You will find the answer in HAL and the reference manual:
- Lock and Unlock the FLASH interface using HAL_FLASH_Unlock() and HAL_FLASH_Lock() functions
- Lock and Unlock the option bytes using HAL_FLASH_OB_Unlock() and HAL_FLASH_OB_Lock() functions
HAL_FLASH_Lock locks FLASH Registers access using SET_BIT(FLASH->CR, FLASH_CR_LOCK);
HAL_FLASH_OB_Lock locks FLASH Option Byte Registers access using SET_BIT(FLASH->CR, FLASH_CR_OPTLOCK);
Please read the description for the LOCK and OPTLOCK bits in the reference manual under section Flash control register (FLASH_CR).
Regards
/Peter
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