Is nrf_rtc_counter_get interrupt safe?

[lybrus]

Hi!

I'm not good at C and microcontrollers programming. Could somebody clarify, if nrf_rtc_counter_get interrupt safe? It just reads value from rtc register->COUNTER (24bit), how many ticks it takes?

Thanks.

[Turbo J]

lybrus said:

how many ticks it takes?

Should take much less than one RTC tick, as this register is latched in the PCLK16M clock domain.

From the NRF52840 PS (chapter 6.22.9): "Read takes the CPU 2 cycles in addition resulting in the COUNTER register read taking a fixed five PCLK16M clock cycles."

Note that this does not include setup instructions - you may need to put the register address into a core register first.

[lybrus]

Thanks for answers. As I understood it's no guarantees that

counter = nrf_rtc_counter_get(&rct_inst);

is (upd)interrupt safe. Another questions, is it possible without "CRITICAL_REGION_..." to have inconsistent counter value? For example, coping value is two ticks, and between them another interrupt occur, and before second tick rtc overflow happend.