S32K116: independence between internal Watchdog and CPU core

[ddd123]

hello NXP team:

         I use S32K116 in our ASIL-B FUSA project, i read the "S32K-RM_Rev.14", i think it`s ok for our project. But customer said: why not use a external WD? .

        Only CPU will configure WD at initialization phase. we use LPO as clock source for WD, FIRC as clock source for CPU and implement Fast WD test. But if CPU occur fault, don`t correctly configure related WD register or something, and fast test can`t find out issue. Dose it affect independence?

          Dose NXP could provide some file/doc/analysis to me?

Thank you, Di !

------------------------------following content from S32K-RM_Rev.14------------------------------------

23.1.4 Watchdog Timeout Reaction

The WDOG timeout reaction is by default configured to generate a system reset.

23.2 Introduction
The Watchdog Timer (WDOG) module is an independent timer that is available for
system use. It provides a safety feature to ensure that software is executing as planned
and that the CPU is not stuck in an infinite loop or executing unintended code. If the
WDOG module is not serviced (refreshed) within a certain period, it resets the MCU.

[davidtosenovjan]

Using of external watchdog is expected is safety application as backup. Quoting safety manual for the device:
"For safety, a redundant watchdog system, External Watchdog Monitor (EWM), is
designed to monitor external circuits, as well as the MCU software flow. This provides a
back-up mechanism to the internal watchdog (WDOG) that resets the MCU's CPU and
peripherals."

Safety manual is a secure file, so following procedure is needed to follow unless you have already done it before:
https://www.nxp.com/docs/en/user-guide/nxp-secure-access-rights-registration.pdf

For better understanding you may also see following link:
https://www.nxp.com/support/support/secure-access-rights:SEC-ACCESS

[ddd123]

Thank you!

 up to now, we don`t use external WD, so i want to analysis and judge whether internal WD is enough. That` is my point. i want to discuss the internal WD. Do you have detailed/further information?

[davidtosenovjan]

I would recommend to consult with RM and SM.

I am not aware specific appnote or other document related specifically to watchdog.