AN4286 datasheet(27/38 Pages) STMICROELECTRONICS

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Bootloader command set

AN4286

27/38

DocID024458 Rev 2

2.9

Write Protect command

The Write Protect command is used to enable the write protection for some or all Flash

memory sectors. When the bootloader receives the Write Protect command, it transmits the

ACK byte to the master. After transmission of the ACK byte, the bootloader waits for the

number of bytes to be received (sectors to be protected) and then receives the Flash

memory sector codes from the application.

At the end of the Write Protect command, the bootloader transmits the ACK byte and

generates a system reset to take into account the new configuration of the option byte.

The Write Protect command sequence is as follows.

•

The bootloader receives one byte that contains N, the number of sectors to be write-

protected - 1 (0 ≤ N ≤ 255)

•

The bootloader receives (N + 1) bytes, each byte contains a sector code.

Note:

The total number of sectors and the sector number to be protected are not checked, which

means that no error is returned when a command is passed with a wrong number of sectors

to be protected or a wrong sector number.

If a second Write Protect command is executed, the Flash memory sectors that had been

protected by the first command become unprotected and only the sectors passed within the

second Write Protect command become protected.

AN4286 Datasheet(PDF) 27 Page - STMicroelectronics