EVTEN & INTEN nRF52 RTC

[RK]

The documentation for EVTEN in the manual, showing the RTC Tasks and Events system (Figure 45) led me to believe that if EVTEN for an event is disabled the EVENT will never get signalled (ie set to 1 in the register) nor will an IRQ get triggered, the diagram shows both those things gated on EVTEN. So I expected that having EVTEN disabled would mean the event would never occur, and never get signalled in the register.

What I actually see however is different. If EVTEN is disabled but INTEN is enabled when the TICK or COMPARE happens, the interrupt fires and the EVENT is signalled in the register. So you get an event for which EVTEN is zero.

So it seems more like the event is only disabled if EVTEN and INTEN are both disabled. If either o them are '1' for that event, the event happens.

Am I misreading the diagram??

[Ole Bauck]

I believe you misread the diagram.

• If EVTEN is set the event flag will be set and event signal will go to PPI.
• If INTEN is set the event flag will be set and IRQ signal will go to NVIC.

So an interrupt can be triggered even though EVTEN is disabled. EVTEN only controls the PPI. The event flag will be set if either EVTEN or INTEN is enabled.

[Ole Bauck]

Adding link to diagram: infocenter.nordicsemi.com/.../rtc.html

[RK]

I did misread it - I looked at the switch and thought it was a double-pole, single throw, both poles activated by the EVTEN state. Now I look at it again - and it actually makes sense. Thanks.

This makes more sense too, seemed wrong to have to enable events as well as interrupts.