nRF52840 Lockup state with reset low

[Mack.wilz]

Came across a weird anomaly the other day when doing some temperature testing. One of our boards came out of it not running code and the reset line on the 52840 was stuck low. Nothing was connected to the line at the time. After hooking it back up to the jlink, the unit came back online and operated as normal. Any ideas what may have caused this? Thanks for any help in advance.

[Kenneth]

It is technically possible to set the reset pin low from the application (e.g. enable internal pull down and/or set output low), then it will be stuck low as you describe. Theoretically also an incomplete power cycle, e.g. that the rise time of VDD is very slow (>100ms) can cause the chip to not start as expected, but that would mean that you had some power issues while doing temperature testing, not sure if that is the case?

Kenneth

[Mack.wilz]

Obviously, we are going to try and avoid this to the best of our ability, but is there any coming back from that without another complete power cycle? I am assuming that we can't detect it because not everything is running correctly.

[Kenneth]

If this is the case, then only a power cycle can help yes. But I would have tested it again just to see if you can see the same once more with the specific board.

Kenneth