GRTC Feature of nRF54L15

RE: GRTC Feature of nRF54L15

runsiv — Thu, 31 Jul 2025 11:58:04 GMT

Hi Greg, please create a new ticket for your question. The GRTC. SYSCOUNTER is not reset after soft reset, controll ap softrest or wakupe from system off mode as seen here

Regards

Runar

RE: GRTC Feature of nRF54L15

Greg Strange — Wed, 30 Jul 2025 22:00:51 GMT

Hi Terje,

I know the GRTC is not a real-time-clock, but we were considering using it as one. To be able to do that it must continue to run even in system OFF mode which your website says it does. It must also maintain its count through a system reset. I thought this would be the case, but I just read that it is used by default as Zephyr's system tick which makes me think it will get re-initialized after every reset. Do you know if it is possible to use the GRTC as a pseudo real-time-clock, or is it going to loose its value on each reset due to Zephyr initialization or due to a the hardware resetting the contents?

RE: GRTC Feature of nRF54L15

tesc — Wed, 08 Jan 2025 15:09:26 GMT

Hi,

GRTC, as the RTC peripherals for the nRF51, nRF52 and nRF53 series, is a Real Time Counter (not to be confused with Real Time Clock.) It is essentially a timer.

GRTC can relay the clock signal from either the LFCLK (32 KHz clock) or divided clock based off of the 16 MHz clock, to the respective dedicated pin. If you have a separate device running off of that clock signal or otherwise counting the pulses, then you could keep track of time that way. Please note then, that unlike a Real Time Clock, the Real Time Counter does not directly provide any means to output the current counter value to external devices, so in order to provide time to other devices you would have to keep track of time on the nRF54L and communicate that time through other means.

The third pin dedicated for the GRTC is for PWM output, which is also part of the capabilities of the GRTC peripheral.

See GRTC - Global real-time counter in the NRF54L15 datasheet for full documentation for the GRTC peripheral.

Regards,
Terje