STM32F303xB/C/D/E, STM32F303x6/8, STM32F328x8, STM32F358xC, STM32F398xE Advanced ARM® Based MCUs Stm32f303 Reference Manual Datasheet En.DM00043574

Reference%20Manual

stm32f3ReferenceManual

reference%20manual

reference%20manual

User Manual: Pdf

Open the PDF directly: View PDF .
Page Count: 1141

Download
Open PDF In Browser	View PDF

RM0316
Reference manual
STM32F303xB/C/D/E, STM32F303x6/8, STM32F328x8,
STM32F358xC, STM32F398xE advanced ARM®-based MCUs
Introduction
This reference manual targets application developers. It provides complete information on
how to use the STM32F303xB/C/D/E, STM32F303x6/x8, STM32F328x8, STM32F358xC
and STM32F398xE microcontroller memory and peripherals. The STM32F303xB/C/D/E,
STM32F303x6/x8, STM32F328x8, STM32F358xC and STM32F398xE devices will be
referred to as STM32F3xx throughout the document, unless otherwise specified.
The STM32F3xx is a family of microcontrollers with different memory sizes, packages and
peripherals.
For ordering information, mechanical and electrical device characteristics please refer to the
relevant datasheets.
®
®
For information on the ARM CORTEX -M4 core with FPU, please refer to the
STM32F3xx/STM32F4xx programming manual (PM0214).

Related documents
• STM32F303xB/C, STM32F303xD/E, STM32F303x6/8, STM32F328x8, STM32F358xC
and STM32F398xE datasheets available from the company website at www.st.com.
®
• STM32F3xx/F4xx Cortex -M4 programming manual (PM0214) available from the
company website at www.st.com.

January 2017

DocID022558 Rev 8

1/1141
www.st.com

1

Contents

RM0316

Contents
1

Overview of the manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

2

Documentation conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3

2.1

List of abbreviations for registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

2.2

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

2.3

Peripheral availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

System and memory overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.1

3.2

3.3

System architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.1.1

S0: I-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.1.2

S1: D-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.1.3

S2: S-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.1.4

S3, S4: DMA-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.1.5

BusMatrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Memory organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.2.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

3.2.2

Memory map and register boundary addresses . . . . . . . . . . . . . . . . . . 51

Embedded SRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.3.1

Parity check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

3.3.2

CCM SRAM write protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

3.4

Flash memory overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

3.5

Boot configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.5.1

4

Embedded Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.1

Flash main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

4.2

Flash memory functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

4.3

2/1141

Embedded boot loader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

4.2.1

Flash memory organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

4.2.2

Read operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

4.2.3

Flash program and erase operations . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Memory protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.3.1

Read protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

4.3.2

Write protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

DocID022558 Rev 8

RM0316

Contents
4.3.3

Option byte block write protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4.4

Flash interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4.5

Flash register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

4.6

4.5.1

Flash access control register (FLASH_ACR) . . . . . . . . . . . . . . . . . . . . 78

4.5.2

Flash key register (FLASH_KEYR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

4.5.3

Flash option key register (FLASH_OPTKEYR) . . . . . . . . . . . . . . . . . . . 79

4.5.4

Flash status register (FLASH_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

4.5.5

Flash control register (FLASH_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

4.5.6

Flash address register (FLASH_AR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

4.5.7

Option byte register (FLASH_OBR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

4.5.8

Write protection register (FLASH_WRPR) . . . . . . . . . . . . . . . . . . . . . . . 83

Flash register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

5

Option byte description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

6

Cyclic redundancy check calculation unit (CRC) . . . . . . . . . . . . . . . . . 88
6.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

6.2

CRC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

6.3

CRC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

6.4

7

6.3.1

CRC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

6.3.2

CRC internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

6.3.3

CRC operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

CRC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
6.4.1

Data register (CRC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

6.4.2

Independent data register (CRC_IDR) . . . . . . . . . . . . . . . . . . . . . . . . . 91

6.4.3

Control register (CRC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

6.4.4

Initial CRC value (CRC_INIT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

6.4.5

CRC polynomial (CRC_POL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

6.4.6

CRC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Power control (PWR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
7.1

7.2

Power supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
7.1.1

Independent A/D and D/A converter supply and reference voltage . . . . 96

7.1.2

Battery backup domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

7.1.3

Voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

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

DocID022558 Rev 8

3/1141
28

Contents

RM0316

7.3

7.4

8

4/1141

7.2.1

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

7.2.2

Programmable voltage detector (PVD) . . . . . . . . . . . . . . . . . . . . . . . . . 99

7.2.3

External NPOR signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
7.3.1

Slowing down system clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

7.3.2

Peripheral clock gating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

7.3.3

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

7.3.4

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

7.3.5

Standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

7.3.6

Auto-wakeup from low-power mode . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Power control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
7.4.1

Power control register (PWR_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

7.4.2

Power control/status register (PWR_CSR) . . . . . . . . . . . . . . . . . . . . . 108

7.4.3

PWR register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Peripheral interconnect matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
8.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

8.2

Connection summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

8.3

Interconnection details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
8.3.1

DMA interconnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

8.3.2

From ADC to ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

8.3.3

From ADC to TIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

8.3.4

From TIM and EXTI to ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

8.3.5

From OPAMP to ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

8.3.6

From TS to ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

8.3.7

From VBAT to ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

8.3.8

From VREFINT to ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

8.3.9

From COMP to TIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

8.3.10

From TIM to COMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

8.3.11

From DAC to COMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

8.3.12

From VREFINT to COMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

8.3.13

From DAC to OPAMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

8.3.14

From TIM to OPAMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

8.3.15

From TIM to TIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

8.3.16

From break input sources to TIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

8.3.17

From HSE, HSI, LSE, LSI, MCO, RTC to TIM . . . . . . . . . . . . . . . . . . . 121

8.3.18

From TIM and EXTI to DAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
DocID022558 Rev 8

RM0316

Contents
8.3.19

9

From TIM to IRTIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Reset and clock control (RCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
9.1

9.2

Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
9.1.1

Power reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

9.1.2

System reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

9.1.3

RTC domain reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
9.2.1

HSE clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

9.2.2

HSI clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

9.2.3

PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

9.2.4

LSE clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

9.2.5

LSI clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

9.2.6

System clock (SYSCLK) selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

9.2.7

Clock security system (CSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

9.2.8

ADC clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

9.2.9

RTC clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

9.2.10

Timers (TIMx) clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

9.2.11

Watchdog clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

9.2.12

I2S clock (only in STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

9.2.13

Clock-out capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

9.2.14

Internal/external clock measurement with TIM16 . . . . . . . . . . . . . . . . 135

9.3

Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

9.4

RCC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
9.4.1

Clock control register (RCC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

9.4.2

Clock configuration register (RCC_CFGR) . . . . . . . . . . . . . . . . . . . . . 138

9.4.3

Clock interrupt register (RCC_CIR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

9.4.4

APB2 peripheral reset register (RCC_APB2RSTR) . . . . . . . . . . . . . . 144

9.4.5

APB1 peripheral reset register (RCC_APB1RSTR) . . . . . . . . . . . . . . 146

9.4.6

AHB peripheral clock enable register (RCC_AHBENR) . . . . . . . . . . . 148

9.4.7

APB2 peripheral clock enable register (RCC_APB2ENR) . . . . . . . . . . 150

9.4.8

APB1 peripheral clock enable register (RCC_APB1ENR) . . . . . . . . . . 152

9.4.9

RTC domain control register (RCC_BDCR) . . . . . . . . . . . . . . . . . . . . . 155

9.4.10

Control/status register (RCC_CSR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

9.4.11

AHB peripheral reset register (RCC_AHBRSTR) . . . . . . . . . . . . . . . . 158

9.4.12

Clock configuration register 2 (RCC_CFGR2) . . . . . . . . . . . . . . . . . . . 159

DocID022558 Rev 8

5/1141
28

Contents

10

RM0316
9.4.13

Clock configuration register 3 (RCC_CFGR3) . . . . . . . . . . . . . . . . . . . 162

9.4.14

RCC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

Flexible static memory controller (FSMC) . . . . . . . . . . . . . . . . . . . . . 168
10.1

FMC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

10.2

Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

10.3

AHB interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
10.3.1

10.4

10.5

10.6

10.7

11

6/1141

Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . 170

External device address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
10.4.1

NOR/PSRAM address mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

10.4.2

NAND Flash memory/PC Card address mapping . . . . . . . . . . . . . . . . 173

NOR Flash/PSRAM controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
10.5.1

External memory interface signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

10.5.2

Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . 177

10.5.3

General timing rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

10.5.4

NOR Flash/PSRAM controller asynchronous transactions . . . . . . . . . 179

10.5.5

Synchronous transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

10.5.6

NOR/PSRAM controller registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

NAND Flash/PC Card controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
10.6.1

External memory interface signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

10.6.2

NAND Flash / PC Card supported memories and transactions . . . . . . 213

10.6.3

Timing diagrams for NAND Flash memory and PC Card . . . . . . . . . . 213

10.6.4

NAND Flash operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

10.6.5

NAND Flash prewait functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

10.6.6

Computation of the error correction code (ECC)
in NAND Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

10.6.7

PC Card/CompactFlash operations . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

10.6.8

NAND Flash/PC Card controller registers . . . . . . . . . . . . . . . . . . . . . . 219

FMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

General-purpose I/Os (GPIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
11.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

11.2

GPIO main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

11.3

GPIO functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
11.3.1

General-purpose I/O (GPIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

11.3.2

I/O pin alternate function multiplexer and mapping . . . . . . . . . . . . . . . 231

DocID022558 Rev 8

RM0316

Contents
11.3.3

I/O port control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

11.3.4

I/O port data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

11.3.5

I/O data bitwise handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

11.3.6

GPIO locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

11.3.7

I/O alternate function input/output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

11.3.8

External interrupt/wakeup lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

11.3.9

Input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

11.3.10 Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
11.3.11

Alternate function configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

11.3.12 Analog configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
11.3.13 Using the HSE or LSE oscillator pins as GPIOs . . . . . . . . . . . . . . . . . 236
11.3.14 Using the GPIO pins in the RTC supply domain . . . . . . . . . . . . . . . . . 236

11.4

GPIO registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
11.4.1

GPIO port mode register (GPIOx_MODER) (x =A..H) . . . . . . . . . . . . . 237

11.4.2

GPIO port output type register (GPIOx_OTYPER) (x = A..H) . . . . . . . 237

11.4.3

GPIO port output speed register (GPIOx_OSPEEDR)
(x = A..H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

11.4.4

GPIO port pull-up/pull-down register (GPIOx_PUPDR)
(x = A..H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

11.4.5

GPIO port input data register (GPIOx_IDR) (x = A..H) . . . . . . . . . . . . 239

11.4.6

GPIO port output data register (GPIOx_ODR) (x = A..H) . . . . . . . . . . 239

11.4.7

GPIO port bit set/reset register (GPIOx_BSRR) (x = A..H) . . . . . . . . . 240

11.4.8

GPIO port configuration lock register (GPIOx_LCKR) . . . . . . . . . . . . . 240

11.4.9

GPIO alternate function low register (GPIOx_AFRL)
(x = A..H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

11.4.10 GPIO alternate function high register (GPIOx_AFRH)
(x = A..H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
11.4.11

GPIO port bit reset register (GPIOx_BRR) (x =A..H) . . . . . . . . . . . . . . 242

11.4.12 GPIO register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

12

System configuration controller (SYSCFG) . . . . . . . . . . . . . . . . . . . . 245
12.1

SYSCFG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
12.1.1

SYSCFG configuration register 1 (SYSCFG_CFGR1) . . . . . . . . . . . . 245

12.1.2

SYSCFG CCM SRAM protection register (SYSCFG_RCR) . . . . . . . . 248

12.1.3

SYSCFG external interrupt configuration register 1
(SYSCFG_EXTICR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

12.1.4

SYSCFG external interrupt configuration register 2
(SYSCFG_EXTICR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

DocID022558 Rev 8

7/1141
28

Contents

RM0316
12.1.5

SYSCFG external interrupt configuration register 3
(SYSCFG_EXTICR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

12.1.6

SYSCFG external interrupt configuration register 4
(SYSCFG_EXTICR4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

12.1.7

SYSCFG configuration register 2 (SYSCFG_CFGR2) . . . . . . . . . . . . 255

12.1.8

SYSCFG configuration register 3 (SYSCFG_CFGR3) . . . . . . . . . . . . 257

12.1.9

SYSCFG configuration register 4 (SYSCFG_CFGR4) . . . . . . . . . . . . 258

12.1.10 SYSCFG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

13

Direct memory access controller (DMA) . . . . . . . . . . . . . . . . . . . . . . . 263
13.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

13.2

DMA main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

13.3

DMA implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

13.4

DMA functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

13.5

14

DMA transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

13.4.2

Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

13.4.3

DMA channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

13.4.4

Programmable data width, data alignment and endians . . . . . . . . . . . 267

13.4.5

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

13.4.6

DMA interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

13.4.7

DMA request mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

DMA registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
13.5.1

DMA interrupt status register (DMA_ISR) . . . . . . . . . . . . . . . . . . . . . . 276

13.5.2

DMA interrupt flag clear register (DMA_IFCR) . . . . . . . . . . . . . . . . . . 277

13.5.3

DMA channel x configuration register (DMA_CCRx)
(x = 1..7 , where x = channel number) . . . . . . . . . . . . . . . . . . . . . . . . 278

13.5.4

DMA channel x number of data register (DMA_CNDTRx) (x = 1..7,
where x = channel number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280

13.5.5

DMA channel x peripheral address register (DMA_CPARx) (x = 1..7,
where x = channel number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280

13.5.6

DMA channel x memory address register (DMA_CMARx) (x = 1..7,
where x = channel number) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

13.5.7

DMA register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282

Interrupts and events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
14.1

8/1141

13.4.1

Nested vectored interrupt controller (NVIC) . . . . . . . . . . . . . . . . . . . . . . 285
14.1.1

NVIC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

14.1.2

SysTick calibration value register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

DocID022558 Rev 8

RM0316

Contents
14.1.3

14.2

14.3

Interrupt and exception vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

Extended interrupts and events controller (EXTI) . . . . . . . . . . . . . . . . . 292
14.2.1

Main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

14.2.2

Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

14.2.3

Wakeup event management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

14.2.4

Asynchronous Internal Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

14.2.5

Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

14.2.6

External and internal interrupt/event line mapping . . . . . . . . . . . . . . . 295

EXTI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
14.3.1

Interrupt mask register (EXTI_IMR1) . . . . . . . . . . . . . . . . . . . . . . . . . . 297

14.3.2

Event mask register (EXTI_EMR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

14.3.3

Rising trigger selection register (EXTI_RTSR1) . . . . . . . . . . . . . . . . . 298

14.3.4

Falling trigger selection register (EXTI_FTSR1) . . . . . . . . . . . . . . . . . 298

14.3.5

Software interrupt event register (EXTI_SWIER1) . . . . . . . . . . . . . . . 299

14.3.6

Pending register (EXTI_PR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

14.3.7

Interrupt mask register (EXTI_IMR2) . . . . . . . . . . . . . . . . . . . . . . . . . . 300

14.3.8

Event mask register (EXTI_EMR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

14.3.9

Rising trigger selection register (EXTI_RTSR2) . . . . . . . . . . . . . . . . . 301

14.3.10 Falling trigger selection register (EXTI_FTSR2) . . . . . . . . . . . . . . . . . 301
14.3.11 Software interrupt event register (EXTI_SWIER2) . . . . . . . . . . . . . . . 301
14.3.12 Pending register (EXTI_PR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
14.3.13 EXTI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

15

Analog-to-digital converters (ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
15.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

15.2

ADC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

15.3

ADC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
15.3.1

ADC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

15.3.2

Pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

15.3.3

Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

15.3.4

ADC1/2 and ADC3/4 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

15.3.5

Slave AHB interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316

15.3.6

ADC voltage regulator (ADVREGEN) . . . . . . . . . . . . . . . . . . . . . . . . . 316

15.3.7

Single-ended and differential input channels . . . . . . . . . . . . . . . . . . . . 316

15.3.8

Calibration (ADCAL, ADCALDIF, ADCx_CALFACT) . . . . . . . . . . . . . . 317

15.3.9

ADC on-off control (ADEN, ADDIS, ADRDY) . . . . . . . . . . . . . . . . . . . 320

15.3.10 Constraints when writing the ADC control bits . . . . . . . . . . . . . . . . . . . 321
DocID022558 Rev 8

9/1141
28

Contents

RM0316
15.3.11 Channel selection (SQRx, JSQRx) . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
15.3.12 Channel-wise programmable sampling time (SMPR1, SMPR2) . . . . . 322
15.3.13 Single conversion mode (CONT=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
15.3.14 Continuous conversion mode (CONT=1) . . . . . . . . . . . . . . . . . . . . . . . 323
15.3.15 Starting conversions (ADSTART, JADSTART) . . . . . . . . . . . . . . . . . . . 324
15.3.16 Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
15.3.17 Stopping an ongoing conversion (ADSTP, JADSTP) . . . . . . . . . . . . . . 325
15.3.18 Conversion on external trigger and trigger polarity (EXTSEL, EXTEN,
JEXTSEL, JEXTEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
15.3.19 Injected channel management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
15.3.20 Discontinuous mode (DISCEN, DISCNUM, JDISCEN) . . . . . . . . . . . . 332
15.3.21 Queue of context for injected conversions . . . . . . . . . . . . . . . . . . . . . . 334
15.3.22 Programmable resolution (RES) - fast conversion mode . . . . . . . . . . 341
15.3.23 End of conversion, end of sampling phase (EOC, JEOC, EOSMP) . . 341
15.3.24 End of conversion sequence (EOS, JEOS) . . . . . . . . . . . . . . . . . . . . . 342
15.3.25 Timing diagrams example (single/continuous modes,
hardware/software triggers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
15.3.26 Data management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
15.3.27 Dynamic low-power features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
15.3.28 Analog window watchdog (AWD1EN, JAWD1EN, AWD1SGL,
AWD1CH, AWD2CH, AWD3CH, AWD_HTx, AWD_LTx, AWDx) . . . . 354
15.3.29 Dual ADC modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358
15.3.30 Temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
15.3.31 VBAT supply monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
15.3.32 Monitoring the internal voltage reference . . . . . . . . . . . . . . . . . . . . . . 374

15.4

ADC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

15.5

ADC registers (for each ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
15.5.1

ADC interrupt and status register (ADCx_ISR, x=1..4) . . . . . . . . . . . . 377

15.5.2

ADC interrupt enable register (ADCx_IER, x=1..4) . . . . . . . . . . . . . . . 379

15.5.3

ADC control register (ADCx_CR, x=1..4) . . . . . . . . . . . . . . . . . . . . . . . 381

15.5.4

ADC configuration register (ADCx_CFGR, x=1..4) . . . . . . . . . . . . . . . 384

15.5.5

ADC sample time register 1 (ADCx_SMPR1, x=1..4) . . . . . . . . . . . . . 388

15.5.6

ADC sample time register 2 (ADCx_SMPR2, x=1..4) . . . . . . . . . . . . . 390

15.5.7

ADC watchdog threshold register 1 (ADCx_TR1, x=1..4) . . . . . . . . . . 390

15.5.8

ADC watchdog threshold register 2 (ADCx_TR2, x = 1..4) . . . . . . . . . 391

15.5.9

ADC watchdog threshold register 3 (ADCx_TR3, x=1..4) . . . . . . . . . . 392

15.5.10 ADC regular sequence register 1 (ADCx_SQR1, x=1..4) . . . . . . . . . . 393
15.5.11 ADC regular sequence register 2 (ADCx_SQR2, x=1..4) . . . . . . . . . . 394
10/1141

DocID022558 Rev 8

RM0316

Contents
15.5.12 ADC regular sequence register 3 (ADCx_SQR3, x=1..4) . . . . . . . . . . 396
15.5.13 ADC regular sequence register 4 (ADCx_SQR4, x=1..4) . . . . . . . . . . 397
15.5.14 ADC regular Data Register (ADCx_DR, x=1..4) . . . . . . . . . . . . . . . . . 398
15.5.15 ADC injected sequence register (ADCx_JSQR, x=1..4) . . . . . . . . . . . 399
15.5.16 ADC offset register (ADCx_OFRy, x=1..4) (y=1..4) . . . . . . . . . . . . . . . 401
15.5.17 ADC injected data register (ADCx_JDRy, x=1..4, y= 1..4) . . . . . . . . . . 402
15.5.18 ADC Analog Watchdog 2 Configuration Register (ADCx_AWD2CR,
x=1..4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402
15.5.19 ADC Analog Watchdog 3 Configuration Register (ADCx_AWD3CR,
x=1..4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
15.5.20 ADC Differential Mode Selection Register (ADCx_DIFSEL, x=1..4) . . 403
15.5.21 ADC Calibration Factors (ADCx_CALFACT, x=1..4) . . . . . . . . . . . . . . 404

15.6

16

ADC common registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405
15.6.1

ADC Common status register (ADCx_CSR, x=12 or 34) . . . . . . . . . . . 405

15.6.2

ADC common control register (ADCx_CCR, x=12 or 34) . . . . . . . . . . 407

15.6.3

ADC common regular data register for dual mode . . . . . . . . . . . . . . . . . .
(ADCx_CDR, x=12 or 34) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410

15.6.4

ADC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410

Digital-to-analog converter (DAC1 and DAC2) . . . . . . . . . . . . . . . . . . 414
16.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414

16.2

DAC1/2 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414

16.3

DAC output buffer enable/DAC output switch . . . . . . . . . . . . . . . . . . . . 416

16.4

DAC channel enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

16.5

Single mode functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

16.6

16.5.1

DAC data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417

16.5.2

DAC channel conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418

16.5.3

DAC output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419

16.5.4

DAC trigger selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419

Dual-mode functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
16.6.1

DAC data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420

16.6.2

DAC channel conversion in dual mode . . . . . . . . . . . . . . . . . . . . . . . . 421

16.6.3

Description of dual conversion modes . . . . . . . . . . . . . . . . . . . . . . . . . 421

16.6.4

DAC output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424

16.6.5

DAC trigger selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425

16.7

Noise generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425

16.8

Triangle-wave generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426

DocID022558 Rev 8

11/1141
28

Contents

RM0316

16.9

DMA request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

16.10 DAC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
16.10.1 DAC control register (DAC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
16.10.2 DAC software trigger register (DAC_SWTRIGR) . . . . . . . . . . . . . . . . . 432
16.10.3 DAC channel1 12-bit right-aligned data holding register
(DAC_DHR12R1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432
16.10.4 DAC channel1 12-bit left-aligned data holding register
(DAC_DHR12L1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
16.10.5 DAC channel1 8-bit right-aligned data holding register
(DAC_DHR8R1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
16.10.6 DAC channel2 12-bit right-aligned data holding register
(DAC_DHR12R2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
16.10.7 DAC channel2 12-bit left-aligned data holding register
(DAC_DHR12L2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434
16.10.8 DAC channel2 8-bit right-aligned data holding register
(DAC_DHR8R2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434
16.10.9 Dual DAC 12-bit right-aligned data holding register
(DAC_DHR12RD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435
16.10.10 Dual DAC 12-bit left-aligned data holding register
(DAC_DHR12LD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435
16.10.11 Dual DAC 8-bit right-aligned data holding register
(DAC_DHR8RD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435
16.10.12 DAC channel1 data output register (DAC_DOR1) . . . . . . . . . . . . . . . . 436
16.10.13 DAC channel2 data output register (DAC_DOR2) . . . . . . . . . . . . . . . . 436
16.10.14 DAC status register (DAC_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436
16.10.15 DAC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438

17

Comparator (COMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440
17.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440

17.2

COMP main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440

17.3

COMP functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441

17.4

12/1141

17.3.1

COMP block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441

17.3.2

COMP pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443

17.3.3

COMP reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444

17.3.4

Comparator LOCK mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444

17.3.5

Hysteresis (on STM32F303xB/C and STM32F358xC only) . . . . . . . . 445

17.3.6

Comparator output blanking function . . . . . . . . . . . . . . . . . . . . . . . . . . 445

17.3.7

Power mode (STM32F303xB/C and STM32F358xC only) . . . . . . . . . 446

COMP interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446

DocID022558 Rev 8

RM0316

Contents

17.5

18

17.5.1

COMP1 control and status register (COMP1_CSR) . . . . . . . . . . . . . . 447

17.5.2

COMP2 control and status register (COMP2_CSR) . . . . . . . . . . . . . . 449

17.5.3

COMP3 control and status register (COMP3_CSR) . . . . . . . . . . . . . . 451

17.5.4

COMP4 control and status register (COMP4_CSR) . . . . . . . . . . . . . . 454

17.5.5

COMP5 control and status register (COMP5_CSR) . . . . . . . . . . . . . . 456

17.5.6

COMP6 control and status register (COMP6_CSR) . . . . . . . . . . . . . . 459

17.5.7

COMP7 control and status register (COMP7_CSR) . . . . . . . . . . . . . . 461

17.5.8

COMP register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

Operational amplifier (OPAMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466
18.1

OPAMP introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

18.2

OPAMP main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

18.3

OPAMP functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

18.4

19

COMP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447

18.3.1

General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

18.3.2

Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

18.3.3

Operational amplifiers and comparators interconnections . . . . . . . . . . 468

18.3.4

Using the OPAMP outputs as ADC inputs . . . . . . . . . . . . . . . . . . . . . . 470

18.3.5

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470

18.3.6

Timer controlled Multiplexer mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471

18.3.7

OPAMP modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472

OPAMP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476
18.4.1

OPAMP1 control register (OPAMP1_CSR) . . . . . . . . . . . . . . . . . . . . . 476

18.4.2

OPAMP2 control register (OPAMP2_CSR) . . . . . . . . . . . . . . . . . . . . . 478

18.4.3

OPAMP3 control register (OPAMP3_CSR) . . . . . . . . . . . . . . . . . . . . . 480

18.4.4

OPAMP4 control register (OPAMP4_CSR) . . . . . . . . . . . . . . . . . . . . . 483

18.4.5

OPAMP register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

Touch sensing controller (TSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487
19.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

19.2

TSC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

19.3

TSC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488
19.3.1

TSC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488

19.3.2

Surface charge transfer acquisition overview . . . . . . . . . . . . . . . . . . . 488

19.3.3

Reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490

19.3.4

Charge transfer acquisition sequence . . . . . . . . . . . . . . . . . . . . . . . . . 491

DocID022558 Rev 8

13/1141
28

Contents

RM0316
19.3.5

Spread spectrum feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

19.3.6

Max count error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

19.3.7

Sampling capacitor I/O and channel I/O mode selection . . . . . . . . . . . 493

19.3.8

Acquisition mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

19.3.9

I/O hysteresis and analog switch control . . . . . . . . . . . . . . . . . . . . . . . 494

19.4

TSC low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495

19.5

TSC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495

19.6

TSC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496
19.6.1

TSC control register (TSC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496

19.6.2

TSC interrupt enable register (TSC_IER) . . . . . . . . . . . . . . . . . . . . . . 498

19.6.3

TSC interrupt clear register (TSC_ICR) . . . . . . . . . . . . . . . . . . . . . . . . 499

19.6.4

TSC interrupt status register (TSC_ISR) . . . . . . . . . . . . . . . . . . . . . . . 500

19.6.5

TSC I/O hysteresis control register (TSC_IOHCR) . . . . . . . . . . . . . . . 500

19.6.6

TSC I/O analog switch control register (TSC_IOASCR) . . . . . . . . . . . 501

19.6.7

TSC I/O sampling control register (TSC_IOSCR) . . . . . . . . . . . . . . . . 501

19.6.8

TSC I/O channel control register (TSC_IOCCR) . . . . . . . . . . . . . . . . . 502

19.6.9

TSC I/O group control status register (TSC_IOGCSR) . . . . . . . . . . . . 502

19.6.10 TSC I/O group x counter register (TSC_IOGxCR) (x = 1..8) . . . . . . . . 503
19.6.11 TSC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504

20

Advanced-control timers (TIM1/TIM8/TIM20) . . . . . . . . . . . . . . . . . . . 506
20.1

TIM1/TIM8/TIM20 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506

20.2

TIM1/TIM8/TIM20 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506

20.3

TIM1/TIM8/TIM20 functional description . . . . . . . . . . . . . . . . . . . . . . . . 508
20.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508

20.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510

20.3.3

Repetition counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 521

20.3.4

External trigger input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523

20.3.5

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524

20.3.6

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528

20.3.7

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531

20.3.8

PWM input mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532

20.3.9

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533

20.3.10 Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534
20.3.11 PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535
20.3.12 Asymmetric PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538

14/1141

DocID022558 Rev 8

RM0316

Contents
20.3.13 Combined PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539
20.3.14 Combined 3-phase PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
20.3.15 Complementary outputs and dead-time insertion . . . . . . . . . . . . . . . . 541
20.3.16 Using the break function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543
20.3.17 Clearing the OCxREF signal on an external event . . . . . . . . . . . . . . . 548
20.3.18 6-step PWM generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550
20.3.19 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
20.3.20 Retriggerable one pulse mode (OPM) . . . . . . . . . . . . . . . . . . . . . . . . . 552
20.3.21 Encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553
20.3.22 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555
20.3.23 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556
20.3.24 Interfacing with Hall sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556
20.3.25 Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559
20.3.26 ADC synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563
20.3.27 DMA burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563
20.3.28 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

20.4

TIM1/TIM8/TIM20 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565
20.4.1

TIM1/TIM8/TIM20 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . 565

20.4.2

TIM1/TIM8/TIM20 control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . 566

20.4.3

TIM1/TIM8/TIM20 slave mode control register (TIMx_SMCR) . . . . . . 569

20.4.4

TIM1/TIM8/TIM20 DMA/interrupt enable register (TIMx_DIER) . . . . . 571

20.4.5

TIM1/TIM8/TIM20 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . 573

20.4.6

TIM1/TIM8/TIM20 event generation register (TIMx_EGR) . . . . . . . . . 575

20.4.7

TIM1/TIM8/TIM20 capture/compare mode register 1 (TIMx_CCMR1) 576

20.4.8

TIM1/TIM8/TIM20 capture/compare mode register 2 (TIMx_CCMR2) 580

20.4.9

TIM1/TIM8/TIM20 capture/compare enable register (TIMx_CCER) . . 582

20.4.10 TIM1/TIM8/TIM20 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . 586
20.4.11 TIM1/TIM8/TIM20 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . 586
20.4.12 TIM1/TIM8/TIM20 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . 586
20.4.13 TIM1/TIM8/TIM20 repetition counter register (TIMx_RCR) . . . . . . . . . 587
20.4.14 TIM1/TIM8/TIM20 capture/compare register 1 (TIMx_CCR1) . . . . . . . 587
20.4.15 TIM1/TIM8/TIM20 capture/compare register 2 (TIMx_CCR2) . . . . . . . 588
20.4.16 TIM1/TIM8/TIM20 capture/compare register 3 (TIMx_CCR3) . . . . . . . 588
20.4.17 TIM1/TIM8/TIM20 capture/compare register 4 (TIMx_CCR4) . . . . . . . 589
20.4.18 TIM1/TIM8/TIM20 break and dead-time register (TIMx_BDTR) . . . . . 589
20.4.19 TIM1/TIM8/TIM20 DMA control register (TIMx_DCR) . . . . . . . . . . . . . 592
20.4.20 TIM1/TIM8/TIM20 DMA address for full transfer (TIMx_DMAR) . . . . . 593

DocID022558 Rev 8

15/1141
28

Contents

RM0316
20.4.21 TIM1/TIM8/TIM20 option registers (TIMx_OR) . . . . . . . . . . . . . . . . . . 594
20.4.22 TIM1/TIM8/TIM20 capture/compare mode register 3 (TIMx_CCMR3) 595
20.4.23 TIM1/TIM8/TIM20 capture/compare register 5 (TIMx_CCR5) . . . . . . . 596
20.4.24 TIM1/TIM8/TIM20 capture/compare register 6 (TIMx_CCR6) . . . . . . . 597
20.4.25 TIM1/TIM8/TIM20 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598

21

General-purpose timers (TIM2/TIM3/TIM4) . . . . . . . . . . . . . . . . . . . . . 601
21.1

TIM2/TIM3/TIM4 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601

21.2

TIM2/TIM3/TIM4 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 601

21.3

TIM2/TIM3/TIM4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . 603
21.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603

21.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605

21.3.3

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 615

21.3.4

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619

21.3.5

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621

21.3.6

PWM input mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622

21.3.7

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623

21.3.8

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624

21.3.9

PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625

21.3.10 Asymmetric PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628
21.3.11 Combined PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629
21.3.12 Clearing the OCxREF signal on an external event . . . . . . . . . . . . . . . 630
21.3.13 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632
21.3.14 Retriggerable one pulse mode (OPM) . . . . . . . . . . . . . . . . . . . . . . . . . 633
21.3.15 Encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634
21.3.16 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 636
21.3.17 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 636
21.3.18 Timers and external trigger synchronization . . . . . . . . . . . . . . . . . . . . 637
21.3.19 Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640
21.3.20 DMA burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645
21.3.21 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646

21.4

16/1141

TIM2/TIM3/TIM4 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647
21.4.1

TIMx control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . 647

21.4.2

TIMx control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . 648

21.4.3

TIMx slave mode control register (TIMx_SMCR) . . . . . . . . . . . . . . . . . 650

21.4.4

TIMx DMA/Interrupt enable register (TIMx_DIER) . . . . . . . . . . . . . . . . 653

21.4.5

TIMx status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654
DocID022558 Rev 8

RM0316

Contents
21.4.6

TIMx event generation register (TIMx_EGR) . . . . . . . . . . . . . . . . . . . . 655

21.4.7

TIMx capture/compare mode register 1 (TIMx_CCMR1) . . . . . . . . . . . 656

21.4.8

TIMx capture/compare mode register 2 (TIMx_CCMR2) . . . . . . . . . . . 660

21.4.9

TIMx capture/compare enable register (TIMx_CCER) . . . . . . . . . . . . . 662

21.4.10 TIMx counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663
21.4.11 TIMx prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664
21.4.12 TIMx auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . . . . . . 664
21.4.13 TIMx capture/compare register 1 (TIMx_CCR1) . . . . . . . . . . . . . . . . . 665
21.4.14 TIMx capture/compare register 2 (TIMx_CCR2) . . . . . . . . . . . . . . . . . 665
21.4.15 TIMx capture/compare register 3 (TIMx_CCR3) . . . . . . . . . . . . . . . . . 666
21.4.16 TIMx capture/compare register 4 (TIMx_CCR4) . . . . . . . . . . . . . . . . . 666
21.4.17 TIMx DMA control register (TIMx_DCR) . . . . . . . . . . . . . . . . . . . . . . . 667
21.4.18 TIMx DMA address for full transfer (TIMx_DMAR) . . . . . . . . . . . . . . . 667
21.4.19 TIMx register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668

22

Basic timers (TIM6/TIM7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670
22.1

TIM6/TIM7 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670

22.2

TIM6/TIM7 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670

22.3

TIM6/TIM7 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671

22.4

23

22.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671

22.3.2

Counting mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673

22.3.3

UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676

22.3.4

Clock source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676

22.3.5

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 677

TIM6/TIM7 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 677
22.4.1

TIM6/TIM7 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . . 677

22.4.2

TIM6/TIM7 control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . . 679

22.4.3

TIM6/TIM7 DMA/Interrupt enable register (TIMx_DIER) . . . . . . . . . . . 679

22.4.4

TIM6/TIM7 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . 680

22.4.5

TIM6/TIM7 event generation register (TIMx_EGR) . . . . . . . . . . . . . . . 680

22.4.6

TIM6/TIM7 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 680

22.4.7

TIM6/TIM7 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681

22.4.8

TIM6/TIM7 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . 681

22.4.9

TIM6/TIM7 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 682

General-purpose timers (TIM15/TIM16/TIM17) . . . . . . . . . . . . . . . . . . 683
23.1

TIM15/TIM16/TIM17 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 683
DocID022558 Rev 8

17/1141
28

Contents

RM0316

23.2

TIM15 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 683

23.3

TIM16/TIM17 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684

23.4

TIM15/TIM16/TIM17 functional description . . . . . . . . . . . . . . . . . . . . . . 687
23.4.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 687

23.4.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 689

23.4.3

Repetition counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693

23.4.4

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694

23.4.5

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696

23.4.6

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 699

23.4.7

PWM input mode (only for TIM15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700

23.4.8

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701

23.4.9

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701

23.4.10 PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702
23.4.11 Combined PWM mode (TIM15 only) . . . . . . . . . . . . . . . . . . . . . . . . . . 703
23.4.12 Complementary outputs and dead-time insertion . . . . . . . . . . . . . . . . 705
23.4.13 Using the break function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 707
23.4.14 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 710
23.4.15 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 711
23.4.16 Timer input XOR function (TIM15 only) . . . . . . . . . . . . . . . . . . . . . . . . 712
23.4.17 External trigger synchronization (TIM15 only) . . . . . . . . . . . . . . . . . . . 713
23.4.18 Slave mode: Combined reset + trigger mode (TIM15 only) . . . . . . . . . 715
23.4.19 DMA burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715
23.4.20 Timer synchronization (TIM15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 717
23.4.21 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 717

23.5

TIM15 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 718
23.5.1

TIM15 control register 1 (TIM15_CR1) . . . . . . . . . . . . . . . . . . . . . . . . 718

23.5.2

TIM15 control register 2 (TIM15_CR2) . . . . . . . . . . . . . . . . . . . . . . . . 719

23.5.3

TIM15 slave mode control register (TIM15_SMCR) . . . . . . . . . . . . . . 721

23.5.4

TIM15 DMA/interrupt enable register (TIM15_DIER) . . . . . . . . . . . . . 722

23.5.5

TIM15 status register (TIM15_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 723

23.5.6

TIM15 event generation register (TIM15_EGR) . . . . . . . . . . . . . . . . . 725

23.5.7

TIM15 capture/compare mode register 1 (TIM15_CCMR1) . . . . . . . . 726

23.5.8

TIM15 capture/compare enable register (TIM15_CCER) . . . . . . . . . . 729

23.5.9

TIM15 counter (TIM15_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 732

23.5.10 TIM15 prescaler (TIM15_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 732
23.5.11 TIM15 auto-reload register (TIM15_ARR) . . . . . . . . . . . . . . . . . . . . . . 732
23.5.12 TIM15 repetition counter register (TIM15_RCR) . . . . . . . . . . . . . . . . . 733
18/1141

DocID022558 Rev 8

RM0316

Contents
23.5.13 TIM15 capture/compare register 1 (TIM15_CCR1) . . . . . . . . . . . . . . . 733
23.5.14 TIM15 capture/compare register 2 (TIM15_CCR2) . . . . . . . . . . . . . . . 734
23.5.15 TIM15 break and dead-time register (TIM15_BDTR) . . . . . . . . . . . . . 734
23.5.16 TIM15 DMA control register (TIM15_DCR) . . . . . . . . . . . . . . . . . . . . . 736
23.5.17 TIM15 DMA address for full transfer (TIM15_DMAR) . . . . . . . . . . . . . 736
23.5.18 TIM15 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737

23.6

TIM16/TIM17 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 739
23.6.1

TIM16/TIM17 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . 739

23.6.2

TIM16/TIM17 control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . 740

23.6.3

TIM16/TIM17 DMA/interrupt enable register (TIMx_DIER) . . . . . . . . . 741

23.6.4

TIM16/TIM17 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . 742

23.6.5

TIM16/TIM17 event generation register (TIMx_EGR) . . . . . . . . . . . . . 743

23.6.6

TIM16/TIM17 capture/compare mode register 1 (TIMx_CCMR1) . . . . 744

23.6.7

TIM16/TIM17 capture/compare enable register (TIMx_CCER) . . . . . . 746

23.6.8

TIM16/TIM17 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . 748

23.6.9

TIM16/TIM17 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . 749

23.6.10 TIM16/TIM17 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . 749
23.6.11 TIM16/TIM17 repetition counter register (TIMx_RCR) . . . . . . . . . . . . 750
23.6.12 TIM16/TIM17 capture/compare register 1 (TIMx_CCR1) . . . . . . . . . . 750
23.6.13 TIM16/TIM17 break and dead-time register (TIMx_BDTR) . . . . . . . . . 751
23.6.14 TIM16/TIM17 DMA control register (TIMx_DCR) . . . . . . . . . . . . . . . . 753
23.6.15 TIM16/TIM17 DMA address for full transfer (TIMx_DMAR) . . . . . . . . . 753
23.6.16 TIM16 option register (TIM16_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 754
23.6.17 TIM16/TIM17 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755

24

Infrared interface (IRTIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757

25

Independent watchdog (IWDG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758
25.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758

25.2

IWDG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758

25.3

IWDG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758
25.3.1

IWDG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758

25.3.2

Window option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759

25.3.3

Hardware watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760

25.3.4

Behavior in Stop and Standby modes . . . . . . . . . . . . . . . . . . . . . . . . . 760

25.3.5

Register access protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760

25.3.6

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 760

DocID022558 Rev 8

19/1141
28

Contents

RM0316

25.4

26

20/1141

25.4.1

Key register (IWDG_KR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761

25.4.2

Prescaler register (IWDG_PR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762

25.4.3

Reload register (IWDG_RLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763

25.4.4

Status register (IWDG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764

25.4.5

Window register (IWDG_WINR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765

25.4.6

IWDG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766

System window watchdog (WWDG) . . . . . . . . . . . . . . . . . . . . . . . . . . 767
26.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767

26.2

WWDG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767

26.3

WWDG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767

26.4

27

IWDG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761

26.3.1

Enabling the watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768

26.3.2

Controlling the downcounter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768

26.3.3

Advanced watchdog interrupt feature . . . . . . . . . . . . . . . . . . . . . . . . . 768

26.3.4

How to program the watchdog timeout . . . . . . . . . . . . . . . . . . . . . . . . 769

26.3.5

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770

WWDG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770
26.4.1

Control register (WWDG_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770

26.4.2

Configuration register (WWDG_CFR) . . . . . . . . . . . . . . . . . . . . . . . . . 771

26.4.3

Status register (WWDG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 771

26.4.4

WWDG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 772

Real-time clock (RTC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773
27.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773

27.2

RTC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774

27.3

RTC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775
27.3.1

RTC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775

27.3.2

GPIOs controlled by the RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 776

27.3.3

Clock and prescalers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 778

27.3.4

Real-time clock and calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 778

27.3.5

Programmable alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 779

27.3.6

Periodic auto-wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 779

27.3.7

RTC initialization and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 780

27.3.8

Reading the calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 781

27.3.9

Resetting the RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782

DocID022558 Rev 8

RM0316

Contents
27.3.10 RTC synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 783
27.3.11 RTC reference clock detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 783
27.3.12 RTC smooth digital calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 784
27.3.13 Time-stamp function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 786
27.3.14 Tamper detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 787
27.3.15 Calibration clock output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 788
27.3.16 Alarm output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 789

27.4

RTC low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 789

27.5

RTC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 789

27.6

RTC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 790
27.6.1

RTC time register (RTC_TR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 790

27.6.2

RTC date register (RTC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791

27.6.3

RTC control register (RTC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793

27.6.4

RTC initialization and status register (RTC_ISR) . . . . . . . . . . . . . . . . . 796

27.6.5

RTC prescaler register (RTC_PRER) . . . . . . . . . . . . . . . . . . . . . . . . . 799

27.6.6

RTC wakeup timer register (RTC_WUTR) . . . . . . . . . . . . . . . . . . . . . . 800

27.6.7

RTC alarm A register (RTC_ALRMAR) . . . . . . . . . . . . . . . . . . . . . . . . 801

27.6.8

RTC alarm B register (RTC_ALRMBR) . . . . . . . . . . . . . . . . . . . . . . . . 802

27.6.9

RTC write protection register (RTC_WPR) . . . . . . . . . . . . . . . . . . . . . 803

27.6.10 RTC sub second register (RTC_SSR) . . . . . . . . . . . . . . . . . . . . . . . . . 803
27.6.11 RTC shift control register (RTC_SHIFTR) . . . . . . . . . . . . . . . . . . . . . . 804
27.6.12 RTC timestamp time register (RTC_TSTR) . . . . . . . . . . . . . . . . . . . . . 805
27.6.13 RTC timestamp date register (RTC_TSDR) . . . . . . . . . . . . . . . . . . . . 806
27.6.14 RTC time-stamp sub second register (RTC_TSSSR) . . . . . . . . . . . . . 807
27.6.15 RTC calibration register (RTC_CALR) . . . . . . . . . . . . . . . . . . . . . . . . . 808
27.6.16 RTC tamper and alternate function configuration register
(RTC_TAFCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 809
27.6.17 RTC alarm A sub second register (RTC_ALRMASSR) . . . . . . . . . . . . 812
27.6.18 RTC alarm B sub second register (RTC_ALRMBSSR) . . . . . . . . . . . . 813
27.6.19 RTC backup registers (RTC_BKPxR) . . . . . . . . . . . . . . . . . . . . . . . . . 814
27.6.20 RTC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 814

28

Inter-integrated circuit (I2C) interface . . . . . . . . . . . . . . . . . . . . . . . . . 816
28.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816

28.2

I2C main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816

28.3

I2C implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817

28.4

I2C functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817
DocID022558 Rev 8

21/1141
28

Contents

RM0316
28.4.1

I2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 818

28.4.2

I2C clock requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819

28.4.3

Mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819

28.4.4

I2C initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 821

28.4.5

Software reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825

28.4.6

Data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826

28.4.7

I2C slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 828

28.4.8

I2C master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837

28.4.9

I2C_TIMINGR register configuration examples . . . . . . . . . . . . . . . . . . 849

28.4.10 SMBus specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850
28.4.11 SMBus initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853
28.4.12 SMBus: I2C_TIMEOUTR register configuration examples . . . . . . . . . 855
28.4.13 SMBus slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856
28.4.14 Wakeup from Stop mode on address match . . . . . . . . . . . . . . . . . . . . 863
28.4.15 Error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863
28.4.16 DMA requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865
28.4.17 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866

28.5

I2C low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866

28.6

I2C interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866

28.7

I2C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868
28.7.1

Control register 1 (I2C_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868

28.7.2

Control register 2 (I2C_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 871

28.7.3

Own address 1 register (I2C_OAR1) . . . . . . . . . . . . . . . . . . . . . . . . . . 874

28.7.4

Own address 2 register (I2C_OAR2) . . . . . . . . . . . . . . . . . . . . . . . . . . 875

28.7.5

Timing register (I2C_TIMINGR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 876

28.7.6

Timeout register (I2C_TIMEOUTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 877

28.7.7

Interrupt and status register (I2C_ISR) . . . . . . . . . . . . . . . . . . . . . . . . 878

28.7.8

Interrupt clear register (I2C_ICR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880

28.7.9

PEC register (I2C_PECR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 881

28.7.10 Receive data register (I2C_RXDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 882
28.7.11 Transmit data register (I2C_TXDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 882
28.7.12 I2C register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883

29

22/1141

Universal synchronous asynchronous receiver
transmitter (USART) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885
29.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885

29.2

USART main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 885
DocID022558 Rev 8

RM0316

Contents

29.3

USART extended features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 886

29.4

USART implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 887

29.5

USART functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 888
29.5.1

USART character description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 890

29.5.2

USART transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 892

29.5.3

USART receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894

29.5.4

USART baud rate generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901

29.5.5

Tolerance of the USART receiver to clock deviation . . . . . . . . . . . . . . 903

29.5.6

USART auto baud rate detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904

29.5.7

Multiprocessor communication using USART . . . . . . . . . . . . . . . . . . . 905

29.5.8

Modbus communication using USART . . . . . . . . . . . . . . . . . . . . . . . . 907

29.5.9

USART parity control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908

29.5.10 USART LIN (local interconnection network) mode . . . . . . . . . . . . . . . 909
29.5.11 USART synchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911
29.5.12 USART Single-wire Half-duplex communication . . . . . . . . . . . . . . . . . 914
29.5.13 USART Smartcard mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914
29.5.14 USART IrDA SIR ENDEC block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 919
29.5.15 USART continuous communication in DMA mode . . . . . . . . . . . . . . . 921
29.5.16 RS232 hardware flow control and RS485 driver enable
using USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923
29.5.17 Wakeup from Stop mode using USART . . . . . . . . . . . . . . . . . . . . . . . . 925

29.6

USART low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927

29.7

USART interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927

29.8

USART registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 929
29.8.1

Control register 1 (USART_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 929

29.8.2

Control register 2 (USART_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 932

29.8.3

Control register 3 (USART_CR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 936

29.8.4

Baud rate register (USART_BRR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 940

29.8.5

Guard time and prescaler register (USART_GTPR) . . . . . . . . . . . . . . 940

29.8.6

Receiver timeout register (USART_RTOR) . . . . . . . . . . . . . . . . . . . . . 941

29.8.7

Request register (USART_RQR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 942

29.8.8

Interrupt and status register (USART_ISR) . . . . . . . . . . . . . . . . . . . . . 943

29.8.9

Interrupt flag clear register (USART_ICR) . . . . . . . . . . . . . . . . . . . . . . 948

29.8.10 Receive data register (USART_RDR) . . . . . . . . . . . . . . . . . . . . . . . . . 949
29.8.11 Transmit data register (USART_TDR) . . . . . . . . . . . . . . . . . . . . . . . . . 949
29.8.12 USART register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 950

DocID022558 Rev 8

23/1141
28

Contents

30

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S) . . . . . . . . . . . . . 952
30.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952

30.2

SPI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 952

30.3

I2S main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953

30.4

SPI/I2S implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 953

30.5

SPI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954
30.5.1

General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954

30.5.2

Communications between one master and one slave . . . . . . . . . . . . . 955

30.5.3

Standard multi-slave communication . . . . . . . . . . . . . . . . . . . . . . . . . . 957

30.5.4

Multi-master communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958

30.5.5

Slave select (NSS) pin management . . . . . . . . . . . . . . . . . . . . . . . . . . 959

30.5.6

Communication formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 960

30.5.7

Configuration of SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 962

30.5.8

Procedure for enabling SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 963

30.5.9

Data transmission and reception procedures . . . . . . . . . . . . . . . . . . . 963

30.5.10 SPI status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 973
30.5.11 SPI error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 974
30.5.12 NSS pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 975
30.5.13 TI mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 975
30.5.14 CRC calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976

30.6

SPI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 978

30.7

I2S functional description (STM32F303xB/C/D/E,
STM32F358xC and STM32F398xE only) . . . . . . . . . . . . . . . . . . . . . . . 979
30.7.1

I2S general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 979

30.7.2

I2S full duplex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 980

30.7.3

Supported audio protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981

30.7.4

Start-up description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 988

30.7.5

Clock generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990

30.7.6

I2S master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 991

30.7.7

I2S slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 993

30.7.8

I2S status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 995

30.7.9

I2S error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996

30.7.10 DMA features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 997

30.8

I2S interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 997

30.9

SPI and I2S registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 998
30.9.1

24/1141

SPI control register 1 (SPIx_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 998

DocID022558 Rev 8

RM0316

Contents
30.9.2

SPI control register 2 (SPIx_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000

30.9.3

SPI status register (SPIx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003

30.9.4

SPI data register (SPIx_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1004

30.9.5

SPI CRC polynomial register (SPIx_CRCPR) . . . . . . . . . . . . . . . . . . 1004

30.9.6

SPI Rx CRC register (SPIx_RXCRCR) . . . . . . . . . . . . . . . . . . . . . . . 1006

30.9.7

SPI Tx CRC register (SPIx_TXCRCR) . . . . . . . . . . . . . . . . . . . . . . . 1006

30.9.8

SPIx_I2S configuration register (SPIx_I2SCFGR) . . . . . . . . . . . . . . . 1007

30.9.9

SPIx_I2S prescaler register (SPIx_I2SPR) . . . . . . . . . . . . . . . . . . . . 1009

30.9.10 SPI/I2S register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010

31

Controller area network (bxCAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1011
31.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1011

31.2

bxCAN main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1011

31.3

bxCAN general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012

31.4

31.5

31.3.1

CAN 2.0B active core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012

31.3.2

Control, status and configuration registers . . . . . . . . . . . . . . . . . . . . 1012

31.3.3

Tx mailboxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012

31.3.4

Acceptance filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013

bxCAN operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013
31.4.1

Initialization mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013

31.4.2

Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013

31.4.3

Sleep mode (low-power) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1014

Test mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015
31.5.1

Silent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015

31.5.2

Loop back mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016

31.5.3

Loop back combined with silent mode . . . . . . . . . . . . . . . . . . . . . . . . 1016

31.6

Behavior in debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017

31.7

bxCAN functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017

31.8

31.7.1

Transmission handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017

31.7.2

Time triggered communication mode . . . . . . . . . . . . . . . . . . . . . . . . . 1018

31.7.3

Reception handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1019

31.7.4

Identifier filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1020

31.7.5

Message storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1024

31.7.6

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1026

31.7.7

Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1026

bxCAN interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1029

DocID022558 Rev 8

25/1141
28

Contents

RM0316

31.9

32

CAN registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1030
31.9.1

Register access protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1030

31.9.2

CAN control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1030

31.9.3

CAN mailbox registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1040

31.9.4

CAN filter registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047

31.9.5

bxCAN register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1051

Universal serial bus full-speed device interface (USB) . . . . . . . . . . 1055
32.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1055

32.2

USB main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1055

32.3

USB implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1055

32.4

USB functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1056
32.4.1

32.5

32.6

33

Programming considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1058
32.5.1

Generic USB device programming . . . . . . . . . . . . . . . . . . . . . . . . . . 1059

32.5.2

System and power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1059

32.5.3

Double-buffered endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1064

32.5.4

Isochronous transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1066

32.5.5

Suspend/Resume events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1068

USB registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1070
32.6.1

Common registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1070

32.6.2

Buffer descriptor table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1082

32.6.3

USB register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086

Debug support (DBG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088
33.1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088

33.2

Reference ARM® documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089

33.3

SWJ debug port (serial wire and JTAG) . . . . . . . . . . . . . . . . . . . . . . . . 1089
33.3.1

33.4

26/1141

Description of USB blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1057

Mechanism to select the JTAG-DP or the SW-DP . . . . . . . . . . . . . . . 1090

Pinout and debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1090
33.4.1

SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091

33.4.2

Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091

33.4.3

Internal pull-up and pull-down on JTAG pins . . . . . . . . . . . . . . . . . . . 1092

33.4.4

Using serial wire and releasing the unused debug pins as GPIOs . . 1093

33.5

STM32F3xx JTAG TAP connection . . . . . . . . . . . . . . . . . . . . . . . . . . . 1093

33.6

ID codes and locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1094
DocID022558 Rev 8

RM0316

Contents
33.6.1

MCU device ID code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095

33.6.2

Boundary scan TAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095

33.6.3

Cortex-M4®F TAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095

33.6.4

Cortex-M4®F JEDEC-106 ID code . . . . . . . . . . . . . . . . . . . . . . . . . . 1096

33.7

JTAG debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096

33.8

SW debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098

33.9

33.8.1

SW protocol introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098

33.8.2

SW protocol sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098

33.8.3

SW-DP state machine (reset, idle states, ID code) . . . . . . . . . . . . . . 1099

33.8.4

DP and AP read/write accesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1099

33.8.5

SW-DP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1100

33.8.6

SW-AP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1101

AHB-AP (AHB access port) - valid for both JTAG-DP
and SW-DP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1101

33.10 Core debug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1102
33.11 Capability of the debugger host to connect under system reset . . . . . .1102
33.12 FPB (Flash patch breakpoint) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1103
33.13 DWT (data watchpoint trigger) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1104
33.14 ITM (instrumentation trace macrocell) . . . . . . . . . . . . . . . . . . . . . . . . . .1104
33.14.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1104
33.14.2 Time stamp packets, synchronization and overflow packets . . . . . . . 1104

33.15 ETM (Embedded trace macrocell) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1106
33.15.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1106
33.15.2 Signal protocol, packet types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1106
33.15.3 Main ETM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1107
33.15.4 Configuration example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1107

33.16 MCU debug component (DBGMCU) . . . . . . . . . . . . . . . . . . . . . . . . . . .1107
33.16.1 Debug support for low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . 1107
33.16.2 Debug support for timers, watchdog, bxCAN and I2C . . . . . . . . . . . . 1108
33.16.3 Debug MCU configuration register . . . . . . . . . . . . . . . . . . . . . . . . . . 1108
33.16.4 Debug MCU APB1 freeze register (DBGMCU_APB1_FZ) . . . . . . . . 1110
33.16.5 Debug MCU APB2 freeze register (DBGMCU_APB2_FZ) . . . . . . . . 1112

33.17 TPIU (trace port interface unit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1112
33.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1112
33.17.2 TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1113
33.17.3 TPUI formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1115

DocID022558 Rev 8

27/1141
28

Contents

RM0316
33.17.4 TPUI frame synchronization packets . . . . . . . . . . . . . . . . . . . . . . . . . 1115
33.17.5 Transmission of the synchronization frame packet . . . . . . . . . . . . . . 1116
33.17.6 Synchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1116
33.17.7 Asynchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1116
33.17.8 TRACECLKIN connection inside the STM32F3xx . . . . . . . . . . . . . . . 1117
33.17.9 TPIU registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1118
33.17.10 Example of configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1119

33.18 DBG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1120

34

Device electronic signature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1121
34.1

Unique device ID register (96 bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1121

34.2

Memory size data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1122
34.2.1

35

28/1141

Flash size data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1122

Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1123

DocID022558 Rev 8

RM0316

List of tables

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.

Available features related to each product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
STM32F303xB/C and STM32F358xC peripheral register boundary
addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
STM32F303xD/E and STM32F398xE peripheral register boundary
addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
STM32F303x6/8 and STM32F328x8 peripheral register boundary
addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
CCM SRAM organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Boot modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Flash module organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Flash memory read protection status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Access status versus protection level and execution modes . . . . . . . . . . . . . . . . . . . . . . . 76
Flash interrupt request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Flash interface - register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Option byte format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Option byte organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Description of the option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
CRC internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
CRC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Low-power mode summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Sleep-now . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Sleep-on-exit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Standby mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
PWR register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
STM32F3xx peripherals interconnect matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
TIM1/8/20_ETR connection to ADCx analog watchdogs . . . . . . . . . . . . . . . . . . . . . . . . . 115
VREFOPAMPx to ADC channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
OPAMP output to ADC input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Comparator outputs to timer inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Timer output selection as comparator blanking source . . . . . . . . . . . . . . . . . . . . . . . . . . 119
DAC output selection as comparator inverting input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
DAC output selection as OPAMP non inverting input . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Timer synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Timer and EXTI signals triggering DAC conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
RCC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
NOR/PSRAM bank selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
NOR/PSRAM External memory address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
NAND/PC Card memory mapping and timing registers . . . . . . . . . . . . . . . . . . . . . . . . . . 173
NAND bank selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Programmable NOR/PSRAM access parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
Non-multiplexed I/O NOR Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
16-bit multiplexed I/O NOR Flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Non-multiplexed I/Os PSRAM/SRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
16-Bit multiplexed I/O PSRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
NOR Flash/PSRAM: Example of supported memories and transactions . . . . . . . . . . . . . 177
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

DocID022558 Rev 8

29/1141
33

List of tables
Table 46.
Table 47.
Table 48.
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.

30/1141

RM0316

FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
FMC_BWTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
FMC_BCRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
FMC_BTRx bit fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
Programmable NAND Flash/PC Card access parameters . . . . . . . . . . . . . . . . . . . . . . . . 211
8-bit NAND Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
16-bit NAND Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
16-bit PC Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
Supported memories and transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
16-bit PC-Card signals and access type. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
ECC result relevant bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
FMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
Port bit configuration table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
GPIO register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
SYSCFG register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
DMA implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
Programmable data width & endian behavior (when bits PINC = MINC = 1) . . . . . . . . . . 267
DMA interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE summary of DMA1 requests
for each channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
STM32F303x6/8 and STM32F328x8 summary of DMA1 requests for each channel. . . . 272
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE summary of DMA2 requests
for each channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
DMA register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE vector table . . . . . . . . . . . . . 285
STM32F303x6/8 and STM32F328x8 vector table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
External interrupt/event controller register map and reset values. . . . . . . . . . . . . . . . . . . 303
ADC external channels mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
ADC internal channels summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
ADC internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
ADC pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
Configuring the trigger polarity for regular external triggers . . . . . . . . . . . . . . . . . . . . . . . 327
ADC1 (master) & 2 (slave) - External triggers for regular channels . . . . . . . . . . . . . . . . . 328
ADC1 & ADC2 - External trigger for injected channels. . . . . . . . . . . . . . . . . . . . . . . . . . . 329
ADC3 & ADC4 - External trigger for regular channels . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
ADC3 & ADC4 - External trigger for injected channels. . . . . . . . . . . . . . . . . . . . . . . . . . . 330
TSAR timings depending on resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
Offset computation versus data resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

DocID022558 Rev 8

RM0316
Table 96.
Table 97.
Table 98.
Table 99.
Table 100.
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.

List of tables
Analog watchdog channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
Analog watchdog 1 comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
Analog watchdog 2 and 3 comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
ADC interrupts per each ADC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376
DELAY bits versus ADC resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409
ADC global register map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410
ADC register map and reset values for each ADC (offset=0x000
for master ADC, 0x100 for slave ADC, x=1..4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411
ADC register map and reset values (master and slave ADC
common registers) offset =0x300, x=1 or 34) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413
DACx pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416
External triggers (DAC1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
External triggers (DAC2). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
DAC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
Comparator input/output summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443
COMP register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464
Connections with dedicated I/O on STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467
Connections with dedicated I/O on STM32F303x6/8 and STM32F328x8 . . . . . . . . . . . . 467
OPAMP register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486
Acquisition sequence summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490
Spread spectrum deviation versus AHB clock frequency . . . . . . . . . . . . . . . . . . . . . . . . . 492
I/O state depending on its mode and IODEF bit value . . . . . . . . . . . . . . . . . . . . . . . . . . . 493
Effect of low-power modes on TSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495
Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495
TSC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504
Behavior of timer outputs versus BRK/BRK2 inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547
Counting direction versus encoder signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554
TIMx internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571
Output control bits for complementary OCx and OCxN channels with break feature . . . . 585
TIM1/TIM8/TIM20 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598
Counting direction versus encoder signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635
TIMx internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652
Output control bit for standard OCx channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663
TIM2/TIM3/TIM4 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668
TIM6/TIM7 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 682
TIMx Internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 722
Output control bits for complementary OCx and OCxN channels with break feature
(TIM15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 731
TIM15 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737
Output control bits for complementary OCx and OCxN channels with break feature
(TIM16/17) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 748
TIM16/TIM17 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755
IWDG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766
WWDG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 772
RTC pin PC13 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777
LSE pin PC14 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777
LSE pin PC15 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777
Effect of low-power modes on RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 789
Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 790
RTC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 814
STM32F3xx I2C implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817

DocID022558 Rev 8

31/1141
33

List of tables
Table 143.
Table 144.
Table 145.
Table 146.
Table 147.
Table 148.
Table 149.
Table 150.
Table 151.
Table 152.
Table 153.
Table 154.
Table 155.
Table 156.
Table 157.
Table 158.
Table 159.
Table 160.
Table 161.
Table 162.
Table 163.
Table 164.
Table 165.
Table 166.
Table 167.
Table 168.
Table 169.
Table 170.
Table 171.
Table 172.
Table 173.
Table 174.
Table 175.
Table 176.
Table 177.
Table 178.
Table 179.
Table 180.
Table 181.
Table 182.
Table 183.
Table 184.
Table 185.
Table 186.
Table 187.
Table 188.
Table 189.
Table 190.
Table 191.

32/1141

RM0316

Comparison of analog vs. digital filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 821
I2C-SMBUS specification data setup and hold times . . . . . . . . . . . . . . . . . . . . . . . . . . . . 824
I2C configuration table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 828
I2C-SMBUS specification clock timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 839
Examples of timings settings for fI2CCLK = 8 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 849
Examples of timings settings for fI2CCLK = 48 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . 849
SMBus timeout specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 852
SMBUS with PEC configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854
Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tTIMEOUT = 25 ms) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855
Examples of TIMEOUTB settings for various I2CCLK frequencies . . . . . . . . . . . . . . . . . 855
Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tIDLE = 50 µs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855
low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866
I2C Interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 866
I2C register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 883
STM32F3xx USART features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 887
Noise detection from sampled data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899
Error calculation for programmed baud rates at fCK = 72MHz in both cases of
oversampling by 16 or by 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902
Tolerance of the USART receiver when BRR [3:0] = 0000. . . . . . . . . . . . . . . . . . . . . . . . 903
Tolerance of the USART receiver when BRR [3:0] is different from 0000 . . . . . . . . . . . . 904
Frame formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908
Effect of low-power modes on the USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927
USART interrupt requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 927
USART register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 950
STM32F303x6/8 and STM32F328x8 SPI implementation . . . . . . . . . . . . . . . . . . . . . . . . 953
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE SPI implementation . . . . . . . 954
SPI interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 978
Audio-frequency precision using standard 8 MHz HSE . . . . . . . . . . . . . . . . . . . . . . . . . . 991
I2S interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 997
SPI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010
Transmit mailbox mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1025
Receive mailbox mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1025
bxCAN register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1051
STM32F3xx USB implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1055
Double-buffering buffer flag definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1065
Bulk double-buffering memory buffers usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1065
Isochronous memory buffers usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1067
Resume event detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1069
Reception status encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1080
Endpoint type encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1081
Endpoint kind meaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1081
Transmission status encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1081
Definition of allocated buffer memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1084
USB register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086
SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091
Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091
JTAG debug port data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096
32-bit debug port registers addressed through the shifted value A[3:2] . . . . . . . . . . . . . 1097
Packet request (8-bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098
ACK response (3 bits). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1099

DocID022558 Rev 8

RM0316
Table 192.
Table 193.
Table 194.
Table 195.
Table 196.
Table 197.
Table 198.
Table 199.
Table 200.
Table 201.
Table 202.
Table 203.

List of tables
DATA transfer (33 bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1099
SW-DP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1100
Cortex-M4®F AHB-AP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1101
Core debug registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1102
Main ITM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1105
Main ETM registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1107
Asynchronous TRACE pin assignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1113
Synchronous TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1113
Flexible TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1114
Important TPIU registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1118
DBG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1120
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1123

DocID022558 Rev 8

33/1141
33

List of figures

RM0316

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.

34/1141

STM32F303xB/C and STM32F358xC system architecture . . . . . . . . . . . . . . . . . . . . . . . . 48
STM32F303x6/8 and STM32F328x8 system architecture . . . . . . . . . . . . . . . . . . . . . . . . 48
STM32F303xDxE and STM32F398xE system architecture . . . . . . . . . . . . . . . . . . . . . . . . 49
Programming procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Flash memory Page Erase procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Flash memory Mass Erase procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
CRC calculation unit block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Power supply overview (STM32F303x devices) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Power supply overview (STM32F3x8 devices) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Power on reset/power down reset waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
PVD thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Simplified diagram of the reset circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
STM32F303xB/C and STM32F358xC clock tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
STM32F303xDxE and STM32F398xE clock tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
STM32F303x6/8 and STM32F328x8 clock tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
HSE/ LSE clock sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Frequency measurement with TIM16 in capture mode. . . . . . . . . . . . . . . . . . . . . . . . . . . 135
FMC block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
FMC memory banks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
Mode1 read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Mode1 write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
ModeA read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
ModeA write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
Mode2 and mode B read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
Mode2 write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
ModeB write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
ModeC read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
ModeC write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
ModeD read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
ModeD write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Muxed read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Muxed write access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
Asynchronous wait during a read access waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
Asynchronous wait during a write access waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
Wait configuration waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
Synchronous multiplexed read mode waveforms - NOR, PSRAM (CRAM) . . . . . . . . . . . 199
Synchronous multiplexed write mode waveforms - PSRAM (CRAM). . . . . . . . . . . . . . . . 201
NAND Flash/PC Card controller waveforms for common memory access. . . . . . . . . . . . 214
Access to non ‘CE don’t care’ NAND-Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
Basic structure of an I/O port bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
Basic structure of a five-volt tolerant I/O port bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
Input floating/pull up/pull down configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
Alternate function configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
High impedance-analog configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
DMA block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
STM32F302xB/C/D/E and STM32F302x6/8 DMA1 request mapping . . . . . . . . . . . . . . . 270
STM32F303x6/8 and STM32F328x8 DMA1 request mapping . . . . . . . . . . . . . . . . . . . . . 271

DocID022558 Rev 8

RM0316
Figure 49.
Figure 50.
Figure 51.
Figure 52.
Figure 53.
Figure 54.
Figure 55.
Figure 56.
Figure 57.
Figure 58.
Figure 59.
Figure 60.
Figure 61.
Figure 62.
Figure 63.
Figure 64.
Figure 65.
Figure 66.
Figure 67.
Figure 68.
Figure 69.
Figure 70.
Figure 71.
Figure 72.
Figure 73.
Figure 74.
Figure 75.
Figure 76.
Figure 77.
Figure 78.
Figure 79.
Figure 80.
Figure 81.
Figure 82.
Figure 83.
Figure 84.
Figure 85.
Figure 86.
Figure 87.
Figure 88.
Figure 89.
Figure 90.
Figure 91.
Figure 92.
Figure 93.
Figure 94.

List of figures
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE DMA2 request mapping . . . 274
External interrupt/event block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
External interrupt/event GPIO mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
ADC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
ADC clock scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
ADC1 and ADC2 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
ADC3 & ADC4 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
ADC calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
Updating the ADC calibration factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
Mixing single-ended and differential channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
Enabling / Disabling the ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
Analog to digital conversion time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
Stopping ongoing regular conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
Stopping ongoing regular and injected conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
Triggers are shared between ADC master & ADC slave . . . . . . . . . . . . . . . . . . . . . . . . . 328
Injected conversion latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
Example of JSQR queue of context (sequence change) . . . . . . . . . . . . . . . . . . . . . . . . . 335
Example of JSQR queue of context (trigger change) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
Example of JSQR queue of context with overflow before conversion . . . . . . . . . . . . . . . 336
Example of JSQR queue of context with overflow during conversion . . . . . . . . . . . . . . . 336
Example of JSQR queue of context with empty queue (case JQM=0). . . . . . . . . . . . . . . 337
Example of JSQR queue of context with empty queue (case JQM=1). . . . . . . . . . . . . . . 337
Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs during an ongoing conversion. . . . . . . . . . . . . . . . . . . . . . . 338
Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs during an ongoing conversion and a new
trigger occurs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs outside an ongoing conversion . . . . . . . . . . . . . . . . . . . . . . 339
Flushing JSQR queue of context by setting JADSTP=1 (JQM=1) . . . . . . . . . . . . . . . . . . 339
Flushing JSQR queue of context by setting ADDIS=1 (JQM=0). . . . . . . . . . . . . . . . . . . . 340
Flushing JSQR queue of context by setting ADDIS=1 (JQM=1). . . . . . . . . . . . . . . . . . . . 340
Example of JSQR queue of context when changing SW and HW triggers. . . . . . . . . . . . 341
Single conversions of a sequence, software trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
Continuous conversion of a sequence, software trigger . . . . . . . . . . . . . . . . . . . . . . . . . . 343
Single conversions of a sequence, hardware trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
Continuous conversions of a sequence, hardware trigger . . . . . . . . . . . . . . . . . . . . . . . . 343
Right alignment (offset disabled, unsigned value) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
Right alignment (offset enabled, signed value). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Left alignment (offset disabled, unsigned value) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
Left alignment (offset enabled, signed value) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
Example of overrun (OVR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348
AUTODLY=1, regular conversion in continuous mode, software trigger . . . . . . . . . . . . . 351
AUTODLY=1, regular HW conversions interrupted by injected conversions
(DISCEN=0; JDISCEN=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
AUTODLY=1, regular HW conversions interrupted by injected conversions . . . . . . . . . . . . .
(DISCEN=1, JDISCEN=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
AUTODLY=1, regular continuous conversions interrupted by injected conversions . . . . 353
AUTODLY=1 in auto- injected mode (JAUTO=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
Analog watchdog’s guarded area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
ADCy_AWDx_OUT signal generation (on all regular channels). . . . . . . . . . . . . . . . . . . . 356
ADCy_AWDx_OUT signal generation (AWDx flag not cleared by SW) . . . . . . . . . . . . . . 357

DocID022558 Rev 8

35/1141
42

List of figures
Figure 95.
Figure 96.
Figure 97.
Figure 98.
Figure 99.
Figure 100.
Figure 101.
Figure 102.
Figure 103.
Figure 104.
Figure 105.
Figure 106.
Figure 107.
Figure 108.
Figure 109.
Figure 110.
Figure 111.
Figure 112.
Figure 113.
Figure 114.
Figure 115.
Figure 116.
Figure 117.
Figure 118.
Figure 119.
Figure 120.
Figure 121.
Figure 122.
Figure 123.
Figure 124.
Figure 125.
Figure 126.
Figure 127.
Figure 128.
Figure 129.
Figure 130.
Figure 131.
Figure 132.
Figure 133.
Figure 134.
Figure 135.
Figure 136.
Figure 137.
Figure 138.
Figure 139.
Figure 140.

36/1141

RM0316

ADCy_AWDx_OUT signal generation (on a single regular channel) . . . . . . . . . . . . . . . . 357
ADCy_AWDx_OUT signal generation (on all injected channels) . . . . . . . . . . . . . . . . . . . 357
Dual ADC block diagram(1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
Injected simultaneous mode on 4 channels: dual ADC mode . . . . . . . . . . . . . . . . . . . . . 360
Regular simultaneous mode on 16 channels: dual ADC mode . . . . . . . . . . . . . . . . . . . . 362
Interleaved mode on 1 channel in continuous conversion mode: dual ADC mode. . . . . . 364
Interleaved mode on 1 channel in single conversion mode: dual ADC mode. . . . . . . . . . 364
Interleaved conversion with injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
Alternate trigger: injected group of each ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
Alternate trigger: 4 injected channels (each ADC) in discontinuous mode . . . . . . . . . . . . 367
Alternate + regular simultaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
Case of trigger occurring during injected conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
DMA Requests in regular simultaneous mode when MDMA=0b00 . . . . . . . . . . . . . . . . . 369
DMA requests in regular simultaneous mode when MDMA=0b10 . . . . . . . . . . . . . . . . . . 370
DMA requests in interleaved mode when MDMA=0b10 . . . . . . . . . . . . . . . . . . . . . . . . . . 370
Temperature sensor channel block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
VBAT channel block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
VREFINT channel block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374
DAC1 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
DAC2 block diagram (only on STM32F303x6/8 and STM32F328) . . . . . . . . . . . . . . . . . 416
Data registers in single DAC channel mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417
Timing diagram for conversion with trigger disabled TEN = 0 . . . . . . . . . . . . . . . . . . . . . 418
Data registers in dual DAC channel mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
DAC LFSR register calculation algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425
DAC conversion (SW trigger enabled) with LFSR wave generation. . . . . . . . . . . . . . . . . 425
DAC triangle wave generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426
DAC conversion (SW trigger enabled) with triangle wave generation . . . . . . . . . . . . . . . 426
Comparator 1 and 2 block diagrams (STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE comparator 7
block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442
STM32F303x6/8 and STM32F328x8 comparators 2/4/6 block diagrams. . . . . . . . . . . . . 442
Comparator hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445
Comparator output blanking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE Comparators and
operational amplifiers interconnections (part 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468
STM32F303xB/C/D/E and STM32F358xC comparators and operational
amplifiers interconnections (part 2 ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 469
STM32F303x6/8 and STM32F328x8 comparator and operational amplifier
connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470
Timer controlled Multiplexer mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472
Standalone mode: external gain setting mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
Follower configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474
PGA mode, internal gain setting (x2/x4/x8/x16), inverting input not used . . . . . . . . . . . . 475
PGA mode, internal gain setting (x2/x4/x8/x16), inverting input used for
filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475
TSC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488
Surface charge transfer analog I/O group structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489
Sampling capacitor voltage variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490
Charge transfer acquisition sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491
Spread spectrum variation principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492
Advanced-control timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 507

DocID022558 Rev 8

RM0316
Figure 141.
Figure 142.
Figure 143.
Figure 144.
Figure 145.
Figure 146.
Figure 147.
Figure 148.
Figure 149.
Figure 150.
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.

List of figures
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 509
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 509
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
Counter timing diagram, update event when ARPE=0 (TIMx_ARR not preloaded) . . . . . 513
Counter timing diagram, update event when ARPE=1 (TIMx_ARR preloaded) . . . . . . . . 513
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516
Counter timing diagram, update event when repetition counter is not used . . . . . . . . . . . 517
Counter timing diagram, internal clock divided by 1, TIMx_ARR = 0x6 . . . . . . . . . . . . . . 518
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519
Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36 . . . . . . . . . . . . . . 519
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520
Counter timing diagram, update event with ARPE=1 (counter underflow) . . . . . . . . . . . . 520
Counter timing diagram, Update event with ARPE=1 (counter overflow) . . . . . . . . . . . . . 521
Update rate examples depending on mode and TIMx_RCR register settings . . . . . . . . . 522
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 524
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526
Control circuit in external clock mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 528
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529
Output stage of capture/compare channel (channel 1, idem ch. 2 and 3) . . . . . . . . . . . . 530
Output stage of capture/compare channel (channel 4). . . . . . . . . . . . . . . . . . . . . . . . . . . 530
Output stage of capture/compare channel (channel 5, idem ch. 6) . . . . . . . . . . . . . . . . . 531
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 533
Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 535
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 536
Center-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537
Generation of 2 phase-shifted PWM signals with 50% duty cycle . . . . . . . . . . . . . . . . . . 539
Combined PWM mode on channel 1 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
3-phase combined PWM signals with multiple trigger pulses per period . . . . . . . . . . . . . 541
Complementary output with dead-time insertion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 542
Dead-time waveforms with delay greater than the negative pulse . . . . . . . . . . . . . . . . . . 542
Dead-time waveforms with delay greater than the positive pulse. . . . . . . . . . . . . . . . . . . 543
Various output behavior in response to a break event on BKIN (OSSI = 1) . . . . . . . . . . . 546
PWM output state following BKIN and BKIN2 pins assertion (OSSI=1) . . . . . . . . . . . . . . 547
PWM output state following BKIN assertion (OSSI=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . 548
Clearing TIMx OCxREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549
6-step generation, COM example (OSSR=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550
Example of one pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
Retriggerable one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553
Example of counter operation in encoder interface mode. . . . . . . . . . . . . . . . . . . . . . . . . 554
Example of encoder interface mode with TI1FP1 polarity inverted. . . . . . . . . . . . . . . . . . 555
Measuring time interval between edges on 3 signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556
Example of Hall sensor interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

DocID022558 Rev 8

37/1141
42

List of figures
Figure 193.
Figure 194.
Figure 195.
Figure 196.
Figure 197.
Figure 198.
Figure 199.
Figure 200.
Figure 201.
Figure 202.
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.

38/1141

RM0316

Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559
Control circuit in Gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561
Control circuit in external clock mode 2 + trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . 562
General-purpose timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 604
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 604
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607
Counter timing diagram, Update event when ARPE=0 (TIMx_ARR not preloaded). . . . . 607
Counter timing diagram, Update event when ARPE=1 (TIMx_ARR preloaded). . . . . . . . 608
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610
Counter timing diagram, Update event when repetition counter
is not used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611
Counter timing diagram, internal clock divided by 1, TIMx_ARR=0x6 . . . . . . . . . . . . . . . 612
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613
Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36 . . . . . . . . . . . . . . 613
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614
Counter timing diagram, Update event with ARPE=1 (counter underflow). . . . . . . . . . . . 614
Counter timing diagram, Update event with ARPE=1 (counter overflow) . . . . . . . . . . . . . 615
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 616
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 618
Control circuit in external clock mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 620
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620
Output stage of capture/compare channel (channel 1). . . . . . . . . . . . . . . . . . . . . . . . . . . 621
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623
Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 626
Center-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627
Generation of 2 phase-shifted PWM signals with 50% duty cycle . . . . . . . . . . . . . . . . . . 628
Combined PWM mode on channels 1 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 630
Clearing TIMx OCxREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 631
Example of one-pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632
Retriggerable one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634
Example of counter operation in encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . 635
Example of encoder interface mode with TI1FP1 polarity inverted . . . . . . . . . . . . . . . . . 636
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637
Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 638
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639
Control circuit in external clock mode 2 + trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . 640
Master/Slave timer example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641
Gating TIM2 with OC1REF of TIM3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642
Gating TIM2 with Enable of TIM3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643
Triggering TIM2 with update of TIM3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643

DocID022558 Rev 8

RM0316
Figure 244.
Figure 245.
Figure 246.
Figure 247.
Figure 248.
Figure 249.
Figure 250.
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.

List of figures
Triggering TIM2 with Enable of TIM3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644
Triggering TIM3 and TIM2 with TIM3 TI1 input. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645
Basic timer block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 672
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 672
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 674
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 675
Counter timing diagram, update event when ARPE = 0 (TIMx_ARR not
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 675
Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 677
TIM15 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685
TIM16/TIM17 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 686
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 688
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 688
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 690
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 690
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 691
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 691
Counter timing diagram, update event when ARPE=0 (TIMx_ARR not
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 692
Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 692
Update rate examples depending on mode and TIMx_RCR register settings . . . . . . . . . 694
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 695
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 697
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697
Output stage of capture/compare channel (channel 1). . . . . . . . . . . . . . . . . . . . . . . . . . . 698
Output stage of capture/compare channel (channel 2 for TIM15) . . . . . . . . . . . . . . . . . . 698
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700
Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703
Combined PWM mode on channel 1 and 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704
Complementary output with dead-time insertion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705
Dead-time waveforms with delay greater than the negative pulse. . . . . . . . . . . . . . . . . . 706
Dead-time waveforms with delay greater than the positive pulse. . . . . . . . . . . . . . . . . . . 706
Output behavior in response to a break . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 709
Example of one pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 710
Measuring time interval between edges on 2 signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 712
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 713
Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715
IR internal hardware connections with TIM16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757
Independent watchdog block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758
Watchdog block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768
Window watchdog timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 769
RTC block diagram
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775

DocID022558 Rev 8

39/1141
42

List of figures
Figure 292.
Figure 293.
Figure 294.
Figure 295.
Figure 296.
Figure 297.
Figure 298.
Figure 299.
Figure 300.
Figure 301.
Figure 302.
Figure 303.
Figure 304.
Figure 305.
Figure 306.
Figure 307.
Figure 308.
Figure 309.
Figure 310.
Figure 311.
Figure 312.
Figure 313.
Figure 314.
Figure 315.
Figure 316.
Figure 317.
Figure 318.
Figure 319.
Figure 320.
Figure 321.
Figure 322.
Figure 323.
Figure 324.
Figure 325.
Figure 326.
Figure 327.
Figure 328.
Figure 329.
Figure 330.
Figure 331.
Figure 332.
Figure 333.
Figure 334.
Figure 335.
Figure 336.
Figure 337.
Figure 338.
Figure 339.
Figure 340.
Figure 341.
Figure 342.
Figure 343.

40/1141

RM0316

I2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 818
I2C bus protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 820
Setup and hold timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 822
I2C initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825
Data reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826
Data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 827
Slave initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831
Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=0. . . . . . . . . . . . . 832
Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=1. . . . . . . . . . . . . 833
Transfer bus diagrams for I2C slave transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834
Transfer sequence flowchart for slave receiver with NOSTRETCH=0 . . . . . . . . . . . . . . . 835
Transfer sequence flowchart for slave receiver with NOSTRETCH=1 . . . . . . . . . . . . . . . 836
Transfer bus diagrams for I2C slave receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 836
Master clock generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 838
Master initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840
10-bit address read access with HEAD10R=0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840
10-bit address read access with HEAD10R=1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841
Transfer sequence flowchart for I2C master transmitter for N≤255 bytes . . . . . . . . . . . . 842
Transfer sequence flowchart for I2C master transmitter for N>255 bytes . . . . . . . . . . . . 843
Transfer bus diagrams for I2C master transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 844
Transfer sequence flowchart for I2C master receiver for N≤255 bytes. . . . . . . . . . . . . . . 846
Transfer sequence flowchart for I2C master receiver for N >255 bytes . . . . . . . . . . . . . . 847
Transfer bus diagrams for I2C master receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848
Timeout intervals for tLOW:SEXT, tLOW:MEXT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 852
Transfer sequence flowchart for SMBus slave transmitter N bytes + PEC. . . . . . . . . . . . 856
Transfer bus diagrams for SMBus slave transmitter (SBC=1) . . . . . . . . . . . . . . . . . . . . . 857
Transfer sequence flowchart for SMBus slave receiver N Bytes + PEC . . . . . . . . . . . . . 858
Bus transfer diagrams for SMBus slave receiver (SBC=1) . . . . . . . . . . . . . . . . . . . . . . . 859
Bus transfer diagrams for SMBus master transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860
Bus transfer diagrams for SMBus master receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 862
I2C interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 867
USART block diagram
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 889
Word length programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891
Configurable stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893
TC/TXE behavior when transmitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894
Start bit detection when oversampling by 16 or 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895
Data sampling when oversampling by 16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899
Data sampling when oversampling by 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899
Mute mode using Idle line detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
Mute mode using address mark detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907
Break detection in LIN mode (11-bit break length - LBDL bit is set) . . . . . . . . . . . . . . . . . 910
Break detection in LIN mode vs. Framing error detection. . . . . . . . . . . . . . . . . . . . . . . . . 911
USART example of synchronous transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
USART data clock timing diagram (M bits = 00). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
USART data clock timing diagram (M bits = 01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 913
RX data setup/hold time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 913
ISO 7816-3 asynchronous protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915
Parity error detection using the 1.5 stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 916
IrDA SIR ENDEC- block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 920
IrDA data modulation (3/16) -Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 921
Transmission using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 922
Reception using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923

DocID022558 Rev 8

RM0316
Figure 344.
Figure 345.
Figure 346.
Figure 347.
Figure 348.
Figure 349.
Figure 350.
Figure 351.
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.

List of figures
Hardware flow control between 2 USARTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923
RS232 RTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 924
RS232 CTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 925
USART interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 928
SPI block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954
Full-duplex single master/ single slave application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955
Half-duplex single master/ single slave application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 956
Simplex single master/single slave application (master in transmit-only/
slave in receive-only mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 957
Master and three independent slaves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958
Multi-master application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959
Hardware/software slave select management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 960
Data clock timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961
Data alignment when data length is not equal to 8-bit or 16-bit . . . . . . . . . . . . . . . . . . . . 962
Packing data in FIFO for transmission and reception . . . . . . . . . . . . . . . . . . . . . . . . . . . 966
Master full-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 969
Slave full-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 970
Master full-duplex communication with CRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 971
Master full-duplex communication in packed mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 972
NSSP pulse generation in Motorola SPI master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 975
TI mode transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976
I2S block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 979
I2S full-duplex block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981
I2S Philips protocol waveforms (16/32-bit full accuracy). . . . . . . . . . . . . . . . . . . . . . . . . . 982
I2S Philips standard waveforms (24-bit frame) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 982
Transmitting 0x8EAA33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 983
Receiving 0x8EAA33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 983
I2S Philips standard (16-bit extended to 32-bit packet frame) . . . . . . . . . . . . . . . . . . . . . 983
Example of 16-bit data frame extended to 32-bit channel frame . . . . . . . . . . . . . . . . . . . 983
MSB Justified 16-bit or 32-bit full-accuracy length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984
MSB justified 24-bit frame length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984
MSB justified 16-bit extended to 32-bit packet frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985
LSB justified 16-bit or 32-bit full-accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985
LSB justified 24-bit frame length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985
Operations required to transmit 0x3478AE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986
Operations required to receive 0x3478AE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986
LSB justified 16-bit extended to 32-bit packet frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986
Example of 16-bit data frame extended to 32-bit channel frame . . . . . . . . . . . . . . . . . . . 987
PCM standard waveforms (16-bit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 987
PCM standard waveforms (16-bit extended to 32-bit packet frame). . . . . . . . . . . . . . . . . 988
Start sequence in master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989
Audio sampling frequency definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990
I2S clock generator architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990
CAN network topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012
bxCAN operating modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015
bxCAN in silent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016
bxCAN in loop back mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016
bxCAN in combined mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017
Transmit mailbox states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1018
Receive FIFO states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1019
Filter bank scale configuration - register organization . . . . . . . . . . . . . . . . . . . . . . . . . . 1022
Example of filter numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023

DocID022558 Rev 8

41/1141
42

List of figures

RM0316

Figure 395.
Figure 396.
Figure 397.
Figure 398.
Figure 399.
Figure 400.
Figure 401.
Figure 402.
Figure 403.

Filtering mechanism - example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1024
CAN error state diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1025
Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1027
CAN frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1028
Event flags and interrupt generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1029
Can mailbox registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1041
USB peripheral block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1056
Packet buffer areas with examples of buffer description table locations . . . . . . . . . . . . 1061
Block diagram of STM32 MCU and
Cortex-M4®F-level debug support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088
Figure 404. SWJ debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1090
Figure 405. JTAG TAP connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1094
Figure 406. TPIU block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1113

42/1141

DocID022558 Rev 8

RM0316

1

Overview of the manual

Overview of the manual
Table 1. Available features related to each product

Peripherals

STM32F303xB/C STM32F303xD/E

STM32F358xC

STM32F398xE

STM32F303x6/8

STM32F328x6/8

Section 9:
Reset and
clock control
(RCC)

Available

Available

Available

Available

Available

Available

Section 11:
Generalpurpose I/Os
(GPIO)

Up to 87

Up to 115

Up to 86

Up to 114

Up to 52

Up to 51

Section 13:
Direct
memory
access
controller
(DMA)

DMA1&2

DMA1&2

DMA1&2

DMA1&2

DMA1

DMA1

Section 15:
Analog-todigital
converters
(ADC)

ADC1,2,3&4

ADC1,2,3&4

ADC1,2,3&4

ADC1,2,3&4

ADC1&2

ADC1&2

Section 16:
Digital-toanalog
converter
(DAC1 and
DAC2)

DAC1 Ch.1&2

DAC1 Ch.1&2

DAC1 Ch.1&2
+ DAC2 Ch.1

DAC1 Ch.1&2
+ DAC2 Ch.1

Section 17:
Comparator
(COMP)

Comp1,2,3,4,5, Comp1,2,3,4,5, Comp1,2,3,4,5 Comp1,2,3,4,
6&7
6&7
,6&7
5,6&7

Comp2,4&6

Comp2,4&6

DAC1 Ch.1&2 DAC1 Ch.1&2

Section 18:
Operational
amplifier
(OPAMP)

Opamp 1,2,3
and 4

Opamp 1,2,3
and 4

Opamp 1,2,3
and 4

Opamp 1,2,3
and 4

Opamp 2

Opamp 2

Section 19:
Touch
sensing
controller
(TSC)

Up to 24

Up to 24

Up to 24

Up to 24

Up to 18

Up to 17

TIM1 and 8

TIM1, TIM8
and TIM20

TIM1 and 8

TIM1, TIM8
and TIM20

TIM1

TIM1

Section 20:
Advancedcontrol timers
(TIM1/TIM8/T
IM20)

DocID022558 Rev 8

43/1141
45

Overview of the manual

RM0316

Table 1. Available features related to each product (continued)
Peripherals

STM32F303xB/C STM32F303xD/E

STM32F358xC

STM32F398xE

STM32F303x6/8

STM32F328x6/8

Section 21:
Generalpurpose
timers
(TIM2/TIM3/T
IM4)

TIM2,3&4

TIM2,3&4

TIM2,3&4

TIM2,3&4

TIM2&3

TIM2&3

Section 23:
Generalpurpose
timers
(TIM15/TIM1
6/TIM17)

TIM15,16&17

TIM15,16&17

TIM15,16&17

TIM15,16&17

TIM15,16&17

TIM15,16&17

Section 22:
Basic timers
(TIM6/TIM7)

TIM6&7

TIM6&7

TIM6&7

TIM6&7

TIM6&7

TIM6&7

Section 24:
Infrared
interface
(IRTIM)

Available

Available

Available

Available

Available

Available

Section 25:
Independent
watchdog
(IWDG)

Available

Available

Available

Available

Available

Available

Section 26:
System
window
watchdog
(WWDG)

Available

Available

Available

Available

Available

Available

Section 27:
Real-time
clock (RTC)

Available

Available

Available

Available

Available

Available

Section 28:
Interintegrated
circuit (I2C)
interface

I2C1, I2C2

I2C1, I2C2,
I2C3

I2C1, I2C2

I2C1, I2C2,
I2C3

I2C1

I2C1

Section 29:
Universal
synchronous
asynchronous
receiver
transmitter
(USART)

Up to 5
USARTs

Up to 5
USARTs

Up to 5
USARTs

Up to 5
USARTs

Up to 3
USARTs

Up to 3
USARTs

Section 30:
Serial
peripheral
interface /
inter-IC sound
(SPI/I2S)

SPI1, SPI2&3
with I2S

SPI1, SPI2,
SPI3, SPI4 with
I2S

SPI1, SPI2&3
with I2S

SPI1, SPI2,
SPI3, SPI4
with I2S

SPI1

SPI1

44/1141

DocID022558 Rev 8

RM0316

Overview of the manual
Table 1. Available features related to each product (continued)

Peripherals

STM32F303xB/C STM32F303xD/E

STM32F358xC

STM32F398xE

STM32F303x6/8

STM32F328x6/8

Section 31:
Controller
area network
(bxCAN)

Available

Available

Available

Available

Available

Available

Section 32:
Universal
serial bus fullspeed device
interface
(USB)

Available

Available

Not Available

Not Available

Not Available

Not Available

DocID022558 Rev 8

45/1141
45

Documentation conventions

RM0316

2

Documentation conventions

2.1

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 bit
(rc_r)
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.

2.2

Glossary
This section gives a brief definition of acronyms and abbreviations used in this document:

2.3

•

The ARM Cortex®-M4 core integrates one debug port: SWD debug port (SWD-DP)
provides a 2-pin (clock and data) interface based on the Serial Wire Debug (SWD)
protocol. Refer to the Cortex®-M4 technical reference manual.

•

Word: data of 32-bit length.

•

Half-word: data of 16-bit length.

•

Byte: data of 8-bit length.

•

IAP (in-application programming): IAP is the ability to re-program the Flash memory
of a microcontroller while the user program is running.

•

ICP (in-circuit programming): ICP is the ability to program the Flash memory of a
microcontroller using the JTAG protocol, the SWD protocol or the bootloader while the
device is mounted on the user application board.

•

Option bytes: product configuration bits stored in the Flash memory.

•

OBL: option byte loader.

•

AHB: advanced high-performance bus.

Peripheral availability
For peripheral availability and number across all sales types, refer to the particular device
datasheet.

46/1141

DocID022558 Rev 8

RM0316

System and memory overview

3

System and memory overview

3.1

System architecture
The STM32F303xB/C/D/E, STM32F358xC and STM32F398xE main system consists of:
•

•

Five masters:
–

Cortex®-M4 core I-bus

–

Cortex®-M4 core D-bus

–

Cortex®-M4 core S-bus

–

GP-DMA1 and GP-DMA2 (general-purpose DMAs)

Seven (eight in STM32F303xDxE and STM32F398xE) slaves:
–

Internal Flash memory on the DCode

–

Internal Flash memory on ICode

–

Up to Internal 40 Kbyte SRAM

–

Internal 8 Kbyte CCM SRAM (16 Kbyte CCM SRAM for STM32F303xE and
STM32F398xE)

–

FMC in STM32F303xDxE and STM32F398xE

–

AHB to APBx (APB1 or APB2), which connect all the APB peripherals

–

AHB dedicated to GPIO ports

–

ADCs 1, 2, 3 and 4.

The STM32F303x6/8 and STM32F328x8 main system consists of:
•

•

Four masters:
–

Cortex®-M4 core I-bus

–

Cortex®-M4 core D-bus

–

Cortex®-M4 core S-bus

–

GP-DMA1 (general-purpose DMA)

Seven slaves:
–

Internal Flash memory on the DCode

–

Internal Flash memory on ICode

–

Up to Internal 12 Kbyte SRAM

–

Internal 4 Kbyte CCM SRAM

–

AHB to APBx (APB1 or APB2), which connect all the APB peripherals

–

AHB dedicated to GPIO ports

–

ADCs 1 and 2

These are interconnected using a multilayer AHB bus architecture as shown in Figure 1:

DocID022558 Rev 8

47/1141
50

System and memory overview

RM0316

Figure 1. STM32F303xB/C and STM32F358xC system architecture

6EXV

*3'0$
*3'0$

'0$
'0$

6
6

'EXV

6

,EXV

6

$50
&257(;0

6

%XV0DWUL[6

0

0

0

0

0

0

0

$+%GHGLFDWHG
WR*3,2SRUWV

,&2'(
)/$6+.
ELWV

)/7,)

'&2'(

$'& $'&
$'& $'&
5&&76&&5&DQG
$+%WR$3%DQG$3%

65$0
XSWR.%
8SWR.%
&&05$0

069

Figure 2. STM32F303x6/8 and STM32F328x8 system architecture

6EXV

*3'0$

'0$

6

'EXV

6

,EXV

6

$50
&257(;0

6

%XV0DWUL[6

0

0

0

0

0

0

0

$+%GHGLFDWHG
WR*3,2SRUWV

,&2'(
)/$6+.
ELWV

)/7,)

'&2'(
$'& $'&
5&&76&&5&DQG
$+%WR$3%DQG$3%

65$0
XSWR.%
8SWR.%
&&05$0

069

48/1141

DocID022558 Rev 8

RM0316

System and memory overview
Figure 3. STM32F303xDxE and STM32F398xE system architecture

6EXV

*3'0$
*3'0$

'0$
'0$

6
6

'EXV

6

,EXV

6

$50
&257(;0

6

%XV0DWUL[6

0

0

0

0

0

0

0

0

)0&
,&2'(
)/$6+.
ELWV

)/7,)

$+%GHGLFDWHG
WR*3,2SRUWV

'&2'(

$'& $'&
$'& $'&
.%65$0
5&&76&&5&DQG
$+%WR$3%DQG$3%
.%&&0
5$0
06Y9

3.1.1

S0: I-bus
This bus connects the Instruction bus of the Cortex®-M4 core to the BusMatrix. This bus is
used by the core to fetch instructions. The targets of this bus are the internal Flash memory,
the SRAM and the CCM SRAM.

3.1.2

S1: D-bus
This bus connects the DCode bus (literal load and debug access) of the Cortex®-M4 core to
the BusMatrix. The targets of this bus are the internal Flash memory, the SRAM and the
CCM SRAM.

3.1.3

S2: S-bus
This bus connects the system bus of the Cortex®-M4 core to the BusMatrix. This bus is
used to access data located in the peripheral or SRAM area. The targets of this bus are the
SRAM, the AHB to APB1/APB2 bridges, the AHB IO port and the ADC.

3.1.4

S3, S4: DMA-bus
This bus connects the AHB master interface of the DMA to the BusMatrix which manages
the access of different Masters to Flash, SRAM and peripherals.

DocID022558 Rev 8

49/1141
50

System and memory overview

3.1.5

RM0316

BusMatrix
The BusMatrix manages the access arbitration between Masters. The arbitration uses a
Round Robin algorithm. The BusMatrix is composed of five masters (CPU AHB, System
bus, DCode bus, ICode bus, DMA1&2 bus) and seven slaves (FLITF, SRAM, CCM SRAM,
AHB2GPIO and AHB2APB1/2 bridges, and ADC).

AHB/APB bridges
The two AHB/APB bridges provide full synchronous connections between the AHB and the
2 APB buses. APB1 is limited to 36 MHz, APB2 operates at full speed (72 MHz).
Refer to Section 3.2.2: Memory map and register boundary addresses on page 51 for the
address mapping of the peripherals connected to this bridge.
After each device reset, all peripheral clocks are disabled (except for the SRAM and FLITF).
Before using a peripheral user has to enable its clock in the RCC_AHBENR,
RCC_APB2ENR or RCC_APB1ENR register.
When a 16- or 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.

50/1141

DocID022558 Rev 8

RM0316

3.2

Memory organization

3.2.1

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 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.

3.2.2

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 2. STM32F303xB/C and STM32F358xC peripheral register boundary
addresses(1)

Bus

AHB3

AHB2

Boundary address

Size
(bytes)

Peripheral

0x5000 0400 - 0x5000 07FF

1K

ADC3 - ADC4

0x5000 0000 - 0x5000 03FF

1K

ADC1 - ADC2

0x4800 1800 - 0x4FFF FFFF

~132 M

0x4800 1400 - 0x4800 17FF

1K

GPIOF

0x4800 1000 - 0x4800 13FF

1K

GPIOE

0x4800 0C00 - 0x4800 0FFF

1K

GPIOD

0x4800 0800 - 0x4800 0BFF

1K

GPIOC

0x4800 0400 - 0x4800 07FF

1K

GPIOB

0x4800 0000 - 0x4800 03FF

1K

GPIOA

0x4002 4400 - 0x47FF FFFF

~128 M

Peripheral register map

Section 15.6.4 on page 410

Reserved

Section 11.4.12 on page 243

Reserved

DocID022558 Rev 8

51/1141
63

RM0316
Table 2. STM32F303xB/C and STM32F358xC peripheral register boundary
addresses(1) (continued)
Bus

AHB1

APB2

52/1141

Boundary address

Size
(bytes)

Peripheral

Peripheral register map

0x4002 4000 - 0x4002 43FF

1K

TSC

0x4002 3400 - 0x4002 3FFF

3K

Reserved

0x4002 3000 - 0x4002 33FF

1K

CRC

0x4002 2400 - 0x4002 2FFF

3K

Reserved

0x4002 2000 - 0x4002 23FF

1K

Flash interface

0x4002 1400 - 0x4002 1FFF

3K

Reserved

0x4002 1000 - 0x4002 13FF

1K

RCC

0x4002 0800 - 0x4002 0FFF

2K

Reserved

0x4002 0400 - 0x4002 07FF

1K

DMA2

0x4002 0000 - 0x4002 03FF

1K

DMA1

0x4001 8000 - 0x4001 FFFF

32 K

Reserved

0x4001 4C00 - 0x4001 7FFF

13 K

Reserved

0x4001 4800 - 0x4001 4BFF

1K

TIM17

0x4001 4400 - 0x4001 47FF

1K

TIM16

0x4001 4000 - 0x4001 43FF

1K

TIM15

0x4001 3C00 - 0x4001 3FFF

1K

Reserved

0x4001 3800 - 0x4001 3BFF

1K

USART1

Section 3.7.12 on page 1130

0x4001 3400 - 0x4001 37FF

1K

TIM8

Section 20.4.25 on page 598

0x4001 3000 - 0x4001 33FF

1K

SPI1

Section 30.9.10 on page 1010

0x4001 2C00 - 0x4001 2FFF

1K

TIM1

Section 20.4.25 on page 598

0x4001 0800 - 0x4001 2BFF

9K

Reserved

0x4001 0400 - 0x4001 07FF

1K

EXTI

Section 14.3.13 on page 303

0x4001 0000 - 0x4001 03FF

1K

SYSCFG + COMP +
OPAMP

Section 12.1.10 on page 261,
Section 17.5.8 on page 464,
Section 18.4.5 on page 486

0x4000 7800 - 0x4000 FFFF

34 K

Reserved

DocID022558 Rev 8

Section 19.6.11 on page 504

Section 6.4.6 on page 93

Section 4.6 on page 83

Section 9.4.14 on page 166

Section 13.5.7 on page 282

Section 23.6.17 on page 755
Section 23.5.18 on page 737

RM0316
Table 2. STM32F303xB/C and STM32F358xC peripheral register boundary
addresses(1) (continued)
Bus

APB1

APB1

Boundary address

Size
(bytes)

Peripheral

Peripheral register map

0x4000 7400 - 0x4000 77FF

1K

DAC1

Section 16.10.15 on page 438

0x4000 7000 - 0x4000 73FF

1K

PWR

Section 7.4.3 on page 110

0x4000 6C00 - 0x4000 6FFF

1K

Reserved

0x4000 6800 - 0x4000 6BFF

1K

Reserved

0x4000 6400 - 0x4000 67FF

1K

bxCAN

0x4000 6000 - 0x4000 63FF

1K

USB SRAM 512 bytes

0x4000 5C00 - 0x4000 5FFF

1K

USB device FS

0x4000 5800 - 0x4000 5BFF

1K

I2C2

0x4000 5400 - 0x4000 57FF

1K

I2C1

0x4000 5000 - 0x4000 53FF

1K

UART5

0x4000 4C00 - 0x4000 4FFF

1K

UART4

0x4000 4800 - 0x4000 4BFF

1K

USART3

0x4000 4400 - 0x4000 47FF

1K

USART2

0x4000 4000 - 0x4000 43FF

1K

I2S3ext

0x4000 3C00 - 0x4000 3FFF

1K

SPI3/I2S3

0x4000 3800 - 0x4000 3BFF

1K

SPI2/I2S2

0x4000 3400 - 0x4000 37FF

1K

I2S2ext

0x4000 3000 - 0x4000 33FF

1K

IWDG

Section 25.4.6 on page 766

0x4000 2C00 - 0x4000 2FFF

1K

WWDG

Section 26.4.4 on page 772

0x4000 2800 - 0x4000 2BFF

1K

RTC

Section 27.6.20 on page 814

0x4000 1800 - 0x4000 27FF

4K

Reserved

0x4000 1400 - 0x4000 17FF

1K

TIM7

0x4000 1000 - 0x4000 13FF

1K

TIM6

0x4000 0C00 - 0x4000 0FFF

1K

Reserved

0x4000 0800 - 0x4000 0BFF

1K

TIM4

0x4000 0400 - 0x4000 07FF

1K

TIM3

0x4000 0000 - 0x4000 03FF

1K

TIM2

0x2000 A000 - 3FFF FFFF

~512 M

Section 31.9.5 on page 1051
Section 32.6.3 on page 1086

Section 28.7.12 on page 883

Section 3.7.12 on page 1130

Section 30.9.10 on page 1010

Section 22.4.9 on page 682

Section 21.4.19 on page 668

Reserved

0x2000 0000 - 0x2000 9FFF

40 K

SRAM

-

0x1FFF F800 - 0x1FFF FFFF

2K

Option bytes

-

0x1FFF D800 - 0x1FFF F7FF

8K

System memory

-

0x1000 2000 - 0x1FFF D7FF

~256 M

0x1000 0000 - 0x1000 1FFF

8K

Reserved
CCM SRAM

DocID022558 Rev 8

-

53/1141
63

RM0316
Table 2. STM32F303xB/C and STM32F358xC peripheral register boundary
addresses(1) (continued)
Bus

Boundary address

Size
(bytes)

0x0804 0000 - 0x0FFF FFFF

~128 M

0x0800 0000 - 0x0803 FFFF

256 K

0x0004 0000 - 0x07FF FFFF

~128 M

0x0000 000 - 0x0003 FFFF

256 K

Peripheral

Peripheral register map

Reserved
Main Flash memory

-

Reserved
Main Flash memory,
system memory or
SRAM depending on
BOOT configuration

-

1. The gray color is used for reserved Flash memory addresses.

Table 3. STM32F303xD/E and STM32F398xE peripheral register boundary
addresses(1)
Bus

AHB4

AHB3

AHB2

54/1141

Boundary address

Size
(bytes)

Peripheral

0xA000 0400 - 0xA000 0FFF

4K

0x8000 0400 - 0x9FFF FFFF

512 M

FMC banks 3 and 4

0x6000 0000 - 0x7FFF FFFF

512 M

FMC banks 1 and 2

0x5000 0800 - 0x5FFF FFFF

384M

Reserved

0x5000 0400 - 0x5000 07FF

1K

ADC3 - ADC4

0x5000 0000 - 0x5000 03FF

1K

ADC1 - ADC2

0x4800 2000 - 0x4FFF FFFF

~132 M

0x4800 1C00 - 0x4800 1FFF

1K

GPIOH

0x4800 1800 - 0x4800 1BFF

1K

GPIOG

0x4800 1400 - 0x4800 17FF

1K

GPIOF

0x4800 1000 - 0x4800 13FF

1K

GPIOE

0x4800 0C00 - 0x4800 0FFF

1K

GPIOD

0x4800 0800 - 0x4800 0BFF

1K

GPIOC

0x4800 0400 - 0x4800 07FF

1K

GPIOB

0x4800 0000 - 0x4800 03FF

1K

GPIOA

0x4002 4400 - 0x47FF FFFF

~128 M

Peripheral register map

FMC control registers
Section 10.7: FMC register
map

Section 15.6.4 on page 410

Reserved

Reserved

DocID022558 Rev 8

Section 11.4.12 on page 243

RM0316
Table 3. STM32F303xD/E and STM32F398xE peripheral register boundary
addresses(1) (continued)
Bus

AHB1

APB2

Boundary address

Size
(bytes)

Peripheral

Peripheral register map

0x4002 4000 - 0x4002 43FF

1K

TSC

0x4002 3400 - 0x4002 3FFF

3K

Reserved

0x4002 3000 - 0x4002 33FF

1K

CRC

0x4002 2400 - 0x4002 2FFF

3K

Reserved

0x4002 2000 - 0x4002 23FF

1K

Flash interface

0x4002 1400 - 0x4002 1FFF

3K

Reserved

0x4002 1000 - 0x4002 13FF

1K

RCC

0x4002 0800 - 0x4002 0FFF

2K

Reserved

0x4002 0400 - 0x4002 07FF

1K

DMA2

0x4002 0000 - 0x4002 03FF

1K

DMA1

0x4001 8000 - 0x4001 FFFF

32 K

Reserved

0x4001 4C00 - 0x4001 4FFF

1K

Reserved

0x4001 5400 - 0x4001 7FFF

11K

Reserved

0x4001 5000 - 0x4001 53FF

1K

TIM20

0x4001 4800 - 0x4001 4BFF

1K

TIM17

0x4001 4400 - 0x4001 47FF

1K

TIM16

0x4001 4000 - 0x4001 43FF

1K

TIM15

Section 23.5.18 on page 737

0x4001 3C00 - 0x4001 3FFF

1K

SPI4

Section 30.9.10 on page 1010

0x4001 3800 - 0x4001 3BFF

1K

USART1

Section 3.7.12 on page 1130

0x4001 3400 - 0x4001 37FF

1K

TIM8

Section 20.4.25 on page 598

0x4001 3000 - 0x4001 33FF

1K

SPI1

Section 30.9.10 on page 1010

0x4001 2C00 - 0x4001 2FFF

1K

TIM1

Section 20.4.25 on page 598

0x4001 0800 - 0x4001 2BFF

9K

Reserved

0x4001 0400 - 0x4001 07FF

1K

EXTI

Section 14.3.13 on page 303

0x4001 0000 - 0x4001 03FF

1K

SYSCFG + COMP +
OPAMP

Section 12.1.10 on page 261,
Section 17.5.8 on page 464,
Section 18.4.5 on page 486

0x4000 7C00 - 0x4000 FFFF

33 K

Reserved

DocID022558 Rev 8

Section 19.6.11 on page 504

Section 6.4.6 on page 93

Section 4.6 on page 83

Section 9.4.14 on page 166

Section 13.5.7 on page 282

Section 23.6.17 on page 755

55/1141
63

RM0316
Table 3. STM32F303xD/E and STM32F398xE peripheral register boundary
addresses(1) (continued)
Bus

APB1

APB1

Boundary address

Peripheral

Peripheral register map

0x4000 7800 - 0x4000 7BFF

1K

I2C3

Section 28.7.12 on page 883

0x4000 7400 - 0x4000 77FF

1K

DAC1

Section 16.10.15 on page 438

0x4000 7000 - 0x4000 73FF

1K

PWR

Section 7.4.3 on page 110

0x4000 6C00 - 0x4000 6FFF

1K

Reserved

0x4000 6800 - 0x4000 6BFF

1K

Reserved

0x4000 6400 - 0x4000 67FF

1K

bxCAN

0x4000 6000 - 0x4000 63FF

1K

USB/CAN SRAM

0x4000 5C00 - 0x4000 5FFF

1K

USB device FS

0x4000 5800 - 0x4000 5BFF

1K

I2C2

0x4000 5400 - 0x4000 57FF

1K

I2C1

0x4000 5000 - 0x4000 53FF

1K

UART5

0x4000 4C00 - 0x4000 4FFF

1K

UART4

0x4000 4800 - 0x4000 4BFF

1K

USART3

0x4000 4400 - 0x4000 47FF

1K

USART2

0x4000 4000 - 0x4000 43FF

1K

I2S3ext

0x4000 3C00 - 0x4000 3FFF

1K

SPI3/I2S3

0x4000 3800 - 0x4000 3BFF

1K

SPI2/I2S2

0x4000 3400 - 0x4000 37FF

1K

I2S2ext

0x4000 3000 - 0x4000 33FF

1K

IWDG

Section 25.4.6 on page 766

0x4000 2C00 - 0x4000 2FFF

1K

WWDG

Section 26.4.4 on page 772

0x4000 2800 - 0x4000 2BFF

1K

RTC

Section 27.6.20 on page 814

0x4000 1800 - 0x4000 27FF

4K

Reserved

0x4000 1400 - 0x4000 17FF

1K

TIM7

0x4000 1000 - 0x4000 13FF

1K

TIM6

0x4000 0C00 - 0x4000 0FFF

1K

Reserved

0x4000 0800 - 0x4000 0BFF

1K

TIM4

0x4000 0400 - 0x4000 07FF

1K

TIM3

0x4000 0000 - 0x4000 03FF

1K

TIM2

0x2000 A000 - 3FFF FFFF

56/1141

Size
(bytes)

~512 M

Section 31.9.5 on page 1051
Section 32.6.3 on page 1086

Section 28.7.12 on page 883

Section 3.7.12 on page 1130

Section 30.9.10 on page 1010

Section 22.4.9 on page 682

Section 21.4.19 on page 668

Reserved

0x2000 0000 - 0x2000 FFFF

64 K

SRAM

-

0x1FFF F800 - 0x1FFF FFFF

2K

Option bytes

-

0x1FFF D800 - 0x1FFF F7FF

8K

System memory

-

0x1000 2000 - 0x1FFF D7FF

~256 M

Reserved

DocID022558 Rev 8

RM0316
Table 3. STM32F303xD/E and STM32F398xE peripheral register boundary
addresses(1) (continued)
Bus

Boundary address

Size
(bytes)

0x1000 0000 - 0x1000 3FFF

16 K

0x0808 0000 - 0x0FFF FFFF

~128 M

0x0800 0000 - 0x0807 FFFF

512 K

0x0008 0000 - 0x07FF FFFF

~128 M

0x0000 000 - 0x0007 FFFF

512 K

Peripheral
CCM SRAM

Peripheral register map
-

Reserved
Main Flash memory

-

Reserved
Main Flash memory,
system memory or
SRAM depending on
BOOT configuration

-

1. The gray color is used for reserved Flash memory addresses.

Table 4. STM32F303x6/8 and STM32F328x8 peripheral register boundary
addresses(1)
Bus

AHB3

AHB2

AHB1

Boundary address

Size
(bytes)

Peripheral

0x5000 0400 - 0x5000 07FF

1K

Reserved

0x5000 0000 - 0x5000 03FF

1K

ADC1 - ADC2

0x4800 1800 - 0x4FFF FFFF

~132 M

0x4800 1400 - 0x4800 17FF

1K

GPIOF

0x4800 1000 - 0x4800 13FF

1K

Reserved

0x4800 0C00 - 0x4800 0FFF

1K

GPIOD

0x4800 0800 - 0x4800 0BFF

1K

GPIOC

0x4800 0400 - 0x4800 07FF

1K

GPIOB

0x4800 0000 - 0x4800 03FF

1K

GPIOA

0x4002 4400 - 0x47FF FFFF

~128 M

0x4002 4000 - 0x4002 43FF

1K

TSC

0x4002 3400 - 0x4002 3FFF

3K

Reserved

0x4002 3000 - 0x4002 33FF

1K

CRC

0x4002 2400 - 0x4002 2FFF

3K

Reserved

0x4002 2000 - 0x4002 23FF

1K

Flash interface

0x4002 1400 - 0x4002 1FFF

3K

Reserved

0x4002 1000 - 0x4002 13FF

1K

RCC

0x4002 0400 - 0x4002 0FFF

3K

Reserved

0x4002 0000 - 0x4002 03FF

1K

DMA1

0x4001 8000 - 0x4001 FFFF

32 K

Reserved

Peripheral register map

Section 15.6.4 on page 410

Reserved

Section 11.4.12 on page 243

Reserved

DocID022558 Rev 8

Section 19.6.11 on page 504

Section 6.4.6 on page 93

Section 4.6 on page 83

Section 9.4.14 on page 166

Section 13.5.7 on page 282

57/1141
63

RM0316
Table 4. STM32F303x6/8 and STM32F328x8 peripheral register boundary
addresses(1) (continued)
Bus

APB2

58/1141

Boundary address

Size
(bytes)

Peripheral

Peripheral register map

0x4001 4C00 - 0x4001 7FFF

13 K

Reserved

0x4001 4800 - 0x4001 4BFF

1K

TIM17

0x4001 4400 - 0x4001 47FF

1K

TIM16

0x4001 4000 - 0x4001 43FF

1K

TIM15

0x4001 3C00 - 0x4001 3FFF

1K

Reserved

0x4001 3800 - 0x4001 3BFF

1K

USART1

0x4001 3400 - 0x4001 37FF

1K

Reserved

0x4001 3000 - 0x4001 33FF

1K

SPI1

Section 30.9.10 on page 1010

0x4001 2C00 - 0x4001 2FFF

1K

TIM1

Section 20.4.25 on page 598

0x4001 0800 - 0x4001 2BFF

9K

Reserved

0x4001 0400 - 0x4001 07FF

1K

EXTI

Section 14.3.13 on page 303

0x4001 0000 - 0x4001 03FF

1K

SYSCFG + COMP +
OPAMP

Section 12.1.10 on page 261,
Section 17.5.8 on page 464,
Section 18.4.5 on page 486

0x4000 9C00 - 0x4000 FFFF

25 K

Reserved

DocID022558 Rev 8

Section 23.6.17 on page 755
Section 23.5.18 on page 737

Section 3.7.12 on page 1130

RM0316
Table 4. STM32F303x6/8 and STM32F328x8 peripheral register boundary
addresses(1) (continued)
Bus

APB1

Boundary address

Size
(bytes)

Peripheral

Peripheral register map

0x4000 9800 - 0x4000 9BFF

1K

DAC2

0x4000 7800 - 0x4000 97FF

8K

Reserved

0x4000 7400 - 0x4000 77FF

1K

DAC1

Section 16.10.15 on page 438

0x4000 7000 - 0x4000 73FF

1K

PWR

Section 7.4.3 on page 110

0x4000 6C00 - 0x4000 6FFF

1K

Reserved

0x4000 6800 - 0x4000 6BFF

1K

Reserved

0x4000 6400 - 0x4000 67FF

1K

bxCAN

0x4000 5800 - 0x4000 63FF

3K

Reserved

0x4000 5400 - 0x4000 57FF

1K

I2C1

0x4000 4C00 - 0x4000 53FF

2K

Reserved

0x4000 4800 - 0x4000 4BFF

1K

USART3

0x4000 4400 - 0x4000 47FF

1K

USART2

0x4000 3400 - 0x4000 43FF

4K

Reserved

0x4000 3000 - 0x4000 33FF

1K

IWDG

Section 25.4.6 on page 766

0x4000 2C00 - 0x4000 2FFF

1K

WWDG

Section 26.4.4 on page 772

0x4000 2800 - 0x4000 2BFF

1K

RTC

Section 27.6.20 on page 814

0x4000 1800 - 0x4000 27FF

4K

Reserved

0x4000 1400 - 0x4000 17FF

1K

TIM7

0x4000 1000 - 0x4000 13FF

1K

TIM6

0x4000 0800 - 0x4000 0FFF

2K

Reserved

0x4000 0400 - 0x4000 07FF

1K

TIM3

0x4000 0000 - 0x4000 03FF

1K

TIM2

0x2000 3000 - 3FFF FFFF

~512 M

Section 16.10.15 on page 438

Section 31.9.5 on page 1051

Section 28.7.12 on page 883

Section 3.7.12 on page 1130

Section 22.4.9 on page 682

Section 21.4.19 on page 668
-

Reserved

0x2000 0000 - 0x2000 2FFF

12 K

SRAM

-

0x1FFF F800 - 0x1FFF FFFF

2K

Option bytes

-

0x1FFF D800 - 0x1FFF F7FF

8K

System memory

-

0x1000 1000 - 0x1FFF D7FF

~256 M

0x1000 0000 - 0x1000 0FFF

4K

0x0804 0000 - 0x0FFF FFFF

~128 M

0x0800 0000 - 0x0800 FFFF

64 K

Reserved
CCM SRAM

-

Reserved
Main Flash memory

DocID022558 Rev 8

-

59/1141
63

RM0316
Table 4. STM32F303x6/8 and STM32F328x8 peripheral register boundary
addresses(1) (continued)
Bus

Boundary address
0x0001 0000 - 0x07FF FFFF

0x0000 000 - 0x0000 FFFF

Size
(bytes)
~128 M

64 K

Peripheral

Peripheral register map

Reserved
Main Flash memory,
system memory or
SRAM depending on
BOOT configuration

-

1. The gray color is used for reserved Flash memory addresses.

3.3

Embedded SRAM
STM32F303xB/C and STM32F358xC devices feature up to 48 Kbytes of static SRAM. It
can be accessed as bytes, halfwords (16 bits) or full words (32 bits):
•

Up to 40 Kbytes of SRAM that can be addressed at maximum system clock frequency
without wait states and can be accessed by both CPU and DMA;

•

8 Kbytes of CCM SRAM. It is used to execute critical routines or to access data. It can
be accessed by the CPU only. No DMA accesses are allowed. This memory can be
addressed at maximum system clock frequency without wait state.
STM32F303xD/E and STM32F398xE devices feature up to 80 Kbytes of static SRAM. It can
be accessed as bytes, halfwords (16 bits) or full words (32 bits):
•
Up to 64 Kbytes of SRAM that can be addressed at maximum system clock frequency
without wait states and can be accessed by both CPU and DMA;
•

16 Kbytes of CCM SRAM. It is used to execute critical routines or to access data. It can
be accessed by the CPU only. No DMA accesses are allowed. This memory can be
addressed at maximum system clock frequency without wait state.
STM32F303x6/8 and STM32F328x8 devices feature the same memory but only up to 16
Kbytes of static SRAM: up to 12 Kbytes of SRAM and 4 Kbytes of CCM SRAM.

3.3.1

Parity check
On the STM32F303xB/C and STM32F358xC devices, for the 40-Kbyte SRAM, a parity
check is implemented only on the first 16 Kbytes.
The SRAM parity check is disabled by default. It is enabled by the user, when needed, using
an option bit.
On the STM32F303x6/8 and STM32F328x8 devices, the parity check is implemented on all
of the SRAM and CCM SRAM.
On the STM32F303xD/E and STM32F398xE devices, the parity check is implemented on
the first 32 Kbytes of SRAM and on the whole CCM SRAM
The data bus width of the SRAM supporting the parity check is 36 bits because 4 bits are
available for parity check (1 bit per byte) in order to increase memory robustness, as
required for instance by Class B or SIL norms.
The parity bits are computed on data and address and stored when writing into the SRAM.
Then, they are automatically checked when reading. If one bit fails, an NMI is generated if
the SRAM parity check is enabled. The same error can also be linked to the Break input of

60/1141

DocID022558 Rev 8

RM0316
TIMER 20, 1, 8, 15, 16 and 17, by setting the SRAM_PARITY_LOCK control bit in the
SYSCFG configuration register 2 (SYSCFG_CFGR2). In case of parity error, the SRAM
Parity Error flag (SRAM_PEF) is set in the SYSCFG configuration register 2
(SYSCFG_CFGR2). For more details, please refer to the SYSCFG configuration register 2
(SYSCFG_CFGR2).
The BYP_ADD_PAR bit in SYSCFG_CFGR2 register can be used to prevent an unwanted
parity error to occur when the user programs a code in the RAM at address 0x2XXXXXXX
(address in the address range 0x20000000-0x20002000) and then executes the code from
RAM at boot (RAM is remapped at address 0x00).

3.3.2

CCM SRAM write protection
The CCM SRAM is write protected with a page granularity of 1 Kbyte.
Table 5. CCM SRAM organization
Page number

Start address

End address

Page 0

0x1000 0000

0x1000 03FF

Page 1

0x1000 0400

0x1000 07FF

Page 2

0x1000 0800

0x1000 0BFF

Page 3

0x1000 0C00

0x1000 0FFF

Page 4(1)

0x1000 1000

0x1000 13FF

5(1)

0x1000 1400

0x1000 17FF

(1)

0x1000 1800

0x1000 1BFF

(1)

Page 7

0x1000 1C00

0x1000 1FFF

Page 8(2)

0x1000 2000

0x1000 23FF

(2)

Page

Page 6

0x1000 2400

0x1000 27FF

(2)

0x1000 2800

0x1000 2BFF

11(2)

0x1000 2C00

0x1000 2FFF

Page 12(2)

0x1000 3000

0x1000 33FF

(2)

0x1000 3400

0x1000 37FF

14(2)

0x1000 3800

0x1000 3BFF

(2)

0x1000 3C00

0x1000 3FFF

Page 9

Page 10
Page

Page 13
Page

Page 15

1. Only on STM32F303xB/C/D/E and STM32F358xC devices.
2. Only on STM32F303xD/E and STM32F398xE devices.

The write protection can be enabled in the CCM SRAM protection register (SYSCFG_RCR)
in the SYSCFG block. This is a register with write ‘1’ once mechanism, which means by
writing ‘1’ on a bit it will setup the write protection for that page of SRAM and it can be
removed/cleared by a system reset only. For more details please refer to the SYSCFG
section.

DocID022558 Rev 8

61/1141
63

RM0316

3.4

Flash memory overview
The Flash memory is composed of two distinct physical areas:
•

The main Flash memory block. It contains the application program and user data if
necessary.

•

The information block. It is composed of two parts:
–

Option bytes for hardware and memory protection user configuration.

–

System memory which contains the proprietary boot loader code. Please, refer to
Section 4: Embedded Flash memory for more details.

Flash memory instructions and data access are performed through the AHB bus. The
prefetch block is used for instruction fetches through the ICode bus. Arbitration is performed
in the Flash memory interface, and priority is given to data access on the DCode bus. It also
implements the logic necessary to carry out the Flash memory operations (Program/Erase)
controlled through the Flash registers.

3.5

Boot configuration
In the STM32F3xx, three different boot modes can be selected through the BOOT0 pin and
nBOOT1 bit in the User option byte, as shown in the following table:
Table 6. Boot modes
Boot mode selection

Boot mode

Aliasing

-

-

nBOOT1

BOOT0

x

0

Main Flash memory

Main flash memory is selected as boot
area

1

1

System memory

System memory is selected as boot area

0

1

Embedded SRAM

Embedded SRAM (on the DCode bus) is
selected as boot area

The values on both BOOT0 pin and nBOOT1 bit are latched on the 4th rising edge of
SYSCLK after a reset.
It is up to the user to set the nBOOT1 and BOOT0 to select the required boot mode. The
BOOT0 pin and nBOOT1 bit are also resampled when exiting from Standby mode.
Consequently they must be kept in the required Boot mode configuration in Standby mode.
After this startup delay has elapsed, the CPU fetches the top-of-stack value from address
0x0000 0000, then starts code execution from the boot memory at 0x0000 0004. Depending
on the selected boot mode, main Flash memory, system memory or SRAM is accessible as
follows:

62/1141

•

Boot from main Flash memory: the main Flash memory is aliased in the boot memory
space (0x0000 0000), but still accessible from its original memory space (0x0800
0000). In other words, the Flash memory contents can be accessed starting from
address 0x0000 0000 or 0x0800 0000.

•

Boot from system memory: the system memory is aliased in the boot memory space
(0x0000 0000), but still accessible from its original memory space (0x1FFF D800).

•

Boot from the embedded SRAM: the SRAM is aliased in the boot memory space
(0x0000 0000), but it is still accessible from its original memory space (0x2000 0000).

DocID022558 Rev 8

RM0316

3.5.1

Embedded boot loader
The embedded boot loader is located in the System memory, programmed by ST during
production. It is used to reprogram the Flash memory through:

Note:

•

USART1 (PA9/PA10), USART2 (PD5/PD6) or USB (DFU) on STM32F303xB/C
devices,

•

USART1 (PA9/PA10), USART2 (PD5/PD6), I2C1 (PB6/PB7) on STM32F358xC
devices,

•

USART1 (PA9/PA10), USART2 (PA2/PA3), I2C1 (PB6/PB7) on STM32F303x6/8 and
STM32F328x8 devices,

•

USART1 (PA9/PA10), USART2 (PA2/PA3) or USB (DFU) on STM32F303xD/E devices.

•

USART1 (PA9/PA10) or USART2 (PA2/PA3) or I2C1 (PB6/PB7) or I2C3 (PA8/PB5) on
STM32F398xE.

For more details see the corresponding datasheets.

DocID022558 Rev 8

63/1141
63

Embedded Flash memory

RM0316

4

Embedded Flash memory

4.1

Flash main features
Up to 512 Kbytes of Flash memory in STM32F303xD/E, up to 256 Kbytes of Flash memory
in STM32F303xB/C and STM32F358xC devices and up to 64 Kbytes of Flash memory in
STM32F303x6/8 and STM32F328x8 devices.
•

Memory organization:
–

Main memory block:
128 Kbit x 64 bits in STM32F303xD/E, 64 Kbits × 64 bits in STM32F303xB/C and
STM32F358xC devices.
16 Kbit x 64 bits in STM32F303x6/8 and STM32F328x8 devices.

–

Information block:
1280 × 64 bits

Flash memory interface (FLITF) features:
•

Read interface with prefetch buffer (2 × 64-bit words)

•

Option byte loader

•

Flash program/Erase operation

•

Read/Write protection

•

low-power mode

4.2

Flash memory functional description

4.2.1

Flash memory organization
The Flash memory is organized as 64-bit wide memory cells that can be used for storing
both code and data constants.
The memory organization is based on a main memory block containing 128 pages of
2 Kbytes in STM32F303xB/C and STM32F358xC devices, 256 pages of 2 Kbytes in the
STM32F303xD/E and an information block as shown in Table 7. In STM32F303x6/8 and
STM32F328x8 devices the memory block contains 32 pages of 2 Kbytes.

64/1141

DocID022558 Rev 8

RM0316

Embedded Flash memory
Table 7. Flash module organization(1)
Flash area

Main memory

Information block

Flash memory
interface registers

1.

Flash memory addresses

Size
(bytes)

Name

0x0800 0000 - 0x0800 07FF

2K

Page 0

0x0800 0800 - 0x0800 0FFF

2K

Page 1

0x0800 1000 - 0x0800 17FF

2K

Page 2

0x0800 1800 - 0x0800 1FFF

2K

Page 3

.
.
.

.
.
.

.
.
.
.
.

.
.
.
.
.

.
.
.
.
.
.

0x0807 F800 - 0x0807 FFFF

2K

Page 255

0x1FFF D800 - 0x1FFF F7FF

8K

System memory

0x1FFF F800 - 0x1FFF F80F

16

Option bytes

0x4002 2000 - 0x4002 2003

4

FLASH_ACR

0x4002 2004 - 0x4002 2007

4

FLASH_KEYR

0x4002 2008 - 0x4002 200B

4

FLASH_OPTKEYR

0x4002 200C - 0x4002 200F

4

FLASH_SR

0x4002 2010 - 0x4002 2013

4

FLASH_CR

0x4002 2014 - 0x4002 2017

4

FLASH_AR

0x4002 2018 - 0x4002 201B

4

Reserved

0x4002 201C - 0x4002 201F

4

FLASH_OBR

0x4002 2020 - 0x4002 2023

4

FLASH_WRPR

.
.
.

The gray color is used for reserved Flash memory addresses.

The information block is divided into two parts:
•

System memory is used to boot the device in System memory boot mode. The area is
reserved for use by STMicroelectronics and contains the boot loader which is used to
reprogram the Flash memory through one of the following interfaces: USART1,
USART2 or USB (DFU) on devices with internal regulator ON and USART or I2C on
devices with internal regulator OFF. It is programmed by ST when the device is
manufactured, and protected against spurious write/erase operations. For further
details, please refer to the AN2606 available from www.st.com.

•

Option bytes

DocID022558 Rev 8

65/1141
87

Embedded Flash memory

4.2.2

RM0316

Read operations
The embedded Flash module can be addressed directly, as a common memory space. Any
data read operation accesses the content of the Flash module through dedicated read
senses and provides the requested data.
The read interface consists of a read controller on one side to access the Flash memory and
an AHB interface on the other side to interface with the CPU. The main task of the read
interface is to generate the control signals to read from the Flash memory and to prefetch
the blocks required by the CPU. The prefetch block is only used for instruction fetches over
the ICode bus. The Literal pool is accessed over the DCode bus. Since these two buses
have the same Flash memory as target, DCode bus accesses have priority over prefetch
accesses.
Read accesses can be performed with the following options managed through the Flash
access control register (FLASH_ACR):
•

Instruction fetch: Prefetch buffer enabled for a faster CPU execution.

•

Latency: number of wait states for a correct read operation (from 0 to 2)

Instruction fetch
The Cortex®-M4 fetches the instruction over the ICode bus and the literal pool
(constant/data) over the DCode bus. The prefetch block aims at increasing the efficiency of
ICode bus accesses.

Prefetch buffer
The prefetch buffer is 2 blocks wide where each block consists of 8 bytes. The prefetch
blocks are direct-mapped. A block can be completely replaced on a single read to the Flash
memory as the size of the block matches the bandwidth of the Flash memory.
The implementation of this prefetch buffer makes a faster CPU execution possible as the
CPU fetches one word at a time with the next word readily available in the prefetch buffer.
This implies that the acceleration ratio is in the order of 2 assuming that the code is aligned
at a 64-bit boundary for the jumps.

Prefetch controller
The prefetch controller decides to access the Flash memory depending on the available
space in the prefetch buffer. The Controller initiates a read request when there is at least
one block free in the prefetch buffer.
After reset, the state of the prefetch buffer is on. The prefetch buffer should be switched
on/off only when no prescaler is applied on the AHB clock (SYSCLK must be equal to
HCLK). The prefetch buffer is usually switched on/off during the initialization routine, while
the microcontroller is running on the internal 8 MHz RC (HSI) oscillator.
Note:

The prefetch buffer must be kept on (FLASH_ACR[4]=’1’) when using a prescaler different
from 1 on the AHB clock.
If there is not any high frequency clock available in the system, Flash memory accesses can
be made on a half cycle of HCLK (AHB clock). This mode can be selected by setting a
control bit in the Flash access control register.
Half-cycle access cannot be used when there is a prescaler different from 1 on the AHB
clock.

66/1141

DocID022558 Rev 8

RM0316

Embedded Flash memory

Access latency
In order to maintain the control signals to read the Flash memory, the ratio of the prefetch
controller clock period to the access time of the Flash memory has to be programmed in the
Flash access control register with the LATENCY[2:0] bits. This value gives the number of
cycles needed to maintain the control signals of the Flash memory and correctly read the
required data. After reset, the value is zero and only one cycle without additional wait states
is required to access the Flash memory.

DCode interface
The DCode interface consists of a simple AHB interface on the CPU side and a request
generator to the Arbiter of the Flash access controller. The DCode accesses have priority
over prefetch accesses. This interface uses the Access Time Tuner block of the prefetch
buffer.

Flash Access controller
Mainly, this block is a simple arbiter between the read requests of the prefetch/ICode and
DCode interfaces.
DCode interface requests have priority over other requests.

4.2.3

Flash program and erase operations
The STM32F3xx embedded Flash memory can be programmed using in-circuit
programming or in-application programming.
The in-circuit programming (ICP) method is used to update the entire contents of the
Flash memory, using the JTAG, SWD protocol or the boot loader to load the user application
into the microcontroller. ICP offers quick and efficient design iterations and eliminates
unnecessary package handling or socketing of devices.
In contrast to the ICP method, in-application programming (IAP) can use any
communication interface supported by the microcontroller (I/Os, USB, CAN, UART, I2C, SPI,
etc.) to download programming data into memory. IAP allows the user to re-program the
Flash memory while the application is running. Nevertheless, part of the application has to
have been previously programmed in the Flash memory using ICP.
The program and erase operations are managed through the following seven Flash
registers:
•

Key register (FLASH_KEYR)

•

Option byte key register (FLASH_OPTKEYR)

•

Flash control register (FLASH_CR)

•

Flash status register (FLASH_SR)

•

Flash address register (FLASH_AR)

•

Option byte register (FLASH_OBR)

•

Write protection register (FLASH_WRPR)

An on going Flash memory operation will not block the CPU as long as the CPU does not
access the Flash memory.
On the contrary, during a program/erase operation to the Flash memory, any attempt to read
the Flash memory will stall the bus. The read operation will proceed correctly once the

DocID022558 Rev 8

67/1141
87

Embedded Flash memory

RM0316

program/erase operation has completed. This means that code or data fetches cannot be
made while a program/erase operation is ongoing.
For program and erase operations on the Flash memory (write/erase), the internal RC
oscillator (HSI) must be ON.

Unlocking the Flash memory
After reset, the FPEC is protected against unwanted write or erase operations. The
FLASH_CR register is not accessible in write mode, except for the OBL LAUNCH bit, used
to reload the OBL. An unlocking sequence should be written to the FLASH_KEYR register
to open the access to the FLASH_CR register. This sequence consists of two write
operations into FLASH_KEYR register:
1.

Write KEY1 = 0x45670123

2.

Write KEY2 = 0xCDEF89AB

Any wrong sequence locks up the FPEC and the FLASH_CR register until the next reset.
In the case of a wrong key sequence, a bus error is detected and a Hard Fault interrupt is
generated. This is done after the first write cycle if KEY1 does not match, or during the
second write cycle if KEY1 has been correctly written but KEY2 does not match.
The FPEC and the FLASH_CR register can be locked again by user software by writing the
LOCK bit in the FLASH_CR register to 1.

Main Flash memory programming
The main Flash memory can be programmed 16 bits at a time. The program operation is
started when the CPU writes a half-word into a main Flash memory address with the PG bit
of the FLASH_CR register set. Any attempt to write data that are not half-word long will
result in a bus error generating a Hard Fault interrupt.

68/1141

DocID022558 Rev 8

RM0316

Embedded Flash memory
Figure 4. Programming procedure

5HDG)/$6+B&5B/2&.

 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.

DocID022558 Rev 8

RM0316

Power control (PWR)
If no external battery is used in the application, it is recommended to connect VBAT
externally to VDD with a 100 nF external ceramic decoupling capacitor (for more details refer
to AN4206).
When the RTC domain is supplied by VDD (analog switch connected to VDD), the following
functions are available:

Note:

•

PC13, PC14 and PC15 can be used as GPIO pins

•

PC13, PC14 and PC15 can be configured by RTC or LSE (refer to Section 27.3: RTC
functional description on page 775)

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 RTC domain is supplied by VBAT (analog switch connected to VBAT because VDD
is not present), the following functions are available:
•

7.1.3

PC13, PC14 and PC15 can be controlled only by RTC or LSE (refer to Section 27.3:
RTC functional description on page 775)

Voltage regulator
The voltage regulator is always enabled after Reset. It works in three different modes
depending on the application modes.
•

In Run mode, the regulator supplies full power to the 1.8 V domain (core, memories
and digital peripherals).

•

In Stop mode the regulator supplies low-power to the 1.8 V domain, preserving
contents of registers and SRAM.

•

In Standby Mode, the regulator is powered off. The contents of the registers and SRAM
are lost except for the Standby circuitry and the RTC Domain.

In the STM32F3x8 devices, the voltage regulator is bypassed and the microcontroller must
be powered from a nominal VDD = 1.8 V ± 8% voltage.

7.2

Power supply supervisor

7.2.1

Power on reset (POR)/power down reset (PDR)
The device has an integrated power-on reset (POR) and power-down reset (PDR) circuits
which are always active and ensure proper operation above a threshold of 2 V.
The device remains in Reset mode when the monitored supply voltage is below a specified
threshold, VPOR/PDR, without the need for an external reset circuit.
•

The POR monitors only the VDD supply voltage. During the startup phase VDDA must
arrive first and be greater than or equal to VDD.

•

The PDR monitors both the VDD and VDDA supply voltages. However, if the application
is designed with VDDA higher than or equal to VDD, the VDDA power supply supervisor
can be disabled (by programming a dedicated VDDA_MONITOR option bit) to reduce
the power consumption.

For more details on the power on /power down reset threshold, refer to the electrical
characteristics section in the datasheet.

DocID022558 Rev 8

97/1141
110

Power control (PWR)

RM0316
Figure 10. Power on reset/power down reset waveform
6$$ 6$$!
0/2
 M6
HYSTERESIS
0$2

4EMPORIZATION
T 2344%-0/

2ESET
-36

98/1141

DocID022558 Rev 8

RM0316

7.2.2

Power control (PWR)

Programmable voltage detector (PVD)
User can use the PVD to monitor the VDD power supply by comparing it to a threshold
selected by the PLS[2:0] bits in the Power control register (PWR_CR).
The PVD is enabled by setting the PVDE bit.
A PVDO flag is available, in the Power control/status register (PWR_CSR), to indicate if VDD
is higher or lower than the PVD threshold. This event is 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
6$$

06$ THRESHOLD

 M6
HYSTERESIS

06$ OUTPUT

-36

Note:

In the STM32F3x8 devices (VDD = 1.8 V ± 8%), the POR, PDR and PVD features are not
available. The Power on reset signal is applied on the NPOR pin. See details in the following
section.

7.2.3

External NPOR signal
In the STM32F3x8 devices, the PB2 I/O is not available and is replaced by the NPOR
functionality used for Power on reset.
To guarantee a proper power on reset, the NPOR pin must be held low when VDDA is
applied. When VDD is stable, the reset state can be exited either by:
•

putting the NPOR pin in high impedance. NPOR pin has an internal pull-up which holds
this input to VDDA

•

or forcing the pin to a high level by connecting it externally to VDDA through a pull-up
resistor.

DocID022558 Rev 8

99/1141
110

Power control (PWR)

7.3

RM0316

Low-power modes
By default, the microcontroller is in Run mode after a system or a power Reset. Several lowpower 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 device features three low-power modes:
•

Sleep mode (CPU clock off, all peripherals including ARM® Cortex®-M4 core
peripherals like NVIC, SysTick, etc. are kept running)

•

Stop mode (all clocks are stopped)

•

Standby mode (1.8V 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 APB and AHB peripherals when they are unused.
Table 17. Low-power mode summary
Mode name

Entry

Sleep
WFI
(Sleep now or
Sleep-on WFE
exit)

Stop

Standby

Caution:

100/1141

wakeup

Any interrupt
Wakeup event

Effect on 1.8V
domain clocks

CPU clock OFF
no effect on other None
clocks or analog
clock sources

Any EXTI line
(configured in the
PDDS and LPDS EXTI registers)
bits +
Specific
SLEEPDEEP bit communication
+ WFI or WFE
peripherals on
reception events All 1.8V domain
clocks OFF
(USART, I2C)
PDDS bit +
SLEEPDEEP bit
+ WFI or WFE

WKUP pin rising
edge, RTC alarm,
external reset in
NRST pin,
IWDG reset

Effect on
VDD
domain
clocks

HSI and
HSE
oscillators
OFF

Voltage
regulator

ON

ON or in lowpower mode
(depends on
Power control
register
(PWR_CR))

OFF

In STM32F3x8 devices with regulator off, Standby mode is not available. Stop mode is still
available but it is meaningless to distinguish between voltage regulator in low-power mode
and voltage regulator in Run mode because the regulator is not used and VDD is applied
externally to the regulator output.

DocID022558 Rev 8

RM0316

7.3.1

Power control (PWR)

Slowing down system clocks
In Run mode the speed of the system clocks (SYSCLK, HCLK, PCLK) 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 9.4.2: Clock configuration register (RCC_CFGR).

7.3.2

Peripheral clock gating
In Run mode, the HCLK and PCLK for individual peripherals and memories can be stopped
at any time to reduce power consumption.
To further reduce power consumption in Sleep mode the peripheral clocks can be disabled
prior to executing the WFI or WFE instructions.
Peripheral clock gating is controlled by the AHB peripheral clock enable register
(RCC_AHBENR), APB1 peripheral clock enable register (RCC_APB1ENR) and APB2
peripheral clock enable register (RCC_APB2ENR).

7.3.3

Sleep mode
Entering Sleep mode
The Sleep mode is entered by executing the WFI (Wait For Interrupt) or WFE (Wait for
Event) instructions. Two options are available to select the Sleep mode entry mechanism,
depending on the SLEEPONEXIT bit in the ARM® Cortex®-M4 System Control register:
•

Sleep-now: if the SLEEPONEXIT bit is cleared, the MCU enters Sleep mode as soon
as WFI or WFE instruction is executed.

•

Sleep-on-exit: if the SLEEPONEXIT bit is set, the MCU enters Sleep mode as soon as
it exits the lowest priority ISR.

In the Sleep mode, all I/O pins keep the same state as in the Run mode.
Refer to Table 18 and Table 19 for details on how to enter Sleep mode.

Exiting Sleep mode
If the WFI instruction is used to enter Sleep mode, any peripheral interrupt acknowledged by
the nested vectored interrupt controller (NVIC) can wake up the device from Sleep mode.
If the WFE instruction is used to enter Sleep mode, the MCU exits Sleep mode as soon as
an event occurs. The wakeup event can be generated either by:
•

enabling an interrupt in the peripheral control register but not in the NVIC, and enabling
the SEVONPEND bit in the ARM® Cortex®-M4 System Control register. When the
MCU resumes from WFE, the peripheral interrupt pending bit and the peripheral NVIC
IRQ channel pending bit (in the NVIC interrupt clear pending register) have to be
cleared.

•

or configuring an external or internal EXTI line in event mode. When the CPU resumes
from WFE, it is not necessary to clear the peripheral interrupt pending bit or the NVIC
IRQ channel pending bit as the pending bit corresponding to the event line is not set.

This mode offers the lowest wakeup time as no time is wasted in interrupt entry/exit.
Refer to Table 18 and Table 19 for more details on how to exit Sleep mode.

DocID022558 Rev 8

101/1141
110

Power control (PWR)

RM0316
Table 18. Sleep-now

Sleep-now mode

Description

Mode entry

WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP = 0 and
– SLEEPONEXIT = 0
Refer to the ARM® Cortex®-M4 System Control register.

Mode exit

If WFI was used for entry:
Interrupt: Refer to Table 82: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE vector table and Table 83: STM32F303x6/8 and
STM32F328x8 vector table.
If WFE was used for entry
Wakeup event: Refer to Section 14.2.3: Wakeup event management

Wakeup latency

None

Table 19. Sleep-on-exit
Sleep-on-exit

7.3.4

Description

Mode entry

WFI (wait for interrupt) while:
– SLEEPDEEP = 0 and
– SLEEPONEXIT = 1
Refer to the ARM® Cortex®-M4 System Control register.

Mode exit

Interrupt: refer to Table 82: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE vector table and Table 83: STM32F303x6/8 and
STM32F328x8 vector table.

Wakeup latency

None

Stop mode
The Stop mode is based on the ARM® Cortex®-M4 deepsleep mode combined with
peripheral clock gating. The voltage regulator can be configured either in normal or lowpower mode in the STM32F3xx devices. In the STM32F3x8 devices, it is meaningless to
distinguish between voltage regulator in low-power mode and voltage regulator in Run
mode because the regulator is not used and VDD is applied externally to the regulator
output. In Stop mode, all clocks in the 1.8 V domain are stopped, the PLL, the HSI and the
HSE RC oscillators are disabled. SRAM and register contents are preserved.
In the Stop mode, all I/O pins keep the same state as in the Run mode.

Entering Stop mode
Refer to Table 20 for details on how to enter the Stop mode.
To further reduce power consumption in Stop mode, the internal voltage regulator can be put
in low-power mode. This is configured by the LPDS bit of the Power control register
(PWR_CR).
If Flash memory programming is ongoing, the Stop mode entry is delayed until the memory
access is finished.

102/1141

DocID022558 Rev 8

RM0316

Power control (PWR)
If an access to the APB domain is ongoing, The Stop mode entry is delayed until the APB
access is finished.
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 25.3: IWDG functional description in Section 25: Independent watchdog
(IWDG).

•

real-time clock (RTC): this is configured by the RTCEN bit in the RTC 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
RTC 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 the ADC, the ADDIS bit must be set in the ADCx_CR register.
To disable the DAC, the ENx bit in the DAC_CR register must be written to 0.
Exiting Stop mode
Refer to Table 20 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.
When the voltage regulator operates in low-power mode, an additional startup delay is
incurred when waking up from Stop mode. By keeping the internal regulator ON during Stop
mode, the consumption is higher although the startup time is reduced.

DocID022558 Rev 8

103/1141
110

Power control (PWR)

RM0316
Table 20. Stop mode

Stop mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– Set SLEEPDEEP bit in ARM® Cortex®-M4 System Control register
– Clear PDDS bit in Power Control register (PWR_CR)
– Select the voltage regulator mode by configuring LPDS bit in PWR_CR

Mode entry

7.3.5

Note: To enter Stop mode, all EXTI Line pending bits (in Pending register
(EXTI_PR1)), all peripherals interrupt pending bits and RTC Alarm flag
must be reset. Otherwise, the Stop mode entry procedure is ignored and
program execution continues.
If the application needs to disable the external oscillator (external clock)
before entering Stop mode, the system clock source must be first switched
to HSI and then clear the HSEON bit.
Otherwise, if before entering Stop mode the HSEON bit is kept at 1, the
security system (CSS) feature must be enabled to detect any external
oscillator (external clock) failure and avoid a malfunction when entering
Stop mode.

Mode exit

If WFI was used for entry:
– Any EXTI Line configured in Interrupt mode (the corresponding EXTI
Interrupt vector must be enabled in the NVIC).
– Some specific communication peripherals (USART, I2C) interrupts, when
programmed in wakeup mode (the peripheral must be programmed in
wakeup mode and the corresponding interrupt vector must be enabled in
the NVIC).
Refer to Table 82: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE vector table and Table 83: STM32F303x6/8 and
STM32F328x8 vector table.
If WFE was used for entry:
Any EXTI Line configured in event mode. Refer to Section 14.2.3:
Wakeup event management on page 293

Wakeup latency

HSI RC wakeup time + regulator wakeup time from Low-power mode

Standby mode
The Standby mode allows to achieve the lowest power consumption. It is based on the
ARM® Cortex®-M4 deepsleep mode, with the voltage regulator disabled. The 1.8 V domain
is consequently powered off. The PLL, the HSI oscillator and the HSE oscillator are also
switched off. SRAM and register contents are lost except for registers in the RTC domain
and Standby circuitry (see Figure 8).

Caution:

In the STM32F3x8 devices, the Standby mode is not available.

Entering Standby mode
Refer to Table 21 for more details on how to enter Standby mode.
In Standby mode, the following features can be selected by programming individual control
bits:
•

104/1141

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

DocID022558 Rev 8

RM0316

Power control (PWR)
Section 25.3: IWDG functional description in Section 25: Independent watchdog
(IWDG).
•

real-time clock (RTC): this is configured by the RTCEN bit in the RTC 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
RTC domain control register (RCC_BDCR)

Exiting Standby mode
The microcontroller exits the Standby mode when an external reset (NRST pin), an IWDG
reset, a rising edge on the WKUP pin or the rising edge of an RTC alarm occurs (see
Figure 291: RTC block diagram). All registers are reset after wakeup from Standby except
for Power control/status register (PWR_CSR).
After waking up from Standby mode, program execution restarts in the same way as after a
Reset (boot pins sampling, vector reset is fetched, etc.). The SBF status flag in the Power
control/status register (PWR_CSR) indicates that the MCU was in Standby mode.
Refer to Table 21 for more details on how to exit Standby mode.
Table 21. Standby mode
Standby mode

Description

Mode entry

WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– Set SLEEPDEEP in ARM® Cortex®-M4 System Control register
– Set PDDS bit in Power Control register (PWR_CR)
– Clear WUF bit in Power Control/Status register (PWR_CSR)

Mode exit

WKUP pin rising edge, RTC alarm event’s rising edge, external Reset in
NRST pin, IWDG Reset.

Wakeup latency

Reset phase

I/O states in Standby mode
In Standby mode, all I/O pins are high impedance except:
•

Reset pad (still available)

•

TAMPER pin if configured for tamper or calibration out

•

WKUP pin, 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 ARM® Cortex®-M4
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.

DocID022558 Rev 8

105/1141
110

Power control (PWR)

7.3.6

RM0316

Auto-wakeup from low-power mode
The RTC can be used to wakeup the MCU from low-power mode without depending on an
external interrupt (Auto-wakeup mode). The RTC provides a programmable time base for
waking up from Stop or Standby mode at regular intervals. For this purpose, two of the three
alternative RTC clock sources can be selected by programming the RTCSEL[1:0] bits in the
RTC domain control register (RCC_BDCR):
•

Low-power 32.768 kHz external crystal oscillator (LSE OSC).
This clock source provides a precise time base with very low-power consumption (less
than 1µA added consumption in 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 add minimum power consumption.

To wakeup from Stop mode with an RTC alarm event, it is necessary to:
•

Configure the EXTI Line 17 to be sensitive to rising edge

•

Configure the RTC to generate the RTC alarm

To wakeup from Standby mode, there is no need to configure the EXTI Line 17.

106/1141

DocID022558 Rev 8

RM0316

Power control (PWR)

7.4

Power control registers
The peripheral registers can be accessed by half-words (16-bit) or words (32-bit).

7.4.1

Power control register (PWR_CR)
Address offset: 0x00
Reset value: 0x0000 0000 (reset by wakeup from 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

7

6

5

15

14

13

12

11

10

9

8

Res

Res

Res

Res

Res

Res

Res

DBP
rw

PLS[2:0]
rw

rw

rw

4

3

2

1

0

PVDE

CSBF

CWUF

PDDS

LPDS

rw

rc_w1

rc_w1

rw

rw

Bits 31:9 Reserved, must be kept at reset value.
Bit 8 DBP: Disable RTC domain write protection.
In reset state, the RTC and backup registers are protected against parasitic write
access. This bit must be set to enable write access to these registers.
0: Access to RTC and Backup registers disabled
1: Access to RTC and Backup registers enabled
Note: If the HSE divided by 128 is used as the RTC clock, this bit must remain set
to 1.
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: 2.2V
001: 2.3V
010: 2.4V
011: 2.5V
100: 2.6V
101: 2.7V
110: 2.8V
111: 2.9V
Notes:
1.
Refer to the electrical characteristics of the datasheet for more details.
2.
Once the PVD_LOCK is enabled (for CLASS B protection) the PLS[2:0] bits
cannot be programmed anymore.
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).

DocID022558 Rev 8

107/1141
110

Power control (PWR)

RM0316

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. (write)
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: Voltage regulator on during Stop mode
1: Voltage regulator in low-power mode during Stop mode

7.4.2

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

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

VREFIN
TRDYF

PVDO

SBF

WUF

r

r

r

r

Res

Res

Res

Res

Res

EWUP3
(1)

rw

EWUP2 EWUP1
rw

Res

Res

rw

Res

1. Not available on STM32F303x6/8 and STM32F328x8.

Bits 31:11 Reserved, must be kept at reset value.
Bit 10 EWUP3: Enable WKUP3 pin
This bit is set and cleared by software.
0: WKUP3 pin is used for general purpose I/O. An event on the WKUP3 pin does
not wakeup the device from Standby mode.
1: WKUP3 pin is used for wakeup from Standby mode and forced in input pull
down configuration (rising edge on WKUP3 pin wakes-up the system from
Standby mode).
Note: This bit is reset by a system Reset.
Bit 9 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.

108/1141

DocID022558 Rev 8

RM0316

Power control (PWR)

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.
Bits 7:4 Reserved, must be kept at reset value.
Bit 3 VREFINTRDYF: VREFINT Ready. Read Only. This bit indicates the state of the
internal reference voltage. It is set when VREFINT is ready. It is reset during
stabilization of VREFINT.
Note: This flag is useful only for the product bypassing the internal regulator and
using external NPOR Pin, the internal POR waits the VREFINT stabilization
before releasing the 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/VDDA is higher than the PVD threshold selected with the PLS[2:0] bits.
1: VDD/VDDA is lower than the PVD threshold selected with the PLS[2:0] bits.
Notes:
1.
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.
2.
Once the PVD is enabled and configured in the PWR_CR register, PVDO can
be used to generate an interrupt through the External Interrupt controller.
3.
Once the PVD_LOCK is enabled (for CLASS B protection) PVDO cannot be
disabled anymore.
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 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 by a system reset or by setting the CWUF
bit in the Power control register (PWR_CR)
0: No wakeup event occurred
1: A wakeup event was received from the WKUP pin or from the RTC alarm
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.

DocID022558 Rev 8

109/1141
110

Power control (PWR)

7.4.3

RM0316

PWR register map
The following table summarizes the PWR registers.

DBP

PVDE

CSBF

CWUF

PDDS

LPDS

0

0

0

0

0

0

0

Res.

Res.

Res.

VREFINTRDYF

PVDO

SBF

WUF

0

0

0

0

EWUP1

0

EWUP2

Res.

Res.

Res.

Res.

0

EWUP3

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PWR_CSR

Res.

0x004

Res.

Reset value

PLS[2:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PWR_CR

0x000

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 22. PWR register map and reset values

0

0

0

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

110/1141

DocID022558 Rev 8

RM0316

Peripheral interconnect matrix

8

Peripheral interconnect matrix

8.1

Introduction
Several STM32F3 peripherals have internal interconnections. Knowing these
interconnections allows the following benefits:

8.2

•

Autonomous communication between peripherals,

•

Efficient synchronization between peripherals,

•

Discard the software latency and minimize GPIOs configuration,

•

Optimum number of available pins even with small packages,

•

Avoid the use of connectors and design an optimized PCB with less dissipated energy.

Connection summary
The following table presents the matrix for the peripheral interconnect.
Table 23. STM32F3xx peripherals interconnect matrix(1)

DMA1

DMA2 (2)

ADC1

ADC2

ADC3(2)

ADC4(2)

COMP1(2)

COMP2

COMP3(2)

COMP4

COMP5(2)

COMP6

COMP7(2)

OPAMP1(2)

OPAMP2

OPAMP3(2)

OPAMP4(2)

TIM1

TIM8

TIM15

TIM16

TIM17

TIM20

TIM2

TIM3

TIM4

DAC1

DAC2(3)

IRTIM

COMP3(2) COMP2 COMP1(2) ADC4 (2) ADC3 (2) ADC2 ADC1

Source

Destination

x

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

(3)

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

x

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

-

-

-

x

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

-

-

-

x

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

-

-

x

x

x

-

-

-

-

x

DocID022558 Rev 8

111/1141
122

Peripheral interconnect matrix

RM0316

Table 23. STM32F3xx peripherals interconnect matrix(1) (continued)

DMA1

DMA2 (2)

ADC1

ADC2

ADC3(2)

ADC4(2)

COMP1(2)

COMP2

COMP3(2)

COMP4

COMP5(2)

COMP6

COMP7(2)

OPAMP1(2)

OPAMP2

OPAMP3(2)

OPAMP4(2)

TIM1

TIM8

TIM15

TIM16

TIM17

TIM20

TIM2

TIM3

TIM4

DAC1

DAC2(3)

IRTIM

SPI4 USART1 TIM8 SPI1 TIM1 OPAMP4(2) OPAMP3 (2) OPAMP2 OPAMP1(2) COMP7(2) COMP6 COMP5(2) COMP4

Source

Destination

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

-

-

x

-

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

x

x

x

x

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

x

-

x

x

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

x

x

x

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

x

x

x

x

x

x

x

-

-

-

x

x

x

x

x

-

x

-

-

-

x

x

x

x

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

x

x

-

-

-

x

x

x

x

-

-

-

-

-

-

-

-

-

x

x

-

x

x

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

112/1141

DocID022558 Rev 8

RM0316

Peripheral interconnect matrix
Table 23. STM32F3xx peripherals interconnect matrix(1) (continued)

DMA1

DMA2 (2)

ADC1

ADC2

ADC3(2)

ADC4(2)

COMP1(2)

COMP2

COMP3(2)

COMP4

COMP5(2)

COMP6

COMP7(2)

OPAMP1(2)

OPAMP2

OPAMP3(2)

OPAMP4(2)

TIM1

TIM8

TIM15

TIM16

TIM17

TIM20

TIM2

TIM3

TIM4

DAC1

DAC2(3)

IRTIM

I2C1 UART5 UART4 USART3 USART2 SPI3/I2S SPI2/I2S TIM7 TIM6 TIM4 TIM3 TIM2 TIM20 TIM17 TIM16 TIM15

Source

Destination

x

-

x

x

x

x

-

-

-

x

x

x

x

-

-

-

-

x

-

-

-

-

x

-

x

-

x

x

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

x

-

-

-

-

-

-

-

-

x

-

x

x

x

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

x

x

x

x

x

x

x

-

x

x

-

-

-

-

-

x

x

x

-

-

-

-

x

x

x

x

-

x

-

x

x

x

x

x

x

-

x

-

-

-

-

-

-

-

x

x

x

-

-

-

x

-

x

x

x

-

x

-

x

x

x

x

-

-

-

-

-

-

-

-

-

-

-

x

x

-

-

-

x

x

x

-

x

-

-

x

x

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

x

-

-

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

DocID022558 Rev 8

113/1141
122

Peripheral interconnect matrix

RM0316

Table 23. STM32F3xx peripherals interconnect matrix(1) (continued)

DMA1

DMA2 (2)

ADC1

ADC2

ADC3(2)

ADC4(2)

COMP1(2)

COMP2

COMP3(2)

COMP4

COMP5(2)

COMP6

COMP7(2)

OPAMP1(2)

OPAMP2

OPAMP3(2)

OPAMP4(2)

TIM1

TIM8

TIM15

TIM16

TIM17

TIM20

TIM2

TIM3

TIM4

DAC1

DAC2(3)

IRTIM

RTC MCO LSI LSE HSI HSE CPU Hardfault SRAM Parity error PVD CSS Vrefint VBAT TS I2C3 DAC2 (1) DAC1 I2C2

Source

Destination

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

-

-

-

-

x

x

x

x

x

x

x

x

-

x

x

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

x

-

x

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

x

x

x

x

x

x

x

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

x

x

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

x

-

-

-

-

-

-

-

-

114/1141

DocID022558 Rev 8

RM0316

Peripheral interconnect matrix

1. X means interconnect, and “-” means no interconnect.
2. Not in STM32F303x6/8 and STM32F328x8.
3. Only in STM32F303x6/8 and STM32F328x8.

8.3

Interconnection details

8.3.1

DMA interconnections
Hardware DMA requests are managed by peripherals. The DMA channels dedicated to
each peripheral are summarized in Section 13.4.7: DMA request mapping.

8.3.2

From ADC to ADC
ADC1 can be used as a "master" to trigger ADC2 "slave" start of conversion.
ADC3 can be used as "master" to trigger ADC4 "slave" start of conversion.
In dual ADC mode, the converted data of the master and slave ADCs can be read in
parallel.
A description of dual ADC mode is provided in Section 15.3.29: Dual ADC modes.

8.3.3

From ADC to TIM
ADCx (x=1..4) can provide trigger event through watchdog signals to advanced-control
timers (TIM1/TIM8/TIM20).
A description of the ADC analog watchdog settings is provided in Section 15.3.28: Analog
window watchdog (AWD1EN, JAWD1EN, AWD1SGL, AWD1CH, AWD2CH, AWD3CH,
AWD_HTx, AWD_LTx, AWDx).
The output (from ADC) is on signals ADCn_AWDx_OUT (n = 1..4, x = 1..3 as there are 3
analog watchdogs per ADC) and the input (to timer) on signal TIMx_ETR (external trigger).
TIMx_ETR is connected to ADCn_AWDx_OUT through bits in TIMx_OR registers; refer to
Section 20.4.21: TIM1/TIM8/TIM20 option registers (TIMx_OR).
Table 24. TIM1/8/20_ETR connection to ADCx analog watchdogs

8.3.4

TIM1

TIM8

TIM20

ADC1

x

-

-

ADC2

-

x

-

ADC3

-

x

x

ADC4

x

-

x

From TIM and EXTI to ADC
General-purpose timers (TIM2/TIM3/TIM4), basic timers (TIM6/TIM7), advanced-control
timers (TIM1/TIM8/TIM20), general-purpose timer (TIM15/TIM16/TIM17) and EXTI can be
used to generate an ADC triggering event.

DocID022558 Rev 8

115/1141
122

Peripheral interconnect matrix

RM0316

The output (from timer) is on signal TIMx_TRGO, TIMx_TRGO2 or TIMx_CCx event.
The input (to ADC) is on signal EXT[15:0], JEXT[15:0].
The connection between timers and ADCs or also EXTI & ADCs is provided in:

8.3.5

•

Table 90: ADC1 (master) & 2 (slave) - External triggers for regular channels

•

Table 91: ADC1 & ADC2 - External trigger for injected channels

•

Table 92: ADC3 & ADC4 - External trigger for regular channels

•

Table 93: ADC3 & ADC4 - External trigger for injected channels

From OPAMP to ADC
There are two interconnection types:
1.

Connect OPAMP output reference voltage to an internal ADC channel. This connection
can be used for OPAMP calibration. For more details, please refer to the Section
Calibration in the OPAMP chapter.
Section 15.3.11: Channel selection (SQRx, JSQRx) provides the exact ADC channels
to be used.
Table 25. VREFOPAMPx to ADC channel

2.

VREFOPAMPx

ADC channel

VREFOPAMP1

ADC1_IN15

VREFOPAMP2

ADC2_IN17

VREFOPAMP3

ADC3_IN17

VREFOPAMP4

ADC4_IN17

OPAMPx output, x = 1..4 can be connected to ADCy channels, y= 1..4 through the
GPIOs. See summary in the table below. Refer to Section 18.3.4: Using the OPAMP
outputs as ADC inputs.
Table 26. OPAMP output to ADC input

8.3.6

OPAMPx output

ADC channel

Used pins

OPAMP1_VOUT

ADC1_IN3

PA2

OPAMP2_VOUT

ADC2_IN3

PA6

OPAMP3_VOUT

ADC3_IN1

PB1

OPAMP4_VOUT

ADC4_IN3

PB12

From TS to ADC
Internal temperature sensor (VTS) is connected internally to ADC1_IN16. Refer to
Section 15.3.30: Temperature sensor.

8.3.7

From VBAT to ADC
VBAT/2 output voltage can be converted using ADC1_IN17. This interconnection is
explained in Section 15.3.31: VBAT supply monitoring.

116/1141

DocID022558 Rev 8

RM0316

8.3.8

Peripheral interconnect matrix

From VREFINT to ADC
VREFINT is internally connected to channel 18 of the four ADCs. This allows the monitoring
of its value as described in Section 15.3.32: Monitoring the internal voltage reference.

8.3.9

From COMP to TIM
The comparators outputs can be redirected internally to different timer inputs:
•

break input 1/2 for fast PWM shutdowns,

•

OCREF_CLR input,

•

Input capture.

To select which timer input must be connected to the comparator output, the bits field
COMPxOUTSEL in the COMPx_CSR register are used.
The following table gives an overview of all possible comparator outputs redirection to the
timer inputs.
Table 27. Comparator outputs to timer inputs

N.A

N.A

N.A

N.A

N.A

N.A

N.A

N.A

N.A

N.A

DocID022558 Rev 8

TIM20
TIM20_BRK_ACTH
TIM20_BRK2

TIM17

TIM20_BRK_ACTH
TIM20_BRK2
TIM20_OCrefClear

TIM16

TIM20_BRK_ACTH
TIM20_BRK2

TIM15

TIM15_IC1
TIM15_BRK_ACTH

TIM3_IC1
TIM3_OCrefClear
TIM3_IC1
TIM3_OCrefClear

TIM4

TIM4_IC1

TIM2_IC4
TIM2_OCrefClear
TIM2_IC4
TIM2_OCrefClear
TIM2_OCrefClear

TIM3_IC2

TIM8_BRK_ACTH
TIM8_BRK2
TIM8_BRK_ACTH
TIM8_BRK2

TIM3

TIM8_BRK_ACTH
TIM8_BRK2

TIM2

TIM1_BRK_ACTH
TIM1_BRK2
TIM1_OCrefClear
TIM1_IC1

TIM8

TIM1_BRK_ACTH
TIM1_BRK2
TIM1_OCrefClear
TIM1_IC1

TIM1

TIM1_BRK_ACTH
TIM1_BRK2
TIM1_OCrefClear

COMP3

COMP2

COMP1

COMP output selection

117/1141
122

Peripheral interconnect matrix

RM0316

Table 27. Comparator outputs to timer inputs (continued)

Note:

N.A

TIM2_IC3

N.A

N.A

N.A

TIM20_BRK
TIM20_BRK2
TIM20_BRK_ACTH
TIM20_BRK2
TIM20_BRK_ACTH
TIM20_BRK2

N.A

TIM20

TIM20_BRK TIM20_BRK2

N.A

N.A

TIM17_IC1

TIM15_OCrefClear
TIM15_IC2

N.A

N.A

TIM17

TIM17_OCrefClear
TIM17_BRK_ACTH

TIM4_IC2
TIM4_IC3

N.A

TIM16

TIM16_BRK_ACTH

TIM15

TIM16_OCrefClear
TIM16_IC1

TIM4

TIM4_IC4

TIM2_IC1
TIM2_IC2
TIM2_OCrefClear

TIM3_IC3
TIM3_OCrefClear

TIM8_BRK
TIM8_BRK2
TIM8_OCrefClear
TIM8_BRK_ACTH
TIM8_BRK2
TIM8_OCrefClear
TIM8_BRK_ACTH
TIM8_BRK2
TIM8_OCrefClear
TIM8_BRK
TIM8_BRK2
TIM8_OCrefClear

N.A

TIM3

TIM3_OCrefClear

TIM1_BRK
TIM1_BRK2

TIM2

TIM1_BRK_ACTH
TIM1_BRK2

TIM8

TIM1_BRK_ACTH
TIM1_BRK2

TIM1

TIM1_BRK
TIM1_BRK2
TIM1_OCrefClear
TIM1_IC2

COMP7

COMP6

COMP5

COMP4

COMP output selection

When the comparator output is configured to be connected internally to timers break input,
the following must be considered:
1/ COMP1/2/3/5/6 can be used to control TIM1/8/20_BRK_ACTH (this break is always
active high with no digital filter) and to control also TIM1/8/20_BRK2 input.
2/ COMP4/7 can be used to control TIM1/8/20_BRK and the TIM1/8/20_BRK2 input (same
as the other comparators).
3/ COMP3/5/7 can be used to control TIMx_BRK_ACTH, x=15;16;17 respectively (this
break is always active high with no digital filter).

118/1141

DocID022558 Rev 8

RM0316

8.3.10

Peripheral interconnect matrix

From TIM to COMP
The timers output can be selected as comparators outputs blanking signals using the
“COMPx_BLANKING” bits in “COMPx_CSR” register. More details on the blanking function
can be found in Section 17.3.6: Comparator output blanking function.
Table 28. Timer output selection as comparator blanking source
COMP blanking source

8.3.11

COMP1

COMP2

COMP3

COMP4

COMP5

COMP6

COMP7

TIM1

TIM1 OC5

TIM1 OC5

TIM1 OC5

-

-

-

TIM1 OC5

TIM8

-

-

-

TIM8 OC5

TIM8 OC5

TIM8 OC5

TIM8 OC5

TIM15

-

-

-

TIM15 OC1

-

TIM15 OC2 TIM15 OC2

TIM2

TIM2 OC3

TIM2 OC3

TIM2 OC4

-

-

TIM2 OC4

-

TIM3

TIM3 OC3

TIM3 OC3

-

TIM3 OC4

TIM3 OC3

-

-

From DAC to COMP
The comparators inverting input may be a DAC channel output (DAC1_CH1 or
DAC1_CH2). DAC2_CH1 may be selected for COMP2, COMP4 and COMP6 in case the
device is STM32F303x6/8 or STM32F328x8.
The selection is made based on “COMPxINMSEL” bits value in “COMPx_CSR” register.
The following table summarizes these interconnections.
Table 29. DAC output selection as comparator inverting input
COMP inverting inputs
COMP1

COMP2

COMP3

COMP4

COMP5

COMP6

COMP7

DAC1_CH1

X

X

X

X

X

X

X

DAC1_CH2

X

X

X

X

X

X

X

DAC2_CH1(1)

X

X

X

1. Only on STM32F303x6/8 and STM32F328x8.

8.3.12

From VREFINT to COMP
Besides to the DAC channel output, Vrefint (x1, x3/4, x1/2, x1/4) can be selected as
comparator inverting input using “COMPxINMSEL” bits in “COMPx_CSR” register.

8.3.13

From DAC to OPAMP
The DAC outputs are connected internally to OPAMP1 & OPAMP3 & OPAMP4 non inverting
inputs as shown in the following summary table.

DocID022558 Rev 8

119/1141
122

Peripheral interconnect matrix

RM0316

Table 30. DAC output selection as OPAMP non inverting input
Non inverting input

DAC channel

8.3.14

OPAMP1

OPAMP3

OPAMP4

DAC1_CH2

DAC1_CH2

DAC1_CH1

From TIM to OPAMP
The switch between OPAMP inverting and non-inverting inputs can be done automatically.
This automatic switch is triggered by the TIM1 CC6 output arriving on the OPAMP input
multiplexers. More details on this feature are available in Section 18.3.6: Timer controlled
Multiplexer mode.

8.3.15

From TIM to TIM
Some STM32F3 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.
A description of the feature with the various synchronization modes is available in:
•

Section 20.3.25: Timer synchronization for the advanced-control timers
(TIM1/TIM8/TIM20)

•

Section 21.3.19: Timer synchronization for the general-purpose timers
(TIM2/TIM3/TIM4)

The slave mode selection is made using “SMS” bits, as described in:
•

Section 20.4.3: TIM1/TIM8/TIM20 slave mode control register (TIMx_SMCR),

•

Section 21.4.3: TIMx slave mode control register (TIMx_SMCR) for the generalpurpose timers (TIM2/TIM3/TIM4),

•

Section 23.4.18: Slave mode: Combined reset + trigger mode (TIM15 only) for the
general purpose timers (TIM2/TIM3/TIM4)

The possible master/slave connections are summarized in the following table providing the
internal trigger connection:

120/1141

DocID022558 Rev 8

RM0316

Peripheral interconnect matrix
Table 31. Timer synchronization

MASTER

SLAVE
TIM1

TIM8

TIM20

TIM2

TIM3

TIM4

TIM15

TIM1

-

TIM8_ITR0

TIM20_ITR0

TIM2_ITR0

TIM3_ITR0

TIM4_ITR0

-

TIM8

-

-

TIM20_ITR1

TIM2_ITR1

-

TIM4_ITR3

-

TIM2

TIM1_ITR1

TIM8_ITR1

-

-

TIM3_ITR1

TIM4_ITR1

TIM15_ITR0

TIM3

TIM1_ITR2

TIM8_ITR3

-

TIM2_ITR2

-

TIM4_ITR2

TIM15_ITR1

TIM4

TIM1_ITR3

TIM8_ITR2

TIM20_ITR2

TIM2_ITR3

TIM3_ITR3

-

-

TIM15

TIM1_ITR0

-

TIM20_ITR3

-

TIM3_ITR2

-

-

TIM16

-

-

-

-

-

-

TIM15_ITR2

TIM17

TIM1_ITR3

-

-

-

-

-

TIM15_ITR3

8.3.16

From break input sources to TIM
In addition to comparators outputs, other sources can be used as trigger for the internal
break events of some timers (TIM1/TIM8/TIM20/TIM15/TIM16/TIM17). For example:
•

the clock failure event generated by CSS, refer to Section 9.2.6: System clock
(SYSCLK) selection for more details,

•

the PVD output, refer to Section 7.2.2: Programmable voltage detector (PVD) for more
details,

•

the SRAM parity error signal, refer to Section 3.3.1: Parity check for more details,

•

the Cortex-M4 LOCKUP (Hardfault) output.

The sources mentioned above can be connected internally to TIMx_BRK_ACTH input,
x = 1,8,15,16,17,20.
The purpose of the break function is to protect power switches driven by PWM signals
generated by the timers.
More details on the break feature are provided in:

8.3.17

•

Section 20.3.16: Using the break function for the advanced-control timers
(TIM1/TIM8/TIM20)

•

Section 23.4.13: Using the break function for the general-purpose timers
(TIM15/TIM16/TIM17)

From HSE, HSI, LSE, LSI, MCO, RTC to TIM
TIM16 can be used for the measurement of internal/external clock sources. TIM16 channel1
input capture is connected to HSE/32, GPIO, RTC clock and MCO to output clocks among
(HSE, HSI, LSE, LSI, SYSCLK, PLLCLK, PLLCLK/2).
The selection is performed through the TI1_RMP [1:0] bits in the TIM16_OR register.
This allows calibrating the HSI/LSI clocks.

DocID022558 Rev 8

121/1141
122

Peripheral interconnect matrix

RM0316

More details are provided in Section 9.2.14: Internal/external clock measurement with
TIM16.

8.3.18

From TIM and EXTI to DAC
A timer counter may be used as a trigger for DAC conversions.
The TRGO event is the internal signal that will trigger conversion.
The following table provides a summary of DACs interconnections with timers:
This is described in Section 16.5.4: DAC trigger selection.
Table 32. Timer and EXTI signals triggering DAC conversions
DAC1

DAC2 (1)

TIM8

X

-

TIM2

X

X

TIM3

X

X

TIM4

X

-

TIM6

X

X

TIM7

X

X

TIM15

X

X

EXTI line9

X

X

1.

8.3.19

Only on STM32F303x6/8 and STM32F328x8 devices.

From TIM to IRTIM
General-purpose timer (TIM16/TIM17) output channels TIMx_OC1 are used to generate the
waveform of infrared signal output. The functionality is described in Section 24: Infrared
interface (IRTIM).

122/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

9

Reset and clock control (RCC)

9.1

Reset
There are three types of reset, defined as system reset, power reset and RTC domain reset.

9.1.1

Power reset
A power reset is generated when one of the following events occurs:
1.

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

2.

When exiting Standby mode

A power reset sets all registers to their reset values except the RTC domain (see Figure 8
on page 94).

9.1.2

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 RTC domain (see Figure 8 on page 94).
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 event (WWDG reset)

3.

Independent watchdog event (IWDG reset)

4.

A software reset (SW reset) (see Software reset)

5.

Low-power management reset (see Low-power management reset)

6.

Option byte loader reset (see Option byte loader reset)

7.

A power reset

The reset source can be identified by checking the reset flags in the Control/Status register,
RCC_CSR (see Section 9.4.10: Control/status register (RCC_CSR)).
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.

DocID022558 Rev 8

123/1141
167

Reset and clock control (RCC)

RM0316
Figure 12. Simplified diagram of the reset circuit
9 ''
5 38

([WHUQDO
UHVHW

)LOWHU

1567

3XOVH
JHQHUDWRU
PLQ—V

6\VWHPUHVHW

::'*UHVHW
,:'*UHVHW
3RZHUUHVHW
6RIWZDUHUHVHW
/RZSRZHUPDQDJHPHQWUHVHW
2SWLRQE\WHORDGHUUHVHW
([LWIURP6WDQGE\PRGH
069

Software reset
The SYSRESETREQ bit in Cortex-M4®F Application Interrupt and Reset Control Register
must be set to force a software reset on the device. Refer to the STM32F3xx/F4xx Cortex®M4 programming manual (PM0214) for more details.

Low-power management reset
There are two ways to generate a low-power management reset:
1.

Reset generated when entering Standby mode:
This type of reset is enabled by resetting nRST_STDBY bit in User Option Bytes. In this
case, whenever a Standby mode entry sequence is successfully executed, the device
is reset instead of entering Standby mode.

2.

Reset when entering Stop mode:
This type of reset is enabled by resetting nRST_STOP bit in User Option Bytes. In this
case, whenever a Stop mode entry sequence is successfully executed, the device is
reset instead of entering Stop mode.

For further information on the User Option Bytes, refer to Section 4: Option bytes.

Option byte loader reset
The option byte loader reset is generated when the OBL_LAUNCH bit (bit 13) is set in the
FLASH_CR register. This bit is used to launch the option byte loading by software.

9.1.3

RTC domain reset
The RTC domain has two specific resets that affect only the RTC domain (Figure 8 on
page 94).
An RTC domain reset only affects the LSE oscillator, the RTC, the Backup registers and the
RCC RTC domain control register (RCC_BDCR). It is generated when one of the following
events occurs.

124/1141

1.

Software reset, triggered by setting the BDRST bit in the RTC domain control register
(RCC_BDCR).

2.

VDD power-up if VBAT has been disconnected when it was low.

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)
The Backup registers are also reset when one of the following events occurs:

9.2

1.

RTC tamper detection event.

2.

Change of the read out protection from level 1 to level 0.

Clocks
Three different clock sources can be used to drive the system clock (SYSCLK):
•

HSI 8 MHZ RC oscillator clock

•

HSE oscillator clock

•

PLL clock

The devices have the following additional clock sources:
•

40 kHz low speed internal RC (LSI RC) which drives the independent watchdog and
optionally the RTC used for Auto-wakeup from Stop/Standby mode.

•

32.768 kHz low speed external crystal (LSE crystal) which optionally drives the realtime clock (RTCCLK)

Each clock source can be switched on or off independently when it is not used, to optimize
power consumption.
Several prescalers can be used to configure the AHB frequency, the high speed APB
(APB2) and the low speed APB (APB1) domains. The maximum frequency of the AHB and
APB2 domains is 72 MHz. The maximum allowed frequency of the APB1 domain is 36 MHz.
All the peripheral clocks are derived from their bus clock (HCLK, PCLK1 or PCLK2) except:
•

The Flash memory programming interface clock (FLITFCLK) which is always the HSI
clock.

•

The 48-MHz USB clock which is derived from the PLL VCO (STM32F303xB/C/D/E
devices)

•

The option byte loader clock which is always the HSI clock

•

The ADCs clock which is derived from the PLL output. It can reach 72 MHz and can
then be divided by 1,2,4,6,8,10,12,16,32,64,128 or 256.

•

The U(S)ARTs clock which is derived (selected by software) from one of the four
following sources:

•

–

system clock

–

HSI clock

–

LSE clock

–

APB1 or APB2 clock (PCLK1 or PCLK2 depending on which APB is mapped the
USART)

The I2C1/2 (I2C1/2/3 in STM32F303xD/E and STM32F398xE) clock which is derived
(selected by software) from one of the two following sources:
–

system clock

–

HSI clock

•

The I2S2 and I2S3 clocks which can be derived from an external dedicated clock
source.

•

The RTC clock which is derived from the LSE, LSI or from the HSE clock divided by 32.

•

The IWDG clock which is always the LSI clock.

DocID022558 Rev 8

125/1141
167

Reset and clock control (RCC)

RM0316

The RCC feeds the Cortex® System Timer (SysTick) external clock with the AHB clock
(HCLK) divided by 8. The SysTick can work either with this clock or directly with the Cortex®
clock (HCLK), configurable in the SysTick Control and Status Register.
Figure 13. STM32F303xB/C and STM32F358xC clock tree
)/,7)&/.
WR)ODVKSURJUDPPLQJLQWHUIDFH
+6,
WR,&[ [ 

6<6&/.

,665&
6<6&/.
WR,6[
[ 


([WFORFN

,6B&.,1

86%
SUHVFDOHU


0+] +6,
+6,5&

86%&/.
WR86%LQWHUIDFH


+&/.
3//65&
3//08/
3//

[[
[



6:
+6,
3//&/.

$+%
$+%
SUHVFDOHU


+6(

$3%
SUHVFDOHU


6<6&/.

26&B287
26&B,1 

26&B,1
26&B287

3&/.
6<6&/.
+6,
/6(


0+]
+6(26&
$3%
SUHVFDOHU



/6(26&

N+]

57&&/.

/6,

0&2

0DLQFORFN
RXWSXW

3//&/.
+6,
/6,
+6(
6<6&/.
/6(

WR8 6 $57[ [ 

WR$3%SHULSKHUDOV

,I $3%SUHVFDOHU
 [HOVH[
3&/.
6<6&/.
+6,
/6(

,:'*&/.
WR,:'*



3&/.

WR7,0

WR57&

/6(
57&6(/>@

/6,5&

N+]

3&/.

,I $3%SUHVFDOHU
 [HOVH[

&66




WR$+%EXVFRUH
PHPRU\DQG'0$
WRFRUWH[6\VWHPWLPHU
)+&/.&RUWH[IUHH
UXQQLQJFORFN
WR$3%SHULSKHUDOV

[

$'&
3UHVFDOHU


0&2

WR7,0

WR86$57

7,0

WR$'&[\
[\  

$'&
3UHVFDOHU


069

1. For full details about the internal and external clock source characteristics, please refer to the “Electrical
characteristics” section in your device datasheet.
2. TIM1 and TIM8 can be clocked from the PLLCLKx2 running up to 144 MHz when the system clock source

126/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)
is the PLL and the AHB and APB2 prescalers are set to ‘1’.
3. The ADC clock can be derived from the AHB clock of the ADC bus interface, divided by a programmable
factor (1, 2 or 4). When the programmable factor is ‘1’, the AHB prescaler must be equal to ‘1’.

Figure 14. STM32F303xDxE and STM32F398xE clock tree
)/,7)&/.
WR)ODVKSURJUDPPLQJLQWHUIDFH

+6,
WR,&[ [ 

6<6&/.

,665&
6<6&/.
WR,6[ [ 

([WFORFN

,6B&.,1

86%
SUHVFDOHU
 

+6,

0+]
+6,5&

86%&/.WR86%LQWHUIDFH
WR)0&

+&/.

3//65&



3//
[[
«[



6:

3//08/

WR$+%EXVFRUHPHPRU\DQG
'0$

+6,

$+%
$+ %
SUHVFDOHU


3//&/.

+6(

35(',9

WR&RUWH[V\VWHPWLPHU
)+&/.&RUWH[IUHHUXQQLQJFORFN

$3%
SUHVFDOHU


3&/.

WR$3%SHULSKHUDOV

,I $3%SUHVFDOHU
 [HOVH[

&66

WR7,0

3/&/.
26&B287
26&B,1

26&B,1
26&B287

6<6&/.
+6,
/6(

0+]
+6(26&

[



/6(26&
N+]

WR8 6 $57[ [ 

$3%
SUHVFDOHU


57&&/.

WR57&

3&/.

WR7,0

WR$3%SHULSKHUDOV

,I $3%SUHVFDOHU
 [HOVH[

/6(
57&6(/>@

3&/.
/6,

/6,5&
N+]
0&2SUHVFDOHU
0&2



0&2

,:'*&/.
WR,:'*



3//&/.
+6,
/6,
+6(
6<6&/.
/6(

6<6&/.
+6,
/6(

[
$'&
SUHVFDOHU


WR86$57

7,0

WR$'&[\
[\ 

$'&SUHVFDOHU


069

DocID022558 Rev 8

127/1141
167

Reset and clock control (RCC)

RM0316

1. For full details about the internal and external clock source characteristics, please refer to the Electrical
characteristics section in the device datasheet.
2. TIMx (x = 1/2/3/4/8/15/16/17/20) can be clocked from the PLL running at 144 MHz when the system clock
source is the PLL and AHB or APB2 subsystem clocks are not divided by more than 2 cumulatively.
3. The ADC clock can be derived from the AHB clock of the ADC bus interface, divided by a programmable
factor (1, 2 or 4). When the programmable factor is “1”, the AHB prescaler must be equal to “1”.

Figure 15. STM32F303x6/8 and STM32F328x8 clock tree
)/,7)&/.
WR)ODVKSURJUDPPLQJLQWHUIDFH
+6,
WR,&[ [ 

6<6&/.

0+] +6,
+6,5&

+&/.
3//65&
3//08/
3//

[[
[



6:
+6,
3//&/.

$+%
$+%
SUHVFDOHU


+6(

$3%
SUHVFDOHU


6<6&/.

26&B287
26&B,1 

26&B,1
26&B287

3&/.
6<6&/.
+6,
/6(


0+]
+6(26&


/6(26&

N+]

$3%
SUHVFDOHU

57&&/.

/6,5&

N+]

/6,

WR86$57

WR$3%SHULSKHUDOV

,I $3%SUHVFDOHU
 [HOVH[

WR7,0

,:'*&/.
WR,:'*

3//12',9

0&235(

 3//&/.
+6,
/6,
+6(
6<6&/.
/6(



0DLQFORFN
RXWSXW

3&/.

WR7,0

WR57&

/6(
57&6(/>@

0&2

)+&/.&RUWH[IUHH
UXQQLQJFORFN
WR$3%SHULSKHUDOV

3&/.

,I $3%SUHVFDOHU
 [HOVH[

&66




WR$+%EXVFRUH
PHPRU\DQG'0$
WRFRUWH[6\VWHPWLPHU

0&2

[

$'&
3UHVFDOHU


7,0

WR$'&

$'&
3UHVFDOHU


069

1. For full details about the internal and external clock source characteristics, please refer to the “Electrical characteristics”
section in your device datasheet.
2. TIM1 can be clocked from the PLL running at 144 MHz when the system clock source is the PLL and AHB or APB2
subsystem clocks are not divided by more than 2 cumulatively.
3. The ADC clock can be derived from the AHB clock of the ADC bus interface, divided by a programmable factor (1, 2 or 4).
When the programmable factor is ‘1’, the AHB prescaler must be equal to ‘1’.

128/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)
FCLK acts as Cortex-M4®F free-running clock. For more details refer to the
STM32F3xx/F4xx Cortex®-M4 programming manual (PM0214).

9.2.1

HSE clock
The high speed external clock signal (HSE) can be generated from two possible clock
sources:
•

HSE external crystal/ceramic resonator

•

HSE user external 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 16. HSE/ LSE clock sources
Clock source

Hardware configuration

26&B,1

26&B287

External clock

*3,2
([WHUQDO
VRXUFH
06Y9

26&B,1
Crystal/Ceramic
resonators

&/

26&B287

/RDG
FDSDFLWRUV

&/

06Y9

DocID022558 Rev 8

129/1141
167

Reset and clock control (RCC)

RM0316

External crystal/ceramic resonator (HSE crystal)
The 4 to 32 MHz external oscillator has the advantage of producing a very accurate rate on
the main clock.
The associated hardware configuration is shown in Figure 16. Refer to the electrical
characteristics section of the datasheet for more details.
The HSERDY flag in the Clock control register (RCC_CR) indicates if the HSE 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 Clock interrupt register (RCC_CIR).
The HSE Crystal can be switched on and off using the HSEON bit in the Clock control
register (RCC_CR).
Caution:

To switch ON the HSE oscillator, 512 HSE clock pulses need to be seen by an internal
stabilization counter after the HSEON bit is set. Even in the case that no crystal or resonator
is connected to the device, excessive external noise on the OSC_IN pin may still lead the
oscillator to start. Once the oscillator is started, it needs another 6 HSE clock pulses to
complete a switching OFF sequence. If for any reason the oscillations are no more present
on the OSC_IN pin, the oscillator cannot be switched OFF, locking the OSC pins from any
other use and introducing unwanted power consumption. To avoid such situation, it is
strongly recommended to always enable the Clock Security System (CSS) which is able to
switch OFF the oscillator even in this case.

External source (HSE bypass)
In this mode, an external clock source must be provided. It can have a frequency of up to
32 MHz. Select this mode by setting the HSEBYP and HSEON bits in the Clock control
register (RCC_CR). The external clock signal (square, sinus or triangle) with ~40-60% duty
cycle depending on the frequency (refer to the datasheet) has to drive the OSC_IN pin while
the OSC_OUT pin can be used a GPIO. See Figure 16.

9.2.2

HSI clock
The HSI clock signal is generated from an internal 8 MHz RC Oscillator and can be used
directly as a system clock or divided by 2 to be 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 Clock control
register (RCC_CR).
If the application is subject to voltage or temperature variations this may affect the RC
oscillator speed. The user can trim the HSI frequency in the application using the
HSITRIM[4:0] bits in the Clock control register (RCC_CR).
For more details on how to measure the HSI frequency variation, refer to Section 9.2.14:
Internal/external clock measurement with TIM16.

130/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)
The HSIRDY flag in the 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 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 9.2.7: Clock security system (CSS) on page 132.

9.2.3

PLL
The internal PLL can be used to multiply the HSI or HSE output clock frequency. Refer to
Figure 13 and Clock control register (RCC_CR).
The PLL configuration (selection of the input clock, and multiplication factor) must be done
before enabling the PLL. Once the PLL is enabled, these parameters cannot be changed.
To modify the PLL configuration, proceed as follows:
1.

Disable the PLL by setting PLLON to 0.

2.

Wait until PLLRDY is cleared. The PLL is now fully stopped.

3.

Change the desired parameter.

4.

Enable the PLL again by setting PLLON to 1.

An interrupt can be generated when the PLL is ready, if enabled in the Clock interrupt
register (RCC_CIR).
The PLL output frequency must be set in the range 16-72 MHz.

9.2.4

LSE clock
The LSE crystal is a 32.768 kHz Low Speed External crystal or ceramic resonator. It has the
advantage of 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 crystal is switched on and off using the LSEON bit in RTC domain control register
(RCC_BDCR). The crystal oscillator driving strength can be changed at runtime using the
LSEDRV[1:0] bits in the RTC domain control register (RCC_BDCR) to obtain the best
compromise between robustness and short start-up time on one side and low-powerconsumption on the other.
The LSERDY flag in the RTC domain control register (RCC_BDCR) indicates whether 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 Clock
interrupt register (RCC_CIR).

Caution:

To switch ON the LSE oscillator, 4096 LSE clock pulses need to be seen by an internal
stabilization counter after the LSEON bit is set. Even in the case that no crystal or resonator
is connected to the device, excessive external noise on the OSC32_IN pin may still lead the
oscillator to start. Once the oscillator is started, it needs another 6 LSE clock pulses to
complete a switching OFF sequence. If for any reason the oscillations are no more present
on the OSC_IN pin, the oscillator cannot be switched OFF, locking the OSC32 pins from any
other use and introducing unwanted power consumption. The only way to recover such
situation is to perform the RTC domain reset by software.

DocID022558 Rev 8

131/1141
167

Reset and clock control (RCC)

RM0316

External source (LSE bypass)
In this mode, an external clock source must be provided. It can have a frequency of up to
1 MHz. Select this mode by setting the LSEBYP and LSEON bits in the RTC 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 can be used as GPIO. See
Figure 16.

9.2.5

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 RTC. The clock frequency is
around 40 kHz (between 30 kHz and 50 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 Control/status register
(RCC_CSR).
The LSIRDY flag in the Control/status register (RCC_CSR) indicates if the LSI 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 Clock interrupt register (RCC_CIR).

9.2.6

System clock (SYSCLK) selection
Three different clock sources can be used to drive the system clock (SYSCLK):
•

HSI oscillator

•

HSE oscillator

•

PLL

After a system reset, the HSI oscillator is selected as system clock. When a clock source is
used directly or through the PLL as a 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 which is not yet ready is
selected, the switch will occur when the clock source becomes ready. Status bits in the
Clock control register (RCC_CR) indicate which clock(s) is (are) ready and which clock is
currently used as a system clock.

9.2.7

Clock security system (CSS)
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, the HSE oscillator is automatically disabled, a clock
failure event is sent to the break input of the advanced-control timers (TIM1/TIM8 and
TIM15/16/17) 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®F NMI (Non-Maskable Interrupt) exception vector.

Note:

Once the CSS is enabled and if the HSE clock fails, the CSS interrupt occurs and an NMI is
automatically generated. The NMI will be executed indefinitely unless the CSS interrupt
pending bit is cleared. As a consequence, in the NMI ISR user must clear the CSS interrupt
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 means: it is
used as PLL input clock, and the PLL clock is used as system clock), a detected failure

132/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)
causes a switch of the system clock to the HSI oscillator and the disabling of the HSE
oscillator. If the HSE clock (divided or not) is the clock entry of the PLL used as system clock
when the failure occurs, the PLL is disabled too.

9.2.8

ADC clock
The ADC clock is derived from the PLL output. It can reach 72 MHz and can be divided by
the following prescalers values: 1, 2, 4, 6, 8,10,12,16, 32, 64, 128 or 256. It is asynchronous
to the AHB clock. Alternatively, the ADC clock can be derived from the AHB clock of the
ADC bus interface, divided by a programmable factor (1, 2 or 4). This programmable factor
is configured using the CKMODE bit fields in the ADCx_CCR.
If the programmed factor is ‘1’, the AHB prescaler must be set to ‘1’.

9.2.9

RTC clock
The RTCCLK clock source can be either the HSE/32, LSE or LSI clock. It is selected by
programming the RTCSEL[1:0] bits in the RTC domain control register (RCC_BDCR). This
selection cannot be modified without resetting the RTC domain. The system must always be
configured so as to get a PCLK frequency greater than or equal to the RTCCLK frequency
for a proper operation of the RTC.
The LSE clock is in the RTC domain, whereas the HSE and LSI clocks are not.
Consequently:
•

•

If LSE is selected as RTC clock:
–

The RTC continues to work even if the VDD supply is switched off, provided the
VBAT supply is maintained.

–

The RTC remains clocked and functional under system reset.

If LSI is selected as the RTC clock:
–

•

–

9.2.10

The RTC state is not guaranteed if the VDD supply is powered off.

If the HSE clock divided by 32 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 1.8 V domain).

Timers (TIMx) clock
APB clock source
The timers clock frequencies are automatically defined by hardware. There are two cases:
1.

If the APB prescaler equals 1, the timer clock frequencies are set to the same
frequency as that of the APB domain.

2.

Otherwise, they are set to twice (×2) the frequency of the APB domain.

PLL clock source
A clock issued from the PLL (PLLCLKx2) can be selected for TIMx (x = 1,8 on the
STM32F303xB/C and STM32F358xC; x = 1,2,3,4,8,15,16,17,20 on STM32F303xD/E;
x = 1 on the STM32F303x6/8 and STM32F328x8). This configuration allows to feed TIMx
with a frequency up to 144 MHz when the system clock source is the PLL.

DocID022558 Rev 8

133/1141
167

Reset and clock control (RCC)

RM0316

In this configuration:

9.2.11

•

On the STM32F303xB/C and STM32F358xC, AHB and APB2 prescalers are set to 1,
i.e. AHB and APB2 clocks are not divided with respect to the system clock.

•

On the STM32F303xD/E, STM32F303x6/8 and STM32F328x8 AHB or APB2
subsystem clocks are not divided by more than 2 cumulatively with respect to the
system clock.

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.

9.2.12

I2S clock (only in STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE)
The I2S clock can be either the System clock or an external clock provided on I2S_CKIN
pin. The selection of the I2S clock source is performed using bit 23 (I2SSRC) of
RCC_CFGR register.

9.2.13

Clock-out capability
The microcontroller clock output (MCO) capability allows the clock to be output onto the
external MCO pin. The configuration registers of the corresponding GPIO port must be
programmed in alternate function mode. One of 5 clock signals can be selected as the MCO
clock.
•

LSI

•

LSE

•

SYSCLK

•

HSI

•

HSE

•

PLL clock dividedby 2

The selection is controlled by the MCO[2:0] bits in the Clock configuration register
(RCC_CFGR).
On the STM32F303xD/E, STM32F303x6/8 and STM32F328x8, the additional bit
PLLNODIV in this register controls the divider bypass for a PLL clock input to MCO. The
MCO frequency can be reduced by a configurable divider, controlled by the MCOPRE[2..0]
bits of the Clock configuration register (RCC_CFGR).

134/1141

DocID022558 Rev 8

RM0316

9.2.14

Reset and clock control (RCC)

Internal/external clock measurement with TIM16
It is possible to indirectly measure the frequency of all on-board clock sources by mean of
the TIM16 channel 1 input capture. As represented on Figure 17.
Figure 17. Frequency measurement with TIM16 in capture mode
7,0

7,B503>@
*3,2
57&&/.
+6(
0&2

7,

069

The input capture channel of the Timer 16 can be a GPIO line or an internal clock of the
MCU. This selection is performed through the TI1_RMP [1:0] bits in the TIM16_OR register.
The possibilities available are the following ones.
•

TIM16 Channel1 is connected to the GPIO. Refer to the alternate function mapping in
the device datasheets.

•

TIM16 Channel1 is connected to the RTCCLK.

•

TIM16 Channel1 is connected to the HSE/32 Clock.

•

TIM16 Channel1 is connected to the microcontroller clock output (MCO), this selection
is controlled by the MCO[2:0] bits of the Clock configuration register (RCC_CFGR).

Calibration of the HSI
The primary purpose of connecting the LSE, through the MCO multiplexer, to the channel 1
input capture is to be able to precisely measure the HSI system clocks (for this, the HSI
should be used as the system clock source). The number of HSI clock counts between
consecutive edges of the LSE signal provides a measure of the internal clock period. Taking
advantage of the high precision of LSE crystals (typically a few tens of ppm’s), it is possible
to 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. the HSI/LSE ratio): the
precision is therefore closely related to the ratio between the two clock sources. The higher
the ratio is, the better the measurement will be.
If LSE is not available, HSE/32 will be the better option in order to reach the most precise
calibration possible.

Calibration of the LSI
The calibration of the LSI will follow the same pattern that for the HSI, but changing the
reference clock. It will be necessary to connect LSI clock to the channel 1 input capture of
the TIM16. Then define the HSE as system clock source, the number of his clock counts
between consecutive edges of the LSI signal provides a measure of the internal low speed
clock period.

DocID022558 Rev 8

135/1141
167

Reset and clock control (RCC)

RM0316

The basic concept consists in providing a relative measurement (e.g. the HSE/LSI ratio): the
precision is therefore closely related to the ratio between the two clock sources. The higher
the ratio is, the better the measurement will be.

9.3

Low-power modes
APB peripheral clocks and DMA clock can be disabled by software.
Sleep mode stops the CPU clock. The memory interface clocks (Flash and RAM interfaces)
can be stopped by software during sleep mode. The AHB to APB bridge clocks are disabled
by hardware during Sleep mode when all the clocks of the peripherals connected to them
are disabled.
Stop mode stops all the clocks in the V18 domain and disables the PLL, the HSI and the
HSE oscillators.
All U(S)ARTs and I2Cs have the capability to enable the HSI oscillator even when the MCU
is in Stop mode (if HSI is selected as the clock source for that peripheral).
All U(S)ARTs can also be driven by the LSE oscillator when the system is in Stop mode (if
LSE is selected as clock source for that peripheral) and the LSE oscillator is enabled
(LSEON) but they do not have the capability to turn on the LSE oscillator.
Standby mode stops all the clocks in the V18 domain and disables the PLL and the HSI and
HSE oscillators.
The CPU’s deepsleep mode can be overridden for debugging by setting the DBG_STOP or
DBG_STANDBY bits in the DBGMCU_CR register.
When waking up from deepsleep after an interrupt (Stop mode) or reset (Standby mode),
the HSI oscillator is selected as system clock.
If a Flash programming operation is on going, deepsleep mode entry is delayed until the
Flash interface access is finished. If an access to the APB domain is ongoing, deepsleep
mode entry is delayed until the APB access is finished.

136/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

9.4

RCC registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.

9.4.1

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

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res

Res

Res

Res

Res

Res

PLL
RDY

PLLON

Res

Res

Res

Res

CSS
ON

HSE
BYP

HSE
RDY

HSE
ON

r

rw

rw

rw

r

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res

HSI
RDY

HSION

r

rw

HSICAL[7:0]
r

r

r

r

r

HSITRIM[4:0]
r

r

r

rw

rw

rw

rw

rw

Bits 31:26 Reserved, must be kept at reset value.
Bit 25 PLLRDY: PLL clock ready flag
Set by hardware to indicate that the PLL is locked.
0: PLL unlocked
1: PLL locked
Bit 24 PLLON: PLL enable
Set and cleared by software to enable PLL.
Cleared by hardware when entering Stop or Standby mode. This bit can not be reset if the PLL
clock is used as system clock or is selected to become the system clock.
0: PLL OFF
1: PLL ON
Bits 23:20 Reserved, must be kept at reset value.
Bit 19 CSSON: Clock security system enable
Set and cleared by software to enable the clock security system. When CSSON is set, the
clock detector is enabled by hardware when the HSE oscillator is ready, and disabled by
hardware if a HSE clock failure is detected.
0: Clock detector OFF
1: Clock detector ON (Clock detector ON if the HSE oscillator is ready, OFF if not).
Bit 18 HSEBYP: HSE crystal oscillator bypass
Set and cleared by software to bypass the oscillator with an external clock. The external clock
must be enabled with the HSEON bit set, to be used by the device. The HSEBYP bit can be
written only if the HSE oscillator is disabled.
0: HSE crystal oscillator not bypassed
1: HSE crystal oscillator bypassed with external clock
Bit 17 HSERDY: HSE clock ready flag
Set by hardware to indicate that the HSE oscillator is stable. This bit needs 6 cycles of the HSE
oscillator clock to fall down after HSEON reset.
0: HSE oscillator not ready
1: HSE oscillator ready

DocID022558 Rev 8

137/1141
167

Reset and clock control (RCC)

RM0316

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]: HSI clock calibration
These bits are initialized automatically at startup.
Bits 7:3 HSITRIM[4:0]: HSI 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 HSI.
The default value is 16, which, when added to the HSICAL value, should trim the HSI to 8 MHz
± 1%. The trimming step (Fhsitrim) is around 40 kHz between two consecutive HSICAL steps.
Bit 2 Reserved, must be kept at reset value.
Bit 1 HSIRDY: HSI clock ready flag
Set by hardware to indicate that HSI oscillator is stable. After the HSION bit is cleared,
HSIRDY goes low after 6 HSI oscillator clock cycles.
0: HSI oscillator not ready
1: HSI oscillator ready
Bit 0 HSION: HSI clock enable
Set and cleared by software.
Set by hardware to force the HSI oscillator ON when leaving Stop or Standby mode or in case
of failure of the HSE crystal oscillator used directly or indirectly as system clock. This bit
cannot be reset if the HSI is used directly or indirectly as system clock or is selected to become
the system clock.
0: HSI oscillator OFF
1: HSI oscillator ON

9.4.2

Clock configuration register (RCC_CFGR)
Address offset: 0x04
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 clock source switch.

31
PLLNO
DIV

30

29

MCOPRE[2:1]

28

27

MCOF /
MCOP
RE0

Res

rw

rw

rw

r / rw

15

14

13

12

PLLSR
C(1)

Res

rw

11

26

rw

24

MCO[2:0]

23

22

I2SSRC

USBPR
E

19

18

PLLMUL[3:0]

17

16

PLL
XTPRE

PLL
SRC

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

0

rw

rw

HPRE[3:0]
rw

rw

rw

1. STM32F303xD/E only

138/1141

20

rw

PPRE1[2:0]
rw

21

10

PPRE2[2:0]
rw

25

DocID022558 Rev 8

rw

SWS[1:0]
rw

r

r

SW[1:0]
rw

rw

RM0316

Reset and clock control (RCC)

Bit 31 PLLNODIV: Do not divide PLL to MCO (in STM32F303x6/8 and STM32F328x8 ,
STM32F303xDxE and STM32F398xE only)
This bit is set and cleared by software. It switch-off divider-by-2 for PLL connection to MCO
0: PLL is divided by 2 before MCO
1: PLL is not divided before MCO
Bits 30:28 MCOPRE: Microcontroller Clock Output Prescaler (in STM32F303x6/8 and STM32F328x8 ,
STM32F303xDxE and STM32F398xE only)
There bits are set and cleared by software. It is highly recommended to change this prescaler
before MCO output is enabled
000: MCO is divided by 1
001: MCO is divided by 2
010: MCO is divided by 4
.....
111: MCO is divided by 128
Bit 28 MCOF: Microcontroller Clock Output Flag (STM32F303xB/C and STM32F358xC only)
Set and reset by hardware.
It is reset by hardware when MCO field is written with a new value
It is set by hardware when the switch to the new MCO source is effective.
Bit 27 Reserved, must be kept at reset value.
Bits 26:24 MCO: Microcontroller clock output
Set and cleared by software.
000: MCO output disabled, no clock on MCO
001: Reserved
010: LSI clock selected.
011: LSE clock selected.
100: System clock (SYSCLK) selected
101: HSI clock selected
110: HSE clock selected
111: PLL clock selected (divided by 1 or 2 depending on PLLNODIV bit).
Note: This clock output may have some truncated cycles at startup or during MCO clock
source switching.
Bit 23 I2SSRC: I2S external clock source selection (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices only)
Set and reset by software to clock I2S2 and I2S3 with an external clock. This bits must be
valid before enabling I2S2-3 clocks.
0: I2S2 and I2S3 clocked by system clock
1: I2S2 and I2S3 clocked by the external clock
Bit 22 USBPRE: USB prescaler
This bit is set and reset by software to generate the 48 MHz USB clock. They must be valid
before enabling USB clocks.
0: PLL clock is divided by 1.5
1: PLL clock is not divided

DocID022558 Rev 8

139/1141
167

Reset and clock control (RCC)

RM0316

Bits 21:18 PLLMUL: PLL multiplication factor
These bits are written by software to define the PLL multiplication factor. These bits can be
written only when PLL is disabled.
Caution: The PLL output frequency must not exceed 72 MHz.
0000: PLL input clock x 2
0001: PLL input clock x 3
0010: PLL input clock x 4
0011: PLL input clock x 5
0100: PLL input clock x 6
0101: PLL input clock x 7
0110: PLL input clock x 8
0111: PLL input clock x 9
1000: PLL input clock x 10
1001: PLL input clock x 11
1010: PLL input clock x 12
1011: PLL input clock x 13
1100: PLL input clock x 14
1101: PLL input clock x 15
1110: PLL input clock x 16
1111: PLL input clock x 16
Bit 17 PLLXTPRE: HSE divider for PLL input clock
This bits is set and cleared by software to select the HSE division factor for the PLL. It can be
written only when the PLL is disabled.
Note: This bit is the same as the LSB of PREDIV in Clock configuration register 2
(RCC_CFGR2) (for compatibility with other STM32 products)
0000: HSE input to PLL not divided
0001: HSE input to PLL divided by 2
Bits 16:15 PLLSRC: PLL entry clock source (STM32F303xD/E and STM32F398xE only)
Set and cleared by software to select PLL clock source. These bits can be written only when
PLL is disabled.
00: HSI/2 used as PREDIV1 entry and PREDIV1 forced to div by 2.
01: HSI used as PREDIV1 entry.
10: HSE used as PREDIV1 entry.
11: Reserved.
Bit 16 PLLSRC: PLL entry clock source (in STM32F303xB/C and STM32F358xC and
STM32F303x6/8 and STM32F328x8 devices)
Set and cleared by software to select PLL clock source. This bit can be written only when PLL
is disabled.
0: HSI/2 selected as PLL input clock
1: HSE/PREDIV selected as PLL input clock (refer to Section 9.4.12: Clock configuration
register 2 (RCC_CFGR2) on page 159
Bit 15 Reserved, must be kept at reset value in STM32F303xB/C, STM32F358xC, STM32F303x6/8
and STM32F328x8 devices, and used with Bit 16 in STM32F303xD/E to select the PLL clock
source.
Bit14 Reserved, must be kept at reset value.

140/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bits 13:11 PPRE2: APB high-speed prescaler (APB2)
Set and cleared by software to control the division factor of the APB2 clock (PCLK).
0xx: HCLK not divided
100: HCLK divided by 2
101: HCLK divided by 4
110: HCLK divided by 8
111: HCLK divided by 16
Bits 10:8 PPRE1: APB Low-speed prescaler (APB1)
Set and cleared by software to control the division factor of the APB1 clock (PCLK).
0xx: HCLK not divided
100: HCLK divided by 2
101: HCLK divided by 4
110: HCLK divided by 8
111: HCLK divided by 16
Bits 7:4 HPRE: HLCK prescaler
Set and cleared by software to control the division factor of the AHB clock.
0xxx: SYSCLK not divided
1000: SYSCLK divided by 2
1001: SYSCLK divided by 4
1010: SYSCLK divided by 8
1011: SYSCLK divided by 16
1100: SYSCLK divided by 64
1101: SYSCLK divided by 128
1110: SYSCLK divided by 256
1111: SYSCLK divided by 512
Note: The prefetch buffer must be kept on when using a prescaler different from 1 on the
AHB clock. Refer to section Read operations on page 66 for more details.
Bits 3:2 SWS: System clock switch status
Set and cleared by hardware to indicate which clock source is used as system clock.
00: HSI oscillator used as system clock
01: HSE oscillator used as system clock
10: PLL used as system clock
11: not applicable
Bits 1:0 SW: System clock switch
Set and cleared by software to select SYSCLK source.
Cleared by hardware to force HSI selection when leaving Stop and Standby mode or in case
of failure of the HSE oscillator used directly or indirectly as system clock (if the Clock Security
System is enabled).
00: HSI selected as system clock
01: HSE selected as system clock
10: PLL selected as system clock
11: not allowed

DocID022558 Rev 8

141/1141
167

Reset and clock control (RCC)

9.4.3

RM0316

Clock interrupt register (RCC_CIR)
Address offset: 0x08
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

CSSC

15

14

13

12

11

10

9

8

Res

PLL
RDYIE

HSE
RDYIE

HSI
RDYIE

LSE
RDYIE

LSI
RDYIE

CSSF

rw

rw

rw

rw

rw

r

22

21

20

19

18

17

16

Res

Res

PLL
RDYC

HSE
RDYC

HSI
RDYC

LSE
RDYC

LSI
RDYC

w

w

w

w

w

6

5

4

3

2

1

0

Res

PLL
RDYF

HSE
RDYF

HSI
RDYF

LSE
RDYF

LSI
RDYF

r

r

r

r

r

w

Res

Res

7

Res

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
Bits 22:21 Reserved, must be kept at reset value.
Bit 20 PLLRDYC: PLL ready interrupt clear
This bit is set by software to clear the PLLRDYF flag.
0: No effect
1: Clear PLLRDYF flag
Bit 19 HSERDYC: HSE ready interrupt clear
This bit is set by software to clear the HSERDYF flag.
0: No effect
1: Clear HSERDYF flag
Bit 18 HSIRDYC: HSI ready interrupt clear
This bit is set software to clear the HSIRDYF flag.
0: No effect
1: Clear HSIRDYF flag
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
Bits 15:13 Reserved, must be kept at reset value.
Bit 12 PLLRDYIE: PLL ready interrupt enable
Set and cleared by software to enable/disable interrupt caused by PLL lock.
0: PLL lock interrupt disabled
1: PLL lock interrupt enabled

142/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bit 11 HSERDYIE: HSE ready interrupt enable
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
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
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
Set and cleared by software to enable/disable interrupt caused by the LSI oscillator
stabilization.
0: LSI ready interrupt disabled
1: LSI ready interrupt enabled
Bit 7 CSSF: Clock security system interrupt flag
Set by hardware when a failure is detected in the HSE oscillator.
Cleared by software setting the CSSC bit.
0: No clock security interrupt caused by HSE clock failure
1: Clock security interrupt caused by HSE clock failure
Bits 6:5 Reserved, must be kept at reset value.
Bit 4 PLLRDYF: PLL ready interrupt flag
Set by hardware when the PLL locks and PLLRDYDIE is set.
Cleared by software setting the PLLRDYC bit.
0: No clock ready interrupt caused by PLL lock
1: Clock ready interrupt caused by PLL lock
Bit 3 HSERDYF: HSE ready interrupt flag
Set by hardware when the HSE clock becomes stable and HSERDYDIE is set.
Cleared by software setting the HSERDYC bit.
0: No clock ready interrupt caused by the HSE oscillator
1: Clock ready interrupt caused by the HSE oscillator

DocID022558 Rev 8

143/1141
167

Reset and clock control (RCC)

RM0316

Bit 2 HSIRDYF: HSI ready interrupt flag
Set by hardware when the HSI clock becomes stable and HSIRDYDIE is set in a response to
setting the HSION (refer to Clock control register (RCC_CR)). When HSION is not set but the
HSI oscillator is enabled by the peripheral through a clock request, this bit is not set and no
interrupt is generated.
Cleared by software 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
Set by hardware when the LSE clock becomes stable and LSERDYDIE is set.
Cleared by software 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
Set by hardware when the LSI clock becomes stable and LSIRDYDIE is set.
Cleared by software setting the LSIRDYC bit.
0: No clock ready interrupt caused by the LSI oscillator
1: Clock ready interrupt caused by the LSI oscillator

9.4.4

APB2 peripheral reset register (RCC_APB2RSTR)
Address offset: 0x0C
Reset value: 0x00000 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

TIM17
RST

TIM16
RST

TIM15
RST

rw

rw

rw

3

2

1

0

Res

SYS
CFG
RST

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM20
RST

15

14

13

12

11

10

9

8

7

6

5

4

SPI4R
ST

USART1
RST

TIM8
RST

SPI1
RST

TIM1
RST

rw

rw

rw

rw

rw

Res

Res

Res

Res

Res

Res

Res

Res

Res

rw

Bits 31:2119 Reserved, must be kept at reset value.
Bit 20 TIM20RST: TIM20 timer reset (only on STM32F303xD/E and STM32F398xE devices)
Set and cleared by software.
0: No effect
1: Reset TIM20 timer
Bit 19 Reserved, must be kept at reset value.
Bit 18 TIM17RST: TIM17 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM17 timer

144/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bit 17 TIM16RST: TIM16 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM16 timer
Bit 16 TIM15RST: TIM15 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM15 timer
Bit 15 SPI4RST: SPI4 reset (only onSTM32F303xD/E and STM32F398xE devices)
Set and cleared by software.
0: No effect
1: Reset SPI4
Bit 14 USART1RST: USART1 reset
Set and cleared by software.
0: No effect
1: Reset USART1
Bit 13 TIM8RST: TIM8 timer reset (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices only)
Set and cleared by software.
0: No effect
1: Reset TIM8 timer
Bit 12 SPI1RST: SPI1 reset
Set and cleared by software.
0: No effect
1: Reset SPI1
Bit 11 TIM1RST: TIM1 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM1 timer
Bits 10:1 Reserved, must be kept at reset value.
Bit 0 SYSCFGRST: SYSCFG, Comparators and operational amplifiers reset
Set and cleared by software.
0: No effect
1: Reset SYSCFG, COMP, and OPAMP

DocID022558 Rev 8

145/1141
167

Reset and clock control (RCC)

9.4.5

RM0316

APB1 peripheral reset register (RCC_APB1RSTR)
Address offset: 0x10
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31

30

Res

I2C3
RST(1)

29
DAC1
RST
rw

rw

15

14

13

12

SPI3
RST

SPI2
RST

rw

rw

Res

28
PWR
RST

Res

27

26

25

24

Res

DAC2R
ST

CAN
RST

rw

rw

11

10

9

WWDG
RST

Res

Res

23

22

21

USB
RST

I2C2
RST

I2C1
RST

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

Res

TIM7
RST

TIM6
RST

Res

TIM4
RST

TIM3
RST

TIM2
RST

rw

rw

rw

rw

rw

8

Res

Res

Res

rw

20

19

18

17

UART5 UART4 USART3 USART2
RST
RST
RST
RST

Bit 31 Reserved, must be kept at reset value.
Bit 30 I2C3RST: I2C3 reset (STM32F303xD/E and STM32F398xE devices only)
Set and cleared by software.
0: No effect
1: Reset I2C3
Bit 29 DAC1RST: DAC1 interface reset
Set and cleared by software.
0: No effect
1: Reset DAC1 interface
Bit 28 PWRRST: Power interface reset
Set and cleared by software.
0: No effect
1: Reset power interface
Bit 27 Reserved, must be kept at reset value.
Bit 26 DAC2RST: DAC2 interface reset (STM32F303x6/8 and STM32F328x8 devices only)
Set and cleared by software.
0: No effect
1: Reset DAC2 interface

Bit 24 Reserved, must be kept at reset value
Bit 23 USBRST: USB reset (STM32F303xB/C/D/E devices only)
Set and reset by software.
0: does not reset USB
1: resets USB

146/1141

DocID022558 Rev 8

Res

rw

1. STM32F303xD/E devices only.

Bit 25 CANRST: CAN reset
Set and reset by software.
0: does not reset the CAN
1: resets the CAN

16

RM0316

Reset and clock control (RCC)

Bit 22 I2C2RST: I2C2 reset (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices
only)
Set and cleared by software.
0: No effect
1: Reset I2C2
Bit 21 I2C1RST: I2C1 reset
Set and cleared by software.
0: No effect
1: Reset I2C1
Bit 20 UART5RST: UART5 reset (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices
only)
Set and cleared by software.
0: No effect
1: Reset UART5
Bit 19 UART4RST: UART4 reset (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices
only)
Set and cleared by software.
0: No effect
1: Reset UART4
Bit 18 USART3RST: USART3 reset
Set and cleared by software.
0: No effect
1: Reset USART3
Bit 17 USART2RST: USART2 reset
Set and cleared by software.
0: No effect
1: Reset USART2
Bit 16 Reserved, must be kept at reset value.
Bit 15 SPI3RST: SPI3 reset (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices only)
Set and cleared by software.
0: No effect
1: Reset SPI3 and I2S3
Bit 14 SPI2RST: SPI2 reset (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices only)
Set and cleared by software.
0: No effect
1: Reset SPI2 and I2S2
Bits 13:12 Reserved, must be kept at reset value.
Bit 11 WWDGRST: Window watchdog reset
Set and cleared by software.
0: No effect
1: Reset window watchdog
Bits 10:6 Reserved, must be kept at reset value.

DocID022558 Rev 8

147/1141
167

Reset and clock control (RCC)

RM0316

Bit 5 TIM7RST: TIM7 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM7
Bit 4 TIM6RST: TIM6 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM6
Bit 3 Reserved, must be kept at reset value.
Bit 2 TIM4RST: TIM4 timer reset (STM32F303xB/C and STM32F358xC devices only)
Set and cleared by software.
0: No effect
1: Reset TIM4
Bit 1 TIM3RST: TIM3 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM3
Bit 0 TIM2RST: TIM2 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM2

9.4.6

AHB peripheral clock enable register (RCC_AHBENR)
Address offset: 0x14
Reset value: 0x0000 0014
Access: no wait state, word, half-word and byte access

Note:

31

When the peripheral clock is not active, the peripheral register values may not be readable
by software and the returned value is always 0x0.
30

29

Res

Res

ADC34
EN
rw

rw

15

14

13

12

Res

Res

Res

28
ADC12EN

Res

27

26

25

Res

Res

Res

11

10

9

Res

Res

Res

24

23

22

21

20

19

18

17

16

TSCEN

IOPG
EN(1)

IOPF
EN

IOPE
EN

IOPD
EN

IOPC
EN

IOPB
EN

IOPA
EN

IOPH
EN(1)

rw

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

Res

CRC
EN

FMC
EN(1)

FLITF
EN

Res

SRAM
EN

DMA2
EN

DMA1
EN

rw

rw

rw

rw

rw

rw

Res

1. Only on STM32F303xDxE.

148/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bits 31:30 Reserved, must be kept at reset value.
Bit 29 ADC34EN: ADC3 and ADC4 enable (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices only)
Set and reset by software.
0: ADC3 and ADC4 clock disabled
1: ADC3 and ADC4 clock enabled
Bit 28 ADC12EN: ADC1 and ADC2 enable
Set and reset by software.
0: ADC1 and ADC2 clock disabled
1: ADC1 and ADC2 clock enabled
Bits 27:25 Reserved, must be kept at reset value.
Bit 24 TSCEN: Touch sensing controller clock enable
Set and cleared by software.
0: TSC clock disabled
1: TSC clock enabled
Bit 23 IOPGEN: IO port G clock enable. (Only on STM32F303xDxE)
Set and cleared by software.
0: IO port G clock disabled
1: IO port G clock enabled
Bit 22 IOPFEN: I/O port F clock enable
Set and cleared by software.
0: I/O port F clock disabled
1: I/O port F clock enabled
Bit 21 IOPEEN: I/O port E clock enable(STM32F303xB/C and STM32F358xC devices only)
Set and cleared by software.
0: I/O port E clock disabled
1: I/O port E clock enabled.
Bit 20 IOPDEN: I/O port D clock enable
Set and cleared by software.
0: I/O port D clock disabled
1: I/O port D clock enabled
Bit 19 IOPCEN: I/O port C clock enable
Set and cleared by software.
0: I/O port C clock disabled
1: I/O port C clock enabled
Bit 18 IOPBEN: I/O port B clock enable
Set and cleared by software.
0: I/O port B clock disabled
1: I/O port B clock enabled
Bit 17 IOPAEN: I/O port A clock enable
Set and cleared by software.
0: I/O port A clock disabled
1: I/O port A clock enabled

DocID022558 Rev 8

149/1141
167

Reset and clock control (RCC)

RM0316

Bit 16 IOPHEN: IO port H clock enable. (Only on STM32F303xDxE)
Set and cleared by software.
0: IO port H clock disabled
1: IO port H clock enabled
Bits 15:7 Reserved, must be kept at reset value.
Bit 6 CRCEN: CRC clock enable
Set and cleared by software.
0: CRC clock disabled
1: CRC clock enabled
Bit 5 FMCEN: FMC clock enable. (Only on STM32F303xDxE)
Set and cleared by software.
0: FMC clock disabled
1: FMC clock enabled
Bit 4 FLITFEN: FLITF clock enable
Set and cleared by software to disable/enable FLITF clock during Sleep mode.
0: FLITF clock disabled during Sleep mode
1: FLITF clock enabled during Sleep mode
Bit 3 Reserved, must be kept at reset value.
Bit 2 SRAMEN: SRAM interface clock enable
Set and cleared by software to disable/enable SRAM interface clock during Sleep mode.
0: SRAM interface clock disabled during Sleep mode.
1: SRAM interface clock enabled during Sleep mode
Bit 1 DMA2EN: DMA2 clock enable (STM32F303xB/C and STM32F358xC devices only)
Set and cleared by software.
0: DMA2 clock disabled
1: DMA2 clock enabled
Bit 0 DMA1EN: DMA1 clock enable
Set and cleared by software.
0: DMA1 clock disabled
1: DMA1 clock enabled

9.4.7

APB2 peripheral clock enable register (RCC_APB2ENR)
Address: 0x18
Reset value: 0x0000 0000
Access: word, half-word and byte access
No wait states, except if the access occurs while an access to a peripheral in the APB2
domain is on going. In this case, wait states are inserted until the access to APB2 peripheral
is finished.

Note:

150/1141

When the peripheral clock is not active, the peripheral register values may not be readable
by software and the returned value is always 0x0.

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM20
EN

Res

TIM17
EN

TIM16
EN

TIM15
EN

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

2

1

0

TIM8
EN

SPI1
EN

TIM1
EN

Res

SYS
CFGEN

rw

rw

rw

rw

SPI4E USART
N
1EN
rw

rw

Res

Res

Res

Res

Res

Res

4
Res

3
Res

Res

rw

Bits 31:21 Reserved, must be kept at reset value.
Bit 20 TIM20EN: TIM20 timer clock enable (STM32F303xD/E and STM32F398xE only)
Set and cleared by software.
0: TIM20 timer clock disabled
1: TIM20 timer clock enabled
Bit 19 Reserved, must be kept at reset value.
Bit 18 TIM17EN: TIM17 timer clock enable
Set and cleared by software.
0: TIM17 timer clock disabled
1: TIM17 timer clock enabled
Bit 17 TIM16EN: TIM16 timer clock enable
Set and cleared by software.
0: TIM16 timer clock disabled
1: TIM16 timer clock enabled
Bit 16 TIM15EN: TIM15 timer clock enable
Set and cleared by software.
0: TIM15 timer clock disabled
1: TIM15 timer clock enabled
Bit 15 SPI4EN: SPI4 clock enable (STM32F303xD/E and STM32F398xE only)
Set and cleared by software.
0: SPI4 clock disabled
1: SPI4 clock enabled
Bit 14 USART1EN: USART1 clock enable
Set and cleared by software.
0: USART1 clock disabled
1: USART1 clock enabled
Bit 13 TIM8EN: TIM8 timer clock enable (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices only)
Set and cleared by software.
0: TIM8 timer clock disabled
1: TIM8 timer clock enabled
Bit 12 SPI1EN: SPI1 clock enable
Set and cleared by software.
0: SPI1 clock disabled
1: SPI1 clock enabled

DocID022558 Rev 8

151/1141
167

Reset and clock control (RCC)

RM0316

Bit 11 TIM1EN: TIM1 timer clock enable
Set and cleared by software.
0: TIM1 timer clock disabled
1: TIM1 timer clock enabled
Bits 10:1 Reserved, must be kept at reset value.
Bit 0 SYSCFGEN: SYSCFG clock enable
Set and cleared by software.
0: SYSCFG clock disabled
1: SYSCFG clock enabled

9.4.8

APB1 peripheral clock enable register (RCC_APB1ENR)
Address: 0x1C
Reset value: 0x0000 0000
Access: word, half-word and byte access
No wait state, except if the access occurs while an access to a peripheral on APB1 domain
is on going. In this case, wait states are inserted until this access to APB1 peripheral is
finished.

Note:

When the peripheral clock is not active, the peripheral register values may not be readable
by software and the returned value is always 0x0.

31

30

29

28

27

26

25

24

23

22

21

20

19

Res

I2C3
EN

DAC1
EN

PWR
EN

Res

DAC2
EN

CAN
EN

Res

USB
EN

I2C2
EN

I2C1
EN

UART5
EN

UART4
EN

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

7

6

5

4

3

2

1

SPI3
EN

SPI2
EN

Res

WWD
GEN

Res

TIM7E
N

TIM6EN

rw

rw

rw

rw

Res

Res

Res

8
Res

Res

rw

Bit 31 Reserved, must be kept at reset value.
Bit 30 I2C3EN: I2C3 clock enable (only in STM32F303xD/E devices)
Set and cleared by software.
0: I2C3 clock disabled
1: I2C3 clock enabled
Bit 29 DAC1EN: DAC1 interface clock enable
Set and cleared by software.
0: DAC1 interface clock disabled
1: DAC1 interface clock enabled
Bit 28 PWREN: Power interface clock enable
Set and cleared by software.
0: Power interface clock disabled
1: Power interface clock enabled
Bit 27 Reserved, must be kept at reset value.

152/1141

DocID022558 Rev 8

Res

18

17

USART3 USART2
EN
EN

TIM4EN TIM3EN
rw

rw

16
Res

0
TIM2
EN
rw

RM0316

Reset and clock control (RCC)

Bit 26 DAC2EN: DAC2 interface clock enable (STM32F303x6/8 and STM32F328x8 devices only)
Set and cleared by software.
0: DAC2 interface clock disabled
1: DAC2 interface clock enabled
Bit 25 CANEN: CAN clock enable
Set and reset by software.
0: CAN clock disabled
1: CAN clock enabled
Bit 24 Reserved, must be kept at reset value.
Bit 23 USBEN: USB clock enable (STM32F303xB/C/D/E devices only)
Set and reset by software.
0: USB clock disabled
1: USB clock enabled
Bit 22 I2C2EN: I2C2 clock enable (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices only)
Set and cleared by software.
0: I2C2 clock disabled
1: I2C2 clock enabled
Bit 21 I2C1EN: I2C1 clock enable
Set and cleared by software.
0: I2C1 clock disabled
1: I2C1 clock enabled
Bit 20 UART5EN: UART5 clock enable (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices only)
Set and cleared by software.
0: UART5 clock disabled
1: UART5 clock enabled
Bit 19 UART4EN: UART4 clock enable (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices only)
Set and cleared by software.
0: UART4 clock disabled
1: UART4 clock enabled
Bit 18 USART3EN: USART3 clock enable
Set and cleared by software.
0: USART3 clock disabled
1: USART3 clock enabled
Bit 17 USART2EN: USART2 clock enable
Set and cleared by software.
0: USART2 clock disabled
1: USART2 clock enabled
Bit 16 Reserved, must be kept at reset value.
Bit 15 SPI3EN: SPI3 clock enable (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices only)
Set and cleared by software.
0: SPI3 clock disabled
1: SPI3 clock enabled

DocID022558 Rev 8

153/1141
167

Reset and clock control (RCC)

RM0316

Bit 14 SPI2EN: SPI2 clock enable (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices only)
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
Set and cleared by software.
0: Window watchdog clock disabled
1: Window watchdog clock enabled
Bits 10:6 Reserved, must be kept at reset value.
Bit 5 TIM7EN: TIM7 timer clock enable
Set and cleared by software.
0: TIM7 clock disabled
1: TIM7 clock enabled
Bit 4 TIM6EN: TIM6 timer clock enable
Set and cleared by software.
0: TIM6 clock disabled
1: TIM6 clock enabled
Bit 3 Reserved, must be kept at reset value.
Bit 2 TIM4EN: TIM4 timer clock enable (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices only)
Set and cleared by software.
0: TIM4 clock disabled
1: TIM4 clock enabled
Bit 1 TIM3EN: TIM3 timer clock enable
Set and cleared by software.
0: TIM3 clock disabled
1: TIM3 clock enabled
Bit 0 TIM2EN: TIM2 timer clock enable
Set and cleared by software.
0: TIM2 clock disabled
1: TIM2 clock enabled

154/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

9.4.9

RTC domain control register (RCC_BDCR)
Address offset: 0x20
Reset value: 0x0000 0018h reset by RTC 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.

Note:

The LSEON, LSEBYP, RTCSEL and RTCEN bits of the RTC domain control register
(RCC_BDCR) are in the RTC domain. As a result, after Reset, these bits are write-protected
and the DBP bit in the Power control register (PWR_CR) has to be set before these can be
modified. These bits are only reset after a RTC domain Reset (see Section 9.1.3: RTC
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

0

RTC
EN

Res

Res

Res

Res

Res

Res

Res

Res

LSE
BYP

LSE
RDY

LSEON

rw

r

rw

rw

rw

RTCSEL[1:0]
rw

rw

LSEDRV[1:0]
rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 BDRST: RTC domain software reset
Set and cleared by software.
0: Reset not activated
1: Resets the entire RTC domain
Bit 15 RTCEN: RTC clock enable
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
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 RTC domain is reset. The BDRST bit can
be used to reset them.
00: No clock
01: LSE oscillator clock used as RTC clock
10: LSI oscillator clock used as RTC clock
11: HSE oscillator clock divided by 32 used as RTC clock
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:3 LSEDRV[1:0]: LSE oscillator drive capability
Set and reset by software to modulate the LSE oscillator’s drive capability. A reset of the RTC
domain restores the default value.
00: ‘Xtal mode’ lower driving capability
01: ‘Xtal mode’ medium high driving capability
10: ‘Xtal mode’ medium low driving capability
11: ‘Xtal mode’ higher driving capability (reset value)
Note: The oscillator is in Xtal mode when it is not in bypass mode.

DocID022558 Rev 8

155/1141
167

Reset and clock control (RCC)

RM0316

Bit 2 LSEBYP: LSE oscillator bypass
Set and cleared by software to bypass oscillator in debug mode. This bit can be written only
when the external 32 kHz oscillator is disabled.
0: LSE oscillator not bypassed
1: LSE oscillator bypassed
Bit 1 LSERDY: LSE oscillator ready
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 oscillator not ready
1: LSE oscillator ready
Bit 0 LSEON: LSE oscillator enable
Set and cleared by software.
0: LSE oscillator OFF
1: LSE oscillator ON

9.4.10

Control/status register (RCC_CSR)
Address: 0x24
Reset value: 0x0C00 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
LPWR
RSTF

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

WWDG
RSTF

IW
WDG
RSTF

SFT
RSTF

POR
RSTF

PIN
RSTF

OB
LRSTF

RMVF

V18PW
RRSTF

Res

Res

Res

Res

Res

Res

Res

6

5

4

3

2

1

0

Res

LSI
RDY

LSION

r

rw

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Bit 31 LPWRSTF: Low-power reset flag
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 Reset.
Bit 30 WWDGRSTF: Window watchdog reset flag
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

156/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bit 29 IWDGRSTF: Independent window watchdog reset flag
Set by hardware when an independent watchdog reset from VDD domain occurs. Cleared by
writing to the RMVF bit.
0: No watchdog reset occurred
1: Watchdog reset occurred
Bit 28 SFTRSTF: Software reset flag
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 flag
Set by hardware when a POR/PDR occurs. Cleared by writing to the RMVF bit.
0: No POR/PDR occurred
1: POR/PDR occurred
Bit 26 PINRSTF: PIN reset flag
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 OBLRSTF: Option byte loader reset flag
Set by hardware when a reset from the OBL occurs. Cleared by writing to the RMVF bit.
0: No reset from OBL occurred
1: Reset from OBL occurred
Bit 24 RMVF: Remove reset flag
Set by software to clear the reset flags.
0: No effect
1: Clear the reset flags
Bit 23 V18PWRRSTF: Reset flag of the 1.8 V domain.
Set by hardware when a POR/PDR of the 1.8 V domain occurred. Cleared by writing to the
RMVF bit.
0: No POR/PDR reset of the 1.8 V domain occurred
1: POR/PDR reset of the 1.8 V domain occurred

Note: On the STM32F3x8 products, this flag is reserved.
Bits 22:2 Reserved, must be kept at reset value.
Bit 1 LSIRDY: LSI oscillator ready
Set and cleared by hardware to indicate when the LSI oscillator is stable. After the LSION bit is
cleared, LSIRDY goes low after 3 LSI oscillator clock cycles.
0: LSI oscillator not ready
1: LSI oscillator ready
Bit 0 LSION: LSI oscillator enable
Set and cleared by software.
0: LSI oscillator OFF
1: LSI oscillator ON

DocID022558 Rev 8

157/1141
167

Reset and clock control (RCC)

9.4.11

RM0316

AHB peripheral reset register (RCC_AHBRSTR)
Address: 0x28
Reset value: 0x0000 0000
Access: no wait states, word, half-word and byte access

31

30

Res

Res

15

14

Res

Res

29

28

ADC34 ADC12
RST
RST
rw

rw

13

12

Res

Res

27

26

25

Res

Res

Res

11

10

9

Res

Res

Res

24

23

TSC
RST

IOPGR
ST(1)

IOPF
RST

IOPE
RST

IOPD
RST

IOPC
RST

rw

rw

rw

rw

rw

8

7

6

5

4

Res

FMCR
ST(1)

Res

Res

Res

22

21

20

19

18

17

16

IOPB
RST

IOPA
RST

IOPHR
ST(1)

rw

rw

rw

rw

3

2

1

0

Res

Res

Res

Res

rw

1. Only on STM32F303xDxE.

Bits 31:30 Reserved, must be kept at reset value.
Bit 29 ADC34RST: ADC3 and ADC4 reset (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices only)
Set and reset by software.
0: does not reset the ADC3 and ADC4
1: resets the ADC3 and ADC4
Bit 28 ADC12RST: ADC1 and ADC2 reset
Set and reset by software.
0: does not reset the ADC1 and ADC2
1: resets the ADC1 and ADC2
Bits 27:25 Reserved, must be kept at reset value.
Bit 24 TSCRST: Touch sensing controller reset
Set and cleared by software.
0: No effect
1: Reset TSC
Bit 23 IOPGRST: I/O port G reset. (Only on STM32F303xDxE)
Set and cleared by software.
0: No effect
1: Reset I/O port G
Bit 22 IOPFRST: I/O port F reset
Set and cleared by software.
0: No effect
1: Reset I/O port F
Bit 21 OPERST: I/O port E reset
Set and cleared by software.
0: No effect
1: Reset I/O port E

158/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bit 20 IOPDRST: I/O port D reset
Set and cleared by software.
0: No effect
1: Reset I/O port D
Bit 19 IOPCRST: I/O port C reset
Set and cleared by software.
0: No effect
1: Reset I/O port C
Bit 18 IOPBRST: I/O port B reset
Set and cleared by software.
0: No effect
1: Reset I/O port B
Bit 17 IOPARST: I/O port A reset
Set and cleared by software.
0: No effect
1: Reset I/O port A
Bit 16 IOPHRST: I/O port H reset (Only on STM32F303xDxE).
Set and cleared by software.
0: No effect
1: Reset I/O port H
Bits 15:6 Reserved, must be kept at reset value.
Bit 5 FMCRST: FMC reset (Only on STM32F303xDxE).
Set and cleared by software.
0: No effect
1: Reset FMC
Bits 4:0 Reserved, must be kept at reset value.

9.4.12

Clock configuration register 2 (RCC_CFGR2)
Address: 0x2C
Reset value: 0x0000 0000
Access: no wait states, 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
rw

rw

rw

rw

rw

rw

rw

ADC34PRES[4:0]
rw

rw

ADC12PRES[4:0]
rw

rw

PREDIV[3:0]
rw

rw

rw

Bits 31:14 Reserved, must be kept at reset value.

DocID022558 Rev 8

159/1141
167

Reset and clock control (RCC)

RM0316

Bits 13:9 ADC34PRES: ADC34 prescaler (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
only)
Set and reset by software to control PLL clock to ADC34 division factor.
0xxxx: ADC34 clock disabled, ADC34 can use AHB clock
10000: PLL clock divided by 1
10001: PLL clock divided by 2
10010: PLL clock divided by 4
10011: PLL clock divided by 6
10100: PLL clock divided by 8
10101: PLL clock divided by 10
10110: PLL clock divided by 12
10111: PLL clock divided by 16
11000: PLL clock divided by 32
11001: PLL clock divided by 64
11010: PLL clock divided by 128
11011: PLL clock divided by 256
others: PLL clock divided by 256
Bits 8:4 ADC12PRES: ADC12 prescaler
Set and reset by software to control PLL clock to ADC12 division factor.
0xxxx: ADC12 clock disabled, ADC12 can use AHB clock
10000: PLL clock divided by 1
10001: PLL clock divided by 2
10010: PLL clock divided by 4
10011: PLL clock divided by 6
10100: PLL clock divided by 8
10101: PLL clock divided by 10
10110: PLL clock divided by 12
10111: PLL clock divided by 16
11000: PLL clock divided by 32
11001: PLL clock divided by 64
11010: PLL clock divided by 128
11011: PLL clock divided by 256
others: PLL clock divided by 256

160/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bits 3:0 PREDIV: PREDIV division factor
These bits are set and cleared by software to select PREDIV division factor. They can be
written only when the PLL is disabled.
Note: Bit 0 is the same bit as bit17 in Clock configuration register (RCC_CFGR), so modifying
bit17 Clock configuration register (RCC_CFGR) also modifies bit 0 in Clock
configuration register 2 (RCC_CFGR2) (for compatibility with other STM32 products)
0000: HSE input to PLL not divided
0001: HSE input to PLL divided by 2
0010: HSE input to PLL divided by 3
0011: HSE input to PLL divided by 4
0100: HSE input to PLL divided by 5
0101: HSE input to PLL divided by 6
0110: HSE input to PLL divided by 7
0111: HSE input to PLL divided by 8
1000: HSE input to PLL divided by 9
1001: HSE input to PLL divided by 10
1010: HSE input to PLL divided by 11
1011: HSE input to PLL divided by 12
1100: HSE input to PLL divided by 13
1101: HSE input to PLL divided by 14
1110: HSE input to PLL divided by 15
1111: HSE input to PLL divided by 16

DocID022558 Rev 8

161/1141
167

Reset and clock control (RCC)

9.4.13

RM0316

Clock configuration register 3 (RCC_CFGR3)
Address: 0x30
Reset value: 0x0000 0000
Access: no wait states, word, half-word and byte access

31

30

29

28

27

26

25

24

TIM34
SW(1)

TIM2
SW(1)

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

0

Res

I2C3
SW(1)

I2C2
SW

I2C1
SW

Res

Res

rw

rw

rw

Res

Res

Res

Res

Res

Res

15

14

13

12

11

10

Res

TIM17
SW(1)

Res

TIM16
SW(1)

TIM15
SW(1)

TIM8S
W

TIM1
SW

rw

rw

rw

rw

TIM20
SW(1)
rw

rw

23

22

UART5SW[1:0]

21

20

UART4SW[1:0]

19

18

17

16

USART3SW[1:0] USART2SW[1:0]
(2)

(2)

USART1SW[1:0]
rw

rw

1. Only on STM32F303xDxE.
2. Not available in STM32F303x6/8 and STM32F328x8 devices.

Bits 31:26 Reserved, must be kept at reset value.
Bit 25 TIM34SW: Timer34 clock source selection
Set and reset by software to select TIM34 clock source.
The bit is writable only when the following conditions occur: system clock source is the PLL
and AHB or APB2 subsystem clocks are not divided by more than 2 cumulatively.
The bit is reset by hardware when exiting from the previous condition (user must set the bit
again in case of a new switch is required)
0: PCLK2 clock (doubled frequency when prescaled) (default)
1: PLL vco output (running up to 144 MHz)
Note: STM32F303xDxE and STM32F398xE only.
Bit 24 TIM2SW: Timer2 clock source selection
Set and reset by software to select TIM2 clock source.
The bit is writable only when the following conditions occur: clock system = PLL, and AHB or
APB2 subsystem clocks are not divided by more than 2 cumulatively.
0: PCLK2 clock (doubled frequency when prescaled) (default)
1: PLL vco output (running up to 144 MHz)
Note: STM32F303xDxE and STM32F398xE only.
Bits 23:22 UART5SW[1:0]: UART5 clock source selection (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices only)
This bit is set and cleared by software to select the UART5 clock source.
00: PCLK selected as UART5 clock source (default)
01: System clock (SYSCLK) selected as UART5 clock
10: LSE clock selected as UART5 clock
11: HSI clock selected as UART5 clock
Bits 21:20 UART4SW[1:0]: UART4 clock source selection (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices only)
This bit is set and cleared by software to select the UART4 clock source.
00: PCLK selected as UART4 clock source (default)
01: System clock (SYSCLK) selected as UART4 clock
10: LSE clock selected as UART4 clock
11: HSI clock selected as UART4 clock

162/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bits 19:18 USART3SW[1:0]: USART3 clock source selection
This bit is set and cleared by software to select the USART3 clock source.
00: PCLK selected as USART3 clock source (default)
01: System clock (SYSCLK) selected as USART3 clock
10: LSE clock selected as USART3 clock
11: HSI clock selected as USART3 clock

Note: USART2SW[1:0] is not available in STM32F303x6/8 and STM32F328x8.
Bits 17:16 USART2SW[1:0]: USART2 clock source selection
This bit is set and cleared by software to select the USART2 clock source.
00: PCLK selected as USART2 clock source (default)
01: System clock (SYSCLK) selected as USART2 clock
10: LSE clock selected as USART2 clock
11: HSI clock selected as USART2 clock

Note: USART2SW[1:0] is not available in STM32F303x6/8 and STM32F328x8.
Bit 15 TIM20SW: Timer20 clock source selection
Set and reset by software to select TIM20 clock source.
The bit is writable only when the following conditions occur: system clock source is the PLL
and AHB or APB2 subsystem clocks are not divided by more than 2 cumulatively.
The bit is reset by hardware when exiting from the previous condition (user must set the bit
again in case of a new switch is required)
0: PCLK2 clock (doubled frequency when prescaled) (default)
1: PLL vco output (running up to 144 MHz)
Note: STM32F303xDxE only.
Bit 14 Reserved, must be kept at reset value.
Bit 13 TIM17SW: Timer17 clock source selection
Set and reset by software to select TIM17 clock source.
The bit is writable only when the following conditions occur: system clock source is the PLL
and AHB or APB2 subsystem clocks are not divided by more than 2 cumulatively.
The bit is reset by hardware when exiting from the previous condition (user must set the bit
again in case of a new switch is required)
0: PCLK2 clock (doubled frequency when prescaled) (default)
1: PLL vco output (running up to 144 MHz)
Note: STM32F303xDxE and STM32F398xE devices only.
Bit 12 Reserved, must be kept at reset value.
Bit 11 TIM16SW: Timer16 clock source selection
Set and reset by software to select TIM16 clock source.
The bit is writable only when the following conditions occur: system clock source is the PLL
and AHB or APB2 subsystem clocks are not divided by more than 2 cumulatively.
The bit is reset by hardware when exiting from the previous condition (user must set the bit
again in case of a new switch is required)
0: PCLK2 clock (doubled frequency when prescaled) (default)
1: PLL vco output (running up to 144 MHz)
Note: STM32F303xD/E and STM32F398xE devices only.

DocID022558 Rev 8

163/1141
167

Reset and clock control (RCC)

RM0316

Bit 10 TIM15SW: Timer15 clock source selection
Set and reset by software to select TIM15 clock source.
The bit is writable only when the following conditions occur: system clock source is the PLL
and AHB or APB2 subsystem clocks are not divided by more than 2 cumulatively.
The bit is reset by hardware when exiting from the previous condition (user must set the bit
again in case of a new switch is required)
0: PCLK2 clock (doubled frequency when prescaled) (default)
1: PLL vco output (running up to 144 MHz)
Note: STM32F303xD/E and STM32F398xE devices only.
Bit 9 TIM8SW: Timer8 clock source selection (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices only)
Set and reset by software to select TIM8 clock source.
In STM32F303xB/C and STM32F358xC, the bit is writable only when the following conditions
occur: clock system = PLL, and AHB and APB2 subsystem clock not divided respect the clock
system.
In STM32F303xD/E and STM32F398xE, the bit is writable only when the following conditions
occur: system clock source is the PLL and AHB or APB2 subsystem clocks are not divided by
more than 2 cumulatively..
The bit is reset by hardware when exiting from the previous condition (user must set the bit
again in case of a new switch is required)
0: PCLK2 clock (doubled frequency when prescaled) (default)
1: PLL vco output (running up to 144 MHz)
Bit 8 TIM1SW: Timer1 clock source selection
Set and reset by software to select TIM1 clock source.
In STM32F303xB/C and STM32F358xC, the bit is writable only when the following conditions
occur: clock system = PLL, and AHB and APB2 subsystem clock not divided respect the clock
system.
In STM32F303x6/8/D/E and STM32F398xE, the bit is writable only when the following
conditions occur: system clock source is the PLL and AHB or APB2 subsystem clocks are not
divided by more than 2 cumulatively.
The bit is reset by hardware when exiting from the previous condition (user must set the bit
again in case of a new switch is required)
0: PCLK2 clock (doubled frequency when prescaled) (default)
1: PLL vco output (running up to 144 MHz)
Bit 7: Reserved, must be kept at reset value.
Bit 6 I2C3SW: I2C3 clock source selection (STM32F303xD/E devices only)
This bit is set and cleared by software to select the I2C3 clock source.
0: HSI clock selected as I2C3 clock source (default)
1: SYSCLK clock selected as I2C3 clock
Bit 5 I2C2SW: I2C2 clock source selection (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices only)
This bit is set and cleared by software to select the I2C2 clock source.
0: HSI clock selected as I2C2 clock source (default)
1: SYSCLK clock selected as I2C2 clock

164/1141

DocID022558 Rev 8

RM0316

Reset and clock control (RCC)

Bit 4 I2C1SW: I2C1 clock source selection
This bit is set and cleared by software to select the I2C1 clock source.
0: HSI clock selected as I2C1 clock source (default)
1: SYSCLK clock selected as I2C1 clock
Bits 3:2 Reserved, must be kept at reset value.
Bits 1:0 USART1SW[1:0]: USART1 clock source selection
This bit is set and cleared by software to select the USART1 clock source.
00: PCLK selected as USART1 clock source (default)
01: System clock (SYSCLK) selected as USART1 clock
10: LSE clock selected as USART1 clock
11: HSI clock selected as USART1 clock

DocID022558 Rev 8

165/1141
167

0x1C

166/1141

RCC_APB1ENR

Reset value

0

0

0

0

Reset value

0

0

0

0
IOPHEN(3)

0

0

0

0

0

0

DocID022558 Rev 8

0

TIM1EN

0

0

0

0

WWDGEN

0

0

0

0

TIM3EN(2)
TIM2EN

1
0
0

Res.

SYSCFGEN

0

DMA2EN(2)
DMA1EN

0

0

TIM2RST

TIM4RST(2)
TIM3RST

Res.

0

Res.

0

SRAMEN

1

Res.

HSIRDYF
LSERDYF
LSIRDYF

0
0
0
0
0

SYSCFGRST

0

Res.

0

HSERDYF

0

Res.

0

Res.

HSION

0
1
1

SWS
[1:0]
SW
[1:0]

Res.
HSIRDY

HPRE[3:0]

Res.

0

Res.

0

Res.

0
PLLRDYF

0

Res.

HSITRIM[4:0]

TIM4EN(2)

0

TIM6RST

FLITFEN

0

Res.

0

TIM6EN

0

Res.

Res.

Res.

0

TIM7RST

0

FMCEN(3)

0

Res.

CSSF

0

Res.

0

Res.

0

CRCEN

LSIRDYIE

0

Res.

1

Res.

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

HSIRDYIE

0
LSERDYIE

x

Res.

Res.

x

Res.

Res.

Res.

0

Res.

WWDGRST

0

Res.

HSICAL[7:0]

TIM7EN

0

x

Res.

Res.

x

Res.

Res.

Res.

Res.

PPRE1
[2:0]

HSERDYIE

TIM1RST

0

Res.

x

Res.

0

PPRE2
[2:0]

Res.

SPI1RST

0

0

x

Res.

TIM8RST(2)

0

0

Res.

PLLSRC(3)
Res.

x

PLLRDYIE

TIM15RST

x

Res.

SPI1EN

0

Res.

0
0

SPI2RST

0
0

Res.

0

TIM8EN(2)

0

SPI2EN(2)
Res.

0
SPI4RST(3)
USART1RST

PLLMUL[3:0
]

Res.

HSEON
PLLSRC

0

0

Res.

Res.

LSIRDYC

0

Res.
0

TIM16RST

0

USART2RST

Res.

Res.

0

SPI3RST

Res.

Res.

0

Res.

Res.

PLLON

0

Res.SPI4EN
USART1EN

Res.
CSSC

PLLRDY

Res.

Res.

Res.

Res.

0

SP3EN

0

HSEBYP

0

HSERDY
PLLXTPRE
0

HSIRDYC

0

LSERDYC

0

CSSON

0

HSERDYC

0

Res.

0

PLLRDYC

USBPRE

0

Res.

Res.

I2SSRC

0

0

UART4RST(2)
USART3RST

UART5RST(2)

Reset value

(2)

(3)

IOPAEN

TIM15EN

0

Res.

IOPBEN

0

TIM16EN
0

TIM17EN
0

USART2EN

IOPCEN

0

Res.

0

UART4EN(2)
USART3EN

IOPDEN

0

Res.TIM20EN(3)

0
I2C2RST
I2C1RST

Res.

0

UART5EN(2)

IOPEEN(2)

0

Res.

(2)

Res.

Res.

Reset value

I2C2EN
I2C1EN
0

Res.

Res.

MCO
[2:0]

USBRST(2)

Res.

(2)

0

(2)

0

Res.

Res.

MCOPRE0 / MCOF
Res.

(1)

Res.

Res.

0

Res.IOPGEN(3)
IOPFEN

0

Res.

Res.

Res.

0

TSCEN

CANRST

0

Res.

Res.

Res.

0

Res.

Res.

DAC2RST(1)

0

Res.

Res.

Res.

Res.

Reset value

USBEN(2)

0

CANEN

0

Res.

0
Res.

RCC_CIR

Res.

Res.
0

MCOPRE[2:1]

0

Res.

PWRRST

Res.

0
(1)

PLLNODIV(1)

0

Res.

0

Res.

Reset value
DAC1RST

Reset value

ADC34EN(2)
ADC12EN

Res.

Res.

Reset value

DAC2EN(1)

RCC_APB2ENR
Res.

RCC_CFGR

Res.

0x18
RCC_AHBENR

PWREN

0x14
RCC_
APB1RSTR

Res.

0x010
RCC_
APB2RSTR

I2C3RST

0x0C

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

Res.

Offset

I2C3EN.
DAC1EN

(3)

9.4.14

Res.

Reset and clock control (RCC)
RM0316

RCC register map
The following table gives the RCC register map and the reset values.
Table 33. RCC register map and reset values

0

0

0

0

0x30
RCC_CFGR3
USART2SW[1:0]

0
0
0
0

DocID022558 Rev 8
0

I2C1SW

0
0

USART1SW[1:0]

LSEON

LSION

0
0

Res.

LSEBYP

0

LSIRDY

0

Res.

LSERDY

Res.

Res.

Res.

Res.

0

Res.

1

Res.

Res.
1

Res.

Res.

FMCRST
Res.

(3)

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LSE
DRV
[1:0]

Res.

0

Res.

I2C3SW
I2C2SW

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTCEN
Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BDRST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

(3)

IOPARST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC
SEL
[1:0]

Res.

Reset value

TIM8SW(2)
TIM1SW

IOPBRST
0

Res

IOPCRST
0

Res(1)

IOPDRST

0

IOPHRST(3)
Res.

IOPERST(2)

0

(1)

TSCRST

0

Res.

Res.

0

0

Res.(1)

Res.

0

0

Res.

Res.

0

Res.

ADC12RST

0

Res.

RCC_AHBRSTR

Res.

0

Res.

V18PWRRSTF

0

Res.

RMVF

0

Res.

OBLRSTF

0

Res.

PINRSTF

0

Res.

PORRSTF

0

IOPGRST(3)
IOPFRST

SFTRSTF

0

Res.

Res.

Res.

Res.

Res.

Res.

IWDGRSTF

0

ADC34RST(2)

Reset value

TIM20SW(3)
Res.

USART3SW[1:0]

(2)

UART4SW[1:0](2)

TIM34SW(3)
TIM2SW(3)

Res.

Res.

Res.

Res.

LPWRSTF
WWDGRSTF

0

0

UART5SW[1:0]

Reset value
Res.

RCC_CFGR2

Res.

0x2C
Reset value

Res.

Reset value
RCC_CSR

Res.

0x28

Res.

0x24
RCC_BDCR

Res.

0x20

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register

Res.

Offset

Res.

RM0316
Reset and clock control (RCC)

Table 33. RCC register map and reset values (continued)

ADC34PRES
[4:0](2)
ADC12PRES
[4:0]

0
PREDIV[3:0]

0
0
0

0
0

1. On STM32F303xB/C and STM32F358xC devices only.

2. On STM32F303x6/8 and STM32F328x8 devices only.

3. On STM32F303xD/E only

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

167/1141

167

Flexible static memory controller (FSMC)

10

Flexible static memory controller (FSMC)

Note:

Only the STM32F303xD/E and STM32F398xE devices include the FSMC.

RM0316

The Flexible static memory controller (FSMC) includes two memory controllers:
•

The NOR/PSRAM memory controller

•

The NAND/PC Card memory controller

This memory controller is also named Flexible memory controller (FMC).

10.1

FMC main features
The FMC functional block makes the interface with: synchronous and asynchronous static
memories, and 16-bit PC card 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)

–

16-bit PC Card compatible devices

–

Two banks of NAND Flash memory with ECC hardware to check up to 8 Kbytes of
data

•

Burst mode support for faster access to synchronous devices such as NOR Flash
memory, PSRAM

•

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 devices

•

External asynchronous wait control

•

Write Data FIFO with 16 x33-bit depth

•

Write Address FIFO with 16x30-bit depth

The FMC embeds two Write FIFOs: a Write Data FIFO with a 16x33-bit depth and a Write
Address FIFO with a 16x30-bit depth.

168/1141

•

The Write Data FIFO 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)

•

The Write Address FIFO 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

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
when crossing a page boundary (for PSRAM). In this case, the AHB burst is broken
into two FIFO entries.
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.

10.2

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 NAND Flash/PC Card controller

•

The external device interface

The block diagram is shown in Figure 18.
Figure 18. FMC block diagram
)0&LQWHUUXSWVWR19,&

)0&B1/ RU1$'9
)0&B&/.
)URPFORFN
FRQWUROOHU
+&/.

125365$0
PHPRU\
FRQWUROOHU

&RQILJXUDWLRQ
UHJLVWHUV

1$1'3&
FDUGPHPRU\
FRQWUROOHU

125365$0
VLJQDOV

)0&B1%/>@

125365$065$0
VKDUHGVLJQDOV

)0&B$>@
)0&B'>@

6KDUHGVLJQDOV

)0&B1(>@
)0&B12(
)0&B1:(
)0&B1:$,7

125365$065$0
VKDUHGVLJQDOV

)0&B1&(>@
)0&B,17>@

1$1'VLJQDOV

)0&B,175
)0&B1&(B
)0&B1&(B
)0&B1,25'
)0&B1,2:5

3&FDUGVLJQDOV

)0&B15(*
)0&B&'
069

DocID022558 Rev 8

169/1141
227

Flexible static memory controller (FSMC)

10.3

RM0316

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 reading or writing to the PC Card banks while the FMC_CD input pin (Card
Presence Detection) is low.

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.

10.3.1

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.

170/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
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)
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).

Configuration registers
The FMC can be configured through a set of registers. Refer to Section 10.5.6, for a
detailed description of the NOR Flash/PSRAM controller registers. Refer to Section 10.6.8,
for a detailed description of the NAND Flash/PC Card registers.

10.4

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 19):
•

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

•

Banks 2 and 3 used to address NAND Flash memory devices (1 device per bank)

•

Bank 4 used to address a PC Card

For each bank the type of memory to be used can be configured by the user application
through the Configuration register.

DocID022558 Rev 8

171/1141
227

Flexible static memory controller (FSMC)

RM0316

Figure 19. FMC memory banks
6XSSRUWHGPHPRU\W\SH

%DQN

$GGUHVV
[

125365$065$0

%DQN
[0%
[)))))))
[

%DQN
[0%
[)))))))

1$1')ODVKPHPRU\

[

%DQN
[0%
[)))))))
[

%DQN
[0%

3&&DUG

[)))))))
069

10.4.1

NOR/PSRAM address mapping
HADDR[27:26] bits are used to select one of the four memory banks as shown in Table 34.
Table 34. 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 35. NOR/PSRAM External memory address

172/1141

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

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)

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].

Wrap support for NOR Flash/PSRAM
Wrap burst mode for synchronous memories is not supported. The memories must be
configured in linear burst mode of undefined length.

10.4.2

NAND Flash memory/PC Card address mapping
In this case, three banks are available, each of them being divided into memory areas as
indicated in Table 36.
Table 36. NAND/PC Card memory mapping and timing registers
Start address

End address

FMC bank

0x9C00 0000

0x9FFF FFFF

0x9800 0000

0x9BFF FFFF Bank 4 - PC card

Attribute

FMC_PATT4 (0xAC)

0x9000 0000

0x93FF FFFF

Common

FMC_PMEM4 (0xA8)

0x8800 0000

0x8BFF FFFF

Attribute

FMC_PATT3 (0x8C)

0x8000 0000

0x83FF FFFF

Common

FMC_PMEM3 (0x88)

0x7800 0000

0x7BFF FFFF

Attribute

FMC_PATT2 (0x6C)

0x7000 0000

0x73FF FFFF

Common

FMC_PMEM2 (0x68)

Bank 3 - NAND Flash

Bank 2- NAND Flash

Memory space

Timing register

I/O

FMC_PIO4 (0xB0)

For NAND Flash memory, the common and attribute memory spaces are subdivided into
three sections (see in Table 37 below) located in the lower 256 Kbytes:
•

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)
Table 37. 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

DocID022558 Rev 8

173/1141
227

Flexible static memory controller (FSMC)

RM0316

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.

10.5

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.
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:

174/1141

•

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 10.5.6: 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 10.5.5: Synchronous transactions for FMC_CLK divider ratio formula).

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
The size of each bank is fixed and equal to 64 Mbytes. Each bank is configured through
dedicated registers (see Section 10.5.6: NOR/PSRAM controller registers).
The programmable memory parameters include access times (see Table 38) and support
for wait management (for PSRAM and NOR Flash accessed in burst mode).
Table 38. Programmable NOR/PSRAM access parameters

10.5.1

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
(HCLK)
read/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

External memory interface signals
Table 39, Table 40 and Table 41 list the signals that are typically used to interface with NOR
Flash memory, SRAM and PSRAM.

Note:

The prefix “N” identifies the signals which are active low.

NOR Flash memory, non-multiplexed I/Os
Table 39. 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).

DocID022558 Rev 8

175/1141
227

Flexible static memory controller (FSMC)

RM0316

NOR Flash memory, 16-bit multiplexed I/Os
Table 40. 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.

PSRAM/SRAM, non-multiplexed I/Os
Table 41. 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 42. 16-Bit multiplexed I/O PSRAM

176/1141

FMC signal name

I/O

Function

CLK

O

Clock (for synchronous access)

A[25:16]

O

Address bus

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
Table 42. 16-Bit multiplexed I/O PSRAM (continued)
FMC signal name

I/O

Function

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).

10.5.2

Supported memories and transactions
Table 43 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.
Table 43. NOR Flash/PSRAM: Example of supported memories and
transactions
Device

NOR Flash
(muxed I/Os
and nonmuxed
I/Os)

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

-

DocID022558 Rev 8

177/1141
227

Flexible static memory controller (FSMC)

RM0316

Table 43. NOR Flash/PSRAM: Example of supported memories and
transactions (continued)
Device

PSRAM
(multiplexed
I/Os and nonmultiplexed
I/Os)

SRAM and
ROM

10.5.3

Mode

R/W

AHB
data
size

Memory
data size

Allowed/
not
allowed

Comments

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]

General timing rules
Signals synchronization

178/1141

•

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.

DocID022558 Rev 8

RM0316

10.5.4

Flexible static memory controller (FSMC)

NOR Flash/PSRAM controller asynchronous transactions
Asynchronous static memories (NOR Flash, PSRAM, SRAM)
•

Signals are synchronized by the internal clock HCLK. This clock is not issued to the
memory

•

The FMC always samples the data before de-asserting the NOE signal. This
guarantees that the memory data hold timing constraint is met (minimum Chip Enable
high to data transition is usually 0 ns)

•

If the extended mode is enabled (EXTMOD bit is set in the FMC_BCRx register), up to
four extended modes (A, B, C and D) are available. It is possible to mix A, B, C and D
modes for read and write operations. For example, read operation can be performed in
mode A and write in mode B.

•

If the extended mode is disabled (EXTMOD bit is reset in the FMC_BCRx register), the
FMC can operate in Mode1 or Mode2 as follows:
–

Mode 1 is the default mode when SRAM/PSRAM memory type is selected (MTYP
= 0x0 or 0x01 in the FMC_BCRx register)

–

Mode 2 is the default mode when NOR memory type is selected (MTYP = 0x10 in
the FMC_BCRx register).

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 20. Mode1 read access waveforms
0HPRU\WUDQVDFWLRQ
$>@
1%/>@
1([
12(
1:(

+LJK
GDWDGULYHQ
E\PHPRU\

'>@
$''6(7
+&/.F\FOHV

'$7$67
+&/.F\FOHV
069

DocID022558 Rev 8

179/1141
227

Flexible static memory controller (FSMC)

RM0316

Figure 21. Mode1 write access waveforms
0HPRU\WUDQVDFWLRQ
$>@
1%/>@
1([
12(
+&/.

1:(

'>@

GDWDGULYHQE\)0&

$''6(7

'$7$67

+&/.F\FOHV

+&/.F\FOHV
069

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 44. FMC_BCRx bit fields

180/1141

Bit
number

Bit name

31-21

Reserved

0x000

20

CCLKEN

As needed

19

CBURSTRW

18:16

Reserved

15

ASYNCWAIT

14

EXTMOD

0x0

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

WRAPMOD

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)

Value to set

0x0 (no effect in asynchronous mode)
0x0
Set to 1 if the memory supports this feature. Otherwise keep at
0.

0x0

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
Table 44. FMC_BCRx bit fields (continued)
Bit
number

Bit name

1

MUXE

0x0

0

MBKEN

0x1

Value to set

Table 45. FMC_BTRx bit fields
Bit
number

Bit name

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.

Value to set

Time between NEx high to NEx low (BUSTURN HCLK)

DocID022558 Rev 8

181/1141
227

Flexible static memory controller (FSMC)

RM0316

Mode A - SRAM/PSRAM (CRAM) OE toggling
Figure 22. ModeA read access waveforms
-EMORY TRANSACTION
!;=

.",;=

.%X

./%
.7%

(IGH

DATA DRIVEN
BY MEMORY

$;=
!$$3%4
(#,+ CYCLES

$!4!34
(#,+ CYCLES
-36

1. NBL[1:0] are driven low during the read access

Figure 23. ModeA write access waveforms
DĞŵŽƌLJƚƌĂŶƐĂĐƚŝŽŶ
΀Ϯϱ͗Ϭ΁

E>΀ϭ͗Ϭ΁

Edž

EK
ϭ,><
Et

ĚĂƚĂĚƌŝǀĞŶďLJ&^D

΀ϭϱ͗Ϭ΁
^d
,><ĐLJĐůĞƐ

;d^dнϭͿ
,><ĐLJĐůĞƐ
D^ϯϰϰϴϬsϭ

182/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
The differences compared with mode1 are the toggling of NOE and the independent read
and write timings.
Table 46. FMC_BCRx bit fields
Bit
number
31-21

Bit name

Value to set

Reserved

0x000

20

CCLKEN

19

CBURSTRW

18:16

As needed
0x0 (no effect in asynchronous mode)

Reserved

0x0
Set to 1 if the memory supports this feature. Otherwise keep at
0.

15

ASYNCWAIT

14

EXTMOD

0x1

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

WRAPMOD

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

0x0

Table 47. FMC_BTRx bit fields
Bit
number

Bit name

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.

Value to set

Time between NEx high to NEx low (BUSTURN HCLK)

DocID022558 Rev 8

183/1141
227

Flexible static memory controller (FSMC)

RM0316

Table 48. FMC_BWTRx bit fields
Bit
number

Bit name

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.

Value to set

Time between NEx high to NEx low (BUSTURN HCLK)

Mode 2/B - NOR Flash
Figure 24. Mode2 and mode B read access waveforms
0HPRU\WUDQVDFWLRQ
$>@
1$'9
1([
12(
1:(

+LJK
GDWDGULYHQ
E\PHPRU\

'>@
$''6(7
+&/.F\FOHV

'$7$67
+&/.F\FOHV
069

184/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
Figure 25. Mode2 write access waveforms
-EMORY TRANSACTION
!;=

.!$6

.%X

./%
.7%

(IGH

DATA DRIVEN
BY MEMORY

$;=
!$$3%4
(#,+ CYCLES

$!4!34
(#,+ CYCLES
-36

Figure 26. ModeB write access waveforms
0HPRU\WUDQVDFWLRQ
$>@
1$'9
1([
12(
+&/.
1:(

'>@

GDWDGULYHQE\)0&

$''6(7
+&/.F\FOHV

'$7$67
+&/.F\FOHV
069

The differences with mode1 are the toggling of NWE and the independent read and write
timings when extended mode is set (Mode B).

DocID022558 Rev 8

185/1141
227

Flexible static memory controller (FSMC)

RM0316

Table 49. FMC_BCRx bit fields
Bit
number

Bit name

31-21

Reserved

0x000

20

CCLKEN

As needed

19

CBURSTRW

18:16

Reserved

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

WRAPMOD

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

Value to set

0x0 (no effect in asynchronous mode)
0x0
Set to 1 if the memory supports this feature. Otherwise keep at
0.

0x0

Table 50. FMC_BTRx bit fields

186/1141

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)

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
Table 51. 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 27. ModeC read access waveforms
-EMORY TRANSACTION
!;=

.!$6

.%X

./%
.7%

(IGH

DATA DRIVEN
BY MEMORY

$;=
!$$3%4
(#,+ CYCLES

$!4!34
(#,+ CYCLES
-36

DocID022558 Rev 8

187/1141
227

Flexible static memory controller (FSMC)

RM0316

Figure 28. ModeC write access waveforms
-EMORY TRANSACTION
!;=

.!$6

.%X

./%
(#,+
.7%

$;=

DATA DRIVEN BY &3-#
!$$3%4
(#,+ CYCLES

$!4!34 
(#,+ CYCLES
-36

The differences compared with mode1 are the toggling of NOE and the independent read
and write timings.
Table 52. FMC_BCRx bit fields

188/1141

Bit No.

Bit name

Value to set

31-21

Reserved

0x000

20

CCLKEN

As needed

19

CBURSTRW

18:16

Reserved

15

ASYNCWAIT

14

EXTMOD

0x1

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

WRAPMOD

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

0x02 (NOR Flash memory)

0x0 (no effect in asynchronous mode)
0x0
Set to 1 if the memory supports this feature. Otherwise keep at 0.

0x0

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
Table 52. FMC_BCRx bit fields (continued)
Bit No.

Bit name

Value to set

1

MUXEN

0x0

0

MBKEN

0x1

Table 53. FMC_BTRx bit fields
Bit No.

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 54. FMC_BWTRx bit fields
Bit No.

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)

DocID022558 Rev 8

189/1141
227

Flexible static memory controller (FSMC)

RM0316

Mode D - asynchronous access with extended address
Figure 29. ModeD read access waveforms
-EMORY TRANSACTION
!;=

.!$6

.%X

./%
.7%

(IGH

DATA DRIVEN
BY MEMORY

$;=
!$$3%4
(#,+ CYCLES

$!4!34
(#,+ CYCLES

!$$(,$
(#,+ CYCLES

-36

Figure 30. ModeD write access waveforms
0HPRU\WUDQVDFWLRQ
$>@

1$'9

1([

12(
+&/.
1:(

'>@

GDWDGULYHQE\)60&
$''6(7
+&/.F\FOHV

190/1141

$''+/'
+&/.F\FOHV

DocID022558 Rev 8

'$7$67
+&/.F\FOHV
069

RM0316

Flexible static memory controller (FSMC)
The differences with mode1 are the toggling of NOE that goes on toggling after NADV
changes and the independent read and write timings.
Table 55. FMC_BCRx bit fields
Bit No.

Bit name

Value to set

31-21

Reserved

0x000

20

CCLKEN

As needed

19

CBURSTRW

18:16

Reserved

15

ASYNCWAIT

14

EXTMOD

0x1

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

WRAPMOD

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

0x0 (no effect in asynchronous mode)
0x0
Set to 1 if the memory supports this feature. Otherwise keep
at 0.

0x0

Table 56. FMC_BTRx bit fields
Bit No.

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)

DocID022558 Rev 8

191/1141
227

Flexible static memory controller (FSMC)

RM0316

Table 57. FMC_BWTRx bit fields
Bit No.

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 31. Muxed read access waveforms
-EMORY TRANSACTION
!;=

.!$6

.%X

./%
.7%

!$;=

(IGH

,OWER ADDRESS
!$$3%4
(#,+ CYCLES

!$$(,$
(#,+ CYCLES

192/1141

DocID022558 Rev 8

DATA DRIVEN
BY MEMORY
$!4!34
(#,+ CYCLES
AI

RM0316

Flexible static memory controller (FSMC)
Figure 32. Muxed write access waveforms
-EMORY TRANSACTION
!;=

.!$6

.%X

./%
(#,+
.7%

,OWER ADDRESS

!$;=

!$$3%4
(#,+ CYCLES

!$$(,$
(#,+ CYCLES

DATA DRIVEN BY &3-#
$!4!34 
(#,+ CYCLES
AI

The difference with mode D is the drive of the lower address byte(s) on the data bus.
Table 58. FMC_BCRx bit fields
Bit No.

Bit name

Value to set

31-21

Reserved

0x000

20

CCLKEN

As needed

19

CBURSTRW

18:16

Reserved

15

ASYNCWAIT

14

EXTMOD

0x0

13

WAITEN

0x0 (no effect in asynchronous mode)

12

WREN

As needed

11

WAITCFG

Don’t care

10

WRAPMOD

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)

0x0 (no effect in asynchronous mode)
0x0
Set to 1 if the memory supports this feature. Otherwise keep at
0.

0x0

DocID022558 Rev 8

193/1141
227

Flexible static memory controller (FSMC)

RM0316

Table 58. FMC_BCRx bit fields (continued)
Bit No.

Bit name

Value to set

1

MUXEN

0x1

0

MBKEN

0x1

Table 59. FMC_BTRx bit fields
Bit No.

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:

194/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
1.

The memory asserts the WAIT signal aligned to NOE/NWE which toggles:
DATAST ≥ ( 4 × HCLK ) + max_wait_assertion_time

2.

The memory asserts the WAIT signal aligned to NEx (or NOE/NWE not toggling):
if
max_wait_assertion_time > address_phase + hold_phase
then:

DATAST ≥ ( 4 × HCLK ) + ( max_wait_assertion_time

– address_phase – hold_phase )

otherwise
DATAST ≥ 4 × HCLK
where max_wait_assertion_time is the maximum time taken by the memory to assert
the WAIT signal once NEx/NOE/NWE is low.
Figure 33 and Figure 34 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 33. Asynchronous wait during a read access waveforms
0HPRU\WUDQVDFWLRQ

$>@

DGGUHVVSKDVH

GDWDVHWXSSKDVH

1([

.7!)4

DONT CARE

DONT CARE

12(

GDWDGULYHQE\PHPRU\

'>@

+&/.

069

1. NWAIT polarity depends on WAITPOL bit setting in FMC_BCRx register.

DocID022558 Rev 8

195/1141
227

Flexible static memory controller (FSMC)

RM0316

Figure 34. Asynchronous wait during a write access waveforms

0HPRU\WUDQVDFWLRQ

$>@
DGGUHVVSKDVH

GDWDVHWXSSKDVH

1([

.7!)4

DONT CARE

DONT CARE
+&/.

1:(

'>@

GDWDGULYHQE\)60&
+&/.
069

1. NWAIT polarity depends on WAITPOL bit setting in FMC_BCRx register.

10.5.5

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 WID 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.

196/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)

Caution:

Some NOR Flash memories include the NADV Low cycle in the data latency count, so that
the exact relation between the NOR Flash latency and the FMC DATLAT parameter can be
either:
•

NOR Flash latency = (DATLAT + 2) CLK clock cycles

•

or NOR Flash latency = (DATLAT + 3) CLK clock cycles

Some recent memories assert NWAIT during the latency phase. In such cases DATLAT can
be set to its minimum value. As a result, the FMC samples the data and waits long enough
to evaluate if the data are valid. Thus the FMC detects when the memory exits latency and
real data are processed.
Other memories do not assert NWAIT during latency. In this case the latency must be set
correctly for both the FMC and the memory, otherwise invalid data are mistaken for good
data, or valid data are lost in the initial phase of the memory access.

Single-burst transfer
When the selected bank is configured in burst mode for synchronous accesses, if for
example an AHB single-burst transaction is requested on 16-bit memories, the FMC
performs a burst transaction of length 1 (if the AHB transfer is 16 bits), or length 2 (if the
AHB transfer is 32 bits) and de-assert the Chip Select signal when the last data is strobed.
Such transfers are not the most efficient in terms of cycles compared to asynchronous read
operations. Nevertheless, a random asynchronous access would first require to re-program
the memory access mode, which would altogether last longer.

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).

DocID022558 Rev 8

197/1141
227

Flexible static memory controller (FSMC)

RM0316

Figure 35. Wait configuration waveforms
0HPRU\WUDQVDFWLRQ EXUVWRIKDOIZRUGV
+&/.
&/.
$>@

DGGU>@

1$'9
1:$,7
:$,7&)* 
1:$,7
:$,7&)* 
LQVHUWHGZDLWVWDWH
$'>@

DGGU>@

GDWD

GDWD

GDWD
DLF

198/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)

Figure 36. Synchronous multiplexed read mode waveforms - NOR, PSRAM (CRAM)
-EMORY TRANSACTION  BURST OF  HALF WORDS
(#,+

#,+

ADDR;=

!;=

.%X

./%

.7%

(IGH

.!$6

.7!)4
7!)4#&'
$!4,!4 
#,+ CYCLES
!$;=

!DDR;=

INSERTED WAIT STATE
DATA

 CLOCK  CLOCK
CYCLE
CYCLE

DATA

$ATA STROBES

DATA

DATA

$ATA STROBES
AIE

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 60. FMC_BCRx bit fields
Bit No.

Bit name

Value to set

31-21

Reserved

0x000

20

CCLKEN

As needed

19

CBURSTRW

18-15

Reserved

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

No effect on synchronous read

DocID022558 Rev 8

199/1141
227

Flexible static memory controller (FSMC)

RM0316

Table 60. FMC_BCRx bit fields (continued)
Bit No.

Bit name

Value to set

10

WRAPMOD

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

0x0

Table 61. FMC_BTRx bit fields

200/1141

Bit No.

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)

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
Figure 37. Synchronous multiplexed write mode waveforms - PSRAM (CRAM)
-EMORY TRANSACTION  BURST OF  HALF WORDS

(#,+

#,+

!;=

ADDR;=

.%X
(I :
./%

.7%

.!$6

.7!)4
7!)4#&'  
$!4,!4 
#,+ CYCLES
!$;=

!DDR;=

INSERTED WAIT STATE
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 62. FMC_BCRx bit fields
Bit No.

Bit name

Value to set

31-20

Reserved

0x000

20

CCLKEN

As needed

19

CBURSTRW

0x1

18-15

Reserved

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

0x1

11

WAITCFG

0x0

DocID022558 Rev 8

201/1141
227

Flexible static memory controller (FSMC)

RM0316

Table 62. FMC_BCRx bit fields (continued)
Bit No.

Bit name

Value to set

10

WRAPMOD

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

0x0

Table 63. FMC_BTRx bit fields

202/1141

Bit No.

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)

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)

10.5.6

NOR/PSRAM controller registers
SRAM/NOR-Flash chip-select control registers 1..4 (FMC_BCR1..4)
Address offset: 8 * (x – 1), x = 1...4
Reset value: 0x0000 30DB for Bank1 and 0x0000 30D2 for Bank 2 to 4

7

6

WAITEN

WREN

WAITCFG

WRAPMOD

WAITPOL

BURSTEN

Res.

FACCEN

rw

rw

rw

rw

rw

rw

rw

rw

rw

5

4

3

rw

2

rw

rw

rw

1

0
MBKEN

8

MUXEN

9

MTYP

14 13 12 11 10

MWID

15

EXTMOD

rw rw

Res.

Res.

Res.

CBURSTRW

Res.

CCLKEN

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

ASCYCWAIT

This register contains the control information of each memory bank, used for SRAMs,
PSRAM and NOR Flash memories.

rw

rw

Bits 31: 21 Reserved, must be kept at reset value
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.
Bits 18:16 Reserved, must be kept at reset value
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

DocID022558 Rev 8

203/1141
227

Flexible static memory controller (FSMC)

RM0316

Bit 14 EXTMOD: Extended mode enable.
This bit enables the FMC to program the write timings for 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 WRAPMOD: Wrapped burst mode support.
Defines whether the controller will or not split an AHB burst wrap access into two linear accesses.
Valid only when accessing memories in burst mode
0: Direct wrapped burst is not enabled (default after reset),
1: Direct wrapped burst is enabled.
Note: This bit has no effect as the CPU and DMA cannot generate wrapping burst transfers.
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.
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)

204/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)

Bits 5:4 MWID: 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, do not use
11: reserved, do not use
Bits 3:2 MTYP: 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 nonmultiplexed
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
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).

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

8

7

6

rw

rw

rw

rw

DocID022558 Rev 8

rw

rw

rw

rw

rw

rw

5

4

3

2

rw

rw

rw

rw

rw

1

0

rw

rw

ADDSET

ADDHLD

9

DATAST

BUSTURN

CLKDIV

DATLAT

ACCMOD

Res.

Res.

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

205/1141
227

Flexible static memory controller (FSMC)

RM0316

Bits 31:30 Reserved, must be kept at reset value
Bits 29:28 ACCMOD: 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: (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: 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 10.5.5: Synchronous transactions for FMC_CLK divider ratio formula)

206/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)

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 BUSTRUN 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 FMC 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 FMC 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 FMC 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 × HCLK clock cycles (default value after reset)

DocID022558 Rev 8

207/1141
227

Flexible static memory controller (FSMC)

RM0316

Bits 15:8 DATAST: Data-phase duration
These bits are written by software to define the duration of the data phase (refer to Figure 20 to
Figure 32), 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, please refer to the respective
figure (Figure 20 to Figure 32).
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.
Bits 7:4 ADDHLD: Address-hold phase duration
These bits are written by software to define the duration of the address hold phase (refer to
Figure 20 to Figure 32), 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, please refer to the respective figure
(Figure 20 to Figure 32).
Note: In synchronous accesses, this value is not used, the address hold phase is always 1
memory clock period duration.
Bits 3:0 ADDSET: Address setup phase duration
These bits are written by software to define the duration of the address setup phase (refer to
Figure 20 to Figure 32), used in SRAMs, ROMs and asynchronous NOR Flash:
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, please refer to the respective figure
(refer to Figure 20 to Figure 32).
Note: In synchronous accesses, this value is don’t care.
In Muxed mode or Mode D, the minimum value for ADDSET is 1.

Note:

208/1141

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).

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)

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.

rw

rw

rw

rw

rw

8

7

6

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

5

4

3

2

rw

rw

rw

rw

rw

1

0

rw

rw

ADDSET

ADDHLD

9

DATAST

BUSTURN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ACCMOD

Res.

Res.

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

Bits 31:30 Reserved, must be kept at reset value
Bits 29:28 ACCMOD: 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: 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 BUSTRUN 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 FMC 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 FMC 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)

DocID022558 Rev 8

209/1141
227

Flexible static memory controller (FSMC)

RM0316

Bits 15:8 DATAST: Data-phase duration.
These bits are written by software to define the duration of the data phase (refer to Figure 20 to
Figure 32), 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: Address-hold phase duration.
These bits are written by software to define the duration of the address hold phase (refer to Figure 20
to Figure 32), 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.
Bits 3:0 ADDSET: 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 20 to Figure 32), 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.

10.6

NAND Flash/PC Card controller
The FMC generates the appropriate signal timings to drive the following types of device:
•

8- and 16-bit NAND Flash memories

•

16-bit PC Card compatible devices

The NAND Flash/PC Card controller can control three external banks, Bank 2, 3 and 4:
•

Bank 2 and Bank 3 support NAND Flash devices

•

Bank 4 supports PC Card devices.

Each bank is configured through dedicated registers (Section 10.6.8). The programmable
memory parameters include access timings (shown in Table 64) and ECC configuration.

210/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
Table 64. Programmable NAND Flash/PC Card access parameters

10.6.1

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

256

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)

0

255

External memory interface signals
The following tables list the signals that are typically used to interface NAND Flash memory
and PC Card.

Note:

The prefix “N” identifies the signals which are active low.

8-bit NAND Flash memory
Table 65. 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

NCE[x]

O

Chip Select, x = 2, 3

NOE(= NRE)

O

Output enable (memory signal name: read enable, NRE)

NWE

O

Write enable

NWAIT/INT[3:2]

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.

DocID022558 Rev 8

211/1141
227

Flexible static memory controller (FSMC)

RM0316

16-bit NAND Flash memory
Table 66. 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[x]

O

Chip Select, x = 2, 3

NOE(= NRE)

O

Output enable (memory signal name: read enable, NRE)

NWE

O

Write enable

NWAIT/INT[3:2]

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.
Table 67. 16-bit PC Card

212/1141

FMC signal name

I/O

Function

A[10:0]

O

Address bus

NIORD

O

Output enable for I/O space

NIOWR

O

Write enable for I/O space

NREG

O

Register signal indicating if access is in Common or Attribute space

D[15:0]

I/O

Bidirectional databus

NCE4_1

O

Chip Select 1

NCE4_2

O

Chip Select 2 (indicates if access is 16-bit or 8-bit)

NOE

O

Output enable in Common and in Attribute space

NWE

O

Write enable in Common and in Attribute space

NWAIT

I

PC Card wait input signal to the FMC (memory signal name IORDY)

INTR

I

PC Card interrupt to the FMC (only for PC Cards that can generate
an interrupt)

CD

I

PC Card presence detection. Active high. If an access is performed
to the PC Card banks while CD is low, an AHB error is generated.
Refer to Section 10.3: AHB interface

DocID022558 Rev 8

RM0316

10.6.2

Flexible static memory controller (FSMC)

NAND Flash / PC Card supported memories and transactions
Table 68 shows the supported devices, access modes and transactions. Transactions not
allowed (or not supported) by the NAND Flash / PC Card controller are shown in gray.
Table 68. Supported memories and transactions
Device

NAND 8-bit

NAND 16-bit

10.6.3

Mode

R/W

AHB
Memory
Allowed/
data size data size not allowed

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 and PC Card
Each PC Card/CompactFlash and NAND Flash memory bank is managed through a set of
registers:
•

Control register: FMC_PCRx

•

Interrupt status register: FMC_SRx

•

ECC register: FMC_ECCRx

•

Timing register for Common memory space: FMC_PMEMx

•

Timing register for Attribute memory space: FMC_PATTx

•

Timing register for I/O space: FMC_PIOx

Each timing configuration register contains three parameters used to define number of
HCLK cycles for the three phases of any PC Card/CompactFlash or NAND Flash access,
plus one parameter that defines the timing for starting driving the data bus when a write
access is performed. Figure 38 shows the timing parameter definitions for common memory
accesses, knowing that Attribute and I/O (only for PC Card) memory space access timings
are similar.

DocID022558 Rev 8

213/1141
227

Flexible static memory controller (FSMC)

RM0316

Figure 38. NAND Flash/PC Card controller waveforms for common memory access
+&/.
$>@
1&([
+LJK

15(*
1,2:
1,25
1:(
12(

0(0[6(7


0(0[:$,7

0(0[+2/'


0(0[+,=

ZULWHBGDWD
UHDGBGDWD

9DOLG

069

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.

10.6.4

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:

214/1141

3.

Program and enable the corresponding memory bank by configuring the FMC_PCRx
and FMC_PMEMx (and for some devices, FMC_PATTx, see Section 10.6.5: 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 Section 10.4.2: NAND Flash memory/PC
Card 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

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
to implement the prewait functionality needed by some NAND Flash memories (see
details in Section 10.6.5: NAND Flash prewait functionality).

10.6.5

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 39).
Figure 39. Access to non ‘CE don’t care’ NAND-Flash
.#% MUST STAY LOW
.#%

#,%

!,%

.7%
(IGH
./%
T2
)/;=

X

! ! ! ! ! ! !
T7"

2."









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_PATT2 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).

DocID022558 Rev 8

215/1141
227

Flexible static memory controller (FSMC)

RM0316

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.

10.6.6

Computation of the error correction code (ECC)
in NAND Flash memory
The FMC PC 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_ECCR2/3 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_PCR2/3 registers.

216/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
To perform an ECC computation:

10.6.7

1.

Enable the ECCEN bit in the FMC_PCR2/3 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_ECCR2/3 register and store it in a variable.

4.

Clear the ECCEN bit and then enable it in the FMC_PCR2/3 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_ECCR2/3 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.

PC Card/CompactFlash operations
Address spaces and memory accesses
The FMC supports CompactFlash devices and PC Cards in Memory mode and I/O mode
(True IDE mode is not supported).
The CompactFlash and PC Cards are made of 3 memory spaces:
•

Common Memory space

•

Attribute space

•

I/O Memory space

The nCE2 and nCE1 pins (FMC_NCE4_2 and FMC_NCE4_1 respectively) select the card
and indicate whether a byte or a word operation is being performed: nCE2 accesses the odd
byte on D15-8 and nCE1 accesses the even byte on D7-0 if A0=0 or the odd byte on D7-0 if
A0=1. The full word is accessed on D15-0 if both nCE2 and nCE1 are low.
The memory space is selected by asserting low nOE for read accesses or nWE for write
accesses, combined with the low assertion of nCE2/nCE1 and nREG.
•

If pin nREG=1 during the memory access, the common memory space is selected

•

If pin nREG=0 during the memory access, the attribute memory space is selected

The I/O space is selected by asserting nIORD space for read accesses or nIOWR for write
accesses [instead of nOE/nWE for memory space], combined with nCE2/nCE1. Note that
nREG must also be asserted low when accessing I/O space.
Three type of accesses are allowed for a 16-bit PC Card:
•

Accesses to Common Memory space for data storage can be either 8-bit accesses at
even addresses or 16-bit AHB accesses.
Note that 8-bit accesses at odd addresses are not supported and nCE2 will not be
driven low. A 32-bit AHB request is translated into two 16-bit memory accesses.

•

Accesses to Attribute Memory space where the PC Card stores configuration
information are limited to 8-bit AHB accesses at even addresses.
Note that a 16-bit AHB access will be converted into a single 8-bit memory transfer:
nCE1 will be asserted low, nCE2 will be asserted high and only the even byte on D7-D0
will be valid. Instead a 32-bit AHB access will be converted into two 8-bit memory

DocID022558 Rev 8

217/1141
227

Flexible static memory controller (FSMC)

RM0316

transfers at even addresses: nCE1 will be asserted low, NCE2 will be asserted high
and only the even bytes will be valid.
•

Accesses to I/O space can be either 8-bit or 16 bit AHB accesses.

nCE2

nCE1

nREG

nOE/nWE

nIORD /nIOWR

A10

A9

A7-1

A0

Table 69. 16-bit PC-Card signals and access type

1

0

1

0

1

X

X

X-X

X

0

1

1

0

1

X

X

X-X

X

0

0

1

0

1

X

X

X-X

0

X

0

0

0

1

0

1

X-X

0

X

0

0

0

1

0

0

X-X

0

1

0

0

0

1

X

X

X-X

1

0

1

0

0

1

X

X

X-X

x

1

0

0

1

0

X

X

X-X

1

0

0

1

0

X

X

1

0

0

1

0

X

1

0

0

1

0

0

0

0

1

0

0

0

0

1

0

1

Space

Access type

Allowed/not
Allowed

Read/Write byte on D7-D0

YES

Read/Write byte on D15-D8

Not supported

Read/Write word on D15-D0

YES

Read or Write Configuration
Registers

YES

Read or Write CIS (Card
Information Structure)

YES

Invalid Read or Write (odd
address)

YES

Invalid Read or Write (odd
address)

YES

0

Read Even Byte on D7-0

YES

X-X

1

Read Odd Byte on D7-0

YES

X

X-X

0

Write Even Byte on D7-0

YES

X

X

X-X

1

Write Odd Byte on D7-0

YES

0

X

X

X-X

0

Read Word on D15-0

YES

1

0

X

X

X-X

0

Write word on D15-0

YES

0

1

0

X

X

X-X

X

Read Odd Byte on D15-8

Not supported

0

1

0

X

X

X-X

X

Write Odd Byte on D15-8

Not supported

Common
Memory
Space

Attribute
Space

Attribute
Space

I/O space

FMC Bank 4 gives access to those 3 memory spaces as described in Section 10.4.2: NAND
Flash memory/PC Card address mapping and Table 36: NAND/PC Card memory mapping
and timing registers.

Wait feature
The CompactFlash or PC Card may request the FMC to extend the length of the access
phase programmed by MEMWAITx/ATTWAITx/IOWAITx bits, asserting the nWAIT signal
after nOE/nWE or nIORD/nIOWR activation if the wait feature is enabled through the

218/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)
PWAITEN bit in the FMC_PCRx register. To detect correctly the nWAIT assertion, the
MEMWAITx/ATTWAITx/IOWAITx bits must be programmed as follows:
max_wait_assertion_time
xxWAITx ≥ 4 + ------------------------------------------------------------------HCLK
where max_wait_assertion_time is the maximum time taken by NWAIT to go low once
nOE/nWE or nIORD/nIOWR is low.
After WAIT de-assertion, the FMC extends the WAIT phase for 4 HCLK clock cycles.

10.6.8

NAND Flash/PC Card controller registers
PC Card/NAND Flash control registers 2..4 (FMC_PCR2..4)
Address offset: 0x40 + 0x20 * (x – 1), x = 2..4

rw

rw

rw

rw

rw

rw

rw

1

0

PWID

Res.

rw

2
PBKEN

rw

3

PWAITEN

rw

TCLR

4

PTYP

rw

TAR

8

7

6

Res.

ECCPS

9

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

ECCEN

Reset value: 0x0000 0018
5

rw

rw

rw

rw

rw

rw

Bits 31:20 Reserved, must be kept at reset value
Bits 19:17 ECCPS: 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: 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.
Bits 12:9 TCLR: 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.

DocID022558 Rev 8

219/1141
227

Flexible static memory controller (FSMC)

RM0316

Bits 5:4 PWID: Data bus width.
Defines the external memory device width.
00: 8 bits
01: 16 bits (default after reset). This value is mandatory for PC Cards.
10: reserved, do not use
11: reserved, do not use
Bit 3 PTYP: Memory type.
Defines the type of device attached to the corresponding memory bank:
0: PC Card, CompactFlash, CF+ or PCMCIA
1: NAND Flash (default after reset)
Bit 2 PBKEN: PC Card/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 PC Card/NAND Flash memory bank:
0: disabled
1: enabled
Note: For a PC Card, when the wait feature is enabled, the MEMWAITx/ATTWAITx/IOWAITx
bits must be programmed to a value as follows:
xxWAITx ≥ 4 + max_wait_assertion_time/HCLK
Where max_wait_assertion_time is the maximum time taken by NWAIT to go low once
nOE/nWE or nIORD/nIOWR is low.
Bit 0

Reserved.

FIFO status and interrupt register 2..4 (FMC_SR2..4)
Address offset: 0x44 + 0x20 * (x-1), x = 2..4
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.

Bits 31:7 Reserved, must be kept at reset value

220/1141

DocID022558 Rev 8

9

8

7

6

5

4

3

2

1

0

Res.

Res.

FEMPT

IFEN

ILEN

IREN

IFS

ILS

IRS

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

Res.

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.

r

rw

rw

rw

rw

rw

rw

RM0316

Flexible static memory controller (FSMC)

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_PMEM2..4)
Address offset: Address: 0x48 + 0x20 * (x – 1), x = 2..4
Reset value: 0xFCFC FCFC
Each FMC_PMEMx (x = 2..4) read/write register contains the timing information for PC Card
or NAND Flash memory bank x. This information is used to access either the common
memory space of the 16-bit PC Card/CompactFlash, or the NAND Flash for command,
address write access and data read/write access.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
MEMHIZx
rw

rw

rw

rw

rw

MEMHOLDx
rw

rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

MEMWAITx
rw

rw

rw

rw

rw

DocID022558 Rev 8

rw

rw

rw

4

3

2

1

0

rw

rw

rw

MEMSETx
rw

rw

rw

rw

rw

rw

rw

221/1141
227

Flexible static memory controller (FSMC)

RM0316

Bits 31:24 MEMHIZx: 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 PC Card/NAND Flash write access to common memory space on socket x. This is only
valid for write transactions:
0000 0000: (0x00) 0 HCLK cycle (for PC Card) / 1 HCLK cycle (for NAND Flash)
1111 1110: (0xFF) 255 HCLK cycles (for PC Card) / 256 HCLK cycles (for NAND Flash)
1111 1111: Reserved
Bits 23:16 MEMHOLDx: Common memory x 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 MEMWAITx: Common memory x wait time
Defines the minimum number of HCLK (+1) clock cycles to assert the command (NWE, NOE),
for PC Card/NAND Flash read or write access to common memory space on socket x. 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 1111: 256 HCLK cycles (+ wait cycle introduced by the Card deasserting NWAIT)
Bits 7:0 MEMSETx: 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 PC Card/NAND Flash read or write access to common memory
space on socket x:
0000 0000: 1 HCLK cycle (for PC Card) / HCLK cycles (for NAND Flash)
1111 1110: 255 HCLK cycles (for PC Card) / 257 HCLK cycles (for NAND Flash)
1111 1111: Reserved

Attribute memory space timing registers 2..4 (FMC_PATT2..4)
Address offset: 0x4C + 0x20 * (x – 1), x = 2..4
Reset value: 0xFCFC FCFC
Each FMC_PATTx (x = 2..4) read/write register contains the timing information for PC
Card/CompactFlash or NAND Flash memory bank x. It is used for 8-bit accesses to the
attribute memory space of the PC Card/CompactFlash or to access 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 10.6.5: NAND Flash prewait functionality).
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
ATTHIZ
rw

rw

rw

222/1141

rw

rw

ATTHOLD
rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

ATTWAIT
rw

rw

rw

rw

rw

rw

DocID022558 Rev 8

rw

rw

4

3

2

1

0

rw

rw

rw

ATTSET
rw

rw

rw

rw

rw

rw

rw

rw

RM0316

Flexible static memory controller (FSMC)

Bits 31:24 ATTHIZ: Attribute memory x 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 PC CARD/NAND Flash write access to attribute memory space on socket x. Only
valid for write transaction:
0000 0000: 0 HCLK cycle
1111 1110: 255 HCLK cycles
1111 1111: Reserved
Bits 23:16 ATTHOLD: Attribute memory x 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: Attribute memory x wait time
Defines the minimum number of HCLK (+1) clock cycles to assert the command (NWE, NOE),
for PC Card/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 1111: 256 HCLK cycles (+ wait cycle introduced by the card deasserting NWAIT)
Bits 7:0 ATTSET: Attribute memory x setup time
Defines the number of HCLK (+1) clock cycles to set up address before the command
assertion (NWE, NOE), for PC CARD/NAND Flash read or write access to attribute memory
space on socket x:
0000 0000: 1 HCLK cycle
1111 1110: 255 HCLK cycles
1111 1111: Reserved.

I/O space timing register 4 (FMC_PIO4)
Address offset: 0xB0
Reset value: 0xFCFCFCFC
The FMC_PIO4 read/write registers contain the timing information used to access the I/O
space of the 16-bit PC Card/CompactFlash.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
IOHIZx
rw

rw

rw

rw

rw

IOHOLDx
rw

rw

rw

rw

rw

rw

rw

rw

9

8

7

6

5

rw

rw

rw

rw

rw

IOWAITx
rw

rw

rw

rw

rw

rw

DocID022558 Rev 8

rw

rw

4

3

2

1

0

rw

rw

rw

IOSETx
rw

rw

rw

223/1141
227

Flexible static memory controller (FSMC)

RM0316

Bits 31:24 IOHIZx: I/O x 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 PC Card write access to I/O space on socket x. Only valid for write transaction:
0000 0000: 0 HCLK cycle
1111 1111: 255 HCLK cycles
Bits 23:16 IOHOLDx: I/O x hold time
Defines the number of HCLK clock cycles during which the address is held (and data for write
access) after the command deassertion (NWE, NOE), for PC Card read or write access to I/O
space on socket x:
0000 0000: reserved
0000 0001: 1 HCLK cycle
1111 1111: 255 HCLK cycles
Bits 15:8 IOWAITx: I/O x wait time
Defines the minimum number of HCLK (+1) clock cycles to assert the command (SMNWE,
SMNOE), for PC Card read or write access to I/O 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, do not use this value
0000 0001: 2 HCLK cycles (+ wait cycle introduced by deassertion of NWAIT)
1111 1111: 256 HCLK cycles (+ wait cycle introduced by the Card deasserting NWAIT)
Bits 7:0 IOSETx: I/O x setup time
Defines the number of HCLK (+1) clock cycles to set up the address before the command
assertion (NWE, NOE), for PC Card read or write access to I/O space on socket x:
0000 0000: 1 HCLK cycle
1111 1111: 256 HCLK cycles

224/1141

DocID022558 Rev 8

RM0316

Flexible static memory controller (FSMC)

ECC result registers 2/3 (FMC_ECCR2/3)
Address offset: 0x54 + 0x20 * (x – 1), x = 2 or 3
Reset value: 0x0000 0000
These registers contain the current error correction code value computed by the ECC
computation modules of the FMC controller (one module per NAND Flash memory bank).
When the CPU reads the data from a NAND Flash memory page at the correct address
(refer to Section 10.6.6: 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_PCRx registers), the CPU must read the computed ECC value
from the FMC_ECCx 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_ECCRx registers 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 15 14 13 12 11 10

9

8

7

6

5

4

3

2

1

0

ECCx
r

Bits 31:0 ECCx: ECC result
This field contains the value computed by the ECC computation logic. Table 70 describes
the contents of these bit fields.

Table 70. ECC result relevant bits
ECCPS[2:0]

Page size in bytes

ECC bits

000

256

ECC[21:0]

001

512

ECC[23:0]

010

1024

ECC[25:0]

011

2048

ECC[27:0]

100

4096

ECC[29:0]

101

8192

ECC[31:0]

DocID022558 Rev 8

225/1141
227

226/1141

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DocID022558 Rev 8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TCLR

Res.

Res.

ECCPS

TAR

TCLR

Res.

ILS PWAITEN PWAITEN PWAITEN

ILS

IRS

ILS

IRS

Res.

PBKEN

Res.

PBKEN
Res.

PBKEN

PTYP

IRS

IREN

PTYP

IFS

IFS

PWID

PTYP

IFS

IREN

IREN

ILEN

ILEN

ILEN

IFEN

IFEN

PWID

IFEN

FEMPT FEMPT FEMPT ECCEN

Res.

TAR
ECCEN

Res.

Res.

ECCPS
PWID

Res.

TCLR

ECCEN

TAR

Res.

Res.
ECCPS

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res. Res. Res. Res.

Res.

Res. Res. Res. Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res. Res. Res. Res.

Res.

DATLAT
CLKDIV
BUSTURN
DATAST
ADDHLD
ADDSET

ACCM
OD
DATLAT
CLKDIV
BUSTURN
DATAST
ADDHLD
ADDSET

ACCM
OD
DATLAT
CLKDIV
BUSTURN
DATAST
ADDHLD
ADDSET

ACCM
OD
DATLAT
CLKDIV
BUSTURN
DATAST
ADDHLD
ADDSET

DATAST
ADDHLD
ADDSET

DATAST
ADDHLD
ADDSET

DATAST
ADDHLD
ADDSET

DATAST
ADDHLD
ADDSET

Res. Res. Res. Res.

Res. Res. Res. Res.

Res. Res. Res. Res.

Res. Res. Res. Res.

Res.
Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CCLKEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

WAITCFG

WAITCFG

WAITCFG

WREN

WAITEN

EXTMOD

WAITCFG

WREN

WAITEN

EXTMOD

MTYP

MTYP

MBKEN

MBKEN

MUXEN

MWID

MWID

MUXEN

FACCEN

Reserved

Reserved
FACCEN

WAITPOL
BURSTEN

WAITPOL
BURSTEN

MBKEN

MUXEN

MTYP

MWID

FACCEN

Reserved

BURSTEN

WAITPOL

MBKEN

MUXEN

MTYP

MWID

FACCEN

Reserved

BURSTEN

WAITPOL

WRAPMOD WRAPMOD WRAPMOD WRAPMOD

WREN

WAITEN

WAITEN
WREN

EXTMOD

EXTMOD

ASYNCWAIT ASYNCWAIT ASYNCWAIT ASYNCWAIT

Res.

Res.

CBURSTRW CBURSTRW CBURSTRW CBURSTRW

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res. Res. Res. Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ACCM
OD
Res.

Res.

Res.

Res.

ACCM
OD

Res.

Res.

Res.

Res.

ACCM
OD

Res.

Res. Res. Res. Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FMC_SR4
Res. Res. Res. Res.

Res.

0xA4
Res.

FMC_SR3

Res.

0x84

Res.

Res.

FMC_SR2
Res. Res. Res. Res.

Res.

0x64
Res.

FMC_PCR4

Res.

Res.

0xA0

Res.

FMC_PCR3
Res.

0x80
Res.

FMC_PCR2
Res. Res. Res. Res.

0x60
ACCM
OD

Res.

FMC_BWTR4

Res.

0x11C

Res.

FMC_BWTR3
Res.

0x114
Res.

FMC_BWTR2
Res.

0x10C
Res.

FMC_BWTR1

Res.

0x104

Res.

FMC_BTR4

Res.

0x1C

Res.

FMC_BTR3

Res.

0x14
ACCM
OD

Res.

FMC_BTR2

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

0x0C
Res.

FMC_BTR1
Res.

0x04
Res.

FMC_BCR4
Res.

0x18
Res.

FMC_BCR3

Res.

0x10

Res. Res. Res. Res. Res. Res. Res. Res.

FMC_BCR2

Res. Res. Res. Res. Res. Res. Res. Res.

0x08

Res.

FMC_BCR1

Res.

0x00

Res.

Register

Res.

10.7

Res.

Offset

Res.

Flexible static memory controller (FSMC)
RM0316

FMC register map
The following table summarizes the FMC registers.
Table 71. FMC register map

RM0316

Flexible static memory controller (FSMC)
Table 71. FMC register map (continued)

Register

0x68

FMC_PMEM2

MEMHIZx

MEMHOLDx

MEMWAITx

0x88

FMC_PMEM3

MEMHIZx

MEMHOLDx

MEMWAITx

MEMSETx

0xA8

FMC_PMEM4

MEMHIZx

MEMHOLDx

MEMWAITx

MEMSETx

0x6C

FMC_PATT2

ATTHIZx

ATTHOLDx

ATTWAITx

ATTSETx

0x8C

FMC_PATT3

ATTHIZx

ATTHOLDx

ATTWAITx

ATTSETx

0xAC

FMC_PATT4

ATTHIZx

ATTHOLDx

ATTWAITx

ATTSETx

0xB0

FMC_PIO4

IOHIZx

IOHOLDx

IOWAITx

IOSETx

0x74

FMC_ECCR2

ECCx

0x94

FMC_ECCR3

ECCx

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Offset

DocID022558 Rev 8

MEMSETx

227/1141
227

General-purpose I/Os (GPIO)

RM0316

11

General-purpose I/Os (GPIO)

11.1

Introduction
Each general-purpose I/O port has four 32-bit configuration registers (GPIOx_MODER,
GPIOx_OTYPER, GPIOx_OSPEEDR and GPIOx_PUPDR), two 32-bit data registers
(GPIOx_IDR and GPIOx_ODR), a 32-bit set/reset register (GPIOx_BSRR), a 32-bit locking
register (GPIOx_LCKR) and two 32-bit alternate function selection registers (GPIOx_AFRH
and GPIOx_AFRL).

11.2

11.3

GPIO main features
•

Output states: push-pull or open drain + pull-up/down

•

Output data from output data register (GPIOx_ODR) or peripheral (alternate function
output)

•

Speed selection for each I/O

•

Input states: floating, pull-up/down, analog

•

Input data to input data register (GPIOx_IDR) or peripheral (alternate function input)

•

Bit set and reset register (GPIOx_ BSRR) for bitwise write access to GPIOx_ODR

•

Locking mechanism (GPIOx_LCKR) provided to freeze the port A, B, C, D, E, F, G, H
on STM32F303xD/E and STM32F398xE, A, B and D I/O configuration in
STM32F303xB/C and STM32F358xC devices and port A, B, C, D and F in
STM32F303x6/8 and STM32F328x8 devices.

•

Analog function

•

Alternate function selection registers

•

Fast toggle capable of changing every two clock cycles

•

Highly flexible pin multiplexing allows the use of I/O pins as GPIOs or as one of several
peripheral functions

GPIO functional description
Subject to the specific hardware characteristics of each I/O port listed in the datasheet, each
port bit of the general-purpose I/O (GPIO) ports can be individually configured by software in
several modes:
•

Input floating

•

Input pull-up

•

Input-pull-down

•

Analog

•

Output open-drain with pull-up or pull-down capability

•

Output push-pull with pull-up or pull-down capability

•

Alternate function push-pull with pull-up or pull-down capability

•

Alternate function open-drain with pull-up or pull-down capability

Each I/O port bit is freely programmable, however the I/O port registers have to be
accessed as 32-bit words, half-words or bytes. The purpose of the GPIOx_BSRR and

228/1141

DocID022558 Rev 8

RM0316

General-purpose I/Os (GPIO)
GPIOx_BRR registers is to allow atomic read/modify accesses to any of the GPIOx_ODR
registers. In this way, there is no risk of an IRQ occurring between the read and the modify
access.
Figure 40 and Figure 41 show the basic structures of a standard and a 5 V tolerant I/O port
bit, respectively. Table 72 gives the possible port bit configurations.
Figure 40. Basic structure of an I/O port bit
!NALOG

4O ON CHIP
PERIPHERAL

!LTERNATE FUNCTION INPUT
)NPUT DATA REGISTER

TRIGGER

ONOFF

0ROTECTION
DIODE

0ULL
UP

)NPUT DRIVER

)/ PIN

/UTPUT DRIVER

6$$

ONOFF

0ROTECTION
DIODE

0ULL
DOWN

0 -/3

633

/UTPUT
CONTROL

633

. -/3

2EADWRITE
633

&ROM ON CHIP
PERIPHERAL

6$$

6$$

/UTPUT DATA REGISTER

"IT SETRESET REGISTERS

2EAD

7RITE

ONOFF

0USH PULL
OPEN DRAIN OR
DISABLED

!LTERNATE FUNCTION OUTPUT

!NALOG
AI

Figure 41. Basic structure of a five-volt tolerant I/O port bit
!NALOG

4O ON CHIP
PERIPHERAL

!LTERNATE FUNCTION INPUT

2EADWRITE
&ROM ON CHIP
PERIPHERAL

)NPUT DATA REGISTER

ONOFF
6$$
44, 3CHMITT
TRIGGER

ONOFF

0ULL
UP

6$$?&4 

0ROTECTION
DIODE

)NPUT DRIVER

/UTPUT DATA REGISTER

7RITE

"IT SETRESET REGISTERS

2EAD

)/ PIN

/UTPUT DRIVER

6$$

ONOFF

0 -/3
/UTPUT
CONTROL

0ULL
DOWN

633

0ROTECTION
DIODE
633

. -/3

!LTERNATE FUNCTION OUTPUT

633

0USH PULL
OPEN DRAIN OR
DISABLED

!NALOG
AIB

1. VDD_FT is a potential specific to five-volt tolerant I/Os and different from VDD.

DocID022558 Rev 8

229/1141
244

General-purpose I/Os (GPIO)

RM0316
Table 72. Port bit configuration table(1)

MODER(i)
[1:0]

01

10

00

11

OTYPER(i)

OSPEEDR(i)
[1:0]

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

Reserved

0

0

GP output

OD

1

0

1

GP output

OD + PU

1

1

0

GP output

OD + PD

1

1

1

Reserved (GP output OD)

0

0

0

AF

PP

0

0

1

AF

PP + PU

0

1

0

AF

PP + PD

1

1

Reserved

0

0

AF

OD

1

0

1

AF

OD + PU

1

1

0

AF

OD + PD

1

1

1

Reserved

0

SPEED
[1:0]

1

0

SPEED
[1:0]

1

x

x

x

0

0

Input

Floating

x

x

x

0

1

Input

PU

x

x

x

1

0

Input

PD

x

x

x

1

1

Reserved (input floating)

x

x

x

0

0

Input/output

x

x

x

0

1

x

x

x

1

0

x

x

x

1

1

Analog

Reserved

1. GP = general-purpose, PP = push-pull, PU = pull-up, PD = pull-down, OD = open-drain, AF = alternate
function.

230/1141

DocID022558 Rev 8

RM0316

11.3.1

General-purpose I/Os (GPIO)

General-purpose I/O (GPIO)
During and just after reset, the alternate functions are not active and most of the I/O ports
are configured in input floating mode.
The debug pins are in AF pull-up/pull-down after reset:
•

PA15: JTDI in pull-up

•

PA14: JTCK/SWCLK in pull-down

•

PA13: JTMS/SWDIO in pull-up

•

PB4: NJTRST in pull-up

•

PB3: JTDO/TRACESWO

When the pin is configured as output, the value written to the output data register
(GPIOx_ODR) is output on the I/O pin. It is possible to use the output driver in push-pull
mode or open-drain mode (only the low level is driven, high level is HI-Z).
The input data register (GPIOx_IDR) captures the data present on the I/O pin at every AHB
clock cycle.
All GPIO pins have weak internal pull-up and pull-down resistors, which can be activated or
not depending on the value in the GPIOx_PUPDR register.

11.3.2

I/O pin alternate function multiplexer and mapping
The device I/O pins are connected to on-board peripherals/modules through a multiplexer
that allows only one peripheral alternate function (AF) connected to an I/O pin at a time. In
this way, there can be no conflict between peripherals available on the same I/O pin.
Each I/O pin has a multiplexer with up to sixteen alternate function inputs (AF0 to AF15) that
can be configured through the GPIOx_AFRL (for pin 0 to 7) and GPIOx_AFRH (for pin 8 to
15) registers:
•

After reset the multiplexer selection is alternate function 0 (AF0). The I/Os are
configured in alternate function mode through GPIOx_MODER register.

•

The specific alternate function assignments for each pin are detailed in the device
datasheet.

In addition to this flexible I/O multiplexing architecture, each peripheral has alternate
functions mapped onto different I/O pins to optimize the number of peripherals available in
smaller packages.
To use an I/O in a given configuration, the user has to proceed as follows:
•

Debug function: after each device reset these pins are assigned as alternate function
pins immediately usable by the debugger host

•

GPIO: configure the desired I/O as output, input or analog in the GPIOx_MODER
register.

•

Peripheral alternate function:

•

–

Connect the I/O to the desired AFx in one of the GPIOx_AFRL or GPIOx_AFRH
register.

–

Select the type, pull-up/pull-down and output speed via the GPIOx_OTYPER,
GPIOx_PUPDR and GPIOx_OSPEEDER registers, respectively.

–

Configure the desired I/O as an alternate function in the GPIOx_MODER register.

Additional functions:

DocID022558 Rev 8

231/1141
244

General-purpose I/Os (GPIO)

RM0316

–

For the ADC, DAC, OPAMP, and COMP, configure the desired I/O in analog mode
in the GPIOx_MODER register and configure the required function in the ADC,
DAC, OPAMP, and COMP registers.

–

For the additional functions like RTC, WKUPx and oscillators, configure the
required function in the related RTC, PWR and RCC registers. These functions
have priority over the configuration in the standard GPIO registers.

Refer to the “Alternate function mapping” table in the device datasheet for the detailed
mapping of the alternate function I/O pins.

11.3.3

I/O port control registers
Each of the GPIO ports has four 32-bit memory-mapped control registers (GPIOx_MODER,
GPIOx_OTYPER, GPIOx_OSPEEDR, GPIOx_PUPDR) to configure up to 16 I/Os. The
GPIOx_MODER register is used to select the I/O mode (input, output, AF, analog). The
GPIOx_OTYPER and GPIOx_OSPEEDR registers are used to select the output type (pushpull or open-drain) and speed. The GPIOx_PUPDR register is used to select the pullup/pull-down whatever the I/O direction.

11.3.4

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 11.4.5: GPIO port input data register (GPIOx_IDR) (x = A..H) and
Section 11.4.6: GPIO port output data register (GPIOx_ODR) (x = A..H) for the register
descriptions.

11.3.5

I/O data bitwise handling
The bit set reset register (GPIOx_BSRR) is a 32-bit register which allows the application to
set and reset each individual bit in the output data register (GPIOx_ODR). The bit set reset
register has twice the size of GPIOx_ODR.
To each bit in GPIOx_ODR, correspond two control bits in GPIOx_BSRR: BS(i) and BR(i).
When written to 1, bit BS(i) sets the corresponding ODR(i) bit. When written to 1, bit BR(i)
resets the ODR(i) corresponding bit.
Writing any bit to 0 in GPIOx_BSRR does not have any effect on the corresponding bit in
GPIOx_ODR. If there is an attempt to both set and reset a bit in GPIOx_BSRR, the set
action takes priority.
Using the GPIOx_BSRR register to change the values of individual bits in GPIOx_ODR is a
“one-shot” effect that does not lock the GPIOx_ODR bits. The GPIOx_ODR bits can always
be accessed directly. The GPIOx_BSRR register provides a way of performing atomic
bitwise handling.
There is no need for the software to disable interrupts when programming the GPIOx_ODR
at bit level: it is possible to modify one or more bits in a single atomic AHB write access.

232/1141

DocID022558 Rev 8

RM0316

11.3.6

General-purpose I/Os (GPIO)

GPIO locking mechanism
It is possible to freeze the GPIO control registers by applying a specific write sequence to
the GPIOx_LCKR register. The frozen registers are GPIOx_MODER, GPIOx_OTYPER,
GPIOx_OSPEEDR, GPIOx_PUPDR, GPIOx_AFRL and GPIOx_AFRH.
To write the GPIOx_LCKR register, a specific write / read sequence has to be applied. When
the right LOCK sequence is applied to bit 16 in this register, the value of LCKR[15:0] is used
to lock the configuration of the I/Os (during the write sequence the LCKR[15:0] value must
be the same). When the LOCK sequence has been applied to a port bit, the value of the port
bit can no longer be modified until the next MCU reset or peripheral reset. Each
GPIOx_LCKR bit freezes the corresponding bit in the control registers (GPIOx_MODER,
GPIOx_OTYPER, GPIOx_OSPEEDR, GPIOx_PUPDR, GPIOx_AFRL and GPIOx_AFRH.
The LOCK sequence (refer to Section 11.4.8: GPIO port configuration lock register
(GPIOx_LCKR)) can only be performed using a word (32-bit long) access to the
GPIOx_LCKR register due to the fact that GPIOx_LCKR bit 16 has to be set at the same
time as the [15:0] bits.
For more details refer to LCKR register description in Section 11.4.8: GPIO port
configuration lock register (GPIOx_LCKR).

11.3.7

I/O alternate function input/output
Two registers are provided to select one of the alternate function inputs/outputs available for
each I/O. With these registers, the user can connect an alternate function to some other pin
as required by the application.
This means that a number of possible peripheral functions are multiplexed on each GPIO
using the GPIOx_AFRL and GPIOx_AFRH alternate function registers. The application can
thus select any one of the possible functions for each I/O. The AF selection signal being
common to the alternate function input and alternate function output, a single channel is
selected for the alternate function input/output of a given I/O.
To know which functions are multiplexed on each GPIO pin, refer to the device datasheet.

11.3.8

External interrupt/wakeup lines
All ports have external interrupt capability. To use external interrupt lines, the port must be
configured in input mode.Section 14.2: Extended interrupts and events controller (EXTI) and
to Section 14.2.3: Wakeup event management.

11.3.9

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 AHB
clock cycle

•

A read access to the input data register provides the I/O state

Figure 42 shows the input configuration of the I/O port bit.

DocID022558 Rev 8

233/1141
244

General-purpose I/Os (GPIO)

RM0316

)NPUT DATA REGISTER

Figure 42. Input floating/pull up/pull down configurations

2EADWRITE

/UTPUT DATA REGISTER

7RITE

"IT SETRESET REGISTERS

2EAD

ON

44, 3CHMITT
TRIGGER

6$$
ONOFF

6$$
PROTECTION
DIODE

PULL
UP

INPUT DRIVER

)/ PIN
ONOFF

OUTPUT DRIVER
PULL
DOWN
633

PROTECTION
DIODE

633

AIB

11.3.10

Output configuration
When the I/O port is programmed as output:
•

The output buffer is enabled:
–

Open drain mode: A “0” in the Output register activates the N-MOS whereas a “1”
in the Output register leaves the port in Hi-Z (the P-MOS is never activated)

–

Push-pull mode: A “0” in the Output register activates the N-MOS whereas a “1” in
the Output register activates the P-MOS

•

The Schmitt trigger input is activated

•

The pull-up and pull-down resistors are activated depending on the value in the
GPIOx_PUPDR register

•

The data present on the I/O pin are sampled into the input data register every AHB
clock cycle

•

A read access to the input data register gets the I/O state

•

A read access to the output data register gets the last written value

Figure 43 shows the output configuration of the I/O port bit.

234/1141

DocID022558 Rev 8

RM0316

General-purpose I/Os (GPIO)

)NPUT DATA REGISTER

Figure 43. 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 in open-drain or push-pull mode

•

The output buffer is driven by the signals coming from the peripheral (transmitter
enable and data)

•

The Schmitt trigger input is activated

•

The weak pull-up and pull-down resistors are activated or not depending on the value
in the GPIOx_PUPDR register

•

The data present on the I/O pin are sampled into the input data register every AHB
clock cycle

•

A read access to the input data register gets the I/O state

Figure 44 shows the Alternate function configuration of the I/O port bit.
Figure 44. 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

11.3.11

)/ 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

DocID022558 Rev 8

235/1141
244

General-purpose I/Os (GPIO)

11.3.12

RM0316

Analog configuration
When the I/O port is programmed as analog configuration:
•

The output buffer is disabled

•

The Schmitt trigger input is deactivated, providing zero consumption for every analog
value of the I/O pin. The output of the Schmitt trigger is forced to a constant value (0).

•

The weak pull-up and pull-down resistors are disabled by hardware

•

Read access to the input data register gets the value “0”

Figure 45 shows the high-impedance, analog-input configuration of the I/O port bit.
Figure 45. High impedance-analog configuration

)NPUT DATA REGISTER

!NALOG

4O ON CHIP
PERIPHERAL

2EADWRITE

&ROM ON CHIP
PERIPHERAL

11.3.13

/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 HSE or LSE oscillator pins as GPIOs
When the HSE or LSE oscillator is switched OFF (default state after reset), the related
oscillator pins can be used as normal GPIOs.
When the HSE or LSE oscillator is switched ON (by setting the HSEON or LSEON bit in the
RCC_CSR register) the oscillator takes control of its associated pins and the GPIO
configuration of these pins has no effect.
When the oscillator is configured in a user external clock mode, only the pin is reserved for
clock input and the OSC_OUT or OSC32_OUT pin can still be used as normal GPIO.

11.3.14

Using the GPIO pins in the RTC supply domain
The PC13/PC14/PC15 GPIO functionality is lost when the core supply domain is powered
off (when the device enters Standby mode). In this case, if their GPIO configuration is not
bypassed by the RTC configuration, these pins are set in an analog input mode.
For details about I/O control by the RTC, refer to Section 27.3: RTC functional description
on page 775.

236/1141

DocID022558 Rev 8

RM0316

General-purpose I/Os (GPIO)

11.4

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 73.
The peripheral registers can be written in word, half word or byte mode.

11.4.1

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

rw

MODER0[1:0]
rw

rw

Bits 2y+1:2y MODERy[1:0]: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O mode.
00: Input mode (reset state)
01: General purpose output mode
10: Alternate function mode
11: Analog mode

Note:

In STM32F303xB/xC and STM32F358x devices, bits 10 and 11 of GPIOF_MODER are
reserved and must be kept at reset state.

11.4.2

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

DocID022558 Rev 8

237/1141
244

General-purpose I/Os (GPIO)

RM0316

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 OTy: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O output type.
0: Output push-pull (reset state)
1: Output open-drain

11.4.3

GPIO port output speed register (GPIOx_OSPEEDR)
(x = A..H)
Address offset: 0x08
Reset value:

31

•

0x0C00 0000 for port A

•

0x0000 00C0 for port B

•

0x0000 0000 for other ports

30

29

OSPEEDR15
[1:0]

28

27

OSPEEDR14
[1:0]

26

25

OSPEEDR13
[1:0]

24

OSPEEDR12
[1:0]

23

22

OSPEEDR11
[1:0]

21

20

OSPEEDR10
[1:0]

19

18

17

16

OSPEEDR9
[1:0]

OSPEEDR8
[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OSPEEDR7
[1:0]

OSPEEDR6
[1:0]

OSPEEDR5
[1:0]

OSPEEDR4
[1:0]

OSPEEDR3
[1:0]

OSPEEDR2
[1:0]

OSPEEDR1
[1:0]

OSPEEDR0
[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 2y+1:2y OSPEEDRy[1:0]: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O output speed.
x0: Low speed
01: Medium speed
11: High speed
Note: Refer to the device datasheet for the frequency specifications and the power supply
and load conditions for each speed.

11.4.4

GPIO port pull-up/pull-down register (GPIOx_PUPDR)
(x = A..H)
Address offset: 0x0C
Reset values:

31

30

PUPDR15[1:0]

•

0x6400 0000 for port A

•

0x0000 0100 for port B

•

0x0000 0000 for other ports
29

28

PUPDR14[1:0]

27

26

PUPDR13[1:0]

25

24

PUPDR12[1:0]

23

22

PUPDR11[1:0]

21

20

PUPDR10[1:0]

19

18

PUPDR9[1:0]

17

16

PUPDR8[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PUPDR7[1:0]
rw

238/1141

rw

PUPDR6[1:0]
rw

rw

PUPDR5[1:0]
rw

rw

PUPDR4[1:0]
rw

rw

PUPDR3[1:0]
rw

rw

DocID022558 Rev 8

PUPDR2[1:0]
rw

rw

PUPDR1[1:0]
rw

rw

PUPDR0[1:0]
rw

rw

RM0316

General-purpose I/Os (GPIO)

Bits 2y+1:2y PUPDRy[1:0]: Port x configuration bits (y = 0..15)
These bits are written by software to configure the I/O pull-up or pull-down
00: No pull-up, pull-down
01: Pull-up
10: Pull-down
11: Reserved

11.4.5

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 bit (y = 0..15)
These bits are read-only. They contain the input value of the corresponding I/O port.

11.4.6

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

ODR15 ODR14 ODR13 ODR12 ODR11 ODR10
rw

rw

rw

rw

rw

rw

9

8

7

6

5

4

3

2

1

0

ODR9

ODR8

ODR7

ODR6

ODR5

ODR4

ODR3

ODR2

ODR1

ODR0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 ODRy: Port output data bit (y = 0..15)
These bits can be read and written by software.
Note: For atomic bit set/reset, the ODR bits can be individually set and/or reset by writing to
the GPIOx_BSRR or GPIOx_BRR registers (x = A..F).

DocID022558 Rev 8

239/1141
244

General-purpose I/Os (GPIO)

11.4.7

RM0316

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. A read to these bits returns the value 0x0000.
0: No action on the corresponding ODRx bit
1: Resets the corresponding ODRx bit
Note: If both BSx and BRx are set, BSx has priority.
Bits 15:0 BSy: Port x set bit y (y= 0..15)
These bits are write-only. A read to these bits returns the value 0x0000.
0: No action on the corresponding ODRx bit
1: Sets the corresponding ODRx bit

11.4.8

GPIO port configuration lock register (GPIOx_LCKR)
x= A, B and D in STM32F303xB/C and STM32F358xC devices, x= A, B, C, D and F in
STM32F303x6/8 and STM32F328x8 devices and x = A, B, C, D, E, F, G, H in
STM32F303xD/E devices.
This register is used to lock the configuration of the port bits when a correct write sequence
is applied to bit 16 (LCKK). The value of bits [15:0] is used to lock the configuration of the
GPIO. During the write sequence, the value of LCKR[15:0] must not change. When the
LOCK sequence has been applied on a port bit, the value of this port bit can no longer be
modified until the next MCU reset or peripheral reset.

Note:

A specific write sequence is used to write to the GPIOx_LCKR register. Only word access
(32-bit long) is allowed during this locking sequence.
Each lock bit freezes a specific configuration register (control and alternate function
registers).
Address offset: 0x1C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LCKK

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

LCK15

LCK14

LCK13

LCK12

LCK11

LCK10

LCK9

LCK8

LCK7

LCK6

LCK5

LCK4

LCK3

LCK2

LCK1

LCK0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

240/1141

DocID022558 Rev 8

RM0316

General-purpose I/Os (GPIO)

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 LCKK: Lock key
This bit can be read any time. It can only be modified using the lock key write sequence.
0: Port configuration lock key not active
1: Port configuration lock key active. The GPIOx_LCKR register is locked until the next MCU
reset or peripheral reset.
LOCK key write sequence:
WR LCKR[16] = ‘1’ + LCKR[15:0]
WR LCKR[16] = ‘0’ + LCKR[15:0]
WR LCKR[16] = ‘1’ + LCKR[15:0]
RD LCKR
RD LCKR[16] = ‘1’ (this read operation is optional but it confirms that the lock is active)
Note: During the LOCK key write sequence, the value of LCK[15:0] must not change.
Any error in the lock sequence aborts the lock.
After the first lock sequence on any bit of the port, any read access on the LCKK bit will
return ‘1’ until the next MCU reset or peripheral reset.
Bits 15:0 LCKy: Port x lock bit y (y= 0..15)
These bits are read/write but can only be written when the LCKK bit is ‘0.
0: Port configuration not locked
1: Port configuration locked

11.4.9

GPIO alternate function low register (GPIOx_AFRL)
(x = A..H)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

AFR7[3:0]

26

25

24

23

22

AFR6[3:0]

21

20

19

AFR5[3:0]

18

17

16

AFR4[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

AFR3[3:0]
rw

rw

rw

AFR2[3:0]
rw

rw

rw

rw

AFR1[3:0]
rw

rw

rw

rw

AFR0[3:0]
rw

rw

rw

rw

rw

Bits 31:0 AFRy[3:0]: Alternate function selection for port x pin y (y = 0..7)
These bits are written by software to configure alternate function I/Os
AFRy 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

DocID022558 Rev 8

241/1141
244

General-purpose I/Os (GPIO)

11.4.10

RM0316

GPIO alternate function high register (GPIOx_AFRH)
(x = A..H)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

AFR15[3:0]

26

25

24

23

22

AFR14[3:0]

21

20

19

AFR13[3:0]

18

17

16

AFR12[3:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

AFR11[3:0]
rw

rw

rw

AFR10[3:0]
rw

rw

rw

rw

AFR9[3:0]
rw

rw

rw

rw

AFR8[3:0]
rw

rw

rw

rw

rw

Bits 31:0 AFRy[3:0]: Alternate function selection for port x pin y (y = 8..15)
These bits are written by software to configure alternate function I/Os
AFRy selection:
0000: AF0
0001: AF1
0010: AF2
0011: AF3
0100: AF4
0101: AF5
0110: AF6
0111: AF7

11.4.11

1000: AF8
1001: AF9
1010: AF10
1011: AF11
1100: AF12
1101: AF13
1110: AF14
1111: AF15

GPIO port bit reset register (GPIOx_BRR) (x =A..H)
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

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

Bits 31:16 Reserved
Bits 15:0 BRy: Port x Reset bit y (y= 0..15)
These bits are write-only. A read to these bits returns the value 0x0000
0: No action on the corresponding ODx bit
1: Reset the corresponding ODx bit

242/1141

DocID022558 Rev 8

0x08

0x08

0x0C
Reset value

GPIOB_OSPEEDR

Reset value

GPIOx_OSPEEDR
(where x = C..H)

Reset value

GPIOA_PUPDR

Reset value
0

0

0

0
0
0

0
0

0

0

1

1
0
1

0
0

0

0

0

0
1
0

0
0

0

0

1

0
0
0

0
0

0

0

0

0
0
0

0
0

0

0

0

0
0
0

0
0

0

0

0

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

GPIOx_OTYPER
(where x = A..H)

Reset value

0
0

0
0

0

0

0

0
0
0

0
0

0

0

0

0

DocID022558 Rev 8
0
0

0
0

0
0

0

0

0

0
0
0

0
0

0
0

0

0

0

0

0
0

0
0

0
0

0

0

0

0

0
0

0
0

0
1

0

0

0

0

0
0

0
0

1
0

0

0

0

0

0
0

0
0

0
0

0

0

0

0

OT1
OT0

MODER0[1:0]

MODER0[1:0]

0

0
0
0
0

0
0

0
0

0

0

0

0

OSPEEDR0[1:0]

MODER1[1:0]

0

OSPEEDR0[1:0]

MODER1[1:0]

0

OSPEEDR0[1:0]

OT2

0

PUPDR0[1:0]

OT3

0

OSPEEDR1[1:0]

MODER2[1:0]

0

OSPEEDR1[1:0]

MODER2[1:0]

0

OSPEEDR1[1:0]

OT4

0

PUPDR1[1:0]

OT5

1

OSPEEDR2[1:0]

MODER3[1:0]

0

OSPEEDR2[1:0]

MODER3[1:0]

0

OSPEEDR2[1:0]

OT6

0

PUPDR2[1:0]

OT7

1

OSPEEDR3[1:0]

MODER4[1:0]

0

OSPEEDR3[1:0]

MODER4[1:0]

0

OSPEEDR3[1:0]

OT8

0

PUPDR3[1:0]

OT9

0

OSPEEDR4[1:0]

0

OSPEEDR4[1:0]

MODER5[1:0]

0

OSPEEDR4[1:0]

MODER5[1:0]

0

PUPDR4[1:0]

OT11
OT10

0

OSPEEDR5[1:0]

MODER6[1:0]

0

OSPEEDR5[1:0]

MODER6[1:0]

0

OSPEEDR5[1:0]

OT12

0

PUPDR5[1:0]

OT13

0

OSPEEDR6[1:0]

0

OSPEEDR6[1:0]

MODER7[1:0]

0

OSPEEDR6[1:0]

MODER7[1:0]

0

PUPDR6[1:0]

OT14

0

OT15

0

OSPEEDR7[1:0]

MODER8[1:0]

0

OSPEEDR7[1:0]

MODER8[1:0]

0

OSPEEDR7[1:0]

0

Res.

0

PUPDR7[1:0]

0

Res.

0

OSPEEDR8[1:0]

MODER9[1:0]

0

OSPEEDR8[1:0]

MODER9[1:0]

0

OSPEEDR8[1:0]

0

Res.

0

PUPDR8[1:0]

0

Res.

0

OSPEEDR9[1:0]

MODER10[1:0]

0

OSPEEDR9[1:0]

MODER10[1:0]

0

OSPEEDR9[1:0]

0

Res.

0

PUPDR9[1:0]

0

Res.

0

OSPEEDR10[1:0]

MODER11[1:0]

0

OSPEEDR10[1:0]

MODER11[1:0]

0

OSPEEDR10[1:0]

0

Res.

0

PUPDR10[1:0]

0

Res.

0

OSPEEDR11[1:0]

MODER12[1:0]

0

OSPEEDR11[1:0]

MODER12[1:0]

0

OSPEEDR11[1:0]

0

Res.

0

PUPDR11[1:0]

0

Res.

0

OSPEEDR12[1:0]

MODER13[1:0]

0

OSPEEDR12[1:0]

MODER13[1:0]

1

OSPEEDR12[1:0]

0

Res.

0

PUPDR12[1:0]

0

Res.

MODER14[1:0]

0

OSPEEDR13[1:0]

MODER14[1:0]

0

OSPEEDR13[1:0]

0

Res.

1

OSPEEDR13[1:0]

0

Res.

MODER15[1:0]
0

PUPDR13[1:0]

GPIOA_OSPEEDR
OSPEEDR14[1:0]

GPIOx_MODER
(where x = C..H)
0

OSPEEDR14[1:0]

Reset value
1

OSPEEDR14[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

OSPEEDR15[1:0]

11.4.12

PUPDR15[1:0]

RM0316
General-purpose I/Os (GPIO)

GPIO register map
The following table gives the GPIO register map and reset values.
Table 73. GPIO register map and reset values

0
0

0
0

0

0

0

0

0

0

243/1141

244

General-purpose I/Os (GPIO)

RM0316

0

0

0

0

Res.

Res.

Res.

Res.

PUPDR0[1:0]

0

BS11

BS9

BS8

BS7

BS6

BS5

BS4

BS3

BS2

BS1

BS0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

LCK9

LCK8

LCK7

LCK6

LCK5

LCK4

LCK3

LCK2

LCK1

LCK0

0

BS10

0

LCK11

0

LCK10

0

BS12

0

BS13

0

LCK12

0

LCK13

0

BS14

0

BS15

0

LCK14

0

LCK15

0

BR0

0

BR1

0

Res.

0

LCKK

0
BR2

ODR0

Res.

x

ODR1

Res.

x

ODR2

Res.

x

ODR3

Res.

x

ODR4

Res.

x

ODR5

Res.

x

ODR6

Res.

x

ODR7

Res.

x

ODR8

Res.

x

ODR9

Res.

x

ODR11

Res.

x
ODR10

Res.

x

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

AFRLAFR7[3: AFRLAFR6[3: AFRLAFR5[3: AFRLAFR4[3: AFRLAFR3[3 AFRLAFR2[3: AFRLAFR1[3 AFRLAFR0[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

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

GPIOx_BRR
(where x = A..H)

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BR15

BR14

BR13

BR12

BR11

BR10

BR9

BR8

BR7

BR6

BR5

BR4

BR3

BR2

BR1

BR0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

1. A, B and D in STM32F303xB/C and STM32F358xC, A, B, C, D and F in STM32F303x6/8 and STM32F328x8, and A, B, C,
D, E, F, G, H in STM32F303xD/E.

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

244/1141

0

AFRHAFR15[ AFRHAFR14[ AFRHAFR13[ AFRHAFR12[ AFRHAFR11[ AFRHAFR10[ AFRHAFR9[3 AFRHAFR8[3
3:0]
3:0]
3:0]
3:0]
3:0]
3:0]
:0]
:0]
Res.

Reset value

x
ODR12

Res.

0x24

GPIOx_AFRH
(where x = A..H)

x
ODR13

Res.

0x20

GPIOx_AFRL
(where x = C..H)

x
ODR14

0x1C

Reset value

x
ODR15

0

Res.

0

Res.

BR3

0

Res.

BR4

0

Res.

BR5

0

Res.

BR6

0

Res.

BR7

0

Res.

BR8

0

Res.

BR9

0

Res.

BR11

BR10

0

Res.

BR12

0

Res.

BR13

0

Res.

BR14

0

Res.

BR15

Reset value
GPIOx_LCKR
(where x = see (1))

Res.

0x18

GPIOx_BSRR
(where x = A..H)

Res.

GPIOx_ODR
(where x = A..H)

Res.

0x14

IDR0

0

IDR1

0

Res.

PUPDR1[1:0]

0

IDR2

1

IDR3

0

Res.

PUPDR2[1:0]

0

IDR4

0

IDR5

0

Res.

PUPDR3[1:0]

0

IDR6

0

IDR7

0

Res.

PUPDR4[1:0]

0

IDR8

0

IDR9

0

Res.

PUPDR5[1:0]

0

IDR11

0

IDR10

0

Reset value

0x28

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.

0x10

Reset value
GPIOx_IDR
(where x = A..H)

Res.

GPIOB_PUPDR

0x0C

PUPDR14[1:0]

Register

PUPDR15[1:0]

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 73. GPIO register map and reset values (continued)

DocID022558 Rev 8

RM0316

12

System configuration controller (SYSCFG)

System configuration controller (SYSCFG)
The STM32F3xx devices feature a set of configuration registers. The main purposes of the
system configuration controller are the following:
•

Enabling/disabling I2C Fm+ on some I/O ports

•

Remapping some DMA trigger sources from TIM16, TIM17, TIM6, DAC1_CH1, and
DAC1_CH2,TIM7, and ADC4 to different DMA channels (also SPI1, I2C1, ADC2 in
STM32F303x6/8 and STM32F328x8)

•

Remapping the memory located at the beginning of the code area

•

Managing the external interrupt line connection to the GPIOs

•

Remapping TIM1 ITR3 source

•

Remapping USB interrupt line

•

Remapping DAC1 and DAC2 triggers

•

Managing robustness feature

•

Configuring encoder mode

•

CCM SRAM pages protection

12.1

SYSCFG registers

12.1.1

SYSCFG configuration register 1 (SYSCFG_CFGR1)
This register is used for specific configurations on memory remap.
Two 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 pin
and the option bit setting.
After reset these bits take the value selected by the BOOT pin (BOOT0) and by the option
bit (BOOT1).
Address offset: 0x00
Reset value: 0x7C00 000X (X is the memory mode selected by the BOOT0 pin and BOOT1
option bit)

31

30

29

28

27

26

FPU_IE[5..0]

25

24

Res

I2C3_
FMP

23

22

21

20

19

18

17

16

I2C_
PB8_
FMP

I2C_
PB7_
FMP

I2C_
PB6_
FMP

ENCODER_
MODE

I2C2_
FMP

I2C1_
FMP

I2C_
PB9_
FMP

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

ADC2_
DMA_
RMP

DAC_
TRIG_
RMP

TIM1_
ITR3_
RMP

USB_
IT_
RMP

Res

Res

MEM_
MODE

rw

rw

rw

rw

DAC2_ TIM7_ TIM6_
CH1_D DAC2_ DAC1_ TIM17_ TIM16_
MA_R DMA_ DMA_ DMA_ DMA_
RMP
RMP
RMP
RMP
MP(1)
rw

rw

rw

rw

rw

(2)

MEM_MODE

rw

rw

1. Only in STM32F303x6/8 and STM32F328x8.
2. Only for STM32F303xD/E and STM32F398xE devices

DocID022558 Rev 8

245/1141
262

System configuration controller (SYSCFG)

RM0316

Bits 31:26 FPU_IE[5..0]: Floating Point Unit interrupts enable bits
FPU_IE[5]: Inexact interrupt enable
FPU_IE[4]: Input normal interrupt enable
FPU_IE[3]: Overflow interrupt enable
FPU_IE[2]: underflow interrupt enable
FPU_IE[1]: Divide-by-zero interrupt enable
FPU_IE[0]: Invalid operation interrupt enable
Bit 25: Reserved, must be kept at reset value.
Bit 24 I2C3_FMP: I2C3 fast mode Plus driving capability activation (STM32F303xD/E devices only)
This bit is set and cleared by software. It enables the Fm+ on I2C3 pins selected through AF
selection bits.
0: Fm+ mode is not enabled on I2C3 pins selected through AF selection bits
1: Fm+ mode is enabled on I2C3 pins selected through AF selection bits.
Bits 23:22 ENCODER_MODE: Encoder mode
This bit is set and cleared by software.
00: No redirection.
01: TIM2 IC1 and TIM2 IC2 are connected to TIM15 IC1 and TIM15 IC2 respectively.
10: TIM3 IC1 and TIM3 IC2 are connected to TIM15 IC1 and TIM15 IC2
respectively .
11: TIM4 IC1 and TIM4 IC2 are connected to TIM15 IC1 and TIM15 IC2
respectively (STM32F303xB/C and STM32F358xC devices only).
Bit 21 I2C2_FMP: I2C2 fast mode Plus driving capability activation (STM32F303xB/C and
STM32F358xC devices only)
This bit is set and cleared by software. It enables the Fm+ on I2C2 pins selected through AF
selection bits.
0: Fm+ mode is not enabled on I2C2 pins selected through AF selection bits
1: Fm+ mode is enabled on I2C2 pins selected through AF selection bits.
Bit 20 I2C1_FMP: I2C1 Fm+ driving capability activation
This bit is set and cleared by software. It enables the Fm+ on I2C1 pins selected through AF
selection bits.
0: Fm+ mode is not enabled on I2C1 pins selected through AF selection bits
1: Fm+ mode is enabled on I2C1 pins selected through AF selection bits.
Bits 19:16 I2C_PBx_FMP: Fm+ driving capability activation on the pad
These bits are set and cleared by software. Each bit enables I2C Fm+ mode for PB6, PB7,
PB8, and PB9 I/Os.
0: PBx pin operates in standard mode (Sm), x = 6..9
1: I2C Fm+ mode enabled on PBx pin, and the Speed control is bypassed.
Bit 15 DAC2_CH1_DMA_RMP:DAC2 channel1 DMA remap (STM32F303x6/8 and STM32F328x8
devices only)
This bit is set and cleared by software. It controls the remapping of DAC2 channel1 DMA
request.
0: No remap
1: Remap (DAC2_CH1 DMA requests mapped on DMA1 channel 5)
Note:

246/1141

In STM32F303x6/8 and STM32F328x8, this bit must be set.

DocID022558 Rev 8

RM0316

System configuration controller (SYSCFG)

Bit 14 TIM7_DAC1_CH2_DMA_RMP: TIM7 and DAC channel2 DMA remap
This bit is set and cleared by software. It controls the remapping of TIM7(UP) and DAC
channel2 DMA request.
0: No remap (TIM7_UP and DAC_CH2 DMA requests mapped on DMA2 channel 4 in
STM32F303xB/C and STM32F358xC devices)
1: Remap (TIM7_UP and DAC_CH2 DMA requests mapped on DMA1 channel 4)
Note:

In STM32F303x6/8 and STM32F328x8, this bit must be set as there is no DMA2 in
these products.

Bits 15:14 Reserved, must be kept at reset value.
Bit 13 TIM6_DAC1_CH1_DMA_RMP: TIM6 and DAC channel1 DMA remap
This bit is set and cleared by software. It controls the remapping of TIM6 (UP) and DAC
channel1 DMA request.
0: No remap (TIM6_UP and DAC_CH1 DMA requests mapped on DMA2 channel 3 in
STM32F303xB/C and STM32F358xC)
1: Remap (TIM6_UP and DAC_CH1 DMA requests mapped on DMA1 channel 3)
Note:

In STM32F303x6/8 and STM32F328x8, this bit must be set as there is no DMA2 in
these products.

Bit 12 TIM17_DMA_RMP: TIM17 DMA request remapping bit
This bit is set and cleared by software. It controls the remapping of TIM17 DMA request.
0: No remap (TIM17_CH1 and TIM17_UP DMA requests mapped on DMA1 channel 1)
1: Remap (TIM17_CH1 and TIM17_UP DMA requests mapped on DMA1 channel 7)
Bit 11 TIM16_DMA_RMP: TIM16 DMA request remapping bit
This bit is set and cleared by software. It controls the remapping of TIM16 DMA request.
0: No remap (TIM16_CH1 and TIM16_UP DMA requests mapped on DMA1 channel 3)
1: Remap (TIM16_CH1 and TIM16_UP DMA requests mapped on DMA1 channel 6)
Bits 10:9 Reserved, must be kept at reset value.
Bit 8 ADC2_DMA_RMP: ADC2 DMA remapping bit
This bit is set and cleared by software. It controls the remapping of ADC24 DMA requests.
0: No remap (ADC24 DMA requests mapped on DMA2 channels 1 and 2)
1: Remap (ADC24 DMA requests mapped on DMA2 channels 3 and 4)
Bit 7 DAC1_TRIG_RMP: DAC trigger remap (when TSEL = 001) This bit is set and cleared by
software. It controls the mapping of the DAC trigger source.
0: No remap (DAC trigger is TIM8_TRGO in STM32F303xB/C and STM32F358xC devices)
1: Remap (DAC trigger is TIM3_TRGO)
Bit 6 TIM1_ITR3_RMP: Timer 1 ITR3 selection
This bit is set and cleared by software. It controls the mapping of TIM1 ITR3.
0: No remap (TIM1_ITR3 = TIM4_TRGO in STM32F303xB/C and STM32F358xC devices)
1: Remap (TIM1_ITR3 = TIM17_OC)

DocID022558 Rev 8

247/1141
262

System configuration controller (SYSCFG)

RM0316

Bit 5 USB_IT_RMP: USB interrupt remap (STM32F303xB/C/D/E devices only)
This bit is set and cleared by software. It controls the USB interrupts mapping.
0: USB_HP, USB_LP and USB_WAKEUP interrupts are mapped on interrupt lines 19, 20
and 42 respectively.
1: USB_HP, USB_LP and USB_WAKEUP interrupts are mapped on interrupt lines 74, 75
and 76 respectively.
Bits 4:3 Reserved, must be kept at reset value.
Bits 2:0 MEM_MODE: Memory mapping selection bits
This bit is set and cleared by software. It controls the memory internal mapping at address
0x0000 0000. After reset these bits take on the memory mapping selected by BOOT0 pin and
BOOT1 option bit.
0x0: Main Flash memory mapped at 0x0000 0000
001: System Flash memory mapped at 0x0000 0000
011: Embedded SRAM (on the D-Code bus) mapped at 0x0000 0000
1xx: FMC Bank (Only the first two banks) (Available on STM32F303xD/E only).

12.1.2

SYSCFG CCM SRAM protection register (SYSCFG_RCR)
The CCM SRAM has a size of 8 Kbytes, organized in 8 pages (1 Kbyte each) in
STM32F303xB/C and STM32F358xC devices. The CCM SRAM has a size of 4 Kbytes,
organized in 4 pages (1 Kbyte each) in STM32F303x6/8 and STM32F328x8. The CCM
SRAM has a size of 16 Kbytes, organized in 16 pages (1 Kbyte each) in STM32F303xD/E.
Each page can be write protected.
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

PAGE15 PAGE14 PAGE13 PAGE12 PAGE11 PAGE10 PAGE9 PAGE8 PAGE7 PAGE6 PAGE5 PAGE4 PAGE PAGE PAGE PAGE
_WP(1) _WP(1) _WP(1) _WP(1) _WP(1) _WP(1) _WP(1) _WP(1) _WP(2) _WP(2) _WP(2) _WP(2) 3_WP 2_WP 1_WP 0_WP
rw

rw

rw

1. Only on STM32F303xD/E and STM32F398xE
2. Only on STM32F303xB/C/D/E devices.

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PAGEx_WP (x= 0 to 15): CCM SRAM page write protection bit)
These bits are set by software. They can be cleared only by system reset.
0: Write protection of pagex is disabled.
1: Write protection of pagex is enabled.

248/1141

DocID022558 Rev 8

rw

RM0316

System configuration controller (SYSCFG)

12.1.3

SYSCFG external interrupt configuration register 1
(SYSCFG_EXTICR1)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

EXTI3[3:0]
rw

rw

rw

EXTI2[3:0]
rw

rw

rw

EXTI1[3:0]

rw

rw

rw

rw

rw

EXTI0[3:0]
rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:12 EXTI3[3:0]: EXTI 3 configuration bits
These bits are written by software to select the source input for the EXTI3 external
interrupt.
x000: PA[3] pin
x001: PB[3] pin
x010: PC[3] pin
x011: PD[3] pin
x100: PE[3] pin
x101:PF[3] pin
x110:PG[3] pin
other configurations: reserved

DocID022558 Rev 8

249/1141
262

System configuration controller (SYSCFG)

RM0316

Bits 11:8 EXTI2[3:0]: EXTI 2 configuration bits
These bits are written by software to select the source input for the EXTI2 external
interrupt.
x000: PA[2] pin
x001: PB[2] pin
x010: PC[2] pin
x011: PD[2] pin
x100: PE[2] pin
x101: PF[2] pin
x110:PG[2] pin
x111:PH[2] pin
other configurations: reserved
Bits 7:4 EXTI1[3:0]: EXTI 1 configuration bits
These bits are written by software to select the source input for the EXTI1 external
interrupt.
x000: PA[1] pin
x001: PB[1] pin
x010: PC[1] pin
x011: PD[1] pin
x100: PE[1] pin
x101: PF[1] pin
x110:PG[1] pin
x111:PH[1] pin
other configurations: reserved
Bits 3:0 EXTI0[3:0]: EXTI 0 configuration bits
These bits are written by software to select the source input for the EXTI0 external
interrupt.
x000: PA[0] pin
x001: PB[0] pin
x010: PC[0] pin
x011: PD[0] pin
x100: PE[0] pin
x101: PF[0] pin
x110:PG[0] pin
x111:PH[0] pin
Note: other configurations: reserved

12.1.4

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]

250/1141

rw

EXTI6[3:0]

EXTI5[3:0]

rw

DocID022558 Rev 8

rw

EXTI4[3:0]
rw

rw

RM0316

System configuration controller (SYSCFG)

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:12 EXTI7[3:0]: EXTI 7 configuration bits
These bits are written by software to select the source input for the EXTI7 external
interrupt.
x000: PA[7] pin
x001: PB[7] pin
x010: PC[7] pin
x011: PD[7] pin
x100: PE[7] pin
x101:PF[7] pin
x110:PG[7] pin
Other configurations: reserved
Bits 11:8 EXTI6[3:0]: EXTI 6 configuration bits
These bits are written by software to select the source input for the EXTI6 external
interrupt.
x000: PA[6] pin
x001: PB[6] pin
x010: PC[6] pin
x011: PD[6] pin
x100: PE[6] pin
x101: PF[6] pin
x110:PG[6] pin
Other configurations: reserved
Bits 7:4 EXTI5[3:0]: EXTI 5 configuration bits
These bits are written by software to select the source input for the EXTI5 external
interrupt.
x000: PA[5] pin
x001: PB[5] pin
x010: PC[5] pin
x011: PD[5] pin
x100: PE[5] pin
x101: PF[5] pin
x110:PG[5] pin
Other configurations: reserved
Bits 3:0 EXTI4[3:0]: EXTI 4 configuration bits
These bits are written by software to select the source input for the EXTI4 external
interrupt.
x000: PA[4] pin
x001: PB[4] pin
x010: PC[4] pin
x011: PD[4] pin
x100: PE[4] pin
x101: PF[4] pin
x110:PG[4] pin
Other configurations: reserved

Note:

Some of the I/O pins mentioned in the above register may not be available on small
packages.

DocID022558 Rev 8

251/1141
262

System configuration controller (SYSCFG)

12.1.5

RM0316

SYSCFG external interrupt configuration register 3
(SYSCFG_EXTICR3)
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

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 15:12 EXTI11[3:0]: EXTI 11 configuration bits
These bits are written by software to select the source input for the EXTI11 external
interrupt.
x000: PA[11] pin
x001: PB[11] pin
x010: PC[11] pin
x011: PD[11] pin
x100: PE[11] pin
x101:PF[11] pin
x110:PG[11] pin
other configurations: reserved

252/1141

DocID022558 Rev 8

RM0316

System configuration controller (SYSCFG)

Bits 11:8 EXTI10[3:0]: EXTI 10 configuration bits
These bits are written by software to select the source input for the EXTI10
external interrupt.
x000: PA[10] pin
x001: PB[10] pin
x010: PC[10] pin
x011:PD[10] pin
x100:PE[10] pin
x101:PF[10] pin
x110:PG[10] pin
other configurations: reserved
Bits 7:4 EXTI9[3:0]: EXTI 9 configuration bits
These bits are written by software to select the source input for the EXTI9 external
interrupt.
x000: PA[9] pin
x001: PB[9] pin
x010: PC[9] pin
x011: PD[9] pin
x100: PE[9] pin
x101: PF[9] pin
x110:PG[9] pin
other configurations: reserved
Bits 3:0 EXTI8[3:0]: EXTI 8 configuration bits
These bits are written by software to select the source input for the EXTI8 external
interrupt.
x000: PA[8] pin
x001: PB[8] pin
x010: PC[8] pin
x011: PD[8] pin
x100: PE[8] pin
x101:PF[8] pin
x110:PG[8] pin
other configurations: reserved

Note:

Some of the I/O pins mentioned in the above register may not be available on small
packages.

DocID022558 Rev 8

253/1141
262

System configuration controller (SYSCFG)

12.1.6

RM0316

SYSCFG external interrupt configuration register 4
(SYSCFG_EXTICR4)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

15

EXTI15[3:0]
rw

rw

rw

EXTI14[3:0]
rw

rw

rw

rw

EXTI13[3:0]
rw

rw

rw

rw

EXTI12[3:0]
rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:12 EXTI15[3:0]: EXTI15 configuration bits
These bits are written by software to select the source input for the EXTI15 external
interrupt.
x000: PA[15] pin
x001: PB[15] pin
x010: PC[15] pin
x011: PD[15] pin
x100: PE[15] pin
x101:PF[15] pin
x110:PG[15] pin
Other configurations: reserved

254/1141

DocID022558 Rev 8

rw

RM0316

System configuration controller (SYSCFG)

Bits 11:8 EXTI14[3:0]: EXTI14 configuration bits
These bits are written by software to select the source input for the EXTI14 external
interrupt.
x000: PA[14] pin
x001: PB[14] pin
x010: PC[14] pin
x011: PD[14] pin
x100: PE[14] pin
x101:PF[14] pin
x110:PG[14] pin
Other configurations: reserved
Bits 7:4 EXTI13[3:0]: EXTI13 configuration bits
These bits are written by software to select the source input for the EXTI13 external
interrupt.
x000: PA[13] pin
x001: PB[13] pin
x010: PC[13] pin
x011: PD[13] pin
x100: PE[13] pin
x101:PF[13] pin
x110:PG[13] pin
Other configurations: reserved
Bits 3:0 EXTI12[3:0]: EXTI12 configuration bits
These bits are written by software to select the source input for the EXTI12 external
interrupt.
x000: PA[12] pin
x001: PB[12] pin
x010: PC[12] pin
x011: PD[12] pin
x100: PE[12] pin
x101:PF[12] pin
x110:PG[12] pin
Other configurations: reserved

Note:

Some of the I/O pins mentioned in the above register may not be available on small
packages.

12.1.7

SYSCFG configuration register 2 (SYSCFG_CFGR2)
Address offset: 0x18
System 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

Res

Res

Res

Res

Res

Res

SRAM_
PEF

Res

Res

Res

BYP_ADDR
_PAR

Res

rc_w1

DocID022558 Rev 8

rw

SRAM_
PVD_
LOCKUP
PARITY
LOCK
_LOCK
_LOCK
rw

rw

rw

255/1141
262

System configuration controller (SYSCFG)

RM0316

Bits 31:9 Reserved, must be kept at reset value
Bit 8 SRAM_PEF: SRAM parity error flag
This bit is set by hardware when an SRAM parity error is detected. It is cleared by
software by writing ‘1’.
0: No SRAM parity error detected
1: SRAM parity error detected
Bits 7:5 Reserved, must be kept at reset value
Bit 4 BYP_ADDR_PAR: Bypass address bit 29 in parity calculation
This bit is set by software and cleared by a system reset. It is used to prevent an
unwanted parity error when the user writes a code in the RAM at address
0x2XXXXXXX (address in the address range 0x20000000-0x20002000) and then
executes the code from RAM at boot (RAM is remapped at address 0x00). In this
case, a read operation will be performed from the range 0x00000000-0x00002000
resulting in a parity error (the parity on the address is different).
0: The ramload operation is performed taking into consideration bit 29 of the
address when the parity is calculated.
1: The ramload operation is performed without taking into consideration bit 29 of
the address when the parity is calculated.
Bit 3 Reserved, must be kept at reset value
Bit 2 PVD_LOCK: PVD lock enable bit
This bit is set by software and cleared by a system reset. It can be used to
enable and lock the PVD connection to TIM1/8/15/16/17 Break input, as well as
the PVDE and PLS[2:0] in the PWR_CR register.
0: PVD interrupt disconnected from TIM1/8/15/16/17 Break input. PVDE and
PLS[2:0] bits can be programmed by the application.
1: PVD interrupt connected to TIM1/8/15/16/17 Break input, PVDE and PLS[2:0]
bits are read only.
Bit 1 SRAM_PARITY_LOCK: SRAM parity lock bit
This bit is set by software and cleared by a system reset. It can be used to
enable and lock the SRAM parity error signal connection to TIM1/8/15/16/17
Break inputs.
0: SRAM parity error signal disconnected from TIM1/8/15/16/17 Break inputs
1: SRAM parity error signal connected to TIM1/8/15/16/17 Break inputs
Bit 0 LOCKUP_LOCK: Cortex®-M4 LOCKUP (Hardfault) output enable bit
This bit is set by software and cleared by a system reset. It can be use to enable
and lock the connection of Cortex®-M4 LOCKUP (Hardfault) output to
TIM1/15/16/17 Break input.
0: Cortex®-M4 LOCKUP output disconnected from TIM1/8/15/16/17 Break
inputs.
1: Cortex®-M4 LOCKUP output connected to TIM1/8/15/16/17 Break inputs

256/1141

DocID022558 Rev 8

RM0316

System configuration controller (SYSCFG)

12.1.8

SYSCFG configuration register 3 (SYSCFG_CFGR3)

Note:

This register is available in STM32F303x6/x8 and STM32F328 devices only.
Address offset: 0x50
System reset value: 0x0000 0200

31

30

29

28

27

26

25

24

23

22

21

20

19

18

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

15

14

13

12

11

10

9

8

7

6

5

4

3

2

Res

Res

Res

Res

Res

Res

ADC2_DMA_
RMP
rw

I2C1_TX_DMA_ I2C1_RX_DMA_ SPI1_TX_DMA_
RMP
RMP
RMP
rw

rw

rw

17

16

1

0

SPI1_RX_DMA_
RMP
rw

Bits 31:10 Reserved, must be kept at reset value
Bit 9 ADC2_DMA_RMP[1]: ADC2 DMA controller remapping bit
0: ADC2 mapped on DMA2
1: ADC2 mapped on DMA1
Bit 8 ADC2_DMA_RMP[0]: ADC2 DMA channel remapping bit
0: ADC2 mapped on DMA1 channel 2
1: ADC2 mapped on DMA1 channel 4
Bits 7:6 I2C1_TX_DMA_RMP: I2C1_TX DMA remapping bit
This bit is set and cleared by software. It defines on which DMA1 channel I2C1_TX
is mapped.
00: I2C1_TX mapped on DMA1 CH6
01: I2C1_TX mapped on DMA1 CH2
10: I2C1_TX mapped on DMA1 CH4
11: I2C1_TX mapped on DMA1 CH6

DocID022558 Rev 8

257/1141
262

System configuration controller (SYSCFG)

RM0316

Bits 5:4 I2C1_RX_DMA_RMP: I2C1_RX DMA remapping bit
This bit is set and cleared by software. It defines on which DMA1 channel I2C1_RX
is mapped.
00: I2C1_RX mapped on DMA1 CH7
01: I2C1_RX mapped on DMA1 CH3
10: I2C1_RX mapped on DMA1 CH5
11: I2C1_RX mapped on DMA1 CH7
Bits 3:2 SPI1_TX_DMA_RMP: SPI1_TX DMA remapping bit
This bit is set and cleared by software. It defines on which DMA1 channel SPI1_TX
is mapped.
00: SPI1_TX mapped on DMA1 CH3
01: SPI1_TX mapped on DMA1 CH5
10: SPI1_TX mapped on DMA1 CH7
11: SPI1_TX mapped on DMA1 CH3
Bits 1:0 SPI1_RX_DMA_RMP: SPI1_RX DMA remapping bit
This bit is set and cleared by software. It defines on which DMA1 channel
SPI1_RXis mapped.
00: SPI1_RX mapped on DMA1 CH2
01: SPI1_RX mapped on DMA1 CH4
10: SPI1_RX mapped on DMA1 CH6
11: SPI1_RX mapped on DMA1 CH2

12.1.9

SYSCFG configuration register 4 (SYSCFG_CFGR4)

Note:

This register is available in STM32F303xD/E and STM32F398xE devices only.
SYSCFG_CFGR4 is added allowing to remap the triggers of the ADCs, mainly the new
TIM20 events.
Address offset: 0x48
System 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

ADC34 ADC34
ADC12
ADC34 ADC34 ADC34 ADC34
ADC12 ADC12 ADC12 ADC12 ADC12 ADC12_ ADC12_
_JEXT _JEXT
_JEXT
_JEXT _EXT1 _EXT6 _EXT5
_JEXT _JEXT _EXT1 _EXT1 _EXT5 EXT3_R EXT2_R
14_RM 11_RM
13_RM
5_RMP 5_RMP _RMP _RMP
6_RMP 3_RMP 5_RMP 3_RMP _RMP
MP
MP
P
P
P
rw

258/1141

rw

rw

rw

rw

rw

rw

rw

DocID022558 Rev 8

rw

rw

rw

rw

rw

rw

RM0316

System configuration controller (SYSCFG)

Bits 31:14 Reserved, must be kept at reset value
Bit 13 ADC34_JEXT14_RMP - Controls the Input trigger of ADC34 injected channel
JEXT14:
0: Trigger source is TIM7_TRGO
1: Trigger source is TIM20_CC2
Bit 12 ADC34_JEXT11_RMP - Controls the Input trigger of ADC34 injected channel
JEXT11:
0: Trigger source is TIM1_CC3
1: Trigger source is TIM20_TRGO2
Bit 11 ADC34_JEXT5_RMP - Controls the Input trigger of ADC34 injected channel
JEXT5:
0: Trigger source is TIM4_CC3
1: Trigger source is TIM20_TRGO
Bit 10 ADC34_EXT15_RMP - Controls the Input trigger of ADC34 regular channel
EXT15:
0: Trigger source is TIM2_CC1
1: Trigger source is TIM20_CC1
Bit 9 ADC34_EXT6_RMP - Controls the Input trigger of ADC34 regular channel EXT6:
0: Trigger source is TIM4_CC1
1: Trigger source is TIM20_TRGO2
Bit 8 ADC34_EXT5_RMP - Controls the Input trigger of ADC34 regular channel EXT5:
0: Trigger source is EXTI line 2 when reset at ‘0’
1: Trigger source is TIM20_TRGO
Bit 7 ADC12_JEXT13_RMP - Controls the Input trigger of ADC12 injected channel
JEXT13:
0: Trigger source is TIM3_CC1
1: Trigger source is TIM20_CC4
Bit 6 ADC12_JEXT6_RMP - Controls the Input trigger of ADC12 injected channel
JEXT6:
0: Trigger source is EXTI line 15
1: Trigger source is TIM20_TRGO2
Bit 5 ADC12_JEXT3_RMP - Controls the Input trigger of ADC12 injected channel
EXT3:
0: Trigger source is TIM2_CC1
1: Trigger source is TIM20_TRGO
Bit 4 ADC12_EXT15_RMP - Controls the Input trigger of ADC12 regular channel
EXT15:
0: Trigger source is TIM3_CC4
1: Trigger source is TIM20_CC3
Bit 3 ADC12_EXT13_RMP - Controls the Input trigger of ADC12 regular channel
EXT13:
0: Trigger source is TIM6_TRGO
1: Trigger source is TIM20_CC2

DocID022558 Rev 8

259/1141
262

System configuration controller (SYSCFG)

RM0316

Bit 2 ADC12_EXT5_RMP - Controls the Input trigger of ADC12 regular channel EXT5
0: Trigger source is TIM4_CC4
1: Trigger source is TIM20_CC1
Bit 1 ADC12_EXT3_RMP - Controls the Input trigger of ADC12 regular channel EXT3:
0: Trigger source is TIM2_CC2
1: Trigger source is TIM20_TRGO2
Bit 0 ADC12_EXT2_RMP - Controls the Input trigger of ADC12 regular channel EXT2:
0: Trigger source is TIM1_CC3
1: Trigger source is TIM20_TRGO

260/1141

DocID022558 Rev 8

0x50

SYSCFG_CFGR3

Reset value

DocID022558 Rev 8
0
0

0

0

0

0

0

0

1

0

EXTI6[3:0]
0
0

0
0

Reset value

0

0

0

0
0

0
0

0
0

0

0

0

0

EXTI1[3:0]
0
0

EXTI5[3:0]
0
0

EXTI9[3:0]
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0
0

.
.

0

0

LOCKUP_LOCK

EXTI10[3:0]

0

0

EXTI2[3:0]

0
0

0

0

0

0
0
0

0

0

SPI1_RX_DMA_RMP

EXTI7[3:0]

0

0

PVD_LOCK

EXTI11[3:0]

0
0

0

0

SRAM_PARITY_LOCK

0

0

0

SPI1_TX_DMA_RMP

18
17
16
15
14
13
12
11
10

I2C_PB7_FMP
I2C_PB6_FMP
DAC2_CH1_DMA_RMP
TIM7_DAC2_DMA_RMP
TIM6_DAC1_DMA_RMP
TIM17_DMA_RMP
TIM16_DMA_RMP
Res

0

Res.

19
I2C_PB8_FMP

0

BYP_ADDR_PAR

20
I2C_PB9_FMP

0

I2C1_RX_DMA_RMP

21
I2C1_FMP

0

Res.
Res.
Res.
Res.
Res.
Res.
Res.

7
6
5
4
3
2

DAC_TRIG_RMP
TIM1_ITR3_RMP
USB_IT_RMP
Res
Res
Res

0
0
0

0

0

0

0

0

1

8
0

MEM_MODE

9
Res
ADC24_DMA_RMP

22
I2C2_FMP

0

Res.

23

24
ENCODER_MODE [1:0]

25
Res

0

Res.

Res.

Res

26

27

0

Res.

Res.

28

0

Res.

Res.

29

0

Res.

Res.

30

0

I2C1_TX_DMA_RMP

Res.

31

0

Res.

Res.

0

SRAM_PEF

Res.

0

ADC2_DMA_RMP

EXTI12[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI3[3:0]

0

Res.

EXTI13[3:0]

Res.

0

0

0

Res.
EXTI14[3:0]

Res.

0

0

Res.

Reset value
EXTI15[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

.
.
.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SYSCFG_RCR

Res.

0

Res.

1

Res.

1

Res.

1

Res.

Res.

Res.

Res.

1

Res.

Res.

Res.

Res.

Res.

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.
FPU_IE[5..0]

Res.

Res.

Res.

Res.

Res.

Res.

0x00

Res.

Res.

Res.

.
.
.
SYSCFG_CFGR2

Res.

0x18
SYSCFG_EXTICR4

Res.

0x14
SYSCFG_EXTICR3

Res.

0x10
SYSCFG_EXTICR2

Res.

0x0C
SYSCFG_EXTICR1

Res.

0x08

Res.

SYSCFG_CFGR1

Res.

0x04
Register

Res.

Offset

Res.

12.1.10

Res.

RM0316
System configuration controller (SYSCFG)

SYSCFG register map

The following table gives the SYSCFG register map and the reset values.
Table 74. SYSCFG register map and reset values

X X

PAGE[15:0]_WP
0
0

EXTI0[3:0]
0
0

EXTI4[3:0]
0
0

EXTI8[3:0]
0
0

0

261/1141

262

262/1141

DocID022558 Rev 8

6
5
4
3
2
1
0

ADC12_JEXT3_RMP
ADC12_EXT15_RMP
ADC12_EXT13_RMP
ADC12_EXT5_RMP
ADC12_EXT3_RMP
ADC12_EXT2_RMP

15
Res.

7

16
Res.

ADC12_JEXT6_RMP

17
Res.

ADC12_JEXT13_RMP

18
Res.

8

19
Res.

9

20
Res.

ADC34_EXT5_RMP

21
Res.

ADC34_EXT6_RMP

22
Res.

11

23
Res.

10

24
Res.

ADC34_EXT15_RMP

25
Res.

12

26
Res.

ADC34_JEXT5_RMP

27
Res.

13

28
Res.

ADC34_JEXT11_RMP

29
Res.

14

Reset value
ADC34_JEXT14_RMP

30

SYSCFG_CFGR4
Res.

31

0x48
Register

Res.

Offset

Res.

System configuration controller (SYSCFG)
RM0316

Table 74. SYSCFG register map and reset values (continued)

0
0
0
0
0
0
0
0
0
0
0
0
0
0

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

RM0316

Direct memory access controller (DMA)

13

Direct memory access controller (DMA)

13.1

Introduction
Direct memory access (DMA) is used in order to provide high-speed data transfer between
peripherals and memory as well as memory to memory. Data can be quickly moved by DMA
without any CPU actions. This keeps CPU resources free for other operations.
The STM32F303xB/C/D/E, STM32F398xC and STM32F398xE devices have two DMA
controllers with 12 channels in total, The STM32F303x6/8 and STM32F328x8 has 1 DMA
controller with 7 channels. Each channel is dedicated to managing memory access requests
from one or more peripherals. Each has an arbiter for handling the priority between DMA
requests.

13.2

13.3

DMA main features
•

12 independently configurable channels (requests) on STM32F302xB/C/D/E and
STM32F302x6/8 devices and 7 independently configurable channels (requests) on
STM32F303x6/8 and STM32F328x8 devices

•

Each channel is connected to dedicated hardware DMA requests, software trigger is
also supported on each channel. This configuration is done by software.

•

Priorities between requests from channels of one DMA are software programmable (4
levels consisting of very high, high, medium, low) or hardware in case of equality
(request 1 has priority over request 2, etc.)

•

Independent source and destination transfer size (byte, half word, word), emulating
packing and unpacking. Source/destination addresses must be aligned on the data
size.

•

Support for circular buffer management

•

3 event flags (DMA Half Transfer, DMA Transfer complete and DMA Transfer Error)
logically ORed together in a single interrupt request for each channel

•

Memory-to-memory transfer

•

Peripheral-to-memory and memory-to-peripheral, and peripheral-to-peripheral
transfers

•

Access to Flash, SRAM, APB and AHB peripherals as source and destination

•

Programmable number of data to be transferred: up to 65535

DMA implementation
This manual describes the full set of features implemented in DMA1. DMA2 supports a
smaller number of channels, but is otherwise identical to DMA1.
Table 75. DMA implementation
Feature
Number of DMA channels

DMA1

DMA2(1)

7

5

1. DMA2 is not available on STM32F303x6/8 and STM32F328x8 devices.

DocID022558 Rev 8

263/1141
284

Direct memory access controller (DMA)

13.4

RM0316

DMA functional description
The block diagram is shown in the following figure.
Figure 46. DMA block diagram
,&RGH
)ODVK

)/,7)

'&RGH
&RUWH[0
6\VWHP

,&RGH65$0 . 
'&RGH65$0 .

&K

'0$

%XVPDWUL[

'0$

*3,2$%&'()
$'&V
&5&

76
%ULGJH

&K
$+%6\VWHPEXV
&K
'0$

%ULGJH

'0$



5HVHW FORFNFRQWURO
5&&

&K
&K
&K

'0$UHTXHVW

$3%

6<6&)* 7,0
86$57 7,0
7,0
63,
7,0
7,0
'$&
3:5
%.3
E[&$1
86%
,&
,&
8$57
8$57
86$57
86$57

$3%

63,,6
63,,6
,:'*
::'*
57&
7,0
7,0
7,0
7,0
7,0

'0$UHTXHVW
069

1. DMA2 is not available in STM32F303x6/8 and STM32F328x8 devices.

The DMA controller performs direct memory transfer by sharing the system bus with the
Cortex-M4®F core. The DMA request may stop the CPU access to the system bus for some
bus cycles, when the CPU and DMA are targeting the same destination (memory or
peripheral). The bus matrix implements round-robin scheduling, thus ensuring at least half
of the system bus bandwidth (both to memory and peripheral) for the CPU.

13.4.1

DMA transactions
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 is sent to the peripheral by the DMA
Controller. The peripheral releases its request as soon as it gets the Acknowledge from the
DMA Controller. Once the request is de-asserted by the peripheral, the DMA Controller

264/1141

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)
release the Acknowledge. If there are more requests, the peripheral can initiate the next
transaction.
In summary, each DMA transfer consists of three operations:

13.4.2

•

The loading of data from the peripheral data register or a location in memory addressed
through an internal current peripheral/memory address register. The start address used
for the first transfer is the base peripheral/memory address programmed in the
DMA_CPARx or DMA_CMARx register.

•

The storage of the data loaded to the peripheral data register or a location in memory
addressed through an internal current peripheral/memory address register. The start
address used for the first transfer is the base peripheral/memory address programmed
in the DMA_CPARx or DMA_CMARx register.

•

The post-decrementing of the DMA_CNDTRx register, which contains the number of
transactions that have still to be performed.

Arbiter
The arbiter manages the channel requests based on their priority and launches the
peripheral/memory access sequences.
The priorities are managed in two stages:
•

Software: each channel priority can be configured in the DMA_CCRx register. There
are four levels:
–

•

13.4.3

Very high priority

–

High priority

–

Medium priority

–

Low priority

Hardware: if 2 requests have the same software priority level, the channel with the
lowest number will get priority versus the channel with the highest number. For
example, channel 2 gets priority over channel 4.

DMA channels
Each channel can handle DMA transfer between a peripheral register located at a fixed
address and a memory address. The amount of data to be transferred (up to 65535) is
programmable. The register which contains the amount of data items to be transferred is
decremented after each transaction.

Programmable data sizes
Transfer data sizes of the peripheral and memory are fully programmable through the
PSIZE and MSIZE bits in the DMA_CCRx register.

Pointer incrementation
Peripheral and memory pointers can optionally be automatically post-incremented after
each transaction depending on the PINC and MINC bits in the DMA_CCRx register. If
incremented mode is enabled, the address of the next transfer will be the address of the
previous one incremented by 1, 2 or 4 depending on the chosen data size. The first transfer
address is the one programmed in the DMA_CPARx/DMA_CMARx registers. During
transfer operations, these registers keep the initially programmed value. The current

DocID022558 Rev 8

265/1141
284

Direct memory access controller (DMA)

RM0316

transfer addresses (in the current internal peripheral/memory address register) are not
accessible by software.
If the channel is configured in non-circular mode, no DMA request is served after the last
transfer (that is once the number of data items to be transferred has reached zero). In order
to reload a new number of data items to be transferred into the DMA_CNDTRx register, the
DMA channel must be disabled.
Note:

If a DMA channel is disabled, the DMA registers are not reset. The DMA channel registers
(DMA_CCRx, DMA_CPARx and DMA_CMARx) retain the initial values programmed during
the channel configuration phase.
In circular mode, after the last transfer, the DMA_CNDTRx register is automatically reloaded
with the initially programmed value. The current internal address registers are reloaded with
the base address values from the DMA_CPARx/DMA_CMARx registers.

Channel configuration procedure
The following sequence should be followed to configure a DMA channel x (where x is the
channel number).
1.

Set the peripheral register address in the DMA_CPARx register. The data will be
moved from/ to this address to/ from the memory after the peripheral event.

2.

Set the memory address in the DMA_CMARx register. The data will be written to or
read from this memory after the peripheral event.

3.

Configure the total number of data to be transferred in the DMA_CNDTRx register.
After each peripheral event, this value will be decremented.

4.

Configure the channel priority using the PL[1:0] bits in the DMA_CCRx register

5.

Configure data transfer direction, circular mode, peripheral & memory incremented
mode, peripheral & memory data size, and interrupt after half and/or full transfer in the
DMA_CCRx register

6.

Activate the channel by setting the ENABLE bit in the DMA_CCRx register.

As soon as the channel is enabled, it can serve any DMA request from the peripheral
connected on the channel.
Once half of the bytes are transferred, 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.

Circular mode
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_CCRx register.
When circular mode is activated, the number of data to be transferred is automatically
reloaded with the initial value programmed during the channel configuration phase, and the
DMA requests continue to be served.

Memory-to-memory mode
The DMA channels can also work without being triggered by a request from a peripheral.
This mode is called Memory to Memory mode.
If the MEM2MEM bit in the DMA_CCRx register is set, then the channel initiates transfers
as soon as it is enabled by software by setting the Enable bit (EN) in the DMA_CCRx

266/1141

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)
register. The transfer stops once the DMA_CNDTRx register reaches zero. Memory to
Memory mode may not be used at the same time as Circular mode.

13.4.4

Programmable data width, data alignment and endians
When PSIZE and MSIZE are not equal, the DMA performs some data alignments as
described in Table 76: Programmable data width & endian behavior (when bits PINC =
MINC = 1).

Table 76. Programmable data width & endian behavior (when bits PINC = MINC = 1)
Number
Source
of data
Destination
port
items to
port width
width
transfer
(NDT)

Source content:
address / data

Transfer operations

Destination
content:
address / data

8

8

4

@0x0 / B0
@0x1 / B1
@0x2 / B2
@0x3 / B3

1: READ B0[7:0] @0x0 then WRITE B0[7:0] @0x0
2: READ B1[7:0] @0x1 then WRITE B1[7:0] @0x1
3: READ B2[7:0] @0x2 then WRITE B2[7:0] @0x2
4: READ B3[7:0] @0x3 then WRITE B3[7:0] @0x3

@0x0 / B0
@0x1 / B1
@0x2 / B2
@0x3 / B3

8

16

4

@0x0 / B0
@0x1 / B1
@0x2 / B2
@0x3 / B3

1: READ B0[7:0] @0x0 then WRITE 00B0[15:0] @0x0
2: READ B1[7:0] @0x1 then WRITE 00B1[15:0] @0x2
3: READ B2[7:0] @0x2 then WRITE 00B2[15:0] @0x4
4: READ B3[7:0] @0x3 then WRITE 00B3[15:0] @0x6

@0x0 / 00B0
@0x2 / 00B1
@0x4 / 00B2
@0x6 / 00B3

8

32

4

@0x0 / B0
@0x1 / B1
@0x2 / B2
@0x3 / B3

1: READ B0[7:0] @0x0 then WRITE 000000B0[31:0] @0x0
2: READ B1[7:0] @0x1 then WRITE 000000B1[31:0] @0x4
3: READ B2[7:0] @0x2 then WRITE 000000B2[31:0] @0x8
4: READ B3[7:0] @0x3 then WRITE 000000B3[31:0] @0xC

@0x0 / 000000B0
@0x4 / 000000B1
@0x8 / 000000B2
@0xC / 000000B3

16

8

4

@0x0 / B1B0
@0x2 / B3B2
@0x4 / B5B4
@0x6 / B7B6

1: READ B1B0[15:0] @0x0 then WRITE B0[7:0] @0x0
2: READ B3B2[15:0] @0x2 then WRITE B2[7:0] @0x1
3: READ B5B4[15:0] @0x4 then WRITE B4[7:0] @0x2
4: READ B7B6[15:0] @0x6 then WRITE B6[7:0] @0x3

@0x0 / B0
@0x1 / B2
@0x2 / B4
@0x3 / B6

16

16

4

@0x0 / B1B0
@0x2 / B3B2
@0x4 / B5B4
@0x6 / B7B6

1: READ B1B0[15:0] @0x0 then WRITE B1B0[15:0] @0x0
2: READ B3B2[15:0] @0x2 then WRITE B3B2[15:0] @0x2
3: READ B5B4[15:0] @0x4 then WRITE B5B4[15:0] @0x4
4: READ B7B6[15:0] @0x6 then WRITE B7B6[15:0] @0x6

@0x0 / B1B0
@0x2 / B3B2
@0x4 / B5B4
@0x6 / B7B6

16

32

4

@0x0 / B1B0
@0x2 / B3B2
@0x4 / B5B4
@0x6 / B7B6

1: READ B1B0[15:0] @0x0 then WRITE 0000B1B0[31:0] @0x0
2: READ B3B2[15:0] @0x2 then WRITE 0000B3B2[31:0] @0x4
3: READ B5B4[15:0] @0x4 then WRITE 0000B5B4[31:0] @0x8
4: READ B7B6[15:0] @0x6 then WRITE 0000B7B6[31:0] @0xC

@0x0 / 0000B1B0
@0x4 / 0000B3B2
@0x8 / 0000B5B4
@0xC / 0000B7B6

32

8

4

@0x0 / B3B2B1B0
@0x4 / B7B6B5B4
@0x8 / BBBAB9B8
@0xC / BFBEBDBC

1: READ B3B2B1B0[31:0] @0x0 then WRITE B0[7:0] @0x0
2: READ B7B6B5B4[31:0] @0x4 then WRITE B4[7:0] @0x1
3: READ BBBAB9B8[31:0] @0x8 then WRITE B8[7:0] @0x2
4: READ BFBEBDBC[31:0] @0xC then WRITE BC[7:0] @0x3

@0x0 / B0
@0x1 / B4
@0x2 / B8
@0x3 / BC

32

16

4

@0x0 / B3B2B1B0
@0x4 / B7B6B5B4
@0x8 / BBBAB9B8
@0xC / BFBEBDBC

1: READ B3B2B1B0[31:0] @0x0 then WRITE B1B0[7:0] @0x0
2: READ B7B6B5B4[31:0] @0x4 then WRITE B5B4[7:0] @0x1
3: READ BBBAB9B8[31:0] @0x8 then WRITE B9B8[7:0] @0x2
4: READ BFBEBDBC[31:0] @0xC then WRITE BDBC[7:0] @0x3

@0x0 / B1B0
@0x2 / B5B4
@0x4 / B9B8
@0x6 / BDBC

32

32

4

@0x0 / B3B2B1B0
@0x4 / B7B6B5B4
@0x8 / BBBAB9B8
@0xC / BFBEBDBC

@0x0 / B3B2B1B0
1: READ B3B2B1B0[31:0] @0x0 then WRITE B3B2B1B0[31:0] @0x0
2: READ B7B6B5B4[31:0] @0x4 then WRITE B7B6B5B4[31:0] @0x4
@0x4 / B7B6B5B4
3: READ BBBAB9B8[31:0] @0x8 then WRITE BBBAB9B8[31:0] @0x8 @0x8 / BBBAB9B8
4: READ BFBEBDBC[31:0] @0xC then WRITE BFBEBDBC[31:0] @0xC @0xC / BFBEBDBC

DocID022558 Rev 8

267/1141
284

Direct memory access controller (DMA)

RM0316

Addressing an AHB peripheral that does not support byte or halfword
write operations
When the DMA initiates an AHB byte or halfword write operation, the data are duplicated on
the unused lanes of the HWDATA[31:0] bus. So when the used AHB slave peripheral does
not support byte or halfword write operations (when HSIZE is not used by the peripheral)
and does not generate any error, the DMA writes the 32 HWDATA bits as shown in the two
examples below:
•

To write the halfword “0xABCD”, the DMA sets the HWDATA bus to “0xABCDABCD”
with HSIZE = HalfWord

•

To write the byte “0xAB”, the DMA sets the HWDATA bus to “0xABABABAB” with
HSIZE = Byte

Assuming that the AHB/APB bridge is an AHB 32-bit slave peripheral that does not take the
HSIZE data into account, it will transform any AHB byte or halfword operation into a 32-bit
APB operation in the following manner:
•

An AHB byte write operation of the data “0xB0” to 0x0 (or to 0x1, 0x2 or 0x3) will be
converted to an APB word write operation of the data “0xB0B0B0B0” to 0x0

•

An AHB halfword write operation of the data “0xB1B0” to 0x0 (or to 0x2) will be
converted to an APB word write operation of the data “0xB1B0B1B0” to 0x0

For instance, to write the APB backup registers (16-bit registers aligned to a 32-bit address
boundary), the software must configure the memory source size (MSIZE) to “16-bit” and the
peripheral destination size (PSIZE) to “32-bit”.

13.4.5

Error management
A DMA transfer error can be generated by reading from or writing to a reserved address
space. When a DMA transfer error occurs during a DMA read or a write access, the faulty
channel is automatically disabled through a hardware clear of its EN bit in the corresponding
Channel configuration register (DMA_CCRx). The channel's transfer error interrupt flag
(TEIF) in the DMA_IFR register is set and an interrupt is generated if the transfer error
interrupt enable bit (TEIE) in the DMA_CCRx register is set.

13.4.6

DMA interrupts
An interrupt can be produced on a Half-transfer, Transfer complete or Transfer error for
each DMA channel. Separate interrupt enable bits are available for flexibility.
Table 77. DMA interrupt requests
Interrupt event

13.4.7

Event flag

Enable control bit

Half-transfer

HTIF

HTIE

Transfer complete

TCIF

TCIE

Transfer error

TEIF

TEIE

DMA request mapping
DMA1 controller
The hardware requests from the peripherals (TIMx(x=1...4, 6, 7, 15..17), ADC1, ADC2,
SPI1, SPI2/I2S, I2Cx(x=1,2), DAC1_Channel[1,2], DAC2_Channel[1] and USARTx

268/1141

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)
(x=1..3)) are simply logically ORed before entering the DMA1. This means that on one
channel, only one request must be enabled at a time. Refer to Figure 47:
STM32F302xB/C/D/E and STM32F302x6/8 DMA1 request mapping and Figure 48:
STM32F303x6/8 and STM32F328x8 DMA1 request mapping.
The peripheral DMA requests can be independently activated/de-activated by programming
the DMA control bit in the registers of the corresponding peripheral.

DocID022558 Rev 8

269/1141
284

Direct memory access controller (DMA)

RM0316

Figure 47. STM32F302xB/C/D/E and STM32F302x6/8 DMA1 request mapping
3HULSKHUDOUHTXHVWVLJQDOV

'0$

)L[HGKDUGZDUHSULRULW\
+LJKSULRULW\

!$#
4)-?#(
4)-?#(
4)-?#(
4)-?50

30)?28
53!24?48
4)-?#(
4)-?50
4)-?#(

30)?48
53!24?28
4)-?#(
4)-?#(
4)-?50
4)-?50
$!#?#( 
4)-?#(
30)?28
4)-?50
53!24?48
)#?48
4)-?#(
4)-?42)'
4)-?#/4)-?#(
4)-?50
30)?48
$!#?#(  53!24?28
)#?28
4)-?50
4)-?#(
4)-?#(
4)-?#(
4)-?50
53!24?28
4)-?42)'
)#?48
4)-?#/4)-?#(
4)-?#(
4)-?42)'
4)-?#(
4)-?50
53!24?48
)#?28
4)-?#(
4)-?#(
4)-?50
4)-?#(
4)-?50 

+:UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW

+:UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW

+:UHTXHVW

,QWHUQDO
'0$
UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW

+:UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW

+:UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW

+:UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW

+:UHTXHVW
6:WULJJHU 
0(00(0ELW

&KDQQHO

/RZSULRULW\
069

1. DMA requests are mapped on this DMA channel only if the corresponding remapping bit is set in the
SYSCFG_CFGR1 register. For more details, please refer to Section 12.1.1: SYSCFG configuration
register 1 (SYSCFG_CFGR1) on page 245.

270/1141

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)
Figure 48. STM32F303x6/8 and STM32F328x8 DMA1 request mapping
3HULSKHUDOUHTXHVWVLJQDOV

'0$

)L[HGKDUGZDUHSULRULW\

+LJKSULRULW\
$'&
7,0B&+
7,0B&+
7,0B83

+:UHTXHVW
6:WULJJHU
0(00(0ELW

63,B5;
86$57B7;
7,0B&+
7,0B83
7,0B&+
$'&
,&B7;
63,B7;
86$57B5;
7,0B&+
7,0B83
'$&B&+
7,0B&+
7,0B83
,&B5;

&KDQQHO

+:UHTXHVW

&KDQQHO

6:WULJJHU
0(00(0ELW

+:UHTXHVW



63,B5;
86$57B7;
,&B7;
7,0B&+
7,0B75,*
7,0B&20
7,0B83


63,B7;
'$&B&+
86$57B5;
$'&
,&B5;
7,0B83
7,0B&+
'$&B&+
7,0B&+
7,0B83
86$57B5;
7,0B75,*
,&B7;
7,0B&20
7,0B&+
7,0B&+
7,0B75,*
7,0B&+
7,0B83 
63,B5;
86$57B7;
,&B5;
7,0B&+
7,0B&+
7,0B&+

7,0B83
63,B7;

,QWHUQDO
'0$
UHTXHVW

&KDQQHO

6:WULJJHU
0(00(0ELW

+:UHTXHVW

&KDQQHO

6:WULJJHU
0(00(0ELW

+:UHTXHVW

&KDQQHO

6:WULJJHU
0(00(0ELW

+:UHTXHVW

&KDQQHO

6:WULJJHU
0(00(0ELW

+:UHTXHVW
6:WULJJHU
0(00(0ELW

&KDQQHO

/RZSULRULW\
069

1. TIM6_UP, DAC1_CH1, TIM7_UP, DAC1_CH2, TIM16_CH1, TIM16_UP, TIM17_CH1, TIM17_UP,
DAC2_CH1, I2C1, SPI1 and DMA request are mapped on this DMA channel only if the corresponding
remapping bit is set in the SYSCFG_CFGR1 or SYSCFG_CFGR3 register. For more details, please refer
to Section 12.1.1: SYSCFG configuration register 1 (SYSCFG_CFGR1) on page 245 and Section 12.1.8:

DocID022558 Rev 8

271/1141
284

Direct memory access controller (DMA)

RM0316

SYSCFG configuration register 3 (SYSCFG_CFGR3) on page 257.
2. SPI1_TX_DMA_RMP[1:0] bits in SYSCFG configuration register 2 (SYSCFG_CFGR2) allow remapping of
SPI1_TX on channel 5 and 7.

Table 78. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE summary of DMA1 requests
for each channel
Peripherals

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel6

Channel7

ADC

ADC1

-

-

-

-

-

-

SPI

-

SPI1_RX

SP1_TX

SPI2_RX

SPI2_TX

-

-

USART

-

USART3_
TX

USART3_RX

USART1_
TX

USART1_
RX

I2C

I2C3_TX(1)

I2C3_RX(1)

-

I2C2_TX

I2C2_RX

I2C1_TX

I2C1_RX

TIM1

-

TIM1_CH1

TIM1_CH2

TIM1_CH4
TIM1_TRIG
TIM1_COM

TIM1_UP

TIM1_CH3

-

TIM2

TIM2_CH3

TIM2_UP

-

-

TIM2_CH1

-

TIM2_CH2
TIM2_CH4

TIM3

-

TIM3_CH3

TIM3_CH4
TIM3_UP

-

-

TIM3_CH1
TIM3_TRIG

-

TIM4

TIM4_CH1

-

-

TIM4_CH2

TIM4_CH3

-

TIM4_UP

TIM6 / DAC

-

-

TIM6_UP
DAC_CH1 (2)

-

-

-

-

TIM7/DAC

-

-

-

TIM7_UP
DAC_CH2

-

-

-

-

-

-

(2)

USART2_RX USART2_TX

TIM15

-

-

-

-

TIM15_CH1
TIM15_UP
TIM15_TRIG
TIM15_COM

TIM16

-

-

TIM16_CH1
TIM16_UP

-

-

TIM16_CH1
TIM16_UP

TIM17

TIM17_CH1
TIM17_UP

-

-

-

-

-

(2)

TIM17_CH1
TIM17_UP(2)

1. Available in STM32F303xD/E only.
2. DMA request mapped on this DMA channel only if the corresponding remapping bit is set in the SYSCFG_CFGR1 register.
For more details, please refer to Section 12.1.1: SYSCFG configuration register 1 (SYSCFG_CFGR1) on page 245.

Table 79. STM32F303x6/8 and STM32F328x8 summary of DMA1 requests for each
channel
Peripheral

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel6

Channel7

ADC

ADC1

ADC2

-

ADC2(1)

-

-

-

SPI1_TX

(1)

(1)

SPI1_RX

SPI1_TX(1)

SPI

-

SPI1_RX

SP1_TX

USART

-

USART3
_TX

USART3
_RX

USART1_TX

USART1
_RX

USART2
_RX

USART2_TX

I2C

-

I2C1_TX(1)

I2C1_RX(1)

I2C1_TX(1)

I2C1_RX(1)

I2C1_TX

I2C1_RX

272/1141

SPI1_RX

(1)

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)
Table 79. STM32F303x6/8 and STM32F328x8 summary of DMA1 requests for each
channel (continued)

Peripheral

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel6

Channel7

TIM1

-

TIM1_CH1

TIM1_CH2

TIM1_CH4
TIM1_TRIG
TIM1_COM

TIM1_UP

TIM1_CH3

-

TIM2

TIM2_CH3

TIM2_UP

-

-

TIM2_CH1

-

TIM2_CH2
TIM2_CH4

TIM3

-

TIM3_CH3

TIM3_CH4
TIM3_UP

-

-

TIM3_CH1
TIM3_TRIG

-

TIM6/DAC

-

-

TIM6_UP
DAC1_CH1

-

-

-

-

TIM7/DAC

-

-

-

TIM7_UP
DAC2_CH2

-

-

-

DAC

-

-

-

-

DAC2_CH1(1)

-

-

-

-

(1)

(1)

TIM15

-

-

-

-

TIM15_CH1
TIM15_UP
TIM15_TRIG
TIM15_COM

TIM16

-

-

TIM16_CH1
TIM16_UP

-

-

TIM16_CH1
TIM16_UP(1)

-

TIM17

TIM17_CH1
TIM17_UP

-

-

-

-

-

TIM17_CH1
TIM17_UP(1)

1. DMA request mapped on this DMA channel only if the corresponding remapping bit is set in the SYSCFG_CFGR1 or
SYSCFGR3 register. For more details, please refer to Section 12.1.1: SYSCFG configuration register 1
(SYSCFG_CFGR1) on page 245 and Section 12.1.8: SYSCFG configuration register 3 (SYSCFG_CFGR3) on page 257.

DMA2 controller
The five requests from the peripherals (TIMx (x= 6,7,8), ADCx (x=2,3,4), SPI/I2S3, UART4,
DAC_Channel[1,2] ) are simply logically ORed before entering the DMA2, this means that
only one request must be enabled at a time. Refer to Figure 49: STM32F303xB/C/D/E,
STM32F358xC and STM32F398xE DMA2 request mapping.
The peripheral DMA requests can be independently activated/de-activated by programming
the DMA control bit in the registers of the corresponding peripheral.

DocID022558 Rev 8

273/1141
284

Direct memory access controller (DMA)

RM0316

Figure 49. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE DMA2 request
mapping
3HULSKHUDOUHTXHVWVLJQDOV

'0$

)L[HGKDUGZDUHSULRULW\
+LJKSULRULW\

!$#
30)?28
4)-?#(
4)-?50

+:UHTXHVW
6:WULJJHU 
0(00(0ELW

!$#
30)?48
4)-?#(
4)-?42)'
4)-?#/-

!$#
5!24?28
4)-?50
$!#?#(
4)-?#(

&KDQQHO

+:UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW



!$#
4)-?50
$!#?#(

+:UHTXHVW

,QWHUQDO
'0$
UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW



!$#
5!24?48
4)-?#(

+:UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW

+:UHTXHVW

&KDQQHO

6:WULJJHU 
0(00(0ELW

/RZSULRULW\
069

1. DMA request mapped on this DMA channel only if the corresponding remapping bit is set in the
SYSCFG_CFGR1 register. For more details, please refer to Section 12.1.1: SYSCFG configuration
register 1 (SYSCFG_CFGR1) on page 245.

274/1141

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)
Table 80 lists the DMA requests for each channel.

Table 80. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE summary of DMA2 requests
for each channel
Peripherals

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

ADC

ADC2

ADC4

ADC2(1)

ADC4(1)

ADC3

SPI

SPI3_RX

SPI3_TX

-

SPI4_RX(2)

SPI4_TX(2)

UART4

-

-

UART4_RX

-

UART4_TX

TIM6 / DAC

-

-

TIM6_UP
DAC_CH1

-

-

TIM7 / DAC

-

-

-

TIM7_UP
DAC_CH2

-

TIM8

TIM8_CH3
TIM8_UP

TIM8_CH4
TIM8_TRIG
TIM8_COM

TIM8_CH1

-

TIM8_CH2

TIM20(2)

TIM20_CH1

TIM20_CH2

TIM20_CH3
TIM20_UP

TIM20_CH4
TIM20_TRIG
TIM20_COM

-

1. DMA request mapped on this DMA channel only if the corresponding remapping bit is set in the SYSCFG_CFGR1 register.
For more details, please refer to Section 12.1.1: SYSCFG configuration register 1 (SYSCFG_CFGR1) on page 245.
2.

Available in STM32F303xD/E only.

DocID022558 Rev 8

275/1141
284

Direct memory access controller (DMA)

13.5

RM0316

DMA registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.
The peripheral registers can be accessed by bytes (8-bit), half-words (16-bit) or words (32bit).

13.5.1

DMA interrupt status register (DMA_ISR)
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.

TEIF7

HTIF7

TCIF7

GIF7

TEIF6

HTIF6

TCIF6

GIF6

TEIF5

HTIF5

TCIF5

GIF5

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

TEIF4

HTIF4

TCIF4

GIF4

TEIF3

HTIF3

TCIF3

GIF3

TEIF2

HTIF2

TCIF2

GIF2

TEIF1

HTIF1

TCIF1

GIF1

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

Bits 31:28 Reserved, must be kept at reset value.
Bits 27, 23, 19, 15, TEIFx: Channel x transfer error flag (x = 1..7)
11, 7, 3 This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_IFCR register.
0: No transfer error (TE) on channel x
1: A transfer error (TE) occurred on channel x
Bits 26, 22, 18, 14, HTIFx: Channel x half transfer flag (x = 1..7)
10, 6, 2 This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_IFCR register.
0: No half transfer (HT) event on channel x
1: A half transfer (HT) event occurred on channel x
Bits 25, 21, 17, 13, TCIFx: Channel x transfer complete flag (x = 1..7)
9, 5, 1 This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_IFCR register.
0: No transfer complete (TC) event on channel x
1: A transfer complete (TC) event occurred on channel x
Bits 24, 20, 16, 12, GIFx: Channel x global interrupt flag (x = 1..7)
8, 4, 0 This bit is set by hardware. It is cleared by software writing 1 to the corresponding bit in the
DMA_IFCR register.
0: No TE, HT or TC event on channel x
1: A TE, HT or TC event occurred on channel x

276/1141

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)

13.5.2

DMA interrupt flag clear register (DMA_IFCR)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

27

26

25

24

23

22

21

20

19

18

17

16

CTEIF7 CHTIF7 CTCIF7 CGIF7 CTEIF6 CHTIF6 CTCIF6 CGIF6 CTEIF5 CHTIF5 CTCIF5 CGIF5
w

w

w

w

w

w

w

w

w

w

w

w

11

10

9

8

7

6

5

4

3

2

1

0

CTEIF4 CHTIF4 CTCIF4 CGIF4 CTEIF3 CHTIF3 CTCIF3 CGIF3 CTEIF2 CHTIF2 CTCIF2 CGIF2 CTEIF1 CHTIF1 CTCIF1 CGIF1
w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

w

Bits 31:28 Reserved, must be kept at reset value.
Bits 27, 23, 19, 15, CTEIFx: Channel x transfer error clear (x = 1..7)
11, 7, 3 This bit is set by software.
0: No effect
1: Clears the corresponding TEIF flag in the DMA_ISR register
Bits 26, 22, 18, 14, CHTIFx: Channel x half transfer clear (x = 1..7)
10, 6, 2 This bit is set by software.
0: No effect
1: Clears the corresponding HTIF flag in the DMA_ISR register
Bits 25, 21, 17, 13, CTCIFx: Channel x transfer complete clear (x = 1..7)
9, 5, 1 This bit is set by software.
0: No effect
1: Clears the corresponding TCIF flag in the DMA_ISR register
Bits 24, 20, 16, 12, CGIFx: Channel x global interrupt clear (x = 1..7)
8, 4, 0 This bit is set by software.
0: No effect
1: Clears the GIF, TEIF, HTIF and TCIF flags in the DMA_ISR register

DocID022558 Rev 8

277/1141
284

Direct memory access controller (DMA)

13.5.3

RM0316

DMA channel x configuration register (DMA_CCRx)
(x = 1..7 , where x = channel number)
Address offset: 0x08 + 0d20 × (channel number – 1)
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.

MEM2
MEM

MINC

PINC

CIRC

DIR

TEIE

HTIE

TCIE

EN

rw

rw

rw

rw

rw

rw

rw

rw

rw

PL[1:0]
rw

rw

MSIZE[1:0]

PSIZE[1:0]

rw

rw

rw

rw

Bits 31:15 Reserved, must be kept at reset value.
Bit 14 MEM2MEM: Memory to memory mode
This bit is set and cleared by software.
0: Memory to memory mode disabled
1: Memory to memory mode enabled
Bits 13:12 PL[1:0]: Channel priority level
These bits are set and cleared by software.
00: Low
01: Medium
10: High
11: Very high
Bits 11:10 MSIZE[1:0]: Memory size
These bits are set and cleared by software.
00: 8-bits
01: 16-bits
10: 32-bits
11: Reserved
Bits 9:8 PSIZE[1:0]: Peripheral size
These bits are set and cleared by software.
00: 8-bits
01: 16-bits
10: 32-bits
11: Reserved
Bit 7 MINC: Memory increment mode
This bit is set and cleared by software.
0: Memory increment mode disabled
1: Memory increment mode enabled
Bit 6 PINC: Peripheral increment mode
This bit is set and cleared by software.
0: Peripheral increment mode disabled
1: Peripheral increment mode enabled

278/1141

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)

Bit 5 CIRC: Circular mode
This bit is set and cleared by software.
0: Circular mode disabled
1: Circular mode enabled
Bit 4 DIR: Data transfer direction
This bit is set and cleared by software.
0: Read from peripheral
1: Read from memory
Bit 3 TEIE: Transfer error interrupt enable
This bit is set and cleared by software.
0: TE interrupt disabled
1: TE interrupt enabled
Bit 2 HTIE: Half transfer interrupt enable
This bit is set and cleared by software.
0: HT interrupt disabled
1: HT interrupt enabled
Bit 1 TCIE: Transfer complete interrupt enable
This bit is set and cleared by software.
0: TC interrupt disabled
1: TC interrupt enabled
Bit 0 EN: Channel enable
This bit is set and cleared by software.
0: Channel disabled
1: Channel enabled

DocID022558 Rev 8

279/1141
284

Direct memory access controller (DMA)

13.5.4

RM0316

DMA channel x number of data register (DMA_CNDTRx) (x = 1..7,
where x = channel number)
Address offset: 0x0C + 0d20 × (channel number – 1)
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

NDT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 NDT[15:0]: Number of data to transfer
Number of data to be transferred (0 up to 65535). This register can only be written when the
channel is disabled. Once the channel is enabled, this register is read-only, indicating the
remaining bytes to be transmitted. This register decrements after each DMA transfer.
Once the transfer is completed, this register can either stay at zero or be reloaded
automatically by the value previously programmed if the channel is configured in circular
mode.
If this register is zero, no transaction can be served whether the channel is enabled or not.

13.5.5

DMA channel x peripheral address register (DMA_CPARx) (x = 1..7,
where x = channel number)
Address offset: 0x10 + 0d20 × (channel number – 1)
Reset value: 0x0000 0000
This register must not be written when the channel is enabled.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PA [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

PA [15:0]
rw

Bits 31:0 PA[31:0]: Peripheral address
Base address of the peripheral data register from/to which the data will be read/written.
When PSIZE is 01 (16-bit), the PA[0] bit is ignored. Access is automatically aligned to a halfword address.
When PSIZE is 10 (32-bit), PA[1:0] are ignored. Access is automatically aligned to a word
address.

280/1141

DocID022558 Rev 8

RM0316

Direct memory access controller (DMA)

13.5.6

DMA channel x memory address register (DMA_CMARx) (x = 1..7,
where x = channel number)
Address offset: 0x14 + 0d20 × (channel number – 1)
Reset value: 0x0000 0000
This register must not be written when the channel is enabled.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MA [31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

MA [15:0]
rw

Bits 31:0 MA[31:0]: Memory address
Base address of the memory area from/to which the data will be read/written.
When MSIZE is 01 (16-bit), the MA[0] bit is ignored. Access is automatically aligned to a halfword address.
When MSIZE is 10 (32-bit), MA[1:0] are ignored. Access is automatically aligned to a word
address.

DocID022558 Rev 8

281/1141
284

0x34

0x3C

0x38

282/1141

DMA_CNDTR3

Reset value

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
0
0
0

Reset value
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

Reserved
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

MEM2MEM Res.
Res.
Res.
Res.
Res.
Res.
Res.

0

0

0

0

0

0

0

0

0

0
0

Reserved
Res.

MEM2MEM Res.
Res.
Res.
Res.
Res.
Res.
Res.

0
0

0

DMA_CPAR3

DMA_CMAR3

0

0
0

Reset value

0

0

DocID022558 Rev 8
0

0

0

0

PL
[1:0]

0
0

0
0

0
0

0

0

Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

PINC
CIRC
DIR
TEIE
HTIE
TCIE
EN

PSIZE [1:0]

MSIZE [1:0]

MINC

0

Res.

0

0

EN

0

PL
[1:0]

Res.

TCIF4
GIF4
TEIF3
HTIF3
TCIF3
GIF3
TEIF2
HTIF2
TCIF2
GIF2
TEIF1
HTIF1
TCIF1
GIF1

0
0
0
0
0
0
0
0
0
0

CHTIF7
CTCIF7
CGIF7
CTEIF6
CHTIF6
CTCIF6
CGIF6
CTEIF5
CHTIF5
CTCIF5

0
0
0
0
0
0
0
0
0
0
0

CGIF4

HTIF4

0

CTCIF4

0

CHTIF4

0

MEM2MEM

GIF5
TEIF4

0

CTEIF4

0

Res.

TCIF5

0

CGIF5

Res.

HTIF5

0
CTCIF3

CTCIF1
CGIF1

0
0
0

MINC
0

EN

CHTIF1

0
TCIE

CTEIF1

0
HTIE

CGIF2

0
TEIE

CTCIF2

0

DIR

CHTIF2

0
PINC

CTEIF2

0
CIRC

CGIF3

PSIZE [1:0]

CHTIF3

MSIZE [1:0]

CTEIF3

0

Res.

0

Res.

Res.

Res.

GIF6
TEIF5

0

0

Res.

0

Res.

Res.

Res.

Res.

0

0

TCIE

Reset value
0

0

HTIE

DMA_CPAR2
0

0

Res.

0

Res.

0
0

TEIE

0

Res.

0

Res.

0

Res.

Reset value
PL
[1:0]

DIR

0

Res.

Res.

TCIF6

0

0

Res.

0

Res.

Res.

HTIF6

0

0

Res.

0

Res.

Res.

GIF7
TEIF6

0

0

PINC

0

Res.

Res.

Res.

TCIF7

0

0

CIRC

0

Res.

Res.

Res.

HTIF7

0

0

Res.

0

Res.

TEIF7

Res.

Res.

0

CTEIF7

Res.

Res.

Res.

Res.

0

0

MINC

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

PSIZE [1:0]

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

MSIZE [1:0]

0

Res.

Reset value

Res.

0

Res.

0

Res.

0

Res.

DMA_CMAR1

Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.
0

Res.

0

Res.

Res.

Res.

0

Res.

DMA_CPAR1

Res.

0

Res.

Res.
0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

Reset value
0

Res.

0

Res.

0

Res.

Res.

Res.
0

Res.

0

Res.

Reset value
0

Res.

DMA_CCR3
0

Res.

0x30
Res.

Reset value

Res.

0x2C
0

Res.

DMA_CMAR2
0

Res.

Reset value
Res.

Reset value

Res.

0x24

Res.

DMA_CNDTR2
0

Res.

DMA_CCR2
0

Res.

0x1C
0

Res.

0x18
Reset value

Res.

Reset value

Res.

0x10

Res.

DMA_CNDTR1

Res.

0x28
DMA_CCR1

Res.

0x20
DMA_IFCR

Res.

0x14
DMA_ISR

Res.

0x08

Res.

0x04

Res.

0x00

Res.

0x0C

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.

13.5.7

Res.

Direct memory access controller (DMA)
RM0316

DMA register map
The following table gives the DMA register map and the reset values.
Table 81. DMA register map and reset values

0
0
0
0
0
0
0

NDT[15:0]

PA[31:0]
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

MA[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

NDT[15:0]

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

MA[31:0]

0

0

0

0

0

0

0

0

NDT[15:0]

PA[31:0]

MA[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

0x84

DMA_CNDTR7
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

Reserved

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MEM2MEM Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0
0
0
0
0

Reserved
Res.
Res.

MEM2MEM Res.
Res.
Res.
Res.
Res.
Res.
Res.

0
0

0

0

Reset value

DocID022558 Rev 8
0

0

0

PL
[1:0]

0

0

0
0

0

0
0

0

0
0

0

0

0

0

Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

PINC
CIRC
DIR
TEIE
HTIE
TCIE
EN

PSIZE [1:0]

MSIZE [1:0]

MINC

0

Res.

0

0

EN

0

PL
[1:0]

Res.

Reset value
0

TCIE

DMA_CPAR6
0

Res.

0

Res.

0

HTIE

0

Res.

0

Res.

0

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

Reserved
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

MEM2MEM 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.

PINC
CIRC
DIR
TEIE
HTIE
TCIE
EN

PSIZE [1:0]

MSIZE [1:0]

MINC

0

TEIE

0

Res.

0

0

Res.

0

Res.

Res.

0

0

DIR

0

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

PINC
CIRC
DIR
TEIE
HTIE
TCIE
EN

Res.

Res.

Res.

Res.

MINC

PSIZE [1:0]

MSIZE [1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MEM2MEM Res.

0

Res.

0

Res.

Res.

0

0

0

CIRC

0

Res.

Res.

0

PL
[1:0]

0

Res.

0

Res.

DMA_CMAR5
0

0

PINC

0

Res.

Res.

0

Res.

0
0

Res.

0

Res.

Reset value
0

MINC

0

Res.

DMA_CPAR5
0

0

PSIZE [1:0]

0

Res.

Res.

0

Res.

Res.

Res.

Reset value
PL
[1:0]

MSIZE [1:0]

0

Res.

0

Res.

Reset value

Res.

0

Res.

Res.

0

Res.

DMA_CMAR4

Res.

0

Res.

Res.

0

Res.

Reset value

Reset value

Res.

0

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA_CPAR4

Res.

0

Res.

0

Res.

0

0

Res.

0

Res.

Res.

0

Res.

0

0

Res.

0

Res.

0

Res.

0

0

Res.

0

Res.

Res.

0

Res.

0

0

Res.

0

Res.

0

Res.

0
0

Res.

0

Res.

Res.

0

Res.

0
0

Res.

0

Res.

Res.

0

Res.

Reset value

Reset value

Res.

0
0

Res.

0

Res.

Res.

Res.

0
0

Res.

0

Res.

Reset value
0

Res.

DMA_CCR7
0
0

Res.

0x80
DMA_CMAR6
0

Res.

0x7C
Reset value
0
0

Res.

0x78
DMA_CNDTR6
0
0

Res.

0x74

Res.

0x70
DMA_CCR6
0

Res.

0x6C
Reset value

Res.

0x68
DMA_CNDTR5
0

Res.

0x64
DMA_CCR5
0

Res.

0x60

Res.

0x5C

Res.

0x58
0

Res.

0x54
Reset value

Res.

0x50
DMA_CNDTR4

Res.

0x4C
DMA_CCR4

Res.

0x48

Res.

0x44

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

Reserved

Res.

0x40

Res.

Register

Res.

Offset

Res.

RM0316
Direct memory access controller (DMA)

Table 81. DMA register map and reset values (continued)

0
0
0
0
0
0
0
0

NDT[15:0]

PA[31:0]

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

MA[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

NDT[15:0]

PA[31:0]
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

MA[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

NDT[15:0]

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

MA[31:0]

0

0

0

0

0

0

0

0

NDT[15:0]

0

0

0

0

0

0

0

0

283/1141

284

Direct memory access controller (DMA)

RM0316

Offset
0x88

DMA_CPAR7

PA[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

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.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Reserved

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Reset value

Res.

0x90 0xA7

0

MA[31:0]

Res.

DMA_CMAR7

Res.

0x8C

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 81. DMA register map and reset values (continued)

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

284/1141

DocID022558 Rev 8

RM0316

Interrupts and events

14

Interrupts and events

14.1

Nested vectored interrupt controller (NVIC)

14.1.1

NVIC main features
•

74 maskable interrupt channels (not including the sixteen Cortex®-M4 with FPU
interrupt lines)

•

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 the PM0214 programming manual for
Cortex®-M4 products.

14.1.2

SysTick calibration value register
The SysTick calibration value is set to 9000, which gives a reference time base of 1 ms with
the SysTick clock set to 9 MHz (max fHCLK/8).

14.1.3

Interrupt and exception vectors
Table 82 is the vector table for STM32F303xB/C and STM32F358xC devices. Table 83 is
the vector table for STM32F303x6/8 and STM32F328x8 devices.

Position

Priority

Table 82. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE vector table
Type of
priority

-

-

-

-

-3

-

Acronym

Description

Address

-

Reserved

0x0000 0000

fixed

Reset

Reset

0x0000 0004

-2

fixed

NMI

Non maskable interrupt. The RCC Clock
Security System (CSS) is linked to the NMI
vector.

0x0000 0008

-

-1

fixed

HardFault

All class of fault

0x0000 000C

-

0

settable

MemManage

Memory management

0x0000 0010

-

1

settable

BusFault

Pre-fetch fault, memory access fault

0x0000 0014

-

2

settable

UsageFault

Undefined instruction or illegal state

0x0000 0018

-

-

-

-

Reserved

DocID022558 Rev 8

0x0000 001C 0x0000 0028

285/1141
304

Interrupts and events

RM0316

Position

Priority

Table 82. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE vector table (continued)
Type of
priority

-

3

settable

SVCall

System service call via SWI instruction

0x0000 002C

-

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 Line16 detection interrupt

0x0000 0044

2

9

settable

TAMPER_STAMP

Tamper and TimeStamp interrupts through
EXTI Line19

0x0000 0048

3

10

settable

RTC_WKUP

RTC wakeup timer interrupt through EXTI
Line20

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_TS

EXTI Line2 and Touch sensing interrupts

0x0000 0060

9

16

settable

EXTI3

EXTI Line3

0x0000 0064

10

17

settable

EXTI4

EXTI Line4

0x0000 0068

11

18

settable

DMA1_Channel1

DMA1 channel 1 interrupt

0x0000 006C

12

19

settable

DMA1_Channel2

DMA1 channel 2 interrupt

0x0000 0070

13

20

settable

DMA1_Channel3

DMA1 channel 3 interrupt

0x0000 0074

14

21

settable

DMA1_Channel4

DMA1 channel 4 interrupt

0x0000 0078

15

22

settable

DMA1_Channel5

DMA1 channel 5 interrupt

0x0000 007C

16

23

settable

DMA1_Channel6

DMA1 channel 6 interrupt

0x0000 0080

17

24

settable

DMA1_Channel7

DMA1 channel 7 interrupt

0x0000 0084

18

Acronym

Description

Address

25

settable

ADC1_2

ADC1 and ADC2 global interrupt

0x0000 0088

(1)

26

settable

USB_HP/CAN_TX

USB High Priority/CAN_TX interrupts

0x0000 008C

20 (1)

27

settable

USB_LP/CAN_RX0

USB Low Priority/CAN_RX0 interrupts

0x0000 0090

21

28

settable

CAN_RX1

CAN_RX1 interrupt

0x0000 0094

22

29

settable

CAN_SCE

CAN_SCE interrupt

0x0000 0098

23

30

settable

EXTI9_5

EXTI Line[9:5] interrupts

0x0000 009C

24

31

settable

TIM1_BRK/TIM15

TIM1 Break/TIM15 global interrupts

0x0000 00A0

25

32

settable

TIM1_UP/TIM16

TIM1 Update/TIM16 global interrupts

0x0000 00A4

26

33

settable

TIM1_TRG_COM
/TIM17

TIM1 trigger and commutation/TIM17
interrupts

0x0000 00A8

27

34

settable

TIM1_CC

TIM1 capture compare interrupt

0x0000 00AC

19

286/1141

DocID022558 Rev 8

RM0316

Interrupts and events

Position

Priority

Table 82. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE vector table (continued)
Type of
priority

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 & EXTI Line23 interrupt

0x0000 00BC

32

39

settable

I2C1_ER

I2C1 error interrupt

0x0000 00C0

33

40

settable

I2C2_EV

I2C2 event interrupt & EXTI Line24 interrupt

0x0000 00C4

34

41

settable

I2C2_ER

I2C2 error interrupt

0x0000 00C8

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 & EXTI Line 25

0x0000 00D4

38

45

settable

USART2

USART2 global interrupt & EXTI Line 26

0x0000 00D8

39

46

settable

USART3

USART3 global interrupt & EXTI Line 28

0x0000 00DC

40

47

settable

EXTI15_10

EXTI Line[15:10] interrupts

0x0000 00E0

41

48

settable

RTC_Alarm

RTC alarm interrupt

0x0000 00E4

49

settable

USBWakeUp

USB wakeup from Suspend (EXTI line 18)

0x0000 00E8

43

50

settable

TIM8_BRK

TIM8 break interrupt

0x0000 00EC

44

51

settable

TIM8_UP

TIM8 update interrupt

0x0000 00F0

45

52

settable

TIM8_TRG_COM

TIM8 Trigger and commutation interrupts

0x0000 00F4

46

53

settable

TIM8_CC

TIM8 capture compare interrupt

0x0000 00F8

47

54

settable

ADC3

ADC3 global interrupt

0x0000 00FC

FMC global interrupt

0x0000 0100

42

(1)

Acronym

FMC

(2)

Description

Address

48

55

settable

49

56

-

Reserved

0x0000 0104

50

57

-

Reserved

0x0000 0108

51

58

settable

SPI3

SPI3 global interrupt

0x0000 010C

52

59

settable

UART4

UART4 global and EXTI Line 34 interrupts

0x0000 0110

53

60

settable

UART5

UART5 global and EXTI Line 35 interrupts

0x0000 0114

54

61

settable

TIM6_DAC

TIM6 global and DAC1 underrun interrupts.

0x0000 0118

55

62

settable

TIM7

TIM7 global interrupt

0x0000 011C

56

63

settable

DMA2_Channel1

DMA2 channel1 global interrupt

0x0000 0120

57

64

settable

DMA2_Channel2

DMA2 channel2 global interrupt

0x0000 0124

58

65

settable

DMA2_Channel3

DMA2 channel3 global interrupt

0x0000 0128

59

66

settable

DMA2_Channel4

DMA2 channel4 global interrupt

0x0000 012C

60

67

settable

DMA2_Channel5

DMA2 channel5 global interrupt

0x0000 0130

DocID022558 Rev 8

287/1141
304

Interrupts and events

RM0316

Position

Priority

Table 82. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE vector table (continued)
Type of
priority

61

68

settable

62

69

-

Reserved

0x0000 0138

63

70

-

Reserved

0x0000 013C

64

71

settable

COMP1_2_3

COMP1 & COMP2 & COMP3 interrupts
combined with EXTI Lines 21, 22 and 29
interrupts.

0x0000 0140

65

72

settable

COMP4_5_6

COMP4 & COMP5 & COMP6 interrupts
combined with EXTI Lines 30, 31 and 32
interrupts.

0x0000 0144

66

73

settable

COMP7

COMP7 interrupt combined with EXTI Line 33
interrupt

0x0000 0148

67

74

-

Reserved

0x0000 014C

68

75

-

Reserved

0x0000 0150

69

76

-

Reserved

0x0000 0154

70

77

-

Reserved

0x0000 0158

71

78

-

Reserved

0x0000 015C

72

79

settable

Acronym

ADC4

I2C3_EV

Description

ADC4 global interrupt

Address

0x0000 0134

(2)

I2C3 Event interrupt

0x0000 0160

(2)

I2C3 Error interrupt

0x0000 0164

73

80

settable

I2C3_ER

74

81

settable

USB_HP

USB High priority interrupt

0x0000 0168

75

82

settable

USB_LP

USB Low priority interrupt

0x0000 016C

76

83

settable

USB_WakeUp_RMP USB wake up from Suspend and EXTI Line
(see note 1)
18

0x0000 0170

77

84

settable

TIM20_BRK(2)

TIM20 Break interrupt

0x0000 0174

78

85

(2)

settable

TIM20_UP

TIM20 Upgrade interrupt

0x0000 0178

TIM20 Trigger and Commutation interrupt

0x0000 017C

79

86

settable

TIM20_TRG_COM(2)

80

87

settable

TIM20_CC(2)

TIM20 Capture Compare interrupt

0x0000 0180

81

88

settable

FPU

Floating point interrupt

0x0000 0184

82

89

-

-

Reserved

0x0000 0188

83

90

-

-

Reserved

0x0000 018C

84

91

settable

-

SPI4

SPI4 Global interrupt(2)

0x0000 0190

1. It is possible to remap the USB interrupts (USB_HP, USB_LP and USB_WKUP) on interrupt lines 74, 75 and 76
respectively by setting the USB_IT_RMP bit in the Section 12.1.1: SYSCFG configuration register 1 (SYSCFG_CFGR1) on
page 245.
2. Available in STM32F303xD/E only.

288/1141

DocID022558 Rev 8

RM0316

Interrupts and events

Position

Priority

Table 83. STM32F303x6/8 and STM32F328x8 vector table
Type of
priority

-

-

-

-

-3

fixed

-

-2

-

Acronym

-

Description

Address

Reserved

0x0000 0000

Reset

Reset

0x0000 0004

fixed

NMI

Non maskable interrupt. The RCC Clock
Security System (CSS) is linked to the NMI
vector.

0x0000 0008

-1

fixed

HardFault

All class of fault

0x0000 000C

-

0

settable

MemManage

Memory management

0x0000 0010

-

1

settable

BusFault

Pre-fetch fault, memory access fault

0x0000 0014

-

2

settable

UsageFault

Undefined instruction or illegal state

0x0000 0018

-

-

-

-

3

settable

SVCall

System service call via SWI instruction

0x0000 002C

-

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 16 detection interrupt

0x0000 0044

2

9

settable

TAMPER_STAMP

Tamper and TimeStamp interrupts
through the EXTI line 19

0x0000 0048

3

10

settable

RTC_WKUP

RTC wakeup timer interrupts through the
EXTI line 20

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_TS

EXTI Line2 and Touch sensing interrupts

0x0000 0060

9

16

settable

EXTI3

EXTI Line3

0x0000 0064

10

17

settable

EXTI4

EXTI Line4

0x0000 0068

11

18

settable

DMA1_Channel1

DMA1 channel 1 interrupt

0x0000 006C

12

19

settable

DMA1_Channel2

DMA1 channel 2 interrupt

0x0000 0070

13

20

settable

DMA1_Channel3

DMA1 channel 3 interrupt

0x0000 0074

14

21

settable

DMA1_Channel4

DMA1 channel 4 interrupt

0x0000 0078

15

22

settable

DMA1_Channel5

DMA1 channel 5 interrupt

0x0000 007C

16

23

settable

DMA1_Channel6

DMA1 channel 6 interrupt

0x0000 0080

-

Reserved

DocID022558 Rev 8

0x0000 001C 0x0000 0028

289/1141
304

Interrupts and events

RM0316

Position

Priority

Table 83. STM32F303x6/8 and STM32F328x8 vector table (continued)
Type of
priority

17

24

settable

DMA1_Channel7

DMA1 channel 7 interrupt

0x0000 0084

18

25

settable

ADC1_2

ADC1 and ADC2 global interrupt

0x0000 0088

19

26

settable

CAN_TX

CAN_TX interrupts

0x0000 008C

20

27

settable

CAN_RX0

CAN_RX0 interrupts

0x0000 0090

21

28

settable

CAN_RX1

CAN_RX1 interrupt

0x0000 0094

22

29

settable

CAN_SCE

CAN_SCE interrupt

0x0000 0098

23

30

settable

EXTI9_5

EXTI Line[9:5] interrupts

0x0000 009C

24

31

settable

TIM1_BRK/TIM15

TIM1 Break/TIM15 global interrupts

0x0000 00A0

25

32

settable

TIM1_UP/TIM16

TIM1 Update/TIM16 global interrupts

0x0000 00A4

26

33

settable

TIM1_TRG_COM
/TIM17

TIM1 trigger and commutation/TIM17
interrupts

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

-

Reserved

31

38

settable

I2C1_EV

I2C1 event interrupt & EXTI Line23 interrupt

0x0000 00BC

32

39

settable

I2C1_ER

I2C1 error interrupt

0x0000 00C0

33

40

-

Reserved

0x0000 00C4

34

41

-

Reserved

0x0000 00C8

35

42

-

SPI1

36

43

-

Reserved

37

44

settable

USART1

USART1 global interrupt & EXTI Line 25

0x0000 00D4

38

45

settable

USART2

USART2 global interrupt & EXTI Line 26

0x0000 00D8

39

46

settable

USART3

USART3 global interrupt & EXTI Line 28

0x0000 00DC

40

47

settable

EXTI15_10

EXTI Line[15:10] interrupts

0x0000 00E0

41

48

settable

RTC_Alarm

RTC alarm interrupt

0x0000 00E4

42

49

-

Reserved

0x0000 00E8

43

50

-

Reserved

0x0000 00EC

44

51

-

Reserved

0x0000 00F0

45

52

-

Reserved

0x0000 00F4

46

53

-

Reserved

0x0000 00F8

47

54

-

Reserved

0x0000 00FC

48

55

-

Reserved

0x0000 0100

290/1141

Acronym

Description

Address

0x0000 00B8

SPI1 global interrupt

0x0000 00CC
0x0000 00D0

DocID022558 Rev 8

RM0316

Interrupts and events

Position

Priority

Table 83. STM32F303x6/8 and STM32F328x8 vector table (continued)
Type of
priority

49

56

-

Reserved

0x0000 0104

50

57

-

Reserved

0x0000 0108

51

58

-

Reserved

0x0000 010C

52

59

-

Reserved

0x0000 0110

53

60

-

Reserved

0x0000 0114

54

61

settable

TIM6_DAC1

TIM6 global and DAC1 underrun interrupts

0x0000 0118

55

62

settable

TIM7_DAC2

TIM7 global and DAC2 underrun interrupt

0x0000 011C

56

63

-

Reserved

0x0000 0120

57

64

-

Reserved

0x0000 0124

58

65

-

Reserved

0x0000 0128

59

66

-

Reserved

0x0000 012C

60

67

-

Reserved

0x0000 0130

61

68

-

Reserved

0x0000 0134

62

69

-

Reserved

0x0000 0138

63

70

-

Reserved

0x0000 013C

64

71

settable

COMP2

COMP2 interrupt combined with EXTI Lines
22 interrupt.

0x0000 0140

65

72

settable

COMP4_6

COMP4 & COMP6 interrupts combined with
EXTI Lines 30 and 32 interrupts respectively.

0x0000 0144

66

73

-

Reserved

0x0000 0148

67

74

-

Reserved

0x0000 014C

68

75

-

Reserved

0x0000 0150

69

76

-

Reserved

0x0000 0154

70

77

-

Reserved

0x0000 0158

71

78

-

Reserved

0x0000 015C

72

79

-

Reserved

0x0000 0160

73

80

-

Reserved

0x0000 0164

74

81

-

Reserved

0x0000 0168

75

82

-

Reserved

0x0000 016C

76

83

-

Reserved

0x0000 0170

77

84

-

Reserved

0x0000 0174

78

85

-

Reserved

0x0000 0178

79

86

-

Reserved

0x0000 017C

Acronym

Description

DocID022558 Rev 8

Address

291/1141
304

Interrupts and events

RM0316

Position

Priority

Table 83. STM32F303x6/8 and STM32F328x8 vector table (continued)
Type of
priority

80

87

-

81

88

settable

14.2

Acronym

Description

Reserved
FPU

Address

0x0000 0180
Floating point interrupt

0x0000 0184

Extended interrupts and events controller (EXTI)
The extended interrupts and events controller (EXTI) manages the external and internal
asynchronous events/interrupts and generates the event request to the CPU/Interrupt
Controller and a wake-up request to the Power Manager.
The EXTI allows the management of up to 36 external/internal event line (28 external event
lines and 8 internal event lines).
The active edge of each external interrupt line can be chosen independently, whilst for
internal interrupt the active edge is always the rising one. An interrupt could be left pending:
in case of an external one, a status register is instantiated and indicates the source of the
interrupt; an event is always a simple pulse and it’s used for triggering the core wake-up. For
internal interrupts, the pending status is assured by the generating peripheral, so no need
for a specific flag. Each input line can be masked independently for interrupt or event
generation, in addition the internal lines are sampled only in STOP mode. This controller
allows also to emulate the (only) external events by software, multiplexed with the
corresponding hardware event line, by writing to a dedicated register.

14.2.1

Main features
The EXTI main features are the following:

292/1141

•

support generation of up to 36 event/interrupt requests

•

Independent configuration of each line as an external or an internal event requests

•

Independent mask on each event/interrupt line

•

Automatic disable of internal lines when system is not in STOP mode

•

Independent trigger for external event/interrupt line

•

Dedicated status bit for external interrupt line

•

Emulation for all the external event requests.

DocID022558 Rev 8

RM0316

14.2.2

Interrupts and events

Block diagram
The extended interrupt/event block diagram is shown in the following figure.
Figure 50. External interrupt/event block diagram
$0%$$3%EXV

3&/.

3HULSKHUDOLQWHUIDFH




3HQGLQJ
UHTXHVW
UHJLVWHU
7R19,&LQWHUUXSW
FRQWUROOHU

,QWHUUXSW
PDVN
UHJLVWHU



6RIWZDUH
LQWHUUXSW
HYHQW
UHJLVWHU









5LVLQJ
)DOOLQJ
WULJJHU
WULJJHU
VHOHFWLRQ VHOHFWLRQ
UHJLVWHU UHJLVWHU








3XOVH
JHQHUDWRU 



(GJHGHWHFW
FLUFXLW

,QSXW
OLQH

(YHQW
PDVN
UHJLVWHU
069

14.2.3

Wakeup event management
STM32F3xx devices are able to handle external or internal events in order to wake up the
core (WFE). The wakeup event can be generated either by:

14.2.4

•

enabling an interrupt in the peripheral control register but not in the NVIC, and enabling
the SEVONPEND bit in the Cortex®-M4 System Control register. When the MCU
resumes from WFE, the EXTI peripheral interrupt pending bit and the peripheral NVIC
IRQ channel pending bit (in the NVIC interrupt clear pending register) have to be
cleared.

•

or by 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.

Asynchronous Internal Interrupts
Some communication peripherals (UART, I2C) are able to generate events when the system
is in run mode and also when the system is in stop mode allowing to wake up the system
from stop mode.

DocID022558 Rev 8

293/1141
304

Interrupts and events

RM0316

To accomplish this, the peripheral is asked to generate both a synchronized (to the system
clock, e.g. APB clock) and an asynchronous version of the event.

14.2.5

Functional description
For the external interrupt lines, to generate the interrupt, the interrupt line should be
configured and enabled. This is done by programming the two trigger registers with the
desired edge detection and by enabling the interrupt request by writing a ‘1’ to the
corresponding bit in the interrupt mask register. When the selected edge occurs on the
external interrupt line, an interrupt request is generated. The pending bit corresponding to
the interrupt line is also set. This request is reset by writing a ‘1’ in the pending register.
For the internal interrupt lines, the active edge is always the rising edge, the interrupt is
enabled by default in the interrupt mask register and there is no corresponding pending bit
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.
For the external lines, an interrupt/event request can also be generated by software by
writing a ‘1’ in the software interrupt/event register.

Note:

The interrupts or events associated to the internal lines can be triggered only when the
system is in STOP mode. If the system is still running, no interrupt/event is generated.

Hardware interrupt selection
To configure a line as interrupt source, use the following procedure:
•

Configure the corresponding mask bit in the EXTI_IMR register.

•

Configure the Trigger Selection bits of the Interrupt line (EXTI_RTSR and EXTI_FTSR)

•

Configure the enable and mask bits that control the NVIC IRQ channel mapped to the
EXTI so that an interrupt coming from one of the EXTI line can be correctly
acknowledged.

Hardware event selection
To configure a line as event source, use the following procedure:
•

Configure the corresponding mask bit in the EXTI_EMR register.

•

Configure the Trigger Selection bits of the Event line (EXTI_RTSR and EXTI_FTSR)

Software interrupt/event selection
Any of the external lines can be configured as software interrupt/event lines. The following is
the procedure to generate a software interrupt.

294/1141

•

Configure the corresponding mask bit (EXTI_IMR, EXTI_EMR)

•

Set the required bit of the software interrupt register (EXTI_SWIER)

DocID022558 Rev 8

RM0316

14.2.6

Interrupts and events

External and internal interrupt/event line mapping
36 interrupt/event lines are available: 8 lines are internal (including the reserved ones); the
remaining 28 lines are external.
The GPIOs are connected to the 16 external interrupt/event lines in the following manner:
Figure 51. External interrupt/event GPIO mapping
(;7,>@ELWVLQWKH6<6&)*B(;7,&5UHJLVWHU
3$
3%
3&
3'
3(
3)
3*
3+

(;7,

(;7,>@ELWVLQWKH6<6&)*B(;7,&5UHJLVWHU
3$
3%
3&
3'
3(
3)
3*
3+

(;7,


(;7,>@ELWVLQWKH6<6&)*B(;7,&5UHJLVWHU
3$
3%
3&
3'
3(
3)
3*

(;7,

069

DocID022558 Rev 8

295/1141
304

Interrupts and events

RM0316

The remaining lines are connected as follows:

Note:

296/1141

•

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 USB Device FS wakeup event (STM32F303xB/C/D/E,
STM32F358xC and STM32F398xE devices)

•

EXTI line 19 is connected to RTC tamper and Timestamps

•

EXTI line 20 is connected to RTC wakeup timer

•

EXTI line 21 is connected to Comparator 1 output (STM32F303xB/C/D/E,
STM32F358xC and STM32F398xE devices)

•

EXTI line 22 is connected to Comparator 2 output

•

EXTI line 23 is connected to I2C1 wakeup

•

EXTI line 24 is connected to I2C2 wakeup (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices)

•

EXTI line 25 is connected to USART1 wakeup

•

EXTI line 26 is connected to USART2 wakeup (STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE devices)

•

EXTI line 27 is connected to I2C3 wakeup)(STM32F303xD/E and STM32F398
devices)

•

EXTI line 28 is connected to USART3 wakeup (STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE devices)

•

EXTI line 29 is connected to Comparator 3 output (STM32F303xB/C/D/E,
STM32F358xC and STM32F398xE devices)

•

EXTI line 30 is connected to Comparator 4 output

•

EXTI line 31 is connected to Comparator 5 output (STM32F303xB/C/D/E,
STM32F358xC and STM32F398xE devices)

•

EXTI line 32 is connected to Comparator 6 output

•

EXTI line 33 is connected to Comparator 7 output (STM32F303xB/C/D/E,
STM32F358xC and STM32F398xE devices)

•

EXTI line 34 is connected to UART4 wakeup (STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE devices)

•

EXTI line 35 is connected to UART5 wakeup (STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE devices)

EXTI lines 23, 24, 25, 26, 27, 28, 34 and 35 are internal.

DocID022558 Rev 8

RM0316

Interrupts and events

14.3

EXTI registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by words (32-bit).

14.3.1

Interrupt mask register (EXTI_IMR1)
Address offset: 0x00
Reset value: 0x1F80 0000 (See note below)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MR31

MR30

MR29

MR28

MR27

MR26

MR25

MR24

MR23

MR22

MR21

MR20

MR19

MR18

MR17

MR16

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

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 31:0 MRx: Interrupt Mask on external/internal line x
0: Interrupt request from Line x is masked
1: Interrupt request from Line x is not masked

Note:

The reset value for the internal lines (23, 24, 25, 26, 27 and 28) is set to ‘1’ in order to
enable the interrupt by default.

14.3.2

Event mask register (EXTI_EMR1)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MR31

MR30

MR29

MR28

MR27

MR26

MR25

MR24

MR23

MR22

MR21

MR20

MR19

MR18

MR17

MR16

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

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 31:0 MRx: Event Mask on external/internal line x
0: Event request from Line x is masked
1: Event request from Line x is not masked

DocID022558 Rev 8

297/1141
304

Interrupts and events

14.3.3

RM0316

Rising trigger selection register (EXTI_RTSR1)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

TR31

TR30

TR29

Res.

Res.

Res.

Res.

Res.

Res.

TR22

TR21

TR20

TR19

TR18

TR17

TR16
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

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 31:29 TRx: Rising trigger event configuration bit of line x (x = 31 to 29)
0: Rising trigger disabled (for Event and Interrupt) for input line
1: Rising trigger enabled (for Event and Interrupt) for input line.
Bits 28:23 Reserved, must be kept at reset value.
Bits 22:0 TRx: Rising trigger event configuration bit of line x (x = 22 to 0)
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 glitches must be generated on these
lines. If a rising edge on an external interrupt line occurs during a write operation in the
EXTI_RTSR register, the pending bit is not set.
Rising and falling edge triggers can be set for the same interrupt line. In this case, both
generate a trigger condition.

14.3.4

Falling trigger selection register (EXTI_FTSR1)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

TR31

TR30

TR29

Res.

Res.

Res.

Res.

Res.

Res.

TR22

TR21

TR20

TR19

TR18

TR17

TR16

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

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 31:29 TRx: Falling trigger event configuration bit of line x (x = 31 to 29)
0: Falling trigger disabled (for Event and Interrupt) for input line
1: Falling trigger enabled (for Event and Interrupt) for input line.
Bits 28:23 Reserved, must be kept at reset value.
Bits 22:0 TRx: Falling trigger event configuration bit of line x (x = 22 to 0)
0: Falling trigger disabled (for Event and Interrupt) for input line
1: Falling trigger enabled (for Event and Interrupt) for input line.

298/1141

DocID022558 Rev 8

RM0316

Interrupts and events

Note:

The external wakeup lines are edge-triggered. No glitches must be generated on these
lines. If a falling edge on an external interrupt line occurs during a write operation 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 case, both
generate a trigger condition.r

14.3.5

Software interrupt event register (EXTI_SWIER1)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

SWIER SWIER SWIER
31
30
29
rw

rw

rw

15

14

13

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

12

11

10

9

8

7

SWIER SWIER SWIER SWIER SWIER SWIER SWIER
15
14
13
12
11
10
9
rw

rw

rw

23

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: 29 SWIERx: Software interrupt on line x (x = 31 to 29)
If the interrupt is enabled on this line in the EXTI_IMR, writing a '1' to this bit when
it is at '0' sets the corresponding pending bit in EXTI_PR resulting in an interrupt
request generation.
This bit is cleared by clearing the corresponding bit in the EXTI_PR register (by
writing a ‘1’ into the bit).
Bits 28:23 Reserved, must be kept at reset value.
Bits 22:0 SWIERx: Software interrupt on line x (x = 22 to 0)
If the interrupt is enabled on this line in the EXTI_IMR, writing a '1' to this bit when
it is at '0' sets the corresponding pending bit in EXTI_PR resulting in an interrupt
request generation.
This bit is cleared by clearing the corresponding bit of EXTI_PR (by writing a ‘1’
into the bit).

14.3.6

Pending register (EXTI_PR1)
Address offset: 0x14
Reset value: undefined

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PR31

PR30

PR29

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

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

DocID022558 Rev 8

299/1141
304

Interrupts and events

RM0316

Bits 31:29 PRx: Pending bit on line x (x = 31 to 29)
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 writing a ‘1’ to the bit.
Bits 28:23 Reserved, must be kept at reset value.
Bits 22:0 PRx: Pending bit on line x (x = 22 to 0)
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 writing a ‘1’ to the bit.

14.3.7

Interrupt mask register (EXTI_IMR2)
Address offset: 0x20
Reset value: 0xFFFF FFFC (See note below)

31

30

29

28

27

26

25

24

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.

MR35

MR34

MR33

MR32

rw

rw

rw

rw

Bits 31:4 Reserved, must be kept at reset value
Bits 3:0 MRx: Interrupt mask on external/internal line x, x = 32..35
0: Interrupt request from Line x is masked
1: Interrupt request from Line x is not masked

Note:

The reset value for the internal lines (34 and 35) and reserved lines is set to ‘1’.

14.3.8

Event mask register (EXTI_EMR2)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MR35

MR34

MR33

MR32

rw

rw

rw

rw

Bits 31:4 Reserved, must be kept at reset value
Bits 3:0 MRx: Event mask on external/internal line x, x = 32..35
0: Event request from Line x is masked
1: Event request from Line x is not masked

300/1141

DocID022558 Rev 8

RM0316

Interrupts and events

14.3.9

Rising trigger selection register (EXTI_RTSR2)
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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TR33

TR32

rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bits 1:0 TRx: Rising trigger event configuration bit of line x (x = 32, 33)
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 glitches must be generated on these
lines. If a rising edge on an external interrupt line occurs during a write operation to the
EXTI_RTSR register, the pending bit is not set.
Rising and falling edge triggers can be set for the same interrupt line. In this case, both
generate a trigger condition.

14.3.10

Falling trigger selection register (EXTI_FTSR2)
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.

TR33

TR32

rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bits 1:0 TRx: Falling trigger event configuration bit of line x (x = 32, 33)
0: Falling trigger disabled (for Event and Interrupt) for input line
1: Falling trigger enabled (for Event and Interrupt) for input line.

Note:

The external wakeup lines are edge-triggered. No glitches must be generated on these
lines. If a falling edge on an external interrupt line occurs during a write operation 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 case, both
generate a trigger condition.r

14.3.11

Software interrupt event register (EXTI_SWIER2)

DocID022558 Rev 8

301/1141
304

Interrupts and events

RM0316

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.

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.

SWIER SWIER
33
32
rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bits 1:0 SWIERx: Software interrupt on line x (x = 32, 33)
If the interrupt is enabled on this line in the EXTI_IMR, writing a '1' to this bit when
it is at '0' sets the corresponding pending bit in EXTI_PR resulting in an interrupt
request generation.
This bit is cleared by clearing the corresponding bit of EXTI_PR (by writing a ‘1’ to
the bit).

14.3.12

Pending register (EXTI_PR2)
Address offset: 0x34
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.

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.

PR33

PR32

rc_w1

rc_w1

Bits 31:2 Reserved, must be kept at reset value.
Bits 1:0 PRx: Pending bit on line x (x = 32,33)
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 writing a ‘1’ into the bit.

302/1141

DocID022558 Rev 8

RM0316

Interrupts and events

14.3.13

EXTI register map
The following table gives the EXTI register map and the reset values.

MR[31:0]
0

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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.

0

0

0

0

0

0

0

0

0

0

0

Res.

0

0

0

0

SWIER[22:0]
0

0

0

0

0

0

0

0

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_EMR2

Res.

0x24

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.

EXTI_RTSR2
0x28

Res.

Reset value

MR32

0

MR33

0

1

1

0

0
MR32

0

0

0

0

0

Reset value

DocID022558 Rev 8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_FTSR2

Res.

0x2C

Res.

Reset value

TR32

0

0

0
TR32

0

MR34

0

MR33

0

MR34

0

Res.

PR[22:0]

Res.

Res.

0

TR33

Res.

0

TR33

Res.

Res.
Res.
Res.

Res.

0

MR35

Res.

Res.
Res.

Res.

Res.

0

Res.

Res.

Res.

EXTI_IMR2

0

TR[22:0]

0

Res.

0

0

TR[22:0]

0

Res.

0

0

MR35

Res.

Res.

Res.

Res.

0

Res.

PR
[31:29]

0

0

0

Reset value

0x20

0

0

Res.

0x14

0

0

0

SWIER
[31:29]
0

0

Res.

EXTI_PR1

0

0

Res.

Reset value

0

0

Res.

EXTI_SWIER1

0

0

Res.

EXTI_FTSR1

0x10

0

Res.

0

0x0C
Reset value

0

Res.

0

EXTI_RTSR1

Reset value

0

MR[31:0]

Res.

EXTI_EMR1
Reset value

0x08

0

Res.

0x04

0

Res.

Reset value

Res.

EXTI_IMR1

TR[31:29]

0x00

Register

TR[31:29]

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 84. External interrupt/event controller register map and reset values

0

0

303/1141
304

0x34

304/1141
EXTI_PR2

DocID022558 Rev 8

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.
SWIER32

Res.

Res.

Res.

Res.

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

PR32

Reset value
SWIER33

Reset value

PR33

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

EXTI_SWIER2

Res.

0x30

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.

Interrupts and events
RM0316

Table 84. External interrupt/event controller register map and reset values (continued)

0
0

RM0316

Analog-to-digital converters (ADC)

15

Analog-to-digital converters (ADC)

15.1

Introduction
This section describes the implementation of up to 4 ADCs:
•

ADC1 and ADC2 are tightly coupled and can operate in dual mode (ADC1 is master).

•

ADC3 and ADC4 are tightly coupled and can operate in dual mode (ADC3 is master).

Each ADC consists of a 12-bit successive approximation analog-to-digital converter.
Each ADC has up to 19 multiplexed channels. A/D conversion of the various channels can
be performed in single, continuous, scan or discontinuous mode. The result of the ADC is
stored in a left-aligned or right-aligned 16-bit data register.
The ADCs are mapped on the AHB bus to allow fast data handling.
The analog watchdog features allow the application to detect if the input voltage goes
outside the user-defined high or low thresholds.
An efficient low-power mode is implemented to allow very low consumption at low
frequency.
Note:

The STM32F303x6/8 and STM32F328x8 devices have only ADC1 and ADC2.

DocID022558 Rev 8

305/1141
413

Analog-to-digital converters (ADC)

15.2

RM0316

ADC main features
•

High-performance features
–

Up to 4x ADC, each can operate in dual mode.
The table below summarizes the different external channels available per ADC.
Table 85. ADC external channels mapping

Device

ADC1

ADC2

ADC3

ADC4

STM32F303xB/C

10

12

15

13

STM32F358

10

11

15

13

STM32F303x6/8

11

14

N.A

N.A

STM32F328

11

13

N.A

N.A

STM32F303xD/E

11

13

15

13

STM32F398xE

11

12

15

13

•

•

306/1141

–

12, 10, 8 or 6-bit configurable resolution

–

ADC conversion time:
Fast channels: 0.19 µs for 12-bit resolution (5.1 Ms/s)
Slow channels: 0.21 µs for 12-bit resolution (4.8 Ms/s)

–

ADC conversion time is independent from the AHB bus clock frequency

–

Faster conversion time by lowering resolution: 0.16 µs for 10-bit resolution

–

Can manage Single-ended or differential inputs (programmable per channels)

–

AHB slave bus interface to allow fast data handling

–

Self-calibration

–

Channel-wise programmable sampling time

–

Up to four injected channels (analog inputs assignment to regular or injected
channels is fully configurable)

–

Hardware assistant to prepare the context of the injected channels to allow fast
context switching

–

Data alignment with in-built data coherency

–

Data can be managed by GP-DMA for regular channel conversions

–

4 dedicated data registers for the injected channels

Low-power features
–

Speed adaptive low-power mode to reduce ADC consumption when operating at
low frequency

–

Allows slow bus frequency application while keeping optimum ADC performance
(0.19 µs conversion time for fast channels can be kept whatever the AHB bus
clock frequency)

–

Provides automatic control to avoid ADC overrun in low AHB bus clock frequency
application (auto-delayed mode)

External analog input channels for each of the 4 ADCs:
–

Up to 5 fast channels from dedicated GPIO pads

–

Up to 11 slow channels from dedicated GPIO pads

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
•

In addition, there are internal dedicated channels available per ADC. See the table
below.:
Table 86. ADC internal channels summary

Product

ADC1

ADC2

ADC3

ADC4

Total of
internal
ADC
channels

STM32F303xB/C/D/E,
STM32F358 and
STM32F398xE

– 1 channel
connected to
– 1 channel
temperature
connected
– 1 channel
– 1 channel
sensor.
to
connected to
connected to
– 1 channel
VREFINT.
VREFINT.
VREFINT.
connected to
– 1 channel
– 1 channel
– 1 channel
VBAT/2
connected
connected to
connected to
– 1 channel
to OPAMP2
OPAMP3
OPAMP4
connected to
reference
reference
reference
VREFINT
voltage
voltage output
voltage output
– 1 channel
output
(VREFOPAMP
(VREFOPAM
connected to
(VREFOPA
3).
P4).
OPAMP1 reference
MP2).
voltage output
(VREFOPAMP1).

7

STM32F303x6/8 and
STM32F328

– 1 channel
connected to
– 1 channel
temperature
connected
sensor.
to
– 1 channel
VREFINT.
connected to
–
1
channel
VBAT/2
connected
– 1 channel
to OPAMP2
connected to
reference
VREFINT
voltage
– 1 channel
output
connected to
(VREFOPA
OPAMP1 reference
MP2).
voltage output
(VREFOPAMP1).

5

DocID022558 Rev 8

N.A

N.A

307/1141
413

Analog-to-digital converters (ADC)
•

•

RM0316

Start-of-conversion can be initiated:
–

by software for both regular and injected conversions

–

by hardware triggers with configurable polarity (internal timers events or GPIO
input events) for both regular and injected conversions

Conversion modes
–

Each ADC can convert a single channel or can scan a sequence of channels

–

Single mode converts selected inputs once per trigger

–

Continuous mode converts selected inputs continuously

–

Discontinuous mode

•

Dual ADC mode

•

Interrupt generation at the end of conversion (regular or injected), end of sequence
conversion (regular or injected), analog watchdog 1, 2 or 3 or overrun events

•

3 analog watchdogs per ADC

•

ADC supply requirements: 1.80 V to 3.6 V

•

ADC input range: VREF– ≤ VIN ≤ VREF+

Figure 52 shows the block diagram of one ADC.

308/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.3

ADC functional description

15.3.1

ADC block diagram
Figure 52 shows the ADC block diagram and Table 88 gives the ADC pin description.
Figure 52. ADC block diagram
95()
ϭ͘ϴƚŽϯ͘ϲs

ͺ:^YZdž
ͺ^YZdž

ĂƵƚŽƉŽǁĞƌͲĚŽǁŶ

-'$7$>@
-'$7$>@
-'$7$>@
-'$7$>@

Eͬ/^

$QDORJ6XSSO\ 9''$
ϭ͘ϴsƚŽϯ͘ϲ9

:hdK

KEd
ƐŝŶŐůĞͬĐŽŶƚ
s23$03[
s76
s5(),17
s%$7
ͺ/E
΀ϭϱ͗ϭ΁
s5()

/ŶƚĞƌƌƵƉƚ

ŽƌƚĞdž
DϰZLWK
)38
/ZY

VODYH

PDVWHU

+%

5'$7$>@

$5($'<
(2603
K
K^
KsZ
:K^
:YKs&
tdž

PDVWHU
D

$+%
ŝŶƚĞƌĨĂĐĞ

DƌĞƋƵĞƐƚ

ŝĂƐΘZĞĨ
>
ƐĞůĨĐĂůŝďƌĂƚŝŽŶ

s,13>@ ,QSXW
s,11>@ VHOHFWLRQ 
VFDQFRQWURO
ĂŶĂůŽŐŝŶƉƵƚ
ĐŚĂŶŶĞůƐ
^DWdž΀Ϯ͗Ϭ΁
ƐĂŵƉůŝŶŐƚŝŵĞ

s,1

D&'
DE

^Z
KEsZd
d
ƐƚĂƌƚ

^ƚĂƌƚΘ^ƚŽƉ
ŽŶƚƌŽů
hd>z
ĂƵƚŽĚĞůĂLJĞĚ

KsZDK
ŽǀĞƌƌƵŶŵŽĚĞ

6:ƚƌŝŐŐĞƌ

^dW
ƐƚŽƉĐŽŶǀ

>/'E
ůĞĨƚͬƌŝŐŚƚ
Z^΀ϭ͗Ϭ΁
ϭϮ͕ϭϬ͕ϴďLƚƐ
:K&&^ddž΀ϭϭ͗Ϭ΁

ydϬ
ydϭ
ydϮ
͘͘͘͘͘͘͘
͘͘͘͘͘͘͘
ydϭϯ
ydϭϰ
ydϭϱ

:K&&^ddžͺ,΀ϭϭ͗Ϭ΁
Śͬǁ
ƚƌŝŐŐĞƌ
ydE΀ϭ͗Ϭ΁
ƚƌŝŐŐĞƌĞŶĂďůĞ
ĂŶĚĞĚŐĞƐĞůĞĐƚŝŽŶ

ydŝŵĂƉƉĞĚDW
SURGXFWOHYHO

/^E
/^Eh΀͗Ϭ΁

$QDORJǁĂƚĐŚĚŽŐϭ͕Ϯ͕ϯ

ŝƐĐŽŶƚŝŶƵŽƵƐ
ŵŽĚĞ

tϭ
tϮ
tϯ

yd^>΀ϯ͗Ϭ΁
ƚƌŝŐŐĞƌƐĞůĞĐƚŝŽŶ

tϭͺKhd
tϮͺKhd
tϯͺKhd

d/DZƐ
dZ

:

6:ƚƌŝŐŐĞƌ
tϭE
:ydϬ
:ydϭ
:ydϮ
͘͘͘͘͘͘͘
͘͘͘͘͘͘͘
:ydϭϯ
:ydϭϰ
:ydϭϱ

:tϭE
+:
ƚƌŝŐŐĞƌ
:ydE΀ϭ͗Ϭ΁
ƚƌŝŐŐĞƌĞŶĂďůĞ
ĂŶĚĞĚŐĞƐĞůĞĐƚŝŽŶ

:ydŝŵĂƉƉĞĚDW
SURGXFWOHYHO

tϭ^'>
:/^E
:/^EhD΀Ϯ͗Ϭ΁
:YD
/ŶũĐĞĚŽŶƚĞdžƚ
YƵĞƵĞDŽĚĞ

t,ϭ΀ϰ͗Ϭ΁
>dϭ΀ϭϭ͗Ϭ΁
,dϭ΀ϭϭ͗Ϭ΁
t,Ϯ΀ϭϴ͗Ϭ΁
>dϮ΀ϳ͗Ϭ΁
t,ϯ΀ϭϴ͗Ϭ΁
,dϮ΀ϳ͗Ϭ΁

:yd^>΀ϯ͗Ϭ΁
ƚƌŝŐŐĞƌƐĞůĞĐƚŝŽŶ

,dϯ΀ϳ͗Ϭ΁
>dϯ΀ϳ͗Ϭ΁
D^ǀϯϬϮϲϬsϯ

DocID022558 Rev 8

309/1141
413

Analog-to-digital converters (ADC)

15.3.2

RM0316

Pins and internal signals
Table 87. ADC internal signals
Signal
type

Description

Inputs

Up to 16 external trigger inputs for the regular conversions (can
be connected to on-chip timers).
These inputs are shared between the ADC master and the ADC
slave.

JEXT[15:0]

Inputs

Up to 16 external trigger inputs for the injected conversions (can
be connected to on-chip timers).
These inputs are shared between the ADC master and the ADC
slave.

ADC1_AWDx_OUT
ADC2_AWDx_OUT
ADC3_AWDx_OUT
ADC4_AWDx_OUT

Output

Internal analog watchdog output signal connected to on-chip
timers. (x = Analog watchdog number 1,2,3)

VREFOPAMP1

Input

Reference voltage output from internal operational amplifier 1

VREFOPAMP2

Input

Reference voltage output from internal operational amplifier 2

VREFOPAMP3

Input

Reference voltage output from internal operational amplifier 3

VREFOPAMP4

Input

Reference voltage output from internal operational amplifier 4

VTS

Input

Output voltage from internal temperature sensor

VREFINT

Input

Output voltage from internal reference voltage

Internal signal name

EXT[15:0]

VBAT

Input
supply

External battery voltage supply

Table 88. ADC pins
Name

Signal type

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 VDDA:
1.8V ≤ VDDA ≤ 3.6 V

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

VINP[18:1]

Positive input analog
channels for each ADC

Connected either to external channels: ADC_INi or
internal channels.

VINN[18:1]

Negative input analog
channels for each ADC

Connected to VREF- or external channels: ADC_INi-1

ADCx_IN15:1 External analog input signals

310/1141

Comments

Up to 16 analog input channels (x = ADC number =
1,2,3 or 4):
– 5 fast channels
– 10 slow channels

DocID022558 Rev 8

RM0316

15.3.3

Analog-to-digital converters (ADC)

Clocks
Dual clock domain architecture
The dual clock-domain architecture means that each ADC clock is independent from the
AHB bus clock.
The input clock of the two ADCs (master and slave) can be selected between two different
clock sources (see Figure 53: ADC clock scheme):
a)

The ADC clock can be a specific clock source, named “ADCxy_CK (xy=12 or 34)
which is independent and asynchronous with the AHB clock”.
It can be configured in the RCC to deliver up to 72 MHz (PLL output). Refer to
RCC Section for more information on generating ADC12_CK and ADC34_CK.
To select this scheme, bits CKMODE[1:0] of the ADCx_CCR register must be
reset.

b)

The ADC clock can be derived from the AHB clock of the ADC bus interface,
divided by a programmable factor (1, 2 or 4). In this mode, a programmable divider
factor can be selected (/1, 2 or 4 according to bits CKMODE[1:0]).
To select this scheme, bits CKMODE[1:0] of the ADCx_CCR register must be
different from “00”.

Note:

Software can use option b) by writing CKMODE[1:0]=01 only if the AHB prescaler of the
RCC is set to 1 (the duty cycle of the AHB clock must be 50% in this configuration).
Option a) has the advantage of reaching the maximum ADC clock frequency whatever the
AHB clock scheme selected. The ADC clock can eventually be divided by the following ratio:
1, 2, 4, 6, 8, 12, 16, 32, 64, 128, 256; using the prescaler configured with bits
ADCxPRES[4:0] in register RCC_CFGR2 (Refer to Section 9: Reset and clock control
(RCC)).
Option b) has the advantage of bypassing the clock domain resynchronizations. This can be
useful when the ADC is triggered by a timer and if the application requires that the ADC is
precisely triggered without any uncertainty (otherwise, an uncertainty of the trigger instant is
added by the resynchronizations between the two clock domains).

DocID022558 Rev 8

311/1141
413

Analog-to-digital converters (ADC)

RM0316
Figure 53. ADC clock scheme
$'& $'&
+&/.

$+%
LQWHUIDFH
%LWV&.02'(>@
RI$'&B&&5
RU
RU

$'&B&.

5&&
 5HVHWDQGFORFN
FRQWUROOHU

2WKHUV

$QDORJ$'&
PDVWHU



$QDORJ$'&
VODYH

%LWV&.02'(>@
RI$'&B&&5

+&/.

$'& $'&
$+%
LQWHUIDFH
%LWV&.02'(>@
RI$'&B&&5

$'&B&.

RU
RU

2WKHUV


$QDORJ$'&
PDVWHU
$QDORJ$'&
VODYH

%LWV&.02'(>@
RI$'&B&&5
06Y9

1.

Refer to the RCC section to see how HCLK, ADC12_CK, and ADC34_CK can be generated.

Clock ratio constraint between ADC clock and AHB clock
There are generally no constraints to be respected for the ratio between the ADC clock and
the AHB clock except if some injected channels are programmed. In this case, it is
mandatory to respect the following ratio:

312/1141

•

FHCLK >= FADC / 4 if the resolution of all channels are 12-bit or 10-bit

•

FHCLK >= FADC / 3 if there are some channels with resolutions equal to 8-bit (and none
with lower resolutions)

•

FHCLK >= FADC / 2 if there are some channels with resolutions equal to 6-bit

DocID022558 Rev 8

RM0316

15.3.4

Analog-to-digital converters (ADC)

ADC1/2 and ADC3/4 connectivity
ADC1 and ADC2 (respectively ADC3 and ADC4) are tightly coupled and share some
external channels as described in Figure 54 and Figure 55.
Figure 54. ADC1 and ADC2 connectivity
670)[[
$'&B,1
$'&B,1
$'&B,1
$'&B,1


$'&B,1
$'&B,1
$'&B,1
$'&B,1
$'&B,1
$'&B,1
$'&B,1
$'&B,1
$'&B,1





95()
95()
95()
923$03
976
9%$7
95(),17

95()
95()
95()
95()
95()

$'&
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@

&KDQQHO6HOHFWLRQ
IDVWFKDQQHO
IDVWFKDQQHO
IDVWFKDQQHO
IDVWFKDQQHO
IDVWFKDQQHO
VORZFKDQQHO
VORZFKDQQHO

95()
9,13
9,11

6$5
$'&

VORZFKDQQHO
VORZFKDQQHO
VORZFKDQQHO

95()

6LQJOHHQGHG
0RGH

VORZFKDQQHO
VORZFKDQQHO
VORZFKDQQHO
UHVHUYHG
VORZFKDQQHO
VORZFKDQQHO
VORZFKDQQHO
VORZFKDQQHO

$'&

$'&B,1
$'&B,1
$'&B,1
$'&B,1
$'&B,1

$'&B,1
$'&B,1
$'&B,1



$'&B,1 
$'&B,1


95()
95()
95()
923$03
95(),17

95()
95()

'LIIHUHQWLDO0RGH
&KDQQHO6HOHFWLRQ
9,13>@
9,11>@
IDVWFKDQQHO
9,13>@
9,11>@
IDVWFKDQQHO
9,13>@
IDVWFKDQQHO
9,11>@
9,13>@
IDVWFKDQQHO
9,11>@
9,13>@
9,11>@
IDVWFKDQQHO
95()
9,13>@
9,11>@
VORZFKDQQHO
9,13
6$5
9,13>@
9,11>@
VORZFKDQQHO
$'&
9,11
9,13>@
9,11>@
VORZFKDQQHO
95()
9,13>@
9,11>@
VORZFKDQQHO
6LQJOHHQGHG
9,13>@
0RGH
9,11>@
VORZFKDQQHO
9,13>@
9,11>@
VORZFKDQQHO
9,13>@
9,11>@
VORZFKDQQHO
9,13>@
9,11>@
VORZFKDQQHO
9,13>@
9,11>@
VORZFKDQQHO
9,13>@
9,11>@
VORZFKDQQHO
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@

UHVHUYHG
VORZFKDQQHO
VORZFKDQQHO

95()

06Y9

DocID022558 Rev 8

313/1141
413

Analog-to-digital converters (ADC)

RM0316

1. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices only.
2. STM32F303x6/8 and STM32F328x8 devices only.

314/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 55. ADC3 & ADC4 connectivity
670)[[
$'&B,1
$'&B,1
$'&B,1

$'&B,1

$'&
9,13>@
9,11>@
9,13>@
9,11>@

$'&B,1QRW
ERQGHGDQG
FRQQHFWHGWR
JURXQG 966

$'&B,1
$'&B,1
$'&B,1
$'&B,1

9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@

&KDQQHO6HOHFWLRQ
IDVWFKDQQHO
IDVWFKDQQHO
IDVWFKDQQHO
IDVWFKDQQHO
IDVWFKDQQHO
VORZFKDQQHO
VORZFKDQQHO

95()

VORZFKDQQHO

$'&B,1

9,13>@
9,11>@

VORZFKDQQHO

$'&B,1

9,13>@
9,11>@

VORZFKDQQHO

$'&B,1

9,13>@
9,11>@

VORZFKDQQHO

$'&B,1
$'&B,1
95()
923$03
95()
95(),17
95()

9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@

6$5
$'&

VORZFKDQQHO

9,13>@
9,11>@

9,13>@
9,11>@
9,13>@
9,11>@

9,11

VORZFKDQQHO

$'&B,1

$'&B,1

95()
9,13

6LQJOHHQGHG
0RGH

VORZFKDQQHO
VORZFKDQQHO
VORZFKDQQHO
VORZFKDQQHO
VORZFKDQQHO

95()

$'&
&KDQQHO6HOHFWLRQ

$'&B,1

9,13>@
9,11>@

IDVWFKDQQHO

$'&B,1

9,13>@
9,11>@

IDVWFKDQQHO

$'&B,1

9,13>@
9,11>@

IDVWFKDQQHO

9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@

$'&B,1
$'&B,1

$'&B,1
$'&B,1
95()
95()
95()
923$03


95(),17

95()
95()

9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@
9,13>@
9,11>@

IDVWFKDQQHO
IDVWFKDQQHO
VORZFKDQQHO

95()
9,13

VORZFKDQQHO
9,11

VORZFKDQQHO

6$5
$'&
95()

VORZFKDQQHO
VORZFKDQQHO

6LQJOHHQGHG
0RGH

VORZFKDQQHO
VORZFKDQQHO
VORZFKDQQHO
UHVHUYHG
VORZFKDQQHO
VORZFKDQQHO

95()

06Y9

DocID022558 Rev 8

315/1141
413

Analog-to-digital converters (ADC)

15.3.5

RM0316

Slave AHB interface
The ADCs implement an AHB slave port for control/status register and data access. The
features of the AHB interface are listed below:
•

Word (32-bit) accesses

•

Single cycle response

•

Response to all read/write accesses to the registers with zero wait states.

The AHB slave interface does not support split/retry requests, and never generates AHB
errors.

15.3.6

ADC voltage regulator (ADVREGEN)
The sequence below is required to start ADC operations:
1.

Enable the ADC internal voltage regulator (refer to the ADC voltage regulator enable
sequence).

2.

The software must wait for the startup time of the ADC voltage regulator
(TADCVREG_STUP) before launching a calibration or enabling the ADC. This
temporization must be implemented by software. TADCVREG_STUP is equal to 10 µs in
the worst case process/temperature/power supply.

After ADC operations are complete, the ADC is disabled (ADEN=0).
It is possible to save power by disabling the ADC voltage regulator (refer to the ADC voltage
regulator disable sequence).
Note:

When the internal voltage regulator is disabled, the internal analog calibration is kept.

ADVREG enable sequence
To enable the ADC voltage regulator, perform the sequence below:
1.

Change ADVREGEN[1:0] bits from ‘10’ (disabled state, reset state) into ‘00’.

2.

Change ADVREGEN[1:0] bits from ‘00’ into ‘01’ (enabled state).

ADVREG disable sequence
To disable the ADC voltage regulator, perform the sequence below:

15.3.7

1.

Change ADVREGEN[1:0] bits from ‘01’ (enabled state) into ‘00’.

2.

Change ADVREGEN[1:0] bits from ‘00’ into ‘10’ (disabled state)

Single-ended and differential input channels
Channels can be configured to be either single-ended input or differential input by writing
into bits DIFSEL[15:1] in the ADCx_DIFSEL register. This configuration must be written
while the ADC is disabled (ADEN=0). Note that DIFSEL[18:16] are fixed to single ended
channels (internal channels only) and are always read as 0.
In single-ended input mode, the analog voltage to be converted for channel “i” is the
difference between the external voltage ADC_INi (positive input) and VREF- (negative input).
In differential input mode, the analog voltage to be converted for channel “i” is the difference
between the external voltage ADC_INi (positive input) and ADC_INi+1 (negative input).

316/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
For a complete description of how the input channels are connected for each ADC, refer to
Figure 54: ADC1 and ADC2 connectivity on page 313 and Figure 55: ADC3 & ADC4
connectivity on page 315.

Caution:

When configuring the channel “i” in differential input mode, its negative input voltage is
connected to ADC_INi+1. As a consequence, channel “i+1” is no longer usable in singleended mode or in differential mode and must never be configured to be converted.
Some channels are shared between ADC1 and ADC2(respectively ADC3 and ADC4): this
can make the channel on the other ADC unusable. Only exception is interleave mode for
ADC master and the slave.
Example: Configuring ADC1_IN5 in differential input mode will make ADC12_IN6 not
usable: in that case, the channels 6 of both ADC1 and ADC2 must never be converted.

Note:

Channels 16, 17 and 18 of ADC1 and channels 17 and 18 of ADC2, ADC3 and ADC4 are
connected to internal analog channels and are internally fixed to single-ended inputs
configuration (corresponding bits DIFSEL[i] is always zero). Channel 15 of ADC1 is also an
internal channel and the user must configure the corresponding bit DIFSEL[15] to zero.

15.3.8

Calibration (ADCAL, ADCALDIF, ADCx_CALFACT)
Each ADC provides an automatic calibration procedure which drives all the calibration
sequence including the power-on/off sequence of the ADC. During the procedure, the ADC
calculates a calibration factor which is 7-bit wide and which is applied internally to the ADC
until the next ADC power-off. During the calibration procedure, the application must not use
the ADC and must wait until calibration is complete.
Calibration is preliminary to any ADC operation. It removes the offset error which may vary
from chip to chip due to process or bandgap variation.
The calibration factor to be applied for single-ended input conversions is different from the
factor to be applied for differential input conversions:
•

Write ADCALDIF=0 before launching a calibration which will be applied for singleended input conversions.

•

Write ADCALDIF=1 before launching a calibration which will be applied for differential
input conversions.

The calibration is then initiated by software by setting bit ADCAL=1. Calibration can only be
initiated when the ADC is disabled (when ADEN=0). ADCAL bit stays at 1 during all the
calibration sequence. It is then cleared by hardware as soon the calibration completes. At
this time, the associated calibration factor is stored internally in the analog ADC and also in
the bits CALFACT_S[6:0] or CALFACT_D[6:0] of ADCx_CALFACT register (depending on
single-ended or differential input calibration)
The internal analog calibration is kept if the ADC is disabled (ADEN=0). However, if the ADC
is disabled for extended periods, then it is recommended that a new calibration cycle is run
before re-enabling the ADC.
The internal analog calibration is kept if the ADC is disabled (ADEN=0). When the ADC
operating conditions change (VREF+ changes are the main contributor to ADC offset
variations, VDDA and temperature change to a lesser extent), it is recommended to re-run a
calibration cycle.
The internal analog calibration is lost each time the power of the ADC is removed (example,
when the product enters in STANDBY or VBAT mode). In this case, to avoid spending time
recalibrating the ADC, it is possible to re-write the calibration factor into the

DocID022558 Rev 8

317/1141
413

Analog-to-digital converters (ADC)

RM0316

ADCx_CALFACT register without recalibrating, supposing that the software has previously
saved the calibration factor delivered during the previous calibration.
The calibration factor can be written if the ADC is enabled but not converting (ADEN=1 and
ADSTART=0 and JADSTART=0). Then, at the next start of conversion, the calibration factor
will automatically be injected into the analog ADC. This loading is transparent and does not
add any cycle latency to the start of the conversion.

Software procedure to calibrate the ADC
1.

Ensure ADVREGEN[1:0]=01 and that ADC voltage regulator startup time has elapsed.

2.

Ensure that ADEN=0.

3.

Select the input mode for this calibration by setting ADCALDIF=0 (Single-ended input)
or ADCALDIF=1 (Differential input).

4.

Set ADCAL=1.

5.

Wait until ADCAL=0.

6.

The calibration factor can be read from ADCx_CALFACT register.
Figure 56. ADC calibration
$'&$/',)

6LQJOHHQGHGLQSXW'LIIHUHQWLDOLQSXW
W&$%

$'&$/
$'&6WDWH

2))

6WDUWXS
[

&$/)$&7B[>@

E\6:

&DOLEUDWH

E\+:

2))
&DOLEUDWLRQIDFWRU

,QGLFDWLYHWLPLQJV

06Y9

Software procedure to re-inject a calibration factor into the ADC

318/1141

1.

Ensure ADEN=1 and ADSTART=0 and JADSTART=0 (ADC enabled and no
conversion is ongoing).

2.

Write CALFACT_S and CALFACT_D with the new calibration factors.

3.

When a conversion is launched, the calibration factor will be injected into the analog
ADC only if the internal analog calibration factor differs from the one stored in bits
CALFACT_S for single-ended input channel or bits CALFACT_D for differential input
channel.

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 57. Updating the ADC calibration factor
5HDG\ QRWFRQYHUWLQJ

$'&VWDWH

&RQYHUWLQJFKDQQHO
6LQJOHHQGHG

5HDG\ &RQYHUWLQJFKDQQHO
6LQJOHHQGHG

8SGDWLQJFDOLEUDWLRQ
,QWHUQDO
FDOLEUDWLRQIDFWRU>@

)

)

6WDUWFRQYHUVLRQ
KDUGZDUHRUVRIZDUH
:5,7($'&B&$/)$&7
&$/)$&7B6>@

E\VZ

)

E\KZ
06Y9

Converting single-ended and differential analog inputs with a single ADC
If the ADC is supposed to convert both differential and single-ended inputs, two calibrations
must be performed, one with ADCALDIF=0 and one with ADCALDIF=1. The procedure is
the following:
1.

Disable the ADC.

2.

Calibrate the ADC in single-ended input mode (with ADCALDIF=0). This updates the
register CALFACT_S[6:0].

3.

Calibrate the ADC in Differential input modes (with ADCALDIF=1). This updates the
register CALFACT_D[6:0].

4.

Enable the ADC, configure the channels and launch the conversions. Each time there
is a switch from a single-ended to a differential inputs channel (and vice-versa), the
calibration will automatically be injected into the analog ADC.
Figure 58. Mixing single-ended and differential channels
7ULJJHUHYHQW

$'&VWDWH

5'< &219&+ 5'< &219&+ 5'< &219&+ 5'<
6LQJOHHQGHG
LQSXWVFKDQQHO

,QWHUQDO
FDOLEUDWLRQIDFWRU>@

)

&$/)$&7B6>@

)

&$/)$&7B'>@

)

'LIIHUHQWLDO
LQSXWVFKDQQHO
)

'LIIHUHQWLDO
LQSXWVFKDQQHO

&219&+
6LQJOHLQSXWV
FKDQQHO
)

06Y9

DocID022558 Rev 8

319/1141
413

Analog-to-digital converters (ADC)

15.3.9

RM0316

ADC on-off control (ADEN, ADDIS, ADRDY)
First of all, follow the procedure explained in Section 15.3.6: ADC voltage regulator
(ADVREGEN)).
Once ADVREGEN[1:0] = 01, the ADC can be enabled and the ADC needs a stabilization
time of tSTAB before it starts converting accurately, as shown in Figure 59. Two control bits
enable or disable the ADC:
•

ADEN=1 enables the ADC. The flag ADRDY will be set once the ADC is ready for
operation.

•

ADDIS=1 disables the ADC and disable the ADC. ADEN and ADDIS are then
automatically cleared by hardware as soon as the analog ADC is effectively disabled.

Regular conversion can then start either by setting ADSTART=1 (refer to Section 15.3.18:
Conversion on external trigger and trigger polarity (EXTSEL, EXTEN, JEXTSEL, JEXTEN))
or when an external trigger event occurs, if triggers are enabled.
Injected conversions start by setting JADSTART=1 or when an external injected trigger
event occurs, if injected triggers are enabled.

Software procedure to enable the ADC

Note:

1.

Set ADEN=1.

2.

Wait until ADRDY=1 (ADRDY is set after the ADC startup time). This can be done
using the associated interrupt (setting ADRDYIE=1).

ADEN bit cannot be set during ADCAL=1 and 4 ADC clock cycle after the ADCAL bit is
cleared by hardware(end of the calibration).

Software procedure to disable the ADC
1.

Check that both ADSTART=0 and JADSTART=0 to ensure that no conversion is
ongoing. If required, stop any regular and injected conversion ongoing by setting
ADSTP=1 and JADSTP=1 and then wait until ADSTP=0 and JADSTP=0.

2.

Set ADDIS=1.

3.

If required by the application, wait until ADEN=0, until the analog ADC is effectively
disabled (ADDIS will automatically be reset once ADEN=0).
Figure 59. Enabling / Disabling the ADC
$'(1
W67$%
$'5'<

$'',6

$'&
VWDW

E\6:

320/1141

2))

6WDUWXS

5'<

&RQYHUWLQJ&+

E\+:

5'<

5(4
2)

2))

06Y9

DocID022558 Rev 8

RM0316

15.3.10

Analog-to-digital converters (ADC)

Constraints when writing the ADC control bits
The software is allowed to write the RCC control bits to configure and enable the ADC clock
(refer to RCC Section), the control bits DIFSEL in the ADCx_DIFSEL register and the
control bits ADCAL and ADEN in the ADCx_CR register, only if the ADC is disabled (ADEN
must be equal to 0).
The software is then allowed to write the control bits ADSTART, JADSTART and ADDIS of
the ADCx_CR register only if the ADC is enabled and there is no pending request to disable
the ADC (ADEN must be equal to 1 and ADDIS to 0).
For all the other control bits of the ADCx_CFGR, ADCx_SMPRx, ADCx_TRx, ADCx_SQRx,
ADCx_JDRy, ADCx_OFRy, ADCx_OFCHR and ADCx_IER registers:
•

For control bits related to configuration of regular conversions, the software is allowed
to write them only if the ADC is enabled (ADEN=1) and if there is no regular conversion
ongoing (ADSTART must be equal to 0).

•

For control bits related to configuration of injected conversions, the software is allowed
to write them only if the ADC is enabled (ADEN=1) and if there is no injected
conversion ongoing (JADSTART must be equal to 0).

The software is allowed to write the control bits ADSTP or JADSTP of the ADCx_CR
register only if the ADC is enabled and eventually converting and if there is no pending
request to disable the ADC (ADSTART or JADSTART must be equal to 1 and ADDIS to 0).
The software can write the register ADCx_JSQR at any time, when the ADC is enabled
(ADEN=1).
Note:

There is no hardware protection to prevent these forbidden write accesses and ADC
behavior may become in an unknown state. To recover from this situation, the ADC must be
disabled (clear ADEN=0 as well as all the bits of ADCx_CR register).

15.3.11

Channel selection (SQRx, JSQRx)
There are up to 18 multiplexed channels per ADC:
•

Up to 5 fast analog inputs coming from GPIO pads (ADC_IN1..5)

•

Up to 10 slow analog inputs coming from GPIO pads (ADC_IN5..15). Depending on the
products, not all of them are available on GPIO pads.

•

ADC1 is connected to 4 internal analog inputs:
–

ADC1_IN15 = VREFOPAMP1 = Reference Voltage for the Operational Amplifier 1 (in
STM32F303xB/C and STM32F358xC)

–

ADC1_IN16 = VTS = Temperature Sensor

–

ADC1_IN17 = VBAT/2 = VBAT channel

–

ADC1_IN18 = VREFINT = Internal Reference Voltage (also connected to
ADC2_IN18, ADC3_IN18 and ADC4_IN18).

•

ADC2_IN17 = VREFOPAMP2 = Reference Voltage for the Operational Amplifier 2

•

ADC3_IN17 = VREFOPAMP3 = Reference Voltage for the Operational Amplifier 3 (in
STM32F303xB/C/D/E and STM32F358C)

•

ADC4_IN17 = VREFOPAMP4 = Reference Voltage for the Operational Amplifier 4 (in
STM32F303xB/C/D/E and STM32F358C)

DocID022558 Rev 8

321/1141
413

Analog-to-digital converters (ADC)

Warning:

Note:

RM0316

The user must ensure that only one of the four ADCs is
converting VREFINT at the same time (it is forbidden to have
several ADCs converting VREFINT at the same time).

To convert one of the internal analog channels, the corresponding analog sources must first
be enabled by programming bits VREFEN, TSEN or VBATEN in the ADCx_CCR registers.
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 ADCx_SQR registers. The
total number of conversions in the regular group must be written in the L[3:0] bits in the
ADCx_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 ADCx_JSQR register.
The total number of conversions in the injected group must be written in the L[1:0] bits
in the ADCx_JSQR register.

ADCx_SQR registers must not be modified while regular conversions can occur. For this,
the ADC regular conversions must be first stopped by writing ADSTP=1 (refer to
Section 15.3.17: Stopping an ongoing conversion (ADSTP, JADSTP)).
It is possible to modify the ADCx_JSQR registers on-the-fly while injected conversions are
occurring. Refer to Section 15.3.21: Queue of context for injected conversions

15.3.12

Channel-wise programmable sampling time (SMPR1, SMPR2)
Before starting a conversion, the ADC must establish a direct connection between the
voltage source under measurement and the embedded sampling capacitor of the ADC. This
sampling time must be enough for the input voltage source to charge the embedded
capacitor to the input voltage level.
Each channel can be sampled with a different sampling time which is programmable using
the SMP[2:0] bits in the ADCx_SMPR1 and ADCx_SMPR2 registers. It is therefore possible
to select among the following sampling time values:
•

SMP = 000: 1.5 ADC clock cycles

•

SMP = 001: 2.5 ADC clock cycles

•

SMP = 010: 4.5 ADC clock cycles

•

SMP = 011: 7.5 ADC clock cycles

•

SMP = 100: 19.5 ADC clock cycles

•

SMP = 101: 61.5 ADC clock cycles

•

SMP = 110: 181.5 ADC clock cycles

•

SMP = 111: 601.5 ADC clock cycles

The total conversion time is calculated as follows:
Tconv = Sampling time + 12.5 ADC clock cycles

322/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Example:
With FADC_CLK = 72 MHz and a sampling time of 1.5 ADC clock cycles:
Tconv = (1.5 + 12.5) ADC clock cycles = 14 ADC clock cycles = 0.194 µs (for fast
channels)
The ADC notifies the end of the sampling phase by setting the status bit EOSMP (only for
regular conversion).

Constraints on the sampling time for fast and slow channels
For each channel, SMP[2:0] bits must be programmed to respect a minimum sampling time
as specified in the ADC charateristics section of the datasheets.

15.3.13

Single conversion mode (CONT=0)
In Single conversion mode, the ADC performs once all the conversions of the channels.
This mode is started with the CONT bit at 0 by either:
•

Setting the ADSTART bit in the ADCx_CR register (for a regular channel)

•

Setting the JADSTART bit in the ADCx_CR register (for an injected channel)

•

External hardware trigger event (for a regular or injected channel)

Inside the regular sequence, after each conversion is complete:
•

The converted data are stored into the 16-bit ADCx_DR register

•

The EOC (end of regular conversion) flag is set

•

An interrupt is generated if the EOCIE bit is set

Inside the injected sequence, after each conversion is complete:
•

The converted data are stored into one of the four 16-bit ADCx_JDRy registers

•

The JEOC (end of injected conversion) flag is set

•

An interrupt is generated if the JEOCIE bit is set

After the regular sequence is complete:
•

The EOS (end of regular sequence) flag is set

•

An interrupt is generated if the EOSIE bit is set

After the injected sequence is complete:
•

The JEOS (end of injected sequence) flag is set

•

An interrupt is generated if the JEOSIE bit is set

Then the ADC stops until a new external regular or injected trigger occurs or until bit
ADSTART or JADSTART is set again.
Note:

To convert a single channel, program a sequence with a length of 1.

15.3.14

Continuous conversion mode (CONT=1)
This mode applies to regular channels only.
In continuous conversion mode, when a software or hardware regular trigger event occurs,
the ADC performs once all the regular conversions of the channels and then automatically
re-starts and continuously converts each conversions of the sequence. This mode is started
with the CONT bit at 1 either by external trigger or by setting the ADSTART bit in the
ADCx_CR register.

DocID022558 Rev 8

323/1141
413

Analog-to-digital converters (ADC)

RM0316

Inside the regular sequence, after each conversion is complete:
•

The converted data are stored into the 16-bit ADCx_DR register

•

The EOC (end of conversion) flag is set

•

An interrupt is generated if the EOCIE bit is set

After the sequence of conversions is complete:
•

The EOS (end of sequence) flag is set

•

An interrupt is generated if the EOSIE bit is set

Then, a new sequence restarts immediately and the ADC continuously repeats the
conversion sequence.
Note:

To convert a single channel, program a sequence with a length of 1.
It is not possible to have both discontinuous mode and continuous mode enabled: it is
forbidden to set both DISCEN=1 and CONT=1.
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 mode section).

15.3.15

Starting conversions (ADSTART, JADSTART)
Software starts ADC regular conversions by setting ADSTART=1.
When ADSTART is set, the conversion starts:
•

Immediately: if EXTEN = 0x0 (software trigger)

•

At the next active edge of the selected regular hardware trigger: if EXTEN /= 0x0

Software starts ADC injected conversions by setting JADSTART=1.
When JADSTART is set, the conversion starts:

Note:

•

Immediately, if JEXTEN = 0x0 (software trigger)

•

At the next active edge of the selected injected hardware trigger: if JEXTEN /= 0x0

In auto-injection mode (JAUTO=1), use ADSTART bit to start the regular conversions
followed by the auto-injected conversions (JADSTART must be kept cleared).
ADSTART and JADSTART also provide information on whether any ADC operation is
currently ongoing. It is possible to re-configure the ADC while ADSTART=0 and
JADSTART=0 are both true, indicating that the ADC is idle.
ADSTART is cleared by hardware:
•

In single mode with software regular trigger (CONT=0, EXTSEL=0x0)
–

•

In all cases (CONT=x, EXTSEL=x)
–

Note:

at any end of regular conversion sequence (EOS assertion) or at any end of subgroup processing if DISCEN = 1
after execution of the ADSTP procedure asserted by the software.

In continuous mode (CONT=1), ADSTART is not cleared by hardware with the assertion of
EOS because the sequence is automatically relaunched.
When a hardware trigger is selected in single mode (CONT=0 and EXTSEL /=0x00),
ADSTART is not cleared by hardware with the assertion of EOS to help the software which
does not need to reset ADSTART again for the next hardware trigger event. This ensures
that no further hardware triggers are missed.

324/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
JADSTART is cleared by hardware:
•

in single mode with software injected trigger (JEXTSEL=0x0)
–

•

at any end of injected conversion sequence (JEOS assertion) or at any end of
sub-group processing if JDISCEN = 1

in all cases (JEXTSEL=x)
–

15.3.16

after execution of the JADSTP procedure asserted by the software.

Timing
The elapsed time between the start of a conversion and the end of conversion is the sum of
the configured sampling time plus the successive approximation time depending on data
resolution:
TADC = TSMPL + TSAR = [ 1.5 |min + 12.5 |12bit ] x TADC_CLK
TADC = TSMPL + TSAR = 20.83 ns |min + 173.6 ns |12bit = 194.4 ns (for FADC_CLK = 72 MHz)

Figure 60. Analog to digital conversion time
$'&VWDWH

5'<

6DPSOLQJ&K 1

$QDORJFKDQQHO

&K 1

&K 1

,QWHUQDO6+
$'67$57

6DPSOLQJ&K 1

&RQYHUWLQJ&K 1

6HW
E\6:

(2603

+ROG$,1 1
W6$5 

6DPSOH$,1 1
W603/ 
6HW
E\+:



&OHDUHG
E\6:
6HW
E\+:

(2&
$'&B'5

6DPSOH$,1 1

'DWD1

&OHDUHG
E\6:

'DWD1

,QGLFDWLYHWLPLQJV
069

1. TSMPL depends on SMP[2:0]
2. TSAR depends on RES[2:0]

15.3.17

Stopping an ongoing conversion (ADSTP, JADSTP)
The software can decide to stop regular conversions ongoing by setting ADSTP=1 and
injected conversions ongoing by setting JADSTP=1.
Stopping conversions will reset the ongoing ADC operation. Then the ADC can be
reconfigured (ex: changing the channel selection or the trigger) ready for a new operation.
Note that it is possible to stop injected conversions while regular conversions are still
operating and vice-versa. This allows, for instance, re-configuration of the injected
conversion sequence and triggers while regular conversions are still operating (and viceversa).
When the ADSTP bit is set by software, any ongoing regular conversion is aborted with
partial result discarded (ADCx_DR register is not updated with the current conversion).

DocID022558 Rev 8

325/1141
413

Analog-to-digital converters (ADC)

RM0316

When the JADSTP bit is set by software, any ongoing injected conversion is aborted with
partial result discarded (ADCx_JDRy register is not updated with the current conversion).
The scan sequence is also aborted and reset (meaning that relaunching the ADC would restart a new sequence).
Once this procedure is complete, bits ADSTP/ADSTART (in case of regular conversion), or
JADSTP/JADSTART (in case of injected conversion) are cleared by hardware and the
software must wait until ADSTART = 0 (or JADSTART = 0) before starting a new conversion.
Note:

In auto-injection mode (JAUTO=1), setting ADSTP bit aborts both regular and injected
conversions (JADSTP must not be used).
Figure 61. Stopping ongoing regular conversions
7ULJJHU

7ULJJHU

$'&VWDWH

6DPSOH
&K 1

5'<

&RQYHUW
&K 1

5'<

6DPSOH
&K 1

&

5'<

-$'67$57

$'67$57

6HW
E\6:

&OHDUHG
E\+:

5(*8/$5&219(56,216RQJRLQJ
;ƐŽĨƚǁĂƌĞŝƐŶŽƚĂůůŽǁĞĚƚŽĐŽŶĨŝŐƵƌĞƌĞŐƵůĂƌĐŽŶǀĞƌƐŝŽŶƐƐĞůĞĐƚŝŽŶĂŶĚƚƌŝŐŐĞƌƐͿ

6HW
E\6:

$'673

$'&B'5

'DWD1

&OHDUHG
E\+:

'DWD1
069

326/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 62. Stopping ongoing regular and injected conversions
2EGULAR TRIGGER
$'&VWDWH

2$9

3AMPLE
#H. 

)NJECTED TRIGGER
#ONVERT
#H. 

2$9

2EGULAR TRIGGER

3AMPLE
#H-

#

2$9 3AMPL

2$9

#LEARED
3ET
*!$34!24 BY 37
BY (7
).*%#4%$ #/.6%23)/.3 ONGOING
SOFTWARE IS NOT ALLOWED TO CONFIGURE INJECTED CONVERSIONS SELECTION AND TRIGGERS
3ET
BY 37

*!$340

!$#?*$2

#LEARED
BY (7

$!4! - 

3ET
BY 37
!$34!24

!$340
!$#?$2

#LEARED
BY (7
2%'5,!2 #/.6%23)/.3 ONGOING
SOFTWARE IS NOT ALLOWED TO CONFIGURE REGULAR CONVERSIONS SELECTION AND TRIGGERS
3ET
BY 37
$!4! . 

#LEARED
BY (7

$!4! . 
069

15.3.18

Conversion on external trigger and trigger polarity (EXTSEL, EXTEN,
JEXTSEL, JEXTEN)
A conversion or a sequence of conversions can be triggered either by software or by an
external event (e.g. timer capture, input pins). 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.
The regular trigger selection is effective once software has set bit ADSTART=1 and the
injected trigger selection is effective once software has set bit JADSTART=1.
Any hardware triggers which occur while a conversion is ongoing are ignored.
•

If bit ADSTART=0, any regular hardware triggers which occur are ignored.

•

If bit JADSTART=0, any injected hardware triggers which occur are ignored.

Table 89 provides the correspondence between the EXTEN[1:0] and JEXTEN[1:0] values
and the trigger polarity.
Table 89. Configuring the trigger polarity for regular external triggers
EXTEN[1:0]/
JEXTEN[1:0]

Source

00

Hardware Trigger detection disabled, software trigger detection enabled

01

Hardware Trigger with detection on the rising edge

10

Hardware Trigger with detection on the falling edge

11

Hardware Trigger with detection on both the rising and falling edges

DocID022558 Rev 8

327/1141
413

Analog-to-digital converters (ADC)

RM0316

Note:

The polarity of the regular trigger cannot be changed on-the-fly.

Note:

The polarity of the injected trigger can be anticipated and changed on-the-fly. Refer to
Section 15.3.21: Queue of context for injected conversions.
The EXTSEL[3:0] and JEXTSEL[3:0] control bits select which out of 16 possible events can
trigger conversion for the regular and injected groups.
A regular group conversion can be interrupted by an injected trigger.

Note:

The regular trigger selection cannot be changed on-the-fly.
The injected trigger selection can be anticipated and changed on-the-fly. Refer to
Section 15.3.21: Queue of context for injected conversions on page 334
Each ADC master shares the same input triggers with its ADC slave as described in
Figure 63.
Figure 63. Triggers are shared between ADC master & ADC slave
$'&0$67(5
(;7
(;7LPDSSHGDW (;7
SURGXFWOHYHO


([WHUQDOUHJXODUWULJJHU

(;7
(;76(/>@

([WHUQDOLQMHFWHGWULJJHU

-(;76(/>@
$'&6/$9(

([WHUQDOUHJXODUWULJJHU

(;76(/>@
-(;7
-(;7LPDSSHGDW -(;7

SURGXFWOHYHO
-(;7

([WHUQDOLQMHFWHGWULJJHU

-(;76(/>@

06Y9

Table 90 to Table 93 give all the possible external triggers of the four ADCs for regular and
injected conversion.
Table 90. ADC1 (master) & 2 (slave) - External triggers for regular channels
Name

Source

Type

EXTSEL[3:0]

EXT0

TIM1_CC1 event

Internal signal from on chip timers

0000

EXT1

TIM1_CC2 event

Internal signal from on chip timers

0001

EXT2

TIM1_CC3 event or
TIM20_TRGO event(1)

Internal signal from on chip timers

0010

328/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Table 90. ADC1 (master) & 2 (slave) - External triggers for regular channels (continued)
Name

Source

Type

EXTSEL[3:0]

EXT3

TIM2_CC2 event or
TIM20_TRGO2(1)

Internal signal from on chip timers

0011

EXT4

TIM3_TRGO event

Internal signal from on chip timers

0100

EXT5

TIM4_CC4 event or TIM20_CC1(1)

Internal signal from on chip timers

0101

EXT6

EXTI line 11

External pin

0110

EXT7

TIM8_TRGO event

Internal signal from on chip timers

0111

EXT8

TIM8_TRGO2 event

Internal signal from on chip timers

1000

EXT9

TIM1_TRGO event

Internal signal from on chip timers

1001

EXT10

TIM1_TRGO2 event

Internal signal from on chip timers

1010

EXT11

TIM2_TRGO event

Internal signal from on chip timers

1011

EXT12

TIM4_TRGO event

Internal signal from on chip timers

1100

EXT13

TIM6_TRGO event or
TIM20_CC2(1)

Internal signal from on chip timers

1101

EXT14

TIM15_TRGO event

Internal signal from on chip timers

1110

Internal signal from on chip timers

1111

EXT15

(1)

TIM3_CC4 event or TIM20_CC3

1. Only for STM32F303xD/E and STM32F398xE devices.

Table 91. ADC1 & ADC2 - External trigger for injected channels
Name

Source

Type

JEXTSEL[3..0]

JEXT0

TIM1_TRGO event

Internal signal from on chip timers

0000

JEXT1

TIM1_CC4 event

Internal signal from on chip timers

0001

JEXT2

TIM2_TRGO event

Internal signal from on chip timers

0010

JEXT3

TIM2_CC1 event or
TIM20_TRGO(1)

Internal signal from on chip timers

0011

JEXT4

TIM3_CC4 event

Internal signal from on chip timers

0100

JEXT5

TIM4_TRGO event

Internal signal from on chip timers

0101

External pin

0110

JEXT6

EXTI line 15 or

TIM20_GRGO2(1)

JEXT7

TIM8_CC4 event

Internal signal from on chip timers

0111

JEXT8

TIM1_TRGO2 event

Internal signal from on chip timers

1000

JEXT9

TIM8_TRGO event

Internal signal from on chip timers

1001

JEXT10

TIM8_TRGO2 event

Internal signal from on chip timers

1010

JEXT11

TIM3_CC3 event

Internal signal from on chip timers

1011

JEXT12

TIM3_TRGO event

Internal signal from on chip timers

1100

Internal signal from on chip timers

1101

JEXT13

(1)

TIM3_CC1 event or TIM20_CC4

JEXT14

TIM6_TRGO event

Internal signal from on chip timers

1110

JEXT15

TIM15_TRGO event

Internal signal from on chip timers

1111

DocID022558 Rev 8

329/1141
413

Analog-to-digital converters (ADC)

RM0316

1. Only for STM32F303xD/E and STM32F398xE devices.

Table 92. ADC3 & ADC4 - External trigger for regular channels
Name

Source

Type

EXTSEL[3..0]

EXT0

TIM3_CC1 event

Internal signal from on chip timers

0000

EXT1

TIM2_CC3 event

Internal signal from on chip timers

0001

EXT2

TIM1_CC3 event

Internal signal from on chip timers

0010

EXT3

TIM8_CC1 event

Internal signal from on chip timers

0011

EXT4

TIM8_TRGO event

Internal signal from on chip timers

0100

EXT5

EXTI line 2 or TIM20_TRGO(1)

External pin

0101

EXT6

TIM4_CC1 event or
TIM20_TRGO2(1)

Internal signal from on chip timers

0110

EXT7

TIM2_TRGO event

Internal signal from on chip timers

0111

EXT8

TIM8_TRGO2 event

Internal signal from on chip timers

1000

EXT9

TIM1_TRGO event

Internal signal from on chip timers

1001

EXT10

TIM1_TRGO2 event

Internal signal from on chip timers

1010

EXT11

TIM3_TRGO event

Internal signal from on chip timers

1011

EXT12

TIM4_TRGO event

Internal signal from on chip timers

1100

EXT13

TIM7_TRGO event

Internal signal from on chip timers

1101

EXT14

TIM15_TRGO event

Internal signal from on chip timers

1110

Internal signal from on chip timers

1111

EXT15

TIM2_CC1 event or TIM20_CC1

(1)

1. Only for STM32F303xD/E and STM32F398xE devices.

Table 93. ADC3 & ADC4 - External trigger for injected channels
Name

Source

Type

JEXTSEL[3..0]

JEXT0

TIM1_TRGO event

Internal signal from on chip timers

0000

JEXT1

TIM1_CC4 event

Internal signal from on chip timers

0001

JEXT2

TIM4_CC3 event

Internal signal from on chip timers

0010

JEXT3

TIM8_CC2 event

Internal signal from on chip timers

0011

JEXT4

TIM8_CC4 event

Internal signal from on chip timers

0100

JEXT5

TIM4_CC3 event or
TIM20_TRGO(1)

Internal signal from on chip timers

0101

JEXT6

TIM4_CC4 event

Internal signal from on chip timers

0110

JEXT7

TIM4_TRGO event

Internal signal from on chip timers

0111

JEXT8

TIM1_TRGO2 event

Internal signal from on chip timers

1000

JEXT9

TIM8_TRGO event

Internal signal from on chip timers

1001

JEXT10

TIM8_TRGO2 event

Internal signal from on chip timers

1010

330/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Table 93. ADC3 & ADC4 - External trigger for injected channels (continued)

Name

Source

Type

JEXTSEL[3..0]

JEXT11

TIM1_CC3 event or
TIM20_TRGO2(1)

Internal signal from on chip timers

1011

JEXT12

TIM3_TRGO event

Internal signal from on chip timers

1100

JEXT13

TIM2_TRGO event

Internal signal from on chip timers

1101

JEXT14

TIM7_TRGO event

Internal signal from on chip timers

1110

JEXT15

TIM15_TRGO event or
TIM20_CC2(1)

Internal signal from on chip timers

1111

1. Only for STM32F303xD/E and STM32F398xE devices.

Note:

In case two trigger sources are available, the selection is made using the corresponding bit
in the SYSCFG_CFGR4 register.

15.3.19

Injected channel management
Triggered injection mode
To use triggered injection, the JAUTO bit in the ADCx_CFGR register must be cleared.

Note:

1.

Start the conversion of a group of regular channels either by an external trigger or by
setting the ADSTART bit in the ADCx_CR register.

2.

If an external injected trigger occurs, or if the JADSTART bit in the ADCx_CR register is
set during the conversion of a regular group of channels, the current conversion is
reset and the injected channel sequence switches are launched (all the injected
channels are converted once).

3.

Then, the regular conversion of the regular group of channels is resumed from the last
interrupted regular conversion.

4.

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 64 shows the corresponding timing diagram.

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 28 ADC clock
cycles (that is two conversions with a sampling time of 1.5 clock periods), the minimum
interval between triggers must be 29 ADC clock cycles.

Auto-injection mode
If the JAUTO bit in the ADCx_CFGR register 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 ADCx_SQR and ADCx_JSQR
registers.
In this mode, the ADSTART bit in the ADCx_CR register must be set to start regular
conversions, followed by injected conversions (JADSTART must be kept cleared). Setting
the ADSTP bit aborts both regular and injected conversions (JADSTP bit must not be used).
In this mode, external trigger on injected channels must be disabled.

DocID022558 Rev 8

331/1141
413

Analog-to-digital converters (ADC)

RM0316

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.
When the DMA is used for exporting regular sequencer’s data in JAUTO mode, it is
necessary to program it in circular mode (CIRC bit set in DMA_CCRx register). If the CIRC
bit is reset (single-shot mode), the JAUTO sequence will be stopped upon DMA Transfer
Complete event.
Figure 64. Injected conversion latency

!$##,+

,QMHFWLRQHYHQW

5HVHW$'&

PD[ODWHQF\



62&
AIB

1. The maximum latency value can be found in the electrical characteristics of the STM32F3xx datasheets.

15.3.20

Discontinuous mode (DISCEN, DISCNUM, JDISCEN)
Regular group mode
This mode is enabled by setting the DISCEN bit in the ADCx_CFGR register.
It is used to convert a short sequence (sub-group) of n conversions (n ≤ 8) that is part of the
sequence of conversions selected in the ADCx_SQR registers. The value of n is specified
by writing to the DISCNUM[2:0] bits in the ADCx_CFGR register.
When an external trigger occurs, it starts the next n conversions selected in the ADCx_SQR
registers until all the conversions in the sequence are done. The total sequence length is
defined by the L[3:0] bits in the ADCx_SQR1 register.

332/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Example:
•

•

Note:

DISCEN=1, n=3, channels to be converted = 1, 2, 3, 6, 7, 8, 9, 10, 11
–

1st trigger: channels converted are 1, 2, 3 (an EOC event is generated at each
conversion).

–

2nd trigger: channels converted are 6, 7, 8 (an EOC event is generated at each
conversion).

–

3rd trigger: channels converted are 9, 10, 11 (an EOC event is generated at each
conversion) and an EOS event is generated after the conversion of channel 11.

–

4th trigger: channels converted are 1, 2, 3 (an EOC event is generated at each
conversion).

–

...

DISCEN=0, channels to be converted = 1, 2, 3, 6, 7, 8, 9, 10,11
–

1st trigger: the complete sequence is converted: channel 1, then 2, 3, 6, 7, 9, 10
and 11. Each conversion generates an EOC event and the last one also generates
an EOS event.

–

all the next trigger events will relaunch the complete sequence.

When a regular group is converted in discontinuous mode, no rollover occurs (the last
subgroup of the sequence can have less than n conversions).
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 1, 2 and 3 in the
1st subgroup.
It is not possible to have both discontinuous mode and continuous mode enabled. In this
case (if DISCEN=1, CONT=1), the ADC behaves as if continuous mode was disabled.

Injected group mode
This mode is enabled by setting the JDISCEN bit in the ADCx_CFGR register. It converts
the sequence selected in the ADCx_JSQR register, channel by channel, after an external
injected trigger event. This is equivalent to discontinuous mode for regular channels where
‘n’ is fixed to 1.
When an external trigger occurs, it starts the next channel conversions selected in the
ADCx_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 ADCx_JSQR register.
Example:
•

Note:

JDISCEN=1, channels to be converted = 1, 2, 3
–

1st trigger: channel 1 converted (a JEOC event is generated)

–

2nd trigger: channel 2 converted (a JEOC event is generated)

–

3rd trigger: channel 3 converted and a JEOC event + a JEOS event are generated

–

...

When all injected channels have been 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 auto-injected mode and discontinuous mode simultaneously:
the bits DISCEN and JDISCEN must be kept cleared by software when JAUTO is set.

DocID022558 Rev 8

333/1141
413

Analog-to-digital converters (ADC)

15.3.21

RM0316

Queue of context for injected conversions
A queue of context is implemented to anticipate up to 2 contexts for the next injected
sequence of conversions.
This context consists of:
•

Configuration of the injected triggers (bits JEXTEN[1:0] and JEXTSEL[3:0] in
ADCx_JSQR register)

•

Definition of the injected sequence (bits JSQx[4:0] and JL[1:0] in ADCx_JSQR register)

All the parameters of the context are defined into a single register ADCx_JSQR and this
register implements a queue of 2 buffers, allowing the bufferization of up to 2 sets of
parameters:

Note:

334/1141

•

The JSQR register can be written at any moment even when injected conversions are
ongoing.

•

Each data written into the JSQR register is stored into the Queue of context.

•

At the beginning, the Queue is empty and the first write access into the JSQR register
immediately changes the context and the ADC is ready to receive injected triggers.

•

Once an injected sequence is complete, the Queue is consumed and the context
changes according to the next JSQR parameters stored in the Queue. This new
context is applied for the next injected sequence of conversions.

•

A Queue overflow occurs when writing into register JSQR while the Queue is full. This
overflow is signaled by the assertion of the flag JQOVF. When an overflow occurs, the
write access of JSQR register which has created the overflow is ignored and the queue
of context is unchanged. An interrupt can be generated if bit JQOVFIE is set.

•

Two possible behaviors are possible when the Queue becomes empty, depending on
the value of the control bit JQM of register ADCx_CFGR:
–

If JQM=0, the Queue is empty just after enabling the ADC, but then it can never be
empty during run operations: the Queue always maintains the last active context
and any further valid start of injected sequence will be served according to the last
active context.

–

If JQM=1, the Queue can be empty after the end of an injected sequence or if the
Queue is flushed. When this occurs, there is no more context in the queue and
both injected software and hardware triggers are disabled. Therefore, any further
hardware or software injected triggers are ignored until the software re-writes a
new injected context into JSQR register.

•

Reading JSQR register returns the current JSQR context which is active at that
moment. When the JSQR context is empty, JSQR is read as 0x0000.

•

The Queue is flushed when stopping injected conversions by setting JADSTP=1 or
when disabling the ADC by setting ADDIS=1:
–

If JQM=0, the Queue is maintained with the last active context.

–

If JQM=1, the Queue becomes empty and triggers are ignored.

When configured in discontinuous mode (bit JDISCEN=1), only the last trigger of the
injected sequence changes the context and consumes the Queue.The 1st trigger only

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
consumes the queue but others are still valid triggers as shown by the discontinuous mode
example below (length = 3 for both contexts):

•
•
•
•
•
•

1st trigger, discontinuous. Sequence 1: context 1 consumed, 1st conversion carried out
2nd trigger, disc. Sequence 1: 2nd conversion.
3rd trigger, discontinuous. Sequence 1: 3rd conversion.
4th trigger, discontinuous. Sequence 2: context 2 consumed, 1st conversion carried out.
5th trigger, discontinuous. Sequence 2: 2nd conversion.
6th trigger, discontinuous. Sequence 2: 3rd conversion.

Behavior when changing the trigger or sequence context
The Figure 65 and Figure 66 show the behavior of the context Queue when changing the
sequence or the triggers.
Figure 65. Example of JSQR queue of context (sequence change)
3

3

3

:ULWH-645
-645TXHXH

(037<

3

$'&-FRQWH[W
 UHWXUQHGE\UHDGLQJ-465  (037<

3

33

3

3

33

7ULJJHU
3
5'<

$'&VWDWH

&RQYHUVLRQ

&RQYHUVLRQ

&RQYHUVLRQ

3
5'<

&RQYHUVLRQ

5'<
069

1. Parameters:
P1: sequence of 3 conversions, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 4 conversions, hardware trigger 1

Figure 66. Example of JSQR queue of context (trigger change)
3

3

3

:ULWH-645
-645TXHXH

(037<

3

33

3

3

33
,JQRUHG

7ULJJHU
,JQRUHG

7ULJJHU
$'&-FRQWH[W
(037<
 UHWXUQHGE\UHDGLQJ-465 
$'&VWDWH

3

3

5'<

&RQYHUVLRQ

&RQYHUVLRQ

3
5'<

&RQYHUVLRQ

5'<

069

1. Parameters:
P1: sequence of 2 conversions, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 2
P3: sequence of 4 conversions, hardware trigger 1

DocID022558 Rev 8

335/1141
413

Analog-to-digital converters (ADC)

RM0316

Queue of context: Behavior when a queue overflow occurs
The Figure 67 and Figure 68 show the behavior of the context Queue if an overflow occurs
before or during a conversion.
Figure 67. Example of JSQR queue of context with overflow before conversion
3

3

3

:ULWH-645
-645
(037<
TXHXH

3

3

!2YHUIORZ
LJQRUHG

33

3

33

&OHDUHGE\6:
-429)
7ULJJHU
7ULJJHU
$'&
-FRQWH[W (037<

3

3

UHWXUQHGE\UHDGLQJ-465 
5'<

$'&VWDWH

&RQYHUVLRQ

&RQYHUVLRQ

5'<

&RQYHUVLRQ

-(26
069

1. Parameters:
P1: sequence of 2 conversions, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 2
P3: sequence of 3 conversions, hardware trigger 1
P4: sequence of 4 conversions, hardware trigger 1

Figure 68. Example of JSQR queue of context with overflow during conversion
3

3

3

:ULWH-645
-645
(037<
TXHXH

3

3

!2YHUIORZ
LJQRUHG

33

3

33

&OHDUHGE\6:
-429)
7ULJJHU
7ULJJHU
$'&
-FRQWH[W (037<

3

3

UHWXUQHGE\UHDGLQJ-465 
$'&VWDWH

5'<

&RQYHUVLRQ

&RQYHUVLRQ

5'<

&RQYHUVLRQ

-(26
069

1. Parameters:
P1: sequence of 2 conversions, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 2
P3: sequence of 3 conversions, hardware trigger 1
P4: sequence of 4 conversions, hardware trigger 1

336/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
It is recommended to manage the queue overflows as described below:
•

After each P context write into JSQR register, flag JQOVF shows if the write has been
ignored or not (an interrupt can be generated).

•

Avoid Queue overflows by writing the third context (P3) only once the flag JEOS of the
previous context P2 has been set. This ensures that the previous context has been
consumed and that the queue is not full.

Queue of context: Behavior when the queue becomes empty
Figure 69 and Figure 70 show the behavior of the context Queue when the Queue becomes
empty in both cases JQM=0 or 1.
Figure 69. Example of JSQR queue of context with empty queue (case JQM=0)

3

7KHTXHXHLVQRWHPSW\
DQGPDLQWDLQV3EHFDXVH-40 

3

4XHXHQRWHPSW\
3PDLQWDLQHG
3

:ULWH-645
33

3

(037<

-645TXHXH

3

3

7ULJJHU
$'&-FRQWH[W
UHWXUQHGE\ (037<
UHDGLQJ-465 

3

3
#ONVERSION

5'<

$'&VWDWH

3
#ONVERSION

5'<

5'<

#ONVERSION

5'<

#ONVERSION

5'< #ONV
069

1. Parameters:
P1: sequence of 1 conversion, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 1 conversion, hardware trigger 1

Note:

When writing P3, the context changes immediately. However, because of internal
resynchronization, there is a latency and if a trigger occurs just after or before writing P3, it
can happen that the conversion is launched considering the context P2. To avoid this
situation, the user must ensure that there is no ADC trigger happening when writing a new
context that applies immediately.
Figure 70. Example of JSQR queue of context with empty queue (case JQM=1)

3

1UEUE BECOMES EMPTY
AND TRIGGERS ARE IGNORED
BECAUSE *1-

3

3

:ULWH-645
-645
TXHXH

(037<

3

33

3

(037<
)GNORED

)GNORED

7ULJJHU
$'&
3
-FRQWH[W (037<
UHWXUQHGE\UHDGLQJ-465 
$'&VWDWH

3

(037<

3

5'<

&RQYHUVLRQ 5'<

&RQYHUVLRQ

(037< [

5'<

3

&RQYHUVLRQ

(037<

5'<
-36

1. Parameters:
P1: sequence of 1 conversion, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 1 conversion, hardware trigger 1

DocID022558 Rev 8

337/1141
413

Analog-to-digital converters (ADC)

RM0316

Flushing the queue of context
The figures below show the behavior of the context Queue in various situations when the
queue is flushed.
Figure 71. Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs during an ongoing conversion.

3

3

4XHXHLVIOXVKHGDQGPDLQWDLQV
WKHODVWDFWLYHFRQWH[W
3LVORVW

3

:ULWH-645
-645TXHXH (037<

3

33

3

6HW
E\6:

-$'673

3

5HVHW
E\+:

-$'67$57

5HVHW
E\+:

6HW
E\6:

7ULJJHU
$'&-FRQWH[W (037<

3

3

UHWXUQHGE\UHDGLQJ-645
5'<

$'&VWDWH

&RQYHUVLRQ 5'<

5'<

673

069

1. Parameters:
P1: sequence of 1 conversion, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 1 conversion, hardware trigger 1

Figure 72. Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs during an ongoing conversion and a new
trigger occurs.
0

0

7RITE *312
*312
QUEUE

%-049

0

1UEUE IS FLUSHED AND MAINTAINS
THE LAST ACTIVE CONTEXT
0
0 IS LOST
0 0
3ET
BY 37

*!$340
*!$34!24

0

0 0

0

2ESET
BY (7
2ESET
BY (7

3ET
BY 37

4RIGGER 
!$# *
%-049 0
CONTEXT
RETURNED BY READING *312
!$# STATE

2$9

0

#ONV 340
!BORTED

2$9

#ONVERSION 2$9 #ONVERSION 2$9
-36

1. Parameters:
P1: sequence of 1 conversion, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 1 conversion, hardware trigger 1

338/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 73. Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs outside an ongoing conversion
3

WKHODVWDFWLYHFRQWH[W
 3LVORVW

3

:ULWH-645
-645TXHXH (037<

33

3

3

6HW
E\6:

-$'673

3

3

5HVHW
E\+:

-$'67$57

5HVHW
E\+:

6HW
E\6:

7ULJJHU
$'&-FRQWH[W (037< 3
UHWXUQHGE\UHDGLQJ-645

3

5'<

$'&VWDWH

&RQYHUVLRQ 5'<

5'<

673

069

1. Parameters:
P1: sequence of 1 conversion, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 1 conversion, hardware trigger 1

Figure 74. Flushing JSQR queue of context by setting JADSTP=1 (JQM=1)
0

1UEUE IS FLUSHED AND
BECOMES EMPTY 0 IS LOST

0

0

7RITE *312
*312 QUEUE

%-049 0

0 0

%-049

%-049

0

%-049

2ESET
BY (7

3ET
BY 37

*!$340
*!$34!24

0

2ESET
BY (7

3ET
BY 37
)GNORED

4RIGGER 
!$# * CONTEXT %-049 0
RETURNED BY READING *312
!$# STATE

2$9

%-049 X

#ONV 340
!BORTED

2$9

#ONVERSION

2$9
-36

1. Parameters:
P1: sequence of 1 conversion, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 1 conversion, hardware trigger 1

DocID022558 Rev 8

339/1141
413

Analog-to-digital converters (ADC)

RM0316

Figure 75. Flushing JSQR queue of context by setting ADDIS=1 (JQM=0)
1UEUE IS FLUSHED AND MAINTAINS
THE LAST ACTIVE CONTEXT
0 WHICH WAS NOT CONSUMED IS LOST
*312 QUEUE

0 0

0
2ESET
BY (7

3ET
BY 37

!$$)3
0
!$# * CONTEXT
RETURNED BY READING *312
!$# STATE

2$9

/&&

2%1 /&&

-36

1. Parameters:
P1: sequence of 1 conversion, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 1 conversion, hardware trigger 1

Figure 76. Flushing JSQR queue of context by setting ADDIS=1 (JQM=1)
YƵĞƵĞŝƐĨůƵƐŚĞĚĂŶĚďĞĐŽŵĞƐĞŵƉƚLJ
;:^YZŝƐƌĞĂĚĂƐϬdžϬϬϬϬͿ
:^YZƋƵĞƵĞ

Wϭ͕WϮ

DWdz
^Ğƚ
ďLJ^ͬt

/^
Wϭ
:ĐŽŶƚĞdžƚ
;ƌĞƚƵƌŶĞĚďLJ ƌĞĂĚŝŶŐ:^YZͿ
ƐƚĂƚĞ

Zz

ZĞƐĞƚ
ďLJ,ͬt
DWdz;ϬdžϬϬϬϬͿ

ZYͲK&&

K&&
D^ϯϬϱϰϳsϮ

1. Parameters:
P1: sequence of 1 conversion, hardware trigger 1
P2: sequence of 1 conversion, hardware trigger 1
P3: sequence of 1 conversion, hardware trigger 1

Changing context from hardware to software (or software to hardware)
injected trigger
When changing the context from hardware trigger to software injected trigger, it is
necessary to stop the injected conversions by setting JADSTP=1 after the last hardware
triggered conversions. This is necessary to re-enable the software trigger (a rising edge on
JADSTART is necessary to start a software injected conversion). Refer to Figure 77.
When changing the context from software trigger to hardware injected trigger, after the last
software trigger, it is necessary to set JADSTART=1 to enable the hardware triggers. Refer
to Figure 77.

340/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Figure 77. Example of JSQR queue of context when changing SW and HW triggers
0

0

0

0

7RITE *312
*312
QUEUE

%-049

0 0

0

0

0 0

0

0

,JQRUHG

+:WULJJHU
!$# *
%-049 0
CONTEXT
RETURNED BY READING *312
!$# STATE

0 0

2$9

0

0

#ONVERSION

2$9

WULJJHUHGE\+:

#ONVERSION

2$9

WULJJHUHGE\+:

2ESET
BY (7 3ET
BY 37
2ESET
BY (7

3ET
BY 37

*!$340

#ONVERSION

2$9 #ONVERSION

WULJJHUHGE\6:

3ET
BY 37

*!$34!24

0

WULJJHUHGE\+:

2ESET
BY (7 3ET
BY 37

-36

1. Parameters:
P1: sequence of 1 conversion, hardware trigger (JEXTEN /=0x0)
P2: sequence of 1 conversion, hardware trigger (JEXTEN /= 0x0)
P3: sequence of 1 conversion, software trigger (JEXTEN = 0x0)
P4: sequence of 1 conversion, hardware trigger (JEXTEN /= 0x0)

15.3.22

Programmable resolution (RES) - fast conversion mode
It is possible to perform faster conversion by reducing the ADC resolution.
The resolution can be configured to be either 12, 10, 8, or 6 bits by programming the control
bits RES[1:0]. Figure 82, Figure 83, Figure 84 and Figure 85 show the conversion result
format with respect to the resolution as well as to the data alignment.
Lower resolution allows faster conversion time for applications where high-data precision is
not required. It reduces the conversion time spent by the successive approximation steps
according to Table 94.
Table 94. TSAR timings depending on resolution
RES
(bits)

15.3.23

TSAR
(ADC clock cycles)

TADC (ADC clock cycles)

TSAR (ns) at
FADC=72 MHz

(with Sampling Time=
1.5 ADC clock cycles)

TADC (ns) at
FADC=72 MHz

12

12.5 ADC clock cycles 173.6 ns

14 ADC clock cycles

194.4 ns

10

10.5 ADC clock cycles 145.8 ns

12 ADC clock cycles

166.7 ns

8

8.5 ADC clock cycles

118.0 ns

10 ADC clock cycles

138.9 ns

6

6.5 ADC clock cycles

90.3 ns

8 ADC clock cycles

111.1 ns

End of conversion, end of sampling phase (EOC, JEOC, EOSMP)
The ADC notifies the application for each end of regular conversion (EOC) event and each
injected conversion (JEOC) event.

DocID022558 Rev 8

341/1141
413

Analog-to-digital converters (ADC)

RM0316

The ADC sets the EOC flag as soon as a new regular conversion data is available in the
ADCx_DR register. An interrupt can be generated if bit EOCIE is set. EOC flag is cleared by
the software either by writing 1 to it or by reading ADCx_DR.
The ADC sets the JEOC flag as soon as a new injected conversion data is available in one
of the ADCx_JDRy register. An interrupt can be generated if bit JEOCIE is set. JEOC flag is
cleared by the software either by writing 1 to it or by reading the corresponding ADCx_JDRy
register.
The ADC also notifies the end of Sampling phase by setting the status bit EOSMP (for
regular conversions only). EOSMP flag is cleared by software by writing 1 to it. An interrupt
can be generated if bit EOSMPIE is set.

15.3.24

End of conversion sequence (EOS, JEOS)
The ADC notifies the application for each end of regular sequence (EOS) and for each end
of injected sequence (JEOS) event.
The ADC sets the EOS flag as soon as the last data of the regular conversion sequence is
available in the ADCx_DR register. An interrupt can be generated if bit EOSIE is set. EOS
flag is cleared by the software either by writing 1 to it.
The ADC sets the JEOS flag as soon as the last data of the injected conversion sequence is
complete. An interrupt can be generated if bit JEOSIE is set. JEOS flag is cleared by the
software either by writing 1 to it.

15.3.25

Timing diagrams example (single/continuous modes,
hardware/software triggers)
Figure 78. Single conversions of a sequence, software trigger

$'67$57 
(2&
(26
$'&VWDWH 

5'<

$'&B'5
E\VZ

&+

&+

&+

&+

'

'

'

5'<
'

E\KZ

&+

&+

&+

&+

5'<

'

'

'

'

,QGLFDWLYHWLPLQJV
069

1. EXTEN=0x0, CONT=0
2. Channels selected = 1,9, 10, 17; AUTDLY=0.

342/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 79. Continuous conversion of a sequence, software trigger

$'67$57 
(2&
(26
$'673
$'&VWDWH  5($'<

&+

$'&B'5
E\VZ

&+

&+

&+

&+

&+

'

'

'

'

'

&+

673

&+

&+

5($'<
'

'
,QGLFDWLYHWLPLQJV

E\KZ

-36

1. EXTEN=0x0, CONT=1
2. Channels selected = 1,9, 10, 17; AUTDLY=0.

Figure 80. Single conversions of a sequence, hardware trigger
$'67$57

(2&
(26
75*; 
$'&VWDWH 

&+

5'<

$'&B'5

E\VZ

E\KZ

&+

&+

&+

'

'

'

WULJJHUHG

5($'<

&+

'

&+

&+

&+

5'<

'

'

'

'

,QGLFDWLYHWLPLQJV

LJQRUHG

069

1. TRGx (over-frequency) is selected as trigger source, EXTEN = 01, CONT = 0
2. Channels selected = 1, 2, 3, 4; AUTDLY=0.

Figure 81. Continuous conversions of a sequence, hardware trigger
$'67$57

(2&
(26
$'673

75*[ 
$'& 

5'<

&+

&+

&+

'

$'&B'5

E\VZ

E\KZ

'

&+

&+

&+

&+

&+

&+

'

'

'

'

'

'

WULJJHUHG

LJQRUHG

6723

5'<

1RWLQVFDOHWLPLQJV

069

1. TRGx is selected as trigger source, EXTEN = 10, CONT = 1
2. Channels selected = 1, 2, 3, 4; AUTDLY=0.

DocID022558 Rev 8

343/1141
413

Analog-to-digital converters (ADC)

15.3.26

RM0316

Data management
Data register, data alignment and offset (ADCx_DR, OFFSETy, OFFSETy_CH,
ALIGN)
Data and alignment
At the end of each regular conversion channel (when EOC event occurs), the result of the
converted data is stored into the ADCx_DR data register which is 16 bits wide.
At the end of each injected conversion channel (when JEOC event occurs), the result of the
converted data is stored into the corresponding ADCx_JDRy data register which is 16 bits
wide.
The ALIGN bit in the ADCx_CFGR register selects the alignment of the data stored after
conversion. Data can be right- or left-aligned as shown in Figure 82, Figure 83, Figure 84
and Figure 85.
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 84 and Figure 85.

Offset
An offset y (y=1,2,3,4) can be applied to a channel by setting the bit OFFSETy_EN=1 into
ADCx_OFRy register. The channel to which the offset will be applied is programmed into the
bits OFFSETy_CH[4:0] of ADCx_OFRy register. In this case, the converted value is
decreased by the user-defined offset written in the bits OFFSETy[11:0]. The result may be a
negative value so the read data is signed and the SEXT bit represents the extended sign
value.
Table 97 describes how the comparison is performed for all the possible resolutions for
analog watchdog 1.
Table 95. Offset computation versus data resolution

Resolution
(bits
RES[1:0])

344/1141

Substraction between raw
converted data and offset:
Raw
converted
Data, left
aligned

Result

Comments

Offset

00: 12-bit

DATA[11:0]

OFFSET[11:0]

signed 12-bit
data

-

01: 10-bit

DATA[11:2],00

OFFSET[11:0]

signed 10-bit
data

The user must configure OFFSET[1:0]
to “00”

10: 8-bit

DATA[11:4],00
00

OFFSET[11:0]

signed 8-bit
data

The user must configure OFFSET[3:0]
to “0000”

11: 6-bit

DATA[11:6],00
0000

OFFSET[11:0]

signed 6-bit
data

The user must configure OFFSET[5:0]
to “000000”

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
When reading data from ADCx_DR (regular channel) or from ADCx_JDRy (injected
channel, y=1,2,3,4) corresponding to the channel “i”:
•

If one of the offsets is enabled (bit OFFSETy_EN=1) for the corresponding channel, the
read data is signed.

•

If none of the four offsets is enabled for this channel, the read data is not signed.

Figure 82, Figure 83, Figure 84 and Figure 85 show alignments for signed and unsigned
data.
Figure 82. Right alignment (offset disabled, unsigned value)
ELWGDWD
ELW




ELW




'

'

'

'

ELWGDWD
ELW














'

'



'

'

'

'

'

'













'

'

'

'

'

'

'













'

ELW
'

'

'

'

'

'

ELW


'

ELW

ELW

ELWGDWD
ELW


'

ELW

ELWGDWD
ELW


'

ELW

'

ELW


'

'

'

'

'

'

069

DocID022558 Rev 8

345/1141
413

Analog-to-digital converters (ADC)

RM0316

Figure 83. Right alignment (offset enabled, signed value)
ELWGDWD
ELW

ELW

6(;7 6(;7 6(;7 6(;7 '

'

'

'

ELWGDWD
ELW

'

ELW
'

'

'

'

'

'

'

ELW

6(;7 6(;7 6(;7 6(;7 6(;7 6(;7

'

'

ELWGDWD
ELW

'

ELW
'

'

'

'

'

'

'

ELW

6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 '

ELWGDWD
ELW

ELW
'

'

'

'

'

'

'

ELW

ELW

6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7

'

'

'

'

'

'

069

Figure 84. Left alignment (offset disabled, unsigned value)
ELWGDWD
ELW
'

'

ELW
'

'

'

'

'

'

'

'

'

'

'

'

ELWGDWD
ELW
'

'

'



'

'

'











'





'

'

'

'

'

'

















ELW












'

'

'

'

'



ELW
'



ELW


ELW

ELWGDWD
ELW


'

ELW

ELWGDWD
ELW
'

'

ELW



ELW


069

346/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 85. Left alignment (offset enabled, signed value)
ELWGDWD
ELW
6(;7 '

ELW
'

'

'

'

'

'

ELWGDWD
ELW
6(;7 '

'

'

'

'

'







ELW
'

'

'

'

'

'

ELWGDWD
ELW
6(;7

'

ELW

'

ELW
'

'











ELW
'

'

'

'

ELWGDWD
ELW

'

'

'

ELW














ELW

6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 6(;7 '

ELW
'

'

'

'

'



069

ADC overrun (OVR, OVRMOD)
The overrun flag (OVR) notifies of a buffer overrun event, when the regular converted data
was not read (by the CPU or the DMA) before new converted data became available.
The OVR flag is set if the EOC flag is still 1 at the time when a new conversion completes.
An interrupt can be generated if bit OVRIE=1.
When an overrun condition occurs, the ADC is still operating and can continue to convert
unless the software decides to stop and reset the sequence by setting bit ADSTP=1.
OVR flag is cleared by software by writing 1 to it.
It is possible to configure if data is preserved or overwritten when an overrun event occurs
by programming the control bit OVRMOD:
•

OVRMOD=0: The overrun event preserves the data register from being overrun: the
old data is maintained and the new conversion is discarded and lost. If OVR remains at
1, any further conversions will occur but the result data will be also discarded.

•

OVRMOD=1: The data register is overwritten with the last conversion result and the
previous unread data is lost. If OVR remains at 1, any further conversions will operate
normally and the ADCx_DR register will always contain the latest converted data.

DocID022558 Rev 8

347/1141
413

Analog-to-digital converters (ADC)

RM0316

Figure 86. Example of overrun (OVR)
$'67$57 
(2&
(26
295
$'673
75*[ 
$'&VWDWH 

5'<

&+

&+

&+

&+

&+

$'&B'5UHDGDFFHVV
$'&B'5
29502' 

'

'

'

'

$'&B'5
29502' 

'

'

'

'

E\VZ

&+

&+

'

'

6723

5'<

2YHUXQ

E\KZ

WULJJHUHG

,QGLFDWLYHWLPLQJV
-36

Note:

There is no overrun detection on the injected channels since there is a dedicated data
register for each of the four injected channels.

Managing a sequence of conversion without using the DMA
If the conversions are slow enough, the conversion sequence can be handled by the
software. In this case the software must use the EOC flag and its associated interrupt to
handle each data. Each time a conversion is complete, EOC is set and the ADCx_DR
register can be read. OVRMOD should be configured to 0 to manage overrun events as an
error.

Managing conversions without using the DMA and without overrun
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). In this case, the OVRMOD bit must be
configured to 1 and OVR flag should be ignored by the software. An overrun event will not
prevent the ADC from continuing to convert and the ADCx_DR register will always contain
the latest conversion.

Managing conversions using the DMA
Since converted channel values are stored into a unique data register, it is useful to use
DMA for conversion of more than one channel. This avoids the loss of the data already
stored in the ADCx_DR register.
When the DMA mode is enabled (DMAEN bit set to 1 in the ADCx_CFGR register in single
ADC mode or MDMA different from 0b00 in dual ADC mode), a DMA request is generated
after each conversion of a channel. This allows the transfer of the converted data from the
ADCx_DR register to the destination location selected by the software.
Despite this, if an overrun occurs (OVR=1) because the DMA could not serve the DMA
transfer request in time, the ADC stops generating DMA requests and the data

348/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
corresponding to the new conversion is not transferred by the DMA. Which means that all
the data transferred to the RAM can be considered as valid.
Depending on the configuration of OVRMOD bit, the data is either preserved or overwritten
(refer to Section : ADC overrun (OVR, OVRMOD)).
The DMA transfer requests are blocked until the software clears the OVR bit.
Two different DMA modes are proposed depending on the application use and are
configured with bit DMACFG of the ADCx_CFGR register in single ADC mode, or with bit
DMACFG of the ADCx_CCR register in dual ADC mode:
•

DMA one shot mode (DMACFG=0).
This mode is suitable when the DMA is programmed to transfer a fixed number of data.

•

DMA circular mode (DMACFG=1)
This mode is suitable when programming the DMA in circular mode.

DMA one shot mode (DMACFG=0)
In this mode, the ADC generates a DMA transfer request each time a new conversion data
is available and stops generating DMA requests once the DMA has reached the last DMA
transfer (when DMA_EOT interrupt occurs - refer to DMA paragraph) even if a conversion
has been started again.
When the DMA transfer is complete (all the transfers configured in the DMA controller have
been done):
•

The content of the ADC data register is frozen.

•

Any ongoing conversion is aborted with partial result discarded.

•

No new DMA request is issued to the DMA controller. This avoids generating an
overrun error if there are still conversions which are started.

•

Scan sequence is stopped and reset.

•

The DMA is stopped.

DMA circular mode (DMACFG=1)
In this mode, the ADC generates a DMA transfer request each time a new conversion data
is available in the data register, even if the DMA has reached the last DMA transfer. This
allows configuring the DMA in circular mode to handle a continuous analog input data
stream.

15.3.27

Dynamic low-power features
Auto-delayed conversion mode (AUTDLY)
The ADC implements an auto-delayed conversion mode controlled by the AUTDLY
configuration bit. Auto-delayed conversions are useful to simplify the software as well as to
optimize performance of an application clocked at low frequency where there would be risk
of encountering an ADC overrun.
When AUTDLY=1, a new conversion can start only if all the previous data of the same group
has been treated:
•

For a regular conversion: once the ADCx_DR register has been read or if the EOC bit
has been cleared (see Figure 87).

•

For an injected conversion: when the JEOS bit has been cleared (see Figure 88).

DocID022558 Rev 8

349/1141
413

Analog-to-digital converters (ADC)

RM0316

This is a way to automatically adapt the speed of the ADC to the speed of the system which
will read the data.
The delay is inserted after each regular conversion (whatever DISCEN=0 or 1) and after
each sequence of injected conversions (whatever JDISCEN=0 or 1).
Note:

There is no delay inserted between each conversions of the injected sequence, except after
the last one.
During a conversion, a hardware trigger event (for the same group of conversions) occurring
during this delay is ignored.

Note:

This is not true for software triggers where it remains possible during this delay to set the
bits ADSTART or JADSTART to re-start a conversion: it is up to the software to read the
data before launching a new conversion.
No delay is inserted between conversions of different groups (a regular conversion followed
by an injected conversion or conversely):
•

If an injected trigger occurs during the automatic delay of a regular conversion, the
injected conversion starts immediately (see Figure 88).

•

Once the injected sequence is complete, the ADC waits for the delay (if not ended) of
the previous regular conversion before launching a new regular conversion (see
Figure 90).

The behavior is slightly different in auto-injected mode (JAUTO=1) where a new regular
conversion can start only when the automatic delay of the previous injected sequence of
conversion has ended (when JEOS has been cleared). This is to ensure that the software
can read all the data of a given sequence before starting a new sequence (see Figure 91).
To stop a conversion in continuous auto-injection mode combined with autodelay mode
(JAUTO=1, CONT=1 and AUTDLY=1), follow the following procedure:
1.

Wait until JEOS=1 (no more conversions are restarted)

2.

Clear JEOS,

3.

Set ADSTP=1

4.

Read the regular data.

If this procedure is not respected, a new regular sequence can re-start if JEOS is cleared
after ADSTP has been set.
In AUTDLY mode, a hardware regular trigger event is ignored if it occurs during an already
ongoing regular sequence or during the delay that follows the last regular conversion of the
sequence. It is however considered pending if it occurs after this delay, even if it occurs
during an injected sequence of the delay that follows it. The conversion then starts at the
end of the delay of the injected sequence.
In AUTDLY mode, a hardware injected trigger event is ignored if it occurs during an already
ongoing injected sequence or during the delay that follows the last injected conversion of
the sequence.

350/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 87. AUTODLY=1, regular conversion in continuous mode, software trigger

$'67$57 
(2&
(26
$'673
$'&B'5UHDGDFFHVV
$'&VWDWH

&+

5'<

'/<

$'&B'5

&+
'

E\VZ

'/<

'/<

&+

'

&+

'/<

6723

'

5'<

'

E\KZ

,QGLFDWLYHWLPLQJV

069

1. AUTDLY=1
2. Regular configuration: EXTEN=0x0 (SW trigger), CONT=1, CHANNELS = 1,2,3
3. Injected configuration DISABLED

Figure 88. AUTODLY=1, regular HW conversions interrupted by injected conversions
(DISCEN=0; JDISCEN=0)
1RWLJQRUHG
RFFXUVGXULQJLQMHFWHGVHTXHQFH

,JQRUHG
5HJXODU
WULJJHU
$'&VWDWH

5'<

&+

'/<

&+

'/<

&+
UHJXODU

UHJXODU
'/< &+

&+

&+

LQMHFWHG

UHJXODU

'/< &+

&+

'/<

'/<

&+
UHJXODU

UHJXODU

LQMHFWHG
'/< &+

'/< &+

(2&
(26
$'&B'5
UHDGDFFHVV
'

$'&B'5

'

'

'

,JQRUHG

,QMHFWHG
WULJJHU

'/< LQM
-(26
'

$'&B-'5

'

$'&B-'5

E\VZ

E\KZ

,QGLFDWLYHWLPLQJV
069

1. AUTDLY=1
2. Regular configuration: EXTEN=0x1 (HW trigger), CONT=0, DISCEN=0, CHANNELS = 1, 2, 3
3. Injected configuration: JEXTEN=0x1 (HW Trigger), JDISCEN=0, CHANNELS = 5,6

DocID022558 Rev 8

351/1141
413

Analog-to-digital converters (ADC)

RM0316

Figure 89. AUTODLY=1, regular HW conversions interrupted by injected conversions
(DISCEN=1, JDISCEN=1)
1RWLJQRUHG
RFFXUVGXULQJLQMHFWHGVHTXHQFH

,JQRUHG
5HJXODU
WULJJHU
$'&
VWDWH

5'<

&+
UHJXODU

&+
'/< 5'< &+ '/< 5'< &+ 5'< &+
'/< 5'< &+ '/< 5'<&+
UHJXODU
UHJXODU
LQMHFWHG
LQMHFWHG UHJXODU
UHJXODU
'/< &+
'/< &+
'/< &+
'/< &+

(2&
(26
$'&B'5UHDGDFFHVV
$'&B'5

'

'
,JQRUHG

,QMHFWHG
WULJJHU

'

'

,JQRUHG
'/< LQM

-(26
$'&B-'5

'
'

$'&B-'5
E\VZ

,QGLFDWLYHWLPLQJV

E\KZ

069

1. AUTDLY=1
2. Regular configuration: EXTEN=0x1 (HW trigger), CONT=0, DISCEN=1, DISCNUM=1, CHANNELS = 1, 2, 3.
3. Injected configuration: JEXTEN=0x1 (HW Trigger), JDISCEN=1, CHANNELS = 5,6

352/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Figure 90. AUTODLY=1, regular continuous conversions interrupted by injected conversions
^dZd;ϭͿ

ƐƚĂƚĞ Zz

,ϭ
ƌĞŐƵůĂƌ

,Ϯ
ƌĞŐƵůĂƌ

>z

>z

,ϲ
,ϱ
ŝŶũĞĐƚĞĚ ŝŶũĞĐƚĞĚ

>z;,ϮͿ

>z;,ϭͿ

>z

,ϯ
ƌĞŐƵůĂƌ

>z

,ϭ
ƌĞŐƵůĂƌ

>z;,ϯͿ

K
K^
ͺZƌĞĂĚĂĐĐĞƐƐ
ϭ

ͺZ

Ϯ

ϯ
/ŐŶŽƌĞĚ

/ŶũĞĐƚĞĚ
ƚƌŝŐŐĞƌ

>z;ŝŶũͿ

:K^
ͺ:Zϭ

ϱ

ͺ:ZϮ

ϲ
ďLJƐͬǁ

ďLJŚͬǁ

/ŶĚŝĐĂƚŝǀĞƚŝŵŝŶŐƐ

D^ϯϭϬϮϯsϮ

1. AUTDLY=1
2. Regular configuration: EXTEN=0x0 (SW trigger), CONT=1, DISCEN=0, CHANNELS = 1, 2, 3
3. Injected configuration: JEXTEN=0x1 (HW Trigger), JDISCEN=0, CHANNELS = 5,6

Figure 91. AUTODLY=1 in auto- injected mode (JAUTO=1)
^dZd;ϭͿ
ƐƚĂƚĞ

EŽĚĞůĂLJ
Zz

,ϭ
ƌĞŐƵůĂƌ

>z;,ϭͿ

,Ϯ
ƌĞŐƵůĂƌ

,ϲ
>z;ŝŶũͿ
,ϱ
ŝŶũĞĐƚĞĚ ŝŶũĞĐƚĞĚ

>z;,ϮͿ

,ϯ
ƌĞŐƵůĂƌ

>z

,ϭ
ƌĞŐƵůĂƌ

K
K^
ͺZƌĞĂĚĂĐĐĞƐƐ
ͺZ

ϭ

Ϯ

ϯ

:K^
ͺ:Zϭ

ϱ
ϲ

ͺ:ZϮ
ďLJƐͬǁ

ďLJŚͬǁ

/ŶĚŝĐĂƚŝǀĞƚŝŵŝŶŐƐ

D^ϯϭϬϮϰsϮ

1. AUTDLY=1
2. Regular configuration: EXTEN=0x0 (SW trigger), CONT=1, DISCEN=0, CHANNELS = 1, 2
3. Injected configuration: JAUTO=1, CHANNELS = 5,6

DocID022558 Rev 8

353/1141
413

Analog-to-digital converters (ADC)

15.3.28

RM0316

Analog window watchdog (AWD1EN, JAWD1EN, AWD1SGL,
AWD1CH, AWD2CH, AWD3CH, AWD_HTx, AWD_LTx, AWDx)
The three AWD analog watchdogs monitor whether some channels remain within a
configured voltage range (window).
Figure 92. Analog watchdog’s guarded area

$QDORJYROWDJH
+LJKHUWKUHVKROG

+75
*XDUGHGDUHD

/RZHUWKUHVKROG

/75
DL

AWDx flag and interrupt
An interrupt can be enabled for each of the 3 analog watchdogs by setting AWDxIE in the
ADCx_IER register (x=1,2,3).
AWDx (x=1,2,3) flag is cleared by software by writing 1 to it.
The ADC conversion result is compared to the lower and higher thresholds before
alignment.
Description of analog watchdog 1
The AWD analog watchdog 1 is enabled by setting the AWD1EN bit in the ADCx_CFGR
register. This watchdog monitors whether either one selected channel or all enabled
channels(1) remain within a configured voltage range (window).
Table 96 shows how the ADCx_CFGR registers should be configured to enable the analog
watchdog on one or more channels.
Table 96. Analog watchdog channel selection
Channels guarded by the analog
watchdog

AWD1SGL bit

AWD1EN bit

JAWD1EN bit

None

x

0

0

All injected channels

0

0

1

All regular channels

0

1

0

All regular and injected channels

0

1

1

Single(1) injected channel

1

0

1

Single(1)

regular channel

1

1

0

regular or injected channel

1

1

1

(1)

Single

1. Selected by the AWD1CH[4:0] bits. The channels must also be programmed to be converted in the
appropriate regular or injected sequence.

The AWD1 analog watchdog status bit is set if the analog voltage converted by the ADC is
below a lower threshold or above a higher threshold.

354/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
These thresholds are programmed in bits HT1[11:0] and LT1[11:0] of the ADCx_TR1
register for the analog watchdog 1. When converting data with a resolution of less than 12
bits (according to bits RES[1:0]), the LSB of the programmed thresholds must be kept
cleared because the internal comparison is always performed on the full 12-bit raw
converted data (left aligned).
Table 97 describes how the comparison is performed for all the possible resolutions for
analog watchdog 1.
Table 97. Analog watchdog 1 comparison
Resolution
(bit
RES[1:0])

Analog watchdog comparison
between:
Comments
Raw converted
data, left aligned(1)

Thresholds

00: 12-bit

DATA[11:0]

LT1[11:0] and
HT1[11:0]

-

01: 10-bit

DATA[11:2],00

LT1[11:0] and
HT1[11:0]

User must configure LT1[1:0] and HT1[1:0] to
00

10: 8-bit

DATA[11:4],0000

LT1[11:0] and
HT1[11:0]

User must configure LT1[3:0] and HT1[3:0] to
0000

11: 6-bit

DATA[11:6],000000

LT1[11:0] and
HT1[11:0]

User must configure LT1[5:0] and HT1[5:0] to
000000

1. The watchdog comparison is performed on the raw converted data before any alignment calculation and
before applying any offsets (the data which is compared is not signed).

Description of analog watchdog 2 and 3
The second and third analog watchdogs are more flexible and can guard several selected
channels by programming the corresponding bits in AWDxCH[18:1] (x=2,3).
The corresponding watchdog is enabled when any bit of AWDxCH[18:0] (x=2,3) is set.
They are limited to a resolution of 8 bits and only the 8 MSBs of the thresholds can be
programmed into HTx[7:0] and LTx[7:0]. Table 98 describes how the comparison is
performed for all the possible resolutions.
Table 98. Analog watchdog 2 and 3 comparison
Resolution
(bits
RES[1:0])

Analog watchdog comparison between:
Raw converted data,
left aligned(1)

Comments
Thresholds

00: 12-bit

DATA[11:4]

LTx[7:0] and
HTx[7:0]

DATA[3:0] are not relevant for the
comparison

01: 10-bit

DATA[11:4]

LTx[7:0] and
HTx[7:0]

DATA[3:2] are not relevant for the
comparison

10: 8-bit

DATA[11:4]

LTx[7:0] and
HTx[7:0]

11: 6-bit

DATA[11:6],00

LTx[7:0] and
HTx[7:0]

DocID022558 Rev 8

User must configure LTx[1:0] and
HTx[1:0] to 00

355/1141
413

Analog-to-digital converters (ADC)

RM0316

1. The watchdog comparison is performed on the raw converted data before any alignment
calculation and before applying any offsets (the data which is compared is not signed).

ADCy_AWDx_OUT signal output generation
Each analog watchdog is associated to an internal hardware signal ADCy_AWDx_OUT
(y=ADC number, x=watchdog number) which is directly connected to the ETR input
(external trigger) of some on-chip timers. Refer to the on-chip timers section to understand
how to select the ADCy_AWDx_OUT signal as ETR.
ADCy_AWDx_OUT is activated when the associated analog watchdog is enabled:

Note:

•

ADCy_AWDx_OUT is set when a guarded conversion is outside the programmed
thresholds.

•

ADCy_AWDx_OUT is reset after the end of the next guarded conversion which is
inside the programmed thresholds (It remains at 1 if the next guarded conversions are
still outside the programmed thresholds).

•

ADCy_AWDx_OUT is also reset when disabling the ADC (when setting ADDIS=1).
Note that stopping regular or injected conversions (setting ADSTP=1 or JADSTP=1)
has no influence on the generation of ADCy_AWDx_OUT.

AWDx flag is set by hardware and reset by software: AWDx flag has no influence on the
generation of ADCy_AWDx_OUT (ex: ADCy_AWDx_OUT can toggle while AWDx flag
remains at 1 if the software did not clear the flag).
Figure 93. ADCy_AWDx_OUT signal generation (on all regular channels)

$'&
67$7(

5'<

&RQYHUVLRQ
LQVLGH

&RQYHUVLRQ
RXWVLGH

&RQYHUVLRQ
LQVLGH

&RQYHUVLRQ &RQYHUVLRQ
RXWVLGH

RXWVLGH

&RQYHUVLRQ
RXWVLGH

&RQYHUVLRQ
LQVLGH

(2&)/$*

$:'[)/$*

FOHDUHG
E\6:

FOHDUHG
E\6:

FOHDUHG
E\6:

FOHDUHG
E\6:

$'&\B$:'[B287

&RQYHUWLQJUHJXODUFKDQQHOV
5HJXODUFKDQQHOVDUHDOOJXDUGHG
069

356/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 94. ADCy_AWDx_OUT signal generation (AWDx flag not cleared by SW)

$'&
67$7(

5'<

&RQYHUVLRQ

&RQYHUVLRQ

LQVLGH

&RQYHUVLRQ

RXWVLGH

&RQYHUVLRQ &RQYHUVLRQ

LQVLGH

RXWVLGH

&RQYHUVLRQ

RXWVLGH

&RQYHUVLRQ

RXWVLGH

LQVLGH

(2&)/$*
QRWFOHDUHG E\6:

$:'[)/$*
$'&\B$:'[B287

&RQYHUWLQJUHJXODUFKDQQHOV
5HJXODUFKDQQHOVDUHDOOJXDUGHG
069

Figure 95. ADCy_AWDx_OUT signal generation (on a single regular channel)
$'&
&RQYHUVLRQ
67$7(
RXWVLGH

&RQYHUVLRQ

&RQYHUVLRQ

&RQYHUVLRQ

LQVLGH

&RQYHUVLRQ

&RQYHUVLRQ

RXWVLGH

&RQYHUVLRQ &RQYHUVLRQ
RXWVLGH

(2&)/$*
(26)/$*
FOHDUHG
E\6:

$:'[)/$*

FOHDUHG
E\6:

$'&\B$:'[B287

&RQYHUWLQJUHJXODUFKDQQHOVDQG
2QO\FKDQQHOLVJXDUGHG
069

Figure 96. ADCy_AWDx_OUT signal generation (on all injected channels)
$'&
67$7(

5'<

&RQYHUVLRQ
LQVLGH

&RQYHUVLRQ
RXWVLGH

&RQYHUVLRQ &RQYHUVLRQ
LQVLGH

RXWVLGH

&RQYHUVLRQ
RXWVLGH

&RQYHUVLRQ
RXWVLGH

&RQYHUVLRQ
LQVLGH

-(26)/$*

$:'[)/$*

FOHDUHG
E\6:

FOHDUHG
E\6:

FOHDUHG
E\6:

FOHDUHG
E\6:

$'&\B$:'[B287

&RQYHUWLQJWKHLQMHFWHGFKDQQHOV 
$OOLQMHFWHGFKDQQHOVDUHJXDUGHG
069

DocID022558 Rev 8

357/1141
413

Analog-to-digital converters (ADC)

15.3.29

RM0316

Dual ADC modes
In devices with two ADCs or more, dual ADC modes can be used (see Figure 97):
•

ADC1 and ADC2 can be used together in dual mode (ADC1 is master)

•

ADC3 and ADC4 can be used together in dual mode (ADC3 is master)

In dual ADC mode the start of conversion is triggered alternately or simultaneously by the
ADCx master to the ADC slave, depending on the mode selected by the bits DUAL[4:0] in
the ADCx_CCR register.
Four possible modes are implemented:
•

Injected simultaneous mode

•

Regular simultaneous mode

•

Interleaved mode

•

Alternate trigger mode

It is also possible to use these modes combined in the following ways:
•

Injected simultaneous mode + Regular simultaneous mode

•

Regular simultaneous mode + Alternate trigger mode

In dual ADC mode (when bits DUAL[4:0] in ADCx_CCR register are not equal to zero), the
bits CONT, AUTDLY, DISCEN, DISCNUM[2:0], JDISCEN, JQM, JAUTO of the
ADCx_CFGR register are shared between the master and slave ADC: the bits in the slave
ADC are always equal to the corresponding bits of the master ADC.
To start a conversion in dual mode, the user must program the bits EXTEN, EXTSEL,
JEXTEN, JEXTSEL of the master ADC only, to configure a software or hardware trigger,
and a regular or injected trigger. (the bits EXTEN[1:0] and JEXTEN[1:0] of the slave ADC
are don’t care).
In regular simultaneous or interleaved modes: once the user sets bit ADSTART or bit
ADSTP of the master ADC, the corresponding bit of the slave ADC is also automatically
set. However, bit ADSTART or bit ADSTP of the slave ADC is not necessary cleared at the
same time as the master ADC bit.
In injected simultaneous or alternate trigger modes: once the user sets bit JADSTART or bit
JADSTP of the master ADC, the corresponding bit of the slave ADC is also automatically
set. However, bit JADSTART or bit JADSTP of the slave ADC is not necessary cleared at
the same time as the master ADC bit.
In dual ADC mode, the converted data of the master and slave ADC can be read in parallel,
by reading the ADC common data register (ADCx_CDR). The status bits can be also read in
parallel by reading the dual-mode status register (ADCx_CSR).

358/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 97. Dual ADC block diagram(1)

5HJXODUGDWDUHJLVWHU
ELWV
,QMHFWHGGDWDUHJLVWHUV
[ELWV
$GGUHVVGDWDEXV

5HJXODU
FKDQQHOV

6ODYH$'&

,QMHFWHG
FKDQQHOV
,QWHUQDOWULJJHUV
$'&[B,1
$'&[B,1

5HJXODUGDWDUHJLVWHU
ELWV

*3,2
SRUWV

,QMHFWHGGDWDUHJLVWHUV
[ELWV

$'&[B,1
7HPSVHQVRU
9%$7
95(),17

5HJXODU
FKDQQHOV
,QMHFWHG
FKDQQHOV

'XDOPRGH
FRQWURO

6WDUWWULJJHUPX[
UHJXODUJURXS

0DVWHU$'&
6WDUWWULJJHUPX[
LQMHFWHGJURXS

06Y9

1.

External triggers also exist on slave ADC but are not shown for the purposes of this diagram.

2.

The ADC common data register (ADCx_CDR) contains both the master and slave ADC regular converted data.

DocID022558 Rev 8

359/1141
413

Analog-to-digital converters (ADC)

RM0316

Injected simultaneous mode
This mode is selected by programming bits DUAL[4:0]=00101
This mode converts an injected group of channels. The external trigger source comes from
the injected group multiplexer of the master ADC (selected by the JEXTSEL[3:0] bits in the
ADCx_JSQR register).
Note:

Do not convert the same channel on the two ADCs (no overlapping sampling times for the
two 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. 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.
•

At the end of injected sequence of conversion event (JEOS) on the master ADC, the
converted data is stored into the master ADCx_JDRy registers and a JEOS interrupt is
generated (if enabled)

•

At the end of injected sequence of conversion event (JEOS) on the slave ADC, the
converted data is stored into the slave ADCx_JDRy registers and a JEOS interrupt is
generated (if enabled)

•

If the duration of the master injected sequence is equal to the duration of the slave
injected one (like in Figure 98), it is possible for the software to enable only one of the
two JEOS interrupt (ex: master JEOS) and read both converted data (from master
ADCx_JDRy and slave ADCx_JDRy registers).
Figure 98. Injected simultaneous mode on 4 channels: dual ADC mode
0$67(5$'&

&+

&+

&+

&+

6/$9($'&

&+

&+

&+

&+

7ULJJHU
6DPSOLQJ

(QGRILQMHFWHGVHTXHQFHRQ
0$67(5DQG6/$9($'&

&RQYHUVLRQ
069

If JDISCEN=1, each simultaneous conversion of the injected sequence requires an injected
trigger event to occur.
This mode can be combined with AUTDLY mode:

360/1141

•

Once a simultaneous injected sequence of conversions has ended, a new injected
trigger event is accepted only if both JEOS bits of the master and the slave ADC have
been cleared (delay phase). Any new injected trigger events occurring during the
ongoing injected sequence and the associated delay phase are ignored.

•

Once a regular sequence of conversions of the master ADC has ended, a new regular
trigger event of the master ADC is accepted only if the master data register (ADCx_DR)
has been read. Any new regular trigger events occurring for the master ADC during the

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
ongoing regular sequence and the associated delay phases are ignored.
There is the same behavior for regular sequences occurring on the slave ADC.

Regular simultaneous mode with independent injected
This mode is selected by programming bits DUAL[4:0] = 00110.
This mode is performed on a regular group of channels. The external trigger source comes
from the regular group multiplexer of the master ADC (selected by the EXTSEL[3:0] bits in
the ADCx_CFGR register). A simultaneous trigger is provided to the slave ADC.
In this mode, independent injected conversions are supported. An injection request (either
on master or on the slave) will abort the current simultaneous conversions, which are restarted once the injected conversion is completed.
Note:

Do not convert the same channel on the two ADCs (no overlapping sampling times for the
two 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 longer conversion time of the 2
sequences. Otherwise, the ADC with the shortest sequence may restart while the ADC with
the longest sequence is completing the previous conversions.
Software is notified by interrupts when it can read the data:
•

At the end of each conversion event (EOC) on the master ADC, a master EOC interrupt
is generated (if EOCIE is enabled) and software can read the ADCx_DR of the master
ADC.

•

At the end of each conversion event (EOC) on the slave ADC, a slave EOC interrupt is
generated (if EOCIE is enabled) and software can read the ADCx_DR of the slave
ADC.

•

If the duration of the master regular sequence is equal to the duration of the slave one
(like in Figure 99), it is possible for the software to enable only one of the two EOC
interrupt (ex: master EOC) and read both converted data from the Common Data
register (ADCx_CDR).

It is also possible to read the regular data using the DMA. Two methods are possible:
•

•

Using two DMA channels (one for the master and one for the slave). In this case bits
MDMA[1:0] must be kept cleared.
–

Configure the DMA master ADC channel to read ADCx_DR from the master. DMA
requests are generated at each EOC event of the master ADC.

–

Configure the DMA slave ADC channel to read ADCx_DR from the slave. DMA
requests are generated at each EOC event of the slave ADC.

Using MDMA mode, which leaves one DMA channel free for other uses:
–

Configure MDMA[1:0]=0b10 or 0b11 (depending on resolution).

–

A single DMA channel is used (the one of the master). Configure the DMA master
ADC channel to read the common ADC register (ADCx_CDR)

–

A single DMA request is generated each time both master and slave EOC events
have occurred. At that time, the slave ADC converted data is available in the
upper half-word of the ADCx_CDR 32-bit register and the master ADC converted
data is available in the lower half-word of ADCx_CCR register.

–

both EOC flags are cleared when the DMA reads the ADCx_CCR register.

DocID022558 Rev 8

361/1141
413

Analog-to-digital converters (ADC)
Note:

RM0316

In MDMA mode (MDMA[1:0]=0b10 or 0b11), the user must program the same number of
conversions in the master’s sequence as in the slave’s sequence. Otherwise, the remaining
conversions will not generate a DMA request.
Figure 99. Regular simultaneous mode on 16 channels: dual ADC mode
0$67(5$'&
6/$9($'&

&+

&+

&+

&+

&+
&+

&+



&+

&+



&+

7ULJJHU
6DPSOLQJ

(QGRIUHJXODUVHTXHQFHRQ
0$67(5DQG6/$9($'&

&RQYHUVLRQ

DLE

If DISCEN=1 then each “n” simultaneous conversions of the regular sequence require a
regular trigger event to occur (“n” is defined by DISCNUM).
This mode can be combined with AUTDLY mode:
•

Once a simultaneous conversion of the sequence has ended, the next conversion in
the sequence is started only if the common data register, ADCx_CDR (or the regular
data register of the master ADC) has been read (delay phase).

•

Once a simultaneous regular sequence of conversions has ended, a new regular
trigger event is accepted only if the common data register (ADCx_CDR) has been read
(delay phase). Any new regular trigger events occurring during the ongoing regular
sequence and the associated delay phases are ignored.

It is possible to use the DMA to handle data in regular simultaneous mode combined with
AUTDLY mode, assuming that multi-DMA mode is used: bits MDMA must be set to 0b10 or
0b11.
When regular simultaneous mode is combined with AUTDLY mode, it is mandatory for the
user to ensure that:

Note:

•

The number of conversions in the master’s sequence is equal to the number of
conversions in the slave’s.

•

For each simultaneous conversions of the sequence, the length of the conversion of
the slave ADC is inferior to the length of the conversion of the master ADC. Note that
the length of the sequence depends on the number of channels to convert and the
sampling time and the resolution of each channels.

This combination of regular simultaneous mode and AUTDLY mode is restricted to the use
case when only regular channels are programmed: it is forbidden to program injected
channels in this combined mode.

Interleaved mode with independent injected
This mode is selected by programming bits DUAL[4:0] = 00111.
This mode can be started only on a regular group (usually one channel). The external
trigger source comes from the regular channel multiplexer of the master ADC.
After an external trigger occurs:

362/1141

•

The master ADC starts immediately.

•

The slave ADC starts after a delay of several ADC clock cycles after the sampling
phase of the master ADC has complete.

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
The minimum delay which separates 2 conversions in interleaved mode is configured in the
DELAY bits in the ADCx_CCR register. This delay starts to count after the end of the
sampling phase of the master conversion. This way, 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).
•

The minimum possible DELAY is 1 to ensure that there is at least one cycle time
between the opening of the analog switch of the master ADC sampling phase and the
closing of the analog switch of the slave ADC sampling phase.

•

The maximum DELAY is equal to the number of cycles corresponding to the selected
resolution. However the user must properly calculate this delay to ensure that an ADC
does not start a conversion while the other ADC is still sampling its input.

If the CONT bit is set on both master and slave ADCs, the selected regular channels of both
ADCs are continuously converted.
Software is notified by interrupts when it can read the data:

Note:

•

At the end of each conversion event (EOC) on the master ADC, a master EOC interrupt
is generated (if EOCIE is enabled) and software can read the ADCx_DR of the master
ADC.

•

At the end of each conversion event (EOC) on the slave ADC, a slave EOC interrupt is
generated (if EOCIE is enabled) and software can read the ADCx_DR of the slave
ADC.

It is possible to enable only the EOC interrupt of the slave and read the common data
register (ADCx_CDR). But in this case, the user must ensure that the duration of the
conversions are compatible to ensure that inside the sequence, a master conversion is
always followed by a slave conversion before a new master conversion restarts.
It is also possible to read the regular data using the DMA. Two methods are possible:
•

•

Using the two DMA channels (one for the master and one for the slave). In this case
bits MDMA[1:0] must be kept cleared.
–

Configure the DMA master ADC channel to read ADCx_DR from the master. DMA
requests are generated at each EOC event of the master ADC.

–

Configure the DMA slave ADC channel to read ADCx_DR from the slave. DMA
requests are generated at each EOC event of the slave ADC.

Using MDMA mode, which allows to save one DMA channel:
–

Configure MDMA[1:0]=0b10 or 0b11 (depending on resolution).

–

A single DMA channel is used (the one of the master). Configure the DMA master
ADC channel to read the common ADC register (ADCx_CDR).

–

A single DMA request is generated each time both master and slave EOC events
have occurred. At that time, the slave ADC converted data is available in the
upper half-word of the ADCx_CDR 32-bit register and the master ADC converted
data is available in the lower half-word of ADCx_CCR register.

–

Both EOC flags are cleared when the DMA reads the ADCx_CCR register.

DocID022558 Rev 8

363/1141
413

Analog-to-digital converters (ADC)

RM0316

Figure 100. Interleaved mode on 1 channel in continuous conversion mode: dual ADC
mode
(QGRIFRQYHUVLRQRQPDVWHU$'&
0$67(5$'&

&+

&+

6/$9($'&
7ULJJHU

&+

&+

$'&&/.
F\FOHV

$'&&/. (QGRIFRQYHUVLRQRQVODYH$'&
F\FOHV

6DPSOLQJ
&RQYHUVLRQ
-36

Figure 101. Interleaved mode on 1 channel in single conversion mode: dual ADC
mode
(QGRIFRQYHUVLRQRQPDVWHU$'&

0$67(5$'&

&+

&+

6/$9($'&
7ULJJHU

&+

&+

$'&&/. (QGRIFRQYHUVLRQ
RQVODYH$'&
F\FOHV
6DPSOLQJ

(QGRIFRQYHUVLRQ
RQVODYH$'&
$'&&/.
F\FOHV

&RQYHUVLRQ
069

If DISCEN=1, each “n” simultaneous conversions (“n” is defined by DISCNUM) of the
regular sequence require a regular trigger event to occur.
In this mode, injected conversions are supported. When injection is done (either on master
or on slave), both the master and the slave regular conversions are aborted and the
sequence is re-started from the master (see Figure 102 below).

364/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
Figure 102. Interleaved conversion with injection
,QMHFWHGWULJJHU

5HVXPH DOZD\VRQPDVWHU

&+
$'& PDVWHU

&+

$'& VODYH

&+
&+

6DPSOLQJ

&+
UHDG
&'5

/HJHQG

&+

&+
&+

UHDG
&'5

&+
&+

FRQYHUVLRQV
DERUWHG

&+
&+

UHDG
&'5

&+
UHDG
&'5

&RQYHUVLRQ

069

Alternate trigger mode
This mode is selected by programming bits DUAL[4:0] = 01001.
This mode can be started only on an injected group. The source of external trigger comes
from the injected group multiplexer of the master ADC.
This mode is only possible when selecting hardware triggers: JEXTEN must not be 0x0.

Injected discontinuous mode disabled (JDISCEN=0 for both ADC)
1.

When the 1st trigger occurs, all injected master ADC channels in the group are
converted.

2.

When the 2nd trigger occurs, all injected slave ADC channels in the group are
converted.

3.

And so on.

A JEOS interrupt, if enabled, is generated after all injected channels of the master ADC in
the group have been converted.
A JEOS interrupt, if enabled, is generated after all injected channels of the slave ADC in the
group have been converted.
JEOC interrupts, if enabled, can also be generated after each injected conversion.
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 channels of
the master ADC in the group.

DocID022558 Rev 8

365/1141
413

Analog-to-digital converters (ADC)

RM0316

Figure 103. Alternate trigger: injected group of each ADC
-(2&RQ
PDVWHU$'&

VWWULJJHU

-(2&RQ
PDVWHU$'&

-(2&-(26RQ
PDVWHU$'&

0$67(5$'&
6/$9($'&
QGWULJJHU

-(2&RQ
VODYH$'&

UGWULJJHU

-(2&RQ
VODYH$'&

-(2&-(26RQ
VODYH$'&

-(2&RQ
PDVWHU$'&

-(2&RQ
PDVWHU$'&

-(2&-(26RQ
PDVWHU$'&

0$67(5$'&
6/$9($'&
WKWULJJHU

-(2&RQ
VODYH$'&

-(2&RQ
VODYH$'&

-(2&-(26RQ
VODYH$'&

6DPSOLQJ
&RQYHUVLRQ
DLP

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.
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.

Injected discontinuous mode enabled (JDISCEN=1 for both ADC)
If the injected discontinuous mode is enabled for both master and slave ADCs:
•

When the 1st trigger occurs, the first injected channel of the master ADC is converted.

•

When the 2nd trigger occurs, the first injected channel of the slave ADC is converted.

•

And so on.

A JEOS interrupt, if enabled, is generated after all injected channels of the master ADC in
the group have been converted.
A JEOS interrupt, if enabled, is generated after all injected channels of the slave ADC in the
group have been converted.
JEOC interrupts, if enabled, can also be generated after each injected conversions.
If another external trigger occurs after all injected channels in the group have been
converted then the alternate trigger process restarts.

366/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Figure 104. Alternate trigger: 4 injected channels (each ADC) in discontinuous mode
VWWULJJHU

UGWULJJHU
WKWULJJHU
WKWULJJHU
-(2&-(26RQ
-(2&RQ
-(2&RQ
-(2&RQ
PDVWHU$'&
PDVWHU$'&
PDVWHU$'&
PDVWHU$'&

0$67(5$'&
6/$9($'&
-(2&RQ
PDVWHU$'&
QGWULJJHU

-(2&RQ
PDVWHU$'&

WKWULJJHU

-(2&RQ
PDVWHU$'&

WKWULJJHU

WKWULJJHU

-(2&-(26RQ
PDVWHU$'&

6DPSOLQJ
&RQYHUVLRQ

DL9P

Combined regular/injected simultaneous mode
This mode is selected by programming bits DUAL[4:0] = 00001.
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. Otherwise, the ADC with the shortest sequence may restart while
the ADC with the longest sequence is completing the previous conversions.

Combined regular simultaneous + alternate trigger mode
This mode is selected by programming bits DUAL[4:0]=00010.
It is possible to interrupt the simultaneous conversion of a regular group to start the alternate
trigger conversion of an injected group. Figure 105 shows the behavior of an alternate
trigger interrupting a simultaneous regular conversion.
The injected alternate conversion is immediately started after the injected event. If a 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:

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. Otherwise, the ADC with the shortest sequence may
restart while the ADC with the longest sequence is completing the previous conversions.

DocID022558 Rev 8

367/1141
413

Analog-to-digital converters (ADC)

RM0316

Figure 105. Alternate + regular simultaneous
VWWULJJHU

$'&0$67(5UHJ

&+

&+

&+

&+

&+

&+

&+

&+

&+

&+

&+

$'&0$67(5LQM
$'&6/$9(UHJ

&+

&+

&+

&+

&+

$'&6/$9(LQM

V\QFKURQRWORVW
QGWULJJHU

DL9P

If a trigger occurs during an injected conversion that has interrupted a regular conversion,
the alternate trigger is served. Figure 106 shows the behavior in this case (note that the 6th
trigger is ignored because the associated alternate conversion is not complete).
Figure 106. Case of trigger occurring during injected conversion
VWWULJJHU

$'&0$67(5UHJ

&+

&+

&+

&+

$'&0$67(5LQM
$'&6/$9(UHJ
$'&6/$9(LQM

UGWULJJHU

&+
&+

&+

&+

&+

&+
&+
&+

&+
QGWULJJHU

WKWULJJHU

&+

&+

&+
&+
&+

&+

&+

&+

&+

&+
WKWULJJHU

WKWULJJHU
LJQRUHG
DL9

368/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

DMA requests in dual ADC mode
In all dual ADC modes, it is possible to use two DMA channels (one for the master, one for
the slave) to transfer the data, like in single mode (refer to Figure 107: DMA Requests in
regular simultaneous mode when MDMA=0b00).
Figure 107. DMA Requests in regular simultaneous mode when MDMA=0b00
7ULJJHU
$'&0DVWHUUHJXODU

7ULJJHU

&+

&+

$'&0DVWHU(2&

$'&6ODYHUHJXODU

&+

&+

$'&6ODYH(2&
'0$UHTXHVWIURP$'&0DVWHU
'0$UHDGV0DVWHU
$'&B'5

'0$UHDGV0DWHU
$'&B'5

'0$UHTXHVWIURP$'&6ODYH
'0$UHDGV6ODYH
$'&B'5

'0$UHDGV6ODYH
$'&B'5

&RQILJXUDWLRQZKHUHHDFKVHTXHQFHFRQWDLQVRQO\RQHFRQYHUVLRQ

06Y9

In simultaneous regular and interleaved modes, it is also possible to save one DMA channel
and transfer both data using a single DMA channel. For this MDMA bits must be configured
in the ADCx_CCR register:
•

MDMA=0b10: A single DMA request is generated each time both master and slave
EOC events have occurred. At that time, two data items are available and the 32-bit
register ADCx_CDR contains the two half-words representing two ADC-converted data
items. The slave ADC data take the upper half-word and the master ADC data take the
lower half-word.
This mode is used in interleaved mode and in regular simultaneous mode when
resolution is 10-bit or 12-bit.
Example:
Interleaved dual mode: a DMA request is generated each time 2 data items are
available:
1st DMA request: ADCx_CDR[31:0] = SLV_ADCx_DR[15:0] |
MST_ADCx_DR[15:0]
2nd DMA request: ADCx_CDR[31:0] = SLV_ADCx_DR[15:0] |
MST_ADCx_DR[15:0]

DocID022558 Rev 8

369/1141
413

Analog-to-digital converters (ADC)

RM0316

Figure 108. DMA requests in regular simultaneous mode when MDMA=0b10
7ULJJHU

7ULJJHU

&+

$'&0DVWHUUHJXODU

7ULJJHU

&+

7ULJJHU
&+

&+

$'&6ODYH(2&
&+

&+

&+

$'&6ODYHUHJXODU

&+

$'&6ODYH(2&
'0$UHTXHVWIURP
$'&0DVWHU
'0$UHTXHVWIURP
$'&6ODYH

&RQILJXUDWLRQZKHUHHDFKVHTXHQFHFRQWDLQVRQO\RQHFRQYHUVLRQ
06Y9

Figure 109. DMA requests in interleaved mode when MDMA=0b10

7ULJJHU
$'&0DVWHUUHJXODU
$'&0DVWHU(2&
$'&6ODYHUHJXODU

7ULJJHU

&+

&+

&+

&+

&+

'HOD\

'HOD\

'HOD\

'HOD\
&+

7ULJJHU

7ULJJHU

7ULJJHU

&+

&+
'HOD\

&+

&+

$'&6ODYH(2&
'0$UHTXHVWIURP
$'&0DVWHU
'0$UHTXHVWIURP
$'&6ODYH

&RQILJXUDWLRQZKHUHHDFKVHTXHQFHFRQWDLQVRQO\RQHFRQYHUVLRQ
06Y9

370/1141

DocID022558 Rev 8

RM0316
Note:

Analog-to-digital converters (ADC)
When using MDMA mode, the user must take care to configure properly the duration of the
master and slave conversions so that a DMA request is generated and served for reading
both data (master + slave) before a new conversion is available.
•

MDMA=0b11: This mode is similar to the MDMA=0b10. The only differences are that
on each DMA request (two data items are available), two bytes representing two ADC
converted data items are transferred as a half-word.
This mode is used in interleaved and regular simultaneous mode when resolution is 6bit or when resolution is 8-bit and data is not signed (offsets must be disabled for all the
involved channels).
Example:
Interleaved dual mode: a DMA request is generated each time 2 data items are
available:
1st DMA request: ADCx_CDR[15:0] = SLV_ADCx_DR[7:0] | MST_ADCx_DR[7:0]
2nd DMA request: ADCx_CDR[15:0] = SLV_ADCx_DR[7:0] | MST_ADCx_DR[7:0]

Overrun detection
In dual ADC mode (when DUAL[4:0] is not equal to b00000), if an overrun is detected on
one of the ADCs, the DMA requests are no longer issued to ensure that all the data
transferred to the RAM are valid (this behavior occurs whatever the MDMA configuration). It
may happen that the EOC bit corresponding to one ADC remains set because the data
register of this ADC contains valid data.

DMA one shot mode/ DMA circular mode when MDMA mode is selected
When MDMA mode is selected (0b10 or 0b11), bit DMACFG of the ADCx_CCR register
must also be configured to select between DMA one shot mode and circular mode, as
explained in section Section : Managing conversions using the DMA (bits DMACFG of
master and slave ADCx_CFGR are not relevant).

Stopping the conversions in dual ADC modes
The user must set the control bits ADSTP/JADSTP of the master ADC to stop the
conversions of both ADC in dual ADC mode. The other ADSTP control bit of the slave ADC
has no effect in dual ADC mode.
Once both ADC are effectively stopped, the bits ADSTART/JADSTART of the master and
slave ADCs are both cleared by hardware.

15.3.30

Temperature sensor
The temperature sensor can be used to measure the junction temperature (TJ) of the
device. The temperature sensor is internally connected to the input channels which are
used to convert the sensor output voltage to a digital value. When not in use, the sensor can
be put in power down mode.
Figure 110 shows the block diagram of connections between the temperature sensor and
the ADC.
The temperature sensor output voltage changes linearly with temperature. The offset of this
line varies from chip to chip due to process variation (up to 45 °C from one chip to another).
The uncalibrated internal temperature sensor is more suited for applications that detect
temperature variations instead of absolute temperatures. To improve the accuracy of the

DocID022558 Rev 8

371/1141
413

Analog-to-digital converters (ADC)

RM0316

temperature sensor measurement, calibration values are stored in system memory for each
device by ST during production.
During the manufacturing process, the calibration data of the temperature sensor and the
internal voltage reference are stored in the system memory area. The user application can
then read them and use them to improve the accuracy of the temperature sensor or the
internal reference. Refer to the STM32F3xx datasheet for additional information.

Main features
•

Supported temperature range: –40 to 125 °C

•

Precision: ±2 °C

The temperature sensor is internally connected to the ADC1_IN16 input channel which is
used to convert the sensor’s output voltage to a digital value. Refer to the electrical
characteristics section of STM32F3xx datasheet for the sampling time value to be applied
when converting the internal temperature sensor.
When not in use, the sensor can be put in power-down mode.
Figure 110 shows the block diagram of the temperature sensor.
Figure 110. Temperature sensor channel block diagram

FRQYHUWHG
GDWD

$'&[
7HPSHUDWXUH
VHQVRU

976

$GGUHVVGDWDEXV

76(1FRQWUROELW

$'&LQSXW

06Y9

Note:

The TSEN bit must be set to enable the conversion of the temperature sensor voltage VTS.

Reading the temperature
To use the sensor:

372/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)
1.

Select the ADC1_IN16 input channel (with the appropriate sampling time).

2.

Program with the appropriate sampling time (refer to electrical characteristics section of
the STM32F3xx datasheet).

3.

Set the TSEN bit in the ADC1_CCR register to wake up the temperature sensor from
power-down mode.

4.

Start the ADC conversion.

5.

Read the resulting VTS data in the ADC data register.

6.

Calculate the actual temperature using the following formula:
Temperature (in °C) = {(V25 – VTS) / Avg_Slope} + 25
Where:
–

V25 = VTS value for 25° C

–

Avg_Slope = average slope of the temperature vs. VTS curve (given in mV/°C or
µV/°C)

Refer to the datasheet electrical characteristics section for the actual values of V25 and
Avg_Slope.
Note:

The sensor has a startup time after waking from power-down mode before it can output VTS
at the correct level. The ADC also has a startup time after power-on, so to minimize the
delay, the ADEN and TSEN bits should be set at the same time.

15.3.31

VBAT supply monitoring
The VBATEN bit in the ADC12_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 by 2. This bridge is automatically enabled
when VBATEN is set, to connect VBAT/2 to the ADC1_IN17 input channel. As a
consequence, the converted digital value is half the VBAT voltage. To prevent any unwanted
consumption on the battery, it is recommended to enable the bridge divider only when
needed, for ADC conversion.
Refer to the electrical characteristics of the STM32F3xx datasheet for the sampling time
value to be applied when converting the VBAT/2 voltage.
Figure 111 shows the block diagram of the VBAT sensing feature.

DocID022558 Rev 8

373/1141
413

Analog-to-digital converters (ADC)

RM0316
Figure 111. VBAT channel block diagram

9%$7
$GGUHVVGDWDEXV

9%$7(1FRQWUROELW

$'&[
9%$7
$'&LQSXW

06Y9

Note:

The VBATEN bit must be set to enable the conversion of internal channel ADC1_IN17
(VBATEN).

15.3.32

Monitoring the internal voltage reference
It is possible to monitor the internal voltage reference (VREFINT) to have a reference point for
evaluating the ADC VREF+ voltage level.
The internal voltage reference is internally connected to the input channel 18 of the four
ADCs (ADCx_IN18).
Refer to the electrical characteristics section of the STM32F3xx datasheet for the sampling
time value to be applied when converting the internal voltage reference voltage.
Figure 111 shows the block diagram of the VREFINT sensing feature.
Figure 112. VREFINT channel block diagram

$'&B95()(1
FRQWUROELW

,QWHUQDO
SRZHUEORFN

95(),17

$'&
$'&
$'&B,1
$'&B,1

06Y9

Note:

The VREFEN bit into ADC12_CCR register must be set to enable the conversion of internal
channels ADC1_IN18 or ADC2_IN18 (VREFINT).
The VREFEN bit into ADC34_CCR register must be set to enable the conversion of internal
channels ADC3_IN18 or ADC4_IN18 (VREFINT).

374/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Calculating the actual VDDA voltage using the internal reference voltage
The VDDA power supply voltage applied to the microcontroller may be subject to variation or
not precisely known. The embedded internal voltage reference (VREFINT) and its calibration
data acquired by the ADC during the manufacturing process at VDDA = 3.3 V can be used to
evaluate the actual VDDA voltage level.
The following formula gives the actual VDDA voltage supplying the device:
VDDA = 3.3 V ₓ VREFINT_CAL / VREFINT_DATA
Where:
•

VREFINT_CAL is the VREFINT calibration value

•

VREFINT_DATA is the actual VREFINT output value converted by ADC

Converting a supply-relative ADC measurement to an absolute voltage value
The ADC is designed to deliver a digital value corresponding to the ratio between the analog
power supply and the voltage applied on the converted channel. For most application use
cases, it is necessary to convert this ratio into a voltage independent of VDDA. For
applications where VDDA is known and ADC converted values are right-aligned user can use
the following formula to get this absolute value:
V DDA
V CHANNELx = ------------------------------------- × ADCx_DATA
FULL_SCALE

For applications where VDDA value is not known, user must use the internal voltage
reference and VDDA can be replaced by the expression provided in the section Calculating
the actual VDDA voltage using the internal reference voltage, resulting in the following
formula:
3.3 V × VREFINT_CAL × ADCx_DATA
V CHANNELx = -------------------------------------------------------------------------------------------------------VREFINT_DATA × FULL_SCALE

Where:

Note:

•

VREFINT_CAL is the VREFINT calibration value

•

ADCx_DATA is the value measured by the ADC on channel x (right-aligned)

•

VREFINT_DATA is the actual VREFINT output value converted by the ADC

•

FULL_SCALE is the maximum digital value of the ADC output. For example with 12-bit
resolution, it will be 212 - 1 = 4095 or with 8-bit resolution, 28 - 1 = 255.

If ADC measurements are done using an output format other than 12 bit right-aligned, all the
parameters must first be converted to a compatible format before the calculation is done.

DocID022558 Rev 8

375/1141
413

Analog-to-digital converters (ADC)

15.4

RM0316

ADC interrupts
For each ADC, an interrupt can be generated:
•

After ADC power-up, when the ADC is ready (flag ADRDY)

•

On the end of any conversion for regular groups (flag EOC)

•

On the end of a sequence of conversion for regular groups (flag EOS)

•

On the end of any conversion for injected groups (flag JEOC)

•

On the end of a sequence of conversion for injected groups (flag JEOS)

•

When an analog watchdog detection occurs (flag AWD1, AWD2 and AWD3)

•

When the end of sampling phase occurs (flag EOSMP)

•

When the data overrun occurs (flag OVR)

•

When the injected sequence context queue overflows (flag JQOVF)

Separate interrupt enable bits are available for flexibility.
Table 99. ADC interrupts per each ADC
Interrupt event

Event flag

Enable control bit

ADRDY

ADRDYIE

End of conversion of a regular group

EOC

EOCIE

End of sequence of conversions of a regular group

EOS

EOSIE

End of conversion of a injected group

JEOC

JEOCIE

End of sequence of conversions of an injected group

JEOS

JEOSIE

Analog watchdog 1 status bit is set

AWD1

AWD1IE

Analog watchdog 2 status bit is set

AWD2

AWD2IE

Analog watchdog 3 status bit is set

AWD3

AWD3IE

EOSMP

EOSMPIE

OVR

OVRIE

JQOVF

JQOVFIE

ADC ready

End of sampling phase
Overrun
Injected context queue overflows

376/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.5

ADC registers (for each ADC)
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.

Note:

The STM32F303x6/8 and STM32F328x8 devices have only ADC1 and ADC2.

15.5.1

ADC interrupt and status register (ADCx_ISR, x=1..4)
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.

AWD2

AWD1

JEOS

JEOC

OVR

EOS

EOC

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

JQOVF AWD3
rc_w1

rc_w1

EOSMP ADRDY
rc_w1

rc_w1

Bits 31:11 Reserved, must be kept at reset value.
Bit 10 JQOVF: Injected context queue overflow
This bit is set by hardware when an Overflow of the Injected Queue of Context occurs. It is cleared by
software writing 1 to it. Refer to Section 15.3.21: Queue of context for injected conversions for more
information.
0: No injected context queue overflow occurred (or the flag event was already acknowledged and
cleared by software)
1: Injected context queue overflow has occurred
Bit 9 AWD3: Analog watchdog 3 flag
This bit is set by hardware when the converted voltage crosses the values programmed in the fields
LT3[7:0] and HT3[7:0] of ADCx_TR3 register. It is cleared by software writing 1 to it.
0: No analog watchdog 3 event occurred (or the flag event was already acknowledged and cleared
by software)
1: Analog watchdog 3 event occurred
Bit 8 AWD2: Analog watchdog 2 flag
This bit is set by hardware when the converted voltage crosses the values programmed in the fields
LT2[7:0] and HT2[7:0] of ADCx_TR2 register. It is cleared by software writing 1 to it.
0: No analog watchdog 2 event occurred (or the flag event was already acknowledged and cleared
by software)
1: Analog watchdog 2 event occurred
Bit 7 AWD1: Analog watchdog 1 flag
This bit is set by hardware when the converted voltage crosses the values programmed in the fields
LT1[11:0] and HT1[11:0] of ADCx_TR1 register. It is cleared by software. writing 1 to it.
0: No analog watchdog 1 event occurred (or the flag event was already acknowledged and cleared
by software)
1: Analog watchdog 1 event occurred

DocID022558 Rev 8

377/1141
413

Analog-to-digital converters (ADC)

RM0316

Bit 6 JEOS: Injected channel end of sequence flag
This bit is set by hardware at the end of the conversions of all injected channels in the group. It is
cleared by software writing 1 to it.
0: Injected conversion sequence not complete (or the flag event was already acknowledged and
cleared by software)
1: Injected conversions complete
Bit 5 JEOC: Injected channel end of conversion flag
This bit is set by hardware at the end of each injected conversion of a channel when a new data is
available in the corresponding ADCx_JDRy register. It is cleared by software writing 1 to it or by
reading the corresponding ADCx_JDRy register
0: Injected channel conversion not complete (or the flag event was already acknowledged and
cleared by software)
1: Injected channel conversion complete
Bit 4 OVR: ADC overrun
This bit is set by hardware when an overrun occurs on a regular channel, meaning that a new
conversion has completed while the EOC flag was already set. It is cleared by software writing 1 to it.
0: No overrun occurred (or the flag event was already acknowledged and cleared by software)
1: Overrun has occurred
Bit 3 EOS: End of regular sequence flag
This bit is set by hardware at the end of the conversions of a regular sequence of channels. It is
cleared by software writing 1 to it.
0: Regular Conversions sequence not complete (or the flag event was already acknowledged and
cleared by software)
1: Regular Conversions sequence complete
Bit 2 EOC: End of conversion flag
This bit is set by hardware at the end of each regular conversion of a channel when a new data is
available in the ADCx_DR register. It is cleared by software writing 1 to it or by reading the ADCx_DR
register
0: Regular channel conversion not complete (or the flag event was already acknowledged and
cleared by software)
1: Regular channel conversion complete
Bit 1 EOSMP: End of sampling flag
This bit is set by hardware during the conversion of any channel (only for regular channels), at the end
of the sampling phase.
0: not at the end of the sampling phase (or the flag event was already acknowledged and cleared by
software)
1: End of sampling phase reached
Bit 0 ADRDY: ADC ready
This bit is set by hardware after the ADC has been enabled (bit ADEN=1) and when the ADC reaches
a state where it is ready to accept conversion requests.
It is cleared by software writing 1 to it.
0: ADC not yet ready to start conversion (or the flag event was already acknowledged and cleared
by software)
1: ADC is ready to start conversion

378/1141

DocID022558 Rev 8

RM0316

15.5.2

Analog-to-digital converters (ADC)

ADC interrupt enable register (ADCx_IER, x=1..4)
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.

JQ
OVFIE

AWD3
IE

AWD2
IE

rw

rw

rw

Res.

Res.

Res.

Res.

AWD1
JEOSIE JEOCIE OVRIE
IE
rw

rw

rw

rw

EOSIE
rw

EOSMP ADRDY
EOCIE
IE
IE
rw

rw

rw

Bits 31:11 Reserved, must be kept at reset value.
Bit 10 JQOVFIE: Injected context queue overflow interrupt enable
This bit is set and cleared by software to enable/disable the Injected Context Queue Overflow interrupt.
0: Injected Context Queue Overflow interrupt disabled
1: Injected Context Queue Overflow interrupt enabled. An interrupt is generated when the JQOVF bit
is set.
Note: Software is allowed to write this bit only when JADSTART=0 (which ensures that no injected
conversion is ongoing).
Bit 9 AWD3IE: Analog watchdog 3 interrupt enable
This bit is set and cleared by software to enable/disable the analog watchdog 2 interrupt.
0: Analog watchdog 3 interrupt disabled
1: Analog watchdog 3 interrupt enabled
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no conversion is ongoing).
Bit 8 AWD2IE: Analog watchdog 2 interrupt enable
This bit is set and cleared by software to enable/disable the analog watchdog 2 interrupt.
0: Analog watchdog 2 interrupt disabled
1: Analog watchdog 2 interrupt enabled
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no conversion is ongoing).
Bit 7 AWD1IE: Analog watchdog 1 interrupt enable
This bit is set and cleared by software to enable/disable the analog watchdog 1 interrupt.
0: Analog watchdog 1 interrupt disabled
1: Analog watchdog 1 interrupt enabled
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no conversion is ongoing).
Bit 6 JEOSIE: End of injected sequence of conversions interrupt enable
This bit is set and cleared by software to enable/disable the end of injected sequence of conversions
interrupt.
0: JEOS interrupt disabled
1: JEOS interrupt enabled. An interrupt is generated when the JEOS bit is set.
Note: Software is allowed to write this bit only when JADSTART=0 (which ensures that no injected
conversion is ongoing).

DocID022558 Rev 8

379/1141
413

Analog-to-digital converters (ADC)

RM0316

Bit 5 JEOCIE: End of injected conversion interrupt enable
This bit is set and cleared by software to enable/disable the end of an injected conversion interrupt.
0: JEOC interrupt disabled.
1: JEOC interrupt enabled. An interrupt is generated when the JEOC bit is set.
Note: Software is allowed to write this bit only when JADSTART=0 (which ensures that no regular
conversion is ongoing).
Bit 4 OVRIE: Overrun interrupt enable
This bit is set and cleared by software to enable/disable the Overrun interrupt of a regular conversion.
0: Overrun interrupt disabled
1: Overrun interrupt enabled. An interrupt is generated when the OVR bit is set.
Note: Software is allowed to write this bit only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Bit 3 EOSIE: End of regular sequence of conversions interrupt enable
This bit is set and cleared by software to enable/disable the end of regular sequence of conversions
interrupt.
0: EOS interrupt disabled
1: EOS interrupt enabled. An interrupt is generated when the EOS bit is set.
Note: Software is allowed to write this bit only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Bit 2 EOCIE: End of regular conversion interrupt enable
This bit is set and cleared by software to enable/disable the end of a regular conversion interrupt.
0: EOC interrupt disabled.
1: EOC interrupt enabled. An interrupt is generated when the EOC bit is set.
Note: Software is allowed to write this bit only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Bit 1 EOSMPIE: End of sampling flag interrupt enable for regular conversions
This bit is set and cleared by software to enable/disable the end of the sampling phase interrupt for
regular conversions.
0: EOSMP interrupt disabled.
1: EOSMP interrupt enabled. An interrupt is generated when the EOSMP bit is set.
Note: Software is allowed to write this bit only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Bit 0 ADRDYIE: ADC ready interrupt enable
This bit is set and cleared by software to enable/disable the ADC Ready interrupt.
0: ADRDY interrupt disabled
1: ADRDY interrupt enabled. An interrupt is generated when the ADRDY bit is set.
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no conversion is ongoing).

380/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.5.3

ADC control register (ADCx_CR, x=1..4)
Address offset: 0x08
Reset value: 0x2000 0000

31

30

AD
CAL

ADCA
LDIF

rs

rw

rw

rw

15

14

13

12

Res.

Res.

29

28

ADVREGEN[1:0]

Res.

Res.

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

3

2

Res.

JAD
STP

AD
STP

rs

rs

Res.

Res.

Res.

Res.

Res.

JAD
AD
START START
rs

rs

1

0

AD
DIS

AD
EN

rs

rs

Bit 31 ADCAL: ADC calibration
This bit is set by software to start the calibration of the ADC. Program first the bit ADCALDIF to
determine if this calibration applies for single-ended or differential inputs mode.
It is cleared by hardware after calibration is complete.
0: Calibration complete
1: Write 1 to calibrate the ADC. Read at 1 means that a calibration in progress.
Note: Software is allowed to launch a calibration by setting ADCAL only when ADEN=0.
Note: Software is allowed to update the calibration factor by writing ADCx_CALFACT only when
ADEN=1 and ADSTART=0 and JADSTART=0 (ADC enabled and no conversion is ongoing)
Bit 30 ADCALDIF: Differential mode for calibration
This bit is set and cleared by software to configure the single-ended or differential inputs mode for the
calibration.
0: Writing ADCAL will launch a calibration in Single-ended inputs Mode.
1: Writing ADCAL will launch a calibration in Differential inputs Mode.
Note: Software is allowed to write this bit only when the ADC is disabled and is not calibrating
(ADCAL=0, JADSTART=0, JADSTP=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).
Bits 29:28 ADVREGEN[1:0]: ADC voltage regulator enable
These bits are set by software to enable the ADC voltage regulator.
Before performing any operation such as launching a calibration or enabling the ADC, the ADC voltage
regulator must first be enabled and the software must wait for the regulator start-up time.
00: Intermediate state required when moving the ADC voltage regulator from the enabled to the
disabled state or from the disabled to the enabled state.
01: ADC Voltage regulator enabled.
10: ADC Voltage regulator disabled (Reset state)
11: reserved
For more details about the ADC voltage regulator enable and disable sequences, refer to
Section 15.3.6: ADC voltage regulator (ADVREGEN).
Note: The software can program this bit field only when the ADC is disabled (ADCAL=0,
JADSTART=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).
Bits 27:6 Reserved, must be kept at reset value.

DocID022558 Rev 8

381/1141
413

Analog-to-digital converters (ADC)

RM0316

Bit 5 JADSTP: ADC stop of injected conversion command
This bit is set by software to stop and discard an ongoing injected conversion (JADSTP Command).
It is cleared by hardware when the conversion is effectively discarded and the ADC injected sequence
and triggers can be re-configured. The ADC is then ready to accept a new start of injected conversions
(JADSTART command).
0: No ADC stop injected conversion command ongoing
1: Write 1 to stop injected conversions ongoing. Read 1 means that an ADSTP command is in
progress.
Note: Software is allowed to set JADSTP only when JADSTART=1 and ADDIS=0 (ADC is enabled
and eventually converting an injected conversion and there is no pending request to disable the
ADC)
Note: In auto-injection mode (JAUTO=1), setting ADSTP bit aborts both regular and injected
conversions (do not use JADSTP)
Bit 4 ADSTP: ADC stop of regular conversion command
This bit is set by software to stop and discard an ongoing regular conversion (ADSTP Command).
It is cleared by hardware when the conversion is effectively discarded and the ADC regular sequence
and triggers can be re-configured. The ADC is then ready to accept a new start of regular conversions
(ADSTART command).
0: No ADC stop regular conversion command ongoing
1: Write 1 to stop regular conversions ongoing. Read 1 means that an ADSTP command is in
progress.
Note: Software is allowed to set ADSTP only when ADSTART=1 and ADDIS=0 (ADC is enabled and
eventually converting a regular conversion and there is no pending request to disable the ADC)
Note: In auto-injection mode (JAUTO=1), setting ADSTP bit aborts both regular and injected
conversions (do not use JADSTP)
Note: In dual ADC regular simultaneous mode and interleaved mode, the bit ADSTP of the master
ADC must be used to stop regular conversions. The other ADSTP bit is inactive.
Bit 3 JADSTART: ADC start of injected conversion
This bit is set by software to start ADC conversion of injected channels. Depending on the
configuration bits JEXTEN, a conversion will start immediately (software trigger configuration) or once
an injected hardware trigger event occurs (hardware trigger configuration).
It is cleared by hardware:
– in single conversion mode when software trigger is selected (JEXTSEL=0x0): at the assertion of the
End of Injected Conversion Sequence (JEOS) flag.
– in all cases: after the execution of the JADSTP command, at the same time that JADSTP is cleared
by hardware.
0: No ADC injected conversion is ongoing.
1: Write 1 to start injected conversions. Read 1 means that the ADC is operating and eventually
converting an injected channel.
Note: Software is allowed to set JADSTART only when ADEN=1 and ADDIS=0 (ADC is enabled and
there is no pending request to disable the ADC)
Note: In auto-injection mode (JAUTO=1), regular and auto-injected conversions are started by setting
bit ADSTART (JADSTART must be kept cleared)

382/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Bit 2 ADSTART: ADC start of regular conversion
This bit is set by software to start ADC conversion of regular channels. Depending on the configuration
bits EXTEN, a conversion will start immediately (software trigger configuration) or once a regular
hardware trigger event occurs (hardware trigger configuration).
It is cleared by hardware:
– in single conversion mode when software trigger is selected (EXTSEL=0x0): at the assertion of the
End of Regular Conversion Sequence (EOS) flag.
– in all cases: after the execution of the ADSTP command, at the same time that ADSTP is cleared by
hardware.
0: No ADC regular conversion is ongoing.
1: Write 1 to start regular conversions. Read 1 means that the ADC is operating and eventually
converting a regular channel.
Note: Software is allowed to set ADSTART only when ADEN=1 and ADDIS=0 (ADC is enabled and
there is no pending request to disable the ADC)
Note: In auto-injection mode (JAUTO=1), regular and auto-injected conversions are started by setting
bit ADSTART (JADSTART must be kept cleared)
Bit 1 ADDIS: ADC disable command
This bit is set by software to disable the ADC (ADDIS command) and put it into power-down state
(OFF state).
It is cleared by hardware once the ADC is effectively disabled (ADEN is also cleared by hardware at
this time).
0: no ADDIS command ongoing
1: Write 1 to disable the ADC. Read 1 means that an ADDIS command is in progress.
Note: Software is allowed to set ADDIS only when ADEN=1 and both ADSTART=0 and JADSTART=0
(which ensures that no conversion is ongoing)
Bit 0 ADEN: ADC enable control
This bit is set by software to enable the ADC. The ADC will be effectively ready to operate once the
flag ADRDY has been set.
It is cleared by hardware when the ADC is disabled, after the execution of the ADDIS command.
0: ADC is disabled (OFF state)
1: Write 1 to enable the ADC.
Note: Software is allowed to set ADEN only when all bits of ADCx_CR registers are 0 (ADCAL=0,
JADSTART=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0) except for bit ADVREGEN
which must be 1 (and the software must have wait for the startup time of the voltage regulator)

DocID022558 Rev 8

383/1141
413

Analog-to-digital converters (ADC)

15.5.4

RM0316

ADC configuration register (ADCx_CFGR, x=1..4)
Address offset: 0x0C
Reset value: 0x0000 00000

31

30

29

Res.

28

27

26

25

24

JAWD1
JAUTO
EN

AWD1CH[4:0]

23

22

AWD1 AWD1S
EN
GL

21

20

JQM

JDISC
EN

19

18

17

16
DISC
EN

DISCNUM[2:0]

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.

AUT
DLY

CONT

OVR
MOD

Res.

DMA
CFG

DMA
EN

rw

rw

rw

rw

rw

EXTEN[1:0]
rw

rw

EXTSEL[3:0]
rw

rw

rw

ALIGN
rw

rw

RES[1:0]
rw

rw

Bit 31 Reserved, must be kept at reset value.
Bits 30:26 AWD1CH[4:0]: Analog watchdog 1 channel selection
These bits are set and cleared by software. They select the input channel to be guarded by the analog
watchdog.
00000: reserved (analog input channel 0 is not mapped)
00001: ADC analog input channel-1 monitored by AWD1
.....
10010: ADC analog input channel-18 monitored by AWD1
others: reserved, must not be used
Note: The channel selected by AWD1CH must be also selected into the SQRi or JSQRi registers.
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).
Bit 25 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
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no regular nor injected conversion is ongoing).
Note: When dual mode is enabled (bits DUAL of ADCx_CCR register are not equal to zero), the bit
JAUTO of the slave ADC is no more writable and its content is equal to the bit JAUTO of the
master ADC.
Bit 24 JAWD1EN: Analog watchdog 1 enable on injected channels
This bit is set and cleared by software
0: Analog watchdog 1 disabled on injected channels
1: Analog watchdog 1 enabled on injected channels
Note: Software is allowed to write this bit only when JADSTART=0 (which ensures that no injected
conversion is ongoing).
Bit 23 AWD1EN: Analog watchdog 1 enable on regular channels
This bit is set and cleared by software
0: Analog watchdog 1 disabled on regular channels
1: Analog watchdog 1 enabled on regular channels
Note: Software is allowed to write this bit only when ADSTART=0 (which ensures that no regular
conversion is ongoing).

384/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Bit 22 AWD1SGL: Enable the watchdog 1 on a single channel or on all channels
This bit is set and cleared by software to enable the analog watchdog on the channel identified by the
AWD1CH[4:0] bits or on all the channels
0: Analog watchdog 1 enabled on all channels
1: Analog watchdog 1 enabled on a single channel
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).
Bit 21 JQM: JSQR queue mode
This bit is set and cleared by software.
It defines how an empty Queue is managed.
0: JSQR Mode 0: The Queue is never empty and maintains the last written configuration into JSQR.
1: JSQR Mode 1: The Queue can be empty and when this occurs, the software and hardware
triggers of the injected sequence are both internally disabled just after the completion of the last valid
injected sequence.
Refer to Section 15.3.21: Queue of context for injected conversions for more information.
Note: Software is allowed to write this bit only when JADSTART=0 (which ensures that no injected
conversion is ongoing).
Note: When dual mode is enabled (bits DUAL of ADCx_CCR register are not equal to zero), the bit
JQM of the slave ADC is no more writable and its content is equal to the bit JQM of the master
ADC.
Bit 20 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
Note: Software is allowed to write this bit only when JADSTART=0 (which ensures that no injected
conversion is ongoing).
Note: It is not possible to use both auto-injected mode and discontinuous mode simultaneously: the
bits DISCEN and JDISCEN must be kept cleared by software when JAUTO is set.
Note: When dual mode is enabled (bits DUAL of ADCx_CCR register are not equal to zero), the bit
JDISCEN of the slave ADC is no more writable and its content is equal to the bit JDISCEN of
the master ADC.
Bits 19:17 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
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Note: When dual mode is enabled (bits DUAL of ADCx_CCR register are not equal to zero), the bits
DISCNUM[2:0] of the slave ADC are no more writable and their content is equal to the bits
DISCNUM[2:0] of the master ADC.

DocID022558 Rev 8

385/1141
413

Analog-to-digital converters (ADC)

RM0316

Bit 16 DISCEN: Discontinuous mode for regular channels
This bit is set and cleared by software to enable/disable Discontinuous mode for regular channels.
0: Discontinuous mode for regular channels disabled
1: Discontinuous mode for regular channels enabled
Note: It is not possible to have both discontinuous mode and continuous mode enabled: it is forbidden
to set both DISCEN=1 and CONT=1.
Note: It is not possible to use both auto-injected mode and discontinuous mode simultaneously: the
bits DISCEN and JDISCEN must be kept cleared by software when JAUTO is set.
Note: Software is allowed to write this bit only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Note: When dual mode is enabled (bits DUAL of ADCx_CCR register are not equal to zero), the bit
DISCEN of the slave ADC is no more writable and its content is equal to the bit DISCEN of the
master ADC.
Bit 15 Reserved, must be kept at reset value.
Bit 14 AUTDLY: Delayed conversion mode
This bit is set and cleared by software to enable/disable the Auto Delayed Conversion mode..
0: Auto-delayed conversion mode off
1: Auto-delayed conversion mode on
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no conversion is ongoing).
Note: When dual mode is enabled (bits DUAL of ADCx_CCR register are not equal to zero), the bit
AUTDLY of the slave ADC is no more writable and its content is equal to the bit AUTDLY of the
master ADC.
Bit 13 CONT: Single / continuous conversion mode for regular conversions
This bit is set and cleared by software. If it is set, regular conversion takes place continuously until it is
cleared.
0: Single conversion mode
1: Continuous conversion mode
Note: It is not possible to have both discontinuous mode and continuous mode enabled: it is forbidden
to set both DISCEN=1 and CONT=1.
Note: Software is allowed to write this bit only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Note: When dual mode is enabled (bits DUAL of ADCx_CCR register are not equal to zero), the bit
CONT of the slave ADC is no more writable and its content is equal to the bit CONT of the
master ADC.
Bit 12 OVRMOD: Overrun Mode
This bit is set and cleared by software and configure the way data overrun is managed.
0: ADCx_DR register is preserved with the old data when an overrun is detected.
1: ADCx_DR register is overwritten with the last conversion result when an overrun is detected.
Note: Software is allowed to write this bit only when ADSTART=0 (which ensures that no regular
conversion is ongoing).

386/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Bits 11:10 EXTEN[1:0]: External trigger enable and polarity selection 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: Hardware trigger detection disabled (conversions can be launched by software)
01: Hardware trigger detection on the rising edge
10: Hardware trigger detection on the falling edge
11: Hardware trigger detection on both the rising and falling edges
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Bits 9:6 EXTSEL[3:0]: External trigger selection for regular group
These bits select the external event used to trigger the start of conversion of a regular group:
0000: Event 0
0001: Event 1
0010: Event 2
0011: Event 3
0100: Event 4
0101: Event 5
0110: Event 6
0111: Event 7
...
1111: Event 15
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no regular
conversion is ongoing).
Bit 5 ALIGN: Data alignment
This bit is set and cleared by software to select right or left alignment. Refer to Figure : Data register,
data alignment and offset (ADCx_DR, OFFSETy, OFFSETy_CH, ALIGN)
0: Right alignment
1: Left alignment
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no conversion is ongoing).
Bits 4:3 RES[1:0]: Data resolution
These bits are written by software to select the resolution of the conversion.
00: 12-bit
01: 10-bit
10: 8-bit
11: 6-bit
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).

DocID022558 Rev 8

387/1141
413

Analog-to-digital converters (ADC)

RM0316

Bit 2 Reserved, must be kept at reset value.
Bit 1 DMACFG: Direct memory access configuration
This bit is set and cleared by software to select between two DMA modes of operation and is effective
only when DMAEN=1.
0: DMA One Shot Mode selected
1: DMA Circular Mode selected
For more details, refer to Section : Managing conversions using the DMA
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no conversion is ongoing).
Note: In dual-ADC modes, this bit is not relevant and replaced by control bit DMACFG of the
ADCx_CCR register.
Bit 0 DMAEN: Direct memory access enable
This bit is set and cleared by software to enable the generation of DMA requests. This allows to use
the GP-DMA to manage automatically the converted data. For more details, refer to Section :
Managing conversions using the DMA.
0: DMA disabled
1: DMA enabled
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which ensures
that no conversion is ongoing).
Note: In dual-ADC modes, this bit is not relevant and replaced by control bits MDMA[1:0] of the
ADCx_CCR register.

15.5.5

ADC sample time register 1 (ADCx_SMPR1, x=1..4)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

Res.

Res.

15

14

SMP
5_0
rw

388/1141

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

Res.

Res.

Res.

SMP4[2:0]
rw

26

SMP9[2:0]

rw

SMP3[2:0]
rw

rw

rw

SMP2[2:0]
rw

rw

rw

SMP1[2:0]
rw

DocID022558 Rev 8

rw

rw

rw

RM0316

Analog-to-digital converters (ADC)

Bits 31:30 Reserved, must be kept at reset value.
Bits 29:3 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.
000: 1.5 ADC clock cycles
001: 2.5 ADC clock cycles
010: 4.5 ADC clock cycles
011: 7.5 ADC clock cycles
100: 19.5 ADC clock cycles
101: 61.5 ADC clock cycles
110: 181.5 ADC clock cycles
111: 601.5 ADC clock cycles
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0
(which ensures that no conversion is ongoing).
Bites 2:0 Reserved

DocID022558 Rev 8

389/1141
413

Analog-to-digital converters (ADC)

15.5.6

RM0316

ADC sample time register 2 (ADCx_SMPR2, x=1..4)
Address offset: 0x18
Reset value: 0x0000 0000

31

30

29

28

27

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

rw

rw

SMP15_0

SMP14[2:0]

rw

rw

rw

26

25

24

23

SMP18[2:0]

22

21

20

SMP17[2:0]

19

18

SMP16[2:0]

17

16

SMP15[2:1]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

SMP13[2:0]
rw

SMP12[2:0]
rw

SMP11[2:0]
rw

SMP10[2:0]
rw

rw

Bits 31:27 Reserved, must be kept at reset value.
Bits 26:0 SMPx[2:0]: Channel x sampling time selection
These bits are written by software to select the sampling time individually for each channel.
During sampling cycles, the channel selection bits must remain unchanged.
000: 1.5 ADC clock cycles
001: 2.5 ADC clock cycles
010: 4.5 ADC clock cycles
011: 7.5 ADC clock cycles
100: 19.5 ADC clock cycles
101: 61.5 ADC clock cycles
110: 181.5 ADC clock cycles
111: 601.5 ADC clock cycles
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0
(which ensures that no conversion is ongoing).

15.5.7

ADC watchdog threshold register 1 (ADCx_TR1, x=1..4)
Address offset: 0x20
Reset value: 0x0FFF 0000

31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

Res.

Res.

Res.

Res.

27

26

25

24

23

22

20

19

18

17

16

4

3

2

1

0

rw

rw

rw

rw

rw

HT1[11:0]

11

10

9

8

7

6

5

LT1[11:0]
rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.

390/1141

21

DocID022558 Rev 8

rw

RM0316

Analog-to-digital converters (ADC)

Bits 27:16 HT1[11:0]: Analog watchdog 1 higher threshold
These bits are written by software to define the higher threshold for the analog watchdog 1.
Refer to Section 15.3.28: Analog window watchdog (AWD1EN, JAWD1EN, AWD1SGL, AWD1CH,
AWD2CH, AWD3CH, AWD_HTx, AWD_LTx, AWDx)
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).
Bits 15:12 Reserved, must be kept at reset value.
Bits 11:0 LT1[11:0]: Analog watchdog 1 lower threshold
These bits are written by software to define the lower threshold for the analog watchdog 1.
Refer to Section 15.3.28: Analog window watchdog (AWD1EN, JAWD1EN, AWD1SGL, AWD1CH,
AWD2CH, AWD3CH, AWD_HTx, AWD_LTx, AWDx)
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).

15.5.8

ADC watchdog threshold register 2 (ADCx_TR2, x = 1..4)
Address offset: 0x24
Reset value: 0x00FF 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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

23

22

21

20

19

18

17

16

HT2[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

LT2[7:0]
rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:16 HT2[7:0]: Analog watchdog 2 higher threshold
These bits are written by software to define the higher threshold for the analog watchdog 2.
Refer to Section 15.3.28: Analog window watchdog (AWD1EN, JAWD1EN, AWD1SGL, AWD1CH,
AWD2CH, AWD3CH, AWD_HTx, AWD_LTx, AWDx)
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).
Bits 15:8 Reserved, must be kept at reset value.
Bits 7:0 LT2[7:0]: Analog watchdog 2 lower threshold
These bits are written by software to define the lower threshold for the analog watchdog 2.
Refer to Section 15.3.28: Analog window watchdog (AWD1EN, JAWD1EN, AWD1SGL, AWD1CH,
AWD2CH, AWD3CH, AWD_HTx, AWD_LTx, AWDx)
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).

DocID022558 Rev 8

391/1141
413

Analog-to-digital converters (ADC)

15.5.9

RM0316

ADC watchdog threshold register 3 (ADCx_TR3, x=1..4)
Address offset: 0x28
Reset value: 0x00FF 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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

23

22

21

20

19

18

17

16

HT3[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

LT3[7:0]
rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:16 HT3[7:0]: Analog watchdog 3 higher threshold
These bits are written by software to define the higher threshold for the analog watchdog 3.
Refer to Section 15.3.28: Analog window watchdog (AWD1EN, JAWD1EN, AWD1SGL, AWD1CH,
AWD2CH, AWD3CH, AWD_HTx, AWD_LTx, AWDx)
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).
Bits 15:8 Reserved, must be kept at reset value.
Bits 7:0 LT3[7:0]: Analog watchdog 3 lower threshold
These bits are written by software to define the lower threshold for the analog watchdog 3.
This watchdog compares the 8-bit of LT3 with the 8 MSB of the converted data.
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).

392/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.5.10

ADC regular sequence register 1 (ADCx_SQR1, x=1..4)
Address offset: 0x30
Reset value: 0x0000 0000

31

30

29

Res.

Res.

Res.

15

14

13

rw

rw

28

26

25

24

SQ4[4:0]
rw

rw

rw

rw

rw

11

10

9

8

rw

rw

Res.
rw

23

22

21

Res.

12

SQ2[3:0]
rw

27

19

18

rw

rw

rw

rw

rw

7

6

5

4

3

2

Res.

Res.

rw

rw

rw

rw

SQ1[4:0]
rw

20
SQ3[4:0]

17

16

Res.

SQ2[4]
rw

1

0

rw

rw

L[3:0]

Bits 31:29 Reserved, must be kept at reset value.
Bits 28:24 SQ4[4:0]: 4th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 4th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 23 Reserved, must be kept at reset value.
Bits 22:18 SQ3[4:0]: 3rd conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 3rd in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 17 Reserved, must be kept at reset value.
Bits 16:12 SQ2[4:0]: 2nd conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 2nd in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 11 Reserved, must be kept at reset value.

DocID022558 Rev 8

393/1141
413

Analog-to-digital converters (ADC)

RM0316

Bits 10:6 SQ1[4:0]: 1st conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 1st in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bits 5:4 Reserved, must be kept at reset value.
Bits 3:0 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
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).

15.5.11

ADC regular sequence register 2 (ADCx_SQR2, x=1..4)
Address offset: 0x34
Reset value: 0x0000 0000

31

30

29

Res.

Res.

Res.

15

14

13

rw

rw

28

26

25

24

SQ9[4:0]
rw

rw

rw

rw

rw

11

10

9

8

rw

rw

Res.
rw

23

22

21

Res.

12

SQ7[3:0]
rw

27

19

18

rw

rw

rw

rw

rw

7

6

5

4

3

2

rw

rw

rw

rw

SQ6[4:0]
rw

20
SQ8[4:0]

Res.

17

16

Res.

SQ7[4]
rw

1

0

rw

rw

SQ5[4:0]
rw

Bits 31:29 Reserved, must be kept at reset value.
Bits 28:24 SQ9[4:0]: 9th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 9th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 23 Reserved, must be kept at reset value.
Bits 22:18 SQ8[4:0]: 8th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 8th in the
regular conversion sequence
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 17 Reserved, must be kept at reset value.

394/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Bits 16:12 SQ7[4:0]: 7th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 7th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 11 Reserved, must be kept at reset value.
Bits 10:6 SQ6[4:0]: 6th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 6th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 5 Reserved, must be kept at reset value.
Bits 4:0 SQ5[4:0]: 5th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 5th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used

DocID022558 Rev 8

395/1141
413

Analog-to-digital converters (ADC)

15.5.12

RM0316

ADC regular sequence register 3 (ADCx_SQR3, x=1..4)
Address offset: 0x38
Reset value: 0x0000 0000

31

30

29

Res.

Res.

Res.

15

14

13

rw

rw

28

26

25

24

SQ14[4:0]
rw

rw

rw

rw

rw

11

10

9

8

rw

rw

Res.
rw

23

22

21

Res.

12

SQ12[3:0]
rw

27

19

18

rw

rw

rw

rw

rw

7

6

5

4

3

2

rw

rw

rw

rw

SQ11[4:0]
rw

20
SQ13[4:0]

Res.

17

16

Res.

SQ12[4]
rw

1

0

rw

rw

SQ10[4:0]
rw

Bits 31:29 Reserved, must be kept at reset value.
Bits 28:24 SQ14[4:0]: 14th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 14th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 23 Reserved, must be kept at reset value.
Bits 22:18 SQ13[4:0]: 13th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 13th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 17 Reserved, must be kept at reset value.
Bits 16:12 SQ12[4:0]: 12th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 12th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 11 Reserved, must be kept at reset value.
Bits 10:6 SQ11[4:0]: 11th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 11th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 5 Reserved, must be kept at reset value.
Bits 4:0 SQ10[4:0]: 10th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 10th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used

396/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.5.13

ADC regular sequence register 4 (ADCx_SQR4, x=1..4)
Address offset: 0x3C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

rw

rw

rw

SQ16[4:0]
rw

Res.

SQ15[4:0]
rw

Bits 31:11 Reserved, must be kept at reset value.
Bits 10:6 SQ16[4:0]: 16th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 16th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 5 Reserved, must be kept at reset value.
Bits 4:0 SQ15[4:0]: 15th conversion in regular sequence
These bits are written by software with the channel number (1..18) assigned as the 15th in the
regular conversion sequence.
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used

DocID022558 Rev 8

397/1141
413

Analog-to-digital converters (ADC)

15.5.14

RM0316

ADC regular Data Register (ADCx_DR, x=1..4)
Address offset: 0x40
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

RDATA[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 RDATA[15:0]: Regular Data converted
These bits are read-only. They contain the conversion result from the last converted regular channel.
The data are left- or right-aligned as described in Section 15.3.26: Data management.

398/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.5.15

ADC injected sequence register (ADCx_JSQR, x=1..4)
Address offset: 0x4C
Reset value: 0x0000 0000

31

30

29

Res.

15

27

26

rw

rw

rw

rw

rw

13

12

11

10

rw

rw

Res.

rw

25

24

23

Res.

14

JSQ2[1:0]
rw

28
JSQ4[4:0]

21

20

rw

rw

rw

rw

rw

8

7

6

5

4

rw

rw

JEXTEN[1:0]
rw

19

18

Res.

9

JSQ1[4:0]
rw

22
JSQ3[4:0]

3

17

rw

rw

rw

2

1

0

rw

rw

JEXTSEL[3:0]
rw

rw

rw

16

JSQ2[4:2]

JL[1:0]
rw

Bit 31 Reserved, must be kept at reset value.
Bits 30:26 JSQ4[4:0]: 4th conversion in the injected sequence
These bits are written by software with the channel number (1..18) assigned as the 4th in the
injected conversion sequence.
Note: Software is allowed to write these bits at any time, once the ADC is enabled (ADEN=1).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 25 Reserved, must be kept at reset value.
Bits 24:20 JSQ3[4:0]: 3rd conversion in the injected sequence
These bits are written by software with the channel number (1..18) assigned as the 3rd in the
injected conversion sequence.
Note: Software is allowed to write these bits at any time, once the ADC is enabled (ADEN=1).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 19 Reserved, must be kept at reset value.
Bits 18:14 JSQ2[4:0]: 2nd conversion in the injected sequence
These bits are written by software with the channel number (1..18) assigned as the 2nd in the
injected conversion sequence.
Note: Software is allowed to write these bits at any time, once the ADC is enabled (ADEN=1).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bit 13 Reserved, must be kept at reset value.
Bits 12:8 JSQ1[4:0]: 1st conversion in the injected sequence
These bits are written by software with the channel number (1..18) assigned as the 1st in the
injected conversion sequence.
Note: Software is allowed to write these bits at any time, once the ADC is enabled (ADEN=1).
Note: Analog input channel 0 is not mapped: value “00000” should not be used

DocID022558 Rev 8

399/1141
413

Analog-to-digital converters (ADC)

RM0316

Bits 7:6 JEXTEN[1:0]: External Trigger Enable and Polarity Selection 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: Hardware trigger detection disabled (conversions can be launched by software)
01: Hardware trigger detection on the rising edge
10: Hardware trigger detection on the falling edge
11: Hardware trigger detection on both the rising and falling edges
Note: Software is allowed to write these bits at any time, once the ADC is enabled (ADEN=1).
Note: If JQM=1 and if the Queue of Context becomes empty, the software and hardware
triggers of the injected sequence are both internally disabled (refer to Section 15.3.21:
Queue of context for injected conversions)
Bits 5:2 JEXTSEL[3:0]: External Trigger Selection for injected group
These bits select the external event used to trigger the start of conversion of an injected group:
0000: Event 0
0001: Event 1
0010: Event 2
0011: Event 3
0100: Event 4
0101: Event 5
0110: Event 6
0111: Event 7
...
1111: Event 15
Note: Software is allowed to write these bits at any time, once the ADC is enabled (ADEN=1).
Bits 1:0 JL[1:0]: Injected channel 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
Note: Software is allowed to write these bits at any time, once the ADC is enabled (ADEN=1).

400/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.5.16

ADC offset register (ADCx_OFRy, x=1..4) (y=1..4)
Address offset: 0x60, 0x64, 0x68, 0x6C
Reset value: 0x0000 0000

31

30

OFFSETy
_EN

29

28

27

26

OFFSETy_CH[4:0]

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.
rw

rw

rw

rw

rw

OFFSETy[11:0]
rw

rw

Bit 31 OFFSETy_EN: Offset y Enable
This bit is written by software to enable or disable the offset programmed into bits
OFFSETy[11:0].
Note: Software is allowed to write this bit only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).
Bits 30:26 OFFSETy_CH[4:0]: Channel selection for the Data offset y
These bits are written by software to define the channel to which the offset programmed into
bits OFFSETy[11:0] will apply.
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0
(which ensures that no conversion is ongoing).
Note: Analog input channel 0 is not mapped: value “00000” should not be used
Bits 25:12 Reserved, must be kept at reset value.
Bits 11:0 OFFSETy[11:0]: Data offset y for the channel programmed into bits OFFSETy_CH[4:0]
These bits are written by software to define the offset y to be subtracted from the raw
converted data when converting a channel (can be regular or injected). The channel to which
applies the data offset y must be programmed in the bits OFFSETy_CH[4:0]. The conversion
result can be read from in the ADCx_DR (regular conversion) or from in the ADCx_JDRyi
registers (injected conversion).
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0
(which ensures that no conversion is ongoing).
Note: If several offset (OFFSETy) point to the same channel, only the offset with the lowest x
value is considered for the subtraction.
Ex: if OFFSET1_CH[4:0]=4 and OFFSET2_CH[4:0]=4, this is OFFSET1[11:0] which is
subtracted when converting channel 4.

DocID022558 Rev 8

401/1141
413

Analog-to-digital converters (ADC)

15.5.17

RM0316

ADC injected data register (ADCx_JDRy, x=1..4, y= 1..4)
Address offset: 0x80 - 0x8C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

JDATA[15:0]
r

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 y. The
data are left -or right-aligned as described in Section 15.3.26: Data management.

15.5.18

ADC Analog Watchdog 2 Configuration Register (ADCx_AWD2CR,
x=1..4)
Address offset: 0xA0
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.

15

14

13

12

11

10

9

8

7

6

5

4

3

18

17

AWD2CH[18:16]
rw

rw

rw

2

1

0

AWD2CH[15:1]
rw

rw

rw

rw

rw

rw

rw

rw

16

Res.
rw

rw

rw

rw

rw

rw

rw

Bits 31:19 Reserved, must be kept at reset value.
Bits 18:1 AWD2CH[18:1]: Analog watchdog 2 channel selection
These bits are set and cleared by software. They enable and select the input channels to be guarded
by the analog watchdog 2.
AWD2CH[i] = 0: ADC analog input channel-i is not monitored by AWD2
AWD2CH[i] = 1: ADC analog input channel-i is monitored by AWD2
When AWD2CH[18:1] = 000..0, the analog Watchdog 2 is disabled
Note: The channels selected by AWD2CH must be also selected into the SQRi or JSQRi registers.
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).
Bit 0 Reserved, must be kept at reset value.

402/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.5.19

ADC Analog Watchdog 3 Configuration Register (ADCx_AWD3CR,
x=1..4)
Address offset: 0xA4
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.

15

14

13

12

11

10

9

8

7

6

5

4

3

18

17

AWD3CH[18:16]

2

1

AWD3CH[15:1]
rw

rw

rw

rw

rw

rw

rw

rw

16

0
Res.

rw

rw

rw

rw

rw

rw

rw

Bits 31:19 Reserved, must be kept at reset value.
Bits 18:1 AWD3CH[18:1]: Analog watchdog 3 channel selection
These bits are set and cleared by software. They enable and select the input channels to be guarded
by the analog watchdog 3.
AWD3CH[i] = 0: ADC analog input channel-i is not monitored by AWD3
AWD3CH[i] = 1: ADC analog input channel-i is monitored by AWD3
When AWD3CH[18:1] = 000..0, the analog Watchdog 3 is disabled
Note: The channels selected by AWD3CH must be also selected into the SQRi or JSQRi registers.
Note: Software is allowed to write these bits only when ADSTART=0 and JADSTART=0 (which
ensures that no conversion is ongoing).
Bit 0 Reserved, must be kept at reset value.

15.5.20

ADC Differential Mode Selection Register (ADCx_DIFSEL, x=1..4)
Address offset: 0xB0
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.

15

14

13

12

11

10

9

8

7

6

5

4

3

18

17
DIFSEL[18:16]

r

r

r

2

1

0

DIFSEL[15:1]
rw

rw

rw

rw

rw

rw

rw

rw

16

Res.
rw

rw

DocID022558 Rev 8

rw

rw

rw

rw

rw

403/1141
413

Analog-to-digital converters (ADC)

RM0316

Bits 31:19 Reserved, must be kept at reset value.
Bits 18:16 DIFSEL[18:16]: Differential mode for channels 18 to 16.
These bits are read only. These channels are forced to single-ended input mode (either connected to a
single-ended I/O port or to an internal channel).
Bits 15:1 DIFSEL[15:1]: Differential mode for channels 15 to 1
These bits are set and cleared by software. They allow to select if a channel is configured as single
ended or differential mode.
DIFSEL[i] = 0: ADC analog input channel-i is configured in single ended mode
DIFSEL[i] = 1: ADC analog input channel-i is configured in differential mode
Note: Software is allowed to write these bits only when the ADC is disabled (ADCAL=0,
JADSTART=0, JADSTP=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).
Note: It is mandatory to keep cleared ADC1_DIFSEL[15] (connected to an internal single ended
channel)
Bit 0 Reserved, must be kept at reset value.

15.5.21

ADC Calibration Factors (ADCx_CALFACT, x=1..4)
Address offset: 0xB4
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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

22

21

20

19

18

17

16

CALFACT_D[6:0]
rw

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

CALFACT_S[6:0]
rw

rw

rw

rw

rw

Bits 31:23 Reserved, must be kept at reset value.
Bits 22:16 CALFACT_D[6:0]: Calibration Factors in differential mode
These bits are written by hardware or by software.
Once a differential inputs calibration is complete, they are updated by hardware with the calibration
factors.
Software can write these bits with a new calibration factor. If the new calibration factor is different
from the current one stored into the analog ADC, it will then be applied once a new differential
calibration is launched.
Note: Software is allowed to write these bits only when ADEN=1, ADSTART=0 and JADSTART=0
(ADC is enabled and no calibration is ongoing and no conversion is ongoing).
Bits 15:7 Reserved, must be kept at reset value.
Bits 6:0 CALFACT_S[6:0]: Calibration Factors In Single-Ended mode
These bits are written by hardware or by software.
Once a single-ended inputs calibration is complete, they are updated by hardware with the
calibration factors.
Software can write these bits with a new calibration factor. If the new calibration factor is different
from the current one stored into the analog ADC, it will then be applied once a new single-ended
calibration is launched.
Note: Software is allowed to write these bits only when ADEN=1, ADSTART=0 and JADSTART=0
(ADC is enabled and no calibration is ongoing and no conversion is ongoing).

404/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.6

ADC common registers
These registers define the control and status registers common to master and slave ADCs:

15.6.1

•

One set of registers is related to ADC1 (master) and ADC2 (slave)

•

One set of registers is related to ADC3 (master) and ADC4 (slave) available in
STM32F303xB/C and STM32F358xC devices

ADC Common status register (ADCx_CSR, x=12 or 34)
Address offset: 0x00 (this offset address is relative to the master ADC 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 0 to it in the corresponding ADCx_SR register.

31

30

Res. Res.

29

28

Res.

Res.

27

26

Res.

JQOVF_
SLV

25

24

AWD3_ AWD2_
SLV
SLV

23
AWD1_
SLV

22

21

JEOS_ JEOC_
SLV
SLV

20

19

18

17

16

OVR_
SLV

EOS_
SLV

EOC_
SLV

EOSMP_
SLV

ADRDY_
SLV

Slave ADC

15

14

Res. Res.

r

r

r

r

r

r

r

r

r

r

r

9

8

7

6

5

4

3

2

1

0

OVR_
MST

EOS_
MST

EOC_
MST

EOSMP_
MST

ADRDY_
MST

r

r

r

13

12

11

10

Res.

Res.

Res.

JQOVF_
MST

AWD3_ AWD2_
MST
MST

AWD1_
MST

JEOS_ JEOC_
MST
MST

Master ADC
r

r

r

r

r

r

r

r

Bits 31:27 Reserved, must be kept at reset value.
Bit 26 JQOVF_SLV: Injected Context Queue Overflow flag of the slave ADC
This bit is a copy of the JQOVF bit in the corresponding ADCx_ISR register.
Bit 25 AWD3_SLV: Analog watchdog 3 flag of the slave ADC
This bit is a copy of the AWD3 bit in the corresponding ADCx_ISR register.
Bit 24 AWD2_SLV: Analog watchdog 2 flag of the slave ADC
This bit is a copy of the AWD2 bit in the corresponding ADCx_ISR register.
Bit 23 AWD1_SLV: Analog watchdog 1 flag of the slave ADC
This bit is a copy of the AWD1 bit in the corresponding ADCx_ISR register.
Bit 22 JEOS_SLV: End of injected sequence flag of the slave ADC
This bit is a copy of the JEOS bit in the corresponding ADCx_ISR register.
Bit 21 JEOC_SLV: End of injected conversion flag of the slave ADC
This bit is a copy of the JEOC bit in the corresponding ADCx_ISR register.
Bit 20 OVR_SLV: Overrun flag of the slave ADC
This bit is a copy of the OVR bit in the corresponding ADCx_ISR register.
Bit 19 EOS_SLV: End of regular sequence flag of the slave ADC
This bit is a copy of the EOS bit in the corresponding ADCx_ISR register.
Bit 18 EOC_SLV: End of regular conversion of the slave ADC
This bit is a copy of the EOC bit in the corresponding ADCx_ISR register.

DocID022558 Rev 8

405/1141
413

Analog-to-digital converters (ADC)

RM0316

Bit 17 EOSMP_SLV: End of Sampling phase flag of the slave ADC
This bit is a copy of the EOSMP2 bit in the corresponding ADCx_ISR register.
Bit 16 ADRDY_SLV: Slave ADC ready
This bit is a copy of the ADRDY bit in the corresponding ADCx_ISR register.
Bits 15:11 Reserved, must be kept at reset value.
Bit 10 JQOVF_MST: Injected Context Queue Overflow flag of the master ADC
This bit is a copy of the JQOVF bit in the corresponding ADCx_ISR register.
Bit 9 AWD3_MST: Analog watchdog 3 flag of the master ADC
This bit is a copy of the AWD3 bit in the corresponding ADCx_ISR register.
Bit 8 AWD2_MST: Analog watchdog 2 flag of the master ADC
This bit is a copy of the AWD2 bit in the corresponding ADCx_ISR register.
Bit 7 AWD1_MST: Analog watchdog 1 flag of the master ADC
This bit is a copy of the AWD1 bit in the corresponding ADCx_ISR register.
Bit 6 JEOS_MST: End of injected sequence flag of the master ADC
This bit is a copy of the JEOS bit in the corresponding ADCx_ISR register.
Bit 5 JEOC_MST: End of injected conversion flag of the master ADC
This bit is a copy of the JEOC bit in the corresponding ADCx_ISR register.
Bit 4 OVR_MST: Overrun flag of the master ADC
This bit is a copy of the OVR bit in the corresponding ADCx_ISR register.
Bit 3 EOS_MST: End of regular sequence flag of the master ADC
This bit is a copy of the EOS bit in the corresponding ADCx_ISR register.
Bit 2 EOC_MST: End of regular conversion of the master ADC
This bit is a copy of the EOC bit in the corresponding ADCx_ISR register.
Bit 1 EOSMP_MST: End of Sampling phase flag of the master ADC
This bit is a copy of the EOSMP bit in the corresponding ADCx_ISR register.
Bit 0 ADRDY_MST: Master ADC ready
This bit is a copy of the ADRDY bit in the corresponding ADCx_ISR register.

406/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

15.6.2

ADC common control register (ADCx_CCR, x=12 or 34)
Address offset: 0x08 (this offset address is relative to the master ADC base address +
0x300)
Reset value: 0x0000 0000

31
Res.

15

30
Res.

14

MDMA[1:0]
rw

rw

29
Res.

28
Res.

13

12

DMA
CFG

Res.

rw

27
Res.

11

26
Res.

10

25

24

23

22

21

20

19

18

Res.

VBAT
EN

TS
EN

VREF
EN

Res.

Res.

Res.

Res.

rw

rw

rw

8

7

6

5

Res.

Res.

Res.

9

DELAY[3:0]
rw

rw

rw

rw

4

3

2

17

16

CKMODE[1:0]
rw

rw

1

0

rw

rw

DUAL[4:0]
rw

rw

rw

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 VBATEN: VBAT enable
This bit is set and cleared by software to enable/disable the VBAT channel.
0: VBAT channel disabled
1: VBAT channel enabled
Note: Software is allowed to write this bit only when the ADCs are disabled (ADCAL=0,
JADSTART=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).
Bit 23 TSEN: Temperature sensor enable
This bit is set and cleared by software to enable/disable the temperature sensor channel.
0: Temperature sensor channel disabled
1: Temperature sensor channel enabled
Note: Software is allowed to write this bit only when the ADCs are disabled (ADCAL=0,
JADSTART=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).
Bit 22 VREFEN: VREFINT enable
This bit is set and cleared by software to enable/disable the VREFINT channel.
0: VREFINT channel disabled
1: VREFINT channel enabled
Note: Software is allowed to write this bit only when the ADCs are disabled (ADCAL=0,
JADSTART=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).
Bits 21:18 Reserved, must be kept at reset value.

DocID022558 Rev 8

407/1141
413

Analog-to-digital converters (ADC)

RM0316

Bits 17:16 CKMODE[1:0]: ADC clock mode
These bits are set and cleared by software to define the ADC clock scheme (which is common
to both master and slave ADCs):
00: CK_ADCx (x=123) (Asynchronous clock mode), generated at product level (refer to
Section 6: Reset and clock control (RCC))
01: HCLK/1 (Synchronous clock mode). This configuration must be enabled only if the AHB
clock prescaler is set to 1 (HPRE[3:0] = 0xxx in RCC_CFGR register) and if the system clock
has a 50% duty cycle.
10: HCLK/2 (Synchronous clock mode)
11: HCLK/4 (Synchronous clock mode)
In all synchronous clock modes, there is no jitter in the delay from a timer trigger to the start of
a conversion.
Note: Software is allowed to write these bits only when the ADCs are disabled (ADCAL=0,
JADSTART=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).
Bits 15:14 MDMA[1:0]: Direct memory access mode for dual ADC mode
This bit-field is set and cleared by software. Refer to the DMA controller section for more
details.
00: MDMA mode disabled
01: reserved
10: MDMA mode enabled for 12 and 10-bit resolution
11: MDMA mode enabled for 8 and 6-bit resolution
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Bit 13 DMACFG: DMA configuration (for dual ADC mode)
This bit is set and cleared by software to select between two DMA modes of operation and is
effective only when DMAEN=1.
0: DMA One Shot Mode selected
1: DMA Circular Mode selected
For more details, refer to Section : Managing conversions using the DMA
Note: Software is allowed to write these bits only when ADSTART=0 (which ensures that no
regular conversion is ongoing).
Bit 12 Reserved, must be kept at reset value.

408/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

Bits 11:8 DELAY: Delay between 2 sampling phases
Set and cleared by software. These bits are used in dual interleaved modes. Refer to
Table 100 for the value of ADC resolution versus DELAY bits values.
Note: Software is allowed to write these bits only when the ADCs are disabled (ADCAL=0,
JADSTART=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:0 DUAL[4:0]: Dual 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, master and slave ADCs working together
00001: Combined regular simultaneous + injected simultaneous mode
00010: Combined regular simultaneous + alternate trigger mode
00011: Combined Interleaved mode + injected simultaneous mode
00100: Reserved
00101: Injected simultaneous mode only
00110: Regular simultaneous mode only
00111: Interleaved mode only
01001: Alternate trigger mode only
All other combinations are reserved and must not be programmed
Note: Software is allowed to write these bits only when the ADCs are disabled (ADCAL=0,
JADSTART=0, ADSTART=0, ADSTP=0, ADDIS=0 and ADEN=0).

Table 100. DELAY bits versus ADC resolution
DELAY bits

12-bit resolution

10-bit resolution

8-bit resolution

6-bit resolution

0000

1 * TADC_CLK

1 * TADC_CLK

1 * TADC_CLK

1 * TADC_CLK

0001

2 * TADC_CLK

2 * TADC_CLK

2 * TADC_CLK

2 * TADC_CLK

0010

3 * TADC_CLK

3 * TADC_CLK

3 * TADC_CLK

3 * TADC_CLK

0011

4 * TADC_CLK

4 * TADC_CLK

4 * TADC_CLK

4 * TADC_CLK

0100

5 * TADC_CLK

5 * TADC_CLK

5 * TADC_CLK

5 * TADC_CLK

0101

6 * TADC_CLK

6 * TADC_CLK

6 * TADC_CLK

6 * TADC_CLK

0110

7 * TADC_CLK

7 * TADC_CLK

7 * TADC_CLK

6 * TADC_CLK

0111

8 * TADC_CLK

8 * TADC_CLK

8 * TADC_CLK

6 * TADC_CLK

1000

9 * TADC_CLK

9 * TADC_CLK

8 * TADC_CLK

6 * TADC_CLK

1001

10 * TADC_CLK

10 * TADC_CLK

8 * TADC_CLK

6 * TADC_CLK

1010

11 * TADC_CLK

10 * TADC_CLK

8 * TADC_CLK

6 * TADC_CLK

1011

12 * TADC_CLK

10 * TADC_CLK

8 * TADC_CLK

6 * TADC_CLK

others

12 * TADC_CLK

10 * TADC_CLK

8 * TADC_CLK

6 * TADC_CLK

DocID022558 Rev 8

409/1141
413

Analog-to-digital converters (ADC)

15.6.3

RM0316

ADC common regular data register for dual mode
(ADCx_CDR, x=12 or 34)
Address offset: 0x0C (this offset address is relative to the master ADC base address +
0x300)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

RDATA_SLV[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

RDATA_MST[15:0]
r

r

Bits 31:16 RDATA_SLV[15:0]: Regular data of the slave ADC
In dual mode, these bits contain the regular data of the slave ADC. Refer to Section 15.3.29:
Dual ADC modes.
The data alignment is applied as described in Section : Data register, data alignment and
offset (ADCx_DR, OFFSETy, OFFSETy_CH, ALIGN))
Bits 15:0 RDATA_MST[15:0]: Regular data of the master ADC.
In dual mode, these bits contain the regular data of the master ADC. Refer to Section 15.3.29:
Dual ADC modes.
The data alignment is applied as described in Section : Data register, data alignment and
offset (ADCx_DR, OFFSETy, OFFSETy_CH, ALIGN))
In MDMA=0b11 mode, bits 15:8 contains SLV_ADC_DR[7:0], bits 7:0 contains
MST_ADC_DR[7:0].

15.6.4

ADC register map
The following table summarizes the ADC registers.

Note:

The STM32F303x6/8 and STM32F328x8 devices have only ADC1 and ADC2.
Table 101. ADC global register map(1)
Offset

Register

0x000 - 0x04C

Master ADCx (ADC1 or ADC3)

0x050 - 0x0FC

Reserved

0x100 - 0x14C

Slave ADCx (ADC2 or ADC4)

0x118 - 0x1FC

Reserved

0x200 - 0x24C

Reserved

0x250 - 0x2FC

Reserved

0x300 - 0x308

Master and slave ADCs common registers (ADC12 or ADC34)

1. The gray color is used for reserved memory addresses.

410/1141

DocID022558 Rev 8

RM0316

Analog-to-digital converters (ADC)

AWD3

AWD2

AWD1

JEOS

JEOC

OVR

EOS

EOC

EOSMP

ADRDY

0

0

0

0

0

0

0

0

0

0

0

JEOCIE

OVRIE

EOSIE

EOCIE

EOSMPIE

ADRDYIE

0

0

0

0

0

0

Res.

Res.

Res.

Res.

JADSTP
0

0

SQ13[4:0]
0

0

0

0

0

Res.
Res.

Res.

Res.

0

0

0

0

SQ12[4:0]
0

0

0

0

0

Reset value
0x500x5C

Reserved

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DMACFG

DMAEN

Res.

Res.

0

0

0

0

0

0

0

0

0

L[3:0]
0

0

0

0

0

0

SQ10[4:0]
0

0

0

SQ5[4:0]
0

0

0

0

0

0

SQ16[4:0]
0

0

LT3[7:0]

SQ11[4:0]
0

0

Res.

Res.
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

JSQ2[4:0]

0

SMP10
[2:0]
0 0 0

0

0

0

0

SQ15[4:0]
0

0

0

0

0

0

0

0

0

0

regular RDATA[15:0]

Res.

JSQ3[4:0]

0

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

JSQ4[4:0]

0

SQ6[4:0]
0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

ADCx_JSQR

Res.

0x4C

Reserved

Res.

0x440x48

Res.

Reset value

0

LT2[7:0]

SQ1[4:0]
0

0
Res.

0x40

Res.

Res.
Res.

0

0

Res.

Res.

Res.

Res.
Res.
0

ALIGN

OVRMOD

0

Reset value
ADCx_DR

0

0

SQ7[4:0]
0

0

Res.

CONT

0

0

1
Res.

0

SMP1
[2:0]
0 0 0
SMP11
[2:0]
0 0 0

0

Res.

0

0

0

SQ2[4:0]

0

Res.

0

0

1

0

0

Res.

SQ8[4:0]
0

EXTEN[1:0]

AUTDLY
Res.

0

0

Res.

0

RES
[1:0]

Res.

0

0

SMP2
[2:0]
0 0 0
SMP12
[2:0]
0 0 0

0

Res.

0

0

LT1[11:0]

Res.

SQ3[4:0]
0

1

Res.

Res.
1

0

0

Res.

Res.

1

SMP3
[2:0]
0 0 0
SMP13
[2:0]
0 0 0

0

0

Res.

Res.

1

0

0

Res.

Res.

1

0

0

0

JEXTEN[1:0]

0

1

0

EXTSEL
[3:0]

Res.

0

1

Res.

0

1

Res.

Res.

1

Res.

0

1

Res.

1

HT3[[7:0]

0

0

1

Res.

1

0

SQ14[4:0]

1

Res.

0

1

Res.

0

1

Res.

Res.

0

1

HT2[[7:0]

Res.

Res.
0

1

Res.

Res.

1

SMP4
[2:0]
0 0 0
SMP14
[2:0]
0 0 0

Res.

SMP6
[2:0]
0 0 0
SMP16
[2:0]
0 0 0

Res.
Res.

JDISCEN

0

DISCEN

JQM

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
AWD1SGL

0

Res.

Res.

Res.

Res.
0

Res.

Res.

Res.

ADCx_SQR4

Res.

Reset value
0x3C

1

Res.

Res.

Res.

ADCx_SQR3

0

SQ9[4:0]
0

Res.

Reset value
0x38

Res.

Res.

Res.

Res.
Res.

ADCx_SQR2

Res.

0x34

0
Res.
SMP5
[2:0]
0 0 0
SMP15
[2:0]
0 0 0
Res.

0

Res.

1

SQ4[4:0]
0

Res.

Reset value

0

Res.

1

1
Res.

ADCx_SQR1

SMP7
[2:0]
0 0 0
SMP17
[2:0]
0 0 0

0

Res.

1

Res.

0x30

0

Res.

1

Reset value
Reserved
Res.

0x2C

0

1

Res.

0x28

0

HT1[11:0]

Reset value
ADCx_TR3

Res.

Res.

Res.

SMP8
[2:0]
0 0 0
SMP18
[2:0]
0 0 0

0

Res.

Res.
Res.
Res.

Res.

Res.

0x24

ADCx_TR2

Res.

Reset value

0

Res.

Res.
Res.

ADCx_TR1

0

Res.

Res.

Reset value
Reserved

0

DISCNUM
[2:0]

Res.

Res.

0x20

0

SMP9
[2:0]
0 0 0

Res.

0x1C

0

Res.

0x18

0

AWD1EN

0

JAUTO
JAWD1EN

AWD1CH[4:0]

Reset value
ADCx_SMPR2

0

Res.

ADCx_SMPR1

Res.

Res.

Reset value
Reserved

1

Res.

ADCx_CFGR

ADVREGEN[1:0]

ADCAL

ADCALDIF
0

Res.

0x14

0

Res.

0x10

Reset value

Res.

0x0C

ADCx_CR

Res.

0x08

ADEN

JEOSIE
0

ADDIS

AWD1IE
0

ADSTART

AWD2IE
0

Res.

AWD3IE
0

Reset value

ADSTP

JQOVFIE
0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ADCx_IER

Res.

0x04

Res.

Reset value

JADSTART

Res.

JQOVF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ADCx_ISR

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 102. ADC register map and reset values for each ADC (offset=0x000
for master ADC, 0x100 for slave ADC, x=1..4)

JSQ1[4:0]

0

0

0

0

0

0

JEXTSEL
[3:0]
0

0

0

0

JL[1:0]

0

0

0

Res

DocID022558 Rev 8

411/1141
413

Analog-to-digital converters (ADC)

RM0316

0

0

0

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

0

0

0

0

0

0

0

0

0

0

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..
0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.
Res.

0

Res.

Res.

Res.
Res.

0

Res.

Res.

Res.
Res.

0

Res.

Res.

Res.
Res.

0

0

Res.

Res.

Res.
Res.

0

0

0

DIFSEL[18:1]
0

0

0

AWD3CH[18:1]

0

0

CALFACT_D[6:0]
0

0

Res..

0

0

0

0

DocID022558 Rev 8

Res.

0

Res.

Res.

Res.
Res.

412/1141

0

Res.

Res.

Res.
Res.

Reset value

0

Res.

Res.

Res.

0xB4

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
ADCx_CALFACT

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ADCx_DIFSEL

Res.

0xB0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Reserved

Res.

Reset value
0xA80xAC

0

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.
Res.

Res.

Res.

0xA4

0

AWD2CH[18:1]
0

Res.

Reset value
ADCx_AWD3CR

0

Res.
Res.

ADCx_AWD2CR

0

JDATA4[15:0]
0

Reserved
Res.

0xA0

0

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Reset value
0x8C0x9C

Res.

Res.

Res.
Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.
Res.

Res.

Res.

0x8C

0

JDATA3[15:0]
0

Res.

Reset value
ADCx_JDR4

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.
Res.

0x88

0

JDATA2[15:0]
0

Res.

Reset value
ADCx_JDR3

0

JDATA1[15:0]
0

Res.

0x84

0

OFFSET4[11:0]

0

Reset value
ADCx_JDR2

0

Res.
Res.

ADCx_JDR1

0x80

Res.

Res.

Res.

Res.

Res.

Res.

0

Reserved

0

OFFSET3[11:0]

0

Res.

OFFSET4_
CH[4:0]
0

Res.

0

Res.

0

Res.

0

Res.

0

0

OFFSET2[11:0]

0

Res.

OFFSET3_
CH[4:0]
0

Res.

0

Res.

0

Res.

0

Res.

0

0

Res.

Reset value

0

Res.

ADCx_OFR4

OFFSET2_
CH[4:0]

0

Res.

0

Res.

Reset value

0

Res.

ADCx_OFR3

0

Res.

0

0

Res.

Reset value

0

Res.

ADCx_OFR2

0

OFFSET1[11:0]

Res.

0x700x7C

0

Res.

0x6C

Reset value

OFFSET1_
CH[4:0]

Res.

0x68

OFFSET1_EN

0x64

ADCx_OFR1

OFFSET2_EN

0x60

OFFSET3_EN

Register

OFFSET4_EN

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 102. ADC register map and reset values for each ADC (offset=0x000
for master ADC, 0x100 for slave ADC, x=1..4) (continued)

CALFACT_S[6:0]
0

0

0

0

0

0

0

RM0316

Analog-to-digital converters (ADC)

0x0C

Reset value
ADCx_CDR
Reset value

0

0

0

0

0 0 0
RDATA_SLV[15:0]
0 0 0 0 0 0

0

0

0

0

0

0

0

0

0

0

0

0

0

ADRDY_MST

EOS_MST

EOSMP_MST

0 0 0
RDATA_MST[15:0]
0 0 0 0 0 0

EOC_MST

JEOS_MST

OVR_MST

Res.

JEOC_MST

0

AWD1_MST

AWD2_MST

master ADC1 or ADC3
0 0 0 0 0 0 0

Res.

AWD3_MST

Res.

0

DELAY[3:0]

0
0

0

Res.

Res.

DMACFG

MDMA[1:0]

0

JQOVF_MST

Res.

Res.

Res.

0
Res.

CKMODE[1:0]

Res.

Res.

Res.

Res.

VREFEN

slave ADC2 or ADC4
0 0 0 0 0 0

Res.

ADRDY_SLV

EOSMP_SLV

EOS_SLV

EOC_SLV

OVR_SLV

AWD1_SLV
TSEN

JEOS_SLV

AWD2_SLV

0

JEOC_SLV

AWD3_SLV

0

Res.

Res.

Res.
0

0

VBATEN

Res.

JQOVF_SLV

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

ADCx_CCR

Res.

0x08

Reset value
Reserved

Res.

0x04

ADCx_CSR

Res.

0x00

Register

Res.

Offset

Res.

Table 103. ADC register map and reset values (master and slave ADC
common registers) offset =0x300, x=1 or 34)

DUAL[4:0]

0

0

0

0

0

0

0

0

0

0

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

DocID022558 Rev 8

413/1141
413

Digital-to-analog converter (DAC1 and DAC2)

16

Digital-to-analog converter (DAC1 and DAC2)

16.1

Introduction

RM0316

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. An input reference voltage,
VREF+(shared with ADC), is available. The output can optionally be buffered for higher
current drive.

16.2

DAC1/2 main features
The STM32F303xB/C/D/E, STM32F358xC and STM32F398xE integrate two 12-bit DAC
channels with output buffer.
The STM32F303x6/8 and STM32F328x8 integrate 3 12-bit DAC channels (1 DAC channel
with output buffer and 2 DAC channels without output buffers).
•

DAC1 integrates two DAC channels:
–

DAC1 channel 1 which output is DAC1_OUT1

–

DAC1 channel 2 which output is DAC1_OUT2

The two channels can be used independently or simultaneously when both channels
are grouped together for synchronous update operations (dual mode).
•

DAC2 integrates only one channel, DAC2 channel 1 which output is DAC2_OUT1
(STM32F303x6/8 and STM32F328x8 devices only).

The DAC main features are the following:
•

Left or right data alignment in 12-bit mode

•

Synchronized update capability

•

Noise-wave generation (DAC1 only)

•

Triangular-wave generation (DAC1 only)

•

Independent or simultaneous conversions (dual mode only)

•

DMA capability for each channel

•

DMA underrun error detection

•

External triggers for conversion

•

Programmable internal buffer

•

Input voltage reference, VDDA

Figure 113 and Figure 114 show the block diagram of a DAC1 and DAC2 channel and
Table 104 gives the pin description.

414/1141

DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)
Figure 113. DAC1 block diagram

'$&FRQWUROUHJLVWHU
76 ( / [>  @ E LWV
6:75,*[

7,0B75*2
7,0B75*2 
7,0B75*2

'0$(1[

7ULJJHUVHOHFWRU[

7,0B75*2
7,0B75*2RU
7,0B75*2 
7,0B75*2

(;7,B

'0$UHTXHVW[
  ELW

&RQWUROORJLF[

7( 1 [

'+5[
/ )6 5[

WU LD Q J OH[

0 $0 3 [>  @ E LWV
: $9 ([ > @E L WV

  ELW

%2))

' 2 5[
  ELW


9 ''$
9 66 $

'LJLWDOWRDQDORJ
FRQYHUWHU[

'$&[B 28 7\

9 5 () 

069

1. TIM8_TRGO and TIM4_TRGO are only available on STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices.
2. On STM32F303x6/8 and STM32F328, there is no output buffer on the DAC1 channel 2. There is instead a
switch allowing to connect the DAC1_OUT2 to the corresponding I/O (PA5) (refer to DAC2 block diagram).

DocID022558 Rev 8

415/1141
439

Digital-to-analog converter (DAC1 and DAC2)

RM0316

Figure 114. DAC2 block diagram (only on STM32F303x6/8 and STM32F328)

'$&FRQWUROUHJLVWHU
76(/[>@
6:75,*[

7,0B75*2
7,0B75*2
7,0B75*2
7,0B75*2

'0$(1[

7ULJJHUVHOHFWRU[

7,0B75*2

(;7,B

'0$UHTXHVW[

'+5[

ELW

&RQWUROORJLF[

7(1[
:$9([>@ELWV

ELW

287(1

'2 5[
ELW

9''$95()

'$&B287

'LJLWDOWRDQDORJ
FRQYHUWHU[

966$

069

Table 104. DACx pins
Name

Signal type

Remarks

VREF+ (1)

Input, analog reference
positive

The higher/positive reference voltage for the DAC

VDDA

Input, analog supply

Analog power supply

VSSA

Input, analog supply ground

Ground for analog power supply

DAC1_OUT1/2
DAC2_OUT1

Analog output signal

DACx channel y analog output

1. On STM32F303x6/8 and STM32F328, the VDDA and VREF+ are internally connected.

Note:

Once the DACx channel y is enabled, the corresponding GPIO pin (PA4, PA5 or PA6) is
automatically connected to the analog converter output (DACx_OUTy). In order to avoid
parasitic consumption, the PA4, PA5 or PA6 pin should first be configured to analog (AIN).

16.3

DAC output buffer enable/DAC output switch
The DAC1 channel 1 and DAC1 channel 2 come with an output buffer that can be used to
reduce the output impedance on DAC1_OUT1/2 output, and to drive external loads directly
without having to add an external operational amplifier. This feature is available on
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE.

416/1141

DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)
In the STM32F303x6/8 and STM32F328, the DAC1 channel 1 comes with an output buffer.
The DAC1 channel2 does not have an output buffer, it has instead a switch allowing to
connect the DAC1_OUT2 to the corresponding I/O (PA5). The switch can be enabled and
disabled through the OUTEN2 bit in the DAC_CR register. The DAC2 channel1 does not
have an output buffer, it has instead a switch allowing to connect the DAC2_OUT1 to the
corresponding I/O (PA6). The switch can be enabled and disabled through the OUTEN1 bit
in the DAC_CR register.
The DAC1 channel output buffer can be enabled and disabled through the BOFF1 bit in the
DAC_CR register.

16.4

DAC channel enable
Each DAC channel can be powered on by setting the corresponding ENx bit in the DAC_CR
register. Each DAC channel is then enabled after a startup time tWAKEUP.

Note:

The ENx bit enables the analog DAC Channelx macrocell only. The DAC Channelx digital
interface is enabled even if the ENx bit is reset.

16.5

Single mode functional description

16.5.1

DAC data format
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.
Figure 115. Data registers in single DAC channel mode










ELWULJKWDOLJQHG
ELWOHIWDOLJQHG
ELWULJKWDOLJQHG
DLE

DocID022558 Rev 8

417/1141
439

Digital-to-analog converter (DAC1 and DAC2)

16.5.2

RM0316

DAC channel 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).
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 PCLK1 clock cycles
later.
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 116. Timing diagram for conversion with trigger disabled TEN = 0
!0"?#,+

$(2

$/2

X!#

X!#

/UTPUT VOLTAGE
AVAILABLE ON $!#?/54 PIN

T3%44,).'

AIB

Independent trigger with single LFSR generation
To configure the DAC in this conversion mode (see Section 16.7: Noise generation), the
following sequence is required:
1.

Set the DAC channel trigger enable bit TENx.

2.

Configure the trigger source by setting TSELx[2:0] bits.

3.

Configure the DAC channel WAVEx[1:0] bits as “01” and the same LFSR mask value in
the MAMPx[3:0] bits

4.

Load the DAC channel data into the desired DAC_DHRx register (DHR12RD,
DHR12LD or DHR8RD).

When a DAC channelx trigger arrives, the LFSRx counter, with the same mask, is added to
the DHRx register and the sum is transferred into DAC_DORx (three APB clock cycles
later). Then the LFSRx counter is updated.

Independent trigger with single triangle generation
To configure the DAC in this conversion mode (see Section 16.8: Triangle-wave generation),
the following sequence is required:

418/1141

1.

Set the DAC channelx trigger enable TENx bits.

2.

Configure the trigger source by setting TSELx[2:0] bits.

3.

Configure the DAC channelx WAVEx[1:0] bits as “1x” and the same maximum
amplitude value in the MAMPx[3:0] bits

4.

Load the DAC channelx data into the desired DAC_DHRx register. (DHR12RD,
DHR12LD or DHR8RD).
DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)
When a DAC channelx trigger arrives, the DAC channelx triangle counter, with the same
triangle amplitude, is added to the DHRx register and the sum is transferred into
DAC_DORx (three APB clock cycles later). The DAC channelx triangle counter is then
updated.

16.5.3

DAC output voltage
Digital inputs are converted to output voltages on a linear conversion between 0 and VREF+.
The analog output voltages on each DAC channel pin are determined by the following
equation:
DOR
DACoutput = V REF+ × -------------4096

16.5.4

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 possible
events will trigger conversion as shown in Table 105.
Table 105. External triggers (DAC1)
Source

Type

TIM6_TRGO event

000

TIM3_TRGO event(1) or
Timer 8 TRGO event(2)
TIM7_TRGO event
TIM15_TRGO event

TSEL[2:0]

001(2)
Internal signal from on-chip
timers

010
011

TIM2_TRGO event

100

TIM4_TRGO event

101

EXTI line9

External pin

110

SWTRIG

Software control bit

111

1. To select TIM3_TRGO event as DAC1 trigger source, the DAC_ TRIG_RMP bit must be set in
SYSCFG_CFGR1 register.
2. When TSEL = 001, the DAC trigger is selected using the DAC_TRIG_RMP bit in the SYSCFG_CFGR1
register. When this bit is cleared, the DAC trigger is the Timer 8 TRGO event. When this bit is set, the DAC
trigger is the Timer 3 TRGO event.

Table 106. External triggers (DAC2)
Source

Type

TIM6_TRGO event

000

TIM3_TRGO event
TIM7_TRGO event

TSEL[2:0]

001
Internal signal from on-chip
timers

010

TIM15_TRGO event

011

TIM2_TRGO event

100

DocID022558 Rev 8

419/1141
439

Digital-to-analog converter (DAC1 and DAC2)

RM0316

Table 106. External triggers (DAC2) (continued)
Source

Type

TSEL[2:0]

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.
If the software trigger is selected, the conversion starts once the SWTRIG bit is set.
SWTRIG is reset by hardware once the DAC_DORx register has been loaded with the
DAC_DHRx register contents.
Note:

TSELx[2:0] bit cannot be changed when the ENx bit is set. When software trigger is
selected, the transfer from the DAC_DHRx register to the DAC_DORx register takes only
one APB1 clock cycle.

16.6

Dual-mode functional description

16.6.1

DAC data format
In Dual DAC channel mode, there are three possibilities:
•

8-bit right alignment: data for DAC channel1 to be loaded in the DAC_DHR8RD [7:0]
bits (stored in the DHR1[11:4] bits) and data for DAC channel2 to be loaded in the
DAC_DHR8RD [15:8] bits (stored in 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 in the DHR2[11:0] bits)

•

12-bit right alignment: data for DAC channel1 to be loaded into the DAC_DHR12RD
[11:0] bits (stored in the DHR1[11:0] bits) and data for DAC channel2 to be loaded into
the DAC_DHR12LD [27:16] bits (stored in the DHR2[11:0] bits)

Depending on the loaded DAC_DHRyyyD register, the data written by the user is shifted
and stored in 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 117. Data registers in dual DAC channel mode










ELWULJKWDOLJQHG
ELWOHIWDOLJQHG
ELWULJKWDOLJQHG
DLE

420/1141

DocID022558 Rev 8

RM0316

16.6.2

Digital-to-analog converter (DAC1 and DAC2)

DAC channel conversion in dual mode
The DAC channel conversion in dual mode is performed in the same way as in single mode
(refer to Section 16.5.2) except that the data have to be loaded by writing to DAC_DHR8Rx,
DAC_DHR12Lx, DAC_DHR12Rx, DAC_DHR8RD, DAC_DHR12LD or DAC_DHR12RD.

16.6.3

Description of dual conversion modes
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 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.
Refer to Section 16.5.2: DAC channel conversion for details on the APB bus (APB or APB1)
that clocks the DAC conversions.

Independent trigger without wave generation
To configure the DAC in this conversion mode, the following sequence is required:
1.

Set the two DAC channel trigger enable bits TEN1 and TEN2

2.

Configure different trigger sources by setting different values in the TSEL1[2:0] and
TSEL2[2:0] bits

3.

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 APB clock cycles later).
When a DAC channel2 trigger arrives, the DHR2 register is transferred into DAC_DOR2
(three APB clock cycles later).

Independent trigger with single LFSR generation
To configure the DAC in this conversion mode (refer to Section 16.7: Noise generation), the
following sequence is required:
1.

Set the two DAC channel trigger enable bits TEN1 and TEN2

2.

Configure different trigger sources by setting different values in the TSEL1[2:0] and
TSEL2[2:0] bits

3.

Configure the two DAC channel WAVEx[1:0] bits as “01” and the same LFSR mask
value in the MAMPx[3:0] bits

4.

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 APB 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 APB clock cycles
later). Then the LFSR2 counter is updated.

DocID022558 Rev 8

421/1141
439

Digital-to-analog converter (DAC1 and DAC2)

RM0316

Independent trigger with different LFSR generation
To configure the DAC in this conversion mode (refer to Section 16.7: Noise generation), the
following sequence is required:
1.

Set the two DAC channel trigger enable bits TEN1 and TEN2

2.

Configure different trigger sources by setting different values in the TSEL1[2:0] and
TSEL2[2:0] bits

3.

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

4.

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 APB 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 APB clock cycles later). Then the LFSR2 counter is updated.

Independent trigger with single triangle generation
To configure the DAC in this conversion mode (refer to Section 16.8: Triangle-wave
generation), the following sequence is required:
1.

Set the DAC channelx trigger enable TENx bits.

2.

Configure different trigger sources by setting different values in the TSELx[2:0] bits

3.

Configure the DAC channelx WAVEx[1:0] bits as “1x” and the same maximum
amplitude value in the MAMPx[3:0] bits

4.

Load the DAC channelx data into the desired DAC_DHRx register.

Refer to Section 16.5.2: DAC channel conversion for details on the APB bus (APB or APB1)
that clocks the DAC conversions.
When a DAC channelx trigger arrives, the DAC channelx triangle counter, with the same
triangle amplitude, is added to the DHRx register and the sum is transferred into
DAC_DORx (three APB clock cycles later). The DAC channelx triangle counter is then
updated.

Independent trigger with different triangle generation
To configure the DAC in this conversion mode (refer to Section 16.8: Triangle-wave
generation), the following sequence is required:
1.

Set the DAC channelx trigger enable TENx bits.

2.

Configure different trigger sources by setting different values in the TSELx[2:0] bits

3.

Configure the DAC channelx WAVEx[1:0] bits as “1x” and set different maximum
amplitude values in the MAMPx[3:0] bits

4.

Load the DAC channelx data into the desired DAC_DHRx register.

When a DAC channelx trigger arrives, the DAC channelx triangle counter, with a triangle
amplitude configured by MAMPx[3:0], is added to the DHRx register and the sum is
transferred into DAC_DORx (three APB clock cycles later). The DAC channelx triangle
counter is then updated.

422/1141

DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)

Simultaneous software start
To configure the DAC in this conversion mode, the following sequence is required:
1.

Load the dual DAC channel data to the desired DHR register (DAC_DHR12RD,
DAC_DHR12LD or DAC_DHR8RD)

In this configuration, one APB clock cycles).

Simultaneous trigger without wave generation
To configure the DAC in this conversion mode, the following sequence is required:
1.

Set the two DAC channel trigger enable bits TEN1 and TEN2

2.

Configure the same trigger source for both DAC channels by setting the same value in
the TSEL1[2:0] and TSEL2[2:0] bits

3.

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 APB clock cycles).

Simultaneous trigger with single LFSR generation
To configure the DAC in this conversion mode (refer to Section 16.7: Noise generation), the
following sequence is required:
1.

Set the two DAC channel trigger enable bits TEN1 and TEN2

2.

Configure the same trigger source for both DAC channels by setting the same value in
the TSEL1[2:0] and TSEL2[2:0] bits

3.

Configure the two DAC channel WAVEx[1:0] bits as “01” and the same LFSR mask
value in the MAMPx[3:0] bits

4.

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 APB 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 APB clock
cycles later). The LFSR2 counter is then updated.

Simultaneous trigger with different LFSR generation
To configure the DAC in this conversion mode (refer to Section 16.7: Noise generation), the
following sequence is required:
1.

Set the two DAC channel trigger enable bits TEN1 and TEN2

2.

Configure the same trigger source for both DAC channels by setting the same value in
the TSEL1[2:0] and TSEL2[2:0] bits

3.

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

4.

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 APB clock
cycles later). The LFSR1 counter is then updated.

DocID022558 Rev 8

423/1141
439

Digital-to-analog converter (DAC1 and DAC2)

RM0316

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 APB clock cycles
later). The LFSR2 counter is then updated.

Simultaneous trigger with single triangle generation
To configure the DAC in this conversion mode (refer to Section 16.8: Triangle-wave
generation), the following sequence is required:
1.

Set the DAC channelx trigger enable TEN1x bits.

2.

Configure the same trigger source for both DAC channels by setting the same value in
the TSELx[2:0] bits.

3.

Configure the DAC channelx WAVEx[1:0] bits as “1x” and the same maximum
amplitude value using the MAMPx[3:0] bits

4.

Load the DAC channelx data into the desired DAC_DHRx registers.

When a trigger arrives, the DAC channelx triangle counter, with the same triangle amplitude,
is added to the DHRx register and the sum is transferred into DAC_DORx (three APB clock
cycles later). The DAC channelx triangle counter is then updated.

Simultaneous trigger with different triangle generation
To configure the DAC in this conversion mode ‘refer to Section 16.8: Triangle-wave
generation), the following sequence is required:
1.

Set the DAC channelx trigger enable TENx bits.

2.

Configure the same trigger source for DAC channelx by setting the same value in the
TSELx[2:0] bits

3.

Configure the DAC channelx WAVEx[1:0] bits as “1x” and set different maximum
amplitude values in the MAMPx[3:0] bits.

4.

Load the DAC channelx data into the desired DAC_DHRx registers.

When a trigger arrives, the DAC channelx triangle counter, with a triangle amplitude
configured by MAMPx[3:0], is added to the DHRx register and the sum is transferred into
DAC_DORx (three APB clock cycles later). Then the DAC channelx triangle counter is
updated.

16.6.4

DAC output voltage
Refer to Section 16.5.3: DAC output voltage.

424/1141

DocID022558 Rev 8

RM0316

16.6.5

Digital-to-analog converter (DAC1 and DAC2)

DAC trigger selection
Refer to Section 16.5.4: DAC trigger selection

16.7

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 APB clock cycles after
each trigger event, following a specific calculation algorithm.
Figure 118. DAC LFSR register calculation algorithm
;25
;
; 













;




;

;









125

DLF

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 119. DAC conversion (SW trigger enabled) with LFSR wave generation

$3%B&/.

'+5

'25

[

[$$$

['

6:75,*
DLE

Note:

The DAC trigger must be enabled for noise generation by setting the TENx bit in the
DAC_CR register.

DocID022558 Rev 8

425/1141
439

Digital-to-analog converter (DAC1 and DAC2)

16.8

RM0316

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 APB 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.
It is possible to reset triangle wave generation by resetting the WAVEx[1:0] bits.
Figure 120. DAC triangle wave generation

N
TIO
EN
EM
CR

N
TIO
TA

)N

EN

EM

CR

TA

$E

-!-0X;= MAX AMPLITUDE
$!#?$(2X BASE VALUE

$!#?$(2X BASE VALUE

AIC

Figure 121. DAC conversion (SW trigger enabled) with triangle wave generation
$3%B&/.

'+5

'25

[$%(

[$%(

[$%)

[$&

6:75,*
DLE

Note:

The DAC trigger must be enabled for triangle 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.

426/1141

DocID022558 Rev 8

RM0316

16.9

Digital-to-analog converter (DAC1 and DAC2)

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
to 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, user 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
acknowledgment 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. Finally, the DAC conversion can be resumed by
enabling both DMA data transfer and conversion trigger.
For each DAC channel, an interrupt is also generated if the corresponding DMAUDRIEx bit
in the DAC_CR register is enabled.

DocID022558 Rev 8

427/1141
439

Digital-to-analog converter (DAC1 and DAC2)

16.10

RM0316

DAC registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by words (32-bit).

16.10.1

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.

Res.

DMAU
DRIE1

DMA
EN1

rw

rw

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
/OUTE
N2

EN2

rw

rw

rw

rw

3

2

1

0

TEN1

BOFF1
/OUTE
N1

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
Note: This bit is available in dual mode only. It is reserved in single mode.
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
Note: This bit is available in dual mode only. It is reserved in single mode.
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
Note: These bits are available only in dual mode when wave generation is supported.
Otherwise, they are reserved and must be kept at reset value.

428/1141

DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)

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)
These bits are available only in dual mode when wave generation is supported.
Otherwise, they are reserved and must be kept at reset value.
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 3 or Timer 8 TRGO event depending on the value of DAC_TRIG_RMP bit in
SYSCFG_CFGR1 register
010: Timer 7 TRGO event
011: Timer 15 TRGO event
100: Timer 2 TRGO event
101: Timer 4 TRGO event
110: EXTI line9
111: Software trigger
Note: Only used if bit TEN2 = 1 (DAC channel2 trigger enabled).
These bits are available in dual mode only. They are reserved in single mode.
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 APB1clock 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.
Note: This bit is available in dual mode only. It is reserved in single mode.
Bit 17 In STM32F303xB/C/D/E, STM32F358xC and STM32F398xE:
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
Note: This bit is available in dual mode only. It is reserved in single mode.
In STM32F303x6/8 and STM32F328x8 DAC1:
OUTEN2: DAC channel2 output switch enable
This bit is set and cleared by software to enable/disable DAC channel2 output switch.
0: DAC channel2 output switch disabled
1: DAC channel2 output switch enabled
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
Note: This bit is available in dual mode only. It is reserved in single mode.
Bits 15:14 Reserved, must be kept at reset value.

DocID022558 Rev 8

429/1141
439

Digital-to-analog converter (DAC1 and DAC2)

RM0316

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
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
Note: These bits are available only when wave generation feature is supported. Otherwise,
they are reserved and must be kept at reset value.
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).
Note: These bits are available only when wave generation feature is supported. Otherwise
they are reserved and must be kept at reset value.
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 3 or Timer 8 TRGO event depending on the value of DAC_TRIG_RMP bit in
SYSCFG_CFGR1 register
010: Timer 7 TRGO event
011: Timer 15 TRGO event
100: Timer 2 TRGO event
101: Timer 4 TRGO event
110: EXTI line9
111: Software trigger
Note: Only used if bit TEN1 = 1 (DAC channel1 trigger enabled).

430/1141

DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)

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 In DAC1:
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
In DAC2: (STM32F303x6/8 and STM32F328x8 only)
OUTEN1: DAC channel1 output switch enable
This bit is set and cleared by software to enable/disable DAC channel1 output switch.
0: DAC channel1 output switch disabled
1: DAC channel1 output switch enabled
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

DocID022558 Rev 8

431/1141
439

Digital-to-analog converter (DAC1 and DAC2)

16.10.2

RM0316

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.

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

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.
This bit is available in dual mode only. It is reserved in single mode.
Bit 0 SWTRIG1: DAC channel1 software trigger
This bit is set and cleared by software to enable/disable the software trigger.
0: Software trigger disabled
1: Software trigger enabled
Note: This bit is cleared by hardware (one APB1 clock cycle later) once the DAC_DHR1
register value has been loaded into the DAC_DOR1 register.

16.10.3

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.

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.

DACC1DHR[11:0]
rw

rw

rw

rw

rw

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.

432/1141

DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)

16.10.4

DAC channel1 12-bit left-aligned data holding register
(DAC_DHR12L1)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

v

Res.

Res.

Res.

DACC1DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:4 DACC1DHR[11:0]: DAC channel1 12-bit left-aligned data
These bits are written by software which specifies 12-bit data for DAC channel1.
Bits 3:0 Reserved, must be kept at reset value.

16.10.5

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.

16.10.6

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

DocID022558 Rev 8

rw

433/1141
439

Digital-to-analog converter (DAC1 and DAC2)

RM0316

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 DACC2DHR[11:0]: DAC channel2 12-bit right-aligned data
These bits are written by software which specifies 12-bit data for DAC channel2.

16.10.7

DAC channel2 12-bit left-aligned data holding register
(DAC_DHR12L2)
Address offset: 0x18
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

DACC2DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

3

2

1

0

Res.

Res.

Res.

Res.

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:4 DACC2DHR[11:0]: DAC channel2 12-bit left-aligned data
These bits are written by software which specify 12-bit data for DAC channel2.
Bits 3:0 Reserved, must be kept at reset value.

16.10.8

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.

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

DACC2DHR[7:0]
rw

rw

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.

434/1141

DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)

16.10.9

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

21

20

19

18

17

16

DACC2DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

DACC1DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:16 DACC2DHR[11:0]: DAC channel2 12-bit right-aligned data
These bits are written by software which specifies 12-bit data for DAC channel2.
Bits 15:12 Reserved, must be kept at reset value.
Bits 11:0 DACC1DHR[11:0]: DAC channel1 12-bit right-aligned data
These bits are written by software which specifies 12-bit data for DAC channel1.

16.10.10 Dual DAC 12-bit left-aligned data holding register
(DAC_DHR12LD)
Address offset: 0x24
Reset value: 0x0000 0000
31

30

29

28

27

rw

rw

rw

rw

rw

15

14

13

12

11

26

25

24

23

22

21

20

DACC2DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

10

9

8

7

6

5

4

DACC1DHR[11:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

19

18

17

16

Res.

Res.

Res.

Res.

3

2

1

0

Res.

Res.

Res.

Res.

rw

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.

16.10.11 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.

DocID022558 Rev 8

435/1141
439

Digital-to-analog converter (DAC1 and DAC2)

15

14

13

12

11

10

9

RM0316

8

7

6

5

DACC2DHR[7:0]
rw

rw

rw

rw

4

3

2

1

0

rw

rw

rw

DACC1DHR[7:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:8 DACC2DHR[7:0]: DAC channel2 8-bit right-aligned data
These bits are written by software which specifies 8-bit data for DAC channel2.
Bits 7:0 DACC1DHR[7:0]: DAC channel1 8-bit right-aligned data
These bits are written by software which specifies 8-bit data for DAC channel1.

16.10.12 DAC channel1 data output register (DAC_DOR1)
Address offset: 0x2C
Reset value: 0x0000 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

15

14

13

12

Res.

Res.

Res.

Res.

DACC1DOR[11:0]
r

r

r

r

r

r

r

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 DACC1DOR[11:0]: DAC channel1 data output
These bits are read-only, they contain data output for DAC channel1.

16.10.13 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

r

r

Bits 31:12 Reserved, must be kept at reset value.
Bits 11:0 DACC2DOR[11:0]: DAC channel2 data output
These bits are read-only, they contain data output for DAC channel2.

16.10.14 DAC status register (DAC_SR)
Address offset: 0x34
Reset value: 0x0000 0000

436/1141

DocID022558 Rev 8

RM0316

Digital-to-analog converter (DAC1 and DAC2)

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)
Note: This bit is available in dual mode only. It is reserved in single mode.
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.

DocID022558 Rev 8

437/1141
439

0x30

438/1141

DAC_DOR2

Reset value

Reset value

DocID022558 Rev 8

0

0

0

0

Res.

0
0
0

Res.

Res.

0
0
0
0
0
0
0
0

Res.
Res.
Res.
Res.
Res.

Reset value

Res.
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

Reset value

0

Reset value

0

0

0

0

0

Res.
Res.
Res.

0

DACC1DHR[11:0]
0

0

0

0

0

0

0

0

0

0

DACC1DHR[7:0]

0

0

DACC2DHR[7:0]

0

0

0

0

0

0

0

0

0

DACC2DHR[11:0]

DACC2DHR[11:0]
0
0
0

0
0
0

DACC1DHR[11:0]
0
0
0

0
0
0

0

Res.

0
Res.

0

0
0
0

Res.

0

0

Res.

0

0
0
0
0

0
0
0
0

Res.

0

Res.

0

DACC2DHR[7:0]

0

DACC1DHR[11:0]
Res.

0

Res.

0

Res.

0

Res.

0

0
0
0
0

0
0
0
0

DACC1DHR[7:0]

0

DACC1DOR[11:0]

0

DACC2DOR[11:0]
Res.

Reset value
0

Res.

0

Res.

0

Res.

0

Res.

Reset value

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

EN2
0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

DMAEN1
0
0
0
0
0
0
0
0
0
0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

EN1
0

Reset value
SWTRIG1

TEN1
BOFF1
0

SWTRIG2

0

Res.

TSEL1[2:0]

WAVE1[1:0]

MAMP1[3:0].

DMAUDRIE1

Res.

Res.

TSEL2[2:0]

WAVE2[1:0]

0

Res.

Res.

Res.

0

Res.

Res.

0

Res.

Res.

TEN2
BOFF2

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

DMAEN2

0

MAMP2[3:0]

DMAUDRIE2

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

DACC2DHR[11:0]
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.
0

Res.

Res.

Res.

DAC_
DHR8RD

Res.

0

Res.

0

Res.

0

Res.

0

Res.

DACC2DHR[11:0]

Res.

0

Res.
0

Res.

Res.

Res.

0

Res.
0

Res.

0

Res.
0

Res.

Res.

0

Res.
0

Res.

Res.

Res.

0

Res.
0

Res.

0

Res.
0

Res.

Res.

Res.

0

Res.
0

Res.

DAC_DOR1
0

Res.

0

Res.

DAC_
DHR12LD

Res.

Reset value

Res.

Reset value

Res.

0x2C
DAC_
DHR12RD

Res.

0x28
DAC_
DHR8R2

Res.

0x24
DAC_
DHR12L2

Res.

0x20
DAC_
DHR12R2

Res.

Reset value

Res.

0x1C
DAC_
DHR8R1

Res.

0x18
DAC_
DHR12L1

Res.

0x14
DAC_
DHR12R1

Res.

0x10

Res.

0x0C

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.

Digital-to-analog converter (DAC1 and DAC2)
RM0316

16.10.15 DAC register map
Table 107 summarizes the DAC registers.
Table 107. DAC register map and reset values

0
0

DACC1DHR[11:0]

0

0

0

0

0

0

0

0

0

0

0

0

RM0316

Digital-to-analog converter (DAC1 and DAC2)

Reset value

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMAUDR1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMAUDR2

DAC_SR

Res.

0x34

Register
name

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 107. DAC register map (continued)and reset values (continued)

0

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

DocID022558 Rev 8

439/1141
439

Comparator (COMP)

RM0316

17

Comparator (COMP)

17.1

Introduction
STM32F303xB/C/D/E, STM32F358xx and STM32F398xx embed seven general purpose
comparators that can be used either as standalone devices (all terminal are available on
I/Os) or combined with the timers. STM32F303x6/8 and STM32F328x8 embed three
comparators, COMP2, COMP4 and COMP6.
The comparators can be used for a variety of functions including:

17.2

440/1141

•

Wake-up from low-power mode triggered by an analog signal,

•

Analog signal conditioning,

•

Cycle-by-cycle current control loop when combined with the DAC and a PWM output
from a timer.

COMP main features
•

Rail-to-rail comparators

•

Each comparator has positive and configurable negative inputs used for flexible voltage
selection:
–

Multiplexed I/O pins

–

DAC1 channel 1, DAC1 channel 2, DAC2 channel1 on STM32F303x6/8 and
STM32F328x8 devices and DAC1 channel 1, DAC1 channel 2 on
STM32F303xB/C/D/E, STM32F358xx and STM32F398xx devices.

–

Internal reference voltage and three submultiple values (1/4, 1/2, 3/4) provided by
scaler (buffered voltage divider)

•

Programmable hysteresis (on STM32F303xB/C and STM32F358xC only)

•

Programmable speed / consumption (on STM32F303xB/C and STM32F358xC only)

•

The outputs can be redirected to an I/O or to timer inputs for triggering:
–

Capture events

–

OCREF_CLR events (for cycle-by-cycle current control)

–

Break events for fast PWM shutdowns

•

COMP1/COMP2, COMP3/COMP4 and COMP5/COMP6 comparators can be
combined in a window comparator. This applies to STM32F303xB/C and
STM32F358xC devices only. COMP7 does not support the window mode.

•

Comparator outputs with blanking source

•

Each comparator has interrupt generation capability with wake-up from Sleep and Stop
modes (through the EXTI controller)

DocID022558 Rev 8

RM0316

Comparator (COMP)

17.3

COMP functional description

17.3.1

COMP block diagram
The block diagram of the comparators is shown in Figure 122: Comparator 1 and 2 block
diagrams (STM32F303xB/C/D/E, STM32F358xC and STM32F398xE) and Figure 123:
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE comparator 7 block diagram.
Figure 122. Comparator 1 and 2 block diagrams (STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE)
:LQGRZ
PRGH
3$

&203B287



&203B,13 

&203LQWHUUXSWUHTXHVW
WR(;7,

&203
&203B,10
3$
3$ '$&B&+
3$ '$&B&+ 
95(),17
ô95(),17
ò95(),17
ó95(),17

3$
3$
3$ '$&B&+
3$ '$&B&+ 
95(),17
ô95(),17
ò95(),17
ó95(),17



7,0B%.,1
7,0B2&UHIBFOU
7,0B,&
7,0B,&
7,0B2&UHIBFOU
7,0B,&
7,0B2&UHIBFOU
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1

3RODULW\
VHOHFWLRQ

3$ 

3$3)3$3$3%

&203B287

&203B,13

:LQGRZ
&203
PRGH


3$3$3$3%

&203LQWHUUXSWUHTXHVW
WR(;7,
3RODULW\
VHOHFWLRQ

&203B,10

7,0B%.,1
7,0B2&UHIBFOU
7,0B,&
7,0B,&
7,0B2&UHIBFOU
7,0B,&
7,0B2&UHIBFOU
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1 7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1
7,0B2&UHIBFOU

069

1. For a complete block diagram of comparators 1 to 6, refer to Section 18: Operational amplifier (OPAMP),
where all block diagrams and interconnections between comparators 1 to 6 and operational amplifiers are
given.
2. Only on STM32F303xB/C and STM32F358xC.
3. Window mode is not supported in STM32F303xD/E and STM32F398xE.

DocID022558 Rev 8

441/1141
465

Comparator (COMP)

RM0316

Figure 123. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE comparator 7
block diagram
&203B287
3$ 

3&

&203B,13 

3&

&203LQWHUUXSWUHTXHVW WR(;7,

&203
&203B,10

3&
3$ '$&B&+
3$ '$&B&+ 
95(),17
ô95(),17
ò95(),17
ó95(),17



7,0B%.,1
7,0B2&UHIBFOU
7,0B,&
7,0B,&
7,0B2&UHIBFOU
7,0B2&UHIBFOU
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,1

3RODULW\
VHOHFWLRQ

7,0B%.,17,0B%.,1
7,0B%.,17,0B%.,17,0B%.,1
7,0B%.,17,0B%.,1
069

1. Only for STM32F303xB/C and STM32F358xC

Figure 124. STM32F303x6/8 and STM32F328x8 comparators 2/4/6 block diagrams
&203B287
3$3$3$3%
3$

&203B,13


&203LQWHUUXSWUHTXHVW
WR(;7,

&203


3$

3RODULW\VHOHFWLRQ

3$ '$&B&+
'$&B&+ 
95(),17
95(),17

&203B,10

95(),17
95(),17
'$&B&+ 

7,0B%.,1
7,0B2&UHIBFOU
7,0B,&
7,0B,&
7,0B2&UHIBFOU
7,0B,&
7,0B2&UHIBFOU

3%
3%


&203
3%

&203LQWHUUXSW


3RODULW\VHOHFWLRQ

3$RU'$&B&+
'$&B&+ 

7,0B%.,1
7,0B2&5HI&OHDU
7,0B,&
7,0B,&
7,0B2&5HI&OHDU

95(),17
95(),17
95(),17
95(),17
'$&B&+ 

3$3&


3%

&203
3%

3$RU'$&B&+
'$&B&+ 

&203,QWHUUXSW


3RODULW\VHOHFWLRQ

95(),17
95(),17
95(),17
95(),17
'$&B&+ 

7,0B%.,1
7,0B2&5HI&OHDU
7,0B2&5HI&OHDU
7,0B,&
7,0B%.,1

06Y9

1. In STM32F303x6/8 and STM32F328x8 devices, DAC1_CH2 and DAC2_CH1 outputs are connected

442/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)
directly, thus PA5 and PA6 are not available as COMPx_INM (x = 2,4,6) inputs. When DAC1_OUT2 and
DAC2_OUT1 are connected internally to comparator non inverting input, the I/Os on which the DAC1_OUT
and DAC2_OUT1 are mapped (PA5 and PA6) can be used as GPIOs.

17.3.2

COMP pins and internal signals
The I/Os used as comparators inputs must be configured in analog mode in the GPIOs
registers.
The comparator output can be connected to the I/Os using the alternate function channel
given in “Alternate function mapping” table in the datasheet.
The table below summarizes the I/Os that can be used as comparators inputs and outputs.
The output can also be internally redirected to a variety of timer input for the following
purposes:
•

Emergency shut-down of PWM signals, using BKIN and BKIN2 inputs

•

Cycle-by-cycle current control, using OCREF_CLR inputs

•

Input capture for timing measures

It is possible to have the comparator output simultaneously redirected internally and
externally.
Table 108. Comparator input/output summary
Comparator inputs/outputs
COMP1

COMP2

COMP3

Comparator
outputs
(motor
control
protection)

COMP5

COMP6

COMP7(3)

+: PB11
+: PD11
-: PB15
-: PD10(3)

+: PC1
+: PA0(2)
-: PC0

DAC1_CH1
DAC1_CH2
DAC2_CH1(1)
Vrefint
¾ Vrefint
½ Vrefint
¼ Vrefint

Comparator
inverting
input:
connection
to internal
signals
Comparator
inputs
connected to
I/Os (+: non
inverting
input;
-: inverting
input)

COMP4

+: PA1
-: PA0

+: PA3(2)
+: PA7
-: PA2

-: PB12
-: PD15(3)
+: PB14
+: PD14(2)

+: PB0
+: PE7(2)
-: PB2
-: PE8(3)

-: PB10
-: PD13(3)
+: PB13
+: PD12(2)

T1BKIN
T1BKIN2
T8BKIN
T8BKIN2
T1BKIN2+ T8BKIN2
TIM20BKIN
TIM20BKIN2
TIM1BKIN2 + TIM8BKIN2 + TIM20BKIN2

DocID022558 Rev 8

443/1141
465

Comparator (COMP)

RM0316

Table 108. Comparator input/output summary (continued)
Comparator inputs/outputs
COMP1

COMP2

COMP3

COMP4

COMP5

COMP6

COMP7(3)

Outputs on
I/Os

PA0
PF4
PA6
PA11
PB8

PA2
PA7(2)
PA12
PB9

PC8
PA8

PB1

PC7
PA9

PA10
PC6

PC2

Outputs to
internal
signals

TIM1_OCrefClear
TIM1_IC1
TIM2_IC4
TIM2_OCrefClear
TIM3_IC1
TIM3_OCrefClear
TIM20_OCref_clr(4)

TIM1_OCrefClear TIM8_OCrefClear TIM8_OCrefClear TIM8_OCrefClear TIM1_OCrefClear
TIM2_OCrefClear
TIM3_IC3
TIM2_IC1
TIM2_IC2
TIM8_OCrefClear
TIM3_IC2
TIM3_OCrefClear TIM3_OCrefClear TIM2_OCrefClear
TIM2_IC3
TIM4_IC1
TIM4_IC2
TIM4_IC3
TIM16_OCrefClear
TIM1_IC2
TIM15_IC1
TIM15_OCrefClear
TIM16_BKIN
TIM16_IC1
TIM17_OCrefClear
TIM15_BKIN
TIM15_IC2
TIM17_IC1
TIM4_IC4
TIM17_BKIN

1. Only on STM32F303x6/8 and STM32F328x8 devices
2. Only on STM32F303xB/C and STM32F358xC devices.
3. Only on STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices.
4. Only on COMP2 on STM32F303x/D/E and STM32F398xE devices.

17.3.3

COMP reset and clocks
The COMP clock provided by the clock controller is synchronous with the PCLK2 (APB2
clock).
There is no clock enable control bit provided in the RCC controller. To use a clock source for
the comparator, the SYSCFG clock enable control bit must be set in the RCC controller.

Note:

Important: The polarity selection logic and the output redirection to the port works
independently from the PCLK2 clock. This allows the comparator to work even in Stop
mode.

17.3.4

Comparator LOCK mechanism
The comparators can be used for safety purposes, such as over-current or thermal
protection. For applications having specific functional safety requirements, it is necessary to
insure that the comparator programming cannot be altered in case of spurious register
access or program counter corruption.
For this purpose, the comparator control and status registers can be write-protected (readonly).
Once the programming is completed, using bits 30:0 of COMPx_CSR, the COMPxLOCK bit
can be set to 1. This causes the whole COMPx_CSR register to become read-only,
including the COMPxLOCK bit.
The write protection can only be reset by a MCU reset.

444/1141

DocID022558 Rev 8

RM0316

17.3.5

Comparator (COMP)

Hysteresis (on STM32F303xB/C and STM32F358xC only)
The comparator includes a programmable hysteresis to avoid spurious output transitions in
case of noisy signals. The hysteresis can be disabled if it is not needed (for instance when
exiting from low-power mode) to be able to force the hysteresis value using external
components.
Figure 125. Comparator hysteresis
).0

).).- 6HYST

#/-0?/54

069

17.3.6

Comparator output blanking function
The purpose of the blanking function is to prevent the current regulation to trip upon short
current spikes at the beginning of the PWM period (typically the recovery current in power
switches anti parallel diodes).It consists of a selection of a blanking window which is a timer
output compare signal. The selection is done by software (refer to the comparator register
description for possible blanking signals). Then, the complementary of the blanking signal is
ANDed with the comparator output to provide the wanted comparator output. See the
example provided in the figure below.

DocID022558 Rev 8

445/1141
465

Comparator (COMP)

RM0316
Figure 126. Comparator output blanking

3:0

&XUUHQWOLPLW
&XUUHQW

5DZFRPSRXWSXW

%ODQNLQJZLQGRZ

)LQDOFRPSRXWSXW

&RPSRXW
&RPSRXW WR7,0B%.«
%ODQN
069

17.3.7

Power mode (STM32F303xB/C and STM32F358xC only)
The comparator power consumption versus propagation delay can be adjusted to have the
optimum trade-off for a given application.The bits COMPxMODE[1:0] in COMPx_CSR
registers can be programmed as follows:

17.4

•

00: High speed / full power

•

01: Medium speed / medium power

•

10: Low speed / low-power

•

11: Very-low speed / ultra-low-power

COMP interrupts
The comparator outputs are internally connected to the Extended interrupts and events
controller. Each comparator has its own EXTI line and can generate either interrupts or
events. The same mechanism is used to exit from low-power modes.
Refer to Interrupt and events section for more details.

446/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)

17.5

COMP registers

17.5.1

COMP1 control and status register (COMP1_CSR)

Note:

This register is available in STM32F303xB/C/D/E, STM32F358xC and STM32F398xE only
Address offset: 0x1C
Reset value: 0x0000 0000

31

30

COMP1 COMP1
LOCK
OUT
rwo

r

15

14

COMP1
POL
rw

29
Res.

13

Res.

28
Res.

12

27
Res.

11

26
Res.

rw

rw

Res.

10

COMP1OUTSEL
rw

25

24
Res.

9
Res.

8
Res.

23
Res.

7
Res.

rw

22
Res.

6

21

20

Res.

5

rw

18

rw

rw

4

3

2

rw

COMP1MODE
[1:0](1)
rw

17

16

COMP1HYST
[1:0](1)

rw

COMP1INMSEL[2:0]
rw

19
COMP1_
BLANKING

rw

rw

rw

1

0

COMP
COMP
1_INP_
1EN
DAC
rw

rw

1. Only in STM32F303xB/C and STM32F358xC.

Bit 31 COMP1LOCK: Comparator 1 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
It allows to have COMP1_CSR register as read-only.
0: COMP1_CSR is read-write.
1: COMP1_CSR is read-only.
Bit 30 COMP1OUT: Comparator 1 output
This read-only bit is a copy of comparator 1output state.
0: Output is low (non-inverting input below inverting input).
1: Output is high (non-inverting input above inverting input).
Bits 29:21 Reserved, must be kept at reset value.
Bits 20:18 COMP1_BLANKING: Comparator 1 blanking source
These bits select which Timer output controls the comparator 1 output blanking.
000: No blanking
001: TIM1 OC5 selected as blanking source
010: TIM2 OC3 selected as blanking source
011: TIM3 OC3 selected as blanking source
Other configurations: reserved
Bits 17:16 COMP1HYST[1:0] Comparator 1 hysteresis
On the STM32F303xB/C and STM32F358xC, these bits control the hysteresis level.
00: No hysteresis
01: Low hysteresis
10: Medium hysteresis
11: High hysteresis
Please refer to the electrical characteristics for the hysteresis values.
On the STM32F303xD/E and STM32F398xE, these bits are reserved and must be kept at reset value.
Bit 15 COMP1POL: Comparator 1 output polarity
This bit is used to invert the comparator 1 output.
0: Output is not inverted
1: Output is inverted

DocID022558 Rev 8

447/1141
465

Comparator (COMP)

RM0316

Bit 14 Reserved, must be kept at reset value.
Bits 13:10 COMP1OUTSEL[3:0]: Comparator 1 output selection
These bits select which Timer input must be connected with the comparator1 output.
0000: No selection
0001: (BRK_ACTH) Timer 1 break input
0010: (BRK2) Timer 1 break input 2
0011: Timer 8 break input 1
0100: Timer 8 break input 2
0101: Timer 1 break input 2 + Timer 8 break input 2
0110: Timer 1 OCrefclear input
0111: Timer 1 input capture 1
1000: Timer 2 input capture 4
1001; Timer 2 OCrefclear input
1010: Timer 3 input capture 1
1011: Timer 3 OCrefclear input
1100: Timer 20 break input 1
1101: Timer 20 break input 2
1110: Timer 1 break input 2 + Timer 8 break input 2 + Timer 20 break input 2
1111: Reserved.
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.
Bits 9:7 Reserved, must be kept at reset value.
Bits 6:4 COMP1INMSEL[2:0]: Comparator 1 inverting input selection
These bits allows to select the source connected to the inverting input of the comparator 1.
000: 1/4 of Vrefint
001: 1/2 of Vrefint
010: 3/4 of Vrefint
011: Vrefint
100: PA4 or DAC1 output if enabled
101: PA5 or DAC2 output if enabled
110: PA0
111: Reserved

448/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)

Bits 3:2 COMP1MODE[1:0]: Comparator 1 mode (only in STM32F303xB/C and STM32F358xC devices)
These bits control the operating mode of the comparator1 and allows to adjust the
speed/consumption.
00: High speed
01: Medium speed
10: Low-power
11: Ultra-low-power
Bit 1 COMP1_INP_DAC: Comparator 1 non inverting input connection to DAC output.
This bit closes a switch between comparator 1 non-inverting input (PA0) and DAC out I/O (PA4).
0: Switch open
1: Switch closed
Note: This switch is solely intended to redirect signals onto high impedance input, such as COMP1
non-inverting input (highly resistive switch).
Bit 0 COMP1EN: Comparator 1 enable
This bit switches COMP1 ON/OFF.
0: Comparator 1 disabled
1: Comparator 1 enabled

17.5.2

COMP2 control and status register (COMP2_CSR)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

COMP COMP
2LOCK 2OUT
rwo

r

15

14

COMP
2POL

29

28

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.

Res.

Res.

Res.

COMP
2INMS
EL[3](1)

Res.

rw
13

Res.

12

11

10

9
COMP2
WIN
MODE(

COMP2OUTSEL[3:0]

8

7

Res.

COMP2
INPSEL

2)

rw

rw

rw

rw

rw

rw

(2)

rw

6

5

20

rw

18

COMP2_BLANKING[2:0]

17

16

COMP2HYST
[1:0](2)

rw

rw

rw

rw

rw

4

3

2

1

0

Res.

COMP2
EN

COMP2INMSEL[2:0]

rw

19

rw

COMP2MODE
[1:0](2)
rw

rw

rw

1. Only in STM32F303x6/8 and STM32F328x8.
2. Only in STM32F303xB/C and STM32F358xC devices.

Bit 31 COMP2LOCK: Comparator 2 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
It allows to have COMP2_CSR register as read-only.
0: COMP2_CSR is read-write.
1: COMP2_CSR is read-only.
Bit 30 COMP2OUT: Comparator 2 output
This read-only bit is a copy of comparator 1output state.
0: Output is low (non-inverting input below inverting input).
1: Output is high (non-inverting input above inverting input).
Bits 29:23 Reserved, must be kept at reset value.
Bit 22 COMP2INMSEL[3]: Comparator 2 inverting input selection. This bit is available only on F303x6/x8 and
F328xx. It is used with Bits [6..4] to configure the Comp inverting input.

DocID022558 Rev 8

449/1141
465

Comparator (COMP)

RM0316

Bit 21 Reserved, must be kept at reset value.
Bits 20:18 COMP2_BLANKING[2:0]: Comparator 2 output blanking source
These bits select which Timer output controls the comparator 1 output blanking.
000: No blanking
001: TIM1 OC5 selected as blanking source
010: TIM2 OC3 selected as blanking source
011: TIM3 OC3 selected as blanking source
Other configurations: reserved
Bits 17:16 COMP2HYST[1:0]: Comparator 2 Hysteresis
On the STM32F303xB/C and STM32F358xC, these bits control the hysteresis level.
00: No hysteresis
01: Low hysteresis
10: Medium hysteresis
11: High hysteresis
Please refer to the electrical characteristics for the hysteresis values.
On the STM32F303xD/E, STM32F303x6/8, STM32F328x8 and STM32F398xx, these bits are
reserved and must be kept at reset value.
Bit 15 COMP2POL: Comparator 2 output polarity
This bit is used to invert the comparator 2 output.
0: Output is not inverted
1: Output is inverted
Bit 14 Reserved, must be kept at reset value.
Bits 13:10 COMP2OUTSEL[3:0]: Comparator 2 output selection
These bits select which Timer input must be connected with the comparator2 output.
0000: No selection
0001: (BRK_ACTH) Timer 1 break input
0010: (BRK2) Timer 1 break input 2
0011: (BRK_ACTH) Timer 8 break input
0100: (BRK2) Timer 8 break input 2
0101: Timer 1 break input2 + Timer 8 break input 2
0110: Timer 1 OCrefclear input
0111: Timer 1 input capture 1
1000: Timer 2 input capture 4
1001: Timer 2 OCrefclear input
1010: Timer 3 input capture 1
1011: Timer 3 OCrefclear input
1100: Timer 20 Break Input selected
1101: Timer 20 Break2 Input selected
1110: Timer 1 Break2 or Timer 8 Break2 or Timer 20 Break2
1111: Timer 20 OCrefClear Input selected
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.

450/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)

Bit 9 COMP2WINMODE: Comparator 2 window mode (only in STM32F303xB/C and STM32F358xC
devices)
This bit selects the window mode: Both non inverting inputs of comparators share the non inverting
input of Comparator 1 (PA1).
0: Comparators 1 and 2 can not be used in window mode.
1: Comparators 1 and 2 can be used in window mode.
Bit 8 Reserved, must be kept at reset value.
Bit 7 COMP2INPSEL: Comparator 2 non inverting input selection (Only in STM32F303xB/C and
STM32F358xC devices)
0: PA7 is selected.
1: PA3 is selected.
Note: On STM32F303x6/8, STM32F303xDxE, STM32F398xE and STM32F328, this bit is reserved.
COMP2_VINP is available on PA7 whatever value is written in bit 7.
Bits 6:4 COMP2INMSEL[2:0]: Comparator 2 inverting input selection
These bits, together with bit 22, allows to select the source connected to the inverting input of the
comparator 2.
0000: 1/4 of Vrefint
0001: 1/2 of Vrefint
0010: 3/4 of Vrefint
0011: Vrefint
0100: PA4 or DAC1_CH1 output if enabled
STM32F303xB/C/D/E, STM32F358xC and STM32F398xC:
0101: PA5 or DAC1_CH2 output if enabled
STM32F303x6/8 and STM32F328x8:
0101: DAC1_CH2 output
0110: PA2
1000 DAC2_CH1 output
Remaining combinations: reserved.
Bits 3:2 COMP2MODE[1:0]: Comparator 2 mode (only in STM32F303xB/C and STM32F358xC devices)
These bits control the operating mode of the comparator2 and allows to adjust the
speed/consumption.
00: High speed
01: Medium speed
10: Low-power
11: Ultra-low-power
Bit 1 Reserved, must be kept at reset value.
Bit 0 COMP2EN: Comparator 2 enable
This bit switches COMP2 ON/OFF.
0: Comparator 2 disabled
1: Comparator 2 enabled

17.5.3

COMP3 control and status register (COMP3_CSR)

Note:

This register is available in STM32F303xB/C/D/E, STM32F358xx and STM32F398xx only.
Address offset: 0x24

DocID022558 Rev 8

451/1141
465

Comparator (COMP)

RM0316

Reset value: 0x0000 0000
31

30

COMP COMP
3LOCK 3OUT
rwo

r

15

14

COMP
3POL

29

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

9

8

7

6

5

Res.

COMP3
INPSEL

Res.

rw

28

COMP3OUTSEL
rw

rw

rw

Res.
rw

(1)

rw

20

rw

18

COMP3_BLANKING

17

16

COMP3HYST
[1:0](1)

rw

rw

rw

rw

rw

4

3

2

1

0

Res.

COMP3
EN

COMP3INMSEL[2:0]
rw

19

rw

COMP3MODE
[1:0](1)
rw

rw

rw

1. Only in STM32F303xB/C and STM32F358xC.

Bit 31 COMP3LOCK: Comparator 3 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
It allows to have COMP3_CSR register as read-only.
0: COMP3_CSR is read-write.
1: COMP3_CSR is read-only.
Bit 30 COMP3OUT: Comparator 3 output
This read-only bit is a copy of comparator 3 output state.
0: Output is low (non-inverting input below inverting input).
1: Output is high (non-inverting input above inverting input).
Bits 29:21 Reserved, must be kept at reset value.
Bits 20:18 COMP3_BLANKING: Comparator 3 blanking source
These bits select which Timer output controls the comparator 3 output blanking.
000: No blanking
001: TIM1 OC5 selected as blanking source
010: Reserved.
011:TIM2 OC4 selected as blanking source
Other configurations: reserved
Bits 17:16 COMP3HYST[1:0] Comparator 3 hysteresis
These bits control the hysteresis level (only in STM32F303xB/C and STM32F358x).
00: No hysteresis
01: Low hysteresis
10: Medium hysteresis
11: High hysteresis
Please refer to the electrical characteristics for the hysteresis values.
On the STM32F303xD/E and STM32F398xx, these bits are reserved and must be kept at reset value.
Bit 15 COMP3POL: Comparator 3 output polarity
This bit is used to invert the comparator 3 output.
0: Output is not inverted
1: Output is inverted
Bit 14 Reserved, must be kept at reset value.

452/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)

Bits 13:10 COMP3OUTSEL[3:0]: Comparator 3 output selection
These bits are set and cleared by software if the COMP3_LOCK bit is not set.
These bits select which Timer input must be connected with the comparator 3 output.
0000: No timer input
0001: (BRK_ACTH) Timer 1 break input
0010: (BRK2) Timer 1 break input 2
0011: (BRK_ACTH) Timer 8 break input
0100: (BRK2) Timer 8 break input 2
0101: Timer 1 break input 2 or Timer 8 break input 2
0110: Timer 1 OCrefclear input
0111: Timer 4 input capture 1
1000: Timer 3 input capture 2
1001: Timer 2 OCrefclear input
1010: Timer 15 input capture 1
1011: Timer 15 break input
1100 = Timer 20 Break Input selected
1101 = Timer 20 Break2 Input selected
1110 = Timer 1 Break2 or Timer 8 Break2 or Timer 20 Break2
Remaining combinations: reserved.
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.
Bits 9:8 Reserved, must be kept at reset value.
Bit 7 COMP3INPSEL: Comparator 3 non inverting input selection
0: PB14
1: PD14
Note: On STM32F303xD/E and STM32F398xE, this bit is reserved. COMP3_VINP is available on
PB14.
Bits 6:4 COMP3INMSEL[2:0]: Comparator 1 inverting input selection
These bits allows to select the source connected to the inverting input of the comparator 3.
000: 1/4 of Vrefint
001: 1/2 of Vrefint
010: 3/4 of Vrefint
011: Vrefint
100: PA4 or DAC1 output if enabled
101: PA5 or DAC2 output if enabled
110: PD15
111: PB12

DocID022558 Rev 8

453/1141
465

Comparator (COMP)

RM0316

Bits 3:2 COMP3MODE[1:0]: Comparator 3 mode (only in STM32F303xB/C and STM32F358xC devices.)
These bits control the operating mode of the comparator 3 and allows to adjust the
speed/consumption.
00: Ultra-low power
01: Low-power
10: Medium speed
11: High speed
Bit 1 Reserved, must be kept at reset value.
Bit 0 COMP3EN: Comparator 3 enable
This bit switches COMP3 ON/OFF.
0: Comparator 3 disabled
1: Comparator 3 enabled

17.5.4

COMP4 control and status register (COMP4_CSR)
Address offset: 0x28
Reset value: 0x0000 0000

31

30

COMP COMP
4LOCK 4OUT
rwo

r

15

14

COMP
4POL

29

Res.

Res.

27

Res.

26

Res.

25

Res.

24

Res.

23

22

21

Res.

COMP
4INMS
EL[3]

Res.

20

19

18

COMP4_BLANKING[2:0]

(1)

rw
13

Res.

rw

28

12

11

10

COMP4OUTSEL[3:0]
rw

rw

rw

9
COMP4
WINMO
DE(2)

rw

8

7

Res.

COMP4
INPSEL

rw

(2)

rw

6

5

rw

16

COMP4HYST
[1:0](2)

rw

rw

rw

rw

rw

4

3

2

1

0

Res.

COMP4
EN

COMP4INMSEL[2:0]
rw

17

rw

COMP4MODE
[1:0](2)
rw

rw

rw

1. Only in STM32F303x6/8 and STM32F328x8.
2. Only in STM32F303xB/C and STM32F358xC.

Bit 31 COMP4LOCK: Comparator 4 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
It allows to have COMP4_CSR register as read-only.
0: COMP4_CSR is read-write.
1: COMP4_CSR is read-only.
Bit 30 COMP4OUT: Comparator 4 output
This read-only bit is a copy of comparator 4 output state.
0: Output is low (non-inverting input below inverting input).
1: Output is high (non-inverting input above inverting input).
Bits 29:23 Reserved, must be kept at reset value.
Bit 22 COMP4INMSEL[3]: Comparator 4 inverting input selection. This bit is available only on F303x6/x8 and
F328xx. It is used with Bits [6..4] to configure the Comp inverting input.
Bit 21 Reserved, must be kept at reset value.

454/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)

Bits 20:18 COMP4_BLANKING: Comparator 4 blanking source
These bits select which Timer output controls the comparator 4 output blanking.
000: No blanking
001: TIM3 OC4 selected as blanking source
010: TIM8 OC5 selected as blanking source
011: TIM15 OC1 selected as blanking source
Other configurations: reserved, must be kept at reset value
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.
Bits 17:16 COMP4HYST[1:0]: Comparator 4 Hysteresis
On the STM32F303xB/C and STM32F358xC, these bits control the hysteresis level.
00: No hysteresis
01: Low hysteresis
10: Medium hysteresis
11: High hysteresis
Please refer to the electrical characteristics for the hysteresis values.
On the STM32F303xD/E, STM32F303x6/8, STM32F398xE and STM32F328x8, these bits are
reserved and must be kept at reset value.
Bit 15 COMP4POL: Comparator 4 output polarity
This bit is used to invert the comparator 4 output.
0: Output is not inverted
1: Output is inverted
Bit 14 Reserved, must be kept at reset value.
Bits 13:10 COMP4OUTSEL[3:0]: Comparator 4 output selection
These bits select which Timer input must be connected with the comparator4 output.
0000: No timer input selected
0001: (BRK) Timer 1 break input
0010: (BRK2) Timer 1 break input 2
0011: (BRK) Timer 8 break input
0100: (BRK2) Timer 8 break input 2
0101: Timer 1 break input 2 or Timer 8 break input 2
0110: Timer 3 input capture 3
0111: Timer 8 OCrefclear input
1000: Timer 15 input capture 2
1001: Timer 4 input capture 2
1010: Timer 15 OCrefclear input
1011: Timer 3 OCrefclear input
1100 = Timer 20 Break Input selected
1101 = Timer 20 Break2 Input selected
1110 = Timer 1 Break2 or Timer 8 Break2 or Timer 20 Break2
Remaining combinations: reserved.
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.

DocID022558 Rev 8

455/1141
465

Comparator (COMP)

RM0316

Bit 9 COMP4WINMODE: Comparator 4 window mode (only in STM32F303xB/C and STM32F358xC
devices)
This bit selects the window mode: both non inverting inputs comparators 3 and 4 share the non
inverting input of Comparator 3 (PB14 or PD14)
0: Comparators 3 and 4 can not be used in window mode.
1: Comparators 3 and 4 can be used in window mode
Bit 8 Reserved, must be kept at reset value.
Bit 7 COMP4INPSEL: Comparator 4 non inverting input selection (Only on STM32F303xB/C and
STM32F358xC)
0: PB0
1: PE7
Note: On STM32F303x6/8, STM32F303xDxE, STM32F398xE and STM32F328xx, this bit is
reserved. COMP4_VINP is available on PB0.
Bits 6:4 COMP4INMSEL[3:0]: Comparator 4 inverting input selection
These bits allows to select the source connected to the inverting input of the comparator 4.
0000: 1/4 of Vrefint
0001: 1/2 of Vrefint
0010: 3/4 of Vrefint
0011: Vrefint
0100: PA4 or DAC1_CH1 output if enabled
STM32F303xB/C/D/E, STM32F358xC and STM32F398xC:
0101: PA5 or DAC1_CH2 output if enabled
STM32F303x6/8 and STM32F328x8:
0101: DAC1_CH2 output
0110: PE8
0111: PB2
1000: DAC2_CH1 output
Remaining combinations: reserved.
Bits 3:2 COMP4MODE[1:0]: Comparator 1 mode (only in STM32F303xB/C and STM32F358xC devices)
These bits control the operating mode of the comparator 4 and allows to adjust the
speed/consumption.
00: Ultra-low-power
01: Low-power
10: Medium speed
11: High speed
Bit 1 Reserved, must be kept at reset value.
Bit 0 COMP4EN: Comparator 4 enable
This bit switches COMP4 ON/OFF.
0: Comparator 4 disabled
1: Comparator 4 enabled

17.5.5

COMP5 control and status register (COMP5_CSR)

Note:

This register is available in STM32F303xB/C/D/E, STM32F358xx and STM32F398xx only.
Address offset: 0x2C

456/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)
Reset value: 0x0000 0000

31

30

COMP COMP
5LOCK 5OUT
rwo

r

15

14

COMP
5POL
rw

29

28

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

9

8

7

6

5

Res.

COMP5
INPSEL

Res.

COMP5OUTSEL
rw

rw

rw

Res.
rw

(1)

rw

20

rw

18

COMP5_BLANKING

17

16

COMP5HYST
[1:0](1)

rw

rw

rw

rw

rw

4

3

2

1

0

Res.

COMP5
EN

COMP5INMSEL[2:0]
rw

19

rw

COMP5MODE
[1:0](1)
rw

rw

rw

1. Only in STM32F303xB/C.

Bit 31 COMP5LOCK: Comparator 5 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
It allows to have COMP5_CSR register as read-only.
0: COMP5_CSR is read-write.
1: COMP5_CSR is read-only.
Bit 30 COMP5OUT: Comparator 5 output
This read-only bit is a copy of comparator 5 output state.
0: Output is low (non-inverting input below inverting input).
1: Output is high (non-inverting input above inverting input).
Bits 29:21 Reserved, must be kept at reset value.
Bits 20:18 COMP5_BLANKING: Comparator 5 blanking source
These bits select which Timer output controls the comparator 5 output blanking.
000: No blanking
001: Reserved.
010: TIM8 OC5 selected as blanking source
011: TIM3 OC3 selected as blanking source
Other configurations: reserved
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.
Bits 17:16 COMP5HYST[1:0] Comparator 5 hysteresis
These bits control the hysteresis level (only on STM32F303xB/C and STM32F358xC devices.).
00: No hysteresis
01: Low hysteresis
10: Medium hysteresis
11: High hysteresis
Please refer to the electrical characteristics for the hysteresis values.
On the STM32F303xD/E and STM32F398xE, these bits are reserved and must be kept at reset
value
Bit 15 COMP5POL: Comparator 5 output polarity
This bit is used to invert the comparator 5 output.
0: Output is not inverted
1: Output is inverted
Bit 14 Reserved, must be kept at reset value.

DocID022558 Rev 8

457/1141
465

Comparator (COMP)

RM0316

Bits 13:10 COMP5OUTSEL[3:0]: Comparator 5 output selection
These bits select which Timer input must be connected with the comparator 5 output.
0000: No timer input selected
0001: (BRK_ACTH) Timer 1 break input
0010: (BRK2) Timer 1 break input 2
0011: (BRK_ACTH) Timer 8 break input
0100: (BRK2) Timer 8 break input 2
0101: Timer 1 break input 2 or Timer 8 break input 2
0110: Timer 2 input capture 1
0111: Timer 8 OCrefclear input
1000: Timer 17 input capture 1
1001: Timer 4 input capture 3
1010: Timer 16 break input
1011: Timer 3 OCrefclear input
1100 = Timer 20 Break Input selected
1101 = Timer 20 Break2 Input selected
1110 = Timer 1 Break2 or Timer 8 Break2 or Timer 20 Break2
Remaining combinations: reserved.
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.
Bits 9:8 Reserved, must be kept at reset value.
Bit 7 COMP5INPSEL: Comparator 5 non inverting input selection
0: PD12
1: PB13
Note: On STM32F303xDxE and STM32F398xE, this bit is reserved. COMP5_VINP is available on
PB13.
Bits 6:4 COMP5INSEL[2:0]: Comparator 5 inverting input selection
These bits allows to select the source connected to the inverting input of the comparator 5.
000: 1/4 of Vrefint
001: 1/2 of Vrefint
010: 3/4 of Vrefint
011: Vrefint
100: PA4 or DAC1 output if enabled
101: PA5 or DAC2 output if enabled
110: PD13
111: PB10
Note: On STM32F303xDxE and STM32F398xE, this bit is reserved. COMP5_VINP is available on
PB13.

458/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)

Bits 3:2 COMP5MODE[1:0]: Comparator 5 mode (Only in STM32F303xB/C and STM32F358xC devices)
These bits control the operating mode of the comparator 5 and allows to adjust the
speed/consumption.
00: Ultra-low power
01: Low-power
10: Medium speed
11: High speed
Bit 1 Reserved, must be kept at reset value.
Bit 0 COMP5EN: Comparator 5 enable
This bit switches COMP5 ON/OFF.
0: Comparator 5 disabled
1: Comparator 5 enabled

17.5.6

COMP6 control and status register (COMP6_CSR)
Address offset: 0x30
Reset value: 0x0000 0000

31

30

COMP COMP
6LOCK 6OUT
rw

r

15

14

COMP
6POL
rw

29

28

Res.

Res.

27

Res.

26

25

Res.

24

Res.

Res.

23

22

21

Res.

COMP
6INMS
EL[3]

Res.

20

19

18

COMP6_BLANKING[2:0]

(1)

rw
13

Res.

12

11

10

COMP6OUTSEL[3:0]
rw

rw

rw

9
COMP6
WINMO
DE(2)

rw

8

7

Res.

COMP6
INPSEL

rw

(2)

rw

6

5

rw

16

COMP6HYST[1:0
](2)

rw

rw

rw

rw

rw

4

3

2

1

0

Res.

COMP6
EN

COMP6INMSEL[2:0]
rw

17

rw

COMP6MODE
[1:0](2)
rw

rw

rw

1. Only in STM32F303x6/8 and STM32F328.
2. Only in STM32F303xB/C and STM32F358xC devices.

Bit 31 COMP6LOCK: Comparator 6 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
It allows to have COMP6_CSR register as read-only.
0: COMP6_CSR is read-write.
1: COMP6_CSR is read-only.
Bit 30 COMP6OUT: Comparator 6 output
This read-only bit is a copy of comparator 6 output state.
0: Output is low (non-inverting input below inverting input).
1: Output is high (non-inverting input above inverting input).
Bits 29:23 Reserved, must be kept at reset value.
Bit 22 COMP6INMSEL[3]: Comparator 6 inverting input selection. This bit is available only on F303x6/x8 and
F328xx. It is used with Bits [6..4] to configure the Comp inverting input.
Bit 21 Reserved, must be kept at reset value.

DocID022558 Rev 8

459/1141
465

Comparator (COMP)

RM0316

Bits 20:18 COMP6_BLANKING: Comparator 6 blanking source
These bits select which Timer output controls the comparator 6 output blanking.
000: No blanking
001: Reserved
010: TIM8 OC5 selected as blanking source
011: TIM2 OC4 selected as blanking source
100: TIM15 OC2 selected as blanking source
Other configurations: reserved
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.
The blanking signal is active high (masking comparator output signal). It is up to the user to program
the comparator and blanking signal polarity correctly.
Bits 17:16 COMP6HYST[1:0]: Comparator 6 Hysteresis
On the STM32F303xB/C and STM32F358xC, these bits control the hysteresis level.
00: No hysteresis
01: Low hysteresis
10: Medium hysteresis
11: High hysteresis
Please refer to the electrical characteristics for the hysteresis values.
On the STM32F303x6/8/D/E, STM32F398xE and STM32F328x8, these bits are reserved and must be
kept at reset value.
Bit 15 COMP6POL: Comparator 6 output polarity
This bit is used to invert the comparator 6 output.
0: Output is not inverted
1: Output is inverted
Bit 14 Reserved, must be kept at reset value.
Bits 13:10 COMP6OUTSEL[3:0]: Comparator 6 output selection
These bits select which Timer input must be connected with the comparator 6 output.
0000: No timer input
0001: (BRK_ACTH) Timer 1 break input
0010: (BRK2) Timer 1 break input 2
0011: (BRK_ACTH) Timer 8 break input
0100: (BRK2) Timer 8 break input 2
0101: Timer 1 break input 2 or Timer 8 break input 2
0110: Timer 2 input capture 2
0111: Timer 8 OCrefclear input
1000: Timer 2 OCrefclear input
1001: Timer 16 OCrefclear input
1010: Timer 16 input capture 1
1011: Timer 4 input capture 4
1100 = Timer 20 Break Input selected
1101 = Timer 20 Break2 Input selected
1110 = Timer 1 Break2 or Timer 8 Break2 or Timer 20 Break2
Remaining combinations: reserved.
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.

460/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)

Bit 9 COMP6WINMODE: Comparator 6 window mode (only in STM32F303xB/C and STM32F358xC
devices)
This bit selects the window mode: both non inverting inputs of comparators 6 share the non inverting
input of Comparator 5 (PD12 or PB13).
0: Comparators 5 and 6 can not be used in window mode.
1: Comparators 5 and 6 can be used in window mode
Bit 8 Reserved, must be kept at reset value.
Bit 7 COMP6INPSEL: Comparator 6 non inverting input selection (only on STM32F303xB/C and
STM32F358xx)
0: PD11
1: PB11
Note: On STM32F303x6/x8/D/E, STM32F328x8 and STM32F398xx, this bit is reserved.
COMP6_VINP is available on PB11 whatever value is written on bit 7.
Bits 6:4 COMP6INMSEL[2:0]: Comparator 6 inverting input selection
These bits allows to select the source connected to the inverting input of the comparator 6.
0000: 1/4 of Vrefint
0001: 1/2 of Vrefint
0010: 3/4 of Vrefint
0011: Vrefint
0100: PA4 or DAC1_CH1 output if enabled
STM32F303xB/C/D/E, STM32F358xC and STM32F398xC:
0101: PA5 or DAC1_CH2 output if enabled
STM32F303x6/8 and STM32F328x8:
0101: DAC1_CH2 output
0110: PD10
0111: PB15
1000: DAC2_CH1
Remaining combinations: reserved.
Bits 3:2 COMP6MODE[1:0]: Comparator 6 mode (only in STM32F303xB/C and STM32F358xC devices)
These bits control the operating mode of the comparator 6 and allows to adjust the
speed/consumption.
00: Ultra-low-power
01: Low-power
10: Medium speed
11: High speed
Bit 1 Reserved, must be kept at reset value.
Bit 0 COMP6EN: Comparator 6 enable
This bit switches COMP6 ON/OFF.
0: Comparator 6 disabled
1: Comparator 6 enabled

17.5.7

COMP7 control and status register (COMP7_CSR)

Note:

This register is available in STM32F303xB/C/D/E, STM32F358xx and STM32F398xx only.
Address offset: 0x34
Reset value: 0x0000 0000

DocID022558 Rev 8

461/1141
465

Comparator (COMP)

31

30

COMP COMP
7LOCK 7OUT
rwo

r

15

14

COMP
7POL

29

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

9

8

7

6

5

Res.

COMP7
INPSEL

Res.

rw

28

RM0316

COMP7OUTSEL
rw

rw

rw

Res.
rw

(1)

rw

20

rw

18

COMP7_BLANKING

17

16

COMP7HYST
[1:0](1)

rw

rw

rw

rw

rw

4

3

2

1

0

Res.

COMP7
EN

COMP7INMSEL[2:0]
rw

19

rw

COMP7MODE
[1:0](1)
rw

rw

rw

1. Only in STM32F303xB/C and STM32F358xC devices.

Bit 31 COMP7LOCK: Comparator 7 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
It allows to have COMP7_CSR register as read-only.
0: COMP7_CSR is read-write.
1: COMP7_CSR is read-only.
Bit 30 COMP7OUT: Comparator 7 output
This read-only bit is a copy of comparator 7 output state.
0: Output is low (non-inverting input below inverting input).
1: Output is high (non-inverting input above inverting input).
Bits 29:21 Reserved, must be kept at reset value.
Bits 20:18 COMP7_BLANKING: Comparator 7 blanking source
These bits select which Timer output controls the comparator 7 output blanking.
000: No blanking
001: TIM1 OC5 selected as blanking source
010: TIM8 OC5 selected as blanking source
011: Reserved
100: TIM15 OC2 selected as blanking source
Other configurations: reserved
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.
Bits 17:16 COMP7HYST[1:0] Comparator 7 hysteresis
These bits control the hysteresis level. (On the STM32F303xB/C and STM32F358xC devices only.)
00: No hysteresis
01: Low hysteresis
10: Medium hysteresis
11: High hysteresis
Please refer to the electrical characteristics for the hysteresis values.
On the STM32F303xD/E and STM32F398xx, these bits are reserved and must be kept at reset value.
Bit 15 COMP7POL: Comparator 7 output polarity
This bit is used to invert the comparator 7 output.
0: Output is not inverted
1: Output is inverted
Bit 14 Reserved, must be kept at reset value.

462/1141

DocID022558 Rev 8

RM0316

Comparator (COMP)

Bits 13:10 COMP7OUTSEL[3:0]: Comparator 7 output selection
These bits select which Timer input must be connected with the comparator 7 output.
0001: (BRK) Timer 1 break input
0010: (BRK2) Timer 1 break input 2
0011: (BRK) Timer 8 break input
0100: (BRK2) Timer 8 break input 2
0101: Timer 1 break input 2 + Timer 8 break input 2
0110: Timer 1 OCrefclear input
0111: Timer 8 OCrefclear input
1000: Timer 2 input capture 3
1001: Timer 1 input capture 2
1010: Timer 17 OCrefclear input
1011: Timer 17 break input
1100 = Timer 20 Break Input selected
1101 = Timer 20 Break2 Input selected
1110 = Timer 1 Break2 or Timer 8 Break2 or Timer 20 Break2
Remaining combinations: reserved.
Note: Depending on the product, when a timer is not available, the corresponding combination is
reserved.
Bits 9:8 Reserved, must be kept at reset value.
Bit 7 COMP7INPSEL: Comparator 7 non inverting input selection
0: PA0
1: PC1
Note: On STM32F303xD/E and STM32F398xx, this bit is reserved. COMP7_VINP is available on
PC1.
Bits 6:4 COMP7INSEL[2:0]: Comparator 7 inverting input selection
These bits allows to select the source connected to the inverting input of the comparator 7.
000: 1/4 of Vrefint
001: 1/2 of Vrefint
010: 3/4 of Vrefint
011: Vrefint
100: PA4 or DAC1 output if enabled
101: PA5 or DAC2 output if enabled
110: PC0
111: Reserved
Bits 3:2 COMP7MODE[1:0]: Comparator 7 mode (Only in STM32F303xB/C and STM32F358xC devices)
These bits control the operating mode of the comparator 7 and allows to adjust the
speed/consumption.
00: Ultra-low power
01: Low-power
10: Medium speed
11: High speed
Bit 1 Reserved, must be kept at reset value.
Bit 0 COMP7EN: Comparator 7 enable
This bit switches COMP7 ON/OFF.
0: Comparator 7 disabled
1: Comparator 7 enabled

DocID022558 Rev 8

463/1141
465

464/1141
COMP4_CSR

Reset value
0
0

COMP5_CSR

Reset value

0

0

COMP6_CSR

Reset value

0

0

0

0

0

0

0

DocID022558 Rev 8

0

0

0
0

0

0
0
0

COMP5OUT
SEL[3:0]

COMP4OUT
SEL[3:0]

0

0
0

0

COMP6OUT
SEL[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

COMP2_INP_DAC
COMP2EN

0
0

Res.
COMP3EN

0

0

0

0

COMP4EN

Res.

COMP1POL

COMP1HYST[1:0]

COMPx_BLANKING[2:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

COMP1EN

COMP1MODE[1:0]

COMP1INSEL[2:0]

Res.

Res.

Res.

COMP1_INP_DAC

0

COMP5EN

Res.

0

Res.

0

Res.

COMP2MODE[1:0]

COMP2INMSEL[2:0]

COMP2INSEL

Res.

COMP2WINMODE

0

COMP6EN

COMP3MODE[1:0]

COMP3INMSEL[2:0]

0

0

COMP4MODE[1:0]

0

COMP3INSEL.

0

COMP4INMSEL[2:0]

Res.

Res.

COMP2POL

0

COMP5MODE[1:0]

0
0

0

COMP5INMSEL[2:0]

0

COMP4INSEL

0

COMP5INSEL.

COMP3OUT
SEL[3:0]
Res.

0

0

Res.

0

0

COMP4WINMODE

Res.

COMP3POL

Res.

.COMP2_BLANKING

Res.

COMP2INMSEL[3]

Res.

Res.

Res.

Res.

Res.

COMP2OUT
SEL[3:0]

Res.

0

Res.

Res.

COMP4POL

0

0

COMP6MODE[1:0]

0

Res.

0

0

COMP6INMSEL[2:0]

0
0

0

COMP6INSEL

0
COMP5POL

COMP3HYST[1:0]

0

0

Res.

0
0

0
COMP1OUT
SEL
[3:0]

COMP6WINMODE

0
0
0

0

Res.

0
0

0

COMP6POL

0
0

Res.

COMP3_BLANKING

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

COMP5HYST[1:0]

COMP4_BLANKING

Res.

COMP4INMSEL[3]

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

.COMP5_BLANKING

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

COMP6_BLANKING

Res.

COMP6INMSEL[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0
Res.

0
Res.

Reset value

Res.

COMP3_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

Register

Res.

Offset

Res.

COMP1OUT

COMP2OUT

0

COMP3OUT

17.5.8

Res.

COMP1LOCK

COMP2LOCK

0

COMP3LOCK

0x30
Reset value

COMP4OUT

0x2C
COMP2_CSR

COMP4LOCK

0x28
0

COMP5OUT

0x24
0

COMP5LOCK

0x20
Reset value

COMP6OUT

0x1C
COMP1_CSR

COMP6LOCK

Comparator (COMP)
RM0316

COMP register map
The following table summarizes the comparator registers.
Table 109. COMP register map and reset values

0
0

0

0

0

0

RM0316

Comparator (COMP)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.
0

COMP7EN

COMP7MODE[1:0]

COMP7INMSEL[2:0]

Res.

COMP7INSEL.

COMP7OUT
SEL[3:0]

Res.

Res.

COMP7POL

COMP7HYST[1:0]

COMP7_BLANKING

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

Reset value

Res.

COMP7_CSR

COMP7OUT

0x34

Register

COMP7LOCK

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 109. COMP register map and reset values (continued)

0

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

DocID022558 Rev 8

465/1141
465

Operational amplifier (OPAMP)

RM0316

18

Operational amplifier (OPAMP)

18.1

OPAMP introduction
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices embed 4 operational
amplifiers OPAMP1, OPAMP2, OPAMP3 and OPAMP4 and STM32F303x6/8 and
STM32F328x8 devices embed 1 operational amplifier OPAMP2. They can either be used as
standalone amplifiers or as follower / programmable gain amplifiers.
The operational amplifier output is internally connected to an ADC channel for measurement
purposes.

18.2

OPAMP main features
•

Rail-to-rail input/output

•

Low offset voltage

•

Capability of being configured as a standalone operational amplifier or as a
programmable gain amplifier (PGA)

•

Access to all terminals

•

Input multiplexer on inverting and non-inverting input

•

Input multiplexer can be triggered by a timer and synchronized with a PWM signal.

18.3

OPAMP functional description

18.3.1

General description
On every OPAMP, there is one 4:1 multiplexer on the non-inverting input and one 2:1
multiplexer on the inverting input.
The inverting and non inverting inputs selection is made using the VM_SEL and VP_SEL
bits respectively in the OPAMPx_CSR register.
The I/Os used as OPAMP input/outputs must be configured in analog mode in the GPIOs
registers.
The connections with dedicated I/O are summarized in the table below and in Figure 127,
Figure 128 and Figure 129.

466/1141

DocID022558 Rev 8

RM0316

Operational amplifier (OPAMP)

Table 110. Connections with dedicated I/O on STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE
OPAMP1
inverting
input

OPAMP1
non
inverting
input

OPAMP2
inverting
input

OPAMP2
non
inverting
input

OPAMP3
inverting
input

OPAMP3
non
inverting
input

OPAMP4
inverting
input

OPAMP4
non
inverting
input

PA3 (VM1)

PA1 (VP0)

PA5 (VM1)

PA7 (VP0)

PB2 (VM1)

PB0 (VP0)

PB10 (VM0)

PB13 (VP0)

PC5 (VM0)

PA7 (VP1)

PC5 (VM0)

PD14 (VP1)

PB10 (VM0)

PB13 (VP1)

PD8 (VM1)

PD11 (VP1)

-

PA3 (VP2)

-

PB0 (VP2)

-

PA1 (VP2)

-

PA4 (VP2)

-

PA5 (VP3)

-

PB14 (VP3)

-

PA5 (VP3)

-

PB11(VP3)

Table 111. Connections with dedicated I/O on STM32F303x6/8 and STM32F328x8

18.3.2

OPAMP2 inverting input

OPAMP2 non inverting input

PA5 (VM1)

PA7 (VP0)

PC5 (VM0)

PD14 (VP1)

-

PB0 (VP2)

Clock
The OPAMP clock provided by the clock controller is synchronized with the PCLK2 (APB2
clock). There is no clock enable control bit provided in the RCC controller. To use a clock
source for the OPAMP, the SYSCFG clock enable control bit must be set in the RCC
controller.

DocID022558 Rev 8

467/1141
486

Operational amplifier (OPAMP)

18.3.3

RM0316

Operational amplifiers and comparators interconnections
Internal connections between the operational amplifiers and the comparators are useful in
motor control applications. These connections are summarized in the following figures.
Figure 127. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE Comparators and
operational amplifiers interconnections (part 1)
3$3)3$3$3%


&203



3$
'$&B&+3$
'$&B&+3$
95(),17
95(),17
95(),17
95(),17

3$
3$

3RODULW\
VHOHFWLRQ

'$&B&+3$


$'&

23$03



3$

3$3$3$3%

3$


&203
,QWHUUXSW

&203

3$ 



3$
'$&B&+3$
'$&B&+3$
95(),17
95(),17
95(),17
95(),17

3$

3RODULW\
VHOHFWLRQ

3%


23$03
3&

$'&



3$
3$

7,0B%.,1
7,0B2&UHI&OHDU
7,0B,&
7,0B,&
7,0B2&UHI&OHDU
7,0B,&
7,0B2&UHI&OHDU
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,17,0B%.,1
7,0B2&UHI&OHDU
3&3$



3%
3'

&203LQWHUUXSW
,QWHUUXSW
7,0B%.,1
7,0B2&UHI&OHDU
7,0B,&
7,0B,&
7,0B2&UHI&OHDU
7,0B,&
7,0B2&UHI&OHDU
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,17,0B%.,1

&203,QWHUUXSW

&203



3%



3'
'$&B&+3$
'$&B&+3$
95(),17
95(),17
95(),17
95(),17

3RODULW\
VHOHFWLRQ

7,0B%.,1
7,0B2&UHI&OHDU
7,0B,&
7,0B,&
7,0B2&5HI&OHDU
7,0B,&
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,17,0B%.,1

069

468/1141

DocID022558 Rev 8

RM0316

Operational amplifier (OPAMP)
Figure 128. STM32F303xB/C/D/E and STM32F358xC comparators and operational
amplifiers interconnections (part 2 )
3%
3( 


&203


3%
3( 
'$&B&+3$
'$&B&+3$
95(),17
95(),17
95(),17
95(),17

3%
3$
'$&B&+3$


$'&

23$03
3%

3RODULW\6HOHFWLRQ



3%

&203LQWHUUXSW
,QWHUUXSW
7,0B%.,1
7,0B2&UHI&OHDU
7,0B,&
7,0B,&
7,0B2&5HI&OHDU
7,0B,&
7,0 B2&5HI&OHDU
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,17,0B%.,1

3&3$

&203

3' 



3%

3RODULW\6HOHFWLRQ

3'
'$&B&+3$
'$&B&+3$
95(),17
95(),17
95(),17
95(),17

3%
'$&

3%

7,0B%.,1
7,0B2&UHI&OHDU
7,0B,&
7,0B,&
7,0B2&5HI&OHDU
7,0 B%.,1
7,0B ,&
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,17,0B%.,1


$'&

23$03

&203LQWHUUXSW



3'
3%

3$3&


3%

&203
3' 

3%



3'

3RODULW\6HOHFWLRQ

'$&B&+3$
'$&B&+3$
95(),17
95(),17
95(),17
95(),17

&203,QWHUUXSW
7,0B%.,1
7,0B2&UHI&OHDU
7,0B,&
7,0B,&
7,0B2&5HI&OHDU
7,0B,&
7,0 B2&5HI&OHDU
7,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,1
7,0B%.,1
7,0B%.,1
7,0B%.,17,0B%.,17,0B%.,1

06Y9

1. Only in STM32F303xB/C and STM32F358 devices.

DocID022558 Rev 8

469/1141
486

Operational amplifier (OPAMP)

RM0316

Figure 129. STM32F303x6/8 and STM32F328x8 comparator and operational amplifier
connections
3$3$3$3%

&203


3$

3RODULW\VHOHFWLRQ

3$ '$&B&+
'$&B&+ 
95(),17
95(),17
95(),17

3$

95(),17
'$&B&+ 

3%
3%

7,0B%.,1
7,0B2&5HI&OHDU
7,0B,&
7,0B,&
7,0B2&5HI&OHDU
7,0B%.,1
7,0B2&5HI&OHDU
7,0B,&


23$03

3&

&203LQWHUUXSW
,QWHUUXSW

$'&



3$
3$

06Y9

1. DAC1_CH2 and DAC2_CH1 outputs are connected directly, thus PA5 and PA6 are not available as inputs
as COMP2_INM. They can be used as GPIOs.

18.3.4

Using the OPAMP outputs as ADC inputs
In order to use OPAMP outputs as ADC inputs, the operational amplifiers must be enabled
and the ADC must use the OPAMP output channel number:

18.3.5

•

For OPAMP1, ADC1 channel 3 is used (only in STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE).

•

For OPAMP2, ADC2 channel 3 is used.

•

For OPAMP3, ADC3 channel 1 is used (only in STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE).

•

For OPAMP4, ADC4 channel 3 is used (only in STM32F303xB/C/D/E, STM32F358xC
and STM32F398xE).

Calibration
The OPAMP interface continuously sends trimmed offset values to the 4 operational
amplifiers. At startup, these values are initialized with the preset ‘factory’ trimming value.
Furthermore each operational amplifier offset can be trimmed by the user.
The user can switch from the ‘factory’ values to the ‘user’ trimmed values using the
USER_TRIM bit in the OPAMP control register. This bit is reset at startup (‘factory’ values
are sent to the operational amplifiers).
The rail-to-rail input stage of the OPAMP is composed of two differential pairs:
•

One pair composed of NMOS transistors

•

One pair composed of PMOS transistors.

As these two pairs are independent, the trimming procedure calibrates each one separately.
The TRIMOFFSETN bits calibrate the NMOS differential pair offset and the TRIMOFFSETP
bits calibrate the PMOS differential pair offset.
To calibrate the NMOS differential pair, the following conditions must be met: CALON=1 and
CALSEL=11. In this case, an internal high voltage reference (0.9 x VDDA) is generated and

470/1141

DocID022558 Rev 8

RM0316

Operational amplifier (OPAMP)
applied on the inverting and non inverting OPAMP inputs connected together. The voltage
applied to both inputs of the OPAMP can be measured (the OPAMP reference voltage can
be output through the TSTREF bit and connected internally to an ADC channel; refer to
Section 15: Analog-to-digital converters (ADC) on page 305). The software should
increment the TRIMOFFSETN bits in the OPAMP control register from 0x00 to the first value
that causes the OUTCAL bit to change from 1 to 0 in the OPAMP register. If the OUTCAL bit
is reset, the offset is calibrated correctly and the corresponding trimming value must be
stored.
The calibration of the PMOS differential pair is performed in the same way, with two
differences: the TRIMOFFSETP bits-fields are used and the CALSEL bits must be
programmed to ‘01’ (an internal low voltage reference (0.1 x VDDA) is generated and applied
on the inverting and non inverting OPAMP inputs connected together).

Note:

During calibration mode, to get the correct OUTCAL value, please make sure the
OFFTRIMmax delay (specified in the datasheet electrical characteristics section) has
elapsed between the write of a trimming value (TRIMOFFSETP or TRIMOFFSETN) and the
read of the OUTCAL value,
To calibrate the NMOS differential pair, use the following software procedure:
1.

Enable OPAMP by setting the OPAMPxEN bit

2.

Enable the user offset trimming by setting the USERTRIM bit

3.

Connect VM and VP to the internal reference voltage by setting the CALON bit

4.

Set CALSEL to 11 (OPAMP internal reference =0.9 x VDDA)

5.

In a loop, increment the TRIMOFFSETN value. To exit from the loop, the OUTCAL bit
must be reset. In this case, the TRIMOFFSETN value must be stored.

The same software procedure must be applied for PMOS differential pair calibration with
CALSEL = 01 (OPAMP internal reference = 0.1 VDDA).

18.3.6

Timer controlled Multiplexer mode
The selection of the OPAMP inverting and non inverting inputs can be done automatically. In
this case, the switch from one input to another is done automatically. This automatic switch
is triggered by the TIM1 CC6 output arriving on the OPAMP input multiplexers.
This is useful for dual motor control with a need to measure the currents on the 3 phases
instantaneously on a first motor and then on the second motor.
The automatic switch is enabled by setting the TCM_EN bit in the OPAMP control register.
The inverting and non inverting inputs selection is performed using the VPS_SEL and
VMS_SEL bit fields in the OPAMP control register. If the TCM_EN bit is cleared, the
selection is done using the VP_SEL and VM_SEL bit fields in the OPAMP control register.

DocID022558 Rev 8

471/1141
486

Operational amplifier (OPAMP)

RM0316
Figure 130. Timer controlled Multiplexer mode

&&5

7FRXQWHU

7FRXQWHU
$'&VDPSOLQJSRLQWV
7RXWSXW RXWRI
7RXWSXW RXWRI
7&&RXWSXWDUULYLQJRQ23$03LQSXWPX[
6HF

/HJHQG

'HI

6HF

'HI

6HF

23$03LQSXWVHOHFWLRQ
'HI GHIDXOW23$03LQSXWVHOHFWLRQ
6HF VHFRQGDU\23$03LQSXWVHOHFWLRQ

23$03LQSXWVHOHFWLRQW\SH

069

18.3.7

OPAMP modes
The operational amplifier inputs and outputs are all accessible on terminals. The amplifiers
can be used in multiple configuration environments:
•

Standalone mode (external gain setting mode)

•

Follower configuration mode

•

PGA modes

Important note: the amplifier output pin is directly connected to the output pad to minimize
the output impedance. It cannot be used as a general purpose I/O, even if the amplifier is
configured as a PGA and only connected to the ADC channel.
Note:

The impedance of the signal must be maintained below a level which avoids the input
leakage to create significant artefacts (due to a resistive drop in the source). Please refer to
the electrical characteristics section in the datasheet for further details.

Standalone mode (external gain setting mode)
The external gain setting mode gives full flexibility to choose the amplifier configuration and
feedback networks. This mode is enabled by writing the VM_SEL bits in the OPAMPx_CR
register to 00 or 01, to connect the inverting inputs to one of the two possible I/Os.

472/1141

DocID022558 Rev 8

RM0316

Operational amplifier (OPAMP)
Figure 131. Standalone mode: external gain setting mode
670
60
60
60
60



$'&

2S$PS
S
S

6-



6-

069

1. This figure gives an example in an inverting configuration. Any other option is possible, including
comparator mode.

Follower configuration mode
The amplifier can be configured as a follower, by setting the VM_SEL bits to 11 in the
OPAMPx_CR register. This allows you for instance to buffer signals with a relatively high
impedance. In this case, the inverting inputs are free and the corresponding ports can be
used as regular I/Os.

DocID022558 Rev 8

473/1141
486

Operational amplifier (OPAMP)

RM0316
Figure 132. Follower configuration
670

60
60
60
60



$'&

S
S
2S$PS

  6-
"WBJMBCMF
*0T
6-



$OZD\VFRQQHFWHG
WR23$03RXWSXW
FDQEHXVHG
GXULQJGHEXJ 

069

1. This figure gives an example in an inverting configuration. Any other option is possible, including
comparator mode.

Programmable Gain Amplifier mode
The Programmable Gain Amplifier (PGA) mode is enabled by writing the VM_SEL bits to 10
in the OPAMPx_CR register. The gain is set using the PGA_GAIN bits which must be set to
0x00..0x11 for gains ranging from 2 to 16.
In this case, the inverting inputs are internally connected to the central point of a built-in gain
setting resistive network. Figure 133: PGA mode, internal gain setting (x2/x4/x8/x16),
inverting input not used shows the internal connection in this mode.
An alternative option in PGA mode allows you to route the central point of the resistive
network on one of the I/Os connected to the non-inverting input. This is enabled using the
PGA_GAIN bits in OPAMPx_CR register:
•

10xx values are setting the gain and connect the central point to one of the two
available inputs

•

11xx values are setting the gain and connect the central point to the second available
input

This feature can be used for instance to add a low-pass filter to PGA, as shown in
Figure 134: PGA mode, internal gain setting (x2/x4/x8/x16), inverting input used for filtering.
Please note that the cut-off frequency is changed if the gain is modified (refer to the
electrical characteristics section of the datasheet for details on resistive network elements.

474/1141

DocID022558 Rev 8

RM0316

Operational amplifier (OPAMP)
Figure 133. PGA mode, internal gain setting (x2/x4/x8/x16), inverting input not used
670

60
60
60
60



$'&

2S$PS
S
S

 6- 



6-

"WBJMBCMF
*0T

$OZD\VFRQQHFWHG
WR23$03RXWSXW
FDQEHXVHG
GXULQJGHEXJ 

069

Figure 134. PGA mode, internal gain setting (x2/x4/x8/x16), inverting input used for
filtering

670

60
60
60
60
6-
6-



$'&

2S$PS
S
S




$OORZV
RSWLRQDOORZ
SDVVILOWHULQJ
1%JDLQ
GHSHQGVRQ
FXWRII
IUHTXHQF\

(TXLYDOHQWWR

 *  ..
 * 
3*$QHWZRUN.. *  ..
 *  ..
069

DocID022558 Rev 8

475/1141
486

Operational amplifier (OPAMP)

RM0316

18.4

OPAMP registers

18.4.1

OPAMP1 control register (OPAMP1_CSR)

Note:

This register is only available in STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices.
Address offset : 0x38
Reset value: 0xXXXX 0000

31
LOCK

30

29

28

27

TSTR
OUTCAL
EF

rw

r

rw

15

14

13

26

25

24

23

22

TRIMOFFSETN

21

11

19

18

rw

10

9

PGA_GAIN

CALSEL

CAL
ON

VPS_SEL

rw

rw

rw

rw

8

7

VMS_SE TCM_
L
EN
rw

6

5

VM_SEL

rw

rw

17

USER_
TRIM

TRIMOFFSETP

rw
12

20

PGA_GAIN

rw
4
Res.

3

rw

2
VP_SEL

1

rw

Bit 30 OUTCAL:
OPAMP output status flag, when the OPAMP is used as comparator during calibration.
0: Non-inverting < inverting
1: Non-inverting > inverting.
Bit 29 TSTREF:
This bit is set and cleared by software. It is used to output the internal reference voltage
(VREFOPAMP1).
0: VREFOPAMP1 is output.
1: VREFOPAMP1 is not output.
Bits 23:19 TRIMOFFSETP: Offset trimming value (PMOS)
Bit 18 USER_TRIM: User trimming enable.
This bit is used to configure the OPAMP offset.
0: User trimming disabled.
1: User trimming enabled.

476/1141

DocID022558 Rev 8

0

FORCE OPAMP
_VP
1EN

Bit 31 LOCK: OPAMP 1 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
This bit is used to configure the OPAMP1_CSR register as read-only.
0: OPAMP1_CSR is read-write.
1: OPAMP1_CSR is read-only.

Bits 28:24 TRIMOFFSETN: Offset trimming value (NMOS)

16

rw

rw

RM0316

Operational amplifier (OPAMP)

Bits 17:14 PGA_GAIN: Gain in PGA mode
0X00 = Non-inverting gain = 2
0X01 = Non-inverting gain = 4
0X10 = Non-inverting gain = 8
0X11 = Non-inverting gain = 16
1000 = Non-inverting gain = 2 - Internal feedback connected to VM0
1001 = Non-inverting gain = 4 - Internal feedback connected to VM0
1010 = Non-inverting gain = 8 - Internal feedback connected to VM0
1011 = Non-inverting gain = 16 - Internal feedback connected to VM0
1100 = Non-inverting gain = 2 - Internal feedback connected to VM1
1101 = Non-inverting gain = 4 - Internal feedback connected to VM1
1110 = Non-inverting gain = 8 - Internal feedback connected to VM1
1111 = Non-inverting gain = 16 - Internal feedback connected to VM1
Bits 13:12 CALSEL: Calibration selection
This bit is set and cleared by software. It is used to select the offset calibration bus used to generate
the internal reference voltage when CALON = 1 or FORCE_VP= 1.
00 = VREFOPAMP = 3.3% VDDA
01 = VREFOPAMP= 10% VDDA
10 = VREFOPAMP= 50% VDDA
11 = VREFOPAMP = 90% VDDA
Bit 11 CALON: Calibration mode enable
This bit is set and cleared by software. It is used to enable the calibration mode connecting VM and
VP to the OPAMP internal reference voltage.
0: Calibration mode disabled.
1: Calibration mode enabled.
Bits 10:9 VPS_SEL: OPAMP1 Non inverting input secondary selection.
These bits are set and cleared by software. They are used to select the OPAMP1 non inverting input
when TCM_EN = 1.
00: PA7 used as OPAMP1 non inverting input
01: PA5 used as OPAMP1 non inverting input
10: PA3 used as OPAMP1 non inverting input
11: PA1 used as OPAMP1 non inverting input
Bit 8 VMS_SEL: OPAMP1 inverting input secondary selection
This bit is set and cleared by software. It is used to select the OPAMP1 inverting input when
TCM_EN = 1.
0: PC5 (VM0) used as OPAMP1 inverting input
1: PA3 (VM1) used as OPAMP1 inverting input
Bit 7 TCM_EN: Timer controlled Mux mode enable
This bit is set and cleared by software. It is used to control automatically the switch between the
default selection (VP_SEL and VM_SEL) and the secondary selection (VPS_SEL and VMS_SEL) of
the inverting and non inverting inputs.
Bits 6:5 VM_SEL: OPAMP1 inverting input selection.
These bits are set and cleared by software. They are used to select the OPAMP1 inverting input.
00: PC5 (VM0) used as OPAMP1 inverting input
01: PA3 (VM1) used as OPAMP1 inverting input
10: Resistor feedback output (PGA mode)
11: follower mode
Bit 4 Reserved, must be kept at reset value.

DocID022558 Rev 8

477/1141
486

Operational amplifier (OPAMP)

RM0316

Bits 3:2 VP_SEL: OPAMP1 Non inverting input selection.
These bits are set and cleared by software. They are used to select the OPAMP1 non inverting
input.
00: PA7 used as OPAMP1 non inverting input
01: PA5 used as OPAMP1 non inverting input
10: PA3 used as OPAMP1 non inverting input
11: PA1 used as OPAMP1 non inverting input
Bit 1 FORCE_VP:
This bit forces a calibration reference voltage on non-inverting input and disables external
connections.
0: Normal operating mode. Non-inverting input connected to inputs.
1: Calibration mode. Non-inverting input connected to calibration reference voltage.
Bit 0 OPAMP1EN: OPAMP1 enable.
This bit is set and cleared by software. It is used to enable the OPAMP1.
0: OPAMP1 is disabled.
1: OPAMP1 is enabled.

18.4.2

OPAMP2 control register (OPAMP2_CSR)
Address offset: 0x3C
Reset value: 0xXXXX 0000

31

30

29

LOCK

OUT
CAL

TSTR
EF

rw

r

rw

15

14

13

28

27

26

25

24

23

22

TRIMOFFSETN

21

11

PGA_GAIN

CALSEL

CAL
ON

rw

rw

rw

19

18

rw

10

9

8

7
TCM_
EN

VM_SEL

rw

rw

VPS_SEL

VMS_
SEL

rw

rw

6

5

17

USER_
TRIM

TRIMOFFSETP

rw
12

20

PGA_GAIN

rw
4
Res.

3

rw

2
VP_SEL

1

rw

Bit 30 OUTCAL:
OPAMP output status flag, when the OPAMP is used as comparator during calibration.
0: Non-inverting < inverting
1: Non-inverting > inverting.
Bit 29 TSTREF:
This bit is set and cleared by software. It is used to output the internal reference voltage
(VREFOPAMP2).
0: VREFOPAMP2 is output.
1: VREFOPAMP2 is not output.
Bits 23:19 TRIMOFFSETP: Offset trimming value (PMOS)

478/1141

DocID022558 Rev 8

0

FORCE OPAMP
_VP
2EN

Bit 31 LOCK: OPAMP 2 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
This bit is used to configure the OPAMP2_CSR register as read-only.
0: OPAMP2_CSR is read-write.
1: OPAMP2_CSR is read-only.

Bits 28:24 TRIMOFFSETN: Offset trimming value (NMOS)

16

rw

rw

RM0316

Operational amplifier (OPAMP)

Bit 18 USER_TRIM: User trimming enable.
This bit is used to configure the OPAMP offset.
0: User trimming disabled.
1: User trimming enabled.
Bits 17:14 PGA_GAIN: gain in PGA mode
0X00 = Non-inverting gain = 2
0X01 = Non-inverting gain = 4
0X10 = Non-inverting gain = 8
0X11 = Non-inverting gain = 16
1000 = Non-inverting gain = 2 - Internal feedback connected to VM0
1001 = Non-inverting gain = 4 - Internal feedback connected to VM0
1010 = Non-inverting gain = 8 - Internal feedback connected to VM0
1011 = Non-inverting gain = 16 - Internal feedback connected to VM0
1100 = Non-inverting gain = 2 - Internal feedback connected to VM1
1101 = Non-inverting gain = 4 - Internal feedback connected to VM1
1110 = Non-inverting gain = 8 - Internal feedback connected to VM1
1111 = Non-inverting gain = 16 - Internal feedback connected to VM1
Bits 13:12 CALSEL: Calibration selection
This bit is set and cleared by software. It is used to select the offset calibration bus used to generate
the internal reference voltage when CALON = 1 or FORCE_VP= 1.
00 = VREFOPAMP = 3.3% VDDA
01 = VREFOPAMP = 10% VDDA
10 = VREFOPAMP = 50% VDDA
11 = VREFOPAMP = 90% VDDA
Bit 11 CALON: Calibration mode enable
This bit is set and cleared by software. It is used to enable the calibration mode connecting VM and
VP to the OPAMP internal reference voltage.
0: calibration mode disabled.
1: calibration mode enabled.
Bits 10:9 VPS_SEL: OPAMP2 Non inverting input secondary selection.
These bits are set and cleared by software. They are used to select the OPAMP2 non inverting input
when TCM_EN = 1.
00: PD14 used as OPAMP2 non inverting input (STM32F303xB/C and STM32F358C devices only)
01: PB14 used as OPAMP2 non inverting input
10: PB0 used as OPAMP2 non inverting input
11: PA7 used as OPAMP2 non inverting input
Bit 8 VMS_SEL: OPAMP2 inverting input secondary selection
This bit is set and cleared by software. It is used to select the OPAMP2 inverting input when
TCM_EN = 1.
0: PC5 (VM0) used as OPAMP2 inverting input
1: PA5 (VM1) used as OPAMP2 inverting input
Bit 7 TCM_EN: Timer controlled Mux mode enable.
This bit is set and cleared by software. It is used to control automatically the switch between the
default selection (VP_SEL and VM_SEL) and the secondary selection (VPS_SEL and VMS_SEL) of
the inverting and non inverting inputs.

DocID022558 Rev 8

479/1141
486

Operational amplifier (OPAMP)

RM0316

Bit 6:5 VM_SEL: OPAMP2 inverting input selection.
Theses bits are set and cleared by software. They are used to select the OPAMP2 inverting input.
00: PC5 (VM0) used as OPAMP2 inverting input
01: PA5 (VM1) used as OPAMP2 inverting input
10: Resistor feedback output (PGA mode)
11: follower mode
Bit 4 Reserved, must be kept at reset value.
Bits 3:2 VP_SEL: OPAMP2 non inverting input selection.
Theses bits are set/reset by software. They are used to select the OPAMP2 non inverting input.
00: PD14 used as OPAMP2 non inverting input (STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE devices only)
01: PB14 used as OPAMP2 non inverting input
10: PB0 used as OPAMP2 non inverting input
11: PA7 used as OPAMP2 non inverting input
Bit 1 FORCE_VP:
This bit forces a calibration reference voltage on non-inverting input and disables external
connections.
0: Normal operating mode. Non-inverting input connected to inputs.
1: Calibration mode. Non-inverting input connected to calibration reference voltage.
Bit 0 OPAMP2EN: OPAMP2 enable.
This bit is set and cleared by software. It is used to select the OPAMP2.
0: OPAMP2 is disabled.
1: OPAMP2 is enabled.

18.4.3

OPAMP3 control register (OPAMP3_CSR)

Note:

This register is only available in STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices.
Address offset: 0x40
Reset value: 0xXXXX 0000

31

30

29

LOCK

OUT
CAL

TSTR
EF

rw

r

rw

15

14

13

28

27

25

24

23

22

TRIMOFFSETN

21

11

PGA_GAIN

CALSEL

rw

rw

rw

20

19

18
USER_
TRIM

TRIMOFFSETP

rw
12

CAL
ON

480/1141

26

rw

10

9

8

7
TCM_
EN

VM_SEL

rw

rw

VPS_SEL

VMS_
SEL

rw

rw

6

5

DocID022558 Rev 8

17

PGA_GAIN

rw
4
Res.

3

2
VP_SEL
rw

16

rw
1

0

FORCE OPAMP
_VP
3EN
rw

rw

RM0316

Operational amplifier (OPAMP)

Bit 31 LOCK: OPAMP 3 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
This bit is used to configure the OPAMP3_CSR register as read-only.
0: OPAMP3_CSR is read-write.
1: OPAMP3_CSR is read-only.
Bit 30 OUTCAL:
OPAMP output status flag, when the OPAMP is used as comparator during calibration.
0: Non-inverting < inverting
1: Non-inverting > inverting.
Bit 29 TSTREF:
This bit is set and cleared by software. It is used to output the internal reference voltage
(VREFOPAMP3).
0: VREFOPAMP3 is output.
1: VREFOPAMP3 is not output.
Bits 28:24 TRIMOFFSETN: Offset trimming value (NMOS)
Bits 23:19 TRIMOFFSETP: Offset trimming value (PMOS)
Bit 18 USER_TRIM: User trimming enable.
This bit is used to configure the OPAMP offset.
0: User trimming disabled.
1: User trimming enabled.
Bits 17:14 PGA_GAIN: gain in PGA mode
0X00 = Non-inverting gain = 2
0X01 = Non-inverting gain = 4
0X10 = Non-inverting gain = 8
0X11 = Non-inverting gain = 16
1000 = Non-inverting gain = 2 - Internal feedback connected to VM0
1001 = Non-inverting gain = 4 - Internal feedback connected to VM0
1010 = Non-inverting gain = 8 - Internal feedback connected to VM0
1011 = Non-inverting gain = 16 - Internal feedback connected to VM0
1100 = Non-inverting gain = 2 - Internal feedback connected to VM1
1101 = Non-inverting gain = 4 - Internal feedback connected to VM1
1110 = Non-inverting gain = 8 - Internal feedback connected to VM1
1111 = Non-inverting gain = 16 - Internal feedback connected to VM1
Bits 13:12 CALSEL: Calibration selection
This bit is set and cleared by software. It is used to select the offset calibration bus used to generate
the internal reference voltage when CALON = 1 or FORCE_VP= 1.
00 = VREFOPAMP = 3.3% VDDA
01 = VREFOPAMP = 10% VDDA
10 = VREFOPAMP = 50% VDDA
11 = VREFOPAMP = 90% VDDA
Bit 11 CALON: Calibration mode enable
This bit is set/cleared by software. It allows enabling the calibration mode connecting VM and VP to
internal reference voltage.
0: calibration mode disabled.
1: calibration mode enabled.

DocID022558 Rev 8

481/1141
486

Operational amplifier (OPAMP)

RM0316

Bits 10:9 VPS_SEL: OPAMP3 non inverting input secondary selection.
These bits are set/reset by software. They allow selecting the OPAMP3 non inverting input when
TCM_EN = 1.
00: PB13 used as OPAMP3 non inverting input
01: PA5 used as OPAMP3 non inverting input
10: PA1 used as OPAMP3 non inverting input
11: PB0used as OPAMP3 non inverting input
Bit 8 VMS_SEL: OPAMP3 inverting input secondary selection
This bit is set and cleared by software. It is used to select the OPAMP3 inverting input when
TCM_EN = 1.
0: PB10 (VM0) used as OPAMP3 inverting input
1: PB2 (VM1) used as OPAMP3 inverting input
Bit 7 TCM_EN: Timer controlled multiplexer mode enable.
This bit is set and cleared by software. It is used to control automatically the switch between the
default selection (VP_SEL and VM_SEL) and the secondary selection (VPS_SEL and VMS_SEL) of
the inverting and non inverting inputs.
Bit 6:5 VM_SEL: OPAMP3 inverting input selection.
Theses bits are set/reset by software. They allow selecting the OPAMP3 inverting input.
00: PB10 (VM0) used as OPAMP3 inverting input
01: PB2 (VM1) used as OPAMP3 inverting input
10: Resistor feedback output (PGA mode)
11: follower mode
Bit 4 Reserved, must be kept at reset value.
Bits 3:2 VP_SEL: OPAMP3 Non inverting input selection.
Theses bits are and cleared by software. They are used to select the OPAMP3 non inverting input.
00: PB13 used as OPAMP3 non inverting input
01: PA5 used as OPAMP3 non inverting input
10: PA1 used as OPAMP3 non inverting input
11: PB0 used as OPAMP3 non inverting input
Bit 1 FORCE_VP:
This bit forces a calibration reference voltage on non-inverting input and disables external
connections.
0: Normal operating mode. Non-inverting input connected to inputs.
1: Calibration mode. Non-inverting input connected to calibration reference voltage.
Bit 0 OPAMP3EN: OPAMP3 enable.
This bit is set and cleared by software. It is used to enable the OPAMP3.
0: OPAMP3 is disabled.
1: OPAMP3 is enabled.

482/1141

DocID022558 Rev 8

RM0316

Operational amplifier (OPAMP)

18.4.4

OPAMP4 control register (OPAMP4_CSR)

Note:

This register is only available in STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices.
Address offset: 0x44
Reset value: 0xXXXX 0000

31

30

29

LOCK

OUT
CAL

TSTR
EF

rw

r

rw

15

14

13

28

27

26

25

24

23

22

TRIMOFFSETN

21

11

PGA_GAIN

CALSEL

CAL
ON

rw

rw

rw

19

18

rw

10

9

8

7
TCM_
EN

VM_SEL

rw

rw

VPS_SEL

VMS_
SEL

rw

rw

6

5

17

USER_
TRIM

TRIMOFFSETP

rw
12

20

PGA_GAIN

rw
4
Res.

3

rw

2
VP_SEL

16

1

0

FORCE OPAMP
_VP
4EN

rw

rw

rw

Bit 31 LOCK: OPAMP 4 lock
This bit is write-once. It is set by software. It can only be cleared by a system reset.
This bit is used to configure the OPAMP4_CSR register as read-only.
0: OPAMP4_CSR is read-write.
1: OPAMP4_CSR is read-only.
Bit 30 OUTCAL:
OPAMP output status flag, when the OPAMP is used as comparator during calibration.
0: Non-inverting < inverting
1: Non-inverting > inverting.
Bit 29 TSTREF:
This bit is set and cleared by software. It is used to output the internal reference voltage
(VREFOPAMP4).
0: VREFOPAMP4 is output.
1: VREFOPAMP4 is not output.
Bits 28:24 TRIMOFFSETN: Offset trimming value (NMOS)
Bits 23:19 TRIMOFFSETP: Offset trimming value (PMOS)
Bit 18 USER_TRIM: User trimming enable.
This bit is used to configure the OPAMP offset.
0: User trimming disabled.
1: User trimming enabled.

DocID022558 Rev 8

483/1141
486

Operational amplifier (OPAMP)

RM0316

Bits 17:14 PGA_GAIN: Gain in PGA mode
0X00 = Non-inverting gain = 2
0X01 = Non-inverting gain = 4
0X10 = Non-inverting gain = 8
0X11 = Non-inverting gain = 16
1000 = Non-inverting gain = 2 - Internal feedback connected to VM0
1001 = Non-inverting gain = 4 - Internal feedback connected to VM0
1010 = Non-inverting gain = 8 - Internal feedback connected to VM0
1011 = Non-inverting gain = 16 - Internal feedback connected to VM0
1100 = Non-inverting gain = 2 - Internal feedback connected to VM1
1101 = Non-inverting gain = 4 - Internal feedback connected to VM1
1110 = Non-inverting gain = 8 - Internal feedback connected to VM1
1111 = Non-inverting gain = 16 - Internal feedback connected to VM1
Bits 13:12 CALSEL: Calibration selection
This bit is set and cleared by software. It is used to select the offset calibration bus used to generate
the internal reference voltage when CALON = 1 or FORCE_VP= 1.
00 = VREFOPAMP = 3.3% VDDA
01 = VREFOPAMP = 10% VDDA
10 = VREFOPAMP = 50% VDDA
11 = VREFOPAMP = 90% VDDA
Bit 11 CALON: Calibration mode enable
This bit is set and cleared by software. It is used to enable the calibration mode connecting VM and
VP to the OPAMP internal reference voltage.
0: Calibration mode disabled.
1: Calibration mode enabled.
Bits 10:9 VPS_SEL: OPAMP4 Non inverting input secondary selection.
These bits are se and cleared by software. They allow selecting the OPAMP4 non inverting input,
when TCM_EN = 1.
00: PD11 used as OPAMP4 non inverting input
01: PB11 used as OPAMP4 non inverting input
10: PA4 used as OPAMP4 non inverting input
11: PB13 used as OPAMP4 non inverting input
Bit 8 VMS_SEL: OPAMP4 inverting input secondary selection
This bit is set and cleared by software. It allows selecting the OPAMP4 inverting input, when
TCM_EN = 1.
0: PB10 (VM0) used as OPAMP4 inverting input
1: PD8 (VM1) used as OPAMP4 inverting input
Bit 7 TCM_EN: Timer controlled Mux mode enable
This bit is set and cleared by software.It is used to control automatically the switch between the
default selection (VP_SEL and VM_SEL) and the secondary selection (VPS_SEL and VMS_SEL) of
the inverting and non inverting inputs.
Bits 6:5 VM_SEL: OPAMP4 inverting input selection.
Theses bits are set/reset by software. They allow selecting the OPAMP4 inverting input.
00: PB10 (VM0) used as OPAMP4 inverting input
01: PD8 (VM1) used as OPAMP4 inverting input
10: Resistor feedback output (PGA mode)
11: follower mode
Bit 4 Reserved, must be kept at reset value.

484/1141

DocID022558 Rev 8

RM0316

Operational amplifier (OPAMP)

Bits 3:2 VP_SEL: OPAMP4 Non inverting input selection.
Theses bits are set and cleared by software. They allow selecting the OPAMP4 non inverting input.
00: PD11 used as OPAMP4 non inverting input
01: PB11 used as OPAMP4 non inverting input
10: PA4 used as OPAMP4 non inverting input
11: PB13 used as OPAMP4 non inverting input
Bit 1 FORCE_VP:
This description will be given in a future version of this document.
Bit 0 OPAMP4EN: OPAMP4 enable.
This bit is set and cleared by software. I allows enabling the OPAMP4.
0: OPAMP4 is disabled.
1: OPAMP4 is enabled.

DocID022558 Rev 8

485/1141
486

Operational amplifier (OPAMP)

18.4.5

RM0316

OPAMP register map
The following table summarizes the OPAMP registers.

0

VP_SEL
0

VP_SEL

0

0

0

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

486/1141

DocID022558 Rev 8

FORCE_VP

OPAMP1EN
0

FORCE_VP
0

0

OPAMP2EN

VP_SEL

Res
Res
0

0

0

0

FORCE_VP

0

VP_SEL

Res

VM_SEL
VM_SEL
0

0

Res

0

VM_SEL

TCM_EN

0

0

VM_SEL

VMS_SEL

0

0

0

OPAMP3EN

0

TCM_EN

VPS_SEL
0

0

0

0

0

FORCE_VP

0

0

0

OPAMP4EN

0

0

VMS_SEL

0

0

0

TCM_EN

0

VPS_SEL

0

0

0

VMS_SEL

X X X X X

0

0

0

TCM_EN

X

CALON

CALSEL
0

0
VPS_SEL

X

0

0

VPS _SEL

X

0

CALON

X

X X X X X

0
CALON

X

X

0

0

VMS_SEL

X

0

0

CALON

X

0

CALSEL

X

X

0

CALSEL

X

X

X X X X X

0

CALSEL

X

X

PGA_GAIN

X

X

X

0

PGA_GAIN

X

X

0

PGA_GAIN

TSTREF

Reset value

X

X

0

PGA_GAIN

OPAMP4_CSR

X

X

USER_TRIM

X

X

X X X X X
USER_TRIM

X

X

X

USER_TRIM

X

X

USER_TRIM

TSTREF

Reset value

X

X

TRIMOFFSETP

OPAMP3_CSR

X

X

TRIMOFFSETP

X

X

TRIMOFFSETP

X

X

TRIMOFFSETP

TSTREF

X

TRIMOFFSETN

LOCK

Reset value

X

TRIMOFFSETN

OPAMP2_CSR

X

TRIMOFFSETN

TSTREF
X

TRIMOFFSETN

LOCK

OUTCAL
X
OUTCAL

0x44

X

LOCK

0x40

Reset value

OUTCAL

0x3C

OPAMP1_CSR

LOCK

0x38

Register

OUTCAL

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 112. OPAMP register map and reset values

0

0

RM0316

Touch sensing controller (TSC)

19

Touch sensing controller (TSC)

19.1

Introduction
The touch sensing controller provides a simple solution for adding capacitive sensing
functionality to any application. Capacitive sensing technology is able to detect finger
presence near an electrode which is protected from direct touch by a dielectric (for example
glass, plastic). The capacitive variation introduced by the finger (or any conductive object) is
measured using a proven implementation based on a surface charge transfer acquisition
principle.
The touch sensing controller is fully supported by the STMTouch touch sensing firmware
library which is free to use and allows touch sensing functionality to be implemented reliably
in the end application.

19.2

TSC main features
The touch sensing controller has the following main features:

Note:

•

Proven and robust surface charge transfer acquisition principle

•

Supports up to 24 capacitive sensing channels

•

Up to 8 capacitive sensing channels can be acquired in parallel offering a very good
response time

•

Spread spectrum feature to improve system robustness in noisy environments

•

full hardware management of the charge transfer acquisition sequence

•

Programmable charge transfer frequency

•

Programmable sampling capacitor I/O pin

•

Programmable channel I/O pin

•

Programmable max count value to avoid long acquisition when a channel is faulty

•

Dedicated end of acquisition and max count error flags with interrupt capability

•

One sampling capacitor for up to 3 capacitive sensing channels to reduce the system
components

•

Compatible with proximity, touchkey, linear and rotary touch sensor implementation

•

Designed to operate with STMTouch touch sensing firmware library

The number of capacitive sensing channels is dependent on the size of the packages and
subject to IO availability.

DocID022558 Rev 8

487/1141
505

Touch sensing controller (TSC)

RM0316

19.3

TSC functional description

19.3.1

TSC block diagram
The block diagram of the touch sensing controller is shown in Figure 135: TSC block
diagram.
Figure 135. TSC block diagram

39.#
0ULSE GENERATOR
F(#,+

'?)/

#LOCK
PRESCALERS

'?)/
'?)/

3PREAD SPECTRUM

'?)/
'?)/
'?)/

'ROUP COUNTERS

)/ CONTROL
LOGIC

'?)/
'?)/

43#?)/'#2
43#?)/'#2
'X?)/
'X?)/
43#?)/'X#2

'X?)/
'X?)/

-36

19.3.2

Surface charge transfer acquisition overview
The surface charge transfer acquisition is a proven, robust and efficient way to measure a
capacitance. It uses a minimum number of external components to operate with a single
ended electrode type. This acquisition is designed around an analog I/O group which is
composed of four GPIOs (see Figure 136). Several analog I/O groups are available to allow
the acquisition of several capacitive sensing channels simultaneously and to support a
larger number of capacitive sensing channels. Within a same analog I/O group, the
acquisition of the capacitive sensing channels is sequential.
One of the GPIOs is dedicated to the sampling capacitor CS. Only one sampling capacitor
I/O per analog I/O group must be enabled at a time.

488/1141

DocID022558 Rev 8

RM0316

Touch sensing controller (TSC)
The remaining GPIOs are dedicated to the electrodes and are commonly called channels.
For some specific needs (such as proximity detection), it is possible to simultaneously
enable more than one channel per analog I/O group.
Figure 136. Surface charge transfer analog I/O group structure

%LECTRODE 

23

'?)/

!NALOG
)/ GROUP

#8

'?)/
#3

%LECTRODE 

23

'?)/

23

'?)/

#8
%LECTRODE 

#8

-36

Note:

Gx_IOy where x is the analog I/O group number and y the GPIO number within the selected
group.
The surface charge transfer acquisition principle consists of charging an electrode
capacitance (CX) and transferring a part of the accumulated charge into a sampling
capacitor (CS). This sequence is repeated until the voltage across CS reaches a given
threshold (VIH in our case). The number of charge transfers required to reach the threshold
is a direct representation of the size of the electrode capacitance.
The Table 113 details the charge transfer acquisition sequence of the capacitive sensing
channel 1. States 3 to 7 are repeated until the voltage across CS reaches the given
threshold. The same sequence applies to the acquisition of the other channels. The
electrode serial resistor RS improves the ESD immunity of the solution.

DocID022558 Rev 8

489/1141
505

Touch sensing controller (TSC)

RM0316
Table 113. Acquisition sequence summary

State

G1_IO1
(electrode)

G1_IO2
(sampling)

#1

Input floating
with analog
switch closed

Output opendrain low with
analog switch
closed

#2
#3

G1_IO4
(electrode)

State description

Input floating with analog switch Discharge all CX and
CS
closed

Input floating
Output pushpull high

Dead time

Input floating

#4
#5

G1_IO3
(electrode)

Charge CX1

Input floating
Input floating with analog switch
closed

Dead time
Input floating

Charge transfer from
CX1 to CS

#6

Input floating

Dead time

#7

Input floating

Measure CS voltage

The voltage variation over the time on the sampling capacitor CS is detailed below:
Figure 137. Sampling capacitor voltage variation

9&6
9''

7KUHVKROG 9,+

W
%XUVWGXUDWLRQ
069

19.3.3

Reset and clocks
The TSC clock source is the AHB clock (HCLK). Two programmable prescalers are used to
generate the pulse generator and the spread spectrum internal clocks:
•

The pulse generator clock (PGCLK) is defined using the PGPSC[2:0] bits of the
TSC_CR register

•

The spread spectrum clock (SSCLK) is defined using the SSPSC bit of the TSC_CR
register

The Reset and Clock Controller (RCC) provides dedicated bits to enable the touch sensing
controller clock and to reset this peripheral. For more information, please refer to Section 9:
Reset and clock control (RCC).

490/1141

DocID022558 Rev 8

RM0316

19.3.4

Touch sensing controller (TSC)

Charge transfer acquisition sequence
An example of a charge transfer acquisition sequence is detailed in Figure 138.
Figure 138. Charge transfer acquisition sequence
#HARGE TRANSFER FREQUENCY
#,+?!("


#8 (I:




$EAD TIME STATE

#3 READING STATE

$EAD TIME STATE

0ULSE LOW STATE
CHARGE TRANSFER
FROM #8 TO #3

#3 READING STATE

0ULSE HIGH STATE
CHARGE OF #8

$EAD TIME STATE

$ISCHARGE
#8 AND #3

$EAD TIME STATE

3TATE

$EAD TIME STATE



3PREAD 3PECTRUM STATE

#3 (I:

T
-36

For higher flexibility, the charge transfer frequency is fully configurable. Both the pulse high
state (charge of CX) and the pulse low state (transfer of charge from CX to CS) duration can
be defined using the CTPH[3:0] and CTPL[3:0] bits in the TSC_CR register. The standard
range for the pulse high and low states duration is 500 ns to 2 µs. To ensure a correct
measurement of the electrode capacitance, the pulse high state duration must be set to
ensure that CX is always fully charged.
A dead time where both the sampling capacitor I/O and the channel I/O are in input floating
state is inserted between the pulse high and low states to ensure an optimum charge
transfer acquisition sequence. This state duration is 2 periods of HCLK.
At the end of the pulse high state and if the spread spectrum feature is enabled, a variable
number of periods of the SSCLK clock are added.
The reading of the sampling capacitor I/O, to determine if the voltage across CS has
reached the given threshold, is performed at the end of the pulse low state and its duration
is one period of HCLK.
Note:

The following TSC control register configurations are forbidden:

•
•
•

bits PGPSC are set to ‘000’ and bits CTPL are set to ‘0000’
bits PGPSC are set to ‘000’ and bits CTPL are set to ‘0001’
bits PGPSC are set to ‘001’ and bits CTPL are set to ‘0000’

DocID022558 Rev 8

491/1141
505

Touch sensing controller (TSC)

19.3.5

RM0316

Spread spectrum feature
The spread spectrum feature allows to generate a variation of the charge transfer
frequency. This is done to improve the robustness of the charge transfer acquisition in noisy
environments and also to reduce the induced emission. The maximum frequency variation
is in the range of 10% to 50% of the nominal charge transfer period. For instance, for a
nominal charge transfer frequency of 250 kHz (4 µs), the typical spread spectrum deviation
is 10% (400 ns) which leads to a minimum charge transfer frequency of ~227 kHz.
In practice, the spread spectrum consists of adding a variable number of SSCLK periods to
the pulse high state using the principle shown below:
Figure 139. Spread spectrum variation principle

$EVIATION VALUE
33$ 






N N

N 

.UMBER OF PULSES
-36

The table below details the maximum frequency deviation with different HCLK settings:
Table 114. Spread spectrum deviation versus AHB clock frequency
fHCLK

Spread spectrum step

Maximum spread spectrum deviation

24 MHz

41.6 ns

10666.6 ns

48 MHz

20.8 ns

5333.3 ns

The spread spectrum feature can be disabled/enabled using the SSE bit in the TSC_CR
register. The frequency deviation is also configurable to accommodate the device HCLK
clock frequency and the selected charge transfer frequency through the SSPSC and
SSD[6:0] bits in the TSC_CR register.

19.3.6

Max count error
The max count error prevents long acquisition times resulting from a faulty capacitive
sensing channel. It consists of specifying a maximum count value for the analog I/O group
counters. This maximum count value is specified using the MCV[2:0] bits in the TSC_CR
register. As soon as an acquisition group counter reaches this maximum value, the ongoing
acquisition is stopped and the end of acquisition (EOAF bit) and max count error (MCEF bit)
flags are both set. An interrupt can also be generated if the corresponding end of acquisition
(EOAIE bit) or/and max count error (MCEIE bit) interrupt enable bits are set.

492/1141

DocID022558 Rev 8

RM0316

19.3.7

Touch sensing controller (TSC)

Sampling capacitor I/O and channel I/O mode selection
To allow the GPIOs to be controlled by the touch sensing controller, the corresponding
alternate function must be enabled through the standard GPIO registers and the GPIOxAFR
registers.
The GPIOs modes controlled by the TSC are defined using the TSC_IOSCR and
TSC_IOCCR register.
When there is no ongoing acquisition, all the I/Os controlled by the touch sensing controller
are in default state. While an acquisition is ongoing, only unused I/Os (neither defined as
sampling capacitor I/O nor as channel I/O) are in default state. The IODEF bit in the
TSC_CR register defines the configuration of the I/Os which are in default state. The table
below summarizes the configuration of the I/O depending on its mode.
Table 115. I/O state depending on its mode and IODEF bit value
IODEF bit

Acquisition
status

Unused I/O
mode

Electrode I/O
mode

Sampling
capacitor I/O
mode

0
(output push-pull
low)

No

Output push-pull
low

Output push-pull
low

Output push-pull
low

0
(output push-pull
low)

ongoing

Output push-pull
low

-

-

1
(input floating)

No

Input floating

Input floating

Input floating

1
(input floating)

ongoing

Input floating

-

-

Unused I/O mode
An unused I/O corresponds to a GPIO controlled by the TSC peripheral but not defined as
an electrode I/O nor as a sampling capacitor I/O.
Sampling capacitor I/O mode
To allow the control of the sampling capacitor I/O by the TSC peripheral, the corresponding
GPIO must be first set to alternate output open drain mode and then the corresponding
Gx_IOy bit in the TSC_IOSCR register must be set.
Only one sampling capacitor per analog I/O group must be enabled at a time.
Channel I/O mode
To allow the control of the channel I/O by the TSC peripheral, the corresponding GPIO must
be first set to alternate output push-pull mode and the corresponding Gx_IOy bit in the
TSC_IOCCR register must be set.
For proximity detection where a higher equivalent electrode surface is required or to speedup the acquisition process, it is possible to enable and simultaneously acquire several
channels belonging to the same analog I/O group.

DocID022558 Rev 8

493/1141
505

Touch sensing controller (TSC)

RM0316

Note:

During the acquisition phase and even if the TSC peripheral alternate function is not
enabled, as soon as the TSC_IOSCR or TSC_IOCCR bit is set, the corresponding GPIO
analog switch is automatically controlled by the touch sensing controller.

19.3.8

Acquisition mode
The touch sensing controller offers two acquisition modes:
•

Normal acquisition mode: the acquisition starts as soon as the START bit in the
TSC_CR register is set.

•

Synchronized acquisition mode: the acquisition is enabled by setting the START bit in
the TSC_CR register but only starts upon the detection of a falling edge or a rising
edge and high level on the SYNC input pin. This mode is useful for synchronizing the
capacitive sensing channels acquisition with an external signal without additional CPU
load.

The GxE bits in the TSC_IOGCSR registers specify which analog I/O groups are enabled
(corresponding counter is counting). The CS voltage of a disabled analog I/O group is not
monitored and this group does not participate in the triggering of the end of acquisition flag.
However, if the disabled analog I/O group contains some channels, they will be pulsed.
When the CS voltage of an enabled analog I/O group reaches the given threshold, the
corresponding GxS bit of the TSC_IOGCSR register is set. When the acquisition of all
enabled analog I/O groups is complete (all GxS bits of all enabled analog I/O groups are
set), the EOAF flag in the TSC_ISR register is set. An interrupt request is generated if the
EOAIE bit in the TSC_IER register is set.
In the case that a max count error is detected, the ongoing acquisition is stopped and both
the EOAF and MCEF flags in the TSC_ISR register are set. Interrupt requests can be
generated for both events if the corresponding bits (EOAIE and MCEIE bits of the TSCIER
register) are set. Note that when the max count error is detected the remaining GxS bits in
the enabled analog I/O groups are not set.
To clear the interrupt flags, the corresponding EOAIC and MCEIC bits in the TSC_ICR
register must be set.
The analog I/O group counters are cleared when a new acquisition is started. They are
updated with the number of charge transfer cycles generated on the corresponding
channel(s) upon the completion of the acquisition.

19.3.9

I/O hysteresis and analog switch control
In order to offer a higher flexibility, the touch sensing controller also allows to take the control
of the Schmitt trigger hysteresis and analog switch of each Gx_IOy. This control is available
whatever the I/O control mode is (controlled by standard GPIO registers or other
peripherals) assuming that the touch sensing controller is enabled. This may be useful to
perform a different acquisition sequence or for other purposes.
In order to improve the system immunity, the Schmitt trigger hysteresis of the GPIOs
controlled by the TSC must be disabled by resetting the corresponding Gx_IOy bit in the
TSC_IOHCR register.

494/1141

DocID022558 Rev 8

RM0316

19.4

Touch sensing controller (TSC)

TSC low-power modes
Table 116. Effect of low-power modes on TSC
Mode
Sleep

Description
No effect
TSC interrupts cause the device to exit Sleep mode.

Stop

TSC registers are frozen
Standby The TSC stops its operation until the Stop or Standby mode is exited.

19.5

TSC interrupts
Table 117. Interrupt control bits
Interrupt event

Enable
control bit

Event flag

Clear flag
bit

Exit the
Sleep
mode

Exit the
Stop mode

Exit the
Standby
mode

End of acquisition

EOAIE

EOAIF

EOAIC

yes

no

no

Max count error

MCEIE

MCEIF

MCEIC

yes

no

no

DocID022558 Rev 8

495/1141
505

Touch sensing controller (TSC)

19.6

RM0316

TSC registers
Refer to Section 2.1 on page 46 of the reference manual for a list of abbreviations used in
register descriptions.
The peripheral registers can be accessed by words (32-bit).

19.6.1

TSC control register (TSC_CR)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

CTPH[3:0]

26

25

24

23

22

21

CTPL[3:0]

20

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

rw

PGPSC[2:0]
rw

rw

Res.
rw

Res.

18

17

SSD[6:0]

rw

SSPSC

19

Res.

Res.

MCV[2:0]
rw

rw

rw

16
SSE

rw

rw

rw

rw

4

3

2

1

0

IODEF

SYNC
POL

AM

START

TSCE

rw

rw

rw

rw

rw

Bits 31:28 CTPH[3:0]: Charge transfer pulse high
These bits are set and cleared by software. They define the duration of the high state of the
charge transfer pulse (charge of CX).
0000: 1x tPGCLK
0001: 2x tPGCLK
...
1111: 16x tPGCLK
Note: These bits must not be modified when an acquisition is ongoing.
Bits 27:24 CTPL[3:0]: Charge transfer pulse low
These bits are set and cleared by software. They define the duration of the low state of the
charge transfer pulse (transfer of charge from CX to CS).
0000: 1x tPGCLK
0001: 2x tPGCLK
...
1111: 16x tPGCLK
Note: These bits must not be modified when an acquisition is ongoing.
Note: Some configurations are forbidden. Please refer to the Section 19.3.4: Charge transfer
acquisition sequence for details.
Bits 23:17 SSD[6:0]: Spread spectrum deviation
These bits are set and cleared by software. They define the spread spectrum deviation which
consists in adding a variable number of periods of the SSCLK clock to the charge transfer
pulse high state.
0000000: 1x tSSCLK
0000001: 2x tSSCLK
...
1111111: 128x tSSCLK
Note: These bits must not be modified when an acquisition is ongoing.

496/1141

DocID022558 Rev 8

RM0316

Touch sensing controller (TSC)

Bit 16 SSE: Spread spectrum enable
This bit is set and cleared by software to enable/disable the spread spectrum feature.
0: Spread spectrum disabled
1: Spread spectrum enabled
Note: This bit must not be modified when an acquisition is ongoing.
Bit 15 SSPSC: Spread spectrum prescaler
This bit is set and cleared by software. It selects the AHB clock divider used to generate the
spread spectrum clock (SSCLK).
0: fHCLK
1: fHCLK /2
Note: This bit must not be modified when an acquisition is ongoing.
Bits 14:12 PGPSC[2:0]: Pulse generator prescaler
These bits are set and cleared by software.They select the AHB clock divider used to generate
the pulse generator clock (PGCLK).
000: fHCLK
001: fHCLK /2
010: fHCLK /4
011: fHCLK /8
100: fHCLK /16
101: fHCLK /32
110: fHCLK /64
111: fHCLK /128
Note: These bits must not be modified when an acquisition is ongoing.
Note: Some configurations are forbidden. Please refer to the Section 19.3.4: Charge transfer
acquisition sequence for details.
Bits 11:8 Reserved, must be kept at reset value.
Bits 7:5 MCV[2:0]: Max count value
These bits are set and cleared by software. They define the maximum number of charge
transfer pulses that can be generated before a max count error is generated.
000: 255
001: 511
010: 1023
011: 2047
100: 4095
101: 8191
110: 16383
111: reserved
Note: These bits must not be modified when an acquisition is ongoing.
Bit 4 IODEF: I/O Default mode
This bit is set and cleared by software. It defines the configuration of all the TSC I/Os when
there is no ongoing acquisition. When there is an ongoing acquisition, it defines the
configuration of all unused I/Os (not defined as sampling capacitor I/O or as channel I/O).
0: I/Os are forced to output push-pull low
1: I/Os are in input floating
Note: This bit must not be modified when an acquisition is ongoing.
Bit 3 SYNCPOL: Synchronization pin polarity
This bit is set and cleared by software to select the polarity of the synchronization input pin.
0: Falling edge only
1: Rising edge and high level

DocID022558 Rev 8

497/1141
505

Touch sensing controller (TSC)

RM0316

Bit 2 AM: Acquisition mode
This bit is set and cleared by software to select the acquisition mode.
0: Normal acquisition mode (acquisition starts as soon as START bit is set)
1: Synchronized acquisition mode (acquisition starts if START bit is set and when the
selected signal is detected on the SYNC input pin)
Note: This bit must not be modified when an acquisition is ongoing.
Bit 1 START: Start a new acquisition
This bit is set by software to start a new acquisition. It is cleared by hardware as soon as the
acquisition is complete or by software to cancel the ongoing acquisition.
0: Acquisition not started
1: Start a new acquisition
Bit 0 TSCE: Touch sensing controller enable
This bit is set and cleared by software to enable/disable the touch sensing controller.
0: Touch sensing controller disabled
1: Touch sensing controller enabled
Note: When the touch sensing controller is disabled, TSC registers settings have no effect.

19.6.2

TSC interrupt enable register (TSC_IER)
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.

Res.

MCEIE

EOAIE

rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 MCEIE: Max count error interrupt enable
This bit is set and cleared by software to enable/disable the max count error interrupt.
0: Max count error interrupt disabled
1: Max count error interrupt enabled
Bit 0 EOAIE: End of acquisition interrupt enable
This bit is set and cleared by software to enable/disable the end of acquisition interrupt.
0: End of acquisition interrupt disabled
1: End of acquisition interrupt enabled

498/1141

DocID022558 Rev 8

RM0316

Touch sensing controller (TSC)

19.6.3

TSC interrupt clear register (TSC_ICR)
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.

MCEIC EOAIC
rw

rw

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 MCEIC: Max count error interrupt clear
This bit is set by software to clear the max count error flag and it is cleared by hardware when
the flag is reset. Writing a ‘0’ has no effect.
0: No effect
1: Clears the corresponding MCEF of the TSC_ISR register
Bit 0 EOAIC: End of acquisition interrupt clear
This bit is set by software to clear the end of acquisition flag and it is cleared by hardware
when the flag is reset. Writing a ‘0’ has no effect.
0: No effect
1: Clears the corresponding EOAF of the TSC_ISR register

DocID022558 Rev 8

499/1141
505

Touch sensing controller (TSC)

19.6.4

RM0316

TSC interrupt status register (TSC_ISR)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MCEF

EOAF

r

r

Bits 31:2 Reserved, must be kept at reset value.
Bit 1 MCEF: Max count error flag
This bit is set by hardware as soon as an analog I/O group counter reaches the max count
value specified. It is cleared by software writing 1 to the bit MCEIC of the TSC_ICR register.
0: No max count error (MCE) detected
1: Max count error (MCE) detected
Bit 0 EOAF: End of acquisition flag
This bit is set by hardware when the acquisition of all enabled group is complete (all GxS bits
of all enabled analog I/O groups are set or when a max count error is detected). It is cleared by
software writing 1 to the bit EOAIC of the TSC_ICR register.
0: Acquisition is ongoing or not started
1: Acquisition is complete

19.6.5

TSC I/O hysteresis control register (TSC_IOHCR)
Address offset: 0x10
Reset value: 0xFFFF FFFF

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

G8_IO4 G8_IO3 G8_IO2 G8_IO1 G7_IO4 G7_IO3 G7_IO2 G7_IO1 G6_IO4 G6_IO3 G6_IO2 G6_IO1 G5_IO4 G5_IO3 G5_IO2 G5_IO1
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

G4_IO4 G4_IO3 G4_IO2 G4_IO1 G3_IO4 G3_IO3 G3_IO2 G3_IO1 G2_IO4 G2_IO3 G2_IO2 G2_IO1 G1_IO4 G1_IO3 G1_IO2 G1_IO1
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 Gx_IOy: Gx_IOy Schmitt trigger hysteresis mode
These bits are set and cleared by software to enable/disable the Gx_IOy Schmitt trigger
hysteresis.
0: Gx_IOy Schmitt trigger hysteresis disabled
1: Gx_IOy Schmitt trigger hysteresis enabled
Note: These bits control the I/O Schmitt trigger hysteresis whatever the I/O control mode is
(even if controlled by standard GPIO registers).

500/1141

DocID022558 Rev 8

RM0316

Touch sensing controller (TSC)

19.6.6

TSC I/O analog switch control register (TSC_IOASCR)
Address offset: 0x18
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

G8_IO4 G8_IO3 G8_IO2 G8_IO1 G7_IO4 G7_IO3 G7_IO2 G7_IO1 G6_IO4 G6_IO3 G6_IO2 G6_IO1 G5_IO4 G5_IO3 G5_IO2 G5_IO1
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

G4_IO4 G4_IO3 G4_IO2 G4_IO1 G3_IO4 G3_IO3 G3_IO2 G3_IO1 G2_IO4 G2_IO3 G2_IO2 G2_IO1 G1_IO4 G1_IO3 G1_IO2 G1_IO1
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 Gx_IOy: Gx_IOy analog switch enable
These bits are set and cleared by software to enable/disable the Gx_IOy analog switch.
0: Gx_IOy analog switch disabled (opened)
1: Gx_IOy analog switch enabled (closed)
Note: These bits control the I/O analog switch whatever the I/O control mode is (even if
controlled by standard GPIO registers).

19.6.7

TSC I/O sampling control register (TSC_IOSCR)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

G8_IO4 G8_IO3 G8_IO2 G8_IO1 G7_IO4 G7_IO3 G7_IO2 G7_IO1 G6_IO4 G6_IO3 G6_IO2 G6_IO1 G5_IO4 G5_IO3 G5_IO2 G5_IO1
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

G4_IO4 G4_IO3 G4_IO2 G4_IO1 G3_IO4 G3_IO3 G3_IO2 G3_IO1 G2_IO4 G2_IO3 G2_IO2 G2_IO1 G1_IO4 G1_IO3 G1_IO2 G1_IO1
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 Gx_IOy: Gx_IOy sampling mode
These bits are set and cleared by software to configure the Gx_IOy as a sampling capacitor
I/O. Only one I/O per analog I/O group must be defined as sampling capacitor.
0: Gx_IOy unused
1: Gx_IOy used as sampling capacitor
Note: These bits must not be modified when an acquisition is ongoing.
During the acquisition phase and even if the TSC peripheral alternate function is not
enabled, as soon as the TSC_IOSCR bit is set, the corresponding GPIO analog switch
is automatically controlled by the touch sensing controller.

DocID022558 Rev 8

501/1141
505

Touch sensing controller (TSC)

19.6.8

RM0316

TSC I/O channel control register (TSC_IOCCR)
Address offset: 0x28
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

G8_IO4 G8_IO3 G8_IO2 G8_IO1 G7_IO4 G7_IO3 G7_IO2 G7_IO1 G6_IO4 G6_IO3 G6_IO2 G6_IO1 G5_IO4 G5_IO3 G5_IO2 G5_IO1
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

G4_IO4 G4_IO3 G4_IO2 G4_IO1 G3_IO4 G3_IO3 G3_IO2 G3_IO1 G2_IO4 G2_IO3 G2_IO2 G2_IO1 G1_IO4 G1_IO3 G1_IO2 G1_IO1
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 Gx_IOy: Gx_IOy channel mode
These bits are set and cleared by software to configure the Gx_IOy as a channel I/O.
0: Gx_IOy unused
1: Gx_IOy used as channel
Note: These bits must not be modified when an acquisition is ongoing.
During the acquisition phase and even if the TSC peripheral alternate function is not
enabled, as soon as the TSC_IOCCR bit is set, the corresponding GPIO analog switch
is automatically controlled by the touch sensing controller.

19.6.9

TSC I/O group control status register (TSC_IOGCSR)
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.

G8S

G7S

G6S

G5S

G4S

G3S

G2S

G1S

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.

Res.

G8E

G7E

G6E

G5E

G4E

G3E

G2E

G1E

rw

rw

rw

rw

rw

rw

rw

rw

502/1141

DocID022558 Rev 8

RM0316

Touch sensing controller (TSC)

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:16 GxS: Analog I/O group x status
These bits are set by hardware when the acquisition on the corresponding enabled analog I/O
group x is complete. They are cleared by hardware when a new acquisition is started.
0: Acquisition on analog I/O group x is ongoing or not started
1: Acquisition on analog I/O group x is complete
Note: When a max count error is detected the remaining GxS bits of the enabled analog I/O
groups are not set.
Bits 15:8 Reserved, must be kept at reset value.
Bits 7:0 GxE: Analog I/O group x enable
These bits are set and cleared by software to enable/disable the acquisition (counter is
counting) on the corresponding analog I/O group x.
0: Acquisition on analog I/O group x disabled
1: Acquisition on analog I/O group x enabled

19.6.10

TSC I/O group x counter register (TSC_IOGxCR) (x = 1..8)
Address offset: 0x30 + 0x04 x Analog I/O group 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

Res.

Res.

r

r

r

r

r

r

CNT[13:0]
r

r

r

r

r

r

r

r

Bits 31:14 Reserved, must be kept at reset value.
Bits 13:0 CNT[13:0]: Counter value
These bits represent the number of charge transfer cycles generated on the analog I/O group
x to complete its acquisition (voltage across CS has reached the threshold).

DocID022558 Rev 8

503/1141
505

0x0038

504/1141

TSC_IOG2CR
0
0
0
0
0
0
0
0
0
0

0x002C
Reserved

Reset value

DocID022558 Rev 8

Reset value

0

0
G1_IO3
G1_IO2
G1_IO1

G2_IO4
G2_IO3
G2_IO2
G2_IO1
G1_IO4
G1_IO3
G1_IO2
G1_IO1

G3_IO4
G3_IO3
G3_IO2
G3_IO1
G2_IO4
G2_IO3
G2_IO2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

G2_IO1

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0

0

CNT[13:0]

CNT[13:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

G1_IO4
G1_IO3
G1_IO2
G1_IO1

Reset value

Reset value
EOAIC

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

TSCE

0
0
0

EOAIE

AM

Res.

START

Res.

0
Res.

Res.

IODEF

Res.

Res.

Res.

Res.

Res.

SYNCPOL

Res.

Res.

Res.

Res.

PGPSC[2:0]

0
MCEIE

Reset value

EOAF

Res.

Res.

0

MCEIC

Res.

0

MCEF

Res.

Res.

0

Res.

Res.

Res.

Res.

MCV
[2:0]

Res.

Res.

Res.

TSC_IER

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0
Res.

0

Res.

0

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

0

G1E

G1_IO4

G3_IO1

G4_IO1

Res.

Res.

SSE
SSPSC

0

G2E

G2_IO1

G3_IO2

G4_IO2

Res.

0

G3E

G2_IO2

G3_IO3

G4_IO3

Res.

Res.

Res.

Res.

0

G4E

G2_IO3

G3_IO4

G4_IO4

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

G5E

G1_IO1

0
G1_IO2

0
G1_IO3

0
G1_IO4

0
G2_IO1

Reset value
G2_IO2

0

G2_IO3

0x0024
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

G6E

0

G7E

0
G2_IO4

0

G2_IO4

0

G8E

0
G3_IO1

0

G3_IO1

0

Res.

0
G3_IO2

0

G3_IO2

0

Res.

0
G3_IO3

0
G3_IO4

0

G3_IO3

Reset value

G3_IO4

0

Res.

0

Res.

0
G4_IO1

0

G4_IO1

0

G4_IO1

0

Res.

0
G4_IO2

0
G4_IO3

0

G4_IO2

0

G4_IO3

0

G4_IO2

0

G4_IO3

0

Res.

0

Res.

Reset value
G4_IO4

1

G4_IO4

1
G5_IO1

G5_IO3

1
G5_IO2

G5_IO4

1

G5_IO1

G5_IO3

G6_IO1

1

G5_IO2

G5_IO4

G6_IO2

1

G5_IO1

G5_IO3

G6_IO1

G6_IO3

1

G5_IO2

G5_IO4

G6_IO2

G6_IO4

1

Res.

G5_IO3

G6_IO1

G6_IO3

G7_IO1

1

Res.

G5_IO4

G6_IO2

G6_IO4

G7_IO2

1

G4_IO4

G6_IO1

G6_IO3

G7_IO1

G7_IO3

1

Res.

G6_IO2

G6_IO4

G7_IO2

G7_IO4

1

Res.

G6_IO3

G7_IO1

G7_IO3

G8_IO1

1

Res.

G1S

0

Res.

G6_IO4

G7_IO2

G7_IO4

G8_IO2

1

G5_IO1

G2S

0

Res.

G7_IO1

G7_IO3

G8_IO1

G8_IO3
0
SSD[6:0]

Res.

G3S

0

Res.

G7_IO2

G7_IO4

G8_IO2

G8_IO4

Reset value

G5_IO2

G4S

0

Res.

G7_IO3

G8_IO1

TSC_IOHCR

Res.

G5S

0

Res.

G7_IO4

G8_IO2

0x001C

Res.

G6S

0

Res.

G8_IO1

0x0014

Res.

Res.

G7S

0

Res.

TSC_IOCCR
G8_IO2

G8_IO3

0
CTPL[3:0]

Res.

Res.

G8S

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

TSC_IOG1CR

Res.

TSC_IOASCR
G8_IO4

Reset value
CTPH[3:0]

Res.

0x0034

TSC_IOGCSR

Res.

0x0030
TSC_ISR

Res.

0x0028
TSC_IOSCR
G8_IO3

0x0020
G8_IO4

0x0018

G8_IO3

0x0010

G8_IO4

0x000C
TSC_ICR

Res.

0x0008

Res.

0x0004
TSC_CR

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

Res.

Offset

Res.

19.6.11

Res.

Touch sensing controller (TSC)
RM0316

TSC register map
Table 118. TSC register map and reset values

0
0

0
0

0
0

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

Reserved

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

Reserved

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

Reserved

RM0316

Touch sensing controller (TSC)

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSC_IOG3CR

Res.

0x003C

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 118. TSC register map and reset values (continued)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CNT[13:0]
0

Reset value

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSC_IOG8CR

0

CNT[13:0]
0

Reset value

0x0050

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSC_IOG7CR

0

CNT[13:0]
0

Reset value

0x004C

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSC_IOG6CR

0

CNT[13:0]
0

Reset value

0x0048

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSC_IOG5CR

0

CNT[13:0]
0

Reset value

0x0044

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSC_IOG4CR

Res.

Reset value

0x0040

CNT[13:0]

0

0

0

0

0

0

0

0

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

DocID022558 Rev 8

505/1141
505

Advanced-control timers (TIM1/TIM8/TIM20)

20

Advanced-control timers (TIM1/TIM8/TIM20)

20.1

TIM1/TIM8/TIM20 introduction

RM0316

The advanced-control timers (TIM1/TIM8/TIM20) consist of a 16-bit auto-reload counter
driven by a programmable prescaler.
It may be used for a variety of purposes, including measuring the pulse lengths of input
signals (input capture) or generating output waveforms (output compare, PWM,
complementary PWM with dead-time insertion).
Pulse lengths and waveform periods can be modulated from a few microseconds to several
milliseconds using the timer prescaler and the RCC clock controller prescalers.
The advanced-control (TIM1/TIM8/TIM20) and general-purpose (TIMx) timers are
completely independent, and do not share any resources. They can be synchronized
together as described in Section 20.3.25: Timer synchronization.
Note:

TIM8 is available on STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices.
TIM20 is available on STM32F303xD/E and STM32F398xE devices only.

20.2

TIM1/TIM8/TIM20 main features
TIM1/TIM8/TIM20 timer features include:

506/1141

•

16-bit up, down, up/down auto-reload counter.

•

16-bit programmable prescaler allowing dividing (also “on the fly”) the counter clock
frequency either by any factor between 1 and 65536.

•

Up to 6 independent channels for:
–

Input Capture (but channels 5 and 6)

–

Output Compare

–

PWM generation (Edge and Center-aligned Mode)

–

One-pulse mode output

•

Complementary outputs with programmable dead-time

•

Synchronization circuit to control the timer with external signals and to interconnect
several timers together.

•

Repetition counter to update the timer registers only after a given number of cycles of
the counter.

•

2 break inputs to put the timer’s output signals in a safe user selectable configuration.

•

Interrupt/DMA generation on the following events:
–

Update: counter overflow/underflow, counter initialization (by software or
internal/external trigger)

–

Trigger event (counter start, stop, initialization or count by internal/external trigger)

–

Input capture

–

Output compare

•

Supports incremental (quadrature) encoder and Hall-sensor circuitry for positioning
purposes

•

Trigger input for external clock or cycle-by-cycle current management

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 140. Advanced-control timer block diagram
/ŶƚĞƌŶĂůĐůŽĐŬ;<ͺ/EdͿ

<ͺd/DϭϴĨƌŽŵZ

dƌŝŐŐĞƌ
ĐŽŶƚƌŽůůĞƌ

dZ&
dZW
WŽůĂƌŝƚLJƐĞůĞĐƚŝŽŶΘĞĚŐĞ
ĚĞƚĞĐƚŽƌΘƉƌĞƐĐĂůĞƌ

dZ

d/DdžͺdZ

/dZϬ
/dZϭ
/dZϮ
/dZϯ

dZ'K
ƚŽŽƚŚĞƌƚŝŵĞƌƐƚŽͬ

/ŶƉƵƚ
ĨŝůƚĞƌ
d'/

/dZ
dZ

dZ'/

d/ϭ&ͺ

^ůĂǀĞ
ĐŽŶƚƌŽůůĞƌ
ŵŽĚĞ

ZĞƐĞƚ͕ĞŶĂďůĞ͕ƵƉͬĚŽǁŶ͕ĐŽƵŶƚ

ŶĐŽĚĞƌ
/ŶƚĞƌĨĂĐĞ

d/ϭ&Wϭ
d/Ϯ&WϮ

ZWƌĞŐŝƐƚĞƌ
h

h/

ƵƚŽͲƌĞůŽĂĚƌĞŐŝƐƚĞƌ

ZĞƉĞƚŝƚŝŽŶ
ĐŽƵŶƚĞƌ

^ƚŽƉ͕ĐůĞĂƌŽƌƵƉͬĚŽǁŶ
<ͺW^

yKZ
d/ϭ
d/Ddžͺ,ϭ

d/Ϯ

d/Ddžͺ,Ϯ

/ŶƉƵƚĨŝůƚĞƌΘ
ĞĚŐĞĚĞƚĞĐƚŽƌ

/ŶƉƵƚĨŝůƚĞƌΘ
ĞĚŐĞĚĞƚĞĐƚŽƌ

d/ϭ&Wϭ
d/ϭ&WϮ

W^
ƉƌĞƐĐĂůĞƌ
/ϭ

WƌĞƐĐĂůĞƌ

dZ
d/Ϯ&Wϭ
d/Ϯ&WϮ

<ͺEd
ϭ/

d/Ddžͺ,ϯ

/ŶƉƵƚĨŝůƚĞƌΘ
ĞĚŐĞĚĞƚĞĐƚŽƌ

d/Ddžͺ,ϰ

/ŶƉƵƚĨŝůƚĞƌΘ
ĞĚŐĞĚĞƚĞĐƚŽƌ

ϭ/
ĂƉƚƵƌĞͬŽŵƉĂƌĞϭƌĞŐŝƐƚĞƌ

Ϯ/
/Ϯ

WƌĞƐĐĂůĞƌ

/ϮW^

d'ƌĞŐŝƐƚĞƌƐ

d'

ĂƉƚƵƌĞͬŽŵƉĂƌĞϮƌĞŐŝƐƚĞƌ

d/ϰ&Wϯ
d/ϰ&Wϰ

KƵƚƉƵƚ
ĐŽŶƚƌŽů

Kϭ
d/Ddžͺ,ϭE
KϭE
d/Ddžͺ,Ϯ

KϮZ&
d'

dZ

d/ϯ&Wϯ
d/ϯ&Wϰ

d/Ddžͺ,ϭ

KϭZ&

Ϯ/

h

KƵƚƉƵƚ
ĐŽŶƚƌŽů

KϮ
d/Ddžͺ,ϮE
KϮE

/ϯ

WƌĞƐĐĂůĞƌ

dZ
d/ϰ

EdĐŽƵŶƚĞƌ

h

/ϭW^

ϯ/
d/ϯ

нͬͲ

h

ϯ/

h

/ϯW^

ĂƉƚƵƌĞͬŽŵƉĂƌĞϯƌĞŐŝƐƚĞƌ

ϰ/

WƌĞƐĐĂůĞƌ

/ϰW^

d'

KƵƚƉƵƚ
ĐŽŶƚƌŽů

Kϯ
d/Ddžͺ,ϯE
KϯE

ϰ/

h
/ϰ

d/Ddžͺ,ϯ

KϯZ&

KƵƚƉƵƚ
ĐŽŶƚƌŽů

Kϰ

ĂƉƚƵƌĞͬŽŵƉĂƌĞϰƌĞŐŝƐƚĞƌ

KϰZ&

ĂƉƚƵƌĞͬŽŵƉĂƌĞϱƌĞŐŝƐƚĞƌ

KϱZ&

KƵƚƉƵƚ Kϱ
ĐŽŶƚƌŽů

ĂƉƚƵƌĞͬŽŵƉĂƌĞϲƌĞŐŝƐƚĞƌ

KϲZ&

KƵƚƉƵƚ Kϲ
ĐŽŶƚƌŽů

d/Ddžͺ,ϰ

dZ

dZ&
Z<
d/Ddžͺ@
7,0[B60&5

(753
I'76

DocID022558 Rev 8

)LOWHU
GRZQFRXQWHU

(7)>@
7,0[B60&5

7RWKH2XWSXWPRGHFRQWUROOHU
7RWKH&.B36&FLUFXLWU\
7RWKH6ODYHPRGHFRQWUROOHU

069

523/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

20.3.5

RM0316

Clock selection
The counter clock can be provided by the following clock sources:
•

Internal clock (CK_INT)

•

External clock mode1: external input pin

•

External clock mode2: external trigger input ETR

•

Encoder mode

Internal clock source (CK_INT)
If the slave mode controller is disabled (SMS=000), then the CEN, DIR (in the TIMx_CR1
register) and UG bits (in the TIMx_EGR register) are actual control bits and can be changed
only by software (except UG which remains cleared automatically). As soon as the CEN bit
is written to 1, the prescaler is clocked by the internal clock CK_INT.
Figure 162 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.
Figure 162. Control circuit in normal mode, internal clock divided by 1

,QWHUQDOFORFN
&(1 &17B(1
8*

&17B,1,7

&RXQWHUFORFN &.B&17 &.B36&
&RXQWHUUHJLVWHU









 

 



  




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.

524/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 163. TI2 external clock connection example
7,0[B60&5
76>@
RU 7,)
7,)
,75[
7,B('

7,

)LOWHU

(GJH
GHWHFWRU

7,)B5LVLQJ
7,)B)DOOLQJ

7,)3



7,)3
(75)

RU
RU

[[


75*,





(75)
&.B,17

,&)>@

&&3

7,0[B&&05

7,0[B&&(5

LQWHUQDOFORFN

(QFRGHU
PRGH
([WHUQDOFORFN
PRGH

([WHUQDOFORFN
PRGH


&.B36&

,QWHUQDOFORFN
PRGH

(&(

606>@

7,0[B60&5

069

For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:

Note:

1.

Configure channel 2 to detect rising edges on the TI2 input by writing CC2S = ‘01’ in
the TIMx_CCMR1 register.

2.

Configure the input filter duration by writing the IC2F[3:0] bits in the TIMx_CCMR1
register (if no filter is needed, keep IC2F=0000).

3.

Select rising edge polarity by writing CC2P=0 and CC2NP=0 in the TIMx_CCER
register.

4.

Configure the timer in external clock mode 1 by writing SMS=111 in the TIMx_SMCR
register.

5.

Select TI2 as the trigger input source by writing TS=110 in the TIMx_SMCR register.

6.

Enable the counter by writing CEN=1 in the TIMx_CR1 register.

The capture prescaler is not used for triggering, so the user does not need to configure it.
When a rising edge occurs on TI2, the counter counts once and the TIF flag is set.
The delay between the rising edge on TI2 and the actual clock of the counter is due to the
resynchronization circuit on TI2 input.

DocID022558 Rev 8

525/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Figure 164. Control circuit in external clock mode 1

7,
&17B(1
&RXQWHUFORFN &.B&17 &.B36&
&RXQWHUUHJLVWHU







7,)

:ULWH7,) 

069

External clock source mode 2
This mode is selected by writing ECE=1 in the TIMx_SMCR register.
The counter can count at each rising or falling edge on the external trigger input ETR.
The Figure 165 gives an overview of the external trigger input block.
Figure 165. External trigger input block

RU 7,)
7,)

(75

RU
RU

75*,


(75SLQ


'LYLGHU


(753
I'76

)LOWHU
GRZQFRXQWHU

(75)
&.B,17

(73

(736>@

(7)>@

7,0[B60&5

7,0[B60&5

7,0[B60&5

LQWHUQDOFORFN

(QFRGHU
PRGH
([WHUQDOFORFN
PRGH

([WHUQDOFORFN
PRGH


&.B36&

,QWHUQDOFORFN
PRGH

(&(

606>@

7,0[B60&5

069

For example, to configure the upcounter to count each 2 rising edges on ETR, use the
following procedure:

526/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
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 166. Control circuit in external clock mode 2

I &.B,17
&17B(1
(75

(753

(75)
&RXQWHUFORFN 
&.B,17 &.B36&
&RXQWHUUHJLVWHU







069

DocID022558 Rev 8

527/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

20.3.6

RM0316

Capture/compare channels
Each Capture/Compare channel is built around a capture/compare register (including a
shadow register), an input stage for capture (with digital filter, multiplexing, and prescaler,
except for channels 5 and 6) and an output stage (with comparator and output control).
Figure 167 to Figure 170 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 167. Capture/compare channel (example: channel 1 input stage)

7,)B('
7RWKHVODYHPRGHFRQWUROOHU
7,
I'76

7,)B5LVLQJ
)LOWHU
7,)
GRZQFRXQWHU

(GJH
GHWHFWRU

7,)B)DOOLQJ

 7,)3




7,)3

,&)>@
7,0[B&&05

&&3&&13
7,0[B&&(5
7,)B5LVLQJ

IURPFKDQQHO
7,)B)DOOLQJ

IURPFKDQQHO



75&
IURPVODYHPRGH
FRQWUROOHU

,&

,&36
'LYLGHU




&&6>@ ,&36>@

&&(

7,0[B&&05

7,0[B&&(5

069

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.

528/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 168. Capture/compare channel 1 main circuit

$3%%XV

5HDG&&5+ 6
5HDG&&5/

KLJK



UHDGBLQBSURJUHVV

&&6>@
,&36

ZULWHBLQBSURJUHVV

,QSXW
PRGH

6 ZULWH&&5+

&DSWXUHFRPSDUHSUHORDGUHJLVWHU

5

5
FRPSDUHBWUDQVIHU

FDSWXUHBWUDQVIHU
&&6>@


ORZ

LIELW

0&8SHULSKHUDOLQWHUIDFH

2XWSXW
PRGH

&17!&&5
&RXQWHU

&&*

&&6>@

8(9
&RPSDUDWRU

&&(

&&6>@

2&3(

&DSWXUHFRPSDUHVKDGRZUHJLVWHU
&DSWXUH

ZULWH&&5/

IURPWLPH
EDVHXQLW

2&3(

7,0B&&05

&17 &&5

7,0B(*5

069

DocID022558 Rev 8

529/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Figure 169. Output stage of capture/compare channel (channel 1, idem ch. 2 and 3)
7,0[B60&5
2&&6
2&5()B&/5

7RWKHPDVWHUPRGH
FRQWUROOHU


(75)




µ¶

RFUHIBFOUBLQW

2&B'7

&17!&&5 2XWSXW
PRGH
&17 &&5
FRQWUROOHU
2&[5()
2&5()

2&5()&

2&5()

'HDGWLPH
JHQHUDWRU

2XWSXW
VHOHFWRU

[






&&3

2XWSXW
HQDEOH
FLUFXLW

2&

2XWSXW
HQDEOH
FLUFXLW

2&1

7,0B&&(5
2&1B'7





µ¶


[




&&1( &&( 7,0B&&(5
2&&( 2&0>@

'7*>@

&&1( &&(

&&13

02( 266, 2665

7,0B&&05

7,0B%'75

7,0B&&(5

7,0B&&(5

7,0B%'75

069

1. OCxREF, where x is the rank of the complementary channel

Figure 170. Output stage of capture/compare channel (channel 4)
7,0[B60&5
2&&6
2&5()B&/5 

7RWKHPDVWHU
PRGHFRQWUROOHU

(75) 

2&5()&

RFUHIBFOUBLQW

2&5()

µ¶

&17!&&5

2XWSXW
PRGH
&17 &&5
FRQWUROOHU
2&5()

2XWSXW
VHOHFWRU









&&(
7,0B&&(5

2XWSXW
HQDEOH
FLUFXLW

&&3
7,0B&&(5

&&( 7,0B&&(5
02(

2&&( 2&0>@
7,0B&&05

2&

266, 7,0B%'75

2,6

7,0B&5
069

530/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 171. Output stage of capture/compare channel (channel 5, idem ch. 6)
7,0[B60&5
2&&6
2&5()B&/5



(75)



RFUHIBFOUBLQW
&17!&&5

2XWSXW
PRGH
&17 &&5
FRQWUROOHU

7RWKHPDVWHU
PRGHFRQWUROOHU

µ¶





2&5() 



&&(

&&3

7,0B&&(5

7,0B&&(5

2&&( 2&0>@

2XWSXW
HQDEOH
FLUFXLW

2&



&&( 7,0B&&(5
02(

266, 7,0B%'75

7,0B&&05
2,6

7,0B&5
069

1. Not available externally.

The capture/compare block is made of one preload register and one shadow register. Write
and read always access the preload register.
In capture mode, captures are actually done in the shadow register, which is copied into the
preload register.
In compare mode, the content of the preload register is copied into the shadow register
which is compared to the counter.

20.3.7

Input capture mode
In Input capture mode, the Capture/Compare Registers (TIMx_CCRx) are used to latch the
value of the counter after a transition detected by the corresponding ICx signal. When a
capture occurs, the corresponding CCXIF flag (TIMx_SR register) is set and an interrupt or
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 (when the input is one of the TIx (ICxF bits in the TIMx_CCMRx register). Let’s
imagine that, when toggling, the input signal is not stable during at must 5 internal clock
cycles. We must program a filter duration longer than these 5 clock cycles. We can
validate a transition on TI1 when 8 consecutive samples with the new level have been

DocID022558 Rev 8

531/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

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:

IC interrupt and/or DMA requests can be generated by software by setting the
corresponding CCxG bit in the TIMx_EGR register.

20.3.8

PWM input mode
This mode is a particular case of input capture mode. The procedure is the same except:

532/1141

•

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.

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
For example, the user can measure the period (in TIMx_CCR1 register) and the duty cycle
(in TIMx_CCR2 register) of the PWM applied on TI1 using the following procedure
(depending on CK_INT frequency and prescaler value):
•

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 CC2P/CC2NP=’10’ (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 0100 in the
TIMx_SMCR register.

•

Enable the captures: write the CC1E and CC2E bits to ‘1’ in the TIMx_CCER register.
Figure 172. PWM input mode timing
7,

7,0[B&17









7,0[B&&5



7,0[B&&5



,&FDSWXUH
,&FDSWXUH
UHVHWFRXQWHU





,&FDSWXUH
SXOVHZLGWK
PHDVXUHPHQW



,&FDSWXUH
SHULRG
PHDVXUHPHQW
DL

20.3.9

Forced output mode
In output mode (CCxS bits = 00 in the TIMx_CCMRx register), each output compare signal
(OCxREF and then OCx/OCxN) can be forced to active or inactive level directly by software,
independently of any comparison between the output compare register and the counter.
To force an output compare signal (OCXREF/OCx) to its active level, user just needs to
write 0101 in the OCxM bits in the corresponding TIMx_CCMRx register. Thus OCXREF is
forced high (OCxREF is always active high) and OCx get opposite value to CCxP polarity
bit.
For example: CCxP=0 (OCx active high) => OCx is forced to high level.
The OCxREF signal can be forced low by writing the OCxM bits to 0100 in the
TIMx_CCMRx register.

DocID022558 Rev 8

533/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

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.

20.3.10

Output compare mode
This function is used to control an output waveform or indicate when a period of time has
elapsed. Channels 1 to 4 can be output, while Channel 5 and 6 are only available inside the
microcontroller (for instance, for compound waveform generation or for ADC triggering).
When a match is found between the capture/compare register and the counter, the output
compare function:
•

Assigns the corresponding output pin to a programmable value defined by the output
compare mode (OCxM bits in the TIMx_CCMRx register) and the output polarity (CCxP
bit in the TIMx_CCER register). The output pin can keep its level (OCXM=0000), be set
active (OCxM=0001), be set inactive (OCxM=0010) or can toggle (OCxM=0011) on
match.

•

Sets a flag in the interrupt status register (CCxIF bit in the TIMx_SR register).

•

Generates an interrupt if the corresponding interrupt mask is set (CCXIE bit in the
TIMx_DIER register).

•

Sends a DMA request if the corresponding enable bit is set (CCxDE bit in the
TIMx_DIER register, CCDS bit in the TIMx_CR2 register for the DMA request
selection).

The TIMx_CCRx registers can be programmed with or without preload registers using the
OCxPE bit in the TIMx_CCMRx register.
In output compare mode, the update event UEV has no effect on OCxREF and OCx output.
The timing resolution is one count of the counter. Output compare mode can also be used to
output a single pulse (in One Pulse mode).

Procedure
1.

Select the counter clock (internal, external, prescaler).

2.

Write the desired data in the TIMx_ARR and TIMx_CCRx registers.

3.

Set the CCxIE bit if an interrupt request is to be generated.

4.

Select the output mode. For example:

5.

–

Write OCxM = 0011 to toggle OCx output pin when CNT matches CCRx

–

Write OCxPE = 0 to disable preload register

–

Write CCxP = 0 to select active high polarity

–

Write CCxE = 1 to enable the output

Enable the counter by setting the CEN bit in the TIMx_CR1 register.

The TIMx_CCRx register can be updated at any time by software to control the output
waveform, provided that the preload register is not enabled (OCxPE=’0’, else TIMx_CCRx
shadow register is updated only at the next update event UEV). An example is given in
Figure 173.

534/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 173. Output compare mode, toggle on OC1
:ULWH%KLQWKH&&5UHJLVWHU

7,0B&17



7,0B&&5

%

$

%

%

%

$

2&5() 2&

0DWFKGHWHFWHGRQ&&5
,QWHUUXSWJHQHUDWHGLIHQDEOHG
069

20.3.11

PWM mode
Pulse Width Modulation mode allows you to generate a signal with a frequency determined
by the value of the TIMx_ARR register and a duty cycle determined by the value of the
TIMx_CCRx register.
The PWM mode can be selected independently on each channel (one PWM per OCx
output) by writing ‘0110’ (PWM mode 1) or ‘0111’ (PWM mode 2) in the OCxM bits in the
TIMx_CCMRx register. You must enable the corresponding preload register by setting the
OCxPE bit in the TIMx_CCMRx register, and eventually the auto-reload preload register (in
upcounting or center-aligned modes) by setting the ARPE bit in the TIMx_CR1 register.
As the preload registers are transferred to the shadow registers only when an update event
occurs, before starting the counter, you have to initialize all the registers by setting the UG
bit in the TIMx_EGR register.
OCx polarity is software programmable using the CCxP bit in the TIMx_CCER register. It
can be programmed as active high or active low. OCx output is enabled by a combination of
the CCxE, CCxNE, MOE, OSSI and OSSR bits (TIMx_CCER and TIMx_BDTR registers).
Refer to the TIMx_CCER register description for more details.
In PWM mode (1 or 2), TIMx_CNT and TIMx_CCRx are always compared to determine
whether TIMx_CCRx ≤ TIMx_CNT or TIMx_CNT ≤ TIMx_CCRx (depending on the direction
of the counter).
The timer is able to generate PWM in edge-aligned mode or center-aligned mode
depending on the CMS bits in the TIMx_CR1 register.

DocID022558 Rev 8

535/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

PWM edge-aligned mode
•

Upcounting configuration
Upcounting is active when the DIR bit in the TIMx_CR1 register is low. Refer to the
Upcounting mode on page 510.
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 174 shows some edge-aligned PWM waveforms in an example where
TIMx_ARR=8.
Figure 174. Edge-aligned PWM waveforms (ARR=8)



&RXQWHUUHJLVWHU

&&5[ 





















2&;5()
&&[,)

2&;5()
&&5[ 
&&[,)

2&;5()

µ¶

&&5[!
&&[,)

2&;5()

µ¶

&&5[ 
&&[,)

069

•

Downcounting configuration
Downcounting is active when DIR bit in TIMx_CR1 register is high. Refer to the
Downcounting mode on page 514
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

536/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
TIMx_CR1 register is updated by hardware and must not be changed by software. Refer to
the Center-aligned mode (up/down counting) on page 517.
Figure 175 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 175. Center-aligned PWM waveforms (ARR=8)
&RXQWHUUHJLVWHU





































2&[5()
&&5[ 
&06 
&06 
&06 

&&[,)

2&[5()
&&5[ 

&06 RU

&&[,)
2&[5()

µ¶

&&5[ 
&&[,)

2&[5()
&&5[!

µ¶

&06 
&06 
&06 

&&[,)

2&[5()
&&5[ 
&&[,)

&06 
&06 
&06 

µ¶

&06 
&06 
&06 

$,E

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

DocID022558 Rev 8

537/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

in the TIMx_CR1 register. Moreover, the DIR and CMS bits must not be changed at the
same time by the software.
•

•

20.3.12

Writing to the counter while running in center-aligned mode is not recommended as it
can lead to unexpected results. In particular:
–

The direction is not updated if you write a value in the counter that is greater than
the auto-reload value (TIMx_CNT>TIMx_ARR). For example, if the counter was
counting up, it continues to count up.

–

The direction is updated if you write 0 or write the TIMx_ARR value in the counter
but no Update Event UEV is generated.

The safest way to use center-aligned mode is to generate an update by software
(setting the UG bit in the TIMx_EGR register) just before starting the counter and not to
write the counter while it is running.

Asymmetric PWM mode
Asymmetric mode allows two center-aligned PWM signals to be generated with a
programmable phase shift. While the frequency is determined by the value of the
TIMx_ARR register, the duty cycle and the phase-shift are determined by a pair of
TIMx_CCRx register. One register controls the PWM during up-counting, the second during
down counting, so that PWM is adjusted every half PWM cycle:
–

OC1REFC (or OC2REFC) is controlled by TIMx_CCR1 and TIMx_CCR2

–

OC3REFC (or OC4REFC) is controlled by TIMx_CCR3 and TIMx_CCR4

Asymmetric PWM mode can be selected independently on two channel (one OCx output
per pair of CCR registers) by writing ‘1110’ (Asymmetric PWM mode 1) or ‘1111’
(Asymmetric PWM mode 2) in the OCxM bits in the TIMx_CCMRx register.
Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
When a given channel is used as asymmetric PWM channel, its complementary channel
can also be used. For instance, if an OC1REFC signal is generated on channel 1
(Asymmetric PWM mode 1), it is possible to output either the OC2REF signal on channel 2,
or an OC2REFC signal resulting from asymmetric PWM mode 1.
Figure 176 represents an example of signals that can be generated using Asymmetric PWM
mode (channels 1 to 4 are configured in Asymmetric PWM mode 1). Together with the
deadtime generator, this allows a full-bridge phase-shifted DC to DC converter to be
controlled.

538/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 176. Generation of 2 phase-shifted PWM signals with 50% duty cycle

&RXQWHUUHJLVWHU

&&5
&&5
&&5
&&5





































2&5()&


2&5()&



069

20.3.13

Combined PWM mode
Combined PWM mode allows two edge or center-aligned PWM signals to be generated with
programmable delay and phase shift between respective pulses. While the frequency is
determined by the value of the TIMx_ARR register, the duty cycle and delay are determined
by the two TIMx_CCRx registers. The resulting signals, OCxREFC, are made of an OR or
AND logical combination of two reference PWMs:
–

OC1REFC (or OC2REFC) is controlled by TIMx_CCR1 and TIMx_CCR2

–

OC3REFC (or OC4REFC) is controlled by TIMx_CCR3 and TIMx_CCR4

Combined PWM mode can be selected independently on two channels (one OCx output per
pair of CCR registers) by writing ‘1100’ (Combined PWM mode 1) or ‘1101’ (Combined PWM
mode 2) in the OCxM bits in the TIMx_CCMRx register.
When a given channel is used as combined PWM channel, its complementary channel must
be configured in the opposite PWM mode (for instance, one in Combined PWM mode 1 and
the other in Combined PWM mode 2).
Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
Figure 177 represents an example of signals that can be generated using Asymmetric PWM
mode, obtained with the following configuration:
–

Channel 1 is configured in Combined PWM mode 2,

–

Channel 2 is configured in PWM mode 1,

–

Channel 3 is configured in Combined PWM mode 2,

–

Channel 4 is configured in PWM mode 1.

DocID022558 Rev 8

539/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Figure 177. Combined PWM mode on channel 1 and 3

2&¶
2&¶

2&
2&
2&5()
2&5()
2&5()¶
2&5()¶

2&5()&
2&5()&¶

2&5()& 2&5()$1'2&5()
2&5()&¶ 2&5()¶252&5()¶

069

20.3.14

Combined 3-phase PWM mode
Combined 3-phase PWM mode allows one to three center-aligned PWM signals to be
generated with a single programmable signal ANDed in the middle of the pulses. The
OC5REF signal is used to define the resulting combined signal. The 3-bits GC5C[3:1] in the
TIMx_CCR5 allow selection on which reference signal the OC5REF is combined. The
resulting signals, OCxREFC, are made of an AND logical combination of two reference
PWMs:
–

If GC5C1 is set, OC1REFC is controlled by TIMx_CCR1 and TIMx_CCR5

–

If GC5C2 is set, OC2REFC is controlled by TIMx_CCR2 and TIMx_CCR5

–

If GC5C3 is set, OC3REFC is controlled by TIMx_CCR3 and TIMx_CCR5

Combined 3-phase PWM mode can be selected independently on channels 1 to 3 by setting
at least one of the 3-bits GC5C[3:1].

540/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 178. 3-phase combined PWM signals with multiple trigger pulses per period

2&

$55
2&

2&
2&
2&
2&
&RXQWHU
2&UHI
2&UHI&

*&&>@

2&UHI&
2&UHI&
3UHORDG
$FWLYH

[[[




[[[


2&UHI
2&UHI
75*2

069

The TRGO2 waveform shows how the ADC can be synchronized on given 3-phase PWM
signals. Please refer to Section 20.3.26: ADC synchronization for more details.

20.3.15

Complementary outputs and dead-time insertion
The advanced-control timers (TIM1/TIM8/TIM20) 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 122: Output control bits for complementary OCx and OCxN channels with break
feature on page 585 for more details. In particular, the dead-time is activated when
switching to the idle state (MOE falling down to 0).

DocID022558 Rev 8

541/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Dead-time insertion is enabled by setting both CCxE and CCxNE bits, and the MOE bit if the
break circuit is present. There is one 10-bit dead-time generator for each channel. From a
reference waveform OCxREF, it generates 2 outputs OCx and OCxN. If OCx and OCxN are
active high:
•

The OCx output signal is the same as the reference signal except for the rising edge,
which is delayed relative to the reference rising edge.

•

The OCxN output signal is the opposite of the reference signal except for the rising
edge, which is delayed relative to the reference falling edge.

If the delay is greater than the width of the active output (OCx or OCxN) then the
corresponding pulse is not generated.
The following figures show the relationships between the output signals of the dead-time
generator and the reference signal OCxREF. (we suppose CCxP=0, CCxNP=0, MOE=1,
CCxE=1 and CCxNE=1 in these examples)
Figure 179. Complementary output with dead-time insertion

2&[5()
2&[
GHOD\
2&[1
GHOD\

069

Figure 180. Dead-time waveforms with delay greater than the negative pulse

2&[5()
2&[
GHOD\
2&[1

069

542/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 181. Dead-time waveforms with delay greater than the positive pulse

2&[5()
2&[
2&[1
GHOD\

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 20.4.18: TIM1/TIM8/TIM20 break and
dead-time register (TIMx_BDTR) for delay calculation.

Re-directing OCxREF to OCx or OCxN
In output mode (forced, output compare or PWM), OCxREF can be re-directed to the OCx
output or to OCxN output by configuring the CCxE and CCxNE bits in the TIMx_CCER
register.
This allows you to send a specific waveform (such as PWM or static active level) on one
output while the complementary remains at its inactive level. Other alternative possibilities
are to have both outputs at inactive level or both outputs active and complementary with
dead-time.
Note:

When only OCxN is enabled (CCxE=0, CCxNE=1), it is not complemented and becomes
active as soon as OCxREF is high. For example, if CCxNP=0 then OCxN=OCxRef. On the
other hand, when both OCx and OCxN are enabled (CCxE=CCxNE=1) OCx becomes
active when OCxREF is high whereas OCxN is complemented and becomes active when
OCxREF is low.

20.3.16

Using the break function
The purpose of the break function is to protect power switches driven by PWM signals
generated with the TIM1 and TIM8 timers. The two break inputs are usually connected to
fault outputs of power stages and 3-phase inverters. When activated, the break circuitry
shuts down the PWM outputs and forces them to a predefined safe state.
When using the break functions, 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 122: Output control bits for
complementary OCx and OCxN channels with break feature on page 585 for more details.
The source for BRK can be:
•

An external source connected to the BKIN pin

•

An internal source: COMP4/7 output

DocID022558 Rev 8

543/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

The source for BRK_ACTH can be :
–

A clock failure event generated by the CSS. For further information on the CSS,
refer to Section 9.2.7: Clock security system (CSS)

–

COMP1/2/3/5/6 output

–

A PVD output

–

SRAM parity error signal

–

Cortex-M4®F LOCKUP (Hardfault) output

The source for BRK2 can be:
•

An external source connected to the BKIN2 pin

•

An internal source coming from a comparator output

The resulting signal on BRK2 is an OR between the external signal on the BKIN2 pin and
the comparator output (if selected as BRK2 event source).
When exiting from reset, the break circuit is disabled and the MOE bit is low. You can enable
the break functions by setting the BKE and BKE2 bits in the TIMx_BDTR register. The break
input polarities can be selected by configuring the BKP and BKP2 bits in the same register.
BKEx and BKPx can be modified at the same time. When the BKEx and BKPx bits are
written, a delay of 1 APB clock cycle is applied before the writing is effective. Consequently,
it is necessary to wait 1 APB clock period to correctly read back the bit after the write
operation.
Because MOE falling edge can be asynchronous, a resynchronization circuit has been
inserted between the actual signal (acting on the outputs) and the synchronous control bit
(accessed in the TIMx_BDTR register). It results in some delays between the asynchronous
and the synchronous signals. In particular, if you write MOE to 1 whereas it was low, you
must insert a delay (dummy instruction) before reading it correctly. This is because you write
the asynchronous signal and read the synchronous signal.
The break can be generated by any of the break inputs (BRK, BRK2, BRK_ACTH), BRK
and BRK2 have:
–

Programmable polarity (BKPx bit in the TIMx_BDTR register)

–

Programmable enable bit (BKEx in the TIMx_BDTR register)

–

Programmable filter (BKxF[3:0] bits in the TIMx_BDTR register) to avoid spurious
events.
When connected to BRK_ACTH, the filter feature is not available and the polarity is always
active high.
Break events can also be generated by software using the BG and B2G bits in the
TIMx_EGR register.
Note:

544/1141

An asynchronous (clockless) operation is only guaranteed when the programmable filter is
disabled. If it is enabled, a fail safe clock mode (for example by using the internal PLL and/or
the CSS) must be used to guarantee that break events are handled.

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
When one of the breaks occurs (selected level on one of the break inputs):

Note:

•

The MOE bit is cleared asynchronously, putting the outputs in inactive state, idle state
or even releasing the control to the GPIO controller (selected by the OSSI bit). This
feature is enabled even if the MCU oscillator is off.

•

Each output channel is driven with the level programmed in the OISx bit in the
TIMx_CR2 register as soon as MOE=0. If OSSI=0, the timer releases the output control
(taken over by the GPIO controller), otherwise the enable output remains high.

•

When complementary outputs are used:
–

The outputs are first put in inactive state (depending on the polarity). This is done
asynchronously so that it works even if no clock is provided to the timer.

–

If the timer clock is still present, then the dead-time generator is reactivated in
order to drive the outputs with the level programmed in the OISx and OISxN bits
after a dead-time. Even in this case, OCx and OCxN cannot be driven to their
active level together. Note that because of the resynchronization on MOE, the
dead-time duration is slightly longer than usual (around 2 ck_tim clock cycles).

–

If OSSI=0, the timer releases the output control (taken over by the GPIO controller
which forces a Hi-Z state), otherwise the enable outputs remain or become high as
soon as one of the CCxE or CCxNE bits is high.

•

The break status flag (BIF and B2IF bits in the TIMx_SR register) is set. An interrupt is
generated if the BIE bit in the TIMx_DIER register is set. A DMA request can be sent if
the BDE bit in the TIMx_DIER register is set.

•

If the AOE bit in the TIMx_BDTR register is set, the MOE bit is automatically set again
at the next update event (UEV). As an example, this can be used to perform a
regulation. Otherwise, MOE remains low until the application sets it to ‘1’ again. In this
case, it can be used for security and you can connect the break input to an alarm from
power drivers, thermal sensors or any security components.

The break inputs are active on level. Thus, the MOE cannot be set while the break input is
active (neither automatically nor by software). In the meantime, the status flag BIF and B2IF
cannot be cleared.
In addition to the break input and the output management, a write protection has been
implemented inside the break circuit to safeguard the application. It allows to freeze the
configuration of several parameters (dead-time duration, OCx/OCxN polarities and state
when disabled, OCxM configurations, break enable and polarity). The application can
choose from 3 levels of protection selected by the LOCK bits in the TIMx_BDTR register.
Refer to Section 20.4.18: TIM1/TIM8/TIM20 break and dead-time register (TIMx_BDTR).
The LOCK bits can be written only once after an MCU reset.
Figure 182 shows an example of behavior of the outputs in response to a break.

DocID022558 Rev 8

545/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Figure 182. Various output behavior in response to a break event on BKIN (OSSI = 1)
%5($. 02( 

2&[5()

2&[
2&[1QRWLPSOHPHQWHG&&[3 2,6[ 

2&[
2&[1QRWLPSOHPHQWHG&&[3 2,6[ 

2&[
2&[1QRWLPSOHPHQWHG&&[3 2,6[ 

2&[
2&[1QRWLPSOHPHQWHG&&[3 2,6[ 

2&[
GHOD\
GHOD\
2&[1
&&[( &&[3 2,6[ &&[1( &&[13 2,6[1 

GHOD\

2&[
GHOD\
GHOD\
2&[1
&&[( &&[3 2,6[ &&[1( &&[13 2,6[1 

GHOD\

2&[
2&[1
&&[( &&[3 2,6[ &&[1( &&[13 2,6[1 

GHOD\

2&[
2&[1
&&[( &&[3 2,6[ &&[1( &&[13 2,6[1 

GHOD\

2&[
2&[1
&&[( &&[3 &&[1( &&[13 2,6[ 2,6[1 RU2,6[ 2,6[1 

069

546/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
The two break inputs have different behaviors on timer outputs:
–

The BRK input can either disable (inactive state) or force the PWM outputs to a
predefined safe state.

–

BRK2 can only disable (inactive state) the PWM outputs.

The BRK has a higher priority than BRK2 input, as described in Table 119.
Note:

BRK2 must only be used with OSSR = OSSI = 1.
Table 119. Behavior of timer outputs versus BRK/BRK2 inputs
Typical use case
BRK2

Timer outputs
state

Active

Inactive

BRK

OCxN output
(low side switches)

OCx output
(high side switches)

X

– Inactive then
forced output
state (after a
deadtime)
– Outputs disabled
if OSSI = 0
(control taken
over by GPIO
logic)

ON after deadtime
insertion

OFF

Active

Inactive

OFF

OFF

Figure 183 gives an example of OCx and OCxN output behavior in case of active signals on
BKIN and BKIN2 inputs. In this case, both outputs have active high polarities (CCxP =
CCxNP = 0 in TIMx_CCER register).
Figure 183. PWM output state following BKIN and BKIN2 pins assertion (OSSI=1)
%.,1

%.,1
2&[
'HDGWLPH

'HDGWLPH

,2VWDWH

$FWLYH

,QDFWLYH

,GOH
069

DocID022558 Rev 8

547/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Figure 184. PWM output state following BKIN assertion (OSSI=0)
%.,1

,2VWDWHGHILQHGE\WKH*3,2FRQWUROOHU +,=

2&[
'HDGWLPH
,2VWDWH

,2VWDWHGHILQHGE\WKH*3,2FRQWUROOHU +,=

$FWLYH

,QDFWLYH

'LVDEOHG
069

20.3.17

Clearing the OCxREF signal on an external event
The OCxREF signal of a given channel can be cleared when a high level is applied on the
ocref_clr_int input (OCxCE enable bit in the corresponding TIMx_CCMRx register set to 1).
OCxREF remains low until the next update event (UEV) occurs. This function can only be
used in Output compare and PWM modes. It does not work in Forced mode. ocref_clr_int
input can be selected between the OCREF_CLR input and ETRF (ETR after the filter) by
configuring the OCCS bit in the TIMx_SMCR register.
When ETRF is chosen, ETR must be configured as follows:
1.

The External Trigger Prescaler should be kept off: bits ETPS[1:0] of the TIMx_SMCR
register set to ‘00’.

2.

The external clock mode 2 must be disabled: bit ECE of the TIMx_SMCR register set to
‘0’.

3.

The External Trigger Polarity (ETP) and the External Trigger Filter (ETF) can be
configured according to the user needs.

Figure 185 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.

548/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 185. Clearing TIMx OCxREF

&&5[
&RXQWHU &17

(75)

2&[5()
2&[&( µ¶
2&[5()
2&[&( µ¶

RFUHIBFOUBLQW
EHFRPHVKLJK

RFUHIBFOUBLQW
VWLOOKLJK
069

Note:

In case of a PWM with a 100% duty cycle (if CCRx>ARR), then OCxREF is enabled again at
the next counter overflow.

DocID022558 Rev 8

549/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

20.3.18

RM0316

6-step PWM generation
When complementary outputs are used on a channel, preload bits are available on the
OCxM, CCxE and CCxNE bits. The preload bits are transferred to the shadow bits at the
COM commutation event. Thus you can program in advance the configuration for the next
step and change the configuration of all the channels at the same time. COM can be
generated by software by setting the COM bit in the TIMx_EGR register or by hardware (on
TRGI rising edge).
A flag is set when the COM event occurs (COMIF bit in the TIMx_SR register), which can
generate an interrupt (if the COMIE bit is set in the TIMx_DIER register) or a DMA request
(if the COMDE bit is set in the TIMx_DIER register).
The Figure 186 describes the behavior of the OCx and OCxN outputs when a COM event
occurs, in 3 different examples of programmed configurations.
Figure 186. 6-step generation, COM example (OSSR=1)

&&5[
&RXQWHU &17

2&[5()

:ULWH&20WR
&20HYHQW
&&[( 
ZULWH2&[0WR
&&[1( 
2&[0  IRUFHGLQDFWLYH

&&[( 
&&[1( 
2&[0 

2&[
([DPSOH 
2&[1

2&[

:ULWH&&[1(WR
DQG2&[0WR
&&[( 
&&[1( 
2&[0  IRUFHGLQDFWLYH

&&[( 
&&[1( 
2&[0 

([DPSOH 
2&[1
ZULWH&&[1(WR
&&[( 
DQG2&[0WR
&&[1( 
2&[0  IRUFHGLQDFWLYH

&&[( 
&&[1( 
2&[0 

2&[
([DPSOH 
2&[1

DL

550/1141

DocID022558 Rev 8

RM0316

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 187. Example of one pulse mode.
7,
2&5()
2&

7,0B$55
&RXQWHU

20.3.19

Advanced-control timers (TIM1/TIM8/TIM20)

7,0B&&5


W'(/$<

W38/6(

W

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.
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).

DocID022558 Rev 8

551/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

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.

20.3.20

Retriggerable one pulse mode (OPM)
This mode allows the counter to be started in response to a stimulus and to generate a
pulse with a programmable length, but with the following differences with Non-retriggerable
one pulse mode described in Section 20.3.19:
–

The pulse starts as soon as the trigger occurs (no programmable delay)

–

The pulse is extended if a new trigger occurs before the previous one is completed

The timer must be in Slave mode, with the bits SMS[3:0] = ‘1000’ (Combined Reset + trigger
mode) in the TIMx_SMCR register, and the OCxM[3:0] bits set to ‘1000’ or ‘1001’ for
Retrigerrable OPM mode 1 or 2.
If the timer is configured in Up-counting mode, the corresponding CCRx must be set to 0
(the ARR register sets the pulse length). If the timer is configured in Down-counting mode,
CCRx must be above or equal to ARR.
Note:

The OCxM[3:0] and SMS[3:0] bit fields are split into two parts for compatibility reasons, the
most significant bit are not contiguous with the 3 least significant ones.
This mode must not be used with center-aligned PWM modes. It is mandatory to have
CMS[1:0] = 00 in TIMx_CR1.

552/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 188. Retriggerable one pulse mode
75*,

&RXQWHU

2XWSXW

069

20.3.21

Encoder interface mode
To select Encoder Interface mode write SMS=‘001’ in the TIMx_SMCR register if the
counter is counting on TI2 edges only, SMS=’010’ if it is counting on TI1 edges only and
SMS=’011’ if it is counting on both TI1 and TI2 edges.
Select the TI1 and TI2 polarity by programming the CC1P and CC2P bits in the TIMx_CCER
register. When needed, you can program the input filter as well. CC1NP and CC2NP must
be kept low.
The two inputs TI1 and TI2 are used to interface to an quadrature encoder. Refer to
Table 120. 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,
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 quadrature encoder and its content, therefore, always represents the encoder’s position.
The count direction correspond to the rotation direction of the connected sensor. The table
summarizes the possible combinations, assuming TI1 and TI2 don’t switch at the same
time.

DocID022558 Rev 8

553/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Table 120. Counting direction versus encoder signals

Active edge

Level on
opposite
signal (TI1FP1
for TI2,
TI2FP2 for
TI1)

TI1FP1 signal

TI2FP2 signal

Rising

Falling

Rising

Falling

Counting on
TI1 only

High

Down

Up

No Count

No Count

Low

Up

Down

No Count

No Count

Counting on
TI2 only

High

No Count

No Count

Up

Down

Low

No Count

No Count

Down

Up

Counting on
TI1 and TI2

High

Down

Up

Up

Down

Low

Up

Down

Down

Up

A quadrature encoder can be connected directly to the MCU without external interface logic.
However, comparators are normally be used to convert the encoder’s differential outputs to
digital signals. This greatly increases noise immunity. The third encoder output which
indicate the mechanical zero position, may be connected to an external interrupt input and
trigger a counter reset.
The Figure 189 gives an example of counter operation, showing count signal generation
and direction control. It also shows how input jitter is compensated where both edges are
selected. This might occur if the sensor is positioned near to one of the switching points. For
this example we assume that the configuration is the following:
•

CC1S=’01’ (TIMx_CCMR1 register, TI1FP1 mapped on TI1).

•

CC2S=’01’ (TIMx_CCMR2 register, TI1FP2 mapped on TI2).

•

CC1P=’0’ and CC1NP=’0’ (TIMx_CCER register, TI1FP1 non-inverted, TI1FP1=TI1).

•

CC2P=’0’ and CC2NP=’0’ (TIMx_CCER register, TI1FP2 non-inverted, TI1FP2= TI2).

•

SMS=’011’ (TIMx_SMCR register, both inputs are active on both rising and falling
edges).

•

CEN=’1’ (TIMx_CR1 register, Counter enabled).
Figure 189. Example of counter operation in encoder interface mode.
IRUZDUG

MLWWHU

EDFNZDUG

MLWWHU

IRUZDUG

7,
7,

&RXQWHU

XS

GRZQ

XS

069

554/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Figure 190 gives an example of counter behavior when TI1FP1 polarity is inverted (same
configuration as above except CC1P=’1’).
Figure 190. Example of encoder interface mode with TI1FP1 polarity inverted.
IRUZDUG

MLWWHU

EDFNZDUG

MLWWHU

IRUZDUG

7,
7,

&RXQWHU

GRZQ

XS

GRZQ

069

The timer, when configured in Encoder Interface mode provides information on the sensor’s
current position. You can obtain dynamic information (speed, acceleration, deceleration) by
measuring the period between two encoder events using a second timer configured in
capture mode. The output of the encoder which indicates the mechanical zero can be used
for this purpose. Depending on the time between two events, the counter can also be read
at regular times. You can do this by latching the counter value into a third input capture
register if available (then the capture signal must be periodic and can be generated by
another timer). when available, it is also possible to read its value through a DMA request.
The IUFREMAP bit in the TIMx_CR1 register forces a continuous copy of the update
interrupt flag (UIF) into the timer counter register’s bit 31 (TIMxCNT[31]). This allows both
the counter value and a potential roll-over condition signaled by the UIFCPY flag to be read
in an atomic way. It eases the calculation of angular speed by avoiding race conditions
caused, for instance, by a processing shared between a background task (counter reading)
and an interrupt (update interrupt).
There is no latency between the UIF and UIFCPY flag assertions.
In 32-bit timer implementations, when the IUFREMAP bit is set, bit 31 of the counter is
overwritten by the UIFCPY flag upon read access (the counter’s most significant bit is only
accessible in write mode).

20.3.22

UIF bit remapping
The IUFREMAP bit in the TIMx_CR1 register forces a continuous copy of the Update
Interrupt Flag UIF into the timer counter register’s bit 31 (TIMxCNT[31]). This allows both
the counter value and a potential roll-over condition signaled by the UIFCPY flag to be read
in an atomic way. In particular cases, it can ease the calculations by avoiding race
conditions, caused for instance by a processing shared between a background task
(counter reading) and an interrupt (Update Interrupt).
There is no latency between the UIF and UIFCPY flags assertion.

DocID022558 Rev 8

555/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

20.3.23

RM0316

Timer input XOR function
The TI1S bit in the TIMx_CR2 register, allows the input filter of channel 1 to be connected to
the output of an XOR gate, combining the three input pins TIMx_CH1, TIMx_CH2 and
TIMx_CH3.
The XOR output can be used with all the timer input functions such as trigger or input
capture. It is convenient to measure the interval between edges on two input signals, as per
Figure 191 below.
Figure 191. Measuring time interval between edges on 3 signals

7,
7,
7,

 ;25

7,0[
&RXQWHU

069

20.3.24

Interfacing with Hall sensors
This is done using the advanced-control timers (TIM1 or TIM8) to generate PWM signals to
drive the motor and another timer TIMx (TIM2, TIM3, TIM4) referred to as “interfacing timer”
in Figure 192. The “interfacing timer” captures the 3 timer input pins (CC1, CC2, CC3)
connected through a XOR to the TI1 input channel (selected by setting the TI1S bit in the
TIMx_CR2 register).
The slave mode controller is configured in reset mode; the slave input is TI1F_ED. Thus,
each time one of the 3 inputs toggles, the counter restarts counting from 0. This creates a
time base triggered by any change on the Hall inputs.
On the “interfacing timer”, capture/compare channel 1 is configured in capture mode,
capture signal is TRC (See Figure 167: Capture/compare channel (example: channel 1
input stage) on page 528). 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.

556/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
Example: you want to change the PWM configuration of your advanced-control timer TIM1
after a programmed delay each time a change occurs on the Hall inputs connected to one of
the TIMx timers.
•

Configure 3 timer inputs ORed to the TI1 input channel by writing the TI1S bit in the
TIMx_CR2 register to ‘1’,

•

Program the time base: write the TIMx_ARR to the max value (the counter must be
cleared by the TI1 change. Set the prescaler to get a maximum counter period longer
than the time between 2 changes on the sensors,

•

Program the channel 1 in capture mode (TRC selected): write the CC1S bits in the
TIMx_CCMR1 register to ‘01’. You can also program the digital filter if needed,

•

Program the channel 2 in PWM 2 mode with the desired delay: write the OC2M bits to
‘111’ and the CC2S bits to ‘00’ in the TIMx_CCMR1 register,

•

Select OC2REF as trigger output on TRGO: write the MMS bits in the TIMx_CR2
register to ‘101’,

In the advanced-control timer TIM1, the right ITR input must be selected as trigger input, the
timer is programmed to generate PWM signals, the capture/compare control signals are
preloaded (CCPC=1 in the TIMx_CR2 register) and the COM event is controlled by the
trigger input (CCUS=1 in the TIMx_CR2 register). The PWM control bits (CCxE, OCxM) are
written after a COM event for the next step (this can be done in an interrupt subroutine
generated by the rising edge of OC2REF).
The Figure 192 describes this example.

DocID022558 Rev 8

557/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Figure 192. Example of Hall sensor interface

7,+

,QWHUIDFLQJWLPHU

7,+
7,+

&RXQWHU &17
&&5

&&5

&$

&$

&

&$

&$%

&

$GYDQFHGFRQWUROWLPHUV 7,0 7,0 

75*2 2&5()

&20
2&

2&1
2&

2&1

2&
2&1

:ULWH&&[(&&[1(
DQG2&[0IRUQH[WVWHS
DL

558/1141

DocID022558 Rev 8

RM0316

20.3.25

Advanced-control timers (TIM1/TIM8/TIM20)

Timer synchronization
The TIMx timers are linked together internally for timer synchronization or chaining. They
can be synchronized in several modes: Reset mode, Gated mode, and Trigger mode.

Slave mode: Reset mode
The counter and its prescaler can be reinitialized in response to an event on a trigger input.
Moreover, if the URS bit from the TIMx_CR1 register is low, an update event UEV is
generated. Then all the preloaded registers (TIMx_ARR, TIMx_CCRx) are updated.
In the following example, the upcounter is cleared in response to a rising edge on TI1 input:
•

Configure the channel 1 to detect rising edges on TI1. Configure the input filter duration
(in this example, we don’t need any filter, so we keep IC1F=0000). The capture
prescaler is not used for triggering, so you don’t need to configure it. The CC1S bits
select the input capture source only, CC1S = 01 in the TIMx_CCMR1 register. Write
CC1P=0 and CC1NP=’0’ in TIMx_CCER register to validate the polarity (and detect
rising edges only).

•

Configure the timer in reset mode by writing SMS=100 in TIMx_SMCR register. Select
TI1 as the input source by writing TS=101 in TIMx_SMCR register.

•

Start the counter by writing CEN=1 in the TIMx_CR1 register.

The counter starts counting on the internal clock, then behaves normally until TI1 rising
edge. When TI1 rises, the counter is cleared and restarts from 0. In the meantime, the
trigger flag is set (TIF bit in the TIMx_SR register) and an interrupt request, or a DMA
request can be sent if enabled (depending on the TIE and TDE bits in TIMx_DIER register).
The following figure shows this behavior when the auto-reload register TIMx_ARR=0x36.
The delay between the rising edge on TI1 and the actual reset of the counter is due to the
resynchronization circuit on TI1 input.
Figure 193. Control circuit in reset mode

7,
8*
&RXQWHUFORFN FNBFQW FNBSVF
&RXQWHUUHJLVWHU

              

7,)

069

DocID022558 Rev 8

559/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

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 194. Control circuit in Gated mode

7,
FQWBHQ
&RXQWHUFORFN FNBFQW FNBSVF
&RXQWHUUHJLVWHU

   



   

7,)

:ULWH7,) 
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:
•

560/1141

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.

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)
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 195. Control circuit in trigger mode
7,
FQWBHQ
&RXQWHUFORFN FNBFQW FNBSVF
&RXQWHUUHJLVWHU





  

7,)
069

Slave mode: Combined reset + trigger mode
In this case, a rising edge of the selected trigger input (TRGI) reinitializes the counter,
generates an update of the registers, and starts the counter.
This mode is used for one-pulse mode.

Slave mode: external clock mode 2 + trigger mode
The external clock mode 2 can be used in addition to another slave mode (except external
clock mode 1 and encoder mode). In this case, the ETR signal is used as external clock
input, and another input can be selected as trigger input (in reset mode, gated mode or
trigger mode). It is recommended not to select ETR as TRGI through the TS bits of
TIMx_SMCR register.
In the following example, the upcounter is incremented at each rising edge of the ETR
signal as soon as a rising edge of TI1 occurs:

DocID022558 Rev 8

561/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)
1.

2.

3.

RM0316

Configure the external trigger input circuit by programming the TIMx_SMCR register as
follows:
–

ETF = 0000: no filter

–

ETPS=00: prescaler disabled

–

ETP=0: detection of rising edges on ETR and ECE=1 to enable the external clock
mode 2.

Configure the channel 1 as follows, to detect rising edges on TI:
–

IC1F=0000: no filter.

–

The capture prescaler is not used for triggering and does not need to be
configured.

–

CC1S=01in TIMx_CCMR1 register to select only the input capture source

–

CC1P=0 and CC1NP=’0’ in TIMx_CCER register to validate the polarity (and
detect rising edge only).

Configure the timer in trigger mode by writing SMS=110 in TIMx_SMCR register. Select
TI1 as the input source by writing TS=101 in TIMx_SMCR register.

A rising edge on TI1 enables the counter and sets the TIF flag. The counter then counts on
ETR rising edges.
The delay between the rising edge of the ETR signal and the actual reset of the counter is
due to the resynchronization circuit on ETRP input.
Figure 196. Control circuit in external clock mode 2 + trigger mode

7,

&(1&17B(1

(75

&RXQWHUFORFN &.B&17 &.B36&

&RXQWHUUHJLVWHU







7,)
069

Note:

562/1141

The clock of the slave timer must be enabled prior to receive events from the master timer,
and must not be changed on-the-fly while triggers are received from the master timer.

DocID022558 Rev 8

RM0316

20.3.26

Advanced-control timers (TIM1/TIM8/TIM20)

ADC synchronization
The timer can generate an ADC triggering event with various internal signals, such as reset,
enable or compare events. It is also possible to generate a pulse issued by internal edge
detectors, such as:
–

Rising and falling edges of OC4ref

–

Rising edge on OC5ref or falling edge on OC6ref

The triggers are issued on the TRGO2 internal line which is redirected to the ADC. There is
a total of 16 possible events, which can be selected using the MMS2[3:0] bits in the
TIMx_CR2 register.
An example of an application for 3-phase motor drives is given in Figure 178 on page 541.
Note:

The clock of the slave timer must be enabled prior to receive events from the master timer,
and must not be changed on-the-fly while triggers are received from the master timer.

Note:

The clock of the ADC must be enabled prior to receive events from the master timer, and
must not be changed on-the-fly while triggers are received from the timer.

20.3.27

DMA burst mode
The TIMx timers have the capability to generate multiple DMA requests upon a single event.
The main purpose is to be able to re-program part of the timer multiple times without
software overhead, but it can also be used to read several registers in a row, at regular
intervals.
The DMA controller destination is unique and must point to the virtual register TIMx_DMAR.
On a given timer event, the timer launches a sequence of DMA requests (burst). Each write
into the TIMx_DMAR register is actually redirected to one of the timer registers.
The DBL[4:0] bits in the TIMx_DCR register set the DMA burst length. The timer recognizes
a burst transfer when a read or a write access is done to the TIMx_DMAR address), i.e. the
number of transfers (either in half-words or in bytes).
The DBA[4:0] bits in the TIMx_DCR registers define the DMA base address for DMA
transfers (when read/write access are done through the TIMx_DMAR address). DBA is
defined as an offset starting from the address of the TIMx_CR1 register:
Example:
00000: TIMx_CR1
00001: TIMx_CR2
00010: TIMx_SMCR
As an example, the timer DMA burst feature is used to update the contents of the CCRx
registers (x = 2, 3, 4) upon an update event, with the DMA transferring half words into the
CCRx registers.

DocID022558 Rev 8

563/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

This is done in the following steps:
1.

Configure the corresponding DMA channel as follows:
–

DMA channel peripheral address is the DMAR register address

–

DMA channel memory address is the address of the buffer in the RAM containing
the data to be transferred by DMA into CCRx registers.

–

Number of data to transfer = 3 (See note below).

–

Circular mode disabled.

2.

Configure the DCR register by configuring the DBA and DBL bit fields as follows:
DBL = 3 transfers, DBA = 0xE.

3.

Enable the TIMx update DMA request (set the UDE bit in the DIER register).

4.

Enable TIMx

5.

Enable the DMA channel

This example is for the case where every CCRx register to be updated once. If every CCRx
register is to be updated twice for example, the number of data to transfer should be 6. Let's
take the example of a buffer in the RAM containing data1, data2, data3, data4, data5 and
data6. The data is transferred to the CCRx registers as follows: on the first update DMA
request, data1 is transferred to CCR2, data2 is transferred to CCR3, data3 is transferred to
CCR4 and on the second update DMA request, data4 is transferred to CCR2, data5 is
transferred to CCR3 and data6 is transferred to CCR4.
Note:

A null value can be written to the reserved registers.

20.3.28

Debug mode
When the microcontroller enters debug mode (Cortex-M4®F core halted), the TIMx counter
either continues to work normally or stops, depending on DBG_TIMx_STOP configuration
bit in DBG module.
For safety purposes, when the counter is stopped (DBG_TIMx_STOP = 1), the outputs are
disabled (as if the MOE bit was reset). The outputs can either be forced to an inactive state
(OSSI bit = 1), or have their control taken over by the GPIO controller (OSSI bit = 0),
typically to force a Hi-Z.
For more details, refer to Section 33.16.2: Debug support for timers, watchdog, bxCAN and
I2C.
For safety purposes, when the counter is stopped (DBG_TIMx_STOP = 1), the outputs are
disabled (as if the MOE bit was reset). The outputs can either be forced to an inactive state
(OSSI bit = 1), or have their control taken over by the GPIO controller (OSSI bit = 0) to force
them to Hi-Z.

564/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

20.4

TIM1/TIM8/TIM20 registers
Refer to for a list of abbreviations used in register descriptions.

20.4.1

TIM1/TIM8/TIM20 control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15
Res.

14
Res.

13
Res.

12

11

10

Res.

UIFRE
MAP

Res.

rw

9

8

CKD[1:0]
rw

7

6

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 15:12 Reserved, must be kept at reset value.
Bit 11 UIFREMAP: UIF status bit remapping
0: No remapping. UIF status bit is not copied to TIMx_CNT register bit 31.
1: Remapping enabled. UIF status bit is copied to TIMx_CNT register bit 31.
Bit 10 Reserved, must be kept at reset value.
Bits 9:8 CKD[1:0]: Clock division
This bit-field indicates the division ratio between the timer clock (CK_INT) frequency and the
dead-time and sampling clock (tDTS)used by the dead-time generators and the digital filters
(ETR, TIx),
00: tDTS=tCK_INT
01: tDTS=2*tCK_INT
10: tDTS=4*tCK_INT
11: Reserved, do not program this value
Bit 7 ARPE: Auto-reload preload enable
0: TIMx_ARR register is not buffered
1: TIMx_ARR register is buffered
Bits 6:5 CMS[1:0]: Center-aligned mode selection
00: Edge-aligned mode. The counter counts up or down depending on the direction bit
(DIR).
01: Center-aligned mode 1. The counter counts up and down alternatively. Output compare
interrupt flags of channels configured in output (CCxS=00 in TIMx_CCMRx register) are set
only when the counter is counting down.
10: Center-aligned mode 2. The counter counts up and down alternatively. Output compare
interrupt flags of channels configured in output (CCxS=00 in TIMx_CCMRx register) are set
only when the counter is counting up.
11: Center-aligned mode 3. The counter counts up and down alternatively. Output compare
interrupt flags of channels configured in output (CCxS=00 in TIMx_CCMRx register) are set
both when the counter is counting up or down.
Note: It is not allowed to switch from edge-aligned mode to center-aligned mode as long as
the counter is enabled (CEN=1)
Bit 4 DIR: Direction
0: Counter used as upcounter
1: Counter used as downcounter
Note: This bit is read only when the timer is configured in Center-aligned mode or Encoder
mode.

DocID022558 Rev 8

565/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

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.

20.4.2

TIM1/TIM8/TIM20 control register 2 (TIMx_CR2)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

23

21

20

MMS2[3:0]
rw

rw
6

15

14

13

12

11

10

9

8

7

Res.

OIS4

OIS3N

OIS3

OIS2N

OIS2

OIS1N

OIS1

TI1S

rw

rw

rw

rw

rw

rw

rw

rw

566/1141

22

rw

rw

5

4

MMS[2:0]
rw

DocID022558 Rev 8

rw

rw

19

18

17

16

Res.

OIS6

Res.

OIS5

rw

rw

3

2

1

0

CCDS

CCUS

Res.

CCPC

rw

rw

rw

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:20 MMS2[3:0]: Master mode selection 2
These bits allow the information to be sent to ADC for synchronization (TRGO2) to be
selected. The combination is as follows:
0000: Reset - the UG bit from the TIMx_EGR register is used as trigger output (TRGO2). If
the reset is generated by the trigger input (slave mode controller configured in reset mode),
the signal on TRGO2 is delayed compared to the actual reset.
0001: Enable - the Counter Enable signal CNT_EN is used as trigger output (TRGO2). It is
useful to start several timers at the same time or to control a window in which a slave timer is
enabled. The Counter Enable signal is generated by a logic OR between the CEN control bit
and the trigger input when configured in Gated mode. When the Counter Enable signal is
controlled by the trigger input, there is a delay on TRGO2, except if the Master/Slave mode
is selected (see the MSM bit description in TIMx_SMCR register).
0010: Update - the update event is selected as trigger output (TRGO2). For instance, a
master timer can then be used as a prescaler for a slave timer.
0011: Compare pulse - the trigger output sends a positive pulse when the CC1IF flag is to
be set (even if it was already high), as soon as a capture or compare match occurs
(TRGO2).
0100: Compare - OC1REF signal is used as trigger output (TRGO2)
0101: Compare - OC2REF signal is used as trigger output (TRGO2)
0110: Compare - OC3REF signal is used as trigger output (TRGO2)
0111: Compare - OC4REF signal is used as trigger output (TRGO2)
1000: Compare - OC5REF signal is used as trigger output (TRGO2)
1001: Compare - OC6REF signal is used as trigger output (TRGO2)
1010: Compare Pulse - OC4REF rising or falling edges generate pulses on TRGO2
1011: Compare Pulse - OC6REF rising or falling edges generate pulses on TRGO2
1100: Compare Pulse - OC4REF or OC6REF rising edges generate pulses on TRGO2
1101: Compare Pulse - OC4REF rising or OC6REF falling edges generate pulses on
TRGO2
1110: Compare Pulse - OC5REF or OC6REF rising edges generate pulses on TRGO2
1111: Compare Pulse - OC5REF rising or OC6REF falling edges generate pulses on
TRGO2
Note: The clock of the slave timer or ADC must be enabled prior to receive events from the
master timer, and must not be changed on-the-fly while triggers are received from the
master timer.
Bit 19 Reserved, must be kept at reset value.
Bit 18 OIS6: Output Idle state 6 (OC6 output)
Refer to OIS1 bit
Bit 17 Reserved, must be kept at reset value.
Bit 16 OIS5: Output Idle state 5 (OC5 output)
Refer to OIS1 bit
Bit 15 Reserved, must be kept at reset value.
Bit 14 OIS4: Output Idle state 4 (OC4 output)
Refer to OIS1 bit
Bit 13 OIS3N: Output Idle state 3 (OC3N output)
Refer to OIS1N bit
Bit 12 OIS3: Output Idle state 3 (OC3 output)
Refer to OIS1 bit

DocID022558 Rev 8

567/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

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[1:0]: Master mode selection
These bits allow to select the information to be sent in master mode to slave timers for
synchronization (TRGO). The combination is as follows:
000: Reset - the UG bit from the TIMx_EGR register is used as trigger output (TRGO). If the
reset is generated by the trigger input (slave mode controller configured in reset mode) then
the signal on TRGO is delayed compared to the actual reset.
001: Enable - the Counter Enable signal CNT_EN is used as trigger output (TRGO). It is
useful to start several timers at the same time or to control a window in which a slave timer is
enable. The Counter Enable signal is generated by a logic OR between CEN control bit and
the trigger input when configured in gated mode. When the Counter Enable signal is
controlled by the trigger input, there is a delay on TRGO, except if the master/slave mode is
selected (see the MSM bit description in TIMx_SMCR register).
010: Update - The update event is selected as trigger output (TRGO). For instance a master
timer can then be used as a prescaler for a slave timer.
011: Compare Pulse - The trigger output send a positive pulse when the CC1IF flag is to be
set (even if it was already high), as soon as a capture or a compare match occurred.
(TRGO).
100: Compare - OC1REF signal is used as trigger output (TRGO)
101: Compare - OC2REF signal is used as trigger output (TRGO)
110: Compare - OC3REF signal is used as trigger output (TRGO)
111: Compare - OC4REF signal is used as trigger output (TRGO)
Note: The clock of the slave timer or ADC must be enabled prior to receive events from the
master timer, and must not be changed on-the-fly while triggers are received from the
master timer.
Bit 3 CCDS: Capture/compare DMA selection
0: CCx DMA request sent when CCx event occurs
1: CCx DMA requests sent when update event occurs

568/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bit 2 CCUS: Capture/compare control update selection
0: When capture/compare control bits are preloaded (CCPC=1), they are updated by setting
the COMG bit only
1: When capture/compare control bits are preloaded (CCPC=1), they are updated by setting
the COMG bit or when an rising edge occurs on TRGI
Note: This bit acts only on channels that have a complementary output.
Bit 1 Reserved, must be kept at reset value.
Bit 0 CCPC: Capture/compare preloaded control
0: CCxE, CCxNE and OCxM bits are not preloaded
1: CCxE, CCxNE and OCxM bits are preloaded, after having been written, they are updated
only when a commutation event (COM) occurs (COMG bit set or rising edge detected on
TRGI, depending on the CCUS bit).
Note: This bit acts only on channels that have a complementary output.

20.4.3

TIM1/TIM8/TIM20 slave mode control register (TIMx_SMCR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SMS[3]

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

ETP

ECE

rw

rw

rw

ETPS[1:0]
rw

rw

ETF[3:0]
rw

rw

rw

MSM
rw

rw

TS[2:0]
rw

rw

OCCS
rw

rw

0

SMS[2:0]
rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 SMS[3]: Slave mode selection - bit 3
Refer to SMS description - bits 2:0
Bit 15 ETP: External trigger polarity
This bit selects whether ETR or ETR is used for trigger operations
0: ETR is non-inverted, active at high level or rising edge.
1: ETR is inverted, active at low level or falling edge.
Bit 14 ECE: External clock enable
This bit enables External clock mode 2.
0: External clock mode 2 disabled
1: External clock mode 2 enabled. The counter is clocked by any active edge on the ETRF
signal.
Note: 1: Setting the ECE bit has the same effect as selecting external clock mode 1 with
TRGI connected to ETRF (SMS=111 and TS=111).
2: It is possible to simultaneously use external clock mode 2 with the following slave
modes: reset mode, gated mode and trigger mode. Nevertheless, TRGI must not be
connected to ETRF in this case (TS bits must not be 111).
3: If external clock mode 1 and external clock mode 2 are enabled at the same time,
the external clock input is ETRF.

DocID022558 Rev 8

569/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bits 13:12 ETPS[1:0]: External trigger prescaler
External trigger signal ETRP frequency must be at most 1/4 of TIMxCLK frequency. A
prescaler can be enabled to reduce ETRP frequency. It is useful when inputting fast external
clocks.
00: Prescaler OFF
01: ETRP frequency divided by 2
10: ETRP frequency divided by 4
11: ETRP frequency divided by 8
Bits 11:8 ETF[3:0]: External trigger filter
This bit-field then defines the frequency used to sample ETRP signal and the length of the
digital filter applied to ETRP. The digital filter is made of an event counter in which N
consecutive events are needed to validate a transition on the output:
0000: No filter, sampling is done at fDTS
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Bit 7 MSM: Master/slave mode
0: No action
1: The effect of an event on the trigger input (TRGI) is delayed to allow a perfect
synchronization between the current timer and its slaves (through TRGO). It is useful if we
want to synchronize several timers on a single external event.
Bits 6:4 TS[2:0]: Trigger selection
This bit-field selects the trigger input to be used to synchronize the counter.
000: Internal Trigger 0 (ITR0)
001: Internal Trigger 1 (ITR1)
010: Internal Trigger 2 (ITR2)
011: Internal Trigger 3 (ITR3)
100: TI1 Edge Detector (TI1F_ED)
101: Filtered Timer Input 1 (TI1FP1)
110: Filtered Timer Input 2 (TI2FP2)
111: External Trigger input (ETRF)
See Table 121: TIMx internal trigger connection on page 571 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 OCCS: OCREF clear selection
This bit is used to select the OCREF clear source.
0:OCREF_CLR_INT is connected to the OCREF_CLR input
1: OCREF_CLR_INT is connected to ETRF

570/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

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.
0000: Slave mode disabled - if CEN = ‘1’ then the prescaler is clocked directly by the internal
clock.
0001: Encoder mode 1 - Counter counts up/down on TI1FP1 edge depending on TI2FP2
level.
0010: Encoder mode 2 - Counter counts up/down on TI2FP2 edge depending on TI1FP1
level.
0011: Encoder mode 3 - Counter counts up/down on both TI1FP1 and TI2FP2 edges
depending on the level of the other input.
0100: Reset Mode - Rising edge of the selected trigger input (TRGI) reinitializes the counter
and generates an update of the registers.
0101: Gated Mode - The counter clock is enabled when the trigger input (TRGI) is high. The
counter stops (but is not reset) as soon as the trigger becomes low. Both start and stop of
the counter are controlled.
0110: Trigger Mode - The counter starts at a rising edge of the trigger TRGI (but it is not
reset). Only the start of the counter is controlled.
0111: External Clock Mode 1 - Rising edges of the selected trigger (TRGI) clock the counter.
1000: Combined reset + trigger mode - Rising edge of the selected trigger input (TRGI)
reinitializes the counter, generates an update of the registers and starts the counter.
Codes above 1000: Reserved.
Note: The gated mode must not be used if TI1F_ED is selected as the trigger input (TS=100).
Indeed, TI1F_ED outputs 1 pulse for each transition on TI1F, whereas the gated mode
checks the level of the trigger signal.
Note: The clock of the slave timer must be enabled prior to receive events from the master
timer, and must not be changed on-the-fly while triggers are received from the master
timer.

Table 121. TIMx internal trigger connection
Slave TIM

ITR0 (TS = 000)

ITR1 (TS = 001)

ITR2 (TS = 010)

ITR3 (TS = 011)

TIM1

TIM15

TIM2

TIM3

TIM4 or TIM17(1)

TIM8

TIM1

TIM2

TIM4

TIM3

TIM20

TIM1

TIM8

TIM4

TIM15

1. TIM1_ITR3 selection is made using bit 6 of the SYSCFG_CFGR1 register.

20.4.4

TIM1/TIM8/TIM20 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

DocID022558 Rev 8

571/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

Bit 15 Reserved, must be kept at reset value.
Bit 14 TDE: Trigger DMA request enable
0: Trigger DMA request disabled
1: Trigger DMA request enabled
Bit 13 COMDE: COM DMA request enable
0: COM DMA request disabled
1: COM DMA request enabled
Bit 12 CC4DE: Capture/Compare 4 DMA request enable
0: CC4 DMA request disabled
1: CC4 DMA request enabled
Bit 11 CC3DE: Capture/Compare 3 DMA request enable
0: CC3 DMA request disabled
1: CC3 DMA request enabled
Bit 10 CC2DE: Capture/Compare 2 DMA request enable
0: CC2 DMA request disabled
1: CC2 DMA request enabled
Bit 9 CC1DE: Capture/Compare 1 DMA request enable
0: CC1 DMA request disabled
1: CC1 DMA request enabled
Bit 8 UDE: Update DMA request enable
0: Update DMA request disabled
1: Update DMA request enabled
Bit 7 BIE: Break interrupt enable
0: Break interrupt disabled
1: Break interrupt enabled
Bit 6 TIE: Trigger interrupt enable
0: Trigger interrupt disabled
1: Trigger interrupt enabled
Bit 5 COMIE: COM interrupt enable
0: COM interrupt disabled
1: COM interrupt enabled
Bit 4 CC4IE: Capture/Compare 4 interrupt enable
0: CC4 interrupt disabled
1: CC4 interrupt enabled
Bit 3 CC3IE: Capture/Compare 3 interrupt enable
0: CC3 interrupt disabled
1: CC3 interrupt enabled

572/1141

DocID022558 Rev 8

RM0316

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

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

20.4.5

TIM1/TIM8/TIM20 status register (TIMx_SR)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CC6IF

CC5IF

rc_w0

rc_w0

15

14

13

Res.

Res.

Res.

12

11

10

9

CC4OF CC3OF CC2OF CC1OF
rc_w0

rc_w0

rc_w0

rc_w0

8

7

6

5

4

3

2

1

0

B2IF

BIF

TIF

COMIF

CC4IF

CC3IF

CC2IF

CC1IF

UIF

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

Bits 31:18 Reserved, must be kept at reset value.
Bit 17 CC6IF: Compare 6 interrupt flag
Refer to CC1IF description (Note: Channel 6 can only be configured as output)
Bit 16 CC5IF: Compare 5 interrupt flag
Refer to CC1IF description (Note: Channel 5 can only be configured as output)
Bits 15:13 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 B2IF: Break 2 interrupt flag
This flag is set by hardware as soon as the break 2 input goes active. It can be cleared by
software if the break 2 input is not active.
0: No break event occurred.
1: An active level has been detected on the break 2 input. An interrupt is generated if BIE=1
in the TIMx_DIER register.

DocID022558 Rev 8

573/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bit 7 BIF: Break interrupt flag
This flag is set by hardware as soon as the break input goes active. It can be cleared by
software if the break input is not active.
0: No break event occurred.
1: An active level has been detected on the break input. An interrupt is generated if BIE=1 in
the TIMx_DIER register.
Bit 6 TIF: Trigger interrupt flag
This flag is set by hardware on trigger event (active edge detected on TRGI input when the
slave mode controller is enabled in all modes but gated mode. It is set when the counter
starts or stops when gated mode is selected. It is cleared by software.
0: No trigger event occurred.
1: Trigger interrupt pending.
Bit 5 COMIF: COM interrupt flag
This flag is set by hardware on COM event (when Capture/compare Control bits - CCxE,
CCxNE, OCxM - have been updated). It is cleared by software.
0: No COM event occurred.
1: COM interrupt pending.
Bit 4 CC4IF: Capture/Compare 4 interrupt flag
Refer to CC1IF description
Bit 3 CC3IF: Capture/Compare 3 interrupt flag
Refer to CC1IF description
Bit 2 CC2IF: Capture/Compare 2 interrupt flag
Refer to CC1IF description
Bit 1 CC1IF: Capture/Compare 1 interrupt flag
If channel CC1 is configured as output: This flag is set by hardware when the counter
matches the compare value, with some exception in center-aligned mode (refer to the CMS
bits in the TIMx_CR1 register description). It is cleared by software.
0: No match.
1: The content of the counter TIMx_CNT matches the content of the TIMx_CCR1 register.
When the contents of TIMx_CCR1 are greater than the contents of TIMx_ARR, the CC1IF
bit goes high on the counter overflow (in upcounting and up/down-counting modes) or
underflow (in downcounting mode)
If channel CC1 is configured as input: This bit is set by hardware on a capture. It is
cleared by software or by reading the TIMx_CCR1 register.
0: No input capture occurred
1: The counter value has been captured in TIMx_CCR1 register (An edge has been
detected on IC1 which matches the selected polarity)
Bit 0 UIF: Update interrupt flag
This bit is set by hardware on an update event. It is cleared by software.
0: No update occurred.
1: Update interrupt pending. This bit is set by hardware when the registers are updated:
– At overflow or underflow regarding the repetition counter value (update if repetition
counter = 0) and if the UDIS=0 in the TIMx_CR1 register.
– When CNT is reinitialized by software using the UG bit in TIMx_EGR register, if URS=0
and UDIS=0 in the TIMx_CR1 register.
– When CNT is reinitialized by a trigger event (refer to Section 20.4.3: TIM1/TIM8/TIM20
slave mode control register (TIMx_SMCR)), if URS=0 and UDIS=0 in the TIMx_CR1
register.

574/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

20.4.6

TIM1/TIM8/TIM20 event generation register (TIMx_EGR)
Address offset: 0x14
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

B2G

BG

TG

COMG

CC4G

CC3G

CC2G

CC1G

UG

w

w

w

w

w

w

w

w

w

Bits 15:9 Reserved, must be kept at reset value.
Bit 8 B2G: Break 2 generation
This bit is set by software in order to generate an event, it is automatically cleared by
hardware.
0: No action
1: A break 2 event is generated. MOE bit is cleared and B2IF flag is set. Related interrupt
can occur if enabled.
Bit 7 BG: Break generation
This bit is set by software in order to generate an event, it is automatically cleared by
hardware.
0: No action
1: A break event is generated. MOE bit is cleared and BIF flag is set. Related interrupt or
DMA transfer can occur if enabled.
Bit 6 TG: Trigger generation
This bit is set by software in order to generate an event, it is automatically cleared by
hardware.
0: No action
1: The TIF flag is set in TIMx_SR register. Related interrupt or DMA transfer can occur if
enabled.
Bit 5 COMG: Capture/Compare control update generation
This bit can be set by software, it is automatically cleared by hardware
0: No action
1: When CCPC bit is set, it allows to update CCxE, CCxNE and OCxM bits
Note: This bit acts only on channels having a complementary output.
Bit 4 CC4G: Capture/Compare 4 generation
Refer to CC1G description
Bit 3 CC3G: Capture/Compare 3 generation
Refer to CC1G description
Bit 2 CC2G: Capture/Compare 2 generation
Refer to CC1G description

DocID022558 Rev 8

575/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

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).

20.4.7

TIM1/TIM8/TIM20 capture/compare mode register 1 (TIMx_CCMR1)
Address offset: 0x18
Reset value: 0x0000 0000
The channels can be used in input (capture mode) or in output (compare mode). The
direction of a channel is defined by configuring the corresponding CCxS bits. All the other
bits of this register have a different function in input and in output mode. For a given bit,
OCxx describes its function when the channel is configured in output, ICxx describes its
function when the channel is configured in input. So you must take care that the same bit
can have a different meaning for the input stage and for the output stage.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC2M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC1M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw
15

14

OC2
CE

13

12

OC2M[2:0]
IC2F[3:0]

rw

rw

rw

11

10

OC2
PE

OC2
FE

9

rw

8

CC2S[1:0]

7

6

OC1
CE

rw

rw

IC1F[3:0]
rw

rw

rw

rw

Output compare mode:
Bits 31:25 Reserved, must be kept at reset value.
Bit 24 OC2M[3]: Output Compare 2 mode - bit 3
Refer to OC2M description on bits 14:12.
Bits 23:17 Reserved, must be kept at reset value.
Bits16 OC1M[3]: Output Compare 1 mode - bit 3
Refer to OC1M description on bits 6:4

576/1141

4

OC1M[2:0]

IC2PSC[1:0]
rw

5

DocID022558 Rev 8

rw

3

2

OC1
PE

OC1
FE

1

0

CC1S[1:0]

IC1PSC[1:0]
rw

rw

rw

rw

rw

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bit 15 OC2CE: Output Compare 2 clear enable
Bits 14:12 OC2M[2:0]: Output Compare 2 mode
Bit 11 OC2PE: Output Compare 2 preload enable
Bit 10 OC2FE: Output Compare 2 fast enable
Bits 9:8 CC2S[1:0]: Capture/Compare 2 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC2 channel is configured as output
01: CC2 channel is configured as input, IC2 is mapped on TI2
10: CC2 channel is configured as input, IC2 is mapped on TI1
11: CC2 channel is configured as input, IC2 is mapped on TRC. This mode is working only if
an internal trigger input is selected through the TS bit (TIMx_SMCR register)
Note: CC2S bits are writable only when the channel is OFF (CC2E = ‘0’ in TIMx_CCER).
Bit 7 OC1CE: Output Compare 1 clear enable
0: OC1Ref is not affected by the ocref_clr_int signal
1: OC1Ref is cleared as soon as a High level is detected on ocref_clr_int signal
(OCREF_CLR input or ETRF input)

DocID022558 Rev 8

577/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bits 6:4 OC1M: Output Compare 1 mode
These bits define the behavior of the output reference signal OC1REF from which OC1 and
OC1N are derived. OC1REF is active high whereas OC1 and OC1N active level depends
on CC1P and CC1NP bits.
0000: Frozen - The comparison between the output compare register TIMx_CCR1 and the
counter TIMx_CNT has no effect on the outputs.(this mode is used to generate a timing
base).
0001: Set channel 1 to active level on match. OC1REF signal is forced high when the
counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).
0010: Set channel 1 to inactive level on match. OC1REF signal is forced low when the
counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).
0011: Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1.
0100: Force inactive level - OC1REF is forced low.
0101: Force active level - OC1REF is forced high.
0110: PWM mode 1 - In upcounting, channel 1 is active as long as TIMx_CNTTIMx_CCR1 else active (OC1REF=’1’).
0111: PWM mode 2 - In upcounting, channel 1 is inactive as long as
TIMx_CNTTIMx_CCR1 else inactive.
1000: Retrigerrable OPM mode 1 - In up-counting mode, the channel is active until a trigger
event is detected (on TRGI signal). Then, a comparison is performed as in PWM mode 1
and the channels becomes active again at the next update. In down-counting mode, the
channel is inactive until a trigger event is detected (on TRGI signal). Then, a comparison is
performed as in PWM mode 1 and the channels becomes inactive again at the next update.
1001: Retrigerrable OPM mode 2 - In up-counting mode, the channel is inactive until a
trigger event is detected (on TRGI signal). Then, a comparison is performed as in PWM
mode 2 and the channels becomes inactive again at the next update. In down-counting
mode, the channel is active until a trigger event is detected (on TRGI signal). Then, a
comparison is performed as in PWM mode 1 and the channels becomes active again at the
next update.
1010: Reserved,
1011: Reserved,
1100: Combined PWM mode 1 - OC1REF has the same behavior as in PWM mode 1.
OC1REFC is the logical OR between OC1REF and OC2REF.
1101: Combined PWM mode 2 - OC1REF has the same behavior as in PWM mode 2.
OC1REFC is the logical AND between OC1REF and OC2REF.
1110: Asymmetric PWM mode 1 - OC1REF has the same behavior as in PWM mode 1.
OC1REFC outputs OC1REF when the counter is counting up, OC2REF when it is counting
down.
1111: Asymmetric PWM mode 2 - OC1REF has the same behavior as in PWM mode 2.
OC1REFC outputs OC1REF when the counter is counting up, OC2REF when it is counting
down.
Note: These bits can not be modified as long as LOCK level 3 has been programmed (LOCK
bits in TIMx_BDTR register) and CC1S=’00’ (the channel is configured in output).
Note: In PWM mode, the OCREF level changes only when the result of the comparison
changes or when the output compare mode switches from “frozen” mode to “PWM”
mode.
Note: On channels having a complementary output, this bit field is preloaded. If the CCPC bit
is set in the TIMx_CR2 register then the OC1M active bits take the new value from the
preloaded bits only when a COM event is generated.

578/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bit 3 OC1PE: Output Compare 1 preload enable
0: Preload register on TIMx_CCR1 disabled. TIMx_CCR1 can be written at anytime, the
new value is taken in account immediately.
1: Preload register on TIMx_CCR1 enabled. Read/Write operations access the preload
register. TIMx_CCR1 preload value is loaded in the active register at each update event.
Note: 1: These bits can not be modified as long as LOCK level 3 has been programmed
(LOCK bits in TIMx_BDTR register) and CC1S=’00’ (the channel is configured in
output).
2: The PWM mode can be used without validating the preload register only in one
pulse mode (OPM bit set in TIMx_CR1 register). Else the behavior is not guaranteed.
Bit 2 OC1FE: Output Compare 1 fast enable
This bit is used to accelerate the effect of an event on the trigger in input on the CC output.
0: CC1 behaves normally depending on counter and CCR1 values even when the trigger is
ON. The minimum delay to activate CC1 output when an edge occurs on the trigger input is
5 clock cycles.
1: An active edge on the trigger input acts like a compare match on CC1 output. Then, OC is
set to the compare level independently from the result of the comparison. Delay to sample
the trigger input and to activate CC1 output is reduced to 3 clock cycles. OCFE acts only if
the channel is configured in PWM1 or PWM2 mode.
Bits 1:0 CC1S: Capture/Compare 1 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC1 channel is configured as output
01: CC1 channel is configured as input, IC1 is mapped on TI1
10: CC1 channel is configured as input, IC1 is mapped on TI2
11: CC1 channel is configured as input, IC1 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC1S bits are writable only when the channel is OFF (CC1E = ‘0’ in TIMx_CCER).

Input capture mode
Bits 31:16 Reserved, must be kept at reset value.
Bits 15:12 IC2F: Input capture 2 filter
Bits 11:10 IC2PSC[1:0]: Input capture 2 prescaler
Bits 9:8 CC2S: Capture/Compare 2 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC2 channel is configured as output
01: CC2 channel is configured as input, IC2 is mapped on TI2
10: CC2 channel is configured as input, IC2 is mapped on TI1
11: CC2 channel is configured as input, IC2 is mapped on TRC. This mode is working only if an
internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC2S bits are writable only when the channel is OFF (CC2E = ‘0’ in TIMx_CCER).

DocID022558 Rev 8

579/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bits 7:4 IC1F[3:0]: Input capture 1 filter
This bit-field defines the frequency used to sample TI1 input and the length of the digital filter applied
to TI1. The digital filter is made of an event counter in which N consecutive events are needed to
validate a transition on the output:
0000: No filter, sampling is done at fDTS
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Bits 3:2 IC1PSC: Input capture 1 prescaler
This bit-field defines the ratio of the prescaler acting on CC1 input (IC1). The prescaler is reset as
soon as CC1E=’0’ (TIMx_CCER register).
00: no prescaler, capture is done each time an edge is detected on the capture input
01: capture is done once every 2 events
10: capture is done once every 4 events
11: capture is done once every 8 events
Bits 1:0 CC1S: Capture/Compare 1 Selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC1 channel is configured as output
01: CC1 channel is configured as input, IC1 is mapped on TI1
10: CC1 channel is configured as input, IC1 is mapped on TI2
11: CC1 channel is configured as input, IC1 is mapped on TRC. This mode is working only if an
internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC1S bits are writable only when the channel is OFF (CC1E = ‘0’ in TIMx_CCER).

20.4.8

TIM1/TIM8/TIM20 capture/compare mode register 2 (TIMx_CCMR2)
Address offset: 0x1C
Reset value: 0x0000 0000
Refer to the above CCMR1 register description.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC4M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC3M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

OC3
PE

OC3
FE

rw
15

14

OC4
CE

13

12

OC4M[2:0]
IC4F[3:0]

rw

580/1141

rw

rw

11

10

OC4
PE

OC4
FE

9

8

CC4S[1:0]

rw

OC3
CE.

OC3M[2:0]

IC4PSC[1:0]
rw

rw

rw

IC3F[3:0]
rw

rw

rw

rw

DocID022558 Rev 8

rw

0

CC3S[1:0]

IC3PSC[1:0]
rw

rw

rw

rw

rw

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Output compare mode
Bits 31:25 Reserved, must be kept at reset value.
Bit 24 OC4M[3]: Output Compare 4 mode - bit 3
Bits 23:17 Reserved, must be kept at reset value.
Bit 16 OC3M[3]: Output Compare 3 mode - bit 3
Bit 15 OC4CE: Output compare 4 clear enable
Bits 14:12 OC4M: Output compare 4 mode
Bit 11 OC4PE: Output compare 4 preload enable
Bit 10 OC4FE: Output compare 4 fast enable
Bits 9:8 CC4S: Capture/Compare 4 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC4 channel is configured as output
01: CC4 channel is configured as input, IC4 is mapped on TI4
10: CC4 channel is configured as input, IC4 is mapped on TI3
11: CC4 channel is configured as input, IC4 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC4S bits are writable only when the channel is OFF (CC4E = ‘0’ in TIMx_CCER).
Bit 7 OC3CE: Output compare 3 clear enable
Bits 6:4 OC3M: Output compare 3 mode
Bit 3 OC3PE: Output compare 3 preload enable
Bit 2 OC3FE: Output compare 3 fast enable
Bits 1:0 CC3S: Capture/Compare 3 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC3 channel is configured as output
01: CC3 channel is configured as input, IC3 is mapped on TI3
10: CC3 channel is configured as input, IC3 is mapped on TI4
11: CC3 channel is configured as input, IC3 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC3S bits are writable only when the channel is OFF (CC3E = ‘0’ in TIMx_CCER).

Input capture mode
Bits 31:16 Reserved, must be kept at reset value.
Bits 15:12 IC4F: Input capture 4 filter
Bits 11:10 IC4PSC: Input capture 4 prescaler
Bits 9:8 CC4S: Capture/Compare 4 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC4 channel is configured as output
01: CC4 channel is configured as input, IC4 is mapped on TI4
10: CC4 channel is configured as input, IC4 is mapped on TI3
11: CC4 channel is configured as input, IC4 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC4S bits are writable only when the channel is OFF (CC4E = ‘0’ in TIMx_CCER).

DocID022558 Rev 8

581/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

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).

20.4.9

TIM1/TIM8/TIM20 capture/compare enable register (TIMx_CCER)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CC6P

CC6E

Res.

Res.

CC5P

CC5E

rw

rw

rw

rw

5

4

CC2P

CC2E

rw

rw

15

14

13

12

CC4NP

Res.

CC4P

CC4E

rw

rw

rw

11

10

CC3NP CC3NE
rw

rw

9

8

CC3P

CC3E

rw

rw

7

6

CC2NP CC2NE
rw

rw

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 CC6P: Capture/Compare 6 output polarity
Refer to CC1P description
Bit 20 CC6E: Capture/Compare 6 output enable
Refer to CC1E description
Bits 19:18 Reserved, must be kept at reset value.
Bit 17 CC5P: Capture/Compare 5 output polarity
Refer to CC1P description
Bit 16 CC5E: Capture/Compare 5 output enable
Refer to CC1E description
Bit 15 CC4NP: Capture/Compare 4 complementary output polarity
Refer to CC1NP description
Bit 14 Reserved, must be kept at reset value.
Bit 13 CC4P: Capture/Compare 4 output polarity
Refer to CC1P description
Bit 12 CC4E: Capture/Compare 4 output enable
Refer to CC1E description
Bit 11 CC3NP: Capture/Compare 3 complementary output polarity
Refer to CC1NP description
Bit 10 CC3NE: Capture/Compare 3 complementary output enable
Refer to CC1NE description

582/1141

DocID022558 Rev 8

3

2

CC1NP CC1NE
rw

rw

1

0

CC1P

CC1E

rw

rw

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bit 9 CC3P: Capture/Compare 3 output polarity
Refer to CC1P description
Bit 8 CC3E: Capture/Compare 3 output enable
Refer to CC1E description
Bit 7 CC2NP: Capture/Compare 2 complementary output polarity
Refer to CC1NP description
Bit 6 CC2NE: Capture/Compare 2 complementary output enable
Refer to CC1NE description
Bit 5 CC2P: Capture/Compare 2 output polarity
Refer to CC1P description
Bit 4 CC2E: Capture/Compare 2 output enable
Refer to CC1E description
Bit 3 CC1NP: Capture/Compare 1 complementary output polarity
CC1 channel configured as output:
0: OC1N active high.
1: OC1N active low.
CC1 channel configured as input:
This bit is used in conjunction with CC1P to define the polarity of TI1FP1 and TI2FP1. Refer
to CC1P description.
Note: This bit is not writable as soon as LOCK level 2 or 3 has been programmed (LOCK bits
in TIMx_BDTR register) and CC1S=”00” (channel configured as output).
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.
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.

DocID022558 Rev 8

583/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bit 1 CC1P: Capture/Compare 1 output polarity
CC1 channel configured as output:
0: OC1 active high
1: OC1 active low
CC1 channel configured as input: CC1NP/CC1P bits select the active polarity of TI1FP1
and TI2FP1 for trigger or capture operations.
00: non-inverted/rising edge. The circuit is sensitive to TIxFP1 rising edge (capture or trigger
operations in reset, external clock or trigger mode), TIxFP1 is not inverted (trigger operation
in gated mode or encoder mode).
01: inverted/falling edge. The circuit is sensitive to TIxFP1 falling edge (capture or trigger
operations in reset, external clock or trigger mode), TIxFP1 is inverted (trigger operation in
gated mode or encoder mode).
10: reserved, do not use this configuration.
11: non-inverted/both edges/ The circuit is sensitive to both TIxFP1 rising and falling edges
(capture or trigger operations in reset, external clock or trigger mode), TIxFP1 is not inverted
(trigger operation in gated mode). This configuration must not be used in encoder mode.
Note: This bit is not writable as soon as LOCK level 2 or 3 has been programmed (LOCK bits
in TIMx_BDTR register).
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.
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.

584/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Table 122. Output control bits for complementary OCx and OCxN channels with break feature
Output states(1)

Control bits
MOE bit OSSI bit OSSR bit CCxE bit CCxNE bit

1

0

0

Output disabled (not driven by the timer: Hi-Z)
OCx=0, OCxN=0

0

0

1

Output disabled (not driven
OCxREF + Polarity
by the timer: Hi-Z)
OCxN = OCxREF xor CCxNP
OCx=0

0

1

0

OCxREF + Polarity
OCx=OCxREF xor CCxP

Output Disabled (not driven by
the timer: Hi-Z)
OCxN=0

X

1

1

OCREF + Polarity + deadtime

Complementary to OCREF (not
OCREF) + Polarity + dead-time

1

0

1

Off-State (output enabled
with inactive state)
OCx=CCxP

OCxREF + Polarity
OCxN = OCxREF x or CCxNP

1

1

0

OCxREF + Polarity
OCx=OCxREF xor CCxP

Off-State (output enabled with
inactive state)
OCxN=CCxNP

X

X

0

0

0

1

1

0

1

1

X

1

OCxN output state

X

0

0

OCx output state

X

Output disabled (not driven by the timer anymore). The
output state is defined by the GPIO controller and can be
High, Low or Hi-Z.
Off-State (output enabled with inactive state)
Asynchronously: OCx=CCxP, OCxN=CCxNP (if BRK or
BRK2 is triggered).
Then (this is valid only if BRK is triggered), if the clock is
present: OCx=OISx and OCxN=OISxN after a dead-time,
assuming that OISx and OISxN do not correspond to OCX
and OCxN both in active state (may cause a short circuit
when driving switches in half-bridge configuration).
Note: BRK2 can only be used if OSSI = OSSR = 1.

1. When both outputs of a channel are not used (control taken over by GPIO), the OISx, OISxN, CCxP and CCxNP bits must
be kept cleared.

Note:

The state of the external I/O pins connected to the complementary OCx and OCxN channels
depends on the OCx and OCxN channel state and the GPIO registers.

DocID022558 Rev 8

585/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

20.4.10

RM0316

TIM1/TIM8/TIM20 counter (TIMx_CNT)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

UIF
CPY

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Re s.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

r

CNT[15:0]
rw

Bit 31 UIFCPY: UIF copy
This bit is a read-only copy of the UIF bit of the TIMx_ISR register. If the UIFREMAP bit in
the TIMxCR1 is reset, bit 31 is reserved and read at 0.
Bits 30:16 Reserved, must be kept at reset value.
Bits 15:0 CNT[15:0]: Counter value

20.4.11

TIM1/TIM8/TIM20 prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

PSC[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 PSC[15:0]: Prescaler value
The counter clock frequency (CK_CNT) is equal to fCK_PSC / (PSC[15:0] + 1).
PSC contains the value to be loaded in the active prescaler register at each update event
(including when the counter is cleared through UG bit of TIMx_EGR register or through
trigger controller when configured in “reset mode”).

20.4.12

TIM1/TIM8/TIM20 auto-reload register (TIMx_ARR)
Address offset: 0x2C
Reset value: 0xFFFF

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

ARR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 ARR[15:0]: Prescaler value
ARR is the value to be loaded in the actual auto-reload register.
Refer to the Section 20.3.1: Time-base unit on page 508 for more details about ARR update
and behavior.
The counter is blocked while the auto-reload value is null.

586/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

20.4.13

TIM1/TIM8/TIM20 repetition counter register (TIMx_RCR)
Address offset: 0x30
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

REP[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 REP[15:0]: Repetition counter value
These bits allow the user to set-up the update rate of the compare registers (i.e. periodic
transfers from preload to active registers) when preload registers are enable, as well as the
update interrupt generation rate, if this interrupt is enable.
Each time the REP_CNT related downcounter reaches zero, an update event is generated
and it restarts counting from REP value. As REP_CNT is reloaded with REP value only at
the repetition update event U_RC, any write to the TIMx_RCR register is not taken in
account until the next repetition update event.
It means in PWM mode (REP+1) corresponds to:
the number of PWM periods in edge-aligned mode
the number of half PWM period in center-aligned mode.

20.4.14

TIM1/TIM8/TIM20 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/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

CCR1[15:0]
rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

Bits 15:0 CCR1[15:0]: Capture/Compare 1 value
If channel CC1 is configured as output:: CCR1 is the value to be loaded in the actual
capture/compare 1 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(bit OC1PE). Else the preload value is copied in the active capture/compare 1 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC1 output.
If channel CC1 is configured as input:: CR1 is the counter value transferred by the last
input capture 1 event (IC1). The TIMx_CCR1 register is read-only and cannot be
programmed.

DocID022558 Rev 8

587/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

20.4.15

RM0316

TIM1/TIM8/TIM20 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/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

CCR2[15:0]
rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

Bits 15:0 CCR2[15:0]: Capture/Compare 2 value
If channel CC2 is configured as output: CCR2 is the value to be loaded in the actual
capture/compare 2 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(bit OC2PE). Else the preload value is copied in the active capture/compare 2 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC2 output.
If channel CC2 is configured as input: CCR2 is the counter value transferred by the last
input capture 2 event (IC2). The TIMx_CCR2 register is read-only and cannot be
programmed.

20.4.16

TIM1/TIM8/TIM20 capture/compare register 3 (TIMx_CCR3)
Address offset: 0x3C
Reset value: 0x0000

15

14

13

12

11

10

9

8

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

7

6

5

4

3

2

1

0

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

CCR3[15:0]
rw/r

Bits 15:0 CCR3[15:0]: Capture/Compare value
If channel CC3 is configured as output: CCR3 is the value to be loaded in the actual
capture/compare 3 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2 register
(bit OC3PE). Else the preload value is copied in the active capture/compare 3 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC3 output.
If channel CC3 is configured as input: CCR3 is the counter value transferred by the last
input capture 3 event (IC3). The TIMx_CCR3 register is read-only and cannot be
programmed.

588/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

20.4.17

TIM1/TIM8/TIM20 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/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

CCR4[15:0]
rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

Bits 15:0 CCR4[15:0]: Capture/Compare value
If channel CC4 is configured as output: CCR4 is the value to be loaded in the actual
capture/compare 4 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2 register
(bit OC4PE). Else the preload value is copied in the active capture/compare 4 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC4 output.
If channel CC4 is configured as input: CCR4 is the counter value transferred by the last
input capture 4 event (IC4). The TIMx_CCR4 register is read-only and cannot be
programmed.

20.4.18

TIM1/TIM8/TIM20 break and dead-time register (TIMx_BDTR)
Address offset: 0x44
Reset value: 0x0000 0000

31
R e s.

30
Res.

29
Res.

28
Res.

27

26

Res.

Res.

15

14

13

12

11

10

MOE

AOE

BKP

BKE

OSSR

OSSI

rw

rw

rw

rw

rw

rw

Note:

25

24

BK2P

BK2E

rw

rw

9

8

23

22

21

rw

19

BK2F[3:0]
rw

18

17

16

BKF[3:0]

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

LOCK[1:0]
rw

20

DTG[7:0]
rw

As the bits BK2P, BK2E, BK2F[3:0], BKF[3:0], AOE, BKP, BKE, OSSI, OSSR and DTG[7:0]
can be write-locked depending on the LOCK configuration, it can be necessary to configure
all of them during the first write access to the TIMx_BDTR register.
Bits 31:26 Reserved, must be kept at reset value.
Bit 25 BK2P: Break 2 polarity
0: Break input BRK2 is active low
1: Break input BRK2 is active high
Note: This bit cannot be modified as long as LOCK level 1 has been programmed (LOCK bits
in TIMx_BDTR register).
Note: Any write operation to this bit takes a delay of 1 APB clock cycle to become effective.

DocID022558 Rev 8

589/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bit 24 BK2E: Break 2 enable
0: Break input BRK2 disabled
1; Break input BRK2 enabled
Note: The BRK2 must only be used with OSSR = OSSI = 1.
Note: This bit cannot be modified when LOCK level 1 has been programmed (LOCK bits in
TIMx_BDTR register).
Note: Any write operation to this bit takes a delay of 1 APB clock cycle to become effective.
Bits 23:20 BK2F[3:0]: Break 2 filter
This bit-field defines the frequency used to sample BRK2 input and the length of the digital
filter applied to BRK2. The digital filter is made of an event counter in which N consecutive
events are needed to validate a transition on the output:
0000: No filter, BRK2 acts asynchronously
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Note: This bit cannot be modified when LOCK level 1 has been programmed (LOCK bits in
TIMx_BDTR register).
Bits 19:16 BKF[3:0]: Break filter
This bit-field defines the frequency used to sample BRK input and the length of the digital
filter applied to BRK. The digital filter is made of an event counter in which N consecutive
events are needed to validate a transition on the output:
0000: No filter, BRK acts asynchronously
0001: fSAMPLING=fCK_INT, N=2
0010: fSAMPLING=fCK_INT, N=4
0011: fSAMPLING=fCK_INT, N=8
0100: fSAMPLING=fDTS/2, N=6
0101: fSAMPLING=fDTS/2, N=8
0110: fSAMPLING=fDTS/4, N=6
0111: fSAMPLING=fDTS/4, N=8
1000: fSAMPLING=fDTS/8, N=6
1001: fSAMPLING=fDTS/8, N=8
1010: fSAMPLING=fDTS/16, N=5
1011: fSAMPLING=fDTS/16, N=6
1100: fSAMPLING=fDTS/16, N=8
1101: fSAMPLING=fDTS/32, N=5
1110: fSAMPLING=fDTS/32, N=6
1111: fSAMPLING=fDTS/32, N=8
Note: This bit cannot be modified when LOCK level 1 has been programmed (LOCK bits in
TIMx_BDTR register).

590/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bit 15 MOE: Main output enable
This bit is cleared asynchronously by hardware as soon as one of the break inputs is active
(BRK or BRK2). It is set by software or automatically depending on the AOE bit. It is acting
only on the channels which are configured in output.
0: In response to a break 2 event. OC and OCN outputs are disabled
In response to a break event or if MOE is written to 0: OC and OCN outputs are disabled or
forced to idle state depending on the OSSI bit.
1: OC and OCN outputs are enabled if their respective enable bits are set (CCxE, CCxNE in
TIMx_CCER register).
See OC/OCN enable description for more details (Section 20.4.9: TIM1/TIM8/TIM20
capture/compare enable register (TIMx_CCER)).
Bit 14 AOE: Automatic output enable
0: MOE can be set only by software
1: MOE can be set by software or automatically at the next update event (if none of the break
inputs BRK and BRK2 is active)
Note: This bit can not be modified as long as LOCK level 1 has been programmed (LOCK bits
in TIMx_BDTR register).
Bit 13 BKP: Break polarity
0: Break input BRK is active low
1: Break input BRK is active high
Note: This bit can not be modified as long as LOCK level 1 has been programmed (LOCK bits
in TIMx_BDTR register).
Note: Any write operation to this bit takes a delay of 1 APB clock cycle to become effective.
Bit 12 BKE: Break enable
0: Break inputs (BRK and CCS clock failure event) disabled
1; Break inputs (BRK and CCS 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 20.4.9: TIM1/TIM8/TIM20
capture/compare enable register (TIMx_CCER)).
0: When inactive, OC/OCN outputs are disabled (the timer releases the output control which
is taken over by the GPIO logic, which forces a Hi-Z state).
1: When inactive, OC/OCN outputs are enabled with their inactive level as soon as CCxE=1
or CCxNE=1 (the output is still controlled by the timer).
Note: This bit can not be modified as soon as the LOCK level 2 has been programmed (LOCK
bits in TIMx_BDTR register).

DocID022558 Rev 8

591/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bit 10 OSSI: Off-state selection for Idle mode
This bit is used when MOE=0 due to a break event or by a software write, on channels
configured as outputs.
See OC/OCN enable description for more details (Section 20.4.9: TIM1/TIM8/TIM20
capture/compare enable register (TIMx_CCER)).
0: When inactive, OC/OCN outputs are disabled (the timer releases the output control which
is taken over by the GPIO logic and which imposes a Hi-Z state).
1: When inactive, OC/OCN outputs are first forced with their inactive level then forced to their
idle level after the deadtime. The timer maintains its control over the output.
Note: This bit can not be modified as soon as the LOCK level 2 has been programmed (LOCK
bits in TIMx_BDTR register).
Bits 9:8 LOCK[1:0]: Lock configuration
These bits offer a write protection against software errors.
00: LOCK OFF - No bit is write protected.
01: LOCK Level 1 = DTG bits in TIMx_BDTR register, OISx and OISxN bits in TIMx_CR2
register and BKE/BKP/AOE bits in TIMx_BDTR register can no longer be written.
10: LOCK Level 2 = LOCK Level 1 + CC Polarity bits (CCxP/CCxNP bits in TIMx_CCER
register, as long as the related channel is configured in output through the CCxS bits) as well
as OSSR and OSSI bits can no longer be written.
11: LOCK Level 3 = LOCK Level 2 + CC Control bits (OCxM and OCxPE bits in
TIMx_CCMRx registers, as long as the related channel is configured in output through the
CCxS bits) can no longer be written.
Note: The LOCK bits can be written only once after the reset. Once the TIMx_BDTR register
has been written, their content is frozen until the next reset.
Bits 7:0 DTG[7:0]: Dead-time generator setup
This bit-field defines the duration of the dead-time inserted between the complementary
outputs. DT correspond to this duration.
DTG[7:5]=0xx => DT=DTG[7:0]x tdtg with tdtg=tDTS.
DTG[7:5]=10x => DT=(64+DTG[5:0])xtdtg with Tdtg=2xtDTS.
DTG[7:5]=110 => DT=(32+DTG[4:0])xtdtg with Tdtg=8xtDTS.
DTG[7:5]=111 => DT=(32+DTG[4:0])xtdtg with Tdtg=16xtDTS.
Example if TDTS=125ns (8MHz), dead-time possible values are:
0 to 15875 ns by 125 ns steps,
16 us to 31750 ns by 250 ns steps,
32 us to 63us by 1 us steps,
64 us to 126 us by 2 us steps
Note: This bit-field can not be modified as long as LOCK level 1, 2 or 3 has been programmed
(LOCK bits in TIMx_BDTR register).

20.4.19

TIM1/TIM8/TIM20 DMA control register (TIMx_DCR)
Address offset: 0x48
Reset value: 0x0000

15

14

13

Res.

Res.

Res.

12

11

10

9

8

DBL[4:0]
rw

rw

rw

rw

7

6

5

Res.

Res.

Res.

rw

Bits 15:13 Reserved, must be kept at reset value.

592/1141

DocID022558 Rev 8

4

3

2

1

0

rw

rw

DBA[4:0]
rw

rw

rw

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bits 12:8 DBL[4:0]: DMA burst length
This 5-bit vector defines the length of DMA transfers (the timer recognizes a burst transfer
when a read or a write access is done to the TIMx_DMAR address), i.e. the number of
transfers. Transfers can be in half-words or in bytes (see example below).
00000: 1 transfer
00001: 2 transfers
00010: 3 transfers
...
10001: 18 transfers
Example: Let us consider the following transfer: DBL = 7 bytes & DBA = TIM2_CR1.
– If DBL = 7 bytes and DBA = TIM2_CR1 represents the address of the byte to be
transferred, the address of the transfer should be given by the following equation:
(TIMx_CR1 address) + DBA + (DMA index), where DMA index = DBL
In this example, 7 bytes are added to (TIMx_CR1 address) + DBA, which gives us the
address from/to which the data will be copied. In this case, the transfer is done to 7 registers
starting from the following address: (TIMx_CR1 address) + DBA
According to the configuration of the DMA Data Size, several cases may occur:
– If you configure the DMA Data Size in half-words, 16-bit data will be transferred to each of
the 7 registers.
– If you configure the DMA Data Size in bytes, the data will also be transferred to 7 registers:
the first register will contain the first MSB byte, the second register, the first LSB byte and
so on. So with the transfer Timer, you also have to specify the size of data transferred by
DMA.
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:0 DBA[4:0]: DMA base address
This 5-bits vector defines the base-address for DMA transfers (when read/write access are
done through the TIMx_DMAR address). DBA is defined as an offset starting from the
address of the TIMx_CR1 register.
Example:
00000: TIMx_CR1,
00001: TIMx_CR2,
00010: TIMx_SMCR,
...

20.4.20

TIM1/TIM8/TIM20 DMA address for full transfer (TIMx_DMAR)
Address offset: 0x4C
Reset value: 0x0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DMAB[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

DMAB[15:0]
rw

rw

DocID022558 Rev 8

593/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bits 31:0 DMAB[31:0]: DMA register for burst accesses
A read or write operation to the DMAR register accesses the register located at the address
(TIMx_CR1 address) + (DBA + DMA index) x 4
where TIMx_CR1 address is the address of the control register 1, DBA is the DMA base
address configured in TIMx_DCR register, DMA index is automatically controlled by the DMA
transfer, and ranges from 0 to DBL (DBL configured in TIMx_DCR).

20.4.21

TIM1/TIM8/TIM20 option registers (TIMx_OR)
Address offset: 0x50
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.

TIM1_ETR_ADC4_ TIM1_ETR_ADC1_
RMP
RMP
or
or
TIM8_ETR_ADC3_ TIM8_ETR_ADC2_
RMP
RMP
or
or
TIM20_ETR_ADC4_ TIM20_ETR_ADC3
_RMP
RMP
rw

rw

rw

rw

Bits 31:4 Reserved, must be kept at reset value
Bits 3:2 TIM1_ETR_ADC4_RMP[1:0]: TIM1_ETR_ADC4 remapping capability
00: TIM1_ETR is not connected to any AWD (analog watchdog)
01: TIM1_ETR is connected to ADC4 AWD1
10: TIM1_ETR is connected to ADC4 AWD2
11: TIM1_ETR is connected to ADC4 AWD3
Note: ADC4 AWD is ‘ORed’ with the other TIM1_ETR source signals. It is consequently
necessary to disable by software other sources (input pins).
TIM8_ETR_ADC3_RMP[1:0]: TIM8_ETR_ADC3 remapping capability
00: TIM8_ETR is not connected to any AWD (analog watchdog)
01: TIM8_ETR is connected to ADC3 AWD1
10: TIM8_ETR is connected to ADC3 AWD2
11: TIM8_ETR is connected to ADC3 AWD3
Note: ADC3 AWD is ‘ORed’ with the other TIM8_ETR source signals. It is consequently
necessary to disable by software other sources (input pins).
TIM20_ETR_ADC4_RMP[1:0]: TIM20_ETR_ADC4 remapping capability
00: TIM20_ETR is not connected to any AWD (analog watchdog)
01: TIM20_ETR is connected to ADC4 AWD1
10: TIM20_ETR is connected to ADC4 AWD2
11: TIM20_ETR is connected to ADC4 AWD3
Note: ADC4 AWD is ‘ORed’ with the other TIM20_ETR source signals. It is consequently
necessary to disable by software other sources (input pins).

594/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bits 1:0 TIM1_ETR_ADC1_RMP[1:0]: TIM1_ETR_ADC1 remapping capability
00: TIM1_ETR is not connected to any AWD
01: TIM1_ETR is connected to ADC1 AWD1
10: TIM1_ETR is connected to ADC1 AWD2
11: TIM1_ETR is connected to ADC1 AWD3
Note: ADC1 AWD is ‘ORed’ with the other TIM1_ETR source signals. It is consequently
necessary to disable by software other sources (input pins).
TIM8_ETR_ADC2_RMP[1:0]: TIM8_ETR_ADC2 remapping capability
00: TIM8_ETR is not connected to any AWD
01: TIM8_ETR is connected to ADC2 AWD1
10: TIM8_ETR is connected to ADC2 AWD2
11: TIM8_ETR is connected to ADC2 AWD3
Note: ADC3 AWD is ‘ORed’ with the other TIM20_ETR source signals. It is consequently
necessary to disable by software other sources (input pins).
TIM20_ETR_ADC3_RMP[1:0]: TIM20_ETR_ADC3 remapping capability
00: TIM20_ETR is not connected to any AWD (analog watchdog)
01: TIM20_ETR is connected to ADC3 AWD1
10: TIM20_ETR is connected to ADC3 AWD2
11: TIM20_ETR is connected to ADC3 AWD3
Note: ADC3 AWD is ‘ORed’ with the other TIM20_ETR source signals. It is consequently
necessary to disable by software other sources (input pins).

20.4.22

TIM1/TIM8/TIM20 capture/compare mode register 3 (TIMx_CCMR3)
Address offset: 0x54
Reset value: 0x0000 0000
Refer to the above CCMR1 register description. Channels 5 and 6 can only be configured in
output.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC6M[3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

OC5M[3]

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OC6
PE

OC6FE

Res.

Res.

OC5
CE.

Res.

Res.

rw

rw

rw

OC6
CE
rw

OC6M[2:0]
rw

rw

rw

rw

rw

OC5M[2:0]
rw

rw

OC5PE OC5FE
rw

rw

rw

Output compare mode
Bits 31:25 Reserved, must be kept at reset value.
Bit 24 OC6M[3]: Output Compare 6 mode - bit 3
Bits 23:17 Reserved, must be kept at reset value.
Bit 16 OC5M[3]: Output Compare 5 mode - bit 3
Bit 15 OC6CE: Output compare 6 clear enable
Bits 14:12 OC6M: Output compare 6 mode
Bit 11 OC6PE: Output compare 6 preload enable
Bit 10 OC6FE: Output compare 6 fast enable

DocID022558 Rev 8

595/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Bits 9:8 Reserved, must be kept at reset value.
Bit 7 OC5CE: Output compare 5 clear enable
Bits 6:4 OC5M: Output compare 5 mode
Bit 3 OC5PE: Output compare 5 preload enable
Bit 2 OC5FE: Output compare 5 fast enable
Bits 1:0 Reserved, must be kept at reset value.

20.4.23

TIM1/TIM8/TIM20 capture/compare register 5 (TIMx_CCR5)
Address offset: 0x58
Reset value: 0x0000 0000

31

30

29

GC5C3 GC5C2 GC5C1

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

CCR5[15:0]
rw

rw

Bit 31 GC5C3: Group Channel 5 and Channel 3
Distortion on Channel 3 output:
0: No effect of OC5REF on OC3REFC
1: OC3REFC is the logical AND of OC3REFC and OC5REF
This bit can either have immediate effect or be preloaded and taken into account after an
update event (if preload feature is selected in TIMxCCMR2).
Note: it is also possible to apply this distortion on combined PWM signals.
Bit 30 GC5C2: Group Channel 5 and Channel 2
Distortion on Channel 2 output:
0: No effect of OC5REF on OC2REFC
1: OC2REFC is the logical AND of OC2REFC and OC5REF
This bit can either have immediate effect or be preloaded and taken into account after an
update event (if preload feature is selected in TIMxCCMR1).
Note: it is also possible to apply this distortion on combined PWM signals.

596/1141

DocID022558 Rev 8

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Bit 29 GC5C1: Group Channel 5 and Channel 1
Distortion on Channel 1 output:
0: No effect of OC5REF on OC1REFC5
1: OC1REFC is the logical AND of OC1REFC and OC5REF
This bit can either have immediate effect or be preloaded and taken into account after an
update event (if preload feature is selected in TIMxCCMR1).
Note: it is also possible to apply this distortion on combined PWM signals.
Bits 28:16 Reserved, must be kept at reset value.
Bits 15:0 CCR5[15:0]: Capture/Compare 5 value
CCR5 is the value to be loaded in the actual capture/compare 5 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR3 register
(bit OC5PE). Else the preload value is copied in the active capture/compare 5 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC5 output.

20.4.24

TIM1/TIM8/TIM20 capture/compare register 6 (TIMx_CCR6)
Address offset: 0x5C
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CCR6[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 CCR6[15:0]: Capture/Compare 6 value
CCR6 is the value to be loaded in the actual capture/compare 6 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR3 register
(bit OC6PE). Else the preload value is copied in the active capture/compare 6 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC6 output.

DocID022558 Rev 8

597/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

20.4.25

RM0316

TIM1/TIM8/TIM20 register map
TIM1/TIM8/TIM20 registers are mapped as 16-bit addressable registers as described in the
table below:

598/1141

URS

UDIS

CEN
CCPC

0

0

0

Res

UIE
UIF

0

0
UG

CC1IE
CC1IF

CC2IE
CC2IF
0

0

0

0

0

0

0

0

CC2
S
[1:0]

OC4M
[2:0]
0

0

0

OC2FE

0

0

IC2
PSC
[1:0]

CC2
S
[1:0]

0

0

0

0

0

0

0

0

0

CC4
S
[1:0]
0

0

0

0

0

0

OC3M
[2:0]
0

0

0

0

0

0

IC1
PSC
[1:0]

CC1
S
[1:0]

0

0

0

0

0

0

CC3
S
[1:0]
0

0

0

0

0

0

0

0

0

0

0

CC3P

CC3E

CC2NP

0

0

0

0

0

0

0

CC1E

0

CC1P

0

CC1NE

0

CC1NP

0

CC2E

0

CC2P

0

CC2NE

0

CC3NE

CC3
S
[1:0]

CC3NP

IC3
PSC
[1:0]

CC4E

IC3F[3:0]

0

CC4P

CC4
S
[1:0]

0

CC1
S
[1:0]

Res

IC4
PSC
[1:0]

0

IC1F[3:0]

OC3CE

OC4CE

CC5E
Res

0

0

OC1M
[2:0]

Res

CC5P

0

0

OC4FE

OC3M[3]

0

IC4F[3:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

CNT[15:0]
0

DocID022558 Rev 8

0

IC2F[3:0]

0

0

0

OC2PE

0

0

0

OC2M
[2:0]

OC3FE

0

OC3PE

0

OC1FE

0

CC1G

CC3IE

0

CC2G

CC4IE

0

OC1PE

0

COM

0

CC4G

0

TG

0

BG

0

B2G

0

OC1CE

CC3IF

Res

0

CC3G

COMIE

Res

CC4IF

TIE

0

COMIF

BIE

0

TIF

UDE

0

BIF

CC1DE

0

B2IF

CC2DE

0

CC1OF

0

CC2OF

0

Res

0

Res

CC3DE

0

CC3OF

0

Res

CC4DE

0

CC4OF

0

Res

COMDE

0

Res

TDE

0

OC4PE

OC2CE
0

SMS[2:0]

0

Res

Res
Res

CC5IF
OC1M[3]
0

TS[2:0]

OCCS
0

Res

Res
Res

Res

CC6E
Res

Res

CC6P

Res

Res

Res

0

Res

Res

Res

Res

Res
Res

Res

0

ARPE

ECE

0

MSM

ETP

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res
Res

Res
Res

0

Res

Reset value

Res

TIMx_CNT

Res

0x24

UIFCPY

Reset value

0

0

Res

Res

Res

Res

Res

Res

Res

Res

OC4M[3]

Res

Res

Res
Res

Res

Res
Res

Res

Res

Res

TIMx_CCER

0

0

Reset value

0x20

0

0

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res
Res

Res

Res

Res

0
Res

Reset value
TIMx_CCMR2
Input Capture
mode

0

0

0

Res

0x1C

0

MMS
[2:0]

0

Reset value
TIMx_CCMR2
Output
Compare mode

0

0

0

Res

Res

Res

Res

Res

Res

Res

OC2M[3]

Res

Res

Res

Res

Res

Res

Res
Res

TIMx_CCMR1
Input Capture
mode

0

0

0

0
Res

Reset value

0x18

0

0

0

ETF[3:0]

Reset value
TIMx_CCMR1
Output
Compare mode

0

Res

0

0

CCUS

0

DIR

OIS2

OIS1N

0

OPM

OIS2N

0

ETP
S
[1:0]

0

CCDS

OIS3

TI1S

OIS3N

OIS1

Res

Res

OIS4

Res

0

0

0

0

CC6IF

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_EGR

0x14

Res

Reset value

0

0

0

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_SR

0

0

Reset value

0x10

0

CMS
[1:0]

SMS[3]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_DIER

CKD
[1:0]

Res

Res

Res

0

Reset value

0x0C

OIS5

Res

OIS6

Res

0
Res

0
Res

0
Res

0

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_SMCR

0x08

0
Res

Reset value

MMS2[3:0]

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_CR2

0x04

Res

Reset value

UIFREMAP

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_CR1

0x00

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

Table 123. TIM1/TIM8/TIM20 register map and reset values
Offset

0

0

0

0

0

0

0

0

0

RM0316

Advanced-control timers (TIM1/TIM8/TIM20)

Res

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

LOC
K
[1:0]
0

0

DBL[4:0]
0

0

0

0

0

DT[7:0]
0

0

0
Res

0

0

0

0

DBA[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

TIMx_OR

Res

Res

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

DocID022558 Rev 8

TIM1_ETR_ADC1_RMP or TIM8_ETR_ADC2_RMP
or TIM20_ETR_ADC3_RMP

0

TIM1_ETR_ADC4_RMP or TIM8_ETR_ADC3_RMP
or TIM20_ETR_ADC4_RMP

Reset value

Res

DMAB[15:0]

Res

0x50

0

Res

BKP

0

TIMx_DMAR

0

Res

AOE

0

BKF[3:0]

Reset value

0x4C

1

OSSI

MOE

0

BK2F[3:0]

1

BKE

BK2E

0

Res

0

BK2P

Res

Res

Res

Res

TIMx_DCR

Res

0x48

Res

Reset value

0

Res

Res

Res

Res

Res

Res

TIMx_BDTR

0

CCR4[15:0]
0

Res

Reset value

0x44

1

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

1

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

1

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_CCR2

0

CCR1[15:0]
0

Res

Reset value

0x38

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_CCR1

0

REP[15:0]
0

Res

Reset value

0x34

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_RCR

0

ARR[15:0]
1

Res

Reset value

0x30

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_ARR

Res

0x2C

0
Res

Reset value

PSC[15:0]

OSSR

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_PSC

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

0x28

Register

Res

Offset

Res

Table 123. TIM1/TIM8/TIM20 register map and reset values (continued)

0

0

0

0

599/1141
600

Advanced-control timers (TIM1/TIM8/TIM20)

RM0316

Res

Res

Res

0

OC5FE

Reset value

OC5CE

0

Res

0

OC5PE

0

OC6FE

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

OC5M
[2:0]
0

CCR5[15:0]
0

0

0

0

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

0

OC6PE

OC6CE

Res

OC5M[3]

Res

Res

Res

Res

Res

Res

Res

0

OC6M
[2:0]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res
Res

Res

Res

TIMx_CCR6

0

0
Res

0

Res

0

Res

GC5C1

0

Res

GC5C2

Reset value

Res

GC5C3

0x5C

TIMx_CCR5

Res

0x58

0

Res

Reset value

OC6M[3]

Res

Res

Res

TIMx_CCMR3
Output
Compare mode

Res

0x54

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 123. TIM1/TIM8/TIM20 register map and reset values (continued)

0

0

0

0

CCR6[15:0]
0

0

0

0

0

0

0

0

0

0

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

600/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)

21

General-purpose timers (TIM2/TIM3/TIM4)

21.1

TIM2/TIM3/TIM4 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 21.3.19: Timer synchronization.

Note:

TIM4 is available only on STM32F303xB/C/D/E, STM32F358xC and STM32F398xE
devices.

21.2

TIM2/TIM3/TIM4 main features
General-purpose TIMx timer features include:
•

16-bit (TIM3 and TIM4) or 32-bit (TIM2) up, down, up/down auto-reload counter.

•

16-bit programmable prescaler used to divide (also “on the fly”) the counter clock
frequency by any factor between 1 and 65535.

•

Up to 4 independent channels for:
–

Input capture

–

Output compare

–

PWM generation (Edge- and Center-aligned modes)

–

One-pulse mode output

•

Synchronization circuit to control the timer with external signals and to interconnect
several timers.

•

Interrupt/DMA generation on the following events:
–

Update: counter overflow/underflow, counter initialization (by software or
internal/external trigger)

–

Trigger event (counter start, stop, initialization or count by internal/external trigger)

–

Input capture

–

Output compare

•

Supports incremental (quadrature) encoder and hall-sensor circuitry for positioning
purposes

•

Trigger input for external clock or cycle-by-cycle current management

DocID022558 Rev 8

601/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 197. General-purpose timer block diagram
,QWHUQDOFORFN &.B,17
7,0[&/.IURP5&&
(75)
(75

7,0[B(75

7ULJJHU
FRQWUROOHU
75*2

3RODULW\VHOHFWLRQ HGJH (753
,QSXWILOWHU
GHWHFWRU SUHVFDOHU
,75
,75
,75
,75

WRRWKHUWLPHUV
WR'$&$'&
7*,

,75
75&

75*,

6ODYH
FRQWUROOHU 5HVHWHQDEOHXSFRXQW
PRGH

7,)B('

(QFRGHU
LQWHUIDFH

7,)3
7,)3

8

$XWRUHORDGUHJLVWHU

6WRSFOHDURUXSGRZQ
&.B36&
;25
7,
7,0[B&+
7,

7,0[B&+

,QSXWILOWHU 
HGJHGHWHFWRU

,QSXWILOWHU 
HGJHGHWHFWRU

7,)3
7,)3

,&

36& &.B&17
SUHVFDOHU
&&, 8
3UHVFDOHU

75&
7,)3
7,)3
75&

,&36
&&,

,&

3UHVFDOHU

7,

7,0[B&+

7,

7,0[B&+

,QSXWILOWHU 
HGJHGHWHFWRU

,QSXWILOWHU 
HGJHGHWHFWRU

,&

3UHVFDOHU

75&
7,)3
7,)3

&17FRXQWHU
&&,

&DSWXUH&RPSDUHUHJLVWHU
 

&DSWXUH&RPSDUHUHJLVWHU 2&5()

&DSWXUH&RPSDUHUHJLVWHU
 

3UHVFDOHU

7,0[B&+

2XWSXW 2&
FRQWURO

7,0[B&+

2&5()

2XWSXW 2&
FRQWURO

7,0[B&+

2XWSXW 2&
FRQWURO

7,0[B&+

&&,

8
,&36

2XWSXW 2&
FRQWURO

&&,

8

,&36
&&,

,&

2&5()

&&,

8

,&36
&&,

7,)3
7,)3



8,
8

&DSWXUH&RPSDUHUHJLVWHU 2&5()

75&
(75)

1RWHV
5HJ

3UHORDGUHJLVWHUVWUDQVIHUUHG
WRDFWLYHUHJLVWHUVRQ8HYHQW
DFFRUGLQJWRFRQWUROELW
(YHQW
,QWHUUXSW '0$RXWSXW

069

602/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)

21.3

TIM2/TIM3/TIM4 functional description

21.3.1

Time-base unit
The main block of the programmable timer is a 16-bit/32-bit counter with its related autoreload register. The counter can count up, down or both up and down but also down or both
up and down. The counter clock can be divided by a prescaler.
The counter, the auto-reload register and the prescaler register can be written or read by
software. This is true even when the counter is running.
The time-base unit includes:
•

Counter Register (TIMx_CNT)

•

Prescaler Register (TIMx_PSC):

•

Auto-Reload Register (TIMx_ARR)

The auto-reload register is preloaded. Writing to or reading from the auto-reload register
accesses the preload register. The content of the preload register are transferred into the
shadow register permanently or at each update event (UEV), depending on the auto-reload
preload enable bit (ARPE) in TIMx_CR1 register. The update event is sent when the counter
reaches the overflow (or underflow when downcounting) and if the UDIS bit equals 0 in the
TIMx_CR1 register. It can also be generated by software. The generation of the update
event is described in detail for each configuration.
The counter is clocked by the prescaler output CK_CNT, which is enabled only when the
counter enable bit (CEN) in TIMx_CR1 register is set (refer also to the slave mode controller
description to get more details on counter enabling).
Note that the actual counter enable signal CNT_EN is set 1 clock cycle after CEN.

Prescaler description
The prescaler can divide the counter clock frequency by any factor between 1 and 65536. It
is based on a 16-bit counter controlled through a 16-bit/32-bit register (in the TIMx_PSC
register). It can be changed on the fly as this control register is buffered. The new prescaler
ratio is taken into account at the next update event.
Figure 198 and Figure 199 give some examples of the counter behavior when the prescaler
ratio is changed on the fly:

DocID022558 Rev 8

603/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 198. Counter timing diagram with prescaler division change from 1 to 2

&.B36&

&(1
7LPHUFORFN

&.B&17


&RXQWHUUHJLVWHU

)

)

)

)$ )% )&









8SGDWHHYHQW 8(9

3UHVFDOHUFRQWUROUHJLVWHU





:ULWHDQHZYDOXHLQ7,0[B36&
3UHVFDOHUEXIIHU



3UHVFDOHUFRXQWHU





















069

Figure 199. Counter timing diagram with prescaler division change from 1 to 4

&.B36&
&(1

7LPHUFORFN

&.B&17


&RXQWHUUHJLVWHU

)

)

)

)$ )% )&





8SGDWHHYHQW 8(9

3UHVFDOHUFRQWUROUHJLVWHU





:ULWHDQHZYDOXHLQ7,0[B36&
3UHVFDOHUEXIIHU

3UHVFDOHUFRXQWHU






















069

604/1141

DocID022558 Rev 8

RM0316

21.3.2

General-purpose timers (TIM2/TIM3/TIM4)

Counter modes
Upcounting mode
In upcounting mode, the counter counts from 0 to the auto-reload value (content of the
TIMx_ARR register), then restarts from 0 and generates a counter overflow event.
An Update event can be generated at each counter overflow or by setting the UG bit in the
TIMx_EGR register (by software or by using the slave mode controller).
The UEV event can be disabled by software by setting the UDIS bit in TIMx_CR1 register.
This is to avoid updating the shadow registers while writing new values in the preload
registers. Then no update event occurs until the UDIS bit has been written to 0. However,
the counter restarts from 0, as well as the counter of the prescaler (but the prescale rate
does not change). In addition, if the URS bit (update request selection) in TIMx_CR1
register is set, setting the UG bit generates an update event UEV but without setting the UIF
flag (thus no interrupt or DMA request is sent). This is to avoid generating both update and
capture interrupts when clearing the counter on the capture event.
When an update event occurs, all the registers are updated and the update flag (UIF bit in
TIMx_SR register) is set (depending on the URS bit):
•

The buffer of the prescaler is reloaded with the preload value (content of the TIMx_PSC
register)

•

The auto-reload shadow register is updated with the preload value (TIMx_ARR)

The following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.
Figure 200. Counter timing diagram, internal clock divided by 1

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU







  

















&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)

069

DocID022558 Rev 8

605/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 201. Counter timing diagram, internal clock divided by 2

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU















&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)

069

Figure 202. Counter timing diagram, internal clock divided by 4

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU









&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

606/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
Figure 203. Counter timing diagram, internal clock divided by N

&.B36&

7LPHUFORFN &.B&17

&RXQWHUUHJLVWHU

)





&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

Figure 204. Counter timing diagram, Update event when ARPE=0 (TIMx_ARR not
preloaded)
&.B36&

&(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU





























&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

))



:ULWHDQHZYDOXHLQ7,0[B$55
069

DocID022558 Rev 8

607/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 205. Counter timing diagram, Update event when ARPE=1 (TIMx_ARR
preloaded)
&.B36&

&(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU

)

)

)

)

) )

















&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

)



$XWRUHORDGVKDGRZ
UHJLVWHU

)

:ULWHDQHZYDOXHLQ7,0[B$55



069

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):

608/1141

•

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.

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
The following figures show some examples of the counter behavior for different clock
frequencies when TIMx_ARR=0x36.
Figure 206. Counter timing diagram, internal clock divided by 1

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU



























)

&RXQWHUXQGHUIORZ
FQWBXGI

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

Figure 207. Counter timing diagram, internal clock divided by 2

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU















&RXQWHUXQGHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)

069

DocID022558 Rev 8

609/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 208. Counter timing diagram, internal clock divided by 4

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU









&RXQWHUXQGHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

Figure 209. Counter timing diagram, internal clock divided by N

&.B36&

7LPHUFORFN &.B&17

&RXQWHUUHJLVWHU



)





&RXQWHUXQGHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

610/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
Figure 210. Counter timing diagram, Update event when repetition counter
is not used
&.B36&

&(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU









 

  





  )

&RXQWHUXQGHUIORZ

8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

))



:ULWHDQHZYDOXHLQ7,0[B$55
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").
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

DocID022558 Rev 8

611/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

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 211. Counter timing diagram, internal clock divided by 1, TIMx_ARR=0x6
&.B36&

&(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU





























&RXQWHUXQGHUIORZ

&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
069

1. Here, center-aligned mode 1 is used (for more details refer to Section 21.4.1: TIMx control register 1
(TIMx_CR1) on page 647).

612/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
Figure 212. Counter timing diagram, internal clock divided by 2

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU















&RXQWHUXQGHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)

069

Figure 213. Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU









&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
1RWH+HUHFHQWHUBDOLJQHGPRGHRULVXSGDWHGZLWKDQ8,)RQRYHUIORZ
069

1. Center-aligned mode 2 or 3 is used with an UIF on overflow.

DocID022558 Rev 8

613/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 214. Counter timing diagram, internal clock divided by N

&.B36&

7LPHUFORFN &.B&17

&RXQWHUUHJLVWHU

)







&RXQWHUXQGHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

Figure 215. Counter timing diagram, Update event with ARPE=1 (counter underflow)
&.B36&

&(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU











 















&RXQWHUXQGHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

)'



:ULWHDQHZYDOXHLQ7,0[B$55
$XWRUHORDGDFWLYH
UHJLVWHU

)'


069

614/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
Figure 216. Counter timing diagram, Update event with ARPE=1 (counter overflow)
&.B36&

&(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU

)

)

)

)$ )% )& 













)

&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

)'



:ULWHDQHZYDOXHLQ7,0[B$55
$XWRUHORDGDFWLYH
)'
UHJLVWHU


069

21.3.3

Clock selection
The counter clock can be provided by the following clock sources:
•

Internal clock (CK_INT)

•

External clock mode1: external input pin (TIx)

•

External clock mode2: external trigger input (ETR)

•

Internal trigger inputs (ITRx): using one timer as prescaler for another timer, for
example, you can configure Timer 13 to act as a prescaler for Timer 2. Refer to : Using
one timer as prescaler for another timer on page 641 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 217 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.

DocID022558 Rev 8

615/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 217. Control circuit in normal mode, internal clock divided by 1

,QWHUQDOFORFN
&(1 &17B(1
8*

&17B,1,7

&RXQWHUFORFN &.B&17 &.B36&
&RXQWHUUHJLVWHU









 

 



  




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.
Figure 218. TI2 external clock connection example
7,0[B60&5
76>@
RU 7,)
7,)
,75[
7,B('

7,

)LOWHU

(GJH
GHWHFWRU

7,)B5LVLQJ
7,)B)DOOLQJ

7,)3



7,)3
(75)

RU
RU

[[


75*,





(75)
&.B,17

,&)>@

&&3

7,0[B&&05

7,0[B&&(5

LQWHUQDOFORFN

(QFRGHU
PRGH
([WHUQDOFORFN
PRGH

([WHUQDOFORFN
PRGH


&.B36&

,QWHUQDOFORFN
PRGH

(&(

606>@

7,0[B60&5

069

For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:
For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:

616/1141

DocID022558 Rev 8

RM0316

Note:

General-purpose timers (TIM2/TIM3/TIM4)
1.

Configure channel 2 to detect rising edges on the TI2 input by writing CC2S= ‘01 in the
TIMx_CCMR1 register.

2.

Configure the input filter duration by writing the IC2F[3:0] bits in the TIMx_CCMR1
register (if no filter is needed, keep IC2F=0000).

The capture prescaler is not used for triggering, so you don’t need to configure it.
3.

Select rising edge polarity by writing CC2P=0 and CC2NP=0 and CC2NP=0 in the
TIMx_CCER register.

4.

Configure the timer in external clock mode 1 by writing SMS=111 in the TIMx_SMCR
register.

5.

Select TI2 as the input source by writing TS=110 in the TIMx_SMCR register.

6.

Enable the counter by writing CEN=1 in the TIMx_CR1 register.

When a rising edge occurs on TI2, the counter counts once and the TIF flag is set.
The delay between the rising edge on TI2 and the actual clock of the counter is due to the
resynchronization circuit on TI2 input.
Figure 219. Control circuit in external clock mode 1

7,
&17B(1
&RXQWHUFORFN &.B&17 &.B36&
&RXQWHUUHJLVWHU







7,)

:ULWH7,) 

069

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 220 gives an overview of the external trigger input block.

DocID022558 Rev 8

617/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 220. External trigger input block

RU 7,)
7,)

(75

RU
RU

75*,


(75SLQ


'LYLGHU


(753
I'76

)LOWHU
GRZQFRXQWHU

(75)
&.B,17

(73

(736>@

(7)>@

7,0[B60&5

7,0[B60&5

7,0[B60&5

LQWHUQDOFORFN

(QFRGHU
PRGH
([WHUQDOFORFN
PRGH

([WHUQDOFORFN
PRGH


&.B36&

,QWHUQDOFORFN
PRGH

(&(

606>@

7,0[B60&5

069

For example, to configure the upcounter to count each 2 rising edges on ETR, use the
following procedure:
1.

As no filter is needed in this example, write ETF[3:0]=0000 in the TIMx_SMCR register.

2.

Set the prescaler by writing ETPS[1:0]=01 in the TIMx_SMCR register

3.

Select rising edge detection on the ETR pin by writing ETP=0 in the TIMx_SMCR
register

4.

Enable external clock mode 2 by writing ECE=1 in the TIMx_SMCR register.

5.

Enable the counter by writing CEN=1 in the TIMx_CR1 register.

The counter counts once each 2 ETR rising edges.
The delay between the rising edge on ETR and the actual clock of the counter is due to the
resynchronization circuit on the ETRP signal.

618/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
Figure 221. Control circuit in external clock mode 2

I &.B,17
&17B(1
(75

(753

(75)
&RXQWHUFORFN 
&.B,17 &.B36&
&RXQWHUUHJLVWHU







069

21.3.4

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).

DocID022558 Rev 8

619/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 222. Capture/compare channel (example: channel 1 input stage)

7,)B('
7RWKHVODYHPRGHFRQWUROOHU
7,)B5LVLQJ

7,

)LOWHU
7,)
GRZQFRXQWHU

I'76

(GJH
GHWHFWRU

7,)B)DOOLQJ

 7,)3




7,)3

&&3&&13

,&)>@

75&

7,0[B&&(5

7,0[B&&05

7,)B5LVLQJ

IURPFKDQQHO
7,)B)DOOLQJ

IURPFKDQQHO

,&



IURPVODYHPRGH
FRQWUROOHU

,&36
'LYLGHU




&&6>@ ,&36>@

&&(

7,0[B&&05

7,0[B&&(5

069

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 223. Capture/compare channel 1 main circuit

$3%%XV

5HDG&&5+ 6
5HDG&&5/

KLJK



UHDGBLQBSURJUHVV

&&6>@
,&36

ZULWHBLQBSURJUHVV

,QSXW
PRGH

6 ZULWH&&5+

&DSWXUHFRPSDUHSUHORDGUHJLVWHU

5

5
FRPSDUHBWUDQVIHU

FDSWXUHBWUDQVIHU
&&6>@


ORZ

LIELW

0&8SHULSKHUDOLQWHUIDFH

2XWSXW
PRGH

&17!&&5
&RXQWHU

&&*

&&6>@

8(9
&RPSDUDWRU

&&(

&&6>@

2&3(

&DSWXUHFRPSDUHVKDGRZUHJLVWHU
&DSWXUH

ZULWH&&5/

IURPWLPH
EDVHXQLW

2&3(

7,0[B&&05

&17 &&5

7,0[B(*5

069

620/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
Figure 224. Output stage of capture/compare channel (channel 1)
7,0[B60&5
2&&6
2&5()B&/5 

7RWKHPDVWHU
PRGHFRQWUROOHU

(75) 

2&5()&

RFUHIBFOUBLQW

2&5()

µ¶

&17!&&5

2XWSXW
PRGH
&17 &&5
FRQWUROOHU
2&5()

2XWSXW
VHOHFWRU









&&(

&&3

7,0[B&&(5

7,0[B&&(5

2XWSXW
HQDEOH
FLUFXLW

&&( 7,0[B&&(5
02(

2&&( 2&0>@
7,0[B&&05

2&

266, 7,0[B%'75

2,6

7,0[B&5
069

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.

21.3.5

Input capture mode
In Input capture mode, the Capture/Compare Registers (TIMx_CCRx) are used to latch the
value of the counter after a transition detected by the corresponding ICx signal. When a
capture occurs, the corresponding CCXIF flag (TIMx_SR register) is set and an interrupt or
a DMA request can be sent if they are enabled. If a capture occurs while the CCxIF flag was
already high, then the over-capture flag CCxOF (TIMx_SR register) is set. CCxIF can be
cleared by software by writing it to 0 or by reading the captured data stored in the
TIMx_CCRx register. CCxOF is cleared when you write it to 0.
The following example shows how to capture the counter value in TIMx_CCR1 when TI1
input rises. To do this, use the following procedure:
1.

Select the active input: TIMx_CCR1 must be linked to the TI1 input, so write the CC1S
bits to 01 in the TIMx_CCMR1 register. As soon as CC1S becomes different from 00,
the channel is configured in input and the TIMx_CCR1 register becomes read-only.

2.

Program the input filter duration you need with respect to the signal you connect to the
timer (when the input is one of the TIx (ICxF bits in the TIMx_CCMRx register). Let’s
imagine that, when toggling, the input signal is not stable during at must 5 internal clock
cycles. We must program a filter duration longer than these 5 clock cycles. We can
validate a transition on TI1 when 8 consecutive samples with the new level have been

DocID022558 Rev 8

621/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

detected (sampled at fDTS frequency). Then write IC1F bits to 0011 in the
TIMx_CCMR1 register.
3.

Select the edge of the active transition on the TI1 channel by writing the CC1P and
CC1NP and CC1NP bits to 000 in the TIMx_CCER register (rising edge in this case).

4.

Program the input prescaler. In our example, we wish the capture to be performed at
each valid transition, so the prescaler is disabled (write IC1PS bits to 00 in the
TIMx_CCMR1 register).

5.

Enable capture from the counter into the capture register by setting the CC1E bit in the
TIMx_CCER register.

6.

If needed, enable the related interrupt request by setting the CC1IE bit in the
TIMx_DIER register, and/or the DMA request by setting the CC1DE bit in the
TIMx_DIER register.

When an input capture occurs:
•

The TIMx_CCR1 register gets the value of the counter on the active transition.

•

CC1IF flag is set (interrupt flag). CC1OF is also set if at least two consecutive captures
occurred whereas the flag was not cleared.

•

An interrupt is generated depending on the CC1IE bit.

•

A DMA request is generated depending on the CC1DE bit.

In order to handle the overcapture, it is recommended to read the data before the
overcapture flag. This is to avoid missing an overcapture which could happen after reading
the flag and before reading the data.
Note:

IC interrupt and/or DMA requests can be generated by software by setting the
corresponding CCxG bit in the TIMx_EGR register.

21.3.6

PWM input mode
This mode is a particular case of input capture mode. The procedure is the same except:

622/1141

•

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.

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
For example, you can measure the period (in TIMx_CCR1 register) and the duty cycle (in
TIMx_CCR2 register) of the PWM applied on TI1 using the following procedure (depending
on CK_INT frequency and prescaler value):
1.

Select the active input for TIMx_CCR1: write the CC1S bits to 01 in the TIMx_CCMR1
register (TI1 selected).

2.

Select the active polarity for TI1FP1 (used both for capture in TIMx_CCR1 and counter
clear): write the CC1P to ‘0’ and the CC1NP bit to ‘0’ (active on rising edge).

3.

Select the active input for TIMx_CCR2: write the CC2S bits to 10 in the TIMx_CCMR1
register (TI1 selected).

4.

Select the active polarity for TI1FP2 (used for capture in TIMx_CCR2): write the CC2P
bit to ‘1’ and the CC2NP bit to ’0’ (active on falling edge).

5.

Select the valid trigger input: write the TS bits to 101 in the TIMx_SMCR register
(TI1FP1 selected).

6.

Configure the slave mode controller in reset mode: write the SMS bits to 100 in the
TIMx_SMCR register.

7.

Enable the captures: write the CC1E and CC2E bits to ‘1 in the TIMx_CCER register.
Figure 225. PWM input mode timing
7,

7,0[B&17









7,0[B&&5



7,0[B&&5



,&FDSWXUH
,&FDSWXUH
UHVHWFRXQWHU





,&FDSWXUH
SXOVHZLGWK
PHDVXUHPHQW



,&FDSWXUH
SHULRG
PHDVXUHPHQW
DL

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.

21.3.7

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.

DocID022558 Rev 8

623/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

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.

21.3.8

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 226.

624/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
Figure 226. Output compare mode, toggle on OC1
:ULWH%KLQWKH&&5UHJLVWHU

7,0B&17



%

$

%

%

$

7,0B&&5

%

2&5() 2&

0DWFKGHWHFWHGRQ&&5
,QWHUUXSWJHQHUDWHGLIHQDEOHG
069

21.3.9

PWM mode
Pulse width modulation mode allows you to generate a signal with a frequency determined
by the value of the TIMx_ARR register and a duty cycle determined by the value of the
TIMx_CCRx register.
The PWM mode can be selected independently on each channel (one PWM per OCx
output) by writing 110 (PWM mode 1) or ‘111 (PWM mode 2) in the OCxM bits in the
TIMx_CCMRx register. You must enable the corresponding preload register by setting the
OCxPE bit in the TIMx_CCMRx register, and eventually the auto-reload preload register (in
upcounting or center-aligned modes) by setting the ARPE bit in the TIMx_CR1 register.
As the preload registers are transferred to the shadow registers only when an update event
occurs, before starting the counter, you have to initialize all the registers by setting the UG
bit in the TIMx_EGR register.
OCx polarity is software programmable using the CCxP bit in the TIMx_CCER register. It
can be programmed as active high or active low. OCx output is enabled by the CCxE bit in
the TIMx_CCER register. Refer to the TIMx_CCERx register description for more details.
In PWM mode (1 or 2), TIMx_CNT and TIMx_CCRx are always compared to determine
whether TIMx_CCRx ≤ TIMx_CNT or TIMx_CNT ≤ TIMx_CCRx (depending on the direction
of the counter). However, to comply with the OCREF_CLR functionality (OCREF can be
cleared by an external event through the ETR signal until the next PWM period), the
OCREF signal is asserted only:
•

When the result of the comparison or

•

When the output compare mode (OCxM bits in TIMx_CCMRx register) switches from
the “frozen” configuration (no comparison, OCxM=‘000) to one of the PWM modes
(OCxM=‘110 or ‘111).

This forces the PWM by software while the timer is running.

DocID022558 Rev 8

625/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

The timer is able to generate PWM in edge-aligned mode or center-aligned mode
depending on the CMS bits in the TIMx_CR1 register.

PWM edge-aligned mode
Upcounting configuration
Upcounting is active when the DIR bit in the TIMx_CR1 register is low. Refer to Upcounting
mode on page 605.
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 100%. PWM is not possible in this mode.

PWM center-aligned mode
Center-aligned mode is active when the CMS bits in TIMx_CR1 register are different from
‘00 (all the remaining configurations having the same effect on the ocxref/OCx signals). The

626/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
compare flag is set when the counter counts up, when it counts down or both when it counts
up and down depending on the CMS bits configuration. The direction bit (DIR) in the
TIMx_CR1 register is updated by hardware and must not be changed by software. Refer to
Center-aligned mode (up/down counting) on page 611.
Figure 228 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 228. Center-aligned PWM waveforms (ARR=8)
&RXQWHUUHJLVWHU





































2&[5()
&&5[ 
&06 
&06 
&06 

&&[,)

2&[5()
&&5[ 

&06 RU

&&[,)
2&[5()

µ¶

&&5[ 
&&[,)

2&[5()
&&5[!

µ¶

&06 
&06 
&06 

&&[,)

2&[5()
&&5[ 
&&[,)

&06 
&06 
&06 

µ¶

&06 
&06 
&06 

$,E

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

DocID022558 Rev 8

627/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

in the TIMx_CR1 register. Moreover, the DIR and CMS bits must not be changed at the
same time by the software.
•

•

21.3.10

Writing to the counter while running in center-aligned mode is not recommended as it
can lead to unexpected results. In particular:
–

The direction is not updated if you write a value in the counter that is greater than
the auto-reload value (TIMx_CNT>TIMx_ARR). For example, if the counter was
counting up, it continues to count up.

–

The direction is updated if you write 0 or write the TIMx_ARR value in the counter
but no Update Event UEV is generated.

The safest way to use center-aligned mode is to generate an update by software
(setting the UG bit in the TIMx_EGR register) just before starting the counter and not to
write the counter while it is running.

Asymmetric PWM mode
Asymmetric mode allows two center-aligned PWM signals to be generated with a
programmable phase shift. While the frequency is determined by the value of the
TIMx_ARR register, the duty cycle and the phase-shift are determined by a pair of
TIMx_CCRx registers. One register controls the PWM during up-counting, the second
during down counting, so that PWM is adjusted every half PWM cycle:
•

OC1REFC (or OC2REFC) is controlled by TIMx_CCR1 and TIMx_CCR2

•

OC3REFC (or OC4REFC) is controlled by TIMx_CCR3 and TIMx_CCR4

Asymmetric PWM mode can be selected independently on two channels (one OCx output
per pair of CCR registers) by writing ‘1110’ (Asymmetric PWM mode 1) or ‘1111’
(Asymmetric PWM mode 2) in the OCxM bits in the TIMx_CCMRx register.
Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
When a given channel is used as asymmetric PWM channel, its secondary channel can also
be used. For instance, if an OC1REFC signal is generated on channel 1 (Asymmetric PWM
mode 1), it is possible to output either the OC2REF signal on channel 2, or an OC2REFC
signal resulting from asymmetric PWM mode 2.
Figure 229 shows an example of signals that can be generated using Asymmetric PWM
mode (channels 1 to 4 are configured in Asymmetric PWM mode 1).
Figure 229. Generation of 2 phase-shifted PWM signals with 50% duty cycle
&RXQWHUUHJLVWHU

&&5
&&5
&&5
&&5





































2&5()&


2&5()&



069

628/1141

DocID022558 Rev 8

RM0316

21.3.11

General-purpose timers (TIM2/TIM3/TIM4)

Combined PWM mode
Combined PWM mode allows two edge or center-aligned PWM signals to be generated with
programmable delay and phase shift between respective pulses. While the frequency is
determined by the value of the TIMx_ARR register, the duty cycle and delay are determined
by the two TIMx_CCRx registers. The resulting signals, OCxREFC, are made of an OR or
AND logical combination of two reference PWMs:
– OC1REFC (or OC2REFC) is controlled by TIMx_CCR1 and TIMx_CCR2
– OC3REFC (or OC4REFC) is controlled by TIMx_CCR3 and TIMx_CCR4
Combined PWM mode can be selected independently on two channels (one OCx output per
pair of CCR registers) by writing ‘1100’ (Combined PWM mode 1) or ‘1101’ (Combined PWM
mode 2) in the OCxM bits in the TIMx_CCMRx register.
When a given channel is used as combined PWM channel, its secondary channel must be
configured in the opposite PWM mode (for instance, one in Combined PWM mode 1 and the
other in Combined PWM mode 2).

Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
Figure 230 shows an example of signals that can be generated using Asymmetric PWM
mode, obtained with the following configuration:
•

Channel 1 is configured in Combined PWM mode 2,

•

Channel 2 is configured in PWM mode 1,

•

Channel 3 is configured in Combined PWM mode 2,

•

Channel 4 is configured in PWM mode 1

DocID022558 Rev 8

629/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Figure 230. Combined PWM mode on channels 1 and 3

2&¶
2&¶

2&
2&
2&5()
2&5()
2&5()¶
2&5()¶

2&5()&
2&5()&¶

2&5()& 2&5()$1'2&5()
2&5()&¶ 2&5()¶252&5()¶

069

21.3.12

Clearing the OCxREF signal on an external event
The OCxREF signal of a given channel can be cleared when a high level is applied on the
ocref_clr_int input (OCxCE enable bit in the corresponding TIMx_CCMRx register set to 1).
OCxREF remains low until the next update event (UEV) occurs. This function can only be
used in Output compare and PWM modes. It does not work in Forced mode.
OCREF_CLR_INPUT can be selected between the OCREF_CLR input and ETRF (ETR
after the filter) by configuring the OCCS bit in the TIMx_SMCR register.
The OCxREF signal for a given channel can be reset by applying a high level on the ETRF
input (OCxCE enable bit set to 1 in the corresponding TIMx_CCMRx register). OCxREF
remains low until the next update event (UEV) occurs.
This function can be used only in the output compare and PWM modes. It does not work in
forced mode.
For example, the OCxREF signal can be connected to the output of a comparator to be
used for current handling. In this case, ETR must be configured as follows:

630/1141

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.

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)
Figure 231 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 231. Clearing TIMx OCxREF

&&5[
&RXQWHU &17

(75)

2&[5()
2&[&( µ¶
2&[5()
2&[&( µ¶

RFUHIBFOUBLQW
EHFRPHVKLJK

RFUHIBFOUBLQW
VWLOOKLJK
069

Note:

In case of a PWM with a 100% duty cycle (if CCRx>ARR), OCxREF is enabled again at the
next counter overflow.

DocID022558 Rev 8

631/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

21.3.13

RM0316

One-pulse mode
One-pulse mode (OPM) is a particular case of the previous modes. It allows the counter to
be started in response to a stimulus and to generate a pulse with a programmable length
after a programmable delay.
Starting the counter can be controlled through the slave mode controller. Generating the
waveform can be done in output compare mode or PWM mode. You select One-pulse mode
by setting the OPM bit in the TIMx_CR1 register. This makes the counter stop automatically
at the next update event UEV.
A pulse can be correctly generated only if the compare value is different from the counter
initial value. Before starting (when the timer is waiting for the trigger), the configuration must
be:
•

CNTTIMx_CCR1 else active (OC1REF=1).
0111: PWM mode 2 - In upcounting, channel 1 is inactive as long as
TIMx_CNTTIMx_CCR1 else inactive.
1000: Retriggerable OPM mode 1 - In up-counting mode, the channel is active until a trigger
event is detected (on TRGI signal). Then, a comparison is performed as in PWM mode 1
and the channels becomes inactive again at the next update. In down-counting mode, the
channel is inactive until a trigger event is detected (on TRGI signal). Then, a comparison is
performed as in PWM mode 1 and the channels becomes inactive again at the next update.
1001: Retriggerable OPM mode 2 - In up-counting mode, the channel is inactive until a
trigger event is detected (on TRGI signal). Then, a comparison is performed as in PWM
mode 2 and the channels becomes inactive again at the next update. In down-counting
mode, the channel is active until a trigger event is detected (on TRGI signal). Then, a
comparison is performed as in PWM mode 1 and the channels becomes active again at the
next update.
1010: Reserved,
1011: Reserved,
1100: Combined PWM mode 1 - OC1REF has the same behavior as in PWM mode 1.
OC1REFC is the logical OR between OC1REF and OC2REF.
1101: Combined PWM mode 2 - OC1REF has the same behavior as in PWM mode 2.
OC1REFC is the logical AND between OC1REF and OC2REF.
1110: Asymmetric PWM mode 1 - OC1REF has the same behavior as in PWM mode 1.
OC1REFC outputs OC1REF when the counter is counting up, OC2REF when it is counting
down.
1111: Asymmetric PWM mode 2 - OC1REF has the same behavior as in PWM mode 2.
OC1REFC outputs OC1REF when the counter is counting up, OC2REF when it is counting
down.
Note: 1: These bits can not be modified as long as LOCK level 3 has been programmed
(LOCK bits in TIMx_BDTR register) and CC1S=00 (the channel is configured in
output).
2: In PWM mode, the OCREF level changes only when the result of the comparison
changes or when the output compare mode switches from “frozen” mode to “PWM”
mode.

658/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)

Bit 3 OC1PE: Output compare 1 preload enable
0: Preload register on TIMx_CCR1 disabled. TIMx_CCR1 can be written at anytime, the
new value is taken in account immediately.
1: Preload register on TIMx_CCR1 enabled. Read/Write operations access the preload
register. TIMx_CCR1 preload value is loaded in the active register at each update event.
Note: 1: These bits can not be modified as long as LOCK level 3 has been programmed
(LOCK bits in TIMx_BDTR register) and CC1S=00 (the channel is configured in
output).
2: The PWM mode can be used without validating the preload register only in onepulse mode (OPM bit set in TIMx_CR1 register). Else the behavior is not guaranteed.
Bit 2 OC1FE: Output compare 1 fast enable
This bit is used to accelerate the effect of an event on the trigger in input on the CC output.
0: CC1 behaves normally depending on counter and CCR1 values even when the trigger is
ON. The minimum delay to activate CC1 output when an edge occurs on the trigger input is
5 clock cycles.
1: An active edge on the trigger input acts like a compare match on CC1 output. Then, OC
is set to the compare level independently from the result of the comparison. Delay to sample
the trigger input and to activate CC1 output is reduced to 3 clock cycles. OCFE acts only if
the channel is configured in PWM1 or PWM2 mode.
Bits 1:0 CC1S: Capture/Compare 1 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC1 channel is configured as output.
01: CC1 channel is configured as input, IC1 is mapped on TI1.
10: CC1 channel is configured as input, IC1 is mapped on TI2.
11: CC1 channel is configured as input, IC1 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC1S bits are writable only when the channel is OFF (CC1E = 0 in TIMx_CCER).

Input capture mode
Bits 31:16 Reserved, always read as 0.
Bits 15:12 IC2F: Input capture 2 filter
Bits 11:10 IC2PSC[1:0]: Input capture 2 prescaler
Bits 9:8 CC2S: Capture/compare 2 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC2 channel is configured as output.
01: CC2 channel is configured as input, IC2 is mapped on TI2.
10: CC2 channel is configured as input, IC2 is mapped on TI1.
11: CC2 channel is configured as input, IC2 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC2S bits are writable only when the channel is OFF (CC2E = 0 in TIMx_CCER).

DocID022558 Rev 8

659/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

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).

21.4.8

TIMx capture/compare mode register 2 (TIMx_CCMR2)
Address offset: 0x1C
Reset value: 0x0000
Refer to the above CCMR1 register description.

31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
Res.

25

24

Res.

OC4M
[3]

23
Res.

22
Res.

21
Res.

20
Res.

19
Res.

18
Res.

17

16

Res.

OC3M
[3]

Res.

Res.

rw
15

14

OC4CE

13

12

OC4M[2:0]

660/1141

rw

rw

10

OC4PE OC4FE

IC4F[3:0]
rw

11

IC4PSC[1:0]
rw

rw

rw

9

8

CC4S[1:0]
rw

rw

rw
7

6

OC3CE

5

4

OC3M[2:0]

rw

DocID022558 Rev 8

rw

2

OC3PE OC3FE

IC3F[3:0]
rw

3

IC3PSC[1:0]
rw

rw

rw

1

0

CC3S[1:0]
rw

rw

RM0316

General-purpose timers (TIM2/TIM3/TIM4)

Output compare mode
Bits 31:25 Reserved, always read as 0.
Bit 24 OC4M[3]: Output Compare 2 mode - bit 3
Bits 23:17 Reserved, always read as 0.
Bit 16 OC3M[3]: Output Compare 1 mode - bit 3
Bit 15 OC4CE: Output compare 4 clear enable
Bits 14:12 OC4M: Output compare 4 mode
Refer to OC1M description (bits 6:4 in TIMx_CCMR1 register)
Bit 11 OC4PE: Output compare 4 preload enable
Bit 10 OC4FE: Output compare 4 fast enable
Bits 9:8 CC4S: Capture/Compare 4 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC4 channel is configured as output
01: CC4 channel is configured as input, IC4 is mapped on TI4
10: CC4 channel is configured as input, IC4 is mapped on TI3
11: CC4 channel is configured as input, IC4 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC4S bits are writable only when the channel is OFF (CC4E = 0 in TIMx_CCER).
Bit 7 OC3CE: Output compare 3 clear enable
Bits 6:4 OC3M: Output compare 3 mode
Refer to OC1M description (bits 6:4 in TIMx_CCMR1 register)
Bit 3 OC3PE: Output compare 3 preload enable
Bit 2 OC3FE: Output compare 3 fast enable
Bits 1:0 CC3S: Capture/Compare 3 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC3 channel is configured as output
01: CC3 channel is configured as input, IC3 is mapped on TI3
10: CC3 channel is configured as input, IC3 is mapped on TI4
11: CC3 channel is configured as input, IC3 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC3S bits are writable only when the channel is OFF (CC3E = 0 in TIMx_CCER).

Input capture mode
Bits 31:16 Reserved, always read as 0.
Bits 15:12 IC4F: Input capture 4 filter
Bits 11:10 IC4PSC: Input capture 4 prescaler
Bits 9:8 CC4S: Capture/Compare 4 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC4 channel is configured as output
01: CC4 channel is configured as input, IC4 is mapped on TI4
10: CC4 channel is configured as input, IC4 is mapped on TI3
11: CC4 channel is configured as input, IC4 is mapped on TRC. This mode is working only if
an internal trigger input is selected through TS bit (TIMx_SMCR register)
Note: CC4S bits are writable only when the channel is OFF (CC4E = 0 in TIMx_CCER).

DocID022558 Rev 8

661/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

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).

21.4.9

TIMx capture/compare enable register (TIMx_CCER)
Address offset: 0x20
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

CC4NP

Res.

CC4P

CC4E

CC3NP

Res.

CC3P

CC3E

CC2NP

Res.

CC2P

CC2E

CC1NP

Res.

CC1P

CC1E

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 15 CC4NP: Capture/Compare 4 output Polarity.
Refer to CC1NP description
Bit 14 Reserved, must be kept at reset value.
Bit 13 CC4P: Capture/Compare 4 output Polarity.
Refer to CC1P description
Bit 12 CC4E: Capture/Compare 4 output enable.
refer to CC1E description
Bit 11 CC3NP: Capture/Compare 3 output Polarity.
Refer to CC1NP description
Bit 10 Reserved, must be kept at reset value.
Bit 9 CC3P: Capture/Compare 3 output Polarity.
Refer to CC1P description
Bit 8 CC3E: Capture/Compare 3 output enable.
Refer to CC1E description
Bit 7 CC2NP: Capture/Compare 2 output Polarity.
Refer to CC1NP description
Bit 6 Reserved, must be kept at reset value.
Bit 5 CC2P: Capture/Compare 2 output Polarity.
refer to CC1P description
Bit 4 CC2E: Capture/Compare 2 output enable.
Refer to CC1E description
Bit 3 CC1NP: Capture/Compare 1 output Polarity.
CC1 channel configured as output: CC1NP must be kept cleared in this case.
CC1 channel configured as input: This bit is used in conjunction with CC1P to define
TI1FP1/TI2FP1 polarity. refer to CC1P description.

662/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)

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 126. Output control bit for standard OCx channels
CCxE bit

OCx output state

0

Output Disabled (OCx=0, OCx_EN=0)

1

OCx=OCxREF + Polarity, OCx_EN=1

Note:

The state of the external IO pins connected to the standard OCx channels depends on the
OCx channel state and the GPIO and AFIO registers.

21.4.10

TIMx counter (TIMx_CNT)
Address offset: 0x24
Reset value: 0x0000

31

30

29

28

27

26

25

CNT[31]
or
UIFCPY

24

23

22

21

20

19

18

17

16

CNT[30:16] (depending on timers)

rw or r

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

CNT[15:0]
rw

DocID022558 Rev 8

663/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

RM0316

Bit 31 Value depends on IUFREMAP in TIMx_CR1.
If UIFREMAP = 0
CNT[31]: Most significant bit of counter value (on TIM2 )
Reserved on other timers
If UIFREMAP = 1
UIFCPY: UIF Copy
This bit is a read-only copy of the UIF bit of the TIMx_ISR register
Bits 30:16 CNT[30:16]: Most significant part counter value (on TIM2 )
Bits 15:0 CNT[15:0]: Least significant part of counter value

21.4.11

TIMx prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

PSC[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 PSC[15:0]: Prescaler value
The counter clock frequency CK_CNT is equal to fCK_PSC / (PSC[15:0] + 1).
PSC contains the value to be loaded in the active prescaler register at each update event
(including when the counter is cleared through UG bit of TIMx_EGR register or through
trigger controller when configured in “reset mode”).

21.4.12

TIMx auto-reload register (TIMx_ARR)
Address offset: 0x2C
Reset value: 0xFFFF FFFF

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ARR[31:16] (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

rw

ARR[15:0]
rw

Bits 31:16 ARR[31:16]: High auto-reload value (on TIM2 )
Bits 15:0 ARR[15:0]: Low Auto-reload Prescaler value
ARR is the value to be loaded in the actual auto-reload register.
Refer to the Section 21.3.1: Time-base unit on page 603 for more details about ARR update
and behavior.
The counter is blocked while the auto-reload value is null.

664/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)

21.4.13

TIMx capture/compare register 1 (TIMx_CCR1)
Address offset: 0x34
Reset value: 0x0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CCR1[31:16] (depending on timers)
rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

CCR1[15:0]
rw/r

Bits 31:16 CCR1[31:16]: High Capture/Compare 1 value (on TIM2 and TIM5)
Bits 15:0 CCR1[15:0]: Low Capture/Compare 1 value
If channel CC1 is configured as output:
CCR1 is the value to be loaded in the actual capture/compare 1 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(bit OC1PE). Else the preload value is copied in the active capture/compare 1 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signaled on OC1 output.
If channel CC1is configured as input:
CCR1 is the counter value transferred by the last input capture 1 event (IC1). The
TIMx_CCR1 register is read-only and cannot be programmed.

21.4.14

TIMx capture/compare register 2 (TIMx_CCR2)
Address offset: 0x38
Reset value: 0x00000000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CCR2[31:16] (depending on timers)
rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

CCR2[15:0]
rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

Bits 31:16 CCR2[31:16]: High Capture/Compare 2 value (on TIM2 and TIM5)
Bits 15:0 CCR2[15:0]: Low Capture/Compare 2 value
If channel CC2 is configured as output:
CCR2 is the value to be loaded in the actual capture/compare 2 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR1 register
(bit OC2PE). Else the preload value is copied in the active capture/compare 2 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC2 output.
If channel CC2 is configured as input:
CCR2 is the counter value transferred by the last input capture 2 event (IC2). The
TIMx_CCR2 register is read-only and cannot be programmed.

DocID022558 Rev 8

665/1141
669

General-purpose timers (TIM2/TIM3/TIM4)

21.4.15

RM0316

TIMx capture/compare register 3 (TIMx_CCR3)
Address offset: 0x3C
Reset value: 0x0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CCR3[31:16] (depending on timers)
rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

CCR3[15:0]
rw/r

Bits 31:16 CCR3[31:16]: High Capture/Compare 3 value (on TIM2 and TIM5)
Bits 15:0 CCR3[15:0]: Low Capture/Compare value
If channel CC3 is configured as output:
CCR3 is the value to be loaded in the actual capture/compare 3 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2 register
(bit OC3PE). Else the preload value is copied in the active capture/compare 3 register when
an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC3 output.
If channel CC3is configured as input:
CCR3 is the counter value transferred by the last input capture 3 event (IC3). The
TIMx_CCR3 register is read-only and cannot be programmed.

21.4.16

TIMx capture/compare register 4 (TIMx_CCR4)
Address offset: 0x40
Reset value: 0x0000

31

30

29

28

27

26

25

24

23

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

15

14

13

12

11

10

9

8

7

22

21

20

19

18

17

16

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

6

5

4

3

2

1

0

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

CCR4[31:16] (depending on timers)

CCR4[15:0]
rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

rw/r

Bits 31:16 CCR4[31:16]: High Capture/Compare 4 value (on TIM2 )
Bits 15:0 CCR4[15:0]: Low Capture/Compare value
1.
if CC4 channel is configured as output (CC4S bits):
CCR4 is the value to be loaded in the actual capture/compare 4 register (preload value).
It is loaded permanently if the preload feature is not selected in the TIMx_CCMR2
register (bit OC4PE). Else the preload value is copied in the active capture/compare 4
register when an update event occurs.
The active capture/compare register contains the value to be compared to the counter
TIMx_CNT and signalled on OC4 output.
2.
if CC4 channel is configured as input (CC4S bits in TIMx_CCMR4 register):
CCR4 is the counter value transferred by the last input capture 4 event (IC4). The
TIMx_CCR4 register is read-only and cannot be programmed.

666/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM2/TIM3/TIM4)

21.4.17

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.

21.4.18

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).

DocID022558 Rev 8

667/1141
669

0x20

668/1141

TIMx_CCER

Reset value

DocID022558 Rev 8
0
0
0

OC4M
[2:0]
CC4S
[1:0]

0
0
0
0
0

0

IC4F[3:0]

0

0

0

0

0
0

0

Reset value

0
0

0
OC1M
[2:0]

0
0

0

0
0

IC4
PSC
[1:0]

CC4S
[1:0]

0

0

0

0

0

0

0

0

0

UG

0

CC1G

UIE

UIF
0

CC2G

CC1IE

CC1IF
0

0
0
0
0
0

OC1FE

0
0
0
0

OCCS
CC2IE

CC2IF
0

CC3G

CC3IE

CC3IF
0

OC1PE

TS[2:0]
SMS[2:0]

0
0
0
0
0
0

Res
CC4IE
0

Res
CC4IF
0

Res

TIE
0

TIF
0

TG

MSM

Res

UIFREMAP

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

DIR
OPM
URS
UDIS
CEN

0
0
0
0
0

TI1S
MMS[2:0]
CCDS
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

0
0
0

0

0
0

0

IC1F[3:0]

0
0

OC3M
[2:0]

0

IC3F[3:0]
IC1
PSC
[1:0]
CC1S
[1:0]

0
0
0

OC3FE

0
0

0

CC4G

Res

UDE

0

Res

CC1OF

0

Res

Res

CC2OF

0

Res

0

CC3OF

0

Res

0

CC4OF

0

Res

0

Res

Res
0

0

Res

0

0

CMS
[1:0]

OC3PE

CC2S
[1:0]
OC1CE

0

CC1DE

0

CC2DE

0

IC3
PSC
[1:0]

CC3S
[1:0]

0

0

0

0

0

CC1E

CC2S
[1:0]

0
OC2FE

0

CC3DE

0

CC4DE

0

COMDE

0

Res

ECE
0

ETF[3:0]

Res

0
Res

ETP
0
TDE

SMS[3]

Res

Res

Res

Res

Res

Res

Res

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

ETPS
[1:0]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Reset value

CC1P

0

0

CC1NP

0

0

CC2E

0
Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Reset value
CKD
[1:0]

CC2P

0
IC2
PSC
[1:0]

OC3CE

IC2F[3:0]

Res

0
0
0

CC3E

0
OC2M
[2:0]
OC2PE

0

CC2NP

0

OC4FE

OC2CE

0

OC4PE

OC1M[3]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Reset value

Res

0

CC3NP

Res

Res

Res

Res

Res

Res

Res

Res

OC2M[3]

Res

Res

Res

Res

Res

Reset value

CC3P

0

CC4E

0

0

CC4P

Reset value

Res

O24CE

Reset value

CC4NP

0
OC3M[3]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res
0

Res

Res

Res

Res

Res

Res

Res

Res

OC4M[3]

Res

Res

Res

Res

Res

Res

Reset value

Res

Res

Res

Res

Res

Res

Res

Res

Reset value

Res

Res

Res

Res

Res

Res

Reset value

Res

Res

Res

TIMx_CCMR2
Input Capture
mode

Res

0x1C

Res

TIMx_CCMR2
Output
Compare mode
Res

TIMx_CCMR1
Input Capture
mode

Res

0x18

Res

TIMx_CCMR1
Output
Compare mode

Res

TIMx_EGR

Res

0x14
Res

TIMx_SR

Res

0x10

Res

TIMx_DIER

Res

0x0C

Res

TIMx_SMCR

Res

0x08

Res

TIMx_CR2

Res

0x04

Res

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

21.4.19

Res

General-purpose timers (TIM2/TIM3/TIM4)
RM0316

TIMx register map
TIMx registers are mapped as described in the table below:
Table 127. TIM2/TIM3/TIM4 register map and reset values

CC1S
[1:0]

0
0
0
0

CC3S
[1:0]

0
0
0
0

0

0

0

0

0

0

RM0316

General-purpose timers (TIM2/TIM3/TIM4)

CNT[31] or UIFCPY

Reset value

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

TIMx_PSC

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

CNT[30:16]
(TIM2 only, reserved on the other timers)

CNT[15:0]

Reset value

1

1

1

1

1

1

1

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

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

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ARR[15:0]
1

1

1

1

1

1

1

1

1

1

1

1

0

0

CCR1[15:0]
0

0

0

0

0

0

0

0

CCR2[31:16]
(TIM2 only, reserved on the other timers)
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CCR4[15:0]

Res

0

0

CCR3[15:0]

CCR4[31:16]
(TIM2 only, reserved on the other timers)

TIMx_CCR4

0

CCR2[15:0]

CCR3[31:16]
(TIM2 only, reserved on the other timers)

0

0

0

0

0

0

0

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_DCR

Res

Reserved
Res

0x44

0

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_DMAR

DBL[4:0]
0

Res

Reset value

0x4C

0

Res

0

TIMx_CCR3

Reset value

0x48

0

Res

0

TIMx_CCR2

Reset value

0x40

0

CCR1[31:16]
(TIM2 only, reserved on the other timers)

TIMx_CCR1

Reset value

0x3C

0

Reserved

Reset value

0x38

0

Res

0x30

0x34

0

ARR[31:16]
(TIM2 a only, reserved on the other timers)

TIMx_ARR
Reset value

0

PSC[15:0]
0

Res

0x2C

0

Res

0x28

TIMx_CNT

Res

0x24

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 127. TIM2/TIM3/TIM4 register map and reset values (continued)

Reset value

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 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

DocID022558 Rev 8

669/1141
669

Basic timers (TIM6/TIM7)

RM0316

22

Basic timers (TIM6/TIM7)

22.1

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 outputs.
The timers are completely independent, and do not share any resources.

22.2

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 65535

•

Synchronization circuit to trigger the DAC

•

Interrupt/DMA generation on the update event: counter overflow
Figure 246. Basic timer block diagram

7ULJJHU
FRQWUROOHU

,QWHUQDOFORFN &.B,17
7,0[&/.IURP5&&

&RQWURO

&.B&17

5HVHWHQDEOH&RXQW

8,
6WRSFOHDURUXS

36&
SUHVFDOHU

WR'$&

$XWRUHORDGUHJLVWHU

8

&.B36&

75*2



8

&17FRXQWHU

1RWHV
5HJ

3UHORDGUHJLVWHUVWUDQVIHUUHG
WRDFWLYHUHJLVWHUVRQ8HYHQW
DFFRUGLQJWRFRQWUROELW
(YHQW
,QWHUUXSW '0$RXWSXW
069

670/1141

DocID022558 Rev 8

RM0316

Basic timers (TIM6/TIM7)

22.3

TIM6/TIM7 functional description

22.3.1

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 247 and Figure 248 give some examples of the counter behavior when the prescaler
ratio is changed on the fly.

DocID022558 Rev 8

671/1141
682

Basic timers (TIM6/TIM7)

RM0316

Figure 247. Counter timing diagram with prescaler division change from 1 to 2

&.B36&

&(1
7LPHUFORFN

&.B&17


&RXQWHUUHJLVWHU

)

)

)

)$ )% )&









8SGDWHHYHQW 8(9

3UHVFDOHUFRQWUROUHJLVWHU





:ULWHDQHZYDOXHLQ7,0[B36&
3UHVFDOHUEXIIHU



3UHVFDOHUFRXQWHU





















069

Figure 248. Counter timing diagram with prescaler division change from 1 to 4

&.B36&
&(1

7LPHUFORFN

&.B&17


&RXQWHUUHJLVWHU

)

)

)

)$ )% )&





8SGDWHHYHQW 8(9

3UHVFDOHUFRQWUROUHJLVWHU





:ULWHDQHZYDOXHLQ7,0[B36&
3UHVFDOHUEXIIHU

3UHVFDOHUFRXQWHU






















069

672/1141

DocID022558 Rev 8

RM0316

22.3.2

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 249. Counter timing diagram, internal clock divided by 1

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU







  

















&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)

069

DocID022558 Rev 8

673/1141
682

Basic timers (TIM6/TIM7)

RM0316

Figure 250. Counter timing diagram, internal clock divided by 2

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU















&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)

069

Figure 251. Counter timing diagram, internal clock divided by 4

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU









&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

674/1141

DocID022558 Rev 8

RM0316

Basic timers (TIM6/TIM7)
Figure 252. Counter timing diagram, internal clock divided by N

&.B36&

7LPHUFORFN &.B&17

&RXQWHUUHJLVWHU

)





&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

Figure 253. Counter timing diagram, update event when ARPE = 0 (TIMx_ARR not
preloaded)
&.B36&

&(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU





























&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

))



:ULWHDQHZYDOXHLQ7,0[B$55
069

DocID022558 Rev 8

675/1141
682

Basic timers (TIM6/TIM7)

RM0316

Figure 254. Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded)
&.B36&

&(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU

)

)

)

)

) )

















&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

)



$XWRUHORDGVKDGRZ
UHJLVWHU

)



:ULWHDQHZYDOXHLQ7,0[B$55

22.3.3

069

UIF bit remapping
The IUFREMAP bit in the TIMx_CR1 register forces a continuous copy of the Update
Interrupt Flag UIF into the timer counter register’s bit 31 (TIMxCNT[31]). This allows to
atomically read both the counter value and a potential roll-over condition signaled by the
UIFCPY flag. In particular cases, it can ease the calculations by avoiding race conditions
caused for instance by a processing shared between a background task (counter reading)
and an interrupt (Update Interrupt).
There is no latency between the assertions of the UIF and UIFCPY flags.

22.3.4

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 255 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.

676/1141

DocID022558 Rev 8

RM0316

Basic timers (TIM6/TIM7)
Figure 255. Control circuit in normal mode, internal clock divided by 1

,QWHUQDOFORFN
&(1 &17B(1
8*

&17B,1,7

&RXQWHUFORFN &.B&17 &.B36&
&RXQWHUUHJLVWHU









 

 





  


069

22.3.5

Debug mode
When the microcontroller enters the debug mode (Cortex-M4®F 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.

22.4

TIM6/TIM7 registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.
The peripheral registers can be accessed by half-words (16-bit) or words (32-bit).

22.4.1

TIM6/TIM7 control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15
Res

14
Res

13
Res

12

11

10

9

8

7

6

5

4

3

2

1

0

Res

UIF
REMAP

Res

Res

Res

ARPE

Res

Res

Res

OPM

URS

UDIS

CEN

rw

rw

rw

rw

rw

rw

Bits 15:12 Reserved, must be kept at reset value.
Bit 11 UIFREMAP: UIF status bit remapping
0: No remapping. UIF status bit is not copied to TIMx_CNT register bit 31.
1: Remapping enabled. UIF status bit is copied to TIMx_CNT register bit 31.
Bits 10:8 Reserved, must be kept at reset value.

DocID022558 Rev 8

677/1141
682

Basic timers (TIM6/TIM7)

RM0316

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).
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.

678/1141

DocID022558 Rev 8

RM0316

Basic timers (TIM6/TIM7)

22.4.2

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: 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.
Note: The clock of the slave timer or ADC must be enabled prior to receive events from the
master timer, and must not be changed on-the-fly while triggers are received from the
master timer.
Bits 3:0 Reserved, must be kept at reset value.

22.4.3

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

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.

DocID022558 Rev 8

679/1141
682

Basic timers (TIM6/TIM7)

22.4.4

RM0316

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

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

0
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 regarding the repetition counter value 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.

22.4.5

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).

22.4.6

TIM6/TIM7 counter (TIMx_CNT)
Address offset: 0x24
Reset value: 0x0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

UIF
CPY

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

r
15

CNT[15:0]
rw

680/1141

rw

rw

rw

rw

rw

rw

rw

rw

DocID022558 Rev 8

RM0316

Basic timers (TIM6/TIM7)

Bit 31 UIFCPY: UIF Copy
This bit is a read-only copy of the UIF bit of the TIMx_ISR register. If the UIFREMAP bit in
TIMx_CR1 is reset, bit 31 is reserved and read as 0.
Bits 30:16 Reserved, must be kept at reset value.
Bits 15:0 CNT[15:0]: Counter value

22.4.7

TIM6/TIM7 prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

PSC[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 PSC[15:0]: Prescaler value
The counter clock frequency CK_CNT is equal to fCK_PSC / (PSC[15:0] + 1).
PSC contains the value to be loaded into the active prescaler register at each update event.
(including when the counter is cleared through UG bit of TIMx_EGR register or through
trigger controller when configured in “reset mode”).

22.4.8

TIM6/TIM7 auto-reload register (TIMx_ARR)
Address offset: 0x2C
Reset value: 0xFFFF

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

ARR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:0 ARR[15:0]: Prescaler value
ARR is the value to be loaded into the actual auto-reload register.
Refer to Section 22.3.1: Time-base unit on page 671 for more details about ARR update and
behavior.
The counter is blocked while the auto-reload value is null.

DocID022558 Rev 8

681/1141
682

0x2C

682/1141

TIMx_ARR

Res

Res

Res
Res

Res

Res
Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

0x180x20

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Reset value

Reset value

DocID022558 Rev 8
0

0

1
0

0

1
0

0

1
0

0

1
0

0

1
0

0

1
0

0

1
0

0

1
0

0

1
0

0

1

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

Reset value

Reset value
UIF

Res

Res

0

UG

Res

Res
Res
Res

Res
Res
UIE

URS
UDIS
CEN

OPM

Res

Res

Res

ARPE

Res

Res

Res

UIFREMAP

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

0

Res

Res

Res

0

Res

0

Res

Reserved
0

Res

MMS
[2:0]

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

0

Res

Res

Res

Res

Reset value

Res

Res

UDE

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

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

0x08

Res

Res

Res

Res

Res

TIMx_PSC

Res

0

Res

Reset value

Res

TIMx_CNT

Res

TIMx_EGR

Res

0x28
TIMx_SR

Res

0x24
TIMx_DIER

Res

0x14
TIMx_CR2

Res

0x10
TIMx_CR1

Res

0x0C

UIFCPY or 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

0x00

Res

Offset

Res

22.4.9

Res

Basic timers (TIM6/TIM7)
RM0316

TIM6/TIM7 register map
TIMx registers are mapped as 16-bit addressable registers as described in the table below:
Table 128. TIM6/TIM7 register map and reset values

0
0
0

0

0

0

Reserved

CNT[15:0]

PSC[15:0]

ARR[15:0]
0
0
0
0
0
0

0

0

0

0

0

0

1

1

1

1

1

1

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

23

General-purpose timers (TIM15/TIM16/TIM17)

23.1

TIM15/TIM16/TIM17 introduction
The TIM15/TIM16/TIM17 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,
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 TIM15/TIM16/TIM17 timers are completely independent, and do not share any
resources. They can be synchronized together as described in Section 23.4.20: Timer
synchronization (TIM15).

23.2

TIM15 main features
TIM15 includes the following features:
•

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 65535

•

Up to 2 independent channels for:
–

Input capture

–

Output compare

–

PWM generation (edge mode)

–

One-pulse mode output

•

Complementary outputs with programmable dead-time (for channel 1 only)

•

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 the reset state or a known state

•

Interrupt/DMA generation on the following events:
–

Update: counter overflow, 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 (interrupt request)

DocID022558 Rev 8

683/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

23.3

RM0316

TIM16/TIM17 main features
The TIM16/TIM17 timers include the following features:

684/1141

•

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 65535

•

One channel for:
–

Input capture

–

Output compare

–

PWM generation (edge-aligned mode)

–

One-pulse mode output

•

Complementary outputs with programmable dead-time

•

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 the reset state or a known state

•

Interrupt/DMA generation on the following events:
–

Update: counter overflow

–

Trigger event (counter start, stop, initialization or count by internal/external trigger)

–

Input capture

–

Output compare

–

Break input

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)
Figure 256. TIM15 block diagram

,QWHUQDOFORFN &.B,17
&.B7,0IURP5&&

,75
,75
,75
,75

7ULJJHU
FRQWUROOHU
7*,

,75
75&
7,)B('

75*,

75*2
WRRWKHUWLPHUV

6ODYH
FRQWUROOHU 5HVHWHQDEOHXSFRXQW
PRGH

7,)3
7,)3

5(3UHJLVWHU
8

8,

$XWRUHORDGUHJLVWHU

5HSHWLWLRQ
FRXQWHU

6WRSFOHDURUXSGRZQ
&.B36&
;25
7,
7,0[B&+

7,0[B&+

7,0[B%.,1

7,

%5.

,QSXWILOWHU 
HGJHGHWHFWRU

,QSXWILOWHU 
HGJHGHWHFWRU

7,)3
7,)3

,&

36& &.B&17
SUHVFDOHU
&&, 8
3UHVFDOHU

75&
7,)3
7,)3
75&

3RODULW\VHOHFWLRQ

,&36
&&,

,&

3UHVFDOHU



&17FRXQWHU
&&,

&DSWXUH&RPSDUHUHJLVWHU

'7*UHJLVWHUV

2&5()
'7*
&&,

8

,&36

8

&DSWXUH&RPSDUHUHJLVWHU 2&5()

7,0[B&+

2XWSXW 2&
FRQWURO
7,0[B&+1
2&1
2XWSXW 2& 7,0[B&+
FRQWURO

%,

%5.B$&7+
,QWHUQDOEUHDNHYHQWVRXUFHV

1RWHV
5HJ

3UHORDGUHJLVWHUVWUDQVIHUUHG
WRDFWLYHUHJLVWHUVRQ8HYHQW
DFFRUGLQJWRFRQWUROELW
(YHQW
,QWHUUXSW '0$RXWSXW

069

1. The internal break event source can be:
A clock failure event generated by CSS. For further information on the CSS, refer to Section 9.2.7: Clock security
system (CSS)
A PVD output
SRAM parity error signal
Cortex-M4®F LOCKUP (Hardfault) output
COMP output

DocID022558 Rev 8

685/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Figure 257. TIM16/TIM17 block diagram

,QWHUQDOFORFN &.B,17
&RXQWHU(QDEOH &(1

5(3UHJLVWHU
$XWRUHORDGUHJLVWHU

8

8,
5HSHWLWLRQ
FRXQWHU

6WRSFOHDURUXSGRZQ
&.B36&

7,0[B&+

7,

,QSXWILOWHU
HGJHVHOHFWRU

7,)3

36&
SUHVFDOHU

&.B&17



&17FRXQWHU

&,

3UHVFDOHU

,&36

'7*UHJLVWHUV
&&,

8

,&

8

&DSWXUHFRPSDUHUHJLVWHU

2&5()

7,0[B&+

'7*

2XWSXW 2&
FRQWURO
7,0[B&+1
2&1

7,0[B%.,1

%5.

3RODULW\VHOHFWLRQ

%,

,QWHUQDOEUHDNHYHQWVRXUFHV

1RWHV
5HJ

3UHORDGUHJLVWHUVWUDQVIHUUHG
WRDFWLYHUHJLVWHUVRQ8HYHQW
DFFRUGLQJWRFRQWUROELW
(YHQW
,QWHUUXSW '0$RXWSXW

069

1. The internal break event source can be:
A clock failure event generated by CSS. For further information on the CSS, refer to Section 9.2.7: Clock security
system (CSS)
A PVD output
SRAM parity error signal
Cortex-M4®F LOCKUP (Hardfault) output
COMP output

686/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

23.4

TIM15/TIM16/TIM17 functional description

23.4.1

Time-base unit
The main block of the programmable advanced-control 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)

•

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 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 258 and Figure 259 give some examples of the counter behavior when the prescaler
ratio is changed on the fly:

DocID022558 Rev 8

687/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Figure 258. Counter timing diagram with prescaler division change from 1 to 2

&.B36&

&(1
7LPHUFORFN

&.B&17


&RXQWHUUHJLVWHU

)

)

)

)$ )% )&









8SGDWHHYHQW 8(9

3UHVFDOHUFRQWUROUHJLVWHU





:ULWHDQHZYDOXHLQ7,0[B36&
3UHVFDOHUEXIIHU



3UHVFDOHUFRXQWHU





















069

Figure 259. Counter timing diagram with prescaler division change from 1 to 4

&.B36&
&(1

7LPHUFORFN

&.B&17


&RXQWHUUHJLVWHU

)

)

)

)$ )% )&





8SGDWHHYHQW 8(9

3UHVFDOHUFRQWUROUHJLVWHU





:ULWHDQHZYDOXHLQ7,0[B36&
3UHVFDOHUEXIIHU

3UHVFDOHUFRXQWHU






















069

688/1141

DocID022558 Rev 8

RM0316

23.4.2

General-purpose timers (TIM15/TIM16/TIM17)

Counter modes
Upcounting mode
In upcounting mode, the counter counts from 0 to the auto-reload value (content of the
TIMx_ARR register), then restarts from 0 and generates a counter overflow event.
If the repetition counter is used, the update event (UEV) is generated after upcounting is
repeated for the number of times programmed in the repetition counter register
(TIMx_RCR). 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.

DocID022558 Rev 8

689/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Figure 260. Counter timing diagram, internal clock divided by 1

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU







  

















&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)

069

Figure 261. Counter timing diagram, internal clock divided by 2

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU















&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)

069

690/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)
Figure 262. Counter timing diagram, internal clock divided by 4

&.B36&

&17B(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU









&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

Figure 263. Counter timing diagram, internal clock divided by N

&.B36&

7LPHUFORFN &.B&17

&RXQWHUUHJLVWHU

)





&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9

8SGDWHLQWHUUXSWIODJ
 8,)
069

DocID022558 Rev 8

691/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Figure 264. Counter timing diagram, update event when ARPE=0 (TIMx_ARR not
preloaded)
&.B36&

&(1

7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU





























&RXQWHURYHUIORZ

8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

))



:ULWHDQHZYDOXHLQ7,0[B$55
069

Figure 265. Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded)
&.B36&

&(1
7LPHUFORFN &.B&17
&RXQWHUUHJLVWHU

)

)

)

)

) )

















&RXQWHURYHUIORZ
8SGDWHHYHQW 8(9
8SGDWHLQWHUUXSWIODJ
 8,)
$XWRUHORDGSUHORDG
UHJLVWHU

)



$XWRUHORDGVKDGRZ
UHJLVWHU

)

:ULWHDQHZYDOXHLQ7,0[B$55

692/1141

DocID022558 Rev 8



069

RM0316

23.4.3

General-purpose timers (TIM15/TIM16/TIM17)

Repetition counter
Section 23.4.1: Time-base unit describes how the update event (UEV) is generated with
respect to the counter overflows. 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 counter overflows, where N is the
value in the TIMx_RCR repetition counter register.
The repetition counter is decremented at each counter overflow.
The repetition counter is an auto-reload type; the repetition rate is maintained as defined by
the TIMx_RCR register value (refer to Figure 266). 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.

DocID022558 Rev 8

693/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Figure 266. Update rate examples depending on mode and TIMx_RCR register
settings
(GJHDOLJQHGPRGH
8SFRXQWLQJ
&RXQWHU
7,0[B&17

7,0[B5&5 8(9

7,0[B5&5 8(9

7,0[B5&5 8(9

7,0[B5&5 8(9

7,0[B5&5 
DQG
UHV\QFKURQL]DWLRQ8(9
E\6:
8(9

8SGDWH(YHQWSUHORDGUHJLVWHUVWUDQVIHUUHGWRDFWLYHUHJLVWHUV
DQGXSGDWHLQWHUUXSWJHQHUDWHG

069

23.4.4

Clock selection
The counter clock can be provided by the following clock sources:
•

Internal clock (CK_INT)

•

External clock mode1: external input pin

•

Internal trigger inputs (ITRx) (only for TIM15): using one timer as the prescaler for
another timer, for example, you can configure TIM1 to act as a prescaler for TIM15.
Refer to Using one timer as prescaler for another timer on page 641 for more details.

Internal clock source (CK_INT)
If the slave mode controller is disabled (SMS=000), then the CEN (in the TIMx_CR1
register) and UG bits (in the TIMx_EGR register) are actual control bits and can be changed

694/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)
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 267 shows the behavior of the control circuit and the upcounter in normal mode,
without prescaler.
Figure 267. Control circuit in normal mode, internal clock divided by 1

,QWHUQDOFORFN
&(1 &17B(1
8*

&17B,1,7

&RXQWHUFORFN &.B&17 &.B36&
&RXQWHUUHJLVWHU









 

 



  




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.
Figure 268. TI2 external clock connection example
7,0[B60&5
76>@

,75[
7,B('

7,

)LOWHU

(GJH
GHWHFWRU

7,)B5LVLQJ
7,)B)DOOLQJ

7,)3



7,)3

[[


75*,



&&3

7,0[B&&05

7,0[B&&(5

&.B36&


&.B,17

,&)>@

([WHUQDOFORFN
PRGH


LQWHUQDOFORFN

,QWHUQDOFORFN
PRGH

606>@
7,0[B60&5

069

DocID022558 Rev 8

695/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

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 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 269. Control circuit in external clock mode 1

7,
&17B(1
&RXQWHUFORFN &.B&17 &.B36&
&RXQWHUUHJLVWHU







7,)

:ULWH7,) 

069

23.4.5

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 270 to Figure 273 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).

696/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)
Figure 270. Capture/compare channel (example: channel 1 input stage)

7,)B('
7RWKHVODYHPRGHFRQWUROOHU
7,)B5LVLQJ

7,

)LOWHU
7,)
GRZQFRXQWHU

I'76

(GJH
GHWHFWRU

7,)B)DOOLQJ

 7,)3




7,)3

,&)>@

&&3

7,0[B&&05

7,0[B&&(5
7,)B5LVLQJ

IURPFKDQQHO
7,)B)DOOLQJ

IURPFKDQQHO

,&



75&
IURPVODYHPRGH
FRQWUROOHU

,&36
'LYLGHU




&&6>@ ,&36>@

&&(

7,0[B&&05

7,0[B&&(5

069

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 271. Capture/compare channel 1 main circuit

$3%%XV

5HDG&&5+ 6
5HDG&&5/

KLJK



UHDGBLQBSURJUHVV

&&6>@
,&36

ZULWHBLQBSURJUHVV

,QSXW
PRGH

6 ZULWH&&5+

&DSWXUHFRPSDUHSUHORDGUHJLVWHU

5

5
FRPSDUHBWUDQVIHU

FDSWXUHBWUDQVIHU
&&6>@


ORZ

LIELW

0&8SHULSKHUDOLQWHUIDFH

2XWSXW
PRGH

&17!&&5
&RXQWHU

&&*

&&6>@

8(9
&RPSDUDWRU

&&(

&&6>@

2&3(

&DSWXUHFRPSDUHVKDGRZUHJLVWHU
&DSWXUH

ZULWH&&5/

IURPWLPH
EDVHXQLW

2&3(

7,0B&&05

&17 &&5

7,0B(*5

069

DocID022558 Rev 8

697/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Figure 272. Output stage of capture/compare channel (channel 1)

7RWKHPDVWHUPRGH
FRQWUROOHU

µ¶
2&5()&

2&5()
&17!&&5 2XWSXW
PRGH
&17 &&5
FRQWUROOHU

2&B'7
'HDGWLPH
JHQHUDWRU

2XWSXW
VHOHFWRU

[






&&3

2XWSXW
HQDEOH
FLUFXLW

2&

2XWSXW
HQDEOH
FLUFXLW

2&1

7,0B&&(5
2&1B'7
µ¶

2&5()





[



&&1( &&( 7,0B&&(5
2&&( 2&0>@

'7*>@

&&1( &&(

&&13

02( 266, 2665

7,0B&&05

7,0B%'75

7,0B&&(5

7,0B&&(5

7,0B%'75

069

Figure 273. Output stage of capture/compare channel (channel 2 for TIM15)
7RWKHPDVWHU
PRGHFRQWUROOHU
2&5()&
2&5()

µ¶

&17!&&5

2XWSXW
PRGH
&17 &&5
FRQWUROOHU
2&5()

2XWSXW
VHOHFWRU









&&(

&&3

7,0B&&(5

7,0B&&(5

2XWSXW
HQDEOH
FLUFXLW

2&

&&( 7,0B&&(5

2&&( 2&0>@
7,0B&&05

069

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.

698/1141

DocID022558 Rev 8

RM0316

23.4.6

General-purpose timers (TIM15/TIM16/TIM17)

Input capture mode
In Input capture mode, the Capture/Compare Registers (TIMx_CCRx) are used to latch the
value of the counter after a transition detected by the corresponding ICx signal. When a
capture occurs, the corresponding CCXIF flag (TIMx_SR register) is set and an interrupt or
a DMA request can be sent if they are enabled. If a capture occurs while the CCxIF flag was
already high, then the over-capture flag CCxOF (TIMx_SR register) is set. CCxIF can be
cleared by software by writing it to ‘0’ or by reading the captured data stored in the
TIMx_CCRx register. CCxOF is cleared when you write it to ‘0’.
The following example shows how to capture the counter value in TIMx_CCR1 when TI1
input rises. To do this, use the following procedure:
1.

Select the active input: TIMx_CCR1 must be linked to the TI1 input, so write the CC1S
bits to 01 in the TIMx_CCMR1 register. As soon as CC1S becomes different from 00,
the channel is configured in input and the TIMx_CCR1 register becomes read-only.

2.

Program the input filter duration you need with respect to the signal you connect to the
timer (when the input is one of the TIx (ICxF bits in the TIMx_CCMRx register). Let’s
imagine that, when toggling, the input signal is not stable during at least 5 internal clock
cycles. We must program a filter duration longer than these 5 clock cycles. We can
validate a transition on TI1 when 8 consecutive samples with the new level have been
detected (sampled at fDTS frequency). Then write IC1F bits to 0011 in the
TIMx_CCMR1 register.

3.

Select the edge of the active transition on the TI1 channel by writing CC1P bit to 0 in
the TIMx_CCER register (rising edge in this case).

4.

Program the input prescaler. In our example, we wish the capture to be performed at
each valid transition, so the prescaler is disabled (write IC1PS bits to ‘00’ in the
TIMx_CCMR1 register).

5.

Enable capture from the counter into the capture register by setting the CC1E bit in the
TIMx_CCER register.

6.

If needed, enable the related interrupt request by setting the CC1IE bit in the
TIMx_DIER register, and/or the DMA request by setting the CC1DE bit in the
TIMx_DIER register.

When an input capture occurs:
•

The TIMx_CCR1 register gets the value of the counter on the active transition.

•

CC1IF flag is set (interrupt flag). CC1OF is also set if at least two consecutive captures
occurred whereas the flag was not cleared.

•

An interrupt is generated depending on the CC1IE bit.

•

A DMA request is generated depending on the CC1DE bit.

In order to handle the overcapture, it is recommended to read the data before the
overcapture flag. This is to avoid missing an overcapture which could happen after reading
the flag and before reading the data.
Note:

IC interrupt and/or DMA requests can be generated by software by setting the
corresponding CCxG bit in the TIMx_EGR register.

DocID022558 Rev 8

699/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

23.4.7

RM0316

PWM input mode (only for TIM15)
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):
1.

Select the active input for TIMx_CCR1: write the CC1S bits to 01 in the TIMx_CCMR1
register (TI1 selected).

2.

Select the active polarity for TI1FP1 (used both for capture in TIMx_CCR1 and counter
clear): write the CC1P and CC1NP bits to ‘0’ (active on rising edge).

3.

Select the active input for TIMx_CCR2: write the CC2S bits to 10 in the TIMx_CCMR1
register (TI1 selected).

4.

Select the active polarity for TI1FP2 (used for capture in TIMx_CCR2): write the CC2P
and CC2NP bits to ‘1’ (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 274. PWM input mode timing
7,

7,0[B&17









7,0[B&&5



7,0[B&&5



,&FDSWXUH
,&FDSWXUH
UHVHWFRXQWHU





,&FDSWXUH
SXOVHZLGWK
PHDVXUHPHQW



,&FDSWXUH
SHULRG
PHDVXUHPHQW
DL

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.

700/1141

DocID022558 Rev 8

RM0316

23.4.8

General-purpose timers (TIM15/TIM16/TIM17)

Forced output mode
In output mode (CCxS bits = 00 in the TIMx_CCMRx register), each output compare signal
(OCxREF and then OCx/OCxN) can be forced to active or inactive level directly by software,
independently of any comparison between the output compare register and the counter.
To force an output compare signal (OCXREF/OCx) to its active level, 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.

23.4.9

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).

DocID022558 Rev 8

701/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

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 274.
Figure 275. Output compare mode, toggle on OC1
:ULWH%KLQWKH&&5UHJLVWHU

7,0B&17



7,0B&&5

%

$

%

%

%

$

2&5() 2&

0DWFKGHWHFWHGRQ&&5
,QWHUUXSWJHQHUDWHGLIHQDEOHG
069

23.4.10

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.

702/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)
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 TIM15/TIM16/TIM17 are capable of upcounting only. Refer to Upcounting mode on
page 689.
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 276 shows some edgealigned PWM waveforms in an example where TIMx_ARR=8.
Figure 276. Edge-aligned PWM waveforms (ARR=8)



&RXQWHUUHJLVWHU

&&5[ 





















2&;5()
&&[,)

2&;5()
&&5[ 
&&[,)

2&;5()

µ¶

&&5[!
&&[,)

2&;5()

µ¶

&&5[ 
&&[,)

069

23.4.11

Combined PWM mode (TIM15 only)
Combined PWM mode allows two edge or center-aligned PWM signals to be generated with
programmable delay and phase shift between respective pulses. While the frequency is
determined by the value of the TIMx_ARR register, the duty cycle and delay are determined

DocID022558 Rev 8

703/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

by the two TIMx_CCRx registers. The resulting signals, OCxREFC, are made of an OR or
AND logical combination of two reference PWMs:
•

OC1REFC (or OC2REFC) is controlled by the TIMx_CCR1 and TIMx_CCR2 registers

Combined PWM mode can be selected independently on two channels (one OCx output per
pair of CCR registers) by writing ‘1100’ (Combined PWM mode 1) or ‘1101’ (Combined PWM
mode 2) in the OCxM bits in the TIMx_CCMRx register.
When a given channel is used as a combined PWM channel, its complementary channel
must be configured in the opposite PWM mode (for instance, one in Combined PWM mode
1 and the other in Combined PWM mode 2).
Note:

The OCxM[3:0] bit field is split into two parts for compatibility reasons, the most significant
bit is not contiguous with the 3 least significant ones.
Figure 277 represents an example of signals that can be generated using Asymmetric PWM
mode, obtained with the following configuration:
•

Channel 1 is configured in Combined PWM mode 2,

•

Channel 2 is configured in PWM mode 1,
Figure 277. Combined PWM mode on channel 1 and 2

2&¶
2&¶

2&
2&
2&5()
2&5()
2&5()¶
2&5()¶

2&5()&
2&5()&¶

2&5()& 2&5()$1'2&5()
2&5()&¶ 2&5()¶252&5()¶

069

704/1141

DocID022558 Rev 8

RM0316

23.4.12

General-purpose timers (TIM15/TIM16/TIM17)

Complementary outputs and dead-time insertion
The TIM15/TIM16/TIM17 general-purpose timers can output one complementary signal and
manage the switching-off and switching-on 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 130: Output control bits for complementary OCx and OCxN channels with break
feature (TIM15) on page 731 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. There is one 10-bit dead-time generator for each channel. From a
reference waveform OCxREF, it generates 2 outputs OCx and OCxN. If OCx and OCxN are
active high:
•

The OCx output signal is the same as the reference signal except for the rising edge,
which is delayed relative to the reference rising edge.

•

The OCxN output signal is the opposite of the reference signal except for the rising
edge, which is delayed relative to the reference falling edge.

If the delay is greater than the width of the active output (OCx or OCxN) then the
corresponding pulse is not generated.
The following figures show the relationships between the output signals of the dead-time
generator and the reference signal OCxREF. (we suppose CCxP=0, CCxNP=0, MOE=1,
CCxE=1 and CCxNE=1 in these examples)
Figure 278. Complementary output with dead-time insertion.

2&[5()
2&[
GHOD\
2&[1
GHOD\

069

DocID022558 Rev 8

705/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Figure 279. Dead-time waveforms with delay greater than the negative pulse.

2&[5()
2&[
GHOD\
2&[1

069

Figure 280. Dead-time waveforms with delay greater than the positive pulse.

2&[5()
2&[
2&[1
GHOD\

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 23.5.15: TIM15 break and dead-time
register (TIM15_BDTR) on page 734 for delay calculation.

Re-directing OCxREF to OCx or OCxN
In output mode (forced, output compare or PWM), OCxREF can be re-directed to the OCx
output or to OCxN output by configuring the CCxE and CCxNE bits in the TIMx_CCER
register.
This allows you to send a specific waveform (such as PWM or static active level) on one
output while the complementary remains at its inactive level. Other alternative possibilities
are to have both outputs at inactive level or both outputs active and complementary with
dead-time.
Note:

706/1141

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.

DocID022558 Rev 8

RM0316

23.4.13

General-purpose timers (TIM15/TIM16/TIM17)

Using the break function
The purpose of the break function is to protect power switches driven by PWM signals
generated with the TIM15/TIM16/TIM17 timers. The break input is usually connected to fault
outputs of power stages and 3-phase inverters. When activated, the break circuitry shuts
down the PWM outputs and forces them to a predefined safe state.
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 130: Output control bits for
complementary OCx and OCxN channels with break feature (TIM15) on page 731 for more
details.
The break source can be:
•

An external source connected to BKIN pin (connected internally to BRK)

•

An internal source (connected internally to BRK_ACTH):
–

A clock failure event generated by CSS. For further information on the CSS, refer
to Section 9.2.7: Clock security system (CSS)

–

An output from a comparator

–

A PVD output

–

SRAM parity error signal

–

Cortex®-M4 LOCKUP (Hardfault) output

When exiting from reset, the break circuit is disabled and the MOE bit is low. The break
function is enabled 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.
The break is generated by the BRK inputs which has:
•

Programmable polarity (BKP bit in the TIMx_BDTR register)

•

Programmable enable bit (BKE bit in the TIMx_BDTR register)

It is also possible to generate break events by software using BG bit in TIMx_EGR register.

DocID022558 Rev 8

707/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

When a break occurs (selected level on the break input):

Note:

•

The MOE bit is cleared asynchronously, putting the outputs in inactive state, idle state
or even releasing the control to the AFIO controller (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, the timer releases the output control
(taken over by the AFIO controller) 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
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).

–

If OSSI=0 then the timer releases the enable outputs (taken over by the AFIO
controller which forces a Hi-Z state) 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.
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 23.5.15: TIM15 break and dead-time register (TIM15_BDTR) on page 734. The
LOCK bits can be written only once after an MCU reset.
The Figure 281 shows an example of behavior of the outputs in response to a break.

708/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)
Figure 281. Output behavior in response to a break
%5($. 02( 

2&[5()

2&[
2&[1QRWLPSOHPHQWHG&&[3 2,6[ 

2&[
2&[1QRWLPSOHPHQWHG&&[3 2,6[ 

2&[
2&[1QRWLPSOHPHQWHG&&[3 2,6[ 

2&[
2&[1QRWLPSOHPHQWHG&&[3 2,6[ 

2&[
GHOD\
GHOD\
2&[1
&&[( &&[3 2,6[ &&[1( &&[13 2,6[1 

GHOD\

2&[
GHOD\
GHOD\
2&[1
&&[( &&[3 2,6[ &&[1( &&[13 2,6[1 

GHOD\

2&[
2&[1
&&[( &&[3 2,6[ &&[1( &&[13 2,6[1 

GHOD\

2&[
2&[1
&&[( &&[3 2,6[ &&[1( &&[13 2,6[1 

GHOD\

2&[
2&[1
&&[( &&[3 &&[1( &&[13 2,6[ 2,6[1 RU2,6[ 2,6[1 

069

DocID022558 Rev 8

709/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

23.4.14

RM0316

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:
•

CNT < CCRx ≤ ARR (in particular, 0 < CCRx)
Figure 282. Example of one pulse mode.

7,
2&5()
2&

&RXQWHU

7,0B$55
7,0B&&5


W'(/$<

W38/6(

W

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.
Let’s use TI2FP2 as trigger 1:

710/1141

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).

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)
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, 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).
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.

23.4.15

UIF bit remapping
The IUFREMAP bit in the TIMx_CR1 register forces a continuous copy of the Update
Interrupt Flag UIF into bit 31 of the timer counter register (TIMxCNT[31]). This allows to
atomically read both the counter value and a potential roll-over condition signaled by the
UIFCPY flag. In particular cases, it can ease the calculations by avoiding race conditions
caused for instance by a processing shared between a background task (counter reading)
and an interrupt (Update Interrupt).
There is no latency between the assertions of the UIF and UIFCPY flags.

DocID022558 Rev 8

711/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

23.4.16

RM0316

Timer input XOR function (TIM15 only)
The TI1S bit in the TIMx_CR2 register, allows the input filter of channel 1 to be connected to
the output of a XOR gate, combining the two input pins TIMx_CH1 and TIMx_CH2.
The XOR output can be used with all the timer input functions such as trigger or input
capture. It is useful for measuring the interval between the edges on two input signals, as
shown in Figure 283.
Figure 283. Measuring time interval between edges on 2 signals
7,
7,

7,;257,

&RXQWHU

069

712/1141

DocID022558 Rev 8

RM0316

23.4.17

General-purpose timers (TIM15/TIM16/TIM17)

External trigger synchronization (TIM15 only)
The TIM timers are linked together internally for timer synchronization or chaining.
The TIM15 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:
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. Write
CC1P=’0’ and CC1NP=’0’ in the 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, 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 284. Control circuit in reset mode

7,
8*
&RXQWHUFORFN FNBFQW FNBSVF
&RXQWHUUHJLVWHU

              

7,)

069

DocID022558 Rev 8

713/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

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. Write
CC1P=1 and CC1NP = ‘0’ in the TIMx_CCER register to validate the polarity (and
detect low level only).

2.

Configure the timer in gated mode by writing SMS=101 in TIMx_SMCR register. Select
TI1 as the input source by writing TS=101 in TIMx_SMCR register.

3.

Enable the counter by writing CEN=1 in the TIMx_CR1 register (in gated mode, the
counter doesn’t start if CEN=0, whatever is the trigger input level).

The counter starts counting on the internal clock as long as TI1 is low and stops as soon as
TI1 becomes high. The TIF flag in the TIMx_SR register is set both when the counter starts
or stops.
The delay between the rising edge on TI1 and the actual stop of the counter is due to the
resynchronization circuit on TI1 input.
Figure 285. Control circuit in gated mode

7,
FQWBHQ
&RXQWHUFORFN FNBFQW FNBSVF
&RXQWHUUHJLVWHU

   



   

7,)

:ULWH7,) 
069

714/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

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.
Write CC2P=’1’ and CC2NP=’0’ in the TIMx_CCER register to validate the polarity (and
detect low level only).

2.

Configure the timer in trigger mode by writing SMS=110 in the TIMx_SMCR register.
Select TI2 as the input source by writing TS=110 in the 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 286. Control circuit in trigger mode
7,
FQWBHQ
&RXQWHUFORFN FNBFQW FNBSVF
&RXQWHUUHJLVWHU





  

7,)
069

23.4.18

Slave mode: Combined reset + trigger mode (TIM15 only)
In this case, a rising edge of the selected trigger input (TRGI) reinitializes the counter,
generates an update of the registers, and starts the counter.
This mode is used for one-pulse mode.

23.4.19

DMA burst mode
The TIMx timers have the capability to generate multiple DMA requests on a single event.
The main purpose is to be able to re-program several timer registers multiple times without
software overhead, but it can also be used to read several registers in a row, at regular
intervals.
The DMA controller destination is unique and must point to the virtual register TIMx_DMAR.
On a given timer event, the timer launches a sequence of DMA requests (burst). Each write
into the TIMx_DMAR register is actually redirected to one of the timer registers.

DocID022558 Rev 8

715/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

The DBL[4:0] bits in the TIMx_DCR register set the DMA burst length. The timer recognizes
a burst transfer when a read or a write access is done to the TIMx_DMAR address), i.e. the
number of transfers (either in half-words or in bytes).
The DBA[4:0] bits in the TIMx_DCR registers define the DMA base address for DMA
transfers (when read/write access are done through the TIMx_DMAR address). DBA is
defined as an offset starting from the address of the TIMx_CR1 register.
Example:
00000: TIMx_CR1,
00001: TIMx_CR2,
00010: TIMx_SMCR,
For example, the timer DMA burst feature could be used to update the contents of the CCRx
registers (x = 2, 3, 4) on an update event, with the DMA transferring half words into the
CCRx registers.
This is done in the following steps:
1.

Configure the corresponding DMA channel as follows:
–

DMA channel peripheral address is the DMAR register address

–

DMA channel memory address is the address of the buffer in the RAM containing
the data to be transferred by DMA into the 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 is to be updated once. If every
CCRx register is to be updated twice for example, the number of data to transfer should be
6. Let's take the example of a buffer in the RAM containing data1, data2, data3, data4, data5
and data6. The data is transferred to the CCRx registers as follows: on the first update DMA
request, data1 is transferred to CCR2, data2 is transferred to CCR3, data3 is transferred to
CCR4 and on the second update DMA request, data4 is transferred to CCR2, data5 is
transferred to CCR3 and data6 is transferred to CCR4.
Note:

716/1141

A null value can be written to the reserved registers.

DocID022558 Rev 8

RM0316

23.4.20

General-purpose timers (TIM15/TIM16/TIM17)

Timer synchronization (TIM15)
The TIMx timers are linked together internally for timer synchronization or chaining. Refer to
Section 21.3.19: Timer synchronization for details.

Note:

The clock of the slave timer must be enabled prior to receive events from the master timer,
and must not be changed on-the-fly while triggers are received from the master timer.

23.4.21

Debug mode
When the microcontroller enters debug mode (Cortex-M4®F 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.
For safety purposes, when the counter is stopped (DBG_TIMx_STOP = 1), the outputs are
disabled (as if the MOE bit was reset). The outputs can either be forced to an inactive state
(OSSI bit = 1), or have their control taken over by the GPIO controller (OSSI bit = 0) to force
them to Hi-Z.

DocID022558 Rev 8

717/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

23.5

RM0316

TIM15 registers
Refer to Section 2.1 for a list of abbreviations used in register descriptions.

23.5.1

TIM15 control register 1 (TIM15_CR1)
Address offset: 0x00
Reset value: 0x0000

15
Res.

14
Res.

13
Res.

12

11

10

Res.

UIF REMAP

Res.

rw

9

8

CKD[1:0]
rw

7

6

5

4

3

2

1

0

ARPE

Res.

Res.

Res.

OPM

URS

UDIS

CEN

rw

rw

rw

rw

rw

rw

Bits 15:12 Reserved, must be kept at reset value.
Bit 11 UIFREMAP: UIF status bit remapping
0: No remapping. UIF status bit is not copied to TIMx_CNT register bit 31.
1: Remapping enabled. UIF status bit is copied to TIMx_CNT register bit 31.
Bit 10 Reserved, must be kept at reset value.
Bits 9:8 CKD[1:0]: Clock division
This bitfield 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
(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 6:4 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 bit CEN)

718/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

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 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 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 and gated mode can work only if the CEN bit has been previously set by
software. However trigger mode can set the CEN bit automatically by hardware.

23.5.2

TIM15 control register 2 (TIM15_CR2)
Address offset: 0x04
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

Res.

OIS2

OIS1N

OIS1

TI1S

rw

rw

rw

rw

6

5

4

MMS[2:0]
rw

rw

rw

3

2

1

0

CCDS

CCUS

Res.

CCPC

rw

rw

rw

Bits 15:11 Reserved, must be kept at reset value.
Bit 10 OIS2: Output idle state 2 (OC2 output)
0: OC2=0 when MOE=0
1: OC2=1 when MOE=0
Note: This bit cannot be modified as long as LOCK level 1, 2 or 3 has been programmed
(LOCK bits in the TIMx_BKR register).
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_BKR 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_BKR register).

DocID022558 Rev 8

719/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Bit 7 TI1S: TI1 selection
0: The TIMx_CH1 pin is connected to TI1 input
1: The TIMx_CH1, CH2 pins are connected to the TI1 input (XOR combination)
Bits 6:4 MMS[1:0]: 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).
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.
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.

720/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

23.5.3

TIM15 slave mode control register (TIM15_SMCR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SMS[3]

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MSM

rw

rw

TS[2:0]
rw

rw

Res.
rw

0

SMS[2:0]
rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 SMS[3]: Slave mode selection - bit 3
Refer to SMS description - bits 2:0.
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 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)
See Table 129: TIMx Internal trigger connection on page 722 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.

DocID022558 Rev 8

721/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

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.
0000: Slave mode disabled - if CEN = ‘1’ then the prescaler is clocked directly by the internal
clock.
0001: Reserved
0010: Reserved
0011: Reserved
0100: Reset Mode - Rising edge of the selected trigger input (TRGI) reinitializes the counter
and generates an update of the registers.
0101: Gated Mode - The counter clock is enabled when the trigger input (TRGI) is high. The
counter stops (but is not reset) as soon as the trigger becomes low. Both start and stop of
the counter are controlled.
0110: Trigger Mode - The counter starts at a rising edge of the trigger TRGI (but it is not
reset). Only the start of the counter is controlled.
0111: External Clock Mode 1 - Rising edges of the selected trigger (TRGI) clock the counter.
1000: Combined reset + trigger mode - Rising edge of the selected trigger input (TRGI)
reinitializes the counter, generates an update of the registers and starts the counter.
Other codes: reserved.
Note: The gated mode must not be used if TI1F_ED is selected as the trigger input
(TS=’100’). Indeed, TI1F_ED outputs 1 pulse for each transition on TI1F, whereas the
gated mode checks the level of the trigger signal.
Note: The clock of the slave timer must be enabled prior to receive events from the master
timer, and must not be changed on-the-fly while triggers are received from the master
timer.

Table 129. TIMx Internal trigger connection

23.5.4

Slave TIM

ITR0 (TS = 000)

ITR1 (TS = 001)

ITR2 (TS = 010)

ITR3 (TS = 011)

TIM15

TIM2

TIM3

TIM16 OC1

TIM17 OC1

TIM15 DMA/interrupt enable register (TIM15_DIER)
Address offset: 0x0C
Reset value: 0x0000

15
Res.

14

13

12

11

TDE

COMD
E

Res.

Res.

rw

rw

10

9

CC2DE CC1DE
rw

rw

8

7

6

5

4

3

2

1

0

UDE

BIE

TIE

COMIE

Res.

Res.

CC2IE

CC1IE

UIE

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
Bits 12:11 Reserved, must be kept at reset value.

722/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

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
Bits 4:3 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

23.5.5

TIM15 status register (TIM15_SR)
Address offset: 0x10
Reset value: 0x0000

15

14

13

12

11

Res.

Res.

Res.

Res.

Res.

10

9

CC2OF CC1OF
rc_w0

rc_w0

8

7

6

5

4

3

2

1

0

Res.

BIF

TIF

COMIF

Res.

Res.

CC2IF

CC1IF

UIF

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

Bits 15:11 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

DocID022558 Rev 8

723/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

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, both edges in case gated mode
is selected). 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 a COM event (once the capture/compare control bits –CCxE,
CCxNE, OCxM– have been updated). It is cleared by software.
0: No COM event occurred
1: COM interrupt pending
Bits 5:3 Reserved, must be kept at reset value.
Bit 2 CC2IF: Capture/Compare 2 interrupt flag
refer to CC1IF description
Bit 1 CC1IF: Capture/Compare 1 interrupt flag
If channel CC1 is configured as output: This flag is set by hardware when the counter
matches the compare value. It is cleared by software.
0: No match.
1: The content of the counter TIMx_CNT matches the content of the TIMx_CCR1 register.
When the contents of TIMx_CCR1 are greater than the contents of TIMx_ARR, the CC1IF
bit goes high on the counter overflow.
If channel CC1 is configured as input: This bit is set by hardware on a capture. It is cleared
by software or by reading the TIMx_CCR1 register.
0: No input capture occurred
1: The counter value has been captured in TIMx_CCR1 register (An edge has been
detected on IC1 which matches the selected polarity)
Bit 0 UIF: Update interrupt flag
This bit is set by hardware on an update event. It is cleared by software.
0: No update occurred.
1: Update interrupt pending. This bit is set by hardware when the registers are updated:
– At overflow 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 23.5.3: TIM15 slave mode
control register (TIM15_SMCR)), if URS=0 and UDIS=0 in the TIMx_CR1 register.

724/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

23.5.6

TIM15 event generation register (TIM15_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

Res.

Res.

CC2G

CC1G

UG

w

w

rw

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
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 the CCPC bit is set, it is possible to update the CCxE, CCxNE and OCxM bits
Note: This bit acts only on channels that have a complementary output.
Bits 4:3 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 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).

DocID022558 Rev 8

725/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

23.5.7

RM0316

TIM15 capture/compare mode register 1 (TIM15_CCMR1)
Address offset: 0x18
Reset value: 0x0000 0000
The channels can be used in input (capture mode) or in output (compare mode). The
direction of a channel is defined by configuring the corresponding CCxS bits. All the other
bits of this register have a different function in input and in output mode. For a given bit,
OCxx describes its function when the channel is configured in output, ICxx describes its
function when the channel is configured in input. So you must take care that the same bit
can have a different meaning for the input stage and for the output stage.

31
Res.

30
Res.

15

14

Res.

29
Res.

13

28
Res.

12

OC2M[2:0]
IC2F[3:0]

rw

rw

rw

27
Res.

26
Res.

11

10

OC2
PE

OC2
FE

25

24

Res.

OC2M
[3]

9

23
Res.

22
Res.

rw

rw

Res.

20
Res.

Res.

18
Res.

17

16

Res.

OC1M
[3]
Res.

rw

rw

8

CC2S[1:0]

7

6

OC1CE

5

4

OC1M[2:0]
IC1F[3:0]

rw

19

Res.

IC2PSC[1:0]
rw

21

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:
Bits 31:25 Reserved, always read as 0
Bit 24 OC2M[3]: Output Compare 2 mode - bit 3
Bits 23:17 Reserved, always read as 0
Bit 16 OC1M[3]: Output Compare 1 mode - bit 3
refer to OC1M description on bits 6:4
Bit 15 Reserved, always read as 0
Bits 14:12 OC2M[2:0]: Output Compare 2 mode
Bit 11 OC2PE: Output Compare 2 preload enable
Bit 10 OC2FE: Output Compare 2 fast enable
Bits 9:8 CC2S[1:0]: Capture/Compare 2 selection
This bit-field defines the direction of the channel (input/output) as well as the used input.
00: CC2 channel is configured as output.
01: CC2 channel is configured as input, IC2 is mapped on TI2.
10: CC2 channel is configured as input, IC2 is mapped on TI1.
11: CC2 channel is configured as input, IC2 is mapped on TRC. This mode is working only if
an internal trigger input is selected through the TS bit (TIMx_SMCR register)
Note: CC2S bits are writable only when the channel is OFF (CC2E = ‘0’ in TIMx_CCER).
Bit 7 OC1CE: Output Compare 1 clear enable
0: OC1Ref is not affected by the OCREF_CLR input.
1: OC1Ref is cleared as soon as a High level is detected on OCREF_CLR input.

726/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

Bits 6:4 OC1M: Output Compare 1 mode
These bits define the behavior of the output reference signal OC1REF from which OC1 and
OC1N are derived. OC1REF is active high whereas OC1 and OC1N active level depends on
CC1P and CC1NP bits.
0000: Frozen - The comparison between the output compare register TIMx_CCR1 and the
counter TIMx_CNT has no effect on the outputs.
0001: Set channel 1 to active level on match. OC1REF signal is forced high when the
counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).
0010: Set channel 1 to inactive level on match. OC1REF signal is forced low when the
counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).
0011: Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1.
0100: Force inactive level - OC1REF is forced low.
0101: Force active level - OC1REF is forced high.
0110: PWM mode 1 - Channel 1 is active as long as TIMx_CNT 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 µs to 31750 ns by 250 ns steps,
32 µs to 63 µs by 1 µs steps,
64 µs to 126 µs by 2 µs 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).

23.5.16

TIM15 DMA control register (TIM15_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 field defines the length of DMA transfers (the timer recognizes a burst transfer when
a read or a write access is done to the TIMx_DMAR address).
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 field 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,
...

23.5.17

TIM15 DMA address for full transfer (TIM15_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

736/1141

rw

rw

rw

rw

rw

rw

rw

rw

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

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).

23.5.18

TIM15 register map
TIM15 registers are mapped as 16-bit addressable registers as described in the table
below:

Reset value

0

0

0

CC2S
[1:0]

0

0

0

0

IC1F[3:0]
0

0

0

0

OPM

URS

UDIS

CEN

CCUS

Res

CCPC
0
UIF

0
CC1IF

0
CC2IF

UIE

0

CC1IE

0

CC2IE

0

0

0

0
UG

0

SMS[2:0]

0

CC1G

0

0

CC2G

0

0

0

0

0

OC1FE

0

OC1M
[2:0]

CCDS

Res
Res

0

Res

COMIF
COMG

0

Res

TIF

COMIE

IC2
PSC
[1:0]

0

0

Res

TI1S

0

TG

TIE

0

0

0

Res

OIS1
Res

MSM
BIE

0

BIF

UDE

0

0

BG

Res

CC2S
[1:0]

0

OC1CE

0
Res

0

CC1OF

0

CC2OF

CC1DE

0

CC2DE

0

0

OC2FE

0

IC2F[3:0]
0

DocID022558 Rev 8

0

0

0

OC2PE

Res.

0

Res

Res

Res

Res

Res

Res

Res

0
Res

Res

Res

Res

Res

OC1M[3]

Res

Res

Res

Res

Res

Res

Res

OC2M[3]

Res

Res

Res

Res

Res

Res

Res
Res

Res

TIM15_CCMR1
Input Capture
mode

0
Res

Reset value
Res

0x18

OC2M
[2:0]

0

0

0

0

TS[2:0]

0

Reset value
TIM15_CCMR1
Output
Compare mode

0

0

Res

OIS2

OIS1N

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

TIM15_EGR

0

Res

Res
Res

Res

Res

Res

COMDE
0

Reset value

0x14

0

Res

Res

Res

Res

TDE
0
Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM15_SR

Res

Reset value

0x10

Res

Res
Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM15_DIER

Res

0x0C

0

0
Res

Reset value

SMS[3]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM15_SMCR

Res

0x08

Res

Reset value

MMS[2:0]

0

CC1S
[1:0]

0

0

0

Res

0

OC1PE

0

Res

0

Res

0

Res

ARPE

UIFREMAP

Res
Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM15_CR2

Res

0x04

Res

Reset value

CKD
[1:0]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM15_CR1

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 131. TIM15 register map and reset values

0

IC1
PSC
[1:0]

CC1S
[1:0]

0

0

0

0

737/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

0

0

0

0

0

0

1

1

1

1

1

1

Res

Res

Res

Res

Res

Res

Res

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

DBL[4:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

DT[7:0]
0

0

0
Res

0

0

Res

LOCK
[1:0]

0

0

0

DBA[4:0]
0

0

0

0

0

0

0

0

0

0

DMAB[15:0]
0

DocID022558 Rev 8

0

REP[7:0]

0

0

0

0

0

0

0

0

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

738/1141

0

Res

OSSI

0

OSSR

0

BKE

0

BKP

0

Res

0

AOE

0

Res

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Reset value

0

CCR2[15:0]

0
Res

TIM15_DMAR

0

MOE

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

0

Reset value

0x4C

0

CCR1[15:0]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res
Res

Res

Res

Res

Res

TIM15_DCR

Res

Reset value

0x48

Res

Res
0

1

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res
Res

Res

Res

TIM15_BDTR

Res

0x44

CC1E

0

1

0
Res

Reset value

CC1P

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res
Res

Res

TIM15_CCR2

Res

0x38

0

ARR[15:0]

0
Res

Reset value

CC1NE

0

0
Res

TIM15_CCR1

CC2E

0

Reset value

0x34

CC1NP

0

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

TIM15_RCR

Res

Reset value

0x30

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res
Res

Res

Res

TIM15_ARR

Res

0x2C

0

PSC[15:0]
0

Res

Reset value

CC2P

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM15_PSC

0

CNT[15:0]

0
Res

0
Res

Reset value

Res

UIFCPY or Res.

0x28

TIM15_CNT

Res

0x24

0

Res

Reset value

CC2NP

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIM15_CCER

Res

0x20

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 131. TIM15 register map and reset values (continued)

0

0

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

23.6

TIM16/TIM17 registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.

23.6.1

TIM16/TIM17 control register 1 (TIMx_CR1)
Address offset: 0x00
Reset value: 0x0000

15
Res

14
Res

13
Res

12

11

10

Res

UIF
REMAP

Res

rw

9

8

CKD[1:0]
rw

7

6

5

4

3

2

1

0

ARPE

Res

Res

Res

OPM

URS

UDIS

CEN

rw

rw

rw

rw

rw

rw

Bits 15:12 Reserved, must be kept at reset value.
Bit 11 UIFREMAP: UIF status bit remapping
0: No remapping. UIF status bit is not copied to TIMx_CNT register bit 31.
1: Remapping enabled. UIF status bit is copied to TIMx_CNT register bit 31.
Bit 10 Reserved, must be kept at reset value.
Bits 9:8 CKD[1:0]: Clock division
This bit-field indicates the division ratio between the timer clock (CK_INT) frequency and the
dead-time and sampling clock (tDTS)used by the dead-time generators and the digital filters
(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 6:4 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 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.

DocID022558 Rev 8

739/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

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 and gated mode can work only if the CEN bit has been previously set by
software. However trigger mode can set the CEN bit automatically by hardware.

23.6.2

TIM16/TIM17 control register 2 (TIMx_CR2)
Address offset: 0x04
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

OIS1N

OIS1

Res

Res

Res

Res

CCDS

CCUS

Res

CCPC

rw

rw

rw

rw

rw

Bits 15:10 Reserved, must be kept at reset value.
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_BKR 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_BKR register).
Bits 7:4 Reserved, must be kept at reset value.
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.
Bit 1 Reserved, must be kept at reset value.

740/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

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 COM bit is set.
Note: This bit acts only on channels that have a complementary output.

23.6.3

TIM16/TIM17 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

COMDE

Res

Res

Res

CC1DE

UDE

BIE

Res

COMIE

Res

Res

Res

CC1IE

UIE

rw

rw

rw

rw

rw

rw

rw

Bits 15:14 Reserved, must be kept at reset value.
Bit 13 COMDE: COM DMA request enable
0: COM DMA request disabled
1: COM DMA request enabled
Bits 12:10 Reserved, must be kept at reset value.
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 Reserved, must be kept at reset value.
Bit 5 COMIE: COM interrupt enable
0: COM interrupt disabled
1: COM interrupt enabled
Bits 4:2 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

DocID022558 Rev 8

741/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

23.6.4

RM0316

TIM16/TIM17 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

CC1OF

Res

BIF

Res

COMIF

Res

Res

Res

CC1IF

UIF

rc_w0

rc_w0

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
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 Reserved, must be kept at reset value.
Bit 5 COMIF: COM interrupt flag
This flag is set by hardware on a COM event (once the capture/compare control bits –CCxE,
CCxNE, OCxM– have been updated). It is cleared by software.
0: No COM event occurred
1: COM interrupt pending
Bits 4:2 Reserved, must be kept at reset value.
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)

742/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

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 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 23.5.3: TIM15 slave
mode control register (TIM15_SMCR)), if URS=0 and UDIS=0 in the TIMx_CR1
register.

23.6.5

TIM16/TIM17 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

Res

COMG

Res

Res

Res

CC1G

UG

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 Reserved, must be kept at reset value.
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 the CCPC bit is set, it is possible to update the CCxE, CCxNE and OCxM bits
Note: This bit acts only on channels that have a complementary output.
Bits 4:2 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 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.

DocID022558 Rev 8

743/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

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).

23.6.6

TIM16/TIM17 capture/compare mode register 1 (TIMx_CCMR1)
Address offset: 0x18
Reset value: 0x0000 0000
The channels can be used in input (capture mode) or in output (compare mode). The
direction of a channel is defined by configuring the corresponding CCxS bits. All the other
bits of this register have a different function in input and in output mode. For a given bit,
OCxx describes its function when the channel is configured in output, ICxx describes its
function when the channel is configured in input. So you must take care that the same bit
can have a different meaning for the input stage and for the output stage.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

OC1M
[3]
Res
rw

15

14

13

12

11

10

9

8

Res

Res

Res

Res

Res

Res

Res

Res

7

6

OC1CE

5

4

OC1M[2:0]

rw

rw

2

OC1PE OC1FE

IC1F[3:0]
rw

3

IC1PSC[1:0]
rw

rw

rw

Output compare mode:
Bits 31:17 Reserved, always read as 0
Bit 16 OC1M[3]: Output Compare 1 mode (bit 3)
Bits 15:8 Reserved
Bit 7 OC1CE: Output Compare 1 clear enable
0: OC1Ref is not affected by the OCREF_CLR input.
1: OC1Ref is cleared as soon as a High level is detected on OCREF_CLR input.

744/1141

DocID022558 Rev 8

1

0

CC1S[1:0]
rw

rw

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

Bits 6:4 OC1M[2:0]: Output Compare 1 mode (bits 2 to 0)
These bits define the behavior of the output reference signal OC1REF from which OC1 and
OC1N are derived. OC1REF is active high whereas OC1 and OC1N active level depends
on CC1P and CC1NP bits.
0000: Frozen - The comparison between the output compare register TIMx_CCR1 and the
counter TIMx_CNT has no effect on the outputs.
0001: Set channel 1 to active level on match. OC1REF signal is forced high when the
counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).
0010: Set channel 1 to inactive level on match. OC1REF signal is forced low when the
counter TIMx_CNT matches the capture/compare register 1 (TIMx_CCR1).
0011: Toggle - OC1REF toggles when TIMx_CNT=TIMx_CCR1.
0100: Force inactive level - OC1REF is forced low.
0101: Force active level - OC1REF is forced high.
0110: PWM mode 1 - Channel 1 is active as long as TIMx_CNT 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 µs to 31750 ns by 250 ns steps,
32 µs to 63 µs by 1 µs steps,
64 µs to 126 µs by 2 µs 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).

752/1141

DocID022558 Rev 8

RM0316

General-purpose timers (TIM15/TIM16/TIM17)

23.6.14

TIM16/TIM17 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 field defines the length of DMA transfers (the timer recognizes a burst transfer when
a read or a write access is done to the TIMx_DMAR address), i.e. the number of transfers.
Transfers can be in half-words or in bytes (see example below).
00000: 1 transfer,
00001: 2 transfers,
00010: 3 transfers,
...
10001: 18 transfers.
Bits 7:5 Reserved, must be kept at reset value.
Bits 4:0 DBA[4:0]: DMA base address
This 5-bit field 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.

23.6.15

TIM16/TIM17 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).

DocID022558 Rev 8

753/1141
756

General-purpose timers (TIM15/TIM16/TIM17)

23.6.16

RM0316

TIM16 option register (TIM16_OR)
Address offset: 0x50
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

TI1RMP
rw

Bits 31:2 Reserved, must be kept at reset value.
Bits1:0 TI1_RMP: Timer 16 input 1 connection.
This bit is set and cleared by software.
00: TIM16 TI1 is connected to GPIO
01: TIM16 TI1 is connected to RTC_clock
10: TIM16 TI1 is connected to HSE/32
11: TIM16 TI1 is connected to MCO

754/1141

DocID022558 Rev 8

rw

0x2C

TIMx_ARR

Res

Res

Res

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

Reset value

DocID022558 Rev 8

0

0

1

0

0

1

0

0

1

0

0

1

0

0

1

0

0

1

0

0

1

Reset value

0

0

1

0

0

1

0

0

1
0

IC1F[3:0]

0
0
0
0
0
0
0
0

Reset value
CC1E

0

UIF

Res

Res

Res

COMIF

0
0

UG

0

CC1IF

Res

Res

Res

BIF

CC1IE
UIE

Res

Res

Res

COMIE

Res

BIE

Res

0

CC1G

OC1M
[2:0]
OC1FE

0
OC1PE

0

CC1P

0

COMG

0

CC1NE

0

Res

UDE
0

Res

BG

Res

0

CC1NP

0

Res

Reset value

Res

Res

0

OC1CE

ARPE

Res

OPM
URS
UDIS
CEN

0
0
0

CCUS
Res
CCPC

Res

Res

Res

0

CCDS

Res

Res

Res

OIS1

Res

0

Res
0

OIS1N

UIFREMAP

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

0

Res

Res

CC1DE

Res

Res

Res

0

CC1OF

Res

Res

Res

COMDE

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

CKD
[1:0]

0

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

0

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

OC1M[3]

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

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

TIMx_PSC

Res

0

Res

Reset value

Res

TIMx_CNT

Res

0x28
TIMx_CCER

Res

TIMx_CCMR1
Input Capture
mode
Res

TIMx_CCMR1
Output
Compare mode

Res

0x24
TIMx_EGR

Res

0x20
TIMx_SR

Res

0x18
TIMx_DIER

Res

TIMx_CR2

Res

0x04

Res

0x14
TIMx_CR1

Res

0x10

UIFCPY or Res.

0x0C

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

0x00

Res

Offset

Res

23.6.17

Res

RM0316
General-purpose timers (TIM15/TIM16/TIM17)

TIM16/TIM17 register map

TIM16/TIM17 registers are mapped as 16-bit addressable registers as described in the table
below:
Table 133. TIM16/TIM17 register map and reset values

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

CNT[15:0]

PSC[15:0]

ARR[15:0]

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

755/1141

756

General-purpose timers (TIM15/TIM16/TIM17)

RM0316

Res

Res

Res

Res

Res

Res

Res

Res

Res

0

0

0

0

0

0

0

0

0

0

0

OSSI

Res

0

0

0

0

DBL[4:0]
0

0

0

DT[7:0]
0

0

0

0

0

0

DBA[4:0]
0

0

0

0

0

0

0

0

0

0

Res

OSSR

0

0

Res

BKE

0

0

Res

BKP

0

TI1_
RMP
[1:0]

0

0

Res

0

Res

0

Res

0

Res

0

Res

0

Res

0
Res

0
Res

Res

0

Res

DMAB[15:0]

Reset value

0

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

756/1141

0

Res

AOE

0

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

0x50

0

0

0
Res

Reset value
TIM16_OR

0

0

0
Res

TIMx_DMAR

0

LOC
K
[1:0]

Reset value

0x4C

0

Res

0

MOE

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_DCR

Res

0x48

Res

Reset value

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

0x44

TIMx_BDTR

0
Res

Reset value

0

CCR1[15:0]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_CCR1

Res

0x34

0
Res

Reset value

REP[7:0]

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

TIMx_RCR

Res

0x30

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 133. TIM16/TIM17 register map and reset values (continued)

DocID022558 Rev 8

0

RM0316

24

Infrared interface (IRTIM)

Infrared interface (IRTIM)
An infrared interface (IRTIM) for remote control is available on the device. It can be used
with an infrared LED to perform remote control functions.
It uses internal connections with TIM16 as shown in Figure 287.
To generate the infrared remote control signals, the IR interface must be enabled and TIM16
channel 1 (TIM16_OC1) must be properly configured to generate correct waveforms.
The infrared receiver can be implemented easily through a basic input capture mode.
Figure 287. IR internal hardware connections with TIM16
7,0B&+

,57,0

,5B287

7,0B&+

069

All standard IR pulse modulation modes can be obtained by programming the two timer
output compare channels.
is used to generate the high frequency carrier signal, while TIM16 generates the modulation
envelope.
The infrared function is output on the IR_OUT pin. The activation of this function is done
through the GPIOx_AFRx register by enabling the related alternate function bit.
The high sink LED driver capability (only available on the PB9 pin) can be activated through
the I2C_PB9_FMP bit in the SYSCFG_CFGR1 register and used to sink the high current
needed to directly control an infrared LED.

DocID022558 Rev 8

757/1141
757

Independent watchdog (IWDG)

RM0316

25

Independent watchdog (IWDG)

25.1

Introduction
The devices feature an embedded watchdog peripheral that offers a combination of high
safety level, timing accuracy and flexibility of use. The Independent watchdog peripheral
detects and solves malfunctions due to software failure, and triggers system reset 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 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. For further information on the window watchdog, refer to Section 26 on page
767.

25.2

IWDG main features
•

Free-running downcounter

•

Clocked from an independent RC oscillator (can operate in Standby and Stop modes)

•

Conditional Reset
–

Reset (if watchdog activated) when the downcounter value becomes lower than
0x000

–

Reset (if watchdog activated) if the downcounter is reloaded outside the window

25.3

IWDG functional description

25.3.1

IWDG block diagram
Figure 288 shows the functional blocks of the independent watchdog module.
Figure 288. Independent watchdog block diagram
#/2%
0RESCALER REGISTER
)7$'?02

 BIT
,3)
PRESCALER
 K(Z

3TATUS REGISTER
)7$'?32

2ELOAD REGISTER
)7$'?2,2

+EY REGISTER
)7$'?+2

 BIT RELOAD VALUE

 BIT DOWNCOUNTER

)7$' RESET

6$$ VOLTAGE DOMAIN
-36

1. The watchdog function is implemented in the CORE voltage domain that is still functional in Stop and
Standby modes.

758/1141

DocID022558 Rev 8

RM0316

Independent watchdog (IWDG)
When the independent watchdog is started by writing the value 0x0000 CCCC 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 0x0000 AAAA is written in the IWDG_KR register, the IWDG_RLR
value is reloaded in the counter and the watchdog reset is prevented.

25.3.2

Window option
The IWDG can also work as a window watchdog by setting the appropriate window in the
IWDG_WINR register.
If the reload operation is performed while the counter is greater than the value stored in the
window register (IWDG_WINR), then a reset is provided.
The default value of the IWDG_WINR is 0x0000 0FFF, so if it is not updated, the window
option is disabled.
As soon as the window value is changed, a reload operation is performed in order to reset
the downcounter to the IWDG_RLR value and ease the cycle number calculation to
generate the next reload.

Configuring the IWDG when the window option is enabled

Note:

1.

Enable the IWDG by writing 0x0000 CCCC in the IWDG_KR register.

2.

Enable register access by writing 0x0000 5555 in the IWDG_KR register.

3.

Write the IWDG prescaler by programming IWDG_PR from 0 to 7.

4.

Write the reload register (IWDG_RLR).

5.

Wait for the registers to be updated (IWDG_SR = 0x0000 0000).

6.

Write to the window register IWDG_WINR. This automatically refreshes the counter
value IWDG_RLR.

Writing the window value allows to refresh the Counter value by the RLR when IWDG_SR is
set to 0x0000 0000.

Configuring the IWDG when the window option is disabled
When the window option it is not used, the IWDG can be configured as follows:
1.

Enable the IWDG by writing 0x0000 CCCC in the IWDG_KR register.

2.

Enable register access by writing 0x0000 5555 in the IWDG_KR register.

3.

Write the IWDG prescaler by programming IWDG_PR from 0 to 7.

4.

Write the reload register (IWDG_RLR).

5.

Wait for the registers to be updated (IWDG_SR = 0x0000 0000).

6.

Refresh the counter value with IWDG_RLR (IWDG_KR = 0x0000 AAAA).

DocID022558 Rev 8

759/1141
766

Independent watchdog (IWDG)

25.3.3

RM0316

Hardware watchdog
If the “Hardware watchdog” feature is enabled through the device option bits, the watchdog
is automatically enabled at power-on, and generates a reset unless the Key register is
written by the software before the counter reaches end of count or if the downcounter is
reloaded inside the window.

25.3.4

Behavior in Stop and Standby modes
Once running, the IWDG cannot be stopped.

25.3.5

Register access protection
Write access to the IWDG_PR, IWDG_RLR and IWDG_WINR registers is protected. To
modify them, you must first write the code 0x0000 5555 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 0x0000 AAAA).
A status register is available to indicate that an update of the prescaler or the down-counter
reload value or the window value is on going.

25.3.6

Debug mode
When the microcontroller enters debug mode (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 33.16.2: Debug support for timers,
watchdog, bxCAN and I2C

760/1141

DocID022558 Rev 8

RM0316

Independent watchdog (IWDG)

25.4

IWDG registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.
The peripheral registers can be accessed by half-words (16-bit) or words (32-bit).

25.4.1

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 0x0000)
These bits must be written by software at regular intervals with the key value 0xAAAA,
otherwise the watchdog generates a reset when the counter reaches 0.
Writing the key value 0x5555 to enable access to the IWDG_PR, IWDG_RLR and
IWDG_WINR registers (see Section 25.3.5: Register access protection)
Writing the key value 0xCCCC starts the watchdog (except if the hardware watchdog option is
selected)

DocID022558 Rev 8

761/1141
766

Independent watchdog (IWDG)

25.4.2

RM0316

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.

2

1

0

15

14

13

12

11

10

9

8

7

6

5

4

3

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 see Section 25.3.5: Register access protection. 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.

762/1141

DocID022558 Rev 8

RM0316

Independent watchdog (IWDG)

25.4.3

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.

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.

RL[11:0]
rw

rw

rw

rw

rw

rw

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 25.3.5: Register access protection. They
are written by software to define the value to be loaded in the watchdog counter each time the
value 0xAAAA 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 the
datasheet for the timeout information.
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.

DocID022558 Rev 8

763/1141
766

Independent watchdog (IWDG)

25.4.4

RM0316

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.

WVU

RVU

PVU

r

r

r

Bits 31:3 Reserved, must be kept at reset value.
Bit 2 WVU: Watchdog counter window value update
This bit is set by hardware to indicate that an update of the window 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).
Window value can be updated only when WVU bit is reset.
This bit is generated only if generic “window” = 1
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.

Note:

764/1141

If several reload, prescaler, or window values are used by the application, it is mandatory to
wait until RVU bit is reset before changing the reload value, to wait until PVU bit is reset
before changing the prescaler value, and to wait until WVU bit is reset before changing the
window value. However, after updating the prescaler and/or the reload/window value it is not
necessary to wait until RVU or PVU or WVU is reset before continuing code execution
except in case of low-power mode entry.

DocID022558 Rev 8

RM0316

Independent watchdog (IWDG)

25.4.5

Window register (IWDG_WINR)
Address offset: 0x10
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.

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.

WIN[11:0]
rw

rw

rw

rw

rw

rw

rw

Bits 31:12 Reserved, must be kept at reset value.
Bits11:0 WIN[11:0]: Watchdog counter window value
These bits are write access protected see Section 25.3.5. These bits contain the high limit of
the window value to be compared to the downcounter.
To prevent a reset, the downcounter must be reloaded when its value is lower than the
window register value and greater than 0x0
The WVU 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 valid if a write operation to this register is ongoing. For this reason the value
read from this register is valid only when the WVU bit in the IWDG_SR register is reset.

DocID022558 Rev 8

765/1141
766

0x0C

0x10

766/1141
Reset value

DocID022558 Rev 8
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
1
1
1
1
1

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0
0

1
1
1
1
1

WIN[11:0]
1
1
1
1

PVU

Res.

Res.

0
Res.

Res.

Res.

0
Res.

Res.

Res.

0

RVU

1
Res.

Res.

Res.

0
Res.

Res.

Res.

0
Res.

Res.

Res.

0
Res.

Res.

Res.

0
Res.

Res.

Res.

0
Res.

Res.

Res.

0
Res.

Res.

Res.

0
Res.

Res.

0

WVU

1
Res.

1
Res.

1
Res.

1
Res.

Res.

Res.

1
Res.

Res.

Res.

1
Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Reset value

Res.

Res.

Res.

Reset value
Res.

IWDG_WINR
Res.

IWDG_SR

Res.

0x08
IWDG_RLR

Res.

0x04
IWDG_PR

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

IWDG_KR
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Register

Res.

0x00

Res.

Offset

Res.

25.4.6

Res.

Independent watchdog (IWDG)
RM0316

IWDG register map
The following table gives the IWDG register map and reset values.
Table 134. IWDG register map and reset values

KEY[15:0]
0
PR[2:0]

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.
0
0

RL[11:0]
0
0
0

0
0
0

1
1
1

RM0316

System window watchdog (WWDG)

26

System window watchdog (WWDG)

26.1

Introduction
The system window watchdog (WWDG) 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.
The 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 WWDG is best suited for applications which require the watchdog to react within an
accurate timing window.

26.2

WWDG main features
•

Programmable free-running downcounter

•

Conditional reset

•

26.3

–

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 290)

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) is decremented 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.
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 and higher than 0x3F. The value to be stored
in the WWDG_CR register must be between 0xFF and 0xC0.
Refer to Figure 289 for WWDG block diagram.

DocID022558 Rev 8

767/1141
772

System window watchdog (WWDG)

RM0316
Figure 289. Watchdog block diagram

5(6(7

:DWFKGRJFRQILJXUDWLRQUHJLVWHU ::'*B&)5


FRPSDUDWRU
ZKHQ
7!:

: : : : : : :

:ULWH::'*B&5
:DWFKGRJFRQWUROUHJLVWHU ::'*B&5
:'*$
3&/.
IURP5&&FORFNFRQWUROOHU


7

7

7 7 7 7 7

ELWGRZQFRXQWHU &17

:'*SUHVFDOHU
:'*7%
06Y9

26.3.1

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.

26.3.2

Controlling the downcounter
This downcounter is free-running, counting down even if the watchdog is disabled. When
the watchdog is enabled, the T6 bit must be set to prevent generating an immediate reset.
The T[5:0] bits contain the number of increments which represents the time delay before the
watchdog produces a reset. The timing varies between a minimum and a maximum value
due to the unknown status of the prescaler when writing to the WWDG_CR register (see
Figure 290). 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 290 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).

26.3.3

Advanced watchdog interrupt feature
The Early Wakeup Interrupt (EWI) can be used if specific safety operations or data logging
must be performed before the actual reset is generated. The EWI interrupt is enabled by
setting the EWI bit in the WWDG_CFR register. When the downcounter reaches the value
0x40, an EWI interrupt is generated and the corresponding interrupt service routine (ISR)
can be used to trigger specific actions (such as communications or data logging), before
resetting the device.
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.

768/1141

DocID022558 Rev 8

RM0316

System window watchdog (WWDG)
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.

26.3.4

How to program the watchdog timeout
You can use the formula in Figure 290 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 290. Window watchdog timing diagram
4;= #.4 DOWNCOUNTER

7;=

X&

2EFRESH NOT ALLOWED 2EFRESH ALLOWED

4IME

4 BIT
2%3%4
AIC

The formula to calculate the timeout value is given by:
WDGTB[1:0]
× ( T [ 5:0 ] + 1 )
tWWDG = t PCLK1 × 4096 × 2

( ms )

where:
tWWDG: WWDG timeout
tPCLK: APB1 clock period measured in ms
4096: value corresponding to internal divider
As an example, lets assume APB1 frequency is equal to 48 MHz, WDGTB[1:0] is set to 3
and T[5:0] is set to 63:
3
t WWDG = 1 ⁄ 48000 × 4096 × 2 × ( 63 + 1 ) = 43.69 ms

DocID022558 Rev 8

769/1141
772

System window watchdog (WWDG)

RM0316

Refer to the datasheet for the minimum and maximum values of the tWWDG.

26.3.5

Debug mode
When the microcontroller enters debug mode (Cortex-M4®F 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.

26.4

WWDG registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.
The peripheral registers can be accessed by half-words (16-bit) or words (32-bit).

26.4.1

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]) PCLK cycles. A reset is produced when it is decremented from 0x40 to 0x3F (T6
becomes cleared).

770/1141

DocID022558 Rev 8

RM0316

System window watchdog (WWDG)

26.4.2

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.

8

7

6

5

4

3

2

1

0

rw

rw

rw

15

14

13

12

11

10

9

Res.

Res.

Res.

Res.

Res.

Res.

EWI
rs

WDGTB[1:0]
rw

rw

W[6:0]
rw

rw

rw

rw

Bits 31:10 Reserved, must be kept at reset value.
Bit 9 EWI: Early wakeup interrupt
When set, an interrupt occurs whenever the counter reaches the value 0x40. This interrupt is
only cleared by hardware after a reset.
Bits 8:7 WDGTB[1:0]: Timer base
The time base of the prescaler can be modified as follows:
00: CK Counter Clock (PCLK div 4096) div 1
01: CK Counter Clock (PCLK div 4096) div 2
10: CK Counter Clock (PCLK div 4096) div 4
11: CK Counter Clock (PCLK div 4096) div 8
Bits 6:0 W[6:0]: 7-bit window value
These bits contain the window value to be compared to the downcounter.

26.4.3

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.

DocID022558 Rev 8

771/1141
772

System window watchdog (WWDG)

26.4.4

RM0316

WWDG register map
The following table gives the WWDG register map and reset values.

0

1

1

1

1

1

Res.

Res.

Res.

Res.

1

1

W[6:0]

Reset value

0

Refer to Section 3.2.2: Memory map and register boundary addresses for the register
boundary addresses.

772/1141

1

Res.

0

1

EWIF

Res.

0

Res.

1

WDGTB0

1

Res.

1

WDGTB1

1

Res.

1

EWI

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WWDG_
SR

Res.

0x08

Res.

Reset value

T[6:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WWDG_
CFR

Res.

0x04

0
Res.

Reset value

WDGA

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WWDG_
CR

Res.

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 135. WWDG register map and reset values

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

27

Real-time clock (RTC)

27.1

Introduction
The RTC provides an automatic wakeup to manage all low-power modes.
The real-time clock (RTC) is an independent BCD timer/counter. The RTC provides a timeof-day clock/calendar with programmable alarm interrupts.
The RTC includes also a periodic programmable wakeup flag with interrupt capability.
Two 32-bit registers contain the seconds, minutes, hours (12- or 24-hour format), day (day
of week), date (day of month), month, and year, expressed in binary coded decimal format
(BCD). The sub-seconds value is also available in binary format.
Compensations for 28-, 29- (leap year), 30-, and 31-day months are performed
automatically. Daylight saving time compensation can also be performed.
Additional 32-bit registers contain the programmable alarm subseconds, seconds, minutes,
hours, day, and date.
A digital calibration feature is available to compensate for any deviation in crystal oscillator
accuracy.
After Backup domain reset, all RTC registers are protected against possible parasitic write
accesses.
As long as the supply voltage remains in the operating range, the RTC never stops,
regardless of the device status (Run mode, low-power mode or under reset).

DocID022558 Rev 8

773/1141
815

Real-time clock (RTC)

27.2

RM0316

RTC main features
The RTC unit main features are the following (see Figure 291: RTC block diagram):
•

Calendar with subseconds, seconds, minutes, hours (12 or 24 format), day (day of
week), date (day of month), month, and year.

•

Daylight saving compensation programmable by software.

•

Programmable alarm with interrupt function. The alarm can be triggered by any
combination of the calendar fields.

•

Automatic wakeup unit generating a periodic flag that triggers an automatic wakeup
interrupt.

•

Reference clock detection: a more precise second source clock (50 or 60 Hz) can be
used to enhance the calendar precision.

•

Accurate synchronization with an external clock using the subsecond shift feature.

•

Digital calibration circuit (periodic counter correction): 0.95 ppm accuracy, obtained in a
calibration window of several seconds

•

Time-stamp function for event saving

•

Tamper detection event with configurable filter and internal pull-up

•

Maskable interrupts/events:

•

774/1141

–

Alarm A

–

Alarm B

–

Wakeup interrupt

–

Time-stamp

–

Tamper detection

16 backup registers.

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

27.3

RTC functional description

27.3.1

RTC block diagram
Figure 291. RTC block diagram

57&B7$03



%DFNXSUHJLVWHUV
DQG57&WDPSHU
FRQWUROUHJLVWHUV

57&B7$03
57&B7$03

7$03[)

57&B76

7LPHVWDPS
UHJLVWHUV

57&B5(),1

76)

/6( +]
+6(
57&&/.

/6,

57&B&$/5
6PRRWK
FDOLEUDWLRQ

57&B35(5
$V\QFKURQRXV
ELWSUHVFDOHU
GHIDXOW 

FNBDSUH
GHIDXOW+]

FNBVSUH
GHIDXOW+]

57&B35(5
6\QFKURQRXV
ELWSUHVFDOHU
GHIDXOW 

&DOHQGDU
6KDGRZUHJLVWHUV
57&B75
57&B'5

6KDGRZUHJLVWHU
57&B665
:8&.6(/>@
3UHVFDOHU


57&B&$/,%
57&B$/$50

2XWSXW
FRQWURO

57&B287

57&B:875
:87)

ELWZDNHXS
DXWRUHORDGWLPHU
26(/>@
$ODUP$
57&B$/50$5
57&B$/50$665

$/5$)

$ODUP%
57&B$/50%5
57&B$/50%665

$/5%)

06Y9

1. RTC_TAMP3 is not available on the STM32F303x6/8 and STM32F328 devices.

DocID022558 Rev 8

775/1141
815

Real-time clock (RTC)

RM0316

The RTC includes:
•

Two alarms

•

Three tamper events from I/Os
–

One timestamp event from I/O

•

Tamper event detection can generate a timestamp event

•

16 x 32-bit backup registers on the STM32F303xB/C and 5 x 32 bit backup registers on
the STM32F303x6/8
–

•

•

27.3.2

Tamper detection erases the backup registers.

•

The backup registers (RTC_BKPxR) are implemented in the RTC domain that
remains powered-on by VBAT when the VDD power is switched off.

Alternate function outputs: RTC_OUT which selects one of the following two outputs:
–

RTC_CALIB: 512 Hz or 1Hz clock output (with an LSE frequency of 32.768 kHz).
This output is enabled by setting the COE bit in the RTC_CR register.

–

RTC_ALARM: This output is enabled by configuring the OSEL[1:0] bits in the
RTC_CR register which select the Alarm A, Alarm B or Wakeup outputs.

Alternate function inputs:
–

RTC_TS: timestamp event

–

RTC_TAMP1: tamper1 event detection

–

RTC_TAMP2: tamper2 event detection

–

RTC_TAMP3: tamper3 event detection

–

RTC_REFIN: 50 or 60 Hz reference clock input

GPIOs controlled by the RTC
RTC_OUT, RTC_TS and RTC_TAMP1 are mapped on the same pin (PC13).
The selection of the RTC_ALARM output is performed through the RTC_TAFCR register as
follows: the PC13VALUE bit is used to select whether the RTC_ALARM output is configured
in push-pull or open drain mode.
When PC13 is not used as RTC alternate function, it can be forced in output push-pull mode
by setting the PC13MODE bit in the RTC_TAFCR. The output data value is then given by
the PC13VALUE bit. In this case, PC13 output push-pull state and data are preserved in
Standby mode.
The output mechanism follows the priority order shown in Table 136.
When PC14 and PC15 are not used as LSE oscillator, they can be forced in output push-pull
mode by setting the PC14MODE and PC15MODE bits in the RTC_TAFCR register
respectively. The output data values are then given by PC14VALUE and PC15VALUE. In
this case, the PC14 and PC15 output push-pull states and data values are preserved in
Standby mode.
The output mechanism follows the priority order shown in Table 137 and Table 138.

776/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)
Table 136. RTC pin PC13 configuration(1)

Pin
configuration
and function

RTC_ALARM
output
enabled

RTC_CALIB
output
enabled

RTC_TAMP1
input
enabled

RTC_TS
input
enabled

PC13MODE
bit

PC13VALUE
bit

RTC_ALARM
output OD

1

Don’t care

Don’t care

Don’t care

Don’t care

0

RTC_ALARM
output PP

1

Don’t care

Don’t care

Don’t care

Don’t care

1

RTC_CALIB
output PP

0

1

Don’t care

Don’t care

Don’t care

Don’t care

RTC_TAMP1
input floating

0

0

1

0

Don’t care

Don’t care

RTC_TS and
RTC_TAMP1
input floating

0

0

1

1

Don’t care

Don’t care

RTC_TS input
floating

0

0

0

1

Don’t care

Don’t care

Output PP
forced

0

0

0

0

1

PC13 output
data value

Wakeup pin or
Standard
GPIO

0

0

0

0

0

Don’t care

1. OD: open drain; PP: push-pull.

Table 137. LSE pin PC14 configuration (1)
Pin configuration and
function

LSEON bit in
RCC_BDCR register

LSEBYP bit in
RCC_BDCR register

PC14MODE
bit

PC14VALUE
bit

LSE oscillator

1

0

Don’t care

Don’t care

LSE bypass

1

1

Don’t care

Don’t care

Output PP forced

0

Don’t care

1

PC14 output data
value

Standard GPIO

0

Don’t care

0

Don’t care

1. OD: open drain; PP: push-pull.

Table 138. LSE pin PC15 configuration (1)
Pin configuration and
function

LSEON bit in
RCC_BDCR register

LSEBYP bit in
RCC_BDCR register

PC15MODE
bit

PC15VALUE
bit

1

0

Don’t care

Don’t care

1

1

0

Don’t care

1

PC15 output data
value

0

Don’t care

0

Don’t care

LSE oscillator
Output PP forced
Standard GPIO
1. OD: open drain; PP: push-pull.

DocID022558 Rev 8

777/1141
815

Real-time clock (RTC)

27.3.3

RM0316

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 9: 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 291: 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 27.3.6: Periodic auto-wakeup for details).

27.3.4

Real-time clock and calendar
The RTC calendar time and date registers are accessed through shadow registers which
are synchronized with PCLK (APB clock). They can also be accessed directly in order to
avoid waiting for the synchronization duration.
•

RTC_SSR for the subseconds

•

RTC_TR for the time

•

RTC_DR for the date

Every two RTCCLK periods, the current calendar value is copied into the shadow registers,
and the RSF bit of RTC_ISR register is set (see Section 27.6.4: RTC initialization and status

778/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)
register (RTC_ISR)). The copy is not performed in Stop and Standby mode. When exiting
these modes, the shadow registers are updated after up to 2 RTCCLK periods.
When the application reads the calendar registers, it accesses the content of the shadow
registers. It is possible to make a direct access to the calendar registers by setting the
BYPSHAD control bit in the RTC_CR register. By default, this bit is cleared, and the user
accesses the shadow registers.
When reading the RTC_SSR, RTC_TR or RTC_DR registers in BYPSHAD=0 mode, the
frequency of the APB clock (fAPB) must be at least 7 times the frequency of the RTC clock
(fRTCCLK).
The shadow registers are reset by system reset.

27.3.5

Programmable alarms
The RTC unit provides programmable alarm: Alarm A and Alarm B. The description below is
given for Alarm A, but can be translated in the same way for Alarm B.
The programmable alarm function is enabled through the ALRAE bit in the RTC_CR
register. The ALRAF is set to 1 if the calendar subseconds, seconds, minutes, hours, date
or day match the values programmed in the alarm registers RTC_ALRMASSR and
RTC_ALRMAR. Each calendar field can be independently selected through the MSKx bits
of the RTC_ALRMAR register, and through the MASKSSx bits of the RTC_ALRMASSR
register. The alarm interrupt is enabled through the ALRAIE bit in the RTC_CR register.

Caution:

If the seconds field is selected (MSK1 bit reset in RTC_ALRMAR), the synchronous
prescaler division factor set in the RTC_PRER register must be at least 3 to ensure correct
behavior.
Alarm A and Alarm B (if enabled by bits OSEL[1:0] in RTC_CR register) can be routed to the
RTC_ALARM output. RTC_ALARM output polarity can be configured through bit POL the
RTC_CR register.

27.3.6

Periodic auto-wakeup
The periodic wakeup flag is generated by a 16-bit programmable auto-reload down-counter.
The wakeup timer range can be extended to 17 bits.
The wakeup function is enabled through the WUTE bit in the RTC_CR register.
The wakeup timer clock input can be:
•

RTC clock (RTCCLK) divided by 2, 4, 8, or 16.
When RTCCLK is LSE(32.768kHz), this allows to configure the wakeup interrupt period
from 122 µs to 32 s, with a resolution down to 61 µs.

•

ck_spre (usually 1 Hz internal clock)
When ck_spre frequency is 1Hz, this allows to achieve a wakeup time from 1 s to
around 36 hours with one-second resolution. This large programmable time range is
divided in 2 parts:
–

from 1s to 18 hours when WUCKSEL [2:1] = 10

–

and from around 18h to 36h when WUCKSEL[2:1] = 11. In this last case 216 is
added to the 16-bit counter current value.When the initialization sequence is
complete (see Programming the wakeup timer on page 781), 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

DocID022558 Rev 8

779/1141
815

Real-time clock (RTC)

RM0316

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 output polarity can be
configured through the POL bit in the RTC_CR register.
System reset, as well as low-power modes (Sleep, Stop and Standby) have no influence on
the wakeup timer.

27.3.7

RTC initialization and configuration
RTC register access
The RTC registers are 32-bit registers. The APB interface introduces 2 wait-states in RTC
register accesses except on read accesses to calendar shadow registers when
BYPSHAD=0.

RTC register write protection
After system reset, the RTC registers are protected against parasitic write access by
clearing the DBP bit in the PWR_CR register (refer to the power control section). DBP bit
must be set in order to enable RTC registers write access.
After Backup domain reset, all the RTC registers are write-protected. Writing to the RTC
registers is enabled by writing a key into the Write Protection register, RTC_WPR.
The following steps are required to unlock the write protection on all the RTC registers
except for RTC_TAFCR, RTC_BKPxR and RTC_ISR[13:8].
1.

Write ‘0xCA’ into the RTC_WPR register.

2.

Write ‘0x53’ into the RTC_WPR register.

Writing a wrong key reactivates the write protection.
The protection mechanism is not affected by system reset.

Calendar initialization and configuration
To program the initial time and date calendar values, including the time format and the
prescaler configuration, the following sequence is required:

780/1141

1.

Set INIT bit to 1 in the RTC_ISR register to enter initialization mode. In this mode, the
calendar counter is stopped and its value can be updated.

2.

Poll INITF bit of in the RTC_ISR register. The initialization phase mode is entered when
INITF is set to 1. It takes around 2 RTCCLK clock cycles (due to clock synchronization).

3.

To generate a 1 Hz clock for the calendar counter, program both the prescaler factors in
RTC_PRER register.

4.

Load the initial time and date values in the shadow registers (RTC_TR and RTC_DR),
and configure the time format (12 or 24 hours) through the FMT bit in the RTC_CR
register.

5.

Exit the initialization mode by clearing the INIT bit. The actual calendar counter value is
then automatically loaded and the counting restarts after 4 RTCCLK clock cycles.
DocID022558 Rev 8

RM0316

Real-time clock (RTC)
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 alarms. The
procedure below is given for Alarm A but can be translated in the same way for Alarm B.

Note:

1.

Clear ALRAE in RTC_CR to disable Alarm A.

2.

Program the Alarm A registers (RTC_ALRMASSR/RTC_ALRMAR).

3.

Set ALRAE in the RTC_CR register to enable Alarm A again.

Each change of the RTC_CR register is taken into account after around 2 RTCCLK clock
cycles due to clock synchronization.

Programming the wakeup timer
The following sequence is required to configure or change the wakeup timer auto-reload
value (WUT[15:0] in RTC_WUTR):

27.3.8

1.

Clear WUTE in RTC_CR to disable the wakeup timer.

2.

Poll WUTWF until it is set in RTC_ISR to make sure the access to wakeup auto-reload
counter and to WUCKSEL[2:0] bits is allowed. It takes around 2 RTCCLK clock cycles
(due to clock synchronization).

3.

Program the wakeup auto-reload value WUT[15:0], and the wakeup clock selection
(WUCKSEL[2:0] bits in RTC_CR). Set WUTE in RTC_CR to enable the timer again.
The wakeup timer restarts down-counting. The WUTWF bit is cleared up to 2 RTCCLK
clock cycles after WUTE is cleared, due to clock synchronization.

Reading the calendar
When BYPSHAD control bit is cleared in the RTC_CR register
To read the RTC calendar registers (RTC_SSR, RTC_TR and RTC_DR) properly, the APB1
clock frequency (fPCLK) must be equal to or greater than seven times the RTC clock
frequency (fRTCCLK). This ensures a secure behavior of the synchronization mechanism.
If the 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

DocID022558 Rev 8

781/1141
815

Real-time clock (RTC)

RM0316

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.
After a system reset, the software must wait until RSF is set before reading the RTC_SSR,
RTC_TR and RTC_DR registers. Indeed, a system reset resets the shadow registers to
their default values.
After an initialization (refer to Calendar initialization and configuration on page 780): the
software must wait until RSF is set before reading the RTC_SSR, RTC_TR and RTC_DR
registers.
After synchronization (refer to Section 27.3.10: RTC synchronization): the software must
wait until RSF is set before reading the RTC_SSR, RTC_TR and RTC_DR registers.

When the BYPSHAD control bit is set in the RTC_CR register (bypass shadow
registers)
Reading the calendar registers gives the values from the calendar counters directly, thus
eliminating the need to wait for the RSF bit to be set. This is especially useful after exiting
from low-power modes (STOP or Standby), since the shadow registers are not updated
during these modes.
When the BYPSHAD bit is set to 1, the results of the different registers might not be
coherent with each other if an RTCCLK edge occurs between two read accesses to the
registers. Additionally, the value of one of the registers may be incorrect if an RTCCLK edge
occurs during the read operation. The software must read all the registers twice, and then
compare the results to confirm that the data is coherent and correct. Alternatively, the
software can just compare the two results of the least-significant calendar register.
Note:

While BYPSHAD=1, instructions which read the calendar registers require one extra APB
cycle to complete.

27.3.9

Resetting the RTC
The calendar shadow registers (RTC_SSR, RTC_TR and RTC_DR) and some bits of the
RTC status register (RTC_ISR) are reset to their default values by all available system reset
sources.
On the contrary, the following registers are reset to their default values by a Backup domain
reset and are not affected by a system reset: the RTC current calendar registers, the RTC
control register (RTC_CR), the prescaler register (RTC_PRER), the RTC calibration register

782/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)
(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, when it is clocked by the LSE, the RTC keeps on running under system reset if
the reset source is different from the Backup domain reset one (refer to the RTC clock
section of the Reset and clock controller for details on the list of RTC clock sources not
affected by system reset). When a Backup domain reset occurs, the RTC is stopped and all
the RTC registers are set to their reset values.

27.3.10

RTC synchronization
The RTC can be synchronized to a remote clock with a high degree of precision. After
reading the sub-second field (RTC_SSR or RTC_TSSSR), a calculation can be made of the
precise offset between the times being maintained by the remote clock and the RTC. The
RTC can then be adjusted to eliminate this offset by “shifting” its clock by a fraction of a
second using RTC_SHIFTR.
RTC_SSR contains the value of the synchronous prescaler counter. This allows one to
calculate the exact time being maintained by the RTC down to a resolution of
1 / (PREDIV_S + 1) seconds. As a consequence, the resolution can be improved by
increasing the synchronous prescaler value (PREDIV_S[14:0]. The maximum resolution
allowed (30.52 μs with a 32768 Hz clock) is obtained with PREDIV_S set to 0x7FFF.
However, increasing PREDIV_S means that PREDIV_A must be decreased in order to
maintain the synchronous prescaler output at 1 Hz. In this way, the frequency of the
asynchronous prescaler output increases, which may increase the RTC dynamic
consumption.
The RTC can be finely adjusted using the RTC shift control register (RTC_SHIFTR). Writing
to RTC_SHIFTR can shift (either delay or advance) the clock by up to a second with a
resolution of 1 / (PREDIV_S + 1) seconds. The shift operation consists of adding the
SUBFS[14:0] value to the synchronous prescaler counter SS[15:0]: this will delay the clock.
If at the same time the ADD1S bit is set, this results in adding one second and at the same
time subtracting a fraction of second, so this will advance the clock.

Caution:

Before initiating a shift operation, the user must check that SS[15] = 0 in order to ensure that
no overflow will occur.
As soon as a shift operation is initiated by a write to the RTC_SHIFTR register, the SHPF
flag is set by hardware to indicate that a shift operation is pending. This bit is cleared by
hardware as soon as the shift operation has completed.

Caution:

This synchronization feature is not compatible with the reference clock detection feature:
firmware must not write to RTC_SHIFTR when REFCKON=1.

27.3.11

RTC reference clock detection
The update of the RTC calendar can be synchronized to a reference clock, RTC_REFIN,
which is usually the mains frequency (50 or 60 Hz). The precision of the RTC_REFIN
reference clock should be higher than the 32.768 kHz LSE clock. When the RTC_REFIN
detection is enabled (REFCKON bit of RTC_CR set to 1), the calendar is still clocked by the
LSE, and RTC_REFIN is used to compensate for the imprecision of the calendar update
frequency (1 Hz).

DocID022558 Rev 8

783/1141
815

Real-time clock (RTC)

RM0316

Each 1 Hz clock edge is compared to the nearest RTC_REFIN clock edge (if one is found
within a given time window). In most cases, the two clock edges are properly aligned. When
the 1 Hz clock becomes misaligned due to the imprecision of the LSE clock, the RTC shifts
the 1 Hz clock a bit so that future 1 Hz clock edges are aligned. Thanks to this mechanism,
the calendar becomes as precise as the reference clock.
The RTC detects if the reference clock source is present by using the 256 Hz clock
(ck_apre) generated from the 32.768 kHz quartz. The detection is performed during a time
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 RTC_REFIN detection is enabled, PREDIV_A and PREDIV_S must be set to their
default values:
•

PREDIV_A = 0x007F

•

PREVID_S = 0x00FF

Note:

RTC_REFIN clock detection is not available in Standby mode.

27.3.12

RTC smooth digital calibration
The RTC frequency can be digitally calibrated with a resolution of about 0.954 ppm with a
range from -487.1 ppm to +488.5 ppm. The correction of the frequency is performed using
series of small adjustments (adding and/or subtracting individual RTCCLK pulses). These
adjustments are fairly well distributed so that the RTC is well calibrated even when observed
over short durations of time.
The smooth digital calibration is performed during a cycle of about 220 RTCCLK pulses, or
32 seconds when the input frequency is 32768 Hz. This cycle is maintained by a 20-bit
counter, cal_cnt[19:0], clocked by RTCCLK.
The smooth calibration register (RTC_CALR) specifies the number of RTCCLK clock cycles
to be masked during the 32-second cycle:
•

Setting the bit CALM[0] to 1 causes exactly one pulse to be masked during the 32-

second cycle.

Note:

784/1141

•

Setting CALM[1] to 1 causes two additional cycles to be masked

•

Setting CALM[2] to 1 causes four additional cycles to be masked

•

and so on up to CALM[8] set to 1 which causes 256 clocks to be masked.

CALM[8:0] (RTC_CALR) specifies the number of RTCCLK pulses to be masked during the
32-second cycle. Setting the bit CALM[0] to ‘1’ causes exactly one pulse to be masked
during the 32-second cycle at the moment when cal_cnt[19:0] is 0x80000; CALM[1]=1
causes two other cycles to be masked (when cal_cnt is 0x40000 and 0xC0000); CALM[2]=1

DocID022558 Rev 8

RM0316

Real-time clock (RTC)
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.

Verifying the RTC calibration
RTC precision is ensured by measuring the precise frequency of RTCCLK and calculating
the correct CALM value and CALP values. An optional 1 Hz output is provided to allow
applications to measure and verify the RTC precision.
Measuring the precise frequency of the RTC over a limited interval can result in a
measurement error of up to 2 RTCCLK clock cycles over the measurement period,
depending on how the digital calibration cycle is aligned with the measurement period.
However, this measurement error can be eliminated if the measurement period is the same
length as the calibration cycle period. In this case, the only error observed is the error due to
the resolution of the digital calibration.
•

By default, the calibration cycle period is 32 seconds.

DocID022558 Rev 8

785/1141
815

Real-time clock (RTC)

RM0316

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:

27.3.13

1.

Poll the RTC_ISR/RECALPF (re-calibration pending flag).

2.

If it is set to 0, write a new value to RTC_CALR, if necessary. RECALPF is then
automatically set to 1

3.

Within three ck_apre cycles after the write operation to RTC_CALR, the new calibration
settings take effect.

Time-stamp function
Time-stamp is enabled by setting the TSE bit of RTC_CR register to 1.
The calendar is saved in the time-stamp registers (RTC_TSSSR, RTC_TSTR, RTC_TSDR)
when a time-stamp event is detected on the RTC_TS pin.
When a time-stamp event occurs, the time-stamp 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 time-stamp
event occurs.
If a new time-stamp event is detected while the time-stamp flag (TSF) is already set, the
time-stamp overflow flag (TSOVF) flag is set and the time-stamp registers (RTC_TSTR and
RTC_TSDR) maintain the results of the previous event.

Note:

TSF is set 2 ck_apre cycles after the time-stamp event occurs due to synchronization
process.
There is no delay in the setting of TSOVF. This means that if two time-stamp events are
close together, TSOVF can be seen as '1' while TSF is still '0'. As a consequence, it is
recommended to poll TSOVF only after TSF has been set.

Caution:

786/1141

If a time-stamp event occurs immediately after the TSF bit is supposed to be cleared, then
both TSF and TSOVF bits are set.To avoid masking a time-stamp event occurring at the
same moment, the application must not write ‘0’ into TSF bit unless it has already read it to
‘1’.

DocID022558 Rev 8

RM0316

Real-time clock (RTC)
Optionally, a tamper event can cause a time-stamp to be recorded. See the description of
the TAMPTS control bit in Section 27.6.16: RTC tamper and alternate function configuration
register (RTC_TAFCR).

27.3.14

Tamper detection
The RTC_TAMPx input events can be configured either for edge detection, or for level
detection with filtering.
The tamper detection can be configured for the following purposes:
•

erase the RTC backup registers

•

generate an interrupt, capable to wakeup from Stop and Standby modes

RTC backup registers
The backup registers (RTC_BKPxR) are not reset by system reset or when the device
wakes up from Standby mode.
The backup registers are reset when a tamper detection event occurs (see Section 27.6.19:
RTC backup registers (RTC_BKPxR) and Tamper detection initialization on page 787).

Tamper detection initialization
Each input can be enabled by setting the corresponding TAMPxE bits to 1 in the
RTC_TAFCR register.
Each RTC_TAMPx tamper detection input is associated with a flag TAMPxF in the RTC_ISR
register.
The TAMPxF flag is asserted after the tamper event on the pin, with the latency provided
below:
•

3 ck_apre cycles when TAMPFLT differs from 0x0 (Level detection with filtering)

•

3 ck_apre cycles when TAMPTS=1 (Timestamp on tamper event)

•

No latency when TAMPFLT=0x0 (Edge detection) and TAMPTS=0

A new tamper occurring on the same pin during this period and as long as TAMPxF is set
cannot be detected.
By setting the TAMPIE bit in the RTC_TAFCR register, an interrupt is generated when a
tamper detection event occurs. .

Timestamp on tamper event
With TAMPTS set to ‘1’, any tamper event causes a timestamp to occur. In this case, either
the TSF bit or the TSOVF bit are set in RTC_ISR, in the same manner as if a normal
timestamp event occurs. The affected tamper flag register TAMPxF is set at the same time
that TSF or TSOVF is set.

Edge detection on tamper inputs
If the TAMPFLT bits are “00”, the RTC_TAMPx pins generate tamper detection events when
either a rising edge or a falling edge is observed depending on the corresponding
TAMPxTRG bit. The internal pull-up resistors on the RTC_TAMPx inputs are deactivated
when edge detection is selected.

DocID022558 Rev 8

787/1141
815

Real-time clock (RTC)
Caution:

RM0316

To avoid losing tamper detection events, the signal used for edge detection is logically
ANDed with the corresponding TAMPxE bit in order to detect a tamper detection event in
case it occurs before the RTC_TAMPx pin is enabled.
•

When TAMPxTRG = 0: if the RTC_TAMPx alternate function is already high before
tamper detection is enabled (TAMPxE bit set to 1), a tamper event is detected as soon
as the RTC_TAMPx input is enabled, even if there was no rising edge on the
RTC_TAMPx input after TAMPxE was set.

•

When TAMPxTRG = 1: if the RTC_TAMPx alternate function is already low before
tamper detection is enabled, a tamper event is detected as soon as the RTC_TAMPx
input is enabled (even if there was no falling edge on the RTC_TAMPx input after
TAMPxE was set.

After a tamper event has been detected and cleared, the RTC_TAMPx 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 RTC_TAMPx input value still indicates a tamper detection. This is
equivalent to a level detection on the RTC_TAMPx alternate function input.
Note:

Tamper detection is still active when VDD power is switched off. To avoid unwanted resetting
of the backup registers, the pin to which the RTC_TAMPx alternate function is mapped
should be externally tied to the correct level.

Level detection with filtering on RTC_TAMPx inputs
Level detection with filtering is performed by setting TAMPFLT to a non-zero value. A tamper
detection event is generated when either 2, 4, or 8 (depending on TAMPFLT) consecutive
samples are observed at the level designated by the TAMPxTRG bits.
The RTC_TAMPx inputs are precharged through the I/O internal pull-up resistance before
its state is sampled, unless disabled by setting TAMPPUDIS to 1,The duration of the
precharge is determined by the TAMPPRCH bits, allowing for larger capacitances on the
RTC_TAMPx inputs.
The trade-off between tamper detection latency and power consumption through the pull-up
can be optimized by using TAMPFREQ to determine the frequency of the sampling for level
detection.
Note:

Refer to the datasheets for the electrical characteristics of the pull-up resistors.

27.3.15

Calibration clock output
When the COE bit is set to 1 in the RTC_CR register, a reference clock is provided on the
RTC_CALIB device output.
If the COSEL bit in the RTC_CR register is reset and PREDIV_A = 0x7F, the RTC_CALIB
frequency is fRTCCLK/64. This corresponds to a calibration output at 512 Hz for an RTCCLK
frequency at 32.768 kHz. The RTC_CALIB duty cycle is irregular: there is a light jitter on
falling edges. It is therefore recommended to use rising edges.
When COSEL is set and “PREDIV_S+1” is a non-zero multiple of 256 (i.e: PREDIV_S[7:0] =
0xFF), the RTC_CALIB frequency is fRTCCLK/(256 * (PREDIV_A+1)). This corresponds to a
calibration output at 1 Hz for prescaler default values (PREDIV_A = Ox7F, PREDIV_S =
0xFF), with an RTCCLK frequency at 32.768 kHz. The 1 Hz output is affected when a shift
operation is on going and may toggle during the shift operation (SHPF=1).

788/1141

DocID022558 Rev 8

RM0316
Note:

Real-time clock (RTC)
When the RTC_CALIB or RTC_ALARM output is selected, the RTC_OUT pin is
automatically configured in output alternate function.
When COSEL bit is cleared, the RTC_CALIB output is the output of the 6th stage of the
asynchronous prescaler.
When COSEL bit is set, the RTC_CALIB output is the output of the 8th stage of the
synchronous prescaler.

27.3.16

Alarm output
The OSEL[1:0] control bits in the RTC_CR register are used to activate the alarm alternate
function output RTC_ALARM, and to select the function which is output. These functions
reflect the contents of the corresponding flags in the RTC_ISR register.
The polarity of the output is determined by the POL control bit in RTC_CR so that the
opposite of the selected flag bit is output when POL is set to 1.

Alarm alternate function output
The RTC_ALARM pin can be configured in output open drain or output push-pull using the
control bit ALARMOUTTYPE in the RTC_TAFCR register.
Note:

Once the RTC_ALARM output is enabled, it has priority over RTC_CALIB (COE bit is don't
care and must be kept cleared).
When the RTC_CALIB or RTC_ALARM output is selected, the RTC_OUT pin is
automatically configured in output alternate function.

27.4

RTC low-power modes
Table 139. Effect of low-power modes on RTC
Mode

Description

Sleep

No effect
RTC interrupts cause the device to exit the Sleep mode.

Stop

The RTC remains active when the RTC clock source is LSE or LSI. RTC alarm, RTC
tamper event, RTC timestamp event, and RTC Wakeup cause the device to exit the Stop
mode.

The RTC remains active when the RTC clock source is LSE or LSI. RTC alarm, RTC
Standby tamper event, RTC timestamp event, and RTC Wakeup cause the device to exit the
Standby mode.

27.5

RTC interrupts
All RTC interrupts are connected to the EXTI controller. Refer to Section 14.3: EXTI
registers.
To enable the RTC Alarm interrupt, the following sequence is required:
1.

Configure and enable the EXTI line corresponding to the RTC Alarm event in interrupt
mode and select the rising edge sensitivity.

2.

Configure and enable the RTC_ALARM IRQ channel in the NVIC.

3.

Configure the RTC to generate RTC alarms.
DocID022558 Rev 8

789/1141
815

Real-time clock (RTC)

RM0316

To enable the RTC Tamper interrupt, the following sequence is required:
1.

Configure and enable the EXTI line corresponding to the RTC Tamper event in interrupt
mode and select the rising edge sensitivity.

2.

Configure and Enable the RTC_TAMP_STAMP IRQ channel in the NVIC.

3.

Configure the RTC to detect the RTC tamper event.

To enable the RTC TimeStamp interrupt, the following sequence is required:
1.

Configure and enable the EXTI line corresponding to the RTC TimeStamp event in
interrupt mode and select the rising edge sensitivity.

2.

Configure and Enable the RTC_TAMP_STAMP IRQ channel in the NVIC.

3.

Configure the RTC to detect the RTC time-stamp event.

To enable the Wakeup timer interrupt, the following sequence is required:
1.

Configure and enable the EXTI line corresponding to the Wakeup timer even in
interrupt mode and select the rising edge sensitivity.

2.

Configure and Enable the RTC_WKUP IRQ channel in the NVIC.

3.

Configure the RTC to detect the RTC Wakeup timer event.
Table 140. Interrupt control bits
Interrupt event

Event flag

Enable
control
bit

Exit from
Sleep
mode

Exit from
Stop
mode

Exit from
Standby
mode

Alarm A

ALRAF

ALRAIE

yes

yes(1)

yes(1)

Alarm B

ALRBF

ALRBIE

yes

yes(1)

yes(1)

RTC_TS input (timestamp)

TSF

TSIE

yes

yes(1)

yes(1)

RTC_TAMP1 input detection

TAMP1F

TAMPIE

yes

yes(1)

yes(1)

RTC_TAMP2 input detection

TAMP2F

TAMPIE

yes

yes(1)

yes(1)

RTC_TAMP3 input detection

TAMP3F

TAMPIE

yes

yes(1)

yes(1)

Wakeup timer interrupt

WUTF

WUTIE

yes

yes(1)

yes(1)

1. Wakeup from STOP and Standby modes is possible only when the RTC clock source is LSE or LSI.

27.6

RTC registers
Refer to Section 2.1 on page 46 of the reference manual for a list of abbreviations used in
register descriptions.
The peripheral registers can be accessed by words (32-bit).

27.6.1

RTC time register (RTC_TR)
The RTC_TR is the calendar time shadow register. This register must be written in
initialization mode only. Refer to Calendar initialization and configuration on page 780 and
Reading the calendar on page 781.
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.
Address offset: 0x00

790/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)
Backup domain reset value: 0x0000 0000
System reset: 0x0000 0000 when BYPSHAD = 0. Not affected when BYPSHAD = 1.

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PM
rw

15

14

13

Res.

12

11

MNT[2:0]
rw

rw

10

9

8

MNU[3:0]
rw

rw

rw

7

rw

20

19

18

HT[1:0]

16

HU[3:0]

rw

rw

rw

rw

rw

5

4

3

2

1

0

rw

rw

ST[2:0]
rw

17

rw

6

Res.

rw

21

rw

SU[3:0]
rw

rw

rw

Bits 31-23 Reserved, must be kept at reset value
Bit 22 PM: AM/PM notation
0: AM or 24-hour format
1: PM
Bits 21:20 HT[1:0]: Hour tens in BCD format
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

27.6.2

RTC date register (RTC_DR)
The RTC_DR is the calendar date shadow register. This register must be written in
initialization mode only. Refer to Calendar initialization and configuration on page 780 and
Reading the calendar on page 781.
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.
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

DocID022558 Rev 8

DT[1:0]
rw

DU[3:0]

791/1141
815

Real-time clock (RTC)

RM0316

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

792/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

27.6.3

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

WUTE

rw

rw

ALRBE ALRAE
rw

22

21

OSEL[1:0]

20

19

18

POL

COSEL

BKP

17

16

SUB1H ADD1H

rw

rw

rw

rw

rw

rw

w

w

7

6

5

4

3

2

1

0

Res.

rw

FMT
rw

BYPS
REFCKON TSEDGE
HAD
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 (with default prescaler setting)
1: Calibration output is 1 Hz (with default prescaler setting)
These frequencies are valid for RTCCLK at 32.768 kHz and prescalers at their default values
(PREDIV_A=127 and PREDIV_S=255). Refer to Section 27.3.15: Calibration clock output
Bit 18 BKP: Backup
This bit can be written by the user to memorize whether the daylight saving time change has
been performed or not.
Bit 17 SUB1H: Subtract 1 hour (winter time change)
When this bit is set, 1 hour is subtracted to the calendar time if the current hour is not 0. This
bit is always read as 0.
Setting this bit has no effect when current hour is 0.
0: No effect
1: Subtracts 1 hour to the current time. This can be used for winter time change outside
initialization mode.

DocID022558 Rev 8

793/1141
815

Real-time clock (RTC)

RM0316

Bit 16 ADD1H: Add 1 hour (summer time change)
When this bit is set, 1 hour is added to the calendar time. This bit is always read as 0.
0: No effect
1: Adds 1 hour to the current time. This can be used for summer time change outside
initialization mode.
Bit 15 TSIE: Time-stamp interrupt enable
0: Time-stamp Interrupt disable
1: Time-stamp Interrupt enable
Bit 14 WUTIE: Wakeup timer interrupt enable
0: Wakeup timer interrupt disabled
1: Wakeup timer interrupt enabled
Bit 13 ALRBIE: Alarm B interrupt enable
0: Alarm B Interrupt disable
1: Alarm B Interrupt enable
Bit 12 ALRAIE: Alarm A interrupt enable
0: Alarm A interrupt disabled
1: Alarm A interrupt enabled
Bit 11 TSE: timestamp enable
0: timestamp disable
1: timestamp enable
Bit 10 WUTE: Wakeup timer enable
0: Wakeup timer disabled
1: Wakeup timer enabled
Bit 9 ALRBE: Alarm B enable
0: Alarm B disabled
1: Alarm B enabled
Bit 8 ALRAE: Alarm A enable
0: Alarm A disabled
1: Alarm A enabled
Bit 7 Reserved, must be kept at reset value.
Bit 6 FMT: Hour format
0: 24 hour/day format
1: AM/PM hour format
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’.

794/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

Bit 4 REFCKON: RTC_REFIN reference clock detection enable (50 or 60 Hz)
0: RTC_REFIN detection disabled
1: RTC_REFIN detection enabled
Note: PREDIV_S must be 0x00FF.
Bit 3 TSEDGE: Time-stamp event active edge
0: RTC_TS input rising edge generates a time-stamp event
1: RTC_TS input falling edge generates a time-stamp event
TSE must be reset when TSEDGE is changed to avoid unwanted TSF setting.
Bits 2:0 WUCKSEL[2:0]: Wakeup clock selection
000: RTC/16 clock is selected
001: RTC/8 clock is selected
010: RTC/4 clock is selected
011: RTC/2 clock is selected
10x: ck_spre (usually 1 Hz) clock is selected
11x: ck_spre (usually 1 Hz) clock is selected and 216 is added to the WUT counter value
(see note below)

Note:

Bits 7, 6 and 4 of this register can be written in initialization mode only (RTC_ISR/INITF = 1).
WUT = Wakeup unit counter value. WUT = (0x0000 to 0xFFFF) + 0x10000 added when
WUCKSEL[2:1 = 11].
Bits 2 to 0 of this register can be written only when RTC_CR WUTE bit = 0 and RTC_ISR
WUTWF bit = 1.
It is recommended not to change the hour during the calendar hour increment as it could
mask the incrementation of the calendar hour.
ADD1H and SUB1H changes are effective in the next second.
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.

Caution:

TSE must be reset when TSEDGE is changed to avoid spuriously setting of TSF.

DocID022558 Rev 8

795/1141
815

Real-time clock (RTC)

27.6.4

RM0316

RTC initialization and status register (RTC_ISR)
This register is write protected (except for RTC_ISR[13:8] bits). The write access procedure
is described in RTC register write protection on page 780.
Address offset: 0x0C
Backup domain reset value: 0x0000 0007
System reset: not affected except INIT, INITF, and RSF bits which are cleared to ‘0’

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RECALPF

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

INIT

INITF

RSF

INITS

ALRB
WF

ALRAWF

rw

r

rc_w0

r

r

r

r

TAMP3F TAMP2F TAMP1F TSOVF
rc_w0

rc_w0

rc_w0

rc_w0

TSF
rc_w0

WUTF ALRBF ALRAF
rc_w0

rc_w0

rc_w0

SHPF WUTWF
r

r

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 TAMP3F: RTC_TAMP3 detection flag
This flag is set by hardware when a tamper detection event is detected on the RTC_TAMP3
input.
It is cleared by software writing 0
Bit 14 TAMP2F: RTC_TAMP2 detection flag
This flag is set by hardware when a tamper detection event is detected on the RTC_TAMP2
input.
It is cleared by software writing 0
Bit 13 TAMP1F: RTC_TAMP1 detection flag
This flag is set by hardware when a tamper detection event is detected on the RTC_TAMP1
input.
It is cleared by software writing 0
Bit 12 TSOVF: Time-stamp overflow flag
This flag is set by hardware when a time-stamp event occurs while TSF is already set.
This flag is cleared by software by writing 0. It is recommended to check and then clear
TSOVF only after clearing the TSF bit. Otherwise, an overflow might not be noticed if a timestamp event occurs immediately before the TSF bit is cleared.
Bit 11 TSF: Time-stamp flag
This flag is set by hardware when a time-stamp event occurs.
This flag is cleared by software by writing 0.
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.

796/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

Bit 9 ALRBF: Alarm B flag
This flag is set by hardware when the time/date registers (RTC_TR and RTC_DR) match the
Alarm B register (RTC_ALRMBR).
This flag is cleared by software by writing 0.
Bit 8 ALRAF: Alarm A flag
This flag is set by hardware when the time/date registers (RTC_TR and RTC_DR) match the
Alarm A register (RTC_ALRMAR).
This flag is cleared by software by writing 0.
Bit 7 INIT: Initialization mode
0: Free running mode
1: Initialization mode used to program time and date register (RTC_TR and RTC_DR), and
prescaler register (RTC_PRER). Counters are stopped and start counting from the new
value when INIT is reset.
Bit 6 INITF: Initialization flag
When this bit is set to 1, the RTC is in initialization state, and the time, date and prescaler
registers can be updated.
0: Calendar registers update is not allowed
1: Calendar registers update is allowed
Bit 5 RSF: Registers synchronization flag
This bit is set by hardware each time the calendar registers are copied into the shadow
registers (RTC_SSRx, RTC_TRx and RTC_DRx). This bit is cleared by hardware in
initialization mode, while a shift operation is pending (SHPF=1), or when in bypass shadow
register mode (BYPSHAD=1). This bit can also be cleared by software.
It is cleared either by software or by hardware in initialization mode.
0: Calendar shadow registers not yet synchronized
1: Calendar shadow registers synchronized
Bit 4 INITS: Initialization status flag
This bit is set by hardware when the calendar year field is different from 0 (Backup domain
reset state).
0: Calendar has not been initialized
1: Calendar has been initialized
Bit 3 SHPF: Shift operation pending
0: No shift operation is pending
1: A shift operation is pending
This flag is set by hardware as soon as a shift operation is initiated by a write to the
RTC_SHIFTR register. It is cleared by hardware when the corresponding shift operation has
been executed. Writing to the SHPF bit has no effect.

DocID022558 Rev 8

797/1141
815

Real-time clock (RTC)

RM0316

Bit 2 WUTWF: Wakeup timer write flag
This bit is set by hardware up to 2 RTCCLK cycles after the WUTE bit has been set to 0 in
RTC_CR, and is cleared up to 2 RTCCLK cycles after the WUTE bit has been set to 1. The
wakeup timer values can be changed when WUTE bit is cleared and WUTWF is set.
0: Wakeup timer configuration update not allowed
1: Wakeup timer configuration update allowed
Bit 1 ALRBWF: Alarm B write flag
This bit is set by hardware when Alarm B values can be changed, after the ALRBE bit has
been set to 0 in RTC_CR.
It is cleared by hardware in initialization mode.
0: Alarm B update not allowed
1: Alarm B update allowed
Bit 0 ALRAWF: Alarm A write flag
This bit is set by hardware when Alarm A values can be changed, after the ALRAE bit has
been set to 0 in RTC_CR.
It is cleared by hardware in initialization mode.
0: Alarm A update not allowed
1: Alarm A update allowed

Note:

798/1141

The bits ALRAF, ALRBF, WUTF and TSF are cleared 2 APB clock cycles after programming
them to 0.

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

27.6.5

RTC prescaler register (RTC_PRER)
This register must be written in initialization mode only. The initialization must be performed
in two separate write accesses. Refer to Calendar initialization and configuration on
page 780.
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.
Address offset: 0x10
Backup domain reset value: 0x007F 00FF
System reset: not affected

31

30

29

28

27

26

25

24

23

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

rw

rw

rw

rw

rw

rw

rw

Res.

22

21

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

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)

DocID022558 Rev 8

799/1141
815

Real-time clock (RTC)

27.6.6

RM0316

RTC wakeup timer register (RTC_WUTR)
This register can be written only when WUTWF is set to 1 in RTC_ISR.
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.
Address offset: 0x14
Backup domain reset value: 0x0000 FFFF
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

WUT[15:0]
rw

Bits 31:16 Reserved, must be kept at reset value
Bits 15:0 WUT[15:0]: Wakeup auto-reload value bits
When the wakeup timer is enabled (WUTE set to 1), the WUTF flag is set every (WUT[15:0]
+ 1) ck_wut cycles. The ck_wut period is selected through WUCKSEL[2:0] bits of the
RTC_CR register
When WUCKSEL[2] = 1, the wakeup timer becomes 17-bits and WUCKSEL[1] effectively
becomes WUT[16] the most-significant bit to be reloaded into the timer.
The first assertion of WUTF occurs (WUT+1) ck_wut cycles after WUTE is set. Setting
WUT[15:0] to 0x0000 with WUCKSEL[2:0] =011 (RTCCLK/2) is forbidden.

800/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

27.6.7

RTC alarm A register (RTC_ALRMAR)
This register can be written only when ALRAWF is set to 1 in RTC_ISR, or in initialization
mode.
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.
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.

DocID022558 Rev 8

801/1141
815

Real-time clock (RTC)

27.6.8

RM0316

RTC alarm B register (RTC_ALRMBR)
This register can be written only when ALRBWF is set to 1 in RTC_ISR, or in initialization
mode.
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.
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

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

802/1141

DocID022558 Rev 8

SU[3:0]
rw

rw

rw

RM0316

Real-time clock (RTC)

27.6.9

RTC write protection register (RTC_WPR)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

w

w

w

w

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

KEY
w

w

w

w

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 KEY: Write protection key
This byte is written by software.
Reading this byte always returns 0x00.
Refer to RTC register write protection for a description of how to unlock RTC register write
protection.

27.6.10

RTC sub second register (RTC_SSR)
Address offset: 0x28
Backup domain reset value: 0x0000 0000
System reset: 0x0000 0000 when BYPSHAD = 0. Not affected when BYPSHAD = 1.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

SS[15:0]
r

r

r

r

r

r

r

r

r

Bits31:16 Reserved, must be kept at reset value
Bits 15:0 SS: Sub second value
SS[15:0] is the value in the synchronous prescaler counter. The fraction of a second is given by
the formula below:
Second fraction = (PREDIV_S - SS) / (PREDIV_S + 1)
Note: SS can be larger than PREDIV_S only after a shift operation. In that case, the correct
time/date is one second less than as indicated by RTC_TR/RTC_DR.

DocID022558 Rev 8

803/1141
815

Real-time clock (RTC)

27.6.11

RM0316

RTC shift control register (RTC_SHIFTR)
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.
Address offset: 0x2C
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ADD1S

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

w

w

w

w

w

w

w

w
15
Res.

SUBFS[14:0]
w

w

w

w

w

w

w

w

Bit 31 ADD1S: Add one second
0: No effect
1: Add one second to the clock/calendar
This bit is write only and is always read as zero. Writing to this bit has no effect when a shift
operation is pending (when SHPF=1, in RTC_ISR).
This function is intended to be used with SUBFS (see description below) in order to effectively
add a fraction of a second to the clock in an atomic operation.
Bits 30:15 Reserved, must be kept at reset value
Bits 14:0 SUBFS: Subtract a fraction of a second
These bits are write only and is always read as zero. Writing to this bit has no effect when a
shift operation is pending (when SHPF=1, in RTC_ISR).
The value which is written to SUBFS is added to the synchronous prescaler counter. Since this
counter counts down, this operation effectively subtracts from (delays) the clock by:
Delay (seconds) = SUBFS / (PREDIV_S + 1)
A fraction of a second can effectively be added to the clock (advancing the clock) when the
ADD1S function is used in conjunction with SUBFS, effectively advancing the clock by:
Advance (seconds) = (1 - (SUBFS / (PREDIV_S + 1))).
Note: Writing to SUBFS causes RSF to be cleared. Software can then wait until RSF=1 to be
sure that the shadow registers have been updated with the shifted time.

804/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

27.6.12

RTC timestamp time register (RTC_TSTR)
The content of this register is valid only when TSF is set to 1 in RTC_ISR. It is cleared when
TSF bit is reset.
Address offset: 0x30
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PM
r

15

14

Res.

13

12

11

MNT[2:0]
r

r

10

9

8

MNU[3:0]
r

r

r

r

7

6

Res.
r

21

20

19

18

HT[1:0]
r

r

r

r

5

4

3

2

ST[2:0]
r

r

17

16

HU[3:0]
r

r

1

0

r

r

SU[3:0]
r

r

r

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.

DocID022558 Rev 8

805/1141
815

Real-time clock (RTC)

27.6.13

RM0316

RTC timestamp date register (RTC_TSDR)
The content of this register is valid only when TSF is set to 1 in RTC_ISR. It is cleared when
TSF bit is reset.
Address offset: 0x34
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

r

r

15

WDU[1:0]
r

r

MT
r

r

MU[3:0]
r

r

r

r

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

806/1141

DocID022558 Rev 8

DT[1:0]
r

DU[3:0]
r

r

r

RM0316

Real-time clock (RTC)

27.6.14

RTC time-stamp sub second register (RTC_TSSSR)
The content of this register is valid only when RTC_ISR/TSF is set. It is cleared when the
RTC_ISR/TSF bit is reset.
Address offset: 0x38
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

SS[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:16 Reserved, must be kept at reset value
Bits 15:0 SS: Sub second value
SS[15:0] is the value of the synchronous prescaler counter when the timestamp event
occurred.

DocID022558 Rev 8

807/1141
815

Real-time clock (RTC)

27.6.15

RM0316

RTC calibration register (RTC_CALR)
This register is write protected. The write access procedure is described in RTC register
write protection on page 780.
Address offset: 0x3C
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

CALP

CALW8

CALW
16

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

CALM[8:0]
rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value
Bit 15 CALP: Increase frequency of RTC by 488.5 ppm
0: No RTCCLK pulses are added.
1: One RTCCLK pulse is effectively inserted every 211 pulses (frequency increased by
488.5 ppm).
This feature is intended to be used in conjunction with CALM, which lowers the frequency of
the calendar with a fine resolution. if the input frequency is 32768 Hz, the number of RTCCLK
pulses added during a 32-second window is calculated as follows: (512 * CALP) - CALM.
Refer to Section 27.3.12: RTC smooth digital calibration.
Bit 14 CALW8: Use an 8-second calibration cycle period
When CALW8 is set to ‘1’, the 8-second calibration cycle period is selected.
Note: CALM[1:0] are stuck at “00” when CALW8=’1’. Refer to Section 27.3.12: RTC smooth
digital calibration.
Bit 13 CALW16: Use a 16-second calibration cycle period
When CALW16 is set to ‘1’, the 16-second calibration cycle period is selected.This bit must
not be set to ‘1’ if CALW8=1.
Note: CALM[0] is stuck at ‘0’ when CALW16=’1’. Refer to Section 27.3.12: RTC smooth
digital calibration.
Bits 12:9 Reserved, must be kept at reset value
Bits 8:0 CALM[8:0]: Calibration minus
The frequency of the calendar is reduced by masking CALM out of 220 RTCCLK pulses (32
seconds if the input frequency is 32768 Hz). This decreases the frequency of the calendar
with a resolution of 0.9537 ppm.
To increase the frequency of the calendar, this feature should be used in conjunction with
CALP. See Section 27.3.12: RTC smooth digital calibration on page 784.

808/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

27.6.16

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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

TAMPP
UDIS
rw

TAMPPRCH
[1:0]
rw

rw

TAMPFLT[1:0]
rw

rw

TAMPFREQ[2:0]
rw

rw

rw

23

22

21

20

19

PC15 PC15 PC14 PC14 PC13
MODE VALUE MODE VALUE MODE

18

17

16

PC13
VALUE

Res.

Res.

1

0

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

TAMPT TAMP3 TAMP3 TAMP2 TAMP2
S
TRG
E
TRG(1)
E(1)
rw

rw

rw

rw

rw

TAMPIE
rw

TAMP1 TAMP1
TRG
E
rw

rw

1. RTC_TAMP3 is not available on the STM32F303x6/8 and STM32F328 devices.

Bits 31:24 Reserved, must be kept at reset value.
Bit 23 PC15MODE: PC15 mode
0: PC15 is controlled by the GPIO configuration registers. Consequently PC15 is floating in
Standby mode.
1: PC15 is forced to push-pull output if LSE is disabled.
Bit 22 PC15VALUE: PC15 value
If the LSE is disabled and PC15MODE = 1, PC15VALUE configures the PC15 output data.
Bit 21 PC14MODE: PC14 mode
0: PC14 is controlled by the GPIO configuration registers. Consequently PC14 is floating in
Standby mode.
1: PC14 is forced to push-pull output if LSE is disabled.
Bit 20 PC14VALUE: PC14 value
If the LSE is disabled and PC14MODE = 1, PC14VALUE configures the PC14 output data.
Bit 19 PC13MODE: PC13 mode
0: PC13 is controlled by the GPIO configuration registers. Consequently PC13 is floating in
Standby mode.
1: PC13 is forced to push-pull output if all RTC alternate functions are disabled.
Bit 18 PC13VALUE: RTC_ALARM output type/PC13 value
If PC13 is used to output RTC_ALARM, PC13VALUE configures the output configuration:
0: RTC_ALARM is an open-drain output
1: RTC_ALARM is a push-pull output
If all RTC alternate functions are disabled and PC13MODE = 1, PC13VALUE configures the
PC13 output data.
Bits 17:16 Reserved, must be kept at reset value.
Bit 15 TAMPPUDIS: RTC_TAMPx pull-up disable
This bit determines if each of the RTC_TAMPx pins are pre-charged before each sample.
0: Precharge RTC_TAMPx pins before sampling (enable internal pull-up)
1: Disable precharge of RTC_TAMPx pins.

DocID022558 Rev 8

809/1141
815

Real-time clock (RTC)

RM0316

Bits 14:13 TAMPPRCH[1:0]: RTC_TAMPx precharge duration
These bit determines the duration of time during which the pull-up/is activated before each
sample. TAMPPRCH is valid for each of the RTC_TAMPx inputs.
0x0: 1 RTCCLK cycle
0x1: 2 RTCCLK cycles
0x2: 4 RTCCLK cycles
0x3: 8 RTCCLK cycles
Bits 12:11 TAMPFLT[1:0]: RTC_TAMPx filter count
These bits determines the number of consecutive samples at the specified level (TAMP*TRG)
needed to activate a Tamper event. TAMPFLT is valid for each of the RTC_TAMPx inputs.
0x0: Tamper event is activated on edge of RTC_TAMPx input transitions to the active level
(no internal pull-up on RTC_TAMPx input).
0x1: Tamper event is activated after 2 consecutive samples at the active level.
0x2: Tamper event is activated after 4 consecutive samples at the active level.
0x3: Tamper event is activated after 8 consecutive samples at the active level.
Bits 10:8 TAMPFREQ[2:0]: Tamper sampling frequency
Determines the frequency at which each of the RTC_TAMPx inputs are sampled.
0x0: RTCCLK / 32768 (1 Hz when RTCCLK = 32768 Hz)
0x1: RTCCLK / 16384 (2 Hz when RTCCLK = 32768 Hz)
0x2: RTCCLK / 8192 (4 Hz when RTCCLK = 32768 Hz)
0x3: RTCCLK / 4096 (8 Hz when RTCCLK = 32768 Hz)
0x4: RTCCLK / 2048 (16 Hz when RTCCLK = 32768 Hz)
0x5: RTCCLK / 1024 (32 Hz when RTCCLK = 32768 Hz)
0x6: RTCCLK / 512 (64 Hz when RTCCLK = 32768 Hz)
0x7: RTCCLK / 256 (128 Hz when RTCCLK = 32768 Hz)
Bit 7 TAMPTS: Activate timestamp on tamper detection event
0: Tamper detection event does not cause a timestamp to be saved
1: Save timestamp on tamper detection event
TAMPTS is valid even if TSE=0 in the RTC_CR register.
Bit 6 TAMP3TRG: Active level for RTC_TAMP3 input
if TAMPFLT != 00:
0: RTC_TAMP3 input staying low triggers a tamper detection event.
1: RTC_TAMP3 input staying high triggers a tamper detection event.
if TAMPFLT = 00:
0: RTC_TAMP3 input rising edge triggers a tamper detection event.
1: RTC_TAMP3input falling edge triggers a tamper detection event.
Bit 5 TAMP3E: RTC_TAMP3 detection enable
0: RTC_TAMP3 input detection disabled
1: RTC_TAMP3 input detection enabled
Bit 4 TAMP2TRG: Active level for RTC_TAMP2 input
if TAMPFLT != 00:
0: RTC_TAMP2 input staying low triggers a tamper detection event.
1: RTC_TAMP2 input staying high triggers a tamper detection event.
if TAMPFLT = 00:
0: RTC_TAMP2 input rising edge triggers a tamper detection event.
1: RTC_TAMP2 input falling edge triggers a tamper detection event.

810/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

Bit 3 TAMP2E: RTC_TAMP2 input detection enable
0: RTC_TAMP2 detection disabled
1: RTC_TAMP2 detection enabled
Bit 2 TAMPIE: Tamper interrupt enable
0: Tamper interrupt disabled
1: Tamper interrupt enabled.
Bit 1 TAMP1TRG: Active level for RTC_TAMP1 input
If TAMPFLT != 00
0: RTC_TAMP1 input staying low triggers a tamper detection event.
1: RTC_TAMP1 input staying high triggers a tamper detection event.
if TAMPFLT = 00:
0: RTC_TAMP1 input rising edge triggers a tamper detection event.
1: RTC_TAMP1 input falling edge triggers a tamper detection event.
Bit 0 TAMP1E: RTC_TAMP1 input detection enable
0: RTC_TAMP1 detection disabled
1: RTC_TAMP1 detection enabled

Caution:

When TAMPFLT = 0, TAMPxE must be reset when TAMPxTRG is changed to avoid
spuriously setting TAMPxF.

DocID022558 Rev 8

811/1141
815

Real-time clock (RTC)

27.6.17

RM0316

RTC alarm A sub second register (RTC_ALRMASSR)
This register can be written only when ALRAE is reset in RTC_CR register, or in initialization
mode.
This register is write protected. The write access procedure is described in RTC register
write protection on page 780
Address offset: 0x44
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

Res.

Res.

Res.

Res.

27

26

25

24

rw

rw

rw

rw

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

MASKSS[3:0]

Res.

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

rw

w

rw

rw

SS[14:0]
rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 MASKSS[3:0]: Mask the most-significant bits starting at this bit
0: No comparison on sub seconds for Alarm A. The alarm is set when the seconds unit is
incremented (assuming that the rest of the fields match).
1: SS[14:1] are don’t care in Alarm A comparison. Only SS[0] is compared.
2: SS[14:2] are don’t care in Alarm A comparison. Only SS[1:0] are compared.
3: SS[14:3] are don’t care in Alarm A comparison. Only SS[2:0] are compared.
...
12: SS[14:12] are don’t care in Alarm A comparison. SS[11:0] are compared.
13: SS[14:13] are don’t care in Alarm A comparison. SS[12:0] are compared.
14: SS[14] is don’t care in Alarm A comparison. SS[13:0] are compared.
15: All 15 SS bits are compared and must match to activate alarm.
The overflow bits of the synchronous counter (bits 15) is never compared. This bit can be
different from 0 only after a shift operation.
Bits23:15 Reserved, must be kept at reset value.
Bits 14:0 SS[14:0]: Sub seconds value
This value is compared with the contents of the synchronous prescaler counter to determine if
Alarm A is to be activated. Only bits 0 up MASKSS-1 are compared.

812/1141

DocID022558 Rev 8

RM0316

Real-time clock (RTC)

27.6.18

RTC alarm B sub second register (RTC_ALRMBSSR)
This register can be written only when ALRBE is reset in RTC_CR register, or in initialization
mode.
This register is write protected.The write access procedure is described in Section : RTC
register write protection.
Address offset: 0x48
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

Res.

Res.

Res.

Res.

27

26

25

24

rw

rw

rw

rw

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

MASKSS[3:0]

Res.

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

rw

rw

rw

rw

w

rw

rw

SS[14:0]
rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 MASKSS[3:0]: Mask the most-significant bits starting at this bit
0x0: No comparison on sub seconds for Alarm B. The alarm is set when the seconds unit is
incremented (assuming that the rest of the fields match).
0x1: SS[14:1] are don’t care in Alarm B comparison. Only SS[0] is compared.
0x2: SS[14:2] are don’t care in Alarm B comparison. Only SS[1:0] are compared.
0x3: SS[14:3] are don’t care in Alarm B comparison. Only SS[2:0] are compared.
...
0xC: SS[14:12] are don’t care in Alarm B comparison. SS[11:0] are compared.
0xD: SS[14:13] are don’t care in Alarm B comparison. SS[12:0] are compared.
0xE: SS[14] is don’t care in Alarm B comparison. SS[13:0] are compared.
0xF: All 15 SS bits are compared and must match to activate alarm.
The overflow bits of the synchronous counter (bits 15) is never compared. This bit can be
different from 0 only after a shift operation.
Bits 23:15

Reserved, must be kept at reset value.

Bits 14:0 SS[14:0]: Sub seconds value
This value is compared with the contents of the synchronous prescaler counter to determine
if Alarm B is to be activated. Only bits 0 up to MASKSS-1 are compared.

DocID022558 Rev 8

813/1141
815

Real-time clock (RTC)

27.6.19

RM0316

RTC backup registers (RTC_BKPxR)
Address offset: 0x50 to 0x8C
Backup domain reset value: 0x0000 0000
System reset: not affected

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

BKP[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

w

rw

rw

BKP[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 BKP[31:0]
The application can write or read data to and from these registers.
They are powered-on by VBAT when VDD is switched off, so that they are not reset by
System reset, and their contents remain valid when the device operates in low-power mode.
This register is reset on a tamper detection event, as long as TAMPxF=1.

27.6.20

RTC register map

0

0

0

0

0

1

1

Res.

Res.

Res.

Res.

Res.

Res.

0

HU[3:0]
0

0

0

0

0

1

Res.
0

0

0

0

0

0

0

0

WUCKS
EL[2:0]

0

0

0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

PREDIV_S[14:0]

1

0

0

ALRAWF

0

0

ALRBWF

0

0

TSEDGE

ALRAF

0

DU[3:0]

SHPF

WUTF

ALRBF

0

0

WUT WF

TSF

0

0

BYPSHAD

TSOVF

0

0

REFCKON

TAMP1F

0

0

RSF

0

0

DT
[1:0]

INITS

ALRAE

0

1

0

Res.

WUTE

ALRBE

0

1

0

Res.

TSE
0

0

FMT

ALRAIE
0

Res.

ALRBIE
0

1

HT
[1:0]

0

SU[3:0]

INITF

Res.
TSIE

WUTIE
0
.TAMP2F

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
0

0

0

0

0

DocID022558 Rev 8

0

0

0

0

0

0

0

1

1

WUT[15:0]

MSK2

0

0

0

1

PM

0

DU[3:0]

0

PREDIV_A[6:0]

MSK3

MSK4

WDSEL

Reset value

DT
[1:0]

MU[3:0]

ADD1H

0

1

RTC_ALRMAR

814/1141

1

0

0

Reset value

0x1C

0

0

0

1

1

1

1

MNT[2:0]
0

0

0

1

1

1

MNU[3:0]
0

0

0

1
MSK1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

RTC_WUTR

Res.

Reset value
0x14

0

0
Res.

RTC_PRER

0

TAMP3F

0

0

0

RECALPF

0

0

0

BKP

0

0

SUB1H

POL

COSEL

0

0

WDU[2:0]

0

Reset value
0x10

0

ST[2:0]

INIT

0

MNU[3:0]

Res.

0

Res.

OSE
L
[1:0]

0

Res.

0

Res.

COE

0

0

MNT[2:0]

MT

0

YU[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_ISR

0x0C

Res.

Reset value

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0x08

Res.

RTC_CR

0

HU[3:0]

YT[3:0]
0

Res.

Reset value

HT
[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_DR

0x04

0
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 141. RTC register map and reset values

0

0

1

ST[2:0]
0

0

0

SU[3:0]
0

0

0

0

RM0316

Real-time clock (RTC)

PM

0

0

0

0

0

0

0

0

0

0

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.

MNT[2:0]

MNU[3:0]

Res.

Reset value

0

0

Res.

Res.

Res.

Res.

WDU[1:0]

0

0

0

0x50
to 0x8C

Reset value

MT
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

ST[2:0]
0

0

0

0

SU[3:0]
0

0

DT
[1:0]

0

0

DU[3:0]

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

0

0

0

CALM[8:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

TAMP1E

CALW16
0

0

TAMPIE

CALW8
0

0

TAMP1TRG

CALP
0

0

TAMP2E

0

TAMP3E

0

TAMPTS

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

0

MU[3:0]

TAMPFLT[1:0]

Res.
Res.

0

0

TAMPPRCH[1:0]

Res.
Res.

Res.

0

Res.

Res.

Res.

PC13VALUE

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

BKP[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

to
RTC_BKP15R
Reset value

0

0

0

RTC_BKP0R

0

0

0

0
Res.

PC13VALUE

Res.

Res.

PC14MODE

0
Res.

PC14VALUE

0

0

SS[15:0]

TAMPPUDIS

Res.

Res.

Res.

Res.

Res.

PC15MODE

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.
Res.

PC15MODE

0

Res.

0

0

0

Res.

0

0

0

MNT[2:0]

Res.

HT[1:0]

0

Res.

Res.

Res.

Res.

Res.

0

MASKSS
[3:0]

Res.

Res.

Res.

RTC_
ALRMBSSR

0
Res.

Reset value
0x48

MASKSS
[3:0]

Res.

Res.

RTC_
ALRMASSR

Res.

0x44

Res.

Reset value

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

PM

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

RTC_TAFCR

0

MNU[3:0]

0

Reset value

0x40

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

RTC_ CALR

Res.

0x3C

0

0

Reset value

0

SUBFS[14:0]

0

0
Res.

RTC_TSSSR

0

Res.

Res.

Res.

Res.

Res.

HU[3:0]

Reset value
0x38

0

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

RTC_TSDR

Res.

Reset value
0x34

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_TSTR

0

0
Res.

0
Res.

Reset value

Res.

ADD1S

0x30

RTC_SHIFTR

Res.

0x2C

0

Res.

Reset value

0

SS[15:0]

TAMPFREQ[2:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RTC_SSR

Res.

0x28

0

SU[3:0]

KEY
0

Res.

Reset value

0

ST[2:0]

TAMP2TRG

HU[3:0]

Res.

HT
[1:0]

TAMP3TRG

DU[3:0]

MSK2

MSK3

Reset value

DT
[1:0]

MSK2

MSK4

WDSEL

0x24

RTC_ALRMBR

Res.

0x20

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 141. 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

0

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

DocID022558 Rev 8

815/1141
815

Inter-integrated circuit (I2C) interface

RM0316

28

Inter-integrated circuit (I2C) interface

28.1

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.

28.2

I2C main features
•

816/1141

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

DocID022558 Rev 8

RM0316

Inter-integrated circuit (I2C) interface
The following additional features are also available depending on the product
implementation (see Section 28.3: I2C implementation):
•

SMBus specification rev 2.0 compatibility:
–

28.3

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 I2C
communication speed to be independent from the PCLK reprogramming

•

Wakeup from Stop mode on address match.

I2C implementation
This manual describes the full set of features implemented in I2C1, I2C3 and I2C3.In the
STM32F3xx devices I2C1, I2C2, and I2C3 (for STM32F303xD/E) are identical and
implement the full set of features as shown in the following table.
Table 142. STM32F3xx I2C implementation
I2C features(1)

I2C1

I2C2(2)

I2C3(3)

7-bit addressing mode

X

X

X

10-bit addressing mode

X

X

X

Standard-mode (up to 100 kbit/s)

X

X

X

Fast-mode (up to 400 kbit/s)

X

X

X

Fast-mode Plus with 20mA output drive I/Os
(up to 1 Mbit/s)

X

X

X

Independent clock

X

X

X

SMBus

X

X

X

Wakeup from Stop mode

X

X

X

1. X = supported.
2. I2C2 is available on only
3. I2C3 is available on STM32F303xD/E only.

28.4

I2C functional description
In addition to receiving and transmitting data, this interface converts it from serial to parallel
format and vice versa. The interrupts are enabled or disabled by software. The interface is
connected to the I2C bus by a data pin (SDA) and by a clock pin (SCL). It can be connected
with a standard (up to 100 kHz), Fast-mode (up to 400 kHz) or Fast-mode Plus (up to
1 MHz) I2C bus.

DocID022558 Rev 8

817/1141
884

Inter-integrated circuit (I2C) interface

RM0316

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.

28.4.1

I2C block diagram
The block diagram of the I2C interface is shown in Figure 292.
Figure 292. I2C block diagram

6<6&/.

,&&/.

)URPV\VWHPFRQILJXUDWLRQ
FRQWUROOHU 6<6&)*
)0GULYH

+6,
'DWDFRQWURO
6KLIWUHJLVWHU
5&&B,&[6:
IURPUHVHWDQG
FORFN
FRQWUROOHU

'LJLWDO
QRLVH
ILOWHU

:83(1

$QDORJ
QRLVH
ILOWHU

*3,2
ORJLF

,&[B6'$

60%86
3(&
JHQHUDWLRQ
FKHFN
:DNHXS
RQ
DGGUHVV
PDWFK

)URPV\VWHPFRQILJXUDWLRQ
FRQWUROOHU 6<6&)*
)0GULYH

&ORFNFRQWURO
0DVWHUFORFN
JHQHUDWLRQ
6ODYHFORFN
VWUHWFKLQJ

'LJLWDO
QRLVH
ILOWHU

$QDORJ
QRLVH
ILOWHU

*3,2
ORJLF

,&[B6&/

60%XV
7LPHRXW
FKHFN

60%XV$OHUW
FRQWURO 
VWDWXV

3&/.

,&[B60%$

5HJLVWHUV

$3%EXV
069

The I2C is clocked by an independent clock source which allows to the I2C to operate
independently from the PCLK frequency.
This independent clock source can be selected for either of the following two clock sources:

818/1141

•

HSI: high speed internal oscillator (default value)

•

SYSCLK: system clock
DocID022558 Rev 8

RM0316

Inter-integrated circuit (I2C) interface
Refer to Section 9: Reset and clock control (RCC) for more details.
I2C I/Os support 20 mA output current drive for Fast-mode Plus operation. This is enabled
by setting the driving capability control bits for SCL and SDA in Section 12.1.1: SYSCFG
configuration register 1 (SYSCFG_CFGR1).

28.4.2

I2C clock requirements
The I2C kernel is clocked by I2CCLK.
The I2CCLK period tI2CCLK must respect the following conditions:
tI2CCLK < (tLOW - tfilters ) / 4 and tI2CCLK < tHIGH
with:
tLOW: SCL low time and tHIGH : SCL high time
tfilters: when enabled, sum of the delays brought by the analog filter and by the digital filter.
Analog filter delay is maximum 260 ns. Digital filter delay is DNF x tI2CCLK.
The PCLK clock period tPCLK must respect the following condition:
tPCLK < 4/3 tSCL
with tSCL: SCL period

Caution:

When the I2C kernel is clocked by PCLK. PCLK must respect the conditions for tI2CCLK.

28.4.3

Mode selection
The interface can operate in one of the four following modes:
•

Slave transmitter

•

Slave receiver

•

Master transmitter

•

Master receiver

By default, it operates in slave mode. The interface automatically switches from slave to
master when it generates a START condition, and from master to slave if an arbitration loss
or a STOP generation occurs, allowing multimaster capability.

Communication flow
In Master mode, the I2C interface initiates a data transfer and generates the clock signal. A
serial data transfer always begins with a START condition and ends with a STOP condition.
Both START and STOP conditions are generated in master mode by software.
In Slave mode, the interface is capable of recognizing its own addresses (7 or 10-bit), and
the General Call address. The General Call address detection can be enabled or disabled
by software. The reserved SMBus addresses can also be enabled by software.
Data and addresses are transferred as 8-bit bytes, MSB first. The first byte(s) following the
START condition contain the address (one in 7-bit mode, two in 10-bit mode). The address
is always transmitted in Master mode.
A 9th clock pulse follows the 8 clock cycles of a byte transfer, during which the receiver must
send an acknowledge bit to the transmitter. Refer to the following figure.

DocID022558 Rev 8

819/1141
884

Inter-integrated circuit (I2C) interface

RM0316
Figure 293. I2C bus protocol

6'$
06%

$&.

6&/




6WDUW
FRQGLWLRQ





6WRS
FRQGLWLRQ
069

Acknowledge can be enabled or disabled by software. The I2C interface addresses can be
selected by software.

820/1141

DocID022558 Rev 8

RM0316

28.4.4

Inter-integrated circuit (I2C) interface

I2C initialization
Enabling and disabling the peripheral
The I2C peripheral clock must be configured and enabled in the clock controller (refer to
Section 9: Reset and clock control (RCC)).
Then the I2C can be enabled by setting the PE bit in the I2C_CR1 register.
When the I2C is disabled (PE=0), the I2C performs a software reset. Refer to
Section 28.4.5: Software reset for more details.

Noise filters
Before enabling the I2C peripheral by setting the PE bit in I2C_CR1 register, the user must
configure the noise filters, if needed. By default, an analog noise filter is present on the SDA
and SCL inputs. This analog filter is compliant with the I2C specification which requires the
suppression of spikes with a pulse width up to 50 ns in Fast-mode and Fast-mode Plus. The
user can disable this analog filter by setting the ANFOFF bit, and/or select a digital filter by
configuring the DNF[3:0] bit in the I2C_CR1 register.
When the digital filter is enabled, the level of the SCL or the SDA line is internally changed
only if it remains stable for more than DNF x I2CCLK periods. This allows to suppress
spikes with a programmable length of 1 to 15 I2CCLK periods.
Table 143. Comparison of analog vs. digital filters

Pulse width of
suppressed spikes
Benefits

Drawbacks

Caution:

Analog filter

Digital filter

≥ 50 ns

Programmable length from 1 to 15 I2C peripheral
clocks

Available in Stop mode

– Programmable length: extra filtering capability
vs. standard requirements
– Stable length

Variation vs. temperature,
voltage, process

Wakeup from Stop mode on address match is not
available when digital filter is enabled

Changing the filter configuration is not allowed when the I2C is enabled.

DocID022558 Rev 8

821/1141
884

Inter-integrated circuit (I2C) interface

RM0316

I2C timings
The timings must be configured in order to guarantee a correct data hold and setup time,
used in master and slave modes. This is done by programming the PRESC[3:0],
SCLDEL[3:0] and SDADEL[3:0] bits in the I2C_TIMINGR register.
The STM32CubeMX tool calculates and provides the I2C_TIMINGR content in the I2C
configuration window
Figure 294. Setup and hold timings
d,K>d/D
6&/IDOOLQJHGJHLQWHUQDO
GHWHFWLRQ

W6<1& 6'$'(/6&/VWUHWFKHGORZE\WKH,&

6'$RXWSXWGHOD\
6&/

6'$

W+''$7
'DWDKROGWLPHLQFDVHRIWUDQVPLVVLRQWKHGDWDLVVHQWRQ6'$RXWSXWDIWHU
WKH6'$'(/GHOD\LILWLVDOUHDG\DYDLODEOHLQ,&B7;'5
d^dhWd/D
6&/'(/
6&/VWUHWFKHGORZE\WKH,&

6&/

6'$

W6867$
'DWDVHWXSWLPHLQFDVHRIWUDQVPLVVLRQWKH6&/'(/FRXQWHUVWDUWV
ZKHQWKHGDWDLVVHQWRQ6'$RXWSXW
06Y9

822/1141

DocID022558 Rev 8

RM0316

Inter-integrated circuit (I2C) 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 I2CCLK clock (2 to 3 I2CCLK periods)

In order to bridge the undefined region of the SCL falling edge, the user must program
SDADEL in such a way that:
{tf (max) +tHD;DAT (min) -tAF(min) - [(DNF +3) x tI2CCLK]} / {(PRESC +1) x tI2CCLK } ≤ SDADEL
SDADEL ≤ {tHD;DAT (max) -tAF(max) - [(DNF+4) x tI2CCLK]} / {(PRESC +1) x tI2CCLK }
Note:

tAF(min) / tAF(max) are part of the equation only when the analog filter is enabled. Refer to
device datasheet for tAF values.
The maximum tHD;DAT could be 3.45 µs, 0.9 µs and 0.45 µs for Standard-mode, Fast-mode
and Fast-mode Plus, but must be less than the maximum of tVD;DAT by a transition time.
This maximum must only be met if the device does not stretch the LOW period (tLOW) of the
SCL signal. If the clock stretches the SCL, the data must be valid by the set-up time before
it releases the clock.
The SDA rising edge is usually the worst case, so in this case the previous equation
becomes:
SDADEL ≤ {tVD;DAT (max) -tr (max) -260 ns - [(DNF+4) x tI2CCLK]} / {(PRESC +1) x tI2CCLK }.

Note:

This condition can be violated when NOSTRETCH=0, because the device stretches SCL
low to guarantee the set-up time, according to the SCLDEL value.
Refer to Table 144: 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 144: I2C-SMBUS specification data setup and hold times for tr and tSU;DAT
standard values.
The SDA and SCL transition time values to be used are the ones in the application. Using
the maximum values from the standard increases the constraints for the SDADEL and
SCLDEL calculation, but ensures the feature whatever the application.

DocID022558 Rev 8

823/1141
884

Inter-integrated circuit (I2C) interface
Note:

RM0316

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 144. 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 I2C_TIMINGR register.
•

When the SCL falling edge is internally detected, a delay is inserted before releasing
the SCL output. This delay is tSCLL = (SCLL+1) x tPRESC where tPRESC = (PRESC+1) x
tI2CCLK.
tSCLL impacts the SCL low time tLOW .

•

When the SCL rising edge is internally detected, a delay is inserted before forcing the
SCL output to low level. This delay is tSCLH = (SCLH+1) x tPRESC where tPRESC =
(PRESC+1) x tI2CCLK. tSCLH impacts the SCL high time tHIGH .

Refer to I2C master initialization for more details.
Caution:

Changing the timing configuration is not allowed when the I2C is enabled.
The I2C slave NOSTRETCH mode must also be configured before enabling the peripheral.
Refer to I2C slave initialization for more details.

Caution:

824/1141

Changing the NOSTRETCH configuration is not allowed when the I2C is enabled.

DocID022558 Rev 8

RM0316

Inter-integrated circuit (I2C) interface
Figure 295. I2C initialization flowchart

,QLWLDOVHWWLQJV

&OHDU3(ELWLQ,&B&5

&RQILJXUH$1)2))DQG'1)>@LQ,&B&5

&RQILJXUH35(6&>@
6'$'(/>@6&/'(/>@6&/+>@
6&//>@LQ,&B7,0,1*5

&RQILJXUH12675(7&+LQ,&B&5

6HW3(ELWLQ,&B&5

(QG

D^ϭϵϴϰϳsϮ

28.4.5

Software reset
A software reset can be performed by clearing the PE bit in the I2C_CR1 register. In that
case I2C lines SCL and SDA are released. Internal states machines are reset and
communication control bits, as well as status bits come back to their reset value. The
configuration registers are not impacted.
Here is the list of impacted register bits:
1.

I2C_CR2 register: START, STOP, NACK

2.

I2C_ISR register: BUSY, TXE, TXIS, RXNE, ADDR, NACKF, TCR, TC, STOPF, BERR,
ARLO, OVR

and in addition when the SMBus feature is supported:
1.

I2C_CR2 register: PECBYTE

2.

I2C_ISR register: PECERR, TIMEOUT, ALERT

PE must be kept low during at least 3 APB clock cycles in order to perform the software
reset. This is ensured by writing the following software sequence: - Write PE=0 - Check
PE=0 - Write PE=1.

DocID022558 Rev 8

825/1141
884

Inter-integrated circuit (I2C) interface

28.4.6

RM0316

Data transfer
The data transfer is managed through transmit and receive data registers and a shift
register.

Reception
The SDA input fills the shift register. After the 8th SCL pulse (when the complete data byte is
received), the shift register is copied into I2C_RXDR register if it is empty (RXNE=0). If
RXNE=1, meaning that the previous received data byte has not yet been read, the SCL line
is stretched low until I2C_RXDR is read. The stretch is inserted between the 8th and 9th
SCL pulse (before the Acknowledge pulse).
Figure 296. Data reception

!#+ PULSE

!#+ PULSE

LEGEND

3#,
3HIFT REGISTER

3#,
STRETCH
XX

DATA

XX

DATA

XX

28.%
RD DATA RD DATA

)#?28$2

DATA

DATA

DATA

-36

826/1141

DocID022558 Rev 8

RM0316

Inter-integrated circuit (I2C) interface

Transmission
If the I2C_TXDR register is not empty (TXE=0), its content is copied into the shift register
after the 9th SCL pulse (the Acknowledge pulse). Then the shift register content is shifted
out on SDA line. If TXE=1, meaning that no data is written yet in I2C_TXDR, SCL line is
stretched low until I2C_TXDR is written. The stretch is done after the 9th SCL pulse.
Figure 297. Data transmission

!#+ PULSE

!#+ PULSE
LEGEND

XX

XX

DATA

3HIFT REGISTER

DATA

3#,

3#,
STRETCH
XX

48%

WR DATA

)#?48$2

DATA

WR DATA

DATA

DATA

-36

Hardware transfer management
The I2C has a byte counter embedded in hardware in order to manage byte transfer and to
close the communication in various modes such as:
–

NACK, STOP and ReSTART generation in master mode

–

ACK control in slave receiver mode

–

PEC generation/checking when SMBus feature is supported

The byte counter is always used in master mode. By default it is disabled in slave mode, but
it can be enabled by software by setting the SBC (Slave Byte Control) bit in the I2C_CR2
register.
The number of bytes to be transferred is programmed in the NBYTES[7:0] bit field in the
I2C_CR2 register. If the number of bytes to be transferred (NBYTES) is greater than 255, or
if a receiver wants to control the acknowledge value of a received data byte, the reload
mode must be selected by setting the RELOAD bit in the I2C_CR2 register. In this mode,
TCR flag is set when the number of bytes programmed in NBYTES has been transferred,
and an interrupt is generated if TCIE is set. SCL is stretched as long as TCR flag is set. TCR
is cleared by software when NBYTES is written to a non-zero value.
When the NBYTES counter is reloaded with the last number of bytes, RELOAD bit must be
cleared.

DocID022558 Rev 8

827/1141
884

Inter-integrated circuit (I2C) interface

RM0316

When RELOAD=0 in master mode, the counter can be used in 2 modes:

Caution:

•

Automatic end mode (AUTOEND = ‘1’ in the I2C_CR2 register). In this mode, the
master automatically sends a STOP condition once the number of bytes programmed
in the NBYTES[7:0] bit field has been transferred.

•

Software end mode (AUTOEND = ‘0’ in the I2C_CR2 register). In this mode, software
action is expected once the number of bytes programmed in the NBYTES[7:0] bit field
has been transferred; the TC flag is set and an interrupt is generated if the TCIE bit is
set. The SCL signal is stretched as long as the TC flag is set. The TC flag is cleared by
software when the START or STOP bit is set in the I2C_CR2 register. This mode must
be used when the master wants to send a RESTART condition.

The AUTOEND bit has no effect when the RELOAD bit is set.
Table 145. I2C configuration table

28.4.7

Function

SBC bit

RELOAD bit

AUTOEND bit

Master Tx/Rx NBYTES + STOP

x

0

1

Master Tx/Rx + NBYTES + RESTART

x

0

0

Slave Tx/Rx
all received bytes ACKed

0

x

x

Slave Rx with ACK control

1

1

x

I2C slave mode
I2C slave initialization
In order to work in slave mode, the user must enable at least one slave address. Two
registers I2C_OAR1 and I2C_OAR2 are available in order to program the slave own
addresses OA1 and OA2.
•

OA1 can be configured either in 7-bit mode (by default) or in 10-bit addressing mode by
setting the OA1MODE bit in the I2C_OAR1 register.
OA1 is enabled by setting the OA1EN bit in the I2C_OAR1 register.

•

If additional slave addresses are required, the 2nd slave address OA2 can be
configured. Up to 7 OA2 LSB can be masked by configuring the OA2MSK[2:0] bits in
the I2C_OAR2 register. Therefore for OA2MSK configured from 1 to 6, only OA2[7:2],
OA2[7:3], OA2[7:4], OA2[7:5], OA2[7:6] or OA2[7] are compared with the received
address. As soon as OA2MSK is not equal to 0, the address comparator for OA2
excludes the I2C reserved addresses (0000 XXX and 1111 XXX), which are not
acknowledged. If OA2MSK=7, all received 7-bit addresses are acknowledged (except
reserved addresses). OA2 is always a 7-bit address.
These reserved addresses can be acknowledged if they are enabled by the specific
enable bit, if they are programmed in the I2C_OAR1 or I2C_OAR2 register with
OA2MSK=0.
OA2 is enabled by setting the OA2EN bit in the I2C_OAR2 register.

•

The General Call address is enabled by setting the GCEN bit in the I2C_CR1 register.

When the I2C is selected by one of its enabled addresses, the ADDR interrupt status flag is
set, and an interrupt is generated if the ADDRIE bit is set.

828/1141

DocID022558 Rev 8

RM0316

Inter-integrated circuit (I2C) 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 I2C must be configured with NOSTRETCH=1 in the
I2C_CR1 register.
After receiving an ADDR interrupt, if several addresses are enabled the user must read the
ADDCODE[6:0] bits in the I2C_ISR register in order to check which address matched. DIR
flag must also be checked in order to know the transfer direction.

Slave clock stretching (NOSTRETCH = 0)
In default mode, the I2C slave stretches the SCL clock in the following situations:
•

When the ADDR flag is set: the received address matches with one of the enabled
slave addresses. This stretch is released when the ADDR flag is cleared by software
setting the ADDRCF bit.

•

In transmission, if the previous data transmission is completed and no new data is
written in I2C_TXDR register, or if the first data byte is not written when the ADDR flag
is cleared (TXE=1). This stretch is released when the data is written to the I2C_TXDR
register.

•

In reception when the I2C_RXDR register is not read yet and a new data reception is
completed. This stretch is released when I2C_RXDR is read.

•

When TCR = 1 in Slave Byte Control mode, reload mode (SBC=1 and RELOAD=1),
meaning that the last data byte has been transferred. This stretch is released when
then TCR is cleared by writing a non-zero value in the NBYTES[7:0] field.

•

After SCL falling edge detection, the I2C stretches SCL low during
[(SDADEL+SCLDEL+1) x (PRESC+1) + 1] x tI2CCLK.

Slave without clock stretching (NOSTRETCH = 1)
When NOSTRETCH = 1 in the I2C_CR1 register, the I2C slave does not stretch the SCL
signal.
•

The SCL clock is not stretched while the ADDR flag is set.

•

In transmission, the data must be written in the I2C_TXDR register before the first SCL
pulse corresponding to its transfer occurs. If not, an underrun occurs, the OVR flag is
set in the I2C_ISR register and an interrupt is generated if the ERRIE bit is set in the
I2C_CR1 register. The OVR flag is also set when the first data transmission starts and
the STOPF bit is still set (has not been cleared). Therefore, if the user clears the
STOPF flag of the previous transfer only after writing the first data to be transmitted in
the next transfer, he ensures that the OVR status is provided, even for the first data to
be transmitted.

•

In reception, the data must be read from the I2C_RXDR register before the 9th SCL
pulse (ACK pulse) of the next data byte occurs. If not an overrun occurs, the OVR flag
is set in the I2C_ISR register and an interrupt is generated if the ERRIE bit is set in the
I2C_CR1 register.

DocID022558 Rev 8

829/1141
884

Inter-integrated circuit (I2C) interface

RM0316

Slave Byte Control mode
In order to allow byte ACK control in slave reception mode, Slave Byte Control mode must
be enabled by setting the SBC bit in the I2C_CR1 register. This is required to be compliant
with SMBus standards.
Reload mode must be selected in order to allow byte ACK control in slave reception mode
(RELOAD=1). To get control of each byte, NBYTES must be initialized to 0x1 in the ADDR
interrupt subroutine, and reloaded to 0x1 after each received byte. When the byte is
received, the TCR bit is set, stretching the SCL signal low between the 8th and 9th SCL
pulses. The user can read the data from the I2C_RXDR register, and then decide to
acknowledge it or not by configuring the ACK bit in the I2C_CR2 register. The SCL stretch is
released by programming NBYTES to a non-zero value: the acknowledge or notacknowledge is sent and next byte can be received.
NBYTES can be loaded with a value greater than 0x1, and in this case, the reception flow is
continuous during NBYTES data reception.
Note:

The SBC bit must be configured when the I2C is disabled, or when the slave is not
addressed, or when ADDR=1.
The RELOAD bit value can be changed when ADDR=1, or when TCR=1.

Caution:

830/1141

Slave Byte Control mode is not compatible with NOSTRETCH mode. Setting SBC when
NOSTRETCH=1 is not allowed.

DocID022558 Rev 8

RM0316

Inter-integrated circuit (I2C) interface
Figure 298. Slave initialization flowchart

6ODYH
LQLWLDOL]DWLRQ

,QLWLDOVHWWLQJV

&OHDU^2$(12$(1`LQ,&B2$5DQG,&B2$5

&RQILJXUH^2$>@2$02'(2$(1
2$>@2$06.>@2$(1*&(1`

&RQILJXUH6%&LQ,&B&5

(QDEOHLQWHUUXSWVDQGRU
'0$LQ,&B&5

(QG

6%&PXVWEHVHWWRVXSSRUW60%XVIHDWXUHV

D^ϭϵϴϱϬsϮ

Slave transmitter
A transmit interrupt status (TXIS) is generated when the I2C_TXDR register becomes
empty. An interrupt is generated if the TXIE bit is set in the I2C_CR1 register.
The TXIS bit is cleared when the I2C_TXDR register is written with the next data byte to be
transmitted.
When a NACK is received, the NACKF bit is set in the I2C_ISR register and an interrupt is
generated if the NACKIE bit is set in the I2C_CR1 register. The slave automatically releases
the SCL and SDA lines in order to let the master perform a STOP or a RESTART condition.
The TXIS bit is not set when a NACK is received.
When a STOP is received and the STOPIE bit is set in the I2C_CR1 register, the STOPF
flag is set in the I2C_ISR register and an interrupt is generated. In most applications, the
SBC bit is usually programmed to ‘0’. In this case, If TXE = 0 when the slave address is
received (ADDR=1), the user can choose either to send the content of the I2C_TXDR
register as the first data byte, or to flush the I2C_TXDR register by setting the TXE bit in
order to program a new data byte.
In Slave Byte Control mode (SBC=1), the number of bytes to be transmitted must be
programmed in NBYTES in the address match interrupt subroutine (ADDR=1). In this case,

DocID022558 Rev 8

831/1141
884

Inter-integrated circuit (I2C) interface

RM0316

the number of TXIS events during the transfer corresponds to the value programmed in
NBYTES.
Caution:

When NOSTRETCH=1, the SCL clock is not stretched while the ADDR flag is set, so the
user cannot flush the I2C_TXDR register content in the ADDR subroutine, in order to
program the first data byte. The first data byte to be sent must be previously programmed in
the I2C_TXDR register:
•

This data can be the data written in the last TXIS event of the previous transmission
message.

•

If this data byte is not the one to be sent, the I2C_TXDR register can be flushed by
setting the TXE bit in order to program a new data byte. The STOPF bit must be
cleared only after these actions, in order to guarantee that they are executed before the
first data transmission starts, following the address acknowledge.
If STOPF is still set when the first data transmission starts, an underrun error will be
generated (the OVR flag is set).
If a TXIS event is needed, (Transmit Interrupt or Transmit DMA request), the user must
set the TXIS bit in addition to the TXE bit, in order to generate a TXIS event.
Figure 299. Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=0
6ODYH
WUDQVPLVVLRQ

6ODYHLQLWLDOL]DWLRQ

1R
,&B,65$''5
"
255 bytes

0DVWHU
WUDQVPLVVLRQ

0DVWHULQLWLDOL]DWLRQ

1%<7(6 [))1 1
5(/2$' 
&RQILJXUHVODYHDGGUHVV
6HW,&B&567$57

1R
1R
,&B,657;,6

,&B,651$&.)

"

"
255 bytes
0DVWHUUHFHSWLRQ

0DVWHULQLWLDOL]DWLRQ

1%<7(6 [))1 1
5(/2$' 
&RQILJXUHVODYHDGGUHVV
6HW,&B&567$57

,&B,655;1(
"

1R

@

5(
I&.

1RWH

7UDQVPLWWHU
UDWHFRQWUROOHU

5HFHLYHUUDWH
FRQWUROOHU

&RQYHQWLRQDOEDXGUDWHJHQHUDWRU
069

1. For details on coding USARTDIV in the USART_BRR register, please refer to Section 29.5.4: USART baud
rate generation.
2. fCK can be fLSE, fHSI, fPCLK, fSYS.

DocID022558 Rev 8

889/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

29.5.1

RM0316

USART character description
The word length can be selected as being either 7 or 8 or 9 bits by programming the M[1:0]
bits in the USART_CR1 register (see Figure 324).

Note:

•

7-bit character length: M[1:0] = 10

•

8-bit character length: M[1:0] = 00

•

9-bit character length: M[1:0] = 01

In 7-bit data length mode, the Smartcard mode, LIN master mode and Auto baud rate (0x7F
and 0x55 frames detection) are not supported. 7-bit mode is supported only on some
USARTs.
By default, the signal (TX or RX) is in low state during the start bit. It is in high state during
the stop bit.
These values can be inverted, separately for each signal, through polarity configuration
control.
An Idle character is interpreted as an entire frame of “1”s (the number of “1”s includes the
number of stop bits).
A Break character is interpreted on receiving “0”s for a frame period. At the end of the
break frame, the transmitter inserts 2 stop bits.
Transmission and reception are driven by a common baud rate generator, the clock for each
is generated when the enable bit is set respectively for the transmitter and receiver.
The details of each block is given below.

890/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 324. Word length programming

ELWZRUGOHQJWK 0  6WRSELW
3RVVLEOH
3DULW\
ELW

'DWDIUDPH
6WDUW
ELW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

6WRS
ELW

1H[W
6WDUW
ELW

&ORFN
6WDUW
ELW

,GOHIUDPH

6WRS
ELW

6WRS
ELW

6WRS
ELW

6WRS
ELW

6WDUW
ELW

6WRS
ELW

6WDUW
ELW

%UHDNIUDPH

6WDUW
ELW


ELWZRUGOHQJWK 0  6WRSELW
3RVVLEOH
3DULW\
ELW

'DWDIUDPH
6WDUW
ELW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

6WRS
ELW

1H[W
6WDUW
ELW

&ORFN
6WDUW
ELW

,GOHIUDPH
%UHDNIUDPH

ELWZRUGOHQJWK 0  6WRSELW
3RVVLEOH
3DULW\
ELW

'DWDIUDPH
6WDUW
ELW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

6WRS
ELW

1H[W
6WDUW
ELW

&ORFN

,GOHIUDPH
%UHDNIUDPH

6WDUW
ELW
6WRS
ELW

/%&/ELWFRQWUROVODVWGDWDFORFNSXOVH
069

DocID022558 Rev 8

891/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

29.5.2

RM0316

USART transmitter
The transmitter can send data words of either 7, 8 or 9 bits depending on the M bits status.
The Transmit Enable bit (TE) must be set in order to activate the transmitter function. The
data in the transmit shift register is output on the TX pin and the corresponding clock pulses
are output on the CK pin.

Character transmission
During an USART transmission, data shifts out least significant bit first (default
configuration) on the TX pin. In this mode, the USART_TDR register consists of a buffer
(TDR) between the internal bus and the transmit shift register (see Figure 323).
Every character is preceded by a start bit which is a logic level low for one bit period. The
character is terminated by a configurable number of stop bits.
The following stop bits are supported by USART: 0.5, 1, 1.5 and 2 stop bits.
Note:

The TE bit must be set before writing the data to be transmitted to the USART_TDR.
The TE bit should not be reset during transmission of data. Resetting the TE bit during the
transmission will corrupt the data on the TX pin as the baud rate counters will get frozen.
The current data being transmitted will be lost.
An idle frame will be sent after the TE bit is enabled.
Configurable stop bits
The number of stop bits to be transmitted with every character can be programmed in
Control register 2, bits 13,12.
•

1 stop bit: This is the default value of number of stop bits.

•

2 stop bits: This will be supported by normal USART, Single-wire and Modem modes.

•

1.5 stop bits: To be used in Smartcard mode.

•

0.5 stop bit: To be used when receiving data in Smartcard mode.

An idle frame transmission will include the stop bits.
A break transmission will be 10 low bits (when M[1:0] = 00) or 11 low bits (when M[1:0] = 01)
or 9 low bits (when M[1:0] = 10) followed by 2 stop bits (see Figure 325). It is not possible to
transmit long breaks (break of length greater than 9/10/11 low bits).

892/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 325. Configurable stop bits
ELWGDWD6WRSELW
3RVVLEOH
SDULW\ELW

'DWDIUDPH
6WDUWELW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

6WRS
ELW

1H[W 1H[WGDWDIUDPH
VWDUW
ELW

&/2&.
/%&/ELWFRQWUROVODVWGDWDFORFNSXOVH

ELWGDWD6WRSELWV
3RVVLEOH
SDULW\ELW

'DWDIUDPH
6WDUWELW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

%LW


6WRS
ELWV

1H[W
VWDUW
ELW

1H[WGDWDIUDPH

ELWGDWD6WRSELWV
3RVVLEOH
SDULW\ELW

'DWDIUDPH
6WDUWELW

%LW

%LW

%LW

%LW

%LW

%LW

%LW

%LW


6WRS
ELWV

1H[W
VWDUW
ELW

1H[WGDWDIUDPH

06Y9

Character transmission procedure
1.

Program the M bits in USART_CR1 to define the word length.

2.

Select the desired baud rate using the USART_BRR register.

3.

Program the number of stop bits in USART_CR2.

4.

Enable the USART by writing the UE bit in USART_CR1 register to 1.

5.

Select DMA enable (DMAT) in USART_CR3 if multibuffer communication is to take
place. Configure the DMA register as explained in multibuffer communication.

6.

Set the TE bit in USART_CR1 to send an idle frame as first transmission.

7.

Write the data to send in the USART_TDR register (this clears the TXE bit). Repeat this
for each data to be transmitted in case of single buffer.

8.

After writing the last data into the USART_TDR register, wait until TC=1. This indicates
that the transmission of the last frame is complete. This is required for instance when
the USART is disabled or enters the Halt mode to avoid corrupting the last
transmission.

Single byte communication
Clearing the TXE bit is always performed by a write to the transmit data register.
The TXE bit is set by hardware and it indicates:
•

The data has been moved from the USART_TDR register to the shift register and the
data transmission has started.

•

The USART_TDR register is empty.

•

The next data can be written in the USART_TDR register without overwriting the
previous data.

This flag generates an interrupt if the TXEIE bit is set.
When a transmission is taking place, a write instruction to the USART_TDR register stores
the data in the TDR register; next, the data is copied in the shift register at the end of the
currently ongoing transmission.

DocID022558 Rev 8

893/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

When no transmission is taking place, a write instruction to the USART_TDR register places
the data in the shift register, the data transmission starts, and the TXE bit is set.
If a frame is transmitted (after the stop bit) and the TXE bit is set, the TC bit goes high. An
interrupt is generated if the TCIE bit is set in the USART_CR1 register.
After writing the last data in the USART_TDR register, it is mandatory to wait for TC=1
before disabling the USART or causing the microcontroller to enter the low-power mode
(see Figure 326: TC/TXE behavior when transmitting).
Figure 326. TC/TXE behavior when transmitting
)DLE PREAMBLE

&RAME 

&RAME 

&RAME 

48 LINE
SET BY HARDWARE
CLEARED BY SOFTWARE

48% FLAG

53!24?$2

SET BY HARDWARE
CLEARED BY SOFTWARE

&

&

&

SET BY HARDWARE

SET
BY HARDWARE

4# FLAG
SOFTWARE
ENABLES THE
53!24

SOFTWARE WAITS UNTIL 48%
AND WRITES & INTO $2

SOFTWARE WAITS UNTIL 48%
AND WRITES & INTO $2

4# IS NOT SET
BECAUSE 48%

SOFTWARE WAITS UNTIL 48%
AND WRITES & INTO $2

4# IS NOT SET
BECAUSE 48%

4# IS SET BECAUSE
48%

SOFTWARE WAITS UNTIL 4#

AIB

Break characters
Setting the SBKRQ bit transmits a break character. The break frame length depends on the
M bits (see Figure 324).
If a ‘1’ is written to the SBKRQ bit, a break character is sent on the TX line after completing
the current character transmission. The SBKF bit is set by the write operation and it is reset
by hardware when the break character is completed (during the stop bits after the break
character). The USART inserts a logic 1 signal (STOP) for the duration of 2 bits at the end of
the break frame to guarantee the recognition of the start bit of the next frame.
In the case the application needs to send the break character following all previously
inserted data, including the ones not yet transmitted, the software should wait for the TXE
flag assertion before setting the SBKRQ bit.

Idle characters
Setting the TE bit drives the USART to send an idle frame before the first data frame.

29.5.3

USART receiver
The USART can receive data words of either 7, 8 or 9 bits depending on the M bits in the
USART_CR1 register.

894/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

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 0X 0X 0 X 0X 0.
Figure 327. Start bit detection when oversampling by 16 or 8
28 STATE

)DLE

3TART BIT

28 LINE
)DEAL
SAMPLE
CLOCK









































 

8

8

SAMPLED VALUES
2EAL
SAMPLE
CLOCK

8

8

8

8

8

8

8

8









/NE BIT TIME

#ONDITIONS
TO VALIDATE
THE START BIT







&ALLING EDGE
DETECTION

Note:



8



8



!T LEAST  BITS
OUT OF  AT 

8









!T LEAST  BITS
OUT OF  AT 

8

8

8

8

AI

If the sequence is not complete, the start bit detection aborts and the receiver returns to the
idle state (no flag is set), where it waits for a falling edge.
The start bit is confirmed (RXNE flag set, interrupt generated if RXNEIE=1) if the 3 sampled
bits are at 0 (first sampling on the 3rd, 5th and 7th bits finds the 3 bits at 0 and second
sampling on the 8th, 9th and 10th bits also finds the 3 bits at 0).
The start bit is validated (RXNE flag set, interrupt generated if RXNEIE=1) but the NF noise
flag is set if,
a)

for both samplings, 2 out of the 3 sampled bits are at 0 (sampling on the 3rd, 5th
and 7th bits and sampling on the 8th, 9th and 10th bits)

or
b)

for one of the samplings (sampling on the 3rd, 5th and 7th bits or sampling on the
8th, 9th and 10th bits), 2 out of the 3 bits are found at 0.

If neither conditions a. or b. are met, the start detection aborts and the receiver returns to the
idle state (no flag is set).

DocID022558 Rev 8

895/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Character reception
During an USART reception, data shifts in least significant bit first (default configuration)
through the RX pin. In this mode, the USART_RDR register consists of a buffer (RDR)
between the internal bus and the receive shift register.
Character reception procedure
1.

Program the M bits in USART_CR1 to define the word length.

2.

Select the desired baud rate using the baud rate register USART_BRR

3.

Program the number of stop bits in USART_CR2.

4.

Enable the USART by writing the UE bit in USART_CR1 register to 1.

5.

Select DMA enable (DMAR) in USART_CR3 if multibuffer communication is to take
place. Configure the DMA register as explained in multibuffer communication.

6.

Set the RE bit USART_CR1. This enables the receiver which begins searching for a
start bit.

When a character is received:
•

The RXNE bit is set to indicate that the content of the shift register is transferred to the
RDR. In other words, data has been received and can be read (as well as its
associated error flags).

•

An interrupt is generated if the RXNEIE bit is set.

•

The error flags can be set if a frame error, noise or an overrun error has been detected
during reception. PE flag can also be set with RXNE.

•

In multibuffer, RXNE is set after every byte received and is cleared by the DMA read of
the Receive data Register.

•

In single buffer mode, clearing the RXNE bit is performed by a software read to the
USART_RDR register. The RXNE flag can also be cleared by writing 1 to the RXFRQ
in the USART_RQR register. The RXNE bit must be cleared before the end of the
reception of the next character to avoid an overrun error.

Break character
When a break character is received, the USART handles it as a framing error.

Idle character
When an idle frame is detected, there is the same procedure as for a received data
character plus an interrupt if the IDLEIE bit is set.

896/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Overrun error
An overrun error occurs when a character is received when RXNE has not been reset. Data
can not be transferred from the shift register to the RDR register until the RXNE bit is
cleared.
The RXNE flag is set after every byte received. An overrun error occurs if RXNE flag is set
when the next data is received or the previous DMA request has not been serviced. When
an overrun error occurs:

Note:

•

The ORE bit is set.

•

The RDR content will not be lost. The previous data is available when a read to
USART_RDR is performed.

•

The shift register will be overwritten. After that point, any data received during overrun
is lost.

•

An interrupt is generated if either the RXNEIE bit is set or EIE bit is set.

•

The ORE bit is reset by setting the ORECF bit in the ICR register.

The ORE bit, when set, indicates that at least 1 data has been lost. There are two
possibilities:
- if RXNE=1, then the last valid data is stored in the receive register RDR and can be read,
- if RXNE=0, then it means that the last valid data has already been read and thus there is
nothing to be read in the RDR. This case can occur when the last valid data is read in the
RDR at the same time as the new (and lost) data is received.

Selecting the clock source and the proper oversampling method
The choice of the clock source is done through the Clock Control system (see Section Reset
and clock control (RCC))). The clock source must be chosen before enabling the USART
(by setting the UE bit).
The choice of the clock source must be done according to two criteria:
•

Possible use of the USART in low-power mode

•

Communication speed.

The clock source frequency is fCK.
When the dual clock domain with the wakeup from Stop mode is supported, the clock
source can be one of the following sources: PCLK (default), LSE, HSI or SYSCLK.
Otherwise, the USART clock source is PCLK.
Choosing LSE or HSI as clock source may allow the USART to receive data while the MCU
is in low-power mode. Depending on the received data and wakeup mode selection, the
USART wakes up the MCU, when needed, in order to transfer the received data by software
reading the USART_RDR register or by DMA.
For the other clock sources, the system must be active in order to allow USART
communication.
The communication speed range (specially the maximum communication speed) is also
determined by the clock source.
The receiver implements different user-configurable oversampling techniques for data
recovery by discriminating between valid incoming data and noise. This allows a trade-off
between the maximum communication speed and noise/clock inaccuracy immunity.

DocID022558 Rev 8

897/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

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 328 and
Figure 329).
Depending on the application:
•

Select oversampling by 8 (OVER8=1) to achieve higher speed (up to fCK/8). In this
case the maximum receiver tolerance to clock deviation is reduced (refer to
Section 29.5.5: Tolerance of the USART receiver to clock deviation on page 903)

•

Select oversampling by 16 (OVER8=0) to increase the tolerance of the receiver to
clock deviations. In this case, the maximum speed is limited to maximum fCK/16 where
fCK is the clock source frequency.

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 158) because this indicates that a glitch occurred during the sampling.

–

select the single sample method (ONEBIT=1) when the line is noise-free to
increase the receiver’s tolerance to clock deviations (see Section 29.5.5:
Tolerance of the USART receiver to clock deviation on page 903). In this case the
NF bit will never be set.

When noise is detected in a frame:
•

The NF bit is set at the rising edge of the RXNE bit.

•

The invalid data is transferred from the Shift register to the USART_RDR register.

•

No interrupt is generated in case of single byte communication. However this bit rises
at the same time as the RXNE bit which itself generates an interrupt. In case of
multibuffer communication an interrupt will be issued if the EIE bit is set in the
USART_CR3 register.

The NF bit is reset by setting NFCF bit in ICR register.
Note:

898/1141

Oversampling by 8 is not available in LIN, Smartcard and IrDA modes. In those modes, the
OVER8 bit is forced to ‘0’ by hardware.

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 328. Data sampling when oversampling by 16

5;OLQH
VDPSOHGYDOXHV
6DPSOHFORFN





































2QHELWWLPH

06Y9

Figure 329. Data sampling when oversampling by 8

5;OLQH
VDPSOHGYDOXHV
6DPSOH
FORFN [





















2QHELWWLPH

06Y9

Table 158. 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

DocID022558 Rev 8

899/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Framing error
A framing error is detected when the stop bit is not recognized on reception at the expected
time, following either a de-synchronization or excessive noise.
When the framing error is detected:
•

The FE bit is set by hardware

•

The invalid data is transferred from the Shift register to the USART_RDR register.

•

No interrupt is generated in case of single byte communication. However this bit rises
at the same time as the RXNE bit which itself generates an interrupt. In case of
multibuffer communication an interrupt will be issued if the EIE bit is set in the
USART_CR3 register.

The FE bit is reset by writing 1 to the FECF in the USART_ICR register.

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.

900/1141

•

0.5 stop bit (reception in Smartcard mode): No sampling is done for 0.5 stop bit. As
a consequence, no framing error and no break frame can be detected when 0.5 stop bit
is selected.

•

1 stop bit: Sampling for 1 stop Bit is done on the 8th, 9th and 10th samples.

•

1.5 stop bits (Smartcard mode): When transmitting in Smartcard mode, the device
must check that the data is correctly sent. Thus the receiver block must be enabled (RE
=1 in the USART_CR1 register) and the stop bit is checked to test if the smartcard has
detected a parity error. In the event of a parity error, the smartcard forces the data
signal low during the sampling - NACK signal-, which is flagged as a framing error.
Then, the FE flag is set with the RXNE at the end of the 1.5 stop bits. Sampling for 1.5
stop bits is done on the 16th, 17th and 18th samples (1 baud clock period after the
beginning of the stop bit). The 1.5 stop bits can be decomposed into 2 parts: one 0.5
baud clock period during which nothing happens, followed by 1 normal stop bit period
during which sampling occurs halfway through. Refer to Section 29.5.13: USART
Smartcard mode on page 914 for more details.

•

2 stop bits: Sampling for 2 stop bits is done on the 8th, 9th and 10th samples of the
first stop bit. If a framing error is detected during the first stop bit the framing error flag
will be set. The second stop bit is not checked for framing error. The RXNE flag will be
set at the end of the first stop bit.

DocID022558 Rev 8

RM0316

29.5.4

Universal synchronous asynchronous receiver transmitter (USART)

USART baud rate generation
The baud rate for the receiver and transmitter (Rx and Tx) are both set to the same value as
programmed in the USART_BRR register.
Equation 1: Baud rate for standard USART (SPI mode included) (OVER8 = 0 or 1)
In case of oversampling by 16, the equation is:
f CK
Tx/Rx baud = -------------------------------USARTDIV

In case of oversampling by 8, the equation is:
2 × f CK
Tx/Rx baud = -------------------------------USARTDIV

Equation 2: Baud rate in Smartcard, LIN and IrDA modes (OVER8 = 0)
In Smartcard, LIN and IrDA modes, only Oversampling by 16 is supported:
f CK
Tx/Rx baud = -------------------------------USARTDIV

USARTDIV is an unsigned fixed point number that is coded on the USART_BRR register.

Note:

•

When OVER8 = 0, BRR = USARTDIV.

•

When OVER8 = 1
–

BRR[2:0] = USARTDIV[3:0] shifted 1 bit to the right.

–

BRR[3] must be kept cleared.

–

BRR[15:4] = USARTDIV[15:4]

The baud counters are updated to the new value in the baud registers after a write operation
to USART_BRR. Hence the baud rate register value should not be changed during
communication.
In case of oversampling by 16 or 8, USARTDIV must be greater than or equal to 0d16.

How to derive USARTDIV from USART_BRR register values
Example 1
To obtain 9600 baud with fCK = 8 MHz.
•

In case of oversampling by 16:
USARTDIV = 8 000 000/9600
BRR = USARTDIV = 833d = 0341h

•

In case of oversampling by 8:
USARTDIV = 2 * 8 000 000/9600
USARTDIV = 1666,66 (1667d = 683h)
BRR[3:0] = 3h >> 1 = 1h
BRR = 0x681

DocID022558 Rev 8

901/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Example 2
To obtain 921.6 Kbaud with fCK = 48 MHz.
•

In case of oversampling by 16:
USARTDIV = 48 000 000/921 600
BRR = USARTDIV = 52d = 34h

•

In case of oversampling by 8:
USARTDIV = 2 * 48 000 000/921 600
USARTDIV = 104 (104d = 68h)
BRR[3:0] = USARTDIV[3:0] >> 1 = 8h >> 1 = 4h
BRR = 0x64

Table 159. Error calculation for programmed baud rates at fCK = 72MHz in both cases of
oversampling by 16 or by 8(1)
Baud rate

Oversampling by 16 (OVER8 = 0)

Oversampling by 8 (OVER8 = 1)

S.No

Desired

Actual

BRR

% Error =
(Calculated Desired)B.Rate /
Desired B.Rate

1

2.4 KBps

2.4 KBps

0x7530

0

2.4 KBps

0xEA60

0

2

9.6 KBps

9.6 KBps

0x1D4C

0

9.6 KBps

0x3A94

0

3

19.2 KBps

19.2 KBps

0xEA6

0

19.2 KBps

0x1D46

0

4

38.4 KBps

38.4 KBps

0x753

0

38.4 KBps

0xEA3

0

5

57.6 KBps

57.6 KBps

0x4E2

0

57.6 KBps

0x9C2

0

6

115.2 KBps

115.2 KBps

0x271

0

115.2 KBps

0x4E1

0

7

230.4 KBps

230.03KBps

0x139

0.16

230.4 KBps

0x270

0

8

460.8 KBps

461.54KBps

0x9C

0.16

460.06KBps

0x134

0.16

9

921.6 KBps

923.08KBps

0x4E

0.16

923.07KBps

0x96

0.16

10

2 MBps

2 MBps

0x24

0

2 MBps

0x44

0

11

3 MBps

3 MBps

0x18

0

3 MBps

0x30

0

12

4MBps

4MBps

0x12

0

4MBps

0x22

0

13

5MBps

N.A

N.A

N.A

4965.51KBps

0x16

0.69

14

6MBps

N.A

N.A

N.A

6MBps

0x14

0

15

7MBps

N.A

N.A

N.A

6857.14KBps

0x12

2

16

9MBps

N.A

N.A

N.A

9MBps

0x10

0

Actual

BRR

% 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.

902/1141

DocID022558 Rev 8

RM0316

29.5.5

Universal synchronous asynchronous receiver transmitter (USART)

Tolerance of the USART receiver to clock deviation
The asynchronous receiver of the USART works correctly only if the total clock system
deviation is less than the tolerance of the USART receiver. The causes which contribute to
the total deviation are:
•

DTRA: Deviation due to the transmitter error (which also includes the deviation of the
transmitter’s local oscillator)

•

DQUANT: Error due to the baud rate quantization of the receiver

•

DREC: Deviation of the receiver’s local oscillator

•

DTCL: Deviation due to the transmission line (generally due to the transceivers which
can introduce an asymmetry between the low-to-high transition timing and the high-tolow transition timing)
DTRA + DQUANT + DREC + DTCL + DWU < USART receiver′ s tolerance

where
DWU is the error due to sampling point deviation when the wakeup from Stop mode is
used.
when M[1:0] = 01:
t WUUSART
DWU = --------------------------11 × Tbit

when M[1:0] = 00:
t WUUSART
DWU = --------------------------10 × Tbit

when M[1:0] = 10:
t WUUSART
DWU = --------------------------9 × Tbit

tWUUSART is the time between detection of the wakeup event and the instant when
clock (requested by the peripheral) and regulator are ready.
The USART receiver can receive data correctly at up to the maximum tolerated
deviation specified in Table 160 and Table 160 depending on the following choices:
•

9-, 10- or 11-bit character length defined by the M bits in the USART_CR1 register

•

Oversampling by 8 or 16 defined by the OVER8 bit in the USART_CR1 register

•

Bits BRR[3:0] of USART_BRR register are equal to or different from 0000.

•

Use of 1 bit or 3 bits to sample the data, depending on the value of the ONEBIT bit in
the USART_CR3 register.
Table 160. Tolerance of the USART receiver when BRR [3:0] = 0000
OVER8 bit = 0

OVER8 bit = 1

M bits
ONEBIT=0

ONEBIT=1

ONEBIT=0

ONEBIT=1

00

3.75%

4.375%

2.50%

3.75%

01

3.41%

3.97%

2.27%

3.41%

10

4.16%

4.86%

2.77%

4.16%

DocID022558 Rev 8

903/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Table 161. Tolerance of the USART receiver when BRR [3:0] is different from 0000
OVER8 bit = 0

OVER8 bit = 1

M bits
ONEBIT=0

ONEBIT=1

ONEBIT=0

ONEBIT=1

00

3.33%

3.88%

2%

3%

01

3.03%

3.53%

1.82%

2.73%

10

3.7%

4.31%

2.22%

3.33%

Note:

The data specified in Table 160 and Table 161 may slightly differ in the special case when
the received frames contain some Idle frames of exactly 10-bit durations when M bits = 00
(11-bit durations when M bits =01 or 9- bit durations when M bits = 10).

29.5.6

USART auto baud rate detection
The USART is able to detect and automatically set the USART_BRR register value based
on the reception of one character. Automatic baud rate detection is useful under two
circumstances:
•

The communication speed of the system is not known in advance

•

The system is using a relatively low accuracy clock source and this mechanism allows
the correct baud rate to be obtained without measuring the clock deviation.

The clock source frequency must be compatible with the expected communication speed
(when oversampling by 16, the baud rate is between fCK/65535 and fCK/16. when
oversampling by 8, the baud rate is between fCK/65535 and fCK/8).
Before activating the auto baud rate detection, the auto baud rate detection mode must be
chosen. There are various modes based on different character patterns.
They can be chosen through the ABRMOD[1:0] field in the USART_CR2 register. In these
auto baud rate modes, the baud rate is measured several times during the synchronization
data reception and each measurement is compared to the previous one.
These modes are:

904/1141

•

Mode 0: Any character starting with a bit at 1. In this case the USART measures the
duration of the Start bit (falling edge to rising edge).

•

Mode 1: Any character starting with a 10xx bit pattern. In this case, the USART
measures the duration of the Start and of the 1st data bit. The measurement is done
falling edge to falling edge, ensuring better accuracy in the case of slow signal slopes.

•

Mode 2: A 0x7F character frame (it may be a 0x7F character in LSB first mode or a
0xFE in MSB first mode). In this case, the baud rate is updated first at the end of the
start bit (BRs), then at the end of bit 6 (based on the measurement done from falling
edge to falling edge: BR6). Bit 0 to bit 6 are sampled at BRs while further bits of the
character are sampled at BR6.

•

Mode 3: A 0x55 character frame. In this case, the baud rate is updated first at the end
of the start bit (BRs), then at the end of bit 0 (based on the measurement done from
falling edge to falling edge: BR0), and finally at the end of bit 6 (BR6). Bit 0 is sampled

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
at BRs, bit 1 to bit 6 are sampled at BR0, and further bits of the character are sampled
at BR6.
In parallel, another check is performed for each intermediate transition of RX line. An
error is generated if the transitions on RX are not sufficiently synchronized with the
receiver (the receiver being based on the baud rate calculated on bit 0).
Prior to activating auto baud rate detection, the USART_BRR register must be initialized by
writing a non-zero baud rate value.
The automatic baud rate detection is activated by setting the ABREN bit in the USART_CR2
register. The USART will then wait for the first character on the RX line. The auto baud rate
operation completion is indicated by the setting of the ABRF flag in the USART_ISR
register. If the line is noisy, the correct baud rate detection cannot be guaranteed. In this
case the BRR value may be corrupted and the ABRE error flag will be set. This also
happens if the communication speed is not compatible with the automatic baud rate
detection range (bit duration not between 16 and 65536 clock periods (oversampling by 16)
and not between 8 and 65536 clock periods (oversampling by 8)).
The RXNE interrupt will signal the end of the operation.
At any later time, the auto baud rate detection may be relaunched by resetting the ABRF
flag (by writing a 0).

Note:

If the USART is disabled (UE=0) during an auto baud rate operation, the BRR value may be
corrupted.

29.5.7

Multiprocessor communication using USART
In multiprocessor communication, the following bits are to be kept cleared:
•

LINEN bit in the USART_CR2 register,

•

HDSEL, IREN and SCEN bits in the USART_CR3 register.

It is possible to perform multiprocessor communication with the USART (with several
USARTs connected in a network). For instance one of the USARTs can be the master, its TX
output connected to the RX inputs of the other USARTs. The others are slaves, their
respective TX outputs are logically ANDed together and connected to the RX input of the
master.
In multiprocessor configurations it is often desirable that only the intended message
recipient should actively receive the full message contents, thus reducing redundant USART
service overhead for all non addressed receivers.
The non addressed devices may be placed in mute mode by means of the muting function.
In order to use the mute mode feature, the MME bit must be set in the USART_CR1
register.
In mute mode:
•

None of the reception status bits can be set.

•

All the receive interrupts are inhibited.

•

The RWU bit in USART_ISR register is set to 1. RWU can be controlled automatically
by hardware or by software, through the MMRQ bit in the USART_RQR register, under
certain conditions.

DocID022558 Rev 8

905/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

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 MMRQ bit is written to 1 and the RWU is
automatically set.
It wakes up when an Idle frame is detected. Then the RWU bit is cleared by hardware but
the IDLE bit is not set in the USART_ISR register. An example of mute mode behavior using
Idle line detection is given in Figure 330.
Figure 330. Mute mode using Idle line detection

5;1(

'DWD 'DWD 'DWD 'DWD

5;

0XWHPRGH

5:8
0054ZULWWHQWR

,'/(

5;1(

'DWD 'DWD

1RUPDOPRGH
,GOHIUDPHGHWHFWHG

06Y9

Note:

If the MMRQ is set while the IDLE character has already elapsed, mute mode will not be
entered (RWU is not set).
If the USART is activated while the line is IDLE, the idle state is detected after the duration
of one IDLE frame (not only after the reception of one character frame).

4-bit/7-bit address mark detection (WAKE=1)
In this mode, bytes are recognized as addresses if their MSB is a ‘1’ otherwise they are
considered as data. In an address byte, the address of the targeted receiver is put in the 4
or 7 LSBs. The choice of 7 or 4-bit address detection is done using the ADDM7 bit. This 4bit/7-bit word is compared by the receiver with its own address which is programmed in the
ADD bits in the USART_CR2 register.
Note:

In 7-bit and 9-bit data modes, address detection is done on 6-bit and 8-bit addresses
(ADD[5:0] and ADD[7:0]) respectively.
The USART enters mute mode when an address character is received which does not
match its programmed address. In this case, the RWU bit is set by hardware. The RXNE
flag is not set for this address byte and no interrupt or DMA request is issued when the
USART enters mute mode.
The USART also enters mute mode when the MMRQ bit is written to 1. The RWU bit is also
automatically set in this case.

906/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
The USART exits from mute mode when an address character is received which matches
the programmed address. Then the RWU bit is cleared and subsequent bytes are received
normally. The RXNE bit is set for the address character since the RWU bit has been
cleared.
An example of mute mode behavior using address mark detection is given in Figure 331.
Figure 331. Mute mode using address mark detection
,QWKLVH[DPSOHWKHFXUUHQWDGGUHVVRIWKHUHFHLYHULV
SURJUDPPHGLQWKH86$57B&5UHJLVWHU
5;1(

,'/(

5;

$GGU  'DWD 'DWD

5:8

,'/(

5;1(

$GGU  'DWD 'DWD $GGU  'DWD

0XWHPRGH

1RUPDOPRGH
0DWFKLQJDGGUHVV

0054ZULWWHQWR
5;1(ZDVFOHDUHG

5;1(

0XWHPRGH

1RQPDWFKLQJDGGUHVV

1RQPDWFKLQJDGGUHVV
06Y9

29.5.8

Modbus communication using USART
The USART offers basic support for the implementation of Modbus/RTU and Modbus/ASCII
protocols. Modbus/RTU is a half duplex, block transfer protocol. The control part of the
protocol (address recognition, block integrity control and command interpretation) must be
implemented in software.
The USART offers basic support for the end of the block detection, without software
overhead or other resources.

Modbus/RTU
In this mode, the end of one block is recognized by a “silence” (idle line) for more than 2
character times. This function is implemented through the programmable timeout function.
The timeout function and interrupt must be activated, through the RTOEN bit in the
USART_CR2 register and the RTOIE in the USART_CR1 register. The value corresponding
to a timeout of 2 character times (for example 22 x bit duration) must be programmed in the
RTO register. when the receive line is idle for this duration, after the last stop bit is received,
an interrupt is generated, informing the software that the current block reception is
completed.

Modbus/ASCII
In this mode, the end of a block is recognized by a specific (CR/LF) character sequence.
The USART manages this mechanism using the character match function.
By programming the LF ASCII code in the ADD[7:0] field and by activating the character
match interrupt (CMIE=1), the software is informed when a LF has been received and can
check the CR/LF in the DMA buffer.

DocID022558 Rev 8

907/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

29.5.9

RM0316

USART parity control
Parity control (generation of parity bit in transmission and parity checking in reception) can
be enabled by setting the PCE bit in the USART_CR1 register. Depending on the frame
length defined by the M bits, the possible USART frame formats are as listed in Table 162.
Table 162. Frame formats
M bits

PCE bit

USART frame(1)

00

0

| SB | 8-bit data | STB |

00

1

| SB | 7-bit data | PB | STB |

01

0

| SB | 9-bit data | STB |

01

1

| SB | 8-bit data | PB | STB |

10

0

| SB | 7-bit data | STB |

10

1

| SB | 6-bit data | PB | STB |

1. Legends: SB: start bit, STB: stop bit, PB: parity bit. In the data register, the PB is always taking the MSB
position (9th, 8th or 7th, depending on the M bits value).

Even parity
The parity bit is calculated to obtain an even number of “1s” inside the frame of the 6, 7 or 8
LSB bits (depending on M bits values) and the parity bit.
As an example, if data=00110101, and 4 bits are set, then the parity bit will be 0 if even
parity is selected (PS bit in USART_CR1 = 0).

Odd parity
The parity bit is calculated to obtain an odd number of “1s” inside the frame made of the 6, 7
or 8 LSB bits (depending on M bits values) and the parity bit.
As an example, if data=00110101 and 4 bits set, then the parity bit will be 1 if odd parity is
selected (PS bit in USART_CR1 = 1).

Parity checking in reception
If the parity check fails, the PE flag is set in the USART_ISR register and an interrupt is
generated if PEIE is set in the USART_CR1 register. The PE flag is cleared by software
writing 1 to the PECF in the USART_ICR register.

Parity generation in transmission
If the PCE bit is set in USART_CR1, then the MSB bit of the data written in the data register
is transmitted but is changed by the parity bit (even number of “1s” if even parity is selected
(PS=0) or an odd number of “1s” if odd parity is selected (PS=1)).

908/1141

DocID022558 Rev 8

RM0316

29.5.10

Universal synchronous asynchronous receiver transmitter (USART)

USART LIN (local interconnection network) mode
This section is relevant only when LIN mode is supported. Please refer to Section 29.4:
USART implementation on page 887.
The LIN mode is selected by setting the LINEN bit in the USART_CR2 register. In LIN
mode, the following bits must be kept cleared:
•

STOP[1:0] and CLKEN in the USART_CR2 register,

•

SCEN, HDSEL and IREN in the USART_CR3 register.

LIN transmission
The procedure explained in Section 29.5.2: USART transmitter has to be applied for LIN
Master transmission. It must be the same as for normal USART transmission with the
following differences:
•

Clear the M bits to configure 8-bit word length.

•

Set the LINEN bit to enter LIN mode. In this case, setting the SBKRQ bit sends 13 ‘0’
bits as a break character. Then 2 bits of value ‘1’ are sent to allow the next start
detection.

LIN reception
When LIN mode is enabled, the break detection circuit is activated. The detection is totally
independent from the normal USART receiver. A break can be detected whenever it occurs,
during Idle state or during a frame.
When the receiver is enabled (RE=1 in USART_CR1), the circuit looks at the RX input for a
start signal. The method for detecting start bits is the same when searching break
characters or data. After a start bit has been detected, the circuit samples the next bits
exactly like for the data (on the 8th, 9th and 10th samples). If 10 (when the LBDL = 0 in
USART_CR2) or 11 (when LBDL=1 in USART_CR2) consecutive bits are detected as ‘0,
and are followed by a delimiter character, the LBDF flag is set in USART_ISR. If the LBDIE
bit=1, an interrupt is generated. Before validating the break, the delimiter is checked for as it
signifies that the RX line has returned to a high level.
If a ‘1’ is sampled before the 10 or 11 have occurred, the break detection circuit cancels the
current detection and searches for a start bit again.
If the LIN mode is disabled (LINEN=0), the receiver continues working as normal USART,
without taking into account the break detection.
If the LIN mode is enabled (LINEN=1), as soon as a framing error occurs (i.e. stop bit
detected at ‘0’, which will be the case for any break frame), the receiver stops until the break
detection circuit receives either a ‘1’, if the break word was not complete, or a delimiter
character if a break has been detected.
The behavior of the break detector state machine and the break flag is shown on the
Figure 332: Break detection in LIN mode (11-bit break length - LBDL bit is set) on page 910.
Examples of break frames are given on Figure 333: Break detection in LIN mode vs.
Framing error detection on page 911.

DocID022558 Rev 8

909/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Figure 332. Break detection in LIN mode (11-bit break length - LBDL bit is set)

&DVHEUHDNVLJQDOQRWORQJHQRXJK !EUHDNGLVFDUGHG/%')LVQRWVHW
%UHDNIUDPH

5;OLQH
&DSWXUHVWUREH
%UHDNVWDWH
PDFKLQH

,GOH

%LW %LW %LW %LW


5HDGVDPSOHV







%LW %LW %LW






%LW %LW %LW %LW






,GOH



&DVHEUHDNVLJQDOMXVWORQJHQRXJK !EUHDNGHWHFWHG/%')LVVHW
%UHDNIUDPH

5;OLQH

'HOLPLWHULVLPPHGLDWH
&DSWXUHVWUREH
%UHDNVWDWH
PDFKLQH

,GOH

%LW %LW %LW %LW


5HDGVDPSOHV







%LW %LW %LW






%LW %LW %LW %






,GOH



/%')

&DVHEUHDNVLJQDOORQJHQRXJK !EUHDNGHWHFWHG/%')LVVHW
%UHDNIUDPH

5;OLQH
&DSWXUHVWUREH
%UHDNVWDWH
,GOH
PDFKLQH
5HDGVDPSOHV

%LW %LW %LW %LW








%LW %LW %LW






%LW %LW %LW %LW ZDLWGHOLPLWHU ,GOH








/%')

06Y9

910/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 333. Break detection in LIN mode vs. Framing error detection
&DVHEUHDNRFFXUULQJDIWHUDQ,GOH
5;OLQH

GDWD

,'/(

%5($.
GDWDWLPH

GDWD [

GDWD KHDGHU

GDWDWLPH

5;1()(
/%')

&DVHEUHDNRFFXUULQJZKLOHGDWDLVEHLQJUHFHLYHG
5;OLQH

GDWD

GDWD

%5($.

GDWDWLPH

GDWD [

GDWD KHDGHU

GDWDWLPH

5;1()(
/%')
06Y9

29.5.11

USART synchronous mode
The synchronous mode is selected by writing the CLKEN bit in the USART_CR2 register to
1. In synchronous mode, the following bits must be kept cleared:
•

LINEN bit in the USART_CR2 register,

•

SCEN, HDSEL and IREN bits in the USART_CR3 register.

In this mode, the USART can be used to control bidirectional synchronous serial
communications in master mode. The CK pin is the output of the USART transmitter clock.
No clock pulses are sent to the CK pin during start bit and stop bit. Depending on the state
of the LBCL bit in the USART_CR2 register, clock pulses are, or are not, generated during
the last valid data bit (address mark). The CPOL bit in the USART_CR2 register is used to
select the clock polarity, and the CPHA bit in the USART_CR2 register is used to select the
phase of the external clock (see Figure 334, Figure 335 and Figure 336).
During the Idle state, preamble and send break, the external CK clock is not activated.
In synchronous mode the USART transmitter works exactly like in asynchronous mode. But
as CK is synchronized with TX (according to CPOL and CPHA), the data on TX is
synchronous.
In this mode the USART receiver works in a different manner compared to the
asynchronous mode. If RE=1, the data is sampled on CK (rising or falling edge, depending
on CPOL and CPHA), without any oversampling. A setup and a hold time must be
respected (which depends on the baud rate: 1/16 bit duration).

DocID022558 Rev 8

911/1141
951

Universal synchronous asynchronous receiver transmitter (USART)
Note:

RM0316

The CK pin works in conjunction with the TX pin. Thus, the clock is provided only if the
transmitter is enabled (TE=1) and data is being transmitted (the data register USART_TDR
written). This means that it is not possible to receive synchronous data without transmitting
data.
The LBCL, CPOL and CPHA bits have to be selected when the USART is disabled (UE=0)
to ensure that the clock pulses function correctly.
Figure 334. USART example of synchronous transmission

5;
7;

'DWDRXW
'DWDLQ
6\QFKURQRXVGHYLFH
HJVODYH63,

86$57

&ORFN

&.

06Y9

Figure 335. USART data clock timing diagram (M bits = 00)
,GOHRUSUHFHGLQJ
6WDUW
WUDQVPLVVLRQ

,GOHRUQH[W
6WRS WUDQVPLVVLRQ

0ELWV 

&ORFN &32/ &3+$ 
&ORFN &32/ &3+$ 

&ORFN &32/ &3+$ 
&ORFN &32/ &3+$ 
'DWDRQ7;
IURPPDVWHU


6WDUW

'DWDRQ5;
IURPVODYH

























/6%



06% 6WRS

06%

/6%
&DSWXUHVWUREH

/%&/ELWFRQWUROVODVWGDWDSXOVH
06Y9

912/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 336. USART data clock timing diagram (M bits = 01)
,GOHRU
SUHFHGLQJ 6WDUW
WUDQVPLVVLRQ

6WRS

0ELWV  GDWDELWV

,GOHRUQH[W
WUDQVPLVVLRQ

&ORFN &32/ 
&3+$ 
&ORFN &32/ 
&3+$ 
&ORFN &32/ 
&3+$ 
&ORFN &32/ 
&3+$ 
'DWDRQ7;
IURPPDVWHU

















6WDUW /6%

'DWDRQ5;
IURPVODYH




06%













/6%

&DSWXUH
VWUREH



6WRS


06%

/%&/ELWFRQWUROVODVWGDWDSXOVH
06Y9

Figure 337. RX data setup/hold time

&.
FDSWXUHVWUREHRQ&.ULVLQJ
HGJHLQWKLVH[DPSOH
'DWDRQ5; IURPVODYH

9DOLG'$7$ELW

W6(783

W+2/'

W6(783 W+2/'ELWWLPH
06Y9

Note:

The function of CK is different in Smartcard mode. Refer to Section 29.5.13: USART
Smartcard mode for more details.

DocID022558 Rev 8

913/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

29.5.12

RM0316

USART Single-wire Half-duplex communication
Single-wire Half-duplex mode is selected by setting the HDSEL bit in the USART_CR3
register. In this mode, the following bits must be kept cleared:
•

LINEN and CLKEN bits in the USART_CR2 register,

•

SCEN and IREN bits in the USART_CR3 register.

The USART can be configured to follow a Single-wire Half-duplex protocol where the TX
and RX lines are internally connected. The selection between half- and Full-duplex
communication is made with a control bit HDSEL in USART_CR3.
As soon as HDSEL is written to 1:
•

The TX and RX lines are internally connected

•

The RX pin is no longer used

•

The TX pin is always released when no data is transmitted. Thus, it acts as a standard
I/O in idle or in reception. It means that the I/O must be configured so that TX is
configured as alternate function open-drain with an external pull-up.

Apart from this, the communication protocol is similar to normal USART mode. Any conflicts
on the line must be managed by software (by the use of a centralized arbiter, for instance).
In particular, the transmission is never blocked by hardware and continues as soon as data
is written in the data register while the TE bit is set.

29.5.13

USART Smartcard mode
This section is relevant only when Smartcard mode is supported. Please refer to
Section 29.4: USART implementation on page 887.
Smartcard mode is selected by setting the SCEN bit in the USART_CR3 register. In
Smartcard mode, the following bits must be kept cleared:
•

LINEN bit in the USART_CR2 register,

•

HDSEL and IREN bits in the USART_CR3 register.

Moreover, the CLKEN bit may be set in order to provide a clock to the smartcard.
The smartcard interface is designed to support asynchronous protocol for smartcards as
defined in the ISO 7816-3 standard. Both T=0 (character mode) and T=1 (block mode) are
supported.
The USART should be configured as:
•

8 bits plus parity: where word length is set to 8 bits and PCE=1 in the USART_CR1
register

•

1.5 stop bits: where STOP=11 in the USART_CR2 register. It is also possible to choose
0.5 stop bit for receiving.

In T=0 (character) mode, the parity error is indicated at the end of each character during the
guard time period.
Figure 338 shows examples of what can be seen on the data line with and without parity
error.

914/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 338. ISO 7816-3 asynchronous protocol
:LWKRXW3DULW\HUURU
6





*XDUGWLPH












S

6WDUWELW
:LWK3DULW\HUURU
6



*XDUGWLPH










6WDUWELW





S
/LQHSXOOHGORZE\UHFHLYHU
GXULQJVWRSLQFDVHRISDULW\HUURU
06Y9

When connected to a smartcard, the TX output of the USART drives a bidirectional line that
is also driven by the smartcard. The TX pin must be configured as open drain.
Smartcard mode implements a single wire half duplex communication protocol.
•

Transmission of data from the transmit shift register is guaranteed to be delayed by a
minimum of 1/2 baud clock. In normal operation a full transmit shift register starts
shifting on the next baud clock edge. In Smartcard mode this transmission is further
delayed by a guaranteed 1/2 baud clock.

•

In transmission, if the smartcard detects a parity error, it signals this condition to the
USART by driving the line low (NACK). This NACK signal (pulling transmit line low for 1
baud clock) causes a framing error on the transmitter side (configured with 1.5 stop
bits). The USART can handle automatic re-sending of data according to the protocol.
The number of retries is programmed in the SCARCNT bit field. If the USART
continues receiving the NACK after the programmed number of retries, it stops
transmitting and signals the error as a framing error. The TXE bit can be set using the
TXFRQ bit in the USART_RQR register.

•

Smartcard auto-retry in transmission: a delay of 2.5 baud periods is inserted between
the NACK detection by the USART and the start bit of the repeated character. The TC
bit is set immediately at the end of reception of the last repeated character (no guardtime). If the software wants to repeat it again, it must insure the minimum 2 baud
periods required by the standard.

•

If a parity error is detected during reception of a frame programmed with a 1.5 stop bits
period, the transmit line is pulled low for a baud clock period after the completion of the
receive frame. This is to indicate to the smartcard that the data transmitted to the
USART has not been correctly received. A parity error is NACKed by the receiver if the
NACK control bit is set, otherwise a NACK is not transmitted (to be used in T=1 mode).
If the received character is erroneous, the RXNE/receive DMA request is not activated.
According to the protocol specification, the smartcard must resend the same character.
If the received character is still erroneous after the maximum number of retries
specified in the SCARCNT bit field, the USART stops transmitting the NACK and
signals the error as a parity error.

•

Smartcard auto-retry in reception: the BUSY flag remains set if the USART NACKs the
card but the card doesn’t repeat the character.

DocID022558 Rev 8

915/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

Note:

RM0316

•

In transmission, the USART inserts the Guard Time (as programmed in the Guard Time
register) between two successive characters. As the Guard Time is measured after the
stop bit of the previous character, the GT[7:0] register must be programmed to the
desired CGT (Character Guard Time, as defined by the 7816-3 specification) minus 12
(the duration of one character).

•

The assertion of the TC flag can be delayed by programming the Guard Time register.
In normal operation, TC is asserted when the transmit shift register is empty and no
further transmit requests are outstanding. In Smartcard mode an empty transmit shift
register triggers the Guard Time counter to count up to the programmed value in the
Guard Time register. TC is forced low during this time. When the Guard Time counter
reaches the programmed value TC is asserted high.

•

The de-assertion of TC flag is unaffected by Smartcard mode.

•

If a framing error is detected on the transmitter end (due to a NACK from the receiver),
the NACK is not detected as a start bit by the receive block of the transmitter.
According to the ISO protocol, the duration of the received NACK can be 1 or 2 baud
clock periods.

•

On the receiver side, if a parity error is detected and a NACK is transmitted the receiver
does not detect the NACK as a start bit.

A break character is not significant in Smartcard mode. A 0x00 data with a framing error is
treated as data and not as a break.
No Idle frame is transmitted when toggling the TE bit. The Idle frame (as defined for the
other configurations) is not defined by the ISO protocol.
Figure 339 details how the NACK signal is sampled by the USART. In this example the
USART is transmitting data and is configured with 1.5 stop bits. The receiver part of the
USART is enabled in order to check the integrity of the data and the NACK signal.
Figure 339. Parity error detection using the 1.5 stop bits
%LW

3DULW\ELW

ELWWLPH

6WRSELW

ELWWLPH

6DPSOLQJDW

6DPSOLQJDW

WKWKWK

WKWKWK
ELWWLPH

6DPSOLQJDW

6DPSOLQJDW

WKWKWK

WKWKWK
06Y9

The USART can provide a clock to the smartcard through the CK output. In Smartcard
mode, CK is not associated to the communication but is simply derived from the internal
peripheral input clock through a 5-bit prescaler. The division ratio is configured in the
prescaler register USART_GTPR. CK frequency can be programmed from fCK/2 to fCK/62,
where fCK is the peripheral input clock.

916/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Block mode (T=1)
In T=1 (block) mode, the parity error transmission is deactivated, by clearing the NACK bit in
the UART_CR3 register.
When requesting a read from the smartcard, in block mode, the software must enable the
receiver Timeout feature by setting the RTOEN bit in the USART_CR2 register and program
the RTO bits field in the RTOR register to the BWT (block wait time) - 11 value. If no answer
is received from the card before the expiration of this period, the RTOF flag will be set and a
timeout interrupt will be generated (if RTOIE bit in the USART_CR1 register is set). If the
first character is received before the expiration of the period, it is signaled by the RXNE
interrupt.
Note:

The RXNE interrupt must be enabled even when using the USART in DMA mode to read
from the smartcard in block mode. In parallel, the DMA must be enabled only after the first
received byte.
After the reception of the first character (RXNE interrupt), the RTO bit fields in the RTOR
register must be programmed to the CWT (character wait time) - 11 value, in order to allow
the automatic check of the maximum wait time between two consecutive characters. This
time is expressed in baudtime units. If the smartcard does not send a new character in less
than the CWT period after the end of the previous character, the USART signals this to the
software through the RTOF flag and interrupt (when RTOIE bit is set).

Note:

The RTO counter starts counting:
- From the end of the stop bit in case STOP = 00.
- From the end of the second stop bit in case of STOP = 10.
- 1 bit duration after the beginning of the STOP bit in case STOP = 11.
- From the beginning of the STOP bit in case STOP = 01.
As in the Smartcard protocol definition, the BWT/CWT values are defined from the
beginning (start bit) of the last character. The RTO register must be programmed to BWT 11 or CWT -11, respectively, taking into account the length of the last character itself.
A block length counter is used to count all the characters received by the USART. This
counter is reset when the USART is transmitting (TXE=0). The length of the block is
communicated by the smartcard in the third byte of the block (prologue field). This value
must be programmed to the BLEN field in the USART_RTOR register. when using DMA
mode, before the start of the block, this register field must be programmed to the minimum
value (0x0). with this value, an interrupt is generated after the 4th received character. The
software must read the LEN field (third byte), its value must be read from the receive buffer.
In interrupt driven receive mode, the length of the block may be checked by software or by
programming the BLEN value. However, before the start of the block, the maximum value of
BLEN (0xFF) may be programmed. The real value will be programmed after the reception of
the third character.
If the block is using the LRC longitudinal redundancy check (1 epilogue byte), the
BLEN=LEN. If the block is using the CRC mechanism (2 epilogue bytes), BLEN=LEN+1
must be programmed. The total block length (including prologue, epilogue and information
fields) equals BLEN+4. The end of the block is signaled to the software through the EOBF
flag and interrupt (when EOBIE bit is set).
In case of an error in the block length, the end of the block is signaled by the RTO interrupt
(Character wait Time overflow).

DocID022558 Rev 8

917/1141
951

Universal synchronous asynchronous receiver transmitter (USART)
Note:

RM0316

The error checking code (LRC/CRC) must be computed/verified by software.

Direct and inverse convention
The Smartcard protocol defines two conventions: direct and inverse.
The direct convention is defined as: LSB first, logical bit value of 1 corresponds to a H state
of the line and parity is even. In order to use this convention, the following control bits must
be programmed: MSBFIRST=0, DATAINV=0 (default values).
The inverse convention is defined as: MSB first, logical bit value 1 corresponds to an L state
on the signal line and parity is even. In order to use this convention, the following control bits
must be programmed: MSBFIRST=1, DATAINV=1.
Note:

When logical data values are inverted (0=H, 1=L), the parity bit is also inverted in the same
way.
In order to recognize the card convention, the card sends the initial character, TS, as the
first character of the ATR (Answer To Reset) frame. The two possible patterns for the TS
are: LHHL LLL LLH and LHHL HHH LLH.
•

(H) LHHL LLL LLH sets up the inverse convention: state L encodes value 1 and
moment 2 conveys the most significant bit (MSB first). when decoded by inverse
convention, the conveyed byte is equal to '3F'.

•

(H) LHHL HHH LLH sets up the direct convention: state H encodes value 1 and
moment 2 conveys the least significant bit (LSB first). when decoded by direct
convention, the conveyed byte is equal to '3B'.

Character parity is correct when there is an even number of bits set to 1 in the nine
moments 2 to 10.
As the USART does not know which convention is used by the card, it needs to be able to
recognize either pattern and act accordingly. The pattern recognition is not done in
hardware, but through a software sequence. Moreover, supposing that the USART is
configured in direct convention (default) and the card answers with the inverse convention,
TS = LHHL LLL LLH => the USART received character will be ‘03’ and the parity will be odd.
Therefore, two methods are available for TS pattern recognition:
Method 1
The USART is programmed in standard Smartcard mode/direct convention. In this case, the
TS pattern reception generates a parity error interrupt and error signal to the card.
•

The parity error interrupt informs the software that the card didn’t answer correctly in
direct convention. Software then reprograms the USART for inverse convention

•

In response to the error signal, the card retries the same TS character, and it will be
correctly received this time, by the reprogrammed USART

Alternatively, in answer to the parity error interrupt, the software may decide to reprogram
the USART and to also generate a new reset command to the card, then wait again for the
TS.

918/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Method 2
The USART is programmed in 9-bit/no-parity mode, no bit inversion. In this mode it receives
any of the two TS patterns as:
(H) LHHL LLL LLH = 0x103 -> inverse convention to be chosen
(H) LHHL HHH LLH = 0x13B -> direct convention to be chosen
The software checks the received character against these two patterns and, if any of them
match, then programs the USART accordingly for the next character reception.
If none of the two is recognized, a card reset may be generated in order to restart the
negotiation.

29.5.14

USART IrDA SIR ENDEC block
This section is relevant only when IrDA mode is supported. Please refer to Section 29.4:
USART implementation on page 887.
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 340).
The SIR Transmit encoder modulates the Non Return to Zero (NRZ) transmit bit stream
output from USART. The output pulse stream is transmitted to an external output driver and
infrared LED. USART supports only bit rates up to 115.2 Kbps for the SIR ENDEC. In
normal mode the transmitted pulse width is specified as 3/16 of a bit period.
The SIR receive decoder demodulates the return-to-zero bit stream from the infrared
detector and outputs the received NRZ serial bit stream to the USART. The decoder input is
normally high (marking state) in the Idle state. The transmit encoder output has the opposite
polarity to the decoder input. A start bit is detected when the decoder input is low.
•

IrDA is a half duplex communication protocol. If the Transmitter is busy (when the
USART is sending data to the IrDA encoder), any data on the IrDA receive line is
ignored by the IrDA decoder and if the Receiver is busy (when the USART is receiving
decoded data from the IrDA decoder), data on the TX from the USART to IrDA is not
encoded. while receiving data, transmission should be avoided as the data to be
transmitted could be corrupted.

•

A 0 is transmitted as a high pulse and a 1 is transmitted as a 0. The width of the pulse
is specified as 3/16th of the selected bit period in normal mode (see Figure 341).

•

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.

DocID022558 Rev 8

919/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

•

The IrDA specification requires the acceptance of pulses greater than 1.41 µs. The
acceptable pulse width is programmable. Glitch detection logic on the receiver end
filters out pulses of width less than 2 PSC periods (PSC is the prescaler value
programmed in the USART_GTPR). Pulses of width less than 1 PSC period are always
rejected, but those of width greater than one and less than two periods may be
accepted or rejected, those greater than 2 periods will be accepted as a pulse. The
IrDA encoder/decoder doesn’t work when PSC=0.

•

The receiver can communicate with a low-power transmitter.

•

In IrDA mode, the STOP bits in the USART_CR2 register must be configured to “1 stop
bit”.

IrDA low-power mode
Transmitter
In low-power mode the pulse width is not maintained at 3/16 of the bit period. Instead, the
width of the pulse is 3 times the low-power baud rate which can be a minimum of 1.42 MHz.
Generally, this value is 1.8432 MHz (1.42 MHz < PSC< 2.12 MHz). A low-power mode
programmable divisor divides the system clock to achieve this value.
Receiver
Receiving in low-power mode is similar to receiving in normal mode. For glitch detection the
USART should discard pulses of duration shorter than 1 PSC period. A valid low is accepted
only if its duration is greater than 2 periods of the IrDA low-power Baud clock (PSC value in
the USART_GTPR).
Note:

A pulse of width less than two and greater than one PSC period(s) may or may not be
rejected.
The receiver set up time should be managed by software. The IrDA physical layer
specification specifies a minimum of 10 ms delay between transmission and reception (IrDA
is a half duplex protocol).
Figure 340. IrDA SIR ENDEC- block diagram

7;

6,5(1
25

86$57

5;

86$57B7;

6,5
7UDQVPLW
(QFRGHU

,U'$B287

6,5
5HFHLYH
'(FRGHU

,U'$B,1
86$57B5;

06Y9

920/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 341. IrDA data modulation (3/16) -Normal Mode

7;

6WDUW
ELW


6WRS
ELW


















,U'$B287
%LWSHULRG

,U'$B,1

5;























06Y9

29.5.15

USART continuous communication in DMA mode
The USART is capable of performing continuous communication using the DMA. The DMA
requests for Rx buffer and Tx buffer are generated independently.

Note:

Please refer to Section 29.4: USART implementation on page 887 to determine if the DMA
mode is supported. If DMA is not supported, use the USART as explained in Section 29.5.2:
USART transmitter or Section 29.5.3: USART receiver. To perform continuous
communication, the user can clear the TXE/ RXNE flags In the USART_ISR register.

Transmission using DMA
DMA mode can be enabled for transmission by setting DMAT bit in the USART_CR3
register. Data is loaded from a SRAM area configured using the DMA peripheral (refer to
Section 13: Direct memory access controller (DMA) on page 263) to the USART_TDR
register whenever the TXE bit is set. To map a DMA channel for USART transmission, use
the following procedure (x denotes the channel number):
1.

Write the USART_TDR register address in the DMA control register to configure it as
the destination of the transfer. The data is moved to this address from memory after
each TXE event.

2.

Write the memory address in the DMA control register to configure it as the source of
the transfer. The data is loaded into the USART_TDR register from this memory area
after each TXE event.

3.

Configure the total number of bytes to be transferred to the DMA control register.

4.

Configure the channel priority in the DMA register

5.

Configure DMA interrupt generation after half/ full transfer as required by the
application.

6.

Clear the TC flag in the USART_ISR register by setting the TCCF bit in the
USART_ICR register.

7.

Activate the channel in the DMA register.

When the number of data transfers programmed in the DMA Controller is reached, the DMA
controller generates an interrupt on the DMA channel interrupt vector.
In transmission mode, once the DMA has written all the data to be transmitted (the TCIF flag
is set in the DMA_ISR register), the TC flag can be monitored to make sure that the USART

DocID022558 Rev 8

921/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

communication is complete. This is required to avoid corrupting the last transmission before
disabling the USART or entering Stop mode. Software must wait until TC=1. The TC flag
remains cleared during all data transfers and it is set by hardware at the end of transmission
of the last frame.
Figure 342. Transmission using DMA
,GOHSUHDPEOH

)UDPH

)UDPH

)UDPH

7;OLQH
6HWE\KDUGZDUH
FOHDUHGE\'0$UHDG

6HWE\KDUGZDUH
FOHDUHGE\'0$UHDG

7;(IODJ

6HWE\KDUGZDUH

,JQRUHGE\WKH'0$EHFDXVH
WKHWUDQVIHULVFRPSOHWH

'0$UHTXHVW
)

86$57B7'5

)

)

7&IODJ

6HWE\
KDUGZDUH

'0$ZULWHV
86$57B7'5
'0$7&,)IODJ
WUDQVIHU
FRPSOHWH

6HWE\KDUGZDUH

6RIWZDUH
FRQILJXUHV'0$ '0$ZULWHV '0$ZULWHV '0$ZULWHV
)LQWR
)LQWR
)LQWR
WRVHQGGDWD
EORFNVDQG 86$57B7'5 86$57B7'5 86$57B7'5
HQDEOHV86$57

&OHDUHG
E\
VRIWZDUH

7KH'0$
WUDQVIHULV
FRPSOHWH
7&,) LQ
'0$B,65

6RIWZDUHZDLWVXQWLO7& 

AIB

Reception using DMA
DMA mode can be enabled for reception by setting the DMAR bit in USART_CR3 register.
Data is loaded from the USART_RDR register to a SRAM area configured using the DMA
peripheral (refer to Section 13: Direct memory access controller (DMA) on page 263)
whenever a data byte is received. To map a DMA channel for USART reception, use the
following procedure:
1.

Write the USART_RDR register address in the DMA control register to configure it as
the source of the transfer. The data is moved from this address to the memory after
each RXNE event.

2.

Write the memory address in the DMA control register to configure it as the destination
of the transfer. The data is loaded from USART_RDR to this memory area after each
RXNE event.

3.

Configure the total number of bytes to be transferred to the DMA control register.

4.

Configure the channel priority in the DMA control register

5.

Configure interrupt generation after half/ full transfer as required by the application.

6.

Activate the channel in the DMA control register.

When the number of data transfers programmed in the DMA Controller is reached, the DMA
controller generates an interrupt on the DMA channel interrupt vector.

922/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 343. Reception using DMA
)UDPH

)UDPH

)UDPH

7;OLQH
6HWE\KDUGZDUH
FOHDUHGE\'0$UHDG

5;1(IODJ
'0$UHTXHVW

)

)

86$57B7'5

)

'0$UHDGV
86$57B7'5
'0$7&,)IODJ
WUDQVIHUFRPSOHWH

6RIWZDUHFRQILJXUHVWKH
'0$WRUHFHLYHGDWD
EORFNVDQGHQDEOHV
WKH86$57

&OHDUHG
E\
VRIWZDUH

6HWE\KDUGZDUH

'0$UHDGV)
IURP86$57B7'5

'0$UHDGV)
IURP86$57B7'5

7KH'0$WUDQVIHU
'0$UHDGV)
LVFRPSOHWH
IURP86$57B7'5 7&,) LQ
'0$B,65
DLE

Error flagging and interrupt generation in multibuffer communication
In multibuffer communication if any error occurs during the transaction the error flag is
asserted after the current byte. An interrupt is generated if the interrupt enable flag is set.
For framing error, overrun error and noise flag which are asserted with RXNE in single byte
reception, there is a separate error flag interrupt enable bit (EIE bit in the USART_CR3
register), which, if set, enables an interrupt after the current byte if any of these errors occur.

29.5.16

RS232 hardware flow control and RS485 driver enable
using USART
It is possible to control the serial data flow between 2 devices by using the CTS input and
the RTS output. The Figure 344 shows how to connect 2 devices in this mode:
Figure 344. Hardware flow control between 2 USARTs

86$57

86$57
7;
7;FLUFXLW

&76
5;

5;
576

5;FLUFXLW

7;

5;FLUFXLW

7;FLUFXLW
576

&76

06Y9

DocID022558 Rev 8

923/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

RS232 RTS and CTS flow control can be enabled independently by writing the RTSE and
CTSE bits respectively to 1 (in the USART_CR3 register).

RS232 RTS flow control
If the RTS flow control is enabled (RTSE=1), then RTS is asserted (tied low) as long as the
USART receiver is ready to receive a new data. When the receive register is full, RTS is deasserted, indicating that the transmission is expected to stop at the end of the current frame.
Figure 345 shows an example of communication with RTS flow control enabled.
Figure 345. RS232 RTS flow control

5;

6WDUW
ELW

'DWD

6WRS
6WDUW
,GOH
ELW
ELW

'DWD

6WRS
ELW

576

5;1(

5;1(
'DWDUHDG
'DWDFDQQRZEHWUDQVPLWWHG

06Y9

RS232 CTS flow control
If the CTS flow control is enabled (CTSE=1), then the transmitter checks the CTS input
before transmitting the next frame. If CTS is asserted (tied low), then the next data is
transmitted (assuming that data is to be transmitted, in other words, if TXE=0), else the
transmission does not occur. when CTS is de-asserted during a transmission, the current
transmission is completed before the transmitter stops.
When CTSE=1, the CTSIF status bit is automatically set by hardware as soon as the CTS
input toggles. It indicates when the receiver becomes ready or not ready for communication.
An interrupt is generated if the CTSIE bit in the USART_CR3 register is set. Figure 346
shows an example of communication with CTS flow control enabled.

924/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
Figure 346. RS232 CTS flow control
&76

&76

&76
7UDQVPLWGDWDUHJLVWHU
7'5

'DWD

7;

'DWD

HPSW\

6WRS 6WDUW
ELW ELW

HPSW\

'DWD

6WRS
6WDUW
,GOH
ELW
ELW

'DWD

:ULWLQJGDWDLQ7'5

'DWD

7UDQVPLVVLRQRI'DWDLV
GHOD\HGXQWLO&76 
06Y9

Note:

For correct behavior, CTS must be asserted at least 3 USART clock source periods before
the end of the current character. In addition it should be noted that the CTSCF flag may not
be set for pulses shorter than 2 x PCLK periods.

RS485 Driver Enable
The driver enable feature is enabled by setting bit DEM in the USART_CR3 control register.
This allows the user to activate the external transceiver control, through the DE (Driver
Enable) signal. The assertion time is the time between the activation of the DE signal and
the beginning of the START bit. It is programmed using the DEAT [4:0] bit fields in the
USART_CR1 control register. The de-assertion time is the time between the end of the last
stop bit, in a transmitted message, and the de-activation of the DE signal. It is programmed
using the DEDT [4:0] bit fields in the USART_CR1 control register. The polarity of the DE
signal can be configured using the DEP bit in the USART_CR3 control register.
In USART, the DEAT and DEDT are expressed in sample time units (1/8 or 1/16 bit duration,
depending on the oversampling rate).

29.5.17

Wakeup from Stop mode using USART
The USART is able to wake up the MCU from Stopmode when the UESM bit is set and the
USART clock is set to HSI or LSE (refer to Section Reset and clock control (RCC)).
•

USART source clock is HSI
If during stop mode the HSI clock is switched OFF, when a falling edge on the USART
receive line is detected, the USART interface requests the HSI clock to be switched
ON. The HSI clock is then used for the frame reception.

•

–

If the wakeup event is verified, the MCU wakes up from low-power mode and data
reception goes on normally.

–

If the wakeup event is not verified, the HSI clock is switched OFF again, the MCU
is not waken up and stays in low-power mode and the clock request is released.

USART source clock is LSE
Same principle as described in case of USART source clock is HSI with the difference
that the LSE is ON in stop mode, but the LSE clock is not propagated to USART if the
DocID022558 Rev 8

925/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

USART is not requesting it. The LSE clock is not OFF but there is a clock gating to
avoid useless consumption.
The MCU wakeup from Stop mode can be done using the standard RXNE interrupt. In this
case, the RXNEIE bit must be set before entering Stop mode.
Alternatively, a specific interrupt may be selected through the WUS bit fields.
In order to be able to wake up the MCU from Stop mode, the UESM bit in the USART_CR1
control register must be set prior to entering Stop mode.
When the wakeup event is detected, the WUF flag is set by hardware and a wakeup
interrupt is generated if the WUFIE bit is set.
Note:

Before entering Stop mode, the user must ensure that the USART is not performing a
transfer. BUSY flag cannot ensure that Stop mode is never entered during a running
reception.
The WUF flag is set when a wakeup event is detected, independently of whether the MCU is
in Stop or in an active mode.
When entering Stop mode just after having initialized and enabled the receiver, the REACK
bit must be checked to ensure the USART is actually enabled.
When DMA is used for reception, it must be disabled before entering Stop mode and reenabled upon exit from Stop mode.
The wakeup from Stop mode feature is not available for all modes. For example it doesn’t
work in SPI mode because the SPI operates in master mode only.

Using Mute mode with Stop mode
If the USART is put into Mute mode before entering Stop mode:
•

Wakeup from Mute mode on idle detection must not be used, because idle detection
cannot work in Stop mode.

•

If the wakeup from Mute mode on address match is used, then the source of wake-up
from Stop mode must also be the address match. If the RXNE flag is set when entering
the Stop mode, the interface will remain in mute mode upon address match and wake
up from Stop.

•

If the USART is configured to wake up the MCU from Stop mode on START bit
detection, the WUF flag is set, but the RXNE flag is not set.

Determining the maximum USART baud rate allowing to wakeup correctly
from Stop mode when the USART clock source is the HSI clock
The maximum baud rate allowing to wakeup correctly from stop mode depends on:
•

the parameter tWUUSART provided in the device datasheet

•

the USART receiver tolerance provided in the Section 29.5.5: Tolerance of the USART
receiver to clock deviation.

Let us take this example: OVER8 = 0, M bits = 10, ONEBIT = 1, BRR [3:0] = 0000.
In these conditions, according to Table 160: Tolerance of the USART receiver when BRR
[3:0] = 0000, the USART receiver tolerance is 4.86 %.
DTRA + DQUANT + DREC + DTCL + DWU < USART receiver's tolerance
DWU max = tWUUSART / (9 x Tbit Min)
Tbit Min = tWUUSART / (9 x DWU max)
926/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)
If we consider an ideal case where the parameters DTRA, DQUANT, DREC and DTCL are
at 0%, the DWU max is 4.86 %. In reality, we need to consider at least the HSI inaccuracy.
Let us consider HSI inaccuracy = 1 %, tWUUSART = 3.125 μs (in case of wakeup from stop
mode, with the main regulator in Run mode).
DWU max = 4.86 % - 1 % = 3.86 %
Tbit min = 3.125 μs / (9 ₓ 3.86 %) = 9 μs
In these conditions, the maximum baud rate allowing to wakeup correctly from Stop mode is
1/9 μs = 111 Kbaud.

29.6

USART low-power modes
Table 163. Effect of low-power modes on the USART
Mode

29.7

Description

Sleep

No effect. USART interrupt causes the device to exit Sleep mode.

Stop

The USART is able to wake up the MCU from Stop mode when the UESM
bit is set and the USART clock is set to HSI or LSE.
The MCU wakeup from Stop mode can be done using either a standard
RXNE or a WUF interrupt.

Standby

The USART is powered down and must be reinitialized when the device
has exited from Standby mode.

USART interrupts
Table 164. USART interrupt requests
Interrupt event
Transmit data register empty
CTS interrupt
Transmission Complete
Receive data register not empty (data ready to be read)

Event flag

Enable Control
bit

TXE

TXEIE

CTSIF

CTSIE

TC

TCIE

RXNE

RXNEIE

Overrun error detected

ORE

Idle line detected

IDLE

IDLEIE

PE

PEIE

LBDF

LBDIE

NF or ORE or FE

EIE

Character match

CMF

CMIE

Receiver timeout

RTOF

RTOIE

End of Block

EOBF

EOBIE

Wakeup from Stop mode

WUF(1)

WUFIE

Parity error
LIN break
Noise Flag, Overrun error and Framing Error in multibuffer
communication.

DocID022558 Rev 8

927/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

1. The WUF interrupt is active only in Stop mode.

The USART interrupt events are connected to the same interrupt vector (see Figure 347).
•

During transmission: Transmission Complete, Clear to Send, Transmit data Register
empty or Framing error (in Smartcard mode) interrupt.

•

During reception: Idle Line detection, Overrun error, Receive data register not empty,
Parity error, LIN break detection, Noise Flag, Framing Error, Character match, etc.

These events generate an interrupt if the corresponding Enable Control Bit is set.
Figure 347. USART interrupt mapping diagram
7&
7&,(
7;(
7;(,(
&76,)
&76,(
,'/(
,'/(,(
86$57
LQWHUUXSW

5;1(,(
25(
5;1(,(
5;1(
3(
3(,(
/%')
/%',(
)(
1)
25(

(,(

&0)
&0,(
572)
572,(
(2%)
(2%,(
:8)
:8),(
06Y9

928/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

29.8

USART registers
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.

29.8.1

Control register 1 (USART_CR1)
Address offset: 0x00
Reset value: 0x0000

31

30

29

28

27

26

Res.

Res.

Res.

M1

EOBIE

RTOIE

rw

rw

rw

25

24

23

22

21

20

19

DEAT[4:0]
rw

rw

rw

18

17

16

rw

rw

DEDT[4:0]
rw

15

14

13

12

11

10

9

8

7

6

OVER8

CMIE

MME

M0

WAKE

PCE

PS

PEIE

TXEIE

TCIE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

5

4

RXNEIE IDLEIE
rw

rw

rw

rw

3

2

1

0

TE

RE

UESM

UE

rw

rw

rw

rw

Bits 31:29 Reserved, must be kept at reset value
Bit 28 M1: Word length
This bit, with bit 12 (M0), determines the word length. It is set or cleared by software.
M[1:0] = 00: 1 Start bit, 8 data bits, n stop bits
M[1:0] = 01: 1 Start bit, 9 data bits, n stop bits
M[1:0] = 10: 1 Start bit, 7 data bits, n stop bits
This bit can only be written when the USART is disabled (UE=0).
Note: In 7-bit data length mode, the Smartcard mode, LIN master mode and Auto baud rate
(0x7F and 0x55 frames detection) are not supported.
Bit 27 EOBIE: End of Block interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated when the EOBF flag is set in the USART_ISR register
Note: If the USART does not support Smartcard mode, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 26 RTOIE: Receiver timeout interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated when the RTOF bit is set in the USART_ISR register.
Note: If the USART does not support the Receiver timeout feature, this bit is reserved and
forced by hardware to ‘0’. Section 29.4: USART implementation on page 887.
Bits 25:21 DEAT[4:0]: Driver Enable assertion time
This 5-bit value defines the time between the activation of the DE (Driver Enable) signal and
the beginning of the start bit. It is expressed in sample time units (1/8 or 1/16 bit duration,
depending on the oversampling rate).
This bit field can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept
cleared. Please refer to Section 29.4: USART implementation on page 887.

DocID022558 Rev 8

929/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Bits 20:16 DEDT[4:0]: Driver Enable de-assertion time
This 5-bit value defines the time between the end of the last stop bit, in a transmitted
message, and the de-activation of the DE (Driver Enable) signal. It is expressed in sample
time units (1/8 or 1/16 bit duration, depending on the oversampling rate).
If the USART_TDR register is written during the DEDT time, the new data is transmitted only
when the DEDT and DEAT times have both elapsed.
This bit field can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept
cleared. Please refer to Section 29.4: USART implementation on page 887.
Bit 15 OVER8: Oversampling mode
0: Oversampling by 16
1: Oversampling by 8
This bit can only be written when the USART is disabled (UE=0).
Note: In LIN, IrDA and modes, this bit must be kept cleared.
Bit 14 CMIE: Character match interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated when the CMF bit is set in the USART_ISR register.
Bit 13 MME: Mute mode enable
This bit activates the mute mode function of the USART. when set, the USART can switch
between the active and mute modes, as defined by the WAKE bit. It is set and cleared by
software.
0: Receiver in active mode permanently
1: Receiver can switch between mute mode and active mode.
Bit 12 M0: Word length
This bit, with bit 28 (M1), determines the word length. It is set or cleared by software. See Bit
28 (M1) description.
This bit can only be written when the USART is disabled (UE=0).
Bit 11 WAKE: Receiver wakeup method
This bit determines the USART wakeup method from Mute mode. It is set or cleared by
software.
0: Idle line
1: Address mark
This bit field can only be written when the USART is disabled (UE=0).
Bit 10 PCE: Parity control enable
This bit selects the hardware parity control (generation and detection). When the parity
control is enabled, the computed parity is inserted at the MSB position (9th bit if M=1; 8th bit
if M=0) and parity is checked on the received data. This bit is set and cleared by software.
Once it is set, PCE is active after the current byte (in reception and in transmission).
0: Parity control disabled
1: Parity control enabled
This bit field can only be written when the USART is disabled (UE=0).
Bit 9 PS: Parity selection
This bit selects the odd or even parity when the parity generation/detection is enabled (PCE
bit set). It is set and cleared by software. The parity will be selected after the current byte.
0: Even parity
1: Odd parity
This bit field can only be written when the USART is disabled (UE=0).

930/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bit 8 PEIE: PE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever PE=1 in the USART_ISR register
Bit 7 TXEIE: interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever TXE=1 in the USART_ISR register
Bit 6 TCIE: Transmission complete interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever TC=1 in the USART_ISR register
Bit 5 RXNEIE: RXNE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever ORE=1 or RXNE=1 in the USART_ISR
register
Bit 4 IDLEIE: IDLE interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: A USART interrupt is generated whenever IDLE=1 in the USART_ISR register
Bit 3 TE: Transmitter enable
This bit enables the transmitter. It is set and cleared by software.
0: Transmitter is disabled
1: Transmitter is enabled
Note: During transmission, a “0” pulse on the TE bit (“0” followed by “1”) sends a preamble
(idle line) after the current word, except in Smartcard mode. In order to generate an idle
character, the TE must not be immediately written to 1. In order to ensure the required
duration, the software can poll the TEACK bit in the USART_ISR register.
In Smartcard mode, when TE is set there is a 1 bit-time delay before the transmission
starts.

DocID022558 Rev 8

931/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

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 UESM: USART enable in Stop mode
When this bit is cleared, the USART is not able to wake up the MCU from Stop mode.
When this bit is set, the USART is able to wake up the MCU from Stop mode, provided that
the USART clock selection is HSI or LSE in the RCC.
This bit is set and cleared by software.
0: USART not able to wake up the MCU from Stop mode.
1: USART able to wake up the MCU from Stop mode. When this function is active, the clock
source for the USART must be HSI or LSE (see Section Reset and clock control (RCC).
Note: It is recommended to set the UESM bit just before entering Stop mode and clear it on
exit from Stop mode.
If the USART does not support the wakeup from Stop feature, this bit is reserved and
forced by hardware to ‘0’. Please refer to Section 29.4: USART implementation on
page 887.
Bit 0 UE: USART enable
When this bit is cleared, the USART prescalers and outputs are stopped immediately, and
current operations are discarded. The configuration of the USART is kept, but all the status
flags, in the USART_ISR are set to their default values. This bit is set and cleared by
software.
0: USART prescaler and outputs disabled, low-power mode
1: USART enabled
Note: In order to go into low-power mode without generating errors on the line, the TE bit
must be reset before and the software must wait for the TC bit in the USART_ISR to be
set before resetting the UE bit.
The DMA requests are also reset when UE = 0 so the DMA channel must be disabled
before resetting the UE bit.

29.8.2

Control register 2 (USART_CR2)
Address offset: 0x04
Reset value: 0x0000

31

30

29

28

27

ADD[7:4]

26

25

24

ADD[3:0]

23
RTOEN

22

21

ABRMOD[1:0]

20

19

18

17

MSBFI
ABREN
DATAINV TXINV
RST

16
RXINV

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

SWAP

LINEN

CLKEN

CPOL

CPHA

LBCL

Res.

LBDIE

LBDL

ADDM7

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

rw

rw

rw

rw

932/1141

STOP[1:0]
rw

rw

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bits 31:28 ADD[7:4]: Address of the USART node
This bit-field gives the address of the USART node or a character code to be recognized.
This is used in multiprocessor communication during Mute mode or Stop mode, for wakeup with 7bit address mark detection. The MSB of the character sent by the transmitter should be equal to 1.
It may also be used for character detection during normal reception, Mute mode inactive (for
example, end of block detection in ModBus protocol). In this case, the whole received character (8bit) is compared to the ADD[7:0] value and CMF flag is set on match.
This bit field can only be written when reception is disabled (RE = 0) or the USART is disabled
(UE=0)
Bits 27:24 ADD[3:0]: Address of the USART node
This bit-field gives the address of the USART node or a character code to be recognized.
This is used in multiprocessor communication during Mute mode or Stop mode, for wakeup with
address mark detection.
This bit field can only be written when reception is disabled (RE = 0) or the USART is disabled
(UE=0)
Bit 23 RTOEN: Receiver timeout enable
This bit is set and cleared by software.
0: Receiver timeout feature disabled.
1: Receiver timeout feature enabled.
When this feature is enabled, the RTOF flag in the USART_ISR register is set if the RX line is idle
(no reception) for the duration programmed in the RTOR (receiver timeout register).
Note: If the USART does not support the Receiver timeout feature, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bits 22:21 ABRMOD[1:0]: Auto baud rate mode
These bits are set and cleared by software.
00: Measurement of the start bit is used to detect the baud rate.
01: Falling edge to falling edge measurement. (the received frame must start with a single bit = 1 ->
Frame = Start10xxxxxx)
10: 0x7F frame detection.
11: 0x55 frame detection
This bit field can only be written when ABREN = 0 or the USART is disabled (UE=0).
Note: If DATAINV=1 and/or MSBFIRST=1 the patterns must be the same on the line, for example
0xAA for MSBFIRST)
If the USART does not support the auto baud rate feature, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 20 ABREN: Auto baud rate enable
This bit is set and cleared by software.
0: Auto baud rate detection is disabled.
1: Auto baud rate detection is enabled.
Note: If the USART does not support the auto baud rate feature, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 19 MSBFIRST: Most significant bit first
This bit is set and cleared by software.
0: data is transmitted/received with data bit 0 first, following the start bit.
1: data is transmitted/received with the MSB (bit 7/8/9) first, following the start bit.
This bit field can only be written when the USART is disabled (UE=0).

DocID022558 Rev 8

933/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Bit 18 DATAINV: Binary data inversion
This bit is set and cleared by software.
0: Logical data from the data register are send/received in positive/direct logic. (1=H, 0=L)
1: Logical data from the data register are send/received in negative/inverse logic. (1=L, 0=H). The
parity bit is also inverted.
This bit field can only be written when the USART is disabled (UE=0).
Bit 17 TXINV: TX pin active level inversion
This bit is set and cleared by software.
0: TX pin signal works using the standard logic levels (VDD =1/idle, Gnd=0/mark)
1: TX pin signal values are inverted. (VDD =0/mark, Gnd=1/idle).
This allows the use of an external inverter on the TX line.
This bit field can only be written when the USART is disabled (UE=0).
Bit 16 RXINV: RX pin active level inversion
This bit is set and cleared by software.
0: RX pin signal works using the standard logic levels (VDD =1/idle, Gnd=0/mark)
1: RX pin signal values are inverted. (VDD =0/mark, Gnd=1/idle).
This allows the use of an external inverter on the RX line.
This bit field can only be written when the USART is disabled (UE=0).
Bit 15 SWAP: Swap TX/RX pins
This bit is set and cleared by software.
0: TX/RX pins are used as defined in standard pinout
1: The TX and RX pins functions are swapped. This allows to work in the case of a cross-wired
connection to another USART.
This bit field can only be written when the USART is disabled (UE=0).
Bit 14 LINEN: LIN mode enable
This bit is set and cleared by software.
0: LIN mode disabled
1: LIN mode enabled
The LIN mode enables the capability to send LIN Sync Breaks (13 low bits) using the SBKRQ bit in
the USART_RQR register, and to detect LIN Sync breaks.
This bit field can only be written when the USART is disabled (UE=0).
Note: If the USART does not support LIN mode, this bit is reserved and forced by hardware to ‘0’.
Please refer to Section 29.4: USART implementation on page 887.
Bits 13:12 STOP[1:0]: STOP bits
These bits are used for programming the stop bits.
00: 1 stop bit
01: 0.5 stop bit
10: 2 stop bits
11: 1.5 stop bits
This bit field can only be written when the USART is disabled (UE=0).
Bit 11 CLKEN: Clock enable
This bit allows the user to enable the CK pin.
0: CK pin disabled
1: CK pin enabled
This bit can only be written when the USART is disabled (UE=0).
Note: If neither synchronous mode nor Smartcard mode is supported, this bit is reserved and forced
by hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.

934/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Note: In order to provide correctly the CK clock to the Smartcard when CK is always available When
CLKEN = 1, regardless of the UE bit value, the steps below must be respected:
- UE = 0
- SCEN = 1
- GTPR configuration (If PSC needs to be configured, it is recommended to configure PSC and
GT in a single access to USART_ GTPR register).
- CLKEN= 1
- UE = 1
Bit 10 CPOL: Clock polarity
This bit allows the user to select the polarity of the clock output on the CK pin in synchronous mode.
It works in conjunction with the CPHA bit to produce the desired clock/data relationship
0: Steady low value on CK pin outside transmission window
1: Steady high value on CK pin outside transmission window
This bit can only be written when the USART is disabled (UE=0).
Note: If synchronous mode is not supported, this bit is reserved and forced by hardware to ‘0’.
Please refer to Section 29.4: USART implementation on page 887.
Bit 9 CPHA: Clock phase
This bit is used to select the phase of the clock output on the CK pin in synchronous mode. It works
in conjunction with the CPOL bit to produce the desired clock/data relationship (see Figure 335 and
Figure 336)
0: The first clock transition is the first data capture edge
1: The second clock transition is the first data capture edge
This bit can only be written when the USART is disabled (UE=0).
Note: If synchronous mode is not supported, this bit is reserved and forced by hardware to ‘0’.
Please refer to Section 29.4: USART implementation on page 887.
Bit 8 LBCL: Last bit clock pulse
This bit is used to select whether the clock pulse associated with the last data bit transmitted (MSB)
has to be output on the CK pin in synchronous mode.
0: The clock pulse of the last data bit is not output to the CK pin
1: The clock pulse of the last data bit is output to the CK pin
Caution: The last bit is the 7th or 8th or 9th data bit transmitted depending on the 7 or 8 or 9 bit
format selected by the M bits in the USART_CR1 register.
This bit can only be written when the USART is disabled (UE=0).
Note: If synchronous mode is not supported, this bit is reserved and forced by hardware to ‘0’.
Please refer to Section 29.4: USART implementation on page 887.
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 LBDF=1 in the USART_ISR register
Note: If LIN mode is not supported, this bit is reserved and forced by hardware to ‘0’. Please refer to
Section 29.4: USART implementation on page 887.

DocID022558 Rev 8

935/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Bit 5 LBDL: LIN break detection length
This bit is for selection between 11 bit or 10 bit break detection.
0: 10-bit break detection
1: 11-bit break detection
This bit can only be written when the USART is disabled (UE=0).
Note: If LIN mode is not supported, this bit is reserved and forced by hardware to ‘0’. Please refer to
Section 29.4: USART implementation on page 887.
Bit 4 ADDM7:7-bit Address Detection/4-bit Address Detection
This bit is for selection between 4-bit address detection or 7-bit address detection.
0: 4-bit address detection
1: 7-bit address detection (in 8-bit data mode)
This bit can only be written when the USART is disabled (UE=0)
Note: In 7-bit and 9-bit data modes, the address detection is done on 6-bit and 8-bit address
(ADD[5:0] and ADD[7:0]) respectively.
Bits 3:0 Reserved, must be kept at reset value.

Note:

The 3 bits (CPOL, CPHA, LBCL) should not be written while the transmitter is enabled.

29.8.3

Control register 3 (USART_CR3)
Address offset: 0x08
Reset value: 0x0000

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WUFIE

15

14

21

20

19

WUS

18

17

SCARCNT2:0]

16
Res.

rw

rw

rw

rw

rw

rw

13

12

11

10

9

8

7

6

5

4

3

2

1

0

ONE
BIT

CTSIE

CTSE

RTSE

DMAT

DMAR

SCEN

NACK

HDSEL

IRLP

IREN

EIE

rw

rw

rw

rw

rw

rw

v

v

rw

rw

rw

rw

DEP

DEM

DDRE

OVR
DIS

rw

rw

rw

rw

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 Reserved, must be kept at reset value.
Bit 23 Reserved, must be kept at reset value.
Bit 22 WUFIE: Wakeup from Stop mode interrupt enable
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An USART interrupt is generated whenever WUF=1 in the USART_ISR register
Note: WUFIE must be set before entering in Stop mode.
The WUF interrupt is active only in Stop mode.
If the USART does not support the wakeup from Stop feature, this bit is reserved and
forced by hardware to ‘0’.

936/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bits 21:20 WUS[1:0]: Wakeup from Stop mode interrupt flag selection
This bit-field specify the event which activates the WUF (wakeup from Stop mode flag).
00: WUF active on address match (as defined by ADD[7:0] and ADDM7)
01:Reserved.
10: WuF active on Start bit detection
11: WUF active on RXNE.
This bit field can only be written when the USART is disabled (UE=0).
Note: If the USART does not support the wakeup from Stop feature, this bit is reserved and
forced by hardware to ‘0’.
Bits 19:17 SCARCNT[2:0]: Smartcard auto-retry count
This bit-field specifies the number of retries in transmit and receive, in Smartcard mode.
In transmission mode, it specifies the number of automatic retransmission retries, before
generating a transmission error (FE bit set).
In reception mode, it specifies the number or erroneous reception trials, before generating a
reception error (RXNE and PE bits set).
This bit field must be programmed only when the USART is disabled (UE=0).
When the USART is enabled (UE=1), this bit field may only be written to 0x0, in order to stop
retransmission.
0x0: retransmission disabled - No automatic retransmission in transmit mode.
0x1 to 0x7: number of automatic retransmission attempts (before signaling error)
Note: If Smartcard mode is not supported, this bit is reserved and forced by hardware to ‘0’.
Please refer to Section 29.4: USART implementation on page 887.
Bit16 Reserved, must be kept at reset value.
Bit 15 DEP: Driver enable polarity selection
0: DE signal is active high.
1: DE signal is active low.
This bit can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept
cleared. Please refer to Section 29.4: USART implementation on page 887.
Bit 14 DEM: Driver enable mode
This bit allows the user to activate the external transceiver control, through the DE signal.
0: DE function is disabled.
1: DE function is enabled. The DE signal is output on the RTS pin.
This bit can only be written when the USART is disabled (UE=0).
Note: If the Driver Enable feature is not supported, this bit is reserved and must be kept
cleared. Section 29.4: USART implementation on page 887.
Bit 13 DDRE: DMA Disable on Reception Error
0: DMA is not disabled in case of reception error. The corresponding error flag is set but
RXNE is kept 0 preventing from overrun. As a consequence, the DMA request is not
asserted, so the erroneous data is not transferred (no DMA request), but next correct
received data will be transferred (used for Smartcard mode).
1: DMA is disabled following a reception error. The corresponding error flag is set, as well as
RXNE. The DMA request is masked until the error flag is cleared. This means that the
software must first disable the DMA request (DMAR = 0) or clear RXNE before clearing the
error flag.
This bit can only be written when the USART is disabled (UE=0).
Note: The reception errors are: parity error, framing error or noise error.

DocID022558 Rev 8

937/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Bit 12 OVRDIS: Overrun Disable
This bit is used to disable the receive overrun detection.
0: Overrun Error Flag, ORE, is set when received data is not read before receiving new data.
1: Overrun functionality is disabled. If new data is received while the RXNE flag is still set
the ORE flag is not set and the new received data overwrites the previous content of the
USART_RDR register.
This bit can only be written when the USART is disabled (UE=0).
Note: This control bit allows checking the communication flow without reading the data.
Bit 11 ONEBIT: One sample bit method enable
This bit allows the user to select the sample method. When the one sample bit method is
selected the noise detection flag (NF) is disabled.
0: Three sample bit method
1: One sample bit method
This bit can only be written when the USART is disabled (UE=0).
Note: ONEBIT feature applies only to data bits, It does not apply to Start bit.
Bit 10 CTSIE: CTS interrupt enable
0: Interrupt is inhibited
1: An interrupt is generated whenever CTSIF=1 in the USART_ISR register
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 9 CTSE: CTS enable
0: CTS hardware flow control disabled
1: CTS mode enabled, data is only transmitted when the CTS input is asserted (tied to 0). If
the CTS input is de-asserted while data is being transmitted, then the transmission is
completed before stopping. If data is written into the data register while CTS is de-asserted,
the transmission is postponed until CTS is asserted.
This bit can only be written when the USART is disabled (UE=0)
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 8 RTSE: RTS enable
0: RTS hardware flow control disabled
1: RTS output enabled, data is only requested when there is space in the receive buffer. The
transmission of data is expected to cease after the current character has been transmitted.
The RTS output is asserted (pulled to 0) when data can be received.
This bit can only be written when the USART is disabled (UE=0).
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
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

938/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bit 5 SCEN: Smartcard mode enable
This bit is used for enabling Smartcard mode.
0: Smartcard Mode disabled
1: Smartcard Mode enabled
This bit field can only be written when the USART is disabled (UE=0).
Note: If the USART does not support Smartcard mode, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 4 NACK: Smartcard NACK enable
0: NACK transmission in case of parity error is disabled
1: NACK transmission during parity error is enabled
This bit field can only be written when the USART is disabled (UE=0).
Note: If the USART does not support Smartcard mode, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 3 HDSEL: Half-duplex selection
Selection of Single-wire Half-duplex mode
0: Half duplex mode is not selected
1: Half duplex mode is selected
This bit can only be written when the USART is disabled (UE=0).
Bit 2 IRLP: IrDA low-power
This bit is used for selecting between normal and low-power IrDA modes
0: Normal mode
1: Low-power mode
This bit can only be written when the USART is disabled (UE=0).
Note: If IrDA mode is not supported, this bit is reserved and forced by hardware to ‘0’. Please
refer to Section 29.4: USART implementation on page 887.
Bit 1 IREN: IrDA mode enable
This bit is set and cleared by software.
0: IrDA disabled
1: IrDA enabled
This bit can only be written when the USART is disabled (UE=0).
Note: If IrDA mode is not supported, this bit is reserved and forced by hardware to ‘0’. Please
refer to Section 29.4: USART implementation on page 887.
Bit 0 EIE: Error interrupt enable
Error Interrupt Enable Bit is required to enable interrupt generation in case of a framing
error, overrun error or noise flag (FE=1 or ORE=1 or NF=1 in the USART_ISR register).
0: Interrupt is inhibited
1: An interrupt is generated when FE=1 or ORE=1 or NF=1 in the USART_ISR register.

DocID022558 Rev 8

939/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

29.8.4

RM0316

Baud rate register (USART_BRR)
This register can only be written when the USART is disabled (UE=0). It may be
automatically updated by hardware in auto baud rate detection mode.
Address offset: 0x0C
Reset value: 0x0000

31

30

29

28

27

26

25

24

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

BRR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:4 BRR[15:4]
BRR[15:4] = USARTDIV[15:4]
Bits 3:0 BRR[3:0]
When OVER8 = 0, BRR[3:0] = USARTDIV[3:0].
When OVER8 = 1:
BRR[2:0] = USARTDIV[3:0] shifted 1 bit to the right.
BRR[3] must be kept cleared.

29.8.5

Guard time and prescaler register (USART_GTPR)
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

940/1141

GT[7:0]

PSC[7:0]

rw

rw

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bits 31:16 Reserved, must be kept at reset value
Bits 15:8 GT[7:0]: Guard time value
This bit-field is used to program the Guard time value in terms of number of baud clock
periods.
This is used in Smartcard mode. The Transmission Complete flag is set after this guard time
value.
This bit field can only be written when the USART is disabled (UE=0).
Note: If Smartcard mode is not supported, this bit is reserved and forced by hardware to ‘0’.
Please refer to Section 29.4: USART implementation on page 887.
Bits 7:0 PSC[7:0]: Prescaler value
In IrDA Low-power and normal IrDA mode:
PSC[7:0] = IrDA Normal and Low-Power Baud Rate
Used for programming the prescaler for dividing the USART source clock to achieve the lowpower frequency:
The source clock is divided by the value given in the register (8 significant bits):
00000000: Reserved - do not program this value
00000001: divides the source clock by 1
00000010: divides the source clock by 2
...
In Smartcard mode:
PSC[4:0]: Prescaler value
Used for programming the prescaler for dividing the USART source clock to provide the
Smartcard clock.
The value given in the register (5 significant bits) is multiplied by 2 to give the division factor
of the source clock frequency:
00000: Reserved - do not program this value
00001: divides the source clock by 2
00010: divides the source clock by 4
00011: divides the source clock by 6
...
This bit field can only be written when the USART is disabled (UE=0).
Note: Bits [7:5] must be kept cleared if Smartcard mode is used.
This bit field is reserved and forced by hardware to ‘0’ when the Smartcard and IrDA
modes are not supported. Please refer to Section 29.4: USART implementation on
page 887.

29.8.6

Receiver timeout register (USART_RTOR)
Address offset: 0x14
Reset value: 0x0000

31

30

29

28

27

26

25

24

23

22

21

BLEN[7:0]

20

19

18

17

16

RTO[23:16]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

RTO[15:0]
rw

DocID022558 Rev 8

941/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Bits 31:24 BLEN[7:0]: Block Length
This bit-field gives the Block length in Smartcard T=1 Reception. Its value equals the number
of information characters + the length of the Epilogue Field (1-LEC/2-CRC) - 1.
Examples:
BLEN = 0 -> 0 information characters + LEC
BLEN = 1 -> 0 information characters + CRC
BLEN = 255 -> 254 information characters + CRC (total 256 characters))
In Smartcard mode, the Block length counter is reset when TXE=0.
This bit-field can be used also in other modes. In this case, the Block length counter is reset
when RE=0 (receiver disabled) and/or when the EOBCF bit is written to 1.
Note: This value can be programmed after the start of the block reception (using the data
from the LEN character in the Prologue Field). It must be programmed only once per
received block.
Bits 23:0 RTO[23:0]: Receiver timeout value
This bit-field gives the Receiver timeout value in terms of number of bit duration.
In standard mode, the RTOF flag is set if, after the last received character, no new start bit is
detected for more than the RTO value.
In Smartcard mode, this value is used to implement the CWT and BWT. See Smartcard
section for more details.
In this case, the timeout measurement is done starting from the Start Bit of the last received
character.
Note: This value must only be programmed once per received character.

Note:

RTOR can be written on the fly. If the new value is lower than or equal to the counter, the
RTOF flag is set.
This register is reserved and forced by hardware to “0x00000000” when the Receiver
timeout feature is not supported. Please refer to Section 29.4: USART implementation on
page 887.

29.8.7

Request register (USART_RQR)
Address offset: 0x18
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.

4

3

2

1

0

15

14

13

12

11

10

9

8

7

6

5

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TXFRQ RXFRQ MMRQ SBKRQ ABRRQ
w

942/1141

DocID022558 Rev 8

w

w

w

w

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bits 31:5 Reserved, must be kept at reset value
Bit 4 TXFRQ: Transmit data flush request
Writing 1 to this bit sets the TXE flag.
This allows to discard the transmit data. This bit must be used only in Smartcard mode,
when data has not been sent due to errors (NACK) and the FE flag is active in the
USART_ISR register.
If the USART does not support Smartcard mode, this bit is reserved and forced by hardware
to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 3 RXFRQ: Receive data flush request
Writing 1 to this bit clears the RXNE flag.
This allows to discard the received data without reading it, and avoid an overrun condition.
Bit 2 MMRQ: Mute mode request
Writing 1 to this bit puts the USART in mute mode and sets the RWU flag.
Bit 1 SBKRQ: Send break request
Writing 1 to this bit sets the SBKF flag and request to send a BREAK on the line, as soon as
the transmit machine is available.
Note: In the case the application needs to send the break character following all previously
inserted data, including the ones not yet transmitted, the software should wait for the
TXE flag assertion before setting the SBKRQ bit.
Bit 0 ABRRQ: Auto baud rate request
Writing 1 to this bit resets the ABRF flag in the USART_ISR and request an automatic baud
rate measurement on the next received data frame.
Note: If the USART does not support the auto baud rate feature, this bit is reserved and
forced by hardware to ‘0’. Please refer to Section 29.4: USART implementation on
page 887.

29.8.8

Interrupt and status register (USART_ISR)
Address offset: 0x1C
Reset value: 0x0200 00C0

31

30

29

28

27

26

25

24

23

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

22

21

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

ABRF

ABRE

Res.

EOBF

RTOF

CTS

CTSIF

LBDF

TXE

TC

RXNE

IDLE

ORE

NF

FE

PE

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

REACK TEACK

20

19

18

17

16

WUF

RWU

SBKF

CMF

BUSY

Bits 31:25 Reserved, must be kept at reset value.
Bits 24:23 Reserved, must be kept at reset value.

DocID022558 Rev 8

943/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Bit 22 REACK: Receive enable acknowledge flag
This bit is set/reset by hardware, when the Receive Enable value is taken into account by
the USART.
When the wakeup from Stop mode is supported, the REACK flag can be used to verify that
the USART is ready for reception before entering Stop mode.
Bit 21 TEACK: Transmit enable acknowledge flag
This bit is set/reset by hardware, when the Transmit Enable value is taken into account by
the USART.
It can be used when an idle frame request is generated by writing TE=0, followed by TE=1
in the USART_CR1 register, in order to respect the TE=0 minimum period.
Bit 20 WUF: Wakeup from Stop mode flag
This bit is set by hardware, when a wakeup event is detected. The event is defined by the
WUS bit field. It is cleared by software, writing a 1 to the WUCF in the USART_ICR register.
An interrupt is generated if WUFIE=1 in the USART_CR3 register.
Note: When UESM is cleared, WUF flag is also cleared.
The WUF interrupt is active only in Stop mode.
If the USART does not support the wakeup from Stop feature, this bit is reserved and
forced by hardware to ‘0’.
Bit 19 RWU: Receiver wakeup from Mute mode
This bit indicates if the USART is in mute mode. It is cleared/set by hardware when a
wakeup/mute sequence is recognized. The mute mode control sequence (address or IDLE)
is selected by the WAKE bit in the USART_CR1 register.
When wakeup on IDLE mode is selected, this bit can only be set by software, writing 1 to the
MMRQ bit in the USART_RQR register.
0: Receiver in active mode
1: Receiver in mute mode
Bit 18 SBKF: Send break flag
This bit indicates that a send break character was requested. It is set by software, by writing
1 to the SBKRQ bit in the USART_RQR register. It is automatically reset by hardware during
the stop bit of break transmission.
0: No break character is transmitted
1: Break character will be transmitted
Bit 17 CMF: Character match flag
This bit is set by hardware, when the character defined by ADD[7:0] is received. It is cleared
by software, writing 1 to the CMCF in the USART_ICR register.
An interrupt is generated if CMIE=1in the USART_CR1 register.
0: No Character match detected
1: Character Match detected
Bit 16 BUSY: Busy flag
This bit is set and reset by hardware. It is active when a communication is ongoing on the
RX line (successful start bit detected). It is reset at the end of the reception (successful or
not).
0: USART is idle (no reception)
1: Reception on going

944/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bit 15 ABRF: Auto baud rate flag
This bit is set by hardware when the automatic baud rate has been set (RXNE will also be
set, generating an interrupt if RXNEIE = 1) or when the auto baud rate operation was
completed without success (ABRE=1) (ABRE, RXNE and FE are also set in this case)
It is cleared by software, in order to request a new auto baud rate detection, by writing 1 to
the ABRRQ in the USART_RQR register.
Note: If the USART does not support the auto baud rate feature, this bit is reserved and
forced by hardware to ‘0’.
Bit 14 ABRE: Auto baud rate error
This bit is set by hardware if the baud rate measurement failed (baud rate out of range or
character comparison failed)
It is cleared by software, by writing 1 to the ABRRQ bit in the USART_CR3 register.
Note: If the USART does not support the auto baud rate feature, this bit is reserved and
forced by hardware to ‘0’.
Bit 13 Reserved, must be kept at reset value.
Bit 12 EOBF: End of block flag
This bit is set by hardware when a complete block has been received (for example T=1
Smartcard mode). The detection is done when the number of received bytes (from the start
of the block, including the prologue) is equal or greater than BLEN + 4.
An interrupt is generated if the EOBIE=1 in the USART_CR2 register.
It is cleared by software, writing 1 to the EOBCF in the USART_ICR register.
0: End of Block not reached
1: End of Block (number of characters) reached
Note: If Smartcard mode is not supported, this bit is reserved and forced by hardware to ‘0’.
Please refer to Section 29.4: USART implementation on page 887.
Bit 11 RTOF: Receiver timeout
This bit is set by hardware when the timeout value, programmed in the RTOR register has
lapsed, without any communication. It is cleared by software, writing 1 to the RTOCF bit in
the USART_ICR register.
An interrupt is generated if RTOIE=1 in the USART_CR1 register.
In Smartcard mode, the timeout corresponds to the CWT or BWT timings.
0: Timeout value not reached
1: Timeout value reached without any data reception
Note: If a time equal to the value programmed in RTOR register separates 2 characters,
RTOF is not set. If this time exceeds this value + 2 sample times (2/16 or 2/8,
depending on the oversampling method), RTOF flag is set.
The counter counts even if RE = 0 but RTOF is set only when RE = 1. If the timeout has
already elapsed when RE is set, then RTOF will be set.
If the USART does not support the Receiver timeout feature, this bit is reserved and
forced by hardware to ‘0’.
Bit 10 CTS: CTS flag
This bit is set/reset by hardware. It is an inverted copy of the status of the CTS input pin.
0: CTS line set
1: CTS line reset
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’.

DocID022558 Rev 8

945/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Bit 9 CTSIF: CTS interrupt flag
This bit is set by hardware when the CTS input toggles, if the CTSE bit is set. It is cleared by
software, by writing 1 to the CTSCF bit in the USART_ICR register.
An interrupt is generated if CTSIE=1 in the USART_CR3 register.
0: No change occurred on the CTS status line
1: A change occurred on the CTS status line
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’.
Bit 8 LBDF: LIN break detection flag
This bit is set by hardware when the LIN break is detected. It is cleared by software, by
writing 1 to the LBDCF in the USART_ICR.
An interrupt is generated if LBDIE = 1 in the USART_CR2 register.
0: LIN Break not detected
1: LIN break detected
Note: If the USART does not support LIN mode, this bit is reserved and forced by hardware
to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 7 TXE: Transmit data register empty
This bit is set by hardware when the content of the USART_TDR register has been
transferred into the shift register. It is cleared by a write to the USART_TDR register.
The TXE flag can also be cleared by writing 1 to the TXFRQ in the USART_RQR register, in
order to discard the data (only in Smartcard T=0 mode, in case of transmission failure).
An interrupt is generated if the TXEIE bit =1 in the USART_CR1 register.
0: data is not transferred to the shift register
1: data is transferred to the shift register)
Note: This bit is used during single buffer transmission.
Bit 6 TC: Transmission complete
This bit is set by hardware if the transmission of a frame containing data is complete and if
TXE is set. An interrupt is generated if TCIE=1 in the USART_CR1 register. It is cleared by
software, writing 1 to the TCCF in the USART_ICR register or by a write to the USART_TDR
register.
An interrupt is generated if TCIE=1 in the USART_CR1 register.
0: Transmission is not complete
1: Transmission is complete
Note: If TE bit is reset and no transmission is on going, the TC bit will be set immediately.
Bit 5 RXNE: Read data register not empty
This bit is set by hardware when the content of the RDR shift register has been transferred
to the USART_RDR register. It is cleared by a read to the USART_RDR register. The RXNE
flag can also be cleared by writing 1 to the RXFRQ in the USART_RQR register.
An interrupt is generated if RXNEIE=1 in the USART_CR1 register.
0: data is not received
1: Received data is ready to be read.

946/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bit 4 IDLE: Idle line detected
This bit is set by hardware when an Idle Line is detected. An interrupt is generated if
IDLEIE=1 in the USART_CR1 register. It is cleared by software, writing 1 to the IDLECF in
the USART_ICR register.
0: No Idle line is detected
1: Idle line is detected
Note: The IDLE bit will not be set again until the RXNE bit has been set (i.e. a new idle line
occurs).
If mute mode is enabled (MME=1), IDLE is set if the USART is not mute (RWU=0),
whatever the mute mode selected by the WAKE bit. If RWU=1, IDLE is not set.
Bit 3 ORE: Overrun error
This bit is set by hardware when the data currently being received in the shift register is
ready to be transferred into the RDR register while RXNE=1. It is cleared by a software,
writing 1 to the ORECF, in the USART_ICR register.
An interrupt is generated if RXNEIE=1 or EIE = 1 in the USART_CR1 register.
0: No overrun error
1: Overrun error is detected
Note: When this bit is set, the RDR register content is not lost but the shift register is
overwritten. An interrupt is generated if the ORE flag is set during multibuffer
communication if the EIE bit is set.
This bit is permanently forced to 0 (no overrun detection) when the OVRDIS bit is set in
the USART_CR3 register.
Bit 2 NF: START bit Noise detection flag
This bit is set by hardware when noise is detected on a received frame. It is cleared by
software, writing 1 to the NFCF bit in the USART_ICR register.
0: No noise is detected
1: Noise is detected
Note: This bit does not generate an interrupt as it appears at the same time as the RXNE bit
which itself generates an interrupt. An interrupt is generated when the NF flag is set
during multibuffer communication if the EIE bit is set.
Note: When the line is noise-free, the NF flag can be disabled by programming the ONEBIT
bit to 1 to increase the USART tolerance to deviations (Refer to Section 29.5.5:
Tolerance of the USART receiver to clock deviation on page 903).
Bit 1 FE: Framing error
This bit is set by hardware when a de-synchronization, excessive noise or a break character
is detected. It is cleared by software, writing 1 to the FECF bit in the USART_ICR register.
In Smartcard mode, in transmission, this bit is set when the maximum number of transmit
attempts is reached without success (the card NACKs the data frame).
An interrupt is generated if EIE = 1 in the USART_CR1 register.
0: No Framing error is detected
1: Framing error or break character is detected
Bit 0 PE: Parity error
This bit is set by hardware when a parity error occurs in receiver mode. It is cleared by
software, writing 1 to the PECF in the USART_ICR register.
An interrupt is generated if PEIE = 1 in the USART_CR1 register.
0: No parity error
1: Parity error

DocID022558 Rev 8

947/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

29.8.9

RM0316

Interrupt flag clear register (USART_ICR)
Address offset: 0x20
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.

WUCF

Res.

Res.

CMCF

Res.

15

14

13

12

11

10

9

8

7

6

5

3

2

Res.

Res.

Res.

TCCF

Res.

rc_w1

EOBCF RTOCF
rc_w1

rc_w1

Res.

CTSCF LBDCF
rc_w1

Res.

rc_w1

rc_w1

rc_w1

4

IDLECF ORECF
rc_w1

rc_w1

1

0

NCF

FECF

PECF

rc_w1

rc_w1

rc_w1

Bits 31:21 Reserved, must be kept at reset value.
Bit 20 WUCF: Wakeup from Stop mode clear flag
Writing 1 to this bit clears the WUF flag in the USART_ISR register.
Note: If the USART does not support the wakeup from Stop feature, this bit is reserved and
forced by hardware to ‘0’.
Bits 19:18 Reserved, must be kept at reset value.
Bit 17 CMCF: Character match clear flag
Writing 1 to this bit clears the CMF flag in the USART_ISR register.
Bits 16:13 Reserved, must be kept at reset value.
Bit 12 EOBCF: End of block clear flag
Writing 1 to this bit clears the EOBF flag in the USART_ISR register.
Note: If the USART does not support Smartcard mode, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 11 RTOCF: Receiver timeout clear flag
Writing 1 to this bit clears the RTOF flag in the USART_ISR register.
Note: If the USART does not support the Receiver timeout feature, this bit is reserved and
forced by hardware to ‘0’. Please refer to Section 29.4: USART implementation on
page 887.
Bit 10 Reserved, must be kept at reset value.
Bit 9 CTSCF: CTS clear flag
Writing 1 to this bit clears the CTSIF flag in the USART_ISR register.
Note: If the hardware flow control feature is not supported, this bit is reserved and forced by
hardware to ‘0’. Please refer to Section 29.4: USART implementation on page 887.
Bit 8 LBDCF: LIN break detection clear flag
Writing 1 to this bit clears the LBDF flag in the USART_ISR register.
Note: If LIN mode is not supported, this bit is reserved and forced by hardware to ‘0’. Please
refer to Section 29.4: USART implementation on page 887.
Bit 7 Reserved, must be kept at reset value.
Bit 6 TCCF: Transmission complete clear flag
Writing 1 to this bit clears the TC flag in the USART_ISR register.
Bit 5 Reserved, must be kept at reset value.
Bit 4 IDLECF: Idle line detected clear flag
Writing 1 to this bit clears the IDLE flag in the USART_ISR register.

948/1141

DocID022558 Rev 8

RM0316

Universal synchronous asynchronous receiver transmitter (USART)

Bit 3 ORECF: Overrun error clear flag
Writing 1 to this bit clears the ORE flag in the USART_ISR register.
Bit 2 NCF: Noise detected clear flag
Writing 1 to this bit clears the NF flag in the USART_ISR register.
Bit 1 FECF: Framing error clear flag
Writing 1 to this bit clears the FE flag in the USART_ISR register.
Bit 0 PECF: Parity error clear flag
Writing 1 to this bit clears the PE flag in the USART_ISR register.

29.8.10

Receive data register (USART_RDR)
Address offset: 0x24
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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

3

2

1

0

r

r

r

r

15

14

13

12

11

10

9

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RDR[8:0]
r

r

r

r

r

Bits 31:9 Reserved, must be kept at reset value.
Bits 8:0 RDR[8:0]: Receive data value
Contains the received data character.
The RDR register provides the parallel interface between the input shift register and the
internal bus (see Figure 323).
When receiving with the parity enabled, the value read in the MSB bit is the received parity
bit.

29.8.11

Transmit data register (USART_TDR)
Address offset: 0x28
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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

15

14

13

12

11

10

9

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TDR[8:0]
rw

rw

rw

DocID022558 Rev 8

rw

rw

949/1141
951

Universal synchronous asynchronous receiver transmitter (USART)

RM0316

Bits 31:9 Reserved, must be kept at reset value.
Bits 8:0 TDR[8:0]: Transmit data value
Contains the data character to be transmitted.
The TDR register provides the parallel interface between the internal bus and the output
shift register (see Figure 323).
When transmitting with the parity enabled (PCE bit set to 1 in the USART_CR1 register),
the value written in the MSB (bit 7 or bit 8 depending on the data length) has no effect
because it is replaced by the parity.
Note: This register must be written only when TXE=1.

29.8.12

USART register map
The table below gives the USART register map and reset values.

UE
Res.
EIE

UESM
Res.
IREN

TE

Res.
IRLP

RE

IDLEIE

Res.

NACK

HDSEL

ADDM7

TCIE

RXNEIE

0

0

0

0

0

0

0

0

0

0

0

0

0

0

BRR[15:0]
0

0

0

Res.

Res.

0

0

SCEN

0

LBDL

TXEIE
Res.

0

LBDIE

0

0

0

DMAT

0

0

0

0

DMAR

RTSE

0

0

Res.

PS
CTSE

0

0

Res.

PEIE
LBCL

CTSIE

0

0

Res.

PCE
CPOL

CPHA

ONEBIT

0

0

Res.

M0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WAKE
CLKEN

0

OVRDIS

MME

0

DEM

CMIE
LINEN

0

DDRE

DEDT0

OVER8
SWAP

0

DEP

DEDT1

0

0

0

0

0

0

0

0

GT[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

USART_RQR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TXFRQ

RXFRQ

MMRQ

SBKRQ

ABRRQ

RTO[23:0]

Res.

BLEN[7:0]

0

PSC[7:0]

Reset value

0

0

0

0

0

0x18
Reset value

950/1141

0

0

0

USART_RTOR

0

0

Reset value

0x14

0

0

0
Res.

USART_GTPR

0

0

Reset value

0x10

0

RXINV

0

0

Res.

DEDT2

0

0

TXINV

DEDT3

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

USART_BRR
0x0C

Res.

Reset value

0

Res.

USART_CR3
0x08

DATAINV

0

SCARCNT2:0]

0

Res.

0

0

STOP
[1:0]

Res.

0

0

MSBFIRST

DEAT0

DEDT4

0

0

WUS

0

0

Res.

0

0

ABREN

DEAT1

0

ADD[3:0]

0

Res.

0

ADD[7:4]

0

ABRMOD0

DEAT2

ABRMOD1

0

USART_CR2
0x04

0

Res.

Reset value

WUFIE

DEAT3

RTOEN

0

Res.

0

Res.

RTOIE

DEAT4

0

Res.

0

Res.

M1

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

Reset value

EOBIE

Res.

USART_CR1
0x00

Res.

Register

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 165. USART register map and reset values

DocID022558 Rev 8

0x28
USART_TDR

Reset value

DocID022558 Rev 8

CTS
CTSIF
LBDF
TXE
TC
RXNE
IDLE
ORE
NF
FE
PE

0
0
0
0
0
0
0
1
1
0
0
0
0
0
0

Res.
CMCF
Res.
Res.
Res.

Res.
CTSCF
LBDCF
Res.
TCCF
Res.
IDLECF

0
0
0

RTOCF

Res.
Res.

Res.

EOBCF
0

Res.

RTOF

0

0

Res.

Res.

EOBF

0

Reset value

TDR[8:0]

X X X X X X

PECF

X X X X X X

FECF

RDR[8:0]

NCF

0

ORECF

Res.

ABRF
ABRE

0
Res.

CMF
BUSY

0

Res.

Res.

Res.

Res.

Res.

SBKF

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

WUF

Res.

RWU

0

Res.

Res.

TEACK
0
WUCF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

REACK

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

USART_RDR

Res.

0x24

Res.

USART_ICR

Res.

0x20
Res.

USART_ISR

Res.

0x1C

Res.

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.

RM0316
Universal synchronous asynchronous receiver transmitter (USART)

Table 165. USART register map and reset values (continued)

0
0
0
0

X
X
X

X
X
X

Refer to Section 3.2 on page 51 for the register boundary addresses.

951/1141

951

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

RM0316

30

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

30.1

Introduction
The SPI/I²S interface can be used to communicate with external devices using the SPI
protocol or the I2S audio protocol. SPI or I2S mode is selectable by software. SPI Motorola
mode is selected by default after a device reset.
The serial peripheral interface (SPI) protocol supports half-duplex, full-duplex and simplex
synchronous, serial communication with external devices. The interface can be configured
as master and in this case it provides the communication clock (SCK) to the external slave
device. The interface is also capable of operating in multimaster configuration.
The Inter-IC sound (I2S) protocol is also a synchronous serial communication interface.It
can operate in slave or master mode with full-duplex and half-duplex communication. It can
address four different audio standards including the Philips I2S standard, the MSB- and
LSB-justified standards and the PCM standard.

Note:

There is no I2S in the STM32F303x6/8 and STM32F328x8

30.2

SPI main features

952/1141

•

Master or slave operation

•

Full-duplex synchronous transfers on three lines

•

Half-duplex synchronous transfer on two lines (with bidirectional data line)

•

Simplex synchronous transfers on two lines (with unidirectional data line)

•

4-bit to 16-bit data size selection

•

Multimaster mode capability

•

8 master mode baud rate prescalers up to fPCLK/2.

•

Slave mode frequency up to fPCLK/2.

•

NSS management by hardware or software for both master and slave: dynamic change
of master/slave operations

•

Programmable clock polarity and phase

•

Programmable data order with MSB-first or LSB-first shifting

•

Dedicated transmission and reception flags with interrupt capability

•

SPI bus busy status flag

•

SPI Motorola support

•

Hardware CRC feature for reliable communication:
–

CRC value can be transmitted as last byte in Tx mode

–

Automatic CRC error checking for last received byte

•

Master mode fault, overrun flags with interrupt capability

•

CRC Error flag

•

Two 32-bit embedded Rx and Tx FIFOs with DMA capability

•

SPI TI mode support

DocID022558 Rev 8

RM0316

30.3

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

I2S main features
•

Full-duplex communication

•

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)

•

30.4

–

I2S (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, SPI2, SPI3 and SPI4.
SPI1 and SPI4 support all the features except I2S mode.

Note:

On STM32F303x6/8 and STM32F328x8 devices, only SPI1 is available.
Table 166. STM32F303x6/8 and STM32F328x8 SPI implementation
SPI Features(1)

SPI1

Hardware CRC calculation

X

Rx/Tx FIFO

X

NSS pulse mode

X

I2S mode
TI mode

X

1. X = supported.

DocID022558 Rev 8

953/1141
1010

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

RM0316

Table 167. STM32F303xB/C/D/E, STM32F358xC and STM32F398xE SPI implementation
SPI Features(1)

SPI1

SPI2

SPI3

SPI4(2)

Hardware CRC calculation

X

X

X

X

Rx/Tx FIFO

X

X

X

X

NSS pulse mode

X

X

X

X

I2S mode

-

X

X

-

TI mode

X

X

X

X

1. X = supported.
2. SPI4 is only in STM32F303xD/E.

30.5

SPI functional description

30.5.1

General description
The SPI allows synchronous, serial communication between the MCU and external devices.
Application software can manage the communication by polling the status flag or using
dedicated SPI interrupt. The main elements of SPI and their interactions are shown in the
following block diagram Figure 348.
Figure 348. SPI block diagram
$GGUHVVDQGGDWDEXV
5HDG
5[
),)2
&5&FRQWUROOHU
026,
0,62

6KLIWUHJLVWHU
5;21/<
&32/
&3+$
'6>@

7[
),)2
:ULWH

%,',2(

6&.

%DXGUDWH
JHQHUDWRU

&5&(1
&5&1(;7
&5&/

&RPPXQLFDWLRQ
FRQWUROOHU

%5>@

,QWHUQDO166
166
ORJLF

166

069

954/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
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 30.5.5: Slave select (NSS) pin management for details.
The SPI bus allows the communication between one master device and one or more slave
devices. The bus consists of at least two wires - one for the clock signal and the other for
synchronous data transfer. Other signals can be added depending on the data exchange
between SPI nodes and their slave select signal management.

30.5.2

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 349. Full-duplex single master/ single slave application

5[VKLIWUHJLVWHU
7[VKLIWUHJLVWHU
63,FORFN
JHQHUDWRU

0,62

0,62

026,

026,

6&.

6&.

166 

166 

0DVWHU

7[VKLIWUHJLVWHU
5[VKLIWUHJLVWHU

6ODYH
06Y9

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 30.5.5: Slave select (NSS) pin management.

DocID022558 Rev 8

955/1141
1010

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

RM0316

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.
Figure 350. Half-duplex single master/ single slave application

5[VKLIWUHJLVWHU
7[VKLIWUHJLVWHU
63,FORFN
JHQHUDWRU

0,62



026,

0,62


Nȍ

5[VKLIWUHJLVWHU

6&.

6&.
166

026,

7[VKLIWUHJLVWHU




0DVWHU

166 
6ODYH
06Y9

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 30.5.5: Slave select (NSS) pin management.
2. In this configuration, the master’s MISO pin and the slave’s MOSI pin can be used as GPIOs.
3. A critical situation can happen when communication direction is changed not synchronously between two
nodes working at bidirectionnal mode and new transmitter accesses the common data line while former
transmitter still keeps an opposite value on the line (the value depends on SPI configuration and
communication data). Both nodes then fight while providing opposite output levels on the common line
temporary till next node changes its direction settings correspondingly, too. It is suggested to insert a serial
resistance between MISO and MOSI pins at this mode to protect the outputs and limit the current blowing
between them at this situation.

Simplex communications
The SPI can communicate in simplex mode by setting the SPI in transmit-only or in receiveonly using the RXONLY bit in the SPIx_CR2 register. In this configuration, only one line is
used for the transfer between the shift registers of the master and slave. The remaining
MISO and MOSI pins pair is not used for communication and can be used as standard
GPIOs.

956/1141

•

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 30.5.5: Slave select (NSS) pin management).
Received data events appear depending on the data buffer configuration. In the master
configuration, the MOSI output is disabled and the pin can be used as a GPIO. The
clock signal is generated continuously as long as the SPI is enabled. The only way to
stop the clock is to clear the RXONLY bit or the SPE bit and wait until the incoming
pattern from the MISO pin is finished and fills the data buffer structure, depending on its
configuration.

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 351. Simplex single master/single slave application (master in transmit-only/
slave in receive-only mode)

5[VKLIWUHJLVWHU
7[VKLIWUHJLVWHU
63,FORFN
JHQHUDWRU



0,62

0,62

026,

026,

6&.

6&.

166 

166 

0DVWHU

7[VKLIWUHJLVWHU
5[VKLIWUHJLVWHU

^ůĂǀĞ
06Y9

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 30.5.5: Slave select (NSS) pin management.
2. An accidental input information is captured at the input of transmitter Rx shift register. All the events
associated with the transmitter receive flow must be ignored in standard transmit only mode (e.g. OVF
flag).
3. In this configuration, both the MISO pins can be used as GPIOs.

Note:

Any simplex communication can be alternatively replaced by a variant of the half-duplex
communication with a constant setting of the transaction direction (bidirectional mode is
enabled while BDIO bit is not changed).

30.5.3

Standard multi-slave communication
In a configuration with two or more independent slaves, the master uses GPIO pins to
manage the chip select lines for each slave (see Figure 352.). 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.

DocID022558 Rev 8

957/1141
1010

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

RM0316

Figure 352. Master and three independent slaves

166
5[VKLIWUHJLVWHU
7[VKLIWUHJLVWHU
63,FORFN
JHQHUDWRU
0DVWHU



0,62

0,62

026,

026,

6&.

6&.

,2

166

7[VKLIWUHJLVWHU
5[VKLIWUHJLVWHU

6ODYH

,2
,2

0,62
026,

7[VKLIWUHJLVWHU
5[VKLIWUHJLVWHU

6&.
166
6ODYH

0,62
026,

7[VKLIWUHJLVWHU
5[VKLIWUHJLVWHU

6&.
166
6ODYH
06Y9

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 11.3.7: I/O alternate function input/output on
page 233.

30.5.4

Multi-master communication
Unless SPI bus is not designed for a multi-master capability primarily, the user can use build
in feature which detects a potential conflict between two nodes trying to master the bus at
the same time. For this detection, NSS pin is used configured at hardware input mode.
The connection of more than two SPI nodes working at this mode is impossible as only one
node can apply its output on a common data line at time.
When nodes are non active, both stay at slave mode by default. Once one node wants to
overtake control on the bus, it switches itself into master mode and applies active level on
the slave select input of the other node via dedicated GPIO pin. After the session is

958/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
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 353. Multi-master application

5[ 7[ VKLIWUHJLVWHU
7[ 5[ VKLIWUHJLVWHU
63,FORFN
JHQHUDWRU

0DVWHU
6ODYH

0,62

0,62

026,

026,

6&.

6&.

*3,2

166

166 

*3,2

5[ 7[ VKLIWUHJLVWHU



7[ 5[ VKLIWUHJLVWHU
63,FORFN
JHQHUDWRU

DĂƐƚĞƌ
;^ůĂǀĞͿ
06Y9

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.

30.5.5

Slave select (NSS) pin management
In slave mode, the NSS works as a standard “chip select” input and lets the slave
communicate with the master. In master mode, NSS can be used either as output or input.
As an input it can prevent multimaster bus collision, and as an output it can drive a slave
select signal of a single slave.
Hardware or software slave select management can be set using the SSM bit in the
SPIx_CR1 register:
•

Software NSS management (SSM = 1): in this configuration, slave select information
is driven internally by the SSI bit value in register SPIx_CR1. The external NSS pin is
free for other application uses.

•

Hardware NSS management (SSM = 0): in this case, there are two possible
configurations. The configuration used depends on the NSS output configuration
(SSOE bit in register SPIx_CR1).
–

NSS output enable (SSM=0,SSOE = 1): this configuration is only used when the
MCU is set as master. The NSS pin is managed by the hardware. The NSS signal
is driven low as soon as the SPI is enabled in master mode (SPE=1), and is kept
low until the SPI is disabled (SPE =0). A pulse can be generated between
continuous communications if NSS pulse mode is activated (NSSP=1). The SPI
cannot work in multimaster configuration with this NSS setting.

–

NSS output disable (SSM=0, SSOE = 0): if the microcontroller is acting as the
master on the bus, this configuration allows multimaster capability. If the NSS pin
is pulled low in this mode, the SPI enters master mode fault state and the device is
automatically reconfigured in slave mode. In slave mode, the NSS pin works as a
standard “chip select” input and the slave is selected while NSS line is at low level.

DocID022558 Rev 8

959/1141
1010

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

RM0316

Figure 354. Hardware/software slave select management
66,FRQWUROELW
660FRQWUROELW



166
,QS

0DVWHU
PRGH

6ODYHPRGH

9GG

2.

1RQDFWLYH

9VV

&RQIOLFW

$FWLYH

166,QSXW

166
SLQ



*3,2
ORJLF

166
2XWSXW
&RQWURO

1662XWSXW
XVHGLQ0DVWHUPRGHDQG166
+:PDQDJHPHQWRQO\
662(FRQWUROELW

166H[WHUQDOORJLF

166LQWHUQDOORJLF

06Y9

30.5.6

Communication formats
During SPI communication, receive and transmit operations are performed simultaneously.
The serial clock (SCK) synchronizes the shifting and sampling of the information on the data
lines. The communication format depends on the clock phase, the clock polarity and the
data frame format. To be able to communicate together, the master and slaves devices must
follow the same communication format.

Clock phase and polarity controls
Four possible timing relationships may be chosen by software, using the CPOL and CPHA
bits in the SPIx_CR1 register. The CPOL (clock polarity) bit controls the idle state value of
the clock when no data is being transferred. This bit affects both master and slave modes. If
CPOL is reset, the SCK pin has a low-level idle state. If CPOL is set, the SCK pin has a
high-level idle state.
If the CPHA bit is set, the second edge on the SCK pin captures the first data bit transacted
(falling edge if the CPOL bit is reset, rising edge if the CPOL bit is set). Data are latched on
each occurrence of this clock transition type. If the CPHA bit is reset, the first edge on the
SCK pin captures the first data bit transacted (falling edge if the CPOL bit is set, rising edge
if the CPOL bit is reset). Data are latched on each occurrence of this clock transition type.
The combination of CPOL (clock polarity) and CPHA (clock phase) bits selects the data
capture clock edge.

960/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 355, shows an SPI full-duplex transfer with the four combinations of the CPHA and
CPOL bits.

Note:

Prior to changing the CPOL/CPHA bits the SPI must be disabled by resetting the SPE bit.
The idle state of SCK must correspond to the polarity selected in the SPIx_CR1 register (by
pulling up SCK if CPOL=1 or pulling down SCK if CPOL=0).
Figure 355. Data clock timing diagram
&3+$ 
&32/ 

&32/ 

026, 

06%LW

0,62 

06%LW

/6%LW

/6%LW

166 WRVODYH

&DSWXUHVWUREH

&3+$ 
&32/ 

&32/ 

026, 

0,62 

/6%LW

06%LW

06%LW

/6%LW

166 WRVODYH

&DSWXUHVWUREH
DLH

1. The order of data bits depends on LSBFIRST bit setting.

Data frame format
The SPI shift register can be set up to shift out MSB-first or LSB-first, depending on the
value of the LSBFIRST bit. The data frame size is chosen by using the DS bits. It can be set
from 4-bit up to 16-bit length and the setting applies for both transmission and reception.
Whatever the selected data frame size, read access to the FIFO must be aligned with the
FRXTH level. When the SPIx_DR register is accessed, data frames are always right-aligned
into either a byte (if the data fits into a byte) or a half-word (see Figure 356). During
communication, only bits within the data frame are clocked and transferred.

DocID022558 Rev 8

961/1141
1010

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

RM0316

Figure 356. Data alignment when data length is not equal to 8-bit or 16-bit
'6 ELWVGDWDLVULJKWDOLJQHGRQE\WH
([DPSOH'6 ELW


 
;;;










'DWDIUDPH

5;

 
;;

7;

'DWDIUDPH
 



'6!ELWVGDWDLVULJKWDOLJQHGRQELW
([DPSOH'6 ELW

'DWDIUDPH

 


7;


'DWDIUDPH

5;
069

Note:

The minimum data length is 4 bits. If a data length of less than 4 bits is selected, it is forced
to an 8-bit data frame size.

30.5.7

Configuration of SPI
The configuration procedure is almost the same for master and slave. For specific mode
setups, follow the dedicated sections. When a standard communication is to be initialized,
perform these steps:
1.
2.

3.

962/1141

Write proper GPIO registers: Configure GPIO for MOSI, MISO and SCK pins.
Write to the SPI_CR1 register:
a)

Configure the serial clock baud rate using the BR[2:0] bits (Note: 4).

b)

Configure the CPOL and CPHA bits combination to define one of the four
relationships between the data transfer and the serial clock (CPHA must be
cleared in NSSP mode). (Note: 2 - except the case when CRC is enabled at TI
mode).

c)

Select simplex or half-duplex mode by configuring RXONLY or BIDIMODE and
BIDIOE (RXONLY and BIDIMODE can't be set at the same time).

d)

Configure the LSBFIRST bit to define the frame format (Note: 2).

e)

Configure the CRCL and CRCEN bits if CRC is needed (while SCK clock signal is
at idle state).

f)

Configure SSM and SSI (Notes: 2 & 3).

g)

Configure the MSTR bit (in multimaster NSS configuration, avoid conflict state on
NSS if master is configured to prevent MODF error).

Write to SPI_CR2 register:
a)

Configure the DS[3:0] bits to select the data length for the transfer.

b)

Configure SSOE (Notes: 1 & 2 & 3).

c)

Set the FRF bit if the TI protocol is required (keep NSSP bit cleared in TI mode).

d)

Set the NSSP bit if the NSS pulse mode between two data units is required (keep
CHPA and TI bits cleared in NSSP mode).

e)

Configure the FRXTH bit. The RXFIFO threshold must be aligned to the read
access size for the SPIx_DR register.

f)

Initialize LDMA_TX and LDMA_RX bits if DMA is used in packed mode.

4.

Write to SPI_CRCPR register: Configure the CRC polynomial if needed.

5.

Write proper DMA registers: Configure DMA streams dedicated for SPI Tx and Rx in
DMA registers if the DMA streams are used.

DocID022558 Rev 8

RM0316
Note:

Serial peripheral interface / inter-IC sound (SPI/I2S)
(1) Step is not required in slave mode.
(2) Step is not required in TI mode.
(3) Step is not required in NSSP mode.
(4) The step is not required in slave mode except slave working at TI mode

30.5.8

Procedure for enabling SPI
It is recommended to enable the SPI slave before the master sends the clock. If not,
undesired data transmission might occur. The data register of the slave must already
contain data to be sent before starting communication with the master (either on the first
edge of the communication clock, or before the end of the ongoing communication if the
clock signal is continuous). The SCK signal must be settled at an idle state level
corresponding to the selected polarity before the SPI slave is enabled.
The master at full-duplex (or in any transmit-only mode) starts to communicate when the
SPI is enabled and TXFIFO is not empty, or with the next write to TXFIFO.
In any master receive only mode (RXONLY=1 or BIDIMODE=1 & BIDIOE=0), master starts
to communicate and the clock starts running immediately after SPI is enabled.
For handling DMA, follow the dedicated section.

30.5.9

Data transmission and reception procedures
RXFIFO and TXFIFO
All SPI data transactions pass through the 32-bit embedded FIFOs. This enables the SPI to
work in a continuous flow, and prevents overruns when the data frame size is short. Each
direction has its own FIFO called TXFIFO and RXFIFO. These FIFOs are used in all SPI
modes except for receiver-only mode (slave or master) with CRC calculation enabled (see
Section 30.5.14: CRC calculation).
The handling of FIFOs depends on the data exchange mode (duplex, simplex), data frame
format (number of bits in the frame), access size performed on the FIFO data registers (8-bit
or 16-bit), and whether or not data packing is used when accessing the FIFOs (see
Section 30.5.13: TI mode).
A read access to the SPIx_DR register returns the oldest value stored in RXFIFO that has
not been read yet. A write access to the SPIx_DR stores the written data in the TXFIFO at
the end of a send queue. The read access must be always aligned with the RXFIFO
threshold configured by the FRXTH bit in SPIx_CR2 register. FTLVL[1:0] and FRLVL[1:0]
bits indicate the current occupancy level of both FIFOs.
A read access to the SPIx_DR register must be managed by the RXNE event. This event is
triggered when data is stored in RXFIFO and the threshold (defined by FRXTH bit) is
reached. When RXNE is cleared, RXFIFO is considered to be empty. In a similar way, write
access of a data frame to be transmitted is managed by the TXE event. This event is
triggered when the TXFIFO level is less than or equal to half of its capacity. Otherwise TXE
is cleared and the TXFIFO is considered as full. In this way, RXFIFO can store up to four
data frames, whereas TXFIFO can only store up to three when the data frame format is not
greater than 8 bits. This difference prevents possible corruption of 3x 8-bit data frames
already stored in the TXFIFO when software tries to write more data in 16-bit mode into

DocID022558 Rev 8

963/1141
1010

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

RM0316

TXFIFO. Both TXE and RXNE events can be polled or handled by interrupts. See
Figure 358 through Figure 361.
Another way to manage the data exchange is to use DMA (see Section 13.2: DMA main
features).
If the next data is received when the RXFIFO is full, an overrun event occurs (see
description of OVR flag at Section 30.5.10: SPI status flags). An overrun event can be
polled or handled by an interrupt.
The BSY bit being set indicates ongoing transaction of a current data frame. When the clock
signal runs continuously, the BSY flag stays set between data frames at master but
becomes low for a minimum duration of one SPI clock at slave between each data frame
transfer.

Sequence handling
A few data frames can be passed at single sequence to complete a message. When
transmission is enabled, a sequence begins and continues while any data is present in the
TXFIFO of the master. The clock signal is provided continuously by the master until TXFIFO
becomes empty, then it stops waiting for additional data.
In receive-only modes, half-duplex (BIDIMODE=1, BIDIOE=0) or simplex (BIDIMODE=0,
RXONLY=1) the master starts the sequence immediately when both SPI is enabled and
receive-only mode is activated. The clock signal is provided by the master and it does not
stop until either SPI or receive-only mode is disabled by the master. The master receives
data frames continuously up to this moment.
While the master can provide all the transactions in continuous mode (SCK signal is
continuous) it has to respect slave capability to handle data flow and its content at anytime.
When necessary, the master must slow down the communication and provide either a
slower clock or separate frames or data sessions with sufficient delays. Be aware there is no
underflow error signal for master or slave in SPI mode, and data from the slave is always
transacted and processed by the master even if the slave could not prepare it correctly in
time. It is preferable for the slave to use DMA, especially when data frames are shorter and
bus rate is high.
Each sequence must be encased by the NSS pulse in parallel with the multislave system to
select just one of the slaves for communication. In a single slave system it is not necessary
to control the slave with NSS, but it is often better to provide the pulse here too, to
synchronize the slave with the beginning of each data sequence. NSS can be managed by
both software and hardware (see Section 30.5.5: Slave select (NSS) pin management).
When the BSY bit is set it signifies an ongoing data frame transaction. When the dedicated
frame transaction is finished, the RXNE flag is raised. The last bit is just sampled and the
complete data frame is stored in the RXFIFO.

Procedure for disabling the SPI
When SPI is disabled, it is mandatory to follow the disable procedures described in this
paragraph. It is important to do this before the system enters a low-power mode when the
peripheral clock is stopped. Ongoing transactions can be corrupted in this case. In some
modes the disable procedure is the only way to stop continuous communication running.
Master in full-duplex or transmit only mode can finish any transaction when it stops
providing data for transmission. In this case, the clock stops after the last data transaction.
Special care must be taken in packing mode when an odd number of data frames are

964/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
transacted to prevent some dummy byte exchange (refer to Data packing section). Before
the SPI is disabled in these modes, the user must follow standard disable procedure. When
the SPI is disabled at the master transmitter while a frame transaction is ongoing or next
data frame is stored in TXFIFO, the SPI behavior is not guaranteed.
When the master is in any receive only mode, the only way to stop the continuous clock is to
disable the peripheral by SPE=0. This must occur in specific time window within last data
frame transaction just between the sampling time of its first bit and before its last bit transfer
starts (in order to receive a complete number of expected data frames and to prevent any
additional “dummy” data reading after the last valid data frame). Specific procedure must be
followed when disabling SPI in this mode.
Data received but not read remains stored in RXFIFO when the SPI is disabled, and must
be processed the next time the SPI is enabled, before starting a new sequence. To prevent
having unread data, ensure that RXFIFO is empty when disabling the SPI, by using the
correct disabling procedure, or by initializing all the SPI registers with a software reset via
the control of a specific register dedicated to peripheral reset (see the SPIiRST bits in the
RCC_APBiRSTR registers).
Standard disable procedure is based on pulling BSY status together with FTLVL[1:0] to
check if a transmission session is fully completed. This check can be done in specific cases,
too, when it is necessary to identify the end of ongoing transactions, for example:
•

When NSS signal is managed by software and master has to provide proper end of
NSS pulse for slave, or

•

When transactions’ streams from DMA or FIFO are completed while the last data frame
or CRC frame transaction is still ongoing in the peripheral bus.

The correct disable procedure is (except when receive only mode is used):
1.

Wait until FTLVL[1:0] = 00 (no more data to transmit).

2.

Wait until BSY=0 (the last data frame is processed).

3.

Disable the SPI (SPE=0).

4.

Read data until FRLVL[1:0] = 00 (read all the received data).

The correct disable procedure for certain receive only modes is:

Note:

1.

Interrupt the receive flow by disabling SPI (SPE=0) in the specific time window while
the last data frame is ongoing.

2.

Wait until BSY=0 (the last data frame is processed).

3.

Read data until FRLVL[1:0] = 00 (read all the received data).

If packing mode is used and an odd number of data frames with a format less than or equal
to 8 bits (fitting into one byte) has to be received, FRXTH must be set when FRLVL[1:0] =
01, in order to generate the RXNE event to read the last odd data frame and to keep good
FIFO pointer alignment.

Data packing
When the data frame size fits into one byte (less than or equal to 8 bits), data packing is
used automatically when any read or write 16-bit access is performed on the SPIx_DR
register. The double data frame pattern is handled in parallel in this case. At first, the SPI
operates using the pattern stored in the LSB of the accessed word, then with the other half
stored in the MSB. Figure 357 provides an example of data packing mode sequence
handling. Two data frames are sent after the single 16-bit access the SPIx_DR register of
the transmitter. This sequence can generate just one RXNE event in the receiver if the

DocID022558 Rev 8

965/1141
1010

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

RM0316

RXFIFO threshold is set to 16 bits (FRXTH=0). The receiver then has to access both data
frames by a single 16-bit read of SPIx_DR as a response to this single RXNE event. The
RxFIFO threshold setting and the following read access must be always kept aligned at the
receiver side, as data can be lost if it is not in line.
A specific problem appears if an odd number of such “fit into one byte” data frames must be
handled. On the transmitter side, writing the last data frame of any odd sequence with an 8bit access to SPIx_DR is enough. The receiver has to change the Rx_FIFO threshold level
for the last data frame received in the odd sequence of frames in order to generate the
RXNE event.
Figure 357. Packing data in FIFO for transmission and reception
166
6&.

7;),)2
63,[B'5

[$

[ [$

[

5;),)2

026,
[$

63,IVP
VKLIW

ELWDFFHVVZKHQZULWHWRGDWDUHJLVWHU
63,B'5 [$ZKHQ7[( 

[$

[

63,IVP
VKLIW

63,[B'5

[
[ [$

ELWDFFHVVZKHQUHDGIURPGDWDUHJLVWHU
63,B'5 [$ZKHQ5[1( 
069

Communication using DMA (direct memory addressing)
To operate at its maximum speed and to facilitate the data register read/write process
required to avoid overrun, the SPI features a DMA capability, which implements a simple
request/acknowledge protocol.
A DMA access is requested when the TXE or RXNE enable bit in the SPIx_CR2 register is
set. Separate requests must be issued to the Tx and Rx buffers.
•

In transmission, a DMA request is issued each time TXE is set to 1. The DMA then
writes to the SPIx_DR register.

•

In reception, a DMA request is issued each time RXNE is set to 1. The DMA then reads
the SPIx_DR register.

See Figure 358 through Figure 361.
When the SPI is used only to transmit data, it is possible to enable only the SPI Tx DMA
channel. In this case, the OVR flag is set because the data received is not read. When the
SPI is used only to receive data, it is possible to enable only the SPI Rx DMA channel.
In transmission mode, when the DMA has written all the data to be transmitted (the TCIF
flag is set in the DMA_ISR register), the BSY flag can be monitored to ensure that the SPI
communication is complete. This is required to avoid corrupting the last transmission before
disabling the SPI or entering the Stop mode. The software must first wait until
FTLVL[1:0]=00 and then until BSY=0.
When starting communication using DMA, to prevent DMA channel management raising
error events, these steps must be followed in order:

966/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
1.

Enable DMA Rx buffer in the RXDMAEN bit in the SPI_CR2 register, if DMA Rx is
used.

2.

Enable DMA streams for Tx and Rx in DMA registers, if the streams are used.

3.

Enable DMA Tx buffer in the TXDMAEN bit in the SPI_CR2 register, if DMA Tx is used.

4.

Enable the SPI by setting the SPE bit.

To close communication it is mandatory to follow these steps in order:
1.

Disable DMA streams for Tx and Rx in the DMA registers, if the streams are used.

2.

Disable the SPI by following the SPI disable procedure.

3.

Disable DMA Tx and Rx buffers by clearing the TXDMAEN and RXDMAEN bits in the
SPI_CR2 register, if DMA Tx and/or DMA Rx are used.

Packing with DMA
If the transfers are managed by DMA (TXDMAEN and RXDMAEN set in the SPIx_CR2
register) packing mode is enabled/disabled automatically depending on the PSIZE value
configured for SPI TX and the SPI RX DMA channel. If the DMA channel PSIZE value is
equal to 16-bit and SPI data size is less than or equal to 8-bit, then packing mode is
enabled. The DMA then automatically manages the write operations to the SPIx_DR
register.
If data packing mode is used and the number of data to transfer is not a multiple of two, the
LDMA_TX/LDMA_RX bits must be set. The SPI then considers only one data for the
transmission or reception to serve the last DMA transfer (for more details refer to Data
packing on page 965.)

DocID022558 Rev 8

967/1141
1010

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

RM0316

Communication diagrams
Some typical timing schemes are explained in this section. These schemes are valid no
matter if the SPI events are handled by polling, interrupts or DMA. For simplicity, the
LSBFIRST=0, CPOL=0 and CPHA=1 setting is used as a common assumption here. No
complete configuration of DMA streams is provided.
The following numbered notes are common for Figure 358 on page 969 through Figure 361
on page 972.

968/1141

1.

The slave starts to control MISO line as NSS is active and SPI is enabled, and is
disconnected from the line when one of them is released. Sufficient time must be
provided for the slave to prepare data dedicated to the master in advance before its
transaction starts.
At the master, the SPI peripheral takes control at MOSI and SCK signals (occasionally
at NSS signal as well) only if SPI is enabled. If SPI is disabled the SPI peripheral is
disconnected from GPIO logic, so the levels at these lines depends on GPIO setting
exclusively.

2.

At the master, BSY stays active between frames if the communication (clock signal) is
continuous. At the slave, BSY signal always goes down for at least one clock cycle
between data frames.

3.

The TXE signal is cleared only if TXFIFO is full.

4.

The DMA arbitration process starts just after the TXDMAEN bit is set. The TXE
interrupt is generated just after the TXEIE is set. As the TXE signal is at an active level,
data transfers to TxFIFO start, until TxFIFO becomes full or the DMA transfer
completes.

5.

If all the data to be sent can fit into TxFIFO, the DMA Tx TCIF flag can be raised even
before communication on the SPI bus starts. This flag always rises before the SPI
transaction is completed.

6.

The CRC value for a package is calculated continuously frame by frame in the
SPIx_TxCRCR and SPIx_RxCRCR registers. The CRC information is processed after
the entire data package has completed, either automatically by DMA (Tx channel must
be set to the number of data frames to be processed) or by SW (the user must handle
CRCNEXT bit during the last data frame processing).
While the CRC value calculated in SPIx_TxCRCR is simply sent out by transmitter,
received CRC information is loaded into RxFIFO and then compared with the
SPIx_RxCRCR register content (CRC error flag can be raised here if any difference).
This is why the user must take care to flush this information from the FIFO, either by
software reading out all the stored content of RxFIFO, or by DMA when the proper
number of data frames is preset for Rx channel (number of data frames + number of
CRC frames) (see the settings at the example assumption).

7.

In data packed mode, TxE and RxNE events are paired and each read/write access to
the FIFO is 16 bits wide until the number of data frames are even. If the TxFIFO is ¾
full FTLVL status stays at FIFO full level. That is why the last odd data frame cannot be
stored before the TxFIFO becomes ½ full. This frame is stored into TxFIFO with an 8bit access either by software or automatically by DMA when LDMA_TX control is set.

8.

To receive the last odd data frame in packed mode, the Rx threshold must be changed
to 8-bit when the last data frame is processed, either by software setting FRXTH=1 or
automatically by a DMA internal signal when LDMA_RX is set.

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 358. Master full-duplex communication
166

6&.



%6<

026,

'7[

06%



'7[

06%

'7[

06%

63(



7;(



(QDEOH7[5['0$RULQWHUUXSWV
'7[

)7/9/



'7[



'7[





'0$RUVRIWZDUHFRQWURODW7[HYHQWV








'5[

0,62

/6%

'5[

/6%

'5[

/6%



5;1(

'0$RUVRIWZDUHFRQWURODW5[HYHQWV
)5/9/



'0$7[7,&)

'5[






'5[


'5[






'0$5[7,&)
06Y9

Assumptions for master full-duplex communication example:
•

Data size > 8 bit

If DMA is used:
•

Number of Tx frames transacted by DMA is set to 3

•

Number of Rx frames transacted by DMA is set to 3

See also : Communication diagrams on page 968 for details about common assumptions
and notes.

DocID022558 Rev 8

969/1141
1010

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

RM0316

Figure 359. Slave full-duplex communication
166

6&.

%6<



06%

'7[

06%

0,62

06%

'7[

'7[




63(



7;(



(QDEOH7[5['0$RULQWHUUXSWV


'7[

)7/9/



'7[

'7[











'5[

026,

'0$RUVRIWZDUHFRQWURODW7[HYHQWV

/6%

'5[



/6%

'5[

/6%

5;1(

'0$RUVRIWZDUHFRQWURODW5[HYHQWV


)5/9/

'0$7[7,&)

'5[






'5[


'5[






'0$5[7,&)
06Y9

Assumptions for slave full-duplex communication example:
•

Data size > 8 bit

If DMA is used:
•

Number of Tx frames transacted by DMA is set to 3

•

Number of Rx frames transacted by DMA is set to 3

See also : Communication diagrams on page 968 for details about common assumptions
and notes.

970/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 360. Master full-duplex communication with CRC
166
6&.
%6<



026,

'7[

06%

'7[

06%

&5&

06%

63(
7;(


(QDEOH7[5['0$RULQWHUUXSWV
'7[

)7/9/



'7[



'0$RUVRIWZDUHFRQWURODW7[HYHQWV







'5[

0,62

/6%

'5[

/6%

&5&

/6%




5;1(
'0$RUVRIWZDUHFRQWURODW5[HYHQWV

)5/9/



'0$7[7,&)



'5[




'5[


'5[


'0$5[7,&)






06Y9

Assumptions for master full-duplex communication with CRC example:
•

Data size = 16 bit

•

CRC enabled

If DMA is used:
•

Number of Tx frames transacted by DMA is set to 2

•

Number of Rx frames transacted by DMA is set to 3

See also : Communication diagrams on page 968 for details about common assumptions
and notes.

DocID022558 Rev 8

971/1141
1010

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

RM0316

Figure 361. Master full-duplex communication in packed mode
166
6&.
%6<


'7[

026,







'7[








'7[






63(




7;(

(QDEOH7[5['0$RULQWHUUXSWV
'7[

'7[

'7[

'0$RUVRIWZDUHFRQWURODW7[HYHQWV


)7/9/




















0,62















'5[

'5[







'5[



5;1(
'0$RUVRIWZDUHFRQWURODW5[HYHQWV

'5[

'5[

)57+; 

'5[



)5/9/



'0$7[7,&)



















'0$5[7,&)
06Y9

Assumptions for master full-duplex communication in packed mode example:
•

Data size = 5 bit

•

Read/write FIFO is performed mostly by 16-bit access

•

FRXTH=0

If DMA is used:
•

Number of Tx frames to be transacted by DMA is set to 3

•

Number of Rx frames to be transacted by DMA is set to 3

•

PSIZE for both Tx and Rx DMA channel is set to 16-bit

•

LDMA_TX=1 and LDMA_RX=1

See also : Communication diagrams on page 968 for details about common assumptions
and notes.

972/1141

DocID022558 Rev 8

RM0316

30.5.10

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

SPI status flags
Three status flags are provided for the application to completely monitor the state of the SPI
bus.

Tx buffer empty flag (TXE)
The TXE flag is set when transmission TXFIFO has enough space to store data to send.
TXE flag is linked to the TXFIFO level. The flag goes high and stays high until the TXFIFO
level is lower or equal to 1/2 of the FIFO depth. An interrupt can be generated if the TXEIE
bit in the SPIx_CR2 register is set. The bit is cleared automatically when the TXFIFO level
becomes greater than 1/2.

Rx buffer not empty (RXNE)
The RXNE flag is set depending on the FRXTH bit value in the SPIx_CR2 register:
•

If FRXTH is set, RXNE goes high and stays high until the RXFIFO level is greater or
equal to 1/4 (8-bit).

•

If FRXTH is cleared, RXNE goes high and stays high until the RXFIFO level is greater
than or equal to 1/2 (16-bit).

An interrupt can be generated if the RXNEIE bit in the SPIx_CR2 register is set.
The RXNE is cleared by hardware automatically when the above conditions are no longer
true.

Busy flag (BSY)
The BSY flag is set and cleared by hardware (writing to this flag has no effect).
When BSY is set, it indicates that a data transfer is in progress on the SPI (the SPI bus is
busy).
The BSY flag can be used in certain modes to detect the end of a transfer so that the
software can disable the SPI or its peripheral clock before entering a low-power mode which
does not provide a clock for the peripheral. This avoids corrupting the last transfer.
The BSY flag is also useful for preventing write collisions in a multimaster system.
The BSY flag is cleared under any one of the following conditions:

Note:

•

When the SPI is correctly disabled

•

When a fault is detected in Master mode (MODF bit set to 1)

•

In Master mode, when it finishes a data transmission and no new data is ready to be
sent

•

In Slave mode, when the BSY flag is set to '0' for at least one SPI clock cycle between
each data transfer.

When the next transmission can be handled immediately by the master (e.g. if the master is
in Receive-only mode or its Transmit FIFO is not empty), communication is continuous and
the BSY flag remains set to '1' between transfers on the master side. Although this is not the
case with a slave, it is recommended to use always the TXE and RXNE flags (instead of the
BSY flags) to handle data transmission or reception operations.

DocID022558 Rev 8

973/1141
1010

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

30.5.11

RM0316

SPI error flags
An SPI interrupt is generated if one of the following error flags is set and interrupt is enabled
by setting the ERRIE bit.

Overrun flag (OVR)
An overrun condition occurs when data is received by a master or slave and the RXFIFO
has not enough space to store this received data. This can happen if the software or the
DMA did not have enough time to read the previously received data (stored in the RXFIFO)
or when space for data storage is limited e.g. the RXFIFO is not available when CRC is
enabled in receive only mode so in this case the reception buffer is limited into a single data
frame buffer (see Section 30.5.14: CRC calculation).
When an overrun condition occurs, the newly received value does not overwrite the
previous one in the RXFIFO. The newly received value is discarded and all data transmitted
subsequently is lost. Clearing the OVR bit is done by a read access to the SPI_DR register
followed by a read access to the SPI_SR register.

Mode fault (MODF)
Mode fault occurs when the master device has its internal NSS signal (NSS pin in NSS
hardware mode, or SSI bit in NSS software mode) pulled low. This automatically sets the
MODF bit. Master mode fault affects the SPI interface in the following ways:
•

The MODF bit is set and an SPI interrupt is generated if the ERRIE bit is set.

•

The SPE bit is cleared. This blocks all output from the device and disables the SPI
interface.

•

The MSTR bit is cleared, thus forcing the device into slave mode.

Use the following software sequence to clear the MODF bit:
1.

Make a read or write access to the SPIx_SR register while the MODF bit is set.

2.

Then write to the SPIx_CR1 register.

To avoid any multiple slave conflicts in a system comprising several MCUs, the NSS pin
must be pulled high during the MODF bit clearing sequence. The SPE and MSTR bits can
be restored to their original state after this clearing sequence. As a security, hardware does
not allow the SPE and MSTR bits to be set while the MODF bit is set. In a slave device the
MODF bit cannot be set except as the result of a previous multimaster conflict.

CRC error (CRCERR)
This flag is used to verify the validity of the value received when the CRCEN bit in the
SPIx_CR1 register is set. The CRCERR flag in the SPIx_SR register is set if the value
received in the shift register does not match the receiver SPIx_RXCRCR value. The flag is
cleared by the software.

TI mode frame format error (FRE)
A TI mode frame format error is detected when an NSS pulse occurs during an ongoing
communication when the SPI is operating in slave mode and configured to conform to the TI
mode protocol. When this error occurs, the FRE flag is set in the SPIx_SR register. The SPI
is not disabled when an error occurs, the NSS pulse is ignored, and the SPI waits for the
next NSS pulse before starting a new transfer. The data may be corrupted since the error
detection may result in the loss of two data bytes.

974/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
The FRE flag is cleared when SPIx_SR register is read. If the ERRIE bit is set, an interrupt
is generated on the NSS error detection. In this case, the SPI should be disabled because
data consistency is no longer guaranteed and communications should be reinitiated by the
master when the slave SPI is enabled again.

30.5.12

NSS pulse mode
This mode is activated by the NSSP bit in the SPIx_CR2 register and it takes effect only if
the SPI interface is configured as Motorola SPI master (FRF=0) with capture on the first
edge (SPIx_CR1 CPHA = 0, CPOL setting is ignored). When activated, an NSS pulse is
generated between two consecutive data frame transfers when NSS stays at high level for
the duration of one clock period at least. This mode allows the slave to latch data. NSSP
pulse mode is designed for applications with a single master-slave pair.
Figure 362 illustrates NSS pin management when NSSP pulse mode is enabled.
Figure 362. NSSP pulse generation in Motorola SPI master mode
0DVWHUFRQWLQXRXVWUDQVIHU &32/ &3+$ 1663 
VDPSOLQJ

VDPSOLQJ VDPSOLQJ

VDPSOLQJ

VDPSOLQJ VDPSOLQJ

166
RXWSXW
6&.
RXWSXW
026,
RXWSXW

06%

0,62
LQSXW 'RQRWFDUH

06%

/6%
/6%

'RQRWFDUH
W6&.

W6&.

W6&.

ELWVWRELWV

06%

/6%

06%

/6%

W6&.

'RQRWFDUH
W6&.

ELWVWRELWV
069

Note:

Similar behavior is encountered when CPOL = 0. In this case the sampling edge is the rising
edge of SCK, and NSS assertion and deassertion refer to this sampling edge.

30.5.13

TI mode
TI protocol in master mode
The SPI interface is compatible with the TI protocol. The FRF bit of the SPIx_CR2 register
can be used to configure the SPI to be compliant with this protocol.
The clock polarity and phase are forced to conform to the TI protocol requirements whatever
the values set in the SPIx_CR1 register. NSS management is also specific to the TI protocol
which makes the configuration of NSS management through the SPIx_CR1 and SPIx_CR2
registers (SSM, SSI, SSOE) impossible in this case.
In slave mode, the SPI baud rate prescaler is used to control the moment when the MISO
pin state changes to HiZ when the current transaction finishes (see Figure 363). 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
DocID022558 Rev 8

975/1141
1010

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

RM0316

baud rate value set in through the BR[2:0] bits in the SPIx_CR1 register. It is given by the
formula:

t baud_rate
t baud_rate
--------------------- + 4 × t pclk < t release < --------------------- + 6 × t pclk
2
2
If the slave detects a misplaced NSS pulse during a data frame transaction the TIFRE flag is
set.
If the data size is equal to 4-bits or 5-bits, the master in full-duplex mode or transmit-only
mode uses a protocol with one more dummy data bit added after LSB. TI NSS pulse is
generated above this dummy bit clock cycle instead of the LSB in each period.
This feature is not available for Motorola SPI communications (FRF bit set to 0).
Figure 363: TI mode transfer shows the SPI communication waveforms when TI mode is
selected.
Figure 363. TI mode transfer

J
P

SO

HU

LQ

W 5(/($6(

VD

LQ

J
JJ

SO

WU L

P
VD

LQ

HU
JJ

SO

WUL

P
VD

WUL

JJ

HU

J

166

6&.
026,
0,62

'RQRWFDUH
RU

06%

/6%

06%

/6%

06%

/6%

06%

/6%

)5$0(

)5$0(
069

30.5.14

CRC calculation
Two separate CRC calculators are implemented in order to check the reliability of
transmitted and received data. The SPI offers CRC8 or CRC16 calculation independently of
the frame data length, which can be fixed to 8-bit or 16-bit. For all the other data frame
lengths, no CRC is available.

CRC principle
CRC calculation is enabled by setting the CRCEN bit in the SPIx_CR1 register before the
SPI is enabled (SPE = 1). The CRC value is calculated using an odd programmable
polynomial on each bit. The calculation is processed on the sampling clock edge defined by
the CPHA and CPOL bits in the SPIx_CR1 register. The calculated CRC value is checked
automatically at the end of the data block as well as for transfer managed by CPU or by the
DMA. When a mismatch is detected between the CRC calculated internally on the received
data and the CRC sent by the transmitter, a CRCERR flag is set to indicate a data corruption
error. The right procedure for handling the CRC calculation depends on the SPI
configuration and the chosen transfer management.

976/1141

DocID022558 Rev 8

RM0316
Note:

Serial peripheral interface / inter-IC sound (SPI/I2S)
The polynomial value should only be odd. No even values are supported.

CRC transfer managed by CPU
Communication starts and continues normally until the last data frame has to be sent or
received in the SPIx_DR register. Then CRCNEXT bit has to be set in the SPIx_CR1
register to indicate that the CRC frame transaction will follow after the transaction of the
currently processed data frame. The CRCNEXT bit must be set before the end of the last
data frame transaction. CRC calculation is frozen during CRC transaction.
The received CRC is stored in the RXFIFO like a data byte or word. That is why in CRC
mode only, the reception buffer has to be considered as a single 16-bit buffer used to
receive only one data frame at a time.
A CRC-format transaction usually takes one more data frame to communicate at the end of
data sequence. However, when setting an 8-bit data frame checked by 16-bit CRC, two
more frames are necessary to send the complete CRC.
When the last CRC data is received, an automatic check is performed comparing the
received value and the value in the SPIx_RXCRC register. Software has to check the
CRCERR flag in the SPIx_SR register to determine if the data transfers were corrupted or
not. Software clears the CRCERR flag by writing '0' to it.
After the CRC reception, the CRC value is stored in the RXFIFO and must be read in the
SPIx_DR register in order to clear the RXNE flag.

CRC transfer managed by DMA
When SPI communication is enabled with CRC communication and DMA mode, the
transmission and reception of the CRC at the end of communication is automatic (with the
exception of reading CRC data in receive only mode). The CRCNEXT bit does not have to
be handled by the software. The counter for the SPI transmission DMA channel has to be
set to the number of data frames to transmit excluding the CRC frame. On the receiver side,
the received CRC value is handled automatically by DMA at the end of the transaction but
user must take care to flush out received CRC information from RXFIFO as it is always
loaded into it. In full-duplex mode, the counter of the reception DMA channel can be set to
the number of data frames to receive including the CRC, which means, for example, in the
specific case of an 8-bit data frame checked by 16-bit CRC:
DMA_RX = Numb_of_data + 2
In receive only mode, the DMA reception channel counter should contain only the amount of
data transferred, excluding the CRC calculation. Then based on the complete transfer from
DMA, all the CRC values must be read back by software from FIFO as it works as a single
buffer in this mode.
At the end of the data and CRC transfers, the CRCERR flag in the SPIx_SR register is set if
corruption occurred during the transfer.
If packing mode is used, the LDMA_RX bit needs managing if the number of data is odd.

Resetting the SPIx_TXCRC and SPIx_RXCRC values
The SPIx_TXCRC and SPIx_RXCRC values are cleared automatically when new data is
sampled after a CRC phase. This allows the use of DMA circular mode (not available in
receive-only mode) in order to transfer data without any interruption, (several data blocks
covered by intermediate CRC checking phases).

DocID022558 Rev 8

977/1141
1010

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

RM0316

If the SPI is disabled during a communication the following sequence must be followed:

Note:

1.

Disable the SPI

2.

Clear the CRCEN bit

3.

Enable the CRCEN bit

4.

Enable the SPI

When the SPI 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 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 during transaction of the CRC phase once the CRCNEXT signal is released. That is why
the CRC calculation can’t be used at NSS Pulse mode when NSS hardware mode should
be applied at slave normally (see more details at the product errata sheet).
At TI mode, despite the fact that clock phase and clock polarity setting is fixed and
independent on SPIx_CR1 register, the corresponding setting CPOL=0 CPHA=1 has to be
kept at the SPIx_CR1 register anyway if CRC is applied. In addition, the CRC calculation
has to be reset between sessions by SPI disable sequence with re-enable the CRCEN bit
described above at both master and slave side, else CRC calculation can be corrupted at
this specific mode.

30.6

SPI interrupts
During SPI communication an interrupts can be generated by the following events:
•

Transmit TXFIFO ready to be loaded

•

Data received in Receive RXFIFO

•

Master mode fault

•

Overrun error

•

TI frame format error

•

CRC protocol error

Interrupts can be enabled and disabled separately.
Table 168. SPI interrupt requests
Interrupt event

Event flag

Enable Control bit

TXE

TXEIE

Data received in RXFIFO

RXNE

RXNEIE

Master Mode fault event

MODF

Transmit TXFIFO ready to be loaded

Overrun error

OVR

TI frame format error

FRE

CRC protocol error

978/1141

CRCERR

DocID022558 Rev 8

ERRIE

RM0316

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

30.7

I2S functional description (STM32F303xB/C/D/E,
STM32F358xC and STM32F398xE only)

30.7.1

I2S general description
The block diagram of the I2S is shown in Figure 364.
Figure 364. I2S block diagram
$GGUHVVDQGGDWDEXV

7[EXIIHU
%6< 295 02')

&+
&5&
7[( 5[1( )5(
8'5
6,'(
(55

ELW
026,6'
6KLIWUHJLVWHU

-)3/
)3EXT?3$
)3EXT?3$ 

/6%ILUVW

&RPPXQLFDWLRQ
FRQWURO

ELW
5[EXIIHU

166:6

,6&)*
>@

,667'
>@

&.
32/

'$7/(1 &+
/(1
>@
,6
02' ,6(

0DVWHUFRQWUROORJLF
%LGL
PRGH

63,
EDXGUDWHJHQHUDWRU

%LGL
2(

&5& &5&
5[
'))
660 66,
(1 1H[W
RQO\

/6%
63( %5 %5 %5 0675 &32/ &3+$
)LUVW

&.
,6FORFNJHQHUDWRU

,6B&.
,602'
0&.

,6[&/.

0&.2(

2''

,6',9>@
069

1. I2S2ext_SD and I2S3ext_SD are the extended SD pins that control the I2S full-duplex mode.

DocID022558 Rev 8

979/1141
1010

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

RM0316

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.
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.

•

I2S2ext_SD and I2S3ext_SD: additional pins (mapped on the MISO pin) to control the
I2S full-duplex 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.

30.7.2

I2S full duplex
To support I2S full-duplex mode, two extra I2S instances called extended I2Ss (I2S2_ext,
I2S3_ext) are available in addition to I2S2 and I2S3 (see Figure 365). The first I2S fullduplex interface is consequently based on I2S2 and I2S2_ext, and the second one on I2S3
and I2S3_ext.

Note:

980/1141

I2S2_ext an I2S3_ext are used only in full-duplex mode.

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 365. I2S full-duplex block diagram

63,,6[

63,[B026,,6[B6' LQRXW

,6[B6&.

,6B:6

,6[BH[W

,6[BH[W6' LQRXW
069

1. Where x can be 2 or 3.

I2Sx can operate in master mode. As a result:
•

Only I2Sx can output SCK and WS in half-duplex mode

•

Only I2Sx can deliver SCK and WS to I2S2_ext and I2S3_ext in full-duplex mode.

The extended I2Ss (I2Sx_ext) can be used only in full-duplex mode. The I2Sx_ext operate
always in slave mode.
Both I2Sx and I2Sx_ext can be configured as transmitters or receivers.

30.7.3

Supported audio protocols
The four-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).
The I2S interface supports four audio standards, configurable using the I2SSTD[1:0] and
PCMSYNC bits in the SPIx_I2SCFGR register.

DocID022558 Rev 8

981/1141
1010

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

RM0316

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 366. I2S Philips protocol waveforms (16/32-bit full accuracy)
&.

:6

WUDQVPLVVLRQ

UHFHSWLRQ

&DQEHELWRUELW

6'

06%

/6%

06%

&KDQQHOOHIW
&KDQQHO
ULJKW
069

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 367. I2S Philips standard waveforms (24-bit frame)
&.
:6

7UDQVPLVVLRQ

5HFHSWLRQ

ELWGDWD

6'

06%

ELWUHPDLQLQJIRUFHG
/6%

&KDQQHOOHIWELW
&KDQQHOULJKW
069

This mode needs two write or read operations to/from the SPIx_DR register.
•

In transmission mode:
If 0x8EAA33 has to be sent (24-bit):

982/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 368. Transmitting 0x8EAA33

)LUVWZULWHWR'DWDUHJLVWHU

6HFRQGZULWHWR'DWDUHJLVWHU

[($$

[;;
2QO\WKH06%DUHVHQW
WRFRPSDUHWKHELWV
/6%VKDYHQRPHDQLQJ
DQGFDQEHDQ\WKLQJ
069

•

In reception mode:
If data 0x8EAA33 is received:
Figure 369. Receiving 0x8EAA33
)LUVWUHDGWR'DWDUHJLVWHU

6HFRQGUHDGWR'DWDUHJLVWHU

[($$

[;;
2QO\WKH06%DUHVHQW
WRFRPSDUHWKHELWV
/6%VKDYHQRPHDQLQJ
DQGFDQEHDQ\WKLQJ
069

Figure 370. I2S Philips standard (16-bit extended to 32-bit packet frame)
&.
:6

7UDQVPLVVLRQ

5HFHSWLRQ

ELWGDWD

6'

06%

ELWUHPDLQLQJIRUFHG
/6%

&KDQQHOOHIWELW

&KDQQHOULJKW

069

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 371 is required.
Figure 371. Example of 16-bit data frame extended to 32-bit channel frame
2QO\RQHDFFHVVWR63,[B'5
[$
069

DocID022558 Rev 8

983/1141
1010

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

RM0316

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 372. MSB Justified 16-bit or 32-bit full-accuracy length
&.
7UDQVPLVVLRQ

:6

5HFHSWLRQ
RUELWGDWD

6'
/6% 06%

06%
&KDQQHOOHIW

&KDQQHOULJKW
069

Data are latched on the falling edge of CK (for transmitter) and are read on the rising edge
(for the receiver).
Figure 373. MSB justified 24-bit frame length
&.
7UDQVPLVVLRQ

:6

5HFHSWLRQ

ELWGDWD

ELWUHPDLQLQJ
IRUFHG

6'
06%

/6%
&KDQQHOOHIWELW
&KDQQHOULJKW
069

984/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 374. MSB justified 16-bit extended to 32-bit packet frame
&.
7UDQVPLVVLRQ

:6

5HFHSWLRQ

ELWGDWD

ELWUHPDLQLQJ
IRUFHG

6'
06%

/6%
&KDQQHOOHIWELW
&KDQQHOULJKW
069

LSB justified standard
This standard is similar to the MSB justified standard (no difference for the 16-bit and 32-bit
full-accuracy frame formats).
The sampling of the input and output signals is the same as for the I2S Philips standard.
Figure 375. LSB justified 16-bit or 32-bit full-accuracy
&.
:6
5HFHSWLRQ

7UDQVPLVVLRQ
RUELWGDWD

6'
/6% 06%

06%
&KDQQHOOHIW

&KDQQHOULJKW

069

Figure 376. LSB justified 24-bit frame length
&.
:6

5HFHSWLRQ
7UDQVPLVVLRQ

6'

ELWGDWD
IRUFHG

ELWUHPDLQLQJ
06%

/6%

&KDQQHOOHIWELW
&KDQQHOULJKW
069

•

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.

DocID022558 Rev 8

985/1141
1010

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

RM0316

Figure 377. Operations required to transmit 0x3478AE
)LUVWZULWHWR'DWDUHJLVWHU
FRQGLWLRQHGE\7;( 

6HFRQGZULWHWR'DWDUHJLVWHU
FRQGLWLRQHGE\7;( 

[;;

[$(

2QO\WKH/6%RIWKH
KDOIZRUGDUHVLJQLILFDQW
$ILHOGRI[LVIRUFHG
LQVWHDGRIWKH06%V

•

069

In reception mode:
If data 0x3478AE are received, two successive read operations from the SPIx_DR
register are required on each RXNE event.
Figure 378. Operations required to receive 0x3478AE
)LUVWUHDGIURP'DWDUHJLVWHU
FRQGLWLRQHGE\5;1( 

6HFRQGUHDGIURP'DWDUHJLVWHU
FRQGLWLRQHGE\5;1( 

[;;

[$(

2QO\WKH/6%RIWKH
KDOIZRUGDUHVLJQLILFDQW
$ILHOGRI[LVIRUFHG
LQVWHDGRIWKH06%V
069

Figure 379. LSB justified 16-bit extended to 32-bit packet frame
&.
5HFHSWLRQ

:6
7UDQVPLVVLRQ

6'

ELWUHPDLQLQJ

ELWGDWD
IRUFHG
06%
&KDQQHOOHIWELW

/6%

&KDQQHOULJKW
069

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 380 is required.

986/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 380. Example of 16-bit data frame extended to 32-bit channel frame
2QO\RQHDFFHVVWRWKH63,['5UHJLVWHU

[$
069

In transmission mode, when a TXE event occurs, the application has to write the data to be
transmitted (in this case 0x76A3). The 0x000 field is transmitted first (extension on 32-bit).
The TXE flag is set again as soon as the effective data (0x76A3) is sent on SD.
In reception mode, RXNE is asserted as soon as the significant half-word is received (and
not the 0x0000 field).
In this way, more time is provided between two write or read operations to prevent underrun
or overrun conditions.

PCM standard
For the PCM standard, there is no need to use channel-side information. The two PCM
modes (short and long frame) are available and configurable using the PCMSYNC bit in
SPIx_I2SCFGR register.
In PCM mode, the output signals (WS, SD) are sampled on the rising edge of CK signal.
The input signals (WS, SD) are captured on the falling edge of CK.
Note that CK and WS are configured as output in MASTER mode.
Figure 381. PCM standard waveforms (16-bit)

&.
:6
VKRUWIUDPH
ELWV

:6
ORQJIUDPH

6'

06%

/6% 06%

069

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.

DocID022558 Rev 8

987/1141
1010

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

RM0316

Figure 382. PCM standard waveforms (16-bit extended to 32-bit packet frame)
&.
:6
VKRUWIUDPH
:6
ORQJIUDPH

8SWRELWV

ELWV

6'

06%

/6%

069

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.

30.7.4

Start-up description
The Figure 383 shows how the serial interface is handled in MASTER mode, when the
SPI/I2S is enabled (via I2SE bit). It shows as well the effect of CKPOL on the generated
signals.

988/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
Figure 383. Start sequence in master mode

0DVWHU,63KLOLSV6WDQGDUG
:6 2
&. 2 &.32/ 
&. 2 &.32/ 
GXP

6' 2

/HIWVDPSOH

5LJKWVDPSOH

,6(

0DVWHU,606%RU/6%MXVWLILHG
:6 2
&. 2 &.32/ 
&. 2 &.32/ 
GXP

6' 2

/HIWVDPSOH

5LJKWVDPSOH

,6(

0DVWHU3&0VKRUWIUDPH
:6 2
&. 2 &.32/ 
&. 2 &.32/ 
6' 2

GXP

6DPSOH

6DPSOH

,6(

0DVWHU3&0ORQJIUDPH
:6 2
&. 2 &.32/ 
&. 2 &.32/ 
6' 2

GXP

6DPSOH

6DPSOH

,6(
GXPQRWVLJQLILFDQWGDWD

06Y9

In slave mode, the user has to enable the audio interface before the WS becomes active.
This means that the I2SE bit must be set to 1 when WS = 1 for I2S Philips standard, or when
WS = 0 for other standards.

DocID022558 Rev 8

989/1141
1010

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

30.7.5

RM0316

Clock generator
The I2S bit rate determines the data flow on the I2S data line and the I2S clock signal
frequency.
I2S bit rate = number of bits per channel × number of channels × sampling audio frequency
For a 16-bit audio, left and right channel, the I2S bit rate is calculated as follows:
I2S bit rate = 16 × 2 × fS
It will be: I2S bit rate = 32 x 2 x fS if the packet length is 32-bit wide.
Figure 384. Audio sampling frequency definition

RUELW
ULJKWFKDQQHO

RUELWOHIW
FKDQQHO
RUELWV
VDPSOLQJSRLQW

)6
VDPSOLQJSRLQW

)6DXGLRVDPSOLQJIUHTXHQF\
069

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 385. I2S clock generator architecture

0&.
,ð6[&/.

ELWOLQHDUGLYLGHU
UHVKDSLQJVWDJH



'LY

'LYLGHUE\







&.

,ð6',9>@

&+/(1

0&.2( 2''

,ð602'

0&.2(

069

1. Where x can be 2 or 3.

Figure 385 presents the communication clock architecture. By default, the I2Sx clock is
always the system clock. To achieve high-quality audio performance, the I2SxCLK clock
source can be an external clock (mapped to the I2S_CKIN pin). Refer to Section 9.4.2:
Clock configuration register (RCC_CFGR).
The audio sampling frequency may be 192 KHz, 96 kHz or 48 kHz. In order to reach the
desired frequency, the linear divider needs to be programmed according to the formulas
below:

990/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
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 169 provides example precision values for different clock configurations.

Note:

Other configurations are possible that allow optimum clock precision.
Table 169. Audio-frequency precision using standard 8 MHz HSE(1)

SYSCLK
(MHz)

I2S_DIV

I2S_ODD
MCLK

16-bit

32-bit

16-bit

32-bit

Target fS
(Hz)

Real fS (KHz)
16-bit

32-bit

Error
16-bit

32-bit

72

11

6

1

0

No

96000

97826.09

93750

1.90%

2.34%

72

23

11

1

1

No

48000

47872.34

48913.04

0.27%

1.90%

72

25

13

1

0

No

44100

44117.65

43269.23

0.04%

1.88%

72

35

17

0

1

No

32000

32142.86

32142.86

0.44%

0.44%

72

51

25

0

1

No

22050

22058.82

22058.82

0.04%

0.04%

72

70

35

1

0

No

16000

15675.75

16071.43

0.27%

0.45%

72

102

51

0

0

No

11025

11029.41

11029.41

0.04%

0.04%

72

140

70

1

1

No

8000

8007.11

7978.72

0.09%

0.27%

72

3

3

0

0

Yes

48000

46875

46875

2.34%

2.34%

72

3

3

0

0

Yes

44100

46875

46875

6.29%

6.29%

72

9

9

0

0

Yes

32000

31250

31250

2.34%

2.34%

72

6

6

1

1

Yes

22050

21634.61

21634.61

1.88%

1.88%

72

9

9

0

0

Yes

16000

15625

15625

2.34%

2.34%

72

13

13

0

0

Yes

11025

10817.30

10817.30

1.88%

1.88%

72

17

17

1

1

Yes

8000

8035.71

8035.71

0.45%

0.45%

1. This table gives only example values for different clock configurations. Other configurations allowing optimum clock
precision are possible.

30.7.6

I2S master mode
The I2S can be configured as follows:
•

In master mode for transmission or reception (half-duplex mode using I2Sx)

•

In master mode transmission and reception (full-duplex mode using I2Sx and
I2Sx_ext).

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.

DocID022558 Rev 8

991/1141
1010

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

RM0316

Procedure
1.

Select the I2SDIV[7:0] bits in the SPIx_I2SPR register to define the serial clock baud
rate to reach the proper audio sample frequency. The ODD bit in the SPIx_I2SPR
register also has to be defined.

2.

Select the CKPOL bit to define the steady level for the communication clock. Set the
MCKOE bit in the SPIx_I2SPR register if the master clock MCK needs to be provided
to the external DAC/ADC audio component (the I2SDIV and ODD values should be
computed depending on the state of the MCK output, for more details refer to
Section 30.7.5: Clock generator).

3.

Set the I2SMOD bit in the SPIx_I2SCFGR register to activate the I2S functions and
choose the I2S standard through the I2SSTD[1:0] and PCMSYNC bits, the data length
through the DATLEN[1:0] bits and the number of bits per channel by configuring the
CHLEN bit. Select also the I2S master mode and direction (Transmitter or Receiver)
through the I2SCFG[1:0] bits in the SPIx_I2SCFGR register.

4.

If needed, select all the potential interrupt sources and the DMA capabilities by writing
the SPIx_CR2 register.

5.

The I2SE bit in SPIx_I2SCFGR register must be set.

WS and CK are configured in output mode. MCK is also an output, if the MCKOE bit in
SPIx_I2SPR is set.

Transmission sequence
The transmission sequence begins when a half-word is written into the Tx buffer.
Lets assume the first data written into the Tx buffer corresponds to the left channel data.
When data are transferred from the Tx buffer to the shift register, TXE is set and data
corresponding to the right channel have to be written into the Tx buffer. The CHSIDE flag
indicates which channel is to be transmitted. It has a meaning when the TXE flag is set
because the CHSIDE flag is updated when TXE goes high.
A full frame has to be considered as a left channel data transmission followed by a right
channel data transmission. It is not possible to have a partial frame where only the left
channel is sent.
The data half-word is parallel loaded into the 16-bit shift register during the first bit
transmission, and then shifted out, serially, to the MOSI/SD pin, MSB first. The TXE flag is
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 30.7.3: Supported audio protocols).
To ensure a continuous audio data transmission, it is mandatory to write the SPIx_DR
register with the next data to transmit before the end of the current transmission.
To switch off the I2S, by clearing I2SE, it is mandatory to wait for TXE = 1 and BSY = 0.

Reception sequence
The operating mode is the same as for transmission mode except for the point 3 (refer to the
procedure described in Section 30.7.6: I2S master mode), where the configuration should
set the master reception mode through the I2SCFG[1:0] bits.
Whatever the data or channel length, the audio data are received by 16-bit packets. This
means that each time the Rx buffer is full, the RXNE flag is set and an interrupt is generated
992/1141

DocID022558 Rev 8

RM0316

Serial peripheral interface / inter-IC sound (SPI/I2S)
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 30.7.3: Supported audio protocols.
If data are received while the previously received data have not been read yet, an overrun is
generated and the OVR flag is set. If the ERRIE bit is set in the SPIx_CR2 register, an
interrupt is generated to indicate the error.
To switch off the I2S, specific actions are required to ensure that the I2S completes the
transfer cycle properly without initiating a new data transfer. The sequence depends on the
configuration of the data and channel lengths, and on the audio protocol mode selected. In
the case of:
•

•

•

16-bit data length extended on 32-bit channel length (DATLEN = 00 and CHLEN = 1)
using the LSB justified mode (I2SSTD = 10)
a)

Wait for the second to last RXNE = 1 (n – 1)

b)

Then wait 17 I2S clock cycles (using a software loop)

c)

Disable the I2S (I2SE = 0)

16-bit data length extended on 32-bit channel length (DATLEN = 00 and CHLEN = 1) in
MSB justified, I2S or PCM modes (I2SSTD = 00, I2SSTD = 01 or I2SSTD = 11,
respectively)
a)

Wait for the last RXNE

b)

Then wait 1 I2S clock cycle (using a software loop)

c)

Disable the I2S (I2SE = 0)

For all other combinations of DATLEN and CHLEN, whatever the audio mode selected
through the I2SSTD bits, carry out the following sequence to switch off the I2S:
a)

Wait for the second to last RXNE = 1 (n – 1)

b)

Then wait one I2S clock cycle (using a software loop)

c)

Disable the I2S (I2SE = 0)

Note:

The BSY flag is kept low during transfers.

30.7.7

I2S slave mode
The I2S can be configured as follows:
•

In slave mode for transmission or reception (half-duplex mode using I2Sx)

•

In slave mode transmission and reception (full-duplex mode using I2Sx and I2Sx_ext).

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:

DocID022558 Rev 8

993/1141
1010

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

Note:

RM0316

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 (see note below).

The I2S slave must be enabled after the external master sets the WS line at high level if the
I2S protocol is selected, or at low level if the LSB or MSB-justified mode is selected.

Transmission sequence
The transmission sequence begins when the external master device sends the clock and
when the NSS_WS signal requests the transfer of data. The slave has to be enabled before
the external master starts the communication. The I2S data register has to be loaded before
the master initiates the communication.
For the I2S, MSB justified and LSB justified modes, the first data item to be written into the
data register corresponds to the data for the left channel. When the communication starts,
the data are transferred from the Tx buffer to the shift register. The TXE flag is then set in
order to request the right channel data to be written into the I2S data register.
The CHSIDE flag indicates which channel is to be transmitted. Compared to the master
transmission mode, in slave mode, CHSIDE is sensitive to the WS signal coming from the
external master. This means that the slave needs to be ready to transmit the first data
before the clock is generated by the master. WS assertion corresponds to left channel
transmitted first.
Note:

The I2SE has to be written at least two PCLK cycles before the first clock of the master
comes on the CK line.
The data half-word is parallel-loaded into the 16-bit shift register (from the internal bus)
during the first bit transmission, and then shifted out serially to the MOSI/SD pin MSB first.
The TXE flag is set after each transfer from the Tx buffer to the shift register and an interrupt
is generated if the TXEIE bit in the SPIx_CR2 register is set.
Note that the TXE flag should be checked to be at 1 before attempting to write the Tx buffer.
For more details about the write operations depending on the I2S standard mode selected,
refer to Section 30.7.3: Supported audio protocols.
To secure a continuous audio data transmission, it is mandatory to write the SPIx_DR
register with the next data to transmit before the end of the current transmission. An
underrun flag is set and an interrupt may be generated if the data are not written into the
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.

994/1141

DocID022558 Rev 8

RM0316

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

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 30.7.7: I2S slave mode), where the configuration should
set the master reception mode using the I2SCFG[1:0] bits in the SPIx_I2SCFGR register.
Whatever the data length or the channel length, the audio data are received by 16-bit
packets. This means that each time the RX buffer is full, the RXNE flag in the SPIx_SR
register is set and an interrupt is generated if the RXNEIE bit is set in the SPIx_CR2
register. Depending on the data length and channel length configuration, the audio value
received for a right or left channel may result from one or two receptions into the RX buffer.
The CHSIDE flag is updated each time data are received to be read from the SPIx_DR
register. It is sensitive to the external WS line managed by the external master component.
Clearing the RXNE bit is performed by reading the SPIx_DR register.
For more details about the read operations depending the I2S standard mode selected, refer
to Section 30.7.3: Supported audio protocols.
If data are received while the preceding received data have not yet been read, an overrun is
generated and the OVR flag is set. If the bit ERRIE is set in the SPIx_CR2 register, an
interrupt is generated to indicate the error.
To switch off the I2S in reception mode, I2SE has to be cleared immediately after receiving
the last RXNE = 1.
Note:

The external master components should have the capability of sending/receiving data in 16bit or 32-bit packets via an audio channel.

30.7.8

I2S status flags
Three status flags are provided for the application to fully monitor the state of the I2S bus.

Busy flag (BSY)
The BSY flag is set and cleared by hardware (writing to this flag has no effect). It indicates
the state of the communication layer of the I2S.
When BSY is set, it indicates that the I2S is busy communicating. There is one exception in
master receive mode (I2SCFG = 11) where the BSY flag is kept low during reception.
The BSY flag is useful to detect the end of a transfer if the software needs to disable the I2S.
This avoids corrupting the last transfer. For this, the procedure described below must be
strictly respected.
The BSY flag is set when a transfer starts, except when the I2S is in master receiver mode.
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:
•

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

DocID022558 Rev 8

995/1141
1010

Serial peripheral interface / inter-IC sound (SPI/I2S)
Note:

RM0316

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).

30.7.9

I2S error flags
There are three error flags for the I2S cell.

Underrun flag (UDR)
In slave transmission mode this flag is set when the first clock for data transmission appears
while the software has not yet loaded any value into SPIx_DR. It is available when the
I2SMOD bit in the SPIx_I2SCFGR register is set. An interrupt may be generated if the
ERRIE bit in the SPIx_CR2 register is set.
The UDR bit is cleared by a read operation on the SPIx_SR register.

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.

996/1141

DocID022558 Rev 8

RM0316

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

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 CK communication clock or on the WS frame synchronization line. An error interrupt can
be generated if the ERRIE bit is set. The desynchronization flag (FRE) is cleared by
software when the status register is read.

30.7.10

DMA features
In I2S mode, the DMA works in exactly the same way as it does in SPI mode. There is no
difference except that the CRC feature is not available in I2S mode since there is no data
transfer protection system.

30.8

I2S interrupts
Table 170 provides the list of I2S interrupts.
Table 170. I2S interrupt requests
Interrupt event

Event flag

Enable control bit

Transmit buffer empty flag

TXE

TXEIE

Receive buffer not empty flag

RXNE

RXNEIE

Overrun error

OVR

Underrun error

UDR

Frame error flag

FRE

DocID022558 Rev 8

ERRIE

997/1141
1010

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

RM0316

SPI and I2S registers

30.9

The peripheral registers can be accessed by half-words (16-bit) or words (32-bit). SPI_DR
in addition by can be accessed by 8-bit access.

30.9.1

SPI control register 1 (SPIx_CR1)
Address offset: 0x00
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

BIDI
MODE

BIDI
OE

CRC
EN

CRC
NEXT

CRCL

RX
ONLY

SSM

SSI

LSB
FIRST

SPE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

5

4

3

BR [2:0]
rw

rw

rw

2

1

0

MSTR

CPOL

CPHA

rw

rw

rw

Bit 15 BIDIMODE: Bidirectional data mode enable. This bit enables half-duplex communication using
common single bidirectional data line. Keep RXONLY bit clear when bidirectional mode is
active.
0: 2-line unidirectional data mode selected
1: 1-line bidirectional data mode selected
Note: This bit is not used in I2S mode.
Bit 14 BIDIOE: Output enable in bidirectional mode
This bit combined with the BIDIMODE bit selects the direction of transfer in bidirectional mode
0: Output disabled (receive-only mode)
1: Output enabled (transmit-only mode)
Note: In master mode, the MOSI pin is used and in slave mode, the MISO pin is used.
This bit is not used in I2S mode.
Bit 13 CRCEN: Hardware CRC calculation enable
0: CRC calculation disabled
1: CRC calculation Enabled
Note: This bit should be written only when SPI is disabled (SPE = ‘0’) for correct operation.
This bit is not used in I2S mode.
Bit 12 CRCNEXT: Transmit CRC next
0: Next transmit value is from Tx buffer
1: Next transmit value is from Tx CRC register
Note: This bit has to be written as soon as the last data is written in the SPIx_DR register.
This bit is not used in I2S mode.
Bit 11 CRCL: CRC length
This bit is set and cleared by software to select the CRC length.
0: 8-bit CRC length
1: 16-bit CRC length
Note: This bit should be written only when SPI is disabled (SPE = ‘0’) for correct operation.
This bit is not used in I2S mode.

998/1141

DocID022558 Rev 8

RM0316

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

Bit 10 RXONLY: Receive only mode enabled.
This bit enables simplex communication using a single unidirectional line to receive data
exclusively. Keep BIDIMODE bit clear when receive only mode is active.This bit is also useful
in a multislave system in which this particular slave is not accessed, the output from the
accessed slave is not corrupted.
0: Full-duplex (Transmit and receive)
1: Output disabled (Receive-only mode)
Note: This bit is not used in I2S mode.
Bit 9 SSM: Software slave management
When the SSM bit is set, the NSS pin input is replaced with the value from the SSI bit.
0: Software slave management disabled
1: Software slave management enabled
Note: This bit is not used in I2S mode and SPI TI mode.
Bit 8 SSI: Internal slave select
This bit has an effect only when the SSM bit is set. The value of this bit is forced onto the NSS
pin and the I/O value of the NSS pin is ignored.
Note: This bit is not used in I2S mode and SPI TI mode.
Bit 7 LSBFIRST: Frame format
0: data is transmitted / received with the MSB first
1: data is transmitted / received with the LSB first
Note: 1. This bit should not be changed when communication is ongoing.
2. This bit is not used in I2S mode and SPI TI mode.
Bit 6 SPE: SPI enable
0: Peripheral disabled
1: Peripheral enabled
Note: When disabling the SPI, follow the procedure described in Procedure for disabling the
SPI on page 964.
This bit is not used in I2S mode.
Bits 5:3 BR[2:0]: Baud rate control
000: fPCLK/2
001: fPCLK/4
010: fPCLK/8
011: fPCLK/16
100: fPCLK/32
101: fPCLK/64
110: fPCLK/128
111: fPCLK/256
Note: These bits should not be changed when communication is ongoing.
This bit is not used in I2S mode.

DocID022558 Rev 8

999/1141
1010

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

RM0316

Bit 2 MSTR: Master selection
0: Slave configuration
1: Master configuration
Note: This bit should not be changed when communication is ongoing.
This bit is not used in I2S mode.
Bit1 CPOL: Clock polarity
0: CK to 0 when idle
1: CK to 1 when idle
Note: This bit should not be changed when communication is ongoing.
This bit is not used in 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.
This bit is not used in I2S mode and SPI TI mode except the case when CRC is applied
at TI mode.

30.9.2

SPI control register 2 (SPIx_CR2)
Address offset: 0x04
Reset value: 0x0700

15

14

13

12

Res.

LDMA
_TX

LDMA
_RX

FRXT
H

rw

rw

rw

11

10

9

8

DS [3:0]
rw

rw

rw

7

6

5

TXEIE RXNEIE ERRIE
rw

rw

rw

rw

4

3

2

FRF

NSSP

SSOE

rw

rw

rw

1

0

TXDMAEN RXDMAEN
rw

rw

Bit 15 Reserved, must be kept at reset value.
Bit 14 LDMA_TX: Last DMA transfer for transmission
This bit is used in data packing mode, to define if the total number of data to transmit by DMA
is odd or even. It has significance only if the TXDMAEN bit in the SPIx_CR2 register is set and
if packing mode is used (data length =< 8-bit and write access to SPIx_DR is 16-bit wide). It
has to be written when the SPI is disabled (SPE = 0 in the SPIx_CR1 register).
0: Number of data to transfer is even
1: Number of data to transfer is odd
Note: Refer to Procedure for disabling the SPI on page 964 if the CRCEN bit is set.
This bit is not used in I²S mode.
Bit 13 LDMA_RX: Last DMA transfer for reception
This bit is used in data packing mode, to define if the total number of data to receive by DMA is
odd or even. It has significance only if the RXDMAEN bit in the SPIx_CR2 register is set and if
packing mode is used (data length =< 8-bit and write access to SPIx_DR is 16-bit wide). It has
to be written when the SPI is disabled (SPE = 0 in the SPIx_CR1 register).
0: Number of data to transfer is even
1: Number of data to transfer is odd
Note: Refer to Procedure for disabling the SPI on page 964 if the CRCEN bit is set.
This bit is not used in I²S mode.

1000/1141

DocID022558 Rev 8

RM0316

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

Bit 12 FRXTH: FIFO reception threshold
This bit is used to set the threshold of the RXFIFO that triggers an RXNE event
0: RXNE event is generated if the FIFO level is greater than or equal to 1/2 (16-bit)
1: RXNE event is generated if the FIFO level is greater than or equal to 1/4 (8-bit)
Note: This bit is not used in I²S mode.
Bits 11:8 DS [3:0]: Data size
These bits configure the data length for SPI transfers:
0000: Not used
0001: Not used
0010: Not used
0011: 4-bit
0100: 5-bit
0101: 6-bit
0110: 7-bit
0111: 8-bit
1000: 9-bit
1001: 10-bit
1010: 11-bit
1011: 12-bit
1100: 13-bit
1101: 14-bit
1110: 15-bit
1111: 16-bit
If software attempts to write one of the “Not used” values, they are forced to the value “0111”(8bit).
Note: This bit is not used in I²S mode.
Bit 7 TXEIE: Tx buffer empty interrupt enable
0: TXE interrupt masked
1: TXE interrupt not masked. Used to generate an interrupt request when the TXE flag is set.
Bit 6 RXNEIE: RX buffer not empty interrupt enable
0: RXNE interrupt masked
1: RXNE interrupt not masked. Used to generate an interrupt request when the RXNE flag is
set.
Bit 5 ERRIE: Error interrupt enable
This bit controls the generation of an interrupt when an error condition occurs (CRCERR,
OVR, MODF in SPI mode, FRE at TI mode and UDR, OVR, and FRE in I2S mode).
0: Error interrupt is masked
1: Error interrupt is enabled
Bit 4 FRF: Frame format
0: SPI Motorola mode
1 SPI TI mode
Note: This bit must be written only when the SPI is disabled (SPE=0).
This bit is not used in I2S mode.

DocID022558 Rev 8

1001/1141
1010

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

RM0316

Bit 3 NSSP: NSS pulse management
This bit is used in master mode only. it allow the SPI to generate an NSS pulse between two
consecutive data when doing continuous transfers. In the case of a single data transfer, it
forces the NSS pin high level after the transfer.
It has no meaning if CPHA = ’1’, or FRF = ’1’.
0: No NSS pulse
1: NSS pulse generated
Note: 1. This bit must be written only when the SPI is disabled (SPE=0).
2. This bit is not used in I2S mode and SPI TI mode.
Bit 2 SSOE: SS output enable
0: SS output is disabled in master mode and the SPI interface can work in multimaster
configuration
1: SS output is enabled in master mode and when the SPI interface is enabled. The SPI
interface cannot work in a multimaster environment.
Note: This bit is not used in I2S mode and SPI TI mode.
Bit 1 TXDMAEN: Tx buffer DMA enable
When this bit is set, a DMA request is generated whenever the TXE flag is set.
0: Tx buffer DMA disabled
1: Tx buffer DMA enabled
Bit 0 RXDMAEN: Rx buffer DMA enable
When this bit is set, a DMA request is generated whenever the RXNE flag is set.
0: Rx buffer DMA disabled
1: Rx buffer DMA enabled

1002/1141

DocID022558 Rev 8

RM0316

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

30.9.3

SPI status register (SPIx_SR)
Address offset: 0x08
Reset value: 0x0002

15
Res.

14
Res.

13
Res.

12

11

10

9

FTLVL[1:0]

FRLVL[2:0]

r

r

r

r

8

7

6

5

4

3

2

1

0

UDR

CHSIDE

TXE

RXNE

r

r

r

r

FRE

BSY

OVR

MODF

CRC
ERR

r

r

r

r

rc_w0

Bits 15:13 Reserved, must be kept at reset value.
Bits 12:11 FTLVL[1:0]: FIFO Transmission Level
These bits are set and cleared by hardware.
00: FIFO empty
01: 1/4 FIFO
10: 1/2 FIFO
11: FIFO full (considered as FULL when the FIFO threshold is greater than 1/2)
Note: These bits are not used in I²S mode.
Bits 10:9 FRLVL[1:0]: FIFO reception level
These bits are set and cleared by hardware.
00: FIFO empty
01: 1/4 FIFO
10: 1/2 FIFO
11: FIFO full
Note: These bits are not used in I²S mode and in SPI receive-only mode while CRC
calculation is enabled.
Bit 8 FRE: Frame format error
This flag is used for SPI in TI slave mode and I2S slave mode. Refer to Section 30.5.11: SPI
error flags and Section 30.7.9: I2S error flags.
This flag is set by hardware and reset when SPIx_SR is read by software.
0: No frame format error
1: A frame format error occurred
Bit 7 BSY: Busy flag
0: SPI (or I2S) not busy
1: SPI (or I2S) is busy in communication or Tx buffer is not empty
This flag is set and cleared by hardware.
Note: The BSY flag must be used with caution: refer to Section 30.5.10: SPI status flags and
Procedure for disabling the SPI on page 964.
Bit 6 OVR: Overrun flag
0: No overrun occurred
1: Overrun occurred
This flag is set by hardware and reset by a software sequence. Refer to I2S error flags on
page 996 for the software sequence.
Bit 5 MODF: Mode fault
0: No mode fault occurred
1: Mode fault occurred
This flag is set by hardware and reset by a software sequence. Refer to Section : Mode fault
(MODF) on page 974 for the software sequence.
Note: This bit is not used in I2S mode.

DocID022558 Rev 8

1003/1141
1010

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

RM0316

Bit 4 CRCERR: CRC error flag
0: CRC value received matches the SPIx_RXCRCR value
1: CRC value received does not match the SPIx_RXCRCR value
This flag is set by hardware and cleared by software writing 0.
Note: This bit is not used in I2S mode.
Bit 3 UDR: Underrun flag
0: No underrun occurred
1: Underrun occurred
This flag is set by hardware and reset by a software sequence. Refer to I2S error flags on
page 996 for the software sequence.
Note: This bit is not used in SPI mode.
Bit 2 CHSIDE: Channel side
0: Channel Left has to be transmitted or has been received
1: Channel Right has to be transmitted or has been received
Note: This bit is not used in SPI mode. It has no significance in PCM mode.
Bit 1 TXE: Transmit buffer empty
0: Tx buffer not empty
1: Tx buffer empty
Bit 0 RXNE: Receive buffer not empty
0: Rx buffer empty
1: Rx buffer not empty

30.9.4

SPI data register (SPIx_DR)
Address offset: 0x0C
Reset value: 0x0000

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DR[15:0]
rw

Bits 15:0 DR[15:0]: Data register
Data received or to be transmitted
The data register serves as an interface between the Rx and Tx FIFOs. When the data
register is read, RxFIFO is accessed while the write to data register accesses TxFIFO (See
Section 30.5.9: Data transmission and reception procedures).
Note: Data is always right-aligned. Unused bits are ignored when writing to the register, and
read as zero when the register is read. The Rx threshold setting must always
correspond with the read access currently used.

30.9.5

SPI CRC polynomial register (SPIx_CRCPR)
Address offset: 0x10
Reset value: 0x0007

15

14

13

12

11

10

9

8

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CRCPOLY[15:0]

1004/1141

rw

rw

DocID022558 Rev 8

RM0316

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

Bits 15:0 CRCPOLY[15:0]: CRC polynomial register
This register contains the polynomial for the CRC calculation.
The CRC polynomial (0007h) is the reset value of this register. Another polynomial can be
configured as required.
Note: The polynomial value should be odd only. No even value is supported.

DocID022558 Rev 8

1005/1141
1010

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

30.9.6

RM0316

SPI Rx CRC register (SPIx_RXCRCR)
Address offset: 0x14
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

RxCRC[15:0]
r

r

r

r

r

r

r

r

r

Bits 15:0 RXCRC[15:0]: Rx CRC register
When CRC calculation is enabled, the RxCRC[15:0] bits contain the computed CRC value of
the subsequently received bytes. This register is reset when the CRCEN bit in SPIx_CR1
register is written to 1. The CRC is calculated serially using the polynomial programmed in the
SPIx_CRCPR register.
Only the 8 LSB bits are considered when the CRC frame format is set to be 8-bit length (CRCL
bit in the SPIx_CR1 is cleared). CRC calculation is done based on any CRC8 standard.
The entire 16-bits of this register are considered when a 16-bit CRC frame format is selected
(CRCL bit in the SPIx_CR1 register is set). CRC calculation is done based on any CRC16
standard.
Note: A read to this register when the BSY Flag is set could return an incorrect value.
These bits are not used in I2S mode.

30.9.7

SPI Tx CRC register (SPIx_TXCRCR)
Address offset: 0x18
Reset value: 0x0000

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

TxCRC[15:0]
r

r

r

r

r

r

r

r

r

Bits 15:0 TxCRC[15:0]: Tx CRC register
When CRC calculation is enabled, the TxCRC[7:0] bits contain the computed CRC value of
the subsequently transmitted bytes. This register is reset when the CRCEN bit of SPIx_CR1 is
written to 1. The CRC is calculated serially using the polynomial programmed in the
SPIx_CRCPR register.
Only the 8 LSB bits are considered when the CRC frame format is set to be 8-bit length
(CRCL bit in the SPIx_CR1 is cleared). CRC calculation is done based on any CRC8
standard.
The entire 16-bits of this register are considered when a 16-bit CRC frame format is selected
(CRCL bit in the SPIx_CR1 register is set). CRC calculation is done based on any CRC16
standard.
Note: A read to this register when the BSY flag is set could return an incorrect value.
These bits are not used in I2S mode.

1006/1141

DocID022558 Rev 8

RM0316

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

SPIx_I2S configuration register (SPIx_I2SCFGR)

30.9.8

Address offset: 0x1C
Reset value: 0x0000
15

14

13

12

11

10

Res.

Res.

Res.

Res.

I2SMOD

I2SE

rw

rw

9

8

I2SCFG
rw

rw

7

6

PCMSYNC

Res.

rw

5

4

I2SSTD
rw

rw

3
CKPOL
rw

2

1

0

DATLEN
rw

CHLEN

rw

rw

Bits 15:12 Reserved: Forced to 0 by hardware
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: These bits should be configured when the I2S is disabled.
They are not used in SPI mode.
Bit 7 PCMSYNC: PCM frame synchronization
0: Short frame synchronization
1: Long frame synchronization
Note: This bit has a meaning only if I2SSTD = 11 (PCM standard is used).
It is not used in SPI mode.
Bit 6 Reserved: forced at 0 by hardware
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 30.7.3 on page 981
Note: For correct operation, these bits should be configured when the I2S is disabled.
They are not used in SPI mode.

DocID022558 Rev 8

1007/1141
1010

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

RM0316

Bit 3 CKPOL: Inactive state clock polarity
0: I2S clock inactive state is low level
1: I2S clock inactive state is high level
Note: For correct operation, this bit should be configured when the I2S is disabled.
It is not used in SPI mode.
The bit CKPOL does not affect the CK edge sensitivity used to receive or transmit the SD and
WS signals.
Bits 2:1 DATLEN: Data length to be transferred
00: 16-bit data length
01: 24-bit data length
10: 32-bit data length
11: Not allowed
Note: For correct operation, these bits should be configured when the I2S is disabled.
They are not used in SPI mode.
Bit 0 CHLEN: Channel length (number of bits per audio channel)
0: 16-bit wide
1: 32-bit wide
The bit write operation has a meaning only if DATLEN = 00 otherwise the channel length is fixed to
32-bit by hardware whatever the value filled in.
Note: For correct operation, this bit should be configured when the I2S is disabled.
It is not used in SPI mode.

1008/1141

DocID022558 Rev 8

RM0316

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

SPIx_I2S prescaler register (SPIx_I2SPR)

30.9.9

Address offset: 0x20
Reset value: 0000 0010 (0x0002)

15

14

13

12

11

10

9

8

7

6

5

4

3

Res.

Res.

Res.

Res.

Res.

Res.

MCKOE

ODD

I2SDIV[7:0]

rw

rw

rw

2

1

0

Bits 15:10 Reserved: Forced to 0 by hardware
Bit 9 MCKOE: Master clock output enable
0: Master clock output is disabled
1: Master clock output is enabled
Note: This bit should be configured when the I2S is disabled. It is used only when the I2S is in master
mode.
It is not used in SPI mode.
Bit 8 ODD: Odd factor for the prescaler
0: Real divider value is = I2SDIV *2
1: Real divider value is = (I2SDIV * 2)+1
Refer to Section 30.7.4 on page 988
Note: This bit should be configured when the I2S is disabled. It is used only when the I2S is in master
mode.
It is not used in SPI mode.
Bits 7:0 I2SDIV[7:0]: I2S linear prescaler
I2SDIV [7:0] = 0 or I2SDIV [7:0] = 1 are forbidden values.
Refer to Section 30.7.4 on page 988
Note: These bits should be configured when the I2S is disabled. They are used only when the I2S is
in master mode.
They are not used in SPI mode.

DocID022558 Rev 8

1009/1141
1010

0x20

1010/1141
SPIx_I2SPR
Reset value

DocID022558 Rev 8
0
0
0

Reset value
0

0

0

0

0

0
0
0

RXDMAEN

0
0

0

DR[15:0]

0
0

CRCPOLY[15:0]
0
0

RxCRC[15:0]
0
0

TxCRC[15:0]

0
0

0
0
0
0

0
0

Refer to Section 3.2.2 on page 51 for the register boundary addresses.
RXNE

SSOE
TXDMAEN

0

TXE

0
CHSIDE

FRF
NSSP

0
UDR

ERRIE
0
CRCERR

RXNEIE
0

OVR

0
MODF

0

0

0

0

BR [2:0]
MSTR
CPOL
CPHA

0

SPE

SSI
LSBFIRST

0

0
0
0
0
0
0
1
0

0
0
0
0
0
0
0

0
0
0
1
1
1

0
0
0
0
0
0

0
0
0
0
0
0

0

0

0
0

0
0

0
0
0

0
0

0
CHLEN

0

0

TXEIE

0

DATLEN

0

1

BSY

SSM

0

CKPOL

0

1

FRE

CRCNEXT
CRCL

BIDIOE
CRCEN
0

I2SSTD

FRLVL[1:0]

1

Res.

0

DS[3:0]

PCMSYNC

0
0

ODD

0
0

0

0

I2SCFG

0
0

MCKOE

0

RXONLY

BIDIMODE

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

I2SE

FRXTH
0
FTLVL[1:0]

LDMA_TX
LDMA_RX
0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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.

0

I2SMOD

Reset value
0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Reset value

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SPIx_I2SCFGR

Res.

SPIx_TXCRCR
Res.

SPIx_RXCRCR

Res.

SPIx_CRCPR

Res.

0x10
Res.

SPIx_DR

Res.

0x0C

Res.

SPIx_SR

Res.

0x08

Res.

0x1C
SPIx_CR2

Res.

0x04

Res.

0x18
SPIx_CR1

Res.

0x00

Res.

0x14

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register

Res.

Offset

Res.

30.9.10

Res.

Serial peripheral interface / inter-IC sound (SPI/I2S)
RM0316

SPI/I2S register map
Table 171 shows the SPI/I2S register map and reset values.
Table 171. SPI register map and reset values

0
0
0
0
0
0
0

I2SDIV
0
0
0

0
1
0

RM0316

Controller area network (bxCAN)

31

Controller area network (bxCAN)

31.1

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.

31.2

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:
–

14 filter banks

•

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

DocID022558 Rev 8

1011/1141

Controller area network (bxCAN)

31.3

RM0316

bxCAN general description
In today’s 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 (and thus 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.

0&8
$SSOLFDWLRQ
&$1
&RQWUROOHU
&$1
&$1
5;
7;
&$1
7UDQVFHLYHU
&$1
&$1
+LJK
/RZ

&$1QRGHQ



&$1QRGH



&$1QRGH


Figure 386. CAN network topology


&$1%XV
069

31.3.1

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.

31.3.2

Control, status and configuration registers
The application uses these registers to:

31.3.3

•

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.

1012/1141

DocID022558 Rev 8

RM0316

31.3.4

Controller area network (bxCAN)

Acceptance filters
The bxCAN provides up to 14 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.

31.4

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 pullup is active on CANTX. The software requests bxCAN to enter initialization or Sleep mode
by setting the INRQ or SLEEP bits in the CAN_MCR register. Once the mode has been
entered, bxCAN confirms it by setting the INAK or SLAK bits in the CAN_MSR register and
the internal pull-up is disabled. When neither INAK nor SLAK are set, bxCAN is in normal
mode. Before entering normal mode bxCAN always has to synchronize on the CAN bus.
To synchronize, bxCAN waits until the CAN bus is idle, this means 11 consecutive recessive
bits have been monitored on CANRX.

31.4.1

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).

31.4.2

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.

DocID022558 Rev 8

1013/1141

Controller area network (bxCAN)

RM0316

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.

31.4.3

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
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 387: bxCAN operating modes. The Sleep mode is exited
once the SLAK bit has been cleared by hardware.

1014/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)
Figure 387. bxCAN operating modes
5HVHW

6OHHS
6/$. 
,1$. 

6/

4

((

5

,1

1
6<

/(

6

1RUPDO

((

.


(3

3
,1

6/

&

5

3
,1

$&


(3

&

4

$

(
6/

4

$

5

.

&

,154$&.

6/$. 
,1$. 

,1546<1&6/((3

.

,QLWLDOL]DWLRQ
6/$. 
,1$. 
DL

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

31.5

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.

31.5.1

Silent mode
The bxCAN can be put in Silent mode by setting the SILM bit in the CAN_BTR register.
In Silent mode, the bxCAN is able to receive valid data frames and valid remote frames, but
it sends only recessive bits on the CAN bus and it cannot start a transmission. If the bxCAN
has to send a dominant bit (ACK bit, overload flag, active error flag), the bit is rerouted
internally so that the CAN Core monitors this dominant bit, although the CAN bus may
remain in recessive state. Silent mode can be used to analyze the traffic on a CAN bus
without affecting it by the transmission of dominant bits (Acknowledge Bits, Error Frames).

DocID022558 Rev 8

1015/1141

Controller area network (bxCAN)

RM0316
Figure 388. bxCAN in silent mode
E[&$1
7;

5;



&$17;

&$15;
069

31.5.2

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 389. bxCAN in loop back mode
BX#!.
48

28

#!.48 #!.28
-36

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.

31.5.3

Loop back combined with silent mode
It is also possible to combine Loop Back mode and Silent mode by setting the LBKM and
SILM bits in the CAN_BTR register. This mode can be used for a “Hot Selftest”, meaning the
bxCAN can be tested like in Loop Back mode but without affecting a running CAN system
connected to the CANTX and CANRX pins. In this mode, the CANRX pin is disconnected
from the bxCAN and the CANTX pin is held recessive.

1016/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)
Figure 390. bxCAN in combined mode
E[&$1
7;

5;



&$17; &$15;
069

31.6

Behavior in debug mode
When the microcontroller enters the debug mode (Cortex-M4®F core halted), the bxCAN
continues to work normally or stops, depending on:
•

the DBF bit in CAN_MCR. For more details, refer to Section 31.9.2: CAN control and
status registers.

31.7

bxCAN functional description

31.7.1

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
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.

DocID022558 Rev 8

1017/1141

Controller area network (bxCAN)

RM0316

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.
Figure 391. Transmit mailbox states
%-049
21#08
48/+8
4-%

4821
0%.$).'
21#0
48/+
4-%
!"21

-AILBOX HAS
HIGHEST PRIORITY

-AILBOX DOES NOT
HAVE HIGHEST PRIORITY
%-049
21#0
48/+
4-%

#!. "US  )$,%

4RANSMIT FAILED .!24

%-049
21#0
48/+
4-%

3#(%$5,%$
21#0
48/+
4-%

!"21

42!.3-)4
21#0
48/+
4-%

4RANSMIT FAILED .!24

4RANSMIT SUCCEEDED

-36

31.7.2

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

1018/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)
and Tx mailboxes). The internal counter is incremented each CAN bit time (refer to
Section 31.7.7: Bit timing). The internal counter is captured on the sample point of the Start
Of Frame bit in both reception and transmission.

31.7.3

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 31.7.4: Identifier filtering.
Figure 392. Receive FIFO states
%-049

6ALID -ESSAGE
2ECEIVED

&-0X
&/62

2ELEASE
-AILBOX

0%.$).'?
&0-X
&/62

2ELEASE
-AILBOX
2&/-

6ALID -ESSAGE
2ECEIVED

0%.$).'?
&0-X
&/62

2ELEASE
-AILBOX
2&/-

6ALID -ESSAGE
2ECEIVED

0%.$).'?
&0-X
&/62

6ALID -ESSAGE
2ECEIVED
2ELEASE
-AILBOX
2&/-

/6%225.
&0-X
&/62

6ALID -ESSAGE
2ECEIVED
-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

DocID022558 Rev 8

1019/1141

Controller area network (bxCAN)

RM0316

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 31.7.5: Message storage

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.

31.7.4

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 14 configurable and scalable filter
banks (13-0) 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.

1020/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)

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 393.
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”.

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 393. 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 393.

DocID022558 Rev 8

1021/1141

Controller area network (bxCAN)

RM0316

&"-X  
&"-X  

&3#X  

Figure 393. Filter bank scale configuration - register organization
&ILTER
.UM

/NE  "IT &ILTER )DENTIFIER -ASK
)$

#!.?&X2;=

#!.?&X2;=

#!.?&X2;=

#!.?&X2;=

-ASK

#!.?&X2;=

#!.?&X2;=

#!.?&X2;=

#!.?&X2;=

-APPING

34)$;=

34)$;=

%8)$;=

%8)$;=

%8)$;=

N

)$% 242 

4WO  "IT &ILTERS )DENTIFIER ,IST
)$

#!.?&X2;=

#!.?&X2;=

#!.?&X2;=

#!.?&X2;=

)$

#!.?&X2;=

#!.?&X2;=

#!.?&X2;=

#!.?&X2;=

-APPING

34)$;=

34)$;=

%8)$;=

%8)$;=

%8)$;=

N
N 

)$% 242 

&"-X  

4WO  "IT &ILTERS )DENTIFIER -ASK
)$
-ASK
)$
-APPING

)$
)$
)$
)$

34)$;=

N

#!.?&X2;=

N 

#!.?&X2;=
34)$;= 242 )$% %8)$;=

#!.?&X2;=
#!.?&X2;=
#!.?&X2;=
#!.?&X2;=
34)$;=

#!.?&X2;=
#!.?&X2;=

N
N 

#!.?&X2;=

N 
N 

#!.?&X2;=
34)$;= 242 )$% %8)$;=

&ILTER "ANK -ODE



-APPING

&ILTER "ANK 3CALE
#ONFIG "ITS 

#!.?&X2;=
#!.?&X2;=

#!.?&X2;=
#!.?&X2;=

&OUR  "IT &ILTERS )DENTIFIER ,IST
&"-X  

&3#X  

-ASK

#!.?&X2;=
#!.?&X2;=

X  FILTER BANK NUMBER
)$)DENTIFIER
 4HESE BITS ARE LOCATED IN THE #!.?&32 REGISTER

4HESE BITS ARE LOCATED IN THE #!.?&-2 REGISTER

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 394 for an example.

1022/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)
Figure 394. Example of filter numbering

)LOWHU
%DQN

),)2

)LOWHU
1XP

)LOWHU
%DQN

),)2

)LOWHU
1XP



,'/LVW ELW






,'0DVN ELW






,'0DVN ELW





,'/LVW ELW






,'/LVW ELW








'HDFWLYDWHG
,'/LVW ELW






'HDFWLYDWHG
,'/LVW ELW






,'0DVN ELW






,'0DVN ELW






'HDFWLYDWHG
,'/LVW ELW








,'/LVW ELW






,'/LVW ELW






,'0DVN ELW





,'0DVN ELW



,' ,GHQWLILHU
069

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:
•

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).

DocID022558 Rev 8

1023/1141

Controller area network (bxCAN)

RM0316
Figure 395. Filtering mechanism - example

([DPSOHRIILOWHUEDQNVLQELW8QLGHQWLILHGPRGHDQG
WKHUHPDLQLQJLQELW,GHQWLILHU0DVNPRGH
0HVVDJH5HFHLYHG
,GHQWLILHU

&WUO

'DWD








,GHQWLILHU 0DVN



,GHQWLILHU/LVW

)LOWHUEDQN
1XP
,GHQWLILHU 
,GHQWLILHU
,GHQWLILHU 





,GHQWLILHU



,GHQWLILHU
0DVN



,GHQWLILHU
0DVN



5HFHLYH),)2
,GHQWLILHU0DWFK

0HVVDJH
6WRUHG

)0,

)LOWHUQXPEHUVWRUHGLQWKH
)LOWHU0DWFK,QGH[ILHOG
ZLWKLQWKH&$1B5'7[5
UHJLVWHU

1R0DWFK
)RXQG

0HVVDJH'LVFDUGHG
069

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.

31.7.5

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.

1024/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)
Table 172. 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 173. 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 396. CAN error state diagram
:KHQ7(&RU5(&!

(55253$66,9(

(5525$&7,9(

:KHQ7(&DQG5(&
:KHQ UHFHVVLYHELWVRFFXU

:KHQ7(&!
%862))
DL

DocID022558 Rev 8

1025/1141

Controller area network (bxCAN)

31.7.6

RM0316

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.

31.7.7

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.

1026/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)
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 397. Bit timing
120,1$/%,77,0(
6<1&B6(*

[WT

%DXG5DWH

%,76(*0(17 %6

%,76(*0(17 %6

W%6


1RPLQDO%LW7LPH

W%6

6$03/(32,17

75$160,732,17

1RPLQDO%LW7LPH [W TW%6W%6
ZLWK
W%6 WT[ 76>@
W%6 WT[ 76>@
WT  %53>@ [W3&/.
ZKHUHWTUHIHUVWRWKHWLPHTXDQWXP
W3&/. WLPHSHULRGRIWKH$3%FORFN
%53>@76>@76>@DUHGHILQHGLQWKH&$1B%75UHJLVWHU

DocID022558 Rev 8

069

1027/1141

Controller area network (bxCAN)

RM0316
Figure 398. CAN frames
,QWHU)UDPH6SDFH
RU2YHUORDG)UDPH

'DWD)UDPH 6WDQGDUG,GHQWLILHU

,QWHU)UDPH6SDFH
$UELWUDWLRQ)LHOG




,'

'/&

$&.)LHOG


&5&)LHOG


 1

$&.

,QWHU)UDPH6SDFH
RU2YHUORDG)UDPH

'DWD)UDPH ([WHQGHG,GHQWLILHU
 1

,QWHU)UDPH6SDFH

$UELWUDWLRQ)LHOG

$UELWUDWLRQ)LHOG



&WUO)LHOG 'DWD)LHOG
 1



$UELWUDWLRQ)LHOG

5HPRWH)UDPH

&5&)LHOG
&WUO)LHOG






'/&



(QGRI)UDPHRU
(UURU'HOLPLWHURU
2YHUORDG'HOLPLWHU





$&.


$&.

(2)

'DWD)UDPHRU
5HPRWH)UDPH

%XV,GOH

,QWHU)UDPH6SDFH
RU(UURU)UDPH

2YHUORDG)UDPH

2YHUORDG 2YHUORDG
(FKR
)ODJ

$&.)LHOG


(UURU
'HOLPLWHU


,QWHU)UDPH6SDFH

6XVSHQG
,QWHUPLVVLRQ
7UDQVPLVVLRQ



(2)

,QWHU)UDPH6SDFH
RU2YHUORDG)UDPH

(UURU)UDPH
)ODJ(FKR



,QWHU)UDPH6SDFH
RU2YHUORDG)UDPH

&5&

575
,'(
U

62)

,'

(UURU
)ODJ


&5&

575
U
U

655
,'(

,QWHU)UDPH6SDFH

'DWD)UDPHRU
5HPRWH)UDPH

&5&)LHOG $&.)LHOG



'/&

62)

,'

$Q\)UDPH


(2)

&5&

575
,'(
U

62)

 1
'DWD)LHOG

&WUO)LHOG

2YHUORDG
'HOLPLWHU

1RWHV
 1 
62) 6WDUW2I)UDPH
,' ,GHQWLILHU
575 5HPRWH7UDQVPLVVLRQ5HTXHVW
,'( ,GHQWLILHU([WHQVLRQ%LW
U 5HVHUYHG%LW
'/& 'DWD/HQJWK&RGH
&5& &\FOLF5HGXQGDQF\&RGH
(UURUIODJGRPLQDQWELWVLIQRGHLVHUURU
DFWLYHHOVHUHFHVVLYHELWV
6XVSHQGWUDQVPLVVLRQDSSOLHVWRHUURU
SDVVLYHQRGHVRQO\
(2) (QGRI)UDPH
$&. $FNQRZOHGJHELW
&WUO &RQWURO


DL

1028/1141

DocID022558 Rev 8

RM0316

31.8

Controller area network (bxCAN)

bxCAN interrupts
Four interrupt vectors are dedicated to bxCAN. Each interrupt source can be independently
enabled or disabled by means of the CAN Interrupt Enable Register (CAN_IER).
Figure 399. Event flags and interrupt generation
&$1B,(5
54&3
54&3
54&3

&$1B765



70(,(

75$160,7
,17(55837

)03,(
)03
)),(

&$1B5)5

)8//



),)2
,17(55837

)29,(
)295

)03,(

),)2
,17(55837

)03
)),(

&$1B5)5

)8//



)29,(
)295

(55,(
(:*,(
(:*)
(39,(

&$1B(65

(39)


%2),(

%2))

(55,(

67$786&+$1*(
(5525
,17(55837

&$1B065
/(&,(

”/(&”



:.8,(
:.8,

&$1B065

6/.,(
6/$.,

069

•

•

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.

DocID022558 Rev 8

1029/1141

Controller area network (bxCAN)
•

The FIFO 1 interrupt can be generated by the following events:

•

31.9

RM0316

–

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).

31.9.1

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 391: 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.

31.9.2

CAN control and status registers
Refer to Section 2.1 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

1030/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)

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 31.7.2:
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 31.7.6: 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.

DocID022558 Rev 8

1031/1141

Controller area network (bxCAN)

RM0316

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.

1032/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)

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

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

DocID022558 Rev 8

6

5

4

3

2

1

0

Res.

Res.

Res.

TERR0

ALST0

TXOK0

RQCP0

rc_w1

rc_w1

rc_w1

rc_w1

1033/1141

Controller area network (bxCAN)

RM0316

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 391.
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.

1034/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)

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 391
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 391
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

DocID022558 Rev 8

rc_w1

rc_w1

FMP0[1:0]
r

r

1035/1141

Controller area network (bxCAN)

RM0316

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.

1036/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)

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
rw

14
Res.

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.

DocID022558 Rev 8

1037/1141

Controller area network (bxCAN)

RM0316

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 31.8: 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

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

1038/1141

20

DocID022558 Rev 8

rw

rw

r
3

2

1

0

Res.

BOFF

EPVF

EWGF

r

r

r

RM0316

Controller area network (bxCAN)

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 31.7.6 on page 1026.
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

24

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

rw

rw

DocID022558 Rev 8

rw

rw

rw

1039/1141

Controller area network (bxCAN)

RM0316

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 31.7.7: Bit timing on page 1026.
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

31.9.3

CAN mailbox registers
This chapter describes the registers of the transmit and receive mailboxes. Refer to
Section 31.7.5: Message storage on page 1024 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.

1040/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)
Figure 400. 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.

DocID022558 Rev 8

1041/1141

Controller area network (bxCAN)

RM0316

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.

1042/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)

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]
rw

DATA4[7:0]

DocID022558 Rev 8

rw

1043/1141

Controller area network (bxCAN)

RM0316

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.

1044/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)

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 31.7.4: Identifier filtering on
page 1020 - 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.

DocID022558 Rev 8

1045/1141

Controller area network (bxCAN)

RM0316

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

DATA4[7:0]
r

r

r

r

Bits 31:24 DATA7[7:0]: Data Byte 7
Data byte 3 of the message.

1046/1141

19

DATA6[7:0]

DATA5[7:0]
r

20

DocID022558 Rev 8

r

r

r

r

RM0316

Controller area network (bxCAN)

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.

31.9.4

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

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FINIT
rw

Bits 31:1 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.

DocID022558 Rev 8

1047/1141

Controller area network (bxCAN)

RM0316

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

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

13

12

11

10

15

14

Res.

Res.

FBM13 FBM12 FBM11 FBM10
rw

Note:

rw

rw

rw

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

Refer to Figure 393: Filter bank scale configuration - register organization on page 1022
Bits 31:14 Reserved, must be kept at reset value.
Bits 13:0 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

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

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

Bits 31:14 Reserved, must be kept at reset value.
Bits 13:0 FSCx: Filter scale configuration
These bits define the scale configuration of Filters 13-0.
0: Dual 16-bit scale configuration
1: Single 32-bit scale configuration

Note:

Refer to Figure 393: Filter bank scale configuration - register organization on page 1022.

CAN filter FIFO assignment register (CAN_FFA1R)
Address offset: 0x214
Reset value: 0x0000 0000

1048/1141

DocID022558 Rev 8

RM0316

Controller area network (bxCAN)
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

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

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

Bits 31:14 Reserved, must be kept at reset value.
Bits 13:0 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

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

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

Bits 31:14 Reserved, must be kept at reset value.
Bits 13:0 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

DocID022558 Rev 8

1049/1141

Controller area network (bxCAN)

RM0316

Filter bank i register x (CAN_FiRx) (i = 0..13, x = 1, 2)
Address offsets: 0x240 to 0x2AC
Reset value: 0xXXXX XXXX
There are 14 filter banks, i= 0 to 13. 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 31.7.4: Identifier filtering on page 1020.
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 174 on page 1051.

1050/1141

DocID022558 Rev 8

0x180

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

DocID022558 Rev 8

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.

31.9.5

Res.

RM0316
Controller area network (bxCAN)

bxCAN register map
Refer to Section 3.2.2 on page 51 for the register boundary addresses.
Table 174. bxCAN register map and reset values

0

0
0

0
0
0
0
0

x

x

0

1051/1141

Controller area network (bxCAN)

RM0316

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

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

1052/1141

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

DocID022558 Rev 8

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 174. bxCAN register map and reset values (continued)

RM0316

Controller area network (bxCAN)

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
Reset value
CAN_RDL1R
Reset value

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FINIT

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.

0

DocID022558 Rev 8

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

0

-

Res.

- - - - - - - - - - - - - - - - - Res.

Reset value

Res.

Res.

FBM[13:0]

CAN_FS1R
0x20C

Res.

1

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

Res.

0

Res.

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

0

Res.

- - - - - - - - - - - - - - - - - -

Res.

Reset value

Res.

CAN_FM1R

Res.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Res.

Reset value

Res.

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

Res.

x

DATA4[7:0]

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

DATA0[7:0]

DATA5[7:0]
x

x

Res.

x

x

x

Res.

x

x

x

Res.

x

- - - -

x

Res.

x

x

Res.

x

x

Res.

x

x

Res.

x

x

DATA1[7:0]

DATA6[7:0]
x

x

DLC[3:0]

Res.

x

x

-

Res.

x

x

x

Res.

x

x

x

Res.

x

x

x

Res.

x

x

DATA2[7:0]

DATA7[7:0]
x

x

x

CAN_FMR

0x204

0x210

x

x

-

0x200

0x208

x

x

Res.

0x1D00x1FF

x

CAN_RDH1R
Reset value

x

DATA3[7:0]

Res.

0x1CC

x

Res.

0x1C8

x

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 174. bxCAN register map and reset values (continued)

FSC[13:0]

1053/1141

Controller area network (bxCAN)

RM0316

Res.

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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

- - - - - - - - - - - - - - - - - -

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1054/1141

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

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.

Res.

0x31C

x

.
.
.
.

Reset value

Res.

Res.

Res.

0x318

0

Res.

Res.

Res.

.
.
.
.

x

CAN_F1R2
Reset value

0

Res.

Res.

Res.

0x24C

x

CAN_F1R1
Reset value

0

Res.

Res.

Res.

0x248

0

FB[31:0]

CAN_F0R2
Reset value

0

Res.

Res.

Res.

Reset value

0

Res.

Res.

Res.

CAN_F0R1

0

Res.

Res.

-

0

Res.

Res.

0x2240x23F

0

Res.

-

FACT[13:0]

Res.

0x220

0x244

Res.

-

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

Res.

Res.

0

0x21C

0x240

FFA[13:0]

- - - - - - - - - - - - - - - - - -

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 174. 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

DocID022558 Rev 8

x

RM0316

32

Universal serial bus full-speed device interface (USB)

Universal serial bus full-speed device interface (USB)
USB is only available on STM32F303xB/C/D/E devices. There is no USB in the
STM32F3x8xx devices.

32.1

Introduction
The USB peripheral implements an interface between a full-speed USB 2.0 bus and the
APB1 bus.
USB suspend/resume are supported which allows to stop the device clocks for low-power
consumption.

32.2

USB main features
•

USB specification version 2.0 full-speed compliant

•

Configurable number of endpoints from 1 to 8

•

Cyclic redundancy check (CRC) generation/checking, Non-return-to-zero Inverted
(NRZI) encoding/decoding and bit-stuffing

•

Isochronous transfers support

•

Double-buffered bulk/isochronous endpoint support

•

USB Suspend/Resume operations

•

Frame locked clock pulse generation

The following additional feature is also available depending on the product implementation
(see Section 32.3: USB implementation):
•

32.3

USB 2.0 Link Power Management support

USB implementation
Table 175 describes the USB implementation in the devices.
Table 175. STM32F3xx USB implementation
USB features(1)
Number of endpoints
Size of dedicated packet buffer memory SRAM
Dedicated packet buffer memory SRAM access scheme
USB 2.0 Link Power Management (LPM) support

STM32F303xB/C

STM32F303xD/E
(2)

8

8

512 bytes

1024 bytes(3)

1 x 16 bits / word

2 x 16 bits / word

-

X

1. X = supported
2. The STM32F303xD/E embeds a full-speed USB device peripheral compliant with the USB
specification version 2.0. The USB interface implements a full-speed (12 Mbit/s) function
interface with added support for USB 2.0 Link Power Management. It has softwareconfigurable endpoint setting with packet memory up-to 1 Kbytes (256 bytes are used for CAN
peripheral if enabled) and suspend/resume support.

DocID022558 Rev 8

1055/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

3. When the CAN peripheral clock is enabled in the RCC_APB1ENR register, only the first
768 Bytes are available to USB while the last 256 Bytes are used by CAN.

32.4

USB functional description
Figure 401 shows the block diagram of the USB peripheral.
Figure 401. USB peripheral block diagram

'3 '0
86%FORFN 0+]
3&/.

$QDORJ
WUDQVFHLYHU
86%
6XVSHQG
WLPHU

3DFNHW
EXIIHU
LQWHUIDFH

$UELWHU

5;7;
&RQWURO
6,(

&RQWURO
UHJLVWHUVDQGORJLF

&ORFN
UHFRYHU\
(QGSRLQW
VHOHFWLRQ

(QGSRLQW
UHJLVWHUV

3DFNHW
EXIIHU
PHPRU\

,QWHUUXSW
UHJLVWHUVDQGORJLF

(QGSRLQW
UHJLVWHUV

5HJLVWHU
5HJLVWHU
PDSSHU
PDSSHU

,QWHUUXSW
PDSSHU

$3%ZUDSSHU
$3%LQWHUIDFH
3&/.

$3%EXV

,54VWR19,&
06Y9

The USB peripheral provides an USB-compliant connection between the host PC and the
function implemented by the microcontroller. Data transfer between the host PC and the
system memory occurs through a dedicated packet buffer memory accessed directly by the
USB peripheral. This dedicated memory size is up to 512 bytes, and up to 16 monodirectional or 8 bidirectional endpoints can be used. The USB peripheral interfaces with the
USB host, detecting token packets, handling data transmission/reception, and processing
handshake packets as required by the USB standard. Transaction formatting is performed
by the hardware, including CRC generation and checking.

1056/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
Each endpoint is associated with a buffer description block indicating where the endpointrelated memory area is located, how large it is or how many bytes must be transmitted.
When a token for a valid function/endpoint pair is recognized by the USB peripheral, the
related data transfer (if required and if the endpoint is configured) takes place. The data
buffered by the USB peripheral is loaded in an internal 16-bit register and memory access to
the dedicated buffer is performed. When all the data has been transferred, if needed, the
proper handshake packet over the USB is generated or expected according to the direction
of the transfer.
At the end of the transaction, an endpoint-specific interrupt is generated, reading status
registers and/or using different interrupt response routines. The microcontroller can
determine:
•

which endpoint has to be served,

•

which type of transaction took place, if errors occurred (bit stuffing, format, CRC,
protocol, missing ACK, over/underrun, etc.).

Special support is offered to isochronous transfers and high throughput bulk transfers,
implementing a double buffer usage, which allows to always have an available buffer for the
USB peripheral while the microcontroller uses the other one.
The unit can be placed in low-power mode (SUSPEND mode), by writing in the control
register, whenever required. At this time, all static power dissipation is avoided, and the USB
clock can be slowed down or stopped. The detection of activity at the USB inputs, while in
low-power mode, wakes the device up asynchronously. A special interrupt source can be
connected directly to a wakeup line to allow the system to immediately restart the normal
clock generation and/or support direct clock start/stop.

32.4.1

Description of USB blocks
The USB peripheral implements all the features related to USB interfacing, which include
the following blocks:
•

Serial Interface Engine (SIE): The functions of this block include: synchronization
pattern recognition, bit-stuffing, CRC generation and checking, PID
verification/generation, and handshake evaluation. It must interface with the USB
transceivers and uses the virtual buffers provided by the packet buffer interface for
local data storage. This unit also generates signals according to USB peripheral
events, such as Start of Frame (SOF), USB_Reset, Data errors etc. and to Endpoint
related events like end of transmission or correct reception of a packet; these signals
are then used to generate interrupts.

•

Timer: This block generates a start-of-frame locked clock pulse and detects a global
suspend (from the host) when no traffic has been received for 3 ms.

•

Packet Buffer Interface: This block manages the local memory implementing a set of
buffers in a flexible way, both for transmission and reception. It can choose the proper
buffer according to requests coming from the SIE and locate them in the memory
addresses pointed by the Endpoint registers. It increments the address after each
exchanged byte until the end of packet, keeping track of the number of exchanged
bytes and preventing the buffer to overrun the maximum capacity.

DocID022558 Rev 8

1057/1141
1087

Universal serial bus full-speed device interface (USB)

Note:

RM0316

•

Endpoint-Related Registers: Each endpoint has an associated register containing the
endpoint type and its current status. For mono-directional/single-buffer endpoints, a
single register can be used to implement two distinct endpoints. The number of
registers is 8, allowing up to 16 mono-directional/single-buffer or up to 7 double-buffer
endpoints in any combination. For example the USB peripheral can be programmed to
have 4 double buffer endpoints and 8 single-buffer/mono-directional endpoints.

•

Control Registers: These are the registers containing information about the status of
the whole USB peripheral and used to force some USB events, such as resume and
power-down.

•

Interrupt Registers: These contain the Interrupt masks and a record of the events. They
can be used to inquire an interrupt reason, the interrupt status or to clear the status of a
pending interrupt.

* Endpoint 0 is always used for control transfer in single-buffer mode.
The USB peripheral is connected to the APB1 bus through an APB1 interface, containing
the following blocks:

32.5

•

Packet Memory: This is the local memory that physically contains the Packet Buffers. It
can be used by the Packet Buffer interface, which creates the data structure and can
be accessed directly by the application software. The size of the Packet Memory is up
to 512 bytes, structured as256 half-words by 16 bits.

•

Arbiter: This block accepts memory requests coming from the APB1 bus and from the
USB interface. It resolves the conflicts by giving priority to APB1 accesses, while
always reserving half of the memory bandwidth to complete all USB transfers. This
time-duplex scheme implements a virtual dual-port SRAM that allows memory access,
while an USB transaction is happening. Multiword APB1 transfers of any length are
also allowed by this scheme.

•

Register Mapper: This block collects the various byte-wide and bit-wide registers of the
USB peripheral in a structured 16-bit wide half-word set addressed by the APB1.

•

APB1 Wrapper: This provides an interface to the APB1 for the memory and register. It
also maps the whole USB peripheral in the APB1 address space.

•

Interrupt Mapper: This block is used to select how the possible USB events can
generate interrupts and map them to three different lines of the NVIC:
–

USB low-priority interrupt (Channel 20): Triggered by all USB events (Correct
transfer, USB reset, etc.). The firmware has to check the interrupt source before
serving the interrupt.

–

USB high-priority interrupt (Channel 19): Triggered only by a correct transfer event
for isochronous and double-buffer bulk transfer to reach the highest possible
transfer rate.

–

USB wakeup interrupt (Channel 42): Triggered by the wakeup event from the USB
Suspend mode.

Programming considerations
In the following sections, the expected interactions between the USB peripheral and the
application program are described, in order to ease application software development.

1058/1141

DocID022558 Rev 8

RM0316

32.5.1

Universal serial bus full-speed device interface (USB)

Generic USB device programming
This part describes the main tasks required of the application software in order to obtain
USB compliant behavior. The actions related to the most general USB events are taken into
account and paragraphs are dedicated to the special cases of double-buffered endpoints
and Isochronous transfers. Apart from system reset, action is always initiated by the USB
peripheral, driven by one of the USB events described below.

32.5.2

System and power-on reset
Upon system and power-on reset, the first operation the application software should perform
is to provide all required clock signals to the USB peripheral and subsequently de-assert its
reset signal so to be able to access its registers. The whole initialization sequence is
hereafter described.
As a first step application software needs to activate register macrocell clock and de-assert
macrocell specific reset signal using related control bits provided by device clock
management logic.
After that, the analog part of the device related to the USB transceiver must be switched on
using the PDWN bit in CNTR register, which requires a special handling. This bit is intended
to switch on the internal voltage references that supply the port transceiver. This circuit has
a defined startup time (tSTARTUP specified in the datasheet) during which the behavior of the
USB transceiver is not defined. It is thus necessary to wait this time, after setting the PDWN
bit in the CNTR register, before removing the reset condition on the USB part (by clearing
the FRES bit in the CNTR register). Clearing the ISTR register then removes any spurious
pending interrupt before any other macrocell operation is enabled.
At system reset, the microcontroller must initialize all required registers and the packet
buffer description table, to make the USB peripheral able to properly generate interrupts and
data transfers. All registers not specific to any endpoint must be initialized according to the
needs of application software (choice of enabled interrupts, chosen address of packet
buffers, etc.). Then the process continues as for the USB reset case (see further
paragraph).

USB reset (RESET interrupt)
When this event occurs, the USB peripheral is put in the same conditions it is left by the
system reset after the initialization described in the previous paragraph: communication is
disabled in all endpoint registers (the USB peripheral will not respond to any packet). As a
response to the USB reset event, the USB function must be enabled, having as USB
address 0, implementing only the default control endpoint (endpoint address is 0 too). This
is accomplished by setting the Enable Function (EF) bit of the USB_DADDR register and
initializing the EP0R register and its related packet buffers accordingly. During USB
enumeration process, the host assigns a unique address to this device, which must be
written in the ADD[6:0] bits of the USB_DADDR register, and configures any other
necessary endpoint.
When a RESET interrupt is received, the application software is responsible to enable again
the default endpoint of USB function 0 within 10 ms from the end of reset sequence which
triggered the interrupt.

Structure and usage of packet buffers
Each bidirectional endpoint may receive or transmit data from/to the host. The received data
is stored in a dedicated memory buffer reserved for that endpoint, while another memory
DocID022558 Rev 8

1059/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

buffer contains the data to be transmitted by the endpoint. Access to this memory is
performed by the packet buffer interface block, which delivers a memory access request
and waits for its acknowledgment. Since the packet buffer memory has to be accessed by
the microcontroller also, an arbitration logic takes care of the access conflicts, using half
APB1 cycle for microcontroller access and the remaining half for the USB peripheral
access. In this way, both the agents can operate as if the packet memory is a dual-port
SRAM, without being aware of any conflict even when the microcontroller is performing
back-to-back accesses. The USB peripheral logic uses a dedicated clock. The frequency of
this dedicated clock is fixed by the requirements of the USB standard at 48 MHz, and this
can be different from the clock used for the interface to the APB1 bus. Different clock
configurations are possible where the APB1 clock frequency can be higher or lower than the
USB peripheral one.
Note:

Due to USB data rate and packet memory interface requirements, the APB1 clock must
have a minimum frequency of 10 MHz to avoid data overrun/underrun problems.
Each endpoint is associated with two packet buffers (usually one for transmission and the
other one for reception). Buffers can be placed anywhere inside the packet memory
because their location and size is specified in a buffer description table, which is also
located in the packet memory at the address indicated by the USB_BTABLE register. Each
table entry is associated to an endpoint register and it is composed of four 16-bit half-words
so that table start address must always be aligned to an 8-byte boundary (the lowest three
bits of USB_BTABLE register are always “000”). Buffer descriptor table entries are
described in the Section 32.6.2: Buffer descriptor table. If an endpoint is unidirectional and it
is neither an Isochronous nor a double-buffered bulk, only one packet buffer is required (the
one related to the supported transfer direction). Other table locations related to unsupported
transfer directions or unused endpoints, are available to the user. Isochronous and doublebuffered bulk endpoints have special handling of packet buffers (Refer to Section 32.5.4:
Isochronous transfers and Section 32.5.3: Double-buffered endpoints respectively). The
relationship between buffer description table entries and packet buffer areas is depicted in
Figure 402.

1060/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
Figure 402. Packet buffer areas with examples of buffer description table locations

B (
B &
B $
B 
B 
B 
B 
B 
B (
B &
B $
B 
B 
B 
B 
B 

&2817B7;B
$''5B7;B
&2817B7;B
$''5B7;B
&2817B5;B
$''5B5;B
&2817B5;B
$''5B5;B
&2817B5;
$''5B5;
&2817B7;
$''5B7;
&2817B5;
$''5B5;
&2817B7;
$''5B7;

%XIIHUGHVFULSWLRQWDEOHORFDWLRQV

%XIIHUIRU
GRXEOHEXIIHUHG
,1(QGSRLQW
%XIIHUIRU
GRXEOHEXIIHUHG
287(QGSRLQW
7UDQVPLVVLRQ
EXIIHUIRU
VLQJOHEXIIHUHG
(QGSRLQW
5HFHSWLRQEXIIHU
IRU
(QGSRLQW
7UDQVPLVVLRQ
EXIIHUIRU
(QGSRLQW
3DFNHWEXIIHUV
06Y9

Each packet buffer is used either during reception or transmission starting from the bottom.
The USB peripheral will never change the contents of memory locations adjacent to the
allocated memory buffers; if a packet bigger than the allocated buffer length is received
(buffer overrun condition) the data will be copied to the memory only up to the last available
location.

Endpoint initialization
The first step to initialize an endpoint is to write appropriate values to the
ADDRn_TX/ADDRn_RX registers so that the USB peripheral finds the data to be
transmitted already available and the data to be received can be buffered. The EP_TYPE
bits in the USB_EPnR register must be set according to the endpoint type, eventually using
the EP_KIND bit to enable any special required feature. On the transmit side, the endpoint
must be enabled using the STAT_TX bits in the USB_EPnR register and COUNTn_TX must
be initialized. For reception, STAT_RX bits must be set to enable reception and
COUNTn_RX must be written with the allocated buffer size using the BL_SIZE and
NUM_BLOCK fields. Unidirectional endpoints, except Isochronous and double-buffered bulk
endpoints, need to initialize only bits and registers related to the supported direction. Once
the transmission and/or reception are enabled, register USB_EPnR and locations
ADDRn_TX/ADDRn_RX, COUNTn_TX/COUNTn_RX (respectively), should not be modified
by the application software, as the hardware can change their value on the fly. When the
data transfer operation is completed, notified by a CTR interrupt event, they can be
accessed again to re-enable a new operation.

DocID022558 Rev 8

1061/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

IN packets (data transmission)
When receiving an IN token packet, if the received address matches a configured and valid
endpoint, the USB peripheral accesses the contents of ADDRn_TX and COUNTn_TX
locations inside the buffer descriptor table entry related to the addressed endpoint. The
content of these locations is stored in its internal 16 bit registers ADDR and COUNT (not
accessible by software). The packet memory is accessed again to read the first byte to be
transmitted (Refer to Structure and usage of packet buffers on page 1059) and starts
sending a DATA0 or DATA1 PID according to USB_EPnR bit DTOG_TX. When the PID is
completed, the first byte, read from buffer memory, is loaded into the output shift register to
be transmitted on the USB bus. After the last data byte is transmitted, the computed CRC is
sent. If the addressed endpoint is not valid, a NAK or STALL handshake packet is sent
instead of the data packet, according to STAT_TX bits in the USB_EPnR register.
The ADDR internal register is used as a pointer to the current buffer memory location while
COUNT is used to count the number of remaining bytes to be transmitted. Each half-word
read from the packet buffer memory is transmitted over the USB bus starting from the least
significant byte. Transmission buffer memory is read starting from the address pointed by
ADDRn_TX for COUNTn_TX/2 half-words. If a transmitted packet is composed of an odd
number of bytes, only the lower half of the last half-word accessed will be used.
On receiving the ACK receipt by the host, the USB_EPnR register is updated in the
following way: DTOG_TX bit is toggled, the endpoint is made invalid by setting
STAT_TX=10 (NAK) and bit CTR_TX is set. The application software must first identify the
endpoint, which is requesting microcontroller attention by examining the EP_ID and DIR bits
in the USB_ISTR register. Servicing of the CTR_TX event starts clearing the interrupt bit;
the application software then prepares another buffer full of data to be sent, updates the
COUNTn_TX table location with the number of byte to be transmitted during the next
transfer, and finally sets STAT_TX to ‘11 (VALID) to re-enable transmissions. While the
STAT_TX bits are equal to ‘10 (NAK), any IN request addressed to that endpoint is NAKed,
indicating a flow control condition: the USB host will retry the transaction until it succeeds. It
is mandatory to execute the sequence of operations in the above mentioned order to avoid
losing the notification of a second IN transaction addressed to the same endpoint
immediately following the one which triggered the CTR interrupt.

OUT and SETUP packets (data reception)
These two tokens are handled by the USB peripheral more or less in the same way; the
differences in the handling of SETUP packets are detailed in the following paragraph about
control transfers. When receiving an OUT/SETUP PID, if the address matches a valid
endpoint, the USB peripheral accesses the contents of the ADDRn_RX and COUNTn_RX
locations inside the buffer descriptor table entry related to the addressed endpoint. The
content of the ADDRn_RX is stored directly in its internal register ADDR. While COUNT is
now reset and the values of BL_SIZE and NUM_BLOCK bit fields, which are read within
COUNTn_RX content are used to initialize BUF_COUNT, an internal 16 bit counter, which is
used to check the buffer overrun condition (all these internal registers are not accessible by
software). Data bytes subsequently received by the USB peripheral are packed in halfwords (the first byte received is stored as least significant byte) and then transferred to the
packet buffer starting from the address contained in the internal ADDR register while
BUF_COUNT is decremented and COUNT is incremented at each byte transfer. When the
end of DATA packet is detected, the correctness of the received CRC is tested and only if no
errors occurred during the reception, an ACK handshake packet is sent back to the
transmitting host.

1062/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
In case of wrong CRC or other kinds of errors (bit-stuff violations, frame errors, etc.), data
bytes are still copied in the packet memory buffer, at least until the error detection point, but
ACK packet is not sent and the ERR bit in USB_ISTR register is set. However, there is
usually no software action required in this case: the USB peripheral recovers from reception
errors and remains ready for the next transaction to come. If the addressed endpoint is not
valid, a NAK or STALL handshake packet is sent instead of the ACK, according to bits
STAT_RX in the USB_EPnR register and no data is written in the reception memory buffers.
Reception memory buffer locations are written starting from the address contained in the
ADDRn_RX for a number of bytes corresponding to the received data packet length, CRC
included (i.e. data payload length + 2), or up to the last allocated memory location, as
defined by BL_SIZE and NUM_BLOCK, whichever comes first. In this way, the USB
peripheral never writes beyond the end of the allocated reception memory buffer area. If the
length of the data packet payload (actual number of bytes used by the application) is greater
than the allocated buffer, the USB peripheral detects a buffer overrun condition. in this case,
a STALL handshake is sent instead of the usual ACK to notify the problem to the host, no
interrupt is generated and the transaction is considered failed.
When the transaction is completed correctly, by sending the ACK handshake packet, the
internal COUNT register is copied back in the COUNTn_RX location inside the buffer
description table entry, leaving unaffected BL_SIZE and NUM_BLOCK fields, which
normally do not require to be re-written, and the USB_EPnR register is updated in the
following way: DTOG_RX bit is toggled, the endpoint is made invalid by setting STAT_RX =
‘10 (NAK) and bit CTR_RX is set. If the transaction has failed due to errors or buffer overrun
condition, none of the previously listed actions take place. The application software must
first identify the endpoint, which is requesting microcontroller attention by examining the
EP_ID and DIR bits in the USB_ISTR register. The CTR_RX event is serviced by first
determining the transaction type (SETUP bit in the USB_EPnR register); the application
software must clear the interrupt flag bit and get the number of received bytes reading the
COUNTn_RX location inside the buffer description table entry related to the endpoint being
processed. After the received data is processed, the application software should set the
STAT_RX bits to ‘11 (Valid) in the USB_EPnR, enabling further transactions. While the
STAT_RX bits are equal to ‘10 (NAK), any OUT request addressed to that endpoint is
NAKed, indicating a flow control condition: the USB host will retry the transaction until it
succeeds. It is mandatory to execute the sequence of operations in the above mentioned
order to avoid losing the notification of a second OUT transaction addressed to the same
endpoint following immediately the one which triggered the CTR interrupt.

Control transfers
Control transfers are made of a SETUP transaction, followed by zero or more data stages,
all of the same direction, followed by a status stage (a zero-byte transfer in the opposite
direction). SETUP transactions are handled by control endpoints only and are very similar to
OUT ones (data reception) except that the values of DTOG_TX and DTOG_RX bits of the
addressed endpoint registers are set to 1 and 0 respectively, to initialize the control transfer,
and both STAT_TX and STAT_RX are set to ‘10 (NAK) to let software decide if subsequent
transactions must be IN or OUT depending on the SETUP contents. A control endpoint must
check SETUP bit in the USB_EPnR register at each CTR_RX event to distinguish normal
OUT transactions from SETUP ones. A USB device can determine the number and
direction of data stages by interpreting the data transferred in the SETUP stage, and is
required to STALL the transaction in the case of errors. To do so, at all data stages before
the last, the unused direction should be set to STALL, so that, if the host reverses the
transfer direction too soon, it gets a STALL as a status stage.

DocID022558 Rev 8

1063/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

While enabling the last data stage, the opposite direction should be set to NAK, so that, if
the host reverses the transfer direction (to perform the status stage) immediately, it is kept
waiting for the completion of the control operation. If the control operation completes
successfully, the software will change NAK to VALID, otherwise to STALL. At the same time,
if the status stage will be an OUT, the STATUS_OUT (EP_KIND in the USB_EPnR register)
bit should be set, so that an error is generated if a status transaction is performed with notzero data. When the status transaction is serviced, the application clears the STATUS_OUT
bit and sets STAT_RX to VALID (to accept a new command) and STAT_TX to NAK (to delay
a possible status stage immediately following the next setup).
Since the USB specification states that a SETUP packet cannot be answered with a
handshake different from ACK, eventually aborting a previously issued command to start
the new one, the USB logic doesn’t allow a control endpoint to answer with a NAK or STALL
packet to a SETUP token received from the host.
When the STAT_RX bits are set to ‘01 (STALL) or ‘10 (NAK) and a SETUP token is
received, the USB accepts the data, performing the required data transfers and sends back
an ACK handshake. If that endpoint has a previously issued CTR_RX request not yet
acknowledged by the application (i.e. CTR_RX bit is still set from a previously completed
reception), the USB discards the SETUP transaction and does not answer with any
handshake packet regardless of its state, simulating a reception error and forcing the host to
send the SETUP token again. This is done to avoid losing the notification of a SETUP
transaction addressed to the same endpoint immediately following the transaction, which
triggered the CTR_RX interrupt.

32.5.3

Double-buffered endpoints
All different endpoint types defined by the USB standard represent different traffic models,
and describe the typical requirements of different kind of data transfer operations. When
large portions of data are to be transferred between the host PC and the USB function, the
bulk endpoint type is the most suited model. This is because the host schedules bulk
transactions so as to fill all the available bandwidth in the frame, maximizing the actual
transfer rate as long as the USB function is ready to handle a bulk transaction addressed to
it. If the USB function is still busy with the previous transaction when the next one arrives, it
will answer with a NAK handshake and the host PC will issue the same transaction again
until the USB function is ready to handle it, reducing the actual transfer rate due to the
bandwidth occupied by re-transmissions. For this reason, a dedicated feature called
‘double-buffering’ can be used with bulk endpoints.
When ‘double-buffering’ is activated, data toggle sequencing is used to select, which buffer
is to be used by the USB peripheral to perform the required data transfers, using both
‘transmission’ and ‘reception’ packet memory areas to manage buffer swapping on each
successful transaction in order to always have a complete buffer to be used by the
application, while the USB peripheral fills the other one. For example, during an OUT
transaction directed to a ‘reception’ double-buffered bulk endpoint, while one buffer is being
filled with new data coming from the USB host, the other one is available for the
microcontroller software usage (the same would happen with a ‘transmission’ doublebuffered bulk endpoint and an IN transaction).
Since the swapped buffer management requires the usage of all 4 buffer description table
locations hosting the address pointer and the length of the allocated memory buffers, the
USB_EPnR registers used to implement double-buffered bulk endpoints are forced to be
used as unidirectional ones. Therefore, only one STAT bit pair must be set at a value
different from ‘00 (Disabled): STAT_RX if the double-buffered bulk endpoint is enabled for

1064/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
reception, STAT_TX if the double-buffered bulk endpoint is enabled for transmission. In
case it is required to have double-buffered bulk endpoints enabled both for reception and
transmission, two USB_EPnR registers must be used.
To exploit the double-buffering feature and reach the highest possible transfer rate, the
endpoint flow control structure, described in previous chapters, has to be modified, in order
to switch the endpoint status to NAK only when a buffer conflict occurs between the USB
peripheral and application software, instead of doing it at the end of each successful
transaction. The memory buffer which is currently being used by the USB peripheral is
defined by the DTOG bit related to the endpoint direction: DTOG_RX (bit 14 of USB_EPnR
register) for ‘reception’ double-buffered bulk endpoints or DTOG_TX (bit 6 of USB_EPnR
register) for ‘transmission’ double-buffered bulk endpoints. To implement the new flow
control scheme, the USB peripheral should know which packet buffer is currently in use by
the application software, so to be aware of any conflict. Since in the USB_EPnR register,
there are two DTOG bits but only one is used by USB peripheral for data and buffer
sequencing (due to the unidirectional constraint required by double-buffering feature) the
other one can be used by the application software to show which buffer it is currently using.
This new buffer flag is called SW_BUF. In the following table the correspondence between
USB_EPnR register bits and DTOG/SW_BUF definition is explained, for the cases of
‘transmission’ and ‘reception’ double-buffered bulk endpoints.
Table 176. Double-buffering buffer flag definition
Buffer flag

‘Transmission’ endpoint

DTOG
SW_BUF

‘Reception’ endpoint

DTOG_TX (USB_EPnR bit 6)

DTOG_RX (USB_EPnR bit 14)

USB_EPnR bit 14

USB_EPnR bit 6

The memory buffer which is currently being used by the USB peripheral is defined by DTOG
buffer flag, while the buffer currently in use by application software is identified by SW_BUF
buffer flag. The relationship between the buffer flag value and the used packet buffer is the
same in both cases, and it is listed in the following table.
Table 177. Bulk double-buffering memory buffers usage
Endpoint
DTOG SW_BUF
Type

Packet buffer used by USB
Peripheral

Packet buffer used by
Application Software

0

1

ADDRn_TX_0 / COUNTn_TX_0 ADDRn_TX_1 / COUNTn_TX_1
Buffer description table locations. Buffer description table locations.

1

0

ADDRn_TX_1 / COUNTn_TX_1
Buffer description table locations

ADDRn_TX_0 / COUNTn_TX_0
Buffer description table locations.

0

0

None (1)

ADDRn_TX_0 / COUNTn_TX_0
Buffer description table locations.

1

1

None (1)

ADDRn_TX_0 / COUNTn_TX_0
Buffer description table locations.

IN

DocID022558 Rev 8

1065/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

Table 177. Bulk double-buffering memory buffers usage (continued)
Endpoint
DTOG SW_BUF
Type

Packet buffer used by USB
Peripheral

Packet buffer used by
Application Software

0

1

ADDRn_RX_0 / COUNTn_RX_0 ADDRn_RX_1 / COUNTn_RX_1
Buffer description table locations. Buffer description table locations.

1

0

ADDRn_RX_1 / COUNTn_RX_1 ADDRn_RX_0 / COUNTn_RX_0
Buffer description table locations. Buffer description table locations.

0

0

None (1)

ADDRn_RX_0 / COUNTn_RX_0
Buffer description table locations.

1

1

None (1)

ADDRn_RX_1 / COUNTn_RX_1
Buffer description table locations.

OUT

1. Endpoint in NAK Status.

Double-buffering feature for a bulk endpoint is activated by:
•

Writing EP_TYPE bit field at ‘00 in its USB_EPnR register, to define the endpoint as a
bulk, and

•

Setting EP_KIND bit at ‘1 (DBL_BUF), in the same register.

The application software is responsible for DTOG and SW_BUF bits initialization according
to the first buffer to be used; this has to be done considering the special toggle-only property
that these two bits have. The end of the first transaction occurring after having set
DBL_BUF, triggers the special flow control of double-buffered bulk endpoints, which is used
for all other transactions addressed to this endpoint until DBL_BUF remain set. At the end of
each transaction the CTR_RX or CTR_TX bit of the addressed endpoint USB_EPnR
register is set, depending on the enabled direction. At the same time, the affected DTOG bit
in the USB_EPnR register is hardware toggled making the USB peripheral buffer swapping
completely software independent. Unlike common transactions, and the first one after
DBL_BUF setting, STAT bit pair is not affected by the transaction termination and its value
remains ‘11 (Valid). However, as the token packet of a new transaction is received, the
actual endpoint status will be masked as ‘10 (NAK) when a buffer conflict between the USB
peripheral and the application software is detected (this condition is identified by DTOG and
SW_BUF having the same value, see Table 177 on page 1065). The application software
responds to the CTR event notification by clearing the interrupt flag and starting any
required handling of the completed transaction. When the application packet buffer usage is
over, the software toggles the SW_BUF bit, writing ‘1 to it, to notify the USB peripheral about
the availability of that buffer. In this way, the number of NAKed transactions is limited only by
the application elaboration time of a transaction data: if the elaboration time is shorter than
the time required to complete a transaction on the USB bus, no re-transmissions due to flow
control will take place and the actual transfer rate will be limited only by the host PC.
The application software can always override the special flow control implemented for
double-buffered bulk endpoints, writing an explicit status different from ‘11 (Valid) into the
STAT bit pair of the related USB_EPnR register. In this case, the USB peripheral will always
use the programmed endpoint status, regardless of the buffer usage condition.

32.5.4

Isochronous transfers
The USB standard supports full speed peripherals requiring a fixed and accurate data
production/consume frequency, defining this kind of traffic as ‘Isochronous’. Typical

1066/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
examples of this data are: audio samples, compressed video streams, and in general any
sort of sampled data having strict requirements for the accuracy of delivered frequency.
When an endpoint is defined to be ‘isochronous’ during the enumeration phase, the host
allocates in the frame the required bandwidth and delivers exactly one IN or OUT packet
each frame, depending on endpoint direction. To limit the bandwidth requirements, no retransmission of failed transactions is possible for Isochronous traffic; this leads to the fact
that an isochronous transaction does not have a handshake phase and no ACK packet is
expected or sent after the data packet. For the same reason, Isochronous transfers do not
support data toggle sequencing and always use DATA0 PID to start any data packet.
The Isochronous behavior for an endpoint is selected by setting the EP_TYPE bits at ‘10 in
its USB_EPnR register; since there is no handshake phase the only legal values for the
STAT_RX/STAT_TX bit pairs are ‘00 (Disabled) and ‘11 (Valid), any other value will produce
results not compliant to USB standard. Isochronous endpoints implement double-buffering
to ease application software development, using both ‘transmission’ and ‘reception’ packet
memory areas to manage buffer swapping on each successful transaction in order to have
always a complete buffer to be used by the application, while the USB peripheral fills the
other.
The memory buffer which is currently used by the USB peripheral is defined by the DTOG
bit related to the endpoint direction (DTOG_RX for ‘reception’ isochronous endpoints,
DTOG_TX for ‘transmission’ isochronous endpoints, both in the related USB_EPnR
register) according to Table 178.
Table 178. Isochronous memory buffers usage
Endpoint
Type

DTOG bit
value

Packet buffer used by the
USB peripheral

Packet buffer used by the
application software

0

ADDRn_TX_0 / COUNTn_TX_0
buffer description table
locations.

ADDRn_TX_1 / COUNTn_TX_1
buffer description table
locations.

1

ADDRn_TX_1 / COUNTn_TX_1
buffer description table
locations.

ADDRn_TX_0 / COUNTn_TX_0
buffer description table
locations.

0

ADDRn_RX_0 / COUNTn_RX_0
buffer description table
locations.

ADDRn_RX_1 / COUNTn_RX_1
buffer description table
locations.

1

ADDRn_RX_1 / COUNTn_RX_1
buffer description table
locations.

ADDRn_RX_0 / COUNTn_RX_0
buffer description table
locations.

IN

OUT

As it happens with double-buffered bulk endpoints, the USB_EPnR registers used to
implement Isochronous endpoints are forced to be used as unidirectional ones. In case it is
required to have Isochronous endpoints enabled both for reception and transmission, two
USB_EPnR registers must be used.
The application software is responsible for the DTOG bit initialization according to the first
buffer to be used; this has to be done considering the special toggle-only property that these
two bits have. At the end of each transaction, the CTR_RX or CTR_TX bit of the addressed
endpoint USB_EPnR register is set, depending on the enabled direction. At the same time,
the affected DTOG bit in the USB_EPnR register is hardware toggled making buffer
swapping completely software independent. STAT bit pair is not affected by transaction
completion; since no flow control is possible for Isochronous transfers due to the lack of
DocID022558 Rev 8

1067/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

handshake phase, the endpoint remains always ‘11 (Valid). CRC errors or buffer-overrun
conditions occurring during Isochronous OUT transfers are anyway considered as correct
transactions and they always trigger an CTR_RX event. However, CRC errors will anyway
set the ERR bit in the USB_ISTR register to notify the software of the possible data
corruption.

32.5.5

Suspend/Resume events
The USB standard defines a special peripheral state, called SUSPEND, in which the
average current drawn from the USB bus must not be greater than 2.5 mA. This
requirement is of fundamental importance for bus-powered devices, while self-powered
devices are not required to comply to this strict power consumption constraint. In suspend
mode, the host PC sends the notification by not sending any traffic on the USB bus for more
than 3 ms: since a SOF packet must be sent every 1 ms during normal operations, the USB
peripheral detects the lack of 3 consecutive SOF packets as a suspend request from the
host PC and set the SUSP bit to ‘1 in USB_ISTR register, causing an interrupt if enabled.
Once the device is suspended, its normal operation can be restored by a so called
RESUME sequence, which can be started from the host PC or directly from the peripheral
itself, but it is always terminated by the host PC. The suspended USB peripheral must be
anyway able to detect a RESET sequence, reacting to this event as a normal USB reset
event.
The actual procedure used to suspend the USB peripheral is device dependent since
according to the device composition, different actions may be required to reduce the total
consumption.
A brief description of a typical suspend procedure is provided below, focused on the USBrelated aspects of the application software routine responding to the SUSP notification of
the USB peripheral:

1068/1141

1.

Set the FSUSP bit in the USB_CNTR register to 1. This action activates the suspend
mode within the USB peripheral. As soon as the suspend mode is activated, the check
on SOF reception is disabled to avoid any further SUSP interrupts being issued while
the USB is suspended.

2.

Remove or reduce any static power consumption in blocks different from the USB
peripheral.

3.

Set LP_MODE bit in USB_CNTR register to 1 to remove static power consumption in
the analog USB transceivers but keeping them able to detect resume activity.

4.

Optionally turn off external oscillator and device PLL to stop any activity inside the
device.

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
When an USB event occurs while the device is in SUSPEND mode, the RESUME
procedure must be invoked to restore nominal clocks and regain normal USB behavior.
Particular care must be taken to insure that this process does not take more than 10 ms
when the wakening event is an USB reset sequence (See “Universal Serial Bus
Specification” for more details). The start of a resume or reset sequence, while the USB
peripheral is suspended, clears the LP_MODE bit in USB_CNTR register asynchronously.
Even if this event can trigger an WKUP interrupt if enabled, the use of an interrupt response
routine must be carefully evaluated because of the long latency due to system clock restart;
to have the shorter latency before re-activating the nominal clock it is suggested to put the
resume procedure just after the end of the suspend one, so its code is immediately
executed as soon as the system clock restarts. To prevent ESD discharges or any other kind
of noise from waking-up the system (the exit from suspend mode is an asynchronous
event), a suitable analog filter on data line status is activated during suspend; the filter width
is about 70 ns.
The following is a list of actions a resume procedure should address:
1.

Optionally turn on external oscillator and/or device PLL.

2.

Clear FSUSP bit of USB_CNTR register.

3.

If the resume triggering event has to be identified, bits RXDP and RXDM in the
USB_FNR register can be used according to Table 179, which also lists the intended
software action in all the cases. If required, the end of resume or reset sequence can
be detected monitoring the status of the above mentioned bits by checking when they
reach the “10” configuration, which represent the Idle bus state; moreover at the end of
a reset sequence the RESET bit in USB_ISTR register is set to 1, issuing an interrupt if
enabled, which should be handled as usual.
Table 179. Resume event detection
[RXDP,RXDM] status

Wakeup event

Required resume software action

“00”

Root reset

None

“10”

None (noise on bus)

Go back in Suspend mode

“01”

Root resume

None

“11”

Not allowed (noise on bus) Go back in Suspend mode

A device may require to exit from suspend mode as an answer to particular events not
directly related to the USB protocol (e.g. a mouse movement wakes up the whole system).
In this case, the resume sequence can be started by setting the RESUME bit in the
USB_CNTR register to ‘1 and resetting it to 0 after an interval between 1 ms and 15 ms (this
interval can be timed using ESOF interrupts, occurring with a 1 ms period when the system
clock is running at nominal frequency). Once the RESUME bit is clear, the resume
sequence will be completed by the host PC and its end can be monitored again using the
RXDP and RXDM bits in the USB_FNR register.
Note:

The RESUME bit must be anyway used only after the USB peripheral has been put in
suspend mode, setting the FSUSP bit in USB_CNTR register to 1.

DocID022558 Rev 8

1069/1141
1087

Universal serial bus full-speed device interface (USB)

32.6

RM0316

USB registers
The USB peripheral registers can be divided into the following groups:
•

Common Registers: Interrupt and Control registers

•

Endpoint Registers: Endpoint configuration and status

•

Buffer Descriptor Table: Location of packet memory used to locate data buffers

All register addresses are expressed as offsets with respect to the USB peripheral registers
base address 0x4000 5C00, except the buffer descriptor table locations, which starts at the
address specified by the USB_BTABLE register. All register addresses are aligned to 32-bit
word boundaries although they are 16-bit wide. On devices with “1 x 16 bits/word” access
scheme, the same address alignment is used to access packet buffer memory locations,
which are located starting from 0x4000 6000.
Refer to Section 2.1 on page 46 for a list of abbreviations used in register descriptions.
The peripheral registers can be accessed by half-words (16-bit) or words (32-bit).

32.6.1

Common registers
These registers affect the general behavior of the USB peripheral defining operating mode,
interrupt handling, device address and giving access to the current frame number updated
by the host PC.

USB control register (USB_CNTR)
Address offset: 0x40
Reset value: 0x0003
15

14

13

12

11

10

9

8

CTR
M

PMAOVR
M

ERR
M

WKUP
M

SUSP
M

RESET
M

SOF
M

ESOF
M

rw

rw

rw

rw

rw

rw

rw

rw

7

6

L1REQ Res
M
.
rw

5

4

3

2

1

0

L1
RESUME

RE
SUME

F
SUSP

LP_
MODE

PDW
N

F
RES

rw

rw

rw

rw

rw

rw

Bit 15 CTRM: Correct transfer interrupt mask
0: Correct Transfer (CTR) Interrupt disabled.
1: CTR Interrupt enabled, an interrupt request is generated when the corresponding bit in the
USB_ISTR register is set.
Bit 14 PMAOVRM: Packet memory area over / underrun interrupt mask
0: PMAOVR Interrupt disabled.
1: PMAOVR Interrupt enabled, an interrupt request is generated when the corresponding bit
in the USB_ISTR register is set.
Bit 13 ERRM: Error interrupt mask
0: ERR Interrupt disabled.
1: ERR Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.
Bit 12 WKUPM: Wakeup interrupt mask
0: WKUP Interrupt disabled.
1: WKUP Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.

1070/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)

Bit 11 SUSPM: Suspend mode interrupt mask
0: Suspend Mode Request (SUSP) Interrupt disabled.
1: SUSP Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.
Bit 10 RESETM: USB reset interrupt mask
0: RESET Interrupt disabled.
1: RESET Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.
Bit 9 SOFM: Start of frame interrupt mask
0: SOF Interrupt disabled.
1: SOF Interrupt enabled, an interrupt request is generated when the corresponding bit in the
USB_ISTR register is set.
Bit 8 ESOFM: Expected start of frame interrupt mask
0: Expected Start of Frame (ESOF) Interrupt disabled.
1: ESOF Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.
Bit 7 L1REQM: LPM L1 state request interrupt mask
0: LPM L1 state request (L1REQ) Interrupt disabled.
1: L1REQ Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.
Note: If LPM is not supported, this bit is not implemented and considered as reserved. Please
refer to Section 32.3: USB implementation.
Bit 6 Reserved.
Bit 5 L1RESUME: LPM L1 Resume request
The microcontroller can set this bit to send a LPM L1 Resume signal to the host. After the
signaling ends, this bit is cleared by hardware.
Note: If LPM is not supported, this bit is not implemented and considered as reserved. Please
refer to Section 32.3: USB implementation.
Bit 4 RESUME: Resume request
The microcontroller can set this bit to send a Resume signal to the host. It must be activated,
according to USB specifications, for no less than 1 ms and no more than 15 ms after which
the Host PC is ready to drive the resume sequence up to its end.
Bit 3 FSUSP: Force suspend
Software must set this bit when the SUSP interrupt is received, which is issued when no
traffic is received by the USB peripheral for 3 ms.
0: No effect.
1: Enter suspend mode. Clocks and static power dissipation in the analog transceiver are left
unaffected. If suspend power consumption is a requirement (bus-powered device), the
application software should set the LP_MODE bit after FSUSP as explained below.

DocID022558 Rev 8

1071/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

Bit 2 LP_MODE: Low-power mode
This mode is used when the suspend-mode power constraints require that all static power
dissipation is avoided, except the one required to supply the external pull-up resistor. This
condition should be entered when the application is ready to stop all system clocks, or
reduce their frequency in order to meet the power consumption requirements of the USB
suspend condition. The USB activity during the suspend mode (WKUP event)
asynchronously resets this bit (it can also be reset by software).
0: No Low-power mode.
1: Enter Low-power mode.
Bit 1 PDWN: Power down
This bit is used to completely switch off all USB-related analog parts if it is required to
completely disable the USB peripheral for any reason. When this bit is set, the USB
peripheral is disconnected from the transceivers and it cannot be used.
0: Exit Power Down.
1: Enter Power down mode.
Bit 0 FRES: Force USB Reset
0: Clear USB reset.
1: Force a reset of the USB peripheral, exactly like a RESET signaling on the USB. The USB
peripheral is held in RESET state until software clears this bit. A “USB-RESET” interrupt is
generated, if enabled.

USB interrupt status register (USB_ISTR)
Address offset: 0x44
Reset value: 0x0000 0000
15

14

13

12

11

10

9

8

7

6

5

4

CTR

PMA
OVR

ERR

WKUP

SUSP

RESET

SOF

ESOF

L1REQ

Res.

Res.

DIR

r

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

rc_w0

r

3

2

1

0

EP_ID[3:0]
r

r

r

r

This register contains the status of all the interrupt sources allowing application software to
determine, which events caused an interrupt request.
The upper part of this register contains single bits, each of them representing a specific
event. These bits are set by the hardware when the related event occurs; if the
corresponding bit in the USB_CNTR register is set, a generic interrupt request is generated.
The interrupt routine, examining each bit, will perform all necessary actions, and finally it will
clear the serviced bits. If any of them is not cleared, the interrupt is considered to be still
pending, and the interrupt line will be kept high again. If several bits are set simultaneously,
only a single interrupt will be generated.
Endpoint transaction completion can be handled in a different way to reduce interrupt
response latency. The CTR bit is set by the hardware as soon as an endpoint successfully
completes a transaction, generating a generic interrupt request if the corresponding bit in
USB_CNTR is set. An endpoint dedicated interrupt condition is activated independently
from the CTRM bit in the USB_CNTR register. Both interrupt conditions remain active until
software clears the pending bit in the corresponding USB_EPnR register (the CTR bit is
actually a read only bit). For endpoint-related interrupts, the software can use the Direction
of Transaction (DIR) and EP_ID read-only bits to identify, which endpoint made the last
interrupt request and called the corresponding interrupt service routine.

1072/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
The user can choose the relative priority of simultaneously pending USB_ISTR events by
specifying the order in which software checks USB_ISTR bits in an interrupt service routine.
Only the bits related to events, which are serviced, are cleared. At the end of the service
routine, another interrupt will be requested, to service the remaining conditions.
To avoid spurious clearing of some bits, it is recommended to clear them with a load
instruction where all bits which must not be altered are written with 1, and all bits to be
cleared are written with ‘0 (these bits can only be cleared by software). Read-modify-write
cycles should be avoided because between the read and the write operations another bit
could be set by the hardware and the next write will clear it before the microprocessor has
the time to serve the event.
The following describes each bit in detail:
Bit 15 CTR: Correct transfer
This bit is set by the hardware to indicate that an endpoint has successfully completed a
transaction; using DIR and EP_ID bits software can determine which endpoint requested the
interrupt. This bit is read-only.
Bit 14 PMAOVR: Packet memory area over / underrun
This bit is set if the microcontroller has not been able to respond in time to an USB memory
request. The USB peripheral handles this event in the following way: During reception an
ACK handshake packet is not sent, during transmission a bit-stuff error is forced on the
transmitted stream; in both cases the host will retry the transaction. The PMAOVR interrupt
should never occur during normal operations. Since the failed transaction is retried by the
host, the application software has the chance to speed-up device operations during this
interrupt handling, to be ready for the next transaction retry; however this does not happen
during Isochronous transfers (no isochronous transaction is anyway retried) leading to a loss
of data in this case. This bit is read/write but only ‘0 can be written and writing ‘1 has no
effect.
Bit 13 ERR: Error
This flag is set whenever one of the errors listed below has occurred:
NANS: No ANSwer. The timeout for a host response has expired.
CRC: Cyclic Redundancy Check error. One of the received CRCs, either in the token or in
the data, was wrong.
BST: Bit Stuffing error. A bit stuffing error was detected anywhere in the PID, data, and/or
CRC.
FVIO: Framing format Violation. A non-standard frame was received (EOP not in the right
place, wrong token sequence, etc.).
The USB software can usually ignore errors, since the USB peripheral and the PC host
manage retransmission in case of errors in a fully transparent way. This interrupt can be
useful during the software development phase, or to monitor the quality of transmission over
the USB bus, to flag possible problems to the user (e.g. loose connector, too noisy
environment, broken conductor in the USB cable and so on). This bit is read/write but only ‘0
can be written and writing ‘1 has no effect.
Bit 12 WKUP: Wakeup
This bit is set to 1 by the hardware when, during suspend mode, activity is detected that
wakes up the USB peripheral. This event asynchronously clears the LP_MODE bit in the
CTLR register and activates the USB_WAKEUP line, which can be used to notify the rest of
the device (e.g. wakeup unit) about the start of the resume process. This bit is read/write but
only ‘0 can be written and writing ‘1 has no effect.

DocID022558 Rev 8

1073/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

Bit 11 SUSP: Suspend mode request
This bit is set by the hardware when no traffic has been received for 3 ms, indicating a
suspend mode request from the USB bus. The suspend condition check is enabled
immediately after any USB reset and it is disabled by the hardware when the suspend mode
is active (FSUSP=1) until the end of resume sequence. This bit is read/write but only ‘0 can
be written and writing ‘1 has no effect.
Bit 10 RESET: USB reset request
Set when the USB peripheral detects an active USB RESET signal at its inputs. The USB
peripheral, in response to a RESET, just resets its internal protocol state machine, generating
an interrupt if RESETM enable bit in the USB_CNTR register is set. Reception and
transmission are disabled until the RESET bit is cleared. All configuration registers do not
reset: the microcontroller must explicitly clear these registers (this is to ensure that the
RESET interrupt can be safely delivered, and any transaction immediately followed by a
RESET can be completed). The function address and endpoint registers are reset by an USB
reset event.
This bit is read/write but only ‘0 can be written and writing ‘1 has no effect.
Bit 9 SOF: Start of frame
This bit signals the beginning of a new USB frame and it is set when a SOF packet arrives
through the USB bus. The interrupt service routine may monitor the SOF events to have a
1 ms synchronization event to the USB host and to safely read the USB_FNR register which
is updated at the SOF packet reception (this could be useful for isochronous applications).
This bit is read/write but only ‘0 can be written and writing ‘1 has no effect.
Bit 8 ESOF: Expected start of frame
This bit is set by the hardware when an SOF packet is expected but not received. The host
sends an SOF packet each 1 ms, but if the hub does not receive it properly, the Suspend
Timer issues this interrupt. If three consecutive ESOF interrupts are generated (i.e. three
SOF packets are lost) without any traffic occurring in between, a SUSP interrupt is
generated. This bit is set even when the missing SOF packets occur while the Suspend
Timer is not yet locked. This bit is read/write but only ‘0 can be written and writing ‘1 has no
effect.
Bit 7 L1REQ: LPM L1 state request
This bit is set by the hardware when LPM command to enter the L1 state is successfully
received and acknowledged. This bit is read/write but only ‘0 can be written and writing ‘1 has
no effect.
Note: If LPM is not supported, this bit is not implemented and considered as reserved. Please
refer to Section 32.3: USB implementation.

1074/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)

Bits 6:5 Reserved.
Bit 4 DIR: Direction of transaction
This bit is written by the hardware according to the direction of the successful transaction,
which generated the interrupt request.
If DIR bit=0, CTR_TX bit is set in the USB_EPnR register related to the interrupting endpoint.
The interrupting transaction is of IN type (data transmitted by the USB peripheral to the host
PC).
If DIR bit=1, CTR_RX bit or both CTR_TX/CTR_RX are set in the USB_EPnR register
related to the interrupting endpoint. The interrupting transaction is of OUT type (data
received by the USB peripheral from the host PC) or two pending transactions are waiting to
be processed.
This information can be used by the application software to access the USB_EPnR bits
related to the triggering transaction since it represents the direction having the interrupt
pending. This bit is read-only.
Bits 3:0 EP_ID[3:0]: Endpoint Identifier
These bits are written by the hardware according to the endpoint number, which generated
the interrupt request. If several endpoint transactions are pending, the hardware writes the
endpoint identifier related to the endpoint having the highest priority defined in the following
way: Two endpoint sets are defined, in order of priority: Isochronous and double-buffered
bulk endpoints are considered first and then the other endpoints are examined. If more than
one endpoint from the same set is requesting an interrupt, the EP_ID bits in USB_ISTR
register are assigned according to the lowest requesting endpoint register, EP0R having the
highest priority followed by EP1R and so on. The application software can assign a register
to each endpoint according to this priority scheme, so as to order the concurring endpoint
requests in a suitable way. These bits are read only.

USB frame number register (USB_FNR)
Address offset: 0x48
Reset value: 0x0XXX where X is undefined
15

14

13

RXDP

RXDM

LCK

r

r

r

12

11

10

9

8

7

6

r

r

r

r

r

LSOF[1:0]
r

r

5

4

3

2

1

0

r

r

r

r

r

FN[10:0]
r

Bit 15 RXDP: Receive data + line status
This bit can be used to observe the status of received data plus upstream port data line. It
can be used during end-of-suspend routines to help determining the wakeup event.
Bit 14 RXDM: Receive data - line status
This bit can be used to observe the status of received data minus upstream port data line. It
can be used during end-of-suspend routines to help determining the wakeup event.

DocID022558 Rev 8

1075/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

Bit 13 LCK: Locked
This bit is set by the hardware when at least two consecutive SOF packets have been
received after the end of an USB reset condition or after the end of an USB resume
sequence. Once locked, the frame timer remains in this state until an USB reset or USB
suspend event occurs.
Bits 12:11 LSOF[1:0]: Lost SOF
These bits are written by the hardware when an ESOF interrupt is generated, counting the
number of consecutive SOF packets lost. At the reception of an SOF packet, these bits are
cleared.
Bits 10:0 FN[10:0]: Frame number
This bit field contains the 11-bits frame number contained in the last received SOF packet.
The frame number is incremented for every frame sent by the host and it is useful for
Isochronous transfers. This bit field is updated on the generation of an SOF interrupt.

USB device address (USB_DADDR)
Address offset: 0x4C
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.

EF

ADD6

ADD5

ADD4

ADD3

ADD2

ADD1

ADD0

rw

rw

rw

rw

rw

rw

rw

rw

Bits 15:8 Reserved
Bit 7 EF: Enable function
This bit is set by the software to enable the USB device. The address of this device is
contained in the following ADD[6:0] bits. If this bit is at ‘0 no transactions are handled,
irrespective of the settings of USB_EPnR registers.
Bits 6:0 ADD[6:0]: Device address
These bits contain the USB function address assigned by the host PC during the
enumeration process. Both this field and the Endpoint Address (EA) field in the associated
USB_EPnR register must match with the information contained in a USB token in order to
handle a transaction to the required endpoint.

Buffer table address (USB_BTABLE)
Address offset: 0x50
Reset value: 0x0000
15

14

13

12

11

10

9

8

7

6

5

4

3

BTABLE[15:3]
rw

rw

1076/1141

rw

rw

rw

rw

rw

rw

rw

rw

DocID022558 Rev 8

rw

rw

rw

2

1

0

Res.

Res.

Res.

RM0316

Universal serial bus full-speed device interface (USB)

Bits 15:3 BTABLE[15:3]: Buffer table
These bits contain the start address of the buffer allocation table inside the dedicated packet
memory. This table describes each endpoint buffer location and size and it must be aligned
to an 8 byte boundary (the 3 least significant bits are always ‘0). At the beginning of every
transaction addressed to this device, the USB peripheral reads the element of this table
related to the addressed endpoint, to get its buffer start location and the buffer size (Refer to
Structure and usage of packet buffers on page 1059).
Bits 2:0 Reserved, forced by hardware to 0.

LPM control and status register (USB_LPMCSR)
Address offset: 0x54
Reset value: 0x0000
Note:

If LPM is not supported, this bit is not implemented and considered as reserved. Please
refer to Section 32.3: USB implementation.

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

BESL[3:0]

REM
WAKE

Res.

LPM
ACK

LPM
EN

r

r

rw

rw

Bits 15:8 Reserved.
Bits 7:4 BESL[3:0]: BESL value
These bits contain the BESL value received with last ACKed LPM Token
Bit 3 REMWAKE: bRemoteWake value
This bit contains the bRemoteWake value received with last ACKed LPM Token
Bit 2 Reserved
Bit 1 LPMACK: LPM Token acknowledge enable
0: the valid LPM Token will be NYET.
1: the valid LPM Token will be ACK.
The NYET/ACK will be returned only on a successful LPM transaction:
No errors in both the EXT token and the LPM token (else ERROR)
A valid bLinkState = 0001B (L1) is received (else STALL)
Bit 0 LPMEN: LPM support enable
This bit is set by the software to enable the LPM support within the USB device. If this bit is
at ‘0 no LPM transactions are handled.

Endpoint-specific registers
The number of these registers varies according to the number of endpoints that the USB
peripheral is designed to handle. The USB peripheral supports up to 8 bidirectional
endpoints. Each USB device must support a control endpoint whose address (EA bits) must
be set to 0. The USB peripheral behaves in an undefined way if multiple endpoints are
enabled having the same endpoint number value. For each endpoint, an USB_EPnR
register is available to store the endpoint specific information.

DocID022558 Rev 8

1077/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

USB endpoint n register (USB_EPnR), n=[0..7]
Address offset: 0x00 to 0x1C
Reset value: 0x0000
15

14

CTR_
RX

DTOG
_RX

rc_w0

t

13

12

STAT_RX[1:0]
t

t

11
SETUP
r

10

9

EP
TYPE[1:0]
rw

rw

8

7

6

EP_
KIND

CTR_
TX

DTOG_
TX

rw

rc_w0

t

5

4

3

STAT_TX[1:0]
t

t

2

1

0

rw

rw

EA[3:0]
rw

rw

They are also reset when an USB reset is received from the USB bus or forced through bit
FRES in the CTLR register, except the CTR_RX and CTR_TX bits, which are kept
unchanged to avoid missing a correct packet notification immediately followed by an USB
reset event. Each endpoint has its USB_EPnR register where n is the endpoint identifier.
Read-modify-write cycles on these registers should be avoided because between the read
and the write operations some bits could be set by the hardware and the next write would
modify them before the CPU has the time to detect the change. For this purpose, all bits
affected by this problem have an ‘invariant’ value that must be used whenever their
modification is not required. It is recommended to modify these registers with a load
instruction where all the bits, which can be modified only by the hardware, are written with
their ‘invariant’ value.

Bit 15 CTR_RX: Correct Transfer for reception
This bit is set by the hardware when an OUT/SETUP transaction is successfully completed
on this endpoint; the software can only clear this bit. If the CTRM bit in USB_CNTR register
is set accordingly, a generic interrupt condition is generated together with the endpoint
related interrupt condition, which is always activated. The type of occurred transaction, OUT
or SETUP, can be determined from the SETUP bit described below.
A transaction ended with a NAK or STALL handshake does not set this bit, since no data is
actually transferred, as in the case of protocol errors or data toggle mismatches.
This bit is read/write but only ‘0 can be written, writing 1 has no effect.
Bit 14 DTOG_RX: Data Toggle, for reception transfers
If the endpoint is not Isochronous, this bit contains the expected value of the data toggle bit
(0=DATA0, 1=DATA1) for the next data packet to be received. Hardware toggles this bit,
when the ACK handshake is sent to the USB host, following a data packet reception having
a matching data PID value; if the endpoint is defined as a control one, hardware clears this
bit at the reception of a SETUP PID addressed to this endpoint.
If the endpoint is using the double-buffering feature this bit is used to support packet buffer
swapping too (Refer to Section 32.5.3: Double-buffered endpoints).
If the endpoint is Isochronous, this bit is used only to support packet buffer swapping since
no data toggling is used for this sort of endpoints and only DATA0 packet are transmitted
(Refer to Section 32.5.4: Isochronous transfers). Hardware toggles this bit just after the end
of data packet reception, since no handshake is used for isochronous transfers.
This bit can also be toggled by the software to initialize its value (mandatory when the
endpoint is not a control one) or to force specific data toggle/packet buffer usage. When the
application software writes ‘0, the value of DTOG_RX remains unchanged, while writing ‘1
makes the bit value toggle. This bit is read/write but it can be only toggled by writing 1.

1078/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)

Bits 13:12 STAT_RX [1:0]: Status bits, for reception transfers
These bits contain information about the endpoint status, which are listed in Table 180:
Reception status encoding on page 1080.These bits can be toggled by software to initialize
their value. When the application software writes ‘0, the value remains unchanged, while
writing ‘1 makes the bit value toggle. Hardware sets the STAT_RX bits to NAK when a
correct transfer has occurred (CTR_RX=1) corresponding to a OUT or SETUP (control only)
transaction addressed to this endpoint, so the software has the time to elaborate the
received data before it acknowledge a new transaction
Double-buffered bulk endpoints implement a special transaction flow control, which control
the status based upon buffer availability condition (Refer to Section 32.5.3: Double-buffered
endpoints).
If the endpoint is defined as Isochronous, its status can be only “VALID” or “DISABLED”, so
that the hardware cannot change the status of the endpoint after a successful transaction. If
the software sets the STAT_RX bits to ‘STALL’ or ‘NAK’ for an Isochronous endpoint, the
USB peripheral behavior is not defined. These bits are read/write but they can be only
toggled by writing ‘1.
Bit 11 SETUP: Setup transaction completed
This bit is read-only and it is set by the hardware when the last completed transaction is a
SETUP. This bit changes its value only for control endpoints. It must be examined, in the
case of a successful receive transaction (CTR_RX event), to determine the type of
transaction occurred. To protect the interrupt service routine from the changes in SETUP
bits due to next incoming tokens, this bit is kept frozen while CTR_RX bit is at 1; its state
changes when CTR_RX is at 0. This bit is read-only.
Bits 10:9 EP_TYPE[1:0]: Endpoint type
These bits configure the behavior of this endpoint as described in Table 181: Endpoint type
encoding on page 1081. Endpoint 0 must always be a control endpoint and each USB
function must have at least one control endpoint which has address 0, but there may be
other control endpoints if required. Only control endpoints handle SETUP transactions,
which are ignored by endpoints of other kinds. SETUP transactions cannot be answered
with NAK or STALL. If a control endpoint is defined as NAK, the USB peripheral will not
answer, simulating a receive error, in the receive direction when a SETUP transaction is
received. If the control endpoint is defined as STALL in the receive direction, then the
SETUP packet will be accepted anyway, transferring data and issuing the CTR interrupt.
The reception of OUT transactions is handled in the normal way, even if the endpoint is a
control one.
Bulk and interrupt endpoints have very similar behavior and they differ only in the special
feature available using the EP_KIND configuration bit.
The usage of Isochronous endpoints is explained in Section 32.5.4: Isochronous transfers
Bit 8 EP_KIND: Endpoint kind
The meaning of this bit depends on the endpoint type configured by the EP_TYPE bits.
Table 182 summarizes the different meanings.
DBL_BUF: This bit is set by the software to enable the double-buffering feature for this bulk
endpoint. The usage of double-buffered bulk endpoints is explained in Section 32.5.3:
Double-buffered endpoints.
STATUS_OUT: This bit is set by the software to indicate that a status out transaction is
expected: in this case all OUT transactions containing more than zero data bytes are
answered ‘STALL’ instead of ‘ACK’. This bit may be used to improve the robustness of the
application to protocol errors during control transfers and its usage is intended for control
endpoints only. When STATUS_OUT is reset, OUT transactions can have any number of
bytes, as required.

DocID022558 Rev 8

1079/1141
1087

Universal serial bus full-speed device interface (USB)

RM0316

Bit 7 CTR_TX: Correct Transfer for transmission
This bit is set by the hardware when an IN transaction is successfully completed on this
endpoint; the software can only clear this bit. If the CTRM bit in the USB_CNTR register is
set accordingly, a generic interrupt condition is generated together with the endpoint related
interrupt condition, which is always activated.
A transaction ended with a NAK or STALL handshake does not set this bit, since no data is
actually transferred, as in the case of protocol errors or data toggle mismatches.
This bit is read/write but only ‘0 can be written.
Bit 6 DTOG_TX: Data Toggle, for transmission transfers
If the endpoint is non-isochronous, this bit contains the required value of the data toggle bit
(0=DATA0, 1=DATA1) for the next data packet to be transmitted. Hardware toggles this bit
when the ACK handshake is received from the USB host, following a data packet
transmission. If the endpoint is defined as a control one, hardware sets this bit to 1 at the
reception of a SETUP PID addressed to this endpoint.
If the endpoint is using the double buffer feature, this bit is used to support packet buffer
swapping too (Refer to Section 32.5.3: Double-buffered endpoints)
If the endpoint is Isochronous, this bit is used to support packet buffer swapping since no
data toggling is used for this sort of endpoints and only DATA0 packet are transmitted (Refer
to Section 32.5.4: Isochronous transfers). Hardware toggles this bit just after the end of data
packet transmission, since no handshake is used for Isochronous transfers.
This bit can also be toggled by the software to initialize its value (mandatory when the
endpoint is not a control one) or to force a specific data toggle/packet buffer usage. When
the application software writes ‘0, the value of DTOG_TX remains unchanged, while writing
‘1 makes the bit value toggle. This bit is read/write but it can only be toggled by writing 1.
Bits 5:4 STAT_TX [1:0]: Status bits, for transmission transfers
These bits contain the information about the endpoint status, listed in Table 183. These bits
can be toggled by the software to initialize their value. When the application software writes
‘0, the value remains unchanged, while writing ‘1 makes the bit value toggle. Hardware sets
the STAT_TX bits to NAK, when a correct transfer has occurred (CTR_TX=1) corresponding
to a IN or SETUP (control only) transaction addressed to this endpoint. It then waits for the
software to prepare the next set of data to be transmitted.
Double-buffered bulk endpoints implement a special transaction flow control, which controls
the status based on buffer availability condition (Refer to Section 32.5.3: Double-buffered
endpoints).
If the endpoint is defined as Isochronous, its status can only be “VALID” or “DISABLED”.
Therefore, the hardware cannot change the status of the endpoint after a successful
transaction. If the software sets the STAT_TX bits to ‘STALL’ or ‘NAK’ for an Isochronous
endpoint, the USB peripheral behavior is not defined. These bits are read/write but they can
be only toggled by writing ‘1.
Bits 3:0 EA[3:0]: Endpoint address
Software must write in this field the 4-bit address used to identify the transactions directed to
this endpoint. A value must be written before enabling the corresponding endpoint.

Table 180. Reception status encoding
STAT_RX[1:0]

1080/1141

Meaning

00

DISABLED: all reception requests addressed to this endpoint are ignored.

01

STALL: the endpoint is stalled and all reception requests result in a STALL
handshake.

10

NAK: the endpoint is naked and all reception requests result in a NAK handshake.

11

VALID: this endpoint is enabled for reception.

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
Table 181. Endpoint type encoding
EP_TYPE[1:0]

Meaning

00

BULK

01

CONTROL

10

ISO

11

INTERRUPT

Table 182. Endpoint kind meaning
EP_TYPE[1:0]

EP_KIND meaning

00

BULK

DBL_BUF

01

CONTROL

STATUS_OUT

10

ISO

Not used

11

INTERRUPT

Not used

Table 183. Transmission status encoding
STAT_TX[1:0]

Meaning

00

DISABLED: all transmission requests addressed to this endpoint are ignored.

01

STALL: the endpoint is stalled and all transmission requests result in a STALL
handshake.

10

NAK: the endpoint is naked and all transmission requests result in a NAK
handshake.

11

VALID: this endpoint is enabled for transmission.

DocID022558 Rev 8

1081/1141
1087

Universal serial bus full-speed device interface (USB)

32.6.2

RM0316

Buffer descriptor table
Although the buffer descriptor table is located inside the packet buffer memory, its entries
can be considered as additional registers used to configure the location and size of the
packet buffers used to exchange data between the USB macro cell and the device.
On devices with “1 x 16 bits/word” access scheme, all packet memory locations are
accessed by the APB using 32-bit aligned addresses, instead of the actual memory location
addresses utilized by the USB peripheral for the USB_BTABLE register and buffer
description table locations.
In the following pages, two address locations are reported for devices with “1 x 16 bits/word”
access scheme: the one to be used by application software while accessing the packet
memory, and the local one relative to USB peripheral access. To obtain the correct memory
address value to be used in the application software while accessing the packet memory,
the actual memory location address must be multiplied by two.
On devices with “2 x 16 bits/word” access scheme, the address location to be used by
application software is the same as the local one relative to USB peripheral access. The
packet memory on these devices should be accessed only by byte (8-bit) or half-word (16bit) accesses. Word (32-bit) accesses are not allowed.
The first packet memory location is located at 0x4000 6000. The buffer descriptor table
entry associated with the USB_EPnR registers is described below.
A thorough explanation of packet buffers and the buffer descriptor table usage can be found
in Structure and usage of packet buffers on page 1059.

Transmission buffer address n (USB_ADDRn_TX)
Address offset (“1 x 16 bits/word” access scheme): [USB_BTABLE] + n*16
Address offset (“2 x 16 bits/word” access scheme): [USB_BTABLE] + n*8
USB local address: [USB_BTABLE] + n*8
Note:

In case of double-buffered or isochronous endpoints in the IN direction, this address location
is referred to as USB_ADDRn_TX_0.
In case of double-buffered or isochronous endpoints in the OUT direction, this address
location is used for USB_ADDRn_RX_0.

15

14

13

12

11

10

9

rw

rw

rw

rw

rw

rw

rw

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

-

ADDRn_TX[15:1]
rw

-

Bits 15:1 ADDRn_TX[15:1]: Transmission buffer address
These bits point to the starting address of the packet buffer containing data to be transmitted
by the endpoint associated with the USB_EPnR register at the next IN token addressed to it.
Bit 0 Must always be written as ‘0 since packet memory is half-word wide and all packet buffers
must be half-word aligned.

Transmission byte count n (USB_COUNTn_TX)
Address offset (“1 x 16 bits/word” access scheme): [USB_BTABLE] + n*16 + 4

1082/1141

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
Address offset (“2 x 16 bits/word” access scheme): [USB_BTABLE] + n*8 + 2
USB local address: [USB_BTABLE] + n*8 + 2

Note:

In case of double-buffered or isochronous endpoints in the IN direction, this address location
is referred to as USB_COUNTn_TX_0.
In case of double-buffered or isochronous endpoints in the OUT direction, this address
location is used for USB_COUNTn_RX_0.

15

14

13

12

11

10

Res.

Res.

Res.

Res.

Res.

Res.

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

COUNTn_TX[9:0]
rw

rw

rw

rw

rw

rw

Bits 15:10 These bits are not used since packet size is limited by USB specifications to 1023 bytes. Their
value is not considered by the USB peripheral.
Bits 9:0 COUNTn_TX[9:0]: Transmission byte count
These bits contain the number of bytes to be transmitted by the endpoint associated with the
USB_EPnR register at the next IN token addressed to it.

Reception buffer address n (USB_ADDRn_RX)
Address offset (“1 x 16 bits/word” access scheme): [USB_BTABLE] + n*16 + 8
Address offset (“2 x 16 bits/word” access scheme): [USB_BTABLE] + n*8 + 4
USB local address: [USB_BTABLE] + n*8 + 4
Note:

In case of double-buffered or isochronous endpoints in the OUT direction, this address
location is referred to as USB_ADDRn_RX_1.
In case of double-buffered or isochronous endpoints in the IN direction, this address location
is used for USB_ADDRn_TX_1.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

ADDRn_RX[15:1]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

-

Bits 15:1 ADDRn_RX[15:1]: Reception buffer address
These bits point to the starting address of the packet buffer, which will contain the data
received by the endpoint associated with the USB_EPnR register at the next OUT/SETUP
token addressed to it.
Bit 0 This bit must always be written as ‘0 since packet memory is half-word wide and all packet
buffers must be half-word aligned.

Reception byte count n (USB_COUNTn_RX)
Address offset (“1 x 16 bits/word” access scheme): [USB_BTABLE] + n*16 + 12
Address offset (“2 x 16 bits/word” access scheme): [USB_BTABLE] + n*8 + 6
USB local address: [USB_BTABLE] + n*8 + 6

DocID022558 Rev 8

1083/1141
1087

Universal serial bus full-speed device interface (USB)
Note:

RM0316

In case of double-buffered or isochronous endpoints in the OUT direction, this address
location is referred to as USB_COUNTn_RX_1.
In case of double-buffered or isochronous endpoints in the IN direction, this address location
is used for USB_COUNTn_TX_1.

15

14

BLSIZE
rw

13

12

11

10

9

8

7

6

NUM_BLOCK[4:0]
rw

rw

rw

5

4

3

2

1

0

r

r

r

r

COUNTn_RX[9:0]

rw

rw

r

r

r

r

r

r

This table location is used to store two different values, both required during packet
reception. The most significant bits contains the definition of allocated buffer size, to allow
buffer overflow detection, while the least significant part of this location is written back by the
USB peripheral at the end of reception to give the actual number of received bytes. Due to
the restrictions on the number of available bits, buffer size is represented using the number
of allocated memory blocks, where block size can be selected to choose the trade-off
between fine-granularity/small-buffer and coarse-granularity/large-buffer. The size of
allocated buffer is a part of the endpoint descriptor and it is normally defined during the
enumeration process according to its maxPacketSize parameter value (See “Universal
Serial Bus Specification”).
Bit 15 BL_SIZE: Block size
This bit selects the size of memory block used to define the allocated buffer area.
–
If BL_SIZE=0, the memory block is 2-byte large, which is the minimum block
allowed in a half-word wide memory. With this block size the allocated buffer size
ranges from 2 to 62 bytes.
–
If BL_SIZE=1, the memory block is 32-byte large, which allows to reach the
maximum packet length defined by USB specifications. With this block size the
allocated buffer size theoretically ranges from 32 to 1024 bytes, which is the longest
packet size allowed by USB standard specifications. However, the applicable size is
limited by the available buffer memory.
Bits 14:10 NUM_BLOCK[4:0]: Number of blocks
These bits define the number of memory blocks allocated to this packet buffer. The actual
amount of allocated memory depends on the BL_SIZE value as illustrated in Table 184.
Bits 9:0 COUNTn_RX[9:0]: Reception byte count
These bits contain the number of bytes received by the endpoint associated with the
USB_EPnR register during the last OUT/SETUP transaction addressed to it.

Table 184. Definition of allocated buffer memory

1084/1141

Value of
NUM_BLOCK[4:0]

Memory allocated
when BL_SIZE=0

Memory allocated
when BL_SIZE=1

0 (‘00000)

Not allowed

32 bytes

1 (‘00001)

2 bytes

64 bytes

2 (‘00010)

4 bytes

96 bytes

3 (‘00011)

6 bytes

128 bytes

...

...

...

14 (‘01110)

28 bytes

480 bytes

DocID022558 Rev 8

RM0316

Universal serial bus full-speed device interface (USB)
Table 184. Definition of allocated buffer memory (continued)
Value of
NUM_BLOCK[4:0]

Memory allocated
when BL_SIZE=0

Memory allocated
when BL_SIZE=1

15 (‘01111)

30 bytes

N/A

16 (‘10000)

32 bytes

N/A

...

...

...

29 (‘11101)

58 bytes

N/A

30 (‘11110)

60 bytes

N/A

31 (‘11111)

62 bytes

N/A

DocID022558 Rev 8

1085/1141
1087

0x4C

USB_DADDR

1086/1141

CTR

PMAOVR

ERR

0

0

0

USB_FNR

Reset value

DocID022558 Rev 8

RXDM

LCK

0

0

0

0

0

x

x

x

x

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
EP_KIND
CTR_TX
DTOG_TX

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

Res.
L1RESUME
RESUME
FSUSP
LPMODE
PDWN
FRES

0

0

0

1

1

STAT_
RX
[1:0]
0
0

0

0

0

0
0

DTOG_RX

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SETUP

EP_KIND
CTR_TX
DTOG_TX

SETUP

DTOG_TX

DTOG_TX

DTOG_TX

DTOG_TX

DTOG_TX

CTR_RX

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CTR_TX

0

EP_KIND

SETUP

CTR_TX

0

EP_KIND
CTR_TX

0

EP_KIND
CTR_TX

0

EP_KIND

CTR_TX

0
EP_KIND

DTOG_TX

0

CTR_TX

0

EP_KIND

0

0
0
0

EP
TYPE
[1:0]
0
0
0
0

EP
TYPE
[1:0]
0
0
0
0

EP
TYPE
[1:0]
0
0
0
0

EP
TYPE
[1:0]
0
0
0
0

EP
TYPE
[1:0]

0
0
0
0

EP
TYPE
[1:0]

0
0
0
0

EP
TYPE
[1:0]

0

0

0

0

EF

LSOF
[1:0]

0

0

0

0

x

0

0

0

0

0

0

0

0

x

0

DIR

STAT_
RX
[1:0]

0

0

Res.

0
0

0

0

Res.

Reserved

L1REQM

STAT_
RX
[1:0]

0

EP
TYPE
[1:0]

L1REQ

0
0

SOFM

0

0

ESOFM

STAT_
RX
[1:0]

SOF

0

0

ESOF

STAT_
RX
[1:0]
SETUP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

STAT_
RX
[1:0]

SETUP

0

0

SETUP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DTOG_RX

USB_EP3R
Res.

CTR_RX
0

STAT_
RX
[1:0]

SETUP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DTOG_RX

DTOG_RX

USB_EP4R
Res.

CTR_RX

0

Res.

USB_EP2R
0

0

SETUP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CTR_RX

USB_EP5R
Res.

0

Res.

Res.

USB_EP1R
0

SUSPM

0

SUSP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

Res.

0

Res.

Reset value

Res.

0

Res.

0

RESETM

WKUPM

0

WKUP

USB_EP6R
Res.

DTOG_RX

0

Res.

CTR_RX

DTOG_RX

DTOG_RX

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Reset value

Res.

Reset value

Res.

0

Res.

Reset value
STAT_
RX
[1:0]

RESET

ERRM

USB_EP7R
DTOG_RX

PMAOVRM
0

Res.

0

Res.

Reset value

Res.

CTR_RX

CTR_RX

0

Res.

Reset value

Res.

Reset value

CTR_RX

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CTRM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

RXDP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Reset value

Res.

0x200x3F

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0x48

Res.

USB_ISTR

Res.

0x44

Res.

USB_CNTR

Res.

0x40

Res.

0x1C

Res.

0x18

Res.

0x14

Res.

0x10

Res.

0x0C

Res.

0x08

Res.

0x04
USB_EP0R

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.

32.6.3

Res.

Universal serial bus full-speed device interface (USB)
RM0316

USB register map

The table below provides the USB register map and reset values.
Table 185. USB register map and reset values

STAT_
TX
[1:0]
0

0

0

0

0

0

0

0

x

0

EA[3:0]

0

STAT_
TX
[1:0]
0

STAT_
TX
[1:0]

STAT_
TX
[1:0]

0

STAT_
TX
[1:0]

0

0

STAT_
TX
[1:0]
0

STAT_
TX
[1:0]

STAT_
TX
[1:0]
0

FN[10:0]

ADD[6:0]

0

0

0

0

x

x

x

x

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

EA[3:0]
0

EA[3:0]
0

EA[3:0]
0

EA[3:0]
0

EA[3:0]
0

EA[3:0]
0

EA[3:0]

EP_ID[3:0]

RM0316

Universal serial bus full-speed device interface (USB)

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

0

0

0

0

BESL[3:0]
0

0

0

0

Res.

0

Res.

0

LPMEN

0

Res.

0

Res.

0

0

0

0
REMWAKE

0

LPMACK

Res.
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

USB_LPMCSR

Res.

0x54

Res.

Reset value

BTABLE[15:3]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

USB_BTABLE

Res.

0x50

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 185. USB register map and reset values (continued)

0

Refer to Section 3.2.2 on page 51 for the register boundary addresses.

DocID022558 Rev 8

1087/1141
1087

Debug support (DBG)

RM0316

33

Debug support (DBG)

33.1

Overview
The STM32F3xx devices are built around a Cortex-M4®F 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
STM32F3xx MCUs.
Two interfaces for debug are available:
•

Serial wire

•

JTAG debug port
Figure 403. Block diagram of STM32 MCU and
Cortex-M4®F-level debug support
34- -#5 DEBUG SUPPORT
#ORTEX - DEBUG SUPPORT
"US MATRIX

#ORTEX -
#ORE

$#ODE
INTERFACE

$ATA

3YSTEM
INTERFACE

*4-3
37$)/

%XTERNAL PRIVATE
PERIPHERAL BUS 00"

*4$)
*4$/
42!#%37/
.*4234
*4#+
37#,+

"RIDGE
37* $0

%4-

!(" !0
42!#%37/
)NTERNAL PRIVATE
PERIPHERAL BUS 00"

.6)#

4RACE PORT
40)5

42!#%#+
42!#%$;=

$74

&0"

)4-

$"'-#5

-36

Note:

1088/1141

The debug features embedded in the Cortex®-M4 core are a subset of the ARM® CoreSight
Design Kit.

DocID022558 Rev 8

RM0316

Debug support (DBG)
The ARM® Cortex-M4®F 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 only on STM32F303xB/C and
STM32F358xC devices larger packages, where the corresponding pins are mapped)

It also includes debug features dedicated to the STM32F3xx:
•

Flexible debug pinout assignment

•

MCU debug box (support for low-power modes, control over peripheral clocks, etc.)

Note:

For further information on the debug feature supported by the ARM® Cortex-M4®F 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®F r0p1 Technical Reference Manual (TRM)

•

ARM® Debug Interface V5

•

ARM® CoreSight Design Kit revision r0p1 Technical Reference Manual

It is available from: http://infocenter.arm.com

33.3

SWJ debug port (serial wire and JTAG)
The STM32F3xx core 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.

DocID022558 Rev 8

1089/1141
1120

Debug support (DBG)

RM0316
Figure 404. SWJ debug port
75$&(6:2 DV\QFKURQRXVWUDFH
6:-'3

-7'2
-7',
1-7567

7'2
7',
Q7567

7'2
7',
Q7567

-7$*'3

7&.
706

Q327567

6:'-7$*
VHOHFW

Q327567
'%*5(6(7Q

6:',706
-7066:',2

)URP
SRZHURQ
UHVHW

'%*',
6:'2

'%*'2
6:'3

6:'2(1

-7&.6:&/.

6:&/.7&.

'%*'2(1
'%*&/.
DL

Figure 404 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 STM32F3xx MCUs are available in various packages with different numbers of
available pins. As a result, some functionality (ETM) related to pin availability may differ
between packages.

1090/1141

DocID022558 Rev 8

RM0316

33.4.1

Debug support (DBG)

SWJ debug port pins
Five pins are used as outputs from the STM32F3xx for the SWJ-DP as alternate functions of
general-purpose I/Os. These pins are available on all packages.
Table 186. SWJ debug port pins
JTAG debug port

SW debug port

SWJ-DP pin name
Type

33.4.2

Description

Type

Debug assignment

Pin
assign
ment

JTMS/SWDIO

I

JTAG Test Mode
Selection

IO

Serial Wire Data
Input/Output

PA13

JTCK/SWCLK

I

JTAG Test Clock

I

Serial Wire Clock

PA14

JTDI

I

JTAG Test Data Input

-

-

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, it is possible to disable some or all of the SWJ-DP ports and so, to release (in gray
in the table below) the associated pins for general-purpose I/O(GPIO) usage. For more
details on how to disable SWJ-DP port pins, please refer to Section 11.3.2: I/O pin alternate
function multiplexer and mapping.
Table 187. Flexible SWJ-DP pin assignment
SWJ IO pin assigned
Available debug ports

PA13 / PA14 /
PA15 /
JTMS/ JTCK/
JTDI
SWDIO SWCLK

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
AFIO_MAPR 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.).

DocID022558 Rev 8

1091/1141
1120

Debug support (DBG)

33.4.3

RM0316

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: Input pull-up

•

JTDI: Input pull-up

•

JTMS/SWDIO: Input pull-up

•

JTCK/SWCLK: Input pull-down

•

JTDO: Input 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.

1092/1141

DocID022558 Rev 8

RM0316

33.4.4

Debug support (DBG)

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.

33.5

STM32F3xx JTAG TAP connection
The STM32F3xx MCUs integrate two serially connected JTAG TAPs, the boundary scan
TAP (IR is 5-bit wide) and the Cortex-M4®F TAP (IR is 4-bit wide).
To access the TAP of the Cortex-M4®F 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).

DocID022558 Rev 8

1093/1141
1120

Debug support (DBG)

RM0316
Figure 405. JTAG TAP connections
6700&8

1-7567
-706
6:'3
6HOHFWHG

706 Q7567

-7',

-7'2

7',

7'2

%RXQGDU\VFDQ

7$3
,5LVELWZLGH

706 Q7567

7',

7'2

&RUWH [07$3
,5LVELWZLGH

DLF

33.6

ID codes and locking mechanism
There are several ID codes inside the STM32F3xx 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.

1094/1141

DocID022558 Rev 8

RM0316

Debug support (DBG)

33.6.1

MCU device ID code
The STM32F3xx 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 1107). This code is accessible using the
JTAG debug port (4 to 5 pins) or the SW debug port (two pins) or by the user software. It is
even accessible while the MCU is under system reset.

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

REV_ID
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

r

r

DEV_ID
r

Bits 31:16 REV_ID[15:0] Revision identifier
This field indicates the revision of the device.
0x1001: Rev Z
0x1003: Rev Y
Bits 15:12 Reserved, must be kept at reset value.
Bits 11:0 DEV_ID[11:0]: Device identifier
This field indicates the device and its revision.
The device ID is:
0x422 for STM32F303xB/C and STM32F358 devices.
0x438 for STM32F303x6/8 and STM32F328 devices.
0x446 for STM32F303xD/E and STM32F398xE devices.

33.6.2

Boundary scan TAP
JTAG ID code
The TAP of the STM32F3xx BSC (boundary scan) integrates a JTAG ID code equal to
0x06432041.

33.6.3

Cortex-M4®F TAP
The TAP of the ARM® Cortex-M4®F 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®F r0p1, see Section 33.2: Reference
ARM® documentation).
Only the DEV_ID(11:0) should be used for identification by the debugger/programmer tools.

DocID022558 Rev 8

1095/1141
1120

Debug support (DBG)

33.6.4

RM0316

Cortex-M4®F JEDEC-106 ID code
The ARM® Cortex-M4®F 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®Fr0p1 Technical Reference Manual
(TRM), for references, please see Section 33.2: Reference ARM® documentation).
Table 188. JTAG debug port data registers
IR(3:0)

Data register

1111

BYPASS
[1 bit]

1110

IDCODE
[32 bits]

ID CODE
0x3BA00477 (ARM® Cortex-M4®F 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 189 for a description of the A(3:2) bits

1010

1096/1141

Details

DocID022558 Rev 8

RM0316

Debug support (DBG)
Table 188. 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.

Table 189. 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

DocID022558 Rev 8

1097/1141
1120

Debug support (DBG)

RM0316

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:
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
Table 190. 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 189)

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®F r0p1 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.

1098/1141

DocID022558 Rev 8

RM0316

Debug support (DBG)
Table 191. 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 192. 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
0x1BA01477 (corresponding to Cortex-M4®F r0p1).

Note:

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®F r0p1 TRM
and the CoreSight Design Kit r0p1TRM.

33.8.4

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

DocID022558 Rev 8

1099/1141
1120

Debug support (DBG)

RM0316

IDCODE read or CTRL/STAT read or ABORT write which are accepted even if the write
buffer is full.
•

33.8.5

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 193. SW-DP registers
A(3:2)

CTRLSEL bit
of SELECT
register

Register

Notes

00

Read

-

IDCODE

The manufacturer code is not set to ST code
0x2BA01477 (identifies the SW-DP)

00

Write

-

ABORT

-

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

1100/1141

R/W

Read/Write

-

DocID022558 Rev 8

RM0316

33.8.6

Debug support (DBG)

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:

33.9

•

The shifted value A[3:2]

•

The current value of the DP SELECT register

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:
d)

Bits [7:4] = the bits [7:4] APBANKSEL of the DP SELECT register

e)

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®F includes 9 x 32-bits registers:
Table 194. Cortex-M4®F 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®F r0p1 TRM for further details.

DocID022558 Rev 8

1101/1141
1120

Debug support (DBG)

33.10

RM0316

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 195. 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®F r0p1 TRM for further details.
To Halt on reset, it is necessary to:

33.11

•

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.

Capability of the debugger host to connect under system
reset
The STM32F3xx MCUs’ reset system 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®F 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.

1102/1141

DocID022558 Rev 8

RM0316

Debug support (DBG)

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:
•

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.

DocID022558 Rev 8

1103/1141
1120

Debug support (DBG)

33.13

RM0316

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®F 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 programming or using 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.

1104/1141

DocID022558 Rev 8

RM0316

Debug support (DBG)
For this, the DWT must be configured to trigger the ITM: the bit CYCCNTENA (bit0) of the
DWT Control Register must be set. In addition, the bit2 (SYNCENA) of the ITM Trace
Control Register must be set.

Note:

If the SYNENA bit is not set, the DWT generates Synchronization triggers to the TPIU which
will send only TPIU synchronization packets and not ITM synchronization packets.
An overflow packet consists is a special timestamp packets which indicates that data has
been written but the FIFO was full.
Table 196. Main ITM registers
Address
@E0000FB0

Register
ITM lock access

Details
Write 0xC5ACCE55 to unlock Write Access to the other ITM
registers
Bits 31-24 = Always 0
Bits 23 = Busy
Bits 22-16 = 7-bits ATB ID which identifies the source of the
trace data.
Bits 15-10 = Always 0
Bits 9:8 = TSPrescale = Time Stamp Prescaler
Bits 7-5 = Reserved

@E0000E80

ITM trace control

Bit 4 = SWOENA = Enable SWV behavior (to clock the
timestamp counter by the SWV clock).
Bit 3 = DWTENA: Enable the DWT Stimulus
Bit 2 = SYNCENA: this bit must be to 1 to enable the DWT to
generate synchronization triggers so that the TPIU can then
emit the synchronization packets.
Bit 1 = TSENA (Timestamp Enable)
Bit 0 = ITMENA: Global Enable Bit of the ITM
Bit 3: mask to enable tracing ports31:24

@E0000E40

ITM trace privilege

Bit 2: mask to enable tracing ports23:16
Bit 1: mask to enable tracing ports15:8
Bit 0: mask to enable tracing ports7:0

@E0000E00

ITM trace enable

@E0000000- Stimulus port
E000007C
registers 0-31

Each bit enables the corresponding Stimulus port to generate
trace.
Write the 32-bits data on the selected Stimulus Port (32
available) to be traced out.

DocID022558 Rev 8

1105/1141
1120

Debug support (DBG)

RM0316

Example of configuration
To output a simple value to the TPIU:

33.15

•

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)

ETM (Embedded trace macrocell)
ETM is available on STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices
only.

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.

1106/1141

DocID022558 Rev 8

RM0316

Debug support (DBG)

33.15.3

Main ETM registers
For more information on registers refer to the chapter 3 of the ARM IHI 0014N specification.
Table 197. Main ETM registers

Address

Register

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

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.

33.15.4

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
STM32F3xx 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:

33.16.1

•

Low-power modes

•

Clock control for timers, watchdog, I2C and bxCAN during a breakpoint

•

Control of the trace pins assignment

Debug support for low-power modes
To enter low-power mode, the instruction WFI or WFE must be executed.
The MCU implements several low-power modes which can either deactivate the CPU clock
or reduce the power of the CPU.

DocID022558 Rev 8

1107/1141
1120

Debug support (DBG)

RM0316

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:
•

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

33.16.2

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.

DBGMCU_CR
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

1108/1141

DocID022558 Rev 8

RM0316

15
Res

Debug support (DBG)

14
Res

13
Res

12
Res

11
Res

10
Res

9

8

Res

Res

7

6

TRACE_
MODE
[1:0]
rw

rw

5
TRACE
_
IOEN
rw

4
Res.

3

2

1

0

Res

DBG_
STAND
BY

DBG_
STOP

DBG_
SLEEP

rw

rw

rw

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
Note: In STM32F303x6/8 and STM32F328x8 devices, synchronous trace is not available,
thus bits 7:5 are reserved and must be kept at 0.
Bits 4:3 Reserved, must be kept at reset value.
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).

DocID022558 Rev 8

1109/1141
1120

Debug support (DBG)

33.16.4

RM0316

Debug MCU APB1 freeze register (DBGMCU_APB1_FZ)
The DBGMCU_APB1_FZ register is used to configure the MCU under DEBUG. It concerns
the APB1 peripherals:
•

Timer clock counter freeze

•

I2C SMBUS timeout freeze

•

Window watchdog and independent watchdog counter freeze support

This DBGMCU_APB1_FZ is mapped on the external PPB bus at address 0xE0042008.
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-bit access are supported.

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DBG_I2C3_SMBUS_TIMEOUT

Res

Res

Res

Res

DBG_CAN_STOP

Res

Res

Res

Res

Res

Res

Res

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res

Res

DBG_IWDG_STOP

DBG_WWDG_STOP

DBG_RTC_STOP

Res

Res

Res

Res

DBG_TIM7_STOP

DBG_TIM6_STOP

Res

DBG_TIM4_STOP(1)

DBG_TIM3_STOP

DBG_TIM2_STOP

rw

Res

rw

15

rw

rw

rw

rw

rw

rw

rw

rw

rw

1.

DBG_I2C1_SMBUS_TIMEOUT

30

DBG_I2C2_SMBUS_TIMEOUT(1)

31

Res

Power on reset (POR): 0x0000 0000 (not reset by system reset)

Only in STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices.

Bits 31 Reserved, must be kept at reset value.
Bit 30 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 25 DBG_CAN_STOP: Debug CAN stopped when core is halted
0: Same behavior as in normal mode
1: The CAN2 receive registers are frozen
Bits 24:23 Reserved, must be kept at reset value.
Bit 22 DBG_I2C2_SMBUS_TIMEOUT: SMBUS timeout mode stopped when core is halted (Available
in STM32F303xB/C and STM32F358xC devices only)
0: Same behavior as in normal mode
1: The SMBUS timeout is frozen

1110/1141

DocID022558 Rev 8

RM0316

Debug support (DBG)

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: Debug RTC stopped when core is halted
0: The clock of the RTC counter is fed even if the core is halted
1: The clock of the RTC counter is stopped when the core is halted
Bits 9:6 Reserved, must be kept at reset value.
Bit 5 DBG_TIM7_STOP: TIM7 counter stopped when core is halted
0: The counter clock of TIM7 is fed even if the core is halted
1: The counter clock of TIM7 is stopped when the core is halted
Bit 4 DBG_TIM6_STOP: TIM6 counter stopped when core is halted
0: The counter clock of TIM6 is fed even if the core is halted
1: The counter clock of TIM6 is stopped when the core is halted
Bit 3 Reserved, must be kept at reset value.
Bit 2 DBG_TIM4_STOP: TIM4 counter stopped when core is halted (Available on STM32F303xB/C
and STM32F358xC devices only)
0: The counter clock of TIM4 is fed even if the core is halted
1: The counter clock of TIM4 is stopped when the core is halted
Bit 1 DBG_TIM3_STOP: TIM3 counter stopped when core is halted
0: The counter clock of TIM3 is fed even if the core is halted
1: The counter clock of TIM3 is stopped when the core is halted
Bit 0 DBG_TIM2_STOP: TIM2 counter stopped when core is halted
0: The counter clock of TIM2 is fed even if the core is halted
1: The counter clock of TIM2 is stopped when the core is halted

DocID022558 Rev 8

1111/1141
1120

Debug support (DBG)

33.16.5

RM0316

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:
•

Timer clock counter freeze

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.

31

30

29

28

27

26

25

24

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

DBG_TIM20_STOP(1)

DBG_TIM17_STOP

DBG_TIM16_STOP

DBG_TIM15_STOP

DBG_TIM8_STOP(2)

DBG_TIM1_STOP

POR: 0x0000 0000 (not reset by system reset)

rw

rw

rw

rw

rw

1. Available only in STM32F303xD/E and STM32F398xE.
2. Only in STM32F303xB/C/D/E, STM32F358xC and STM32F398xE devices.

Bits 31:6 Reserved, must be kept at reset value.
Bits 5:0 DBG_TIMx_STOP: TIMx counter stopped when core is halted (x=1, 8,15..17)
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
Note: Bit1 and Bit 5 are reserved in STM32F303x6/8 and STM32F328x8.

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).

1112/1141

DocID022558 Rev 8

RM0316

Debug support (DBG)
Figure 406. TPIU block diagram
42!#%#,+). DOMAIN

#,+ DOMAIN
40)5

42!#%#,+).

!SYNCHRONOUS
&)&/

%4-

42!#%#+
40)5
FORMATTER

4RACE OUT
SERIALIZER

42!#%$!4!
;=

!SYNCHRONOUS
&)&/

)4-

42!#%37/

%XTERNAL 00" BUS

AI

33.17.2

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 198. Asynchronous TRACE pin assignment
Trace synchronous mode
TPUI pin name
Type

TRACESWO

•

O

Description
TRACE Async Data Output

STM32F3xx pin
assignment
PB3

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 199. Synchronous TRACE pin assignment
Trace synchronous mode
TPUI pin name
Type

Description

STM32F3xx pin
assignment

TRACECK

O

TRACE Clock

PE2

TRACED[3:0]

O

TRACE Sync Data Outputs
Can be 1, 2 or 4.

PE[6:3]

DocID022558 Rev 8

1113/1141
1120

Debug support (DBG)

RM0316

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 MCU Debug component configuration
register. This configuration has to be done by the debugger host.
In addition, the number of pins to assign depends on the trace configuration (asynchronous
or synchronous).
•

Asynchronous mode: 1 extra pin is needed

•

Synchronous mode (Available in STM32F3xx only): 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.
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 200. Flexible TRACE pin assignment
DBGMCU_CR
register

TRACE IO pin assigned

Pins
TRACE assigned for:
TRACE
PB3 / JTDO/
PE2 /
PE3 /
PE4 /
PE5 /
PE6 /
_MODE
_IOEN
TRACESWO TRACECK TRACED[0] TRACED[1] TRACED[2] TRACED[3]
[1:0]
0

XX

No Trace
(default state)

1

00

Asynchronous
TRACESWO
Trace

1

01

Synchronous
Trace 1 bit

1

10

Synchronous
Trace 2 bit

1

11

Synchronous
Trace 4 bit

Released (1)

-

TRACECK TRACED[0]
Released (1)

Released
(usable as GPIO)

-

TRACECK TRACED[0] TRACED[1]

-

-

-

-

TRACECK TRACED[0] TRACED[1] TRACED[2] TRACED[3]

1. When Serial Wire mode is used, it is released. But when JTAG is used, it is assigned to JTDO.

Note:

1114/1141

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.

DocID022558 Rev 8

RM0316

Debug support (DBG)
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:

33.17.3

•

0x1 for 1 pin (default state)

•

0x2 for 2 pins

•

0x8 for 4 pins

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.

DocID022558 Rev 8

1115/1141
1120

Debug support (DBG)

33.17.5

RM0316

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:

33.17.6

•

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
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.

•

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 STM32F3xx 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%.

1116/1141

DocID022558 Rev 8

RM0316

33.17.8

Debug support (DBG)

TRACECLKIN connection inside the STM32F3xx
In the STM32F3xx, 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 STM32F3xx 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.

DocID022558 Rev 8

1117/1141
1120

Debug support (DBG)

33.17.9

RM0316

TPIU registers
The TPIU APB registers can be read and written only if the bit TRCENA of the Debug
Exception and Monitor Control Register (DEMCR) is set. Otherwise, the registers are read
as zero (the output of this bit enables the PCLK of the TPIU).
Table 201. Important TPIU registers
Address

Register

0xE0040004 Current port size

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)

Selected pin
protocol

Allows the Trace Port Protocol to be selected:
Bit1:0=
00: Sync Trace Port Mode
01: Serial Wire Output - manchester (default value)
10: Serial Wire Output - NRZ
11: reserved

0xE0040304

Formatter and
flush control

Bit 31-9 = always ‘0
Bit 8 = TrigIn = always ‘1 to indicate that triggers are indicated
Bit 7-4 = always 0
Bit 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®F, always read as 0x00000008

0xE00400F0

1118/1141

Description

DocID022558 Rev 8

RM0316

Debug support (DBG)

33.17.10 Example of configuration
•

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

DocID022558 Rev 8

1119/1141
1120

0xE004 200C

1120/1141
DBGMCU_
APB2_FZ

DocID022558 Rev 8
0
0
0

Reset value

Reset value

1. The reset value is product dependent. For more information, refer to Section 33.6.1: MCU device ID code.
DBG_TIM3_STOP
DBG_TIM2_STOP

0
0
0

DBG_TIM8_STOP
DBG_TIM1_STOP

0

DBG_TIM4_STOP

0

DBG_TIM15_STOP

0

Res
Res

Res
Res
Res

Res

X
X

DBG_STOP

X

Res

TRACE_IOEN

TRACE_MODE[1:0]

Res

Res

Res

Res

Res

X

DBG_SLEEP

0

Res

Res

X

DBG_TIM16_STOP

Res

X
DBG_STANDBY

0

DBG_TIM6_STOP

0

DBG_TIM7_STOP

Res

Res

Res

X

Res

Res

X

DBG_TIM17_STOP

Res

X

DBG_TIM20_STOP

Res

X

Res

Res

X

Res

Res

Res

X

Res

Res

Res

DBG_RTC_STOP

DBGMCU_CR

Res

X

Res

X

DBG_WWDG_STOP

X

Res

X

DBG_IWDG_STOP

X

Res

X X X X

Res

X

Res

X

Res

X

Res

X

Res

Res

Res

Res

Res

X

Res

X

Res

Res

Res

Res

Res

REV_ID

Res

Res

Res

Res

Res

Res

0

Res

DBG_I2C1_SMBUS_TIMEOUT

0

Res

Res
DBG_I2C2_SMBUS_TIMEOUT

0

Res

Res

Res

DBG_CAN_STOP

Res

Res

X

Res

DBGMCU_
IDCODE

Res

0

Res

Res

Res

Res

Res

Reset value(1)

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

.

Res

Reset value

Res

DBGMCU_
APB1_FZ
Res

Register

DBG_I2C3_SMBUS_TIMEOUT

0xE0042000

Addr.

Res

0xE0042004

33.18

Res

0xE004 2008

Debug support (DBG)
RM0316

DBG register map

The following table summarizes the Debug registers
Table 202. DBG register map and reset values

DEV_ID

0
0
0

0
0
0
0

RM0316

Device electronic signature

34

Device electronic signature
The device electronic signature is stored in the System memory area of the Flash memory
module, and can be read using the debug interface or by the CPU. It contains factoryprogrammed identification and calibration data that allow the user firmware or other external
devices to automatically match to the characteristics of the STM32F3xx microcontroller.

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 part of the 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 cannot be altered by the user.
Base address: 0x1FFF F7AC
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

UID[31:16]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

UID[15:0]
r

r

r

r

r

r

r

r

r

Bits 31:0 UID[31:0]: X and Y coordinates on the wafer expressed in BCD format

DocID022558 Rev 8

1121/1141
1122

Device electronic signature

RM0316

Address offset: 0x04
Read only = 0xXXXX XXXX where X is factory-programmed
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

UID[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

UID[47:32]
r

r

r

r

r

r

r

r

r

Bits 31:8 UID[63:40]: LOT_NUM[23:0]
Lot number (ASCII encoded)
Bits 7:0 UID[39:32]: WAF_NUM[7:0]
Wafer number (8-bit unsigned number)

Address offset: 0x08
Read only = 0xXXXX XXXX where X is factory-programmed
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

UID[95:80]
r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

UID[79:64]
r

r

r

r

r

r

r

r

r

Bits 31:0 UID[95:64]: LOT_NUM[55:24]
Lot number (ASCII encoded)

34.2

Memory size data register

34.2.1

Flash size data register
Base address: 0x1FFF F7CC
Address offset: 0x00
Read only = 0xXXXX where X is factory-programmed

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

FLASH_SIZE
r

r

Bits 15:0 FLASH_SIZE[15:0]: Flash memory size
This bitfield indicates the size of the device Flash memory expressed in Kbytes.
As an example, 0x040 corresponds to 64 Kbytes.

1122/1141

DocID022558 Rev 8

RM0316

35

Revision history

Revision history
Table 203. Document revision history
Date

Revision

16-Dec-2013

1

Initial release.

2

EMBEDDED SRAM and FLASH MEMORY:
Updated Section 1.1: System architecture and Section 2.3.1: Parity
check.
Updated RDPRT description in Section 1.5.7: Option byte register
(FLASH_OBR). Updated WRP3 at address 0x1FFF F80C in Table 8:
Description of the option bytes.
Updated FLASH_SR register in Section 1.6: Flash register map.
Updated Table 8: Description of the option bytes.
PWR:
Updated Figure 1: Power supply overview (STM32F303x devices),
Section 1.1: Power supplies introduction, and Section 1.1.1:
Independent A/D and D/A converter supply and reference voltage.
Changed AN2586 to AN4206 in Section 1.1.2: Battery backup
domain.
Added EWUP3, updated EWUP2 description, and added
VREFINTRDYF bit in Section 1.4.2: Power control/status register
(PWR_CSR).
RCC:
Added USART3EN, UART4EN and UART5EN in Table 1: RCC
register map and reset values.
Changed max. LSI clock frequency to 50 kHz in Section 1.2.5: LSI
clock. Added Section 1.2.12: I2S clock (only in STM32F303xB/C and
STM32F358xC).
Updated Section 1.4.2: Clock configuration register (RCC_CFGR),
SYSCFGRST in Section 1.4.4: APB2 peripheral reset register
(RCC_APB2RSTR), SPI2RST/SPI3RST Section 1.4.5: APB1
peripheral reset register (RCC_APB1RSTR), and ADC34EN/ ADC12
EN in Section 1.4.6: AHB peripheral clock enable register
(RCC_AHBENR).
Replaced APB by APB2 in Section 1.4.4: APB2 peripheral reset
register (RCC_APB2RSTR).
Updated Section 1.4.5: APB1 peripheral reset register
(RCC_APB1RSTR) and Section 1.4.2: Clock configuration register
(RCC_CFGR).
Updated Section 1.4.14: RCC register map.

08-Mar-2013

Changes

DocID022558 Rev 8

1123/1141
1137

Revision history

RM0316
Table 203. Document revision history (continued)
Date

08-Mar-2013

1124/1141

Revision

Changes

GPIOs:
Updated GPIOA_OSPEEDR and GPIOB_OSPEEDR reset value in
Table 23: GPIO register map and reset values
Replaced JTMS/SWDAT by JTMS/SWDIO in Section 9.3.1: Generalpurpose I/O (GPIO).
Added note related to GPIOF_MODER in Section 9.4.1: GPIO port
mode register (GPIOx_MODER) (x = A..F).
Section 9.4.12: GPIO register map: updated GPIOA_MODER reset
value, added GPIOB_MODER, GPIOA_OSPEEDR,
GPIOB_OSPEEDR, GPIOB_PUPDR, update GPIOA_PUPDR reset
value, updated GPIOx_LCKR register.
SYSCFG:
Updated Section 1.1.1: SYSCFG configuration register 1
(SYSCFG_CFGR1), Section 1.1.6: SYSCFG external interrupt
configuration register 4 (SYSCFG_EXTICR4) and Section 1.1.7:
SYSCFG configuration register 2 (SYSCFG_CFGR2).
DMA:
Updated Figure 22: DMA block diagram.
2
(continued) Modified Figure 11.3.7: DMA request mapping.
INTERRUPTS and EVENTS:
Updated Table 1: STM32F302xB/C vector table.
Modified address offsets for EXTI_IMR2, EXTI_EMR2, EXTI_RTSR2,
EXTI_FTSR2: 0x2C, EXTI_SWIER2, and EXTI_PR2.
Updated note related to EXTI_FTSR1 in Section 14.3.4 and
Section 14.3.10.
Updated note in Section 1.3.7: Interrupt mask register (EXTI_IMR2).
Section 1.3.13: EXTI register map
ADC:
Updated Section 1.1: Introduction. Updated Figure 1: ADC block
diagram, Figure 3: ADC1 and ADC2 connectivity, and Figure 4: ADC3
& ADC4 connectivity. Added Section 1.3.5: Slave AHB interface.
Updated caution note and note in Section 1.3.7: Single-ended and
differential input channels. Modified Section 1.3.8: Calibration
(ADCAL, ADCALDIF, ADC_CALFACT).
Changed ADC_CALFACT_S and ADC_CALFACT_D, by
CALFACT_S and CALFACT_D, respectively.

DocID022558 Rev 8

RM0316

Revision history
Table 203. Document revision history (continued)
Date

08-Mar-2013

Revision

Changes

ADC (continued)
Updated step3 of Section : Converting single-ended and differential
analog inputs with a single ADC.
Corrected the table name of Table: ADC3 & ADC4 - External trigger
for regular channels.
Removed table Minimum sampling time to be respected for fast
channels and related examples in Section: Channel-wise
programmable sampling time (SMPR1, SMPR2) and reference made
to the datasheet instead.
Updated Section: Stopping an ongoing conversion (ADSTP,
JADSTP).
Added note to Section: Auto-injection mode.
Removed double buffer mode in Section: Managing conversions
using the DMA.
Updated Figure: Flushing JSQR queue of context by setting
JADSTP=1 (JQM=0). Case when JADSTP occurs outside an ongoing
conversion and added Section: Disabling the queue.
Updated Section: Auto-delayed conversion mode (AUTDLY), Section:
Regular simultaneous mode with independent injected.
DAC:
2
(continued) Changed TIM5 into TIM15, and AIEC line9 into EXTI line9 in Table 50:
External triggers. Changed TIM5 into TIM15 in the description of bits
21:19 of DAC_CR.
COMP:
Changed COMPx_OUT_TIM_SEL to COMPxOUTSEL in
COMPx_CSR registers (x = 1 to 7) (see Section 17).
Replaced COMP1SW1 by COMP1_INP_DAC in Section 15.5.1:
COMP1 control and status register (COMP1_CSR).
Replaced COMP2_WINDOW_MODE by COMP2WINMODE in
Section 15.5.2: COMP2 control and status register (COMP2_CSR).
OPAMP:
Replaced AOPx by OPAMPx in Section 1: Operational amplifier
(OPAMP).
Updated Section 1.3: OPAMP functional description introduction and
added Section 1.3.2: Clock.
OPAMPx_CSR registers (Section 18.4.1 to Section 18.4.4) changed
OUT-CAL, CAL_SEL, and CAL_ON to OUTCAL, CALSEL, CALON in
OPAMPx_CSR registers (x = 1 to 4). Set access right to ‘rw’ for
TSTREF. Renamed OPAMPx_EN bits into OPAMPxEN.
Replaced any occurence of VOPAMPx with VREFOPAMPx

DocID022558 Rev 8

1125/1141
1137

Revision history

RM0316
Table 203. Document revision history (continued)
Date

08-Mar-2013

1126/1141

Revision

Changes

Advanced control timers (TIM1/8):
Corrected Figure 1: Advanced-control timer block diagram.
Updated Section 1.3.15: Using the break function.
Updated Section 1.3.15: Using the break function
General purpose timers (TIM2/3/4)
Updated Section 1.4.3: TIMx slave mode control register
(TIMx_SMCR). Modified UIF bit in Section 1.4.5: TIMx status register
(TIMx_SR). Updated Section 1.4.6: TIMx event generation register
(TIMx_EGR) and Section 1.4.9: TIMx capture/compare enable
register (TIMx_CCER).
General purpose timers (TIM15/16/17)
Updated Figure 2: TIM16 and TIM17 block diagram.
Updated Section 1.4.13: Using the break function
RTC
Changed power-on reset to backup domain reset in the whole section.
Updated Section 24.7.15: RTC tamper and alternate function
configuration register (RTC_TAFCR).
I2C:
Updated Figure 212: Setup and hold timings.
2
(continued) Updated Table 75: Comparison of analog vs. digital filters.
Corrected Figure 228: Transfer sequence flowchart for I2C master
transmitter for N>255 bytes. Removed maximum values of parameter
“Data hold time” and added row “Data valid time” in Table 76: I2CSMBUS specification data setup and hold times.
Added Section 25.5: I2C low-power modes.
Added caution note in Section 25.4.15: Wakeup from Stop mode on
address match.
Moved Section 24.7: I2C debug mode to Section 28.4.17 and
renamed it Debug mode.
Modified definition of ARLO bit in Section 25.7.7: Interrupt and Status
register (I2Cx_ISR).
SPI/I2S:
Remove CRC error in Section 27.6: SPI interrupts.
USART:
Updated Section 3.5.10: LIN (local interconnection network) mode on
page 1087
Removed note on bit 19(RWU) in Section 29.8.8: Interrupt and status
register (USART_ISR) on page 943.
Updated Table 99: USART features to remove DMA for USART5

DocID022558 Rev 8

RM0316

Revision history
Table 203. Document revision history (continued)
Date

08-Mar-2013

Revision

Changes

Replaced in Bit 2 MMRQ Section 25.7.7: Request register
(USART_RQR) “resets the RWU flag” by “sets the RWU flag”
Added ‘In Smartcard, LIN and IrDA modes, only Oversampling by 16
is supported’ in Section 25.5.4: Baud rate generation
Corrected and updated stop bits in Figure 198: Word length
programming
2
TSC:
(continued)
Changed power-on reset value to reset value in Section 28.6.2: TSC
interrupt enable register (TSC_IER).
CAN
Updated Figure 317: Bit timing
DEBUG:
Updated Figure 3: JTAG TAP connections.

DocID022558 Rev 8

1127/1141
1137

Revision history

RM0316
Table 203. Document revision history (continued)
Date

25-Apr-2014

1128/1141

Revision

Changes

3

Modified scope of document from ”STM32F302xx, STM32F303xx,
STM32F313xx” to “STM32F303xB/xC, STM32F303x4/x6/x8,
STM32F328xx and STM32F358xx”.
Reordered sections of the manual.
Added Section 1: Overview of the manual
Removed ‘always read at "0" (w_r0)’ in Section 1: Documentation
conventions
CRC:
Removed first iteration of the CRC v2 fully programmable polynomial
in Section 5.2: CRC main features.
EMBEDDED SRAM and FLASH MEMORY:
Updated Table 2: Flash memory read protection status
Updated SRAM description in Section 3.3: Embedded SRAM
DAC:
Added DAC2 for STM32F303x4/6/8 devices
Replaced "VDDA" by "VREF+" in Section 14.3.5: DAC output voltage
COMP:
Added ‘(BRK)’ and ‘(BRK2)’ to the COMPxOUTSEL bit descriptions in
the Section 15.5: COMP registers
Updated figures in Section 15.3.1: COMP block diagram.
OPAMP
Updated Figure 3: STM32F303x6/8 and STM32F328x8 comparator
and operational amplifier connections.
DMA:
Added Table 24: STM32F303x6/8 and STM32F328x8 DMA1 request
mapping
Added Table 29: STM32F303x6/8 and STM32F328x8 summary of
DMA1 requests for each channel
System configuration controller:
Added STM32F303x4/6/8 dedicated bits in Section 1.1.1: SYSCFG
configuration register 1 (SYSCFG_CFGR1)
Added Section 1.1.8: SYSCFG configuration register 3
(SYSCFG_CFGR3)
ADC:
Updated Section 1.2: ADC main features
Updated Section 1.3.6: ADC voltage regulator (ADVREGEN)
Updated Section 1.3.3: Clocks

DocID022558 Rev 8

RM0316

Revision history
Table 203. Document revision history (continued)
Date

25-Apr-2014

Revision

Changes

Updated Section 1.3.11: Channel selection (SQRx, JSQRx)
Changed ADC1_IN18 to ADC1_IN17 in Section 1.3.31: VBAT supply
monitoring
Replaced DEEPPWD and ADVREGEN bits of ADCx_CR by
ADVREGEN[1:0]
Updated Section 1.6.2: ADC common control register (ADCx_CCR,
x=12 or 34)
Interrupts:
Added Table 1: STM32F302xB/C vector table
Removed ‘or by changing the sensitivity of the edge detector.’ in
Section 1.3.6: Pending register (EXTI_PR1) and Section 1.3.12:
Pending register (EXTI_PR2)and updated bit description of
Section 1.3.5: Software interrupt event register (EXTI_SWIER1) and
Section 1.3.11: Software interrupt event register (EXTI_SWIER2)
Updated the programming manual reference sentence in
Section 1.2.1: Main features
PWR:
Updated bit0 ‘WUF’ description in Section 1.4.1: Power control
register (PWR_CR)
Updated the mode entry note inTable 4: Stop mode
Added Figure 2: Power supply overview (STM32F3x8 devices).
RCC:
Replaced ‘PCLK’ with ‘SYSCLK’ in the I2CxSW bits description of
Section 1.4.13: Clock configuration register 3 (RCC_CFGR3)
3
(2) under Figure 2: STM32F303xB/C and
(continued) Modified note
STM32F358xC clock tree.
Advanced control timers (TIM1/8):
Modified Section 1.3.15: Using the break function.
IRTIM:
Swapped TIM16 and TIM17 in Figure 203: IR internal hardware
connections with TIM16 and TIM17
RTC:
Updated WUT input clock in Figure 207: RTC block diagram in
STM32F03x, STM32F04x and STM32F05x devices
Corrected bit SHPF read and clear parameters in Section 24.7.4: RTC
initialization and status register (RTC_ISR)
I2C:
Updated tHD;DAT in Table 76: I2C-SMBUS specification data setup
and hold times
Replaced 50ns into tAF(min) and 260ns into tAF(max) in section I2C
timings
Added Access paragraph with wait state information on all registers
USART:
Updated Mode 2 and 3 in Section 25.5.6: Auto baud rate detection
Corrected TXFRQ description in Section 25.7.7: Request register
(USART_RQR)
Modified Note: regarding USARTDIV in Section 26.5.4: Baud rate
generation

DocID022558 Rev 8

1129/1141
1137

Revision history

RM0316
Table 203. Document revision history (continued)
Date

18-Aug-2014

1130/1141

Revision

Changes

4

System and memory overview
– Section 3.1: System architecture
System configuration controller (SYSCFG)
– Section 10.1.8: SYSCFG configuration register 3
(SYSCFG_CFGR3)
Analog-to-digital converter (ADC)
– Section 13.3.18: Conversion on external trigger and trigger polarity
(EXTSEL, EXTEN, JEXTSEL, JEXTEN)
– Figure 30: ADC1 and ADC2 connectivity
– Figure 31: ADC3 & ADC4 connectivity
Digital to analog converter (DAC)
– Figure 89: DAC1 block diagram
Operational amplifier
– Figure 104: STM32F303xB/C and STM32F358xC Comparators and
operational amplifiers interconnections (part 1)
– Figure 105: STM32F303xB/C and STM32F358xC comparators and
operational amplifiers interconnections (part 2)
Comparator
– Section 15.5.2: COMP2 control and status register (COMP2_CSR)
Digital-to-analog converter (DAC)
– Figure 89: DAC1 block diagram
Serial peripheral interface / inter-IC sound (SPI/I2S)
– Table 116: STM32F303xB/C and STM32F358xC SPI
implementation
Universal synchronous asynchronous receiver transmitter
(USART)
– Feature list
– Table 107: STM32F3xx USART features
– Section 27.5.2: Transmitter
– Section 27.7.1: Control register 1 (USARTx_CR1)

DocID022558 Rev 8

RM0316

Revision history
Table 203. Document revision history (continued)
Date

23-Jan-2015

Revision

5

Changes
Extended the applicability to STM32F303xD/E.
Added Section 8: Peripheral interconnect matrix.
Updated the following:
Cover page
Flexible memory controller (FMC)
– Added the chapter (applies to STM32F303xD/E only).
System and memory overview
– Section 3.1: System architecture
Embedded Flash memory
– Section 4.1: Flash main features
– Section 4.2.1: Flash memory organization
Reset and clock control (RCC)
– Section 9.2.10: Timers (TIMx) clock
– Section 9.4.2: Clock configuration register (RCC_CFGR)
System configuration controller (SYSCFG)
– Section 12.1.1: SYSCFG configuration register 1
(SYSCFG_CFGR1)
– Section 12.1.2: SYSCFG CCM SRAM protection register
(SYSCFG_RCR)
– Section 12.1.8: SYSCFG configuration register 3
(SYSCFG_CFGR3)
Direct memory access controller (DMA)
– Table 80: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE summary of DMA2 requests for each channel
Interrupts and events
– Table 82: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE vector table
Analog to digital converter (ADC)
– Table: ADC1 (master) & 2 (slave) - External triggers for regular
channels
– Table: ADC1 & ADC2 - External trigger for injected channels
– Table: ADC3 & ADC4 - External trigger for regular channels
– Table: ADC3 & ADC4 - External trigger for injected channels

DocID022558 Rev 8

1131/1141
1137

Revision history

RM0316
Table 203. Document revision history (continued)
Date

23-Jan-2015

1132/1141

Revision

Changes

Comparator (COMP)
– Section 17.2: COMP main features
– Figure 123: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE comparator 7 block diagram
– Table 108: Comparator input/output summary
Section 17.5: COMP registers
Advanced-control timers (TIM1/TIM8/TIM20)
– Introduced the TIM20 for STM32F303xD/E
5
Inter-integrated circuit (I2C) interface)
(continued) – Table 142: STM32F3xx I2C implementation
Universal synchronous asynchronous receiver transmitter
(USART)
– Table 157: STM32F3xx USART features
Serial peripheral interface / inter-IC sound (SPI/I2S)
– Table 167: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE SPI implementation
Universal serail bus full-speed device interface (USB)
– Table: STM32F3xx USB implementation

DocID022558 Rev 8

RM0316

Revision history
Table 203. Document revision history (continued)
Date

25-Aug-2015

Revision

Changes

6

Reset and clock control (RCC)
– Added notes about UARTSW2[1:0] and UARTSW3[1:0] availability
for the STM32F3xx covered by this document in Section 9.4.13:
Clock configuration register 3 (RCC_CFGR3),
– Updated bit 23 (V18PWRRSTF) name and description in
Section 9.4.10: Control/status register (RCC_CSR).
Flexible static memory controller (FSMC)
– Renamed the section as “Static memory controller”
– Updated bit BUSTURN description in Section : SRAM/NOR-Flash
chip-select timing registers 1..4 (FMC_BTR1..4),
– Updated the maximum value for memory setup time and memory
hold in Table 37: Programmable NOR/PSRAM access parameters,
– Updated MEMSET, MEMHOLD and MEMHIZ bit descriptions of
FMC_PMEM register in Section : Common memory space timing
register 2..4 (FMC_PMEM2..4),
– Updated ATTSET, ATTHOLD and ATTHIZ bit descriptions of
FMC_PATT register in Section : Attribute memory space timing
registers 2..4 (FMC_PATT2..4),
– Updated BURSTRUN bit description of FMC_BTR1..4 register in
Section : SRAM/NOR-Flash chip-select timing registers 1..4
(FMC_BTR1..4).
Analog-to-digital converters (ADC)
– Updated the number of ADC1 and ADC2 channels for
STM32F303x6/8 and STM32F328 in Table 84: ADC external
channels mapping.
Advanced-control timers (TIM1/TIM8/TIM20)
– Bit SMS description in Section 20.4.3: TIM1/TIM8/TIM20 slave
mode control register (TIMx_SMCR).
Basic timers (TIM6/TIM7)
– Updated Bit MMS description in Section 22.4.2: TIM6/TIM7 control
register 2 (TIMx_CR2).
General-purpose timers (TIM15/16/17)
– Updated IC1F[3:0] bit description in Section 23.6.6: TIM16&TIM17
capture/compare mode register 1 (TIMx_CCMR1).
Universal synchronous asynchronous receiver transmitter
(USART)
– Updated the DMA support for UART5 in Table 158: STM32F3xx
USART features.
Controller area network (bxCAN)
– Replaced tCAN with tq
Universal serial bus full-speed device interface (USB)
– Added LPM register descriptions.

DocID022558 Rev 8

1133/1141
1137

Revision history

RM0316
Table 203. Document revision history (continued)
Date

11-May-2016

1134/1141

Revision

Changes

7

Updated I2C2 section:
– Updated Figure 294: Setup and hold timings.
– Updated Section 28.4.4: I2C initialization updating and adding
notes in Section : I2C timings.
– Updated Section 28.7.5: Timing register (I2C_TIMINGR)
SCLDEL[3:0] and SDADEL[3:0] bits description.
– Updated Section 28.4.4: I2C initialization, Section 28.4.8: I2C
master mode and Section 28.7.5: Timing register (I2C_TIMINGR)
adding the sentence “The STM32CubeMX tool calculates and
provides the I2C_TIMIGR content in the I2C configuration window”.
Updated Touch sensing controller section:
– Updated Section 19.3.4: Charge transfer acquisition sequence
adding note about the TSC control register configuration forbidden.
– Updated Section 19.6.1: TSC control register (TSC_CR) adding
note for CTPL[3:0] bits and PGPSC[2:0] bits.
Updated USART section:
– Updated Section 29.5.17: Wakeup from Stop mode using USART
adding paragraph “how to determine the maximum USART
baudrate”.
– Updated whole USART document replacing any occurrence of:
nCTS by CTS, nRTS by RTS, SCLK by CK.
– Updated Section 29.8.9: Interrupt flag clear register (USART_ICR)
replacing “w” by “rc_wl”.
– Updated Section 29.8.8: Interrupt and status register (USART_ISR)
RTOF field replacing USARTx_CR2 by USARTx_CR1.
– Updated Section 29.8.3: Control register 3 (USART_CR3) ‘ONEBIT’
bit 11 description adding a note.
– Updated Section 29: Universal synchronous asynchronous receiver
transmitter (USART) changing register name USARTx_regname in
USART_regname.
Updated RTC section:
– Updated WUCKSEL bits in Figure 281: RTC block diagram.
– Added case of RTC clocked by LSE in Section 27.3.9: Resetting the
RTC.
– Updated Figure 281: RTC block diagram adding note.
– Updated Section 27.6.16: RTC tamper and alternate function
configuration register (RTC_TAFCR) adding note on TAMP3 bits,
and TAMP2E and TAMP2TRG in black in the register.

DocID022558 Rev 8

RM0316

Revision history
Table 203. Document revision history (continued)
Date

11-May-2016

Revision

Changes

Updated RCC section:
– Updated Section 9.4.9: RTC domain control register (RCC_BDCR)
LSEDRV[1:0] bits: ‘01’ and ‘10’ combinations swapped.
– Updated Figure 13: STM32F303xB/C and STM32F358xC clock
tree, Figure 14: STM32F303xDxE and STM32F398xE clock tree
and Figure 15: STM32F303x6/8 and STM32F328x8 clock tree
adding LSE input for main clock output generation.
– Updated Section 9.2.9: RTC clock adding “the RTC remains
clocked and functional under system reset” when the RTC clock is
LSE.
– Updated Figure 14: STM32F303xDxE and STM32F398xE clock
tree adding x2 factor going to TIM2/3/4 when PLLCLK is timer clock
source.
– Updated Figure 15: STM32F303x6/8 and STM32F328x8 clock tree
replacing ‘USARTx (x=1,2,3)’ by ‘USART1’.
– Updated Section 9.4.2: Clock configuration register (RCC_CFGR)
renaming USBPRES by USBPRE and adding bit22 USBPRE
description.
Updated TIMER section:
– Updated Section 21.3.13: One-pulse mode modifying “IC2S=01” by
“CC2S=01”.
– Updated Section 23.4.18: Slave mode: Combined reset + trigger
mode (TIM15 only) adding (TIM15 only) on the title.
7
– Updated Section 23.5.7: TIM15 capture/compare mode register 1
(continued)
(TIM15_CCMR1) and Section 23.5.18: TIM15 register map
replacing bit 7 ‘reserved’ by OC1CE.
– Updated Section 23.6.6: TIM16/TIM17 capture/compare mode
register 1 (TIMx_CCMR1) and Section 23.6.17: TIM16/TIM17
register map replacing bit 7 ‘reserved’ by OC1CE.
– Updated Figure 20: Advanced-control timers (TIM1/TIM8/TIM20),
Section 21: General-purpose timers (TIM2/TIM3/TIM4), Section 22:
Basic timers (TIM6/TIM7) and Section 23: General-purpose timers
(TIM15/TIM16/TIM17) PSC[15:0] bits description.
– Updated Section 20.4.5: TIM1/TIM8/TIM20 status register
(TIMx_SR) and Section 20.4.25: TIM1/TIM8/TIM20 register map
CC5IF and CC6IF bit names.
Updated FMC section:
– Updated Section 10.5.4: NOR Flash/PSRAM controller
asynchronous transactions putting ‘de-asserting the NOE signal’.
– Updated Section : FIFO status and interrupt register 2..4
(FMC_SR2..4) bit0 (IRS) and Bit2 (IFS) adding a note.
– Updated Section : SRAM/NOR-Flash chip-select timing registers
1..4 (FMC_BTR1..4) adding new paragraph.
– Updated Section : SRAM/NOR-Flash write timing registers 1..4
(FMC_BWTR1..4) adding new paragraph.
– Updated Figure 38: NAND Flash/PC Card controller waveforms for
common memory access replacing ‘MEMxHIZ’ by ‘MEMxHIZ+1’
and adding note 2.

DocID022558 Rev 8

1135/1141
1137

Revision history

RM0316
Table 203. Document revision history (continued)
Date

11-May-2016

1136/1141

Revision

Changes

– Updated Section 10.6.5: NAND Flash prewait functionality.
– Updated Common memory space timing register 2..4
(FMC_PMEM2..4) MEMHOLD[7:0] description.
– Updated Attribute memory space timing registers 2..4
(FMC_PATT2..4) ATTHOLD[7:0] description.
– Updated Section 10.3: AHB interface.
– Updated Figure 32: Muxed write access waveforms correct NWE
falling edge.
Updated Embedded Flash memory:
– Updated Section 4.5.1: Flash access control register (FLASH_ACR)
bits LATENCY[2:0] replacing SYSCLK by HCLK.
Updated ADC section:
– Updated Section 15.3.3: Clocks note, replacing option a) by option
b) and removing ‘or 10’.
Operational amplifier section (OPAMP):
– Updated Table 110: Connections with dedicated I/O on
7
STM32F303xB/C/D/E, STM32F358xC and STM32F398xE.
(continued) Updated comparator section:
– Updated Figure 122: Comparator 1 and 2 block diagrams
(STM32F303xB/C/D/E, STM32F358xC and STM32F398xE)
adding note 4.
– Updated Section 17.5.2: COMP2 control and status register
(COMP2_CSR), Section 17.5.4: COMP4 control and status register
(COMP4_CSR) and Section 17.5.6: COMP6 control and status
register (COMP6_CSR) modifying note 3 and the bit 9 description.
Updated interrupts and events section:
– Updated Section 14.2.6: External and internal interrupt/event line
mapping line 26/28/29/31/33 and adding note for EXTI lines.
Updated USB section:
– Updated Table 175: STM32F3xx USB implementation removing
‘and STM32F358xC’.
Updated DEBUG section:
– Updated Section 33.6.1: MCU device ID code DBGMCU_IDCODE
description.

DocID022558 Rev 8

RM0316

Revision history
Table 203. Document revision history (continued)
Date

17-Jan-2017

Revision

Changes

8

Updated comparator section:
Updated Table 108: Comparator input/output summary.
Updated root part numbers in:
– Section 17.1: Introduction.
– Section 17.2: COMP main features.
– Section 17.5.1: COMP1 control and status register (COMP1_CSR).
– Section 17.5.2: COMP2 control and status register (COMP2_CSR)
– Section 17.5.3: COMP3 control and status register (COMP3_CSR).
– Section 17.5.4: COMP4 control and status register (COMP4_CSR)
– Section 17.5.5: COMP5 control and status register (COMP5_CSR).
– Section 17.5.6: COMP6 control and status register (COMP6_CSR)
– Section 17.5.7: COMP7 control and status register (COMP7_CSR).
Updated Section 17.5.2: COMP2 control and status register
(COMP2_CSR) note in the bit 7 description replacing ‘PA3’ by ‘PA7’.
Added note ‘depending on the product, when a timer is not available,
the corresponding combination is reserved’ in all the
COMPxOUTSEL[3:0] bit description for x = 1...7 and
COMPx_BLANKING bit description for x = 4...7.
Updated Figure 122: Comparator 1 and 2 block diagrams
(STM32F303xB/C/D/E, STM32F358xC and STM32F398xE).
Updated Figure 123: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE comparator 7 block diagram.
Updated USART section:
– Updated Section 29.8.8: Interrupt and status register (USART_ISR)
RWU bit available independently of the wakeup from stop feature
availability.
– Updated Section 29.8.12: USART register map RWU bit.
Updated RTC section:
– Updated Figure 291: RTC block diagram removing 1 Hz and 512 Hz
text and changing mux connections (ck_spre by ck_apre).
– Updated note in Section 27.3.15: Calibration clock output.
– Updated ADD1H and SUB1H bit descriptions in Section 27.6.3:
RTC control register (RTC_CR).
– Updated Section : RTC backup registers and Section 27.6.19: RTC
backup registers (RTC_BKPxR): RTC_BKPxR registers cannot be
reset when the Flash readout protection is disabled.
Updated CRC section:
– Added Table 15: CRC internal input/output signals in Section 6.3.2:
CRC internal signals.
Updated OPAMP section:
– Updated Figure 127: STM32F303xB/C/D/E, STM32F358xC and
STM32F398xE Comparators and operational amplifiers
interconnections (part 1).
– Updated Figure 128: STM32F303xB/C/D/E and STM32F358xC
comparators and operational amplifiers interconnections (part 2 ).

DocID022558 Rev 8

1137/1141
1137

RM0316

Index

Index
A
ADCx_AWD2CR . . . . . . . . . . . . . . . . . . . . . .402
ADCx_AWD3CR . . . . . . . . . . . . . . . . . . . . . .403
ADCx_CALFACT . . . . . . . . . . . . . . . . . . . . . .404
ADCx_CCR . . . . . . . . . . . . . . . . . . . . . . . . . .407
ADCx_CDR . . . . . . . . . . . . . . . . . . . . . . . . . .410
ADCx_CFGR . . . . . . . . . . . . . . . . . . . . . . . . .384
ADCx_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . .381
ADCx_CSR . . . . . . . . . . . . . . . . . . . . . . . . . .405
ADCx_DIFSEL . . . . . . . . . . . . . . . . . . . . . . . .403
ADCx_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . .398
ADCx_IER . . . . . . . . . . . . . . . . . . . . . . . . . . .379
ADCx_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . .377
ADCx_JDRy . . . . . . . . . . . . . . . . . . . . . . . . . .402
ADCx_JSQR . . . . . . . . . . . . . . . . . . . . . . . . .399
ADCx_OFRy . . . . . . . . . . . . . . . . . . . . . . . . .401
ADCx_SMPR1 . . . . . . . . . . . . . . . . . . . . . . . .388
ADCx_SMPR2 . . . . . . . . . . . . . . . . . . . . . . . .390
ADCx_SQR1 . . . . . . . . . . . . . . . . . . . . . . . . .393
ADCx_SQR2 . . . . . . . . . . . . . . . . . . . . . . . . .394
ADCx_SQR3 . . . . . . . . . . . . . . . . . . . . . . . . .396
ADCx_SQR4 . . . . . . . . . . . . . . . . . . . . . . . . .397
ADCx_TR1 . . . . . . . . . . . . . . . . . . . . . . . . . . .390
ADCx_TR2 . . . . . . . . . . . . . . . . . . . . . . . . . . .391
ADCx_TR3 . . . . . . . . . . . . . . . . . . . . . . . . . . .392

C
CAN_BTR . . . . . . . . . . . . . . . . . . . . . . . . . .1039
CAN_ESR . . . . . . . . . . . . . . . . . . . . . . . . . .1038
CAN_FA1R . . . . . . . . . . . . . . . . . . . . . . . . .1049
CAN_FFA1R . . . . . . . . . . . . . . . . . . . . . . . .1048
CAN_FiRx . . . . . . . . . . . . . . . . . . . . . . . . . .1050
CAN_FM1R . . . . . . . . . . . . . . . . . . . . . . . . .1048
CAN_FMR . . . . . . . . . . . . . . . . . . . . . . . . . .1047
CAN_FS1R . . . . . . . . . . . . . . . . . . . . . . . . .1048
CAN_IER . . . . . . . . . . . . . . . . . . . . . . . . . . .1037
CAN_MCR . . . . . . . . . . . . . . . . . . . . . . . . . .1030
CAN_MSR . . . . . . . . . . . . . . . . . . . . . . . . . .1032
CAN_RDHxR . . . . . . . . . . . . . . . . . . . . . . . .1046
CAN_RDLxR . . . . . . . . . . . . . . . . . . . . . . . .1046
CAN_RDTxR . . . . . . . . . . . . . . . . . . . . . . . .1045
CAN_RF0R . . . . . . . . . . . . . . . . . . . . . . . . .1035
CAN_RF1R . . . . . . . . . . . . . . . . . . . . . . . . .1036
CAN_RIxR . . . . . . . . . . . . . . . . . . . . . . . . . .1044
CAN_TDHxR . . . . . . . . . . . . . . . . . . . . . . . .1043
CAN_TDLxR . . . . . . . . . . . . . . . . . . . . . . . .1043
CAN_TDTxR . . . . . . . . . . . . . . . . . . . . . . . .1042

CAN_TIxR . . . . . . . . . . . . . . . . . . . . . . . . . . 1041
CAN_TSR . . . . . . . . . . . . . . . . . . . . . . . . . . 1033
COMP1_CSR . . . . . . . . . . . . . . . . . . . . . . . . 447
COMP2_CSR . . . . . . . . . . . . . . . . . . . . . . . . 449
COMP3_CSR . . . . . . . . . . . . . . . . . . . . . . . . 451
COMP4_CSR . . . . . . . . . . . . . . . . . . . . . . . . 454
COMP5_CSR . . . . . . . . . . . . . . . . . . . . . . . . 456
COMP6_CSR . . . . . . . . . . . . . . . . . . . . . . . . 459
COMP7_CSR . . . . . . . . . . . . . . . . . . . . . . . . 461
CRC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
CRC_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
CRC_IDR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
CRC_INIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
CRC_POL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

D
DAC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
DAC_DHR12L1 . . . . . . . . . . . . . . . . . . . . . . . 433
DAC_DHR12L2 . . . . . . . . . . . . . . . . . . . . . . . 434
DAC_DHR12LD . . . . . . . . . . . . . . . . . . . . . . 435
DAC_DHR12R1 . . . . . . . . . . . . . . . . . . . . . . 432
DAC_DHR12R2 . . . . . . . . . . . . . . . . . . . . . . 433
DAC_DHR12RD . . . . . . . . . . . . . . . . . . . . . . 435
DAC_DHR8R1 . . . . . . . . . . . . . . . . . . . . . . . 433
DAC_DHR8R2 . . . . . . . . . . . . . . . . . . . . . . . 434
DAC_DHR8RD . . . . . . . . . . . . . . . . . . . . . . . 435
DAC_DOR1 . . . . . . . . . . . . . . . . . . . . . . . . . . 436
DAC_DOR2 . . . . . . . . . . . . . . . . . . . . . . . . . . 436
DAC_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436
DAC_SWTRIGR . . . . . . . . . . . . . . . . . . . . . . 432
DBGMCU_APB1_FZ . . . . . . . . . . . . . . . . . . 1110
DBGMCU_APB2_FZ . . . . . . . . . . . . . . . . . . 1112
DBGMCU_CR . . . . . . . . . . . . . . . . . . . . . . . 1108
DBGMCU_IDCODE . . . . . . . . . . . . . . . . . . 1095
DMA_CCRx . . . . . . . . . . . . . . . . . . . . . . . . . . 278
DMA_CMARx . . . . . . . . . . . . . . . . . . . . . . . . 281
DMA_CNDTRx . . . . . . . . . . . . . . . . . . . . . . . 280
DMA_CPARx . . . . . . . . . . . . . . . . . . . . . . . . . 280
DMA_IFCR . . . . . . . . . . . . . . . . . . . . . . . . . . 277
DMA_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

E
EXTI_EMR . . . . . . . . . . . . . . . . . . . . . . 297,
EXTI_FTSR . . . . . . . . . . . . . . . . . . . . . . 298,
EXTI_IMR . . . . . . . . . . . . . . . . . . . . . . . 297,
EXTI_PR . . . . . . . . . . . . . . . . . . . . . . . . 299,
EXTI_RTSR . . . . . . . . . . . . . . . . . . . . . . 298,

DocID022558 Rev 8

300
301
300
302
301

1138/1141

Index

RM0316

EXTI_SWIER . . . . . . . . . . . . . . . . . . . . .299, 301

OPAMP4_CSR . . . . . . . . . . . . . . . . . . . . . . . 483

F

P

FLASH_ACR . . . . . . . . . . . . . . . . . . . . . . . . . .78
FLASH_CR . . . . . . . . . . . . . . . . . . . . . . . . . . .80
FLASH_KEYR . . . . . . . . . . . . . . . . . . . . . . . . .78
FLASH_OPTKEYR . . . . . . . . . . . . . . . . . . . . .79
FLASH_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
FMPI2C_ISR . . . . . . . . . . . . . . . . . . . . . . . . .878
FSMC_BCR1..4 . . . . . . . . . . . . . . . . . . . . . . .203
FSMC_BTR1..4 . . . . . . . . . . . . . . . . . . . . . . .205
FSMC_BWTR1..4 . . . . . . . . . . . . . . . . . . . . .209

purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 683
PWR_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
PWR_CSR . . . . . . . . . . . . . . . . . . . . . . . . . . 108

G
GPIOx_AFRH . . . . . . . . . . . . . . . . . . . . . . . . .242
GPIOx_AFRL . . . . . . . . . . . . . . . . . . . . . . . . .241
GPIOx_BRR . . . . . . . . . . . . . . . . . . . . . . . . . .242
GPIOx_BSRR . . . . . . . . . . . . . . . . . . . . . . . .240
GPIOx_IDR . . . . . . . . . . . . . . . . . . . . . . . . . .239
GPIOx_LCKR . . . . . . . . . . . . . . . . . . . . . . . . .240
GPIOx_MODER . . . . . . . . . . . . . . . . . . . . . . .237
GPIOx_ODR . . . . . . . . . . . . . . . . . . . . . . . . .239
GPIOx_OSPEEDR . . . . . . . . . . . . . . . . . . . . .238
GPIOx_OTYPER . . . . . . . . . . . . . . . . . . . . . .237
GPIOx_PUPDR . . . . . . . . . . . . . . . . . . . . . . .238

I
I2C_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .868
I2C_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .871
I2C_ICR . . . . . . . . . . . . . . . . . . . . . . . . . . . . .880
I2C_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . . . .878
I2C_OAR1 . . . . . . . . . . . . . . . . . . . . . . . . . . .874
I2C_OAR2 . . . . . . . . . . . . . . . . . . . . . . . . . . .875
I2C_PECR . . . . . . . . . . . . . . . . . . . . . . . . . . .881
I2C_RXDR . . . . . . . . . . . . . . . . . . . . . . . . . . .882
I2C_TIMEOUTR . . . . . . . . . . . . . . . . . . . . . . .877
I2C_TIMINGR . . . . . . . . . . . . . . . . . . . . . . . .876
I2C_TXDR . . . . . . . . . . . . . . . . . . . . . . . . . . .882
I2Cx_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .871
IWDG_KR . . . . . . . . . . . . . . . . . . . . . . . . . . .761
IWDG_PR . . . . . . . . . . . . . . . . . . . . . . . . . . .762
IWDG_RLR . . . . . . . . . . . . . . . . . . . . . . . . . .763
IWDG_SR . . . . . . . . . . . . . . . . . . . . . . . . . . .764
IWDG_WINR . . . . . . . . . . . . . . . . . . . . . . . . .765

O
OPAMP1_CSR . . . . . . . . . . . . . . . . . . . . . . . .476
OPAMP2_CSR . . . . . . . . . . . . . . . . . . . . . . . .478
OPAMP3_CSR . . . . . . . . . . . . . . . . . . . . . . . .480

1139/1141

R
RCC_AHBENR . . . . . . . . . . . . . . . . . . . . . . . 148
RCC_AHBRSTR . . . . . . . . . . . . . . . . . . . . . . 158
RCC_APB1ENR . . . . . . . . . . . . . . . . . . . . . . 152
RCC_APB1RSTR . . . . . . . . . . . . . . . . . . . . . 146
RCC_APB2ENR . . . . . . . . . . . . . . . . . . . . . . 150
RCC_APB2RSTR . . . . . . . . . . . . . . . . . . . . . 144
RCC_BDCR . . . . . . . . . . . . . . . . . . . . . . . . . 155
RCC_CFGR . . . . . . . . . . . . . . . . . . . . . . . . . 138
RCC_CFGR2 . . . . . . . . . . . . . . . . . . . . . . . . 159
RCC_CFGR3 . . . . . . . . . . . . . . . . . . . . . . . . 162
RCC_CIR . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
RCC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
RCC_CSR . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
RTC_ALRMAR . . . . . . . . . . . . . . . . . . . . . . . 801
RTC_ALRMBR . . . . . . . . . . . . . . . . . . . . . . . 802
RTC_ALRMBSSR . . . . . . . . . . . . . . . . . . . . . 813
RTC_BKPxR . . . . . . . . . . . . . . . . . . . . . . . . . 814
RTC_CALR . . . . . . . . . . . . . . . . . . . . . . . . . . 808
RTC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 793
RTC_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791
RTC_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 796
RTC_PRER . . . . . . . . . . . . . . . . . . . . . . . . . . 799
RTC_SHIFTR . . . . . . . . . . . . . . . . . . . . . . . . 804
RTC_SSR . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
RTC_TAFCR . . . . . . . . . . . . . . . . . . . . . . . . . 809
RTC_TR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 790
RTC_TSDR . . . . . . . . . . . . . . . . . . . . . . . . . . 806
RTC_TSSSR . . . . . . . . . . . . . . . . . . . . . . . . . 807
RTC_TSTR . . . . . . . . . . . . . . . . . . . . . . . . . . 805
RTC_WPR . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
RTC_WUTR . . . . . . . . . . . . . . . . . . . . . . . . . 800

S
SPIx_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 998
SPIx_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . . 1000
SPIx_CRCPR . . . . . . . . . . . . . . . . . . . . . . . 1004
SPIx_DR . . . . . . . . . . . . . . . . . . . . . . . . . . . 1004
SPIx_I2SCFGR . . . . . . . . . . . . . . . . . . . . . . 1007
SPIx_I2SPR . . . . . . . . . . . . . . . . . . . . . . . . 1009
SPIx_RXCRCR . . . . . . . . . . . . . . . . . . . . . . 1006
SPIx_SR . . . . . . . . . . . . . . . . . . . . . . . . . . . 1003
SPIx_TXCRCR . . . . . . . . . . . . . . . . . . . . . . 1006

DocID022558 Rev 8

RM0316

Index

SYSCFG_EXTICR1 . . . . . . . . . . . . . . . . . . . .249
SYSCFG_EXTICR2 . . . . . . . . . . . . . . . . . . . .250
SYSCFG_EXTICR3 . . . . . . . . . . . . . . . . . . . .252
SYSCFG_EXTICR4 . . . . . . . . . . . . . . . . . . . .254
SYSCFG_MEMRMP . . . . . . . . . . . 245, 257-258

T
TIM15_ARR . . . . . . . . . . . . . . . . . . . . . . . . . .732
TIM15_BDTR . . . . . . . . . . . . . . . . . . . . . . . . .734
TIM15_CCER . . . . . . . . . . . . . . . . . . . . . . . . .729
TIM15_CCMR1 . . . . . . . . . . . . . . . . . . . . . . .726
TIM15_CCR1 . . . . . . . . . . . . . . . . . . . . . . . . .733
TIM15_CCR2 . . . . . . . . . . . . . . . . . . . . . . . . .734
TIM15_CNT . . . . . . . . . . . . . . . . . . . . . . . . . .732
TIM15_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . .718
TIM15_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . .719
TIM15_DCR . . . . . . . . . . . . . . . . . . . . . . . . . .736
TIM15_DIER . . . . . . . . . . . . . . . . . . . . . . . . .722
TIM15_DMAR . . . . . . . . . . . . . . . . . . . . . . . .736
TIM15_EGR . . . . . . . . . . . . . . . . . . . . . . . . . .725
TIM15_PSC . . . . . . . . . . . . . . . . . . . . . . . . . .732
TIM15_RCR . . . . . . . . . . . . . . . . . . . . . . . . . .733
TIM15_SMCR . . . . . . . . . . . . . . . . . . . . . . . .721
TIM15_SR . . . . . . . . . . . . . . . . . . . . . . . . . . .723
TIM16_OR . . . . . . . . . . . . . . . . . . . . . . . . . . .754
TIMx_ARR . . . . . . . . . . . . . . 586, 664, 681, 749
TIMx_BDTR . . . . . . . . . . . . . . . . . . . . . .589, 751
TIMx_CCER . . . . . . . . . . . . . . . . . 582, 662, 746
TIMx_CCMR1 . . . . . . . . . . . . . . . 576, 656, 744
TIMx_CCMR2 . . . . . . . . . . . . . . . . . . . .580, 660
TIMx_CCMR3 . . . . . . . . . . . . . . . . . . . . . . . .595
TIMx_CCR1 . . . . . . . . . . . . . . . . . 587, 665, 750
TIMx_CCR2 . . . . . . . . . . . . . . . . . . . . . .588, 665
TIMx_CCR3 . . . . . . . . . . . . . . . . . . . . . .588, 666
TIMx_CCR4 . . . . . . . . . . . . . . . . . . . . . .589, 666
TIMx_CCR5 . . . . . . . . . . . . . . . . . . . . . . . . . .596
TIMx_CCR6 . . . . . . . . . . . . . . . . . . . . . . . . . .597
TIMx_CNT . . . . . . . . . . . . . . 586, 663, 680, 748
TIMx_CR1 . . . . . . . . . . . . . . 565, 647, 677, 739
TIMx_CR2 . . . . . . . . . . . . . . 566, 648, 679, 740
TIMx_DCR . . . . . . . . . . . . . . . . . . 592, 667, 753
TIMx_DIER . . . . . . . . . . . . . . 571, 653, 679, 741
TIMx_DMAR . . . . . . . . . . . . . . . . . 593, 667, 753
TIMx_EGR . . . . . . . . . . . . . . 575, 655, 680, 743
TIMx_OR . . . . . . . . . . . . . . . . . . . . . . . . . . . .594
TIMx_PSC . . . . . . . . . . . . . . 586, 664, 681, 749
TIMx_RCR . . . . . . . . . . . . . . . . . . . . . . .587, 750
TIMx_SMCR . . . . . . . . . . . . . . . . . . . . . .569, 650
TIMx_SR . . . . . . . . . . . . . . . 573, 654, 680, 742
TSC_CR . . . . . . . . . . . . . . . . . . . . . . . . . . . . .496
TSC_ICR . . . . . . . . . . . . . . . . . . . . . . . . . . . .499

TSC_IER . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498
TSC_IOASCR . . . . . . . . . . . . . . . . . . . . . . . . 501
TSC_IOCCR . . . . . . . . . . . . . . . . . . . . . . . . . 502
TSC_IOGCSR . . . . . . . . . . . . . . . . . . . . . . . . 502
TSC_IOGxCR . . . . . . . . . . . . . . . . . . . . . . . . 503
TSC_IOHCR . . . . . . . . . . . . . . . . . . . . . . . . . 500
TSC_IOSCR . . . . . . . . . . . . . . . . . . . . . . . . . 501
TSC_ISR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500

U
USART_BRR . . . . . . . . . . . . . . . . . . . . . . . . . 940
USART_CR1 . . . . . . . . . . . . . . . . . . . . . . . . . 929
USART_CR2 . . . . . . . . . . . . . . . . . . . . . . . . . 932
USART_CR3 . . . . . . . . . . . . . . . . . . . . . . . . . 936
USART_GTPR . . . . . . . . . . . . . . . . . . . . . . . 940
USART_ICR . . . . . . . . . . . . . . . . . . . . . . . . . 948
USART_ISR . . . . . . . . . . . . . . . . . . . . . . . . . 943
USART_RDR . . . . . . . . . . . . . . . . . . . . . . . . 949
USART_RQR . . . . . . . . . . . . . . . . . . . . . . . . 942
USART_RTOR . . . . . . . . . . . . . . . . . . . . . . . 941
USART_TDR . . . . . . . . . . . . . . . . . . . . . . . . . 949
USB_ADDRn_RX . . . . . . . . . . . . . . . . . . . . 1083
USB_ADDRn_TX . . . . . . . . . . . . . . . . . . . . 1082
USB_BTABLE . . . . . . . . . . . . . . . . . . . . . . . 1076
USB_CNTR . . . . . . . . . . . . . . . . . . . . . . . . . 1070
USB_COUNTn_RX . . . . . . . . . . . . . . . . . . . 1083
USB_COUNTn_TX . . . . . . . . . . . . . . . . . . . 1082
USB_DADDR . . . . . . . . . . . . . . . . . . . . . . . 1076
USB_EPnR . . . . . . . . . . . . . . . . . . . . . . . . . 1078
USB_FNR . . . . . . . . . . . . . . . . . . . . . . . . . . 1075
USB_ISTR . . . . . . . . . . . . . . . . . . . . . . . . . . 1072
USB_LPMCSR . . . . . . . . . . . . . . . . . . . . . . 1077

W
WWDG_CFR . . . . . . . . . . . . . . . . . . . . . . . . . 771
WWDG_CR . . . . . . . . . . . . . . . . . . . . . . . . . . 770
WWDG_SR . . . . . . . . . . . . . . . . . . . . . . . . . . 771

DocID022558 Rev 8

1140/1141

RM0316

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

DocID022558 Rev 8

1141/1141
1141



---

Source Exif Data:

File Type                       : PDF
File Type Extension             : pdf
MIME Type                       : application/pdf
PDF Version                     : 1.3
Linearized                      : No
Page Layout                     : SinglePage
Page Mode                       : UseNone
Page Count                      : 1141
Creator                         : C2 v4.2.0220 build 670 - c2_rendition_config : Techlit_Active
Producer                        : Acrobat Distiller 9.0.0 (Windows); modified using iText 2.1.7 by 1T3XT
Title                           : STM32F303xB/C/D/E, STM32F303x6/8, STM32F328x8, STM32F358xC, STM32F398xE advanced ARM®-based MCUs
Keywords                        : Technical Literature, 022558, Product Development, Specification, Reference manual, STM32F303CB, STM32F303RB, STM32F303VB, STM32F303CC, STM32F303RC, STM32F303VC, STM32F303CD, STM32F303CE, STM32F303C6, STM32F303C8, STM32F303K6, STM32F303K8, STM32F303R6, STM32F303R8, STM32F303RD, STM32F303VD, STM32F303ZD, STM32F303RE, STM32F303VE, STM32F303ZE, STM32F328C8, STM32F328K8, STM32F328R8, STM32F358CC, STM32F358RC, STM32F358VC, STM32F398RE, STM32F398VE, STM32F398ZE, STM32F398CE
Modify Date                     : 2017:01:19 13:36:59+01:00
Subject                         : -
Author                          : STMICROELECTRONICS
Create Date                     : 2017:01:17 17:03:01Z

EXIF Metadata provided by EXIF.tools