S32K watchdog

bbenib — Fri, 05 Mar 2021 13:43:15 GMT

Hi,

I set the watchdog timeout to 20 ms with the followings:

-No IRQ

Prescaler: enabled

-TOVAL: 10

-Clock: LPO_Clock

And we wanted to measure that this is true, we pulled a GPIO high after the last watchdog trigger and watched this pin and the reset pin and measured the time from the rising edge of the GPIO to the falling edge of the reset pin, and the result was ~30 ms.

We took other measurements:

Presc	TOVAL	Calculated timeout	Real timeout
FALSE	2560	20 ms	22.6 ms
FALSE	5120	40 ms	45.1 ms
FALSE	7680	60 ms	67.7 ms
TRUE	10	20 ms	29.3 ms
TRUE	20	40 ms	51.9 ms
TRUE	30	60 ms	74.4 ms

It seems that if the prescaler is used then a strange 6.4 ms offset will be added to the timeout.

Could you please help us what could cause this strange behavior?

Thank you!

Re: S32K watchdog

danielmartynek — Thu, 11 Mar 2021 16:11:28 GMT

Hi @bbenib

Thank you for reporting it.

The issue is currently being investigating.

Based on my tests, the WDOG_CNT is held at 0 for 3 WDOG clock cycles thus the offset.

I will update the thread once I have more information.

Best regards,

Daniel

Re: S32K watchdog

bbenib — Fri, 12 Mar 2021 10:58:13 GMT

Thank you!

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