NRF54L15 GRTC SYSCOUNTER

RE: NRF54L15 GRTC SYSCOUNTER

Susheel Nuguru — Wed, 15 Apr 2026 06:39:48 GMT

Chen, I think NVIC_SystemReset() is a valid workaround for preserving GRTC, because on our chips that is the same final path Zephyr uses anyways.

RE: NRF54L15 GRTC SYSCOUNTER

kyozc — Mon, 13 Apr 2026 00:10:25 GMT

Thanks for the analysis.

Instead of modifying the Kconfig, I'm considering using NVIC_SystemReset() directly. This bypasses sys_clock_disable() and should preserve the GRTC counter.

Two quick questions:

Is NVIC_SystemReset() safe for preserving GRTC without affecting other AON registers?
Any known issues on nRF54L15 with skipping de-init for peripherals like Radio/DMA, assuming we re-init them after reset?

Thanks,
Chen

RE: NRF54L15 GRTC SYSCOUNTER

Susheel Nuguru — Fri, 10 Apr 2026 12:55:23 GMT

It seems possible that the nrfx_grtc_timer has an issue in how it handles the soft reset (CTRL-AP reset)

sys_reboot->sys_clock_disable()->nrf_grtc_timer.c:sys_clock_disable()->nrfx_grtc_uninit->

#if NRFY_GRTC_HAS_EXTENDED && NRFX_IS_ENABLED(NRFX_GRTC_CONFIG_AUTOSTART)
    nrfy_grtc_sys_counter_auto_mode_set(NRF_GRTC, false);
    nrfy_grtc_sys_counter_set(NRF_GRTC, false);
    nrf_grtc_task_trigger(NRF_GRTC, NRF_GRTC_TASK_STOP);
    nrf_grtc_task_trigger(NRF_GRTC, NRF_GRTC_TASK_CLEAR);
#endif // NRFY_GRTC_HAS_EXTENDED && NRFX_IS_ENABLED(NRFX_GRTC_CONFIG_AUTOSTART)

It looks like NRFX_GRTC_CONFIG_AUTOSTART is the reason here as if it is set to 1 then nrfx_grtc stops and clears the GRTC counters

try setting CONFIG_NRF_GRTC_START_SYSCOUNTER=n in your prj.conf and make sure you start the syscounter in app and see if your issue goes away.