UICR Erase when the Battery is disconnected of the device

[Julien]

Hi,

We encountered a problem if we take off the battery during functionning.

The UICR Register is completly erase when we put back the battery.

The issue is with lost our adress for the bootloader, so our device is completly broke.

Have you any idea about this problem.

The issue are encountered with NRF52840 and S140.

We use the same application with NRF52832 and S132 and we have no erase on UICR.

Thanks,

Julien Ferrer

[Vidar Berg]

Hi Julien,

This is certainly not expected behavior. Is there anything in your application code that uses the NVMC-> ERASEUICR task? Also, does this always happen after you re-insert the battery, or does it occur more intermittently?

And unlike on the 52832, it's not possible to only erase the UICR after readback protection is enabled (ERASEUICR task is blocked):  Access port protection behavior

Best regards,

Vidar

[Julien]

Hi,

Yes, at the start we are erasing the UICR to rewrite data. The problem came from our pcb design where at the startup the power supply takes time to stabilize, and go below the brown-out voltage during this operation.

I tried to use the POFCON register to prevent from writing the NVMC if voltage is to low, but my devies stay blocked in a loop. Maybe i need to read an event or something like that ?

So my solution is to put a delay at the start, in order to let time from the power supply to be stabilized.

Thanks,  

[Vidar Berg]

Hi,

Does this UICR update always happen on startup, or just the first time the device is started after being programmed in production? Either way, it sounds like maybe the update routine should be made more robust to withstand unexpected resets.

Do you keep a backup of the UICR in flash?

[Julien]

The UICR update happen at every startup,

For the moment , the UICR is not stored on flash but it could be the good solution.

[Vidar Berg]

There is also the problem that UICR can't be erased if you plan to enable the  debugger readback protection on the device like I mentioned in my first reply. Would it be an option to keep this data in a regular flash page instead?

[Julien]

We did not plan to use the readback protection

[Vidar Berg]

Then it will ok to use UICR. I just wanted to make sure you were aware of this behavior.