AN4286 datasheet(24/38 Pages) STMICROELECTRONICS

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AN4286

Bootloader command set

2.8

Erase Memory command

The Erase Memory command allows the master to erase the Flash memory pages or

sectors using two-byte addressing mode. When the bootloader receives the Erase Memory

command, it transmits the ACK byte to the master. After transmission of the ACK byte, the

bootloader receives two bytes (number of pages or sectors to be erased), the Flash memory

page codes (each one coded on two bytes, MSB first) and a checksum byte (XOR of the

sent bytes). If the checksum is correct, the bootloader erases the memory and sends an

ACK byte to the master. Otherwise it sends a NACK byte to the master and the command is

aborted.

Erase Memory command specifications

The bootloader receives two bytes that contain N, the number of pages or sectors to be

erased.

•

For N = 0xFFFY (where Y is from 0 to F) a special erase is performed.

–

0xFFFF for a global mass erase.

–

0xFFFE for a Bank 1 mass erase (only for products supporting this feature).

–

0xFFFD for a Bank 2 mass erase (only for products supporting this feature).

–

Values from 0xFFFC to 0xFFF0 are reserved.

•

For other values where 0 ≤ N < maximum number of pages or sectors: N + 1 pages or

sectors are erased.

The bootloader then receives the following.

•

In the case of a special erase, one byte: checksum of the previous bytes: (that is, 0x00

for 0xFFFF).

•

In the case of N+1 pages or sector erase, the bootloader receives (2 x (N + 1)) bytes,

each half-word containing a page number (coded on two bytes, MSB first). Then all

previous byte checksums (in one byte).

Note:

No error is returned when performing erase operations on write-protected sectors.The

maximum number of pages or sectors is relative to the product and thus should be

respected.

The master sends bytes to the STM32 as follows.

•

Start Of Frame: 0x5A

•

Byte 1: 0x44

•

Byte 2: 0xBB

•

Wait for ACK (as described in section 1)

•

Bytes 3-4:

–

Special erase: global erase (0xFFFY where Y={F, E, D})

–

Number of pages or sectors to be erased (N+1 where: 0 ≤ N < maximum number

of pages or sectors).

•

Remaining bytes:

–

Checksum of bytes 3-4 in the case of a special erase (0x00, 0x01 or 0x02).

–

(2 x (N + 1)) bytes (page numbers coded on two bytes MSB first) then the

checksum for bytes 3-4 and all the following bytes).

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