Can NRF_RTC1->COUNTER value be ready safely from main loop on nRF51822/nRF51922

[Chris Uroda]

Hi,

Can the value of NRF_RTC1->COUNTER be read safely from the main loop without first stopping the RTC or temporarily disabling the RTC1 interrupt etc? (nRF51822 or nRF51922)

I would assume that the answer is yes, given the read will be atomic because the register is 24bits wide and it is a 32Bit system.

thanks -Chris

[Ling LI]

The answer is yes. From nRF51 reference manual 2.0, 18.1.9, page 108:

...To ensure COUNTER is safely sampled (considering a LFCLK transition may occur during a read), the CPU and core memory bus are halted for 3 cycles...