3.6.3 Embedded SRAM
Table 22. RAM_SM_0
SM CODE RAM_SM_0
Description Periodical software test for SRAM memory
Ownership End user or ST
Detailed implementation
To enhance the coverage on SRAM data cells and to ensure adequate coverage for permanent faults
affecting the address decoder it is required to execute a periodical software test on the system RAM
memory. The selection of the algorithm must ensure the target SFF coverage for both the RAM cells and
the address decoder. Evidences of the effectiveness of the coverage of the selected method must be also
collected
Error reporting Depends on implementation
Fault detection time Depends on implementation
Addressed fault model Permanent
Dependency on MCU
configuration
RAM size can change according to the part number
Initialization Depends on implementation
Periodicity Periodic
Test for the diagnostic
Self-diagnostic capabilities can be embedded in the software, according the test implementation design
strategy chosen
Multiple faults protection CPU_SM_0: periodical core self-test software
Recommendations and known
limitations
Usage of a March test C- is recommended.
Because the nature of this test can be destructive, RAM contents restore must be implemented. Possible
interferences with interrupt-serving routines fired during test execution must be also considered (such
routines can access to RAM invalid contents).
Note: unused RAM section can be excluded by the testing, under end user responsibility on actual RAM
usage by final application software
Table 23. RAM_SM_2
SM CODE RAM_SM_2
Description Stack hardening for application software
Ownership End user
Detailed implementation
The stack hardening method is used to enhance the 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
Error reporting Refer to CPU_SM_4
Fault detection time Refer to CPU_SM_4
Addressed fault model Refer to CPU_SM_4
Dependency on MCU configuration Refer to CPU_SM_4
Initialization Refer to CPU_SM_4
Periodicity Refer to CPU_SM_4
Test for the diagnostic Refer to CPU_SM_4
UM1845
Description of hardware and software diagnostics
UM1845 - Rev 4
page 22/108
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