nRF 5340 RESETREAS register is not cumulative?

[skruffen]

I have noticed that the RESETREAS register does not accumulate flags even though the documentation says it should. "Unless cleared, the RESETREAS register will be cumulative."
https://docs.nordicsemi.com/bundle/ps_nrf5340/page/chapters/reset/doc/reset.html#d660e1219

If a reset occurs from the Reset pin, the register shows 1(integer).
If then a reset via AIRCR.SYSRESETREQ occurs, then the register still shows 1(integer).

The other way around (with the RESETREAS register cleared of course), if a reset occurs via AIRCR.SYSRESETREQ, the register shows 8(integer).
But, then if a reset pin reset occurs straight after, the register shows 1(integer).

Is this error in the documentation, fault with the hardware, or have I missed something?

Thanks in advance

[Vidar Berg]

Hi,

This is due to errata 55 ( [55] RESET: Bits in RESETREAS are set when they should not be) and the corresponding workaround implemented in the startup code.

Best regards,

Vidar

[skruffen]

Thank you,

So if non-reset-pin resets will accumulate, but if a reset-pin reset occurs the reset-pin bit will set and the rest cleared in the RESETREAS register?

[Vidar Berg]

Correct. For this reason, it is often advisable to check the reset reason after every boot and clear the reset bits.