June 2021 AN4286 Rev 10 1/48

AN4286

Application note

SPI protocol used in the STM32 bootloader

Introduction

This application note describes the SPI protocol used in the STM32 microcontroller

bootloader, detailing each supported command.

This document applies to the STM32 products embedding bootloader versions V8.x, V9.x,

V11.x, V12.x and V13.x, as specified in AN2606 “STM32 microcontroller system memory

boot mode”, available on www.st.com. These products are listed in Table 1, and are referred

to as STM32 throughout the document.

For more information about the SPI hardware resources and requirements for your device

bootloader, refer to the already mentioned AN2606.

Table 1. Applicable products

Product family Product series

Microcontrollers

STM32F4 Series

STM32F7 Series

STM32G0 Series

STM32G4 Series

STM32H7 Series

STM32L0 Series

STM32L4 Series

STM32L5 Series

STM32WB Series

STM32WL Series

www.st.com

Contents AN4286

2/48 AN4286 Rev 10

Contents

1 SPI bootloader code sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Bootloader command set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.1 Safety of communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 Get command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3 Get Version command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.4 Get ID command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.5 Read Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.6 Go command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.7 Write Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.8 Erase Memory command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.9 Write Protect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.10 Write Unprotect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.11 Readout Protect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.12 Readout Unprotect command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2.13 Get Checksum command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

2.14 Special command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

2.15 Extended Special command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3 Evolution of the bootloader protocol versions . . . . . . . . . . . . . . . . . . 46

4 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47