PM0068 Reading/programming the STM32F101xF/G and STM32F103xF/G embedded Flash memo-

Doc ID 17100 Rev 2

19/31

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 F804

Datax: Two bytes for user data storage.

These addresses can be programmed using the option byte programming

procedure.

Bits [31:24]: nData1

Bits [23:16]: Data1 (stored in FLASH_OBR[25:18])

Bits [15:8]: nData0

Bits [7:0]: Data0 (stored in FLASH_OBR[17:10])

0x1FFF F808

WRPx: Flash memory write protection option bytes

Bits [31:24]: nWRP1

Bits [23:16]: WRP1 (stored in FLASH_WRPR[15:8])

Bits [15:8]: nWRP0

Bits [7:0]: WRP0 (stored in FLASH_WRPR[7:0])

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])

One bit of the user option bytes WRPx is used to protect 2 pages of 2 Kbytes in

the main memory block. However, bit 7 of WRP3 write protects pages 62 to 511.

0: Write protection active

1: Write protection not active

In total, four user option bytes are used to protect 1 Mbytes of 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, and bit 7 write-protects pages 62 to

511.

Table 5.

Description of the option bytes (continued)

Flash memory

address

Option bytes