To Next Page

To Previous Page

RM0444 Rev 5 91/1390

RM0444 Embedded Flash memory (FLASH)

118

If the word and its complement are matching, the option word/byte is copied into the option

If the comparison between the word and its complement fails, a status bit OPTVERR is set.

Mismatch values are forced into the option registers:

– For USR OPT option, the value of mismatch is 1 for all option bits, except the

BOR_EN bit that is 0 (BOR disabled).

– For WRP option, the value of mismatch is the default value “No protection”.

– For RDP option, the value of mismatch is the default value “Level 1”.

– For PCROP, the value of mismatch is “all memory protected”.

– For BOOT_LOCK, the value of mismatch is “boot forced from Main Flash

memory”.

Upon system reset, the option bytes are copied into the following option registers that can

be read and written by software:

• FLASH_OPTR

• FLASH_PCROPyxSR (x = A or B, y = 1 or 2)

• FLASH_PCROPyxER (x = A or B, y = 1 or 2)

• FLASH_WRPyxR (x = A or B, y = 1 or 2)

• FLASH_SECR

These registers are also used to modify options. If these registers are not modified by user,

they reflect the options states of the system. See Modifying user options for more details.

3.5 FLASH memory protection

The Main Flash memory can be protected against external accesses with the read

protection (RDP). The pages can also be protected against unwanted write (WRP) due to

loss of program counter context. The write-protection WRP granularity is 2 Kbytes. Apart

from the RDP and WRP, the Flash memory can also be protected against read and write by

third party (PCROP). The PCROP granularity (subpage size) is 512 bytes.

3.5.1 FLASH read protection (RDP)

The read protection is activated by setting the RDP option byte and then, by applying a

system reset to reload the new RDP option byte. The read protection protects the Main

Flash memory, the option bytes, the backup registers (TAMP_BKPxR in TAMP) and the

SRAM.

Note: If the read protection is set while the debugger is still connected through SWD, apply power

reset instead of system reset.

There are three levels of read protection from no protection (Level 0) to maximum protection

or no debug (Level 2).

The Flash memory is protected when the RDP option byte and its complement contain the

pair of values shown in Table 17.

ST STM32G0 1 Series User Manual

Questions and Answers: