Table 26. FLASH_SM_3
SM CODE FLASH_SM_3
Description Option byte write protection
Ownership ST
Detailed implementation
This safety mechanism prevents unintended writes on the option byte. The use of this method
is encouraged to enhance end application robustness for systematic faults.
Error reporting Write protection exception
Fault detection time Not applicable
Addressed fault model None (systematic only)
Dependency on Device configuration None
Initialization None (always enabled)
Periodicity Continuous
Test for the diagnostic Not applicable
Multiple-fault protection CPU_SM_0: Periodic core self-test software
Recommendations and known limitations
This method addresses systematic faults in software application and it have zero efficiency in
addressing hardware random faults affecting the option byte value during running time. No DC
value is therefore associated.
Table 27. FLASH_SM_4
SM CODE FLASH_SM_4
Description Static data encapsulation
Ownership End user
Detailed implementation
If static data are stored in Flash memory, encapsulation by a checksum field with encoding
capability (such as CRC) must be implemented.
Checksum validity is checked by Application software before static data consuming.
Error reporting Depends on implementation
Fault detection time Depends on implementation
Addressed fault model Permanent/transient
Dependency on Device configuration None
Initialization Depends on implementation
Periodicity On demand
Test for the diagnostic Not applicable
Multiple-fault protection CPU_SM_0: Periodic core self-test software
Recommendations and known limitations None
Table 28. FLASH_SM_5
SM CODE FLASH_SM_5
Description Option byte redundancy with load verification
Ownership ST
Detailed implementation
During option byte loading after each power-on reset, the bit-wise complementarity of the
option byte and its corresponding complemented option byte is verified. Mismatches are
reported as an error.
Error reporting Option byte error (OPTVERR) generation
UM2305
Hardware and software diagnostics
UM2305 - Rev 10
page 23/110