ST STM32F105 Series Application Note page 55

AN2662
The host sends the messages as follows
Command message: Std ID = 0x31, DLC = 0x05, data[0] = 0xXX: MSB address,... , data[3]
= 0xYY: LSB address, data[4] = N(number of bytes to be written), 0 < N <= 255).
then the host send N/8 message
Data message: Std ID = 0x31, DLC_1 = to 8, data = byte_11, ... byte_18...
Data message_M: Std ID = 0x04, DLC_M = 1 to 8, data = byte_m1, ..., byte_M8
Note: 1 DLC_1 + DLC_2 + ... DLC_M = 256 maximum
2 After each message the host receives the ACK or NACK message from the device
3 The bootloader does not check the standard ID of the data, so any ID from 0h to 0xFF can
be used. It is recommended to use 0x04.
Doc ID 14156 Rev 1
CAN bootloader
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