Watcgdog timer resets my GRTC

[Nikollao]

I am using the nrf54l15-dk. I had a look at the datasheet and it shows that a watchdog reset does not reset the GRTC. On my code, I tested that and I see that GRTC resets when WDT resets. Is there any option to avoid this? Something which I may need to configure? 

[Simonr]

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

[bzhou]

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!

[Jayant Tang]

Hello Simonr,

I'm a little confused about what you said:

Simonr said:

The table in the datasheet is what is correct,

and

Simonr said:

the WDT is indeed supposed to reset the GRTC

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

Best regards,

Jayant

[Simonr]

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

[bzhou]

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