Programming User Option Bytes - ST STM32F413 Reference Manual

Embedded Flash memory interface
Bit 14
Bits 13:0
3.6.2

Programming user option bytes

To run any operation on this sector, the option lock bit (OPTLOCK) in the Flash option
control register (FLASH_OPTCR) must be cleared. To be allowed to clear this bit, you have
to perform the following sequence:
1. Write OPTKEY1 = 0x0819 2A3B in the Flash option key register (FLASH_OPTKEYR)
2. Write OPTKEY2 = 0x4C5D 6E7F in the Flash option key register (FLASH_OPTKEYR)
The user option bytes can be protected against unwanted erase/program operations by
setting the OPTLOCK bit by software.
Modifying user option bytes
To modify the user option value, follow the sequence below:
1. Check that no Flash memory operation is ongoing by checking the BSY bit in the
FLASH_SR register
2. Write the desired option value in the FLASH_OPTCR register.
3. Set the option start bit (OPTSTRT) in the FLASH_OPTCR register
4. Wait for the BSY bit to be cleared.
Note: The value of an option is automatically modified by first erasing the user configuration sector
and then programming all the option bytes with the values contained in the FLASH_OPTCR
register.
3.6.3 Read protection (RDP)
The user area in the Flash memory can be protected against read operations by an
entrusted code. Three read protection levels are defined:
•
Level 0: no read protection
When the read protection level is set to Level 0 by writing 0xAA into the read protection
option byte (RDP), all read/write operations (if no write protection is set) from/to the
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Table 10. Description of the option bytes
nWRP15_14: Non Write Protection of sector 15 and 14
If SPRMOD is reset (default value):
0: Write protection active on sector 15 and 14.
1: Write protection not active on sector 15 and 14.
If SPRMOD is set (active):
0: PCROP protection not active on sector 15 and 14.
1: PCROP protection active on sector 15 and 14.
nWRPi
If SPRMOD is reset (default value):
0: Write protection active on sector i.
1: Write protection not active on sector i.
If SPRMOD is set (active):
0: PCROP protection not active on sector i.
1: PCROP protection active on sector i.
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