Table 18. Ram_Sm_2; Table 19. Ram_Sm_3 - ST STM32L4 Series User Manual

SM CODE
Description
Ownership
Detailed implementation
Error reporting
Fault detection time
Addressed fault model
Dependency on Device configuration
Initialization
Periodicity
Test for the diagnostic
Multiple-fault protection
Recommendations and known limitations
SM CODE
Description
Ownership
Detailed implementation
Error reporting
Fault detection time
Addressed fault model
Dependency on Device configuration
Initialization
Periodicity
Test for the diagnostic
Multiple-fault protection
UM2305 - Rev 10
Table 18. RAM_SM_2
Stack hardening for Application software
End user
The stack hardening method is used to enhance Application software robustness to SRAM
faults that affect the address decoder. The method is based on source code modification,
introducing information redundancy in the stack-passed information to the called functions.
Method contribution is relevant in case the combination between the final Application software
structure and the compiler settings requires a significant use of the stack for passing function
parameters.
Implementation is the same as method CPU_SM_4.
Refer to CPU_SM_4
Refer to CPU_SM_4
Refer to CPU_SM_4
Refer to CPU_SM_4
Refer to CPU_SM_4
Refer to CPU_SM_4
Refer to CPU_SM_4
Refer to CPU_SM_4
Refer to CPU_SM_4
Table 19. RAM_SM_3
Information redundancy for safety-related variables in Application software
End user
To address transient faults affecting SRAM controller, it is required to implement information
redundancy on the safety-related system variables stored in the RAM.
The guidelines for the implementation of this method are the following:
• The system variables that are safety-related (in the sense that a wrong value due to
a failure in reading on the RAM affects the safety functions) are well-identified and
documented.
• The arithmetic computation or decision based on such variables are executed twice and
the two final results are compared.
• Safety-related variables are stored and updated in two redundant locations, and
comparison is checked before consuming data.
• Enumerated fields must use non-trivial values, checked for coherence with the same
frequency as for periodically executed diagnostics (see
software diagnostics).
• Data vectors stored in SRAM must be protected by a encoding checksum (such as
CRC).
Depends on implementation
Depends on implementation
Permanent/transient
None
Depends on implementation
On demand
Not applicable
CPU_SM_0: Periodic core self-test software
Hardware and software diagnostics
RAM_SM_2
RAM_SM_3
(1)
in Section 3.6 Hardware and
UM2305
page 19/110