (LANs) employs the
CSMA/CD (carrier sense multiple access with collision detection) as the access method.
The Ethernet peripheral consists of a MAC 802.3 (media access control) controller with
media independent interface (MII) and a dedicated DMA controller.
The MAC block implements the LAN CSMA/CD sublayer for the following families of
systems: 10 Mbit/s and 100 Mbit/s of data rates for baseband and broadband systems.
Half- and full-duplex operation modes are supported. The collision detection access method
is applied only to the half-duplex operation mode. The MAC control frame sublayer is
supported.
The MAC sublayer performs the following functions associated with a data link control
procedure:
•

•

Data encapsulation (transmit and receive)
–

Framing (frame boundary delimitation, frame synchronization)

–

Addressing (handling of source and destination addresses)

–

Error detection

Media access management
–

Medium allocation (collision avoidance)

–

Contention resolution (collision handling)

Basically there are two operating modes of the MAC sublayer:

38.5.1

•

Half-duplex mode: the stations contend for the use of the physical medium, using the
CSMA/CD algorithms.

•

Full duplex mode: simultaneous transmission and reception without contention
resolution (CSMA/CD algorithm are unnecessary) when all the following conditions are
met:
–

physical medium capability to support simultaneous transmission and reception

–

exactly 2 stations connected to the LAN

–

both stations configured for full-duplex operation

MAC 802.3 frame format
The MAC block implements the MAC sublayer and the optional MAC control sublayer
(10/100 Mbit/s) as specified by the IEEE 802.3-2002 standard.
Two frame formats are specified for data communication systems using the CSMA/CD
MAC:
•

Basic MAC frame format

•

Tagged MAC frame format (extension of the basic MAC frame format)

RM0385 Rev 7

1527/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Figure 501 and Figure 502 describe the frame structure (untagged and tagged) that
includes the following fields:
•

Preamble: 7-byte field used for synchronization purposes (PLS circuitry)
Hexadecimal value: 55-55-55-55-55-55-55
Bit pattern: 01010101 01010101 01010101 01010101 01010101 01010101 01010101
(right-to-left bit transmission)

•

Start frame delimiter (SFD): 1-byte field used to indicate the start of a frame.
Hexadecimal value: D5
Bit pattern: 11010101 (right-to-left bit transmission)

•

Destination and Source Address fields: 6-byte fields to indicate the destination and
source station addresses as follows (see Figure 500):
–

Each address is 48 bits in length

–

The first LSB bit (I/G) in the destination address field is used to indicate an
individual (I/G = 0) or a group address (I/G = 1). A group address could identify
none, one or more, or all the stations connected to the LAN. In the source address
the first bit is reserved and reset to 0.

–

The second bit (U/L) distinguishes between locally (U/L = 1) or globally (U/L = 0)
administered addresses. For broadcast addresses this bit is also 1.

–

Each byte of each address field must be transmitted least significant bit first.

The address designation is based on the following types:
•

Individual address: this is the physical address associated with a particular station on
the network.

•

Group address. A multidestination address associated with one or more stations on a
given network. There are two kinds of multicast address:
–

Multicast-group address: an address associated with a group of logically related
stations.

–

Broadcast address: a distinguished, predefined multicast address (all 1’s in the
destination address field) that always denotes all the stations on a given LAN.
Figure 500. Address field format

MSB

46-bit address

U/L I/G LSB

I/G = 0 Individual address
I/G = 1 Group address
U/L = 0 Globally administered address
U/L = 1 Locally administered address

Bit transmission order (right to left)
ai15628

•

QTag Prefix: 4-byte field inserted between the Source address field and the MAC Client
Length/Type field. This field is an extension of the basic frame (untagged) to obtain the
tagged MAC frame. The untagged MAC frames do not include this field. The
extensions for tagging are as follows:
–

1528/1709

2-byte constant Length/Type field value consistent with the Type interpretation
(greater than 0x0600) equal to the value of the 802.1Q Tag Protocol Type (0x8100

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
hexadecimal). This constant field is used to distinguish tagged and untagged MAC
frames.
–

•

2-byte field containing the Tag control information field subdivided as follows: a 3bit user priority, a canonical format indicator (CFI) bit and a 12-bit VLAN Identifier.
The length of the tagged MAC frame is extended by 4 bytes by the QTag Prefix.

MAC client length/type: 2-byte field with different meaning (mutually exclusive),
depending on its value:
–

If the value is less than or equal to maxValidFrame (0d1500) then this field
indicates the number of MAC client data bytes contained in the subsequent data
field of the 802.3 frame (length interpretation).

–

If the value is greater than or equal to MinTypeValue (0d1536 decimal, 0x0600)
then this field indicates the nature of the MAC client protocol (Type interpretation)
related to the Ethernet frame.

Regardless of the interpretation of the length/type field, if the length of the data field is
less than the minimum required for proper operation of the protocol, a PAD field is
added after the data field but prior to the FCS (frame check sequence) field. The
length/type field is transmitted and received with the higher-order byte first.
For length/type field values in the range between maxValidLength and minTypeValue
(boundaries excluded), the behavior of the MAC sublayer is not specified: they may or
may not be passed by the MAC sublayer.
•

Data and PAD fields: n-byte data field. Full data transparency is provided, it means that
any arbitrary sequence of byte values may appear in the data field. The size of the
PAD, if any, is determined by the size of the data field. Max and min length of the data
and PAD field are:
–

Maximum length = 1500 bytes

–

Minimum length for untagged MAC frames = 46 bytes

–

Minimum length for tagged MAC frames = 42 bytes

When the data field length is less than the minimum required, the PAD field is added to
match the minimum length (42 bytes for tagged frames, 46 bytes for untagged frames).
•

Frame check sequence: 4-byte field that contains the cyclic redundancy check (CRC)
value. The CRC computation is based on the following fields: source address,
destination address, QTag prefix, length/type, LLC data and PAD (that is, all fields
except the preamble, SFD). The generating polynomial is the following:
G( x) = x

32

+x

26

+x

23

+x

22

+x

16

+x

12

+x

11

+x

10

8

7

5

4

2

+x +x +x +x +x +x+1

The CRC value of a frame is computed as follows:
•

The first 2 bits of the frame are complemented

•

The n-bits of the frame are the coefficients of a polynomial M(x) of degree (n – 1). The
first bit of the destination address corresponds to the xn – 1 term and the last bit of the
data field corresponds to the x0 term

•

M(x) is multiplied by x32 and divided by G(x), producing a remainder R(x) of degree ≤
31

•

The coefficients of R(x) are considered as a 32-bit sequence

•

The bit sequence is complemented and the result is the CRC

•

The 32-bits of the CRC value are placed in the frame check sequence. The x32 term is
the first transmitted, the x0 term is the last one

RM0385 Rev 7

1529/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Figure 501. MAC frame format
7 bytes

Preamble

1 byte

SFD

6 bytes

Destination address

6 bytes

Source address

2 bytes

MAC client length/type

Bytes within
frame transmitted
top to bottom

MAC client data
46-1500 bytes

PAD

4 bytes

Frame check sequence

MSB

LSB
Bit transmission order (right to left)
ai15629

Figure 502. Tagged MAC frame format
7 bytes
1 byte
6 bytes
6 bytes
QTag Prefix
4 bytes
2 bytes
42-1500 bytes

Preamble
SFD

bytes within
frame transmitted
top to bottom

Destination address
MSB

Source address
Length/type = 802.1QTagType
Tag control information

1

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

MAC client length/type
MAC client data
User priority CFI

Pad
4 bytes

LSB

VLAN identifier (VID, 12 bits)

Frame check sequence

MSB

LSB
Bit transmission order (r ight to left)
ai15630

Each byte of the MAC frame, except the FCS field, is transmitted low-order bit first.
An invalid MAC frame is defined by one of the following conditions:

1530/1709

•

The frame length is inconsistent with the expected value as specified by the length/type
field. If the length/type field contains a type value, then the frame length is assumed to
be consistent with this field (no invalid frame)

•

The frame length is not an integer number of bytes (extra bits)

•

The CRC value computed on the incoming frame does not match the included FCS

RM0385 Rev 7

RM0385

38.5.2

Ethernet (ETH): media access control (MAC) with DMA controller

MAC frame transmission
The DMA controls all transactions for the transmit path. Ethernet frames read from the
system memory are pushed into the FIFO by the DMA. The frames are then popped out and
transferred to the MAC core. When the end-of-frame is transferred, the status of the
transmission is taken from the MAC core and transferred back to the DMA. The Transmit
FIFO has a depth of 2 Kbyte. FIFO-fill level is indicated to the DMA so that it can initiate a
data fetch in required bursts from the system memory, using the AHB interface. The data
from the AHB Master interface is pushed into the FIFO.
When the SOF is detected, the MAC accepts the data and begins transmitting to the MII.
The time required to transmit the frame data to the MII after the application initiates
transmission is variable, depending on delay factors like IFG delay, time to transmit
preamble/SFD, and any back-off delays for Half-duplex mode. After the EOF is transferred
to the MAC core, the core completes normal transmission and then gives the status of
transmission back to the DMA. If a normal collision (in Half-duplex mode) occurs during
transmission, the MAC core makes the transmit status valid, then accepts and drops all
further data until the next SOF is received. The same frame should be retransmitted from
SOF on observing a Retry request (in the Status) from the MAC. The MAC issues an
underflow status if the data are not provided continuously during the transmission. During
the normal transfer of a frame, if the MAC receives an SOF without getting an EOF for the
previous frame, then the SOF is ignored and the new frame is considered as the
continuation of the previous frame.
There are two modes of operation for popping data towards the MAC core:
•

In Threshold mode, as soon as the number of bytes in the FIFO crosses the configured
threshold level (or when the end-of-frame is written before the threshold is crossed),
the data is ready to be popped out and forwarded to the MAC core. The threshold level
is configured using the TTC bits of ETH_DMABMR.

•

In Store-and-forward mode, only after a complete frame is stored in the FIFO, the frame
is popped towards the MAC core. If the Tx FIFO size is smaller than the Ethernet frame
to be transmitted, then the frame is popped towards the MAC core when the Tx FIFO
becomes almost full.

The application can flush the Transmit FIFO of all contents by setting the FTF
(ETH_DMAOMR register [20]) bit. This bit is self-clearing and initializes the FIFO pointers to
the default state. If the FTF bit is set during a frame transfer to the MAC core, then transfer
is stopped as the FIFO is considered to be empty. Hence an underflow event occurs at the
MAC transmitter and the corresponding Status word is forwarded to the DMA.

Automatic CRC and pad generation
When the number of bytes received from the application falls below 60 (DA+SA+LT+Data),
zeros are appended to the transmitting frame to make the data length exactly 46 bytes to
meet the minimum data field requirement of IEEE 802.3. The MAC can be programmed not
to append any padding. The cyclic redundancy check (CRC) for the frame check sequence
(FCS) field is calculated and appended to the data being transmitted. When the MAC is
programmed to not append the CRC value to the end of Ethernet frames, the computed
CRC is not transmitted. An exception to this rule is that when the MAC is programmed to
append pads for frames (DA+SA+LT+Data) less than 60 bytes, CRC will be appended at the
end of the padded frames.

RM0385 Rev 7

1531/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

The CRC generator calculates the 32-bit CRC for the FCS field of the Ethernet frame. The
encoding is defined by the following polynomial.
G( x) = x

32

+x

26

+x

23

+x

22

+x

16

+x

12

+x

11

+x

10

8

7

5

4

2

+x +x +x +x +x +x+1

Transmit protocol
The MAC controls the operation of Ethernet frame transmission. It performs the following
functions to meet the IEEE 802.3/802.3z specifications. It:
•

generates the preamble and SFD

•

generates the jam pattern in Half-duplex mode

•

controls the Jabber timeout

•

controls the flow for Half-duplex mode (back pressure)

•

generates the transmit frame status

•

contains time stamp snapshot logic in accordance with IEEE 1588

When a new frame transmission is requested, the MAC sends out the preamble and SFD,
followed by the data. The preamble is defined as 7 bytes of 0b10101010 pattern, and the
SFD is defined as 1 byte of 0b10101011 pattern. The collision window is defined as 1 slot
time (512 bit times for 10/100 Mbit/s Ethernet). The jam pattern generation is applicable only
to Half-duplex mode, not to Full-duplex mode.
In MII mode, if a collision occurs at any time from the beginning of the frame to the end of
the CRC field, the MAC sends a 32-bit jam pattern of 0x5555 5555 on the MII to inform all
other stations that a collision has occurred. If the collision is seen during the preamble
transmission phase, the MAC completes the transmission of the preamble and SFD and
then sends the jam pattern.
A jabber timer is maintained to cut off the transmission of Ethernet frames if more than 2048
(default) bytes have to be transferred. The MAC uses the deferral mechanism for flow
control (back pressure) in Half-duplex mode. When the application requests to stop
receiving frames, the MAC sends a JAM pattern of 32 bytes whenever it senses the
reception of a frame, provided that transmit flow control is enabled. This results in a collision
and the remote station backs off. The application requests flow control by setting the BPA bit
(bit 0) in the ETH_MACFCR register. If the application requests a frame to be transmitted,
then it is scheduled and transmitted even when back pressure is activated. Note that if back
pressure is kept activated for a long time (and more than 16 consecutive collision events
occur) then the remote stations abort their transmissions due to excessive collisions. If IEEE
1588 time stamping is enabled for the transmit frame, this block takes a snapshot of the
system time when the SFD is put onto the transmit MII bus.

Transmit scheduler
The MAC is responsible for scheduling the frame transmission on the MII. It maintains the
interframe gap between two transmitted frames and follows the truncated binary exponential
backoff algorithm for Half-duplex mode. The MAC enables transmission after satisfying the
IFG and backoff delays. It maintains an idle period of the configured interframe gap (IFG bits
in the ETH_MACCR register) between any two transmitted frames. If frames to be
transmitted arrive sooner than the configured IFG time, the MII waits for the enable signal
from the MAC before starting the transmission on it. The MAC starts its IFG counter as soon
as the carrier signal of the MII goes inactive. At the end of the programmed IFG value, the
MAC enables transmission in Full-duplex mode. In Half-duplex mode and when IFG is

1532/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
configured for 96 bit times, the MAC follows the rule of deference specified in Section
4.2.3.2.1 of the IEEE 802.3 specification. The MAC resets its IFG counter if a carrier is
detected during the first two-thirds (64-bit times for all IFG values) of the IFG interval. If the
carrier is detected during the final one third of the IFG interval, the MAC continues the IFG
count and enables the transmitter after the IFG interval. The MAC implements the truncated
binary exponential backoff algorithm when it operates in Half-duplex mode.

Transmit flow control
When the Transmit Flow Control Enable bit (TFE bit in ETH_MACFCR) is set, the MAC
generates Pause frames and transmits them as necessary, in Full-duplex mode. The Pause
frame is appended with the calculated CRC, and is sent. Pause frame generation can be
initiated in two ways.
A pause frame is sent either when the application sets the FCB bit in the ETH_MACFCR
register or when the receive FIFO is full (packet buffer).
•

If the application has requested flow control by setting the FCB bit in ETH_MACFCR,
the MAC generates and transmits a single Pause frame. The value of the pause time in
the generated frame contains the programmed pause time value in ETH_MACFCR. To
extend the pause or end the pause prior to the time specified in the previously
transmitted Pause frame, the application must request another Pause frame
transmission after programming the Pause Time value (PT in ETH_MACFCR register)
with the appropriate value.

•

If the application has requested flow control when the receive FIFO is full, the MAC
generates and transmits a Pause frame. The value of the pause time in the generated
frame is the programmed pause time value in ETH_MACFCR. If the receive FIFO
remains full at a configurable number of slot-times (PLT bits in ETH_MACFCR) before
this Pause time runs out, a second Pause frame is transmitted. The process is
repeated as long as the receive FIFO remains full. If this condition is no more satisfied
prior to the sampling time, the MAC transmits a Pause frame with zero pause time to
indicate to the remote end that the receive buffer is ready to receive new data frames.

Single-packet transmit operation
The general sequence of events for a transmit operation is as follows:
1.

If the system has data to be transferred, the DMA controller fetches them from the
memory through the AHB Master interface and starts forwarding them to the FIFO. It
continues to receive the data until the end of frame is transferred.

2.

When the threshold level is crossed or a full packet of data is received into the FIFO,
the frame data are popped and driven to the MAC core. The DMA continues to transfer
data from the FIFO until a complete packet has been transferred to the MAC. Upon
completion of the frame, the DMA controller is notified by the status coming from the
MAC.

Transmit operation—Two packets in the buffer
1.

Because the DMA must update the descriptor status before releasing it to the Host,
there can be at the most two frames inside a transmit FIFO. The second frame is
fetched by the DMA and put into the FIFO only if the OSF (operate on second frame)
bit is set. If this bit is not set, the next frame is fetched from the memory only after the
MAC has completely processed the frame and the DMA has released the descriptors.

2.

If the OSF bit is set, the DMA starts fetching the second frame immediately after
completing the transfer of the first frame to the FIFO. It does not wait for the status to
be updated. In the meantime, the second frame is received into the FIFO while the first

RM0385 Rev 7

1533/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

frame is being transmitted. As soon as the first frame has been transferred and the
status is received from the MAC, it is pushed to the DMA. If the DMA has already
completed sending the second packet to the FIFO, the second transmission must wait
for the status of the first packet before proceeding to the next frame.

Retransmission during collision
While a frame is being transferred to the MAC, a collision event may occur on the MAC line
interface in Half-duplex mode. The MAC would then indicate a retry attempt by giving the
status even before the end of frame is received. Then the retransmission is enabled and the
frame is popped out again from the FIFO. After more than 96 bytes have been popped
towards the MAC core, the FIFO controller frees up that space and makes it available to the
DMA to push in more data. This means that the retransmission is not possible after this
threshold is crossed or when the MAC core indicates a late collision event.

Transmit FIFO flush operation
The MAC provides a control to the software to flush the Transmit FIFO through the use of Bit
20 in the Operation mode register. The Flush operation is immediate and the Tx FIFO and
the corresponding pointers are cleared to the initial state even if the Tx FIFO is in the middle
of transferring a frame to the MAC Core. This results in an underflow event in the MAC
transmitter, and the frame transmission is aborted. The status of such a frame is marked
with both underflow and frame flush events (TDES0 bits 13 and 1). No data are coming to
the FIFO from the application (DMA) during the Flush operation. Transfer transmit status
words are transferred to the application for the number of frames that is flushed (including
partial frames). Frames that are completely flushed have the Frame flush status bit (TDES0
13) set. The Flush operation is completed when the application (DMA) has accepted all of
the Status words for the frames that were flushed. The Transmit FIFO Flush control register
bit is then cleared. At this point, new frames from the application (DMA) are accepted. All
data presented for transmission after a Flush operation are discarded unless they start with
an SOF marker.

Transmit status word
At the end of the Ethernet frame transfer to the MAC core and after the core has completed
the transmission of the frame, the transmit status is given to the application. The detailed
description of the Transmit Status is the same as for bits [23:0] in TDES0. If IEEE 1588 time
stamping is enabled, a specific frames’ 64-bit time stamp is returned, along with the transmit
status.

Transmit checksum offload
Communication protocols such as TCP and UDP implement checksum fields, which helps
determine the integrity of data transmitted over a network. Because the most widespread
use of Ethernet is to encapsulate TCP and UDP over IP datagrams, the Ethernet controller
has a transmit checksum offload feature that supports checksum calculation and insertion in
the transmit path, and error detection in the receive path. This section explains the operation
of the checksum offload feature for transmitted frames.
Note:

1534/1709

The checksum for TCP, UDP or ICMP is calculated over a complete frame, then inserted
into its corresponding header field. Due to this requirement, this function is enabled only
when the Transmit FIFO is configured for Store-and-forward mode (that is, when the TSF bit

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
is set in the ETH_ETH_DMAOMR register). If the core is configured for Threshold (cutthrough) mode, the Transmit checksum offload is bypassed.
The user must make sure the Transmit FIFO is deep enough to store a complete frame
before that frame is transferred to the MAC Core transmitter. If the FIFO depth is less than
the input Ethernet frame size, the payload (TCP/UDP/ICMP) checksum insertion function is
bypassed and only the frame’s IPv4 Header checksum is modified, even in Store-andforward mode.
The transmit checksum offload supports two types of checksum calculation and insertion.
This checksum can be controlled for each frame by setting the CIC bits (Bits 28:27 in
TDES1, described in TDES1: Transmit descriptor Word1 on page 1568).
See IETF specifications RFC 791, RFC 793, RFC 768, RFC 792, RFC 2460 and RFC 4443
for IPv4, TCP, UDP, ICMP, IPv6 and ICMPv6 packet header specifications, respectively.
•

IP header checksum
In IPv4 datagrams, the integrity of the header fields is indicated by the 16-bit header
checksum field (the eleventh and twelfth bytes of the IPv4 datagram). The checksum
offload detects an IPv4 datagram when the Ethernet frame’s Type field has the value
0x0800 and the IP datagram’s Version field has the value 0x4. The input frame’s
checksum field is ignored during calculation and replaced by the calculated value. IPv6
headers do not have a checksum field; thus, the checksum offload does not modify
IPv6 header fields. The result of this IP header checksum calculation is indicated by the
IP Header Error status bit in the Transmit status (Bit 16). This status bit is set whenever
the values of the Ethernet Type field and the IP header’s Version field are not
consistent, or when the Ethernet frame does not have enough data, as indicated by the
IP header Length field. In other words, this bit is set when an IP header error is
asserted under the following circumstances:
a)

For IPv4 datagrams:

–

The received Ethernet type is 0x0800, but the IP header’s Version field does not
equal 0x4

–

The IPv4 Header Length field indicates a value less than 0x5 (20 bytes)

–

The total frame length is less than the value given in the IPv4 Header Length field

b)

For IPv6 datagrams:

–

The Ethernet type is 0x86DD but the IP header Version field does not equal 0x6

–

The frame ends before the IPv6 header (40 bytes) or extension header (as given
in the corresponding Header Length field in an extension header) has been
completely received. Even when the checksum offload detects such an IP header
error, it inserts an IPv4 header checksum if the Ethernet Type field indicates an
IPv4 payload.

RM0385 Rev 7

1535/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller
•

RM0385

TCP/UDP/ICMP checksum
The TCP/UDP/ICMP checksum processes the IPv4 or IPv6 header (including
extension headers) and determines whether the encapsulated payload is TCP, UDP or
ICMP.
Note that:
a)

For non-TCP, -UDP, or -ICMP/ICMPv6 payloads, this checksum is bypassed and
nothing further is modified in the frame.

b)

Fragmented IP frames (IPv4 or IPv6), IP frames with security features (such as an
authentication header or encapsulated security payload), and IPv6 frames with
routing headers are bypassed and not processed by the checksum.

The checksum is calculated for the TCP, UDP, or ICMP payload and inserted into its
corresponding field in the header. It can work in the following two modes:
–

In the first mode, the TCP, UDP, or ICMPv6 pseudo-header is not included in the
checksum calculation and is assumed to be present in the input frame’s checksum
field. The checksum field is included in the checksum calculation, and then
replaced by the final calculated checksum.

–

In the second mode, the checksum field is ignored, the TCP, UDP, or ICMPv6
pseudo-header data are included into the checksum calculation, and the
checksum field is overwritten with the final calculated value.

Note that: for ICMP-over-IPv4 packets, the checksum field in the ICMP packet must
always be 0x0000 in both modes, because pseudo-headers are not defined for such
packets. If it does not equal 0x0000, an incorrect checksum may be inserted into the
packet.
The result of this operation is indicated by the payload checksum error status bit in the
Transmit Status vector (bit 12). The payload checksum error status bit is set when
either of the following is detected:
–

the frame has been forwarded to the MAC transmitter in Store-and-forward mode
without the end of frame being written to the FIFO

–

the packet ends before the number of bytes indicated by the payload length field in
the IP header is received.

When the packet is longer than the indicated payload length, the bytes are ignored as
stuff bytes, and no error is reported. When the first type of error is detected, the TCP,
UDP or ICMP header is not modified. For the second error type, still, the calculated
checksum is inserted into the corresponding header field.

MII/RMII transmit bit order
Each nibble from the MII is transmitted on the RMII a dibit at a time with the order of dibit
transmission shown in Figure 503. Lower order bits (D1 and D0) are transmitted first
followed by higher order bits (D2 and D3).

1536/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

LSB

RMII_TXD[1:0]

Figure 503. Transmission bit order

D0

LSB

MSB
D1

Bibit stream

D0

D1
MII_TXD[3:0]
D2

MSB

D3
Nibble stream
ai15632

MII/RMII transmit timing diagrams
Figure 504. Transmission with no collision
MII_TX_CLK

MII_TX_EN

MII_TXD[3:0]

PR

EA

MB

LE

MII_CS

MII_COL

Low
ai15631

RM0385 Rev 7

1537/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Figure 505. Transmission with collision
MII_TX_CLK

MII_TX_EN

MII_TXD[3:0]

PR

EAM

BLE

SFD

DA

DA

JAM

JAM

JAM

JAM

MII_CS

MII_COL

ai15651

Figure 506 shows a frame transmission in MII and RMII.
Figure 506. Frame transmission in MMI and RMII modes
MII_RX_CLK

MII_TX_EN

MII_TXD[3:0]

RMII_REF_CLK

RMII_TX_EN

RMII_TXD[1:0]

ai15652

38.5.3

MAC frame reception
The MAC received frames are pushes into the Rx FIFO. The status (fill level) of this FIFO is
indicated to the DMA once it crosses the configured receive threshold (RTC in the
ETH_DMAOMR register) so that the DMA can initiate pre-configured burst transfers
towards the AHB interface.
In the default Cut-through mode, when 64 bytes (configured with the RTC bits in the
ETH_DMAOMR register) or a full packet of data are received into the FIFO, the data are
popped out and the DMA is notified of its availability. Once the DMA has initiated the
transfer to the AHB interface, the data transfer continues from the FIFO until a complete

1538/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
packet has been transferred. Upon completion of the EOF frame transfer, the status word is
popped out and sent to the DMA controller.
In Rx FIFO Store-and-forward mode (configured by the RSF bit in the ETH_DMAOMR
register), a frame is read out only after being written completely into the Receive FIFO. In
this mode, all error frames are dropped (if the core is configured to do so) such that only
valid frames are read out and forwarded to the application. In Cut-through mode, some error
frames are not dropped, because the error status is received at the end of the frame, by
which time the start of that frame has already been read out of the FIFO.
A receive operation is initiated when the MAC detects an SFD on the MII. The core strips the
preamble and SFD before proceeding to process the frame. The header fields are checked
for the filtering and the FCS field used to verify the CRC for the frame. The frame is dropped
in the core if it fails the address filter.

Receive protocol
The received frame preamble and SFD are stripped. Once the SFD has been detected, the
MAC starts sending the Ethernet frame data to the receive FIFO, beginning with the first
byte following the SFD (destination address). If IEEE 1588 time stamping is enabled, a
snapshot of the system time is taken when any frame's SFD is detected on the MII. Unless
the MAC filters out and drops the frame, this time stamp is passed on to the application.
If the received frame length/type field is less than 0x600 and if the MAC is programmed for
the auto CRC/pad stripping option, the MAC sends the data of the frame to RxFIFO up to
the count specified in the length/type field, then starts dropping bytes (including the FCS
field). If the Length/Type field is greater than or equal to 0x600, the MAC sends all received
Ethernet frame data to Rx FIFO, regardless of the value on the programmed auto-CRC strip
option. The MAC watchdog timer is enabled by default, that is, frames above 2048 bytes
(DA + SA + LT + Data + pad + FCS) are cut off. This feature can be disabled by
programming the watchdog disable (WD) bit in the MAC configuration register. However,
even if the watchdog timer is disabled, frames greater than 16 KB in size are cut off and a
watchdog timeout status is given.

Receive CRC: automatic CRC and pad stripping
The MAC checks for any CRC error in the receiving frame. It calculates the 32-bit CRC for
the received frame that includes the Destination address field through the FCS field. The
encoding is defined by the following polynomial.
G( x) = x

32

+x

26

+x

23

+x

22

+x

16

+x

12

+x

11

+x

10

8

7

5

4

2

+x +x +x +x +x +x+1

Regardless of the auto-pad/CRC strip, the MAC receives the entire frame to compute the
CRC check for the received frame.

Receive checksum offload
Both IPv4 and IPv6 frames in the received Ethernet frames are detected and processed for
data integrity. The user can enable the receive checksum offload by setting the IPCO bit in
the ETH_MACCR register. The MAC receiver identifies IPv4 or IPv6 frames by checking for
value 0x0800 or 0x86DD, respectively, in the received Ethernet frame Type field. This
identification applies to VLAN-tagged frames as well. The receive checksum offload
calculates IPv4 header checksums and checks that they match the received IPv4 header
checksums. The IP Header Error bit is set for any mismatch between the indicated payload

RM0385 Rev 7

1539/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

type (Ethernet Type field) and the IP header version, or when the received frame does not
have enough bytes, as indicated by the IPv4 header’s Length field (or when fewer than 20
bytes are available in an IPv4 or IPv6 header). The receive checksum offload also identifies
a TCP, UDP or ICMP payload in the received IP datagrams (IPv4 or IPv6) and calculates the
checksum of such payloads properly, as defined in the TCP, UDP or ICMP specifications. It
includes the TCP/UDP/ICMPv6 pseudo-header bytes for checksum calculation and checks
whether the received checksum field matches the calculated value. The result of this
operation is given as a Payload Checksum Error bit in the receive status word. This status
bit is also set if the length of the TCP, UDP or ICMP payload does not match the expected
payload length given in the IP header. As mentioned in TCP/UDP/ICMP checksum on
page 1536, the receive checksum offload bypasses the payload of fragmented IP
datagrams, IP datagrams with security features, IPv6 routing headers, and payloads other
than TCP, UDP or ICMP. This information (whether the checksum is bypassed or not) is
given in the receive status, as described in the RDES0: Receive descriptor Word0 section.
In this configuration, the core does not append any payload checksum bytes to the received
Ethernet frames.
As mentioned in RDES0: Receive descriptor Word0 on page 1575, the meaning of certain
register bits changes as shown in Table 275.
Table 275. Frame statuses
Bit 18:
Bit 27: Header Bit 28: Payload
Ethernet frame checksum error checksum error

Frame status

0

0

0

The frame is an IEEE 802.3 frame (Length
field value is less than 0x0600).

1

0

0

IPv4/IPv6 Type frame in which no checksum
error is detected.

1

0

1

IPv4/IPv6 Type frame in which a payload
checksum error (as described for PCE) is
detected

1

1

0

IPv4/IPv6 Type frame in which IP header
checksum error (as described for IPCO HCE)
is detected.

1

1

1

IPv4/IPv6 Type frame in which both PCE and
IPCO HCE are detected.

0

0

1

IPv4/IPv6 Type frame in which there is no IP
HCE and the payload check is bypassed due
to unsupported payload.

0

1

1

Type frame which is neither IPv4 or IPv6
(checksum offload bypasses the checksum
check completely)

0

1

0

Reserved

Receive frame controller
If the RA bit is reset in the MAC CSR frame filter register, the MAC performs frame filtering
based on the destination/source address (the application still needs to perform another level
of filtering if it decides not to receive any bad frames like runt, CRC error frames, etc.). On
detecting a filter-fail, the frame is dropped and not transferred to the application. When the
filtering parameters are changed dynamically, and in case of (DA-SA) filter-fail, the rest of
1540/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
the frame is dropped and the Rx Status Word is immediately updated (with zero frame
length, CRC error and Runt Error bits set), indicating the filter fail. In Ethernet power down
mode, all received frames are dropped, and are not forwarded to the application.

Receive flow control
The MAC detects the receiving Pause frame and pauses the frame transmission for the
delay specified within the received Pause frame (only in Full-duplex mode). The Pause
frame detection function can be enabled or disabled with the RFCE bit in ETH_MACFCR.
Once receive flow control has been enabled, the received frame destination address begins
to be monitored for any match with the multicast address of the control frame
(0x0180 C200 0001). If a match is detected (the destination address of the received frame
matches the reserved control frame destination address), the MAC then decides whether or
not to transfer the received control frame to the application, based on the level of the PCF
bit in ETH_MACFFR.
The MAC also decodes the type, opcode, and Pause Timer fields of the receiving control
frame. If the byte count of the status indicates 64 bytes, and if there is no CRC error, the
MAC transmitter pauses the transmission of any data frame for the duration of the decoded
Pause time value, multiplied by the slot time (64 byte times for both 10/100 Mbit/s modes).
Meanwhile, if another Pause frame is detected with a zero Pause time value, the MAC
resets the Pause time and manages this new pause request.
If the received control frame matches neither the type field (0x8808), the opcode (0x00001),
nor the byte length (64 bytes), or if there is a CRC error, the MAC does not generate a
Pause.
In the case of a pause frame with a multicast destination address, the MAC filters the frame
based on the address match.
For a pause frame with a unicast destination address, the MAC filtering depends on whether
the DA matched the contents of the MAC address 0 register and whether the UPDF bit in
ETH_MACFCR is set (detecting a pause frame even with a unicast destination address).
The PCF register bits (bits [7:6] in ETH_MACFFR) control filtering for control frames in
addition to address filtering.

Receive operation multiframe handling
Since the status is available immediately following the data, the FIFO is capable of storing
any number of frames into it, as long as it is not full.

Error handling
If the Rx FIFO is full before it receives the EOF data from the MAC, an overflow is declared
and the whole frame is dropped, and the overflow counter in the (ETH_DMAMFBOCR
register) is incremented. The status indicates a partial frame due to overflow. The Rx FIFO
can filter error and undersized frames, if enabled (using the FEF and FUGF bits in
ETH_DMAOMR).
If the Receive FIFO is configured to operate in Store-and-forward mode, all error frames can
be filtered and dropped.
In Cut-through mode, if a frame's status and length are available when that frame's SOF is
read from the Rx FIFO, then the complete erroneous frame can be dropped. The DMA can
flush the error frame being read from the FIFO, by enabling the receive frame flash bit. The
data transfer to the application (DMA) is then stopped and the rest of the frame is internally
read and dropped. The next frame transfer can then be started, if available.

RM0385 Rev 7

1541/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Receive status word
At the end of the Ethernet frame reception, the MAC outputs the receive status to the
application (DMA). The detailed description of the receive status is the same as for
bits[31:0] in RDES0, given in RDES0: Receive descriptor Word0.

Frame length interface
In case of switch applications, data transmission and reception between the application and
MAC happen as complete frame transfers. The application layer should be aware of the
length of the frames received from the ingress port in order to transfer the frame to the
egress port. The MAC core provides the frame length of each received frame inside the
status at the end of each frame reception.
Note:

A frame length value of 0 is given for partial frames written into the Rx FIFO due to overflow.

MII/RMII receive bit order
Each nibble is transmitted to the MII from the dibit received from the RMII in the nibble
transmission order shown in Figure 507. The lower-order bits (D0 and D1) are received first,
followed by the higher-order bits (D2 and D3).

LSB
D0

LSB

RMII_RXD[1:0]

Figure 507. Receive bit order

MSB
D1

Di-bit stream

D0

D1
MII_RXD[3:0]
D2

MSB

D3
Nibble stream

1542/1709

RM0385 Rev 7

ai15633

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Figure 508. Reception with no error
MII_RX_CLK

MII_RX_DV

MII_RXD[3:0]

PREAMBLE

SFD

FCS

MII_RX_ERR

ai15634

Figure 509. Reception with errors
MII_RX_CLK

MII_RX_DV

MII_RXD[3:0]

PREAMBLE

SFD

DA

DA

XX

XX

XX

MII_RX_ERR

ai15635

Figure 510. Reception with false carrier indication
MII_RX_CLK

MII_RX_DV

MII_RXD[3:0]

XX

XX

XX

XX

0E

XX

XX

XX

XX

MII_RX_ERR
ai15636

RM0385 Rev 7

1543/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

38.5.4

RM0385

MAC interrupts
Interrupts can be generated from the MAC core as a result of various events.
The ETH_MACSR register describes the events that can cause an interrupt from the MAC
core. The user can prevent each event from asserting the interrupt by setting the
corresponding mask bits in the Interrupt Mask register.
The interrupt register bits only indicate the block from which the event is reported. The user
has to read the corresponding status registers and other registers to clear the interrupt. For
example, bit 3 of the Interrupt register, set high, indicates that the Magic packet or Wake-onLAN frame is received in Power-down mode. The user must read the ETH_MACPMTCSR
Register to clear this interrupt event.
Figure 511. MAC core interrupt masking scheme
TSTS
AND

TSTI

TSTIM
OR

Interrupt

PMTS
PMTIM

AND

PMTI

ai15637

38.5.5

MAC filtering
Address filtering
Address filtering checks the destination and source addresses on all received frames and
the address filtering status is reported accordingly. Address checking is based on different
parameters (Frame filter register) chosen by the application. The filtered frame can also be
identified: multicast or broadcast frame.
Address filtering uses the station's physical (MAC) address and the Multicast Hash table for
address checking purposes.

Unicast destination address filter
The MAC supports up to 4 MAC addresses for unicast perfect filtering. If perfect filtering is
selected (HU bit in the Frame filter register is reset), the MAC compares all 48 bits of the
received unicast address with the programmed MAC address for any match. Default
MacAddr0 is always enabled, other addresses MacAddr1–MacAddr3 are selected with an
individual enable bit. Each byte of these other addresses (MacAddr1–MacAddr3) can be
masked during comparison with the corresponding received DA byte by setting the
corresponding Mask Byte Control bit in the register. This helps group address filtering for the
DA. In Hash filtering mode (when HU bit is set), the MAC performs imperfect filtering for
unicast addresses using a 64-bit Hash table. For hash filtering, the MAC uses the 6 upper
CRC (see note 1 below) bits of the received destination address to index the content of the
Hash table. A value of 000000 selects bit 0 in the selected register, and a value of 111111
selects bit 63 in the Hash Table register. If the corresponding bit (indicated by the 6-bit CRC)
1544/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
is set to 1, the unicast frame is said to have passed the Hash filter; otherwise, the frame has
failed the Hash filter.

Note:

This CRC is a 32-bit value coded by the following polynomial (for more details refer to
Section 38.5.3: MAC frame reception):
G(x ) = x

32

+x

26

+x

23

+x

22

+x

16

+x

12

+x

11

+x

10

8

7

5

4

2

+x +x +x +x +x +x+1

Multicast destination address filter
The MAC can be programmed to pass all multicast frames by setting the PAM bit in the
Frame filter register. If the PAM bit is reset, the MAC performs the filtering for multicast
addresses based on the HM bit in the Frame filter register. In Perfect filtering mode, the
multicast address is compared with the programmed MAC destination address registers
(1–3). Group address filtering is also supported. In Hash filtering mode, the MAC performs
imperfect filtering using a 64-bit Hash table. For hash filtering, the MAC uses the 6 upper
CRC (see note 1 below) bits of the received multicast address to index the content of the
Hash table. A value of 000000 selects bit 0 in the selected register and a value of 111111
selects bit 63 in the Hash Table register. If the corresponding bit is set to 1, then the
multicast frame is said to have passed the Hash filter; otherwise, the frame has failed the
Hash filter.
Note:

This CRC is a 32-bit value coded by the following polynomial (for more details refer to
Section 38.5.3: MAC frame reception):
G(x ) = x

32

+x

26

+x

23

+x

22

+x

16

+x

12

+x

11

+x

10

8

7

5

4

2

+x +x +x +x +x +x+1

Hash or perfect address filter
The DA filter can be configured to pass a frame when its DA matches either the Hash filter
or the Perfect filter by setting the HPF bit in the Frame filter register and setting the
corresponding HU or HM bits. This configuration applies to both unicast and multicast
frames. If the HPF bit is reset, only one of the filters (Hash or Perfect) is applied to the
received frame.

Broadcast address filter
The MAC does not filter any broadcast frames in the default mode. However, if the MAC is
programmed to reject all broadcast frames by setting the BFD bit in the Frame filter register,
any broadcast frames are dropped.

Unicast source address filter
The MAC can also perform perfect filtering based on the source address field of the
received frames. By default, the MAC compares the SA field with the values programmed in
the SA registers. The MAC address registers [1:3] can be configured to contain SA instead
of DA for comparison, by setting bit 30 in the corresponding register. Group filtering with SA
is also supported. The frames that fail the SA filter are dropped by the MAC if the SAF bit in
the Frame filter register is set. Otherwise, the result of the SA filter is given as a status bit in
the Receive Status word (see RDES0: Receive descriptor Word0).
When the SAF bit is set, the result of the SA and DA filters is AND’ed to decide whether the
frame needs to be forwarded. This means that either of the filter fail result will drop the
frame. Both filters have to pass the frame for the frame to be forwarded to the application.
RM0385 Rev 7

1545/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Inverse filtering operation
For both destination and source address filtering, there is an option to invert the filter-match
result at the final output. These are controlled by the DAIF and SAIF bits in the Frame filter
register, respectively. The DAIF bit is applicable for both Unicast and Multicast DA frames.
The result of the unicast/multicast destination address filter is inverted in this mode.
Similarly, when the SAIF bit is set, the result of the unicast SA filter is inverted. Table 276
and Table 277 summarize destination and source address filtering based on the type of
frame received.
Table 276. Destination address filtering
Frame
type

Broadcast

Unicast

Multicast

1546/1709

PM

HPF

HU

DAIF

HM

PAM DB

1

X

X

X

X

X

X

Pass

0

X

X

X

X

X

0

Pass

0

X

X

X

X

X

1

Fail

1

X

X

X

X

X

X

Pass all frames

0

X

0

0

X

X

X

Pass on perfect/group filter match

0

X

0

1

X

X

X

Fail on perfect/Group filter match

0

0

1

0

X

X

X

Pass on hash filter match

0

0

1

1

X

X

X

Fail on hash filter match

0

1

1

0

X

X

X

Pass on hash or perfect/Group filter
match

0

1

1

1

X

X

X

Fail on hash or perfect/Group filter match

1

X

X

X

X

X

X

Pass all frames

X

X

X

X

X

1

X

Pass all frames

0

X

X

0

0

0

X

Pass on Perfect/Group filter match and
drop PAUSE control frames if PCF = 0x

0

0

X

0

1

0

X

Pass on hash filter match and drop
PAUSE control frames if PCF = 0x

0

1

X

0

1

0

X

Pass on hash or perfect/Group filter
match and drop PAUSE control frames if
PCF = 0x

0

X

X

1

0

0

X

Fail on perfect/Group filter match and
drop PAUSE control frames if PCF = 0x

0

0

X

1

1

0

X

Fail on hash filter match and drop PAUSE
control frames if PCF = 0x

0

1

X

1

1

0

X

Fail on hash or perfect/Group filter match
and drop PAUSE control frames if PCF =
0x

RM0385 Rev 7

DA filter operation

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Table 277. Source address filtering
Frame type

Unicast

38.5.6

PM

SAIF

SAF

SA filter operation

1

X

X

Pass all frames

0

0

0

Pass status on perfect/Group filter match but do not drop
frames that fail

0

1

0

Fail status on perfect/group filter match but do not drop frame

0

0

1

Pass on perfect/group filter match and drop frames that fail

0

1

1

Fail on perfect/group filter match and drop frames that fail

MAC loopback mode
The MAC supports loopback of transmitted frames onto its receiver. By default, the MAC
loopback function is disabled, but this feature can be enabled by programming the
Loopback bit in the MAC ETH_MACCR register.

38.5.7

MAC management counters: MMC
The MAC management counters (MMC) maintain a set of registers for gathering statistics
on the received and transmitted frames. These include a control register for controlling the
behavior of the registers, two 32-bit registers containing generated interrupts (receive and
transmit), and two 32-bit registers containing masks for the Interrupt register (receive and
transmit). These registers are accessible from the application. Each register is 32 bits wide.
Section 38.8: Ethernet register descriptions describes the various counters and lists the
addresses of each of the statistics counters. This address is used for read/write accesses to
the desired transmit/receive counter.
The Receive MMC counters are updated for frames that pass address filtering. Dropped
frames statistics are not updated unless the dropped frames are runt frames of less than 6
bytes (DA bytes are not received fully).

Good transmitted and received frames
Transmitted frames are considered “good” if transmitted successfully. In other words, a
transmitted frame is good if the frame transmission is not aborted due to any of the following
errors:
+ Jabber Timeout
+ No Carrier/Loss of Carrier
+ Late Collision
+ Frame Underflow
+ Excessive Deferral
+ Excessive Collision

RM0385 Rev 7

1547/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Received frames are considered “good” if none of the following errors exists:
+ CRC error
+ Runt Frame (shorter than 64 bytes)
+ Alignment error (in 10/ 100 Mbit/s only)
+ Length error (non-Type frames only)
+ Out of Range (non-Type frames only, longer than maximum size)
+ MII_RXER Input error
The maximum frame size depends on the frame type, as follows:
+ Untagged frame maxsize = 1518
+ VLAN Frame maxsize = 1522

38.5.8

Power management: PMT
This section describes the power management (PMT) mechanisms supported by the MAC.
PMT supports the reception of network (remote) wakeup frames and Magic Packet frames.
PMT generates interrupts for wakeup frames and Magic Packets received by the MAC. The
PMT block is enabled with remote wakeup frame enable and Magic Packet enable. These
enable bits (WFE and MPE) are in the ETH_MACPMTCSR register and are programmed by
the application. When the power down mode is enabled in the PMT, then all received frames
are dropped by the MAC and they are not forwarded to the application. The MAC comes out
of the power down mode only when either a Magic Packet or a Remote wakeup frame is
received and the corresponding detection is enabled.

Remote wakeup frame filter register
There are eight wakeup frame filter registers. To write on each of them, load the wakeup
frame filter register value by value. The wanted values of the wakeup frame filter are loaded
by sequentially loading eight times the wakeup frame filter register. The read operation is
identical to the write operation. To read the eight values, the user has to read eight times the
wakeup frame filter register to reach the last register. Each read/write points the wakeup
frame filter register to the next filter register.

1548/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Figure 512. Wakeup frame filter register
Wakeup frame filter reg0

Filter 0 Byte Mask

Wakeup frame filter reg1

Filter 1 Byte Mask

Wakeup frame filter reg2

Filter 2 Byte Mask

Wakeup frame filter reg3
Wakeup frame filter reg4
Wakeup frame filter reg5

Filter 3 Byte Mask
RSVD

Filter 3
Command

Filter 3 Offset

RSVD

Filter 2
Command

Filter 2 Offset

RSVD

Filter 1
Command

Filter 1 Offset

RSVD

Filter 0
Command

Filter 0 Offset

Wakeup frame filter reg6

Filter 1 CRC - 16

Filter 0 CRC - 16

Wakeup frame filter reg7

Filter 3 CRC - 16

Filter 2 CRC - 16

ai15647

•

Filter i Byte Mask
This register defines which bytes of the frame are examined by filter i (0, 1, 2, and 3) in
order to determine whether or not the frame is a wakeup frame. The MSB (thirty-first
bit) must be zero. Bit j [30:0] is the Byte Mask. If bit j (byte number) of the Byte Mask is
set, then Filter i Offset + j of the incoming frame is processed by the CRC block;
otherwise Filter i Offset + j is ignored.

•

Filter i Command
This 4-bit command controls the filter i operation. Bit 3 specifies the address type,
defining the pattern’s destination address type. When the bit is set, the pattern applies
to only multicast frames. When the bit is reset, the pattern applies only to unicast
frames. Bit 2 and bit 1 are reserved. Bit 0 is the enable bit for filter i; if bit 0 is not set,
filter i is disabled.

•

Filter i Offset
This register defines the offset (within the frame) from which the frames are examined
by filter i. This 8-bit pattern offset is the offset for the filter i first byte to be examined.
The minimum allowed is 12, which refers to the 13th byte of the frame (offset value 0
refers to the first byte of the frame).

•

Filter i CRC-16
This register contains the CRC_16 value calculated from the pattern, as well as the
byte mask programmed to the wakeup filter register block.

Remote wakeup frame detection
When the MAC is in sleep mode and the remote wakeup bit is enabled in the
ETH_MACPMTCSR register, normal operation is resumed after receiving a remote wakeup
frame. The application writes all eight wakeup filter registers, by performing a sequential
write to the wakeup frame filter register address. The application enables remote wakeup by
writing a 1 to bit 2 in the ETH_MACPMTCSR register. PMT supports four programmable
filters that provide different receive frame patterns. If the incoming frame passes the
address filtering of Filter Command, and if Filter CRC-16 matches the incoming examined
pattern, then the wakeup frame is received. Filter_offset (minimum value 12, which refers to
the 13th byte of the frame) determines the offset from which the frame is to be examined.
Filter Byte Mask determines which bytes of the frame must be examined. The thirty-first bit
of Byte Mask must be set to zero. The wakeup frame is checked only for length error, FCS
error, dribble bit error, MII error, collision, and to ensure that it is not a runt frame. Even if the
RM0385 Rev 7

1549/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

wakeup frame is more than 512 bytes long, if the frame has a valid CRC value, it is
considered valid. Wakeup frame detection is updated in the ETH_MACPMTCSR register for
every remote wakeup frame received. If enabled, a PMT interrupt is generated to indicate
the reception of a remote wakeup frame.

Magic packet detection
The Magic Packet frame is based on a method that uses Advanced Micro Device’s Magic
Packet technology to power up the sleeping device on the network. The MAC receives a
specific packet of information, called a Magic Packet, addressed to the node on the network.
Only Magic Packets that are addressed to the device or a broadcast address are checked to
determine whether they meet the wakeup requirements. Magic Packets that pass address
filtering (unicast or broadcast) are checked to determine whether they meet the remote
Wake-on-LAN data format of 6 bytes of all ones followed by a MAC address appearing 16
times. The application enables Magic Packet wakeup by writing a 1 to bit 1 in the
ETH_MACPMTCSR register. The PMT block constantly monitors each frame addressed to
the node for a specific Magic Packet pattern. Each received frame is checked for a
0xFFFF FFFF FFFF pattern following the destination and source address field. The PMT
block then checks the frame for 16 repetitions of the MAC address without any breaks or
interruptions. In case of a break in the 16 repetitions of the address, the 0xFFFF FFFF FFFF
pattern is scanned for again in the incoming frame. The 16 repetitions can be anywhere in
the frame, but must be preceded by the synchronization stream (0xFFFF FFFF FFFF). The
device also accepts a multicast frame, as long as the 16 duplications of the MAC address
are detected. If the MAC address of a node is 0x0011 2233 4455, then the MAC scans for
the data sequence:
Destination address source address ……………….. FFFF FFFF FFFF
0011 2233 4455 0011 2233 4455 0011 2233 4455 0011 2233 4455
0011 2233 4455 0011 2233 4455 0011 2233 4455 0011 2233 4455
0011 2233 4455 0011 2233 4455 0011 2233 4455 0011 2233 4455
0011 2233 4455 0011 2233 4455 0011 2233 4455 0011 2233 4455
…CRC
Magic Packet detection is updated in the ETH_MACPMTCSR register for received Magic
Packet. If enabled, a PMT interrupt is generated to indicate the reception of a Magic Packet.

System consideration during power-down
The Ethernet PMT block is able to detect frames while the system is in the Stop mode,
provided that the EXTI line 19 is enabled.
The MAC receiver state machine should remain enabled during the power-down mode. This
means that the RE bit has to remain set in the ETH_MACCR register because it is involved
in magic packet/ wake-on-LAN frame detection. The transmit state machine should however
be turned off during the power-down mode by clearing the TE bit in the ETH_MACCR
register. Moreover, the Ethernet DMA should be disabled during the power-down mode,
because it is not necessary to copy the magic packet/wake-on-LAN frame into the SRAM.
To disable the Ethernet DMA, clear the ST bit and the SR bit (for the transmit DMA and the
receive DMA, respectively) in the ETH_DMAOMR register.
The recommended power-down and wakeup sequences are as follows:

1550/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
1.

Disable the transmit DMA and wait for any previous frame transmissions to complete.
These transmissions can be detected when the transmit interrupt ETH_DMASR
register[0] is received.

2.

Disable the MAC transmitter and MAC receiver by clearing the RE and TE bits in the
ETH_MACCR configuration register.

3.

Wait for the receive DMA to have emptied all the frames in the Rx FIFO.

4.

Disable the receive DMA.

5.

Configure and enable the EXTI line 19 to generate either an event or an interrupt.

6.

If you configure the EXTI line 19 to generate an interrupt, you also have to correctly
configure the ETH_WKUP_IRQ Handler function, which should clear the pending bit of
the EXTI line 19.

7.

Enable Magic packet/Wake-on-LAN frame detection by setting the MFE/ WFE bit in the
ETH_MACPMTCSR register.

8.

Enable the MAC power-down mode, by setting the PD bit in the ETH_MACPMTCSR
register.

9.

Enable the MAC Receiver by setting the RE bit in the ETH_MACCR register.

10. Enter the system’s Stop mode (for more details refer to Section 4.3.5: Stop mode):
11. On receiving a valid wakeup frame, the Ethernet peripheral exits the power-down
mode.
12. Read the ETH_MACPMTCSR to clear the power management event flag, enable the
MAC transmitter state machine, and the receive and transmit DMA.
13. Configure the system clock: enable the HSE and set the clocks.

38.5.9

Precision time protocol (IEEE1588 PTP)
The IEEE 1588 standard defines a protocol that allows precise clock synchronization in
measurement and control systems implemented with technologies such as network
communication, local computing and distributed objects. The protocol applies to systems
that communicate by local area networks supporting multicast messaging, including (but not
limited to) Ethernet. This protocol is used to synchronize heterogeneous systems that
include clocks of varying inherent precision, resolution and stability. The protocol supports
system-wide synchronization accuracy in the submicrosecond range with minimum network
and local clock computing resources. The message-based protocol, known as the precision
time protocol (PTP), is transported over UDP/IP. The system or network is classified into
Master and Slave nodes for distributing the timing/clock information. The protocol’s
technique for synchronizing a slave node to a master node by exchanging PTP messages is
described in Figure 513.

RM0385 Rev 7

1551/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Figure 513. Networked time synchronization
Master clock time

Slave clock time
Sync message

t1

t2m

Follow_up message
containing value of t1

Data at
slave clock
t2 t2

t1, t2
t3m

Delay_Req message

t3 t1, t2, t3

t4
Delay_Resp message
containing value of t4

time

t1, t2, t3, t4
ai15669

1.

The master broadcasts PTP Sync messages to all its nodes. The Sync message
contains the master’s reference time information. The time at which this message
leaves the master’s system is t1. For Ethernet ports, this time has to be captured at the
MII.

2.

A slave receives the Sync message and also captures the exact time, t2, using its
timing reference.

3.

The master then sends the slave a Follow_up message, which contains the t1
information for later use.

4.

The slave sends the master a Delay_Req message, noting the exact time, t3, at which
this frame leaves the MII.

5.

The master receives this message and captures the exact time, t4, at which it enters its
system.

6.

The master sends the t4 information to the slave in the Delay_Resp message.

7.

The slave uses the four values of t1, t2, t3, and t4 to synchronize its local timing
reference to the master’s timing reference.

Most of the protocol implementation occurs in the software, above the UDP layer. As
described above, however, hardware support is required to capture the exact time when
specific PTP packets enter or leave the Ethernet port at the MII. This timing information has
to be captured and returned to the software for a proper, high-accuracy implementation of
PTP.

Reference timing source
To get a snapshot of the time, the core requires a reference time in 64-bit format (split into
two 32-bit channels, with the upper 32 bits providing time in seconds, and the lower 32 bits
indicating time in nanoseconds) as defined in the IEEE 1588 specification.

1552/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
The PTP reference clock input is used to internally generate the reference time (also called
the System Time) and to capture time stamps. The frequency of this reference clock must
be greater than or equal to the resolution of time stamp counter. The synchronization
accuracy target between the master node and the slaves is around 100 ns.
The generation, update and modification of the System Time are described in the System
Time correction methods.
The accuracy depends on the PTP reference clock input period, the characteristics of the
oscillator (drift) and the frequency of the synchronization procedure.
Due to the synchronization from the Tx and Rx clock input domain to the PTP reference
clock domain, the uncertainty on the time stamp latched value is 1 reference clock period. If
we add the uncertainty due to resolution, we will add half the period for time stamping.

Transmission of frames with the PTP feature
When a frame’s SFD is output on the MII, a time stamp is captured. Frames for which time
stamp capture is required are controllable on a per-frame basis. In other words, each
transmitted frame can be marked to indicate whether a time stamp must be captured or not
for that frame. The transmitted frames are not processed to identify PTP frames. Frame
control is exercised through the control bits in the transmit descriptor. Captured time stamps
are returned to the application in the same way as the status is provided for frames. The
time stamp is sent back along with the Transmit status of the frame, inside the
corresponding transmit descriptor, thus connecting the time stamp automatically to the
specific PTP frame. The 64-bit time stamp information is written back to the TDES2 and
TDES3 fields, with TDES2 holding the time stamp’s 32 least significant bits.

Reception of frames with the PTP feature
When the IEEE 1588 time stamping feature is enabled, the Ethernet MAC captures the time
stamp of all frames received on the MII. The MAC provides the time stamp as soon as the
frame reception is complete. Captured time stamps are returned to the application in the
same way as the frame status is provided. The time stamp is sent back along with the
Receive status of the frame, inside the corresponding receive descriptor. The 64-bit time
stamp information is written back to the RDES2 and RDES3 fields, with RDES2 holding the
time stamp’s 32 least significant bits.

System Time correction methods
The 64-bit PTP time is updated using the PTP input reference clock, HCLK. This PTP time
is used as a source to take snapshots (time stamps) of the Ethernet frames being
transmitted or received at the MII. The System Time counter can be initialized or corrected
using either the Coarse or the Fine correction method.
In the Coarse correction method, the initial value or the offset value is written to the Time
stamp update register (refer to Section 38.8.3: IEEE 1588 time stamp registers on
page 1610). For initialization, the System Time counter is written with the value in the Time
stamp update registers, whereas for system time correction, the offset value (Time stamp
update register) is added to or subtracted from the system time.
In the Fine correction method, the slave clock (reference clock) frequency drift with respect
to the master clock (as defined in IEEE 1588) is corrected over a period of time, unlike in the
Coarse correction method where it is corrected in a single clock cycle. The longer correction
time helps maintain linear time and does not introduce drastic changes (or a large jitter) in
the reference time between PTP Sync message intervals. In this method, an accumulator

RM0385 Rev 7

1553/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

sums up the contents of the Addend register as shown in Figure 514. The arithmetic carry
that the accumulator generates is used as a pulse to increment the system time counter.
The accumulator and the addend are 32-bit registers. Here, the accumulator acts as a highprecision frequency multiplier or divider. Figure 514 shows this algorithm.
Figure 514. System time update using the Fine correction method
Addend register

Addend update

+
Accumulator register

Constant value

Increment Subsecond
register

+

Subsecond register

Increment Second register
Second register

ai15670

The system time update logic requires a 50 MHz clock frequency to achieve 20 ns accuracy.
The frequency division is the ratio of the reference clock frequency to the required clock
frequency. Hence, if the reference clock (HCLK) is, let us say, 66 MHz, the ratio is calculated
as 66 MHz/50 MHz = 1.32. Hence, the default addend value to be set in the register is
232/1.32, which is equal to 0xC1F0 7C1F.
If the reference clock drifts lower, to 65 MHz for example, the ratio is 65/50 or 1.3 and the
value to set in the addend register is 232/1.30 equal to 0xC4EC 4EC4. If the clock drifts
higher, to 67 MHz for example, the addend register must be set to 0xBF0 B7672. When the
clock drift is zero, the default addend value of 0xC1F0 7C1F (232/1.32) should be
programmed.
In Figure 514, the constant value used to increment the subsecond register is 0d43. This
makes an accuracy of 20 ns in the system time (in other words, it is incremented by 20 ns
steps).
The software has to calculate the drift in frequency based on the Sync messages, and to
update the Addend register accordingly. Initially, the slave clock is set with
FreqCompensationValue0 in the Addend register. This value is as follows:
FreqCompensationValue0 = 232 / FreqDivisionRatio
If MasterToSlaveDelay is initially assumed to be the same for consecutive Sync messages,
the algorithm described below must be applied. After a few Sync cycles, frequency lock
occurs. The slave clock can then determine a precise MasterToSlaveDelay value and resynchronize with the master using the new value.

1554/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
The algorithm is as follows:
•

At time MasterSyncTime (n) the master sends the slave clock a Sync message. The
slave receives this message when its local clock is SlaveClockTime (n) and computes
MasterClockTime (n) as:
MasterClockTime (n) = MasterSyncTime (n) + MasterToSlaveDelay (n)

•

The master clock count for current Sync cycle, MasterClockCount (n) is given by:
MasterClockCount (n) = MasterClockTime (n) – MasterClockTime (n – 1) (assuming
that MasterToSlaveDelay is the same for Sync cycles n and n – 1)

•

The slave clock count for current Sync cycle, SlaveClockCount (n) is given by:
SlaveClockCount (n) = SlaveClockTime (n) – SlaveClockTime (n – 1)

•

The difference between master and slave clock counts for current Sync cycle,
ClockDiffCount (n) is given by:
ClockDiffCount (n) = MasterClockCount (n) – SlaveClockCount (n)

•

The frequency-scaling factor for slave clock, FreqScaleFactor (n) is given by:
FreqScaleFactor (n) = (MasterClockCount (n) + ClockDiffCount (n)) /
SlaveClockCount (n)

•

The frequency compensation value for Addend register, FreqCompensationValue (n) is
given by:
FreqCompensationValue (n) = FreqScaleFactor (n) × FreqCompensationValue (n – 1)

In theory, this algorithm achieves lock in one Sync cycle; however, it may take several
cycles, due to changing network propagation delays and operating conditions.
This algorithm is self-correcting: if for any reason the slave clock is initially set to a value
from the master that is incorrect, the algorithm corrects it at the cost of more Sync cycles.

Programming steps for system time generation initialization
The time stamping feature can be enabled by setting bit 0 in the Time stamp control register
(ETH__PTPTSCR). However, it is essential to initialize the time stamp counter after this bit
is set to start time stamp operation. The proper sequence is the following:
1.

Mask the Time stamp trigger interrupt by setting bit 9 in the MACIMR register.

2.

Program Time stamp register bit 0 to enable time stamping.

3.

Program the Subsecond increment register based on the PTP clock frequency.

4.

If you are using the Fine correction method, program the Time stamp addend register
and set Time stamp control register bit 5 (addend register update).

5.

Poll the Time stamp control register until bit 5 is cleared.

6.

To select the Fine correction method (if required), program Time stamp control register
bit 1.

7.

Program the Time stamp high update and Time stamp low update registers with the
appropriate time value.

8.

Set Time stamp control register bit 2 (Time stamp init).

9.

The Time stamp counter starts operation as soon as it is initialized with the value
written in the Time stamp update register.

10. Enable the MAC receiver and transmitter for proper time stamping.
Note:

If time stamp operation is disabled by clearing bit 0 in the ETH_PTPTSCR register, the
above steps must be repeated to restart the time stamp operation.

RM0385 Rev 7

1555/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Programming steps for system time update in the Coarse correction method
To synchronize or update the system time in one process (coarse correction method),
perform the following steps:
1.

Write the offset (positive or negative) in the Time stamp update high and low registers.

2.

Set bit 3 (TSSTU) in the Time stamp control register.

3.

The value in the Time stamp update registers is added to or subtracted from the system
time when the TSSTU bit is cleared.

Programming steps for system time update in the Fine correction method
To synchronize or update the system time to reduce system-time jitter (fine correction
method), perform the following steps:
1.

With the help of the algorithm explained in System Time correction methods, calculate
the rate by which you want to speed up or slow down the system time increments.

2.

Update the time stamp.

3.

Wait the time you want the new value of the Addend register to be active. You can do
this by activating the Time stamp trigger interrupt after the system time reaches the
target value.

4.

Program the required target time in the Target time high and low registers. Unmask the
Time stamp interrupt by clearing bit 9 in the ETH_MACIMR register.

5.

Set Time stamp control register bit 4 (TSARU).

6.

When this trigger causes an interrupt, read the ETH_MACSR register.

7.

Reprogram the Time stamp addend register with the old value and set ETH_TPTSCR
bit 5 again.

PTP trigger internal connection with TIM2
The MAC provides a trigger interrupt when the system time becomes greater than the target
time. Using an interrupt introduces a known latency plus an uncertainty in the command
execution time.
In order to avoid this uncertainty, a PTP trigger output signal is set high when the system
time is greater than the target time. It is internally connected to the TIM2 input trigger. With
this signal, the input capture feature, the output compare feature and the waveforms of the
timer can be used, triggered by the synchronized PTP system time. No uncertainty is
introduced since the clock of the timer (PCLK1: TIM2 APB1 clock) and PTP reference clock
(HCLK) are synchronous.
This PTP trigger signal is connected to the TIM2 ITR1 input selectable by software. The
connection is enabled through bits 11 and 10 in the TIM2 option register (TIM2_OR).
Figure 515 shows the connection.
Figure 515. PTP trigger output to TIM2 ITR1 connection
PTP trigger
Ethernet MAC

ITR1
TIM2

ai15671

1556/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

PTP pulse-per-second output signal
This PTP pulse output is used to check the synchronization between all nodes in the
network. To be able to test the difference between the local slave clock and the master
reference clock, both clocks were given a pulse-per-second (PPS) output signal that may be
connected to an oscilloscope if necessary. The deviation between the two signals can
therefore be measured. The pulse width of the PPS output is 125 ms.
The PPS output is enabled through bits 11 and 10 in the TIM2 option register (TIM2_OR).
The default frequency of the PPS output is 1 Hz. PPSFREQ[3:0] (in ETH_PTPPPSCR) can
be used to set the frequency of the PPS output to 2PPSFREQ Hz.
When set to 1 Hz, the PPS pulse width is 125 ms with binary rollover (TSSSR=0, bit 9 in
ETH_PTPTSCR) and 100 ms with digital rollover (TSSSR=1). When set to 2 Hz and higher,
the duty cycle of the PPS output is 50% with binary rollover.
With digital rollover (TSSSR=1), it is recommended not to use the PPS output with a
frequency other than 1 Hz as it would have irregular waveforms (though its average
frequency would always be correct during any one-second window).
Figure 516. PPS output

PPS output
Ethernet MAC
ai15672

38.6

Ethernet functional description: DMA controller operation
The DMA has independent transmit and receive engines, and a CSR space. The transmit
engine transfers data from system memory into the Tx FIFO while the receive engine
transfers data from the Rx FIFO into system memory. The controller utilizes descriptors to
efficiently move data from source to destination with minimum CPU intervention. The DMA
is designed for packet-oriented data transfers such as frames in Ethernet. The controller can
be programmed to interrupt the CPU in cases such as frame transmit and receive transfer
completion, and other normal/error conditions. The DMA and the STM32F75xxx and
STM32F74xxx communicate through two data structures:
•

Control and status registers (CSR)

•

Descriptor lists and data buffers.

Control and status registers are described in detail in Section 38.8: Ethernet register
descriptions. Descriptors are described in detail in Normal Tx DMA descriptors.
The DMA transfers the received data frames to the receive buffer in the STM32F75xxx and
STM32F74xxx memory, and transmits data frames from the transmit buffer in the
STM32F75xxx and STM32F74xxx memory. Descriptors that reside in the STM32F75xxx
and STM32F74xxx memory act as pointers to these buffers. There are two descriptor lists:
one for reception, and one for transmission. The base address of each list is written into
DMA Registers 3 and 4, respectively. A descriptor list is forward-linked (either implicitly or
explicitly). The last descriptor may point back to the first entry to create a ring structure.
Explicit chaining of descriptors is accomplished by configuring the second address chained
in both the receive and transmit descriptors (RDES1[14] and TDES0[20]). The descriptor
lists reside in the Host’s physical memory space. Each descriptor can point to a maximum of

RM0385 Rev 7

1557/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

two buffers. This enables the use of two physically addressed buffers, instead of two
contiguous buffers in memory. A data buffer resides in the Host’s physical memory space,
and consists of an entire frame or part of a frame, but cannot exceed a single frame. Buffers
contain only data. The buffer status is maintained in the descriptor. Data chaining refers to
frames that span multiple data buffers. However, a single descriptor cannot span multiple
frames. The DMA skips to the next frame buffer when the end of frame is detected. Data
chaining can be enabled or disabled. The descriptor ring and chain structure is shown in
Figure 517.
Figure 517. Descriptor ring and chain structure
Ring structure

Chain structure
Buffer 1

Descriptor 0

Buffer 2

Descriptor 0

Buffer 1

Buffer 1
Descriptor 1

Buffer 2

Descriptor 1

Buffer 1

Buffer 1
Descriptor 2

Buffer 2
Descriptor 2

Buffer 1

Buffer 1
Descriptor n

Buffer 2
Next descriptor
ai15638

38.6.1

Initialization of a transfer using DMA
Initialization for the MAC is as follows:

38.6.2

1.

Write to ETH_DMABMR to set STM32F75xxx and STM32F74xxx bus access
parameters.

2.

Write to the ETH_DMAIER register to mask unnecessary interrupt causes.

3.

The software driver creates the transmit and receive descriptor lists. Then it writes to
both the ETH_DMARDLAR and ETH_DMATDLAR registers, providing the DMA with
the start address of each list.

4.

Write to MAC Registers 1, 2, and 3 to choose the desired filtering options.

5.

Write to the MAC ETH_MACCR register to configure and enable the transmit and
receive operating modes. The PS and DM bits are set based on the auto-negotiation
result (read from the PHY).

6.

Write to the ETH_DMAOMR register to set bits 13 and 1 and start transmission and
reception.

7.

The transmit and receive engines enter the running state and attempt to acquire
descriptors from the respective descriptor lists. The receive and transmit engines then
begin processing receive and transmit operations. The transmit and receive processes
are independent of each other and can be started or stopped separately.

Host bus burst access
The DMA attempts to execute fixed-length burst transfers on the AHB master interface if
configured to do so (FB bit in ETH_DMABMR). The maximum burst length is indicated and

1558/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
limited by the PBL field (ETH_DMABMR [13:8]). The receive and transmit descriptors are
always accessed in the maximum possible burst size (limited by PBL) for the 16 bytes to be
read.
The Transmit DMA initiates a data transfer only when there is sufficient space in the
Transmit FIFO to accommodate the configured burst or the number of bytes until the end of
frame (when it is less than the configured burst length). The DMA indicates the start address
and the number of transfers required to the AHB Master Interface. When the AHB Interface
is configured for fixed-length burst, then it transfers data using the best combination of
INCR4, INCR8, INCR16 and SINGLE transactions. Otherwise (no fixed-length burst), it
transfers data using INCR (undefined length) and SINGLE transactions.
The Receive DMA initiates a data transfer only when sufficient data for the configured burst
is available in Receive FIFO or when the end of frame (when it is less than the configured
burst length) is detected in the Receive FIFO. The DMA indicates the start address and the
number of transfers required to the AHB master interface. When the AHB interface is
configured for fixed-length burst, then it transfers data using the best combination of INCR4,
INCR8, INCR16 and SINGLE transactions. If the end of frame is reached before the fixedburst ends on the AHB interface, then dummy transfers are performed in order to complete
the fixed-length burst. Otherwise (FB bit in ETH_DMABMR is reset), it transfers data using
INCR (undefined length) and SINGLE transactions.
When the AHB interface is configured for address-aligned beats, both DMA engines ensure
that the first burst transfer the AHB initiates is less than or equal to the size of the configured
PBL. Thus, all subsequent beats start at an address that is aligned to the configured PBL.
The DMA can only align the address for beats up to size 16 (for PBL > 16), because the
AHB interface does not support more than INCR16.

38.6.3

Host data buffer alignment
The transmit and receive data buffers do not have any restrictions on start address
alignment. In our system with 32-bit memory, the start address for the buffers can be aligned
to any of the four bytes. However, the DMA always initiates transfers with address aligned to
the bus width with dummy data for the byte lanes not required. This typically happens during
the transfer of the beginning or end of an Ethernet frame.
•

Example of buffer read:
If the Transmit buffer address is 0x0000 0FF2, and 15 bytes need to be transferred,
then the DMA will read five full words from address 0x0000 0FF0, but when transferring
data to the Transmit FIFO, the extra bytes (the first two bytes) will be dropped or
ignored. Similarly, the last 3 bytes of the last transfer will also be ignored. The DMA
always ensures it transfers a full 32-bit data items to the Transmit FIFO, unless it is the
end of frame.

•

Example of buffer write:
If the Receive buffer address is 0x0000 0FF2, and 16 bytes of a received frame need to
be transferred, then the DMA will write five full 32-bit data items from address
0x0000 0FF0. But the first 2 bytes of the first transfer and the last 2 bytes of the third
transfer will have dummy data.

38.6.4

Buffer size calculations
The DMA does not update the size fields in the transmit and receive descriptors. The DMA
updates only the status fields (xDES0) of the descriptors. The driver has to calculate the
sizes. The transmit DMA transfers the exact number of bytes (indicated by buffer size field in

RM0385 Rev 7

1559/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

TDES1) towards the MAC core. If a descriptor is marked as first (FS bit in TDES0 is set),
then the DMA marks the first transfer from the buffer as the start of frame. If a descriptor is
marked as last (LS bit in TDES0), then the DMA marks the last transfer from that data buffer
as the end of frame. The receive DMA transfers data to a buffer until the buffer is full or the
end of frame is received. If a descriptor is not marked as last (LS bit in RDES0), then the
buffer(s) that correspond to the descriptor are full and the amount of valid data in a buffer is
accurately indicated by the buffer size field minus the data buffer pointer offset when the
descriptor’s FS bit is set. The offset is zero when the data buffer pointer is aligned to the
databus width. If a descriptor is marked as last, then the buffer may not be full (as indicated
by the buffer size in RDES1). To compute the amount of valid data in this final buffer, the
driver must read the frame length (FL bits in RDES0[29:16]) and subtract the sum of the
buffer sizes of the preceding buffers in this frame. The receive DMA always transfers the
start of next frame with a new descriptor.
Note:

Even when the start address of a receive buffer is not aligned to the system databus width
the system should allocate a receive buffer of a size aligned to the system bus width. For
example, if the system allocates a 1024 byte (1 KB) receive buffer starting from address
0x1000, the software can program the buffer start address in the receive descriptor to have
a 0x1002 offset. The receive DMA writes the frame to this buffer with dummy data in the first
two locations (0x1000 and 0x1001). The actual frame is written from location 0x1002. Thus,
the actual useful space in this buffer is 1022 bytes, even though the buffer size is
programmed as 1024 bytes, due to the start address offset.

38.6.5

DMA arbiter
The arbiter inside the DMA takes care of the arbitration between transmit and receive
channel accesses to the AHB master interface. Two types of arbitrations are possible:
round-robin, and fixed-priority. When round-robin arbitration is selected (DA bit in
ETH_DMABMR is reset), the arbiter allocates the databus in the ratio set by the PM bits in
ETH_DMABMR, when both transmit and receive DMAs request access simultaneously.
When the DA bit is set, the receive DMA always gets priority over the transmit DMA for data
access.

38.6.6

Error response to DMA
For any data transfer initiated by a DMA channel, if the slave replies with an error response,
that DMA stops all operations and updates the error bits and the fatal bus error bit in the
Status register (ETH_DMASR register). That DMA controller can resume operation only
after soft- or hard-resetting the peripheral and re-initializing the DMA.

38.6.7

Tx DMA configuration
TxDMA operation: default (non-OSF) mode
The transmit DMA engine in default mode proceeds as follows:

1560/1709

1.

The user sets up the transmit descriptor (TDES0-TDES3) and sets the OWN bit
(TDES0[31]) after setting up the corresponding data buffer(s) with Ethernet frame data.

2.

Once the ST bit (ETH_DMAOMR register[13]) is set, the DMA enters the Run state.

3.

While in the Run state, the DMA polls the transmit descriptor list for frames requiring
transmission. After polling starts, it continues in either sequential descriptor ring order
or chained order. If the DMA detects a descriptor flagged as owned by the CPU, or if an
error condition occurs, transmission is suspended and both the Transmit Buffer

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Unavailable (ETH_DMASR register[2]) and Normal Interrupt Summary (ETH_DMASR
register[16]) bits are set. The transmit engine proceeds to Step 9.
4.

If the acquired descriptor is flagged as owned by DMA (TDES0[31] is set), the DMA
decodes the transmit data buffer address from the acquired descriptor.

5.

The DMA fetches the transmit data from the STM32F75xxx and STM32F74xxx
memory and transfers the data.

6.

If an Ethernet frame is stored over data buffers in multiple descriptors, the DMA closes
the intermediate descriptor and fetches the next descriptor. Steps 3, 4, and 5 are
repeated until the end of Ethernet frame data is transferred.

7.

When frame transmission is complete, if IEEE 1588 time stamping was enabled for the
frame (as indicated in the transmit status) the time stamp value is written to the transmit
descriptor (TDES2 and TDES3) that contains the end-of-frame buffer. The status
information is then written to this transmit descriptor (TDES0). Because the OWN bit is
cleared during this step, the CPU now owns this descriptor. If time stamping was not
enabled for this frame, the DMA does not alter the contents of TDES2 and TDES3.

8.

Transmit Interrupt (ETH_DMASR register [0]) is set after completing the transmission
of a frame that has Interrupt on Completion (TDES1[31]) set in its last descriptor. The
DMA engine then returns to Step 3.

9.

In the Suspend state, the DMA tries to re-acquire the descriptor (and thereby returns to
Step 3) when it receives a transmit poll demand, and the Underflow Interrupt Status bit
is cleared.

Figure 518 shows the TxDMA transmission flow in default mode.

RM0385 Rev 7

1561/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Figure 518. TxDMA operation in default mode
Start TxDMA

Start

Stop TxDMA

(Re-)fetch next
descriptor

(AHB)
error?

Poll demand

Yes

No

TxDMA suspended

No

Own
bit set?
Yes

Transfer data from
buffer(s)

(AHB)
error?

Yes

No

No

Frame xfer
complete?
Yes

Close intermediate
descriptor

Wait for Tx status

Time stamp
present?

Yes

Write time stamp to
TDES2 and TDES3

No

Write status word
to TDES0

No

(AHB)
error?

No

(AHB)
error?

Yes

Yes

ai15639

TxDMA operation: OSF mode
While in the Run state, the transmit process can simultaneously acquire two frames without
closing the Status descriptor of the first (if the OSF bit is set in ETH_DMAOMR register[2]).
As the transmit process finishes transferring the first frame, it immediately polls the transmit
descriptor list for the second frame. If the second frame is valid, the transmit process
transfers this frame before writing the first frame’s status information. In OSF mode, the
Run-state transmit DMA operates according to the following sequence:

1562/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
1.

The DMA operates as described in steps 1–6 of the TxDMA (default mode).

2.

Without closing the previous frame’s last descriptor, the DMA fetches the next
descriptor.

3.

If the DMA owns the acquired descriptor, the DMA decodes the transmit buffer address
in this descriptor. If the DMA does not own the descriptor, the DMA goes into Suspend
mode and skips to Step 7.

4.

The DMA fetches the Transmit frame from the STM32F75xxx and STM32F74xxx
memory and transfers the frame until the end of frame data are transferred, closing the
intermediate descriptors if this frame is split across multiple descriptors.

5.

The DMA waits for the transmission status and time stamp of the previous frame. When
the status is available, the DMA writes the time stamp to TDES2 and TDES3, if such
time stamp was captured (as indicated by a status bit). The DMA then writes the status,
with a cleared OWN bit, to the corresponding TDES0, thus closing the descriptor. If
time stamping was not enabled for the previous frame, the DMA does not alter the
contents of TDES2 and TDES3.

6.

If enabled, the Transmit interrupt is set, the DMA fetches the next descriptor, then
proceeds to Step 3 (when Status is normal). If the previous transmission status shows
an underflow error, the DMA goes into Suspend mode (Step 7).

7.

In Suspend mode, if a pending status and time stamp are received by the DMA, it
writes the time stamp (if enabled for the current frame) to TDES2 and TDES3, then
writes the status to the corresponding TDES0. It then sets relevant interrupts and
returns to Suspend mode.

8.

The DMA can exit Suspend mode and enter the Run state (go to Step 1 or Step 2
depending on pending status) only after receiving a Transmit Poll demand
(ETH_DMATPDR register).

Figure 519 shows the basic flowchart in OSF mode.

RM0385 Rev 7

1563/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Figure 519. TxDMA operation in OSF mode
Start TxDMA

Start

Stop TxDMA

(Re-)fetch next
descriptor

(AHB)
error?

Poll
demand

Yes

No

TxDMA suspended

Own
bit set?

No

Yes
Previous frame
status available

Transfer data from
buffer(s)

(AHB)
error?

Time stamp
present?

Yes

No

Yes
No

Write time stamp to
TDES2 & TDES3
for previous frame

Frame xfer
complete?

No

Yes

No

Yes

Wait for previous
frame’s Tx status

Close intermediate
descriptor

(AHB)
error?

Yes

Time stamp
present?

No

Yes

Write time stamp to
TDES2 & TDES3
for previous frame

No

Write status word to
prev. frame’s TDES0

Write status word to
prev. frame’s TDES0

No

Second
frame?

(AHB)
error?

No

No

(AHB)
error?

Yes

(AHB)
error?
Yes

Yes

ai15640

Transmit frame processing
The transmit DMA expects that the data buffers contain complete Ethernet frames,
excluding preamble, pad bytes, and FCS fields. The DA, SA, and Type/Len fields contain
valid data. If the transmit descriptor indicates that the MAC core must disable CRC or pad
insertion, the buffer must have complete Ethernet frames (excluding preamble), including
the CRC bytes. Frames can be data-chained and span over several buffers. Frames have to
be delimited by the first descriptor (TDES0[28]) and the last descriptor (TDES0[29]). As the
transmission starts, TDES0[28] has to be set in the first descriptor. When this occurs, the
frame data are transferred from the memory buffer to the Transmit FIFO. Concurrently, if the
last descriptor (TDES0[29]) of the current frame is cleared, the transmit process attempts to
acquire the next descriptor. The transmit process expects TDES0[28] to be cleared in this
descriptor. If TDES0[29] is cleared, it indicates an intermediary buffer. If TDES0[29] is set, it
indicates the last buffer of the frame. After the last buffer of the frame has been transmitted,
1564/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
the DMA writes back the final status information to the transmit descriptor 0 (TDES0) word
of the descriptor that has the last segment set in transmit descriptor 0 (TDES0[29]). At this
time, if Interrupt on Completion (TDES0[30]) is set, Transmit Interrupt (in ETH_DMASR
register [0]) is set, the next descriptor is fetched, and the process repeats. Actual frame
transmission begins after the Transmit FIFO has reached either a programmable transmit
threshold (ETH_DMAOMR register[16:14]), or a full frame is contained in the FIFO. There is
also an option for the Store and forward mode (ETH_DMAOMR register[21]). Descriptors
are released (OWN bit TDES0[31] is cleared) when the DMA finishes transferring the frame.

Transmit polling suspended
Transmit polling can be suspended by either of the following conditions:
•

The DMA detects a descriptor owned by the CPU (TDES0[31]=0) and the Transmit
buffer unavailable flag is set (ETH_DMASR register[2]). To resume, the driver must
give descriptor ownership to the DMA and then issue a Poll Demand command.

•

A frame transmission is aborted when a transmit error due to underflow is detected.
The appropriate Transmit Descriptor 0 (TDES0) bit is set. If the second condition
occurs, both the Abnormal Interrupt Summary (in ETH_DMASR register [15]) and
Transmit Underflow bits (in ETH_DMASR register[5]) are set, and the information is
written to Transmit Descriptor 0, causing the suspension. If the DMA goes into
Suspend state due to the first condition, then both the Normal Interrupt Summary
(ETH_DMASR register [16]) and Transmit Buffer Unavailable (ETH_DMASR
register[2]) bits are set. In both cases, the position in the transmit list is retained. The
retained position is that of the descriptor following the last descriptor closed by the
DMA. The driver must explicitly issue a Transmit Poll Demand command after rectifying
the suspension cause.

Normal Tx DMA descriptors
The normal transmit descriptor structure consists of four 32-bit words as shown in
Figure 520. The bit descriptions of TDES0, TDES1, TDES2 and TDES3 are given below.
Note that enhanced descriptors must be used if time stamping is activated (ETH_PTPTSCR
bit 0, TSE=1) or if IPv4 checksum offload is activated (ETH_MACCR bit 10, IPCO=1).
Figure 520. Normal transmit descriptor
31

TDES 0
TDES 1
TDES 2

TDES 3

O
W
N

0
Ctrl
[30:26]

Reserved
[31:29]

T
T Res.
S 24
E

Ctrl
[23:20]

T
Reserved T
[19:18]
S
S

Buffer 2 byte count
[28:16]

Reserved
[15:13]

Status [16:0]
Buffer 1 byte count
[12:0]

Buffer 1 address [31:0] / Time stamp low [31:0]

Buffer 2 address [31:0] or Next descriptor address [31:0] / Time stamp high [31:0]

ai15642b

RM0385 Rev 7

1565/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller
•

RM0385

TDES0: Transmit descriptor Word0
The application software has to program the control bits [30:26]+[23:20] plus the OWN
bit [31] during descriptor initialization. When the DMA updates the descriptor (or writes
it back), it resets all the control bits plus the OWN bit, and reports only the status bits.

31

30

29

28

27

26

25

24

OWN

IC

LS

FS

DC

DP

TTSE

Res.

23

22
CIC

21

20

19

18

17

16

TER

TCH

Res.

Res.

TTSS

IHE

rw

rw

2

1

0

ED

UF

DB

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

ES

JT

FF

IPE

LCA

NC

LCO

EC

VF

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

CC

Bit 31 OWN: Own bit
When set, this bit indicates that the descriptor is owned by the DMA. When this bit is reset, it
indicates that the descriptor is owned by the CPU. The DMA clears this bit either when it
completes the frame transmission or when the buffers allocated in the descriptor are read
completely. The ownership bit of the frame’s first descriptor must be set after all subsequent
descriptors belonging to the same frame have been set.
Bit 30 IC: Interrupt on completion
When set, this bit sets the Transmit Interrupt (Register 5[0]) after the present frame has
been transmitted.
Bit 29 LS: Last segment
When set, this bit indicates that the buffer contains the last segment of the frame.
Bit 28 FS: First segment
When set, this bit indicates that the buffer contains the first segment of a frame.
Bit 27 DC: Disable CRC
When this bit is set, the MAC does not append a cyclic redundancy check (CRC) to the end
of the transmitted frame. This is valid only when the first segment (TDES0[28]) is set.
Bit 26 DP: Disable pad
When set, the MAC does not automatically add padding to a frame shorter than 64 bytes.
When this bit is reset, the DMA automatically adds padding and CRC to a frame shorter than
64 bytes, and the CRC field is added despite the state of the DC (TDES0[27]) bit. This is
valid only when the first segment (TDES0[28]) is set.
Bit 25 TTSE: Transmit time stamp enable
When TTSE is set and when TSE is set (ETH_PTPTSCR bit 0), IEEE1588 hardware time
stamping is activated for the transmit frame described by the descriptor. This field is only valid
when the First segment control bit (TDES0[28]) is set.
Bit 24 Reserved, must be kept at reset value.
Bits 23:22 CIC: Checksum insertion control
These bits control the checksum calculation and insertion. Bit encoding is as shown below:
00: Checksum Insertion disabled
01: Only IP header checksum calculation and insertion are enabled
10: IP header checksum and payload checksum calculation and insertion are enabled, but
pseudo-header checksum is not calculated in hardware
11: IP Header checksum and payload checksum calculation and insertion are enabled, and
pseudo-header checksum is calculated in hardware.

1566/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 21 TER: Transmit end of ring
When set, this bit indicates that the descriptor list reached its final descriptor. The DMA
returns to the base address of the list, creating a descriptor ring.
Bit 20 TCH: Second address chained
When set, this bit indicates that the second address in the descriptor is the next descriptor
address rather than the second buffer address. When TDES0[20] is set, TBS2
(TDES1[28:16]) is a “don’t care” value. TDES0[21] takes precedence over TDES0[20].
Bits 19:18 Reserved, must be kept at reset value.
Bit 17 TTSS: Transmit time stamp status
This field is used as a status bit to indicate that a time stamp was captured for the described
transmit frame. When this bit is set, TDES2 and TDES3 have a time stamp value captured for the
transmit frame. This field is only valid when the descriptor’s Last segment control bit (TDES0[29])
is set.
Note that when enhanced descriptors are enabled (EDFE=1 in ETH_DMABMR), TTSS=1
indicates that TDES6 and TDES7 have the time stamp value.
Bit 16 IHE: IP header error
When set, this bit indicates that the MAC transmitter detected an error in the IP datagram
header. The transmitter checks the header length in the IPv4 packet against the number of
header bytes received from the application and indicates an error status if there is a
mismatch. For IPv6 frames, a header error is reported if the main header length is not 40
bytes. Furthermore, the Ethernet length/type field value for an IPv4 or IPv6 frame must
match the IP header version received with the packet. For IPv4 frames, an error status is
also indicated if the Header Length field has a value less than 0x5.
Bit 15 ES: Error summary
Indicates the logical OR of the following bits:
TDES0[14]: Jabber timeout
TDES0[13]: Frame flush
TDES0[11]: Loss of carrier
TDES0[10]: No carrier
TDES0[9]: Late collision
TDES0[8]: Excessive collision
TDES0[2]:Excessive deferral
TDES0[1]: Underflow error
TDES0[16]: IP header error
TDES0[12]: IP payload error
Bit 14 JT: Jabber timeout
When set, this bit indicates the MAC transmitter has experienced a jabber timeout. This bit is
only set when the MAC configuration register’s JD bit is not set.
Bit 13 FF: Frame flushed
When set, this bit indicates that the DMA/MTL flushed the frame due to a software Flush
command given by the CPU.
Bit 12 IPE: IP payload error
When set, this bit indicates that MAC transmitter detected an error in the TCP, UDP, or ICMP
IP datagram payload. The transmitter checks the payload length received in the IPv4 or IPv6
header against the actual number of TCP, UDP or ICMP packet bytes received from the
application and issues an error status in case of a mismatch.

RM0385 Rev 7

1567/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 11 LCA: Loss of carrier
When set, this bit indicates that a loss of carrier occurred during frame transmission (that is,
the MII_CRS signal was inactive for one or more transmit clock periods during frame
transmission). This is valid only for the frames transmitted without collision when the MAC
operates in Half-duplex mode.
Bit 10 NC: No carrier
When set, this bit indicates that the Carrier Sense signal form the PHY was not asserted
during transmission.
Bit 9 LCO: Late collision
When set, this bit indicates that frame transmission was aborted due to a collision occurring
after the collision window (64 byte times, including preamble, in MII mode). This bit is not
valid if the Underflow Error bit is set.
Bit 8 EC: Excessive collision
When set, this bit indicates that the transmission was aborted after 16 successive collisions
while attempting to transmit the current frame. If the RD (Disable retry) bit in the MAC
Configuration register is set, this bit is set after the first collision, and the transmission of the
frame is aborted.
Bit 7 VF: VLAN frame
When set, this bit indicates that the transmitted frame was a VLAN-type frame.
Bits 6:3 CC: Collision count
This 4-bit counter value indicates the number of collisions occurring before the frame was
transmitted. The count is not valid when the Excessive collisions bit (TDES0[8]) is set.
Bit 2 ED: Excessive deferral
When set, this bit indicates that the transmission has ended because of excessive deferral
of over 24 288 bit times if the Deferral check (DC) bit in the MAC Control register is set high.
Bit 1 UF: Underflow error
When set, this bit indicates that the MAC aborted the frame because data arrived late from
the RAM memory. Underflow error indicates that the DMA encountered an empty transmit
buffer while transmitting the frame. The transmission process enters the Suspended state
and sets both Transmit underflow (Register 5[5]) and Transmit interrupt (Register 5[0]).
Bit 0 DB: Deferred bit
When set, this bit indicates that the MAC defers before transmission because of the
presence of the carrier. This bit is valid only in Half-duplex mode.

•

TDES1: Transmit descriptor Word1

31

30

29

Res.

Res.

Res.

15

14

13

Res.

Res.

Res.

28

27

26

25

24

23

22

21

20

19

18

17

16

TBS2
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

TBS1
rw

rw

rw

rw

rw

rw

rw

31:29 Reserved, must be kept at reset value.
28:16 TBS2: Transmit buffer 2 size
These bits indicate the second data buffer size in bytes. This field is not valid if TDES0[20] is
set.

1568/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

15:13 Reserved, must be kept at reset value.
12:0 TBS1: Transmit buffer 1 size
These bits indicate the first data buffer byte size, in bytes. If this field is 0, the DMA ignores
this buffer and uses Buffer 2 or the next descriptor, depending on the value of TCH
(TDES0[20]).

•

TDES2: Transmit descriptor Word2
TDES2 contains the address pointer to the first buffer of the descriptor or it contains
time stamp data.

31

30

29

28

27

26

25

24

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

TBAP1/TBAP/TTSL

TBAP1/TBAP/TTSL
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 TBAP1: Transmit buffer 1 address pointer / Transmit frame time stamp low
These bits have two different functions: they indicate to the DMA the location of data in
memory, and after all data are transferred, the DMA can then use these bits to pass back time
stamp data.
TBAP: When the software makes this descriptor available to the DMA (at the moment that the
OWN bit is set to 1 in TDES0), these bits indicate the physical address of Buffer 1. There is no
limitation on the buffer address alignment. See Host data buffer alignment on page 1559 for further
details on buffer address alignment.
TTSL: Before it clears the OWN bit in TDES0, the DMA updates this field with the 32 least
significant bits of the time stamp captured for the corresponding transmit frame (overwriting
the value for TBAP1). This field has the time stamp only if time stamping is activated for this
frame (see TTSE, TDES0 bit 25) and if the Last segment control bit (LS) in the descriptor is
set.

•

TDES3: Transmit descriptor Word3
TDES3 contains the address pointer either to the second buffer of the descriptor or the
next descriptor, or it contains time stamp data.

31

30

29

28

27

26

25

24

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

TBAP2/TBAP2/TTSH

TBAP2/TBAP2/TTSH
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

1569/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bits 31:0 TBAP2: Transmit buffer 2 address pointer (Next descriptor address) / Transmit frame time
stamp high
These bits have two different functions: they indicate to the DMA the location of data in
memory, and after all data are transferred, the DMA can then use these bits to pass back
time stamp data.
TBAP2: When the software makes this descriptor available to the DMA (at the moment when
the OWN bit is set to 1 in TDES0), these bits indicate the physical address of Buffer 2 when a
descriptor ring structure is used. If the Second address chained (TDES1 [20]) bit is set, this
address contains the pointer to the physical memory where the next descriptor is present. The
buffer address pointer must be aligned to the bus width only when TDES1 [20] is set. (LSBs are
ignored internally.)
TTSH: Before it clears the OWN bit in TDES0, the DMA updates this field with the 32 most
significant bits of the time stamp captured for the corresponding transmit frame (overwriting
the value for TBAP2). This field has the time stamp only if activated for this frame (see
TDES0 bit 25, TTSE) and if the Last segment control bit (LS) in the descriptor is set.

Enhanced Tx DMA descriptors
Enhanced descriptors (enabled with EDFE=1, ETHDMABMR bit 7), must be used if time
stamping is activated (TSE=1, ETH_PTPTSCR bit 0) or if IPv4 checksum offload is
activated (IPCO=1, ETH_MACCR bit 10).
Enhanced descriptors comprise eight 32-bit words, twice the size of normal descriptors.
TDES0, TDES1, TDES2 and TDES3 have the same definitions as for normal transmit
descriptors (refer to Normal Tx DMA descriptors). TDES6 and TDES7 hold the time stamp.
TDES4, TDES5, TDES6 and TDES7 are defined below.
When the Enhanced descriptor mode is selected, the software needs to allocate 32-bytes (8
DWORDS) of memory for every descriptor. When time stamping or IPv4 checksum offload
are not being used, the enhanced descriptor format may be disabled and the software can
use normal descriptors with the default size of 16 bytes.

1570/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Figure 521. Enhanced transmit descriptor
31

TDES 0
TDES 1

O
W
N

0
Ctrl
[30:26]

Reserved
[31:29]

T
T Res.
S 24
E

T
Reserved T
[19:18]
S
S

Ctrl
[23:20]

Buffer 2 byte count
[28:16]

TDES 2

Status [16:0]

Reserved
[15:13]

Buffer 1 byte count
[12:0]

Buffer 1 address [31:0]

Buffer 2 address [31:0] or Next descriptor address [31:0]

TDES 3
TDES 4

Reserved

TDES 5

Reserved

TDES 6

Time stamp low [31:0]

TDES 7

Time stamp high [31:0]

ai17105b

•

TDES4: Transmit descriptor Word4
Reserved

•

TDES5: Transmit descriptor Word5
Reserved

•
31

30

TDES6: Transmit descriptor Word6
29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

TTSL
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8
TTSL

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 TTSL: Transmit frame time stamp low
This field is updated by DMA with the 32 least significant bits of the time stamp captured
for the corresponding transmit frame. This field has the time stamp only if the Last segment
control bit (LS) in the descriptor is set.

•
31

30

TDES7: Transmit descriptor Word7
29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

TTSH
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8
TTSH

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

1571/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bits 31:0 TTSH: Transmit frame time stamp high
This field is updated by DMA with the 32 most significant bits of the time stamp captured for
the corresponding transmit frame. This field has the time stamp only if the Last segment control
bit (LS) in the descriptor is set.

38.6.8

Rx DMA configuration
The Receive DMA engine’s reception sequence is illustrated in Figure 522 and described
below:
1.

The CPU sets up Receive descriptors (RDES0-RDES3) and sets the OWN bit
(RDES0[31]).

2.

Once the SR (ETH_DMAOMR register[1]) bit is set, the DMA enters the Run state.
While in the Run state, the DMA polls the receive descriptor list, attempting to acquire
free descriptors. If the fetched descriptor is not free (is owned by the CPU), the DMA
enters the Suspend state and jumps to Step 9.

3.

The DMA decodes the receive data buffer address from the acquired descriptors.

4.

Incoming frames are processed and placed in the acquired descriptor’s data buffers.

5.

When the buffer is full or the frame transfer is complete, the Receive engine fetches the
next descriptor.

6.

If the current frame transfer is complete, the DMA proceeds to step 7. If the DMA does
not own the next fetched descriptor and the frame transfer is not complete (EOF is not
yet transferred), the DMA sets the Descriptor error bit in RDES0 (unless flushing is
disabled). The DMA closes the current descriptor (clears the OWN bit) and marks it as
intermediate by clearing the Last segment (LS) bit in the RDES1 value (marks it as last
descriptor if flushing is not disabled), then proceeds to step 8. If the DMA owns the next
descriptor but the current frame transfer is not complete, the DMA closes the current
descriptor as intermediate and returns to step 4.

7.

If IEEE 1588 time stamping is enabled, the DMA writes the time stamp (if available) to
the current descriptor’s RDES2 and RDES3. It then takes the received frame’s status
and writes the status word to the current descriptor’s RDES0, with the OWN bit cleared
and the Last segment bit set.

8.

The Receive engine checks the latest descriptor’s OWN bit. If the CPU owns the
descriptor (OWN bit is at 0) the Receive buffer unavailable bit (in ETH_DMASR
register[7]) is set and the DMA Receive engine enters the Suspended state (step 9). If
the DMA owns the descriptor, the engine returns to step 4 and awaits the next frame.

9.

Before the Receive engine enters the Suspend state, partial frames are flushed from
the Receive FIFO (you can control flushing using bit 24 in the ETH_DMAOMR
register).

10. The Receive DMA exits the Suspend state when a Receive Poll demand is given or the
start of next frame is available from the Receive FIFO. The engine proceeds to step 2
and re-fetches the next descriptor.
The DMA does not acknowledge accepting the status until it has completed the time stamp
write-back and is ready to perform status write-back to the descriptor. If software has
enabled time stamping through CSR, when a valid time stamp value is not available for the
frame (for example, because the receive FIFO was full before the time stamp could be
written to it), the DMA writes all ones to RDES2 and RDES3. Otherwise (that is, if time
stamping is not enabled), RDES2 and RDES3 remain unchanged.

1572/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Figure 522. Receive DMA operation
Start RxDMA

Stop RxDMA

(Re-)Fetch next
descriptor

Poll demand /
new frame available

(AHB)
erro r?

RxDMA suspended

Ye s

No

Ye s
Frame transfer
complete?

Yes

Start

No

Own bit set?

No

Ye s

Flush disabled ?

Frame data
available ?

No

Ye s

Flush the
remaining frame

Write data to buffer(s)

No

Wait for frame data

(AHB)
erro r?

Ye s

No
Fetch next descriptor

(AHB)
erro r?

Ye s

No

Flush
disabled ?
No

Set descriptor error

No

Ye s

Own bit set
for next desc?

Frame transfer
complete?

No

Ye s

Ye s

Close RDES0 as
intermediate descriptor

Time stamp
present?

Ye s

Write time stamp to
RDES2 & RDES3

No
Close RDES0 as last
descriptor

No

(AHB)
erro r?

No

(AHB)
erro r?

Ye s

Ye s

ai15643

RM0385 Rev 7

1573/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Receive descriptor acquisition
The receive engine always attempts to acquire an extra descriptor in anticipation of an
incoming frame. Descriptor acquisition is attempted if any of the following conditions is/are
satisfied:
•

The receive Start/Stop bit (ETH_DMAOMR register[1]) has been set immediately after
the DMA has been placed in the Run state.

•

The data buffer of the current descriptor is full before the end of the frame currently
being transferred

•

The controller has completed frame reception, but the current receive descriptor has
not yet been closed.

•

The receive process has been suspended because of a CPU-owned buffer
(RDES0[31] = 0) and a new frame is received.

•

A Receive poll demand has been issued.

Receive frame processing
The MAC transfers the received frames to the STM32F75xxx and STM32F74xxx memory
only when the frame passes the address filter and the frame size is greater than or equal to
the configurable threshold bytes set for the Receive FIFO, or when the complete frame is
written to the FIFO in Store-and-forward mode. If the frame fails the address filtering, it is
dropped in the MAC block itself (unless Receive All ETH_MACFFR [31] bit is set). Frames
that are shorter than 64 bytes, because of collision or premature termination, can be purged
from the Receive FIFO. After 64 (configurable threshold) bytes have been received, the
DMA block begins transferring the frame data to the receive buffer pointed to by the current
descriptor. The DMA sets the first descriptor (RDES0[9]) after the DMA AHB Interface
becomes ready to receive a data transfer (if DMA is not fetching transmit data from the
memory), to delimit the frame. The descriptors are released when the OWN (RDES0[31]) bit
is reset to 0, either as the data buffer fills up or as the last segment of the frame is
transferred to the receive buffer. If the frame is contained in a single descriptor, both the last
descriptor (RDES0[8]) and first descriptor (RDES0[9]) bits are set. The DMA fetches the
next descriptor, sets the last descriptor (RDES0[8]) bit, and releases the RDES0 status bits
in the previous frame descriptor. Then the DMA sets the receive interrupt bit (ETH_DMASR
register [6]). The same process repeats unless the DMA encounters a descriptor flagged as
being owned by the CPU. If this occurs, the receive process sets the receive buffer
unavailable bit (ETH_DMASR register[7]) and then enters the Suspend state. The position
in the receive list is retained.

Receive process suspended
If a new receive frame arrives while the receive process is in Suspend state, the DMA refetches the current descriptor in the STM32F75xxx and STM32F74xxx memory. If the
descriptor is now owned by the DMA, the receive process re-enters the Run state and starts
frame reception. If the descriptor is still owned by the host, by default, the DMA discards the
current frame at the top of the Rx FIFO and increments the missed frame counter. If more
than one frame is stored in the Rx FIFO, the process repeats. The discarding or flushing of
the frame at the top of the Rx FIFO can be avoided by setting the DMA Operation mode
register bit 24 (DFRF). In such conditions, the receive process sets the receive buffer
unavailable status bit and returns to the Suspend state.

1574/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Normal Rx DMA descriptors
The normal receive descriptor structure consists of four 32-bit words (16 bytes). These are
shown in Figure 523. The bit descriptions of RDES0, RDES1, RDES2 and RDES3 are given
below.
Note that enhanced descriptors must be used if time stamping is activated (TSE=1,
ETH_PTPTSCR bit 0) or if IPv4 checksum offload is activated (IPCO=1, ETH_MACCR bit
10).
Figure 523. Normal Rx DMA descriptor structure
O
RDES 0 W
N

Status [30:0]

RDES 1 CT Reserved
RL [30:29]

Buffer 2 byte count
[28:16]

RDES 2

CTRL Res.
[15:14]

Buffer 1 byte count
[12:0]

Buffer 1 address [31:0]

Buffer 2 address [31:0] or Next descriptor address [31:0]

RDES 3

ai15644

•

RDES0: Receive descriptor Word0
RDES0 contains the received frame status, the frame length and the descriptor
ownership information.

31

30

OWN

AFM

29

28

27

26

25

24

23

22

21

20

19

18

17

16

FL

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

ES

DE

SAF

LE

OE

VLAN

FS

LS

IPHCE/TSV

LCO

FT

RWT

RE

DE

CE

PCE/ESA

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 OWN: Own bit
When set, this bit indicates that the descriptor is owned by the DMA of the MAC Subsystem.
When this bit is reset, it indicates that the descriptor is owned by the Host. The DMA clears this bit
either when it completes the frame reception or when the buffers that are associated with this
descriptor are full.
Bit 30 AFM: Destination address filter fail
When set, this bit indicates a frame that failed the DA filter in the MAC Core.
Bits 29:16 FL: Frame length
These bits indicate the byte length of the received frame that was transferred to host memory
(including CRC). This field is valid only when last descriptor (RDES0[8]) is set and descriptor error
(RDES0[14]) is reset.
This field is valid when last descriptor (RDES0[8]) is set. When the last descriptor and error
summary bits are not set, this field indicates the accumulated number of bytes that have been
transferred for the current frame.

RM0385 Rev 7

1575/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 15 ES: Error summary
Indicates the logical OR of the following bits:
RDES0[1]: CRC error
RDES0[3]: Receive error
RDES0[4]: Watchdog timeout
RDES0[6]: Late collision
RDES0[7]: Giant frame (This is not applicable when RDES0[7] indicates an IPV4 header
checksum error.)
RDES0[11]: Overflow error
RDES0[14]: Descriptor error.
This field is valid only when the last descriptor (RDES0[8]) is set.
Bit 14 DE: Descriptor error
When set, this bit indicates a frame truncation caused by a frame that does not fit within the current
descriptor buffers, and that the DMA does not own the next descriptor. The frame is truncated.
This field is valid only when the last descriptor (RDES0[8]) is set.
Bit 13 SAF: Source address filter fail
When set, this bit indicates that the SA field of frame failed the SA filter in the MAC Core.
Bit 12 LE: Length error
When set, this bit indicates that the actual length of the received frame does not match the value in
the Length/ Type field. This bit is valid only when the Frame type (RDES0[5]) bit is reset.
Bit 11 OE: Overflow error
When set, this bit indicates that the received frame was damaged due to buffer overflow.
Bit 10 VLAN: VLAN tag
When set, this bit indicates that the frame pointed to by this descriptor is a VLAN frame tagged
by the MAC core.
Bit 9 FS: First descriptor
When set, this bit indicates that this descriptor contains the first buffer of the frame. If the size of the
first buffer is 0, the second buffer contains the beginning of the frame. If the size of the second buffer
is also 0, the next descriptor contains the beginning of the frame.
Bit 8 LS: Last descriptor
When set, this bit indicates that the buffers pointed to by this descriptor are the last buffers of
the frame.
Bit 7 IPHCE/TSV: IPv header checksum error / time stamp valid
If IPHCE is set, it indicates an error in the IPv4 or IPv6 header. This error can be due to inconsistent
Ethernet Type field and IP header Version field values, a header checksum mismatch in IPv4, or an
Ethernet frame lacking the expected number of IP header bytes. This bit can take on special
meaning as specified in Table 278.
If enhanced descriptor format is enabled (EDFE=1, bit 7 of ETH_DMABMR), this bit takes on
the TSV function (otherwise it is IPHCE). When TSV is set, it indicates that a snapshot of the
timestamp is written in descriptor words 6 (RDES6) and 7 (RDES7). TSV is valid only when
the Last descriptor bit (RDES0[8]) is set.
Bit 6 LCO: Late collision
When set, this bit indicates that a late collision has occurred while receiving the frame in Halfduplex mode.

1576/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 5 FT: Frame type
When set, this bit indicates that the Receive frame is an Ethernet-type frame (the LT field is greater
than or equal to 0x0600). When this bit is reset, it indicates that the received frame is an
IEEE802.3 frame. This bit is not valid for Runt frames less than 14 bytes. When the normal
descriptor format is used (ETH_DMABMR EDFE=0), FT can take on special meaning as
specified in Table 278.
Bit 4 RWT: Receive watchdog timeout
When set, this bit indicates that the Receive watchdog timer has expired while receiving the
current frame and the current frame is truncated after the watchdog timeout.
Bit 3 RE: Receive error
When set, this bit indicates that the RX_ERR signal is asserted while RX_DV is asserted
during frame reception.
Bit 2 DE: Dribble bit error
When set, this bit indicates that the received frame has a non-integer multiple of bytes (odd
nibbles). This bit is valid only in MII mode.
Bit 1 CE: CRC error
When set, this bit indicates that a cyclic redundancy check (CRC) error occurred on the
received frame. This field is valid only when the last descriptor (RDES0[8]) is set.
Bit 0 PCE/ESA: Payload checksum error / extended status available
When set, it indicates that the TCP, UDP or ICMP checksum the core calculated does not
match the received encapsulated TCP, UDP or ICMP segment’s Checksum field. This bit is
also set when the received number of payload bytes does not match the value indicated in
the Length field of the encapsulated IPv4 or IPv6 datagram in the received Ethernet frame.
This bit can take on special meaning as specified in Table 278.
If the enhanced descriptor format is enabled (EDFE=1, bit 7 in ETH_DMABMR), this bit takes
on the ESA function (otherwise it is PCE). When ESA is set, it indicates that the extended
status is available in descriptor word 4 (RDES4). ESA is valid only when the last descriptor bit
(RDES0[8]) is set.

Bits 5, 7, and 0 reflect the conditions discussed in Table 278.

RM0385 Rev 7

1577/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Table 278. Receive descriptor 0 - encoding for bits 7, 5 and 0 (normal descriptor
format only, EDFE=0)
Bit 5:
frame
type

•

Bit 7: IPC Bit 0: payload
checksum
checksum
error
error

Frame status

0

0

0

IEEE 802.3 Type frame (Length field value is less than
0x0600.)

1

0

0

IPv4/IPv6 Type frame, no checksum error detected

1

0

1

IPv4/IPv6 Type frame with a payload checksum error (as described
for PCE) detected

1

1

0

IPv4/IPv6 Type frame with an IP header checksum error (as
described for IPC CE) detected

1

1

1

IPv4/IPv6 Type frame with both IP header and payload checksum
errors detected

0

0

1

IPv4/IPv6 Type frame with no IP header checksum error and the
payload check bypassed, due to an unsupported payload

0

1

1

A Type frame that is neither IPv4 or IPv6 (the checksum offload
engine bypasses checksum completely.)

0

1

0

Reserved

RDES1: Receive descriptor Word1

31

30

29

DIC

Res.

Res.

rw
15

14

13

RER

RCH

Res.

rw

rw

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

RBS2
rw

rw

rw

rw

rw

rw

12

11

10

9

8

7

RBS
rw

rw

rw

rw

rw

rw

rw

Bit 31 DIC: Disable interrupt on completion
When set, this bit prevents setting the Status register’s RS bit (CSR5[6]) for the received frame
ending in the buffer indicated by this descriptor. This, in turn, disables the assertion of the interrupt to
Host due to RS for that frame.
Bits 30:29 Reserved, must be kept at reset value.
Bits 28:16 RBS2: Receive buffer 2 size
These bits indicate the second data buffer size, in bytes. The buffer size must be a multiple of 4,
8, or 16, depending on the bus widths (32, 64 or 128, respectively), even if the value of RDES3
(buffer2 address pointer) is not aligned to bus width. If the buffer size is not an appropriate multiple
of 4, 8 or 16, the resulting behavior is undefined. This field is not valid if RDES1 [14] is set.
Bit 15 RER: Receive end of ring
When set, this bit indicates that the descriptor list reached its final descriptor. The DMA returns to the
base address of the list, creating a descriptor ring.

1578/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 14 RCH: Second address chained
When set, this bit indicates that the second address in the descriptor is the next descriptor address
rather than the second buffer address. When this bit is set, RBS2 (RDES1[28:16]) is a “don’t
care” value. RDES1[15] takes precedence over RDES1[14].
Bit 13 Reserved, must be kept at reset value.
Bits 12:0 RBS1: Receive buffer 1 size
Indicates the first data buffer size in bytes. The buffer size must be a multiple of 4, 8 or 16,
depending upon the bus widths (32, 64 or 128), even if the value of RDES2 (buffer1 address
pointer) is not aligned. When the buffer size is not a multiple of 4, 8 or 16, the resulting behavior is
undefined. If this field is 0, the DMA ignores this buffer and uses Buffer 2 or next descriptor
depending on the value of RCH (bit 14).

•

RDES2: Receive descriptor Word2
RDES2 contains the address pointer to the first data buffer in the descriptor, or it
contains time stamp data.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

RBP1 / RTSL
rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

RBP1 / RTSL
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 RBAP1 / RTSL: Receive buffer 1 address pointer / Receive frame time stamp low
These bits take on two different functions: the application uses them to indicate to the DMA
where to store the data in memory, and then after transferring all the data the DMA may use
these bits to pass back time stamp data.
RBAP1: When the software makes this descriptor available to the DMA (at the moment that
the OWN bit is set to 1 in RDES0), these bits indicate the physical address of Buffer 1. There are
no limitations on the buffer address alignment except for the following condition: the DMA uses the
configured value for its address generation when the RDES2 value is used to store the start of
frame. Note that the DMA performs a write operation with the RDES2[3/2/1:0] bits as 0 during the
transfer of the start of frame but the frame data is shifted as per the actual Buffer address pointer.
The DMA ignores RDES2[3/2/1:0] (corresponding to bus width of 128/64/32) if the address pointer
is to a buffer where the middle or last part of the frame is stored.
RTSL: Before it clears the OWN bit in RDES0, the DMA updates this field with the 32 least
significant bits of the time stamp captured for the corresponding receive frame (overwriting
the value for RBAP1). This field has the time stamp only if time stamping is activated for this
frame and if the Last segment control bit (LS) in the descriptor is set.

•

RDES3: Receive descriptor Word3
RDES3 contains the address pointer either to the second data buffer in the descriptor
or to the next descriptor, or it contains time stamp data.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

RBP2 / RTSH
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

RBP2 / RTSH
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

1579/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bits 31:0 RBAP2 / RTSH: Receive buffer 2 address pointer (next descriptor address) / Receive frame
time stamp high
These bits take on two different functions: the application uses them to indicate to the DMA
the location of where to store the data in memory, and then after transferring all the data the
DMA may use these bits to pass back time stamp data.
RBAP1: When the software makes this descriptor available to the DMA (at the moment that
the OWN bit is set to 1 in RDES0), these bits indicate the physical address of buffer 2 when a
descriptor ring structure is used. If the second address chained (RDES1 [24]) bit is set, this address
contains the pointer to the physical memory where the next descriptor is present. If RDES1 [24] is
set, the buffer (next descriptor) address pointer must be bus width-aligned (RDES3[3, 2, or
1:0] = 0, corresponding to a bus width of 128, 64 or 32. LSBs are ignored internally.)
However, when RDES1 [24] is reset, there are no limitations on the RDES3 value, except for the
following condition: the DMA uses the configured value for its buffer address generation when the
RDES3 value is used to store the start of frame. The DMA ignores RDES3[3, 2, or 1:0]
(corresponding to a bus width of 128, 64 or 32) if the address pointer is to a buffer where the
middle or last part of the frame is stored.
RTSH: Before it clears the OWN bit in RDES0, the DMA updates this field with the 32 most
significant bits of the time stamp captured for the corresponding receive frame (overwriting
the value for RBAP2). This field has the time stamp only if time stamping is activated and if
the Last segment control bit (LS) in the descriptor is set.

Enhanced Rx DMA descriptors format with IEEE1588 time stamp
Enhanced descriptors (enabled with EDFE=1, ETHDMABMR bit 7), must be used if time
stamping is activated (TSE=1, ETH_PTPTSCR bit 0) or if IPv4 checksum offload is
activated (IPCO=1, ETH_MACCR bit 10).
Enhanced descriptors comprise eight 32-bit words, twice the size of normal descriptors.
RDES0, RDES1, RDES2 and RDES3 have the same definitions as for normal receive
descriptors (refer to Normal Rx DMA descriptors). RDES4 contains extended status while
RDES6 and RDES7 hold the time stamp. RDES4, RDES5, RDES6 and RDES7 are defined
below.
When the Enhanced descriptor mode is selected, the software needs to allocate 32 bytes (8
DWORDS) of memory for every descriptor. When time stamping or IPv4 checksum offload
are not being used, the enhanced descriptor format may be disabled and the software can
use normal descriptors with the default size of 16 bytes.

1580/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Figure 524. Enhanced receive descriptor field format with IEEE1588 time stamp
enabled
31

0

O
RDES 0 W
N

Status [30:0]

RDES 1 CT Reserved
RL [30:29]

Buffer 2 byte count
[28:16]

RDES 2

CTRL Res.
[15:14]

Buffer 1 byte count
[12:0]

Buffer 1 address [31:0]

RDES 3

Buffer 2 address [31:0] or Next descriptor address [31:0]

RDES 4

Extended Status [31:0]

RDES 5

Reserved

RDES 6

Time stamp low [31:0]

Time stamp high [31:0]

RDES 7

ai17104

•

RDES4: Receive descriptor Word4

The extended status, shown below, is valid only when there is status related to IPv4
checksum or time stamp available as indicated by bit 0 in RDES0.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

2

1

0

15

14

13

12

Res.

Res.

PV

PFT

rw

rw

PMT
rw

rw

rw

7

6

5

4

3

IPV6PR

IPV4PR

IPCB

IPPE

IPHE

rw

rw

rw

rw

rw

rw

IPPT
rw

rw

rw

Bits 31:14 Reserved, must be kept at reset value.
Bit 13 PV: PTP version
When set, indicates that the received PTP message uses the IEEE 1588 version 2 format.
When cleared, it uses version 1 format. This is valid only if the message type is non-zero.
Bit 12 PFT: PTP frame type
When set, this bit indicates that the PTP message is sent directly over Ethernet. When this bit
is cleared and the message type is non-zero, it indicates that the PTP message is sent over
UDP-IPv4 or UDP-IPv6. The information on IPv4 or IPv6 can be obtained from bits 6 and 7.

RM0385 Rev 7

1581/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bits 11:8 PMT: PTP message type
These bits are encoded to give the type of the message received.
– 0000: No PTP message received
– 0001: SYNC (all clock types)
– 0010: Follow_Up (all clock types)
– 0011: Delay_Req (all clock types)
– 0100: Delay_Resp (all clock types)
– 0101: Pdelay_Req (in peer-to-peer transparent clock) or Announce (in ordinary or boundary
clock)
– 0110: Pdelay_Resp (in peer-to-peer transparent clock) or Management (in ordinary or
boundary clock)
– 0111: Pdelay_Resp_Follow_Up (in peer-to-peer transparent clock) or Signaling (for ordinary
or boundary clock)
– 1xxx - Reserved
Bit 7 IPV6PR: IPv6 packet received
When set, this bit indicates that the received packet is an IPv6 packet.
Bit 6 IPV4PR: IPv4 packet received
When set, this bit indicates that the received packet is an IPv4 packet.
Bit 5 IPCB: IP checksum bypassed
When set, this bit indicates that the checksum offload engine is bypassed.
Bit 4 IPPE: IP payload error
When set, this bit indicates that the 16-bit IP payload checksum (that is, the TCP, UDP, or
ICMP checksum) that the core calculated does not match the corresponding checksum field
in the received segment. It is also set when the TCP, UDP, or ICMP segment length does not
match the payload length value in the IP Header field.
Bit 3 IPHE: IP header error
When set, this bit indicates either that the 16-bit IPv4 header checksum calculated by the
core does not match the received checksum bytes, or that the IP datagram version is not
consistent with the Ethernet Type value.
Bits 2:0 IPPT: IP payload type

if IPv4 checksum offload is activated (IPCO=1, ETH_MACCR bit 10), these bits
–
–
–
–
–

•

indicate the type of payload encapsulated in the IP datagram. These bits are ‘00’ if there is an IP
header error or fragmented IP.
000: Unknown or did not process IP payload
001: UDP
010: TCP
011: ICMP
1xx: Reserved

RDES5: Receive descriptor Word5
Reserved.

•

RDES6: Receive descriptor Word6
The table below describes the fields that have different meaning for RDES6 when the
receive descriptor is closed and time stamping is enabled.

1582/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

RTSL

RTSL
rw

rw

rw

rw

rw

rw

rw

rw

.

Bits 31:0 RTSL: Receive frame time stamp low
The DMA updates this field with the 32 least significant bits of the time stamp captured for the
corresponding receive frame. The DMA updates this field only for the last descriptor of the receive
frame indicated by last descriptor status bit (RDES0[8]). When this field and the RTSH field in
RDES7 show all ones, the time stamp must be treated as corrupt.

•

RDES7: Receive descriptor Word7
The table below describes the fields that have a different meaning for RDES7 when the
receive descriptor is closed and time stamping is enabled.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

RTSH
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8
RTSH

rw

rw

rw

rw

rw

rw

rw

rw

.

Bits 31:0 RTSH: Receive frame time stamp high
The DMA updates this field with the 32 most significant bits of the time stamp captured for the
corresponding receive frame. The DMA updates this field only for the last descriptor of the receive
frame indicated by last descriptor status bit (RDES0[8]).
When this field and RDES7’s RTSL field show all ones, the time stamp must be treated as
corrupt.

38.6.9

DMA interrupts
Interrupts can be generated as a result of various events. The ETH_DMASR register
contains all the bits that might cause an interrupt. The ETH_DMAIER register contains an
enable bit for each of the events that can cause an interrupt.
There are two groups of interrupts, Normal and Abnormal, as described in the ETH_DMASR
register. Interrupts are cleared by writing a 1 to the corresponding bit position. When all the
enabled interrupts within a group are cleared, the corresponding summary bit is cleared. If
the MAC core is the cause for assertion of the interrupt, then any of the TSTS or PMTS bits
in the ETH_DMASR register is set high.
Interrupts are not queued and if the interrupt event occurs before the driver has responded
to it, no additional interrupts are generated. For example, the Receive Interrupt bit
(ETH_DMASR register [6]) indicates that one or more frames were transferred to the
STM32F75xxx and STM32F74xxx buffer. The driver must scan all descriptors, from the last
recorded position to the first one owned by the DMA.
An interrupt is generated only once for simultaneous, multiple events. The driver must scan
the ETH_DMASR register for the cause of the interrupt. The interrupt is not generated again
unless a new interrupting event occurs, after the driver has cleared the appropriate bit in the

RM0385 Rev 7

1583/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

ETH_DMASR register. For example, the controller generates a Receive interrupt
(ETH_DMASR register[6]) and the driver begins reading the ETH_DMASR register. Next,
receive buffer unavailable (ETH_DMASR register[7]) occurs. The driver clears the Receive
interrupt. Even then, a new interrupt is generated, due to the active or pending Receive
buffer unavailable interrupt.
Figure 525. Interrupt scheme
TS
TIE

TBUS
TBUIE

MMCI

AND

PMTI
TSTI

AND
RS
RIE

OR

AND

AND

ERS
ERIE

NIS
NISE

AND
OR

Interrupt

FBES
FBEIE

TPSS
TPSSIE

AND
TJTS

AND
ROS
ROIE

TUS
TUIE

AND
AISE

AND

AND

AND
RBU

RWTS
RWTIE

TJTIE

AIS

RBUIE

OR
AND

RPSS
RPSSIE

AND

AND

ETS
ETIE

AND
ai15646

38.7

Ethernet interrupts
The Ethernet controller has two interrupt vectors: one dedicated to normal Ethernet
operations and the other, used only for the Ethernet wakeup event (with wakeup frame or
Magic Packet detection) when it is mapped on EXTI lIne19.
The first Ethernet vector is reserved for interrupts generated by the MAC and the DMA as
listed in the MAC interrupts and DMA interrupts sections.
The second vector is reserved for interrupts generated by the PMT on wakeup events. The
mapping of a wakeup event on EXTI line19 causes the STM32F75xxx and STM32F74xxx to
exit the low-power mode, and generates an interrupt.
When an Ethernet wakeup event mapped on EXTI Line19 occurs and the MAC PMT
interrupt is enabled and the EXTI Line19 interrupt, with detection on rising edge, is also
enabled, both interrupts are generated.
A watchdog timer (see ETH_DMARSWTR register) is given for flexible control of the RS bit
(ETH_DMASR register). When this watchdog timer is programmed with a non-zero value, it

1584/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
gets activated as soon as the RxDMA completes a transfer of a received frame to system
memory without asserting the Receive Status because it is not enabled in the corresponding
Receive descriptor (RDES1[31]). When this timer runs out as per the programmed value,
the RS bit is set and the interrupt is asserted if the corresponding RIE is enabled in the
ETH_DMAIER register. This timer is disabled before it runs out, when a frame is transferred
to memory and the RS is set because it is enabled for that descriptor.

Note:

Reading the PMT control and status register automatically clears the Wakeup Frame
Received and Magic Packet Received PMT interrupt flags. However, since the registers for
these flags are in the CLK_RX domain, there may be a significant delay before this update
is visible by the firmware. The delay is especially long when the RX clock is slow (in 10 Mbit
mode) and when the AHB bus is high-frequency.
Since interrupt requests from the PMT to the CPU are based on the same registers in the
CLK_RX domain, the CPU may spuriously call the interrupt routine a second time even after
reading PMT_CSR. Thus, it may be necessary that the firmware polls the Wakeup Frame
Received and Magic Packet Received bits and exits the interrupt service routine only when
they are found to be at ‘0’.

38.8

Ethernet register descriptions
The peripheral registers can be accessed by bytes (8-bit), half-words (16-bit) or words
(32-bit).

38.8.1

MAC register description
Ethernet MAC configuration register (ETH_MACCR)
Address offset: 0x0000
Reset value: 0x0000 8000
The MAC configuration register is the operation mode register of the MAC. It establishes
receive and transmit operating modes.

31

30

29

28

27

26

25

24

23

22

21

20

Res.

Res.

Res.

Res.

Res.

Res.

CSTF

Res.

WD

JD

Res.

Res.

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

FES

ROD

LM

DM

IPCO

RD

Res.

APCS

BL

DC

TE

RE

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

19

18

17

IFG

16
CSD

rw

rw

Bits 31:26 Reserved, must be kept at reset value.
Bit 25 CSTF: CRC stripping for Type frames
When set, the last 4 bytes (FCS) of all frames of Ether type (type field greater than 0x0600)
will be stripped and dropped before forwarding the frame to the application.
Bit 24 Reserved, must be kept at reset value.

RM0385 Rev 7

1585/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 23 WD: Watchdog disable
When this bit is set, the MAC disables the watchdog timer on the receiver, and can receive
frames of up to 16 384 bytes.
When this bit is reset, the MAC allows no more than 2 048 bytes of the frame being received
and cuts off any bytes received after that.
Bit 22 JD: Jabber disable
When this bit is set, the MAC disables the jabber timer on the transmitter, and can transfer
frames of up to 16 384 bytes.
When this bit is reset, the MAC cuts off the transmitter if the application sends out more than
2 048 bytes of data during transmission.
Bits 21:20 Reserved, must be kept at reset value.
Bits 19:17 IFG: Interframe gap
These bits control the minimum interframe gap between frames during transmission.
000: 96 bit times
001: 88 bit times
010: 80 bit times
….
111: 40 bit times
Note: In Half-duplex mode, the minimum IFG can be configured for 64 bit times (IFG = 100)
only. Lower values are not considered.
Bit 16 CSD: Carrier sense disable
When set high, this bit makes the MAC transmitter ignore the MII CRS signal during frame
transmission in Half-duplex mode. No error is generated due to Loss of Carrier or No Carrier
during such transmission.
When this bit is low, the MAC transmitter generates such errors due to Carrier Sense and
even aborts the transmissions.
Bit 15 Reserved, must be kept at reset value.
Bit 14 FES: Fast Ethernet speed
Indicates the speed in Fast Ethernet (MII) mode:
0: 10 Mbit/s
1: 100 Mbit/s
Bit 13 ROD: Receive own disable
When this bit is set, the MAC disables the reception of frames in Half-duplex mode.
When this bit is reset, the MAC receives all packets that are given by the PHY while
transmitting.
This bit is not applicable if the MAC is operating in Full-duplex mode.
Bit 12 LM: Loopback mode
When this bit is set, the MAC operates in loopback mode at the MII. The MII receive clock
input (RX_CLK) is required for the loopback to work properly, as the transmit clock is not
looped-back internally.
Bit 11 DM: Duplex mode
When this bit is set, the MAC operates in a Full-duplex mode where it can transmit and
receive simultaneously.
Bit 10 IPCO: IPv4 checksum offload
When set, this bit enables IPv4 checksum checking for received frame payloads'
TCP/UDP/ICMP headers. When this bit is reset, the checksum offload function in the
receiver is disabled and the corresponding PCE and IP HCE status bits (see Table 275) are
always cleared.

1586/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 9 RD: Retry disable
When this bit is set, the MAC attempts only 1 transmission. When a collision occurs on the
MII, the MAC ignores the current frame transmission and reports a Frame Abort with
excessive collision error in the transmit frame status.
When this bit is reset, the MAC attempts retries based on the settings of BL.
Note: This bit is applicable only in the Half-duplex mode.
Bit 8 Reserved, must be kept at reset value.
Bit 7 APCS: Automatic pad/CRC stripping
When this bit is set, the MAC strips the Pad/FCS field on incoming frames only if the
length’s field value is less than or equal to 1 500 bytes. All received frames with length field
greater than or equal to 1 501 bytes are passed on to the application without stripping the
Pad/FCS field.
When this bit is reset, the MAC passes all incoming frames unmodified.
Bits 6:5 BL: Back-off limit
The Back-off limit determines the random integer number (r) of slot time delays (4 096 bit
times for 1000 Mbit/s and 512 bit times for 10/100 Mbit/s) the MAC waits before
rescheduling a transmission attempt during retries after a collision.
Note: This bit is applicable only to Half-duplex mode.
00: k = min (n, 10)
01: k = min (n, 8)
10: k = min (n, 4)
11: k = min (n, 1),
where n = retransmission attempt. The random integer r takes the value in the range 0 ≤ r ≤
2k
Bit 4 DC: Deferral check
When this bit is set, the deferral check function is enabled in the MAC. The MAC issues a
Frame Abort status, along with the excessive deferral error bit set in the transmit frame
status when the transmit state machine is deferred for more than 24 288 bit times in 10/100Mbit/s mode. Deferral begins when the transmitter is ready to transmit, but is prevented
because of an active CRS (carrier sense) signal on the MII. Defer time is not cumulative. If
the transmitter defers for 10 000 bit times, then transmits, collides, backs off, and then has
to defer again after completion of back-off, the deferral timer resets to 0 and restarts.
When this bit is reset, the deferral check function is disabled and the MAC defers until the
CRS signal goes inactive. This bit is applicable only in Half-duplex mode.
Bit 3 TE: Transmitter enable
When this bit is set, the transmit state machine of the MAC is enabled for transmission on
the MII. When this bit is reset, the MAC transmit state machine is disabled after the
completion of the transmission of the current frame, and does not transmit any further
frames.
Bit 2 RE: Receiver enable
When this bit is set, the receiver state machine of the MAC is enabled for receiving frames
from the MII. When this bit is reset, the MAC receive state machine is disabled after the
completion of the reception of the current frame, and will not receive any further frames from
the MII.
Bits 1:0 Reserved, must be kept at reset value.

RM0385 Rev 7

1587/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Ethernet MAC frame filter register (ETH_MACFFR)
Address offset: 0x0004
Reset value: 0x0000 0000
The MAC frame filter register contains the filter controls for receiving frames. Some of the
controls from this register go to the address check block of the MAC, which performs the
first level of address filtering. The second level of filtering is performed on the incoming
frame, based on other controls such as pass bad frames and pass control frames.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

RA

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

rw
15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

HPF

SAF

SAIF

rw

rw

rw

6
PCF

rw

rw

5

4

3

2

1

0

BFD

PAM

DAIF

HM

HU

PM

rw

rw

rw

rw

rw

rw

Bit 31 RA: Receive all
When this bit is set, the MAC receiver passes all received frames on to the application,
irrespective of whether they have passed the address filter. The result of the SA/DA filtering
is updated (pass or fail) in the corresponding bits in the receive status word. When this bit is
reset, the MAC receiver passes on to the application only those frames that have passed the
SA/DA address filter.
Bits 30:11 Reserved, must be kept at reset value.
Bit 10 HPF: Hash or perfect filter
When this bit is set and if the HM or HU bit is set, the address filter passes frames that
match either the perfect filtering or the hash filtering.
When this bit is cleared and if the HU or HM bit is set, only frames that match the Hash filter
are passed.
Bit 9 SAF: Source address filter
The MAC core compares the SA field of the received frames with the values programmed in
the enabled SA registers. If the comparison matches, then the SAMatch bit in the RxStatus
word is set high. When this bit is set high and the SA filter fails, the MAC drops the frame.
When this bit is reset, the MAC core forwards the received frame to the application. It also
forwards the updated SA Match bit in RxStatus depending on the SA address comparison.
Bit 8 SAIF: Source address inverse filtering
When this bit is set, the address check block operates in inverse filtering mode for the SA
address comparison. The frames whose SA matches the SA registers are marked as failing
the SA address filter.
When this bit is reset, frames whose SA does not match the SA registers are marked as
failing the SA address filter.

1588/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bits 7:6 PCF: Pass control frames
These bits control the forwarding of all control frames (including unicast and multicast
PAUSE frames). Note that the processing of PAUSE control frames depends only on RFCE
in Flow Control Register[2].
00: MAC prevents all control frames from reaching the application
01: MAC forwards all control frames to application except Pause control frames
10: MAC forwards all control frames to application even if they fail the address filter
11: MAC forwards control frames that pass the address filter.
These bits control the forwarding of all control frames (including unicast and multicast
PAUSE frames). Note that the processing of PAUSE control frames depends only on RFCE
in Flow Control Register[2].
00 or 01: MAC prevents all control frames from reaching the application
10: MAC forwards all control frames to application even if they fail the address filter
11: MAC forwards control frames that pass the address filter.
Bit 5 BFD: Broadcast frames disable
When this bit is set, the address filters filter all incoming broadcast frames.
When this bit is reset, the address filters pass all received broadcast frames.
Bit 4 PAM: Pass all multicast
When set, this bit indicates that all received frames with a multicast destination address (first
bit in the destination address field is '1') are passed.
When reset, filtering of multicast frame depends on the HM bit.
Bit 3 DAIF: Destination address inverse filtering
When this bit is set, the address check block operates in inverse filtering mode for the DA
address comparison for both unicast and multicast frames.
When reset, normal filtering of frames is performed.
Bit 2 HM: Hash multicast
When set, MAC performs destination address filtering of received multicast frames
according to the hash table.
When reset, the MAC performs a perfect destination address filtering for multicast frames,
that is, it compares the DA field with the values programmed in DA registers.
Bit 1 HU: Hash unicast
When set, MAC performs destination address filtering of unicast frames according to the
hash table.
When reset, the MAC performs a perfect destination address filtering for unicast frames, that
is, it compares the DA field with the values programmed in DA registers.
Bit 0 PM: Promiscuous mode
When this bit is set, the address filters pass all incoming frames regardless of their
destination or source address. The SA/DA filter fails status bits in the receive status word
are always cleared when PM is set.

Ethernet MAC hash table high register (ETH_MACHTHR)
Address offset: 0x0008
Reset value: 0x0000 0000
The 64-bit Hash table is used for group address filtering. For hash filtering, the contents of
the destination address in the incoming frame are passed through the CRC logic, and the
upper 6 bits in the CRC register are used to index the contents of the Hash table. This CRC

RM0385 Rev 7

1589/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

is a 32-bit value coded by the following polynomial (for more details refer to Section 38.5.3:
MAC frame reception):
G( x) = x

32

+x

26

+x

23

+x

22

+x

16

+x

12

+x

11

+x

10

8

7

5

4

2

+x +x +x +x +x +x+1

The most significant bit determines the register to be used (hash table high/hash table low),
and the other 5 bits determine which bit within the register. A hash value of 0b0 0000 selects
bit 0 in the selected register, and a value of 0b1 1111 selects bit 31 in the selected register.
For example, if the DA of the incoming frame is received as 0x1F52 419C B6AF (0x1F is the
first byte received on the MII interface), then the internally calculated 6-bit Hash value is
0x2C and the HTH register bit[12] is checked for filtering. If the DA of the incoming frame is
received as 0xA00A 9800 0045, then the calculated 6-bit Hash value is 0x07 and the HTL
register bit[7] is checked for filtering.
If the corresponding bit value in the register is 1, the frame is accepted. Otherwise, it is
rejected. If the PAM (pass all multicast) bit is set in the ETH_MACFFR register, then all
multicast frames are accepted regardless of the multicast hash values.
The Hash table high register contains the higher 32 bits of the multicast Hash table.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

HTH
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

HTH
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 HTH: Hash table high
This field contains the upper 32 bits of Hash table.

Ethernet MAC hash table low register (ETH_MACHTLR)
Address offset: 0x000C
Reset value: 0x0000 0000
The Hash table low register contains the lower 32 bits of the multi-cast Hash table.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

HTL
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

HTL

Bits 31:0 HTL: Hash table low
This field contains the lower 32 bits of the Hash table.

Ethernet MAC MII address register (ETH_MACMIIAR)
Address offset: 0x0010
Reset value: 0x0000 0000
The MII address register controls the management cycles to the external PHY through the
management interface.
1590/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

PA
rw

rw

rw

MR
rw

rw

rw

rw

rw

Res.
rw

rw

CR
rw

rw

rw

1

0

MW

MB

rw

rc_w1

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:11 PA: PHY address
This field tells which of the 32 possible PHY devices are being accessed.
Bits 10:6 MR: MII register
These bits select the desired MII register in the selected PHY device.
Bit 5 Reserved, must be kept at reset value.
Bits 4:2 CR: Clock range
The CR clock range selection determines the HCLK frequency and is used to decide the
frequency of the MDC clock:
Selection HCLK MDC Clock
000 60-100 MHz HCLK/42
001 100-150 MHz HCLK/62
010 20-35 MHz HCLK/16
011 35-60 MHz HCLK/26
100 150-216 MHz HCLK/102
101, 110, 111 Reserved
Bit 1 MW: MII write
When set, this bit tells the PHY that this will be a Write operation using the MII Data register. If
this bit is not set, this will be a Read operation, placing the data in the MII Data register.
Bit 0 MB: MII busy
This bit should read a logic 0 before writing to ETH_MACMIIAR and ETH_MACMIIDR. This
bit must also be reset to 0 during a Write to ETH_MACMIIAR. During a PHY register access,
this bit is set to 0b1 by the application to indicate that a read or write access is in progress.
ETH_MACMIIDR (MII Data) should be kept valid until this bit is cleared by the MAC during a
PHY Write operation. The ETH_MACMIIDR is invalid until this bit is cleared by the MAC
during a PHY Read operation. The ETH_MACMIIAR (MII Address) should not be written to
until this bit is cleared.

Ethernet MAC MII data register (ETH_MACMIIDR)
Address offset: 0x0014
Reset value: 0x0000 0000
The MAC MII Data register stores write data to be written to the PHY register located at the
address specified in ETH_MACMIIAR. ETH_MACMIIDR also stores read data from the PHY
register located at the address specified by ETH_MACMIIAR.

RM0385 Rev 7

1591/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

MD
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 MD: MII data
This contains the 16-bit data value read from the PHY after a Management Read operation,
or the 16-bit data value to be written to the PHY before a Management Write operation.

Ethernet MAC flow control register (ETH_MACFCR)
Address offset: 0x0018
Reset value: 0x0000 0000
The Flow control register controls the generation and reception of the control (Pause
Command) frames by the MAC. A write to a register with the Busy bit set to '1' causes the
MAC to generate a pause control frame. The fields of the control frame are selected as
specified in the 802.3x specification, and the Pause Time value from this register is used in
the Pause Time field of the control frame. The Busy bit remains set until the control frame is
transferred onto the cable. The Host must make sure that the Busy bit is cleared before
writing to the register.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

ZQPD

Res.

UPFD

RFCE

TFCE

FCB/BPA

rw

rw

rw

rc_w1/rw

PT

rw

PLT
rw

rw

Bits 31:16 PT: Pause time
This field holds the value to be used in the Pause Time field in the transmit control frame. If
the Pause Time bits is configured to be double-synchronized to the MII clock domain, then
consecutive write operations to this register should be performed only after at least 4 clock
cycles in the destination clock domain.
Bits 15:8 Reserved, must be kept at reset value.
Bit 7 ZQPD: Zero-quanta pause disable
When set, this bit disables the automatic generation of Zero-quanta pause control frames on
the deassertion of the flow-control signal from the FIFO layer.
When this bit is reset, normal operation with automatic Zero-quanta pause control frame
generation is enabled.
Bit 6 Reserved, must be kept at reset value.

1592/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bits 5:4 PLT: Pause low threshold
This field configures the threshold of the Pause timer at which the Pause frame is
automatically retransmitted. The threshold values should always be less than the Pause
Time configured in bits[31:16]. For example, if PT = 100H (256 slot-times), and PLT = 01,
then a second PAUSE frame is automatically transmitted if initiated at 228 (256 – 28) slottimes after the first PAUSE frame is transmitted.
Selection Threshold
00 Pause time minus 4 slot times
01 Pause time minus 28 slot times
10 Pause time minus 144 slot times
11 Pause time minus 256 slot times
Slot time is defined as time taken to transmit 512 bits (64 bytes) on the MII interface.
Bit 3 UPFD: Unicast pause frame detect
When this bit is set, the MAC detects the Pause frames with the station’s unicast address
specified in the ETH_MACA0HR and ETH_MACA0LR registers, in addition to detecting
Pause frames with the unique multicast address.
When this bit is reset, the MAC detects only a Pause frame with the unique multicast
address specified in the 802.3x standard.
Bit 2 RFCE: Receive flow control enable
When this bit is set, the MAC decodes the received Pause frame and disables its transmitter
for a specified (Pause Time) time.
When this bit is reset, the decode function of the Pause frame is disabled.
Bit 1 TFCE: Transmit flow control enable
In Full-duplex mode, when this bit is set, the MAC enables the flow control operation to
transmit Pause frames. When this bit is reset, the flow control operation in the MAC is
disabled, and the MAC does not transmit any Pause frames.
In Half-duplex mode, when this bit is set, the MAC enables the back-pressure operation.
When this bit is reset, the back pressure feature is disabled.
Bit 0 FCB/BPA: Flow control busy/back pressure activate
This bit initiates a Pause Control frame in Full-duplex mode and activates the back pressure
function in Half-duplex mode if TFCE bit is set.
In Full-duplex mode, this bit should be read as 0 before writing to the Flow control register.
To initiate a Pause control frame, the Application must set this bit to 1. During a transfer of
the Control frame, this bit continues to be set to signify that a frame transmission is in
progress. After completion of the Pause control frame transmission, the MAC resets this bit
to 0. The Flow control register should not be written to until this bit is cleared.
In Half-duplex mode, when this bit is set (and TFCE is set), back pressure is asserted by the
MAC core. During back pressure, when the MAC receives a new frame, the transmitter
starts sending a JAM pattern resulting in a collision. When the MAC is configured to Fullduplex mode, the BPA is automatically disabled.

Ethernet MAC VLAN tag register (ETH_MACVLANTR)
Address offset: 0x001C
Reset value: 0x0000 0000
The VLAN tag register contains the IEEE 802.1Q VLAN Tag to identify the VLAN frames.
The MAC compares the 13th and 14th bytes of the receiving frame (Length/Type) with
0x8100, and the following 2 bytes are compared with the VLAN tag; if a match occurs, the
received VLAN bit in the receive frame status is set. The legal length of the frame is
increased from 1518 bytes to 1522 bytes.

RM0385 Rev 7

1593/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

VLANTC

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

VLANTI
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 VLANTC: 12-bit VLAN tag comparison
When this bit is set, a 12-bit VLAN identifier, rather than the complete 16-bit VLAN tag, is
used for comparison and filtering. Bits[11:0] of the VLAN tag are compared with the
corresponding field in the received VLAN-tagged frame.
When this bit is reset, all 16 bits of the received VLAN frame’s fifteenth and sixteenth bytes
are used for comparison.
Bits 15:0 VLANTI: VLAN tag identifier (for receive frames)
This contains the 802.1Q VLAN tag to identify VLAN frames, and is compared to the fifteenth
and sixteenth bytes of the frames being received for VLAN frames. Bits[15:13] are the user
priority, Bit[12] is the canonical format indicator (CFI) and bits[11:0] are the VLAN tag’s VLAN
identifier (VID) field. When the VLANTC bit is set, only the VID (bits[11:0]) is used for
comparison.
If VLANTI (VLANTI[11:0] if VLANTC is set) is all zeros, the MAC does not check the fifteenth
and sixteenth bytes for VLAN tag comparison, and declares all frames with a Type field value
of 0x8100 as VLAN frames.

Ethernet MAC remote wakeup frame filter register (ETH_MACRWUFFR)
Address offset: 0x0028
Reset value: 0x0000 0000
This is the address through which the remote wakeup frame filter registers are written/read
by the application. The Wakeup frame filter register is actually a pointer to eight (not
transparent) such wakeup frame filter registers. Eight sequential write operations to this
address with the offset (0x0028) will write all wakeup frame filter registers. Eight sequential
read operations from this address with the offset (0x0028) will read all wakeup frame filter
registers. This register contains the higher 16 bits of the 7th MAC address. Refer to Remote
wakeup frame filter register section for additional information.

1594/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Figure 526. Ethernet MAC remote wakeup frame filter register (ETH_MACRWUFFR)
Wakeup frame filter reg0

Filter 0 Byte Mask

Wakeup frame filter reg1

Filter 1 Byte Mask

Wakeup frame filter reg2

Filter 2 Byte Mask

Wakeup frame filter reg3
Wakeup frame filter reg4
Wakeup frame filter reg5

Filter 3 Byte Mask
RSVD

Filter 3
Command

Filter 3 Offset

RSVD

Filter 2
Command

Filter 2 Offset

RSVD

Filter 1
Command

Filter 1 Offset

RSVD

Filter 0
Command

Filter 0 Offset

Wakeup frame filter reg6

Filter 1 CRC - 16

Filter 0 CRC - 16

Wakeup frame filter reg7

Filter 3 CRC - 16

Filter 2 CRC - 16

ai15648

RM0385 Rev 7

1595/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Ethernet MAC PMT control and status register (ETH_MACPMTCSR)
Address offset: 0x002C
Reset value: 0x0000 0000
The ETH_MACPMTCSR programs the request wakeup events and monitors the wakeup
events.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

WFFRPR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rs
15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

GU

Res.

Res.

WFR

MPR

Res.

Res.

WFE

MPE

PD

rc_r

rc_r

rw

rw

rs

rw

Bit 31 WFFRPR: Wakeup frame filter register pointer reset
When set, it resets the Remote wakeup frame filter register pointer to 0b000. It is
automatically cleared after 1 clock cycle.
Bits 30:10 Reserved, must be kept at reset value.
Bit 9 GU: Global unicast
When set, it enables any unicast packet filtered by the MAC (DAF) address recognition to be
a wakeup frame.
Bits 8:7 Reserved, must be kept at reset value.
Bit 6 WFR: Wakeup frame received
When set, this bit indicates the power management event was generated due to reception of
a wakeup frame. This bit is cleared by a read into this register.
Bit 5 MPR: Magic packet received
When set, this bit indicates the power management event was generated by the reception of
a Magic Packet. This bit is cleared by a read into this register.
Bits 4:3 Reserved, must be kept at reset value.
Bit 2 WFE: Wakeup frame enable
When set, this bit enables the generation of a power management event due to wakeup
frame reception.
Bit 1 MPE: Magic Packet enable
When set, this bit enables the generation of a power management event due to Magic
Packet reception.
Bit 0 PD: Power down
When this bit is set, all received frames will be dropped. This bit is cleared automatically
when a magic packet or wakeup frame is received, and Power-down mode is disabled.
Frames received after this bit is cleared are forwarded to the application. This bit must only
be set when either the Magic Packet Enable or Wakeup Frame Enable bit is set high.

1596/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Ethernet MAC debug register (ETH_MACDBGR)
Address offset: 0x0034
Reset value: 0x0000 0000
This debug register gives the status of all the main modules of the transmit and receive data
paths and the FIFOs. An all-zero status indicates that the MAC core is in Idle state (and
FIFOs are empty) and no activity is going on in the data paths.
31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

TFF

TFNE

Res.

TFWA

ro

ro

15

14

13

12

11

10

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

9

8
RFFL

ro

7
Res.

ro

21

ro

ro

6

5
RFRCS

ro

20
TFRS

19

ro

ro

4

3

RFWRA

Res.

ro

18

MTP

ro

17

MTFCS
ro

ro

2

1

MSFRWCS
ro

16
MMTEA

ro

ro
0
MMRPEA
ro

Bits 31:26 Reserved, must be kept at reset value.
Bit 25 TFF: Tx FIFO full
When high, it indicates that the Tx FIFO is full and hence no more frames will be accepted
for transmission.
Bit 24 TFNE: Tx FIFO not empty
When high, it indicates that the TxFIFO is not empty and has some data left for
transmission.
Bit 23 Reserved, must be kept at reset value.
Bit 22 TFWA: Tx FIFO write active
When high, it indicates that the TxFIFO write controller is active and transferring data to the
TxFIFO.
Bits 21:20 TFRS: Tx FIFO read status
This indicates the state of the TxFIFO read controller:
00: Idle state
01: Read state (transferring data to the MAC transmitter)
10: Waiting for TxStatus from MAC transmitter
11: Writing the received TxStatus or flushing the TxFIFO
Bit 19 MTP: MAC transmitter in pause
When high, it indicates that the MAC transmitter is in Pause condition (in full-duplex mode
only) and hence will not schedule any frame for transmission
Bits 18:17 MTFCS: MAC transmit frame controller status
This indicates the state of the MAC transmit frame controller:
00: Idle
01: Waiting for Status of previous frame or IFG/backoff period to be over
10: Generating and transmitting a Pause control frame (in full duplex mode)
11: Transferring input frame for transmission
Bit 16 MMTEA: MAC MII transmit engine active
When high, it indicates that the MAC MII transmit engine is actively transmitting data and
that it is not in the Idle state.
Bits 15:10 Reserved, must be kept at reset value.

RM0385 Rev 7

1597/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bits 9:8 RFFL: Rx FIFO fill level
This gives the status of the Rx FIFO fill-level:
00: RxFIFO empty
01: RxFIFO fill-level below flow-control de-activate threshold
10: RxFIFO fill-level above flow-control activate threshold
11: RxFIFO full
Bit 7 Reserved, must be kept at reset value.
Bits 6:5 RFRCS: Rx FIFO read controller status
It gives the state of the Rx FIFO read controller:
00: IDLE state
01: Reading frame data
10: Reading frame status (or time-stamp)
11: Flushing the frame data and status
Bit 4 RFWRA: Rx FIFO write controller active
When high, it indicates that the Rx FIFO write controller is active and transferring a received
frame to the FIFO.
Bit 3 Reserved, must be kept at reset value.
Bits 2:1 MSFRWCS: MAC small FIFO read / write controllers status
When high, these bits indicate the respective active state of the small FIFO read and write
controllers of the MAC receive frame controller module.
Bit 0 MMRPEA: MAC MII receive protocol engine active
When high, it indicates that the MAC MII receive protocol engine is actively receiving data
and is not in the Idle state.

Ethernet MAC interrupt status register (ETH_MACSR)
Address offset: 0x0038
Reset value: 0x0000 0000
The ETH_MACSR register contents identify the events in the MAC that can generate an
interrupt.
15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

TSTS

Res.

Res.

6

5

MMCTS MMCRS

rc_r

r

r

4

3

2

1

0

MMCS

PMTS

Res.

Res.

Res.

r

r

Bits 15:10 Reserved, must be kept at reset value.
Bit 9 TSTS: Time stamp trigger status
This bit is set high when the system time value equals or exceeds the value specified in the
Target time high and low registers. This bit is cleared by reading the ETH_PTPTSSR
register.
Bits 8:7 Reserved, must be kept at reset value.
Bit 6 MMCTS: MMC transmit status
This bit is set high whenever an interrupt is generated in the ETH_MMCTIR Register. This bit
is cleared when all the bits in this interrupt register (ETH_MMCTIR) are cleared.
Bit 5 MMCRS: MMC receive status
This bit is set high whenever an interrupt is generated in the ETH_MMCRIR register. This bit
is cleared when all the bits in this interrupt register (ETH_MMCRIR) are cleared.

1598/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 4 MMCS: MMC status
This bit is set high whenever any of bits 6:5 is set high. It is cleared only when both bits are
low.
Bit 3 PMTS: PMT status
This bit is set whenever a Magic packet or Wake-on-LAN frame is received in Power-down
mode (See bits 5 and 6 in the ETH_MACPMTCSR register Ethernet MAC PMT control and
status register (ETH_MACPMTCSR)). This bit is cleared when both bits[6:5], of this last
register, are cleared due to a read operation to the ETH_MACPMTCSR register.
Bits 2:0 Reserved, must be kept at reset value.

Ethernet MAC interrupt mask register (ETH_MACIMR)
Address offset: 0x003C
Reset value: 0x0000 0000
The ETH_MACIMR register bits make it possible to mask the interrupt signal due to the
corresponding event in the ETH_MACSR register.
15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

TSTIM

Res.

Res.

Res.

Res.

Res.

PMTIM

Res.

Res.

Res.

rw

rw

Bits 15:10 Reserved, must be kept at reset value.
Bit 9 TSTIM: Time stamp trigger interrupt mask
When set, this bit disables the time stamp interrupt generation.
Bits 8:4 Reserved, must be kept at reset value.
Bit 3 PMTIM: PMT interrupt mask
When set, this bit disables the assertion of the interrupt signal due to the setting of the PMT
Status bit in ETH_MACSR.
Bits 2:0 Reserved, must be kept at reset value.

Ethernet MAC address 0 high register (ETH_MACA0HR)
Address offset: 0x0040
Reset value: 0x8000 FFFF
The MAC address 0 high register holds the upper 16 bits of the 6-byte first MAC address of
the station. Note that the first DA byte that is received on the MII interface corresponds to
the LS Byte (bits [7:0]) of the MAC address low register. For example, if 0x1122 3344 5566
is received (0x11 is the first byte) on the MII as the destination address, then the MAC
address 0 register [47:0] is compared with 0x6655 4433 2211.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MO

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

1
15

MACA0H
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

1599/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 31 MO: Always 1.
Bits 30:16 Reserved, must be kept at reset value.
Bits 15:0 MACA0H: MAC address0 high [47:32]
This field contains the upper 16 bits (47:32) of the 6-byte MAC address0. This is used by the
MAC for filtering for received frames and for inserting the MAC address in the transmit flow
control (Pause) frames.

Ethernet MAC address 0 low register (ETH_MACA0LR)
Address offset: 0x0044
Reset value: 0xFFFF FFFF
The MAC address 0 low register holds the lower 32 bits of the 6-byte first MAC address of
the station.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MACA0L
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MACA0L
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MACA0L: MAC address0 low [31:0]
This field contains the lower 32 bits of the 6-byte MAC address0. This is used by the MAC
for filtering for received frames and for inserting the MAC address in the transmit flow control
(Pause) frames.

Ethernet MAC address 1 high register (ETH_MACA1HR)
Address offset: 0x0048
Reset value: 0x0000 FFFF
The MAC address 1 high register holds the upper 16 bits of the 6-byte second MAC address
of the station.

rw

rw

15

14

13

12

rw

rw

rw

rw

11

10

9

8

MBC

23

22

21

20

19

18

17

16
Res.

rw

24

Res.

rw

25

Res.

SA

26

Res.

AE

27

Res.

28

Res.

29

Res.

30

Res.

31

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MACA1H
rw

rw

1600/1709

rw

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 31 AE: Address enable
When this bit is set, the address filters use the MAC address1 for perfect filtering. When this
bit is cleared, the address filters ignore the address for filtering.
Bit 30 SA: Source address
When this bit is set, the MAC address1[47:0] is used for comparison with the SA fields of the
received frame.
When this bit is cleared, the MAC address1[47:0] is used for comparison with the DA fields
of the received frame.
Bits 29:24 MBC: Mask byte control
These bits are mask control bits for comparison of each of the MAC address1 bytes. When
they are set high, the MAC core does not compare the corresponding byte of received
DA/SA with the contents of the MAC address1 registers. Each bit controls the masking of the
bytes as follows:
– Bit 29: ETH_MACA1HR [15:8]
– Bit 28: ETH_MACA1HR [7:0]
– Bit 27: ETH_MACA1LR [31:24]
…
– Bit 24: ETH_MACA1LR [7:0]
Bits 23:16 Reserved, must be kept at reset value.
Bits 15:0 MACA1H: MAC address1 high [47:32]
This field contains the upper 16 bits (47:32) of the 6-byte second MAC address.

Ethernet MAC address1 low register (ETH_MACA1LR)
Address offset: 0x004C
Reset value: 0xFFFF FFFF
The MAC address 1 low register holds the lower 32 bits of the 6-byte second MAC address
of the station.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MACA1L
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MACA1L
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MACA1L: MAC address1 low [31:0]
This field contains the lower 32 bits of the 6-byte MAC address1. The content of this field is
undefined until loaded by the application after the initialization process.

Ethernet MAC address 2 high register (ETH_MACA2HR)
Address offset: 0x0050
Reset value: 0x0000 FFFF
The MAC address 2 high register holds the upper 16 bits of the 6-byte second MAC address
of the station.

RM0385 Rev 7

1601/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

rw

rw

15

14

13

12

rw

rw

rw

rw

11

10

9

8

MBC

23

22

21

20

19

18

17

16
Res.

rw

24

Res.

rw

25

Res.

SA

26

Res.

AE

27

Res.

28

Res.

29

Res.

30

Res.

31

RM0385

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MACA2H
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 AE: Address enable
When this bit is set, the address filters use the MAC address2 for perfect filtering. When
reset, the address filters ignore the address for filtering.
Bit 30 SA: Source address
When this bit is set, the MAC address 2 [47:0] is used for comparison with the SA fields of
the received frame.
When this bit is reset, the MAC address 2 [47:0] is used for comparison with the DA fields of
the received frame.
Bits 29:24 MBC: Mask byte control
These bits are mask control bits for comparison of each of the MAC address2 bytes. When
set high, the MAC core does not compare the corresponding byte of received DA/SA with the
contents of the MAC address 2 registers. Each bit controls the masking of the bytes as
follows:
– Bit 29: ETH_MACA2HR [15:8]
– Bit 28: ETH_MACA2HR [7:0]
– Bit 27: ETH_MACA2LR [31:24]
…
– Bit 24: ETH_MACA2LR [7:0]
Bits 23:16Reserved, must be kept at reset value.
MACA2H: MAC address2 high [47:32]
Bits 15:0
This field contains the upper 16 bits (47:32) of the 6-byte MAC address2.

Ethernet MAC address 2 low register (ETH_MACA2LR)
Address offset: 0x0054
Reset value: 0xFFFF FFFF
The MAC address 2 low register holds the lower 32 bits of the 6-byte second MAC address
of the station.
31

30

29

28

27

26

25

24

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MACA2L

MACA2L
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MACA2L: MAC address2 low [31:0]
This field contains the lower 32 bits of the 6-byte second MAC address2. The content of this
field is undefined until loaded by the application after the initialization process.

1602/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Ethernet MAC address 3 high register (ETH_MACA3HR)
Address offset: 0x0058
Reset value: 0x0000 FFFF
The MAC address 3 high register holds the upper 16 bits of the 6-byte second MAC address
of the station.

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

23

22

21

20

19

18

17

16
Re
s.

24

Re
s.

25

Re
s.

26
MBC

Re
s.

27

Re
s.

28

Re
s.

29

Re
s.

30
SA

Re
s.

31
AE

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MACA3H
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 AE: Address enable
When this bit is set, the address filters use the MAC address3 for perfect filtering. When this
bit is cleared, the address filters ignore the address for filtering.
Bit 30 SA: Source address
When this bit is set, the MAC address 3 [47:0] is used for comparison with the SA fields of the
received frame.
When this bit is cleared, the MAC address 3[47:0] is used for comparison with the DA fields
of the received frame.
Bits 29:24 MBC: Mask byte control
These bits are mask control bits for comparison of each of the MAC address3 bytes. When
these bits are set high, the MAC core does not compare the corresponding byte of received
DA/SA with the contents of the MAC address 3 registers. Each bit controls the masking of the
bytes as follows:
– Bit 29: ETH_MACA3HR [15:8]
– Bit 28: ETH_MACA3HR [7:0]
– Bit 27: ETH_MACA3LR [31:24]
…
– Bit 24: ETH_MACA3LR [7:0]
Bits 23:16 Reserved, must be kept at reset value.
Bits 15:0 MACA3H: MAC address3 high [47:32]
This field contains the upper 16 bits (47:32) of the 6-byte MAC address3.

Ethernet MAC address 3 low register (ETH_MACA3LR)
Address offset: 0x005C
Reset value: 0xFFFF FFFF
The MAC address 3 low register holds the lower 32 bits of the 6-byte second MAC address
of the station.

RM0385 Rev 7

1603/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

31

30

29

28

27

26

25

24

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

23

RM0385

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MACA3L

MACA3L
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MACA3L: MAC address3 low [31:0]
This field contains the lower 32 bits of the 6-byte second MAC address3. The content of this
field is undefined until loaded by the application after the initialization process.

1604/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

38.8.2

MMC register description
Ethernet MMC control register (ETH_MMCCR)
Address offset: 0x0100
Reset value: 0x0000 0000
The Ethernet MMC Control register establishes the operating mode of the management
counters.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MCFHP

MCP

MCF

ROR

CSR

CR

rw

rw

rw

rw

rw

rw

Bits 31:6 Reserved, must be kept at reset value.
MCFHP: MMC counter Full-Half preset
When MCFHP is low and bit4 is set, all MMC counters get preset to almost-half value. All
Bit 5 frame-counters get preset to 0x7FFF_FFF0 (half - 16)
When MCFHP is high and bit4 is set, all MMC counters get preset to almost-full value. All
frame-counters get preset to 0xFFFF_FFF0 (full - 16)
MCP: MMC counter preset
When set, all counters will be initialized or preset to almost full or almost half as per
Bit 4 Bit5 above. This bit will be cleared automatically after 1 clock cycle. This bit along
with bit5 is useful for debugging and testing the assertion of interrupts due to MMC
counter becoming half-full or full.
Bit 3 MCF: MMC counter freeze
When set, this bit freezes all the MMC counters to their current value. (None of the MMC
counters are updated due to any transmitted or received frame until this bit is cleared to 0. If
any MMC counter is read with the Reset on Read bit set, then that counter is also cleared in
this mode.)
Bit 2 ROR: Reset on read
When this bit is set, the MMC counters is reset to zero after read (self-clearing after reset).
The counters are cleared when the least significant byte lane (bits [7:0]) is read.
Bit 1 CSR: Counter stop rollover
When this bit is set, the counter does not roll over to zero after it reaches the maximum
value.
Bit 0 CR: Counter reset
When it is set, all counters are reset. This bit is cleared automatically after 1 clock cycle.

Ethernet MMC receive interrupt register (ETH_MMCRIR)
Address offset: 0x0104
Reset value: 0x0000 0000
The Ethernet MMC receive interrupt register maintains the interrupts generated when
receive statistic counters reach half their maximum values. (MSB of the counter is set.) It is

RM0385 Rev 7

1605/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

a 32-bit wide register. An interrupt bit is cleared when the respective MMC counter that
caused the interrupt is read. The least significant byte lane (bits [7:0]) of the respective
counter must be read in order to clear the interrupt bit.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RGUFS

Res.

rc_r
15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

6

5

RFAES RFCES
rc_r

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

rc_r

Bits 31:18 Reserved, must be kept at reset value.
Bit 17 RGUFS: Received Good Unicast Frames Status
This bit is set when the received, good unicast frames, counter reaches half the maximum
value.
Bits 16:7 Reserved, must be kept at reset value.
Bit 6 RFAES: Received frames alignment error status
This bit is set when the received frames, with alignment error, counter reaches half the
maximum value.
Bit 5 RFCES: Received frames CRC error status
This bit is set when the received frames, with CRC error, counter reaches half the maximum
value.
Bits 4:0 Reserved, must be kept at reset value.

Ethernet MMC transmit interrupt register (ETH_MMCTIR)
Address offset: 0x0108
Reset value: 0x0000 0000
The Ethernet MMC transmit Interrupt register maintains the interrupts generated when
transmit statistic counters reach half their maximum values. (MSB of the counter is set.) It is
a 32-bit wide register. An interrupt bit is cleared when the respective MMC counter that
caused the interrupt is read. The least significant byte lane (bits [7:0]) of the respective
counter must be read in order to clear the interrupt bit.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TGFS

Res.

Res.

Res.

Res.

Res.

rc_r
15

14

TGFMSCS TGFSCS
rc_r

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rc_r

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 TGFS: Transmitted good frames status
This bit is set when the transmitted, good frames, counter reaches half the maximum value.
Bits 20:16 Reserved, must be kept at reset value.

1606/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 15 TGFMSCS: Transmitted good frames more single collision status
This bit is set when the transmitted, good frames after more than a single collision, counter
reaches half the maximum value.
Bit 14 TGFSCS: Transmitted good frames single collision status
This bit is set when the transmitted, good frames after a single collision, counter reaches half
the maximum value.
Bits 13:0 Reserved, must be kept at reset value.

Ethernet MMC receive interrupt mask register (ETH_MMCRIMR)
Address offset: 0x010C
Reset value: 0x0000 0000
The Ethernet MMC receive interrupt mask register maintains the masks for interrupts
generated when the receive statistic counters reach half their maximum value. (MSB of the
counter is set.) It is a 32-bit wide register.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RGUFM

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

RFAEM RFCEM
rw

rw

Bits 31:18 Reserved, must be kept at reset value.
Bit 17 RGUFM: Received good unicast frames mask
Setting this bit masks the interrupt when the received, good unicast frames, counter
reaches half the maximum value.
Bits 16:7 Reserved, must be kept at reset value.
Bit 6 RFAEM: Received frames alignment error mask
Setting this bit masks the interrupt when the received frames, with alignment error, counter
reaches half the maximum value.
Bit 5 RFCEM: Received frame CRC error mask
Setting this bit masks the interrupt when the received frames, with CRC error, counter
reaches half the maximum value.
Bits 4:0 Reserved, must be kept at reset value.

Ethernet MMC transmit interrupt mask register (ETH_MMCTIMR)
Address offset: 0x0110
Reset value: 0x0000 0000
The Ethernet MMC transmit interrupt mask register maintains the masks for interrupts
generated when the transmit statistic counters reach half their maximum value. (MSB of the
counter is set). It is a 32-bit wide register.

RM0385 Rev 7

1607/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TGFM

Res.

Res.

Res.

Res.

Res.

rw
15

14

TGFMSCM TGFSCM
rw

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 TGFM: Transmitted good frames mask
Setting this bit masks the interrupt when the transmitted, good frames, counter reaches half
the maximum value.
Bits 20:16 Reserved, must be kept at reset value.
Bit 15 TGFMSCM: Transmitted good frames more single collision mask
Setting this bit masks the interrupt when the transmitted good frames after more than a
single collision counter reaches half the maximum value.
Bit 14 TGFSCM: Transmitted good frames single collision mask
Setting this bit masks the interrupt when the transmitted good frames after a single collision
counter reaches half the maximum value.
Bits 13:0 Reserved, must be kept at reset value.

Ethernet MMC transmitted good frames after a single collision counter
register (ETH_MMCTGFSCCR)
Address offset: 0x014C
Reset value: 0x0000 0000
This register contains the number of successfully transmitted frames after a single collision
in Half-duplex mode.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

TGFSCC
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

TGFSCC
r

Bits 31:0 TGFSCC: Transmitted good frames single collision counter
Transmitted good frames after a single collision counter.

Ethernet MMC transmitted good frames after more than a single collision
counter register (ETH_MMCTGFMSCCR)
Address offset: 0x0150
Reset value: 0x0000 0000
This register contains the number of successfully transmitted frames after more than a
single collision in Half-duplex mode.

1608/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

TGFMSCC

TGFMSCC
r

r

r

r

r

r

r

r

r

Bits 31:0 TGFMSCC: Transmitted good frames more single collision counter
Transmitted good frames after more than a single collision counter

Ethernet MMC transmitted good frames counter register (ETH_MMCTGFCR)
Address offset: 0x0168
Reset value: 0x0000 0000
This register contains the number of good frames transmitted.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

18

17

16

TGFC

TGFC
r

r

r

r

r

r

r

r

Bits 31:0 TGFC: Transmitted good frames counter

Ethernet MMC received frames with CRC error counter register
(ETH_MMCRFCECR)
Address offset: 0x0194
Reset value: 0x0000 0000
This register contains the number of frames received with CRC error.
31

30

29

28

27

26

25

24

23

22

21

20

19

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

RFCEC

RFCEC
r

r

r

r

r

r

r

r

Bits 31:0 RFCEC: Received frames CRC error counter
Received frames with CRC error counter

Ethernet MMC received frames with alignment error counter register
(ETH_MMCRFAECR)
Address offset: 0x0198
Reset value: 0x0000 0000
This register contains the number of frames received with alignment (dribble) error.

RM0385 Rev 7

1609/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

23

22

21

RM0385

31

30

29

28

27

26

25

24

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

RFAEC

RFAEC
r

r

r

r

r

r

r

r

Bits 31:0 RFAEC: Received frames alignment error counter
Received frames with alignment error counter

MMC received good unicast frames counter register (ETH_MMCRGUFCR)
Address offset: 0x01C4
Reset value: 0x0000 0000
This register contains the number of good unicast frames received.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

17

16

RGUFC

RGUFC
r

r

r

r

r

r

r

r

Bits 31:0 RGUFC: Received good unicast frames counter

38.8.3

IEEE 1588 time stamp registers
This section describes the registers required to support precision network clock
synchronization functions under the IEEE 1588 standard.

Ethernet PTP time stamp control register (ETH_PTPTSCR)
Address offset: 0x0700
Reset value: 0x0000 2000
This register controls the time stamp generation and update logic.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSPFF
MAE

15

14

13

12

11

10

9

8

7

6

5

4

3

Res.

Res.

TSCNT

rw

TSSMR
TSSIPV TSSIPV TSSPT TSPTP
TSSAR
TSSEME
TSSSR
ME
4FE
6FE
POEFE PSV2E
FE
rw

rw

1610/1709

rw

rw

rw

rw

rw

rw

RM0385 Rev 7

TTSARU TSITE TSSTU
rw

rw

rw

rw

2

1

0

TSSTI

TSFCU

TSE

rw

rw

rw

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bits 31:19 Reserved, must be kept at reset value.
Bit 18 TSPFFMAE: Time stamp PTP frame filtering MAC address enable
When set, this bit uses the MAC address (except for MAC address 0) to filter the PTP frames
when PTP is sent directly over Ethernet.
Bits 17:16 TSCNT: Time stamp clock node type
The following are the available types of clock node:
00: Ordinary clock
01: Boundary clock
10: End-to-end transparent clock
11: Peer-to-peer transparent clock
Bit 15 TSSMRME: Time stamp snapshot for message relevant to master enable
When this bit is set, the snapshot is taken for messages relevant to the master node only.
When this bit is cleared the snapshot is taken for messages relevant to the slave node only.
This is valid only for the ordinary clock and boundary clock nodes.
Bit 14 TSSEME: Time stamp snapshot for event message enable
When this bit is set, the time stamp snapshot is taken for event messages only (SYNC,
Delay_Req, Pdelay_Req or Pdelay_Resp). When this bit is cleared the snapshot is taken for
all other messages except for Announce, Management and Signaling.
Bit 13 TSSIPV4FE: Time stamp snapshot for IPv4 frames enable
When this bit is set, the time stamp snapshot is taken for IPv4 frames.
Bit 12 TSSIPV6FE: Time stamp snapshot for IPv6 frames enable
When this bit is set, the time stamp snapshot is taken for IPv6 frames.
Bit 11 TSSPTPOEFE: Time stamp snapshot for PTP over ethernet frames enable
When this bit is set, the time stamp snapshot is taken for frames which have PTP messages
in Ethernet frames (PTP over Ethernet) also. By default snapshots are taken for UDPIPEthernet PTP packets.
Bit 10 TSPTPPSV2E: Time stamp PTP packet snooping for version2 format enable
When this bit is set, the PTP packets are snooped using the version 2 format. When the bit is
cleared, the PTP packets are snooped using the version 1 format.
Note: IEEE 1588 Version 1 and Version 2 formats as indicated in IEEE standard 1588-2008
(Revision of IEEE STD. 1588-2002).
Bit 9 TSSSR: Time stamp subsecond rollover: digital or binary rollover control
When this bit is set, the Time stamp low register rolls over when the subsecond counter
reaches the value 0x3B9A C9FF (999 999 999 in decimal), and increments the Time Stamp
(high) seconds.
When this bit is cleared, the rollover value of the subsecond register reaches 0x7FFF FFFF.
The subsecond increment has to be programmed correctly depending on the PTP’s
reference clock frequency and this bit value.
Bit 8 TSSARFE: Time stamp snapshot for all received frames enable
When this bit is set, the time stamp snapshot is enabled for all frames received by the core.
Bits 7:6 Reserved, must be kept at reset value.
Bit 5 TSARU: Time stamp addend register update
When this bit is set, the Time stamp addend register’s contents are updated to the PTP block
for fine correction. This bit is cleared when the update is complete. This register bit must be
read as zero before you can set it.

RM0385 Rev 7

1611/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 4 TSITE: Time stamp interrupt trigger enable
When this bit is set, a time stamp interrupt is generated when the system time becomes
greater than the value written in the Target time register. When the Time stamp trigger
interrupt is generated, this bit is cleared.
Bit 3 TSSTU: Time stamp system time update
When this bit is set, the system time is updated (added to or subtracted from) with the value
specified in the Time stamp high update and Time stamp low update registers. Both the
TSSTU and TSSTI bits must be read as zero before you can set this bit. Once the update is
completed in hardware, this bit is cleared.
Bit 2 TSSTI: Time stamp system time initialize
When this bit is set, the system time is initialized (overwritten) with the value specified in the
Time stamp high update and Time stamp low update registers. This bit must be read as zero
before you can set it. When initialization is complete, this bit is cleared.
Bit 1 TSFCU: Time stamp fine or coarse update
When set, this bit indicates that the system time stamp is to be updated using the Fine
Update method. When cleared, it indicates the system time stamp is to be updated using the
Coarse method.
Bit 0 TSE: Time stamp enable
When this bit is set, time stamping is enabled for transmit and receive frames. When this bit
is cleared, the time stamp function is suspended and time stamps are not added for transmit
and receive frames. Because the maintained system time is suspended, you must always
initialize the time stamp feature (system time) after setting this bit high.

The table below indicates the messages for which a snapshot is taken depending on the
clock, enable master and enable snapshot for event message register settings.
Table 279. Time stamp snapshot dependency on registers bits
TSCNT
(bits 17:16)

TSSMRME
(bit 15)(1)

TSSEME
(bit 14)

00 or 01

X(2)

0

SYNC, Follow_Up, Delay_Req, Delay_Resp

00 or 01

1

1

Delay_Req

00 or 01

0

1

SYNC

10

N/A

0

SYNC, Follow_Up, Delay_Req, Delay_Resp

10

N/A

1

SYNC, Follow_Up

11

N/A

0

SYNC, Follow_Up, Delay_Req, Delay_Resp,
Pdelay_Req, Pdelay_Resp

11

N/A

1

SYNC, Pdelay_Req, Pdelay_Resp

Messages for which snapshots are taken

1. N/A = not applicable.
2. X = don’t care.

Ethernet PTP subsecond increment register (ETH_PTPSSIR)
Address offset: 0x0704
Reset value: 0x0000 0000
This register contains the 8-bit value by which the subsecond register is incremented. In
Coarse update mode (TSFCU bit in ETH_PTPTSCR), the value in this register is added to

1612/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
the system time every clock cycle of HCLK. In Fine update mode, the value in this register is
added to the system time whenever the accumulator gets an overflow.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

rw

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

STSSI
rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 STSSI: System time subsecond increment
The value programmed in this register is added to the contents of the subsecond value of the
system time in every update.
For example, to achieve 20 ns accuracy, the value is: 20 / 0.467 = ~ 43 (or 0x2A).

Ethernet PTP time stamp high register (ETH_PTPTSHR)
Address offset: 0x0708
Reset value: 0x0000 0000
This register contains the most significant (higher) 32 time bits. This read-only register
contains the seconds system time value. The Time stamp high register, along with Time
stamp low register, indicates the current value of the system time maintained by the MAC.
Though it is updated on a continuous basis.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

STS
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

STS

Bits 31:0 STS: System time second
The value in this field indicates the current value in seconds of the System Time maintained
by the core.

Ethernet PTP time stamp low register (ETH_PTPTSLR)
Address offset: 0x070C
Reset value: 0x0000 0000
This register contains the least significant (lower) 32 time bits. This read-only register
contains the subsecond system time value.

RM0385 Rev 7

1613/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

31

30

29

28

27

26

25

24

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

STPNS

23

22

21

RM0385

20

19

18

17

16

STSS

STSS
r

r

r

r

r

r

r

r

Bit 31 STPNS: System time positive or negative sign
This bit indicates a positive or negative time value. When set, the bit indicates that time
representation is negative. When cleared, it indicates that time representation is positive.
Because the system time should always be positive, this bit is normally zero.
Bits 30:0 STSS: System time subseconds
The value in this field has the subsecond time representation, with 0.46 ns accuracy.

Ethernet PTP time stamp high update register (ETH_PTPTSHUR)
Address offset: 0x0710
Reset value: 0x0000 0000
This register contains the most significant (higher) 32 bits of the time to be written to, added
to, or subtracted from the System Time value. The Time stamp high update register, along
with the Time stamp update low register, initializes or updates the system time maintained
by the MAC. You have to write both of these registers before setting the TSSTI or TSSTU
bits in the Time stamp control register.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

TSUS

TSUS
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 TSUS: Time stamp update second
The value in this field indicates the time, in seconds, to be initialized or added to the system
time.

1614/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Ethernet PTP time stamp low update register (ETH_PTPTSLUR)
Address offset: 0x0714
Reset value: 0x0000 0000
This register contains the least significant (lower) 32 bits of the time to be written to, added
to, or subtracted from the System Time value.
31

30

29

28

27

26

25

24

TSUPNS

23

22

21

20

19

18

17

16

TSUSS

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

TSUSS
rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 TSUPNS: Time stamp update positive or negative sign
This bit indicates positive or negative time value. When set, the bit indicates that time
representation is negative. When cleared, it indicates that time representation is positive.
When TSSTI is set (system time initialization) this bit should be zero. If this bit is set when
TSSTU is set, the value in the Time stamp update registers is subtracted from the system
time. Otherwise it is added to the system time.
Bits 30:0 TSUSS: Time stamp update subseconds
The value in this field indicates the subsecond time to be initialized or added to the system
time. This value has an accuracy of 0.46 ns (in other words, a value of 0x0000_0001 is
0.46 ns).

Ethernet PTP time stamp addend register (ETH_PTPTSAR)
Address offset: 0x0718
Reset value: 0x0000 0000
This register is used by the software to readjust the clock frequency linearly to match the
master clock frequency. This register value is used only when the system time is configured
for Fine update mode (TSFCU bit in ETH_PTPTSCR). This register content is added to a
32-bit accumulator in every clock cycle and the system time is updated whenever the
accumulator overflows.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

TSA
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8
TSA

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 TSA: Time stamp addend
This register indicates the 32-bit time value to be added to the Accumulator register to
achieve time synchronization.

RM0385 Rev 7

1615/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Ethernet PTP target time high register (ETH_PTPTTHR)
Address offset: 0x071C
Reset value: 0x0000 0000
This register contains the higher 32 bits of time to be compared with the system time for
interrupt event generation. The Target time high register, along with Target time low register,
is used to schedule an interrupt event (TSARU bit in ETH_PTPTSCR) when the system time
exceeds the value programmed in these registers.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

TTSH
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8
TTSH

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 TTSH: Target time stamp high
This register stores the time in seconds. When the time stamp value matches or exceeds
both Target time stamp registers, the MAC, if enabled, generates an interrupt.

Ethernet PTP target time low register (ETH_PTPTTLR)
Address offset: 0x0720
Reset value: 0x0000 0000
This register contains the lower 32 bits of time to be compared with the system time for
interrupt event generation.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

TTSL
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

TTSL

Bits 31:0 TTSL: Target time stamp low
This register stores the time in (signed) nanoseconds. When the value of the time stamp
matches or exceeds both Target time stamp registers, the MAC, if enabled, generates an
interrupt.

Ethernet PTP time stamp status register (ETH_PTPTSSR)
Address offset: 0x0728
Reset value: 0x0000 0000
This register contains the time stamp status register.

1616/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSTTR

TSSO

ro

ro

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 TSTTR: Time stamp target time reached
When set, this bit indicates that the value of the system time is greater than or equal to the
value specified in the Target time high and low registers. This bit is cleared when the
ETH_PTPTSSR register is read.
Bit 0 TSSO: Time stamp second overflow
When set, this bit indicates that the second value of the time stamp has overflowed beyond
0xFFFF FFFF.

Ethernet PTP PPS control register (ETH_PTPPPSCR)
Address offset: 0x072C
Reset value: 0x0000 0000
This register controls the frequency of the PPS output.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

3

2

1

0

15

14

13

12

11

10

9

8

7

6

5

4

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PPSFREQ
rw

rw

rw

rw

Bits 31:4 Reserved, must be kept at reset value.
Bits 3:0 PPSFREQ: PPS frequency selection
The PPS output frequency is set to 2PPSFREQ Hz.
0000: 1 Hz with a pulse width of 125 ms for binary rollover and, of 100 ms for digital rollover
0001: 2 Hz with 50% duty cycle for binary rollover (digital rollover not recommended)
0010: 4 Hz with 50% duty cycle for binary rollover (digital rollover not recommended)
0011: 8 Hz with 50% duty cycle for binary rollover (digital rollover not recommended)
0100: 16 Hz with 50% duty cycle for binary rollover (digital rollover not recommended)
...
1111: 32768 Hz with 50% duty cycle for binary rollover (digital rollover not recommended)
Note: If digital rollover is used (TSSSR=1, bit 9 in ETH_PTPTSCR), it is recommended not to
use the PPS output with a frequency other than 1 Hz. Otherwise, with digital rollover,
the PPS output has irregular waveforms at higher frequencies (though its average
frequency will always be correct during any one-second window).

RM0385 Rev 7

1617/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

38.8.4

RM0385

DMA register description
This section defines the bits for each DMA register. Non-32 bit accesses are allowed as long
as the address is word-aligned.

Ethernet DMA bus mode register (ETH_DMABMR)
Address offset: 0x1000
Reset value: 0x0002 0101
The bus mode register establishes the bus operating modes for the DMA.
31

30

29

28

27

26

25

24

23

Res.

Res.

Res.

Res.

Res.

MB

AAB

FPM

USP

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

DA

SR

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rs

PM
rw

PBL

22

21

19

18

17

RDP

EDFE
rw

20

DSL
rw

16
FB

Bits 31:27 Reserved, must be kept at reset value.
Bit 26 MB: Mixed burst
When this bit is set high and the FB bit is low, the AHB master interface starts all bursts of a
length greater than 16 with INCR (undefined burst). When this bit is cleared, it reverts to
fixed burst transfers (INCRx and SINGLE) for burst lengths of 16 and below.
Bit 25 AAB: Address-aligned beats
When this bit is set high and the FB bit equals 1, the AHB interface generates all bursts
aligned to the start address LS bits. If the FB bit equals 0, the first burst (accessing the data
buffer’s start address) is not aligned, but subsequent bursts are aligned to the address.
Bit 24 FPM: 4xPBL mode
When set high, this bit multiplies the PBL value programmed (bits [22:17] and bits [13:8])
four times. Thus the DMA transfers data in a maximum of 4, 8, 16, 32, 64 and 128 beats
depending on the PBL value.
Bit 23 USP: Use separate PBL
When set high, it configures the RxDMA to use the value configured in bits [22:17] as PBL
while the PBL value in bits [13:8] is applicable to TxDMA operations only. When this bit is
cleared, the PBL value in bits [13:8] is applicable for both DMA engines.
Bits 22:17 RDP: Rx DMA PBL
These bits indicate the maximum number of beats to be transferred in one RxDMA
transaction. This is the maximum value that is used in a single block read/write operation.
The RxDMA always attempts to burst as specified in RDP each time it starts a burst transfer
on the host bus. RDP can be programmed with permissible values of 1, 2, 4, 8, 16, and 32.
Any other value results in undefined behavior.
These bits are valid and applicable only when USP is set high.
Bit 16 FB: Fixed burst
This bit controls whether the AHB Master interface performs fixed burst transfers or not.
When set, the AHB uses only SINGLE, INCR4, INCR8 or INCR16 during start of normal
burst transfers. When reset, the AHB uses SINGLE and INCR burst transfer operations.

1618/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bits 15:14 PM: Rx Tx priority ratio
RxDMA requests are given priority over TxDMA requests in the following ratio:
00: 1:1
01: 2:1
10: 3:1
11: 4:1
This is valid only when the DA bit is cleared.
Bits 13:8 PBL: Programmable burst length
These bits indicate the maximum number of beats to be transferred in one DMA transaction.
This is the maximum value that is used in a single block read/write operation. The DMA
always attempts to burst as specified in PBL each time it starts a burst transfer on the host
bus. PBL can be programmed with permissible values of 1, 2, 4, 8, 16, and 32. Any other
value results in undefined behavior. When USP is set, this PBL value is applicable for
TxDMA transactions only.
The PBL values have the following limitations:
– The maximum number of beats (PBL) possible is limited by the size of the Tx FIFO and Rx
FIFO.
– The FIFO has a constraint that the maximum beat supported is half the depth of the FIFO.
– If the PBL is common for both transmit and receive DMA, the minimum Rx FIFO and Tx
FIFO depths must be considered.
– Do not program out-of-range PBL values, because the system may not behave properly.
Bit 7 EDFE: Enhanced descriptor format enable
When this bit is set, the enhanced descriptor format is enabled and the descriptor size is
increased to 32 bytes (8 DWORDS). This is required when time stamping is activated
(TSE=1, ETH_PTPTSCR bit 0) or if IPv4 checksum offload is activated (IPCO=1,
ETH_MACCR bit 10).
Bits 6:2 DSL: Descriptor skip length
This bit specifies the number of words to skip between two unchained descriptors. The
address skipping starts from the end of current descriptor to the start of next descriptor.
When DSL value equals zero, the descriptor table is taken as contiguous by the DMA, in
Ring mode.
Bit 1 DA: DMA Arbitration
0: Round-robin with Rx:Tx priority given in bits [15:14]
1: Rx has priority over Tx
Bit 0 SR: Software reset
When this bit is set, the MAC DMA controller resets all MAC Subsystem internal registers
and logic. It is cleared automatically after the reset operation has completed in all of the core
clock domains. Read a 0 value in this bit before re-programming any register of the core.

Ethernet DMA transmit poll demand register (ETH_DMATPDR)
Address offset: 0x1004
Reset value: 0x0000 0000
This register is used by the application to instruct the DMA to poll the transmit descriptor list.
The transmit poll demand register enables the Transmit DMA to check whether or not the
current descriptor is owned by DMA. The Transmit Poll Demand command is given to wake
up the TxDMA if it is in Suspend mode. The TxDMA can go into Suspend mode due to an
underflow error in a transmitted frame or due to the unavailability of descriptors owned by

RM0385 Rev 7

1619/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

transmit DMA. User can issue this command anytime and the TxDMA resets it once it starts
re-fetching the current descriptor from host memory.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

TPD
rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

TPD
rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

Bits 31:0 TPD: Transmit poll demand
When these bits are written with any value, the DMA reads the current descriptor pointed to
by the ETH_DMACHTDR register. If that descriptor is not available (owned by Host),
transmission returns to the Suspend state and ETH_DMASR register bit 2 is asserted. If the
descriptor is available, transmission resumes.

EHERNET DMA receive poll demand register (ETH_DMARPDR)
Address offset: 0x1008
Reset value: 0x0000 0000
This register is used by the application to instruct the DMA to poll the receive descriptor list.
The Receive poll demand register enables the receive DMA to check for new descriptors.
This command is given to wake up the RxDMA from Suspend state. The RxDMA can go into
Suspend state only due to the unavailability of descriptors owned by it.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

RPD
rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

RPD
rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

rw_wt

Bits 31:0 RPD: Receive poll demand
When these bits are written with any value, the DMA reads the current descriptor pointed to
by the ETH_DMACHRDR register. If that descriptor is not available (owned by Host),
reception returns to the Suspended state and ETH_DMASR register bit 7 is not asserted. If
the descriptor is available, the Receive DMA returns to active state.

Ethernet DMA receive descriptor list address register (ETH_DMARDLAR)
Address offset: 0x100C
Reset value: 0x0000 0000
The Receive descriptor list address register points to the start of the receive descriptor list.
The descriptor list resides in the STM32F75xxx and STM32F74xxx physical memory space
and must be word-aligned. The DMA internally converts it to bus-width aligned address by
making the corresponding LS bits low. Writing to the ETH_DMARDLAR register is permitted
only when reception is stopped. When stopped, the ETH_DMARDLAR register must be
written to before the receive Start command is given.

1620/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

SRL

SRL
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 SRL: Start of receive list
This field contains the base address of the first descriptor in the receive descriptor list. The
LSB bits [1/2/3:0] for 32/64/128-bit bus width) are internally ignored and taken as all-zero by
the DMA. Hence these LSB bits are read only.

Ethernet DMA transmit descriptor list address register (ETH_DMATDLAR)
Address offset: 0x1010
Reset value: 0x0000 0000
The Transmit descriptor list address register points to the start of the transmit descriptor list.
The descriptor list resides in the STM32F75xxx and STM32F74xxx physical memory space
and must be word-aligned. The DMA internally converts it to bus-width-aligned address by
taking the corresponding LSB to low. Writing to the ETH_DMATDLAR register is permitted
only when transmission has stopped. Once transmission has stopped, the
ETH_DMATDLAR register can be written before the transmission Start command is given.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

STL
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8
STL

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 STL: Start of transmit list
This field contains the base address of the first descriptor in the transmit descriptor list. The
LSB bits [1/2/3:0] for 32/64/128-bit bus width) are internally ignored and taken as all-zero
by the DMA. Hence these LSB bits are read-only.

Ethernet DMA status register (ETH_DMASR)
Address offset: 0x1014
Reset value: 0x0000 0000
The Status register contains all the status bits that the DMA reports to the application. The
ETH_DMASR register is usually read by the software driver during an interrupt service
routine or polling. Most of the fields in this register cause the host to be interrupted. The
ETH_DMASR register bits are not cleared when read. Writing 1 to (unreserved) bits in
ETH_DMASR register[16:0] clears them and writing 0 has no effect. Each field (bits [16:0])
can be masked by masking the appropriate bit in the ETH_DMAIER register.

RM0385 Rev 7

1621/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

31

30

29

28

27

26

Res.

Res.

TSTS

PMTS

MMCS

Res.

r

r

r

25

24

23

22

r

r

EBS
r

21

RM0385

20

19

r

r

TPS

r

r

18

17

16

r

rc-w1

RPS
r

NIS

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

AIS

ERS

FBES

Res.

Res.

ETS

RWTS

RPSS

RBUS

RS

TUS

ROS

TJTS

TBUS

TPSS

TS

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

rc-w1

Bits 31:30 Reserved, must be kept at reset value.
Bit 29 TSTS: Time stamp trigger status
This bit indicates an interrupt event in the MAC core's Time stamp generator block. The
software must read the MAC core’s status register, clearing its source (bit 9), to reset this bit
to 0. When this bit is high an interrupt is generated if enabled.
Bit 28 PMTS: PMT status
This bit indicates an event in the MAC core’s PMT. The software must read the
corresponding registers in the MAC core to get the exact cause of interrupt and clear its
source to reset this bit to 0. The interrupt is generated when this bit is high if enabled.
Bit 27 MMCS: MMC status
This bit reflects an event in the MMC of the MAC core. The software must read the
corresponding registers in the MAC core to get the exact cause of interrupt and clear the
source of interrupt to make this bit as 0. The interrupt is generated when this bit is high if
enabled.
Bit 26 Reserved, must be kept at reset value.
Bits 25:23 EBS: Error bits status
These bits indicate the type of error that caused a bus error (error response on the AHB
interface). Valid only with the fatal bus error bit (ETH_DMASR register [13]) set. This field
does not generate an interrupt.
Bit 231 Error during data transfer by TxDMA
0 Error during data transfer by RxDMA
Bit 24 1 Error during read transfer
0 Error during write transfer
Bit 25 1 Error during descriptor access
0 Error during data buffer access
Bits 22:20 TPS: Transmit process state
These bits indicate the Transmit DMA FSM state. This field does not generate an interrupt.
000: Stopped; Reset or Stop Transmit Command issued
001: Running; Fetching transmit transfer descriptor
010: Running; Waiting for status
011: Running; Reading Data from host memory buffer and queuing it to transmit buffer (Tx
FIFO)
100, 101: Reserved for future use
110: Suspended; Transmit descriptor unavailable or transmit buffer underflow
111: Running; Closing transmit descriptor

1622/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bits 19:17 RPS: Receive process state
These bits indicate the Receive DMA FSM state. This field does not generate an interrupt.
000: Stopped: Reset or Stop Receive Command issued
001: Running: Fetching receive transfer descriptor
010: Reserved for future use
011: Running: Waiting for receive packet
100: Suspended: Receive descriptor unavailable
101: Running: Closing receive descriptor
110: Reserved for future use
111: Running: Transferring the receive packet data from receive buffer to host memory
Bit 16 NIS: Normal interrupt summary
The normal interrupt summary bit value is the logical OR of the following when the
corresponding interrupt bits are enabled in the ETH_DMAIER register:
– ETH_DMASR [0]: Transmit interrupt
– ETH_DMASR [2]: Transmit buffer unavailable
– ETH_DMASR [6]: Receive interrupt
– ETH_DMASR [14]: Early receive interrupt
Only unmasked bits affect the normal interrupt summary bit.
This is a sticky bit and it must be cleared (by writing a 1 to this bit) each time a corresponding
bit that causes NIS to be set is cleared.
Bit 15 AIS: Abnormal interrupt summary
The abnormal interrupt summary bit value is the logical OR of the following when the
corresponding interrupt bits are enabled in the ETH_DMAIER register:
– ETH_DMASR [1]:Transmit process stopped
– ETH_DMASR [3]:Transmit jabber timeout
– ETH_DMASR [4]: Receive FIFO overflow
– ETH_DMASR [5]: Transmit underflow
– ETH_DMASR [7]: Receive buffer unavailable
– ETH_DMASR [8]: Receive process stopped
– ETH_DMASR [9]: Receive watchdog timeout
– ETH_DMASR [10]: Early transmit interrupt
– ETH_DMASR [13]: Fatal bus error
Only unmasked bits affect the abnormal interrupt summary bit.
This is a sticky bit and it must be cleared each time a corresponding bit that causes AIS to be
set is cleared.
Bit 14 ERS: Early receive status
This bit indicates that the DMA had filled the first data buffer of the packet. Receive Interrupt
ETH_DMASR [6] automatically clears this bit.
Bit 13 FBES: Fatal bus error status
This bit indicates that a bus error occurred, as detailed in [25:23]. When this bit is set, the
corresponding DMA engine disables all its bus accesses.
Bits 12:11 Reserved, must be kept at reset value.
Bit 10 ETS: Early transmit status
This bit indicates that the frame to be transmitted was fully transferred to the Transmit FIFO.
Bit 9

RWTS: Receive watchdog timeout status
This bit is asserted when a frame with a length greater than 2 048 bytes is received.

RM0385 Rev 7

1623/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 8 RPSS: Receive process stopped status
This bit is asserted when the receive process enters the Stopped state.
Bit 7 RBUS: Receive buffer unavailable status
This bit indicates that the next descriptor in the receive list is owned by the host and cannot
be acquired by the DMA. Receive process is suspended. To resume processing receive
descriptors, the host should change the ownership of the descriptor and issue a Receive Poll
Demand command. If no Receive Poll Demand is issued, receive process resumes when the
next recognized incoming frame is received. ETH_DMASR [7] is set only when the previous
receive descriptor was owned by the DMA.
Bit 6 RS: Receive status
This bit indicates the completion of the frame reception. Specific frame status information
has been posted in the descriptor. Reception remains in the Running state.
Bit 5 TUS: Transmit underflow status
This bit indicates that the transmit buffer had an underflow during frame transmission.
Transmission is suspended and an underflow error TDES0[1] is set.
Bit 4 ROS: Receive overflow status
This bit indicates that the receive buffer had an overflow during frame reception. If the partial
frame is transferred to the application, the overflow status is set in RDES0[11].
Bit 3 TJTS: Transmit jabber timeout status
This bit indicates that the transmit jabber timer expired, meaning that the transmitter had
been excessively active. The transmission process is aborted and placed in the Stopped
state. This causes the transmit jabber timeout TDES0[14] flag to be asserted.
Bit 2 TBUS: Transmit buffer unavailable status
This bit indicates that the next descriptor in the transmit list is owned by the host and cannot
be acquired by the DMA. Transmission is suspended. Bits [22:20] explain the transmit
process state transitions. To resume processing transmit descriptors, the host should change
the ownership of the bit of the descriptor and then issue a Transmit Poll Demand command.
Bit 1 TPSS: Transmit process stopped status
This bit is set when the transmission is stopped.
Bit 0 TS: Transmit status
This bit indicates that frame transmission is finished and TDES1[31] is set in the first
descriptor.

Ethernet DMA operation mode register (ETH_DMAOMR)
Address offset: 0x1018
Reset value: 0x0000 0000
The operation mode register establishes the Transmit and Receive operating modes and
commands. The ETH_DMAOMR register should be the last CSR to be written as part of
DMA initialization.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

DTCEFD

RSF

DFRF

Res.

Res.

TSF

FTF

Res.

Res.

Res.

TTC

rw

rw

rw

rw

rs
4

15

14
TTC

rw

rw

1624/1709

13

12

11

10

9

8

7

6

5

ST

Res.

Res.

Res.

Res.

Res.

FEF

FUGF

Res.

rw

rw

rw

RM0385 Rev 7

rw
3
RTC

rw

rw

2

1

0

OSF

SR

Res.

rw

rw

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bits 31:27 Reserved, must be kept at reset value.
Bit 26 DTCEFD: Dropping of TCP/IP checksum error frames disable
When this bit is set, the core does not drop frames that only have errors detected by the
receive checksum offload engine. Such frames do not have any errors (including FCS error)
in the Ethernet frame received by the MAC but have errors in the encapsulated payload only.
When this bit is cleared, all error frames are dropped if the FEF bit is reset.
Bit 25 RSF: Receive store and forward
When this bit is set, a frame is read from the Rx FIFO after the complete frame has been
written to it, ignoring RTC bits. When this bit is cleared, the Rx FIFO operates in Cut-through
mode, subject to the threshold specified by the RTC bits.
Bit 24 DFRF: Disable flushing of received frames
When this bit is set, the RxDMA does not flush any frames due to the unavailability of
receive descriptors/buffers as it does normally when this bit is cleared. (See Receive
process suspended on page 1574)
Bits 23:22 Reserved, must be kept at reset value.
Bit 21 TSF: Transmit store and forward
When this bit is set, transmission starts when a full frame resides in the Transmit FIFO.
When this bit is set, the TTC values specified by the ETH_DMAOMR register bits [16:14] are
ignored.
When this bit is cleared, the TTC values specified by the ETH_DMAOMR register bits
[16:14] are taken into account.
This bit should be changed only when transmission is stopped.
Bit 20 FTF: Flush transmit FIFO
When this bit is set, the transmit FIFO controller logic is reset to its default values and thus
all data in the Tx FIFO are lost/flushed. This bit is cleared internally when the flushing
operation is complete. The Operation mode register should not be written to until this bit is
cleared.
Bits 19:17 Reserved, must be kept at reset value.
Bits 16:14 TTC: Transmit threshold control
These three bits control the threshold level of the Transmit FIFO. Transmission starts when
the frame size within the Transmit FIFO is larger than the threshold. In addition, full frames
with a length less than the threshold are also transmitted. These bits are used only when the
TSF bit (Bit 21) is cleared.
000: 64
001: 128
010: 192
011: 256
100: 40
101: 32
110: 24
111: 16

RM0385 Rev 7

1625/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 13 ST: Start/stop transmission
When this bit is set, transmission is placed in the Running state, and the DMA checks the
transmit list at the current position for a frame to be transmitted. Descriptor acquisition is
attempted either from the current position in the list, which is the transmit list base address
set by the ETH_DMATDLAR register, or from the position retained when transmission was
stopped previously. If the current descriptor is not owned by the DMA, transmission enters
the Suspended state and the transmit buffer unavailable bit (ETH_DMASR [2]) is set. The
Start Transmission command is effective only when transmission is stopped. If the command
is issued before setting the DMA ETH_DMATDLAR register, the DMA behavior is
unpredictable.
When this bit is cleared, the transmission process is placed in the Stopped state after
completing the transmission of the current frame. The next descriptor position in the transmit
list is saved, and becomes the current position when transmission is restarted. The Stop
Transmission command is effective only when the transmission of the current frame is
complete or when the transmission is in the Suspended state.
Bits 12:8 Reserved, must be kept at reset value.
Bit 7 FEF: Forward error frames
When this bit is set, all frames except runt error frames are forwarded to the DMA.
When this bit is cleared, the Rx FIFO drops frames with error status (CRC error, collision
error, giant frame, watchdog timeout, overflow). However, if the frame’s start byte (write)
pointer is already transferred to the read controller side (in Threshold mode), then the
frames are not dropped. The Rx FIFO drops the error frames if that frame's start byte is not
transferred (output) on the ARI bus.
Bit 6 FUGF: Forward undersized good frames
When this bit is set, the Rx FIFO forwards undersized frames (frames with no error and
length less than 64 bytes) including pad-bytes and CRC).
When this bit is cleared, the Rx FIFO drops all frames of less than 64 bytes, unless such a
frame has already been transferred due to lower value of receive threshold (e.g., RTC = 01).
Bit 5 Reserved, must be kept at reset value.
Bits 4:3 RTC: Receive threshold control
These two bits control the threshold level of the Receive FIFO. Transfer (request) to DMA
starts when the frame size within the Receive FIFO is larger than the threshold. In addition,
full frames with a length less than the threshold are transferred automatically.
Note: Note that value of 11 is not applicable if the configured Receive FIFO size is 128 bytes.
Note: These bits are valid only when the RSF bit is zero, and are ignored when the RSF bit is
set to 1.
00: 64
01: 32
10: 96
11: 128
Bit 2 OSF: Operate on second frame
When this bit is set, this bit instructs the DMA to process a second frame of Transmit data
even before status for first frame is obtained.

1626/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 1 SR: Start/stop receive
When this bit is set, the receive process is placed in the Running state. The DMA attempts to
acquire the descriptor from the receive list and processes incoming frames. Descriptor
acquisition is attempted from the current position in the list, which is the address set by the
DMA ETH_DMARDLAR register or the position retained when the receive process was
previously stopped. If no descriptor is owned by the DMA, reception is suspended and the
receive buffer unavailable bit (ETH_DMASR [7]) is set. The Start Receive command is
effective only when reception has stopped. If the command was issued before setting the
DMA ETH_DMARDLAR register, the DMA behavior is unpredictable.
When this bit is cleared, RxDMA operation is stopped after the transfer of the current frame.
The next descriptor position in the receive list is saved and becomes the current position
when the receive process is restarted. The Stop Receive command is effective only when
the Receive process is in either the Running (waiting for receive packet) or the Suspended
state.
Bit 0 Reserved, must be kept at reset value.

Ethernet DMA interrupt enable register (ETH_DMAIER)
Address offset: 0x101C
Reset value: 0x0000 0000
The Interrupt enable register enables the interrupts reported by ETH_DMASR. Setting a bit
to 1 enables a corresponding interrupt. After a hardware or software reset, all interrupts are
disabled.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

NISE
rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

AISE

ERIE

FBEIE

Res.

Res.

ETIE

RWTIE

RPSIE

RBUIE

RIE

TUIE

ROIE

TJTIE

TBUIE

TPSIE

TIE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 NISE: Normal interrupt summary enable
When this bit is set, a normal interrupt is enabled. When this bit is cleared, a normal
interrupt is disabled. This bit enables the following bits:
– ETH_DMASR [0]: Transmit Interrupt
– ETH_DMASR [2]: Transmit buffer unavailable
– ETH_DMASR [6]: Receive interrupt
– ETH_DMASR [14]: Early receive interrupt

RM0385 Rev 7

1627/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 15 AISE: Abnormal interrupt summary enable
When this bit is set, an abnormal interrupt is enabled. When this bit is cleared, an abnormal
interrupt is disabled. This bit enables the following bits:
– ETH_DMASR [1]: Transmit process stopped
– ETH_DMASR [3]: Transmit jabber timeout
– ETH_DMASR [4]: Receive overflow
– ETH_DMASR [5]: Transmit underflow
– ETH_DMASR [7]: Receive buffer unavailable
– ETH_DMASR [8]: Receive process stopped
– ETH_DMASR [9]: Receive watchdog timeout
– ETH_DMASR [10]: Early transmit interrupt
– ETH_DMASR [13]: Fatal bus error
Bit 14 ERIE: Early receive interrupt enable
When this bit is set with the normal interrupt summary enable bit (ETH_DMAIER
register[16]), the early receive interrupt is enabled.
When this bit is cleared, the early receive interrupt is disabled.
Bit 13 FBEIE: Fatal bus error interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER
register[15]), the fatal bus error interrupt is enabled.
When this bit is cleared, the fatal bus error enable interrupt is disabled.
Bits 12:11 Reserved, must be kept at reset value.
Bit 10 ETIE: Early transmit interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER register
[15]), the early transmit interrupt is enabled.
When this bit is cleared, the early transmit interrupt is disabled.
Bit 9 RWTIE: receive watchdog timeout interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER
register[15]), the receive watchdog timeout interrupt is enabled.
When this bit is cleared, the receive watchdog timeout interrupt is disabled.
Bit 8 RPSIE: Receive process stopped interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER
register[15]), the receive stopped interrupt is enabled. When this bit is cleared, the receive
stopped interrupt is disabled.
Bit 7 RBUIE: Receive buffer unavailable interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER
register[15]), the receive buffer unavailable interrupt is enabled.
When this bit is cleared, the receive buffer unavailable interrupt is disabled.
Bit 6 RIE: Receive interrupt enable
When this bit is set with the normal interrupt summary enable bit (ETH_DMAIER
register[16]), the receive interrupt is enabled.
When this bit is cleared, the receive interrupt is disabled.
Bit 5 TUIE: Underflow interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER
register[15]), the transmit underflow interrupt is enabled.
When this bit is cleared, the underflow interrupt is disabled.

1628/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Bit 4

ROIE: Overflow interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER
register[15]), the receive overflow interrupt is enabled.
When this bit is cleared, the overflow interrupt is disabled.

Bit 3 TJTIE: Transmit jabber timeout interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER
register[15]), the transmit jabber timeout interrupt is enabled.
When this bit is cleared, the transmit jabber timeout interrupt is disabled.
Bit 2 TBUIE: Transmit buffer unavailable interrupt enable
When this bit is set with the normal interrupt summary enable bit (ETH_DMAIER
register[16]), the transmit buffer unavailable interrupt is enabled.
When this bit is cleared, the transmit buffer unavailable interrupt is disabled.
Bit 1 TPSIE: Transmit process stopped interrupt enable
When this bit is set with the abnormal interrupt summary enable bit (ETH_DMAIER
register[15]), the transmission stopped interrupt is enabled.
When this bit is cleared, the transmission stopped interrupt is disabled.
Bit 0 TIE: Transmit interrupt enable
When this bit is set with the normal interrupt summary enable bit (ETH_DMAIER
register[16]), the transmit interrupt is enabled.
When this bit is cleared, the transmit interrupt is disabled.

The Ethernet interrupt is generated only when the TSTS or PMTS bits of the DMA Status
register is asserted with their corresponding interrupt are unmasked, or when the NIS/AIS
Status bit is asserted and the corresponding Interrupt Enable bits (NISE/AISE) are enabled.

Ethernet DMA missed frame and buffer overflow counter register
(ETH_DMAMFBOCR)
Address offset: 0x1020
Reset value: 0x0000 0000
The DMA maintains two counters to track the number of missed frames during reception.
This register reports the current value of the counter. The counter is used for diagnostic
purposes. Bits [15:0] indicate missed frames due to the STM32F75xxx and STM32F74xxx
buffer being unavailable (no receive descriptor was available). Bits [27:17] indicate missed
frames due to Rx FIFO overflow conditions and runt frames (good frames of less than 64
bytes).
31

30

29

28

Res.

Res.

Res.

OFOC

15

14

13

27

26

25

24

23

22

21

20

19

18

17

MFA

16
OMFC

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

12

11

10

9

8

7

6

5

4

3

2

1

0

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

MFC
rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

rc_r

Bits 31:29 Reserved, must be kept at reset value.
Bit 28 OFOC: Overflow bit for FIFO overflow counter
Bits 27:17 MFA: Missed frames by the application
Indicates the number of frames missed by the application

RM0385 Rev 7

1629/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bit 16 OMFC: Overflow bit for missed frame counter
Bits 15:0 MFC: Missed frames by the controller
Indicates the number of frames missed by the Controller due to the host receive buffer being
unavailable. This counter is incremented each time the DMA discards an incoming frame.

Ethernet DMA receive status watchdog timer register (ETH_DMARSWTR)
Address offset: 0x1024
Reset value: 0x0000 0000
This register, when written with a non-zero value, enables the watchdog timer for the receive
status (RS, ETH_DMASR[6]).
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RSWTC
rw

rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 RSWTC: Receive status (RS) watchdog timer count
Indicates the number of HCLK clock cycles multiplied by 256 for which the watchdog timer
is set. The watchdog timer gets triggered with the programmed value after the RxDMA
completes the transfer of a frame for which the RS status bit is not set due to the setting of
RDES1[31] in the corresponding descriptor. When the watchdog timer runs out, the RS bit
is set and the timer is stopped. The watchdog timer is reset when the RS bit is set high due
to automatic setting of RS as per RDES1[31] of any received frame.

Ethernet DMA current host transmit descriptor register (ETH_DMACHTDR)
Address offset: 0x1048
Reset value: 0x0000 0000
The Current host transmit descriptor register points to the start address of the current
transmit descriptor read by the DMA.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

HTDAP

HTDAP
r

r

r

r

r

r

r

r

Bits 31:0 HTDAP: Host transmit descriptor address pointer
Cleared . Pointer updated by DMA during operation.

Ethernet DMA current host receive descriptor register (ETH_DMACHRDR)
Address offset: 0x104C

1630/1709

RM0385 Rev 7

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller
Reset value: 0x0000 0000
The Current host receive descriptor register points to the start address of the current receive
descriptor read by the DMA.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

HRDAP

HRDAP
r

r

r

r

r

r

r

r

Bits 31:0 HRDAP: Host receive descriptor address pointer
Cleared On Reset. Pointer updated by DMA during operation.

Ethernet DMA current host transmit buffer address register
(ETH_DMACHTBAR)
Address offset: 0x1050
Reset value: 0x0000 0000
The Current host transmit buffer address register points to the current transmit buffer
address being read by the DMA.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

HTBAP
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

HTBAP

Bits 31:0 HTBAP: Host transmit buffer address pointer
Cleared On Reset. Pointer updated by DMA during operation.

Ethernet DMA current host receive buffer address register
(ETH_DMACHRBAR)
Address offset: 0x1054
Reset value: 0x0000 0000
The current host receive buffer address register points to the current receive buffer address
being read by the DMA.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

HRBAP
r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8
HRBAP

r

r

r

r

r

r

r

r

RM0385 Rev 7

1631/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

Bits 31:0 HRBAP: Host receive buffer address pointer
Cleared On Reset. Pointer updated by DMA during operation.

38.8.5

Ethernet register maps
Table 280 gives the ETH register map and reset values.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

BL

PCF

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

MR

Res.

PA

Res.

0

0

0

0

0

0

0

0

0

0

0

ETH_MACVLANT
R

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

VLANTC

0

0

0

0

0

0

0

0

0

0

0

MD

TFCE

0

0

FCB/BPA

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PD

0

0

MPE

0

0

RFCE

0

0

WFE

Reset value

Res.

PT

M
MB
W

UPFD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

CR

0

Res.

0

ZQPD

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

ETH_MACFCR

0

0

0

PLT

0
VLANTI

0

0

0

0

0

0

0

0

0

0

0

Frame filter reg0\Frame filter reg1\Frame filter reg2\Frame filter reg3\Frame filter reg4\...\Frame filter reg7

MMRPEA

MSFRWCS
Res.

Res.

Res.

Res.

PMTS

0

1

1

1

0
MACA0H

1

RM0385 Rev 7

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

MO

Reset value

Res.

Res.
MMCS
Res.

Res.

0

MMCTS

0

Res.

Res.

Res.

Res.

0

0

0

ETH_MACA0HR

Res.

Reset value

TSTIM

Res.

Res.

Res.

Res.

-

ETH_MACIMR

0

PMTIM

0

MMCRS

0

Res.

0

Res.

RFRCS

Res.

RFFL
0

0
Res.

Reset value

0

Res.

Res.
Res.

-

Res.

0

TSTS

Res.

Res.

Res.

Res.

Res.

MMTEA
0

Res.

0

Res.

0

MTFCS

MTP
0

Res.

0

Res.

ETH_MACSR

0

TFRS

0

TFWA

TFNEGU

0

Res.

TFF

Res.

Res.

Res.

Reset value

Res.

0
RFWRA

MPR

Res.

WFR

Res.

GU

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0
Res.

ETH_MACDBGR

Res.

WFFRPR
0

Res.

Reset value

Res.

0

-

1632/1709

TE

0

RE

0

DC

Res.

RD

HU

IPCO

Res.

PM

0

Reset value

ETH_MACPMTC
SR

0x40

APCS

LM

DM

Res.

HM

0

Res.

0

Res.

0

0x2C

0x3C

Res.

FES

ROD
Res.

Res.

Res.

CSD
Res.

Res.

Res.

PAM

0

Reset value

0x38

0

0

HTL[31:0]

ETH_MACRWUF
FR
0x28
Reset value

0x34

0

DAIF

0

Res.

0x1C

0

BFD

0

Res.

0x18

ETH_MACMIIDR

0

SAIF

0

Reset value
0x14

0

SAF

0

Res.

ETH_MACMIIAR

0

HPF

0

ETH_MACHTLR
Reset value

0

Res.

Reset value

0
Res.

Res.
Res.

Res.

JD

Res.
Res.

WD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

HTH[31:0]

Res.

0x10

0

0

Res.

0x0C

0

ETH_MACHTHR

Res.

0x08

0

IFG

Res.

Reset value

Res.

ETH_MACFFR RA

Res.

0x04

0

0
Res.

Reset value

CSTF

Res.

Res.

Res.

ETH_MACCR

Res.

0x00

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 280. Ethernet register map and reset values

1

1

1

1

1

1

1

1

1

1

1

1

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

0

0

0

0

0

0

0

1

1

1

1

1

1

1

Res.

Res.

Res.

Res.

Res.

Res.

MBC[6:0]

1

Res.

1

Res.

1

0

MBC

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1
Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

1

1

1

1

1

1

1

1

1

1

1

1

MACA1H
1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

MACA2H
1

1

1

1

1

1

1

1

1

0

1

Res.

Res.

Res.

Res.

Res.

Res.

0

1

1

1

1

1

1

1

1

1

1

MACA3H
1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

0

0

0

0

0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

ETH_MMCCR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
RFCEM

Res.

Res.
RFAEM

Res.

ETH_MMCRFCE
CR
0x194
Reset value
0
ETH_MMCRFAE
CR
0x198
Reset value
0

RFCES

Res.
Res.

Res.

Res.
Res.

Res.

Res.
Res.

Res.

Res.
Res.

Res.

Res.
Res.

Res.

Res.
Res.

0

Res.

Res.

TGFSCS
Res.

Res.

Res.

0
Res.

ETH_MMCTGFC
R
0x168
Reset value
0

0

Res.

ETH_MMCTGFM
SCCR
0x150
Reset value
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

TGFMSCM

TGFSCM

Res.

Res.

Res.

Reset value
ETH_MMCTGFS
CCR
0x14C
Reset value
0

0

Res.

TGFMSCS

0

RFAES

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.
Res.

RGUFM

Res.

Res.
Res.

Res.

TGFM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ETH_MMCTIMR

0

0
Res.

Reset value

0x110

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ETH_MMCRIMR

Res.

0x10C

0
Res.

Reset value

TGFS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ETH_MMCTIR

Res.

0x108

0
Res.

Reset value

RGUFS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ETH_MMCRIR

Res.

0x104

Res.

Reset value

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

Reset value

Res.

MACA3L

Res.

ETH_MACA3LR

CR

0

1

CSR

0

1

MCF

0

1

ROR

0

1

MCP

0

1

Res.

0

MBC

1
Res.

ETH_MACA3HR AE SA
Reset value

1

MACA2L
1
Res.

ETH_MACA2LR
Reset value

1

MACA1L

ETH_MACA2HR AE SA
Reset value

1

1

ETH_MACA1LR
Reset value

1

MCFHP

Reset value

1

Res.

0x100

ETH_MACA1HR AE SA

1

Res.

0x5C

1

Res.

0x58

1

Res.

0x54

1

Res.

0x50

MACA0L
1

Res.

0x4C

Reset value

Res.

0x48

ETH_MACA0LR

Res.

0x44

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 280. Ethernet register map and reset values (continued)

0

0

TGFSCC
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

TGFMSCC
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

TGFC
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RFCEC
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RFAEC
0

0

0

0

0

0

0

0

0

0

0

0

0

0

RM0385 Rev 7

0

0

1633/1709
1635

Ethernet (ETH): media access control (MAC) with DMA controller

RM0385

0

0

ETH_PTPTSLR
Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

STSSI
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

STSS
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ETH_PTPTSHUR

0

TSUS

Reset value

0

ETH_PTPTSLUR
Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

TSUSS
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ETH_PTPTSAR

0

TSA
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ETH_PTPTTHR

0

TTSH
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ETH_PTPTSSR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RM0385 Rev 7

0

0

TS

0

0

0

0

0

0

0

0

RTC

0

Res.

0

0

TPSS

0

0

TBUS

0

0

SR

0

0

OSF

0

ROS

0

TJTS

0

TUS

0

Res.

0

RS

0

RBUS

Res.

0

FEF

Res.

0

0

FUGF

Res.

0

0

RPSS

FTF

0

0

Res.

TSF

0

0

ETS

Res.

0

0

RWTS

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

FBES

0

0
AIS

0

0

0

ERS

0

NIS

0

RPS

0

TPS

0

Res.

0

0

EBS

0

0

DFRF

Res.

Res.

Res.

0

0

RSF

ETH_DMASR

0

DTCEFD

0

MMCS

0

Res.

0

TSTS

0

PMTS

0
Res.

STL
0

1634/1709

0

SRL

Reset value

Reset value

0

RPD

ETH_DMATDLAR

ETH_DMAOMR

0

ST

Reset value

0

DSL

SR

0

PBL

0

DA

0

EDFE

USP

0

FB

FPM

0

TTC

Reset value

Reset value

0x1018

0

Res.

0x1014

0

ETH_DMARPDR

ETH_DMARDLA
R
0x100C
Reset value
0
0x1010

0

PM

0

TPD

Res.

0x1008

0

RDP

ETH_DMATPDR

Res.

0x1004

AAB

Reset value

MB

Res.

Res.

Res.

ETH_DMABMR

Res.

0x1000

Res.

Reset value

TSSO

Reset value

Res.

TTSL

Res.

ETH_PTPTTLR

TSTTR

Reset value

0

Res.

0

Reset value

0

STS[31:0]

Reset value

STPNS

ETH_PTPTSHR

0

TSE

0

0

TSSTI

0

0

TSFCU

0

0

TSITE

1

0

TSSTU

0

0

Res.

0

0

TTSARU

Res.

Res.

TSSSR

Res.

TSSARFE

Res.

Res.

0

Res.

Res.

Res.

TSPTPPSV2E

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

TSSIPV6FE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0x728

0

Res.

0x720

0

Res.

0x71C

0

Res.

0x718

0

Res.

0x714

0

Res.

0x710

0

Reset value

TSUPNS

0x70C

0

Res.

0x708

ETH_PTPSSIR

0

Res.

0x704

Res.

Reset value

0

TSSPTPOEFE

Res.

0

Res.

ETH_PTPTSCR

0

Res.

0

TSSEME

0

TSSIPV4FE

0

Res.

0

TSSMRME

0

Res.

0

Res.

0

TSCNT

0

Res.

0

Res.

0

Res.

0

TSPFFMAE

0

Res.

Reset value

Res.

RGUFC

Res.

0x700

ETH_MMCRGUF
CR

Res.

0x1C4

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 280. Ethernet register map and reset values (continued)

0

0

RM0385

Ethernet (ETH): media access control (MAC) with DMA controller

Reset value
0x104C

0x1050

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0x1054

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RSWTC
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

HRDAP
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

HTBAP
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ETH_
DMACHRBAR
Reset value

0

HTDAP

ETH_
DMACHTBAR
Reset value

TIE

0

ETH_
DMACHRDR
Reset value

TPSIE

0

ETH_
DMACHTDR

0

MFC

Reset value
0x1048

TBUIE

0

ROIE

0

TJTIE

0

RIE

RPSIE

RBUIE

0

TUIE

RWTIE

Res.

ETIE

Res.

FBEIE
0

OMFC

0

Res.

MFA

OFOC

Res.
Res.

0

Res.

Res.

Res.
Res.

0x1024

ETH_
DMARSWTR

Res.

Reset value

AISE

0

Reset value
ETH_DMAMFBO
CR
0x1020

ERIE

Res.

NISE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ETH_DMAIER

Res.

0x101C

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 280. Ethernet register map and reset values (continued)

0

0

HRBAP
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Refer to Section 2.2.2 on page 69 for the register boundary addresses.

RM0385 Rev 7

1635/1709
1635

HDMI-CEC controller (HDMI-CEC)

RM0385

39

HDMI-CEC controller (HDMI-CEC)

39.1

Introduction
Consumer electronics control (CEC) is part of HDMI (high-definition multimedia interface)
standard as appendix supplement 1. It contains a protocol that provides high-level control
functions between various audiovisual products. CEC operates at low speeds, with
minimum processing and memory overhead.
The HDMI-CEC controller provides hardware support for this protocol.

39.2

HDMI-CEC controller main features
•

Complies with HDMI-CEC v1.4 specification

•

32 kHz CEC kernel with 2 clock source options
–

HSI RC oscillator with fixed prescaler (HSI/488)

–

LSE oscillator

•

Works in Stop mode for ultra-low-power applications

•

Configurable signal-free time before start of transmission
–

Automatic by hardware, according to CEC state and transmission history

–

Fixed by software (7 timing options)

•

Configurable peripheral address (OAR)

•

Supports Listen mode
–

•

•

•

Configurable Rx-tolerance margin
–

Standard tolerance

–

Extended tolerance

Receive-error detection
–

Bit rising error (BRE), with optional stop of reception (BRESTP)

–

Short bit period error (SBPE)

–

Long bit period error (LBPE)

Configurable error-bit generation
–

on BRE detection (BREGEN)

–

on LBPE detection (LBPEGEN)

–

always generated on SBPE detection

•

Transmission error detection (TXERR)

•

Arbitration lost detection (ARBLST)
–

1636/1709

Enables reception of CEC messages sent to destination address different from
OAR without interfering with the CEC line

With automatic transmission retry

•

Transmission underrun detection (TXUDR)

•

Reception overrun detection (RXOVR)

RM0385 Rev 7

RM0385

HDMI-CEC controller (HDMI-CEC)

39.3

HDMI-CEC functional description

39.3.1

HDMI-CEC pin
The CEC bus consists of a single bidirectional line that is used to transfer data in and out of
the device. It is connected to a +3.3 V supply voltage via a 27 kΩ pull-up resistor. The output
stage of the device must have an open-drain or open-collector to allow a wired-AND
connection.
The HDMI-CEC controller manages the CEC bidirectional line as an alternate function of a
standard GPIO, assuming that it is configured as alternate function open drain. The 27 kΩ
pull-up must be added externally to the microcontroller.
To not interfere with the CEC bus when the application power is removed, it is mandatory to
isolate the CEC pin from the bus in such conditions. This can be done by using a MOS
transistor, as shown on Figure 527.
Table 281. HDMI pin
Name

CEC

39.3.2

Signal type

Remarks
Two states:
– 1 = high impedance
– 0 = low impedance
A 27 kΩ resistor must be added externally.

Bidirectional

HDMI-CEC block diagram
Figure 527. HDMI-CEC block diagram

STM32
HDMI_CEC
controller

CEC interrupt
Cortex
Core

AHB

CEC
ITF

APB

3.3V
27 kΩ

HSI
LSE

RCC

Event
control

CLK

3.3V
G

RX

32 kHz
CEC TX
Kernel
Wake-int

CEC
PAD

CEC line S

D

Remote
CEC
device

MSv35920V2

39.3.3

Message description
All transactions on the CEC line consist of an initiator and one or more followers. The
initiator is responsible for sending the message structure and the data. The follower is the
recipient of any data and is responsible for setting any acknowledgment bits.
A message is conveyed in a single frame that consists of a start bit followed by a header
block and optionally an opcode and a variable number of operand blocks.

RM0385 Rev 7

1637/1709
1654

HDMI-CEC controller (HDMI-CEC)

RM0385

All these blocks are made of a 8-bit payload - most significant bit is transmitted first followed by an end of message (EOM) bit and an acknowledge (ACK) bit.
The EOM bit is set in the last block of a message and kept reset in all others. In case a
message contains additional blocks after an EOM is indicated, those additional blocks must
be ignored. The EOM bit may be set in the header block to ‘ping’ other devices, to make
sure they are active.
The acknowledge bit is always set to high impedance by the initiator so that it can be driven
low either by the follower that has read its own address in the header, or by the follower that
needs to reject a broadcast message.
The header consists of the source logical address field, and the destination logical address
field. Note that the special address 0xF is used for broadcast messages.
Figure 528. Message structure
0 to 14 operands
high
START
impedance BIT

OPCODE

HEADER

OPERAND

OPERAND

high
impedance

MS31004V1

Figure 529. Blocks
0

HEADER BLOCK

INITIATOR[3:0]

DESTINATION[3:0] EOM ACK
0

OPCODE/OPERAND BLOCK

DATA[7:0]

EOM ACK

MS31005V1

39.3.4

Bit timing
The format of the start bit is unique and identifies the start of a message. It must be
validated by its low duration and its total duration.
All remaining data bits in the message, after the start bit, have consistent timing. The highto-low transition at the end of the data bit is the start of the next data bit except for the final
bit where the CEC line remains high.

1638/1709

RM0385 Rev 7

RM0385

HDMI-CEC controller (HDMI-CEC)
Figure 530. Bit timings
4.5 ms +/-0.2 ms
START BIT
3.7 ms +/-0.2 ms
high impedance
low impedance

2.4 ms +/-0.35 ms

DATA BIT
INITIATOR LOGICAL 0

1.5 ms +/-0.2 ms

high impedance
low impedance

2.4 ms +/-0.35 ms

DATA BIT
INITIATOR LOGICAL 1

0.6 ms +/-0.2 ms

high impedance
low impedance

2.4 ms +/-0.35 ms
DATA BIT

1.5 ms +/-0.2 ms

FOLLOWER LOGICAL 0

0.35 ms max

high impedance
low impedance
MS31006V1

39.4

Arbitration
All devices transmitting - or retransmitting - a message onto the CEC line must ensure that it
has been inactive for a number of bit periods. This signal-free time is defined as the time
starting from the final bit of the previous frame and depends on the initiating device and the
current status as shown in the table below.
Figure 531. Signal free time
Signal free time

PREVIOUS MESSAGE

NEW MESSAGE
MS31007V1

Since only one initiator is allowed at any one time, an arbitration mechanism is provided to
avoid conflict when more than one initiator begins transmitting at the same time.
CEC line arbitration starts with the leading edge of the start bit and continues until the end of
the initiator address bits within the header block. During this period, the initiator must
monitor the CEC line, if whilst driving the line to high impedance it reads it back to 0.
Assuming then it has lost arbitration, it stops transmitting and becomes a follower.

RM0385 Rev 7

1639/1709
1654

HDMI-CEC controller (HDMI-CEC)

RM0385
Figure 532. Arbitration phase

Arbitration phase
high impedance START
BIT

INITIATOR[3:0]

DESTINATION[3:0]

EOM ACK

MS31008V1

Figure 533 shows an example for a SFT of three nominal bit periods
Figure 533. SFT of three nominal bit periods

last bit of previous frame

Start bit

MS31009V1

A configurable time window is counted before starting the transmission.
In the SFT = 0 configuration, HDMI-CEC performs automatic SFT calculation ensuring
compliance with the HDMI-CEC standard:
•

2.5 data bit periods if the CEC is the last bus initiator with unsuccessful transmission

•

4 data bit periods if the CEC is the new bus initiator

•

6 data bit periods if the CEC is the last bus initiator with successful transmission

This is done to guarantee the maximum priority to a failed transmission and the lowest one
to the last initiator that completed successfully its transmission.
Otherwise there is the possibility to configure the SFT bits to count a fixed timing value.
Possible values are 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5 data bit periods.

39.4.1

SFT option bit
In case of SFTOPT = 0 configuration, SFT starts being counted when the start-oftransmission command is set by software (TXSOM=1).
In case of SFTOPT=1, SFT starts automatically being counted by the HDMI-CEC device
when a bus-idle or line error condition is detected. If the SFT timer is completed at the time
TXSOM command is set then transmission starts immediately without latency. If the SFT
timer is still running instead, the system waits until the timer elapses before transmission
can start.

1640/1709

RM0385 Rev 7

RM0385

HDMI-CEC controller (HDMI-CEC)
In case of SFTOPT = 1 a bus-event condition starting the SFT timer is detected in the
following cases:
•

In case of a regular end of transmission/reception, when TXEND/RXEND bits are set at
the minimum nominal data bit duration of the last bit in the message (ACK bit).

•

In case of a transmission error detection, SFT timer starts when the TXERR
transmission error is detected (TXERR=1).

•

In case of a missing acknowledge from the CEC follower, the SFT timer starts when the
TXACKE bit is set, that is at the nominal sampling time of the ACK bit.

•

In case of a transmission underrun error, the SFT timer starts when the TXUDR bit is
set at the end of the ACK bit.

•

In case of a receive error detection implying reception abort, the SFT timer starts at the
same time the error is detected. If an error bit is generated, then SFT starts being
counted at the end of the error bit.

•

In case of a wrong start bit or of any uncodified low impedance bus state from idle, the
SFT timer is restarted as soon as the bus comes back to hi-impedance idleness.

39.5

Error handling

39.5.1

Bit error
If a data bit - excluding the start bit - is considered invalid, the follower is expected to notify
such error by generating a low bit period on the CEC line of 1.4 to 1.6 times the nominal
data bit period, i.e. 3.6 ms nominally.
Figure 534. Error bit timing

ERROR BIT

3.6 ms +/-0.24 ms

high impedance
low impedance

MS31010V1

39.5.2

Message error
A message is considered lost and therefore may be retransmitted under the following
conditions:
•

a message is not acknowledged in a directly addressed message

•

a message is negatively acknowledged in a broadcast message

•

a low impedance is detected on the CEC line while it is not expected (line error)

Three kinds of error flag can be detected when the CEC interface is receiving a data bit:

39.5.3

Bit Rising Error (BRE)
BRE (bit rising error): is set when a bit rising edge is detected outside the windows where it
is expected (see Figure 535). BRE flag also generates a CEC interrupt if the BREIE=1.

RM0385 Rev 7

1641/1709
1654

HDMI-CEC controller (HDMI-CEC)

RM0385

In the case of a BRE detection, the message reception can be stopped according to the
BRESTP bit value and an error bit can be generated if BREGEN bit is set.
When BRE is detected in a broadcast message with BRESTP=1 an error bit is generated
even if BREGEN=0 to enforce initiator’s retry of the failed transmission. Error bit generation
can be disabled by configuring BREGEN=0, BRDNOGEN=1.

39.5.4

Short Bit Period Error (SBPE)
SBPE is set when a bit falling edge is detected earlier than expected (see Figure 535).
SBPE flag also generates a CEC interrupt if the SBPEIE=1.
An error bit is always generated on the line in case of a SBPE error detection. An Error Bit is
not generated upon SBPE detection only when Listen mode is set (LSTN=1) and the
following conditions are met:

39.5.5

•

A directly addressed message is received containing SBPE

•

A broadcast message is received containing SBPE AND BRDNOGEN=1

Long Bit Period Error (LBPE)
LBPE is set when a bit falling edge is not detected in a valid window (see Figure 535). LBPE
flag also generates a CEC interrupt if the LBPEIE=1.
LBPE always stops the reception, an error bit is generated on the line when LBPEGEN bit is
set.
When LBPE is detected in a broadcast message an error bit is generated even if
LBPEGEN=0 to enforce initiator’s retry of the failed transmission. Error bit generation can
be disabled by configuring LBPEGEN=0, BRDNOGEN=1.

Note:

The BREGEN=1, BRESTP=0 configuration must be avoided
Figure 535. Error handling
Legend:
BRE Checking Window

BRE

Tolerance margins

CEC initiator bit-timing

BRE
LBPE

SBPE

Ts

T1

Tn1

T2

Tns

T3

Tn0

T4

T5

Tnf

T6
MS31011V1

1642/1709

RM0385 Rev 7

RM0385

HDMI-CEC controller (HDMI-CEC)
Table 282. Error handling timing parameters
Time

RXTOL

ms

Ts

x

0

1

0.3

0

0.4

x

0.6

0

0.8

1

0.9

The latest time for a low - high transition when
indicating a logical 1.

x

1.05

Nominal sampling time.

1

1.2

0

1.3

The earliest time a device is permitted return to a
high impedance state (logical 0).

x

1.5

0

1.7

1

1.8

1

1.85

0

2.05

x

2.4

0

2.75

1

2.95

T1
Tn1
T2
Tns
T3
Tn0
T4
T5
Tnf
T6

Description
Bit start event.
The earliest time for a low - high transition when
indicating a logical 1.
The nominal time for a low - high transition when
indicating a logical 1.

The nominal time a device is permitted return to a
high impedance state (logical 0).
The latest time a device is permitted return to a high
impedance state (logical 0).
The earliest time for the start of a following bit.
The nominal data bit period.
The latest time for the start of a following bit.

RM0385 Rev 7

1643/1709
1654

HDMI-CEC controller (HDMI-CEC)

39.5.6

RM0385

Transmission Error Detection (TXERR)
The CEC initiator sets the TXERR flag if detecting low impedance on the CEC line when it is
transmitting high impedance and is not expecting a follower asserted bit. TXERR flag also
generates a CEC interrupt if the TXERRIE=1.
TXERR assertion stops the message transmission. Application is in charge to retry the
failed transmission up to 5 times.
TXERR checks are performed differently depending on the different states of the CEC line
and on the RX tolerance configuration.
Figure 536. TXERR detection
Legend:
TXERR Checking Window

CEC initiator bit-timing

Tolerance margins

Tx acknowledge
Tx arbitration bit-1
Tx data bit-1

Ts

T1

Tn1

T2

Tns

T3

Tn0

T4

T5

Tnf

T6

Tx arbitration bit-0
Tx data bit-0

MS31012V1

Table 283. TXERR timing parameters
Time

RXTOL

ms

Ts

x

0

1

0.3

0

0.4

x

0.6

0

0.8

1

0.9

The latest time for a low - high transition when
indicating a logical 1.

x

1.05

Nominal sampling time.

1

1.2

0

1.3

The earliest time a device is permitted return to a
high impedance state (logical 0).

T1
Tn1
T2
Tns
T3

1644/1709

Description
Bit start event.
The earliest time for a low - high transition when
indicating a logical 1.
The nominal time for a low - high transition when
indicating a logical 1.

RM0385 Rev 7

RM0385

HDMI-CEC controller (HDMI-CEC)
Table 283. TXERR timing parameters (continued)
Time

RXTOL

ms

Tn0

x

1.5

0

1.7

1

1.8

1

1.85

0

2.05

x

2.4

0

2.75

1

2.95

T4
T5
Tnf
T6

39.6

Description
The nominal time a device is permitted return to a
high impedance state (logical 0).
The latest time a device is permitted return to a high
impedance state (logical 0).
The earliest time for the start of a following bit.
The nominal data bit period.
The latest time for the start of a following bit.

HDMI-CEC interrupts
An interrupt can be produced:
•

during reception if a Receive Block Transfer is finished or if a Receive Error occurs.

•

during transmission if a Transmit Block Transfer is finished or if a Transmit Error
occurs.
Table 284. HDMI-CEC interrupts
Interrupt event

Event flag

Enable Control bit

RXBR

RXBRIE

End of reception

RXEND

RXENDIE

Rx-Overrun

RXOVR

RXOVRIE

BRE

BREIE

Rx-Short Bit Period Error

SBPE

SBPEIE

Rx-Long Bit Period Error

LBPE

LBPEIE

Rx-Missing Acknowledge Error

RXACKE

RXACKEIE

Arbitration lost

ARBLST

ARBLSTIE

TXBR

TXBRIE

End of transmission

TXEND

TXENDIE

Tx-Buffer Underrun

TXUDR

TXUDRIE

Tx-Error

TXERR

TXERRIE

TXACKE

TXACKEIE

Rx-Byte Received

RxBit Rising Error

Tx-Byte Request

Tx-Missing Acknowledge Error

RM0385 Rev 7

1645/1709
1654

HDMI-CEC controller (HDMI-CEC)

39.7

RM0385

HDMI-CEC registers
Refer to Section 1.1 on page 62 for a list of abbreviations used in register descriptions.

39.7.1

CEC control register (CEC_CR)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

TXE
OM

TXS
OM

CECEN

rs

rs

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Bits 31:3 Reserved, must be kept at reset value.

1646/1709

RM0385 Rev 7

Res.

Res.

Res.

RM0385

HDMI-CEC controller (HDMI-CEC)

Bit 2 TXEOM: Tx End Of Message
The TXEOM bit is set by software to command transmission of the last byte of a CEC message.
TXEOM is cleared by hardware at the same time and under the same conditions as for TXSOM.
0: TXDR data byte is transmitted with EOM=0
1: TXDR data byte is transmitted with EOM=1
Note: TXEOM must be set when CECEN=1.
TXEOM must be set before writing transmission data to TXDR.
If TXEOM is set when TXSOM=0, transmitted message will consist of 1 byte (HEADER) only
(PING message)
Bit 1 TXSOM: Tx Start Of Message
TXSOM is set by software to command transmission of the first byte of a CEC message. If the CEC
message consists of only one byte, TXEOM must be set before of TXSOM.
Start-Bit is effectively started on the CEC line after SFT is counted. If TXSOM is set while a message
reception is ongoing, transmission will start after the end of reception.
TXSOM is cleared by hardware after the last byte of the message is sent with a positive
acknowledge (TXEND=1), in case of transmission underrun (TXUDR=1), negative acknowledge
(TXACKE=1), and transmission error (TXERR=1). It is also cleared by CECEN=0. It is not cleared
and transmission is automatically retried in case of arbitration lost (ARBLST=1).
TXSOM can be also used as a status bit informing application whether any transmission request is
pending or under execution. The application can abort a transmission request at any time by
clearing the CECEN bit.
0: No CEC transmission is on-going
1: CEC transmission command
Note: TXSOM must be set when CECEN=1.
TXSOM must be set when transmission data is available into TXDR.
HEADER first four bits containing own peripheral address are taken from TXDR[7:4], not from
CEC_CFGR.OAR which is used only for reception.
Bit 0 CECEN: CEC enable
The CECEN bit is set and cleared by software. CECEN=1 starts message reception and enables the
TXSOM control. CECEN=0 disables the CEC peripheral, clears all bits of CEC_CR register and
aborts any on-going reception or transmission.
0: CEC peripheral is off
1: CEC peripheral is on

39.7.2

CEC configuration register (CEC_CFGR)
This register is used to configure the HDMI-CEC controller.
Address offset: 0x04
Reset value: 0x0000 0000

Caution: It is mandatory to write CEC_CFGR only when CECEN=0.
31

30

29

28

27

26

25

24

LSTN

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

2

1

0

OAR[14:0]

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

Res.

SFT
OP

BRDN
OGEN

LBPE
GEN

BRE
GEN

BRE
STP

RX
TOL

rw

rw

rw

rw

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

RM0385 Rev 7

SFT[2:0]
rw

rw

rw

1647/1709
1654

HDMI-CEC controller (HDMI-CEC)

RM0385

Bit 31 LSTN: Listen mode
LSTN bit is set and cleared by software.
0: CEC peripheral receives only message addressed to its own address (OAR). Messages
addressed to different destination are ignored. Broadcast messages are always received.
1: CEC peripheral receives messages addressed to its own address (OAR) with positive
acknowledge. Messages addressed to different destination are received, but without interfering with
the CEC bus: no acknowledge sent.
Bits 30:16 OAR[14:0]: Own addresses configuration
The OAR bits are set by software to select which destination logical addresses has to be considered
in receive mode. Each bit, when set, enables the CEC logical address identified by the given bit
position.
At the end of HEADER reception, the received destination address is compared with the enabled
addresses. In case of matching address, the incoming message is acknowledged and received. In
case of non-matching address, the incoming message is received only in listen mode (LSTN=1), but
without acknowledge sent. Broadcast messages are always received.
Example:
OAR = 0b000 0000 0010 0001 means that CEC acknowledges addresses 0x0 and 0x5.
Consequently, each message directed to one of these addresses is received.
Bits 15:9 Reserved, must be kept at reset value.
Bit 8 SFTOP: SFT Option Bit
The SFTOPT bit is set and cleared by software.
0: SFT timer starts when TXSOM is set by software
1: SFT timer starts automatically at the end of message transmission/reception.
Bit 7 BRDNOGEN: Avoid Error-Bit Generation in Broadcast
The BRDNOGEN bit is set and cleared by software.
0: BRE detection with BRESTP=1 and BREGEN=0 on a broadcast message generates an Error-Bit
on the CEC line. LBPE detection with LBPEGEN=0 on a broadcast message generates an Error-Bit
on the CEC line
1: Error-Bit is not generated in the same condition as above. An Error-Bit is not generated even in
case of an SBPE detection in a broadcast message if listen mode is set.
Bit 6 LBPEGEN: Generate Error-Bit on Long Bit Period Error
The LBPEGEN bit is set and cleared by software.
0: LBPE detection does not generate an Error-Bit on the CEC line
1: LBPE detection generates an Error-Bit on the CEC line
Note: If BRDNOGEN=0, an Error-bit is generated upon LBPE detection in broadcast even if
LBPEGEN=0
Bit 5 BREGEN: Generate Error-Bit on Bit Rising Error
The BREGEN bit is set and cleared by software.
0: BRE detection does not generate an Error-Bit on the CEC line
1: BRE detection generates an Error-Bit on the CEC line (if BRESTP is set)
Note: If BRDNOGEN=0, an Error-bit is generated upon BRE detection with BRESTP=1 in broadcast
even if BREGEN=0

1648/1709

RM0385 Rev 7

RM0385

HDMI-CEC controller (HDMI-CEC)

Bit 4 BRESTP: Rx-Stop on Bit Rising Error
The BRESTP bit is set and cleared by software.
0: BRE detection does not stop reception of the CEC message. Data bit is sampled at 1.05 ms.
1: BRE detection stops message reception
Bit 3 RXTOL: Rx-Tolerance
The RXTOL bit is set and cleared by software.
0: Standard tolerance margin:
–
Start-Bit, +/- 200 µs rise, +/- 200 µs fall.
–
Data-Bit: +/- 200 µs rise. +/- 350 µs fall.
1: Extended Tolerance
–
Start-Bit: +/- 400 µs rise, +/- 400 µs fall
–
Data-Bit: +/-300 µs rise, +/- 500 µs fall
Bits 2:0 SFT[2:0]: Signal Free Time
SFT bits are set by software. In the SFT=0x0 configuration the number of nominal data bit periods
waited before transmission is ruled by hardware according to the transmission history. In all the
other configurations the SFT number is determined by software.
″
0x0
–
2.5 Data-Bit periods if CEC is the last bus initiator with unsuccessful transmission
(ARBLST=1, TXERR=1, TXUDR=1 or TXACKE= 1)
–
4 Data-Bit periods if CEC is the new bus initiator
–
6 Data-Bit periods if CEC is the last bus initiator with successful transmission (TXEOM=1)
″
0x1: 0.5 nominal data bit periods
″
0x2: 1.5 nominal data bit periods
″
0x3: 2.5 nominal data bit periods
″
0x4: 3.5 nominal data bit periods
″
0x5: 4.5 nominal data bit periods
″
0x6: 5.5 nominal data bit periods
″
0x7: 6.5 nominal data bit periods

RM0385 Rev 7

1649/1709
1654

HDMI-CEC controller (HDMI-CEC)

39.7.3

RM0385

CEC Tx data register (CEC_TXDR)
Address offset: 0x8
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
w

w

w

w

w

w

w

TXD[7:0]
w

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 TXD[7:0]: Tx data
TXD is a write-only register containing the data byte to be transmitted.

39.7.4

CEC Rx data register (CEC_RXDR)
Address offset: 0xC
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

r

r

r

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RXD[7:0]
r

r

r

r

r

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 RXD[7:0]: Rx data
RXD is read-only and contains the last data byte which has been received from the CEC line.

39.7.5

CEC Interrupt and Status Register (CEC_ISR)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

TX
ACKE

TX
ERR

TX
UDR

TX
END

TXBR

ARB
LST

RX
ACKE

LBPE

SBPE

BRE

RX
OVR

RX
END

RXBR

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

1650/1709

RM0385 Rev 7

RM0385

HDMI-CEC controller (HDMI-CEC)

Bits 31:13 Reserved, must be kept at reset value.
Bit 12 TXACKE: Tx-Missing Acknowledge Error
In transmission mode, TXACKE is set by hardware to inform application that no acknowledge was
received. In case of broadcast transmission, TXACKE informs application that a negative
acknowledge was received. TXACKE aborts message transmission and clears TXSOM and TXEOM
controls.
TXACKE is cleared by software write at 1.
Bit 11 TXERR: Tx-Error
In transmission mode, TXERR is set by hardware if the CEC initiator detects low impedance on the
CEC line while it is released. TXERR aborts message transmission and clears TXSOM and TXEOM
controls.
TXERR is cleared by software write at 1.
Bit 10 TXUDR: Tx-Buffer Underrun
In transmission mode, TXUDR is set by hardware if application was not in time to load TXDR before
of next byte transmission. TXUDR aborts message transmission and clears TXSOM and TXEOM
control bits.
TXUDR is cleared by software write at 1
Bit 9 TXEND: End of Transmission
TXEND is set by hardware to inform application that the last byte of the CEC message has been
successfully transmitted. TXEND clears the TXSOM and TXEOM control bits.
TXEND is cleared by software write at 1.
Bit 8 TXBR: Tx-Byte Request
TXBR is set by hardware to inform application that the next transmission data has to be written to
TXDR. TXBR is set when the 4th bit of currently transmitted byte is sent. Application must write the
next byte to TXDR within 6 nominal data-bit periods before transmission underrun error occurs
(TXUDR).
TXBR is cleared by software write at 1.
Bit 7 ARBLST: Arbitration Lost
ARBLST is set by hardware to inform application that CEC device is switching to reception due to
arbitration lost event following the TXSOM command. ARBLST can be due either to a contending
CEC device starting earlier or starting at the same time but with higher HEADER priority. After
ARBLST assertion TXSOM bit keeps pending for next transmission attempt.
ARBLST is cleared by software write at 1.
Bit 6 RXACKE: Rx-Missing Acknowledge
In receive mode, RXACKE is set by hardware to inform application that no acknowledge was seen
on the CEC line. RXACKE applies only for broadcast messages and in listen mode also for not
directly addressed messages (destination address not enabled in OAR). RXACKE aborts message
reception.
RXACKE is cleared by software write at 1.
Bit 5 LBPE: Rx-Long Bit Period Error
LBPE is set by hardware in case a Data-Bit waveform is detected with Long Bit Period Error. LBPE is
set at the end of the maximum bit-extension tolerance allowed by RXTOL, in case falling edge is still
longing. LBPE always stops reception of the CEC message. LBPE generates an Error-Bit on the
CEC line if LBPEGEN=1. In case of broadcast, Error-Bit is generated even in case of LBPEGEN=0.
LBPE is cleared by software write at 1.
Bit 4 SBPE: Rx-Short Bit Period Error
SBPE is set by hardware in case a Data-Bit waveform is detected with Short Bit Period Error. SBPE
is set at the time the anticipated falling edge occurs. SBPE generates an Error-Bit on the CEC line.
SBPE is cleared by software write at 1.

RM0385 Rev 7

1651/1709
1654

HDMI-CEC controller (HDMI-CEC)

RM0385

Bit 3 BRE: Rx-Bit Rising Error
BRE is set by hardware in case a Data-Bit waveform is detected with Bit Rising Error. BRE is set
either at the time the misplaced rising edge occurs, or at the end of the maximum BRE tolerance
allowed by RXTOL, in case rising edge is still longing. BRE stops message reception if BRESTP=1.
BRE generates an Error-Bit on the CEC line if BREGEN=1.
BRE is cleared by software write at 1.
Bit 2 RXOVR: Rx-Overrun
RXOVR is set by hardware if RXBR is not yet cleared at the time a new byte is received on the CEC
line and stored into RXD. RXOVR assertion stops message reception so that no acknowledge is
sent. In case of broadcast, a negative acknowledge is sent.
RXOVR is cleared by software write at 1.
Bit 1 RXEND: End Of Reception
RXEND is set by hardware to inform application that the last byte of a CEC message is received
from the CEC line and stored into the RXD buffer. RXEND is set at the same time of RXBR.
RXEND is cleared by software write at 1.
Bit 0 RXBR: Rx-Byte Received
The RXBR bit is set by hardware to inform application that a new byte has been received from the
CEC line and stored into the RXD buffer.
RXBR is cleared by software write at 1.

39.7.6

CEC interrupt enable register (CEC_IER)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

3

2

1

0

Res.

Res.

Res.

TXACK TXERR
TX
TXEND
IE
IE
UDRIE
IE
rw

rw

rw

rw

8

7

6

5

4

TXBR
IE

ARBLST
IE

RXACK
IE

LBPE
IE

SBPE
IE

rw

rw

rw

rw

rw

Bits 31:13 Reserved, must be kept at reset value.
Bit 12 TXACKIE: Tx-Missing Acknowledge Error Interrupt Enable
The TXACKEIE bit is set and cleared by software.
0: TXACKE interrupt disabled
1: TXACKE interrupt enabled
Bit 11 TXERRIE: Tx-Error Interrupt Enable
The TXERRIE bit is set and cleared by software.
0: TXERR interrupt disabled
1: TXERR interrupt enabled
Bit 10 TXUDRIE: Tx-Underrun Interrupt Enable
The TXUDRIE bit is set and cleared by software.
0: TXUDR interrupt disabled
1: TXUDR interrupt enabled

1652/1709

RM0385 Rev 7

RXOVR RXEND RXBR
BREIE
IE
IE
IE
rw

rw

rw

rw

RM0385

HDMI-CEC controller (HDMI-CEC)

Bit 9 TXENDIE: Tx-End Of Message Interrupt Enable
The TXENDIE bit is set and cleared by software.
0: TXEND interrupt disabled
1: TXEND interrupt enabled
Bit 8 TXBRIE: Tx-Byte Request Interrupt Enable
The TXBRIE bit is set and cleared by software.
0: TXBR interrupt disabled
1: TXBR interrupt enabled
Bit 7 ARBLSTIE: Arbitration Lost Interrupt Enable
The ARBLSTIE bit is set and cleared by software.
0: ARBLST interrupt disabled
1: ARBLST interrupt enabled
Bit 6 RXACKIE: Rx-Missing Acknowledge Error Interrupt Enable
The RXACKIE bit is set and cleared by software.
0: RXACKE interrupt disabled
1: RXACKE interrupt enabled
Bit 5 LBPEIE: Long Bit Period Error Interrupt Enable
The LBPEIE bit is set and cleared by software.
0: LBPE interrupt disabled
1: LBPE interrupt enabled
Bit 4 SBPEIE: Short Bit Period Error Interrupt Enable
The SBPEIE bit is set and cleared by software.
0: SBPE interrupt disabled
1: SBPE interrupt enabled
Bit 3 BREIE: Bit Rising Error Interrupt Enable
The BREIE bit is set and cleared by software.
0: BRE interrupt disabled
1: BRE interrupt enabled
Bit 2 RXOVRIE: Rx-Buffer Overrun Interrupt Enable
The RXOVRIE bit is set and cleared by software.
0: RXOVR interrupt disabled
1: RXOVR interrupt enabled
Bit 1 RXENDIE: End Of Reception Interrupt Enable
The RXENDIE bit is set and cleared by software.
0: RXEND interrupt disabled
1: RXEND interrupt enabled
Bit 0 RXBRIE: Rx-Byte Received Interrupt Enable
The RXBRIE bit is set and cleared by software.
0: RXBR interrupt disabled
1: RXBR interrupt enabled
Caution: (*) It is mandatory to write CEC_IER only when CECEN=0

RM0385 Rev 7

1653/1709
1654

0x14
CEC_IER

1654/1709

RM0385 Rev 7
TXEND
TXBR
ARBLST
RXACKE
LBPE
SBPE
BRE
RXOVR
RXEND
RXBR

0
0
0
0
0
0
0
0
0
0
0
0
0

TXBRIE
ARBLSTIE
RXACKIE
LBPEIE
SBPEIE
BREIE
RXOVRIE
RXENDIE
RXBRIE

Reset value

TXENDIE

Res.

Res.

CEC_TXDR

Res.

0

TXUDR

0

TXUDRIE

0

Res.

0

TXERR

0

TXERRIE

0

Res.

0

TXACKE

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LSTN

Reset value
SFTOPT
BRDNOGEN
LBPEGEN
BREGEN
BRESTP
RXTOL

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OAR[14:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CEC_CFGR

TXACKIE

Reset value
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CEC_ISR

Res.

0x10

Res.

CEC_RXDR

Res.

0x0C
Res.

0x08

Res.

0x04

Reset value
0

Reset value

Refer to Section 2.2.2 on page 69 for the register boundary addresses.
0
0
0

0
0
0
0
0
0

TXSOM
CECEN

Reset value
TXEOM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CEC_CR

Res.

0x00

Res.

Offset
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register
name

Res.

39.7.7

Res.

HDMI-CEC controller (HDMI-CEC)
RM0385

HDMI-CEC register map
The following table summarizes the HDMI-CEC registers.
Table 285. HDMI-CEC register map and reset values

0
0
0

SFT[2:0]

TXD[7:0]
0

0
0
0

0
0
0

RXD[7:0]

0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0

RM0385

Debug support (DBG)

40

Debug support (DBG)

40.1

Overview
The STM32F75xxx and STM32F74xxx are built around a Cortex®-M7 with FPU core which
contains hardware extensions for advanced debugging features. The debug extensions
allow the core to be stopped either on a given instruction fetch (breakpoint) or data access
(watchpoint). When stopped, the core’s internal state and the system’s external state may
be examined. Once examination is complete, the core and the system may be restored and
program execution resumed.
The debug features are used by the debugger host when connecting to and debugging the
STM32F75xxx and STM32F74xxx MCUs.
Two interfaces for debug are available:
•

Serial wire

•

JTAG debug port
Figure 537. Block diagram of STM32 MCU and Cortex®-M7 with FPU -level
debug support

STM32F7xx debug support
Cortex-M7 debug support
Bus matrix

D

Dcode
interface

Cortex-M7
core

Data

System
interface

JTMS/
SWDIO
External private
Peripheral bus (PPB)

JTDI
Bridge
JTDO
NJTRST

SWJ-DP
DAP

TRACESWO
Trace port
TPIU

AHB-AP

TRACECK
TRACED[3:0]

Internal private
Peripheral bus (PPB)

NVIC

JTCK/
SWCLK

DWT

DBGMCU

FPB
ETM
ITM

MSv34190V1

Note:

®

The debug features embedded in the Cortex -M7 with FPU core are a subset of the Arm®
CoreSight Components Technical Reference Manual.

RM0385 Rev 7

1655/1709
1687

Debug support (DBG)

RM0385

The Arm® Cortex®-M7 with FPU core provides integrated on-chip debug support. It is
comprised of:
•

SWJ-DP: Serial wire / JTAG debug port

•

AHP-AP: AHB access port

•

ITM: Instrumentation trace macrocell

•

FPB: Flash patch breakpoint

•

DWT: Data watchpoint trigger

•

TPIU: Trace port unit interface (available on larger packages, where the corresponding
pins are mapped)

•

ETM: Embedded Trace Macrocell (available on larger packages, where the
corresponding pins are mapped)

It also includes debug features dedicated to the STM32F75xxx and STM32F74xxx:
•

Flexible debug pinout assignment

•

MCU debug box (support for low-power modes, control over peripheral clocks, etc.)

Note:

For further information on debug functionality supported by the Arm® Cortex®-M7 with FPU
core, refer to the Cortex®-M7 with FPU technical reference manual and to the CoreSight
Components Technical Reference Manual (see Section 40.2: Reference Arm®
documentation).

40.2

Reference Arm® documentation
•

Cortex®-M7 with FPU technical reference manual (TRM)
(see Related documents on page 1)

40.3

•

Arm® Debug Interface V5 architecture specification

•

Arm® CoreSight Components Technical Reference Manual

SWJ debug port (serial wire and JTAG)
The core of the STM32F75xxx and STM32F74xxx integrates the Serial Wire / JTAG Debug
Port (SWJ-DP). It is an Arm® standard CoreSight debug port that combines a JTAG-DP (5pin) interface and a SW-DP (2-pin) interface.
•

The JTAG Debug Port (JTAG-DP) provides a 5-pin standard JTAG interface to the
AHP-AP port.

•

The Serial Wire Debug Port (SW-DP) provides a 2-pin (clock + data) interface to the
AHP-AP port.

In the SWJ-DP, the two JTAG pins of the SW-DP are multiplexed with some of the five JTAG
pins of the JTAG-DP.

1656/1709

RM0385 Rev 7

RM0385

Debug support (DBG)
Figure 538. SWJ debug port

Figure 538 shows that the asynchronous TRACE output (TRACESWO) is multiplexed with
TDO. This means that the asynchronous trace can only be used with SW-DP, not JTAG-DP.

40.3.1

Mechanism to select the JTAG-DP or the SW-DP
By default, the JTAG-Debug Port is active.
If the debugger host wants to switch to the SW-DP, it must provide a dedicated JTAG
sequence on TMS/TCK (respectively mapped to SWDIO and SWCLK) which disables the
JTAG-DP and enables the SW-DP. This way it is possible to activate the SWDP using only
the SWCLK and SWDIO pins.
This sequence is:

40.4

1.

Send more than 50 TCK cycles with TMS (SWDIO) =1

2.

Send the 16-bit sequence on TMS (SWDIO) = 0111100111100111 (MSB transmitted
first)

3.

Send more than 50 TCK cycles with TMS (SWDIO) =1

Pinout and debug port pins
The STM32F75xxx and STM32F74xxx MCUs are available in various packages with
different numbers of available pins. As a result, some functionality related to pin availability
(TPIU parallel output interface) may differ between packages.

RM0385 Rev 7

1657/1709
1687

Debug support (DBG)

40.4.1

RM0385

SWJ debug port pins
Five pins are used as outputs from the STM32F75xxx and STM32F74xxx for the SWJ-DP
as alternate functions of general-purpose I/Os. These pins are available on all packages.
Table 286. SWJ debug port pins
JTAG debug port

SW debug port

SWJ-DP pin name
Type

40.4.2

Description

Type

Debug assignment

Pin
assign
ment

JTMS/SWDIO

I

JTAG Test Mode
Selection

IO

Serial Wire Data
Input/Output

PA13

JTCK/SWCLK

I

JTAG Test Clock

I

Serial Wire Clock

PA14

JTDI

I

JTAG Test Data Input

-

JTDO/TRACESWO

O

JTAG Test Data Output

-

NJTRST

I

JTAG Test nReset

-

-

PA15

TRACESWO if async trace
is enabled
-

PB3
PB4

Flexible SWJ-DP pin assignment
After RESET (SYSRESETn or PORESETn), all five pins used for the SWJ-DP are assigned
as dedicated pins immediately usable by the debugger host (note that the trace outputs are
not assigned except if explicitly programmed by the debugger host).
However, the STM32F75xxx and STM32F74xxx MCUs offer the possibility of disabling
some or all of the SWJ-DP ports and so, of releasing (in gray in the table below) the
associated pins for general-purpose IO (GPIO) usage. For more details on how to disable
SWJ-DP port pins, refer to Section 6.3.2: I/O pin alternate function multiplexer and mapping.
Table 287. Flexible SWJ-DP pin assignment
SWJ IO pin assigned
Available debug ports

Note:

1658/1709

PA13 / PA14 /
PA15 /
JTMS / JTCK /
JTDI
SWDIO SWCLK

PB3 /
JTDO

PB4 /
NJTRST
X

Full SWJ (JTAG-DP + SW-DP) - Reset State

X

X

X

X

Full SWJ (JTAG-DP + SW-DP) but without NJTRST

X

X

X

X

JTAG-DP Disabled and SW-DP Enabled

X

X

-

JTAG-DP Disabled and SW-DP Disabled

-

-

Released

-

When the APB bridge write buffer is full, it takes one extra APB cycle when writing the
GPIO_AFR register. This is because the deactivation of the JTAGSW pins is done in two
cycles to guarantee a clean level on the nTRST and TCK input signals of the core.
•

Cycle 1: the JTAGSW input signals to the core are tied to 1 or 0 (to 1 for TRST, TDI and
TMS, to 0 for TCK)

•

Cycle 2: the GPIO controller takes the control signals of the SWJTAG IO pins (like
controls of direction, pull-up/down, Schmitt trigger activation, etc.).

RM0385 Rev 7

RM0385

40.4.3

Debug support (DBG)

Internal pull-up and pull-down on JTAG pins
It is necessary to ensure that the JTAG input pins are not floating since they are directly
connected to flip-flops to control the debug mode features. Special care must be taken with
the SWCLK/TCK pin which is directly connected to the clock of some of these flip-flops.
To avoid any uncontrolled IO levels, the device embeds internal pull-ups and pull-downs on
the JTAG input pins:
•

NJTRST: Internal pull-up

•

JTDI: Internal pull-up

•

JTMS/SWDIO: Internal pull-up

•

TCK/SWCLK: Internal pull-down

Once a JTAG IO is released by the user software, the GPIO controller takes control again.
The reset states of the GPIO control registers put the I/Os in the equivalent state:
•

NJTRST: AF input pull-up

•

JTDI: AF input pull-up

•

JTMS/SWDIO: AF input pull-up

•

JTCK/SWCLK: AF input pull-down

•

JTDO: AF output floating

The software can then use these I/Os as standard GPIOs.
Note:

The JTAG IEEE standard recommends to add pull-ups on TDI, TMS and nTRST but there is
no special recommendation for TCK. However, for JTCK, the device needs an integrated
pull-down.
Having embedded pull-ups and pull-downs removes the need to add external resistors.

RM0385 Rev 7

1659/1709
1687

Debug support (DBG)

40.4.4

RM0385

Using serial wire and releasing the unused debug pins as GPIOs
To use the serial wire DP to release some GPIOs, the user software must change the GPIO
(PA15, PB3 and PB4) configuration mode in the GPIO_MODER register. This releases
PA15, PB3 and PB4 which now become available as GPIOs.
When debugging, the host performs the following actions:

Note:

•

Under system reset, all SWJ pins are assigned (JTAG-DP + SW-DP).

•

Under system reset, the debugger host sends the JTAG sequence to switch from the
JTAG-DP to the SW-DP.

•

Still under system reset, the debugger sets a breakpoint on vector reset.

•

The system reset is released and the Core halts.

•

All the debug communications from this point are done using the SW-DP. The other
JTAG pins can then be reassigned as GPIOs by the user software.

For user software designs, note that:
To release the debug pins, remember that they will be first configured either in input-pull-up
(nTRST, TMS, TDI) or pull-down (TCK) or output tristate (TDO) for a certain duration after
reset until the instant when the user software releases the pins.
When debug pins (JTAG or SW or TRACE) are mapped, changing the corresponding IO pin
configuration in the IOPORT controller has no effect.

40.5

STM32F75xxx and STM32F74xxx JTAG Debug Port
connection
The STM32F75xxx and STM32F74xxx MCUs integrate two serially connected JTAG Debug
Ports, the boundary scan Debug Port (IR is 5-bit wide) and the Cortex®-M7 with FPU Debug
Port (IR is 4-bit wide).
To access the Debug Port of the Cortex®-M7 with FPU for debug purposes:

Note:

1660/1709

1.

First, it is necessary to shift the BYPASS instruction of the boundary scan Debug Port.

2.

Then, for each IR shift, the scan chain contains 9 bits (=5+4) and the unused Debug
Port instruction must be shifted in using the BYPASS instruction.

3.

For each data shift, the unused Debug Port, which is in BYPASS mode, adds 1 extra
data bit in the data scan chain.

Important: Once Serial-Wire is selected using the dedicated Arm® JTAG sequence, the
boundary scan Debug Port is automatically disabled (JTMS forced high).

RM0385 Rev 7

RM0385

Debug support (DBG)
Figure 539. JTAG Debug Port connections

STM32F7xx
NJTRST
JTMS
SW-DP
Selected

TMS

JTDI

TDI

nTRST

TDO

Boundary scan
TAP
IR is 5-bit wide

TMS

TDI

nTRST

TDO

Cortex-M7 DP
IR is 4-bit wide

JTDO

MSv36635V1

RM0385 Rev 7

1661/1709
1687

Debug support (DBG)

40.6

RM0385

ID codes and locking mechanism
There are several ID codes inside the STM32F75xxx and STM32F74xxx MCUs. ST strongly
recommends tools designers to lock their debuggers using the MCU DEVICE ID code
located in the external PPB memory map at address 0xE0042000.

40.6.1

MCU device ID code
The STM32F75xxx and STM32F74xxx MCUs integrate an MCU ID code. This ID identifies
the ST MCU part-number and the die revision. It is part of the DBG_MCU component and is
mapped on the external PPB bus (see Section 40.16 on page 1675). This code is
accessible using the JTAG debug port (4 to 5 pins) or the SW debug port (two pins) or by
the user software. It is even accessible while the MCU is under system reset.
Only the DEV_ID(11:0) should be used for identification by the debugger/programmer tools.

DBGMCU_IDCODE
Address: 0xE004 2000
Only 32-bits access supported. Read-only.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

5

4

3

2

1

0

r

r

r

r

r

REV_ID
r

r

r

r

r

r

r

r

r

r

11

10

9

8

7

6

15

14

13

12

Res.

Res.

Res.

Res.

DEV_ID
r

r

r

r

r

r

r

Bits 31:16 REV_ID[15:0] Revision identifier
This field indicates the revision of the device:
0x1000 = Revision A
0x1001 = Revision Z
Bits 15:12

Reserved, must be kept at reset value.

Bits 11:0 DEV_ID[11:0]: Device identifier
The device ID is 0x449.

40.6.2

Boundary scan Debug Port
JTAG ID code
The Debug Port of the STM32F75xxx and STM32F74xxx BSC (boundary scan) integrates a
JTAG ID code equal to 0x06449041.

40.6.3

Cortex®-M7 with FPU Debug Port
The Debug Port of the Arm® Cortex®-M7 with FPU integrates a JTAG ID code. This ID code
is the Arm® default one and has not been modified. This code is only accessible by the
JTAG Debug Port.
This code is 0x5BA00477 (corresponds to Cortex®-M7 with FPU, see Section 40.2:
Reference Arm® documentation).

1662/1709

RM0385 Rev 7

RM0385

40.6.4

Debug support (DBG)

Cortex®-M7 with FPU JEDEC-106 ID code
The Arm® Cortex®-M7 with FPU integrates a JEDEC-106 ID code. It is located in the 4KB
ROM table mapped on the internal PPB bus at address 0xE00FF000_0xE00FFFFF.
This code is accessible by the JTAG Debug Port (4 to 5 pins) or by the SW Debug Port (two
pins) or by the user software.

40.7

JTAG debug port
A standard JTAG state machine is implemented with a 4-bit instruction register (IR) and five
data registers (for full details, refer to the Cortex®-M7 with FPU technical reference manual
(TRM), for references, see Section 40.2: Reference Arm® documentation).
Table 288. JTAG debug port data registers
IR(3:0)

Data register

Details

1111

BYPASS
[1 bit]

-

1110

IDCODE
[32 bits]

ID CODE
0x06449041 (Arm® Cortex®-M7 with FPU ID Code)

DPACC
[35 bits]

Debug port access register
This initiates a debug port and allows access to a debug port register.
– When transferring data IN:
Bits 34:3 = DATA[31:0] = 32-bit data to transfer for a write request
Bits 2:1 = A[3:2] = 2-bit address of a debug port register.
Bit 0 = RnW = Read request (1) or write request (0).
– When transferring data OUT:
Bits 34:3 = DATA[31:0] = 32-bit data which is read following a read
request
Bits 2:0 = ACK[2:0] = 3-bit Acknowledge:
010 = OK/FAULT
001 = WAIT
OTHER = reserved
Refer to Table 289 for a description of the A(3:2) bits

1010

RM0385 Rev 7

1663/1709
1687

Debug support (DBG)

RM0385
Table 288. JTAG debug port data registers (continued)

IR(3:0)

1664/1709

Data register

Details

1011

APACC
[35 bits]

Access port access register
Initiates an access port and allows access to an access port register.
– When transferring data IN:
Bits 34:3 = DATA[31:0] = 32-bit data to shift in for a write request
Bits 2:1 = A[3:2] = 2-bit address (sub-address AP registers).
Bit 0 = RnW= Read request (1) or write request (0).
– When transferring data OUT:
Bits 34:3 = DATA[31:0] = 32-bit data which is read following a read
request
Bits 2:0 = ACK[2:0] = 3-bit Acknowledge:
010 = OK/FAULT
001 = WAIT
OTHER = reserved
There are many AP Registers (see AHB-AP) addressed as the
combination of:
– The shifted value A[3:2]
– The current value of the DP SELECT register

1000

ABORT
[35 bits]

Abort register
– Bits 31:1 = Reserved
– Bit 0 = DAPABORT: write 1 to generate a DAP abort.

RM0385 Rev 7

RM0385

Debug support (DBG)
Table 289. 32-bit debug port registers addressed through the shifted value A[3:2]
Address A(3:2) value
0x0

Description

00

Reserved, must be kept at reset value.

01

DP CTRL/STAT register. Used to:
– Request a system or debug power-up
– Configure the transfer operation for AP accesses
– Control the pushed compare and pushed verify operations.
– Read some status flags (overrun, power-up acknowledges)

0x8

10

DP SELECT register: Used to select the current access port and the
active 4-words register window.
– Bits 31:24: APSEL: select the current AP
– Bits 23:8: reserved
– Bits 7:4: APBANKSEL: select the active 4-words register window on the
current AP
– Bits 3:0: reserved

0xC

11

DP RDBUFF register: Used to allow the debugger to get the final result
after a sequence of operations (without requesting new JTAG-DP
operation)

0x4

40.8

SW debug port

40.8.1

SW protocol introduction
This synchronous serial protocol uses two pins:
•

SWCLK: clock from host to target

•

SWDIO: bidirectional

The protocol allows two banks of registers (DPACC registers and APACC registers) to be
read and written to.
Bits are transferred LSB-first on the wire.
For SWDIO bidirectional management, the line must be pulled-up on the board (100 kΩ
recommended by Arm®).
Each time the direction of SWDIO changes in the protocol, a turnaround time is inserted
where the line is not driven by the host nor the target. By default, this turnaround time is one
bit time, however this can be adjusted by configuring the SWCLK frequency.

40.8.2

SW protocol sequence
Each sequence consist of three phases:
1.

Packet request (8 bits) transmitted by the host

2.

Acknowledge response (3 bits) transmitted by the target

3.

Data transfer phase (33 bits) transmitted by the host or the target

RM0385 Rev 7

1665/1709
1687

Debug support (DBG)

RM0385
Table 290. Packet request (8-bits)

Bit

Name

Description

0

Start

Must be “1”

1

APnDP

0: DP Access
1: AP Access

2

RnW

0: Write Request
1: Read Request

4:3

A(3:2)

Address field of the DP or AP registers (refer to Table 289)

5

Parity

Single bit parity of preceding bits

6

Stop

0

7

Park

Not driven by the host. Must be read as “1” by the target because of
the pull-up

Refer to the Cortex®-M7 with FPU TRM for a detailed description of DPACC and APACC
registers.
The packet request is always followed by the turnaround time (default 1 bit) where neither
the host nor target drive the line.
Table 291. ACK response (3 bits)
Bit
0..2

Name

Description
001: FAULT
010: WAIT
100: OK

ACK

The ACK Response must be followed by a turnaround time only if it is a READ transaction
or if a WAIT or FAULT acknowledge has been received.
Table 292. DATA transfer (33 bits)
Bit
0..31
32

Name

Description

WDATA or RDATA Write or Read data
Parity

Single parity of the 32 data bits

The DATA transfer must be followed by a turnaround time only if it is a READ transaction.

40.8.3

SW-DP state machine (reset, idle states, ID code)
The State Machine of the SW-DP has an internal ID code which identifies the SW-DP. It
follows the JEP-106 standard. This ID code is the default Arm® one and is set to
0x5BA02477 (corresponding to Cortex®-M7 with FPU).

1666/1709

RM0385 Rev 7

RM0385
Note:

Debug support (DBG)
Note that the SW-DP state machine is inactive until the target reads this ID code.
•

The SW-DP state machine is in RESET STATE either after power-on reset, or after the
DP has switched from JTAG to SWD or after the line is high for more than 50 cycles

•

The SW-DP state machine is in IDLE STATE if the line is low for at least two cycles
after RESET state.

•

After RESET state, it is mandatory to first enter into an IDLE state AND to perform a
READ access of the DP-SW ID CODE register. Otherwise, the target will issue a
FAULT acknowledge response on another transactions.

Further details of the SW-DP state machine can be found in the Cortex®-M7 with FPU TRM
and the CoreSight Components Technical Reference Manual.

40.8.4

40.8.5

DP and AP read/write accesses
•

Read accesses to the DP are not posted: the target response can be immediate (if
ACK=OK) or can be delayed (if ACK=WAIT).

•

Read accesses to the AP are posted. This means that the result of the access is
returned on the next transfer. If the next access to be done is NOT an AP access, then
the DP-RDBUFF register must be read to obtain the result.
The READOK flag of the DP-CTRL/STAT register is updated on every AP read access
or RDBUFF read request to know if the AP read access was successful.

•

The SW-DP implements a write buffer (for both DP or AP writes), that enables it to
accept a write operation even when other transactions are still outstanding. If the write
buffer is full, the target acknowledge response is “WAIT”. With the exception of
IDCODE read or CTRL/STAT read or ABORT write which are accepted even if the write
buffer is full.

•

Because of the asynchronous clock domains SWCLK and HCLK, two extra SWCLK
cycles are needed after a write transaction (after the parity bit) to make the write
effective internally. These cycles should be applied while driving the line low (IDLE
state)
This is particularly important when writing the CTRL/STAT for a power-up request. If the
next transaction (requiring a power-up) occurs immediately, it will fail.

SW-DP registers
Access to these registers are initiated when APnDP=0
Table 293. SW-DP registers
A(3:2)

R/W

CTRLSEL bit
of SELECT
register

Register

00

Read

-

IDCODE

00

Write

-

ABORT

RM0385 Rev 7

Notes
The manufacturer code is not set to ST
code. 0x5BA02477 (identifies the SW-DP)
-

1667/1709
1687

Debug support (DBG)

RM0385
Table 293. SW-DP registers (continued)

A(3:2)

CTRLSEL bit
of SELECT
register

Register

Notes

01

Read/Write

0

DPCTRL/STAT

Purpose is to:
– request a system or debug power-up
– configure the transfer operation for AP
accesses
– control the pushed compare and pushed
verify operations.
– read some status flags (overrun, powerup acknowledges)

01

Read/Write

1

WIRE
CONTROL

Purpose is to configure the physical serial
port protocol (like the duration of the
turnaround time)

10

Read

-

READ
RESEND

Enables recovery of the read data from a
corrupted debugger transfer, without
repeating the original AP transfer.

10

Write

-

SELECT

The purpose is to select the current access
port and the active 4-words register window

READ
BUFFER

This read buffer is useful because AP
accesses are posted (the result of a read AP
request is available on the next AP
transaction).
This read buffer captures data from the AP,
presented as the result of a previous read,
without initiating a new transaction

11

40.8.6

R/W

Read/Write

-

SW-AP registers
Access to these registers are initiated when APnDP=1
There are many AP Registers (see AHB-AP) addressed as the combination of:

1668/1709

•

The shifted value A[3:2]

•

The current value of the DP SELECT register

RM0385 Rev 7

RM0385

40.9

Debug support (DBG)

AHB-AP (AHB access port) - valid for both JTAG-DP
and SW-DP
Features:
•

System access is independent of the processor status.

•

Either SW-DP or JTAG-DP accesses AHB-AP.

•

The AHB-AP is an AHB master into the Bus Matrix. Consequently, it can access all the
data buses (Dcode Bus, System Bus, internal and external PPB bus) but the ICode
bus.

•

Bitband transactions are supported.

•

AHB-AP transactions bypass the FPB.

The address of the 32-bits AHP-AP registers are 6-bits wide (up to 64 words or 256 bytes)
and consists of:
c)

Bits [7:4] = the bits [7:4] APBANKSEL of the DP SELECT register

d)

Bits [3:2] = the 2 address bits of A(3:2) of the 35-bit packet request for SW-DP.

The AHB-AP of the Cortex®-M7 with FPU includes 9 x 32-bits registers:
Table 294. Cortex®-M7 with FPU AHB-AP registers
Address
offset

Register name

Notes
Configures and controls transfers through the AHB
interface (size, hprot, status on current transfer, address
increment type

0x00

AHB-AP Control and Status
Word

0x04

AHB-AP Transfer Address

-

0x0C

AHB-AP Data Read/Write

-

0x10

AHB-AP Banked Data 0

0x14

AHB-AP Banked Data 1

0x18

AHB-AP Banked Data 2

0x1C

AHB-AP Banked Data 3

0xF8

AHB-AP Debug ROM Address Base Address of the debug interface

0xFC

AHB-AP ID Register

Directly maps the 4 aligned data words without rewriting
the Transfer Address Register.

-

Refer to the Cortex®-M7 with FPU TRM for further details.

RM0385 Rev 7

1669/1709
1687

Debug support (DBG)

40.10

RM0385

Core debug
Core debug is accessed through the core debug registers. Debug access to these registers
is by means of the Advanced High-performance Bus (AHB-AP) port. The processor can
access these registers directly over the internal Private Peripheral Bus (PPB).
It consists of 4 registers:
Table 295. Core debug registers

Note:

Register

Description

DHCSR

The 32-bit Debug Halting Control and Status Register
This provides status information about the state of the processor enable core debug
halt and step the processor

DCRSR

The 17-bit Debug Core Register Selector Register:
This selects the processor register to transfer data to or from.

DCRDR

The 32-bit Debug Core Register Data Register:
This holds data for reading and writing registers to and from the processor selected
by the DCRSR (Selector) register.

DEMCR

The 32-bit Debug Exception and Monitor Control Register:
This provides Vector Catching and Debug Monitor Control. This register contains a
bit named TRCENA which enable the use of a TRACE.

Important: these registers are not reset by a system reset. They are only reset by a poweron reset.
Refer to the Cortex®-M7 with FPU TRM for further details.
To Halt on reset, it is necessary to:

1670/1709

•

enable the bit0 (VC_CORRESET) of the Debug and Exception Monitor Control
Register

•

enable the bit0 (C_DEBUGEN) of the Debug Halting Control and Status Register.

RM0385 Rev 7

RM0385

40.11

Debug support (DBG)

Capability of the debugger host to connect under system
reset
The reset system of the STM32F75xxx and STM32F74xxx MCU comprises the following
reset sources:
•

POR (power-on reset) which asserts a RESET at each power-up.

•

Internal watchdog reset

•

Software reset

•

External reset

The Cortex®-M7 with FPU differentiates the reset of the debug part (generally
PORRESETn) and the other one (SYSRESETn)
This way, it is possible for the debugger to connect under System Reset, programming the
Core Debug Registers to halt the core when fetching the reset vector. Then the host can
release the system reset and the core will immediately halt without having executed any
instructions. In addition, it is possible to program any debug features under System Reset.
Note:

It is highly recommended for the debugger host to connect (set a breakpoint in the reset
vector) under system reset.

40.12

FPB (Flash patch breakpoint)
Typically in Cortex-M architecture the FPB unit allows to:
•

implement hardware breakpoints

•

patch code and data from code space to system space. This feature gives the
possibility to correct software bugs located in the Code Memory Space.

Where the use of a Software Patch or a Hardware Breakpoint is exclusive.
But there are some major changes in Pelican FPB:
•

Flash patching is no more supported (there is no FP_REMAP register)

•

All comparators are for instruction addresses (up to 8 instruction breakpoints)

•

Programmer’s model for breakpoint comparators is enhanced to allow hardware
breakpoint in full address range.

RM0385 Rev 7

1671/1709
1687

Debug support (DBG)

40.13

RM0385

DWT (data watchpoint trigger)
The DWT unit consists of four comparators. They are configurable as:
•

a hardware watchpoint or

•

a trigger to an ETM or

•

a PC sampler or

•

a data address sampler

The DWT also provides some means to give some profiling informations. For this, some
counters are accessible to give the number of:
•

Clock cycle

•

Folded instructions

•

Load store unit (LSU) operations

•

Sleep cycles

•

CPI (clock per instructions)

•

Interrupt overhead

40.14

ITM (instrumentation trace macrocell)

40.14.1

General description
The ITM is an application-driven trace source that supports printf style debugging to trace
Operating System (OS) and application events, and emits diagnostic system information.
The ITM emits trace information as packets which can be generated as:
•

Software trace. Software can write directly to the ITM stimulus registers to emit
packets.

•

Hardware trace. The DWT generates these packets, and the ITM emits them.

•

Time stamping. Timestamps are emitted relative to packets. The ITM contains a 21-bit
counter to generate the timestamp. The Cortex®-M7 with FPU clock or the bit clock rate
of the Serial Wire Viewer (SWV) output clocks the counter.

The packets emitted by the ITM are output to the TPIU (Trace Port Interface Unit). The
formatter of the TPIU adds some extra packets (refer to TPIU) and then output the complete
packets sequence to the debugger host.
The bit TRCEN of the Debug Exception and Monitor Control Register must be enabled
before you program or use the ITM.

40.14.2

Time stamp packets, synchronization and overflow packets
Time stamp packets encode time stamp information, generic control and synchronization. It
uses a 21-bit timestamp counter (with possible prescalers) which is reset at each time
stamp packet emission. This counter can be either clocked by the CPU clock or the SWV
clock.
A synchronization packet consists of 6 bytes equal to 0x80_00_00_00_00_00 which is
emitted to the TPIU as 00 00 00 00 00 80 (LSB emitted first).
A synchronization packet is a timestamp packet control. It is emitted at each DWT trigger.

1672/1709

RM0385 Rev 7

RM0385

Debug support (DBG)
For this, the DWT must be configured to trigger the ITM: the bit CYCCNTENA (bit0) of the
DWT Control Register must be set. In addition, the bit2 (SYNCENA) of the ITM Trace
Control Register must be set.

Note:

If the SYNENA bit is not set, the DWT generates Synchronization triggers to the TPIU which
will send only TPIU synchronization packets and not ITM synchronization packets.
An overflow packet consists is a special timestamp packets which indicates that data has
been written but the FIFO was full.
Table 296. Main ITM registers
Address
@E0000FB0

Register
ITM lock access

Details
Write 0xC5ACCE55 to unlock Write Access to the other ITM
registers
Bits 31-24 = Always 0
Bits 23 = Busy
Bits 22-16 = 7-bits ATB ID which identifies the source of the
trace data.
Bits 15-10 = Always 0
Bits 9:8 = TSPrescale = Time Stamp Prescaler
Bits 7-5 = Reserved

@E0000E80

ITM trace control

Bit 4 = SWOENA = Enable SWV behavior (to clock the
timestamp counter by the SWV clock).
Bit 3 = DWTENA: Enable the DWT Stimulus
Bit 2 = SYNCENA: this bit must be to 1 to enable the DWT to
generate synchronization triggers so that the TPIU can then
emit the synchronization packets.
Bit 1 = TSENA (Timestamp Enable)
Bit 0 = ITMENA: Global Enable Bit of the ITM
Bit 3: mask to enable tracing ports31:24

@E0000E40

ITM trace privilege

Bit 2: mask to enable tracing ports23:16
Bit 1: mask to enable tracing ports15:8
Bit 0: mask to enable tracing ports7:0

@E0000E00

ITM trace enable

@E0000000- Stimulus port
E000007C
registers 0-31

Each bit enables the corresponding Stimulus port to generate
trace.
Write the 32-bits data on the selected Stimulus Port (32
available) to be traced out.

RM0385 Rev 7

1673/1709
1687

Debug support (DBG)

RM0385

Example of configuration
To output a simple value to the TPIU:
•

Configure the TPIU and assign TRACE I/Os by configuring the DBGMCU_CR (refer to
Section 40.17.2: TRACE pin assignment and Section 40.16.3: Debug MCU
configuration register)

•

Write 0xC5ACCE55 to the ITM Lock Access Register to unlock the write access to the
ITM registers

•

Write 0x00010005 to the ITM Trace Control Register to enable the ITM with Sync
enabled and an ATB ID different from 0x00

•

Write 0x1 to the ITM Trace Enable Register to enable the Stimulus Port 0

•

Write 0x1 to the ITM Trace Privilege Register to unmask stimulus ports 7:0

•

Write the value to output in the Stimulus Port Register 0: this can be done by software
(using a printf function)

40.15

ETM (Embedded trace macrocell)

40.15.1

General description
The ETM enables the reconstruction of program execution. Data are traced using the Data
Watchpoint and Trace (DWT) component or the Instruction Trace Macrocell (ITM) whereas
instructions are traced using the Embedded Trace Macrocell (ETM).
The ETM transmits information as packets and is triggered by embedded resources. These
resources must be programmed independently and the trigger source is selected using the
Trigger Event Register (0xE0041008). An event could be a simple event (address match
from an address comparator) or a logic equation between 2 events. The trigger source is
one of the fourth comparators of the DWT module, The following events can be monitored:
•

Clock cycle matching

•

Data address matching

For more informations on the trigger resources refer to Section 40.13: DWT (data
watchpoint trigger).
The packets transmitted by the ETM are output to the TPIU (Trace Port Interface Unit). The
formatter of the TPIU adds some extra packets (refer to Section 40.17: Pelican TPIU (trace
port interface unit)) and then outputs the complete packet sequence to the debugger host.
Note:

N.B: Cortex-M7 ETM is compliant with Arm ETM architecture v4, which programming model
is not backward compatible with Cortex-M4 ETM one (ETM architecture v3.5).

40.15.2

Signal protocol, packet types
This part is described in the chapter 6 ETM v4 architecture specification (IHI0064B).

1674/1709

RM0385 Rev 7

RM0385

40.15.3

Debug support (DBG)

Main ETM registers
For more information on registers refer to the Pelican ETM technical reference manual
(DDI0494-2a) and the ETM v4 architecture specification (IHI0064B).

40.15.4

Configuration example
To output a simple value to the TPIU:
•

Configure trace I/Os: enable TRACE_CLKINEN in the STM32F75xxx and
STM32F74xxx debug configuration register (DBGMCU_CR).

•

Write @ E000EDFC 01000000; SCS: set TRCENA, otherwise trace registers are not
accessible.

•

Write @ E00400F0 00000000; TPIU: select SYNC PORT Mode
Write @ E0040004 00000008; TPIU: select TPIU PORT SIZE=4
Write @ E0001020 002002CA; WT: PC MATCH Comparator (PC=0x2002CA)
Write @ E0001024 00000000; DWT: No mask apply on comparator
Write @ E0001028 00000008; DWT: ETM trig on PC on match

•
•
•
•

ETM:
•
Write @ E0041004 00000000; Disable ETM
•
Read @ E004100C 00000003; ETM should be in Idle state
•
Write @ E0041040 00000002; Instruction trace source ID = 0x2
•
Write @ E0041080 00000001; Resource for ViewInst enabling event is “always
TRUE”

40.16

•

Write @ E004108C 000000FF; Processor comparator selection for Start:

•

Write @ E0041004 00000001; Enable ETM

pc_match0 (=>DWT match)

MCU debug component (DBGMCU)
The MCU debug component helps the debugger provide support for:

40.16.1

•

Low-power modes

•

Clock control for timers, watchdog, I2C and bxCAN during a breakpoint

•

Control of the trace pins assignment

Debug support for low-power modes
To enter low-power mode, the instruction WFI or WFE must be executed.
The MCU implements several low-power modes which can either deactivate the CPU clock
or reduce the power of the CPU.
The core does not allow FCLK or HCLK to be turned off during a debug session. As these
are required for the debugger connection, during a debug, they must remain active. The
MCU integrates special means to allow the user to debug software in low-power modes.

RM0385 Rev 7

1675/1709
1687

Debug support (DBG)

RM0385

For this, the debugger host must first set some debug configuration registers to change the
low-power mode behavior:

40.16.2

•

In Sleep mode, DBG_SLEEP bit of DBGMCU_CR register must be previously set by
the debugger. This will feed HCLK with the same clock that is provided to FCLK
(system clock previously configured by the software).

•

In Stop mode, the bit DBG_STOP must be previously set by the debugger. This will
enable the internal RC oscillator clock to feed FCLK and HCLK in STOP mode.

Debug support for timers, watchdog, bxCAN and I2C
During a breakpoint, it is necessary to choose how the counter of timers and watchdog
should behave:
•

They can continue to count inside a breakpoint. This is usually required when a PWM is
controlling a motor, for example.

•

They can stop to count inside a breakpoint. This is required for watchdog purposes.

For the bxCAN, the user can choose to block the update of the receive register during a
breakpoint.
For the I2C, the user can choose to block the SMBUS timeout during a breakpoint.
For timers having complementary outputs, when the counter is stopped
(DBG_TIMx_STOP=1), the outputs are disabled (as if the MOE bit was reset) for safety
purposes.

40.16.3

Debug MCU configuration register
This register allows the configuration of the MCU under DEBUG. This concerns:
•

Low-power mode support

•

Timer and watchdog counter support

•

bxCAN communication support

•

Trace pin assignment

This DBGMCU_CR is mapped on the External PPB bus at address 0xE0042004
It is asynchronously reset by the PORESET (and not the system reset). It can be written by
the debugger under system reset.
If the debugger host does not support these features, it is still possible for the user software
to write to these registers.

1676/1709

RM0385 Rev 7

RM0385

Debug support (DBG)

40.16.4

DBGMCU_CR register
Address: 0xE004 2004
Only 32-bit access supported
POR Reset: 0x0000 0000 (not reset by system reset)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

DBG_
STAND
BY

DBG_
STOP

DBG_
SLEEP

rw

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TRACE_
MODE
[1:0]
rw

rw

TRACE
_CLKIN
EN
rw

Res.

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:5 TRACE_MODE[1:0] and TRACE_CLKINEN: Trace clock and pin assignment control
– With TRACE_CLKINEN=0:
TRACE_MODE=xx: TRACE output disabled (both synchronous and asynchronous)
– With TRACE_CLKINEN=1:
–
TRACE_MODE[1:0]=00: Aynchronous trace interface enabled at pad level
(TRACESWO available only on TDO pad when using Serial Wire mode) /
Synchronous trace interface enabled
–
TRACE_MODE[1:0] different to =00: Asynchronous trace interface disabled /
Synchronous trace interface enabled
Bits 4:3 Reserved, must be kept at reset value.

RM0385 Rev 7

1677/1709
1687

Debug support (DBG)

RM0385

Bit 2 DBG_STANDBY: Debug Standby mode
0: (FCLK=Off, HCLK=Off) The whole digital part is unpowered.
From software point of view, exiting from Standby is identical than fetching reset vector
(except a few status bit indicated that the MCU is resuming from Standby)
1: (FCLK=On, HCLK=On) In this case, the digital part is not unpowered and FCLK and
HCLK are provided by the internal RC oscillator which remains active. In addition, the MCU
generate a system reset during Standby mode so that exiting from Standby is identical than
fetching from reset
Bit 1 DBG_STOP: Debug Stop mode
0: (FCLK=Off, HCLK=Off) In STOP mode, the clock controller disables all clocks (including
HCLK and FCLK). When exiting from STOP mode, the clock configuration is identical to the
one after RESET (CPU clocked by the 8 MHz internal RC oscillator (HSI)). Consequently,
the software must reprogram the clock controller to enable the PLL, the Xtal, etc.
1: (FCLK=On, HCLK=On) In this case, when entering STOP mode, FCLK and HCLK are
provided by the internal RC oscillator which remains active in STOP mode. When exiting
STOP mode, the software must reprogram the clock controller to enable the PLL, the Xtal,
etc. (in the same way it would do in case of DBG_STOP=0)
Bit 0 DBG_SLEEP: Debug Sleep mode
0: (FCLK=On, HCLK=Off) In Sleep mode, FCLK is clocked by the system clock as
previously configured by the software while HCLK is disabled.
In Sleep mode, the clock controller configuration is not reset and remains in the previously
programmed state. Consequently, when exiting from Sleep mode, the software does not
need to reconfigure the clock controller.
1: (FCLK=On, HCLK=On) In this case, when entering Sleep mode, HCLK is fed by the same
clock that is provided to FCLK (system clock as previously configured by the software).

40.16.5

Debug MCU APB1 freeze register (DBGMCU_APB1_FZ)
The DBGMCU_APB1_FZ register is used to configure the MCU under DEBUG. It concerns
APB2 peripherals. It is mapped on the external PPB bus at address 0xE004 2008
It is asynchronously reset by the POR (and not the system reset). It can be written by the
debugger under system reset.
Address: 0xE004 2008
Only 32-bit access is supported.
Power-on-reset (POR): 0x0000 0000 (not reset by system reset)

1678/1709

RM0385 Rev 7

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

DBG_CAN2_STOP

DBG_CAN1_STOP

DBG_I2C4_SMBUS_TIMEOUT

DBG_I2C3_SMBUS_TIMEOUT

DBG_I2C2_SMBUS_TIMEOUT

DBG_I2C1_SMBUS_TIMEOUT

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

DBG_WWDG_STOP

DBG_RTC_STOP

DBG_LPTIM1_STOP

DBG_TIM14_STOP

DBG_TIM13_STOP

DBG_TIM12_STOP

DBG_TIM7_STOP

DBG_TIM6_STOP

DBG_TIM5_STOP

DBG_TIM4_STOP

DBG_TIM3_STOP

DBG_TIM2_STOP

Debug support (DBG)

DBG_IWDG_STOP

RM0385

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:27

Reserved, must be kept at reset value.

Bit 26 DBG_CAN2_STOP: Debug CAN2 stopped when Core is halted
0: Same behavior as in normal mode
1: The CAN2 receive registers are frozen
Bit 25 DBG_CAN1_STOP: Debug CAN2 stopped when Core is halted
0: Same behavior as in normal mode
1: The CAN2 receive registers are frozen
Bit 24 DBG_I2C4_SMBUS_TIMEOUT: SMBUS timeout mode stopped when Core is halted
0: Same behavior as in normal mode
1: The SMBUS timeout is frozen
Bit 23 DBG_I2C3_SMBUS_TIMEOUT: SMBUS timeout mode stopped when Core is halted
0: Same behavior as in normal mode
1: The SMBUS timeout is frozen
Bit 22 DBG_I2C2_SMBUS_TIMEOUT: SMBUS timeout mode stopped when Core is halted
0: Same behavior as in normal mode
1: The SMBUS timeout is frozen
Bit 21 DBG_I2C1_SMBUS_TIMEOUT: SMBUS timeout mode stopped when Core is halted
0: Same behavior as in normal mode
1: The SMBUS timeout is frozen
Bits 20:13

Reserved, must be kept at reset value.

Bit 12 DBG_IWDG_STOP: Debug independent watchdog stopped when core is halted
0: The independent watchdog counter clock continues even if the core is halted
1: The independent watchdog counter clock is stopped when the core is halted
Bit 11 DBG_WWDG_STOP: Debug Window Watchdog stopped when Core is halted
0: The window watchdog counter clock continues even if the core is halted
1: The window watchdog counter clock is stopped when the core is halted

RM0385 Rev 7

1679/1709
1687

Debug support (DBG)

RM0385

Bit 10 DBG_RTC_STOP: RTC stopped when Core is halted
0: The RTC counter clock continues even if the core is halted
1: The RTC counter clock is stopped when the core is halted
Bit 9 DBG_LPTIM1_STOP: LPTMI1 counter stopped when core is halted
0: The clock of LPTIM1 counter is fed even if the core is halted
1: The clock of LPTIM1 counter is stopped when the core is halted
Bits 8:0 DBG_TIMx_STOP: TIMx counter stopped when core is halted (x=2..7, 12..14)
0: The clock of the involved Timer Counter is fed even if the core is halted
1: The clock of the involved Timer counter is stopped and the outputs are disabled when the
core is halted

40.16.6

Debug MCU APB2 Freeze register (DBGMCU_APB2_FZ)
The DBGMCU_APB2_FZ register is used to configure the MCU under Debug. It concerns
APB2 peripherals.
This register is mapped on the external PPB bus at address 0xE004 200C
It is asynchronously reset by the POR (and not the system reset). It can be written by the
debugger under system reset.
Address: 0xE004 200C
Only 32-bit access is supported.
POR: 0x0000 0000 (not reset by system reset)

31
Res.

30

29

Res.

Res.

28
Res.

27
Res.

26
Res.

25
Res.

24
Res.

23
Res.

22
Res.

21
Res.

20
Res.

19
Res.

18

rw
15
Res.

14

13

Res.

Res.

12
Res.

11
Res.

10
Res.

9
Res.

8
Res.

7
Res.

6
Res.

5
Res.

4
Res.

3
Res.

17

2
Res.

rw

rw

1

0

DBG_TIM8_ DBG_TIM1_
STOP
STOP
rw

Bits 31:19

16

DBG_TIM11 DBG_TIM10 DBG_TIM9_
_STOP
_STOP
STOP

rw

Reserved, must be kept at reset value.

Bits 18:16 DBG_TIMx_STOP: TIMx counter stopped when core is halted (x=9..11)
0: The clock of the involved Timer Counter is fed even if the core is halted
1: The clock of the involved Timer counter is stopped and the outputs are disabled when the
core is halted
Bits 15:2

Reserved, must be kept at reset value.

Bit 1 DBG_TIM8_STOP: TIM8 counter stopped when core is halted
0: The clock of the involved Timer Counter is fed even if the core is halted
1: The clock of the involved Timer counter is stopped and the output is disabled when the
core is halted
Bit 0 DBG_TIM1_STOP: TIM1 counter stopped when core is halted
0: The clock of the involved Timer Counter is fed even if the core is halted
1: The clock of the involved Timer counter is stopped and the output is disabled when the
core is halted

1680/1709

RM0385 Rev 7

RM0385

Debug support (DBG)

40.17

Pelican TPIU (trace port interface unit)

40.17.1

Introduction
The TPIU acts as a bridge between the on-chip trace data from the ITM, the ETM and the
external trace capture device.
The output data stream encapsulates the trace source ID, that is then captured by a trace
port analyzer (TPA).
The core embeds a simple TPIU, especially designed for low-cost debug (consisting of a
special version of the CoreSight TPIU).
Figure 540. TPIU block diagram

RM0385 Rev 7

1681/1709
1687

Debug support (DBG)

40.17.2

RM0385

TRACE pin assignment
•

Asynchronous mode
The asynchronous mode requires 1 extra pin and is available on all packages. It is only
available if using Serial Wire mode (not in JTAG mode).
Table 297. Asynchronous TRACE pin assignment
Trace synchronous mode
TPIU pin name
Type

TRACESWO

•

O

Description
TRACE Async Data Output

Synchronous mode
The synchronous mode requires from 2 to 6 extra pins depending on the data trace
size and is only available in the larger packages. In addition it is available in JTAG
mode and in Serial Wire mode and provides better bandwidth output capabilities than
asynchronous trace.
Table 298. Synchronous TRACE pin assignment
Trace synchronous mode
TPIU pin name
Type

Description

TRACECK

O

TRACE Clock

TRACED[3:0]

O

TRACE Sync Data Outputs
Can be 1, 2 or 4.

TPIU TRACE pin assignment
By default, these pins are NOT assigned. They can be assigned by setting the
TRACE_CLKINEN and TRACE_MODE bits in the MCU Debug component configuration
register. This configuration has to be done by the debugger host.
In addition, the number of pins to assign depends on the trace configuration (asynchronous
or synchronous).
•

Asynchronous mode: 1 extra pin is needed

•

Synchronous mode: from 2 to 5 extra pins are needed depending on the size of the
data trace port register (1, 2 or 4):
–

TRACECK

–

TRACED(0) if port size is configured to 1, 2 or 4

–

TRACED(1) if port size is configured to 2 or 4

–

TRACED(2) if port size is configured to 4

–

TRACED(3) if port size is configured to 4

To assign the TRACE pin, the debugger host must program the bits TRACE_CLKINEN and
TRACE_MODE[1:0] of the Debug MCU configuration register (DBGMCU_CR). By default
the TRACE pins are not assigned.
This register is mapped on the external PPB and is reset by the PORESET (and not by the
SYSTEM reset). It can be written by the debugger under SYSTEM reset.

1682/1709

RM0385 Rev 7

RM0385

Debug support (DBG)
Table 299. Flexible TRACE pin assignment

DBGMCU_CR
register

TRACE IO pin assigned

Pins
TRAC TRACE assigned for:
JTDO/
E_CL _MODE
TRACECK TRACED[0] TRACED[1] TRACED[2] TRACED[3]
TRACESWO
KINEN [1:0]
0

XX

No Trace
(default state)

1

00

Asynchronous
TRACESWO
Trace

1

different Synchronous
of 00
Trace 1 bit(2)

1

different Synchronous
of 00
Trace 2 bit(2)

1

different Synchronous
of 00
Trace 4 bit(2)

Released (1)

-

TRACECK TRACED[0]
Released (1)

Released
(usable as GPIO)

-

TRACECK TRACED[0] TRACED[1]

-

-

-

-

TRACECK TRACED[0] TRACED[1] TRACED[2] TRACED[3]

1. When Serial Wire mode is used, it is released. But when JTAG is used, it is assigned to JTDO.
2. Selected with Bit[3:0] Current port size from TPIU register.

Note:

By default, the TRACECLKIN input clock of the TPIU is tied to GND. It is assigned to HCLK
two clock cycles after the bit TRACE_CLKINEN has been set.
The debugger must then program the Trace Mode by writing the PROTOCOL[1:0] bits in the
SPP_R (Selected Pin Protocol) register of the TPIU.
•

PROTOCOL=00: Trace Port Mode (synchronous)

•

PROTOCOL=01 or 10: Serial Wire (Manchester or NRZ) Mode (asynchronous mode).
Default state is 01

It then also configures the TRACE port size by writing the bits [3:0] in the CPSPS_R
(Current Sync Port Size Register) of the TPIU:
•

0x1 for 1 pin (default state)

•

0x2 for 2 pins

•

0x8 for 4 pins

RM0385 Rev 7

1683/1709
1687

Debug support (DBG)

40.17.3

RM0385

TPIU formatter
The purpose of this formatter is to build 128 bit frames containing trace data from,
potentially, both the ETM and the ITM, and to allow at a trace analyzer level a correlation
between trace packets and emitters.
The formatter protocol outputs data in 16-byte frames:
•

seven bytes of data

•

eight bytes of mixed-use bytes consisting of:

•

–

1 bit (LSB) to indicate it is a DATA byte (‘0) or an ID byte (‘1).

–

7 bits (MSB) which can be data or change of source ID trace.

one byte of auxiliary bits where each bit corresponds to one of the eight mixed-use
bytes:
–

if the corresponding byte was a data, this bit gives bit0 of the data.

–

if the corresponding byte was an ID change, this bit indicates when that ID change
takes effect.

Note:

Refer to the Arm® CoreSight Architecture Specification v1.0 (Arm® IHI 0029B) for further
information

40.17.4

TPIU frame synchronization packets
The TPIU can generate two types of synchronization packets:
•

The Frame Synchronization packet (or Full Word Synchronization packet)
It consists of the word: 0x7F_FF_FF_FF (LSB emitted first). This sequence can not
occur at any other time provided that the ID source code 0x7F has not been used.
It is output periodically between frames.
In continuous mode, the TPA must discard all these frames once a synchronization
frame has been found.

•

The Half-Word Synchronization packet
It consists of the half word: 0x7F_FF (LSB emitted first).
It is output periodically between or within frames.
These packets are only generated in continuous mode and enable the TPA to detect
that the TRACE port is in IDLE mode (no TRACE to be captured). When detected by
the TPA, it must be discarded.

40.17.5

Transmission of the synchronization frame packet
There is no Synchronization Counter register implemented in the TPIU of the core.
Consequently, the synchronization trigger can only be generated by the DWT. Refer to the
registers DWT Control Register (bits SYNCTAP[11:10]) and the DWT Current PC Sampler
Cycle Count Register.
The TPIU Frame synchronization packet (0x7F_FF_FF_FF) is emitted:
•

1684/1709

after each TPIU reset release. This reset is synchronously released with the rising
edge of the TRACECLKIN clock. This means that this packet is transmitted when the

RM0385 Rev 7

RM0385

Debug support (DBG)
TRACE_CLKINEN bit in the DBGMCU_CFG register is set. In this case, the word
0x7F_FF_FF_FF is not followed by any formatted packet.
•

40.17.6

at each DWT trigger (assuming DWT has been previously configured). Two cases
occur:
–

If the bit SYNENA of the ITM is reset, only the word 0x7F_FF_FF_FF is emitted
without any formatted stream which follows.

–

If the bit SYNENA of the ITM is set, then the ITM synchronization packets will
follow (0x80_00_00_00_00_00), formatted by the TPIU (trace source ID added).

Synchronous mode
The trace data output size can be configured to 4, 2 or 1 pin: TRACED(3:0)
The output clock is output to the debugger (TRACECK)
Here, TRACECLKIN is driven internally and is connected to HCLK only when TRACE is
used.

Note:

In this synchronous mode, it is not required to provide a stable clock frequency.
The TRACE I/Os (including TRACECK) are driven by the rising edge of TRACLKIN (equal
to HCLK). Consequently, the output frequency of TRACECK is equal to HCLK/2.

40.17.7

Asynchronous mode
This is a low cost alternative to output the trace using only 1 pin: this is the asynchronous
output pin TRACESWO. Obviously there is a limited bandwidth.
Single IO trace mode is typically suitable for ITM trace output. Also, formatter is disabled in
case of asynchronous trace, so merging of ETM and ITM trace streams is not possible.
TRACESWO is multiplexed with JTDO when using the SW-DP pin. This way, this
functionality is available in all STM32F75xxx and STM32F74xxx packages.
This asynchronous mode requires a constant frequency for TRACECLKIN. For the standard
UART (NRZ) capture mechanism, 5% accuracy is needed. The Manchester encoded
version is tolerant up to 10%.

40.17.8

TRACECLKIN connection inside the
STM32F75xxx and STM32F74xxx
In the STM32F75xxx and STM32F74xxx, this TRACECLKIN input is internally connected to
HCLK. This means that when in asynchronous trace mode, the application is restricted to
use time frames where the CPU frequency is stable.

Note:

Important: when using asynchronous trace: it is important to be aware that:
The default clock of the STM32F75xxx and STM32F74xxx MCUs is the internal RC
oscillator. Its frequency under reset is different from the one after reset release. This is
because the RC calibration is the default one under system reset and is updated at each
system reset release.
Consequently, the trace port analyzer (TPA) should not enable the trace (with the
TRACE_CLKINEN bit) under system reset, because a Synchronization Frame Packet will
be issued with a different bit time than trace packets which will be transmitted after reset
release.

RM0385 Rev 7

1685/1709
1687

Debug support (DBG)

40.17.9

RM0385

TPIU registers
The TPIU APB registers can be read and written only if the bit TRCENA of the Debug
Exception and Monitor Control Register (DEMCR) is set. Otherwise, the registers are read
as zero (the output of this bit enables the PCLK of the TPIU).
Table 300. Important TPIU registers

Address

Register

Description
Allows the trace port size to be selected:
Bit 0: Port size = 1
Bit 1: Port size = 2
Bit 2: Port size = 3, not supported
Bit 3: Port Size = 4
Only 1 bit must be set. By default, the port size is one bit. (0x00000001)

0xE0040004

Current port size

0xE00400F0

Allows the Trace Port Protocol to be selected:
Bit1:0=
00: Sync Trace Port Mode
Selected pin protocol
01: Serial Wire Output - manchester (default value)
10: Serial Wire Output - NRZ
11: reserved

0xE0040304

Formatter and flush
control

Bits 31-9 = always ‘0
Bit 8 = TrigIn = always ‘1 to indicate that triggers are indicated
Bits 7-4 = always 0
Bits 3-2 = always 0
Bit 1 = EnFCont. In Sync Trace mode (Select_Pin_Protocol register
bit1:0=00), this bit is forced to ‘1: the formatter is automatically enabled in
continuous mode. In asynchronous mode (Select_Pin_Protocol register
bit1:0 <> 00), this bit can be written to activate or not the formatter.
Bit 0 = always 0
The resulting default value is 0x102
Note: In synchronous mode, because the TRACECTL pin is not mapped
outside the chip, the formatter is always enabled in continuous mode -this
way the formatter inserts some control packets to identify the source of the
trace packets).

0xE0040300

Formatter and flush
status

Not used in Cortex®-M7 with FPU, always read as 0x00000008

40.17.10 Example of configuration

1686/1709

•

Set the bit TRCENA in the Debug Exception and Monitor Control Register (DEMCR)

•

Write the TPIU Current Port Size Register to the desired value (default is 0x1 for a 1-bit
port size)

•

Write TPIU Formatter and Flush Control Register to 0x102 (default value)

•

Write the TPIU Select Pin Protocol to select the sync or async mode. Example: 0x2 for
async NRZ mode (UART like)

•

Write the DBGMCU control register to 0x20 (bit IO_TRACEN) to assign TRACE I/Os
for async mode. A TPIU Sync packet is emitted at this time (FF_FF_FF_7F)

•

Configure the ITM and write the ITM Stimulus register to output a value

RM0385 Rev 7

0xE004
200C
DBGMCU_
APB2_FZ
Res.

0
0

0
0
0

RM0385 Rev 7
DBG_IWDG_STOP
DBG_WWDG_STOP
DBG_LPTIM1_STOP
DBG_RTC_STOP
DBG_TIM14_STOP
DBG_TIM13_STOP
DBG_TIM12_STOP
DBG_TIM7_STOP
DBG_TIM6_STOP
DBG_TIM5_STOP
DBG_TIM4_STOP
DBG_TIM3_STOP
DBG_TIM2_STOP

0
0
0
0
0
0
0
0
0
0
0
0
0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
DBG_TIM8_STOP
DBG_TIM1_STOP

Res.

Res.

X
X
X
X
X
X
X

Res.
Res.
Res.
TRACE_
MODE
[1:0]
TRACE_
Res.

X
X

0
0
0

DBG_STOP

X

DBG_SLEEP

X

Res.
DBG_STANDBY

X

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

0

Res.

Res.

DBG_TIM8_STOP

X

DBG_I2C2_SMBUS_TIMEOUT

X

Res.

X

Res.

Res.

Res.

Res.

Res.

REV_ID

Res.

DBG_TIM9_STOP

X

DBG_TIM5_STOP

X

Res.

0

DBG_TIM10_STOP

X

DBG_TIM6_STOP

X

Res.

0

Res.

X

Res.

DBG_I2C1_SMBUS_TIMEOUT

0

Res.

X

Res.
DBG_TIM7_STOP

DBG_I2C2_SMBUS_TIMEOUT

0

Res.

X

Res.

DBG_I2C3_SMBUS_TIMEOUT

0

Res.

Reset value

Res.

DBG_CAN1_STOP
DBG_I2C4_SMBUS_TIMEOUT

0

Res.

Reset value

Res.

Res.
X

Res.

Res.
X

Res..

DBGMCU_CR

DBG_CAN2_STOP

X

Res.

X

Res.

X

Res.

Res.

Res.

X

Res.

DBGMCU
_IDCODE

DBG_TIM11_STOP

Reset value
Res.

DBGMCU_
APB1_FZ

Res.

0xE004
2008
Reset value(1)

Res.

0xE004
2004

Res.

0xE004
2000

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register

Res.

Addr.

Res.

40.18

Res.

RM0385
Debug support (DBG)

DBG register map

The following table summarizes the Debug registers.
Table 301. DBG register map and reset values

DEV_ID

0
0
0

0
0

1. The reset value is product dependent. For more information, refer to Section 40.6.1: MCU device ID code.

1687/1709

1687

Device electronic signature

41

RM0385

Device electronic signature
The electronic signature is stored in the Flash memory area. It can be read using the
JTAG/SWD or the CPU. It contains factory-programmed identification data that allow the
user firmware or other external devices to automatically match its interface to the
characteristics of the STM32F75xxx and STM32F74xxx microcontrollers.

41.1

Unique device ID register (96 bits)
The unique device identifier is ideally suited:
•

for use as serial numbers (for example USB string serial numbers or other end
applications)

•

for use as security keys in order to increase the security of code in Flash memory while
using and combining this unique ID with software cryptographic primitives and
protocols before programming the internal Flash memory

•

to activate secure boot processes, etc.

The 96-bit unique device identifier provides a reference number which is unique for any
device and in any context. These bits can never be altered by the user.
The 96-bit unique device identifier can also be read in single bytes/half-words/words in
different ways and then be concatenated using a custom algorithm.

Base address: 0x1FF0 F420
Address offset: 0x00
Read only = 0xXXXX XXXX where X is factory-programmed
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

UID[31:0]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

Bits 31:0 UID[31:0]: X and Y coordinates on the wafer

1688/1709

RM0385 Rev 7

r

r

RM0385

Device electronic signature
Address offset: 0x04
Read only = 0xXXXX XXXX where X is factory-programmed

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

UID[63:48]

UID[47:32]
r

r

r

r

r

r

r

r

r

Bits 31:8 UID[63:40]: LOT_NUM[23:0]
Lot number (ASCII encoded).
Bots 7:0 UID[39:32]: WAF_NUM[7:0]
Wafer number (8-bit unsigned number).

Address offset: 0x08
Read only = 0xXXXX XXXX where X is factory-programmed
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

UID[95:80]
r

r

r

r

r

r

r

15

14

13

12

11

10

9

r

r

r

r

r

r

r

r

r

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

UID[79:64]
r

r

r

r

r

r

r

r

r

Bits 31:0 UID[95:64]: LOT_NUM[55:24]
Lot number (ASCII encoded).

41.2

Flash size
Base address: 0x1FF0 F442
Address offset: 0x00
Read only = 0xXXXX where X is factory-programmed

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

F_SIZE
r

r

r

r

r

r

r

r

Bits 15:0 F_ID(15:0): Flash memory size
This bitfield indicates the size of the device Flash memory expressed in Kbytes.
As an example, 0x0400 corresponds to 1024 Kbytes.

RM0385 Rev 7

1689/1709
1690

Device electronic signature

41.3

RM0385

Package data register
Base address: 0x1FFF 7BF0
Address offset: 0x00
Read only = 0xXXXX where X is factory-programmed

15

14

13

12

11

Res.

Res.

Res.

Res.

Res.

10

9

8

PKG[2:0]
rw

rw

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 15:11 Reserved, must be kept at reset value.
Bits 10:8 PGK[2:0]: Package type
0x1xx: LQFP208 and TFBGA216 package
0x011: LQFP176 and UFBGA176 package
0x010: WLCSP143 and LQFP144 package
0x001: LQFP100 package
0x000: Reserved
Bits 7:0 Reserved, must be kept at reset value.

1690/1709

RM0385 Rev 7

RM0385

42

Revision history

Revision history
Table 302. Document revision history
Date

Revision

21-May-2015

1

Initial release.

2

Updated FMC Section:
Updated Table 82: Programmable NAND Flash access parameters
memory setup time, memory hold max value.
Updated c7amba_fmc_V2_UserSpec:
- Updated Section : Common memory space timing register 2..4
(FMC_PMEM) MEMSEY, MEMHOLD, MEMHIZ registers.
- Updated Section : Attribute memory space timing registers
(FMC_PATT) ATTSET, ATTHOLD, ATTHIZ register.
- Updated Table 88: FMC register map and the bitfield description adding
[x:x].
and FMC_SDCR2 Bit 13 to bit 31 reserved.
- Updated Section : SRAM/NOR-Flash chip-select control registers 1..4
(FMC_BCR1..4) CPSIZE[2:0] bits description adding 011 configuration.
Updated SYSARCHI section:
- Updated Section 2.1.8: DMA memory bus and Section 2.1.9: DMA
peripheral bus adding ‘internal Flash memory’.
- Updated Section 2.1.6: CPU AHBS bus.
Updated Flash memory section:
- Updated Section 3.3.1: Flash memory organization.
- Updated Section 3.3.8: Flash Interrupts replacing FLASH_SR by
FLASH_CR register.
Updated c7amba_ioport_UserSpec removing GPIO port bit reset
register (GPIOx_BRR) (x = A..K) in the bit field and in Table 22: GPIO
register map and reset values.
Updated c7amba_spi2s1_v3_x_UserSpec Section 32.1: Introduction
hidding “full duplex and”.
Updated LTDC section:
- All registers updated, adding [x:x] in the register bit description, register
map and putting bold character format.
- Updated Section 18.4.2: Layer programmable parameters.
- Updated Section 18.7.4: LTDC Total Width Configuration Register
(LTDC_TWCR) TOTALW[11:0] bit field.
- Updated Section 18.7.5: LTDC Global Control Register (LTDC_GCR)
bit 29 description.
Updated USART section:
-Updated note in Section 31.5.13: USART Smartcard mode about the
RTO counter start.
- Updated Table 178: USART interrupt requests removing error in the
line receiver timeout error.

21-Jul-2015

Changes

RM0385 Rev 7

1691/1709
1702

Revision history

RM0385
Table 302. Document revision history (continued)

Date

1692/1709

Revision

Changes

21-Jul-2015

Updated PWR section:
Updated: Table 14, Table 15, Table 17 and Table 18 adding ‘No interrupt
(for WFI) or event (for WFE) is pending’.
Update RTC section:
2
- Updated Section : Programming the wakeup timer point 3: Program the
(continued) wakeup auto-reload value.
- Updated Section 29.6.4: RTC initialization and status register
(RTC_ISR) bit 2 ‘WUTWF: wakeup timer write flag’ description.
Updated DCMI section:
Updated Section 17.1: DCMI introduction. Output mode not supported.

03-Nov-2015

Updated RCC (Reset and Clock Control) section:
- Updated Section 5.3.23: RCC PLLI2S configuration register
(RCC_PLLI2SCFGR) PLLI2S[2:0] by PLLI2SR[2:0].
- Updated Section 5.3.2: RCC PLL configuration register
(RCC_PLLCFGR) PLLN[8:0].
- Updated Section 5.3.23: RCC PLLI2S configuration register
(RCC_PLLI2SCFGR) PLLI2SN[8:0].
- Updated Section 5.3.24: RCC PLLSAI configuration register
(RCC_PLLSAICFGR) PLLSAIN[8:0].
Updated RTC2 section:
Updated Figure 284: RTC block diagram.
Updated GPIO section:
Updated Section 6.4.3: GPIO port output speed register
(GPIOx_OSPEEDR) (x = A..K) OSPEEDRy[1:0] definition.
Updated general-purpose timer:
- Updated Table 150: TIMx internal trigger connection TIM2 ITR1 and
TIM3_ITR2.
- Updated Section 23.4.19: TIM2 option register (TIM2_OR) PTP by
ETH_PTP.
- Updated Section 23.3.13: One-pulse mode replacing by “Map TI2FP2
on TI2 by writing CC2S=01 in the TIMx_CCMR1 register”.
- Removed TIM3_OR register in the bit shield and in the register map.
Updated Lptimer1 section:
- Updated Section 26.3: LPTIM implementation removing LPTIM2 in the
description, removing LPTIM2 option register (LPTIM2_OR) in the bit
field and in the register map.
- Updated Table 159: STM32F75xxx and STM32F74xxx LPTIM features
removing LPTIM2 column.
Updated ethernet section:
Updated Section 38.3: Ethernet pins on page 1518 removing the column
port at the alternate function mapping table and adding reference to the
mapping of the datasheet.
Updated lcdtft section:
Updated Section 18.7.26: LTDC register map fixing AHBP[11:0],
AAV[11:0], TOTALW[11:0] and HSW[11:0] at 12 bits.

3

RM0385 Rev 7

RM0385

Revision history
Table 302. Document revision history (continued)
Date

Revision

Changes

Updated SPI2S section:
- Updated Section 32.5.2: Communications between one master and
one slave and Section 32.5.3: Standard multi-slave communication
figures 340, 341, 342 and 343.
- Notes updated and added below the figures.
- Added Section 32.5.4: Multi-master communication.
Updated FMC section:
- Updated Section 13.4.3: SDRAM address mapping.
- Updated Section 13.8: FMC register map.
- Changed figures for Mode1, ModeA, Mode2, ModeB, ModeC and
Muxed write access waveforms (from FSMC to FMC).
- Updated Section 13.5.4: NOR Flash/PSRAM controller asynchronous
transactions.
3
03-Nov-2015
(continued) - Updated Section : FIFO status and interrupt register (FMC_SR) adding
note for Bit0 (IRS) and Bit2 (IFS).
- Updated Section : SRAM/NOR-Flash chip-select timing registers 1..4
(FMC_BTR1..4).
Updated Section : SRAM/NOR-Flash write timing registers 1..4
(FMC_BWTR1..4).
Updated MMAP section:
- Updated Section 2.5: Boot configuration embedded bootloader
description.
Updated I2C2 section:
- Updated : I2C timings and Figure 305: Setup and hold timings.
Update USB_OTG section:
- Updated Section 37: USB on-the-go full-speed/high-speed
(OTG_FS/OTG_HS).

21-Dec-2015

4

Updated USART section:
Replaced nCTS by CTS - nRTS by RTS - SCLK by CK everywhere in
the document.
Replaced "w" by "rc_w1" in Section 31.8.9: Interrupt flag clear register
(USARTx_ICR).
Updated RTOF bit description in USARTx_ISR.
Update Low-power timer section:
Removed LPTIM1 option register (LPTIM1_OR).
Updated advanced control timer section:
Updated Section 22.3.16: Using the break function description.
Updated BxCan section: Dual can IP implemented.
Updated USB section:
Updated Section : Choosing the value of TRDT in OTG_GUSBCFG.
Updated TRDT bit description in Section 37.15.4: OTG USB
configuration register (OTG_GUSBCFG).
Added Table 234: TRDT values (FS) and Table 235: TRDT values (HS).
Updated Section 37.15.4: OTG USB configuration register
(OTG_GUSBCFG) PHYSEL bit “r” to “rw” and PHYSEL description for
USB OTG_HS.

RM0385 Rev 7

1693/1709
1702

Revision history

RM0385
Table 302. Document revision history (continued)

Date

Revision

Changes

Updated RTC section:
Updated reference to TAMPTS bit in Section 29.3.13: Time-stamp
function.
Updated ADC section:
Added note in Section 15.13.7: ADC watchdog higher threshold register
(ADC_HTR) and Section 15.13.8: ADC watchdog lower threshold
register (ADC_LTR).
Updated LTDC section:
Updated Section 18.3.2: LTDC reset and clocks.
Updated SDMMC section:
Updated limit from 48 to 50 MHz in Section 35.1: SDMMC main features,
Section 35.3: SDMMC functional description, Section 35.8.1: SDMMC
power control register (SDMMC_POWER), Section 35.8.2: SDMMC
clock control register (SDMMC_CLKCR) and in Section 35.8.4: SDMMC
command register (SDMMC_CMD).
Updated general purpose timer section:
Updated reset value to 0xFFFF in Section 23.4.12: TIMx auto-reload
register (TIMx_ARR).
Updated CC1IF bit description in Section 23.4.5: TIMx status register
(TIMx_SR).
4
Added Section 23.3.14: Retriggerable one pulse mode (OPM).
21-Dec-2015
(continued) Update PWR power controller section:
Updated Section 4.4.2: PWR power control/status register
(PWR_CSR1) ‘EIWUP’ bit 8 introduced in the register field and register
map.
Updated Table 17 and Table 18 PPDS bit is cleared in Power Control
register (PWR_CR1).
Updated Table 18: Standby mode entry and exit WUIF bit is cleared in
PWR_CSR1, EIWUP bit is set in PWR_CSR1.
Updated Section : RTC alternate functions to wake up the device from
the Standby mode adding new “c” bullet for the three cases.
Updated USART section:
Updated Section 31.8.3: Control register 3 (USARTx_CR3) ‘ONEBIT’ bit
11 description adding a note.
Updated Electronic signature section:
Updated Section 41.1: Unique device ID register (96 bits) UID[31:0] bits
used for X,Y coordinates on the wafer, Lot number and Wafer number.
Updated interrupts section:
Updated Section 11.9.1: Interrupt mask register (EXTI_IMR) MRx to IMx
bit description in the bit field and register map.
Updated Section 11.9.2: Event mask register (EXTI_EMR) MRx to EMx
bit description in the bit field and register map.

1694/1709

RM0385 Rev 7

RM0385

Revision history
Table 302. Document revision history (continued)
Date

Revision

Changes

Updated FMC section:
Updated BUSTURN bit description in Section : SRAM/NOR-Flash chipselect timing registers 1..4 (FMC_BTR1..4).
Updated Section 13.7.3: SDRAM controller functional description.
Updated Figure 53: NAND Flash controller waveforms for common
memory access adding note 2.
Updated Section 13.6.5: NAND Flash prewait functionality.
Updated Common memory space timing register 2..4 (FMC_PMEM)
4
21-Dec-2015
(continued) MEMHOLD[7:0] description.
Updated Attribute memory space timing registers (FMC_PATT)
ATTHOLD[7:0] description.
Updated Section 13.3: AHB interface.
Updated Table 62: FMC_BCRx bit fields bit 10 and 11 description.
Updated Flash memory section:
Updated Section 3.5: FLASH memory protection read protection (RDP)
description and note added.

26-Apr-2016

5

Updated PWR section:
– Updated Table 13: Features over all modes cryptographic processor
(CRYP), USB OTG_FS, USB OTG_HS and Ethernet rows.
Updated DMA section:
– Updated Section 8.5.5: DMA stream x configuration register
(DMA_SxCR) bit 18 “DBM or reserved” by “DBM” and “rw or r” by “rw”.
Updated DMA2D1 section:
– Updated Section 9.3.12: DMA2D transfer control (start, suspend, abort
and completion) putting “automatic CLUT transfers can also be
aborted or suspended by using the ABORT or the SUSP bit of the
DMA2D_CR register”.
– Updated Section 9.5.8: DMA2D foreground PFC control register
(DMA2D_FGPFCCR) START bit property in the table by “rs”.
– Updated Section 9.5.10: DMA2D background PFC control register
(DMA2D_BGPFCCR) START bit property in the table by “rs”. and
START bit description putting “data transfer or automatic foreground
CLUT transfer”.
Updated RTC section:
– Added case of RTC clocked by LSE in Section 29.3.9: Resetting the
RTC.
Updated RCC section:
– Updated Section 5.2.8: RTC/AWU clock adding “the RTC remains
clocked and functional under system reset” when the RTC clock is
LSE.
– Updated Section 5.3.26: RCC dedicated clocks configuration register
(DCKCFGR2) and Section 5.3.27: RCC register map bit28 renamed
SDMMC1SEL.
Updated HASH section:
– Updated Figure 146: Message data swapping feature.

RM0385 Rev 7

1695/1709
1702

Revision history

RM0385
Table 302. Document revision history (continued)

Date

Revision

Changes

Updated TIMER section:
– Updated Section 25.4.7: TIM6/TIM7 prescaler (TIMx_PSC) PSC[15:0]
bits description.
– Updated Section 24.4.9: TIM9/TIM12 prescaler (TIMx_PSC)
PSC[15:0] bits description.
– Updated Section 24.5.1: TIM10/TIM11/TIM13/TIM14 control register 1
(TIMx_CR1) adding OPM bit-field.
– Updated Section 24.5.12: TIM10/TIM11/TIM13/TIM14 register map
adding OPM bit.
– Updated Section 22.4.5: TIM1/TIM8 status register (TIMx_SR) and
Section 22.4.25: TIM8 register map CC5IF and CC6IF bit names.
– Updated Section 26: Low-power timer (LPTIM) changing register
name LPTIMx_regname in LPTIM_regname.
Updated FMC section:
– Updated Section : SRAM/NOR-Flash chip-select timing registers 1..4
(FMC_BTR1..4) busturn bits description.
– Updated Figure 47: Muxed write access waveforms NWE signal
negative edge.
5
26-Apr-2016
–
Updated
Figure 53: NAND Flash controller waveforms for common
(continued)
memory access replacing ‘MEMxHIZ’ by ‘MEMxHIZ+1’.
– Updated Section : Common memory space timing register 2..4
(FMC_PMEM) MEMHOLD[7:0] and Section : Attribute memory space
timing registers (FMC_PATT) ATTHOLD[7:0] replacing 257 HCLK by
256 HCLK.
– Updated Section : SDRAM Control registers 1,2 (FMC_SDCR1,2)
adding RPIPE[1:0] description.
Updated I2C2 section:
– Updated Section 30.4.4: I2C initialization, Section 30.4.8: I2C master
mode and Section 30.7.5: Timing register (I2C_TIMINGR).
Updated cover adding the PM0253 programming manual in the related
document list.
Updated system configuration:
– Updated Section 2.1.12: LCD-TFT controller DMA bus description.
Updated USART section:
– Updated Section 31: Universal synchronous asynchronous receiver
transmitter (USART) changing register name USARTx_regname in
USART_regname.

1696/1709

RM0385 Rev 7

RM0385

Revision history
Table 302. Document revision history (continued)
Date

Revision

Changes

Updated LDC-TFT section:
– Updated Section 18: LCD-TFT display controller (LTDC).
– Updated Section 18.7.15: LTDC layer x window horizontal position
configuration register (LTDC_LxWHPCR) removing “all values within
this range are allowed” and updating the WHSPPOS[11:0] and
WHSTPOS[11:0] bit description.
– Updated Section 18.7.15: LTDC layer x window horizontal position
configuration register (LTDC_LxWHPCR) removing “all values within
this range are allowed” and updating the WVSPPOS[10:0] and
WVSTPOS[10:0] bit description.
– Updated Table 115: LTDC pins and signal interface modifying ‘Data
5
Enable’ by ‘Not Data Enable’.
26-Apr-2016
(continued)
Updated Power Controller (PWR) section:
– Updated Section 4.1.4: Voltage regulator removing low voltage mode
in under-drive mode.
– Updated Section : Entering low-power mode removing low voltage.
Updated Flash memory section:
– Updated Section 3.3.7: Flash programming sequences adding note
about the FLASH_CR register.
– Updated Section 3.3.7: Flash programming sequences adding a note
in Section : Standard programming.
– Updated Section : Modifying user option bytes adding a note about the
FLASH_OPTCR register.

RM0385 Rev 7

1697/1709
1702

Revision history

RM0385
Table 302. Document revision history (continued)

Date

05-Oct-2016

1698/1709

Revision

Changes

6

Updated RCC section:
– Updated Section 5.3.3: RCC clock configuration register
(RCC_CFGR) two cautions replacing 90 MHz by 108 MHz and
45 MHz by 54 MHz.
– Updated Section 5.3.2: RCC PLL configuration register
(RCC_PLLCFGR) PLLP[1:0] bit description replacing ‘180 MHz’ by
‘216 MHz’.
Updated RTC section:
– Updated Figure 284: RTC block diagram RTC_WUTR ‘ck_spre’ input.
– Updated ADD1H and SUB1H bit descriptions in Section 29.6.3: RTC
control register (RTC_CR).
– Updated Section : RTC backup registers and Section 29.6.20: RTC
backup registers (RTC_BKPxR) RTC_BKPxR registers cannot be
reset when the Flash readout protection is disabled.
– Added caution at the end of Section 29.6.3: RTC control register
(RTC_CR).
– Updated caution at the end of Section 29.6.16: RTC tamper
configuration register (RTC_TAMPCR).
Updated FMC section:
– Updated Section : SDRAM Control registers 1,2 (FMC_SDCR1,2)
replacing ‘KCK_FMC’ by ‘HCLK’ in RPIPE[1:0] description.
– Updated Section : SRAM/NOR-Flash chip-select timing registers 1..4
(FMC_BTR1..4) and Section : SRAM/NOR-Flash write timing registers
1..4 (FMC_BWTR1..4) BUSTURN[3:0] bit description replacing ‘FMC’
by ‘HCLK’ clock cycle.
Updated LCD-TFT section:
– Updated Section 18.4.2: Layer programmable parameters modifying
configuring ‘WHSTPOS[10:0] and WHSPPOS[10:0]’ by
‘WVSTPOS[10:0] and WVSPPOS[10:0]’ in the LTDC_LxWVPCR
register.
– Updated Figure 113: Layer window programmable parameters.
– Updated Section : Example of synchronous timings configuration
LTDC_SSCR register.
Updated USART section:
– Updated Section 31.8.8: Interrupt and status register (USART_ISR)
RWU bit available independently of the wakeup from stop feature
availability.
– Updated Section 31.8.12: USART register map.
– Updated Table 192: Error calculation for programmed baud rates at
fCK = 216 MHz in both cases of oversampling by 8 (OVER8 = 1).
Updated I2C2 section:
– Updated Section 30.4.8: I2C master mode note in Master
communication initialization (address phase) paragraph.
– Updated Section 30.7.2: Control register 2 (I2C_CR2) completing the
note of bit 13 ‘START’ description.

RM0385 Rev 7

RM0385

Revision history
Table 302. Document revision history (continued)
Date

Revision

Changes

Updated DEBUG section:
– Updated Section 40.16.2: Debug support for timers, watchdog, bxCAN
and I2C adding a paragraph for timers having complementary outputs.
– Updated Section 40.16.5: Debug MCU APB1 freeze register
(DBGMCU_APB1_FZ) and Section 40.16.6: Debug MCU APB2
Freeze register (DBGMCU_APB2_FZ) DBG_TIMx_STOP bit
description.
Updated TIMER section:
– Updated Section 22.3.27: DMA burst mode adding note ‘reserved
registers can be written with a null value’.
– Updated Section 22.3.28: Debug mode adding ‘for safety purposes’
paragraph.
– Updated Table 146: Output control bits for complementary OCx and
OCxN channels with break feature in Section 22: Advanced-control
6
05-Oct-2016
timers (TIM1/TIM8).
(continued)
– Updated Section 23.4.13: TIMx capture/compare register 1
(TIMx_CCR1), Section 23.4.14: TIMx capture/compare register 2
(TIMx_CCR2), Section 23.4.15: TIMx capture/compare register 3
(TIMx_CCR3) and Section 23.4.16: TIMx capture/compare register 4
(TIMx_CCR4) bit description adding ‘the CCRx register is read-only
and cannot written’ and putting rw/r for all the bits.
Updated ADC section:
Updated all ‘CCx’ by ‘CHx’ references and removing ‘event’ in:
– Figure 70: Single ADC block diagram.
– Table 95: External trigger for regular channels.
– Table 96: External trigger for injected channels.
– Section 15.13.3: ADC control register 2 (ADC_CR2) EXTSEL[3:0] and
JEXTSEL[3:0] bit description.

RM0385 Rev 7

1699/1709
1702

Revision history

RM0385
Table 302. Document revision history (continued)

Date

07-Mar-2018

Revision

7

Changes
Updated Arm word and added logo.
Updated USB section:
– Complete re-mastering of the section
– Added Section 37.4.2: USB OTG pin and internal signals.
– Updated Section 37.15.13: OTG core ID register (OTG_CID).
– Updated Section 37.15.38: OTG all endpoints interrupt mask register
(OTG_DAINTMSK) replacing bit 18 by bit 19 in OEPM bit description.
Updated memory organization section
Added Figure 2: Memory map.
Updated SPDIRX section:
– All reference to spdifrx_ck_symb removed.
– Updated Figure 413: SPDIFRX block diagram.
– Removed ‘symbol clock generation’ paragraph.
Updated general-purpose timer section:
– Updated Section 24.5.11: TIM11 option register 1 (TIM11_OR)
TI1_RMP[1:0] bits 1/0 description by SPDIFRX_FRAME_SYNC ....
SPDIF frames.
– Updated Section 23.4.3: TIMx slave mode control register
(TIMx_SMCR) Bits 6:4 TS: Trigger selection description removing
‘reserved’.
– Updated Section : SDRAM Control registers 1,2 (FMC_SDCR1,2) bits
[1:0] ‘01’ description for SPDIFRX_FRAME_SYNC’.
– Added Section 24.3.12: Retriggerable one pulse mode (OPM) (TIM12
only).
– Added Section 24.3.13: UIF bit remapping.
– Added Section 24.3.14: Timer input XOR function.
Updated RCC section
– Updated Figure 13: Clock tree OTG_HS_SCL renamed by
OTG_HS_ULPI_CK.
– Updated Section 5.3.21: RCC clock control & status register
(RCC_CSR) bit RMVF put in read/write.
– Updated Section 5.3.27: RCC register map PADRSTF in PINRSTF.
– Updated Section 5.3.20: RCC backup domain control register
(RCC_BDCR) adding LSEDRV[1:0] in the description.
– Updated Section 5.3.14: RCC APB2 peripheral clock enable register
(RCC_APB2ENR) ADC1EN, ADC2EN and ADC2EN are enabled
when bit set to ‘1’.
Updated Document conventions section:
– Updated Section 1.1: List of abbreviations for registers
Updated PWR section:
– Updated Section 4.1.5: Battery backup domain note removing ‘only
one I/O at a time can be used as an output’ sentence.
– Updated Section 4.4.2: PWR power control/status register
(PWR_CSR1) bits[19:18] UDRDY[1:0] description.
– Updated Section 4.1.3: Battery backup domain step 3 of ‘Access to

the backup SRAM’ paragraph.

1700/1709

RM0385 Rev 7

RM0385

Revision history
Table 302. Document revision history (continued)
Date

Revision

Changes
Updated Flash memory section:
– Updated Section 3.7.7: Flash option control register
(FLASH_OPTCR1) and Section 3.7.8: Flash interface register map
reset value at ‘0x0040 0000.
Updated FMC section:
– Updated Section : SDRAM Control registers 1,2 (FMC_SDCR1,2)
replacing ‘KCK_FMC’ by ‘HCLK’ in RPIPE[1:0] description.080’.
– Updated SDRAM controller read cycle: CAS latency = 3, RPIPE

delay = 0 to 2: Five data.

Updated RTC section:.
– Updated Section 29.6.3: RTC control register (RTC_CR) WUTE bit
description adding note.
– Updated Figure 302: RTC block diagram WUCKSEL dividers for
/2,4,8,16.
Updated ETHERNET section:
– Updated Section : Ethernet MAC MII address register
(ETH_MACMIIAR) bits[4:2] clock range of setting 100 is valid for 150216 MHz.
Updated QUADSPI section:
– Added Table 89: QUADSPI pins.
7
07-Mar-2018
(continued) – Updated Section 14.5.1: QUADSPI control register (QUADSPI_CR)
PRESCALER[7:0] bit description.
Updated DCMI section:
– Section DCMI pins merged with Section 17.4.3: DCMI physical
interface.
– External signals HSYNC, VSYNC and PIXCLK standardized to
DCMI_HSYNC, DCMI_VSYNC and DCIM_PIXCLK in the whole
document.
Updated LTDC section:
– Updated Section 18.3.3: LTDC reset and clocks.
– Updated CFBP bitfield size in LTDC_LxCFBLR.
Updated RNG section:
– Updated Section 19: True random number generator (RNG).
Updated CRYP section:
– Updated Section 20: Cryptographic processor (CRYP).
Updated HASH section.
– Updated Section 21: Hash processor (HASH).
Updated LPTIM section:
– Added Section 26.4.2: LPTIM trigger mapping.
– Added Table 163: Interrupt events.

RM0385 Rev 7

1701/1709
1702

Revision history

RM0385
Table 302. Document revision history (continued)

Date

Revision

Changes

Updated I2C2 section:
– Updated Figure 305: Setup and hold timings.
Updated Serial audio section:
– Updated Section 33.5.10: SAI register map MCJDIV by MCKDIV bit
name.
– Added Section 33.3.2: SAI pins and internal signals.
Updated USART section:
– Updated Table 190: STM32F75xxx and STM32F74xxx USART
features adding note 2.
Updated SPI2S section:
7
07-Mar-2018
(continued) – Removed text note ‘When the SPI is in slave mode ....the clock is
stable in steady state’.
– Updated Section 32.5.9: Data transmission and reception procedures
cross reference ‘communication using DMA’.
– Updated Section 32.7.2: I2S full duplex
– Updated Section 32.1: Introduction.
– Updated Section 32.9.9: SPIx_I2S prescaler register (SPIx_I2SPR)
removing example.
Updated SDMMC section:
– Updated Section 35.8.8: SDMMC data length register
(SDMMC_DLEN) note.

1702/1709

RM0385 Rev 7

Index

RM0385

Index
A
ADC_CCR . . . . . . . . . . . . . . . . . . . . . . . . . . .455
ADC_CDR . . . . . . . . . . . . . . . . . . . . . . . . . . .458
ADC_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . . .444
ADC_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . .446
ADC_CSR . . . . . . . . . . . . . . . . . . . . . . . . . . .454
ADC_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . .454
ADC_HTR . . . . . . . . . . . . . . . . . . . . . . . . . . .449
ADC_JDRx . . . . . . . . . . . . . . . . . . . . . . . . . . .453
ADC_JOFRx . . . . . . . . . . . . . . . . . . . . . . . . .449
ADC_JSQR . . . . . . . . . . . . . . . . . . . . . . . . . .453
ADC_LTR . . . . . . . . . . . . . . . . . . . . . . . . . . . .450
ADC_SMPR1 . . . . . . . . . . . . . . . . . . . . . . . . .448
ADC_SMPR2 . . . . . . . . . . . . . . . . . . . . . . . . .449
ADC_SQR1 . . . . . . . . . . . . . . . . . . . . . . . . . .450
ADC_SQR2 . . . . . . . . . . . . . . . . . . . . . . . . . .451
ADC_SQR3 . . . . . . . . . . . . . . . . . . . . . . . . . .452
ADC_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . . .443

C
CAN_BTR . . . . . . . . . . . . . . . . . . . . . . . . . .1310
CAN_ESR . . . . . . . . . . . . . . . . . . . . . . . . . .1309
CAN_FA1R . . . . . . . . . . . . . . . . . . . . . . . . .1320
CAN_FFA1R . . . . . . . . . . . . . . . . . . . . . . . .1319
CAN_FiRx . . . . . . . . . . . . . . . . . . . . . . . . . .1321
CAN_FM1R . . . . . . . . . . . . . . . . . . . . . . . . .1318
CAN_FMR . . . . . . . . . . . . . . . . . . . . . . . . . .1318
CAN_FS1R . . . . . . . . . . . . . . . . . . . . . . . . .1319
CAN_IER . . . . . . . . . . . . . . . . . . . . . . . . . . .1308
CAN_MCR . . . . . . . . . . . . . . . . . . . . . . . . . .1301
CAN_MSR . . . . . . . . . . . . . . . . . . . . . . . . . .1303
CAN_RDHxR . . . . . . . . . . . . . . . . . . . . . . . .1317
CAN_RDLxR . . . . . . . . . . . . . . . . . . . . . . . .1317
CAN_RDTxR . . . . . . . . . . . . . . . . . . . . . . . .1316
CAN_RF0R . . . . . . . . . . . . . . . . . . . . . . . . .1306
CAN_RF1R . . . . . . . . . . . . . . . . . . . . . . . . .1307
CAN_RIxR . . . . . . . . . . . . . . . . . . . . . . . . . .1315
CAN_TDHxR . . . . . . . . . . . . . . . . . . . . . . . .1314
CAN_TDLxR . . . . . . . . . . . . . . . . . . . . . . . .1314
CAN_TDTxR . . . . . . . . . . . . . . . . . . . . . . . .1313
CAN_TIxR . . . . . . . . . . . . . . . . . . . . . . . . . .1312
CAN_TSR . . . . . . . . . . . . . . . . . . . . . . . . . .1304
CEC_CFGR . . . . . . . . . . . . . . . . . . . . . . . . .1647
CEC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . .1646
CEC_IER . . . . . . . . . . . . . . . . . . . . . . . . . . .1652
CEC_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . .1650
CEC_RXDR . . . . . . . . . . . . . . . . . . . . . . . . .1650

1703/1709

CEC_TXDR . . . . . . . . . . . . . . . . . . . . . . . . . 1650
CRC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
CRC_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
CRC_IDR . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
CRC_INIT . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
CRC_POL . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
CRYP_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
CRYP_DIN . . . . . . . . . . . . . . . . . . . . . . . . . . 611
CRYP_DMACR . . . . . . . . . . . . . . . . . . . . . . . 613
CRYP_DOUT . . . . . . . . . . . . . . . . . . . . . . . . 612
CRYP_IMSCR . . . . . . . . . . . . . . . . . . . . . . . . 613
CRYP_IV0LR . . . . . . . . . . . . . . . . . . . . . . . . 618
CRYP_IV0RR . . . . . . . . . . . . . . . . . . . . . . . . 619
CRYP_IV1LR . . . . . . . . . . . . . . . . . . . . . . . . 619
CRYP_IV1RR . . . . . . . . . . . . . . . . . . . . . . . . 619
CRYP_K0LR . . . . . . . . . . . . . . . . . . . . . . . . . 615
CRYP_K0RR . . . . . . . . . . . . . . . . . . . . . . . . . 616
CRYP_K1LR . . . . . . . . . . . . . . . . . . . . . . . . . 616
CRYP_K1RR . . . . . . . . . . . . . . . . . . . . . . . . . 616
CRYP_K2LR . . . . . . . . . . . . . . . . . . . . . . . . . 617
CRYP_K2RR . . . . . . . . . . . . . . . . . . . . . . . . . 617
CRYP_K3LR . . . . . . . . . . . . . . . . . . . . . . . . . 618
CRYP_K3RR . . . . . . . . . . . . . . . . . . . . . . . . . 618
CRYP_MISR . . . . . . . . . . . . . . . . . . . . . . . . . 614
CRYP_RISR . . . . . . . . . . . . . . . . . . . . . . . . . 614
CRYP_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . 611

D
DAC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
DAC_DHR12L1 . . . . . . . . . . . . . . . . . . . . . . . 477
DAC_DHR12L2 . . . . . . . . . . . . . . . . . . . . . . . 478
DAC_DHR12LD . . . . . . . . . . . . . . . . . . . . . . 479
DAC_DHR12R1 . . . . . . . . . . . . . . . . . . . . . . 476
DAC_DHR12R2 . . . . . . . . . . . . . . . . . . . . . . 478
DAC_DHR12RD . . . . . . . . . . . . . . . . . . . . . . 479
DAC_DHR8R1 . . . . . . . . . . . . . . . . . . . . . . . 477
DAC_DHR8R2 . . . . . . . . . . . . . . . . . . . . . . . 478
DAC_DHR8RD . . . . . . . . . . . . . . . . . . . . . . . 480
DAC_DOR1 . . . . . . . . . . . . . . . . . . . . . . . . . . 480
DAC_DOR2 . . . . . . . . . . . . . . . . . . . . . . . . . . 480
DAC_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481
DAC_SWTRIGR . . . . . . . . . . . . . . . . . . . . . . 476
DBGMCU_APB2_FZ . . . . . . . . . . . . . 1678, 1680
DBGMCU_CR . . . . . . . . . . . . . . . . . . . . . . . 1677
DBGMCU_IDCODE . . . . . . . . . . . . . . . . . . 1662
DCMI_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . 494
DCMI_CWSIZE . . . . . . . . . . . . . . . . . . . . . . . 505
DCMI_CWSTRT . . . . . . . . . . . . . . . . . . . . . . 505

RM0385 Rev 7

RM0385

Index

DCMI_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . .506
DCMI_ESCR . . . . . . . . . . . . . . . . . . . . . . . . .503
DCMI_ESUR . . . . . . . . . . . . . . . . . . . . . . . . .504
DCMI_ICR . . . . . . . . . . . . . . . . . . . . . . . . . . .502
DCMI_IER . . . . . . . . . . . . . . . . . . . . . . . . . . .500
DCMI_MIS . . . . . . . . . . . . . . . . . . . . . . . . . . .501
DCMI_RIS . . . . . . . . . . . . . . . . . . . . . . . . . . .499
DCMI_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . .498
DMA_HIFCR . . . . . . . . . . . . . . . . . . . . . . . . .245
DMA_HISR . . . . . . . . . . . . . . . . . . . . . . . . . . .244
DMA_LIFCR . . . . . . . . . . . . . . . . . . . . . . . . . .245
DMA_LISR . . . . . . . . . . . . . . . . . . . . . . . . . . .243
DMA_SxCR . . . . . . . . . . . . . . . . . . . . . . . . . .246
DMA_SxFCR . . . . . . . . . . . . . . . . . . . . . . . . .251
DMA_SxM0AR . . . . . . . . . . . . . . . . . . . . . . . .250
DMA_SxM1AR . . . . . . . . . . . . . . . . . . . . . . . .250
DMA_SxNDTR . . . . . . . . . . . . . . . . . . . . . . . .249
DMA_SxPAR . . . . . . . . . . . . . . . . . . . . . . . . .250

E
ETH_DMABMR . . . . . . . . . . . . . . . . . . . . . .1618
ETH_DMACHRBAR . . . . . . . . . . . . . . . . . . .1631
ETH_DMACHRDR . . . . . . . . . . . . . . . . . . . .1630
ETH_DMACHTBAR . . . . . . . . . . . . . . . . . . .1631
ETH_DMACHTDR . . . . . . . . . . . . . . . . . . . .1630
ETH_DMAIER . . . . . . . . . . . . . . . . . . . . . . .1627
ETH_DMAMFBOCR . . . . . . . . . . . . . . . . . .1629
ETH_DMAOMR . . . . . . . . . . . . . . . . . . . . . .1624
ETH_DMARDLAR . . . . . . . . . . . . . . . . . . . .1620
ETH_DMARPDR . . . . . . . . . . . . . . . . . . . . .1620
ETH_DMARSWTR . . . . . . . . . . . . . . . . . . . .1630
ETH_DMASR . . . . . . . . . . . . . . . . . . . . . . . .1621
ETH_DMATDLAR . . . . . . . . . . . . . . . . . . . .1621
ETH_DMATPDR . . . . . . . . . . . . . . . . . . . . .1619
ETH_MACA0HR . . . . . . . . . . . . . . . . . . . . .1599
ETH_MACA0LR . . . . . . . . . . . . . . . . . . . . . .1600
ETH_MACA1HR . . . . . . . . . . . . . . . . . . . . .1600
ETH_MACA1LR . . . . . . . . . . . . . . . . . . . . . .1601
ETH_MACA2HR . . . . . . . . . . . . . . . . . . . . .1601
ETH_MACA2LR . . . . . . . . . . . . . . . . . . . . . .1602
ETH_MACA3HR . . . . . . . . . . . . . . . . . . . . .1603
ETH_MACA3LR . . . . . . . . . . . . . . . . . . . . . .1603
ETH_MACCR . . . . . . . . . . . . . . . . . . . . . . . .1585
ETH_MACDBGR . . . . . . . . . . . . . . . . . . . . .1597
ETH_MACFCR . . . . . . . . . . . . . . . . . . . . . . .1592
ETH_MACFFR . . . . . . . . . . . . . . . . . . . . . . .1588
ETH_MACHTHR . . . . . . . . . . . . . . . . . . . . .1589
ETH_MACHTLR . . . . . . . . . . . . . . . . . . . . . .1590
ETH_MACIMR . . . . . . . . . . . . . . . . . . . . . . .1599
ETH_MACMIIAR . . . . . . . . . . . . . . . . . . . . .1590
ETH_MACMIIDR . . . . . . . . . . . . . . . . . . . . .1591

ETH_MACPMTCSR . . . . . . . . . . . . . . . . . . 1596
ETH_MACRWUFFR . . . . . . . . . . . . . . . . . . 1594
ETH_MACSR . . . . . . . . . . . . . . . . . . . . . . . 1598
ETH_MACVLANTR . . . . . . . . . . . . . . . . . . . 1593
ETH_MMCCR . . . . . . . . . . . . . . . . . . . . . . . 1605
ETH_MMCRFAECR . . . . . . . . . . . . . . . . . . 1609
ETH_MMCRFCECR . . . . . . . . . . . . . . . . . . 1609
ETH_MMCRGUFCR . . . . . . . . . . . . . . . . . . 1610
ETH_MMCRIMR . . . . . . . . . . . . . . . . . . . . . 1607
ETH_MMCRIR . . . . . . . . . . . . . . . . . . . . . . 1605
ETH_MMCTGFCR . . . . . . . . . . . . . . . . . . . 1609
ETH_MMCTGFMSCCR . . . . . . . . . . . . . . . 1608
ETH_MMCTGFSCCR . . . . . . . . . . . . . . . . . 1608
ETH_MMCTIMR . . . . . . . . . . . . . . . . . . . . . 1607
ETH_MMCTIR . . . . . . . . . . . . . . . . . . . . . . . 1606
ETH_PTPPPSCR . . . . . . . . . . . . . . . . . . . . 1617
ETH_PTPSSIR . . . . . . . . . . . . . . . . . . . . . . 1612
ETH_PTPTSAR . . . . . . . . . . . . . . . . . . . . . . 1615
ETH_PTPTSCR . . . . . . . . . . . . . . . . . . . . . 1610
ETH_PTPTSHR . . . . . . . . . . . . . . . . . . . . . 1613
ETH_PTPTSHUR . . . . . . . . . . . . . . . . . . . . 1614
ETH_PTPTSLR . . . . . . . . . . . . . . . . . . . . . . 1613
ETH_PTPTSLUR . . . . . . . . . . . . . . . . . . . . 1615
ETH_PTPTSSR . . . . . . . . . . . . . . . . . . . . . . 1616
ETH_PTPTTHR . . . . . . . . . . . . . . . . . . . . . . 1616
ETH_PTPTTLR . . . . . . . . . . . . . . . . . . . . . . 1616
EXTI_EMR . . . . . . . . . . . . . . . . . . . . . . . . . . 297
EXTI_FTSR . . . . . . . . . . . . . . . . . . . . . . . . . . 298
EXTI_IMR . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
EXTI_PR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
EXTI_RTSR . . . . . . . . . . . . . . . . . . . . . . . . . . 298
EXTI_SWIER . . . . . . . . . . . . . . . . . . . . . . . . . 299

F
FLITF_FCR . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
FLITF_FKEYR . . . . . . . . . . . . . . . . . . . . . . . . . 92
FLITF_FOPTCR . . . . . . . . . . . . . . . . . . . . 95-96
FLITF_FOPTKEYR . . . . . . . . . . . . . . . . . . . . . 92
FLITF_FSR . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
FMC_BCR1..4 . . . . . . . . . . . . . . . . . . . . . . . . 345
FMC_BTR1..4 . . . . . . . . . . . . . . . . . . . . . . . . 347
FMC_BWTR1..4 . . . . . . . . . . . . . . . . . . . . . . 350
FMC_ECCR . . . . . . . . . . . . . . . . . . . . . . . . . 363
FMC_PATT . . . . . . . . . . . . . . . . . . . . . . . . . . 361
FMC_PCR . . . . . . . . . . . . . . . . . . . . . . . . . . . 358
FMC_PMEM . . . . . . . . . . . . . . . . . . . . . . . . . 360
FMC_SDCMR . . . . . . . . . . . . . . . . . . . . . . . . 378
FMC_SDCR1,2 . . . . . . . . . . . . . . . . . . . . . . . 374
FMC_SDRTR . . . . . . . . . . . . . . . . . . . . . . . . 379
FMC_SDSR . . . . . . . . . . . . . . . . . . . . . . . . . . 380
FMC_SDTR1,2 . . . . . . . . . . . . . . . . . . . . . . . 376

RM0385 Rev 7

1704/1709

Index

RM0385

FMC_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . .359

G
GPIOx_AFRH . . . . . . . . . . . . . . . . . . . . . . . . .213
GPIOx_AFRL . . . . . . . . . . . . . . . . . . . . . . . . .212
GPIOx_BSRR . . . . . . . . . . . . . . . . . . . . . . . .210
GPIOx_IDR . . . . . . . . . . . . . . . . . . . . . . . . . .210
GPIOx_LCKR . . . . . . . . . . . . . . . . . . . . . . . . .211
GPIOx_MODER . . . . . . . . . . . . . . . . . . . . . . .208
GPIOx_ODR . . . . . . . . . . . . . . . . . . . . . . . . .210
GPIOx_OSPEEDR . . . . . . . . . . . . . . . . . . . . .209
GPIOx_OTYPER . . . . . . . . . . . . . . . . . . . . . .208
GPIOx_PUPDR . . . . . . . . . . . . . . . . . . . . . . .209

H
HASH_CR . . . . . . . . . . . . . . . . . . . . . . . . . . .635
HASH_CSR0 . . . . . . . . . . . . . . . . . . . . . . . . .644
HASH_CSRx . . . . . . . . . . . . . . . . . . . . . . . . .644
HASH_DIN . . . . . . . . . . . . . . . . . . . . . . . . . . .638
HASH_HR0 . . . . . . . . . . . . . . . . . . . . . . . . . .640
HASH_HR1 . . . . . . . . . . . . . . . . . . . . . . . . . .640
HASH_HR2 . . . . . . . . . . . . . . . . . . . . . . . . . .641
HASH_HR3 . . . . . . . . . . . . . . . . . . . . . . . . . .641
HASH_HR4 . . . . . . . . . . . . . . . . . . . . . . . . . .641
HASH_HR5 . . . . . . . . . . . . . . . . . . . . . . . . . .641
HASH_HR6 . . . . . . . . . . . . . . . . . . . . . . . . . .642
HASH_HR7 . . . . . . . . . . . . . . . . . . . . . . . . . .642
HASH_IMR . . . . . . . . . . . . . . . . . . . . . . . . . . .642
HASH_SR . . . . . . . . . . . . . . . . . . . . . . . . . . .643
HASH_STR . . . . . . . . . . . . . . . . . . . . . . . . . .639

I
I2C_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . . .1004
I2C_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . .1007
I2C_ICR . . . . . . . . . . . . . . . . . . . . . . . . . . . .1016
I2C_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . . .1014
I2C_OAR1 . . . . . . . . . . . . . . . . . . . . . . . . . .1010
I2C_OAR2 . . . . . . . . . . . . . . . . . . . . . . . . . .1011
I2C_PECR . . . . . . . . . . . . . . . . . . . . . . . . . .1017
I2C_RXDR . . . . . . . . . . . . . . . . . . . . . . . . . .1018
I2C_TIMEOUTR . . . . . . . . . . . . . . . . . . . . . .1013
I2C_TIMINGR . . . . . . . . . . . . . . . . . . . . . . .1012
I2C_TXDR . . . . . . . . . . . . . . . . . . . . . . . . . .1018
I2Cx_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . .1007
IWDG_KR . . . . . . . . . . . . . . . . . . . . . . . . . . .896
IWDG_PR . . . . . . . . . . . . . . . . . . . . . . . . . . .897
IWDG_RLR . . . . . . . . . . . . . . . . . . . . . . . . . .898
IWDG_SR . . . . . . . . . . . . . . . . . . . . . . . . . . .899
IWDG_WINR . . . . . . . . . . . . . . . . . . . . . . . . .900

1705/1709

L
LPTIM_ARR . . . . . . . . . . . . . . . . . . . . . . . . . 891
LPTIM_CFGR . . . . . . . . . . . . . . . . . . . . . . . . 887
LPTIM_CMP . . . . . . . . . . . . . . . . . . . . . . . . . 890
LPTIM_CNT . . . . . . . . . . . . . . . . . . . . . . . . . 891
LPTIM_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . 889
LPTIM_ICR . . . . . . . . . . . . . . . . . . . . . . . . . . 885
LPTIM_IER . . . . . . . . . . . . . . . . . . . . . . . . . . 886
LPTIM_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . 884
LTDC_AWCR . . . . . . . . . . . . . . . . . . . . . . . . 522
LTDC_BCCR . . . . . . . . . . . . . . . . . . . . . . . . . 525
LTDC_BPCR . . . . . . . . . . . . . . . . . . . . . . . . . 521
LTDC_CDSR . . . . . . . . . . . . . . . . . . . . . . . . . 529
LTDC_CPSR . . . . . . . . . . . . . . . . . . . . . . . . . 528
LTDC_GCR . . . . . . . . . . . . . . . . . . . . . . . . . . 523
LTDC_ICR . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
LTDC_IER . . . . . . . . . . . . . . . . . . . . . . . . . . . 526
LTDC_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
LTDC_LIPCR . . . . . . . . . . . . . . . . . . . . . . . . 528
LTDC_LxBFCR . . . . . . . . . . . . . . . . . . . . . . . 536
LTDC_LxCACR . . . . . . . . . . . . . . . . . . . . . . . 534
LTDC_LxCFBAR . . . . . . . . . . . . . . . . . . . . . . 537
LTDC_LxCFBLNR . . . . . . . . . . . . . . . . . . . . . 538
LTDC_LxCFBLR . . . . . . . . . . . . . . . . . . . . . . 537
LTDC_LxCKCR . . . . . . . . . . . . . . . . . . . . . . . 533
LTDC_LxCLUTWR . . . . . . . . . . . . . . . . . . . . 539
LTDC_LxCR . . . . . . . . . . . . . . . . . . . . . . . . . 530
LTDC_LxDCCR . . . . . . . . . . . . . . . . . . . . . . . 535
LTDC_LxPFCR . . . . . . . . . . . . . . . . . . . . . . . 533
LTDC_LxWHPCR . . . . . . . . . . . . . . . . . . . . . 531
LTDC_LxWVPCR . . . . . . . . . . . . . . . . . . . . . 532
LTDC_SRCR . . . . . . . . . . . . . . . . . . . . . . . . . 525
LTDC_SSCR . . . . . . . . . . . . . . . . . . . . . . . . . 521
LTDC_TWCR . . . . . . . . . . . . . . . . . . . . . . . . 523

O
OTG_CID . . . . . . . . . . . . . . . . . . . . . . . . . . 1387
OTG_DAINT . . . . . . . . . . . . . . . . . . . . . . . . 1415
OTG_DAINTMSK . . . . . . . . . . . . . . . . . . . . 1415
OTG_DCFG . . . . . . . . . . . . . . . . . . . . . . . . 1407
OTG_DCTL . . . . . . . . . . . . . . . . . . . . . . . . . 1409
OTG_DEACHINT . . . . . . . . . . . . . . . . . . . . 1419
OTG_DEACHINTMSK . . . . . . . . . . . . . . . . 1419
OTG_DIEPCTL0 . . . . . . . . . . . . . . . . . . . . . 1422
OTG_DIEPCTLx . . . . . . . . . . . . . . . . . . . . . 1424
OTG_DIEPDMAx . . . . . . . . . . . . . . . . . . . . 1429
OTG_DIEPEMPMSK . . . . . . . . . . . . . . . . . . 1418
OTG_DIEPINTx . . . . . . . . . . . . . . . . . . . . . . 1426
OTG_DIEPMSK . . . . . . . . . . . . . . . . . . . . . 1412
OTG_DIEPTSIZ0 . . . . . . . . . . . . . . . . . . . . 1428
OTG_DIEPTSIZx . . . . . . . . . . . . . . . . . . . . . 1430

RM0385 Rev 7

RM0385

Index

OTG_DIEPTXF0 . . . . . . . . . . . . . . . . . . . . .1384
OTG_DIEPTXFx . . . . . . . . . . . . . . . . . . . . .1392
OTG_DOEPCTL0 . . . . . . . . . . . . . . . . . . . .1431
OTG_DOEPCTLx . . . . . . . . . . . . . . . . . . . . .1436
OTG_DOEPDMAx . . . . . . . . . . . . . . . . . . . .1435
OTG_DOEPINTx . . . . . . . . . . . . . . . . . . . . .1432
OTG_DOEPMSK . . . . . . . . . . . . . . . . . . . . .1413
OTG_DOEPTSIZ0 . . . . . . . . . . . . . . . . . . . .1434
OTG_DOEPTSIZx . . . . . . . . . . . . . . . . . . . .1438
OTG_DSTS . . . . . . . . . . . . . . . . . . . . . . . . .1411
OTG_DTHRCTL . . . . . . . . . . . . . . . . . . . . . .1417
OTG_DTXFSTSx . . . . . . . . . . . . . . . . . . . . .1429
OTG_DVBUSDIS . . . . . . . . . . . . . . . . . . . . .1416
OTG_DVBUSPULSE . . . . . . . . . . . . . . . . . .1416
OTG_GAHBCFG . . . . . . . . . . . . . . . . . . . . .1365
OTG_GCCFG . . . . . . . . . . . . . . . . . . . . . . .1386
OTG_GINTMSK . . . . . . . . . . . . . . . . . . . . . .1378
OTG_GINTSTS . . . . . . . . . . . . . . . . . . . . . .1373
OTG_GLPMCFG . . . . . . . . . . . . . . . . . . . . .1387
OTG_GOTGCTL . . . . . . . . . . . . . . . . . . . . .1360
OTG_GOTGINT . . . . . . . . . . . . . . . . . . . . . .1363
OTG_GRSTCTL . . . . . . . . . . . . . . . . . . . . . .1370
OTG_GRXFSIZ . . . . . . . . . . . . . . . . . . . . . .1384
OTG_GRXSTSP . . . . . . . . . . . . . . . . . . . . .1381
OTG_GRXSTSR . . . . . . . . . . . . . . . . . . . . .1381
OTG_GUSBCFG . . . . . . . . . . . . . . . . . . . . .1367
OTG_HAINT . . . . . . . . . . . . . . . . . . . . . . . . .1396
OTG_HAINTMSK . . . . . . . . . . . . . . . . . . . . .1397
OTG_HCCHARx . . . . . . . . . . . . . . . . . . . . .1400
OTG_HCDMAx . . . . . . . . . . . . . . . . . . . . . .1406
OTG_HCFG . . . . . . . . . . . . . . . . . . . . . . . . .1393
OTG_HCINTMSKx . . . . . . . . . . . . . . . . . . . .1404
OTG_HCINTx . . . . . . . . . . . . . . . . . . . . . . . .1402
OTG_HCSPLTx . . . . . . . . . . . . . . . . . . . . . .1401
OTG_HCTSIZx . . . . . . . . . . . . . . . . . . . . . . .1405
OTG_HFIR . . . . . . . . . . . . . . . . . . . . . . . . . .1394
OTG_HFNUM . . . . . . . . . . . . . . . . . . . . . . .1395
OTG_HNPTXFSIZ . . . . . . . . . . . . . . . . . . . .1384
OTG_HNPTXSTS . . . . . . . . . . . . . . . . . . . .1385
OTG_HPRT . . . . . . . . . . . . . . . . . . . . . . . . .1398
OTG_HPTXFSIZ . . . . . . . . . . . . . . . . . . . . .1392
OTG_HPTXSTS . . . . . . . . . . . . . . . . . . . . . .1395
OTG_HS_DIEPEACHMSK1 . . . . . . . . . . . .1420
OTG_HS_DOEPEACHMSK1 . . . . . . . . . . .1421
OTG_PCGCCTL . . . . . . . . . . . . . . . . . . . . .1439

P
PWR_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
PWR_CSR . . . . . . . . . . . . . . . . . . 125, 127, 129

Q
QUADSPI _PIR . . . . . . . . . . . . . . . . . . . . . . . 411
QUADSPI _PSMAR . . . . . . . . . . . . . . . . . . . 410
QUADSPI _PSMKR . . . . . . . . . . . . . . . . . . . 410
QUADSPI_ABR . . . . . . . . . . . . . . . . . . . . . . . 409
QUADSPI_AR . . . . . . . . . . . . . . . . . . . . . . . . 408
QUADSPI_CCR . . . . . . . . . . . . . . . . . . . . . . 406
QUADSPI_CR . . . . . . . . . . . . . . . . . . . . . . . . 400
QUADSPI_DCR . . . . . . . . . . . . . . . . . . . . . . 403
QUADSPI_DLR . . . . . . . . . . . . . . . . . . . . . . . 405
QUADSPI_DR . . . . . . . . . . . . . . . . . . . . . . . . 409
QUADSPI_FCR . . . . . . . . . . . . . . . . . . . . . . . 405
QUADSPI_LPTR . . . . . . . . . . . . . . . . . . . . . . 411
QUADSPI_SR . . . . . . . . . . . . . . . . . . . . . . . . 404

R
RCC_AHB1ENR . . . . . . . . . . . . . . . . . . . . . . 163
RCC_AHB1LPENR . . . . . . . . . . . . . . . . . . . . 173
RCC_AHB1RSTR . . . . . . . . . . . . . . . . . . . . . 153
RCC_AHB2ENR . . . . . . . . . . . . . . . . . . . . . . 165
RCC_AHB2LPENR . . . . . . . . . . . . . . . . . . . . 175
RCC_AHB2RSTR . . . . . . . . . . . . . . . . . . . . . 156
RCC_AHB3ENR . . . . . . . . . . . . . . . . . . . . . . 166
RCC_AHB3LPENR . . . . . . . . . . . . . . . . . . . . 176
RCC_AHB3RSTR . . . . . . . . . . . . . . . . . . . . . 157
RCC_APB1ENR . . . . . . . . . . . . . . . . . . . . . . 166
RCC_APB1LPENR . . . . . . . . . . . . . . . . . . . . 177
RCC_APB1RSTR . . . . . . . . . . . . . . . . . . . . . 157
RCC_APB2ENR . . . . . . . . . . . . . . . . . . . . . . 170
RCC_APB2LPENR . . . . . . . . . . . . . . . . . . . . 181
RCC_APB2RSTR . . . . . . . . . . . . . . . . . . . . . 161
RCC_BDCR . . . . . . . . . . . . . . . . . . . . . . . . . 183
RCC_CFGR . . . . . . . . . . . . . . . . . . . . . . . . . 148
RCC_CIR . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
RCC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
RCC_CSR . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
RCC_PLLCFGR . . . . . . . . . . . . . . 146, 187, 190
RCC_SSCGR . . . . . . . . . . . . . . . . . . . . . . . . 186
RNG_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
RNG_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553
RNG_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
RTC_ALRMAR . . . . . . . . . . . . . . . . . . . . . . . 938
RTC_ALRMBR . . . . . . . . . . . . . . . . . . . . . . . 939
RTC_ALRMBSSR . . . . . . . . . . . . . . . . . . . . . 950
RTC_BKPxR . . . . . . . . . . . . . . . . . . . . . . . . . 951
RTC_CALR . . . . . . . . . . . . . . . . . . . . . . . . . . 945
RTC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 930
RTC_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 929
RTC_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 933
RTC_OR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 951
RTC_PRER . . . . . . . . . . . . . . . . . . . . . . . . . . 936

RM0385 Rev 7

1706/1709

Index

RM0385

RTC_SHIFTR . . . . . . . . . . . . . . . . . . . . . . . . .941
RTC_SSR . . . . . . . . . . . . . . . . . . . . . . . . . . .940
RTC_TR . . . . . . . . . . . . . . . . . . . . . . . . . . . . .928
RTC_TSDR . . . . . . . . . . . . . . . . . . . . . . . . . .943
RTC_TSSSR . . . . . . . . . . . . . . . . . . . . . . . . .944
RTC_TSTR . . . . . . . . . . . . . . . . . . . . . . . . . .942
RTC_WPR . . . . . . . . . . . . . . . . . . . . . . . . . . .940
RTC_WUTR . . . . . . . . . . . . . . . . . . . . . . . . . .937

S
SAI_ACLRFR . . . . . . . . . . . . . . . . . . . . . . . .1185
SAI_ACR1 . . . . . . . . . . . . . . . . . . . . . . . . . .1174
SAI_ACR2 . . . . . . . . . . . . . . . . . . . . . . . . . .1177
SAI_ADR . . . . . . . . . . . . . . . . . . . . . . . . . . .1186
SAI_AFRCR . . . . . . . . . . . . . . . . . . . . . . . . .1179
SAI_AIM . . . . . . . . . . . . . . . . . . . . . . . . . . . .1182
SAI_ASLOTR . . . . . . . . . . . . . . . . . . . . . . . .1181
SAI_ASR . . . . . . . . . . . . . . . . . . . . . . . . . . .1183
SAI_BCLRFR . . . . . . . . . . . . . . . . . . . . . . . .1185
SAI_BCR1 . . . . . . . . . . . . . . . . . . . . . . . . . .1174
SAI_BCR2 . . . . . . . . . . . . . . . . . . . . . . . . . .1177
SAI_BDR . . . . . . . . . . . . . . . . . . . . . . . . . . .1186
SAI_BFRCR . . . . . . . . . . . . . . . . . . . . . . . . .1179
SAI_BIM . . . . . . . . . . . . . . . . . . . . . . . . . . . .1182
SAI_BSLOTR . . . . . . . . . . . . . . . . . . . . . . . .1181
SAI_BSR . . . . . . . . . . . . . . . . . . . . . . . . . . .1183
SAI_GCR . . . . . . . . . . . . . . . . . . . . . . . . . . .1174
SDMMC_ARG . . . . . . . . . . . . . . . . . . . . . . .1266
SDMMC_CLKCR . . . . . . . . . . . . . . . . . . . . .1264
SDMMC_DCOUNT . . . . . . . . . . . . . . . . . . .1272
SDMMC_DCTRL . . . . . . . . . . . . . . . . . . . . .1269
SDMMC_DLEN . . . . . . . . . . . . . . . . . . . . . .1269
SDMMC_DTIMER . . . . . . . . . . . . . . . . . . . .1268
SDMMC_FIFO . . . . . . . . . . . . . . . . . . . . . . .1278
SDMMC_ICR . . . . . . . . . . . . . . . . . . . . . . . .1273
SDMMC_MASK . . . . . . . . . . . . . . . . . . . . . .1275
SDMMC_POWER . . . . . . . . . . . . . . . . . . . .1264
SDMMC_RESPCMD . . . . . . . . . . . . . . . . . .1267
SDMMC_RESPx . . . . . . . . . . . . . . . . . . . . .1267
SDMMC_STA . . . . . . . . . . . . . . . . . . . . . . . .1272
SPDIFRX_CR . . . . . . . . . . . . . . . . . . . . . . .1210
SPDIFRX_CSR . . . . . . . . . . . . . . . . . . . . . .1219
SPDIFRX_DIR . . . . . . . . . . . . . . . . . . . . . . .1219
SPDIFRX_DR . . . . . . . . . . . . . . . . . . . . . . .1216
SPDIFRX_FMT1_DR . . . . . . . . . . . . . . . . . .1217
SPDIFRX_FMT2_DR . . . . . . . . . . . . . . . . . .1218
SPDIFRX_IFCR . . . . . . . . . . . . . . . . . . . . . .1215
SPDIFRX_IMR . . . . . . . . . . . . . . . . . . . . . . .1212
SPDIFRX_SR . . . . . . . . . . . . . . . . . . . . . . . .1213
SPIx_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . .1132
SPIx_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . .1134

1707/1709

SPIx_CRCPR . . . . . . . . . . . . . . . . . . . . . . . 1138
SPIx_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . 1138
SPIx_I2SCFGR . . . . . . . . . . . . . . . . . . . . . . 1141
SPIx_I2SPR . . . . . . . . . . . . . . . . . . . . . . . . 1143
SPIx_RXCRCR . . . . . . . . . . . . . . . . . . . . . . 1140
SPIx_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . 1137
SPIx_TXCRCR . . . . . . . . . . . . . . . . . . . . . . 1140
SYSCFG_EXTICR1 . . . . . . . . . . . . . . . . . . . 218
SYSCFG_EXTICR2 . . . . . . . . . . . . . . . . . . . 218
SYSCFG_EXTICR3 . . . . . . . . . . . . . . . . . . . 219
SYSCFG_EXTICR4 . . . . . . . . . . . . . . . . . . . 220
SYSCFG_MEMRMP . . . . . . . . . . . . . . . . . . . 216

T
TIM2_OR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807
TIM5_OR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807
TIMx_ARR . . . . . . . . . . .726, 803, 846, 857, 871
TIMx_BDTR . . . . . . . . . . . . . . . . . . . . . . . . . . 729
TIMx_CCER . . . . . . . . . . . . . 722, 801, 844, 855
TIMx_CCMR1 . . . . . . . . . . . . 716, 795, 840, 853
TIMx_CCMR2 . . . . . . . . . . . . . . . . . . . . 720, 799
TIMx_CCMR3 . . . . . . . . . . . . . . . . . . . . . . . . 734
TIMx_CCR1 . . . . . . . . . . 727, 803, 846, 857-858
TIMx_CCR2 . . . . . . . . . . . . . . . . . . 728, 804, 846
TIMx_CCR3 . . . . . . . . . . . . . . . . . . . . . . 728, 804
TIMx_CCR4 . . . . . . . . . . . . . . . . . . . . . . 729, 805
TIMx_CCR5 . . . . . . . . . . . . . . . . . . . . . . . . . . 735
TIMx_CCR6 . . . . . . . . . . . . . . . . . . . . . . . . . . 736
TIMx_CNT . . . . . . . . . . .726, 802, 845, 856, 870
TIMx_CR1 . . . . . . . . . . .705, 786, 835, 850, 867
TIMx_CR2 . . . . . . . . . . . . . . . . . . . 706, 787, 869
TIMx_DCR . . . . . . . . . . . . . . . . . . . . . . . 732, 806
TIMx_DIER . . . . . . . . . .711, 792, 838, 851, 869
TIMx_DMAR . . . . . . . . . . . . . . . . . . . . . 733, 806
TIMx_EGR . . . . . . . . . . .715, 794, 839, 852, 870
TIMx_PSC . . . . . . . . . . .726, 803, 845, 857, 871
TIMx_RCR . . . . . . . . . . . . . . . . . . . . . . . . . . . 727
TIMx_SMCR . . . . . . . . . . . . . . . . . 709, 789, 836
TIMx_SR . . . . . . . . . . . .713, 793, 838, 851, 870

U
USART_BRR . . . . . . . . . . . . . . . . . . . . . . . . 1073
USART_CR1 . . . . . . . . . . . . . . . . . . . . . . . . 1064
USART_CR2 . . . . . . . . . . . . . . . . . . . . . . . . 1067
USART_CR3 . . . . . . . . . . . . . . . . . . . . . . . . 1070
USART_GTPR . . . . . . . . . . . . . . . . . . . . . . 1074
USART_ICR . . . . . . . . . . . . . . . . . . . . . . . . 1081
USART_ISR . . . . . . . . . . . . . . . . . . . . . . . . 1077
USART_RDR . . . . . . . . . . . . . . . . . . . . . . . 1082
USART_RQR . . . . . . . . . . . . . . . . . . . . . . . 1076
USART_RTOR . . . . . . . . . . . . . . . . . . . . . . 1075

RM0385 Rev 7

RM0385

Index

USART_TDR . . . . . . . . . . . . . . . . . . . . . . . .1083

W
WWDG_CFR . . . . . . . . . . . . . . . . . . . . . . . . .906
WWDG_CR . . . . . . . . . . . . . . . . . . . . . . . . . .906
WWDG_SR . . . . . . . . . . . . . . . . . . . . . . . . . .907

RM0385 Rev 7

1708/1709

RM0385

IMPORTANT NOTICE – PLEASE READ CAREFULLY
STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, enhancements, modifications, and
improvements to ST products and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on
ST products before placing orders. ST products are sold pursuant to ST’s terms and conditions of sale in place at the time of order
acknowledgement.
Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or
the design of Purchasers’ products.
No license, express or implied, to any intellectual property right is granted by ST herein.
Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product.
ST and the ST logo are trademarks of ST. All other product or service names are the property of their respective owners.
Information in this document supersedes and replaces information previously supplied in any prior versions of this document.
© 2018 STMicroelectronics – All rights reserved

RM0385 Rev 7

1709/1709
1709



---

Source Exif Data:

File Type                       : PDF
File Type Extension             : pdf
MIME Type                       : application/pdf
PDF Version                     : 1.3
Linearized                      : No
Page Layout                     : SinglePage
Page Mode                       : UseNone
Page Count                      : 1709
Producer                        : Acrobat Distiller 11.0 (Windows); modified using iText 2.1.7 by 1T3XT
Keywords                        : Technical Literature, 026670, Product Development, Specification, Reference manual, STM32F745IE, STM32F745IG, STM32F745VE, STM32F745VG, STM32F745ZE, STM32F745ZG, STM32F746BE, STM32F746BG, STM32F746IE, STM32F746IG, STM32F746NE, STM32F746NG, STM32F746VE, STM32F746VG, STM32F746ZE, STM32F746ZG, STM32F756BG, STM32F756IG, STM32F756NG, STM32F756VG, STM32F756ZG
Modify Date                     : 2018:03:09 11:08:09+01:00
Subject                         : -
Creator                         : C2 v4.2.0220 build 670 - c2_rendition_config : Techlit_Active
Revision                        : 7
Title                           : STM32F75xxx and STM32F74xxx advanced Arm®-based 32-bit MCUs
Alternate Name                  : RM0385
Classification                  : Unclassified
Doc ID                          : RM0385
Document Type                   : Reference manual
Create Date                     : 2018:03:07 11:29:41Z
Author                          : STMICROELECTRONICS

EXIF Metadata provided by EXIF.tools