S12ZVx - How does Core Self Test affect the Stack overflow and underflow metrics?

[AdrianR]

Core FMEDA for S12ZVL128 increases the fault metrics for Failure Modes: Stack overflow and Stack underflow when Software Functional Self Test Routine for Core periodically executed within Fault Tolerant Time Interval [SM_0037] [SM_0051] is disabled vs. enabled. What is the explanation of the effect of SCST over Stack of/uf?

[aarul]

Hello Adrian

The SCST Library is able to detect random HW faults in the CPU core which might cause stack overflow or underflow, e.g. fault in the logic which updates stack pointer address during stacking/unstacking.

The SCST Library Safety Manual also recommends implementation of additional safety measure on application side for stack pointer monitoring:

Recommendation ID: REQ_FSL_S12Z_SCST05

S12Z_SCST Library during its execution may erroneously corrupt core registers including

stack pointer due to a HW fault. Application should implement corresponding safety measure

for detecting/preventing the described scenario. It is suggested to check stack consistency as

well as local variables, if declared and used.

Regards

-Aarul