RTC(s) interrupts and events

[Bar]

Hello all.

I need to work with the RTC especially its events and interrupts, and I have some misunderstanding after read its manual.

I need to use it for low power systick with embOS RTOS of Segger and for calendar.

 I see there is 3 RTC, 3 compares. But when read in the RTC chapter I see there is only 1 prescaler. So:

1. Is there a real 3 seperate RTC with the some prescaler?

2. If not is there 3 separate counters which has dedicate comparator for each of them?

3. If so do I have 1 event for TICK and 3 events for each comparator?

4. And what is the difference between interrupt en and event en in the RTC section?

Thanks

Bar

[ovrebekk]

Hi Bar

The nRF52840 has 3 separate RTC modules (RTC0, RTC1 and RTC2), and each of these has one PRESCALER register and 4 CC registers (CC[0], CC[1], CC[2] and CC[3]). 

1. As mentioned above the 3 RTC's have independent PRESCALER registers. 

2. Yes, 3 separate RTC counters with 4 CC registers each. 

3. There is 1 TICK event and 4 COMPARE events for each of the 3 RTC modules. 

4. Most peripherals in the nRF52 series only have the INTEN register, but since the RTC is optimized for ultra low power consumption they also added the EVTEN register which allows you to disable or enable events completely. 

If you only need to pass an event over the PPI peripheral to a task in some other peripheral then you only need to enable the event in EVTEN. If you also want the event to generate an interrupt you need to enable it in INTEN also. 

Events that you don't use for anything should be disabled in both INTEN and EVTEN to reduce the current consumption in sleep. 

Best regards
Torbjørn