void UnlockFlash()
{
    FLASH->KEYR = 0x45670123;
    FLASH->KEYR = 0xCDEF89AB;
}



void LockFlash()
{
    SET_BIT(FLASH->CR, FLASH_CR_LOCK);
}



void UserFlash_Erase()
{
    //Unlock FLASH register
    UnlockFlash();

    //Check that no Flash memory operation is ongoing by checking the BSY bit in the FLASH_SR register
    while (READ_BIT(FLASH->SR, FLASH_SR_BSY));

    //Set the SER bit
    SET_BIT(FLASH->CR, FLASH_CR_SER);

    //Select the sector out of the 12 sectors
    MODIFY_REG(FLASH->CR, FLASH_CR_SNB, USER_FLASH_SECTOR_INDEX << FLASH_CR_SNB_Pos);

    //Set the STRT bit in the FLASH_CR register
    SET_BIT(FLASH->CR, FLASH_CR_STRT);

    //Wait for the BSY bit to be cleared
    while(READ_BIT(FLASH->SR, FLASH_SR_BSY));

    //Lock FLASH register
    LockFlash();
}