AN4286 datasheet(20/38 Pages) STMICROELECTRONICS

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AN4286

Bootloader command set

Figure 15. Go command: slave side

2.7

Write Memory command

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

below) of the RAM, Flash memory or Option byte area.

When the bootloader receives the Write Memory command, it transmits the ACK byte to the

application. After transmission of the ACK byte, the bootloader waits for an address

(4 bytes, byte 1 being the address MSB and byte 4 being the LSB) and a checksum byte,

and then checks the received address.

If the received address is valid and the checksum is correct, the bootloader transmits an

ACK byte; otherwise it transmits a NACK byte and aborts the command. When the address

is valid and the checksum is correct, the bootloader then does the following.

•

Gets a byte, N, which contains the number of data bytes to be received.

•

Receives the user data ((N + 1) bytes) and the checksum (XOR of N and of all data

bytes).

•

Programs the user data to memory starting from the received address.

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