CPU locked up before watchdog started

[Paul]

I am having power on lock up issues with my latest product design using nRF51422. There is no external power monitoring ICs or reset ICs. The system is relied on internal POR. But in some of our test we found out that on power up CPU may get locked up or freeze. The watchdog is enabled at the very beginning of the main.c

This is not very hard to reproduce by tapping the 3.3V power lead on and off.

I think I understand the problem: Unstable power supply fooled POR and hand up the CPU before the watchdog even has a chance to start.

It is in production now. So I am looking for a software solution if possible. Otherwise a reset IC needs to put into the design.

Thanks

Paul

[Kenneth]

Hi, we need more information that would allow us to find exact cause, please create a case on My Page and add the following details:
•Schematic and layout.
•A description of test setup.
•Frequency of occurrence and build code.
•Analog capture of VDD, nRESET, DEC1 and DEC2.