PM0063

Reading/programming the STM32F100xx embedded Flash memory

Doc ID 16211 Rev 2

21/30

On every system reset, the option byte loader (OBL) reads the information block and stores

the data into the Option byte register (FLASH_OBR) and the Write protection register

(FLASH_WRPR). Each option byte also has its complement in the information block. During

option loading, by verifying the option bit and its complement, it is possible to check that the

loading has correctly taken place. If this is not the case, an option byte error (OPTERR) is

generated. When a comparison error occurs the corresponding option byte is forced to

0xFF. The comparator is disabled when the option byte and its complement are both equal

to 0xFF (Electrical Erase state).

All option bytes (but not their complements) are available to configure the product. The

option registers are accessible in read mode by the CPU. See Section 3: Register

descriptions for more details.

0x1FFF F80C

WRPx: Flash memory write protection option bytes

Bits [31:24]: nWRP3

Bits [23:16]: WRP3 (stored in FLASH_WRPR[31:24])

Bits [15:8]: nWRP2

Bits [7:0]: WRP2 (stored in FLASH_WRPR[23:16])

●

For low-density value line devices, one bit of the user option bytes WRPx is

used to protect 4 pages of 1 Kbyte in main memory block.

–

0: Write protection active

–

1: Write protection not active

In total, one user option byte is used to protect the 32-Kbyte main Flash memory.

WRP0: Write-protects pages 0 to 31

●

For medium-density value line devices, one bit of the user option bytes WRPx

is used to protect 4 pages of 1 Kbyte in main memory block.

–

0: Write protection active

–

1: Write protection not active

In total, four user option bytes are used to protect the 128-Kbyte main Flash

memory.

WRP0: Write-protects pages 0 to 31

WRP1: Write-protects pages 32 to 63

WRP2: Write-protects pages 64 to 95

WRP3: Write-protects pages 96 to 127

●

For high-density value line devices, one bit of the user option bytes WRPx is

used to protect 2 pages of 2 Kbytes in main memory block. However, the bit 7

of WRP3 write protects pages 62 to 255.

–

0: Write protection active

–

1: Write protection not active

In total, four user option bytes are used to protect the 512-Kbyte main Flash

memory.

WRP0: Write-protects pages 0 to 15

WRP1: Write-protects pages 16 to 31

WRP2: Write-protects pages 32 to 47

WRP3: bits 0-6 write-protect pages 48 to 61

bit 7 write-protects pages 62 to 255.

Table 7.

Description of the option bytes (continued)

Flash memory

address

Option bytes