STM32F446xx Advanced ARM® Based 32 Bit MCUs Stm32f446re Ref Manual

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RM0390
Reference manual
STM32F446xx advanced ARM®-based 32-bit MCUs

Introduction
This reference manual targets application developers. It provides complete information on
how to use the STM32F446xx microcontroller memory and peripherals.
The STM32F446xx constitute a family of microcontrollers with different memory sizes,
packages and peripherals.
For ordering information, mechanical and electrical device characteristics refer to the
corresponding datasheets.
For information on the ARM® Cortex®-M4 with FPU core, refer to the Cortex®-M4 Technical
Reference Manual.

Related documents
Available from STMicroelectronics web site www.st.com:
• STM32F446xx datasheets
For information on the Cortex®-M4 with FPU, refer to the STM32F3xx/F4xxx Cortex®-M4
with FPU programming manual (PM0214).

July 2017

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Contents

RM0390

Contents
1

2

Documentation conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
1.1

List of abbreviations for registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

1.2

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

1.3

Peripheral availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Memory and bus architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.1

2.2

2.3

3

2.1.1

I-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

2.1.2

D-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

2.1.3

S-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

2.1.4

DMA memory bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

2.1.5

DMA peripheral bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

2.1.6

USB OTG HS DMA bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

2.1.7

BusMatrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

2.1.8

AHB/APB bridges (APB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Memory organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.2.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

2.2.2

Memory map and register boundary addresses . . . . . . . . . . . . . . . . . . 56

2.2.3

Embedded SRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

2.2.4

Flash memory overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

2.2.5

Bit banding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Boot configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Embedded Flash memory interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

3.2

Main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

3.3

Embedded Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

3.4

Read interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

3.5

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System architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

3.4.1

Relation between CPU clock frequency and Flash memory read time . 65

3.4.2

Adaptive real-time memory accelerator (ART Accelerator™) . . . . . . . . 66

Erase and program operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
3.5.1

Unlocking the Flash control register . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

3.5.2

Program/erase parallelism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

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4

5

3.5.3

Erase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

3.5.4

Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

3.5.5

Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

Option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.6.1

Description of user option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

3.6.2

Programming user option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

3.6.3

Read protection (RDP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

3.6.4

Write protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

3.6.5

Proprietary code readout protection (PCROP) . . . . . . . . . . . . . . . . . . . 77

3.7

One-time programmable bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

3.8

Flash interface registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
3.8.1

Flash access control register (FLASH_ACR) . . . . . . . . . . . . . . . . . . . . 79

3.8.2

Flash key register (FLASH_KEYR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

3.8.3

Flash option key register (FLASH_OPTKEYR) . . . . . . . . . . . . . . . . . . . 80

3.8.4

Flash status register (FLASH_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

3.8.5

Flash control register (FLASH_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

3.8.6

Flash option control register (FLASH_OPTCR) . . . . . . . . . . . . . . . . . . . 84

3.8.7

Flash interface register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

CRC calculation unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.1

CRC introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.2

CRC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.3

CRC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.4

CRC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.4.1

Data register (CRC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

4.4.2

Independent data register (CRC_IDR) . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.4.3

Control register (CRC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.4.4

CRC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Power controller (PWR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.1

5.2

Power supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
5.1.1

Independent A/D converter supply and reference voltage . . . . . . . . . . . 92

5.1.2

Battery backup domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

5.1.3

Voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Power supply supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.2.1

Power-on reset (POR)/power-down reset (PDR) . . . . . . . . . . . . . . . . . . 97

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5.3

5.4

5.5

6

Brownout reset (BOR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

5.2.3

Programmable voltage detector (PVD) . . . . . . . . . . . . . . . . . . . . . . . . . 98

Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.3.1

Slowing down system clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

5.3.2

Peripheral clock gating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

5.3.3

Low power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

5.3.4

Sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

5.3.5

Stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

5.3.6

Standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

5.3.7

Programming the RTC alternate functions to wake up the device from
the Stop and Standby modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Power control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
5.4.1

PWR power control register (PWR_CR) . . . . . . . . . . . . . . . . . . . . . . . 110

5.4.2

PWR power control/status register (PWR_CSR) . . . . . . . . . . . . . . . . . 112

PWR register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114

Reset and clock control (RCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.1

6.2

6.3

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5.2.2

Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
6.1.1

System reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

6.1.2

Power reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

6.1.3

Backup domain reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
6.2.1

HSE clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

6.2.2

HSI clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

6.2.3

PLL configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

6.2.4

LSE clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

6.2.5

LSI clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

6.2.6

System clock (SYSCLK) selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

6.2.7

Clock security system (CSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

6.2.8

RTC/AWU clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

6.2.9

Watchdog clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

6.2.10

Clock-out capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

6.2.11

Internal/external clock measurement using TIM5/TIM11 . . . . . . . . . . . 124

RCC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.3.1

RCC clock control register (RCC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . 126

6.3.2

RCC PLL configuration register (RCC_PLLCFGR) . . . . . . . . . . . . . . . 128

6.3.3

RCC clock configuration register (RCC_CFGR) . . . . . . . . . . . . . . . . . 130

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6.3.4

RCC clock interrupt register (RCC_CIR) . . . . . . . . . . . . . . . . . . . . . . . 132

6.3.5

RCC AHB1 peripheral reset register (RCC_AHB1RSTR) . . . . . . . . . . 135

6.3.6

RCC AHB2 peripheral reset register (RCC_AHB2RSTR) . . . . . . . . . . 137

6.3.7

RCC AHB3 peripheral reset register (RCC_AHB3RSTR) . . . . . . . . . . 137

6.3.8

RCC APB1 peripheral reset register (RCC_APB1RSTR) . . . . . . . . . . 138

6.3.9

RCC APB2 peripheral reset register (RCC_APB2RSTR) . . . . . . . . . . 141

6.3.10

RCC AHB1 peripheral clock enable register (RCC_AHB1ENR) . . . . . 143

6.3.11

RCC AHB2 peripheral clock enable register (RCC_AHB2ENR) . . . . . 144

6.3.12

RCC AHB3 peripheral clock enable register (RCC_AHB3ENR) . . . . . 145

6.3.13

RCC APB1 peripheral clock enable register (RCC_APB1ENR) . . . . . 145

6.3.14

RCC APB2 peripheral clock enable register (RCC_APB2ENR) . . . . . 148

6.3.15

RCC AHB1 peripheral clock enable in low power mode register
(RCC_AHB1LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

6.3.16

RCC AHB2 peripheral clock enable in low power mode register
(RCC_AHB2LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

6.3.17

RCC AHB3 peripheral clock enable in low power mode register
(RCC_AHB3LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

6.3.18

RCC APB1 peripheral clock enable in low power mode register
(RCC_APB1LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

6.3.19

RCC APB2 peripheral clock enabled in low power mode register
(RCC_APB2LPENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

6.3.20

RCC Backup domain control register (RCC_BDCR) . . . . . . . . . . . . . . 158

6.3.21

RCC clock control & status register (RCC_CSR) . . . . . . . . . . . . . . . . 160

6.3.22

RCC spread spectrum clock generation register (RCC_SSCGR) . . . . 161

6.3.23

RCC PLLI2S configuration register (RCC_PLLI2SCFGR) . . . . . . . . . 162

6.3.24

RCC PLL configuration register (RCC_PLLSAICFGR) . . . . . . . . . . . . 165

6.3.25

RCC Dedicated Clock Configuration Register (RCC_DCKCFGR) . . . 166

6.3.26

RCC clocks gated enable register (CKGATENR) . . . . . . . . . . . . . . . . 168

6.3.27

RCC dedicated clocks configuration register 2 (DCKCFGR2) . . . . . . . 169

6.3.28

RCC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

General-purpose I/Os (GPIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
7.1

GPIO introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

7.2

GPIO main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

7.3

GPIO functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
7.3.1

General-purpose I/O (GPIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

7.3.2

I/O pin multiplexer and mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

7.3.3

I/O port control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

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7.3.4

I/O port data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

7.3.5

I/O data bitwise handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

7.3.6

GPIO locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

7.3.7

I/O alternate function input/output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

7.3.8

External interrupt/wakeup lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

7.3.9

Input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

7.3.10

Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

7.3.11

Alternate function configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

7.3.12

Analog configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

7.3.13

Using the OSC32_IN/OSC32_OUT pins as GPIO PC14/PC15
port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

7.3.14

Using the OSC_IN/OSC_OUT pins as GPIO PH0/PH1 port pins . . . . 184

7.3.15

Selection of RTC additional_AF1 and RTC_AF2 alternate functions . 185

GPIO registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
7.4.1

GPIO port mode register (GPIOx_MODER) (x = A..H) . . . . . . . . . . . . 186

7.4.2

GPIO port output type register (GPIOx_OTYPER) (x = A..H) . . . . . . . 187

7.4.3

GPIO port output speed register (GPIOx_OSPEEDR) (x = A..H) . . . . 187

7.4.4

GPIO port pull-up/pull-down register (GPIOx_PUPDR) (x = A..H) . . . 188

7.4.5

GPIO port input data register (GPIOx_IDR) (x = A..H) . . . . . . . . . . . . 188

7.4.6

GPIO port output data register (GPIOx_ODR) (x = A..H) . . . . . . . . . . 189

7.4.7

GPIO port bit set/reset register (GPIOx_BSRR) (x = A..H) . . . . . . . . . 189

7.4.8

GPIO port configuration lock register (GPIOx_LCKR) (x = A..H) . . . . . 189

7.4.9

GPIO alternate function low register (GPIOx_AFRL) (x = A..H) . . . . . 191

7.4.10

GPIO alternate function high register (GPIOx_AFRH) (x = A..H) . . . . 191

7.4.11

GPIO register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

System configuration controller (SYSCFG) . . . . . . . . . . . . . . . . . . . . 194
8.1

I/O compensation cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

8.2

SYSCFG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
8.2.1

SYSCFG memory remap register (SYSCFG_MEMRMP) . . . . . . . . . . 194

8.2.2

SYSCFG peripheral mode configuration register (SYSCFG_PMC) . . 196

8.2.3

SYSCFG external interrupt configuration register 1
(SYSCFG_EXTICR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

8.2.4

SYSCFG external interrupt configuration register 2
(SYSCFG_EXTICR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

8.2.5

SYSCFG external interrupt configuration register 3
(SYSCFG_EXTICR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

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8.2.6

SYSCFG external interrupt configuration register 4
(SYSCFG_EXTICR4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

8.2.7

Compensation cell control register (SYSCFG_CMPCR) . . . . . . . . . . . 199

8.2.8

SYSCFG configuration register (SYSCFG_CFGR) . . . . . . . . . . . . . . . 199

8.2.9

SYSCFG register maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

Direct memory access controller (DMA) . . . . . . . . . . . . . . . . . . . . . . . 202
9.1

DMA introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

9.2

DMA main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

9.3

DMA functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
9.3.1

DMA block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

9.3.2

DMA overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

9.3.3

DMA transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

9.3.4

Channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

9.3.5

Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

9.3.6

DMA streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

9.3.7

Source, destination and transfer modes . . . . . . . . . . . . . . . . . . . . . . . 207

9.3.8

Pointer incrementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

9.3.9

Circular mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

9.3.10

Double buffer mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

9.3.11

Programmable data width, packing/unpacking, endianness . . . . . . . . 212

9.3.12

Single and burst transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

9.3.13

FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

9.3.14

DMA transfer completion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

9.3.15

DMA transfer suspension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

9.3.16

Flow controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

9.3.17

Summary of the possible DMA configurations . . . . . . . . . . . . . . . . . . . 219

9.3.18

Stream configuration procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

9.3.19

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

9.4

DMA interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

9.5

DMA registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
9.5.1

DMA low interrupt status register (DMA_LISR) . . . . . . . . . . . . . . . . . . 223

9.5.2

DMA high interrupt status register (DMA_HISR) . . . . . . . . . . . . . . . . . 224

9.5.3

DMA low interrupt flag clear register (DMA_LIFCR) . . . . . . . . . . . . . . 225

9.5.4

DMA high interrupt flag clear register (DMA_HIFCR) . . . . . . . . . . . . . 225

9.5.5

DMA stream x configuration register (DMA_SxCR) (x = 0..7) . . . . . . . 226

9.5.6

DMA stream x number of data register (DMA_SxNDTR) (x = 0..7) . . . 229

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DMA stream x peripheral address register (DMA_SxPAR) (x = 0..7) . 230

9.5.8

DMA stream x memory 0 address register (DMA_SxM0AR) (x = 0..7) 230

9.5.9

DMA stream x memory 1 address register (DMA_SxM1AR) (x = 0..7) 230

9.5.10

DMA stream x FIFO control register (DMA_SxFCR) (x = 0..7) . . . . . . 231

9.5.11

DMA register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

Interrupts and events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
10.1

10.2

10.3

11

9.5.7

Nested vectored interrupt controller (NVIC) . . . . . . . . . . . . . . . . . . . . . . 237
10.1.1

NVIC features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

10.1.2

SysTick calibration value register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

10.1.3

Interrupt and exception vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

External interrupt/event controller (EXTI) . . . . . . . . . . . . . . . . . . . . . . . . 237
10.2.1

EXTI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

10.2.2

EXTI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

10.2.3

Wakeup event management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

10.2.4

Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

10.2.5

External interrupt/event line mapping . . . . . . . . . . . . . . . . . . . . . . . . . 244

EXTI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
10.3.1

Interrupt mask register (EXTI_IMR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

10.3.2

Event mask register (EXTI_EMR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

10.3.3

Rising trigger selection register (EXTI_RTSR) . . . . . . . . . . . . . . . . . . 246

10.3.4

Falling trigger selection register (EXTI_FTSR) . . . . . . . . . . . . . . . . . . 246

10.3.5

Software interrupt event register (EXTI_SWIER) . . . . . . . . . . . . . . . . 247

10.3.6

Pending register (EXTI_PR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

10.3.7

EXTI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

Flexible memory controller (FMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
11.1

FMC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

11.2

Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

11.3

AHB interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
11.3.1

11.4

11.5

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Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . 251

External device address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
11.4.1

NOR/PSRAM address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

11.4.2

NAND Flash memory address mapping . . . . . . . . . . . . . . . . . . . . . . . 254

11.4.3

SDRAM address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

NOR Flash/PSRAM controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

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11.6

11.7

11.8

12

11.5.1

External memory interface signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

11.5.2

Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . 260

11.5.3

General timing rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

11.5.4

NOR Flash/PSRAM controller asynchronous transactions . . . . . . . . . 262

11.5.5

Synchronous transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279

11.5.6

NOR/PSRAM controller registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286

NAND Flash controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
11.6.1

External memory interface signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

11.6.2

NAND Flash supported memories and transactions . . . . . . . . . . . . . . 295

11.6.3

Timing diagrams for NAND Flash memory . . . . . . . . . . . . . . . . . . . . . 295

11.6.4

NAND Flash operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

11.6.5

NAND Flash prewait functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

11.6.6

Computation of the error correction code (ECC)
in NAND Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298

11.6.7

NAND Flashcontroller registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

SDRAM controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
11.7.1

SDRAM controller main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

11.7.2

SDRAM External memory interface signals . . . . . . . . . . . . . . . . . . . . . 305

11.7.3

SDRAM controller functional description . . . . . . . . . . . . . . . . . . . . . . . 306

11.7.4

Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

11.7.5

SDRAM controller registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314

FMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322

Quad-SPI interface (QUADSPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
12.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

12.2

QUADSPI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

12.3

QUADSPI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
12.3.1

QUADSPI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324

12.3.2

QUADSPI pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

12.3.3

QUADSPI Command sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326

12.3.4

QUADSPI signal interface protocol modes . . . . . . . . . . . . . . . . . . . . . 328

12.3.5

QUADSPI indirect mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

12.3.6

QUADSPI status flag polling mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

12.3.7

QUADSPI memory-mapped mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

12.3.8

QUADSPI Flash memory configuration . . . . . . . . . . . . . . . . . . . . . . . . 333

12.3.9

QUADSPI delayed data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

12.3.10 QUADSPI configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

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12.3.11 QUADSPI usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
12.3.12 Sending the instruction only once . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
12.3.13 QUADSPI error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
12.3.14 QUADSPI busy bit and abort functionality . . . . . . . . . . . . . . . . . . . . . . 337
12.3.15 nCS behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

12.4

QUADSPI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

12.5

QUADSPI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
12.5.1

QUADSPI control register (QUADSPI_CR) . . . . . . . . . . . . . . . . . . . . . 340

12.5.2

QUADSPI device configuration register (QUADSPI_DCR) . . . . . . . . . 343

12.5.3

QUADSPI status register (QUADSPI_SR) . . . . . . . . . . . . . . . . . . . . . 344

12.5.4

QUADSPI flag clear register (QUADSPI_FCR) . . . . . . . . . . . . . . . . . . 345

12.5.5

QUADSPI data length register (QUADSPI_DLR) . . . . . . . . . . . . . . . . 345

12.5.6

QUADSPI communication configuration register (QUADSPI_CCR) . . 346

12.5.7

QUADSPI address register (QUADSPI_AR) . . . . . . . . . . . . . . . . . . . . 348

12.5.8

QUADSPI alternate bytes registers (QUADSPI_ABR) . . . . . . . . . . . . 349

12.5.9

QUADSPI data register (QUADSPI_DR) . . . . . . . . . . . . . . . . . . . . . . . 349

12.5.10 QUADSPI polling status mask register (QUADSPI _PSMKR) . . . . . . . 350
12.5.11 QUADSPI polling status match register (QUADSPI _PSMAR) . . . . . . 350
12.5.12 QUADSPI polling interval register (QUADSPI _PIR) . . . . . . . . . . . . . . 351
12.5.13 QUADSPI low-power timeout register (QUADSPI_LPTR) . . . . . . . . . . 351
12.5.14 QUADSPI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352

13

Analog-to-digital converter (ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
13.1

ADC introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

13.2

ADC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

13.3

ADC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
13.3.1

ADC on-off control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355

13.3.2

ADC1/2 and ADC3 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356

13.3.3

ADC clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

13.3.4

Channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

13.3.5

Single conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360

13.3.6

Continuous conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360

13.3.7

Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360

13.3.8

Analog watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361

13.3.9

Scan mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

13.3.10 Injected channel management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
13.3.11 Discontinuous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
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13.4

Data alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364

13.5

Channel-wise programmable sampling time . . . . . . . . . . . . . . . . . . . . . 365

13.6

Conversion on external trigger and trigger polarity . . . . . . . . . . . . . . . . 366

13.7

Fast conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

13.8

Data management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368

13.9

13.8.1

Using the DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368

13.8.2

Managing a sequence of conversions without using the DMA . . . . . . 368

13.8.3

Conversions without DMA and without overrun detection . . . . . . . . . . 369

Multi ADC mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
13.9.1

Injected simultaneous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

13.9.2

Regular simultaneous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

13.9.3

Interleaved mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

13.9.4

Alternate trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

13.9.5

Combined regular/injected simultaneous mode . . . . . . . . . . . . . . . . . . 378

13.9.6

Combined regular simultaneous + alternate trigger mode . . . . . . . . . . 378

13.10 Temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
13.11 Battery charge monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
13.12 ADC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
13.13 ADC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
13.13.1 ADC status register (ADC_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
13.13.2 ADC control register 1 (ADC_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 383
13.13.3 ADC control register 2 (ADC_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 385
13.13.4 ADC sample time register 1 (ADC_SMPR1) . . . . . . . . . . . . . . . . . . . . 387
13.13.5 ADC sample time register 2 (ADC_SMPR2) . . . . . . . . . . . . . . . . . . . . 387
13.13.6 ADC injected channel data offset register x (ADC_JOFRx) (x=1..4) . . 388
13.13.7 ADC watchdog higher threshold register (ADC_HTR) . . . . . . . . . . . . . 388
13.13.8 ADC watchdog lower threshold register (ADC_LTR) . . . . . . . . . . . . . . 389
13.13.9 ADC regular sequence register 1 (ADC_SQR1) . . . . . . . . . . . . . . . . . 389
13.13.10 ADC regular sequence register 2 (ADC_SQR2) . . . . . . . . . . . . . . . . . 390
13.13.11 ADC regular sequence register 3 (ADC_SQR3) . . . . . . . . . . . . . . . . . 391
13.13.12 ADC injected sequence register (ADC_JSQR) . . . . . . . . . . . . . . . . . . 392
13.13.13 ADC injected data register x (ADC_JDRx) (x= 1..4) . . . . . . . . . . . . . . 392
13.13.14 ADC regular data register (ADC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . 393
13.13.15 ADC Common status register (ADC_CSR) . . . . . . . . . . . . . . . . . . . . . 393
13.13.16 ADC common control register (ADC_CCR) . . . . . . . . . . . . . . . . . . . . . 394

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13.13.17 ADC common regular data register for dual and triple modes
(ADC_CDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
13.13.18 ADC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

14

Digital-to-analog converter (DAC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400
14.1

DAC introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400

14.2

DAC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400

14.3

DAC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

14.4

14.3.1

DAC channel enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401

14.3.2

DAC output buffer enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

14.3.3

DAC data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402

14.3.4

DAC conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403

14.3.5

DAC output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404

14.3.6

DAC trigger selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404

14.3.7

DMA request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405

14.3.8

Noise generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405

14.3.9

Triangle-wave generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406

Dual DAC channel conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407
14.4.1

Independent trigger without wave generation . . . . . . . . . . . . . . . . . . . 408

14.4.2

Independent trigger with single LFSR generation . . . . . . . . . . . . . . . . 408

14.4.3

Independent trigger with different LFSR generation . . . . . . . . . . . . . . 408

14.4.4

Independent trigger with single triangle generation . . . . . . . . . . . . . . . 409

14.4.5

Independent trigger with different triangle generation . . . . . . . . . . . . . 409

14.4.6

Simultaneous software start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409

14.4.7

Simultaneous trigger without wave generation . . . . . . . . . . . . . . . . . . 410

14.4.8

Simultaneous trigger with single LFSR generation . . . . . . . . . . . . . . . 410

14.4.9

Simultaneous trigger with different LFSR generation . . . . . . . . . . . . . 410

14.4.10 Simultaneous trigger with single triangle generation . . . . . . . . . . . . . . 411
14.4.11 Simultaneous trigger with different triangle generation . . . . . . . . . . . . 411

14.5

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DAC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
14.5.1

DAC control register (DAC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412

14.5.2

DAC software trigger register (DAC_SWTRIGR) . . . . . . . . . . . . . . . . . 415

14.5.3

DAC channel1 12-bit right-aligned data holding register
(DAC_DHR12R1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415

14.5.4

DAC channel1 12-bit left aligned data holding register
(DAC_DHR12L1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416

14.5.5

DAC channel1 8-bit right aligned data holding register
(DAC_DHR8R1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416

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14.5.6

DAC channel2 12-bit right aligned data holding register
(DAC_DHR12R2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

14.5.7

DAC channel2 12-bit left aligned data holding register
(DAC_DHR12L2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

14.5.8

DAC channel2 8-bit right-aligned data holding register
(DAC_DHR8R2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

14.5.9

Dual DAC 12-bit right-aligned data holding register
(DAC_DHR12RD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418

14.5.10 DUAL DAC 12-bit left aligned data holding register
(DAC_DHR12LD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
14.5.11 DUAL DAC 8-bit right aligned data holding register
(DAC_DHR8RD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
14.5.12 DAC channel1 data output register (DAC_DOR1) . . . . . . . . . . . . . . . . 419
14.5.13 DAC channel2 data output register (DAC_DOR2) . . . . . . . . . . . . . . . . 419
14.5.14 DAC status register (DAC_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
14.5.15 DAC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421

15

Digital camera interface (DCMI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
15.1

DCMI introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422

15.2

DCMI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422

15.3

DCMI clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422

15.4

DCMI functional overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

15.5

15.6

15.4.1

DCMI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

15.4.2

DMA interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424

15.4.3

DCMI physical interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424

15.4.4

Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426

15.4.5

Capture modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429

15.4.6

Crop feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430

15.4.7

JPEG format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431

15.4.8

FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431

Data format description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432
15.5.1

Data formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432

15.5.2

Monochrome format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432

15.5.3

RGB format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433

15.5.4

YCbCr format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433

15.5.5

YCbCr format - Y only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433

15.5.6

Half resolution image extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

DCMI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

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15.7

DCMI register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434
15.7.1

DCMI control register (DCMI_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

15.7.2

DCMI status register (DCMI_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438

15.7.3

DCMI raw interrupt status register (DCMI_RIS) . . . . . . . . . . . . . . . . . . 439

15.7.4

DCMI interrupt enable register (DCMI_IER) . . . . . . . . . . . . . . . . . . . . 440

15.7.5

DCMI masked interrupt status register (DCMI_MIS) . . . . . . . . . . . . . . 441

15.7.6

DCMI interrupt clear register (DCMI_ICR) . . . . . . . . . . . . . . . . . . . . . . 442

15.7.7

DCMI embedded synchronization code register (DCMI_ESCR) . . . . . 443

15.7.8

DCMI embedded synchronization unmask register (DCMI_ESUR) . . 444

15.7.9

DCMI crop window start (DCMI_CWSTRT) . . . . . . . . . . . . . . . . . . . . . 445

15.7.10 DCMI crop window size (DCMI_CWSIZE) . . . . . . . . . . . . . . . . . . . . . . 445
15.7.11 DCMI data register (DCMI_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
15.7.12 DCMI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447

16

Advanced-control timers (TIM1&TIM8) . . . . . . . . . . . . . . . . . . . . . . . . 448
16.1

TIM1&TIM8 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448

16.2

TIM1&TIM8 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448

16.3

TIM1&TIM8 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450
16.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450

16.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452

16.3.3

Repetition counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461

16.3.4

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

16.3.5

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

16.3.6

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470

16.3.7

PWM input mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471

16.3.8

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471

16.3.9

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472

16.3.10 PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
16.3.11 Complementary outputs and dead-time insertion . . . . . . . . . . . . . . . . 476
16.3.12 Using the break function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478
16.3.13 Clearing the OCxREF signal on an external event . . . . . . . . . . . . . . . 481
16.3.14 6-step PWM generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
16.3.15 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483
16.3.16 Encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484
16.3.17 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487
16.3.18 Interfacing with Hall sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487
16.3.19 TIMx and external trigger synchronization . . . . . . . . . . . . . . . . . . . . . . 489

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16.3.20 Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492
16.3.21 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

16.4

TIM1&TIM8 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493
16.4.1

TIM1&TIM8 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . 493

16.4.2

TIM1&TIM8 control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . 494

16.4.3

TIM1&TIM8 slave mode control register (TIMx_SMCR) . . . . . . . . . . . 496

16.4.4

TIM1&TIM8 DMA/interrupt enable register (TIMx_DIER) . . . . . . . . . . 498

16.4.5

TIM1&TIM8 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . 500

16.4.6

TIM1&TIM8 event generation register (TIMx_EGR) . . . . . . . . . . . . . . 501

16.4.7

TIM1&TIM8 capture/compare mode register 1 (TIMx_CCMR1) . . . . . 503

16.4.8

TIM1&TIM8 capture/compare mode register 2 (TIMx_CCMR2) . . . . . 506

16.4.9

TIM1&TIM8 capture/compare enable register (TIMx_CCER) . . . . . . . 507

16.4.10 TIM1&TIM8 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511
16.4.11 TIM1&TIM8 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 511
16.4.12 TIM1&TIM8 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . 511
16.4.13 TIM1&TIM8 repetition counter register (TIMx_RCR) . . . . . . . . . . . . . . 512
16.4.14 TIM1&TIM8 capture/compare register 1 (TIMx_CCR1) . . . . . . . . . . . . 512
16.4.15 TIM1&TIM8 capture/compare register 2 (TIMx_CCR2) . . . . . . . . . . . . 513
16.4.16 TIM1&TIM8 capture/compare register 3 (TIMx_CCR3) . . . . . . . . . . . . 513
16.4.17 TIM1&TIM8 capture/compare register 4 (TIMx_CCR4) . . . . . . . . . . . . 514
16.4.18 TIM1&TIM8 break and dead-time register (TIMx_BDTR) . . . . . . . . . . 514
16.4.19 TIM1&TIM8 DMA control register (TIMx_DCR) . . . . . . . . . . . . . . . . . . 516
16.4.20 TIM1&TIM8 DMA address for full transfer (TIMx_DMAR) . . . . . . . . . . 517
16.4.21 TIM1&TIM8 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518

17

General-purpose timers (TIM2 to TIM5) . . . . . . . . . . . . . . . . . . . . . . . . 520
17.1

TIM2 to TIM5 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520

17.2

TIM2 to TIM5 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520

17.3

TIM2 to TIM5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521
17.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521

17.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523

17.3.3

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532

17.3.4

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535

17.3.5

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537

17.3.6

PWM input mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538

17.3.7

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539

17.3.8

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
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17.3.9

PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541

17.3.10 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
17.3.11 Clearing the OCxREF signal on an external event . . . . . . . . . . . . . . . 545
17.3.12 Encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546
17.3.13 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549
17.3.14 Timers and external trigger synchronization . . . . . . . . . . . . . . . . . . . . 549
17.3.15 Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
17.3.16 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

17.4

TIM2 to TIM5 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558
17.4.1

TIMx control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . 558

17.4.2

TIMx control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . 560

17.4.3

TIMx slave mode control register (TIMx_SMCR) . . . . . . . . . . . . . . . . . 561

17.4.4

TIMx DMA/Interrupt enable register (TIMx_DIER) . . . . . . . . . . . . . . . . 563

17.4.5

TIMx status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

17.4.6

TIMx event generation register (TIMx_EGR) . . . . . . . . . . . . . . . . . . . . 566

17.4.7

TIMx capture/compare mode register 1 (TIMx_CCMR1) . . . . . . . . . . . 567

17.4.8

TIMx capture/compare mode register 2 (TIMx_CCMR2) . . . . . . . . . . . 570

17.4.9

TIMx capture/compare enable register (TIMx_CCER) . . . . . . . . . . . . . 571

17.4.10 TIMx counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573
17.4.11 TIMx prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573
17.4.12 TIMx auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . . . . . . 573
17.4.13 TIMx capture/compare register 1 (TIMx_CCR1) . . . . . . . . . . . . . . . . . 574
17.4.14 TIMx capture/compare register 2 (TIMx_CCR2) . . . . . . . . . . . . . . . . . 574
17.4.15 TIMx capture/compare register 3 (TIMx_CCR3) . . . . . . . . . . . . . . . . . 575
17.4.16 TIMx capture/compare register 4 (TIMx_CCR4) . . . . . . . . . . . . . . . . . 575
17.4.17 TIMx DMA control register (TIMx_DCR) . . . . . . . . . . . . . . . . . . . . . . . 576
17.4.18 TIMx DMA address for full transfer (TIMx_DMAR) . . . . . . . . . . . . . . . 576
17.4.19 TIM2 option register (TIM2_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577
17.4.20 TIM5 option register (TIM5_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 578
17.4.21 TIMx register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579

18

General-purpose timers (TIM9 to TIM14) . . . . . . . . . . . . . . . . . . . . . . . 581
18.1

TIM9 to TIM14 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581

18.2

TIM9 to TIM14 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581

18.3
16/1327

18.2.1

TIM9/TIM12 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581

18.2.2

TIM10/TIM11 and TIM13/TIM14 main features . . . . . . . . . . . . . . . . . . 582

TIM9 to TIM14 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . 584
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18.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584

18.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586

18.3.3

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589

18.3.4

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591

18.3.5

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592

18.3.6

PWM input mode (only for TIM9/12) . . . . . . . . . . . . . . . . . . . . . . . . . . 593

18.3.7

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594

18.3.8

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595

18.3.9

PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596

18.3.10 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597
18.3.11 TIM9/12 external trigger synchronization . . . . . . . . . . . . . . . . . . . . . . . 599
18.3.12 Timer synchronization (TIM9/12) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602
18.3.13 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602

18.4

TIM9 and TIM12 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602
18.4.1

TIM9/12 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . . . . 602

18.4.2

TIM9/12 slave mode control register (TIMx_SMCR) . . . . . . . . . . . . . . 604

18.4.3

TIM9/12 Interrupt enable register (TIMx_DIER) . . . . . . . . . . . . . . . . . 605

18.4.4

TIM9/12 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 606

18.4.5

TIM9/12 event generation register (TIMx_EGR) . . . . . . . . . . . . . . . . . 608

18.4.6

TIM9/12 capture/compare mode register 1 (TIMx_CCMR1) . . . . . . . . 608

18.4.7

TIM9/12 capture/compare enable register (TIMx_CCER) . . . . . . . . . . 612

18.4.8

TIM9/12 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613

18.4.9

TIM9/12 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613

18.4.10 TIM9/12 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . . . 613
18.4.11 TIM9/12 capture/compare register 1 (TIMx_CCR1) . . . . . . . . . . . . . . . 614
18.4.12 TIM9/12 capture/compare register 2 (TIMx_CCR2) . . . . . . . . . . . . . . . 614
18.4.13 TIM9/12 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 615

18.5

TIM10/11/13/14 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617
18.5.1

TIM10/11/13/14 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . 617

18.5.2

TIM10/11/13/14 Interrupt enable register (TIMx_DIER) . . . . . . . . . . . . 618

18.5.3

TIM10/11/13/14 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . 618

18.5.4

TIM10/11/13/14 event generation register (TIMx_EGR) . . . . . . . . . . . 619

18.5.5

TIM10/11/13/14 capture/compare mode register 1
(TIMx_CCMR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620

18.5.6

TIM10/11/13/14 capture/compare enable register
(TIMx_CCER) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623

18.5.7

TIM10/11/13/14 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . 624

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18.5.8

TIM10/11/13/14 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . 624

18.5.9

TIM10/11/13/14 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . 624

18.5.10 TIM10/11/13/14 capture/compare register 1 (TIMx_CCR1) . . . . . . . . . 625
18.5.11 TIM11 option register 1 (TIM11_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . 625
18.5.12 TIM10/11/13/14 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626

19

Basic timers (TIM6&TIM7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628
19.1

TIM6&TIM7 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628

19.2

TIM6&TIM7 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628

19.3

TIM6&TIM7 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629

19.4

20

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629

19.3.2

Counting mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631

19.3.3

Clock source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633

19.3.4

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634

TIM6&TIM7 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634
19.4.1

TIM6&TIM7 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . 634

19.4.2

TIM6&TIM7 control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . 636

19.4.3

TIM6&TIM7 DMA/Interrupt enable register (TIMx_DIER) . . . . . . . . . . 636

19.4.4

TIM6&TIM7 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . 637

19.4.5

TIM6&TIM7 event generation register (TIMx_EGR) . . . . . . . . . . . . . . 637

19.4.6

TIM6&TIM7 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637

19.4.7

TIM6&TIM7 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 638

19.4.8

TIM6&TIM7 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . 638

19.4.9

TIM6&TIM7 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639

Independent watchdog (IWDG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640
20.1

IWDG introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

20.2

IWDG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

20.3

IWDG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

20.4

18/1327

19.3.1

20.3.1

Hardware watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

20.3.2

Register access protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

20.3.3

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641

IWDG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642
20.4.1

Key register (IWDG_KR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642

20.4.2

Prescaler register (IWDG_PR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643

20.4.3

Reload register (IWDG_RLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644

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20.4.4

Status register (IWDG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644

20.4.5

IWDG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645

Window watchdog (WWDG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646
21.1

WWDG introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646

21.2

WWDG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646

21.3

WWDG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646

21.4

How to program the watchdog timeout . . . . . . . . . . . . . . . . . . . . . . . . . . 648

21.5

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

21.6

WWDG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650
21.6.1

Control register (WWDG_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650

21.6.2

Configuration register (WWDG_CFR) . . . . . . . . . . . . . . . . . . . . . . . . . 651

21.6.3

Status register (WWDG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

21.6.4

WWDG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652

Real-time clock (RTC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653
22.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653

22.2

RTC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653

22.3

RTC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655
22.3.1

Clock and prescalers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655

22.3.2

Real-time clock and calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655

22.3.3

Programmable alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 656

22.3.4

Periodic auto-wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 656

22.3.5

RTC initialization and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 657

22.3.6

Reading the calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659

22.3.7

Resetting the RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660

22.3.8

RTC synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660

22.3.9

RTC reference clock detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661

22.3.10 RTC coarse digital calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661
22.3.11 RTC smooth digital calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 662
22.3.12 Timestamp function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664
22.3.13 Tamper detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665
22.3.14 Calibration clock output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667
22.3.15 Alarm output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667

22.4

RTC and low power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668

22.5

RTC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668

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22.6

RTC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670
22.6.1

RTC time register (RTC_TR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670

22.6.2

RTC date register (RTC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671

22.6.3

RTC control register (RTC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672

22.6.4

RTC initialization and status register (RTC_ISR) . . . . . . . . . . . . . . . . . 674

22.6.5

RTC prescaler register (RTC_PRER) . . . . . . . . . . . . . . . . . . . . . . . . . 676

22.6.6

RTC wakeup timer register (RTC_WUTR) . . . . . . . . . . . . . . . . . . . . . . 677

22.6.7

RTC calibration register (RTC_CALIBR) . . . . . . . . . . . . . . . . . . . . . . . 677

22.6.8

RTC alarm A register (RTC_ALRMAR) . . . . . . . . . . . . . . . . . . . . . . . . 679

22.6.9

RTC alarm B register (RTC_ALRMBR) . . . . . . . . . . . . . . . . . . . . . . . . 680

22.6.10 RTC write protection register (RTC_WPR) . . . . . . . . . . . . . . . . . . . . . 681
22.6.11 RTC sub second register (RTC_SSR) . . . . . . . . . . . . . . . . . . . . . . . . . 681
22.6.12 RTC shift control register (RTC_SHIFTR) . . . . . . . . . . . . . . . . . . . . . . 682
22.6.13 RTC time stamp time register (RTC_TSTR) . . . . . . . . . . . . . . . . . . . . 683
22.6.14 RTC time stamp date register (RTC_TSDR) . . . . . . . . . . . . . . . . . . . . 683
22.6.15 RTC timestamp sub second register (RTC_TSSSR) . . . . . . . . . . . . . . 684
22.6.16 RTC calibration register (RTC_CALR) . . . . . . . . . . . . . . . . . . . . . . . . . 684
22.6.17 RTC tamper and alternate function configuration register
(RTC_TAFCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685
22.6.18 RTC alarm A sub second register (RTC_ALRMASSR) . . . . . . . . . . . . 687
22.6.19 RTC alarm B sub second register (RTC_ALRMBSSR) . . . . . . . . . . . . 688
22.6.20 RTC backup registers (RTC_BKPxR) . . . . . . . . . . . . . . . . . . . . . . . . . 689
22.6.21 RTC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 690

23

20/1327

Fast-mode Plus Inter-integrated circuit (FMPI2C) interface . . . . . . . 692
23.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 692

23.2

FMPI2C main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 692

23.3

FMPI2C implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693

23.4

FMPI2C functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693
23.4.1

FMPI2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694

23.4.2

FMPI2C clock requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695

23.4.3

Mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695

23.4.4

FMPI2C initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697

23.4.5

Software reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701

23.4.6

Data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702

23.4.7

FMPI2C slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704

23.4.8

FMPI2C master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713

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23.4.9

FMPI2C_TIMINGR register configuration examples . . . . . . . . . . . . . . 725

23.4.10 SMBus specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 725
23.4.11 SMBus initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 728
23.4.12 SMBus: FMPI2C_TIMEOUTR register configuration examples . . . . . 730
23.4.13 SMBus slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 731
23.4.14 Error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737
23.4.15 DMA requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 739
23.4.16 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 740

23.5

FMPI2C low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 740

23.6

FMPI2C interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741

23.7

FMPI2C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 742
23.7.1

Control register 1 (FMPI2C_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 742

23.7.2

Control register 2 (FMPI2C_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745

23.7.3

Own address 1 register (FMPI2C_OAR1) . . . . . . . . . . . . . . . . . . . . . . 748

23.7.4

Own address 2 register (FMPI2C_OAR2) . . . . . . . . . . . . . . . . . . . . . . 749

23.7.5

Timing register (FMPI2C_TIMINGR) . . . . . . . . . . . . . . . . . . . . . . . . . . 750

23.7.6

Timeout register (FMPI2C_TIMEOUTR) . . . . . . . . . . . . . . . . . . . . . . . 751

23.7.7

Interrupt and status register (FMPI2C_ISR) . . . . . . . . . . . . . . . . . . . . 752

23.7.8

Interrupt clear register (FMPI2C_ICR) . . . . . . . . . . . . . . . . . . . . . . . . . 754

23.7.9

PEC register (FMPI2C_PECR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755

23.7.10 Receive data register (FMPI2C_RXDR) . . . . . . . . . . . . . . . . . . . . . . . 756
23.7.11 Transmit data register (FMPI2C_TXDR) . . . . . . . . . . . . . . . . . . . . . . . 756
23.7.12 FMPI2C register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757

24

Inter-integrated circuit (I2C) interface . . . . . . . . . . . . . . . . . . . . . . . . . 759
24.1

I2C introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759

24.2

I2C main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760

24.3

I2C functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761
24.3.1

Mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761

24.3.2

I2C slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762

24.3.3

I2C master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765

24.3.4

Error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 771

24.3.5

Programmable noise filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 772

24.3.6

SDA/SCL line control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773

24.3.7

SMBus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773

24.3.8

DMA requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 776

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24.3.9

Packet error checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777

24.4

I2C interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 778

24.5

I2C debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780

24.6

I2C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780
24.6.1

I2C Control register 1 (I2C_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780

24.6.2

I2C Control register 2 (I2C_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782

24.6.3

I2C Own address register 1 (I2C_OAR1) . . . . . . . . . . . . . . . . . . . . . . . 784

24.6.4

I2C Own address register 2 (I2C_OAR2) . . . . . . . . . . . . . . . . . . . . . . . 784

24.6.5

I2C Data register (I2C_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 785

24.6.6

I2C Status register 1 (I2C_SR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 785

24.6.7

I2C Status register 2 (I2C_SR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 789

24.6.8

I2C Clock control register (I2C_CCR) . . . . . . . . . . . . . . . . . . . . . . . . . 790

24.6.9

I2C TRISE register (I2C_TRISE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791

24.6.10 I2C FLTR register (I2C_FLTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 792
24.6.11 I2C register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793

25

Universal synchronous asynchronous receiver
transmitter (USART) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 794
25.1

USART introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 794

25.2

USART main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 795

25.3

USART implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 796

25.4

USART functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 796
25.4.1

USART character description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 799

25.4.2

Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800

25.4.3

Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803

25.4.4

Fractional baud rate generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808

25.4.5

USART receiver tolerance to clock deviation . . . . . . . . . . . . . . . . . . . . 817

25.4.6

Multiprocessor communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 818

25.4.7

Parity control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820

25.4.8

LIN (local interconnection network) mode . . . . . . . . . . . . . . . . . . . . . . 821

25.4.9

USART synchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 823

25.4.10 Single-wire half-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . 825
25.4.11 Smartcard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826
25.4.12 IrDA SIR ENDEC block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 828
25.4.13 Continuous communication using DMA . . . . . . . . . . . . . . . . . . . . . . . . 830
25.4.14 Hardware flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832

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25.5

USART interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834

25.6

USART registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835
25.6.1

Status register (USART_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835

25.6.2

Data register (USART_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 838

25.6.3

Baud rate register (USART_BRR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 838

25.6.4

Control register 1 (USART_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 839

25.6.5

Control register 2 (USART_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841

25.6.6

Control register 3 (USART_CR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 842

25.6.7

Guard time and prescaler register (USART_GTPR) . . . . . . . . . . . . . . 844

25.6.8

USART register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845

Serial peripheral interface/ inter-IC sound (SPI/I2S) . . . . . . . . . . . . . 846
26.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 846
26.1.1

SPI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 846

26.1.2

SPI extended features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 847

26.1.3

I2S features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 847

26.2

SPI/I2S implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 847

26.3

SPI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848
26.3.1

General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848

26.3.2

Communications between one master and one slave . . . . . . . . . . . . . 849

26.3.3

Standard multi-slave communication . . . . . . . . . . . . . . . . . . . . . . . . . . 852

26.3.4

Multi-master communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853

26.3.5

Slave select (NSS) pin management . . . . . . . . . . . . . . . . . . . . . . . . . . 853

26.3.6

Communication formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855

26.3.7

SPI configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857

26.3.8

Procedure for enabling SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857

26.3.9

Data transmission and reception procedures . . . . . . . . . . . . . . . . . . . 858

26.3.10 Procedure for disabling the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860
26.3.11 Communication using DMA (direct memory addressing) . . . . . . . . . . 861
26.3.12 SPI status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863
26.3.13 SPI error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 864

26.4

SPI special features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865
26.4.1

TI mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865

26.4.2

CRC calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866

26.5

SPI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868

26.6

I2S functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869

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26.6.1

I2S general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869

26.6.2

I2S full-duplex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 870

26.6.3

Supported audio protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 871

26.6.4

Clock generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 878

26.6.5

I2S master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880

26.6.6

I2S slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 882

26.6.7

I2S status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883

26.6.8

I2S error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 884

26.6.9

I2S interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885

26.6.10 DMA features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885

26.7

SPI and I2S registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 886
26.7.1

SPI control register 1 (SPI_CR1) (not used in I2S mode) . . . . . . . . . . 886

26.7.2

SPI control register 2 (SPI_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 888

26.7.3

SPI status register (SPI_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 889

26.7.4

SPI data register (SPI_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891

26.7.5

SPI CRC polynomial register (SPI_CRCPR) (not used in I2S
mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891

26.7.6

SPI RX CRC register (SPI_RXCRCR) (not used in I2S mode) . . . . . . 892

26.7.7

SPI TX CRC register (SPI_TXCRCR) (not used in I2S mode) . . . . . . 892

26.7.8

SPI_I2S configuration register (SPI_I2SCFGR) . . . . . . . . . . . . . . . . . . 893

26.7.9

SPI_I2S prescaler register (SPI_I2SPR) . . . . . . . . . . . . . . . . . . . . . . . 894

26.7.10 SPI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896

27

SPDIF receiver interface (SPDIFRX) . . . . . . . . . . . . . . . . . . . . . . . . . . 897
27.1

SPDIFRX interface introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 897

27.2

SPDIFRX main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 897

27.3

SPDIFRX functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 897
27.3.1

S/PDIF protocol (IEC-60958) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 898

27.3.2

SPDIFRX decoder (SPDIFRX_DC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 900

27.3.3

SPDIFRX tolerance to clock deviation . . . . . . . . . . . . . . . . . . . . . . . . . 904

27.3.4

SPDIFRX synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904

27.3.5

SPDIFRX handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906

27.3.6

Data reception management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908

27.3.7

Dedicated control flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910

27.3.8

Reception errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910

27.3.9

Clocking strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 913

27.3.10 Symbol clock generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914

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27.3.11 DMA Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915
27.3.12 Interrupt Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 916
27.3.13 Register protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917

27.4

27.5

Programming procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917
27.4.1

Initialization phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 918

27.4.2

Handling of interrupts coming from SPDIFRX . . . . . . . . . . . . . . . . . . . 919

27.4.3

Handling of interrupts coming from DMA . . . . . . . . . . . . . . . . . . . . . . . 919

SPDIFRX interface registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 920
27.5.1

Control register (SPDIFRX_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 920

27.5.2

Interrupt mask register (SPDIFRX_IMR) . . . . . . . . . . . . . . . . . . . . . . . 923

27.5.3

Status register (SPDIFRX_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 924

27.5.4

Interrupt flag clear register (SPDIFRX_IFCR) . . . . . . . . . . . . . . . . . . . 926

27.5.5

Data input register (SPDIFRX_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 927

27.5.6

Data input register (SPDIFRX_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 928

27.5.7

Data input register (SPDIFRX_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 929

27.5.8

Channel status register (SPDIFRX_CSR) . . . . . . . . . . . . . . . . . . . . . . 930

27.5.9

Debug Information register (SPDIFRX_DIR) . . . . . . . . . . . . . . . . . . . . 931

27.5.10 SPDIFRX version register (SPDIFRX_VERR) . . . . . . . . . . . . . . . . . . . 932
27.5.11 SPDIFRX identification register (SPDIFRX_IDR) . . . . . . . . . . . . . . . . 932
27.5.12 SPDIFRX size identification register (SPDIFRX_SIDR) . . . . . . . . . . . 933
27.5.13 SPDIFRX interface register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 934

28

Serial audio interface (SAI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 935
28.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 935

28.2

SAI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 936

28.3

SAI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 937
28.3.1

SAI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 937

28.3.2

SAI pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 938

28.3.3

Main SAI modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 938

28.3.4

SAI synchronization mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 939

28.3.5

Audio data size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 940

28.3.6

Frame synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 941

28.3.7

Slot configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 944

28.3.8

SAI clock generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 946

28.3.9

Internal FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 948

28.3.10 AC’97 link controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 950
28.3.11 SPDIF output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952
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28.3.12 Specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954
28.3.13 Error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958
28.3.14 Disabling the SAI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961
28.3.15 SAI DMA interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 962

28.4

SAI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 962

28.5

SAI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 964
28.5.1

Global configuration register (SAI_GCR) . . . . . . . . . . . . . . . . . . . . . . . 964

28.5.2

Configuration register 1 (SAI_ACR1 / SAI_BCR1) . . . . . . . . . . . . . . . 964

28.5.3

Configuration register 2 (SAI_ACR2 / SAI_BCR2) . . . . . . . . . . . . . . . 967

28.5.4

Frame configuration register (SAI_AFRCR / SAI_BFRCR) . . . . . . . . . 969

28.5.5

Slot register (SAI_ASLOTR / SAI_BSLOTR) . . . . . . . . . . . . . . . . . . . . 971

28.5.6

Interrupt mask register 2 (SAI_AIM / SAI_BIM) . . . . . . . . . . . . . . . . . . 972

28.5.7

Status register (SAI_ASR / SAI_BSR) . . . . . . . . . . . . . . . . . . . . . . . . . 973

28.5.8

Clear flag register (SAI_ACLRFR / SAI_BCLRFR) . . . . . . . . . . . . . . . 975

28.5.9

Data register (SAI_ADR / SAI_BDR) . . . . . . . . . . . . . . . . . . . . . . . . . . 976

28.5.10 SAI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 977

29

Secure digital input/output interface (SDIO) . . . . . . . . . . . . . . . . . . . . 979
29.1

SDIO main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 979

29.2

SDIO bus topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 979

29.3

SDIO functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981

29.4

29.3.1

SDIO adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 983

29.3.2

SDIO APB2 interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 994

Card functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 995
29.4.1

Card identification mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 995

29.4.2

Card reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996

29.4.3

Operating voltage range validation . . . . . . . . . . . . . . . . . . . . . . . . . . . 996

29.4.4

Card identification process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996

29.4.5

Block write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 997

29.4.6

Block read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 998

29.4.7

Stream access, stream write and stream read
(MultiMediaCard only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 998

29.4.8

Erase: group erase and sector erase . . . . . . . . . . . . . . . . . . . . . . . . 1000

29.4.9

Wide bus selection or deselection . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000

29.4.10 Protection management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000
29.4.11 Card status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1004
29.4.12 SD status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1007

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29.4.13 SD I/O mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1011
29.4.14 Commands and responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012

29.5

29.6

Response formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015
29.5.1

R1 (normal response command) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016

29.5.2

R1b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016

29.5.3

R2 (CID, CSD register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016

29.5.4

R3 (OCR register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017

29.5.5

R4 (Fast I/O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017

29.5.6

R4b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017

29.5.7

R5 (interrupt request) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1018

29.5.8

R6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1018

SDIO I/O card-specific operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1019
29.6.1

SDIO I/O read wait operation by SDIO_D2 signalling . . . . . . . . . . . . 1019

29.6.2

SDIO read wait operation by stopping SDIO_CK . . . . . . . . . . . . . . . 1020

29.6.3

SDIO suspend/resume operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 1020

29.6.4

SDIO interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1020

29.7

HW flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1020

29.8

SDIO registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1021
29.8.1

SDIO power control register (SDIO_POWER) . . . . . . . . . . . . . . . . . . 1021

29.8.2

SDIO clock control register (SDIO_CLKCR) . . . . . . . . . . . . . . . . . . . 1021

29.8.3

SDIO argument register (SDIO_ARG) . . . . . . . . . . . . . . . . . . . . . . . . 1023

29.8.4

SDIO command register (SDIO_CMD) . . . . . . . . . . . . . . . . . . . . . . . 1023

29.8.5

SDIO command response register (SDIO_RESPCMD) . . . . . . . . . . 1024

29.8.6

SDIO response 1..4 register (SDIO_RESPx) . . . . . . . . . . . . . . . . . . 1024

29.8.7

SDIO data timer register (SDIO_DTIMER) . . . . . . . . . . . . . . . . . . . . 1025

29.8.8

SDIO data length register (SDIO_DLEN) . . . . . . . . . . . . . . . . . . . . . 1026

29.8.9

SDIO data control register (SDIO_DCTRL) . . . . . . . . . . . . . . . . . . . . 1026

29.8.10 SDIO data counter register (SDIO_DCOUNT) . . . . . . . . . . . . . . . . . . 1028
29.8.11 SDIO status register (SDIO_STA) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1028
29.8.12 SDIO interrupt clear register (SDIO_ICR) . . . . . . . . . . . . . . . . . . . . . 1029
29.8.13 SDIO mask register (SDIO_MASK) . . . . . . . . . . . . . . . . . . . . . . . . . . 1031
29.8.14 SDIO FIFO counter register (SDIO_FIFOCNT) . . . . . . . . . . . . . . . . . 1033
29.8.15 SDIO data FIFO register (SDIO_FIFO) . . . . . . . . . . . . . . . . . . . . . . . 1034
29.8.16 SDIO register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1035

30

Controller area network (bxCAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1037
30.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1037
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30.2

bxCAN main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1037

30.3

bxCAN general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1038

30.4

30.5

31

28/1327

30.3.1

CAN 2.0B active core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1038

30.3.2

Control, status and configuration registers . . . . . . . . . . . . . . . . . . . . 1038

30.3.3

Tx mailboxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1038

30.3.4

Acceptance filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1039

bxCAN operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1039
30.4.1

Initialization mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1040

30.4.2

Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1040

30.4.3

Sleep mode (low-power) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1040

Test mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1041
30.5.1

Silent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1042

30.5.2

Loop back mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1042

30.5.3

Loop back combined with silent mode . . . . . . . . . . . . . . . . . . . . . . . . 1042

30.6

Behavior in debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1043

30.7

bxCAN functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1043
30.7.1

Transmission handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1043

30.7.2

Time triggered communication mode . . . . . . . . . . . . . . . . . . . . . . . . . 1045

30.7.3

Reception handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1045

30.7.4

Identifier filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047

30.7.5

Message storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1051

30.7.6

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1053

30.7.7

Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1053

30.8

bxCAN interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1056

30.9

CAN registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1057
30.9.1

Register access protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1057

30.9.2

CAN control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1057

30.9.3

CAN mailbox registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1067

30.9.4

CAN filter registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1074

30.9.5

bxCAN register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1078

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS) . . . . . . . 1082
31.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1082

31.2

USB_OTG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1084
31.2.1

General features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1084

31.2.2

Host-mode features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1085

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31.2.3

Peripheral-mode features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1085

31.3

USB_OTG Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086

31.4

USB OTG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086

31.5

31.6

31.7

31.8

31.9

31.4.1

USB OTG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086

31.4.2

OTG core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087

31.4.3

Full-speed OTG PHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088

31.4.4

Embedded full speed OTG PHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088

31.4.5

High-speed OTG PHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089

31.4.6

External Full-speed OTG PHY using the I2C interface . . . . . . . . . . . 1089

OTG dual role device (DRD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089
31.5.1

ID line detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089

31.5.2

HNP dual role device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1090

31.5.3

SRP dual role device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1090

USB peripheral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1090
31.6.1

SRP-capable peripheral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091

31.6.2

Peripheral states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091

31.6.3

Peripheral endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1092

USB host . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095
31.7.1

SRP-capable host . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095

31.7.2

USB host states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096

31.7.3

Host channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1097

31.7.4

Host scheduler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098

SOF trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1099
31.8.1

Host SOFs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1100

31.8.2

Peripheral SOFs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1100

Power options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1100

31.10 Dynamic update of the OTG_HFIR register . . . . . . . . . . . . . . . . . . . . . .1101
31.11 USB data FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1101
31.11.1 Peripheral FIFO architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1102
31.11.2 Host FIFO architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1103
31.11.3 FIFO RAM allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1104

31.12 OTG_FS system performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1106
31.13 OTG_FS/OTG_HS interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1106
31.14 OTG_FS/OTG_HS control and status registers . . . . . . . . . . . . . . . . . . .1108
31.14.1 CSR memory map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1108

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31.15 OTG_FS/OTG_HS registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1114
31.15.1 OTG control and status register (OTG_GOTGCTL) . . . . . . . . . . . . . 1114
31.15.2 OTG interrupt register (OTG_GOTGINT) . . . . . . . . . . . . . . . . . . . . . 1117
31.15.3 OTG AHB configuration register (OTG_GAHBCFG) . . . . . . . . . . . . . 1118
31.15.4 OTG USB configuration register (OTG_GUSBCFG) . . . . . . . . . . . . . 1120
31.15.5 OTG reset register (OTG_GRSTCTL) . . . . . . . . . . . . . . . . . . . . . . . . 1124
31.15.6 OTG core interrupt register (OTG_GINTSTS) . . . . . . . . . . . . . . . . . . 1126
31.15.7 OTG interrupt mask register (OTG_GINTMSK) . . . . . . . . . . . . . . . . . 1131
31.15.8 OTG_FS Receive status debug read/OTG status read and
pop registers (OTG_GRXSTSR/OTG_GRXSTSP) . . . . . . . . . . . . . . 1135
31.15.9 OTG Receive FIFO size register (OTG_GRXFSIZ) . . . . . . . . . . . . . . 1136
31.15.10 OTG Host non-periodic transmit FIFO size register
(OTG_HNPTXFSIZ)/Endpoint 0 Transmit FIFO size
(OTG_DIEPTXF0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1137
31.15.11 OTG non-periodic transmit FIFO/queue status register
(OTG_HNPTXSTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1138
31.15.12 OTG I2C access register (OTG_GI2CCTL) . . . . . . . . . . . . . . . . . . . . 1139
31.15.13 OTG general core configuration register (OTG_GCCFG) . . . . . . . . . 1140
31.15.14 OTG core ID register (OTG_CID) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1141
31.15.15 OTG core LPM configuration register (OTG_GLPMCFG) . . . . . . . . . 1141
31.15.16 OTG Host periodic transmit FIFO size register
(OTG_HPTXFSIZ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1145
31.15.17 OTG device IN endpoint transmit FIFO size register
(OTG_DIEPTXFx) (x = 1..5[FS] /8[HS], where x is the
FIFO_number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1145
31.15.18 Host-mode registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1146
31.15.19 OTG Host configuration register (OTG_HCFG) . . . . . . . . . . . . . . . . . 1146
31.15.20 OTG Host frame interval register (OTG_HFIR) . . . . . . . . . . . . . . . . . 1147
31.15.21 OTG Host frame number/frame time remaining register
(OTG_HFNUM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1148
31.15.22 OTG_Host periodic transmit FIFO/queue status register
(OTG_HPTXSTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1148
31.15.23 OTG Host all channels interrupt register (OTG_HAINT) . . . . . . . . . . 1149
31.15.24 OTG Host all channels interrupt mask register
(OTG_HAINTMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1150
31.15.25 OTG Host port control and status register (OTG_HPRT) . . . . . . . . . 1150
31.15.26 OTG Host channel-x characteristics register (OTG_HCCHARx)
(x = 0..15[HS] / 11[FS], where x = Channel_number) . . . . . . . . . . . . 1153
31.15.27 OTG Host channel-x split control register (OTG_HCSPLTx)
(x = 0..15, where x = Channel_number) . . . . . . . . . . . . . . . . . . . . . . 1154

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31.15.28 OTG Host channel-x interrupt register (OTG_HCINTx)
(x = 0..15[HS] / 11[FS], where x = Channel_number) . . . . . . . . . . . . 1155
31.15.29 OTG Host channel-x interrupt mask register (OTG_HCINTMSKx)
(x = 0..15[HS] / 11[FS], where x = Channel_number) . . . . . . . . . . . . 1157
31.15.30 OTG Host channel-x transfer size register (OTG_HCTSIZx)
(x = 0..15[HS] / 11[FS], where x = Channel_number) . . . . . . . . . . . . 1158
31.15.31 OTG Host channel-x DMA address register (OTG_HCDMAx)
(x = 0..15, where x = Channel_number) . . . . . . . . . . . . . . . . . . . . . . 1160
31.15.32 Device-mode registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1160
31.15.33 OTG device configuration register (OTG_DCFG) . . . . . . . . . . . . . . . 1160
31.15.34 OTG device control register (OTG_DCTL) . . . . . . . . . . . . . . . . . . . . 1162
31.15.35 OTG device status register (OTG_DSTS) . . . . . . . . . . . . . . . . . . . . . 1165
31.15.36 OTG device IN endpoint common interrupt mask register
(OTG_DIEPMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1166
31.15.37 OTG device OUT endpoint common interrupt mask register
(OTG_DOEPMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1167
31.15.38 OTG device all endpoints interrupt register (OTG_DAINT) . . . . . . . . 1168
31.15.39 OTG all endpoints interrupt mask register
(OTG_DAINTMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1169
31.15.40 OTG device VBUS discharge time register
(OTG_DVBUSDIS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1170
31.15.41 OTG device VBUS pulsing time register
(OTG_DVBUSPULSE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1170
31.15.42 OTG Device threshold control register (OTG_DTHRCTL) . . . . . . . . 1171
31.15.43 OTG device each endpoint interrupt register (OTG_DEACHINT) . . . 1172
31.15.44 OTG device IN endpoint FIFO empty interrupt mask register
(OTG_DIEPEMPMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1172
31.15.45 OTG device each endpoint interrupt register mask
(OTG_DEACHINTMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1173
31.15.46 OTG device control IN endpoint 0 control register
(OTG_DIEPCTL0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1173
31.15.47 OTG device endpoint-x control register (OTG_DIEPCTLx)
(x = 1..5[FS] / 0..8[HS], where x = Endpoint_number) . . . . . . . . . . . . 1175
31.15.48 OTG device control OUT endpoint 0 control register
(OTG_DOEPCTL0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1177
31.15.49 OTG device endpoint-x control register (OTG_DOEPCTLx)
(x = 1..5[FS] /8[HS], where x = Endpoint_number) . . . . . . . . . . . . . . 1179
31.15.50 OTG device endpoint-x interrupt register (OTG_DIEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint_number) . . . . . . . . . . . . . . 1181
31.15.51 OTG device endpoint-x interrupt register (OTG_DOEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint_number) . . . . . . . . . . . . . . 1183

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31.15.52 OTG device IN endpoint 0 transfer size register
(OTG_DIEPTSIZ0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1184
31.15.53 OTG Device channel-x DMA address register (OTG_DIEPDMAx)
(x = 0..15, where x= Channel_number) . . . . . . . . . . . . . . . . . . . . . . . 1184
31.15.54 OTG Device channel-x DMA address register (OTG_DOEPDMAx)
(x = 0..15, where x= Channel_number) . . . . . . . . . . . . . . . . . . . . . . . 1185
31.15.55 OTG device OUT endpoint 0 transfer size register
(OTG_DOEPTSIZ0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1185
31.15.56 OTG device IN endpoint-x transfer size register (OTG_DIEPTSIZx)
(x = 1..5[FS] /8[HS], where x= Endpoint_number) . . . . . . . . . . . . . . . 1186
31.15.57 OTG device IN endpoint transmit FIFO status register
(OTG_DTXFSTSx) (x = 0..5[FS] /8[HS], where
x = Endpoint_number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1187
31.15.58 OTG device OUT endpoint-x transfer size register
(OTG_DOEPTSIZx) (x = 1..5[FS] /8[HS],
where x = Endpoint_number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1188
31.15.59 OTG power and clock gating control register (OTG_PCGCCTL) . . . 1189
31.15.60 OTG_FS/OTG_HS register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1190

31.16 OTG_FS/OTG_HS programming model . . . . . . . . . . . . . . . . . . . . . . . 1202
31.16.1 Core initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1202
31.16.2 Host initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1203
31.16.3 Device initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1203
31.16.4 DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1204
31.16.5 Host programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1204
31.16.6 Device programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1237
31.16.7 Worst case response time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1257
31.16.8 OTG programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1259

32

HDMI-CEC controller (HDMI-CEC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1266
32.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1266

32.2

HDMI-CEC controller main features . . . . . . . . . . . . . . . . . . . . . . . . . . . 1266

32.3

HDMI-CEC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267

32.4

32.3.1

HDMI-CEC pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267

32.3.2

HDMI-CEC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267

32.3.3

Message description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268

32.3.4

Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268

Arbitration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1269
32.4.1

32.5

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SFT option bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1270

Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1271

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32.5.1

Bit error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1271

32.5.2

Message error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1271

32.5.3

Bit Rising Error (BRE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1272

32.5.4

Short Bit Period Error (SBPE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1272

32.5.5

Long Bit Period Error (LBPE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1272

32.5.6

Transmission Error Detection (TXERR) . . . . . . . . . . . . . . . . . . . . . . . 1274

32.6

HDMI-CEC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1275

32.7

HDMI-CEC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1276
32.7.1

CEC control register (CEC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1276

32.7.2

CEC configuration register (CEC_CFGR) . . . . . . . . . . . . . . . . . . . . . 1277

32.7.3

CEC Tx data register (CEC_TXDR) . . . . . . . . . . . . . . . . . . . . . . . . . 1280

32.7.4

CEC Rx Data Register (CEC_RXDR) . . . . . . . . . . . . . . . . . . . . . . . . 1280

32.7.5

CEC Interrupt and Status Register (CEC_ISR) . . . . . . . . . . . . . . . . . 1280

32.7.6

CEC interrupt enable register (CEC_IER) . . . . . . . . . . . . . . . . . . . . . 1282

32.7.7

HDMI-CEC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1284

Debug support (DBG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1285
33.1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1285

33.2

Reference ARM® documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286

33.3

SWJ debug port (serial wire and JTAG) . . . . . . . . . . . . . . . . . . . . . . . . 1286
33.3.1

33.4

Mechanism to select the JTAG-DP or the SW-DP . . . . . . . . . . . . . . . 1287

Pinout and debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1287
33.4.1

SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1288

33.4.2

Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . 1288

33.4.3

Internal pull-up and pull-down on JTAG pins . . . . . . . . . . . . . . . . . . . 1289

33.4.4

Using serial wire and releasing the unused debug pins as GPIOs . . 1289

33.5

STM32F446xx JTAG TAP connection . . . . . . . . . . . . . . . . . . . . . . . . . 1290

33.6

ID codes and locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1291
33.6.1

MCU device ID code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1291

33.6.2

Boundary scan TAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1291

33.6.3

Cortex®-M4 with FPU TAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1291

33.6.4

Cortex®-M4 with FPU JEDEC-106 ID code . . . . . . . . . . . . . . . . . . . . 1292

33.7

JTAG debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1292

33.8

SW debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1294
33.8.1

SW protocol introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1294

33.8.2

SW protocol sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1294

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33.9

33.8.3

SW-DP state machine (reset, idle states, ID code) . . . . . . . . . . . . . . 1295

33.8.4

DP and AP read/write accesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1296

33.8.5

SW-DP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1296

33.8.6

SW-AP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297

AHB-AP (AHB access port) - valid for both JTAG-DP
and SW-DP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1298

33.10 Core debug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1299
33.11 Capability of the debugger host to connect under system reset . . . . . 1300
33.12 FPB (Flash patch breakpoint) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1300
33.13 DWT (data watchpoint trigger) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1301
33.14 ITM (instrumentation trace macrocell) . . . . . . . . . . . . . . . . . . . . . . . . . 1301
33.14.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1301
33.14.2 Time stamp packets, synchronization and overflow packets . . . . . . . 1301

33.15 ETM (Embedded trace macrocell) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1303
33.15.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1303
33.15.2 Signal protocol, packet types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1303
33.15.3 Main ETM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1304
33.15.4 Configuration example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1304

33.16 MCU debug component (DBGMCU) . . . . . . . . . . . . . . . . . . . . . . . . . . 1304
33.16.1 Debug support for low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . 1305
33.16.2 Debug support for timers, watchdog, bxCAN and I2C . . . . . . . . . . . . 1305
33.16.3 Debug MCU configuration register . . . . . . . . . . . . . . . . . . . . . . . . . . 1305
33.16.4 Debug MCU APB1 freeze register (DBGMCU_APB1_FZ) . . . . . . . . 1308
33.16.5 Debug MCU APB2 Freeze register (DBGMCU_APB2_FZ) . . . . . . . . 1310

33.17 TPIU (trace port interface unit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1311
33.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1311
33.17.2 TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1312
33.17.3 TPUI formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1314
33.17.4 TPUI frame synchronization packets . . . . . . . . . . . . . . . . . . . . . . . . . 1314
33.17.5 Transmission of the synchronization frame packet . . . . . . . . . . . . . . 1314
33.17.6 Synchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1315
33.17.7 Asynchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1315
33.17.8 TRACECLKIN connection in STM32F446xx . . . . . . . . . . . . . . . . . . . 1315
33.17.9 TPIU registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1315
33.17.10 Example of configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1316

33.18 DBG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1317

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Device electronic signature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1318
34.1

Unique device ID register (96 bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1318

34.2

Flash size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1319

34.3

Package data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1319

Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1320

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List of tables

RM0390

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.

36/1327

STM32F446xx register boundary addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Boot modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Memory mapping vs. Boot mode/physical remap in STM32F446xx. . . . . . . . . . . . . . . . . . 61
Flash module organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Number of wait states according to CPU clock (HCLK) frequency . . . . . . . . . . . . . . . . . . . 65
Program/erase parallelism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Flash interrupt request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Option byte organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Description of the option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Access versus read protection level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
OTP area organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Flash register map and reset value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
CRC calculation unit register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Voltage regulator configuration mode versus device operating mode . . . . . . . . . . . . . . . . 95
Low-power mode summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Sleep-now entry and exit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Stop operating modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Stop mode entry and exit for STM32F446xx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Standby mode entry and exit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
PWR register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
RCC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Port bit configuration table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
RTC_AF1 pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
RTC_AF2 pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
GPIO register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
SYSCFG register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
DMA1 request mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
DMA2 request mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
Source and destination address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
Source and destination address registers in double buffer mode (DBM=1) . . . . . . . . . . . 212
Packing/unpacking & endian behavior (bit PINC = MINC = 1) . . . . . . . . . . . . . . . . . . . . . 213
Restriction on NDT versus PSIZE and MSIZE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
FIFO threshold configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
Possible DMA configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
DMA interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
DMA register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
Vector table for STM32F446xx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
External interrupt/event controller register map and reset values. . . . . . . . . . . . . . . . . . . 248
NOR/PSRAM bank selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
NOR/PSRAM External memory address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
NAND memory mapping and timing registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
NAND bank selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
SDRAM bank selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
SDRAM address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
SDRAM address mapping with 8-bit data bus width. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
SDRAM address mapping with 16-bit data bus width. . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Programmable NOR/PSRAM access parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

DocID026976 Rev 3

RM0390
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
Non-multiplexed I/O NOR Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
16-bit multiplexed I/O NOR Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Non-multiplexed I/Os PSRAM/SRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
16-Bit multiplexed I/O PSRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
NOR Flash/PSRAM: example of supported memories and transactions . . . . . . . . . . . . . 261
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
Programmable NAND Flash access parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
8-bit NAND Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
16-bit NAND Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
ECC result relevant bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
SDRAM signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
FMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
QUADSPI pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
QUADSPI interrupt requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
QUADSPI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
ADC pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
Analog watchdog channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
Configuring the trigger polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
External trigger for regular channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
External trigger for injected channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
ADC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
ADC global register map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
ADC register map and reset values for each ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
ADC register map and reset values (common ADC registers) . . . . . . . . . . . . . . . . . . . . . 399
DAC pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
External triggers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
DAC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
DCMI external signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424
Positioning of captured data bytes in 32-bit words (8-bit width) . . . . . . . . . . . . . . . . . . . . 425
Positioning of captured data bytes in 32-bit words (10-bit width) . . . . . . . . . . . . . . . . . . . 425
Positioning of captured data bytes in 32-bit words (12-bit width) . . . . . . . . . . . . . . . . . . . 426
Positioning of captured data bytes in 32-bit words (14-bit width) . . . . . . . . . . . . . . . . . . . 426

DocID026976 Rev 3

37/1327
41

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.

38/1327

RM0390

Data storage in monochrome progressive video format . . . . . . . . . . . . . . . . . . . . . . . . . . 432
Data storage in RGB progressive video format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
Data storage in YCbCr progressive video format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
Data storage in YCbCr progressive video format - Y extraction mode . . . . . . . . . . . . . . . 434
DCMI interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434
DCMI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447
Counting direction versus encoder signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
TIMx Internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498
Output control bits for complementary OCx and OCxN channels
with break feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510
TIM1&TIM8 register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518
Counting direction versus encoder signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547
TIMx internal trigger connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 562
Output control bit for standard OCx channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572
TIM2 to TIM5 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579
TIMx internal trigger connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605
Output control bit for standard OCx channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613
TIM9/12 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 615
Output control bit for standard OCx channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623
TIM10/11/13/14 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626
TIM6&TIM7 register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639
Min/max IWDG timeout period at 32 kHz (LSI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641
IWDG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645
WWDG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652
Effect of low power modes on RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668
Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669
RTC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 690
STM32F446xx FMPI2C implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693
I2C-SMBUS specification data setup and hold times . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700
FMPI2C configuration table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704
I2C-SMBUS specification clock timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715
SMBus timeout specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 727
SMBUS with PEC configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729
Examples of TIMEOUTA settings for various FMPI2CCLK frequencies
(max tTIMEOUT = 25 ms) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 730
Examples of TIMEOUTB settings for various FMPI2CCLK frequencies. . . . . . . . . . . . . . 730
Examples of TIMEOUTA settings for various FMPI2CCLK frequencies
(max tIDLE = 50 µs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 730
low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 740
FMPI2C Interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741
FMPI2C register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757
Maximum DNF[3:0] value to be compliant with Thd:dat(max) . . . . . . . . . . . . . . . . . . . . . 772
SMBus vs. I2C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774
I2C Interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 778
I2C register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793
USART features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 796
Noise detection from sampled data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807
Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 12 MHz,
oversampling by 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 810
Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 12 MHz,
oversampling by 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 810
Error calculation for programmed baud rates at fPCLK = 16 MHz or fPCLK = 24 MHz,

DocID026976 Rev 3

RM0390

List of tables

oversampling by 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 811
Table 148. Error calculation for programmed baud rates at fPCLK = 16 MHz or fPCLK = 24 MHz,
oversampling by 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 812
Table 149. Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 16 MHz,
oversampling by 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 812
Table 150. Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 16 MHz,
oversampling by 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 813
Table 151. Error calculation for programmed baud rates at fPCLK = 30 MHz or fPCLK = 60 MHz,
oversampling by 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 814
Table 152. Error calculation for programmed baud rates at fPCLK = 30 MHz or fPCLK = 60 MHz,
oversampling by 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 814
Table 153. Error calculation for programmed baud rates at fPCLK = 42 MHz or fPCLK = 84 Hz,
oversampling by 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 815
Table 154. Error calculation for programmed baud rates at fPCLK = 42 MHz or fPCLK = 84 MHz,
oversampling by 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816
Table 155. USART receiver tolerance when DIV fraction is 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 818
Table 156. USART receiver tolerance when DIV_Fraction is different from 0 . . . . . . . . . . . . . . . . . . 818
Table 157. Frame formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820
Table 158. USART interrupt requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834
Table 159. USART register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845
Table 160. SPI interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868
Table 161. Audio-frequency precision using standard 8 MHz HSE . . . . . . . . . . . . . . . . . . . . . . . . . . 879
Table 162. I2S interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885
Table 163. SPI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896
Table 164. Transition sequence for preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
Table 165. Minimum SPDIFRX_CLK frequency versus audio sampling rate . . . . . . . . . . . . . . . . . . . 913
Table 166. Conditions of spdifrx_symb_ck generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915
Table 167. Bit field property versus SPDIFRX state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917
Table 168. SPDIFRX interface register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 934
Table 169. SAI internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 938
Table 170. SAI pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 938
Table 171. External synchronization selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 940
Table 172. Example of possible audio frequency sampling range . . . . . . . . . . . . . . . . . . . . . . . . . . . 947
Table 173. SOPD pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953
Table 174. Parity bit calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953
Table 175. Audio sampling frequency versus symbol rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954
Table 176. SAI interrupt sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 962
Table 177. SAI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 977
Table 178. SDIO I/O definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 982
Table 179. Command format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 987
Table 180. Short response format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 988
Table 181. Long response format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 988
Table 182. Command path status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 988
Table 183. Data token format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 991
Table 184. DPSM flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992
Table 185. Transmit FIFO status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 993
Table 186. Receive FIFO status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 993
Table 187. Card status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1004
Table 188. SD status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1007
Table 189. Speed class code field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1008
Table 190. Performance move field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1009
Table 191. AU_SIZE field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1009

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41

List of tables
Table 192.
Table 193.
Table 194.
Table 195.
Table 196.
Table 197.
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.

40/1327

RM0390

Maximum AU size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1009
Erase size field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010
Erase timeout field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010
Erase offset field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010
Block-oriented write commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013
Block-oriented write protection commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1014
Erase commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1014
I/O mode commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1014
Lock card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015
Application-specific commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015
R1 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016
R2 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016
R3 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017
R4 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017
R4b response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017
R5 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1018
R6 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1019
Response type and SDIO_RESPx registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1025
SDIO register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1035
Transmit mailbox mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1052
Receive mailbox mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1052
bxCAN register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1078
OTG_HS speeds supported . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1083
OTG_FS speeds supported . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1083
Core global control and status registers (CSRs). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1108
Host-mode control and status registers (CSRs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1109
Device-mode control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1111
Data FIFO (DFIFO) access register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1114
Power and clock gating control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 1114
TRDT values (FS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1123
TRDT values (HS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1123
Minimum duration for soft disconnect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1164
OTG_FS/OTG_HS register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1190
HDMI pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267
Error handling timing parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1273
TXERR timing parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1274
HDMI-CEC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1275
HDMI-CEC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1284
SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1288
Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1288
JTAG debug port data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1292
32-bit debug port registers addressed through the shifted value A[3:2] . . . . . . . . . . . . . 1294
Packet request (8-bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1295
ACK response (3 bits). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1295
DATA transfer (33 bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1295
SW-DP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1296
Cortex®-M4 with FPU AHB-AP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1298
Core debug registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1299
Main ITM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1302
Main ETM registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1304
Asynchronous TRACE pin assignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1312
Synchronous TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1312

DocID026976 Rev 3

RM0390
Table 244.
Table 245.
Table 246.
Table 247.

List of tables
Flexible TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1313
Important TPIU registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1316
DBG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1317
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1320

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List of figures

RM0390

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.
Figure 48.

42/1327

System architecture for STM32F446xx devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Flash memory interface connection inside system architecture . . . . . . . . . . . . . . . . . . . . . 63
Sequential 32-bit instruction execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
RDP levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
PCROP levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
CRC calculation unit block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Power supply overview for STM32F446xx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Backup domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Power-on reset/power-down reset waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
BOR thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
PVD thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Simplified diagram of the reset circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Clock tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
HSE/ LSE clock sources (hardware configuration) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Frequency measurement with TIM5 in Input capture mode . . . . . . . . . . . . . . . . . . . . . . . 124
Frequency measurement with TIM11 in Input capture mode . . . . . . . . . . . . . . . . . . . . . . 125
Basic structure of a 5 V tolerant I/O port bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Selecting an alternate function on STM32F446xx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Input floating/pull up/pull down configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Alternate function configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
High impedance-analog configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
DMA block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
Peripheral-to-memory mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
Memory-to-peripheral mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Memory-to-memory mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
FIFO structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
External interrupt/event controller block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
External interrupt/event GPIO mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
FMC block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
FMC memory banks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Mode1 read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
Mode1 write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
ModeA read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
ModeA write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
Mode2 and mode B read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
Mode2 write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
ModeB write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
ModeC read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
ModeC write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
ModeD read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
ModeD write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
Muxed read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
Muxed write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
Asynchronous wait during a read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
Asynchronous wait during a write access waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
Wait configuration waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

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Figure 49.
Figure 50.
Figure 51.
Figure 52.
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Figure 56.
Figure 57.
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Figure 59.
Figure 60.
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Figure 63.
Figure 64.
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Figure 68.
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Figure 90.
Figure 91.
Figure 92.
Figure 93.
Figure 94.
Figure 95.
Figure 96.
Figure 97.
Figure 98.
Figure 99.
Figure 100.

List of figures
Synchronous multiplexed read mode waveforms - NOR, PSRAM (CRAM) . . . . . . . . . . . 282
Synchronous multiplexed write mode waveforms - PSRAM (CRAM). . . . . . . . . . . . . . . . 284
NAND Flash controller waveforms for common memory access . . . . . . . . . . . . . . . . . . . 296
Access to non ‘CE don’t care’ NAND-Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
Burst write SDRAM access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
Burst read SDRAM access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Logic diagram of Read access with RBURST bit set (CAS=1, RPIPE=0) . . . . . . . . . . . . 309
Read access crossing row boundary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
Write access crossing row boundary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
Self-refresh mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
Power-down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
QUADSPI block diagram when dual-flash mode is disabled . . . . . . . . . . . . . . . . . . . . . . 324
QUADSPI block diagram when dual-flash mode is enabled . . . . . . . . . . . . . . . . . . . . . . 325
An example of a read command in quad mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
An example of a DDR command in quad mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
nCS when CKMODE = 0 (T = CLK period). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
nCS when CKMODE = 1 in SDR mode (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . 337
nCS when CKMODE = 1 in DDR mode (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . 338
nCS when CKMODE = 1 with an abort (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . . 338
Single ADC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
ADC1 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
ADC2 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
ADC3 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358
Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
Analog watchdog’s guarded area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
Injected conversion latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
Right alignment of 12-bit data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
Left alignment of 12-bit data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
Left alignment of 6-bit data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
Multi ADC block diagram(1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
Injected simultaneous mode on 4 channels: dual ADC mode . . . . . . . . . . . . . . . . . . . . . 373
Injected simultaneous mode on 4 channels: triple ADC mode . . . . . . . . . . . . . . . . . . . . . 373
Regular simultaneous mode on 16 channels: dual ADC mode . . . . . . . . . . . . . . . . . . . . 374
Regular simultaneous mode on 16 channels: triple ADC mode . . . . . . . . . . . . . . . . . . . . 374
Interleaved mode on 1 channel in continuous conversion mode: dual ADC mode. . . . . . 375
Interleaved mode on 1 channel in continuous conversion mode: triple ADC mode . . . . . 376
Alternate trigger: injected group of each ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
Alternate trigger: 4 injected channels (each ADC) in discontinuous mode . . . . . . . . . . . . 377
Alternate trigger: injected group of each ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
Alternate + regular simultaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
Case of trigger occurring during injected conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
Temperature sensor and VREFINT channel block diagram . . . . . . . . . . . . . . . . . . . . . . 380
DAC channel block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
DAC output buffer connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402
Data registers in single DAC channel mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
Data registers in dual DAC channel mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
Timing diagram for conversion with trigger disabled TEN = 0 . . . . . . . . . . . . . . . . . . . . . 404
DAC LFSR register calculation algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406
DAC conversion (SW trigger enabled) with LFSR wave generation. . . . . . . . . . . . . . . . . 406
DAC triangle wave generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407
DAC conversion (SW trigger enabled) with triangle wave generation . . . . . . . . . . . . . . . 407
DCMI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

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List of figures
Figure 101.
Figure 102.
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Figure 143.
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Top-level block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424
DCMI signal waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425
Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427
Frame capture waveforms in snapshot mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
Frame capture waveforms in continuous grab mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430
Coordinates and size of the window after cropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430
Data capture waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431
Pixel raster scan order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432
Advanced-control timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 451
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 451
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453
Counter timing diagram, update event when ARPE=0
(TIMx_ARR not preloaded) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454
Counter timing diagram, update event when ARPE=1
(TIMx_ARR preloaded) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457
Counter timing diagram, update event when repetition counter is not used . . . . . . . . . . . 458
Counter timing diagram, internal clock divided by 1, TIMx_ARR = 0x6 . . . . . . . . . . . . . . 459
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459
Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36 . . . . . . . . . . . . . . 460
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460
Counter timing diagram, update event with ARPE=1 (counter underflow) . . . . . . . . . . . . 461
Counter timing diagram, update event with ARPE=1 (counter overflow) . . . . . . . . . . . . . 461
Update rate examples depending on mode and TIMx_RCR register settings . . . . . . . . . 463
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 464
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466
Control circuit in external clock mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 468
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468
Output stage of capture/compare channel (channels 1 to 3) . . . . . . . . . . . . . . . . . . . . . . 469
Output stage of capture/compare channel (channel 4). . . . . . . . . . . . . . . . . . . . . . . . . . . 469
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471
Output compare mode, toggle on OC1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474
Center-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475
Complementary output with dead-time insertion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477
Dead-time waveforms with delay greater than the negative pulse. . . . . . . . . . . . . . . . . . 477
Dead-time waveforms with delay greater than the positive pulse. . . . . . . . . . . . . . . . . . . 477
Output behavior in response to a break.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480
Clearing TIMx OCxREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481
6-step generation, COM example (OSSR=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
Example of one pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483
Example of counter operation in encoder interface mode. . . . . . . . . . . . . . . . . . . . . . . . . 486

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RM0390
Figure 151.
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.

List of figures
Example of encoder interface mode with TI1FP1 polarity inverted. . . . . . . . . . . . . . . . . . 486
Example of Hall sensor interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489
Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491
Control circuit in external clock mode 2 + trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . 492
General-purpose timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 522
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 523
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525
Counter timing diagram, Update event when ARPE=0 (TIMx_ARR not preloaded). . . . . 525
Counter timing diagram, Update event when ARPE=1 (TIMx_ARR preloaded). . . . . . . . 526
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528
Counter timing diagram, Update event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528
Counter timing diagram, internal clock divided by 1, TIMx_ARR=0x6 . . . . . . . . . . . . . . . 529
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530
Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36 . . . . . . . . . . . . . . 530
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530
Counter timing diagram, Update event with ARPE=1 (counter underflow). . . . . . . . . . . . 531
Counter timing diagram, Update event with ARPE=1 (counter overflow) . . . . . . . . . . . . . 531
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 532
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534
Control circuit in external clock mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 536
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 536
Output stage of capture/compare channel (channel 1). . . . . . . . . . . . . . . . . . . . . . . . . . . 537
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539
Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542
Center-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543
Example of one-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
Clearing TIMx OCxREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546
Example of counter operation in encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . 548
Example of encoder interface mode with TI1FP1 polarity inverted . . . . . . . . . . . . . . . . . 548
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549
Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
Control circuit in external clock mode 2 + trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . 552
Master/Slave timer example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
Gating timer 2 with OC1REF of timer 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553
Gating timer 2 with Enable of timer 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554
Triggering timer 2 with update of timer 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555
Triggering timer 2 with Enable of timer 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556
Triggering timer 1 and 2 with timer 1 TI1 input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557

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List of figures
Figure 203.
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.

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General-purpose timer block diagram (TIM9 and TIM12) . . . . . . . . . . . . . . . . . . . . . . . . 582
General-purpose timer block diagram (TIM10/11/13/14) . . . . . . . . . . . . . . . . . . . . . . . . . 583
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 585
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 585
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587
Counter timing diagram, update event when ARPE=0
(TIMx_ARR not preloaded) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 588
Counter timing diagram, update event when ARPE=1
(TIMx_ARR preloaded) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 588
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 589
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 591
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592
Output stage of capture/compare channel (channel 1). . . . . . . . . . . . . . . . . . . . . . . . . . . 592
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594
Output compare mode, toggle on OC1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597
Example of one pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600
Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601
Basic timer block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 630
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 630
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632
Counter timing diagram, update event when ARPE = 0
(TIMx_ARR not preloaded) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633
Counter timing diagram, update event when ARPE=1
(TIMx_ARR preloaded) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 634
Independent watchdog block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641
Watchdog block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647
Window watchdog timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648
RTC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654
FMPI2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694
I2C bus protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696
Setup and hold timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698
FMPI2C initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701
Data reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702
Data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703
Slave initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 706
Transfer sequence flowchart for FMPI2C slave transmitter, NOSTRETCH=0 . . . . . . . . . 708
Transfer sequence flowchart for FMPI2C slave transmitter, NOSTRETCH=1 . . . . . . . . . 709
Transfer bus diagrams for FMPI2C slave transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 710
Transfer sequence flowchart for slave receiver with NOSTRETCH=0 . . . . . . . . . . . . . . 711

DocID026976 Rev 3

RM0390
Figure 251.
Figure 252.
Figure 253.
Figure 254.
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.
Figure 302.

List of figures
Transfer sequence flowchart for slave receiver with NOSTRETCH=1 . . . . . . . . . . . . . . 712
Transfer bus diagrams for FMPI2C slave receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 712
Master clock generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714
Master initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 716
10-bit address read access with HEAD10R=0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 716
10-bit address read access with HEAD10R=1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 717
Transfer sequence flowchart for FMPI2C master transmitter for N≤255 bytes. . . . . . . . . 718
Transfer sequence flowchart for FMPI2C master transmitter for N>255 bytes. . . . . . . . . 719
Transfer bus diagrams for FMPI2C master transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . 720
Transfer sequence flowchart for FMPI2C master receiver for N≤255 bytes . . . . . . . . . . . 722
Transfer sequence flowchart for FMPI2C master receiver for N >255 bytes . . . . . . . . . . 723
Transfer bus diagrams for FMPI2C master receiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724
Timeout intervals for tLOW:SEXT, tLOW:MEXT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 727
Transfer sequence flowchart for SMBus slave transmitter N bytes + PEC. . . . . . . . . . . . 731
Transfer bus diagrams for SMBus slave transmitter (SBC=1) . . . . . . . . . . . . . . . . . . . . . 732
Transfer sequence flowchart for SMBus slave receiver N Bytes + PEC . . . . . . . . . . . . . 733
Bus transfer diagrams for SMBus slave receiver (SBC=1) . . . . . . . . . . . . . . . . . . . . . . . 734
Bus transfer diagrams for SMBus master transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 735
Bus transfer diagrams for SMBus master receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737
FMPI2C interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 742
I2C bus protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761
I2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762
Transfer sequence diagram for slave transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764
Transfer sequence diagram for slave receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765
Transfer sequence diagram for master transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768
Transfer sequence diagram for master receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770
I2C interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 779
USART block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 798
Word length programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 799
Configurable stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 801
TC/TXE behavior when transmitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 802
Start bit detection when oversampling by 16 or 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
Data sampling when oversampling by 16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 806
Data sampling when oversampling by 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807
Mute mode using Idle line detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819
Mute mode using address mark detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819
Break detection in LIN mode (11-bit break length - LBDL bit is set) . . . . . . . . . . . . . . . . . 822
Break detection in LIN mode vs. Framing error detection. . . . . . . . . . . . . . . . . . . . . . . . . 823
USART example of synchronous transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 824
USART data clock timing diagram (M=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 824
USART data clock timing diagram (M=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825
RX data setup/hold time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825
ISO 7816-3 asynchronous protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826
Parity error detection using the 1.5 stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 827
IrDA SIR ENDEC- block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829
IrDA data modulation (3/16) -Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829
Transmission using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831
Reception using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832
Hardware flow control between 2 USARTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832
RTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833
CTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833
USART interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835

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List of figures
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.
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Figure 351.

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SPI block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848
Full-duplex single master/ single slave application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 849
Half-duplex single master/ single slave application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850
Simplex single master/single slave application (master in transmit-only/
slave in receive-only mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 851
Master and three independent slaves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 852
Multi-master application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853
Hardware/software slave select management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854
Data clock timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856
TXE/RXNE/BSY behavior in master / full-duplex mode (BIDIMODE=0,
RXONLY=0) in the case of continuous transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 859
TXE/RXNE/BSY behavior in slave / full-duplex mode (BIDIMODE=0,
RXONLY=0) in the case of continuous transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860
Transmission using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 862
Reception using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863
TI mode transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866
I2S block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 869
Full-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 871
I2S Philips protocol waveforms (16/32-bit full accuracy, CPOL = 0). . . . . . . . . . . . . . . . . 872
I2S Philips standard waveforms (24-bit frame with CPOL = 0) . . . . . . . . . . . . . . . . . . . . . 872
Transmitting 0x8EAA33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873
Receiving 0x8EAA33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873
I2S Philips standard (16-bit extended to 32-bit packet frame with CPOL = 0) . . . . . . . . . 873
Example of 16-bit data frame extended to 32-bit channel frame . . . . . . . . . . . . . . . . . . . 874
MSB Justified 16-bit or 32-bit full-accuracy length with CPOL = 0 . . . . . . . . . . . . . . . . . . 874
MSB justified 24-bit frame length with CPOL = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874
MSB justified 16-bit extended to 32-bit packet frame with CPOL = 0 . . . . . . . . . . . . . . . . 875
LSB justified 16-bit or 32-bit full-accuracy with CPOL = 0 . . . . . . . . . . . . . . . . . . . . . . . . 875
LSB justified 24-bit frame length with CPOL = 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 875
Operations required to transmit 0x3478AE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876
Operations required to receive 0x3478AE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876
LSB justified 16-bit extended to 32-bit packet frame with CPOL = 0 . . . . . . . . . . . . . . . . 876
Example of 16-bit data frame extended to 32-bit channel frame . . . . . . . . . . . . . . . . . . . 877
PCM standard waveforms (16-bit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 877
PCM standard waveforms (16-bit extended to 32-bit packet frame). . . . . . . . . . . . . . . . . 877
Audio sampling frequency definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 878
I2S clock generator architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 878
SPDIFRX block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 898
S/PDIF Sub-Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 898
S/PDIF block format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899
S/PDIF Preambles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899
Channel coding example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900
SPDIFRX decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901
Noise filtering and edge detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901
Thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
Synchronization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905
Synchronization process scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
SPDIFRX States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907
SPDIFRX_DR register format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909
Channel/user data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910
S/PDIF overrun error when RXSTEO = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
S/PDIF overrun error when RXSTEO = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 913

DocID026976 Rev 3

RM0390
Figure 352.
Figure 353.
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.

List of figures
SPDIFRX interface interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 916
Functional block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 937
Audio frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 941
FS role is start of frame + channel side identification (FSDEF = TRIS = 1) . . . . . . . . . . . 943
FS role is start of frame (FSDEF = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 944
Slot size configuration with FBOFF = 0 in SAI_xSLOTR . . . . . . . . . . . . . . . . . . . . . . . . . 945
First bit offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 945
Audio block clock generator overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 946
AC’97 audio frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 950
Example of typical AC’97 configuration on devices featuring at least
2 embedded SAIs (three external AC’97 decoders) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 951
SPDIF format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952
SAI_xDR register ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953
Data companding hardware in an audio block in the SAI . . . . . . . . . . . . . . . . . . . . . . . . . 956
Tristate strategy on SD output line on an inactive slot . . . . . . . . . . . . . . . . . . . . . . . . . . . 957
Tristate on output data line in a protocol like I2S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958
Overrun detection error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959
FIFO underrun event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 960
“No response” and “no data” operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 980
(Multiple) block read operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 980
(Multiple) block write operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 980
Sequential read operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981
Sequential write operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981
SDIO block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981
SDIO adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 983
Control unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984
SDIO_CK clock dephasing (BYPASS = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984
SDIO adapter command path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985
Command path state machine (SDIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986
SDIO command transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 987
Data path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989
Data path state machine (DPSM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990
CAN network topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1038
Dual CAN block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1039
bxCAN operating modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1041
bxCAN in silent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1042
bxCAN in loop back mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1042
bxCAN in combined mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1043
Transmit mailbox states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1045
Receive FIFO states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1046
Filter bank scale configuration - register organization . . . . . . . . . . . . . . . . . . . . . . . . . . 1049
Example of filter numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1050
Filtering mechanism - example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1051
CAN error state diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1052
Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1054
CAN frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1055
Event flags and interrupt generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1056
Can mailbox registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1068
OTG full-speed block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086
OTG high-speed block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087
OTG_FS A-B device connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089
USB_FS peripheral-only connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091

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50

List of figures
Figure 403.
Figure 404.
Figure 405.
Figure 406.
Figure 407.
Figure 408.
Figure 409.
Figure 410.
Figure 411.
Figure 412.
Figure 413.
Figure 414.
Figure 415.
Figure 416.
Figure 417.
Figure 418.
Figure 419.
Figure 420.
Figure 421.
Figure 422.
Figure 423.
Figure 424.
Figure 425.
Figure 426.
Figure 427.
Figure 428.
Figure 429.
Figure 430.
Figure 431.
Figure 432.
Figure 433.
Figure 434.
Figure 435.
Figure 436.
Figure 437.
Figure 438.
Figure 439.
Figure 440.
Figure 441.
Figure 442.
Figure 443.
Figure 444.

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RM0390

USB_FS host-only connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095
SOF connectivity (SOF trigger output to TIM and ITR1 connection) . . . . . . . . . . . . . . . 1099
Updating OTG_HFIR dynamically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1101
Device-mode FIFO address mapping and AHB FIFO access mapping . . . . . . . . . . . . . 1102
Host-mode FIFO address mapping and AHB FIFO access mapping . . . . . . . . . . . . . . . 1103
Interrupt hierarchy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1107
Transmit FIFO write task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1206
Receive FIFO read task . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1207
Normal bulk/control OUT/SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1209
Bulk/control IN transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1213
Normal interrupt OUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1216
Normal interrupt IN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1221
Isochronous OUT transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1223
Isochronous IN transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1226
Normal bulk/control OUT/SETUP transactions - DMA . . . . . . . . . . . . . . . . . . . . . . . . . . 1228
Normal bulk/control IN transaction - DMA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1230
Normal interrupt OUT transactions - DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1231
Normal interrupt IN transactions - DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1232
Normal isochronous OUT transaction - DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1233
Normal isochronous IN transactions - DMA mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1234
Receive FIFO packet read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1240
Processing a SETUP packet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1242
Bulk OUT transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1248
TRDT max timing case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1259
A-device SRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260
B-device SRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1261
A-device HNP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1262
B-device HNP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1264
HDMI-CEC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267
Message structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268
Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268
Bit timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1269
Signal free time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1269
Arbitration phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1270
SFT of three nominal bit periods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1270
Error bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1271
Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1273
TXERR detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1274
Block diagram of STM32 MCU and Cortex®-M4 with FPU-level debug support . . . . . . 1285
SWJ debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1287
JTAG TAP connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1290
TPIU block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1311

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RM0390

Documentation conventions

1

Documentation conventions

1.1

List of abbreviations for registers
The following abbreviations 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 (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 (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 by read Software can read this bit. Reading this bit automatically clears it to ‘0’. Writing this
(rc_r)
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.

Reserved (Res.)

Reserved bit, must be kept at reset value.

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Documentation conventions

1.2

RM0390

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®-M4 with FPU
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.

•

I-Code: this bus connects the Instruction bus of the CPU core to the Flash instruction

•

interface. Prefetch is performed on this bus.

•

D-Code: this bus connects the D-Code bus (literal load and debug access) of the CPU

•

to the Flash data interface.

•

Option bytes: product configuration bits stored in the Flash memory.

•

OBL: option byte loader.

•

AHB: advanced high-performance bus.

•

CPU: refers to the Cortex®-M4 with FPUcore.

Peripheral availability
For peripheral availability and number across all sales types, refer to the particular device
datasheet.

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Memory and bus architecture

2

Memory and bus architecture

2.1

System architecture
In STM32F446xx, the main system consists of 32-bit multilayer AHB bus matrix that
interconnects:
•

•

Seven masters:
–

Cortex®-M4 with FPU core I-bus, D-bus and S-bus

–

DMA1 memory bus

–

DMA2 memory bus

–

DMA2 peripheral bus

–

USB OTG HS DMA bus

Seven slaves:
–

Internal Flash memory ICode bus

–

Internal Flash memory DCode bus

–

Main internal SRAM1 (112 KB)

–

Auxiliary internal SRAM2 (16 KB)

–

AHB1 peripherals including AHB to APB bridges and APB peripherals

–

AHB2 peripherals

–

FMC / QUADSPI

The bus matrix provides access from a master to a slave, enabling concurrent access and
efficient operation even when several high-speed peripherals work simultaneously. This
architecture is shown in Figure 1.

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Memory and bus architecture

RM0390

86%B+6B0

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+6

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Figure 1. System architecture for STM32F446xx devices

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2.1.1

I-bus
This bus connects the Instruction bus of the Cortex®-M4 with FPU core to the BusMatrix.
This bus is used by the core to fetch instructions. The target of this bus is a memory
containing code (internal Flash memory/SRAM or external memories through the FMC).

2.1.2

D-bus
This bus connects the databus of the Cortex®-M4 with FPU to the BusMatrix. This bus is
used by the core for literal load and debug access. The target of this bus is a memory
containing code or data (internal Flash memory or external memories through the FMC).

2.1.3

S-bus
This bus connects the system bus of the Cortex®-M4 with FPU core to a BusMatrix. This
bus is used to access data located in a peripheral or in SRAM. Instructions may also be
fetch on this bus (less efficient than ICode). The targets of this bus are the internal SRAM,
SRAM2, the AHB1 peripherals including the APB peripherals, the AHB2 peripherals and the
external memories through the FMC and QUADSPI.

2.1.4

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:

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Memory and bus architecture
internal Flash, internal SRAMs (SRAM1, SRAM2) and external memories through the FMC
and QUADSPI.

2.1.5

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
Flash, internal SRAMs (SRAM1, SRAM2) and external memories through the FMC and the
QUADSPI.

2.1.6

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 SRAMs (SRAM1, SRAM2), internal Flash memory, and external
memories through the FMC and QUADSPI.

2.1.7

BusMatrix
The BusMatrix manages the access arbitration between masters. The arbitration uses a
round-robin algorithm.

2.1.8

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.
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 and Flash
memory interface). Before using a peripheral you have to enable its clock 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.

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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.
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 Memory map and register boundary addresses and peripheral sections.

2.2.2

Memory map and register boundary addresses
See the datasheet corresponding to your device for a comprehensive diagram of the
memory map.
The following table gives the boundary addresses of the peripherals available in the
devices.
Table 1. STM32F446xx register boundary addresses

Boundary address

Peripheral

0xA000 0000 - 0xA000 0FFF

FMC control register

0xA000 1000 - 0xA000 1FFF

QUADSPI register

0x5005 0000 - 0x5005 03FF

DCMI

0x5000 0000 - 0x5003 FFFF

USB OTG FS

0x4004 0000 - 0x4007 FFFF

USB OTG HS

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

Section 6.3.28: RCC register map on page 171

0x4002 3000 - 0x4002 33FF

CRC

Section 4.4.4: CRC register map on page 90

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Bus

Register map

AHB3 Section 11.8: FMC register map on page 322
AHB3

Section 12.5.14: QUADSPI register map on
page 352

AHB2 Section 15.7.12: DCMI register map on page 447
AHB2

Section 31.15.60: OTG_FS/OTG_HS register map
on page 1190
Section 31.15.60: OTG_FS/OTG_HS register map
on page 1190
Section 9.5.11: DMA register map on page 233

AHB1 Section 13.13.18: ADC register map on page 397
Section 3.8: Flash interface registers on page 79

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Table 1. STM32F446xx register boundary addresses (continued)
Boundary address

Peripheral

Bus

Register map

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

0x4001 5C00 - 0x4001 5FFF

SAI2

0x4001 5800 - 0x4001 5BFF

SAI1

0x4001 4800 - 0x4001 4BFF

TIM11

0x4001 4400 - 0x4001 47FF

TIM10

0x4001 4000 - 0x4001 43FF

TIM9

0x4001 3C00 - 0x4001 3FFF

EXTI

0x4001 3800 - 0x4001 3BFF

SYSCFG

0x4001 3400 - 0x4001 37FF

SPI4

APB2 Section 26.7.10: SPI register map on page 896

0x4001 3000 - 0x4001 33FF

SPI1

Section 26.7.10: SPI register map on page 896

0x4001 2C00 - 0x4001 2FFF

SDMMC

Section 29.8.16: SDIO register map on page 1035

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

AHB1 Section 7.4.11: GPIO register map on page 192

APB2 Section 28.5.10: SAI register map on page 977

Section 18.5.12: TIM10/11/13/14 register map on
page 626
APB2
Section 10.3.7: EXTI register map on page 248
Section 8.2.9: SYSCFG register maps on
page 201

APB2

Section 25.6.8: USART register map on page 845
Section 16.4.21: TIM1&TIM8 register map on
page 518

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Table 1. STM32F446xx register boundary addresses (continued)
Boundary address

Peripheral

Bus

0x4000 7400 - 0x4000 77FF

DAC

Section 14.5.15: DAC register map on page 421

0x4000 7000 - 0x4000 73FF

PWR

Section 5.5: PWR register map on page 114

0x4000 6C00 - 0x4000 6FFF

HDMI-CEC

Section 32.7.7: HDMI-CEC register map on
page 1284

0x4000 6800 - 0x4000 6BFF

CAN2

0x4000 6400 - 0x4000 67FF

CAN1

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

SPDIF-RX

0x4000 3C00 - 0x4000 3FFF

SPI3 / I2S3

0x4000 3800 - 0x4000 3BFF

SPI2 / I2S2

0x4000 3000 - 0x4000 33FF

IWDG

0x4000 2C00 - 0x4000 2FFF

WWDG

0x4000 2800 - 0x4000 2BFF

RTC & BKP Registers

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

Section 30.9.5: bxCAN register map on page 1078

Section 24.6.11: I2C register map on page 793

Section 25.6.8: USART register map on page 845

APB1

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Register map

Section 27.5.13: SPDIFRX interface register map
on page 934
Section 26.7.10: SPI register map on page 896
Section 20.4.5: IWDG register map on page 645
Section 21.6.4: WWDG register map on page 652
Section 22.6.21: RTC register map on page 690
Section 18.5.12: TIM10/11/13/14 register map on
page 626
Section 19.4.9: TIM6&TIM7 register map on
page 639

Section 17.4.21: TIMx register map on page 579

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2.2.3

Embedded SRAM
The STM32F446xx feature 4 Kbytes of backup SRAM (see Section 5.1.2: Battery backup
domain) plus 128 Kbytes of system SRAM.
The embedded SRAM can be accessed as bytes, half-words (16 bits) or full words (32 bits).
Read and write operations are performed at CPU speed with 0 wait state. The embedded
SRAM is divided into up to two blocks:
•

SRAM1 and SRAM2 mapped at address 0x2000 0000 and accessible by all AHB
masters.

The AHB masters support concurrent SRAM accesses (from the USB OTG HS): for
instance, the USB OTG HS can read/write from/to SRAM2 while the CPU is reading/writing
from/to SRAM1.
The CPU can access the SRAM1 and SRAM2 through the System Bus or through the ICode/D-Code buses when boot from SRAM is selected or when physical remap is selected
(Section 8.2.1: SYSCFG memory remap register (SYSCFG_MEMRMP) in the SYSCFG
controller). To get the max performance on SRAM execution, physical remap should be
selected (boot or software selection).

2.2.4

Flash memory overview
The Flash memory interface manages CPU AHB I-Code and D-Code 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 a system of instruction
prefetch and cache lines.
The Flash memory is organized as follows:
•

A main memory block divided into sectors.

•

System memory from which the device boots in System memory boot mode

•

512 OTP (one-time programmable) bytes for user data.

•

Option bytes to configure read and write protection, BOR level, watchdog
software/hardware and reset when the device is in Standby or Stop mode.

Refer to Section 3: Embedded Flash memory interface for more details.

2.2.5

Bit banding
The Cortex®-M4 with FPU memory map includes two bit-band regions. These regions map
each word in an alias region of memory to a bit in a bit-band region of memory. Writing to a
word in the alias region has the same effect as a read-modify-write operation on the
targeted bit in the bit-band region.
In the STM32F446xx devices both the peripheral registers and the SRAM are mapped to a
bit-band region, so that single bit-band write and read operations are allowed. The
operations are only available for Cortex®-M4 with FPU accesses, and not from other bus
masters (e.g. DMA).

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A mapping formula shows how to reference each word in the alias region to a corresponding
bit in the bit-band region. The mapping formula is:
bit_word_addr = bit_band_base + (byte_offset x 32) + (bit_number × 4)
where:
–

bit_word_addr is the address of the word in the alias memory region that maps to
the targeted bit

–

bit_band_base is the starting address of the alias region

–

byte_offset is the number of the byte in the bit-band region that contains the
targeted bit

–

bit_number is the bit position (0-7) of the targeted bit

Example
The following example shows how to map bit 2 of the byte located at SRAM address
0x20000300 to the alias region:
0x22006008 = 0x22000000 + (0x300*32) + (2*4)
Writing to address 0x22006008 has the same effect as a read-modify-write operation on bit
2 of the byte at SRAM address 0x20000300.
Reading address 0x22006008 returns the value (0x01 or 0x00) of bit 2 of the byte at SRAM
address 0x20000300 (0x01: bit set; 0x00: bit reset).
For more information on bit-banding, refer to the Cortex®-M4 with FPU programming
manual (see Related documents on page 1).

2.3

Boot configuration
Due to its fixed memory map, the code area starts from address 0x0000 0000 (accessed
through the ICode/DCode buses) while the data area (SRAM) starts from address
0x2000 0000 (accessed through the system bus). The Cortex®-M4 with FPU CPU always
fetches the reset vector on the ICode bus, which implies to have the boot area available only
in the code area (typically, Flash memory). STM32F446xx microcontrollers implement a
special mechanism to be able to boot from other memories (like the internal SRAM).
In the STM32F446xx, three different boot modes can be selected through the BOOT[1:0]
pins as shown in Table 2.
Table 2. Boot modes
Boot mode selection pins
Boot mode

Aliasing

BOOT1

BOOT0

x

0

Main Flash memory Main Flash memory is selected as the boot area

0

1

System memory

System memory is selected as the boot area

1

1

Embedded SRAM

Embedded SRAM is selected as the boot area

The values on the BOOT pins are latched on the 4th rising edge of SYSCLK after a reset. It
is up to the user to set the BOOT1 and BOOT0 pins after reset to select the required boot
mode.

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BOOT0 is a dedicated pin while BOOT1 is shared with a GPIO pin. Once BOOT1 has been
sampled, the corresponding GPIO pin is free and can be used for other purposes.
The BOOT pins are 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 this startup delay is over, the CPU fetches the top-of-stack value from address
0x0000 0000, then starts code execution from the boot memory starting from 0x0000 0004.
Note:

When the device boots from SRAM, in the application initialization code, you have to
relocate the vector table in SRAM using the NVIC exception table and the offset register.

Embedded bootloader
The embedded bootloader mode is used to reprogram the Flash memory using one of the
following serial interfaces:
•

USART

•

CAN2

•

I2C

•

SPI

•

USB OTG FS in Device mode (DFU: device firmware upgrade).

The USART peripherals operate at the internal 16 MHz oscillator (HSI) frequency, while the
CAN and USB OTG FS require an external clock (HSE) multiple of 1 MHz (ranging from 4 to
26 MHz).
The embedded bootloader code is located in system memory. It is programmed by ST
during production. For additional information, refer to application note AN2606.

Physical remap in STM32F446xx
Once the boot pins are selected, the application software can modify the memory
accessible in the code area (in this way the code can be executed through the ICode bus in
place of the System bus). This modification is performed by programming the Section 8.2.1:
SYSCFG memory remap register (SYSCFG_MEMRMP) in the SYSCFG controller.
The following memories can thus be remapped:
•

Main Flash memory

•

System memory

•

Embedded SRAM1 (112 KB)

•

FMC bank 1 (NOR/PSRAM 1 and 2)

•

FMC SDRAM bank 1

Table 3. Memory mapping vs. Boot mode/physical remap in STM32F446xx
Addresses

Boot/Remap in
Boot/Remap in
Boot/Remap in
main Flash memory embedded SRAM System memory

Remap in FMC

0x2001 C000 - 0x2001 FFFF

SRAM2 (16 KB)

SRAM2 (16 KB)

SRAM2 (16 KB)

SRAM2 (16 KB)

0x2000 0000 - 0x2001 BFFF

SRAM1 (112 KB)

SRAM1 (112 KB)

SRAM1 (112 KB)

SRAM1 (112 KB)

0x1FFF 0000 - 0x1FFF 77FF

System memory

System memory

System memory

System memory

0x0810 0000 - 0x0FFF FFFF

Reserved

Reserved

Reserved

Reserved

0x0800 0000 - 0x081F FFFF

Flash memory

Flash memory

Flash memory

Flash memory

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Table 3. Memory mapping vs. Boot mode/physical remap in STM32F446xx (continued)
Addresses

0x0400 0000 - 0x07FF FFFF

0x0000 0000 0x001F FFFF(1)(2)

Boot/Remap in
Boot/Remap in
Boot/Remap in
main Flash memory embedded SRAM System memory
Reserved

Reserved

Flash (512 KB)
Aliased

SRAM1 (112 KB)
Aliased

Remap in FMC

Reserved

FMC bank 1
NOR/PSRAM 2
(128 MB Aliased)

System memory
(30 KB) Aliased

FMC bank 1
NOR/PSRAM 1
(128 MB Aliased)
or FMC SDRAM
bank 1 (128 MB
Aliased)

1. When the FMC is remapped at address 0x0000 0000, only the first two regions of bank 1 memory controller (bank 1
NOR/PSRAM 1 and NOR/PSRAM 2) or SDRAM bank 1 can be remapped. In remap mode, the CPU can access the
external memory via ICode bus instead of System bus which boosts up the performance.
2. Even when aliased in the boot memory space, the related memory is still accessible at its original memory space.

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Embedded Flash memory interface

3

Embedded Flash memory interface

3.1

Introduction
The Flash memory interface manages CPU AHB I-Code and D-Code 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.

3.2

Main features
•

Flash memory read operations

•

Flash memory program/erase operations

•

Read / write protections

•

Prefetch on I-Code

•

64 cache lines of 128 bits on I-Code

•

8 cache lines of 128 bits on D-Code

Figure 2 shows the Flash memory interface connection inside the system architecture.
Figure 2. Flash memory interface connection inside system architecture

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3.3

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Embedded Flash memory
The Flash memory has the following main features:
•

Capacity up to 512 KBytes

•

128 bits wide data read

•

Byte, half-word, word and double word write

•

Sector and mass erase

•

Memory organization
The Flash memory is organized as follows:
–

A main memory block divided into 4 sectors of 16 KBytes, 1 sector of 64 KBytes,
and 3 sectors of 128 Kbytes

–

System memory from which the device boots in System memory boot mode

–

512 OTP (one-time programmable) bytes 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, watchdog
software/hardware and reset when the device is in Standby or Stop mode.

Low-power modes (for details refer to the Power control (PWR) section of the reference
manual)
Table 4. Flash module organization
Block

Name

Block base addresses

Size

Sector 0

0x0800 0000 - 0x0800 3FFF

16 Kbytes

Sector 1

0x0800 4000 - 0x0800 7FFF

16 Kbytes

Sector 2

0x0800 8000 - 0x0800 BFFF

16 Kbytes

Sector 3

0x0800 C000 - 0x0800 FFFF

16 Kbytes

Sector 4

0x0801 0000 - 0x0801 FFFF

64 Kbytes

Sector 5

0x0802 0000 - 0x0803 FFFF

128 Kbytes

Sector 6

0x0804 0000 - 0x0805 FFFF

128 Kbytes

Sector 7

0x0806 0000 - 0x0807 FFFF

128 Kbytes

System memory

0x1FFF 0000 - 0x1FFF 77FF

30 Kbytes

OTP area

0x1FFF 7800 - 0x1FFF 7A0F

528 bytes

Option bytes

0x1FFF C000 - 0x1FFF C00F

16 bytes

Main memory

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Embedded Flash memory interface

3.4

Read interface

3.4.1

Relation between CPU clock frequency and Flash memory read time
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 prefetch buffer must be disabled when the supply voltage is below 2.1 V. The
correspondence between wait states and CPU clock frequency is given in Table 5.

Note:

On STM32F446xx devices:
- when VOS[1:0] = '0x01', the maximum value of fHCLK is 120 MHz.
- when VOS[1:0] = '0x10', the maximum value of fHCLK is 144 MHz. It can be extended to
168 MHz by activating the over-drive mode.
- when VOS[1:0] = '0x11, the maximum value of fHCLK is 168 MHz. It can be extended to
180 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 5.1.3: Voltage regulator for details on how to
activate the over-drive mode).
Table 5. 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

0 WS (1 CPU cycle)

0 < HCLK ≤ 30

0 1, 1->2, 0->2) there is no mass
erase.
•

Level 2: debug/chip read protection 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 or system memory bootloader is no more allowed.

–

JTAG, SWV (single-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 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.
Note:

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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.

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Embedded Flash memory interface
--

Memory area

Table 10. Access versus read protection level
Protection
Level

Debug features, Boot from RAM or
from System memory bootloader
Read

Main Flash Memory

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 is only erased when the RDP changes from level 1 to 0. The OTP area remains unchanged.

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Figure 4 shows how to go from one RDP level to another.
Figure 4. RDP levels
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3.6.4

Write protections
Up to 7 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.

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Embedded Flash memory interface
If an erase operation is requested, the WRPERR bit is set when:
•

Mass, bank, sector erase are configured (MER and SER = 1)

•

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 = 1 and nWRPi = 0 with 0 ≤ i ≤ 117 bits in the FLASH_OPTCRx register

•

A sector erase is requested on a write protected sector. (SER = 1, SNB = i and
nWRPi = 0 with 0 ≤ i ≤ 117 bits in the FLASH_OPTCRx register)

•

The Flash memory is readout protected and an intrusion is detected.

If a program operation is requested, the WRPERR bit is set when:

3.6.5

•

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 user configuration sector

•

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.

Proprietary code readout protection (PCROP)
Flash memory user sectors (0 to 7) can be protected against D-bus read accesses by using
the proprietary readout protection (PCROP).
The PCROP protection is selected as follows, through the SPRMOD option bit in the
FLASH_CR register:
•

SPRMOD = 0: nWRPi control the write protection of respective user sectors

•

SPRMOD = 1: nWRPi control the read and write protection (PCROP) of respective
user sectors.

When a sector is readout protected (PCROP mode activated), it can only be accessed for
code fetch through ICODE Bus on Flash interface:
•

Any read access performed through the D-bus triggers a RDERR flag error.

•

Any program/erase operation on a PCROPed sector triggers a WRPERR flag error.

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Figure 5. PCROP levels
7RITE OPTIONS
30-/$  ACTIVE
AND VALID N720I

,EVEL 
2$0  X!!
2$0  X##
DEFAULT

7RITE OPTIONS
30-/$  ACTIVE
AND VALID N720I

7RITE OPTIONS
30-/$  ACTIVE
AND VALID N720I

.O RESTRICTION ON
7RITE OPTIONS

,EVEL 

,EVEL 

2$0  X##

2$0  X!!

7RITE OPTIONS
30-/$  ACTIVE
AND VALID N720I

7RITE OPTIONS
30-/$  ACTIVE
AND VALID N720I

5SER OPTION SECTOR ERASE
0ROGRAM NEW OPTIONS

'LOBAL MASS ERASE
5SER OPTION SECTION ERASE
0ROGRAM NEW OPTIONS
6ALID N720I MEANS THAT NONE OF THE N720 BITS SET CAN BE RESET TRANSITION FROM  TO 

-36

The deactivation of the SPRMOD and/or the unprotection of PCROPed user sectors can
only occur when, at the same time, the RDP level changes from 1 to 0. If this condition is not
respected, the user option byte modification is canceled and the write error WRPERR flag is
set. The modification of the users option bytes (BOR_LEV, RST_STDBY, ..) is allowed since
none of the active nWRPi bits is reset and SPRMOD is kept active.
Note:

The active value of nWRPi bits is inverted when PCROP mode is active (SPRMOD =1).
If SPRMOD = 1 and nWRPi =1, then user sector i of bank 1, respectively bank 2 is
read/write protected (PCROP).

3.7

One-time programmable bytes
Table 11 shows the organization of the one-time programmable (OTP) part of the OTP area.
Table 11. OTP area organization
Block
0

1
.
.
.

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[128:96]

[95:64]

[63:32]

[31:0]

Address byte 0

OTP0

OTP0

OTP0

OTP0

0x1FFF 7800

OTP0

OTP0

OTP0

OTP0

0x1FFF 7810

OTP1

OTP1

OTP1

OTP1

0x1FFF 7820

OTP1

OTP1

OTP1

OTP1

0x1FFF 7830

.
.
.

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.
.
.

RM0390

Embedded Flash memory interface
Table 11. OTP area organization (continued)
Block

[128:96]

[95:64]

[63:32]

[31:0]

Address byte 0

OTP15

OTP15

OTP15

OTP15

0x1FFF 79E0

OTP15

OTP15

OTP15

OTP15

0x1FFF 79F0

LOCKB15 ...
LOCKB12

LOCKB11 ...
LOCKB8

LOCKB7 ...
LOCKB4

LOCKB3 ...
LOCKB0

0x1FFF 7A00

15
Lock block

The OTP area is divided into 16 OTP data blocks of 32 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.

3.8

Flash interface registers

3.8.1

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.

12

11

3

2

1

0

15

14

13

Res.

Res.

Res.

DCRST ICRST
rw

w

10

9

8

7

6

5

4

DCEN

ICEN

PRFTEN

Res.

Res.

Res.

Res.

rw

rw

rw

LATENCY
rw

rw

rw

rw

Bits 31:13 Reserved, must be kept cleared.
Bit 12 DCRST: Data cache reset
0: Data cache is not reset
1: Data cache is reset
This bit can be written only when the D cache is disabled.
Bit 11 ICRST: Instruction cache reset
0: Instruction cache is not reset
1: Instruction cache is reset
This bit can be written only when the I cache is disabled.
Bit 10 DCEN: Data cache enable
0: Data cache is disabled
1: Data cache is enabled

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Bit 9 ICEN: Instruction cache enable
0: Instruction cache is disabled
1: Instruction cache 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: 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

3.8.2

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

w

w

w

w

w

w

w

w

KEY[15:0]
w

Bits 31:0 FKEYR: 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

3.8.3

Flash option key register (FLASH_OPTKEYR)
The Flash option key register is used to allow program and erase operations in the user
configuration sector.
Address offset: 0x08
Reset value: 0x0000 0000
Access: no wait state, word access

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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: 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

3.8.4

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
r

15

14

13

12

11

10

9

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

RDERR PGSERR PGPERR PGAERR WRPERR
rw

rc_w1

rc_w1

rc_w1

rc_w1

3

2

1

0

Res.

Res.

OPERR

EOP

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 15:9 Reserved, must be kept cleared.
Bit 8 RDERR: Read Protection Error (pcrop)
Set by hardware when an address to be read through the Dbus belongs to a read protected
part of the flash.
Reset by writing 1.
Bit 7 PGSERR: Programming 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.

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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.
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.

3.8.5

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

9

8

7

6

5

4

3

2

1

0

MER

SER

PG

rw

rw

rw

rs
15

14

13

12

11

10

Res.

Res.

Res.

Res.

Res.

Res.

PSIZE[1:0]
rw

rw

rs

Res.

SNB[3:0]
rw

rw

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

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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.
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: Sector number
These bits select the sector to erase.
0000 sector 0
0001 sector 1
...
0101 sector 5
0110 sector 6
0111 sector 7
1000 not allowed
...
1011 not allowed
1100 user specific sector
1101 user configuration sector
1110 not allowed
1111 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.

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Flash option control register (FLASH_OPTCR)
The FLASH_OPTCR register is used to modify the user option bytes.
Address offset: 0x14
Reset value: 0x0FFF AAED. The option bits 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

SPRMOD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw
15

14

13

12

11

10

9

8

rw

rw

rw

7
nRST_
STDBY

rw

rw

rw

rw

22

21

20

19

18

17

16

rw

rw

1

0

nWRP[7:0]
rw

RDP[7:0]
rw

23

rw

rw

rw

rw

rw

rw

6

5

4

3

2

nRST_ WDG_S
STOP
W
rw

rw

Res.

BOR_LEV
rw

rw

OPTST OPTLO
RT
CK
rs

rs

Bit 31 SPRMOD: Selection of Protection Mode of nWPRi bits
0: PCROP disabled, nWPRi bits used for Write Protection on sector i
1: PCROP enabled, nWPRi bits used for PCROP Protection on sector i
Bits 30:24 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 of sectors after reset. They
can be written to program a new write protect value into Flash memory.
0: Write protection active on selected sector
1: Write protection not active on selected sector
These bits contain the value of the write-protection and read-protection (PCROP) option
bytes for sectors 0 to 7 after reset. They can be written to program a new write-protect or
PCROP value into Flash memory.
If SPRMOD is reset:
0: Write protection active on sector i
1: Write protection not active on sector i
If SPRMOD is set:
0: PCROP protection not active on sector i
1: PCROP protection active on sector i
Bits 15:8 RDP: 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

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Bits 7:5 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: WDG_SW
Note: When changing the WDG mode from hardware to software or from software to
hardware, a system reset is required to make the change effective.
Bit 4 Reserved, must be kept cleared. Always read as “0”.
Bits 3:2 BOR_LEV: 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 about BOR characteristics, refer to the “Electrical characteristics” section
in the device 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.

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Flash interface register map

KEY[31:16]

FLASH_
OPTKEYR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

FLASH_SR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BSY

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RDERR

PGSERR

PGPERR

PGAERR

WRPERR

Res.

OPTKEYR[15:0]

Res.

OPTKEYR[31:16]

0

Reset value

0

0

0

0

0

1

1

1

1

1

1

1

0

1

0

1

0

Res.
0

Refer to Table 1 on page 56 for the register boundary addresses.

DocID026976 Rev 3

0

1

1

1

1

0

0

0

0

0

0

1

0
BOR_LEV

1

0

Res.

1

RDP[7:0]

0

WDG_SW

1

0

nRST_STOP

nWRP[7:0]

0

SNB[3:0]

nRST_STDBY

0

PSIZE[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EOPIE
0

Res.

ERRIE
0

Res.

Res.
Res.

Res.
Res.

Res.

0

Res.

Reset value

Res.

FLASH_OPTCR
0x14

Res.

1

Res.

Reset value

0x10

Res.

FLASH_CR

LOCK

0

SPRMOD

Reset value

Res.

0x0C

86/1327

0

KEY[15:0]

EOP

0

0

OPERR

0

0

PG

0

0

SER

0

0

OPTLOCK

0

Res.

0

Res.

ICEN

PRFTEN

0

Res.

DCEN
0

Res.

0x08

0

MER

Reset value

0

LATENCY

OPTSTRT

FLASH_KEYR

STRT

0x04

ICRST

Res.

Reset value

DCRST

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 12. Flash register map and reset value

1

RM0390

CRC calculation unit

4

CRC calculation unit

4.1

CRC introduction
The CRC (cyclic redundancy check) calculation unit is used to get a CRC code from a 32-bit
data word and a fixed generator polynomial.
Among other applications, CRC-based techniques are used to verify data transmission or
storage integrity. In the scope of the EN/IEC 60335-1 standard, they offer a way 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.

4.2

CRC main features
•

Uses CRC-32 (Ethernet) polynomial: 0x4C11DB7
–

X32 + X26 + X23 + X22 + X16 + X12 + X11 + X10 +X8 + X7 + X5 + X4 + X2+ X +1

•

Single input/output 32-bit data register

•

CRC computation done in four AHB clock cycles (HCLK)

•

General-purpose 8-bit register (can be used for temporary storage)

The block diagram is shown in Figure 6.
Figure 6. CRC calculation unit block diagram

$+%EXV
ELW UHDGDFFHVV
'DWDUHJLVWHU RXWSXW

&5&FRPSXWDWLRQ SRO\QRPLDO[&'%
ELW ZULWHDFFHVV
'DWDUHJLVWHU LQSXW
DL

4.3

CRC functional description
The CRC calculation unit mainly consists of a single 32-bit data register, which:
•

is used as an input register to enter new data in the CRC calculator (when writing into
the register)

•

holds the result of the previous CRC calculation (when reading the register)

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Each write operation into the data register creates a combination of the previous CRC value
and the new one (CRC computation is done on the whole 32-bit data word, and not byte per
byte).
The write operation is stalled until the end of the CRC computation, thus allowing back-toback write accesses or consecutive write and read accesses.
The CRC calculator can be reset to 0xFFFF FFFF with the RESET control bit in the
CRC_CR register. This operation does not affect the contents of the CRC_IDR register.

4.4

CRC registers
The CRC calculation unit contains two data registers and a control register.The peripheral
The CRC registers have to be accessed by words (32 bits).

4.4.1

Data register (CRC_DR)
Address offset: 0x00
Reset value: 0xFFFF FFFF

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

DR [31:16]

DR [15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 Data register bits
Used as an input register when writing new data into the CRC calculator.
Holds the previous CRC calculation result when it is read.

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4.4.2

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.
rw

rw

rw

rw

rw

rw

rw

IDR[7:0]
rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 General-purpose 8-bit data register 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.

4.4.3

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RESET
w

Bits 31:1 Reserved, must be kept at reset value.
Bit 0 RESET bit
Resets the CRC calculation unit and sets the data register to 0xFFFF FFFF.
This bit can only be set, it is automatically cleared by hardware.

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0x08

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CRC_CR

Reset value

DocID026976 Rev 3
RESET

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.

Res.

Res.

CRC_IDR

Res.

0x04
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Register
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.

Offset

Res.

4.4.4

Res.

CRC calculation unit
RM0390

CRC register map
Table 13. CRC calculation unit register map and reset values

CRC_DR
Data register

Reset value
0xFFFF FFFF

Independent data register
0x0000

0

RM0390

Power controller (PWR)

5

Power controller (PWR)

5.1

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.
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 STM32F446xx datasheet.
Figure 7. Power supply overview for STM32F446xx
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1. VDDA and VSSA must be connected to VDD and VSS, respectively.

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Power controller (PWR)

5.1.1

RM0390

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.

5.1.2

•

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.

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

The switch to the VBAT supply is controlled by the power-down reset embedded in the Reset
block.

Warning:

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
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:

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•

PC14 and PC15 can be used as either GPIO or LSE pins

•

PC13 can be used as a GPIOas the RTC_AF1 pin (refer to Table 24: RTC_AF1 pin for
more details about this pin configuration)
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RM0390
Note:

Power controller (PWR)
Due to the fact that the switch only sinks a limited amount of current (3 mA), the use of
GPIOs PC13 to PC15 in output mode is 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 the RTC_AF1 pin (refer to Table 24: RTC_AF1 pin for more
details about this pin configuration).

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 6.3.13: RCC APB1 peripheral clock enable register
(RCC_APB1ENR))

2.

Set the DBP bit in the Section 5.4.1: PWR power control register (PWR_CR) and PWR
power control register (PWR_CR) to enable access to the backup domain

3.

Select the RTC clock source: see Section 6.2.8: RTC/AWU clock

4.

Enable the RTC clock by programming the RTCEN [15] bit in the Section 6.3.20: 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 6.3.13).

2.

Set the DBP bit in the PWR power control register (PWR_CR) to enable access to the
backup domain

3.

Enable the backup SRAM clock by setting BKPSRAMEN bit in the RCC APB1
peripheral clock enable register (RCC_APB1ENR).

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 20 backup data registers (80 bytes)
which are reset when a tamper detection event occurs. For more details refer to .

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

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Power controller (PWR)

RM0390

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_CSR register.
The backup SRAM is not mass erased by a tamper event.
When the Flash is read out protected, the backup SRAM is also read protected to prevent
confidential data (such as cryptographic private key) from being accessed. When the
protection level change from level 1 to level 0 is requested, the backup SRAM content is
erased. Refer to the description of Read protection (RDP) option byte.
Figure 8. Backup domain

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5.1.3

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.
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_CR 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

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Power controller (PWR)
scale 3 is automatically selected.(see Section 5.4.1: PWR power control register
(PWR_CR).
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.

–

Low voltage mode.

–

Under‐drive mode: the 1.2 V domain is preserved in reduced leakage mode. This
mode is only available when the main regulator or the low‐power regulator is in
low voltage mode (see Table 14).

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 STM32F446xx datasheet.
Table 14. 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

-

Low-voltage mode

-

-

MR or LPR

-

Over-drive mode(2)

MR

MR

-

-

Under-drive mode

-

-

MR or LPR

-

Power-down mode

-

-

-

Yes

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.

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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_CR register to enable the Over-drive mode and wait for the
ODRDY flag to be set in the PWR_CSR register.

4.

Set the ODSW bit in the PWR_CR 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_CSR 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, SAI1 and
SAI2 clocks, 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_CR 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:

96/1327

1.

Select HSI or HSE as system clock source.

2.

Disable the peripheral clocks that are not generated by the System PLL (I2S clock,
SAI1 and SAI2 clocks, USB_48MHz clock,....)

3.

Reset simultaneously the ODEN and the ODSW bits in the PWR_CR register to switch
back the voltage regulator to Normal mode and disable the Over-drive mode.

4.

Wait for the ODWRDY flag of PWR_CSR to be reset.

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RM0390

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,
SAI1 and SAI2 clocks, USB_48MHz clock,....).

3.

Reset the ODSW bit in the PWR_CR 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_CSR to be reset.

5.

Reset the ODEN bit in the PWR_CR 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.

5.2

Power supply supervisor

5.2.1

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
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5.2.2

RM0390

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 5.2.1: 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
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5.2.3

Programmable voltage detector (PVD)
You 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 Section 5.4.1: PWR power control register (PWR_CR).
The PVD is enabled by setting the PVDE bit.
A PVDO flag is available, in the Section 5.4.2: PWR power control/status register
(PWR_CSR), to indicate if VDD is higher or lower than the PVD threshold. This event is

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Power controller (PWR)
internally connected 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
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5.3

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®-M4 with FPU 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.

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Table 15. Low-power mode summary

Mode name

Sleep
(Sleep now
or Sleep-onexit)

Stop

Standby

5.3.1

Entry

Wakeup

WFI or Return
from ISR

Any interrupt

WFE

Wakeup event

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

PDDS and LPDS
bits +
Any EXTI line (configured
SLEEPDEEP bit
in the EXTI registers,
+ WFI or Return internal and external lines)
from ISR or WFE

PDDS bit +
SLEEPDEEP bit
+ WFI or Return
from ISR or WFE

WKUP pin rising edge,
RTC alarm (Alarm A or
Alarm B), RTC Wakeup
event, RTC tamper
events, RTC time stamp
event, external reset in
NRST pin, IWDG reset

All 1.2 V domain
clocks OFF

HSI and
HSE
oscillators
OFF

ON or in low- power
mode (depends on
PWR power control
register (PWR_CR)

OFF

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 6.3.3: RCC clock configuration register (RCC_CFGR).

5.3.2

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 for STM32F446xx is controlled by the AHB1 peripheral clock enable
register (RCC_AHB1ENR), AHB2 peripheral by the clock enable register
(RCC_AHB2ENR), AHB3 by the peripheral clock enable register (RCC_AHB3ENR) (see
Section 6.3.10: RCC AHB1 peripheral clock enable register (RCC_AHB1ENR),
Section 6.3.11: RCC AHB2 peripheral clock enable register (RCC_AHB2ENR) and
Section 6.3.12: RCC AHB3 peripheral clock enable register (RCC_AHB3ENR),
respectively).
Disabling the peripherals clocks in Sleep mode can be performed automatically by resetting
the corresponding bit in RCC_AHBxLPENR and RCC_APBxLPENR registers.

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5.3.3

Power controller (PWR)

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®-M4 System
Control register is set on Return from ISR.

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®-M4 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®-M4 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 and Shutdown modes 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 239: RTC block diagram).

5.3.4

Sleep mode
Entering Sleep mode
The Sleep mode is entered according to Entering low power mode, when the SLEEPDEEP
bit in the Cortex®-M4 System Control register is cleared.
Refer to Table 16 for details on how to enter the Sleep mode.

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Exiting Sleep mode
The Sleep mode is exited according to Exiting low power mode.
Refer to Table 16 for details on how to exit the Sleep mode.
Table 16. Sleep-now entry and exit
Sleep-now mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP = 0
Refer to the Cortex®-M4 with FPU System Control register.

Mode entry

5.3.5

On Return from ISR while:
– SLEEPDEEP = 0 and
– SLEEPONEXIT = 1
Refer to the Cortex®-M4 with FPU System Control register.

Mode exit

If WFI or Return from ISR was used for entry:
– Interrupt: refer to Table 38: Vector table for STM32F446xx
If WFE was used for entry and SEVONPEND = 0
– Wakeup event: refer to Section 10.2.3: Wakeup event management
If WFE was used for entry and SEVONPEND = 1
– Interrupt event when disabled in NVIC: refer to Table 38: Vector table for
STM32F446xx
– Wakeup event: refer to Section 10.2.3: Wakeup event management.

Wakeup latency

None

Stop mode
The Stop mode is based on the Cortex®-M4 with FPU deepsleep mode combined with
peripheral clock gating. The voltage regulator can be configured either in normal or lowpower 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_CR register. However this will induce an additional startup delay when waking up
from Stop mode (see Table 17).

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Table 17. 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

-

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

Voltage Regulator Mode

Normal
mode

STOP LP-FPD

STOP UMRFPD

-

3

-

1

0

-

LPDS FPDS
bit
bit

1

0

Underdrive
Mode
STOP ULP-FPD

3

-

1

1

Wakeup latency

Entering Stop mode
The Stop mode is entered according to Entering low power mode, when the SLEEPDEEP
bit in Cortex®-M4 System Control register is set.
Refer to Table 18 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_CR).
Stop mode can be entered from Run mode and Low power run mode.
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.

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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 20.3: IWDG functional description.

•

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).

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
The Stop mode is exited according to Exiting low power mode.
Refer to Table 18 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 or low voltage 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.

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Table 18. Stop mode entry and exit for STM32F446xx
Stop mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– Set SLEEPDEEP bit in Cortex®-M4 with FPU System Control register
– Clear PDDS bit in Power Control register (PWR_CR)
– Select the voltage regulator mode by configuring LPDS, MRUDS, LPUDS and
UDEN bits in PWR_CR (see Table 17: Stop operating modes).

Mode entry

On Return from ISR while:
– SLEEPDEEP bit is set in Cortex®-M4 with FPU System Control register
– SLEEPONEXIT = 1
– LPMS = “000” in PWR_C1: volatage regulator in main regulator mode
– LPMS = “001” in PWR_C1: volatage regulator in low power regulator mode
Note: To enter the Stop mode, all EXTI Line pending bits in Pending register
(EXTI_PR), all peripheral interrupts pending bits, the RTC Alarms (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.

Mode exit

Wakeup latency

5.3.6

If WFI or Return from ISTR was used for entry:
All EXTI lines configured in Interrupt mode (the corresponding EXTI Interrupt
vector must be enabled in the NVIC). Refer to Table 38: Vector table for
STM32F446xx.
If WFE was used for entry and SEVONPEND = 0:
All EXTI Lines configured in event mode. Refer to Section 10.2.3: Wakeup
event management
If WFE was used for entry and SEVONPEND = 1:
Any EXTI line 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 38: Vector
table for STM32F446xx.
Wakeup event: refer to Section 10.2.3: Wakeup event management
Refer to Table 17: Stop operating modes

Standby mode
The Standby mode allows to achieve the lowest power consumption. It is based on the
Cortex®-M4 with FPU 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 7).

Entering Standby mode
The Standby mode is entered according to Entering low power mode, when the
SLEEPDEEP bit in the Cortex®-M4 with FPU System Control register is set.

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Refer to Table 19 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 20.3: IWDG functional description.

•

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 according to Exiting low power mode. The SBF
status flag in the PWR power control/status register (PWR_CSR) indicates that the MCU
was in Standby mode. All registers are reset after wakeup from standby except for PWR
power control/status register (PWR_CSR).
Refer to Table 19 for more details on how to exit Standby mode.
Table 19. Standby mode entry and exit
Standby mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP is set in Cortex®-M4 with FPU with FPU System Control
register
– PDDS bit is set in Power Control register (PWR_CR)
– no interrupt (for WFI or event (for WFE) is pending
– WUF bit is cleared in Power Control/Status register (PWR_CR)
– the RTC flag corresponding to the chosen wakeup source (RTC Alarm A,
RTC Alarm B, RTC wakeup, Tamper or Timestamp flags) is cleared

Mode entry

Mode exit
Wakeup latency

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On Return from ISR while:
– SLEEPDEEP bit is set in Cortex®-M4 with FPU with FPU System Control
register and
– SLEEPONEXIT = 1 and
– PDDS bit is set in Power Control register (PWR_CR) and
– no interrupt is pending and
– WUF bit is cleared in Power Control/Status register (PWR_SR) and
– the RTC flag corresponding to the chosen wakeup source (RTC Alarm A,
RTC Alarm B, RTC wakeup, Tamper or Timestamp flags) is cleared
WKUP pin rising edge, RTC alarm (Alarm A and Alarm B), RTC wakeup,
tamper event, time stamp event, external reset in NRST pin, IWDG reset.
Reset phase.

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I/O states in Standby mode
In Standby mode, all I/O pins are high impedance except for:
•

Reset pad (still available)

•

RTC_AF1 pin (PC13) if configured for tamper, time stamp, RTC Alarm out, or RTC
clock calibration out

•

WKUP pin (PA0), if enabled

Debug mode
By default, the debug connection is lost if the application puts the MCU in Stop or Standby
mode while the debug features are used. This is due to the fact that the Cortex®-M4 with
FPU 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 33.16.1: Debug support for low-power modes.

5.3.7

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.
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.

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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

RTC alternate functions to wake up the device from the Standby mode
•

•

•

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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

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

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

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Power controller (PWR)

Safe RTC alternate function wakeup flag clearing sequence
If the selected RTC alternate function is set before the PWR wakeup flag (WUTF) is cleared,
it will not be detected on the next event as detection is made once on the rising edge.
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:
•

•

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)

Clear the PWR Wakeup (WUF) flag

d)

Enable the RTC alarm interrupt

e)

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)

Clear the RTC Wakeup (WUTF) flag

c)

Clear the PWR Wakeup (WUF) flag

d)

Enable the RTC Wakeup interrupt

e)

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)

Clear the PWR Wakeup (WUF) flag

d)

Enable the RTC tamper interrupt

e)

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)

Clear the PWR Wakeup (WUF) flag

d)

Enable the RTC TimeStamp interrupt

e)

Re-enter the low-power mode

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5.4

Power control registers

5.4.1

PWR power control register (PWR_CR)
Address offset: 0x00
Reset value: 0x0000 C000 (reset by wakeup from Standby mode)

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

ADCDC1

Res.

FPDS

DBP

rw

rw

VOS[1:0]
rw

rw

rw

MRUDS LPUDS
rw

rw

21

rw

19

18

UDEN[1:0]

17

16

ODSWEN

ODEN
rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

PVDE

CSBF

CWUF

PDDS

LPDS

rw

rc_w1

rc_w1

rw

rw

PLS[2:0]
rw

20

FISSR FMSSR

rw

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 FISSR: Flash Interface Stop while System Run
0: Flash interface clock run (Default value)
1: Flash Interface clock off.
Note: This bit could not be set while executing with the Flash itself. It should be done with a
specific routine executed from RAM.
Bit 20 FMSSR: Flash Memory Stop while System Run
0: Flash standard mode (Default value)
1: Flash forced to be in STOP or Deep Power Down mode (depending of FPDS value bit) by
hardware.
Note: This bit could not be set while executing with the Flash itself. It should be done with a
specific routine executed from RAM
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.

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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
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 STM32F446xx datasheet 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 and when
the Prefetch is OFF.
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_CSR 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

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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 SBF Standby Flag (write).
Bit 2 CWUF: Clear wakeup flag
This bit is always read as 0.
0: No effect
1: Clear the WUF Wakeup Flag after 2 System clock cycles
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

5.4.2

PWR power control/status register (PWR_CSR)
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.

19

rc_w1
15

14

13

12

11

10

9

Res.

VOSRDY

Res.

Res.

Res.

Res.

BRE

r

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rw

8

7

EWUP1 EWUP2
rw

18

UDRDY[1:0]
rc_w1

17

16

ODSWRDY

ODRDY

r

r

6

5

4

3

2

1

0

Res.

Res.

Res.

BRR

PVDO

SBF

WUF

r

r

r

r

rw

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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 the Under-drive mode is entered in Stop mode and
exited. 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 EWUP1: Enable WKUP1 pin
This bit is set and cleared by software.
0: WKUP1 pin is used for general purpose I/O. An event on the WKUP1 pin does not
wakeup the device from Standby mode.
1: WKUP1 pin is used for wakeup from Standby mode and forced in input pull down
configuration (rising edge on WKUP1 pin wakes-up the system from Standby mode).
Note: This bit is reset by a system reset.
Bit 7 EWUP2: Enable WKUP2 pin
This bit is set and cleared by software
0: WKUP2 pin is used for general purpose I/O. An event on the WKUP2 pin does not
wakeup the device from Standby mode.
1: WKUP2 pin is used for wakeup from Standby mode and forced in input pull down
configuration (rising edge on WKUP2 pin wakes-up the system from Standby mode).
Note: This bit is reset by a system reset.
Bits 7:4 Reserved, must be kept at reset value.

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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.
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_CR)
0: Device has not been in Standby mode
1: Device has been in Standby mode
Bit 0 WUF: Wakeup flag
This bit is set by hardware and cleared either by a system reset or by setting the CWUF bit in
the PWR_CR register.
0: No wakeup event occurred
1: A wakeup event was received from the WKUP pin or from the RTC alarm (Alarm A or
Alarm B), RTC Tamper event, RTC TimeStamp event or RTC Wakeup).
Note: An additional wakeup event is detected if the WKUP pin is enabled (by setting the
EWUP bit) when the WKUP pin level is already high.

5.5

PWR register map
The following table summarizes the PWR registers.

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PDDS

LPDS

Res.

0

0

0

0

SBF

Res.

0

0

WUF

EWUP2.

0

CSBF

EWUP1

0

0

CWUF

0

PVDO

0

PVDE

0

Res.

DBP
0

BRR

FPDS
0

Refer to Table 1 on page 56 for the register boundary addresses.

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PLS[2:0]

LPUDS

VOS[1:0]

0

BRE

Res.

0

0

Res.

VOSRDY

0

Res.

0

MRUDS

1

Res.

1

ADCDC1

0

Res.

ODEN

0

0

Res.

0

ODSWEN
0

ODRDY

UDEN[1:0]
0
UDRDY[1:0]

FMSSR
0
Res.

Res.

FISSR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

ODSWRDY

Reset value

Res.

PWR_CSR

Res.

0x004

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PWR_CR

Res.

0x000

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 20. PWR register map and reset values

0

0

0

0

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Reset and clock control (RCC)

6

Reset and clock control (RCC)

6.1

Reset
There are three types of reset, defined as system Reset, power Reset and backup domain
Reset.

6.1.1

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®-M4 with FPU Application Interrupt and Reset Control
Register must be set to force a software reset on the device. Refer to the Cortex®-M4 with
FPU 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.

For further information on the user option bytes, refer to Section 3: Embedded Flash
memory (FLASH).

6.1.2

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)

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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.
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
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The Backup domain has two specific resets that affect only the Backup domain (see
Figure 12).

6.1.3

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:

6.2

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

•

Two main PLL (PLL) clocks

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.
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Reset and clock control (RCC)
Figure 13. Clock tree

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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_DCKCFGR register is reset, if APBx prescaler is 1, then TIMxCLK = PCLKx,

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otherwise TIMxCLK = 2x PCLKx.
3. When TIMPRE bit in the RCC_DCKCFGR register is set, if APBx prescaler is 1,2 or 4, then TIMxCLK =
HCLK, otherwise TIMxCLK = 4x PCLKx.

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
and, guarantee the appropriate frequency for peripherals that need a specific clock like USB
OTG FS and HS, I2S, SAI, and SDIO.
Several prescalers are used to configure the AHB frequency, the high-speed APB (APB2)
and the low-speed APB (APB1) domains. The maximum frequency of the AHB domain is
180 MHz. The maximum allowed frequency of the high-speed APB2 domain is 90 MHz. The
maximum allowed frequency of the low-speed APB1 domain is 45 MHz
All peripheral clocks are derived from the system clock (SYSCLK) except for:
•

The USB OTG FS clock (48 MHz), which is coming from a specific output of the PLL
(PLLP) or PLLSAI (PLLSAIP)

•

The SDIO clock (48 MHz) which is coming from a specific output of the PLL48CLK
(PLLQ, PLLSAIP), or System Clock.

•

I2S1/2 clocks
To achieve high-quality audio performance and for a better configuration flexibility, the
I2S1 clock and I2S2 clock (which are respectively clocks for I2Ss mapped on APB1
and APB2) can be derived from four sources: specific main PLL output, a specific
PLLI2S output, from an external clock mapped on the I2S_CKIN pin or from HSI/HSE

•

SAIs clock
The SAI1/SAI2 clocks are generated from a specific PLL (Main PLL, PLLSAI, or
PLLI2S), from an external clock mapped on the I2S_CKIN pin or from HSI/HSE clock.
The PLLSAI can be used as clock source for SAI1 peripheral in case the PLLI2S is
programmed to achieve another audio sampling frequency (49.152 MHz or
11.2896 MHz), and the application requires both frequencies at the same time.

•

The USB OTG HS (60 MHz) clock which is provided from the external PHY.

•

SPDIF-Rx clock
The SPDIF-Rx clock is generated from a specific output of PLLI2S or from a specific
output of main PLL.

•

HDMI-CEC clock which is generated from LSE or HSI divided by 488.

•

FMPI2C1 clock which can also be generated from HSI, SYSCLK or APB1 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_DKCFGR 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_DKCFGR 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.

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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®-M4 with FPU free-running clock. For more details, refer to the
Cortex®-M4 with FPU technical reference manual.

6.2.1

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.
Figure 14. HSE/ LSE clock sources (hardware configuration)

OSC_OUT
External clock

(HI-Z)
External
source

OSC_IN OSC_OUT
Crystal/ceramic
resonators
CL1

Load
capacitors

CL2

External source (HSE bypass)
In this mode, an external clock source must be provided. You select this mode 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

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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).

6.2.2

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
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. You can trim the HSI frequency 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 6.2.7: Clock security system (CSS) on page 122.

6.2.3

PLL configuration
The STM32F446xx devices feature three PLLs:
•

•

A main PLL (PLL) clocked by the HSE or HSI oscillator and featuring three different
output clocks:
–

The first output is used to generate the high speed system clock (up to 180 MHz)

–

The second output can be used to generate the clock for the USB OTG FS
(48 MHz) or the SDIO (≤ 48 MHz).

–

The third output can be used to generate the clock for I2S1 and I2S2 clocks,
SPDIF-Rx clock or the high speed system clock.

Two dedicated PLLs (PLLI2S and PLLSAI) used to generate an accurate clock to
achieve high-quality audio performance on the I2S and SAIs interfaces. PLLSAI and
PLLI2S are also used to generate SPDIF-Rx clock or the 48 MHz clock for USB OTG
FS and SDIO.

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, R and Q).
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The PLLI2S and PLLSAI use the same input clock as PLL (PLLSRC bit is common to both
PLLs). However, the PLLI2S and PLLSAI have dedicated enable/disable and division
factors (M, N, P, R 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 Clock Configuration Register (RCC_DCKCFGR) can be
used to configure PLL, PLLI2S, and PLLSAI.

6.2.4

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. You select this mode 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.

6.2.5

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).

6.2.6

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

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control register (RCC_CR) indicate which clock(s) is (are) ready and which clock is currently
used as the system clock.

6.2.7

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
interrupt CSSI), allowing the MCU to perform rescue operations. The CSSI is linked to the
Cortex®-M4 with FPU 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 was enabled, it is also
disabled when the HSE fails.

6.2.8

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.

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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:
–

•

If LSI is selected as the Auto-wakeup unit (AWU) clock:
–

•

The RTC continues to work even if the VDD supply is switched off, provided the
VBAT supply is maintained.
The AWU state is not guaranteed if the VDD supply is powered off. Refer to
Section 6.2.5: LSI clock on page 121 for more details on LSI calibration.

If the HSE clock is used as the RTC clock:
–

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).

Note:

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.

6.2.9

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.

6.2.10

Clock-out capability
Two microcontroller clock output (MCO) pins are available:
•

MCO1
You 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
You 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.

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The selected clock to output onto MCO must not exceed 100 MHz (the maximum I/O
speed).

6.2.11

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 16.

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.
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 ultralow-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
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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, by SPDIF-Rx Frame Synch 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).
Figure 16. Frequency measurement with TIM11 in Input capture mode
7,0

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6.3

RM0390

RCC registers
Refer to Section 1.1: List of abbreviations for registers for a list of abbreviations used in
register descriptions.

6.3.1

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

PLLSAI PLLSAI PLLI2S PLLI2S
RDY
ON
RDY
ON

25

24

23

22

21

20

19

18

17

16

PLL
RDY

PLL
ON

Res.

Res.

Res.

Res.

CSS
ON

HSE
BYP

HSE
RDY

HSE
ON

rw

rw

r

rw

7

6

5

4

3

2

1

0

Res.

HSI
RDY

HSI
ON

r

rw

r

rw

r

rw

r

rw

13

12

11

10

9

8

HSICAL[7:0]
r

r

r

r

r

HSITRIM[4:0]
r

r

r

rw

rw

rw

rw

rw

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

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RM0390

Reset and clock control (RCC)

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
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

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Reset and clock control (RCC)

6.3.2

RM0390

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

30

Res.

15

•

f(VCO clock) = f(PLL clock input) × (PLLN / PLLM)

•

f(PLL general clock output) = f(VCO clock) / PLLP

•

f(USB OTG FS, SDIO) = f(VCO clock) / PLLQ
29

28

27

PLLR[2:0]

26

25

24

PLLQ[3:0]

rw

rw

rw

rw

14

13

12

11

Res.

rw

rw

rw

10

9

8

23

22

21

20

19

18

Res.

PLLSRC

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

Bit 31 Reserved, must be kept at reset value.
Bits 30:28 PLLR[2:0]: Main PLL division factor for I2Ss, SAIs, SYSTEM and SPDIF-Rx clocks
Set and cleared by software to control the frequency of the clock. These bits should be
written only if PLL is disabled.
Clock frequency = VCO frequency / PLLR with 2 ≤ PLLR ≤ 7
000: PLLR = 0, wrong configuration
001: PLLR = 1, wrong configuration
010: PLLR = 2
011: PLLR = 3
...
111: PLLR = 7
Bits 27:24 PLLQ[3:0]: Main PLL (PLL) division factor for USB OTG FS, SDIOclocks
Set and cleared by software to control the frequency of USB OTG FS clock and the
SDIOclock. These bits should be written only if PLL is disabled.
Caution: The USB OTG FS requires a 48 MHz clock to work correctly. The SDIOneeds 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

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RM0390

Reset and clock control (RCC)

Bits 21:18 Reserved, must be kept at reset value.
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 180 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 PLL (PLL) input clock
Set and cleared by software to divide the PLL input clock before the VCO. These bits can be
written only when the PLL is 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

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Reset and clock control (RCC)

6.3.3

RM0390

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[1:0]
rw
15

28

14

rw

26

25

24

MCO1 PRE[2:0]

rw

rw

rw

rw

rw

rw

12

11

10

9

8

Res.

Res.

rw

rw

PPRE1[2:0]
rw

23

22

Res.

13

PPRE2[2:0]
rw

27

MCO2 PRE[2:0]

rw

21

6

5

rw

18

17

16

rw

rw

rw

rw

rw

4

3

2

1

0

rw

r

HPRE[3:0]
rw

19

RTCPRE[4:0]

rw
7

20

MCO1

rw

SWS[1:0]
r

SW[1:0}
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 Reserved, must be kept at reset value.
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

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RM0390

Reset and clock control (RCC)

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 90 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 45 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.

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Reset and clock control (RCC)

RM0390

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[1:0]: 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: PLL_R used as the system clock
Bits 1:0 SW[1:0]: 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_P selected as system clock
11: PLL_R selected as system clock

6.3.4

RCC clock interrupt register (RCC_CIR)
Address offset: 0x0C
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

HSE
RDYIE

HSI
RDYIE

LSE
RDYIE

LSI
RDYIE

CSSF

rw

rw

rw

rw

r

Res.

PLLSAI PLLI2S
PLL
RDYIE RDYIE RDYIE
rw

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rw

rw

CSSC

22

21

PLLSAI PLLI2S
RDYC RDYC

20

19

18

17

16

PLL
RDYC

HSE
RDYC

HSI
RDYC

LSE
RDYC

LSI
RDYC
w

w

w

w

w

w

w

w

7

6

5

4

3

2

1

0

PLL
RDYF

HSE
RDYF

HSI
RDYF

LSE
RDYF

LSI
RDYF

r

r

r

r

r

PLLSAI PLLI2S
RDYF RDYF

DocID026976 Rev 3

r

r

RM0390

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

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Reset and clock control (RCC)

RM0390

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

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RM0390

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

6.3.5

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

30

29

Res.

Res.

OTGHS
RST

15

14

Res.

Res.

28

27

26

25

24

23

22

21

20

19

18

17

16

DMA2
RST

DMA1
RST

Res.

Res.

Res.

Res.

Res.

rw

rw

6

5

4

3

2

1

0

Res.

Res.

Res.

Res

Res.

Res.

13

12

11

10

9

8

7

Res.

CRC
RST

Res.

Res.

Res.

Res.

rw

rw

GPIOH GPIOG GPIOF GPIOE GPIOD GPIOC GPIOB GPIOA
RST
RST
RST
RST
RST
RST
RST
RST
rw

rw

rw

rw

rw

rw

rw

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 28:23 Reserved, must be kept at reset value.

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Reset and clock control (RCC)

RM0390

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
Bits 11:8 Reserved, must be kept at reset value.
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
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

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RM0390

Reset and clock control (RCC)

6.3.6

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

Res.

DCMI
RST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

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
Bits 6:1 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

6.3.7

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: QUADSPI module reset
Set and reset by software
0: does not reset QUADSPI module
1: resets QUADSPI module

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Reset and clock control (RCC)

RM0390

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

6.3.8

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

Res.

Res.

DAC
RST

PWR
RST

CECRS
T

CAN2
RST

rw

rw

rw

13

12

11

Res.

WWDG
RST

15

14

SPI3
RST

SPI2
RST

rw

rw

Res.

25

24

CAN1 FMPI2C1
RST
RST
rw

10
Res.

23

22

21

I2C3
RST

I2C2
RST

I2C1
RST

rw

rw

rw

rw

19

18

17

16

UART5 UART4 UART3 UART2 SPDIFRX
RST
RST
RST
RST
RST
rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

0

Res.

TIM14
RST

TIM13
RST

TIM12
RST

TIM7
RST

TIM6
RST

TIM5
RST

TIM4
RST

TIM3
RST

TIM2
RST

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:30 Reserved, must be kept at reset value.
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: CEC reset
Set and cleared by software.
0: does not reset CEC
1: resets 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 IFMPI2C1RST: FMPI2C1 reset
Set and cleared by software
0: does not reset FMPI2C1
1: resets FMPI2C1

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RM0390

Reset and clock control (RCC)

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
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: SPDIF-Rx reset
Set and cleared by software.
0: does not reset SPDIF-Rx
1: resets SPDIF-Rx
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
Bits 10:9 Reserved, must be kept at reset value.

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Reset and clock control (RCC)

RM0390

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
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

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RM0390

Reset and clock control (RCC)

6.3.9

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

25

24

23

22

SAI2
RST

SAI1
RST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

15

14

13

12

11

10

9

8

7

6

Res.

SYSCFG
RST

SPI4
RST

SPI1
RST

SDIO
RST

Res.

Res.

ADC
RST

Res

Res

rw

rw

rw

rw

rw

21

20

19

18

17

16

TIM11
RST

TIM10
RST

TIM9
RST

Res.

Res.

Res.

rw

rw

rw

5

4

3

2

1

0

Res.

Res.

TIM8
RST

TIM1
RST

rw

rw

USART6 USART1
RST
RST
rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bit 23 SAI2RST: SAI2 reset
This bit is set and reset 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
Bits 21:19 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
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

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Reset and clock control (RCC)

RM0390

Bit 12 SPI1RST: SPI1 reset
This bit is set and cleared by software.
0: does not reset SPI1
1: resets SPI1
Bit 11 SDIORST: SDIO reset
This bit is set and cleared by software.
0: does not reset the SDIO module
1: resets the SDIO 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

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RM0390

Reset and clock control (RCC)

6.3.10

RCC AHB1 peripheral clock enable register (RCC_AHB1ENR)
Address offset: 0x30
Reset value: 0x0010 0000
Access: no wait state, word, half-word and byte access.

31

30

29

Res.

OTGHS
ULPIEN

OTGHS
EN

rw

rw

15

14

Res.

Res.

28

27

26

25

24

23

22

21

DMA2
EN

DMA1
EN

rw

rw

6

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

9

8

7

Res.

CRC
EN
rw

Res.

Res.

Res.

Res.

GPIOH GPIOG
EN
EN
rw

19

18

17

16

Res.

Res.

BKP
SRAMEN

Res.

Res.

5

4

3

2

1

0

GPIOF
EN

GPIOE
EN

GPIOD
EN

GPIOC
EN

GPIOB
EN

GPIOA
EN

rw

rw

rw

rw

rw

rw

rw

20

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
Bits 28:23 Reserved, must be kept at reset value.
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
Bits 20:19 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
Bits 11:8 Reserved, must be kept at reset value.

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Reset and clock control (RCC)

RM0390

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
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

6.3.11

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTGFSEN

Res.

Res.

Res.

Res.

Res.

Res.

DCMIEN

rw

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rw

RM0390

Reset and clock control (RCC)

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
Bits 6:1 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

6.3.12

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

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 QSPIEN: QUADSPI memory controller module clock enable
This bit is set and cleared by software.
0: QUADSPI module clock disabled
1: QUADSPI module clock enabled
Bit 0 FMCEN: Flexible memory controller module clock enable
This bit is set and cleared by software.
0: FMC module clock disabled
1: FMC module clock enabled

6.3.13

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.

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Reset and clock control (RCC)

31

30

29

28

27

Res.

Res.

DAC
EN

PWR
EN

CEC
EN

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

SPI3
EN

SPI2
EN

Res.

WWDG
EN

Res.

rw

rw

Res.

rw

26

RM0390

25

24

23

22

21

I2C3
EN

I2C2
EN

I2C1
EN

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

TIM14
EN

TIM13
EN

TIM12
EN

TIM7
EN

TIM6
EN

TIM5
EN

TIM4
EN

TIM3
EN

TIM2
EN

rw

rw

rw

rw

rw

rw

rw

rw

rw

CAN2 CAN1 FMPI2C1
EN
EN
EN

Res.

Bits 31:30 Reserved, must be kept at reset value.
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: CEC interface clock enable
This bit is set and cleared by software.
0: CEC interface clock disabled
1: CEC interface 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 FMPI2C1EN: FMPI2C1 clock enable
This bit is set and cleared by software.
0: FMPI2C1 clock disabled
1: FMPI2C1 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
Bit 21 I2C1EN: I2C1 clock enable
This bit is set and cleared by software.
0: I2C1 clock disabled
1: I2C1 clock enabled

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20

19

18

17

16

UART5 UART4 USART3 USART2 SPDIFRX
EN
EN
EN
EN
EN
rw

RM0390

Reset and clock control (RCC)

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: SPDIF-Rx clock enable
This bit is set and cleared by software.
0: SPDIF-Rx clock disabled
1: SPDIF-Rx clock enabled
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
Bits 10:9 Reserved, must be kept at reset value.
Bit 8 TIM14EN: TIM14 clock enable
This bit is set and cleared by software.
0: TIM14 clock disabled
1: TIM14 clock enabled
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

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Reset and clock control (RCC)

RM0390

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

6.3.14

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

25

24

23

22

SAI2
EN

SAI1
EN

rw

rw

7

6

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

Res.

SYSCFG
EN

SPI4
EN

SPI1
EN

SDIO
EN

ADC3
EN

ADC2
EN

ADC1
EN

rw

rw

rw

rw

rw

rw

rw

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Res.

Res.

DocID026976 Rev 3

21

20

19

18

17

16

TIM11
EN

TIM10
EN

TIM9
EN

rw

rw

rw

2

1

0

Res.

TIM8
EN

TIM1
EN

rw

rw

Res.

Res.

Res.

5

4

3

USART6 USART1
EN
EN
rw

rw

Res.

RM0390

Reset and clock control (RCC)

Bits 31:24 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
Bits 21:19 Reserved, must be kept at reset value.
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
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 SDIOEN: SDIO clock enable
This bit is set and cleared by software.
0: SDIO module clock disabled
1: SDIO module clock enabled
Bit 10 ADC3EN: ADC3 clock enable
This bit is set and cleared by software.
0: ADC3 clock disabled
1: ADC3 clock disabled

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Reset and clock control (RCC)

RM0390

Bit 9

ADC2EN: ADC2 clock enable
This bit is set and cleared by software.
0: ADC2 clock disabled
1: ADC2 clock disabled

Bit 8

ADC1EN: ADC1 clock enable
This bit is set and cleared by software.
0: ADC1 clock disabled
1: ADC1 clock disabled

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
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

6.3.15

RCC AHB1 peripheral clock enable in low power mode register
(RCC_AHB1LPENR)
Address offset: 0x50
Reset value: 0x6067 90FF
Access: no wait state, word, half-word and byte access.

31

30

Res.

OTGHS
ULPI
LPEN
rw

rw

15

14

FLITF
LPEN

Res.

rw

150/1327

29
OTGHS
LPEN

28

27

26

25

24

23

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

9

8

7

Res.

CRC
LPEN

Res.

Res.

Res.

Res.

rw

22

21

DMA2
LPEN

DMA1
LPEN

rw

rw

6

5

20

19

Res.

Res.

4

3

18

17

16

BKP
SRAM2 SRAM1
SRAM
LPEN LPEN
LPEN
rw

rw

rw

2

1

0

GPIOH GPIOG GPIOF GPIOE GPIOD GPIOC GPIOB GPIOA
LPEN LPEN LPEN LPEN LPEN LPEN LPEN LPEN
rw

DocID026976 Rev 3

rw

rw

rw

rw

rw

rw

rw

RM0390

Reset and clock control (RCC)

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
Bits 28:23 Reserved, must be kept at reset value.
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
Bits 20:19 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
Bits 14:13 Reserved, must be kept at reset value.
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
Bits 11:8 Reserved, must be kept at reset value.
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

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RM0390

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

6.3.16

RCC AHB2 peripheral clock enable in low power mode register
(RCC_AHB2LPENR)
Address offset: 0x54
Reset value: 0x0000 0081
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
LPEN

Res.

DCMI
LPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

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Res.

Res.

Res.

Res.

rw

RM0390

Reset and clock control (RCC)

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
Bits 6:1 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

6.3.17

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

rw

Bits 31:2Reserved, must be kept at reset value.
Bit 1 QSPILPEN: QUADSPI memory controller module clock enable during Sleep mode
This bit is set and cleared by software.
0: QUADSPI module clock disabled during Sleep mode
1: QUADSPI module 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

6.3.18

RCC APB1 peripheral clock enable in low power mode register
(RCC_APB1LPENR)
Address offset: 0x60
Reset value: 0x3FFF C9FF
Access: no wait state, word, half-word and byte access.

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Reset and clock control (RCC)

31

30

29

Res.

Res.

DAC
LPEN
rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

SPI3
LPEN

SPI2
LPEN

Res.

WWDG
LPEN

Res.

TIM14
LPEN

rw

rw

Res.

28

27

RM0390

26

PWR CECLP CAN2
LPEN
EN
LPEN

rw

Res.

25

24

23

22

21

I2C2
LPEN

I2C1
LPEN

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

TIM7
LPEN

TIM6
LPEN

TIM5
LPEN

TIM4
LPEN

TIM3
LPEN

TIM2
LPEN

rw

rw

rw

rw

rw

rw

CAN1 FMPI2C1 I2C3
LPEN
LPEN
LPEN

rw

TIM13 TIM12
LPEN LPEN
rw

rw

20

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: CEC clock enable during Sleep mode
This bit is set and cleared by software.
0: CEC clock disabled during Sleep mode
1: CEC clock enabled during Sleep mode
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 FMPI2C1LPEN: FMPI2C1 clock enable during Sleep mode
This bit is set and cleared by software.
0: FMPI2C1 clock disabled during Sleep mode
1: FMPI2C1 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

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18

17

16

UART5 UART4 USART3 USART2 SPDIFRX
LPEN
LPEN
LPEN
LPEN
LPEN

Bits 31:30 Reserved, must be kept at reset value.

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

19

rw

RM0390

Reset and clock control (RCC)

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 SPDIFLPEN: SPDIF-Rx clock enable during Sleep mode
This bit is set and cleared by software.
0: SPDIF-Rx clock disabled during Sleep mode
1: SPDIF-Rx clock enabled during Sleep mode
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
Bits 10:9 Reserved, must be kept at reset value.
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

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RM0390

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
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

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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

DocID026976 Rev 3

RM0390

Reset and clock control (RCC)

6.3.19

RCC APB2 peripheral clock enabled in low power mode register
(RCC_APB2LPENR)
Address offset: 0x64
Reset value: 0x0x00C7 FF33
Access: no wait state, word, half-word and byte access.

31

30

29

28

27

26

25

24

23

22

SAI2
LPEN

SAI1
LPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

15

14

13

12

11

10

9

8

7

6

Res.

SYSCFG
LPEN

SPI4
LPEN

SPI1
LPEN

SDIO
LPEN

ADC3
LPEN

ADC2
LPEN

ADC1
LPEN

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

21

20

19

18

17

16

TIM11
LPEN

TIM10
LPEN

TIM9
LPEN

Res.

Res.

Res.

rw

rw

rw

5

4

3

2

1

0

Res.

Res.

TIM8
LPEN

TIM1
LPEN

rw

rw

USART6 USART1
LPEN
LPEN
rw

rw

Bits 31:24 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
Bits 21:19 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
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

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RM0390

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 SDIOLPEN: SDIO clock enable during Sleep mode
This bit is set and cleared by software.
0: SDIO module clock disabled during Sleep mode
1: SDIO 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 disabled 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 disabled 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 disabled 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
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

6.3.20

RCC Backup domain control register (RCC_BDCR)
Address offset: 0x70

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RM0390

Reset and clock control (RCC)
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, 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_CR) has to be set
before these can be modified. Refer to Section 6.1.1: System reset on page 115 for further
information. These bits are only reset after a Backup domain Reset (see Section 6.1.3:
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.

Res.

LSEMOD

LSEBYP

rw

rw

rw

rw

RTCSEL[1:0]
rw

rw

0

LSERDY LSEON
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.
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 7:4 Reserved, must be kept at reset value.
Bit 3 LSEMOD: External low-speed oscillator mode
This bit is set and cleared by software to select the low speed oscillator crystal mode. Two
power modes are available. This bit can be written only when the LSE clock is disabled.
0: LSE oscillator "low power" mode selection
1: LSE oscillator "high drive" mode selection

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RM0390

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

6.3.21

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

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.

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.

Res.

Res.

LSIRDY

LSION

r

rw

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

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RM0390

Reset and clock control (RCC)

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
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

6.3.22

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.

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Reset and clock control (RCC)

31

30

29

28

SSCGEN

SPREADSEL

Res.

Res.

rw

rw

15

14

13

12

RM0390

27

26

25

rw

rw

rw

11

10

9

24

23

22

rw

rw

7

6

20

19

18

17

16

rw

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

INCSTEP

8

INCSTEP
rw

21

MODPER

rw

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
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.

6.3.23

RCC PLLI2S configuration register (RCC_PLLI2SCFGR)
Address offset: 0x84
Reset value: 0x2400 3010
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 / PLLI2SM)
f(PLL I2S clock output) = f(VCO clock) / PLLI2SR
f(PLL SPDIFRX clock output) = f(VCO clock) / PLLI2SP

31

30

Res.

15

29

28

27

PLLI2SR[2:0]

25

24

rw

rw

rw

rw

rw

rw

rw

14

13

12

11

10

9

8

Res.

23

22

21

20

19

18

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

PLLI2SN[8:0]
rw

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26

PLLI2SQ[3:0]

rw

rw

rw

rw

17

16

PLLI2SP[1:0]
rw

rw

1

0

rw

rw

PLLI2SM[5:0]
rw

rw

rw

rw

DocID026976 Rev 3

rw

rw

rw

rw

RM0390

Reset and clock control (RCC)

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 26.6.4: Clock generator 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 SAI1 clock
These bits are set and cleared by software to control the SAI1 clock frequency.
They should be written when the PLLI2S is disabled.
SAI1 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 SPDIF-Rx clock
These bits are set and cleared by software to control the SPDIF-Rx clock frequency.
They should be written when the PLLI2S is disabled.
Caution: The software has to set these bits correctly to ensure that the output frequency
doesn’t exceed 120 MHz on this output.
PLL output clock frequency = VCO frequency / PLLI2SP with PLLI2SIP = 2, 4, 6 or 8
00: PLLI2SP =2
01: PLLI2SP = 4
10: PLLI2SP = 6
11: PLLI2SP = 8

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Reset and clock control (RCC)

RM0390

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 PLLI2SM[5:0]: Division factor for audio PLL (PLLI2S) input clock
Set and cleared by software to divide PLLI2S input clock before the VCO.
These bits can be written only when PLLI2S is 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 / PLLI2S with 2 ≤ PLLI2SM ≤ 63
000000: PLLI2SM = 0, wrong configuration
000001: PLLI2SM = 1, wrong configuration
000010: PLLI2SM = 2
000011: PLLI2SM = 3
000100: PLLI2SM = 4
...
111110: PLLI2SM = 62
111111: PLLI2SM = 63

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RM0390

Reset and clock control (RCC)

6.3.24

RCC PLL 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:
•

f(VCO clock) = f(PLLSAI clock input) × (PLLSAIN / PLLM)

•

f(PLL SAI 48MHz clock output) = f(VCO clock) / PLLSAIP

•

f(PLL SAI1 clock output) = f(VCO clock) / PLLSAIQ

31

30

29

28

Res.

Res.

Res.

Res.

27

rw
15

14

13

12

26

25

24

PLLSAIQ[3:0]

11

Res.

rw

rw

rw

10

9

8

23

22

21

20

19

18

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

PLLSAIN[8:0]
rw

rw

rw

rw

rw

3

2

17

16

PLLSAIP[1:0]
rw

rw

1

0

rw

rw

PLLSAIM[5:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 PLLSAIQ: PLLSAI division factor for SAIs clock
Set and reset by software to control the frequency of SAIs 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.
Bits 17:16 PLLSAIP: PLLSAI division factor for 48 MHz clock
These bits are set and cleared by software to control the output clock frequency.
They should be written when the PLLSAI is disabled.
Caution: The software has to set these bits correctly to ensure that the output frequency not
exceed 120 MHz on this output
PLL output clock frequency = VCO frequency / PLLSAIP with PLLSAIP = 2, 4, 6 or 8
00: PLLSAIP =2
01: PLLSAIP = 4
10: PLLSAIP = 6
11: PLLSAIP = 8

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RM0390

Bit 15 Reserved, must be kept at reset value.
Bits 14:6 PLLSAIN: 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: PLLSAIN = 50
...
001100011: PLLSAIN = 99
001100100: PLLSAIN = 100
001100101: PLLSAIN = 101
001100110: PLLSAIN = 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 PLLSAIM: Division factor for audio PLLSAI input clock
Set and cleared by software to divide PLLSAI input clock before the VCO.
These bits can be written only when PLLSAI is 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 / PLLSAI with 2 <= PLLSAIM <= 63
000000: PLLSAIM = 0, wrong configuration
000001: PLLSAIM = 1, wrong configuration
000010: PLLSAIM = 2
000011: PLLSAIM = 3
000100: PLLSAIM = 4
...
111110: PLLSAIM = 62
111111: PLLSAIM = 63

6.3.25

RCC Dedicated Clock Configuration Register (RCC_DCKCFGR)
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 peripherals according to the following formula:
f(PLLSAIDIVQ clock output) = f(PLLSAI_Q) / PLLSAIDIVQ
f(PLLI2SDIVQ clock output) = f(PLLI2S_Q) / PLLI2SDIVQ

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RM0390

Reset and clock control (RCC)

31

30

29

Res.

Res.

Res.

15

14

13

Res.

Res.

Res.

28

27

I2S2SRC
rw

rw

12

11

26

25

I2S1SRC

24
TIMPRE

rw

rw

rw

10

9

8

PLLSAIDIVQ
rw

rw

rw

rw

23

22

SAI2SRC
rw

rw

21

SAI1SRC
rw

rw
4

7

6

5

Res.

Res.

Res.

rw

20

19

18

17

16

Res.

Res.

Res.

Res.

2

1

0

rw

rw

3

PLLIS2DIVQ
rw

rw

rw

Bits 31:29 Reserved, must be kept at reset value.
Bits 28:27 I2S2SRC: I2S APB2 clock source selection
Set and reset by software to control the frequency of the APB2 I2S clock.
These bits should be written when the PLL, PLLSAI and PLLI2S are disabled.
00: I2S2 clock frequency = f(PLLI2S_R)
01: I2S2 clock frequency = I2S_CKIN Alternate function input frequency
10: I2S2 clock frequency = f(PLL_R)
11: I2S2 clock frequency = HSI/HSE depends on PLLSRC bit (PLLCFGR[22])
Bits 26:25 I2S1SRC: I2S APB1 clock source selection
Set and reset by software to control the frequency of the APB1 I2S clock.
These bits should be written when the PLL, PLLSAI and PLLI2S are disabled.
00: I2S1 clock frequency = f(PLLI2S_R)
01: I2S1 clock frequency = I2S_CKIN Alternate function input frequency
10: I2S1 clock frequency = f(PLL_R)
11: I2S1 clock frequency = HSI/HSE depends on PLLSRC bit (PLLCFGR[22])
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 SAI2SRC: SAI2 clock source selection
These bits are set and cleared by software to control the SAI2 clock frequency.
They should be written when the PLL, 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 = f(PLL_R)
11: SAI2 clock frequency = HSI/HSE depends on PLLSRC (PLLCFGR[22])
Bits 21:20 SAI1SRC: SAI1 clock source selection
These bits are set and cleared by software to control the SAI1-A 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 = f(PLL_R)
11: I2S_CKIN Alternate function input frequency
Bits 19:13 Reserved, must be kept at reset value.

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Reset and clock control (RCC)

RM0390

Bits 12:8 PLLSAIDIVQ[4:0]: PLLSAI division factor for SAIs clock
These bits are set and reset by software to control the SAIs 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 PLLI2SDIVQ[4:0]: PLLI2S division factor for SAIs clock
These bits are set and reset by software to control the SAIs 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

6.3.26

RCC clocks gated enable register (CKGATENR)
Address offset: 0x90
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.
This register allows to enable or disable the clock gating for the specified IPs.

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.

RCC
FLITF SRAM SPARE CM4DBG
_CKEN _CKEN _CKEN _CKEN _CKEN
rw

rw

rw

rw

Bits 31:7 Reserved, must be kept at reset value.
Bit 6 RCC_CKEN: RCC clock enable
0: the clock gating is enabled
1: the clock gating is disabled, the clock is always enabled.
Bit 5 FLITF_CKEN: Flash Interface clock enable
0: the clock gating is enabled
1: the clock gating is disabled, the clock is always enabled.

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rw

AHB2APB2 AHB2APB1
_CKEN
_CKEN
rw

rw

RM0390

Reset and clock control (RCC)

Bit 4 SRAM_CKEN: SRQAM controller clock enable
0: the clock gating is enabled
1: the clock gating is disabled, the clock is always enabled.
Bit 3 SPARE_CKEN: Spare clock enable
0: the clock gating is enabled
1: the clock gating is disabled, the clock is always enabled.
Bit 2 CM4DBG_CKEN: Cortex M4 ETM clock enable
0: the clock gating is enabled
1: the clock gating is disabled, the clock is always enabled.
Bit 1 AHB2APB2_CKEN: AHB to APB2 Bridge clock enable
0: the clock gating is enabled
1: the clock gating is disabled, the clock is always enabled.
Bit 0 AHB2APB1_CKEN: AHB to APB1 Bridge clock enable
0: the clock gating is enabled
1: the clock gating is disabled, the clock is always enabled.

6.3.27

RCC dedicated clocks configuration register 2 (DCKCFGR2)
Address offset: 0x94
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.
This register allows to enable or disable the clock gating for the specified IPs.

31

30

29

28

27

26

Res.

Res.

SPDIFRX
SEL

SDIO
SEL

CK48M
SEL

CEC
SEL

rw

rw

rw

rw

15

14

13

12

11

Res.

Res.

Res.

Res.

Res.

25

24

23

22

FMPI2C1SEL
[1:0]

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Bits 31:30 Reserved, must be kept at reset value.
Bit 29 SPDIFRXSEL: SPDIF-Rx clock selection
1: f(PLLI2S_P)
0: f(PLL_R)
Bit 28 SDIOSEL: SDIO clock selection
1: Clock System
0: Clock 48 MHz
Bit 27 CK48MSEL: SDIO/USBFS/HS clock selection
1: f(PLLSAI_P)
0: f(PLL_Q)
Bit 26 CECSEL: HDMI CEC clock source selection
1: LSE
0: HSI/488

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Reset and clock control (RCC)

RM0390

Bits 25:24 Reserved, must be kept at reset value.
Bits 23:22 FMPI2C1SEL[1:0]: I2C4 kernel clock source selection
00: APB clock selected as FMPI2C1 clock
01: System clock selected as FMPI2C1 clock
10: HSI clock selected as FMPI2C1 clock
11: APB clock selected as FMPI2C1 clock (same as “00”)
Bits 21:0 Reserved, must be kept at reset value.

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0x1C

0x20
Reserved

RCC_APB1
RSTR
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.

CAN2RST

CAN1RST

FMPI2C1RST

I2C3RST

I2C2RST

I2C1RST

UART5RST

UART4RST

UART3RST

UART2RST

SPDIFRXRST

SPI3RST

SPI2RST

Res.

Res.

WWDGRST

Res.

Res.

TIM14RST

TIM13RST

TIM12RST

TIM7RST

TIM6RST

TIM5RST

TIM4RST

TIM3RST

TIM2RST

Reset value

CECRST

Reset value

PWRRST

RCC_AHB3
RSTR

Res.

0x18

DocID026976 Rev 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

0

LSIRDYF
0

GPIOARST

0

0
0
0
0
0
0
0
0

DCMIRST

PLLN[8:0]
1

HPRE[3:0]

0
0

Reset value
HSION

Res.
HSIRDY

0

FMCRST

HSIRDYF
LSERDYF

0
GPIOBRST

0
GPIOCRST

0

Res.

0

Res.

0

0

Res.

HSITRIM[4:0]

QSPIRST

PLLRDYF
HSERDYF

0
GPIODRST

0

Res.

PLLI2SRDYF

0

GPIOERST

0

Res.

Res.

0

0

Res.

Reset value
0

0

Res.

PLLSAIRDYF

0

GPIOFRST

0

GPIOGRST

0

Res.

0

Res.

0

1

Res.

Res.

HSICAL[7:0]

Res.

CSSF

0

GPIOHRST

0

OTGFSRST

LSIRDYIE

0

Res.

x

Res.

Res.

PPRE1
[2:0]

x

Res.

0

HSIRDYIE

0
LSERDYIE

0

Res.

0

Res.

0

Res.

Res.

0

x

Res.

x

Res.

0

PLLRDYIE

0

HSERDYIE

0

Res.

PPRE2
[2:0]

1

Res.

1

x

Res.

0

PLLI2SRDYIE

0

CRCRST

0

x

Res.

0

PLLSAIRDYIE

0

Res.

0

Res.

HSEON
Res.

x

Res.

0

Res.

RTCPRE[4:0]

Res.

Res.
PLLP
[1:0]

x

Res.

Res.

0

Res.

Res.

HSEBYP
HSERDY
0

Res.

Res.

Res.

Res.

Res.

CSSON
Res.

PLL ON
Res.

PLL RDY

0

Res.

Res.

0

Res.

LSIRDYC

0

Res.

Res.

Res.

PLLSRC

Res.

PLL I2SON

0

Res.

Res.

Res.

Res.

0

Res.

HSIRDYC
LSERDYC

0

Res.

0

Res.

0

0

Res.

HSERDYC

0

0

Res.

MCO
1
[1:0]

Res.

PLLRDYC

0

DMA1RST
0

Res.

0

DMA2RST

0

Res.

0

Res.

Reset value
Res.

MCO1
PRE
[2:0]

PLLI2SRDYC

RCC_CIR
0

Res.

0

Res.

PLLQ[3:0]

PLLSAIRDYC

0

Res.
0

Res.

0

Res.

PLL SAION
PLL I2SRDY

0

CSSC

0

Res.

Res.

0

Res.

0

Res.

PLL SAIRDY

0

Res.

Res.

0

Res.
0

Res.

Res.

Res.

Res.

0
0

Res.

Res.

Res.

0
MCO2
PRE
[2:0]
1

Res.

Reset value
0

Res.

Res.

Res.

MCO
2
[1:0]
0

Res.

RCC_CFGR
1

Res.

0

Res.
PLLR
[2:0]

Res.

Res.
OTGHSRST

RCC_PLL
CFGR
Res.
0

Res.

Reset value

Res.

Res.

Res.

Reset value

Res.

Res.

RCC_AHB2
RSTR

Res.

0x14
RCC_AHB1
RSTR

Res

0x10

DACRST

0x0C
Reset value

Res.

0x08

Res.

0x04
RCC_CR

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.

Addr.
offset

Res.

6.3.28

Res.

RM0390
Reset and clock control (RCC)

RCC register map
Table 21 gives the register map and reset values.
Table 21. RCC register map and reset values

1
1

PLLM[5:0]
0

0

0

SWS
[1:0]
SW
[1:0]

0
0
0
0
0
0
0
0

0

0
0

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0x48

0x4C

172/1327

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.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

PWREN
CECEN
CAN2EN
CAN1EN
FMPI2C1EN
I2C3EN
I2C2EN
I2C1EN
UART5EN
UART4EN
USART3EN
USART2EN
SPDIFRXEN
SPI3EN
SPI2EN
Res.
Res.
WWDGEN
Res.
Res.

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

Res.
Res.
Res.
Res.
SAI2EN
SAI1EN
Res.
Res.
Res.
TIM11EN
TIM10EN
TIM9EN
Res.
SYSCFGEN
SPI4EN
SPI1EN
SDIOEN
ADC3EN

Reset value
0

Res.

Reset value
Res.

Reset value
Res.

Reset value

DocID026976 Rev 3

0

0

0

0

0

0

0

0

0

0
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

TIM14EN
TIM13EN
TIM12EN
TIM7EN
TIM6EN
TIM5EN
TIM4EN
TIM3EN
TIM2EN

0
0
0
0
0
0
0
0
0

Res.
Res.
USART6EN
USART1EN
Res.
Res.
TIM8EN
TIM1EN

0

ADC1EN

FMCEN

Reset value
QSPIEN

Res.
Res.
Res.
Res.
Res.
DCMIEN

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Res.
Res.
Res.
Res.
Res.
CRCEN
Res.
Res.
Res.
Res.
GPIOHEN
GPIOGEN
GPIOFEN
GPIOEEN
GPIODEN
GPIOCEN
GPIOBEN
GPIOAEN

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIM10RST
TIM9RST

SP45RST
SPI1RST
SDIORST

USART1RST

TIM8RST
TIM1RST

Res.

Res.

USART6RST

Res.

Res.

ADCRST

Res.

Res.

SYSCFGRST

Res.

TIM11RST

Res.

Res.

Res.

SAI1RST

0

Res.

Res.

Res.

BKPSRAMEN

0

Res.

0

Res.

Res.

OTGFSEN

Res.

Res.

0

Res.

Res.
SAI2RST

0

Res.

Reset value

Res.

Res.

Res.

Res.

0

0

Res.

Res.

Res.

Res.

DMA1EN

0

Res.

Res.

0

Res.

Res.

DMA2EN

0

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

0

ADC2EN

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTGHSEN

0

Res.

Res.

OTGHSULPIEN

0

Res.

Res.
Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Reserved

Res.

Reset value

Res.

Reserved

Res.

RCC_
APB2ENR

Res.

0x44

Res.

RCC_
APB1ENR

Res.

0x40

Res.

Reserved

Res.

0x3C

Res.

RCC_
AHB3ENR

DACEN

0x38

Res.

Reset value

Res.

RCC_
AHB2ENR

Res.

0x34

Res.

RCC_
AHB1ENR

Res.

0x30

Res.

Reset value
Res.

Reset value

Res.

Reserved

Res.

0x2C

Res.

Reserved

Res.

0x28

Res.

RCC_APB2
RSTR

Res.

0x24

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.

Addr.
offset

Res.

Reset and clock control (RCC)
RM0390

Table 21. RCC register map and reset values (continued)

0
0

0

0
0

0

0

0

0

0

0

RMVF

Reset value

0

0

0

0

1

1

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.

Res.

Res.

BDRST

RTCEN

Res.

Res.

Res.

Res.

Res.

RTCSEL 1

RTCSEL 0

Res.

Res.

Res.

Res.

LSEMOD

LSEBYP

LSERDY

LSEON

0

DocID026976 Rev 3

Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

TIM13LPEN
TIM12LPEN
TIM7LPEN
TIM6LPEN
TIM5LPEN
TIM4LPEN
TIM3LPEN
TIM2LPEN

1
1
1
1
1
1
1
1

Res.
USART6LPEN
USART1LPEN
Res.
Res.
TIM8LPEN
TIM1LPEN

QSPILPEN
FMCLPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

1
Res.

1

Res.

1

TIM14LPEN

1

LSION

SPI1LPEN

Reset value

Res.

SPI4LPEN

1

LSIRDY

SYSCFGLPEN

1

Res.

Res.
1

Res.

TIM9LPEN

1

Res.

Res.

Res.

TIM10LPEN

1

Res.

Res.

Res.

TIM11LPEN

1

Res.

Res.

WWDGLPEN

Res.

1
1

Res.

Res.

Res.

Res.

1
1

Res.

Res.

Res.

1

Res.

Res.

SPI2LPEN

1

Res.

Res.

SPI3LPEN

1

Res.

Res.

1

Res.

Res.

Reset value

Res.

Res.

USART2LPEN
SPDIFRXLPEN

1

ADC1LPEN

Res.

USART3LPEN

1

ADC2LPEN

Res.

UART4LPEN

1

SDIOLPEN

Res.

1

ADC3LPEN

Res.

I2C1LPEN
UART5LPEN

1

Res.

Res.

Res.

Res.

Res.

Res.

I2C2LPEN

1

SAI1LPEN

Res.

FLITFLPEN

Res.

Res.

GPIOHLPEN
GPIOGLPEN
GPIOFLPEN
GPIOELPEN
GPIODLPEN
GPIOCLPEN
GPIOBLPEN
GPIOALPEN

1
1
1
1
1
1
1

Res.
Res.
Res.
Res.
Res.
Res.
DCMILPEN

Res.

Res.

Res.

Res.

CRCLPEN

1

OTGFSLPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SRAM1LPEN

Res.
Res.

SRAM2LPEN

Res.

Res.
BKPSRAMLPEN

Res.

Res.

Res.

DMA1LPEN

Res.
Res.

DMA2LPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

Res.

Res.

Res.

Res.

Res.

I2C3LPEN

1

SAI2LPEN

Res.

Res.

Res.

1

Res.

Res.

FMPI2C1LPEN

1

Res.

Res.

Res.

Res.

1

Res.

Res.

CAN1LPEN

1

Res.

Res.

Res.

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CAN2LPEN

1

Res.

Res.

OTGHSLPEN

Res.

Res.

1

Res.

0

Res.

Res.

Res.

Res.

0

0

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

CECLPEN

1

Res.

Res.

OTGHSULPILPEN

Res.

1

Res.

Res.

Res.

0

Res.

Res.

PWRLPEN

1

Res.

Res.

Res.

Res.

1

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.
1

Res.

Res.

Res.

Reset value
DACLPEN

Reset value

Res.

Res.

Reset value

Res.

Res.
1

Res.

Res.

Res.

0

Res.

Res.

Reset value

Res.

RCC_BDCR
Res.

Reset value

Res.

Reserved
Res.

Reset value

Res.

Reserved

Res.

RCC_APB2
LPENR

Res.

RCC_APB1
LPENR
Res.

Reset value

Res.

RCC_CSR

BORRSTF

0x74

PADRSTF

0x70

PORRSTF

0x6C

SFTRSTF

0x68

WDGRSTF

0x64

WWDGRSTF

0x60
Reserved

Res.

0x5C
RCC_AHB3
LPENR

Res.

0x58
RCC_AHB2
LPENR

Res.

0x54
RCC_AHB1
LPENR

Res.

0x50

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.

Addr.
offset

LPWRRSTF

RM0390
Reset and clock control (RCC)

Table 21. RCC register map and reset values (continued)

1

1
1

1
1
1
1

0

0

173/1327

174

0x94
RCC_DCK
CFGR2

Reset value

174/1327
0
0
0
0
FMP
I2C1
SEL
[1:0]

0

DocID026976 Rev 3
0

SRAM_CKEN
SPARE_CKEN
CM4DBG_CKEN
AHB2APB2_CKEN
AHB2APB1_CKEN

0
0
0
0
0
0
0

Res.
Res.
Res.
Res.
Res.

Reset value
FLITF_CKEN

PLLSAIDIVQ
[4:0]

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MODPER

Res.

0

Res.

0

Res.

0

Res.

0

0

RCC_CKEN

0

0

0

Res.

0

0

Res.

1

0

0

Res.

INCSTEP

Res.

0

Res.

0

0

Res.

0

Res.

1

0

Res.

0

Res.

0

Res.

0

Res.

1

0

Res.

1

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

PLLI
2SP
[1:0]

0

Res.

PLLSAIP[1:0]

Res.

Res.

Res.

0

Res.

Res.

0

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

0

0

Res.

0
Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

0
SAI1SCR[1:0]

1
0

Res.

0

Res.

0
0

Res.

0

Res.

PLLSAIQ
[3:0]

SAI2SCR[1:0]

0
0

Res.

Res.

Res.

PLLI2SQ
[3:0]
0

Res.

0

Res.

PLLSAIR
[2:0]
1
0

Res.

0

Res.

0

TIMPRE

Res.

Res.

PLLI2SR
[2:0]
0

Res.

0

Res.

0

I2S1SRC[1:0]

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

0
0

Res.

0

Res.

Reset value
I2S2SRC[1:0]

1

Res.

Res.

SPREADSEL

Reset value
Res.

RCC_SS
CGR

0

Res.

RCC_CK
GATENR

CECSEL

0x90

CK48MSEL

RCC_DCK
CFGR
0
1

Res.

Reset value

SDIOSEL

0x8C
0

Res.

0x88
RCC_PLL
SAI
CFGR

Res.

Reset value

Res.

RCC_PLLI2
SCFGR

Res.

0x80

Res.

Reset value
Res.

Reserved

SPDIFRXSEL

0x7C

SSCGEN

Reset value

Res.

Reserved

Res.

0x78

Res.

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

Register
name

Res.

Addr.
offset

Res.

Reset and clock control (RCC)
RM0390

Table 21. RCC register map and reset values (continued)

0
0
0
0
0
0

PLLI2SN[8:0]
PLLI2SM[5:0]

0

PLLSAIN[8:0]

0

1
0

0
0

0

0

0

Refer to Section 2.2.2: Memory map and register boundary addresses for the register
boundary addresses.
0

0

0

PLLSAIM[5:0]

0

PLLI2SDIVQ
[4:0]

0
0
0
0
0

RM0390

General-purpose I/Os (GPIO)

7

General-purpose I/Os (GPIO)

7.1

GPIO 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), a 32-bit set/reset register (GPIOx_BSRR), a 32-bit locking
register (GPIOx_LCKR) and two 32-bit alternate function selection register (GPIOx_AFRH
and GPIOx_AFRL).

7.2

7.3

GPIO main features
•

Up to 16 I/Os under control

•

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 configuration

•

Analog function

•

Alternate function input/output selection registers (at most 16 AFs per I/O)

•

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 register is
to allow atomic read/modify accesses to any of the GPIO registers. In this way, there is no
risk of an IRQ occurring between the read and the modify access.

DocID026976 Rev 3

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193

General-purpose I/Os (GPIO)

RM0390

Figure 17 shows the basic structure of a 5 V tolerant I/O port bit, Table 22 gives the possible
port bit configurations.
Figure 17. Basic structure of a 5 V tolerant I/O port bit

!NALOG

4O ON CHIP
PERIPHERAL

!LTERNATE FUNCTION INPUT
)NPUT DATA REGISTER

2EADWRITE
&ROM ON CHIP
PERIPHERAL

6$$
44, 3CHMITT
TRIGGER

ONOFF

6$$?&4 

0ROTECTION
DIODE

0ULL
UP

)NPUT DRIVER

/UTPUT DATA REGISTER

"IT SETRESET REGISTERS

2EAD

7RITE

ONOFF

)/ PIN

/UTPUT DRIVER

6$$

ONOFF

0ROTECTION
DIODE

0ULL
DOWN

0 -/3

633

/UTPUT
CONTROL

633

. -/3
633

!LTERNATE FUNCTION OUTPUT

0USH PULL
OPEN DRAIN OR
DISABLED

!NALOG
AIB

1. VDD_FT is a potential specific to 5 V tolerant I/Os and different from VDD.

Table 22. Port bit configuration table(1)
MODER(i)[1:0]

01

10

176/1327

OTYPER(i)

OSPEEDR(i)[B:A]

PUPDR(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

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

0

0

AF

OD

1

0

1

AF

OD + PU

1

1

0

AF

OD + PD

1

1

1

0
1

0
1

SPEED[B:A]

SPEED[B:A]

DocID026976 Rev 3

Reserved

Reserved

Reserved

RM0390

General-purpose I/Os (GPIO)
Table 22. Port bit configuration table(1) (continued)
MODER(i)[1:0]

00

11

OTYPER(i)

OSPEEDR(i)[B:A]

PUPDR(i)[1:0]

I/O configuration

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

x

x

x

0

0

x

x

x

0

1

x

x

x

1

0

x

x

x

1

1

Reserved (input floating)
Input / output

Analog

Reserved

1. GP = general-purpose, PP = push-pull, PU = pull-up, PD = pull-down, OD = open-drain, AF = alternate
function.

7.3.1

General-purpose I/O (GPIO)
During and just after reset, the alternate functions are not active and 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 N-MOS is activated when 0 is output).
The input data register (GPIOx_IDR) captures the data present on the I/O pin at every AHB1
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.

7.3.2

I/O pin multiplexer and mapping
The microcontroller I/O pins are connected to onboard peripherals/modules through a
multiplexer that allows only one peripheral’s alternate function (AF) connected to an I/O pin
at a time. In this way, there can be no conflict between peripherals sharing the same I/O pin.
Each I/O pin has a multiplexer with 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 all I/Os are connected to the system’s alternate function 0 (AF0)

•

The peripherals’ alternate functions are mapped from AF1 to AF13

•

Cortex®-M4 with FPU EVENTOUT is mapped on AF15

This structure is shown in Figure 18.

DocID026976 Rev 3

177/1327
193

General-purpose I/Os (GPIO)

RM0390

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, proceed as follows:
•

System function
Connect the I/O to AF0 and configure it depending on the function used:

Note:

–

JTAG/SWD, after each device reset these pins are assigned as dedicated pins
immediately usable by the debugger host (not controlled by the GPIO controller)

–

RTC_REFIN: this pin should be configured in Input floating mode

–

MCO1 and MCO2: these pins have to be configured in alternate function mode.

You can disable some or all of the JTAG/SWD pins and so release the associated pins for
GPIO usage.
For more details refer to Section 6.2.10: Clock-out capability.
Table 23. Flexible SWJ-DP pin assignment
SWJ I/O pin assigned
PA13 /
JTMS/
SWDIO

PA14 /
JTCK/
SWCLK

PA15 /
JTDI

PB3 /
JTDO

PB4/
NJTRST

Full SWJ (JTAG-DP + SW-DP) - Reset state

X

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

Available debug ports

JTAG-DP Disabled and SW-DP Disabled

•

Released

GPIO
Configure the desired I/O as output or input in the GPIOx_MODER register.

•

Peripheral alternate function
For the ADC and DAC, configure the desired I/O as analog in the GPIOx_MODER
register.
For other peripherals:

•

–

Configure the desired I/O as an alternate function in the GPIOx_MODER register

–

Select the type, pull-up/pull-down and output speed via the GPIOx_OTYPER,
GPIOx_PUPDR and GPIOx_OSPEEDER registers, respectively

–

Connect the I/O to the desired AFx in the GPIOx_AFRL or GPIOx_AFRH register

EVENTOUT
Configure the I/O pin used to output the Cortex®-M4 with FPU EVENTOUT signal by
connecting it to AF15

Note:

EVENTOUT is not mapped onto the following I/O pins: PC13, PC14, PC15, PH0 and PH1.
Refer to the “Alternate function mapping” table in the datasheets for the detailed mapping of
the system and peripherals’ alternate function I/O pins.

178/1327

DocID026976 Rev 3

RM0390

General-purpose I/Os (GPIO)
Figure 18. Selecting an alternate function on STM32F446xx
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$) V\VWHP
$) 7,07,0
$) 7,0
$) 7,0&(&
$) ,&&(&
$) 63,
$) 63,6$,
$) 63,86$578$5763',),1
$) 63,86$578$5763',),1
$) &$17,048$'63,
$) 6$,48$'63,27*B+627*B)6
$)
$) )0&6',227*B+6 
$) '&0,
$)
$) (9(17287

3LQ[ [ 


$)5/>@
)RUSLQVWRWKH*3,2[B$)5+>@UHJLVWHUVHOHFWVWKHGHGLFDWHGDOWHUQDWHIXQFWLRQ
$) V\VWHP
$) 7,07,0
$) 7,0
$) 7,0&(&
$) ,&&(&
$) 63,
$) 63,6$,
$) 63,86$578$5763',),1
$) 63,86$578$5763',),1
$) &$17,048$'63,
$) 6$,48$'63,27*B+627*B)6
$)
$) )0&6',227*B+6 
$) '&0,
$)
$) (9(17287

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$)5+>@
069

1. Configured in FS.

7.3.3

I/O port control registers
Each of the GPIOs has four 32-bit memory-mapped control registers (GPIOx_MODER,
GPIOx_OTYPER, GPIOx_OSPEEDR, GPIOx_PUPDR) to configure up to 16 I/Os. The

DocID026976 Rev 3

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GPIOx_MODER register is used to select the I/O direction (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 I/O speed pins are directly connected to the
corresponding GPIOx_OSPEEDR register bits whatever the I/O direction). The
GPIOx_PUPDR register is used to select the pull-up/pull-down whatever the I/O direction.

7.3.4

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 7.4.5: GPIO port input data register (GPIOx_IDR) (x = A..H) and Section 7.4.6:
GPIO port output data register (GPIOx_ODR) (x = A..H) for the register descriptions.

7.3.5

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: BSRR(i) and
BSRR(i+SIZE). When written to 1, bit BSRR(i) sets the corresponding ODR(i) bit. When
written to 1, bit BSRR(i+SIZE) 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.
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 AHB1 write access.

7.3.6

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 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 7.4.8: GPIO port configuration lock register
(GPIOx_LCKR) (x = A..H)) 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.

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General-purpose I/Os (GPIO)
For more details refer to LCKR register description in Section 7.4.8: GPIO port configuration
lock register (GPIOx_LCKR) (x = A..H).

7.3.7

I/O alternate function input/output
Two registers are provided to select one out of the sixteen alternate function inputs/outputs
available for each I/O. With these registers, you can connect an alternate function to some
other pin as required by your 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 one I/O.
To know which functions are multiplexed on each GPIO pin, refer to the datasheets.

Note:

The application is allowed to select one of the possible peripheral functions for each I/O at a
time.

7.3.8

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 10.2: External interrupt/event controller (EXTI)
and Section 10.2.3: Wakeup event management.

7.3.9

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 AHB1
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.

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RM0390

)NPUT DATA REGISTER

Figure 19. Input floating/pull up/pull down configurations

2EADWRITE

/UTPUT DATA REGISTER

7RITE

"IT SETRESET REGISTERS

2EAD

ON

44, 3CHMITT
TRIGGER

6$$ 6$$
ONOFF
PULL
UP

INPUT DRIVER

PROTECTION
DIODE
)/ PIN

ONOFF
OUTPUT DRIVER
PULL
DOWN
633

PROTECTION
DIODE

633

AIB

7.3.10

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 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 AHB1
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.

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General-purpose I/Os (GPIO)

)NPUT DATA REGISTER

Figure 20. Output configuration

7RITE

2EADWRITE

ON

6$$

6$$

44, 3CHMITT
TRIGGER

ONOFF

)NPUT DRIVER

/UTPUT DATA REGISTER

"IT SETRESET REGISTERS

2EAD

PROTECTION
DIODE

PULL
UP

/UTPUT DRIVER

6$$

)/ PIN

ONOFF

0 -/3
/UTPUT
CONTROL

PROTECTION
DIODE

PULL
DOWN

633

633

. -/3
0USH PULL OR
633
/PEN DRAIN

AIB

Alternate function configuration
When the I/O port is programmed as alternate function:
•

The output buffer can be configured as open-drain or push-pull

•

The output buffer is driven by the signal 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 AHB1
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
!LTERNATE FUNCTION INPUT

2EAD

2EADWRITE
&ROM ON CHIP
PERIPHERAL

6$$ 6$$
44, 3CHMITT
TRIGGER

ONOFF
PROTECTION
DIODE

0ULL
UP

)NPUT DRIVER
/UTPUT DATA REGISTER

7RITE

ON

)NPUT DATA REGISTER

4O ON CHIP
PERIPHERAL

"IT SETRESET REGISTERS

7.3.11

)/ PIN
/UTPUT DRIVER

ONOFF

6$$
0 -/3

/UTPUT
CONTROL

PROTECTION
DIODE

0ULL
DOWN

633

633

. -/3
633

PUSH PULL OR
OPEN DRAIN

!LTERNATE FUNCTION OUTPUT
AIB

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7.3.12

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Analog configuration
When the I/O port is programmed as analog configuration:

Note:

•

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

•

Read access to the input data register gets the value “0”

In the analog configuration, the I/O pins cannot be 5 Volt tolerant.
Figure 22 shows the high-impedance, analog-input configuration of the I/O port bit.
Figure 22. High impedance-analog configuration

)NPUT DATA REGISTER

!NALOG

4O ON CHIP
PERIPHERAL

2EADWRITE

&ROM ON CHIP
PERIPHERAL

7.3.13

/UTPUT DATA REGISTER

7RITE

"IT SETRESET REGISTERS

2EAD

OFF

6$$

44, 3CHMITT
TRIGGER

PROTECTION
DIODE

)NPUT DRIVER

)/ PIN
PROTECTION
DIODE
633

!NALOG
AI

Using the OSC32_IN/OSC32_OUT pins as GPIO PC14/PC15
port pins
The LSE oscillator pins OSC32_IN and OSC32_OUT can be used as general-purpose
PC14 and PC15 I/Os, respectively, when the LSE oscillator is off. The PC14 and PC15 I/Os
are only configured as LSE oscillator pins OSC32_IN and OSC32_OUT when the LSE
oscillator is ON. This is done by setting the LSEON bit in the RCC_BDCR register. The LSE
has priority over the GPIO function.

Note:

The PC14/PC15 GPIO functionality is lost when the 1.2 V domain is powered off (by the
device entering the standby mode) or when the backup domain is supplied by VBAT (VDD no
more supplied). In this case the I/Os are set in analog input mode.

7.3.14

Using the OSC_IN/OSC_OUT pins as GPIO PH0/PH1 port pins
The HSE oscillator pins OSC_IN/OSC_OUT can be used as general-purpose PH0/PH1
I/Os, respectively, when the HSE oscillator is OFF. (after reset, the HSE oscillator is off). The
PH0/PH1 I/Os are only configured as OSC_IN/OSC_OUT HSE oscillator pins when the
HSE oscillator is ON. This is done by setting the HSEON bit in the RCC_CR register. The
HSE has priority over the GPIO function.

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7.3.15

General-purpose I/Os (GPIO)

Selection of RTC additional_AF1 and RTC_AF2 alternate functions
The STM32F446xx feature two GPIO pins RTC_AF1 and RTC_AF2 that can be used for the
detection of a tamper or time stamp event, or RTC_ALARM, or RTC_CALIB RTC outputs.
•

The RTC_AF1 (PC13) can be used for the following purposes:

RTC_ALARM output: this output can be RTC Alarm A, RTC Alarm B or RTC Wakeup
depending on the OSEL[1:0] bits in the RTC_CR register
•

RTC_CALIB output: this feature is enabled by setting the COE[23] in the RTC_CR
register

•

RTC_TAMP1: tamper event detection

•

RTC_TS: time stamp event detection

The RTC_AF2 (PA0) can be used for the following purposes:
•

RTC_TAMP1: tamper event detection

•

RTC_TAMP2: tamper event detection

•

RTC_TS: time stamp event detection

The selection of the corresponding pin is performed through the RTC_TAFCR register as
follows:
•

TAMP1INSEL is used to select which pin is used as the RTC_TAMP1 tamper input

•

TSINSEL is used to select which pin is used as the RTC_TS time stamp input

•

ALARMOUTTYPE is used to select whether the RTC_ALARM is output in push-pull or
open-drain mode

The output mechanism follows the priority order listed in Table 24 and Table 25.
Table 24. RTC_AF1 pin(1)
Pin
Time
TAMP1INSEL
TSINSEL
ALARMOUTTYPE
RTC_ALARM RTC_CALIB Tamper
configuration
stamp
TAMPER1
TIMESTAMP
RTC_ALARM
enabled
enabled
enabled
and function
enabled pin selection pin selection
configuration

Alarm out
output OD

1

Don’t care

Don’t
care

Don’t
care

Don’t care

Don’t care

0

Alarm out
output PP

1

Don’t care

Don’t
care

Don’t
care

Don’t care

Don’t care

1

Calibration
out output PP

0

1

Don’t
care

Don’t
care

Don’t care

Don’t care

Don’t care

TAMPER1
input floating

0

0

1

0

0

Don’t care

Don’t care

TIMESTAMP
and
TAMPER1
input floating

0

0

1

1

0

0

Don’t care

TIMESTAMP
input floating

0

0

0

1

Don’t care

0

Don’t care

Standard
GPIO

0

0

0

0

Don’t care

Don’t care

Don’t care

1. OD: open drain; PP: push-pull.

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Table 25. RTC_AF2 pin
Time TAMP1INSEL
TSINSEL
ALARMOUTTYPE
stamp
TAMPER1
TIMESTAMP
RTC_ALARM
enabled pin selection pin selection
configuration

Tamper
enabled

Pin configuration and function
TAMPER1 input floating

1

0

1

Don’t care

Don’t care

TIMESTAMP and TAMPER1 input
floating

1

1

1

1

Don’t care

TIMESTAMP input floating

0

1

Don’t care

1

Don’t care

Standard GPIO

0

0

Don’t care

Don’t care

Don’t care

7.4

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 26.
The GPIO registers can be accessed by byte (8 bits), half-words (16 bits) or words (32 bits).

7.4.1

GPIO port mode register (GPIOx_MODER) (x = A..H)
Address offset: 0x00
Reset values:

31

30

MODER15[1:0]

•

0xA800 0000 for port A

•

0x0000 0280 for port B

•

0x0000 0000 for other ports
29

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

Bits 2y:2y+1 MODERy[1:0]: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O direction mode.
00: Input (reset state)
01: General purpose output mode
10: Alternate function mode
11: Analog mode

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General-purpose I/Os (GPIO)

7.4.2

GPIO port output type register (GPIOx_OTYPER) (x = A..H)
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 output type of the I/O port.
0: Output push-pull (reset state)
1: Output open-drain

7.4.3

GPIO port output speed register (GPIOx_OSPEEDR) (x = A..H)
Address offset: 0x08
Reset values:

31

30

OSPEEDR15
[1:0]

•

0x0000 00C0 for port B

•

0x0000 0000 for other ports
29

28

OSPEEDR14
[1:0]

27

26

OSPEEDR13
[1:0]

25

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:2y+1 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: Fast speed
11: High speed
Note: Refer to the product datasheets for the values of OSPEEDRy bits versus VDD
range and external load.

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GPIO port pull-up/pull-down register (GPIOx_PUPDR) (x = A..H)
Address offset: 0x0C
Reset values:

31

30

rw

15

14

PUPDR7[1:0]
rw

0x6400 0000 for port A

•

0x0000 0100 for port B

•

0x0000 0000 for other ports
29

PUPDR15[1:0]
rw

•

rw

28

PUPDR14[1:0]
rw

rw

13

12

PUPDR6[1:0]
rw

rw

27

26

PUPDR13[1:0]
rw

rw

11

10

PUPDR5[1:0]
rw

rw

25

24

PUPDR12[1:0]
rw

rw

9

8

PUPDR4[1:0]
rw

rw

23

22

PUPDR11[1:0]
rw

rw

7

6

PUPDR3[1:0]
rw

rw

21

20

PUPDR10[1:0]
rw

rw

5

4

19

PUPDR2[1:0]
rw

18

PUPDR9[1:0]
rw

rw

3

2

PUPDR1[1:0]

rw

rw

rw

17

16

PUPDR8[1:0]
rw

rw

1

0

PUPDR0[1:0]
rw

rw

Bits 2y:2y+1 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

7.4.5

GPIO port input data register (GPIOx_IDR) (x = A..H)
Address offset: 0x10
Reset value: 0x0000 XXXX (where X means 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.

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 (y = 0..15)
These bits are read-only and can be accessed in word mode only. They contain the input
value of the corresponding I/O port.

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7.4.6

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

ODR9

ODR8

ODR7

ODR6

ODR5

ODR4

ODR3

ODR2

ODR1

ODR0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

ODR15 ODR14 ODR13 ODR12 ODR11 ODR10
rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 ODRy: Port output data (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 reset by writing to the
GPIOx_BSRR register (x = A..H).

7.4.7

GPIO port bit set/reset register (GPIOx_BSRR) (x = A..H)
Address offset: 0x18
Reset value: 0x0000 0000

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 and can be accessed in word, half-word or byte mode. 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 and can be accessed in word, half-word or byte mode. A read to
these bits returns the value 0x0000.
0: No action on the corresponding ODRx bit
1: Sets the corresponding ODRx bit

7.4.8

GPIO port configuration lock register (GPIOx_LCKR) (x = A..H)
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 reset.

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Note:

RM0390

A specific write sequence is used to write to the GPIOx_LCKR register. Only word access
(32-bit long) is allowed during this write sequence.
Each lock bit freezes a specific configuration register (control and alternate function
registers).
Address offset: 0x1C
Reset value: 0x0000 0000
Access: 32-bit word only, read/write register

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
Res.

17

16

Res.

LCK
K16
rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

LCK
K15

LCK
K14

LCK
K13

LCK
K12

LCK
K11

LCK
K10

LCK
K9

LCK
K8

LCK
K7

LCK
K6

LCK
K5

LCK
K4

LCK
K3

LCK
K2

LCK
K1

LCK
K0

rw

rw

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 LCKK[16]: 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 an MCU reset
occurs.
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 CPU 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

190/1327

DocID026976 Rev 3

RM0390

General-purpose I/Os (GPIO)

7.4.9

GPIO alternate function low register (GPIOx_AFRL) (x = A..H)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

AFRL7[3:0]

26

25

24

23

22

AFRL6[3:0]

21

20

19

AFRL5[3:0]

18

17

16

AFRL4[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

rw

rw

rw

rw

rw

rw

rw

rw

AFRL3[3:0]
rw

AFRL2[3:0]
rw

rw

AFRL1[3:0]
rw

AFRL0[3:0]
rw

rw

17

16

Bits 31:0 AFRLy: Alternate function selection for port x bit y (y = 0..7)
These bits are written by software to configure alternate function I/Os
AFRLy selection:
0000: AF0
0001: AF1
0010: AF2
0011: AF3
0100: AF4
0101: AF5
0110: AF6
0111: AF7

7.4.10

1000: AF8
1001: AF9
1010: AF10
1011: AF11
1100: AF12
1101: AF13
1110: AF14
1111: AF15

GPIO alternate function high register (GPIOx_AFRH) (x = A..H)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

AFRH15[3:0]

26

25

24

23

AFRH14[3:0]

22

21

20

19

AFRH13[3:0]

18

AFRH12[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

AFRH11[3:0]
rw

rw

rw

AFRH10[3:0]
rw

rw

rw

rw

AFRH9[3:0]
rw

rw

rw

rw

AFRH8[3:0]
rw

rw

rw

rw

rw

Bits 31:0 AFRHy: Alternate function selection for port x bit y (y = 8..15)
These bits are written by software to configure alternate function I/Os
AFRHy 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

DocID026976 Rev 3

191/1327
193

0x08

0x0C

0x0C

192/1327
Reset value

GPIOB_
OSPEEDER

Reset value

GPIOA_PUPDR

Reset value

GPIOB_PUPDR

Reset value
0

0

0

0
0
0

0
0

1

1

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

0

0

0

0
0
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..H)

Reset value

0
0

0
0

0

0

0

0

DocID026976 Rev 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

0

0

0
0
0

0
0

0
0

0

0

0

0

0
0

0
0

0
1

0

0

1

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

PUPDR0[1:0]

OT2

0

PUPDR0[1:0]

OT3

0

OSPEEDR1[1:0]

MODER2[1:0]

0

OSPEEDR1[1:0]

MODER2[1:0]

0

PUPDR1[1:0]

OT4

0

PUPDR1[1:0]

OT5

1

OSPEEDR2[1:0]

MODER3[1:0]

0

OSPEEDR2[1:0]

MODER3[1:0]

0

PUPDR2[1:0]

OT6

0

PUPDR2[1:0]

OT7

1

OSPEEDR3[1:0]

MODER4[1:0]

0

OSPEEDR3[1:0]

MODER4[1:0]

0

PUPDR3[1:0]

OT8

0

PUPDR3[1:0]

OT9

0

OSPEEDR4[1:0]

0

OSPEEDR4[1:0]

MODER5[1:0]

0

PUPDR4[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

PUPDR5[1:0]

OT12

0

PUPDR5[1:0]

OT13

0

OSPEEDR6[1:0]

0

OSPEEDR6[1:0]

MODER7[1:0]

0

PUPDR6[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

PUPDR7[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

PUPDR8[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

PUPDR9[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

PUPDR10[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

PUPDR11[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

PUPDR12[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.

1

PUPDR13[1:0]

0

Res.

MODER15[1:0]
0

PUPDR13[1:0]

GPIOx_
OSPEEDER
(where x = A..H
except B)
OSPEEDR14[1:0]

GPIOx_MODER
(where x = C..H)
0

OSPEEDR14[1:0]

Reset value
1

PUPDR14[1:0]

0x08
GPIOB_
MODER

MODER15[1:0]

Reset value

PUPDR14[1:0]

0x04
Reset value

Res.

0x00

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

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

OSPEEDR15[1:0]

Offset

PUPDR15[1:0]

7.4.11

PUPDR15[1:0]

General-purpose I/Os (GPIO)
RM0390

GPIO register map

The following table gives the GPIO register map and the reset values.
Table 26. GPIO register map and reset values

0
0

0
0

0

0

0

0

0

0

RM0390

General-purpose I/Os (GPIO)

0

0

0

GPIOx_IDR
(where x = A..H)

Res.

Res.

Res.

Res.

Res.

PUPDR0[1:0]

0

ODR5

ODR4

ODR3

ODR2

ODR1

ODR0
BS0

ODR6

BS1

ODR7

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
LCK0

ODR8

0

LCK1

ODR9

BS2

ODR11

ODR10

BS3

ODR12

0

LCK2

ODR13

0

LCK3

ODR14

0

BS4

Res.

0

BS5

Res.

0

LCK4

Res.

0

LCK5

Res.

0
BS6

Res.

0
BS7

Res.

0

LCK6

Res.

0

LCK7

Res.

0

BS8

Res.

0

BS9

Res.

0

LCK8

Res.

Reset value

0

LCK9

Res.

GPIOx_AFRH
(where x = A..H)

0

BS11

Res.

GPIOx_AFRL
(where x = A..H)

0

BS10

GPIOx_LCKR
(where x = A..H)

x

LCK11

0

x

LCK10

0

x

BS12

BR3

0

x

BS13

BR4

0

x

LCK12

BR5

0

x

LCK13

BR6

0

x

BS14

BR7

0

x

BS15

BR8

0

x

LCK14

BR9

0

x

LCK15

BR11

BR10

0

x

BR0

BR12

0

x

BR1

BR13

0

x

Res.

BR14

0

x

LCKK

BR15

Reset value

x

BR2

GPIOx_BSRR
(where x = A..H)

x
ODR15

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

GPIOx_ODR
(where x = A..H)

IDR0

0

IDR1

0

Res.

PUPDR1[1:0]

0

IDR2

0

IDR3

0

Reset value

0x24

PUPDR2[1:0]

0

IDR4

0

IDR5

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

0x20

PUPDR3[1:0]

0

IDR6

0

IDR7

0

Res.

0x1C

PUPDR4[1:0]

0

IDR8

0

IDR9

0

Reset value

0x18

PUPDR5[1:0]

0

IDR11

0

IDR10

0

Reset value

0x14

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]

0

Res.

PUPDR15[1:0]

Reset value

Res.

0x10

GPIOx_PUPDR
(where x = C..H)

Res.

0x0C

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 26. GPIO register map and reset values (continued)

AFRL7[3:0]

AFRL6[3:0]

AFRL5[3:0]

AFRL4[3:0]

AFRL3[3:0]

AFRL2[3:0]

AFRL1[3:0]

AFRL0[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

0

0

0

0

0

0

0

0

AFRH15[3:0
]

AFRH14[3:0 AFRH13[3:0 AFRH12[3:0
]
]
]

AFRH11[3:0
]

AFRH10[3:0
]

AFRH9[3:0]

AFRH8[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

0

0

0

0

0

0

0

0

Refer to Table 1 on page 56 for the register boundary addresses.

DocID026976 Rev 3

193/1327
193

System configuration controller (SYSCFG)

8

RM0390

System configuration controller (SYSCFG)
The system configuration controller is mainly used to remap the memory accessible in the
code area and to manage the external interrupt line connection to the GPIOs.

8.1

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.

8.2

SYSCFG registers

8.2.1

SYSCFG memory remap register (SYSCFG_MEMRMP)
This register is used for specific configurations on memory remap:
•

Three bits are used to configure the type of memory accessible at address
0x0000 0000. These bits are used to select the physical remap by software and so,
bypass the BOOT pins.

•

After reset these bits take the value selected by the BOOT pins. When booting from
main Flash memory with BOOT pins set to 10 [(BOOT1,BOOT0) = (1,0)] this register
takes the value 0x00.

•

Other bits are used to swap FMC SDRAM Bank 1/2 with FMC Bank 3/4.

There are two possible FMC remap at address 0x0000 0000:
•

FMC Bank 1 (NOR/PSRAM 1 and 2) remap:
Only the first two regions of Bank 1 memory controller (Bank1 NOR/PSRAM 1 and
NOR/PSRAM 2) can be remapped.

•

FMC SDRAM Bank 1 remap.

In remap mode at address 0x0000 0000, the CPU can access the external memory via
ICode bus instead of System bus which boosts up the performance.
Address offset: 0x00
Reset value: 0x0000 000X (X is the memory mode selected by the BOOT pins)
Note:

194/1327

Booting from NOR Flash memory or SDRAM is not allowed. The regions can only be
mapped at 0x0000 0000 through software remap.

DocID026976 Rev 3

RM0390

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.

11

10

2

1

0

15

14

13

12

Res.

Res.

Res.

Res.

SWP_FMC
rw

9

8

7

6

5

4

3

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

MEM_MODE[2:0]
rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:10 SWP_FMC: FMC memory mapping swap
Set and cleared by software. These bits are used to swap the FMC SDRAM
Banks 1/2 from address 0xC000 0000 and 0xD000 0000 to address 0x6000
0000 and 0x7000 0000 in order to enable the code execution from SDRAM
Banks without a physical remapping at 0x0000 0000 address. NOR/PSRAM
Bank which is by default mapped at 0x6000 0000 is remapped at 0xC000 0000
when SDRAM bank1 is mapped at 0x6000 0000.
00: No FMC memory mapping swap
01: SDRAM banks mapping are swapped. SDRAM Bank 1 and 2 are mapped at
0x6000 0000 and 0x7000 0000 address, respectively. NOR/PSRAM Bank is
mapped at 0xC000 0000.
10: Reserved
11: Reserved
Bits 9:3 Reserved, must be kept at reset value.
Bits 2:0 MEM_MODE: Memory mapping selection
Set and cleared by software. This bit controls the memory internal mapping at
address 0x0000 0000. After reset these bits take the value selected by the Boot
pins (except for FMC).
000: Main Flash memory mapped at 0x0000 0000
001: System Flash memory mapped at 0x0000 0000
010: FMC Bank1 (NOR/PSRAM 1 and 2) mapped at 0x0000 0000
011: Embedded SRAM (SRAM1) mapped at 0x0000 0000
100: FMC/SDRAM Bank 1 mapped at 0x0000 0000
Other configurations are reserved
Note: Refer to Section 2.2.2: Memory map and register boundary addresses for
details about the memory mapping at address 0x0000 0000.

DocID026976 Rev 3

195/1327
201

System configuration controller (SYSCFG)

8.2.2

RM0390

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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

18

17

16

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.

Res.

Res.

Res.

Res.

ADCxDC2

Bits 31:19 Reserved, must be kept at reset value.
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.

8.2.3

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

196/1327

rw

rw

EXTI2[3:0]
rw

rw

rw

EXTI1[3:0]

rw

rw

rw

rw

DocID026976 Rev 3

rw

EXTI0[3:0]
rw

rw

rw

rw

rw

RM0390

System configuration controller (SYSCFG)

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.
Note: 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

8.2.4

SYSCFG external interrupt configuration register 2
(SYSCFG_EXTICR2)
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

EXTI7[3:0]
rw

EXTI6[3:0]

EXTI5[3:0]

rw

rw

EXTI4[3:0]
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)
Note: 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

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System configuration controller (SYSCFG)

8.2.5

RM0390

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.
Note: 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

8.2.6

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.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

EXTI15[3:0]
rw

198/1327

rw

rw

EXTI14[3:0]
rw

rw

EXTI13[3:0]
rw

DocID026976 Rev 3

rw

EXTI12[3:0]
rw

rw

rw

RM0390

System configuration controller (SYSCFG)

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.
Note: 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
0110: PG[x] pin

8.2.7

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

r

rw

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 7:1 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

8.2.8

SYSCFG configuration register (SYSCFG_CFGR)
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.

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.

r

FMPI2C1_SDA FMPI2C1_SCL
rw

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System configuration controller (SYSCFG)

RM0390

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 FMPI2C1_SDA
Set and cleared by software. When set it forces FM+ drive capability on
FMPI2C1_SDA pin selected through GPIO port mode register and GPIO alternate
function selection bits
Bit 0 FMPI2C1_SCL
Set and cleared by software. When set it forces FM+ drive capability on
FMPI2C1_SCL pin selected through GPIO port mode register and GPIO alternate
function selection bits

200/1327

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0x2C
SYSCFG_CFGR

DocID026976 Rev 3
0
0
0
0
0
0
0
0
0
0
0

Reserved
Reserved
CMP_PD

0

Reset value
0

0

0

0

0

0

0

0

EXTI5[3:0]
0

EXTI9[3:0]
0

0
0

0
0

0
0

FMPI2C1_SCL

Reset value
0

0

0

FMPI2C1_SDA

0

Reserved

EXTI6[3:0]

0

Reserved

0

Reserved

0
0

0

0

ADC1DC2

Reserved

EXTI1[3:0]

Reserved

0

Reserved

0

0

Reserved

0

Reserved

0
0
0

0

Reserved

0

READY

EXTI10[3:0]

0
0

0

Reserved

EXTI12[3:0]

Reserved

EXTI7[3:0]

EXTI2[3:0]

Reserved
EXTI13[3:0]

Reserved

EXTI11[3:0]

0
0

0

Reserved

x
x
x

Reserved
Reserved
Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

0

Reserved

0

0

0

Reserved

EXTI14[3:0]

Reserved

ADC2DC2

Reserved

EXTI3[3:0]

Reserved

EXTI15[3:0]

Reserved

Reset value
Reserved

ADC3DC2

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reset value

Reserved

Reset value

Reserved

0
0

Reserved

Reset value

Reserved

0

Reserved

Reserved

Reserved

Reset value

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

0

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

0

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

0

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reset value

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

SYSCFG_CMPCR

Reserved

0x20
SYSCFG_EXTICR4

Reserved

0x14
SYSCFG_EXTICR3

Reserved

0x10
SYSCFG_EXTICR2

Reserved

0x0C
SYSCFG_EXTICR1

Reserved

0x08
SYSCFG_PMC

Reserved

0x04

Reserved

Register
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
SYSCFG_
MEMRMP
Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

SWP_FMC

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Reserved

Offset

Reserved

8.2.9

Reserved

RM0390
System configuration controller (SYSCFG)

SYSCFG register maps

The following table summarizes the SYSCFG register map and the reset values.
Table 27. SYSCFG register map and reset values

MEM_
MODE

EXTI0[3:0]
0

0

0

0

0

EXTI4[3:0]
0

EXTI8[3:0]
0

0

0
0

Refer to Table 1 on page 56 for the register boundary addresses.

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9

Direct memory access controller (DMA)

9.1

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 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. And each has an arbiter for handling the priority
between DMA requests.

9.2

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:
–

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-toperipheral 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.

•

202/1327

Each stream can be configured by hardware 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

•

Each of the 8 streams are connected to dedicated hardware DMA channels (requests)

•

Priorities between DMA stream requests are software-programmable (4 levels
consisting of very high, high, medium, low) or hardware in case of equality (request 0
has priority over request 1, etc.)

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RM0390

Direct memory access controller (DMA)
•

Each stream also supports software trigger for memory-to-memory transfers (only
available for the DMA2 controller)

•

Each stream request can be selected via 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:
–

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

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Direct memory access controller (DMA)

RM0390

9.3

DMA functional description

9.3.1

DMA block diagram
Figure 23 shows the block diagram of a DMA.
Figure 23. DMA block diagram

342%!- 

0ERIPHERAL PORT

&)&/

&)&/

-EMORY PORT

342%!- 

342%!- 

342%!- 
&)&/
342%!- 

342%!- 

342%!- 
&)&/

342%!- 
&)&/
342%!- 

342%!- 

342%!- 

342%!- 
&)&/

&)&/
342%!- 

2%1?342?#(
2%1?342?#(

&)&/

!RBITER

342%!- 

2%1?342?#(

2%1?342%!-
2%1?342%!-
2%1?342%!-
2%1?342%!-
2%1?342%!-
2%1?342%!-
2%1?342%!-
2%1?342%!-

342%!- 

2%1?342?#(
2%1?342?#(

342%!- 

2%1?342?#(

!(" MASTER

2%1?342?#(
2%1?342?#(

!(" MASTER

$-! CONTROLLER

2%1?342?#(

#HANNEL
SELECTION

!(" SLAVE
PROGRAMMING
INTERFACE

0ROGRAMMING PORT

AIB

9.3.2

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 can carry 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).

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9.3.3

Direct memory access controller (DMA)

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, which contains 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.

9.3.4

Channel selection
Each stream is associated with a DMA request that can be selected out of 8 possible
channel requests. The selection is controlled by the CHSEL[2:0] bits in the DMA_SxCR
register.
Figure 24. Channel selection
5(4B675[B&+
5(4B675[B&+
5(4B675[B&+
5(4B675($0[

5(4B675[B&+
5(4B675[B&+
5(4B675[B&+
5(4B675[B&+
5(4B675[B&+


'0$B6[&5



  



&+6(/>@
DLE

The 8 requests from the peripherals (TIM, ADC, SPI, I2C, etc.) are independently connected
to each channel and their connection depends on the product implementation.
Table 28 and Table 29 give examples of DMA request mappings.

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RM0390

Table 28. 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

-

FMPI2C1_RX

TIM4_CH2

-

FMPI2C1_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

-

TIM3_CH1
TIM3_TRIG

TIM3_CH2

-

TIM3_CH3

Channel 5

-

-

TIM3_CH4
TIM3_UP

Channel 6

TIM5_CH3
TIM5_UP

TIM5_CH4
TIM5_TRIG

TIM5_CH1

TIM5_CH4
TIM5_TRIG

TIM5_CH2

-

TIM5_UP

-

Channel 7

-

TIM6_UP

I2C2_RX

I2C2_RX

USART3_TX

DAC1

DAC2

I2C2_TX

Table 29. 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

-

-

DCMI

Channel 2

ADC3

ADC3

-

-

-

-

-

-

Channel 3

SPI1_RX

-

SPI1_RX

SPI1_TX

SAI2_A

SPI1_TX

SAI2_B

QUADSPI

Channel 4

SPI4_RX

SPI4_TX

USART1_RX

SDIO

USART1_RX

SDIO

USART1_TX

Channel 5

-

USART6_RX

USART6_RX

SPI4_RX

SPI4_TX

-

USART6_TX

USART6_TX

TIM1_UP

TIM1_CH3

-

-

-

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

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9.3.5

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:
•

•

9.3.6

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.

9.3.7

Source, destination and transfer modes
Both source and destination transfers can address peripherals and memories in the entire
4 GB 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 30 describes the corresponding source and destination addresses.
Table 30. 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

-

-

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Direct memory access controller (DMA)

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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
$-!?3X-!2

$-! CONTROLLER

$-!?3X-!2

!(" MEMORY
PORT

-EMORY BUS

-EMORY
DESTINATION
2%1?342%!-X

&)&/
LEVEL

!RBITER

&)&/

!(" PERIPHERAL
PORT

0ERIPHERAL BUS

PERIPHERAL
SOURCE

$-!?3X0!2

0ERIPHERAL $-! REQUEST

AI

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.

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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
$-!?3X-!2

$-! CONTROLLER

$-!?3X-!2

!(" MEMORY
PORT

-EMORY BUS

-EMORY
SOURCE
2%1?342%!-X

&)&/
LEVEL

!RBITER

&)&/

!(" PERIPHERAL
PORT

$-!?3X0!2

0ERIPHERAL BUS

0ERIPHERAL
DESTINATION

0ERIPHERAL $-! REQUEST

AI

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.

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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
$-!?3X-!2

$-! CONTROLLER

$-!?3X-!2

!(" MEMORY
PORT

-EMORY BUS

-EMORY 
DESTINATION
!RBITER
3TREAM ENABLE

&)&/
LEVEL

&)&/

!(" PERIPHERAL
PORT

$-!?3X0!2

0ERIPHERAL BUS

-EMORY 
SOURCE

AI

1. For double-buffer mode.

9.3.8

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 are
accessed through a single register.
If the Increment mode is enabled, the address of the next transfer will be 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.

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9.3.9

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.

9.3.10

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 don’t care) 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 31: 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

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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 31. 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.

9.3.11

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 32: Packing/unpacking & 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 9.3.12: 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 MSIZE bits are
don’t care).

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Table 32. Packing/unpacking & endian behavior (bit PINC = MINC = 1)

Number
AHB
AHB
of data
memory peripheral
items to
port
port
transfer
width
width
(NDT)

Peripheral port address / byte lane
Memory
transfer
number

Memory port
address / byte
lane

Peripheral
transfer
number

PINCOS = 1

PINCOS = 0

8

8

4

1
2
3
4

0x0 / B1|B0[15:0]

2

0x0 / B0[7:0]
0x1 / B1[7:0]
0x2 / B2[7:0]
0x3 / B3[7:0]

0x0 / B1|B0[15:0]

16

1
2
3
4

1

8

2

0x4 / B3|B2[15:0]

0x2 / B3|B2[15:0]

1
2
3
4

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

0x0 / B1|B0[15:0]

2

0x2 / B3|B2[15:0]

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 / B1|B0[15:0]

1

0x0 / B1|B0[15:0]

0x0 / B1|B0[15:0]

2

0x2 / B1|B0[15:0]

2

0x4 / B3|B2[15:0]

0x2 / B3|B2[15:0]

1
2

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]

1

0x0 /B3|B2|B1|B0 [31:0] 1

0x0 /B3|B2|B1|B0
[31:0]

0x0 /
B3|B2|B1|B0[31:0]

8

32

1

16

8

4

16

16

2

16

32

1

32

8

4

32

16

2

32

32

1

Note:

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]

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 33.
Table 33. 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

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9.3.12

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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 KB address boundary because the minimum address space that
can be allocated to a single slave is 1 KB. This means that the 1 KB address boundary
should not be crossed by a burst block transfer, otherwise an AHB error would be
generated, that is not reported by the DMA registers.

9.3.13

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.

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Figure 28. FIFO structure
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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) will be generated when the stream is enabled, then the stream will be
automatically disabled. The allowed and forbidden configurations are described in Table 34.
The forbidden configurations are highlighted in gray in the table.
Table 34. 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

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forbidden

1 burst of 16 beats

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Table 34. 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 will be managed in single mode by the
DMA, even if a burst transaction was 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 will be 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 will be sent with the data width set in
the MSIZE bit in the DMA_SxCR register. This means that memory will be written with an

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undesired 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 will be 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 don’t care)

•

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.

9.3.14

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).

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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:

Note that 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.

9.3.16

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
which are able to signal the end of the transfer, that is:
–

SDIO

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

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Direct memory access controller (DMA)
be forced by hardware to 0xFFFF as soon as the stream is enabled, to respect the following
schemes:
•

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
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 will not be 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.

9.3.17

Summary of the possible DMA configurations
Table 35 summarizes the different possible DMA configurations. The forbidden
configurations are highlighted in gray in the table.
Table 35. 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

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Transfer
type

Direct
mode

single

possible

burst

forbidden

single

possible

burst

forbidden

single

possible

burst

forbidden

single

possible

burst

forbidden

single
burst

forbidden

Double
buffer mode
possible

forbidden

possible

forbidden

forbidden

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RM0390

Stream configuration procedure
The following sequence should 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 have 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 should be cleared before the stream can be re-enabled.

2.

Set the peripheral port register address in the DMA_SxPAR register. The data will be
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 will be 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:

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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.

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9.3.19

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 9.3.10: 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 34: 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 are 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.

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9.4

RM0390

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 36.
Table 36. 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:

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Before setting an Enable control bit to ‘1’, the corresponding event flag should be cleared,
otherwise an interrupt is immediately generated.

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Direct memory access controller (DMA)

9.5

DMA registers
The DMA registers have to be accessed by words (32 bits).

9.5.1

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

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

r

r

r

r

Bits 31:28, 15:12 Reserved, must be kept at reset value.
Bits 27, 21, 11, 5 TCIFx: 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 HTIFx: 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 TEIFx: 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 DMEIFx: 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 FEIFx: 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

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RM0390

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 TCIFx: 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: A transfer complete event occurred on stream x
Bits 26, 20, 10, 4 HTIFx: 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 TEIFx: 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 DMEIFx: 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 FEIFx: 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

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9.5.3

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 CTCIFx: 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 CHTIFx: 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 CTEIFx: 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 CDMEIFx: 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 CFEIFx: 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

9.5.4

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 CTCIFx: 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 CHTIFx: 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 CTEIFx: 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

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Bits 24, 18, 8, 2 CDMEIFx: 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 CFEIFx: 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

9.5.5

DMA stream x configuration register (DMA_SxCR) (x = 0..7)
This register is used to configure the concerned stream.
Address offset: 0x10 + 0x18 × stream number
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

24

CHSEL[2:0]

rw

rw

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: 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.

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PFCTRL

Bits 31:28 Reserved, must be kept at reset value.

Bit 20 Reserved, must be kept at reset value.

16
PL[1:0]

RM0390

Direct memory access controller (DMA)

Bit 19 CT: Current target (only in double buffer mode)
This bits is set and cleared by hardware. It can also be written by software.
0: The current target memory is Memory 0 (addressed by the DMA_SxM0AR pointer)
1: The 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 bits 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’.

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RM0390

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: The 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

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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.

9.5.6

DMA stream x number of data register (DMA_SxNDTR) (x = 0..7)
Address offset: 0x14 + 0x18 × stream number
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
Number of data items to be transferred (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 has 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.

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Direct memory access controller (DMA)

9.5.7

RM0390

DMA stream x peripheral address register (DMA_SxPAR) (x = 0..7)
Address offset: 0x18 + 0x18 × stream number
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 will be read/written.
These bits are write-protected and can be written only when bit EN = '0' in the DMA_SxCR register.

9.5.8

DMA stream x memory 0 address register (DMA_SxM0AR) (x = 0..7)
Address offset: 0x1C + 0x18 × stream number
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

M0A[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 M0A[31:0]: Memory 0 address
Base address of Memory area 0 from/to which the data will be 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).

9.5.9

DMA stream x memory 1 address register (DMA_SxM1AR) (x = 0..7)
Address offset: 0x20 + 0x18 × stream number
Reset value: 0x0000 0000

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

M1A[31:16]

M1A[15:0]
rw

230/1327

rw

rw

rw

rw

rw

rw

rw

rw

DocID026976 Rev 3

RM0390

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 will be 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.

9.5.10

DMA stream x FIFO control register (DMA_SxFCR) (x = 0..7)
Address offset: 0x24 + 0x24 × stream number
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).

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Direct memory access controller (DMA)

RM0390

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.
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’.

232/1327

DocID026976 Rev 3

0x002C

0x0030

DMA_S1NDTR

Reset value

0

0

0

0

0

0

0

0

0

0

Res

0

0

0

0

0

0

0

0

0
0

DMA_S0M1AR

DMA_S1PAR

0

0
0

0
0

0

0

0

0

Reset value

0

DocID026976 Rev 3
0

0

0
0

0

0

0

0

0

0

0

0

CDMEIF5
0

Reset value

0

0

TCIE
HTIE
TEIE
DMEIE
EN

0

PFCTRL

DIR[1:0]

CTCIF4
CHTIF4
CTEIF4
CDMEIF4

CHTIF1
CTEIF1
CDMEIF1
CFEIF1
CTCIF0
CHTIF0
CTEIF0
CDMEIF0

0
0
0
0
0
0
0
0
0

TEIF5
DMEIF5
FEIF5
TCIF4
HTIF4
TEIF4
DMEIF4

HTIF1
TEIF1
DMEIF1
FEIF1
TCIF0
HTIF0
TEIF0
DMEIF0

0
0
0
0
0

0
0
0
0
0
0
0
0

0
0
0
0
0

0
0
0
0

DMA_S0FCR

0
FS[2:0]

Reserved
FEIF0

Reserved
FEIF4

Res.

TCIF1

Res.

Res.

Res.

Res.

0

CFEIF0

HTIF5

0

Res

TCIF5

Res

Res

Res

Res

0

Reserved

Res

CTCIF1

Res

Res

Res

Res

Res.
FEIF2

0

CFEIF4

CFEIF2

0

Reserved

CFEIF5

Res

CTEIF5
PINC
CIRC

CHTIF5
MINC

Res

Res
CTCIF5

PSIZE[1:0]

MSIZE[1:0]

0

EN

DMA_S0M0AR
0
0

0

DMDIS

0
0
0

0

DMEIE

0

Res

0
0

0

TEIE

0

FEIE

DMA_S0PAR
0

0

HTIE

0

Res

Reset value
0

0

TCIE

0

Res

0
0

0

PFCTRL

0

Res

0
0

Res

0

Res

0

DIR[1:0]

0

Res

0
0
0
PINCOS

FEIF6

0
Res

0

Res

Res
CFEIF6

Res

0

CIRC

0

Res

0
0
PL[1:0]

0

PINC

0

Res

0
0

Res
0

Res

TEIF2
DMEIF2

0

DMEIF6

CDMEIF2

CDMEIF6

0

DBM

0

Res

HTIF2

0

TEIF6

CTEIF2

CTEIF6

0

CT

0

Res

TCIF2

0

HTIF6

CHTIF2

0

TCIF6

CTCIF2

0
CHTIF6

0

CTCIF6

0

FEIF7

0

Res

0

Res.
FEIF3

0
Res

0

MINC

0

Res

0
CFEIF3

Reserved

0

PSIZE[1:0]

0

Res

0
0

CFEIF7

TEIF3

DMEIF7

DMEIF3

TEIF7

Res.

Res.

HTIF3

HTIF7

Res.

0

MSIZE[1:0]

0

Res

0
0

PINCOS

0

Res

0
0
0

PL[1:0]

0
0

Res

0

PBURST[1:0]

0

Res

0

Res

0

Res

0
Reserved

0

DBM

0

Res

0

Res

0

Res

0
MBURST[1:0]

CDMEIF3

0

Res

0

Res

CDMEIF7

TEIF3

0

CT

0

Res

0

Res

CHTIF3

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

DMA_LISR
Res.

Register

TCIF3

TCIF7

Res

Res

0

Res

0

Res

0
CTEIF7

CTCIF3

Res

Res

Res

Res

0

Res

0

Res

0
CHTIF7

Res
CHSEL[2:0]

CTCIF7

Res

DMA_S0CR
Res

Res

Res

0

PBURST[1:0]

0

Res

0

Res

Res

Res

0

MBURST[1:]

0

Res

0

Res

Res

Res

0

Res

0

Res

Reset value

Res

0

Res

0

Res

0

Res

0
0
0

Res

Reset value

CHSEL[2:0]

0

Res

0
0
Res

Res

Res

Reset value

Res

DMA_S1CR
0
Res

Res

Reset value

Res

Reset value

Res

0x0028
DMA_HIFCR

Res

Reset value

Res

0x0024
Reset value

Res

0x0020

Res

Reset value
0

Res

0x001C
0

Res

Reset value

Res

0x0018
DMA_S0NDTR

Res

0x0014
DMA_LIFCR

Res

0x0010
DMA_HISR

Res

0x000C

Res

0x0008

Res

0x0004

Res

0x0000

Res

Offset

Res

9.5.11

Res

RM0390
Direct memory access controller (DMA)

DMA register map
Table 37 summarizes the DMA registers.
Table 37. DMA register map and reset values

0

0

0

0

NDT[15:.]

0
0
0
0
0
0
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

FTH
[1:0]

1
0
0
0
0
1

NDT[15:.]

0

0

0

0

0

0

0

PA[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

233/1327

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Direct memory access controller (DMA)

RM0390

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

234/1327

DMEIE

EN

0

1

TEIE

0

0

HTIE

0

0

0

0

0

0

0

0

DIR[1:0]

0

0

TCIE

0

CIRC

PSIZE[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

M0A[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S3M1AR
Reset value

0

0

PA[31:0]

DMA_S3M0AR
Reset value

0

1

NDT[15:.]
0

DMA_S3PAR

MSIZE[1:0]

PINCOS

PL[1:0]

Reset value

0

FTH
[1:0]

PFCTRL

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

Res

Res

DMA_S3NDTR

Res

Res

Res

Res

Res

0

FS[2:0]

DMDIS

0

Res

M1A[31:0]
0

0x0060

0x0068

0

M0A[31:0]

Reset value

0x0064

0

Reset value

DMA_S3CR

1

PA[31:0]

DMA_S2M1AR

0x0058

0

NDT[15:.]

Reset value

0x005C

0

0

EN

0

0

TEIE

0

0

DMEIE

0

1

HTIE

0

FTH
[1:0]

TCIE

0

CIRC

0

PINC

0

MINC

0

PSIZE[1:0]

MSIZE[1:0]

PINCOS

PL[1:0]
0

Res

Res

0

Res

Res

DBM

Res

0

Res

Res

CT

0

Res

0

Res

0

Res

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]

0

Res

Res

0

DMA_S2M0AR
Reset value

0x0054

0

DMA_S2PAR
Reset value

0x0050

0

Reset value

0x0048

0x004C

Res

DMA_S2NDTR

Res

0x0044

Res

Reset value

Res

Res

Res

Res

DMA_S2CR

0x0040

0

Res

Reset value

FS[2:0]

DMDIS

Reset value

Res

M1A[31:0]

Res

DMA_S1M1AR

0

Res

0

Res

0x003C

0

Res

0x0038

0

PFCTRL

Reset value

Res

M0A[31:0]

FEIE

DMA_S1M0AR

DIR
[1:0]

Offset

0x0034

Register

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 37. DMA register map and reset values (continued)

0

0

0

0

M1A[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DocID026976 Rev 3

0

0

RM0390

Direct memory access controller (DMA)

0
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0x00A8
0x00AC

EN

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

FEIE

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

0

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

0

DMA_S5FCR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

FEIE

Res

Reset value

EN

0

1

DMEIE

0

0

TEIE

0

0

0

0

0

0

0

0

DIR[1:0]

0

0

HTIE

0

0

TCIE

0

CIRC

PSIZE[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

PA[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMA_S6M0AR
Reset value

0

1

NDT[15:.]
0

DMA_S6PAR

MSIZE[1:0]

PINCOS

PL[1:0]

Reset value

0

FTH
[1:0]

PFCTRL

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

Res

Res

DMA_S6NDTR

Res

Res

Res

Res

Res

0

FS[2:0]

DMDIS

Reset value

Res

M1A[31:0]

Res

DMA_S5M1AR

DMA_S6CR

1

EN

0

0
DMEIE

0

DIR[1:0]

0

CIRC

0

0

TEIE

0

0

HTIE

0

0

NDT[15:.]
0

DMA_S5PAR

0

1

TCIE

0

FTH
[1:0]

PFCTRL

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

FS[2:0]

DMDIS

0

Reset value

DMDIS
TEIE

DMEIE

0

M1A[31:0]

Reset value
0x00A4

HTIE

0

Reset value

0x00A0

0

Res

0x009C

0

Res

0x0098

0

Res

0x0094

0

0

Reset value

1

0

Res

0x0090

0

0

Reset value

DMA_S5NDTR

0

0

Res

DMA_S4M1AR

DMA_S5CR

0

M0A[31:0]

Reset value
0x008C

0

0

NDT[15:.]

Reset value

0x0088

Res

Res
0

DIR
[1:0]

0

CIRC

0

1

TCIE

0

FTH
[1:0]

PFCTRL

0

PINC

0

FS[2:0]

PA[31:0]

DMA_S4M0AR
Reset value

0

MINC

Res

Reset value

0

PSIZE[1:0]

0

DMA_S4PAR
Reset value

MSIZE[1:0]

PINCOS

0
Res

PL[1:0]

DBM

Res

0
Res

Res

CT

Res

0
Res

Res

Res

0

Res

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]

0

Res

Res

Res

Res

0

Res

0x0084

0

Res

0x0080

0

Res

0x007C

0

Res

0x0078

0

Res

0x0074

Res

Reset value
DMA_S4NDTR

Res

Res

Res

DMA_S4CR

Res

0x0070

0

Res

Reset value

FEIE

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

DMA_S3FCR

Res

0x006C

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 37. 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

0

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0

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RM0390

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

0

0

0

FTH
[1:0]

0

0

1

EN

0

TEIE

0

DMEIE

1

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

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

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

FEIE

Res

Reset value

0

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

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1

0

0

DMDIS

Reset value

Res

M1A[31:0]

Res

DMA_S7M1AR

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0

HTIE

0

0

TCIE

0

FS[2:0]

0

0

DIR[1:0]

0

CIRC

0

0

PFCTRL

0

PINC

0

MINC

0

0

PA[31:0]

DMA_S7M0AR
Reset value

0

PSIZE[1:0]

0

Reset value
Reset value

MSIZE[1:0]

PINCOS

PL[1:0]
0

Res

Res

0

Res

Res

DBM

Res

0

Res

Res

CT

0

Res

0

Res

0

Res

Res

PBURST[1:0]

MBURST[1:0]

CHSEL[2:0]

0

Res

Res

Res

0

Res

0x00CC

0

Res

0x00C8

0

DMA_S7PAR

0x00C0
0x00C4

Res

0x00BC

Res

Reset value
DMA_S7NDTR

Res

Res

Res

Res

DMA_S7CR

0x00B8

0

Res

Reset value

0

DMDIS

0

Res

0

Res

0

Res

M1A[31:0]

Reset value

Res

0x00B4

DMA_S6M1AR

Res

0x00B0

Register

FEIE

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 37. DMA register map and reset values (continued)

0

FTH
[1:0]
0

1

RM0390

Interrupts and events

10

Interrupts and events

10.1

Nested vectored interrupt controller (NVIC)

10.1.1

NVIC features
The nested vector interrupt controller NVIC includes the following features:
•

96 maskable interrupt channels (not including the 16 interrupt lines of Cortex®-M4 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 PM0214.

10.1.2

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).

10.1.3

Interrupt and exception vectors
See Table 38 for the vector table.

10.2

External interrupt/event controller (EXTI)
The external interrupt/event controller consists of up to 23 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.

Position

Priority

Table 38. Vector table for STM32F446xx
Type of
priority

-

-

-

-

Reserved

0x0000 0000

-

-3

fixed

Reset

Reset

0x0000 0004

-

-2

fixed

NMI

Non maskable interrupt, Clock Security System

0x0000 0008

-

-1

fixed

HardFault

All class of fault

0x0000 000C

-

0

settable

MemManage

Memory management

0x0000 0010

Acronym

Description

Address

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Position

Priority

Table 38. Vector table for STM32F446xx (continued)
Type of
priority

-

1

settable

BusFault

Pre-fetch fault, memory access fault

0x0000 0014

-

2

settable

UsageFault

Undefined instruction or illegal state

0x0000 0018

-

-

-

-

Reserved

0x0000 001C 0x0000 002B

-

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

22

29

settable

CAN1_SCE

CAN1 SCE interrupt

0x0000 0098

23

30

settable

EXTI9_5

EXTI Line[9:5] interrupts

0x0000 009C

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Acronym

Description

Address

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Interrupts and events

Position

Priority

Table 38. Vector table for STM32F446xx (continued)
Type of
priority

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

31

38

settable

I2C1_EV

I2C1 event interrupt

0x0000 00BC

32

39

settable

I2C1_ER

I2C1 error interrupt

0x0000 00C0

I2C2_EV

I

2C2

event interrupt

0x0000 00C4

I2C2

error interrupt

0x0000 00C8

33

40

settable

Acronym

Description

Address

34

41

settable

I2C2_ER

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

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

47

54

settable

DMA1_Stream7

DMA1 Stream7 global interrupt

0x0000 00FC

48

55

settable

FMC

FMC global interrupt

0x0000 0100

49

56

settable

SDIO

SDIO 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

TIM8 Break interrupt and TIM12 global interrupt 0x0000 00EC

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Position

Priority

Table 38. Vector table for STM32F446xx (continued)
Type of
priority

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

-

-

Reserved

0x0000 0134

62

69

-

-

Reserved

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

72

79

settable

Acronym

Description

Address

I2C3_EV

I

2C3

event interrupt

0x0000 0160

I2C3

error interrupt

0x0000 0164

73

80

settable

I2C3_ER

74

81

settable

OTG_HS_EP1_OUT

USB On The Go HS End Point 1 Out
global interrupt

0x0000 0168

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

-

-

Reserved

0x0000 017C

80

87

-

-

Reserved

0x0000 0180

81

88

settable

FPU

FPU global interrupt

0x0000 0184

82

89

-

-

Reserved

0x0000 0188

83

90

-

-

Reserved

0x0000 018C

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Interrupts and events

Position

Priority

Table 38. Vector table for STM32F446xx (continued)
Type of
priority

84

91

settable

SPI4

SPI 4 global interrupt

0x0000 0190

85

92

-

-

Reserved

0x0000 0194

86

93

-

-

Reserved

0x0000 0198

87

94

settable

SAI1

SAI1 global interrupt

0x0000 019C

88

95

-

-

Reserved

0x0000 01A0

89

96

-

-

Reserved

0x0000 01A4

90

97

-

-

Reserved

0x0000 01A8

91

98

settable

SAI2

SAI2 global interrupt

0x0000 01AC

92

99

settable

QuadSPI

QuadSPI global interrupt

0x0000 01B0

93

100

settable

HDMI-CEC

HDMI-CEC global interrupt

0x0000 01B4

94

101

settable

SPDIF-Rx

SPDIF-Rx global interrupt

0x0000 01B8

95

102

settable

FMPI2C1

FMPI2C1 event interrupt

0x0000 01BC

96

103

settable

FMPI2C1 error

FMPI2C1 error interrupt

0x0000 01C0

10.2.1

Acronym

Description

Address

EXTI main features
The main features of the EXTI controller are the following:
•

independent trigger and mask on each interrupt/event line

•

dedicated status bit for each interrupt line

•

generation of up to 23 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 STM32F446xx datasheets for details on
this parameter.

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10.2.2

RM0390

EXTI block diagram
Figure 29 shows the block diagram.
Figure 29. External interrupt/event controller block diagram
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10.2.3

Wakeup event management
The STM32F446xx microcontrollers 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®-M4 with FPU 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 10.2.4.

10.2.4

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

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Interrupts and events
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.

Hardware interrupt selection
To configure the 23 lines as interrupt sources, use the following procedure:
•

Configure the mask bits of the 23 interrupt lines (EXTI_IMR)

•

Configure the Trigger selection bits of the interrupt lines (EXTI_RTSR and EXTI_FTSR)

•

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 23 lines
can be correctly acknowledged.

Hardware event selection
To configure the 23 lines as event sources, use the following procedure:
•

Configure the mask bits of the 23 event lines (EXTI_EMR)

•

Configure the Trigger selection bits of the event lines (EXTI_RTSR and EXTI_FTSR)

Software interrupt/event selection
The 23 lines can be configured as software interrupt/event lines. The following is the
procedure to generate a software interrupt.
•

Configure the mask bits of the 23 interrupt/event lines (EXTI_IMR, EXTI_EMR)

•

Set the required bit in the software interrupt register (EXTI_SWIER)

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10.2.5

RM0390

External interrupt/event line mapping
Up to 114 GPIOs are connected to the 16 external interrupt/event lines in the following
manner:
Figure 30. External interrupt/event GPIO mapping
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The seven other EXTI lines are connected as follows:

244/1327

•

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 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

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Interrupts and events

10.3

EXTI registers
Refer to Section 1.1 on page 51 for a list of abbreviations used in register descriptions.

10.3.1

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.

Res.

MR22

MR21

MR20

MR19

MR18

MR17

MR16

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

MR15

MR14

MR13

MR12

MR11

MR10

MR9

MR8

MR7

MR6

MR5

MR4

MR3

MR2

MR1

MR0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:23 Reserved, must be kept at reset value.
Bits 22:0 MRx: Interrupt mask on line x
0: Interrupt request from line x is masked
1: Interrupt request from line x is not masked

10.3.2

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.

Res.

MR22

MR21

MR20

MR19

MR18

MR17

MR16

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

MR15

MR14

MR13

MR12

MR11

MR10

MR9

MR8

MR7

MR6

MR5

MR4

MR3

MR2

MR1

MR0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:23 Reserved, must be kept at reset value.
Bits 22:0 MRx: Event mask on line x
0: Event request from line x is masked
1: Event request from line x is not masked

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10.3.3

RM0390

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.

Res.

TR22

TR21

TR20

Res.

TR18

TR17

TR16

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 31:23 Reserved, must be kept at reset value.
Bits 22:20 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
Bit 19 Reserved, must be kept at reset value.
Bits 18:0 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.

10.3.4

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.

Res.

TR22

TR21

TR20

Res.

TR18

TR17

TR16

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 31:23 Reserved, must be kept at reset value.
Bits 22:20 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.
Bit 19 Reserved, must be kept at reset value.
Bits 18:0 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.

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Interrupts and events

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.

10.3.5

Software interrupt event register (EXTI_SWIER)
Address offset: 0x10
Reset value: 0x0000 0000

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

SWIER SWIER SWIER SWIER SWIER SWIER SWIER
15
14
13
12
11
10
9
rw

rw

rw

rw

rw

rw

rw

22

21

20

19

18

17

16

SWIER SWIER SWIER SWIER SWIER SWIER SWIER
22
21
20
19
18
17
16
rw

rw

rw

rw

rw

rw

rw

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 31:23 Reserved, must be kept at reset value.
Bits 22:0 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).

10.3.6

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.

Res.

PR22

PR21

PR20

PR19

PR18

PR17

PR16

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 31:23 Reserved, must be kept at reset value.
Bits 22:0 PRx: Pending bit on line x
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’.

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10.3.7

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EXTI register map
Table 39 gives the EXTI register map and the reset values.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_FTSR

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

TR[22:0
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PR[22:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

Refer to Table 1 on page 56 for the register boundary addresses.

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0

TR[22:0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_PR

0

SWIER[22:0]
0

Res.

Reset value

0x14

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_SWIER

Res.

0x10

0

TR[22:0]
0

Res.

Reset value

0

TR[22:0]
0

Res.

Reset value

0x0C

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_RTSR

0

MR[22:0]
0

Res.

Reset value

0x08

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_EMR

Res.

0x04

0
Res.

Reset value

MR[22:0]

Res.

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 39. External interrupt/event controller register map and reset values

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11

Flexible memory controller (FMC)

Flexible memory controller (FMC)
The Flexible memory controller (FMC) includes three memory controllers:

11.1

•

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-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.
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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.

11.2

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 external device interface

The block diagram is shown in the figure below.
Figure 31. FMC block diagram
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11.3

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®-M4 with FPU 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.

11.3.1

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.

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RM0390

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[1:0].
Bytes to be written are addressed by NBL[1:0].
All memory bytes are read (NBL[1:0] 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
Wrap burst mode for synchronous memories is not supported. The memories must be
configured in linear burst mode of undefined length.

Configuration registers
The FMC can be configured through a set of registers. Refer to Section 11.5.6, for a detailed
description of the NOR Flash/PSRAM controller registers. Refer to Section 11.6.7, for a
detailed description of the NAND Flash registers and to Section 11.7.5 for a detailed
description of the SDRAM controller registers.

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11.4

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 32):
•

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 32. FMC memory banks
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11.4.1

RM0390

NOR/PSRAM address mapping
HADDR[27:26] bits are used to select one of the four memory banks as shown in Table 40.
Table 40. 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 41. 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

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].
Whatever the external memory width, FMC_A[0] should be connected to external memory address A[0].

11.4.2

NAND Flash memory address mapping
The NAND bank is divided into memory areas as indicated in Table 42.
Table 42. 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 43 below) located in the lower 256 Kbytes:

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•

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)

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Flexible memory controller (FMC)
Table 43. 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.

11.4.3

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 44.
Table 44. 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 45. 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

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].
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’.

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The HADDR[27:0] bits are translated to external SDRAM address depending on the
SDRAM controller configuration:
•

Data size:8 or 16 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 46. 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]

Res.

Bank
[1:0]

Row[11:0]
Row[11:0]
Row[11:0]

Bank
[1:0]
Bank
[1:0]

Res.

Res.

Row[11:0]

Bank
[1:0]

Res.

Res.

Row[10:0]
Bank
[1:0]

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.

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Table 47. 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.

11.5

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

PSRAM (Cellular RAM)
–

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.

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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 11.5.6: 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 11.5.5: 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 11.5.6: NOR/PSRAM controller registers).
The programmable memory parameters include access times (see Table 48) and support
for wait management (for PSRAM and NOR Flash accessed in burst mode).
Table 48. Programmable NOR/PSRAM access parameters

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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

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11.5.1

Flexible memory controller (FMC)

External memory interface signals
Table 49, Table 50 and Table 51 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 49. 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[15:0]

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 50. 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.

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PSRAM/SRAM, non-multiplexed I/Os
Table 51. 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[15:0]

I/O

Data bidirectional bus

NE[x]

O

Chip Select, x = 1..4 (called NCE by PSRAM (Cellular RAM 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[1:0]

O

Byte lane output. Byte 0 and Byte 1 control (upper and lower byte enable)

The maximum capacity is 512 Mbits.

PSRAM, 16-bit multiplexed I/Os
Table 52. 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 (Cellular RAM 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).

11.5.2

Supported memories and transactions
Table 53 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.

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Table 53. 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

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]

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11.5.3

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General timing rules
Signals synchronization

11.5.4

•

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)

262/1327

•

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).

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Flexible memory controller (FMC)

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 33. Mode1 read access waveforms
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Figure 34. Mode1 write access waveforms
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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 54. 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

11

Reserved

0x0

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.

As needed

Table 55. FMC_BTRx bit fields

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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).

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Flexible memory controller (FMC)

Mode A - SRAM/PSRAM (CRAM) OE toggling
Figure 35. ModeA read access waveforms
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1. NBL[1:0] are driven low during the read access

Figure 36. ModeA write access waveforms
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The differences compared with Mode1 are the toggling of NOE and the independent read
and write timings.
Table 56. 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 57. FMC_BTRx bit fields

266/1327

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).

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Table 58. 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 37. Mode2 and mode B read access waveforms
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Figure 38. Mode2 write access waveforms

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Figure 39. ModeB write access waveforms

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The differences with Mode1 are the toggling of NWE and the independent read and write
timings when extended mode is set (Mode B).

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Table 59. 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 60. FMC_BTRx bit fields
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).

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Table 61. 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 40. ModeC read access waveforms
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Flexible memory controller (FMC)
Figure 41. ModeC write access waveforms
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The differences compared with Mode1 are the toggling of NOE and the independent read
and write timings.
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

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

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Table 62. 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 63. 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 64. FMC_BWTRx bit fields

272/1327

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).

DocID026976 Rev 3

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Flexible memory controller (FMC)

Mode D - asynchronous access with extended address
Figure 42. ModeD read access waveforms
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Figure 43. ModeD write access waveforms
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The differences with Mode1 are the toggling of NOE that goes on toggling after NADV
changes and the independent read and write timings.
Table 65. 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 66. FMC_BTRx bit fields

274/1327

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).

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Flexible memory controller (FMC)
Table 67. 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 44. Muxed read access waveforms
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Figure 45. Muxed write access waveforms

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The difference with ModeD is the drive of the lower address byte(s) on the data bus.
Table 68. FMC_BCRx bit fields

276/1327

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

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Flexible memory controller (FMC)
Table 68. 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 69. 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:

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1.

RM0390

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 46 and Figure 47 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 46. Asynchronous wait during a read access waveforms
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1. NWAIT polarity depends on WAITPOL bit setting in FMC_BCRx register.

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Figure 47. Asynchronous wait during a write access waveforms
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1. NWAIT polarity depends on WAITPOL bit setting in FMC_BCRx register.

11.5.5

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 ))
Whatever MWID size: 16 or 8-bit, the FMC_CLK divider ratio is always defined by the
programmed CLKDIV value.
Example:
•

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.

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Caution:

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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 Cellular RAM 1.5
Cellular RAM 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).

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Figure 48. Wait configuration waveforms
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RM0390

Figure 49. Synchronous multiplexed read mode waveforms - NOR, PSRAM (CRAM)
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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 70. FMC_BCRx bit fields

282/1327

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)

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Flexible memory controller (FMC)
Table 70. 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 71. FMC_BTRx bit fields
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).

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Figure 50. Synchronous multiplexed write mode waveforms - PSRAM (CRAM)
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DATA

DATA

 CLOCK  CLOCK

AIF

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 72. FMC_BCRx bit fields
Bit number

Bit name

31-22

Reserved

21

WFDIS

As needed

20

CCLKEN

As needed

19
18:16
15

284/1327

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.

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Table 72. 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 73. FMC_BTRx bit fields
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).

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11.5.6

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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

rw

rw

rw

rw

rw

5

4

3

2

1

0

MUX
EN

MBK
EN

rw

rw

MWID
rw

18

rw

16

CPSIZE[2:0]

MTYP[1:0]
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.

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Bits 18:16 CPSIZE[2:0]: CRAM page size.
These are used for Cellular RAM 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.

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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: reserved
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).

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31

30

Res.

Res.

15

14

29

28

27

26

ACCMOD

25

24

23

22

DATLAT

rw

20

19

18

CLKDIV

17

16

BUSTURN

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

DATAST
rw

21

rw

rw

rw

ADDHLD
rw

rw

rw

rw

rw

rw

ADDSET
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 11.5.5: Synchronous transactions for FMC_CLK divider ratio formula)

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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 33
to Figure 45), 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 33 to Figure 45).
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.

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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 33 to Figure 45), 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 33
to Figure 45).
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 33 to Figure 45), 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 33 to Figure 45).
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
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
rw

rw

rw

rw

rw

19

rw

rw

rw

rw

rw

17

16

BUSTURN
rw

rw

rw

rw

3

2

1

0

ADDHLD
rw

18

ADDSET[3:0]
rw

rw

rw

rw

rw

Bits 31:30 Reserved, must be kept at reset value

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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 33 to
Figure 45), 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 42 to Figure 45), 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.

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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 33 to Figure 45), 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.

11.6

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 11.6.7). The
programmable memory parameters include access timings (shown in Table 74) and ECC
configuration.
Table 74. Programmable NAND Flash access parameters

11.6.1

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 75. 8-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[7:0]

I/O

8-bit multiplexed, bidirectional address/data bus

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Table 75. 8-bit NAND Flash (continued)

FMC signal name

I/O

Function

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 76. 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.

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Flexible memory controller (FMC)

NAND Flash supported memories and transactions
Table 77 shows the supported devices, access modes and transactions. Transactions not
allowed (or not supported) by the NAND Flash controller are shown in gray.
Table 77. Supported memories and transactions
Device

NAND 8-bit

NAND 16-bit

11.6.3

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 51 shows the timing parameter definitions for common memory accesses, knowing
that Attribute memory space access timings are similar.

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Figure 51. NAND Flash controller waveforms for common memory access
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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.

11.6.4

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:

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3.

Program and enable the corresponding memory bank by configuring the FMC_PCR
and FMC_PMEM (and for some devices, FMC_PATT, see Section 11.6.5: 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 11.4.2: NAND Flash memory address mapping for timing
configuration).

4.

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.

5.

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

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to implement the prewait functionality needed by some NAND Flash memories (see
details in Section 11.6.5: NAND Flash prewait functionality).

11.6.5

6.

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).

7.

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.

8.

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 52).
Figure 52. Access to non ‘CE don’t care’ NAND-Flash
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AI

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).

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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.

11.6.6

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.

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To perform an ECC computation:

11.6.7

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 Flashcontroller 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

11

TAR
rw

rw

10

9

TCLR
rw

rw

rw

rw

8

7

6

Res.

Res.

ECCEN

rw

rw

5

4
PWID

rw

19

18

17

16

ECCPS

TAR

rw

rw

rw

3

2

1

rw
0

PTYP PBKEN PWAITEN
rw

rw

rw

Res.

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.

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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.

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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

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.
31

30

29

28

rw

rw

rw

rw

27

26

25

24

23

22

21

rw

rw

rw

rw

rw

rw

MEMHIZx
rw

20

19

18

17

16

rw

rw

rw

MEMHOLDx

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15

14

13

12

11

10

RM0390

9

8

7

6

5

MEMWAITx
rw

rw

rw

rw

rw

4

3

2

1

0

rw

rw

rw

MEMSETx
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 11.6.5: NAND Flash prewait functionality).

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Flexible memory controller (FMC)

31

30

29

28

rw

rw

rw

rw

15

14

13

12

27

26

25

24

23

22

21

20

rw

rw

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

5

4

ATTHIZ

rw

rw

rw

rw

18

17

16

rw

rw

rw

rw

3

2

1

0

rw

rw

rw

ATTHOLD

ATTWAIT
rw

19

ATTSET
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.

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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 11.6.6: 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

ECCx

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

ECCx

r

r

r

r

r

r

r

r

Bits 31:0 ECC: ECC result
This field contains the value computed by the ECC computation logic. Table 78 describes
the contents of these bit fields.

Table 78. ECC result relevant bits

304/1327

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]

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Flexible memory controller (FMC)

11.7

SDRAM controller

11.7.1

SDRAM controller main features
The main features of the SDRAM controller are the following:

11.7.2

•

Two SDRAM banks with independent configuration

•

8-bit, 16-bit data bus width

•

13-bits Address Row, 11-bits Address Column, 4 internal banks: 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 79. SDRAM signals
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[15:0]

I/O

Bidirectional data bus

FMC_D[15:0]

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[1:0]

O

Output Byte Mask for write accesses
(memory signal name: DQM[1:0]

FMC_NBL[1:0]

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11.7.3

RM0390

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.

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Note:

Flexible memory controller (FMC)
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 53. Burst write SDRAM access waveforms

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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).

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RM0390
Figure 54. Burst read SDRAM access
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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 = 0: 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:

308/1327

•

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.

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Flexible memory controller (FMC)
Figure 55. Logic diagram of Read access with RBURST bit set (CAS=1, RPIPE=0)
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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:
•

RBURST control bit should be set to ‘1’ in the FMC_SDCR1 register.

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RM0390

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 53 and Figure 54 for read and burst write access crossing a row boundary.

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Flexible memory controller (FMC)
Figure 56. Read access crossing row boundary
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Figure 57. Write access crossing row boundary

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-36

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RM0390

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 and the selected SDRAM device is connected to
Bank 1, the automatic activation of the next row in device connected to SDRAM Bank2
is not supported. A PALL software command must be issused on Bank1 before any any
access on Bank2.

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.

11.7.4

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.

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:

312/1327

•

A Self-refresh command is issued to both devices

•

One of the devices is not activated (SDRAM bank is not initialized).

DocID026976 Rev 3

RM0390

Flexible memory controller (FMC)
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.
Figure 58. Self-refresh mode
4

4

4

4N 

4 

4 

3$#,+

T2!3MIN
3$#+%

#/--!.$

02%#(!2'%

./0

!54/
2%&2%3(

./0

OR #/--!.$
).(%2)4

!54/
2%&2%3(

$/-
$/-,$/-5

! !
! !

!,,
"!.+3

!

$ATA;= (I :
T832

T20
0RECHARGE ALL
ACTIVE BANKS

%XIT 3ELF REFRESH MODE
RESTART REFRESH TIMEBASE
#,+ STABLE PRIOR TO EXISTING
3ELF REFRESH MODE

%NTER 3ELF REFRESH MODE

-36

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Flexible memory controller (FMC)

RM0390

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.
Figure 59. Power-down mode

3$#,+

3$#+%

#/--!.$

./0

./0

!#4)6%

T2#$
!LL BANKS IDLE

)NPUT BUFFERS GATED OFF
T2!3

%NTER 0OWER DOWN

%XIT 0OWER DOWN

T2#
-36

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.

11.7.5

SDRAM controller registers
SDRAM Control registers 1,2 (FMC_SDCR1,2)
Address offset: 0x140+ 4* (x – 1), x = 1,2

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RM0390

Flexible memory controller (FMC)
Reset value: 0x0000 02D0
This register contains the control parameters for each SDRAM memory bank

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

0

NR
rw

rw

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 KCK_FMC clock cycles, for reading data after CAS latency.
00: No KCK_FMC clock cycle delay
01: One KCK_FMC clock cycle delay
10: Two KCK_FMC 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

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Flexible memory controller (FMC)

RM0390

Bits 5:4 MWID[1:0]: Memory data bus width.
These bits define the memory device width.
00: 8 bits
01: 16 bits
10: reserved
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

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RM0390

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.

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RM0390

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

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RM0390

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.

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Flexible memory controller (FMC)

RM0390

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

320/1327

DocID026976 Rev 3

MODES2

MODES1

r

r

r

r

0
RE
r

RM0390

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

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Flexible memory controller (FMC)

11.8

RM0390

FMC register map

Reset value

322/1327

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

1

DocID026976 Rev 3

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 80. 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

RM0390

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

1

0

0

0

1

1

1

0

0

1

ATTSET[7:0]
0

0

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RPIPE[
1:0]

0

1

1

1

1

1

0

1

1

1

1

1

1

1

1

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

0

1

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

TMRD[3:0]

1

1

1

1

0

0

0

0

0

0

0

0

0

0

1

MODE[2:0]

COUNT[12:0]

0

0

0

0

0

0

0

0

0

0

Reset value

0

TMRD[3:0]

0

NRFS[3:0]
0

0

TXSR[3:0]

BUSY

0

0

TXSR[3:0]

Res.

0

0

Res.

0

1

Res.

0

1

TRAS[3:0]

MRD[12:0]

Res.

Res.

Res.

Res.

Res.

Res.

1

1

TRAS[3:0]

TRC[3:0]
1

0

0
CRE

1

0

Res.

Res.
Res.

1

1

Res.

Res.
Res.

1

1

0

Res.

Res.

1

1

Res.

Res.

1

REIE

Res.

1

1

Res.

1

1

TWR[3:0]

Res.

1

Res.

1

Res.

1

Res.

1

TRC[3:0]

Res.

1

Res.

1

1

SDCLK
CAS
MWID
WP
NB
NR[1:0] NC
[1:0]
[1:0]
[1:0]

0

0

0

Res.

Res.

Res.

Res.

0

MWID
CAS
SDCLK
NR[1:0] NC
NB
WP
[1:0]
[1:0]
[1:0]

Res.

1

TRP[3:0]

1

Res.

Res.

Res.

Res.

Res.

FMC_SDSR

0

Res.

1

TWR[3:0]

Reset value

0x158

0

MODES1[1:0]

0

Res.

1

1

Res.

Res.

Res.

Res.

Res.

0x154

0

MEMSETx[7:0]

CTB2

0

Res.

1

TRCD[3:0]

Reset value
FMC_SDRTR

0

MODES2[1:0]

0

Res.

1

TRP[3:0]

Res.

Res.

Res.
Res.

FMC_SDCMR

0

CTB1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Reset value
Res.

0x150

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 80. FMC register map (continued)

0

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

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12

Quad-SPI interface (QUADSPI)

12.1

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.

12.2

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

12.3

QUADSPI functional description

12.3.1

QUADSPI block diagram
Figure 60. QUADSPI block diagram when dual-flash mode is disabled
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Quad-SPI interface (QUADSPI)
Figure 61. QUADSPI block diagram when dual-flash mode is enabled
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12.3.2

QUADSPI pins
Table 81 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 81. 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.

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12.3.3

RM0390

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 62. An example of a read command in quad mode
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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.

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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

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RM0390

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.

12.3.4

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.

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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 63. An example of a DDR command in quad mode
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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.

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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.

12.3.5

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

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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 ≤ 11).
Thus, when FTHRES ≥ 13, 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 11 < FLEVEL < FTHRES.

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12.3.6

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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.

12.3.7

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.

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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.

12.3.8

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).

12.3.9

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.

12.3.10

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

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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.

12.3.11

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.

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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.

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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.

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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.

12.3.12

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).

12.3.13

QUADSPI error management
An error can be generated in the following case:

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•

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.

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12.3.14

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.

12.3.15

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 64.
Figure 64. nCS when CKMODE = 0 (T = CLK period)
7

7

Q&6

6&/.
069

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 65.
Figure 65. nCS when CKMODE = 1 in SDR mode (T = CLK period)
7

7

Q&6

6&/.
069

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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 66. 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 66. nCS when CKMODE = 1 in DDR mode (T = CLK period)
7

7

7

Q&6

6&/.
069

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 67.
Figure 67. nCS when CKMODE = 1 with an abort (T = CLK period)
7

&ORFNVWDOOHG

7

Q&6

6&/.

$ERUW
069

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.

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12.4

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 82. 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

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12.5

QUADSPI registers

12.5.1

QUADSPI control register (QUADSPI_CR)
Address offset: 0x0000
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

PRESCALER

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
rw

rw

rw

rw

rw

DMAEN ABORT
rw

rw

EN
w1s

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

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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.

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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

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12.5.2

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
rw

rw

Res.

Res.

rw

Res.

20

19

18

17

16

rw

FSIZE
rw

rw

rw

rw

4

3

2

1

0

Res.

CKMODE

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.

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RM0390

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.

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12.5.4

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

w1o

w1o

w1o

w1o

Bits 31: 4 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

12.5.5

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

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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.

12.5.6

QUADSPI communication configuration register (QUADSPI_CCR)
Address offset: 0x0014
Reset value: 0x0000 0000

31

30

29

28

DDRM

DHHC

Res.

SIOO
rw

rw

rw

rw

rw

13

12

11

10

9

8

rw

rw

15

14

ABMODE
rw

rw

ADSIZE
rw

rw

27

26

25

FMODE[1:0]

DMODE

ADMODE
rw

rw

24

23

22

21

Res.

7

rw

19

18

17

DCYC[4:0]

ABSIZE

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.

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IMODE
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Quad-SPI interface (QUADSPI)

Bit 28 SIOO: Send instruction only once mode
See Section 12.3.12: Sending the instruction only once on page 336. 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.

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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.

12.5.7

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

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Quad-SPI interface (QUADSPI)

12.5.8

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.

12.5.9

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].

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12.5.10

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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.

12.5.11

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.

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Quad-SPI interface (QUADSPI)

12.5.12

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.

12.5.13

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.

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12.5.14

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QUADSPI register map

0

0

0

0

0

0

0

0

0

0

Reset value

0x0020

0

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

ABORT

EN

Res.

TEF

0

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

MASK[31:0]
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

QUADSPI_PIR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MATCH[31:0]
0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

INTERVAL[15:0]
0

Reset value

0

DocID026976 Rev 3

0

0

0

0

TIMEOUT[15:0]
0

0

0

Refer to Section 2.2.2 for the register boundary addresses.

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DATA[31:0]

QUADSPI_
PSMAR

QUADSPI_
LPTR

CKMODE

TCF

0

ALTERNATE[31:0]

Reset value
0x0030

TCEN

0

ADDRESS[31:0]
0

Res.

0x002C

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

QUADSPI_AR

0x0018

0x001C

0

ADMODE[1:0]

0

0

ADSIZE[1:0]

0

0

ABMODE[1:0]

0

0

ABSIZE[1:0]

0

0

Res.

Reset value

0

DMODE[1:0]

QUADSPI_CCR

0

FMODE[1:0]

0

Res.

0

SIOO

Reset value

DHHC

0x0014

Res.

DFM
Res.

Res.

0

DL[31:0]

DDRM

0x0010

SSHIFT

0

Reset value
QUADSPI_DLR

Res.

FSEL
Res.

Res.

SMF

0

Res.

0

CSMF

0

TOF

0

0

CTOF

0

0

BUSY

0

0

Res.

0

Res.

Res.

Res.

FLEVEL[6:0]

0

0

0
Res.

0

0

Res.

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

QUADSPI_FCR

Res.

Res.

0

Reset value

0x000C

CSHT

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

Res.

0

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.

0

Res.

Res.

Res.

Res.

Res.

Res.

QUADSPI_SR

Res.

Reset value

0x0008

0

Res.

QUADSPI_DCR

Res.

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.

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 83. QUADSPI register map and reset values

0

0

0

0

0

0

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Analog-to-digital converter (ADC)

13

Analog-to-digital converter (ADC)

13.1

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.

13.2

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 68 shows the block diagram of the ADC.
Note:

VREF–, if available (depending on package), must be tied to VSSA.

13.3

ADC functional description
Figure 68 shows a single ADC block diagram and Table 84 gives the ADC pin description.

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Figure 68. Single ADC block diagram
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Analog-to-digital converter (ADC)
Table 84. ADC pins
Name

13.3.1

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.
Conversion starts when either the SWSTART or the JSWSTART bit is set.
You 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).

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13.3.2

RM0390

ADC1/2 and ADC3 connectivity
ADC1, ADC2 and ADC3 are tightly coupled and share some external channels as described
in Figure 69, Figure 70 and Figure 71.
Figure 69. ADC1 connectivity

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RM0390

Analog-to-digital converter (ADC)
Figure 70. ADC2 connectivity

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Analog-to-digital converter (ADC)

RM0390
Figure 71. ADC3 connectivity

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RM0390

13.3.3

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).

13.3.4

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.

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13.3.5

RM0390

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.

13.3.6

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).

13.3.7

Timing diagram
As shown in Figure 72, 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.

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Analog-to-digital converter (ADC)
Figure 72. Timing diagram

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13.3.8

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 85 shows how the ADC_CR1 register should be configured to enable the analog
watchdog on one or more channels.
Figure 73. Analog watchdog’s guarded area

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Table 85. 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

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RM0390

Table 85. 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

13.3.9

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.

13.3.10

Injected channel management
Triggered injection
To use triggered injection, the JAUTO bit must be cleared in the ADC_CR1 register.

362/1327

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 74 shows the corresponding timing diagram.

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RM0390
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 74. Injected conversion latency
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13.3.11

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.

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RM0390

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.

13.4

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 75 and Figure 76.
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.

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Analog-to-digital converter (ADC)
Figure 75. Right alignment of 12-bit data
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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 77.
Figure 77. Left alignment of 6-bit data
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13.5

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

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13.6

RM0390

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 86 provides the correspondence between the EXTEN[1:0]
and JEXTEN[1:0] values and the trigger polarity.
Table 86. 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 87 gives the possible external trigger for regular conversion.
Table 87. External trigger for regular channels
Source

EXTSEL[3:0]

TIM1_CH1 event

0000

TIM1_CH2 event

0001

TIM1_CH3 event

0010

TIM2_CH2 event

0011

TIM2_CH3 event

0100

TIM2_CH4 event

0101

TIM2_TRGO event

0110

TIM3_CH1 event

Internal signal from on-chip timers

0111

TIM3_TRGO event

1000

TIM4_CH4 event

1001

TIM5_CH1 event

1010

TIM5_CH2 event

1011

TIM5_CH3 event

1100

TIM8_CH1 event

1101

TIM8_TRGO event

1110

EXTI line11

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External pin

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RM0390

Analog-to-digital converter (ADC)
Table 88 gives the possible external trigger for injected conversion.
Table 88. External trigger for injected channels
Source

Connection type

JEXTSEL[3:0]

TIM1_CH4 event

0000

TIM1_TRGO event

0001

TIM2_CH1 event

0010

TIM2_TRGO event

0011

TIM3_CH2 event

0100

TIM3_CH4 event

0101

TIM4_CH1 event

0110

TIM4_CH2 event

Internal signal from on-chip timers

0111

TIM4_CH3 event

1000

TIM4_TRGO event

1001

TIM5_CH4 event

1010

TIM5_TRGO event

1011

TIM8_CH2 event

1100

TIM8_CH3 event

1101

TIM8_CH4 event

1110

EXTI line15

External pin

1111

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.

13.7

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

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13.8

Data management

13.8.1

Using the DMA

RM0390

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:

13.8.2

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:

368/1327

1.

Clear the ADC OVR bit in ADC_SR register

2.

Trigger the ADC to start the conversion.

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13.8.3

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.

13.9

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 78).
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).

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Figure 78. Multi ADC block diagram(1)
2EGULAR DATA REGISTER
BITS
BITS

)NJECTED DATA REGISTERS
 X  BITS

2EGULAR
CHANNELS

!$# 3LAVE

)NJECTED
CHANNELS

2EGULAR DATA REGISTER

BITS
BITS
)NJECTED DATA REGISTERS
 X  BITS

2EGULAR
CHANNELS

INTERNAL TRIGGERS
#OMMON REGULAR DATA REGISTER
 BITS 

$UAL4RIPLE
MODE CONTROL

!DDRESSDATA BUS

!$# 3LAVE

)NJECTED
CHANNELS

#OMMON PART

2EGULAR DATA REGISTER
 BITS
)NJECTED DATA REGISTERS
 X  BITS

!$#X?).
!$#X?).

'0)/
0ORTS

2EGULAR
CHANNELS

!$#X?).

)NJECTED
CHANNELS

4EMP SENSOR
62%&).4
6"!4
%84)?

!$# -ASTER
3TART TRIGGER MUX
REGULAR GROUP

%84)?
3TART TRIGGER MUX
INJECTED GROUP

AI

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.

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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]

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–

RM0390

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.

13.9.1

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.

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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 79. Injected simultaneous mode on 4 channels: dual ADC mode
!$#
!$#

#(
#(

#(
#(



#(

#(

#(

#( 

#(
#(
%ND OF CONVERSION ON !$# AND !$#

4RIGGER
3AMPLING
#ONVERSION

AI

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 80. Injected simultaneous mode on 4 channels: triple ADC mode


!$#

#(

#(

#(

#(

!$#

#(

#(

#(

!$#

#(

#(

#(

#( 
#( 

#(
#(
#(

%ND OF CONVERSION ON !$# !$# AND !$#

4RIGGER
3AMPLING
#ONVERSION

13.9.2

AI

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.

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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 81. Regular simultaneous mode on 16 channels: dual ADC mode
!$#
!$#

#(
#(

#(
#(



#(

#(

#(

#( 

#(
#(
%ND OF CONVERSION ON !$# AND !$#

4RIGGER
3AMPLING
#ONVERSION

AI

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 82. Regular simultaneous mode on 16 channels: triple ADC mode
!$#

#(

#(



#(

#(

#( 
#( 

!$#

#(

#(

#(

!$#

#(

#(

#(

#(
#(
#(

%ND OF CONVERSION ON !$# !$# AND !$#

4RIGGER
3AMPLING
#ONVERSION

13.9.3

AI

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:

374/1327

•

ADC1 starts immediately

•

ADC2 starts after a delay of several ADC clock cycles

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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 83. Interleaved mode on 1 channel in continuous conversion mode: dual ADC
mode
%ND OF CONVERSION ON !$#


#(

!$#
!$#

#(

4RIGGER

#ONVERSION

#(


3AMPLING

#(

%ND OF CONVERSION ON !$#
 !$##,+
CYCLES

AI

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
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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 84. Interleaved mode on 1 channel in continuous conversion mode: triple ADC
mode
%ND OF CONVERSION ON !$#
$-! REQUEST EVERY  CONVERSIONS
!$#

#(

!$#
!$#



#(

#(

#(

#(

#(

#(




#(
#(

3AMPLING
#ONVERSION

%ND OF CONVERSION ON !$#

4RIGGER

%ND OF CONVERSION ON !$#
 !$##,+
CYCLES

13.9.4

AI

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.

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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 85. Alternate trigger: injected group of each ADC
ST TRIGGER

%/# *%/#
ON !$#

RD TRIGGER

N TH TRIGGER

%/# *%/#
ON !$#

!$#



!$#

ND TRIGGER

%/# *%/#
ON !$#
TH TRIGGER

%/# *%/#
ON !$#

3AMPLING
N  TH TRIGGER

#ONVERSION
AI

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 86. Alternate trigger: 4 injected channels (each ADC) in discontinuous mode
ST TRIGGER

RD TRIGGER

TH TRIGGER

TH TRIGGER
*%/# ON !$#

3AMPLING
#ONVERSION

!$#
!$#
*%/# ON !$#
ND TRIGGER

TH TRIGGER

TH TRIGGER

TH TRIGGER

AI

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

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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 87. Alternate trigger: injected group of each ADC
ST TRIGGER

%/# *%/#
ON !$#

TH TRIGGER

%/# *%/#
ON !$#

!$#

N TH TRIGGER

3AMPLING
#ONVERSION



!$#

ND TRIGGER
N  TH TRIGGER

RD TRIGGER
%/# *%/#
ON !$#

N  TH TRIGGER

TH TRIGGER
%/# *%/#
ON !$#

AI

13.9.5

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.

13.9.6

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 88 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:

378/1327

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).

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RM0390

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 88. Alternate + regular simultaneous
ST TRIGGER

#(

!$# REG

#(

#(

#(

#(

#(

#(

#(

#(

#(

#(

#(

!$# INJ
#(

!$# REG

#(

#(

#(

!$# INJ

SYNCHRO NOT LOST
ND TRIGGER

AI

If a trigger occurs during an injected conversion that has interrupted a regular conversion, it
is ignored. Figure 89 shows the behavior in this case (2nd trigger is ignored).
Figure 89. Case of trigger occurring during injected conversion
ST TRIGGER

#(

!$# REG

#(

#(

RD TRIGGER

#(

#(

#(

#(

!$# INJ
#(

!$# REG

#(

#(

#(
#(

#(

#(

#(

#(

#(

!$# INJ

ND TRIGGER

ND TRIGGER
AI

13.10

Temperature sensor
The temperature sensor can be used to measure the ambient temperature (TA) of the
device.
•

On STM32F446xx 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.

Figure 90 shows the block diagram of the temperature sensor.

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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 90. Temperature sensor and VREFINT channel block diagram
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069

1. VSENSE is input to ADC1_IN18.

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.

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Note:

Analog-to-digital converter (ADC)
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.

13.11

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:
•

VBAT/4 to the ADC1_IN18 input channel

Note:

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.

13.12

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 89. ADC interrupts
Interrupt event

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

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13.13

RM0390

ADC registers
Refer to Section 1.1 on page 51 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).

13.13.1

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

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13.13.2

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

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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

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13.13.3

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 CC1 event
0001: Timer 1 CC2 event
0010: Timer 1 CC3 event
0011: Timer 2 CC2 event
0100: Timer 2 CC3 event
0101: Timer 2 CC4 event
0110: Timer 2 TRGO event
0111: Timer 3 CC1 event
1000: Timer 3 TRGO event
1001: Timer 4 CC4 event
1010: Timer 5 CC1 event
1011: Timer 5 CC2 event
1100: Timer 5 CC3 event
1101: Timer 8 CC1 event
1110: Timer 8 TRGO event
1111: EXTI line 11
Bit 23 Reserved, must be kept at reset value.
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
Note: This bit can be set only when ADON = 1 otherwise no conversion is launched.

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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 CC4 event
0001: Timer 1 TRGO event
0010: Timer 2 CC1 event
0011: Timer 2 TRGO event
0100: Timer 3 CC2 event
0101: Timer 3 CC4 event
0110: Timer 4 CC1 event
0111: Timer 4 CC2 event
1000: Timer 4 CC3 event
1001: Timer 4 TRGO event
1010: Timer 5 CC4 event
1011: Timer 5 TRGO event
1100: Timer 8 CC2 event
1101: Timer 8 CC3 event
1110: Timer 8 CC4 event
1111: EXTI line15
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 75 and Figure 76.
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
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

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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.
Note: 0: Disable ADC conversion and go to power down mode
1: Enable ADC

13.13.4

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

SMP15_0

13

12

rw

rw

25

24

23

SMP18[2:0]

11

SMP14[2:0]

rw

26

rw

rw

rw

10

9

8

SMP13[2:0]
rw

rw

22

21

rw

rw

rw

rw

rw

7

6

5

rw

19

18

SMP16[2:0]

SMP12[2:0]

rw

20

SMP17[2:0]

rw

rw

rw

rw

4

3

2

rw

16

SMP15[2:1]

SMP11[2:0]
rw

17

rw

rw

1

0

SMP10[2:0]
rw

rw

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

13.13.5

ADC sample time register 2 (ADC_SMPR2)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

Res.

Res.

15

14

SMP5_0
rw

29

28

27

25

24

23

SMP8[2:0]

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

26

SMP9[2:0]

rw

SMP3[2:0]
rw

SMP2[2:0]
rw

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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

13.13.6

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.

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

JOFFSETx[11:0]
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.

13.13.7

ADC watchdog higher threshold register (ADC_HTR)
Address offset: 0x24
Reset value: 0x0000 0FFF

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

rw

HT[11:0]
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.

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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.

13.13.8

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.

13.13.9

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

12

11

10

9

8

SQ16_0
rw

SQ15[4:0]
rw

rw

rw

23

22

21

20

19

L[3:0]

rw

rw

rw

17

16

SQ16[4:1]

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

SQ14[4:0]
rw

18

rw

SQ13[4:0]
rw

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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

13.13.10 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

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13.13.11 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

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13.13.12 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]

JSQ3[4:0]

rw

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.

13.13.13 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]

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RM0390

Analog-to-digital converter (ADC)

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 75 and Figure 76.

13.13.14 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 75 and
Figure 76.

13.13.15 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

17

16

EOC3

AWD3

ADC3
r

r

r

r

r

r

5

4

3

2

1

0

EOC1

AWD1

r

r

OVR1

STRT1 JSTRT1 JEOC 1

ADC2
r

18

STRT3 JSTRT3 JEOC 3

ADC1
r

r

r

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.

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Analog-to-digital converter (ADC)

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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.

13.13.16 ADC common control register (ADC_CCR)
Address offset: 0x04 (this offset address is relative to ADC1 base address + 0x300)
Reset value: 0x0000 0000

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Analog-to-digital converter (ADC)

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.

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Analog-to-digital converter (ADC)

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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.

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Analog-to-digital converter (ADC)

13.13.17 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.

13.13.18 ADC register map
The following table summarizes the ADC registers.
Table 90. 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

DocID026976 Rev 3

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 91. ADC register map and reset values for each ADC

0

0

0

0

0

AWDCH[4:0]
0

0

0

0

0

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RM0390

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

ADC_JOFR1

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

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

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

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

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

Regular DATA[15:0]
0

DocID026976 Rev 3

0

JDATA[15:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

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JOFFSET1[11:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

0x4C

0

JDATA[15:0]

0
Res.

Reset value
ADC_DR

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.

Res.

Res.

ADC_JDR1

0

Res.

0

Reset value
0x3C

0

0

Regular channel sequence SQx_x bits

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.

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.

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.

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.

0x20

0

0
Res.

Reset value
ADC_JOFR4

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

ADC_JOFR3

0

0
Res.

Reset value
0x1C

0

0
Res.

Reset value
0x18

0

Sample time bits SMPx_x

Reset value

ADC_JOFR2

0

DMA

Res.

Res.

Res.
0

Sample time bits SMPx_x

ADC_SMPR2

0x14

0

Res.

JEXTEN[1:0]

JSWSTART

Res.

0

ADON

0

CONT

0

EOCS

0

ADC_SMPR1

Res.

0x10

0

JEXTSEL
[3:0]

Res.

0x0C

0

EXTSEL [3:0]

ALIGN

Reset value

EXTEN[1:0]

ADC_CR2

0x08

Res.

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 91. ADC register map and reset values for each ADC (continued)

0

0

0

0

0

0

0

0

0

0

RM0390

Analog-to-digital converter (ADC)

0x08

ADC_CDR
Reset value

0

0

0

0

0

0

0

0

0

0
0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

DDS

DMA[1:0]
0

JEOC

EOC

AWD

STRT
0

0

0

0

0

ADC1

DELAY [3:0]

Regular DATA2[15:0]
0

0

JSTRT

0

Res.

0

OVR

0

Res.

0

ADC2
ADCPRE[1:0]

Res.

Res.

0

Res.

0

Res.

VBATE

Reset value

TSVREFE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ADC_CCR

Res.

0x04

EOC

0

AWD

0

JEOC

STRT

0

ADC3

JSTRT

0

Res.

0

OVR

0

Res.

EOC

AWD

0

JEOC

STRT

0

JSTRT

Res.

Reset value

OVR

Res.

Res.

Res.

Res.

Res.

Res.

ADC_CSR

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 92. ADC register map and reset values (common ADC registers)

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

0

0

0

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

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Digital-to-analog converter (DAC)

RM0390

14

Digital-to-analog converter (DAC)

14.1

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.

14.2

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 91 shows the block diagram of a DAC channel and Table 93 gives the pin
description.

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Digital-to-analog converter (DAC)
Figure 91. DAC channel block diagram

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Table 93. 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).

14.3

DAC functional description

14.3.1

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.

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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.

14.3.2

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 92. DAC output buffer connection
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14.3.3

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.

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Figure 93. Data registers in single DAC channel mode










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•

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 94. Data registers in dual DAC channel mode










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14.3.4

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.

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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 95. Timing diagram for conversion with trigger disabled TEN = 0
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14.3.5

AIB

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

14.3.6

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 94.
Table 94. 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.

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Digital-to-analog converter (DAC)
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.

14.3.7

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.

14.3.8

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.

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Figure 96. DAC LFSR register calculation algorithm

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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 97. DAC conversion (SW trigger enabled) with LFSR wave generation
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Note:

The DAC trigger must be enabled for noise generation by setting the TENx bit in the
DAC_CR register.

14.3.9

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.

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It is possible to reset triangle wave generation by resetting the WAVEx[1:0] bits.
Figure 98. DAC triangle wave generation

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Figure 99. DAC conversion (SW trigger enabled) with triangle wave generation
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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.

14.4

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.

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14.4.1

RM0390

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).

14.4.2

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.

14.4.3

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.

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14.4.4

Digital-to-analog converter (DAC)

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.

14.4.5

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.

14.4.6

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.

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14.4.7

RM0390

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).

14.4.8

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.

14.4.9

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.

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14.4.10

Digital-to-analog converter (DAC)

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.

14.4.11

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.

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14.5

RM0390

DAC registers
Refer to Section 1 on page 51 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by words (32 bits).

14.5.1

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)

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Digital-to-analog converter (DAC)

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

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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

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Digital-to-analog converter (DAC)

14.5.2

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.

14.5.3

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.

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Digital-to-analog converter (DAC)

14.5.4

RM0390

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.

14.5.5

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.

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Digital-to-analog converter (DAC)

14.5.6

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.

14.5.7

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.

14.5.8

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

rw

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RM0390

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.

14.5.9

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.

14.5.10

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.

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Digital-to-analog converter (DAC)

14.5.11

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.

14.5.12

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.

14.5.13

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

r

r

r

r

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Digital-to-analog converter (DAC)

RM0390

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.

14.5.14

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.

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DAC_SR

Reset value

0

DocID026976 Rev 3

Reset value

Reset value
0
0
0
0

0

0

0

0

0

0

0

0

0

Res.

0

Res.

0

Res.

0

Res.

0

0

0

0
0
0
0

Res.
Res.
Res.

0

0

0

0

Res.

0
0
0
0
0
0
0
0

Res.
Res.
Res.
Res.
Res.
Res.
Res.

0

0

0

0

0

0

DACC1DHR[11:0]

Reset value

0

0

DACC1DHR[7:0]

0

Reset value

0

0
0
0
0

0
0

DACC2DHR[7:0]

0

0

0

DACC2DHR[11:0]

DACC2DHR[7:0]

0

0
0
0
0

0
0

DACC1DHR[11:0]
0
0
0
0

0
0
0
0

0

0
0

0
0

0

0
0

0
0
0
0

Res.

0

0

Res.

DACC2DHR[11:0]

0

Res.

0

0

0

Res.

0

0
0
0
0

Res.

0
Res.

0
Res.

0
Res.

0

0

0

DACC1DOR[11:0]

0

DACC2DOR[11:0]
0
0
0

0
0
0

0

0

0

Res.

0

Res.
0

0

Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

Reserved

Res.

0

Res.

0
Res.

Reset value

Res.

0

Res.

0

Res.

Reset value
0

Res.

Reset value

Res.

0

Res.

0
0

Res.

Reset value

Res.

Reset value
Res.

Res.

Res.

Res.

Res.

EN2

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

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.

TEN2
BOFF2
0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

WAVE2[2:0]

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMAEN2

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMAUDRIE2

0

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

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.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

DMAUDR1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

MAMP2[3:0]

Res.

Res.

Res.

0

Res.

0
0

Res.

0

Res.

0

Res.

Res.
0
0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.
DACC2DHR[11:0]
0

Res.

Res.

Res.

Res.

DAC_
DHR8RD
0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

Res.

0
0

Res.

Res.

Res.

Res.

Res.

0
0

Res.

DAC_
DOR2
Res.

Reset value
DAC_
DHR12LD
Reset value
0

Res.

0x30
DAC_
DOR1

Res.

0x2C
DAC_
DHR12RD

Res.

0x28
DAC_
DHR8R2

Res.

0x24
DAC_
DHR12L2

Res.

0x20
DAC_
DHR12R2

Res.

Reset value

DMAUDR2

0x1C
DAC_
DHR8R1

Res.

0x18
DAC_
DHR12L1

Res.

0x14

Res.

0x10

Res.

0x0C
DAC_
DHR12R1

Res.

0x08
DAC_
SWTRIGR

Res.

0x04
DAC_CR

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.

14.5.15

Res.

RM0390
Digital-to-analog converter (DAC)

DAC register map
Table 95 summarizes the DAC registers.
Table 95. DAC register map

0
0

DACC1DHR[11:0]

DACC1DHR[11:0]
0
0
0
0

0
0
0
0

Reserved

DACC1DHR[7:0]

0

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

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Digital camera interface (DCMI)

RM0390

15

Digital camera interface (DCMI)

15.1

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.
This interface is also able to transmit a parallel data flow, allowing it to emulate a camera
module interfacing with another camera interface.
It may also be used as a generic synchronous parallel interface ensuring a high data rate
transfer, in receive or in transmit mode. It is a slave interface, the external clock and data
flow control being ensured externally (by another device or by other resources of the
STM32, e.g. timers).

15.2

15.3

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.

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15.4

Digital camera interface (DCMI)

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.
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.

15.4.1

DCMI block diagram
Figure 100 shows the DCMI block diagram.
Figure 100. DCMI block diagram

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Figure 101. Top-level block diagram
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15.4.2

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.

15.4.3

DCMI physical interface
The interface is composed of 11/13/15/17 inputs. Only the Slave mode is supported.
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 96 shows the DCMI pins.
Table 96. 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

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Figure 102. DCMI signal waveforms
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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 97 gives an
example of the positioning of captured data bytes in two 32-bit words.
Table 97. 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 98.
Table 98. 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]

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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 99.
Table 99. 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 100.
Table 100. Positioning of captured data bytes in 32-bit words (14-bit width)

15.4.4

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 103 shows the corresponding timing diagram.

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Digital camera interface (DCMI)
Figure 103. Timing diagram
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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
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.

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Note:

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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 halfframe 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 15.7.7: 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
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.

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15.4.5

Digital camera interface (DCMI)

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 104. Frame capture waveforms in snapshot mode

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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.

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Figure 105. Frame capture waveforms in continuous grab mode

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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.

15.4.6

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 106. Coordinates and size of the window after cropping
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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.

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Digital camera interface (DCMI)
If the 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 107. Data capture waveforms
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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.

15.4.7

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.

15.4.8

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.

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15.5

Data format description

15.5.1

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 108. Pixel raster scan order

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15.5.2

Monochrome format
Characteristics:
•

Raster format

•

8 bits per pixel

Table 101 shows how the data are stored.
Table 101. Data storage in monochrome progressive video format

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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

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15.5.3

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 102 shows how the data are stored.
Table 102. Data storage in RGB progressive video format

15.5.4

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 103.
Table 103. Data storage in YCbCr progressive video format

15.5.5

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

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pixel , encoded in 8 bits, is stored as shown in Table 104.
The result is a monochrome image having the same resolution as the original YCbCr data.
Table 104. Data storage in YCbCr progressive video format - Y extraction mode

15.5.6

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.

15.6

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 105 gives the list of all interrupts.
Table 105. DCMI interrupts
Interrupt name

15.7

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.

15.7.1

DCMI control register (DCMI_CR)
Address offset: 0x00
Reset value: 0x0000 0x0000

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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
EDM

rw

9

8
FCRC

rw

rw

rw

7

6

5

VSPOL HSPOL PCKPOL
rw

rw

rw

17

16
BSM
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

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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.

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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.

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15.7.2

RM0390

DCMI status register (DCMI_SR)
Address offset: 0x04
Reset value: 0x0000 0x0000

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.

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RM0390

Digital camera interface (DCMI)

15.7.3

DCMI raw interrupt status register (DCMI_RIS)
Address offset: 0x08
Reset value: 0x0000 0x0000

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.

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Digital camera interface (DCMI)

15.7.4

RM0390

DCMI interrupt enable register (DCMI_IER)
Address offset: 0x0C
Reset value: 0x0000 0x0000

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).

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Digital camera interface (DCMI)

15.7.5

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

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.

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Digital camera interface (DCMI)

15.7.6

RM0390

DCMI interrupt clear register (DCMI_ICR)
Address offset: 0x14
Reset value: 0x0000 0x0000

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 15:5 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

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Digital camera interface (DCMI)

15.7.7

DCMI embedded synchronization code register (DCMI_ESCR)
Address offset: 0x18
Reset value: 0x0000 0x0000

31

30

29

28

27

26

25

24

23

22

21

20

FEC

19

18

17

16

LEC

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

LSC

FSC

Bits 31:24 FEC: 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: 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: 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: 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.

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15.7.8

RM0390

DCMI embedded synchronization unmask register (DCMI_ESUR)
Address offset: 0x1C
Reset value: 0x0000 0x0000

31

30

29

28

27

26

25

24

23

22

21

20

FEU

19

18

17

16

LEU

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

LSU

FSU

Bits 31:24 FEU: 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: 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: 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: 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

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RM0390

15.7.9

Digital camera interface (DCMI)

DCMI crop window start (DCMI_CWSTRT)
Address offset: 0x20
Reset value: 0x0000 0x0000

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.

15.7.10

DCMI crop window size (DCMI_CWSIZE)
Address offset: 0x24
Reset value: 0x0000 0x0000

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

VLINE13:0]

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
....

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Digital camera interface (DCMI)

RM0390

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
....

15.7.11

DCMI data register (DCMI_DR)
Address offset: 0x28
Reset value: 0x0000 0x0000

31

30

29

28

27

26

25

24

23

22

21

20

Byte3
r

r

r

r

15

14

13

12

r

r

r

r

r

r

r

r

11

10

9

8

7

6

5

4

Byte1
r

r

r

r

19

18

17

16

r

r

r

r

3

2

1

0

r

r

r

r

Byte2

Byte0
r

r

r

r

r

r

r

r

Bits 31:24 Data byte 3
Bits 23:16 Data byte 2
Bits 15:8 Data byte 1
Bits 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.

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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
0

0

VST[12:0

VLINE13:0]

0

DocID026976 Rev 3
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

Res.

0x04

Res.

0x00

Res.

Offset

Res.

15.7.12

Res.

RM0390
Digital camera interface (DCMI)

DCMI register map

Table 106 summarizes the DCMI registers.
Table 106. 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 56 for the register boundary addresses.

447/1327

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Advanced-control timers (TIM1&TIM8)

RM0390

16

Advanced-control timers (TIM1&TIM8)

16.1

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 length 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 (TIMx) timers are completely
independent, and do not share any resources. They can be synchronized together as
described in Section 16.3.20.

16.2

TIM1&TIM8 main features
TIM1&TIM8 timer features include:

448/1327

•

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 4 independent channels for:
–

Input Capture

–

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.

•

Break input to put the timer’s output signals in reset state or in a known state.

•

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

–

Break input

•

Supports incremental (quadrature) encoder and Hall-sensor circuitry for positioning
purposes

•

Trigger input for external clock or cycle-by-cycle current management

DocID026976 Rev 3

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Advanced-control timers (TIM1&TIM8)

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Advanced-control timers (TIM1&TIM8)

RM0390

16.3

TIM1&TIM8 functional description

16.3.1

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 110 and Figure 111 give some examples of the counter behavior when the prescaler
ratio is changed on the fly:

450/1327

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Advanced-control timers (TIM1&TIM8)
Figure 110. Counter timing diagram with prescaler division change from 1 to 2

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Figure 111. Counter timing diagram with prescaler division change from 1 to 4

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Advanced-control timers (TIM1&TIM8)

16.3.2

RM0390

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 plus one
(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.
Figure 112. Counter timing diagram, internal clock divided by 1
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Advanced-control timers (TIM1&TIM8)
Figure 113. Counter timing diagram, internal clock divided by 2
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Figure 114. Counter timing diagram, internal clock divided by 4
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Figure 115. Counter timing diagram, internal clock divided by N
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RM0390

Figure 116. Counter timing diagram, update event when ARPE=0
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Figure 117. Counter timing diagram, update event when ARPE=1
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RM0390

Advanced-control timers (TIM1&TIM8)

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 plus one
(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.

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Advanced-control timers (TIM1&TIM8)

RM0390

Figure 118. Counter timing diagram, internal clock divided by 1
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Figure 119. Counter timing diagram, internal clock divided by 2
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Advanced-control timers (TIM1&TIM8)
Figure 120. Counter timing diagram, internal clock divided by 4

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Figure 121. Counter timing diagram, internal clock divided by N
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RM0390

Figure 122. Counter timing diagram, update event when repetition counter is not used
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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

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Advanced-control timers (TIM1&TIM8)
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 123. Counter timing diagram, internal clock divided by 1, TIMx_ARR = 0x6
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1. Here, center-aligned mode 1 is used (for more details refer to Section 16.4: TIM1&TIM8 registers).

Figure 124. Counter timing diagram, internal clock divided by 2
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Figure 125. Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36
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1.

Center-aligned mode 2 or 3 is used with an UIF on overflow.

Figure 126. Counter timing diagram, internal clock divided by N
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Advanced-control timers (TIM1&TIM8)
Figure 127. Counter timing diagram, update event with ARPE=1 (counter underflow)
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Figure 128. Counter timing diagram, update event with ARPE=1 (counter overflow)
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16.3.3

Repetition counter
Section 16.3.1: 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.

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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 128 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 129). 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.
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 started. If the RCR was written before starting the counter, the UEV occurs
on the overflow. If the RCR was written after starting the counter, the UEV occurs on the
underflow. For example for RCR = 3, the UEV is generated on each 4th overflow or
underflow event depending on when RCR was written.

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Advanced-control timers (TIM1&TIM8)
Figure 129. Update rate examples depending on mode and TIMx_RCR register
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16.3.4

RM0390

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

•

Internal trigger inputs (ITRx): using one timer as prescaler for another timer, for
example, you can configure Timer 1 to act as a prescaler for Timer 2. Refer to Using
one timer as prescaler for another timer for more details.

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 130 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.
Figure 130. Control circuit in normal mode, internal clock divided by 1

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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.

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Advanced-control timers (TIM1&TIM8)
Figure 131. TI2 external clock connection example
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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 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.

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RM0390

Figure 132. Control circuit in external clock mode 1
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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 133 gives an overview of the external trigger input block.
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For example, to configure the upcounter to count each 2 rising edges on ETR, use the
following procedure:

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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 134. Control circuit in external clock mode 2

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16.3.5

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 135 to Figure 138 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).

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Figure 135. Capture/compare channel (example: channel 1 input stage)
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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.
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Advanced-control timers (TIM1&TIM8)
Figure 137. Output stage of capture/compare channel (channels 1 to 3)
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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.

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16.3.6

RM0390

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:
•

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.

•

Program the input filter duration you need with respect to the signal you connect to the
timer (by programming ICxF bits in the TIMx_CCMRx register if the input is a TIx input).
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.

•

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).

•

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).

•

Enable capture from the counter into the capture register by setting the CC1E bit in the
TIMx_CCER register.

•

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:

470/1327

IC interrupt and/or DMA requests can be generated by software by setting the
corresponding CCxG bit in the TIMx_EGR register.

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16.3.7

Advanced-control timers (TIM1&TIM8)

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.

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):
•

Select the active input for TIMx_CCR1: write the CC1S bits to 01 in the TIMx_CCMR1
register (TI1 selected).

•

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).

•

Select the active input for TIMx_CCR2: write the CC2S bits to 10 in the TIMx_CCMR1
register (TI1 selected).

•

Select the active polarity for TI1FP2 (used for capture in TIMx_CCR2): write the CC2P
and CC2NP bits to ‘1’ (active on falling edge).

•

Select the valid trigger input: write the TS bits to 101 in the TIMx_SMCR register
(TI1FP1 selected).

•

Configure the slave mode controller in reset mode: write the SMS bits to 100 in the
TIMx_SMCR register.

•

Enable the captures: write the CC1E and CC2E bits to ‘1’ in the TIMx_CCER register.
Figure 139. PWM input mode timing
TI1

TIMx_CNT

0004

0000

0001

0002

TIMx_CCR1

0004

TIMx_CCR2

0002

IC1 capture
IC2 capture
reset counter

0003

0004

IC2 capture
pulse width
measurement

0000

IC1 capture
period
measurement
ai15413

16.3.8

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.

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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.
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 100 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 and DMA requests can be sent
accordingly. This is described in the output compare mode section below.

16.3.9

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 bit if an interrupt request is to be generated.

4.

5.

Select the output mode. For example:
–

Write OCxM = 011 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 140.

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Figure 140. Output compare mode, toggle on OC1.
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16.3.10

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 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.

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PWM edge-aligned mode
•

Upcounting configuration
Upcounting is active when the DIR bit in the TIMx_CR1 register is low. Refer to
Upcounting mode.
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 141 shows some edge-aligned PWM waveforms in an example where
TIMx_ARR=8.
Figure 141. Edge-aligned PWM waveforms (ARR=8)



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Downcounting configuration
Downcounting is active when DIR bit in TIMx_CR1 register is high. Refer to
Downcounting mode.
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
TIMx_CR1 register is updated by hardware and must not be changed by software. Refer to
Center-aligned mode (up/down counting).
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Figure 142 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 142. Center-aligned PWM waveforms (ARR=8)
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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
in the TIMx_CR1 register. Moreover, the DIR and CMS bits must not be changed at the
same time by the software.

•

Writing to the counter while running in center-aligned mode is not recommended as it
can lead to unexpected results. In particular:

•

16.3.11

–

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.

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 109 for more details. In particular, the dead-time is activated when switching to the
IDLE state (MOE falling down to 0).
Dead-time insertion is enabled by setting both CCxE and CCxNE bits, and the MOE bit if the
break circuit is present. DTG[7:0] bits of the TIMx_BDTR register are used to control the
dead-time generation for all channels. 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).

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Advanced-control timers (TIM1&TIM8)
Figure 143. Complementary output with dead-time insertion.
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Figure 144. Dead-time waveforms with delay greater than the negative pulse.

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Figure 145. Dead-time waveforms with delay greater than the positive pulse.
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069

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 16.4.18: 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

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RM0390

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.

16.3.12

Using the break function
When using the break function, the output enable signals and inactive levels are modified
according to additional control bits (MOE, OSSI and OSSR bits in the TIMx_BDTR register,
OISx and OISxN bits in the TIMx_CR2 register). In any case, the OCx and OCxN outputs
cannot be set both to active level at a given time. Refer to Table 109 for more details.
The break source can be either the break input pin or a clock failure event, generated by the
Clock Security System (CSS), from the Reset Clock Controller. For further information on
the Clock Security System, refer to Section 6.2.7.
When exiting from reset, the break circuit is disabled and the MOE bit is low. You can enable
the break function by setting the BKE bit in the TIMx_BDTR register. The break input
polarity can be selected by configuring the BKP bit in the same register. BKE and BKP can
be modified at the same time. When the BKE and BKP 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.
When a break occurs (selected level on the break input):

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•

The MOE bit is cleared asynchronously, putting the outputs in inactive state, idle state
or in reset state (selected by the OSSI bit). This feature functions 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 then the timer releases the enable
output else the enable output remains high.

•

When complementary outputs are used:
–

The outputs are first put in reset state 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

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Advanced-control timers (TIM1&TIM8)
active level together. Note that because of the resynchronization on MOE, the
dead-time duration is a bit longer than usual (around 2 ck_tim clock cycles).
–

Note:

If OSSI=0 then the timer releases the enable outputs else the enable outputs
remain or become high as soon as one of the CCxE or CCxNE bits is high.

•

The break status flag (BIF bit in the TIMx_SR register) is set. An interrupt can be
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. This can be used to perform a regulation, for instance.
Else, MOE remains low until you write 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 is acting 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 cannot
be cleared.
The break can be generated by the BRK input which has a programmable polarity and an
enable bit BKE in the TIMx_BDTR Register.
There are two solutions to generate a break:
•

By using the BRK input which has a programmable polarity and an enable bit BKE in
the TIMx_BDTR register

•

By software through the BG bit of the TIMx_EGR register.

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 you to freeze the
configuration of several parameters (dead-time duration, OCx/OCxN polarities and state
when disabled, OCxM configurations, break enable and polarity). You can choose from 3
levels of protection selected by the LOCK bits in the TIMx_BDTR register. Refer to
Section 16.4.18: TIM1&TIM8 break and dead-time register (TIMx_BDTR). The LOCK bits
can be written only once after an MCU reset.
Figure 146 shows an example of behavior of the outputs in response to a break.

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Figure 146. Output behavior in response to a break.
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16.3.13

Advanced-control timers (TIM1&TIM8)

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.
This function can only be used in output compare and PWM modes, and does not work in
forced mode.
For example, the ETR signal can be connected to the output of a comparator to be used for
current handling. In this case, the ETR must be configured as follow:
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 147 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.
Figure 147. Clearing TIMx OCxREF

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In case of a PWM with a 100% duty cycle (if CCRx>ARR), then OCxREF is enabled again at
the next counter overflow.

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16.3.14

RM0390

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).
Figure 148 describes the behavior of the OCx and OCxN outputs when a COM event
occurs, in 3 different examples of programmed configurations.
Figure 148. 6-step generation, COM example (OSSR=1)

counter (CNT)

(CCRx)

OCxREF
Write COM to 1

COM event

Example 1

CCxE=1
write OCxM to 100
CCxNE=0
OCxM=100 (forced inactive)

CCxE=1
CCxNE=0
OCxM=100

Write CCxNE to 1
and OCxM to 101
CCxE=1
CCxNE=0
OCxM=100 (forced inactive)

CCxE=0
CCxNE=1
OCxM=101

OCx
OCxN

OCx
Example 2
OCxN

write CCxNE to 0
CCxE=1
and OCxM to 100
CCxNE=0
OCxM=100 (forced inactive)

Example 3

CCxE=1
CCxNE=0
OCxM=100

OCx
OCxN
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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 149. Example of one pulse mode.
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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:
•

Map TI2FP2 to TI2 by writing CC2S=’01’ in the TIMx_CCMR1 register.

•

TI2FP2 must detect a rising edge, write CC2P=’0’ and CC2NP=’0’ in the TIMx_CCER
register.

•

Configure TI2FP2 as trigger for the slave mode controller (TRGI) by writing TS=’110’ in
the TIMx_SMCR register.

•

TI2FP2 is used to start the counter by writing SMS to ‘110’ in the TIMx_SMCR register
(trigger mode).

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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.

16.3.16

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 incremental encoder. Refer to
Table 107. 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

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Advanced-control timers (TIM1&TIM8)
configure TIMx_ARR before starting. in the same way, the capture, compare, prescaler,
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.
In this mode, the counter is modified automatically following the speed and the direction of
the incremental encoder and its content, therefore, always represents the encoder’s
position. The count direction correspond to the rotation direction of the connected sensor.
Table 107 summarizes the possible combinations, assuming TI1 and TI2 don’t switch at the
same time.
Table 107. Counting direction versus encoder signals
Level on opposite signal
(TI1FP1 for TI2,
TI2FP2 for TI1)

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

Active edge

TI1FP1 signal

TI2FP2 signal

An external incremental 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.
Figure 150 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’, CC1NP=’0’, and IC1F = ‘0000’ (TIMx_CCER register, TI1FP1 non-inverted,
TI1FP1=TI1).

•

CC2P=’0’, CC2NP=’0’, and IC2F = ‘0000’ (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).

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Figure 150. Example of counter operation in encoder interface mode.
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Figure 151 gives an example of counter behavior when TI1FP1 polarity is inverted (same
configuration as above except CC1P=’1’).
Figure 151. Example of encoder interface mode with TI1FP1 polarity inverted.
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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
generated by a real-time clock.

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16.3.17

Advanced-control timers (TIM1&TIM8)

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 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. An example of this feature used to interface Hall sensors is given in
Section 16.3.18 below.

16.3.18

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 or TIM5) referred to as
“interfacing timer” in Figure 152. The “interfacing timer” captures the 3 timer input pins
(TIMx_CH1, TIMx_CH2, and TIMx_CH3) 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 135). 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.
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 channel 1 in capture mode (TRC selected): write the CC1S bits in the
TIMx_CCMR1 register to ‘11’. You can also program the digital filter if needed,

•

Program 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).

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Figure 152 describes this example.
Figure 152. Example of Hall sensor interface
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16.3.19

Advanced-control timers (TIM1&TIM8)

TIMx and external trigger synchronization
The TIMx timer 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:
•

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 153. Control circuit in reset mode

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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 154. Control circuit in gated mode
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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:
•

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.
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 155. Control circuit in trigger mode
7,
&17B(1
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&RXQWHUUHJLVWHU





  

7,)
069

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:
1.

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.

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2.

3.

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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=01 in 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 156. Control circuit in external clock mode 2 + trigger mode
7,

&(1&17B(1

(75

&RXQWHUFORFN &.B&17 &.B36&

&RXQWHUUHJLVWHU







7,)
069

16.3.20

Timer synchronization
The TIM timers are linked together internally for timer synchronization or chaining. Refer to
Section 17.3.15: Timer synchronization on page 552 for details.

16.3.21

Debug mode
When the microcontroller enters debug mode (Cortex®-M4 with FPU 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 34.16.2: Debug support
for timers, watchdog, bxCAN and I2C.

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16.4

TIM1&TIM8 registers
Refer to Section 1.1: List of abbreviations for registers for a list of abbreviations used in
register descriptions.
The peripheral registers must be written by half-words (16 bits) or words (32 bits). Read
accesses can be done by bytes (8 bits), half-word (16 bits) or words (32 bits).

16.4.1

TIM1&TIM8 control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15

14

13

12

11

10

Res.

Res.

Res.

Res.

Res.

Res.

9

8

CKD[1:0]
rw

7

6

ARPE

rw

rw

5

CMS[1:0]
rw

rw

4

3

2

1

0

DIR

OPM

URS

UDIS

CEN

rw

rw

rw

rw

rw

Bits 15:10 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.

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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.

16.4.2

TIM1&TIM8 control register 2 (TIMx_CR2)
Address offset: 0x04
Reset value: 0x0000

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

6

rw

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

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4

MMS[2:0]

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rw

3

2

1

0

CCDS

CCUS

Res.

CCPC

rw

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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)
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
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.

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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.

16.4.3

TIM1&TIM8 slave mode control register (TIMx_SMCR)
Address offset: 0x08
Reset value: 0x0000

15

14

ETP

ECE

rw

rw

13

12

11

ETPS[1:0]
rw

rw

10

9

8

ETF[3:0]
rw

rw

7

6

MSM

rw

rw

rw

5

4

TS[2:0]
rw

rw

3

2

Res.
rw

1

0

SMS[2:0]
rw

rw

rw

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.
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

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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 108: TIMx Internal trigger connection 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.
Bit 3 Reserved, must be kept at reset value.

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Bits 2:0 SMS: 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.
000: Slave mode disabled - if CEN = ‘1’ then the prescaler is clocked directly by the internal
clock.
001: Encoder mode 1 - Counter counts up/down on TI2FP2 edge depending on TI1FP1
level.
010: Encoder mode 2 - Counter counts up/down on TI1FP1 edge depending on TI2FP2
level.
011: Encoder mode 3 - Counter counts up/down on both TI1FP1 and TI2FP2 edges
depending on the level of the other input.
100: Reset Mode - Rising edge of the selected trigger input (TRGI) reinitializes the counter
and generates an update of the registers.
101: 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.
110: 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.
111: External Clock Mode 1 - Rising edges of the selected trigger (TRGI) clock the counter.
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.

Table 108. TIMx Internal trigger connection

16.4.4

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

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

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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
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

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16.4.5

RM0390

TIM1&TIM8 status register (TIMx_SR)
Address offset: 0x10
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

CC4OF

CC3OF

CC2OF

CC1OF

Res.

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

rc_w0

rc_w0

rc_w0

Bits 15:13 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 Reserved, must be kept at reset value.
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.
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

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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 16.4.3: TIM1&TIM8 slave
mode control register (TIMx_SMCR)), if URS=0 and UDIS=0 in the TIMx_CR1 register.

16.4.6

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.

Res.

BG

TG

COMG

CC4G

CC3G

CC2G

CC1G

UG

w

w

w

w

w

w

w

w

Bits 15:8 Reserved, must be kept at reset value.
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.

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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
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).

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16.4.7

TIM1&TIM8 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 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.

15

14

OC2
CE

13

12

OC2M[2:0]
IC2F[3:0]

rw

rw

rw

11

10

OC2
PE

OC2
FE

9

8

CC2S[1:0]

7

6

OC1
CE

rw

rw

4

OC1M[2:0]

IC2PSC[1:0]
rw

5

IC1F[3:0]
rw

rw

rw

rw

rw

3

2

OC1
PE

OC1
FE

1

0

CC1S[1:0]

IC1PSC[1:0]
rw

rw

rw

rw

rw

Output compare mode:
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
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

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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.
000: 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).
001: 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).
010: 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).
011: Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1.
100: Force inactive level - OC1REF is forced low.
101: Force active level - OC1REF is forced high.
110: PWM mode 1 - In upcounting, channel 1 is active as long as TIMx_CNTTIMx_CCR1 else active (OC1REF=’1’).
111: PWM mode 2 - In upcounting, channel 1 is inactive as long as TIMx_CNTTIMx_CCR1 else
inactive.
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 1 or 2, 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.
3: 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.
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.

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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 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).
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

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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).

16.4.8

TIM1&TIM8 capture/compare mode register 2 (TIMx_CCMR2)
Address offset: 0x1C
Reset value: 0x0000
Refer to the above CCMR1 register description.

15

14

OC4
CE

13

12

OC4M[2:0]
IC4F[3:0]

rw

rw

rw

11

10

OC4
PE

OC4
FE

9

8

CC4S[1:0]

7

6

OC3
CE.

rw

rw

4

OC3M[2:0]

IC4PSC[1:0]
rw

5

IC3F[3:0]
rw

rw

rw

rw

rw

3

2

OC3
PE

OC3
FE

1

0

CC3S[1:0]

IC3PSC[1:0]
rw

rw

rw

rw

rw

Output compare mode
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

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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 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).
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).

16.4.9

TIM1&TIM8 capture/compare enable register (TIMx_CCER)
Address offset: 0x20
Reset value: 0x0000

15

14

13

12

Res.

Res.

CC4P

CC4E

rw

rw

11

10

CC3NP CC3NE
rw

rw

9

8

CC3P

CC3E

rw

rw

7

6

CC2NP CC2NE
rw

rw

5

4

CC2P

CC2E

rw

rw

3

2

CC1NP CC1NE
rw

rw

1

0

CC1P

CC1E

rw

rw

Bits 15:14 Reserved, must be kept at reset value.
Bit 13 CC4P: Capture/Compare 4 output polarity
refer to CC1P description

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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
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: 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.
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” (the channel is configured in output).
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.
Note: 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.

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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: 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.
Note: This bit is not writable as soon as LOCK level 2 or 3 has been programmed (LOCK bits
in TIMx_BDTR register).
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.
Note: 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.

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Table 109. Output control bits for complementary OCx and OCxN channels
with break feature
Output states(1)

Control bits
MOE OSSI OSSR CCxE CCxNE
OCx output state
bit
bit
bit
bit
bit
0

Output Disabled (not driven by
the timer)
OCx=0, OCx_EN=0

Output Disabled (not driven by the timer)
OCxN=0, OCxN_EN=0

1

Output Disabled (not driven by
the timer)
OCx=0, OCx_EN=0

OCxREF + Polarity OCxN=OCxREF xor
CCxNP, OCxN_EN=1

0

OCxREF + Polarity
OCx=OCxREF xor CCxP,
OCx_EN=1

Output Disabled (not driven by the timer)
OCxN=0, OCxN_EN=0

1

OCREF + Polarity + dead-time
OCx_EN=1

Complementary to OCREF (not
OCREF)
+ Polarity + dead-time
OCxN_EN=1

0

Output Disabled (not driven by
the timer)
OCx=CCxP, OCx_EN=0

Output Disabled (not driven by the timer)
OCxN=CCxNP, OCxN_EN=0

1

Off-State (output enabled with
inactive state)
OCx=CCxP, OCx_EN=1

OCxREF + Polarity
OCxN=OCxREF xor CCxNP,
OCxN_EN=1

0

OCxREF + Polarity
OCx=OCxREF xor CCxP,
OCx_EN=1

Off-State (output enabled with inactive
state)
OCxN=CCxNP, OCxN_EN=1

1

OCREF + Polarity + dead-time
OCx_EN=1

Complementary to OCREF (not
OCREF) + Polarity + dead-time
OCxN_EN=1

0

Output Disabled (not driven by
the timer)
OCx=CCxP, OCx_EN=0

Output Disabled (not driven by the timer)
OCxN=CCxNP, OCxN_EN=0

0

0

1

1

X

0

1

1

0

1

0

0
1
0

1

X
0

0
1

1

0
1

OCxN output state

1

Output Disabled (not driven by the timer)
Asynchronously: OCx=CCxP, OCx_EN=0, OCxN=CCxNP, OCxN_EN=0
Then if the clock is present: OCx=OISx and OCxN=OISxN after a deadtime, assuming that OISx and OISxN do not correspond to OCX and
OCxN both in active state.
Output Disabled (not driven by
the timer)
OCx=CCxP, OCx_EN=0

Output Disabled (not driven by the timer)
OCxN=CCxNP, OCxN_EN=0

Off-State (output enabled with inactive state)
Asynchronously: OCx=CCxP, OCx_EN=1, OCxN=CCxNP, OCxN_EN=1
Then if the clock is present: OCx=OISx and OCxN=OISxN after a deadtime, assuming that OISx and OISxN do not correspond to OCX and
OCxN both in active state

1. When both outputs of a channel are not used (CCxE = CCxNE = 0), the OISx, OISxN, CCxP and CCxNP bits must be kept
cleared.

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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.

16.4.10

TIM1&TIM8 counter (TIMx_CNT)
Address offset: 0x24
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

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CNT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 CNT[15:0]: Counter value

16.4.11

TIM1&TIM8 prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

rw

7

PSC[15:0]
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”).

16.4.12

TIM1&TIM8 auto-reload register (TIMx_ARR)
Address offset: 0x2C
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

ARR[15:0]
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 Section 16.3.1: Time-base unit for more details about ARR update and behavior.
The counter is blocked while the auto-reload value is null.

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16.4.13

RM0390

TIM1&TIM8 repetition counter register (TIMx_RCR)
Address offset: 0x30
Reset value: 0x0000

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

REP[7:0]
rw

rw

rw

rw

rw

Bits 15:8 Reserved, must be kept at reset value.
Bits 7:0 REP[7:0]: 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.

16.4.14

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:
CCR1 is the counter value transferred by the last input capture 1 event (IC1).

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16.4.15

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_CCMR2 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).

16.4.16

TIM1&TIM8 capture/compare register 3 (TIMx_CCR3)
Address offset: 0x3C
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

CCR3[15:0]
rw

rw

rw

rw

rw

rw

rw

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_CCMR3 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).

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16.4.17

RM0390

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_CCMR4 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).

16.4.18

TIM1&TIM8 break and dead-time register (TIMx_BDTR)
Address offset: 0x44
Reset value: 0x0000

15

14

13

12

11

10

MOE

AOE

BKP

BKE

OSSR

OSSI

rw

rw

rw

rw

rw

rw

Note:

9

8

7

6

5

LOCK[1:0]
rw

rw

4

3

2

1

0

rw

rw

rw

DTG[7:0]
rw

rw

rw

rw

rw

As the bits 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.
Bit 15 MOE: Main output enable
This bit is cleared asynchronously by hardware as soon as the break input is active. 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: OC and OCN outputs are disabled or forced to idle state.
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 16.4.9: TIM1&TIM8
capture/compare enable register (TIMx_CCER) on page 507).
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 the break input is
not be active)
Note: This bit can not be modified as long as LOCK level 1 has been programmed (LOCK bits
in TIMx_BDTR register).

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RM0390

Advanced-control timers (TIM1&TIM8)

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
0: Break inputs (BRK and CSS clock failure event) disabled
1; Break inputs (BRK and CSS clock failure event) 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 16.4.9: TIM1&TIM8
capture/compare enable register (TIMx_CCER) on page 507).
0: When inactive, OC/OCN outputs are disabled (OC/OCN enable output signal=0).
1: When inactive, OC/OCN outputs are enabled with their inactive level as soon as CCxE=1
or CCxNE=1. Then, OC/OCN enable output signal=1
Note: This bit can not be modified as soon as the LOCK level 2 has been programmed (LOCK
bits in TIMx_BDTR register).
Bit 10 OSSI: Off-state selection for Idle mode
This bit is used when MOE=0 on channels configured as outputs.
See OC/OCN enable description for more details (Section 16.4.9: TIM1&TIM8
capture/compare enable register (TIMx_CCER) on page 507).
0: When inactive, OC/OCN outputs are disabled (OC/OCN enable output signal=0).
1: When inactive, OC/OCN outputs are forced first with their idle level as soon as CCxE=1 or
CCxNE=1. OC/OCN enable output signal=1)
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.

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RM0390

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).

16.4.19

TIM1&TIM8 DMA control register (TIMx_DCR)
Address offset: 0x48
Reset value: 0x0000

15

14

13

Res.

Res.

Res.

12

11

rw

rw

10

9

8

rw

rw

DBL[4:0]
rw

7

6

5

Res.

Res.

Res.

4

3

rw

rw

2

1

0

rw

rw

DBA[4:0]
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 detects a burst transfer
when a read or a write access to the TIMx_DMAR register address is performed).
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-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,
...
Example: Let us consider the following transfer: DBL = 7 transfers and DBA = TIMx_CR1. In
this case the transfer is done to/from 7 registers starting from the TIMx_CR1 address.

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Advanced-control timers (TIM1&TIM8)

16.4.20

TIM1&TIM8 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).

Example of how to use the DMA burst feature
In this example the timer DMA burst feature is used to update the contents of the CCRx
registers (x = 2, 3, 4) with the DMA transferring half words into the CCRx registers.
This is done in the following steps:
1.

Note:

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.

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0x30

518/1327

TIMx_RCR

Reset value

DocID026976 Rev 3

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Reset value

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0
0
0
0
0
0
0
0
0

CC3E

0

0

0

0

0

IC2F[3:0]

0
0

OC4M
[2:0]

0
0

IC4F[3:0]

0

0
CC2S
[1:0]

0
0

0
0

0
0

0

0

0

0
0

0

0

0

0

UDE
BIE
TIE
COMIE
CC4IE
CC3IE
CC2IE
CC1IE
UIE

0
0
0
0
0
0

0

0

0

0

Res.

IC2
CC2S
PSC
[1:0]
[1:0]
0

0
0

CC4S
[1:0]

IC4
CC4S
PSC
[1:0]
[1:0]
0

0

0

0

0

CC2IF
CC1IF
UIF

0
0
0
0

CC1G
UG

0
0
OC1M
[2:0]

0
0
0

0

0

0

0
0
0
0
0
0
0

CNT[15:0]

PSC[15:0]

ARR[15:0]

REP[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

CC2G

CC3IF

0

0
0
0

OC1FE

CC4IF

OIS1
TI1S

Res.

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

MMS[2:0]
CCDS
CCUS
Res.
CCPC

0
0

0

0
0

TS[2:0]

IC1F[3:0]

0
0

OC3M
[2:0]

0
0

IC3F[3:0]

0

Res.

OIS1N

0

CC3G

COMIF
0

COMG

OIS2

0

OC1PE

TIF
0

TG

MSM

OIS2N

0

CC4G

BIF
0

BG

Res.

ETF[3:0]

OC1CE

OIS3

0

0

0
0

OC3FE

0

Res.

OIS3N

OIS4

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

CMS
[1:0]

OC3PE

0

OC3CE

CC1DE

0

CC1OF

0

CC2OF

0

CC3OF

0

CC4OF

0

Res.

CC2DE

0

0

0

Res.

0

0

0

OC2FE

OC2M
[2:0]

OC4FE

0

CC3DE

0

0

0

Res.

0

0

0

OC2PE

0

CC4DE

0

COMDE

0

Res.

ECE

0

TDE

ETP

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.

Res.

0

CC1E

0

CC2NP

0
0

0

CC1P

0

CC3P

0
0

0

CC1NE

0

CC3NE

0
Res.

Reset value

OC4PE

Res.

OC2CE

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

ETPS
[1:0]

0

CC1NP

0

CC3NP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

CC2E

0

CC4E

O24CE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
0

CC2P

0

CC4P

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
CKD
[1:0]

CC2NE

0

Res.

Reset value
0

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.

TIMx_ARR

Res.

0x2C

TIMx_PSC

Res.

0x28

TIMx_CNT

Res.

0x24
TIMx_CCER

Res.

0x20
Res.

Reset value
TIMx_CCMR1
Output Compare
mode
Reset value
TIMx_CCMR1
Input Capture
mode
Reset value
TIMx_CCMR2
Output Compare
mode
Reset value
TIMx_CCMR2
Input Capture
mode
Reset value
Res.

TIMx_EGR

Res.

0x14

Res.

TIMx_SR

Res.

0x10

Res.

TIMx_DIER

Res.

0x0C

Res.

TIMx_SMCR

Res.

0x08

Res.

TIMx_CR2

Res.

0x1C
TIMx_CR1

Res.

0x04

Res.

0x00

Res.

0x18

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.

16.4.21

Res.

Advanced-control timers (TIM1&TIM8)
RM0390

TIM1&TIM8 register map
TIM1&TIM8 registers are mapped as 16-bit addressable registers as described in the table
below:
Table 110. TIM1&TIM8 register map and reset values

0
0

0
0

0

0

SMS[2:0]
0
0
0

CC1S
[1:0]

IC1
CC1S
PSC
[1:0]
[1:0]

0

0

0

0

0

CC3S
[1:0]

IC3
CC3S
PSC
[1:0]
[1:0]
0

RM0390

Advanced-control timers (TIM1&TIM8)

TIMx_CCR1

CCR1[15:0]

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

DT[7:0]

0

DBL[4:0]
0

0

0

0

0
Res.

0

0

LOCK
[1:0]

Res.

0

0

Res.

OSSI
0

BKE

0
OSSR

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

BKP

0

0
Res.

TIMx_DMAR

0

AOE

0

Reset value
0x4C

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_DCR

Res.

Reset value
0x48

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_BDTR

0

CCR4[15:0]
0

Res.

Reset value
0x44

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_CCR4

0

CCR3[15:0]
0

Res.

Reset value
0x40

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_CCR3

0

CCR2[15:0]
0

Res.

Reset value
0x3C

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_CCR2

Res.

0x38

0
Res.

Reset value

MOE

0x34

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 110. TIM1&TIM8 register map and reset values (continued)

0

0

0

DBA[4:0]
0

0

0

0

0

0

0

0

0

0

DMAB[15:0]
0

0

0

0

0

0

0

0

0

0

0

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

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General-purpose timers (TIM2 to TIM5)

RM0390

17

General-purpose timers (TIM2 to TIM5)

17.1

TIM2 to 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 17.3.15.

17.2

TIM2 to TIM5 main features
General-purpose TIMx timer features include:

520/1327

•

16-bit (TIM3 and 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 65536.

•

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

DocID026976 Rev 3

RM0390

General-purpose timers (TIM2 to TIM5)
Figure 157. General-purpose timer block diagram

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069

17.3

TIM2 to TIM5 functional description

17.3.1

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. 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.

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RM0390

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 158 and Figure 159 give some examples of the counter behavior when the prescaler
ratio is changed on the fly:
Figure 158. Counter timing diagram with prescaler division change from 1 to 2
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069

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General-purpose timers (TIM2 to TIM5)
Figure 159. Counter timing diagram with prescaler division change from 1 to 4
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069

17.3.2

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.

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Figure 160. Counter timing diagram, internal clock divided by 1
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Figure 161. Counter timing diagram, internal clock divided by 2
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Figure 162. Counter timing diagram, internal clock divided by 4
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General-purpose timers (TIM2 to TIM5)
Figure 163. Counter timing diagram, internal clock divided by N
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Figure 164. Counter timing diagram, Update event when ARPE=0 (TIMx_ARR not
preloaded)
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Figure 165. Counter timing diagram, Update event when ARPE=1 (TIMx_ARR
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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):
•

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.

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General-purpose timers (TIM2 to TIM5)
Figure 166. Counter timing diagram, internal clock divided by 1
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Figure 167. Counter timing diagram, internal clock divided by 2
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Figure 168. Counter timing diagram, internal clock divided by 4
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Figure 169. Counter timing diagram, internal clock divided by N
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Figure 170. Counter timing diagram, Update event
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069

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").

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General-purpose timers (TIM2 to TIM5)
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
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 171. Counter timing diagram, internal clock divided by 1, TIMx_ARR=0x6
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069

1. Here, center-aligned mode 1 is used (for more details refer to Section 17.4.1: TIMx control register 1 (TIMx_CR1)
on page 558).

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Figure 172. Counter timing diagram, internal clock divided by 2
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Figure 173. Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36
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1. Center-aligned mode 2 or 3 is used with an UIF on overflow.

Figure 174. Counter timing diagram, internal clock divided by N
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General-purpose timers (TIM2 to TIM5)
Figure 175. Counter timing diagram, Update event with ARPE=1 (counter underflow)
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Figure 176. Counter timing diagram, Update event with ARPE=1 (counter overflow)
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17.3.3

RM0390

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) available on TIM2, TIM3 and TIM4
only.

•

Internal trigger inputs (ITRx): using one timer as prescaler for another timer, for
example, you can configure Timer to act as a prescaler for Timer 2. Refer to Using one
timer as prescaler for another 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 177 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.
Figure 177. Control circuit in normal mode, internal clock divided by 1

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069

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.

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Figure 178. TI2 external clock connection example
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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).

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 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.

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Figure 179. Control circuit in external clock mode 1

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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 180 gives an overview of the external trigger input block.
Figure 180. External trigger input block
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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.

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General-purpose timers (TIM2 to TIM5)
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 181. Control circuit in external clock mode 2

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17.3.4

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).

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Figure 182. Capture/compare channel (example: channel 1 input stage)
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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 183. Capture/compare channel 1 main circuit
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General-purpose timers (TIM2 to TIM5)
Figure 184. Output stage of capture/compare channel (channel 1)
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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.

17.3.5

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:
•

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.

•

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

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new level have been detected (sampled at fDTS frequency). Then write IC1F bits to
0011 in the TIMx_CCMR1 register.
•

Select the edge of the active transition on the TI1 channel by writing the CC1P and
CC1NP bits to 00 in the TIMx_CCER register (rising edge in this case).

•

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).

•

Enable capture from the counter into the capture register by setting the CC1E bit in the
TIMx_CCER register.

•

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.

17.3.6

PWM input mode
This mode is a particular case of input capture mode. The procedure is the same except:

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•

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.

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General-purpose timers (TIM2 to 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):
•

Select the active input for TIMx_CCR1: write the CC1S bits to 01 in the TIMx_CCMR1
register (TI1 selected).

•

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).

•

Select the active input for TIMx_CCR2: write the CC2S bits to 10 in the TIMx_CCMR1
register (TI1 selected).

•

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).

•

Select the valid trigger input: write the TS bits to 101 in the TIMx_SMCR register
(TI1FP1 selected).

•

Configure the slave mode controller in reset mode: write the SMS bits to 100 in the
TIMx_SMCR register.

•

Enable the captures: write the CC1E and CC2E bits to ‘1 in the TIMx_CCER register.
Figure 185. PWM input mode timing
TI1

TIMx_CNT

0004

0000

0001

0002

TIMx_CCR1

0004

TIMx_CCR2

0002

IC1 capture
IC2 capture
reset counter

0003

0004

IC2 capture
pulse width
measurement

0000

IC1 capture
period
measurement
ai15413

17.3.7

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.

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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.

17.3.8

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 186.

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General-purpose timers (TIM2 to TIM5)
Figure 186. Output compare mode, toggle on OC1
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17.3.9

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 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 ETRF (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 changes, 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.
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.

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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 523.
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 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

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General-purpose timers (TIM2 to TIM5)
TIMx_CR1 register is updated by hardware and must not be changed by software. Refer to
Center-aligned mode (up/down counting) on page 528.
Figure 188 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 188. Center-aligned PWM waveforms (ARR=8)

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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

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in the TIMx_CR1 register. Moreover, the DIR and CMS bits must not be changed at the
same time by the software.
•

•

17.3.10

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.

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: CNTCCRx.
Figure 189. Example of one-pulse mode
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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.

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General-purpose timers (TIM2 to TIM5)
Let’s use TI2FP2 as trigger 1:
•

Map TI2FP2 on TI2 by writing CC2S=01 in the TIMx_CCMR1 register.

•

TI2FP2 must detect a rising edge, write CC2P=0 and CC2NP=’0’ in the TIMx_CCER
register.

•

Configure TI2FP2 as trigger for the slave mode controller (TRGI) by writing TS=110 in
the TIMx_SMCR register.

•

TI2FP2 is used to start the counter by writing SMS to ‘110 in the TIMx_SMCR register
(trigger mode).

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_CCR + 1).

•

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) is 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.

17.3.11

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.
This function can only be used in output compare and PWM modes, and does not work in
forced mode.
For example, the ETR 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:

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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.

Figure 190 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 190. Clearing TIMx OCxREF
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1. In case of a PWM with a 100% duty cycle (if CCRx>ARR), OCxREF is enabled again at the next counter
overflow.

17.3.12

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.
The two inputs TI1 and TI2 are used to interface to an incremental encoder. Refer to
Table 111. 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, prescaler,
trigger output features continue to work as normal.

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In this mode, the counter is modified automatically following the speed and the direction of
the incremental 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.
Table 111. Counting direction versus encoder signals
Level on opposite
signal (TI1FP1 for
TI2, TI2FP2 for TI1)

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

Active edge

TI1FP1 signal

TI2FP2 signal

An external incremental 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.
Figure 191 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, TI2FP2 mapped on TI2)

•

CC1P= ‘0’, CC1NP = ‘0’, IC1F =’0000’ (TIMx_CCER register, TI1FP1 noninverted,
TI1FP1=TI1)

•

CC2P= ‘0’, CC2NP = ‘0’, IC2F =’0000’ (TIMx_CCER register, TI2FP2 noninverted,
TI2FP2=TI2)

•

SMS= ‘011’ (TIMx_SMCR register, both inputs are active on both rising and falling
edges)

•

CEN = 1 (TIMx_CR1 register, Counter is enabled)

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Figure 191. Example of counter operation in encoder interface mode
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Figure 192 gives an example of counter behavior when TI1FP1 polarity is inverted (same
configuration as above except CC1P=1).
Figure 192. Example of encoder interface mode with TI1FP1 polarity inverted
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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
generated by a Real-Time clock.

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17.3.13

General-purpose timers (TIM2 to TIM5)

Timer input XOR function
The TI1S bit in the TIM_CR2 register, allows the input filter of channel 1 to be connected to
the output of a XOR gate, combining the three input pins TIMx_CH1 to TIMx_CH3.
The XOR output can be used with all the timer input functions such as trigger or input
capture.

17.3.14

Timers and external trigger synchronization
The TIMx 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:
•

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 193. Control circuit in reset mode

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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 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 194. Control circuit in gated mode

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1. The configuration “CCxP=CCxNP=1” (detection of both rising and falling edges) does not have any effect
in gated mode because gated mode acts on a level and not on an edge.

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:
•

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. CC2S bits are
selecting the input capture source only, CC2S=01 in TIMx_CCMR1 register. Write
CC2P=1 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.

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General-purpose timers (TIM2 to TIM5)
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 195. Control circuit in trigger mode

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069

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 when operating 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:
1.

2.

3.

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 = 01 in TIMx_CCMR1 register to select only the input capture source

–

CC1P = 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.

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RM0390

Figure 196. Control circuit in external clock mode 2 + trigger mode
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17.3.15

Timer synchronization
The TIMx timers are linked together internally for timer synchronization or chaining. When
one Timer is configured in Master Mode, it can reset, start, stop or clock the counter of
another Timer configured in Slave Mode.
Figure 197 presents an overview of the trigger selection and the master mode selection
blocks.

Using one timer as prescaler for another
Figure 197. Master/Slave timer example

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General-purpose timers (TIM2 to TIM5)
For example, you can configure Timer 1 to act as a prescaler for Timer 2. Refer to
Figure 197. To do this:

Note:

•

Configure Timer 1 in master mode so that it outputs a periodic trigger signal on each
update event UEV. If you write MMS=010 in the TIM1_CR2 register, a rising edge is
output on TRGO1 each time an update event is generated.

•

To connect the TRGO1 output of Timer 1 to Timer 2, Timer 2 must be configured in
slave mode using ITR0 as internal trigger. You select this through the TS bits in the
TIM2_SMCR register (writing TS=000).

•

Then you put the slave mode controller in external clock mode 1 (write SMS=111 in the
TIM2_SMCR register). This causes Timer 2 to be clocked by the rising edge of the
periodic Timer 1 trigger signal (which correspond to the timer 1 counter overflow).

•

Finally both timers must be enabled by setting their respective CEN bits (TIMx_CR1
register).

If OCx is selected on Timer 1 as trigger output (MMS=1xx), its rising edge is used to clock
the counter of timer 2.

Using one timer to enable another timer
In this example, we control the enable of Timer 2 with the output compare 1 of Timer 1.
Refer to Figure 197 for connections. Timer 2 counts on the divided internal clock only when
OC1REF of Timer 1 is high. Both counter clock frequencies are divided by 3 by the
prescaler compared to CK_INT (fCK_CNT = fCK_INT/3).

Note:

•

Configure Timer 1 master mode to send its Output Compare 1 Reference (OC1REF)
signal as trigger output (MMS=100 in the TIM1_CR2 register).

•

Configure the Timer 1 OC1REF waveform (TIM1_CCMR1 register).

•

Configure Timer 2 to get the input trigger from Timer 1 (TS=000 in the TIM2_SMCR
register).

•

Configure Timer 2 in gated mode (SMS=101 in TIM2_SMCR register).

•

Enable Timer 2 by writing ‘1 in the CEN bit (TIM2_CR1 register).

•

Start Timer 1 by writing ‘1 in the CEN bit (TIM1_CR1 register).

The counter 2 clock is not synchronized with counter 1, this mode only affects the Timer 2
counter enable signal.
Figure 198. Gating timer 2 with OC1REF of timer 1

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In the example in Figure 198, the Timer 2 counter and prescaler are not initialized before
being started. So they start counting from their current value. It is possible to start from a
given value by resetting both timers before starting Timer 1. You can then write any value
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RM0390

you want in the timer counters. The timers can easily be reset by software using the UG bit
in the TIMx_EGR registers.
In the next example, we synchronize Timer 1 and Timer 2. Timer 1 is the master and starts
from 0. Timer 2 is the slave and starts from 0xE7. The prescaler ratio is the same for both
timers. Timer 2 stops when Timer 1 is disabled by writing ‘0 to the CEN bit in the TIM1_CR1
register:
•

Configure Timer 1 master mode to send its Output Compare 1 Reference (OC1REF)
signal as trigger output (MMS=100 in the TIM1_CR2 register).

•

Configure the Timer 1 OC1REF waveform (TIM1_CCMR1 register).

•

Configure Timer 2 to get the input trigger from Timer 1 (TS=000 in the TIM2_SMCR
register).

•

Configure Timer 2 in gated mode (SMS=101 in TIM2_SMCR register).

•

Reset Timer 1 by writing ‘1 in UG bit (TIM1_EGR register).

•

Reset Timer 2 by writing ‘1 in UG bit (TIM2_EGR register).

•

Initialize Timer 2 to 0xE7 by writing ‘0xE7’ in the timer 2 counter (TIM2_CNTL).

•

Enable Timer 2 by writing ‘1 in the CEN bit (TIM2_CR1 register).

•

Start Timer 1 by writing ‘1 in the CEN bit (TIM1_CR1 register).

•

Stop Timer 1 by writing ‘0 in the CEN bit (TIM1_CR1 register).
Figure 199. Gating timer 2 with Enable of timer 1

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Using one timer to start another timer
In this example, we set the enable of Timer 2 with the update event of Timer 1. Refer to
Figure 197 for connections. Timer 2 starts counting from its current value (which can be
nonzero) on the divided internal clock as soon as the update event is generated by Timer 1.
When Timer 2 receives the trigger signal its CEN bit is automatically set and the counter

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General-purpose timers (TIM2 to TIM5)
counts until we write ‘0 to the CEN bit in the TIM2_CR1 register. Both counter clock
frequencies are divided by 3 by the prescaler compared to CK_INT (fCK_CNT = fCK_INT/3).
•

Configure Timer 1 master mode to send its Update Event (UEV) as trigger output
(MMS=010 in the TIM1_CR2 register).

•

Configure the Timer 1 period (TIM1_ARR registers).

•

Configure Timer 2 to get the input trigger from Timer 1 (TS=000 in the TIM2_SMCR
register).

•

Configure Timer 2 in trigger mode (SMS=110 in TIM2_SMCR register).

•

Start Timer 1 by writing ‘1 in the CEN bit (TIM1_CR1 register).
Figure 200. Triggering timer 2 with update of timer 1

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As in the previous example, you can initialize both counters before starting counting.
Figure 201 shows the behavior with the same configuration as in Figure 198, but in trigger
mode instead of gated mode (SMS=110 in the TIM2_SMCR register).

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RM0390

Figure 201. Triggering timer 2 with Enable of timer 1

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Using one timer as prescaler for another timer
For example, you can configure Timer 1 to act as a prescaler for Timer 2. Refer to
Figure 197 for connections. To do this:
•

Configure Timer 1 master mode to send its Update Event (UEV) as trigger output
(MMS=010 in the TIM1_CR2 register). then it outputs a periodic signal on each counter
overflow.

•

Configure the Timer 1 period (TIM1_ARR registers).

•

Configure Timer 2 to get the input trigger from Timer 1 (TS=000 in the TIM2_SMCR
register).

•

Configure Timer 2 in external clock mode 1 (SMS=111 in TIM2_SMCR register).

•

Start Timer 2 by writing ‘1 in the CEN bit (TIM2_CR1 register).

•

Start Timer 1 by writing ‘1 in the CEN bit (TIM1_CR1 register).

Starting 2 timers synchronously in response to an external trigger
In this example, we set the enable of timer 1 when its TI1 input rises, and the enable of
Timer 2 with the enable of Timer 1. Refer to Figure 197 for connections. To ensure the

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General-purpose timers (TIM2 to TIM5)
counters are aligned, Timer 1 must be configured in Master/Slave mode (slave with respect
to TI1, master with respect to Timer 2):
•

Configure Timer 1 master mode to send its Enable as trigger output (MMS=001 in the
TIM1_CR2 register).

•

Configure Timer 1 slave mode to get the input trigger from TI1 (TS=100 in the
TIM1_SMCR register).

•

Configure Timer 1 in trigger mode (SMS=110 in the TIM1_SMCR register).

•

Configure the Timer 1 in Master/Slave mode by writing MSM=1 (TIM1_SMCR register).

•

Configure Timer 2 to get the input trigger from Timer 1 (TS=000 in the TIM2_SMCR
register).

•

Configure Timer 2 in trigger mode (SMS=110 in the TIM2_SMCR register).

When a rising edge occurs on TI1 (Timer 1), both counters starts counting synchronously on
the internal clock and both TIF flags are set.
Note:

In this example both timers are initialized before starting (by setting their respective UG
bits). Both counters starts from 0, but you can easily insert an offset between them by
writing any of the counter registers (TIMx_CNT). You can see that the master/slave mode
insert a delay between CNT_EN and CK_PSC on timer 1.
Figure 202. Triggering timer 1 and 2 with timer 1 TI1 input

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17.3.16

Debug mode
When the microcontroller enters debug mode (Cortex®-M4 with FPU core - halted), the
TIMx counter either continues to work normally or stops, depending on DBG_TIMx_STOP
configuration bit in DBGMCU module. For more details, refer to Section 33.16.2: Debug
support for timers, watchdog, bxCAN and I2C.

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17.4

RM0390

TIM2 to TIM5 registers
Refer to Section 1.1 on page 51 for a list of abbreviations used in register descriptions.
The 32-bit peripheral registers have to be written by words (32 bits). All other 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).

17.4.1

TIMx control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15

14

13

12

11

10

Res.

Res.

Res.

Res.

Res.

Res.

9

8

CKD[1:0]
rw

7

6

ARPE

rw

rw

5
CMS

rw

rw

4

3

2

1

0

DIR

OPM

URS

UDIS

CEN

rw

rw

rw

rw

rw

Bits 15:10 Reserved, must be kept at reset value.
Bits 9:8 CKD: Clock division
This bit-field indicates the division ratio between the timer clock (CK_INT) frequency and
sampling clock used by the digital filters (ETR, 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 6:5 CMS: 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.
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)

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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.
CEN is cleared automatically in one-pulse mode, when an update event occurs.

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17.4.2

RM0390

TIMx control register 2 (TIMx_CR2)
Address offset: 0x04
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TI1S
rw

6

5

4

MMS[2:0]
rw

rw

rw

3

2

1

0

CCDS

Res.

Res.

Res.

rw

Bits 15:8 Reserved, must be kept at reset value.
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
enabled. 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)
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
Bits 2:0 Reserved, must be kept at reset value.

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17.4.3

TIMx slave mode control register (TIMx_SMCR)
Address offset: 0x08
Reset value: 0x0000

15

14

ETP

ECE

rw

rw

13

12

11

ETPS[1:0]
rw

rw

10

9

8

ETF[3:0]
rw

rw

7

6

MSM

rw

rw

rw

5

4

TS[2:0]
rw

rw

3

2

Res.
rw

1

0

SMS[2:0]
rw

rw

rw

Bit 15 ETP: External trigger polarity
This bit selects whether ETR or ETR is used for trigger operations
0: ETR is noninverted, 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.
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.
Bits 13:12 ETPS: External trigger prescaler
External trigger signal ETRP frequency must be at most 1/4 of CK_INT 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

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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: 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 112 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.
Bit 3 Reserved, must be kept at reset value.
Bits 2:0 SMS: 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.
000: Slave mode disabled - if CEN = ‘1 then the prescaler is clocked directly by the internal
clock.
001: Encoder mode 1 - Counter counts up/down on TI2FP2 edge depending on TI1FP1
level.
010: Encoder mode 2 - Counter counts up/down on TI1FP1 edge depending on TI2FP2
level.
011: Encoder mode 3 - Counter counts up/down on both TI1FP1 and TI2FP2 edges
depending on the level of the other input.
100: Reset Mode - Rising edge of the selected trigger input (TRGI) reinitializes the counter
and generates an update of the registers.
101: 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.
110: 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.
111: External Clock Mode 1 - Rising edges of the selected trigger (TRGI) clock the counter.
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.

Table 112. TIMx internal trigger connections

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ITR0 (TS = 000)

ITR1 (TS = 001)

ITR2 (TS = 010)

ITR3 (TS = 011)

TIM2

TIM1

TIM8

TIM3

TIM4

TIM3

TIM1

TIM2

TIM5

TIM4

TIM4

TIM1

TIM2

TIM3

TIM8

TIM5

TIM2

TIM3

TIM4

TIM8

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General-purpose timers (TIM2 to TIM5)

17.4.4

TIMx DMA/Interrupt enable register (TIMx_DIER)
Address offset: 0x0C
Reset value: 0x0000

15

14

13

Res.

TDE

Res.

rw

12

rw

Bit 15

11

10

9

CC4DE CC3DE CC2DE CC1DE
rw

rw

rw

8

7

6

5

4

3

2

1

0

UDE

Res.

TIE

Res.

CC4IE

CC3IE

CC2IE

CC1IE

UIE

rw

rw

rw

rw

rw

rw

rw

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

Reserved, always read as 0

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

Reserved, must be kept at reset value.

Bit 6 TIE: Trigger interrupt enable
0: Trigger interrupt disabled.
1: Trigger interrupt enabled.
Bit 5

Reserved, must be kept at reset value.

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

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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

17.4.5

TIMx status register (TIMx_SR)
Address offset: 0x10
Reset value: 0x0000

15

14

13

Res.

Res.

Res.

12

rc_w0

Bits 15:13

11

10

9

CC4OF CC3OF CC2OF CC1OF
rc_w0

rc_w0

8

7

6

5

4

3

2

1

0

Res.

Res.

TIF

Res.

CC4IF

CC3IF

CC2IF

CC1IF

UIF

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

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
Bits 8:7

Reserved, must be kept at reset value.

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

Reserved, must be kept at reset value.

Bit 4 CC4IF: Capture/Compare 4 interrupt flag
refer to CC1IF description
Bit 3 CC3IF: Capture/Compare 3 interrupt flag
refer to CC1IF description

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General-purpose timers (TIM2 to TIM5)

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 (for TIM2 to TIM5) 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.

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17.4.6

RM0390

TIMx 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.

CC4G

CC3G

CC2G

CC1G

UG

w

w

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 TIMx_SR register. Related interrupt or DMA transfer can occur if
enabled.
Bit 5 Reserved, must be kept at reset value.
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
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: Re-initialize 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).

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General-purpose timers (TIM2 to TIM5)

17.4.7

TIMx 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 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.

15

14

OC2CE

13

12

OC2M[2:0]
IC2F[3:0]

rw

rw

rw

11

10

OC2PE OC2FE
IC2PSC[1:0]
rw

rw

rw

9

8

CC2S[1:0]
rw

7

6

OC1CE

rw

5

4

OC1M[2:0]
IC1F[3:0]

rw

rw

rw

3

2

OC1PE OC1FE
IC1PSC[1:0]
rw

rw

rw

1

0

CC1S[1:0]
rw

rw

Output compare mode
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
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

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RM0390

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.
000: 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).
001: 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).
010: 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).
011: Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1.
100: Force inactive level - OC1REF is forced low.
101: Force active level - OC1REF is forced high.
110: PWM mode 1 - In upcounting, channel 1 is active as long as TIMx_CNTTIMx_CCR1 else active (OC1REF=1).
111: PWM mode 2 - In upcounting, channel 1 is inactive as long as TIMx_CNTTIMx_CCR1 else
inactive.
Note: In PWM mode 1 or 2, 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.
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).

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General-purpose timers (TIM2 to TIM5)

Input capture mode
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).
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).

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17.4.8

RM0390

TIMx capture/compare mode register 2 (TIMx_CCMR2)
Address offset: 0x1C
Reset value: 0x0000
Refer to the above CCMR1 register description.

15

14

OC4CE

13

12

OC4M[2:0]
IC4F[3:0]

rw

rw

rw

11

10

OC4PE OC4FE
IC4PSC[1:0]
rw

rw

rw

9

8

CC4S[1:0]
rw

7

6

OC3CE

rw

5

4

OC3M[2:0]
IC3F[3:0]

rw

rw

rw

3

2

OC3PE OC3FE
IC3PSC[1:0]
rw

rw

rw

1

0

CC3S[1:0]
rw

rw

Output compare mode
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).

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General-purpose timers (TIM2 to TIM5)

Input capture mode
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).
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).

17.4.9

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

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RM0390

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.
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 113. Output control bit for standard OCx channels
CCxE bit

Note:

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OCx output state

0

Output Disabled (OCx=0, OCx_EN=0)

1

OCx=OCxREF + Polarity, OCx_EN=1

The state of the external IO pins connected to the standard OCx channels depends on the
OCx channel state and the GPIO registers.
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General-purpose timers (TIM2 to TIM5)

17.4.10

TIMx counter (TIMx_CNT)
Address offset: 0x24
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

CNT[15:0]
rw

rw

rw

rw

rw

rw

rw

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

Bits 15:0 CNT[15:0]: Counter value

17.4.11

TIMx prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

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.

17.4.12

TIMx auto-reload register (TIMx_ARR)
Address offset: 0x2C
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

ARR[15:0]

Bits 15:0

rw

ARR[15:0]: Auto-reload value
ARR is the value to be loaded in the actual auto-reload register.
Refer to the Section 17.3.1: Time-base unit on page 521 for more details about ARR update
and behavior.
The counter is blocked while the auto-reload value is null.

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17.4.13

RM0390

TIMx capture/compare register 1 (TIMx_CCR1)
Address offset: 0x34
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CCR1[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

rw

rw

rw

rw

rw

rw

rw

CCR1[15:0]
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).

17.4.14

TIMx capture/compare register 2 (TIMx_CCR2)
Address offset: 0x38
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

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

CCR2[31:16] (depending on timers)

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_CCMR 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).

574/1327

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RM0390

General-purpose timers (TIM2 to TIM5)

17.4.15

TIMx capture/compare register 3 (TIMx_CCR3)
Address offset: 0x3C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CCR3[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

rw

rw

rw

rw

rw

rw

rw

CCR3[15:0]
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_CCMR 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 signaled on OC3 output.
If channel CC3 is configured as input:
CCR3 is the counter value transferred by the last input capture 3 event (IC3).

17.4.16

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

rw

rw

rw

rw

rw

rw

rw

CCR4[15:0]
rw

rw

Bits 31:16 CCR4[31:16]: High Capture/Compare 4 value (onTIM2 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_CCMR 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).

DocID026976 Rev 3

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General-purpose timers (TIM2 to TIM5)

17.4.17

RM0390

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.

17.4.18

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).

Example of how to use the DMA burst feature
In this example the timer DMA burst feature is used to update the contents of the CCRx
registers (x = 2, 3, 4) with the DMA transferring half words into the CCRx registers.
This is done in the following steps:
576/1327

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RM0390

General-purpose timers (TIM2 to TIM5)
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

Note:

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.

17.4.19

TIM2 option register (TIM2_OR)
Address offset: 0x50
Reset value: 0x0000

15

14

13

12

Res.

Res.

Res.

Res.

11

10

ITR1_RMP
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: Internal trigger 1 remap
Set and cleared by software.
00: TIM8_TRGOUT
01: Reserved
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.

DocID026976 Rev 3

577/1327
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General-purpose timers (TIM2 to TIM5)

17.4.20

RM0390

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
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: 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 TIM5_CH4 input for calibration purposes.
Wakeup interrupt should be enabled.
Bits 5:0 Reserved, must be kept at reset value.

578/1327

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0x20

0x24

TIMx_CCER

TIMx_CNT

Reset value

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

CC2NP

Res.

0

DocID026976 Rev 3
0

0
0

0

0
0

0
CC2S
[1:0]

0
0
0

OC4M
[2:0]
CC4S
[1:0]

0
0
0
0
0

0

0

IC4F[3:0]

0

0
CC2S
[1:0]
OC1CE

0
0
0

CNT[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

0

0
0

0

0

IC4
PSC
[1:0]

CC4S
[1:0]

0

0

Reset value

0

0

0
0

0

0
0

UIE

UIF

UG

OC1M
[2:0]

CC1G

0

CC2G

CC1IE

CC1IF
0

0
0
0
0
0

OC1FE

CC2IE

CC2IF
0

CC3G

CC3IE

CC3IF
0

OC1PE

0
0
0
0

0
0

Res.
CC4IE
0

Res.
CC4IF
0

Res.
0

CC4G

TIE
0

TIF
0

TG

Res.

0
Res.

Res.

UDE

Res.

0

Res.

CC1OF

0

Res.

CC1DE

CC2OF

0

Res.

0

CC3OF

0

Res.

0

CC4OF

0

Res.

CC2DE

0

0

MSM

DIR
OPM
URS
UDIS
CEN

CCDS
Res.
Res.
Res.

0
0
0

0

TS[2:0]

0

IC1F[3:0]

0
0

OC3M
[2:0]

0

IC3F[3:0]

Res.

MMS[2:0]

ARPE

TI1S

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.

0

0

IC1
PSC
[1:0]
CC1S
[1:0]

0
0
0

OC3FE

0
OC2FE

0

CC3DE

0

CC4DE

0

COMDE

0

Res.

ECE

0

TDE

ETP

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

OC3PE

OC2M
[2:0]
OC2PE

0
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

CNT[15:0]

0

0

0

0

0

0

IC3
PSC
[1:0]

CC3S
[1:0]

0

0

0

0

CC1E

0
IC2
PSC
[1:0]

OC3CE

IC2F[3:0]

OC4FE

0

OC4PE

OC2CE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ETPS
[1:0]
ETF[3:0]

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
0

CMS
[1:0]

CC1P

O24CE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
0

CC1NP

0

CC3E

TIMx_CCMR2
Output Compare
mode
Res.

Res.

Res.

Res.

Res.

Reset value
0

CC2E

0

CC3P

0

Res.

Res.

Res.

Reset value
CKD
[1:0]

CC2P

0

Res.

0

0

CC3NP

Reset value

CC4E

Reset value

CC4P

Reset value

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

CC4NP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_CCMR2
Input Capture
mode

Res.

0x1C
TIMx_CCMR1
Input Capture
mode

Res.

TIMx_CCMR1
Output Compare
mode

Res.

0x18
TIMx_EGR

Res.

0x14
TIMx_SR

Res.

0x10
TIMx_DIER

Res.

0x0C
TIMx_SMCR

Res.

0x08
TIMx_CR2

Res.

0x04
TIMx_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

Res.

Offset

Res.

17.4.21

Res.

RM0390
General-purpose timers (TIM2 to TIM5)

TIMx register map
TIMx registers are mapped as described in the table below:
Table 114. TIM2 to TIM5 register map and reset values

SMS[2:0]
0
0
0

CC1S
[1:0]

0
0
0
0

CC3S
[1:0]

0
0
0
0

0

0

0

0

0

579/1327

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General-purpose timers (TIM2 to TIM5)

RM0390

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

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.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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.

0

Res.

0

Res.

DBL[4:0]
0

0

Res.

0
Res.

Res.

Res.

0
Res.

Res.
Res.

0

0

Res.

Reset value

0

0

ITR1_
RMP

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.
Res.
Res.

0

0

Res.

Res.

0

0

Res.
Res.
Res.
Res.

0

0

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.
Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

0

0

0
Res.

0

0

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

0

0

0

DBA[4:0]
0

0

0

0

0

DMAB[15:0]
0

Res.

0

0

0

Res.

TIM5_OR

0

0

Reset value

0x50

0

0

TIMx_DCR

TIM2_OR

0

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.

0

Res.

0

Res.

0

Res.

0

0

CCR4[15:0]

Res.

0

0

CCR3[15:0]

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0
Res.

0

0

IT4_
RMP

Res.

0

0

Res.

0

0

Res.

0

Reset value

0x50

0

Res.

0

Reserved

TIMx_DMAR

0

CCR2[15:0]

Reset value

0x4C

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

CCR1[15:0]

0
Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0x48

0

Res.

0x44

0

Res.

Reset value

0

0

CCR4[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_CCR4

0

0

0

0

0

0

CCR3[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_CCR3

0

0

0

0

0

0

CCR2[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_CCR2

0

0

Res.

0x40

0

0

ARR[15:0]

CCR1[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_CCR1

0

Res.

Reserved

0

Res.

0

Reset value

0

Res.

0x3C

0

Res.

Reset value

Reset value

0

Res.

0x38

0

ARR[31:16]
(TIM2 and TIM5 only, reserved on the other timers)

TIMx_ARR

Reset value

0

Res.

0x34

0

Res.

0x30

0

Res.

0x2C

PSC[15:0]

Res.

TIMx_PSC

Res.

0x28

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 114. TIM2 to TIM5 register map and reset values (continued)

0

0

Refer to Section 2.2.2: Memory map and register boundary addresses for the register
boundary addresses.

580/1327

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RM0390

General-purpose timers (TIM9 to TIM14)

18

General-purpose timers (TIM9 to TIM14)

18.1

TIM9 to TIM14 introduction
The TIM9 to TIM14 general-purpose timers consist of 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 to TIM14 timers are completely independent, and do not share any resources.
They can be synchronized together as described in Section 18.3.12.

18.2

TIM9 to TIM14 main features

18.2.1

TIM9/TIM12 main features
The features of the TIM9 to TIM14 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

DocID026976 Rev 3

581/1327
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General-purpose timers (TIM9 to TIM14)

RM0390

Figure 203. General-purpose timer block diagram (TIM9 and TIM12)
Internal clock (CK_INT)

ITR0
ITR1

TGI

ITR

ITR2

TRC

Trigger
controller

TRGI

ITR3
TI1F_ED

Slave
mode
controller

Reset, Enable, Count

TI1FP1
TI2FP2

U

Auto-reload register
Stop, Clear

CK_PSC

PSC

CK_CNT

Prescaler

+/-

Input filter &
Edge detector

TIMx_CH1

TI1FP1
TI1FP2

IC1
Prescaler

CC1I

TIMx_CH2

Input filter &
Edge detector

Capture/Compare 1 register

OC1REF

output

OC1

control

TRC
TI2

IC1PS U

U

CNT

COUNTER

CC1I

TI1

UI

TI2FP1
TI2FP2

CC2I

IC2

CC2I

IC2PS U
Prescaler

TIMx_CH1

Capture/Compare 2 register

OC2REF

output

OC2

TIMx_CH2

control

TRC

Notes:
Reg

Preload registers transferred
to active registers on U event
according to control bit
event
interrupt

ai17190

18.2.2

TIM10/TIM11 and TIM13/TIM14 main features
The features of general-purpose timers TIM10/TIM11 and 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:

•

582/1327

–

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

DocID026976 Rev 3

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General-purpose timers (TIM9 to TIM14)
Figure 204. General-purpose timer block diagram (TIM10/11/13/14)

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RM0390

18.3

TIM9 to TIM14 functional description

18.3.1

Time-base unit
The main block of the timer is a 16-bit 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 205 and Figure 206 give some examples of the counter behavior when the prescaler
ratio is changed on the fly.

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General-purpose timers (TIM9 to TIM14)
Figure 205. Counter timing diagram with prescaler division change from 1 to 2
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Figure 206. Counter timing diagram with prescaler division change from 1 to 4
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18.3.2

RM0390

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 and 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 207. Counter timing diagram, internal clock divided by 1
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General-purpose timers (TIM9 to TIM14)
Figure 208. Counter timing diagram, internal clock divided by 2
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Figure 209. Counter timing diagram, internal clock divided by 4
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Figure 210. Counter timing diagram, internal clock divided by N
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RM0390

Figure 211. Counter timing diagram, update event when ARPE=0
(TIMx_ARR not preloaded)
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Figure 212. Counter timing diagram, update event when ARPE=1
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RM0390

18.3.3

General-purpose timers (TIM9 to TIM14)

Clock selection
The counter clock can be provided by the following clock sources:
•

Internal clock (CK_INT)

•

External clock mode1 (for TIM9 and TIM12): external input pin (TIx)

•

Internal trigger inputs (ITRx) (for TIM9 and TIM12): connecting the trigger output from
another timer. Refer to Using one timer as prescaler for another for more details.

Internal clock source (CK_INT)
The internal clock source is the default clock source for TIM10/TIM11 and TIM13/TIM14.
For TIM9 and 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 213 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.
Figure 213. Control circuit in normal mode, internal clock divided by 1
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External clock source mode 1(TIM9 and 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.

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RM0390

Figure 214. TI2 external clock connection example
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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 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 215. Control circuit in external clock mode 1
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RM0390

18.3.4

General-purpose timers (TIM9 to TIM14)

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 216 to Figure 218 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 216. Capture/compare channel (example: channel 1 input stage)
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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.

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RM0390

Figure 217. Capture/compare channel 1 main circuit
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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.

18.3.5

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

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General-purpose timers (TIM9 to TIM14)
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
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.

18.3.6

PWM input mode (only for TIM9/12)
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):

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RM0390

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.
Figure 219. PWM input mode timing
TI1

TIMx_CNT

0004

0000

0001

0002

TIMx_CCR1

0004

TIMx_CCR2

0002

IC1 capture
IC2 capture
reset counter

0003

0004

IC2 capture
pulse width
measurement

0000

IC1 capture
period
measurement
ai15413

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.

18.3.7

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.
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 ‘100’ 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.

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18.3.8

General-purpose timers (TIM9 to TIM14)

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=’000’), be set
active (OCxM=’001’), be set inactive (OCxM=’010’) or can toggle (OCxM=’011’) 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).

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 = ‘011’ 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 220.

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RM0390

Figure 220. Output compare mode, toggle on OC1.
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18.3.9

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.
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.

PWM edge-aligned mode
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 221 shows some edgealigned PWM waveforms in an example where TIMx_ARR=8.

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General-purpose timers (TIM9 to TIM14)
Figure 221. Edge-aligned PWM waveforms (ARR=8)



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18.3.10

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)

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RM0390

Figure 222. Example of one pulse mode.
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069

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).

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.

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.

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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.

18.3.11

TIM9/12 external trigger synchronization
The TIM9/12 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.

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RM0390

Figure 223. Control circuit in reset mode
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069

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:
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.

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Figure 224. Control circuit in gated mode
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069

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.
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 225. Control circuit in trigger mode
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18.3.12

RM0390

Timer synchronization (TIM9/12)
The TIM timers are linked together internally for timer synchronization or chaining. Refer to
Section 17.3.15: Timer synchronization for details.

18.3.13

Debug mode
When the microcontroller enters debug mode (Cortex®-M4 with FPU 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 33.16.2: Debug support
for timers, watchdog, bxCAN and I2C.

18.4

TIM9 and TIM12 registers
Refer to Section 1.1 on page 51 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).

18.4.1

TIM9/12 control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15

14

13

12

11

10

Res.

Res.

Res.

Res.

Res.

Res.

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 15:10 Reserved, must be kept at reset value.
Bits 9:8 CKD: 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.
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).

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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:
–
Counter overflow
–
Setting the UG bit
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.

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18.4.2

RM0390

TIM9/12 slave mode control register (TIMx_SMCR)
Address offset: 0x08
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MSM
rw

6

5

4

TS[2:0]
rw

rw

3

2

Res.
rw

1

0

SMS[2:0]
rw

rw

rw

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.
Bits 6:4 TS: 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 115 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 2:0 SMS: 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
descriptions.
000: Slave mode disabled - if CEN = 1 then the prescaler is clocked directly by the internal
clock
001: Reserved
010: Reserved
011: Reserved
100: Reset mode - Rising edge of the selected trigger input (TRGI) reinitializes the counter
and generates an update of the registers
101: 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. Counter starts and stops
are both controlled
110: Trigger mode - The counter starts on a rising edge of the trigger TRGI (but it is not
reset). Only the start of the counter is controlled
111: External clock mode 1 - Rising edges of the selected trigger (TRGI) clock the counter
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.

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Table 115. TIMx internal trigger connections

18.4.3

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

TIM9/12 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.

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18.4.4

RM0390

TIM9/12 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

Reserved, must be kept at reset value.

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

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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.

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18.4.5

RM0390

TIM9/12 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.
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.

18.4.6

TIM9/12 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.

15

14

Res.

13

12

OC2M[2:0]
IC2F[3:0]

rw

rw

rw

11

10

OC2PE OC2FE
IC2PSC[1:0]
rw

rw

rw

9

8

CC2S[1:0]
rw

rw

7

6

Res.

4

rw

rw

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3

2

OC1PE OC1FE

IC1F[3:0]

Output compare mode
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IC1PSC[1:0]
rw

rw

rw

1

0

CC1S[1:0]
rw

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RM0390

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Bit 15

Reserved, must be kept at reset value.

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 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: 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 the active levels of OC1 and OC1N
depend on the CC1P and CC1NP bits, respectively.
000: 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).
001: 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).
010: 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).
011: Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1
100: Force inactive level - OC1REF is forced low
101: Force active level - OC1REF is forced high
110: PWM mode 1 - In upcounting, channel 1 is active as long as TIMx_CNTTIMx_CCR1, else it is active (OC1REF=’1’)
111: PWM mode 2 - In upcounting, channel 1 is inactive as long as TIMx_CNTTIMx_CCR1
else it is inactive.
Note: In PWM mode 1 or 2, 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.

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RM0390

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 into account immediately
1: Preload register on TIMx_CCR1 enabled. Read/Write operations access the preload
register. TIMx_CCR1 preload value is loaded into the active register at each update event
Note: The PWM mode can be used without validating the preload register only in one-pulse
mode (OPM bit set in the 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 the counter and CCR1 values even when the
trigger is ON. The minimum delay to activate the 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 the CC1 output. Then,
OC is set to the compare level independently of the result of the comparison. Delay to
sample the trigger input and to activate CC1 output is reduced to 3 clock cycles. OC1FE
acts only if the channel is configured in PWM1 or PWM2 mode.
Bits 1:0 CC1S: Capture/Compare 1 selection
This bitfield 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 works only if an
internal trigger input is selected through the TS bit (TIMx_SMCR register)
Note: The CC1S bits are writable only when the channel is OFF (CC1E = 0 in TIMx_CCER).

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General-purpose timers (TIM9 to TIM14)

Input capture mode
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 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).
Bits 7:4 IC1F: Input capture 1 filter
This bitfield defines the frequency used to sample the 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 fDTS1000: fSAMPLING=fDTS/8, N=6
0001: fSAMPLING=fCK_INT, N=21001: fSAMPLING=fDTS/8, N=8
0010: fSAMPLING=fCK_INT, N=41010: fSAMPLING=fDTS/16, N=5
0011: fSAMPLING=fCK_INT, N=8 1011: fSAMPLING=fDTS/16, N=6
0100: fSAMPLING=fDTS/2, N=61100: fSAMPLING=fDTS/16, N=8
0101: fSAMPLING=fDTS/2, N=81101: fSAMPLING=fDTS/32, N=5
0110: fSAMPLING=fDTS/4, N=61110: fSAMPLING=fDTS/32, N=6
0111: fSAMPLING=fDTS/4, N=81111: fSAMPLING=fDTS/32, N=8
Bits 3:2 IC1PSC: Input capture 1 prescaler
This bitfield defines the ratio of the prescaler acting on the 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 bitfield 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: The CC1S bits are writable only when the channel is OFF (CC1E = 0 in TIMx_CCER).

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General-purpose timers (TIM9 to TIM14)

18.4.7

RM0390

TIM9/12 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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CC2NP

Res.

CC2P

CC2E

CC1NP

Res.

CC1P

CC1E

rw

rw

rw

rw

rw

rw

Bits 15:8 Reserved, must be kept at reset value.
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 complementary output Polarity
CC1 channel configured as output: CC1NP must be kept cleared
CC1 channel configured as input: CC1NP is used in conjunction with CC1P to define
TI1FP1/TI2FP1 polarity (refer to CC1P description).
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.
Note: 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.

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RM0390

General-purpose timers (TIM9 to TIM14)
Table 116. 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 states of the external I/O pins connected to the standard OCx channels depend on the
state of the OCx channel and on the GPIO registers.

18.4.8

TIM9/12 counter (TIMx_CNT)
Address offset: 0x24
Reset value: 0x0000 0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CNT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 CNT[15:0]: Counter value

18.4.9

TIM9/12 prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

rw

PSC[15:0]
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 into the active prescaler register at each update event.

18.4.10

TIM9/12 auto-reload register (TIMx_ARR)
Address offset: 0x2C
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

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 into the actual auto-reload register.
Refer to Section 18.3.1: Time-base unit for more details about ARR update and behavior.
The counter is blocked while the auto-reload value is null.

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18.4.11

RM0390

TIM9/12 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 into the actual capture/compare 1 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(OC1PE bit). Else the preload value is copied into the active capture/compare 1 register
when an update event occurs.
The active capture/compare register contains the value to be compared to the TIMx_CNT
counter and signaled on the OC1 output.
If channel CC1is configured as input:
CCR1 is the counter value transferred by the last input capture 1 event (IC1).

18.4.12

TIM9/12 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 into the actual capture/compare 2 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2 register
(OC2PE bit). Else the preload value is copied into the active capture/compare 2 register
when an update event occurs.
The active capture/compare register contains the value to be compared to the TIMx_CNT
counter and signalled on the OC2 output.
If channel CC2 is configured as input:
CCR2 is the counter value transferred by the last input capture 2 event (IC2).

614/1327

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0x30

Reserved

DocID026976 Rev 3
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
IC2
PSC
[1:0]
CC2S
[1:0]

0
0

0

0

0
0

0

Reset value

0

0
0

0
CC1NP Res.

0
Res.

0

CC2E

0

Res.

Res.
0

0

CC2P

OC2FE

0

Res.

OC2PE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IC2F[3:0]
CC2S
[1:0]

0

0

0

0

0

0

IC1F[3:0]

CC1G
UG

Res.

Res.

Res.

TG

Res.

0
0
0

PSC[15:0]
0
0
0

0

0

0

0

0

0

UIF

0

CC2IE
CC1IE
UIE

0
CC1IF

Res.

Res.

Res.

TIE

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

CC2IF

Res.

Res.

Res.

TIF

Res.

Res.

CC1OF

Res.
Res.

CC2OF

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.

CC2G

0
0
0
0

OC1FE

0
OC1PE

OC1M
[2:0]

CNT[15:0]

ARR[15:0]
Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

CC1E

0

Res.

0
0

0

0

0
0

0
0
0

0

0

0

0

0

0

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

Res.

Res.

Res.

0
0

0

CC2NP Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
URS
CEN

SMS[2:0]

UDIS

OPM
0

Res.

Res.

Res.

Res.

ARPE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MSM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TS[2:0]

Res.

0

Res.

Res.

Res.

Res.

Res.

0

0

Res.

0

Res.

Res.

Res.

Reset value
OC2M
[2:0]

0

CC1P

0

Res.

Res.

TIMx_CCER
Res.

Res.

Res.

Reset value
0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
CKD
[1:0]

Res.

0

Res.

Reset value

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.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_ARR

Res.

TIMx_PSC

Res.

TIMx_CNT

Res.

0x2C
TIMx_CCMR1
Input Capture
mode

Res.

0x28
Res.

TIMx_CCMR1
Output Compare
mode

Res.

0x24
Res.

0x20
Reserved

Res.

0x1C

Res.

0x18
TIMx_EGR

Res.

0x14
TIMx_SR

Res.

0x10
TIMx_DIER

Res.

0x0C
TIMx_SMCR

Res.

0x08
TIMx_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

Res.

Offset

Res.

18.4.13

Res.

RM0390
General-purpose timers (TIM9 to TIM14)

TIM9/12 register map
TIM9/12 registers are mapped as 16-bit addressable registers as described below:
Table 117. TIM9/12 register map and reset values

0
0
0

0
0
0

0
0
0

0
0
0

CC1
S
[1:0]

0
0
0
0

IC1
PSC
[1:0]
CC1
S
[1:0]

0
0
0
0
0

615/1327

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General-purpose timers (TIM9 to TIM14)

RM0390

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

DocID026976 Rev 3

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.

CCR2[15:0]

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

616/1327

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reserved

Res.

Reset value
0x3C to
0x4C

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_CCR2

Res.

0x38

0
Res.

Reset value

CCR1[15:0]

Res.

TIMx_CCR1

Res.

0x34

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 117. TIM9/12 register map and reset values (continued)

RM0390

General-purpose timers (TIM9 to TIM14)

18.5

TIM10/11/13/14 registers
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).

18.5.1

TIM10/11/13/14 control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15

14

13

12

11

10

Res.

Res.

Res.

Res.

Res.

Res.

9

8

CKD[1:0]
rw

7

6

5

4

3

2

1

0

ARPE

Res.

Res.

Res.

Res.

URS

UDIS

CEN

rw

rw

rw

rw

rw

Bits 15:10 Reserved, must be kept at reset value.
Bits 9:8 CKD: 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 6:3 Reserved, must be kept at reset value.
Bit 2 URS: Update request source
This bit is set and cleared by software to select the update interrupt (UEV) sources.
0: Any of the following events generate an UEV if enabled:
–
Counter overflow
–
Setting the UG bit
1: Only counter overflow generates an UEV if enabled.
Bit 1 UDIS: Update disable
This bit is set and cleared by software to enable/disable update interrupt (UEV) event
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

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General-purpose timers (TIM9 to TIM14)

18.5.2

RM0390

TIM10/11/13/14 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.

Res.

Res.

Res.

Res.

Res.

CC1IE

UIE

rw

rw

0

Bits 15:2

Reserved, must be kept at reset value.

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

18.5.3

TIM10/11/13/14 status register (TIMx_SR)
Address offset: 0x10
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

Res.

Res.

Res.

Res.

Res.

Res.

CC1OF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CC1IF

UIF

rc_w0

rc_w0

rc_w0

Bits 15:10

Reserved, must be kept at reset value.

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 8:2

618/1327

Reserved, must be kept at reset value.

DocID026976 Rev 3

RM0390

General-purpose timers (TIM9 to TIM14)

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.

18.5.4

TIM10/11/13/14 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.

Res.

Res.

Res.

Res.

Res.

CC1G

UG

w

w

Bits 15:2 Reserved, must be kept at reset value.
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 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 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-initialize 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.

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General-purpose timers (TIM9 to TIM14)

18.5.5

RM0390

TIM10/11/13/14 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 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.

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

5

4

OC1M[2:0]

rw

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rw

3

2

OC1PE OC1FE

IC1F[3:0]
rw

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IC1PSC[1:0]
rw

rw

rw

1

0

CC1S[1:0]
rw

rw

RM0390

General-purpose timers (TIM9 to TIM14)

Output compare mode
Bits 15:7

Reserved, must be kept at reset value.

Bits 6:4 OC1M: Output compare 1 mode
These bits define the behavior of the output reference signal OC1REF from which OC1 is
derived. OC1REF is active high whereas OC1 active level depends on CC1P bit.
000: Frozen. The comparison between the output compare register TIMx_CCR1 and the
counter TIMx_CNT has no effect on the outputs.
001: 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).
010: 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).
011: Toggle - OC1REF toggles when TIMx_CNT = TIMx_CCR1.
100: Force inactive level - OC1REF is forced low.
101: Force active level - OC1REF is forced high.
110: PWM mode 1 - Channel 1 is active as long as TIMx_CNT < TIMx_CCR1 else inactive.
111: PWM mode 2 - Channel 1 is inactive as long as TIMx_CNT < TIMx_CCR1 else active.
Note: In PWM mode 1 or 2, the OCREF level changes when the result of the comparison
changes or when the output compare mode switches from frozen to PWM mode.
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: 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. OC is then
set to the compare level independently of the result of the comparison. Delay to sample the
trigger input and to activate CC1 output is reduced to 3 clock cycles. OC1FE 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:
11:
Note: CC1S bits are writable only when the channel is OFF (CC1E = 0 in TIMx_CCER).

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General-purpose timers (TIM9 to TIM14)

RM0390

Input capture mode
Bits 15:8

Reserved, must be kept at reset value.

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 fDTS1000: fSAMPLING=fDTS/8, N=6
0001: fSAMPLING=fCK_INT, N=21001: fSAMPLING=fDTS/8, N=8
0010: fSAMPLING=fCK_INT, N=41010: fSAMPLING=fDTS/16, N=5
0011: fSAMPLING=fCK_INT, N=81011: fSAMPLING=fDTS/16, N=6
0100: fSAMPLING=fDTS/2, N=61100: fSAMPLING=fDTS/16, N=8
0101: fSAMPLING=fDTS/2, N=81101: fSAMPLING=fDTS/32, N=5
0110: fSAMPLING=fDTS/4, N=61110: fSAMPLING=fDTS/32, N=6
0111: fSAMPLING=fDTS/4, N=81111: 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: Reserved
11: Reserved
Note: CC1S bits are writable only when the channel is OFF (CC1E = 0 in TIMx_CCER).

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RM0390

General-purpose timers (TIM9 to TIM14)

18.5.6

TIM10/11/13/14 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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CC1NP

Res.

CC1P

CC1E

rw

rw

rw

Bits 15:4 Reserved, must be kept at reset value.
Bit 3 CC1NP: Capture/Compare 1 complementary output Polarity.
CC1 channel configured as output: CC1NP must be kept cleared.
CC1 channel configured as input: CC1NP bit is used in conjunction with CC1P to define
TI1FP1 polarity (refer to CC1P description).
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:
The CC1P bit selects TI1FP1 and TI2FP1 polarity for trigger or capture operations.
00: noninverted/rising edge
Circuit is sensitive to TI1FP1 rising edge (capture mode), TI1FP1 is not inverted.
01: inverted/falling edge
Circuit is sensitive to TI1FP1 falling edge (capture mode), TI1FP1 is inverted.
10: reserved, do not use this configuration.
11: noninverted/both edges
Circuit is sensitive to both TI1FP1 rising and falling edges (capture mode), TI1FP1 is not
inverted.
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 118. Output control bit for standard OCx channels
CCxE bit

Note:

OCx output state

0

Output Disabled (OCx=’0’, OCx_EN=’0’)

1

OCx=OCxREF + Polarity, OCx_EN=’1’

The state of the external I/O pins connected to the standard OCx channels depends on the
OCx channel state and the GPIO registers.

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General-purpose timers (TIM9 to TIM14)

18.5.7

RM0390

TIM10/11/13/14 counter (TIMx_CNT)
Address offset: 0x24
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

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CNT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 CNT[15:0]: Counter value

18.5.8

TIM10/11/13/14 prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

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.

18.5.9

TIM10/11/13/14 auto-reload register (TIMx_ARR)
Address offset: 0x2C
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

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 Section 18.3.1: Time-base unit for more details about ARR update and behavior.
The counter is blocked while the auto-reload value is null.

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RM0390

General-purpose timers (TIM9 to TIM14)

18.5.10

TIM10/11/13/14 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 CC1is configured as input:
CCR1 is the counter value transferred by the last input capture 1 event (IC1).

18.5.11

TIM11 option register 1 (TIM11_OR)
Address offset: 0x50
Reset value: 0x0000

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.

1

0

TI1_RMP[1:0]
rw

Bits 15:2
Bits 1:0

Reserved, must be kept at reset value.
TI1_RMP[1:0]: TIM11 Input 1 remapping capability
Set and cleared by software.
00,11: TIM11 Channel1 is connected to the GPIO (refer to the Alternate function mapping
table in the datasheets).
01: SPDIFRX_FRAME_SYNC is connected to TIM11_CH1 to measure the clock drift of
received SPDIF frames.
10: HSE_RTC clock (HSE divided by programmable prescaler) is connected to the
TIM11_CH1 input for measurement purposes.

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0x30

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Reserved

DocID026976 Rev 3

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.

Reset value

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.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_ARR

Res.

0x2C

TIMx_PSC

Res.

0x28
TIMx_CNT

Res.

0x24

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.

TIMx_CCER
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0

0
Res.

0

0
Res.

0

0
Res.

0

0
Res.

0

0
Res.

0

0
Res.
Res.

0

0
Res.
Res.
Res.

Res.

Reset value

0

0
0

0

0
0

0

0
0

IC1F[3:0]

Reset value
0
0
0

0
Res.

CC1S
[1:0]

CC1E

IC1
PSC
[1:0]

Res.

OC1FE

0

CC1P

0

Res.

0

OC1PE

OC1M
[2:0]

Res.

Reset value

0

UIF

Res.

Res.

Res.

Res.

0
0

UG

Reset value
CC1IF

0
CC1G

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CC1OF

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.
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.
CC1IE
UIE

Reset value
Res.

Reset value

Res.

URS
UDIS
CEN

Res.

Res.

Res.

Res.

ARPE

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.

Res.

Res.

Res.

Res.

Res.

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.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
CKD
[1:0]

CC1NP Res.

Reserved

Res.

0x20
TIMx_CCMR1
Input capture
mode

Res.

TIMx_CCMR1
Output compare
mode
Res.

TIMx_EGR

Res.

TIMx_SR

Res.

TIMx_DIER

Res.

0x1C
Res.

0x18

Res.

0x14

Res.

0x10

Res.

0x0C

Res.

TIMx_SMCR

Res.

0x08

Res.

TIMx_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.

18.5.12

Res.

General-purpose timers (TIM9 to TIM14)
RM0390

TIM10/11/13/14 register map
TIMx registers are mapped as 16-bit addressable registers as described in the table below:
Table 119. TIM10/11/13/14 register map and reset values

0
0
0

0
0

0
0

CC1S
[1:0]

0
0
0
0

0

0
0

CNT[15:0]

PSC[15:0]
0
0
0
0
0
0

0

0

0

0

0

0

ARR[15:0]

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.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Reset value
0

DocID026976 Rev 3

0
0
0
0
0
0
0
0

Reset value
0
0
0
0
0

0

Res.

0
Res.

Res.

Res.

TIMx_CCR1
Res.

Res.

Res.

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

Register

TI1_RMP

Res.

TIMx_OR
Res.

0x50
Reserved
Res.

0x38 to
0x4C
Res.

0x34

Res.

Offset

Res.

RM0390
General-purpose timers (TIM9 to TIM14)

Table 119. TIM10/11/13/14 register map and reset values (continued)

CCR1[15:0]
0

0

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

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Basic timers (TIM6&TIM7)

RM0390

19

Basic timers (TIM6&TIM7)

19.1

TIM6&TIM7 introduction
The basic timers TIM6 and TIM7 consist of a 16-bit auto-reload counter driven by a
programmable prescaler.
They may be used as generic timers for time-base generation but they are also specifically
used to drive the digital-to-analog converter (DAC). In fact, the timers are internally
connected to the DAC and are able to drive it through their trigger output.
The timers are completely independent, and do not share any resources.

19.2

TIM6&TIM7 main features
Basic timer (TIM6&TIM7) features include:
•

16-bit auto-reload upcounter

•

16-bit programmable prescaler used to divide (also “on the fly”) the counter clock
frequency by any factor between 1 and 65536

•

Synchronization circuit to trigger the DAC

•

Interrupt/DMA generation on the update event: counter overflow
Figure 226. Basic timer block diagram

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RM0390

Basic timers (TIM6&TIM7)

19.3

TIM6&TIM7 functional description

19.3.1

Time-base unit
The main block of the programmable timer is a 16-bit upcounter with its related auto-reload
register. 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. The preload register is accessed each time an
attempt is made to write or read the auto-reload register. The contents 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 the TIMx_CR1 register. The
update event is sent when the counter reaches the overflow value 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 the TIMx_CR1 register is set.
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 register (in the TIMx_PSC register).
It can be changed on the fly as the TIMx_PSC control register is buffered. The new
prescaler ratio is taken into account at the next update event.
Figure 227 and Figure 228 give some examples of the counter behavior when the prescaler
ratio is changed on the fly.

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Basic timers (TIM6&TIM7)

RM0390

Figure 227. Counter timing diagram with prescaler division change from 1 to 2
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Figure 228. Counter timing diagram with prescaler division change from 1 to 4
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19.3.2

Basic timers (TIM6&TIM7)

Counting mode
The counter counts from 0 to the auto-reload value (contents of the TIMx_ARR register),
then restarts from 0 and generates a counter overflow event.
An update event can be generate 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 the TIMx_CR1
register. This avoids updating the shadow registers while writing new values into the preload
registers. In this way, no update event occurs until the UDIS bit has been written to 0,
however, the counter and the prescaler counter both restart from 0 (but the prescale rate
does not change). In addition, if the URS (update request selection) bit in the TIMx_CR1
register is set, setting the UG bit generates an update event UEV, but the UIF flag is not set
(so no interrupt or DMA request is sent).
When an update event occurs, all the registers are updated and the update flag (UIF bit in
the TIMx_SR register) is set (depending on the URS bit):
•

The buffer of the prescaler is reloaded with the preload value (contents 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 229. Counter timing diagram, internal clock divided by 1
&.B,17

&17B(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU









  















&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ 8,)
069

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RM0390

Figure 230. Counter timing diagram, internal clock divided by 2
&.B,17
&17B(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU















&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ 8,)
069

Figure 231. Counter timing diagram, internal clock divided by 4
&.B,17
&17B(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU









&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ 8,)
06Y9

Figure 232. Counter timing diagram, internal clock divided by N
&.B,17

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU

)





&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ 8,)
06Y9

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Basic timers (TIM6&TIM7)
Figure 233. Counter timing diagram, update event when ARPE = 0
(TIMx_ARR not preloaded)
&.B,17
&17B(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU



            

&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ 8,)
$XWRUHORDGUHJLVWHU

))



:ULWHDQHZYDOXHLQ7,0[B$55
06Y9

Figure 234. Counter timing diagram, update event when ARPE=1
(TIMx_ARR preloaded)
&.B36&
&17B(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU

)

) ) ) ) )        

&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ 8,)
$XWRUHORDGSUHORDGUHJLVWHU

$XWRUHORDGVKDGRZUHJLVWHU

)



)



:ULWHDQHZYDOXHLQ7,0[B$55
06Y9

19.3.3

Clock source
The counter clock is provided by the Internal clock (CK_INT) source.
The CEN (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 for UG that remains cleared
automatically). As soon as the CEN bit is written to 1, the prescaler is clocked by the internal
clock CK_INT.
Figure 235 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.

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Figure 235. Control circuit in normal mode, internal clock divided by 1

,QWHUQDOFORFN
&(1 &17B(1
8*

&17B,1,7

&RXQWHUFORFN &.B&17 &.B36&
&RXQWHUUHJLVWHU









 



 

  




069

19.3.4

Debug mode
When the microcontroller enters the debug mode (Cortex®-M4 with FPU core - halted), the
TIMx counter either continues to work normally or stops, depending on the
DBG_TIMx_STOP configuration bit in the DBG module. For more details, refer to
Section 33.16.2: Debug support for timers, watchdog, bxCAN and I2C.

19.4

TIM6&TIM7 registers
Refer to Section 1.1 on page 51 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).

19.4.1

TIM6&TIM7 control register 1 (TIMx_CR1)
Address offset: 0x00
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.

ARPE

Res.

Res.

Res.

OPM

URS

UDIS

CEN

rw

rw

rw

rw

rw

Bits 15:8 Reserved, must be kept at reset value.
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.
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 CEN bit).

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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 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). 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: 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.
CEN is cleared automatically in one-pulse mode, when an update event occurs.

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19.4.2

RM0390

TIM6&TIM7 control register 2 (TIMx_CR2)
Address offset: 0x04
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

6

5

4

MMS[2:0]
rw

rw

3

2

1

0

Res.

Res.

Res.

Res.

rw

Bits 15:7 Reserved, must be kept at reset value.
Bits 6:4 MMS[2:0]: Master mode selection
These bits are used 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 a trigger output (TRGO). If
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 a 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 enabled. 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 the TIMx_SMCR
register).
010: Update - The update event is selected as a trigger output (TRGO). For instance a
master timer can then be used as a prescaler for a slave timer.
Bits 3:0 Reserved, must be kept at reset value.

19.4.3

TIM6&TIM7 DMA/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.

UDE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

UIE

rw

Bits 15:9 Reserved, must be kept at reset value.
Bit 8 UDE: Update DMA request enable
0: Update DMA request disabled.
1: Update DMA request enabled.
Bits 7:1 Reserved, must be kept at reset value.
Bit 0 UIE: Update interrupt enable
0: Update interrupt disabled.
1: Update interrupt enabled.

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Basic timers (TIM6&TIM7)

19.4.4

TIM6&TIM7 status register (TIMx_SR)
Address offset: 0x10
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.

Res.

Res.

Res.

Res.

Res.

Res.

UIF
rc_w0

Bits 15:1 Reserved, must be kept at reset value.
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 and if UDIS = 0 in the TIMx_CR1 register.
– When CNT is reinitialized by software using the UG bit in the TIMx_EGR register, if URS = 0
and UDIS = 0 in the TIMx_CR1 register.

19.4.5

TIM6&TIM7 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.

Res.

Res.

Res.

Res.

Res.

Res.

UG
w

Bits 15:1 Reserved, must be kept at reset value.
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 timer counter and generates an update of the registers. Note that the
prescaler counter is cleared too (but the prescaler ratio is not affected).

19.4.6

TIM6&TIM7 counter (TIMx_CNT)
Address offset: 0x24
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

CNT[15:0]
rw

rw

Bits 15:0

rw

rw

rw

rw

rw

rw

rw

CNT[15:0]: Counter value

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19.4.7

RM0390

TIM6&TIM7 prescaler (TIMx_PSC)
Address offset: 0x28
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

PSC[15:0]
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 into the active prescaler register at each update event.

19.4.8

TIM6&TIM7 auto-reload register (TIMx_ARR)
Address offset: 0x2C
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

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 into the actual auto-reload register.
Refer to Section 19.3.1: Time-base unit on page 629 for more details about ARR update and
behavior.
The counter is blocked while the auto-reload value is null.

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0x2C
TIMx_ARR
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_PSC

Res.

0x28
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0x20
Reserved
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

TIMx_CNT
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Reset value

Reset value

Reset value

DocID026976 Rev 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
Res.
Res.
Res.

Res.
Res.
Res.

0

Res.

ARR[15:0]
Res.

0

Res.

PSC[15:0]
Res.

0

Res.

CNT[15:0]
Res.

0
0
0
0
0
0

0
0
0
0
0
0

0

0

0

0

0

0

0

0

0

Reset value

Reset value
UG

Res.

Res.

UIF

Res.

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.
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.
UDE
Res.
Res.
Res.
Res.
Res.
Res.
Res.
UIE

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.

URS
UDIS
CEN

OPM

Res.

Res.

Res.

ARPE

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.

Res.

Res.

Res.

MMS[2:0]

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

TIMx_DIER
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.

Res.

Reserved

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.

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.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TIMx_EGR

Res.

0x14
TIMx_SR

Res.

0x10

Res.

Reserved

Res.

0x0C

Res.

0x1C

Res.

0x08
TIMx_CR2

Res.

Reserved

Res.

0x24
0x18

Res.

0x04
TIMx_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

Res.

Offset

Res.

19.4.9

Res.

RM0390
Basic timers (TIM6&TIM7)

TIM6&TIM7 register map
TIMx registers are mapped as 16-bit addressable registers as described in the table below:
Table 120. TIM6&TIM7 register map and reset values

0
0
0

0

0

0

0

Refer to Table 1 on page 56 for the register boundary addresses.

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20

Independent watchdog (IWDG)

20.1

IWDG introduction
The devices feature two embedded watchdog peripherals that offer a combination of high
safety level, timing accuracy and flexibility of use. Both watchdog peripherals (Independent
and Window) serve to detect and resolve malfunctions due to software failure, and to trigger
system reset or an interrupt (window watchdog only) when the counter reaches a given
timeout value.
The independent watchdog (IWDG) is clocked by its own dedicated low-speed clock (LSI)
and thus stays active even if the main clock fails. The window watchdog (WWDG) clock is
prescaled from the APB1 clock and has a configurable time-window that can be
programmed to detect abnormally late or early application behavior.
The IWDG is best suited for applications that require the watchdog to run as a totally
independent process outside the main application, but have lower timing accuracy
constraints. The WWDG is best suited for applications that require the watchdog to react
within an accurate timing window. For further information on the window watchdog, refer to
Section 21: Window watchdog (WWDG).

20.2

20.3

IWDG main features
•

Free-running downcounter

•

Clocked from an independent RC oscillator (can operate in Standby and Stop modes)

•

Reset (if watchdog activated) when the downcounter value of 0x000 is reached

IWDG functional description
Figure 236 shows the functional blocks of the independent watchdog module.
When the independent watchdog is started by writing the value 0xCCCC in the Key register
(IWDG_KR), the counter starts counting down from the reset value of 0xFFF. When it
reaches the end of count value (0x000) a reset signal is generated (IWDG reset).
Whenever the key value 0xAAAA is written in the IWDG_KR register, the IWDG_RLR value
is reloaded in the counter and the watchdog reset is prevented.

20.3.1

Hardware watchdog
If the “Hardware watchdog” feature is enabled through the device option bits, the watchdog
is automatically enabled at power-on, and will generate a reset unless the Key register is
written by the software before the counter reaches end of count.

20.3.2

Register access protection
Write access to the IWDG_PR and IWDG_RLR registers is protected. To modify them, you
must first write the code 0x5555 in the IWDG_KR register. A write access to this register
with a different value will break the sequence and register access will be protected again.
This implies that it is the case of the reload operation (writing 0xAAAA).

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Independent watchdog (IWDG)
A status register is available to indicate that an update of the prescaler or the down-counter
reload value is on going.

20.3.3

Debug mode
When the microcontroller enters debug mode (Cortex®-M4 with FPU core halted), the IWDG
counter either continues to work normally or stops, depending on DBG_IWDG_STOP
configuration bit in DBG module. For more details, refer to Section 34.16.4: Debug MCU
APB1 freeze register (DBGMCU_APB1_FZ).
Figure 236. Independent watchdog block diagram
#/2%
0RESCALER REGISTER
)7$'?02

3TATUS REGISTER
)7$'?32

2ELOAD REGISTER
)7$'?2,2

+EY REGISTER
)7$'?+2

 BIT RELOAD VALUE

 BIT
,3)
 K(Z PRESCALER

 BIT DOWNCOUNTER

)7$' RESET

6$$ VOLTAGE DOMAIN
-36

Note:

The watchdog function is implemented in the VDD voltage domain that is still functional in
Stop and Standby modes.
Table 121. Min/max IWDG timeout period at 32 kHz (LSI)(1)
Prescaler divider

PR[2:0] bits

Min timeout (ms) RL[11:0]=
0x000

Max timeout (ms) RL[11:0]=
0xFFF

/4

0

0.125

512

/8

1

0.25

1024

/16

2

0.5

2048

/32

3

1

4096

/64

4

2

8192

/128

5

4

16384

/256

6

8

32768

1. These timings are given for a 32 kHz clock but the microcontroller internal RC frequency can vary. Refers
to LSI oscillator characteristics table in device datasheet for from max and min values.

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20.4

RM0390

IWDG registers
Refer to Section 1.1 on page 51 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by half-words (16 bits) or words (32 bits).

20.4.1

Key register (IWDG_KR)
Address offset: 0x00
Reset value: 0x0000 0000 (reset by Standby mode)

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

w

w

w

w

w

w

w

KEY[15:0]
w

w

w

w

w

w

w

w

w

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 KEY[15:0]: Key value (write only, read 0000h)
These bits must be written by software at regular intervals with the key value AAAAh,
otherwise the watchdog generates a reset when the counter reaches 0.
Writing the key value 5555h to enable access to the IWDG_PR and IWDG_RLR registers
(see Section 20.3.2)
Writing the key value CCCCh starts the watchdog (except if the hardware watchdog option is
selected)

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Independent watchdog (IWDG)

20.4.2

Prescaler register (IWDG_PR)
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.

PR[2:0]
rw

rw

rw

Bits 31:3 Reserved, must be kept at reset value.
Bits 2:0 PR[2:0]: Prescaler divider
These bits are write access protected seeSection 20.3.2. They are written by software to
select the prescaler divider feeding the counter clock. PVU bit of IWDG_SR must be reset in
order to be able to change the prescaler divider.
000: divider /4
001: divider /8
010: divider /16
011: divider /32
100: divider /64
101: divider /128
110: divider /256
111: divider /256
Note: Reading this register returns the prescaler value from the VDD voltage domain. This
value may not be up to date/valid if a write operation to this register is ongoing. For this
reason the value read from this register is valid only when the PVU bit in the IWDG_SR
register is reset.

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20.4.3

RM0390

Reload register (IWDG_RLR)
Address offset: 0x08
Reset value: 0x0000 0FFF (reset by Standby mode)

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

rw

RL[11:0]
rw

Bits 31:12 Reserved, must be kept at reset value.
Bits11:0 RL[11:0]: Watchdog counter reload value
These bits are write access protected see Section 20.3.2. They are written by software to
define the value to be loaded in the watchdog counter each time the value AAAAh is written
in the IWDG_KR register. The watchdog counter counts down from this value. The timeout
period is a function of this value and the clock prescaler. Refer to Table 121.
The RVU bit in the IWDG_SR register must be reset in order to be able to change the reload
value.
Note: Reading this register returns the reload value from the VDD voltage domain. This value
may not be up to date/valid if a write operation to this register is ongoing on this
register. For this reason the value read from this register is valid only when the RVU bit
in the IWDG_SR register is reset.

20.4.4

Status register (IWDG_SR)
Address offset: 0x0C
Reset value: 0x0000 0000 (not reset by Standby mode)

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.

RVU

PVU

r

r

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 RVU: Watchdog counter reload value update
This bit is set by hardware to indicate that an update of the reload value is ongoing. It is reset
by hardware when the reload value update operation is completed in the VDD voltage domain
(takes up to 5 RC 40 kHz cycles).
Reload value can be updated only when RVU bit is reset.
Bit 0 PVU: Watchdog prescaler value update
This bit is set by hardware to indicate that an update of the prescaler value is ongoing. It is
reset by hardware when the prescaler update operation is completed in the VDD voltage
domain (takes up to 5 RC 40 kHz cycles).
Prescaler value can be updated only when PVU bit is reset.

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RM0390

Independent watchdog (IWDG)

Note:

If several reload values or prescaler values are used by application, it is mandatory to wait
until RVU bit is reset before changing the reload value and to wait until PVU bit is reset
before changing the prescaler value. However, after updating the prescaler and/or the
reload value it is not necessary to wait until RVU or PVU is reset before continuing code
execution (even in case of low-power mode entry, the write operation is taken into account
and will complete)

20.4.5

IWDG register map
The following table gives the IWDG register map and reset values.

Res.
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.

IWDG_PR

Res.

0x04

Res.

Reset value

KEY[15:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IWDG_KR

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 122. IWDG register map and reset values

PR[2:0]

Res.

0

0

0

1

1

1

1

1

1

1

1

1

1

1

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RVU

PVU

RL[11:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IWDG_SR

Res.

0x0C

Res.

Reset value

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IWDG_RLR

Res.

0x08

Res.

Reset value

0

0

0

Reset value

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

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Window watchdog (WWDG)

RM0390

21

Window watchdog (WWDG)

21.1

WWDG introduction
The window watchdog is used to detect the occurrence of a software fault, usually
generated by external interference or by unforeseen logical conditions, which causes the
application program to abandon its normal sequence. The watchdog circuit generates an
MCU reset on expiry of a programmed time period, unless the program refreshes the
contents of the downcounter before the T6 bit becomes cleared. An MCU reset is also
generated if the 7-bit downcounter value (in the control register) is refreshed before the
downcounter has reached the window register value. This implies that the counter must be
refreshed in a limited window.

21.2

WWDG main features
•

Programmable free-running downcounter

•

Conditional reset

•

21.3

–

Reset (if watchdog activated) when the downcounter value becomes less than
0x40

–

Reset (if watchdog activated) if the downcounter is reloaded outside the window
(see Figure 238)

Early wakeup interrupt (EWI): triggered (if enabled and the watchdog activated) when
the downcounter is equal to 0x40.

WWDG functional description
If the watchdog is activated (the WDGA bit is set in the WWDG_CR register) and when the
7-bit downcounter (T[6:0] bits) rolls over from 0x40 to 0x3F (T6 becomes cleared), it initiates
a reset. If the software reloads the counter while the counter is greater than the value stored
in the window register, then a reset is generated.

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Window watchdog (WWDG)
Figure 237. Watchdog block diagram
5(6(7

:DWFKGRJFRQILJXUDWLRQUHJLVWHU ::'*B&)5


FRPSDUDWRU
ZKHQ
7!:

: : : : : : :

:ULWH::'*B&5
:DWFKGRJFRQWUROUHJLVWHU ::'*B&5
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3&/.
IURP5&&FORFNFRQWUROOHU


7

7 7 7

7 7 7

ELWGRZQFRXQWHU &17

:'*SUHVFDOHU
:'*7%
06Y9

The application program must write in the WWDG_CR register at regular intervals during
normal operation to prevent an MCU reset. This operation must occur only when the counter
value is lower than the window register value. The value to be stored in the WWDG_CR
register must be between 0xFF and 0xC0.

Enabling the 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.

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 238). 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 238 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).

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.

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RM0390

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.

21.4

How to program the watchdog timeout
The formula in Figure 238 must be used 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 238. Window watchdog timing diagram
4;= #.4 DOWNCOUNTER

7;=

X&

4IME

2EFRESH NOT ALLOWED 2EFRESH ALLOWED
4 BIT
2%3%4

AIC

The formula to calculate the timeout value is given by:
t WWDG = t PCLK1 × 4096 × 2

WDGTB[1:0]

where:
tWWDG: WWDG timeout
tPCLK1: APB1 clock period measured in ms
4096: value corresponding to internal divider.

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× ( T5:0] + 1 )

( ms )

RM0390

Window watchdog (WWDG)
As an example, let us assume APB1 frequency is equal to 24 MHz, WDGTB[1:0] is set to 3
and T[5:0] is set to 63:
3
t WWDG = 1 ⁄ 24000 × 4096 × 2 × ( 63 + 1 ) = 21.85 ms
Refer to the datasheets for the minimum and maximum values of the tWWDG.

21.5

Debug mode
When the microcontroller enters debug mode (Cortex®-M4 with FPU core halted), the
WWDG counter either continues to work normally or stops, depending on
DBG_WWDG_STOP configuration bit in DBG module. For more details, refer to
Section 33.16.2: Debug support for timers, watchdog, bxCAN and I2C.

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21.6

RM0390

WWDG registers
Refer to Section 1.1 on page 51 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by half-words (16 bits) or words (32 bits).

21.6.1

Control register (WWDG_CR)
Address offset: 0x00
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

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WDGA

T[6:0]

rs

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. It is decremented every (4096 x
2WDGTB[1:0]) PCLK1 cycles. A reset is produced when it rolls over from 0x40 to 0x3F (T6
becomes cleared).

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Window watchdog (WWDG)

21.6.2

Configuration register (WWDG_CFR)
Address offset: 0x04
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.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

EWI

WDGTB[1:0]

W[6:0]

rs

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.
Bits 8:7 WDGTB[1:0]: Timer base
The time base of the prescaler can be modified as follows:
00: CK Counter Clock (PCLK1 div 4096) div 1
01: CK Counter Clock (PCLK1 div 4096) div 2
10: CK Counter Clock (PCLK1 div 4096) div 4
11: CK Counter Clock (PCLK1 div 4096) div 8
Bits 6:0 W[6:0]: 7-bit window value
These bits contain the window value to be compared to the downcounter.

21.6.3

Status register (WWDG_SR)
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.

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’. A write of ‘1’ has no effect. This bit is also set if the interrupt is not
enabled.

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WDGTB1
WDGTB0

0
0
0
1
1
1
1
1

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.

EWI

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WWDG_CFR

Res.

0x04
Reset value
0

Reset value

Refer to Section 2.2.2 on page 56 for the register boundary addresses.
1
1
1
1

W[6:0]

1
1

1
1

Res.

1

EWIF

WWDG_CR

Res.

0x00
WDGA

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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

Register

Res.

Offset

Res.

21.6.4

Res.

Window watchdog (WWDG)
RM0390

WWDG register map
The following table gives the WWDG register map and reset values.
Table 123. WWDG register map and reset values

T[6:0]

0

RM0390

Real-time clock (RTC)

22

Real-time clock (RTC)

22.1

Introduction
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 also includes an automatic wakeup unit to
manage low power modes.
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).

22.2

RTC main features
The RTC unit main features are the following (see Figure 239):
•

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.

•

Two programmable alarms with interrupt function. The alarms 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.

•

Maskable interrupts/events:

•

–

Alarm A

–

Alarm B

–

Wakeup interrupt

–

Timestamp

–

Tamper detection

Digital calibration circuit (periodic counter correction)
–

5 ppm accuracy

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–

RM0390

0.95 ppm accuracy, obtained in a calibration window of several seconds

•

Timestamp function for event saving (1 event)

•

Tamper detection:
–

2 tamper events with configurable filter and internal pull-up.

•

20 backup registers (80 bytes). The backup registers are reset when a tamper
detection event occurs.

•

Alternate function output (RTC_OUT) which selects one of the following two outputs:
–

RTC_CALIB: 512 Hz or 1 Hz clock output (with an LSE frequency of 32.768 kHz).
This output is enabled by setting the COE bit in the RTC_CR register. It is routed
to the device RTC_AF1 function.

–

RTC_ALARM (Alarm A, Alarm B or wakeup).
This output is selected by configuring the OSEL[1:0] bits in the RTC_CR register.
It is routed to the device RTC_AF1 function.

•

RTC alternate function inputs:
–

RTC_TS: timestamp event detection. It is routed to the device RTC_AF1 and
RTC_AF2 functions.

–

RTC_TAMP1: TAMPER1 event detection. It is routed to the device RTC_AF1 and
RTC_AF2 functions.

–

RTC_TAMP2: TAMPER2 event detection.

–

RTC_REFIN: reference clock input (usually the mains, 50 or 60 Hz).

Refer to Section 7.3.15: Selection of RTC additional functions.
Figure 239. RTC block diagram

24#?43
4IME STAMP
REGISTE RS

 (Z
 (Z
24##,+

24#?#!,)"

CK?APRE
DEFAULT  (Z

24#?02%2
!SYN CH
 BIT PRESCALER
DEFAULT  

#OARSE
#ALIBRATION
24#?#!,)"2

/UTPUT
CONTROL

24#?02%2
3YN CHRONOUS
 BIT PRESCALER
DEFAULT  

CK SPRE
DEFAULT  (Z

3HADOW REGISTER
,3%  (Z
(3%?24#
 -(Z MAX

43&

24#?332

3MOOTH
CALIBRATION
24#?#!,2

,3)



#ALENDAR

24#?/54
24#?!&

!,2!&

24#?!,!2-

3HADOW REGISTERS
24#?42
24#?$2

!LARM "
24#?!,2-"2
24#?!,2-"332
REGISTERS

75#+3%,;=
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!LARM !
24#?!,2-!2
24#?!,2-!332
REGISTERS



!,2"&

24#?!&

24#?7542
754&

 BIT WAKEUP
AUTO RELOAD TIMER

24#?4!-0
24#?4!-0

"ACKUP AND
24# TAMPER
CONTROL REGISTERS

4!-0%

43%

-36

1. On STM32F446xx devices, the RTC_AF1 and RTC_AF2 additional function are connected to PC13 and PA0, respectively.

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Real-time clock (RTC)

22.3

RTC functional description

22.3.1

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 6: 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 239: RTC block diagram):

Note:

•

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.
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 22.3.4 for details).

22.3.2

Real-time clock and calendar
The RTC calendar time and date registers are accessed through shadow registers which
are synchronized with PCLK1 (APB1 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

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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 22.6.4). 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.

22.3.3

Programmable alarms
The RTC unit provides two programmable alarms, Alarm A and Alarm B.
The programmable alarm functions are enabled through the ALRAIE and ALRBIE bits in the
RTC_CR register. The ALRAF and ALRBF flags are set to 1 if the calendar subseconds,
seconds, minutes, hours, date or day match the values programmed in the alarm registers
RTC_ALRMASSR/RTC_ALRMAR and RTC_ALRMBSSR/RTC_ALRMBR, respectively.
Each calendar field can be independently selected through the MSKx bits of the
RTC_ALRMAR and RTC_ALRMBR registers, and through the MASKSSx bits of the
RTC_ALRMASSR and RTC_ALRMBSSR registers. The alarm interrupts are enabled
through the ALRAIE and ALRBIE bits in the RTC_CR register.
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 polarity can be configured through bit POL in the
RTC_CR register.

Caution:

If the seconds field is selected (MSK0 bit reset in RTC_ALRMAR or RTC_ALRMBR), the
synchronous prescaler division factor set in the RTC_PRER register must be at least 3 to
ensure correct behavior.

22.3.4

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(32.768 kHz), this allows to configure the wakeup interrupt
period from 122 µs to 32 s, with a resolution down to 61µs.

•

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:

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–

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

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Real-time clock (RTC)
complete (see Programming the wakeup timer), 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_CR2
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 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.

22.3.5

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 with the
DBP bit of the PWR power control register (PWR_CR). The DBP bit must be set 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_ISR[13:8], RTC_TAFCR, and RTC_BKPxR.
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 from 1 to 2 RTCCLK clock cycles (due to clock
synchronization).

3.

To generate a 1 Hz clock for the calendar counter, program first the synchronous
prescaler factor in RTC_PRER register, and then program the asynchronous prescaler

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factor. Even if only one of the two fields needs to be changed, 2 separate write
accesses must be performed to the 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.

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 alarm (Alarm
A or Alarm B):

Note:

1.

Clear ALRAE or ALRBIE in RTC_CR to disable Alarm A or Alarm B.

2.

Poll ALRAWF or ALRBWF in RTC_ISR until it is set to make sure the access to alarm
registers is allowed. This takes 1 to 2 RTCCLK clock cycles (due to clock
synchronization).

3.

Program the Alarm A or Alarm B registers (RTC_ALRMASSR/RTC_ALRMAR or
RTC_ALRMBSSR/RTC_ALRMBR).

4.

Set ALRAE or ALRBIE in the RTC_CR register to enable Alarm A or Alarm B again.

Each change of the RTC_CR register is taken into account after 1 to 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):

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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 1 to 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. Due to clock synchronization, the WUTWF
bit is cleared up to 2 RTCCLK clocks cycles after WUTE is cleared.

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22.3.6

Real-time clock (RTC)

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 APB1
clock frequency (fPCLK1) must be equal to or greater than seven times the fRTCCLK RTC
clock frequency. This ensures a secure behavior of the synchronization mechanism.
If the APB1 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 APB1 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
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.

Note:

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): the software must
wait until RSF is set before reading the RTC_SSR, RTC_TR and RTC_DR registers.
After synchronization (refer to Section 22.3.8): 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.

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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 resetted 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 registers (RTC_CALIBR or RTC_CALR), the RTC shift register (RTC_SHIFTR),
the RTC timestamp registers (RTC_TSSSR, RTC_TSTR and RTC_TSDR), the RTC tamper
and alternate function configuration register (RTC_TAFCR), 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).
In addition, the RTC keeps on running under system reset if the reset source is different
from a backup domain reset. When a backup domain reset occurs, the RTC is stopped and
all the RTC registers are set to their reset values.

22.3.8

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’s 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’s output at 1 Hz. In this way, the frequency of the
asynchronous prescaler’s 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:

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This synchronization feature is not compatible with the reference clock detection feature:
firmware must not write to RTC_SHIFTR when REFCKON=1.

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22.3.9

Real-time clock (RTC)

RTC reference clock detection
The RTC calendar update can be synchronized to a reference clock RTC_REFIN, usually
the mains (50 or 60 Hz). The RTC_REFIN reference clock should have a higher precision
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 reference 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
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 asynchronous prescaler which
outputs the ck_apre 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 reference clock detection is enabled, PREDIV_A and PREDIV_S must be set to
their default values:
•

PREDIV_A = 0x007F

•

PREDIV_S = 0x00FF

Note:

The reference clock detection is not available in Standby mode.

Caution:

The reference clock detection feature cannot be used in conjunction with the coarse digital
calibration: RTC_CALIBR must be kept at 0x0000 0000 when REFCKON=1.

22.3.10

RTC coarse digital calibration
Two digital calibration methods are available: coarse and smooth calibration. To perform
coarse calibration refer to Section 22.6.7: RTC calibration register (RTC_CALIBR).
The two calibration methods are not intended to be used together, the application must
select one of the two methods. Coarse calibration is provided for compatibly reasons. To
perform smooth calibration refer to Section 22.3.11: RTC smooth digital calibration and to
Section 22.6.16: RTC calibration register (RTC_CALR)
The coarse digital calibration can be used to compensate crystal inaccuracy by adding
(positive calibration) or masking (negative calibration) clock cycles at the output of the
asynchronous prescaler (ck_apre).
Positive and negative calibration are selected by setting the DCS bit in RTC_CALIBR
register to ‘0’ and ‘1’, respectively.

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When positive calibration is enabled (DCS = ‘0’), 2 ck_apre cycles are added every minute
(around 15360 ck_apre cycles) for 2xDC minutes. This causes the calendar to be updated
sooner, thereby adjusting the effective RTC frequency to be a bit higher.
When negative calibration is enabled (DCS = ‘1’), 1 ck_apre cycle is removed every minute
(around 15360 ck_apre cycles) for 2xDC minutes. This causes the calendar to be updated
later, thereby adjusting the effective RTC frequency to be a bit lower.
DC is configured through bits DC[4:0] of RTC_CALIBR register. This number ranges from 0
to 31 corresponding to a time interval (2xDC) ranging from 0 to 62.
The coarse digital calibration can be configured only in initialization mode, and starts when
the INIT bit is cleared. The full calibration cycle lasts 64 minutes. The first 2xDC minutes of
the 64 -minute cycle are modified as just described.
Negative calibration can be performed with a resolution of about 2 ppm while positive
calibration can be performed with a resolution of about 4 ppm. The maximum calibration
ranges from -63 ppm to 126 ppm.
The calibration can be performed either on the LSE or on the HSE clock.
Caution:

Digital calibration may not work correctly if PREDIV_A < 6.

Case of RTCCLK=32.768 kHz and PREDIV_A+1=128
The following description assumes that ck_apre frequency is 256 Hz obtained with an LSE
clock nominal frequency of 32.768 kHz, and PREDIV_A set to 127 (default value).
The ck_spre clock frequency is only modified during the first 2xDC minutes of the 64-minute
cycle. For example, when DC equals 1, only the first 2 minutes are modified. This means
that the first 2xDC minutes of each 64-minute cycle have, once per minute, one second
either shortened by 256 or lengthened by 128 RTCCLK cycles, given that each ck_apre
cycle represents 128 RTCCLK cycles (with PREDIV_A+1=128).
Therefore each calibration step has the effect of adding 512 or subtracting 256 oscillator
cycles for every 125829120 RTCCLK cycles (64min x 60 s/min x 32768 cycles/s). This is
equivalent to +4.069 ppm or-2.035 ppm per calibration step. As a result, the calibration
resolution is +10.5 or -5.27 seconds per month, and the total calibration ranges from +5.45
to -2.72 minutes per month.
In order to measure the clock deviation, a 512 Hz clock is output for calibration.Refer to
Section 22.3.14: Calibration clock output.

22.3.11

RTC smooth digital calibration
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.

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Real-time clock (RTC)
The smooth calibration register (RTC_CALR) specifies the number of RTCCLK clock cycles
to be masked during the 32-second cycle:

Note:

•

Setting the bit CALM[0] to 1 causes exactly one pulse to be masked during the 32second cycle.

•

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_CALRx) 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.
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.

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Verifying the RTC calibration
RTC precision is performed 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 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:

22.3.12

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.

Timestamp function
Timestamp is enabled by setting the TSE bit of RTC_CR register to 1.
The calendar is saved in the timestamp registers (RTC_TSSSR, RTC_TSTR, RTC_TSDR)
when a timestamp event is detected on the pin to which the TIMESTAMP alternate function
is mapped. When a timestamp event occurs, the timestamp flag bit (TSF) in RTC_ISR
register is set.
By setting the TSIE bit in the RTC_CR register, an interrupt is generated when a timestamp
event occurs.

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If a new timestamp event is detected while the timestamp flag (TSF) is already set, the
timestamp overflow flag (TSOVF) flag is set and the timestamp registers (RTC_TSTR and
RTC_TSDR) maintain the results of the previous event.

Note:

TSF is set 2 ck_apre cycles after the timestamp event occurs due to synchronization
process.
There is no delay in the setting of TSOVF. This means that if two timestamp 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 timestamp event occurs immediately after the TSF bit is supposed to be cleared, then
both TSF and TSOVF bits are set. To avoid masking a timestamp event occurring at the
same moment, the application must not write ‘0’ into TSF bit unless it has already read it to
‘1’.
Optionally, a tamper event can cause a timestamp to be recorded. See the description of the
TAMPTS control bit in Section 22.6.17: RTC tamper and alternate function configuration
register (RTC_TAFCR). If the timestamp event is on the same pin as a tamper event
configured in filtered mode (TAMPFLT set to a non-zero value), the timestamp on tamper
detection event mode must be selected by setting TAMPTS='1' in RTC_TAFCR register.

TIMESTAMP alternate function
The TIMESTAMP alternate function (RTC_TS) can be mapped either to RTC_AF1 or to
RTC_AF2 depending on the value of the TSINSEL bit in the RTC_TAFCR register (see
Section 22.6.17: RTC tamper and alternate function configuration register (RTC_TAFCR)).
Mapping the timestamp event on RTC_AF2 is not allowed if RTC_AF1 is used as TAMPER
in filtered mode (TAMPFLT set to a non-zero value).

22.3.13

Tamper detection
Two tamper detection inputs are available. They can be configured either for edge detection,
or for level detection with filtering.

RTC backup registers
The backup registers (RTC_BKPxR) are twenty 32-bit registers for storing 80 bytes of user
application data. They are implemented in the backup domain that remains powered-on by
VBAT when the VDD power is switched off. They are not reset by system reset or when the
device wakes up from Standby mode. They are reset by a backup domain reset
The backup registers are reset when a tamper detection event occurs (see Section 22.6.20:
RTC backup registers (RTC_BKPxR) and Tamper detection initialization on page 665.

Tamper detection initialization
Each tamper detection input is associated with the TAMP1F/TAMP2F flags in the RTC_ISR2
register. Each input can be enabled by setting the corresponding TAMP1E/TAMP2E bits to 1
in the RTC_TAFCR register.
A tamper detection event resets all backup registers (RTC_BKPxR).
By setting the TAMPIE bit in the RTC_TAFCR register, an interrupt is generated when a
tamper detection event occurs.

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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 (TAMP1F, TAMP2F) is set at the
same time that TSF or TSOVF is set.

Edge detection on tamper inputs
If the TAMPFLT bits are “00”, the TAMPER pins generate tamper detection events
(RTC_TAMP[2:1]) when either a rising edge is observed or an falling edge is observed
depending on the corresponding TAMPxTRG bit. The internal pull-up resistors on the
TAMPER inputs are deactivated when edge detection is selected.
Caution:

To avoid losing tamper detection events, the signal used for edge detection is logically
ANDed with TAMPxE in order to detect a tamper detection event in case it occurs before the
TAMPERx pin is enabled.
•

When TAMPxTRG = 0: if the TAMPERx alternate function is already high before
tamper detection is enabled (TAMPxE bit set to 1), a tamper event is detected as soon
as TAMPERx is enabled, even if there was no rising edge on TAMPERx after TAMPxE
was set.

•

When TAMPxTRG = 1: if the TAMPERx alternate function is already low before tamper
detection is enabled, a tamper event is detected as soon as TAMPERx is enabled
(even if there was no falling edge on TAMPERx after TAMPxE was set.

After a tamper event has been detected and cleared, the TAMPERx alternate function
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 TAMPERx value still indicates a tamper detection. This is equivalent to a
level detection on the TAMPERx alternate function.
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 TAMPER alternate function is mapped should
be externally tied to the correct level.

Level detection with filtering on tamper 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
(TAMP1TRG/TAMP2TRG).
The TAMPER inputs are pre-charged 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 tamper
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.
Note:

Refer to the datasheets for the electrical characteristics of the pull-up resistors.

TAMPER alternate function detection
The TAMPER1 alternate function (RTC_TAMP1) can be mapped either to RTC_AF1(PC13)
or RTC_AF2 (PA0) depending on the value of TAMP1INSEL bit in RTC_TAFCR register
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Real-time clock (RTC)
(see Section 22.6.17). TAMPE bit must be cleared when TAMP1INSEL is modified to avoid
unwanted setting of TAMPF.
The TAMPER 2 alternate function corresponds to RTC_TAMP2 pin.

22.3.14

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 output is not impacted by the calibration value programmed in
RTC_CALIBR register. The RTC_CALIB duty cycle is irregular: there is a light jitter on falling
edges. It is therefore recommended to use rising edges.
If 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.

Calibration alternate function output
When the COE bit in the RTC_CR register is set to 1, the calibration alternate function
(RTC_CALIB) is enabled on RTC_AF1.
Note:

When RTC_CALIB or RTC_ALARM is selected, RTC_AF1 is automatically configured in
output alternate function.

22.3.15

Alarm output
Three functions can be selected on Alarm output: ALRAF, ALRBF and WUTF. These
functions reflect the contents of the corresponding flags in the RTC_ISR register.
The OSEL[1:0] control bits in the RTC_CR register are used to activate the alarm alternate
function output (RTC_ALARM) in RTC_AF1, and to select the function which is output on
RTC_ALARM.
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 alternate function output
RTC_ALARM can be configured in output open drain or output push-pull using the control
bit ALARMOUTTYPE in the RTC_TAFCR register.
Note:

Once RTC_ALARM is enabled, it has priority over RTC_CALIB (COE bit is don't care on
RTC_AF1).
When RTC_CALIB or RTC_ALARM is selected, RTC_AF1 is automatically configured in
output alternate function.

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22.4

RM0390

RTC and low power modes
Table 124. 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 time stamp 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 time stamp event, and RTC Wakeup cause the device to exit the
Standby mode.

22.5

RTC interrupts
All RTC interrupts are connected to the EXTI controller.
To enable the RTC Alarm interrupt, the following sequence is required:
1.

Configure and enable the EXTI Line 17 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 (Alarm A or Alarm B).

To enable the RTC Wakeup interrupt, the following sequence is required:
1.

Configure and enable the EXTI Line 22 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 generate the RTC wakeup timer event.

To enable the RTC Tamper interrupt, the following sequence is required:
1.

Configure and enable the EXTI Line 21 in interrupt mode and select the rising edge
sensitivity.

2.

Configure and Enable the 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:

668/1327

1.

Configure and enable the EXTI Line 21 in interrupt mode and select the rising edge
sensitivity.

2.

Configure and Enable the TAMP_STAMP IRQ channel in the NVIC.

3.

Configure the RTC to detect the RTC timestamp event.

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Table 125. Interrupt control bits
Event flag

Enable
control
bit

Exit the
Sleep
mode

Exit the
Stop
mode

Exit the
Standby
mode

Alarm A

ALRAF

ALRAIE

yes

yes(1)

yes(1)

Alarm B

ALRBF

ALRBIE

yes

yes(1)

yes(1)

Wakeup

WUTF

WUTIE

yes

yes(1)

yes(1)

TSF

TSIE

yes

yes(1)

yes(1)

Tamper1 detection

TAMP1F

TAMPIE

yes

yes(1)

yes(1)

Tamper2 detection(2)

TAMP2F

TAMPIE

yes

yes(1)

yes(1)

Interrupt event

TimeStamp

1. Wakeup from STOP and Standby modes is possible only when the RTC clock source is LSE or LSI.
2. If RTC_TAMPER2 pin is present. Refer to device datasheet pinout.

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22.6

RM0390

RTC registers
Refer to Section 1.1 on page 51 of this reference manual for a list of abbreviations used in
register descriptions.
The peripheral registers have to be accessed by words (32 bits).

22.6.1

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 and Reading the
calendar.
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

15

14

Res.

13

12

11

MNT[2:0]
rw

rw

10

9

8

MNU[3:0]
rw

rw

rw

19

18

HT[1:0]

17

16

HU[3:0]

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

7

rw

20

rw

Res.

rw

21

ST[2:0]
rw

rw

SU[3:0]
rw

rw

rw

Bits 31-24 Reserved, must be kept at reset value
Bit 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

Note:

670/1327

This register is write protected. The write access procedure is described in RTC register
write protection on page 657.

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22.6.2

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 and Reading the
calendar.
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

12

11

10

9

8

rw

rw

rw

rw

WDU[2:0]
rw

rw

MT
rw

rw

MU[3:0]

23

22

21

20

19

18

YT[3:0]

17

16

YU[3:0]

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

Res.

Res.

rw

rw

rw

rw

rw

DT[1:0]
rw

DU[3:0]

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

Note:

This register is write protected. The write access procedure is described in RTC register
write protection.

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22.6.3

RM0390

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.

Res.

COE

15

14

13

12

11

10

9

8

TSIE
rw

WUTIE ALRBIE ALRAIE
rw

rw

rw

TSE
rw

WUTE ALRBE ALRAE
rw

rw

rw

22

21

OSEL[1:0]

20

19

POL

COSEL

18

17

16

BKP SUB1H ADD1H

rw

rw

rw

rw

rw

rw

w

w

7

6

5

4

3

2

1

0

DCE

FMT

rw

rw

BYPSHAD REFCKON TSEDGE
rw

rw

rw

WUCKSEL[2:0]
rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
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
1: Calibration output is 1 Hz
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 22.3.14: 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.
Bit 17 SUB1H: Subtract 1 hour (winter time change)
When this bit is set outside initialization mode, 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.

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Bit 16 ADD1H: Add 1 hour (summer time change)
When this bit is set outside initialization mode, 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
Bit 15 TSIE: Timestamp interrupt enable
0: Timestamp Interrupt disable
1: Timestamp 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: Time stamp enable
0: Time stamp disable
1: Time stamp enable
Bit 10 WUTE: Wakeup timer enable
0: Wakeup timer disabled
1: Wakeup timer enabled
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 DCE: Coarse digital calibration enable
0: Digital calibration disabled
1: Digital calibration enabled
PREDIV_A must be 6 or greater
Bit 6 FMT: Hour format
0: 24 hour/day format
1: AM/PM hour format
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 APB1 clock is less than seven times the frequency of RTCCLK,
BYPSHAD must be set to ‘1’.

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RM0390

Bit 4 REFCKON: Reference clock detection enable (50 or 60 Hz)
0: Reference clock detection disabled
1: Reference clock detection enabled
Note: PREDIV_S must be 0x00FF.
Bit 3 TSEDGE: Timestamp event active edge
0: TIMESTAMP rising edge generates a timestamp event
1: TIMESTAMP falling edge generates a timestamp 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:

WUT = Wakeup unit counter value. WUT = (0x0000 to 0xFFFF) + 0x10000 added when
WUCKSEL[2:1 = 11].
Bits 7, 6 and 4 of this register can be written in initialization mode only (RTC_ISR/INITF = 1).
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 657.

22.6.4

RTC initialization and status register (RTC_ISR)
Address offset: 0x0C
Backup domain reset value: 0x0000 0007
System reset value: Not affected except INIT, INITF and RSF 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.

Res.

RECALPF
r

15

14

Res.

TAMP2F
rc_w0

13

12

TAMP1F TSOVF
rc_w0

rc_w0

11

10

TSF

WUTF

ALRBF ALRAF

9

8

rc_w0

rc_w0

rc_w0

7

6

5

INIT

INITF

RSF

rw

r

rc_w0

rc_w0

4

3

2

1

0

INITS SHPF WUT WF ALRB WF ALRA WF
r

r

r

r

r

Bits 31:17 Reserved, must be kept at reset value
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 Reserved, must be kept at reset value.

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Bit 14 TAMP2F: TAMPER2 detection flag
This flag is set by hardware when a tamper detection event is detected on tamper input 2.
It is cleared by software writing 0.
Bit 13 TAMP1F: Tamper detection flag
This flag is set by hardware when a tamper detection event is detected.
It is cleared by software writing 0.
Bit 12 TSOVF: Timestamp overflow flag
This flag is set by hardware when a timestamp 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: Timestamp flag
This flag is set by hardware when a timestamp event occurs.
This flag is cleared by software by writing 0.
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.
0: Calendar shadow registers not yet synchronized
1: Calendar shadow registers synchronized

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RM0390

Bit 4 INITS: Initialization status flag
This bit is set by hardware when the calendar year field is different from 0 (backup domain
reset value 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. It is cleared by hardware when the corresponding shift operation has been
executed. Writing to SHPF has no effect.
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. It 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 ALRBIE 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 ALRAF, ALRBF, WUTF and TSF bits are cleared 2 APB clock cycles after programming
them to 0.
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 657.

22.6.5

RTC prescaler register (RTC_PRER)
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

Res.

21

20

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

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rw

rw

rw

rw

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Real-time clock (RTC)

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)

Note:

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 657
This register is write protected. The write access procedure is described in RTC register
write protection on page 657.

22.6.6

RTC wakeup timer register (RTC_WUTR)
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

WUT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

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.
Note: 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.

Note:

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 657.

22.6.7

RTC calibration register (RTC_CALIBR)
Address offset: 0x18
Backup domain reset value: 0x0000 0000
System reset: not affected

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Real-time clock (RTC)

RM0390

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

rw

rw

15

14

13

12

11

10

9

8

7

6

5

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DCS

Res.

Res.

rw

DC[4:0]
rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value
Bit 7 DCS: Digital calibration sign
0: Positive calibration: calendar update frequency is increased
1: Negative calibration: calendar update frequency is decreased
Bits 6:5 Reserved, must be kept at reset value.
Bits 4:0 DC[4:0]: Digital calibration
DCS = 0 (positive calibration)
00000: +0 ppm
00001: +4 ppm (rounded value)
00010: +8 ppm (rounded value)
..
11111: +126 ppm (rounded value)
DCS = 1 (negative calibration)
00000: -0 ppm
00001: -2 ppm (rounded value)
00010: -4 ppm (rounded value)
..
11111: - 63 ppm (rounded value)
Refer to Case of RTCCLK=32.768 kHz and PREDIV_A+1=128 for the exact step value.

Note:

This register can be written in initialization mode only (RTC_ISR/INITF = ‘1’).
This register is write protected. The write access procedure is described in RTC register
write protection on page 657.

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RM0390

Real-time clock (RTC)

22.6.8

RTC alarm A register (RTC_ALRMAR)
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

MSK1

rw

rw

rw

ST[2:0]
rw

rw

SU[3:0]
rw

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.

Note:

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 657.

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Real-time clock (RTC)

22.6.9

RM0390

RTC alarm B register (RTC_ALRMBR)
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

Note:

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 657.

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RM0390

Real-time clock (RTC)

22.6.10

RTC write protection register (RTC_WPR)
Address offset: 0x24
Backup domain 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

w

KEY

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.

22.6.11

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.

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

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 in the synchronous prescaler’s 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.

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RM0390

RTC shift control register (RTC_SHIFTR)
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’s 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.
Refer to Section 22.3.8: RTC synchronization.

Note:

682/1327

This register is write protected. The write access procedure is described in RTC register
write protection on page 657

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RM0390

Real-time clock (RTC)

22.6.13

RTC time stamp time register (RTC_TSTR)
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

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

Res.

MNT[2:0]
r

r

MNU[3:0]

Res.

r

21

20

19

18

HT[1:0]

ST[2:0]

r

r

r

17

16

HU[3:0]

SU[3:0]
r

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.

Note:

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.

22.6.14

RTC time stamp date register (RTC_TSDR)
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

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r

DU[3:0]
r

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RM0390

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

Note:

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.

22.6.15

RTC timestamp sub second register (RTC_TSSSR)
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.

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

SS[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 Reserved
Bits 15:0 SS: Sub second value
SS[15:0] is the value of the synchronous prescaler’s counter when the timestamp event
occurred.

Note:

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.

22.6.16

RTC calibration register (RTC_CALR)
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.

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

rw

rw

rw

rw

rw

rw

rw

rw

CALP

CALW8 CALW16

rw

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RM0390

Real-time clock (RTC)

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 22.3.11: 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.
CALM[1:0] are stuck at “00” when CALW8=’1’.
Refer to Section 22.3.11: 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 22.3.11: 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 22.3.11: RTC smooth digital calibration on page 662.

Note:

This register is write protected. The write access procedure is described in RTC register
write protection.

22.6.17

RTC tamper and alternate function configuration register
(RTC_TAFCR)
Address offset: 0x40
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.

ALARMOUT
TYPE

TSIN
SEL

TAMP1I
NSEL

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

TAMP
PUDIS
rw

TAMP
PRCH[1:0]
rw

rw

TAMP
FLT[1:0]
rw

rw

TAMP
FREQ[2:0]
rw

rw

TAMPTS
rw

Res.

Res.

rw

DocID026976 Rev 3

TAMP2
TAMP2E
TRG
rw

rw

TAMPIE
rw

TAMP1TRG TAMP1E
rw

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RM0390

Bits 31:19 Reserved, must be kept at reset value. Always read as 0.
Bit 18 ALARMOUTTYPE: RTC_ALARM output type
0: RTC_ALARM is an open-drain output
1: RTC_ALARM is a push-pull output
Bit 17 TSINSEL: TIMESTAMP mapping
0: RTC_AF1 used as TIMESTAMP
1: RTC_AF2 used as TIMESTAMP
Bit 16 TAMP1INSEL: TAMPER1 mapping
0: RTC_AF1 used as TAMPER1
1: RTC_AF2 used as TAMPER1
Note: TAMP1E must be reset when TAMP1INSEL is changed to avoid unwanted setting of
TAMP1F.
Bit 15 TAMPPUDIS: TAMPER pull-up disable
This bit determines if each of the tamper pins are pre-charged before each sample.
0: Precharge tamper pins before sampling (enable internal pull-up)
1: Disable precharge of tamper pins
Note:
Bits 14:13 TAMPPRCH[1:0]: Tamper 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 tamper inputs.
0x0: 1 RTCCLK cycle
0x1: 2 RTCCLK cycles
0x2: 4 RTCCLK cycles
0x3: 8 RTCCLK cycles
Bits 12:11 TAMPFLT[1:0]: Tamper filter count
These bits determines the number of consecutive samples at the specified level
(TAMP*TRG) necessary to activate a Tamper event. TAMPFLT is valid for each of the tamper
inputs.
0x0: Tamper is activated on edge of tamper input transitions to the active level (no internal
pull-up on tamper input).
0x1: Tamper is activated after 2 consecutive samples at the active level.
0x2: Tamper is activated after 4 consecutive samples at the active level.
0x3: Tamper 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 tamper 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.

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RM0390

Real-time clock (RTC)

Bits 6:5 Reserved. Always read as 0.
Bit 4 TAMP2TRG: Active level for tamper 2
if TAMPFLT != 00
0: TAMPER2 staying low triggers a tamper detection event.
1: TAMPER2 staying high triggers a tamper detection event.
if TAMPFLT = 00:
0: TAMPER2 rising edge triggers a tamper detection event.
1: TAMPER2 falling edge triggers a tamper detection event.
Bit 3 TAMP2E: Tamper 2 detection enable
0: Tamper 2 detection disabled
1: Tamper 2 detection enabled
Bit 2 TAMPIE: Tamper interrupt enable
0: Tamper interrupt disabled
1: Tamper interrupt enabled
Bit 1 TAMP1TRG: Active level for tamper 1
if TAMPFLT != 00:
0: TAMPER1 staying low triggers a tamper detection event.
1: TAMPER1 staying high triggers a tamper detection event.
if TAMPFLT = 00:
0: TAMPER1 rising edge triggers a tamper detection event.
1: TAMPER1 falling edge triggers a tamper detection event.
Caution: When TAMPFLT = 0, TAMP1E must be reset when TAMP1TRG is changed to avoid
spuriously setting TAMP1F.
Bit 0 TAMP1E: Tamper 1 detection enable
0: Tamper 1 detection disabled
1: Tamper 1 detection enabled

22.6.18

RTC alarm A sub second register (RTC_ALRMASSR)
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

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Real-time clock (RTC)

RM0390

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.
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’s counter to
determine if Alarm A is to be activated. Only bits 0 up MASKSS-1 are compared.

Note:

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 657

22.6.19

RTC alarm B sub second register (RTC_ALRMBSSR)
Address offset: 0x48
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

r

r

r

r

rw

rw

rw

rw

15

14

13

12

11

10

9

8

MASKSS[3:0]

Res.
r

688/1327

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

r

r

r

r

r

r

r

7

6

5

4

3

2

1

0

rw

rw

rw

rw

w

rw

rw

SS[14:0]
rw

rw

rw

rw

rw

rw

rw

rw

DocID026976 Rev 3

RM0390

Real-time clock (RTC)

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’s counter to
determine if Alarm B is to be activated. Only bits 0 up to MASKSS-1 are compared.

Note:

This register can be written only when ALRBIE 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

22.6.20

RTC backup registers (RTC_BKPxR)
Address offset: 0x50 to 0x9C
Backup domain reset value: 0x0000 0000
System reset: not affected

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

w

rw

rw

BKP[31:16]

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.

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Real-time clock (RTC)

22.6.21

RM0390

RTC register map

0

0

YT[3:0]

0

0

0

YU[3:0]

Res.

TSE

WUTE

ALRBE

ALRAE

DCE

FMT

BYPSHAD

REFCKON

TSEDGE

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

TAMP2F

TAMP1F

TSOVF

TSF

WUTF

ALRBF

ALRAF

INIT

INITF

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.
Res.

0

1

0

0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

WUT[15:0]
1

1

1

1

1

1

1

1

1

1

1
Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RTC_WPR

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

HU[3:0]

0

0

MNT[2:0]

0

0

0

0

MNU[3:0]
0

0

0

0

MNU[3:0]

ST[2:0]

0

0

ST[2:0]

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

SU[3:0]
0

0

0

0

SU[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

0

0

0

0

0

0

SUBFS[14:0]
0

DocID026976 Rev 3

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Reset value

Res.

RTC_SHIFTR

0

0

0

SS[15:0]
0

ADD1S

Reset value

0

0

KEY[7:0]
0

Res.

Reset value

0

MSK1

0

HT
[1:0]

0

MNT[2:0]

DC[4:0]

MSK2

0

0

MSK2

0

0

HU[3:0]

MSK2

0

PM

0

DU[3:0]

0

PM

0

0

MSK3

Reset value

0

HT
[1:0]

MSK3

MSK4

WDSEL

MSK4

WDSEL

DT
[1:0]

690/1327

1

Res.

Res.

0

RTC_ALRMBR

0x2C

0

Res.

Res.

Res.

Res.

0

0

RTC_SSR

0

DCS

Res.
Res.

Res.

0

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

Res.

1

0

PREDIV_S[14:0]

Res.

1
Res.

PREDIV_A[6:0]

ALRAWF

ALRAIE

0

ALRBWF

ALRBIE

0

SHPF

TSIE

WUTIE

0

WUTWF

ADD1H

0

RSF

BKP

SUB1H

0

INITS

POL

0

0

0

1

0

0

0

0

0

Reset value

0x28

0

0

DT
[1:0]

0x24

0

0

Res.

0x20

0

0

RTC_ALRMAR

0

DU[3:0]

0

0
DU[3:0]

0

0

Reset value

0x1C

0

COSEL

1

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_CALIBR

0

DT
[1:0]

0

0

Reset value

0x18

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_WUTR

0

0

WCKSEL
[2:0]

Reset value

0x14

MU[3:0]

0

Res.

0

0

Res.

1

0

Res.

0

0

Res.

0

0

SU[3:0]

OSEL
[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_PRER

0

WDU[2:0]

Reset value

0x10

0

ST[2:0]

COE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_ISR

0x0C

Res.

Reset value

0

MNU[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_CR

0x08

Res.

Reset value

MNT[2:0]

Res.

0

HU[3:0]

Res.

0

Res.

HT
[1:0]

MT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_DR

0x04

Res.

Reset value

PM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_TR

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 126. RTC register map and reset values

0

0

0

0

0

0

0

0

RM0390

Real-time clock (RTC)

Reset value

0

0

0

0x50
to 0x9C

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.
0

0

0

0

0

Res.

TAMP1E

0

0

TAMPIE

0

0

TAMP1ETRG

0

0

TAMP2E

0

0

TAMP2TRG

0

0

CALM[8:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

SS[14:0]
0

0

0

0

0

Res.

Res.

Res.

0

Res.

Res.

0

Res.

SU[3:0]

0

TAMPTS

Res.

Res.
TAMPPUDIS

0

Res.

0

0

TAMPFREQ[2:0]

Res.

Res.

0

TAMP1INSEL

0

Res.

Res.

Res.

Res.

0

TSINSEL

0

Res.

Res.

0

ALARMOUTTYPE

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

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

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

BKP[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

to
RTC_BKP19R
Reset value

0

0

0

RTC_BKP0R

0

0

0
Res.

MASKSS[3:0]

0

0

0
Res.

0

Res.

0

Res.

Res.

Res.

Res.

RTC_
ALRMBSSR

0x48

0
Res.

Reset value

MASKSS[3:0]

Res.

Res.

Res.

Res.

RTC_
ALRMASSR

0x44

Res.

Reset value

0

ST[2:0]

SS[15:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_TAFCR

Res.

0x40

Res.

Reset value

0

TAMPFLT[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_ CALR

0

Res.

0

CALW16

0

TAMPPRCH[1:0]

0

Reset value

0x3C

MNT[2:0]

Res.

0

CALW8

0

MNU[3:0]

CALP

HT[1:0]
0

Res.

PM
0

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_TSSSR

Res.

0x38

Res.

Reset value

HU[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_TSTR

0x30

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 126. RTC register map and reset values (continued)

0

0

0

BKP[31:0]
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 56 for the register boundary addresses.
Caution:

In Table 126, the reset value is the value after a backup domain reset. The majority of the
registers are not affected by a system reset. For more information, refer to Section 22.3.7:
Resetting the RTC.

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Fast-mode Plus Inter-integrated circuit (FMPI2C) interface

RM0390

23

Fast-mode Plus Inter-integrated circuit (FMPI2C)
interface

23.1

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.

23.2

FMPI2C main features
•

692/1327

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

DocID026976 Rev 3

RM0390

Fast-mode Plus Inter-integrated circuit (FMPI2C) interface
The following additional features are also available depending on the product
implementation (see Section 23.3: FMPI2C implementation):
•

SMBus specification rev 2.0 compatibility:
–

23.3

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 1.1 standard compatibility

•

Independent clock: a choice of independent clock sources allowing the FMPI2C
communication speed to be independent from the PCLK reprogramming

FMPI2C implementation
This manual describes the full set of features implemented in FMPI2C1.
Table 127. STM32F446xx FMPI2C implementation
I2C features(1)

FMPI2C1

Independent clock

X

SMBus

X

Wakeup from Stop mode

-

1. X = supported.

23.4

FMPI2C 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.

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Fast-mode Plus Inter-integrated circuit (FMPI2C) interface

23.4.1

RM0390

FMPI2C block diagram
The block diagram of the FMPI2C interface is shown in Figure 240.
Figure 240. FMPI2C block diagram

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The FMPI2C is clocked by an independent clock source which allows to the FMPI2C 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 6: Reset and clock control (RCC) for more details.

694/1327

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RM0390

23.4.2

Fast-mode Plus Inter-integrated circuit (FMPI2C) interface

FMPI2C clock requirements
The FMPI2C kernel is clocked by FMPI2CCLK.
The FMPI2CCLK 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 FMPI2C kernel is clocked by PCLK, this clock must respect the conditions for
tI2CCLK.

23.4.3

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 FMPI2C 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.

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Fast-mode Plus Inter-integrated circuit (FMPI2C) interface

RM0390

Figure 241. I2C bus protocol

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Acknowledge can be enabled or disabled by software. The FMPI2C interface addresses can
be selected by software.

696/1327

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RM0390

23.4.4

Fast-mode Plus Inter-integrated circuit (FMPI2C) interface

FMPI2C initialization
Enabling and disabling the peripheral
The FMPI2C peripheral clock must be configured and enabled in the clock controller (refer
to Section 6: Reset and clock control (RCC)).
Then the FMPI2C can be enabled by setting the PE bit in the FMPI2C_CR1 register.
When the FMPI2C is disabled (PE=0), the I2C performs a software reset. Refer to
Section 23.4.5: Software reset for more details.

Noise filters
Before enabling the FMPI2C peripheral by setting the PE bit in FMPI2C_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 Fastmode 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 FMPI2C_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 FMPI2CCLK periods. This allows to suppress
spikes with a programmable length of 1 to 15 FMPI2CCLK periods.
Caution:

Changing the filter configuration is not allowed when the FMPI2C is enabled.

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RM0390

FMPI2C 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 FMPI2C_TIMINGR register.
The STM32CubeMX tool calculates and provides the I2C_TIMINGR content in the I2C
configuration window
Figure 242. Setup and hold timings
d,K>d/D
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698/1327

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RM0390

Fast-mode Plus Inter-integrated circuit (FMPI2C) interface
•

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 FMPI2CCLK clock (2 to 3 FMPI2CCLK
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 128: 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 128: I2C-SMBUS specification data setup and hold times for tr and tSU;DAT
standard values.

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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.
Note:

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 128. 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

-

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

µs

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 FMPI2C_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 FMPI2C master initialization for more details.
Caution:

Changing the timing configuration is not allowed when the FMPI2C is enabled.
The FMPI2C slave NOSTRETCH mode must also be configured before enabling the
peripheral. Refer to FMPI2C slave initialization for more details.

Caution:

700/1327

Changing the NOSTRETCH configuration is not allowed when the FMPI2C is enabled.

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Fast-mode Plus Inter-integrated circuit (FMPI2C) interface
Figure 243. FMPI2C initialization flowchart

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23.4.5

Software reset
A software reset can be performed by clearing the PE bit in the FMPI2C_CR1 register. In
that case FMPI2C 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.

FMPI2C_CR2 register: START, STOP, NACK

2.

FMPI2C_ISR register: BUSY, TXE, TXIS, RXNE, ADDR, NACKF, TCR, TC, STOPF,
BERR, ARLO, OVR

and in addition when the SMBus feature is supported:
1.

FMPI2C_CR2 register: PECBYTE

2.

FMPI2C_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.

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23.4.6

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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 FMPI2C_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 FMPI2C_RXDR is read. The stretch is inserted between the 8th and
9th SCL pulse (before the Acknowledge pulse).
Figure 244. Data reception

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Fast-mode Plus Inter-integrated circuit (FMPI2C) interface

Transmission
If the FMPI2C_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 FMPI2C_TXDR,
SCL line is stretched low until FMPI2C_TXDR is written. The stretch is done after the 9th
SCL pulse.
Figure 245. Data transmission

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Hardware transfer management
The FMPI2C 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
FMPI2C_CR2 register.
The number of bytes to be transferred is programmed in the NBYTES[7:0] bit field in the
FMPI2C_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 FMPI2C_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.

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When RELOAD=0 in master mode, the counter can be used in 2 modes:

Caution:

•

Automatic end mode (AUTOEND = ‘1’ in the FMPI2C_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 FMPI2C_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 FMPI2C_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 129. FMPI2C configuration table

23.4.7

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

FMPI2C slave mode
FMPI2C slave initialization
In order to work in slave mode, the user must enable at least one slave address. Two
registers FMPI2C_OAR1 and FMPI2C_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 FMPI2C_OAR1 register.
OA1 is enabled by setting the OA1EN bit in the FMPI2C_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 FMPI2C_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 FMPI2C 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 FMPI2C_OAR1 or FMPI2C_OAR2 register
with OA2MSK=0.
OA2 is enabled by setting the OA2EN bit in the FMPI2C_OAR2 register.

•

The General Call address is enabled by setting the GCEN bit in the FMPI2C_CR1
register.

When the FMPI2C 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.

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Fast-mode Plus Inter-integrated circuit (FMPI2C) interface
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 FMPI2C must be configured with NOSTRETCH=1 in
the FMPI2C_CR1 register.
After receiving an ADDR interrupt, if several addresses are enabled the user must read the
ADDCODE[6:0] bits in the FMPI2C_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 FMPI2C 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 FMPI2C_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
FMPI2C_TXDR register.

•

In reception when the FMPI2C_RXDR register is not read yet and a new data reception
is completed. This stretch is released when FMPI2C_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 FMPI2C stretches SCL low during
[(SDADEL+SCLDEL+1) x (PRESC+1) + 1] x tI2CCLK.

Slave without clock stretching (NOSTRETCH = 1)
When NOSTRETCH = 1 in the FMPI2C_CR1 register, the FMPI2C slave does not stretch
the SCL signal.
•

The SCL clock is not stretched while the ADDR flag is set.

•

In transmission, the data must be written in the FMPI2C_TXDR register before the first
SCL pulse corresponding to its transfer occurs. If not, an underrun occurs, the OVR
flag is set in the FMPI2C_ISR register and an interrupt is generated if the ERRIE bit is
set in the FMPI2C_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 FMPI2C_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 FMPI2C_ISR register and an interrupt is generated if the ERRIE bit is
set in the FMPI2C_CR1 register.

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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 FMPI2C_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 FMPI2C_RXDR register, and then decide to
acknowledge it or not by configuring the ACK bit in the FMPI2C_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 FMPI2C 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 246. Slave initialization flowchart
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Fast-mode Plus Inter-integrated circuit (FMPI2C) interface

Slave transmitter
A transmit interrupt status (TXIS) is generated when the FMPI2C_TXDR register becomes
empty. An interrupt is generated if the TXIE bit is set in the FMPI2C_CR1 register.
The TXIS bit is cleared when the FMPI2C_TXDR register is written with the next data byte
to be transmitted.
When a NACK is received, the NACKF bit is set in the FMPI2C_ISR register and an
interrupt is generated if the NACKIE bit is set in the FMPI2C_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 FMPI2C_CR1 register, the
STOPF flag is set in the FMPI2C_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
FMPI2C_TXDR register as the first data byte, or to flush the FMPI2C_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 FMPI2C_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 FMPI2C_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 FMPI2C_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.

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Figure 247. Transfer sequence flowchart for FMPI2C slave transmitter,
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24.3.4

•

Wait until BTF = 1 (data N-2 in DR, data N-1 in shift register, SCL stretched low until
data N-2 is read)

•

Set ACK low

•

Read data N-2

•

Wait until BTF = 1 (data N-1 in DR, data N in shift register, SCL stretched low until a
data N-1 is read)

•

Set STOP high

•

Read data N-1 and N

Error conditions
The following are the error conditions which may cause communication to fail.

Bus error (BERR)
This error occurs when the I2C interface detects an external Stop or Start condition during
an address or a data transfer. In this case:
•

the BERR bit is set and an interrupt is generated if the ITERREN bit is set

•

in Slave mode: data are discarded and the lines are released by hardware:

•

–

in case of a misplaced Start, the slave considers it is a restart and waits for an
address, or a Stop condition

–

in case of a misplaced Stop, the slave behaves like for a Stop condition and the
lines are released by hardware

In Master mode: the lines are not released and the state of the current transmission is
not affected. It is up to the software to abort or not the current transmission

Acknowledge failure (AF)
This error occurs when the interface detects a nonacknowledge bit. In this case:
•

the AF bit is set and an interrupt is generated if the ITERREN bit is set

•

a transmitter which receives a NACK must reset the communication:
–

If Slave: lines are released by hardware

–

If Master: a Stop or repeated Start condition must be generated by software

Arbitration lost (ARLO)
This error occurs when the I2C interface detects an arbitration lost condition. In this case,
•

the ARLO bit is set by hardware (and an interrupt is generated if the ITERREN bit is
set)

•

the I2C Interface goes automatically back to slave mode (the MSL bit is cleared). When
the I2C loses the arbitration, it is not able to acknowledge its slave address in the same
transfer, but it can acknowledge it after a repeated Start from the winning master.

•

lines are released by hardware

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Overrun/underrun error (OVR)
An overrun error can occur in slave mode when clock stretching is disabled and the I2C
interface is receiving data. The interface has received a byte (RxNE=1) and the data in DR
has not been read, before the next byte is received by the interface. In this case,
•

The last received byte is lost.

•

In case of Overrun error, software should clear the RxNE bit and the transmitter should
re-transmit the last received byte.

Underrun error can occur in slave mode when clock stretching is disabled and the I2C
interface is transmitting data. The interface has not updated the DR with the next byte
(TxE=1), before the clock comes for the next byte. In this case,
•

The same byte in the DR register will be sent again

•

The user should make sure that data received on the receiver side during an underrun
error are discarded and that the next bytes are written within the clock low time
specified in the I2C bus standard.

For the first byte to be transmitted, the DR must be written after ADDR is cleared and before
the first SCL rising edge. If not possible, the receiver must discard the first data.

24.3.5

Programmable noise filter
In Fm mode, the I2C standard requires that spikes are suppressed to a length of 50 ns on
SDA and SCL lines.
An analog noise filter is implemented in the SDA and SCL I/Os. This filter is enabled by
default and can be disabled by setting the ANOFF bit in the I2C_FLTR register.
A digital noise filter can be enabled by configuring the DNF[3:0] bits to a non-zero value.
This suppresses the spikes on SDA and SCL inputs with a length of up to DNF[3:0] *
TPCLK1.
Enabling the digital noise filter increases the SDA hold time by (DNF[3:0] +1)* TPCLK.
To be compliant with the maximum hold time of the I2C-bus specification version 2.1
(Thd:dat), the DNF bits must be programmed using the constraints shown in Table 139, and
assuming that the analog filter is disabled.

Note:

DNF[3:0] must only be configured when the I2C is disabled (PE = 0). If the analog filter is
also enabled, the digital filter is added to the analog filter.
Table 139. Maximum DNF[3:0] value to be compliant with Thd:dat(max)
Maximum DNF value
PCLK1 frequency

772/1327

Sm mode

Fm mode

2 <= FPCLK1 <= 5

2

0

5 < FPCLK1 <= 10

12

0

10 < FPCLK1 <= 20

15

1

20 < FPCLK1 <= 30

15

7

30 < FPCLK1 <= 40

15

13

40 < FPCLK1 <= 50

15

15

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Note:

For each frequency range, the constraint is given based on the worst case which is the
minimum frequency of the range. Greater DNF values can be used if the system can
support maximum hold time violation.

24.3.6

SDA/SCL line control
•

•

24.3.7

If clock stretching is enabled:
–

Transmitter mode: If TxE=1 and BTF=1: the interface holds the clock line low
before transmission to wait for the microcontroller to write the byte in the Data
Register (both buffer and shift register are empty).

–

Receiver mode: If RxNE=1 and BTF=1: the interface holds the clock line low after
reception to wait for the microcontroller to read the byte in the Data Register (both
buffer and shift register are full).

If clock stretching is disabled in Slave mode:
–

Overrun Error in case of RxNE=1 and no read of DR has been done before the
next byte is received. The last received byte is lost.

–

Underrun Error in case TxE=1 and no write into DR has been done before the next
byte must be transmitted. The same byte will be sent again.

–

Write Collision not managed.

SMBus
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. A system may use SMBus to pass messages to and from devices instead of
toggling individual control lines.
The System Management Bus Specification refers to three types of devices. A slave is a
device that is receiving or responding 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.

Similarities between SMBus and I2C
•

2 wire bus protocol (1 Clk, 1 Data) + SMBus Alert line optional

•

Master-slave communication, Master provides clock

•

Multi master capability

•

SMBus data format similar to I2C 7-bit addressing format (Figure 271).

Differences between SMBus and I2C
The following table describes the differences between SMBus and I2C.

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Table 140. SMBus vs. I2C
I2C

SMBus
Max. speed 100 kHz

Max. speed 400 kHz

Min. clock speed 10 kHz

No minimum clock speed

35 ms clock low timeout

No timeout

Logic levels are fixed

Logic levels are VDD dependent

Different address types (reserved, dynamic etc.)

7-bit, 10-bit and general call slave address types

Different bus protocols (quick command, process
No bus protocols
call etc.)

SMBus application usage
With System Management Bus, a device can provide manufacturer information, tell the
system what its model/part number is, save its state for a suspend event, report different
types of errors, accept control parameters, and return its status. SMBus provides a control
bus for system and power management related tasks.

Device identification
Any device that exists on the System Management Bus as a slave has a unique address
called the Slave Address. For the list of reserved slave addresses, refer to the SMBus
specification version. 2.0 (http://smbus.org/).

Bus protocols
The SMBus specification supports up to 9 bus protocols. For more details of these protocols
and SMBus address types, refer to SMBus specification version. 2.0. These protocols
should be implemented by the user software.

Address resolution protocol (ARP)
SMBus slave address conflicts can be resolved by dynamically assigning a new unique
address to each slave device. The Address Resolution Protocol (ARP) has the following
attributes:
•

Address assignment uses the standard SMBus physical layer arbitration mechanism

•

Assigned addresses remain constant while device power is applied; address retention
through device power loss is also allowed

•

No additional SMBus packet overhead is incurred after address assignment. (i.e.
subsequent accesses to assigned slave addresses have the same overhead as
accesses to fixed address devices.)

•

Any SMBus master can enumerate the bus

Unique device identifier (UDID)
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).
For the details on 128 bit UDID and more information on ARP, refer to SMBus specification
version 2.0.

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SMBus alert mode
SMBus Alert is an optional signal with an interrupt line for devices that want to trade their
ability to master for a pin. SMBA is a wired-AND signal just as the SCL and SDA signals are.
SMBA is used in conjunction with the SMBus General Call Address. Messages invoked with
the SMBus are 2 bytes long.
A slave-only device can signal the host through SMBA that it wants to talk by setting ALERT
bit in I2C_CR1 register. The host processes the interrupt and simultaneously accesses all
SMBA devices through the Alert Response Address (known as ARA having a value 0001
100X). Only the device(s) which pulled SMBA low will acknowledge the Alert Response
Address. This status is identified using SMBALERT Status flag in I2C_SR1 register. The
host performs a modified Receive Byte operation. The 7 bit device address provided by the
slave transmit device is placed in the 7 most significant bits of the byte. The eighth bit can
be a zero or one.
If more than one device pulls SMBA low, the highest priority (lowest address) device will win
communication rights via standard arbitration during the slave address transfer. After
acknowledging the slave address the device must disengage its SMBA pull-down. If the
host still sees SMBA low when the message transfer is complete, it knows to read the ARA
again.
A host which does not implement the SMBA signal may periodically access the ARA.
For more details on SMBus Alert mode, refer to SMBus specification version 2.0
(http://smbus.org/).

Timeout error
There are differences in the timing specifications between I2C and SMBus.
SMBus defines a clock low timeout, TIMEOUT of 35 ms. Also SMBus specifies TLOW:
SEXT as the cumulative clock low extend time for a slave device. SMBus specifies TLOW:
MEXT as the cumulative clock low extend time for a master device. For more details on
these timeouts, refer to SMBus specification version 2.0.
The status flag Timeout or Tlow Error in I2C_SR1 shows the status of this feature.

How to use the interface in SMBus mode
To switch from I2C mode to SMBus mode, the following sequence should be performed.
•

Set the SMBus bit in the I2C_CR1 register

•

Configure the SMBTYPE and ENARP bits in the I2C_CR1 register as required for the
application

If you want to configure the device as a master, follow the Start condition generation
procedure in Section 24.3.3: I2C master mode. Otherwise, follow the sequence in
Section 24.3.2: I2C slave mode.
The application has to control the various SMBus protocols by software.
•

SMB Device Default Address acknowledged if ENARP=1 and SMBTYPE=0

•

SMB Host Header acknowledged if ENARP=1 and SMBTYPE=1

•

SMB Alert Response Address acknowledged if SMBALERT=1

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DMA requests
DMA requests (when enabled) are generated only for data transfer. DMA requests are
generated by Data Register becoming empty in transmission and Data Register becoming
full in reception. The DMA must be initialized and enabled before the I2C data transfer. The
DMAEN bit must be set in the I2C_CR2 register before the ADDR event. In master mode or
in slave mode when clock stretching is enabled, the DMAEN bit can also be set during the
ADDR event, before clearing the ADDR flag. The DMA request must be served before the
end of the current byte transfer. When the number of data transfers which has been
programmed for the corresponding DMA stream is reached, the DMA controller sends an
End of Transfer EOT signal to the I2C interface and generates a Transfer Complete interrupt
if enabled:
•

Master transmitter: In the interrupt routine after the EOT interrupt, disable DMA
requests then wait for a BTF event before programming the Stop condition.

•

Master receiver
–

When the number of bytes to be received is equal to or greater than two, the DMA
controller sends a hardware signal, EOT_1, corresponding to the last but one data
byte (number_of_bytes – 1). If, in the I2C_CR2 register, the LAST bit is set, I2C
automatically sends a NACK after the next byte following EOT_1. The user can
generate a Stop condition in the DMA Transfer Complete interrupt routine if
enabled.

–

When a single byte must be received: the NACK must be programmed during EV6
event, i.e. program ACK=0 when ADDR=1, before clearing ADDR flag. Then the
user can program the STOP condition either after clearing ADDR flag, or in the
DMA Transfer Complete interrupt routine.

Transmission using DMA
DMA mode can be enabled for transmission by setting the DMAEN bit in the I2C_CR2
register. Data will be loaded from a Memory area configured using the DMA peripheral (refer
to the DMA specification) to the I2C_DR register whenever the TxE bit is set. To map a DMA
stream x for I2C transmission (where x is the stream number), perform the following
sequence:
1.

Set the I2C_DR register address in the DMA_SxPAR register. The data will be moved
to this address from the memory after each TxE event.

2.

Set the memory address in the DMA_SxMA0R register (and in DMA_SxMA1R register
in the case of a bouble buffer mode). The data will be loaded into I2C_DR from this
memory after each TxE event.

3.

Configure the total number of bytes to be transferred in the DMA_SxNDTR register.
After each TxE event, this value will be decremented.

4.

Configure the DMA stream priority using the PL[0:1] bits in the DMA_SxCR register

5.

Set the DIR bit in the DMA_SxCR register and configure interrupts after half transfer or
full transfer depending on application requirements.

6.

Activate the stream by setting the EN bit in the DMA_SxCR register.

When the number of data transfers which has been programmed in the DMA Controller
registers is reached, the DMA controller sends an End of Transfer EOT/ EOT_1 signal to the
I2C interface and the DMA generates an interrupt, if enabled, on the DMA stream interrupt
vector.
Note:

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Reception using DMA
DMA mode can be enabled for reception by setting the DMAEN bit in the I2C_CR2 register.
Data will be loaded from the I2C_DR register to a Memory area configured using the DMA
peripheral (refer to the DMA specification) whenever a data byte is received. To map a DMA
stream x for I2C reception (where x is the stream number), perform the following sequence:
1.

Set the I2C_DR register address in DMA_SxPAR register. The data will be moved from
this address to the memory after each RxNE event.

2.

Set the memory address in the DMA_SxMA0R register (and in DMA_SxMA1R register
in the case of a bouble buffer mode). The data will be loaded from the I2C_DR register
to this memory area after each RxNE event.

3.

Configure the total number of bytes to be transferred in the DMA_SxNDTR register.
After each RxNE event, this value will be decremented.

4.

Configure the stream priority using the PL[0:1] bits in the DMA_SxCR register

5.

Reset the DIR bit and configure interrupts in the DMA_SxCR register after half transfer
or full transfer depending on application requirements.

6.

Activate the stream by setting the EN bit in the DMA_SxCR register.

When the number of data transfers which has been programmed in the DMA Controller
registers is reached, the DMA controller sends an End of Transfer EOT/ EOT_1 signal to the
I2C interface and DMA generates an interrupt, if enabled, on the DMA stream interrupt
vector.
Note:

Do not enable the ITBUFEN bit in the I2C_CR2 register if DMA is used for reception.

24.3.9

Packet error checking
A PEC calculator has been implemented to improve the reliability of communication. The
PEC is calculated by using the C(x) = x8 + x2 + x + 1 CRC-8 polynomial serially on each bit.
•

PEC calculation is enabled by setting the ENPEC bit in the I2C_CR1 register. PEC is a
CRC-8 calculated on all message bytes including addresses and R/W bits.
–

In transmission: set the PEC transfer bit in the I2C_CR1 register after the TxE
event corresponding to the last byte. The PEC will be transferred after the last
transmitted byte.

–

In reception: set the PEC bit in the I2C_CR1 register after the RxNE event
corresponding to the last byte so that the receiver sends a NACK if the next
received byte is not equal to the internally calculated PEC. In case of MasterReceiver, a NACK must follow the PEC whatever the check result. The PEC must

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be set before the ACK of the CRC reception in slave mode. It must be set when
the ACK is set low in master mode.

24.4

•

A PECERR error flag/interrupt is also available in the I2C_SR1 register.

•

If DMA and PEC calculation are both enabled:–

In transmission: when the I2C interface receives an EOT signal from the DMA
controller, it automatically sends a PEC after the last byte.

–

In reception: when the I2C interface receives an EOT_1 signal from the DMA
controller, it will automatically consider the next byte as a PEC and will check it. A
DMA request is generated after PEC reception.

•

To allow intermediate PEC transfers, a control bit is available in the I2C_CR2 register
(LAST bit) to determine if it is really the last DMA transfer or not. If it is the last DMA
request for a master receiver, a NACK is automatically sent after the last received byte.

•

PEC calculation is corrupted by an arbitration loss.

I2C interrupts
The table below gives the list of I2C interrupt requests.
Table 141. I2C Interrupt requests
Interrupt event
Start bit sent (Master)

Enable control bit

SB

Address sent (Master) or Address matched (Slave)

ADDR

10-bit header sent (Master)

ADD10

Stop received (Slave)

STOPF

Data byte transfer finished

BTF

Receive buffer not empty

RxNE

Transmit buffer empty

TxE

Bus error

BERR

Arbitration loss (Master)

ARLO

Acknowledge failure

ITEVFEN

ITEVFEN and ITBUFEN

AF

Overrun/Underrun

OVR

PEC error

PECERR

Timeout/Tlow error

TIMEOUT

SMBus Alert

Note:

Event flag

ITERREN

SMBALERT

SB, ADDR, ADD10, STOPF, BTF, RxNE and TxE are logically ORed on the same interrupt
channel.
BERR, ARLO, AF, OVR, PECERR, TIMEOUT and SMBALERT are logically ORed on the
same interrupt channel.

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Figure 277. I2C interrupt mapping diagram
SB

ITEVFEN

ADDR
ADD10
STOPF

it_event
BTF
TxE

ITBUFEN

RxNE
ITERREN

BERR
ARLO

it_error

AF
OVR
PECERR
TIMEOUT
SMBALERT

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I2C debug mode

24.5

When the microcontroller enters the debug mode (Cortex®-M4 with FPU core halted), the
SMBUS timeout either continues to work normally or stops, depending on the
DBG_I2Cx_SMBUS_TIMEOUT configuration bits in the DBG module. For more details,
refer to Section 33.16.2: Debug support for timers, watchdog, bxCAN and I2C.

I2C registers

24.6

Refer to Section 1.1 on page 51 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by half-words (16 bits) or words (32 bits).

I2C Control register 1 (I2C_CR1)

24.6.1

Address offset: 0x00
Reset value: 0x0000
15

14

13

12

11

10

9

SW
RST

Res.

ALERT

PEC

POS

ACK

STOP

rw

rw

rw

rw

rw

rw

8

7

NO
START STRET
CH
rw

rw

6

5

4

ENGC ENPEC ENARP
rw

rw

rw

3

2

1

0

SMB
TYPE

Res.

SM
BUS

PE

rw

rw

rw

Bit 15 SWRST: Software reset
When set, the I2C is under reset state. Before resetting this bit, make sure the I2C lines are
released and the bus is free.
0: I2C Peripheral not under reset
1: I2C Peripheral under reset state
Note: This bit can be used to reinitialize the peripheral after an error or a locked state. As an
example, if the BUSY bit is set and remains locked due to a glitch on the bus, the
SWRST bit can be used to exit from this state.
Bit 14 Reserved, must be kept at reset value
Bit 13 ALERT: SMBus alert
This bit is set and cleared by software, and cleared by hardware when PE=0.
0: Releases SMBA pin high. Alert Response Address Header followed by NACK.
1: Drives SMBA pin low. Alert Response Address Header followed by ACK.
Bit 12 PEC: Packet error checking
This bit is set and cleared by software, and cleared by hardware when PEC is transferred or
by a START or Stop condition or when PE=0.
0: No PEC transfer
1: PEC transfer (in Tx or Rx mode)
Note: PEC calculation is corrupted by an arbitration loss.

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Bit 11 POS: Acknowledge/PEC Position (for data reception)
This bit is set and cleared by software and cleared by hardware when PE=0.
0: ACK bit controls the (N)ACK of the current byte being received in the shift register. The
PEC bit indicates that current byte in shift register is a PEC.
1: ACK bit controls the (N)ACK of the next byte which will be received in the shift register.
The PEC bit indicates that the next byte in the shift register is a PEC
Note: The POS bit must be used only in 2-byte reception configuration in master mode. It
must be configured before data reception starts, as described in the 2-byte reception
procedure recommended in Master receiver.
Bit 10 ACK: Acknowledge enable
This bit is set and cleared by software and cleared by hardware when PE=0.
0: No acknowledge returned
1: Acknowledge returned after a byte is received (matched address or data)
Bit 9 STOP: Stop generation
The bit is set and cleared by software, cleared by hardware when a Stop condition is
detected, set by hardware when a timeout error is detected.
In Master Mode:
0: No Stop generation.
1: Stop generation after the current byte transfer or after the current Start condition is sent.
In Slave mode:
0: No Stop generation.
1: Release the SCL and SDA lines after the current byte transfer.
Bit 8 START: Start generation
This bit is set and cleared by software and cleared by hardware when start is sent or PE=0.
In Master Mode:
0: No Start generation
1: Repeated start generation
In Slave mode:
0: No Start generation
1: Start generation when the bus is free
Bit 7 NOSTRETCH: Clock stretching disable (Slave mode)
This bit is used to disable clock stretching in slave mode when ADDR or BTF flag is set, until
it is reset by software.
0: Clock stretching enabled
1: Clock stretching disabled
Bit 6 ENGC: General call enable
0: General call disabled. Address 00h is NACKed.
1: General call enabled. Address 00h is ACKed.
Bit 5 ENPEC: PEC enable
0: PEC calculation disabled
1: PEC calculation enabled
Bit 4 ENARP: ARP enable
0: ARP disable
1: ARP enable
SMBus Device default address recognized if SMBTYPE=0
SMBus Host address recognized if SMBTYPE=1
Bit 3 SMBTYPE: SMBus type
0: SMBus Device
1: SMBus Host

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Bit 2 Reserved, must be kept at reset value
Bit 1 SMBUS: SMBus mode
0: I2C mode
1: SMBus mode
Bit 0 PE: Peripheral enable
0: Peripheral disable
1: Peripheral enable
Note: If this bit is reset while a communication is on going, the peripheral is disabled at the
end of the current communication, when back to IDLE state.
All bit resets due to PE=0 occur at the end of the communication.
In master mode, this bit must not be reset before the end of the communication.

Note:

When the STOP, START or PEC bit is set, the software must not perform any write access
to I2C_CR1 before this bit is cleared by hardware. Otherwise there is a risk of setting a
second STOP, START or PEC request.

24.6.2

I2C Control register 2 (I2C_CR2)
Address offset: 0x04
Reset value: 0x0000

15
Res.

14
Res.

13
Res.

12

11

10

9

8

7

6

LAST

DMA
EN

ITBUF
EN

ITEVT
EN

ITERR
EN

Res.

Res.

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

FREQ[5:0]
rw

rw

rw

rw

Bits 15:13 Reserved, must be kept at reset value
Bit 12 LAST: DMA last transfer
0: Next DMA EOT is not the last transfer
1: Next DMA EOT is the last transfer
Note: This bit is used in master receiver mode to permit the generation of a NACK on the last
received data.
Bit 11 DMAEN: DMA requests enable
0: DMA requests disabled
1: DMA request enabled when TxE=1 or RxNE =1
Bit 10 ITBUFEN: Buffer interrupt enable
0: TxE = 1 or RxNE = 1 does not generate any interrupt.
1: TxE = 1 or RxNE = 1 generates Event Interrupt (whatever the state of DMAEN)
Bit 9 ITEVTEN: Event interrupt enable
0: Event interrupt disabled
1: Event interrupt enabled
This interrupt is generated when:
–
SB = 1 (Master)
–
ADDR = 1 (Master/Slave)
–
ADD10= 1 (Master)
–
STOPF = 1 (Slave)
–
BTF = 1 with no TxE or RxNE event
–
TxE event to 1 if ITBUFEN = 1
–
RxNE event to 1if ITBUFEN = 1

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ITERREN: Error interrupt enable
0: Error interrupt disabled
1: Error interrupt enabled
This interrupt is generated when:
–
BERR = 1
–
ARLO = 1
–
AF = 1
–
OVR = 1
–
PECERR = 1
–
TIMEOUT = 1
–
SMBALERT = 1
Bits 7:6 Reserved, must be kept at reset value
Bits 5:0 FREQ[5:0]: Peripheral clock frequency
The FREQ bits must be configured with the APB clock frequency value (I2C peripheral
connected to APB). The FREQ field is used by the peripheral to generate data setup and
hold times compliant with the I2C specifications. The minimum allowed frequency is 2 MHz,
the maximum frequency is limited by the maximum APB frequency (42 MHz) and cannot
exceed 50 MHz (peripheral intrinsic maximum limit).
0b000000: Not allowed
0b000001: Not allowed
0b000010: 2 MHz
...
0b110010: 50 MHz
Higher than 0b101010: Not allowed

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I2C Own address register 1 (I2C_OAR1)

24.6.3

Address offset: 0x08
Reset value: 0x0000
15

14

13

12

11

10

ADD
MODE

Res.

Res.

Res.

Res.

Res.

rw

9

8

7

6

5

ADD[9:8]
rw

rw

4

3

2

1

ADD[7:1]
rw

rw

rw

0
ADD0

rw

rw

rw

rw

4

3

2

1

rw

Bit 15 ADDMODE Addressing mode (slave mode)
0: 7-bit slave address (10-bit address not acknowledged)
1: 10-bit slave address (7-bit address not acknowledged)
Bit 14
Bits 13:10

Should always be kept at 1 by software.
Reserved, must be kept at reset value

Bits 9:8 ADD[9:8]: Interface address
7-bit addressing mode: don’t care
10-bit addressing mode: bits9:8 of address
Bits 7:1 ADD[7:1]: Interface address
bits 7:1 of address
Bit 0 ADD0: Interface address
7-bit addressing mode: don’t care
10-bit addressing mode: bit 0 of address

I2C Own address register 2 (I2C_OAR2)

24.6.4

Address offset: 0x0C
Reset value: 0x0000
15
Res.

14

13

Res.

Res.

12
Res.

11
Res.

10
Res.

9

8

Res.

7

6

5

Res.

ADD2[7:1]
rw

rw

rw

rw

rw

Bits 15:8 Reserved, must be kept at reset value
Bits 7:1 ADD2[7:1]: Interface address
bits 7:1 of address in dual addressing mode
Bit 0 ENDUAL: Dual addressing mode enable
0: Only OAR1 is recognized in 7-bit addressing mode
1: Both OAR1 and OAR2 are recognized in 7-bit addressing mode

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DUAL

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I2C Data register (I2C_DR)

24.6.5

Address offset: 0x10
Reset value: 0x0000
15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

rw

DR[7:0]
rw

rw

rw

rw

Bits 15:8 Reserved, must be kept at reset value
Bits 7:0 DR[7:0] 8-bit data register
Byte received or to be transmitted to the bus.
– Transmitter mode: Byte transmission starts automatically when a byte is written in the DR
register. A continuous transmit stream can be maintained if the next data to be transmitted is
put in DR once the transmission is started (TxE=1)
– Receiver mode: Received byte is copied into DR (RxNE=1). A continuous transmit stream
can be maintained if DR is read before the next data byte is received (RxNE=1).
Note: In slave mode, the address is not copied into DR.

Write collision is not managed (DR can be written if TxE=0).
If an ARLO event occurs on ACK pulse, the received byte is not copied into DR
and so cannot be read.

I2C Status register 1 (I2C_SR1)

24.6.6

Address offset: 0x14
Reset value: 0x0000
15

14

SMB TIMEO
ALERT
UT
rc_w0

rc_w0

13

12

11

10

9

8

7

6

5

Res.

PEC
ERR

OVR

AF

ARLO

BERR

TxE

RxNE

Res.

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

r

r

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3

STOPF ADD10
r

r

2

1

0

BTF

ADDR

SB

r

r

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Bit 15 SMBALERT: SMBus alert
In SMBus host mode:
0: no SMBALERT
1: SMBALERT event occurred on pin
In SMBus slave mode:
0: no SMBALERT response address header
1: SMBALERT response address header to SMBALERT LOW received
– Cleared by software writing 0, or by hardware when PE=0.
Bit 14 TIMEOUT: Timeout or Tlow error
0: No timeout error
1: SCL remained LOW for 25 ms (Timeout)
or
Master cumulative clock low extend time more than 10 ms (Tlow:mext)
or
Slave cumulative clock low extend time more than 25 ms (Tlow:sext)
– When set in slave mode: slave resets the communication and lines are released by
hardware
– When set in master mode: Stop condition sent by hardware
– Cleared by software writing 0, or by hardware when PE=0.
Note: This functionality is available only in SMBus mode.
Bit 13 Reserved, must be kept at reset value
Bit 12 PECERR: PEC Error in reception
0: no PEC error: receiver returns ACK after PEC reception (if ACK=1)
1: PEC error: receiver returns NACK after PEC reception (whatever ACK)
– Cleared by software writing 0, or by hardware when PE=0.
– Note: When the received CRC is wrong, PECERR is not set in slave mode if the PEC control
bit is not set before the end of the CRC reception. Nevertheless, reading the PEC value
determines whether the received CRC is right or wrong.
Bit 11 OVR: Overrun/Underrun
0: No overrun/underrun
1: Overrun or underrun
– Set by hardware in slave mode when NOSTRETCH=1 and:
– In reception when a new byte is received (including ACK pulse) and the DR register has not
been read yet. New received byte is lost.
– In transmission when a new byte should be sent and the DR register has not been written
yet. The same byte is sent twice.
– Cleared by software writing 0, or by hardware when PE=0.
Note: If the DR write occurs very close to SCL rising edge, the sent data is unspecified and a
hold timing error occurs
Bit 10 AF: Acknowledge failure
0: No acknowledge failure
1: Acknowledge failure
– Set by hardware when no acknowledge is returned.
– Cleared by software writing 0, or by hardware when PE=0.

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Bit 9 ARLO: Arbitration lost (master mode)
0: No Arbitration Lost detected
1: Arbitration Lost detected
Set by hardware when the interface loses the arbitration of the bus to another master
– Cleared by software writing 0, or by hardware when PE=0.
After an ARLO event the interface switches back automatically to Slave mode (MSL=0).
Note: In SMBUS, the arbitration on the data in slave mode occurs only during the data phase,
or the acknowledge transmission (not on the address acknowledge).
Bit 8 BERR: Bus error
0: No misplaced Start or Stop condition
1: Misplaced Start or Stop condition
– Set by hardware when the interface detects an SDA rising or falling edge while SCL is high,
occurring in a non-valid position during a byte transfer.
– Cleared by software writing 0, or by hardware when PE=0.
Bit 7 TxE: Data register empty (transmitters)
0: Data register not empty
1: Data register empty
– Set when DR is empty in transmission. TxE is not set during address phase.
– Cleared by software writing to the DR register or by hardware after a start or a stop condition
or when PE=0.
TxE is not set if either a NACK is received, or if next byte to be transmitted is PEC (PEC=1)
Note: TxE is not cleared by writing the first data being transmitted, or by writing data when
BTF is set, as in both cases the data register is still empty.
Bit 6 RxNE: Data register not empty (receivers)
0: Data register empty
1: Data register not empty
– Set when data register is not empty in receiver mode. RxNE is not set during address phase.
– Cleared by software reading or writing the DR register or by hardware when PE=0.
RxNE is not set in case of ARLO event.
Note: RxNE is not cleared by reading data when BTF is set, as the data register is still full.
Bit 5 Reserved, must be kept at reset value
Bit 4 STOPF: Stop detection (slave mode)
0: No Stop condition detected
1: Stop condition detected
– Set by hardware when a Stop condition is detected on the bus by the slave after an
acknowledge (if ACK=1).
– Cleared by software reading the SR1 register followed by a write in the CR1 register, or by
hardware when PE=0
Note: The STOPF bit is not set after a NACK reception.
It is recommended to perform the complete clearing sequence (READ SR1 then
WRITE CR1) after the STOPF is set. Refer to Figure 274: Transfer sequence diagram
for slave receiver on page 765.

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RM0390

Bit 3 ADD10: 10-bit header sent (Master mode)
0: No ADD10 event occurred.
1: Master has sent first address byte (header).
– Set by hardware when the master has sent the first byte in 10-bit address mode.
– Cleared by software reading the SR1 register followed by a write in the DR register of the
second address byte, or by hardware when PE=0.
Note: ADD10 bit is not set after a NACK reception
Bit 2 BTF: Byte transfer finished
0: Data byte transfer not done
1: Data byte transfer succeeded
– Set by hardware when NOSTRETCH=0 and:
– In reception when a new byte is received (including ACK pulse) and DR has not been read
yet (RxNE=1).
– In transmission when a new byte should be sent and DR has not been written yet (TxE=1).
– Cleared by software by either a read or write in the DR register or by hardware after a start or
a stop condition in transmission or when PE=0.
Note: The BTF bit is not set after a NACK reception
The BTF bit is not set if next byte to be transmitted is the PEC (TRA=1 in I2C_SR2
register and PEC=1 in I2C_CR1 register)
Bit 1 ADDR: Address sent (master mode)/matched (slave mode)
This bit is cleared by software reading SR1 register followed reading SR2, or by hardware
when PE=0.
Address matched (Slave)
0: Address mismatched or not received.
1: Received address matched.
– Set by hardware as soon as the received slave address matched with the OAR registers
content or a general call or a SMBus Device Default Address or SMBus Host or SMBus Alert
is recognized. (when enabled depending on configuration).
Note: In slave mode, it is recommended to perform the complete clearing sequence (READ
SR1 then READ SR2) after ADDR is set. Refer to Figure 274: Transfer sequence
diagram for slave receiver on page 765.
Address sent (Master)
0: No end of address transmission
1: End of address transmission
– For 10-bit addressing, the bit is set after the ACK of the 2nd byte.
– For 7-bit addressing, the bit is set after the ACK of the byte.
Note: ADDR is not set after a NACK reception
Bit 0 SB: Start bit (Master mode)
0: No Start condition
1: Start condition generated.
– Set when a Start condition generated.
– Cleared by software by reading the SR1 register followed by writing the DR register, or by
hardware when PE=0

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I2C Status register 2 (I2C_SR2)

24.6.7

Address offset: 0x18
Reset value: 0x0000
Note:

15

Reading I2C_SR2 after reading I2C_SR1 clears the ADDR flag, even if the ADDR flag was
set after reading I2C_SR1. Consequently, I2C_SR2 must be read only when ADDR is found
set in I2C_SR1 or when the STOPF bit is cleared.
14

13

12

11

10

9

8

PEC[7:0]
r

r

r

r

r

r

r

7

6

5

4

3

2

1

0

DUALF

SMB
HOST

SMB
DEFAU
LT

GEN
CALL

Res.

TRA

BUSY

MSL

r

r

r

r

r

r

r

r

Bits 15:8 PEC[7:0] Packet error checking register
This register contains the internal PEC when ENPEC=1.
Bit 7 DUALF: Dual flag (Slave mode)
0: Received address matched with OAR1
1: Received address matched with OAR2
– Cleared by hardware after a Stop condition or repeated Start condition, or when PE=0.
Bit 6 SMBHOST: SMBus host header (Slave mode)
0: No SMBus Host address
1: SMBus Host address received when SMBTYPE=1 and ENARP=1.
– Cleared by hardware after a Stop condition or repeated Start condition, or when PE=0.
Bit 5 SMBDEFAULT: SMBus device default address (Slave mode)
0: No SMBus Device Default address
1: SMBus Device Default address received when ENARP=1
– Cleared by hardware after a Stop condition or repeated Start condition, or when PE=0.
Bit 4 GENCALL: General call address (Slave mode)
0: No General Call
1: General Call Address received when ENGC=1
– Cleared by hardware after a Stop condition or repeated Start condition, or when PE=0.
Bit 3 Reserved, must be kept at reset value

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RM0390

Bit 2 TRA: Transmitter/receiver
0: Data bytes received
1: Data bytes transmitted
This bit is set depending on the R/W bit of the address byte, at the end of total address
phase.
It is also cleared by hardware after detection of Stop condition (STOPF=1), repeated Start
condition, loss of bus arbitration (ARLO=1), or when PE=0.
Bit 1 BUSY: Bus busy
0: No communication on the bus
1: Communication ongoing on the bus
– Set by hardware on detection of SDA or SCL low
– cleared by hardware on detection of a Stop condition.
It indicates a communication in progress on the bus. This information is still updated when
the interface is disabled (PE=0).
Bit 0 MSL: Master/slave
0: Slave Mode
1: Master Mode
– Set by hardware as soon as the interface is in Master mode (SB=1).
– Cleared by hardware after detecting a Stop condition on the bus or a loss of arbitration
(ARLO=1), or by hardware when PE=0.

Note:

Reading I2C_SR2 after reading I2C_SR1 clears the ADDR flag, even if the ADDR flag was
set after reading I2C_SR1. Consequently, I2C_SR2 must be read only when ADDR is found
set in I2C_SR1 or when the STOPF bit is cleared.

24.6.8

I2C Clock control register (I2C_CCR)
Address offset: 0x1C
Reset value: 0x0000

Note:

fPCLK1 must be at least 2 MHz to achieve Sm mode I²C frequencies. It must be at least 4
MHz to achieve Fm mode I²C frequencies. It must be a multiple of 10MHz to reach the
400 kHz maximum I²C Fm mode clock.
The CCR register must be configured only when the I2C is disabled (PE = 0).

15

14

13

12

F/S

DUTY

Res.

Res.

rw

rw

11

10

9

8

7

6

rw

rw

rw

rw

rw

rw

4

3

2

1

0

rw

rw

rw

rw

rw

CCR[11:0]

Bit 15 F/S: I2C master mode selection
0: Sm mode I2C
1: Fm mode I2C

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Inter-integrated circuit (I2C) interface

RM0390

Bit 14 DUTY: Fm mode duty cycle
0: Fm mode tlow/thigh = 2
1: Fm mode tlow/thigh = 16/9 (see CCR)
Bits 13:12 Reserved, must be kept at reset value
Bits 11:0 CCR[11:0]: Clock control register in Fm/Sm mode (Master mode)
Controls the SCL clock in master mode.
Sm mode or SMBus:
Thigh = CCR * TPCLK1
Tlow = CCR * TPCLK1
Fm mode:
If DUTY = 0:
Thigh = CCR * TPCLK1
Tlow = 2 * CCR * TPCLK1
If DUTY = 1: (to reach 400 kHz)
Thigh = 9 * CCR * TPCLK1
Tlow = 16 * CCR * TPCLK1
For instance: in Sm mode, to generate a 100 kHz SCL frequency:
If FREQR = 08, TPCLK1 = 125 ns so CCR must be programmed with 0x28
(0x28 <=> 40d x 125 ns = 5000 ns.)
Note: The minimum allowed value is 0x04, except in FAST DUTY mode where the minimum
allowed value is 0x01
thigh = tr(SCL) + tw(SCLH). See device datasheet for the definitions of parameters.
tlow = tf(SCL) + tw(SCLL). See device datasheet for the definitions of parameters.
I2C communication speed, fSCL ~ 1/(thigh + tlow). The real frequency may differ due to
the analog noise filter input delay.
The CCR register must be configured only when the I2C is disabled (PE = 0).

I2C TRISE register (I2C_TRISE)

24.6.9

Address offset: 0x20
Reset value: 0x0002
15

14

13

12

11

10

9

8

7

6

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

5

4

3

2

1

0

rw

rw

TRISE[5:0]
rw

rw

rw

rw

Bits 15:6 Reserved, must be kept at reset value
Bits 5:0 TRISE[5:0]: Maximum rise time in Fm/Sm mode (Master mode)
These bits should provide the maximum duration of the SCL feedback loop in master mode.
The purpose is to keep a stable SCL frequency whatever the SCL rising edge duration.
These bits must be programmed with the maximum SCL rise time given in the I2C bus
specification, incremented by 1.
For instance: in Sm mode, the maximum allowed SCL rise time is 1000 ns.
If, in the I2C_CR2 register, the value of FREQ[5:0] bits is equal to 0x08 and TPCLK1 = 125 ns
therefore the TRISE[5:0] bits must be programmed with 09h.
(1000 ns / 125 ns = 8 + 1)
The filter value can also be added to TRISE[5:0].
If the result is not an integer, TRISE[5:0] must be programmed with the integer part, in order
to respect the tHIGH parameter.
Note: TRISE[5:0] must be configured only when the I2C is disabled (PE = 0).

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Inter-integrated circuit (I2C) interface

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I2C FLTR register (I2C_FLTR)

24.6.10

Address offset: 0x24
Reset value: 0x0000
15

14

13

12

11

10

9

8

7

6

5

4

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ANOFF
rw

3

2

rw

rw

1

0

DNF[3:0]
rw

rw

Bits 15:5 Reserved, must be kept at reset value
Bit 4 ANOFF: Analog noise filter OFF
0: Analog noise filter enable
1: Analog noise filter disable
Note: ANOFF must be configured only when the I2C is disabled (PE = 0).
Bits 3:0 DNF[3:0]: Digital noise filter
These bits are used to configure the digital noise filter on SDA and SCL inputs. The digital filter
will suppress the spikes with a length of up to DNF[3:0] * TPCLK1.
0000: Digital noise filter disable
0001: Digital noise filter enabled and filtering capability up to 1* TPCLK1.
...
1111: Digital noise filter enabled and filtering capability up to 15* TPCLK1.
Note: DNF[3:0] must be configured only when the I2C is disabled (PE = 0). If the analog filter
is also enabled, the digital filter is added to the analog filter.

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I2C_FLTR

DocID026976 Rev 3

Reset value
0
0
0

0
0

0

Reset value
0

0

0

ADD[7:1]

0

0
0
0

0

0

0

0

0

0

0

0

ADD0

0
0

0

0

0

0

0

SMBUS
PE

Res.

ENARP

0

ADD2[7:1]
ENDUAL

0

SB

ITERREN

SMBTYPE

Res.

ITEVTEN

ENGC

Res.

ITBUFEN

Res.

0

0
0
0
0
0

CCR[11:0]
MSL

0

0

BTF

0
0

ADDR

0

TRA

0

BUSY

Reset value
0

ADD10

Reset value
0

ENPEC

START
NOSTRETCH

Res.
LAST
0
ADD[
9:8]

GENCALL
Res.

0

Res.

ACK
STOP
0

0

SMBHOST

Res.

0

Res.

Res.

0

0

SMBDEFAULT

STOPF

PEC[7:0]
RxNE
Res.

0
TxE

0
BERR

0

DUALF

Res.

PEC
POS
0

DMAEN

Res.

ALERT

0

ANOFF

0

Res.

0
Res.

Res.

Res.

0

Res.
0

Res.

0

Res.

AF
ARLO

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SWRST
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.

0

Res.

OVR

Res.

Res.

Res.

ADDMODE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.

0

Res.

PECERR

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

TIMEOUT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

0

Res.

DUTY

SMBALERT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Reset value
0

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

F/S

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.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

I2C_TRISE

Res.

0x20
I2C_CCR

Res.

0x1C
I2C_SR2

Res.

0x18
I2C_SR1

Res.

0x14
I2C_DR

Res.

0x10
I2C_OAR2

Res.

0x0C
I2C_OAR1

Res.

0x08
I2C_CR2

Res.

0x04
I2C_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

Res.

Offset

Res.

24.6.11

Res.

RM0390
Inter-integrated circuit (I2C) interface

I2C register map
The table below provides the I2C register map and reset values.
Table 142. I2C register map and reset values

0
0

FREQ[5:0]
0
0

0
0

0
0
0

1

0

0

0

DR[7:0]
0
0
0
0
0

0
0
0
0

0

0

0

0

TRISE[5:0]

0

DNF[3:0]

0

Refer to Section 2.2.2 for the register boundary addresses.

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Universal synchronous asynchronous receiver transmitter (USART)

25

Universal synchronous asynchronous receiver
transmitter (USART)

25.1

USART introduction

RM0390

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 fractional baud rate generator.
It supports synchronous one-way communication and half-duplex single wire
communication. It also supports the LIN (local interconnection network), Smartcard Protocol
and IrDA (infrared data association) SIR ENDEC specifications, and modem operations
(CTS/RTS). It allows multiprocessor communication.
High speed data communication is possible by using the DMA for multibuffer configuration.

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25.2

Universal synchronous asynchronous receiver transmitter (USART)

USART main features
•

Full duplex, asynchronous communications

•

NRZ standard format (Mark/Space)

•

Configurable oversampling method by 16 or by 8 to give flexibility between speed and
clock tolerance

•

Fractional baud rate generator systems
–

Common programmable transmit and receive baud rate (refer to the datasheets
for the value of the baud rate at the maximum APB frequency.

•

Programmable data word length (8 or 9 bits)

•

Configurable stop bits - support for 1 or 2 stop bits

•

LIN Master Synchronous Break send capability and LIN slave break detection
capability
–

13-bit break generation and 10/11 bit break detection when USART is hardware
configured for LIN

•

Transmitter clock output for synchronous transmission

•

IrDA SIR encoder decoder
–

•

Support for 3/16 bit duration for normal mode

Smartcard emulation capability
–

The Smartcard interface supports the asynchronous protocol Smartcards as
defined in the ISO 7816-3 standards

–

0.5, 1.5 stop bits for Smartcard operation

•

Single-wire half-duplex communication

•

Configurable multibuffer communication using DMA (direct memory access)
–

Buffering of received/transmitted bytes in reserved SRAM using centralized DMA

•

Separate enable bits for transmitter and receiver

•

Transfer detection flags:

•

•

•

–

Receive buffer full

–

Transmit buffer empty

–

End of transmission flags

Parity control:
–

Transmits parity bit

–

Checks parity of received data byte

Four error detection flags:
–

Overrun error

–

Noise detection

–

Frame error

–

Parity error

Ten interrupt sources with flags:
–

CTS changes

–

LIN break detection

–

Transmit data register empty

–

Transmission complete

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25.3

–

Receive data register full

–

Idle line received

–

Overrun error

–

Framing error

–

Noise error

–

Parity error

RM0390

•

Multiprocessor communication - enter into mute mode if address match does not occur

•

Wake up from mute mode (by idle line detection or address mark detection)

•

Two receiver wakeup modes: Address bit (MSB, 9th bit), Idle line

USART implementation
This section describes the full set of features implemented in USART1. Refer to Table 143:
USART features for the differences between USART instances.
Table 143. 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

USART modes/features(1)

USART data length

8 or 9 bits

1. X = supported.

25.4

USART functional description
The interface is externally connected to another device by three pins (see Figure 278). Any
USART bidirectional communication requires a minimum of two pins: Receive Data In (RX)
and Transmit Data Out (TX):
RX: Receive Data Input 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 (at USART level, data are then received on SW_RX).

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Universal synchronous asynchronous receiver transmitter (USART)
Through these pins, serial data is transmitted and received in normal USART mode as
frames comprising:
•

An Idle Line prior to transmission or reception

•

A start bit

•

A data word (8 or 9 bits) least significant bit first

•

0.5,1, 1.5, 2 Stop bits indicating that the frame is complete

•

This interface uses a fractional baud rate generator - with a 12-bit mantissa and 4-bit
fraction

•

A status register (USART_SR)

•

Data Register (USART_DR)

•

A baud rate register (USART_BRR) - 12-bit mantissa and 4-bit fraction.

•

A Guardtime Register (USART_GTPR) in case of Smartcard mode.

Refer to Section 25.6: USART registers for the definition of each bit.
The following pin is required to interface in synchronous mode:
•

SCLK: Transmitter 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 (e.g. LCD drivers). The clock phase and polarity
are software programmable. In smartcard mode, SCLK can provide the clock to the
smartcard.

The following pins are required in Hardware flow control mode:
•

nCTS: Clear To Send blocks the data transmission at the end of the current transfer
when high

•

nRTS: Request to send indicates that the USART is ready to receive a data (when
low).

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Figure 278. USART block diagram
PWDATA

PRDATA
Write

Read
(CPU or DMA)

(CPU or DMA)
TX
RX
SW_RX

(Data register) DR

Transmit data register (TDR)

Receive data register (RDR)

Transmit Shift Register

Receive Shift Register

IrDA
SIR
ENDEC
block

IRDA_OUT
IRDA_IN

GTPR
GT

PSC

CR3

SCLK control

DMAT DMAR SCEN NACK HD IRLP IREN

LINE

STOP[1:0] CKEN CPOL CPHA LBCL

CR2

CR1
UE

USART Address

nRTS
nCTS

SCLK

CR2

M

WAKE PCE

PS

PEIE

Hardware
flow
controller
Wakeup
unit

Transmit
control

Receiver
clock

Receiver
control

SR

CR1
IDLE TE
TXEIE TCIE RXNE
IE
IE

CTS LBD

RE RWU SBK

TXE TC RXNE IDLE ORE NF FE PE

USART
interrupt
control

USART_BRR

CR1
OVER8

Transmitter
clock

/ [8 x (2 - OVER8)]

Transmitter rate
control

TE

/USARTDIV

SAMPLING
DIVIDER

DIV_Mantissa
15

fPCLKx(x=1,2)

DIV_Fraction
4

0

Receiver rate
control

RE

Conventional baud rate generator

USARTDIV = DIV_Mantissa + (DIV_Fraction / 8 × (2 – OVER8))

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RM0390

25.4.1

Universal synchronous asynchronous receiver transmitter (USART)

USART character description
Word length may be selected as being either 8 or 9 bits by programming the M bit in the
USART_CR1 register (see Figure 279).
The TX pin is in low state during the start bit. It is in high state during the stop bit.
An Idle character is interpreted as an entire frame of “1”s followed by the start bit of the
next frame which contains data (The number of “1” ‘s will include 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 either 1 or 2 stop bits (logic “1” bit) to acknowledge the
start bit.
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.
Figure 279.JWord length programming

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Universal synchronous asynchronous receiver transmitter (USART)

25.4.2

RM0390

Transmitter
The transmitter can send data words of either 8 or 9 bits depending on the M bit status.
When the transmit enable bit (TE) is set, the data in the transmit shift register is output on
the TX pin and the corresponding clock pulses are output on the SCLK pin.

Character transmission
During an USART transmission, data shifts out least significant bit first on the TX pin. In this
mode, the USART_DR register consists of a buffer (TDR) between the internal bus and the
transmit shift register (see Figure 278).
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 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.

•

0.5 stop bit: To be used when receiving data in Smartcard mode.

•

1.5 stop bits: To be used when transmitting and receiving data in Smartcard mode.

An idle frame transmission will include the stop bits.
A break transmission will be 10 low bits followed by the configured number of stop bits
(when m = 0) and 11 low bits followed by the configured number of stop bits (when m = 1). It
is not possible to transmit long breaks (break of length greater than 10/11 low bits).

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RM0390

Universal synchronous asynchronous receiver transmitter (USART)
Figure 280. Configurable stop bits
8-bit Word length (M bit is reset)

Possible
parity
bit

Data frame
Start
Bit

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

Stop
bit

Bit7

CLOCK

Next data frame
Next
start
bit

****
**
** LBCL bit controls last data clock pulse

a) 1 Stop Bit
Possible
Parity
Bit

Data frame
Start
Bit

Bit0

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

1 1/2 stop bits
Possible
parity
bit

Data frame
Bit0

c) 2 Stop Bits
Start
Bit

Bit0

Next
start
bit

Bit7

b) 1 1/2 stop Bits

Start
Bit

Next data frame

Bit1

Bit2

Bit3

Bit4

Bit5

Bit6

Possible
Parity
Bit

Data frame
Bit1

Bit2

Bit7

Bit3

Bit4

Bit5

Bit6

Bit7

Next data frame
2 Stop
Bits

Next
Start
Bit

Next data frame
Next
start
bit
1/2 stop bit

d) 1/2 Stop Bit

Procedure:
1.

Enable the USART by writing the UE bit in USART_CR1 register to 1.

2.

Program the M bit in USART_CR1 to define the word length.

3.

Program the number of stop bits in USART_CR2.

4.

Select DMA enable (DMAT) in USART_CR3 if Multi buffer Communication is to take
place. Configure the DMA register as explained in multibuffer communication.

5.

Select the desired baud rate using the USART_BRR register.

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_DR 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_DR 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 data register.
The TXE bit is set by hardware and it indicates:
•

The data has been moved from TDR to the shift register and the data transmission has
started.

•

The TDR register is empty.

•

The next data can be written in the USART_DR register without overwriting the
previous data.

This flag generates an interrupt if the TXEIE bit is set.

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Universal synchronous asynchronous receiver transmitter (USART)

RM0390

When a transmission is taking place, a write instruction to the USART_DR register stores
the data in the TDR register and which is copied in the shift register at the end of the current
transmission.
When no transmission is taking place, a write instruction to the USART_DR register places
the data directly in the shift register, the data transmission starts, and the TXE bit is
immediately 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 into the USART_DR 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 281: TC/TXE behavior when transmitting).
The TC bit is cleared by the following software sequence:

Note:

1.

A read from the USART_SR register

2.

A write to the USART_DR register

The TC bit can also be cleared by writing a ‘0 to it. This clearing sequence is recommended
only for Multibuffer communication.
Figure 281. TC/TXE behavior when transmitting
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4# IS SET BECAUSE
48%

SOFTWARE WAITS UNTIL 4#

AIB

Break characters
Setting the SBK bit transmits a break character. The break frame length depends on the M
bit (see Figure 279).
If the SBK bit is set to ‘1 a break character is sent on the TX line after completing the current
character transmission. This bit is reset by hardware when the break character is completed
(during the stop bit of the break character). The USART inserts a logic 1 bit at the end of the
last break frame to guarantee the recognition of the start bit of the next frame.
Note:

802/1327

If the software resets the SBK bit before the commencement of break transmission, the
break character will not be transmitted. For two consecutive breaks, the SBK bit should be
set after the stop bit of the previous break.

DocID026976 Rev 3

RM0390

Universal synchronous asynchronous receiver transmitter (USART)

Idle characters
Setting the TE bit drives the USART to send an idle frame before the first data frame.

25.4.3

Receiver
The USART can receive data words of either 8 or 9 bits depending on the M bit in the
USART_CR1 register.

Start bit detection
The start bit detection sequence is the same when oversampling by 16 or by 8.
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 0 X 0 0 0 0.
Figure 282. Start bit detection when oversampling by 16 or 8
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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 NE noise
flag is set if, for both samplings, at least 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). If this condition is not met,
the start detection aborts and the receiver returns to the idle state (no flag is set).
If, 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, the start bit is validated but the NE noise
flag bit is set.

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Universal synchronous asynchronous receiver transmitter (USART)

RM0390

Character reception
During an USART reception, data shifts in least significant bit first through the RX pin. In this
mode, the USART_DR register consists of a buffer (RDR) between the internal bus and the
received shift register.
Procedure:
1.

Enable the USART by writing the UE bit in USART_CR1 register to 1.

2.

Program the M bit in USART_CR1 to define the word length.

3.

Program the number of stop bits in USART_CR2.

4.

Select DMA enable (DMAR) in USART_CR3 if multibuffer communication is to take
place. Configure the DMA register as explained in multibuffer communication. STEP 3

5.

Select the desired baud rate using the baud rate register USART_BRR

6.

Set the RE bit USART_CR1. This enables the receiver which begins searching for a
start bit.

When a character is received

Note:

•

The RXNE bit is set. It indicates 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.

•

In multibuffer, RXNE is set after every byte received and is cleared by the DMA read to
the Data Register.

•

In single buffer mode, clearing the RXNE bit is performed by a software read to the
USART_DR register. The RXNE flag can also be cleared by writing a zero to it. The
RXNE bit must be cleared before the end of the reception of the next character to avoid
an overrun error.

The RE bit should not be reset while receiving data. If the RE bit is disabled during
reception, the reception of the current byte will be aborted.

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 a data received character
plus an interrupt if the IDLEIE bit is set.

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.

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RM0390

Universal synchronous asynchronous receiver transmitter (USART)
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_DR 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 both the EIE and DMAR bits
are set.

•

The ORE bit is reset by a read to the USART_SR register followed by a USART_DR
register read operation.

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. It may also occur
when the new data is received during the reading sequence (between the USART_SR
register read access and the USART_DR read access).

Selecting the proper oversampling method
The receiver implements different user-configurable oversampling techniques (except in
synchronous mode) for data recovery by discriminating between valid incoming data and
noise.
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 283 and
Figure 284).
Depending on the application:
•

select oversampling by 8 (OVER8=1) to achieve higher speed (up to fPCLK/8). In this
case the maximum receiver tolerance to clock deviation is reduced (refer to
Section 25.4.5: USART receiver tolerance to clock deviation)

•

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 fPCLK/16

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Universal synchronous asynchronous receiver transmitter (USART)

RM0390

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 144) 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 tolerance to clock deviations (see Section 25.4.5: USART
receiver tolerance to clock deviation). 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_DR 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 a USART_SR register read operation followed by a USART_DR
register read operation.
Note:

Oversampling by 8 is not available in the Smartcard, IrDA and LIN modes. In those modes,
the OVER8 bit is forced to ‘0 by hardware.
Figure 283. Data sampling when oversampling by 16
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RM0390

Universal synchronous asynchronous receiver transmitter (USART)
Figure 284. Data sampling when oversampling by 8
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Table 144. 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 desynchronization 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_DR 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 a USART_SR register read operation followed by a USART_DR
register read operation.

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.

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Universal synchronous asynchronous receiver transmitter (USART)

25.4.4

RM0390

1.

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.

2.

1 stop bit: Sampling for 1 stop Bit is done on the 8th, 9th and 10th samples.

3.

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 bit. 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 bit 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 25.4.11 for more
details.

4.

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.

Fractional 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 Mantissa and Fraction values of USARTDIV.
Equation 1: Baud rate for standard USART (SPI mode included)
f CK
Tx/Rx baud = ------------------------------------------------------------------------------------8 × ( 2 – OVER8 ) × USARTDIV

Equation 2: Baud rate in Smartcard, LIN and IrDA modes
f CK
Tx/Rx baud = ---------------------------------------------16 × USARTDIV

USARTDIV is an unsigned fixed point number that is coded on the USART_BRR register.

Note:

•

When OVER8=0, the fractional part is coded on 4 bits and programmed by the
DIV_fraction[3:0] bits in the USART_BRR register

•

When OVER8=1, the fractional part is coded on 3 bits and programmed by the
DIV_fraction[2:0] bits in the USART_BRR register, and bit DIV_fraction[3] must be kept
cleared.

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.

How to derive USARTDIV from USART_BRR register values when OVER8=0
Example 1:
If DIV_Mantissa = 0d27 and DIV_Fraction = 0d12 (USART_BRR = 0x1BC), then
Mantissa (USARTDIV) = 0d27

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RM0390

Universal synchronous asynchronous receiver transmitter (USART)
Fraction (USARTDIV) = 12/16 = 0d0.75
Therefore USARTDIV = 0d27.75
Example 2:
To program USARTDIV = 0d25.62
This leads to:
DIV_Fraction = 16*0d0.62 = 0d9.92
The nearest real number is 0d10 = 0xA
DIV_Mantissa = mantissa (0d25.620) = 0d25 = 0x19
Then, USART_BRR = 0x19A hence USARTDIV = 0d25.625
Example 3:
To program USARTDIV = 0d50.99
This leads to:
DIV_Fraction = 16*0d0.99 = 0d15.84
The nearest real number is 0d16 = 0x10 => overflow of DIV_frac[3:0] => carry must be
added up to the mantissa
DIV_Mantissa = mantissa (0d50.990 + carry) = 0d51 = 0x33
Then, USART_BRR = 0x330 hence USARTDIV = 0d51.000

How to derive USARTDIV from USART_BRR register values when OVER8=1
Example 1:
If DIV_Mantissa = 0x27 and DIV_Fraction[2:0]= 0d6 (USART_BRR = 0x1B6), then
Mantissa (USARTDIV) = 0d27
Fraction (USARTDIV) = 6/8 = 0d0.75
Therefore USARTDIV = 0d27.75
Example 2:
To program USARTDIV = 0d25.62
This leads to:
DIV_Fraction = 8*0d0.62 = 0d4.96
The nearest real number is 0d5 = 0x5
DIV_Mantissa = mantissa (0d25.620) = 0d25 = 0x19
Then, USART_BRR = 0x195 => USARTDIV = 0d25.625
Example 3:
To program USARTDIV = 0d50.99
This leads to:
DIV_Fraction = 8*0d0.99 = 0d7.92

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Universal synchronous asynchronous receiver transmitter (USART)

RM0390

The nearest real number is 0d8 = 0x8 => overflow of the DIV_frac[2:0] => carry must be
added up to the mantissa
DIV_Mantissa = mantissa (0d50.990 + carry) = 0d51 = 0x33
Then, USART_BRR = 0x0330 => USARTDIV = 0d51.000
Table 145. Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 12 MHz,
oversampling by 16(1)
Oversampling by 16 (OVER8=0)
Baud rate7

fPCLK = 8 MHz

fPCLK = 12 MHz

Value
% Error =
programmed
(Calculated in the baud Desired) B.rate /
rate register
Desired B.rate

Actual

Value
programmed
in the baud
rate register

% Error

S.No

Desired

Actual

1

1.2 KBps

1.2 KBps

416.6875

0

1.2 KBps

625

0

2

2.4 KBps

2.4 KBps

208.3125

0.01

2.4 KBps

312.5

0

3

9.6 KBps

9.604 KBps

52.0625

0.04

9.6 KBps

78.125

0

4

19.2 KBps

19.185 KBps

26.0625

0.08

19.2 KBps

39.0625

0

5

38.4 KBps

38.462 KBps

13

0.16

38.339 KBps

19.5625

0.16

6

57.6 KBps

57.554 KBps

8.6875

0.08

57.692 KBps

13

0.16

7

115.2 KBps 115.942 KBps

4.3125

0.64

115.385 KBps

6.5

0.16

8

230.4 KBps 228.571 KBps

2.1875

0.79

230.769 KBps

3.25

0.16

9

460.8 KBps 470.588 KBps

1.0625

2.12

461.538 KBps

1.625

0.16

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 146. Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 12 MHz,
oversampling by 8(1)
Oversampling by 8 (OVER8 = 1)
Baud rate

fPCLK = 8 MHz

fPCLK = 12 MHz

% Error =
Value
(Calculated programmed
Desired)
in the baud
B.rate /
rate register
Desired
B.rate

Value
programmed
% Error
in the baud
rate register

S.No

Desired

Actual

1

1.2 KBps

1.2 KBps

833.375

0

1.2 KBps

1250

0

2

2.4 KBps

2.4 KBps

416.625

0.01

2.4 KBps

625

0

3

9.6 KBps

9.604 KBps

104.125

0.04

9.6 KBps

156.25

0

4

19.2 KBps

19.185 KBps

52.125

0.08

19.2 KBps

78.125

0

5

38.4 KBps

38.462 KBps

26

0.16

38.339 KBps

39.125

0.16

810/1327

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Actual

RM0390

Universal synchronous asynchronous receiver transmitter (USART)

Table 146. Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 12 MHz,
oversampling by 8(1) (continued)
Oversampling by 8 (OVER8 = 1)
Baud rate

fPCLK = 8 MHz

fPCLK = 12 MHz

% Error =
Value
(Calculated programmed
Desired)
in the baud
B.rate /
rate register
Desired
B.rate

Value
programmed
% Error
in the baud
rate register

S.No

Desired

Actual

6

57.6 KBps

57.554 KBps

17.375

0.08

57.692 KBps

26

0.16

7

115.2 KBps

115.942 KBps

8.625

0.64

115.385 KBps

13

0.16

8

230.4 KBps

228.571 KBps

4.375

0.79

230.769 KBps

6.5

0.16

9

460.8 KBps

470.588 KBps

2.125

2.12

461.538 KBps

3.25

0.16

10

921.6 KBps

888.889 KBps

1.125

3.55

923.077 KBps

1.625

0.16

Actual

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 147. Error calculation for programmed baud rates at fPCLK = 16 MHz or fPCLK = 24 MHz,
oversampling by 16(1)
Oversampling by 16 (OVER8 = 0)
Baud rate

fPCLK

= 16 MHz

fPCLK

Value
% Error =
programmed
(Calculated in the baud Desired) B.rate /
rate register Desired B.rate

= 24 MHz

Value
programmed
% Error
in the baud
rate register

S.No

Desired

Actual

1

1.2 KBps

1.2 KBps

833.3125

0

1.2

1250

0

2

2.4 KBps

2.4 KBps

416.6875

0

2.4

625

0

3

9.6 KBps

9.598 KBps

104.1875

0.02

9.6

156.25

0

4

19.2 KBps

19.208 KBps

52.0625

0.04

19.2

78.125

0

5

38.4 KBps

38.369 KBps

26.0625

0.08

38.4

39.0625

0

6

57.6 KBps

57.554 KBps

17.375

0.08

57.554

26.0625

0.08

7

115.2 KBps

115.108 KBps

8.6875

0.08

115.385

13

0.16

8

230.4 KBps

231.884 KBps

4.3125

0.64

230.769

6.5

0.16

9

460.8 KBps

457.143 KBps

2.1875

0.79

461.538

3.25

0.16

10

921.6 KBps

941.176 KBps

1.0625

2.12

923.077

1.625

0.16

Actual

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.

DocID026976 Rev 3

811/1327
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Universal synchronous asynchronous receiver transmitter (USART)

RM0390

Table 148. Error calculation for programmed baud rates at fPCLK = 16 MHz or fPCLK = 24 MHz,
oversampling by 8(1)
Oversampling by 8 (OVER8=1)
Baud rate

fPCLK = 16 MHz

fPCLK = 24 MHz

Value
% Error =
programmed
(Calculated in the baud Desired) B.rate /
rate register
Desired B.rate

Value
programmed
% Error
in the baud
rate register

S.No

Desired

Actual

1

1.2 KBps

1.2 KBps

1666.625

0

1.2 KBps

2500

0

2

2.4 KBps

2.4 KBps

833.375

0

2.4 KBps

1250

0

3

9.6 KBps

9.598 KBps

208.375

0.02

9.6 KBps

312.5

0

4

19.2 KBps

19.208 KBps

104.125

0.04

19.2 KBps

156.25

0

5

38.4 KBps

38.369 KBps

52.125

0.08

38.4 KBps

78.125

0

6

57.6 KBps

57.554 KBps

34.75

0.08

57.554 KBps

52.125

0.08

7

115.2 KBps

115.108 KBps

17.375

0.08

115.385 KBps

26

0.16

8

230.4 KBps

231.884 KBps

8.625

0.64

230.769 KBps

13

0.16

9

460.8 KBps

457.143 KBps

4.375

0.79

461.538 KBps

6.5

0.16

10

921.6 KBps

941.176 KBps

2.125

2.12

923.077 KBps

3.25

0.16

11

2 MBps

2000 KBps

1

0

2000 KBps

1.5

0

12

3 MBps

NA

NA

NA

3000 KBps

1

0

Actual

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 149. Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 16 MHz,
oversampling by 16(1)
Oversampling by 16 (OVER8=0)
Baud rate

fPCLK = 8 MHz

fPCLK = 16 MHz

S.No

Desired

Actual

Value
programmed
in the baud
rate register

1.

2.4 KBps

2.400 KBps

208.3125

0.00%

2.400 KBps

416.6875

0.00%

2.

9.6 KBps

9.604 KBps

52.0625

0.04%

9.598 KBps

104.1875

0.02%

3.

19.2 KBps

19.185 KBps

26.0625

0.08%

19.208 KBps

52.0625

0.04%

4.

57.6 KBps

57.554 KBps

8.6875

0.08%

57.554 KBps

17.3750

0.08%

5.

115.2 KBps

115.942 KBps

4.3125

0.64%

115.108 KBps

8.6875

0.08%

6.

230.4 KBps

228.571 KBps

2.1875

0.79%

231.884 KBps

4.3125

0.64%

7.

460.8 KBps

470.588 KBps

1.0625

2.12%

457.143 KBps

2.1875

0.79%

812/1327

% Error =
(Calculated Desired)B.Rate
/Desired B.Rate

Actual

DocID026976 Rev 3

Value
programmed
% Error
in the baud
rate register

RM0390

Universal synchronous asynchronous receiver transmitter (USART)

Table 149. Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 16 MHz,
oversampling by 16(1) (continued)
Oversampling by 16 (OVER8=0)
Baud rate

fPCLK = 8 MHz

fPCLK = 16 MHz

Desired

Actual

Value
programmed
in the baud
rate register

8.

896 KBps

NA

NA

NA

888.889 KBps

1.1250

0.79%

9.

921.6 KBps

NA

NA

NA

941.176 KBps

1.0625

2.12%

S.No

% Error =
(Calculated Desired)B.Rate
/Desired B.Rate

Actual

Value
programmed
% Error
in the baud
rate register

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 150. Error calculation for programmed baud rates at fPCLK = 8 MHz or fPCLK = 16 MHz,
oversampling by 8(1)
Oversampling by 8 (OVER8=1)
Baud rate

fPCLK = 8 MHz

fPCLK = 16 MHz

% Error =
Value
(Calculated programmed
in the baud Desired)B.Rate
rate register /Desired B.Rate

Actual

Value
programmed
in the baud
rate register

%
Error

S.No

Desired

Actual

1.

2.4 KBps

2.400 KBps

416.625

0.01%

2.400 KBps

833.375

0.00%

2.

9.6 KBps

9.604 KBps

104.125

0.04%

9.598 KBps

208.375

0.02%

3.

19.2 KBps

19.185 KBps

52.125

0.08%

19.208 KBps

104.125

0.04%

4.

57.6 KBps

57.557 KBps

17.375

0.08%

57.554 KBps

34.750

0.08%

5.

115.2 KBps

115.942 KBps

8.625

0.64%

115.108 KBps

17.375

0.08%

6.

230.4 KBps

228.571 KBps

4.375

0.79%

231.884 KBps

8.625

0.64%

7.

460.8 KBps

470.588 KBps

2.125

2.12%

457.143 KBps

4.375

0.79%

8.

896 KBps

888.889 KBps

1.125

0.79%

888.889 KBps

2.250

0.79%

9.

921.6 KBps

888.889 KBps

1.125

3.55%

941.176 KBps

2.125

2.12%

10.

1.792 MBps

NA

NA

NA

1.7777 MBps

1.125

0.79%

11. 1.8432 MBps

NA

NA

NA

1.7777 MBps

1.125

3.55%

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.

DocID026976 Rev 3

813/1327
845

Universal synchronous asynchronous receiver transmitter (USART)

RM0390

Table 151. Error calculation for programmed baud rates at fPCLK = 30 MHz or fPCLK = 60 MHz,
oversampling by 16(1)(2)
Oversampling by 16 (OVER8=0)
Baud rate

fPCLK = 30 MHz

fPCLK = 60 MHz

S.No

Desired

Actual

Value
programmed
in the baud
rate register

% Error =
(Calculated Desired)B.Rate
/Desired B.Rate

1.

2.4 KBps

2.400 KBps

781.2500

0.00%

2.400 KBps

1562.5000

0.00%

2.

9.6 KBps

9.600 KBps

195.3125

0.00%

9.600 KBps

390.6250

0.00%

3.

19.2 KBps

19.194 KBps

97.6875

0.03%

19.200 KBps

195.3125

0.00%

4.

57.6 KBps

57.582KBps

32.5625

0.03%

57.582 KBps

65.1250

0.03%

5.

115.2 KBps

115.385 KBps

16.2500

0.16%

115.163 KBps

32.5625

0.03%

6.

230.4 KBps

230.769 KBps

8.1250

0.16%

230.769 KBps

16.2500

0.16%

7.

460.8 KBps

461.538 KBps

4.0625

0.16%

461.538 KBps

8.1250

0.16%

8.

896 KBps

909.091 KBps

2.0625

1.46%

895.522 KBps

4.1875

0.05%

9.

921.6 KBps

909.091 KBps

2.0625

1.36%

923.077 KBps

4.0625

0.16%

10. 1.792 MBps

1.1764 MBps

1.0625

1.52%

1.8182 MBps

2.0625

1.36%

11. 1.8432 MBps

1.8750 MBps

1.0000

1.73%

1.8182 MBps

2.0625

1.52%

12. 3.584 MBps

NA

NA

NA

3.2594 MBps

1.0625

1.52%

13. 3.6864 MBps

NA

NA

NA

3.7500 MBps

1.0000

1.73%

Actual

Value
programmed
in the baud
rate register

%
Error

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.
2. Only USART1 and USART6 are clocked with PCLK2. Other USARTs are clocked with PCLK1. Refer to the device
datasheets for the maximum values for PCLK1 and PCLK2.

Table 152. Error calculation for programmed baud rates at fPCLK = 30 MHz or fPCLK = 60 MHz,
oversampling by 8(1) (2)
Oversampling by 8 (OVER8=1)
Baud rate

fPCLK = 30 MHz

fPCLK =60 MHz

Value
% Error =
programmed
(Calculated in the baud Desired)B.Rate
rate register /Desired B.Rate

Actual

Value
programmed
in the baud
rate register

%
Error

S.No

Desired

Actual

1.

2.4 KBps

2.400 KBps

1562.5000

0.00%

2.400 KBps

3125.0000

0.00%

2.

9.6 KBps

9.600 KBps

390.6250

0.00%

9.600 KBps

781.2500

0.00%

3.

19.2 KBps

19.194 KBps

195.3750

0.03%

19.200 KBps

390.6250

0.00%

4.

57.6 KBps

57.582 KBps

65.1250

0.16%

57.582 KBps

130.2500

0.03%

5.

115.2 KBps

115.385 KBps

32.5000

0.16%

115.163 KBps

65.1250

0.03%

6.

230.4 KBps

230.769 KBps

16.2500

0.16%

230.769 KBps

32.5000

0.16%

814/1327

DocID026976 Rev 3

RM0390

Universal synchronous asynchronous receiver transmitter (USART)

Table 152. Error calculation for programmed baud rates at fPCLK = 30 MHz or fPCLK = 60 MHz,
oversampling by 8(1) (2) (continued)
Oversampling by 8 (OVER8=1)
Baud rate

S.No

fPCLK = 30 MHz

fPCLK =60 MHz

Value
% Error =
programmed
(Calculated in the baud Desired)B.Rate
rate register /Desired B.Rate

Actual

Value
programmed
in the baud
rate register

%
Error

Desired

Actual

7.

460.8 KBps

461.538 KBps

8.1250

0.16%

461.538 KBps

16.2500

0.16%

8.

896 KBps

909.091 KBps

4.1250

1.46%

895.522 KBps

8.3750

0.05%

9.

921.6 KBps

909.091 KBps

4.1250

1.36%

923.077 KBps

8.1250

0.16%

10.

1.792 MBps

1.7647 MBps

2.1250

1.52%

1.8182 MBps

4.1250

1.46%

11. 1.8432 MBps

1.8750 MBps

2.0000

1.73%

1.8182 MBps

4.1250

1.36%

12.

3.584 MBps

3.7500 MBps

1.0000

4.63%

3.5294 MBps

2.1250

1.52%

13. 3.6864 MBps

3.7500 MBps

1.0000

1.73%

3.7500 MBps

2.0000

1.73%

7.168 MBps

NA

NA

NA

7.5000 MBps

1.0000

4.63%

15. 7.3728 MBps

NA

NA

NA

7.5000 MBps

1.0000

1.73%

14.

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.
2. Only USART1 and USART6 are clocked with PCLK2. Other USARTs are clocked with PCLK1. Refer to the device
datasheets for the maximum values for PCLK1 and PCLK2.

Table 153. Error calculation for programmed baud rates at fPCLK = 42 MHz or fPCLK = 84 Hz,
oversampling by 16(1)(2)
Oversampling by 16 (OVER8=0)
Baud rate

fPCLK = 42 MHz

fPCLK = 84 MHz

S.No

Desired

Actual

Value
programmed
in the baud
rate register

% Error =
(Calculated Desired)B.Rate
/Desired B.Rate

1

1.2 KBps

1.2 KBps

2187.5

0

1.2 KBps

NA

0

2

2.4 KBps

2.4 KBps

1093.75

0

2.4 KBps

2187.5

0

3

9.6 KBps

9.6 KBps

273.4375

0

9.6 KBps

546.875

0

4

19.2 KBps

19.195 KBps

136.75

0.02

19.2 KBps

273.4375

0

5

38.4 KBps

38.391 KBps

68.375

0.02

38.391 KBps

136.75

0.02

6

57.6 KBps

57.613 KBps

45.5625

0.02

57.613 KBps

91.125

0.02

7

115.2 KBps

115.068 KBps

22.8125

0.11

115.226 KBps

45.5625

0.02

8

230.4 KBps

230.769 KBps

11.375

0.16

230.137 KBps

22.8125

0.11

9

460.8 KBps

461.538 KBps

5.6875

0.16

461.538 KBps

11.375

0.16

DocID026976 Rev 3

Actual

Value
programmed
in the baud
rate register

%
Error

815/1327
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Universal synchronous asynchronous receiver transmitter (USART)

RM0390

Table 153. Error calculation for programmed baud rates at fPCLK = 42 MHz or fPCLK = 84 Hz,
oversampling by 16(1)(2) (continued)
Oversampling by 16 (OVER8=0)
Baud rate

fPCLK = 42 MHz

fPCLK = 84 MHz

Desired

Actual

Value
programmed
in the baud
rate register

10

921.6 KBps

913.043 KBps

2.875

0.93

923.076 KBps

5.6875

0.93

11

1.792 MBps

1.826 MBps

1.4375

1.9

1.787 MBps

2.9375

0.27

12 1.8432 MBps

1.826 MBps

1.4375

0.93

1.826 MBps

2.875

0.93

3.584 MBps

NA

NA

NA

3.652 MBps

1.4375

1.9

14 3.6864 MBps

NA

NA

NA

3.652 MBps

1.4375

0.93

S.No

13

% Error =
(Calculated Desired)B.Rate
/Desired B.Rate

Actual

Value
programmed
in the baud
rate register

%
Error

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.
2. Only USART1 and USART6 are clocked with PCLK2. Other USARTs are clocked with PCLK1. Refer to the device
datasheets for the maximum values for PCLK1 and PCLK2.

Table 154. Error calculation for programmed baud rates at fPCLK = 42 MHz or fPCLK = 84 MHz,
oversampling by 8(1)(2)
Oversampling by 8 (OVER8=1)
Baud rate

fPCLK = 42 MHz

fPCLK = 84 MHz

Value
% Error =
programmed
(Calculated in the baud Desired)B.Rate
rate register /Desired B.Rate

Actual

Value
programmed
in the baud
rate register

%
Error

S.No

Desired

Actual

1.

1.2 KBps

1.2 KBps

NA

0

1.2 KBps

NA

0

2.

2.4 KBps

2.4 KBps

2187.5

0

2.4 KBps

NA

0

3.

9.6 KBps

9.6 KBps

546.875

0

9.6 KBps

1093.75

0

4.

19.2 KBps

19.195 KBps

273.5

0.02

19.2 KBps

546.875

0

5.

38.4 KBps

38.391 KBps

136.75

0.02

38.391 KBps

273.5

0.02

6.

57.6 KBps

57.613 KBps

91.125

0.02

57.613 KBps

182.25

0.02

7.

115.2 KBps

115.068 KBps

45.625

0.11

115.226 KBps

91.125

0.02

8.

230.4 KBps

230.769 KBps

22.75

0.11

230.137 KBps

45.625

0.11

9.

460.8 KBps

461.538 KBps

11.375

0.16

461.538 KBps

22.75

0.16

10.

921.6 KBps

913.043 KBps

5.75

0.93

923.076 KBps

11.375

0.93

11.

1.792 MBps

1.826 MBps

2.875

1.9

1.787Mbps

5.875

0.27

12.

1.8432 MBps

1.826 MBps

2.875

0.93

1.826 MBps

5.75

0.93

13.

3.584 MBps

3.5 MBps

1.5

2.34

3.652 MBps

2.875

1.9

14.

3.6864 MBps

3.82 MBps

1.375

3.57

3.652 MBps

2.875

0.93

816/1327

DocID026976 Rev 3

RM0390

Universal synchronous asynchronous receiver transmitter (USART)

Table 154. Error calculation for programmed baud rates at fPCLK = 42 MHz or fPCLK = 84 MHz,
oversampling by 8(1)(2) (continued)
Oversampling by 8 (OVER8=1)
Baud rate

S.No

fPCLK = 42 MHz

fPCLK = 84 MHz

Value
% Error =
programmed
(Calculated in the baud Desired)B.Rate
rate register /Desired B.Rate

Actual

Value
programmed
in the baud
rate register

%
Error

Desired

Actual

15.

7.168 MBps

NA

NA

NA

7 MBps

1.5

2.34

16.

7.3728 MBps

NA

NA

NA

7.636 MBps

1.375

3.57

18.

9 MBps

NA

NA

NA

9.333 MBps

1.125

3.7

20.

10.5 MBps

NA

NA

NA

10.5 MBps

1

0

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.
2. Only USART1 and USART6 are clocked with PCLK2. Other USARTs are clocked with PCLK1. Refer to the device
datasheets for the maximum values for PCLK1 and PCLK2.

25.4.5

USART receiver tolerance to clock deviation
The USART asynchronous receiver works correctly only if the total clock system deviation is
smaller than the USART receiver tolerance. The causes which contribute to the total
deviation are:
•

DTRA: Deviation due to the transmitter error (which also includes the deviation of the
transmitter local oscillator)

•

DQUANT: Error due to the baud rate quantization of the receiver

•

DREC: Deviation of the receiver 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 tolerance
The USART receiver tolerance to properly receive data is equal to the maximum tolerated
deviation and depends on the following choices:
•

10- or 11-bit character length defined by the M bit in the USART_CR1 register

•

oversampling by 8 or 16 defined by the OVER8 bit in the USART_CR1 register

•

use of fractional baud rate or not

•

use of 1 bit or 3 bits to sample the data, depending on the value of the ONEBIT bit in
the USART_CR3 register

DocID026976 Rev 3

817/1327
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Universal synchronous asynchronous receiver transmitter (USART)

RM0390

Table 155. USART receiver tolerance when DIV fraction is 0
M bit

OVER8 bit = 0

OVER8 bit = 1

ONEBIT=0

ONEBIT=1

ONEBIT=0

ONEBIT=1

0

3.75%

4.375%

2.50%

3.75%

1

3.41%

3.97%

2.27%

3.41%

Table 156. USART receiver tolerance when DIV_Fraction is different from 0
M bit

OVER8 bit = 0

OVER8 bit = 1

ONEBIT=0

ONEBIT=1

ONEBIT=0

ONEBIT=1

0

3.33%

3.88%

2%

3%

1

3.03%

3.53%

1.82%

2.73%

Note:

The figures specified in Table 155 and Table 156 may slightly differ in the special case when
the received frames contain some Idle frames of exactly 10-bit times when M=0 (11-bit times
when M=1).

25.4.6

Multiprocessor communication
There is a possibility of performing multiprocessor communication with the USART (several
USARTs connected in a network). For instance one of the USARTs can be the master, its TX
output is connected to the RX input of the other USART. 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 mute mode:
•

None of the reception status bits can be set.

•

All the receive interrupts are inhibited.

•

The RWU bit in USART_CR1 register is set to 1. RWU can be controlled automatically
by hardware or written by the software 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.

Idle line detection (WAKE=0)
The USART enters mute mode when the RWU bit is written to 1.
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_SR register. RWU can also be written to 0 by software.
An example of mute mode behavior using Idle line detection is given in Figure 285.

818/1327

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Universal synchronous asynchronous receiver transmitter (USART)
Figure 285. Mute mode using Idle line detection
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Address mark detection (WAKE=1)
In this mode, bytes are recognized as addresses if their MSB is a ‘1 else they are
considered as data. In an address byte, the address of the targeted receiver is put on the 4
LSB. This 4-bit word is compared by the receiver with its own address which is programmed
in the ADD bits in the USART_CR2 register.
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 nor DMA request is issued as the
USART would have entered mute mode.
It 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.
The RWU bit can be written to as 0 or 1 when the receiver buffer contains no data (RXNE=0
in the USART_SR register). Otherwise the write attempt is ignored.
An example of mute mode behavior using address mark detection is given in Figure 286.
Figure 286. Mute mode using address mark detection
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25.4.7

RM0390

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 bit, the possible USART frame formats are as listed in Table 157.
Table 157. Frame formats
M bit

PCE bit

USART frame(1)

0

0

| SB | 8 bit data | STB |

0

1

| SB | 7-bit data | PB | STB |

1

0

| SB | 9-bit data | STB |

1

1

| SB | 8-bit data PB | STB |

1. Legends: SB: start bit, STB: stop bit, PB: parity bit.

Even parity
The parity bit is calculated to obtain an even number of “1s” inside the frame made of the 7
or 8 LSB bits (depending on whether M is equal to 0 or 1) and the parity bit.
E.g.: data=00110101; 4 bits set => 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 7 or
8 LSB bits (depending on whether M is equal to 0 or 1) and the parity bit.
E.g.: data=00110101; 4 bits set => 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_SR register and an interrupt is
generated if PEIE is set in the USART_CR1 register. The PE flag is cleared by a software
sequence (a read from the status register followed by a read or write access to the
USART_DR data register).
Note:

In case of wakeup by an address mark: the MSB bit of the data is taken into account to
identify an address but not the parity bit. And the receiver does not check the parity of the
address data (PE is not set in case of a parity error).

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)).
Note:

820/1327

The software routine that manages the transmission can activate the software sequence
which clears the PE flag (a read from the status register followed by a read or write access
to the data register). When operating in half-duplex mode, depending on the software, this
can cause the PE flag to be unexpectedly cleared.

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25.4.8

Universal synchronous asynchronous receiver transmitter (USART)

LIN (local interconnection network) mode
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 same procedure explained in Section 25.4.2 has to be applied for LIN Master
transmission than for normal USART transmission with the following differences:
•

Clear the M bit to configure 8-bit word length.

•

Set the LINEN bit to enter LIN mode. In this case, setting the SBK bit sends 13 ‘0 bits
as a break character. Then a bit of value ‘1 is sent to allow the next start detection.

LIN reception
A break detection circuit is implemented on the USART interface. 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 LBD flag is set in USART_SR. 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 in Figure 287.
Examples of break frames are given on Figure 288, where we suppose that LBDL=1 (11-bit
break length), and M=0 (8-bit data).

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Figure 287. Break detection in LIN mode (11-bit break length - LBDL bit is set)
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Universal synchronous asynchronous receiver transmitter (USART)
Figure 288. Break detection in LIN mode vs. Framing error detection
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25.4.9

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.

The USART allows the user to control a bidirectional synchronous serial communications in
master mode. The SCLK pin is the output of the USART transmitter clock. No clock pulses
are sent to the SCLK pin during start bit and stop bit. Depending on the state of the LBCL bit
in the USART_CR2 register clock pulses will or will not be generated during the last valid
data bit (address mark). The CPOL bit in the USART_CR2 register allows the user to select
the clock polarity, and the CPHA bit in the USART_CR2 register allows the user to select the
phase of the external clock (see Figure 289, Figure 290 and Figure 291).
During the Idle state, preamble and send break, the external SCLK clock is not activated.
In synchronous mode the USART transmitter works exactly like in asynchronous mode. But
as SCLK 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 SCLK (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 time).
Note:

The SCLK pin works in conjunction with the TX pin. Thus, the clock is provided only if the
transmitter is enabled (TE=1) and a data is being transmitted (the data register USART_DR

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RM0390

has been written). This means that it is not possible to receive a synchronous data without
transmitting data.
The LBCL, CPOL and CPHA bits have to be selected when both the transmitter and the
receiver are disabled (TE=RE=0) to ensure that the clock pulses function correctly. These
bits should not be changed while the transmitter or the receiver is enabled.
It is advised that TE and RE are set in the same instruction in order to minimize the setup
and the hold time of the receiver.
The USART supports master mode only: it cannot receive or send data related to an input
clock (SCLK is always an output).
Figure 289. USART example of synchronous transmission
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Figure 290. USART data clock timing diagram (M=0)
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Universal synchronous asynchronous receiver transmitter (USART)
Figure 291. USART data clock timing diagram (M=1)
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Note:

The function of SCLK is different in Smartcard mode. Refer to the Smartcard mode chapter
for more details.

25.4.10

Single-wire half-duplex communication
The 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 ‘HALF DUPLEX SEL’ (HDSEL in USART_CR3).

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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 floating input (or output high open-drain) when not driven by the USART.

Apart from this, the communications are similar to what is done in normal USART mode.
The conflicts on the line must be managed by the software (by the use of a centralized
arbiter, for instance). In particular, the transmission is never blocked by hardware and
continue to occur as soon as a data is written in the data register while the TE bit is set.

25.4.11

Smartcard
The 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 Smartcards as
defined in the ISO 7816-3 standard. The USART should be configured as:

Note:

•

8 bits plus parity: where M=1 and PCE=1 in the USART_CR1 register

•

1.5 stop bits when transmitting and receiving: where STOP=11 in the USART_CR2
register.

It is also possible to choose 0.5 stop bit for receiving but it is recommended to use 1.5 stop
bits for both transmitting and receiving to avoid switching between the two configurations.
Figure 293 shows examples of what can be seen on the data line with and without parity
error.
Figure 293. ISO 7816-3 asynchronous protocol
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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 is a single wire half duplex communication protocol.
•

826/1327

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 will start
DocID026976 Rev 3

RM0390

Universal synchronous asynchronous receiver transmitter (USART)
shifting on the next baud clock edge. In Smartcard mode this transmission is further
delayed by a guaranteed 1/2 baud clock.

Note:

•

If a parity error is detected during reception of a frame programmed with a 0.5 or 1.5
stop bit 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 USART has not been correctly received. This NACK signal (pulling
transmit line low for 1 baud clock) will cause a framing error on the transmitter side
(configured with 1.5 stop bits). The application can handle re-sending of data according
to the protocol. A parity error is ‘NACK’ed by the receiver if the NACK control bit is set,
otherwise a NACK is not transmitted.

•

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 will not be 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
will not detect the NACK as a start bit.

A break character is not significant in Smartcard mode. A 0x00 data with a framing error will
be 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 294 details how the NACK signal is sampled by the USART. In this example the
USART is transmitting a 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 294. Parity error detection using the 1.5 stop bits
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The USART can provide a clock to the smartcard through the SCLK output. In smartcard
mode, SCLK 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

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prescaler register USART_GTPR. SCLK frequency can be programmed from fCK/2 to
fCK/62, where fCK is the peripheral input clock.

25.4.12

IrDA SIR ENDEC block
The 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 295).
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 115.2Kbps 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 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.

828/1327

•

IrDA is a half duplex communication protocol. If the Transmitter is busy (i.e. the USART
is sending data to the IrDA encoder), any data on the IrDA receive line will be ignored
by the IrDA decoder and if the Receiver is busy (USART is receiving decoded data
from the USART), data on the TX from the USART to IrDA will not be encoded by IrDA.
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 296).

•

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.

•

The IrDA specification requires the acceptance of pulses greater than 1.41 us. 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 IrDA low-power Baud Register, 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”.

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Universal synchronous asynchronous receiver transmitter (USART)

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. A valid low is accepted only if
its duration is greater than 2 periods of the IrDA low-power Baud clock (PSC value in
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 295. IrDA SIR ENDEC- block diagram
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Figure 296. IrDA data modulation (3/16) -Normal mode

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Universal synchronous asynchronous receiver transmitter (USART)

25.4.13

RM0390

Continuous communication using DMA
The USART is capable of continuous communication using the DMA. The DMA requests for
Rx buffer and Tx buffer are generated independently.

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 the
DMA specification) to the USART_DR 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_DR register address in the DMA control register to configure it as the
destination of the transfer. The data will be 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 will be loaded into the USART_DR 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 bit in the SR register by writing 0 to it.

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
communication is complete. This is required to avoid corrupting the last transmission before
disabling the USART or entering the Stop mode. The software must wait until TC=1. The TC
flag remains cleared during all data transfers and it is set by hardware at the last frame end
of transmission.

830/1327

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RM0390

Universal synchronous asynchronous receiver transmitter (USART)
Figure 297. Transmission using DMA
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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_DR register to a SRAM area configured using the DMA
peripheral (refer to the DMA specification) whenever a data byte is received. To map a DMA
channel for USART reception, use the following procedure:
1.

Write the USART_DR register address in the DMA control register to configure it as the
source of the transfer. The data will be 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 will be loaded from USART_DR to this memory area after each
RXNE event.

3.

Configure the total number of bytes to be transferred in 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. The DMAR bit should
be cleared by software in the USART_CR3 register during the interrupt subroutine.

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Figure 298. Reception using DMA
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Error flagging and interrupt generation in multibuffer communication
In case of multibuffer communication if any error occurs during the transaction the error flag
will be asserted after the current byte. An interrupt will be generated if the interrupt enable
flag is set. For framing error, overrun error and noise flag which are asserted with RXNE in
case of single byte reception, there will be separate error flag interrupt enable bit (EIE bit in
the USART_CR3 register), which if set will issue an interrupt after the current byte with
either of these errors.

25.4.14

Hardware flow control
It is possible to control the serial data flow between 2 devices by using the nCTS input and
the nRTS output. The Figure 299 shows how to connect 2 devices in this mode:
Figure 299. Hardware flow control between 2 USARTs
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RTS and CTS flow control can be enabled independently by writing respectively RTSE and
CTSE bits to 1 (in the USART_CR3 register).

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Universal synchronous asynchronous receiver transmitter (USART)

RTS flow control
If the RTS flow control is enabled (RTSE=1), then nRTS is asserted (tied low) as long as the
USART receiver is ready to receive a new data. When the receive register is full, nRTS is
deasserted, indicating that the transmission is expected to stop at the end of the current
frame. Figure 300 shows an example of communication with RTS flow control enabled.
Figure 300. RTS flow control
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CTS flow control
If the CTS flow control is enabled (CTSE=1), then the transmitter checks the nCTS input
before transmitting the next frame. If nCTS is asserted (tied low), then the next data is
transmitted (assuming that a data is to be transmitted, in other words, if TXE=0), else the
transmission does not occur. When nCTS is deasserted 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 nCTS
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. The figure
below shows an example of communication with CTS flow control enabled.
Figure 301. CTS flow control
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Note:

Special behavior of break frames: when the CTS flow is enabled, the transmitter does not
check the nCTS input state to send a break.

25.5

USART interrupts
Table 158. USART interrupt requests
Interrupt event

Event flag

Enable control bit

Transmit Data Register Empty

TXE

TXEIE

CTS flag

CTS

CTSIE

Transmission Complete

TC

TCIE

Received Data Ready to be Read

RXNE

Overrun Error Detected

ORE

Idle Line Detected

IDLE

IDLEIE

Parity Error

PE

PEIE

Break Flag

LBD

LBDIE

Noise Flag, Overrun error and Framing Error
in multibuffer communication

NF or ORE or FE

EIE

RXNEIE

The USART interrupt events are connected to the same interrupt vector (see Figure 302).
•

During transmission: Transmission Complete, Clear to Send or Transmit Data Register
empty interrupt.

•

While receiving: Idle Line detection, Overrun error, Receive Data register not empty,
Parity error, LIN break detection, Noise Flag (only in multi buffer communication) and
Framing Error (only in multi buffer communication).

These events generate an interrupt if the corresponding Enable Control Bit is set.

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Universal synchronous asynchronous receiver transmitter (USART)
Figure 302. USART interrupt mapping diagram
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25.6

USART registers
Refer to Section 1.1 on page 51 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by half-words (16 bits) or words (32 bits).

25.6.1

Status register (USART_SR)
Address offset: 0x00
Reset value: 0x00C0 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.

CTS

LBD

TXE

TC

RXNE

IDLE

ORE

NF

FE

PE

rc_w0

rc_w0

r

rc_w0

rc_w0

r

r

r

r

r

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Bits 31:10 Reserved, must be kept at reset value
Bit 9 CTS: CTS flag
This bit is set by hardware when the nCTS input toggles, if the CTSE bit is set. It is cleared
by software (by writing it to 0). An interrupt is generated if CTSIE=1 in the USART_CR3
register.
0: No change occurred on the nCTS status line
1: A change occurred on the nCTS status line
Note: This bit is not available for UART4 & UART5.
Bit 8 LBD: LIN break detection flag
This bit is set by hardware when the LIN break is detected. It is cleared by software (by
writing it to 0). An interrupt is generated if LBDIE = 1 in the USART_CR2 register.
0: LIN Break not detected
1: LIN break detected
Note: An interrupt is generated when LBD=1 if LBDIE=1
Bit 7 TXE: Transmit data register empty
This bit is set by hardware when the content of the TDR register has been transferred into
the shift register. An interrupt is generated if the TXEIE bit =1 in the USART_CR1 register. It
is cleared by a write to the USART_DR 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
a software sequence (a read from the USART_SR register followed by a write to the
USART_DR register). The TC bit can also be cleared by writing a '0' to it. This clearing
sequence is recommended only for multibuffer communication.
0: Transmission is not complete
1: Transmission is complete
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_DR register. An interrupt is generated if RXNEIE=1 in the USART_CR1
register. It is cleared by a read to the USART_DR register. The RXNE flag can also be
cleared by writing a zero to it. This clearing sequence is recommended only for multibuffer
communication.
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 the
IDLEIE=1 in the USART_CR1 register. It is cleared by a software sequence (an read to the
USART_SR register followed by a read to the USART_DR 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 itself (i.e. a new idle
line occurs).

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Universal synchronous asynchronous receiver transmitter (USART)

Bit 3 ORE: Overrun error
This bit is set by hardware when the word currently being received in the shift register is
ready to be transferred into the RDR register while RXNE=1. An interrupt is generated if
RXNEIE=1 in the USART_CR1 register. It is cleared by a software sequence (an read to the
USART_SR register followed by a read to the USART_DR register).
0: No Overrun error
1: Overrun error is detected
Note: When this bit is set, the RDR register content will not be lost but the shift register will be
overwritten. An interrupt is generated on ORE flag in case of Multi Buffer
communication if the EIE bit is set.
Bit 2 NF: Noise detected flag
This bit is set by hardware when noise is detected on a received frame. It is cleared by a
software sequence (an read to the USART_SR register followed by a read to the
USART_DR register).
0: No noise is detected
1: Noise is detected
Note: This bit does not generate interrupt as it appears at the same time as the RXNE bit
which itself generates an interrupting interrupt is generated on NF flag in case of Multi
Buffer 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 25.4.5: USART
receiver tolerance to clock deviation on page 817).
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 a software sequence (an read to the USART_SR register
followed by a read to the USART_DR register).
0: No Framing error is detected
1: Framing error or break character is detected
Note: This bit does not generate interrupt as it appears at the same time as the RXNE bit
which itself generates an interrupt. If the word currently being transferred causes both
frame error and overrun error, it will be transferred and only the ORE bit will be set.
An interrupt is generated on FE flag in case of Multi Buffer communication if the EIE bit
is set.
Bit 0 PE: Parity error
This bit is set by hardware when a parity error occurs in receiver mode. It is cleared by a
software sequence (a read from the status register followed by a read or write access to the
USART_DR data register). The software must wait for the RXNE flag to be set before
clearing the PE bit.
An interrupt is generated if PEIE = 1 in the USART_CR1 register.
0: No parity error
1: Parity error

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25.6.2

RM0390

Data register (USART_DR)
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.
rw

rw

rw

rw

rw

rw

rw

rw

DR[8:0]
rw

Bits 31:9 Reserved, must be kept at reset value
Bits 8:0 DR[8:0]: Data value
Contains the Received or Transmitted data character, depending on whether it is read from
or written to.
The Data register performs a double function (read and write) since it is composed of two
registers, one for transmission (TDR) and one for reception (RDR)
The TDR register provides the parallel interface between the internal bus and the output shift
register (see Figure 1).
The RDR register provides the parallel interface between the input shift register and the
internal bus.
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.
When receiving with the parity enabled, the value read in the MSB bit is the received parity
bit.

25.6.3

Baud rate register (USART_BRR)

Note:

The baud counters stop counting if the TE or RE bits are disabled respectively.
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

DIV_Mantissa[11:0]
rw

rw

rw

rw

rw

rw

rw

DIV_Fraction[3:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value
Bits 15:4 DIV_Mantissa[11:0]: mantissa of USARTDIV
These 12 bits define the mantissa of the USART Divider (USARTDIV)
Bits 3:0 DIV_Fraction[3:0]: fraction of USARTDIV
These 4 bits define the fraction of the USART Divider (USARTDIV). When OVER8=1, the
DIV_Fraction3 bit is not considered and must be kept cleared.

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Universal synchronous asynchronous receiver transmitter (USART)

25.6.4

Control register 1 (USART_CR1)
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

OVER8

Res.

UE

M

WAKE

PCE

PS

PEIE

TXEIE

TCIE

TE

RE

RWU

SBK

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

RXNEIE IDLEIE
rw

rw

Bits 31:16 Reserved, must be kept at reset value
Bit 15 OVER8: Oversampling mode
0: oversampling by 16
1: oversampling by 8
Note: Oversampling by 8 is not available in the Smartcard, IrDA and LIN modes: when
SCEN=1,IREN=1 or LINEN=1 then OVER8 is forced to ‘0 by hardware.
Bit 14 Reserved, must be kept at reset value
Bit 13 UE: USART enable
When this bit is cleared the USART prescalers and outputs are stopped and the end of the
current
byte transfer in order to reduce power consumption. This bit is set and cleared by software.
0: USART prescaler and outputs disabled
1: USART enabled
Bit 12 M: Word length
This bit determines the word length. It is set or cleared by software.
0: 1 Start bit, 8 Data bits, n Stop bit
1: 1 Start bit, 9 Data bits, n Stop bit
Note: The M bit must not be modified during a data transfer (both transmission and reception)
Bit 11 WAKE: Wakeup method
This bit determines the USART wakeup method, it is set or cleared by software.
0: Idle Line
1: Address Mark
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
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

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Bit 8 PEIE: PE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated whenever PE=1 in the USART_SR register
Bit 7 TXEIE: TXE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated whenever TXE=1 in the USART_SR register
Bit 6 TCIE: Transmission complete interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated whenever TC=1 in the USART_SR register
Bit 5 RXNEIE: RXNE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated whenever ORE=1 or RXNE=1 in the USART_SR
register
Bit 4 IDLEIE: IDLE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated whenever IDLE=1 in the USART_SR 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: 1: 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.
2: 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 RWU: Receiver wakeup
This bit determines if the USART is in mute mode or not. It is set and cleared by software
and can be cleared by hardware when a wakeup sequence is recognized.
0: Receiver in active mode
1: Receiver in mute mode
Note: 1: Before selecting Mute mode (by setting the RWU bit) the USART must first receive a
data byte, otherwise it cannot function in Mute mode with wakeup by Idle line detection.
2: In Address Mark Detection wakeup configuration (WAKE bit=1) the RWU bit cannot
be modified by software while the RXNE bit is set.
Bit 0 SBK: Send break
This bit set is used to send break characters. It can be set and cleared by software. It should
be set by software, and will be reset by hardware during the stop bit of break.
0: No break character is transmitted
1: Break character will be transmitted

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Universal synchronous asynchronous receiver transmitter (USART)

25.6.5

Control register 2 (USART_CR2)
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.

LINEN

CLKEN

CPOL

CPHA

LBCL

Res.

LBDIE

LBDL

Res.

rw

rw

rw

rw

rw

rw

rw

rw

rw

STOP[1:0]
rw

rw

ADD[3:0]
rw

rw

Bits 31:15 Reserved, must be kept at reset value
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 Synch Breaks (13 low bits) using the SBK bit in
the USART_CR1 register, and to detect LIN Sync breaks.
Bits 13:12 STOP: 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 bit
Note: The 0.5 Stop bit and 1.5 Stop bit are not available for UART4 & UART5.
Bit 11 CLKEN: Clock enable
This bit allows the user to enable the SCLK pin.
0: SCLK pin disabled
1: SCLK pin enabled
This bit is not available for UART4 & UART5.
Bit 10 CPOL: Clock polarity
This bit allows the user to select the polarity of the clock output on the SCLK pin in synchronous
mode. It works in conjunction with the CPHA bit to produce the desired clock/data relationship
0: Steady low value on SCLK pin outside transmission window.
1: Steady high value on SCLK pin outside transmission window.
This bit is not available for UART4 & UART5.
Bit 9 CPHA: Clock phase
This bit allows the user to select the phase of the clock output on the SCLK pin in synchronous
mode. It works in conjunction with the CPOL bit to produce the desired clock/data relationship (see
figures 290 to 291)
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 is not available for UART4 & UART5.

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Bit 8 LBCL: Last bit clock pulse
This bit allows the user to select whether the clock pulse associated with the last data bit
transmitted (MSB) has to be output on the SCLK pin in synchronous mode.
0: The clock pulse of the last data bit is not output to the SCLK pin
1: The clock pulse of the last data bit is output to the SCLK pin
Note: 1: The last bit is the 8th or 9th data bit transmitted depending on the 8 or 9 bit format selected
by the M bit in the USART_CR1 register.
2: This bit is not available for UART4 & UART5.
Bit 7 Reserved, must be kept at reset value
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 LBD=1 in the USART_SR register
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
Bit 4 Reserved, must be kept at reset value
Bits 3:0 ADD[3:0]: Address of the USART node
This bit-field gives the address of the USART node.
This is used in multiprocessor communication during mute mode, for wake up with address mark
detection.

Note:

These 3 bits (CPOL, CPHA, LBCL) should not be written while the transmitter is enabled.

25.6.6

Control register 3 (USART_CR3)
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.

ONEBIT

CTSIE

CTSE

RTSE

DMAT

DMAR

SCEN

NACK

HDSEL

IRLP

IREN

EIE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value
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
Bit 10 CTSIE: CTS interrupt enable
0: Interrupt is inhibited
1: An interrupt is generated whenever CTS=1 in the USART_SR register
Note: This bit is not available for UART4 & UART5.

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Bit 9 CTSE: CTS enable
0: CTS hardware flow control disabled
1: CTS mode enabled, data is only transmitted when the nCTS input is asserted (tied to 0).
If the nCTS input is deasserted while a data is being transmitted, then the transmission is
completed before stopping. If a data is written into the data register while nCTS is
deasserted, the transmission is postponed until nCTS is asserted.
Note: This bit is not available for UART4 & UART5.
Bit 8 RTSE: RTS enable
0: RTS hardware flow control disabled
1: RTS interrupt 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 nRTS output is asserted (tied to 0) when a data can be received.
Note: This bit is not available for UART4 & UART5.
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
Note: This bit is not available for UART4 & UART5.
Bit 4 NACK: Smartcard NACK enable
0: NACK transmission in case of parity error is disabled
1: NACK transmission during parity error is enabled
Note: This bit is not available for UART4 & UART5.
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
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
Bit 1 IREN: IrDA mode enable
This bit is set and cleared by software.
0: IrDA disabled
1: IrDA enabled

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Universal synchronous asynchronous receiver transmitter (USART)

RM0390

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_SR register) in
case of Multi Buffer Communication (DMAR=1 in the USART_CR3 register).
0: Interrupt is inhibited
1: An interrupt is generated whenever DMAR=1 in the USART_CR3 register and FE=1 or
ORE=1 or NF=1 in the USART_SR register.

25.6.7

Guard time and prescaler register (USART_GTPR)
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

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

GT[7:0]
rw

PSC[7:0]
rw

Bits 31:16 Reserved, must be kept at reset value
Bits 15:8 GT[7:0]: Guard time value
This bit-field gives the Guard time value in terms of number of baud clocks.
This is used in Smartcard mode. The Transmission Complete flag is set after this guard time
value.
Note: This bit is not available for UART4 & UART5.
Bits 7:0 PSC[7:0]: Prescaler value
– In IrDA Low-power mode:
PSC[7:0] = IrDA Low-Power Baud Rate
Used for programming the prescaler for dividing the system clock to achieve the low-power
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 normal IrDA mode: PSC must be set to 00000001.
– In smartcard mode:
PSC[4:0]: Prescaler value
Used for programming the prescaler for dividing the system 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
...
Note: 1: Bits [7:5] have no effect if Smartcard mode is used.
2: This bit is not available for UART4 & UART5.

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0x18
USART_GTPR
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

USART_CR3

Res.

0x14
Reset value

Reset value

DocID026976 Rev 3
0

RXNEIE
IDLEIE
TE
RE
RWU
SBK

0
0
0
0
0
0
0
0
0
0

STOP
[1:0]
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

GT[7:0]
PSC[7:0]

0

EIE

0

IREN

0

IRLP

0

IDLE
ORE
NF
FE
PE

TXE
TC

LBD
1

RXNE

CTS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

NACK

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

HDSEL

LBDL

0

SCEN

TCIE

0

LBDIE

Reset value

DMAR

TXEIE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

DMAT

0
Res.

Reset value
PEIE

Reset value
0
LBCL

UE
0

RTSE

0

PS

0

CPHA

0

CTSE

0

PCE

0

CPOL

0

CTSIE

0

M

0

WAKE

0

CLKEN

0

Res.

0

ONEBIT

0

Res.

0

LINEN

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

OVER8

0

0

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.

USART_CR2

Res.

0x10
USART_CR1

Res.

0x0C
USART_BRR

Res.

0x08
USART_DR

Res.

0x04
USART_SR

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

Res.

Offset

Res.

25.6.8

Res.

RM0390
Universal synchronous asynchronous receiver transmitter (USART)

USART register map
The table below gives the USART register map and reset values.
Table 159. USART register map and reset values

1
0
0
0
0
0
0

DR[8:0]
0

DIV_Mantissa[15:4]

0
0
0
0
0

0
0
0

0

0

0

0
0
0

DIV_Fraction
[3:0]

ADD[3:0]

0
0
0
0

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

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RM0390

26

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

26.1

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 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 MSBand LSB-justified standards and the PCM standard.

26.1.1

846/1327

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)

•

8-bit to 16-bit transfer frame format 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

•

1-byte/word transmission and reception buffer with DMA capability: Tx and Rx requests

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RM0390

26.1.2

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

SPI extended features
•

26.1.3

I2S 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)

•

26.2

SPI TI mode support

I2S (I2S1, I2S2 and I2S3) clock can be derived from an external clock mapped on the
I2S_CKIN pin.

SPI/I2S implementation
This manual describes the full set of features implemented in SPI1 and SPI2.

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

26.3

SPI functional description

26.3.1

General description

RM0390

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 303.
Figure 303. SPI block diagram
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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 26.3.5: 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.

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26.3.2

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

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 304. Full-duplex single master/ single slave application

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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 26.3.5: 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.

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Figure 305. Half-duplex single master/ single slave application

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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 26.3.5: 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.

850/1327

•

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 26.3.5: 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.

DocID026976 Rev 3

RM0390

Serial peripheral interface/ inter-IC sound (SPI/I2S)
Figure 306. Simplex single master/single slave application (master in transmit-only/
slave in receive-only mode)

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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 26.3.5: 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).

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

26.3.3

RM0390

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 307.). 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.
Figure 307. Master and three independent slaves

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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 7.3.7: I/O alternate function input/output on
page 181).

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RM0390

26.3.4

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

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
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 308. Multi-master application

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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.

26.3.5

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:
•

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).

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

RM0390

–

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).

–

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.
Figure 309. Hardware/software slave select management
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RM0390

26.3.6

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

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.
Figure 310, 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).

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Figure 310. Data clock timing diagram
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Note:

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. Each data frame is 8 or 16 bit long depending on the size of the
data programmed using the DFF bit in the SPI_CR1 register. The selected data frame
format is applicable both for transmission and reception.

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26.3.7

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

SPI configuration
The configuration procedure is almost the same for master and slave. For specific mode
setups, follow the dedicated chapters. When a standard communication is to be initialized,
perform these steps:
1.

Write proper GPIO registers: Configure GPIO for MOSI, MISO and SCK pins.

2.

Write to the SPI_CR1 register:

3.

Note:

a)

Configure the serial clock baud rate using the BR[2:0] bits (Note: 3).

b)

Configure the CPOL and CPHA bits combination to define one of the four
relationships between the data transfer and the serial clock. (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 CRCEN and CRCEN bits if CRC is needed (while SCK clock signal
is at idle state).

f)

Configure SSM and SSI (Note: 2).

g)

Configure the MSTR bit (in multimaster NSS configuration, avoid conflict state on
NSS if master is configured to prevent MODF error).

h)

Set the DFF bit to configure the data frame format (8 or 16 bits).

Write to SPI_CR2 register:
a)

Configure SSOE (Note: 1 & 2).

b)

Set the FRF bit if the TI protocol is required.

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.

(1) Step is not required in slave mode.
(2) Step is not required in TI mode.
(3) The step is not required in slave mode except slave working at TI mode.

26.3.8

Procedure for enabling SPI
It is recommended to enable the SPI slave before the master sends the clock. Otherwise,
undesired data transmission might occur. The slave data register 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.
At full-duplex (or in any transmit-only mode), the master starts communicating when the SPI
is enabled and data to be sent is written in the Tx Buffer.
In any master receive-only mode (RXONLY=1 or BIDIMODE=1 & BIDIOE=0), the master
starts communicating and the clock starts running immediately after the SPI is enabled.
The slave starts communicating when it receives a correct clock signal from the master. The
slave software must write the data to be sent before the SPI master initiates the transfer.
Refer to Section 26.3.11: Communication using DMA (direct memory addressing) for details
on how to handle DMA.
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26.3.9

RM0390

Data transmission and reception procedures
Rx and Tx buffers
In reception, data are received and then stored into an internal Rx buffer while in
transmission, data are first stored into an internal Tx buffer before being transmitted. A read
access to the SPI_DR register returns the Rx buffered value whereas a write access to the
SPI_DR stores the written data into the Tx buffer.

Tx buffer handling
The data frame is loaded from the Tx buffer into the shift register during the first bit
transmission. Bits are then shifted out serially from the shift register to a dedicated output
pin depending on LSBFIRST bit setting.The TXE flag (Tx buffer empty) is set when the data
are transferred from the Tx buffer to the shift register. It indicates that the internal Tx buffer is
ready to be loaded with the next data. An interrupt can be generated if the TXEIE bit of the
SPI_CR2 register is set. Clearing the TXE bit is performed by writing to the SPI_DR register.
A continuous transmit stream can be achieved if the next data to be transmitted are stored
in the Tx buffer while previous frame transmission is still ongoing. When the software writes
to Tx buffer while the TXE flag is not set, the data waiting for transaction is overwritten.

Rx buffer handling
The RXNE flag (Rx buffer not empty) is set on the last sampling clock edge, when the data
are transferred from the shift register to the Rx buffer. It indicates that data are ready to be
read from the SPI_DR register. An interrupt can be generated if the RXNEIE bit in the
SPI_CR2 register is set. Clearing the RXNE bit is performed by reading the SPI_DR
register.
If a device has not cleared the RXNE bit resulting from the previous data byte transmitted,
an overrun condition occurs when the next value is buffered. The OVR bit is set and an
interrupt is generated if the ERRIE bit is set.
Another way to manage the data exchange is to use DMA (see Section 9.2: DMA main
features).

Sequence handling
The BSY bit is set when a current data frame transaction is ongoing. When the clock signal
runs continuously, the BSY flag remains set between data frames on the master side.
However, on the slave side, it becomes low for a minimum duration of one SPI clock cycle
between each data frame transfer.
For some configurations, the BSY flag can be used during the last data transfer to wait until
the completion of the transfer.
When a receive-only mode is configured on the master side, either in half-duplex
(BIDIMODE=1, BIDIOE=0) or simplex configuration (BIDIMODE=0, RXONLY=1), the
master starts the receive sequence as soon as the SPI is enabled. Then the clock signal is
provided by the master and it does not stop until either the SPI or the 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

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underflow error signal for slave operating in SPI mode, and that data from the slave are
always transacted and processed by the master even if the slave cannot not prepare them
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 single slave systems, using NSS to
control the slave is not necessary. However, the NSS pulse can be used to synchronize the
slave with the beginning of each data transfer sequence. NSS can be managed either by
software or by hardware (see Section 26.3.4: Multi-master communication).
Refer to Figure 311 and Figure 312 for a description of continuous transfers in master / fullduplex and slave full-duplex mode.
Figure 311. TXE/RXNE/BSY behavior in master / full-duplex mode (BIDIMODE=0,
RXONLY=0) in the case of continuous transfers

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Figure 312. TXE/RXNE/BSY behavior in slave / full-duplex mode (BIDIMODE=0,
RXONLY=0) in the case of continuous transfers
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26.3.10

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.
Standard disable procedure is based on pulling BSY status together with TXE flag 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 an arbitrary GPIO toggle and the master has to
provide proper end of NSS pulse for slave, or

•

When transactions’ streams from DMA 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):

860/1327

1.

Wait until RXNE=1 to receive the last data.

2.

Wait until TXE=1 and then wait until BSY=0 before disabling the SPI.

3.

Read received data.

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Note:

Serial peripheral interface/ inter-IC sound (SPI/I2S)
During discontinuous communications, there is a 2 APB clock period delay between the
write operation to the SPI_DR register and BSY bit setting. As a consequence it is
mandatory to wait first until TXE is set and then until BSY is cleared after writing the last
data.
The correct disable procedure for certain receive-only modes is:
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 received data.

Note:

To stop a continuous receive sequence, a specific time window must be respected during
the reception of the last data frame. It starts when the first bit is sampled and ends before
the last bit transfer starts.

26.3.11

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.

Refer to Figure 313 and Figure 314 for a description of the DMA transmission and reception
waveforms.
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 TXE = 1 and
then until BSY = 0.
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.

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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.
Figure 313. Transmission using DMA

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Serial peripheral interface/ inter-IC sound (SPI/I2S)
Figure 314. Reception using DMA

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26.3.12

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)
When it is set, the TXE flag indicates that the Tx buffer is empty and that the next data to be
transmitted can be loaded into the buffer. The TXE flag is cleared by writing to the SPI_DR
register.

Rx buffer not empty (RXNE)
When set, the RXNE flag indicates that there are valid received data in the Rx buffer. It is
cleared by reading from the SPI_DR register.

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). There is one exception in master bidirectional receive mode (MSTR=1 and BDM=1
and BDOE=0) where the BSY flag is kept low during reception.
The BSY flag can be used in certain modes to detect the end of a transfer, thus preventing
corruption of the last transfer when the SPI peripheral clock is disabled before entering a
low-power mode or an NSS pulse end is handled by software.
The BSY flag is also useful for preventing write collisions in a multimaster system.

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The BSY flag is cleared under any one of the following conditions:
•

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.

Note:

It is recommended to use always the TXE and RXNE flags (instead of the BSY flags) to
handle data transmission or reception operations.

26.3.13

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 the master or the slave completes the reception of the
next data frame while the read operation of the previous frame from the Rx buffer has not
completed (case RXNE flag is set).
In this case, the content of the Rx buffer is not updated with the new data received. A read
operation from the SPI_DR register returns the frame previously received. All other
subsequently transmitted data are 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.

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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_RXCRC 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.
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 re-initiated by the
master when the slave SPI is enabled again.

26.4

SPI special features

26.4.1

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 315). 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
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.
This feature is not available for Motorola SPI communications (FRF bit set to 0).

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To detect TI frame errors in slave transmitter only mode by using the Error interrupt
(ERRIE=1), the SPI must be configured in 2-line unidirectional mode by setting BIDIMODE
and BIDIOE to 1 in the SPI_CR1 register. When BIDIMODE is set to 0, OVR is set to 1
because the data register is never read and error interrupts are always generated, while
when BIDIMODE is set to 1, data are not received and OVR is never set.
Figure 315 shows the SPI communication waveforms when TI mode is selected.
Figure 315. TI mode transfer

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26.4.2

CRC calculation
Two separate CRC calculators (on transmission and reception data flows) are implemented
in order to check the reliability of transmitted and received data. The SPI offers CRC8 or
CRC16 calculation depending on the data format selected through the DFF bit. The CRC is
calculated serially using the polynomial programmed in the SPI_CRCPR register.

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.
Note:

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.

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The received CRC is stored in the Rx buffer like any other data frame.
A CRC-format transaction takes one more data frame to communicate at the end of data
sequence.
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 Rx buffer 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 the CRC frame received from SPI_DR as it is always loaded
into it.
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.

Resetting the SPIx_TXCRC and SPIx_RXCRC values
The SPIx_TXCRC and SPIx_RXCRC values are cleared automatically when CRC
calculation is enabled.
When the SPI is configured in slave mode with the CRC feature enabled, a CRC calculation
is performed even if a high level is applied on the NSS pin. This may happen for example in
case of a multislave environment where the communication master addresses slaves
alternately.
Between a slave disabling (high level on NSS) and a new slave enabling (low level on NSS),
the CRC value should be cleared on both master and slave sides to resynchronize the
master and slave respective CRC calculation.
To clear the CRC, follow the below sequence:

Note:

1.

Disable the SPI

2.

Clear the CRCEN bit

3.

Enable the CRCEN bit

4.

Enable the SPI

When the SPI is in slave mode, the CRC calculator is sensitive to the SCK slave input clock
as soon as the CRCEN bit is set, and this is the case whatever the value of the SPE bit. In
order to avoid any wrong CRC calculation, the software must enable the CRC calculation
only when the clock is stable (in steady state). When the SPI interface is configured as a
slave, the NSS internal signal needs to be kept low between the data phase and the CRC
phase once the CRCNEXT signal is released.
At TI mode, despite the fact that the clock phase and clock polarity setting is fixed and
independent on the 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

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has to be reset between sessions by the SPI disable sequence by re-enabling the CRCEN
bit described above at both master and slave sides, else the CRC calculation can be
corrupted at this specific mode.

26.5

SPI interrupts
During SPI communication an interrupts can be generated by the following events:
•

Transmit Tx buffer ready to be loaded

•

Data received in Rx buffer

•

Master mode fault

•

Overrun error

•

TI frame format error

Interrupts can be enabled and disabled separately.
Table 160. SPI interrupt requests
Interrupt event

Event flag

Enable Control bit

TXE

TXEIE

Data received in Rx buffer

RXNE

RXNEIE

Master Mode fault event

MODF

Transmit Tx buffer ready to be loaded

Overrun error

OVR

CRC error

CRCERR

TI frame format error

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

26.6

I2S functional description

26.6.1

I2S general description
The block diagram of the I2S is shown in Figure 316.
Figure 316. I2S block diagram

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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.

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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.

26.6.2

I2S full-duplex
Figure 317 shows how to perform full-duplex communications using two SPI2S instances. In
this case, the WS and CK IOs of both SPI2S must be connected together.
For the master full-duplex mode, one of the SPI2S block must be programmed in master
(I2SCFG = ‘10’ or ‘11’), and the other SPI2S 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 SPI2S 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 SPI2S 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.

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Serial peripheral interface/ inter-IC sound (SPI/I2S)
Figure 317. Full-duplex communication
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26.6.3

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).

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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 318. I2S Philips protocol waveforms (16/32-bit full accuracy, CPOL = 0)
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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 319. I2S Philips standard waveforms (24-bit frame with CPOL = 0)
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This mode needs two write or read operations to/from the SPIx_DR register.

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Serial peripheral interface/ inter-IC sound (SPI/I2S)
•

In transmission mode:
If 0x8EAA33 has to be sent (24-bit):
Figure 320. Transmitting 0x8EAA33
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In reception mode:
If data 0x8EAA33 is received:
Figure 321. Receiving 0x8EAA33
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Figure 322. I2S Philips standard (16-bit extended to 32-bit packet frame with
CPOL = 0)
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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 323 is required.

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Figure 323. Example of 16-bit data frame extended to 32-bit channel frame
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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 324. MSB Justified 16-bit or 32-bit full-accuracy length with CPOL = 0
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Data are latched on the falling edge of CK (for transmitter) and are read on the rising edge
(for the receiver).
Figure 325. MSB justified 24-bit frame length with CPOL = 0
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Serial peripheral interface/ inter-IC sound (SPI/I2S)
Figure 326. MSB justified 16-bit extended to 32-bit packet frame with CPOL = 0
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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).
Figure 327. LSB justified 16-bit or 32-bit full-accuracy with CPOL = 0
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Figure 328. LSB justified 24-bit frame length with CPOL = 0
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•

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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.
Figure 329. Operations required to transmit 0x3478AE
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In reception mode:
If data 0x3478AE are received, two successive read operations from the SPIx_DR
register are required on each RXNE event.
Figure 330. Operations required to receive 0x3478AE
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Figure 331. LSB justified 16-bit extended to 32-bit packet frame with CPOL = 0
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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 332 is required.

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Serial peripheral interface/ inter-IC sound (SPI/I2S)
Figure 332. Example of 16-bit data frame extended to 32-bit channel frame
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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.
Figure 333. PCM standard waveforms (16-bit)
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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.
Figure 334. PCM standard waveforms (16-bit extended to 32-bit packet frame)
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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.

26.6.4

Clock generator
The I2S bitrate determines the data flow on the I2S data line and the I2S clock signal
frequency.
I2S bitrate = number of bits per channel × number of channels × sampling audio frequency
For a 16-bit audio, left and right channel, the I2S bitrate is calculated as follows:
I2S bitrate = 16 × 2 × fS
It will be: I2S bitrate = 32 x 2 x fS if the packet length is 32-bit wide.
Figure 335. Audio sampling frequency definition
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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 336 presents the communication clock architecture. The I2Sx clock is always the
system clock.
Figure 336. I2S clock generator architecture

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Serial peripheral interface/ inter-IC sound (SPI/I2S)
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:
When the master clock is generated (MCKOE in the SPIx_I2SPR register is set):
fS = I2SxCLK / [(16*2)*((2*I2SDIV)+ODD)*8)] when the channel frame is 16-bit wide
fS = I2SxCLK / [(32*2)*((2*I2SDIV)+ODD)*4)] when the channel frame is 32-bit wide
When the master clock is disabled (MCKOE bit cleared):
fS = I2SxCLK / [(16*2)*((2*I2SDIV)+ODD))] when the channel frame is 16-bit wide
fS = I2SxCLK / [(32*2)*((2*I2SDIV)+ODD))] when the channel frame is 32-bit wide
Table 161 provides example precision values for different clock configurations.

Note:

Other configurations are possible that allow optimum clock precision.
Table 161. 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

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48

32

8

1

No

44100

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48

16

23

1

No

32000

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48

32

11

1

No

32000

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48

16

34

0

No

22050

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48

32

17

0

No

22050

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48

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47

0

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16000

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48

32

23

1

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16000

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48

16

68

0

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11025

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48

32

34

0

No

11025

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48

16

94

0

No

8000

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48

32

47

0

No

8000

7978.7234

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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%

DocID026976 Rev 3

Target fS
(Hz)

Real fS (KHz)

Error

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Table 161. Audio-frequency precision using standard 8 MHz HSE(1) (continued)
SYSCLK
(MHz)

Data
length

I2SDIV

I2SODD

MCLK

Target fS
(Hz)

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%

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.

26.6.5

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 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 26.6.4: 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

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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
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 26.6.3: 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 26.6.5: 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 26.6.3: 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
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•

b)

Then wait 1 I2S clock cycle (using a software loop)

c)

Disable the I2S (I2SE = 0)

RM0390

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)

c)

Disable the I2S (I2SE = 0)

Note:

The BSY flag is kept low during transfers.

26.6.6

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.

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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 26.6.3: 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
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 26.6.6: 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 26.6.3: 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.

26.6.7

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.

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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.
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).

26.6.8

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

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ERRIE bit in the SPIx_CR2 register is set.
The UDR bit is cleared by a read operation on the SPIx_SR register.

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.

Enable it again when the correct level is detected on the WS line (WS line is high in I2S
mode or low for MSB- or LSB-justified or PCM modes.

Desynchronization between master and slave devices may be due to noisy environment on
the SCK 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.

26.6.9

I2S interrupts
Table 162 provides the list of I2S interrupts.
Table 162. I2S interrupt requests
Interrupt event

26.6.10

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

ERRIE

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.

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SPI and I2S registers

26.7

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.
Refer to Section 1.1 for a list of abbreviations used in register descriptions.
The peripheral registers can be accessed by half-words (16 bits) or words (32 bits).

SPI control register 1 (SPI_CR1) (not used in I2S mode)

26.7.1

Address offset: 0x00
Reset value: 0x0000
15

14

13

12

11

10

BIDI
MODE

BIDI
OE

CRC
EN

CRC
NEXT

DFF

RX
ONLY

rw

rw

rw

rw

rw

rw

9

8

7

6

SSM

SSI

LSB
FIRST

SPE

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: This bit is not used in I2S mode.
In master mode, the MOSI pin is used while the MISO pin is used in slave 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.
It is not used in I2S mode.
Bit 12 CRCNEXT: CRC transfer next
0: Data phase (no CRC phase)
1: Next transfer is CRC (CRC phase)
Note: When the SPI is configured in full-duplex or transmitter only modes, CRCNEXT must be
written as soon as the last data is written to the SPI_DR register.
When the SPI is configured in receiver only mode, CRCNEXT must be set after the
second last data reception.
This bit should be kept cleared when the transfers are managed by DMA.
It is not used in I2S mode.

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Bit 11 DFF: Data frame format
0: 8-bit data frame format is selected for transmission/reception
1: 16-bit data frame format is selected for transmission/reception
Note: This bit should be written only when SPI is disabled (SPE = ‘0’) for correct operation.
It is not used in I2S mode.
Bit 10 RXONLY: Receive only mode enable
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 IO 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: MSB transmitted first
1: LSB transmitted first
Note: This bit should not be changed when communication is ongoing.
It is not used in I2S mode and SPI TI mode
Bit 6 SPE: SPI enable
0: Peripheral disabled
1: Peripheral enabled
Note: This bit is not used in I2S mode.
When disabling the SPI, follow the procedure described in Section 26.3.10: Procedure
for disabling the SPI.
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.
They are not used in I2S mode.

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Bit 2 MSTR: Master selection
0: Slave configuration
1: Master configuration
Note: This bit should not be changed when communication is ongoing.
It is not used in I2S mode.
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.
It is not used in I2S mode and 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.
It is not used in I2S mode and SPI TI mode except the case when CRC is applied
at TI mode.

26.7.2

SPI control register 2 (SPI_CR2)
Address offset: 0x04
Reset value: 0x0000

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

TXEIE RXNEIE ERRIE
rw

rw

rw

4

3

2

FRF

Res.

SSOE

rw

rw

1

0

TXDMAEN RXDMAEN
rw

rw

Bits 15:8 Reserved, must be kept at reset value.
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 (OVR,
CRCERR, MODF, FRE in SPI mode, and UDR, OVR, 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 is not used in I2S mode.
Bit 3 Reserved. Forced to 0 by hardware.

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Bit 2 SSOE: SS output enable
0: SS output is disabled in master mode and the cell can work in multimaster configuration
1: SS output is enabled in master mode and when the cell is enabled. The cell 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, the DMA request is made 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, the DMA request is made whenever the RXNE flag is set.
0: Rx buffer DMA disabled
1: Rx buffer DMA enabled

26.7.3

SPI status register (SPI_SR)
Address offset: 0x08
Reset value: 0x0002

15
Res.

14

13

Res.

Res.

12
Res.

11
Res.

10
Res.

9

8

Res.

7

6

5

4

3

2

1

0

UDR

CHSIDE

TXE

RXNE

r

r

r

r

FRE

BSY

OVR

MODF

CRC
ERR

r

r

r

r

rc_w0

Bits 15:9 Reserved. Forced to 0 by hardware.
Bit 8 FRE: Frame Error
0: No frame error
1: Frame error occurred.
This bit is set by hardware and cleared by software when the SPI_SR register is read.
This bit is used in SPI TI mode or in I2S mode whatever the audio protocol selected. It
detects a change on NSS or WS line which takes place in slave mode at a non expected
time, informing about a desynchronization between the external master device and the
slave.
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: BSY flag must be used with caution: refer to Section 26.3.12: SPI status flags and
Section 26.3.10: Procedure for disabling the SPI.
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 Section 26.3.13: SPI
error flags for the software sequence.

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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 26.4 on
page 865 for the software sequence.
Note: This bit is not used in I2S mode
Bit 4 CRCERR: CRC error flag
0: CRC value received matches the SPI_RXCRCR value
1: CRC value received does not match the SPI_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 Section 26.6.8: I2S
error flags 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 for SPI mode and is meaningless 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

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26.7.4

SPI data register (SPI_DR)
Address offset: 0x0C
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

DR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 DR[15:0]: Data register
Data received or to be transmitted.
The data register is split into 2 buffers - one for writing (Transmit Buffer) and another one for
reading (Receive buffer). A write to the data register will write into the Tx buffer and a read
from the data register will return the value held in the Rx buffer.
Note: These notes apply to SPI mode:
Depending on the data frame format selection bit (DFF in SPI_CR1 register), the data
sent or received is either 8-bit or 16-bit. This selection has to be made before enabling
the SPI to ensure correct operation.
For an 8-bit data frame, the buffers are 8-bit and only the LSB of the register
(SPI_DR[7:0]) is used for transmission/reception. When in reception mode, the MSB of
the register (SPI_DR[15:8]) is forced to 0.
For a 16-bit data frame, the buffers are 16-bit and the entire register, SPI_DR[15:0] is
used for transmission/reception.

SPI CRC polynomial register (SPI_CRCPR) (not used in I2S
mode)

26.7.5

Address offset: 0x10
Reset value: 0x0007
15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CRCPOLY[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

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: These bits are not used for the I2S mode.

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SPI RX CRC register (SPI_RXCRCR) (not used in I2S mode)

26.7.6

Address offset: 0x14
Reset value: 0x0000
15

14

13

12

11

10

9

r

r

r

r

r

r

r

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

RXCRC[15:0]
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 SPI_CR1
register is written to 1. The CRC is calculated serially using the polynomial programmed in
the SPI_CRCPR register.
Only the 8 LSB bits are considered when the data frame format is set to be 8-bit data (DFF
bit of SPI_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 data frame format is selected
(DFF bit of the SPI_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 for I2S mode.

SPI TX CRC register (SPI_TXCRCR) (not used in I2S mode)

26.7.7

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 SPI_CR1
is written to 1. The CRC is calculated serially using the polynomial programmed in the
SPI_CRCPR register.
Only the 8 LSB bits are considered when the data frame format is set to be 8-bit data (DFF
bit of SPI_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 data frame format is selected
(DFF bit of the SPI_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 for I2S mode.

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RM0390

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

SPI_I2S configuration register (SPI_I2SCFGR)

26.7.8

Address offset: 0x1C
Reset value: 0x0000
15

14

13

Res.

Res.

Res.

12

11

ASTRE
I2SMOD
N
rw

rw

10
I2SE
rw

9

8

I2SCFG
rw

rw

7

6

PCMSY
NC

Res.

rw

5

4

I2SSTD
rw

3
CKPOL

rw

rw

2

1

DATLEN
rw

rw

0
CHLEN
rw

Bits 15:13 Reserved, must be kept at reset value.
Bit 12 ASTREN: Asynchronous start enable.
0: The Asynchronous start is disabled. When the I2S is enabled in slave mode, the I2S slave starts
the transfer when the I2S clock is received and an appropriate transition (depending on the protocol
selected) is detected on the WS signal.
1: The Asynchronous start is enabled. When the I2S is enabled in slave mode, the I2S slave starts
immediately the transfer when the I2S clock is received from the master without checking the
expected transition of WS signal.
Note: Note: The appropriate transition is a falling edge on WS signal when I2S Philips Standard is
used, or a rising edge for other standards.
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 or I2S 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: This bit should be configured when the I2S is disabled.
It is 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

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RM0390

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 26.6.3 on page 871. Not used in SPI mode.
Note: For correct operation, these bits should be configured when the I2S is disabled.
Bit 3 CKPOL: Steady state clock polarity
0: I2S clock steady state is low level
1: I2S clock steady state is high level
Note: For correct operation, this bit should be configured when the I2S is disabled.
This bit is not used in SPI mode
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.
This bit is 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. Not used in SPI mode.
Note: For correct operation, this bit should be configured when the I2S is disabled.

SPI_I2S prescaler register (SPI_I2SPR)

26.7.9

Address offset: 0x20
Reset value: 0000 0010 (0x0002)
15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

Res.

MCKOE

ODD

I2SDIV

rw

rw

rw

Bits 15:10 Reserved, must be kept at reset value.

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5

4

3

2

1

0

RM0390

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

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.
This bit 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 26.6.4 on page 878. Not used in SPI mode.
Note: This bit should be configured when the I2S is disabled. It is used only when the I2S is in master
mode.
Bits 7:0 I2SDIV: I2S Linear prescaler
I2SDIV [7:0] = 0 or I2SDIV [7:0] = 1 are forbidden values.
Refer to Section 26.6.4 on page 878. Not used in SPI mode.
Note: These bits should be configured when the I2S is disabled. It is used only when the I2S is in
master mode.

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0x1C
SPI_DR

SPI_CRCPR

SPI_RXCRCR

SPI_TXCRCR

SPI_I2SCFGR

0x20

896/1327

SPI_I2SPR
0 0 0 0

Reset value

Reset value

Reset value

Reset value

Reset value
0 0 0 0 0 0

Reset value

Refer to Section 2.2.2 on page 56 for the register boundary addresses.

DocID026976 Rev 3
CHLEN

0x10
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
TXEIE
RXNEIE
ERRIE
FRF
Res.
SSOE
TXDMAEN
RXDMAEN

Register
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

SPI_CR1
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
BIDIMODE
BIDIOE
CRCEN
CRCNEXT
DFF
RXONLY
SSM
SSI
LSBFIRST
SPE

MSTR
CPOL
CPHA

BR
[2:0]

DATLEN

0x0C

CKPOL

Reset value

I2SSTD

0x18
SPI_SR
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
FRE
BSY
OVR
MODF
CRCERR
UDR
CHSIDE
TXE
RXNE

Reset value

PCMSYNC
Res.

0x08

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Reset value

I2SCFG

0x14
SPI_CR2

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0x04

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0x00

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Offset

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
ASTREN
I2SMOD
I2SE

26.7.10

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
MCKOE
ODD

Serial peripheral interface/ inter-IC sound (SPI/I2S)
RM0390

SPI register map
The table provides shows the SPI register map and reset values.
Table 163. SPI register map and reset values

0 0 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

DR[15:0]

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CRCPOLY[15:0]

0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1
RxCRC[15:0]

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
TxCRC[15:0]

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0

I2SDIV

0 0 0 0 0 0 0 0 1 0

RM0390

SPDIF receiver interface (SPDIFRX)

27

SPDIF receiver interface (SPDIFRX)

27.1

SPDIFRX interface introduction
The SPDIFRX interface handles S/PDIF audio protocol.

27.2

27.3

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 337 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.
In addition the SPDIFRX also provides a signal named spdifrx_symb_ck toggling at the
symbol rate.

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RM0390
Figure 337. SPDIFRX block diagram

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1. ‘n’ is fixed to 4.

27.3.1

S/PDIF protocol (IEC-60958)
S/PDIF block
A S/PDIF frame is composed of two sub-frames (see Figure 339). 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 338. S/PDIF Sub-Frame Format



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RM0390

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 339. S/PDIF block format
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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 340.
Figure 340. S/PDIF Preambles

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RM0390

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 341. Channel coding example
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27.3.2

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:

900/1327

•

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

DocID026976 Rev 3

RM0390

SPDIF receiver interface (SPDIFRX)
Figure 342 gives a detailed view of the SPDIFRX decoder.
Figure 342. SPDIFRX decoder
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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 343. Noise filtering and edge detection
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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.

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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 342). 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 346
for additional information.
As shown in the figure hereafter, THLO is ideally equal to 1.5 UI, and to THHI 2.5 UI.

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RM0390

SPDIF receiver interface (SPDIFRX)
Figure 344. Thresholds
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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 164
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 164. Transition sequence for preamble
Preamble type

Biphase data
pattern

TRANS3

TRANS2

TRANS1

TRANS0

Preamble B

11101000

TL

TS

TS

TL

Preamble M

11100010

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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 27.3.8: 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.

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27.3.3

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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:

27.3.4

•

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 345
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 27.4: 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 349).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.

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SPDIF receiver interface (SPDIFRX)
Figure 345. Synchronization flowchart
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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 346 in order to continuously track S/PDIF synchronization.

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Figure 346. Synchronization process scheduling
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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 347 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)”.

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SPDIF receiver interface (SPDIFRX)
Figure 347. SPDIFRX States
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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.

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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.

27.3.6

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_dat_dma and
spdifrx_ctrl_dma) or interrupts for transferring the audio samples into the memory. The
recommended option is DMA, refer to Section 27.3.11: 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 348.

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SPDIF receiver interface (SPDIFRX)
Figure 348. SPDIFRX_DR register format
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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 350).
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 27.3.7: 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.

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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 349).
If CS[0] corresponds to the first bit of a new block, the bit SOB will be set to 1. Refer to
Section 27.5.8: 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 349. Channel/user data format
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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.

27.3.8

Reception errors
Frame structure and synchronization error
The SPDIFRX, detects errors, when one of the following condition occurs:
•

910/1327

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).

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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 347 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 350.

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Figure 350. S/PDIF overrun error when RXSTEO = 0
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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 351.
The OVR flag is cleared by software, by setting the OVRCF bit to 1.

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SPDIF receiver interface (SPDIFRX)
Figure 351. S/PDIF overrun error when RXSTEO = 1
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27.3.9

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 337).

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 165. Minimum SPDIFRX_CLK frequency versus audio sampling rate
Symbol Rate

Minimum SPDIFRX_CLK frequency

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

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27.3.10

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Symbol clock generation
The SPDIFRX block provides a symbol clock on signal named spdifrx_symb_ck, which
can be used as the reference kernel clock for another audio device such as SAI or SPI/I2S.
It could be used for SPDIFRX to I2S bridge function.
The symbol clock is built using the values of WIDTH24, WIDTH40 and the symbol
boundaries.
•

During the reception of the sub-frame sync preambles, the falling and rising edges of
the symbol clock are built from the WIDTH24 and WIDTH40 values. Note that
WIDTH24 and WIDTH40 are also used for the generation of the symbol clock, when
the SPDIFRX is STATE_STOP or STATE_IDLE. See Table 166 for details.

•

During the reception of the sub-frame payload, the SPDIFRX uses the symbols
boundaries to generate the rising edge, the WIDTH24 and WIDTH40 values for the
generation of the falling edge.

The duty cycle of the symbol clock is close to 50% during the reception of the sub-frame
payload. However, the duty cycle can be altered when the SPDIFRX transitions from a
symbol clock generated with WIDTH24 and WIDTH40 to a clock generated by the symbol
clock boundaries or vice-versa.
The symbol clock will have an important jitter mainly due to:
•

The re-sampling of the S/PDIF signal with SPDIFRX_CLK clock

•

The transition of the symbol clock generation mode

For that reason the application shall consider the quality degradation if the symbol clock is
used as the reference clock for A/D or D/A converters.
The generation of this symbol clock is controlled by the CKSEN bit. When CKSEN = ‘1’, the
clock symbol is generated when the SPDIFRX completes successfully the first fine
synchronization (SYNCD = 1), and when it is receiving correct data from the selected
SPDIFRX input.
When the SPDIFRX goes to STATE_STOP, or STATE_IDLE, the symbol clock is gated if the
bit CKSBKPEN = ‘0’. If the CKSBKPEN = ‘1’, then a backup symbol clock is still generated if
the SPDIFRX is properly synchronized (i.e. valid values available for WIDTH24 and
WIDTH40). Table 166 gives more details on the conditions controlling the generation of the
symbol clock.

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SPDIF receiver interface (SPDIFRX)

Any state

CKSBKPEN

SPDIFRX states and conditions

CKSEN

Table 166. Conditions of spdifrx_symb_ck generation
spdifrx_s
ymb_ck
state

0

X

Disabled

0

Enabled

0

Disabled

– SPDIFRX in STATE_SYNC and completing successfully the fine synchronization
(SYNCD = '1') or,
– SPDIFRX in STATE_RCV, and valid data are received via the selected SPDIFRX input.
–
–
–
–

SPDIFRX in STATE_IDLE or,
SPDIFRX in STATE_STOP or,
SPDIFRX did not complete the fine synchronization (on-going)
SPDIFRX is in STATE_RCV, but no data (transitions) detected on the selected SPDIFRX
input.

– SPDIFRX in STATE_IDLE, but with valid values for WIDTH40 and WIDTH24 or
– SPDIFRX in STATE_SYNC and completing successfully the fine synchronization (SYNCD
= '1') or,
– SPDIFRX in STATE_SYNC the on-going fine synchronization is not completed, but
WIDTH40 and WIDTH24 contain the valid values from the previous synchronization or,
– SPDIFRX in STATE_RCV, and valid data are received via the selected SPDIFRX input or,
– SPDIFRX in STATE_STOP, but with valid values for WIDTH40 and WIDTH24.

1

Enabled

1

– SPDIFRX in IDLE, with invalid values for WIDTH40 and WIDTH24 or,
– SPDIFRX in STOP with invalid values for WIDTH40 and WIDTH24 (SERR = '1') or,
– SPDIFRX in STATE_SYNC with invalid values for WIDTH40 and WIDTH24, and did not
completed the on-going fine synchronization or,
– SPDIFRX in STATE_RCV and no transitions detected on the selected SPDIFRX input

1

Disabled

Note that when the flag SERR is set to ‘1’, neither the symbol clock nor the backup clock
can be generated, since there is no synchronization.
Note that when both CKSEN and CKSBKPEN are set to ‘1’, the symbol clock will loose
some transitions when the SPDIFRX switches from STATE_SYNC or STATE_RCV to
STATE_STOP, or STATE_IDLE.
The bits CKSEN and CKSBKPEN are located into Control register (SPDIFRX_CR).

27.3.11

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

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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 27.3.7: Dedicated control flow.

27.3.12

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 352. SPDIFRX interface interrupt mapping diagram
6<1&'
6<1&',(
5;1(
5;1(,(
3(55
3(55,(
295

25

295,(

63',)5;B,54

&651(
&651(,(
6%'
6%',(

)(55

25

6(55
7(55
,)(,(
06Y9

Clearing interrupt source

Note:

916/1327

•

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).

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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.

27.3.13

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 167. 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.

27.4

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

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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.

27.4.1

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 165 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.

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27.4.2

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.

•

27.4.3

–

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.

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27.5

SPDIFRX interface registers

27.5.1

Control register (SPDIFRX_CR)
Address offset: 0x00
Reset value: 0x00000000
20

19

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw
1.

12

rw

rw

11

10

9

8

7

6

rw

rw

rw

rw

rw

rw

5

4

rw

rw

17

16

INSEL[2:0](1)

rw

rw

rw

3

2

1

0

rw

rw

SPDIFRXEN[1:0](1)

Res.

13

rw

DRFMT[1:0](1)

14

NBTR[1:0](1)

15

rw

18

RXDMAEN(1)

21

RXSTEO(1)

22

CKSEN

23

CKSBKPEN

24

PMSK(1)

25

VMSK(1)

26

CUMSK(1)

27

PTMSK(1)

28

CBDMAEN(1)

29

CHSEL(1)

30

WFA (1)

31

rw

Refer to Section 27.3.13: Register protection for additional information on fields properties.

Bits 31:22 Reserved, forced by hardware to 0.
Bit 21 CKSBKPEN: Backup Symbol Clock Enable
This bit is set/reset by software
1: The SPDIFRX generates a backup symbol clock if CKSEN = ‘1’
0: The SPDIFRX does not generate a backup symbol clock
Bit 20 CKSEN: Symbol Clock Enable
This bit is set/reset by software
1: The SPDIFRX generates a symbol clock
0: The SPDIFRX does not generate a symbol clock
Bit 19 Reserved, forced by hardware to 0.par
Bits18:16 INSEL[2:0]: SPDIFRX input selection
0b000: SPDIFRX_IN1 selected
0b001: SPDIFRX_IN2 selected
0b010: SPDIFRX_IN3 selected
0b011: SPDIFRX_IN4 selected
others reserved
Bit 15 Reserved, forced by hardware to 0.
Bit 14 WFA: Wait For Activity
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

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Bits 13:12 NBTR[1:0]: Maximum allowed re-tries during synchronization phase
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
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
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.
Bit 9 PTMSK: Mask of Preamble Type bits
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
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
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
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
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)

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Bit 3 RXSTEO: STerEO Mode
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
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
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:

922/1327

1

it is not possible to transition from STATE_RCV to STATE_SYNC, the user
shall first go the STATE_IDLE.

2

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.

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27.5.2

SPDIF receiver interface (SPDIFRX)

Interrupt mask register (SPDIFRX_IMR)
Address offset: 0x04
Reset value: 0x00000000

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.

IFEIE

SYNCDIE

SBLKIE

OVRIE

PERRIE

CSRNEIE

RXNEIE

rw

rw

rw

rw

rw

rw

rw

Bits 31:7 Reserved, forced by hardware to 0.
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

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27.5.3

RM0390

Status register (SPDIFRX_SR)
Address offset: 0x08
Reset value: 0x00000000

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

PERR

CSRNE

RXNE

r

r

r

r

r

r

r

r

r

Bit 31 Reserved, forced by hardware to 0.
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, forced by hardware to 0.
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

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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.

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27.5.4

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Interrupt flag clear register (SPDIFRX_IFCR)
Address offset: 0x0C
Reset value: 0x00000000

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.

SYNCDCF

SBDCF

OVRCF

PERRCF

Res.

Res.

w

w

w

w

Bits 31:6 Reserved, forced by hardware to 0.
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

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SPDIF receiver interface (SPDIFRX)

27.5.5

Data input register (SPDIFRX_DR)
Address offset: 0x10
Reset value: 0x00000000
This register can take 3 different formats according to DRFMT. Here is the format when
DRFMT = 0b00:

31

30

Res.

Res.

15

14

29

28

PT[1:0]

27

26

25

24

C

U

V

PE

23

22

21

20

19

18

17

16

DR[23:16]

r

r

r

r

r

r

r

r

r

r

r

r

r

r

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

DR[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:30 Reserved: forced by hardware to 0
Bits 29:28 PT: 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: Data value
Contains the 24 received data bits, aligned on D[23]

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27.5.6

RM0390

Data input register (SPDIFRX_DR)
Address offset: 0x10
Reset value: 0x00000000
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

DR[7:0]
r

r

r

r

r

r

r

r

PT[1:0]
r

r

Bits 31:8 DR: Data value
Contains the 24 received data bits, aligned on D[23]
Bits 7:6 Reserved: forced by hardware to 0
Bits 5:4 PT: 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

928/1327

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RM0390

SPDIF receiver interface (SPDIFRX)

27.5.7

Data input register (SPDIFRX_DR)
Address offset: 0x10
Reset value: 0x00000000
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

DRNL1[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 DRNL2: Data value
This field contains the Channel A
Bits 15:0 DRNL1: Data value
This field contains the Channel B

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27.5.8

RM0390

Channel status register (SPDIFRX_CSR)
Address offset: 0x14
Reset value: 0x00000000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SOB

15

14

13

12

11

10

9

23

22

21

20

19

18

17

16

CS[7:0]

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

USR[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:25 Reserved
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.

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RM0390

SPDIF receiver interface (SPDIFRX)

27.5.9

Debug Information register (SPDIFRX_DIR)
Address offset: 0x18
Reset value: 0x00000000

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

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

THI[12:0]
r

r

r

r

r

r

r

Bits 31:29 Reserved, forced by hardware to 0.
Bits 16:28 TLO: 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, forced by hardware to 0.
Bits 12:0 THI: 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.

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27.5.10

RM0390

SPDIFRX version register (SPDIFRX_VERR)
Address offset: 0x03F4
Reset value: 0x0000 0012

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

MAJREV[3:0]

MINREV[3:0]

r

r

Bits 31:8 Reserved, must be kept at reset value
Bits 7:4 MAJREV[3:0]: Major revision
These bits return the SPDIFRX major revision.
Major revision is 1.
Bits 3:0 MINREV[3:0]: Minor revision
These bits return the SPDIFRX minor revision.
Minor revision is 2.

27.5.11

SPDIFRX identification register (SPDIFRX_IDR)
Address offset: 0x03F8
Reset value: 0x0013 0041

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

6

5

4

3

2

1

0

ID[31:16]
r
15

14

13

12

11

10

9

8

7
ID[15:0]
r

Bits 31:0 ID[31:0]: SPDIFRX identifier
These bits return the SPDIFRX identifier value.

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RM0390

SPDIF receiver interface (SPDIFRX)

27.5.12

SPDIFRX size identification register (SPDIFRX_SIDR)
Address offset: 0x03FC
Reset value: 0xA3C5 DD01

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

6

5

4

3

2

1

0

SID[31:16]
r
15

14

13

12

11

10

9

8

7
SID[15:0]
r

Bits 31:0 SID[31:0]: Size identification
These bits return the size of the memory region allocated to SPDIFRX registers.
The size of this memory region is of 1 Kbyte.

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27.5.13

RM0390

SPDIFRX interface register map
Table 168 gives the SPDIFRX interface register map and reset values.

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

RXNE

Res.

CSRNE

Res.

0

0

0

0
Res.

Res.

0

Res.

Res.

OVR

Res.

PERR

Res.

0

OVRCF

Res.

0

PERRCF

Res.

SBD

Res.

0

SBDCF

Res.

SYNCD

Res.

0

SYNCDCF

Res.

FERR

0

SERR

0

Res.

0

Res.

0

TERR

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

0

0

0

0

PT[1:0]

Res.

Res.

Reset value
C U V

PE

DR[23:0]

SPDIFRX_DR

0x10

DR[23:0]

Res.

0x03F8
0x03FC

Res.

Res.

SOB

0

0

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.

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

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

1

0

0

1

0

1

0

0

0

0

0

1

0

0

0

0

0

0

1

ID[15:0]
0

0

1

0

0

1

1

0

0

0

0

0

0

0

SID[31:16]
1

0

MAJREV[3:0] MINREV[3:0]
0

0

0

THI[12:0]

ID[31:16]
0

PE

USR[15:0]

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

934/1327

0

0

SPDIFRX_SIDR
Reset value

0

TLO[12:0]

SPDIFRX_IDR
Reset value

0

CS[7:0]
0

C U V

DRNL1[15:0]
0

Res.

Res.

Res.
Res.

0x03F4

Reset value
SPDIFRX_VER
R
Reset value

Res.

0x18

0
Res.

Reset value
SPDIFRX_DIR

0

Res.

SPDIFRX_CSR

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0
Res.

0x14

0
Res.

DRNL2[15:0]
Reset value

PT[1:0]

Res.

0

Res.

SPDIFRX_IFCR

0

Res.

0x0C

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.
0
Res.

CKSEN
0

Res.

0

Res.

Res.

CKSBKPEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SPDIFRX_IMR

Res.

0x04

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SPDIFRX_CR

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 168. SPDIFRX interface register map and reset values

1

0

0

SID[15:0]
0

0

0

1

0

1

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1

1

0

1

1

1

0

1

0

RM0390

Serial audio interface (SAI)

28

Serial audio interface (SAI)

28.1

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.

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Serial audio interface (SAI)

28.2

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.

•

•

936/1327

RM0390

–

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.

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RM0390

Serial audio interface (SAI)

28.3

SAI functional description

28.3.1

SAI block diagram
Figure 353 shows the SAI block diagram while Table 169 and Table 170 list SAI internal and
external signals.
Figure 353. Functional block diagram
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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).

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Serial audio interface (SAI)

RM0390

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.

28.3.2

SAI pins and internal signals
Table 169. SAI internal signals
Internal signal name Signal type
sai_a_gbl_it/
sai_b_gbl_it
sai_a_dma,
sai_b_dma

Digital
output

Digital
output

sai_sync_in_sck,
sai_sync_in_fs

Digital input

sai_pclk

Audio block A and B global interrupts.

Digital
Audio block A and B DMA acknowledges and requests.
input/output

sai_sync_out_sck,
sai_sync_out_fs

sai_a_ker_ck/
sai_b_ker_ck

Description

Internal clock and frame synchronization output signals
exchanged with other SAI blocks.
Internal clock and frame synchronization input signals
exchanged with other SAI blocks.

Digital input Audio block A/B kernel clock.
Digital input APB clock.

Table 170. SAI pins
Name
SAI_SCK_A/B
SAI_MCLK_A/B

28.3.3

Signal type

Comments

Digital
Audio block A/B bit clock.
input/output
Digital
output

Audio block A/B master clock.

SAI_SD_A/B

Digital
Data line for block A/B.
input/output

SAI_FS_A/B

Digital
Frame synchronization line for audio block A/B.
input/output

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:

938/1327

•

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.
DocID026976 Rev 3

RM0390

Serial audio interface (SAI)
Both SCK_x, FS_x and MCLK_x are configured as outputs.

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 bit SAIXEN 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:

28.3.4

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).

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Serial audio interface (SAI)

RM0390

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 171. External synchronization selection
Block instance

28.3.5

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.

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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 354 illustrates this flexibility.
Figure 354. Audio frame
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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 Section : 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 28.3.8: 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 28.3.13: 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.

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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 28.3.13: Error flags).
In master mode, the frame synchronization is sent continuously each time an audio frame is
complete until the SAIXEN 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 28.3.13: 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.

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Figure 355. FS role is start of frame + channel side identification (FSDEF = TRIS = 1)
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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.

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RM0390
Figure 356. FS role is start of frame (FSDEF = 0)
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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.

28.3.7

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 Section : 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 357. 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.

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Figure 357. Slot size configuration with FBOFF = 0 in SAI_xSLOTR
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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 358. First bit offset
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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 28.3.10: AC’97 link controller.

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28.3.8

RM0390

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 359 illustrates the architecture of the audio block clock generator.
Figure 359. Audio block clock generator overview

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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 172.

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Table 172. 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 28.3.6: 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 28.3.11: SPDIF output for details on clock generator programming in
SPDIF mode.

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28.3.9

RM0390

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 Section : Interrupt
generation in transmitter mode and Section : 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

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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.

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28.3.10

RM0390

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 360 shows an AC’97 audio frame structure.
Figure 360. AC’97 audio frame
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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 361.
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.

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Figure 361. Example of typical AC’97 configuration on devices featuring at least
2 embedded SAIs (three external AC’97 decoders)

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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 28.3.8: SAI clock generator shall be used with FRL =
255, in order to generate the proper frame rate (FFS_x).

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28.3.11

RM0390

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 362.
Figure 362. SPDIF format
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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 173). The next 28 bits of channel information are
composed of 24 bits data + 4 status bits.

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Serial audio interface (SAI)
Table 173. 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 363. SAI_xDR register ordering

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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 174.
Table 174. 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

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RM0390

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
SAIXEN 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 SAIXEN bit in SAI_xCR1 register.

Clock generator programming in SPDIF generator mode
For the SPDIF generator, the SAI shall provide a bit clock equal to the symbol-rate. The
table hereafter shows usual examples of symbol rates with respect to the audio sampling
rate.
Table 175. 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 rate (FS) and the bit-clock rate
(FSCK_X) is given by the formula:

28.3.12

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.

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Serial audio interface (SAI)
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.

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 364. 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).

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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 (bit SAIXEN = 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 364. Data companding hardware in an audio block in the SAI
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1. Not applicable when AC’97 or SPDIF are selected.

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

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Serial audio interface (SAI)
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 365 illustrates these behaviors.
Figure 365. Tristate strategy on SD output line on an inactive slot
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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 366 (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).
Figure 366. Tristate on output data line in a protocol like I2S

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If the TRIS bit in the SAI_xCR2 register is cleared, all the High impedance states on the SD
output line on Figure 365 and Figure 366 are replaced by a drive with a value of 0.

28.3.13

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

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Serial audio interface (SAI)
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 367).
The OVRUDR flag is cleared when COVRUDR bit is set in the SAI_xCLRFR register.
Figure 367. Overrun detection error
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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 368). 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.

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Figure 368. FIFO underrun event
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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 SAIXEN bit in SAI_xCR1 register. To make sure the
SAI is disabled, read back the SAIXEN 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 (SAIXEN bit set to 1).

4.

The SAI block will wait for the assertion on FS to restart the synchronization with
master.

The SAIXEN 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.

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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
Section : 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.

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 SAIXEN 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 SAIXEN bit.

28.3.14

Disabling the SAI
The SAI audio block can be disabled at any moment by clearing SAIXEN bit in the
SAI_xCR1 register. All the already started frames are automatically completed before the
SAI is stops working. SAIXEN 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.

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RM0390

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 28.3.9: Internal FIFOs). DMA transfer
direction is linked to the SAI audio sub-block configuration:
•

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.

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.

28.4

SAI interrupts
The SAI supports 7 interrupt sources as shown in Table 176.
Table 176. 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 28.3.9: 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

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Table 176. SAI interrupt sources (continued)

Interrupt
source

Interrupt
group

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

Audio block mode

Interrupt enable

Interrupt clear

Follow the sequence below to enable an interrupt:
1.

Disable SAI interrupt.

2.

Configure SAI.

3.

Configure SAI interrupt source.

4.

Enable SAI.

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28.5

SAI registers

28.5.1

Global configuration register (SAI_GCR)
Address offset: 0x00
Reset value: 0x0000 0000

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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 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).

28.5.2

Configuration register 1 (SAI_ACR1 / SAI_BCR1)
Address offset: Block A: 0x004
Address offset: Block B: 0x024
Reset value: 0x0000 0040

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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 SAIXEN: Audio block enable where x is A or B
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 SAIx 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: SAIx audio block disabled
1: SAIx audio block enabled.
Note: When SAIx block is configured in master mode, the clock must be present on the input of SAIx
before setting SAIXEN 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 SAIXEN 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.

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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

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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.

28.5.3

Configuration register 2 (SAI_ACR2 / SAI_BCR2)
Address offset: Block A: 0x008
Address offset: Block B: 0x028
Reset value: 0x0000 0000

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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: SAIXEN.
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.

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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: 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

28.5.4

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

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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.

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28.5.5

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
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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.

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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 1 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.

28.5.6

Interrupt mask register 2 (SAI_AIM / SAI_BIM)
Address offset: block A: 0x014
Address offset: block B: 0x034
Reset value: 0x0000 0000

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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.

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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.

28.5.7

Status register (SAI_ASR / SAI_BSR)
Address offset: block A: 0x018
Address offset: block B: 0x038
Reset value: 0x0000 0008

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Bits 31:19 Reserved, must be kept at reset value
Bits 18:16 FLVL: 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.

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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 28.3.6: 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.

28.5.8

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

DocID026976 Rev 3

CCNRDY
w

Res.

CMUTE COVRUD
CWCKCFG
DET
R
w

w

w

975/1327
978

Serial audio interface (SAI)

RM0390

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.

28.5.9

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

976/1327

rw

rw

rw

rw

rw

rw

rw

rw

DocID026976 Rev 3

0x001C or
0x003C

SAI_xCLRFR

Reset value

0

0

0

DocID026976 Rev 3

0

0

0

OVRUDR

0

0

0

1

0

0

OVRUDR

0

MUTEDET
MUTEDET
OVRUDRIE

0

MUTEDET

FREQIE
WCKCFG

0

FREQ

0

WCKCFG

FSALL[6:0]

Res.

TRIS
FFLUS

0
0
0
0

0
0

FTH

0

MUTE

0

1

MUTE VAL

0

MODE[1:0]

PRTCFG[1:0]

Res.

0

WCKCFG

CNRDYIE

LSBFIRST
DS[2:0]

CKSTR

SYNCEN[1:0]

MONO

Res.
OUTDRIV

0

Res.

CPL

COMP[1:0]

SAIXEN

Res.
Res.

DMAEN

Res.

Res.

NODIV

Reset value

CNRDY

Reset value

CNRDY

0

AFSDETIE

0

AFSDET

0

CAFSDET

SLOTSZ[1:0}

0
0

LFSDET

Res.

MUTECN[5:0]

LFSDET

0

Res.

Res.

MCJDIV[3:0]

0

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

NBSLOT[3:0]
0

Res.

0

Res.

Res.
0

Res.

0

Res.

Res.
0

Res.

0

Res.

Res.

Res.

Res.

Res.

FSDEF

0

0

LFSDET

Reset value
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

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
and reset
value

Res.

Offset

Res.

28.5.10

Res.

RM0390
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.

SAI register map
The following table summarizes the SAI registers.
Table 177. 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

977/1327

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Serial audio interface (SAI)

RM0390

Offset

0x0020 or
0x0040

Register
and reset
value

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 177. SAI register map and reset values (continued)

SAI_xDR

DATA[31:0]

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

Refer to Section 2.2 on page 56 for the register boundary addresses.

978/1327

DocID026976 Rev 3

0

0

0

0

0

0

0

0

0

RM0390

Secure digital input/output interface (SDIO)

29

Secure digital input/output interface (SDIO)

29.1

SDIO main features
The SD/SDIO MMC card host interface (SDIO) 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 SDIO 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 SDIO 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 SDIO supports only one SD/SDIO/MMC4.2 card at any one time
and a stack of MMC4.1 or previous.

29.2

SDIO 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.

DocID026976 Rev 3

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1036

Secure digital input/output interface (SDIO)

RM0390

Figure 369. “No response” and “no data” operations
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06Y9

Figure 370. (Multiple) block read operation
)URPKRVWWRFDUG )URPFDUGWRKRVW
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6',2B&0'

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6WRSFRPPDQG
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5HVSRQVH

6',2B'

&RPPDQG

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'DWDEORFN FUF

5HVSRQVH

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06Y9

Figure 371. (Multiple) block write operation
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6',2B&0'

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6WRSFRPPDQG
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0XOWLSOHEORFNZULWHRSHUDWLRQ
06Y9

Note:

980/1327

The SDIO will not send any data as long as the Busy signal is asserted (SDIO_D0 pulled
low).

DocID026976 Rev 3

RM0390

Secure digital input/output interface (SDIO)
Figure 372. Sequential read operation
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FDUG V
)URPFDUGWRKRVW

6WRSFRPPDQG
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Figure 373. Sequential write operation
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06Y9

29.3

SDIO functional description
The SDIO consists of two parts:
•

The SDIO 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 SDIO adapter registers, and generates interrupt and
DMA request signals.
Figure 374. SDIO block diagram
6',2
6',2B&.
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DocID026976 Rev 3

06Y9

981/1327
1036

Secure digital input/output interface (SDIO)

RM0390

By default SDIO_D0 is used for data transfer. After initialization, the host can change the
databus width.
If a MultiMediaCard is connected to the bus, SDIO_D0, SDIO_D[3:0] or SDIO_D[7:0] can be
used for data transfer. MMC V3.31 or previous, supports only 1 bit of data so only SDIO_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 SDIO_D0 or SDIO_D[3:0]. All data lines are operating in push-pull mode.
SDIO_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)

SDIO_CK is the clock to the card: one bit is transferred on both command and data lines
with each clock cycle.
The SDIO uses two clock signals:
•

SDIO adapter clock SDIOCLK = 50 MHz)

•

APB2 bus clock (PCLK2)

PCLK2 and SDIO_CK clock frequencies must respect the following condition:
Frequenc ( PCLK2 ) > ( ( 3xWidth ) ⁄ 32 ) × Frequency ( SDIO_CK )

The signals shown in Table 178 are used on the MultiMediaCard/SD/SD I/O card bus.
Table 178. SDIO I/O definitions
Pin

982/1327

Direction

Description

SDIO_CK

Output

MultiMediaCard/SD/SDIO card clock. This pin is the clock from
host to card.

SDIO_CMD

Bidirectional

MultiMediaCard/SD/SDIO card command. This pin is the
bidirectional command/response signal.

SDIO_D[7:0]

Bidirectional

MultiMediaCard/SD/SDIO card data. These pins are the
bidirectional databus.

DocID026976 Rev 3

RM0390

29.3.1

Secure digital input/output interface (SDIO)

SDIO adapter
Figure 375 shows a simplified block diagram of an SDIO adapter.
Figure 375. SDIO adapter
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06Y9

The SDIO 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 SDIO adapter clock domain (SDIOCLK).

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 SDIO 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:
•

power-off

•

power-up

•

power-on

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Secure digital input/output interface (SDIO)

RM0390

Figure 376. Control unit
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The control unit is illustrated in Figure 376. 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 SDIO_CK signal. The SDIO_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 SDIO_CK dephasing. When not in bypass mode
the SDIO command and data output are generated on the SDIOCLK falling edge
succeeding the rising edge of SDIO_CK. (SDIO_CK rising edge occurs on SDIOCLK rising
edge) when SDIO_CLKCR[13] bit is reset (NEGEDGE = 0). When SDIO_CLKCR[13] bit is
set (NEGEDGE = 1) SDIO command and data changed on the SDIO_CK falling edge.
When SDIO_CLKCR[10] is set (BYPASS = 1), SDIO_CK rising edge occurs on SDIOCLK
rising edge. The data and the command change on SDIOCLK falling edge whatever
NEGEDGE value.
The data and command responses are latched using SDIO_CK rising edge.
Figure 377. SDIO_CK clock dephasing (BYPASS = 0)
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6',2B&.

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984/1327

1(*('*( 

DocID026976 Rev 3

06Y9

RM0390

Secure digital input/output interface (SDIO)

Command path
The command path unit sends commands to and receives responses from the cards.
Figure 378. SDIO adapter command path

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•

Command path state machine (CPSM)
–

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 379 on
page 986). When the response is received, the received CRC code and the
internally generated code are compared, and the appropriate status flags are set.

DocID026976 Rev 3

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Secure digital input/output interface (SDIO)

RM0390

Figure 379. Command path state machine (SDIO)
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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 SDIO_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:

986/1327

The CPSM remains in the Idle state for at least eight SDIO_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.

DocID026976 Rev 3

RM0390

Secure digital input/output interface (SDIO)
Figure 380. SDIO command transfer
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•

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 179.
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
SDIO_CMD output is in the Hi-Z state, as shown in Figure 380 on page 987. Data
on SDIO_CMD are synchronous with the rising edge of SDIO_CK. Table 179
shows the command format.
Table 179. 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 SDIO supports two response types. Both use CRC error checking:

Note:

•

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.

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Table 180. 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 181. 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 29.8.4 on page 1023). The command path
implements the status flags shown in Table 182:
Table 182. 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

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Data path
The data path subunit transfers data to and from cards. Figure 381 shows a block diagram
of the data path.
Figure 381. Data path
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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
(SDIO_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 (SDIO_D[7:0]). If the wide bus mode is not enabled,
only one bit per clock cycle is transferred over SDIO_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 SDIO_CK frequency. Data on the card bus signals is synchronous to
the rising edge of SDIO_CK. The DPSM has six states, as shown in Figure 382: Data path
state machine (DPSM).

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Figure 382. Data path state machine (DPSM)
/N RESET

$03- DISABLED

2EAD 7AIT

$03- ENABLED AND
2EAD 7AIT 3TARTED
AND 3$ )/ MODE ENABLED
$ISABLED OR &)&/ UNDERRUN OR
END OF DATA OR #2# FAIL

)DLE
$ISABLED OR #2# FAIL
OR TIMEOUT

%NABLE AND NOT SEND
2EAD7AIT 3TOP

$ISABLED OR
END OF DATA
$ISABLED OR
2X &)&/ EMPTY OR TIMEOUT OR
START BIT ERROR

"USY
.OT BUSY

%NABLE AND SEND

7AIT?2

$ATA RECEIVED AND
2EAD 7AIT 3TARTED AND
3$ )/ MODE ENABLED

%ND OF PACKET

7AIT?3

%ND OF PACKET OR
END OF DATA OR
&)&/ OVERRUN
$ISABLED OR #2# FAIL
3TART BIT

$ATA READY

3END

2ECEIVE
AIB

•

Idle: the data path is inactive, and the SDIO_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
SDIO_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:
•

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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.

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Secure digital input/output interface (SDIO)
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 SDIO_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 183. Data token format
Description

Start bit

Data

CRC16

End bit

Block Data

0

-

yes

1

Stream Data

0

-

no

1

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DPSM Flags
The status of the data path subunit transfer is reported by several status flags
Table 184. 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 SDIO_DCOUNT register decrements and reaches 0.
DATAEND indicates the end of a transfer on SDIO 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 SDIO clock domain (SDIOCLK) 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 SDIO 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.

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Table 185. 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
SDIO Clear register.
Note: In case of TXUNDERR, and DMA is used to fill SDIO FIFO, user software
should disable DMA stream, and then write DMAEN bit in SDIO_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 186 lists the receive FIFO status flags.
The receive FIFO is accessible via 32 sequential addresses.
Table 186. Receive FIFO status flags
Flag

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 SDIO
Clear register.
Note: In case of RXOVERR, and DMA is used to read SDIO FIFO, user software
should disable DMA stream, and then write DMAEN bit in SDIO_DCTRL
with ‘0’ (to disable DMA request generation).

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29.3.2

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SDIO APB2 interface
The APB2 interface generates the interrupt and DMA requests, and accesses the SDIO
adapter registers and the data FIFO. It consists of a data path, register decoder, and
interrupt/DMA logic.

SDIO 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.

SDIO/DMA interface
SDIO 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:
a)

Note:

994/1327

Program the SDIO data length register (SDIO data timer register should be
already programmed before the card identification process)

b)

Program DMA channel (refer to DMA configuration for SDIO controller)

c)

Program the SDIO data control register: DTEN with ‘1’ (SDIO 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 SDIO argument register with the address location of the card from
where data is to be transferred

e)

Program the SDIO command register: CmdIndex with 17(READ_BLOCK);
WaitResp with ‘1’ (SDIO card host waits for a response); CPSMEN with ‘1’ (SDIO
card host enabled to send a command). Other fields are at their reset value.

f)

Wait for SDIO_STA[6] = CMDREND interrupt, (CMDREND is set if there is no
error on command path).

g)

Wait for SDIO_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 SDIO_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.

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Example of write procedure using DMA
Send CMD24 (WRITE_BLOCK) as follows:
a)

Program the SDIO data length register (SDIO data timer register should be
already programmed before the card identification process)

b)

Program DMA channel (refer to DMA configuration for SDIO controller)

c)

Program the SDIO argument register with the address location of the card from
where data is to be transferred

d)

Program the SDIO command register: CmdIndex with 24(WRITE_BLOCK);
WaitResp with ‘1’ (SDIO card host waits for a response); CPSMEN with ‘1’ (SDIO
card host enabled to send a command). Other fields are at their reset value.

e)

Wait for SDIO_STA[6] = CMDREND interrupt, then Program the SDIO data control
register: DTEN with ‘1’ (SDIO 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 SDIO_STA[10] = DBCKEND, (DBCKEND is set in case of no errors)

DMA configuration for SDIO 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 SDIO_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

SDIO host allows only to use the DMA in peripheral flow controller mode. DMA stream used
to serve SDIO must be configured in peripheral flow controller mode
SDIO generates only DMA burst requests to DMA controller. DMA must be configured in
incremental burst mode on peripheral side.

29.4

Card functional description

29.4.1

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.

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29.4.2

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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).

29.4.3

Operating voltage range validation
All cards can communicate with the SDIO 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 SDIO 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 SDIO card host. The SDIO 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 SDIO
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 SDIO card host is able to
select a common voltage range or when the user requires notification that cards are not
usable.

29.4.4

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 SDIO_CMD
line output drivers are open-drain and allow parallel card operation during this process. The
registration process is accomplished as follows:

996/1327

1.

The bus is activated.

2.

The SDIO 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 SDIO 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 SDIO
card host and enters the Identification state.

7.

The SDIO 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

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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 SDIO 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 SDIO_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 SDIO 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 SDIO 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 SDIO 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
SDIO card host can reissue this command to change the RCA. The RCA of the card is
the last assigned value.

8.

The SDIO card host repeats steps 5 through 7 with all active cards.

For the SD I/O card, the registration process is accomplished as follows:
1.

29.4.5

The bus is activated.

2.

The SDIO 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 SDIO 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
SDIO 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 SDIO_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.

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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 SDIO_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
SDIO_D line(s) without interrupting the write operation. When reselecting the card, it will
reactivate busy indication by pulling SDIO_D to low if programming is still in progress and
the write buffer is unavailable.

29.4.6

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).

29.4.7

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 SDIO card host to
the card, beginning at the specified address and continuing until the SDIO 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 SDIO
card host, any additional transferred data are discarded.
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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
SDIO 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 SDIO 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.

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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 SDIO_D low. The actual erase
time may be quite long, and the host may issue CMD7 to deselect the card.

29.4.9

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).

29.4.10

Protection management
Three write protection methods for the cards are supported in the SDIO card host module:
1.

internal card write protection (card responsibility)

2.

mechanical write protection switch (SDIO 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
a data block containing 32 write protection bits (representing 32 write protect groups starting

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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 SDIO card host module that the card is
write-protected. The SDIO 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 SDIO 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 SDIO 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 SDIO card host module before it sends the card lock/unlock
command, and has the structure shown in Table 200.
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
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.

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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 200), 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 SDIO card host module performs all the required steps for setting the password (see
Setting the password on page 1001), however it is necessary to set the LOCK_UNLOCK bit
in Step 3 when the new password command is sent.

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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 200), 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 200) 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.

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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 187 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 SDIO 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 187. Card status

Bits

31

30

29

Identifier

ADDRESS_
OUT_OF_RANGE

ADDRESS_MISALIGN

BLOCK_LEN_ERROR

1004/1327

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)

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Table 187. 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

EX

’0’= no error
’1’= error

An invalid selection of erase groups for
erase occurred.

C

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

ERASE_PARAM

26

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

’0’= enabled
’1’= disabled

C

C

The command has been executed without
A
using the internal ECC.

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Table 187. Card status (continued)
Bits

Identifier

Type

Value

Description

Clear
condition

ERASE_RESET

’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)

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

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.

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

13

1
0

Reserved for manufacturer test mode

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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 SDIO 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 188 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 SDIO 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 188. 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

SR

SIZE_OF_PROTE
SR
CT ED_AREA

447: 440 SPEED_CLASS

SR

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Table 188. 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 189. Speed class code field
SPEED_CLASS

1008/1327

Value definition

00h

Class 0

01h

Class 2

02h

Class 4

03h

Class 6

04h – FFh

Reserved

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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 190. 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 191. 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 192. The
card can be set to any AU size between RU size and maximum AU size.
Table 192. Maximum AU size
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

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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 193. 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 194. 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 195. Erase offset field
ERASE_OFFSET

1010/1327

Value definition

0h

0 [sec]

1h

1 [sec]

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Table 195. Erase offset field (continued)
ERASE_OFFSET

29.4.13

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 SDIO_D1 when operating in the 4-bit
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 (SDIO_D[3:0]). The
MultiMediaCard/SD module samples the level of pin 8 (SDIO_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 SDIO_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

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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.

29.4.14

Commands and responses
Application-specific and general commands
The SDIO 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.

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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 SDIO_D line(s).

•

addressed (point-to-point) data transfer command (ADTC): sent to the card that is
selected; includes a data transfer on the SDIO_D line(s).

Command formats
See Table 179 on page 987 for command formats.

Commands for the MultiMediaCard/SD module
Table 196. 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.

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Table 197. 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 198. 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 199. I/O mode commands
CMD
index

Type

CMD39 ac

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Argument

[31:16] RCA
[15:15] register
write flag
[14:8] register
address
[7:0] register data

Response
format

R4

Abbreviation

FAST_IO

DocID026976 Rev 3

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.

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Table 199. I/O mode commands (continued)

CMD
index

Type

CMD40 bcr

Response
format

Argument
[31:0] stuff bits

R5

Abbreviation

Description

GO_IRQ_STATE Places the system in the interrupt mode.

CMD41 Reserved

Table 200. Lock card
CMD
index

Type

CMD42 adtc

Response
format

Argument

[31:0] stuff bits

Abbreviation

R1b

Description
Sets/resets the password or locks/unlocks
the card. The size of the data block is set
by the SET_BLOCK_LEN command.

LOCK_UNLOCK

CMD43
...
Reserved
CMD54

Table 201. 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.

29.5

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 SDIO command line SDIO_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:

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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 202. R1 response
Bit position

29.5.2

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.

29.5.3

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 SDIO_D0 low. The actual erase time may be quite long, and the
host may issue CMD7 to deselect the card.
Table 203. R2 response
Bit position

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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

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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 204. R3 response
Bit position

29.5.5

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 205. 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

29.5.6

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 206. R4b response
Bit position

Width (bits

Value

Description

47

1

0

Start bit

46

1

0

Transmission bit

[45:40]

6

X

Reserved

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Table 206. 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.

29.5.7

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 207. 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

29.5.8

Description

R6
Only for SD I/O. The normal response to CMD3 by a memory device. It is shown in
Table 208.

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Table 208. 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:

29.6

•

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 SDIO_D2 signalling

•

SDIO read wait operation by stopping the clock

•

SDIO suspend/resume operation (write and read suspend)

•

SDIO interrupts

The SDIO supports these operations only if the SDIO_DCTRL[11] bit is set, except for read
suspend that does not need specific hardware implementation.

29.6.1

SDIO I/O read wait operation by SDIO_D2 signalling
It is possible to start the readwait interval before the first block is received: when the data
path is enabled (SDIO_DCTRL[0] bit set), the SDIO-specific operation is enabled
(SDIO_DCTRL[11] bit set), read wait starts (SDIO_DCTRL[10] =0 and SDIO_DCTRL[8] =1)
and data direction is from card to SDIO (SDIO_DCTRL[1] = 1), the DPSM directly moves
from Idle to Readwait. In Readwait the DPSM drives SDIO_D2 to 0 after 2 SDIO_CK clock
cycles. In this state, when you set the RWSTOP bit (SDIO_DCTRL[9]), the DPSM remains
in Wait for two more SDIO_CK clock cycles to drive SDIO_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 SDIO can detect SDIO interrupts on SDIO_D1.

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SDIO read wait operation by stopping SDIO_CK
If the SDIO card does not support the previous read wait method, the SDIO can perform a
read wait by stopping SDIO_CK (SDIO_DCTRL is set just like in the method presented in
Section 29.6.1, but SDIO_DCTRL[10] =1): DSPM stops the clock two SDIO_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 SDIO_CK is stopped, any command can be issued to the card. During a read/wait
interval, the SDIO can detect SDIO interrupts on SDIO_D1.

29.6.3

SDIO suspend/resume operation
While sending data to the card, the SDIO can suspend the write operation. the
SDIO_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
(SDIO_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.

29.6.4

SDIO interrupts
SDIO interrupts are detected on the SDIO_D1 line once the SDIO_DCTRL[11] bit is set.
When SDIO interrupt is detected, SDIO_STA[22] (SDIOIT) bit is set. This static bit can be
cleared with clear bit SDIO_ICR[22] (SDIOITC). An interrupt can be generated when
SDIOIT status bit is set. Separated interrupt enable SDIO_MASK[22] bit (SDIOITE) is
available to enable and disable interrupt request.
When SD card interrupt occurs (SDIO_STA[22] bit set), host software follows below steps to
handle it.
1.

Disable SDIOIT interrupt signaling by clearing SDIOITE bit (SDIO_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 (SDIO_ICR[22] = ‘1’),

4.

Enable SDIOIT interrupt signaling by writing ‘1’ to SDIOITE bit (SDIO_MASK[22] = ‘1’).

Steps 2 to 4 can be executed out of the SDIO interrupt service routine.

29.7

HW flow control
The HW flow control functionality is used to avoid FIFO underrun (TX mode) and overrun
(RX mode) errors.
The behavior is to stop SDIO_CK and freeze SDIO state machines. The data transfer is
stalled while the FIFO is unable to transmit or receive data. Only state machines clocked by

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SDIOCLK 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 SDIO_CLKCR[14] register bit must be set to 1. After reset
Flow Control is disabled.

29.8

SDIO registers
The device communicates to the system via 32-bit-wide control registers accessible via
APB2.

29.8.1

SDIO power control register (SDIO_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 SDIOCLK clock periods
plus two PCLK2 clock periods.

29.8.2

SDIO clock control register (SDIO_CLKCR)
Address offset: 0x04
Reset value: 0x0000 0000
The SDIO_CLKCR register controls the SDIO_CK output clock.

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

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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 SDIO Status register definition in Section 29.8.11.
Bit 13 NEGEDGE: SDIO_CK dephasing selection bit
0b: Command and Data changed on the SDIOCLK falling edge succeeding the rising edge
of SDIO_CK. (SDIO_CK rising edge occurs on SDIOCLK rising edge).
1b: Command and Data changed on the SDIO_CK falling edge.
When BYPASS is active, the data and the command change on SDIOCLK falling edge
whatever NEGEDGE value.
Bits 12:11 WIDBUS: Wide bus mode enable bit
00: Default bus mode: SDIO_D0 used
01: 4-wide bus mode: SDIO_D[3:0] used
10: 8-wide bus mode: SDIO_D[7:0] used
Bit 10 BYPASS: Clock divider bypass enable bit
0: Disable bypass: SDIOCLK is divided according to the CLKDIV value before driving the
SDIO_CK output signal.
1: Enable bypass: SDIOCLK directly drives the SDIO_CK output signal.
Bit 9 PWRSAV: Power saving configuration bit
For power saving, the SDIO_CK clock output can be disabled when the bus is idle by setting
PWRSAV:
0: SDIO_CK clock is always enabled
1: SDIO_CK is only enabled when the bus is active
Bit 8 CLKEN: Clock enable bit
0: SDIO_CK is disabled
1: SDIO_CK is enabled
Bits 7:0 CLKDIV: Clock divide factor
This field defines the divide factor between the input clock (SDIOCLK) and the output clock
(SDIO_CK): SDIO_CK frequency = SDIOCLK / [CLKDIV + 2].

Note:

1

While the SD/SDIO card or MultiMediaCard is in identification mode, the SDIO_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 SDIOCLK clock periods
plus two PCLK2 clock periods. SDIO_CK can also be stopped during the read wait interval
for SD I/O cards: in this case the SDIO_CLKCR register does not control SDIO_CK.

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29.8.3

SDIO argument register (SDIO_ARG)
Address offset: 0x08
Reset value: 0x0000 0000
The SDIO_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.

29.8.4

SDIO command register (SDIO_CMD)
Address offset: 0x0C
Reset value: 0x0000 0000
The SDIO_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
SDIO_DCTRL[2] = 1.

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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 SDIOCLK 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.

29.8.5

SDIO command response register (SDIO_RESPCMD)
Address offset: 0x10
Reset value: 0x0000 0000
The SDIO_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.

29.8.6

SDIO response 1..4 register (SDIO_RESPx)
Address offset: (0x10 + (4 × x)); x = 1..4
Reset value: 0x0000 0000
The SDIO_RESP1/2/3/4 registers contain the status of a card, which is part of the received
response.

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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 209.

The Card Status size is 32 or 127 bits, depending on the response type.
Table 209. Response type and SDIO_RESPx registers
Register

Short response

Long response

SDIO_RESP1

Card Status[31:0]

Card Status [127:96]

SDIO_RESP2

Unused

Card Status [95:64]

SDIO_RESP3

Unused

Card Status [63:32]

SDIO_RESP4

Unused

Card Status [31:1]0b

The most significant bit of the card status is received first. The SDIO_RESP4 register LSB is
always 0b.

29.8.7

SDIO data timer register (SDIO_DTIMER)
Address offset: 0x24
Reset value: 0x0000 0000
The SDIO_DTIMER register contains the data timeout period, in card bus clock periods.
A counter loads the value from the SDIO_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:

A data transfer must be written to the data timer register and the data length register before
being written to the data control register.

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SDIO data length register (SDIO_DLEN)
Address offset: 0x28
Reset value: 0x0000 0000
The SDIO_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 SDIO_DCTRL). A data transfer must be written to the data timer register and the
data length register before being written to the data control register.
For an SDIO multibyte transfer the value in the data length register must be between 1 and
512.

29.8.9

SDIO data control register (SDIO_DCTRL)
Address offset: 0x2C
Reset value: 0x0000 0000
The SDIO_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

rw

rw

rw

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 SDIO_D2
1: Read Wait control using SDIO_CK

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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 SDIO_DCTRL must be updated to enable a new data transfer

Note:

After a data write, data cannot be written to this register for three SDIOCLK (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.

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SDIO data counter register (SDIO_DCOUNT)
Address offset: 0x30
Reset value: 0x0000 0000
The SDIO_DCOUNT register loads the value from the data length register (see
SDIO_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.

29.8.11

SDIO status register (SDIO_STA)
Address offset: 0x34
Reset value: 0x0000 0000
The SDIO_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 SDIO Interrupt Clear register (see SDIO_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

CMDR
RX
TXUND DTIME CTIME
END OVERR ERR
OUT
OUT

Bits 31:23 Reserved, must be kept at reset value.
Bit 22 SDIOIT: SDIO interrupt received
Bit 21 RXDAVL: Data available in receive FIFO

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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 SDIO FIFO (DMAEN bit is set in SDIO_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 SDIO FIFO (DMAEN bit is set in SDIO_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 SDIO_CK clock periods.
Bit 1 DCRCFAIL: Data block sent/received (CRC check failed)
Bit 0 CCRCFAIL: Command response received (CRC check failed)

29.8.12

SDIO interrupt clear register (SDIO_ICR)
Address offset: 0x38
Reset value: 0x0000 0000
The SDIO_ICR register is a write-only register. Writing a bit with 1b clears the corresponding
bit in the SDIO_STA Status register.

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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

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DTIME CTIME
OVERR UNDERR
OUTC OUTC
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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

29.8.13

SDIO mask register (SDIO_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

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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.

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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

29.8.14

SDIO FIFO counter register (SDIO_FIFOCNT)
Address offset: 0x48
Reset value: 0x0000 0000
The SDIO_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
SDIO_DLEN) when the data transfer enable bit, DTEN, is set in the data control register
(SDIO_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.

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Secure digital input/output interface (SDIO)

RM0390

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.

29.8.15

SDIO data FIFO register (SDIO_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:
SDIO base + 0x080 to SDIO base + 0xFC.

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RM0390

29.8.16

Secure digital input/output interface (SDIO)

SDIO register map
The following table summarizes the SDIO 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

SDIO_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.

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

SDIO_
RESPCMD

CLKDIV

BYPASS

0

WIDBUS

0

Res.

0x0C

SDIO_ARG

0

Res.

0x08

Reset value
SDIO_
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

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DTEN

0

DTDIR

0

DTMODE

0

DMAEN

0

DBLOCKSIZE

DATALENGTH

RWSTART

Res.
Res.

0

RWSTOP

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

SDIO_
DLEN

Res.

DATATIME

Reset value

SDIO_
DCOUNT

0

0

Reset value
0x30

0

CARDSTATUS4

SDIO_
DTIMER

SDIO_
DCTRL

0

CARDSTATUS3

Reset value

0x2C

0

CARDSTATUS2

Res.

0x28

0

SDIO_
RESP4
Reset value

0x24

0

Res.

0x20

0

SDIO_
RESP3
Reset value

0

RWMOD

Reset value
0x1C

0

SDIO_
RESP2

Res.

0x18

0

SDIOEN

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.

SDIO_
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.

SDIO_
POWER

Res.

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 210. SDIO 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

DATACOUNT
0

0

0

0

0

0

0

0

0

DocID026976 Rev 3

0

0

0

0

0

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0x48
SDIO_
FIFOCNT

Reset value

1036/1327
0
0
0
0
0
0
0
Res.

Res.

Res.

Res.

Res.

SDIO_
MASK

Res.

0x3C

Reset value

0
0

0
0
0
0

0

0
0

0
0

0
0

0

SDIO_FIFO
0

0
0

0

RXACTIE
TXACTIE
CMDACTIE
DBCKENDIE

0
0

0

0
0
0
0
0
0
0

0

0

DocID026976 Rev 3
0

0

0

0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
DBCKENDC
DATAENDC
CMDSENTC
CMDRENDC
RXOVERRC
TXUNDERRC
DTIMEOUTC
CTIMEOUTC
DCRCFAILC
CCRCFAILC

0
CCRCFAILIE

0

DCRCFAILIE

DBCKEND

0

CTIMEOUTIE

TXACT
CMDACT

0

DTIMEOUTIE

RXACT

0

RXOVERRIE

TXFIFOHE

0

TXUNDERRIE

TXFIFOF
RXFIFOHF

0

CMDSENTIE

TXFIFOE
RXFIFOF

0

CMDRENDIE

TXDAVL
RXFIFOE
0

DATAEND
CMDSENT
CMDREND
RXOVERR
TXUNDERR
DTIMEOUT
CTIMEOUT
DCRCFAIL
CCRCFAIL

Res.

RXDAVL
0

Res.

SDIOIT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

DATAENDIE

Res.

0

Res.

TXFIFOHEIE

0

TXFIFOFIE

0

RXFIFOHFIE

TXFIFOEIE

0
RXFIFOFIE

RXFIFOEIE

Reset value
TXDAVLIE

Reset value

RXDAVLIE

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

SDIO_STA
Res.

Register

SDIOITC

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

SDIOITIE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SDIO_ICR

Res.

0x38

Res.

0x34

Res.

Offset

Res.

Secure digital input/output interface (SDIO)
RM0390

Table 210. SDIO register map (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

FIFOCOUNT

FIF0Data
0
0
0
0
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.

RM0390

Controller area network (bxCAN)

30

Controller area network (bxCAN)

30.1

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.

30.2

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

•

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 384: Dual CAN
block diagram)

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Controller area network (bxCAN)

30.3

RM0390

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.

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30.3.1

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.

30.3.2

Control, status and configuration registers
The application uses these registers to:

30.3.3

•

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.

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RM0390

30.3.4

Controller area network (bxCAN)

Acceptance filters
The bxCAN provides up to 28 scalable/configurable identifier filter banks, 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 384. Dual CAN block diagram
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30.4

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 pull-

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Controller area network (bxCAN)

RM0390

up 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.

30.4.1

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).

30.4.2

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.

30.4.3

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

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RM0390

Controller area network (bxCAN)
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 385: bxCAN operating modes. The Sleep mode is exited
once the SLAK bit has been cleared by hardware.
Figure 385. bxCAN operating modes
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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

30.5

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.

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Controller area network (bxCAN)

30.5.1

RM0390

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 386. bxCAN in silent mode
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30.5.2

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 387. bxCAN in loop back mode
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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.

30.5.3

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

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RM0390

Controller area network (bxCAN)
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 388. bxCAN in combined mode
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30.6

Behavior in debug mode
When the microcontroller enters the debug mode (Cortex®-M4 with FPU 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.

•

the DBF bit in CAN_MCR. For more details, refer to Section 30.9.2: CAN control and
status registers.

30.7

bxCAN functional description

30.7.1

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
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
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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.

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Figure 389. Transmit mailbox states
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-36

30.7.2

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 30.7.7: Bit timing). The internal counter is captured on the sample point of the Start
Of Frame bit in both reception and transmission.

30.7.3

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 30.7.4: Identifier filtering.

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Figure 390. Receive FIFO states

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-36

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 30.7.5: Message storage

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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.

30.7.4

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 391.
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”.

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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 391. 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 391.

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069

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.
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 392 for an example.

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Figure 392. Example of filter numbering

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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:

1050/1327

•

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).

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Figure 393. Filtering mechanism - example
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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.

30.7.5

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.

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Table 211. 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 212. 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 394. CAN error state diagram
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30.7.6

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.

30.7.7

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.

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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 395. Bit timing
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Figure 396. CAN frames
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30.8

RM0390

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).
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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.

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Controller area network (bxCAN)
•

The FIFO 1 interrupt can be generated by the following events:

•

30.9

–

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).

30.9.1

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 389: 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.

30.9.2

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
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

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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 30.7.2:
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 30.7.6: 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).
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.

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Controller area network (bxCAN)

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.
Bit 8 TXM: Transmit mode
The CAN hardware is currently transmitter.
Bits 7:5 Reserved, must be kept at reset value.

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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

r

r

r

r

r

r

25

CODE[1:0]
r

15

14

13

12

11

10

9

ABRQ1

Res.

Res.

Res.

TERR1

ALST1

TXOK1

rc_w1

rc_w1

rc_w1

rs

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24

23

22

21

20

19

18

17

16

ABRQ2

Res.

Res.

Res.

TERR2

ALST2

TXOK2

RQCP2

rc_w1

rc_w1

rc_w1

rc_w1

r

rs

8

7

RQCP1 ABRQ0
rc_w1

rs

DocID026976 Rev 3

6

5

4

3

2

1

0

Res.

Res.

Res.

TERR0

ALST0

TXOK0

RQCP0

rc_w1

rc_w1

rc_w1

rc_w1

RM0390

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 389.
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.

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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 389
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 389
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

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rc_w1

rc_w1

FMP0[1:0]
r

r

RM0390

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.

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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.

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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 30.8: 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

r

5

4

LEC[2:0]
rw

DocID026976 Rev 3

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rw

r
3

2

1

0

Res.

BOFF

EPVF

EWGF

r

r

r

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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 30.7.6 on page 1053.
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

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RM0390

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 30.7.7: Bit timing on page 1053.
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

30.9.3

CAN mailbox registers
This chapter describes the registers of the transmit and receive mailboxes. Refer to
Section 30.7.5: Message storage on page 1051 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.

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Figure 398. Can mailbox registers

&$1B5,5

&$1B5,5

&$1B7,5

&$1B7,5

&$1B7,5

&$1B5'75

&$1B5'75

&$1B7'75

&$1B7'75

&$1B7'75

&$1B5/5

&$1B5/5

&$1B7'/5

&$1B7'/5

&$1B7'/5

&$1B5+5

&$1B5+5

&$1B7'+5

&$1B7'+5

&$1B7'+5

),)2

),)2

7KUHH7;PDLOER[HV
069

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.

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RM0390

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.

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Controller area network (bxCAN)

RM0390

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]

1070/1327

rw

DATA4[7:0]

DocID026976 Rev 3

rw

RM0390

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.

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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 30.7.4: Identifier filtering on
page 1047 - 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.

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RM0390

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

r

r

r

r

15

14

13

12

27

26

25

24

23

22

21

r

r

r

r

r

r

r

r

11

10

9

8

7

6

5

4

DATA3[7:0]

r

r

r

r

19

18

17

16

r

r

r

r

3

2

1

0

r

r

r

18

17

16

DATA2[7:0]

DATA1[7:0]
r

20

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

r

r

r

r

15

14

13

12

27

26

25

24

23

22

21

r

r

r

r

r

r

r

r

r

r

r

r

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

DATA7[7:0]

r

r

r

r

19

DATA6[7:0]

DATA5[7:0]
r

20

DATA4[7:0]
r

r

r

r

r

r

r

r

Bits 31:24 DATA7[7:0]: Data Byte 7
Data byte 3 of the message.

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Controller area network (bxCAN)

RM0390

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.

30.9.4

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

rw

rw

rw

rw

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FINIT

rw

rw

Bits 31:14 Reserved, must be kept at reset value.
Bits 13:8 CANSB[5:0]: CAN start bank
These bits are set and cleared by software. They define the start bank for the CAN interface
(Slave) in the range 1 to 27.
Bits 7:1 Reserved, must be kept at reset value.
Bit 0 FINIT: Filter initialization mode
Initialization mode for filter banks
0: Active filters mode.
1: Initialization mode for the filters.

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Controller area network (bxCAN)

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.
31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

27

26

rw

Note:

rw

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 391: Filter bank scale configuration - register organization on page 1049
Bits 31:28 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 391: Filter bank scale configuration - register organization on page 1049.

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.
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Controller area network (bxCAN)

RM0390

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

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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 30.7.4: Identifier filtering on page 1047.
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 the Table 213 on page 1078.

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1078/1327

CAN_BTR

Reset value

0

0

- - - -

0

0

1

0

0

0

1

1

- - - - - -

0

0

0

0

0

-

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

x

x

x

x

x

x

x

x

x

x

x

x

TS2[2:0]

-

0

x

x

x

x

x

x

x
LECIE
BOFIE
EPVIE
EWGIE
Res.
FOVIE1
FFIE1

- - 0
0
0
0

0
0

TS1[3:0]

STID[10:0]/EXID[28:18]

x

DocID026976 Rev 3

x

x

Res.

x
Res.
Res.
Res.
Res.
Res.

x

- - - - - - - - -

x

BRP[9:0]

EXID[17:0]

0
0
0

0

0

0

0

0

x

x

x

0

Res.

FFIE0
FMPIE0
TMEIE

ABRQ0
Res.

TERR0
ALST0
TXOK0

0
0

- - 0
0
0
0
0

- - 0
0
0

CAN_RF0R
Res.
Res.
Res.
Res.

Res.
Res.
Res.
Res.
Res.
Res.

Res.
Res.
Res.
Res.
Res.
RFOM0
FOVR0
FULL0
Res.

Reset value

- - - - - - - - - - - - - - - - - - - - - - - - - 0
0
0

-

CAN_RF1R

Reset value

- - - - - - - - - - - - - - - - - - - - - - - - - FOVR1
FULL1
Res.

0
0
0

0
0

FMP1[1:0]

RFOM1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FMP0[1:0]

Res.

Res.

Res.

Res.

DBF
RESET
Res.

Res.
Res.
Res.

INRQ

INAK

0

0
0
0
1
0

RQCP0

TXFP
SLEEP
1

ERRI

0
SLAK

NART
0

WKUI

0

SLAKI

RFLM

Res.
ABOM

Res.

Res.

AWUM

TXM

Res.

0

Res.

RXM

Res.

0

Res.

SAMP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TTCM

RX

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

CODE[1:0]

Res.

- - -

TXRQ

EWGF

0
EPVF

x
0
BOFF

RQCP1

0

Res.

Res.

0

Res.

TXOK1

0

Res.

0

Res.

ALST1

0

Res.

Res.

1

IDE

TERR1

- - -

TME[2:0]

Res.

Res.

1

FOVIE0

Res.

0

Res.

- - - - - - - - - - - - - - - - - - - -

FMPIE1

ABRQ1

0

Res.

Res.

Reset value

Res.

RQCP2

0

Res.

CAN_MSR

Res.

TXOK2

1

Res.

- - - - - - -

Res.

ALST2

1

Res.

0

Res.

Res.

TERR2

1

Res.

1

Res.

Res.

- - - - - - - - - - - - - - Res.

Reset value

LEC[2:0]

Res.

Res.

Res.

0

Res.

ERRIE

0
Res.

0

WKUIE

Res.

0

Res.

ABRQ2

0

LOW[2:0]

0

Res.

CAN_MCR

RTR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

TEC[7:0]
0

Res.

REC[7:0]

Res.

0x018
SLKIE

- - - - - - - - - - - - - -

Res.

0

Res.

CAN_ESR

SJW[1:0]

0

Res.

Reset value

Res.

CAN_IER

Res.

0x014
Res.

0x010

Res.

0x00C
Reset value

Res.

CAN_TSR

Res.

0x008

Res.

0x004

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.

Reset value
0

Res.

CAN_TI0R
0

Res.

0x0200x17F
0

Res.

0x01C
0

SILM

Reset value

LBKM

Offset

Res.

30.9.5

Res.

Controller area network (bxCAN)
RM0390

bxCAN register map
Refer to Section 2.2.2 on page 56 for the register boundary addresses. The registers from
offset 0x200 to 0x31C are present only in CAN1.
Table 213. bxCAN register map and reset values

0

0
0

0
0
0
0
0

x

x

0

RM0390

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

x

DocID026976 Rev 3

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 213. bxCAN register map and reset values (continued)

1079/1327
1081

Controller area network (bxCAN)

RM0390

x

x

x

x

x

x

x

x

x

x

x

CAN_RI1R

x

x

x

x

x

x

x

x

x

x

x

DATA2[7:0]
x

x

x

x

DATA7[7:0]
x

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
x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Res.

Res.

Res.
FINIT

Res.

0

0

0

0

0

0

0

0

0

-

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

- - - -

Res.

Res.

Res.

Reset value

-

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

1

1

1

0

- - - - - - -

1

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.

0

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.

FSC[27:0]

Res.

Res.

Res.
Res.

Res.

- - - Res.

Res.

Reset value

Res.

CAN_FS1R

-

CANSB[5:0]

FBM[27:0]

Res.

Res.

Res.

CAN_FM1R

Res.

- - - - - - - - - - - - - - - - - Res.

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

DATA4[7:0]

Res.

x

x

Res.

x

x

Res.

DATA5[7:0]
x

x

DATA0[7:0]

Res.

x

x

x

Res.

x

x

x

Res.

x

x

x

Res.

x

x

x

Res.

x

- - - -

Res.

x

x

Res.

x

x

DATA1[7:0]

DATA6[7:0]
x

x

Res.

x

x

x

Res.

x

x

x

Res.

x

x

x

Res.

x

x

Res.

x

x

DATA2[7:0]

DATA7[7:0]
x

x

Res.

x

x

Res.

x

x

Res.

x

x

DLC[3:0]

Res.

x

x

-

Res.

x

x

x

Reset value

0x20C

1080/1327

x

x

CAN_FMR

0x204

0x210

x

x

-

0x200

0x208

x

x

Res.

x

Res.

0x1D00x1FF

x

DATA3[7:0]

CAN_RDH1R
Reset value

x

x

Res.

CAN_RDL1R
Reset value

0x1CC

x

Res.

0x1C8

x

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 213. bxCAN register map and reset values (continued)

DocID026976 Rev 3

RM0390

Controller area network (bxCAN)

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

-

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.

CAN_FA1R

Res.

Res.

Res.

Res.

FFA[27:0]

- - - -

Reset value

- - - -

0

0

0

0

0

0

0

0

0

0

0

0

FACT[27:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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

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

Res.

Res.

0x31C

x

.
.
.
.

Reset value

Res.

Res.

Res.

0x318

Res.

Res.

Res.

.
.
.
.

x

CAN_F1R2
Reset value

Res.

Res.

Res.

0x24C

x

CAN_F1R1
Reset value

Res.

Res.

Res.

0x248

x

FB[31:0]

CAN_F0R2
Reset value

Res.

Res.

Res.

0x244

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

CAN_F0R1

Res.

Res.

Res.

0x240

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.

0x21C

Res.

Reset value
0x218

Res.

CAN_FFA1R
0x214

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 213. 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

x

DocID026976 Rev 3

x

1081/1327
1081

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31

USB on-the-go full-speed/high-speed
(OTG_FS/OTG_HS)

31.1

Introduction

RM0390

Portions Copyright (c) 2004, 2005 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)

UTMI

USB Transceiver Macrocell Interface

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 214: OTG_HS speeds supported below.OTG_FS supports the speeds defined in the
Table 215: 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.

1082/1327

DocID026976 Rev 3

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Table 214. 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 215. OTG_FS speeds supported
HS (480 Mb/s)

FS (12 Mb/s)

LS (1.5 Mb/s)

Host mode

-

X

X

Device mode

-

X

-

DocID026976 Rev 3

1083/1327
1265

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31.2

RM0390

USB_OTG main features
The main features can be divided into three categories: general, host-mode and devicemode features.

31.2.1

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 3 PHY interfaces

•

•

•

An on-chip full-speed PHY

–

An I2C interface for external full-speed I2C 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 1.3 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:

•

1084/1327

–

–

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

DocID026976 Rev 3

RM0390

31.2.2

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:

•

31.2.3

–

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] / 8[HS] dedicated Tx-IN FIFOs (one for each active IN EP)
to put less load on the application

•

Support for the soft disconnect feature.

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31.3

USB_OTG Implementation

31.4

USB OTG functional description

31.4.1

USB OTG block diagram

RM0390

Figure 399. OTG full-speed block diagram

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 400. OTG high-speed block diagram

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31.4.2

OTG core
The USB OTG receives the 48 MHz clock from the reset and clock controller (RCC), via an
external quartz. 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 31.13: 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 OTG_HS
PHY or external OTG_FS PHY using I2C interface.

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31.4.3

RM0390

Full-speed OTG PHY
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
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.

Note:

The content of this section applies only to USB OTG FS.

31.4.4

Embedded full speed OTG PHY
The full-speed OTG PHY includes the following components:

1088/1327

•

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.
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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.

Note:

The content of this section applies only to USB OTG HS.

31.4.5

High-speed OTG PHY
The USB OTG HS core includes an ULPI interface to connect an external HS PHY.

Note:

The content of this section applies only to USB OTG HS.

31.4.6

External Full-speed OTG PHY using the I2C interface
The USB OTG HS core embeds an I2C interface allowing to connect an external FS PHY.

Note:

The content of this section applies only to USB OTG HS.

31.5

OTG dual role device (DRD)
Figure 401. OTG_FS A-B device connection
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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.

31.5.1

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

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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.
•

31.5.2

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.

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 31.16: OTG_FS/OTG_HS
programming model.

31.5.3

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 31.16:
OTG_FS/OTG_HS programming model.

31.6

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
–

•

OTG A-Peripheral
–

•

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 402: USB_FS peripheral-only connection)
–

1090/1327

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

The force device mode bit (FDMOD) in the Section 31.15.4: 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.

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Note:

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
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 VDD chip-supply
from VBUS.
Figure 402. USB_FS peripheral-only connection
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31.6.1

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.

31.6.2

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
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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.

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.

31.6.3

Peripheral endpoints
The OTG_FS/OTG_HS core instantiates the following USB endpoints:
•

1092/1327

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

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
(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
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

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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
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:

1094/1327

•

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

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31.7

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

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
–

•

–
•

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

OTG B-host

The force host mode bit in the 31.15.4 global USB configuration register (FHMOD
bit in OTG_GUSBCFG) forces the OTG_FS/OTG_HS core to work as a USB hostonly. 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.
Figure 403. USB_FS host-only connection

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1. 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.
2. VDD range is between 2 V and 3.6 V.

31.7.1

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.

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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. When the
application decides to power on VBUS using the chosen GPIO, 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 and it can be used as GPIO.
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.

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

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
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.

31.7.3

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

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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.
The mask bits for each interrupt source of each channel are also available in the
OTG_HCINTMSKx register.
•

31.7.4

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

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
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 nonperiodic
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
PTXQSAV bits in the OTG_HNPTXSTS register or NPTQXSAV bits in the
OTG_HNPTXSTS register.

SOF trigger
Figure 404. SOF connectivity (SOF trigger output to TIM and ITR1 connection)
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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.

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31.8.1

RM0390

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 12 system
clock 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.

31.8.2

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 12 system clock 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.
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.

31.9

Power options
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

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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.

31.10

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 405.
Figure 405. Updating OTG_HFIR dynamically
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31.11

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
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.

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31.11.1

RM0390

Peripheral FIFO architecture
Figure 406. Device-mode FIFO address mapping and AHB FIFO access mapping
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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.

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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.

31.11.2

Host FIFO architecture
Figure 407. Host-mode FIFO address mapping and AHB FIFO access mapping
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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.

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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.

31.11.3

FIFO RAM allocation
Device mode
Receive FIFO RAM allocation: the application should allocate RAM for SETUP Packets:

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•

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.

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Device RxFIFO =
(4 * number of control endpoints + 6) + ((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 = (4 * 1 + 6) + ((1,024 / 4) +1) + (2 * 4) + 1 = 276
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.

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31.12

RM0390

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 1.25Kbyte 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.

31.13

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 408 shows the interrupt hierarchy.

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Figure 408. Interrupt hierarchy
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1. The core interrupt register bits are shown in OTG core interrupt register (OTG_GINTSTS) on page 1126.

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31.14

RM0390

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.

31.14.1

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 216. Core global control and status registers (CSRs)
Acronym

Address
offset

Register name

OTG_GOTGCTL

0x000

OTG control and status register (OTG_GOTGCTL) on page 1114

OTG_GOTGINT

0x004

OTG interrupt register (OTG_GOTGINT) on page 1117

OTG_GAHBCFG

0x008

OTG AHB configuration register (OTG_GAHBCFG) on page 1118

OTG_GUSBCFG

0x00C

OTG USB configuration register (OTG_GUSBCFG) on page 1120

OTG_GRSTCTL

0x010

OTG reset register (OTG_GRSTCTL) on page 1124

OTG_GINTSTS

0x014

OTG core interrupt register (OTG_GINTSTS) on page 1126

OTG_GINTMSK

0x018

OTG interrupt mask register (OTG_GINTMSK) on page 1131

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Table 216. Core global control and status registers (CSRs) (continued)

Acronym

Address
offset

Register name

OTG_GRXSTSR

0x01C

OTG_GRXSTSP

0x020

OTG_FS Receive status debug read/OTG status read and pop registers
(OTG_GRXSTSR/OTG_GRXSTSP) on page 1135

OTG_GRXFSIZ

0x024

OTG Receive FIFO size register (OTG_GRXFSIZ) on page 1136

OTG_HNPTXFSIZ/
OTG_DIEPTXF0(1)

0x028

OTG Host non-periodic transmit FIFO size register
(OTG_HNPTXFSIZ)/Endpoint 0 Transmit FIFO size (OTG_DIEPTXF0)

OTG_HNPTXSTS

0x02C

OTG non-periodic transmit FIFO/queue status register (OTG_HNPTXSTS)
on page 1138

OTG_GI2CCTL

0x030

OTG I2C access register (OTG_GI2CCTL) on page 1139

OTG_GCCFG

0x038

OTG general core configuration register (OTG_GCCFG) on page 1140

OTG_CID

0x03C

OTG core ID register (OTG_CID) on page 1141

OTG_GLPMCFG

0x54

OTG core LPM configuration register (OTG_GLPMCFG) on page 1141

OTG_HPTXFSIZ

0x100

OTG Host periodic transmit FIFO size register (OTG_HPTXFSIZ) on
page 1145

OTG_DIEPTXFx

0x104
0x124
...
0x184

OTG device IN endpoint transmit FIFO size register (OTG_DIEPTXFx)
(x = 1..5[FS] /8[HS], where x is the FIFO_number) on page 1145 for
USB_OTG FS

OTG_DIEPTXFx

0x104
0x124
...
0x1B4

OTG device IN endpoint transmit FIFO size register (OTG_DIEPTXFx)
(x = 1..5[FS] /8[HS], where x is the FIFO_number) on page 1145 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 217. Host-mode control and status registers (CSRs)
Acronym

Offset
address

Register name

OTG_HCFG

0x400

OTG Host configuration register (OTG_HCFG) on page 1146

OTG_HFIR

0x404

OTG Host frame interval register (OTG_HFIR) on page 1147

OTG_HFNUM

0x408

OTG Host frame number/frame time remaining register (OTG_HFNUM) on
page 1148

OTG_HPTXSTS

0x410

OTG_Host periodic transmit FIFO/queue status register (OTG_HPTXSTS)
on page 1148

OTG_HAINT

0x414

OTG Host all channels interrupt register (OTG_HAINT) on page 1149

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Table 217. Host-mode control and status registers (CSRs) (continued)
Acronym

Offset
address

Register name

OTG_HAINTMSK

0x418

OTG Host all channels interrupt mask register (OTG_HAINTMSK) on
page 1150

OTG_HPRT

0x440

OTG Host port control and status register (OTG_HPRT) on page 1150

OTG_HCCHARx

0x500
0x520
...
0x660

OTG Host channel-x characteristics register (OTG_HCCHARx)
(x = 0..15[HS] / 11[FS], where x = Channel_number) on page 1153 for
USB_OTG FS

OTG_HCCHARx

0x500
0x520
...
0x6E0

OTG Host channel-x characteristics register (OTG_HCCHARx)
(x = 0..15[HS] / 11[FS], where x = Channel_number) on page 1153 for
USB_OTG HS

OTG_HCSPLTx

0x504
0x524
....
0x6E4

OTG Host channel-x split control register (OTG_HCSPLTx) (x = 0..15,
where x = Channel_number) on page 1154

OTG_HCDMAx

0x514
0x534
....
0x6F4

OTG Host channel-x DMA address register (OTG_HCDMAx) (x = 0..15,
where x = Channel_number) on page 1160

OTG_HCINTx

0x508
0x528
....
0x668

OTG Host channel-x interrupt register (OTG_HCINTx) (x = 0..15[HS] /
11[FS], where x = Channel_number) on page 1155 for USB_OTG FS

OTG_HCINTx

0x508
0x528
....
0x6E8

OTG Host channel-x interrupt register (OTG_HCINTx) (x = 0..15[HS] /
11[FS], where x = Channel_number) on page 1155 for USB_OTG HS

OTG_HCINTMSKx

0x50C
0x52C
....
0x66C

OTG Host channel-x interrupt mask register (OTG_HCINTMSKx)
(x = 0..15[HS] / 11[FS], where x = Channel_number) on page 1157 for
USB_OTG FS

OTG_HCINTMSKx

0x50C
0x52C
....
0x6EC

OTG Host channel-x interrupt mask register (OTG_HCINTMSKx)
(x = 0..15[HS] / 11[FS], where x = Channel_number) on page 1157 for
USB_OTG HS

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Table 217. Host-mode control and status registers (CSRs) (continued)

Acronym

Offset
address

Register name

OTG_HCTSIZx

0x510
0x530
....
0x670

OTG Host channel-x transfer size register (OTG_HCTSIZx) (x = 0..15[HS]
/ 11[FS], where x = Channel_number) on page 1158 for USB_OTG FS

OTG_HCTSIZx

0x510
0x530
....
0x6F0

OTG Host channel-x transfer size register (OTG_HCTSIZx) (x = 0..15[HS]
/ 11[FS], where x = Channel_number) on page 1158 for USB_OTG HS

Device-mode CSR map
These registers must be programmed every time the core changes to device mode.
Table 218. Device-mode control and status registers
Acronym

Offset
address

Register name

OTG_DCFG

0x800

OTG device configuration register (OTG_DCFG) on page 1160

OTG_DCTL

0x804

OTG device control register (OTG_DCTL) on page 1162

OTG_DSTS

0x808

OTG device status register (OTG_DSTS) on page 1165

OTG_DIEPMSK

0x810

OTG device IN endpoint common interrupt mask register
(OTG_DIEPMSK) on page 1166

OTG_DOEPMSK

0x814

OTG device OUT endpoint common interrupt mask register
(OTG_DOEPMSK) on page 1167

OTG_DAINT

0x818

OTG device all endpoints interrupt register (OTG_DAINT) on
page 1168

OTG_DAINTMSK

0x81C

OTG all endpoints interrupt mask register (OTG_DAINTMSK) on
page 1169

OTG_DVBUSDIS

0x828

OTG device VBUS discharge time register (OTG_DVBUSDIS) on
page 1170

OTG_DVBUSPULSE

0x82C

OTG device VBUS pulsing time register (OTG_DVBUSPULSE) on
page 1170

OTG_DTHRCTL

0x0830

OTG Device threshold control register (OTG_DTHRCTL) on page 1171

OTG_DIEPEMPMSK

0x834

OTG device IN endpoint FIFO empty interrupt mask register
(OTG_DIEPEMPMSK) on page 1172

OTG_DEACHINT

0x838

OTG device each endpoint interrupt register (OTG_DEACHINT) on
page 1172

OTG_DEACHINTMSK

0x83C

OTG device each endpoint interrupt register mask
(OTG_DEACHINTMSK) on page 1173

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Table 218. Device-mode control and status registers (continued)
Acronym

Offset
address

Register name

OTG_DIEPCTL0

0x900

OTG device control IN endpoint 0 control register (OTG_DIEPCTL0) on
page 1173 for USB_OTG FS

OTG_DIEPCTLx

0x920
0x940
...
0x9A0

OTG device endpoint-x control register (OTG_DIEPCTLx) (x = 1..5[FS]
/ 0..8[HS], where x = Endpoint_number) on page 1175 for USB_OTG
FS

OTG_DIEPCTLx

0x900
0x920
...
0x9E0

OTG device endpoint-x control register (OTG_DIEPCTLx) (x = 1..5[FS]
/ 0..8[HS], where x = Endpoint_number) on page 1175 for USB_OTG
HS

OTG_DIEPINTx

0x908
0x928
....
0x9A8

OTG device endpoint-x interrupt register (OTG_DIEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint_number) on page 1181 for
USB_OTG FS

OTG_DIEPINTx

0x908
0x928
...
0x9E8

OTG device endpoint-x interrupt register (OTG_DIEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint_number) on page 1181 for
USB_OTG HS

OTG_DIEPTSIZ0

0x910

OTG device IN endpoint 0 transfer size register (OTG_DIEPTSIZ0) on
page 1184

OTG_DIEPDMAx

0x914

OTG Device channel-x DMA address register (OTG_DIEPDMAx)
(x = 0..15, where x= Channel_number) on page 1184

OTG_DTXFSTSx

0x918
0x938
....
0x9B8

OTG device IN endpoint transmit FIFO status register
(OTG_DTXFSTSx) (x = 0..5[FS] /8[HS], where x = Endpoint_number)
on page 1187 for USB_OTG FS

OTG_DTXFSTSx

0x918
0x938
.....
0x9F8

OTG device IN endpoint transmit FIFO status register
(OTG_DTXFSTSx) (x = 0..5[FS] /8[HS], where x = Endpoint_number)
on page 1187 for USB_OTG HS

OTG_DIEPTSIZx

0x930
0x950
...
0x9B0

OTG device IN endpoint-x transfer size register (OTG_DIEPTSIZx)
(x = 1..5[FS] /8[HS], where x= Endpoint_number) on page 1186 for
USB_OTG FS

OTG_DIEPTSIZx

0x930
0x950
...
0x9F0

OTG device IN endpoint-x transfer size register (OTG_DIEPTSIZx)
(x = 1..5[FS] /8[HS], where x= Endpoint_number) on page 1186 for
USB_OTG HS

OTG_DOEPCTL0

0xB00

OTG device control OUT endpoint 0 control register
(OTG_DOEPCTL0) on page 1177

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Table 218. Device-mode control and status registers (continued)

Acronym

Offset
address

Register name

OTG_DOEPDMAx

0xB14

OTG Device channel-x DMA address register (OTG_DOEPDMAx)
(x = 0..15, where x= Channel_number) on page 1185

OTG_DOEPCTLx

0xB20
0xB40
...
0xBA0

OTG device endpoint-x control register (OTG_DOEPCTLx) (x =
1..5[FS] /8[HS], where x = Endpoint_number) on page 1179 for
USB_OTG FS

OTG_DOEPCTLx

0xB20
0xB40
...
0xBE0

OTG device endpoint-x control register (OTG_DOEPCTLx) (x =
1..5[FS] /8[HS], where x = Endpoint_number) on page 1179 for
USB_OTG HS

OTG_DOEPINTx

0xB08
0xB28
...
0xBA8

OTG device endpoint-x interrupt register (OTG_DOEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint_number) on page 1183 for
USB_OTG FS

OTG_DOEPINTx

0xB08
0XB28
...
0xBE8

OTG device endpoint-x interrupt register (OTG_DOEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint_number) on page 1183 for
USB_OTG HS

OTG_DOEPTSIZ0

0xB10

OTG device OUT endpoint 0 transfer size register (OTG_DOEPTSIZ0)
on page 1185

OTG_DOEPTSIZx

0xB30
0xB50
...
0xBB0

OTG device OUT endpoint-x transfer size register (OTG_DOEPTSIZx)
(x = 1..5[FS] /8[HS], where x = Endpoint_number) on page 1188 for
USB_OTG FS

OTG_DOEPTSIZx

0xB30
0xB50
..
0xBF0

OTG device OUT endpoint-x transfer size register (OTG_DOEPTSIZx)
(x = 1..5[FS] /8[HS], where x = Endpoint_number) on page 1188 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.

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Table 219. Data FIFO (DFIFO) access register map
FIFO access register section

Address range

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

...

...

...

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 220. Power and clock gating control and status registers
Register name

31.15

Acronym

Offset address: 0xE00–0xFFF

Power and clock gating control register

PCGCCTL

0xE00-0xE04

Reserved

-

0xE05–0xFFF

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.

31.15.1

OTG control and status register (OTG_GOTGCTL)
Address offset: 0x000
Reset value: 0x0X01 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

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.

EHEN

HNP
RQ

HNG
SCS

rw

r

rw

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EN
EN
rw

rw

19

18

BSVLD ASVLD

rw

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16

DBCT

CID
STS

rw

r

r

r

r

4

3

2

1

0

SRQ

SRQ
SCS

rw

r

BVALO BVALO AVALO AVALO VBVAL VBVAL
VAL
EN
VAL
EN
OVAL
OEN
rw

17

rw

rw

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RM0390

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Bits 31:21 Reserved, must be kept at reset value.
Bit 20 OTGVER: OTG version
Selects the OTG revision.
0:OTG Version 1.3.
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, you 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.
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.

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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.
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.

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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 you use 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. This discharge time varies between
different PHYs and can be obtained from the PHY vendor.
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.

31.15.2

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.

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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.

31.15.3

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.

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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

rw

rw

rw

0
GINT
MSK

rw

rw

Configuration register for USB OTG HS
Bits 31:20 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.

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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: 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.

31.15.4

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

15

14

13

12

11

10

7

6

5

4

3

2

1

0

Res.

PHY
SEL

Res.

Res.

Res.

Res.

Res.

Note:

8

TRDT

SRP
CAP

rw

rw

rw

TOCAL

r

rw

Configuration register for USB OTG FS

31

30

29

Res.

FD
MOD

FH
MOD

rw

rw

15

14

13

PHYL
PC.

9
HNP
CAP

Res.

rw

Note:

1120/1327

28

27

26

25
ULPIIP
D

PTCI

PCCI

rw

rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

TRDT

HNP
CAP

SRP
CAP

Res.

PHY
SEL

Res.

rw

rw

rw

Res.

Res.

Res.

12

11

10

24

23

22

21

20

19

ULPIE ULPIE ULPIC
TSDPS
VBUSI VBUSD
SM.

rw

Configuration register for USB OTG HS

DocID026976 Rev 3

Res.

18

17

ULPIA ULPIFS
R.
L.

TOCAL
rw

16
Res.

0

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/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 for USB OTG HS and FS
Bits 25:15 Reserved, must be kept at reset value for USB OTG FS
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.

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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 valu for USB OTG HS.

Bit 15 PHYLPCS: 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: USB turnaround time
These bits allows to set the turnaround time in PHY clocks. They must be configured
according to Table 221: TRDT values (FS) or Table 222: 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.

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

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.
Bits 5:3 Reserved, must be kept at reset value.
Bits 2:0 TOCAL: 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.

Table 221. 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 222. TRDT values (HS)
AHB frequency range (MHz)
TRDT minimum value
Min

Max

30

-

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31.15.5

RM0390

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.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

TXFNUM

TXF
FLSH

RXF
FLSH

Res.

rw

rs

rs

r

r

Note:

FCRST PSRST CSRST

rs

rs

r

Configuration register for USB OTG FS

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.

10

9

8

7

6

5

4

3

2

1

0

TXFNUM

TXF
FLSH

RXF
FLSH

Res.

Res.

rw

rs

rs

r

r

15

14

13

12

11

Res.

Res.

Res.

Res.

Res.

Note:

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: 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.

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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.
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.

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RM0390

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 you
dynamically change 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.

31.15.6

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.

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31

30

29

28

27

26

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

ISOO
DRP

ENUM
DNE

USB
RST

USB
SUSP

ESUSP

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

23

HPRT
INT

RST
DET

r

r

rc_w1

9

8

7

Res.

GO
NAK
EFF
r

Res.

22

21

20

19

18

17

16

Res.

IPXFR/
IN
COMP
ISO
OUT

IISOI
XFR

OEP
INT

IEPINT

Res.

Res.

rc_w1

rc_w1

r

r

6

5

4

3

2

1

0

GI
NAK
EFF

NPTXF
E

RXF
LVL

SOF

OTG
INT

MMIS

CMOD

r

r

r

rc_w1

r

rc_w1

r

23

22

21

20

19

18

17

16

Res.

DATAF
SUSP

IPXFR/
IN
COMP
ISO
OUT

IISOI
XFR

OEP
INT

IEPINT

Res.

Res.

rc_w1

rc_w1

rc_w1

r

r

Configuration register for USB OTG FS

31

30

29

28

WKUP
INT

SRQ
INT

DISC
INT

CIDS
CHG

rc_w1

rc_w1

rc_w1

rc_w1

15

14

13

12

27

Res.

11

26

25

PTXFE HCINT

24
HPRT
INT

r

r

r

10

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

EOPF

ISOO
DRP

ENUM
DNE

USB
RST

USB
SUSP

ESUSP

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Note:

24

PTXFE HCINT

EOPF

Note:

25

Res.

Configuration register for USB OTG HS
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.

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RM0390

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.
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.

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

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.
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.

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RM0390

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.
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.

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

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.

31.15.7

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

30

WUIM

SRQIM

rw

rw

15

14

EOPF
M

ISOOD
RPM

rw

rw

29

28

DISCIN CIDSC
T
HGM

27

26

LPMIN PTXFE
TM
M

25

24

HCIM

PRTIM

RSTDE
TM

rw

rw

rw

rw

rw

rw

r

13

12

11

10

9

8

ENUM USBRS USBSU ESUSP
DNEM
T
SPM
M
rw

rw

rw

rw

23

Res.

Res.

22

21

20

Res.

IPXFR
M/IISO
OXFR
M

IISOIX
FRM

rw

rw

rw

5

4

3

7

6

GONA GINAK NPTXF RXFLV
KEFFM EFFM
EM
LM
rw

rw

DocID026976 Rev 3

rw

rw

19

18

OEPIN
IEPINT
T

SOFM
rw

17

16

Res.

Res.

1

0

rw
2

OTGIN
MMISM
T
rw

Res.

rw

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Note:
31
WUIM

RM0390

Configuration register for USB OTG FS
30
SRQIM

29

28

DISCIN CIDSC
T
HGM

27

26

LPMIN PTXFE
TM
M

25
HCIM

24

23

22

21

20
IISOIX
FRM

PRTIM

RSTDE
TM

FSUS
PM

IPXFR
M/IISO
OXFR
M

19

OEPIN
IEPINT
T

rw

rw

rw

rw

rw

rw

rw

r

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

EOPF
M

ISOOD
RPM

rw

rw

Note:

ENUM USBRS USBSU ESUSP
DNEM
T
SPM
M
rw

rw

rw

Res.

Res.

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 device mode.
Bit 28 CIDSCHGM: Connector ID status change mask
0: Masked interrupt
1: Unmasked interrupt
Note: Accessible in both host and device modes.
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.

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18

SOFM
rw

17

16

Res.

Res.

1

0

rw
2

OTGIN
MMISM
T
rw

rw

Res.

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

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.
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.

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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.
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.

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RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31.15.8

OTG_FS 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

18

PKTSTS

r

r

r

r

r

16
DPID

r

r

r

r

r

4

3

2

1

0

BCNT
r

17

CHNUM
r

r

r

r

r

r

r

r

r

Bits 31:21 Reserved, must be kept at reset value.
Bits 20:17 PKTSTS: 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: Byte count
Indicates the byte count of the received IN data packet.
Bits 3:0 CHNUM: Channel number
Indicates the channel number to which the current received packet belongs.

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RM0390

Device mode:
31

30

29

28

27

26

25

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

DPID

9

24

23

22

21

20

FRMNUM

19

18

PKTSTS

r

r

r

r

r

r

16
DPID

r

r

r

r

r

r

r

r

r

8

7

6

5

4

3

2

1

0

BCNT

r

17

EPNUM
r

r

r

r

r

r

r

r

r

Bits 31:25 Reserved, must be kept at reset value.
Bits 24:21 FRMNUM: 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: 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: Data PID
Indicates the Data PID of the received OUT data packet
00: DATA0
10: DATA1
01: DATA2
11: MDATA
Bits 14:4 BCNT: Byte count
Indicates the byte count of the received data packet.
Bits 3:0 EPNUM: Endpoint number
Indicates the endpoint number to which the current received packet belongs.

31.15.9

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

rw

RXFD
rw

rw

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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 RXFD: 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.

31.15.10 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
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
rw

rw

rw

rw

rw

rw

rw

rw

rw

Host mode
Bits 31:16 NPTXFD: 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: Non-periodic transmit RAM start address
This field configures the memory start address for non-periodic transmit FIFO RAM.

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.

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RM0390

31.15.11 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

20

19

18

17

16

NPTQXSAV

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
r

r

r

r

r

r

r

r

r

Bit 31 Reserved, must be kept at reset value.
Bits 30:24 NPTXQTOP: 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: 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: 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

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31.15.12 OTG I2C access register (OTG_GI2CCTL)
Address offset: 0x030
Reset value: 0x0000 0000
31

30

29

28

BSY
DNE

RW.

Res.

I2CD
ATSE

rw

rw

15

14

13

27

26

I2CDEVADR

rw

rw

rw

12

11

10

25

24

23

Res.

ACK

I2CEN

rw

rw

rw

rw

rw

8

7

6

5

4

9

22

21

rw

rw

rw

rw

19

18

17

16

rw

rw

rw

rw

3

2

1

0

rw

rw

rw

ADDR

REGADDR
rw

20

RWDATA
rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 BSYDNE: I2C Busy/Done
The application sets this bit to 1 to start a request on the I2C interface. When the transfer is
complete, the core deasserts this bit to 0. As long as the bit is set indicating that the I2C
interface is busy, the application cannot start another request on the interface.
Bit 30 RW: Read/Write Indicator
This bit indicates whether a read or write register transfer must be performed on the
interface.
0: Write
1: Read
Note: Read/write bursting is not supported for registers.
Bit 29 Reserved, must be kept at reset value.
Bit 28 I2CDATSE0: I2C DatSe0 USB mode
This bit is used to select the full-speed interface USB mode.
0: VP_VM USB mode
1: DAT_SE0 USB mode
Bits 27:26 I2CDEVADR: I2C Device Address
This bit selects the address of the I2C slave on the USB 1.1 full-speed serial transceiver
corresponding to the one used by the core for OTG signalling.
Bit 25 Reserved, must be kept at reset value.
Bit 24 ACK: I2C ACK
This bit indicates whether an ACK response was received from the I2C slave. It is valid when
BSYDNE is cleared by the core, after the application has initiated an I2C access.
0: NAK
1: ACK
Bit 23 I2CEN: I2C Enable
This bit enables the I2C master to initiate transactions on the I2C interface.

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Bits 22:16 ADDR: I2C Address
This is the 7-bit I2C device address used by the application to access any external I2C slave,
including the I2C slave on a USB 1.1 OTG full-speed serial transceiver.
Bits 15:8 REGADDR: I2C Register Address
These bits allow to program the address of the register to be read from or written to.
Bits 7:0 RWDATA: I2C Read/Write Data
After a register read operation, these bits hold the read data for the application.
During a write operation, the application can use this register to program the data to be
written to a register.

Note:

Configuration register applies only to USB OTG HS

31.15.13 OTG general core configuration register (OTG_GCCFG)
Address offset: 0x038
Reset value: 0x0000 XXX0
31
Res.

30

29

Res.

Res.

28
Res.

27
Res.

26
Res.

25
Res.

24
Res.

23
Res.

22
Res.

21
VBDEN

20
Res.

19
Res.

18
Res.

17

16

Res.

PWR
DWN

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.

Res.

Res.

Res.

Res.

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 20:17 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 3:0 Reserved, must be kept at reset value.

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31.15.14 OTG core ID register (OTG_CID)
Address offset: 0x03C
Reset value: 0x0000 3X00 for USB OTG FS
Reset value: 0x0000 3100 for USB OTG HS
This is a read only register containing the Product ID.
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PRODUCT_ID

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

PRODUCT_ID

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 PRODUCT_ID: Product ID field
Application-programmable ID field.

31.15.15 OTG core LPM configuration register (OTG_GLPMCFG)
Address offset: 0x54
Reset value: 0x0000 0000
31

30

29

28
EN
BESL

Res.

Res.

Res.

15

14

13

SLP
STS

r

LPMRSP

r

r

27

26

25

24

23

SND
LPM

LPMRCNTSTS

22

21

20

19

LPMRCNT

16
L1RSM
OK

LPMCHIDX

rw

r

r

r

rs

rw

rw

rw

rw

rw

rw

rw

r

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

L1DS
EN

rw

BESLTHRS

rw

rw

rw

rw

BESL

rw/r

rw/r

rw/r

rw/r

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: 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.

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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: 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: 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
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

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Bits 14:13 LPMRST: 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.
Bits11:8 BESLTHRS: 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.

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Bits 5:2 BESL: 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

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31.15.16 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

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

PTXSA

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 PTXFD: Host periodic Tx FIFO depth
This value is in terms of 32-bit words.
Minimum value is 16
Bits 15:0 PTXSA: Host periodic Tx FIFO start address
This field configures the memory start address for periodic transmit FIFO RAM.

31.15.17 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 + (FIFO_number – 1) × 0x04
Reset values:
FIFO_number = 8[HS] / 5[FS]: 0x0200 0200 + (8[HS] / 5[FS]
31

30

29

28

27

26

25

24

23

* 0x200)

22

21

20

19

18

17

16

INEPTXFD

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

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 INEPTXFD: IN endpoint Tx FIFO depth
This value is in terms of 32-bit words.
Minimum value is 16
Bits 15:0 INEPTXSA: 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.

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31.15.18 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:

31.15.19 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

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.

FSLSS
r

FSLSPCS
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: 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).

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31.15.20 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

rw

FRIVL
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 cannot be reloaded dynamically
1: The HFIR can be dynamically reloaded during runtime.
This bit needs to be programmed during initial configuration and its value must not be
changed during runtime.
Bits 15:0 FRIVL: 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.
Bits 15:0 FRIVL: 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.

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31.15.21 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
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
r

r

r

r

r

r

r

r

r

Bits 31:16 FTREM: 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: Frame number
This field increments when a new SOF is transmitted on the USB, and is cleared to 0 when
it reaches 0x3FFF.

31.15.22 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

20

19

18

17

16

PTXQSAV

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
r

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Bits 31:24 PTXQTOP: 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: 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: 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

31.15.23 OTG Host all channels interrupt register (OTG_HAINT)
Address offset: 0x414
Reset value: 0x0000 000
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 408. 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

r

HAINT
r

r

r

r

r

r

r

r

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Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 HAINT: Channel interrupts
One bit per channel: Bit 0 for Channel 0, bit 15 for Channel 15

31.15.24 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
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 HAINTM: Channel interrupt mask
0: Masked interrupt
1: Unmasked interrupt
One bit per channel: Bit 0 for channel 0, bit 15 for channel 15

31.15.25 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 408. 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.

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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.
r

r

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

POCA

PEN
CHNG

PENA

r

rc_w1

rc_w1

PTCTL
rw

rw

PPWR
rw

rw

PLSTS
r

Res.
r

PRST

PSUSP

PRES

POC
CHNG

rw

rs

rw

rc_w1

18

17
PSPD

16
PTCTL

PCDET PCSTS
rc_w1

r

Bits 31:19 Reserved, must be kept at reset value.
Bits 18:17 PSPD: 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: 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: 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.
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

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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 (WKUINT 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 (WKUINT 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.

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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

31.15.26 OTG Host channel-x characteristics register (OTG_HCCHARx)
(x = 0..15[HS] / 11[FS], where x = Channel_number)
Address offset: 0x500 + (Channel_number × 0x20)
Reset value: 0x0000 0000
31

30

CHENA CHDIS

29

28

27

26

ODD
FRM

25

24

23

22

21

DAD

20

19

MCNT

18

EPTYP

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
rw

rw

rw

MPSIZ
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: Device address
This field selects the specific device serving as the data source or sink.

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Bits 21:20 MCNT: 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: 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: Endpoint number
Indicates the endpoint number on the device serving as the data source or sink.
Bits 10:0 MPSIZ: Maximum packet size
Indicates the maximum packet size of the associated endpoint.

31.15.27 OTG Host channel-x split control register (OTG_HCSPLTx)
(x = 0..15, where x = Channel_number)
Address offset: 0x504 + (Channel_number × 0x20)
Reset value: 0x0000 0000
31
SPLIT
EN

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.

COMP
LSPLT

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw
15

XACTPOS
rw

rw

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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: 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: Hub address
This field holds the device address of the transaction translator’s hub.
Bits 6:0 PRTADDR: Port address
This field is the port number of the recipient transaction translator.

Note:

Configuration register applies only to USB OTG HS

31.15.28 OTG Host channel-x interrupt register (OTG_HCINTx)
(x = 0..15[HS] / 11[FS], where x = Channel_number)
Address offset: 0x508 + (Channel_number × 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 408. 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:

Res.

Res.

Res.

BBERR TXERR
rc_w1

rc_w1

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.

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15
Res.

14
Res.

Note:

13
Res.

12
Res.

11
Res.

10

9

DTERR

FRM
OR

8

rc_w1

rc_w1

7

BBERR TXERR
rc_w1

rc_w1

RM0390

6

5

4

3

2

1

0

CHH

XFRC

rc_w1

rc_w1

NYET

ACK

NAK

STALL

AHBE
RR

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.

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31.15.29 OTG Host channel-x interrupt mask register (OTG_HCINTMSKx)
(x = 0..15[HS] / 11[FS], where x = Channel_number)
Address offset: 0x50C + (Channel_number × 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

AHBE
RRM

CHHM

XFRC
M

rw

rw

rw

rw

rw

Res.

Note:

Res.

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

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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 AHBERR: 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

31.15.30 OTG Host channel-x transfer size register (OTG_HCTSIZx)
(x = 0..15[HS] / 11[FS], where x = Channel_number)
Address offset: 0x510 + (Channel_number × 0x20)
Reset value: 0x0000 0000
31

30

Res.

15

29

28

27

26

25

DPID

24

23

22

21

20

19

18

PKTCNT

17

16

XFRSIZ

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
rw

rw

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Bit 31 Reserved, must be kept at reset value.
Bits 30:29 DPID: 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: 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: 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).

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31.15.31 OTG Host channel-x DMA address register (OTG_HCDMAx)
(x = 0..15, where x = Channel_number)
Address offset: 0x514 + (Channel_number × 0x20)
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DMAADDR

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
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DMAADDR: 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.

Note:

Configuration register applies only to USB OTG HS

31.15.32 Device-mode registers
These registers must be programmed every time the core changes to device mode

31.15.33 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

Res.

NZLSO
HSK

ERRAT
IM

Res.

Res.

rw

PFIVL
rw

Note:

DAD
rw

rw

rw

rw

rw

rw

rw

rw

23

22

21

20

Res.

Res.

Res.

7

6

5

DSPD

rw

rw

rw

19

18

17

16

Res.

Res.

Res.

Res.

Res.

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

ERRAT
IM

XCVR
DLY

rw

rw

1160/1327

13

12

Res.

11

10

25

24

PERSCHIVL
rw

rw

9

8

PFIVL
rw

DAD
rw

rw

rw

rw

rw

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RM0390
Note:

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
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: 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
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
Bits 12:11 PFIVL: 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: Device address
The application must program this field after every SetAddress control command.
Bit 3 Reserved, must be kept at reset value.

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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: 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: 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 external ULPI PHY
10: Reserved
11: Full speed using internal embedded PHY

31.15.34 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.

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

Res.

Res.

Res.

TCTL
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.

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

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
A write to this field clears the Global OUT NAK.
Bit 9 SGONAK: Set global OUT NAK
A write 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
A write to this field clears the Global IN NAK.
Bit 7 SGINAK: Set global IN NAK
A write 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: 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
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.

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RM0390

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 223 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 223. Minimum duration for soft disconnect
Operating speed

1164/1327

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

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RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31.15.35 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.

23

22

14

13

12

11

10

9

8

FNSOF
r

r

r

r

7
Res.

r

r

r

20

19

DEVLNSTS
r

15

21

6
Res.

r

18

17

16

r

FNSOF
r

r

r

r

r

5

4

3

2

1

Res.

Res.

EERR
r

ENUMSPD
r

0
SUSP
STS

r

r

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:22 DEVLNSTS: 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: 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: 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).

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RM0390

31.15.36 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.

Res.

Res.

INEPN
EM

TOM

Res.

EPDM

XFRC
M

rw

rw

rw

Note:

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

BMA

TXFU
RM

Res.

INEPN
EM

EPDM

XFRC
M

rw

rw

rw

rw

/
Res.

Res.

NAKM

rw

Note:

Res.

Res.

Res.

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 12:7 Reserved, must be kept at reset value for USB OTG FS.
Bits 12:10 Reserved, must be kept at reset value for USB OTG HS.
Bit 9 BIM: BNA interrupt mask mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Bit 8 TXFURM: FIFO underrun mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Bit 7 Reserved, must be kept at reset value for USB OTG HS.
Bit 6 INEPNEM: IN endpoint NAK effective mask
0: Masked interrupt
1: Unmasked interrupt

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TOM
rw

Res.

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 5 INEPNMM: IN token received with EP mismatch mask
0: Masked interrupt
1: Unmasked interrupt
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 Reserved, must be kept at reset value.
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

31.15.37 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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EPDM

XFRC
M

rw

rw

Note:

OTEPD STUPM
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.

NYET
MSK

Res.

Res.

Res.

Res.

BOIM

TXFU
RM

Res.

B2B
STUP

Res.

Res.

EPDM

XFRC
M

rw

rw

rw

rw

rw

rw

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M
rw

rw

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Note:

RM0390

Configuration register for USB OTG HS
Bits 31:5 Reserved, must be kept at reset value for USB OTG FS.
Bits 31:15 Reserved, must be kept at reset value for USB OTG HS.
Bit 14 NYET: NYET interrupt mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Bit 9 BOIM: BNA interrupt mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Bit 8 TXFURM: FIFO underrun mask for USB OTG HS
0: Masked interrupt
1: Unmasked interrupt
Bit 7 Reserved, must be kept at reset value for USB OTG HS.
Bit 6 B2BSTUP: Back-to-back SETUP packets received mask. Applies to control OUT endpoints
only. This is for USB OTG HS.
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 Reserved, must be kept at reset value.
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

31.15.38 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).

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

OEPINT
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

IEPINT
r

r

r

r

r

r

r

r

Bits 31:16 OEPINT: 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: IN endpoint interrupt bits
One bit per IN endpoint:
Bit 0 for IN endpoint 0, bit 3 for endpoint 3.

31.15.39 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
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

IEPM
rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 OEPM: 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: 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

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RM0390

31.15.40 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
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 VBUSDT: 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.

31.15.41 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
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 DVBUSP: Device VBUS pulsing time
Specifies the VBUS pulsing time during SRP. This value equals:
VBUS pulsing time in PHY clocks / 1 024

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31.15.42 OTG Device threshold control register (OTG_DTHRCTL)
Address offset: 0x0830
Reset value: 0x0000 0000
31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

27
ARPEN

26

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

24

23

22

Res.

rw
11

25

10

21

20

19

18

16
RXTH
REN

RXTHRLEN

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

TXTHRLEN
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: Receive threshold length
This field specifies the receive thresholding size in DWORDS. 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 DWORDS. 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.

Bits 10:2 TXTHRLEN: Transmit threshold length
This field specifies the transmit thresholding size in DWORDS. 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 DWORDS.
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.

Note:

Configuration register applies only to USB OTG HS

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RM0390

31.15.43 OTG device each endpoint interrupt register (OTG_DEACHINT)
Address offset: 0x0838
Reset value: 0x0000 0000
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
INT

Res.

r
15
Res.

14
Res.

13
Res.

12
Res.

11
Res.

10
Res.

9

8

Res.

Res.

7
Res.

6
Res.

5
Res.

4
Res.

3
Res.

2

1

0

Res.

IEP1
INT

Res.

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

Note:

Reserved, must be kept at reset value.

Configuration register applies only to USB OTG HS

31.15.44 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
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 INEPTXFEM: 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

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31.15.45 OTG device each endpoint interrupt register mask
(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

8

Res.

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

Note:

Reserved, must be kept at reset value.

Configuration register applies only to USB OTG HS

31.15.46 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

28

27

Res.

Res.

SNAK

26

25

CNAK

24

23

22

TXFNUM

21
STALL

20

19

Res.

18

EPTYP

17

16

NAK
STS

Res.

rs

rs

w

w

rw

rw

rw

rw

rs

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

USBA
EP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

MPSIZ
rw

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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: 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.

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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: 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

31.15.47 OTG device endpoint-x control register (OTG_DIEPCTLx)
(x = 1..5[FS] / 0..8[HS], where x = Endpoint_number)
Address offset: 0x900 + (Endpoint_number × 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

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

17

16

NAK
STS

EO
NUM/
DPID

rw

rw

r

r

4

3

2

1

0

rw

rw

rw

rw

rw

MPSIZ
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.

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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: 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.

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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: Maximum packet size
The application must program this field with the maximum packet size for the current logical
endpoint. This value is in bytes.

31.15.48 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

28

27

Res.

Res.

SNAK

26
CNAK

25

24

23

22

Res.

Res.

Res.

Res.

21

20

STALL

SNPM

19

18

EPTYP

17

16

NAK
STS

Res.

w

r

w

w

rs

rw

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

USBA
EP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

MPSIZ
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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: Endpoint type
Hardcoded to 2’b00 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 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: 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

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31.15.49 OTG device endpoint-x control register (OTG_DOEPCTLx)
(x = 1..5[FS] /8[HS], where x = Endpoint_number)
Address offset for OUT endpoints: 0xB00 + (Endpoint_number × 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

MPSIZ
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.

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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: 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

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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: Maximum packet size
The application must program this field with the maximum packet size for the current logical
endpoint. This value is in bytes.

31.15.50 OTG device endpoint-x interrupt register (OTG_DIEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint_number)
Address offset: 0x908 + (Endpoint_number × 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 408. 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

TXFE

INEP
NE

Res.

EP
DISD

XFRC

r

r

rc_w1

rc_w1

Res.

Res.

Note:

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ITTXFE

TOC

rc_w1

rc_w1

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

BNA

TXFIF
OUD
RN

TXFE

INEP
NE

Res.

ITTXFE

TOC

Res.

EP
DISD

XFRC

r

r

rc_w1

rc_w1

rc_w1

rc_w1

Res.

Res.

NAK

BERR

PKTD
RPSTS

rc_w1 rc_w1 rc_w1

Note:

Res.

rc_w1 rc_w1

Configuration register for USB OTG HS

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Bits 31:8 Reserved, must be kept at reset value.
Bits 31:14 Reserved, must be kept at reset value for USB OTG HS
Bit 13 NAK: NAK input for USB OTG HS
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 for USB OTG HS
Bit 11 PKTDRPSTS: Packet dropped status for USB OTG HS
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 for USB OTG HS.
Bit 9 BNA: Buffer not available interrupt for USB OTG HS
The core generates this interrupt when the descriptor accessed is not ready for the Core to
process, such as host busy or DMA done.
Bit 8 TXFIFOUDRN: Transmit Fifo Underrun (TxfifoUndrn) for USB OTG HS
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 Reserved, must be kept at reset value.
Bit 4 ITTXFE: IN token received when Tx FIFO is empty
Applies to non-periodic IN endpoints only.
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.
Bit 3 TOC: Timeout condition
Applies only to Control IN endpoints.
Indicates that the core has detected a timeout condition on the USB for the last IN token on
this endpoint.
Bit 2 Reserved, must be kept at reset value.
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.

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31.15.51 OTG device endpoint-x interrupt register (OTG_DOEPINTx)
(x = 0..5[FS] /8[HS], where x = Endpoint_number)
Address offset: 0xB08 + (Endpoint_number × 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 408. 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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

B2B
STUP

Res.

OTEP
DIS

STUP

Res.

EP
DISD

XFRC

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

Bits 31:7 Reserved, must be kept at reset value.
Bit 6 B2BSTUP: Back-to-back SETUP packets received
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 Reserved, must be kept at reset value.
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 Reserved, must be kept at reset value.
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.

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RM0390

31.15.52 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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

6

5

20

19

PKTCNT
rw

rw

4

3

18

17

16

Res.

Res.

Res.

2

1

0

rw

rw

rw

XFRSIZ
rw

rw

rw

rw

Bits 31:21 Reserved, must be kept at reset value.
Bits 20:19 PKTCNT: 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: 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.

31.15.53 OTG Device channel-x DMA address register (OTG_DIEPDMAx)
(x = 0..15, where x= Channel_number)
Address offset: 0x914 + (Channel_number × 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
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
rw

rw

1184/1327

rw

rw

rw

rw

rw

rw

rw

DocID026976 Rev 3

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bits 31:0 DMAADDR: 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.

31.15.54 OTG Device channel-x DMA address register (OTG_DOEPDMAx)
(x = 0..15, where x= Channel_number)
Address offset: 0xB14 + (Channel_number × 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
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
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DMAADDR: 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.

31.15.55 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

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

5

4

3
XFRSIZ

rw

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rw

rw

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RM0390

Bit 31 Reserved, must be kept at reset value.
Bits 30:29 STUPCNT: 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: 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.

31.15.56 OTG device IN endpoint-x transfer size register (OTG_DIEPTSIZx)
(x = 1..5[FS] /8[HS], where x= Endpoint_number)
Address offset: 0x910 + (Endpoint_number × 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

30

Res.

15

29

28

27

26

25

MCNT

24

23

22

21

20

19

18

PKTCNT

17

16

XFRSIZ

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
rw

rw

1186/1327

rw

rw

rw

rw

rw

rw

rw

DocID026976 Rev 3

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Bit 31 Reserved, must be kept at reset value.
Bits 30:29 MCNT: 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: 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: 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.

31.15.57 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 + (Endpoint_number × 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
r

r

r

r

r

r

r

r

r

31:16 Reserved, must be kept at reset value.
15:0 INEPTFSAV: 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

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RM0390

31.15.58 OTG device OUT endpoint-x transfer size register
(OTG_DOEPTSIZx) (x = 1..5[FS] /8[HS],
where x = Endpoint_number)
Address offset: 0xB10 + (Endpoint_number × 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

24

23

22

21

20

19

18

PKTCNT

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: 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
STUPCNT: 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: 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.

1188/1327

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RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

31.15.59 OTG power and clock gating control register (OTG_PCGCCTL)
Address offset: 0xE00
Reset value: 0x0x200B 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

r/w

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.
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.

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0x010

0x010

1190/1327
OTG_
GRSTCTL

Reset value
1

OTG_
GRSTCTL

Reset value

1

0

DocID026976 Rev 3
0
1
0

Res.
Res.
0

0
0

0
0

0
0

0

TXFNUM

0

TXFNUM

0
0
0

0

0
FCRST
PSRST
CSRST

0
0
0

CSRST

1

Res.

0

PSRST

0
Res.

Res.

Res.

0
0
0
0

Res.
Res.
Res.

DMAEN
HBSTLEN

TOCAL

0

0

0

GINTMSK

BVALOVAL
BVALOEN
AVALOVAL
AVALOEN
VBVALOVAL
VBVALOEN
SRQ
SRQSCS

0
0
0
0
0
0
0

Res.
Res.

Res.
Res.
Res.
Res.
Res.
SEDET
Res.
Res.

GINTMSK

0
Res.

Res.

Res.

Res.

Res.

Res.

TXFELVL

TXFELVL
Res.

PTXFELVL
0

PHYSEL

HNPRQ
HNGSCS
0

SRSSCHG

DHNPEN
HSHNPEN
0

HNSSCHG

EHEN

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

DBCT
CIDSTS

Res.

0

Res.

Res.

Res.

PTXFELVL

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ASVLD
HNGDET

Res.

0

Res.

1

Res.

0

Res.

0

PHYSEL

1
SRPCAP

TRDT
HNPCAP

1

0

RXFFLSH

0

SRPCAP

TRDT

HNPCAP

Reset value
0

RXFFLSH

1

Res.

Res.

Res.

Res.

Res.

Reset value

TXFFLSH

Res.

Res.

Res.

Res.

Res.

BSVLD

DBCDNE
ADTOCHG

Res.

0

0

TXFFLSH

Res.

PHYLPC.
0

0

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

ULPIFSL.

0

Res.

Res.

Res.

Res.

Res.
OTGVER

IDCHNG

0

Res.

Res.

Res.

0

Res.

ULPIAR.

0

Res.

Res.

Res.

Res.

Res.

0

Res.

ULPICSM

0

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

ULPIEVBUSD

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

ULPIEVBUSI

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

TSDPS

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

PCCI

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

PTCI

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

ULPIIPD

Res.

Res.
0

Res.

Res.

Res.

Res.

FHMOD

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0
Res.

FDMOD

0

Res.

FHMOD

Reset value
0

Res.

OTG_
GUSBCFG
FDMOD

Reset value

Res.

OTG_
GUSBCFG

Res.

OTG_
GAHBCFG

Res.

0x00C
OTG_
GAHBCFG

Res.

0x00C

DMAREQ

0x008
OTG_
GOTGINT

Res.

0x008
OTG_
GOTGCTL

Res.

0x004

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.

0x000

AHBIDL

Offset

AHBIDL

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
RM0390

31.15.60 OTG_FS/OTG_HS register map
The table below gives the USB OTG register map and reset values.
Table 224. OTG_FS/OTG_HS register map and reset values

0

0

0

TOCAL

0
0
0

0

0

0x020

OTG_
GRXSTSPR
(Device mode)

Reset value

Res.

Res.

Res.

Res.

OTG_
GRXSTSR
(host mode)

Res.

0

0

0

0

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
GRXSTSR
(Device mode)

Res.

0x01C
Res.

Res.

Res.

Res.

Res.

Res.

SRQIM
DISCINT
CIDSCHGM

Reset value
0
0
0
0

OTG_
GINTMSK
SRQIM
DISCINT
CIDSCHGM
LPMINTM
PTXFEM
HCIM
PRTIM
RSTDETM

Reset value
0
0
0
0
0
0
0
0
0

OTG_
GRXSTSR
(host mode)
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

Reset value

Reset value

0
PKTSTS

0

FRMNUM

0

0

FRMNUM

0
0

0

0

0
0

0

0

0
0

PKTSTS

0

PKTSTS

0

PKTSTS

0
0

0

0

0

DocID026976 Rev 3
USBRST
USBSUSPM
ESUSPM

0
0
0
0

ISOODRPM
USBRST
USBSUSPM
ESUSPM

0
0
0
0
0
0

DPID

0

0

0

0
0

0

0

0
0

0

0

0
0

0

0

0
0

0

0

0
0

DPID

0

DPID

0

DPID

0
0

0

0

0
0

0

0

0

SOFM
OTGINT
MMISM

0
0
0
0
0
0

RXFLVLM
SOFM
OTGINT
MMISM

0
0
0
0
0
0
0

BCNT

0

0

0

0
0

0

0

0
0

0

0

0
0

0

0

0
0

BCNT

0

BCNT

0

BCNT

0
0

0

0

0
0

0

0

0

Res.

RXFLVLM

0

Res.

NPTXFEM

0

GINAKEFFM

0

NPTXFEM

0

GINAKEFFM

0

GONAKEFFM

0

GONAKEFFM

0

GONAKEFF
GINAKEFF
NPTXFE
RXFLVL
SOF
OTGINT
MMIS
CMOD

GONAKEFF
GINAKEFF
NPTXFE
RXFLVL
SOF
OTGINT
MMIS
CMOD

Res.

Res.

0

Res.

ESUSP

0

Res.

ESUSP

USBRST
USBSUSP

0

Res.

USBRST
USBSUSP

ISOODRP
ENUMDNE
0

Res.

ISOODRP
ENUMDNE

EOPF

Res.

Res.

0

Res.

ISOODRPM
ENUMDNEM

0

ENUMDNEM

EOPF

Res.
0

Res.

EOPFM

0

EOPFM

Res.

IEPINT
0

Res.

OEPINT
0

Res.

IISOIXFR
0

Res.

IPXFR/INCOMPISOOUT
0

Res.

0

IEPINT

0

IEPINT

0

OEPINT

0

IISOIXFRM

0

OEPINT

0

IISOIXFRM

0

IPXFRM/IISOOXFRM

0

IPXFRM/IISOOXFRM

1

FSUSPM

IEPINT

OTG_
GINTMSK
OEPINT

1
IISOIXFR

Res.

0

Res.

CIDSCHG

0
IPXFR/INCOMPISOOUT

RSTDET

SRQINT
DISCINT

0
Res.

WKUINT

Reset value
DATAFSUSP

OTG_
GINTSTS

Res.

0

RSTDETM

HCINT
HPRTINT
0

HPRTINT

0

PRTIM

PTXFE

1

HCINT

0

HCIM

LPMINT

1

PTXFE

CIDSCHG

0

PTXFEM

SRQINT
DISCINT

0

LPMINTM

WKUINT

0

WUIM

0x018
Reset value

WUIM

0x018
OTG_
GINTSTS

Res.

0x014

Res.

0x014

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.

RM0390
USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Table 224. OTG_FS/OTG_HS register map and reset values (continued)

0
0
1
0
0
0
0
0

0
0
1
0
0
0
0
0

CHNUM

0

EPNUM

0

CHNUM

0

EPNUM

0

1191/1327

1265

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0390

Res.

Res.

Res.

Res.

Res.

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

0

0

0

0

0

0

0

0

0

1

0

0

0

RWDATA

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

REGADDR

Res.

ADDR

0

Res.

0

0

Res.

0

NPTXFSAV

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

1

0

0

0

0

0

0

L1DSEN

0

Res.

0

Res.

1

Res.

0

VBDEN

0

Res.

0

I2CEN

0

Res.

0

ACK

0

0

Res.

0

0

Res.

OTG_
GCCFG

0

0

NPTQXSAV

Res.

0

I2CDEVADR

0

0

Res.

Reset value

0

Res.

OTG_
GI2CCTL

RW

0

Res.

0

BSYDNE

0

0

1

0

0

0

0

LPM
RSP

BESLTHRS

0

0

0

0

Res.

1

SLPSTS

0

0

PWRDWN

0

1

Res.

0

0

NPTXFSA/TX0FSA

NPTXQTOP

Res.

0x038

0

I2CDATSE

OTG_
HNPTXSTS

0

Res.

0

Res.

Reset value

Reset value

0x030

0

NPTXFD/TX0FD

Res.

0x02C

0

Res.

OTG_
HNPTXFSIZ/
OTG_
DIEPTXF0

Res.

0x028

RXFD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
GRXFSIZ

0x024

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 224. OTG_FS/OTG_HS register map and reset values (continued)

0

0

0

Reset value

0

0

0x100

OTG_
HPTXFSIZ
Reset value

0x104

0x204

1192/1327

0

0

LPM
RCNT
0

0

0

0

0

0

0

0

LPMCHIDX

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

1

INEPTXFD
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

INEPTXSA
0

0

0

0

0

0

0

0

0

0

0

1

INEPTXFD
0

0

BESL

PTXSA

0

0

0

0

INEPTXSA
0

0

0

0

0

0

.
.
.
.

0

0

0

0

0

1

1

0

0

0

.
.
.
.

OTG_
DIEPTXF5
Reset value

.
.
.
.

0

OTG_
DIEPTXF2
Reset value

.
.
.
.

0

PTXFSIZ

OTG_
DIEPTXF1
Reset value

0x108

0

0

LPMEN

0

0

0

LPMACK

LPMR
CNTSTS

Reset value

0

REMWAKE

0

L1SSEN

0

L1RSMOK

0

SNDLPM

0

ENBESL

OTG_
GLPMCFG

0

Res.

Reset value

PRODUCT_ID

Res.

0x054

OTG_CID

Res.

0x03C

INEPTXFD
0

0

0

0

0

0

1

0

0

0

INEPTXSA
0

0

0

0

0

0

.
.
.
.

0
.
.
.
.

DocID026976 Rev 3

0

0

0

1

1

0

0

0

0

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

0

0

0

0

0

0

OTG_
HCFG

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

Reset value

0

0

0

0

0

0

0

0

1

0

0

0

OTG_
HAINT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

PSPD

0

1

1

1

1

1

1

Res.

Res.

Res.

Res.

Res.

Res.

LSDEV

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

HUBADDR

0

0

0

0

0

0

0

0

0

PRTADDR

0

0

EPNUM

0

0

0

0

0

0

0

MPSIZ

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

0

Res.

Res.

0

TXERR

Res.

1

BBERR

Res.

0

FRMOR

Res.

0

DTERR

Res.

Res.

1

Res.

OTG_
HCINT0

0

0

0

0

PKTCNT
0

1

Res.

0

0

1

Res.

0

0

1

Res.

0

0

EPDIR

0

0

COMPLSPLT

0

EPTYP

0

0

Res.

0

MCNT

0

0

XAC
TPO
S

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Reset value

Res.

CHDIS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
HCCHAR0

Res.

0

0

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Reset value

ODDFRM

0

Res.

0

Res.

0

OTG_
HCSPLT0

DAD

0

PTCTL

SPLITEN

0

Res.

1

HAINTM
0

Res.

1

HAINT
0

Res.

1

PCSTS

0

0

0

PCDET

0

0

0

0

0

0

0

0

0

CHH

0

0

0

XFRC

0

0

0

PENA

0

Reset value

0

PTXFSAVL

0

Res.

0

PTXQSAV

DPID

1

PENCHNG

0

0

OTG_
HCTSIZ0

1

STALL

0

Res.

PTXQTOP

0

Reset value

0x510

0

POCA

0

CHENA

0x508

0

NAK

0

Res.

0x500

1

POCCHNG

0

Reset value

0x504

0

PRES

0

0

OTG_
HPRT

1

PSUSP

0

Reset value

0x440

0

PRST

0

0

Res.

0

Reset value

OTG_
HAINTMSK

1

PLSTS

OTG_
HPTXSTS

0

Reset value

0x418

1

PPWR

0

0

FRNUM

Res.

0x414

1

FTREM
0

0

FRIVL

ACK

OTG_
HFNUM
Reset value

0x410

0

0

Res.

0x408

RLDCTRL

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
HFIR

Res.

0x404

Res.

Reset value

0
FSLSPCS

0

Res.

0

FSLSS

Reset value

Res.

INEPTXSA

Res.

INEPTXFD

Res.

0x400

OTG_
DIEPTXF7

Res.

0x244

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 224. OTG_FS/OTG_HS register map and reset values (continued)

0

0

0

0

XFRSIZ
0

0

0

0

0

0

0

DocID026976 Rev 3

0

0

0

0

0

0

0

0

0

0

0

1193/1327
1265

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

RM0390

1194/1327

0

0

0

XFRCM

0

0

0

0

0

0

0

Res.

0

CHHM

0

0

Res.

0

0

MPSIZ

0

0

0

0

0

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

XFRCM

0

0

0

CHHM

0

0

STALLM

0

0

NAKM

0

0

ACKM

0

0

XFRC

0

CHH

0

STALL

0

NAK

0

ACK

0

TXERR

0

Res.

EPNUM

XFRSIZ
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

EPDIR
0

0

0

0

0

0

0

0

0

0

0

0

0

FRMORM

0

DTERRM

0

Res.

0

Res.

0

Res.

0

MPSIZ

Res.

0

EPNUM

Res.

0

Res.

DAD

LSDEV

0

EPTYP

CHDIS

ODDFRM

0

MCNT

CHENA

.
.
.
.

0

0

0

Res.NYET

ACKM

NAKM

STALLM

0

0

0

0

0

0

0

0

0

0

XFRCM

TXERRM

0

CHHM

BBERRM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

.
.
.
.

0

0

0

0

.
.
.
.
Res.

.
.
.
.

Reset value

0

Res.NYET

0

Reset value

OTG_
HCTSIZ11

NAKM

0

Reset value

0x670

STALLM

0

PKTCNT

.
.
.
.

.
.
.
.

ACKM

0

TXERRM

0

OTG_
HCCHAR11

OTG_
HCINTMSK11

TXERRM

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

DPID

Res.

0x66C

Res.NYET

0

Res.

0

BBERR

Res.

0

FRMOR

Res.

0

BBERRM

OTG_
HCINT1

DAD

0

FRMORM

0

Res.

.
.
.
.

0

DTERR

0

Res.

0

MCNT

0

.
.
.
.

0x660

0

DTERRM

0

Reset value
.
.
.
.

0

Res.

0

OTG_
HCTSIZ1

0

Res.

0

Res.

0

Reset value

0x530

0

Res.

0

OTG_
HCINTMSK1

0

Res.

0

Res.

0

EPDIR

0

Res.

0

Reset value

0x52C

0

Res.

0

Res.

0

Res.

0

Res.

0

0

Res.

0

Res.

0

0

LSDEV

0

Res.

0

0

EPTYP

Reset value

Res.

CHDIS

OTG_
HCCHAR1

Res.

0
ODDFRM

0

Res.

0

CHENA

Reset value

Res.

0x528

0
DMAADDR

Res.

0x520

BBERRM

OTG_
HCDMA0

0x514

FRMORM

Res.

Reset value

DTERRM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
HCINTMSK0

Res.

0x50C

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 224. OTG_FS/OTG_HS register map and reset values (continued)

DPID
0

0

PKTCNT
0

0

0

0

0

0

XFRSIZ
0

0

0

0

0

0

0

DocID026976 Rev 3

0

0

0

0

0

0

0

0

0

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

0

0

0

0

0

0

0

0

0

0

Res.

0

0

0

0

0

MPSIZ

0

0

0

0

0

0

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PRTADDR

0

0

0

0

0

0

0

0

0

0

0

ACKM

NAKM

STALLM

0

0

0

0

XFRCM

TXERRM

ResNYET

0

CHHM

BBERRM
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

STALL

0

0

NAK

0

0

ACK

0

0

Res.

0

0

TXERR

0

0

BBERR

0

0

FRMOR

0

0

DTERR

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

Res.

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

.
.
.
.

Reset value
.
.
.
.

0

XFRC

0

Res.

OTG_
HCINT11

0

Res.

0x728

0

Res.

0

DMAADDR

.
.
.
.

0

XFRSIZ

OTG_
HCDMA15
Reset value

0

FRMORM

HUBADDR

PKTCNT

.
.
.
.

.
.
.
.

0

CHH

DPID

.
.
.
.

Res.

0x6F4

0

.
.
.
.

Reset value
.
.
.
.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

.
.
.
.
OTG_
HCTSIZ15

0

.
.
.
.
Res.

.
.
.
.

Res.

0x6F0

0

DTERRM

Res.

COMPLSPLT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Reset value

XAC
TPO
S

Reset value
.
.
.
.

0

.
.
.
.

OTG_
HCSPLT15

OTG_
HCINTMSK15

EPNUM

Res.

0

LSDEV

MCNT

0

Res.

0x6EC

0

Res.

.
.
.
.

0

DAD

.
.
.
.

Res.

0x6E4

Reset value

SPLITEN

.
.
.
.

OTG_
HCCHAR15

Res.

0x6E0

EPDIR

.
.
.
.
EPTYP

.
.
.
.
CHDIS

.
.
.
.

ODDFRM

Register

CHENA

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 224. OTG_FS/OTG_HS register map and reset values (continued)

.
.
.
.

.
.
.
.

DocID026976 Rev 3

1195/1327
1265

0x814

0x818

1196/1327

OTG_
DOEPMSK

Reset value

0

0

0

0

0

0

OTG_
DAINT

0

0

0

0

0

0

0

0

0

0

DocID026976 Rev 3

Reset value

0

0

0

0

0

0

0

BOIM

0

OEPINT

0

0

0
XFRCM

0
0
0

0

0

0
XFRCM

SDIS
RWUSIG

0
0

0

IEPINT

0

0

0

0

0

DSPD

DSPD

DSPD

CHH
XFRC

Res.

0

NZLSOHSK

0
NZLSOHSK

0
NZLSOHSK

0

0

0

0
1
0

SUSPSTS

Res.

NAK
Res.

STALL
Res.

0

XFRCM

GINSTS

0

EERR

ACK
0

ENUMSPD

0

Res.

Res.
0

0
0
0
0

Res.

0

Res.

0

0
0
0

Res.
EPDM

0

EPDM

0

Res.

0

Res.

GONSTS

0

TCTL

SGINAK

0
Res.

0

EPDM

TOM

0

STUPM

Reset value

STUPM

0

OTEPDM

ITTXFEMSK

0

OTEPDM

0

INEPNMM

0

Res.

0

Res.

TXERR

0

INEPNEM

0

0

Res.

0

0

B2BSTUP

BBERR
0

DAD

0
DAD

0

DAD

FRMOR

0

SGONAK

0

CGINAK

FNSOF

Res.

0

Res.

0

0

Res.

0

Res.

0

Res.
DTERR

Res.
0

CGONAK

PFIVL

0

0

Res.

0

Res.

PFIVL

Res.

Res.

Res.

0

POPRGDNE

PFIVL

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.

Res.

0

Res.

Res.

Res.

ERRATIM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.
0

TXFURM

0

NAKM

Res.

XCVRDLY

Res.

ERRATIM

Res.

0

Res.

0

Res.

ERRATIM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Reset value

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.
0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

DSBESLRJCT

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

PERSCHIVL

Res.

Res.

Res.

0

Res.

0

Res.

DEV
LN
STS

Res.

0

Res.

Res.

Reset value

NYETMSK

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

OTG_
DOEPMSK

Res.

0x814
OTG_
DIEPMSK

Res.

0x810
OTG_
DSTS

Res.

0x808
OTG_
DCTL

Res.

0x804
OTG_
DCFG

Res.

0x800
OTG_
DCFG

Res.

0x800
OTG_
DCFG

Res.

0x800
OTG_
HCINT15

Res.

0x7A8

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.

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
RM0390

Table 224. OTG_FS/OTG_HS register map and reset values (continued)

0
0

0
0

0
0

0
0
0

0

0

0

0

0x910

0x914

OTG_
DIEPTSIZ0

Reset value

0

0

0

0

0

0

0

0

0

TXFNUM

Reset value

0

0

0

0

PKT
CNT

0
USBAEP

0
0

Res.

OTG_
DIEPDMA

0

0

0

DocID026976 Rev 3

0

0

0

0

0

0

0

0
0
0
0
0
0
0
0
0

Res.

0

0

ITTXFE

TOC

Res.

0

1
Res.

0

MPSIZ

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0
0
0

1
0
1
0
1
1
1

0
1
1
1
0
0
0

0
0
0
0
0
0

0
0
0

Res.

0

ISOTHREN

INEPTXFEM

0

NONISOTHREN

Res.

DVBUSP

0

Res.

0

Res.

Res.

VBUSDT

0

IEP1INT

0

Res.

TXTHRLEN

IEP1INTM

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0
Res.

0

Res.

0

Res.

0
Res.

1

Res.

0

1

Res.

0

1

0

1

0

0

0

XFRC

0

INEPNE

0
Res.

1

Res.

Res.

0

Res.

0
Res.

0

Res.

0

1

Res.

1

0

EPDISD

0

TXFE

Reset value
0

Res.

0
Res.

Res.

1

Res.

Res.

0

0

Res.

Res.

0

Res.

0

0

Res.

0

0

Res.

0
Res.

0

Res.

0

Res.

0

Res.

1

Res.

Res.

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

0
0

Res.

Reset value
0

Res.

Reset value

Res.

0

0

Res.

Reset value
0

Res.

0

Res.

Res.

0

Res.

RXTHREN

0

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

USBAEP

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0
OEP1INT

Res.

Res.

Res.

Res.

0

Res.

Reset value
OEP1INTM

Res.

Res.

Res.

Res.

Res.

0

Res.

EONUM/DPID

0

Res.

0
NAKSTS

EPTYP

Res.

STALL

Res.

Res.

0

Res.

NAKSTS

0

Res.

EPTYP

0

Res.

0

Res.

Res.

STALL

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

OEPM

Res.

Res.

Res.

Res.

Res.

Res.

ARPEN

0

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

CNAK

CNAK

Res.

Res.

0

Res.

Res.

SNAK

Res.

Res.

Res.

0

Res.

OTG_
DIEPINT0
SNAK

Res.

Res.

Res.

0

OTG_
DVBUSDIS

Res.

0

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

0
RXTHRLEN

Res.

0

Res.

Reset value

Res.

0

0
0

Res.

0

0
0

Res.

0
TXFNUM

Res.

0
0

Res.

0
0

Res.

Reset value
0

SD0PID/SEVNFRM

Res.

Res.

Res.

OTG_
DAINTMSK

Res.

OTG_
DIEPCTL0
0

Res.

Res.

0

Res.

Res.

Res.

Reset value

Res.

Res.

OTG_DEACHI
NTMSK
Res.

OTG_
DEACHINT

Res.

EPDIS

0

EPDIS

0x908
Reset value

SODDFRM/SD1PID

0x900
OTG_
DIEPCTL0

Res.

0x900

Res.

0x83C
OTG_DIE
PEMPMSK

Res.

0x838
OTG_
DTHRCTL

Res.

0x834
OTG_DVB
USPULSE

Res.

0x830

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.

0x82C

EPENA

0x828

EPENA

0x81C

Res.

Offset

Res.

RM0390
USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Table 224. OTG_FS/OTG_HS register map and reset values (continued)

IEPM

0

0

0
0

MPSIZ

0

0

XFRSIZ

DMAADDR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1197/1327

1265

0x9A8

.
.
.
.

1198/1327

OTG_
DIEPINT5
0
0
0
0
0
0
0

.
.
.
.

.
.
.
.

.
.
.
.

DocID026976 Rev 3
0
0
0
0
0
0
0
0
0
0
0
0

XFRC

.
.
.
.

EPDISD

0

Res.

0

0

TOC

0
0

ITTXFE

PKTCNT

Res.

Res.
Res.
Res.
Res.
Res.

0

Res.

0

0

0

0

1

0

Reset value

0

0

0

0

0

0
0
0

XFRSIZ
1
0

0
0

0

0

0
0
0

INEPTFSAV

0

MPSIZ

0
0

0
0
0

0
0

MPSIZ

0

0
0

0
0
0

0
0
0
0

0
0
0
0

0
0
0
0

0
0
0

Res.

0

XFRC

0

EPDISD

TOC

0

Res.

0

ITTXFE

0

INEPNE

1

TXFE

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

USBAEP

Res.

Res.

EONUM/DPID

Res.

Res.

NAKSTS

Res.

EPTYP

Res.

Res.

STALL

0

INEPNE

Res.

0

TXFE

Res.

0

Res.

0

Res.

Res.

0

Res.

Reset value
0

Res.

.
.
.
.
0

Res.

0
0

Res.

0
0

Res.

0
0

Res.

Reset value
0

Res.

0
0

Res.

Res.

0

Res.

0
USBAEP

0

Res.

Res.

0

Res.

TXFNUM
0

0

Res.

0
0

0

Res.

0
0

0

Res.

0
0

USBAEP

0

Res.

Res.

Reset value

Res.

0
0
EONUM/DPID

0

Res.

OTG_
DIEPINT1

EONUM/DPID

0

Res.

0
Res.

0

Res.

0

Res.

0

NAKSTS

0

Res.

0

NAKSTS

0

Res.

0

Res.

0

Res.

0

EPTYP

0

Res.

CNAK

0

EPTYP

0

Res.

SNAK

0

Res.

0

Res.

SD0PID/SEVNFRM

0

Res.

0

Res.

EPDIS
SODDFRM/SD1PID

0

Res.

0

Res.

MCNT

0

Res.

0
TXFNUM
STALL

0

Res.

EPENA

Reset value

Res.

0

STALL

0

Res.

OTG_
DIEPCTL1
TXFNUM

Res.

CNAK

0

Res.

SNAK

0

Res.

SD0PID/SEVNFRM

0

Res.

EPDIS
SODDFRM

0

Res.

CNAK

0
SNAK

Reset value
SD0PID/SEVNFRM

OTG_
DIEPCTL5

Res.

.
.
.
.
0

Res.

0x9A0
Reset value

Res.

.
.
.
.
OTG_
DIEPCTL2

EPDIS

0x940
OTG_
DTXFSTS1

SODDFRM

Reset value

Res.

0x938
OTG_
DIEPTSIZ1

Res.

0x930
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
DTXFSTS0

Res.

0x928

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.

0x920

EPENA

0x918

EPENA

Offset

Res.

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
RM0390

Table 224. OTG_FS/OTG_HS register map and reset values (continued)

INEPTFSAV

.
.
.
.

MPSIZ

1

0

0

0

0

0

0xB00

0xB08

OTG_
DOEPCTL0

Reset value

0

0

OTG_
DOEPINT0

0

0

0

0

Res.

Res.

Reset value

DocID026976 Rev 3
0
0

0
0

0
0
0
0
0
0
0
0
0

.
.
.
.
XFRSIZ

0

Res.

0

0

0

0
0
0

.
.
.
.

INEPTFSAV

0
0
0
0
0

0

0

XFRC

TOC

0

ITTXFE

INEPNE

0

0

1

MPSIZ

0

0

0

Res.
Res.
Res.
Res.

0

0

0

XFRC

0

0

1

0

EPDISD

0

Res.

0

0

Res.

XFRSIZ

0

Res.

.
.
.
.
0

TXFE

Reset value
0

EPDISD

0

Res.

0

0

0

Res.

1

Res.

PKTCNT
0

0

STUP

0

Res.

0

1

OTEPDIS

0

Res.

PKTCNT

0

Res.

0

Res.

0

Res.

0

B2BSTUP

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

.
.
.
.
0

Res.

Reset value

Res.

0

Res.

.
.
.
.

Res.

0

Res.

USBAEP
0

Res.

0

Res.

.
.
.
.

Res.

0

Res.

EONUM/DPID
0

Res.

0

Res.

NAKSTS
0

Res.

0

Res.

EPTYP

.
.
.
.

USBAEP

0

Res.

Res.

STALL

Reset value

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

NAKSTS

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.
0

EPTYP

SNPM

0

Res.

0

Res.

0

STALL

0

Res.

TXFNUM

Res.

Res.

0

Res.

0

Res.
0

Res.

0

Res.

0

Res.

0

Res.

CNAK

0

Res.

0
0

Res.

0

Res.

SNAK

0

Res.

0

Res.

SD0PID/SEVNFRM

0

Res.

0

Res.

EPDIS
SODDFRM

0

Res.

0

Res.

MCNT
0

Res.

0

Res.

0

Res.

EPENA

0

Res.

CNAK

0

Res.

0

Res.

0

SNAK

OTG_
DTXFSTS7
0

Res.

Reset value

Res.

OTG_
DIEPTSIZ7

Res.

OTG_
DIEPINT7
0

Res.

Reset value

MCNT

OTG_
DIEPTSIZ5

Res.

0x9B0

Res.

0x9F8
0

Res.

.
.
.
.
Reset value

Res.

0x9F0

EPDIS

.
.
.
.
OTG_
DIEPCTL7

Res.

0x9E8

Res.

.
.
.
.

Res.

.
.
.
.

Res.

0x9E0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
DTXFSTS5

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.

0x9B8

EPENA

Offset

Res.

RM0390
USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Table 224. OTG_FS/OTG_HS register map and reset values (continued)

INEPTFSAV
0
0
0
0

MPSIZ

0
0

0
0
0

0
0

0

0

1199/1327

1265

0xBE0

OTG_
DOEPCTL7

Reset value

0

1200/1327

0

0

0

0

0

0

0
0

0
0

0
0
0

0

.
.
.
.
.
.
.
.

0
0
0

.
.
.
.

DocID026976 Rev 3
0
0
0
0
0

Res.

0

0

0

0

0
0
0
0

Res.

0
0
0

Res.

0

Res.

0
0
0

Res.

0

Res.
Res.

0
0
0

PKTCNT

0

PKTCNT
Res.
Res.
Res.
Res.

0
DMAADDR
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

MPSIZ

0
0
0
0

Reset value

XFRSIZ

MPSIZ

.
.
.
.

MPSIZ

0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0

0
0
0
0

0

0

0

0

0

0

0
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

EPDISD

STUP

0

OTEPDIS

0

Res.

0

Res.

0
B2BSTUP

0

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

USBAEP

0

Res.

0
0

Res.

EONUM/DPID

0

Res.

0
0

USBAEP

0

0

EONUM/DPID

NAKSTS

0

EPTYP

0

Res.

0

0

NAKSTS

0

Res.

0

Res.

0
SNPM

Res.

0

Res.

Res.

0
STALL

0

Res.

0

EPTYP

0

SNPM

0

STALL

0

USBAEP

0
0
Res.

0

EONUM/DPID

0
0
Res.

0

Res.

OTG_
DOEPDMA

NAKSTS

0
Res.

0

Res.

Res.

0

EPTYP

0
0
0

SNPM

0
0

STALL

0
0

Res.

0
0

Res.

0
0

Res.

0
0

Res.

0
0

Res.

0
Res.

Res.
0

CNAK

Res.
0

SNAK

Res.
0

SD0PID/SEVNFRM

Res.
0

EPDIS

OTG_
DOEPINT1
0

SODDFRM

Reset value

Res.

RXDPID/
STUPCNT

OTG_
DOEPCTL1

Res.

.
.
.
.
0

Res.

0
CNAK

Reset value

CNAK

OTG_
DOEPCTL5
SNAK

.
.
.
.

SD0PID/SEVNFRM

Reset value

SNAK

OTG_
DOEPTSIZ2
RXDPID/
STUPCNT

Reset value

EPDIS

OTG_
DOEPTSIZ1

SD0PID/SEVNFRM

0xBA0
0

EPENA

0xB14

SODDFRM

0xB28
Reset value

Res.

Reset value

EPDIS

0xB50
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PKTCNT

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

STUPCNT

Res.

OTG_
DOEPTSIZ0

SODDFRM

0xB30

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.

0xB20

EPENA

0xB10

EPENA

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
RM0390

Table 224. OTG_FS/OTG_HS register map and reset values (continued)

XFRSIZ

0
0

XFRSIZ

RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

0

0

0

0

0

0

0

0

0

0

0

0

XFRC

Res.

EPDISD

STUP

Res.

OTEPDIS

0

0

0

0

0

XFRC

0

EPDISD

STUP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTEPDIS

0

0

0

RXDPID/
STUPCNT
0

0

0

0

0

0

0

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.

SUSP

PHYSLEEP

ENL1GTG

PHYSUSP

Res.

Res.

GATEHCLK

STPPCLK

XFRSIZ

Res.

PKTCNT

Res.

Res.

OTG_
PCGCCTL

0

.
.
.
.

Reset value

0xE00

0

Res.

OTG_
DOEPTSIZ7

0

Res.

0

.
.
.
.
Res.

0xBF0

0

Res.

0

Reset value
.
.
.
.

0

.
.
.
.
Res.

OTG_
DOEPINT7

0

B2BSTUP

0

Reserved

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0xBE8

0

XFRSIZ

.
.
.
.
Res.

.
.
.
.

0

PKTCNT

Res.

Reset value

RXDPID/
STUPCNT

OTG_
DOEPTSIZ5

0

.
.
.
.

Res.

0xBB0

.
.
.
.
Res.

.
.
.
.

B2BSTUP

Res.

Reset value

Reserved

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OTG_
DOEPINT5

Res.

0xBA8

Res.

.
.
.
.
Res.

.
.
.
.
Res.

.
.
.
.

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 224. OTG_FS/OTG_HS register map and reset values (continued)

0

0

0

0

0

0

Reset value

Refer to Section 2.2.2: Memory map and register boundary addresses for the register
boundary addresses.

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31.16

OTG_FS/OTG_HS programming model

31.16.1

Core initialization

RM0390

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.

1202/1327

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.

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31.16.2

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)

Host initialization
To initialize the core as host, the application must perform the following steps:
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.

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.

31.16.3

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 1237.

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At this point, the device is ready to accept SOF packets and perform control transfers on
control endpoint 0.

31.16.4

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.

31.16.5

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.

Program the OTG_GINTMSK register to unmask the following:

2.

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.

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
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
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 HS_OTG 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 HS_OTG 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 HS_OTG 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 DWORD write of a packet. The
application must ensure that at least one free space is available in the periodic/non-

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RM0390

periodic request queue before starting to write to the transmit FIFO. The application
must always write to the transmit FIFO in DWORDs. If the packet size is non-DWORD
aligned, the application must use padding. The OTG_FS/OTG_HS host determines the
actual packet size based on the programmed maximum packet size and transfer size.
Figure 409. Transmit FIFO write task
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SETUP transactions
This section describes how the core handles SETUP packets and the application’s
sequence for handling SETUP transactions.

1240/1327

•

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

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
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
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.

The core internally sets the IN NAK and OUT NAK bits for the control IN/OUT
endpoints on which the SETUP packet was received.

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.
–

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.

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RM0390

Figure 424. Processing a SETUP packet

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•

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:

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
1.

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:

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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.

3.

1244/1327

–

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.

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 non-

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
isochronous 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:

7.

–

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)

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:

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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:
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.

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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

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could fail to detect the XFRC interrupt (OTG_DOEPINTx) under the following
circumstances:

2.

–

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
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.

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1.

Put the core in the Global OUT NAK mode.

2.

Disable the required endpoint
–

RM0390

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.
•

Bulk OUT transaction

Figure 425 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 425. Bulk OUT transaction
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069

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.

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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.
1.

2.

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:

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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.
–

SNAK = 1 in OTG_DIEPCTLx

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.

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).
–

6.

CNAK = 1 in OTG_DIEPCTLx

If the application masked this interrupt earlier, it must be unmasked as follows:
–

•

INEPNEM = 0 in OTG_DIEPMSK

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:

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1.

The application must stop writing data on the AHB for the IN endpoint to be disabled.

2.

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.

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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:
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:

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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

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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:
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 1252 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

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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:

1254/1327

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

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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.
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
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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.

6.

Program the following fields in the OTG_DIEPCTLx register to disable the endpoint:
–

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:

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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

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.

31.16.7

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.

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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 426 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 221: TRDT values (FS) or Table 222: TRDT
values (HS).

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RM0390

USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 426. TRDT max timing case
NS



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AI

31.16.8

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.

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RM0390

Figure 427. A-device SRP
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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 427:
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.

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
Figure 428. B-device SRP
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AI

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 428:
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

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RM0390

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 429. A-device HNP

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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 429:
1.

1262/1327

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

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
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.

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RM0390

Figure 430. B-device HNP

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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 430:
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

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USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
determine host negotiation success. The application must read the current Mode bit in
the Core interrupt register (OTG_GINTSTS) to determine host mode operation.
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.

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HDMI-CEC controller (HDMI-CEC)

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32

HDMI-CEC controller (HDMI-CEC)

32.1

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.

32.2

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)
–

1266/1327

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)

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HDMI-CEC controller (HDMI-CEC)

32.3

HDMI-CEC functional description

32.3.1

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 STM32.
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 could be done by using a MOS
transistor, as shown on Figure 431.
Table 225. HDMI pin
Name

CEC

32.3.2

Signal type

Remarks
two states:
1 = high impedance
0 = low impedance
A 27 kΩ must be added externally.

bidirectional

HDMI-CEC block diagram
Figure 431. HDMI-CEC block diagram

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32.3.3

RM0390

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 which consists of a start bit followed by a header
block and optionally an opcode and a variable number of operand blocks.
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 the event
that a message contains additional blocks after an EOM is indicated, those additional blocks
should 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 which has read its own address in the header or by the follower
which 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 432. Message structure
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32.3.4

Bit timing
The format of the start bit is unique and identifies the start of a message. It should 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 high to
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.

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HDMI-CEC controller (HDMI-CEC)
Figure 434. Bit timings
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32.4

Arbitration
All devices that have to transmit - or retransmit - a message onto the CEC line have to
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 435. Signal free time
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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 commences 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 shall
monitor the CEC line, if whilst driving the line to high impedance it reads it back to 0, it then
assumes it has lost arbitration, stops transmitting and becomes a follower.

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Figure 436. Arbitration phase

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The Figure 437 shows an example for a SFT of three nominal bit periods
Figure 437. SFT of three nominal bit periods

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A configurable time window is counted before starting the transmission.
In the SFT=0x0 configuration the HDMI-CEC device 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.

32.4.1

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

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HDMI-CEC controller (HDMI-CEC)
timer is still running instead, the system waits until the timer elapses before transmission
can start.
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.

32.5

Error handling

32.5.1

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 438. Error bit timing

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32.5.2

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:

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32.5.3

RM0390

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 439). BRE flag also generates a CEC interrupt if the BREIE=1.
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.

32.5.4

Short Bit Period Error (SBPE)
SBPE is set when a bit falling edge is detected earlier than expected (see Figure 439).
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:

32.5.5

•

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 439). 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:

1272/1327

The BREGEN=1, BRESTP=0 configuration must be avoided

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HDMI-CEC controller (HDMI-CEC)
Figure 439. Error handling
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Table 226. 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.

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32.5.6

RM0390

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 440. TXERR detection
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Table 227. 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

1274/1327

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.

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HDMI-CEC controller (HDMI-CEC)
Table 227. 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

32.6

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 228. 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

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32.7

RM0390

HDMI-CEC registers
Refer to Section 1.1 on page 51 for a list of abbreviations used in register descriptions.

32.7.1

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.

TX
EOM

TX
SOM

CEC
EN

rs

rs

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Bits 31:3 Reserved, must be kept at reset value.
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).

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HDMI-CEC controller (HDMI-CEC)

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’s 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

32.7.2

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

Res.

22

21

20

19

18

17

16

2

1

0

OAR[14:0]

rw
15

23

rw
14
Res.

13
Res.

12
Res.

11
Res.

10
Res.

9

8

7

6

5

4

3

Res.

SFT
OPT

BRDN
OGEN

LBPE
GEN

BRE
GEN

BRE
STP

RX
TOL

SFT[2:0]

rw

rw

rw

rw

rw

rw

rw

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: 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.

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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

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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: 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

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32.7.3

RM0390

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 register.
TXD is a write-only register containing the data byte to be transmitted.

32.7.4

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.

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

RXD[7:0]
r

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 RXD[7:0]: Rx Data register.
RXD is read-only and contains the last data byte which has been received from the CEC line.

32.7.5

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

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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.

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RM0390

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.

32.7.6

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

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RXOVR RXEND RXBR
BREIE
IE
IE
IE
rw

rw

rw

rw

RM0390

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

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CEC_IER

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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
TXEND

Reset value

TXENDIE

Res.

Res.

CEC_TXDR

Res.

0

TXUDR

0

TXUDRIE

0

Res.

0

TXERR

0

TXACKE

0

TXACKIE

0

TXERRIE

0

Res.

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.

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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CEC_ISR

Res.

0x10

Res.

CEC_RXDR

Res.

0x0C
Res.

0x08
Reset value
0

Reset value

Refer to Section 2.2.2 on page 56 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.

0x04

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.

32.7.7

Res.

HDMI-CEC controller (HDMI-CEC)
RM0390

HDMI-CEC register map
The following table summarizes the HDMI-CEC registers.
Table 229. 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

RM0390

Debug support (DBG)

33

Debug support (DBG)

33.1

Overview
The STM32F446xx are built around a Cortex®-M4 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
STM32F446xx MCUs.
Two interfaces for debug are available:
•

Serial wire

•

JTAG debug port
Figure 441. Block diagram of STM32 MCU and Cortex®-M4 with FPU-level debug
support
34-&XX DEBUG SUPPORT
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Note:

The debug features embedded in the Cortex®-M4 with FPU core are a subset of the ARM®
CoreSight Design Kit.

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The ARM® Cortex®-M4 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

•

TPUI: 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 STM32F446xx:
•

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®-M4 with FPU
core, refer to the Cortex®-M4 with FPU-r0p1 Technical Reference Manual and to the
CoreSight Design Kit-r0p1 TRM (see Section 33.2: Reference ARM® documentation).

33.2

Reference ARM® documentation
•

Cortex®-M4 with FPU r0p1 Technical Reference Manual (TRM)
(see Related documents on page 1)

33.3

•

ARM® Debug Interface V5

•

ARM® CoreSight Design Kit revision r0p1 Technical Reference Manual

SWJ debug port (serial wire and JTAG)
The core of the STM32F446xx integrates the Serial Wire / JTAG Debug Port (SWJ-DP). It is
an ARM® standard CoreSight debug port that combines a JTAG-DP (5-pin) 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.

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Figure 442. SWJ debug port
TRACESWO (asynchronous trace)
SWJ-DP
JTDO
JTDI
NJTRST

TDO
TDI
nTRST

TDO
TDI
nTRST

JTAG-DP

TCK
TMS

nPOTRST

SWD/JTAG
select

nPOTRST
DBGRESETn

SWDITMS
JTMS/SWDIO

From
power-on
reset

DBGDI
SWDO

DBGDO
SW-DP

SWDOEN

JTCK/SWCLK

SWCLKTCK

DBGDOEN
DBGCLK
ai17139

Figure 442 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.

33.3.1

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:

33.4

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 STM32F446xx MCUs is available in various packages with different numbers of
available pins. As a result, some functionality (ETM) related to pin availability may differ
between packages.

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SWJ debug port pins
Five pins are used as outputs from the STM32F446xx for the SWJ-DP as alternate functions
of general-purpose I/Os. These pins are available on all packages.
Table 230. SWJ debug port pins
JTAG debug port

SW debug port

SWJ-DP pin name

33.4.2

Pin
assignment

Type

Description

Type

Debug assignment

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

-

-

PA15

JTDO/TRACESWO

O

JTAG Test Data Output

-

TRACESWO if async
trace is enabled

PB3

NJTRST

I

JTAG Test nReset

-

-

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 STM32F446xx MCUs offers the possibility of disabling some or all of the SWJDP ports and so, of releasing the associated pins for general-purpose IO (GPIO) usage. For
more details on how to disable SWJ-DP port pins, refer to Section 7.3.2: I/O pin multiplexer
and mapping.
Table 231. Flexible SWJ-DP pin assignment
SWJ IO pin assigned
Available debug ports

PA13 / PA14 /
PA15 /
JTMS / JTCK /
JTDI
SWDIO SWCLK

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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

Note:

PB3 /
JTDO

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 nTRST, 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.).

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33.4.3

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.

33.4.4

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.

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STM32F446xx JTAG TAP connection
The STM32F446xx MCUs integrate two serially connected JTAG TAPs, the boundary scan
TAP (IR is 5-bit wide) and the Cortex®-M4 with FPU TAP (IR is 4-bit wide).
To access the TAP of the Cortex®-M4 with FPU for debug purposes:

Note:

1.

First, it is necessary to shift the BYPASS instruction of the boundary scan TAP.

2.

Then, for each IR shift, the scan chain contains 9 bits (=5+4) and the unused TAP
instruction must be shifted in using the BYPASS instruction.

3.

For each data shift, the unused TAP, 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 TAP is automatically disabled (JTMS forced high).
Figure 443. JTAG TAP connections

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33.6

ID codes and locking mechanism
There are several ID codes inside the STM32F446xx 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.

33.6.1

MCU device ID code
The STM32F446xx MCUs integrate an MCU ID code. This ID identifies the ST MCU partnumber and the die revision. It is part of the DBG_MCU component and is mapped on the
external PPB bus (see Section 33.16 on page 1304). This code is accessible using the
JTAG debug pCat.2ort (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
Bits 15:12

Reserved, must be kept at reset value.

Bits 11:0 DEV_ID[11:0]: Device identifier
The device ID is 0x421

33.6.2

Boundary scan TAP
JTAG ID code
The TAP of the STM32F446xx BSC (boundary scan) integrates a JTAG ID code equal to
0x06413041.

33.6.3

Cortex®-M4 with FPU TAP
The TAP of the ARM® Cortex®-M4 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 0x4BA00477 (corresponds to Cortex®-M4 with FPU r0p1, see Section 33.2:
Reference ARM® documentation).

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Cortex®-M4 with FPU JEDEC-106 ID code
The ARM® Cortex®-M4 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.

33.7

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®-M4 with FPU r0p1 Technical Reference
Manual (TRM), for references, see Section 33.2: Reference ARM® documentation).
Table 232. JTAG debug port data registers
IR(3:0)

Data register

Details

1111

BYPASS
[1 bit]

-

1110

IDCODE
[32 bits]

ID CODE
0x4BA00477 (ARM® Cortex®-M4 with FPU r0p1 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 233 for a description of the A(3:2) bits

1010

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Table 232. JTAG debug port data registers (continued)
IR(3:0)

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.

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Table 233. 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

33.8

SW debug port

33.8.1

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.

33.8.2

SW protocol sequence
Each sequence consist of three phases:

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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

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Table 234. 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 233)

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®-M4 with FPUr0p1 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 235. 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 236. 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.

33.8.3

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
0x2BA01477 (corresponding to Cortex®-M4 with FPU r0p1).

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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®-M4 with FPU r0p1
TRM and the CoreSight Design Kit r0p1 TRM.

33.8.4

33.8.5

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 237. SW-DP registers
A(3:2)

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R/W

CTRLSEL bit
of SELECT
register

Register

00

Read

-

IDCODE

00

Write

-

ABORT

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The manufacturer code is not set to ST
code. 0x2BA01477 (identifies the SW-DP)
-

RM0390

Debug support (DBG)
Table 237. 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

33.8.6

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:
•

The shifted value A[3:2]

•

The current value of the DP SELECT register

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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 resisters 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®-M4 with FPU includes 9 x 32-bits registers:
Table 238. Cortex®-M4 with FPU AHB-AP registers
Address
offset

Register name

Notes

0x00

AHB-AP Control and Status
Word

Configures and controls transfers through the AHB
interface (size, hprot, status on current transfer, address
increment type

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®-M4 with FPU r0p1 TRM for further details.

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33.10

Debug support (DBG)

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 239. 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®-M4 with FPU r0p1 TRM for further details.
To Halt on reset, it is necessary to:
•

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.

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Capability of the debugger host to connect under system
reset
The reset system of the STM32F446xx 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®-M4 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.

33.12

FPB (Flash patch breakpoint)
The FPB unit:
•

implements hardware breakpoints

•

patches code and data from code space to system space. This feature gives the
possibility to correct software bugs located in the Code Memory Space.

The use of a Software Patch or a Hardware Breakpoint is exclusive.
The FPB consists of:

1300/1327

•

2 literal comparators for matching against literal loads from Code Space and remapping
to a corresponding area in the System Space.

•

6 instruction comparators for matching against instruction fetches from Code Space.
They can be used either to remap to a corresponding area in the System Space or to
generate a Breakpoint Instruction to the core.

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33.13

Debug support (DBG)

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

33.14

ITM (instrumentation trace macrocell)

33.14.1

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®-M4 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.

33.14.2

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.

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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 240. Main ITM registers
Address
@E0000FB0

Register

Details
Write 0xC5ACCE55 to unlock Write Access to the other ITM
registers

ITM lock access

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

1302/1327

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.

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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 33.17.2: TRACE pin assignment and Section 33.16.3: 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)

33.15

ETM (Embedded trace macrocell)

33.15.1

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 33.13: 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 33.17: TPIU (trace port
interface unit)) and then outputs the complete packet sequence to the debugger host.

33.15.2

Signal protocol, packet types
This part is described in the chapter 7 ETMv3 Signal Protocol of the ARM® IHI 0014N
document.

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Main ETM registers
For more information on registers refer to the chapter 3 of the ARM® IHI 0014N
specification.
Table 241. Main ETM registers
Address

Details

0xE0041FB0 ETM Lock Access

Write 0xC5ACCE55 to unlock the write access to the
other ETM registers.

0xE0041000 ETM Control

This register controls the general operation of the ETM,
for instance how tracing is enabled.

0xE0041010 ETM Status

This register provides information about the current status
of the trace and trigger logic.

0xE0041008 ETM Trigger Event

This register defines the event that will control trigger.

0xE004101C

33.15.4

Register

ETM Trace Enable
Control

This register defines which comparator is selected.

0xE0041020 ETM Trace Enable Event

This register defines the trace enabling event.

0xE0041024 ETM Trace Start/Stop

This register defines the traces used by the trigger source
to start and stop the trace, respectively.

Configuration example
To output a simple value to the TPIU:

33.16

•

Configure the TPIU and enable the I/IO_TRACEN to assign TRACE I/Os in the
STM32F446xx debug configuration register.

•

Write 0xC5ACCE55 to the ETM Lock Access Register to unlock the write access to the
ITM registers

•

Write 0x00001D1E to the control register (configure the trace)

•

Write 0000406F to the Trigger Event register (define the trigger event)

•

Write 0000006F to the Trace Enable Event register (define an event to start/stop)

•

Write 00000001 to the Trace Start/stop register (enable the trace)

•

Write 0000191E to the ETM Control Register (end of configuration)

MCU debug component (DBGMCU)
The MCU debug component helps the debugger provide support for:

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•

Low-power modes

•

Clock control for timers, watchdog, I2C and bxCAN during a breakpoint

•

Control of the trace pins assignment

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Debug support (DBG)

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.
For this, the debugger host must first set some debug configuration registers to change the
low-power mode behavior:

33.16.2

•

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.

33.16.3

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.

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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_
STANDBY

DBG_
STOP

DBG_
SLEEP

rw

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TRACE_
MODE[1:0]
rw

TRACE
_IOEN

rw

rw

Res.

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:5 TRACE_MODE[1:0] and TRACE_IOEN: Trace pin assignment control
– With TRACE_IOEN=0:
TRACE_MODE=xx: TRACE pins not assigned (default state)
– With TRACE_IOEN=1:
–
TRACE_MODE=00: TRACE pin assignment for Asynchronous Mode
–
TRACE_MODE=01: TRACE pin assignment for Synchronous Mode with a
TRACEDATA size of 1
–
TRACE_MODE=10: TRACE pin assignment for Synchronous Mode with a
TRACEDATA size of 2
–
TRACE_MODE=11: TRACE pin assignment for Synchronous Mode with a
TRACEDATA size of 4
Bits 4:3 Reserved, must be kept at reset value.

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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).

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Debug MCU APB1 freeze register (DBGMCU_APB1_FZ)
The DBGMCU_APB1_FZ register is used to configure the MCU under Debug. It concerns
APB1 peripherals. It is mapped on the external PPB bus at address 0xE004 2008.
The register 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-bits access are supported.

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_I2CFMP_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_IWDG_STOP

DBG_WWDG_STOP

DBG_RTC_STOP

Res.

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

Power-on reset (POR): 0x0000 0000 (not reset by system reset)

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_I2CFMP_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

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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
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

Reserved, must be kept at reset value.

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 when the core is halted

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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)
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.

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.

Res.

Res.

DBG_TIM1_STOP

rw

DBG_TIM8_STOP

DBG_TIM9_STOP

29

DBG_TIM10_STOP

30

DBG_TIM11_STOP

31

rw

rw

Bits 31:19

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 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 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 when the core is halted

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33.17

TPIU (trace port interface unit)

33.17.1

Introduction
The TPIU acts as a bridge between the on-chip trace data from the ITM and the ETM.
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 444. TPIU block diagram
TRACECLKIN domain

CLK domain
TPIU

TRACECLKIN
ETM

Asynchronous
FIFO

TRACECK
TPIU
formatter

ITM

Asynchronous
FIFO

Trace out
(serializer)

TRACEDATA
[3:0]
TRACESWO

External PPB bus

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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 242. Asynchronous TRACE pin assignment
Trace synchronous mode
TPUI pin name
Type

TRACESWO

O

Description
TRACE Async Data Output(1)

1. Refer to the Alternate function mapping table in the datasheet

•

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 243. Synchronous TRACE pin assignment
Trace synchronous mode
TPUI pin name
Type

Description

TRACECK

O

TRACE Clock(1)

TRACED[3:0]

O

TRACE Sync Data Outputs(1)
Can be 1, 2 or 4.

1. Refer to the Alternate function mapping table in the datasheet

TPUI TRACE pin assignment
By default, these pins are NOT assigned. They can be assigned by setting the
TRACE_IOEN and TRACE_MODE bits in the Debug MCU 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_IOEN and
TRACE_MODE[1:0] of the Debug MCU configuration Register (DBGMCU_CR). By default
the TRACE pins are not assigned.

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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.
Table 244. Flexible TRACE pin assignment

DBGMCU_CR
register
TRACE
TRACE
_MODE
_IOEN
[1:0]

TRACE IO pin assigned
Pins
assigned
for:

PE2/
TRACED[0] TRACED[1] TRACED[2] TRACED[3]
PB3 /JTDO/
(1)
(1)
(1)
(1)
TRACESWO TRACECK

0

XX

No Trace
Released (2)
(default state)

1

00

Asynchronous
TRACESWO
Trace

1

01

Synchronous
Trace 1 bit

TRACECK TRACED[0]

1

10

Synchronous
Trace 2 bit

Released (2) TRACECK TRACED[0] TRACED[1]

1

11

Synchronous
Trace 4 bit

-

Released
(usable as GPIO)

-

-

-

-

-

TRACECK TRACED[0] TRACED[1] TRACED[2] TRACED[3]

1. Refer to the Alternate function mapping table in the datasheets.
2. When Serial Wire mode is used, it is released. But when JTAG is used, it is assigned to JTDO.

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_IOEN 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

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TPUI formatter
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

33.17.4

TPUI frame synchronization packets
The TPUI 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.

33.17.5

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 TPUI Frame synchronization packet (0x7F_FF_FF_FF) is emitted:
•

1314/1327

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

DocID026976 Rev 3

RM0390

Debug support (DBG)
TRACE_IOEN bit in the DBGMCU_CFG register is set. In this case, the word
0x7F_FF_FF_FF is not followed by any formatted packet.
•

33.17.6

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 TPUI (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.

33.17.7

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.
TRACESWO is multiplexed with JTDO when using the SW-DP pin. This way, this
functionality is available in all STM32F446xx 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%.

33.17.8

TRACECLKIN connection in STM32F446xx
In the STM32F446xx, this TRACECLKIN input is internally connected to HCLK. This means
that when in asynchronous trace mode, the application is restricted to use to 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 STM32F446xx 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_IOEN 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.

33.17.9

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).
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1317

Debug support (DBG)

RM0390
Table 245. 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®-M4 with FPU, always read as 0x00000008

33.17.10 Example of configuration

1316/1327

•

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

DocID026976 Rev 3

0xE004
200C
DBGMCU_
APB2_FZ
X
X
X

DBGMCU_CR
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0
0
0

0
0

DocID026976 Rev 3
DBG_IWDG_STOP
DBG_WWDG_STOP
DBG_I2C3_SMBUS_TIMEOUT
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

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
DBG_TIM8_STOP
DBG_TIM1_STOP

0
0

Res.

Res.

Res.

Res.

0

X
X

Res.

X
X
X
X

0
0
0

Res.

DBG_STOP

X

DBG_SLEEP

X

X

DBG_STANDBY

X

Res.

X

TRACE_
MODE
[1:0]
TRACE_

Res.

X

Res.

X

Res.

Res.

Res.

Res.

DBG_I2C2_SMBUS_TIMEOUT
Res.

0

Res.

X

Res.

Res.

Res.

Res.

Res.

REV_ID

Res.

X

DBG_TIM8_STOP

X

Res.

X

DBG_TIM5_STOP

X

Res.

X

DBG_TIM9_STOP
Res.

DBG_TIM10_STOP

X

DBG_TIM6_STOP

0

Res.

X

Res.

0

Res.

X

DBG_TIM7_STOP

DBG_I2C2_SMBUS_TIMEOUT

0

Res.

X

Res.

DBG_I2C3_SMBUS_TIMEOUT

0

Res.

X

DBG_I2C1_SMBUS_TIMEOUT
Res.

Reserved

0

Res.

Reset value

Res.

DBG_CAN1_STOP

0

Res.

Res.
DBG_CAN2_STOP

Reset value

Res.

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.

33.18

Res.

RM0390
Debug support (DBG)

DBG register map

.
Table 246. 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 33.6.1: MCU device ID code.

1317/1327

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Device electronic signature

34

RM0390

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 STM32F446xx microcontrollers.

34.1

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: 0x1FFF 7A10
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

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

20

19

18

17

16

U_ID(31:16)

U_ID(15:0)
r

r

r

r

r

r

r

r

r

Bits 31:0 U_ID(31:0): 31:0 unique ID bits

Address offset: 0x04
Read only = 0xXXXX XXXX where X is factory-programmed
31

30

29

28

27

26

25

24

23

22

21

U_ID(63:48)
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

U_ID(47:32)
r

r

Bits 31:0 U_ID(63:32): 63:32 unique ID bits

1318/1327

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RM0390

Device electronic signature
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

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

U_ID(95:80)

U_ID(79:64)
r

r

r

r

r

r

r

r

r

Bits 31:0 U_ID(95:64): 95:64 Unique ID bits.

34.2

Flash size
Base address: 0x1FFF 7A22
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, 0x0200 corresponds to 512 Kbytes.

34.3

Package data register
Base address: 0x1FFF7BF0
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]
r

r

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

r

Bits 15:11 Reserved, must be kept at reset value.
Bits 10:8 PKG[2:0]: Package type
0x011: LQFP144, UFBGA144 (7x7) and UFBGA144 (10x10) packages
0x010: WLCSP81 package
0x001: LQFP100 package
0x000: LQFP64 package
Bits 7:0 Reserved, must be kept at reset value.

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1319

Revision history

35

RM0390

Revision history
Table 247. Document revision history
Date

Revision

17-Mar-2015

1

Initial release.

2

Updated Section 5.1.2: Battery backup domain.
Updated Table 19: Standby mode entry and exit.
Updated Section 6.3.2: RCC PLL configuration register (RCC_PLLCFGR),
Section 6.3.23: RCC PLLI2S configuration register (RCC_PLLI2SCFGR)
and Section 6.3.24: RCC PLL configuration register (RCC_PLLSAICFGR).
Updated Section 11.3: AHB interface, Section 11.4.3: SDRAM address
mapping, Section 11.5.4: NOR Flash/PSRAM controller asynchronous
transactions, Section 11.5.6: NOR/PSRAM controller registers,
SRAM/NOR-Flash write timing registers 1..4 (FMC_BWTR1..4), FIFO
status and interrupt register (FMC_SR), Common memory space timing
register 2..4 (FMC_PMEM) and Attribute memory space timing registers
(FMC_PATT), SDRAM initialization.
Updated Table 74: Programmable NAND Flash access parameters.
Updated figures 31, 42, 43, 44 and 45 in Section 11.
Updated footnote 5 of Figure 52, and added footnote 2 to Figure 51 and
footnote 1 to Figure 90.
Updated Section 12.5.7: QUADSPI address register (QUADSPI_AR).
Updated Section 13.2: ADC main features and Section 13.13.2: ADC
control register 1 (ADC_CR1).
Updated figures 109, 138, 152 and Input capture mode in Section 16.
Updated Figure 182, Section 17.4.3: TIMx slave mode control register
(TIMx_SMCR) and Input capture mode in Section 17.
Updated Table 115: TIMx internal trigger connections and Input capture
mode in Section 18.
Updated Figure 237: Watchdog block diagram and Section 21.4: How to
program the watchdog timeout.
Updated Section 22.6.4: RTC initialization and status register (RTC_ISR).
Updated Section 23.7.5: Timing register (FMPI2C_TIMINGR).
Updated Section 24.6.2: I2C Control register 2 (I2C_CR2).
Added Section 25.3: USART implementation.
Updated tables in Section 25.4.4: Fractional baud rate generation.
Updated figures 304, 305, 306 and 307, and their footnotes in
Section 26.3: SPI functional description.
Updated Section 29.1: SDIO main features, Section 29.3: SDIO functional
description, Section 29.8.1: SDIO power control register (SDIO_POWER),
Section 29.8.2: SDIO clock control register (SDIO_CLKCR) and
Section 29.8.4: SDIO command register (SDIO_CMD).
Updated Section 30.7.4: Identifier filtering, CAN filter mode register
(CAN_FM1R), CAN filter scale register (CAN_FS1R), CAN filter FIFO
assignment register (CAN_FFA1R), CAN filter activation register
(CAN_FA1R) and Section 30.9.5: bxCAN register map.
Updated Section 31.15.5: OTG reset register (OTG_GRSTCTL).
Updated Section 33.6.1: MCU device ID code and Section 33.6.3:
Cortex®-M4 with FPU TAP.

12-Jan-2016

1320/1327

Changes

DocID026976 Rev 3

RM0390

Revision history
Table 247. Document revision history (continued)
Date

04-Jul-2017

Revision

Changes

3

Updated Section 1.1: List of abbreviations for registers.
Updated Section 5.4.2: PWR power control/status register (PWR_CSR).
Replaced former Section 9.3.1: General description with Section 9.3.1:
DMA block diagram and Section 9.3.1: DMA block diagram.
Updated Section 11.1: FMC main features, SRAM/NOR-Flash chip-select
timing registers 1..4 (FMC_BTR1..4), Common memory space timing
register 2..4 (FMC_PMEM), Attribute memory space timing registers
(FMC_PATT) and SDRAM Control registers 1,2 (FMC_SDCR1,2).
Updated Table 54: FMC_BCRx bit fields and Table 72: FMC_BCRx bit
fields.
Updated Figure 38: Mode2 write access waveforms and Figure 51: NAND
Flash controller waveforms for common memory access.
Added Section 12.3.2: QUADSPI pins.
Updated Section 12.3.7: QUADSPI memory-mapped mode,
Section 12.3.13: QUADSPI error management and Section 12.5.1:
QUADSPI control register (QUADSPI_CR).
Updated notes in Section 13.13.7: ADC watchdog higher threshold register
(ADC_HTR) and Section 13.13.8: ADC watchdog lower threshold register
(ADC_LTR).
Removed former Section 15.3: DCMI pins and added Section 15.4.1:
DCMI block diagram.
Updated Table 96: DCMI external signals.
Changed D, PIXCLK, HSYNC and VSYNC with, respectively, DCMI_D,
DCMI_HSYNC, DCMI_VSYNC and DCMI_VSYNC in Section 15: Digital
camera interface (DCMI).
Updated FMPI2C master initialization, Section 23.7.2: Control register 2
(FMPI2C_CR2), Section 23.7.3: Own address 1 register (FMPI2C_OAR1),
Section 23.7.4: Own address 2 register (FMPI2C_OAR2) and
Section 23.7.5: Timing register (FMPI2C_TIMINGR).
Updated Figure 246: Slave initialization flowchart.
Updated Section 25.6.1: Status register (USART_SR).
Updated Section 26.1: Introduction, Section 26.3.7: SPI configuration and
notes in Resetting the SPIx_TXCRC and SPIx_RXCRC values and in
Section 26.7.1: SPI control register 1 (SPI_CR1) (not used in I2S mode).
Added Section 26.6.2: I2S full-duplex.
Updated Section 27.2: SPDIFRX main features, Section 27.3: SPDIFRX
functional description, Section 27.5.1: Control register (SPDIFRX_CR) and
Section 27.5.3: Status register (SPDIFRX_SR).
Added Section 27.3.10: Symbol clock generation, Section 27.3.11: DMA
Interface, Section 27.5.10: SPDIFRX version register (SPDIFRX_VERR),
Section 27.5.11: SPDIFRX identification register (SPDIFRX_IDR) and
Section 27.5.12: SPDIFRX size identification register (SPDIFRX_SIDR).
Updated Table 168: SPDIFRX interface register map and reset values.

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1321/1327
1322

Revision history

RM0390
Table 247. Document revision history (continued)

Date

04-Jul-2017

1322/1327

Revision

Changes

3
cont’d

Added Section 28.3.2: SAI pins and internal signals and updated
Section 28.3.8: SAI clock generator, Section 28.3.9: Internal FIFOs,
Section 28.5.1: Global configuration register (SAI_GCR), Section 28.5.2:
Configuration register 1 (SAI_ACR1 / SAI_BCR1).
Updated Figure 353: Functional block diagram and Figure 359: Audio
block clock generator overview.
Updated Table 172: Example of possible audio frequency sampling range
and Table 176: SAI interrupt sources.
Updated Section 31.1: Introduction, Section 31.2.3: Peripheral-mode
features, Section 31.9: Power options, Section 31.11.3: FIFO RAM
allocation, Section 31.15.1: OTG control and status register
(OTG_GOTGCTL), Section 31.15.3: OTG AHB configuration register
(OTG_GAHBCFG), Section 31.15.4: OTG USB configuration register
(OTG_GUSBCFG), Section 31.15.5: OTG reset register
(OTG_GRSTCTL), Section 31.15.6: OTG core interrupt register
(OTG_GINTSTS), Section 31.15.9: OTG Receive FIFO size register
(OTG_GRXFSIZ), Section 31.15.11: OTG non-periodic transmit
FIFO/queue status register (OTG_HNPTXSTS), Section 31.15.13: OTG
general core configuration register (OTG_GCCFG), Section 31.15.17:
OTG device IN endpoint transmit FIFO size register (OTG_DIEPTXFx)
(x = 1..5[FS] /8[HS], where x is the FIFO_number), Section 31.15.37: OTG
device OUT endpoint common interrupt mask register (OTG_DOEPMSK),
Section 31.15.47: OTG device endpoint-x control register
(OTG_DIEPCTLx) (x = 1..5[FS] / 0..8[HS], where x = Endpoint_number),
Section 31.15.49: OTG device endpoint-x control register
(OTG_DOEPCTLx) (x = 1..5[FS] /8[HS], where x = Endpoint_number),
Section 31.15.50: OTG device endpoint-x interrupt register
(OTG_DIEPINTx) (x = 0..5[FS] /8[HS], where x = Endpoint_number),
Section 31.15.51: OTG device endpoint-x interrupt register
(OTG_DOEPINTx) (x = 0..5[FS] /8[HS], where x = Endpoint_number),
Section 31.15.56: OTG device IN endpoint-x transfer size register
(OTG_DIEPTSIZx) (x = 1..5[FS] /8[HS], where x= Endpoint_number),
Section 31.15.57: OTG device IN endpoint transmit FIFO status register
(OTG_DTXFSTSx) (x = 0..5[FS] /8[HS], where x = Endpoint_number),
Section 31.15.58: OTG device OUT endpoint-x transfer size register
(OTG_DOEPTSIZx) (x = 1..5[FS] /8[HS], where x = Endpoint_number),
Section 31.16.3: Device initialization, Section 31.16.4: DMA mode,
Section 31.16.5: Host programming model and Section 31.16.6: Device
programming model.
Added Section 31.15.15: OTG core LPM configuration register
(OTG_GLPMCFG) and Section 31.15.53: OTG Device channel-x DMA
address register (OTG_DIEPDMAx) (x = 0..15, where x=
Channel_number).
Added Table 214: OTG_HS speeds supported and Table 215: OTG_FS
speeds supported.
Updated Table 216: Core global control and status registers (CSRs),
Table 218: Device-mode control and status registers and Table 224:
OTG_FS/OTG_HS register map and reset values.
Updated Section 32.1: Introduction.
Added Section 32.3.2: HDMI-CEC block diagram.

DocID026976 Rev 3

Index

Index
A
ADC_CCR . . . . . . . . . . . . . . . . . . . . . . . . . . .394
ADC_CDR . . . . . . . . . . . . . . . . . . . . . . . . . . .397
ADC_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . . .383
ADC_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . .385
ADC_CSR . . . . . . . . . . . . . . . . . . . . . . . . . . .393
ADC_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . .393
ADC_HTR . . . . . . . . . . . . . . . . . . . . . . . . . . .388
ADC_JDRx . . . . . . . . . . . . . . . . . . . . . . . . . . .392
ADC_JOFRx . . . . . . . . . . . . . . . . . . . . . . . . .388
ADC_JSQR . . . . . . . . . . . . . . . . . . . . . . . . . .392
ADC_LTR . . . . . . . . . . . . . . . . . . . . . . . . . . . .389
ADC_SMPR1 . . . . . . . . . . . . . . . . . . . . . . . . .387
ADC_SMPR2 . . . . . . . . . . . . . . . . . . . . . . . . .387
ADC_SQR1 . . . . . . . . . . . . . . . . . . . . . . . . . .389
ADC_SQR2 . . . . . . . . . . . . . . . . . . . . . . . . . .390
ADC_SQR3 . . . . . . . . . . . . . . . . . . . . . . . . . .391
ADC_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . . .382

C
CAN_BTR . . . . . . . . . . . . . . . . . . . . . . . . . .1066
CAN_ESR . . . . . . . . . . . . . . . . . . . . . . . . . .1065
CAN_FA1R . . . . . . . . . . . . . . . . . . . . . . . . .1076
CAN_FFA1R . . . . . . . . . . . . . . . . . . . . . . . .1075
CAN_FiRx . . . . . . . . . . . . . . . . . . . . . . . . . .1077
CAN_FM1R . . . . . . . . . . . . . . . . . . . . . . . . .1075
CAN_FMR . . . . . . . . . . . . . . . . . . . . . . . . . .1074
CAN_FS1R . . . . . . . . . . . . . . . . . . . . . . . . .1075
CAN_IER . . . . . . . . . . . . . . . . . . . . . . . . . . .1064
CAN_MCR . . . . . . . . . . . . . . . . . . . . . . . . . .1057
CAN_MSR . . . . . . . . . . . . . . . . . . . . . . . . . .1059
CAN_RDHxR . . . . . . . . . . . . . . . . . . . . . . . .1073
CAN_RDLxR . . . . . . . . . . . . . . . . . . . . . . . .1073
CAN_RDTxR . . . . . . . . . . . . . . . . . . . . . . . .1072
CAN_RF0R . . . . . . . . . . . . . . . . . . . . . . . . .1062
CAN_RF1R . . . . . . . . . . . . . . . . . . . . . . . . .1063
CAN_RIxR . . . . . . . . . . . . . . . . . . . . . . . . . .1071
CAN_TDHxR . . . . . . . . . . . . . . . . . . . . . . . .1070
CAN_TDLxR . . . . . . . . . . . . . . . . . . . . . . . .1070
CAN_TDTxR . . . . . . . . . . . . . . . . . . . . . . . .1069
CAN_TIxR . . . . . . . . . . . . . . . . . . . . . . . . . .1068
CAN_TSR . . . . . . . . . . . . . . . . . . . . . . . . . .1060
CEC_CFGR . . . . . . . . . . . . . . . . . . . . . . . . .1277
CEC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . .1276
CEC_IER . . . . . . . . . . . . . . . . . . . . . . . . . . .1282
CEC_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . .1280
CEC_RXDR . . . . . . . . . . . . . . . . . . . . . . . . .1280

CEC_TXDR . . . . . . . . . . . . . . . . . . . . . . . . . 1280
CKGATENR . . . . . . . . . . . . . . . . . . . . . . . . . 168
CRC_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
CRC_IDR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

D
DAC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
DAC_DHR12L1 . . . . . . . . . . . . . . . . . . . . . . . 416
DAC_DHR12L2 . . . . . . . . . . . . . . . . . . . . . . . 417
DAC_DHR12LD . . . . . . . . . . . . . . . . . . . . . . 418
DAC_DHR12R1 . . . . . . . . . . . . . . . . . . . . . . 415
DAC_DHR12R2 . . . . . . . . . . . . . . . . . . . . . . 417
DAC_DHR12RD . . . . . . . . . . . . . . . . . . . . . . 418
DAC_DHR8R1 . . . . . . . . . . . . . . . . . . . . . . . 416
DAC_DHR8R2 . . . . . . . . . . . . . . . . . . . . . . . 417
DAC_DHR8RD . . . . . . . . . . . . . . . . . . . . . . . 419
DAC_DOR1 . . . . . . . . . . . . . . . . . . . . . . . . . . 419
DAC_DOR2 . . . . . . . . . . . . . . . . . . . . . . . . . . 419
DAC_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
DAC_SWTRIGR . . . . . . . . . . . . . . . . . . . . . . 415
DBGMCU_APB1 . . . . . . . . . . . . . . . . . . . . . 1308
DBGMCU_APB2_FZ . . . . . . . . . . . . . . . . . . 1310
DBGMCU_CR . . . . . . . . . . . . . . . . . . . . . . . 1306
DBGMCU_IDCODE . . . . . . . . . . . . . . . . . . 1291
DCMI_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . 434
DCMI_CWSIZE . . . . . . . . . . . . . . . . . . . . . . . 445
DCMI_CWSTRT . . . . . . . . . . . . . . . . . . . . . . 445
DCMI_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
DCMI_ESCR . . . . . . . . . . . . . . . . . . . . . . . . . 443
DCMI_ESUR . . . . . . . . . . . . . . . . . . . . . . . . . 444
DCMI_ICR . . . . . . . . . . . . . . . . . . . . . . . . . . . 442
DCMI_IER . . . . . . . . . . . . . . . . . . . . . . . . . . . 440
DCMI_MIS . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
DCMI_RIS . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
DCMI_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
DMA_HIFCR . . . . . . . . . . . . . . . . . . . . . . . . . 225
DMA_HISR . . . . . . . . . . . . . . . . . . . . . . . . . . 224
DMA_LIFCR . . . . . . . . . . . . . . . . . . . . . . . . . 225
DMA_LISR . . . . . . . . . . . . . . . . . . . . . . . . . . 223
DMA_SxCR . . . . . . . . . . . . . . . . . . . . . . . . . . 226
DMA_SxFCR . . . . . . . . . . . . . . . . . . . . . . . . . 231
DMA_SxM0AR . . . . . . . . . . . . . . . . . . . . . . . 230
DMA_SxM1AR . . . . . . . . . . . . . . . . . . . . . . . 230
DMA_SxNDTR . . . . . . . . . . . . . . . . . . . . . . . 229
DMA_SxPAR . . . . . . . . . . . . . . . . . . . . . . . . . 230

DocID026976 Rev 3

1323/1327

Index

E

GPIOx_PUPDR . . . . . . . . . . . . . . . . . . . . . . . 188

EXTI_EMR . . . . . . . . . . . . . . . . . . . . . . . . . . .245
EXTI_FTSR . . . . . . . . . . . . . . . . . . . . . . . . . .246
EXTI_IMR . . . . . . . . . . . . . . . . . . . . . . . . . . . .245
EXTI_PR . . . . . . . . . . . . . . . . . . . . . . . . . . . .247
EXTI_RTSR . . . . . . . . . . . . . . . . . . . . . . . . . .246
EXTI_SWIER . . . . . . . . . . . . . . . . . . . . . . . . .247

F
FLASH_ACR . . . . . . . . . . . . . . . . . . . . . . . . . .79
FLASH_FCR . . . . . . . . . . . . . . . . . . . . . . . . . .82
FLASH_FKEYR . . . . . . . . . . . . . . . . . . . . . . . .80
FLASH_FOPTCR . . . . . . . . . . . . . . . . . . . . . . .84
FLASH_FOPTKEYR . . . . . . . . . . . . . . . . . . . .80
FLASH_FSR . . . . . . . . . . . . . . . . . . . . . . . . . .81
FMC_BCR1..4 . . . . . . . . . . . . . . . . . . . . . . . .286
FMC_BTR1..4 . . . . . . . . . . . . . . . . . . . . . . . .288
FMC_BWTR1..4 . . . . . . . . . . . . . . . . . . . . . . .291
FMC_ECCR . . . . . . . . . . . . . . . . . . . . . . . . . .304
FMC_PATT . . . . . . . . . . . . . . . . . . . . . . . . . .302
FMC_PCR . . . . . . . . . . . . . . . . . . . . . . . . . . .299
FMC_PMEM . . . . . . . . . . . . . . . . . . . . . . . . . .301
FMC_SDCMR . . . . . . . . . . . . . . . . . . . . . . . .318
FMC_SDCR1,2 . . . . . . . . . . . . . . . . . . . . . . .314
FMC_SDRTR . . . . . . . . . . . . . . . . . . . . . . . . .319
FMC_SDSR . . . . . . . . . . . . . . . . . . . . . . . . . .320
FMC_SDTR1,2 . . . . . . . . . . . . . . . . . . . . . . . .316
FMC_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . .300
FMPI2C_CR1 . . . . . . . . . . . . . . . . . . . . . . . . .742
FMPI2C_CR2 . . . . . . . . . . . . . . . . . . . . . . . . .745
FMPI2C_ICR . . . . . . . . . . . . . . . . . . . . . . . . .754
FMPI2C_ISR . . . . . . . . . . . . . . . . . . . . . . . . .752
FMPI2C_OAR1 . . . . . . . . . . . . . . . . . . . . . . .748
FMPI2C_OAR2 . . . . . . . . . . . . . . . . . . . . . . .749
FMPI2C_PECR . . . . . . . . . . . . . . . . . . . . . . .755
FMPI2C_RXDR . . . . . . . . . . . . . . . . . . . . . . .756
FMPI2C_TIMEOUTR . . . . . . . . . . . . . . . . . . .751
FMPI2C_TIMINGR . . . . . . . . . . . . . . . . . . . . .750
FMPI2C_TXDR . . . . . . . . . . . . . . . . . . . . . . .756

G
GPIOx_AFRH . . . . . . . . . . . . . . . . . . . . . . . . .191
GPIOx_AFRL . . . . . . . . . . . . . . . . . . . . . . . . .191
GPIOx_BSRR . . . . . . . . . . . . . . . . . . . . . . . .189
GPIOx_IDR . . . . . . . . . . . . . . . . . . . . . . . . . .188
GPIOx_LCKR . . . . . . . . . . . . . . . . . . . . . . . . .189
GPIOx_MODER . . . . . . . . . . . . . . . . . . . . . . .186
GPIOx_ODR . . . . . . . . . . . . . . . . . . . . . . . . .189
GPIOx_OSPEEDR . . . . . . . . . . . . . . . . . . . . .187
GPIOx_OTYPER . . . . . . . . . . . . . . . . . . . . . .187

1324/1327

I
I2C_CCR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 790
I2C_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780
I2C_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782
I2C_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 785
I2C_OAR1 . . . . . . . . . . . . . . . . . . . . . . . 748, 784
I2C_OAR2 . . . . . . . . . . . . . . . . . . . . . . . 749, 784
I2C_SR1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 785
I2C_SR2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 789
I2C_TIMEOUTR . . . . . . . . . . . . . . . . . . . . . . 751
I2C_TIMINGR . . . . . . . . . . . . . . . . . . . . . . . . 750
I2C_TRISE . . . . . . . . . . . . . . . . . . . . . . . . . . 791
I2Cx_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 745
IWDG_KR . . . . . . . . . . . . . . . . . . . . . . . . . . . 642
IWDG_PR . . . . . . . . . . . . . . . . . . . . . . . . . . . 643
IWDG_RLR . . . . . . . . . . . . . . . . . . . . . . . . . . 644
IWDG_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . 644

O
OTG_CID . . . . . . . . . . . . . . . . . . . . . . . . . . 1141
OTG_DAINT . . . . . . . . . . . . . . . . . . . . . . . . 1168
OTG_DAINTMSK . . . . . . . . . . . . . . . . . . . . 1169
OTG_DCFG . . . . . . . . . . . . . . . . . . . . . . . . 1160
OTG_DCTL . . . . . . . . . . . . . . . . . . . . . . . . . 1162
OTG_DEACHINT . . . . . . . . . . . . . . . . . . . . 1172
OTG_DEACHINTMSK . . . . . . . . . . . . . . . . 1173
OTG_DIEPCTL0 . . . . . . . . . . . . . . . . . . . . . 1173
OTG_DIEPCTLx . . . . . . . . . . . . . . . . . . . . . 1175
OTG_DIEPEMPMSK . . . . . . . . . . . . . . . . . . 1172
OTG_DIEPINTx . . . . . . . . . . . . . . . . . . . . . . 1181
OTG_DIEPMSK . . . . . . . . . . . . . . . . . . . . . 1166
OTG_DIEPTSIZ0 . . . . . . . . . . . . . . . . . . . . 1184
OTG_DIEPTSIZx . . . . . . . . . . . . . . . . 1184-1186
OTG_DIEPTXF0 . . . . . . . . . . . . . . . . . . . . . 1137
OTG_DIEPTXFx . . . . . . . . . . . . . . . . . . . . . 1145
OTG_DOEPCTL0 . . . . . . . . . . . . . . . . . . . . 1177
OTG_DOEPCTLx . . . . . . . . . . . . . . . . . . . . 1179
OTG_DOEPINTx . . . . . . . . . . . . . . . . . . . . . 1183
OTG_DOEPMSK . . . . . . . . . . . . . . . . . . . . . 1167
OTG_DOEPTSIZ0 . . . . . . . . . . . . . . . . . . . . 1185
OTG_DOEPTSIZx . . . . . . . . . . . . . . . . . . . . 1188
OTG_DSTS . . . . . . . . . . . . . . . . . . . . . . . . . 1165
OTG_DTHRCTL . . . . . . . . . . . . . . . . . . . . . 1171
OTG_DTXFSTSx . . . . . . . . . . . . . . . . . . . . 1187
OTG_DVBUSDIS . . . . . . . . . . . . . . . . . . . . 1170
OTG_DVBUSPULSE . . . . . . . . . . . . . . . . . 1170
OTG_GAHBCFG . . . . . . . . . . . . . . . . . . . . . 1118
OTG_GCCFG . . . . . . . . . . . . . . . . . . . . . . . 1140
OTG_GI2CCTL . . . . . . . . . . . . . . . . . . . . . . 1139

DocID026976 Rev 3

Index
OTG_GINTMSK . . . . . . . . . . . . . . . . . . . . . .1131
OTG_GINTSTS . . . . . . . . . . . . . . . . . . . . . .1126
OTG_GLPMCFG . . . . . . . . . . . . . . . . . . . . .1141
OTG_GOTGCTL . . . . . . . . . . . . . . . . . . . . .1114
OTG_GOTGINT . . . . . . . . . . . . . . . . . . . . . .1117
OTG_GRSTCTL . . . . . . . . . . . . . . . . . . . . . .1124
OTG_GRXFSIZ . . . . . . . . . . . . . . . . . . . . . .1136
OTG_GRXSTSP . . . . . . . . . . . . . . . . . . . . .1135
OTG_GRXSTSR . . . . . . . . . . . . . . . . . . . . .1135
OTG_GUSBCFG . . . . . . . . . . . . . . . . . . . . .1120
OTG_HAINT . . . . . . . . . . . . . . . . . . . . . . . . .1149
OTG_HAINTMSK . . . . . . . . . . . . . . . . . . . . .1150
OTG_HCCHARx . . . . . . . . . . . . . . . . . . . . .1153
OTG_HCDMAx . . . . . . . . . . . . . . . . . . . . . .1160
OTG_HCFG . . . . . . . . . . . . . . . . . . . . . . . . .1146
OTG_HCINTMSKx . . . . . . . . . . . . . . . . . . . .1157
OTG_HCINTx . . . . . . . . . . . . . . . . . . . . . . . .1155
OTG_HCSPLTx . . . . . . . . . . . . . . . . . . . . . .1154
OTG_HCTSIZx . . . . . . . . . . . . . . . . . . . . . . .1158
OTG_HFIR . . . . . . . . . . . . . . . . . . . . . . . . . .1147
OTG_HFNUM . . . . . . . . . . . . . . . . . . . . . . .1148
OTG_HNPTXFSIZ . . . . . . . . . . . . . . . . . . . .1137
OTG_HNPTXSTS . . . . . . . . . . . . . . . . . . . .1138
OTG_HPRT . . . . . . . . . . . . . . . . . . . . . . . . .1150
OTG_HPTXFSIZ . . . . . . . . . . . . . . . . . . . . .1145
OTG_HPTXSTS . . . . . . . . . . . . . . . . . . . . . .1148
OTG_PCGCCTL . . . . . . . . . . . . . . . . . . . . .1189

P
PWR_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
PWR_CSR . . . . . . . . . . . . . . . . . . . . . . . . . . .112

Q
QUADSPI _PIR . . . . . . . . . . . . . . . . . . . . . . .351
QUADSPI _PSMAR . . . . . . . . . . . . . . . . . . . .350
QUADSPI _PSMKR . . . . . . . . . . . . . . . . . . . .350
QUADSPI_ABR . . . . . . . . . . . . . . . . . . . . . . .349
QUADSPI_AR . . . . . . . . . . . . . . . . . . . . . . . .348
QUADSPI_CCR . . . . . . . . . . . . . . . . . . . . . . .346
QUADSPI_CR . . . . . . . . . . . . . . . . . . . . . . . .340
QUADSPI_DCR . . . . . . . . . . . . . . . . . . . . . . .343
QUADSPI_DLR . . . . . . . . . . . . . . . . . . . . . . .345
QUADSPI_DR . . . . . . . . . . . . . . . . . . . . . . . .349
QUADSPI_FCR . . . . . . . . . . . . . . . . . . . . . . .345
QUADSPI_LPTR . . . . . . . . . . . . . . . . . . . . . .351
QUADSPI_SR . . . . . . . . . . . . . . . . . . . . . . . .344

R
RCC_AHB1ENR . . . . . . . . . . . . . . . . . . . . . .143
RCC_AHB1LPENR . . . . . . . . . . . . . . . . . . . .150

RCC_AHB1RSTR . . . . . . . . . . . . . . . . . . . . . 135
RCC_AHB2ENR . . . . . . . . . . . . . . . . . . . . . . 144
RCC_AHB2LPENR . . . . . . . . . . . . . . . . . . . . 152
RCC_AHB2RSTR . . . . . . . . . . . . . . . . . . . . . 137
RCC_AHB3ENR . . . . . . . . . . . . . . . . . . . . . . 145
RCC_AHB3LPENR . . . . . . . . . . . . . . . . . . . . 153
RCC_AHB3RSTR . . . . . . . . . . . . . . . . . . . . . 137
RCC_APB1ENR . . . . . . . . . . . . . . . . . . . . . . 145
RCC_APB1LPENR . . . . . . . . . . . . . . . . . . . . 153
RCC_APB1RSTR . . . . . . . . . . . . . . . . . . . . . 138
RCC_APB2ENR . . . . . . . . . . . . . . . . . . . . . . 148
RCC_APB2LPENR . . . . . . . . . . . . . . . . . . . . 157
RCC_APB2RSTR . . . . . . . . . . . . . . . . . . . . . 141
RCC_BDCR . . . . . . . . . . . . . . . . . . . . . . . . . 158
RCC_CFGR . . . . . . . . . . . . . . . . . . . . . . . . . 130
RCC_CIR . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
RCC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
RCC_CSR . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
RCC_DCKCFGR . . . . . . . . . . . . . . . . . . . . . . 166
RCC_PLLCFGR . . . . . . . . . . . . . . 128, 162, 165
RCC_SSCGR . . . . . . . . . . . . . . . . . . . . . . . . 161
RTC_ALRMAR . . . . . . . . . . . . . . . . . . . . . . . 679
RTC_ALRMBR . . . . . . . . . . . . . . . . . . . . . . . 680
RTC_ALRMBSSR . . . . . . . . . . . . . . . . . . . . . 688
RTC_BKxR . . . . . . . . . . . . . . . . . . . . . . . . . . 689
RTC_CALIBR . . . . . . . . . . . . . . . . . . . . . . . . 677
RTC_CALR . . . . . . . . . . . . . . . . . . . . . . . . . . 684
RTC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672
RTC_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671
RTC_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674
RTC_PRER . . . . . . . . . . . . . . . . . . . . . . . . . . 676
RTC_SHIFTR . . . . . . . . . . . . . . . . . . . . . . . . 682
RTC_SSR . . . . . . . . . . . . . . . . . . . . . . . . . . . 681
RTC_TR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670
RTC_TSDR . . . . . . . . . . . . . . . . . . . . . . . . . . 683
RTC_TSSSR . . . . . . . . . . . . . . . . . . . . . . . . . 684
RTC_TSTR . . . . . . . . . . . . . . . . . . . . . . . . . . 683
RTC_WPR . . . . . . . . . . . . . . . . . . . . . . . . . . . 681
RTC_WUTR . . . . . . . . . . . . . . . . . . . . . . . . . 677

S
SAI_ACLRFR . . . . . . . . . . . . . . . . . . . . . . . . 975
SAI_ACR1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 964
SAI_ACR2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 967
SAI_ADR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976
SAI_AFRCR . . . . . . . . . . . . . . . . . . . . . . . . . 969
SAI_AIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 972
SAI_ASLOTR . . . . . . . . . . . . . . . . . . . . . . . . 971
SAI_ASR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 973
SAI_BCLRFR . . . . . . . . . . . . . . . . . . . . . . . . 975
SAI_BCR1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 964

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SAI_BCR2 . . . . . . . . . . . . . . . . . . . . . . . . . . .967
SAI_BDR . . . . . . . . . . . . . . . . . . . . . . . . . . . .976
SAI_BFRCR . . . . . . . . . . . . . . . . . . . . . . . . . .969
SAI_BIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . .972
SAI_BSLOTR . . . . . . . . . . . . . . . . . . . . . . . . .971
SAI_BSR . . . . . . . . . . . . . . . . . . . . . . . . . . . .973
SAI_GCR . . . . . . . . . . . . . . . . . . . . . . . . . . . .964
SDIO_ARG . . . . . . . . . . . . . . . . . . . . . . . . . .1023
SDIO_CLKCR . . . . . . . . . . . . . . . . . . . . . . .1021
SDIO_DCOUNT . . . . . . . . . . . . . . . . . . . . . .1028
SDIO_DCTRL . . . . . . . . . . . . . . . . . . . . . . .1026
SDIO_DLEN . . . . . . . . . . . . . . . . . . . . . . . . .1026
SDIO_DTIMER . . . . . . . . . . . . . . . . . . . . . . .1025
SDIO_FIFO . . . . . . . . . . . . . . . . . . . . . . . . .1034
SDIO_FIFOCNT . . . . . . . . . . . . . . . . . . . . . .1033
SDIO_ICR . . . . . . . . . . . . . . . . . . . . . . . . . .1029
SDIO_MASK . . . . . . . . . . . . . . . . . . . . . . . .1031
SDIO_POWER . . . . . . . . . . . . . . . . . . . . . . .1021
SDIO_RESPCMD . . . . . . . . . . . . . . . . . . . .1024
SDIO_RESPx . . . . . . . . . . . . . . . . . . . . . . . .1024
SDIO_STA . . . . . . . . . . . . . . . . . . . . . . . . . .1028
SPI_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .886
SPI_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .888
SPI_CRCPR . . . . . . . . . . . . . . . . . . . . . . . . . .891
SPI_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . .891
SPI_I2SCFGR . . . . . . . . . . . . . . . . . . . . . . . .893
SPI_I2SPR . . . . . . . . . . . . . . . . . . . . . . . . . . .894
SPI_RXCRCR . . . . . . . . . . . . . . . . . . . . . . . .892
SPI_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . . .889
SPI_TXCRCR . . . . . . . . . . . . . . . . . . . . . . . .892
SYSCFG_EXTICR1 . . . . . . . . . . . . . . . . . . . .196
SYSCFG_EXTICR2 . . . . . . . . . . . . . . . . . . . .197
SYSCFG_EXTICR3 . . . . . . . . . . . . . . . . . . . .198
SYSCFG_EXTICR4 . . . . . . . . . . . . . . . . . . . .198
SYSCFG_MEMRMP . . . . . . . . . . . . . . . . . . .194

TIMx_DCR . . . . . . . . . . . . . . . . . . . . . . . 516, 576
TIMx_DIER . . . . . . . . . .498, 563, 605, 618, 636
TIMx_DMAR . . . . . . . . . . . . . . . . . . . . . 517, 576
TIMx_EGR . . . . . . . . . . .501, 566, 608, 619, 637
TIMx_PSC . . . . . . . . . . .511, 573, 613, 624, 638
TIMx_RCR . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
TIMx_SMCR . . . . . . . . . . . . . . . . . 496, 561, 604
TIMx_SR . . . . . . . . . . . .500, 564, 606, 618, 637

U
USART_BRR . . . . . . . . . . . . . . . . . . . . . . . . . 838
USART_CR1 . . . . . . . . . . . . . . . . . 839, 920, 923
USART_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . 841
USART_CR3 . . . . . . . . . . . . . . . . . . . . . . . . . 842
USART_DR . . . . . . . . . . . . . . . . . . 838, 927-931
USART_GTPR . . . . . . . . . . . . . . . . . . . . . . . 844
USART_SR . . . . . . . . . . . . . . . . . . 835, 924, 926

W
WWDG_CFR . . . . . . . . . . . . . . . . . . . . . . . . . 651
WWDG_CR . . . . . . . . . . . . . . . . . . . . . . . . . . 650
WWDG_SR . . . . . . . . . . . . . . . . . . . . . . . . . . 651

T
TIM2_OR . . . . . . . . . . . . . . . . . . . . . . . . . . . .577
TIM5_OR . . . . . . . . . . . . . . . . . . . . . . . . . . . .578
TIMx_ARR . . . . . . . . . . . . . . 573, 613, 624, 638
TIMx_BDTR . . . . . . . . . . . . . . . . . . . . . . . . . .514
TIMx_CCER . . . . . . . . . . . . . 507, 571, 612, 623
TIMx_CCMR1 . . . . . . . . . . . 503, 567, 608, 620
TIMx_CCMR2 . . . . . . . . . . . . . . . . . . . .506, 570
TIMx_CCR1 . . . . . . . . . . . . . 512, 574, 614, 625
TIMx_CCR2 . . . . . . . . . . . . . . . . . 513, 574, 614
TIMx_CCR3 . . . . . . . . . . . . . . . . . . . . . .513, 575
TIMx_CCR4 . . . . . . . . . . . . . . . . . . . . . .514, 575
TIMx_CNT . . . . . . . . . . 511, 573, 613, 624, 637
TIMx_CR1 . . . . . . . . . . 493, 558, 602, 617, 634
TIMx_CR2 . . . . . . . . . . . . . . . . . . 494, 560, 636

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RM0390

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.
© 2017 STMicroelectronics – All rights reserved

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Page Count                      : 1327
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Keywords                        : Technical Literature, 026976, Product Development, Specification, Reference manual, STM32F446
Subject                         : -
Modify Date                     : 2017:07:04 15:18:44+02:00
Creator                         : C2 v4.2.0220 build 670 - c2_rendition_config : Techlit_Active
Title                           : STM32F446xx advanced ARM®-based 32-bit MCUs
Revision                        : 3
Classification                  : Unclassified
Alternate Name                  : RM0390
Alternate ID                    : 026976
Document Type                   : Reference manual
Author                          : STMICROELECTRONICS
Create Date                     : 2017:07:04 11:30:07Z

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