How do I know if nrf52 woke up from sleep mode or not when booting?

[neosarchizo]

I want to make my device automatically go to sleep mode when the power is connected. And when the device wakes up from sleep mode, it should not automatically go to sleep.

But I can't find a suitable commands for this.

How do I know if nrf52 woke up from sleep mode or not when booting?

[John]

I believe the POWER peripheral has a RESETREAS register. There are various ways to wake from system OFF mode and there are bits you can check for each of the methods of waking the chip from its OFF state. Note, the bits in the RESETREAS register are persistent so you should clear them after checking them. 

[neosarchizo]

Thanks. It works.

And I also refer to the link below.

[136] System: Bits in RESETREAS are set when they should not be