AN3154 datasheet(20/34 Pages) STMICROELECTRONICS

20 / 34 page

Bootloader command set

AN3154

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DocID017063 Rev 5

Figure 15. Go command: device side

The STM32 send the messages as follows:

ACK message: Std ID = 0x21, DLC = 1, data[0] = ACK if content of the command is correct

else data[0] = NACK

3.7

Write Memory command

The Write Memory command is used to write data to any valid memory address (see note)

of RAM, Flash memory, or Option byte area. When the bootloader receives the Write

Memory command, (message with 5 bytes data length, data[0] is the address MSB, data[3]

is the LSB and data[4] is the number of data bytes to be received), it then checks the

received address. For the Option byte area, the start address must be the base address of

the Option byte area (see note) to avoid writing inopportunely in this area.

Note:

Refer to Section 3.1: Get command for more details about the valid memory addresses for

the device you are using.

If the received address is valid, the bootloader transmits an ACK message, otherwise it

transmits a NACK message and aborts the command. When the address is valid, the

bootloader:

•

Receives the user data (N bytes) so the device receives N/8 messages (each message

contains 8 data bytes)

•

Programs the user data into memory starting from the received address

•

At the end of the command, if the write operation was successful, the bootloader

transmits the ACK message; otherwise it transmits a NACK message to the application

and aborts the command

The maximum length of the block to be written for the STM32 is 256 bytes.

If the Write Memory command is issued to the Option byte area, all options are erased

before writing the new values, and at the end of the command the bootloader generates a

system Reset to take into account the new configuration of the option byte.

AN3154 Datasheet(PDF) 20 Page - STMicroelectronics