topic Re: Question about SCST Lib test in S32K

Question about SCST Lib test

Loky — Fri, 12 Dec 2025 07:24:15 GMT

Hi team:

I think all SCST tests can be interrupted, right?

But I don't understand this sentence.

If I put SCST test1 in Task1(Low priority), Test1 is preempted by Task2(High priority) while Test1 is running. I think stack pointer and stack content will be modified. So, I don't understand this sentence meaning. Can you explain it?

Re: Question about SCST Lib test

petervlna — Fri, 12 Dec 2025 10:32:11 GMT

Hello,

Not all SCST atomic tests are safely preemptible.
Some test groups replace the interrupt vector table or temporarily block interrupts, and they expect to run to completion without being interrupted by normal application ISRs or excessive task-preemption jitter.

If an “alien” interrupt or a context change occurs during those tests, the SCST library detects it and flags “TEST_WAS_INTERRUPTED”, and your app must handle that (e.g., reschedule or reset, depending on your safety strategy).

Best regards,

Peter

Re: Question about SCST Lib test

Loky — Sun, 14 Dec 2025 06:55:09 GMT

Hi Peter:

Can you tell me which SCST atomic tests can be interrupted and which will block?

Best regards,

Loky

Re: Question about SCST Lib test

petervlna — Wed, 17 Dec 2025 08:47:06 GMT

Hello,

I was talking to safety expert:

“I would simplify it by saying that every test must have atomic execution. Putting it into a task with Low Priority doesn’t necessarily ensure that it will be completed within the FDTI time frame. ’ll send it to the SCST team to see if they can clarify.”

Best regards,

Peter

Re: Question about SCST Lib test

Loky — Thu, 18 Dec 2025 07:20:55 GMT

Ok, I think I only want to know which SCST tests can be interrupted and which will block, so that I can decide maybe which test will put into task or put at startup. Waiting for your message, thank you

Re: Question about SCST Lib test

petervlna — Mon, 05 Jan 2026 08:42:30 GMT

Hello,

All SCST atomic tests must be treated as non‑preemptible.
Some groups modify the interrupt vector table or temporarily block interrupts, so they cannot be safely interrupted and will raise TEST_WAS_INTERRUPTED if preempted.

Because NXP does not publish a list of “interruptible vs. blocking” tests, the practical rule from NXP support is:
Schedule every SCST test group so it runs atomically, e.g. at startup or in a controlled high‑priority safety window, and ensure its execution time fits within your SysTick period.

Best regards,
Peter