Watcgdog timer resets my GRTC

RE: Watcgdog timer resets my GRTC

bzhou — Thu, 25 Sep 2025 07:19:53 GMT

Simonr Here is the new link regarding the GRTC reset issue: GRTC resets after sys_reboot() when using MCUboot (NCS v3.1.0) - Nordic Q&A - Nordic DevZone - Nordic DevZone

RE: Watcgdog timer resets my GRTC

Simonr — Thu, 25 Sep 2025 06:57:03 GMT

I failed brutally to word myself there. I've edited my reply to reflect what I meant. The datasheet is incorrect and we will work on fixing this in the future. The WDT will reset the GRTC.

bzhou can you create a separate DevZone ticket for these questions and link to this ticket if necessary?

Best regards,

Simon

RE: Watcgdog timer resets my GRTC

Jayant Tang — Thu, 25 Sep 2025 06:36:55 GMT

Hello Simonr,

I'm a little confused about what you said:

[quote userid="75734" url="~/f/nordic-q-a/124294/watcgdog-timer-resets-my-grtc/549115"]The table in the datasheet is what is correct,[/quote]

and

[quote userid="75734" url="~/f/nordic-q-a/124294/watcgdog-timer-resets-my-grtc/549115"]the WDT is indeed supposed to reset the GRTC[/quote]

Because if the datasheet is correct, the WDT will not reset the GRTC.

Best regards,

Jayant

RE: Watcgdog timer resets my GRTC

bzhou — Thu, 25 Sep 2025 05:58:46 GMT

Hello Simonr,

We're using GRTC on the nRF54L15 to implement RTC calendar functionality. During development, we observed that when using sysbuild with MCUboot, calling sys_reboot(SYS_REBOOT_COLD) or sys_reboot(SYS_REBOOT_WARM) causes grtc.SYSCOUNT to reset. However, if MCUboot is not used, SYSCOUNT remains unchanged across reboots.

This behavior breaks our calendar logic, which relies on GRTC continuity. We're using NCS version v3.1.0.

We suspect MCUboot or its initialization flow is affecting GRTC, possibly via driver reinitialization or a configuration like CONFIG_NRF_GRTC_CLEAR_AT_INIT.

Questions:

What part of MCUboot or sysbuild causes GRTC.SYSCOUNT to reset?
Is there a recommended way to preserve GRTC across reboots when using MCUboot?
Can we disable GRTC clearing during boot, or use retention RAM to store offsets?

Thanks in advance!

RE: Watcgdog timer resets my GRTC

Simonr — Thu, 18 Sep 2025 07:21:33 GMT

Hi Nikollao

I had a chat with a developer today, and the mystery is solved. The table in the datasheet is what is not correct, as the WDT is indeed supposed to reset the GRTC, so what you're seeing is the intended behavior. We will update the datasheet to reflect this as soon as we can. Thank you for your report!

Best regards,

Simon

RE: Watcgdog timer resets my GRTC

Simonr — Tue, 16 Sep 2025 14:33:27 GMT

I'm sorry about the late reply, but I am still looking into this issue, and will need some more time before I have a proper answer for you. Thank you so much for your patience. I'll get back to you with an update by Friday at the latest.

Best regards,

Simon

RE: Watcgdog timer resets my GRTC

Nikollao — Mon, 15 Sep 2025 10:38:53 GMT

Any updates on this ?

RE: Watcgdog timer resets my GRTC

Nikollao — Thu, 11 Sep 2025 13:23:32 GMT

Hi, so I am pretty sure I don't do anything to reset the grtc, i simply let the watchdog reset and grtc is reset. the default watchdog reset is reset_soc, if I try to use reset_cpu_core which is a software reset, watchdog does not get initialised. I think the watchdog reset itself causes the grtc reset. can you please have a proper look into this

RE: Watcgdog timer resets my GRTC

Simonr — Thu, 11 Sep 2025 13:18:41 GMT

So, the WDT reset doesn't reset the GRTC in and of itself, but something tied to the watchdog reset must be resetting the GRTC or SYS counter in your application.

Best regards,

Simon