STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx Advanced Arm® Based 32 Bit MCUs Reference Manual STM32L4

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RM0394
Reference manual
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx
advanced Arm®-based 32-bit MCUs
Introduction
This reference manual targets application developers. It provides complete information on
how to use the STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx microcontroller memory and
peripherals.
The STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx is a family of microcontrollers with
different memory sizes, packages and peripherals.
For ordering information, mechanical and electrical device characteristics please refer to the
corresponding datasheets.
For information on the Arm® Cortex®-M4 core, please refer to the Cortex®-M4 Technical
Reference Manual.

Related documents
• Cortex®-M4 Technical Reference Manual, available from: http://infocenter.arm.com
• STM32L412xx, STM32L422xx, STM32L431xx, STM32L432xx, STM32L433xx,
STM32L442xx, STM32L443xx, STM32L451xx, STM32L452xx, STM32L462xx
datasheets
• STM32F3, STM32F4, STM32L4 and STM32L4+ Series Cortex®-M4 (PM0214)

October 2018

RM0394 Rev 4

1/1600
www.st.com

1

Contents

RM0394

Contents
1

2

Documentation conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
1.1

General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

1.2

List of abbreviations for registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

1.3

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

1.4

Availability of peripherals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

1.5

Product specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

System and memory overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
2.1

2.2

3

2/1600

System architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
2.1.1

S0: I-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

2.1.2

S1: D-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

2.1.3

S2: S-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

2.1.4

S3, S4: DMA-bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

2.1.5

BusMatrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Memory organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
2.2.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

2.2.2

Memory map and register boundary addresses . . . . . . . . . . . . . . . . . . 67

2.3

Bit banding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

2.4

Embedded SRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
2.4.1

SRAM2 parity check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

2.4.2

SRAM2 Write protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

2.4.3

SRAM2 Read protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2.4.4

SRAM2 Erase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2.5

Flash memory overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

2.6

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

Embedded Flash memory (FLASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

3.2

FLASH main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

3.3

FLASH functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.3.1

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

3.3.2

Error code correction (ECC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

3.3.3

Read access latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

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3.4

3.5

4

3.3.4

Adaptive real-time memory accelerator (ART Accelerator™) . . . . . . . . 80

3.3.5

Flash program and erase operations . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

3.3.6

Flash main memory erase sequences . . . . . . . . . . . . . . . . . . . . . . . . . . 83

3.3.7

Flash main memory programming sequences . . . . . . . . . . . . . . . . . . . . 84

FLASH option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
3.4.1

Option bytes description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

3.4.2

Option bytes programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

FLASH memory protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.5.1

Read protection (RDP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

3.5.2

Proprietary code readout protection (PCROP) . . . . . . . . . . . . . . . . . . . 97

3.5.3

Write protection (WRP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

3.6

FLASH interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

3.7

FLASH registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3.7.1

Flash access control register (FLASH_ACR) . . . . . . . . . . . . . . . . . . . 100

3.7.2

Flash Power-down key register (FLASH_PDKEYR) . . . . . . . . . . . . . . 101

3.7.3

Flash key register (FLASH_KEYR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

3.7.4

Flash option key register (FLASH_OPTKEYR) . . . . . . . . . . . . . . . . . . 102

3.7.5

Flash status register (FLASH_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

3.7.6

Flash control register (FLASH_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

3.7.7

Flash ECC register (FLASH_ECCR) . . . . . . . . . . . . . . . . . . . . . . . . . . 106

3.7.8

Flash option register (FLASH_OPTR) . . . . . . . . . . . . . . . . . . . . . . . . . 107

3.7.9

Flash PCROP Start address register (FLASH_PCROP1SR) . . . . . . . 109

3.7.10

Flash PCROP End address register (FLASH_PCROP1ER) . . . . . . . . 109

3.7.11

Flash WRP area A address register (FLASH_WRP1AR) . . . . . . . . . . 110

3.7.12

Flash WRP area B address register (FLASH_WRP1BR) . . . . . . . . . . 110

3.7.13

FLASH register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Firewall (FW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
4.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114

4.2

Firewall main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114

4.3

Firewall functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
4.3.1

Firewall AMBA bus snoop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

4.3.2

Functional requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

4.3.3

Firewall segments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

4.3.4

Segment accesses and properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

4.3.5

Firewall initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

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4.3.6

4.4

5

Firewall registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
4.4.1

Code segment start address (FW_CSSA) . . . . . . . . . . . . . . . . . . . . . . 121

4.4.2

Code segment length (FW_CSL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

4.4.3

Non-volatile data segment start address (FW_NVDSSA) . . . . . . . . . . 122

4.4.4

Non-volatile data segment length (FW_NVDSL) . . . . . . . . . . . . . . . . . 122

4.4.5

Volatile data segment start address (FW_VDSSA) . . . . . . . . . . . . . . . 123

4.4.6

Volatile data segment length (FW_VDSL) . . . . . . . . . . . . . . . . . . . . . . 123

4.4.7

Configuration register (FW_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

4.4.8

Firewall register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Power control (PWR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
5.1

5.2

5.3

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Firewall states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Power supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
5.1.1

Independent analog peripherals supply . . . . . . . . . . . . . . . . . . . . . . . . 128

5.1.2

Independent USB transceivers supply . . . . . . . . . . . . . . . . . . . . . . . . . 129

5.1.3

Independent LCD supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

5.1.4

Battery backup domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

5.1.5

Voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

5.1.6

VDD12 domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

5.1.7

Dynamic voltage scaling management . . . . . . . . . . . . . . . . . . . . . . . . 133

Power supply supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
5.2.1

Power-on reset (POR) / power-down reset (PDR) / brown-out reset
(BOR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

5.2.2

Programmable voltage detector (PVD) . . . . . . . . . . . . . . . . . . . . . . . . 135

5.2.3

Peripheral Voltage Monitoring (PVM) . . . . . . . . . . . . . . . . . . . . . . . . . 136

Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
5.3.1

Run mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

5.3.2

Low-power run mode (LP run) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

5.3.3

Low power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

5.3.4

Sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

5.3.5

Low-power sleep mode (LP sleep) . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

5.3.6

Stop 0 mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

5.3.7

Stop 1 mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

5.3.8

Stop 2 mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

5.3.9

Standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

5.3.10

Shutdown mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

5.3.11

Auto-wakeup from low-power mode . . . . . . . . . . . . . . . . . . . . . . . . . . 157

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6

PWR registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
5.4.1

Power control register 1 (PWR_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . 158

5.4.2

Power control register 2 (PWR_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . 159

5.4.3

Power control register 3 (PWR_CR3) . . . . . . . . . . . . . . . . . . . . . . . . . 160

5.4.4

Power control register 4 (PWR_CR4) . . . . . . . . . . . . . . . . . . . . . . . . . 161

5.4.5

Power status register 1 (PWR_SR1) . . . . . . . . . . . . . . . . . . . . . . . . . . 163

5.4.6

Power status register 2 (PWR_SR2) . . . . . . . . . . . . . . . . . . . . . . . . . . 164

5.4.7

Power status clear register (PWR_SCR) . . . . . . . . . . . . . . . . . . . . . . . 165

5.4.8

Power Port A pull-up control register (PWR_PUCRA) . . . . . . . . . . . . . 166

5.4.9

Power Port A pull-down control register (PWR_PDCRA) . . . . . . . . . . 166

5.4.10

Power Port B pull-up control register (PWR_PUCRB) . . . . . . . . . . . . . 167

5.4.11

Power Port B pull-down control register (PWR_PDCRB) . . . . . . . . . . 167

5.4.12

Power Port C pull-up control register (PWR_PUCRC) . . . . . . . . . . . . 168

5.4.13

Power Port C pull-down control register (PWR_PDCRC) . . . . . . . . . . 168

5.4.14

Power Port D pull-up control register (PWR_PUCRD) . . . . . . . . . . . . 169

5.4.15

Power Port D pull-down control register (PWR_PDCRD) . . . . . . . . . . 169

5.4.16

Power Port E pull-up control register (PWR_PUCRE) . . . . . . . . . . . . . 170

5.4.17

Power Port E pull-down control register (PWR_PDCRE) . . . . . . . . . . 170

5.4.18

Power Port H pull-up control register (PWR_PUCRH) . . . . . . . . . . . . 171

5.4.19

Power Port H pull-down control register (PWR_PDCRH) . . . . . . . . . . 171

5.4.20

PWR register map and reset value table . . . . . . . . . . . . . . . . . . . . . . . 173

Reset and clock control (RCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
6.1

6.2

Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
6.1.1

Power reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

6.1.2

System reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

6.1.3

Backup domain reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
6.2.1

HSE clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

6.2.2

HSI16 clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

6.2.3

MSI clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

6.2.4

HSI48 clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

6.2.5

PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

6.2.6

LSE clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

6.2.7

LSI clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

6.2.8

System clock (SYSCLK) selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

6.2.9

Clock source frequency versus voltage scaling . . . . . . . . . . . . . . . . . . 186

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6.2.10

Clock security system (CSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

6.2.11

Clock security system on LSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

6.2.12

ADC clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

6.2.13

RTC clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

6.2.14

Timer clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

6.2.15

Watchdog clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

6.2.16

Clock-out capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

6.2.17

Internal/external clock measurement with TIM15/TIM16 . . . . . . . . . . . 189

6.2.18

Peripheral clock enable register
(RCC_AHBxENR, RCC_APBxENRy) . . . . . . . . . . . . . . . . . . . . . . . . . 191

6.3

Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

6.4

RCC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
6.4.1

Clock control register (RCC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

6.4.2

Internal clock sources calibration register (RCC_ICSCR) . . . . . . . . . . 196

6.4.3

Clock configuration register (RCC_CFGR) . . . . . . . . . . . . . . . . . . . . . 196

6.4.4

PLL configuration register (RCC_PLLCFGR) . . . . . . . . . . . . . . . . . . . 198

6.4.5

PLLSAI1 configuration register (RCC_PLLSAI1CFGR) . . . . . . . . . . . 201

6.4.6

Clock interrupt enable register (RCC_CIER) . . . . . . . . . . . . . . . . . . . . 204

6.4.7

Clock interrupt flag register (RCC_CIFR) . . . . . . . . . . . . . . . . . . . . . . 206

6.4.8

Clock interrupt clear register (RCC_CICR) . . . . . . . . . . . . . . . . . . . . . 207

6.4.9

AHB1 peripheral reset register (RCC_AHB1RSTR) . . . . . . . . . . . . . . 208

6.4.10

AHB2 peripheral reset register (RCC_AHB2RSTR) . . . . . . . . . . . . . . 209

6.4.11

AHB3 peripheral reset register (RCC_AHB3RSTR) . . . . . . . . . . . . . . 211

6.4.12

APB1 peripheral reset register 1 (RCC_APB1RSTR1) . . . . . . . . . . . . 211

6.4.13

APB1 peripheral reset register 2 (RCC_APB1RSTR2) . . . . . . . . . . . . 214

6.4.14

APB2 peripheral reset register (RCC_APB2RSTR) . . . . . . . . . . . . . . 215

6.4.15

AHB1 peripheral clock enable register (RCC_AHB1ENR) . . . . . . . . . 216

6.4.16

AHB2 peripheral clock enable register (RCC_AHB2ENR) . . . . . . . . . 218

6.4.17

AHB3 peripheral clock enable register(RCC_AHB3ENR) . . . . . . . . . . 219

6.4.18

APB1 peripheral clock enable register 1 (RCC_APB1ENR1) . . . . . . . 220

6.4.19

APB1 peripheral clock enable register 2 (RCC_APB1ENR2) . . . . . . . 222

6.4.20

APB2 peripheral clock enable register (RCC_APB2ENR) . . . . . . . . . . 224

6.4.21

AHB1 peripheral clocks enable in Sleep and Stop modes register
(RCC_AHB1SMENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

6.4.22

AHB2 peripheral clocks enable in Sleep and Stop modes register
(RCC_AHB2SMENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

6.4.23

AHB3 peripheral clocks enable in Sleep and Stop modes register
(RCC_AHB3SMENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

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6.4.24

APB1 peripheral clocks enable in Sleep and Stop modes register 1
(RCC_APB1SMENR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

6.4.25

APB1 peripheral clocks enable in Sleep and Stop modes register 2
(RCC_APB1SMENR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

6.4.26

APB2 peripheral clocks enable in Sleep and Stop modes register
(RCC_APB2SMENR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

6.4.27

Peripherals independent clock configuration register (RCC_CCIPR) . 234

6.4.28

Backup domain control register (RCC_BDCR) . . . . . . . . . . . . . . . . . . 237

6.4.29

Control/status register (RCC_CSR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

6.4.30

Clock recovery RC register (RCC_CRRCR) . . . . . . . . . . . . . . . . . . . . 241

6.4.31

Peripherals independent clock configuration register (RCC_CCIPR2) 242

6.4.32

RCC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

Clock recovery system (CRS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
7.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

7.2

CRS main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

7.3

CRS functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
7.3.1

CRS block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

7.3.2

Synchronization input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

7.3.3

Frequency error measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249

7.3.4

Frequency error evaluation and automatic trimming . . . . . . . . . . . . . . 250

7.3.5

CRS initialization and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

7.4

CRS low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

7.5

CRS interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

7.6

CRS registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
7.6.1

CRS control register (CRS_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

7.6.2

CRS configuration register (CRS_CFGR) . . . . . . . . . . . . . . . . . . . . . . 253

7.6.3

CRS interrupt and status register (CRS_ISR) . . . . . . . . . . . . . . . . . . . 254

7.6.4

CRS interrupt flag clear register (CRS_ICR) . . . . . . . . . . . . . . . . . . . . 256

7.6.5

CRS register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

General-purpose I/Os (GPIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
8.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

8.2

GPIO main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

8.3

GPIO functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
8.3.1

General-purpose I/O (GPIO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

8.3.2

I/O pin alternate function multiplexer and mapping . . . . . . . . . . . . . . . 261

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8.3.3

I/O port control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

8.3.4

I/O port data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

8.3.5

I/O data bitwise handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

8.3.6

GPIO locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

8.3.7

I/O alternate function input/output . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

8.3.8

External interrupt/wakeup lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

8.3.9

Input configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

8.3.10

Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

8.3.11

Alternate function configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

8.3.12

Analog configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

8.3.13

Using the HSE or LSE oscillator pins as GPIOs . . . . . . . . . . . . . . . . . 266

8.3.14

Using the GPIO pins in the RTC supply domain . . . . . . . . . . . . . . . . . 266

8.3.15

Using PH3 as GPIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

GPIO registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
8.4.1

GPIO port mode register (GPIOx_MODER) (x =A to E and H) . . . . . . 267

8.4.2

GPIO port output type register (GPIOx_OTYPER) (x = A to E and H) 268

8.4.3

GPIO port output speed register (GPIOx_OSPEEDR)
(x = A to E and H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

8.4.4

GPIO port pull-up/pull-down register (GPIOx_PUPDR)
(x = A to E and H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

8.4.5

GPIO port input data register (GPIOx_IDR) (x = A to E and H) . . . . . . 269

8.4.6

GPIO port output data register (GPIOx_ODR) (x = A to E and H) . . . . 269

8.4.7

GPIO port bit set/reset register (GPIOx_BSRR) (x = A to E and H) . . 270

8.4.8

GPIO port configuration lock register (GPIOx_LCKR)
(x = A to E and H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270

8.4.9

GPIO alternate function low register (GPIOx_AFRL)
(x = A to E and H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

8.4.10

GPIO alternate function high register (GPIOx_AFRH)
(x = A to E and H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

8.4.11

GPIO port bit reset register (GPIOx_BRR) (x = A to E and H) . . . . . . 273

8.4.12

GPIO register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274

System configuration controller (SYSCFG) . . . . . . . . . . . . . . . . . . . . 276
9.1

SYSCFG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

9.2

SYSCFG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
9.2.1

SYSCFG memory remap register (SYSCFG_MEMRMP) . . . . . . . . . . 276

9.2.2

SYSCFG configuration register 1 (SYSCFG_CFGR1) . . . . . . . . . . . . 277

9.2.3

SYSCFG external interrupt configuration register 1
(SYSCFG_EXTICR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
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9.2.4

SYSCFG external interrupt configuration register 2
(SYSCFG_EXTICR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280

9.2.5

SYSCFG external interrupt configuration register 3
(SYSCFG_EXTICR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

9.2.6

SYSCFG external interrupt configuration register 4
(SYSCFG_EXTICR4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283

9.2.7

SYSCFG SRAM2 control and status register (SYSCFG_SCSR) . . . . 284

9.2.8

SYSCFG configuration register 2 (SYSCFG_CFGR2) . . . . . . . . . . . . 285

9.2.9

SYSCFG SRAM2 write protection register (SYSCFG_SWPR) . . . . . . 286

9.2.10

SYSCFG SRAM2 key register (SYSCFG_SKR) . . . . . . . . . . . . . . . . . 286

9.2.11

SYSCFG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

Peripherals interconnect matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
10.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

10.2

Connection summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

10.3

Interconnection details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
10.3.1

From timer (TIM1/TIM2/TIM15/TIM16) to timer (TIM1/TIM2/TIM15/TIM16)
289

10.3.2

From timer (TIM1/TIM2/TIM6/TIM15) and EXTI to ADC (ADC1) . . . . . 290

10.3.3

From ADC (ADC1) to timer (TIM1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

10.3.4

From timer (TIM2/TIM6/TIM7) and EXTI to DAC (DAC1/DAC2) . . . . . 290

10.3.5

From HSE, LSE, LSI, MSI, MCO, RTC to timer (TIM2/TIM15/TIM16) . 291

10.3.6

From RTC, COMP1, COMP2 to low-power timer (LPTIM1/LPTIM2) . . 291

10.3.7

From timer (TIM1/TIM2/TIM15) to comparators
(COMP1/COMP2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

10.3.8

From ADC (ADC1) to ADC (ADC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

10.3.9

From USB to timer (TIM2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

10.3.10 From internal analog source to ADC (ADC1) and OPAMP
(OPAMP1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
10.3.11 From comparators (COMP1/COMP2) to timers
(TIM1/TIM2/TIM15/TIM16) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
10.3.12 From system errors to timers (TIM1/TIM15/TIM16) . . . . . . . . . . . . . . . 294
10.3.13 From timers (TIM16) to IRTIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

11

Direct memory access controller (DMA) . . . . . . . . . . . . . . . . . . . . . . . 295
11.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

11.2

DMA main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

11.3

DMA implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
11.3.1

DMA1 and DMA2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
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11.3.2

11.4

12

13

10/1600

DMA request mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

DMA functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
11.4.1

DMA block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

11.4.2

DMA transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

11.4.3

DMA arbitration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

11.4.4

DMA channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

11.4.5

DMA data width, alignment and endianness . . . . . . . . . . . . . . . . . . . . 306

11.4.6

DMA error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307

11.5

DMA interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

11.6

DMA registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
11.6.1

DMA interrupt status register (DMA_ISR) . . . . . . . . . . . . . . . . . . . . . . 308

11.6.2

DMA interrupt flag clear register (DMA_IFCR) . . . . . . . . . . . . . . . . . . 311

11.6.3

DMA channel x configuration register (DMA_CCRx) . . . . . . . . . . . . . . 312

11.6.4

DMA channel x number of data to transfer register (DMA_CNDTRx) . 315

11.6.5

DMA channel x peripheral address register (DMA_CPARx) . . . . . . . . 315

11.6.6

DMA channel x memory address register (DMA_CMARx) . . . . . . . . . 316

11.6.7

DMA channel selection register (DMA_CSELR) . . . . . . . . . . . . . . . . . 317

11.6.8

DMA register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . 317

Nested vectored interrupt controller (NVIC) . . . . . . . . . . . . . . . . . . . . 320
12.1

NVIC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

12.2

SysTick calibration value register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

12.3

Interrupt and exception vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

Extended interrupts and events controller (EXTI) . . . . . . . . . . . . . . . 325
13.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

13.2

EXTI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

13.3

EXTI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
13.3.1

EXTI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326

13.3.2

Wakeup event management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326

13.3.3

Peripherals asynchronous Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 327

13.3.4

Hardware interrupt selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

13.3.5

Hardware event selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

13.3.6

Software interrupt/event selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

13.4

EXTI interrupt/event line mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

13.5

EXTI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330

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13.5.1

Interrupt mask register 1 (EXTI_IMR1) . . . . . . . . . . . . . . . . . . . . . . . . 330

13.5.2

Event mask register 1 (EXTI_EMR1) . . . . . . . . . . . . . . . . . . . . . . . . . . 330

13.5.3

Rising trigger selection register 1 (EXTI_RTSR1) . . . . . . . . . . . . . . . . 331

13.5.4

Falling trigger selection register 1 (EXTI_FTSR1) . . . . . . . . . . . . . . . . 331

13.5.5

Software interrupt event register 1 (EXTI_SWIER1) . . . . . . . . . . . . . . 332

13.5.6

Pending register 1 (EXTI_PR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333

13.5.7

Interrupt mask register 2 (EXTI_IMR2) . . . . . . . . . . . . . . . . . . . . . . . . 333

13.5.8

Event mask register 2 (EXTI_EMR2) . . . . . . . . . . . . . . . . . . . . . . . . . . 334

13.5.9

Rising trigger selection register 2 (EXTI_RTSR2) . . . . . . . . . . . . . . . . 334

13.5.10 Falling trigger selection register 2 (EXTI_FTSR2) . . . . . . . . . . . . . . . . 335
13.5.11 Software interrupt event register 2 (EXTI_SWIER2) . . . . . . . . . . . . . . 335
13.5.12 Pending register 2 (EXTI_PR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
13.5.13 EXTI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337

14

Cyclic redundancy check calculation unit (CRC) . . . . . . . . . . . . . . . . 338
14.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

14.2

CRC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

14.3

CRC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

14.4

15

14.3.1

CRC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

14.3.2

CRC internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

14.3.3

CRC operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

CRC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
14.4.1

Data register (CRC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

14.4.2

Independent data register (CRC_IDR) . . . . . . . . . . . . . . . . . . . . . . . . 341

14.4.3

Control register (CRC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

14.4.4

Initial CRC value (CRC_INIT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

14.4.5

CRC polynomial (CRC_POL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

14.4.6

CRC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343

Quad-SPI interface (QUADSPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
15.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

15.2

QUADSPI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

15.3

QUADSPI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
15.3.1

QUADSPI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

15.3.2

QUADSPI pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

15.3.3

QUADSPI command sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346

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15.3.4

QUADSPI signal interface protocol modes . . . . . . . . . . . . . . . . . . . . . 348

15.3.5

QUADSPI indirect mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350

15.3.6

QUADSPI status flag polling mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 352

15.3.7

QUADSPI memory-mapped mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 352

15.3.8

QUADSPI Flash memory configuration . . . . . . . . . . . . . . . . . . . . . . . . 353

15.3.9

QUADSPI delayed data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

15.3.10 QUADSPI configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
15.3.11 QUADSPI usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
15.3.12 Sending the instruction only once . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
15.3.13 QUADSPI error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
15.3.14 QUADSPI busy bit and abort functionality . . . . . . . . . . . . . . . . . . . . . . 357
15.3.15 nCS behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357

15.4

QUADSPI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

15.5

QUADSPI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
15.5.1

QUADSPI control register (QUADSPI_CR) . . . . . . . . . . . . . . . . . . . . . 360

15.5.2

QUADSPI device configuration register (QUADSPI_DCR) . . . . . . . . . 363

15.5.3

QUADSPI status register (QUADSPI_SR) . . . . . . . . . . . . . . . . . . . . . 364

15.5.4

QUADSPI flag clear register (QUADSPI_FCR) . . . . . . . . . . . . . . . . . . 365

15.5.5

QUADSPI data length register (QUADSPI_DLR) . . . . . . . . . . . . . . . . 365

15.5.6

QUADSPI communication configuration register (QUADSPI_CCR) . . 366

15.5.7

QUADSPI address register (QUADSPI_AR) . . . . . . . . . . . . . . . . . . . . 368

15.5.8

QUADSPI alternate bytes registers (QUADSPI_ABR) . . . . . . . . . . . . 369

15.5.9

QUADSPI data register (QUADSPI_DR) . . . . . . . . . . . . . . . . . . . . . . . 369

15.5.10 QUADSPI polling status mask register (QUADSPI _PSMKR) . . . . . . . 370
15.5.11 QUADSPI polling status match register (QUADSPI _PSMAR) . . . . . . 370
15.5.12 QUADSPI polling interval register (QUADSPI _PIR) . . . . . . . . . . . . . . 371
15.5.13 QUADSPI low-power timeout register (QUADSPI_LPTR) . . . . . . . . . . 371
15.5.14 QUADSPI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

16

12/1600

Analog-to-digital converters (ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
16.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

16.2

ADC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

16.3

ADC implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

16.4

ADC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376
16.4.1

ADC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376

16.4.2

ADC pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377

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16.4.3

Clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378

16.4.4

ADC1/2 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380

16.4.5

Slave AHB interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382

16.4.6

ADC Deep-power-down mode (DEEPPWD) and ADC voltage regulator
(ADVREGEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382

16.4.7

Single-ended and differential input channels . . . . . . . . . . . . . . . . . . . . 383

16.4.8

Calibration (ADCAL, ADCALDIF, ADC_CALFACT) . . . . . . . . . . . . . . . 383

16.4.9

ADC on-off control (ADEN, ADDIS, ADRDY) . . . . . . . . . . . . . . . . . . . 386

16.4.10 Constraints when writing the ADC control bits . . . . . . . . . . . . . . . . . . . 387
16.4.11 Channel selection (SQRx, JSQRx) . . . . . . . . . . . . . . . . . . . . . . . . . . . 388
16.4.12 Channel-wise programmable sampling time (SMPR1, SMPR2) . . . . . 389
16.4.13 Single conversion mode (CONT=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
16.4.14 Continuous conversion mode (CONT=1) . . . . . . . . . . . . . . . . . . . . . . . 390
16.4.15 Starting conversions (ADSTART, JADSTART) . . . . . . . . . . . . . . . . . . . 391
16.4.16 ADC timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392
16.4.17 Stopping an ongoing conversion (ADSTP, JADSTP) . . . . . . . . . . . . . . 392
16.4.18 Conversion on external trigger and trigger polarity
(EXTSEL, EXTEN,JEXTSEL, JEXTEN) . . . . . . . . . . . . . . . . . . . . . . . 394
16.4.19 Injected channel management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
16.4.20 Discontinuous mode (DISCEN, DISCNUM, JDISCEN) . . . . . . . . . . . . 398
16.4.21 Queue of context for injected conversions . . . . . . . . . . . . . . . . . . . . . . 399
16.4.22 Programmable resolution (RES) - fast conversion mode . . . . . . . . . . 407
16.4.23 End of conversion, end of sampling phase (EOC, JEOC, EOSMP) . . 408
16.4.24 End of conversion sequence (EOS, JEOS) . . . . . . . . . . . . . . . . . . . . . 408
16.4.25 Timing diagrams example (single/continuous modes,
hardware/software triggers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409
16.4.26 Data management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411
16.4.27 Managing conversions using the DFSDM . . . . . . . . . . . . . . . . . . . . . . 416
16.4.28 Dynamic low-power features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417
16.4.29 Analog window watchdog (AWD1EN, JAWD1EN, AWD1SGL,
AWD1CH, AWD2CH, AWD3CH, AWD_HTx, AWD_LTx, AWDx) . . . . 422
16.4.30 Oversampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426
16.4.31 Dual ADC modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432
16.4.32 Temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445
16.4.33 VBAT supply monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447
16.4.34 Monitoring the internal voltage reference . . . . . . . . . . . . . . . . . . . . . . 448

16.5

ADC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450

16.6

ADC registers (for each ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451

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16.6.1

ADC interrupt and status register (ADC_ISR) . . . . . . . . . . . . . . . . . . . 451

16.6.2

ADC interrupt enable register (ADC_IER) . . . . . . . . . . . . . . . . . . . . . . 453

16.6.3

ADC control register (ADC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455

16.6.4

ADC configuration register (ADC_CFGR) . . . . . . . . . . . . . . . . . . . . . . 458

16.6.5

ADC configuration register 2 (ADC_CFGR2) . . . . . . . . . . . . . . . . . . . 462

16.6.6

ADC sample time register 1 (ADC_SMPR1) . . . . . . . . . . . . . . . . . . . . 464

16.6.7

ADC sample time register 2 (ADC_SMPR2) . . . . . . . . . . . . . . . . . . . . 465

16.6.8

ADC watchdog threshold register 1 (ADC_TR1) . . . . . . . . . . . . . . . . . 465

16.6.9

ADC watchdog threshold register 2 (ADC_TR2) . . . . . . . . . . . . . . . . . 466

16.6.10 ADC watchdog threshold register 3 (ADC_TR3) . . . . . . . . . . . . . . . . . 467
16.6.11 ADC regular sequence register 1 (ADC_SQR1) . . . . . . . . . . . . . . . . . 468
16.6.12 ADC regular sequence register 2 (ADC_SQR2) . . . . . . . . . . . . . . . . . 469
16.6.13 ADC regular sequence register 3 (ADC_SQR3) . . . . . . . . . . . . . . . . . 470
16.6.14 ADC regular sequence register 4 (ADC_SQR4) . . . . . . . . . . . . . . . . . 471
16.6.15 ADC regular data register (ADC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . 471
16.6.16 ADC injected sequence register (ADC_JSQR) . . . . . . . . . . . . . . . . . . 472
16.6.17 ADC offset y register (ADC_OFRy) . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
16.6.18 ADC injected channel y data register (ADC_JDRy) . . . . . . . . . . . . . . . 474
16.6.19 ADC Analog Watchdog 2 Configuration Register (ADC_AWD2CR) . . 475
16.6.20 ADC Analog Watchdog 3 Configuration Register (ADC_AWD3CR) . . 475
16.6.21 ADC Differential mode Selection Register (ADC_DIFSEL) . . . . . . . . . 476
16.6.22 ADC Calibration Factors (ADC_CALFACT) . . . . . . . . . . . . . . . . . . . . . 476

16.7

17

14/1600

ADC common registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477
16.7.1

ADC common status register (ADC_CSR) . . . . . . . . . . . . . . . . . . . . . 477

16.7.2

ADC common control register (ADC_CCR) . . . . . . . . . . . . . . . . . . . . 479

16.7.3

Common regular data register for dual mode (ADC_CDR) . . . . . . . . . 482

16.7.4

ADC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482

Digital-to-analog converter (DAC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486
17.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

17.2

DAC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486

17.3

DAC implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487

17.4

DAC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488
17.4.1

DAC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488

17.4.2

DAC channel enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489

17.4.3

DAC data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489

17.4.4

DAC conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491
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17.4.5

DAC output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491

17.4.6

DAC trigger selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 491

17.4.7

DMA requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

17.4.8

Noise generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493

17.4.9

Triangle-wave generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

17.4.10

DAC channel modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494

17.4.11 DAC channel buffer calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498
17.4.12 Dual DAC channel conversion (if available) . . . . . . . . . . . . . . . . . . . . 499

17.5

DAC low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504

17.6

DAC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504

17.7

DAC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505
17.7.1

DAC control register (DAC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505

17.7.2

DAC software trigger register (DAC_SWTRGR) . . . . . . . . . . . . . . . . . 508

17.7.3

DAC channel1 12-bit right-aligned data holding register
(DAC_DHR12R1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508

17.7.4

DAC channel1 12-bit left aligned data holding register
(DAC_DHR12L1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509

17.7.5

DAC channel1 8-bit right aligned data holding register
(DAC_DHR8R1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509

17.7.6

DAC channel2 12-bit right aligned data holding register
(DAC_DHR12R2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510

17.7.7

DAC channel2 12-bit left aligned data holding register
(DAC_DHR12L2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510

17.7.8

DAC channel2 8-bit right-aligned data holding register
(DAC_DHR8R2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510

17.7.9

Dual DAC 12-bit right-aligned data holding register
(DAC_DHR12RD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511

17.7.10 Dual DAC 12-bit left aligned data holding register
(DAC_DHR12LD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511
17.7.11 Dual DAC 8-bit right aligned data holding register
(DAC_DHR8RD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
17.7.12 DAC channel1 data output register (DAC_DOR1) . . . . . . . . . . . . . . . . 512
17.7.13 DAC channel2 data output register (DAC_DOR2) . . . . . . . . . . . . . . . . 513
17.7.14 DAC status register (DAC_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513
17.7.15 DAC calibration control register (DAC_CCR) . . . . . . . . . . . . . . . . . . . 515
17.7.16 DAC mode control register (DAC_MCR) . . . . . . . . . . . . . . . . . . . . . . . 515
17.7.17 DAC channel 1 sample and hold sample time register
(DAC_SHSR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517
17.7.18 DAC channel 2 sample and hold sample time register
(DAC_SHSR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517

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17.7.19 DAC sample and hold time register (DAC_SHHR) . . . . . . . . . . . . . . . 518
17.7.20 DAC sample and hold refresh time register (DAC_SHRR) . . . . . . . . . 518
17.7.21 DAC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520

18

19

20

Voltage reference buffer (VREFBUF) . . . . . . . . . . . . . . . . . . . . . . . . . . 522
18.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522

18.2

VREFBUF functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522

18.3

VREFBUF registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523
18.3.1

VREFBUF control and status register (VREFBUF_CSR) . . . . . . . . . . 523

18.3.2

VREFBUF calibration control register (VREFBUF_CCR) . . . . . . . . . . 524

18.3.3

VREFBUF register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524

Comparator (COMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525
19.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525

19.2

COMP main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525

19.3

COMP functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526
19.3.1

COMP block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526

19.3.2

COMP pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526

19.3.3

COMP reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528

19.3.4

Comparator LOCK mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528

19.3.5

Window comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528

19.3.6

Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529

19.3.7

Comparator output blanking function . . . . . . . . . . . . . . . . . . . . . . . . . . 530

19.3.8

COMP power and speed modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530

19.4

COMP low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531

19.5

COMP interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531

19.6

COMP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 532
19.6.1

Comparator 1 control and status register (COMP1_CSR) . . . . . . . . . . 532

19.6.2

Comparator 2 control and status register (COMP2_CSR) . . . . . . . . . . 534

19.6.3

COMP register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537

Operational amplifiers (OPAMP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538
20.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538

20.2

OPAMP main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538

20.3

OPAMP functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538
20.3.1

16/1600

OPAMP reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538

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20.3.2

Initial configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539

20.3.3

Signal routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539

20.3.4

OPAMP modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539

20.3.5

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543

20.4

OPAMP low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545

20.5

OPAMP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546
20.5.1

OPAMP1 control/status register (OPAMP1_CSR) . . . . . . . . . . . . . . . . 546

20.5.2

OPAMP1 offset trimming register in normal mode (OPAMP1_OTR) . . 547

20.5.3

OPAMP1 offset trimming register in low-power mode
(OPAMP1_LPOTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547

20.5.4

OPAMP register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

Digital filter for sigma delta modulators (DFSDM) . . . . . . . . . . . . . . . 549
21.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549

21.2

DFSDM main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 550

21.3

DFSDM implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551

21.4

DFSDM functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
21.4.1

DFSDM block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552

21.4.2

DFSDM pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553

21.4.3

DFSDM reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554

21.4.4

Serial channel transceivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555

21.4.5

Configuring the input serial interface . . . . . . . . . . . . . . . . . . . . . . . . . . 564

21.4.6

Parallel data inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

21.4.7

Channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

21.4.8

Digital filter configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566

21.4.9

Integrator unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568

21.4.10 Analog watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568
21.4.11 Short-circuit detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571
21.4.12 Extreme detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571
21.4.13 Data unit block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572
21.4.14 Signed data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573
21.4.15 Launching conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573
21.4.16 Continuous and fast continuous modes . . . . . . . . . . . . . . . . . . . . . . . . 574
21.4.17 Request precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574
21.4.18 Power optimization in run mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575

21.5

DFSDM interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575

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21.6

DFSDM DMA transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577

21.7

DFSDM channel y registers (y=0..3) . . . . . . . . . . . . . . . . . . . . . . . . . . . 577

21.8

21.7.1

DFSDM channel y configuration register (DFSDM_CHyCFGR1) . . . . 577

21.7.2

DFSDM channel y configuration register (DFSDM_CHyCFGR2) . . . . 580

21.7.3

DFSDM channel y analog watchdog and short-circuit detector register
(DFSDM_CHyAWSCDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 580

21.7.4

DFSDM channel y watchdog filter data register
(DFSDM_CHyWDATR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581

21.7.5

DFSDM channel y data input register (DFSDM_CHyDATINR) . . . . . . 582

DFSDM filter x module registers (x=0..1) . . . . . . . . . . . . . . . . . . . . . . . . 583
21.8.1

DFSDM filter x control register 1 (DFSDM_FLTxCR1) . . . . . . . . . . . . 583

21.8.2

DFSDM filter x control register 2 (DFSDM_FLTxCR2) . . . . . . . . . . . . 585

21.8.3

DFSDM filter x interrupt and status register (DFSDM_FLTxISR) . . . . . 587

21.8.4

DFSDM filter x interrupt flag clear register (DFSDM_FLTxICR) . . . . . 588

21.8.5

DFSDM filter x injected channel group selection register
(DFSDM_FLTxJCHGR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589

21.8.6

DFSDM filter x control register (DFSDM_FLTxFCR) . . . . . . . . . . . . . . 590

21.8.7

DFSDM filter x data register for injected group
(DFSDM_FLTxJDATAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591

21.8.8

DFSDM filter x data register for the regular channel
(DFSDM_FLTxRDATAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592

21.8.9

DFSDM filter x analog watchdog high threshold register
(DFSDM_FLTxAWHTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592

21.8.10 DFSDM filter x analog watchdog low threshold register
(DFSDM_FLTxAWLTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593
21.8.11 DFSDM filter x analog watchdog status register
(DFSDM_FLTxAWSR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594
21.8.12 DFSDM filter x analog watchdog clear flag register
(DFSDM_FLTxAWCFR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594
21.8.13 DFSDM filter x extremes detector maximum register
(DFSDM_FLTxEXMAX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595
21.8.14 DFSDM filter x extremes detector minimum register
(DFSDM_FLTxEXMIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595
21.8.15 DFSDM filter x conversion timer register (DFSDM_FLTxCNVTIMR) . . 596
21.8.16 DFSDM register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597

22

18/1600

Liquid crystal display controller (LCD) . . . . . . . . . . . . . . . . . . . . . . . . 602
22.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602

22.2

LCD main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603

22.3

LCD functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
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22.3.1

General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604

22.3.2

Frequency generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605

22.3.3

Common driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606

22.3.4

Segment driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609

22.3.5

Voltage generator and contrast control . . . . . . . . . . . . . . . . . . . . . . . . 613

22.3.6

Double buffer memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617

22.3.7

COM and SEG multiplexing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617

22.3.8

Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622

22.4

LCD low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623

22.5

LCD interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623

22.6

LCD registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625
22.6.1

LCD control register (LCD_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625

22.6.2

LCD frame control register (LCD_FCR) . . . . . . . . . . . . . . . . . . . . . . . . 626

22.6.3

LCD status register (LCD_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629

22.6.4

LCD clear register (LCD_CLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 630

22.6.5

LCD display memory (LCD_RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 630

22.6.6

LCD register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632

Touch sensing controller (TSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634
23.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634

23.2

TSC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634

23.3

TSC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635
23.3.1

TSC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635

23.3.2

Surface charge transfer acquisition overview . . . . . . . . . . . . . . . . . . . 635

23.3.3

Reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637

23.3.4

Charge transfer acquisition sequence . . . . . . . . . . . . . . . . . . . . . . . . . 638

23.3.5

Spread spectrum feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639

23.3.6

Max count error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639

23.3.7

Sampling capacitor I/O and channel I/O mode selection . . . . . . . . . . . 640

23.3.8

Acquisition mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641

23.3.9

I/O hysteresis and analog switch control . . . . . . . . . . . . . . . . . . . . . . . 641

23.4

TSC low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642

23.5

TSC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642

23.6

TSC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643
23.6.1

TSC control register (TSC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643

23.6.2

TSC interrupt enable register (TSC_IER) . . . . . . . . . . . . . . . . . . . . . . 645

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23.6.3

TSC interrupt clear register (TSC_ICR) . . . . . . . . . . . . . . . . . . . . . . . . 646

23.6.4

TSC interrupt status register (TSC_ISR) . . . . . . . . . . . . . . . . . . . . . . . 647

23.6.5

TSC I/O hysteresis control register (TSC_IOHCR) . . . . . . . . . . . . . . . 647

23.6.6

TSC I/O analog switch control register (TSC_IOASCR) . . . . . . . . . . . 648

23.6.7

TSC I/O sampling control register (TSC_IOSCR) . . . . . . . . . . . . . . . . 648

23.6.8

TSC I/O channel control register (TSC_IOCCR) . . . . . . . . . . . . . . . . . 649

23.6.9

TSC I/O group control status register (TSC_IOGCSR) . . . . . . . . . . . . 649

23.6.10 TSC I/O group x counter register (TSC_IOGxCR) . . . . . . . . . . . . . . . . 650
23.6.11 TSC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

24

True random number generator (RNG) . . . . . . . . . . . . . . . . . . . . . . . . 653
24.1

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

24.2

RNG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653

24.3

RNG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654

20/1600

RNG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654

24.3.2

RNG internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654

24.3.3

Random number generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655

24.3.4

RNG initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 657

24.3.5

RNG operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 657

24.3.6

RNG clocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 658

24.3.7

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 658

24.4

RNG low-power usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659

24.5

RNG interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659

24.6

RNG processing time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659

24.7

Entropy source validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660

24.8

25

24.3.1

24.7.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660

24.7.2

Validation conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660

RNG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661
24.8.1

RNG control register (RNG_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661

24.8.2

RNG status register (RNG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 662

24.8.3

RNG data register (RNG_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663

24.8.4

RNG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664

AES hardware accelerator (AES) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665
25.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665

25.2

AES main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665

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25.3

AES implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666

25.4

AES functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666
25.4.1

AES block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666

25.4.2

AES internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666

25.4.3

AES cryptographic core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667

25.4.4

AES procedure to perform a cipher operation . . . . . . . . . . . . . . . . . . . 672

25.4.5

AES decryption key preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676

25.4.6

AES ciphertext stealing and data padding . . . . . . . . . . . . . . . . . . . . . . 677

25.4.7

AES task suspend and resume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 678

25.4.8

AES basic chaining modes (ECB, CBC) . . . . . . . . . . . . . . . . . . . . . . . 679

25.4.9

AES counter (CTR) mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684

25.4.10 AES Galois/counter mode (GCM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 686
25.4.11 AES Galois message authentication code (GMAC) . . . . . . . . . . . . . . 691
25.4.12 AES counter with CBC-MAC (CCM) . . . . . . . . . . . . . . . . . . . . . . . . . . 693
25.4.13 .AES data registers and data swapping . . . . . . . . . . . . . . . . . . . . . . . . 698
25.4.14 AES key registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700
25.4.15 AES initialization vector registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700
25.4.16 AES DMA interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 700
25.4.17 AES error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703

25.5

AES interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703

25.6

AES processing latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704

25.7

AES registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705
25.7.1

AES control register (AES_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705

25.7.2

AES status register (AES_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 708

25.7.3

AES data input register (AES_DINR) . . . . . . . . . . . . . . . . . . . . . . . . . 709

25.7.4

AES data output register (AES_DOUTR) . . . . . . . . . . . . . . . . . . . . . . 710

25.7.5

AES key register 0 (AES_KEYR0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 710

25.7.6

AES key register 1 (AES_KEYR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 711

25.7.7

AES key register 2 (AES_KEYR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 711

25.7.8

AES key register 3 (AES_KEYR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 712

25.7.9

AES initialization vector register 0 (AES_IVR0) . . . . . . . . . . . . . . . . . . 712

25.7.10 AES initialization vector register 1 (AES_IVR1) . . . . . . . . . . . . . . . . . . 712
25.7.11 AES initialization vector register 2 (AES_IVR2) . . . . . . . . . . . . . . . . . . 713
25.7.12 AES initialization vector register 3 (AES_IVR3) . . . . . . . . . . . . . . . . . . 713
25.7.13 AES key register 4 (AES_KEYR4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714
25.7.14 AES key register 5 (AES_KEYR5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714

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25.7.15 AES key register 6 (AES_KEYR6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714
25.7.16 AES key register 7 (AES_KEYR7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715
25.7.17 AES suspend registers (AES_SUSPxR) . . . . . . . . . . . . . . . . . . . . . . . 715
25.7.18 AES register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 716

26

Advanced-control timers (TIM1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 718
26.1

TIM1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 718

26.2

TIM1 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 719

26.3

TIM1 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 721
26.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 721

26.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 723

26.3.3

Repetition counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 734

26.3.4

External trigger input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736

26.3.5

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737

26.3.6

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 741

26.3.7

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 744

26.3.8

PWM input mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745

26.3.9

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746

26.3.10 Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 747
26.3.11 PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 748
26.3.12 Asymmetric PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 751
26.3.13 Combined PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 752
26.3.14 Combined 3-phase PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 753
26.3.15 Complementary outputs and dead-time insertion . . . . . . . . . . . . . . . . 754
26.3.16 Using the break function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 756
26.3.17 Bidirectional break inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762
26.3.18 Clearing the OCxREF signal on an external event . . . . . . . . . . . . . . . 763
26.3.19 6-step PWM generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764
26.3.20 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765
26.3.21 Retriggerable one pulse mode (OPM) . . . . . . . . . . . . . . . . . . . . . . . . . 766
26.3.22 Encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767
26.3.23 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 769
26.3.24 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770
26.3.25 Interfacing with Hall sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770
26.3.26 Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773
26.3.27 ADC synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777
26.3.28 DMA burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777

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26.3.29 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 778

26.4

TIM1 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 779
26.4.1

TIM1 control register 1 (TIM1_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . 779

26.4.2

TIM1 control register 2 (TIM1_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . 780

26.4.3

TIM1 slave mode control register (TIM1_SMCR) . . . . . . . . . . . . . . . . 783

26.4.4

TIM1 DMA/interrupt enable register (TIM1_DIER) . . . . . . . . . . . . . . . 785

26.4.5

TIM1 status register (TIM1_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 787

26.4.6

TIM1 event generation register (TIM1_EGR) . . . . . . . . . . . . . . . . . . . 789

26.4.7

TIM1 capture/compare mode register 1 [alternate]
(TIM1_CCMR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 790

26.4.8

TIM1 capture/compare mode register 1 [alternate]
(TIM1_CCMR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791

26.4.9

TIM1 capture/compare mode register 2 [alternate]
(TIM1_CCMR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 794

26.4.10 TIM1 capture/compare mode register 2 [alternate]
(TIM1_CCMR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 795
26.4.11 TIM1 capture/compare enable register
(TIM1_CCER) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 797
26.4.12 TIM1 counter (TIM1_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800
26.4.13 TIM1 prescaler (TIM1_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800
26.4.14 TIM1 auto-reload register (TIM1_ARR) . . . . . . . . . . . . . . . . . . . . . . . . 800
26.4.15 TIM1 repetition counter register (TIM1_RCR) . . . . . . . . . . . . . . . . . . . 801
26.4.16 TIM1 capture/compare register 1 (TIM1_CCR1) . . . . . . . . . . . . . . . . . 801
26.4.17 TIM1 capture/compare register 2 (TIM1_CCR2) . . . . . . . . . . . . . . . . . 802
26.4.18 TIM1 capture/compare register 3 (TIM1_CCR3) . . . . . . . . . . . . . . . . . 802
26.4.19 TIM1 capture/compare register 4 (TIM1_CCR4) . . . . . . . . . . . . . . . . . 803
26.4.20 TIM1 break and dead-time register
(TIM1_BDTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
26.4.21 TIM1 DMA control register (TIM1_DCR) . . . . . . . . . . . . . . . . . . . . . . . 806
26.4.22 TIM1 DMA address for full transfer
(TIM1_DMAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807
26.4.23 TIM1 option register 1 (TIM1_OR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 808
26.4.24 TIM1 capture/compare mode register 3
(TIM1_CCMR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808
26.4.25 TIM1 capture/compare register 5 (TIM1_CCR5) . . . . . . . . . . . . . . . . . 809
26.4.26 TIM1 capture/compare register 6 (TIM1_CCR6) . . . . . . . . . . . . . . . . . 810
26.4.27 TIM1 option register 2 (TIM1_OR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 811
26.4.28 TIM1 option register 3 (TIM1_OR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . 812
26.4.29 TIM1 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 814

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27

RM0394

General-purpose timers (TIM2/TIM3) . . . . . . . . . . . . . . . . . . . . . . . . . . 817
27.1

TIM2/TIM3 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817

27.2

TIM2/TIM3 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 817

27.3

TIM2/TIM3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819
27.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819

27.3.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 821

27.3.3

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831

27.3.4

Capture/Compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835

27.3.5

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837

27.3.6

PWM input mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 838

27.3.7

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 839

27.3.8

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840

27.3.9

PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841

27.3.10 Asymmetric PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 844
27.3.11 Combined PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 845
27.3.12 Clearing the OCxREF signal on an external event . . . . . . . . . . . . . . . 846
27.3.13 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848
27.3.14 Retriggerable one pulse mode (OPM) . . . . . . . . . . . . . . . . . . . . . . . . . 849
27.3.15 Encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850
27.3.16 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 852
27.3.17 Timer input XOR function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 852
27.3.18 Timers and external trigger synchronization . . . . . . . . . . . . . . . . . . . . 853
27.3.19 Timer synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856
27.3.20 DMA burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860
27.3.21 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 861

27.4

TIM2/TIM3 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 862
27.4.1

TIMx control register 1 (TIMx_CR1)(x = 2 to 3) . . . . . . . . . . . . . . . . . . 862

27.4.2

TIMx control register 2 (TIMx_CR2)(x = 2 to 3) . . . . . . . . . . . . . . . . . . 863

27.4.3

TIMx slave mode control register (TIMx_SMCR)(x = 2 to 3) . . . . . . . . 865

27.4.4

TIMx DMA/Interrupt enable register (TIMx_DIER)(x = 2 to 3) . . . . . . . 868

27.4.5

TIMx status register (TIMx_SR)(x = 2 to 3) . . . . . . . . . . . . . . . . . . . . . 869

27.4.6

TIMx event generation register (TIMx_EGR)(x = 2 to 3) . . . . . . . . . . . 870

27.4.7

TIMx capture/compare mode register 1 (TIMx_CCMR1)(x = 2 to 3) . . 871

27.4.8

TIMx capture/compare mode register 2 (TIMx_CCMR2)(x = 2 to 3) . . 875

27.4.9

TIMx capture/compare enable register (TIMx_CCER)(x = 2 to 3) . . . . 877

27.4.10 TIMx counter (TIMx_CNT)(x = 2 to 3) . . . . . . . . . . . . . . . . . . . . . . . . . 878

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27.4.11 TIMx prescaler (TIMx_PSC)(x = 2 to 3) . . . . . . . . . . . . . . . . . . . . . . . . 879
27.4.12 TIMx auto-reload register (TIMx_ARR)(x = 2 to 3) . . . . . . . . . . . . . . . 879
27.4.13 TIMx capture/compare register 1 (TIMx_CCR1)(x = 2 to 3) . . . . . . . . 880
27.4.14 TIMx capture/compare register 2 (TIMx_CCR2)(x = 2 to 3) . . . . . . . . 880
27.4.15 TIMx capture/compare register 3 (TIMx_CCR3)(x = 2 to 3) . . . . . . . . 881
27.4.16 TIMx capture/compare register 4 (TIMx_CCR4)(x = 2 to 3) . . . . . . . . 881
27.4.17 TIMx DMA control register (TIMx_DCR)(x = 2 to 3) . . . . . . . . . . . . . . . 882
27.4.18 TIMx DMA address for full transfer (TIMx_DMAR)(x = 2 to 3) . . . . . . . 882
27.4.19 TIM2 option register 1 (TIM2_OR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 883
27.4.20 TIM2 option register 2 (TIM2_OR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 883
27.4.21 TIMx register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 884

28

General-purpose timers (TIM15/TIM16) . . . . . . . . . . . . . . . . . . . . . . . . 887
28.1

TIM15/TIM16 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 887

28.2

TIM15 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 887

28.3

TIM16 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 888

28.4

Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 890

28.5

TIM15/TIM16 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891
28.5.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891

28.5.2

Counter modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893

28.5.3

Repetition counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 897

28.5.4

Clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 898

28.5.5

Capture/compare channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900

28.5.6

Input capture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902

28.5.7

PWM input mode (only for TIM15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903

28.5.8

Forced output mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904

28.5.9

Output compare mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905

28.5.10 PWM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
28.5.11 Combined PWM mode (TIM15 only) . . . . . . . . . . . . . . . . . . . . . . . . . . 907
28.5.12 Complementary outputs and dead-time insertion . . . . . . . . . . . . . . . . 908
28.5.13 Using the break function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910
28.5.14 One-pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915
28.5.15 Retriggerable one pulse mode (OPM) (TIM15 only) . . . . . . . . . . . . . . 916
28.5.16 UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917
28.5.17 Timer input XOR function (TIM15 only) . . . . . . . . . . . . . . . . . . . . . . . . 918
28.5.18 External trigger synchronization (TIM15 only) . . . . . . . . . . . . . . . . . . . 919
28.5.19 Slave mode – combined reset + trigger mode . . . . . . . . . . . . . . . . . . . 921
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28.5.20 DMA burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 921
28.5.21 Timer synchronization (TIM15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923
28.5.22 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 923

28.6

TIM15 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 924
28.6.1

TIM15 control register 1 (TIM15_CR1) . . . . . . . . . . . . . . . . . . . . . . . . 924

28.6.2

TIM15 control register 2 (TIM15_CR2) . . . . . . . . . . . . . . . . . . . . . . . . 925

28.6.3

TIM15 slave mode control register (TIM15_SMCR) . . . . . . . . . . . . . . 927

28.6.4

TIM15 DMA/interrupt enable register (TIM15_DIER) . . . . . . . . . . . . . 928

28.6.5

TIM15 status register (TIM15_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 929

28.6.6

TIM15 event generation register (TIM15_EGR) . . . . . . . . . . . . . . . . . 931

28.6.7

TIM15 capture/compare mode register 1 (TIM15_CCMR1) . . . . . . . . 932

28.6.8

TIM15 capture/compare enable register (TIM15_CCER) . . . . . . . . . . 936

28.6.9

TIM15 counter (TIM15_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 939

28.6.10 TIM15 prescaler (TIM15_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 939
28.6.11 TIM15 auto-reload register (TIM15_ARR) . . . . . . . . . . . . . . . . . . . . . . 939
28.6.12 TIM15 repetition counter register (TIM15_RCR) . . . . . . . . . . . . . . . . . 940
28.6.13 TIM15 capture/compare register 1 (TIM15_CCR1) . . . . . . . . . . . . . . . 940
28.6.14 TIM15 capture/compare register 2 (TIM15_CCR2) . . . . . . . . . . . . . . . 941
28.6.15 TIM15 break and dead-time register (TIM15_BDTR) . . . . . . . . . . . . . 941
28.6.16 TIM15 DMA control register (TIM15_DCR) . . . . . . . . . . . . . . . . . . . . . 943
28.6.17 TIM15 DMA address for full transfer (TIM15_DMAR) . . . . . . . . . . . . . 944
28.6.18 TIM15 option register 1 (TIM15_OR1) . . . . . . . . . . . . . . . . . . . . . . . . . 944
28.6.19 TIM15 option register 2 (TIM15_OR2) . . . . . . . . . . . . . . . . . . . . . . . . . 945
28.6.20 TIM15 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 946

28.7

TIM16 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 949
28.7.1

TIM16 control register 1 (TIM16_CR1) . . . . . . . . . . . . . . . . . . . . . . . . 949

28.7.2

TIM16 control register 2 (TIM16_CR2) . . . . . . . . . . . . . . . . . . . . . . . . 950

28.7.3

TIM16 DMA/interrupt enable register (TIM16_DIER) . . . . . . . . . . . . . 951

28.7.4

TIM16 status register (TIM16_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 952

28.7.5

TIM16 event generation register (TIM16_EGR) . . . . . . . . . . . . . . . . . 953

28.7.6

TIM16 capture/compare mode register 1 (TIM16_CCMR1) . . . . . . . . 954

28.7.7

TIM16 capture/compare enable register (TIM16_CCER) . . . . . . . . . . 956

28.7.8

TIM16 counter (TIM16_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958

28.7.9

TIM16 prescaler (TIM16_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959

28.7.10 TIM16 auto-reload register (TIM16_ARR) . . . . . . . . . . . . . . . . . . . . . . 959
28.7.11 TIM16 repetition counter register (TIM16_RCR) . . . . . . . . . . . . . . . . . 960
28.7.12 TIM16 capture/compare register 1 (TIM16_CCR1) . . . . . . . . . . . . . . . 960

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28.7.13 TIM16 break and dead-time register (TIM16_BDTR) . . . . . . . . . . . . . 961
28.7.14 TIM16 DMA control register (TIM16_DCR) . . . . . . . . . . . . . . . . . . . . . 963
28.7.15 TIM16 DMA address for full transfer (TIM16_DMAR) . . . . . . . . . . . . . 963
28.7.16 TIM16 option register 1 (TIM16_OR1) . . . . . . . . . . . . . . . . . . . . . . . . . 964
28.7.17 TIM16 option register 2 (TIM16_OR2) . . . . . . . . . . . . . . . . . . . . . . . . . 964
28.7.18 TIM16 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 966

29

Basic timers (TIM6/TIM7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 968
29.1

TIM6/TIM7 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 968

29.2

TIM6/TIM7 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 968

29.3

TIM6/TIM7 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 969

29.4

30

29.3.1

Time-base unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 969

29.3.2

Counting mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 971

29.3.3

UIF bit remapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 974

29.3.4

Clock source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 974

29.3.5

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 975

TIM6/TIM7 registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 975
29.4.1

TIM6/TIM7 control register 1 (TIMx_CR1) . . . . . . . . . . . . . . . . . . . . . . 975

29.4.2

TIM6/TIM7 control register 2 (TIMx_CR2) . . . . . . . . . . . . . . . . . . . . . . 977

29.4.3

TIM6/TIM7 DMA/Interrupt enable register (TIMx_DIER) . . . . . . . . . . . 977

29.4.4

TIM6/TIM7 status register (TIMx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . 978

29.4.5

TIM6/TIM7 event generation register (TIMx_EGR) . . . . . . . . . . . . . . . 978

29.4.6

TIM6/TIM7 counter (TIMx_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 978

29.4.7

TIM6/TIM7 prescaler (TIMx_PSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 979

29.4.8

TIM6/TIM7 auto-reload register (TIMx_ARR) . . . . . . . . . . . . . . . . . . . 979

29.4.9

TIM6/TIM7 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 980

Low-power timer (LPTIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981
30.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981

30.2

LPTIM main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981

30.3

LPTIM implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981

30.4

LPTIM functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 982
30.4.1

LPTIM block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 982

30.4.2

LPTIM trigger mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 983

30.4.3

LPTIM reset and clocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984

30.4.4

Glitch filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984

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30.4.5

Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985

30.4.6

Trigger multiplexer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985

30.4.7

Operating mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 986

30.4.8

Timeout function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 988

30.4.9

Waveform generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989

30.4.10 Register update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990
30.4.11 Counter mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 991
30.4.12 Timer enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 991
30.4.13 Timer counter reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992
30.4.14 Encoder mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992
30.4.15 Repetition Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 994
30.4.16 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 995

30.5

LPTIM low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996

30.6

LPTIM interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996

30.7

LPTIM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 997
30.7.1

LPTIM interrupt and status register (LPTIM_ISR) . . . . . . . . . . . . . . . . 997

30.7.2

LPTIM interrupt clear register (LPTIM_ICR) . . . . . . . . . . . . . . . . . . . . 999

30.7.3

LPTIM interrupt enable register (LPTIM_IER) . . . . . . . . . . . . . . . . . . 1000

30.7.4

LPTIM configuration register (LPTIM_CFGR) . . . . . . . . . . . . . . . . . . 1002

30.7.5

LPTIM control register (LPTIM_CR) . . . . . . . . . . . . . . . . . . . . . . . . . 1004

30.7.6

LPTIM compare register (LPTIM_CMP) . . . . . . . . . . . . . . . . . . . . . . 1006

30.7.7

LPTIM autoreload register (LPTIM_ARR) . . . . . . . . . . . . . . . . . . . . . 1006

30.7.8

LPTIM counter register (LPTIM_CNT) . . . . . . . . . . . . . . . . . . . . . . . . 1007

30.7.9

LPTIM1 option register (LPTIM1_OR) . . . . . . . . . . . . . . . . . . . . . . . . 1007

30.7.10 LPTIM2 option register (LPTIM2_OR) . . . . . . . . . . . . . . . . . . . . . . . . 1008
30.7.11 LPTIM configuration register 2 (LPTIM_CFGR2) . . . . . . . . . . . . . . . 1008
30.7.12 LPTIM repetition register (LPTIM_RCR) . . . . . . . . . . . . . . . . . . . . . . 1009
30.7.13 LPTIM register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010

31

Infrared interface (IRTIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012

32

Independent watchdog (IWDG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013

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32.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013

32.2

IWDG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013

32.3

IWDG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013
32.3.1

IWDG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013

32.3.2

Window option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1014
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32.4

33

Hardware watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015

32.3.4

Low-power freeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015

32.3.5

Behavior in Stop and Standby modes . . . . . . . . . . . . . . . . . . . . . . . . 1015

32.3.6

Register access protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015

32.3.7

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1015

IWDG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016
32.4.1

Key register (IWDG_KR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1016

32.4.2

Prescaler register (IWDG_PR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1017

32.4.3

Reload register (IWDG_RLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1018

32.4.4

Status register (IWDG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1019

32.4.5

Window register (IWDG_WINR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1020

32.4.6

IWDG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1021

System window watchdog (WWDG) . . . . . . . . . . . . . . . . . . . . . . . . . 1022
33.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1022

33.2

WWDG main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1022

33.3

WWDG functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1022

33.4

34

32.3.3

33.3.1

WWDG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023

33.3.2

Enabling the watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023

33.3.3

Controlling the downcounter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023

33.3.4

Advanced watchdog interrupt feature . . . . . . . . . . . . . . . . . . . . . . . . 1023

33.3.5

How to program the watchdog timeout . . . . . . . . . . . . . . . . . . . . . . . 1024

33.3.6

Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1025

WWDG registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1026
33.4.1

Control register (WWDG_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1026

33.4.2

Configuration register (WWDG_CFR) . . . . . . . . . . . . . . . . . . . . . . . . 1026

33.4.3

Status register (WWDG_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1027

33.4.4

WWDG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1028

Real-time clock (RTC) applied to
STM32L41xxx and STM32L42xxx devices only . . . . . . . . . . . . . . . . 1029
34.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1029

34.2

RTC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1029

34.3

RTC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1030
34.3.1

RTC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1030

34.3.2

RTC pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1032

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34.3.3

GPIOs controlled by the RTC and TAMP . . . . . . . . . . . . . . . . . . . . . . 1033

34.3.4

Clock and prescalers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1035

34.3.5

Real-time clock and calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036

34.3.6

Calendar ultra-low power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036

34.3.7

Programmable alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036

34.3.8

Periodic auto-wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1037

34.3.9

RTC initialization and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 1038

34.3.10 Reading the calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1040
34.3.11 Resetting the RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1041
34.3.12 RTC synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1041
34.3.13 RTC reference clock detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1041
34.3.14 RTC smooth digital calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1042
34.3.15 Timestamp function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1044
34.3.16 Calibration clock output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1045
34.3.17 Tamper and alarm output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1046

34.4

RTC low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1046

34.5

RTC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047

34.6

RTC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047
34.6.1

RTC time register (RTC_TR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047

34.6.2

RTC date register (RTC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1049

34.6.3

RTC sub second register (RTC_SSR) . . . . . . . . . . . . . . . . . . . . . . . . 1050

34.6.4

RTC initialization control and status register (RTC_ICSR) . . . . . . . . 1050

34.6.5

RTC prescaler register (RTC_PRER) . . . . . . . . . . . . . . . . . . . . . . . . 1052

34.6.6

RTC wakeup timer register (RTC_WUTR) . . . . . . . . . . . . . . . . . . . . . 1052

34.6.7

RTC control register (RTC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1053

34.6.8

RTC write protection register (RTC_WPR) . . . . . . . . . . . . . . . . . . . . 1056

34.6.9

RTC calibration register (RTC_CALR) . . . . . . . . . . . . . . . . . . . . . . . . 1057

34.6.10 RTC shift control register (RTC_SHIFTR) . . . . . . . . . . . . . . . . . . . . . 1058
34.6.11 RTC timestamp time register (RTC_TSTR) . . . . . . . . . . . . . . . . . . . . 1059
34.6.12 RTC timestamp date register (RTC_TSDR) . . . . . . . . . . . . . . . . . . . 1059
34.6.13 RTC timestamp sub second register (RTC_TSSSR) . . . . . . . . . . . . . 1060
34.6.14 RTC alarm A register (RTC_ALRMAR) . . . . . . . . . . . . . . . . . . . . . . . 1060
34.6.15 RTC alarm A sub second register (RTC_ALRMASSR) . . . . . . . . . . . 1061
34.6.16 RTC alarm B register (RTC_ALRMBR) . . . . . . . . . . . . . . . . . . . . . . . 1062
34.6.17 RTC alarm B sub second register (RTC_ALRMBSSR) . . . . . . . . . . . 1063
34.6.18 RTC status register (RTC_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1064
34.6.19 RTC masked interrupt status register (RTC_MISR) . . . . . . . . . . . . . 1065
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34.6.20 RTC status clear register (RTC_SCR) . . . . . . . . . . . . . . . . . . . . . . . . 1066
34.6.21 RTC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1067

35

36

Tamper and backup registers (TAMP) . . . . . . . . . . . . . . . . . . . . . . . . 1069
35.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1069

35.2

TAMP main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1069

35.3

TAMP functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1070
35.3.1

TAMP block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1070

35.3.2

TAMP pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1070

35.3.3

Tamper detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1071

35.4

TAMP low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1073

35.5

TAMP interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1073

35.6

TAMP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1074
35.6.1

TAMP control register 1 (TAMP_CR1) . . . . . . . . . . . . . . . . . . . . . . . . 1074

35.6.2

TAMP control register 2 (TAMP_CR2) . . . . . . . . . . . . . . . . . . . . . . . . 1075

35.6.3

TAMP filter control register (TAMP_FLTCR) . . . . . . . . . . . . . . . . . . . 1076

35.6.4

TAMP interrupt enable register (TAMP_IER) . . . . . . . . . . . . . . . . . . . 1077

35.6.5

TAMP status register (TAMP_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1078

35.6.6

TAMP masked interrupt status register (TAMP_MISR) . . . . . . . . . . . 1079

35.6.7

TAMP status clear register (TAMP_SCR) . . . . . . . . . . . . . . . . . . . . . 1079

35.6.8

TAMP backup x register (TAMP_BKPxR) . . . . . . . . . . . . . . . . . . . . . 1080

35.6.9

TAMP register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1081

Real-time clock (RTC) applied to
STM32L43x/44x/45x/46x devices only . . . . . . . . . . . . . . . . . . . . . . . . 1082
36.1

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

36.2

RTC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1083

36.3

RTC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1084
36.3.1

RTC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1084

36.3.2

GPIOs controlled by the RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1085

36.3.3

Clock and prescalers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087

36.3.4

Real-time clock and calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088

36.3.5

Programmable alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088

36.3.6

Periodic auto-wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088

36.3.7

RTC initialization and configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 1089

36.3.8

Reading the calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091

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36.3.9

Resetting the RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1092

36.3.10 RTC synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1092
36.3.11 RTC reference clock detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1093
36.3.12 RTC smooth digital calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1094
36.3.13 Time-stamp function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096
36.3.14 Tamper detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1096
36.3.15 Calibration clock output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098
36.3.16 Alarm output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1099

36.4

RTC low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1099

36.5

RTC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1100

36.6

RTC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1101
36.6.1

RTC time register (RTC_TR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1101

36.6.2

RTC date register (RTC_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1102

36.6.3

RTC control register (RTC_CR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1103

36.6.4

RTC initialization and status register (RTC_ISR) . . . . . . . . . . . . . . . . 1106

36.6.5

RTC prescaler register (RTC_PRER) . . . . . . . . . . . . . . . . . . . . . . . . 1109

36.6.6

RTC wakeup timer register (RTC_WUTR) . . . . . . . . . . . . . . . . . . . . . 1110

36.6.7

RTC alarm A register (RTC_ALRMAR) . . . . . . . . . . . . . . . . . . . . . . . 1111

36.6.8

RTC alarm B register (RTC_ALRMBR) . . . . . . . . . . . . . . . . . . . . . . . 1112

36.6.9

RTC write protection register (RTC_WPR) . . . . . . . . . . . . . . . . . . . . 1113

36.6.10 RTC sub second register (RTC_SSR) . . . . . . . . . . . . . . . . . . . . . . . . 1113
36.6.11 RTC shift control register (RTC_SHIFTR) . . . . . . . . . . . . . . . . . . . . . 1114
36.6.12 RTC timestamp time register (RTC_TSTR) . . . . . . . . . . . . . . . . . . . . 1115
36.6.13 RTC timestamp date register (RTC_TSDR) . . . . . . . . . . . . . . . . . . . 1116
36.6.14 RTC time-stamp sub second register (RTC_TSSSR) . . . . . . . . . . . . 1117
36.6.15 RTC calibration register (RTC_CALR) . . . . . . . . . . . . . . . . . . . . . . . . 1118
36.6.16 RTC tamper configuration register (RTC_TAMPCR) . . . . . . . . . . . . . 1119
36.6.17 RTC alarm A sub second register (RTC_ALRMASSR) . . . . . . . . . . . 1122
36.6.18 RTC alarm B sub second register (RTC_ALRMBSSR) . . . . . . . . . . . 1123
36.6.19 RTC option register (RTC_OR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1124
36.6.20 RTC backup registers (RTC_BKPxR) . . . . . . . . . . . . . . . . . . . . . . . . 1124
36.6.21 RTC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1125

37

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Inter-integrated circuit (I2C) interface . . . . . . . . . . . . . . . . . . . . . . . . 1127
37.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1127

37.2

I2C main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1127

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37.3

I2C implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1128

37.4

I2C functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1128
37.4.1

I2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1129

37.4.2

I2C clock requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1130

37.4.3

Mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1130

37.4.4

I2C initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1131

37.4.5

Software reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1135

37.4.6

Data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1136

37.4.7

I2C slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1138

37.4.8

I2C master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1147

37.4.9

I2C_TIMINGR register configuration examples . . . . . . . . . . . . . . . . . 1159

37.4.10 SMBus specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1160
37.4.11 SMBus initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1163
37.4.12 SMBus: I2C_TIMEOUTR register configuration examples . . . . . . . . 1165
37.4.13 SMBus slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1165
37.4.14 Wakeup from Stop mode on address match . . . . . . . . . . . . . . . . . . . 1173
37.4.15 Error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1173
37.4.16 DMA requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1175
37.4.17 Debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1176

37.5

I2C low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1176

37.6

I2C interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1177

37.7

I2C registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1177
37.7.1

I2C control register 1 (I2C_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1177

37.7.2

I2C control register 2 (I2C_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1180

37.7.3

I2C own address 1 register (I2C_OAR1) . . . . . . . . . . . . . . . . . . . . . . 1183

37.7.4

I2C own address 2 register (I2C_OAR2) . . . . . . . . . . . . . . . . . . . . . . 1184

37.7.5

I2C timing register (I2C_TIMINGR) . . . . . . . . . . . . . . . . . . . . . . . . . . 1185

37.7.6

I2C timeout register (I2C_TIMEOUTR) . . . . . . . . . . . . . . . . . . . . . . . 1186

37.7.7

I2C interrupt and status register (I2C_ISR) . . . . . . . . . . . . . . . . . . . . 1187

37.7.8

I2C interrupt clear register (I2C_ICR)( . . . . . . . . . . . . . . . . . . . . . . . . 1189

37.7.9

I2C PEC register (I2C_PECR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1190

37.7.10 I2C receive data register (I2C_RXDR) . . . . . . . . . . . . . . . . . . . . . . . 1191
37.7.11 I2C transmit data register (I2C_TXDR) . . . . . . . . . . . . . . . . . . . . . . . 1191
37.7.12 I2C register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1192

38

Universal synchronous receiver transmitter (USART)
/universal asynchronous receiver transmitter (UART) . . . . . . . . . . 1194
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38.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1194

38.2

USART main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1194

38.3

USART extended features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1195

38.4

USART implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1196

38.5

USART functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1196
38.5.1

USART character description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1199

38.5.2

USART transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1201

38.5.3

USART receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1203

38.5.4

USART baud rate generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1210

38.5.5

Tolerance of the USART receiver to clock deviation . . . . . . . . . . . . . 1212

38.5.6

USART auto baud rate detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1213

38.5.7

Multiprocessor communication using USART . . . . . . . . . . . . . . . . . . 1214

38.5.8

Modbus communication using USART . . . . . . . . . . . . . . . . . . . . . . . 1216

38.5.9

USART parity control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1217

38.5.10 USART LIN (local interconnection network) mode . . . . . . . . . . . . . . 1218
38.5.11 USART synchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1220
38.5.12 USART Single-wire Half-duplex communication . . . . . . . . . . . . . . . . 1223
38.5.13 USART Smartcard mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1223
38.5.14 USART IrDA SIR ENDEC block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1228
38.5.15 USART continuous communication in DMA mode . . . . . . . . . . . . . . 1230
38.5.16 RS232 hardware flow control and RS485 driver enable
using USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1232
38.5.17 Wakeup from Stop mode using USART . . . . . . . . . . . . . . . . . . . . . . . 1234

38.6

USART low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236

38.7

USART interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236

38.8

USART registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1238
38.8.1

Control register 1 (USART_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1238

38.8.2

Control register 2 (USART_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1241

38.8.3

Control register 3 (USART_CR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1245

38.8.4

Baud rate register (USART_BRR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1249

38.8.5

Guard time and prescaler register (USART_GTPR) . . . . . . . . . . . . . 1249

38.8.6

Receiver timeout register (USART_RTOR) . . . . . . . . . . . . . . . . . . . . 1251

38.8.7

Request register (USART_RQR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1252

38.8.8

Interrupt and status register (USART_ISR) . . . . . . . . . . . . . . . . . . . . 1253

38.8.9

Interrupt flag clear register (USART_ICR) . . . . . . . . . . . . . . . . . . . . . 1257

38.8.10 Receive data register (USART_RDR) . . . . . . . . . . . . . . . . . . . . . . . . 1259

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38.8.11 Transmit data register (USART_TDR) . . . . . . . . . . . . . . . . . . . . . . . . 1259
38.8.12 USART register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260

39

Low-power universal asynchronous receiver
transmitter (LPUART) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1262
39.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1262

39.2

LPUART main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263

39.3

LPUART implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263

39.4

LPUART functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1264
39.4.1

LPUART character description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1266

39.4.2

LPUART transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268

39.4.3

LPUART receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1270

39.4.4

LPUART baud rate generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1273

39.4.5

Tolerance of the LPUART receiver to clock deviation . . . . . . . . . . . . 1275

39.4.6

Multiprocessor communication using LPUART . . . . . . . . . . . . . . . . . 1276

39.4.7

LPUART parity control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1278

39.4.8

Single-wire Half-duplex communication using LPUART . . . . . . . . . . 1279

39.4.9

Continuous communication in DMA mode using LPUART . . . . . . . . 1279

39.4.10 RS232 Hardware flow control and RS485 Driver Enable
using LPUART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1282
39.4.11 Wakeup from Stop mode using LPUART . . . . . . . . . . . . . . . . . . . . . . 1285

39.5

LPUART low-power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286

39.6

LPUART interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1287

39.7

LPUART registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1289
39.7.1

Control register 1 (LPUART_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1289

39.7.2

Control register 2 (LPUART_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1291

39.7.3

Control register 3 (LPUART_CR3) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1294

39.7.4

Baud rate register (LPUART_BRR) . . . . . . . . . . . . . . . . . . . . . . . . . . 1296

39.7.5

Request register (LPUART_RQR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1296

39.7.6

Interrupt & status register (LPUART_ISR) . . . . . . . . . . . . . . . . . . . . . 1297

39.7.7

Interrupt flag clear register (LPUART_ICR) . . . . . . . . . . . . . . . . . . . . 1300

39.7.8

Receive data register (LPUART_RDR) . . . . . . . . . . . . . . . . . . . . . . . 1301

39.7.9

Transmit data register (LPUART_TDR) . . . . . . . . . . . . . . . . . . . . . . . 1301

39.7.10 LPUART register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1303

40

Serial peripheral interface (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1304
40.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1304
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40.2

SPI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1304

40.3

SPI implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1304

40.4

SPI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1305
40.4.1

General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1305

40.4.2

Communications between one master and one slave . . . . . . . . . . . . 1306

40.4.3

Standard multi-slave communication . . . . . . . . . . . . . . . . . . . . . . . . . 1308

40.4.4

Multi-master communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1309

40.4.5

Slave select (NSS) pin management . . . . . . . . . . . . . . . . . . . . . . . . . 1310

40.4.6

Communication formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1311

40.4.7

Configuration of SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1313

40.4.8

Procedure for enabling SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1314

40.4.9

Data transmission and reception procedures . . . . . . . . . . . . . . . . . . 1314

40.4.10 SPI status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1324
40.4.11 SPI error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1325
40.4.12 NSS pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1326
40.4.13 TI mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1326
40.4.14 CRC calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327

41

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40.5

SPI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1329

40.6

SPI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1330
40.6.1

SPI control register 1 (SPIx_CR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1330

40.6.2

SPI control register 2 (SPIx_CR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1332

40.6.3

SPI status register (SPIx_SR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1334

40.6.4

SPI data register (SPIx_DR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1335

40.6.5

SPI CRC polynomial register (SPIx_CRCPR) . . . . . . . . . . . . . . . . . . 1336

40.6.6

SPI Rx CRC register (SPIx_RXCRCR) . . . . . . . . . . . . . . . . . . . . . . . 1336

40.6.7

SPI Tx CRC register (SPIx_TXCRCR) . . . . . . . . . . . . . . . . . . . . . . . 1336

40.6.8

SPI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1338

Serial audio interface (SAI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1339
41.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1339

41.2

SAI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1339

41.3

SAI implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1340

41.4

SAI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1341
41.4.1

SAI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1341

41.4.2

SAI pins and internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1342

41.4.3

Main SAI modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1342

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41.4.4

SAI synchronization mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1343

41.4.5

Audio data size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1344

41.4.6

Frame synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1344

41.4.7

Slot configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1347

41.4.8

SAI clock generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1349

41.4.9

Internal FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1351

41.4.10 AC’97 link controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353
41.4.11 SPDIF output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1354
41.4.12 Specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1357
41.4.13 Error flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1361
41.4.14 Disabling the SAI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1364
41.4.15 SAI DMA interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1364

41.5

SAI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1365

41.6

SAI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1366
41.6.1

Configuration register 1 (SAI_ACR1) . . . . . . . . . . . . . . . . . . . . . . . . . 1366

41.6.2

Configuration register 1 (SAI_BCR1) . . . . . . . . . . . . . . . . . . . . . . . . . 1368

41.6.3

Configuration register 2 (SAI_ACR2) . . . . . . . . . . . . . . . . . . . . . . . . . 1370

41.6.4

Configuration register 2 (SAI_BCR2) . . . . . . . . . . . . . . . . . . . . . . . . . 1372

41.6.5

Frame configuration register (SAI_AFRCR) . . . . . . . . . . . . . . . . . . . 1374

41.6.6

Frame configuration register (SAI_BFRCR) . . . . . . . . . . . . . . . . . . . 1375

41.6.7

Slot register (SAI_ASLOTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1377

41.6.8

Slot register (SAI_BSLOTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1378

41.6.9

Interrupt mask register (SAI_AIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1379

41.6.10 Interrupt mask register (SAI_BIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1380
41.6.11 Status register (SAI_ASR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1381
41.6.12 Status register (SAI_BSR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1383
41.6.13 Clear flag register (SAI_ACLRFR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1385
41.6.14 Clear flag register (SAI_BCLRFR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1386
41.6.15 Data register (SAI_ADR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1387
41.6.16 Data register (SAI_BDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1388
41.6.17 SAI register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1389

42

Single Wire Protocol Master Interface (SWPMI) . . . . . . . . . . . . . . . . 1390
42.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1390

42.2

SWPMI main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1391

42.3

SWPMI functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1392
42.3.1

SWPMI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1392
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42.3.2

SWP initialization and activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1392

42.3.3

SWP bus states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1393

42.3.4

SWPMI_IO (internal transceiver) bypass . . . . . . . . . . . . . . . . . . . . . . 1394

42.3.5

SWPMI Bit rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1394

42.3.6

SWPMI frame handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395

42.3.7

Transmission procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395

42.3.8

Reception procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1400

42.3.9

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1404

42.3.10 Loopback mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1406

42.4

SWPMI low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1406

42.5

SWPMI interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1407

42.6

SWPMI registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1408
42.6.1

SWPMI Configuration/Control register (SWPMI_CR) . . . . . . . . . . . . 1408

42.6.2

SWPMI Bitrate register (SWPMI_BRR) . . . . . . . . . . . . . . . . . . . . . . . 1409

42.6.3

SWPMI Interrupt and Status register (SWPMI_ISR) . . . . . . . . . . . . . 1410

42.6.4

SWPMI Interrupt Flag Clear register (SWPMI_ICR) . . . . . . . . . . . . . 1411

42.6.5

SWPMI Interrupt Enable register (SMPMI_IER) . . . . . . . . . . . . . . . . 1412

42.6.6

SWPMI Receive Frame Length register (SWPMI_RFL) . . . . . . . . . . 1413

42.6.7

SWPMI Transmit data register (SWPMI_TDR) . . . . . . . . . . . . . . . . . 1414

42.6.8

SWPMI Receive data register (SWPMI_RDR) . . . . . . . . . . . . . . . . . 1414

42.6.9

SWPMI Option register (SWPMI_OR) . . . . . . . . . . . . . . . . . . . . . . . . 1414

42.6.10 SWPMI register map and reset value table . . . . . . . . . . . . . . . . . . . . 1416

43

SD/SDIO/MMC card host interface (SDMMC) . . . . . . . . . . . . . . . . . . 1417
43.1

SDMMC main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1417

43.2

SDMMC bus topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1417

43.3

SDMMC functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1419

43.4

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43.3.1

SDMMC adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1421

43.3.2

SDMMC APB2 interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1432

Card functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1433
43.4.1

Card identification mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1433

43.4.2

Card reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1433

43.4.3

Operating voltage range validation . . . . . . . . . . . . . . . . . . . . . . . . . . 1434

43.4.4

Card identification process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1434

43.4.5

Block write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1435

43.4.6

Block read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1436

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43.4.7

Stream access, stream write and stream read
(MultiMediaCard only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1436

43.4.8

Erase: group erase and sector erase . . . . . . . . . . . . . . . . . . . . . . . . 1438

43.4.9

Wide bus selection or deselection . . . . . . . . . . . . . . . . . . . . . . . . . . . 1438

43.4.10 Protection management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1438
43.4.11 Card status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1442
43.4.12 SD status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1445
43.4.13 SD I/O mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1449
43.4.14 Commands and responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1450

43.5

43.6

Response formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453
43.5.1

R1 (normal response command) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454

43.5.2

R1b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454

43.5.3

R2 (CID, CSD register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454

43.5.4

R3 (OCR register) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455

43.5.5

R4 (Fast I/O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455

43.5.6

R4b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455

43.5.7

R5 (interrupt request) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456

43.5.8

R6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456

SDIO I/O card-specific operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1457
43.6.1

SDIO I/O read wait operation by SDMMC_D2 signalling . . . . . . . . . . 1457

43.6.2

SDIO read wait operation by stopping SDMMC_CK . . . . . . . . . . . . . 1458

43.6.3

SDIO suspend/resume operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 1458

43.6.4

SDIO interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1458

43.7

HW flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1458

43.8

SDMMC registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1459
43.8.1

SDMMC power control register (SDMMC_POWER) . . . . . . . . . . . . . 1459

43.8.2

SDMMC clock control register (SDMMC_CLKCR) . . . . . . . . . . . . . . 1459

43.8.3

SDMMC argument register (SDMMC_ARG) . . . . . . . . . . . . . . . . . . . 1461

43.8.4

SDMMC command register (SDMMC_CMD) . . . . . . . . . . . . . . . . . . 1461

43.8.5

SDMMC command response register (SDMMC_RESPCMD) . . . . . . 1462

43.8.6

SDMMC response 1..4 register (SDMMC_RESPx) . . . . . . . . . . . . . . 1462

43.8.7

SDMMC data timer register (SDMMC_DTIMER) . . . . . . . . . . . . . . . . 1463

43.8.8

SDMMC data length register (SDMMC_DLEN) . . . . . . . . . . . . . . . . . 1464

43.8.9

SDMMC data control register (SDMMC_DCTRL) . . . . . . . . . . . . . . . 1464

43.8.10 SDMMC data counter register (SDMMC_DCOUNT) . . . . . . . . . . . . . 1467
43.8.11 SDMMC status register (SDMMC_STA) . . . . . . . . . . . . . . . . . . . . . . 1467
43.8.12 SDMMC interrupt clear register (SDMMC_ICR) . . . . . . . . . . . . . . . . 1468

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43.8.13 SDMMC mask register (SDMMC_MASK) . . . . . . . . . . . . . . . . . . . . . 1470
43.8.14 SDMMC FIFO counter register (SDMMC_FIFOCNT) . . . . . . . . . . . . 1472
43.8.15 SDMMC data FIFO register (SDMMC_FIFO) . . . . . . . . . . . . . . . . . . 1473
43.8.16 SDMMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1474

44

Controller area network (bxCAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1476
44.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1476

44.2

bxCAN main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1476

44.3

bxCAN general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1477

44.4

44.5

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44.3.1

CAN 2.0B active core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1477

44.3.2

Control, status and configuration registers . . . . . . . . . . . . . . . . . . . . 1477

44.3.3

Tx mailboxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1477

44.3.4

Acceptance filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478

bxCAN operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478
44.4.1

Initialization mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478

44.4.2

Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1479

44.4.3

Sleep mode (low-power) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1479

Test mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1480
44.5.1

Silent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1480

44.5.2

Loop back mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1481

44.5.3

Loop back combined with silent mode . . . . . . . . . . . . . . . . . . . . . . . . 1481

44.6

Behavior in debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1482

44.7

bxCAN functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1482
44.7.1

Transmission handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1482

44.7.2

Time triggered communication mode . . . . . . . . . . . . . . . . . . . . . . . . . 1484

44.7.3

Reception handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1484

44.7.4

Identifier filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1485

44.7.5

Message storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1489

44.7.6

Error management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1491

44.7.7

Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1491

44.8

bxCAN interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1494

44.9

CAN registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1495
44.9.1

Register access protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1495

44.9.2

CAN control and status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1495

44.9.3

CAN mailbox registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1505

44.9.4

CAN filter registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1512

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RM0394

Contents
44.9.5

45

Universal serial bus full-speed device interface (USB) . . . . . . . . . . 1520
45.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1520

45.2

USB main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1520

45.3

USB implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1520

45.4

USB functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1521
45.4.1

45.5

45.6

46

bxCAN register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1516

Description of USB blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1522

Programming considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1523
45.5.1

Generic USB device programming . . . . . . . . . . . . . . . . . . . . . . . . . . 1523

45.5.2

System and power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1524

45.5.3

Double-buffered endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1529

45.5.4

Isochronous transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1531

45.5.5

Suspend/Resume events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1532

USB and USB SRAM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1535
45.6.1

Common registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1535

45.6.2

Buffer descriptor table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1548

45.6.3

USB register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1551

Debug support (DBG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1553
46.1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1553

46.2

Reference Arm® documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1554

46.3

SWJ debug port (serial wire and JTAG) . . . . . . . . . . . . . . . . . . . . . . . . 1554
46.3.1

46.4

Mechanism to select the JTAG-DP or the SW-DP . . . . . . . . . . . . . . . 1555

Pinout and debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1555
46.4.1

SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1556

46.4.2

Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . 1556

46.4.3

Internal pull-up and pull-down on JTAG pins . . . . . . . . . . . . . . . . . . . 1557

46.4.4

Using serial wire and releasing the unused debug pins as GPIOs . . 1558

46.5

STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx JTAG TAP connection 1558

46.6

ID codes and locking mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1559

46.7

46.6.1

MCU device ID code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1560

46.6.2

Boundary scan TAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1560

46.6.3

Cortex®-M4 TAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1560

46.6.4

Cortex®-M4 JEDEC-106 ID code . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1561

JTAG debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1561
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Contents

RM0394

46.8

46.9

SW debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1563
46.8.1

SW protocol introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1563

46.8.2

SW protocol sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1563

46.8.3

SW-DP state machine (reset, idle states, ID code) . . . . . . . . . . . . . . 1564

46.8.4

DP and AP read/write accesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1564

46.8.5

SW-DP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1565

46.8.6

SW-AP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1566

AHB-AP (AHB access port) - valid for both JTAG-DP
and SW-DP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1566

46.10 Core debug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1567
46.11 Capability of the debugger host to connect under system reset . . . . . 1567
46.12 FPB (Flash patch breakpoint) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1568
46.13 DWT (data watchpoint trigger) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1568
46.14 ITM (instrumentation trace macrocell) . . . . . . . . . . . . . . . . . . . . . . . . . 1569
46.14.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1569
46.14.2 Time stamp packets, synchronization and overflow packets . . . . . . . 1569

46.15 ETM (Embedded trace macrocell) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1571
46.15.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1571
46.15.2 Signal protocol, packet types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1571
46.15.3 Main ETM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1571
46.15.4 Configuration example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1572

46.16 MCU debug component (DBGMCU) . . . . . . . . . . . . . . . . . . . . . . . . . . 1572
46.16.1 Debug support for low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . 1572
46.16.2 Debug support for timers, RTC, watchdog, bxCAN and I2C . . . . . . . 1573
46.16.3 Debug MCU configuration register (DBGMCU_CR) . . . . . . . . . . . . . 1573
46.16.4 Debug MCU APB1 freeze register1(DBGMCU_APB1FZR1) . . . . . . 1574
46.16.5 Debug MCU APB1 freeze register 2 (DBGMCU_APB1FZR2) . . . . . 1575
46.16.6 Debug MCU APB2 freeze register (DBGMCU_APB2FZR) . . . . . . . . 1576

46.17 TPIU (trace port interface unit) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1577
46.17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1577
46.17.2 TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1577
46.17.3 TPUI formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1579
46.17.4 TPUI frame synchronization packets . . . . . . . . . . . . . . . . . . . . . . . . . 1580
46.17.5 Transmission of the synchronization frame packet . . . . . . . . . . . . . . 1580
46.17.6 Synchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1580
46.17.7 Asynchronous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1581

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Contents
46.17.8 TRACECLKIN connection inside the
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx . . . . . . . . . . . . . . . . 1581
46.17.9 TPIU registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1582
46.17.10 Example of configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1583

46.18 DBG register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1584

47

48

Device electronic signature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1585
47.1

Unique device ID register (96 bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1585

47.2

Flash size data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1586

47.3

Package data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1587

Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1588

RM0394 Rev 4

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43

List of tables

RM0394

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.

44/1600

Product specific features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx memory map and peripheral register
boundary addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
SRAM2 organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
SRAM2 organization
(continuation for STM32L43x/44x/45x/46x devices only) . . . . . . . . . . . . . . . . . . . . . . . . . . 72
SRAM2 organization
(continuation for STM32L45x and STM32L46x devices only) . . . . . . . . . . . . . . . . . . . . . . 72
Boot modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Memory mapping vs. Boot mode/Physical remap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Flash module - single bank organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Number of wait states according to CPU clock (HCLK) frequency . . . . . . . . . . . . . . . . . . . 79
Option byte format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Option byte organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Flash memory read protection status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
Access status versus protection level and execution modes . . . . . . . . . . . . . . . . . . . . . . . 96
Flash interrupt request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Flash interface - register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Segment accesses according to the Firewall state. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Segment granularity and area ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Firewall register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
PVM features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Low-power mode summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Functionalities depending on the working mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Low-power run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
Sleep. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
Low-power sleep. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
Stop 0 mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Stop 1 mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Stop 2 mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Standby mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Shutdown mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
PWR register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Clock source frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
RCC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
Effect of low-power modes on CRS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
CRS register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Port bit configuration table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
GPIO register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
SYSCFG register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx peripherals interconnect matrix . . . . . . 288
DMA1 and DMA2 implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
DMA1 requests for each channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
DMA2 requests for each channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
Programmable data width and endian behavior (when PINC = MINC = 1) . . . . . . . . . . . 306
DMA interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
DMA register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

RM0394 Rev 4

RM0394
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.

List of tables
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table . . . . . . . . . . . . . . . . . . . . . . 321
EXTI lines connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
Extended interrupt/event controller register map and reset values. . . . . . . . . . . . . . . . . . 337
CRC internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
CRC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
QUADSPI pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
QUADSPI interrupt requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
QUADSPI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372
Main ADC features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
ADC internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
ADC input/output pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
Configuring the trigger polarity for regular external triggers . . . . . . . . . . . . . . . . . . . . . . . 394
Configuring the trigger polarity for injected external triggers . . . . . . . . . . . . . . . . . . . . . . 394
ADC1 and ADC2 - External triggers for regular channels. . . . . . . . . . . . . . . . . . . . . . . . . 395
ADC1 and ADC2 - External trigger for injected channels . . . . . . . . . . . . . . . . . . . . . . . . . 396
TSAR timings depending on resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408
Offset computation versus data resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411
Analog watchdog channel selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
Analog watchdog 1 comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423
Analog watchdog 2 and 3 comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423
Maximum output results versus N and M (gray cells indicate truncation). . . . . . . . . . . . . 427
Oversampler operating modes summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431
ADC interrupts per each ADC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450
DELAY bits versus ADC resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481
ADC global register map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
ADC register map and reset values for each ADC (offset=0x000
for master ADC, 0x100 for slave ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482
ADC register map and reset values (master and slave ADC
common registers) offset = 0x300 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
DAC implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487
DAC input/output pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489
DAC trigger selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492
Sample and refresh timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 496
Channel output modes summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497
Effect of low-power modes on DAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504
DAC interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504
DAC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520
VREF buffer modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522
VREFBUF register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524
COMP1 input plus assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526
COMP1 input minus assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
COMP2 input plus assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
COMP2 input minus assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527
Comparator behavior in the low power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531
Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531
COMP register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537
Operational amplifier possible connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539
Operating modes and calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544
Effect of low-power modes on the OPAMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545
OPAMP register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548
DFSDM1 implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551
DFSDM external pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553

RM0394 Rev 4

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49

List of tables
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.
Table 143.

46/1600

RM0394

DFSDM internal signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553
DFSDM triggers connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553
DFSDM break connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554
Filter maximum output resolution (peak data values from filter output)
for some FOSR values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568
Integrator maximum output resolution (peak data values from integrator
output) for some IOSR values and FOSR = 256 and Sinc3 filter type (largest data) . . . . 568
DFSDM interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 576
DFSDM register map and reset values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597
Example of frame rate calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605
Blink frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613
Remapping capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 618
LCD behavior in low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623
LCD interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623
LCD register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632
Acquisition sequence summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637
Spread spectrum deviation versus AHB clock frequency . . . . . . . . . . . . . . . . . . . . . . . . . 639
I/O state depending on its mode and IODEF bit value . . . . . . . . . . . . . . . . . . . . . . . . . . . 640
Effect of low-power modes on TSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642
Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642
TSC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651
RNG internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654
RNG interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659
RNG register map and reset map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664
AES internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666
CTR mode initialization vector definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685
GCM last block definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 687
GCM mode IVI bitfield initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 688
Initialization of AES_IVRx registers in CCM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695
Key endianness in AES_KEYRx registers (128- or 256-bit key length) . . . . . . . . . . . . . . 700
DMA channel configuration for memory-to-AES data transfer . . . . . . . . . . . . . . . . . . . . . 701
DMA channel configuration for AES-to-memory data transfer . . . . . . . . . . . . . . . . . . . . . 702
AES interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704
Processing latency (in clock cycle) for ECB, CBC and CTR. . . . . . . . . . . . . . . . . . . . . . . 704
Processing latency for GCM and CCM (in clock cycle) . . . . . . . . . . . . . . . . . . . . . . . . . . 704
AES register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 716
Behavior of timer outputs versus BRK/BRK2 inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 761
Counting direction versus encoder signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 768
TIM1 internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 785
Output control bits for complementary OCx and OCxN channels with break feature . . . . 799
TIM1 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 814
Counting direction versus encoder signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 851
TIMx internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 867
Output control bit for standard OCx channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 878
TIM2/TIM3 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 884
TIMx Internal trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 928
Output control bits for complementary OCx and OCxN channels with break feature
(TIM15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 938
TIM15 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 946
Output control bits for complementary OCx and OCxN channels with break feature
(TIM16/17) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 958
TIM16 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 966

RM0394 Rev 4

RM0394
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.
Table 192.
Table 193.

List of tables
TIM6/TIM7 register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 980
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx LPTIM features . . . . . . . . . . . . . . . . . . . 982
LPTIM1 external trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 983
LPTIM2 external trigger connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 983
Prescaler division ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985
Encoder counting scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 993
Effect of low-power modes on the LPTIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996
Interrupt events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 996
LPTIM register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1010
IWDG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1021
WWDG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1028
RTC input/output pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1032
RTC internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1032
RTC interconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1032
PC13 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1033
RTC_OUT mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1035
Effect of low-power modes on RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1046
RTC pins functionality over modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047
Interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047
RTC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1067
TAMP input/output pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1070
TAMP internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1071
TAMP interconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1071
Effect of low-power modes on TAMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1073
Interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1074
TAMP register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1081
RTC pin PC13 configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1085
RTC_OUT mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086
RTC functions over modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087
Effect of low-power modes on RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1099
Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1100
RTC register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1125
I2C implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1128
Comparison of analog vs. digital filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1131
I2C-SMBUS specification data setup and hold times . . . . . . . . . . . . . . . . . . . . . . . . . . . 1134
I2C configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1138
I2C-SMBUS specification clock timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1149
Examples of timing settings for fI2CCLK = 8 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1159
Examples of timings settings for fI2CCLK = 16 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . 1159
Examples of timings settings for fI2CCLK = 48 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . 1160
SMBus timeout specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1162
SMBUS with PEC configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1164
Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tTIMEOUT = 25 ms) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1165
Examples of TIMEOUTB settings for various I2CCLK frequencies . . . . . . . . . . . . . . . . 1165
Examples of TIMEOUTA settings for various I2CCLK frequencies
(max tIDLE = 50 µs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1165
Effect of low-power modes on the I2C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1176
I2C Interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1177
I2C register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1192
USART/LPUART implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1196
Noise detection from sampled data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1208

RM0394 Rev 4

47/1600
49

List of tables

RM0394

Table 194. Error calculation for programmed baud rates at fCK = 72MHz in both cases of
oversampling by 16 or by 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1211
Table 195. Tolerance of the USART receiver when BRR [3:0] = 0000. . . . . . . . . . . . . . . . . . . . . . . 1213
Table 196. Tolerance of the USART receiver when BRR [3:0] is different from 0000 . . . . . . . . . . . 1213
Table 197. Frame formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1217
Table 198. Effect of low-power modes on the USART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236
Table 199. USART interrupt requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236
Table 200. USART register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1260
Table 201. USART/LPUART implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1264
Table 202. Error calculation for programmed baud rates at fck = 32,768 KHz. . . . . . . . . . . . . . . . . 1274
Table 203. Error calculation for programmed baud rates at fck = 80 MHz . . . . . . . . . . . . . . . . . . . . 1274
Table 204. Tolerance of the LPUART receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1275
Table 205. Frame formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1278
Table 206. Effect of low-power modes on the LPUART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1286
Table 207. LPUART interrupt requests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1287
Table 208. LPUART register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1303
Table 209. SPI implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1305
Table 210. SPI interrupt requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1329
Table 211. SPI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1338
Table 212. STM32L43xxx/44xxx/45xxx/46xxx SAI interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1340
Table 213. SAI internal input/output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1342
Table 214. SAI input/output pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1342
Table 215. External synchronization selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1344
Table 216. Example of possible audio frequency sampling range . . . . . . . . . . . . . . . . . . . . . . . . . . 1350
Table 217. SOPD pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1355
Table 218. Parity bit calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1355
Table 219. Audio sampling frequency versus symbol rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1356
Table 220. SAI interrupt sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1365
Table 221. SAI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1389
Table 222. Effect of low-power modes on SWPMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1406
Table 223. Interrupt control bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1407
Table 224. Buffer modes selection for transmission/reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1409
Table 225. SWPMI register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1416
Table 226. SDMMC I/O definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1420
Table 227. Command format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1425
Table 228. Short response format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1426
Table 229. Long response format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1426
Table 230. Command path status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1426
Table 231. Data token format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1429
Table 232. DPSM flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1430
Table 233. Transmit FIFO status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1431
Table 234. Receive FIFO status flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1431
Table 235. Card status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1442
Table 236. SD status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1445
Table 237. Speed class code field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1446
Table 238. Performance move field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1447
Table 239. AU_SIZE field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1447
Table 240. Maximum AU size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1447
Table 241. Erase size field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1448
Table 242. Erase timeout field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1448
Table 243. Erase offset field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1448
Table 244. Block-oriented write commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1451

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RM0394
Table 245.
Table 246.
Table 247.
Table 248.
Table 249.
Table 250.
Table 251.
Table 252.
Table 253.
Table 254.
Table 255.
Table 256.
Table 257.
Table 258.
Table 259.
Table 260.
Table 261.
Table 262.
Table 263.
Table 264.
Table 265.
Table 266.
Table 267.
Table 268.
Table 269.
Table 270.
Table 271.
Table 272.
Table 273.
Table 274.
Table 275.
Table 276.
Table 277.
Table 278.
Table 279.
Table 280.
Table 281.
Table 282.
Table 283.
Table 284.
Table 285.
Table 286.
Table 287.
Table 288.
Table 289.
Table 290.

List of tables
Block-oriented write protection commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1452
Erase commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1452
I/O mode commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1452
Lock card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453
Application-specific commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453
R1 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454
R2 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454
R3 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455
R4 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455
R4b response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455
R5 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456
R6 response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1457
Response type and SDMMC_RESPx registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1463
SDMMC register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1474
Transmit mailbox mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1490
Receive mailbox mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1490
bxCAN register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1516
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx USB implementation . . . . . . . . . . . . . . 1520
Double-buffering buffer flag definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1530
Bulk double-buffering memory buffers usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1530
Isochronous memory buffers usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1532
Resume event detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1534
Reception status encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1546
Endpoint type encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1547
Endpoint kind meaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1547
Transmission status encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1547
Definition of allocated buffer memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1550
USB register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1551
SWJ debug port pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1556
Flexible SWJ-DP pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1556
JTAG debug port data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1561
32-bit debug port registers addressed through the shifted value A[3:2] . . . . . . . . . . . . . 1562
Packet request (8-bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1563
ACK response (3 bits). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1564
DATA transfer (33 bits) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1564
SW-DP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1565
Cortex®-M4 AHB-AP registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1566
Core debug registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1567
Main ITM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1569
Main ETM registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1571
Asynchronous TRACE pin assignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1577
Synchronous TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1578
Flexible TRACE pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1578
Important TPIU registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1582
DBG register map and reset values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1584
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1588

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49

List of figures

RM0394

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.

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System architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Memory map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Sequential 16-bit instructions execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Changing the Read protection (RDP) level. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx firewall connection schematics . . . . . . . 115
Firewall functional states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Power supply overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Internal main regulator overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Brown-out reset waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
PVD thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Low-power modes possible transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Simplified diagram of the reset circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Clock tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
HSE/ LSE clock sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Frequency measurement with TIM15 in capture mode. . . . . . . . . . . . . . . . . . . . . . . . . . . 189
Frequency measurement with TIM16 in capture mode. . . . . . . . . . . . . . . . . . . . . . . . . . . 190
CRS block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
CRS counter behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
Basic structure of an I/O port bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Basic structure of a 5-Volt tolerant I/O port bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Input floating/pull up/pull down configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
Output configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
Alternate function configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
High impedance-analog configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
DMA1 request mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
DMA2 request mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
DMA block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
Configurable interrupt/event block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
External interrupt/event GPIO mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
CRC calculation unit block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
QUADSPI block diagram when dual-flash mode is disabled . . . . . . . . . . . . . . . . . . . . . . 344
QUADSPI block diagram when dual-flash mode is enabled . . . . . . . . . . . . . . . . . . . . . . 345
An example of a read command in quad mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
An example of a DDR command in quad mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
nCS when CKMODE = 0 (T = CLK period). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
nCS when CKMODE = 1 in SDR mode (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . 357
nCS when CKMODE = 1 in DDR mode (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . 358
nCS when CKMODE = 1 with an abort (T = CLK period) . . . . . . . . . . . . . . . . . . . . . . . . . 358
ADC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376
ADC clock scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
ADC1 connectivity
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
ADC2 connectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
ADC calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 384
Updating the ADC calibration factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385
Mixing single-ended and differential channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385
Enabling / Disabling the ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387
Analog to digital conversion time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392
Stopping ongoing regular conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393

RM0394 Rev 4

RM0394
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
Stopping ongoing regular and injected conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393
Triggers sharing between ADC master and ADC slave . . . . . . . . . . . . . . . . . . . . . . . . . . 395
Injected conversion latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
Example of JSQR queue of context (sequence change) . . . . . . . . . . . . . . . . . . . . . . . . . 401
Example of JSQR queue of context (trigger change) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
Example of JSQR queue of context with overflow before conversion . . . . . . . . . . . . . . . 402
Example of JSQR queue of context with overflow during conversion . . . . . . . . . . . . . . . 402
Example of JSQR queue of context with empty queue (case JQM=0). . . . . . . . . . . . . . . 403
Example of JSQR queue of context with empty queue (case JQM=1). . . . . . . . . . . . . . . 404
Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs during an ongoing conversion. . . . . . . . . . . . . . . . . . . . . . . 404
Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs during an ongoing conversion and a new
trigger occurs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405
Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs outside an ongoing conversion . . . . . . . . . . . . . . . . . . . . . . 405
Flushing JSQR queue of context by setting JADSTP=1 (JQM=1) . . . . . . . . . . . . . . . . . . 406
Flushing JSQR queue of context by setting ADDIS=1 (JQM=0). . . . . . . . . . . . . . . . . . . . 406
Flushing JSQR queue of context by setting ADDIS=1 (JQM=1). . . . . . . . . . . . . . . . . . . . 407
Single conversions of a sequence, software trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409
Continuous conversion of a sequence, software trigger . . . . . . . . . . . . . . . . . . . . . . . . . . 409
Single conversions of a sequence, hardware trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410
Continuous conversions of a sequence, hardware trigger . . . . . . . . . . . . . . . . . . . . . . . . 410
Right alignment (offset disabled, unsigned value) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
Right alignment (offset enabled, signed value). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413
Left alignment (offset disabled, unsigned value) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413
Left alignment (offset enabled, signed value) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414
Example of overrun (OVR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
AUTODLY=1, regular conversion in continuous mode, software trigger . . . . . . . . . . . . . 418
AUTODLY=1, regular HW conversions interrupted by injected conversions
(DISCEN=0; JDISCEN=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
AUTODLY=1, regular HW conversions interrupted by injected conversions . . . . . . . . . . . . .
(DISCEN=1, JDISCEN=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
AUTODLY=1, regular continuous conversions interrupted by injected conversions . . . . 421
AUTODLY=1 in auto- injected mode (JAUTO=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
Analog watchdog guarded area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
ADCy_AWDx_OUT signal generation (on all regular channels). . . . . . . . . . . . . . . . . . . . 424
ADCy_AWDx_OUT signal generation (AWDx flag not cleared by software) . . . . . . . . . . 425
ADCy_AWDx_OUT signal generation (on a single regular channel) . . . . . . . . . . . . . . . . 425
ADCy_AWDx_OUT signal generation (on all injected channels) . . . . . . . . . . . . . . . . . . . 425
20-bit to 16-bit result truncation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426
Numerical example with 5-bit shift and rounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426
Triggered regular oversampling mode (TROVS bit = 1) . . . . . . . . . . . . . . . . . . . . . . . . . . 428
Regular oversampling modes (4x ratio) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
Regular and injected oversampling modes used simultaneously . . . . . . . . . . . . . . . . . . . 430
Triggered regular oversampling with injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430
Oversampling in auto-injected mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431
Dual ADC block diagram(1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
Injected simultaneous mode on 4 channels: dual ADC mode . . . . . . . . . . . . . . . . . . . . . 434
Regular simultaneous mode on 16 channels: dual ADC mode . . . . . . . . . . . . . . . . . . . . 436
Interleaved mode on 1 channel in continuous conversion mode: dual ADC mode. . . . . . 437
Interleaved mode on 1 channel in single conversion mode: dual ADC mode. . . . . . . . . . 438

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59

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.
Figure 141.
Figure 142.
Figure 143.

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Interleaved conversion with injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
Alternate trigger: injected group of each ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
Alternate trigger: 4 injected channels (each ADC) in discontinuous mode . . . . . . . . . . . . 440
Alternate + regular simultaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
Case of trigger occurring during injected conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
Interleaved single channel CH0 with injected sequence CH11, CH12 . . . . . . . . . . . . . . . 442
Two Interleaved channels (CH1, CH2) with injected sequence CH11, CH12
- case 1: Master interrupted first . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442
Two Interleaved channels (CH1, CH2) with injected sequence CH11, CH12
- case 2: Slave interrupted first . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442
DMA Requests in regular simultaneous mode when MDMA=0b00 . . . . . . . . . . . . . . . . . 443
DMA requests in regular simultaneous mode when MDMA=0b10 . . . . . . . . . . . . . . . . . . 444
DMA requests in interleaved mode when MDMA=0b10 . . . . . . . . . . . . . . . . . . . . . . . . . . 444
Temperature sensor channel block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
VBAT channel block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448
VREFINT channel block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448
Dual-channel DAC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488
Data registers in single DAC channel mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490
Data registers in dual DAC channel mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 490
Timing diagram for conversion with trigger disabled TEN = 0 . . . . . . . . . . . . . . . . . . . . . 491
DAC LFSR register calculation algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493
DAC conversion (SW trigger enabled) with LFSR wave generation . . . . . . . . . . . . . . . . 493
DAC triangle wave generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494
DAC conversion (SW trigger enabled) with triangle wave generation . . . . . . . . . . . . . . . 494
DAC Sample and Hold mode phase diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497
Comparators block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526
Window mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529
Comparator hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 529
Comparator output blanking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530
Standalone mode: external gain setting mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
Follower configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541
PGA mode, internal gain setting (x2/x4/x8/x16), inverting input not used . . . . . . . . . . . . 542
PGA mode, internal gain setting (x2/x4/x8/x16), inverting input used for
filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543
Single DFSDM block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 552
Input channel pins redirection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556
Channel transceiver timing diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558
Clock absence timing diagram for SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559
Clock absence timing diagram for Manchester coding . . . . . . . . . . . . . . . . . . . . . . . . . . . 560
First conversion for Manchester coding (Manchester synchronization) . . . . . . . . . . . . . . 562
DFSDM_CHyDATINR registers operation modes and assignment . . . . . . . . . . . . . . . . . 565
Example: Sinc3 filter response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567
LCD controller block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
1/3 bias, 1/4 duty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 606
Static duty case 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607
Static duty case 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608
1/2 duty, 1/2 bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
1/3 duty, 1/3 bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610
1/4 duty, 1/3 bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611
1/8 duty, 1/4 bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612
LCD voltage control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 615
Deadtime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616

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RM0394
Figure 144.
Figure 145.
Figure 146.
Figure 147.
Figure 148.
Figure 149.
Figure 150.
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Figure 155.
Figure 156.
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Figure 186.
Figure 187.
Figure 188.
Figure 189.
Figure 190.
Figure 191.
Figure 192.
Figure 193.
Figure 194.
Figure 195.

List of figures
SEG/COM mux feature example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621
Flowchart example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622
TSC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635
Surface charge transfer analog I/O group structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 636
Sampling capacitor voltage variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637
Charge transfer acquisition sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 638
Spread spectrum variation principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 639
RNG block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654
Entropy source model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655
AES block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666
ECB encryption and decryption principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668
CBC encryption and decryption principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669
CTR encryption and decryption principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670
GCM encryption and authentication principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671
GMAC authentication principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671
CCM encryption and authentication principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672
STM32 cryptolib AES flowchart examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673
STM32 cryptolib AES flowchart examples (continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . 674
Encryption key derivation for ECB/CBC decryption (Mode 2). . . . . . . . . . . . . . . . . . . . . . 677
Example of suspend mode management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 678
ECB encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 679
ECB decryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 679
CBC encryption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 680
CBC decryption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 680
ECB/CBC encryption (Mode 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 681
ECB/CBC decryption (Mode 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 682
Message construction in CTR mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684
CTR encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685
CTR decryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685
Message construction in GCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 687
GCM authenticated encryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 688
Message construction in GMAC mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 692
GMAC authentication mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 692
Message construction in CCM mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693
CCM mode authenticated decryption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695
128-bit block construction with respect to data swap . . . . . . . . . . . . . . . . . . . . . . . . . . . . 699
DMA transfer of a 128-bit data block during input phase . . . . . . . . . . . . . . . . . . . . . . . . . 701
DMA transfer of a 128-bit data block during output phase . . . . . . . . . . . . . . . . . . . . . . . . 702
AES interrupt signal generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703
Advanced-control timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 720
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 722
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 722
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 725
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 725
Counter timing diagram, update event when ARPE=0 (TIMx_ARR not preloaded) . . . . . 726
Counter timing diagram, update event when ARPE=1 (TIMx_ARR preloaded) . . . . . . . . 726
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 728
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 728
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729

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List of figures
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.
Figure 244.
Figure 245.
Figure 246.
Figure 247.

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Counter timing diagram, update event when repetition counter is not used . . . . . . . . . . . 730
Counter timing diagram, internal clock divided by 1, TIMx_ARR = 0x6 . . . . . . . . . . . . . . 731
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 732
Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36 . . . . . . . . . . . . . . 732
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 733
Counter timing diagram, update event with ARPE=1 (counter underflow) . . . . . . . . . . . . 733
Counter timing diagram, Update event with ARPE=1 (counter overflow) . . . . . . . . . . . . . 734
Update rate examples depending on mode and TIMx_RCR register settings . . . . . . . . . 735
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736
TIM1 ETR input circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 737
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 738
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 739
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 739
Control circuit in external clock mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 740
Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 741
Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 742
Output stage of capture/compare channel (channel 1, idem ch. 2 and 3) . . . . . . . . . . . . 743
Output stage of capture/compare channel (channel 4). . . . . . . . . . . . . . . . . . . . . . . . . . . 743
Output stage of capture/compare channel (channel 5, idem ch. 6) . . . . . . . . . . . . . . . . . 744
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746
Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 748
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 749
Center-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 750
Generation of 2 phase-shifted PWM signals with 50% duty cycle . . . . . . . . . . . . . . . . . . 752
Combined PWM mode on channel 1 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 753
3-phase combined PWM signals with multiple trigger pulses per period . . . . . . . . . . . . . 754
Complementary output with dead-time insertion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755
Dead-time waveforms with delay greater than the negative pulse . . . . . . . . . . . . . . . . . . 755
Dead-time waveforms with delay greater than the positive pulse. . . . . . . . . . . . . . . . . . . 756
Break and Break2 circuitry overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 758
Various output behavior in response to a break event on BRK (OSSI = 1) . . . . . . . . . . . 760
PWM output state following BRK and BRK2 pins assertion (OSSI=1) . . . . . . . . . . . . . . . 761
PWM output state following BRK assertion (OSSI=0) . . . . . . . . . . . . . . . . . . . . . . . . . . . 762
Output redirection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 762
Clearing TIMx OCxREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 763
6-step generation, COM example (OSSR=1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764
Example of one pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 765
Retriggerable one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767
Example of counter operation in encoder interface mode. . . . . . . . . . . . . . . . . . . . . . . . . 768
Example of encoder interface mode with TI1FP1 polarity inverted. . . . . . . . . . . . . . . . . . 769
Measuring time interval between edges on 3 signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770
Example of Hall sensor interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 772
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773
Control circuit in Gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775
Control circuit in external clock mode 2 + trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . 776
General-purpose timer block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 818
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 820
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 820
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 821
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 822

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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.
Figure 292.
Figure 293.
Figure 294.
Figure 295.
Figure 296.
Figure 297.
Figure 298.

List of figures
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 822
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 823
Counter timing diagram, Update event when ARPE=0 (TIMx_ARR not preloaded). . . . . 823
Counter timing diagram, Update event when ARPE=1 (TIMx_ARR preloaded). . . . . . . . 824
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 826
Counter timing diagram, Update event when repetition counter
is not used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 827
Counter timing diagram, internal clock divided by 1, TIMx_ARR=0x6 . . . . . . . . . . . . . . . 828
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829
Counter timing diagram, internal clock divided by 4, TIMx_ARR=0x36 . . . . . . . . . . . . . . 829
Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830
Counter timing diagram, Update event with ARPE=1 (counter underflow). . . . . . . . . . . . 830
Counter timing diagram, Update event with ARPE=1 (counter overflow) . . . . . . . . . . . . . 831
Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 832
TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832
Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833
External trigger input block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834
Control circuit in external clock mode 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835
Capture/Compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . 836
Capture/Compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 836
Output stage of Capture/Compare channel (channel 1) . . . . . . . . . . . . . . . . . . . . . . . . . . 837
PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 839
Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841
Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 842
Center-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 843
Generation of 2 phase-shifted PWM signals with 50% duty cycle . . . . . . . . . . . . . . . . . . 844
Combined PWM mode on channels 1 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 846
Clearing TIMx OCxREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 847
Example of one-pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848
Retriggerable one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850
Example of counter operation in encoder interface mode . . . . . . . . . . . . . . . . . . . . . . . . 851
Example of encoder interface mode with TI1FP1 polarity inverted . . . . . . . . . . . . . . . . . 852
Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853
Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854
Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855
Control circuit in external clock mode 2 + trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . 856
Master/Slave timer example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856
Gating TIMz with OC1REF of TIMy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857
Gating TIMz with Enable of TIMy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 858
Triggering TIMz with update of TIMy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 859
Triggering TIMz with Enable of TIMy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 859
Triggering TIMy3 and TIMz2 with TIMy3 TI1 input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860
TIM15 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 889
TIM16 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 890
Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 892
Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 892
Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894
Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894
Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895

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Figure 299. Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895
Figure 300. Counter timing diagram, update event when ARPE=0 (TIMx_ARR not
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896
Figure 301. Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896
Figure 302. Update rate examples depending on mode and TIMx_RCR register settings . . . . . . . . . 898
Figure 303. Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 899
Figure 304. TI2 external clock connection example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899
Figure 305. Control circuit in external clock mode 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900
Figure 306. Capture/compare channel (example: channel 1 input stage) . . . . . . . . . . . . . . . . . . . . . . 901
Figure 307. Capture/compare channel 1 main circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901
Figure 308. Output stage of capture/compare channel (channel 1). . . . . . . . . . . . . . . . . . . . . . . . . . . 902
Figure 309. Output stage of capture/compare channel (channel 2 for TIM15) . . . . . . . . . . . . . . . . . . 902
Figure 310. PWM input mode timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904
Figure 311. Output compare mode, toggle on OC1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
Figure 312. Edge-aligned PWM waveforms (ARR=8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907
Figure 313. Combined PWM mode on channel 1 and 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908
Figure 314. Complementary output with dead-time insertion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909
Figure 315. Dead-time waveforms with delay greater than the negative pulse. . . . . . . . . . . . . . . . . . 909
Figure 316. Dead-time waveforms with delay greater than the positive pulse. . . . . . . . . . . . . . . . . . . 910
Figure 317. Break circuitry overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
Figure 318. Output behavior in response to a break . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914
Figure 319. Example of one pulse mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915
Figure 320. Retriggerable one pulse mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917
Figure 321. Measuring time interval between edges on 2 signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 918
Figure 322. Control circuit in reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 919
Figure 323. Control circuit in gated mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 920
Figure 324. Control circuit in trigger mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 921
Figure 325. Basic timer block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 968
Figure 326. Counter timing diagram with prescaler division change from 1 to 2 . . . . . . . . . . . . . . . . . 970
Figure 327. Counter timing diagram with prescaler division change from 1 to 4 . . . . . . . . . . . . . . . . . 970
Figure 328. Counter timing diagram, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 971
Figure 329. Counter timing diagram, internal clock divided by 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 972
Figure 330. Counter timing diagram, internal clock divided by 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 972
Figure 331. Counter timing diagram, internal clock divided by N. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 973
Figure 332. Counter timing diagram, update event when ARPE = 0 (TIMx_ARR not
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 973
Figure 333. Counter timing diagram, update event when ARPE=1 (TIMx_ARR
preloaded). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 974
Figure 334. Control circuit in normal mode, internal clock divided by 1 . . . . . . . . . . . . . . . . . . . . . . . . 975
Figure 335. Low-power timer block diagram for STM32L43xxx/44xxx/45xxx/46xxx . . . . . . . . . . . . . . 982
Figure 336. Low-power timer block diagram for STM32L41xxx/42xxx . . . . . . . . . . . . . . . . . . . . . . . . 983
Figure 337. Glitch filter timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985
Figure 338. LPTIM output waveform, single counting mode configuration . . . . . . . . . . . . . . . . . . . . . 986
Figure 339. LPTIM output waveform, single counting mode configuration
when repetition register content is different than zero (with PRELOAD = 1) . . . . . . . . . . 987
Figure 340. LPTIM output waveform, Single counting mode configuration
and Set-once mode activated (WAVE bit is set) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 987
Figure 341. LPTIM output waveform, Continuous counting mode configuration . . . . . . . . . . . . . . . . . 988
Figure 342. Waveform generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990
Figure 343. Encoder mode counting sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 994
Figure 344. Continuous counting mode when repetition register LPTIM_RCR

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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.
Figure 395.

List of figures
different from zero (with PRELOAD = 1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 995
IRTIM internal hardware connections with TIM15 and TIM16
. . . . . . . . . . . . . . . . . . 1012
Independent watchdog block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013
Watchdog block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023
Window watchdog timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1024
RTC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1031
TAMP block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1070
RTC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1084
I2C block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1129
I2C bus protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1131
Setup and hold timings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1132
I2C initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1135
Data reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1136
Data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1137
Slave initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1140
Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=0. . . . . . . . . . . . 1142
Transfer sequence flowchart for I2C slave transmitter, NOSTRETCH=1. . . . . . . . . . . . 1143
Transfer bus diagrams for I2C slave transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1144
Transfer sequence flowchart for slave receiver with NOSTRETCH=0 . . . . . . . . . . . . . 1145
Transfer sequence flowchart for slave receiver with NOSTRETCH=1 . . . . . . . . . . . . . 1146
Transfer bus diagrams for I2C slave receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1146
Master clock generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1148
Master initialization flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1150
10-bit address read access with HEAD10R=0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1150
10-bit address read access with HEAD10R=1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1151
Transfer sequence flowchart for I2C master transmitter for N≤255 bytes . . . . . . . . . . . 1152
Transfer sequence flowchart for I2C master transmitter for N>255 bytes . . . . . . . . . . . 1153
Transfer bus diagrams for I2C master transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1154
Transfer sequence flowchart for I2C master receiver for N≤255 bytes. . . . . . . . . . . . . . 1156
Transfer sequence flowchart for I2C master receiver for N >255 bytes . . . . . . . . . . . . . 1157
Transfer bus diagrams for I2C master receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1158
Timeout intervals for tLOW:SEXT, tLOW:MEXT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1162
Transfer sequence flowchart for SMBus slave transmitter N bytes + PEC. . . . . . . . . . . 1166
Transfer bus diagrams for SMBus slave transmitter (SBC=1) . . . . . . . . . . . . . . . . . . . . 1167
Transfer sequence flowchart for SMBus slave receiver N Bytes + PEC . . . . . . . . . . . . 1168
Bus transfer diagrams for SMBus slave receiver (SBC=1). . . . . . . . . . . . . . . . . . . . . . . 1169
Bus transfer diagrams for SMBus master transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 1170
Bus transfer diagrams for SMBus master receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1172
USART block diagram
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1198
Word length programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1200
Configurable stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1202
TC/TXE behavior when transmitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1203
Start bit detection when oversampling by 16 or 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1204
Data sampling when oversampling by 16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1208
Data sampling when oversampling by 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1208
Mute mode using Idle line detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1215
Mute mode using address mark detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1216
Break detection in LIN mode (11-bit break length - LBDL bit is set) . . . . . . . . . . . . . . . . 1219
Break detection in LIN mode vs. Framing error detection. . . . . . . . . . . . . . . . . . . . . . . . 1220
USART example of synchronous transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1221
USART data clock timing diagram (M bits = 00). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1221
USART data clock timing diagram (M bits = 01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1222

RM0394 Rev 4

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59

List of figures
Figure 396.
Figure 397.
Figure 398.
Figure 399.
Figure 400.
Figure 401.
Figure 402.
Figure 403.
Figure 404.
Figure 405.
Figure 406.
Figure 407.
Figure 408.
Figure 409.
Figure 410.
Figure 411.
Figure 412.
Figure 413.
Figure 414.
Figure 415.
Figure 416.
Figure 417.
Figure 418.
Figure 419.
Figure 420.
Figure 421.
Figure 422.
Figure 423.
Figure 424.
Figure 425.
Figure 426.
Figure 427.
Figure 428.
Figure 429.
Figure 430.
Figure 431.
Figure 432.
Figure 433.
Figure 434.
Figure 435.
Figure 436.
Figure 437.
Figure 438.
Figure 439.
Figure 440.
Figure 441.
Figure 442.
Figure 443.
Figure 444.
Figure 445.
Figure 446.

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RM0394

RX data setup/hold time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1222
ISO 7816-3 asynchronous protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1224
Parity error detection using the 1.5 stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1225
IrDA SIR ENDEC- block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229
IrDA data modulation (3/16) -Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1230
Transmission using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1231
Reception using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1232
Hardware flow control between 2 USARTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1232
RS232 RTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1233
RS232 CTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1234
USART interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1237
LPUART block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1265
Word length programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267
Configurable stop bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268
TC/TXE behavior when transmitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1270
Mute mode using Idle line detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1277
Mute mode using address mark detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1278
Transmission using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1281
Reception using DMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1282
Hardware flow control between 2 LPUARTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1282
RS232 RTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1283
RS232 CTS flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1284
LPUART interrupt mapping diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1288
SPI block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1305
Full-duplex single master/ single slave application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1306
Half-duplex single master/ single slave application . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1307
Simplex single master/single slave application (master in transmit-only/
slave in receive-only mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1308
Master and three independent slaves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1309
Multi-master application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1310
Hardware/software slave select management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1311
Data clock timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1312
Data alignment when data length is not equal to 8-bit or 16-bit . . . . . . . . . . . . . . . . . . . 1313
Packing data in FIFO for transmission and reception . . . . . . . . . . . . . . . . . . . . . . . . . . 1317
Master full-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1320
Slave full-duplex communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1321
Master full-duplex communication with CRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1322
Master full-duplex communication in packed mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1323
NSSP pulse generation in Motorola SPI master mode . . . . . . . . . . . . . . . . . . . . . . . . . . 1326
TI mode transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1327
SAI functional block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1341
Audio frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1344
FS role is start of frame + channel side identification (FSDEF = TRIS = 1) . . . . . . . . . . 1346
FS role is start of frame (FSDEF = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1347
Slot size configuration with FBOFF = 0 in SAI_xSLOTR . . . . . . . . . . . . . . . . . . . . . . . . 1348
First bit offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1348
Audio block clock generator overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1349
AC’97 audio frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353
SPDIF format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1354
SAI_xDR register ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1355
Data companding hardware in an audio block in the SAI . . . . . . . . . . . . . . . . . . . . . . . . 1359
Tristate strategy on SD output line on an inactive slot . . . . . . . . . . . . . . . . . . . . . . . . . . 1360

RM0394 Rev 4

RM0394
Figure 447.
Figure 448.
Figure 449.
Figure 450.
Figure 451.
Figure 452.
Figure 453.
Figure 454.
Figure 455.
Figure 456.
Figure 457.
Figure 458.
Figure 459.
Figure 460.
Figure 461.
Figure 462.
Figure 463.
Figure 464.
Figure 465.
Figure 466.
Figure 467.
Figure 468.
Figure 469.
Figure 470.
Figure 471.
Figure 472.
Figure 473.
Figure 474.
Figure 475.
Figure 476.
Figure 477.
Figure 478.
Figure 479.
Figure 480.
Figure 481.
Figure 482.
Figure 483.
Figure 484.
Figure 485.
Figure 486.
Figure 487.
Figure 488.
Figure 489.
Figure 490.
Figure 491.
Figure 492.
Figure 493.
Figure 494.
Figure 495.
Figure 496.
Figure 497.

List of figures
Tristate on output data line in a protocol like I2S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1361
Overrun detection error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1362
FIFO underrun event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1362
S1 signal coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1390
S2 signal coding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1391
SWPMI block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1392
SWP bus states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1394
SWP frame structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395
SWPMI No software buffer mode transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1396
SWPMI No software buffer mode transmission, consecutive frames . . . . . . . . . . . . . . . 1397
SWPMI Multi software buffer mode transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1399
SWPMI No software buffer mode reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1401
SWPMI single software buffer mode reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1402
SWPMI Multi software buffer mode reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1404
SWPMI single buffer mode reception with CRC error. . . . . . . . . . . . . . . . . . . . . . . . . . . 1405
“No response” and “no data” operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1418
(Multiple) block read operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1418
(Multiple) block write operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1418
Sequential read operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1419
Sequential write operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1419
SDMMC block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1419
SDMMC adapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1421
Control unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1422
SDMMC_CK clock dephasing (BYPASS = 0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1423
SDMMC adapter command path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1423
Command path state machine (SDMMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1424
SDMMC command transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1425
Data path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1427
Data path state machine (DPSM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1428
CAN network topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1477
Single-CAN block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478
bxCAN operating modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1480
bxCAN in silent mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1481
bxCAN in loop back mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1481
bxCAN in combined mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1482
Transmit mailbox states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1483
Receive FIFO states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1484
Filter bank scale configuration - register organization . . . . . . . . . . . . . . . . . . . . . . . . . . 1487
Example of filter numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1488
Filtering mechanism - example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1489
CAN error state diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1490
Bit timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1492
CAN frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1493
Event flags and interrupt generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1494
CAN mailbox registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1506
USB peripheral block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1521
Packet buffer areas with examples of buffer description table locations . . . . . . . . . . . . 1525
Block diagram of STM32 MCU and Cortex®-M4-level debug support . . . . . . . . . . . . . . 1553
SWJ debug port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1555
JTAG TAP connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1559
TPIU block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1577

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Documentation conventions

RM0394

1

Documentation conventions

1.1

General information
The STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx devices have an Arm®(a) Cortex®-M4
core

1.2

List of abbreviations for registers
The following abbreviations(b) are used in register descriptions:

read/write (rw)

Software can read and write to this bit.

read-only (r)

Software can only read this bit.

write-only (w)

Software can only write to this bit. Reading this bit returns the reset value.

read/clear write0 (rc_w0)

Software can read as well as clear this bit by writing 0. Writing 1 has no
effect on the bit value.

read/clear write1 (rc_w1)

Software can read as well as clear this bit by writing 1. Writing 0 has no
effect on the bit value.

read/clear write (rc_w)

Software can read as well as clear this bit by writing to the register. The
value written to this bit is not important.

read/clear by read (rc_r)

Software can read this bit. Reading this bit automatically clears it to 0.
Writing this bit has no effect on the bit value.

read/set by read (rs_r)

Software can read this bit. Reading this bit automatically sets it to 1.
Writing this bit has no effect on the bit value.

read/set (rs)

Software can read as well as set this bit. Writing 0 has no effect on the bit
value.

read/write once (rwo)

Software can only write once to this bit and can also read it at any time.
Only a reset can return the bit to its reset value.

toggle (t)

The software can toggle this bit by writing 1. Writing 0 has no effect.

read-only write trigger (rt_w1) Software can read this bit. Writing 1 triggers an event but has no effect on
the bit value.
Reserved (Res.)

Reserved bit, must be kept at reset value.

a. Arm is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.
b. This is an exhaustive list of all abbreviations applicable to STM microcontrollers, some of them may not be
used in the current document.

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RM0394

1.3

Documentation conventions

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

1.4

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.

•

APB: advanced peripheral bus.

Availability of peripherals
For availability of peripherals and their number across all sales types, refer to the particular
device datasheet.

1.5

Product specific features
Table 1. Product specific features
STM32
L412xx

STM32
L422xx

STM32
L431xx

STM32
L432xx

STM32
L433xx

STM32
L442xx

STM32
L443xx

STM32
L451xx

STM32
L452xx

STM32
L462xx

ADC

ADC1
ADC2

ADC1
ADC2

ADC1
-

ADC1
-

ADC1
-

ADC1
-

ADC1
-

ADC1
-

ADC1
-

ADC1
-

DAC

-

-

DAC1

DAC1

DAC1

DAC1

DAC1

DAC1

DAC1

DAC1

COMP

COMP1
-

COMP1
-

COMP1
COMP2

COMP1
COMP2

COMP1
COMP2

COMP1
COMP2

COMP1
COMP2

COMP1
COMP2

COMP1
COMP2

COMP1
COMP2

DFSDM

-

-

-

-

-

-

-

LCD

-

-

-

-

LCD

-

LCD

Feature

DFSDM1 DFSDM1 DFSDM1
-

-

-

AES

-

AES

-

-

-

AES

AES

-

-

AES

TIM

TIM1
TIM2
TIM6
TIM15
TIM16

TIM1
TIM2
TIM6
TIM15
TIM16

TIM1
TIM2
TIM6
TIM7
TIM15
TIM16

TIM1
TIM2
TIM6
TIM7
TIM15
TIM16

TIM1
TIM2
TIM6
TIM7
TIM15
TIM16

TIM1
TIM2
TIM6
TIM7
TIM15
TIM16

TIM1
TIM2
TIM6
TIM7
TIM15
TIM16

TIM1
TIM2
TIM3
TIM6
TIM15
TIM16

TIM1
TIM2
TIM3
TIM6
TIM15
TIM16

TIM1
TIM2
TIM3
TIM6
TIM15
TIM16

I2C

I2C1
I2C2
I2C3
-

I2C1
I2C2
I2C3
-

I2C1
I2C2
I2C3
-

I2C1
I2C3
-

I2C1
I2C2
I2C3
-

I2C1
I2C3
-

I2C1
I2C2
I2C3
-

I2C1
I2C2
I2C3
I2C4

I2C1
I2C2
I2C3
I2C4

I2C1
I2C2
I2C3
I2C4

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Documentation conventions

RM0394

Table 1. Product specific features (continued)
Feature

USART

STM32
L412xx

STM32
L422xx

STM32
L431xx

STM32
L432xx

STM32
L433xx

STM32
L442xx

STM32
L443xx

STM32
L451xx

STM32
L452xx

STM32
L462xx

USART1 USART1 USART1 USART1 USART1 USART1 USART1 USART1 USART1 USART1
USART2 USART2 USART2 USART2 USART2 USART2 USART2 USART2 USART2 USART2
USART3 USART3 USART3
USART3
USART3 USART3 USART3 USART3
UART4 UART4 UART4

LPUART LPUART1 LPUART1 LPUART1 LPUART1 LPUART1 LPUART1 LPUART1 LPUART1 LPUART1 LPUART1
SPI

SPI1
SPI2
-

SPI1
SPI2
-

SPI1
SPI2
SPI3

SPI1
SPI3

SPI1
SPI2
SPI3

SPI1
SPI3

SPI1
SPI2
SPI3

SPI1
SPI2
SPI3

SPI1
SPI2
SPI3

SPI1
SPI2
SPI3

SAI

-

-

SAI

SAI

SAI

SAI

SAI

SAI

SAI

SAI

SWPMI

-

-

SWPMI1 SWPMI1 SWPMI1 SWPMI1 SWPMI1

-

-

-

SDMMC
USB
CAN1

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-

-

SDMMC

-

SDMMC

-

USB FS

USB FS

-

USB FS

USB FS

USB FS

USB FS

-

USB FS

USB FS

-

-

CAN1

CAN1

CAN1

CAN1

CAN1

CAN1

CAN1

CAN1

RM0394 Rev 4

SDMMC SDMMC SDMMC SDMMC

RM0394

System and memory overview

2

System and memory overview

2.1

System architecture
The main system consists of 32-bit multilayer AHB bus matrix that interconnects:
•

•

Five masters:
–

Cortex®-M4 with FPU core I-bus

–

Cortex®-M4 with FPU core D-bus

–

Cortex®-M4 with FPU core S-bus

–

DMA1

–

DMA2

Seven slaves:
–

Internal Flash memory on the ICode bus

–

Internal Flash memory on DCode bus

–

Internal SRAM1

–

Internal SRAM2

–

AHB1 peripherals including AHB to APB bridges and APB peripherals (connected
to APB1 and APB2)

–

AHB2 peripherals

–

The external memory controller (QUADSPI)

The bus matrix provides access from a master to a slave, enabling concurrent access and
efficient operation even when several high-speed peripherals work simultaneously. This
architecture is shown in Figure 1:

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Figure 1. System architecture

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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,
SRAM1, SRAM2 and external memories through QUADSPI.

2.1.2

S1: D-bus
This bus connects the data bus of the Cortex®-M4 core to the BusMatrix. This bus is used
by the core for literal load and debug access. The targets of this bus are the internal Flash
memory, SRAM1, SRAM2 and external memories through QUADSPI.

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RM0394

2.1.3

System and memory overview

S2: S-bus
This bus connects the system bus of the Cortex®-M4 core to the BusMatrix. This bus is
used by the core to access data located in a peripheral or SRAM area. The targets of this
bus are the SRAM1, the AHB1 peripherals including the APB1 and APB2 peripherals, the
AHB2 peripherals and the external memories through the QUADSPI.

2.1.4

S3, S4: DMA-bus
This bus connects the AHB master interface of the DMA to the BusMatrix.The targets of this
bus are the SRAM1 and SRAM2, the AHB1 peripherals including the APB1 and APB2
peripherals, the AHB2 peripherals and the external memories through the QUADSPI.

2.1.5

BusMatrix
The BusMatrix manages the access arbitration between masters. The arbitration uses a
Round Robin algorithm. The BusMatrix is composedof five masters (CPU AHB, system bus,
DCode bus, ICode bus, DMA1 and DMA2 bus) and seven slaves (FLASH, SRAM1,
SRAM2, AHB1 (including APB1 and APB2), AHB2 and QUADSPI).

AHB/APB bridges
The two AHB/APB bridges provide full synchronous connections between the AHB and the
two APB buses, allowing flexible selection of the peripheral frequency.
Refer to Section 2.2.2: Memory map and register boundary addresses on page 67 for the
address mapping of the peripherals connected to this bridge.
After each device reset, all peripheral clocks are disabled (except for the SRAM1/2 and
Flash memory interface). Before using a peripheral you have to enable its clock in the
RCC_AHBxENR and the RCC_APBxENR registers.
Note:

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.

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2.2

Memory organization

2.2.1

Introduction
Program memory, data memory, registers and I/O ports are organized within the same linear
4-Gbyte address space.
The bytes are coded in memory in Little Endian format. The lowest numbered byte in a word
is considered the word’s least significant byte and the highest numbered byte the most
significant.
The addressable memory space is divided into eight main blocks, of 512 Mbytes each.

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RM0394

2.2.2

Memory map and register boundary addresses
Figure 2. Memory map
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1. 0x2000 8000 for STM32L41xxx and STM32L42xxx devices
0x2000 C000 for STM32L43xxx and STM32L44xxx devices
0x2002 0000 for STM32L45xxx and STM32L46xxx devices
2. 0x1000 2000 for STM32L41xxx and STM32L42xxx devices
0x1000 4000 for STM32L43xxx and STM32L44xxx devices
0x1000 8000 for STM32L45xxx and STM32L46xxx devices

It is forbidden to access QUADSPI Flash bank area before having properly configured and
enabled the QUADSPI peripheral.
All the memory map areas that are not allocated to on-chip memories and peripherals are
considered “Reserved”. For the detailed mapping of available memory and register areas,
refer to the following table.

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RM0394
The following table gives the boundary addresses of the peripherals available in the
devices.
Table 2. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx memory map and peripheral register
boundary addresses
Bus

AHB2

Boundary address

Size (bytes)

Peripheral

0x5006 0800 - 0x5006 0BFF

1 KB

RNG

0x5006 0400 - 0x5006 07FF

1 KB

Reserved
AES

Peripheral register map
Section 24.8.4: RNG register map

(1)

Section 25.7.18: AES register map

0x5006 0000 - 0x5006 03FF

1 KB

0x5004 0400 - 0x5005 FFFF

127 KB

0x5004 0000 - 0x5004 03FF

1 KB

ADC

0x5000 0000 - 0x5003 FFFF

16 KB

Reserved

-

0x4800 2000 - 0x4FFF FFFF

~127 MB

Reserved

-

0x4800 1C00 - 0x4800 1FFF

1 KB

GPIOH

0x4800 1400 - 0x4800 1BFF

2 KB

Reserved

Reserved

Section 16.7.4: ADC register map on
page 482

(2) (3)

Section 8.4.12: GPIO register map
Section 8.4.12: GPIO register map

0x4800 1000 - 0x4800 13FF

1 KB

GPIOE

0x4800 0C00 - 0x4800 0FFF

1 KB

GPIOD(2)

Section 8.4.12: GPIO register map

0x4800 0800 - 0x4800 0BFF

1 KB

GPIOC

Section 8.4.12: GPIO register map

0x4800 0400 - 0x4800 07FF

1 KB

GPIOB

Section 8.4.12: GPIO register map

0x4800 0000 - 0x4800 03FF

1 KB

GPIOA

Section 8.4.12: GPIO register map

0x4002 4400 - 0x47FF FFFF

~127 MB

0x4002 4000 - 0x4002 43FF

1 KB

TSC

0x4002 3400 - 0x4002 3FFF

1 KB

Reserved

0x4002 3000 - 0x4002 33FF

1 KB

CRC

0x4002 2400 - 0x4002 2FFF

3 KB

Reserved

0x4002 2000 - 0x4002 23FF

1 KB

FLASH
registers

AHB1 0x4002 1400 - 0x4002 1FFF

3 KB

Reserved

0x4002 1000 - 0x4002 13FF

1 KB

RCC

0x4002 0800 - 0x4002 0FFF

2 KB

Reserved

0x4002 0400 - 0x4002 07FF

1 KB

DMA2

Section 11.6.8: DMA register map and reset
values

0x4002 0000 - 0x4002 03FF

1 KB

DMA1

Section 11.6.8: DMA register map and reset
values

0x4001 6400 - 0x4001 FFFF

39 KB

Reserved

APB2 0x4001 6000 - 0x4001 63FF

1 KB

DFSDM1(3)

0x4001 5800 - 0x4001 5FFF

2 kB

Reserved

68/1600

Reserved

RM0394 Rev 4

Section 23.6.11: TSC register map
Section 14.4.6: CRC register map
Section 3.7.13: FLASH register map
Section 6.4.32: RCC register map
-

Section 21.8.16: DFSDM register map
-

RM0394
Table 2. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx memory map and peripheral register
boundary addresses (continued)
Bus

Boundary address

Size (bytes)

Peripheral
(3)

Peripheral register map
Section 41.6.17: SAI register map

0x4001 5400 - 0x4001 57FF

1 KB

SAI1

0x4001 4400 - 0x4000 53FF

2 KB

Reserved

0x4001 4400 - 0x4001 47FF

1 KB

TIM16

Section 28.7.18: TIM16 register map

0x4001 4000 - 0x4001 43FF

1 KB

TIM15

Section 28.6.20: TIM15 register map

0x4001 3C00 - 0x4001 3FFF

1 KB

Reserved

0x4001 3800 - 0x4001 3BFF

1 KB

USART1

0x4001 3400 - 0x4001 37FF

1 KB

Reserved

0x4001 3000 - 0x4001 33FF

1 KB

SPI1

Section 40.6.8: SPI register map

APB2 0x4001 2C00 - 0x4001 2FFF

1 KB

TIM1

Section 26.4.29: TIM1 register map

0x4001 2800 - 0x4001 2BFF

1 KB

SDMMC(2) (3)

Section 43.8.16: SDMMC register map

0x4001 2000 - 0x4001 27FF

2 KB

Reserved

0x4001 1C00 - 0x4001 1FFF

1 KB

FIREWALL

0x4001 0800- 0x4001 1BFF

5 KB

Reserved

0x4001 0400 - 0x4001 07FF

1 KB

EXTI

0x4001 0200 - 0x4001 03FF
0x4001 0030 - 0x4001 01FF

Section 38.8.12: USART register map
-

-

1 KB

Section 4.4.8: Firewall register map
Section 13.5.13: EXTI register map

COMP

0x4001 0000 - 0x4001 002F

APB1

-

VREFBUF

Section 19.6.3: COMP register map
(3)

SYSCFG

Section 18.3.3: VREFBUF register map
Section 9.2.11: SYSCFG register map

0x4000 9800 - 0x4000 FFFF

26 KB

Reserved

0x4000 9400 - 0x4000 97FF

1 KB

LPTIM2

0x4000 8C00 - 0x4000 93FF

2 KB

Reserved

0x4000 8800 - 0x4000 8BFF

1 KB

SWPMI1(4)

Section 42.6.10: SWPMI register map and
reset value table

0x4000 8400 - 0x4000 87FF

1 KB

I2C4(5)

Section 37.7.12: I2C register map

0x4000 8000 - 0x4000 83FF

1 KB

LPUART1

Section 39.7.10: LPUART register map

0x4000 7C00 - 0x4000 7FFF

1 KB

LPTIM1

Section 30.7.13: LPTIM register map

0x4000 7800 - 0x4000 7BFF

1 KB

OPAMP

Section 20.5.4: OPAMP register map

0x4000 7400 - 0x4000 77FF

1 KB

DAC1

(3)

0x4000 7000 - 0x4000 73FF

1 KB

PWR

0x4000 6C00 - 0x4000 6FFF

1 KB

USB SRAM(6)

0x4000 6800 - 0x4000 6BFF

1 KB

USB FS(6)

0x4000 6400 - 0x4000 67FF

1 KB

CAN1(3)

Section 44.9: CAN registers

0x4000 6000 - 0x4000 63FF

1 KB

CRS

Section 7.6.5: CRS register map

0x4000 5C00- 0x4000 5FFF

1 KB

I2C3

Section 37.7.12: I2C register map

0x4000 5800 - 0x4000 5BFF

1 KB

I2C2

Section 37.7.12: I2C register map

RM0394 Rev 4

Section 30.7.13: LPTIM register map
-

Section 17.7.21: DAC register map
Section 5.4.20: PWR register map and reset
value table
Section 45.6.3: USB register map

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Table 2. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx memory map and peripheral register
boundary addresses (continued)
Bus

Boundary address

Size (bytes)

Peripheral

0x4000 5400 - 0x4000 57FF

1 KB

I2C1

0x4000 5000 - 0x4000 53FF

1 KB

Reserved

Peripheral register map
Section 37.7.12: I2C register map

(5)

Section 38.8.12: USART register map

0x4000 4C00 - 0x4000 4FFF

1 KB

USART4

0x4000 4800 - 0x4000 4BFF

1 KB

USART3

Section 38.8.12: USART register map

0x4000 4400 - 0x4000 47FF

1 KB

USART2

Section 38.8.12: USART register map

0x4000 4000 - 0x4000 43FF

1 KB

Reserved
(3)

Section 40.6.8: SPI register map

0x4000 3C00 - 0x4000 3FFF

1 KB

SPI3

0x4000 3800 - 0x4000 3BFF

1 KB

SPI2

0x4000 3400 - 0x4000 37FF

1 KB

Reserved

APB1 0x4000 3000 - 0x4000 33FF

1 KB

IWDG

Section 32.4.6: IWDG register map

0x4000 2C00 - 0x4000 2FFF

1 KB

WWDG

Section 33.4.4: WWDG register map

0x4000 2800 - 0x4000 2BFF

1 KB

RTC

Section 36.6.21: RTC register map

0x4000 2400 - 0x4000 27FF

1 KB

LCD(7)

Section 22.6.6: LCD register map

0x4000 1800 - 0x4000 2400

3 KB

Reserved

0x4000 1400 - 0x4000 17FF

1 KB

TIM7

(3) (8)

0x4000 1000 - 0x4000 13FF

1 KB

TIM6

0x4000 0800 - 0x4000 0FFF

2 KB

Reserved

0x4000 0400 - 0x4000 07FF

1 KB

TIM3(5)

Section 27.4.21: TIMx register map

0x4000 0000 - 0x4000 03FF

1 KB

TIM2

Section 27.4.21: TIMx register map

Section 40.6.8: SPI register map
-

Section 29.4.9: TIM6/TIM7 register map
Section 29.4.9: TIM6/TIM7 register map
-

1. Available on STM32L44xxx and STM32L46xxx devices only.
2. Not available on STM32L42xxx, STM32L432xx and STM32L442xx devices.
3. Not available on STM32L41xxx and STM32L42xxx devices.
4. Available on STM32L43xxx and STM32L44xxx devices only.
5. Available on STM32L45xxx and STM32L46xxx devices only.
6. Available on STM32L4x2xx and STM32L4x3xx devices only.
7. Available on STM32L4x3xx devices only.
8. Not available on STM32L45xxx and STM32L46xxx devices.

2.3

Bit banding
The Cortex®-M4 memory map includes two bit-band regions. These regions map each word
in an alias region of memory to a bit in a bit-band region of memory. Writing to a word in the
alias region has the same effect as a read-modify-write operation on the targeted bit in the
bit-band region.
In the STM32L43xxx/44xxx/45xxx/46xxx devices both the peripheral registers and the
SRAM1 are mapped to a bit-band region, so that single bit-band write and read operations
are allowed. The operations are only available for Cortex®-M4 accesses, and not from other
bus masters (e.g. DMA).

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A mapping formula shows how to reference each word in the alias region to a corresponding
bit in the bit-band region. The mapping formula is:
bit_word_addr = bit_band_base + (byte_offset x 32) + (bit_number × 4)
where:
–

bit_word_addr is the address of the word in the alias memory region that maps to
the targeted bit

–

bit_band_base is the starting address of the alias region

–

byte_offset is the number of the byte in the bit-band region that contains the
targeted bit

–

bit_number is the bit position (0-7) of the targeted bit

Example
The following example shows how to map bit 2 of the byte located at SRAM1 address
0x20000300 to the alias region:
0x22006008 = 0x22000000 + (0x300*32) + (2*4)
Writing to address 0x22006008 has the same effect as a read-modify-write operation on bit
2 of the byte at SRAM1 address 0x20000300.
Reading address 0x22006008 returns the value (0x01 or 0x00) of bit 2 of the byte at SRAM1
address 0x20000300 (0x01: bit set; 0x00: bit reset).
For more information on bit-banding, refer to the Cortex®-M4 programming manual (see
Related documents on page 1).

2.4

Embedded SRAM
The STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx devices feature up to 196 Kbytes
SRAM:
• Up to 128 Kbytes SRAM1
• Up to 32 Kbyte SRAM2.
These SRAM can be accessed as bytes, half-words (16 bits) or full words (32 bits). These
memories can be addressed at maximum system clock frequency without wait state and
thus by both CPU and DMA.
The CPU can access the SRAM1 through the system bus or through the ICode/DCode
buses when boot from SRAM1 is selected or when physical remap is selected
(Section 9.2.1: SYSCFG memory remap register (SYSCFG_MEMRMP) in the SYSCFG
controller). To get the maximum performance on SRAM1 execution, physical remap should
be selected (boot or software selection).
Execution can be performed from CCM SRAM with maximum performance without any
remap thanks to access through ICode bus.

2.4.1

SRAM2 parity check
The user can enable the SRAM2 parity check using the option bit SRAM2_PE in the user
option byte (refer to Section 3.4.1: Option bytes description).
The data bus width 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.

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The parity bits are computed and stored when writing into the SRAM2. Then, they are
automatically checked when reading. If one bit fails, an NMI is generated. The same error
can also be linked to the BRK_IN Break input of TIM1/TIM15/TIM16, with the SPL control bit
in the SYSCFG configuration register 2 (SYSCFG_CFGR2). The SRAM2 Parity Error flag
(SPF) is available in the SYSCFG configuration register 2 (SYSCFG_CFGR2).
Note:

When enabling the RAM parity check, it is advised to initialize by software the whole RAM
memory at the beginning of the code, to avoid getting parity errors when reading noninitialized locations.

2.4.2

SRAM2 Write protection
The SRAM2 can be write protected with a page granularity of 1 Kbyte.
Table 3. SRAM2 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

0x1000 1000

0x1000 13FF

Page 5

0x1000 1400

0x1000 17FF

Page 6

0x1000 1800

0x1000 1BFF

Page 7

0x1000 1C00

0x1000 1FFF

Table 4. SRAM2 organization
(continuation for STM32L43x/44x/45x/46x devices only)
Page number

Start address

End address

Page 8

0x1000 2000

0x1000 23FF

Page 9

0x1000 2400

0x1000 27FF

Page 10

0x1000 2800

0x1000 2BFF

Page 11

0x1000 2C00

0x1000 2FFF

Page 12

0x1000 3000

0x1000 33FF

Page 13

0x1000 3400

0x1000 37FF

Page 14

0x1000 3800

0x1000 3BFF

Page 15

0x1000 3C00

0x1000 3FFF

Table 5. SRAM2 organization
(continuation for STM32L45x and STM32L46x devices only)

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Page number

Start address

End address

Page 16

0x1000 4000

0x1000 43FF

Page 17

0x1000 4400

0x1000 47FF

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Table 5. SRAM2 organization
(continuation for STM32L45x and STM32L46x devices only) (continued)
Page number

Start address

End address

Page 18

0x1000 4800

0x1000 4BFF

Page 19

0x1000 4C00

0x1000 4FFF

Page 20

0x1000 5000

0x1000 53FF

Page 21

0x1000 5400

0x1000 57FF

Page 22

0x1000 5800

0x1000 5BFF

Page 23

0x1000 5C00

0x1000 5FFF

Page 24

0x1000 6000

0x1000 63FF

Page 25

0x1000 6400

0x1000 67FF

Page 26

0x1000 6800

0x1000 6BFF

Page 27

0x1000 6C00

0x1000 6FFF

Page 28

0x1000 7000

0x1000 73FF

Page 29

0x1000 7400

0x1000 77FF

Page 30

0x1000 7800

0x1000 7BFF

Page 31

0x1000 7C00

0x1000 7FFF

The write protection can be enabled in SYSCFG SRAM2 write protection register
(SYSCFG_SWPR) 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.

2.4.3

SRAM2 Read protection
The SRAM2 is protected with the Read protection (RDP). Refer to Section 3.5.1: Read
protection (RDP) for more details.

2.4.4

SRAM2 Erase
The SRAM2 can be erased with a system reset using the option bit SRAM2_RST in the user
option byte (refer to Section 3.4.1: Option bytes description).
The SRAM2 erase can also be requested by software by setting the bit SRAM2ER in the
SYSCFG SRAM2 control and status register (SYSCFG_SCSR).

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2.5

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 three parts:
–

Option bytes for hardware and memory protection user configuration.

–

System memory that contains the ST proprietary code.

–

OTP (one-time programmable) area

The Flash interface implements instruction access and data access based on the AHB
protocol. It also implements the logic necessary to carry out the Flash memory operations
(program/erase) controlled through the Flash registers Refer to Section 3: Embedded Flash
memory (FLASH) for more details.

2.6

Boot configuration
In the STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx, three different boot modes can be
selected through the BOOT0 pin or the nBOOT0 bit into the FLASH_OPTR register (if the
nSWBOOT0 bit is cleared into the FLASH_OPTR register), and nBOOT1 bit in the
FLASH_OPTR register, as shown in the following table.
Table 6. Boot modes
nBOOT1

nBOOT0

BOOT0

nSWBOOT0

FLASH_OPTR[23]

FLASH_OPTR[27]

pin PH3

FLASH_OPTR[26]

Main Flash
empty(1)

X

X

0

1

0

Main Flash memory is
selected as boot area

X

X

0

1

1

System memory is
selected as boot area

X

1

X

0

X

Main Flash memory is
selected as boot area

0

X

1

1

X

Embedded SRAM1 is
selected as boot area

0

0

X

0

X

Embedded SRAM1 is
selected as boot area

1

X

1

1

X

System memory is
selected as boot area

1

0

X

0

X

System memory is
selected as boot area

Boot Memory Space
Alias

1. A Flash empty check mechanism is implemented to force the boot from system Flash if the first Flash memory location is
not programmed (0xFFFF FFFF) and if the boot selection was configured to boot from the main Flash.

The values on both BOOT0 (coming from the pin or the option bit) and nBOOT1 bit are latched
on the 4th edge of the internal startup clock source after reset release. It is up to the user to
set nBOOT1 and BOOT0 to select the required boot mode.

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The BOOT0 pin or user option bit (depending on the nSWBOOT0 bit value in the
FLASH_OPTR register), and nBOOT1 bit are also re-sampled 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 SRAM1 is
accessible as follows:
•

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 0000).

•

Boot from the embedded SRAM1: the SRAM1 is aliased in the boot memory space
(0x0000 0000), but it is still accessible from its original memory space (0x2000 0000).

PH3/BOOT0 GPIO is configured in:

Note:

•

Input mode during the complete reset phase if the option bit nSWBOOT0 is set into the
FLASH_OPTR register and then switches automatically in analog mode after reset is
released (BOOT0 pin).

•

Input mode from the reset phase to the completion of the option byte loading if the bit
nSWBOOT0 is cleared into the FLASH_OPTR register (BOOT0 value coming from the
option bit). It switches then automatically to the analog mode even if the reset phase is
not complete.

When the device boots from SRAM, in the application initialization code, you have to
relocate the vector table in SRAM using the NVIC exception table and the offset register.

Physical remap
Once the boot mode is selected, the application software can modify the memory accessible
in the code area (in this way the code can be executed through the ICode bus in
place of the System bus). This modification is performed by programming the SYSCFG
memory remap register (SYSCFG_MEMRMP) in the SYSCFG controller.
The following memories can thus be remapped:
• Main Flash memory
• System memory
• Embedded SRAM1
• Quad-SPI memory
Table 7. Memory mapping vs. Boot mode/Physical remap
Addresses

Boot/Remap in
main Flash memory

Boot/Remap in
embedded
SRAM1

Boot/Remap in Remap in QUADSystem memory
SPI

0x2000 0000 - 0x2001 7FFFF(1)

SRAM1

SRAM1

SRAM1

SRAM1

0x1FFF 0000 - 0x1FFF FFFF

System memory/OTP/Options
bytes

System memory/OTP/Options
bytes

System memory/OTP/Options
bytes

System memory/OTP/Options
bytes

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Table 7. Memory mapping vs. Boot mode/Physical remap (continued)
Boot/Remap in
main Flash memory

Addresses
0x1008 0000(1) - 0x1FFE FFFF

Boot/Remap in
embedded
SRAM1

Boot/Remap in Remap in QUADSystem memory
SPI

Reserved

Reserved

Reserved

Reserved

SRAM2

SRAM2

SRAM2

SRAM2

Reserved

Reserved

Reserved

Reserved

0x0800 0000 - 0x0807 FFFF(1)

Flash memory

Flash memory

Flash memory

Flash memory

0x0400 0000 - 0x07FF FFFF

Reserved

Reserved

Reserved

QUADSPI bank
(128 MB) Aliased

0x0010 0000 - 0x03FF FFFF

Reserved

Reserved

Reserved

QUADSPI bank
(128 MB) Aliased

SRAM1 Aliased

System memory
Aliased

QUADSPI bank
(128 MB) Aliased

0x1000 0000 - 0x1007 FFFF
(1)

0x0808 0000

(1)

- 0x0FFF FFFF

0x0000 0000 - 0x000F FFFF(2) (3) Flash Aliased
1.

Address depends on the memory size available on given device.

2. When the QUADSPI is remapped at address 0x0000 0000, only 128 MB are remapped. In remap mode, the CPU can access the external memory via ICode bus instead of System bus which boosts up the performance.
3. Even when aliased in the boot memory space, the related memory is still accessible at its original memory space.

Embedded boot loader
The embedded boot loader is located in the System memory, programmed by ST during
production. Refer to AN2606 STM32 microcontroller system memory boot mode.

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Embedded Flash memory (FLASH)

3

Embedded Flash memory (FLASH)

3.1

Introduction
The Flash memory interface manages CPU AHB ICode and DCode accesses to the Flash
memory. It implements the erase and program Flash memory operations and the read and
write protection mechanisms.
The Flash memory interface accelerates code execution with a system of instruction
prefetch and cache lines.

3.2

FLASH main features
•

72-bit wide data read (64 bits plus 8 ECC bits)

•

72-bit wide data write (64 bits plus 8 ECC bits)

•

Page erase (2 Kbyte) and mass erase

Flash memory interface features:
•

Flash memory read operations

•

Flash memory program/erase operations

•

Read protection activated by option (RDP)

•

Prefetch on ICODE

•

Instruction Cache: 32 cache lines of 4 x 64 bits on ICode (1 KB RAM)

•

Data Cache: 8 cache lines of 4 x 64 bits on DCode (256B RAM)

•

Error Code Correction (ECC): 8 bits for 64-bit double-word

•

Option byte loader

•

Low-power mode

3.3

FLASH functional description

3.3.1

Flash memory organization
The Flash memory is organized as 72-bit wide memory cells (64 bits plus 8 ECC bits) that
can be used for storing both code and data constants.
The Flash memory is organized as follows:
•

An Information block containing:
–

System memory from which the device boots in System memory boot mode. The
area is reserved for use by STMicroelectronics and contains the boot loader that is
used to reprogram the Flash memory through one of the following interfaces:
USART1, USART2, USART3, USB (DFU), I2C1, I2C2, I2C3, SPI1, SPI2, SPI3. It
is programmed by STMicroelectronics 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.

–

1 Kbyte (128 double word) OTP (one-time programmable) bytes for user data. The
OTP data cannot be erased and can be written only once. If only one bit is at 0,

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the entire double word cannot be written anymore, even with the value 0x0000
0000 0000 0000.
–

Option bytes for user configuration.

The memory organization is based on a main area and an information block as shown in
Table 8.
Table 8. Flash module - single bank organization
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

-

-

-

0x0801 F800 - 0x0801 FFFF

2K

Page 63(1)

-

-

-

0x0803 F800 - 0x0803 FFFF

2K

Page 127(2)

-

-

-

0x0807 F800 - 0x0807 FFFF

2K

Page 255(3)

0x1FFF 0000 - 0x1FFF 6FFF

28 K

System memory

0x1FFF 7000 - 0x1FFF 73FF

1K

OTP area

0x1FFF 7800 - 0x1FFF 780F

16

Option bytes

Flash area

Main memory

Information block

1. Main Flash memory space of 128K devices is limited to page 63.
2. Main Flash memory space of 256K devices is limited to page 127.
3. Main Flash memory space of 512K devices is limited to page 255.

3.3.2

Error code correction (ECC)
Data in Flash memory are 72-bits words: 8 bits are added per double word (64 bits). The
ECC mechanism supports:
•

One error detection and correction

•

Two errors detection

When one error is detected and corrected, the flag ECCC (ECC correction) is set in Flash
ECC register (FLASH_ECCR). If ECCCIE is set, an interrupt is generated.
When two errors are detected, a flag ECCD (ECC detection) is set in FLASH_ECCR
register. In this case, a NMI is generated.
When an ECC error is detected, the address of the failing double word saved in
ADDR_ECC[20:0] in the FLASH_ECCR register. ADDR_ECC[2:0] are always cleared.
When ECCC or ECCD is set, ADDR_ECC not updated if a new ECC error occurs.
FLASH_ECCR is updated only when ECC flags are cleared.

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Note:

Embedded Flash memory (FLASH)
For a virgin data: 0xFF FFFF FFFF FFFF FFFF, one error is detected and corrected but two
errors detection is not supported.
When an ECC error is reported, a new read at the failing address may not generate an ECC
error if the data is still present in the current buffer, even if ECCC and ECCD are cleared.

3.3.3

Read access latency
To correctly read data from Flash memory, the number of wait states (LATENCY) must be
correctly programmed in the Flash access control register (FLASH_ACR) according to the
frequency of the CPU clock (HCLK) and the internal voltage range of the device VCORE.
Refer to Section 5.1.7: Dynamic voltage scaling management. Table 9 shows the
correspondence between wait states and CPU clock frequency.
Table 9. Number of wait states according to CPU clock (HCLK) frequency
HCLK (MHz)

Wait states (WS)
(LATENCY)

VCORE Range 1(1)

VCORE Range 2(2)

0 WS (1 CPU cycles)

≤ 16

≤6

1 WS (2 CPU cycles)

≤ 32

≤ 12

2 WS (3 CPU cycles)

≤ 48

≤ 18

3 WS (4 CPU cycles)

≤ 64

≤ 26

4 WS (5 CPU cycles)

≤ 80

≤ 26

1. Also for SMPS Range1 or SMPS Range2 high.
2. Also for SMPS Range2 low.

After reset, the CPU clock frequency is 4 MHz and 0 wait state (WS) is configured in the
FLASH_ACR register.
When changing the CPU frequency, the following software sequences must be applied in
order to tune the number of wait states needed to access the Flash memory:

Increasing the CPU frequency:
1.

Program the new number of wait states to the LATENCY bits in the Flash access
control register (FLASH_ACR).

2.

Check that the new number of wait states is taken into account to access the Flash
memory by reading the FLASH_ACR register.

3.

Modify the CPU clock source by writing the SW bits in the RCC_CFGR register.

4.

If needed, modify the CPU clock prescaler by writing the HPRE bits in RCC_CFGR.

5.

Check that the new CPU clock source or/and the new CPU clock prescaler value is/are
taken into account by reading the clock source status (SWS bits) or/and the AHB
prescaler value (HPRE bits), respectively, in the RCC_CFGR register.

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Decreasing the CPU frequency:

3.3.4

1.

Modify the CPU clock source by writing the SW bits in the RCC_CFGR register.

2.

If needed, modify the CPU clock prescaler by writing the HPRE bits in RCC_CFGR.

3.

Check that the new CPU clock source or/and the new CPU clock prescaler value is/are
taken into account by reading the clock source status (SWS bits) or/and the AHB
prescaler value (HPRE bits), respectively, in the RCC_CFGR register.

4.

Program the new number of wait states to the LATENCY bits in Flash access control
register (FLASH_ACR).

5.

Check that the new number of wait states is used to access the Flash memory by
reading the FLASH_ACR register.

Adaptive real-time memory accelerator (ART Accelerator™)
The proprietary Adaptive real-time (ART) memory accelerator is optimized for STM32
industry-standard Arm® Cortex®-M4 with FPU processors. It balances the inherent
performance advantage of the Arm® Cortex®-M4 with FPU over Flash memory
technologies, which normally requires the processor to wait for the Flash memory at higher
operating frequencies.
To release the processor full performance, the accelerator implements an instruction
prefetch queue and branch cache which increases program execution speed from the 64bit Flash memory. Based on CoreMark benchmark, the performance achieved thanks to the
ART accelerator is equivalent to 0 wait state program execution from Flash memory at a
CPU frequency up to 80 MHz.

Instruction prefetch
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.
Each Flash memory read operation provides 64 bits from either two instructions of 32 bits or
four instructions of 16 bits according to the program launched. This 64-bits current
instruction line is saved in a current buffer. So, in case of sequential code, at least two CPU
cycles are needed to execute the previous read instruction line. Prefetch on the ICode bus
can be used to read the next sequential instruction line from the Flash memory while the
current instruction line is being requested by the CPU.
Prefetch is enabled by setting the PRFTEN bit in the Flash access control register
(FLASH_ACR). This feature is useful if at least one wait state is needed to access the Flash
memory.
Figure 3 shows the execution of sequential 16-bit instructions with and without prefetch
when 3 WS are needed to access the Flash memory.

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Embedded Flash memory (FLASH)
Figure 3. Sequential 16-bit instructions execution
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When the code is not sequential (branch), the instruction may not be present in the currently
used instruction line or in the prefetched instruction line. In this case (miss), the penalty in
terms of number of cycles is at least equal to the number of wait states.

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If a loop is present in the current buffer, no new flash access is performed.

Instruction cache memory (I-Cache)
To limit the time lost due to jumps, it is possible to retain 32 lines of 4*64 bits in an instruction
cache memory.This feature can be enabled by setting the instruction cache enable (ICEN)
bit in the Flash access control register (FLASH_ACR). Each time a miss occurs (requested
data not present in the currently used instruction line, in the prefetched instruction line or in
the instruction cache memory), the line read is copied into the instruction cache memory. If
some data contained in the instruction cache memory are requested by the CPU, they are
provided without inserting any delay. Once all the instruction cache memory lines have been
filled, the LRU (least recently used) policy is used to determine the line to replace in the
instruction memory cache. This feature is particularly useful in case of code containing
loops.
The Instruction cache memory is enable after system reset.

Data cache memory (D-Cache)
Literal pools are fetched from Flash memory through the DCode bus during the execution
stage of the CPU pipeline. Each DCode bus read access fetches 64 bits which are saved in
a current buffer. The CPU pipeline is consequently stalled until the requested literal pool is
provided. To limit the time lost due to literal pools, accesses through the AHB databus
DCode have priority over accesses through the AHB instruction bus ICode.
If some literal pools are frequently used, the data cache memory can be enabled by setting
the data cache enable (DCEN) bit in the Flash access control register (FLASH_ACR). This
feature works like the instruction cache memory, but the retained data size is limited to 8
rows of 4*64 bits.
The Data cache memory is enable after system reset.
Note:

The D-Cache is active only when data is requested by the CPU (not by DMA1 and DMA2).
Data in option bytes block are not cacheable.

3.3.5

Flash program and erase operations
The STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx 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 contents of the Flash memory are not guaranteed if a device reset occurs during a
Flash memory operation.
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 program/erase
operation has completed.

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Embedded Flash memory (FLASH)

Unlocking the Flash memory
After reset, write is not allowed in the Flash control register (FLASH_CR) to protect the
Flash memory against possible unwanted operations due, for example, to electric
disturbances. The following sequence is used to unlock this register:
1.

Write KEY1 = 0x45670123 in the Flash key register (FLASH_KEYR)

2.

Write KEY2 = 0xCDEF89AB in the FLASH_KEYR register.

Any wrong sequence will lock up the FLASH_CR register until the next system reset. In the
case of a wrong key sequence, a bus error is detected and a Hard Fault interrupt is
generated.
The FLASH_CR register can be locked again by software by setting the LOCK bit in the
FLASH_CR register.
Note:

The FLASH_CR register cannot be written when the BSY bit in the Flash status register
(FLASH_SR) is set. Any attempt to write to it with the BSY bit set will cause the AHB bus to
stall until the BSY bit is cleared.

3.3.6

Flash main memory erase sequences
The Flash memory erase operation can be performed at page level or on the whole Flash
memory (Mass Erase). Mass Erase does not affect the Information block (system flash,
OTP and option bytes).

Page erase
To erase a page (2 Kbyte), follow the procedure below:

Note:

1.

Check that no Flash memory operation is ongoing by checking the BSY bit in the Flash
status register (FLASH_SR).

2.

Check and clear all error programming flags due to a previous programming. If not,
PGSERR is set.

3.

Set the PER bit and select the page you wish to erase (PNB) in the Flash control
register (FLASH_CR).

4.

Set the STRT bit in the FLASH_CR register.

5.

Wait for the BSY bit to be cleared in the FLASH_SR register.

The internal oscillator HSI16 (16 MHz) is enabled automatically when STRT bit is set, and
disabled automatically when STRT bit is cleared, except if the HSI16 is previously enabled
with HSION in RCC_CR register.
If the page erase is part of write-protected area (by WRP or PCROP), WRPERR is set and
the page erase request is aborted.

Mass erase
To perform a Mass Erase, follow the procedure below:

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Note:

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1.

Check that no Flash memory operation is ongoing by checking the BSY bit in the
FLASH_SR register.

2.

Check and clear all error programming flags due to a previous programming. If not,
PGSERR is set.

3.

Set the MER1 bit in the Flash control register (FLASH_CR).

4.

Set the STRT bit in the FLASH_CR register.

5.

Wait for the BSY bit to be cleared in the Flash control register (FLASH_CR).

The internal oscillator HSI16 (16 MHz) is enabled automatically when STRT bit is set, and
disabled automatically when STRT bit is cleared, except if the HSI16 is previously enabled
with HSION in RCC_CR register.
If the Flash memory contains a write-protected area (by WRP or PCROP), WRPERR is set
and the mass erase request is aborted.

3.3.7

Flash main memory programming sequences
The Flash memory is programmed 72 bits at a time (64 bits + 8 bits ECC).
Programming in a previously programmed address is not allowed except if the data to write
is full zero, and any attempt will set PROGERR flag in the Flash status register
(FLASH_SR).
It is only possible to program double word (2 x 32-bit data).
•

Any attempt to write byte or half-word will set SIZERR flag in the FLASH_SR register.

•

Any attempt to write a double word which is not aligned with a double word address will
set PGAERR flag in the FLASH_SR register.

Standard programming
The Flash memory programming sequence in standard mode is as follows:

Note:

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1.

Check that no Flash main memory operation is ongoing by checking the BSY bit in the
Flash status register (FLASH_SR).

2.

Check and clear all error programming flags due to a previous programming. If not,
PGSERR is set.

3.

Set the PG bit in the Flash control register (FLASH_CR).

4.

Perform the data write operation at the desired memory address, inside main memory
block or OTP area. Only double word can be programmed.
–

Write a first word in an address aligned with double word

–

Write the second word

5.

Wait until the BSY bit is cleared in the FLASH_SR register.

6.

Check that EOP flag is set in the FLASH_SR register (meaning that the programming
operation has succeed), and clear it by software.

7.

Clear the PG bit in the FLASH_CR register if there no more programming request
anymore.

When the flash interface has received a good sequence (a double word), programming is
automatically launched and BSY bit is set. The internal oscillator HSI16 (16 MHz) is enabled

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Embedded Flash memory (FLASH)
automatically when PG bit is set, and disabled automatically when PG bit is cleared, except
if the HSI16 is previously enabled with HSION in RCC_CR register.
If the user needs to program only one word, double word must be completed with the erase
value 0xFFFF FFFF to launch automatically the programming.
ECC is calculated from the double word to program.

Fast programming
This mode allows to program a row (32 double word) and to reduce the page programming
time by eliminating the need for verifying the flash locations before they are programmed
and to avoid rising and falling time of high voltage for each double word. During fast
programming, the CPU clock frequency (HCLK) must be at least 8 MHz.
Only the main memory can be programmed in Fast programming mode.
The Flash main memory programming sequence in standard mode is as follows:
1.

Perform a mass erase of the bank to program. If not, PGSERR is set.

2.

Check that no Flash main memory operation is ongoing by checking the BSY bit in the
Flash status register (FLASH_SR).

3.

Check and clear all error programming flag due to a previous programming.

4.

Set the FSTPG bit in Flash control register (FLASH_CR).

5.

Note:

Write the 32 double words to program a row. Only double words can be programmed:
–

Write a first word in an address aligned with double word

–

Write the second word.

6.

Wait until the BSY bit is cleared in the FLASH_SR register.

7.

Check that EOP flag is set in the FLASH_SR register (meaning that the programming
operation has succeed), and clear it by software.

8.

Clear the FSTPG bit in the FLASH_CR register if there no more programming request
anymore.

If the flash is attempted to be written in Fast programming mode while a read operation is on
going in the same bank, the programming is aborted without any system notification (no
error flag is set).
When the Flash interface has received the first double word, programming is automatically
launched. The BSY bit is set when the high voltage is applied for the first double word, and it
is cleared when the last double word has been programmed or in case of error. The internal
oscillator HSI16 (16 MHz) is enabled automatically when FSTPG bit is set, and disabled
automatically when FSTPG bit is cleared, except if the HSI16 is previously enabled with
HSION in RCC_CR register.
The 32 double word must be written successively. The high voltage is kept on the flash for
all the programming. Maximum time between two double words write requests is the time
programming (around 20us). If a second double word arrives after this time programming,
fast programming is interrupted and MISSERR is set.
High voltage mustn’t exceed 8 ms for a full row between 2 erases. This is guaranteed by the
sequence of 32 double words successively written with a clock system greater or equal to
8MHz. An internal time-out counter counts 7ms when Fast programming is set and stops the
programming when time-out is over. In this case the FASTERR bit is set.
If an error occurs, high voltage is stopped and next double word to programmed is not
programmed. Anyway, all previous double words have been properly programmed.

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Programming errors
Several kind of errors can be detected. In case of error, the Flash operation (programming
or erasing) is aborted.
•

PROGERR: Programming Error
In standard programming: PROGERR is set if the word to write is not previously erased
(except if the value to program is full zero).

•

SIZERR: Size Programming Error
In standard programming or in fast programming: only double word can be
programmed and only 32-bit data can be written. SIZERR is set if a byte or an halfword is written.

•

PGAERR: Alignment Programming error
PGAERR is set if one of the following conditions occurs:

•

–

In standard programming: the first word to be programmed is not aligned with a
double word address, or the second word doesn’t belong to the same double word
address.

–

In fast programming: the data to program doesn’t belong to the same row than the
previous programmed double words, or the address to program is not greater than
the previous one.

PGSERR: Programming Sequence Error
PGSERR is set if one of the following conditions occurs:

•

–

In the standard programming sequence or the fast programming sequence: a data
is written when PG and FSTPG are cleared.

–

In the standard programming sequence or the fast programming sequence: MER1
and PER are not cleared when PG or FSTPG is set.

–

In the fast programming sequence: the Mass erase is not performed before setting
FSTPG bit.

–

In the mass erase sequence: PG, FSTPG, and PER are not cleared when MER1 is
set.

–

PGSERR is set also if PROGERR, SIZERR, PGAERR, MISSERR, FASTERR or
PGSERR is set due to a previous programming error.

WRPERR: Write Protection Error
WRPERR is set if one of the following conditions occurs:

•

–

Attempt to program or erase in a write protected area (WRP) or in a PCROP area.

–

Attempt to perform a erase when one page or more is protected by WRP or
PCROP.

–

The debug features are connected or the boot is executed from SRAM or from
System flash when the read protection (RDP) is set to Level 1.

–

Attempt to modify the option bytes when the read protection (RDP) is set to
Level 2.

MISSERR: Fast Programming Data Miss Error
In fast programming: all the data must be written successively. MISSERR is set if the
previous data programmation is finished and the next data to program is not written yet.

•

FASTERR: Fast Programming Error
In fast programming: FASTERR is set if one of the following conditions occurs:
–

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Embedded Flash memory (FLASH)
–

When the row fast programming has been interrupted by a MISSERR, PGAERR,
WRPERR or SIZERR.

If an error occurs during a program or erase operation, one of the following error flags is set
in the FLASH_SR register:
PROGERR, SIZERR, PGAERR, PGSERR, MISSERR (Program error flags),
WRPERR (Protection error flag)
In this case, if the error interrupt enable bit ERRIE is set in the Flash status register
(FLASH_SR), an interrupt is generated and the operation error flag OPERR is set in the
FLASH_SR register.
Note:

If several successive errors are detected (for example, in case of DMA transfer to the Flash
memory), the error flags cannot be cleared until the end of the successive write requests.

Programming and caches
If a Flash memory write access concerns some data in the data cache, the Flash write
access modifies the data in the Flash memory and the data in the cache.
If an erase operation in Flash memory also concerns data in the data or instruction cache,
you have to make sure that these data are rewritten before they are accessed during code
execution. If this cannot be done safely, it is recommended to flush the caches by setting the
DCRST and ICRST bits in the Flash access control register (FLASH_ACR).
Note:

The I/D cache should be flushed only when it is disabled (I/DCEN = 0).

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3.4

FLASH option bytes

3.4.1

Option bytes description
The option bytes are configured by the end user depending on the application requirements.
As a configuration example, the watchdog may be selected in hardware or software mode
(refer to Section 3.4.2: Option bytes programming).
A double word is split up as follows in the option bytes:
Table 10. Option byte format

63-24

23-16

15 -8

7-0

Complemented Complemented Complemented Complemented
option byte 3
option byte 2
option byte 1
option byte 0

31-24

23-16

15 -8

7-0

Option
byte 3

Option
byte 2

Option
byte 1

Option
byte 0

The organization of these bytes inside the information block is as shown in Table 11: Option
byte organization.
The option bytes can be read from the memory locations listed in Table 11: Option byte
organization or from the Option byte registers:
•

Flash option register (FLASH_OPTR)

•

Flash PCROP Start address register (FLASH_PCROP1SR)

•

Flash PCROP End address register (FLASH_PCROP1ER)

•

Flash WRP area A address register (FLASH_WRP1AR)

•

Flash WRP area B address register (FLASH_WRP1BR)
Table 11. Option byte organization
63

[62:56]

0x1FFF 7800

[47:40]

[39:32]

USER OPT
Unused
PCROP_RDP

0x1FFF 7808

0x1FFF 7810

[55:48]

Unused

31

[30:24]

RDP

Unused

PCROP1_STRT

PCROP1_END

[23:16]

[15:8]

USER OPT

PCROP_RDP

Address

Unused

[7:0]
RDP

PCROP1_STRT

PCROP1_END

0x1FFF 7818

Unused

WRP1A
_END

Unused

WRP1A
_STRT

Unused

WRP1A_
END

Unused

WRP1A
_STRT

0x1FFF 7820

Unused

WRP1B
_END

Unused

WRP1B
_STRT

Unused

WRP1B_
END

Unused

WRP1B
_STRT

User and read protection option bytes
Flash memory address: 0x1FFF 7800
ST production value: 0xFFEF F8AA

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Embedded Flash memory (FLASH)

31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

Res.

27

nRST_ nRST_ nRST_
SHDW STDBY STOP
r

r

r

26

25

24

23

n
nSW SRAM2 SRAM2
n
BOOT0 BOOT0 _RST
_PE BOOT1
r

r

r

r

r

11

10

9

8

7

Res.

22

21

20

Res.

Res.

Res.

6

5

4

BOR_LEV[2:0]
r

r

19

18

17

16

WWDG IWGD_ IWDG_ IWDG_
_SW STDBY STOP
SW
r

r

r

r

3

2

1

0

r

r

r

RDP[7:0]
r

r

r

r

r

r

Bits 31:28 Reserved, must be kept at reset value.
Bit 27 nBOOT0: nBOOT0 option bit
0: nBOOT0 = 0
1: nBOOT0 = 1
Bit 26 nSWBOOT0: Software BOOT0
0: BOOT0 taken from the option bit nBOOT0
1: BOOT0 taken from PH3/BOOT0 pin
Bit 25 SRAM2_RST: SRAM2 Erase when system reset
0: SRAM2 erased when a system reset occurs
1: SRAM2 is not erased when a system reset occurs
Bit 24 SRAM2_PE: SRAM2 parity check enable
0: SRAM2 parity check enable
1: SRAM2 parity check disable
Bit 23 nBOOT1: Boot configuration
Together with the BOOT0 pin, this bit selects boot mode from the Flash main
memory, SRAM1 or the System memory. Refer to Section 2.6: Boot
configuration.
Bits 22:20 Reserved, must be kept at reset value.
Bit 19 WWDG_SW: Window watchdog selection
0: Hardware window watchdog
1: Software window watchdog
Bit 18 IWDG_STDBY: Independent watchdog counter freeze in Standby mode
0: Independent watchdog counter is frozen in Standby mode
1: Independent watchdog counter is running in Standby mode
Bit 17 IWDG_STOP: Independent watchdog counter freeze in Stop mode
0: Independent watchdog counter is frozen in Stop mode
1: Independent watchdog counter is running in Stop mode
Bit 16 IDWG_SW: Independent watchdog selection
0: Hardware independent watchdog
1: Software independent watchdog
Bit 15 Reserved, must be kept at reset value.
Bit 14 nRST_SHDW
0: Reset generated when entering the Shutdown mode
1: No reset generated when entering the Shutdown mode
Bit 13 nRST_STDBY
0: Reset generated when entering the Standby mode
1: No reset generate when entering the Standby mode

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Bit 12 nRST_STOP
0: Reset generated when entering the Stop mode
1: No reset generated when entering the Stop mode
Bit 11 Reserved, must be kept at reset value.
Bits10:8 BOR_LEV: BOR reset Level
These bits contain the VDD supply level threshold that activates/releases the
reset.
000: BOR Level 0. Reset level threshold is around 1.7 V
001: BOR Level 1. Reset level threshold is around 2.0 V
010: BOR Level 2. Reset level threshold is around 2.2 V
011: BOR Level 3. Reset level threshold is around 2.5 V
100: BOR Level 4. Reset level threshold is around 2.8 V
Bits 7:0 RDP: Read protection level
0xAA: Level 0, read protection not active
0xCC: Level 2, chip read protection active
Others: Level 1, memories read protection active

PCROP Start address option bytes
Flash memory address: 0x1FFF 7808
ST production value: 0xFFFF FFFF
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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

PCROP1_STRT[15:0]
r

r

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PCROP1_STRT: PCROP area start offset
PCROP1_STRT contains the first double-word of the PCROP area.

PCROP End address option bytes
Flash memory address: 0x1FFF 7810
ST production value: 0xFFFF 0000
31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PCROP
_RDP

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

r

r

r

r

r

r

r

r
15

PCROP1_END[15:0]
r

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r

r

r

r

r

r

r

r

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Embedded Flash memory (FLASH)

Bit 31 PCROP_RDP: PCROP area preserved when RDP level decreased
This bit is set only. It is reset after a full mass erase due to a change of RDP
from Level 1 to Level 0.
0: PCROP area is not erased when the RDP level is decreased from Level 1 to
Level 0.
1: PCROP area is erased when the RDP level is decreased from Level 1 to
Level 0 (full mass erase).
Bits 30:16 Reserved, must be kept at reset value.
Bits 15:0 PCROP1_END: Bank 1 PCROP area end offset
PCROP1_END contains the last double-word of the bank 1 PCROP area.

WRP Area A address option bytes
Flash memory address: 0x1FFF 7818
ST production value: 0xFF00 FFFF
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

WRP1A_END[7:0]
r

r

r

r

r

r

r

r

7

6

5

4

3

2

1

0

r

r

r

r

r

r

18

17

16

WRP1A_STRT[7:0]
r

r

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:16 WRP1A_END: WRP first area “A” end offset
WRPA1_END contains the last page of the WRP first area.
Bits 15:8 Reserved, must be kept at reset value.
Bits 7:0 WRP1A_STRT: WRP first area “A” start offset
WRPA1_STRT contains the first page of the WRP first area.

WRP Area B address option bytes
Flash memory address: 0x1FFF 7820
ST production value: 0xFF00 FFFF
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

WRP1B_END[7:0]
r

r

r

r

r

r

r

r

7

6

5

4

3

2

1

0

r

r

r

r

r

r

WRP1B_STRT[7:0]
r

r

Bits 31:24 Reserved, must be kept at reset value.

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Bits 23:16 WRP1B_END: WRP first area “B” end offset
WRPB1_END contains the last page of the WRP second area.
Bits 15:8 Reserved, must be kept at reset value.
Bits 7:0 WRP1B_STRT: WRP first area “B” start offset
WRPB1_STRT contains the first page of the WRP second area.

3.4.2

Option bytes programming
After reset, the options related bits in the Flash control register (FLASH_CR) are writeprotected. To run any operation on the option bytes page, the option lock bit OPTLOCK in
the Flash control register (FLASH_CR) must be cleared. The following sequence is used to
unlock this register:
1.

Unlock the FLASH_CR with the LOCK clearing sequence (refer to Unlocking the Flash
memory).

2.

Write OPTKEY1 = 0x08192A3B in the Flash option key register (FLASH_OPTKEYR).

3.

Write OPTKEY2 = 0x4C5D6E7F in the FLASH_OPTKEYR register.

The user options can be protected against unwanted erase/program operations by setting
the OPTLOCK bit by software.
Note:

If LOCK is set by software, OPTLOCK is automatically set too.

Modifying user options
The option bytes are programmed differently from a main memory user address.
To modify the user options value, follow the procedure below:

Note:

1.

Check that no Flash memory operation is on going by checking the BSY bit in the Flash
status register (FLASH_SR).

2.

Clear OPTLOCK option lock bit with the clearing sequence described above.

3.

Write the desired options value in the options registers: Flash option register
(FLASH_OPTR), Flash PCROP Start address register (FLASH_PCROP1SR), Flash
PCROP End address register (FLASH_PCROP1ER), Flash WRP area A address
register (FLASH_WRP1AR), Flash WRP area B address register (FLASH_WRP1BR).

4.

Set the Options Start bit OPTSTRT in the Flash control register (FLASH_CR).

5.

Wait for the BSY bit to be cleared.

Any modification of the value of one option is automatically performed by erasing user
option bytes pages first and then programming all the option bytes with the values contained
in the flash option registers.

Option byte loading
After the BSY bit is cleared, all new options are updated into the flash but they are not
applied to the system. They will have effect on the system when they are loaded. Option
bytes loading (OBL) is performed in two cases:
–

when OBL_LAUNCH bit is set in the Flash control register (FLASH_CR).

–

after a power reset (BOR reset or exit from Standby/Shutdown modes).

Option byte loader performs a read of the options block and stores the data into internal
option registers. These internal registers configure the system and cannot be read with by

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Embedded Flash memory (FLASH)
software. Setting OBL_LAUNCH generates a reset so the option byte loading is performed
under system reset.
Each option bit has also its complement in the same double word. During option loading, a
verification of the option bit and its complement allows to check the loading has correctly
taken place.
During option byte loading, the options are read by double word with ECC. If the word and
its complement are matching, the option word/byte is copied into the option register.
If the comparison between the word and its complement fails, a status bit OPTVERR is set.
Mismatch values are forced into the option registers:
–

For USR OPT option, the value of mismatch is all options at ‘1’, except for
BOR_LEV which is “000” (lowest threshold)

–

For WRP option, the value of mismatch is the default value “No protection”

–

For RDP option, the value of mismatch is the default value “Level 1”

–

For PCROP, the value of mismatch is “all memory protected”

On system reset rising, internal option registers are copied into option registers which can
be read and written by software (FLASH_OPTR, FLASH_PCROP1SR,
FLASH_PCROP1ER, FLASH_WRP1AR, FLASH_WRP1BR). These registers are also used
to modify options. If these registers are not modified by user, they reflects the options states
of the system. See Section : Modifying user options for more details.

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FLASH memory protection
The Flash main memory can be protected against external accesses with the Read
protection (RDP). The pages of the Flash memory can also be protected against unwanted
write due to loss of program counter contexts. The write-protection (WRP) granularity is one
page (2 KByte). Apart of the flash memory can also be protected against read and write
from third parties (PCROP). The PCROP granularity is double word (64-bit).

3.5.1

Read protection (RDP)
The read protection is activated by setting the RDP option byte and then, by applying a
system reset to reload the new RDP option byte. The read protection protects to the Flash
main memory, the option bytes, the backup registers (RTC_BKPxR in the RTC) and the
SRAM2.

Note:

If the read protection is set while the debugger is still connected through JTAG/SWD, apply
a POR (power-on reset) instead of a system reset.
There are three levels of read protection from no protection (level 0) to maximum protection
or no debug (level 2).
The Flash memory is protected when the RDP option byte and its complement contain the
pair of values shown in Table 12.
Table 12. Flash memory read protection status
RDP byte value

RDP complement value

Read protection level

0xAA

0x55

Level 0

Any value except 0xAA or
0xCC

Any value (not necessarily
complementary) except 0x55 and
0x33

Level 1 (default)

0xCC

0x33

Level 2

The System memory area is read accessible whatever the protection level. It is never
accessible for program/erase operation.

Level 0: no protection
Read, program and erase operations into the Flash main memory area are possible. The
option bytes, the SRAM2 and the backup registers are also accessible by all operations.

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Embedded Flash memory (FLASH)

Level 1: Read protection
This is the default protection level when RDP option byte is erased. It is defined as well
when RDP value is at any value different from 0xAA and 0xCC, or even if the complement is
not correct.
•
Caution:

User mode: Code executing in user mode (Boot Flash) can access Flash main
memory, option bytes, SRAM2 and backup registers with all operations.

In case the Level 1 is configured and no PCROP area is defined, it is mandatory to set
PCROP_RDP bit to 1 (full mass erase when the RDP level is decreased from Level 1 to
Level 0). In case the Level 1 is configured and a PCROP area is defined, if user code needs
to be protected by RDP but not by PCROP, it must not be placed in a page containing a
PCROP area.

Level 2: No debug
In this level, the protection level 1 is guaranteed. In addition, the Cortex®-M4 debug port, the
boot from RAM (boot RAM mode) and the boot from System memory (boot loader mode)
are no more available. In user execution mode (boot FLASH mode), all operations are
allowed on the Flash Main memory. On the contrary, only read operations can be performed
on the option bytes.
Option bytes cannot be programmed nor erased. Thus, the level 2 cannot be removed at all:
it is an irreversible operation. When attempting to modify the options bytes, the protection
error flag WRPERR is set in the Flash_SR register and an interrupt can be generated.
Note:

The debug feature is also disabled under reset.
STMicroelectronics is not able to perform analysis on defective parts on which the level 2
protection has been set.

Changing the Read protection level
It is easy to move from level 0 to level 1 by changing the value of the RDP byte to any value
(except 0xCC). By programming the 0xCC value in the RDP byte, it is possible to go to level
2 either directly from level 0 or from level 1. Once in level 2, it is no more possible to modify
the Read protection level.
When the RDP is reprogrammed to the value 0xAA to move from Level 1 to Level 0, a mass
erase of the Flash main memory is performed if PCROP_RDP is set in the Flash PCROP
End address register (FLASH_PCROP1ER). The backup registers (RTC_BKPxR in the
RTC) and the SRAM2 are also erased. The user options except PCROP protection are set
to their previous values copied from FLASH_OPTR, FLASH_WRPxyR (x=1 and y =A or B).
PCROP is disable. The OTP area is not affected by mass erase and remains unchanged.
If the bit PCROP_RDP is cleared in the FLASH_PCROP1ER, the full mass erase is
replaced by a partial mass erase that is successive page erases in the bank where PCROP
is active, except for the pages protected by PCROP. This is done in order to keep the
PCROP code. Only when the Flash memory is erased, options are re-programmed with
their previous values. This is also true for FLASH_PCROPxSR and FLASH_PCROPxER
registers (x=1).
Note:

Full Mass Erase or Partial Mass Erase is performed only when Level 1 is active and Level 0
requested. When the protection level is increased (0->1, 1->2, 0->2) there is no mass erase.
To validate the protection level change, the option bytes must be reloaded through the
OBL_LAUNCH bit in Flash control register.

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Figure 4. Changing the Read protection (RDP) level
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069

Table 13. Access status versus protection level and execution modes
Area

Flash main
memory
System
memory (2)

Protection
level

Debug/ BootFromRam/
BootFromLoader(1)

User execution (BootFromFlash)
Read

Write

Erase

Read

Write

Erase

1

Yes

Yes

Yes

No

No

No(3)

2

Yes

Yes

Yes

N/A

N/A

N/A

1

Yes

No

No

Yes

No

No

2

Yes

No

No

N/A

N/A

N/A

1

Yes

Yes(3)

Yes

Yes

Yes(3)

Yes

2

Yes

No

No

N/A

N/A

N/A

1

Yes

Yes(4)

N/A

No

No

N/A

2

Yes

Yes(4)

N/A

N/A

N/A

N/A

1

Yes

Yes

N/A

No

No

No(5)

2

Yes

Yes

N/A

N/A

N/A

N/A

Option bytes

OTP

Backup
registers

96/1600

RM0394 Rev 4

RM0394

Embedded Flash memory (FLASH)

Table 13. Access status versus protection level and execution modes (continued)
Protection
level

Area

Debug/ BootFromRam/
BootFromLoader(1)

User execution (BootFromFlash)
Read

Write

Erase

Read

Write

Erase

1

Yes

Yes

N/A

No

No

No(6)

2

Yes

Yes

N/A

N/A

N/A

N/A

SRAM2
1. When the protection level 2 is active, the Debug port, the boot from RAM and the boot from system memory are disabled.
2. The system memory is only read-accessible, whatever the protection level (0, 1 or 2) and execution mode.
3. The Flash main memory is erased when the RDP option byte is programmed with all level protections disabled (0xAA).
4. OTP can only be written once.
5. The backup registers are erased when RDP changes from level 1 to level 0.
6. The SRAM2 is erased when RDP changes from level 1 to level 0.

3.5.2

Proprietary code readout protection (PCROP)
Apart of the flash memory can be protected against read and write from third parties. The
protected area is execute-only: it can only be reached by the STM32 CPU, as an instruction
code, while all other accesses (DMA, debug and CPU data read, write and erase) are
strictly prohibited. The PCROP area has a double word (64-bit) granularity. An additional
option bit (PCROP_RDP) allows to select if the PCROP area is erased or not when the RDP
protection is changed from Level 1 to Level 0 (refer to Changing the Read protection level).
The PCROP area is defined by a start page offset and an end page offset. These offsets are
defined in the PCROP address registers Flash PCROP Start address register
(FLASH_PCROP1SR), Flash PCROP End address register (FLASH_PCROP1ER).
The PCROP area is defined from the address: Flash memory Base address +
[PCROP1_STRT x 0x8] (included) to the address: Flash memory Base address +
[(PCROP1_END+1) x 0x8] (excluded). The minimum PCROP area size is two double-words
(128 bits).
For example, to protect by PCROP from the address 0x0806 2F80 (included) to the address
0x0807 0004 (included):
•

if boot in flash is selected, FLASH_PCROP1SR and FLASH_PCROP1ER registers
must be programmed with:
–

PCROP1_STRT = 0xC5F0.

–

PCROP1_END = 0xE000.

Any read access performed through the D-bus to a PCROP protected area will trigger
RDERR flag error.
Any PCROP protected address is also write protected and any write access to one of these
addresses will trigger WRPERR.
Any PCROP area is also erase protected. Consequently, any erase to a page in this zone is
impossible (including the page containing the start address and the end address of this
zone). Moreover, a software mass erase cannot be performed if one zone is PCROP
protected.

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Embedded Flash memory (FLASH)

RM0394

For previous example, due to erase by page, all pages from page 0xC5 to 0xE0 are
protected in case of page erase. (All addresses from 0x0806 2800 to 0x0807 07FF can’t be
erased).
Deactivation of PCROP can only occurs when the RDP is changing from level 1 to level 0. If
the user options modification tries to clear PCROP or to decrease the PCROP area, the
options programming is launched but PCROP area stays unchanged. On the contrary, it is
possible to increase the PCROP area.
When option bit PCROP_RDP is cleared, when the RDP is changing from level 1 to level 0,
Full Mass Erase is replaced by Partial Mass Erase in order to keep the PCROP area (refer
to Changing the Read protection level). In this case, PCROP1_STRT and PCROP1_END
are also not erased.
Note:

It is recommended to align PCROP area with page granularity when using PCROP_RDP, or
to leave free the rest of the page where PCROP zone starts or ends.

3.5.3

Write protection (WRP)
The user area in Flash memory can be protected against unwanted write operations. Two
write-protected (WRP) areas can be defined, with page (2 KByte) granularity. The area is
defined by a start page offset and an end page offset related to the physical Flash memory
base address. These offsets are defined in the WRP address registers: Flash WRP area A
address register (FLASH_WRP1AR), Flash WRP area B address register
(FLASH_WRP1BR).
The WRP “y” area (y=A,B) is defined from the address: Flash memory Base address +
[WRP1y_STRT x 0x800] (included) to the address: Flash memory Base address +
[(WRP1y_END+1) x 0x800] (excluded).
For example, to protect by WRP from the address 0x0806 2800 (included) to the address
0x0807 07FF (included):
•

if boot in flash is selected, FLASH_WRP1AR register must be programmed with:
–

WRP1A_STRT = 0xC5.

–

WRP1A_END = 0xE0.

WRP1B_STRT and WRP1B_END in FLASH_WRP1BR can be used instead (area “B”
in Flash memory).
When WRP is active, it cannot be erased or programmed. Consequently, a software mass
erase cannot be performed if one area is write-protected.
If an erase/program operation to a write-protected part of the Flash memory is attempted,
the write protection error flag (WRPERR) is set in the FLASH_SR register. This flag is also
set for any write access to:

Note:

98/1600

–

OTP area

–

part of the Flash memory that can never be written like the ICP

–

PCROP area.

When the memory read protection level is selected (RDP level = 1), it is not possible to
program or erase Flash memory if the CPU debug features are connected (JTAG or single
wire) or boot code is being executed from RAM or System flash, even if WRP is not
activated.

RM0394 Rev 4

RM0394

Embedded Flash memory (FLASH)

Note:

To validate the WRP options, the option bytes must be reloaded through the OBL_LAUNCH
bit in Flash control register.

3.6

FLASH interrupts
Table 14. Flash interrupt request
Interrupt event

Event flag

Event flag/interrupt
clearing method

Interrupt enable control
bit

End of operation

EOP(1)

Write EOP=1

EOPIE

Operation error

OPERR(2)

Write OPERR=1

ERRIE

RDERR

Write RDERR=1

RDERRIE

ECCC

Write ECCC=1

ECCCIE

Read error
ECC correction
1. EOP is set only if EOPIE is set.
2. OPERR is set only if ERRIE is set.

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113

Embedded Flash memory (FLASH)

RM0394

3.7

FLASH registers

3.7.1

Flash access control register (FLASH_ACR)
Address offset: 0x00
Reset value: 0x0000 0600
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

SLEEP
_PD

DCEN

ICEN

PRFTEN

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

RUN_
DCRST ICRST
PD

rw

rw

rw

rw

LATENCY[2:0]
rw

rw

rw

--

Bits 31:15 Reserved, must be kept at reset value.
Bit 14 SLEEP_PD: Flash Power-down mode during Sleep or Low-power sleep mode
This bit determines whether the flash memory is in Power-down mode or Idle
mode when the device is in Sleep or Low-power sleep mode.
0: Flash in Idle mode during Sleep and Low-power sleep modes
1: Flash in Power-down mode during Sleep and Low-power sleep modes
Caution: The flash must not be put in power-down while a program or an erase
operation is on-going.
Bit 13 RUN_PD: Flash Power-down mode during Run or Low-power run mode
This bit is write-protected with FLASH_PDKEYR.
This bit determines whether the flash memory is in Power-down mode or Idle
mode when the device is in Run or Low-power run mode. The flash memory can
be put in power-down mode only when the code is executed from RAM. The
Flash must not be accessed when RUN_PD is set.
0: Flash in Idle mode
1: Flash in Power-down mode
Caution: The flash must not be put in power-down while a program or an erase
operation is on-going.
Bit 12 DCRST: Data cache reset
0: Data cache is not reset
1: Data cache is reset
This bit can be written only when the data cache is disabled.
Bit 11 ICRST: Instruction cache reset
0: Instruction cache is not reset
1: Instruction cache is reset
This bit can be written only when the instruction cache is disabled.
Bit 10 DCEN: Data cache enable
0: Data cache is disabled
1: Data cache is enabled

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RM0394 Rev 4

RM0394

Embedded Flash memory (FLASH)

Bit 9 ICEN: Instruction cache enable
0: Instruction cache is disabled
1: Instruction cache is enabled
Bit 8 PRFTEN: Prefetch enable
0: Prefetch disabled
1: Prefetch enabled
Bits 7:3 Reserved, must be kept at reset value.
Bits 2:0 LATENCY[2:0]: Latency
These bits represent the period to the Flash access time.
000: Zero wait state
001: One wait state
010: Two wait states
011: Three wait states
100: Four wait states
others: Reserved

3.7.2

Flash Power-down key register (FLASH_PDKEYR)
Address offset: 0x04
Reset value: 0x0000 0000
Access: no wait state, word access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PDKEYR[31:16]
w

w

w

w

w

w

w

15

14

13

12

11

10

9

w

w

w

w

w

w

w

w

w

8

7

6

5

4

3

2

1

0

w

w

w

w

w

w

w

PDKEYR[15:0]
w

w

w

w

w

w

w

w

w

Bits 31:0 PDKEYR: Power-down in Run mode Flash key
The following values must be written consecutively to unlock the RUN_PD bit in
FLASH_ACR:
PDKEY1: 0x0415 2637
PDKEY2: 0xFAFB FCFD

3.7.3

Flash key register (FLASH_KEYR)
Address offset: 0x08
Reset value: 0x0000 0000
Access: no wait state, word access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

KEYR[31:16]
w

w

w

w

w

w

w

15

14

13

12

11

10

9

w

w

w

w

w

w

w

w

w

8

7

6

5

4

3

2

1

0

w

w

w

w

w

w

w

KEYR[15:0]
w

w

w

w

w

w

w

w

w

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RM0394

Bits 31:0 KEYR: Flash key
The following values must be written consecutively to unlock the FLASH_CR
register allowing flash programming/erasing operations:
KEY1: 0x4567 0123
KEY2: 0xCDEF 89AB

3.7.4

Flash option key register (FLASH_OPTKEYR)
Address offset: 0x0C
Reset value: 0x0000 0000
Access: no wait state, word access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

OPTKEYR[31:16]
w

w

w

w

w

w

w

15

14

13

12

11

10

9

w

w

w

w

w

w

w

w

w

8

7

6

5

4

3

2

1

0

w

w

w

w

w

w

w

OPTKEYR[15:0]
w

w

w

w

w

w

w

w

w

Bits 31:0 OPTKEYR: Option byte key
The following values must be written consecutively to unlock the FLASH_OPTR
register allowing option byte programming/erasing operations:
KEY1: 0x0819 2A3B
KEY2: 0x4C5D 6E7F

3.7.5

Flash status register (FLASH_SR)
Address offset: 0x10
Reset value:
Access: no wait state, word, half-word and byte access

31
Res.

30
Res.

15

14

OPTV
ERR

RD
ERR

rc_w1

rc_w1

102/1600

29
Res.

13
Res.

28
Res.

12
Res.

27
Res.

11
Res.

26
Res.

25
Res.

24
Res.

23
Res.

22
Res.

21
Res.

20
Res.

19
Res.

10

9

8

7

6

5

4

3

Res.

FAST
ERR

MISS
ERR

PGS
ERR

SIZ
ERR

PGA
ERR

WRP
ERR

PROG
ERR

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

rc_w1

RM0394 Rev 4

18

17

16

Res.

PEMPT
Y

BSY

rs

r

2

1

0

Res.

OP
ERR

EOP

rc_w1

rc_w1

RM0394

Embedded Flash memory (FLASH)

Bits 31:18 Reserved, must be kept at reset value.
Bit 17 PEMPTY: Program EMPTY
Set by hardware on power-on reset or after OBL_LAUNCH command execution
if the Flash is not programmed and the user intends to boot from the main Flash.
Cleared by hardware on power-on reset or after OBL_LAUNCH command
execution if the Flash is programmed and the user intends to boot from main
Flash. This bit can also be set and cleared by software.
1: The bit value is toggling
0: No effect
This bit can be set to clear the Program Empty bit if an OBL_LAUNCH is done by
software after Flash programming (boot in main flash selected). It finally forces
the boot in the main flash, without loosing the debugger connection.
Bit 16 BSY: Busy
This indicates that a Flash operation is in progress. This is set on the beginning
of a Flash operation and reset when the operation finishes or when an error
occurs.
Bit 15 OPTVERR: Option validity error
Set by hardware when the options read may not be the one configured by the
user. If option haven’t been properly loaded, OPTVERR is set again after each
system reset.
Cleared by writing 1.
Bit 14 RDERR: PCROP read error
Set by hardware when an address to be read through the D-bus belongs to a
read protected area of the flash (PCROP protection). An interrupt is generated if
RDERRIE is set in FLASH_CR.
Cleared by writing 1.
Bits 13:10 Reserved, must be kept at reset value.
Bit 9 FASTERR: Fast programming error
Set by hardware when a fast programming sequence (activated by FSTPG) is
interrupted due to an error (alignment, size, write protection or data miss). The
corresponding status bit (PGAERR, SIZERR, WRPERR or MISSERR) is set at
the same time.
Cleared by writing 1.
Bit 8 MISERR: Fast programming data miss error
In Fast programming mode, 32 double words must be sent to flash successively,
and the new data must be sent to the flash logic control before the current data is
fully programmed. MISSERR is set by hardware when the new data is not
present in time.
Cleared by writing 1.
Bit 7 PGSERR: Programming sequence error
Set by hardware when a write access to the Flash memory is performed by the
code while PG or FSTPG have not been set previously. Set also by hardware
when PROGERR, SIZERR, PGAERR, MISSERR or FASTERR is set due to a
previous programming error.
Cleared by writing 1.

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113

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RM0394

Bit 6 SIZERR: Size error
Set by hardware when the size of the access is a byte or half-word during a
program or a fast program sequence. Only double word programming is allowed
(consequently: word access).
Cleared by writing 1.
Bit 5 PGAERR: Programming alignment error
Set by hardware when the data to program cannot be contained in the same 64bit Flash memory row in case of standard programming, or if there is a change of
page during fast programming.
Cleared by writing 1.
Bit 4 WRPERR: Write protection error
Set by hardware when an address to be erased/programmed belongs to a writeprotected part (by WRP, PCROP or RDP level 1) of the Flash memory.
Cleared by writing 1.
Bit 3 PROGERR: Programming error
Set by hardware when a double-word address to be programmed contains a
value different from '0xFFFF FFFF' before programming, except if the data to
write is '0x0000 0000'.
Cleared by writing 1.
Bit 2 Reserved, must be kept at reset value.
Bit 1 OPERR: Operation error
Set by hardware when a Flash memory operation (program / erase) completes
unsuccessfully.
This bit is set only if error interrupts are enabled (ERRIE = 1).
Cleared by writing ‘1’.
Bit 0 EOP: End of operation
Set by hardware when one or more Flash memory operation (programming /
erase) has been completed successfully.
This bit is set only if the end of operation interrupts are enabled (EOPIE = 1).
Cleared by writing 1.

3.7.6

Flash control register (FLASH_CR)
Address offset: 0x14
Reset value: 0xC000 0000
Access: no wait state when no Flash memory operation is on going, word, half-word and
byte access

31

30

LOCK

OPT
LOCK

29

28

27

26

25

24

Res.

Res.

OBL_
LAUNCH

RD
ERRIE

ERR
IE

EOP
IE

rs

rs

rc_w1

rw

rw

rw

15

14

13

12

11

10

9

8

Res.

Res.

Res.

Res.

Res.

22

21

20

19

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

PNB[7:0]
rw

104/1600

23

rw

rw

rw

RM0394 Rev 4

rw

rw

rw

rw

18

17

16

FSTPG

OPT
STRT

STRT

rw

rs

rs

2

1

0

MER1

PER

PG

rw

rw

rw

RM0394

Embedded Flash memory (FLASH)

Bit 31 LOCK: FLASH_CR Lock
This bit is set only. When set, the FLASH_CR register is locked. It is cleared by
hardware after detecting the unlock sequence.
In case of an unsuccessful unlock operation, this bit remains set until the next
system reset.
Bit 30 OPTLOCK: Options Lock
This bit is set only. When set, all bits concerning user option in FLASH_CR
register and so option page are locked. This bit is cleared by hardware after
detecting the unlock sequence. The LOCK bit must be cleared before doing the
unlock sequence for OPTLOCK bit.
In case of an unsuccessful unlock operation, this bit remains set until the next
reset.
Bits 29:28 Reserved, must be kept at reset value.
Bit 27 OBL_LAUNCH: Force the option byte loading
When set to 1, this bit forces the option byte reloading. This bit is cleared only
when the option byte loading is complete. It cannot be written if OPTLOCK is set.
0: Option byte loading complete
1: Option byte loading requested
Bit 26 RDERRIE: PCROP read error interrupt enable
This bit enables the interrupt generation when the RDERR bit in the FLASH_SR
is set to 1.
0: PCROP read error interrupt disabled
1: PCROP read error interrupt enabled
Bit 25 ERRIE: Error interrupt enable
This bit enables the interrupt generation when the OPERR bit in the FLASH_SR
is set to 1.
0: OPERR error interrupt disabled
1: OPERR error interrupt enabled
Bit 24 EOPIE: End of operation interrupt enable
This bit enables the interrupt generation when the EOP bit in the FLASH_SR is
set to 1.
0: EOP Interrupt disabled
1: EOP Interrupt enabled
Bits 23:19 Reserved, must be kept at reset value
Bit 18 FSTPG: Fast programming
0: Fast programming disabled
1: Fast programming enabled
Bit 17 OPTSTRT: Options modification start
This bit triggers an options operation when set.
This bit is set only by software, and is cleared when the BSY bit is cleared in
FLASH_SR.
Bit 16 STRT: Start
This bit triggers an erase operation when set. If MER1, MER2 and PER bits are
reset and the STRT bit is set, an unpredictable behavior may occur without
generating any error flag. This condition should be forbidden.
This bit is set only by software, and is cleared when the BSY bit is cleared in
FLASH_SR.
Bits 15:11 Reserved, must be kept at reset value.

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113

Embedded Flash memory (FLASH)

RM0394

Bits 10:3 PNB[7:0]: Page number selection
These bits select the page to erase:
00000000: page 0
00000001: page 1
...
11111111: page 255
Note: Bit 10 is used on STM32L45x and STM32L46x devices only.
Bit 2 MER1: Mass erase
This bit triggers the mass erase (all user pages) when set.
Bit 1 PER: Page erase
0: page erase disabled
1: page erase enabled
Bit 0 PG: Programming
0: Flash programming disabled
1: Flash programming enabled

3.7.7

Flash ECC register (FLASH_ECCR)
Address offset: 0x18
Reset value: 0x0000 0000
Access: no wait state when no Flash memory operation is on going, word, half-word and
byte access

31

30

ECCD

ECCC

rc_w1

rc_w1

15

r

29

28

27

26

25

24
ECCC
IE

Res.

Res.

Res.

Res.

Res.

14

13

12

11

10

9

r

r

r

r

r

r

23

22

21

20

19
Res.

17

16

Res.

Res.

Res.

r

r

r

7

6

5

4

3

2

1

0

r

r

r

r

r

r

r

rw
8

18

SYSF_
ECC
r

ADDR_ECC[18:16]

ADDR_ECC[15:0]
r

r

Bit 31 ECCD: ECC detection
Set by hardware when two ECC errors have been detected. When this bit is set,
a NMI is generated
Cleared by writing 1.
Bit 30 ECCC: ECC correction
Set by hardware when one ECC error has been detected and corrected. An
interrupt is generated if ECCIE is set.
Cleared by writing 1.
Bits 29:25 Reserved, must be kept at reset value.
Bit 24 ECCIE: ECC correction interrupt enable
0: ECCC interrupt disabled
1: ECCC interrupt enabled.
Bits 23:21 Reserved, must be kept at reset value.

106/1600

RM0394 Rev 4

RM0394

Embedded Flash memory (FLASH)

Bit 20 SYSF_ECC: System Flash ECC fail
This bit indicates that the ECC error correction or double ECC error detection is
located in the System Flash.
Bit 19 Reserved, must be kept at reset value.
Bits 18:0 ADDR_ECC: ECC fail address
This bit indicates which address in the bank is concerned by the ECC error
correction or by the double ECC error detection.

3.7.8

Flash option register (FLASH_OPTR)
Address offset: 0x20
Reset value: 0xXXXX XXXX. Register bits 0 to 31 are loaded with values from Flash
memory at OBL.
Access: no wait state when no Flash memory operation is on going; word, half-word and
byte access

31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

Res.

nRST_ nRST_ nRST_
SHDW STDBY STOP
rw

rw

rw

27

26

25

24

23

n
nSW SRAM2 SRAM2 nBOOT
BOOT0 BOOT0 _RST
_PE
1
rw

rw

rw

rw

rw

11

10

9

8

7

Res.

22

21

Res.

Res.

Res.

6

5

4

BOR_LEV[2:0]
rw

rw

20

19

18

17

16

WWDG IWGD_ IWDG_ IWDG_
_SW STDBY StOP
SW
rw

rw

rw

rw

3

2

1

0

rw

rw

rw

RDP[7:0]
rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bit 27 nBOOT0: nBOOT0 option bit
0: nBOOT0 = 0
1: nBOOT0 = 1
Bit 26 nSWBOOT0: Software BOOT0
0: BOOT0 taken from the option bit nBOOT0
1: BOOT0 taken from PH3/BOOT0 pin
Bit 25 SRAM2_RST: SRAM2 Erase when system reset
0: SRAM2 erased when a system reset occurs
1: SRAM2 is not erased when a system reset occurs
Bit 24 SRAM2_PE: SRAM2 parity check enable
0: SRAM2 parity check enable
1: SRAM2 parity check disable
Bit 23 nBOOT1: Boot configuration
Together with the BOOT0 pin, this bit selects boot mode from the Flash main
memory, SRAM1 or the System memory. Refer to Section 2.6: Boot
configuration.
Bits 22:20 Reserved, must be kept at reset value.
Bit 19 WWDG_SW: Window watchdog selection
0: Hardware window watchdog
1: Software window watchdog

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113

Embedded Flash memory (FLASH)

RM0394

Bit 18 IWDG_STDBY: Independent watchdog counter freeze in Standby mode
0: Independent watchdog counter is frozen in Standby mode
1: Independent watchdog counter is running in Standby mode
Bit 17 IWDG_STOP: Independent watchdog counter freeze in Stop mode
0: Independent watchdog counter is frozen in Stop mode
1: Independent watchdog counter is running in Stop mode
Bit 16 IDWG_SW: Independent watchdog selection
0: Hardware independent watchdog
1: Software independent watchdog
Bit 15 Reserved, must be kept at reset value
Bit 14 nRST_SHDW
0: Reset generated when entering the Shutdown mode
1: No reset generated when entering the Shutdown mode
Bit 13 nRST_STDBY
0: Reset generated when entering the Standby mode
1: No reset generate when entering the Standby mode
Bit 12 nRST_STOP
0: Reset generated when entering the Stop mode
1: No reset generated when entering the Stop mode
Bit 11 Reserved, must be kept at reset value
Bits10:8 BOR_LEV: BOR reset Level
These bits contain the VDD supply level threshold that activates/releases the
reset.
000: BOR Level 0. Reset level threshold is around 1.7 V
001: BOR Level 1. Reset level threshold is around 2.0 V
010: BOR Level 2. Reset level threshold is around 2.2 V
011: BOR Level 3. Reset level threshold is around 2.5 V
100: BOR Level 4. Reset level threshold is around 2.8 V
Bits 7:0 RDP: Read protection level
0xAA: Level 0, read protection not active
0xCC: Level 2, chip read protection active
Others: Level 1, memories read protection active
Note: Take care about PCROP_RDP configuration in Level 1. Refer to Section :
Level 1: Read protection for more details.

108/1600

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RM0394

Embedded Flash memory (FLASH)

3.7.9

Flash PCROP Start address register (FLASH_PCROP1SR)
Address offset: 0x24
Reset value: 0xFFFF XXXX. Register bits are loaded with values from Flash memory at
OBL. Reserved bits are read as “1”.
Access: no wait state when no Flash memory operation is on going; word, half-word 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

rw

rw

rw

rw

rw

rw

rw

PCROP1_STRT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value
Bits 15:0 PCROP1_STRT: PCROP area start offset
PCROP1_STRT contains the first double-word of the PCROP area.

3.7.10

Flash PCROP End address register (FLASH_PCROP1ER)
Address offset: 0x28
Reset value: 0xXFFF XXXX. Register bits are loaded with values from Flash memory at
OBL. Reserved bits are read as “1”.
Access: no wait state when no Flash memory operation is on going; word, half-word access.
PCROP_RDP bit can be accessed with byte access.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

PCROP
_RDP

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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

rs

PCROP1_END[15:0]
rw

rw

Bit 31 PCROP_RDP: PCROP area preserved when RDP level decreased
This bit is set only. It is reset after a full mass erase due to a change of RDP
from Level 1 to Level 0.
0: PCROP area is not erased when the RDP level is decreased from Level 1 to
Level 0.
1: PCROP area is erased when the RDP level is decreased from Level 1 to
Level 0 (full mass erase).
Bits 30:16 Reserved, must be kept at reset value
Bits 15:0 PCROP1_END: PCROP area end offset
PCROP1_END contains the last double-word of the PCROP area.

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Embedded Flash memory (FLASH)

3.7.11

RM0394

Flash WRP area A address register (FLASH_WRP1AR)
Address offset: 0x2C
Reset value: 0xFFXX FFXX. Register bits are loaded with values from Flash memory at
OBL. Reserved bits are read as “1”.
Access: no wait state when no Flash memory operation is on going; word, half-word and
byte access

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

WRP1A_END[7:0]
rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

WRP1A_STRT[7:0]
rw

rw

rw

rw

rw

Bits 31:24 Reserved, must be kept at reset value
Bits 23:16 WRP1A_END: WRP first area “A” end offset
WRP1A_END contains the last page of the WRP first area.
Note: Number of used bits depends on the size of Flash memory available on
given device.
Bits 15:8 Reserved, must be kept at reset value
Bits 7:0 WRP1A_STRT: WRP first area “A” start offset
WRP1A_STRT contains the first page of the WRP first area.
Note: Number of used bits depends on the size of Flash memory available on
given device.

3.7.12

Flash WRP area B address register (FLASH_WRP1BR)
Address offset: 0x30
Reset value: 0xFFXX FFXX. Register bits are loaded with values from Flash memory at
OBL. Reserved bits are read at “1”.
Access: no wait state when no Flash memory operation is on going; word, half-word and
byte access

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

rw

rw

rw

rw

7

6

5

4

19

18

17

16

rw

rw

rw

rw

3

2

1

0

rw

rw

rw

WRP1B_END[7:0]

WRP1B_STRT[7:0]
rw

110/1600

20

RM0394 Rev 4

rw

rw

rw

rw

RM0394

Embedded Flash memory (FLASH)

Bits 31:24 Reserved, must be kept at reset value
Bits 23:16 WRP1B_END: WRP second area “B” end offset
WRP1B_END contains the last page of the WRP second area.
Note: Number of used bits depends on the size of Flash memory available on
given device.
Bits 15:8 Reserved, must be kept at reset value
Bits 7:0 WRP1B_STRT: WRP second area “B” start offset
WRP1B_STRT contains the first page of the WRP second area.
Note: Number of used bits depends on the size of Flash memory available on
given device.

RM0394 Rev 4

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113

Embedded Flash memory (FLASH)

3.7.13

RM0394

FLASH register map

ICEN

PRFTEN

1

1

0

FLASH_
PDKEYR
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

FLASH_OPT
KEYR

0

0

0

0

0

0

0

0

0

0

0

112/1600

0

0

0

0

0

0

0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

0

0

0

0

0

0

0

0

0

X

0

0

0

0

0

0

Res.

Res.

Res.

0

IWDG_SW

Res.
nRST_SHDW

nRST_STDBY

nRST_STOP

Res.

Res.

Res.

IWDG_STOP

Res.

Res.

nBOOT1

Res.

Res.

SRAM2_PE

Res.

Res.

nSWBOOT0
SRAM2_RST

FLASH_
PCROP1SR

Res.

X

nBOOT0

X

X

Res.

X

X

X

X

X

X

X

RM0394 Rev 4

X

X

X

X

X

Res.
X

X

X

X

X

X

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

RDP[7:0]

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Res.

Res.

Res.

Res.

Res.

PCROP1_END[15:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.
Res.

Res.
Res.

Res.
Res.

Res.

Res.
Res.

WRP1A_END[7:0]
X

0

0

PCROP1_STRT[15:0]
X

Res.

0

X

X

Res.

0

X

X

Res.

0

X

X

PCROP_RDP.

0

X

X

X

0

X

X

FLASH_
WRP1AR

0

X

X

X

0

IWDG_STBY

0

Res.

0

WWDG_SW

0

Res.

0

X

X

Reset value

0

BOR_
LEV[2:0]

Reset value

0

0

ADDR_ECC[18:0]

0

FLASH_OPTR

FLASH_
PCROP1ER

0

Res.

0

0

0

PNB[7:0]

0

Res.
SYSF_ECC

Res.
Res.

0

EOP

Res.
Res.
Res.

0

PG

Res.
EOPIE

Res.
ECCCIE

0

PER

Res.
ERRIE

Res.

0

Res.
OPERR

Res.
RDERRIE

Res.

0

MER1

Res.

0

0

PROGERR

Res.

Res.
OBL_LAUNCH

0

Res.

0

0

Res.

ECCC

0

0

Res.

ECCD

Reset value

Res.

OPTLOCK

FLASH_ECCR

Res.

1

Res.

1

Res.

LOCK

Reset value

Res.

FLASH_CR

0

WRPERR

FLASH_SR

0

PGAERR

0

SIZERR

0

PGSERR

0

MISERR

0

Res.
FASTERR

0

Res.

0

Res.

0

Reset value

0

Res.

0

Res.

0

Res.

0

RDERR

0

Res.

0x2C

0

OPTVERR

0

Reset value

0x28

0

BSY

0

Res.

0x24

0

STRT

0

Res.

0x20

0

OPTSTRT

Reset value

Res.

0x18

0

OPTKEYR[31:0]

Reset value

0x14

0

Res.

Reset value

0

KEYR[31:0]

Res.

0x10

0

Res.

0x0C

0

Res.

0x08

0

FLASH_KEYR

Res.

Reset value

LATENCY
[2:0]

PDKEYR[31:0]

Res.
FSTPG

0x04

Res.

DCEN

0

Res.

ICRST

0

Res.

DCRST

0

Res.

RUN_PD

0

Reset value

Res.

Res.
SLEEP_PD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FLASH_ACR

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 15. Flash interface - register map and reset values

X

X

X

WRP1A_STRT[7:0]
X

X

X

X

X

X

X

X

RM0394

Embedded Flash memory (FLASH)

Reset value

X

X

X

X

X

X

X

Res.

Res.

Res.

Res.

Res.

Res.

WRP1B_END[7:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FLASH_
WRP1BR

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 15. Flash interface - register map and reset values (continued)

X

WRP1B_STRT[7:0]
X

X

X

X

X

X

X

X

Refer to Section 2.2.2 on page 67 for the register boundary addresses.

RM0394 Rev 4

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113

Firewall (FW)

RM0394

4

Firewall (FW)

4.1

Introduction
The Firewall is made to protect a specific part of code or data into the Non-Volatile Memory,
and/or to protect the Volatile data into the SRAM 1 from the rest of the code executed
outside the protected area.

4.2

Firewall main features
•

•

The code to protect by the Firewall (Code Segment) may be located in:
–

The Flash memory map

–

The SRAM 1 memory, if declared as an executable protected area during the
Firewall configuration step.

The data to protect can be located either
–

in the Flash memory (non-volatile data segment)

–

in the SRAM 1 memory (volatile data segment)

The software can access these protected areas once the Firewall is opened. The Firewall
can be opened or closed using a mechanism based on “call gate” (Refer to Opening the
Firewall).
The start address of each segment and its respective length must be configured before
enabling the Firewall (Refer to Section 4.3.5: Firewall initialization).
Each illegal access into these protected segments (if the Firewall is enabled) generates a
reset which immediately kills the detected intrusion.
Any DMA access to protected segments is forbidden whatever the Firewall state (opened or
closed). It is considered as an illegal access and generates a reset.

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RM0394

Firewall (FW)

4.3

Firewall functional description

4.3.1

Firewall AMBA bus snoop
The Firewall peripheral is snooping the AMBA buses on which the memories (volatile and
non-volatile) are connected. A global architecture view is illustrated in Figure 5.
Figure 5. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx firewall connection
schematics

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4.3.2

Functional requirements
There are several requirements to guaranty the highest security level by the application
code/data which needs to be protected by the Firewall and to avoid unwanted Firewall alarm
(reset generation).

Debug consideration
In debug mode, if the Firewall is opened, the accesses by the debugger to the protected
segments are not blocked. For this reason, the Read out level 2 protection must be active in
conjunction with the Firewall implementation.
If the debug is needed, it is possible to proceed in the following way:
•

A dummy code having the same API as the protected code may be developed during
the development phase of the final user code. This dummy code may send back
coherent answers (in terms of function and potentially timing if needed), as the
protected code should do in production phase.

•

In the development phase, the protected code can be given to the customer-end under
NDA agreement and its software can be developed in level 0 protection. The customer-

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Firewall (FW)

RM0394
end code needs to embed an IAP located in a write protected segment in order to allow
future code updates when the production parts will be Level 2 ROP.

Write protection
In order to offer a maximum security level, the following points need to be respected:
•

It is mandatory to keep a write protection on the part of the code enabling the Firewall.
This activation code should be located outside the segments protected by the Firewall.

•

The write protection is also mandatory on the code segment protected by the Firewall.

•

The page including the reset vector must be write-protected.

Interrupts management
The code protected by the Firewall must not be interruptible. It is up to the user code to
disable any interrupt source before executing the code protected by the Firewall. If this
constraint is not respected, if an interruption comes while the protected code is executed
(Firewall opened), the Firewall will be closed as soon as the interrupt subroutine is
executed. When the code returns back to the protected code area, a Firewall alarm will raise
since the “call gate” sequence will not be applied and a reset will be generated.
Concerning the interrupt vectors and the first user page in the Flash memory:
•

If the first user page (including the reset vector) is protected by the Firewall, the NVIC
vector should be reprogrammed outside the protected segment.

•

If the first user page is not protected by the Firewall, the interrupt vectors may be kept
at this location.

There is no interrupt generated by the Firewall.

4.3.3

Firewall segments
The Firewall has been designed to protect three different segment areas:

Code segment
This segment is located into the Flash memory. It should contain the code to execute which
requires the Firewall protection. The segment must be reached using the “call gate” entry
sequence to open the Firewall. A system reset is generated if the “call gate” entry sequence
is not respected (refer to Opening the Firewall) and if the Firewall is enabled using the
FWDIS bit in the system configuration register. The length of the segment and the segment
base address must be configured before enabling the Firewall (refer to Section 4.3.5:
Firewall initialization).

Non-volatile data segment
This segment contains non-volatile data used by the protected code which must be
protected by the Firewall. The access to this segment is defined into Section 4.3.4: Segment
accesses and properties. The Firewall must be opened before accessing the data in this
area. The Non-Volatile data segment should be located into the Flash memory. The
segment length and the base address of the segment must be configured before enabling
the Firewall (refer to Section 4.3.5: Firewall initialization).

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RM0394

Firewall (FW)

Volatile data segment
Volatile data used by the protected code located into the code segment must be defined into
the SRAM 1 memory. The access to this segment is defined into the Section 4.3.4: Segment
accesses and properties. Depending on the Volatile data segment configuration, the
Firewall must be opened or not before accessing this segment area. The segment length
and the base address of the segment as well as the segment options must be configured
before enabling the Firewall (refer to Section 4.3.5: Firewall initialization).
The Volatile data segment can also be defined as executable (for the code execution) or
shared using two bit of the Firewall configuration register (bit VDS for the volatile data
sharing option and bit VDE for the volatile data execution capability). For more details, refer
to Table 16.

4.3.4

Segment accesses and properties
All DMA accesses to the protected segments are forbidden, whatever the Firewall state, and
generate a system reset.

Segment access depending on the Firewall state
Each of the three segments has specific properties which are presented in Table 16.
Table 16. Segment accesses according to the Firewall state
Segment

Code segment

Non-volatile data
segment

Volatile data
segment

Firewall opened
access allowed

Read and execute

Read and write

Read and Write
Execute if VDE = 1 and
VDS = 0 into the Firewall
configuration register

Firewall closed
access allowed

Firewall disabled
access allowed

No access allowed.
Any access to the segment
(except the “call gate” entry)
generates a system reset

All accesses are allowed
(according to the Flash page
protection properties in which
the code is located)

No access allowed

All accesses are allowed
(according to the Flash page
protection properties in which
the code is located)

No access allowed if VDS = 0
and VDE = 0 into the Firewall
configuration register
Read/write/execute accesses
allowed if VDS = 1 (whatever
VDE bit value)
Execute if VDE = 1 and VDS = 0
but with a “call gate” entry to
open the Firewall at first.

All accesses are allowed

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Firewall (FW)

RM0394

The Volatile data segment is a bit different from the two others. The segment can be:
•

Shared (VDS bit in the register)
It means that the area and the data located into this segment can be shared between
the protected code and the user code executed in a non-protected area. The access is
allowed whether the Firewall is opened or closed or disabled.
The VDS bit gets priority over the VDE bit, this last bit value being ignored in such a
case. It means that the Volatile data segment can execute parts of code located there
without any need to open the Firewall before executing the code.

•

Execute
The VDE bit is considered as soon as the VDS bit = 0 in the FW_CR register. If the
VDS bit = 1, refer to the description above on the Volatile data segment sharing. If VDS
= 0 and VDE = 1, the Volatile data segment is executable. To avoid a system reset
generation from the Firewall, the “call gate” sequence should be applied on the Volatile
data segment to open the Firewall as an entry point for the code execution.

Segments properties
Each segment has a specific length register to define the segment size to be protected by
the Firewall: CSL register for the Code segment length register, NVDSL for the Non-volatile
data segment length register, and VDSL register for the Volatile data segment length
register. Granularity and area ranges for each of the segments are presented in Table 17.
Table 17. Segment granularity and area ranges
Segment

Granularity

Code segment
Non-volatile data segment

Area range

256 byte

1024 Kbytes - 256 bytes

256 byte

1024 Kbytes - 256 bytes

Volatile data segment

(1)

64 byte

96 Kbytes - 64 bytes

Volatile data segment

(2)

64 byte

128 Kbyte - 64 byte

1. Applicable to STM32L43xxx and STM32L44xxx devices only.
2. Applicable to STM32L45xxx and STM32L46xxx devices only.

4.3.5

Firewall initialization
The initialization phase should take place at the beginning of the user code execution (refer
to the Write protection).
The initialization phase consists of setting up the addresses and the lengths of each
segment which needs to be protected by the Firewall. It must be done before enabling the
Firewall, because the enabling bit can be written once. Thus, when the Firewall is enabled, it
cannot be disabled anymore until the next system reset.
Once the Firewall is enabled, the accesses to the address and length segments are no
longer possible. All write attempts are discarded.
A segment defined with a length equal to 0 is not considered as protected by the Firewall.
As a consequence, there is no reset generation from the Firewall when an access to the
base address of this segment is performed.
After a reset, the Firewall is disabled by default (FWDIS bit in the SYSCFG register is set). It
has to be cleared to enable the Firewall feature.

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Firewall (FW)
Below is the initialization procedure to follow:
1.

Configure the RCC to enable the clock to the Firewall module

2.

Configure the RCC to enable the clock of the system configuration registers

3.

Set the base address and length of each segment (CSSA, CSL, NVDSSA, NVDSL,
VDSSA, VDSL registers)

4.

Set the configuration register of the Firewall (FW_CR register)

5.

Enable the Firewall clearing the FWDIS bit in the system configuration register.

The Firewall configuration register (FW_CR register) is the only one which can be managed
in a dynamic way even if the Firewall is enabled:

4.3.6

•

when the Non-Volatile data segment is undefined (meaning the NVDSL register is
equal to 0), the accesses to this register are possible whatever the Firewall state
(opened or closed).

•

when the Non-Volatile data segment is defined (meaning the NVDSL register is
different from 0), the accesses to this register are only possible when the Firewall is
opened.

Firewall states
The Firewall has three different states as shown in Figure 6:
•

Disabled: The FWDIS bit is set by default after the reset. The Firewall is not active.

•

Closed: The Firewall protects the accesses to the three segments (Code, Non-volatile
data, and Volatile data segments).

•

Opened: The Firewall allows access to the protected segments as defined in
Section 4.3.4: Segment accesses and properties.
Figure 6. Firewall functional states

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Firewall (FW)

RM0394

Opening the Firewall
As soon as the Firewall is enabled, it is closed. It means that most of the accesses to the
protected segments are forbidden (refer to Section 4.3.4: Segment accesses and
properties). In order to open the Firewall to interact with the protected segments, it is
mandatory to apply the “call gate” sequence described hereafter.
“call gate” sequence
The “call gate” is composed of 3 words located on the first three 32-bit addresses of the
base address of the code segment and of the Volatile data segment if it is declared as
not shared (VDS = 0) and executable (VDE = 1).
–

1st word: Dummy 32-bit words always closed in order to protect the “call gate”
opening from an access due to a prefetch buffer.

–

2nd and 3rd words: 2 specific 32-bit words called “call gate” and always opened.

To open the Firewall, the code currently executed must jump to the 2nd word of the “call
gate” and execute the code from this point. The 2nd word and 3rd word execution must not
be interrupted by any intermediate instruction fetch; otherwise, the Firewall is not
considered open and comes back to a close state. Then, executing the 3rd word after
receiving the intermediate instruction fetch would generate a system reset as a
consequence.
As soon as the Firewall is opened, the protected segments can be accessed as described in
Section 4.3.4: Segment accesses and properties.

Closing the Firewall
The Firewall is closed immediately after it is enabled (clearing the FWDIS bit in the system
configuration register).
To close the Firewall, the protected code must:
•

Write the correct value in the Firewall Pre Arm Flag into the FW_CR register.

•

Jump to any executable location outside the Firewall segments.

If the Firewall Pre Arm Flag is not set when the protected code jumps to a non protected
segment, a reset is generated. This control bit is an additional protection to avoid an
undesired attempt to close the Firewall with the private information not yet cleaned (see the
note below).
For security reasons, following the application for which the Firewall is used, it is advised to
clean all private information from CPU registers and hardware cells.

120/1600

RM0394 Rev 4

RM0394

Firewall (FW)

4.4

Firewall registers

4.4.1

Code segment start address (FW_CSSA)
Address offset: 0x00
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

23

22

21

20

19

18

17

16

ADD[23:16]
rw

15

14

13

12

11

10

9

8

ADD[15:8]

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:24 Reserved, must be kept at reset value.
Bits 23:8 ADD[23:8]: code segment start address
The LSB bits of the start address (bit 7:0) are reserved and forced to 0 in order to allow a
256-byte granularity.
Note: These bits can be written only before enabling the Firewall. Refer to Section 4.3.5:
Firewall initialization.
Bits 7:0 Reserved, must be kept at the reset value.

4.4.2

Code segment length (FW_CSL)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

21

20

19

18

17

16

LENG[21:16]
rw

15

14

13

12

11

LENG15:8]

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:22 Reserved, must be kept at the reset value.
Bits 21:8 LENG[21:8]: code segment length
LENG[21:8] selects the size of the code segment expressed in bytes but is a multiple of
256 bytes.
The segment area is defined from {ADD[23:8],0x00} to {ADD[23:8]+LENG[21:8], 0x00} - 0x01
Note: If LENG[21:8] = 0 after enabling the Firewall, this segment is not defined, thus not
protected by the Firewall.
These bits can only be written before enabling the Firewall. Refer to Section 4.3.5:
Firewall initialization.
Bits 7:0 Reserved, must be kept at the reset value.

RM0394 Rev 4

121/1600
125

Firewall (FW)

4.4.3

RM0394

Non-volatile data segment start address (FW_NVDSSA)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

23

22

21

20

19

18

17

16

ADD[23:16]
rw

15

14

13

12

11

10

9

8

ADD[15:8]

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:24 Reserved, must be kept at the reset value.
Bits 23:8 ADD[23:8]: Non-volatile data segment start address
The LSB bits of the start address (bit 7:0) are reserved and forced to 0 in order to allow a
256-byte granularity.
Note: These bits can only be written before enabling the Firewall. Refer to Section 4.3.5:
Firewall initialization.
Bits 7:0 Reserved, must be kept at the reset value.

4.4.4

Non-volatile data segment length (FW_NVDSL)
Address offset: 0x0C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

21

20

19

18

17

16

LENG[21:16]
rw

15

14

13

12

11

LENG[15:8]

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:22 Reserved, must be kept at the reset value.
Bits 21:8 LENG[21:8]: Non-volatile data segment length
LENG[21:8] selects the size of the Non-volatile data segment expressed in bytes but is a
multiple of 256 bytes.
The segment area is defined from {ADD[23:8],0x00} to {ADD[23:8]+LENG[21:8], 0x00} - 0x01
Note: If LENG[21:8] = 0 after enabling the Firewall, this segment is not defined, thus not
protected by the Firewall.
These bits can only be written before enabling the Firewall. Refer to Section 4.3.5:
Firewall initialization.
Bits 7:0 Reserved, must be kept at the reset value.

122/1600

RM0394 Rev 4

RM0394

Firewall (FW)

4.4.5

Volatile data segment start address (FW_VDSSA)
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.

ADD
[16]
rw

15

14

13

12

11

10

9

8

7

6

ADD[15:6]

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:17 Reserved, must be kept at the reset value.
Bits 16:6 ADD[16:6]: Volatile data segment start address
The LSB bits of the start address (bit 5:0) are reserved and forced to 0 in order to allow a
64-byte granularity.
Note: These bits can only be written before enabling the Firewall. Refer to Section 4.3.5:
Firewall initialization
Bits 5:0 Reserved, must be kept at the reset value.

4.4.6

Volatile data segment length (FW_VDSL)
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.

LENG
[16]
rw

15

14

13

12

11

10

9

8

7

LENG[15:6]

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:17 Reserved, must be kept at the reset value.
Bits 16:6 LENG[16:6]: volatile data segment length
LENG[16:6] selects the size of the volatile data segment expressed in bytes but is a multiple
of 64 bytes.
The segment area is defined from {ADD[16:6],0x00} to {ADD[16:6]+LENG[16:6], 0x00} - 0x01
Note: If LENG[16:6] = 0 after enabling the Firewall, this segment is not defined, thus not
protected by the Firewall.
These bits can only be written before enabling the Firewall. Refer to Section 4.3.5:
Firewall initialization.
Bits 5:0 Reserved, must be kept at the reset value.

RM0394 Rev 4

123/1600
125

Firewall (FW)

4.4.7

RM0394

Configuration register (FW_CR)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

VDE

VDS

FPA

rw

rw

rw

Bits 31:3 Reserved, must be kept at the reset value.
Bit 2 VDE: Volatile data execution
0: Volatile data segment cannot be executed if VDS = 0
1: Volatile data segment is declared executable whatever VDS bit value
When VDS = 1, this bit has no meaning. The Volatile data segment can be executed whatever
the VDE bit value.
If VDS = 1, the code can be executed whatever the Firewall state (opened or closed)
If VDS = 0, the code can only be executed if the Firewall is opened or applying the “call gate”
entry sequence if the Firewall is closed.
Refer to Segment access depending on the Firewall state.
Bit 1 VDS: Volatile data shared
0: Volatile data segment is not shared and cannot be hit by a non protected executable code
when the Firewall is closed. If it is accessed in such a condition, a system reset will be
generated by the Firewall.
1: Volatile data segment is shared with non protected application code. It can be accessed
whatever the Firewall state (opened or closed).
Refer to Segment access depending on the Firewall state.
Bit 0 FPA: Firewall prearm
0: any code executed outside the protected segment when the Firewall is opened will
generate a system reset.
1: any code executed outside the protected segment will close the Firewall.
Refer to Closing the Firewall.

This register is protected in the same way as the Non-volatile data segment (refer to
Section 4.3.5: Firewall initialization).

124/1600

RM0394 Rev 4

0x20

0x18
Res.
Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
VDE
VDS
FPA

Reset Value
Res.

FW_CR
Res.

Reset Value
Res.

0x1C
Res.

Reset Value

Res.

0
0
0

RM0394 Rev 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

Res.
Res.
Res.
Res.
Res.
Res.

Res.
Res.
Res.
Res.
Res.
Res.

0

Res.

0

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

0

0

Res.

0

0

Res.

LENG

0

Res.

ADD

0

Res.

LENG

0

Res.

ADD

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

FW_CSSA
Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Register

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ADD

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LENG

0

0

Res.

0
0

Res.

Reset Value
0

0

Res.

0

0

Res.

Reset Value
0

0

Res.

0

0

0

0

Res.

0

0

0

Res.

0

0

Res.

0

Res.

0

0

Res.

0

Res.

0

Res.

0

0

Res.

0

Res.

0

Res.

0

0

Res.

0

Res.

0

Res.

0

Res.

0

0

Res.

Reset Value
0

Res.

0

Res.

Reset Value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset Value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset Value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FW_VDSL
Res.

FW_VDSSA

Res.

0x14
FW_NVDSL

Res.

0x10
FW_NVDSSA

Res.

0xC
FW_CSL

Res.

0x8

Res.

0x4

Res.

0x0

Res.

Offset

Res.

4.4.8

Res.

RM0394
Firewall (FW)

Firewall register map

The table below provides the Firewall register map and reset values.
Table 18. Firewall register map and reset values

Refer to Section 2.2.2 on page 67 for the register boundary addresses.

125/1600

125

Power control (PWR)

RM0394

5

Power control (PWR)

5.1

Power supplies
The STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx devices require a 1.71 V to 3.6 V
operating supply voltage (VDD). Several peripherals are supplied through independent
power domains: VDDA, VDDUSB, VLCD. Those supplies must not be provided without a valid
operating supply on the VDD pin.
•

VDD = 1.71 V to 3.6 V
VDD is the external power supply for the I/Os, the internal regulator and the system
analog such as reset, power management and internal clocks. It is provided externally
through VDD pins.

•

Note:

VDD12 = 1.05 V to 1.32 V
External power supply, connected to VCORE, bypassing internal regulator when
connected to an external SMPS. It is provided externally through VDD12 pins and only
available on packages with the external SMPS supply option.

On STM32L412xx and STM32L422xx devices, VDD12 range is extended down to 1.00 V
for better efficiency.
•

VDDA = 1.62 V (ADCs/COMPs) / 1.8 V (DACs/OPAMPs) / 2.4 V (VREFBUF) to 3.6 V
VDDA is the external analog power supply for A/D converters, D/A converters, voltage
reference buffer, operational amplifiers and comparators. The VDDA voltage level is
independent from the VDD voltage. VDDA should be preferably connected to VDD when
these peripherals are not used.

•

VDDUSB = 3.0 V to 3.6 V (available on STM32L4x2xx and STM32L4x3xx devices only)
VDDUSB is the external independent power supply for USB transceivers. The VDDUSB
voltage level is independent from the VDD voltage. VDDUSB should be preferably
connected to VDD when the USB is not used.
On small packages, VDDUSB power supply may not be present as a dedicated pin and
is internally bonded to VDD. For such devices, VDD has to respect the VDDUSB supply
range when USB is used.

•

VLCD = 2.5 V to 3.6 V (available on STM32L4x3xx devices only)
The LCD controller can be powered either externally through VLCD pin, or internally
from an internal voltage generated by the embedded step-up converter. VLCD is
multiplexed with PC3 which can be used as GPIO when the LCD is not used.

•

VBAT = 1.55 V to 3.6 V
VBAT is the power supply for RTC, external clock 32 kHz oscillator and backup registers
(through power switch) when VDD is not present. VBAT is internally bonded to VDD for
small packages without dedicated pin.
VBAT is internally bonded to VDD for small packages without dedicated pin.

•

VREF-, VREF+
VREF+ is the input reference voltage for ADCs and DACs. It is also the output of the
internal voltage reference buffer when enabled.
When VDDA < 2 V, VREF+ must be equal to VDDA.

126/1600

RM0394 Rev 4

RM0394

Power control (PWR)
When VDDA ≥ 2 V, VREF+ must be between 2 V and VDDA.
VREF+ can be grounded when ADC and DAC are not active.
The internal voltage reference buffer supports two output voltages, which are
configured with VRS bit in the VREFBUF_CSR register:
–

VREF+ around 2.048 V. This requires VDDA equal to or higher than 2.4 V.

–

VREF+ around 2.5 V. This requires VDDA equal to or higher than 2.8 V.

VREF- and VREF+ pins are not available on all packages. When not available on the
package, they are bonded to VSSA and VDDA, respectively.
When the VREF+ is double-bonded with VDDA in a package, the internal voltage
reference buffer is not available and must be kept disable (refer to related device
datasheet for packages pinout description). Internal voltage reference buffer is not
supported on STM32L41xxx and STM32L42xxx devices, regardless the presence of
VREF+ pin.
VREF- must always be equal to VSSA.
An embedded linear voltage regulator is used to supply the internal digital power VCORE.
VCORE is the power supply for digital peripherals and memories.

RM0394 Rev 4

127/1600
174

Power control (PWR)

RM0394
Figure 7. Power supply overview
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1. Available on STM32L4x3xx devices only.
2. Available on STM32L4x2xx and STM32L4x3xx devices only.

5.1.1

Independent analog peripherals supply
To improve ADC and DAC conversion accuracy and to extend the supply flexibility, the
analog peripherals have an independent power supply which can be separately filtered and
shielded from noise on the PCB.
•

The analog peripherals voltage supply input is available on a separate VDDA pin.

•

An isolated supply ground connection is provided on VSSA pin.

The VDDA supply voltage can be different from VDD. The presence of VDDA must be checked
before enabling any of the analog peripherals supplied by VDDA (A/D converter, D/A
converter, comparators, operational amplifier, voltage reference buffer).
The VDDA supply can be monitored by the Peripheral Voltage Monitoring, and compared
with two thresholds (1.65 V for PVM3 or 1.8 V for PVM4), refer to Section 5.2.3: Peripheral
Voltage Monitoring (PVM) for more details.

128/1600

RM0394 Rev 4

RM0394

Power control (PWR)
When a single supply is used, VDDA can be externally connected to VDD through the
external filtering circuit in order to ensure a noise-free VDDA reference voltage.

ADC and DAC reference voltage
To ensure a better accuracy on low-voltage inputs and outputs, the user can connect to
VREF+ a separate reference voltage lower than VDDA. VREF+ is the highest voltage,
represented by the full scale value, for an analog input (ADC) or output (DAC) signal.
VREF+ can be provided either by an external reference or by an internal buffered voltage
reference (VREFBUF), except STM32L41xxx and STM32L42xxx devices, which does not
support VREFBUF.
The internal voltage reference is enabled by setting the ENVR bit in the Section 18.3.1:
VREFBUF control and status register (VREFBUF_CSR). The voltage reference is set to
2.5 V when the VRS bit is set and to 2.048 V when the VRS bit is cleared. The internal
voltage reference can also provide the voltage to external components through VREF+ pin.
Refer to the device datasheet and to Section 18: Voltage reference buffer (VREFBUF) for
further information.

5.1.2

Independent USB transceivers supply
This section is applicable to STM32L4x2xx and STM32L4x3xx devices only.
The USB transceivers are supplied from a separate VDDUSB power supply pin. VDDUSB
range is from 3.0 V to 3.6 V and is completely independent from VDD or VDDA.
On small packages, VDDUSB power supply may not be present as a dedicated pin, but
internally bonded to VDD. For such devices, VDD has to respect the VDDUSB supply range
when USB is used.
After reset, the USB features supplied by VDDUSB are logically and electrically isolated and
therefore are not available. The isolation must be removed before using the USB FS
peripheral, by setting the USV bit in the PWR_CR2 register, once the VDDUSB supply is
present.
The VDDUSB supply is monitored by the Peripheral Voltage Monitoring (PVM1) and
compared with the internal reference voltage (VREFINT, around 1.2 V), refer to Section 5.2.3:
Peripheral Voltage Monitoring (PVM) for more details.

5.1.3

Independent LCD supply
This section is applicable to STM32L4x3xx devices only.
The VLCD pin is provided to control the contrast of the glass LCD. This pin can be used in
two ways:
•

It can receive from an external circuitry the desired maximum voltage that is provided
on segment and common lines to the glass LCD by the microcontroller.

•

It can also be used to connect an external capacitor that is used by the microcontroller
for its voltage step-up converter. This step-up converter is controlled by software to
provide the desired voltage to segment and common lines of the glass LCD.

The voltage provided to segment and common lines defines the contrast of the glass LCD
pixels. This contrast can be reduced when you configure the dead time between frames.
•

When an external power supply is provided to the VLCD pin, it should range from 2.5 V

RM0394 Rev 4

129/1600
174

Power control (PWR)

RM0394

to 3.6 V. It does not depend on VDD.
•

5.1.4

When the LCD is based on the internal step-up converter, the VLCD pin should be
connected to a capacitor (see the product datasheet for further information).

Battery backup domain
To retain the content of the Backup registers and supply the RTC function when VDD is
turned off, the VBAT pin can be connected to an optional backup voltage supplied by a
battery or by another source.
VBAT pin is not available on low pin-count packages, VBAT is internally connected to VDD.
The VBAT pin powers the RTC unit, the LSE oscillator and the PC13 to PC15 I/Os, allowing
the RTC to operate even when the main power supply is turned off. The switch to the VBAT
supply is controlled by the power-down reset embedded in the Reset block.

Warning:

During tRSTTEMPO (temporization at VDD startup) or after a PDR
has been detected, the power switch between VBAT and VDD
remains connected to VBAT.
During the startup phase, if VDD is established in less than
tRSTTEMPO (refer to the datasheet for the value of tRSTTEMPO)
and VDD > VBAT + 0.6 V, a current may be injected into VBAT
through an internal diode connected between VDD and the
power switch (VBAT).
If the power supply/battery connected to the VBAT pin cannot
support this current injection, it is strongly recommended to
connect an external low-drop diode between this power
supply and the VBAT pin.

If no external battery is used in the application, it is recommended to connect VBAT
externally to VDD with a 100 nF external ceramic decoupling capacitor.
When the backup domain is supplied by VDD (analog switch connected to VDD), the
following pins are available:

Note:

•

PC13, PC14 and PC15, which can be used as GPIO pins

•

PC13, PC14 and PC15, which can be configured by RTC or LSE (refer to Section 36.3:
RTC functional description on page 1084)

•

PA0/RTC_TAMP2 and PE6/RTC_TAMP3 when they are configured by the RTC as
tamper pins

Due to the fact that the analog switch can transfer only a limited amount of current (3 mA),
the use of GPIO 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 a LED).
When the backup domain is supplied by VBAT (analog switch connected to VBAT because
VDD is not present), the following functions are available:

130/1600

•

PC13, PC14 and PC15 can be controlled only by RTC or LSE (refer to Section 36.3:
RTC functional description)

•

PA0/RTC_TAMP2 and PE6/RTC_TAMP3 when they are configured by the RTC as
tamper pins

RM0394 Rev 4

RM0394

Power control (PWR)

Backup domain access
After a system reset, the backup domain (RTC registers and backup registers) is protected
against possible unwanted write accesses. To enable access to the backup domain,
proceed as follows:
1.

Enable the power interface clock by setting the PWREN bits in the Section 6.4.18:
APB1 peripheral clock enable register 1 (RCC_APB1ENR1)

2.

Set the DBP bit in the Power control register 1 (PWR_CR1) to enable access to the
backup domain

3.

Select the RTC clock source in the Backup domain control register (RCC_BDCR).

4.

Enable the RTC clock by setting the RTCEN [15] bit in the Backup domain control
register (RCC_BDCR).

VBAT battery charging
When VDD is present, It is possible to charge the external battery on VBAT through an
internal resistance.
The VBAT charging is done either through a 5 kOhm resistor or through a 1.5 kOhm resistor
depending on the VBRS bit value in the PWR_CR4 register.
The battery charging is enabled by setting VBE bit in the PWR_CR4 register. It is
automatically disabled in VBAT mode.

5.1.5

Voltage regulator
Two embedded linear voltage regulators supply all the digital circuitries, except for the
Standby circuitry and the backup domain. The main regulator output voltage (VCORE) can be
programmed by software to two different power ranges (Range 1 and Range 2) in order to
optimize the consumption depending on the system’s maximum operating frequency (refer
to Section 6.2.9: Clock source frequency versus voltage scaling and to Section 3.3.3: Read
access latency.
The voltage regulators are always enabled after a reset. Depending on the application
modes, the VCORE supply is provided either by the main regulator (MR) or by the low-power
regulator (LPR).
•

In Run, Sleep and Stop 0 modes, both regulators are enabled and the main regulator
(MR) supplies full power to the VCORE domain (core, memories and digital peripherals).

•

In low-power run and low-power sleep modes, the main regulator is off and the lowpower regulator (LPR) supplies low power to the VCORE domain, preserving the
contents of the registers, SRAM1 and SRAM2.

•

In Stop 1 and Stop 2 modes, the main regulator is off and the low-power regulator
(LPR) supplies low power to the VCORE domain, preserving the contents of the
registers, SRAM1 and SRAM2.

•

In Standby mode with SRAM2 content preserved (RRS bit is set in the PWR_CR3
register), the main regulator (MR) is off and the low-power regulator (LPR) provides the
supply to SRAM2 only. The core, digital peripherals (except Standby circuitry and
backup domain) and SRAM1 are powered off.

•

In Standby mode, both regulators are powered off. The contents of the registers,
SRAM1 and SRAM2 is lost except for the Standby circuitry and the backup domain.

•

In Shutdown mode, both regulators are powered off. When exiting from Shutdown
mode, a power-on reset is generated. Consequently, the contents of the registers,

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SRAM1 and SRAM2 is lost, except for the backup domain.

5.1.6

VDD12 domain
VDD12 is intended to be connected with external SMPS (Switched-mode Power Supply) to
generate the VCORE logic supply in Run, Sleep and Stop 0 modes only.
VDD12 pins correspond to the internal VCORE powering the digital part of Core, memories
and peripherals. This improves significantly power consumption gain by 50% or more
depending of the SMPS performances.
The main benefit occurs in Run and Sleep modes whereas in Stop 0 mode, the gain is less
significant.
The Figure 8 shows a schematic to understand how the internal regulator stops supplying
VCORE when an external voltage VDD12 is provided.
As VDD12 shares the same pin as output of the internal regulator, applying a slightly higher
voltage (typically +50 mV) on the VDD12 blocks the PMOS and the regulator consumption
is negligible.
Figure 8. Internal main regulator overview
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A switch, controlled by chosen GPIO, is inserted between the SMPS output and VDD12.
There are two possible states:
•

Connected: Switch is closed so SMPS powers VDD12

•

Disconnected: Switch is open and VDD12 is disconnected from SMPS output

Proper software management through GPIOs to enable/disable SMPS and
connect/disconnect SMPS through the switch, is required to conform with the rules
described below.
(See also Section 5.1.7: Dynamic voltage scaling management)
It is mandatory to respect the following rules to avoid any damage or instability on either
digital parts or internal regulators:
•

In Run, Sleep and Stop 0 modes, VDD12 can be connected and should respect
–

VDD12 < 1.32 V

–

VDD12 ≥ VCORE + 50mV giving for Main Regulator
Range 1, VCORE = 1.2 V so VDD12 should be greater than 1.25 V

132/1600

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Power control (PWR)
Range 2, VCORE = 1.0 V so VDD12 should be greater than 1.05 V
–
•

In all other modes, ie LPRun, LPSleep, Stop 1, Stop 2, Standby and Shutdown modes,
VDD12 must be disconnected from SMPS output, ie pin must be connected to an high
impedance output:
–

•

VDD12 ≥ 1.08 V in Range 2 when SYSCLK frequency ≥ 26 MHz

VDD12 connected to HiZ (voltage is provided by internal regulators)

Transitions of VDD12 from connected to disconnected is only allowed when SYSCLK
frequency ≤ 26 MHz to avoid to big voltage drop on main regulator side.

Note:

In case of reset while having the VDD12 ≤ 1.25 V, VDD12 should switch to HiZ in less than
regulator switching time from Range 2 to Range 1 (~1 us).

Note:

On STM32L412xx and STM32L422xx devices, VDD12 Range 2 is extended down to 1.00 V
for better efficiency, thus following formula applies when bit EXT_SMPS_ON in the Power
control register 4 (PWR_CR4) is set:
Range 2, VCORE = 1.0 V so VDD12 should be greater than 1.00 V

Note:

For more details on VDD12 management, refer to AN4978 "Design recommendations for
STM32L4xxxx with external SMPS, for ultra-low-power applications with high performance

5.1.7

Dynamic voltage scaling management
The dynamic voltage scaling is a power management technique which consists in
increasing or decreasing the voltage used for the digital peripherals (VCORE), according to
the application performance and power consumption needs.
Dynamic voltage scaling to increase VCORE is known as over-volting. It allows to improve
the device performance.
Dynamic voltage scaling to decrease VCORE is known as under-volting. It is performed to
save power, particularly in laptop and other mobile devices where the energy comes from a
battery and is thus limited.
• Range 1: High-performance range.
The main regulator provides a typical output voltage at 1.2 V. The system clock frequency
can be up to 80 MHz. The Flash access time for read access is minimum, write and erase
operations are possible.
• Range 2: Low-power range.
The main regulator provides a typical output voltage at 1.0 V. The system clock frequency
can be up to 26 MHz.The Flash access time for a read access is increased as compared to
Range 1; write and erase operations are possible.
Voltage scaling is selected through the VOS bit in the PWR_CR1 register.
The sequence to go from Range 1 to Range 2 is:
1.Reduce the system frequency to a value lower than 26 MHz
2. Adjust number of wait states according new frequency target in Range 2
(LATENCY bits in the FLASH_ACR).
3. Program the VOS bits to “10” in the PWR_CR1 register.
The sequence to go from Range 2 to Range 1 is:

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1. Program the VOS bits to “01” in the PWR_CR1 register.
2. Wait until the VOSF flag is cleared in the PWR_SR2 register.
3. Adjust number of wait states according new frequency target in Range 1
(LATENCY bits in the FLASH_ACR).
4. Increase the system frequency.
When supplying VDD12 with an external SMPS, we are defining 3 new states:
•

“SMPS range 1”: main regulator is in Range 1 and VCORE is supplied by external
SMPS with VDD12 higher than 1.25 V

•

“SMPS range 2 High”: main regulator is in Range 2 and VCORE is supplied by external
SMPS with VDD12 higher than 1.08 V

•

“SMPS range 2 Low”: main regulator is in Range 2 and VCORE is supplied by external
SMPS with VDD12 higher than 1.05 V(a)

In order to match the upper rules described in Section 5.1.6: VDD12 domain, the transition
sequences can only be one of the following:
•

Range 1 to “SMPS Range 1”:
1. Start SMPS converter (if not always enabled by HW).
2. Check that SMPS converter output is at the correct level i.e. 1.25 V ≤ VDD12 <
1.32 V.
3. Connect VDD12 to external SMPS converter through the switch.

•

Range 2 to “SMPS Range 2 Low & High”:
1. Start SMPS (if not always enabled by HW).
2. Check that SMPS output is at the correct level ie 1.05 V(a) ≤ VDD12 < 1.32 V.
3. Connect VDD12 to external SMPS converter through the switch.

If 1.08 V ≤ VDD12 (ie SMPS Range 2 High), then the following steps can be applied:
4. Adjust the number of wait states in the FLASH_ACR (up to max frequency of
Range 1 refer to Section 3.3.3: Read access latency).
5. Increase the system frequency up to the maximum allowed value for Voltage
Range 1 (ie 80 MHz).
• “SMPS Range 1” to Range 1:
or
• SMPS Range 2 Low & High” to Range 2:
1. If in Range 1, reduce the system frequency to a value lower or equal to 26 MHz.
2. Adjust number of wait states according new frequency target corresponding to
Voltage Range (LATENCY bits in the FLASH_ACR).
3. Disconnect VDD12 by opening the switch.
4. Stop SMPS (if required and not kept always enabled).
If in Range 1, then the following step can be applied:
5. Increase the system frequency if needed.

a. On STM32L412xx and STM32L422xx devices, minimum limit of 1.00 V applies when bit EXT_SMPS_ON in
the Power control register 4 (PWR_CR4) is set.

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Power control (PWR)

5.2

Power supply supervisor

5.2.1

Power-on reset (POR) / power-down reset (PDR) / brown-out reset
(BOR)
The device has an integrated power-on reset (POR) / power-down reset (PDR), coupled
with a brown-out reset (BOR) circuitry. The BOR is active in all power modes except
Shutdown mode, and cannot be disabled.
Five BOR thresholds can be selected through option bytes.
During power-on, the BOR keeps the device under reset until the supply voltage VDD
reaches the specified VBORx threshold. When VDD drops below the selected threshold, a
device reset is generated. When VDD is above the VBORx upper limit, the device reset is
released and the system can start.
For more details on the brown-out reset thresholds, refer to the electrical characteristics
section in the datasheet.
On STM32L412xx and STM32L422xx devices, continuous monitoring of the power supply
might be changed to periodical sampling to reduce power consumption in Stop2, Standby
and Shutdown modes by setting ENULP bit in Power control register 3 (PWR_CR3). When
sampling mode will be selected, fast supply drop between two samples will not be detected.
Figure 9. Brown-out reset waveform
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1. The reset temporization tRSTTEMPO is present only for the BOR lowest threshold (VBOR0).

5.2.2

Programmable voltage detector (PVD)
You can use the PVD to monitor the VDD power supply by comparing it to a threshold
selected by the PLS[2:0] bits in the Power control register 2 (PWR_CR2).
The PVD is enabled by setting the PVDE bit.
A PVDO flag is available, in the Power status register 2 (PWR_SR2), 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 rising/falling edge
sensitivity of the EXTI Line16 should be configured according to PVD output behavior i.e. if
the EXTI line 16 is configured to rising edge sensitivity, the interrupt will be generated when
VDD drops below the PVD threshold. As an example the service routine could perform
emergency shutdown tasks.
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Figure 10. PVD thresholds
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5.2.3

Peripheral Voltage Monitoring (PVM)
Only VDD is monitored by default, as it is the only supply required for all system-related
functions. The other supplies (VDDA and VDDUSB) can be independent from VDD and can be
monitored with four Peripheral Voltage Monitoring (PVM).
Each of the three PVMx (x=1, 3, 4) is a comparator between a fixed threshold VPVMx and
the selected power supply. PVMOx flags indicate if the independent power supply is higher
or lower than the PVMx threshold: PVMOx flag is cleared when the supply voltage is above
the PVMx threshold, and is set when the supply voltage is below the PVMx threshold.
Each PVM output is connected to an EXTI line and can generate an interrupt if enabled
through the EXTI registers. The PVMx output interrupt is generated when the independent
power supply drops below the PVMx threshold and/or when it rises above the PVMx
threshold, depending on EXTI line rising/falling edge configuration.
Each PVM can remain active in Stop 0, Stop 1 and Stop 2 modes, and the PVM interrupt
can wake up from the Stop mode.
Table 19. PVM features
PVM

Power supply

PVM threshold

EXTI line

PVM1(1)

VDDUSB

VPVM1 (around 1.2 V)

35

PVM3

VDDA

VPVM3 (around 1.65 V)

37

PVM4

VDDA

VPVM4 (around 1.8 V)

38

1. Available on STM32L4x2xx and STM32L4x3xx devices only.

The independent supplies (VDDA and VDDUSB) are not considered as present by default,
and a logical and electrical isolation is applied to ignore any information coming from the
peripherals supplied by these dedicated supplies.

136/1600

•

If these supplies are shorted externally to VDD, the application should assume they are
available without enabling any Peripheral Voltage Monitoring.

•

If these supplies are independent from VDD, the Peripheral Voltage Monitoring (PVM)
RM0394 Rev 4

RM0394

Power control (PWR)
can be enabled to confirm whether the supply is present or not.
The following sequence must be done before using the USB FS peripheral on
STM32L4x2xx and STM32L4x3xx devices:
1.

2.

If VDDUSB is independent from VDD:
a)

Enable the PVM1 by setting PVME1 bit in the Power control register 2
(PWR_CR2).

b)

Wait for the PVM1 wakeup time

c)

Wait until PVMO1 bit is cleared in the Power status register 2 (PWR_SR2).

d)

Optional: Disable the PVM1 for consumption saving.

Set the USV bit in the Power control register 2 (PWR_CR2) to remove the VDDUSB
power isolation.

The following sequence must be done before using any of these analog peripherals: analog
to digital converters, digital to analog converters, comparators, operational amplifiers,
voltage reference buffer:
1.

2.

5.3

If VDDA is independent from VDD:
a)

Enable the PVM3 (or PVM4) by setting PVME3 (or PVME4) bit in the Power
control register 2 (PWR_CR2).

b)

Wait for the PVM3 (or PVM4) wakeup time

c)

Wait until PVMO3 (or PVMO4) bit is cleared in the Power status register 2
(PWR_SR2).

d)

Optional: Disable the PVM3 (or PVM4) for consumption saving.

Enable the analog peripheral, which automatically removes the VDDA isolation.

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 seven low-power modes:
•

Sleep mode: CPU clock off, all peripherals including Cortex®-M4 core peripherals such
as NVIC, SysTick, etc. can run and wake up the CPU when an interrupt or an event
occurs. Refer to Section 5.3.4: Sleep mode.

•

Low-power run mode: This mode is achieved when the system clock frequency is
reduced below 2 MHz. The code is executed from the SRAM or the Flash memory. The
regulator is in low-power mode to minimize the regulator's operating current. Refer to
Section 5.3.2: Low-power run mode (LP run).

•

Low-power sleep mode: This mode is entered from the Low-power run mode: Cortex®M4 is off. Refer to Section 5.3.5: Low-power sleep mode (LP sleep).

•

Stop 0, Stop 1 and Stop 2 modes: SRAM1, SRAM2 and all registers content are
retained. All clocks in the VCORE domain are stopped, the PLL, the MSI, the HSI16 and
the HSE are disabled. The LSI and the LSE can be kept running.
The RTC can remain active (Stop mode with RTC, Stop mode without RTC).
Some peripherals with the wakeup capability can enable the HSI16 RC during the Stop

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mode to detect their wakeup condition.
In Stop 2 mode, most of the VCORE domain is put in a lower leakage mode.
Stop 1 offers the largest number of active peripherals and wakeup sources, a smaller
wakeup time but a higher consumption than Stop 2. In Stop 0 mode, the main regulator
remains ON, which allows the fastest wakeup time but with much higher consumption.
The active peripherals and wakeup sources are the same as in Stop 1 mode.
The system clock, when exiting from Stop 0, Stop 1 or Stop 2 mode, can be either MSI
up to 48 MHz or HSI16, depending on the software configuration.
Refer to Section 5.3.6: Stop 0 mode and Section 5.3.8: Stop 2 mode.
•

Standby mode: VCORE domain is powered off. However, it is possible to preserve the
SRAM2 contents:
–

Standby mode with SRAM2 retention when the bit RRS is set in PWR_CR3
register. In this case, SRAM2 is supplied by the low-power regulator.

–

Standby mode when the bit RRS is cleared in PWR_CR3 register. In this case the
main regulator and the low-power regulator are powered off.

All clocks in the VCORE domain are stopped, the PLL, the MSI, the HSI16 and the HSE
are disabled. The LSI and the LSE can be kept running.
The RTC can remain active (Standby mode with RTC, Standby mode without RTC).
The system clock, when exiting Standby modes, is MSI from 1 MHz up to 8 MHz.
Refer to Section 5.3.9: Standby mode.
•

Shutdown mode: VCORE domain is powered off. All clocks in the VCORE domain are
stopped, the PLL, the MSI, the HSI16, the LSI and the HSE are disabled. The LSE can
be kept running. The system clock, when exiting the Shutdown mode, is MSI at 4 MHz.
In this mode, the supply voltage monitoring is disabled and the product behavior is not
guaranteed in case of a power voltage drop. Refer to Section 5.3.10: Shutdown mode.

In addition, the power consumption in Run mode can be reduced by one of the following
means:

138/1600

•

Slowing down the system clocks

•

Gating the clocks to the APB and AHB peripherals when they are unused.

RM0394 Rev 4

RM0394

Power control (PWR)
Figure 11. Low-power modes possible transitions
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RM0394
Table 20. Low-power mode summary

Mode name

Entry

WFI or Return
Sleep
(Sleep-now or from ISR
Sleep-on-exit) WFE
Low-power
run

Low-power
sleep

Stop 0

Stop 1

Stop 2

Wakeup

Wakeup
source(1)

system clock

Any interrupt
Wakeup event

Set LPR bit

Clear LPR bit

Set LPR bit +
WFI or Return
from ISR

Any interrupt

Set LPR bit +
WFE

Wakeup event

LPR

Same as before
entering Sleep
mode

CPU clock OFF
no effect on other clocks ON
or analog clock sources

ON

Same as Lowpower run clock

None

OFF

ON

Same as before
entering Lowpower sleep
mode

OFF
CPU clock OFF
no effect on other clocks
or analog clock sources
OFF

ON

ON

ON

HSI16 when
Any EXTI line
STOPWUCK=1 in
(configured in the RCC_CFGR
LPMS=”001” +
SLEEPDEEP bit EXTI registers)
MSI with the
+ WFI or Return Specific
frequency before
from ISR or WFE peripherals
entering the Stop
events
mode when
LPMS=”010” +
STOPWUCK=0.
SLEEPDEEP bit
+ WFI or Return
All clocks OFF except
LSI and LSE
from ISR or WFE
WKUP pin edge,
RTC event,
external reset in
NRST pin,
IWDG reset

Standby

LPMS=”011” +
Clear RRS bit +
SLEEPDEEP bit
+ WFI or Return
from ISR or WFE

WKUP pin edge,
RTC event,
external reset in
NRST pin,
IWDG reset

Shutdown

LPMS=”1--” +
SLEEPDEEP bit
+ WFI or Return
from ISR or WFE

WKUP pin edge,
RTC event,
external reset in
NRST pin

ON
OFF

MSI from 1 MHz
up to 8 MHz

MSI 4 MHz

1. Refer to Table 21: Functionalities depending on the working mode.

140/1600

MR

LPMS=”000” +
SLEEPDEEP bit
+ WFI or Return
from ISR or WFE

LPMS=”011”+
Set RRS bit +
SLEEPDEEP bit
+ WFI or Return
from ISR or WFE

Standby with
SRAM2

Effect on clocks

Voltage
regulators

RM0394 Rev 4

All clocks OFF except
LSE

OFF

OFF

OFF

OFF

RM0394

Power control (PWR)
Table 21. Functionalities depending on the working mode(1)

-

Wakeup capability

-

Wakeup capability

-

CPU

Y

-

Y

-

-

-

-

-

-

-

-

-

-

Flash memory

(2)

O

(2)

(2)

O

(2)

-

-

-

-

-

-

-

-

-

Y

Y(3)

Y

Y(3)

Y

-

Y

-

-

-

-

-

-

SRAM2

Y

(3)

Y

(3)

Y

-

Y

-

(4)

O

-

-

-

-

QUADSPI

O

O

O

O

-

-

-

-

-

-

-

-

-

Backup Registers

Y

Y

Y

Y

Y

-

Y

-

Y

-

Y

-

Y

Brown-out reset (BOR)

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

-

-

-

Programmable Voltage
Detector (PVD)

O

O

O

O

O

O

O

O

-

-

-

-

-

Peripheral Voltage Monitor
(PVMx; x=1,3,4)

O

O

O

O

O

O

O

O

-

-

-

-

-

DMA

O

O

O

O

-

-

-

-

-

-

-

-

-

-

(5)

-

-

-

-

-

-

Peripheral

SRAM1

Run

O

Sleep

Y

O

Y

-

Wakeup capability

Wakeup capability

Standby Shutdown

Low-power sleep

Stop 2

Low-power run

Stop 0/1

VBAT

Oscillator HSI16

O

O

O

O

(5)

Oscillator HSI48

O

O

-

-

-

-

-

-

-

-

-

-

-

High Speed External (HSE)

O

O

O

O

-

-

-

-

-

-

-

-

-

Low Speed Internal (LSI)

O

O

O

O

O

-

O

-

O

-

-

-

-

Low Speed External (LSE)

O

O

O

O

O

-

O

-

O

-

O

-

O

Multi-Speed Internal (MSI)

O

O

O

O

-

-

-

-

-

-

-

-

-

Clock Security System
(CSS)

O

O

O

O

-

-

-

-

-

-

-

-

-

Clock Security System on
LSE

O

O

O

O

O

O

O

O

O

O

-

-

-

RTC / Auto wakeup

O

O

O

O

O

O

O

O

O

O

O

O

O

Number of RTC Tamper
pins

3

3

3

3

3

O

3

O

3

O

3

O

3

LCD(6)

O

O

O

O

O

O

O

O

-

-

-

-

-

O(15)

O(15)

-

-

-

O

-

-

-

-

-

-

-

O

O

O

O

(10)

-

-

-

-

-

-

-

USB FS

(7)

USARTx (x=1,2,3(8),4(9))

O

RM0394 Rev 4

O

(10)

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Table 21. Functionalities depending on the working mode(1) (continued)

O

O

(10)

I2Cx (x=1,2,4(9))

O

O

O

O

(11)

I2C3

O

O

O

O

(11)

(11)

(11)

SPIx (x=1,2(8),3)

O

O

O

O

-

-

CAN

O

O

O

O

-

SDMMC1(8)(12)

O

O

O

O

SWPMI1

O

O

O

SAIx (x=1)(12)

O

O

DFSDM1(9)

O

0)

(10)

-

-

-

-

-

-

-

-

-

-

-

-

(11)

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

O

-

O

-

-

-

-

-

-

-

O

O

-

-

-

-

-

-

-

-

-

O

O

O

-

-

-

-

-

-

-

-

-

O

O

O

O

-

-

-

-

-

-

-

-

-

DACx (x=1

O

O

O

O

O

-

-

-

-

-

-

-

-

VREFBUF(19)

O

O

O

O

O

-

-

-

-

-

-

-

-

O

O

O

O

O

-

-

-

-

-

-

-

-

COMPx (x=1,2

O

O

O

O

O

O

O

O

-

-

-

-

-

Temperature sensor

O

O

O

O

-

-

-

-

-

-

-

-

-

Timers (TIMx)

O

O

O

O

-

-

-

-

-

-

-

-

-

Low-power timer 1
(LPTIM1)

O

O

O

O

O

O

O

O

-

-

-

-

-

Low-power timer 2
(LPTIM2)

O

O

O

O

O

O

(14)

O

-

-

-

-

-

Independent watchdog
(IWDG)

O

O

O

O

O

O

O

O

O

O

-

-

-

Window watchdog (WWDG)

O

O

O

O

-

-

-

-

-

-

-

-

-

SysTick timer

O

O

O

O

-

-

-

-

-

-

-

-

-

Touch sensing controller
(TSC)

O

O

O

O

-

-

-

-

-

-

-

-

-

O(15)

O(15)

-

-

-

-

-

-

-

-

-

-

-

(12)

(14))

ADCx (x=1,2

(12),2(13))

OPAMPx (x=1)
(19))

Random number generator
(RNG)

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-

O

O

O

RM0394 Rev 4

O

O(1

(10)

O

(11)

O

O

O

O

O

-

Wakeup capability

O

Wakeup capability

O

Sleep

Wakeup capability

Low-power UART
(LPUART1)

Run

-

Standby Shutdown

-

Peripheral

Wakeup capability

Low-power sleep

Stop 2

Low-power run

Stop 0/1

VBAT

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Table 21. Functionalities depending on the working mode(1) (continued)

-

Wakeup capability

-

Wakeup capability

-

AES hardware
accelerator(16)

O

O

O

O

-

-

-

-

-

-

-

-

-

CRC calculation unit

O

O

O

O

-

-

-

-

-

-

-

-

-

O

(17)

up
to 5
pins

(19)

up
to 5
pins

Peripheral

GPIOs

Run

Sleep

O

O

O

O

-

O

O

O

(18)

Wakeup capability

Wakeup capability

Standby Shutdown

Low-power sleep

Stop 2

Low-power run

Stop 0/1

VBAT

-

(18)

1. Legend: Y = Yes (Enable). O = Optional (Disable by default. Can be enabled by software). - = Not available.
2. The Flash can be configured in power-down mode. By default, it is not in power-down mode.
3. The SRAM clock can be gated on or off.
4. SRAM2 content is preserved when the bit RRS is set in PWR_CR3 register.
5. Some peripherals with wakeup from Stop capability can request HSI16 to be enabled. In this case, HSI16 is woken up by
the peripheral, and only feeds the peripheral which requested it. HSI16 is automatically put off when the peripheral does not
need it anymore.
6. Available on STM32L4x3xx devices only.
7. Available on STM32L4x2xx and STM32L4x3xx devices only.
8. Not available on STM32L432xx and STM32L442xx devices.
9. Available on STM32L45xxx and STM32L46xxx devices only.
10. UART and LPUART reception is functional in Stop mode, and generates a wakeup interrupt on Start, address match or
received frame event.
11. I2C address detection is functional in Stop mode, and generates a wakeup interrupt in case of address match.
12. Not available on STM32L41xxx and STM32L42xxx devices.
13. Available on STM32L43xxx/44xxx devices only.
14. Available on STM32L41xxx and STM32L42xxx devices only.
15. Voltage scaling Range 1, SMPS Range 1 or SMPS Range 2 High only.
16. Available on STM32L42xxx, STM32L44xxx and STM32L46xxx devices only.
17. I/Os can be configured with internal pull-up, pull-down or floating in Standby mode.
18. The I/Os with wakeup from Standby/Shutdown capability are: PA0, PC13, PE6, PA2, PC5.
19. I/Os can be configured with internal pull-up, pull-down or floating in Shutdown mode but the configuration is lost when
exiting the Shutdown mode.

Debug mode
By default, the debug connection is lost if the application puts the MCU in Stop 0, Stop1,
Stop 2, Standby or Shutdown mode while the debug features are used. This is due to the
fact that the 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. For more details, refer to
Section 46.16.1: Debug support for low-power modes.

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Run mode
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 the
peripherals before entering the Sleep mode.
For more details, refer to Section 6.4.3: Clock configuration register (RCC_CFGR).

Peripheral clock gating
In Run mode, the HCLK and PCLK for individual peripherals and memories can be stopped
at any time to reduce the power consumption.
To further reduce the power consumption in Sleep mode, the peripheral clocks can be
disabled prior to executing the WFI or WFE instructions.
The peripheral clock gating is controlled by the RCC_AHBxENR and RCC_APBxENR
registers.
Disabling the peripherals clocks in Sleep mode can be performed automatically by resetting
the corresponding bit in the RCC_AHBxSMENR and RCC_APBxSMENR registers.

5.3.2

Low-power run mode (LP run)
To further reduce the consumption when the system is in Run mode, the regulator can be
configured in low-power mode. In this mode, the system frequency should not exceed
2 MHz.
Please refer to the product datasheet for more details on voltage regulator and peripherals
operating conditions.

I/O states in Low-power run mode
In Low-power run mode, all I/O pins keep the same state as in Run mode.

Entering the Low-power run mode
To enter the Low-power run mode, proceed as follows:
1.

Optional: Jump into the SRAM and power-down the Flash by setting the RUN_PD bit in
the Flash access control register (FLASH_ACR).

2.

Decrease the system clock frequency below 2 MHz.

3.

Force the regulator in low-power mode by setting the LPR bit in the PWR_CR1 register.

Refer to Table 22: Low-power run on how to enter the Low-power run mode.

Exiting the Low-power run mode
To exit the Low-power run mode, proceed as follows:
1.

Force the regulator in main mode by clearing the LPR bit in the PWR_CR1 register.

2.

Wait until REGLPF bit is cleared in the PWR_SR2 register.

3.

Increase the system clock frequency.

Refer to Table 22: Low-power run on how to exit the Low-power run mode.

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Table 22. Low-power run
Low-power run mode

5.3.3

Description

Mode entry

Decrease the system clock frequency below 2 MHz
LPR = 1

Mode exit

LPR = 0
Wait until REGLPF = 0
Increase the system clock frequency

Wakeup latency

Regulator wakeup time from low-power mode

Low power modes
Entering low power mode
Low power modes are entered by the MCU by executing the WFI (Wait For Interrupt), or
WFE (Wait for Event) instructions, or when the SLEEPONEXIT bit in the Cortex®-M4
System Control register is set on Return from ISR.
Entering Low-power mode through WFI or WFE will be executed only if no interrupt is
pending or no event is pending.

Exiting low power mode
From Sleep modes, and Stop modes the MCU exit low power mode depending on the way
the low power mode was entered:
•
If the WFI instruction or Return from ISR was used to enter the low power mode, any
peripheral interrupt acknowledged by the NVIC can wake up the device.
•

If the WFE instruction is used to enter the low power mode, the MCU exits the low
power mode as soon as an event occurs. The wakeup event can be generated either
by:
–

NVIC IRQ interrupt.
- When SEVONPEND = 0 in the Cortex®-M4 System Control register. By enabling
an interrupt in the peripheral control register and in the NVIC. When the MCU
resumes from WFE, the peripheral interrupt pending bit and the NVIC peripheral
IRQ channel pending bit (in the NVIC interrupt clear pending register) have to be
cleared.
Only NVIC interrupts with sufficient priority will wakeup and interrupt the MCU.
- When SEVONPEND = 1 in the Cortex®-M4 System Control register.
By enabling an interrupt in the peripheral control register and optionally in the
NVIC. When the MCU resumes from WFE, the peripheral interrupt pending bit and

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when enabled the NVIC peripheral IRQ channel pending bit (in the NVIC interrupt
clear pending register) have to be cleared.
All NVIC interrupts will wakeup the MCU, even the disabled ones. Only enabled
NVIC interrupts with sufficient priority will wakeup and interrupt the MCU.
–

Event
Configuring a EXTI line in event mode. When the CPU resumes from WFE, it is
not necessary to clear the EXTI peripheral interrupt pending bit or the NVIC IRQ
channel pending bit as the pending bits corresponding to the event line is not set.

It may be necessary to clear the interrupt flag in the peripheral.
From Standby modes, and Shutdown modes the MCU exit low power mode through an
external reset (NRST pin), an IWDG reset, a rising edge on one of the enabled WKUPx pins
or a RTC event occurs (see Figure 351: RTC block diagrams).
After waking up from Standby or Shutdown mode, program execution restarts in the same
way as after a Reset (boot pin sampling, option bytes loading, reset vector is fetched, etc.).

5.3.4

Sleep mode
I/O states in Sleep mode
In Sleep mode, all I/O pins keep the same state as in Run mode.

Entering the Sleep mode
The Sleep mode is entered according Section : Entering low power mode, when the
SLEEPDEEP bit in the Cortex®-M4 System Control register is clear.
Refer to Table 23: Sleep for details on how to enter the Sleep mode.

Exiting the Sleep mode
The Sleep mode is exit according Section : Exiting low power mode.
Refer to Table 23: Sleep for more details on how to exit the Sleep mode.
Table 23. Sleep
Sleep-now mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP = 0
– No interrupt (for WFI) or event (for WFE) is pending
Refer to the Cortex®-M4 System Control register.

Mode entry

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On return from ISR while:
– SLEEPDEEP = 0 and
– SLEEPONEXIT = 1
– No interrupt is pending
Refer to the Cortex®-M4 System Control register.

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Table 23. Sleep (continued)
Sleep-now mode

Description
If WFI or return from ISR was used for entry
Interrupt: refer to Table 46:
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table

Mode exit

If WFE was used for entry and SEVONPEND = 0:
Wakeup event: refer to Section 13.3.2: Wakeup event management
If WFE was used for entry and SEVONPEND = 1:
Interrupt even when disabled in NVIC: refer to Table 46:
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table or Wakeup
event: refer to Section 13.3.2: Wakeup event management

Wakeup latency

5.3.5

None

Low-power sleep mode (LP sleep)
Please refer to the product datasheet for more details on voltage regulator and peripherals
operating conditions.

I/O states in Low-power sleep mode
In Low-power sleep mode, all I/O pins keep the same state as in Run mode.

Entering the Low-power sleep mode
The Low-power sleep mode is entered from low-power run mode according Section :
Entering low power mode, when the SLEEPDEEP bit in the Cortex®-M4 System Control
register is clear.
Refer to Table 24: Low-power sleep for details on how to enter the Low-power sleep mode.

Exiting the Low-power sleep mode
The low-power Sleep mode is exit according Section : Exiting low power mode. When
exiting the Low-power sleep mode by issuing an interrupt or an event, the MCU is in Lowpower run mode.
Refer to Table 24: Low-power sleep for details on how to exit the Low-power sleep mode.

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Table 24. Low-power sleep

Low-power sleep-now
mode

Description
Low-power sleep mode is entered from the Low-power run mode.
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP = 0
– No interrupt (for WFI) or event (for WFE) is pending
Refer to the Cortex®-M4 System Control register.

Mode entry

Low-power sleep mode is entered from the Low-power run mode.
On return from ISR while:
– SLEEPDEEP = 0 and
– SLEEPONEXIT = 1
– No interrupt is pending
Refer to the Cortex®-M4 System Control register.
If WFI or Return from ISR was used for entry
Interrupt: refer to Table 46:
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table
If WFE was used for entry and SEVONPEND = 0:
Wakeup event: refer to Section 13.3.2: Wakeup event management

5.3.6

Mode exit

If WFE was used for entry and SEVONPEND = 1:
Interrupt even when disabled in NVIC: refer to Table 46:
STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table
Wakeup event: refer to Section 13.3.2: Wakeup event management
After exiting the Low-power sleep mode, the MCU is in Low-power run
mode.

Wakeup latency

None

Stop 0 mode
The Stop 0 mode is based on the Cortex®-M4 deepsleep mode combined with the
peripheral clock gating. The voltage regulator is configured in main regulator mode. In Stop
0 mode, all clocks in the VCORE domain are stopped; the PLL, the MSI, the HSI16 and the
HSE oscillators are disabled. Some peripherals with the wakeup capability (I2Cx (x=1,2,3),
U(S)ARTx(x=1,2,3) and LPUART) can switch on the HSI16 to receive a frame, and switch
off the HSI16 after receiving the frame if it is not a wakeup frame. In this case, the HSI16
clock is propagated only to the peripheral requesting it.
SRAM1, SRAM2 and register contents are preserved.
The BOR is always available in Stop 0 mode. The consumption is increased when
thresholds higher than VBOR0 are used.

I/O states in Stop 0 mode
In the Stop 0 mode, all I/O pins keep the same state as in the Run mode.

Entering the Stop 0 mode
The Stop 0 mode is entered according Section : Entering low power mode, when the
SLEEPDEEP bit in the Cortex®-M4 System Control register is set.

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Refer to Table 25: Stop 0 mode for details on how to enter the Stop 0 mode.
If Flash memory programming is ongoing, the Stop 0 mode entry is delayed until the
memory access is finished.
If an access to the APB domain is ongoing, The Stop 0 mode entry is delayed until the APB
access is finished.
In Stop 0 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 32.3: IWDG functional description.

•

real-time clock (RTC): this is configured by the RTCEN bit in the Backup domain
control register (RCC_BDCR)

•

Internal RC oscillator (LSI): this is configured by the LSION bit in the Control/status
register (RCC_CSR).

•

External 32.768 kHz oscillator (LSE): this is configured by the LSEON bit in the Backup
domain control register (RCC_BDCR).

Several peripherals can be used in Stop 0 mode and can add consumption if they are
enabled and clocked by LSI or LSE, or when they request the HSI16 clock: LCD, LPTIM1,
LPTIM2, I2Cx (x=1,2,3,4) U(S)ARTx(x=1,2,3,4), LPUART.
The DACx (x=1,2), the OPAMP and the comparators can be used in Stop 0 mode, the PVMx
(x=1,3,4) and the PVD as well. If they are not needed, they must be disabled by software to
save their power consumptions.
The ADCx (x=1), temperature sensor and VREFBUF buffer can consume power during the
Stop 0 mode, unless they are disabled before entering this mode.

Exiting the Stop 0 mode
The Stop 0 mode is exit according Section : Entering low power mode.
Refer to Table 25: Stop 0 mode for details on how to exit Stop 0 mode.
When exiting Stop 0 mode by issuing an interrupt or a wakeup event, the HSI16 oscillator is
selected as system clock if the bit STOPWUCK is set in Clock configuration register
(RCC_CFGR). The MSI oscillator is selected as system clock if the bit STOPWUCK is
cleared. The wakeup time is shorter when HSI16 is selected as wakeup system clock. The
MSI selection allows wakeup at higher frequency, up to 48 MHz.
When exiting the Stop 0 mode, the MCU is either in Run mode Range 1 or Run Mode Range
2 depending on VOS bit in PWR_CR1.

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Table 25. Stop 0 mode

Stop 0 mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– No interrupt (for WFI) or event (for WFE) is pending
– LPMS = “000” in PWR_CR1

Mode entry

On Return from ISR while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– SLEEPONEXIT = 1
– No interrupt is pending
– LPMS = “000” in PWR_CR1
Note: To enter Stop 0 mode, all EXTI Line pending bits (in Pending
register 1 (EXTI_PR1)), and the peripheral flags generating wakeup
interrupts must be cleared. Otherwise, the Stop 0 mode entry
procedure is ignored and program execution continues.

Mode exit

If WFI or Return from ISR was used for entry
Any EXTI Line configured in Interrupt mode (the corresponding EXTI
Interrupt vector must be enabled in the NVIC). The interrupt source can
be external interrupts or peripherals with wakeup capability. Refer to
Table 46: STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table.
If WFE was used for entry and SEVONPEND = 0:
Any EXTI Line configured in event mode. Refer to Section 13.3.2:
Wakeup event management.
If WFE was used for entry and SEVONPEND = 1:
Any EXTI Line configured in Interrupt mode (even if the corresponding
EXTI Interrupt vector is disabled in the NVIC). The interrupt source can
be external interrupts or peripherals with wakeup capability. Refer
toTable 46: STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table.
Wakeup event: refer to Section 13.3.2: Wakeup event management

Wakeup latency

5.3.7

Longest wakeup time between: MSI or HSI16 wakeup time and Flash
wakeup time from Stop 0 mode.

Stop 1 mode
The Stop 1 mode is the same as Stop 0 mode except that the main regulator is OFF, and
only the low-power regulator is ON. Stop 1 mode can be entered from Run mode and from
Low-power run mode.
Refer to Table 26: Stop 1 mode for details on how to enter and exit Stop 1 mode.

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Table 26. Stop 1 mode
Stop 1 mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– No interrupt (for WFI) or event (for WFE) is pending
– LPMS = “001” in PWR_CR1

Mode entry

On Return from ISR while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– SLEEPONEXIT = 1
– No interrupt is pending
– LPMS = “001” in PWR_CR1
Note: To enter Stop 1 mode, all EXTI Line pending bits (in Pending
register 1 (EXTI_PR1)), and the peripheral flags generating wakeup
interrupts must be cleared. Otherwise, the Stop 1 mode entry
procedure is ignored and program execution continues.

Mode exit

If WFI or Return from ISR was used for entry
Any EXTI Line configured in Interrupt mode (the corresponding EXTI
Interrupt vector must be enabled in the NVIC). The interrupt source can
be external interrupts or peripherals with wakeup capability. Refer to
Table 46: STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table.
If WFE was used for entry and SEVONPEND = 0:
Any EXTI Line configured in event mode. Refer to Section 13.3.2:
Wakeup event management.
If WFE was used for entry and SEVONPEND = 1:
Any EXTI Line configured in Interrupt mode (even if the corresponding
EXTI Interrupt vector is disabled in the NVIC). The interrupt source can
be external interrupts or peripherals with wakeup capability. Refer
toTable 46: STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table.
Wakeup event: refer to Section 13.3.2: Wakeup event management

Wakeup latency

5.3.8

Longest wakeup time between: MSI or HSI16 wakeup time and regulator
wakeup time from Low-power mode + Flash wakeup time from Stop 1
mode.

Stop 2 mode
The Stop 2 mode is based on the Cortex®-M4 deepsleep mode combined with peripheral
clock gating. In Stop 2 mode, all clocks in the VCORE domain are stopped, the PLL, the MSI,
the HSI16 and the HSE oscillators are disabled. Some peripherals with wakeup capability
(I2C3 and LPUART) can switch on the HSI16 to receive a frame, and switch off the HSI16
after receiving the frame if it is not a wakeup frame. In this case the HSI16 clock is
propagated only to the peripheral requesting it.
SRAM1, SRAM2 and register contents are preserved.
The BOR is always available in Stop 2 mode. The consumption is increased when
thresholds higher than VBOR0 are used.

Note:

The comparators outputs, the LPUART outputs and the LPTIM1 outputs are forced to low
speed (OSPEEDy=00) during the Stop 2 mode.

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I/O states in Stop 2 mode
In the Stop 2 mode, all I/O pins keep the same state as in the Run mode.

Entering Stop 2 mode
The Stop 2 mode is entered according Section : Entering low power mode, when the
SLEEPDEEP bit in the Cortex®-M4 System Control register is set.
Refer to Table 27: Stop 2 mode for details on how to enter the Stop 2 mode.
Stop 2 mode can only be entered from Run mode. It is not possible to enter Stop 2 mode
from the Low-power run mode.
If Flash memory programming is ongoing, the Stop 2 mode entry is delayed until the
memory access is finished.
If an access to the APB domain is ongoing, The Stop 2 mode entry is delayed until the APB
access is finished.
In Stop 2 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 32.3: IWDG functional description in Section 32: Independent watchdog
(IWDG).

•

Real-time clock (RTC): this is configured by the RTCEN bit in the Backup domain
control register (RCC_BDCR)

•

Internal RC oscillator (LSI): this is configured by the LSION bit in the Control/status
register (RCC_CSR).

•

External 32.768 kHz oscillator (LSE): this is configured by the LSEON bit in the Backup
domain control register (RCC_BDCR).

Several peripherals can be used in Stop 2 mode and can add consumption if they are
enabled and clocked by LSI or LSE, or when they request the HSI16 clock: LCD, LPTIM1,
I2C3, LPUART.
The comparators can be used in Stop 2 mode, the PVMx (x=1,3,4) and the PVD as well. If
they are not needed, they must be disabled by software to save their power consumptions.
The ADCx, OPAMPx, DACx, temperature sensor and VREFBUF buffer can consume power
during Stop 2 mode, unless they are disabled before entering this mode.
All the peripherals which cannot be enabled in Stop 2 mode must be either disabled by
clearing the Enable bit in the peripheral itself, or put under reset state by setting the
corresponding bit in the AHB1 peripheral reset register (RCC_AHB1RSTR), AHB2
peripheral reset register (RCC_AHB2RSTR), AHB3 peripheral reset register
(RCC_AHB3RSTR), APB1 peripheral reset register 1 (RCC_APB1RSTR1), APB1
peripheral reset register 2 (RCC_APB1RSTR2), APB2 peripheral reset register
(RCC_APB2RSTR).

Exiting Stop 2 mode
The Stop 2 mode is exit according Section : Exiting low power mode.
Refer to Table 27: Stop 2 mode for details on how to exit Stop 2 mode.

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When exiting Stop 2 mode by issuing an interrupt or a wakeup event, the HSI16 oscillator is
selected as system clock if the bit STOPWUCK is set in Clock configuration register
(RCC_CFGR). The MSI oscillator is selected as system clock if the bit STOPWUCK is
cleared. The wakeup time is shorter when HSI16 is selected as wakeup system clock. The
MSI selection allows wakeup at higher frequency, up to 48 MHz.
When exiting the Stop 2 mode, the MCU is in Run mode (Range 1 or Range 2 depending on
VOS bit in PWR_CR1).
Table 27. Stop 2 mode
Stop 2 mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– No interrupt (for WFI) or event (for WFE) is pending
– LPMS = “010” in PWR_CR1

Mode entry

On return from ISR while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– SLEEPONEXIT = 1
– No interrupt is pending
– LPMS = “010” in PWR_CR1
Note: To enter Stop 2 mode, all EXTI Line pending bits (in Pending
register 1 (EXTI_PR1)), and the peripheral flags generating wakeup
interrupts must be cleared. Otherwise, the Stop mode entry
procedure is ignored and program execution continues.

Mode exit

If WFI or Return from ISR was used for entry:
Any EXTI Line configured in Interrupt mode (the corresponding EXTI
Interrupt vector must be enabled in the NVIC). The interrupt source can
be external interrupts or peripherals with wakeup capability. Refer to
Table 46: STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table.
If WFE was used for entry and SEVONPEND = 0:
Any EXTI Line configured in event mode. Refer to Section 13.3.2:
Wakeup event management.
If WFE was used for entry and SEVONPEND = 1:
Any EXTI Line configured in Interrupt mode (even if the corresponding
EXTI Interrupt vector is disabled in the NVIC). The interrupt source can
be external interrupts or peripherals with wakeup capability. Refer to
Table 46: STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table.
Any EXTI Line configured in event mode. Refer to Section 13.3.2:
Wakeup event management.

Wakeup latency

5.3.9

Longest wakeup time between: MSI or HSI16 wakeup time and regulator
wakeup time from Low-power mode + Flash wakeup time from Stop 2
mode.

Standby mode
The Standby mode allows to achieve the lowest power consumption with BOR. It is based
on the Cortex®-M4 deepsleep mode, with the voltage regulators disabled (except when
SRAM2 content is preserved). The PLL, the HSI16, the MSI and the HSE oscillators are
also switched off.

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SRAM1 and register contents are lost except for registers in the Backup domain and
Standby circuitry (see Figure 7). SRAM2 content can be preserved if the bit RRS is set in
the PWR_CR3 register. In this case the Low-power regulator is ON and provides the supply
to SRAM2 only.
The BOR is always available in Standby mode. The consumption is increased when
thresholds higher than VBOR0 are used.

I/O states in Standby mode
In the Standby mode, the IO’s are by default in floating state. If the APC bit of PWR_CR3
register has been set, the I/Os can be configured either with a pull-up (refer to
PWR_PUCRx registers (x=A,B,C,D,E,F,G,H)), or with a pull-down (refer to PWR_PDCRx
registers (x=A,B,C,D,E,F,G,H)), or can be kept in analog state if none of the PWR_PUCRx
or PWR_PDCRx register has been set. The pull-down configuration has highest priority over
pull-up configuration in case both PWR_PUCRx and PWR_PDCRx are set for the same IO.
Some I/Os (listed in Section 8.3.1: General-purpose I/O (GPIO)) are used for JTAG/SW
debug and can only be configured to their respective reset pull-up or pull-down state during
Standby mode setting their respective bit in the PWR_PUCRx or PWR_PDCRx registers to
‘1’, or will be configured to floating state if the bit is kept at ‘0’.
The RTC outputs on PC13 are functional in Standby mode. PC14 and PC15 used for LSE
are also functional. 5 wakeup pins (WKUPx, x=1,2...5) and the 3 RTC tampers are available.

Entering Standby mode
The Standby mode is entered according Section : Entering low power mode, when the
SLEEPDEEP bit in the Cortex®-M4 System Control register is set.
Refer to Table 28: Standby mode for details on how to enter Standby mode.
In Standby mode, the following features can be selected by programming individual control
bits:
•

Independent watchdog (IWDG): the IWDG is started by writing to its Key register or by
hardware option. Once started it cannot be stopped except by a reset. See
Section 32.3: IWDG functional description in Section 32: Independent watchdog
(IWDG).

•

real-time clock (RTC): this is configured by the RTCEN bit in the Backup domain
control register (RCC_BDCR)

•

Internal RC oscillator (LSI): this is configured by the LSION bit in the Control/status
register (RCC_CSR).

•

External 32.768 kHz oscillator (LSE): this is configured by the LSEON bit in the Backup
domain control register (RCC_BDCR)

Exiting Standby mode
The Standby mode is exited according Section : Entering low power mode. The SBF status
flag in the Power control register 3 (PWR_CR3) indicates that the MCU was in Standby
mode. All registers are reset after wakeup from Standby except for Power control register 3
(PWR_CR3).
Refer to Table 28: Standby mode for more details on how to exit Standby mode.

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Power control (PWR)
When exiting Standby mode, I/O’s that were configured with pull-up or pull-down during
Standby through registers PWR_PUCRx or PWR_PDCRx will keep this configuration upon
exiting Standby mode until the bit APC of PWR_CR3 register has been cleared. Once the bit
APC is cleared, they will be either configured to their reset values or to the pull-up/pull-down
state according the GPIOx_PUPDR registers. The content of the PWR_PUCRx or
PWR_PDCRx registers however is not lost and can be re-used for a sub-sequent entering
into Standby mode.
Some I/Os (listed in Section 8.3.1: General-purpose I/O (GPIO)) are used for JTAG/SW
debug and have internal pull-up or pull-down activated after reset so will be configured at
this reset value as well when exiting Standby mode.
For IO’s, with a pull-up or pull-down pre-defined after reset (some JTAG/SW IO’s) or with
GPIOx_PUPDR programming done after exiting from Standby, in case those programming
is different from the PWR_PUCRx or PWR_PDCRx programmed value during Standby, both
a pull-down and pull-up will be applied until the bit APC is cleared, releasing the
PWR_PUCRx or PWR_PDCRx programmed value.
Table 28. Standby mode
Standby mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– No interrupt (for WFI) or event (for WFE) is pending
– LPMS = “011” in PWR_CR1
– WUFx bits are cleared in power status register 1 (PWR_SR1)

Mode entry

On return from ISR while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– SLEEPONEXIT = 1
– No interrupt is pending
– LPMS = “011” in PWR_CR1 and
– WUFx bits are cleared in power status register 1 (PWR_SR1)
– The RTC flag corresponding to the chosen wakeup source (RTC Alarm
A, RTC Alarm B, RTC wakeup, tamper or timestamp flags) is cleared

Mode exit

WKUPx pin edge, RTC event, external Reset in NRST pin, IWDG Reset,
BOR reset

Wakeup latency

Reset phase

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Shutdown mode
The Shutdown mode allows to achieve the lowest power consumption. It is based on the
deepsleep mode, with the voltage regulator disabled. The VCORE domain is consequently
powered off. The PLL, the HSI16, the MSI, the LSI and the HSE oscillators are also
switched off.
SRAM1, SRAM2 and register contents are lost except for registers in the Backup domain.
The BOR is not available in Shutdown mode. No power voltage monitoring is possible in this
mode, therefore the switch to Backup domain is not supported.

I/O states in Shutdown mode
In the Shutdown mode, are by default in floating state. If the APC bit of PWR_CR3 register
has been set, the I/Os can be configured either with a pull-up (refer to PWR_PUCRx
registers (x=A,B,C,D,E,F,G,H), or with a pull-down (refer to PWR_PDCRx registers
(x=A,B,C,D,E,F,G,H)), or can be kept in analog state if none of the PWR_PUCRx or
PWR_PDCRx register has been set. The pull-down configuration has highest priority over
pull-up configuration in case both PWR_PUCRx and PWR_PDCRx are set for the same IO.
However this configuration is lost when exiting the Shutdown mode due to the power-on
reset.
Some I/Os (listed in Section 8.3.1: General-purpose I/O (GPIO)) are used for JTAG/SW
debug and can only be configured to their respective reset pull-up or pull-down state during
Standby mode setting their respective bit in the PWR_PUCRx or PWR_PDCRx registers to
‘1’, or will be configured to floating state if the bit is kept at ‘0’.
The RTC outputs on PC13 are functional in Shutdown mode. PC14 and PC15 used for LSE
are also functional. 5 wakeup pins (WKUPx, x=1,2...5) and the 3 RTC tampers are available.

Entering Shutdown mode
The Shutdown mode is entered according Entering low power mode, when the
SLEEPDEEP bit in the Cortex®-M4 System Control register is set.
Refer to Table 29: Shutdown mode for details on how to enter Shutdown mode.
In Shutdown mode, the following features can be selected by programming individual
control bits:
•

real-time clock (RTC): this is configured by the RTCEN bit in the Backup domain
control register (RCC_BDCR). Caution: in case of VDD power-down the RTC content
will be lost.

•

external 32.768 kHz oscillator (LSE): this is configured by the LSEON bit in the Backup
domain control register (RCC_BDCR)

Exiting Shutdown mode
The Shutdown mode is exit according Section : Exiting low power mode. A power-on reset
occurs when exiting from Shutdown mode. All registers (except for the ones in the Backup
domain) are reset after wakeup from Shutdown.
Refer to Table 29: Shutdown mode for more details on how to exit Shutdown mode.
When exiting Shutdown mode, I/Os that were configured with pull-up or pull-down during
Shutdown through registers PWR_PUCRx or PWR_PDCRx will lose their configuration and
will be configured in floating state or to their pull-up pull-down reset value (for some I/Os

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Power control (PWR)
listed in Section 8.3.1: General-purpose I/O (GPIO)).
Table 29. Shutdown mode
Shutdown mode

Description
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– No interrupt (for WFI) or event (for WFE) is pending
– LPMS = “1XX” in PWR_CR1
– WUFx bits are cleared in power status register 1 (PWR_SR1)

Mode entry

5.3.11

On return from ISR while:
– SLEEPDEEP bit is set in Cortex®-M4 System Control register
– SLEEPONEXT = 1
– No interrupt is pending
– LPMS = “1XX” in PWR_CR1 and
– WUFx bits are cleared in power status register 1 (PWR_SR1)
– The RTC flag corresponding to the chosen wakeup source (RTC
Alarm A, RTC Alarm B, RTC wakeup, tamper or timestamp flags) is
cleared

Mode exit

WKUPx pin edge, RTC event, external Reset in NRST pin

Wakeup latency

Reset phase

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 (0, 1 or 2) 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 Backup domain control register (RCC_BDCR):
•

Low-power 32.768 kHz external crystal oscillator (LSE OSC)
This clock source provides a precise time base with very low-power consumption.

•

Low-power internal RC Oscillator (LSI)
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 18 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 18.
To wakeup from Stop mode with an RTC wakeup event, it is necessary to:
•

Configure the EXTI Line 20 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 20.
The LCD Start of frame interrupt can also be used as a periodic wakeup from Stop (0, 1 or 2)
mode. The LCD is not available in Standby mode.
The LCD clock is derived from the RTC clock selected by RTCSEL[1:0].

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PWR registers
The peripheral registers can be accessed by half-words (16-bit) or words (32-bit).

5.4.1

Power control register 1 (PWR_CR1)
Address offset: 0x00
Reset value: 0x0000 0200. This register is reset after 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.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

LPR

Res.

Res.

Res.

DBP

Res.

Res.

Res.

Res.

Res.

rw

VOS[1:0]
rw

rw

rw

LPMS[2:0]
rw

rw

rw

Bits 31:15 Reserved, must be kept at reset value.
Bit 14 LPR: Low-power run
When this bit is set, the regulator is switched from main mode (MR) to low-power mode
(LPR).
Note: Stop 2 mode cannot be entered when LPR bit is set. Stop 1 is entered instead.
Bits 13:11 Reserved, must be kept at reset value.
Bits 10:9 VOS: Voltage scaling range selection
00: Cannot be written (forbidden by hardware)
01: Range 1
10: Range 2
11: Cannot be written (forbidden by hardware)
Bit 8 DBP: Disable backup 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
Bits 7:3 Reserved, must be kept at reset value.
Bits 2:0 LPMS[2:0]: Low-power mode selection
These bits select the low-power mode entered when CPU enters the deepsleep mode.
000: Stop 0 mode
001: Stop 1 mode
010: Stop 2 mode
011: Standby mode
1xx: Shutdown mode
Note: If LPR bit is set, Stop 2 mode cannot be selected and Stop 1 mode shall be entered
instead of Stop 2.
In Standby mode, SRAM2 can be preserved or not, depending on RRS bit configuration
in PWR_CR3.

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Power control (PWR)

5.4.2

Power control register 2 (PWR_CR2)
Address offset: 0x04
Reset value: 0x0000 0000. This register is reset when exiting the 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.

USV(1)

Res.

Res.

PVME4 PVME3

rw

rw

rw

Res.

PVME1

PLS[2:0]

(1)

rw

rw

rw

PVDE
rw

rw

1. Available on STM32L4x2xx and STM32L4x3xx devices only.

Bits 31:11 Reserved, must be kept at reset value.
Bit 10 USV(1): VDDUSB USB supply valid
This bit is used to validate the VDDUSB supply for electrical and logical isolation purpose.
Setting this bit is mandatory to use the USB FS peripheral. If VDDUSB is not always
present in the application, the PVM can be used to determine whether this supply is ready or
not.
0: VDDUSB is not present. Logical and electrical isolation is applied to ignore this supply.
1: VDDUSB is valid.
Bits 9:8 Reserved, must be kept at reset value.
Bit 7 PVME4: Peripheral voltage monitoring 4 enable: VDDA vs. 1.8 V
0: PVM4 (VDDA monitoring vs. 1.8 V threshold) disable.
1: PVM4 (VDDA monitoring vs. 1.8 V threshold) enable.
Bit 6 PVME3: Peripheral voltage monitoring 3 enable: VDDA vs. 1.62 V
0: PVM3 (VDDA monitoring vs. 1.62 V threshold) disable.
1: PVM3 (VDDA monitoring vs. 1.62 V threshold) enable.
Bit 5 Reserved, must be kept at reset value.

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Bit 4 PVME1(1): Peripheral voltage monitoring 1 enable: VDDUSB vs. 1.2 V
0: PVM1 (VDDUSB monitoring vs. 1.2 V threshold) disable.
1: PVM1 (VDDUSB monitoring vs. 1.2 V threshold) enable.
Bits 3:1 PLS[2:0]: Power voltage detector level selection.
These bits select the voltage threshold detected by the power voltage detector:
000: VPVD0 around 2.0 V
001: VPVD1 around 2.2 V
010: VPVD2 around 2.4 V
011: VPVD3 around 2.5 V
100: VPVD4 around 2.6 V
101: VPVD5 around 2.8 V
110: VPVD6 around 2.9 V
111: External input analog voltage PVD_IN (compared internally to VREFINT)
Note: These bits are write-protected when the bit PVDL (PVD Lock) is set in the
SYSCFG_CBR register.
These bits are reset only by a system reset.
Bit 0 PVDE: Power voltage detector enable
0: Power voltage detector disable.
1: Power voltage detector enable.
Note: This bit is write-protected when the bit PVDL (PVD Lock) is set in the SYSCFG_CBR
register.
This bit is reset only by a system reset.
1. Available on STM32L4x2xx and STM32L4x3xx devices only.

5.4.3

Power control register 3 (PWR_CR3)
Address offset: 0x08
Reset value: 0x0000 8000. This register is not reset when exiting Standby modes and with
the PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a 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

EIWUL

Res.

Res.

Res.

(1)

APC

Res.

RRS

Res.

Res.

Res.

EWUP
5

EWUP
4

EWUP
3

EWUP
2

EWUP
1

rw

rw

rw

rw

rw

rw

rw

rw

ENULP

rw

1. This bit is available on STM32L412xx and STM32L422xx devices only.

Bits 31:16 Reserved, must be kept at reset value.
Bit 15 EIWUL: Enable internal wakeup line
0: Internal wakeup line disable.
1: Internal wakeup line enable.
Bits 14:12 Reserved, must be kept at reset value.

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Bit 11 ENULP: Enable ULP sampling
When this bit is set, the BORL, BORH and PVD are periodically sampled instead continuous
monitoring to reduce power consumption. Fast supply drop between two sample/compare
phases will not be detected in this mode. This bit has impact only on STOP2, Standby and
shutdown low power modes.(1)
Bit 10 APC: Apply pull-up and pull-down configuration
When this bit is set, the I/O pull-up and pull-down configurations defined in the PWR_PUCRx
and PWR_PDCRx registers are applied. When this bit is cleared, the PWR_PUCRx and
PWR_PDCRx registers are not applied to the I/Os, instead the I/Os will be in floating mode
during Standby or configured according GPIO controller GPIOx_PUPDR register during RUN
mode.
Bit 9 Reserved, must be kept at reset value.
Bit 8 RRS: SRAM2 retention in Standby mode
0: SRAM2 is powered off in Standby mode (SRAM2 content is lost).
1: SRAM2 is powered by the low-power regulator in Standby mode (SRAM2 content is kept).
Bits 7:5 Reserved, must be kept at reset value.
Bit 4 EWUP5: Enable Wakeup pin WKUP5
When this bit is set, the external wakeup pin WKUP5 is enabled and triggers a wakeup from
Standby or Shutdown event when a rising or a falling edge occurs.The active edge is
configured via the WP5 bit in the PWR_CR4 register.
Bit 3 EWUP4: Enable Wakeup pin WKUP4
When this bit is set, the external wakeup pin WKUP4 is enabled and triggers a wakeup from
Standby or Shutdown event when a rising or a falling edge occurs. The active edge is
configured via the WP4 bit in the PWR_CR4 register.
Bit 2 EWUP3: Enable Wakeup pin WKUP3
When this bit is set, the external wakeup pin WKUP3 is enabled and triggers a wakeup from
Standby or Shutdown event when a rising or a falling edge occurs. The active edge is
configured via the WP3 bit in the PWR_CR4 register.
Bit 1 EWUP2: Enable Wakeup pin WKUP2
When this bit is set, the external wakeup pin WKUP2 is enabled and triggers a wakeup from
Standby or Shutdown event when a rising or a falling edge occurs. The active edge is
configured via the WP2 bit in the PWR_CR4 register.
Bit 0 EWUP1: Enable Wakeup pin WKUP1
When this bit is set, the external wakeup pin WKUP1 is enabled and triggers a wakeup from
Standby or Shutdown event when a rising or a falling edge occurs. The active edge is
configured via the WP1 bit in the PWR_CR4 register.
1. This bit is available on STM32L12x and STM3L422xx devices only.

5.4.4

Power control register 4 (PWR_CR4)
Address offset: 0x0C
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
the PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a read).

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31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

EXT_S
MPS_O
N(1)

Res.

Res.

Res.

VBRS

VBE

Res.

Res.

Res.

WP5

WP4

WP3

WP2

WP1

rw

rw

rw

rw

rw

rw

rw

Res.

rw

1. This bit is available on STM32L412xx and STM32L422xx devices only.

Bits 31:14 Reserved, must be kept at reset value.
Bit 13 EXT_SMPS_ON: External SMPS On(1)
This bit informs the internal regulator about external SMPS switch status to decrease regulator
output to 0.95 V in Range 2, allowing the external SMPS output down to 1.00 V.
0: the external SMPS switch is open
1: the external SMPS switch is closed, internal regulator output is set to 0.95 V
Bits 12:10 Reserved, must be kept at reset value.
Bit 9 VBRS: VBAT battery charging resistor selection
0: Charge VBAT through a 5 kOhms resistor
1: Charge VBAT through a 1.5 kOhms resistor
Bit 8 VBE: VBAT battery charging enable
0: VBAT battery charging disable
1: VBAT battery charging enable
Bits 7:5 Reserved, must be kept at reset value.
Bit 4 WP5: Wakeup pin WKUP5 polarity
This bit defines the polarity used for an event detection on external wake-up pin, WKUP5
0: Detection on high level (rising edge)
1: Detection on low level (falling edge)
Bit 3 WP4: Wakeup pin WKUP4 polarity
This bit defines the polarity used for an event detection on external wake-up pin, WKUP4
0: Detection on high level (rising edge)
1: Detection on low level (falling edge)
Bit 2 WP3: Wakeup pin WKUP3 polarity
This bit defines the polarity used for an event detection on external wake-up pin, WKUP3
0: Detection on high level (rising edge)
1: Detection on low level (falling edge)
Bit 1 WP2: Wakeup pin WKUP2 polarity
This bit defines the polarity used for an event detection on external wake-up pin, WKUP2
0: Detection on high level (rising edge)
1: Detection on low level (falling edge)
Bit 0 WP1: Wakeup pin WKUP1 polarity
This bit defines the polarity used for an event detection on external wake-up pin, WKUP1
0: Detection on high level (rising edge)
1: Detection on low level (falling edge)
1. This bit is available on STM32L412xx and STM32L422xx devices only.

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Power control (PWR)

5.4.5

Power status register 1 (PWR_SR1)
Address offset: 0x10
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
the PWRRST bit in the RCC_APB1RSTR1 register.
Access: 2 additional APB cycles are needed to read this register vs. 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

WUFI

Res.

EXT_S
MPS_R
DY(1)

Res.

Res.

Res.

Res.

SBF

Res.

Res.

Res.

WUF5

WUF4

WUF3

WUF2

WUF1

r

r

r

r

r

r

r

r

1. This bit is available on STM32L412xx and STM32L422xx devices only.

Bits 31:16 Reserved, must be kept at reset value.
Bit 15 WUFI: Wakeup flag internal
This bit is set when a wakeup is detected on the internal wakeup line. It is cleared when all
internal wakeup sources are cleared.
Bit 14 Reserved, must be kept at reset value.
Bit 13 EXT_SMPS_RDY: External SMPS Ready(1)
This bit informs the state of regulator transition from Range 1 to Range 2..
0: Internal regulator not ready in Range 2, the external SMPS cannot be connected
1: Internal regulator ready in Range 2, the external SMPS can be connected
Bits 12:9 Reserved, must be kept at reset value.
Bit 8 SBF: Standby flag
This bit is set by hardware when the device enters the Standby mode and is cleared by
setting the CSBF bit in the PWR_SCR register, or by a power-on reset. It is not cleared by the
system reset.
0: The device did not enter the Standby mode
1: The device entered the Standby mode
Bits 7:5 Reserved, must be kept at reset value.
Bit 4 WUF5: Wakeup flag 5
This bit is set when a wakeup event is detected on wakeup pin, WKUP5. It is cleared by
writing ‘1’ in the CWUF5 bit of the PWR_SCR register.
Bit 3 WUF4: Wakeup flag 4
This bit is set when a wakeup event is detected on wakeup pin,WKUP4. It is cleared by
writing ‘1’ in the CWUF4 bit of the PWR_SCR register.

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Bit 2 WUF3: Wakeup flag 3
This bit is set when a wakeup event is detected on wakeup pin, WKUP3. It is cleared by
writing ‘1’ in the CWUF3 bit of the PWR_SCR register.
Bit 1 WUF2: Wakeup flag 2
This bit is set when a wakeup event is detected on wakeup pin, WKUP2. It is cleared by
writing ‘1’ in the CWUF2 bit of the PWR_SCR register.
Bit 0 WUF1: Wakeup flag 1
This bit is set when a wakeup event is detected on wakeup pin, WKUP1. It is cleared by
writing ‘1’ in the CWUF1 bit of the PWR_SCR register.
1. This bit is available on STM32L412xx and STM32L422xx devices only.

5.4.6

Power status register 2 (PWR_SR2)
Address offset: 0x14
Reset value: 0x0000 0000. This register is partially reset when exiting Standby/Shutdown
modes.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PVMO4 PVMO3
r

r

Res.

PVMO1
(1)

PVDO

VOSF

r

r

r

REGLP REGLP
F
S
r

r

1. Available on STM32L4x2xx and STM32L4x3xx devices only.

Bits 31:16 Reserved, must be kept at reset value.
Bit 15 PVMO4: Peripheral voltage monitoring output: VDDA vs. 1.8 V
0: VDDA voltage is above PVM4 threshold (around 1.8 V).
1: VDDA voltage is below PVM4 threshold (around 1.8 V).
Note: PVMO4 is cleared when PVM4 is disabled (PVME4 = 0). After enabling PVM4, the
PVM4 output is valid after the PVM4 wakeup time.
Bit 14 PVMO3: Peripheral voltage monitoring output: VDDA vs. 1.62 V
0: VDDA voltage is above PVM3 threshold (around 1.62 V).
1: VDDA voltage is below PVM3 threshold (around 1.62 V).
Note: PVMO3 is cleared when PVM3 is disabled (PVME3 = 0). After enabling PVM3, the
PVM3 output is valid after the PVM3 wakeup time.
Bit 13 Reserved, must be kept at reset value.
Bit 12 PVMO1(1): Peripheral voltage monitoring output: VDDUSB vs. 1.2 V
0: VDDUSB voltage is above PVM1 threshold (around 1.2 V).
1: VDDUSB voltage is below PVM1 threshold (around 1.2 V).
Note: PVMO1 is cleared when PVM1 is disabled (PVME1 = 0). After enabling PVM1, the
PVM1 output is valid after the PVM1 wakeup time.
Bit 11 PVDO: Power voltage detector output
0: VDD is above the selected PVD threshold
1: VDD is below the selected PVD threshold

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RM0394

Power control (PWR)

Bit 10 VOSF: Voltage scaling flag
A delay is required for the internal regulator to be ready after the voltage scaling has been
changed. VOSF indicates that the regulator reached the voltage level defined with VOS bits
of the PWR_CR1 register.
0: The regulator is ready in the selected voltage range
1: The regulator output voltage is changing to the required voltage level
Bit 9 REGLPF: Low-power regulator flag
This bit is set by hardware when the MCU is in Low-power run mode. When the MCU exits
from the Low-power run mode, this bit remains at 1 until the regulator is ready in main mode.
A polling on this bit must be done before increasing the product frequency.
This bit is cleared by hardware when the regulator is ready.
0: The regulator is ready in main mode (MR)
1: The regulator is in low-power mode (LPR)
Bit 8 REGLPS: Low-power regulator started
This bit provides the information whether the low-power regulator is ready after a power-on
reset or a Standby/Shutdown. If the Standby mode is entered while REGLPS bit is still
cleared, the wakeup from Standby mode time may be increased.
0: The low-power regulator is not ready
1: The low-power regulator is ready
Bits 7:0 Reserved, must be kept at reset value.
1. Available on STM32L4x2xx and STM32L4x3xx devices only.

5.4.7

Power status clear register (PWR_SCR)
Address offset: 0x18
Reset value: 0x0000 0000.
Access: 3 additional APB cycles are needed to write this register vs. a standard APB write.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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.

CWUF
5

CWUF
4

CWUF
3

CWUF
2

CWUF
1

w

w

w

w

w

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CSBF

Res.

w

Res.

Bits 31:9 Reserved, must be kept at reset value.
Bit 8 CSBF: Clear standby flag
Setting this bit clears the SBF flag in the PWR_SR1 register.
Bits 7:5 Reserved, must be kept at reset value.
Bit 4 CWUF5: Clear wakeup flag 5
Setting this bit clears the WUF5 flag in the PWR_SR1 register.
Bit 3 CWUF4: Clear wakeup flag 4
Setting this bit clears the WUF4 flag in the PWR_SR1 register.

RM0394 Rev 4

165/1600
174

Power control (PWR)

RM0394

Bit 2 CWUF3: Clear wakeup flag 3
Setting this bit clears the WUF3 flag in the PWR_SR1 register.
Bit 1 CWUF2: Clear wakeup flag 2
Setting this bit clears the WUF2 flag in the PWR_SR1 register.
Bit 0 CWUF1: Clear wakeup flag 1
Setting this bit clears the WUF1 flag in the PWR_SR1 register.

5.4.8

Power Port A pull-up control register (PWR_PUCRA)
Address offset: 0x20.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a 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

PU15

Res.

PU13

PU12

PU11

PU10

PU9

PU8

PU7

PU6

PU5

PU4

PU3

PU2

PU1

PU0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bit 15 PU15: Port A pull-up bit 15
When set, this bit activates the pull-up on PA[15] when APC bit is set in PWR_CR3 register.
If the corresponding PD15 bit is also set, the pull-up is not activated and the pull-down is
activated instead with highest priority.
Bit 14 Reserved, must be kept at reset value.
Bits 13:0 PUy: Port A pull-up bit y (y=0..13)
When set, this bit activates the pull-up on PA[y] when APC bit is set in PWR_CR3 register. If
the corresponding PDy bit is also set, the pull-up is not activated and the pull-down is
activated instead with highest priority.

5.4.9

Power Port A pull-down control register (PWR_PDCRA)
Address offset: 0x24.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a read).

166/1600

RM0394 Rev 4

RM0394

Power control (PWR)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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.

PD14

Res.

PD12

PD11

PD10

PD9

PD8

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:15 Reserved, must be kept at reset value.
Bit 14 PD14: Port A pull-down bit 14
When set, this bit activates the pull-down on PA[14] when APC bit is set in PWR_CR3
register.
Bit 13 Reserved, must be kept at reset value.
Bits 12:0 PDy: Port A pull-down bit y (y=0..12)
When set, this bit activates the pull-down on PA[y] when APC bit is set in PWR_CR3 register.

5.4.10

Power Port B pull-up control register (PWR_PUCRB)
Address offset: 0x28.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a 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

PU15

PU14

PU13

PU12

PU11

PU10

PU9

PU8

PU7

PU6

PU5

PU4

PU3

PU2

PU1

PU0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PUy: Port B pull-up bit y (y=0..15)
When set, this bit activates the pull-up on PB[y] when APC bit is set in PWR_CR3 register. If
the corresponding PDy bit is also set, the pull-up is not activated and the pull-down is
activated instead with highest priority.

5.4.11

Power Port B pull-down control register (PWR_PDCRB)
Address offset: 0x2C.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a read).

RM0394 Rev 4

167/1600
174

Power control (PWR)

RM0394

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PD15

PD14

PD13

PD12

PD11

PD10

PD9

PD8

PD7

PD6

PD5

Res.

PD3

PD2

PD1

PD0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:5 PDy: Port B pull-down bit y (y=5..15)
When set, this bit activates the pull-down on PB[y] when APC bit is set in PWR_CR3 register.
Bit 4 Reserved, must be kept at reset value.
Bits 3:0 PDy: Port B pull-down bit y (y=0..3)
When set, this bit activates the pull-down on PB[y] when APC bit is set in PWR_CR3 register.

5.4.12

Power Port C pull-up control register (PWR_PUCRC)
Address offset: 0x30.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a 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

PU15

PU14

PU13

PU12

PU11

PU10

PU9

PU8

PU7

PU6

PU5

PU4

PU3

PU2

PU1

PU0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PUy: Port C pull-up bit y (y=0..15)
When set, this bit activates the pull-up on PC[y] when APC bit is set in PWR_CR3 register. If
the corresponding PDy bit is also set, the pull-up is not activated and the pull-down is
activated instead with highest priority.

5.4.13

Power Port C pull-down control register (PWR_PDCRC)
Address offset: 0x34.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a read).

168/1600

RM0394 Rev 4

RM0394

Power control (PWR)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PD15

PD14

PD13

PD12

PD11

PD10

PD9

PD8

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PDy: Port C pull-down bit y (y=0..15)
When set, this bit activates the pull-down on PC[y] when APC bit is set in PWR_CR3 register.

5.4.14

Power Port D pull-up control register (PWR_PUCRD)
Not available on STM32L432xx and STM32L442xx devices.
Address offset: 0x38.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a 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

PU15

PU14

PU13

PU12

PU11

PU10

PU9

PU8

PU7

PU6

PU5

PU4

PU3

PU2

PU1

PU0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PUy: Port D pull-up bit y (y=0..15)
When set, this bit activates the pull-up on PD[y] when APC bit is set in PWR_CR3 register. If
the corresponding PDy bit is also set, the pull-up is not activated and the pull-down is
activated instead with highest priority.

5.4.15

Power Port D pull-down control register (PWR_PDCRD)
Not available on STM32L432xx and STM32L442xx devices.
Address offset: 0x3C.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a read).

RM0394 Rev 4

169/1600
174

Power control (PWR)

RM0394

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PD15

PD14

PD13

PD12

PD11

PD10

PD9

PD8

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PDy: Port D pull-down bit y (y=0..15)
When set, this bit activates the pull-down on PD[y] when APC bit is set in PWR_CR3 register.

5.4.16

Power Port E pull-up control register (PWR_PUCRE)
Not available on STM32L432xx and STM32L442xx devices.
Address offset: 0x20.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a 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

PU15

PU14

PU13

PU12

PU11

PU10

PU9

PU8

PU7

PU6

PU5

PU4

PU3

PU2

PU1

PU0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PUy: Port E pull-up bit y (y=0..15)
When set, this bit activates the pull-up on PE[y] when APC bit is set in PWR_CR3 register. If
the corresponding PDy bit is also set, the pull-up is not activated and the pull-down is
activated instead with highest priority.

5.4.17

Power Port E pull-down control register (PWR_PDCRE)
Not available on STM32L432xx and STM32L442xx devices.
Address offset: 0x44.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a read).

170/1600

RM0394 Rev 4

RM0394

Power control (PWR)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PD15

PD14

PD13

PD12

PD11

PD10

PD9

PD8

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 PDy: Port E pull-down bit y (y=0..15)
When set, this bit activates the pull-down on PE[y] when APC bit is set in PWR_CR3 register.

5.4.18

Power Port H pull-up control register (PWR_PUCRH)
Address offset: 0x58.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a read).

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PU3

Res.

PU1

PU0

rw

rw

rw

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 PU3: Port H pull-up bit 3
When set, this bit activates the pull-up on PH[y] when APC bit is set in PWR_CR3 register. If
the corresponding PDy bit is also set, the pull-up is not activated and the pull-down is
activated instead with highest priority.
Bit 2 Reserved, must be kept at reset value.
Bits 1:0 PUy: Port H pull-up bit y (y=0..1)
When set, this bit activates the pull-up on PH[y] when APC bit is set in PWR_CR3 register.
If the corresponding PDy bit is also set, the pull-up is not activated and the pull-down is
activated instead with highest priority.

5.4.19

Power Port H pull-down control register (PWR_PDCRH)
Address offset: 0x5C.
Reset value: 0x0000 0000. This register is not reset when exiting Standby modes and with
PWRRST bit in the RCC_APB1RSTR1 register.
Access: Additional APB cycles are needed to access this register vs. a standard APB
access (3 for a write and 2 for a read).
RM0394 Rev 4

171/1600
174

Power control (PWR)

RM0394

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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.

PD3

Res.

PD1

PD0

rw

rw

rw

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 PD3: Port H pull-down bit 3
When set, this bit activates the pull-down on PH[y] when APC bit is set in PWR_CR3 register.
Bit 2 Reserved, must be kept at reset value.
Bits 1:0 PDy: Port H pull-down bit y (y=0..1)
When set, this bit activates the pull-down on PH[y] when APC bit is set in PWR_CR3 register.

172/1600

RM0394 Rev 4

0x040

PWR_PUCRE

RM0394 Rev 4

PD13

PD12

PD11

PD10

PD9

PD8

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PU12

PU11

PU10

PU9

PU8

PU7

PU6

PU5

PU4

PU3

PU2

PU1

PU0

Reset value

PU13

PU13

PU12

PU11

PU10

PU9

PU8

PU7

PU6

PU5

PU4

PU3

PU2

PU1

PU0

Reset value

PU14

PD14

PD13

PD12

PD11

PD10

PD9

PD8

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

Reset value

PD14

PU14
PU13
PU12
PU11
PU10
PU9
PU8
PU7
PU6
PU5
PU4
PU3
PU2
PU1
PU0

Reset value

PU14

PU1
PU0

PU1
PU0

0
0

PD0

0
PD1

PU2

0
PD2

PU3

Reset value
Res.
Res.
Res.
Res.
Res.
Res.

Res.
CWUF5
CWUF4
CWUF3
CWUF2
CWUF1

0

Res.

0
Res.

0

0
0
0
0
0
0
0
0
0
0
0

WP4
WP3
WP2
WP1

0
0
0
0
0

WUF4
WUF3
WUF2
WUF1

0

WP5

EWUP5
EWUP4
EWUP3
EWUP2
EWUP1

0

WUF5

0
0
0
0

PLS [2:0]
PVDE

PVME1

Res.

PVME3

Res.
Res.

PVME4

Res.

Res.

Res.

0

Res.

Res.

Res.
RRS

USV

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.

0
Res.

0

Res.

VBE

APC

Res.
VBRS

Reset value

SBF

ENULP

Res.

Res.

0

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

EIWUL

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

REGLPF
REGLPS

0

Res.

Res.

0
CSBF

PVDO
VOSF

PVMO1
0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

1

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

PD0

PU2

PU4
0
PD3

0
0

Res.

Res.

PVMO3

Res.

WUFI

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
0

PD1

PU3

PU5
0

PD4

PU6
0

PD5

PU7

0

PD6

PU8

0

PD7

PU9

0

PD8

0

PD9

PU10

0

PD10

PU11

0

PD11

0

PD12

PU12

0
PU13

PVMO4

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.

0

Res.

Res.

PU15

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

PD2

PU4

0

Res.

Reset value
PD14

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
Res.

Res.

Res.

LPR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DBP

VOS
[1:0]

PD3

PU5

PD5

PU6

PD6

PU7

PD7

PU8

PD8

PU9

PD9

PU10

PD10

PU11

PD11

PU12

PD12

PU13

PD13

PU14

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PU15

PD14

Reset value
PD15

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

PU15

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

PD15

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

PU15

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

PD15

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

PU15

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PWR_PDCRD

Res.

0x03C

PWR_PUCRD

Res.

0x038

PWR_PDCRC

Res.

0x034
PWR_PUCRC

Res.

0x030
PWR_PDCRB

Res.

0x02C
PWR_PUCRB

Res.

0x028
PWR_PDCRA

Res.

0x024
PWR_PUCRA

Res.

0x020
PWR_SCR

Res.

0x018
PWR_SR2

Res.

0x014
PWR_SR1

Res.

0x010
PWR_CR4

Res.

0x00C
PWR_CR3

Res.

0x008
PWR_CR2

Res.

0x004
PWR_CR1

Res.

0x000

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.

5.4.20

Res.

RM0394
Power control (PWR)

PWR register map and reset value table
Table 30. PWR register map and reset values

LPMS
[2:0]

0
0
0
0
0

0
0
0
0
0

0
0
0
0
0

0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0

0
0
0
0

0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

173/1600

174

0x05C

174/1600
PWR_PDCRH

Reset value

RM0394 Rev 4

PD11
PD10
PD9
PD8
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0

0
0
0
0
0
0
0
0
0
0
0
0

0

0

Refer toSection 2.2.2: Memory map and register boundary addresses for the register
boundary addresses.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
PU3
Res.
PU0

PD12
0

0
0

PD0

PD13
0
PU1

PD14
0

PD1

Res.

Reset value

PD3

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PD15

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.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PWR_PUCRH

Res.

0x058
PWR_PDCRE

Res.

0x044

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.

Power control (PWR)
RM0394

Table 30. PWR register map and reset values (continued)

0
0

RM0394

Reset and clock control (RCC)

6

Reset and clock control (RCC)

6.1

Reset
There are three types of reset, defined as system reset, power reset and backup domain
reset.

6.1.1

Power reset
A power reset is generated when one of the following events occurs:
1.

a Brown-out reset (BOR).

2.

when exiting from Standby mode.

3.

when exiting from Shutdown mode.

A Brown-out reset, including power-on or power-down reset (POR/PDR), sets all registers to
their reset values except the Backup domain.
When exiting Standby mode, all registers in the VCORE domain are set to their reset value.
Registers outside the VCORE domain (RTC, WKUP, IWDG, and Standby/Shutdown modes
control) are not impacted.
When exiting Shutdown mode, a Brown-out reset is generated, resetting all registers except
those in the Backup domain.

6.1.2

System reset
A system reset sets all registers to their reset values unless specified otherwise in the
register description.
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 firewall event (FIREWALL reset)

5.

A software reset (SW reset) (see Software reset)

6.

Low-power mode security reset (see Low-power mode security reset)

7.

Option byte loader reset (see Option byte loader reset)

8.

A Brown-out reset

The reset source can be identified by checking the reset flags in the Control/Status register,
RCC_CSR (see Section 6.4.29: 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.
In case on an internal reset, the internal pull-up RPU is deactivated in order to save the
power consumption through the pull-up resistor.

RM0394 Rev 4

175/1600
246

Reset and clock control (RCC)

RM0394
Figure 12. Simplified diagram of the reset circuit
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069

Software reset
The SYSRESETREQ bit in Cortex®-M4 Application Interrupt and Reset Control Register
must be set to force a software reset on the device (refer to the STM32F3, STM32F4,
STM32L4 and STM32L4+ Series Cortex®-M4 (PM0214)).

Low-power mode security reset
To prevent that critical applications mistakenly enter a low-power mode, two low-power
mode security resets are available. If enabled in option bytes, the resets are generated in
the following conditions:
1.

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.

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.

3.

Entering Shutdown mode: this type of reset is enabled by resetting nRST_SHDW bit in
User option bytes. In this case, whenever a Shutdown mode entry sequence is
successfully executed, the device is reset instead of entering Shutdown mode.

For further information on the User Option Bytes, refer to Section 3.4.1: Option bytes
description.

Option byte loader reset
The option byte loader reset is generated when the OBL_LAUNCH bit (bit 27) is set in the
FLASH_CR register. This bit is used to launch the option byte loading by software.

6.1.3

Backup domain reset
The backup domain has two specific resets.
A backup domain reset is generated when one of the following events occurs:

176/1600

RM0394 Rev 4

RM0394

Reset and clock control (RCC)
1.

Software reset, triggered by setting the BDRST bit in the Backup domain control
register (RCC_BDCR).

2.

VDD or VBAT power on, if both supplies have previously been powered off.

A backup domain reset only affects the LSE oscillator, the RTC, the Backup registers and
the RCC Backup domain control register.

6.2

Clocks
Four different clock sources can be used to drive the system clock (SYSCLK):
•

HSI16 (high speed internal)16 MHz RC oscillator clock

•

MSI (multispeed internal) RC oscillator clock

•

HSE oscillator clock, from 4 to 48 MHz

•

PLL clock

The MSI is used as system clock source after startup from Reset, configured at 4 MHz.
The devices have the following additional clock sources:
•

32 kHz low speed internal RC (LSI RC) which drives the independent watchdog and
optionally the RTC used for Auto-wakeup from Stop and Standby modes.

•

32.768 kHz low speed external crystal (LSE crystal) which optionally drives the realtime clock (RTCCLK).

•

RC 48 MHz internal clock sources (HSI48) to potentially drive the USB FS, the
SDMMC and the RNG.

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, the
APB1 and the APB2 domains is 80 MHz.

RM0394 Rev 4

177/1600
246

Reset and clock control (RCC)

RM0394

All the peripheral clocks are derived from their bus clock (HCLK, PCLK1 or PCLK2) except:
•

The 48 MHz clock, used for USB FS, SDMMC and RNG. This clock is derived (selected
by software) from one of the four following sources:
–

main PLL VCO (PLL48M1CLK)

–

PLLSAI1 VCO (PLL48M2CLK)

–

MSI clock

–

HSI48 internal oscillator

When the MSI clock is auto-trimmed with the LSE, it can be used by the USB FS
device.
•

•

The ADCs clock which is derived (selected by software) from one of the following
sources:
–

system clock (SYSCLK)

–

PLLSAI1 VCO (PLLADC1CLK)(not available on STM3L41xxx and STM32L42xxx
devices)

The U(S)ARTs clocks which are derived (selected by software) from one of the four
following sources:
–

system clock (SYSCLK)

–

HSI16 clock

–

LSE clock

–

APB1 or APB2 clock (PCLK1 or PCLK2 depending on which APB is mapped the
U(S)ART)

The wakeup from Stop mode is supported only when the clock is HSI16 or LSE.
•

The I2Cs clocks which are derived (selected by software) from one of the three
following sources:
–

system clock (SYSCLK)

–

HSI16 clock

–

APB1 clock (PCLK1)

The wakeup from Stop mode is supported only when the clock is HSI16.
•

•

The SAI1 clock which derived (selected by software) from one of the following
sources:
–

an external clock mapped on SAI1_EXTCLK for SAI1

–

PLLSAI1 VCO (PLLSAICLK)

–

main PLL VCO (PLLSAICLK)

–

HSI16 clock

The SWPMI1 clock which is derived (selected by software) from one of the two
following sources:
–

HSI16 clock

–

APB1 clock (PCLK1)

The wakeup from Stop mode is supported only when the clock is HSI16.
•

•

178/1600

The DFSDM1 clock (only applicable for STM32L45x/46x) which is derived (selected by
software) from one of the two following sources:
–

system clock (SYSCLK)

–

APB2 clock (PCLK2)

The low-power timers (LPTIMx) clock which are derived (selected by software) from

RM0394 Rev 4

RM0394

Reset and clock control (RCC)
one of the five following sources:
–

LSI clock

–

LSE clock

–

HSI16 clock

–

APB1 clock (PCLK1)

–

External clock mapped on LPTIMx_IN1

The functionality in Stop mode (including wakeup) is supported only when the clock is
LSI or LSE, or in external clock mode.
•

The RTC and LCD clock which is derived (selected by software) from one of the three
following sources:
–

LSE clock

–

LSI clock

–

HSE clock divided by 32

The functionality in Stop mode (including wakeup) is supported only when the clock is
LSI or LSE.
•

The IWDG clock which is always the LSI clock.

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.
FCLK acts as Cortex®-M4 free-running clock. For more details refer to the STM32F3,
STM32F4, STM32L4 and STM32L4+ Series Cortex®-M4 programming manual (PM0214).

RM0394 Rev 4

179/1600
246

Reset and clock control (RCC)

RM0394
Figure 13. Clock tree
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180/1600

RM0394 Rev 4

069

RM0394

Reset and clock control (RCC)
1. For full details about the internal and external clock source characteristics, please refer to the “Electrical
characteristics” section in your device datasheet.
2. 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’.

6.2.1

HSE clock
The high speed external clock signal (HSE) can be generated from two possible clock
sources:
•

HSE external crystal/ceramic resonator

•

HSE 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 14. HSE/ LSE clock sources
Clock source

Hardware configuration

OSC_IN

OSC_OUT

External clock

GPIO
External
source

External clock
(available on some
package, please
refer to the
corresponding
datasheet)

CK_IN
GPIO
External
source

OSC_IN OSC_OUT
Crystal/Ceramic
resonators
CL1

RM0394 Rev 4

Load
capacitors

CL2

181/1600
246

Reset and clock control (RCC)

RM0394

External crystal/ceramic resonator (HSE crystal)
The 4 to 48 MHz external oscillator has the advantage of producing a very accurate rate on
the main clock.
The associated hardware configuration is shown in Figure 14. Refer to the electrical
characteristics section of the datasheet for more details.
The HSERDY flag in the 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 enable register (RCC_CIER).
The HSE Crystal can be switched on and off using the HSEON bit in the Clock control
register (RCC_CR).

External source (HSE bypass)
In this mode, an external clock source must be provided. It can have a frequency of up to
48 MHz. You 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 14.

6.2.2

HSI16 clock
The HSI16 clock signal is generated from an internal 16 MHz RC Oscillator.
The HSI16 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.
The HSI16 clock can be selected as system clock after wakeup from Stop modes (Stop 0,
Stop 1 or Stop 2). Refer to Section 6.3: Low-power modes. It can also be used as a backup
clock source (auxiliary clock) if the HSE crystal oscillator fails. Refer to Section 6.2.10: Clock
security system (CSS).

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 Internal
clock sources calibration register (RCC_ICSCR).
If the application is subject to voltage or temperature variations this may affect the RC
oscillator speed. You can trim the HSI16 frequency in the application using the
HSITRIM[6:0] bits in the Internal clock sources calibration register (RCC_ICSCR).
For more details on how to measure the HSI16 frequency variation, refer to Section 6.2.17:
Internal/external clock measurement with TIM15/TIM16.
The HSIRDY flag in the Clock control register (RCC_CR) indicates if the HSI16 RC is stable
or not. At startup, the HSI16 RC output clock is not released until this bit is set by hardware.
The HSI16 RC can be switched on and off using the HSION bit in the Clock control register
(RCC_CR).

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Reset and clock control (RCC)
The HSI16 signal can also be used as a backup source (Auxiliary clock) if the HSE crystal
oscillator fails. Refer to Section 6.2.10: Clock security system (CSS) on page 186.

6.2.3

MSI clock
The MSI clock signal is generated from an internal RC oscillator. Its frequency range can be
adjusted by software by using the MSIRANGE[3:0] bits in the Clock control register
(RCC_CR). Twelve frequency ranges are available: 100 kHz, 200 kHz, 400 kHz, 800 kHz,
1 MHz, 2 MHz, 4 MHz (default value), 8 MHz, 16 MHz, 24 MHz, 32 MHz and 48 MHz.
The MSI clock is used as system clock after restart from Reset, wakeup from Standby and
Shutdown low-power modes. After restart from Reset, the MSI frequency is set to its default
value 4 MHz. Refer to Section 6.3: Low-power modes.
The MSI clock can be selected as system clock after a wakeup from Stop mode (Stop 0,
Stop 1 or Stop 2). Refer to Section 6.3: Low-power modes. It can also be used as a backup
clock source (auxiliary clock) if the HSE crystal oscillator fails. Refer to Section 6.2.10: Clock
security system (CSS).
The MSI RC oscillator has the advantage of providing a low-cost (no external components)
low-power clock source. In addition, when used in PLL-mode with the LSE, it provides a
very accurate clock source which can be used by the USB FS device, and feed the main
PLL to run the system at the maximum speed 80 MHz.
The MSIRDY flag in the Clock control register (RCC_CR) indicates wether the MSI RC is
stable or not. At startup, the MSI RC output clock is not released until this bit is set by
hardware. The MSI RC can be switched on and off by using the MSION bit in the Clock
control register (RCC_CR).

Hardware auto calibration with LSE (PLL-mode)
When a 32.768 kHz external oscillator is present in the application, it is possible to configure
the MSI in a PLL-mode by setting the MSIPLLEN bit in the Clock control register (RCC_CR).
When configured in PLL-mode, the MSI automatically calibrates itself thanks to the LSE.
This mode is available for all MSI frequency ranges. At 48 MHz, the MSI in PLL-mode can
be used for the USB FS device, saving the need of an external high-speed crystal.

Software calibration
The MSI RC oscillator frequency 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 an
ambient temperature, TA, of 25 °C. After reset, the factory calibration value is loaded in the
MSICAL[7:0] bits in the Internal clock sources calibration register (RCC_ICSCR). If the
application is subject to voltage or temperature variations, this may affect the RC oscillator
speed. You can trim the MSI frequency in the application by using the MSITRIM[7:0] bits in
the RCC_ICSCR register. For more details on how to measure the MSI frequency variation
please refer to Section 6.2.17: Internal/external clock measurement with TIM15/TIM16.

6.2.4

HSI48 clock
The HSI48 clock signal is generated from an internal 48 MHz RC oscillator and can be used
directly for USB and for random number generator (RNG) as well as SDMMC.
The internal 48 MHz RC oscillator is mainly dedicated to provide a high precision clock to
the USB peripheral by means of a special Clock Recovery System (CRS) circuitry. The CRS
can use the USB SOF signal, the LSE or an external signal to automatically and quickly

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adjust the oscillator frequency on-fly. It is disabled as soon as the system enters Stop or
Standby mode. When the CRS is not used, the HSI48 RC oscillator runs on its default
frequency which is subject to manufacturing process variations.
For more details on how to configure and use the CRS peripheral please refer to Section 7:
Clock recovery system (CRS).
The HSI48RDY flag in the Clock recovery RC register (RCC_CRRCR) indicates whether the
HSI48 RC oscillator is stable or not. At startup, the HSI48 RC oscillator output clock is not
released until this bit is set by hardware.
The HSI48 can be switched on and off using the HSI48ON bit in the Clock recovery RC
register (RCC_CRRCR).

6.2.5

PLL
The device embeds PLLs: PLL, PLLSAI1. Each PLL provides up to three independent
outputs. The internal PLLs can be used to multiply the HSI16, HSE or MSI output clock
frequency. The PLLs input frequency must be between 4 and 16 MHz. The selected clock
source is divided by a programmable factor PLLM from 1 to 8 to provide a clock frequency in
the requested input range. Refer to Figure 13: Clock treeand PLL configuration register
(RCC_PLLCFGR).
The PLLs 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 in Clock control register (RCC_CR).

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.

5.

Enable the desired PLL outputs by configuring PLLPEN, PLLQEN, PLLREN in PLL
configuration register (RCC_PLLCFGR).

An interrupt can be generated when the PLL is ready, if enabled in the Clock interrupt
enable register (RCC_CIER).
The same procedure is applied for changing the configuration of the PLLSAI1:
1.

Disable the PLLSAI1/PLLSAI2 by setting PLLSAI1ON to 0 in Clock control register
(RCC_CR).

2.

Wait until PLLSAI1RDY is cleared. The PLLSAI1 is now fully stopped.

3.

Change the desired parameter.

4.

Enable the PLLSAI1 again by setting PLLSAI1ON to 1.

5.

Enable the desired PLL outputs by configuring PLLSAI1PEN, PLLSAI1QEN,
PLLSAI1REN in PLLSAI1 configuration register (RCC_PLLSAI1CFGR).

The PLL output frequency must not exceed 80 MHz.
The enable bit of each PLL output clock (PLLPEN, PLLQEN, PLLREN, PLLSAI1PEN,
PLLSAI1QEN, PLLSAI1REN) can be modified at any time without stopping the
corresponding PLL. PLLREN cannot be cleared if PLLCLK is used as system clock.

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6.2.6

Reset and clock control (RCC)

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 Backup domain control
register (RCC_BDCR). The crystal oscillator driving strength can be changed at runtime
using the LSEDRV[1:0] bits in the Backup domain control register (RCC_BDCR) to obtain
the best compromise between robustness and short start-up time on one side and lowpower-consumption on the other side. The LSE drive can be decreased to the lower drive
capability (LSEDRV=00) when the LSE is ON. However, once LSEDRV is selected, the
drive capability can not be increased if LSEON=1.
The LSERDY flag in the Backup 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 enable register (RCC_CIER).
Distribution of the external 32 kHz clock (LSE) outside the RTC block could be disabled by
setting LSESYSDIS bit in Backup domain control register (RCC_BDCR) to reduce power
consumption. Propagation will be stoped regardless the use of LSE by other IP's. This
feature is present on STM32L412xx and STM32L422xx devices only.

External source (LSE bypass)
In this mode, an external clock source must be provided. It can have a frequency of up to
1 MHz. You select this mode by setting the LSEBYP and LSEON bits in the AHB1 peripheral
clocks enable in Sleep and Stop modes register (RCC_AHB1SMENR). 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 14.

6.2.7

LSI clock
The LSI RC acts as a low-power clock source that can be kept running in Stop and Standby
mode for the independent watchdog (IWDG), RTC and LCD. The clock frequency is 32 kHz.
For more details, refer to the electrical characteristics section of the datasheets.
The LSI RC can be switched on and off using the LSION bit in the 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 enable register (RCC_CIER).

6.2.8

System clock (SYSCLK) selection
Four different clock sources can be used to drive the system clock (SYSCLK):
•

MSI oscillator

•

HSI16 oscillator

•

HSE oscillator

•

PLL

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The system clock maximum frequency is 80 MHz. After a system reset, the MSI oscillator, at
4 MHz, 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
Internal clock sources calibration register (RCC_ICSCR) indicate which clock(s) is (are)
ready and which clock is currently used as a system clock.

6.2.9

Clock source frequency versus voltage scaling
The following table gives the different clock source frequencies depending on the product
voltage range.
Table 31. Clock source frequency
Clock frequency

Product voltage
range

MSI

HSI16

HSE

PLL/PLLSAI1

Range 1 (1)

48 MHz

16 MHz

48 MHz

80 MHz
(VCO max = 344 MHz)

Range 2(2)

24 MHz range

16 MHz

26 MHz

26 MHz
(VCO max = 128 MHz)

1. Also for SMPS Range1 and SMPS Range2 High
2. Also for SMPS Range2 Low

6.2.10

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 and TIM15/16)
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 NMI (Non-Maskable Interrupt) exception vector.

Note:

Once the CSS is enabled and if the HSE clock fails, the CSS interrupt occurs and a 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 clear register (RCC_CICR).
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
causes a switch of the system clock to the MSI or the HSI16 oscillator depending on the
STOPWUCK configuration in the Clock configuration register (RCC_CFGR), 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.

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6.2.11

Reset and clock control (RCC)

Clock security system on LSE
A Clock Security System on LSE can be activated by software writing the LSECSSON bit in
the Backup domain control register (RCC_BDCR). This bit can be disabled only by a
hardware reset or RTC software reset, or after a failure detection on LSE. LSECSSON must
be written after LSE and LSI are enabled (LSEON and LSION enabled) and ready (LSERDY
and LSIRDY set by hardware), and after the RTC clock has been selected by RTCSEL.
The CSS on LSE is working in all modes except VBAT. It is working also under system reset
(excluding power on reset). If a failure is detected on the external 32 kHz oscillator, the LSE
clock is no longer supplied to the RTC but no hardware action is made to the registers. If the
MSI was in PLL-mode, this mode is disabled.
In Standby mode a wakeup is generated. In other modes an interrupt can be sent to wakeup
the software (see Clock interrupt enable register (RCC_CIER), Clock interrupt flag register
(RCC_CIFR), Clock interrupt clear register (RCC_CICR)).
The software MUST then disable the LSECSSON bit, stop the defective 32 kHz oscillator
(disabling LSEON), and change the RTC clock source (no clock or LSI or HSE, with
RTCSEL), or take any required action to secure the application.
The frequency of LSE oscillator have to be higher than 30 kHz to avoid false positive CSS
detection.

6.2.12

ADC clock
The ADC clock is derived from the system clock, or from the PLLSAI1 output(a). It can reach
80 MHz and can be divided by the following prescalers values: 1,2,4,6,8,10,12,16,32,64,128
or 256 by configuring the ADC1_CCR register. 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 ADC1_CCR.
If the programmed factor is ‘1’, the AHB prescaler must be set to ‘1’.

6.2.13

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 Backup domain control register (RCC_BDCR).
This selection cannot be modified without resetting the Backup domain. The system must
always be configured so as to get a PCLK frequency greater then or equal to the RTCCLK
frequency for a proper operation of the RTC.

a. Except STM32L41xxx/42xxx devices

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The LSE clock is in the Backup domain, whereas the HSE and LSI clocks are not.
Consequently:
•

If LSE is selected as RTC clock:
–

•

If LSI is selected as the RTC clock:
–

•

The RTC continues to work even if the VDD supply is switched off, provided the
VBAT supply is maintained.
The RTC state is not guaranteed if the VDD supply is powered off.

If the HSE clock divided by a prescaler 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 VCORE domain).

When the RTC clock is LSE or LSI, the RTC remains clocked and functional under system
reset.

6.2.14

Timer clock
The timer clock frequencies are automatically defined by hardware. There are two cases:

6.2.15

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.

Watchdog clock
If the Independent watchdog (IWDG) is started by either hardware option or software
access, the LSI oscillator is forced ON and cannot be disabled. After the LSI oscillator
temporization, the clock is provided to the IWDG.

6.2.16

Clock-out capability
•

MCO
The microcontroller clock output (MCO) capability allows the clock to be output onto the
external MCO pin. One of eight clock signals can be selected as the MCO clock.
–

LSI

–

LSE

–

SYSCLK

–

HSI16

–

HSI48

–

HSE

–

PLLCLK

–

MSI

The selection is controlled by the MCOSEL[:0] bits of the Clock configuration register
(RCC_CFGR). The selected clock can be divided with the MCOPRE[2:0] field of the

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Reset and clock control (RCC)
Clock configuration register (RCC_CFGR).
•

LSCO
Another output (LSCO) allows a low speed clock to be output onto the external LSCO
pin:
–

LSI

–

LSE

This output remains available in Stop (Stop 0, Stop 1 and Stop 2) and Standby modes.
The selection is controlled by the LSCOSEL, and enabled with the LSCOEN in the
Backup domain control register (RCC_BDCR).
The MCO clock output requires the corresponding alternate function selected on the MCO
pin, the LSCO pin should be left in default POR state.

6.2.17

Internal/external clock measurement with TIM15/TIM16
It is possible to indirectly measure the frequency of all on-board clock sources by mean of
the TIM15 or TIM16 channel 1 input capture, as represented on Figure 15 and Figure 16
Figure 15. Frequency measurement with TIM15 in capture mode

7,0

7,B503
*3,2

7,
/6(
069

The input capture channel of the Timer 15 can be a GPIO line or an internal clock of the
MCU. This selection is performed through the TI1_RMP bit in the TIM15_OR register. The
possibilities are the following ones:
•

TIM15 Channel1 is connected to the GPIO. Refer to the alternate function mapping in
the device datasheets.

•

TIM15 Channel1 is connected to the LSE.
Figure 16. Frequency measurement with TIM16 in capture mode

7,0

7,B503>@
*3,2

7,

/6,
/6(
57&ZDNHXSLQWHUUXSW

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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 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 LSI clock.

•

TIM16 Channel1 is connected to the LSE clock.

•

TIM16 Channel1 is connected to the RTC wakeup interrupt signal. In this case the RTC
interrupt should be enabled.

Calibration of the HSI16 and the MSI
For TIM15 and TIM16, the primary purpose of connecting the LSE to the channel 1 input
capture is to be able to precisely measure the HSI16 and MSI system clocks (for this, either
the HSI16 or MSI should be used as the system clock source). The number of HSI16 (MSI,
respectively) 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,
temperature and/or voltage related frequency deviations.
The MSI and HSI16 oscillator both have dedicated user-accessible calibration bits for this
purpose.
The basic concept consists in providing a relative measurement (e.g. the HSI16/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.
It is however not possible to have a good enough resolution when the MSI clock is low
(typically below 1 MHz). In this case, it is advised to:
•

accumulate the results of several captures in a row

•

use the timer’s input capture prescaler (up to 1 capture every 8 periods)

•

use the RTC wakeup interrupt signal (when the RTC is clocked by the LSE) as the
input for the channel1 input capture. This improves the measurement precision. For
this purpose the RTC wakeup interrupt must be enable.

Calibration of the LSI
The calibration of the LSI will follow the same pattern that for the HSI16, 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.
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.

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6.2.18

Reset and clock control (RCC)

Peripheral clock enable register
(RCC_AHBxENR, RCC_APBxENRy)
Each peripheral clock can be enabled by the xxxxEN bit of the RCC_AHBxENR,
RCC_APBxENRy registers.
When the peripheral clock is not active, the peripheral registers read or write accesses are
not supported.
The enable bit has a synchronization mechanism to create a glitch free clock for the
peripheral. After the enable bit is set, there is a 2 clock cycles delay before the clock be
active.

Caution:

Just after enabling the clock for a peripheral, software must wait for a delay before
accessing the peripheral registers.

6.3

Low-power modes
•

AHB and APB peripheral clocks, including DMA clock, can be disabled by software.

•

Sleep and Low Power Sleep modes stops the CPU clock. The memory interface clocks
(Flash and SRAM1 and SRAM2 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 modes (Stop 0, Stop 1 and Stop 2) stops all the clocks in the VCORE domain and
disables the PLL, the HSI16, the MSI and the HSE oscillators.
All U(S)ARTs, LPUARTs and I2Cs have the capability to enable the HSI16 oscillator
even when the MCU is in Stop mode (if HSI16 is selected as the clock source for that
peripheral).
All U(S)ARTs and LPUARTs 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). In that case the LSE remains always ON in Stop mode
(they do not have the capability to turn on the LSE oscillator).

•

Standby and Shutdown modes stops all the clocks in the VCORE domain and disables
the PLL, the HSI16, the MSI and the 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 leaving the Stop modes (Stop 0, Stop 1 or Stop 2), the system clock is either MSI or
HSI16, depending on the software configuration of the STOPWUCK bit in the RCC_CFGR
register. The frequency (range and user trim) of the MSI oscillator is the one configured
before entering Stop mode. The user trim of HSI16 is kept. If the MSI was in PLL-mode
before entering Stop mode, the PLL-mode stabilization time must be waited for after wakeup
even if the LSE was kept ON during the Stop mode.
When leaving the Standby and Shutdown modes, the system clock is MSI. The MSI
frequency at wakeup from Standby mode is configured with the MSISRANGE is the
RCC_CSR register, from 1 to 8 MHz. The MSI frequency at wakeup from Shutdown mode is
4 MHz. The user trim is lost.
If a Flash memory programming operation is on going, Stop, Standby and Shutdown modes
entry is delayed until the Flash memory interface access is finished. If an access to the APB
domain is ongoing, Stop, Standby and Shutdown modes entry is delayed until the APB
access is finished.
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6.4

RCC registers

6.4.1

Clock control register (RCC_CR)
Address offset: 0x00
Access: no wait state, word, half-word and byte access

31
Res.

30
Res.

15
Res.

29

14

Res.

13

Res.

Res.

28

27

26

Res.

PLL
SAI1

PLL
SAI1

RDY(1)

ON(1)

r

rw

12

11

10

Res.

HSI
ASFS

HSI
RDY

rw

r

25

24

23

22

21

20

19

18

17

16

PLL
RDY

PLLON

Res.

Res.

Res.

Res.

CSS
ON

HSE
BYP

HSE
RDY

HSE
ON

r

rw

rs

rw

r

rw

9

8

3

2

7

HSI
HSION
KERON
rw

rw

6

5

4

MSI
MSI
RGSEL PLLEN

MSIRANGE[3:0]
rw

rw

rw

rw

rs

rw

1

0

MSI
RDY

MSION

r

rw

1. Not available on STM3L41xxx and STM32L42xxx devices

Bits 31: Reserved, must be kept at reset value.
Bit 27 PLLSAI1RDY: SAI1 PLL clock ready flag
Set by hardware to indicate that the PLLSAI1 is locked.
0: PLLSAI1 unlocked
1: PLLSAI1 locked
Bit 26 PLLSAI1ON: SAI1 PLL enable
Set and cleared by software to enable PLLSAI1.
Cleared by hardware when entering Stop, Standby or Shutdown mode.
0: PLLSAI1 OFF
1: PLLSAI1 ON
Bit 25 PLLRDY: Main PLL clock ready flag
Set by hardware to indicate that the main PLL is locked.
0: PLL unlocked
1: PLL locked
Bit 24 PLLON: Main PLL enable
Set and cleared by software to enable the main PLL.
Cleared by hardware when entering Stop, Standby or Shutdown mode. This bit cannot be
reset if the PLL clock is used as the system clock.
0: PLL OFF
1: PLL ON
Bits 23:20 Reserved, must be kept at reset value.
Bit 19 CSSON: Clock security system enable
Set 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. This bit is set only and is cleared by reset.
0: Clock security system OFF (clock detector OFF)
1: Clock security system ON (Clock detector ON if the HSE oscillator is stable, OFF if not).

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Reset and clock control (RCC)

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.
0: HSE oscillator not ready
1: HSE oscillator ready
Note: Once the HSEON bit is cleared, HSERDY goes low after 6 HSE clock cycles.
Bit 16 HSEON: HSE clock enable
Set and cleared by software.
Cleared by hardware to stop the HSE oscillator when entering Stop, Standby or Shutdown
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 15:12 Reserved, must be kept at reset value.
Bit 11 HSIASFS: HSI16 automatic start from Stop
Set and cleared by software. When the system wakeup clock is MSI, this bit is used to
wakeup the HSI16 is parallel of the system wakeup.
0: HSI16 oscillator is not enabled by hardware when exiting Stop mode with MSI as wakeup
clock.
1: HSI16 oscillator is enabled by hardware when exiting Stop mode with MSI as wakeup
clock.
Bit 10 HSIRDY: HSI16 clock ready flag
Set by hardware to indicate that HSI16 oscillator is stable. This bit is set only when HSI16 is
enabled by software by setting HSION.
0: HSI16 oscillator not ready
1: HSI16 oscillator ready
Note: Once the HSION bit is cleared, HSIRDY goes low after 6 HSI16 clock cycles.
Bit 9 HSIKERON: HSI16 always enable for peripheral kernels.
Set and cleared by software to force HSI16 ON even in Stop modes. The HSI16 can only
feed USARTs and I2Cs peripherals configured with HSI16 as kernel clock. Keeping the
HSI16 ON in Stop mode allows to avoid slowing down the communication speed because of
the HSI16 startup time. This bit has no effect on HSION value.
0: No effect on HSI16 oscillator.
1: HSI16 oscillator is forced ON even in Stop mode.
Bit 8 HSION: HSI16 clock enable
Set and cleared by software.
Cleared by hardware to stop the HSI16 oscillator when entering Stop, Standby or Shutdown
mode.
Set by hardware to force the HSI16 oscillator ON when STOPWUCK=1 or HSIASFS = 1
when leaving Stop modes, or in case of failure of the HSE crystal oscillator.
This bit is set by hardware if the HSI16 is used directly or indirectly as system clock.
0: HSI16 oscillator OFF
1: HSI16 oscillator ON

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Reset and clock control (RCC)

RM0394

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.
0: HSE oscillator not ready
1: HSE oscillator ready
Note: Once the HSEON bit is cleared, HSERDY goes low after 6 HSE clock cycles.
Bit 16 HSEON: HSE clock enable
Set and cleared by software.
Cleared by hardware to stop the HSE oscillator when entering Stop, Standby or Shutdown
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 15:12 Reserved, must be kept at reset value.
Bit 11 HSIASFS: HSI16 automatic start from Stop
Set and cleared by software. When the system wakeup clock is MSI, this bit is used to
wakeup the HSI16 is parallel of the system wakeup.
0: HSI16 oscillator is not enabled by hardware when exiting Stop mode with MSI as wakeup
clock.
1: HSI16 oscillator is enabled by hardware when exiting Stop mode with MSI as wakeup
clock.
Bit 10 HSIRDY: HSI16 clock ready flag
Set by hardware to indicate that HSI16 oscillator is stable. This bit is set only when HSI16 is
enabled by software by setting HSION.
0: HSI16 oscillator not ready
1: HSI16 oscillator ready
Note: Once the HSION bit is cleared, HSIRDY goes low after 6 HSI16 clock cycles.
Bit 9 HSIKERON: HSI16 always enable for peripheral kernels.
Set and cleared by software to force HSI16 ON even in Stop modes. The HSI16 can only
feed USARTs and I2Cs peripherals configured with HSI16 as kernel clock. Keeping the
HSI16 ON in Stop mode allows to avoid slowing down the communication speed because of
the HSI16 startup time. This bit has no effect on HSION value.
0: No effect on HSI16 oscillator.
1: HSI16 oscillator is forced ON even in Stop mode.
Bit 8 HSION: HSI16 clock enable
Set and cleared by software.
Cleared by hardware to stop the HSI16 oscillator when entering Stop, Standby or Shutdown
mode.
Set by hardware to force the HSI16 oscillator ON when STOPWUCK=1 or HSIASFS = 1
when leaving Stop modes, or in case of failure of the HSE crystal oscillator.
This bit is set by hardware if the HSI16 is used directly or indirectly as system clock.
0: HSI16 oscillator OFF
1: HSI16 oscillator ON

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RM0394

Reset and clock control (RCC)

Bits 7:4 MSIRANGE[3:0]: MSI clock ranges
These bits are configured by software to choose the frequency range of MSI when
MSIRGSEL is set.12 frequency ranges are available:
0000: range 0 around 100 kHz
0001: range 1 around 200 kHz
0010: range 2 around 400 kHz
0011: range 3 around 800 kHz
0100: range 4 around 1M Hz
0101: range 5 around 2 MHz
0110: range 6 around 4 MHz (reset value)
0111: range 7 around 8 MHz
1000: range 8 around 16 MHz
1001: range 9 around 24 MHz
1010: range 10 around 32 MHz
1011: range 11 around 48 MHz
others: not allowed (hardware write protection)
Note: Warning: MSIRANGE can be modified when MSI is OFF (MSION=0) or when MSI is
ready (MSIRDY=1). MSIRANGE must NOT be modified when MSI is ON and NOT
ready (MSION=1 and MSIRDY=0)
Bit 3 MSIRGSEL: MSI clock range selection
Set by software to select the MSI clock range with MSIRANGE[3:0]. Write 0 has no effect.
After a standby or a reset MSIRGSEL is at 0 and the MSI range value is provided by
MSISRANGE in CSR register.
0: MSI Range is provided by MSISRANGE[3:0] in RCC_CSR register
1: MSI Range is provided by MSIRANGE[3:0] in the RCC_CR register
Bit 2 MSIPLLEN: MSI clock PLL enable
Set and cleared by software to enable/ disable the PLL part of the MSI clock source.
MSIPLLEN must be enabled after LSE is enabled (LSEON enabled) and ready (LSERDY set
by hardware).There is a hardware protection to avoid enabling MSIPLLEN if LSE is not
ready.
This bit is cleared by hardware when LSE is disabled (LSEON = 0) or when the Clock
Security System on LSE detects a LSE failure (refer to RCC_CSR register).
0: MSI PLL OFF
1: MSI PLL ON
Bit 1 MSIRDY: MSI clock ready flag
This bit is set by hardware to indicate that the MSI oscillator is stable.
0: MSI oscillator not ready
1: MSI oscillator ready
Note: Once the MSION bit is cleared, MSIRDY goes low after 6 MSI clock cycles.
Bit 0 MSION: MSI clock enable
This bit is set and cleared by software.
Cleared by hardware to stop the MSI oscillator when entering Stop, Standby or Shutdown
mode.
Set by hardware to force the MSI oscillator ON when exiting Standby or Shutdown mode.
Set by hardware to force the MSI oscillator ON when STOPWUCK=0 when exiting from Stop
modes, or in case of a failure of the HSE oscillator
Set by hardware when used directly or indirectly as system clock.
0: MSI oscillator OFF
1: MSI oscillator ON

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Reset and clock control (RCC)

6.4.2

RM0394

Internal clock sources calibration register (RCC_ICSCR)
Address offset: 0x04
Reset value: 0x40XX 00XX where X is factory-programmed.
Access: no wait state, word, half-word and byte access

31

30

29

28

Res.

27

26

25

24

23

22

21

HSITRIM[6:0]

20

19

18

17

16

HSICAL[7:0]

rw

rw

rw

rw

rw

rw

rw

r

r

r

r

r

r

r

r

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rwr

rw

rw

r

r

r

r

r

r

MSITRIM[7:0]
rw

rw

MSICAL[7:0]
r

r

Bit 31 Reserved, must be kept at reset value.
Bits 30:24 HSITRIM[6:0]: HSI16 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 HSI16.
The default value is 64 when added to the HSICAL value, trim the HSI16 to 16 MHz ± 1 %.
Bits 23:16 HSICAL[7:0]: HSI16 clock calibration
These bits are initialized at startup with the factory-programmed HSI16 calibration trim value.
When HSITRIM is written, HSICAL is updated with the sum of HSITRIM and the factory trim
value.
Bits 15:8 MSITRIM[7:0]: MSI clock trimming
These bits provide an additional user-programmable trimming value that is added to the
MSICAL[7:0] bits. It can be programmed to adjust to variations in voltage and temperature
that influence the frequency of the MSI.
Bits 7:0 MSICAL[7:0]: MSI clock calibration
These bits are initialized at startup with the factory-programmed MSI calibration trim value.
When MSITRIM is written, MSICAL is updated with the sum of MSITRIM and the factory trim
value.

6.4.3

Clock configuration register (RCC_CFGR)
Address offset: 0x08
Reset value: 0x0000 0000
Access: 0 ≤ wait state ≤ 2, word, half-word and byte access
1 or 2 wait states inserted only if the access occurs during clock source switch.
From 0 to 15 wait states inserted if the access occurs when the APB or AHB prescalers
values update is on going.

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RM0394

31

Reset and clock control (RCC)

30

Res.

29

28

27

MCOPRE[2:0]

26

25

24

MCOSEL[3:0]

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

STOP
WUCK

Res.

rw

PPRE2[2:0]
rw

rw

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

7

6

5

4

3

2

1

0

PPRE1[2:0]
rw

rw

rw

HPRE[3:0]
rw

rw

rw

rw

SWS[1:0]
rw

r

r

SW[1:0]
rw

rw

Bit 31 Reserved, must be kept at reset value.
Bits 30:28 MCOPRE[2:0]: Microcontroller clock output prescaler
These 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
011: MCO is divided by 8
100: MCO is divided by 16
Others: not allowed
Bits 27:24 MCOSEL[3:0]: Microcontroller clock output
Set and cleared by software.
0000: MCO output disabled, no clock on MCO
0001: SYSCLK system clock selected
0010: MSI clock selected.
0011: HSI16 clock selected.
0100: HSE clock selected
0101: Main PLL clock selected
0110: LSI clock selected
0111: LSE clock selected
1000: Internal HSI48 clock selected
Others: Reserved
Note: This clock output may have some truncated cycles at startup or during MCO clock
source switching.
Bits 23:16 Reserved, must be kept at reset value.
Bit 15 STOPWUCK: Wakeup from Stop and CSS backup clock selection
Set and cleared by software to select the system clock used when exiting Stop mode.
The selected clock is also used as emergency clock for the Clock Security System on HSE.
Warning: STOPWUCK must not be modified when the Clock Security System is enabled by
HSECSSON in RCC_CR register and the system clock is HSE (SWS=”10”) or a switch on
HSE is requested (SW=”10”).
0: MSI oscillator selected as wakeup from stop clock and CSS backup clock.
1: HSI16 oscillator selected as wakeup from stop clock and CSS backup clock
Bit 14 Reserved, must be kept at reset value.
Bits 13:11 PPRE2[2:0]: APB high-speed prescaler (APB2)
Set and cleared by software to control the division factor of the APB2 clock (PCLK2).
0xx: HCLK not divided
100: HCLK divided by 2
101: HCLK divided by 4
110: HCLK divided by 8
111: HCLK divided by 16

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Reset and clock control (RCC)

RM0394

Bits 10:8 PPRE1[2:0]:APB low-speed prescaler (APB1)
Set and cleared by software to control the division factor of the APB1 clock (PCLK1).
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[3:0]: AHB prescaler
Set and cleared by software to control the division factor of the AHB clock.

Caution:

Depending on the device voltage range, the software has to set
correctly these bits to ensure that the system frequency does not
exceed the maximum allowed frequency (for more details please refer to
Section 5.1.7: Dynamic voltage scaling management). After a write
operation to these bits and before decreasing the voltage range, this
register must be read to be sure that the new value has been taken into
account.

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
Bits 3:2 SWS[1:0]: System clock switch status
Set and cleared by hardware to indicate which clock source is used as system clock.
00: MSI oscillator used as system clock
01: HSI16 oscillator used as system clock
10: HSE used as system clock
11: PLL used as system clock
Bits 1:0 SW[1:0]: System clock switch
Set and cleared by software to select system clock source (SYSCLK).
Configured by HW to force MSI oscillator selection when exiting Standby or Shutdown mode.
Configured by HW to force MSI or HSI16 oscillator selection when exiting Stop mode or in
case of failure of the HSE oscillator, depending on STOPWUCK value.
00: MSI selected as system clock
01: HSI16 selected as system clock
10: HSE selected as system clock
11: PLL selected as system clock

6.4.4

PLL configuration register (RCC_PLLCFGR)
Address offset: 0x0C
Reset value: 0x0000 1000
Access: no wait state, word, half-word and byte access
This register is used to configure the PLL clock outputs according to the formulas:
• f(VCO clock) = f(PLL clock input) × (PLLN / PLLM)

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RM0394

Reset and clock control (RCC)
• f(PLL_P) = f(VCO clock) / PLLP
• f(PLL_Q) = f(VCO clock) / PLLQ
• f(PLL_R) = f(VCO clock) / PLLR

31

30

29

28

27

PLLPDIV[4:0]

26

25

PLLR[1:0]

24
PLL
REN

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

Res.

PLLN[7:0]
rw

rw

rw

rw

23
Res.

7

22

PLLQ[1:0]

rw

rw

20
PLL
QEN

rw

rw

rw

6

5

4

Res.
rw

21

PLLM[2:0]
rw

rw

rw

19

18

Res.

Res.

3

2

Res.

Res.

17

16

PLLP

PLL
PEN

rw

rw

1

0

PLLSRC[1:0]
rw

rw

Bits 31:27 PLLPDIV[4:0]: Main PLL division factor for PLLSAI2CLK
Set and cleared by software to control the SAI1 clock frequency. PLLSAICLK output clock
frequency = VCO frequency / PLLPDIV.
00000: PLLSAICLK is controlled by the bit PLLP
00001: Reserved.
00010: PLLSAICLK = VCO / 2
....
11111: PLLSAICLK = VCO / 31
Bits 26:25 PLLR[1:0]: Main PLL division factor for PLLCLK (system clock)
Set and cleared by software to control the frequency of the main PLL output clock PLLCLK.
This output can be selected as system clock. These bits can be written only if PLL is
disabled.
PLLCLK output clock frequency = VCO frequency / PLLR with PLLR = 2, 4, 6, or 8
00: PLLR = 2
01: PLLR = 4
10: PLLR = 6
11: PLLR = 8

Caution:

The software has to set these bits correctly not to exceed 80 MHz on
this domain.

Bit 24 PLLREN: Main PLL PLLCLK output enable
Set and reset by software to enable the PLLCLK output of the main PLL (used as system
clock).
This bit cannot be written when PLLCLK output of the PLL is used as System Clock.
In order to save power, when the PLLCLK output of the PLL is not used, the value of
PLLREN should be 0.
0: PLLCLK output disable
1: PLLCLK output enable
Bit 23 Reserved, must be kept at reset value.

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Reset and clock control (RCC)

RM0394

Bits 22:21 PLLQ[1:0]: Main PLL division factor for PLL48M1CLK (48 MHz clock).
Set and cleared by software to control the frequency of the main PLL output clock
PLL48M1CLK. This output can be selected for USB, RNG, SDMMC (48 MHz clock). These
bits can be written only if PLL is disabled.
PLL48M1CLK output clock frequency = VCO frequency / PLLQ with PLLQ = 2, 4, 6, or 8
00: PLLQ = 2
01: PLLQ = 4
10: PLLQ = 6
11: PLLQ = 8

Caution:

The software has to set these bits correctly not to exceed 80 MHz on
this domain.

Bit 20 PLLQEN: Main PLL PLL48M1CLK output enable
Set and reset by software to enable the PLL48M1CLK output of the main PLL.
In order to save power, when the PLL48M1CLK output of the PLL is not used, the value of
PLLQEN should be 0.
0: PLL48M1CLK output disable
1: PLL48M1CLK output enable
Bits 19:18 Reserved, must be kept at reset value.
Bit 17 PLLP: Main PLL division factor for PLLSAICLK (SAI1 clock).
Set and cleared by software to control the frequency of the main PLL output clock
PLLSAICLK. This output can be selected for SAI1. These bits can be written only if PLL is
disabled.
When the PLLPDIV[4:0] is set to “00000”PLLSAICLK output clock frequency = VCO
frequency / PLLP with PLLP =7, or 17
0: PLLP = 7
1: PLLP = 17

Caution:

The software has to set these bits correctly not to exceed 80 MHz on
this domain.

Bit 16 PLLPEN: Main PLL PLLSAICLK output enable
Set and reset by software to enable the PLLSAICLK output of the main PLL.
In order to save power, when the PLLSAICLK output of the PLL is not used, the value of
PLLPEN should be 0.
0: PLLSAICLK output disable
1: PLLSAICLK output enable
Bit 15 Reserved, must be kept at reset value.

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RM0394

Reset and clock control (RCC)

Bits 14:8 PLLN[6:0]: Main PLL multiplication factor for VCO
Set and cleared by software to control the multiplication factor of the VCO. These bits can be
written only when the PLL is disabled.
VCO output frequency = VCO input frequency x PLLN with 8 =< PLLN =< 86
0000000: PLLN = 0 wrong configuration
0000001: PLLN = 1 wrong configuration
...
0000111: PLLN = 7 wrong configuration
0001000: PLLN = 8
0001001: PLLN = 9
...
1010101: PLLN = 85
1010110: PLLN = 86
1010111: PLLN = 87 wrong configuration
...
1111111: PLLN = 127 wrong configuration

Caution:

The software has to set correctly these bits to assure that the VCO
output frequency is between 64 and 344 MHz.

Bit 7 Reserved, must be kept at reset value.
Bits 6:4 PLLM: Division factor for the main PLL and audio PLL (PLLSAI1) input clock
Set and cleared by software to divide the PLL PLLSAI1 input clock before the VCO. These
bits can be written only when all PLLs are disabled.
VCO input frequency = PLL input clock frequency / PLLM with 1 <= PLLM <= 8
000: PLLM = 1
001: PLLM = 2
010: PLLM = 3
011: PLLM = 4
100: PLLM = 5
101: PLLM = 6
110: PLLM = 7
111: PLLM = 8

Caution:

The software has to set these bits correctly to ensure that the VCO input
frequency ranges from 4 to 16 MHz.

Bits 3:2 Reserved, must be kept at reset value.
Bits 1:0 PLLSRC: Main PLL PLLSAI1 entry clock source
Set and cleared by software to select PLL PLLSAI1 clock source. These bits can be written
only when PLL PLLSAI1 are disabled.
In order to save power, when no PLL is used, the value of PLLSRC should be 00.
00: No clock sent to PLL PLLSAI1
01: MSI clock selected as PLL PLLSAI1 clock entry
10: HSI16 clock selected as PLL PLLSAI1 clock entry
11: HSE clock selected as PLL PLLSAI1 clock entry

6.4.5

PLLSAI1 configuration register (RCC_PLLSAI1CFGR)(a)
Address offset: 0x10
Reset value: 0x0000 1000
Access: no wait state, word, half-word and byte access
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Reset and clock control (RCC)

RM0394

This register is used to configure the PLLSAI1 clock outputs according to the formulas:
• f(VCOSAI1 clock) = f(PLL clock input) × (PLLSAI1N / PLLM)
• f(PLLSAI1_P) = f(VCOSAI1 clock) / PLLSAI1P
• f(PLLSAI1_Q) = f(VCOSAI1 clock) / PLLSAI1Q
• f(PLLSAI1_R) = f(VCOSAI1 clock) / PLLSAI1R
31

30

29

28

27

PLLSAI1PDIV[4:0]

26

25

PLLSAI1R[1:0]

24
PLL
SAI1
REN

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

Res.

PLLSAI1N[6:0]
rw

rw

rw

rw

rw

rw

23
Res.

22

21

PLLSAI1Q[1:0]

20
PLL
SAI1
QEN

19

18

Res.

Res.

17

16

PLL
SAI1P

PLL
SAI1
PEN

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:27 PLLSAI1PDIV[4:0]: PLLSAI1 division factor for PLLSAI1CLK
Set and cleared by software to control the SAI1 clock frequency. PLLSAI1CLK output clock
frequency = VCOSAI1 frequency / PLLPDIV.
00000: PLLSAI1CLK is controlled by the bit PLLP
00001: Reserved.
00010: PLLSAI1CLK = VCOSAI1 / 2
....
11111: PLLSAI1CLK = VCOSAI1 / 31
Bits 26:25 PLLSAI1R[1:0]: PLLSAI1 division factor for PLLADC1CLK (ADC clock)
Set and cleared by software to control the frequency of the PLLSAI1 output clock
PLLADC1CLK. This output can be selected as ADC clock. These bits can be written only if
PLLSAI1 is disabled.
PLLADC1CLK output clock frequency = VCOSAI1 frequency / PLLSAI1R with PLLSAI1R =
2, 4, 6, or 8
00: PLLSAI1R = 2
01: PLLSAI1R = 4
10: PLLSAI1R = 6
11: PLLSAI1R = 8
Bit 24 PLLSAI1REN: PLLSAI1 PLLADC1CLK output enable
Set and reset by software to enable the PLLADC1CLK output of the PLLSAI1 (used as clock
for ADC).
In order to save power, when the PLLADC1CLK output of the PLLSAI1 is not used, the value
of PLLSAI1REN should be 0.
0: PLLADC1CLK output disable
1: PLLADC1CLK output enable
Bit 23 Reserved, must be kept at reset value.

a. Not available on STM3L41xxx and STM32L42xxx devices.

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RM0394

Reset and clock control (RCC)

Bits 22:21 PLLSAI1Q[1:0]: PLLSAI1 division factor for PLL48M2CLK (48 MHz clock)
Set and cleared by software to control the frequency of the PLLSAI1 output clock
PLL48M2CLK. This output can be selected for USB, RNG, SDMMC (48 MHz clock). These
bits can be written only if PLLSAI1 is disabled.
PLL48M2CLK output clock frequency = VCOSAI1 frequency / PLLQ with PLLQ = 2, 4, 6, or
8
00: PLLQ = 2
01: PLLQ = 4
10: PLLQ = 6
11: PLLQ = 8

Caution:

The software has to set these bits correctly not to exceed 80 MHz on
this domain.

Bit 20 PLLSAI1QEN: PLLSAI1 PLL48M2CLK output enable
Set and reset by software to enable the PLL48M2CLK output of the PLLSAI1.
In order to save power, when the PLL48M2CLK output of the PLLSAI1 is not used, the value
of PLLSAI1QEN should be 0.
0: PLL48M2CLK output disable
1: PLL48M2CLK output enable
Bits 19:18 Reserved, must be kept at reset value.
Bit 17 PLLSAI1P: PLLSAI1 division factor for PLLSAI1CLK (SAI1 clock).
Set and cleared by software to control the frequency of the PLLSAI1 output clock
PLLSAI1CLK. This output can be selected for SAI1. These bits can be written only if
PLLSAI1 is disabled.
When the PLLSAI1PDIV[4:0] is set to “00000”,PLLSAI1CLK output clock frequency =
VCOSAI1 frequency / PLLSAI1P with PLLSAI1P =7, or 17
0: PLLSAI1P = 7
1: PLLSAI1P = 17
Bit 16 PLLSAI1PEN: PLLSAI1 PLLSAI1CLK output enable
Set and reset by software to enable the PLLSAI1CLK output of the PLLSAI1.
In order to save power, when the PLLSAI1CLK output of the PLLSAI1 is not used, the value
of PLLSAI1PEN should be 0.
0: PLLSAI1CLK output disable
1: PLLSAI1CLK output enable

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Reset and clock control (RCC)

RM0394

Bit 15 Reserved, must be kept at reset value.
Bits 14:8 PLLSAI1N[6:0]: PLLSAI1 multiplication factor for VCO
Set and cleared by software to control the multiplication factor of the VCO. These bits can be
written only when the PLLSAI1 is disabled.
VCOSAI1 output frequency = VCOSAI1 input frequency x PLLSAI1N
with 8 =< PLLSAI1N =< 86
0000000: PLLSAI1N = 0 wrong configuration
0000001: PLLSAI1N = 1 wrong configuration
...
0000111: PLLSAI1N = 7 wrong configuration
0001000: PLLSAI1N = 8
0001001: PLLSAI1N = 9
...
1010101: PLLSAI1N = 85
1010110: PLLSAI1N = 86
1010111: PLLSAI1N = 87 wrong configuration
...
1111111: PLLSAI1N = 127 wrong configuration

Caution:

The software has to set correctly these bits to ensure that the VCO
output frequency is between 64 and 344 MHz.

Bits 7:0 Reserved, must be kept at reset value.

6.4.6

Clock interrupt enable register (RCC_CIER)
Address offset: 0x18
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

PLL
SAI1
RDYIE

PLL
RDYIE

HSE
RDYIE

HSI
RDYIE

MSI
RDYIE

LSE
RDYIE

LSI
RDYIE

rw

rw

rw

rw

rw

rw

Res.

Res.

Res.

Res.

Res.

HSI48
RDYIE

LSE
CSSIE

rw

rw

Res.

(1)

rw

1. Not available on STM3L41xxx and STM32L42xxx devices

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RM0394

Reset and clock control (RCC)

Bits 31:11 Reserved, must be kept at reset value.
Bit 10 HSI48RDYIE: HSI48 ready interrupt enable
Set and cleared by software to enable/disable interrupt caused by the internal HSI48
oscillator.
0: HSI48 ready interrupt disabled
1: HSI48 ready interrupt enabled
Bit 9 LSECSSIE: LSE clock security system interrupt enable
Set and cleared by software to enable/disable interrupt caused by the clock security system
on LSE.
0: Clock security interrupt caused by LSE clock failure disabled
1: Clock security interrupt caused by LSE clock failure enabled
Bits 8:7 Reserved, must be kept at reset value.
Bit 6 PLLSAI1RDYIE: PLLSAI1 ready interrupt enable
Set and cleared by software to enable/disable interrupt caused by PLSAI1L lock.
0: PLLSAI1 lock interrupt disabled
1: PLLSAI1 lock interrupt enabled
Bit 5 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
Bit 4 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 3 HSIRDYIE: HSI16 ready interrupt enable
Set and cleared by software to enable/disable interrupt caused by the HSI16 oscillator
stabilization.
0: HSI16 ready interrupt disabled
1: HSI16 ready interrupt enabled
Bit 2 MSIRDYIE: MSI ready interrupt enable
Set and cleared by software to enable/disable interrupt caused by the MSI oscillator
stabilization.
0: MSI ready interrupt disabled
1: MSI ready interrupt enabled
Bit 1 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 0 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

RM0394 Rev 4

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Reset and clock control (RCC)

6.4.7

RM0394

Clock interrupt flag register (RCC_CIFR)
Address offset: 0x1C
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

PLLSAI
1RDYF
(1)

PLL
RDYF

HSE
RDYF

HSI
RDYF

MSI
RDYF

LSE
RDYF

LSI
RDYF

r

r

r

r

r

r

r

Res.

Res.

Res.

Res.

Res.

HSI48
RDYF

LSE
CSSF

CSSF

r

r

1. Not available on STM3L41xxx and STM32L42xxx devices

Bits 31:11 Reserved, must be kept at reset value.
Bit 10 HSI48RDYF: HSI48 ready interrupt flag
Set by hardware when the HSI48 clock becomes stable and HSI48RDYIE is set in a
response to setting the HSI48ON (refer to Clock recovery RC register (RCC_CRRCR)).
Cleared by software setting the HSI48RDYC bit.
0: No clock ready interrupt caused by the HSI48 oscillator
1: Clock ready interrupt caused by the HSI48 oscillator
Bit 9 LSECSSF: LSE Clock security system interrupt flag
Set by hardware when a failure is detected in the LSE oscillator.
Cleared by software setting the LSECSSC bit.
0: No clock security interrupt caused by LSE clock failure
1: Clock security interrupt caused by LSE clock failure
Bit 8 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
Bit 7 Reserved, must be kept at reset value.
Bit 6 PLLSAI1RDYF: PLLSAI1 ready interrupt flag
Set by hardware when the PLLSAI1 locks and PLLSAI1RDYDIE is set.
Cleared by software setting the PLLSAI1RDYC bit.
0: No clock ready interrupt caused by PLLSAI1 lock
1: Clock ready interrupt caused by PLLSAI1 lock
Bit 5 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

206/1600

RM0394 Rev 4

RM0394

Reset and clock control (RCC)

Bit 4 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
Bit 3 HSIRDYF: HSI16 ready interrupt flag
Set by hardware when the HSI16 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 HSI16 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 HSI16 oscillator
1: Clock ready interrupt caused by the HSI16 oscillator
Bit 2 MSIRDYF: MSI ready interrupt flag
Set by hardware when the MSI clock becomes stable and MSIRDYDIE is set.
Cleared by software setting the MSIRDYC bit.
0: No clock ready interrupt caused by the MSI oscillator
1: Clock ready interrupt caused by the MSI 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

6.4.8

Clock interrupt clear register (RCC_CICR)
Address offset: 0x20
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

PLL
SAI1
RDYC

PLL
RDYC

HSE
RDYC

HSI
RDYC

MSI
RDYC

LSE
RDYC

LSI
RDYC

w

w

w

w

w

w

Res.

Res.

Res.

Res.

Res.

HSI48
RDYC

LSE
CSSC

CSSC

w

w

(1)

w

1. Not available on STM3L41xxx and STM32L42xxx devices

RM0394 Rev 4

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246

Reset and clock control (RCC)

RM0394

Bits 31:11 Reserved, must be kept at reset value.
Bit 10 HSI48RDYC: HSI48 oscillator ready interrupt clear
This bit is set by software to clear the HSI48RDYF flag.
0: No effect
1: Clear the HSI48RDYC flag
Bit 9 LSECSSC: LSE Clock security system interrupt clear
This bit is set by software to clear the LSECSSF flag.
0: No effect
1: Clear LSECSSF flag
Bit 8 CSSC: Clock security system interrupt clear
This bit is set by software to clear the CSSF flag.
0: No effect
1: Clear CSSF flag
Bit 7 Reserved, must be kept at reset value.
Bit 6 PLLSAI1RDYC: PLLSAI1 ready interrupt clear
This bit is set by software to clear the PLLSAI1RDYF flag.
0: No effect
1: Clear PLLSAI1RDYF flag
Bit 5 PLLRDYC: PLL ready interrupt clear
This bit is set by software to clear the PLLRDYF flag.
0: No effect
1: Clear PLLRDYF flag
Bit 4 HSERDYC: HSE ready interrupt clear
This bit is set by software to clear the HSERDYF flag.
0: No effect
1: Clear HSERDYF flag
Bit 3 HSIRDYC: HSI16 ready interrupt clear
This bit is set software to clear the HSIRDYF flag.
0: No effect
1: Clear HSIRDYF flag
Bit 2 MSIRDYC: MSI ready interrupt clear
This bit is set by software to clear the MSIRDYF flag.
0: No effect
1: MSIRDYF cleared
Bit 1 LSERDYC: LSE ready interrupt clear
This bit is set by software to clear the LSERDYF flag.
0: No effect
1: LSERDYF cleared
Bit 0 LSIRDYC: LSI ready interrupt clear
This bit is set by software to clear the LSIRDYF flag.
0: No effect
1: LSIRDYF cleared

6.4.9

AHB1 peripheral reset register (RCC_AHB1RSTR)
Address offset: 0x28

208/1600

RM0394 Rev 4

RM0394

Reset and clock control (RCC)
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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSC
RST

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

CRC
RST

Res.

Res.

Res.

FLASH
RST

Res.

Res.

Res.

Res.

Res.

Res.

DMA2
RST

DMA1
RST

rw

rw

rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 TSCRST: Touch Sensing Controller reset
Set and cleared by software.
0: No effect
1: Reset TSC
Bits 15:13 Reserved, must be kept at reset value.
Bit 12 CRCRST: CRC reset
Set and cleared by software.
0: No effect
1: Reset CRC
Bits 11:9 Reserved, must be kept at reset value.
Bit 8 FLASHRST: Flash memory interface reset
Set and cleared by software. This bit can be activated only when the Flash memory is in
power down mode.
0: No effect
1: Reset Flash memory interface
Bits 7:2 Reserved, must be kept at reset value.
Bit 1 DMA2RST: DMA2 reset
Set and cleared by software.
0: No effect
1: Reset DMA2
Bit 0 DMA1RST: DMA1 reset
Set and cleared by software.
0: No effect
1: Reset DMA1

6.4.10

AHB2 peripheral reset register (RCC_AHB2RSTR)
Address offset: 0x2C
Reset value: 0x00000 0000
Access: no wait state, word, half-word and byte access

RM0394 Rev 4

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246

Reset and clock control (RCC)

RM0394

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RNG
RST

Res.

rw
15
Res.

14

13

Res.

ADC
RST

12
Res.

rw

rw

11
Res.

10
Res.

9
Res.

8

7

Res.

GPIOH
RST

6
Res.

rw

5
Res.

4

rw

2. Not available on STM32L41xxx, STM32L42xxx, STM32L432xx and STM32L442xx devices.

Bit 18 RNGRST: Random number generator reset
Set and cleared by software.
0: No effect
1: Reset RNG
Bit 17 Reserved, must be kept at reset value.
Bit 16 AESRST: AES hardware accelerator reset
Set and cleared by software.
0: No effect
1: Reset AES
Bits 15:14 Reserved, must be kept at reset value.
Bit 13 ADCRST: ADC reset
Set and cleared by software.
0: No effect
1: Reset ADC interface
Bits 12:8 Reserved, must be kept at reset value.
Bit 7 GPIOHRST: IO port H reset
Set and cleared by software.
0: No effect
1: Reset IO port H
Bits 6:5 Reserved, must be kept at reset value.
Bit 4 GPIOERST: IO port E reset
Set and cleared by software.
0: No effect
1: Reset IO port E
Bit 3 GPIODRST: IO port D reset
Set and cleared by software.
0: No effect
1: Reset IO port D

210/1600

RM0394 Rev 4

2

AES
RST(1)
rw

1

0

GPIOE GPIOD GPIOC GPIOB GPIOA
RST
RST
RST
RST(2) RST(2)

1. Available on STM32L42xxx, STM32L44xxx and STM32L46xxx devices only.

Bits 31:19 Reserved, must be kept at reset value.

3

16

rw

rw

rw

rw

RM0394

Reset and clock control (RCC)

Bit 2 GPIOCRST: IO port C reset
Set and cleared by software.
0: No effect
1: Reset IO port C
Bit 1 GPIOBRST: IO port B reset
Set and cleared by software.
0: No effect
1: Reset IO port B
Bit 0 GPIOARST: IO port A reset
Set and cleared by software.
0: No effect
1: Reset IO port A

6.4.11

AHB3 peripheral reset register (RCC_AHB3RSTR)
Address offset: 0x30
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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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.

QSPI
RST

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Bits 31:9 Reserved, must be kept at reset value.
Bit 8 QSPIRST: QUADSPI1 memory interface reset
Set and cleared by software.
0: No effect
1: Reset QUADSPI
Bits 7:0 Reserved, must be kept at reset value.

6.4.12

APB1 peripheral reset register 1 (RCC_APB1RSTR1)
Address offset: 0x38
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

RM0394 Rev 4

211/1600
246

Reset and clock control (RCC)

31

30

29

LPTIM1 OPAMP DAC1
RST
RST
RST(1)
rw

28

27

PWR
RST

Res.

rw

rw

rw

15

14

13

12

SPI3
RST(1)

SPI2
RST

rw

rw

Res.

Res.

11
Res.

RM0394

26

25

USBFS

CAN1

RST(2)

RST(1)

rw

rw

10

9

Res.

LCD
RST(5)

24

23

22

21

20

I2C2
RST(3)

I2C1
RST

Res.

rw

rw

rw

7

6

CRSRS I2C3R
T
ST

8
Res.

Res.

rw

1. Not available on STM3L41xxx and STM32L42xxx devices
2. Available on STM32L4x2xx and STM32L4x3xx devices only.
3. Not available on STM32L432xx and STM32L442xx devices.
4. Available on STM32L45xxx and STM32L46xxx devices only.
5. Available on STM32L4x3xx devices only.
6. Available on STM32L43xxx and STM32L44xxx devices only.

Bit 31 LPTIM1RST: Low Power Timer 1 reset
Set and cleared by software.
0: No effect
1: Reset LPTIM1
Bit 30 OPAMPRST: OPAMP interface reset
Set and cleared by software.
0: No effect
1: Reset OPAMP interface
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 PWR
Bit 27 Reserved, must be kept at reset value.
Bit 26 USBFSRST: USB FS reset
Set and cleared by software.
0: No effect
1: Reset the USB FS
Bit 25 CAN1RST: CAN1 reset
Set and reset by software.
0: No effect
1: Reset the CAN1
Bit 24 CRSRST: CRS reset
Set and cleared by software.
0: No effect
1: Reset the CRS

212/1600

RM0394 Rev 4

Res.

5

4

TIM7
RST(6)

TIM6
RST

rw

rw

19

18

17

UART4 USART3 USART2
RST
RST(4) RST(3)
rw

rw

3

2

Res.

Res.

16
Res.

rw
1

0

TIM3
RST(4)

TIM2
RST

rw

rw

RM0394

Reset and clock control (RCC)

Bit 23 I2C3RST: I2C3 reset
Set and reset by software.
0: No effect
1: Reset I2C3
Bit 22 I2C2RST: I2C2 reset
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 Reserved, must be kept at reset value.
Bit 19 UART4RST: UART4 reset
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
Set and cleared by software.
0: No effect
1: Reset SPI3
Bit 14 SPI2RST: SPI2 reset
Set and cleared by software.
0: No effect
1: Reset SPI2
Bits 13:10 Reserved, must be kept at reset value.
Bit 9 LCDRST: LCD interface reset
Set and cleared by software.
0: No effect
1: Reset LCD
Bits 8:6 Reserved, must be kept at reset value.
Bit 5 TIM7RST: TIM7 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM7

RM0394 Rev 4

213/1600
246

Reset and clock control (RCC)

RM0394

Bit 4 TIM6RST: TIM6 timer reset
Set and cleared by software.
0: No effect
1: Reset TIM6
Bits 3:2 Reserved, must be kept at reset value.
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

6.4.13

APB1 peripheral reset register 2 (RCC_APB1RSTR2)
Address offset: 0x3C
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.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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.

LPTIM2
RST

Res.

Res.

SWP
MI1
RST(1)

I2C4
RST
(2)

LP
UART1
RST

rw

rw

rw

rw

1. Not available on STM32L41xxx and STM32L42xxx devices.
2. Available on STM32L45xxx and STM32L46xxx devices only.

Bits 31:6 Reserved, must be kept at reset value.
Bit 5 LPTIM2RST: Low-power timer 2 reset
Set and cleared by software.
0: No effect
1: Reset LPTIM2
Bits 4:3 Reserved, must be kept at reset value.

214/1600

RM0394 Rev 4

RM0394

Reset and clock control (RCC)

Bit 2 SWPMI1RST: Single wire protocol reset
Set and cleared by software.
0: No effect
1: Reset SWPMI1
Bit 1 I2C4RST: I2C4 reset
Set and cleared by software
0: No effect
1: Reset I2C4
Bit 0 LPUART1RST: Low-power UART 1 reset
Set and cleared by software.
0: No effect
1: Reset LPUART1

6.4.14

APB2 peripheral reset register (RCC_APB2RSTR)
Address offset: 0x40
Reset value: 0x00000 0000
Access: no wait state, word, half-word and byte access

31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
:Res.

25

24

23

22

21

20

19

18

17

16

Res.

DFSD
M1
RST(1)

Res.

Res.

SAI1
RST(2)

Res.

Res.

Res.

TIM16
RST

TIM15
RST

rw

rw

rw
15

14

Res.

USART
1
RST
rw

13
Res.

12

11

10

SPI1
RST

TIM1
RST

SD
MMC1
RST(3)

rw

rw

rw

9
Res.

rw

8
Res.

7
Res.

6
Res.

5
Res.

4
Res.

3
Res.

2
Res.

1

0

Res.

SYS
CFG
RST
rw

1. Available on STM32L45xxx and STM32L46xxx devices only.
2. Not available on STM3L41xxx and STM32L42xxx devices.
3. Not available on STM3L41xxx and STM32L42xxx, STM32L432 and STM32L442 devices.

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 DFSDM1RST: Digital filters for sigma-delta modulators (DFSDM1) reset
Set and cleared by software.
0: No effect
1: Reset DFSDM1
Bit 23 Reserved, must be kept at reset value.
Bit 21 SAI1RST: Serial audio interface 1 (SAI1) reset
Set and cleared by software.
0: No effect
1: Reset SAI1
Bits 20:18 Reserved, must be kept at reset value.

RM0394 Rev 4

215/1600
246

Reset and clock control (RCC)

RM0394

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 Reserved, must be kept at reset value.
Bit 14 USART1RST: USART1 reset
Set and cleared by software.
0: No effect
1: Reset USART1
Bit 13 Reserved, must be kept at reset value.
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
Bit 10 SDMMC1RST: SDMMC reset
Set and cleared by software.
0: No effect
1: Reset SDMMC
Bits 9:1 Reserved, must be kept at reset value.
Bit 0 SYSCFGRST: SYSCFG + COMP + VREFBUF reset
0: No effect
1: Reset SYSCFG + COMP + VREFBUF

6.4.15

AHB1 peripheral clock enable register (RCC_AHB1ENR)
Address offset: 0x48
Reset value: 0x0000 0100
Access: no wait state, word, half-word and byte access

Note:

216/1600

When the peripheral clock is not active, the peripheral registers read or write access is not
supported.

RM0394 Rev 4

RM0394

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.

Res.

Res.

Res.

Res.

TSC
EN

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

CRCEN

Res.

Res.

Res.

FLASH
EN

Res.

Res.

Res.

Res.

Res.

Res.

DMA2
EN

DMA1
EN

rw

rw

rw

rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 TSCEN: Touch Sensing Controller clock enable
Set and cleared by software.
0: TSC clock disable
1: TSC clock enable
Bits 15:13 Reserved, must be kept at reset value.
Bit 12 CRCEN: CRC clock enable
Set and cleared by software.
0: CRC clock disable
1: CRC clock enable
Bits 11:9 Reserved, must be kept at reset value.
Bit 8 FLASHEN: Flash memory interface clock enable
Set and cleared by software. This bit can be disabled only when the Flash is in power down
mode.
0: Flash memory interface clock disable
1: Flash memory interface clock enable
Bits 7:2 Reserved, must be kept at reset value.
Bit 1 DMA2EN: DMA2 clock enable
Set and cleared by software.
0: DMA2 clock disable
1: DMA2 clock enable
Bit 0 DMA1EN: DMA1 clock enable
Set and cleared by software.
0: DMA1 clock disable
1: DMA1 clock enable

RM0394 Rev 4

217/1600
246

Reset and clock control (RCC)

6.4.16

RM0394

AHB2 peripheral clock enable register (RCC_AHB2ENR)
Address offset: 0x4C
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access

Note:

When the peripheral clock is not active, the peripheral registers read or write access is not
supported.

31
Res.

30

29

Res.

Res.

28
Res.

27
Res.

26
Res.

25

24

Res.

Res.

23
Res.

22
Res.

21
Res.

20
Res.

19

18

Res.

RNG
EN

17
res.

rw
15
Res.

14
res.

13
ADCEN

12
res.

11
Res.

10
Res.

9
Res.

8

7

res.

GPIOH
EN

rw

6
res.

rw

1. Available on STM32L42xxx, STM32L44xxx and STM32L46xxx devices only.

Bits 31:19 Reserved, must be kept at reset value.
Bit 18 RNGEN: Random Number Generator clock enable
Set and cleared by software.
0: Random Number Generator clock disabled
1: Random Number Generator clock enabled
Bit 17 Reserved, must be kept at reset value.
Bit 16 AESEN: AES accelerator clock enable
Set and cleared by software.
0: AES clock disabled
1: AES clock enabled
Bits 15:14 Reserved, must be kept at reset value.
Bit 13 ADCEN: ADC clock enable
Set and cleared by software.
0: ADC clock disabled
1: ADC clock enabled
Bits 12:8 Reserved, must be kept at reset value.
Bit 7 GPIOHEN: IO port H clock enable
Set and cleared by software.
0: IO port H clock disabled
1: IO port H clock enabled
Bits 6:5 Reserved, must be kept at reset value.
Bit 4 GPIOEEN: IO port E clock enable
Set and cleared by software.
0: IO port E clock disabled
1: IO port E clock enabled

218/1600

RM0394 Rev 4

5
res.

4

3

2

16
AESEN
(1)

rw
1

0

GPIOE GPIOD GPIOC GPIOB GPIOA
EN
EN
EN
EN
EN
rw

rw

rw

rw

rw

RM0394

Reset and clock control (RCC)

Bit 3 GPIODEN: IO port D clock enable
Set and cleared by software.
0: IO port D clock disabled
1: IO port D clock enabled
Bit 2 GPIOCEN: IO port C clock enable
Set and cleared by software.
0: IO port C clock disabled
1: IO port C clock enabled
Bit 1 GPIOBEN: IO port B clock enable
Set and cleared by software.
0: IO port B clock disabled
1: IO port B clock enabled
Bit 0 GPIOAEN: IO port A clock enable
Set and cleared by software.
0: IO port A clock disabled
1: IO port A clock enabled

6.4.17

AHB3 peripheral clock enable register(RCC_AHB3ENR)
Address offset: 0x50
Reset value: 0x00000 0000
Access: no wait state, word, half-word and byte access

Note:

When the peripheral clock is not active, the peripheral registers read or write access is not
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.

QSPI
EN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:9 Reserved, must be kept at reset value.
Bit 8 QSPIEN: Quad SPI memory interface clock enable
Set and cleared by software.
0: QUADSPI clock disable
1: QUADSPI clock enable
Bits 7:0 Reserved, must be kept at reset value.

RM0394 Rev 4

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246

Reset and clock control (RCC)

6.4.18

RM0394

APB1 peripheral clock enable register 1 (RCC_APB1ENR1)
Address: 0x58
Reset value: 0x0000 0400
Access: no wait state, word, half-word and byte access

Note:

When the peripheral clock is not active, the peripheral registers read or write access is not
supported.

31

30

29

LPTIM1 OPAMP DAC1
EN
EN
EN(1)
rw

28
PWR
EN

27

26

Res.

USB
FSEN

25

24

23

22

21

20

19

(2)

CAN1
EN(1)

CRSEN

I2C3
EN

I2C2
EN(3)

I2C1
EN

Res.

UART4
EN(4)

rw

rw

rw

rw

rw

rw

8

7

6

5

Res.

TIM7
EN(6)

TIM6EN

rw

rw

rw

rw

rw

13

12

11

10

9

Res.

WWD
GEN

RTCA
PBEN

LCD
EN(5)

rs

rw

rw

15

14

SPI3
EN(1)

SPI2
EN(3)

rw

rw

Res.

Res.

Res.

1. Not available on STM32L41xxx and STM32L42xxx devices
2. Available on STM32L4x2xx and STM32L4x3xx devices only.
3. Not available on STM32L432xx and STM32L442xx devices.
4. Available on STM32L45xxx and STM32L46xxx devices only.
5. Available on STM32L4x3xx devices only.
6. Available on STM32L43xxx and STM32L44xxx devices only.

Bit 31 LPTIM1EN: Low power timer 1 clock enable
Set and cleared by software.
0: LPTIM1 clock disabled
1: LPTIM1 clock enabled
Bit 30 OPAMPEN: OPAMP interface clock enable
Set and cleared by software.
0: OPAMP interface clock disabled
1: OPAMP interface 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.
Bit 26 USBFSEN: USB FS clock enable
Set and cleared by software.
0: USB FS clock disabled
1: USB FS clock enabled

220/1600

RM0394 Rev 4

4

18

USART3 USART2
EN
EN(3)

rw

rw

3

2

Res.

17

Res.

16
Res.

rw
1

0

TIM3EN
(1)

TIM2
EN

rw

rw

RM0394

Reset and clock control (RCC)

Bit 25 CAN1EN: CAN1 clock enable
Set and cleared by software.
0: CAN1 clock disabled
1: CAN1 clock enabled
Bit 24 CRSEN: CRS clock enable
Set and cleared by software.
0: CRS clock disabled
1: CRS clock enabled
Bit 23 I2C3EN: I2C3 clock enable
Set and cleared by software.
0: I2C3 clock disabled
1: I2C3 clock enabled
Bit 22 I2C2EN: I2C2 clock enable
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 Reserved, must be kept at reset value.
Bit 19 UART4EN: UART4 clock enable
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
Set and cleared by software.
0: SPI3 clock disabled
1: SPI3 clock enabled
Bit 14 SPI2EN: SPI2 clock enable
Set and cleared by software.
0: SPI2 clock disabled
1: SPI2 clock enabled
Bits 13:12 Reserved, must be kept at reset value.

RM0394 Rev 4

221/1600
246

Reset and clock control (RCC)

RM0394

Bit 11 WWDGEN: Window watchdog clock enable
Set by software to enable the window watchdog clock. Reset by hardware system reset.
This bit can also be set by hardware if the WWDG_SW option bit is reset.
0: Window watchdog clock disabled
1: Window watchdog clock enabled
Bit 10 RTCAPBEN: RTC APB clock enable
Set and cleared by software
0: RTC APB clock disabled
1: RTC APB clock enabled
Bit 9 LCDEN: LCD clock enable
Set and cleared by software.
0: LCD clock disabled
1: LCD clock enabled
Bits 8:6 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
Bits 3:2 Reserved, must be kept at reset value.
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

6.4.19

APB1 peripheral clock enable register 2 (RCC_APB1ENR2)
Address offset: 0x5C
Reset value: 0x00000 0000
Access: no wait state, word, half-word and byte access

Note:

222/1600

When the peripheral clock is not active, the peripheral registers read or write access is not
supported.

RM0394 Rev 4

RM0394

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.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

SWP
MI1

I2C4EN
(2)

LP
UART1
EN

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LPTIM2
EN

Res.

EN

(1)

rw

1. Available on STM32L43xxx and STM32L44xxx devices only.
2. Available on STM32L45xxx and STM32L46xxx devices only.

Bits 31:6 Reserved, must be kept at reset value.
Bit 5 LPTIM2EN Low power timer 2 clock enable
Set and cleared by software.
0: LPTIM2 clock disable
1: LPTIM2 clock enable
Bits 4:3 Reserved, must be kept at reset value.
Bit 2 SWPMI1EN: Single wire protocol clock enable
Set and cleared by software.
0: SWPMI1 clock disable
1: SWPMI1 clock enable
Bit 1 I2C4EN: I2C4 clock enable
Set and cleared by software
0: I2C4 clock disabled
1: I2C4 clock enabled
Bit 0 LPUART1EN: Low power UART 1 clock enable
Set and cleared by software.
0: LPUART1 clock disable
1: LPUART1 clock enable

RM0394 Rev 4

223/1600
246

Reset and clock control (RCC)

6.4.20

RM0394

APB2 peripheral clock enable register (RCC_APB2ENR)
Address: 0x60
Reset value: 0x0000 0000
Access: word, half-word and byte access

Note:

When the peripheral clock is not active, the peripheral registers read or write access is not
supported.

31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
Res.

25

24

23

22

21

20

19

18

17

16

Res.

DFSD
M1
EN(1)

Res.

Res.

SAI1
EN(2)

Res.

Res.

Res.

TIM16
EN

TIM15
EN

rw

rw

rw
15

14

Res.

USART
1
EN
rw

13
Res.

12

rw

11

10

9

8

7

6

5

4

3

2

1

0

SPI1
EN

TIM1
EN

SD
MMC1
EN(3)

Res.

Res.

FW
EN

Res.

Res.

Res.

Res.

Res.

Res.

SYS
CFGEN

rw

rw

rw

rs

1. Available on STM32L45xxx and STM32L46xxx devices only.
2. Not available on STM32L41xxx/42xxx devices.
3. Not available on STM3L41xxx and STM32L42xxx, STM32L432 and STM32L442 devices.

Bits 31:25 Reserved, must be kept at reset value.
Bit 24 DFSDM1EN: DFSDM1 timer clock enable
Set and cleared by software.
0: DFSDM1 clock disabled
1: DFSDM1 clock enabled
Bits 23:22 Reserved, must be kept at reset value.
Bit 21 SAI1EN: SAI1 clock enable
Set and cleared by software.
0: SAI1 clock disabled
1: SAI1 clock enabled
Bits 20:18 Reserved, must be kept at reset value.
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 Reserved, must be kept at reset value.
Bit 14 USART1EN: USART1clock enable
Set and cleared by software.
0: USART1clock disabled
1: USART1clock enabled
Bit 13 Reserved, must be kept at reset value.

224/1600

RM0394 Rev 4

rw

RM0394

Reset and clock control (RCC)

Bit 12 SPI1EN: SPI1 clock enable
Set and cleared by software.
0: SPI1 clock disabled
1: SPI1 clock enabled
Bit 11 TIM1EN: TIM1 timer clock enable
Set and cleared by software.
0: TIM1 timer clock disabled
1: TIM1P timer clock enabled
Bit 10 SDMMC1EN: SDMMC clock enable
Set and cleared by software.
0: SDMMC clock disabled
1: SDMMC clock enabled
Bits 9:8 Reserved, must be kept at reset value.
Bit 7 FWEN: Firewall clock enable
Set by software, reset by hardware. Software can only write 1. A write at 0 has no effect.
0: Firewall clock disabled
1: Firewall clock enabled
Bits 6:1 Reserved, must be kept at reset value.
Bit 0 SYSCFGEN: SYSCFG + COMP + VREFBUF clock enable
Set and cleared by software.
0: SYSCFG + COMP + VREFBUF clock disabled
1: SYSCFG + COMP + VREFBUF clock enabled(1)
1. Not available on STM3L41xxx and STM32L42xxx.

6.4.21

AHB1 peripheral clocks enable in Sleep and Stop modes register
(RCC_AHB1SMENR)
Address offset: 0x68
Reset value:
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

TSC
SMEN

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

CRCSMEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA2
SMEN

DMA1
SMEN

rw

rw

rw

rw

SRAM1 FLASH
SMEN SMEN
rw

rw

Bits 31:17 Reserved, must be kept at reset value.
Bit 16 TSCSMEN: Touch Sensing Controller clocks enable during Sleep and Stop modes
Set and cleared by software.
0: TSC clocks disabled by the clock gating(1) during Sleep and Stop modes
1: TSC clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 15:13 Reserved, must be kept at reset value.

RM0394 Rev 4

225/1600
246

Reset and clock control (RCC)

RM0394

Bit 12 CRCSMEN: CRC clocks enable during Sleep and Stop modes
Set and cleared by software.
0: CRC clocks disabled by the clock gating(1) during Sleep and Stop modes
1: CRC clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 11:10 Reserved, must be kept at reset value.
Bit 9 SRAM1SMEN: SRAM1 interface clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SRAM1 interface clocks disabled by the clock gating(1) during Sleep and Stop modes
1: SRAM1 interface clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 8 FLASHSMEN: Flash memory interface clocks enable during Sleep and Stop modes
Set and cleared by software.
0: Flash memory interface clocks disabled by the clock gating(1) during Sleep and Stop
modes
1: Flash memory interface clocks enabled by the clock gating(1) during Sleep and Stop
modes
Bits 7:2 Reserved, must be kept at reset value.
Bit 1 DMA2SMEN: DMA2 clocks enable during Sleep and Stop modes
Set and cleared by software during Sleep mode.
0: DMA2 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: DMA2 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 0 DMA1SMEN: DMA1 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: DMA1 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: DMA1 clocks enabled by the clock gating(1) during Sleep and Stop modes
1. This register only configures the clock gating, not the clock source itself. Most of the peripherals are clocked by a single
clock (AHB or APB clock), which is always disabled in Stop mode. In this case setting the bit has no effect in Stop mode.

6.4.22

AHB2 peripheral clocks enable in Sleep and Stop modes register
(RCC_AHB2SMENR)
Address offset: 0x6C
Reset value: 0x0005 229F
Access: no wait state, word, half-word and byte access

31
Res.

30
Res.

29
Res.

28
Res.

27
Res.

26
Res.

25
Res.

24
Res.

23
Res.

22
Res.

21
Res.

20
Res.

19
Res.

18
RNG
SMEN

17

16

Res.

AES
SMEN
(1)

rw
15

14

13

12

11

10

9

8

7

6

5

Res.

Res.

ADC
SMEN

Res.

Res.

Res.

SRAM2
SMEN

Res.

GPIOH
SMEN

Res.

Res.

rw

rw

rw

1. Available on STM32L44xxx and STM32L46xxx devices only.
2. Not available on STM32L432xx and STM32L442xx devices.
3. Not available on STM3L41xxx and STM32L42xxx.

226/1600

RM0394 Rev 4

4

3

2

rw
1

0

GPIOE
SMEN GPIOD GPIOC GPIOB GPIOA
SMEN SMEN SMEN SMEN
(2) (3)
rw

rw

rw

rw

rw

RM0394

Reset and clock control (RCC)

Bits 31:19 Reserved, must be kept at reset value.
Bit 18 RNGSMEN: Random Number Generator clocks enable during Sleep and Stop modes
Set and cleared by software.
0: Random Number Generator clocks disabled by the clock gating during Sleep and Stop
modes
1: Random Number Generator clocks enabled by the clock gating during Sleep and Stop
modes
Bit 17 Reserved, must be kept at reset value.
Bit 16 AESSMEN: AES accelerator clocks enable during Sleep and Stop modes
Set and cleared by software.
0: AES clocks disabled by the clock gating(1) during Sleep and Stop modes
1: AES clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 15:14 Reserved, must be kept at reset value.
Bit 13 ADCSMEN: ADC clocks enable during Sleep and Stop modes
Set and cleared by software.
0: ADC clocks disabled by the clock gating(1) during Sleep and Stop modes
1: ADC clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 12:10 Reserved, must be kept at reset value.
Bit 9 SRAM2SMEN: SRAM2 interface clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SRAM2 interface clocks disabled by the clock gating(1) during Sleep and Stop modes
1: SRAM2 interface clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 8 Reserved, must be kept at reset value.
Bit 7 GPIOHSMEN: IO port H clocks enable during Sleep and Stop modes
Set and cleared by software.
0: IO port H clocks disabled by the clock gating(1) during Sleep and Stop modes
1: IO port H clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 6:5 Reserved, must be kept at reset value.
Bit 4 GPIOESMEN: IO port E clocks enable during Sleep and Stop modes
Set and cleared by software.
0: IO port E clocks disabled by the clock gating(1) during Sleep and Stop modes
1: IO port E clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 3 GPIODSMEN: IO port D clocks enable during Sleep and Stop modes
Set and cleared by software.
0: IO port D clocks disabled by the clock gating(1) during Sleep and Stop modes
1: IO port D clocks enabled by the clock gating(1) during Sleep and Stop modes

RM0394 Rev 4

227/1600
246

Reset and clock control (RCC)

RM0394

Bit 2 GPIOCSMEN: IO port C clocks enable during Sleep and Stop modes
Set and cleared by software.
0: IO port C clocks disabled by the clock gating(1) during Sleep and Stop modes
1: IO port C clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 1 GPIOBSMEN: IO port B clocks enable during Sleep and Stop modes
Set and cleared by software.
0: IO port B clocks disabled by the clock gating(1) during Sleep and Stop modes
1: IO port B clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 0 GPIOASMEN: IO port A clocks enable during Sleep and Stop modes
Set and cleared by software.
0: IO port A clocks disabled by the clock gating(1) during Sleep and Stop modes
1: IO port A clocks enabled by the clock gating(1) during Sleep and Stop modes

6.4.23

AHB3 peripheral clocks enable in Sleep and Stop modes register
(RCC_AHB3SMENR)
Address offset: 0x70
Reset value: 0x000 0100
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

QSPI
SMEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

Bits 31:9 Reserved, must be kept at reset value.
Bit 8 QSPISMEN Quad SPI memory interface clocks enable during Sleep and Stop modes
Set and cleared by software.
0: QUADSPI clocks disabled by the clock gating(1) during Sleep and Stop modes
1: QUADSPI clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 7:0 Reserved, must be kept at reset value.
1. This register only configures the clock gating, not the clock source itself. Most of the peripherals are clocked by a single
clock (AHB or APB clock), which is always disabled in Stop mode. In this case setting the bit has no effect in Stop mode.

6.4.24

APB1 peripheral clocks enable in Sleep and Stop modes register 1
(RCC_APB1SMENR1)
Address: 0x78
Reset value: 0xF7E6 CE31
Access: no wait state, word, half-word and byte access

228/1600

RM0394 Rev 4

RM0394

31

Reset and clock control (RCC)

30

29

28

DAC1
LPTIM1 OPAMP SMEN PWR
SMEN
SMEN SMEN
(1)
rw

rw

rw

rw

15

14

13

12

(1)

SPI2
SMEN

Res.

Res.

rw

rw

SPI3
SMEN

27

26

25

24

23

Res.

USB
FSSM
EN(2)

CAN1
SMEN
(1)

CRSS
MEN

I2C3
SMEN

11

rw

rw

rw

10

9

8

LCD
SMEN

Res.

RTCA
WWDG
PBSM
SMEN
EN
rw

rw

(5)

22

21

20

(3)

I2C1
SMEN

Res.

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

Res.

Res.

TIM7
SMEN

TIM6
SMEN

Res.

Res.

TIM3
SMEN

rw

rw

I2C2
SMEN

rw

19

18

17

16

UART4 USART3 USART2
SMEN(4) SMEN(3) SMEN

Res.

0

(1)

TIM2
SMEN

rw

rw

1. Not available on STM3L41xxx and STM32L42xxx.
2. Available on STM32L4x2xx and STM32L4x3xx devices only.
3. Not available on STM32L432xx and STM32L442xx devices.
4. Available on STM32L45xxx and STM32L46xxx devices only.
5. Available on STM32L4x3xx devices only.

Bit 31 LPTIM1SMEN: Low power timer 1 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: LPTIM1 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: LPTIM1 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 30 OPAMPSMEN: OPAMP interface clocks enable during Sleep and Stop modes
Set and cleared by software.
0: OPAMP interface clocks disabled by the clock gating(1) during Sleep and Stop modes
1: OPAMP interface clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 29 DAC1SMEN: DAC1 interface clocks enable during Sleep and Stop modes
Set and cleared by software.
0: DAC1 interface clocks disabled by the clock gating(1) during Sleep and Stop modes
1: DAC1 interface clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 28 PWRSMEN: Power interface clocks enable during Sleep and Stop modes
Set and cleared by software.
0: Power interface clocks disabled by the clock gating(1) during Sleep and Stop modes
1: Power interface clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 27 Reserved, must be kept at reset value.
Bit 26 USBFSSMEN: USB FS clock enable during Sleep and Stop modes
Set and cleared by software.
0: USB FS clock disabled by the clock gating(1) during Sleep and Stop modes
1: USB FS clock enabled by the clock gating(1) during Sleep and Stop modes
Bit 25 CAN1SMEN: CAN1 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: CAN1 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: CAN1 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 24 CRSSMEN: CRS clock enable during Sleep and Stop modes
Set and cleared by software.
0: CRS clocks disabled by the clock gating(1) during Sleep and Stop modes
1: CRS clocks enabled by the clock gating(1) during Sleep and Stop modes

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Bit 23 I2C3SMEN: I2C3 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: I2C3 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: I2C3 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 22 I2C2SMEN: I2C2 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: I2C2 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: I2C2 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 21 I2C1SMEN: I2C1 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: I2C1 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: I2C1 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 20 Reserved, must be kept at reset value.
Bit 19 UART4SMEN: UART4 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: UART4 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: UART4 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 18 USART3SMEN: USART3 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: USART3 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: USART3 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 17 USART2SMEN: USART2 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: USART2 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: USART2 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 16 Reserved, must be kept at reset value.
Bit 15 SPI3SMEN: SPI3 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SPI3 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: SPI3 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 14 SPI2SMEN: SPI2 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SPI2 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: SPI2 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 13:12 Reserved, must be kept at reset value.
Bit 11 WWDGSMEN: Window watchdog clocks enable during Sleep and Stop modes
Set and cleared by software. This bit is forced to ‘1’ by hardware when the hardware WWDG
option is activated.
0: Window watchdog clocks disabled by the clock gating(1) during Sleep and Stop modes
1: Window watchdog clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 10 RTCAPBSMEN: RTC APB clock enable during Sleep and Stop modes
Set and cleared by software
0: RTC APB clock disabled by the clock gating(1) during Sleep and Stop modes
1: RTC APB clock enabled by the clock gating(1) during Sleep and Stop modes

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RM0394

Reset and clock control (RCC)

Bit 9 LCDSMEN: LCD clocks enable during Sleep and Stop modes
Set and cleared by software.
0: LCD clocks disabled by the clock gating(1) during Sleep and Stop modes
1: LCD clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 8:6 Reserved, must be kept at reset value.
Bit 5 TIM7SMEN: TIM7 timer clocks enable during Sleep and Stop modes
Set and cleared by software.
0: TIM7 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: TIM7 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 4 TIM6SMEN: TIM6 timer clocks enable during Sleep and Stop modes
Set and cleared by software.
0: TIM6 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: TIM6 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 3:2 Reserved, must be kept at reset value.
Bit 1 TIM3SMEN: TIM3 timer clocks enable during Sleep and Stop modes
Set and cleared by software.
0: TIM3 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: TIM3 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 0 TIM2SMEN: TIM2 timer clocks enable during Sleep and Stop modes
Set and cleared by software.
0: TIM2 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: TIM2 clocks enabled by the clock gating(1) during Sleep and Stop modes
1. This register only configures the clock gating, not the clock source itself. Most of the peripherals are clocked by a single
clock (AHB or APB clock), which is always disabled in Stop mode. In this case setting the bit has no effect in Stop mode.

6.4.25

APB1 peripheral clocks enable in Sleep and Stop modes register 2
(RCC_APB1SMENR2)
Address offset: 0x7C
Reset value: 0x0000 0025
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

SWP
MI1
SMEN

Res.

(1)

LP
UART1
SMEN

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

LPTIM
2SMEN
rw

Res.

1. Available on STM32L43xxx and STM32L44xxx devices only.

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Bits 31:6 Reserved, must be kept at reset value.
Bit 5 LPTIM2SMEN Low power timer 2 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: LPTIM2 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: LPTIM2 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 4:3 Reserved, must be kept at reset value.
Bit 2 SWPMI1SMEN: Single wire protocol clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SWPMI1 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: SWPMI1 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 1 Reserved, must be kept at reset value.
Bit 0 LPUART1SMEN: Low power UART 1 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: LPUART1 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: LPUART1 clocks enabled by the clock gating(1) during Sleep and Stop modes
1. This register only configures the clock gating, not the clock source itself. Most of the peripherals are clocked by a single
clock (AHB or APB clock), which is always disabled in Stop mode. In this case setting the bit has no effect in Stop mode.

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RM0394

Reset and clock control (RCC)

6.4.26

APB2 peripheral clocks enable in Sleep and Stop modes register
(RCC_APB2SMENR)
Address: 0x80
Reset value: 0x0235 7C01
Access: word, half-word and byte access

31
Res.

30

29

Res.

Res.

28
Res.

27
Res.

26
Res.

25
Res.

24
Res.

23
Res.

22

21

20

19

18

17

16

Res.

SAI1
SMEN

Res.

Res.

Res.

TIM16
SMEN

TIM15
SMEN

rw

rw

(1)

rw
15

Res.

14

13

USART1
SMEN
rw

Res.

12

11

10

9

8

7

6

5

4

3

2

1

0

SPI1
SMEN

TIM1
SMEN

SD
MMC1
SMEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

(1)

SYS
CFG
SMEN

rw

rw

rw

rw

1. Not available on STM3L41xxx and STM32L42xxx.

Bits 31:22 Reserved, must be kept at reset value.
Bit 21 SAI1SMEN: SAI1 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SAI1 clocks disabled by the clock gating(1) during Sleep and Stop modes
1: SAI1 clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 20:18 Reserved, must be kept at reset value.
Bit 17 TIM16SMEN: TIM16 timer clocks enable during Sleep and Stop modes
Set and cleared by software.
0: TIM16 timer clocks disabled by the clock gating(1) during Sleep and Stop modes
1: TIM16 timer clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 16 TIM15SMEN: TIM15 timer clocks enable during Sleep and Stop modes
Set and cleared by software.
0: TIM15 timer clocks disabled by the clock gating(1) during Sleep and Stop modes
1: TIM15 timer clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 15 Reserved, must be kept at reset value.
Bit 14 USART1SMEN: USART1clocks enable during Sleep and Stop modes
Set and cleared by software.
0: USART1clocks disabled by the clock gating(1) during Sleep and Stop modes
1: USART1clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 13 Reserved, must be kept at reset value.
Bit 12 SPI1SMEN: SPI1 clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SPI1 clocks disabled by the clock gating during(1) Sleep and Stop modes
1: SPI1 clocks enabled by the clock gating during(1) Sleep and Stop modes

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Bit 11 TIM1SMEN: TIM1 timer clocks enable during Sleep and Stop modes
Set and cleared by software.
0: TIM1 timer clocks disabled by the clock gating(1) during Sleep and Stop modes
1: TIM1P timer clocks enabled by the clock gating(1) during Sleep and Stop modes
Bit 10 SDMMC1SMEN: SDMMC clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SDMMC clocks disabled by the clock gating(1) during Sleep and Stop modes
1: SDMMC clocks enabled by the clock gating(1) during Sleep and Stop modes
Bits 9:1 Reserved, must be kept at reset value.
Bit 0 SYSCFGSMEN: SYSCFG + COMP + VREFBUF clocks enable during Sleep and Stop modes
Set and cleared by software.
0: SYSCFG + COMP + VREFBUF clocks disabled by the clock gating(1) during Sleep and
Stop modes
1: SYSCFG + COMP + VREFBUF clocks enabled by the clock gating(1) during Sleep and
Stop modes(2)
1. This register only configures the clock gating, not the clock source itself. Most of the peripherals are clocked by a single
clock (AHB or APB clock), which is always disabled in Stop mode. In this case setting the bit has no effect in Stop mode.
2. Not available on STM3L41xxx and STM32L42xxx.

6.4.27

Peripherals independent clock configuration register (RCC_CCIPR)
Address: 0x88
Reset value: 0x0000 0000
Access: no wait states, word, half-word and byte access

31

30

Res.

SWP
MI1
SEL

15

(1)

28

ADCSEL[1:0](2)

27

26

CLK48SEL[1:0]

rw

rw

rw

rw

rw

14

13

12

11

10

I2C2SEL[1:0](3)
rw

29

rw

I2C1SEL[1:0]
rw

rw

LPUART1SEL
[1:0]
rw

25

24

Res.

Res.

9

8

Res.

Res.

rw

23

22

SAI1SEL[1:0]
(2)

20

LPTIM2SEL[1:0]

19

18

LPTIM1SEL[1:0

17

16

I2C3SEL[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

UART4SEL

USART3SEL

[1:0](4)

[1:0](3)

rw

1. Available on STM32L43x and STM32L44x devices only.
2. Not available on STM3L41xxx and STM32L42xxx.
3. Not available on STM32L432xx and STM32L442xx devices.
4. Available on STM32L45xxx and STM32L46xxx devices only.

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RM0394 Rev 4

rw

rw

rw

USART2SEL
[1:0]
rw

rw

USART1SEL
[1:0]
rw

rw

RM0394

Reset and clock control (RCC)

Bit 31 Reserved, must be kept at reset value.
Bit 30 SWPMI1SEL: SWPMI1 clock source selection
This bit is set and cleared by software to select the SWPMI1 clock source.
0: APB1 (PCLK1) selected as SWPMI1 clock
1: HSI16 clock selected as SWPMI1 clock
Bits 29:28 ADCSEL[1:0]: ADCs clock source selection
These bits are set and cleared by software to select the clock source used by the ADC
interface.
00: No clock selected
01: PLLSAI1 “R” clock (PLLADC1CLK) selected as ADCs clock(1)
11: System clock selected as ADCs clock
Bits 27:26 CLK48SEL[1:0]: 48 MHz clock source selection
These bits are set and cleared by software to select the 48 MHz clock source used by USB
FS, RNG and SDMMC.
00: HSI48 clock selected as 48 MHz clock
01: PLLSAI1 “Q” clock (PLL48M2CLK) selected as 48 MHz clock
10: PLL “Q” clock (PLL48M1CLK) selected as 48 MHz clock
11: MSI clock selected as 48 MHz clock
Bits 25:24 Reserved, must be kept at reset value.
Bits 23:22 SAI1SEL[1:0]: SAI1 clock source selection(1)
These bits are set and cleared by software to select the SAI1 clock source.
00: PLLSAI1 “P” clock (PLLSAI1CLK) selected as SAI1 clock
01: Reserved
Note: When there is no PLL enabled, the HSI16 clock source is connected automatically to
the SAI1 to allow audio detection without the need to turn on the PLL source.
10: PLL “P” clock (PLLSAI3CLK) selected as SAI1 clock
11: External input SAI1_EXTCLK selected as SAI1 clock

Caution:

If the selected clock is the external clock, it is not possible to switch to
another clock if the external clock is not present.

Bits 21:20 LPTIM2SEL[1:0]: Low power timer 2 clock source selection
These bits are set and cleared by software to select the LPTIM2 clock source.
00: PCLK selected as LPTIM2 clock
01: LSI clock selected as LPTIM2 clock
10: HSI16 clock selected as LPTIM2 clock
11: LSE clock selected as LPTIM2 clock
Bits 19:18 LPTIM1SEL[1:0]: Low power timer 1 clock source selection
These bits are set and cleared by software to select the LPTIM1 clock source.
00: PCLK selected as LPTIM1 clock
01: LSI clock selected as LPTIM1 clock
10: HSI16 clock selected as LPTIM1 clock
11: LSE clock selected as LPTIM1 clock
Bits 17:16 I2C3SEL[1:0]: I2C3 clock source selection
These bits are set and cleared by software to select the I2C3 clock source.
00: PCLK selected as I2C3 clock
01: System clock (SYSCLK) selected as I2C3 clock
10: HSI16 clock selected as I2C3 clock
11: Reserved

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Bits 15:14 I2C2SEL[1:0]: I2C2 clock source selection
These bits are set and cleared by software to select the I2C2 clock source.
00: PCLK selected as I2C2 clock
01: System clock (SYSCLK) selected as I2C2 clock
10: HSI16 clock selected as I2C2 clock
11: Reserved
Bits 13:12 I2C1SEL[1:0]: I2C1 clock source selection
These bits are set and cleared by software to select the I2C1 clock source.
00: PCLK selected as I2C1 clock
01: System clock (SYSCLK) selected as I2C1 clock
10: HSI16 clock selected as I2C1 clock
11: Reserved
Bits 11:10 LPUART1SEL[1:0]: LPUART1 clock source selection
These bits are set and cleared by software to select the LPUART1 clock source.
00: PCLK selected as LPUART1 clock
01: System clock (SYSCLK) selected as LPUART1 clock
10: HSI16 clock selected as LPUART1 clock
11: LSE clock selected as LPUART1 clock
Bits 9:8 Reserved, must be kept at reset value.
Bits 7:6 UART4SEL[1:0]: UART4 clock source selection
This bit is set and cleared by software to select the UART4 clock source.
00: PCLK selected as UART4 clock
01: System clock (SYSCLK) selected as UART4 clock
10: HSI16 clock selected as UART4 clock
11: LSE clock selected as UART4 clock
Bits 5:4 USART3SEL[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
01: System clock (SYSCLK) selected as USART3 clock
10: HSI16 clock selected as USART3 clock
11: LSE clock selected as USART3 clock
Bits 3:2 USART2SEL[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
01: System clock (SYSCLK) selected as USART2 clock
10: HSI16 clock selected as USART2 clock
11: LSE clock selected as USART2 clock
Bits 1:0 USART1SEL[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
01: System clock (SYSCLK) selected as USART1 clock
10: HSI16 clock selected as USART1 clock
11: LSE clock selected as USART1 clock
1. Not available on STM3L41xxx and STM32L42xxx.

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RM0394

Reset and clock control (RCC)

6.4.28

Backup domain control register (RCC_BDCR)
Address offset: 0x90
Reset value: 0x0000 0000, reset by Backup domain Reset, except LSCOSEL, LSCOEN
and BDRST which are reset only by Backup domain power-on 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:

31
Res.

15
RTC
EN
rw

The bits of the Backup domain control register (RCC_BDCR) are outside of the VCORE
domain. As a result, after Reset, these bits are write-protected and the DBP bit in the
Section 5.4.1: Power control register 1 (PWR_CR1) has to be set before these can be
modified. Refer to Section 5.1.4: Battery backup domain on page 130 for further
information. These bits (except LSCOSEL, LSCOEN and BDRST) are only reset after a
Backup domain Reset (see Section 6.1.3: Backup domain reset). Any internal or external
Reset will not have any effect on these bits.
30
Res.

14
Res.

29
Res.

13
Res.

28
Res.

12
Res.

27
Res.

11
Res.

26

25

24

23

22

21

20

19

18

17

16

Res.

LSCO
SEL

LSCO
EN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

BDRST

rw

rw

9

8

10
Res.

RTCSEL[1:0]
rw

rw
7
LSESY
SDIS(1)

rw

6

5

LSE
LSE
CSSD CSSON

rw

r

rw

4

3

LSEDRV[1:0]
rw

rw

2

1

0

LSE
BYP

LSE
RDY

LSEON

rw

r

rw

1. This bit is available on STM32L412xx and STM32L422xx devices only.

Bits 31:26 Reserved, must be kept at reset value.
Bit 25 LSCOSEL: Low speed clock output selection
Set and cleared by software.
0: LSI clock selected
1: LSE clock selected
Bit 24 LSCOEN: Low speed clock output enable
Set and cleared by software.
0: Low speed clock output (LSCO) disable
1: Low speed clock output (LSCO) enable
Bits 23:17 Reserved, must be kept at reset value.
Bit 16 BDRST: Backup domain software reset
Set and cleared by software.
0: Reset not activated
1: Reset the entire Backup 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.

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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 Backup domain is reset, or unless a
failure is detected on LSE (LSECSSD is set). 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
Bit 7 LSESYSDIS: Disable the Clock LSE propagation to the system.(1)
Set by software to disable the Clock LSE propagation to the system. Only RTC will be clocked
by LSE when this bit is set.
1: No clock LSE propagation
0: Clock LSE propagation enabled
Bit 6 LSECSSD CSS on LSE failure Detection
Set by hardware to indicate when a failure has been detected by the Clock Security System
on the external 32 kHz oscillator (LSE).
0: No failure detected on LSE (32 kHz oscillator)
1: Failure detected on LSE (32 kHz oscillator)
Bit 5 LSECSSON CSS on LSE enable
Set by software to enable the Clock Security System on LSE (32 kHz oscillator).
LSECSSON must be enabled after the LSE oscillator is enabled (LSEON bit enabled) and
ready (LSERDY flag set by hardware), and after the RTCSEL bit is selected.
Once enabled this bit cannot be disabled, except after a LSE failure detection (LSECSSD
=1). In that case the software MUST disable the LSECSSON bit.
0: CSS on LSE (32 kHz external oscillator) OFF
1: CSS on LSE (32 kHz external oscillator) ON
Bits 4:3 LSEDRV[1:0] LSE oscillator drive capability
Set by software to modulate the LSE oscillator’s drive capability.
00: ‘Xtal mode’ lower driving capability
01: ‘Xtal mode’ medium low driving capability
10: ‘Xtal mode’ medium high driving capability
11: ‘Xtal mode’ higher driving capability
The oscillator is in Xtal mode when it is not in bypass mode.

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RM0394

Reset and clock control (RCC)

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 (LSEON=0 and LSERDY=0).
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
1. This bit is available on STM32L412xx and STM32L422xx devices only.

6.4.29

Control/status register (RCC_CSR)
Address: 0x94
Reset value: 0x0C00 0600, reset by system Reset, except reset flags by power Reset only.
Access: 0 ≤ wait state ≤ 3, word, half-word and byte access
Wait states are inserted in case of successive accesses to this register.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

LPWR
RSTF

WWDG
RSTF

IWWG
RSTF

SFT
RSTF

BOR
RSTF

PIN
RSTF

OBL
RSTF

FW
RSTF

RMVF

Res.

Res.

Res.

Res.

Res.

Res.

Res.

6

5

4

3

2

1

0

Res.

LSIPR
EDIV(1)

Res.

Res.

LSI
RDY

LSION

r

rw

r

r

r

r

r

r

r

r

rw

15

14

13

12

11

10

9

8

7

Res.

Res.

Res.

Res.

MSISRANGE[3:0]
rw

rw

rw

Res.
rw

Res.

rw

1. This bit is available on STM32L412xx and STM32L422xx devices only.

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Reset and clock control (RCC)

RM0394

Bit 31 LPWRRSTF: Low-power reset flag
Set by hardware when a reset occurs due to illegal Stop, Standby or Shutdown mode entry.
Cleared by writing to the RMVF bit.
0: No illegal mode reset occurred
1: Illegal mode reset occurred
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
Bit 29 IWDGRSTF: Independent window watchdog reset flag
Set by hardware when an independent watchdog reset domain occurs.
Cleared by writing to the RMVF bit.
0: No independent watchdog reset occurred
1: Independent 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 BORRSTF: BOR flag
Set by hardware when a BOR occurs.
Cleared by writing to the RMVF bit.
0: No BOR occurred
1: BOR 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 Option Byte loading occurs.
Cleared by writing to the RMVF bit.
0: No reset from Option Byte loading occurred
1: Reset from Option Byte loading occurred
Bit 24 FWRSTF: Firewall reset flag
Set by hardware when a reset from the firewall occurs.
Cleared by writing to the RMVF bit.
0: No reset from the firewall occurred
1: Reset from the firewall occurred
Bit 23 RMVF: Remove reset flag
Set by software to clear the reset flags.
0: No effect
1: Clear the reset flags
Bits 22:12 Reserved, must be kept at reset value.

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RM0394

Reset and clock control (RCC)

Bits 11:8 MSISRANGE[3:1] MSI range after Standby mode
Set by software to chose the MSI frequency at startup. This range is used after exiting
Standby mode until MSIRGSEL is set. After a pad or a power-on reset, the range is always
4 MHz. MSISRANGE can be written only when MSIRGSEL = ‘1’.
0100: Range 4 around 1 MHz
0101: Range 5 around 2 MHz
0101: Range 6 around 4 MHz (reset value)
0111: Range 7 around 8 MHz
others: Reserved

Note:

Changing the MSISRANGE does not change the current MSI frequency.

Bits 7:25 Reserved, must be kept at reset value.
Bit 4 LSIPREDIV: Internal Low Speed oscillator pre-divided by 128
Set and reset by hardware to indicate when the Low Speed Internal RC oscillator has to be
divided by 128. The software has to switch off the LSI before to change this bit.
0: LSI RC oscillator is not divided
1: LSI RC oscillator divided by 128
Bits 3:2 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. This bit can be set even if
LSION = 0 if the LSI is requested by the Clock Security System on LSE, by the Independent
Watchdog or by the RTC.
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

6.4.30

Clock recovery RC register (RCC_CRRCR)
Address: 0x98
Reset value: 0x0000 XXX0 where X is factory-programmed.
Access: no wait state, word, half-word and byte access

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

HSI48
RDY

HSI48
ON

r

rw

HSI48CAL[8:0]
r

r

r

r

r

Res.
r

r

r

r

RM0394 Rev 4

Res.

Res.

Res.

241/1600
246

Reset and clock control (RCC)

RM0394

Bits 31:16 Reserved, must be kept at reset value
Bits 15:7 HSI48CAL[8:0]: HSI48 clock calibration
These bits are initialized at startup with the factory-programmed HSI48 calibration trim value.
They are ready only.
Bits 6:2 Reserved, must be kept at reset value
Bit 1 HSI48RDY: HSI48 clock ready flag
Set by hardware to indicate that HSI48 oscillator is stable. This bit is set only when HSI48 is
enabled by software by setting HSI48ON.
0: HSI48 oscillator not ready
1: HSI48 oscillator ready
Bit 0 HSI48ON: HSI48 clock enable
Set and cleared by software.
Cleared by hardware to stop the HSI48 when entering in Stop, Standby or Shutdown modes.
0: HSI48 oscillator OFF
1: HSI48 oscillator ON

6.4.31

Peripherals independent clock configuration register (RCC_CCIPR2)
Address: 0x9C
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access
Wait states are inserted in case of successive accesses to this 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.

1

0

15

14

13

12

11

10

9

8

7

6

5

4

3

2

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

I2C4SEL[1:0]
r

Bits 31:2 Reserved, must be kept at reset value.
Bits 1:0 I2C4SEL[1:0]: I2C4 clock source selection
These bits are set and cleared by software to select the I2C4 clock source.
00: PCLK selected as I2C4 clock
01: System clock (SYSCLK) selected as I2C4 clock
10: HSI16 clock selected as I2C4 clock
11: reserved

6.4.32

RCC register map
The following table gives the RCC register map and the reset values.

242/1600

RM0394 Rev 4

rw

Reset value

0x10

0x18

0x1C

0x20
RCC_
PLLSAI1
CFGR

RCC_CIFR

RCC_CICR
PLLPDIV[4:0]
PLLR
[1:0]

0 0 0 0 0 0 0 0

PLL
PLLSAI1PDI
SAI1
V
R
[4:0]
[1:0]
PLL
Q
[1:0]

PLL
SAI1
Q
[1:0]
PLLQEN
Res.
Res.
PLLP
PLLPEN
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

RCC_CR

HSICAL[7:0]

0 0 0 0 0 0 0
0

0 0 0

Reset value
0 0 0 0 0 0 0 0

RCC_CIER
0 0 0
0 0

0 0

Reset value

Reset value

Reset value

RM0394 Rev 4
PLLN
[6:0]

0 0 1 0 0 0 0
PLLSAI1N
[6:0]

0 0

0 0 0

0 0 0

Res.
Res.
Res.
Res.
PLLSAI1RDY
PLLSAI1ON
PLLRDY
PLLON
Res.
Res.
Res.
Res.
CSSON
HSEBYP
HSERDY
HSEON
Res.
Res.
Res.
Res.
HSIASFS
HSIRDY
HSIKERON
HSION
MSITRIM[7:0]

PLLM
[2:0]

0 0 0

MSIRGSEL
MSIPLLEN
MSIRDY
MSION

MSIRANG
E
[3:0]

Res.
Res.

0 0 0 0

Res.

Reset value
1 0 0 0 0 0 0 x x x x x x x x 0 0 0 0 0 0 0 0 x x x x x x x x

RCC_CFGR
MCOP
MCOSEL
RE
[3:0]
[2:0]
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
STOPWUCK
Res.

0 0 0 0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

0x0C
RCC_PLL
CFGR
HSITRIM[6:0]

PLLSAI1QEN
Res.
Res.
PLLSAI1P
PLLSAI1PEN
Res.

Reset value

PLLREN
Res.

0x08
Res.

RCC_ICSCR

Res.

Reset value

PLLSAI1REN
Res.

0x04

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
HSI48RDYIE
LSECSSIE.
Res.
Res.
PLLSAI1RDYIE
PLLRDYIE
HSERDYIE
HSIRDYIE
MSIRDYIE
LSERDYIE
LSIRDYIE

0x00

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
HSI48RDYF
LSECSSF
CSSF
Res.
PLLSAI1RDYF
PLLRDYF
HSERDYF
HSIRDYF
MSIRDYF
LSERDYF
LSIRDYF

Offset

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
HSI48RDYC
LSECSSC
CSSC
Res.
PLLSAI1RDYC
PLLRDYC
HSERDYC
HSIRDYC
MSIRDYC
LSERDYC
LSIRDYC

RM0394
Reset and clock control (RCC)

Table 32. RCC register map and reset values

0 0 0 0 0 1 1 0 0 0 1 1
MSICAL[7:0]

PPRE2 PPRE1
SWS SW
HPRE[3:0]
[2:0]
[2:0]
[1:0] [1:0]
0 0 0 0 0 0 0 0 0 0 0 0 0 0
PLL
SRC
[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

243/1600

246

RCC_
0x38 APB1RSTR1

Reset value

RCC_
0x3C APB1RSTR2

0x48

0x4C
RCC_
APB2RSTR

Reset value

RCC_AHB1
ENR

RCC_AHB2
ENR

Reset value

244/1600
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
QSPIRST
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
0

Reset value
0

0 0 0 0
0 0 0 0 0 0

0
0 0 0

0
0 0

Reset value

0

RM0394 Rev 4

0

0

0

Reset value

0 0

0

0

0

0

GPIOHRST
Res.
Res.
GPIOERST
GPIODRST
GPIOCRST
GPIOBRST
GPIOARST

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
RNGRST.
Res.
AESRST.
Res.
Res.
ADCRST.
Res.
Res.
Res.
Res.

Reset value

Res.
Res.
Res.
Res.
GPIOHEN
Res.
Res.
GPIOEEN
GPIODEN
GPIOCEN
GPIOBEN
GPIOAEN

0x40
RCC_
AHB3RSTR

LPTIM1RST
OPAMPRST
DAC1RST
PWRRST
Res.
USBFSRST
CAN1RST
CRSRST
I2C3RST
I2C2RST
I2C1RST
Res.
UART4RST
USART3RST
USART2RST
Res.
SPI3RST
SPI2RST
Res.
Res.
Res.
Res.
LCDRST
Res.
Res.
Res.
TIM7RST
TIM6RST
Res.
Res.
TIM3RST
TIM2RST

0x30
RCC_
AHB2RSTR

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
LPTIM2RST
Res.
Res.
SWPMI1RST
I2C4RST
LPUART1RST

0x2C

Res.
Res.
Res.
Res.
Res.
Res.
Res.
DFSDM1RST
Res.
Res.
SAI1RST
Res.
Res.
Res.
TIM16RST
TIM15RST
Res.
USART1RST
Res.
SPI1RST
TIM1RST
SDMMC1RST
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
SYSCFGRST

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

RCC_
AHB1RSTR
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
TSCRST.
Res.
Res.
Res.
CRCRST.
Res.
Res.
Res.
FLASHRST.
Res.
Res.
Res.
Res.
Res.
Res.
DMA2RST
DMA1RST

0x28

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
TSCEN.
Res.
Res.
Res.
CRCEN
Res.
Res.
Res.
FLASHEN
Res.
Res.
Res.
Res.
Res.
Res.
DMA2EN
DMA1EN

Offset

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
RNGEN
Res.
AESEN
Res.
Res.
ADCEN

Reset and clock control (RCC)
RM0394

Table 32. RCC register map and reset values (continued)

0

0

0 0

0

0

Reset value

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

0x78
Reset value

RCC_
0x68 AHB1SMENR

RCC_
0x6C AHB2SMENR

RCC_
AHB3SMENR
0x70

RCC_
APB1SM
ENR1

Reset value
0

1 1 1 1

1
0

Reset value

1 1 1
SPI1EN
TIM1EN
SDMMC1EN
Res.
Res.
FWEN
Res.
Res.
Res.
Res.
Res.
Res.
SYSCFGEN

LPTIM1EN
OPAMPEN
DAC1EN
PWREN
Res.
USBFSEN
CAN1EN
CRSEN
I2C3EN
I2C2EN
I2C1EN
Res.
UART4EN
USART3EN
USART2EN
Res.
SP3EN
SPI2EN
Res.
Res.
WWDGEN
RTCAPBEN
LCDEN
Res.
Res.
Res.
TIM7EN
TIM6EN
Res.
Res.
TIM3EN
TIM2EN

Reset value
0 0 0 0

RCC_
APB1ENR2
0 0 0 0 0 0

TIM16EN
TIM15EN
Res.
USART1EN

SAI1EN
Res.
Res.

RCC_
APB1ENR1

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
LPTIM2EN
Res.
Res.
SWPMI1EN
I2C4EN
LPUART1EN

Reset value

0 0 0

Reset value

1

1 1 1

RM0394 Rev 4

0 0

0 0
0 0 0

0

1
1

1
1

Reset value

1 1

1

1
GPIOHSMEN
Res.
Res.
GPIOESMEN
GPIODSMEN
GPIOCSMEN
GPIOBSMEN
GPIOASMEN

0x60
RCC_
APB2ENR
Res.
Res.
Res.
Res.
Res.
Res.
Res.
DFSDM1EN
Res.

0x5C

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
TSCSMEN.
Res.
Res.
Res.
CRCSMEN
Res.
Res.
SRAM1SMEN
FLASHSMEN
Res.
Res.
Res.
Res.
Res.
Res.
DMA2SMEN
DMA1SMEN

0x58
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
QSPIEN
Res.
Res.
Res.
Res.
Res.
Res.
Res.

RCC_AHB3
ENR

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
RNGSMEN
Res.
AESSMEN
Res.
Res.
ADCFSSMEN
Res.
Res.
Res.
SRAM2SMEN

0x50
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Register

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
QSPISMEN
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Offset

LPTIM1SMEN
OPAMPSMEN
DAC1SMEN
PWRSMEN
Res.
USBFSSMEN
CAN1SMEN
CRSSMEN
I2C3SMEN
I2C2SMEN
I2C1SMEN
Res.
UART4SMEN
USART3SMEN
USART2SMEN
Res.
SP3SMEN
SPI2SMEN
Res.
Res.
WWDGSMEN
RTCAPBSMEN
LCDSMEN
Res.
Res.
Res.
TIM7SMEN
TIM6SMEN
Res.
Res.
TIM3SMEN
TIM2SMEN

RM0394
Reset and clock control (RCC)

Table 32. RCC register map and reset values (continued)

0

0 1 0
0 0

Reset value
0

0

1 1

1
1

1 1

0 0

0 0 0

0

1 1

1 1 1 1 1

1

1 1

245/1600

246

0x94

0x98

0x9C
RCC_BDCR

Reset value

RCC_CRRCR

RCC_CCIPR2

246/1600
0 0

Reset value

Reset value

RM0394 Rev 4
0 0

RCC_CSR

Reset value
0 0 0 0 0 0 0 0 0
RTC
SEL
[1:0]

MSIS
RANGE
[3:0]

0 1 1 0

HSI48CAL[8:0]

1

1 1 1

LSE
DRV
[1:0]

0

x x x x x x x x x

USART1SEL

USART2SEL

USART3SEL

Res.
Res.
Res.
Res.
Res.
Res.
Res.
DFSDM1SMEN
Res.
Res.
SAI1SMEN
Res.
Res.
Res.
TIM16SMEN
TIM15SMEN
Res.
USART1SMEN
Res.
SPI1SMEN
TIM1SMEN
SDMMC1SMEN
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
SYSCFGSMEN

Reset value

LSEBYP
LSERDY
LSEON

0 0 0 0 0 0 0 0 0 0 0 0 0 0
UART4SEL

Res.
Res.

1
LPUART1SEL

1 1

I2C1SEL

I2C2SEL

I2C3SEL

LPTIM1SEL

LPTIM2SEL

1

LSESYSDIS
LSECSSD
LSECSSON

0 0 0 0 0
SAI1SEL

Res.
Res.

CLK48SEL

1

Res.
Res.
Res.
LSIPREDIV
Res.
Res.
LSIRDY
LSION

Reset value
ADCSEL

Reset value

Res.
Res.
Res.
Res.
Res.
HSI48RDY
HSI48ON

0x90
RCC_CCIPR
DFSDM1SEL
SWPMI1SEL

RCC_
0x80 APB2SMENR

Res.
Res.
Res.
Res.
Res.
Res.
LSCOSEL
LSCOEN
Res.
Res.
Res.
Res.
Res.
Res.
Res.
BDRST
RTCEN
Res.
Res.
Res.
Res.
Res.

0x88

LPWRRSTF
WWDGRSTF
IWDGRSTF
SFTRSTF
BORRSTF
PINRSTF
OBLRSTF
FIREWALLRSTF
RMVF
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Register
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

RCC_
APB1SM
ENR2
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
LPTIM2SMEN
Res.
Res.
SWPMI1SMEN
I2C4SMEN
LPUART1SMEN

0x7C

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Offset

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.

Reset and clock control (RCC)
RM0394

Table 32. RCC register map and reset values (continued)

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

I2C4
SEL
[1:0]

0 0

RM0394

Clock recovery system (CRS)

7

Clock recovery system (CRS)

7.1

Introduction
The clock recovery system (CRS) is an advanced digital controller acting on the internal
fine-granularity trimmable RC oscillator HSI48. The CRS provides powerful means for
oscillator output frequency evaluation, based on comparison with a selectable
synchronization signal. It is capable of doing automatic adjustment of oscillator trimming
based on the measured frequency error value, while keeping the possibility of a manual
trimming.
The CRS is ideally suited to provide a precise clock to the USB peripheral. In such case, the
synchronization signal can be derived from the start-of-frame (SOF) packet signalization on
the USB bus, which is sent by a USB host at precise 1-ms intervals.
The synchronization signal can also be derived from the LSE oscillator output or it can be
generated by user software.

7.2

CRS main features
•

Selectable synchronization source with programmable prescaler and polarity:
–

External pin

–

LSE oscillator output

–

USB SOF packet reception

•

Possibility to generate synchronization pulses by software

•

Automatic oscillator trimming capability with no need of CPU action

•

Manual control option for faster start-up convergence

•

16-bit frequency error counter with automatic error value capture and reload

•

Programmable limit for automatic frequency error value evaluation and status reporting

•

Maskable interrupts/events:
–

Expected synchronization (ESYNC)

–

Synchronization OK (SYNCOK)

–

Synchronization warning (SYNCWARN)

–

Synchronization or trimming error (ERR)

RM0394 Rev 4

247/1600
257

Clock recovery system (CRS)

RM0394

7.3

CRS functional description

7.3.1

CRS block diagram
Figure 17. CRS block diagram
&56B6<1&
*3,2
6<1&65&

6:6<1&

26&B,1

6<1&GLYLGHU
«

/6(
26&B287

6<1&

86%B'3

)(/,0

86%
86%B'0

75,0

5&&

)(',5

5&0+]

)(&$3

ELWFRXQWHU

5(/2$'

+6,

7R86%
7R51*
06Y9

7.3.2

Synchronization input
The CRS synchronization (SYNC) source, selectable through the CRS_CFGR register, can
be the signal from the LSE clock or the USB SOF signal. For a better robustness of the
SYNC input, a simple digital filter (2 out of 3 majority votes, sampled by the HSI48 clock) is
implemented to filter out any glitches. This source signal also has a configurable polarity
and can then be divided by a programmable binary prescaler to obtain a synchronization
signal in a suitable frequency range (usually around 1 kHz).
For more information on the CRS synchronization source configuration, refer to
Section 7.6.2: CRS configuration register (CRS_CFGR).
It is also possible to generate a synchronization event by software, by setting the SWSYNC
bit in the CRS_CR register.

248/1600

RM0394 Rev 4

RM0394

7.3.3

Clock recovery system (CRS)

Frequency error measurement
The frequency error counter is a 16-bit down/up counter which is reloaded with the RELOAD
value on each SYNC event. It starts counting down till it reaches the zero value, where the
ESYNC (expected synchronization) event is generated. Then it starts counting up to the
OUTRANGE limit where it eventually stops (if no SYNC event is received) and generates a
SYNCMISS event. The OUTRANGE limit is defined as the frequency error limit (FELIM field
of the CRS_CFGR register) multiplied by 128.
When the SYNC event is detected, the actual value of the frequency error counter and its
counting direction are stored in the FECAP (frequency error capture) field and in the FEDIR
(frequency error direction) bit of the CRS_ISR register. When the SYNC event is detected
during the downcounting phase (before reaching the zero value), it means that the actual
frequency is lower than the target (and so, that the TRIM value should be incremented),
while when it is detected during the upcounting phase it means that the actual frequency is
higher (and that the TRIM value should be decremented).
Figure 18. CRS counter behavior
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RM0394 Rev 4

249/1600
257

Clock recovery system (CRS)

7.3.4

RM0394

Frequency error evaluation and automatic trimming
The measured frequency error is evaluated by comparing its value with a set of limits:
–

TOLERANCE LIMIT, given directly in the FELIM field of the CRS_CFGR register

–

WARNING LIMIT, defined as 3 * FELIM value

–

OUTRANGE (error limit), defined as 128 * FELIM value

The result of this comparison is used to generate the status indication and also to control the
automatic trimming which is enabled by setting the AUTOTRIMEN bit in the CRS_CR
register:
•

•

•

•

Note:

When the frequency error is below the tolerance limit, it means that the actual trimming
value in the TRIM field is the optimal one and that then, no trimming action is
necessary.
–

SYNCOK status indicated

–

TRIM value not changed in AUTOTRIM mode

When the frequency error is below the warning limit but above or equal to the tolerance
limit, it means that some trimming action is necessary but that adjustment by one
trimming step is enough to reach the optimal TRIM value.
–

SYNCOK status indicated

–

TRIM value adjusted by one trimming step in AUTOTRIM mode

When the frequency error is above or equal to the warning limit but below the error
limit, it means that a stronger trimming action is necessary, and there is a risk that the
optimal TRIM value will not be reached for the next period.
–

SYNCWARN status indicated

–

TRIM value adjusted by two trimming steps in AUTOTRIM mode

When the frequency error is above or equal to the error limit, it means that the
frequency is out of the trimming range. This can also happen when the SYNC input is
not clean or when some SYNC pulse is missing (for example when one USB SOF is
corrupted).
–

SYNCERR or SYNCMISS status indicated

–

TRIM value not changed in AUTOTRIM mode

If the actual value of the TRIM field is so close to its limits that the automatic trimming would
force it to overflow or underflow, then the TRIM value is set just to the limit and the
TRIMOVF status is indicated.
In AUTOTRIM mode (AUTOTRIMEN bit set in the CRS_CR register), the TRIM field of
CRS_CR is adjusted by hardware and is read-only.

7.3.5

CRS initialization and configuration
RELOAD value
The RELOAD value should be selected according to the ratio between the target frequency
and the frequency of the synchronization source after prescaling. It is then decreased by
one in order to reach the expected synchronization on the zero value. The formula is the
following:
RELOAD = (fTARGET / fSYNC) - 1
The reset value of the RELOAD field corresponds to a target frequency of 48 MHz and a
synchronization signal frequency of 1 kHz (SOF signal from USB).

250/1600

RM0394 Rev 4

RM0394

Clock recovery system (CRS)

FELIM value
The selection of the FELIM value is closely coupled with the HSI48 oscillator characteristics
and its typical trimming step size. The optimal value corresponds to half of the trimming step
size, expressed as a number of HSI48 oscillator clock ticks. The following formula can be
used:
FELIM = (fTARGET / fSYNC) * STEP[%] / 100% / 2
The result should be always rounded up to the nearest integer value in order to obtain the
best trimming response. If frequent trimming actions are not wanted in the application, the
trimming hysteresis can be increased by increasing slightly the FELIM value.
The reset value of the FELIM field corresponds to (fTARGET / fSYNC) = 48000 and to a typical
trimming step size of 0.14%.
Caution:

There is no hardware protection from a wrong configuration of the RELOAD and FELIM
fields which can lead to an erratic trimming response. The expected operational mode
requires proper setup of the RELOAD value (according to the synchronization source
frequency), which is also greater than 128 * FELIM value (OUTRANGE limit).

7.4

CRS low-power modes
Table 33. Effect of low-power modes on CRS
Mode
Sleep

Description
No effect.
CRS interrupts cause the device to exit the Sleep mode.

Stop

CRS registers are frozen.
The CRS stops operating until the Stop or Standby mode is exited and the HSI48 oscillator
Standby restarted.

7.5

CRS interrupts
Table 34. Interrupt control bits
Interrupt event

Event flag

Enable
control bit

Clear
flag bit

Expected synchronization

ESYNCF

ESYNCIE

ESYNCC

Synchronization OK

SYNCOKF

SYNCOKIE

SYNCOKC

Synchronization warning

SYNCWARNF

SYNCWARNIE

SYNCWARNC

Synchronization or trimming error
(TRIMOVF, SYNCMISS, SYNCERR)

ERRF

ERRIE

ERRC

RM0394 Rev 4

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Clock recovery system (CRS)

7.6

RM0394

CRS registers
Refer to Section 1.2 on page 60 of the reference manual for a list of abbreviations used in
register descriptions.
The peripheral registers can be accessed by words (32-bit).

7.6.1

CRS control register (CRS_CR)
Address offset: 0x00
Reset value: 0x0000 2000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

5

4

3

2

1

Res.

ESYNC
IE

Res.

Res.

TRIM[5:0]
rw

rw

rw

rw

rw

rw

7

6

SW
SYNC

AUTO
TRIMEN

CEN

rt_w1

rw

rw

rw

SYNC
ERRIE
WARNIE
rw

0
SYNC
OKIE

rw

rw

Bits 31:14 Reserved, must be kept at reset value.
Bits 13:8 TRIM[5:0]: HSI48 oscillator smooth trimming
These bits provide a user-programmable trimming value to the HSI48 oscillator. They can be
programmed to adjust to variations in voltage and temperature that influence the frequency
of the HSI48 oscillator.
The default value is 32, which corresponds to the middle of the trimming interval. The
trimming step is specified in the product datasheet. A higher TRIM value corresponds to a
higher output frequency.
When the AUTOTRIMEN bit is set, this field is controlled by hardware and is read-only.
Bit 7 SWSYNC: Generate software SYNC event
This bit is set by software in order to generate a software SYNC event. It is automatically
cleared by hardware.
0: No action
1: A software SYNC event is generated.
Bit 6 AUTOTRIMEN: Automatic trimming enable
This bit enables the automatic hardware adjustment of TRIM bits according to the measured
frequency error between two SYNC events. If this bit is set, the TRIM bits are read-only. The
TRIM value can be adjusted by hardware by one or two steps at a time, depending on the
measured frequency error value. Refer to Section 7.3.4: Frequency error evaluation and
automatic trimming for more details.
0: Automatic trimming disabled, TRIM bits can be adjusted by the user.
1: Automatic trimming enabled, TRIM bits are read-only and under hardware control.
Bit 5 CEN: Frequency error counter enable
This bit enables the oscillator clock for the frequency error counter.
0: Frequency error counter disabled
1: Frequency error counter enabled
When this bit is set, the CRS_CFGR register is write-protected and cannot be modified.
Bit 4 Reserved, must be kept at reset value.

252/1600

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RM0394

Clock recovery system (CRS)

Bit 3 ESYNCIE: Expected SYNC interrupt enable
0: Expected SYNC (ESYNCF) interrupt disabled
1: Expected SYNC (ESYNCF) interrupt enabled
Bit 2 ERRIE: Synchronization or trimming error interrupt enable
0: Synchronization or trimming error (ERRF) interrupt disabled
1: Synchronization or trimming error (ERRF) interrupt enabled
Bit 1 SYNCWARNIE: SYNC warning interrupt enable
0: SYNC warning (SYNCWARNF) interrupt disabled
1: SYNC warning (SYNCWARNF) interrupt enabled
Bit 0 SYNCOKIE: SYNC event OK interrupt enable
0: SYNC event OK (SYNCOKF) interrupt disabled
1: SYNC event OK (SYNCOKF) interrupt enabled

7.6.2

CRS configuration register (CRS_CFGR)
This register can be written only when the frequency error counter is disabled (CEN bit is
cleared in CRS_CR). When the counter is enabled, this register is write-protected.
Address offset: 0x04
Reset value: 0x2022 BB7F

31

30

SYNCPOL

Res.

rw

29

28

SYNCSRC[1:0]

27

26

Res.

25

24

23

22

21

SYNCDIV[2:0]

20

19

18

17

16

FELIM[7:0]

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

RELOAD[15:0]
rw

rw

Bit 31 SYNCPOL: SYNC polarity selection
This bit is set and cleared by software to select the input polarity for the SYNC signal source.
0: SYNC active on rising edge (default)
1: SYNC active on falling edge
Bit 30 Reserved, must be kept at reset value.
Bits 29:28 SYNCSRC[1:0]: SYNC signal source selection
These bits are set and cleared by software to select the SYNC signal source.
00: GPIO selected as SYNC signal source
01: LSE selected as SYNC signal source
10: USB SOF selected as SYNC signal source (default). Supported on STM32L4x2xx and
STM32L4x3xx devices only.
11: Reserved
Note: When using USB LPM (Link Power Management) and the device is in Sleep mode, the
periodic USB SOF will not be generated by the host. No SYNC signal will therefore be
provided to the CRS to calibrate the HSI48 oscillator on the run. To guarantee the
required clock precision after waking up from Sleep mode, the LSE or reference clock
on the GPIOs should be used as SYNC signal.
Bit 27 Reserved, must be kept at reset value.

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Clock recovery system (CRS)

RM0394

Bits 26:24 SYNCDIV[2:0]: SYNC divider
These bits are set and cleared by software to control the division factor of the SYNC signal.
000: SYNC not divided (default)
001: SYNC divided by 2
010: SYNC divided by 4
011: SYNC divided by 8
100: SYNC divided by 16
101: SYNC divided by 32
110: SYNC divided by 64
111: SYNC divided by 128
Bits 23:16 FELIM[7:0]: Frequency error limit
FELIM contains the value to be used to evaluate the captured frequency error value latched
in the FECAP[15:0] bits of the CRS_ISR register. Refer to Section 7.3.4: Frequency error
evaluation and automatic trimming for more details about FECAP evaluation.
Bits 15:0 RELOAD[15:0]: Counter reload value
RELOAD is the value to be loaded in the frequency error counter with each SYNC event.
Refer to Section 7.3.3: Frequency error measurement for more details about counter
behavior.

7.6.3

CRS interrupt and status register (CRS_ISR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

r

r

FECAP[15:0]
r

r

r

r

r

15

14

13

12

11

10

Res.

TRIM
OVF
r

r

r

FEDIR

Res.

r

Res.

Res.

r

r

r

r

r

r

r

r

r

9

8

7

6

5

4

3

2

1

0

SYNC
MISS

SYNC
ERR

ESYNCF

ERRF

SYNC
WARNF

SYNC
OKF

r

r

r

r

Res.

Res.

Res.

Res.

Bits 31:16 FECAP[15:0]: Frequency error capture
FECAP is the frequency error counter value latched in the time of the last SYNC event.
Refer to Section 7.3.4: Frequency error evaluation and automatic trimming for more details
about FECAP usage.
Bit 15 FEDIR: Frequency error direction
FEDIR is the counting direction of the frequency error counter latched in the time of the last
SYNC event. It shows whether the actual frequency is below or above the target.
0: Upcounting direction, the actual frequency is above the target.
1: Downcounting direction, the actual frequency is below the target.
Bits 14:11 Reserved, must be kept at reset value.
Bit 10 TRIMOVF: Trimming overflow or underflow
This flag is set by hardware when the automatic trimming tries to over- or under-flow the
TRIM value. An interrupt is generated if the ERRIE bit is set in the CRS_CR register. It is
cleared by software by setting the ERRC bit in the CRS_ICR register.
0: No trimming error signalized
1: Trimming error signalized

254/1600

RM0394 Rev 4

RM0394

Clock recovery system (CRS)

Bit 9 SYNCMISS: SYNC missed
This flag is set by hardware when the frequency error counter reached value FELIM * 128
and no SYNC was detected, meaning either that a SYNC pulse was missed or that the
frequency error is too big (internal frequency too high) to be compensated by adjusting the
TRIM value, and that some other action should be taken. At this point, the frequency error
counter is stopped (waiting for a next SYNC) and an interrupt is generated if the ERRIE bit is
set in the CRS_CR register. It is cleared by software by setting the ERRC bit in the
CRS_ICR register.
0: No SYNC missed error signalized
1: SYNC missed error signalized
Bit 8 SYNCERR: SYNC error
This flag is set by hardware when the SYNC pulse arrives before the ESYNC event and the
measured frequency error is greater than or equal to FELIM * 128. This means that the
frequency error is too big (internal frequency too low) to be compensated by adjusting the
TRIM value, and that some other action should be taken. An interrupt is generated if the
ERRIE bit is set in the CRS_CR register. It is cleared by software by setting the ERRC bit in
the CRS_ICR register.
0: No SYNC error signalized
1: SYNC error signalized
Bits 7:4 Reserved, must be kept at reset value.
Bit 3 ESYNCF: Expected SYNC flag
This flag is set by hardware when the frequency error counter reached a zero value. An
interrupt is generated if the ESYNCIE bit is set in the CRS_CR register. It is cleared by
software by setting the ESYNCC bit in the CRS_ICR register.
0: No expected SYNC signalized
1: Expected SYNC signalized
Bit 2 ERRF: Error flag
This flag is set by hardware in case of any synchronization or trimming error. It is the logical
OR of the TRIMOVF, SYNCMISS and SYNCERR bits. An interrupt is generated if the ERRIE
bit is set in the CRS_CR register. It is cleared by software in reaction to setting the ERRC bit
in the CRS_ICR register, which clears the TRIMOVF, SYNCMISS and SYNCERR bits.
0: No synchronization or trimming error signalized
1: Synchronization or trimming error signalized
Bit 1 SYNCWARNF: SYNC warning flag
This flag is set by hardware when the measured frequency error is greater than or equal to
FELIM * 3, but smaller than FELIM * 128. This means that to compensate the frequency
error, the TRIM value must be adjusted by two steps or more. An interrupt is generated if the
SYNCWARNIE bit is set in the CRS_CR register. It is cleared by software by setting the
SYNCWARNC bit in the CRS_ICR register.
0: No SYNC warning signalized
1: SYNC warning signalized
Bit 0 SYNCOKF: SYNC event OK flag
This flag is set by hardware when the measured frequency error is smaller than FELIM * 3.
This means that either no adjustment of the TRIM value is needed or that an adjustment by
one trimming step is enough to compensate the frequency error. An interrupt is generated if
the SYNCOKIE bit is set in the CRS_CR register. It is cleared by software by setting the
SYNCOKC bit in the CRS_ICR register.
0: No SYNC event OK signalized
1: SYNC event OK signalized

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257

Clock recovery system (CRS)

7.6.4

RM0394

CRS interrupt flag clear register (CRS_ICR)
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.

ESYNCC

ERRC

SYNC
WARNC

SYNC
OKC

rw

rw

rw

rw

Bits 31:4 Reserved, must be kept at reset value.
Bit 3 ESYNCC: Expected SYNC clear flag
Writing 1 to this bit clears the ESYNCF flag in the CRS_ISR register.
Bit 2 ERRC: Error clear flag
Writing 1 to this bit clears TRIMOVF, SYNCMISS and SYNCERR bits and consequently also
the ERRF flag in the CRS_ISR register.
Bit 1 SYNCWARNC: SYNC warning clear flag
Writing 1 to this bit clears the SYNCWARNF flag in the CRS_ISR register.
Bit 0 SYNCOKC: SYNC event OK clear flag
Writing 1 to this bit clears the SYNCOKF flag in the CRS_ISR register.

256/1600

RM0394 Rev 4

RM0394

7.6.5

Clock recovery system (CRS)

CRS register map

SWSYNC

CEN

Res.

ESYNCIE

ERRIE

SYNCWARNIE

SYNCOKIE

0

0

0

0

0

0

0

0

0

0

0

CRS_ICR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

0

Reset value

SYNCOKF

0

0

0

0

0
SYNCOKC

0

ERRF

0

1

SYNCWARNF

0

1

ERRC

0

1

SYNCWARNC

0

1
ESYNCF

0

1

ESYNCC

0

1

Res.

0

1

Res.

0

0

Res.

0

1
SYNCERR

0

1

Res.

0

0

SYNCMISS

0

1

Res.

0

Res.

1

Res.

1

Res.

0

Res.

FECAP[15:0]

1

Res.

0

Res.

1

TRIMOVF

0

Reset value

0x0C

0

Res.

0

Res.

0

Res.

1

Res.

0

Res.

0

Res.

0

Res.

CRS_ISR

0

0

RELOAD[15:0]

Res.

0

0

FELIM[7:0]

Res.

0

0

FEDIR

1

SYNC
DIV
[2:0]

Res.

0

Res.

Reset value

SYNC
SRC
[1:0]

Res.

0x08

CRS_CFGR

Res.

0x04

1
SYNCPOL

Reset value

TRIM[5:0]

AUTOTRIMEN

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CRS_CR

Res.

0x00

Res.

Offset 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 35. CRS register map and reset values

0

0

0

0

Refer to Section 2.2.2 on page 67 for the register boundary addresses.

RM0394 Rev 4

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257

General-purpose I/Os (GPIO)

RM0394

8

General-purpose I/Os (GPIO)

8.1

Introduction
Each general-purpose I/O port has four 32-bit configuration registers (GPIOx_MODER,
GPIOx_OTYPER, GPIOx_OSPEEDR and GPIOx_PUPDR), two 32-bit data registers
(GPIOx_IDR and GPIOx_ODR) and a 32-bit set/reset register (GPIOx_BSRR). In addition
all GPIOs have a 32-bit locking register (GPIOx_LCKR) and two 32-bit alternate function
selection registers (GPIOx_AFRH and GPIOx_AFRL).

8.2

8.3

GPIO main features
•

Output states: push-pull or open drain + pull-up/down

•

Output data from output data register (GPIOx_ODR) or peripheral (alternate function
output)

•

Speed selection for each I/O

•

Input states: floating, pull-up/down, analog

•

Input data to input data register (GPIOx_IDR) or peripheral (alternate function input)

•

Bit set and reset register (GPIOx_ BSRR) for bitwise write access to GPIOx_ODR

•

Locking mechanism (GPIOx_LCKR) provided to freeze the I/O port configurations

•

Analog function

•

Alternate function selection registers

•

Fast toggle capable of changing every two clock cycles

•

Highly flexible pin multiplexing allows the use of I/O pins as GPIOs or as one of several
peripheral functions

GPIO functional description
Subject to the specific hardware characteristics of each I/O port listed in the datasheet, each
port bit of the general-purpose I/O (GPIO) ports can be individually configured by software in
several modes:
•

Input floating

•

Input pull-up

•

Input-pull-down

•

Analog

•

Output open-drain with pull-up or pull-down capability

•

Output push-pull with pull-up or pull-down capability

•

Alternate function push-pull with pull-up or pull-down capability

•

Alternate function open-drain with pull-up or pull-down capability

Each I/O port bit is freely programmable, however the I/O port registers have to be
accessed as 32-bit words, half-words or bytes. The purpose of the GPIOx_BSRR and
GPIOx_BRR registers is to allow atomic read/modify accesses to any of the GPIOx_ODR
registers. In this way, there is no risk of an IRQ occurring between the read and the modify
access.

258/1600

RM0394 Rev 4

RM0394

General-purpose I/Os (GPIO)
Figure 19 and Figure 20 show the basic structures of a standard and a 5-Volt tolerant I/O
port bit, respectively. Table 36 gives the possible port bit configurations.
Figure 19. Basic structure of an I/O port bit
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1. VDD_FT is a potential specific to five-volt tolerant I/Os and different from VDD.

RM0394 Rev 4

259/1600
275

General-purpose I/Os (GPIO)

RM0394
Table 36. Port bit configuration table(1)

MODE(i)
[1:0]

01

10

00

11

OTYPER(i)

OSPEED(i)
[1:0]

PUPD(i)
[1:0]

I/O configuration

0

0

0

GP output

PP

0

0

1

GP output

PP + PU

0

1

0

GP output

PP + PD

1

1

Reserved

0

0

GP output

OD

1

0

1

GP output

OD + PU

1

1

0

GP output

OD + PD

1

1

1

Reserved (GP output OD)

0

0

0

AF

PP

0

0

1

AF

PP + PU

0

1

0

AF

PP + PD

1

1

Reserved

0

0

AF

OD

1

0

1

AF

OD + PU

1

1

0

AF

OD + PD

1

1

1

Reserved

0

SPEED
[1:0]

1

0

SPEED
[1:0]

1

x

x

x

0

0

Input

Floating

x

x

x

0

1

Input

PU

x

x

x

1

0

Input

PD

x

x

x

1

1

Reserved (input floating)

x

x

x

0

0

Input/output

x

x

x

0

1

x

x

x

1

0

x

x

x

1

1

Analog

Reserved

1. GP = general-purpose, PP = push-pull, PU = pull-up, PD = pull-down, OD = open-drain, AF = alternate
function.

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RM0394

8.3.1

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 analog mode.
The debug pins are in AF pull-up/pull-down after reset:
•

PA15: JTDI in pull-up

•

PA14: JTCK/SWCLK in pull-down

•

PA13: JTMS/SWDAT in pull-up

•

PB4: NJTRST in pull-up

•

PB3: JTDO in floating state no pull-up/pull-down

PH3/BOOT0 is in input mode during the reset until at least the end of the option byte loading
phase. See Section 8.3.15: Using PH3 as GPIO.
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.

8.3.2

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 (except PH3) 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.

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General-purpose I/Os (GPIO)
–
•

RM0394

Configure the desired I/O as an alternate function in the GPIOx_MODER register.

Additional functions:
–

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.

8.3.3

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.

8.3.4

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 8.4.5: GPIO port input data register (GPIOx_IDR) (x = A to E and H) and
Section 8.4.6: GPIO port output data register (GPIOx_ODR) (x = A to E and H) for the
register descriptions.

8.3.5

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.

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RM0394 Rev 4

RM0394

8.3.6

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 8.4.8: GPIO port configuration lock register
(GPIOx_LCKR) (x = A to E and H)) can only be performed using a word (32-bit long)
access to the GPIOx_LCKR register due to the fact that GPIOx_LCKR bit 16 has to be set
at the same time as the [15:0] bits.
For more details refer to LCKR register description in Section 8.4.8: GPIO port configuration
lock register (GPIOx_LCKR) (x = A to E and H).

8.3.7

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.
No alternate function is mapped on PH3.

8.3.8

External interrupt/wakeup lines
All ports have external interrupt capability. To use external interrupt lines, the port can be
configured in input, output or alternate function mode (the port must not be configured in
analog mode). Refer to Section 13: Extended interrupts and events controller (EXTI) and
toSection 13.3.2: Wakeup event management.

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General-purpose I/Os (GPIO)

8.3.9

RM0394

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 21 shows the input configuration of the I/O port bit.

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Figure 21. Input floating/pull up/pull down configurations

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8.3.10

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 22 shows the output configuration of the I/O port bit.

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RM0394 Rev 4

RM0394

General-purpose I/Os (GPIO)

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8.3.11

Alternate function configuration
When the I/O port is programmed as alternate function:
The output buffer can be configured in open-drain or push-pull mode

•

The output buffer is driven by the signals coming from the peripheral (transmitter
enable and data)

•

The Schmitt trigger input is activated

•

The weak pull-up and pull-down resistors are activated or not depending on the value
in the GPIOx_PUPDR register

•

The data present on the I/O pin are sampled into the input data register every AHB
clock cycle

•

A read access to the input data register gets the I/O state

The alternate function configuration described above is not applied when the selected
alternate function is an LCD function or a SWPMI_IO. In this case, the I/O, programmed as
an alternate function output, is configured as described in the analog configuration.
Figure 23 shows the Alternate function configuration of the I/O port bit.
Figure 23. Alternate function configuration
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RM0394 Rev 4

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General-purpose I/Os (GPIO)

8.3.12

RM0394

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 24 shows the high-impedance, analog-input configuration of the I/O port bits.
Figure 24. High impedance-analog configuration

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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.

8.3.14

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 36.3: RTC functional description.

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RM0394

General-purpose I/Os (GPIO)

8.3.15

Using PH3 as GPIO
PH3 may be used as boot pin (BOOT0) or as a GPIO. Depending on the nSWBOOT0 bit in
the user option byte, it switches from the input mode to the analog input mode:

8.4

•

After the option byte loading phase if nSWBOOT0 = 1.

•

After reset if nSWBOOT0 = 0.

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 37.
The peripheral registers can be written in word, half word or byte mode.

8.4.1

GPIO port mode register (GPIOx_MODER) (x =A to E and H)
Address offset:0x00
Reset value:

31

30

•

0xABFF FFFF (for port A)

•

0xFFFF FEBF (for port B)

•

0xFFFF FFFF for ports C..E

•

0x0000 000F (for port H)
29

MODE15[1:0]

28

MODE14[1:0]

27

26

MODE13[1:0]

25

24

MODE12[1:0]

23

22

MODE11[1:0]

21

20

MODE10[1:0]

19

18

17

16

MODE9[1:0]

MODE8[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

MODE7[1:0]

MODE6[1:0]

MODE5[1:0]

MODE4[1:0]

MODE3[1:0]

MODE2[1:0]

MODE1[1:0]

MODE0[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MODE[15:0][1:0]: Port x configuration I/O pin y (y = 15 to 0)
These bits are written by software to configure the I/O mode.
00: Input mode
01: General purpose output mode
10: Alternate function mode
11: Analog mode (reset state)

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8.4.2

RM0394

GPIO port output type register (GPIOx_OTYPER) (x = A to E and H)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OT15

OT14

OT13

OT12

OT11

OT10

OT9

OT8

OT7

OT6

OT5

OT4

OT3

OT2

OT1

OT0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 OT[15:0]: Port x configuration I/O pin y (y = 15 to 0)
These bits are written by software to configure the I/O output type.
0: Output push-pull (reset state)
1: Output open-drain

8.4.3

GPIO port output speed register (GPIOx_OSPEEDR)
(x = A to E and H)
Address offset: 0x08
Reset value: 0x0C00 0000 (for port A)
Reset value: 0x0000 0000 (for the other ports)

31

30

OSPEED15
[1:0]

29

28

27

26

25

24

23

22

21

20

19

18

17

16

OSPEED14
[1:0]

OSPEED13
[1:0]

OSPEED12
[1:0]

OSPEED11
[1:0]

OSPEED10
[1:0]

OSPEED9
[1:0]

OSPEED8
[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

OSPEED7
[1:0]

OSPEED6
[1:0]

OSPEED5
[1:0]

OSPEED4
[1:0]

OSPEED3
[1:0]

OSPEED2
[1:0]

OSPEED1
[1:0]

OSPEED0
[1:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 OSPEED[15:0][1:0]: Port x configuration I/O pin y (y = 15 to 0)
These bits are written by software to configure the I/O output speed.
00: Low speed
01: Medium speed
10: High speed
11: Very high speed
Note: Refer to the device datasheet for the frequency specifications and the power supply
and load conditions for each speed..

8.4.4

GPIO port pull-up/pull-down register (GPIOx_PUPDR)
(x = A to E and H)
Address offset: 0x0C
Reset value: 0x6400 0000 (for port A)

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RM0394

General-purpose I/Os (GPIO)
Reset value: 0x0000 0100 (for port B)
Reset value: 0x0000 0000 (for other ports)

31

30

29

PUPD15[1:0]

28

PUPD14[1:0]

27

26

25

PUPD13[1:0]

24

23

22

21

20

19

18

17

16

PUPD12[1:0]

PUPD11[1:0]

PUPD10[1:0]

PUPD9[1:0]

PUPD8[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

PUPD7[1:0]

PUPD6[1:0]

PUPD5[1:0]

PUPD4[1:0]

PUPD3[1:0]

PUPD2[1:0]

PUPD1[1:0]

PUPD0[1:0]

rw

rw

rw

rw

rw

rw

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rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 PUPD[15:0][1:0]: Port x configuration I/O pin y (y = 15 to 0)
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

8.4.5

GPIO port input data register (GPIOx_IDR) (x = A to E and H)
Address offset: 0x10
Reset value: 0x0000 XXXX

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

ID15

ID14

ID13

ID12

ID11

ID10

ID9

ID8

ID7

ID6

ID5

ID4

ID3

ID2

ID1

ID0

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 ID[15:0]: Port x input data I/O pin y (y = 15 to 0)
These bits are read-only. They contain the input value of the corresponding I/O port.

8.4.6

GPIO port output data register (GPIOx_ODR) (x = A to E and H)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OD15

OD14

OD13

OD12

OD11

OD10

OD9

OD8

OD7

OD6

OD5

OD4

OD3

OD2

OD1

OD0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

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General-purpose I/Os (GPIO)

RM0394

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 OD[15:0]: Port output data I/O pin y (y = 15 to 0)
These bits can be read and written by software.
Note: For atomic bit set/reset, the OD bits can be individually set and/or reset by writing to the
GPIOx_BSRR or GPIOx_BRR registers (x = A..F).

8.4.7

GPIO port bit set/reset register (GPIOx_BSRR) (x = A to E and 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 BR[15:0]: Port x reset I/O pin y (y = 15 to 0)
These bits are write-only. A read to these bits returns the value 0x0000.
0: No action on the corresponding ODx bit
1: Resets the corresponding ODx bit
Note: If both BSx and BRx are set, BSx has priority.
Bits 15:0 BS[15:0]: Port x set I/O pin y (y = 15 to 0)
These bits are write-only. A read to these bits returns the value 0x0000.
0: No action on the corresponding ODx bit
1: Sets the corresponding ODx bit

8.4.8

GPIO port configuration lock register (GPIOx_LCKR)
(x = A to E and H)
This register is used to lock the configuration of the port bits when a correct write sequence
is applied to bit 16 (LCKK). The value of bits [15:0] is used to lock the configuration of the
GPIO. During the write sequence, the value of LCKR[15:0] must not change. When the
LOCK sequence has been applied on a port bit, the value of this port bit can no longer be
modified until the next 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
rw

270/1600

RM0394 Rev 4

RM0394

General-purpose I/Os (GPIO)

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

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 LCK[15:0]: Port x lock I/O pin y (y = 15 to 0)
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

8.4.9

GPIO alternate function low register (GPIOx_AFRL)
(x = A to E and H)
Address offset: 0x20
Reset value: 0x0000 0000

31

30

29

28

27

AFSEL7[3:0]

26

25

24

23

AFSEL6[3:0]

22

21

20

19

AFSEL5[3:0]

18

17

16

AFSEL4[3:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

AFSEL3[3:0]
rw

rw

rw

AFSEL2[3:0]
rw

rw

AFSEL1[3:0]

RM0394 Rev 4

rw

rw

AFSEL0[3:0]
rw

rw

rw

271/1600
275

General-purpose I/Os (GPIO)

RM0394

Bits 31:0 AFSEL[7:0][3:0]: Alternate function selection for port x I/O pin y (y = 7 to 0)
These bits are written by software to configure alternate function I/Os.
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

8.4.10

GPIO alternate function high register (GPIOx_AFRH)
(x = A to E and H)
Address offset: 0x24
Reset value: 0x0000 0000

31

30

29

28

27

AFSEL15[3:0]

26

25

24

23

AFSEL14[3:0]

22

21

20

19

AFSEL13[3:0]

18

17

16

AFSEL12[3:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

AFSEL11[3:0]
rw

rw

rw

AFSEL10[3:0]
rw

rw

AFSEL9[3:0]
rw

rw

AFSEL8[3:0]
rw

Bits 31:0 AFSEL[15:8][3:0]: Alternate function selection for port x I/O pin y (y = 15 to 8)
These bits are written by software to configure alternate function I/Os.
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

272/1600

RM0394 Rev 4

rw

rw

RM0394

General-purpose I/Os (GPIO)

8.4.11

GPIO port bit reset register (GPIOx_BRR) (x = A to E and 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, must be kept at reset value.
Bits 15:0 BR[15:0]: Port x reset IO pin y (y = 15 to 0)
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

RM0394 Rev 4

273/1600
275

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

0x10

GPIOx_IDR
(where x = A..E,H)

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

ID15

ID14

ID13

ID12

ID11

ID10

ID9

ID8

274/1600

ID7

ID6

ID5

ID4

ID3

ID2

ID1

ID0

0

0
0
0

0

0
0
0

0
0

0

0
0
0

0
0

0
0

0

0

RM0394 Rev 4

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

GPIOx_OTYPER
(where x = A..E,H)

Reset value

0
0

0
0

0
0

0

0

Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
0
0

0
0

0
0

0
0

0

0
0
0

0
0

0
0

0
0

0

0

0
0

0
0

0
0

0
0

0

0

0
0

0
0

0
0

0
0

1

0

0
0

0
0

0
0

0
0

0

0

0
0

0
0

0
0

0
0

0

0

OT1
OT0

MODE0[1:0]

MODE0[1:0]

1

0
0
0
0

0
0

0
0

0
0

0

0

OSPEED0[1:0]

MODE1[1:0]

1

OSPEED0[1:0]

MODE1[1:0]

1

PUPD0[1:0]

OT2

1

PUPD0[1:0]

OT3

1

OSPEED1[1:0]

MODE2[1:0]

0

OSPEED1[1:0]

MODE2[1:0]

1

PUPD1[1:0]

OT4

1

PUPD1[1:0]

OT5

1

OSPEED2[1:0]

MODE3[1:0]

0

OSPEED2[1:0]

MODE3[1:0]

1

PUPD2[1:0]

OT6

1

PUPD2[1:0]

OT7

1

OSPEED3[1:0]

MODE4[1:0]

1

OSPEED3[1:0]

MODE4[1:0]

1

PUPD3[1:0]

OT8

1

PUPD3[1:0]

OT9

1

OSPEED4[1:0]

1

OSPEED4[1:0]

MODE5[1:0]

1

PUPD4[1:0]

MODE5[1:0]

1

PUPD4[1:0]

OT11
OT10

1

OSPEED5[1:0]

MODE6[1:0]

1

OSPEED5[1:0]

MODE6[1:0]

1

PUPD5[1:0]

OT12

1

PUPD5[1:0]

OT13

1

OSPEED6[1:0]

1

OSPEED6[1:0]

MODE7[1:0]

MODE8[1:0]

MODE9[1:0]

MODE10[1:0]

MODE11[1:0]

MODE12[1:0]

MODE13[1:0]

MODE14[1:0]

1

PUPD6[1:0]

MODE7[1:0]

MODE8[1:0]

MODE9[1:0]

MODE10[1:0]

MODE11[1:0]

MODE12[1:0]

MODE13[1:0]

MODE14[1:0]

1

PUPD6[1:0]

OT14

OSPEED7[1:0]

1

OT15

OSPEED7[1:0]

1

Res.

1

PUPD7[1:0]

OSPEED8[1:0]

OSPEED9[1:0]

OSPEED10[1:0]

OSPEED11[1:0]

OSPEED12[1:0]

OSPEED13[1:0]

OSPEED14[1:0]

MODE15[1:0]

1

PUPD7[1:0]

OSPEED8[1:0]

0

PUPD8[1:0]

0

PUPD8[1:0]

OSPEED9[1:0]

0

PUPD9[1:0]

0

PUPD9[1:0]

OSPEED10[1:0]

0
PUPD10[1:0]

0

PUPD10[1:0]

0
0

1

1

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

PUPD0[1:0]

0
0
0
1

1

PUPD1[1:0]

0
OSPEED11[1:0]

0
PUPD11[1:0]

1

PUPD11[1:0]

0
0
1

1

PUPD2[1:0]

0
OSPEED12[1:0]

0
PUPD12[1:0]

OSPEED13[1:0]

0

PUPD12[1:0]

PUPD13[1:0]

0

PUPD13[1:0]

0
0
0
0
1

1

PUPD3[1:0]

0
1
0
0
1

1

PUPD4[1:0]

Reset value
1
0
1
1

1

PUPD5[1:0]

GPIOB_PUPDR
0
1
1

1

PUPD6[1:0]

0x0C
0
0
0
1

1

PUPD7[1:0]

Reset value
0
1
1

PUPD8[1:0]

GPIOA_PUPDR
0
1
0

PUPD9[1:0]

0x0C
0
1
1

PUPD10[1:0]

Reset value
1
0

PUPD11[1:0]

GPIOx_OSPEEDR
(where x = B..E,H)
0
1

PUPD12[1:0]

Reset value
0

PUPD13[1:0]

GPIOA_OSPEEDR

OSPEED14[1:0]

GPIOx_MODER
(where x = C..E,H)
1

PUPD14[1:0]

Reset value

PUPD14[1:0]

0x08
GPIOB_MODER

MODE15[1:0]

0x00
1

PUPD14[1:0]

0x08
1

Res.

0x04
Reset value

Res.

Reset value

OSPEED15[1:0]

0x00
MODE0[1:0]

MODE1[1:0]

MODE2[1:0]

MODE3[1:0]

MODE4[1:0]

MODE5[1:0]

MODE6[1:0]

MODE7[1:0]

MODE8[1:0]

MODE9[1:0]

MODE10[1:0]

MODE11[1:0]

MODE12[1:0]

MODE13[1:0]

MODE14[1:0]

MODE15[1:0]

GPIOA_MODER

OSPEED15[1:0]

0x00

PUPD15[1:0]

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Offset Register name

PUPD15[1:0]

8.4.12

PUPD15[1:0]

GPIOx_PUPDR
(where x = C..E and
H)

Res.

Reset value

0x0C

Res.

General-purpose I/Os (GPIO)
RM0394

GPIO register map
The following table gives the GPIO register map and reset values.
Table 37. GPIO register map and reset values

1
1

1
1

1

1

0

0

0

0

RM0394

General-purpose I/Os (GPIO)

LCK3

LCK2

LCK1

LCK0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0x28

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

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Res.

OD0

LCK4

0

OD1

LCK5

0

BS0

LCK6

0

OD2

LCK7

0

0

BS1

LCK8

0

OD3

LCK9

0

0

BS2

LCK10

0

OD4

LCK11

0

0

BS3

LCK12

Reset value
GPIOx_BRR
(where x = A..E,H)

OD5

LCK13

0x24

GPIOx_AFRH
(where x = A..E,H)

0

BS4

LCK14

0x20

OD6

LCK15

0

0

BS5

LCKK

0

OD7

Res.

0

0

BS6

Res.

0

OD8

Res.

0

0

BS7

Res.

0

OD9

Res.

0

0

BS8

Res.

0

0

BS9

Res.

0

OD11

Res.

0

OD10

Res.

0

0

BS10

Res.

0

OD12

Res.

0

0

BS11

Res.

0

OD13

Res.

0

0

BS12

Res.

0

OD14

Res.

0

GPIOx_AFRL
(where x = A..E,H)

0

BS13

0x1C

0

BS14

0

OD15

BR1

0

0

BS15

BR2

0

Res.

BR3

0

0
BR0

BR4

0

Res.

BR5

0

Res.

BR6

0

Res.

BR7

0

Res.

BR8

0

Res.

BR9

0

Res.

BR10

0

Res.

BR11

0

Res.

BR12

0

Res.

BR13

0

Res.

BR14

0

Res.

BR15

Reset value
GPIOx_LCKR
(where x = A..E,H)

Res.

0x18

GPIOx_BSRR
(where x = A..E,H)

Res.

GPIOx_ODR
(where x = A..E,H)

Res.

0x14

Res.

Offset Register name

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 37. GPIO register map and reset values (continued)

Reset value

Reset value

Reset value

AFSEL7[3:0] AFSEL6[3:0] AFSEL5[3:0] AFSEL4[3:0] AFSEL3[3:0] AFSEL2[3:0] AFSEL1[3:0] AFSEL0[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

AFSEL15[3:0 AFSEL14[3:0 AFSEL13[3:0 AFSEL12[3:0 AFSEL11[3:0
AFSEL10[3:0] AFSEL9[3:0] AFSEL8[3:0]
]
]
]
]
]

Reset value

Refer to Section 2.2 for the register boundary addresses.

RM0394 Rev 4

275/1600
275

System configuration controller (SYSCFG)

RM0394

9

System configuration controller (SYSCFG)

9.1

SYSCFG main features
The STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx devices feature a set of configuration
registers. The main purposes of the system configuration controller are the following:
•

Remapping memory areas

•

Managing the external interrupt line connection to the GPIOs

•

Managing robustness feature

•

Setting SRAM2 write protection and software erase

•

Configuring FPU interrupts

•

Enabling the firewall

•

Enabling /disabling I2C Fast-mode Plus driving capability on some I/Os and voltage
booster for I/Os analog switches.

9.2

SYSCFG registers

9.2.1

SYSCFG memory remap register (SYSCFG_MEMRMP)
This register is used for specific configurations on memory remap.
Address offset: 0x00
Reset value: 0x0000 000X (X is the memory mode selected by the BOOT0 pin and BOOT1
option bit)

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

MEM_MODE
rw

rw

rw

Bits 31:3 Reserved, must be kept at reset value.
Bits 2:0 MEM_MODE: Memory mapping selection
These bits control the memory internal mapping at address 0x0000 0000. These bits are
used to select the physical remap by software and so, bypass the BOOT mode setting. After
reset these bits take the value selected by BOOT0 (pin or option bit depending on
nSWBOOT0 option bit) and BOOT1 option bit.
000: Main Flash memory mapped at 0x00000000.
001: System Flash memory mapped at 0x00000000.
010: Reserved
011: SRAM1 mapped at 0x00000000.
100: Reserved
101: Reserved
110: QUADSPI memory mapped at 0x00000000.
111: Reserved

276/1600

RM0394 Rev 4

RM0394

System configuration controller (SYSCFG)

Note:

In remap mode, the CPU can access the external memory via ICode bus instead of System
bus which boosts up the performance.

9.2.2

SYSCFG configuration register 1 (SYSCFG_CFGR1)
Address offset: 0x04
Reset value: 0x7C00 0001

31

30

29

28

27

26

FPU_IE[5..0]
rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

Res

Res

Res

Res

Res

Res

25

24

Res

Res

9

8

Res

BOOST
EN

23

22

21

20

19

18

17

16

I2C_
PB8_
FMP

I2C_
PB7_
FMP

I2C_
PB6_
FMP

I2C4_
FMP

I2C3_
FMP

I2C2_
FMP

I2C1_
FMP

I2C_
PB9_
FMP

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

Res

Res

Res

Res

Res

Res

Res

FWDIS

rw

rc_w0

Bits 31:26 FPU_IE[5..0]: Floating Point Unit interrupts enable bits
FPU_IE[5]: Inexact interrupt enable
FPU_IE[4]: Input denormal 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
Bits 25:24 Reserved, must be kept at reset value.
Bit 23 I2C4_FMP: Fast-mode Plus driving capability activation
This bit enables the Fm+ driving mode on I2C4 pins selected through AF selection bits.
0: Fm+ mode is not enabled on I2C4 pins selected through AF selection bits
1: Fm+ mode is enabled on I2C4 pins selected through AF selection bits.
Bit 22 I2C3_FMP: I2C3 Fast-mode Plus driving capability activation
This bit enables the Fm+ driving mode 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.
Bit 21 I2C2_FMP: I2C2 Fast-mode Plus driving capability activation
This bit enables the Fm+ driving mode 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 Fast-mode Plus driving capability activation
This bit enables the Fm+ driving mode 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.
Bit 19 I2C_PB9_FMP: Fast-mode Plus (Fm+) driving capability activation on PB9
This bit enables the Fm+ driving mode for PB9.
0: PB9 pin operates in standard mode.
1: Fm+ mode enabled on PB9 pin, and the Speed control is bypassed.

RM0394 Rev 4

277/1600
287

System configuration controller (SYSCFG)

RM0394

Bit 18 I2C_PB8_FMP: Fast-mode Plus (Fm+) driving capability activation on PB8
This bit enables the Fm+ driving mode for PB8.
0: PB8 pin operates in standard mode.
1: Fm+ mode enabled on PB8 pin, and the Speed control is bypassed.
Bit 17 I2C_PB7_FMP: Fast-mode Plus (Fm+) driving capability activation on PB7
This bit enables the Fm+ driving mode for PB7.
0: PB7 pin operates in standard mode.
1: Fm+ mode enabled on PB7 pin, and the Speed control is bypassed.
Bit 16 I2C_PB6_FMP: Fast-mode Plus (Fm+) driving capability activation on PB6
This bit enables the Fm+ driving mode for PB6.
0: PB6 pin operates in standard mode.
1: Fm+ mode enabled on PB6 pin, and the Speed control is bypassed.
Bits 15:9 Reserved, must be kept at reset value.
Bit 8 BOOSTEN: I/O analog switch voltage booster enable
0: I/O analog switches are supplied by VDDA voltage. This is the recommended configuration
when using the ADC in high VDDA voltage operation.
1: I/O analog switches are supplied by a dedicated voltage booster (supplied by VDD). This is
the recommended configuration when using the ADC in low VDDA voltage operation.
Bits 7:1 Reserved, must be kept at reset value.
Bit 0 FWDIS: Firewall disable
This bit is cleared by software to protect the access to the memory segments according to
the Firewall configuration. Once enabled, the firewall cannot be disabled by software. Only a
system reset set the bit.
0 : Firewall protection enabled
1 : Firewall protection disabled

9.2.3

SYSCFG external interrupt configuration register 1
(SYSCFG_EXTICR1)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res

EXTI3[2:0]
rw

278/1600

rw

Res
rw

EXTI2[2:0]
rw

rw

Res
rw

RM0394 Rev 4

EXTI1[2:0]
rw

rw

Res
rw

EXTI0[2:0]
rw

rw

rw

RM0394

System configuration controller (SYSCFG)

Bits 31:15 Reserved, must be kept at reset value.
Bits 14:12 EXTI3[2:0]: EXTI 3 configuration bits
These bits are written by software to select the source input for the EXTI3
external interrupt.
000: PA[3] pin
001: PB[3] pin
010: PC[3] pin
011: PD[3] pin
100: PE[3] pin
101: Reserved
110: Reserved
111: PH[3] pin
Bit 11 Reserved, must be kept at reset value.
Bits 10:8 EXTI2[2:0]: EXTI 2 configuration bits
These bits are written by software to select the source input for the EXTI2
external interrupt.
000: PA[2] pin
001: PB[2] pin
010: PC[2] pin
011: PD[2] pin
100: PE[2] pin
101: Reserved
110: Reserved
111: Reserved
Bit 7 Reserved, must be kept at reset value.
Bits 6:4 EXTI1[2:0]: EXTI 1 configuration bits
These bits are written by software to select the source input for the EXTI1
external interrupt.
000: PA[1] pin
001: PB[1] pin
010: PC[1] pin
011: PD[1] pin
100: PE[1] pin
101: Reserved
110: Reserved
111: PH[1] pin
Bit 3 Reserved, must be kept at reset value.
Bits 2:0 EXTI0[2:0]: EXTI 0 configuration bits
These bits are written by software to select the source input for the EXTI0
external interrupt.
000: PA[0] pin
001: PB[0] pin
010: PC[0] pin
011: PD[0] pin
100: PE[0] pin
101: Reserved
110: Reserved
111: PH[0] pin

RM0394 Rev 4

279/1600
287

System configuration controller (SYSCFG)

9.2.4

RM0394

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

Res

EXTI7[2:0]
rw

rw

Res
rw

EXTI6[2:0]
rw

rw

Res
rw

EXTI5[2:0]
rw

rw

Res
rw

EXTI4[2:0]
rw

rw

Bits 31:15 Reserved, must be kept at reset value.
Bits 14:12 EXTI7[2:0]: EXTI 7 configuration bits
These bits are written by software to select the source input for the EXTI7
external interrupt.
000: PA[7] pin
001: PB[7] pin
010: PC[7] pin
011: PD[7] pin
100: PE[7] pin
101: Reserved
110: Reserved
111: Reserved
Bit 11 Reserved, must be kept at reset value.
Bits 10:8 EXTI6[2:0]: EXTI 6 configuration bits
These bits are written by software to select the source input for the EXTI6
external interrupt.
000: PA[6] pin
001: PB[6] pin
010: PC[6] pin
011: PD[6] pin
100: PE[6] pin
101: Reserved
110: Reserved
111: Reserved
Bit 7 Reserved, must be kept at reset value.

280/1600

RM0394 Rev 4

rw

RM0394

System configuration controller (SYSCFG)

Bits 6:4 EXTI5[2:0]: EXTI 5 configuration bits
These bits are written by software to select the source input for the EXTI5
external interrupt.
000: PA[5] pin
001: PB[5] pin
010: PC[5] pin
011: PD[5] pin
100: PE[5] pin
101: Reserved
110: Reserved
111: Reserved
Bit 3 Reserved, must be kept at reset value.
Bits 2:0 EXTI4[2:0]: EXTI 4 configuration bits
These bits are written by software to select the source input for the EXTI4
external interrupt.
000: PA[4] pin
001: PB[4] pin
010: PC[4] pin
011: PD[4] pin
100: PE[4] pin
101: Reserved
110: Reserved
111: Reserved

Note:

Some of the I/O pins mentioned in the above register may not be available on small
packages.

9.2.5

SYSCFG external interrupt configuration register 3
(SYSCFG_EXTICR3)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res

EXTI11[2:0]
rw

rw

Res
rw

EXTI10[2:0]
rw

rw

Res
rw

RM0394 Rev 4

EXTI9[2:0]
rw

rw

Res
rw

EXTI8[2:0]
rw

rw

rw

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287

System configuration controller (SYSCFG)

RM0394

Bits 31:15 Reserved, must be kept at reset value.
Bits 14:12 EXTI11[2:0]: EXTI 11 configuration bits
These bits are written by software to select the source input for the EXTI11
external interrupt.
000: PA[11] pin
001: PB[11] pin
010: PC[11] pin
011: PD[11] pin
100: PE[11] pin
101: Reserved
110: Reserved
111: Reserved
Bit 11 Reserved, must be kept at reset value.
Bits 10:8 EXTI10[2:0]: EXTI 10 configuration bits
These bits are written by software to select the source input for the EXTI10
external interrupt.
000: PA[10] pin
001: PB[10] pin
010: PC[10] pin
011: PD[10] pin
100: PE[10] pin
101: Reserved
110: Reserved
111: Reserved
Bit 7 Reserved, must be kept at reset value.
Bits 6:4 EXTI9[2:0]: EXTI 9 configuration bits
These bits are written by software to select the source input for the EXTI9
external interrupt.
000: PA[9] pin
001: PB[9] pin
010: PC[9] pin
011: PD[9] pin
100: PE[9] pin
101: Reserved
110: Reserved
111: Reserved
Bit 3 Reserved, must be kept at reset value.
Bits 2:0 EXTI8[2:0]: EXTI 8 configuration bits
These bits are written by software to select the source input for the EXTI8
external interrupt.
000: PA[8] pin
001: PB[8] pin
010: PC[8] pin
011: PD[8] pin
100: PE[8] pin
101: Reserved
110: Reserved
111: Reserved

Note:

282/1600

Some of the I/O pins mentioned in the above register may not be available on small
packages.

RM0394 Rev 4

RM0394

System configuration controller (SYSCFG)

9.2.6

SYSCFG external interrupt configuration register 4
(SYSCFG_EXTICR4)
Address offset: 0x14
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res

EXTI15[2:0]
rw

rw

Res
rw

EXTI14[2:0]
rw

rw

Res
rw

EXTI13[2:0]
rw

rw

Res
rw

EXTI12[2:0]
rw

rw

rw

Bits 31:15 Reserved, must be kept at reset value.
Bits 14:12 EXTI15[2:0]: EXTI15 configuration bits
These bits are written by software to select the source input for the EXTI15 external
interrupt.
000: PA[15] pin
001: PB[15] pin
010: PC[15] pin
011: PD[15] pin
100: PE[15] pin
101: Reserved
110: Reserved
111: Reserved
Bit 11 Reserved, must be kept at reset value.
Bits 10:8 EXTI14[2:0]: EXTI14 configuration bits
These bits are written by software to select the source input for the EXTI14 external
interrupt.
000: PA[14] pin
001: PB[14] pin
010: PC[14] pin
011: PD[14] pin
100: PE[14] pin
101: Reserved
110: Reserved
111: Reserved
Bit 7 Reserved, must be kept at reset value.

RM0394 Rev 4

283/1600
287

System configuration controller (SYSCFG)

RM0394

Bits 6:4 EXTI13[2:0]: EXTI13 configuration bits
These bits are written by software to select the source input for the EXTI13 external
interrupt.
000: PA[13] pin
001: PB[13] pin
010: PC[13] pin
011: PD[13] pin
100: PE[13] pin
101: Reserved
110: Reserved
111: Reserved
Bit 3 Reserved, must be kept at reset value.
Bits 2:0 EXTI12[2:0]: EXTI12 configuration bits
These bits are written by software to select the source input for the EXTI12 external
interrupt.
000: PA[12] pin
001: PB[12] pin
010: PC[12] pin
011: PD[12] pin
100: PE[12] pin
101: Reserved
110: Reserved
111: Reserved

Note:

Some of the I/O pins mentioned in the above register may not be available on small
packages.

9.2.7

SYSCFG SRAM2 control and status register (SYSCFG_SCSR)
Address offset: 0x18
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

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

Res

SRAM2 SRAM2
BSY
ER
r

rw

Bits 31:2 Reserved, must be kept at reset value
Bit 1 SRAM2BSY: SRAM2 busy by erase operation
0: No SRAM2 erase operation is on going.
1: SRAM2 erase operation is on going.
Bit 0 SRAM2ER: SRAM2 Erase
Setting this bit starts a hardware SRAM2 erase operation. This bit is
automatically cleared at the end of the SRAM2 erase operation.
Note: This bit is write-protected: setting this bit is possible only after the correct
key sequence is written in the SYSCFG_SKR register.

284/1600

RM0394 Rev 4

RM0394

System configuration controller (SYSCFG)

9.2.8

SYSCFG configuration register 2 (SYSCFG_CFGR2)
Address offset: 0x1C
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

Res

Res

Res

Res

Res

SPF

Res

Res

Res

Res

ECCL

PVDL

SPL

CLL

rs

rs

rs

rs

rc_w1

Bits 31:9 Reserved, must be kept at reset value
Bit 8 SPF: SRAM2 parity error flag
This bit is set by hardware when an SRAM2 parity error is detected. It is cleared
by software by writing ‘1’.
0: No SRAM2 parity error detected
1: SRAM2 parity error detected
Bits 7:4 Reserved, must be kept at reset value
Bit 3 ECCL: ECC Lock
This bit is set by software and cleared only by a system reset. It can be used to
enable and lock the Flash ECC error connection to TIM1/15/16 Break input.
0: ECC error disconnected from TIM1/15/16 Break input.
1: ECC error connected to TIM1/15/16 Break input.
Bit 2 PVDL: PVD lock enable bit
This bit is set by software and cleared only by a system reset. It can be used to
enable and lock the PVD connection to TIM1/15/16 Break input, as well as the
PVDE and PLS[2:0] in the PWR_CR2 register.
0: PVD interrupt disconnected from TIM1/15/16 Break input. PVDE and PLS[2:0]
bits can be programmed by the application.
1: PVD interrupt connected to TIM1/15/16 Break input, PVDE and PLS[2:0] bits
are read only.
Bit 1 SPL: SRAM2 parity lock bit
This bit is set by software and cleared only by a system reset. It can be used to
enable and lock the SRAM2 parity error signal connection to TIM1/15/16 Break
inputs.
0: SRAM2 parity error signal disconnected from TIM1/15/16 Break inputs
1: SRAM2 parity error signal connected to TIM1/15/16 Break inputs
Bit 0 CLL: Cortex®-M4 LOCKUP (Hardfault) output enable bit
This bit is set by software and cleared only by a system reset. It can be used to
enable and lock the connection of Cortex®-M4 LOCKUP (Hardfault) output to
TIM1/15/16 Break input
0: Cortex®-M4 LOCKUP output disconnected from TIM1/15/16 Break inputs
1: Cortex®-M4 LOCKUP output connected to TIM1/15/16 Break inputs

RM0394 Rev 4

285/1600
287

System configuration controller (SYSCFG)

9.2.9

RM0394

SYSCFG SRAM2 write protection register (SYSCFG_SWPR)
Address offset: 0x20
System reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

P31WP P30WP P29WP P28WP P27WP P26WP P25WP P24WP P23WP P22WP P21WP P20WP P19WP P18WP P17WP P16WP
rs

rs

rs

rs

rs

rs

rs

rs

rs

rs

rs

rs

rs

rs

rs

rs

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

P9WP

P8WP

P7WP

P6WP

P5WP

P4WP

P3WP

P2WP

P1WP

P0WP

rs

rs

rs

rs

rs

rs

rs

rs

rs

rs

P15WP P14WP P13WP P12WP P11WP P10WP
rs

rs

rs

rs

rs

rs

Bits 31:0 PxWP (x = 0 to 31): SRAM2 page x write protection
These bits are set by software and cleared only by a system reset.
0: Write protection of SRAM2 page x is disabled.
1: Write protection of SRAM2 page x is enabled.
Note: PxWP (x = 16 to 31) available on STM32L45x and STM32L46x devices
only.

9.2.10

SYSCFG SRAM2 key register (SYSCFG_SKR)
Address offset: 0x24
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

Res

Res

Res

Res

Res

Res
w

w

w

w

w

w

w

KEY[7:0]
w

Bits 31:8 Reserved, must be kept at reset value
Bits 7:0 KEY[7:0]: SRAM2 write protection key for software erase
The following steps are required to unlock the write protection of the SRAM2ER
bit in the SYSCFG_CFGR2 register.
1. Write "0xCA” into Key[7:0]
2. Write "0x53” into Key[7:0]
Writing a wrong key reactivates the write protection.

286/1600

RM0394 Rev 4

P27WP

P26WP

P25WP

P24WP

P23WP

P22WP

P21WP

P20WP

P19WP

P18WP

P17WP

P16WP

P15WP

P14WP

P13WP

P12WP

P11WP

P10WP

P9WP

P8WP

P7WP

P6WP

P5WP

P4WP

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

SYSCFG_SKR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0x24
SYSCFG_SWPR

Res.

0x20

P28WP

RM0394 Rev 4

Reset value

0

0

0

0

0

0
CLL

0

SPL

0

0
0

0
0

KEY

0

0

0

0

0

0

0

0

0
0
0

Reset value
SRAM2ER

0

SRAM2BSY

EXTI13
[2:0]

P0WP

Res.

Res.

Res.

I2C_PB8_FMP
I2C_PB7_FMP
I2C_PB6_FMP

x
x
x

Res.
Res.
Res.
FWDIS

Res.

Res.

Res.

Res.

BOOSTEN

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

0

Res.

EXTI9
[2:0]

Res.

0

0

Res.

0

Res.

Res.
EXTI5
[2:0]

PVDL

0

EXTI1
[2:0]

ECCL

0

0

0

Res.

0

Res.

EXTI14
[2:0]

Res.

Res.

I2C_PB9_FMP

0

P1WP

Reset value
0

Res.

0

Res.

EXTI10
[2:0]

Res.

0

Res.

Res.
EXTI6
[2:0]

0

Res.

0
0

0

0

Res.

0

EXTI2
[2:0]

Res.

0
0

0

SPF

0

Res.

EXTI15
[2:0]

0

Res.

0

Res.

0
Res.

EXTI11
[2:0]

Res.

EXTI7
[2:0]

Res.

0
0

0

Res.

Reset value
EXTI3
[2:0]

Res.

Reset value

Res.

0

0

Res.

Reset value

Res.

0

Res.

Reset value

Res.

I2C1_FMP

0

Res.

I2C2_FMP

0

Res.

I2C3_FMP

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

I2C4_FMP

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

1

P2WP

SYSCFG_CFGR2
1

Res.

SYSCFG_SCSR
1

Res.

SYSCFG_EXTICR4
1

Res.

SYSCFG_EXTICR3
0

Res.

SYSCFG_EXTICR2

Res.

SYSCFG_EXTICR1
FPU_IE[5..0]

P3WP

0x1C

P29WP

0x18

Res.

0x14

Res.

0x10
SYSCFG_CFGR1

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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

SYSCFG_
MEMRMP

Res.

0x00

Res.

Register

Res.

Offset

Res.

0x0C

P30WP

0x08

P31WP

0x04

Res.

9.2.11

Res.

RM0394
System configuration controller (SYSCFG)

SYSCFG register map

The following table gives the SYSCFG register map and the reset values.
Table 38. SYSCFG register map and reset values

MEM_
MODE

0
0
0
1

EXTI0
[2:0]
0

0

0

0

EXTI4
[2:0]
0

EXTI8
[2:0]
0

EXTI12
[2:0]

0
0

0
0
0
0

Refer to Section 2.2.2 on page 67 for the register boundary addresses.

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Peripherals interconnect matrix

RM0394

10

Peripherals interconnect matrix

10.1

Introduction
Several peripherals have direct connections between them.
This allows autonomous communication and or synchronization between peripherals,
saving CPU resources thus power supply consumption.
In addition, these hardware connections remove software latency and allow design of
predictable system.
Depending on peripherals, these interconnections can operate in Run, Sleep, Low-power
run and sleep, Stop 0, Stop 1 and Stop 2 modes.

10.2

Connection summary

Table 39. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx peripherals interconnect matrix(1) (2)

TIM1

TIM2

TIM6

TIM7

TIM15

TIM16

LPTIM1

LPTIM2

ADC1

ADC2

OPAMP1

DAC1

DAC2

COMP1

COMP2

IRTIM

Destination

TIM1

-

1

-

-

1

-

-

-

2

2

-

-

-

7

-

-

TIM2

1

-

-

-

-

-

-

-

2

2

-

4

4

7

-

-

TIM6

-

-

-

-

-

-

-

-

2

2

-

4

4

-

-

-

TIM7

-

-

-

-

-

-

-

-

-

-

-

4

4

-

-

-

TIM15

1

-

-

-

-

-

-

-

2

2

-

4

4

-

7

12

TIM16

-

-

-

-

1

-

-

-

-

-

-

-

-

-

-

12

LPTIM1

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

LPTIM2

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

ADC1

3

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

T. Sensor

-

-

-

-

-

-

-

-

9

-

-

-

-

-

-

-

VBAT

-

-

-

-

-

-

-

-

9

-

-

-

-

-

-

-

VREFINT

-

-

-

-

-

-

-

-

9

-

-

-

-

-

-

-

OPAMP1

-

-

-

-

-

-

-

-

9

9

-

-

-

-

-

-

DAC1

-

-

-

-

-

-

-

-

9

-

9

-

-

-

-

-

DAC2

-

-

-

-

-

-

-

-

9

-

-

-

-

-

-

-

HSE

-

-

-

-

-

5

-

-

-

-

-

-

-

-

-

-

LSE

-

5

-

-

5

5

-

-

-

-

-

-

-

-

-

-

MSI

-

-

-

-

-

5

-

-

-

-

-

-

-

-

-

-

LSI

-

-

-

-

-

5

-

-

-

-

-

-

-

-

-

-

Source

-

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RM0394

Peripherals interconnect matrix

Table 39. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx peripherals interconnect matrix(1) (2)

TIM1

TIM2

TIM6

TIM7

TIM15

TIM16

LPTIM1

LPTIM2

ADC1

ADC2

OPAMP1

DAC1

DAC2

COMP1

COMP2

IRTIM

Destination

MCO

-

-

-

-

-

5

-

-

-

-

-

-

-

-

-

-

EXTI

-

-

-

-

-

-

-

-

2

2

-

4

4

-

-

-

RTC

-

-

-

-

-

5

6

6

-

-

-

-

-

-

-

-

COMP1

10

10

-

-

10

10

6

6

-

-

-

-

-

-

-

-

COMP2

10

10

-

-

10

10

6

6

-

-

-

-

-

-

-

-

SYST ERR

11

-

-

-

11

11

-

-

-

-

-

-

-

-

-

-

USB(3)

-

8

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Source

-

1. Numbers in table are links to corresponding detailed sub-section in Section 10.3: Interconnection details.
2.

The “-” symbol in grayed cells means no interconnect.

3. Not available for STM32L431xx devices.

10.3

Interconnection details

10.3.1

From timer (TIM1/TIM2/TIM15/TIM16) to timer (TIM1/TIM2/TIM15/TIM16)
Purpose
Some of the TIMx timers are linked together internally for timer synchronization or chaining.
When one timer is configured in Master Mode, it can reset, start, stop or clock the counter of
another timer configured in Slave Mode.
A description of the feature is provided in: Section 27.3.19: Timer synchronization.
The modes of synchronization are detailed in:
•

Section 27.3.19: Timer synchronization for advanced-control timers (TIM1)

•

Section 27.3.18: Timers and external trigger synchronization for general-purpose
timers (TIM2)

•

Section 28.5.18: External trigger synchronization (TIM15 only) for general-purpose
timer (TIM15)

Triggering signals
The output (from Master) is on signal TIMx_TRGO (and TIMx_TRGO2 for TIM1) following a
configurable timer event.
The input (to slave) is on signals TIMx_ITR0/ITR1/ITR2/ITR3
The input and output signals for TIM1 are shown in Figure 183: Advanced-control timer
block diagram.
The possible master/slave connections are given in:
•

Table 132: TIM1 internal trigger connection

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Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.2

From timer (TIM1/TIM2/TIM6/TIM15) and EXTI to ADC (ADC1)
Purpose
General-purpose timers (TIM2), basic timer (TIM6), advanced-control timer (TIM1), generalpurpose timer (TIM15) and EXTI can be used to generate an ADC triggering event.
TIMx synchronization is described in: Section 26.3.5: Clock selection (TIM1).
ADC synchronization is described in: Section 16.4.18: Conversion on external trigger and
trigger polarity (EXTSEL, EXTEN,JEXTSEL, JEXTEN).

Triggering signals
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 ADC is provided in:
•

Table 59: ADC1 and ADC2 - External triggers for regular channels

•

Table 60: ADC1 and ADC2 - External trigger for injected channels

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.3

From ADC (ADC1) to timer (TIM1)
Purpose
ADC1 can provide trigger event through watchdog signals to advanced-control timers
(TIM1).
A description of the ADC analog watchdog setting is provided in: Section 16.4.29: Analog
window watchdog (AWD1EN, JAWD1EN, AWD1SGL, AWD1CH, AWD2CH, AWD3CH,
AWD_HTx, AWD_LTx, AWDx).
Trigger settings on the timer are provided in: Section 26.3.4: External trigger input.

Triggering signals
The output (from ADC) is on signals ADCn_AWDx_OUT n = 1, 2, 3 (for ADC1) x = 1, 2, 3 (3
watchdog per ADC) and the input (to timer) on signal TIMx_ETR (external trigger).

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.4

From timer (TIM2/TIM6/TIM7) and EXTI to DAC (DAC1/DAC2)
Purpose
General-purpose timer (TIM2), basic timers (TIM6, TIM7), and EXTI can be used as
triggering event to start a DAC conversion.

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Peripherals interconnect matrix

Triggering signals
The output (from timer) is on signal TIMx_TRGO directly connected to corresponding DAC
inputs.
Selection of input triggers on DAC is provided in Section 17.4.6: DAC trigger selection
(single and dual mode).

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.5

From HSE, LSE, LSI, MSI, MCO, RTC to timer (TIM2/TIM15/TIM16)
Purpose
External clocks (HSE, LSE), internal clocks (LSI, MSI), microcontroller output clock (MCO),
GPIO and RTC wakeup interrupt can be used as input to general-purpose timer (TIM15/16)
channel 1.
This allows to calibrate the HSI16/MSI system clocks (with TIM15/TIM16 and LSE) or LSI
(with TIM16 and HSE). This is also used to precisely measure LSI (with TIM16 and HSI16)
or MSI (with and HSI16) oscillator frequency.
When Low Speed External (LSE) oscillator is used, no additional hardware connections are
required.
This feature is described in Section 6.2.17: Internal/external clock measurement with
TIM15/TIM16.
External clock LSE can be used as input to general-purpose timers (TIM2) on TIM2_ETR
pin, see Section 27.4.19: TIM2 option register 1 (TIM2_OR1).

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.6

From RTC, COMP1, COMP2 to low-power timer (LPTIM1/LPTIM2)
Purpose
RTC alarm A/B, RTC_TAMP1/2/3 input detection, COMP1/2_OUT can be used as trigger to
start LPTIM counters (LPTIM1/2).

Triggering signals
This trigger feature is described in Section 30.4.6: Trigger multiplexer (and following
sections).
The input selection is described in Table 146: LPTIM1 external trigger connection.

Active power mode
Run, Sleep, Low-power run, Low-power sleep, Stop 0, Stop 1, Stop 2 (LPTIM1 only).

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10.3.7

RM0394

From timer (TIM1/TIM2/TIM15) to comparators
(COMP1/COMP2)
Purpose
Advanced-control timer (TIM1), general-purpose timer (TIM2) and general-purpose timer
(TIM15) can be used as blanking window input to COMP1/COMP2
The blanking function is described in Section 19.3.7: Comparator output blanking function.
The blanking sources are given in:
•

Section 19.6.1: Comparator 1 control and status register (COMP1_CSR) bits 20:18
BLANKING[2:0]

•

Section 19.6.2: Comparator 2 control and status register (COMP2_CSR) bits 20:18
BLANKING[2:0]

Triggering signals
Timer output signal TIMx_Ocx are the inputs to blanking source of COMP1/COMP2.

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.8

From ADC (ADC1) to ADC (ADC2)
Purpose
ADC1 can be used as a “master” to trigger ADC2 “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 16.4.31: Dual ADC modes.

Triggering signals
Internal to the ADCs.

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.9

From USB to timer (TIM2)
Purpose
USB (FS SOF) can generate a trigger to general-purpose timer (TIM2).
Connection of USB to TIM2 is described in .

Triggering signals
Internal signal generated by USB FS Start Of Frame.

Active power mode
Run, Sleep.
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10.3.10

Peripherals interconnect matrix

From internal analog source to ADC (ADC1) and OPAMP
(OPAMP1)
Purpose
Internal temperature sensor (VTS) and VBAT monitoring channel are connected to ADC1
input channels.
Internal reference voltage (VREFINT) is connected to ADC1 input channels.
OPAMP1 output can be connected to ADC1 input channel through the GPIO.
DAC1_OUT1 and DAC1_OUT2 outputs can be connected to input channel.
DAC1_OUT1 can be connected to OPAMP1_VINP.
This is according:
•

Section 16.2: ADC main features

•

Section 16.4.11: Channel selection (SQRx, JSQRx)

•

Figure 41: ADC1 connectivity

•

Table 90: Operational amplifier possible connections

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.11

From comparators (COMP1/COMP2) to timers
(TIM1/TIM2/TIM15/TIM16)
Purpose
Comparators (COMP1/COMP2) output values can be connected to timers
(TIM1/TIM2/TIM15/TIM16) input captures or TIMx_ETR signals.
The connection to ETR is described in Section 26.3.4: External trigger input.
Comparators (COMP1/COMP2) output values can also generate break input signals for
timers (TIM1) on input pins TIMx_BKIN or TIMx_BKIN2 through GPIO alternate function
selection using open drain connection of IO, see Section 26.3.17: Bidirectional break inputs.
The possible connections are given in:
•

Section 26.4.23: TIM1 option register 1 (TIM1_OR1)

•

Section 26.4.27: TIM1 option register 2 (TIM1_OR2)

•

Section 27.4.19: TIM2 option register 1 (TIM2_OR1)

•

Section 27.4.20: TIM2 option register 2 (TIM2_OR2)

•

Section 28.3: TIM16 main features

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

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10.3.12

RM0394

From system errors to timers (TIM1/TIM15/TIM16)
Purpose
CSS, CPU hardfault, RAM parity error, FLASH ECC double error detection, PVD can
generate system errors in the form of timer break toward timers (TIM1/TIM15/TIM16).
The purpose of the break function is to protect power switches driven by PWM signals
generated by the timers.
List of possible source of break are described in:
•

Section 26.3.16: Using the break function (TIM1)

•

Section 28.5.13: Using the break function (TIM15/TIM16)

•

Figure 292: TIM15 block diagram

•

Figure 293: TIM16 block diagram

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

10.3.13

From timers (TIM16) to IRTIM
Purpose
General-purpose timer (TIM16) output channel TIMx_OC1 are used to generate the
waveform of infrared signal output.
The functionality is described in Section 31: Infrared interface (IRTIM).

Active power mode
Run, Sleep, Low-power run, Low-power sleep.

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RM0394

Direct memory access controller (DMA)

11

Direct memory access controller (DMA)

11.1

Introduction
The direct memory access (DMA) controller is a bus master and system peripheral.
The DMA is used to perform programmable data transfers between memory-mapped
peripherals and/or memories, upon the control of an off-loaded CPU.
The DMA controller features a single AHB master architecture.
There are two instances of DMA, DMA1 and DMA2.
Each channel is dedicated to managing memory access requests from one or more
peripherals. Each DMA includes an arbiter for handling the priority between DMA requests.

11.2

DMA main features
•

Single AHB master

•

Peripheral-to-memory, memory-to-peripheral, memory-to-memory and peripheral-toperipheral data transfers

•

Access, as source and destination, to on-chip memory-mapped devices such as Flash
memory, SRAM, and AHB and APB peripherals

•

All DMA channels independently configurable:

•

–

Each channel is associated either with a DMA request signal coming from a
peripheral, or with a software trigger in memory-to-memory transfers. This
configuration is done by software.

–

Priority between the requests is programmable by software (4 levels per channel:
very high, high, medium, low) and by hardware in case of equality (such as
request to channel 1 has priority over request to channel 2).

–

Transfer size of source and destination are independent (byte, half-word, word),
emulating packing and unpacking. Source and destination addresses must be
aligned on the data size.

–

Support of transfers from/to peripherals to/from memory with circular buffer
management

–

Programmable number of data to be transferred: 0 to 216 - 1

Generation of an interrupt request per channel. Each interrupt request is caused from
any of the three DMA events: transfer complete, half transfer, or transfer error.

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Direct memory access controller (DMA)

11.3

DMA implementation

11.3.1

DMA1 and DMA2

RM0394

DMA1 and DMA2 are implemented with the hardware configuration parameters shown
in Table 40.
Table 40. DMA1 and DMA2 implementation
Feature

DMA1

DMA2

7

7

Number of channels

11.3.2

DMA request mapping
DMA controller
The hardware requests from the peripherals (TIM1/2/3/6/7/15/16, ADC1, DAC_CH1/2,
SPI1/2/3, I2C1/2/3/4, SDMMC1, QUADSPI, SWPMI1, SAI1, AES, USART1/2/3, UART4 and
LPUART1) are mapped to the DMA channels through the DMA_CSELR channel selection
registers (see Figure 25 and Figure 26).
The peripheral DMA requests can be independently activated/de-activated by programming
the DMA control bit in the registers of the corresponding peripheral.
Table 41 show the list of DMA requests for each channel.

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Direct memory access controller (DMA)
Figure 25. DMA1 request mapping

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319

Direct memory access controller (DMA)

RM0394

Figure 26. DMA2 request mapping
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Table 41. DMA1 requests for each channel
CxS[3:0]

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel 6

Channel 7

0000

ADC1

ADC2(1)

-

-

DFSDM1_
FLT0(2)

DFSDM1_
FLT1(2)

-

0001

-

SPI1_RX

SPI1_TX

SPI2_RX(3)

SPI2_TX(3)

SAI2_A(4)

SAI2_B(4)

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RM0394

Direct memory access controller (DMA)
Table 41. DMA1 requests for each channel (continued)

CxS[3:0]

Channel 1

0010

-

0011

Channel 2

Channel 3

USART3_TX USART3_RX

Channel 4

Channel 5

Channel 6

Channel 7

USART1_TX USART1_RX USART2_RX USART2_TX

(3)

(3)

-

I2C3_TX

I2C3_RX

I2C2_TX(3)

I2C2_RX(3)

I2C1_TX

I2C1_RX

0100

TIM2_CH3

TIM2_UP

TIM16_CH1
TIM16_UP

-

TIM2_CH1

TIM16_CH1
TIM16_UP

TIM2_CH2
TIM2_CH4

0101

-

TIM3_CH3(2)

QUADSPI

TIM3_CH1(2)
TIM3_TRIG

-

0110

-

-

0111

-

TIM1_CH1

TIM3_CH4(2)
TIM7_UP.
TIM3_UP(2) DAC_CH2(5)

(2)

TIM6_UP
DAC_CH1

-

-

-

-

TIM1_CH2

TIM1_CH4
TIM1_TRIG
TIM1_COM

TIM15_CH1
TIM15_UP
TIM15_TRIG
TIM15_COM

TIM1_UP

TIM1_CH3

1. Available on STM32L412xx and STM32L422xx devices only.
2. Available on STM32L45xxx and STM32L46xxx devices only.
3. Not available on STM32L432xx and STM32L442xx devices.
4. Not available on STM32L412xx and STM32L422xx devices.
5. Available on STM32L43xx and STM32L44xx devices only.

Table 42. DMA2 requests for each channel
CxS[3:0]

Channel 1

Channel 2

Channel 3

Channel 4

Channel 5

Channel 6

Channel 7

0000

I2C4_RX(1)

I2C4_TX(1)

ADC1

ADC2(2)

-

-

-

0001

SAI1_A

SAI1_B

-

-

-

SAI1_A

SAI1_B

0010

-

-

0011

SPI3_RX

SPI3_TX

0100
0101
0110
0111

AES_IN
-

(4)

UART4_RX

(1)

-

-

TIM6_UP
DAC_CH1

TIM7_UP
DAC_CH2(3)

-

QUADSPI

(3)

SPI1_RX

SPI1_TX

-

LPUART1_
TX

LPUART1_
RX

-

-

-

-

I2C1_RX

I2C1_TX

AES_OUT(4)

AES_OUT(4)

-

AES_IN(4)

-

-

-

-

SDMMC1(5)

SDMMC1(5)

-

-

SWPMI1_RX SWPMI1_TX
(3)

UART4_TX

(1)

USART1_TX USART1_RX

1. Available on STM32L45xxx and STM32L46xxx devices only.
2. Available on STM32L41xxx and STM32L42xxx devices only.
3. Available on STM32L43xxx and STM32L44xxx devices only.
4. Available on STM32L44xxx and STM32L46xxx devices only
5. Not available on STM32L432xx and STM32L442xx devices.

11.4

DMA functional description
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11.4.1

RM0394

DMA block diagram
The DMA block diagram is shown in Figure 27.
Figure 27. DMA block diagram

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The DMA controller performs direct memory transfer by sharing the AHB system bus with
other system masters. The bus matrix implements round-robin scheduling. DMA requests
may stop the CPU access to the system bus for a number of bus cycles, when CPU and
DMA target the same destination (memory or peripheral).
According to its configuration through the AHB slave interface, the DMA controller arbitrates
between the DMA channels and their associated received requests. The DMA controller
also schedules the DMA data transfers over the single AHB port master.
The DMA controller generates an interrupt per channel to the interrupt controller.

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11.4.2

Direct memory access controller (DMA)

DMA transfers
The software configures the DMA controller at channel level, in order to perform a block
transfer, composed of a sequence of AHB bus transfers.
A DMA block transfer may be requested from a peripheral, or triggered by the software in
case of memory-to-memory transfer.
After an event, the following steps of a single DMA transfer occur:
1.

The peripheral sends a single DMA request signal to the DMA controller.

2.

The DMA controller serves the request, depending on the priority of the channel
associated to this peripheral request.

3.

As soon as the DMA controller grants the peripheral, an acknowledge is sent to the
peripheral by the DMA controller.

4.

The peripheral releases its request as soon as it gets the acknowledge from the DMA
controller.

5.

Once the request is de-asserted by the peripheral, the DMA controller releases the
acknowledge.

The peripheral may order a further single request and initiate another single DMA transfer.
The request/acknowledge protocol is used when a peripheral is either the source or the
destination of the transfer. For example, in case of memory-to-peripheral transfer, the
peripheral initiates the transfer by driving its single request signal to the DMA controller. The
DMA controller reads then a single data in the memory and writes this data to the peripheral.
For a given channel x, a DMA block transfer consists of a repeated sequence of:
•

•

a single DMA transfer, encapsulating two AHB transfers of a single data, over the DMA
AHB bus master:
–

a single data read (byte, half-word or word) from the peripheral data register or a
location in the memory, addressed through an internal current peripheral/memory
address register.
The start address used for the first single transfer is the base address of the
peripheral or memory, and is programmed in the DMA_CPARx or DMA_CMARx
register.

–

a single data write (byte, half-word or word) to the peripheral data register or a
location in the memory, addressed through an internal current peripheral/memory
address register.
The start address used for the first transfer is the base address of the peripheral or
memory, and is programmed in the DMA_CPARx or DMA_CMARx register.

post-decrementing of the programmed DMA_CNDTRx register
This register contains the remaining number of data items to transfer (number of AHB
‘read followed by write’ transfers).

This sequence is repeated until DMA_CNDTRx is null.
Note:

The AHB master bus source/destination address must be aligned with the programmed size
of the transferred single data to the source/destination.

11.4.3

DMA arbitration
The DMA arbiter manages the priority between the different channels.

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When an active channel x is granted by the arbiter (hardware requested or software
triggered), a single DMA transfer is issued (such as a AHB ‘read followed by write’ transfer
of a single data). Then, the arbiter considers again the set of active channels and selects the
one with the highest priority.
The priorities are managed in two stages:
•

•

software: priority of each channel is configured in the DMA_CCRx register, to one of
the four different levels:
–

very high

–

high

–

medium

–

low

hardware: if two requests have the same software priority level, the channel with the
lowest index gets priority. For example, channel 2 gets priority over channel 4.

When a channel x is programmed for a block transfer in memory-to-memory mode,
re arbitration is considered between each single DMA transfer of this channel x. Whenever
there is another concurrent active requested channel, the DMA arbiter automatically
alternates and grants the other highest-priority requested channel, which may be of lower
priority than the memory-to-memory channel.

11.4.4

DMA channels
Each channel may handle a DMA transfer between a peripheral register located at a fixed
address, and a memory address. The amount of data items to transfer is programmable.
The register that contains the amount of data items to transfer is decremented after each
transfer.
A DMA channel is programmed at block transfer level.

Programmable data sizes
The transfer sizes of a single data (byte, half-word, or word) to the peripheral and memory
are programmable through, respectively, the PSIZE[1:0] and MSIZE[1:0] fields of the
DMA_CCRx register.

Pointer incrementation
The peripheral and memory pointers may be automatically incremented after each transfer,
depending on the PINC and MINC bits of the DMA_CCRx register.
If the incremented mode is enabled (PINC or MINC set to 1), the address of the next
transfer is the address of the previous one incremented by 1, 2 or 4, depending on the data
size defined in PSIZE[1:0] or MSIZE[1:0]. The first transfer address is the one programmed
in the DMA_CPARx or DMA_CMARx register. During transfers, these registers keep the
initially programmed value. The current transfer addresses (in the current internal
peripheral/memory address register) are not accessible by software.
If the channel x is configured in non-circular mode, no DMA request is served after the last
data transfer (once the number of single data to transfer reaches zero). The DMA channel
must be disabled in order to reload a new number of data items into the DMA_CNDTRx
register.

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Note:

Direct memory access controller (DMA)
If the channel x 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 data 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 and DMA_CMARx registers.

Channel configuration procedure
The following sequence is needed to configure a DMA channel x:
1.

Set the peripheral register address in the DMA_CPARx register.
The data is moved from/to this address to/from the memory after the peripheral event,
or after the channel is enabled in memory-to-memory mode.

2.

Set the memory address in the DMA_CMARx register.
The data is written to/read from the memory after the peripheral event or after the
channel is enabled in memory-to-memory mode.

3.

Configure the total number of data to transfer in the DMA_CNDTRx register.
After each data transfer, this value is decremented.

4.

Configure the parameters listed below in the DMA_CCRx register:

5.

–

the channel priority

–

the data transfer direction

–

the circular mode

–

the peripheral and memory incremented mode

–

the peripheral and memory data size

–

the interrupt enable at half and/or full transfer and/or transfer error

Activate the channel by setting the EN bit in the DMA_CCRx register.

A channel, as soon as enabled, may serve any DMA request from the peripheral connected
to this channel, or may start a memory-to-memory block transfer.
Note:

The two last steps of the channel configuration procedure may be merged into a single
access to the DMA_CCRx register, to configure and enable the channel.
When a channel is enabled and still active (not completed), the software must perform two
separate write accesses to the DMA_CCRx register, to disable the channel, then to
reprogram the channel for another next block transfer.
Some fields of the DMA_CCRx register are read-only when the EN bit is set to 1.

Stop and resume a channel
Once the software activates a channel, it waits for the completion of the programmed
transfer. The DMA controller is not able to resume an aborted active channel with a possible
suspended bus transfer.
To correctly stop and disable a channel, the software clears the EN bit of the DMA_CCRx
register. The software secures that no pending request from the peripheral is served by the
DMA controller before the transfer completion. The software waits for the transfer complete
or transfer error interrupt.
When a channel transfer error occurs, the EN bit of the DMA_CCRx register is cleared by
hardware. This EN bit can not be set again by software to re-activate the channel x, until the
TEIFx bit of the DMA_ISR register is set.

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Circular mode (in memory-to-peripheral/peripheral-to-memory transfers)
The circular mode is available to handle circular buffers and continuous data flows (such as
ADC scan mode). This feature is enabled using the CIRC bit in the DMA_CCRx register.
Note:

The circular mode must not be used in memory-to-memory mode. Before enabling a
channel in circular mode (CIRC = 1), the software must clear the MEM2MEM bit of the
DMA_CCRx register. When the circular mode is activated, the amount of data to transfer is
automatically reloaded with the initial value programmed during the channel configuration
phase, and the DMA requests continue to be served.
In order to stop a circular transfer, the software needs to stop the peripheral from generating
DMA requests (such as quit the ADC scan mode), before disabling the DMA channel.
The software must explicitly program the DMA_CNDTRx value before starting/enabling a
transfer, and after having stopped a circular transfer.

Memory-to-memory mode
The DMA channels may operate without being triggered by a request from a peripheral. This
mode is called memory-to-memory mode, and is initiated by software.
If the MEM2MEM bit in the DMA_CCRx register is set, the channel, if enabled, initiates
transfers. The transfer stops once the DMA_CNDTRx register reaches zero.
Note:

The memory-to-memory mode must not be used in circular mode. Before enabling a
channel in memory-to-memory mode (MEM2MEM = 1), the software must clear the CIRC
bit of the DMA_CCRx register.

Peripheral-to-peripheral mode
Any DMA channel can operate in peripheral-to-peripheral mode:
•

when the hardware request from a peripheral is selected to trigger the DMA channel
This peripheral is the DMA initiator and paces the data transfer from/to this peripheral
to/from a register belonging to another memory-mapped peripheral (this one being not
configured in DMA mode).

•

when no peripheral request is selected and connected to the DMA channel
The software configures a register-to-register transfer by setting the MEM2MEM bit of
the DMA_CCRx register.

Programming transfer direction, assigning source/destination
The value of the DIR bit of the DMA_CCRx register sets the direction of the transfer, and
consequently, it identifies the source and the destination, regardless the source/destination
type (peripheral or memory):
•

304/1600

DIR = 1 defines typically a memory-to-peripheral transfer. More generally, if DIR = 1:
–

The source attributes are defined by the DMA_MARx register, the MSIZE[1:0]
field and MINC bit of the DMA_CCRx register.
Regardless of their usual naming, these ‘memory’ register, field and bit are used to
define the source peripheral in peripheral-to-peripheral mode.

–

The destination attributes are defined by the DMA_PARx register, the PSIZE[1:0]
field and PINC bit of the DMA_CCRx register.

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Direct memory access controller (DMA)
Regardless of their usual naming, these ‘peripheral’ register, field and bit are used
to define the destination memory in memory-to-memory mode.
•

DIR = 0 defines typically a peripheral-to-memory transfer. More generally, if DIR = 0:
–
The source attributes are defined by the DMA_PARx register, the PSIZE[1:0] field
and PINC bit of the DMA_CCRx register.
Regardless of their usual naming, these ‘peripheral’ register, field and bit are used
to define the source memory in memory-to-memory mode
–

The destination attributes are defined by the DMA_MARx register, the
MSIZE[1:0] field and MINC bit of the DMA_CCRx register.
Regardless of their usual naming, these ‘memory’ register, field and bit are used to
define the destination peripheral in peripheral-to-peripheral mode.

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DMA data width, alignment and endianness
When PSIZE[1:0] and MSIZE[1:0] are not equal, the DMA controller performs some data
alignments as described in Table 43.
Table 43. Programmable data width and endian behavior (when PINC = MINC = 1)

Source
port
width
(MSIZE
if
DIR = 1,
else
PSIZE)

Destinat
ion port
Number
width
of data
(PSIZE
items to
if
transfer
DIR = 1,
(NDT)
else
MSIZE)

Source content:
address / data
(DMA_CMARx if
DIR = 1, else
DMA_CPARx)

DMA transfers

Destination
content:
address / data
(DMA_CPARx if
DIR = 1, else
DMA_CMARx)

8

8

8

@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[15:0] @0x0
2: read B7B6B5B4[31:0] @0x4 then write B5B4[15:0] @0x2
3: read BBBAB9B8[31:0] @0x8 then write B9B8[15:0] @0x4
4: read BFBEBDBC[31:0] @0xC then write BDBC[15:0] @0x6

@0x0 / B1B0
@0x2 / B5B4
@0x4 / B9B8
@0x6 / BDBC

32

32

4

@0x0 / B3B2B1B0
@0x4 / B7B6B5B4
@0x8 / BBBAB9B8
@0xC / BFBEBDBC

1: read B3B2B1B0[31:0] @0x0 then write B3B2B1B0[31:0] @0x0
2: read B7B6B5B4[31:0] @0x4 then write B7B6B5B4[31:0] @0x4
3: read BBBAB9B8[31:0] @0x8 then write BBBAB9B8[31:0] @0x8
4: read BFBEBDBC[31:0] @0xC then write BFBEBDBC[31:0] @0xC

@0x0 / B3B2B1B0
@0x4 / B7B6B5B4
@0x8 / BBBAB9B8
@0xC / BFBEBDBC

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Direct memory access controller (DMA)

Addressing AHB peripherals not supporting byte/half-word write transfers
When the DMA controller initiates an AHB byte or half-word write transfer, the data are
duplicated on the unused lanes of the AHB master 32-bit data bus (HWDATA[31:0]).
When the AHB slave peripheral does not support byte or half-word write transfers and does
not generate any error, the DMA controller writes the 32 HWDATA bits as shown in the two
examples below:
•

To write the half-word 0xABCD, the DMA controller sets the HWDATA bus to
0xABCDABCD with a half-word data size (HSIZE = HalfWord in AHB master bus).

•

To write the byte 0xAB, the DMA controller sets the HWDATA bus to 0xABABABAB
with a byte data size (HSIZE = Byte in the AHB master bus).

Assuming the AHB/APB bridge is an AHB 32-bit slave peripheral that does not take into
account the HSIZE data, any AHB byte or half-word transfer is changed into a 32-bit APB
transfer as described below:

11.4.6

•

An AHB byte write transfer of 0xB0 to one of the 0x0, 0x1, 0x2 or 0x3 addresses, is
converted to an APB word write transfer of 0xB0B0B0B0 to the 0x0 address.

•

An AHB half-word write transfer of 0xB1B0 to the 0x0 or 0x2 addresses, is converted to
an APB word write transfer of 0xB1B0B1B0 to the 0x0 address.

DMA error management
A DMA transfer error is generated when reading from or writing to a reserved address
space. When a DMA transfer error occurs during a DMA read or write access, the faulty
channel x is automatically disabled through a hardware clear of its EN bit in the
corresponding DMA_CCRx register.
The TEIFx bit of the DMA_ISR register is set. An interrupt is then generated if the TEIE bit of
the DMA_CCRx register is set.
The EN bit of the DMA_CCRx register can not be set again by software (channel x reactivated) until the TEIFx bit of the DMA_ISR register is cleared (by setting the CTEIFx bit of
the DMA_IFCR register).
When the software is notified with a transfer error over a channel which involves a
peripheral, the software has first to stop this peripheral in DMA mode, in order to disable any
pending or future DMA request. Then software may normally reconfigure both DMA and the
peripheral in DMA mode for a new transfer.

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11.5

RM0394

DMA interrupts
An interrupt can be generated on a half transfer, transfer complete or transfer error for each
DMA channel x. Separate interrupt enable bits are available for flexibility.
Table 44. DMA interrupt requests
Event flag

Interrupt
enable bit

Half transfer on channel x

HTIFx

HTIEx

Transfer complete on channel x

TCIFx

TCIEx

Transfer error on channel x

TEIFx

TEIEx

Half transfer or transfer complete or transfer error on channel x

GIFx

-

Interrupt request

Channel x interrupt

11.6

Interrupt event

DMA registers
Refer to Section 1.2 for a list of abbreviations used in register descriptions.
The DMA registers have to be accessed by words (32-bit).

11.6.1

DMA interrupt status register (DMA_ISR)
Address offset: 0x00
Reset value: 0x0000 0000
Every status bit is cleared by hardware when the software sets the corresponding clear bit
or the corresponding global clear bit CGIFx, in the DMA_IFCR register.

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.
Bit 27 TEIF7: transfer error (TE) flag for channel 7
0: no TE event
1: a TE event occurred
Bit 26 HTIF7: half transfer (HT) flag for channel 7
0: no HT event
1: a HT event occurred
Bit 25 TCIF7: transfer complete (TC) flag for channel 7
0: no TC event
1: a TC event occurred
Bit 24 GIF7: global interrupt flag for channel 7
0: no TE, HT or TC event
1: a TE, HT or TC event occurred

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Direct memory access controller (DMA)

Bit 23 TEIF6: transfer error (TE) flag for channel 6
0: no TE event
1: a TE event occurred
Bit 22 HTIF6: half transfer (HT) flag for channel 6
0: no HT event
1: a HT event occurred
Bit 21 TCIF6: transfer complete (TC) flag for channel 6
0: no TC event
1: a TC event occurred
Bit 20 GIF6: global interrupt flag for channel 6
0: no TE, HT or TC event
1: a TE, HT or TC event occurred
Bit 19 TEIF5: transfer error (TE) flag for channel 5
0: no TE event
1: a TE event occurred
Bit 18 HTIF5: half transfer (HT) flag for channel 5
0: no HT event
1: a HT event occurred
Bit 17 TCIF5: transfer complete (TC) flag for channel 5
0: no TC event
1: a TC event occurred
Bit 16 GIF5: global interrupt flag for channel 5
0: no TE, HT or TC event
1: a TE, HT or TC event occurred
Bit 15 TEIF4: transfer error (TE) flag for channel 4
0: no TE event
1: a TE event occurred
Bit 14 HTIF4: half transfer (HT) flag for channel 4
0: no HT event
1: a HT event occurred
Bit 13 TCIF4: transfer complete (TC) flag for channel 4
0: no TC event
1: a TC event occurred
Bit 12 GIF4: global interrupt flag for channel 4
0: no TE, HT or TC event
1: a TE, HT or TC event occurred
Bit 11 TEIF3: transfer error (TE) flag for channel 3
0: no TE event
1: a TE event occurred
Bit 10 HTIF3: half transfer (HT) flag for channel 3
0: no HT event
1: a HT event occurred
Bit 9 TCIF3: transfer complete (TC) flag for channel 3
0: no TC event
1: a TC event occurred

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Bit 8 GIF3: global interrupt flag for channel 3
0: no TE, HT or TC event
1: a TE, HT or TC event occurred
Bit 7 TEIF2: transfer error (TE) flag for channel 2
0: no TE event
1: a TE event occurred
Bit 6 HTIF2: half transfer (HT) flag for channel 2
0: no HT event
1: a HT event occurred
Bit 5 TCIF2: transfer complete (TC) flag for channel 2
0: no TC event
1: a TC event occurred
Bit 4 GIF2: global interrupt flag for channel 2
0: no TE, HT or TC event
1: a TE, HT or TC event occurred
Bit 3 TEIF1: transfer error (TE) flag for channel 1
0: no TE event
1: a TE event occurred
Bit 2 HTIF1: half transfer (HT) flag for channel 1
0: no HT event
1: a HT event occurred
Bit 1 TCIF1: transfer complete (TC) flag for channel 1
0: no TC event
1: a TC event occurred
Bit 0 GIF1: global interrupt flag for channel 1
0: no TE, HT or TC event
1: a TE, HT or TC event occurred

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Direct memory access controller (DMA)

11.6.2

DMA interrupt flag clear register (DMA_IFCR)
Address offset: 0x04
Reset value: 0x0000 0000
Setting the global clear bit CGIFx of the channel x in this DMA_IFCR register, causes the
DMA hardware to clear the corresponding GIFx bit and any individual flag among TEIFx,
HTIFx, TCIFx, in the DMA_ISR register.
Setting any individual clear bit among CTEIFx, CHTIFx, CTCIFx in this DMA_IFCR register,
causes the DMA hardware to clear the corresponding individual flag and the global flag
GIFx in the DMA_ISR register, provided that none of the two other individual flags is set.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

CTEIF7

CHTIF7

CTCIF7

CGIF7

CTEIF6

CHTIF6

CTCIF6

CGIF6

CTEIF5

CHTIF5

CTCIF5

CGIF5

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

CTEIF4

CHTIF4

CTCIF4

CGIF4

CTEIF3

CHTIF3

CTCIF3

CGIF3

CTEIF2

CHTIF2

CTCIF2

CGIF2

CTEIF1

CHTIF1

CTCIF1

CGIF1

Writing 0 into any flag clear bit has no effect.

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.
Bit 27 CTEIF7: transfer error flag clear for channel 7
Bit 26 CHTIF7: half transfer flag clear for channel 7
Bit 25 CTCIF7: transfer complete flag clear for channel 7
Bit 24 CGIF7: global interrupt flag clear for channel 7
Bit 23 CTEIF6: transfer error flag clear for channel 6
Bit 22 CHTIF6: half transfer flag clear for channel 6
Bit 21 CTCIF6: transfer complete flag clear for channel 6
Bit 20 CGIF6: global interrupt flag clear for channel 6
Bit 19 CTEIF5: transfer error flag clear for channel 5
Bit 18 CHTIF5: half transfer flag clear for channel 5
Bit 17 CTCIF5: transfer complete flag clear for channel 5
Bit 16 CGIF5: global interrupt flag clear for channel 5
Bit 15 CTEIF4: transfer error flag clear for channel 4
Bit 14 CHTIF4: half transfer flag clear for channel 4
Bit 13 CTCIF4: transfer complete flag clear for channel 4
Bit 12 CGIF4: global interrupt flag clear for channel 4
Bit 11 CTEIF3: transfer error flag clear for channel 3
Bit 10 CHTIF3: half transfer flag clear for channel 3
Bit 9 CTCIF3: transfer complete flag clear for channel 3

RM0394 Rev 4

311/1600
319

Direct memory access controller (DMA)

RM0394

Bit 8 CGIF3: global interrupt flag clear for channel 3
Bit 7 CTEIF2: transfer error flag clear for channel 2
Bit 6 CHTIF2: half transfer flag clear for channel 2
Bit 5 CTCIF2: transfer complete flag clear for channel 2
Bit 4 CGIF2: global interrupt flag clear for channel 2
Bit 3 CTEIF1: transfer error flag clear for channel 1
Bit 2 CHTIF1: half transfer flag clear for channel 1
Bit 1 CTCIF1: transfer complete flag clear for channel 1
Bit 0 CGIF1: global interrupt flag clear for channel 1

11.6.3

DMA channel x configuration register (DMA_CCRx)
Address offset: 0x08 + 0x14 * (x - 1), (x = 1 to 7)
Reset value: 0x0000 0000
The register fields/bits MEM2MEM, PL[1:0], MSIZE[1:0], PSIZE[1:0], MINC, PINC, and DIR
are read-only when EN = 1.
The states of MEM2MEM and CIRC bits must not be both high at the same time.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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
0: disabled
1: enabled
Note: this bit is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is read-only when the channel is enabled (EN = 1).
Bits 13:12 PL[1:0]: priority level
00: low
01: medium
10: high
11: very high
Note: this field is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is read-only when the channel is enabled (EN = 1).

312/1600

RM0394 Rev 4

RM0394

Direct memory access controller (DMA)

Bits 11:10 MSIZE[1:0]: memory size
Defines the data size of each DMA transfer to the identified memory.
In memory-to-memory mode, this field identifies the memory source if DIR = 1 and the
memory destination if DIR = 0.
In peripheral-to-peripheral mode, this field identifies the peripheral source if DIR = 1 and the
peripheral destination if DIR = 0.
00: 8 bits
01: 16 bits
10: 32 bits
11: reserved
Note: this field is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is read-only when the channel is enabled (EN = 1).
Bits 9:8 PSIZE[1:0]: peripheral size
Defines the data size of each DMA transfer to the identified peripheral.
In memory-to-memory mode, this field identifies the memory destination if DIR = 1 and the
memory source if DIR = 0.
In peripheral-to-peripheral mode, this field identifies the peripheral destination if DIR = 1 and
the peripheral source if DIR = 0.
00: 8 bits
01: 16 bits
10: 32 bits
11: reserved
Note: this field is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is read-only when the channel is enabled (EN = 1).
Bit 7 MINC: memory increment mode
Defines the increment mode for each DMA transfer to the identified memory.
In memory-to-memory mode, this field identifies the memory source if DIR = 1 and the
memory destination if DIR = 0.
In peripheral-to-peripheral mode, this field identifies the peripheral source if DIR = 1 and the
peripheral destination if DIR = 0.
0: disabled
1: enabled
Note: this bit is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is read-only when the channel is enabled (EN = 1).
Bit 6 PINC: peripheral increment mode
Defines the increment mode for each DMA transfer to the identified peripheral.
n memory-to-memory mode, this field identifies the memory destination if DIR = 1 and the
memory source if DIR = 0.
In peripheral-to-peripheral mode, this field identifies the peripheral destination if DIR = 1 and
the peripheral source if DIR = 0.
0: disabled
1: enabled
Note: this bit is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is read-only when the channel is enabled (EN = 1).

RM0394 Rev 4

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319

Direct memory access controller (DMA)

RM0394

Bit 5 CIRC: circular mode
0: disabled
1: enabled
Note: this bit is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is not read-only when the channel is enabled (EN = 1).
Bit 4 DIR: data transfer direction
This bit must be set only in memory-to-peripheral and peripheral-to-memory modes.
0: read from peripheral
–
Source attributes are defined by PSIZE and PINC, plus the DMA_CPARx register.
This is still valid in a memory-to-memory mode.
–
Destination attributes are defined by MSIZE and MINC, plus the DMA_CMARx
register. This is still valid in a peripheral-to-peripheral mode.
1: read from memory
–
Destination attributes are defined by PSIZE and PINC, plus the DMA_CPARx
register. This is still valid in a memory-to-memory mode.
–
Source attributes are defined by MSIZE and MINC, plus the DMA_CMARx register.
This is still valid in a peripheral-to-peripheral mode.
Note: this bit is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is read-only when the channel is enabled (EN = 1).
Bit 3 TEIE: transfer error interrupt enable
0: disabled
1: enabled
Note: this bit is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is not read-only when the channel is enabled (EN = 1).
Bit 2 HTIE: half transfer interrupt enable
0: disabled
1: enabled
Note: this bit is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is not read-only when the channel is enabled (EN = 1).
Bit 1 TCIE: transfer complete interrupt enable
0: disabled
1: enabled
Note: this bit is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is not read-only when the channel is enabled (EN = 1).
Bit 0 EN: channel enable
When a channel transfer error occurs, this bit is cleared by hardware. It can not be set again
by software (channel x re-activated) until the TEIFx bit of the DMA_ISR register is cleared (by
setting the CTEIFx bit of the DMA_IFCR register).
0: disabled
1: enabled
Note: this bit is set and cleared by software.

314/1600

RM0394 Rev 4

RM0394

Direct memory access controller (DMA)

11.6.4

DMA channel x number of data to transfer register (DMA_CNDTRx)
Address offset: 0x0C + 0x14 * (x - 1), (x = 1 to 7)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

NDT[15:0]
rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 NDT[15:0]: number of data to transfer (0 to 216 - 1)
This field is updated by hardware when the channel is enabled:
–
It is decremented after each single DMA ‘read followed by write’ transfer, indicating
the remaining amount of data items to transfer.
–
It is kept at zero when the programmed amount of data to transfer is reached, if the
channel is not in circular mode (CIRC = 0 in the DMA_CCRx register).
–
It is reloaded automatically by the previously programmed value, when the transfer
is complete, if the channel is in circular mode (CIRC = 1).
If this field is zero, no transfer can be served whatever the channel status (enabled or not).
Note: this field is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is read-only when the channel is enabled (EN = 1).

11.6.5

DMA channel x peripheral address register (DMA_CPARx)
Address offset: 0x10 + 0x14 * (x - 1), (x = 1 to 7)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

rw

rw

rw

rw

rw

rw

rw

rw

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

PA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

PA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0394 Rev 4

315/1600
319

Direct memory access controller (DMA)

RM0394

Bits 31:0 PA[31:0]: peripheral address
It contains the base address of the peripheral data register from/to which the data will be
read/written.
When PSIZE[1:0] = 01 (16 bits), bit 0 of PA[31:0] is ignored. Access is automatically aligned
to a half-word address.
When PSIZE = 10 (32 bits), bits 1 and 0 of PA[31:0] are ignored. Access is automatically
aligned to a word address.
In memory-to-memory mode, this register identifies the memory destination address if
DIR = 1 and the memory source address if DIR = 0.
In peripheral-to-peripheral mode, this register identifies the peripheral destination address
DIR = 1 and the peripheral source address if DIR = 0.
Note: this register is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is not read-only when the channel is enabled (EN = 1).

11.6.6

DMA channel x memory address register (DMA_CMARx)
Address offset: 0x14 + 0x14 * (x - 1), (x = 1 to 7)
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

MA[15:0]
rw

Bits 31:0 MA[31:0]: peripheral address
It contains the base address of the memory from/to which the data will be read/written.
When MSIZE[1:0] = 01 (16 bits), bit 0 of MA[31:0] is ignored. Access is automatically aligned
to a half-word address.
When MSIZE = 10 (32 bits), bits 1 and 0 of MA[31:0] are ignored. Access is automatically
aligned to a word address.
In memory-to-memory mode, this register identifies the memory source address if DIR = 1
and the memory destination address if DIR = 0.
In peripheral-to-peripheral mode, this register identifies the peripheral source address
DIR = 1 and the peripheral destination address if DIR = 0.
Note: this register is set and cleared by software.
It must not be written when the channel is enabled (EN = 1).
It is not read-only when the channel is enabled (EN = 1).

316/1600

RM0394 Rev 4

RM0394

Direct memory access controller (DMA)

11.6.7

DMA channel selection register (DMA_CSELR)
Address offset: 0xA8
Reset value: 0x0000 0000
This register is used to manage the mapping of DMA channels as detailed in Section 11.3.2:
DMA request mapping.

31

30

29

28

Res.

Res.

Res.

Res.

15

14

13

12

27

26

rw

rw

24

23

22

20

19

18

17

16

C5S[3:0]

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

11

10

9

8

7

6

5

4

3

2

1

0

C3S[3:0]
rw

21

C6S[3:0]

rw

C4S[3:0]
rw

25

C7S[3:0]

rw

rw

C2S[3:0]

rw

rw

rw

rw

C1S[3:0]

rw

rw

rw

rw

rw

rw

Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 C7S[3:0]: DMA channel 7 selection
Details available in Section 11.3.2: DMA request mapping
Bits 23:20 C6S[3:0]: DMA channel 6 selection
Details available in Section 11.3.2: DMA request mapping
Bits 19:16 C5S[3:0]: DMA channel 5 selection
Details available in Section 11.3.2: DMA request mapping
Bits 15:12 C4S[3:0]: DMA channel 4 selection
Details available in Section 11.3.2: DMA request mapping
Bits 11:8 C3S[3:0]: DMA channel 3 selection
Details available in Section 11.3.2: DMA request mapping
Bits 7:4 C2S[3:0]: DMA channel 2 selection
Details available in Section 11.3.2: DMA request mapping
Bits 3:0 C1S[3:0]: DMA channel 1 selection
Details available in Section 11.3.2: DMA request mapping

11.6.8

DMA register map and reset values
Table 45 gives the DMA register map and reset values.

TCIF1

GIF1
CGIF1

0

0

0

0

0

0

0
EN

HTIF1

CTCIF1

0

CHTIF1

0

0

TCIE

0

0

HTIE

GIF2

TEIF1

0

CTEIF1

0

TEIE

TCIF2

RM0394 Rev 4

0

0

0

CGIF2

0

0

DIR

HTIF2

Reset value

0

CTCIF2

0

CHTIF2

0

PINC

0

CIRC

GIF3

TEIF2

0

CTEIF2

0

MINC

TCIF3

0

0

0

0

0

0

0

0

0

PSIZE[1:0]

0

CGIF3

HTIF3

0

CTCIF3

0

MSIZE[1:0]

0

CHTIF3

GIF4

TEIF3

0

CTEIF3

TCIF4

0

PL[1:0]

0

CGIF4

HTIF4

0

CTCIF4

0

CHTIF4

0

MEM2MEM

GIF5

TEIF4

0

CTEIF4

0

Res.

TCIF5

0

CGIF5

0

Res.

HTIF5

0

CTCIF5

0

CHTIF5

0

Res.

0

Res.

GIF6

TEIF5

0

CTEIF5

0

Res.

TCIF6

0

CGIF6

0

Res.

HTIF6

0

CTCIF6

0

CHTIF6

0

Res.

0

Res.

GIF7

TEIF6

0

CTEIF6

0

Res.

TCIF7

0

CGIF7

0

Res.

HTIF7

0

CTCIF7

0

CHTIF7

0

Res.

0

Res.

Res.

0

CTEIF7

Res.

Res.

DMA_CCR1

Res.

0x008

Res.

Reset value

0

Res.

Res.

Res.

DMA_IFCR

Res.

0x004

Res.

Reset value

TEIF7

DMA_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

0x000

Register

Res.

Offset

Res.

Table 45. DMA register map and reset values

0

317/1600
319

Direct memory access controller (DMA)

RM0394

Res.

Reset value
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

318/1600

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PINC

DIR

TEIE

HTIE

TCIE

EN

0

CIRC

PSIZE[1:0]

MSIZE[1:0]

PL[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

MSIZE[1:0]

PL[1:0]

PSIZE[1:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CIRC

DIR

TEIE

HTIE

TCIE

EN

PSIZE[1:0]

MSIZE[1:0]

PL[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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

PINC

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

CIRC

DIR

TEIE

HTIE

TCIE

EN

MSIZE[1:0]

PSIZE[1:0]
0

PINC

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

PL[1:0]

MEM2MEM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reserved.

0

0

0

0

0

0

0

NDTR[15:0]
0

DMA_CPAR5
Reset value

0

MEM2MEM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.
0

Reset value
0x060

0

MA[31:0]

Res.

0x05C

0

MINC

0

Reset value
DMA_CNDTR5

0

PA[31:0]

Reserved
DMA_CCR5

0

NDTR[15:0]
0

Res.

0x058

0

Reserved.

DMA_CMAR4
Reset value

0

EN

0

Res.

0x054

0

TCIE

0

Res.

0x050

0

HTIE

0

DMA_CPAR4
Reset value

0

DIR

0

Reset value
0x04C

0

MA[31:0]

Res.

DMA_CNDTR4

0

TEIE

0

Reset value
0x048

0

CIRC

0

Reserved
DMA_CCR4

0

PINC

0

Res.

Reset value

0

MINC

0

Res.

0x044

0

DMA_CMAR3

Res.

0x040

0

PA[31:0]

Res.

0x03C

0

NDTR[15:0]
0

DMA_CPAR3
Reset value

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
0x038

0

MEM2MEM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

DMA_CNDTR3

Res.

Reset value
0x034

0

Reserved.
Res.

Reserved
DMA_CCR3

0

MA[31:0]

Res.

Reset value

0

MINC

0

Res.

0x030

0

DMA_CMAR2

Res.

0x02C

0

PA[31:0]

Res.

0x028

0

NDTR[15:0]
0

DMA_CPAR2
Reset value

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value
0x024

0

MEM2MEM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

Res.

Res.

0x020

0

0
Res.

Reset value
DMA_CNDTR2

0

Reserved.
Res.

Reserved
DMA_CCR2

0

Res.

Reset value

0

MA[31:0]

Res.

0x01C

0

DMA_CMAR1

Res.

0x018

Reset value

0

PA[31:0]

Res.

0x014

0

DMA_CPAR1

Res.

0x010

NDTR[15:0]

MINC

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA_CNDTR1

Res.

0x00C

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 45. DMA 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

PA[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

RM0394 Rev 4

0

0

0

RM0394

Direct memory access controller (DMA)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reset value

PSIZE[1:0]

MSIZE[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

CIRC

DIR

TEIE

HTIE

TCIE

EN

0

PINC

PSIZE[1:0]

MSIZE[1:0]

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PL[1:0]

MEM2MEM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.
Res.

Res.

Res.

0

0

0

0

0

0

0

0

NDTR[15:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

MA[31:0]
0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Reserved.
Res.

Reserved
DMA_CSELR

0

0

0

PA[31:0]

Res.

0x0A8

0

0

0

DMA_CMAR7
Reset value

0

Reserved.

Res.

0x090 to
0x0A4

0

EN

0

Res.

0x08C

0

TCIE

0

DMA_CPAR7
Reset value

0

HTIE

0

Reset value
0x088

0

MA[31:0]

Res.

0x084

0

DIR

0

Reset value
DMA_CNDTR7

0

TEIE

0

Reserved
DMA_CCR7

0

PINC

0

Res.

Reset value

0

CIRC

0

Res.

0x080

0

DMA_CMAR6

Res.

0x07C

0

PA[31:0]

Res.

0x078

0

NDTR[15:0]
0

DMA_CPAR6
Reset value

0

MINC

Reset value
0x074

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA_CNDTR6

Res.

Reset value
0x070

0

PL[1:0]

Res.

MEM2MEM

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

DMA_CCR6

0

Reserved.
Res.

Reserved

MINC

MA[31:0]
0

Res.

0x06C

Reset value

Res.

0x068

DMA_CMAR5

Res.

0x064

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 45. DMA register map and reset values (continued)

C7S[3:0]
0

0

0

C6S[3:0]
0

0

0

0

C5S[3:0]
0

0

0

0

C4S[3:0]
0

0

0

0

C3S[3:0]
0

0

C2S[3:0]
0

0

C1S[3:0]
0

0

0

Refer to Section 2.2.2 for register boundary addresses.

RM0394 Rev 4

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319

Nested vectored interrupt controller (NVIC)

12

Nested vectored interrupt controller (NVIC)

12.1

NVIC main features

RM0394

•

67 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
CortexTM-M4 products.

12.2

SysTick calibration value register
The SysTick calibration value is set to 0x4000270F, which gives a reference time base of
1 ms with the SysTick clock set to 10 MHz (max fHCLK/8).

320/1600

RM0394 Rev 4

RM0394

Nested vectored interrupt controller (NVIC)

12.3

Interrupt and exception vectors
The grey rows in Table 46 describe the vectors without specific position.
Refer to device datasheet for availability of each peripheral.

Position

Priority

Table 46. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx 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 classes 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

-

4

settable

Debug

Monitor

0x0000 0030

-

-

-

Reserved

0x0000 0034

-

5

settable

PendSV

Pendable request for system service

0x0000 0038

-

6

settable

SysTick

System tick timer

0x0000 003C

0

7

settable

WWDG

Window Watchdog interrupt

0x0000 0040

1

8

settable

PVD_PVM

PVD/PVM1/PVM2(1)/PVM3/PVM4 through
EXTI
lines 16/35/36/37/38 interrupts

0x0000 0044

2

9

settable

RTC_TAMP_STAMP RTC Tamper or TimeStamp /CSS on LSE
/CSS_LSE
through EXTI line 19 interrupts

3

10

settable

RTC_WKUP

RTC Wakeup timer through EXTI line 20
interrupt

0x0000 004C

4

11

settable

FLASH

Flash global interrupt

0x0000 0050

5

12

settable

RCC

RCC global interrupt

0x0000 005C

6

13

settable

EXTI0

EXTI Line0 interrupt

0x0000 005C

7

14

settable

EXTI1

EXTI Line1 interrupt

0x0000 005C

8

15

settable

EXTI2

EXTI Line2 interrupt

0x0000 0060

9

16

settable

EXTI3

EXTI Line3 interrupt

0x0000 0064

10

17

settable

EXTI4

EXTI Line4 interrupt

0x0000 0068

-

-

Reserved

RM0394 Rev 4

0x0000 001C 0x0000 0028

0x0000 0048

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Nested vectored interrupt controller (NVIC)

RM0394

Position

Priority

Table 46. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table (continued)
Type of
priority

11

18

settable

DMA1_CH1

DMA1 channel 1 interrupt

0x0000 006C

12

19

settable

DMA1_CH2

DMA1 channel 2 interrupt

0x0000 0070

13

20

settable

DMA1_CH3

DMA1 channel 3 interrupt

0x0000 0074

14

21

settable

DMA1_CH4

DMA1 channel 4 interrupt

0x0000 0078

15

22

settable

DMA1_CH5

DMA1 channel 5 interrupt

0x0000 007C

16

23

settable

DMA1_CH6

DMA1 channel 6 interrupt

0x0000 0080

17

24

settable

DMA1_CH7

DMA1 channel 7 interrupt

0x0000 0084

18

25

settable

Acronym

ADC1_2

ADC1 and ADC2

global interrupt

0x0000 0088
0x0000 008C

CAN1_RX0(1)

CAN1_RX0 interrupts

0x0000 0090

settable

CAN1_RX1(1)

CAN1_RX1 interrupt

0x0000 0094

(1)

CAN1_SCE interrupt

0x0000 0098

26

settable

CAN1_TX

20

27

settable

28

(1)

(2)

Address

CAN1_TX interrupts

19

21

Description

22

29

settable

CAN1_SCE

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

TIM1 trigger and commutation interrupt

0x0000 00A8

27

34

settable

TIM1_CC

TIM1 capture compare interrupt

0x0000 00AC

28

35

settable

TIM2

TIM2 global interrupt

0x0000 00B0

TIM3 global interrupt

0x0000 00B4

Reserved

0x0000 00B8

29

36

settable

30

37

settable

31

38

settable

I2C1_EV

I2C1 event interrupt

0x0000 00BC

32

39

settable

I2C1_ER

I2C1 error interrupt

0x0000 00C0

settable

I2C2_EV(4)

I2C2 event interrupt

0x0000 00C4

(4)

I2C2 error interrupt

0x0000 00C8

33

40

TIM3

(3)

-

34

41

settable

I2C2_ER

35

42

settable

SPI1

SPI1 global interrupt

0x0000 00CC

36

43

settable

SPI2(4)

SPI2 global interrupt

0x0000 00D0

37

44

settable

USART1

USART1 global interrupt

0x0000 00D4

38

45

settable

USART2

USART2 global interrupt

0x0000 00D8

(4)

39

46

settable

USART3

USART3 global interrupt

0x0000 00DC

40

47

settable

EXTI15_10

EXTI Line[15:10] interrupts

0x0000 00E0

41

48

settable

RTC_ALARM

RTC alarms through EXTI line 18 interrupts

0x0000 00E4

42

49

settable

-

Reserved

0x0000 00E8

43

50

settable

-

Reserved

0x0000 00EC

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RM0394 Rev 4

RM0394

Nested vectored interrupt controller (NVIC)

Position

Priority

Table 46. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table (continued)
Type of
priority

44

51

settable

-

Reserved

0x0000 00F0

45

52

settable

-

Reserved

0x0000 00F4

46

53

settable

-

Reserved

0x0000 00F8

47

54

settable

-

Reserved

0x0000 00FC

48

55

settable

-

Reserved

0x0000 0100

49

56

settable

SDMMC1 global interrupt

0x0000 0104

50

57

settable

Reserved

0x0000 0108

51

58

settable

SPI3 global interrupt

0x0000 010C

UART4 global interrupt

0x0000 0110

Reserved

0x0000 0114

52

59

settable

53

60

settable

54

61

settable

Acronym

Description

SDMMC1(4)(1)
SPI3
UART4

(3)

TIM6_DACUNDER
(5)

DAC1(1)

TIM6 global and

underrun interrupts

Address

0x0000 0118

TIM7 global interrupt

0x0000 011C

DMA2_CH1

DMA2 channel 1 interrupt

0x0000 0120

settable

DMA2_CH2

DMA2 channel 2 interrupt

0x0000 0124

65

settable

DMA2_CH3

DMA2 channel 3 interrupt

0x0000 0128

59

66

settable

DMA2_CH4

DMA2 channel 4 interrupt

0x0000 012C

60

67

settable

DMA2_CH5

DMA2 channel 5 interrupt

0x0000 0130

61

68

settable

DFSDM1_FLT0(3)

DFSDM1_FLT0 global interrupt

0x0000 0134

(3)

DFSDM1_FLT1 global interrupt

0x0000 0138

Reserved

0x0000 013C

55

62

settable

TIM7

56

63

settable

57

64

58

62

69

settable

63

70

settable

DFSDM1_FLT1
-

(1)

through EXTI lines 21/22

64

71

settable

COMP

COMP1/COMP2
interrupts

65

72

settable

LPTIM1

LPTIM1 global interrupt

0x0000 0144

66

73

settable

LPTIM2

LPTIM2 global interrupt

0x0000 0148

USB event interrupt through EXTI line 17

0x0000 014C

(6)

0x0000 0140

67

74

settable

USB_FS

68

75

settable

DMA2_CH6

DMA2 channel 6 interrupt

0x0000 0150

69

76

settable

DMA2_CH7

DMA2 channel 7 interrupt

0x0000 0154

70

77

settable

LPUART1

LPUART1 global interrupt

0x0000 0158

71

78

settable

QUADSPI

QUADSPI global interrupt

0x0000 015C

72

79

settable

I2C3_EV

I2C3 event interrupt

0x0000 0160

73

80

settable

I2C3_ER

I2C3 error interrupt

0x0000 0164

74

81

settable

SAI1(1)

SAI1 global interrupt

0x0000 0168

75

74

settable

Reserved

0x0000 016C

-

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Nested vectored interrupt controller (NVIC)

RM0394

Position

Priority

Table 46. STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx vector table (continued)
Type of
priority

76

75

settable

SWPMI1(5)

SWPMI1 global interrupt

0x0000 0170

77

76

settable

TSC

TSC global interrupt

0x0000 0174

settable

LCD(7)

LCD global interrupt

0x0000 0178

(8)

AES global interrupt

0x0000 017C

78

77

Acronym

Description

Address

79

78

settable

AES

80

79

settable

RNG

RNG global interrupt

0x0000 0180

81

88

settable

FPU

Floating point interrupt

0x0000 0184

82

89

settable

CRS

CRS interrupt

0x0000 0188

83

90

settable

I2C4_EV(3)

I2C4 event interrupt, wakeup through EXTI
line 40

0x0000 018C

84

91

settable

I2C4_ER(3)

I2C4 error interrupt

0x0000 0190

1. Not available on STM32L41xxx and STM32L42xxx devices.
2. Available on STM32L41xxx and ST32L42xxx devices only.
3. Available on STM32L45xxx and STM32L46xxx devices only.
4. Not available on STM32L432xx and STM32L442xx devices.
5. Available on STM32L43xxx and STM32L44xxx devices only.
6. Available on STM32L4x2xx and STM32L4x3xx devices only.
7. Available on STM32L4x3xx devices only.
8. Available on STM32L42xx, STM32L44xxx and STM32L46xxx devices only.

324/1600

RM0394 Rev 4

RM0394

Extended interrupts and events controller (EXTI)

13

Extended interrupts and events controller (EXTI)

13.1

Introduction
The EXTI main features are as follows:
•

13.2

Generation of up to 37 event/interrupt requests
–

25 configurable lines

–

12 direct lines

•

Independent mask on each event/interrupt line

•

Configurable rising or falling edge (configurable lines only)

•

Dedicated status bit (configurable lines only)

•

Emulation of event/interrupt requests (configurable lines only)

EXTI main features
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 Controller.
The EXTI allows the management of up to 38 event lines which can wake up from the Stop
0 and Stop 1 modes. Not all events can wake up from the Stop 2 mode (refer to Table 47:
EXTI lines connections).
The lines are either configurable or direct:
•

The lines are configurable: the active edge can be chosen independently, and a status
flag indicates the source of the interrupt. The configurable lines are used by the I/Os
external interrupts, and by few peripherals.

•

The lines are direct: they are used by some peripherals to generate a wakeup from
Stop event or interrupt. The status flag is provided by the peripheral.

Each line can be masked independently for an interrupt or an event generation.
This controller also allows to emulate events or interrupts by software, multiplexed with the
corresponding hardware event line, by writing to a dedicated register.

13.3

EXTI functional description
For the configurable interrupt lines, the interrupt line should be configured and enabled in
order to generate an interrupt. 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
interrupt line, an interrupt request is generated. The pending bit corresponding to the
interrupt line is also set. This request is cleared by writing a ‘1’ in the pending register.
For the direct interrupt lines, the interrupt is enabled by default in the interrupt mask register
and there is no corresponding pending bit in the pending register.
To generate an 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

RM0394 Rev 4

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Extended interrupts and events controller (EXTI)

RM0394

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 configurable 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 direct lines are triggered only when the system is
in Stop mode. If the system is still running, no interrupt/event is generated by the EXTI.

13.3.1

EXTI block diagram
The extended interrupt/event block diagram is shown on Figure 28.
Figure 28. Configurable interrupt/event block diagram
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13.3.2

Wakeup event management
The STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx is able to handle external or internal
events in order to wake up the core (WFE). The wakeup event can be generated either by:

326/1600

•

enabling an interrupt in the peripheral control register but not in the NVIC, and enabling
the SEVONPEND bit in the CortexTM-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 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.

RM0394 Rev 4

RM0394

13.3.3

Extended interrupts and events controller (EXTI)

Peripherals asynchronous Interrupts
Some peripherals 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.
To accomplish this, the peripheral generates both a synchronized (to the system clock, e.g.
APB clock) and an asynchronous version of the event. This asynchronous event is
connected to an EXTI direct line.

Note:

Few peripherals with wakeup from Stop capability are connected to an EXTI configurable
line. In this case, the EXTI configuration is necessary to allow the wakeup from Stop mode.

13.3.4

Hardware interrupt selection
To configure a line as an interrupt source, use the following procedure:
1.

Configure the corresponding mask bit in the EXTI_IMR register.

2.

Configure the Trigger Selection bits of the Interrupt line (EXTI_RTSR and EXTI_FTSR).

3.

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 lines can be correctly
acknowledged.

Note:

The direct lines do not require any EXTI configuration.

13.3.5

Hardware event selection
To configure a line as an event source, use the following procedure:

13.3.6

1.

Configure the corresponding mask bit in the EXTI_EMR register.

2.

Configure the Trigger Selection bits of the Event line (EXTI_RTSR and EXTI_FTSR).

Software interrupt/event selection
Any of the configurable lines can be configured as a software interrupt/event line. The
procedure to generate a software interrupt is as follows:

13.4

1.

Configure the corresponding mask bit (EXTI_IMR, EXTI_EMR).

2.

Set the required bit of the software interrupt register (EXTI_SWIER).

EXTI interrupt/event line mapping
In the STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx, 38 interrupt/event lines are available.
The GPIOs are connected to 16 configurable interrupt/event lines (see Figure 29).

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Extended interrupts and events controller (EXTI)

RM0394

Figure 29. External interrupt/event GPIO mapping
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The 38 lines are connected as shown in Table 47: EXTI lines connections.
Table 47. EXTI lines connections
EXTI line

Line source(1)

Line type

0-15

GPIO

configurable

16

PVD

17

328/1600

USB FS wakeup event

configurable
(3)(2)

direct

18

RTC alarms

configurable

19

RTC tamper or timestamp or
CSS_LSE

configurable

20

RTC wakeup timer

configurable

21

COMP1 output

configurable

22

COMP2 output

configurable

23

I2C1 wakeup(3)

direct

RM0394 Rev 4

RM0394

Extended interrupts and events controller (EXTI)
Table 47. EXTI lines connections (continued)
Line source(1)

EXTI line
24

I2C2 wakeup

25
26
27
28

I2C3 wakeup
USART1

USART3

direct
direct

wakeup(3)

direct

(3)

direct

USART2 wakeup

30
29

Line type

(3)(4)

wakeup(3)(4)
-

direct
-

UART4 wakeup

(3)(5)

direct

31

LPUART1 wakeup

direct

32

LPTIM1

direct

33

LPTIM2 (6)

direct

34

SWPMI1

wakeup(3)(7)

direct

35

PVM1 wakeup

configurable

36

-

-

37

PVM3 wakeup

configurable

38

PVM4 wakeup

configurable

39

(8)

direct

(5)

direct

LCD wakeup

40

I2C4 wakeup

1. All the lines can wake up from the Stop 0 and Stop 1 modes. All the lines, except the ones
mentioned above, can wake up from the Stop 2 mode.
2. Not available for STM32L431xx devices.
3. This line source cannot wake up from the Stop 2 mode.
4. Not available on STM32L432xx and STM32L442xx devices.
5. Available on STM32L45xxx and STM32L46xxx devices only.
6. This line can wake up from Stop 2 mode on STM32L41xxx and STM32L42xx devices only.
7. Available on STM32L43xxx and STM32L44xxx devices only.
8. Available on STM32L4x3 devices only.

RM0394 Rev 4

329/1600
337

Extended interrupts and events controller (EXTI)

13.5

RM0394

EXTI registers
Refer to Section 1.2 on page 60 for a list of abbreviations used in register descriptions.
The peripheral registers have to be accessed by words (32-bit).

13.5.1

Interrupt mask register 1 (EXTI_IMR1)
Address offset: 0x00
Reset value: 0xFF82 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

IM31

Res.

Res.

IM28

IM27

IM26

IM25

IM24

IM23

IM22

IM21

IM20

IM19

IM18

IM17

IM16

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

IM15

IM14

IM13

IM12

IM11

IM10

IM9

IM8

IM7

IM6

IM5

IM4

IM3

IM2

IM1

IM0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bit 31 IM31: Interrupt Mask on line 31
0: Interrupt request from Line 31 is masked
1: Interrupt request from Line 31 is not masked
Bits 30:29 Reserved, must be kept at reset value.
Bits 28:0 IMx: Interrupt Mask on line x (x = 28 to 0)
0: Interrupt request from Line x is masked
1: Interrupt request from Line x is not masked

Note:

The reset value for the direct lines (line 17, lines from 23 to 34, line 39) is set to ‘1’ in order
to enable the interrupt by default.

13.5.2

Event mask register 1 (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

EM31

Res.

Res.

EM28

EM27

EM26

EM25

EM24

EM23

EM22

EM21

EM20

EM19

EM18

EM17

EM16

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

EM15

EM14

EM13

EM12

EM11

EM10

EM9

EM8

EM7

EM6

EM5

EM4

EM3

EM2

EM1

EM0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

330/1600

RM0394 Rev 4

RM0394

Extended interrupts and events controller (EXTI)

Bit 31 EM31: Event mask on line 31
0: Event request from line 31 is masked
1: Event request from line 31 is not masked
Bits 30:29 Reserved, must be kept at reset value.
Bits 28:0 EMx: Event mask on line x (x = 28 to 0)
0: Event request from line x is masked
1: Event request from line x is not masked

13.5.3

Rising trigger selection register 1 (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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

RT22

RT21

RT20

RT19

RT18

Res.

RT16

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

RT15

RT14

RT13

RT12

RT11

RT10

RT9

RT8

RT7

RT6

RT5

RT4

RT3

RT2

RT1

RT0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:23 Reserved, must be kept at reset value.
Bits 22:18 RTx: Rising trigger event configuration bit of line x (x = 22 to 18)
0: Rising trigger disabled (for Event and Interrupt) for input line
1: Rising trigger enabled (for Event and Interrupt) for input line
Bit 17 Reserved, must be kept at reset value.
Bits 16:0 RTx: Rising trigger event configuration bit of line x (x = 16 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 configurable wakeup lines are edge-triggered. No glitch must be generated on these
lines. If a rising edge on a configurable 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.

13.5.4

Falling trigger selection register 1 (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

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

FT22

FT21

FT20

FT19

FT18

Res.

FT16

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

FT15

FT14

FT13

FT12

FT11

FT10

FT9

FT8

FT7

FT6

FT5

FT4

FT3

FT2

FT1

FT0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

RM0394 Rev 4

rw

331/1600
337

Extended interrupts and events controller (EXTI)

RM0394

Bits 31:23 Reserved, must be kept at reset value.
Bits 22:18 FTx: Falling trigger event configuration bit of line x (x = 22 to 18)
0: Falling trigger disabled (for Event and Interrupt) for input line
1: Falling trigger enabled (for Event and Interrupt) for input line
Bit 17 Reserved, must be kept at reset value.
Bits 16:0 FTx: Falling trigger event configuration bit of line x (x = 16 to 0)
0: Falling trigger disabled (for Event and Interrupt) for input line
1: Falling trigger enabled (for Event and Interrupt) for input line

Note:

The configurable wakeup lines are edge-triggered. No glitch must be generated on these
lines. If a falling edge on a configurable 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.

13.5.5

Software interrupt event register 1 (EXTI_SWIER1)
Address offset: 0x10
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

SWI
22

SWI
21

SWI
20

SWI
19

SWI
18

17

16

Res.

SWI
16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

SWI
15

SWI
14

SWI
13

SWI
12

SWI
11

SWI
10

SWI
9

SWI
8

SWI
7

SWI
6

SWI
5

SWI
4

SWI
3

SWI
2

SWI
1

SWI
0

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:23 Reserved, must be kept at reset value.
Bits 22: 18 SWIx: Software interrupt on line x (x = 22 o 18)
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).
Bit 17 Reserved, must be kept at reset value.
Bits 16:0 SWIx: Software interrupt on line x (x = 16 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).

332/1600

RM0394 Rev 4

RM0394

Extended interrupts and events controller (EXTI)

13.5.6

Pending register 1 (EXTI_PR1)
Address offset: 0x14
Reset value: undefined

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

PIF22

PIF21

PIF20

PIF19

PIF18

Res.

PIF16

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

PIF15

PIF14

PIF13

PIF12

PIF11

PIF10

PIF9

PIF8

PIF7

PIF6

PIF5

PIF4

PIF3

PIF2

PIF1

PIF0

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

rc_w1

Bits 31:23 Reserved, must be kept at reset value.
Bits 22:18 PIFx: Pending interrupt flag on line x (x = 22 to 18)
0: No trigger request occurred
1: Selected trigger request occurred
This bit is set when the selected edge event arrives on the interrupt line. This bit
is cleared by writing a ‘1’ to the bit.
Bit 17 Reserved, must be kept at reset value.
Bits 16:0 PIFx: Pending interrupt flag on line x (x = 16 to 0)
0: No trigger request occurred
1: Selected trigger request occurred
This bit is set when the selected edge event arrives on the interrupt line. This bit
is cleared by writing a ‘1’ to the bit.

13.5.7

Interrupt mask register 2 (EXTI_IMR2)
Address offset: 0x20
Reset value: 0x0000 0087

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

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

IM39

IM38

IM37

IM36

IM35

IM34

IM33

IM32

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value
Bits 7:0 IMx: Interrupt mask on line x (x = 39 to 32)
0: Interrupt request from line x is masked
1: Interrupt request from line x is not masked

Note:

The reset value for the direct lines (line 17, lines from 23 to 34, line 39,) is set to ‘1’ in order
to enable the interrupt by default.

RM0394 Rev 4

333/1600
337

Extended interrupts and events controller (EXTI)

13.5.8

RM0394

Event mask register 2 (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

EM39

EM38

EM37

EM36

EM35

EM34

EM33

EM32

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value
Bits 7:0 EMx: Event mask on line x (x = 39 to 32)
0: Event request from line x is masked
1: Event request from line x is not masked

13.5.9

Rising trigger selection register 2 (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.

RT38

RT37

RT36

RT35

Res.

Res.

Res.

rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:3 RTx: Rising trigger event configuration bit of line x (x = 35 to 38)
0: Rising trigger disabled (for Event and Interrupt) for input line
1: Rising trigger enabled (for Event and Interrupt) for input line
Bits 2:0 Reserved, must be kept at reset value.

Note:

The configurable wakeup lines are edge-triggered. No glitch must be generated on these
lines. If a rising edge on a configurable 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.

334/1600

RM0394 Rev 4

RM0394

Extended interrupts and events controller (EXTI)

13.5.10

Falling trigger selection register 2 (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.

FT38

FT37

FT36

FT35

Res.

Res.

Res.

rw

rw

rw

rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:3 FTx: Falling trigger event configuration bit of line x (x = 35 to 38)
0: Falling trigger disabled (for Event and Interrupt) for input line
1: Falling trigger enabled (for Event and Interrupt) for input line
Bits 2:0 Reserved, must be kept at reset value.

Note:

The configurable wakeup lines are edge-triggered. No glitch must be generated on these
lines. If a falling edge on a configurable 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.

13.5.11

Software interrupt event register 2 (EXTI_SWIER2)
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.

SWI
38

SWI
37

SWI
36

SWI
35

Res.

Res.

Res.

rw

rw

rw

rw

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 SWIx: Software interrupt on line x (x = 35 to 38)
If the interrupt is enabled on this line in EXTI_IMR, writing a '1' to this bit when it
is at '0' sets the corresponding pending bit of 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).
Bits 2:0 Reserved, must be kept at reset value.

RM0394 Rev 4

335/1600
337

Extended interrupts and events controller (EXTI)

13.5.12

RM0394

Pending register 2 (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.

PIF38

PIF37

PIF36

PIF35

Res.

Res.

Res.

rc_w1

rc_w1

rc_w1

rc_w1

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 PIFx: Pending interrupt flag on line x (x = 35 to 38)
0: No trigger request occurred
1: Selected trigger request occurred
This bit is set when the selected edge event arrives on the interrupt line. This bit
is cleared by writing a ‘1’ into the bit.
Bits 2:0 Reserved, must be kept at reset value.

336/1600

RM0394 Rev 4

0x34

EXTI_PR2

RM0394 Rev 4
EM32

PIF0

0
0

IM32

0
0
0
0

0
0
0
0
0
0
0
0
0
0
0

0
0
0
0
0
0
0
0
0
0
0

RT0

0
FT0

0

SWI0

0

EM1
EM0

0
0
0
0
0

0

0
0
0
0
0

0

0
0
0
0
0

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

IM3
IM2
IM1
IM0

0
0
0
0
0

0

Res.

0

RT1

0
FT1

0

EM2

0
EM3

IM6

0

RT2

IM7

0

RT3

IM8

0

IM5
IM4

IM9

0

RT5
RT4

IM11
IM10

0

FT2

EM6

RT6

IM12
0
EM5
EM4

EM7

RT7

IM13
0

FT3

FT6

EM8

RT8

IM14
0

FT5
FT4

FT7

EM9

RT9

IM15
0

SWI1

SWI6

FT8

IM16
0

SWI2

SWI7

FT9

RT10

IM17
1

SWI3

SWI8

EM10

0

RT11

IM18
0

SWI5
SWI4

SWI9

EM11

0

RT12

IM19
0

Res.

PIF1

0
IM33

0

Res.

FT10

EM12

0

RT13

IM20
0

Res.

EM33

PIF2

0

Res.

SWI10

FT11

EM13

0

RT14

IM21
0

Res.

PIF3

0
IM34

PIF5
PIF4

0
IM35

PIF6

0

Res.

SWI11

FT12

EM14

0

RT15

IM22
0

Res.

EM34

PIF7

0

Res.

SWI12

FT13

EM15

0

RT16

IM23
1

Res.

PIF8

0

Res.

SWI13

FT14

EM16

0

Res.

IM24
1

Res.

EM35

0

RT35

PIF9

0

IM36

PIF10

0

Res.

SWI14

FT15

EM17

0

Res.

IM25
1

Res.

FT35

EM36

0

RT36

PIF11

0

IM37

PIF12

0

Res.

SWI15

EM18

0

Res.

IM26
1

Res.

SWI35

0

PIF35

FT36

EM37

0

RT37

PIF13

0

IM38

PIF14

0

IM39

PIF15

0

Res.

FT16

EM19

0

Res.

IM27
1

Res.

SWI36

0

PIF36

FT37

EM38

0

RT38

EM39

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

SWI16

EM20

0

RT18

EM21

0

RT19

EM22

0

RT20

EM23

0

RT21

EM24

0

Res.

Res.
IM28

1

Res.

SWI37

Reset value

PIF37

Reset value
FT38

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

SWI38

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

PIF38

Reset value
PIF16

0

Res.

0

Res.

0

Res.

0

Res.

0
Res.

FT18

0

Res.

SWI18

FT19

0

Res.

PIF18

0

Res.

SWI19

FT20

0

Res.

PIF19

0

Res.

SWI20

FT21

0

Res.

PIF20

0

Res.

SWI21

0

Res.

PIF21

0

Res.

EM25

0

0

Res.

Res.

Res.

Res.

Res.

EM26

0

RT22

EM27

0

Res.

Res.
EM28

0

Res.

Res.

0

0

Res.

Res.

Res.

Res.

Res.

FT22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IM31

Res.

EM31

Res.

Res.

0

0

Res.

Res.

Res.

Res.

Res.

SWI22

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.

Res.

Res.

Res.

Res.

PIF22

Res.

Res.

Res.

Res.

Res.

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

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.

Reset value

Res.

Res.

Res.

Res.

EXTI_SWIER2

Res.

EXTI_FTSR2
Res.

EXTI_RTSR2

Res.

EXTI_EMR2

Res.

EXTI_IMR2
Res.

EXTI_PR1

Res.

0x30
EXTI_RTSR1

Res.

0x2C
0

Res.

0x28
Reset value

Res.

0x24
EXTI_EMR1

Res.

0x20
EXTI_SWIER1

Res.

0x14
1

Res.

0x10
EXTI_FTSR1

Res.

0x0C
Reset value

Res.

0x08

Res.

0x04
EXTI_IMR1

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.

13.5.13

Res.

RM0394
Extended interrupts and events controller (EXTI)

EXTI register map
Table 48 gives the EXTI register map and the reset values.

Table 48. Extended interrupt/event controller register map and reset values

1
0
0
0
0
1
1
1

337/1600

337

Cyclic redundancy check calculation unit (CRC)

14

Cyclic redundancy check calculation unit (CRC)

14.1

Introduction

RM0394

The CRC (cyclic redundancy check) calculation unit is used to get a CRC code from 8-, 16or 32-bit data word and a generator polynomial.
Among other applications, CRC-based techniques are used to verify data transmission or
storage integrity. In the scope of the functional safety standards, they offer a means of
verifying the Flash memory integrity. The CRC calculation unit helps compute a signature of
the software during runtime, to be compared with a reference signature generated at link
time and stored at a given memory location.

14.2

CRC main features
•

Uses CRC-32 (Ethernet) polynomial: 0x4C11DB7
X32 + X26 + X23 + X22 + X16 + X12 + X11 + X10 +X8 + X7 + X5 + X4 + X2+ X +1

338/1600

•

Alternatively, uses fully programmable polynomial with programmable size (7, 8, 16, 32
bits)

•

Handles 8-,16-, 32-bit data size

•

Programmable CRC initial value

•

Single input/output 32-bit data register

•

Input buffer to avoid bus stall during calculation

•

CRC computation done in 4 AHB clock cycles (HCLK) for the 32-bit data size

•

General-purpose 8-bit register (can be used for temporary storage)

•

Reversibility option on I/O data

RM0394 Rev 4

RM0394

Cyclic redundancy check calculation unit (CRC)

14.3

CRC functional description

14.3.1

CRC block diagram
Figure 30. CRC calculation unit block diagram
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14.3.2

CRC internal signals
Table 49. CRC internal input/output signals

14.3.3

Signal name

Signal type

crc_hclk

Digital input

Description
AHB clock

CRC operation
The CRC calculation unit has a single 32-bit read/write data register (CRC_DR). It is used to
input new data (write access), and holds the result of the previous CRC calculation (read
access).
Each write operation to the data register creates a combination of the previous CRC value
(stored in CRC_DR) and the new one. CRC computation is done on the whole 32-bit data
word or byte by byte depending on the format of the data being written.
The CRC_DR register can be accessed by word, right-aligned half-word and right-aligned
byte. For the other registers only 32-bit access is allowed.
The duration of the computation depends on data width:
•

4 AHB clock cycles for 32-bit

•

2 AHB clock cycles for 16-bit

•

1 AHB clock cycles for 8-bit

An input buffer allows to immediately write a second data without waiting for any wait states
due to the previous CRC calculation.
The data size can be dynamically adjusted to minimize the number of write accesses for a
given number of bytes. For instance, a CRC for 5 bytes can be computed with a word write
followed by a byte write.

RM0394 Rev 4

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Cyclic redundancy check calculation unit (CRC)

RM0394

The input data can be reversed, to manage the various endianness schemes. The reversing
operation can be performed on 8 bits, 16 bits and 32 bits depending on the REV_IN[1:0] bits
in the CRC_CR register.
For example: input data 0x1A2B3C4D is used for CRC calculation as:
•

0x58D43CB2 with bit-reversal done by byte

•

0xD458B23C with bit-reversal done by half-word

•

0xB23CD458 with bit-reversal done on the full word

The output data can also be reversed by setting the REV_OUT bit in the CRC_CR register.
The operation is done at bit level: for example, output data 0x11223344 is converted into
0x22CC4488.
The CRC calculator can be initialized to a programmable value using the RESET control bit
in the CRC_CR register (the default value is 0xFFFFFFFF).
The initial CRC value can be programmed with the CRC_INIT register. The CRC_DR
register is automatically initialized upon CRC_INIT register write access.
The CRC_IDR register can be used to hold a temporary value related to CRC calculation. It
is not affected by the RESET bit in the CRC_CR register.

Polynomial programmability
The polynomial coefficients are fully programmable through the CRC_POL register, and the
polynomial size can be configured to be 7, 8, 16 or 32 bits by programming the
POLYSIZE[1:0] bits in the CRC_CR register. Even polynomials are not supported.
If the CRC data is less than 32-bit, its value can be read from the least significant bits of the
CRC_DR register.
To obtain a reliable CRC calculation, the change on-fly of the polynomial value or size can
not be performed during a CRC calculation. As a result, if a CRC calculation is ongoing, the
application must either reset it or perform a CRC_DR read before changing the polynomial.
The default polynomial value is the CRC-32 (Ethernet) polynomial: 0x4C11DB7.

340/1600

RM0394 Rev 4

RM0394

Cyclic redundancy check calculation unit (CRC)

14.4

CRC registers

14.4.1

Data register (CRC_DR)
Address offset: 0x00
Reset value: 0xFFFF FFFF

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DR[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DR[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DR[31:0]: Data register bits
This register is used to write new data to the CRC calculator.
It holds the previous CRC calculation result when it is read.
If the data size is less than 32 bits, the least significant bits are used to write/read the
correct value.

14.4.2

Independent data register (CRC_IDR)
Address offset: 0x04
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

IDR[7:0]
rw

Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 IDR[7:0]: General-purpose 8-bit data register bits
These bits can be used as a temporary storage location for one byte.
This register is not affected by CRC resets generated by the RESET bit in the CRC_CR register

RM0394 Rev 4

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343

Cyclic redundancy check calculation unit (CRC)

14.4.3

RM0394

Control register (CRC_CR)
Address offset: 0x08
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

REV_
OUT

Res.

Res.

RESET

Res.

Res.

Res.

Res.

Res.

Res.

Res.

rw

REV_IN[1:0]
rw

rw

POLYSIZE[1:0]
rw

rw

rs

Bits 31:8 Reserved, must be kept at reset value.
Bit 7 REV_OUT: Reverse output data
This bit controls the reversal of the bit order of the output data.
0: Bit order not affected
1: Bit-reversed output format
Bits 6:5 REV_IN[1:0]: Reverse input data
These bits control the reversal of the bit order of the input data
00: Bit order not affected
01: Bit reversal done by byte
10: Bit reversal done by half-word
11: Bit reversal done by word
Bits 4:3 POLYSIZE[1:0]: Polynomial size
These bits control the size of the polynomial.
00: 32 bit polynomial
01: 16 bit polynomial
10: 8 bit polynomial
11: 7 bit polynomial
Bits 2:1 Reserved, must be kept at reset value.
Bit 0 RESET: RESET bit
This bit is set by software to reset the CRC calculation unit and set the data register to the value
stored in the CRC_INIT register. This bit can only be set, it is automatically cleared by hardware

14.4.4

Initial CRC value (CRC_INIT)
Address offset: 0x10
Reset value: 0xFFFF FFFF

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

CRC_INIT[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

CRC_INIT[15:0]
rw

342/1600

rw

rw

rw

rw

rw

rw

rw

rw

RM0394 Rev 4

RM0394

Cyclic redundancy check calculation unit (CRC)

Bits 31:0 CRC_INIT[31:0]: Programmable initial CRC value
This register is used to write the CRC initial value.

14.4.5

CRC polynomial (CRC_POL)
Address offset: 0x14
Reset value: 0x04C1 1DB7

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

POL[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

POL[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 POL[31:0]: Programmable polynomial
This register is used to write the coefficients of the polynomial to be used for CRC calculation.
If the polynomial size is less than 32 bits, the least significant bits have to be used to program the
correct value.

14.4.6

CRC register map

Offset

Register
name

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 50. CRC register map and reset values

CRC_DR

DR[31:0]
1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

CRC_IDR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Reset value

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

Res.

CRC_CR
0x08

Reset value

0x10

CRC_INIT
Reset value

0x14

1

1

1

1

1

1

1

0

0

0

IDR[7:0]

REV_OUT

0x04

1

Res.

1

RESET

1

0

0

0

0

Res.

1

POLYSIZE[1:0]

1

REV_IN[1:0]

Reset value

Res.

0x00

0

0

0

0

0

1

1

1

1

1

0

CRC_INIT[31:0]
1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

CRC_POL

Polynomial coefficients

Reset value

0x04C11DB7

1

1

1

1

1

1

1

1

Refer to Section 2.2.2 on page 67 for the register boundary addresses.

RM0394 Rev 4

343/1600
343

Quad-SPI interface (QUADSPI)

RM0394

15

Quad-SPI interface (QUADSPI)

15.1

Introduction
The QUADSPI is a specialized communication interface targeting single, dual or quad SPI
Flash memories. It can operate in any of the three following modes:
•

indirect mode: all the operations are performed using the QUADSPI registers

•

status polling mode: the external Flash memory status register is periodically read and
an interrupt can be generated in case of flag setting

•

memory-mapped mode: the external Flash memory is mapped to the device address
space and is seen by the system as if it was an internal memory

Both throughput and capacity can be increased two-fold using dual-flash mode, where two
Quad-SPI Flash memories are accessed simultaneously.

15.2

QUADSPI main features
•

Three functional modes: indirect, status-polling, and memory-mapped

•

Dual-flash mode, where 8 bits can be sent/received simultaneously by accessing two
Flash memories in parallel.

•

SDR and DDR support

•

Fully programmable opcode for both indirect and memory mapped mode

•

Fully programmable frame format for both indirect and memory mapped mode

•

Integrated FIFO for reception and transmission

•

8, 16, and 32-bit data accesses are allowed

•

DMA channel for indirect mode operations

•

Interrupt generation on FIFO threshold, timeout, operation complete, and access error

15.3

QUADSPI functional description

15.3.1

QUADSPI block diagram
Figure 31. QUADSPI block diagram when dual-flash mode is disabled
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344/1600

RM0394 Rev 4

RM0394

Quad-SPI interface (QUADSPI)
Figure 32. QUADSPI block diagram when dual-flash mode is enabled
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15.3.2

QUADSPI pins
Table 51 lists the QUADSPI pins, six for interfacing with a single Flash memory, or 10 to 11
for interfacing with two Flash memories (FLASH 1 and FLASH 2) in dual-flash mode.
Table 51. QUADSPI pins
Signal name

Signal type

Description

CLK

Digital output

Clock to FLASH 1 and FLASH 2

BK1_IO0/SO

Digital input/output

Bidirectional IO in dual/quad modes or serial output
in single mode, for FLASH 1

BK1_IO1/SI

Digital input/output

Bidirectional IO in dual/quad modes or serial input
in single mode, for FLASH 1

BK1_IO2

Digital input/output

Bidirectional IO in quad mode, for FLASH 1

BK1_IO3

Digital input/output

Bidirectional IO in quad mode, for FLASH 1

BK2_IO0/SO

Digital input/output

Bidirectional IO in dual/quad modes or serial output
in single mode, for FLASH 2

BK2_IO1/SI

Digital input/output

Bidirectional IO in dual/quad modes or serial input
in single mode, for FLASH 2

BK2_IO2

Digital input/output

Bidirectional IO in quad mode, for FLASH 2

BK2_IO3

Digital input/output

Bidirectional IO in quad mode, for FLASH 2

BK1_nCS

Digital output

Chip select (active low) for FLASH 1. Can also be
used for FLASH 2 if QUADSPI is always used in
dual-flash mode.

BK2_nCS

Digital output

Chip select (active low) for FLASH 2. Can also be
used for FLASH 1 if QUADSPI is always used in
dual-flash mode.

RM0394 Rev 4

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372

Quad-SPI interface (QUADSPI)

15.3.3

RM0394

QUADSPI command sequence
The QUADSPI communicates with the Flash memory using commands. Each command
can include 5 phases: instruction, address, alternate byte, dummy, data. Any of these
phases can be configured to be skipped, but at least one of the instruction, address,
alternate byte, or data phase must be present.
nCS falls before the start of each command and rises again after each command finishes.
Figure 33. An example of a read command in quad mode
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Instruction phase
During this phase, an 8-bit instruction, configured in INSTRUCTION field of
QUADSPI_CCR[7:0] register, is sent to the Flash memory, specifying the type of operation
to be performed.
Though most Flash memories can receive instructions only one bit at a time from the
IO0/SO signal (single SPI mode), the instruction phase can optionally send 2 bits at a time
(over IO0/IO1 in dual SPI mode) or 4 bits at a time (over IO0/IO1/IO2/IO3 in quad SPI
mode). This can be configured using the IMODE[1:0] field of QUADSPI_CCR[9:8] register.
When IMODE = 00, the instruction phase is skipped, and the command sequence starts
with the address phase, if present.

Address phase
In the address phase, 1-4 bytes are sent to the Flash memory to indicate the address of the
operation. The number of address bytes to be sent is configured in the ADSIZE[1:0] field of
QUADSPI_CCR[13:12] register. In indirect and automatic-polling modes, the address bytes
to be sent are specified in the ADDRESS[31:0] field of QUADSPI_AR register, while in
memory-mapped mode the address is given directly via the AHB (from the Cortex® or from
a DMA).
The address phase can send 1 bit at a time (over SO in single SPI mode), 2 bits at a time
(over IO0/IO1 in dual SPI mode), or 4 bits at a time (over IO0/IO1/IO2/IO3 in quad SPI
mode). This can be configured using the ADMODE[1:0] field of QUADSPI_CCR[11:10]
register.
When ADMODE = 00, the address phase is skipped, and the command sequence proceeds
directly to the next phase, if any.

346/1600

RM0394 Rev 4

RM0394

Quad-SPI interface (QUADSPI)

Alternate-bytes phase
In the alternate-bytes phase, 1-4 bytes are sent to the Flash memory, generally to control
the mode of operation. The number of alternate bytes to be sent is configured in the
ABSIZE[1:0] field of QUADSPI_CCR[17:16] register. The bytes to be sent are specified in
the QUADSPI_ABR register.
The alternate-bytes phase can send 1 bit at a time (over SO in single SPI mode), 2 bits at a
time (over IO0/IO1 in dual SPI mode), or 4 bits at a time (over IO0/IO1/IO2/IO3 in quad SPI
mode). This can be configured using the ABMODE[1:0] field of QUADSPI_CCR[15:14]
register.
When ABMODE = 00, the alternate-bytes phase is skipped, and the command sequence
proceeds directly to the next phase, if any.
There may be times when only a single nibble needs to be sent during the alternate-byte
phase rather than a full byte, such as when dual-mode is used and only two cycles are used
for the alternate bytes. In this case, firmware can use quad-mode (ABMODE = 11) and send
a byte with bits 7 and 3 of ALTERNATE set to ‘1’ (keeping the IO3 line high), and bits 6 and
2 set to ‘0’ (keeping the IO2 line low). In this case the upper two bits of the nibble to be sent
are placed in bits 4:3 of ALTERNATE while the lower two bits are placed in bits 1 and 0. For
example, if the nibble 2 (0010) is to be sent over IO0/IO1, then ALTERNATE should be set
to 0x8A (1000_1010).

Dummy-cycles phase
In the dummy-cycles phase, 1-31 cycles are given without any data being sent or received,
in order to allow the Flash memory the time to prepare for the data phase when higher clock
frequencies are used. The number of cycles given during this phase is specified in the
DCYC[4:0] field of QUADSPI_CCR[22:18] register. In both SDR and DDR modes, the
duration is specified as a number of full CLK cycles.
When DCYC is zero, the dummy-cycles phase is skipped, and the command sequence
proceeds directly to the data phase, if present.
The operating mode of the dummy-cycles phase is determined by DMODE.
In order to assure enough “turn-around” time for changing the data signals from output
mode to input mode, there must be at least one dummy cycle when using dual or quad
mode to receive data from the Flash memory.

Data phase
During the data phase, any number of bytes can be sent to, or received from the Flash
memory.
In indirect and automatic-polling modes, the number of bytes to be sent/received is specified
in the QUADSPI_DLR register.
In indirect write mode the data to be sent to the Flash memory must be written to the
QUADSPI_DR register, while in indirect read mode the data received from the Flash
memory is obtained by reading from the QUADSPI_DR register.
In memory-mapped mode, the data which is read is sent back directly over the AHB to the
Cortex or to a DMA.
The data phase can send/receive 1 bit at a time (over SO/SI in single SPI mode), 2 bits at a
time (over IO0/IO1 in dual SPI mode), or 4 bits at a time (over IO0/IO1/IO2/IO3 in quad SPI

RM0394 Rev 4

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372

Quad-SPI interface (QUADSPI)

RM0394

mode). This can be configured using the ABMODE[1:0] field of QUADSPI_CCR[15:14]
register.
When DMODE = 00, the data phase is skipped, and the command sequence finishes
immediately by raising nCS. This configuration must only be used in only indirect write
mode.

15.3.4

QUADSPI signal interface protocol modes
Single SPI mode
Legacy SPI mode allows just a single bit to be sent/received serially. In this mode, data is
sent to the Flash memory over the SO signal (whose I/O shared with IO0). Data received
from the Flash memory arrives via SI (whose I/O shared with IO1).
The different phases can each be configured separately to use this single bit mode by
setting the IMODE/ADMODE/ABMODE/DMODE fields (in QUADSPI_CCR) to 01.
In each phase which is configured in single mode:
•

IO0 (SO) is in output mode

•

IO1 (SI) is in input mode (high impedance)

•

IO2 is in output mode and forced to ‘0’ (to deactivate the “write protect” function)

•

IO3 is in output mode and forced to ‘1’ (to deactivate the “hold” function)

This is the case even for the dummy phase if DMODE = 01.

Dual SPI mode
In dual SPI mode, two bits are sent/received simultaneously over the IO0/IO1 signals.
The different phases can each be configured separately to use dual SPI mode by setting the
IMODE/ADMODE/ABMODE/DMODE fields of QUADSPI_CCR register to 10.
In each phase which is configured in dual mode:
•

IO0/IO1 are at high-impedance (input) during the data phase for read operations, and
outputs in all other cases

•

IO2 is in output mode and forced to ‘0’

•

IO3 is in output mode and forced to ‘1’

In the dummy phase when DMODE = 01, IO0/IO1 are always high-impedance.

Quad SPI mode
In quad SPI mode, four bits are sent/received simultaneously over the IO0/IO1/IO2/IO3
signals.
The different phases can each be configured separately to use quad SPI mode by setting
the IMODE/ADMODE/ABMODE/DMODE fields of QUADSPI_CCR register to 11.
In each phase which is configured in quad mode, IO0/IO1/IO2/IO3 are all are at highimpedance (input) during the data phase for read operations, and outputs in all other cases.
In the dummy phase when DMODE = 11, IO0/IO1/IO2/IO3 are all high-impedance.
IO2 and IO3 are used only in Quad SPI mode. If none of the phases are configured to use
Quad SPI mode, then the pins corresponding to IO2 and IO3 can be used for other functions
even while QUADSPI is active.

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Quad-SPI interface (QUADSPI)

SDR mode
By default, the DDRM bit (QUADSPI_CCR[31]) is 0 and the QUADSPI operates in single
data rate (SDR) mode.
In SDR mode, when the QUADSPI is driving the IO0/SO, IO1, IO2, IO3 signals, these
signals transition only with the falling edge of CLK.
When receiving data in SDR mode, the QUADSPI assumes that the Flash memories also
send the data using CLK’s falling edge. By default (when SSHIFT = 0), the signals are
sampled using the following (rising) edge of CLK.

DDR mode
When the DDRM bit (QUADSPI_CCR[31]) is set to 1, the QUADSPI operates in double data
rate (DDR) mode.
In DDR mode, when the QUADSPI is driving the IO0/SO, IO1, IO2, IO3 signals in the
address/alternate-byte/data phases, a bit is sent on each of the falling and rising edges of
CLK.
The instruction phase is not affected by DDRM. The instruction is always sent using CLK’s
falling edge.
When receiving data in DDR mode, the QUADSPI assumes that the Flash memories also
send the data using both rising and falling CLK edges. When DDRM = 1, firmware must
clear SSHIFT bit (bit 4 of QUADSPI_CR). Thus, the signals are sampled one half of a CLK
cycle later (on the following, opposite edge).
Figure 34. An example of a DDR command in quad mode
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Dual-flash mode
When the DFM bit (bit 6 of QUADSPI_CR) is 1, the QUADSPI is in dual-flash mode, where
two external quad SPI Flash memories (FLASH 1 and FLASH 2) are used in order to
send/receive 8 bits (or 16 bits in DDR mode) every cycle, effectively doubling the throughput
as well as the capacity.
Each of the Flash memories use the same CLK and optionally the same nCS signals, but
each have separate IO0, IO1, IO2, and IO3 signals.
Dual-flash mode can be used in conjunction with single-bit, dual-bit, and quad-bit modes, as
well as with either SDR or DDR mode.

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The Flash memory size, as specified in FSIZE[4:0] (QUADSPI_DCR[20:16]), should reflect
the total Flash memory capacity, which is double the size of one individual component.
If address X is even, then the byte which the QUADSPI gives for address X is the byte at the
address X/2 of FLASH 1, and the byte which the QUADSPI gives for address X+1 is the
byte at the address X/2 of FLASH 2. In other words, bytes at even addresses are all stored
in FLASH 1 and bytes at odd addresses are all stored in FLASH 2.
When reading the Flash memories status registers in dual-flash mode, twice as many bytes
should be read compared to doing the same read in single-flash mode. This means that if
each Flash memory gives 8 valid bits after the instruction for fetching the status register,
then the QUADSPI must be configured with a data length of 2 bytes (16 bits), and the
QUADSPI will receive one byte from each Flash memory. If each Flash memory gives a
status of 16 bits, then the QUADSPI must be configured to read 4 bytes to get all the status
bits of both Flash memories in dual-flash mode. The least-significant byte of the result (in
the data register) is the least-significant byte of FLASH 1 status register, while the next byte
is the least-significant byte of FLASH 2 status register. Then, the third byte of the data
register is FLASH 1 second byte, while the forth byte is FLASH 2 second byte (in the case
that the Flash memories have 16-bit status registers).
An even number of bytes must always be accessed in dual-flash mode. For this reason, bit
0 of the data length field (QUADSPI_DLR[0]) is stuck at 1 when DRM = 1.
In dual-flash mode, the behavior of FLASH 1 interface signals are basically the same as in
normal mode. FLASH 2 interface signals have exactly the same waveforms as FLASH 1
during the instruction, address, alternate-byte, and dummy-cycles phases. In other words,
each Flash memory always receives the same instruction and the same address. Then,
during the data phase, the BK1_IOx and BK2_IOx buses are both transferring data in
parallel, but the data that are sent to (or received from) FLASH 1 are distinct from those of
FLASH 2.

15.3.5

QUADSPI indirect mode
When in indirect mode, commands are started by writing to QUADSPI registers and data is
transferred by writing or reading the data register, in the same way as for other
communication peripherals.
When FMODE = 00 (QUADSPI_CCR[27:26]), the QUADSPI is in indirect write mode,
where bytes are sent to the Flash memory during the data phase. Data are provided by
writing to the data register (QUADSPI_DR).
When FMODE = 01, the QUADSPI is in indirect read mode, where bytes are received from
the Flash memory during the data phase. Data are recovered by reading QUADSPI_DR.
The number of bytes to be read/written is specified in the data length register
(QUADSPI_DLR). If QUADSPI_DLR = 0xFFFF_FFFF (all 1’s), then the data length is
considered undefined and the QUADSPI simply continues to transfer data until the end of
Flash memory (as defined by FSIZE) is reached. If no bytes are to be transferred, DMODE
(QUADSPI_CCR[25:24]) should be set to 00.
If QUADSPI_DLR = 0xFFFF_FFFF and FSIZE = 0x1F (max value indicating a 4GB Flash
memory), then in this special case the transfers continue indefinitely, stopping only after an
abort request or after the QUADSPI is disabled. After the last memory address is read (at
address 0xFFFF_FFFF), reading continues with address = 0x0000_0000.
When the programmed number of bytes to be transmitted or received is reached, TCF is set
and an interrupt is generated if TCIE = 1. In the case of undefined number of data, the TCF

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Quad-SPI interface (QUADSPI)
is set when the limit of the external SPI memory is reached according to the Flash memory
size defined in the QUADSPI_CR.

Triggering the start of a command
Essentially, a command starts as soon as firmware gives the last information that is
necessary for this command. Depending on the QUADSPI configuration, there are three
different ways to trigger the start of a command in indirect mode. The commands starts
immediately after:
1.

a write is performed to INSTRUCTION[7:0] (QUADSPI_CCR), if no address is
necessary (when ADMODE = 00) and if no data needs to be provided by the firmware
(when FMODE = 01 or DMODE = 00)

2.

a write is performed to ADDRESS[31:0] (QUADSPI_AR), if an address is necessary
(when ADMODE != 00) and if no data needs to be provided by the firmware (when
FMODE = 01 or DMODE = 00)

3.

a write is performed to DATA[31:0] (QUADSPI_DR), if an address is necessary (when
ADMODE != 00) and if data needs to be provided by the firmware (when FMODE = 00
and DMODE != 00)

Writes to the alternate byte register (QUADSPI_ABR) never trigger the communication start.
If alternate bytes are required, they must be programmed before.
As soon as a command is started, the BUSY bit (bit 5 of QUADSPI_SR) is automatically set.

FIFO and data management
In indirect mode, data go through a 16-byte FIFO which is internal to the QUADSPI.
FLEVEL[4:0] (QUADSPI_SR[12:8]) indicates how many bytes are currently being held in
the FIFO.
In indirect write mode (FMODE = 00), firmware adds data to the FIFO when it writes
QUADSPI_DR. Word writes add 4 bytes to the FIFO, halfword writes add 2 bytes, and byte
writes add only 1 byte. If firmware adds too many bytes to the FIFO (more than is indicated
by DL[31:0]), the extra bytes are flushed from the FIFO at the end of the write operation
(when TCF is set).
Byte/halfword accesses to QUADSPI_DR must be done only to the least significant
byte/halfword of the 32-bit register.
FTHRES[3:0] is used to define a FIFO threshold. When the threshold is reached, the FTF
(FIFO threshold flag) is set. In indirect read mode, FTF is set when the number of valid
bytes to be read from the FIFO is above the threshold. FTF is also set if there are data in the
FIFO after the last byte is read from the Flash memory, regardless of the FTHRES setting.
In indirect write mode, FTF is set when the number of empty bytes in the FIFO is above the
threshold.
If FTIE = 1, there is an interrupt when FTF is set. If DMAEN = 1, a DMA transfer is initiated
when FTF is set. FTF is cleared by HW as soon as the threshold condition is no longer true
(after enough data has been transferred by the CPU or DMA).
In indirect read mode when the FIFO becomes full, the QUADSPI temporarily stops reading
bytes from the Flash memory to avoid an overrun. Note that the reading of the Flash
memory does not restart until 4 bytes become vacant in the FIFO (when FLEVEL ≤ 11).
Thus, when FTHRES ≥ 13, the application must take care to read enough bytes to assure
that the QUADSPI starts retrieving data from the Flash memory again. Otherwise, the FTF
flag stays at '0' as long as 11 < FLEVEL < FTHRES.

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15.3.6

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QUADSPI status flag polling mode
In automatic-polling mode, the QUADSPI periodically starts a command to read a defined
number of status bytes (up to 4). The received bytes can be masked to isolate some status
bits and an interrupt can be generated when the selected bits have a defined value.
The accesses to the Flash memory begin in the same way as in indirect read mode: if no
address is required (AMODE = 00), accesses begin as soon as the QUADSPI_CCR is
written. Otherwise, if an address is required, the first access begins when QUADSPI_AR is
written. BUSY goes high at this point and stays high even between the periodic accesses.
The contents of MASK[31:0] (QUADSPI_PSMAR) are used to mask the data from the Flash
memory in automatic-polling mode. If the MASK[n] = 0, then bit n of the result is masked
and not considered. If MASK[n] = 1, and the content of bit[n] is the same as MATCH[n]
(QUADSPI_PSMAR), then there is a match for bit n.
If the polling match mode bit (PMM, bit 23 of QUADSPI_CR) is 0, then “AND” match mode is
activated. This means status match flag (SMF) is set only when there is a match on all of the
unmasked bits.
If PMM = 1, then “OR” match mode is activated. This means SMF is set if there is a match
on any of the unmasked bits.
An interrupt is called when SMF is set if SMIE = 1.
If the automatic-polling-mode-stop (APMS) bit is set, operation stops and BUSY goes to 0
as soon as a match is detected. Otherwise, BUSY stays at ‘1’ and the periodic accesses
continue until there is an abort or the QUADSPI is disabled (EN = 0).
The data register (QUADSPI_DR) contains the latest received status bytes (the FIFO is
deactivated). The content of the data register is not affected by the masking used in the
matching logic. The FTF status bit is set as soon as a new reading of the status is complete,
and FTF is cleared as soon as the data is read.

15.3.7

QUADSPI memory-mapped mode
When configured in memory-mapped mode, the external SPI device is seen as an internal
memory.
It is forbidden to access QUADSPI Flash bank area before having properly configured and
enabled the QUADSPI peripheral.
No more than 256MB can addressed even if the Flash memory capacity is larger.
If an access is made to an address outside of the range defined by FSIZE but still within the
256MB range, then a bus error is given. The effect of this error depends on the bus master
that attempted the access:
•

If it is the Cortex® CPU, bus fault exception is generated when enabled (or a hard fault
exception when bus fault is disabled)

•

If it is a DMA, a DMA transfer error is generated and the corresponding DMA channel is
automatically disabled.

Byte, halfword, and word access types are all supported.
Support for execute in place (XIP) operation is implemented, where the QUADSPI
anticipates the next access and load in advance the byte at the following address. If the
subsequent access is indeed made at a continuous address, the access will be completed
faster since the value is already prefetched.

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Quad-SPI interface (QUADSPI)
By default, the QUADSPI never stops its prefetch operation, keeping the previous read
operation active with nCS maintained low, even if no access to the Flash memory occurs for
a long time. Since Flash memories tend to consume more when nCS is held low, the
application might want to activate the timeout counter (TCEN = 1, bit 3 of QUADSPI_CR) so
that nCS is released after a period of TIMEOUT[15:0] (QUADSPI_LPTR) cycles have
elapsed without any access since when the FIFO becomes full with prefetch data.
BUSY goes high as soon as the first memory-mapped access occurs. Because of the
prefetch operations, BUSY does not fall until there is a timeout, there is an abort, or the
peripheral is disabled.

15.3.8

QUADSPI Flash memory configuration
The device configuration register (QUADSPI_DCR) can be used to specify the
characteristics of the external SPI Flash memory.
The FSIZE[4:0] field defines the size of external memory using the following formula:
Number of bytes in Flash memory = 2[FSIZE+1]
FSIZE+1 is effectively the number of address bits required to address the Flash memory.
The Flash memory capacity can be up to 4GB (addressed using 32 bits) in indirect mode,
but the addressable space in memory-mapped mode is limited to 256MB.
If DFM = 1, FSIZE indicates the total capacity of the two Flash memories together.
When the QUADSPI executes two commands, one immediately after the other, it raises the
chip select signal (nCS) high between the two commands for only one CLK cycle by default.
If the Flash memory requires more time between commands, the chip select high time
(CSHT) field can be used to specify the minimum number of CLK cycles (up to 8) that nCS
must remain high.
The clock mode (CKMODE) bit indicates the CLK signal logic level in between commands
(when nCS = 1).

15.3.9

QUADSPI delayed data sampling
By default, the QUADSPI samples the data driven by the Flash memory one half of a CLK
cycle after the Flash memory drives the signal.
In case of external signal delays, it may be beneficial to sample the data later. Using the
SSHIFT bit (bit 4 of QUADSPI_CR), the sampling of the data can be shifted by half of a CLK
cycle.
Clock shifting is not supported in DDR mode: the SSHIFT bit must be clear when DDRM bit
is set.

15.3.10

QUADSPI configuration
The QUADSPI configuration is done in two phases:
•

QUADSPI IP configuration

•

QUADSPI Flash memory configuration

Once configured and enabled, the QUADSPI can be used in one of its three operating
modes: indirect mode, status-polling mode, or memory-mapped mode.
QUADSPI IP configuration

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The QUADSPI IP is configured using the QUADSPI_CR. The user shall configure the clock
prescaler division factor and the sample shifting settings for the incoming data.
DDR mode can be set through the DDRM bit. Once enabled, the address and the alternate
bytes are sent on both clock edges and the data are sent/received on both clock edges.
Regardless of the DDRM bit setting, instructions are always sent in SDR mode.
The DMA requests are enabled setting the DMAEN bit. In case of interrupt usage, their
respective enable bit can be also set during this phase.
FIFO level for either DMA request generation or interrupt generation is programmed in the
FTHRES bits.
If timeout counter is needed, the TCEN bit can be set and the timeout value programmed in
the QUADSPI_LPTR register.
Dual-flash mode can be activated by setting DFM to 1.

QUADSPI Flash memory configuration
The parameters related to the targeted external Flash memory are configured through the
QUADSPI_DCR register.The user shall program the Flash memory size in the FSIZE bits,
the Chip Select minimum high time in the CSHT bits, and the functional mode (Mode 0 or
Mode 3) in the MODE bit.

15.3.11

QUADSPI usage
The operating mode is selected using FMODE[1:0] (QUADSPI_CCR[27:26]).

Indirect mode procedure
When FMODE is programmed to 00, indirect write mode is selected and data can be sent to
the Flash memory. With FMODE = 01, indirect read mode is selected where data can be
read from the Flash memory.
When the QUADSPI is used in indirect mode, the frames are constructed in the following
way:
1.

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Specify a number of data bytes to read or write in the QUADSPI_DLR.

2.

Specify the frame format, mode and instruction code in the QUADSPI_CCR.

3.

Specify optional alternate byte to be sent right after the address phase in the
QUADSPI_ABR.

4.

Specify the operating mode in the QUADSPI_CR. If FMODE = 00 (indirect write mode)
and DMAEN = 1, then QUADSPI_AR should be specified before QUADSPI_CR,
because otherwise QUADSPI_DR might be written by the DMA before QUADSPI_AR
is updated (if the DMA controller has already been enabled)

5.

Specify the targeted address in the QUADSPI_AR.

6.

Read/Write the data from/to the FIFO through the QUADSPI_DR.

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Quad-SPI interface (QUADSPI)
When writing the control register (QUADSPI_CR) the user specifies the following settings:
•

The enable bit (EN) set to ‘1’

•

The DMA enable bit (DMAEN) for transferring data to/from RAM

•

Timeout counter enable bit (TCEN)

•

Sample shift setting (SSHIFT)

•

FIFO threshold level (FTRHES) to indicate when the FTF flag should be set

•

Interrupt enables

•

Automatic polling mode parameters: match mode and stop mode (valid when
FMODE = 11)

•

Clock prescaler

When writing the communication configuration register (QUADSPI_CCR) the user specifies
the following parameters:
•

The instruction byte through the INSTRUCTION bits

•

The way the instruction has to be sent through the IMODE bits (1/2/4 lines)

•

The way the address has to be sent through the ADMODE bits (None/1/2/4 lines)

•

The address size (8/16/24/32-bit) through the ADSIZE bits

•

The way the alternate bytes have to be sent through the ABMODE (None/1/2/4 lines)

•

The alternate bytes number (1/2/3/4) through the ABSIZE bits

•

The presence or not of dummy bytes through the DBMODE bit

•

The number of dummy bytes through the DCYC bits

•

The way the data have to be sent/received (None/1/2/4 lines) through the DMODE bits

If neither the address register (QUADSPI_AR) nor the data register (QUADSPI_DR) need to
be updated for a particular command, then the command sequence starts as soon as
QUADSPI_CCR is written. This is the case when both ADMODE and DMODE are 00, or if
just ADMODE = 00 when in indirect read mode (FMODE = 01).
When an address is required (ADMODE is not 00) and the data register does not need to be
written (when FMODE = 01 or DMODE = 00), the command sequence starts as soon as the
address is updated with a write to QUADSPI_AR.
In case of data transmission (FMODE = 00 and DMODE! = 00), the communication start is
triggered by a write in the FIFO through QUADSPI_DR.

Status flag polling mode
The status flag polling mode is enabled setting the FMODE field (QUADSPI_CCR[27:26]) to
10. In this mode, the programmed frame will be sent and the data retrieved periodically.
The maximum amount of data read in each frame is 4 bytes. If more data is requested in
QUADSPI_DLR, it will be ignored and only 4 bytes will be read.
The periodicity is specified in the QUADSPI_PISR register.
Once the status data has been retrieved, it can internally be processed i order to:
•

set the status match flag and generate an interrupt if enabled

•

stop automatically the periodic retrieving of the status bytes

The received value can be masked with the value stored in the QUADSPI_PSMKR and
ORed or ANDed with the value stored in the QUADSPI_PSMAR.

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In case of match, the status match flag is set and an interrupt is generated if enabled, and
the QUADSPI can be automatically stopped if the AMPS bit is set.
In any case, the latest retrieved value is available in the QUADSPI_DR.

Memory-mapped mode
In memory-mapped mode, the external Flash memory is seen as internal memory but with
some latency during accesses. Only read operations are allowed to the external Flash
memory in this mode.
Memory-mapped mode is entered by setting the FMODE to 11 in the QUADSPI_CCR
register.
The programmed instruction and frame is sent when a master is accessing the memory
mapped space.
The FIFO is used as a prefetch buffer to anticipate linear reads. Any access to
QUADSPI_DR in this mode returns zero.
The data length register (QUADSPI_DLR) has no meaning in memory-mapped mode.

15.3.12

Sending the instruction only once
Some Flash memories (e.g. Winbound) might provide a mode where an instruction must be
sent only with the first command sequence, while subsequent commands start directly with
the address. One can take advantage of such a feature using the SIOO bit
(QUADSPI_CCR[28]).
SIOO is valid for all functional modes (indirect, automatic polling, and memory-mapped). If
the SIOO bit is set, the instruction is sent only for the first command following a write to
QUADSPI_CCR. Subsequent command sequences skip the instruction phase, until there is
a write to QUADSPI_CCR.
SIOO has no effect when IMODE = 00 (no instruction).

15.3.13

QUADSPI error management
An error can be generated in the following case:

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•

In indirect mode or status flag polling mode when a wrong address has been
programmed in the QUADSPI_AR (according to the Flash memory size defined by
FSIZE[4:0] in the QUADSPI_DCR): this will set the TEF and an interrupt is generated if
enabled.

•

Also in indirect mode, if the address plus the data length exceeds the Flash memory
size, TEF will be set as soon as the access is triggered.

•

In memory-mapped mode, when an out of range access is done by a master or when
the QUADSPI is disabled: this will generate a bus error as a response to the faulty bus
master request.

•

When a master is accessing the memory mapped space while the memory mapped
mode is disabled: this will generate a bus error as a response to the faulty bus master
request.

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15.3.14

Quad-SPI interface (QUADSPI)

QUADSPI busy bit and abort functionality
Once the QUADSPI starts an operation with the Flash memory, the BUSY bit is
automatically set in the QUADSPI_SR.
In indirect mode, the BUSY bit is reset once the QUADSPI has completed the requested
command sequence and the FIFO is empty.
In automatic-polling mode, BUSY goes low only after the last periodic access is complete,
due to a match when APMS = 1, or due to an abort.
After the first access in memory-mapped mode, BUSY goes low only on a timeout event or
on an abort.
Any operation can be aborted by setting the ABORT bit in the QUADSPI_CR. Once the
abort is completed, the BUSY bit and the ABORT bit are automatically reset, and the FIFO
is flushed.

Note:

Some Flash memories might misbehave if a write operation to a status registers is aborted.

15.3.15

nCS behavior
By default, nCS is high, deselecting the external Flash memory. nCS falls before an
operation begins and rises as soon as it finishes.
When CKMODE = 0 (“mode0”, where CLK stays low when no operation is in progress) nCS
falls one CLK cycle before an operation first rising CLK edge, and nCS rises one CLK cycle
after the operation final rising CLK edge, as shown in Figure 35.
Figure 35. nCS when CKMODE = 0 (T = CLK period)
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When CKMODE=1 (“mode3”, where CLK goes high when no operation is in progress) and
DDRM=0 (SDR mode), nCS still falls one CLK cycle before an operation first rising CLK
edge, and nCS rises one CLK cycle after the operation final rising CLK edge, as shown in
Figure 36.
Figure 36. nCS when CKMODE = 1 in SDR mode (T = CLK period)
7

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When CKMODE = 1 (“mode3”) and DDRM = 1 (DDR mode), nCS falls one CLK cycle
before an operation first rising CLK edge, and nCS rises one CLK cycle after the operation
final active rising CLK edge, as shown in Figure 37. Because DDR operations must finish
with a falling edge, CLK is low when nCS rises, and CLK rises back up one half of a CLK
cycle afterwards.
Figure 37. nCS when CKMODE = 1 in DDR mode (T = CLK period)
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When the FIFO stays full in a read operation or if the FIFO stays empty in a write operation,
the operation stalls and CLK stays low until firmware services the FIFO. If an abort occurs
when an operation is stalled, nCS rises just after the abort is requested and then CLK rises
one half of a CLK cycle later, as shown in Figure 38.
Figure 38. nCS when CKMODE = 1 with an abort (T = CLK period)
7

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When not in dual-flash mode (DFM = 0), only FLASH 1 is accessed and thus the BK2_nCS
stays high. In dual-flash mode, BK2_nCS behaves exactly the same as BK1_nCS. Thus, if
there is a FLASH 2 and if the application always stays in dual-flash mode, then FLASH 2
may use BK1_nCS and the pin outputting BK2_nCS can be used for other functions.

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15.4

Quad-SPI interface (QUADSPI)

QUADSPI interrupts
An interrupt can be produced on the following events:
•

Timeout

•

Status match

•

FIFO threshold

•

Transfer complete

•

Transfer error

Separate interrupt enable bits are available for flexibility.
Table 52. QUADSPI interrupt requests
Interrupt event

Event flag

Enable control bit

Timeout

TOF

TOIE

Status match

SMF

SMIE

FIFO threshold

FTF

FTIE

Transfer complete

TCF

TCIE

Transfer error

TEF

TEIE

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15.5

QUADSPI registers

15.5.1

QUADSPI control register (QUADSPI_CR)
Address offset: 0x0000
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

PRESCALER[7:0]

23

22

21

20

19

18

17

16

PMM

APMS

Res.

TOIE

SMIE

FTIE

TCIE

TEIE

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

FSEL

DFM

Res.

SSHIFT

TCEN

rw

rw

rw

rw

FTHRES[3:0]
rw

rw

rw

rw

DMAEN ABORT
rw

rw

EN
rw

Bits 31:24 PRESCALER[7:0]: Clock prescaler
This field defines the scaler factor for generating CLK based on the AHB clock
(value+1).
0: FCLK = FAHB, AHB clock used directly as QUADSPI CLK (prescaler bypassed)
1: FCLK = FAHB/2
2: FCLK = FAHB/3
...
255: FCLK = FAHB/256
For odd clock division factors, CLK’s duty cycle is not 50%. The clock signal remains
low one cycle longer than it stays high.
This field can be modified only when BUSY = 0.
Bit 23 PMM: Polling match mode
This bit indicates which method should be used for determining a “match” during
automatic polling mode.
0: AND match mode. SMF is set if all the unmasked bits received from the Flash
memory match the corresponding bits in the match register.
1: OR match mode. SMF is set if any one of the unmasked bits received from the Flash
memory matches its corresponding bit in the match register.
This bit can be modified only when BUSY = 0.
Bit 22 APMS: Automatic poll mode stop
This bit determines if automatic polling is stopped after a match.
0: Automatic polling mode is stopped only by abort or by disabling the QUADSPI.
1: Automatic polling mode stops as soon as there is a match.
This bit can be modified only when BUSY = 0.
Bit 21 Reserved, must be kept at reset value.
Bit 20 TOIE: TimeOut interrupt enable
This bit enables the TimeOut interrupt.
0: Interrupt disable
1: Interrupt enabled
Bit 19 SMIE: Status match interrupt enable
This bit enables the status match interrupt.
0: Interrupt disable
1: Interrupt enabled

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RM0394

Quad-SPI interface (QUADSPI)

Bit 18 FTIE: FIFO threshold interrupt enable
This bit enables the FIFO threshold interrupt.
0: Interrupt disabled
1: Interrupt enabled
Bit 17 TCIE: Transfer complete interrupt enable
This bit enables the transfer complete interrupt.
0: Interrupt disabled
1: Interrupt enabled
Bit 16 TEIE: Transfer error interrupt enable
This bit enables the transfer error interrupt.
0: Interrupt disable
1: Interrupt enabled
Bits 15:12 Reserved, must be kept at reset value.
Bits 11:8 FTHRES[3:0]: FIFO threshold level
Defines, in indirect mode, the threshold number of bytes in the FIFO that will cause the
FIFO threshold flag (FTF, QUADSPI_SR[2]) to be set.
In indirect write mode (FMODE = 00):
0: FTF is set if there are 1 or more free bytes available to be written to in the FIFO
1: FTF is set if there are 2 or more free bytes available to be written to in the FIFO
...
15: FTF is set if there are 16 free bytes available to be written to in the FIFO
In indirect read mode (FMODE = 01):
0: FTF is set if there are 1 or more valid bytes that can be read from the FIFO
1: FTF is set if there are 2 or more valid bytes that can be read from the FIFO
...
15: FTF is set if there are 16 valid bytes that can be read from the FIFO
If DMAEN = 1, then the DMA controller for the corresponding channel must be disabled
before changing the FTHRES value.
Bit 7 FSEL: Flash memory selection
This bit selects the Flash memory to be addressed in single flash mode (when DFM =
0).
0: FLASH 1 selected
1: FLASH 2 selected
This bit can be modified only when BUSY = 0.
This bit is ignored when DFM = 1.
Bit 6 DFM: Dual-flash mode
This bit activates dual-flash mode, where two external Flash memories are used
simultaneously to double throughput and capacity.
0: Dual-flash mode disabled
1: Dual-flash mode enabled
This bit can be modified only when BUSY = 0.
Bit 5 Reserved, must be kept at reset value.

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RM0394

Bit 4 SSHIFT: Sample shift
By default, the QUADSPI samples data 1/2 of a CLK cycle after the data is driven by the
Flash memory. This bit allows the data is to be sampled later in order to account for
external signal delays.
0: No shift
1: 1/2 cycle shift
Firmware must assure that SSHIFT = 0 when in DDR mode (when DDRM = 1).
This field can be modified only when BUSY = 0.
Bit 3 TCEN: Timeout counter enable
This bit is valid only when memory-mapped mode (FMODE = 11) is selected. Activating
this bit causes the chip select (nCS) to be released (and thus reduces consumption) if
there has not been an access after a certain amount of time, where this time is defined
by TIMEOUT[15:0] (QUADSPI_LPTR).
Enable the timeout counter.
By default, the QUADSPI never stops its prefetch operation, keeping the previous read
operation active with nCS maintained low, even if no access to the Flash memory
occurs for a long time. Since Flash memories tend to consume more when nCS is held
low, the application might want to activate the timeout counter (TCEN = 1, bit 3 of
QUADSPI_CR) so that nCS is released after a period of TIMEOUT[15:0]
(QUADSPI_LPTR) cycles have elapsed without an access since when the FIFO
becomes full with prefetch data.
0: Timeout counter is disabled, and thus the chip select (nCS) remains active
indefinitely after an access in memory-mapped mode.
1: Timeout counter is enabled, and thus the chip select is released in memory-mapped
mode after TIMEOUT[15:0] cycles of Flash memory inactivity.
This bit can be modified only when BUSY = 0.
Bit 2 DMAEN: DMA enable
In indirect mode, DMA can be used to input or output data via the QUADSPI_DR
register. DMA transfers are initiated when the FIFO threshold flag, FTF, is set.
0: DMA is disabled for indirect mode
1: DMA is enabled for indirect mode
Bit 1 ABORT: Abort request
This bit aborts the on-going command sequence. It is automatically reset once the abort
is complete.
This bit stops the current transfer.
In polling mode or memory-mapped mode, this bit also reset the APM bit or the DM bit.
0: No abort requested
1: Abort requested
Bit 0 EN: Enable
Enable the QUADSPI.
0: QUADSPI is disabled
1: QUADSPI is enabled

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RM0394

Quad-SPI interface (QUADSPI)

15.5.2

QUADSPI device configuration register (QUADSPI_DCR)
Address offset: 0x0004
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

Res.

Res.

Res.

Res.

Res.

CSHT[2:0]
rw

rw

Res.

Res.

rw

Res.

20

19

18

17

16

rw

FSIZE[4:0]
rw

rw

rw

rw

4

3

2

1

0

Res.

CK
MODE

Res.

Res.

Res.

rw

Bits 31:21 Reserved, must be kept at reset value.
Bits 20:16 FSIZE[4:0]: Flash memory size
This field defines the size of external memory using the following formula:
Number of bytes in Flash memory = 2[FSIZE+1]
FSIZE+1 is effectively the number of address bits required to address the Flash
memory. The Flash memory capacity can be up to 4GB (addressed using 32 bits) in
indirect mode, but the addressable space in memory-mapped mode is limited to
256MB.
If DFM = 1, FSIZE indicates the total capacity of the two Flash memories together.
This field can be modified only when BUSY = 0.
Bits 15:11 Reserved, must be kept at reset value.
Bits 10:8 CSHT[2:0]: Chip select high time
CSHT+1 defines the minimum number of CLK cycles which the chip select (nCS) must
remain high between commands issued to the Flash memory.
0: nCS stays high for at least 1 cycle between Flash memory commands
1: nCS stays high for at least 2 cycles between Flash memory commands
...
7: nCS stays high for at least 8 cycles between Flash memory commands
This field can be modified only when BUSY = 0.
Bits 7:1 Reserved, must be kept at reset value.
Bit 0 CKMODE: Mode 0 / mode 3
This bit indicates the level that CLK takes between commands (when nCS = 1).
0: CLK must stay low while nCS is high (chip select released). This is referred to as
mode 0.
1: CLK must stay high while nCS is high (chip select released). This is referred to as
mode 3.
This field can be modified only when BUSY = 0.

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Quad-SPI interface (QUADSPI)

15.5.3

RM0394

QUADSPI status register (QUADSPI_SR)
Address offset: 0x0008
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

BUSY

TOF

SMF

FTF

TCF

TEF

r

r

r

r

r

r

FLEVEL[4:0]
r

r

r

r

r

Bits 31:13 Reserved, must be kept at reset value.
Bits 12:8 FLEVEL[4:0]: FIFO level
This field gives the number of valid bytes which are being held in the FIFO. FLEVEL = 0
when the FIFO is empty, and 16 when it is full. In memory-mapped mode and in
automatic status polling mode, FLEVEL is zero.
Bits 7:6 Reserved, must be kept at reset value.
Bit 5 BUSY: Busy
This bit is set when an operation is on going. This bit clears automatically when the
operation with the Flash memory is finished and the FIFO is empty.
Bit 4 TOF: Timeout flag
This bit is set when timeout occurs. It is cleared by writing 1 to CTOF.
Bit 3 SMF: Status match flag
This bit is set in automatic polling mode when the unmasked received data matches the
corresponding bits in the match register (QUADSPI_PSMAR). It is cleared by writing 1
to CSMF.
Bit 2 FTF: FIFO threshold flag
In indirect mode, this bit is set when the FIFO threshold has been reached, or if there is
any data left in the FIFO after reads from the Flash memory are complete. It is cleared
automatically as soon as threshold condition is no longer true.
In automatic polling mode this bit is set every time the status register is read, and the bit
is cleared when the data register is read.
Bit 1 TCF: Transfer complete flag
This bit is set in indirect mode when the programmed number of data has been
transferred or in any mode when the transfer has been aborted.It is cleared by writing 1
to CTCF.
Bit 0 TEF: Transfer error flag
This bit is set in indirect mode when an invalid address is being accessed in indirect
mode. It is cleared by writing 1 to CTEF.

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RM0394

Quad-SPI interface (QUADSPI)

15.5.4

QUADSPI flag clear register (QUADSPI_FCR)
Address offset: 0x000C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

CTOF

CSMF

Res.

CTCF

CTEF

w

w

w

w

Bits 31:5 Reserved, must be kept at reset value.
Bit 4 CTOF: Clear timeout flag
Writing 1 clears the TOF flag in the QUADSPI_SR register
Bit 3 CSMF: Clear status match flag
Writing 1 clears the SMF flag in the QUADSPI_SR register
Bit 2 Reserved, must be kept at reset value.
Bit 1 CTCF: Clear transfer complete flag
Writing 1 clears the TCF flag in the QUADSPI_SR register
Bit 0 CTEF: Clear transfer error flag
Writing 1 clears the TEF flag in the QUADSPI_SR register

15.5.5

QUADSPI data length register (QUADSPI_DLR)
Address offset: 0x0010
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DL[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DL[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

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RM0394

Bits 31:0 DL[31:0]: Data length
Number of data to be retrieved (value+1) in indirect and status-polling modes. A value
no greater than 3 (indicating 4 bytes) should be used for status-polling mode.
All 1s in indirect mode means undefined length, where QUADSPI will continue until the
end of memory, as defined by FSIZE.
0x0000_0000: 1 byte is to be transferred
0x0000_0001: 2 bytes are to be transferred
0x0000_0002: 3 bytes are to be transferred
0x0000_0003: 4 bytes are to be transferred
...
0xFFFF_FFFD: 4,294,967,294 (4G-2) bytes are to be transferred
0xFFFF_FFFE: 4,294,967,295 (4G-1) bytes are to be transferred
0xFFFF_FFFF: undefined length -- all bytes until the end of Flash memory (as defined
by FSIZE) are to be transferred. Continue reading indefinitely if FSIZE = 0x1F.
DL[0] is stuck at ‘1’ in dual-flash mode (DFM = 1) even when ‘0’ is written to this bit, thus
assuring that each access transfers an even number of bytes.
This field has no effect when in memory-mapped mode (FMODE = 10).
This field can be written only when BUSY = 0.

15.5.6

QUADSPI communication configuration register (QUADSPI_CCR)
Address offset: 0x0014
Reset value: 0x0000 0000

31

30

29

28

DDRM

DHHC

Res.

SIOO

13

rw

rw

15

14

ABMODE[1:0]
rw

rw

26

25

24

FMODE[1:0]

DMODE[1:0]

rw

rw

rw

rw

rw

12

11

10

9

8

ADSIZE[1:0]
rw

27

rw

ADMODE[1:0]
rw

rw

23

22

21

Res.

7

rw

19

18

DCYC[4:0]

17

ABSIZE[1:0]

rw

rw

rw

rw

rw

rw

6

5

4

3

2

1

0

rw

rw

rw

INSTRUCTION[7:0]
rw

rw

rw

rw

rw

Bit 31 DDRM: Double data rate mode
This bit sets the DDR mode for the address, alternate byte and data phase:
0: DDR Mode disabled
1: DDR Mode enabled
This field can be written only when BUSY = 0.
Bit 30 DHHC: DDR hold
Delay the data output by 1/4 of the QUADSPI output clock cycle in DDR mode:
0: Delay the data output using analog delay
1: Delay the data output by 1/4 of a QUADSPI output clock cycle.
This feature is only active in DDR mode.
This field can be written only when BUSY = 0.
Bit 29 Reserved, must be kept at reset value.

366/1600

16

rw

IMODE[1:0]
rw

20

RM0394 Rev 4

RM0394

Quad-SPI interface (QUADSPI)

Bit 28 SIOO: Send instruction only once mode
See Section 15.3.12: Sending the instruction only once on page 356. This bit has no
effect when IMODE = 00.
0: Send instruction on every transaction
1: Send instruction only for the first command
This field can be written only when BUSY = 0.
Bits 27:26 FMODE[1:0]: Functional mode
This field defines the QUADSPI functional mode of operation.
00: Indirect write mode
01: Indirect read mode
10: Automatic polling mode
11: Memory-mapped mode
If DMAEN = 1 already, then the DMA controller for the corresponding channel must be
disabled before changing the FMODE value.
This field can be written only when BUSY = 0.
Bits 25:24 DMODE[1:0]: Data mode
This field defines the data phase’s mode of operation:
00: No data
01: Data on a single line
10: Data on two lines
11: Data on four lines
This field also determines the dummy phase mode of operation.
This field can be written only when BUSY = 0.
Bit 23 Reserved, must be kept at reset value.
Bits 22:18 DCYC[4:0]: Number of dummy cycles
This field defines the duration of the dummy phase. In both SDR and DDR modes, it
specifies a number of CLK cycles (0-31).
This field can be written only when BUSY = 0.
Bits 17:16 ABSIZE[1:0]: Alternate bytes size
This bit defines alternate bytes size:
00: 8-bit alternate byte
01: 16-bit alternate bytes
10: 24-bit alternate bytes
11: 32-bit alternate bytes
This field can be written only when BUSY = 0.
Bits 15:14 ABMODE[1:0]: Alternate bytes mode
This field defines the alternate-bytes phase mode of operation:
00: No alternate bytes
01: Alternate bytes on a single line
10: Alternate bytes on two lines
11: Alternate bytes on four lines
This field can be written only when BUSY = 0.

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RM0394

Bits 13:12 ADSIZE[1:0]: Address size
This bit defines address size:
00: 8-bit address
01: 16-bit address
10: 24-bit address
11: 32-bit address
This field can be written only when BUSY = 0.
Bits 11:10 ADMODE[1:0]: Address mode
This field defines the address phase mode of operation:
00: No address
01: Address on a single line
10: Address on two lines
11: Address on four lines
This field can be written only when BUSY = 0.
Bits 9:8 IMODE[1:0]: Instruction mode
This field defines the instruction phase mode of operation:
00: No instruction
01: Instruction on a single line
10: Instruction on two lines
11: Instruction on four lines
This field can be written only when BUSY = 0.
Bits 7:0 INSTRUCTION[7:0]: Instruction
Instruction to be send to the external SPI device.
This field can be written only when BUSY = 0.

15.5.7

QUADSPI address register (QUADSPI_AR)
Address offset: 0x0018
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ADDRESS[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

ADDRESS[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 ADDRESS[31:0]: Address
Address to be send to the external Flash memory
Writes to this field are ignored when BUSY = 0 or when FMODE = 11 (memory-mapped
mode).
In dual flash mode, ADDRESS[0] is automatically stuck to ‘0’ as the address should
always be even

368/1600

RM0394 Rev 4

RM0394

Quad-SPI interface (QUADSPI)

15.5.8

QUADSPI alternate bytes registers (QUADSPI_ABR)
Address offset: 0x001C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

ALTERNATE[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

ALTERNATE[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 ALTERNATE[31:0]: Alternate Bytes
Optional data to be send to the external SPI device right after the address.
This field can be written only when BUSY = 0.

15.5.9

QUADSPI data register (QUADSPI_DR)
Address offset: 0x0020
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

DATA[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

DATA[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 DATA[31:0]: Data
Data to be sent/received to/from the external SPI device.
In indirect write mode, data written to this register is stored on the FIFO before it is sent
to the Flash memory during the data phase. If the FIFO is too full, a write operation is
stalled until the FIFO has enough space to accept the amount of data being written.
In indirect read mode, reading this register gives (via the FIFO) the data which was
received from the Flash memory. If the FIFO does not have as many bytes as requested
by the read operation and if BUSY=1, the read operation is stalled until enough data is
present or until the transfer is complete, whichever happens first.
In automatic polling mode, this register contains the last data read from the Flash
memory (without masking).
Word, halfword, and byte accesses to this register are supported. In indirect write mode,
a byte write adds 1 byte to the FIFO, a halfword write 2, and a word write 4. Similarly, in
indirect read mode, a byte read removes 1 byte from the FIFO, a halfword read 2, and a
word read 4. Accesses in indirect mode must be aligned to the bottom of this register: a
byte read must read DATA[7:0] and a halfword read must read DATA[15:0].

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372

Quad-SPI interface (QUADSPI)

15.5.10

RM0394

QUADSPI polling status mask register (QUADSPI _PSMKR)
Address offset: 0x0024
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MASK[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MASK[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MASK[31:0]: Status mask
Mask to be applied to the status bytes received in polling mode.
For bit n:
0: Bit n of the data received in automatic polling mode is masked and its value is not
considered in the matching logic
1: Bit n of the data received in automatic polling mode is unmasked and its value is
considered in the matching logic
This field can be written only when BUSY = 0.

15.5.11

QUADSPI polling status match register (QUADSPI _PSMAR)
Address offset: 0x0028
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

MATCH[31:16]
rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

rw

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

MATCH[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:0 MATCH[31:0]: Status match
Value to be compared with the masked status register to get a match.
This field can be written only when BUSY = 0.

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RM0394 Rev 4

RM0394

Quad-SPI interface (QUADSPI)

15.5.12

QUADSPI polling interval register (QUADSPI _PIR)
Address offset: 0x002C
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

INTERVAL[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 INTERVAL[15:0]: Polling interval
Number of CLK cycles between to read during automatic polling phases.
This field can be written only when BUSY = 0.

15.5.13

QUADSPI low-power timeout register (QUADSPI_LPTR)
Address offset: 0x0030
Reset value: 0x0000 0000

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

rw

rw

rw

rw

rw

rw

rw

TIMEOUT[15:0]
rw

rw

rw

rw

rw

rw

rw

rw

rw

Bits 31:16 Reserved, must be kept at reset value.
Bits 15:0 TIMEOUT[15:0]: Timeout period
After each access in memory-mapped mode, the QUADSPI prefetches the subsequent
bytes and holds these bytes in the FIFO. This field indicates how many CLK cycles the
QUADSPI waits after the FIFO becomes full until it raises nCS, putting the Flash
memory in a lower-consumption state.
This field can be written only when BUSY = 0.

RM0394 Rev 4

371/1600
372

Quad-SPI interface (QUADSPI)

15.5.14

RM0394

QUADSPI register map

0x001C

Reset value

0

0

0

0

0

0

0

0

0

0

0x0020

0x0024

0

0

0

DCYC[4:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ABORT

EN

Res.

TEF

Res.

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

INSTRUCTION[7:0]

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

QUADSPI_PIR

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

MATCH[31:0]
0

0

0

0

0

0

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

Res.

0

INTERVAL[15:0]
0

Reset value

0

0

0

RM0394 Rev 4

0

0

TIMEOUT[15:0]
0

0

0

0

0

0

0

Refer to Section 2.2.2 on page 67 for the register boundary addresses.

372/1600

0

MASK[31:0]

Reset value

QUADSPI_
LPTR

CKMODE

TCF

0

DATA[31:0]

Reset value

0x0030

TCEN

0

ALTERNATE[31:0]

QUADSPI_
PSMAR

0x002C

DMAEN
FTF
0

ADDRESS[31:0]
0

Res.

0x0028

0

QUADSPI_
PSMKR
Reset value

Res.

SMF
0

CTEF

0

QUADSPI_DR
Reset value

Res.

Res.

0

CTCF

0

IMODE[1:0]

0

QUADSPI_ABR
Reset value

SSHIFT

Res.
Res.

0

CSMF

0

TOF

0

CTOF

0

BUSY

0

Res.

0

ADMODE[1:0]

0

QUADSPI_AR

0x0018

0

0
Res.

0

ADSIZE[1:0]

0

0

ABMODE[1:0]

0

0

ABSIZE[1:0]

0

0

Res.

0

0

DMODE[1:0]

DHHC

Reset value

0

FMODE[1:0]

QUADSPI_CCR

0

Res.

0

SIOO

0

0x0014

0

DL[31:0]

Reset value

DDRM

QUADSPI_DLR

0

0

Reset value
0x0010

0

0
Res.

DFM

Res.

Res.

FSEL

0

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.

QUADSPI_FCR

0

FLEVEL[5:0]

Reset value

0x000C

Res.

0

Res.

0

CSHT

Res.

0

0

Res.

0

0

Res.

0

0

Res.

Res.

0

Res.

Res.

Res.

0
Res.

Res.

Res.

FSIZE[4:0]

FTHRES
[3:0]

Res.

Res.

Res.

Res.

Res.

Res.

0
Res.

Res.

Res.

0

Res.

Res.

Res.

TEIE

Res.

Res.

Res.

0

Res.

Res.
Res.

QUADSPI_SR

Res.

Reset value

0x0008

0

Res.

QUADSPI_DCR
0x0004

0

Res.

0

FTIE

0

TCIE

0

Res.

0

SMIE

0

Res.

0

Res.

0

Res.

0

TOIE

0

PRESCALER[7:0]

Res.

0

QUADSPI_CR
0x0000

Res.

PMM

APMS

Reset value

Res.

Offset

31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

Table 53. QUADSPI register map and reset values
Register
name

0

0

RM0394

Analog-to-digital converters (ADC)

16

Analog-to-digital converters (ADC)

16.1

Introduction
This section describes the implementation of up to 2 ADCs:
•

ADC1 and ADC2 are tightly coupled and can operate in dual mode (ADC1 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.
A built-in hardware oversampler allows to improve analog performances while off-loading
the related computational burden from the CPU.
An efficient low-power mode is implemented to allow very low consumption at low
frequency.

RM0394 Rev 4

373/1600
485

Analog-to-digital converters (ADC)

16.2

RM0394

ADC main features
•

High-performance features
–

Up to 2 ADCs which can operate in dual mode:
ADC1 is connected to 16 external channels + 3 internal channels
ADC2 is connected to 16 external channels

–

12, 10, 8 or 6-bit configurable resolution

–

ADC conversion time:
Fast channels: 0.188 µs for 12-bit resolution (5.33 Ms/s)
Slow channels: 0.238 µs for 12-bit resolution (4.21 Ms/s)

•

374/1600

–

ADC conversion time is independent from the AHB bus clock frequency

–

Faster conversion time by lowering resolution: 0.16 µs for 10-bit resolution

–

Manage single-ended or differential inputs

–

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 DMA for regular channel conversions

–

Data can be routed to DFSDM for post processing

–

4 dedicated data registers for the injected channels

Oversampler
–

16-bit data register

–

Oversampling ratio adjustable from 2 to 256x

–

Programmable data shift up to 8-bit

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
•

•

•

•

•

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
(0.188 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)

Several external analog input channel per ADC
–

Up to 5 fast channels from GPIO pads

–

Up to 11 slow channels from GPIO pads

In addition, there are several internal dedicated channels
–

The internal reference voltage (VREFINT), connected to ADC1

–

The internal temperature sensor (VTS), connected to ADC1

–

The VBAT monitoring channel (VBAT/3), connected to ADC1

–

DAC1 internal channels, connected to ADC1

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 for ADC1 and 2

•

Interrupt generation at ADC ready, the end of sampling, 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 input range: VREF– ≤ VIN ≤ VREF+

Figure 39 shows the block diagram of one ADC.

16.3

ADC implementation
Table 54. Main ADC features
References
Dual mode
DFSDM

interface(1)

SMPPLUS control(2)

ADC1

ADC2(2)

X(2)

X

X

-

-

X

1. Available only on STM32L451xx/452xx/462xx.
2. Available only on STM32L412xx/422xx.

RM0394 Rev 4

375/1600
485

Analog-to-digital converters (ADC)

RM0394

16.4

ADC functional description

16.4.1

ADC block diagram
Figure 39 shows the ADC block diagram and Table 56 gives the ADC pin description.
Figure 39. ADC block diagram
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376/1600

RM0394 Rev 4

RM0394

16.4.2

Analog-to-digital converters (ADC)

ADC pins and internal signals
Table 55. ADC internal input/output 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.

ADC_AWDx_OUT

Output

Internal analog watchdog output signal connected to on-chip
timers. (x = Analog watchdog number 1,2,3)

Internal signal name

EXT[15:0]

VTS

Input

Output voltage from internal temperature sensor

dac_out1

Input

DAC internal channel 1

VREFINT

Input

Output voltage from internal reference voltage

dac_out2

Input

DAC internal channel 2

VBAT

Input
supply

External battery voltage supply

Table 56. ADC input/output pins
Pin name

Signal type

Comments

VREF+

Input, analog reference
positive

The higher/positive reference voltage for the ADC,
1.62 V ≤ VREF+ ≤ VDDA

VDDA

Input, analog supply

Analog power supply equal VDDA:
1.62 V ≤ VDDA ≤ 3.6 V

VREF−

Input, analog reference
negative

The lower/negative reference voltage for the ADC.
VREF− is internally connected to VSSA

VSSA

Input, analog supply
ground

Ground for analog power supply. On device package
which do not have a dedicated VSSA pin, VSSA is
internally connected to VSS.

VINP[18:0]

Positive analog input
channels for each ADC

Connected either to external channels: ADCx_INPi or
internal channels.

VINN[18:0]

Negative analog input
channels for each ADC

Connected to VREF− or external channels:
ADCx_INNi and ADCx_INP[i+1]

ADCx_INN[16:1]

External analog input
signals

Up to 16 analog input channels (x = ADC number = 1
or 2):
– 5 fast channels (ADCx_INN1 to INN5)
– Up to 11 slow channels (ADCx_INN6 to INN16)

ADCx_INP[16:1]

External analog input
signals

Up to 16 analog input channels (x = ADC number = 1
or 2):
– 5 fast channels (ADCx_INP1 to INP5)
– Up to 11 slow channels (ADCx_INP6 to INP16)

RM0394 Rev 4

377/1600
485

Analog-to-digital converters (ADC)

16.4.3

RM0394

Clocks
Dual clock domain architecture
The dual clock-domain architecture means that the ADC clock is independent from the AHB
bus clock.
The input clock is the same for the three ADCs and can be selected between two different
clock sources (see Figure 40: ADC clock scheme):
1.

The ADC clock can be a specific clock source. It can be derived from the following
clock sources:
–

The system clock

–

PLLSAI1 (single ADC implementation)

Refer to RCC Section for more information on how to generate ADC dedicated clock.
To select this scheme, bits CKMODE[1:0] of the ADCx_CCR register must be reset.
2.

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:

For option 2), a prescaling factor of 1 (CKMODE[1:0]=01) can be used only if the AHB
prescaler is set to 1 (HPRE[3:0] = 0xxx in RCC_CFGR register).
Option 1) 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 PRESC[3:0] in
the ADCx_CCR register.
Option 2) 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).

378/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 40. ADC clock scheme

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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:
•

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

RM0394 Rev 4

379/1600
485

Analog-to-digital converters (ADC)

16.4.4

RM0394

ADC1/2 connectivity
ADC1 and ADC2 are tightly coupled and share some external channels as described in the
below figures.
Figure 41. ADC1 connectivity
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380/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 42. ADC2 connectivity
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RM0394 Rev 4

381/1600
485

Analog-to-digital converters (ADC)

16.4.5

RM0394

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.

16.4.6

ADC Deep-power-down mode (DEEPPWD) and ADC voltage regulator
(ADVREGEN)
By default, the ADC is in Deep-power-down mode where its supply is internally switched off
to reduce the leakage currents (the reset state of bit DEEPPWD is 1 in the ADC_CR
register).
To start ADC operations, it is first needed to exit Deep-power-down mode by setting bit
DEEPPWD=0.
Then, it is mandatory to enable the ADC internal voltage regulator by setting the bit
ADVREGEN=1 into ADC_CR register. The software must wait for the startup time of the
ADC voltage regulator (TADCVREG_STUP) before launching a calibration or enabling the
ADC. This delay must be implemented by software.
For the startup time of the ADC voltage regulator, refer to device datasheet for
TADCVREG_STUP parameter.
After ADC operations are complete, the ADC can be disabled (ADEN=0). It is possible to
save power by also disabling the ADC voltage regulator. This is done by writing bit
ADVREGEN=0.
Then, to save more power by reducing the leakage currents, it is also possible to re-enter in
ADC Deep-power-down mode by setting bit DEEPPWD=1 into ADC_CR register. This is
particularly interesting before entering STOP mode.

Note:

Writing DEEPPWD=1 automatically disables the ADC voltage regulator and bit ADVREGEN
is automatically cleared.
When the internal voltage regulator is disabled (ADVREGEN=0), the internal analog
calibration is kept.
In ADC Deep-power-down mode (DEEPPWD=1), the internal analog calibration is lost and
it is necessary to either relaunch a calibration or re-apply the calibration factor which was
previously saved (refer to Section 16.4.8: Calibration (ADCAL, ADCALDIF,
ADC_CALFACT)).

382/1600

RM0394 Rev 4

RM0394

16.4.7

Analog-to-digital converters (ADC)

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 ADC_DIFSEL register. This configuration must be written while
the ADC is disabled (ADEN=0). Note that DIFSEL[18:16,0] are fixed to single ended
channels 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 VINP[i] (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 VINP[i] (positive input) and VINN[i] (negative input).
When ADC is configured as differential mode, both inputs should be biased at (VREF+) / 2
voltage.
The input signal are supposed to be differential (common mode voltage should be fixed).
For a complete description of how the input channels are connected for each ADC, refer to
Section 16.4.4: ADC1/2 connectivity.

Caution:

When configuring the channel “i” in differential input mode, its negative input voltage VINN[i]
is connected to VINP[i+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/ADC2: this can make the channel on the other ADC
unusable. Only exception is interleaved mode for ADC master and the slave.

Note:

ADC channels 0, 16, 17, 18 are forced to single-ended configuration (corresponding bits
DIFSEL[i] is always zero), either because connected to a single-ended external analog input
or connected to an internal channel.

16.4.8

Calibration (ADCAL, ADCALDIF, ADC_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 ADC_CALFACT register (depending on
single-ended or differential input calibration)

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485

Analog-to-digital converters (ADC)

RM0394

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 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 ADC_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. It is recommended to recalibrate when
VREF+ voltage changed more than 10%.

Software procedure to calibrate the ADC
1.

Ensure DEEPPWD=0, ADVREGEN=1 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 ADC_CALFACT register.
Figure 43. ADC calibration
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Software procedure to re-inject a calibration factor into the ADC
1.

384/1600

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.

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 44. Updating the ADC calibration factor
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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 45. Mixing single-ended and differential channels

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RM0394 Rev 4

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485

Analog-to-digital converters (ADC)

16.4.9

RM0394

ADC on-off control (ADEN, ADDIS, ADRDY)
First of all, follow the procedure explained in Section 16.4.6: ADC Deep-power-down mode
(DEEPPWD) and ADC voltage regulator (ADVREGEN)).
Once DEEPPWD=0 and ADVREGEN=1, the ADC can be enabled and the ADC needs a
stabilization time of tSTAB before it starts converting accurately, as shown in Figure 46. 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. 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 16.4.18:
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

Caution:

1.

Clear the ADRDY bit in the ADC_ISR register by writing ‘1’.

2.

Set ADEN=1.

3.

Wait until ADRDY=1 (ADRDY is set after the ADC startup time). This can be done
using the associated interrupt (setting ADRDYIE=1).

4.

Clear the ADRDY bit in the ADC_ISR register by writing ‘1’ (optional).

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

386/1600

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).

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 46. Enabling / Disabling the ADC
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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 ADC_DIFSEL register and the control
bits ADCAL and ADEN in the ADC_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 ADC_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 ADC_CFGR, ADC_SMPRx, ADC_SQRy, ADC_JDRy,
ADC_OFRy, ADC_OFCHRy and ADC_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 ADSTP or JADSTP control bits of the ADC_CR register
only if the ADC is enabled, possibly 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 ADC_JSQR at any time, when the ADC is enabled
(ADEN=1). Refer to Section 16.6.16: ADC injected sequence register (ADC_JSQR) for
additional details.
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 ADC_CR register).

RM0394 Rev 4

387/1600
485

Analog-to-digital converters (ADC)

16.4.11

RM0394

Channel selection (SQRx, JSQRx)
There are up to 19 multiplexed channels per ADC:

Note:

•

5 fast analog inputs coming from GPIO pads (ADCx_INP/INN[1..5])

•

Up to 11 slow analog inputs coming from GPIO pads (ADCx_INP/INN[6..16]).
Depending on the products, not all of them are available on GPIO pads.

•

The ADCs are connected to the following internal analog inputs:
–

the internal reference voltage (VREFINT) is connected to ADC1_INP0/INN0.

–

the internal temperature sensor (VTS) is connected to ADC1_INP17/INN17.

–

the VBAT monitoring channel (VBAT/3) is connected to ADC1_INP18/INN18.

–

the DAC1 internal channel is connected to ADC1_INP/INN17.

To convert one of the internal analog channels, the corresponding analog sources must first
be enabled by programming bits VREFEN, CH17SEL or CH18SEL 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:
ADCx_INP/INN3, ADCx_INP/INN8, ADCx_INP/INN2, ADCx/INN2, ADCx_INP/INN0,
ADCx_INP/INN2, ADCx_INP/INN2, ADCx_INP/INN15.
•

A regular group is composed of up to 16 conversions. The regular channels and their
order in the conversion sequence must be selected in the ADC_SQRy registers. The
total number of conversions in the regular group must be written in the L[3:0] bits in the
ADC_SQR1 register.

•

An injected group is composed of up to 4 conversions. The injected channels and
their order in the conversion sequence must be selected in the ADC_JSQR register.
The total number of conversions in the injected group must be written in the L[1:0] bits
in the ADC_JSQR register.

ADC_SQRy 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 16.4.17: Stopping an ongoing conversion (ADSTP, JADSTP)).
The software is allowed to modify on-the-fly the ADC_JSQR register when JADSTART is set
to 1 (injected conversions ongoing) only when the context queue is enabled (JQDIS=0 in
ADC_CFGR register). Refer to Section 16.4.21: Queue of context for injected conversions

388/1600

RM0394 Rev 4

RM0394

16.4.12

Analog-to-digital converters (ADC)

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 ADC_SMPR1 and ADC registers. It is therefore possible to select
among the following sampling time values:
•

SMP = 000: 2.5 ADC clock cycles

•

SMP = 001: 6.5 ADC clock cycles

•

SMP = 010: 12.5 ADC clock cycles

•

SMP = 011: 24.5 ADC clock cycles

•

SMP = 100: 47.5 ADC clock cycles

•

SMP = 101: 92.5 ADC clock cycles

•

SMP = 110: 247.5 ADC clock cycles

•

SMP = 111: 640.5 ADC clock cycles

The total conversion time is calculated as follows:
TCONV = Sampling time + 12.5 ADC clock cycles
Example:
With FADC_CLK = 80 MHz and a sampling time of 2.5 ADC clock cycles:
TCONV = (2.5 + 12.5) ADC clock cycles = 15 ADC clock cycles = 187.5 ns (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 characteristics section of the datasheets.

I/O analog switches voltage booster
The I/O analog switches resistance increases when the VDDA voltage is too low. This
requires to have the sampling time adapted accordingly (cf datasheet for electrical
characteristics). This resistance can be minimized at low VDDA by enabling an internal
voltage booster with BOOSTEN bit in the SYSCFG_CFGR1 register.

16.4.13

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 ADC_CR register (for a regular channel)

•

Setting the JADSTART bit in the ADC_CR register (for an injected channel)

•

External hardware trigger event (for a regular or injected channel)

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Analog-to-digital converters (ADC)

RM0394

Inside the regular sequence, after each conversion is complete:
•

The converted data are stored into the 16-bit ADC_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 ADC_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.

16.4.14

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
restarts 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
ADC_CR register.
Inside the regular sequence, after each conversion is complete:
•

The converted data are stored into the 16-bit ADC_DR register

•

The EOC (end of conversion) flag is set

•

An interrupt is generated if the EOCIE bit is set

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).

390/1600

RM0394 Rev 4

RM0394

16.4.15

Analog-to-digital converters (ADC)

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.
JADSTART is cleared by hardware:
•

in single mode with software injected trigger (JEXTSEL=0x0)
–

•

in all cases (JEXTSEL=x)
–

Note:

at any end of injected conversion sequence (JEOS assertion) or at any end of
subgroup processing if JDISCEN = 1
after execution of the JADSTP procedure asserted by the software.

When the software trigger is selected, ADSTART bit should not be set if the EOC flag is still
high.

RM0394 Rev 4

391/1600
485

Analog-to-digital converters (ADC)

16.4.16

RM0394

ADC 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:
TCONV= TSMPL + TSAR = [ 2.5 |min + 12.5 |12bit ] x TADC_CLK
TCONV = TSMPL + TSAR = 31.25 ns |min + 156.25 ns |12bit = 187.5 ns (for FADC_CLK = 80 MHz)

Figure 47. Analog to digital conversion time
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16.4.17

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 (ADC_DR register is not updated with the current conversion).
When the JADSTP bit is set by software, any ongoing injected conversion is aborted with
partial result discarded (ADC_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 poll ADSTART (or JADSTART) until the bit is reset before assuming the ADC
is completely stopped.

392/1600

RM0394 Rev 4

RM0394
Note:

Analog-to-digital converters (ADC)
In auto-injection mode (JAUTO=1), setting ADSTP bit aborts both regular and injected
conversions (JADSTP must not be used).
Figure 48. Stopping ongoing regular conversions

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RM0394 Rev 4

393/1600
485

Analog-to-digital converters (ADC)

16.4.18

RM0394

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.
When the Injected Queue is enabled (bit JQDIS=0), injected software triggers are not
possible.
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 57 provides the correspondence between the EXTEN[1:0] and JEXTEN[1:0] values
and the trigger polarity.
Table 57. Configuring the trigger polarity for regular external triggers
EXTEN[1:0]

Note:

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

The polarity of the regular trigger cannot be changed on-the-fly.
Table 58. Configuring the trigger polarity for injected external triggers

Note:

JEXTEN[1:0]

Source

00

– If JQDIS=1 (Queue disabled): Hardware trigger detection disabled, software
trigger detection enabled
– If JQDIS=0 (Queue enabled), Hardware and software trigger detection disabled

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

The polarity of the injected trigger can be anticipated and changed on-the-fly when the
queue is enabled (JQDIS=0). Refer to Section 16.4.21: Queue of context for injected
conversions.
The EXTSEL and JEXTSEL 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.

394/1600

RM0394 Rev 4

RM0394
Note:

Analog-to-digital converters (ADC)
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 16.4.21: Queue of context for injected conversions on page 399
Each ADC master shares the same input triggers with its ADC slave as described in
Figure 50.
Figure 50. Triggers sharing between ADC master and ADC slave
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Table 59 toTable 60 give all the possible external triggers of the three ADCs for regular and
injected conversion.
Table 59. ADC1 and ADC2 - External triggers for regular channels
Name

Source

Type

EXTSEL[3:0]

EXT0

TIM1_CH1

Internal signal from on-chip timers

0000

EXT1

TIM1_CH2

Internal signal from on-chip timers

0001

EXT2

TIM1_CH3

Internal signal from on-chip timers

0010

EXT3

TIM2_CH2

Internal signal from on-chip timers

0011

EXT4

TIM3_TRGO(1)

Internal signal from on-chip timers

0100

EXT5

-

-

0101

EXT6

EXTI line 11

External pin

0110

EXT9

TIM1_TRGO

Internal signal from on-chip timers

1001

EXT10

TIM1_TRGO2

Internal signal from on-chip timers

1010

EXT11

TIM2_TRGO

Internal signal from on-chip timers

1011

RM0394 Rev 4

395/1600
485

Analog-to-digital converters (ADC)

RM0394

Table 59. ADC1 and ADC2 - External triggers for regular channels (continued)
Name

Source

Type

EXTSEL[3:0]

EXT13

TIM6_TRGO

Internal signal from on-chip timers

1101

EXT14

TIM15_TRGO

Internal signal from on-chip timers

1110

1. Available only on STM32L451xx/452xx/462xx.

Table 60. ADC1 and ADC2 - External trigger for injected channels
Name

Source

Type

JEXTSEL[3..0]

JEXT0

TIM1_TRGO

Internal signal from on-chip timers

0000

JEXT1

TIM1_CH4

Internal signal from on-chip timers

0001

JEXT2

TIM2_TRGO

Internal signal from on-chip timers

0010

JEXT3

TIM2_CH1

Internal signal from on-chip timers

0011

Internal signal from on-chip timers

0100

(1)

JEXT4

TIM3_CH4

JEXT5

-

-

0101

JEXT6

EXTI line 15

External pin

0110

JEXT8

TIM1_TRGO2

Internal signal from on-chip timers

1000

JEXT14

TIM6_TRGO

Internal signal from on-chip timers

1110

JEXT15

TIM15_TRGO

Internal signal from on-chip timers

1111

1. Available only on STM32L451xx/452xx/462xx.

16.4.19

Injected channel management
Triggered injection mode
To use triggered injection, the JAUTO bit in the ADC_CFGR register must be cleared.

Note:

396/1600

1.

Start the conversion of a group of regular channels either by an external trigger or by
setting the ADSTART bit in the ADC_CR register.

2.

If an external injected trigger occurs, or if the JADSTART bit in the ADC_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 51 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.

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

Auto-injection mode
If the JAUTO bit in the ADC_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 ADC_SQRy and ADC_JSQR
registers.
In this mode, the ADSTART bit in the ADC_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.
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 51. Injected conversion latency

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STM32L41xxx/42xxx/43xxx/44xxx/45xxx/46xxx datasheet.

RM0394 Rev 4

397/1600
485

Analog-to-digital converters (ADC)

16.4.20

RM0394

Discontinuous mode (DISCEN, DISCNUM, JDISCEN)
Regular group mode
This mode is enabled by setting the DISCEN bit in the ADC_CFGR register.
It is used to convert a short sequence (subgroup) of n conversions (n ≤ 8) that is part of the
sequence of conversions selected in the ADC_SQRy registers. The value of n is specified
by writing to the DISCNUM[2:0] bits in the ADC_CFGR register.
When an external trigger occurs, it starts the next n conversions selected in the ADC_SQRy
registers until all the conversions in the sequence are done. The total sequence length is
defined by the L[3:0] bits in the ADC_SQR1 register.
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, 8, 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.

398/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

Injected group mode
This mode is enabled by setting the JDISCEN bit in the ADC_CFGR register. It converts the
sequence selected in the ADC_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
ADC_JSQR registers until all the conversions in the sequence are done. The total sequence
length is defined by the JL[1:0] bits in the ADC_JSQR register.
Example:
•

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.

16.4.21

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. JQDIS bit of ADC_CFGR register must be reset to enable this
feature. Only hardware-triggered conversions are possible when the context queue is
enabled.
This context consists of:
•

Configuration of the injected triggers (bits JEXTEN[1:0] and JEXTSEL bits in
ADC_JSQR register)

•

Definition of the injected sequence (bits JSQx[4:0] and JL[1:0] in ADC_JSQR register)

All the parameters of the context are defined into a single register ADC_JSQR and this
register implements a queue of 2 buffers, allowing the bufferization of up to 2 sets of
parameters:
•

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.

RM0394 Rev 4

399/1600
485

Analog-to-digital converters (ADC)

Note:

•

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 ADC_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
hardware triggers are disabled. Therefore, any further hardware 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
consumes the queue but others are still valid triggers as shown by the discontinuous mode
example below (length = 3 for both contexts):

•
•
•
•
•
•

400/1600

RM0394

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.

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

Behavior when changing the trigger or sequence context
The Figure 52 and Figure 53 show the behavior of the context Queue when changing the
sequence or the triggers.
Figure 52. Example of JSQR queue of context (sequence change)
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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 53. Example of JSQR queue of context (trigger change)
3

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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

RM0394 Rev 4

401/1600
485

Analog-to-digital converters (ADC)

RM0394

Queue of context: Behavior when a queue overflow occurs
The Figure 54 and Figure 55 show the behavior of the context Queue if an overflow occurs
before or during a conversion.
Figure 54. Example of JSQR queue of context with overflow before conversion
3

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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 55. Example of JSQR queue of context with overflow during conversion
3

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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

402/1600

RM0394 Rev 4

RM0394

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 56 and Figure 57 show the behavior of the context Queue when the Queue becomes
empty in both cases JQM=0 or 1.
Figure 56. Example of JSQR queue of context with empty queue (case JQM=0)

3

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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.

RM0394 Rev 4

403/1600
485

Analog-to-digital converters (ADC)

RM0394

Figure 57. Example of JSQR queue of context with empty queue (case JQM=1)

3

1UEUE BECOMES EMPTY
AND TRIGGERS ARE IGNORED
BECAUSE *1-

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-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

Flushing the queue of context
The figures below show the behavior of the context Queue in various situations when the
queue is flushed.
Figure 58. Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs during an ongoing conversion.
3

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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

404/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 59. 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

1UEUE IS FLUSHED AND MAINTAINS
THE LAST ACTIVE CONTEXT
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-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 60. Flushing JSQR queue of context by setting JADSTP=1 (JQM=0).
Case when JADSTP occurs outside an ongoing conversion
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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

RM0394 Rev 4

405/1600
485

Analog-to-digital converters (ADC)

RM0394

Figure 61. Flushing JSQR queue of context by setting JADSTP=1 (JQM=1)
0

1UEUE IS FLUSHED AND
BECOMES EMPTY 0 IS LOST

0

0

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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

Figure 62. 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
3ET
BY 37

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2ESET
BY (7

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

406/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 63. Flushing JSQR queue of context by setting ADDIS=1 (JQM=1)
1UEUE IS FLUSHED AND BEOMES EMPTY
*312 IS READ AS X
*312 QUEUE

0 0

%-049
2ESET
BY (7

3ET
BY 37

!$$)3
0
!$# * CONTEXT
RETURNED BY READING *312
!$# STATE

2$9

%-049 X

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

Queue of context: Starting the ADC with an empty queue
The following procedure must be followed to start ADC operation with an empty queue, in
case the first context is not known at the time the ADC is initialized. This procedure is only
applicable when JQM bit is reset:
5.

Write a dummy JSQR with JEXTEN not equal to 0 (otherwise triggering a software
conversion)

6.

Set JADSTART

7.

Set JADSTP

8.

Wait until JADSTART is reset

9.

Set JADSTART.

Disabling the queue
It is possible to disable the queue by setting bit JQDIS=1 into the ADC_CFGR register.

16.4.22

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 68, Figure 69, Figure 70 and Figure 71 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 61.

RM0394 Rev 4

407/1600
485

Analog-to-digital converters (ADC)

RM0394

Table 61. TSAR timings depending on resolution
RES
(bits)

16.4.23

TSAR
(ADC clock cycles)

TSAR (ns) at
FADC=80 MHz

TCONV (ADC clock cycles)
(with Sampling Time=
2.5 ADC clock cycles)

TCONV (ns) at
FADC=80 MHz

12

12.5 ADC clock cycles 156.25 ns

15 ADC clock cycles

187.5 ns

10

10.5 ADC clock cycles 131.25 ns

13 ADC clock cycles

162.5 ns

8

8.5 ADC clock cycles

106.25 ns

11 ADC clock cycles

137.5 ns

6

6.5 ADC clock cycles

81.25 ns

9 ADC clock cycles

112.5 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.
The ADC sets the EOC flag as soon as a new regular conversion data is available in the
ADC_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 ADC_DR.
The ADC sets the JEOC flag as soon as a new injected conversion data is available in one
of the ADC_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 ADC_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.

16.4.24

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 ADC_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.

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16.4.25

Analog-to-digital converters (ADC)

Timing diagrams example (single/continuous modes,
hardware/software triggers)
Figure 64. Single conversions of a sequence, software trigger

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1. EXTEN=0x0, CONT=0
2. Channels selected = 1,9, 10, 17; AUTDLY=0.

Figure 65. Continuous conversion of a sequence, software trigger
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1. EXTEN=0x0, CONT=1
2. Channels selected = 1,9, 10, 17; AUTDLY=0.

RM0394 Rev 4

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RM0394

Figure 66. Single conversions of a sequence, hardware trigger
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1. TRGx (over-frequency) is selected as trigger source, EXTEN = 01, CONT = 0
2. Channels selected = 1, 2, 3, 4; AUTDLY=0.

Figure 67. Continuous conversions of a sequence, hardware trigger
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1. TRGx is selected as trigger source, EXTEN = 10, CONT = 1
2. Channels selected = 1, 2, 3, 4; AUTDLY=0.

16.4.26

Data management
Data register, data alignment and offset (ADC_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 ADC_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 ADC_JDRy data register which is 16 bits
wide.
The ALIGN bit in the ADC_CFGR register selects the alignment of the data stored after
conversion. Data can be right- or left-aligned as shown in Figure 68, Figure 69, Figure 70

410/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
and Figure 71.
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 70 and Figure 71.

Note:

Left-alignment is not supported in oversampling mode. When ROVSE and/or JOVSE bit is
set, the ALIGN bit value is ignored and the ADC only provides right-aligned data.

Offset
An offset y (y=1,2,3,4) can be applied to a channel by setting the bit OFFSETy_EN=1 into
ADC_OFRy register. The channel to which the offset will be applied is programmed into the
bits OFFSETy_CH[4:0] of ADC_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.
Note:

Offset correction is not supported in oversampling mode. When ROVSE and/or JOVSE bit is
set, the value of the OFFSETy_EN bit in ADC_OFRy register is ignored (considered as
reset).
Table 64 describes how the comparison is performed for all the possible resolutions for
analog watchdog 1.
Table 62. Offset computation versus data resolution

Resolution
(bits
RES[1:0])

Subtraction 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”

When reading data from ADC_DR (regular channel) or from ADC_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 68, Figure 69, Figure 70 and Figure 71 show alignments for signed and unsigned
data.

RM0394 Rev 4

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485

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RM0394

Figure 68. Right alignment (offset disabled, unsigned value)
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412/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 70. Left alignment (offset disabled, unsigned value)
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413/1600
485

Analog-to-digital converters (ADC)

RM0394

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 ADC_DR register will always contain the latest converted data.
Figure 72. Example of overrun (OVR)

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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 ADC_DR
register can be read. OVRMOD should be configured to 0 to manage overrun events as an
error.

414/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

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 ADC_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 ADC_DR register.
When the DMA mode is enabled (DMAEN bit set to 1 in the ADC_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
ADC_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
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 ADC_CFGR register in single ADC mode, or with bit
DMACFG of the ADC_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.

RM0394 Rev 4

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485

Analog-to-digital converters (ADC)

RM0394

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.

16.4.27

Managing conversions using the DFSDM
The ADC conversion results can be transferred directly to the Digital filter for sigma delta
modulators (DFSDM).
In this case, the DFSDMCFG bit must be set to 1 and DMAEN bit must be cleared to 0.
The ADC transfers all the 16 bits of the regular data register data to the DFSDM and resets
the EOC flag once the transfer is complete.
The data format must be 16-bit signed:
ADC_DR[15:12] = sign extended
ADC_DR[11] = sign
ADC_DR[11:0] = data
To obtain 16-bit signed format in 12-bit ADC mode, the software needs to configure the
OFFSETy[11:0] to 0x800 after having set OFFSETy_EN to 1.
Only right aligned data format is available for the DFSDM interface (see Figure 69: Right
alignment (offset enabled, signed value)).

16.4.28

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 ADC_DR register has been read or if the EOC bit
has been cleared (see Figure 73).

•

For an injected conversion: when the JEOS bit has been cleared (see Figure 74).

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.

416/1600

RM0394 Rev 4

RM0394
Note:

Analog-to-digital converters (ADC)
This is not true for software triggers where it remains possible during this delay to set the
bits ADSTART or JADSTART to restart 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 74).

•

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 76).

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 77).
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 restart 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.

RM0394 Rev 4

417/1600
485

Analog-to-digital converters (ADC)

RM0394

Figure 73. AUTODLY=1, regular conversion in continuous mode, software trigger
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2. Regular configuration: EXTEN=0x0 (SW trigger), CONT=1, CHANNELS = 1,2,3
3. Injected configuration DISABLED

Figure 74. AUTODLY=1, regular HW conversions interrupted by injected conversions
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3. Injected configuration: JEXTEN=0x1 (HW Trigger), JDISCEN=0, CHANNELS = 5,6

418/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

Figure 75. AUTODLY=1, regular HW conversions interrupted by injected conversions
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3. Injected configuration: JEXTEN=0x1 (HW Trigger), JDISCEN=1, CHANNELS = 5,6

RM0394 Rev 4

419/1600
485

Analog-to-digital converters (ADC)

RM0394

Figure 76. AUTODLY=1, regular continuous conversions interrupted by injected conversions
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3. Injected configuration: JEXTEN=0x1 (HW Trigger), JDISCEN=0, CHANNELS = 5,6

Figure 77. AUTODLY=1 in auto- injected mode (JAUTO=1)
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420/1600

RM0394 Rev 4

RM0394

16.4.29

Analog-to-digital converters (ADC)

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 78. Analog watchdog guarded area

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AWDx flag and interrupt
An interrupt can be enabled for each of the 3 analog watchdogs by setting AWDxIE in the
ADC_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 ADC_CFGR
register. This watchdog monitors whether either one selected channel or all enabled
channels(1) remain within a configured voltage range (window).
Table 63 shows how the ADC_CFGR registers should be configured to enable the analog
watchdog on one or more channels.
Table 63. 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

1

0

1

1

1

0

1

1

1

(1)

Single

injected channel

Single(1) regular channel
(1)

Single

regular or injected channel

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.

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485

Analog-to-digital converters (ADC)

RM0394

These thresholds are programmed in bits HT1[11:0] and LT1[11:0] of the ADC_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 64 describes how the comparison is performed for all the possible resolutions for
analog watchdog 1.
Table 64. Analog watchdog 1 comparison
Resolution
(bit
RES[1:0])

Analog watchdog comparison
between:
Comments
Raw converted data,
(1)
left aligned

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],0000 LT1[11:0] and
00
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 AWDCHx[19:0] (x=2,3).
The corresponding watchdog is enabled when any bit of AWDCHx[19:0] (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 65 describes how the comparison is
performed for all the possible resolutions.
Table 65. Analog watchdog 2 and 3 comparison
Analog watchdog comparison between:
Resolution
(bits RES[1:0])

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] User must configure LTx[1:0] and HTx[1:0] to 00

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).

422/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

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 79. ADCy_AWDx_OUT signal generation (on all regular channels)

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485

Analog-to-digital converters (ADC)

RM0394

Figure 80. ADCy_AWDx_OUT signal generation (AWDx flag not cleared by software)
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Figure 81. ADCy_AWDx_OUT signal generation (on a single regular channel)
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Figure 82. ADCy_AWDx_OUT signal generation (on all injected channels)
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424/1600

RM0394 Rev 4

RM0394

16.4.30

Analog-to-digital converters (ADC)

Oversampler
The oversampling unit performs data pre-processing to offload the CPU. It is able to handle
multiple conversions and average them into a single data with increased data width, up to
16-bit.
It provides a result with the following form, where N and M can be adjusted:

n = N–1

1
Result = ----- ×
M

∑

Conversion(t n)

n=0

It allows to perform by hardware the following functions: averaging, data rate reduction,
SNR improvement, basic filtering.
The oversampling ratio N is defined using the OVFS[2:0] bits in the ADC_CFGR2 register,
and can range from 2x to 256x. The division coefficient M consists of a right bit shift up to
8 bits, and is defined using the OVSS[3:0] bits in the ADC_CFGR2 register.
The summation unit can yield a result up to 20 bits (256x 12-bit results), which is first shifted
right. It is then truncated to the 16 least significant bits, rounded to the nearest value using
the least significant bits left apart by the shifting, before being finally transferred into the
ADC_DR data register.
Note:

If the intermediary result after the shifting exceeds 16-bit, the result is truncated as is,
without saturation.
Figure 83. 20-bit to 16-bit result truncation












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The Figure 84 gives a numerical example of the processing, from a raw 20-bit accumulated
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Figure 84. Numerical example with 5-bit shift and rounding

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Table 66 gives the data format for the various N and M combinations, for a raw conversion
data equal to 0xFFF.

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485

Analog-to-digital converters (ADC)

RM0394

Table 66. Maximum output results versus N and M (gray cells indicate truncation)
Over
Max
sampling
Raw data
ratio

No-shift
OVSS =
0000

1-bit
shift
OVSS =
0001

2-bit
shift
OVSS =
0010

3-bit
shift
OVSS =
0011

4-bit
shift
OVSS =
0100

5-bit
shift
OVSS =
0101

6-bit
shift
OVSS =
0110

7-bit
shift
OVSS =
0111

8-bit
shift
OVSS =
1000

2x

0x1FFE

0x1FFE

0x0FFF

0x0800

0x0400

0x0200

0x0100

0x0080

0x0040

0x020

4x

0x3FFC

0x3FFC

0x1FFE

0x0FFF

0x0800

0x0400

0x0200

0x0100

0x0080

0x0040

8x

0x7FF8

0x7FF8

0x3FFC

0x1FFE

0x0FFF

0x0800

0x0400

0x0200

0x0100

0x0080

16x

0xFFF0

0xFFF0

0x7FF8

0x3FFC

0x1FFE

0x0FFF

0x0800

0x0400

0x0200

0x0100

32x

0x1FFE0

0xFFE0

0xFFF0

0x7FF8

0x3FFC

0x1FFE

0x0FFF

0x0800

0x0400

0x0200

64x

0x3FFC0

0xFFC0

0xFFE0

0xFFF0

0x7FF8

0x3FFC 0x1FFE

0x0FFF

0x0800

0x0400

128x

0x7FF80

0xFF80

0xFFC0

0xFFE0

0xFFF0

0x7FF8

0x3FFC

0x1FFE

0x0FFF

0x0800

256x

0xFFF00

0xFF00

0xFF80

0xFFC0

0xFFE0

0xFFF0

0x7FF8

0x3FFC 0x1FFE

0x0FFF

There are no changes for conversion timings in oversampled mode: the sample time is
maintained equal during the whole oversampling sequence. A new data is provided every N
conversions, with an equivalent delay equal to N x TCONV = N x (tSMPL + tSAR). The flags are
set as follow:
•

the end of the sampling phase (EOSMP) is set after each sampling phase

•

the end of conversion (EOC) occurs once every N conversions, when the oversampled
result is available

•

the end of sequence (EOS) occurs once the sequence of oversampled data is
completed (i.e. after N x sequence length conversions total)

ADC operating modes supported when oversampling (single ADC mode)
In oversampling mode, most of the ADC operating modes are maintained:

Note:

•

Single or continuous mode conversions

•

ADC conversions start either by software or with triggers

•

ADC stop during a conversion (abort)

•

Data read via CPU or DMA with overrun detection

•

Low-power modes (AUTDLY)

•

Programmable resolution: in this case, the reduced conversion values (as per RES[1:0]
bits in ADC_CFGR1 register) are accumulated, truncated, rounded and shifted in the
same way as 12-bit conversions are

The alignment mode is not available when working with oversampled data. The ALIGN bit in
ADC_CFGR1 is ignored and the data are always provided right-aligned.
Offset correction is not supported in oversampling mode. When ROVSE and/or JOVSE bit is
set, the value of the OFFSETy_EN bit in ADC_OFRy register is ignored (considered as
reset).

426/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

Analog watchdog
The analog watchdog functionality is maintained (AWDSGL and AWDEN bits), with the
following difference:

Note:

–

the RES[1:0] bits are ignored, comparison is always done on using the full 12-bit
values HT[11:0] and LT[11:0]

–

the comparison is performed on the most significant 12-bit of the 16-bit
oversampled results ADC_DR[15:4]

Care must be taken when using high shifting values, this will reduce the comparison range.
For instance, if the oversampled result is shifted by 4 bits, thus yielding a 12-bit data rightaligned, the effective analog watchdog comparison can only be performed on 8 bits. The
comparison is done between ADC_DR[11:4] and HT[0:7] / LT[[0:7], and HT[11:8] / LT[11:8]
must be kept reset.

Triggered mode
The averager can also be used for basic filtering purpose. Although not a very powerful filter
(slow roll-off and limited stop band attenuation), it can be used as a notch filter to reject
constant parasitic frequencies (typically coming from the mains or from a switched mode
power supply). For this purpose, a specific discontinuous mode can be enabled with
TROVS bit in ADC_CFGR2, to be able to have an oversampling frequency defined by a
user and independent from the conversion time itself.
The Figure 85 below shows how conversions are started in response to triggers during
discontinuous mode.
If the TROVS bit is set, the content of the DISCEN bit is ignored and considered as 1.
Figure 85. Triggered regular oversampling mode (TROVS bit = 1)
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Injected and regular sequencer management when oversampling
In oversampling mode, it is possible to have differentiated behavior for injected and regular
sequencers. The oversampling can be enabled for both sequencers with some limitations if
they have to be used simultaneously (this is related to a unique accumulation unit).

RM0394 Rev 4

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485

Analog-to-digital converters (ADC)

RM0394

Oversampling regular channels only
The regular oversampling mode bit ROVSM defines how the regular oversampling
sequence is resumed if it is interrupted by injected conversion:
•

in continued mode, the accumulation restarts from the last valid data (prior to the
conversion abort request due to the injected trigger). This ensures that oversampling
will be completed whatever the injection frequency (providing at least one regular
conversion can be completed between triggers);

•

in resumed mode, the accumulation restarts from 0 (previous conversions results are
ignored). This mode allows to guarantee that all data used for oversampling were
converted back-to-back within a single timeslot. Care must be taken to have a injection
trigger period above the oversampling period length. If this condition is not respected,
the oversampling cannot be completed and the regular sequencer will be blocked.

The Figure 86 gives examples for a 4x oversampling ratio.
Figure 86. Regular oversampling modes (4x ratio)
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Oversampling Injected channels only
The Injected oversampling mode bit JOVSE enables oversampling solely for conversions in
the injected sequencer.

428/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

Oversampling regular and Injected channels
It is possible to have both ROVSE and JOVSE bits set. In this case, the regular
oversampling mode is forced to resumed mode (ROVSM bit ignored), as represented on
Figure 87 below.
Figure 87. Regular and injected oversampling modes used simultaneously
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Triggered regular oversampling with injected conversions
It is possible to have triggered regular mode with injected conversions. In this case, the
injected mode oversampling mode must be disabled, and the ROVSM bit is ignored
(resumed mode is forced). The JOVSE bit must be reset. The behavior is represented on
Figure 88 below.
Figure 88. Triggered regular oversampling with injection
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RM0394 Rev 4

429/1600
485

Analog-to-digital converters (ADC)

RM0394

Auto-injected mode
It is possible to oversample auto-injected sequences and have all conversions results stored
in registers to save a DMA resource. This mode is available only with both regular and
injected oversampling active: JAUTO = 1, ROVSE = 1 and JOVSE = 1, other combinations
are not supported. The ROVSM bit is ignored in auto-injected mode. The Figure 89 below
shows how the conversions are sequenced.
Figure 89. Oversampling in auto-injected mode
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It is possible to have also the triggered mode enabled, using the TROVS bit. In this case,
the ADC must be configured as following: JAUTO = 1, DISCEN = 0, JDISCEN = 0, ROVSE
= 1, JOVSE = 1 and TROVSE = 1.

Dual ADC modes supported when oversampling
It is possible to have oversampling enabled when working in dual ADC configuration, for the
injected simultaneous mode and regular simultaneous mode. In this case, the two ADCs
must be programmed with the very same settings (including oversampling).
All other dual ADC modes are not supported when either regular or injected oversampling is
enabled (ROVSE = 1 or JOVSE = 1).

Combined modes summary
The Table 67 below summarizes all combinations, including modes not supported.
Table 67. Oversampler operating modes summary
Regular
Injected
Oversampling Oversampling
ROVSE

JOVSE

Oversampler
mode
ROVSM

Triggered
Regular mode

0 = continued

TROVS

Comment

1 = resumed

430/1600

1

0

0

0

Regular continued mode

1

0

0

1

Not supported

1

0

1

0

Regular resumed mode

1

0

1

1

Triggered regular resumed
mode

1

1

0

X

Not supported

1

1

1

0

Injected and regular resumed
mode

1

1

1

1

Not supported

0

1

X

X

Injected oversampling

RM0394 Rev 4

RM0394

16.4.31

Analog-to-digital converters (ADC)

Dual ADC modes
Dual ADC modes can be used in devices with two ADCs or more (see Figure 90).
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

•

Injected simultaneous mode + Interleaved 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 ADC_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).

RM0394 Rev 4

431/1600
485

Analog-to-digital converters (ADC)

RM0394
Figure 90. Dual ADC block diagram(1)

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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.

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)

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 bits in the
ADC_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 ADC_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 ADC_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 91), 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
ADC_JDRy and slave ADC_JDRy registers).
Figure 91. Injected simultaneous mode on 4 channels: dual ADC mode
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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:
•

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 (ADC_DR)
has been read. Any new regular trigger events occurring for the master ADC during the

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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 bits in the
ADC_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 ADC_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 ADC_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 92), 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:
•

•

Note:

434/1600

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 ADC_DR from the master. DMA
requests are generated at each EOC event of the master ADC.

–

Configure the DMA slave ADC channel to read ADC_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.

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.
RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 92. Regular simultaneous mode on 16 channels: dual ADC mode
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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:
•

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.

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

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RM0394

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.
The software is notified by interrupts when it can read the data at the end of each
conversion event (EOC) on the slave ADC. A slave and master EOC interrupts are
generated (if EOCIE is enabled) and the software can read the ADC_DR of the slave/master
ADC.
Note:

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
recommended to use the MDMA mode.
It is also possible to have the regular data transferred by DMA. In this case, individual DMA
requests on each ADC cannot be used and it is mandatory to use the MDMA mode, as
following:
•

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.

Figure 93. Interleaved mode on 1 channel in continuous conversion mode: dual ADC
mode

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RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 94. Interleaved mode on 1 channel in single conversion mode: dual ADC mode

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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 restarted from the master (see Figure 95 below).
Figure 95. Interleaved conversion with injection
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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.
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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.
Figure 96. Alternate trigger: injected group of each ADC
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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.
438/1600

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
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.

Figure 97. Alternate trigger: 4 injected channels (each ADC) in discontinuous mode
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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 98 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.

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Figure 98. Alternate + regular simultaneous
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If a trigger occurs during an injected conversion that has interrupted a regular conversion,
the alternate trigger is served. Figure 99 shows the behavior in this case (note that the 6th
trigger is ignored because the associated alternate conversion is not complete).
Figure 99. Case of trigger occurring during injected conversion
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Combined injected simultaneous plus interleaved
This mode is selected by programming bits DUAL[4:0]=00011
It is possible to interrupt an interleaved conversion with a simultaneous injected event.

Caution:

440/1600

In this case the interleaved conversion is interrupted immediately and the simultaneous
injected conversion starts. At the end of the injected sequence the interleaved conversion is
resumed. When the interleaved regular conversion resumes, the first regular conversion
which is performed is alway the master’s one. Figure 100, Figure 101 and Figure 102 show
the behavior using an example.
In this mode, it is mandatory to use the Common Data Register to read the regular data with
a single read access. On the contrary, master-slave data coherency is not guaranteed.

RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 100. Interleaved single channel CH0 with injected sequence CH11, CH12

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Figure 101. Two Interleaved channels (CH1, CH2) with injected sequence CH11, CH12
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Figure 102. Two Interleaved channels (CH1, CH2) with injected sequence CH11, CH12
- case 2: Slave interrupted first
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Analog-to-digital converters (ADC)

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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 103: DMA Requests in
regular simultaneous mode when MDMA=0b00).
Figure 103. DMA Requests in regular simultaneous mode when MDMA=0b00
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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_ADC_DR[15:0] | MST_ADC_DR[15:0]
2nd DMA request: ADCx_CDR[31:0] = SLV_ADC_DR[15:0] |
MST_ADC_DR[15:0]

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RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 104. DMA requests in regular simultaneous mode when MDMA=0b10
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Figure 105. DMA requests in interleaved mode when MDMA=0b10

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Analog-to-digital converters (ADC)
Note:

RM0394

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_ADC_DR[7:0] | MST_ADC_DR[7:0]
2nd DMA request: ADCx_CDR[15:0] = SLV_ADC_DR[7:0] | MST_ADC_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 ADC_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.

16.4.32

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 ADC 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. It support the temperature range –40 to 125 °C.
Figure 106 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).

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RM0394

Analog-to-digital converters (ADC)
The uncalibrated internal temperature sensor is more suited for applications that detect
temperature variations instead of absolute temperatures. To improve the accuracy of the
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 datasheet for additional information).
The temperature sensor is internally connected to the ADC input channel which is used to
convert the sensor’s output voltage to a digital value. Refer to the electrical characteristics
section of the device 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 106 shows the block diagram of the temperature sensor. The dac_out1 signal and
the temperature sensor share the same input.
Figure 106. Temperature sensor channel block diagram

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Reading the temperature
To use the sensor:
1.

Select the ADC input channels which is connected to VTS.

2.

Program with the appropriate sampling time (refer to electrical characteristics section of
the device datasheet).

3.

Set the CH17SEL bit in the ADCx_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:

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TS_CAL2_TEMP – TS_CAL1_TEMP
Temperature ( in °C ) = -------------------------------------------------------------------------------------------------- × ( TS_DATA – TS_CAL1 ) + 30 °C
TS_CAL2 – TS_CAL1

Where:
•

TS_CAL2 is the temperature sensor calibration value acquired at TS_CAL2_TEMP.

•

TS_CAL1 is the temperature sensor calibration value acquired at TS_CAL1_TEMP.

•

TS_DATA is the actual temperature sensor output value converted by ADC.
Refer to the device datasheet for more information about TS_CAL1 and TS_CAL2
calibration points.

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 CH17SEL bits should be set at the same time.

16.4.33

VBAT supply monitoring
The CH18SEL bit in the ADCx_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 3. This bridge is automatically enabled
when CH18SEL is set, to connect VBAT/3 to the ADC input channels. As a consequence, the
converted digital value is one third of 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 device datasheet for the sampling time value to
be applied when converting the VBAT/3 voltage.
The figure below shows the block diagram of the VBAT sensing feature. The dac_out2 signal
and VBAT sensing input share the same input.

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RM0394 Rev 4

RM0394

Analog-to-digital converters (ADC)
Figure 107. VBAT channel block diagram

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1. The CH18SEL bit must be set to enable the conversion of internal channel for VBAT/3.

16.4.34

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 0 of the ADC1
(ADC1_INP0).
Refer to the electrical characteristics section of the product datasheet for the sampling time
value to be applied when converting the internal voltage reference voltage.
Figure 108 shows the block diagram of the VREFINT sensing feature.
Figure 108. VREFINT channel block diagram

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1. The VREFEN bit into ADCx_CCR register must be set to enable the conversion of internal channels
(VREFINT).

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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 = 3.0 V can be used to
evaluate the actual VDDA voltage level.
The following formula gives the actual VDDA voltage supplying the device:
VDDA = 3.0 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 you 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, you must use the internal voltage
reference and VDDA can be replaced by the expression provided in Calculating the actual
VDDA voltage using the internal reference voltage, resulting in the following formula:
3.0 V × VREFINT_CAL × ADCx_DATA
V CHANNELx = -------------------------------------------------------------------------------------------------------VREFINT_DATA × FULL_SCALE

Where:

Note:

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•

VREFINT_CAL is the VREFINT calibration value

•

ADC_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.

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16.5

Analog-to-digital converters (ADC)

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 68. 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

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16.6

RM0394

ADC registers (for each ADC)
Refer to Section 1.2 on page 60 for a list of abbreviations used in register descriptions.

16.6.1

ADC interrupt and status register (ADC_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.

Res.

Res.

Res.

Res.

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 16.4.21: 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 ADC_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 ADC_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 ADC_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
Bit 6 JEOS: Injected