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PM0073 データシート(PDF) 21 Page - STMicroelectronics |
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PM0073 データシート(HTML) 21 Page - STMicroelectronics |
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21 / 34 page ![]() PM0073 Reading/programming the STM32Wxxx embedded Flash memory Doc ID 17766 Rev 5 21/34 Case 2 - Read protection maintained active after the write unprotection, useful for in- application programming with a user bootloader: 1. Erase the entire option byte area by using the OPTER bit in the Flash memory control register (FLASH_CR). 2. Reset the device (system reset) to reload the option bytes (and the new WRP[3:0] bytes), and to disable the write protection. 2.3.3 Option byte block write protection The option bytes are always read-accessible and write-protected by default. To gain write access (Program/Erase) to the option bytes, a sequence of keys (same as for lock) has to be written into the OPTKEYR. A correct sequence of keys gives write access to the option bytes; this is indicated by OPTWRE in the FLASH_CR register being set. Write access can be disabled by resetting the bit through software. 2.4 Option byte description There are eight option bytes. They are configured by the end user depending on the application requirements. As a configuration example, the watchdog may be selected in hardware or software mode. A 32-bit word is split up as follows in the option bytes. The organization of these bytes inside the information block is as shown in Table 8: Option byte organization (wireless line devices). The option bytes can be read from the memory locations listed in Table 8: Option byte organization (wireless line devices) or from the Option byte register (FLASH_OBR). Note: The new programmed option bytes (user, read/write protection) are loaded after a system reset. Table 7. Option byte format 31-24 23-16 15 -8 7-0 complemented option byte1 Option byte 1 complemented option byte0 Option byte 0 Table 8. Option byte organization (wireless line devices) Address [31:24] [23:16] [15:8] [7:0] 0x0804 0800 nRsvd0 Rsvd0 nRDP RDP 0x0804 0804 nRsvd2 Rsvd2 nRvsd1 Rvsd1 0x0804 0808 nWRP1 WRP1 nWRP0 WRP0 0x0804 080C nWRP3 WRP3 nWRP2 WRP2 |
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