nRF52 APPPROTECT

[Eric Stutzenberger]

Hi,

Is there a way on the nRF52 to clear the APPPROTECT bits once they have been set?

On the nRF51, it was still possible to erase the chip to clear the readback protection. However, on the nRF52, the APPPROTECT bits seem to fully disable the debugger.

Thanks,

Eric

[Eric Stutzenberger]

The tools don't seem to support this yet (unless my nRF GO Studio is out of date) but using JLink from the command line I was able to clear these by manually executing the following commands:

Erase Enable: w4 4001e504 2

Erase all: w4 4001e50c 1

Update

I tried to reproduce this after having cleared these bits, but now I again cannot get the the JLink to recognize the core. I'm not sure what caused it to work this morning such that I could do this.

[David García Polo]

I do not think you had reset the device after writing the APPROTECT register. A reset is needed to load the configuration from UICR. That is why you could still access the core and the NVMC module. Once reset the debug access port connected to the core and the system bus is disabled. Only a special access port in address 1 is available.

[Eric Stutzenberger]

I had definitely power cycled the board. I asked the question specifically because it was in this state. I then had unplugged it and was using another board. In the morning, I plugged the same board back in and was able to recover it through above method. Probably a fluke.