How to unlock a locked nRF54L10

RE: How to unlock a locked nRF54L10

Август — Tue, 21 Apr 2026 07:12:11 GMT

Hi Abhijith,

Thank you for the clarification.

This requirement comes directly from our customer, and we’re just trying to verify the production flow. To test the behavior, we took one board and enabled ERASEPROTECT and APPROTECT as per the specification.

The result confirms what you mentioned: once these protections are set, we can no longer perform eraseall to modify the UICR registers. Therefore, firmware updates will only be possible via application-level updates (OTA/DFU) after this step.

This is a good confirmation for our production process.

Kind regards,

Abryct

RE: How to unlock a locked nRF54L10

Menon — Mon, 20 Apr 2026 16:50:44 GMT

Hello,

[quote user="xinglog"]Do you have any other solutions or methods to write these UICR registers?[/quote]

Once the value is written, you need to perform an eraseall to overwrite the UICR. However, with ERASEPROTECT enabled, eraseall cannot be performed

See the section UICR. I don’t think there is an alternative for this. This behavior is likely intentional, as it is designed as a security measure for final production.

Kind Regards,

Abhijith

RE: How to unlock a locked nRF54L10

Август — Mon, 20 Apr 2026 01:20:34 GMT

Hello Abhijith,

Thank you so much for your help! This information is really helpful and solved my problem perfectly.

I have another question: since ERASEPROTECT is enabled, I cannot write to UICR_ERASEPROTECT_PROTECT0 and UICR_ERASEPROTECT_PROTECT1. If we want to write these registers in code, we need to erase the UICR first.

Do you have any other solutions or methods to write these UICR registers?

Thank you very much for your support!

Kind Regards,

Abryct

RE: How to unlock a locked nRF54L10

Menon — Thu, 16 Apr 2026 14:33:04 GMT

Hello,

I understand your confusion, and what you said is correct, debug access is denied when APPROTECT is enabled. However, you can still access the device via CTRL-AP. Please refer to the script I shared in my first response. It is a J-Link script, so you need to use J-Link Commander here, not nrfutil.

Kind Regards,

Abhijith

RE: How to unlock a locked nRF54L10

Август — Thu, 16 Apr 2026 02:21:38 GMT

RE: How to unlock a locked nRF54L10

Август — Thu, 16 Apr 2026 01:49:05 GMT

Hi Abhijith,

Thank you so much for your detailed explanation.

Since my firmware supports OTA updates, I plan to upgrade my application firmware first, and have the application firmware write a chosen non-zero key value to the device's ERASEPROTECT disable register.

However, I'm a bit concerned that APPROTECT will block debug access, which might prevent my debug tool from writing the exact same key value to the corresponding register on the debug side.

I will give this approach a try and see how it goes.

Thanks again for your help!

Best regards,

Abryct

RE: How to unlock a locked nRF54L10

Menon — Wed, 15 Apr 2026 14:33:06 GMT

Hello,

If both APPROTECT and ERASEPROTECT are activated simultaneously, the device cannot be recovered unless it already contains compatible firmware that supports the unlock procedure.

Please refer to the note under the Enabling Device Protection section. If the currently locked device does not already include this firmware path, it cannot be added afterward through normal debug access, as APPROTECT blocks debug access and ERASEPROTECT prevents erase operations.

To enable recovery, the application firmware must write a chosen non-zero key value to the device’s ERASEPROTECT disable register. At the same time, the debug tool must write the exact same key value to the corresponding register on the debug side. Once both sides have written the same key, the tool can perform an erase (recover) operation to unlock the device.

Kind Regards,

Abhijith

RE: How to unlock a locked nRF54L10

Август — Mon, 13 Apr 2026 00:51:39 GMT

Hello Abhijith,

We don’t have any existing application firmware implementation that writes to ERASEPROTECT.DISABLE. However, our firmware can support this functionality if you have a suggested method for doing so.

Best regards,

RE: How to unlock a locked nRF54L10

Menon — Thu, 09 Apr 2026 13:25:37 GMT

Hello,

Do you have any application firmware implementation that writes to ERASEPROTECT.DISABLE, if so could you share what condition it is written?

Kind Regards,

Abhijith

RE: How to unlock a locked nRF54L10

Август — Wed, 08 Apr 2026 09:15:33 GMT

RE: How to unlock a locked nRF54L10

Август — Wed, 08 Apr 2026 09:00:14 GMT

Hi,

Thank you for your prompt reply.

However, my device has Access Port Protection and Erase Protection enabled.

I have learned that configuration via code is required:
When ERASEPROTECT is already enabled, to disable it:

The debug side must write a non-zero 32-bit KEY to CTRL-AP.ERASEPROTECT.DISABLE.
Simultaneously, the CPU-side firmware must write the same KEY to the CPU- side ERASEPROTECT.DISABLE.

RE: How to unlock a locked nRF54L10

Menon — Tue, 07 Apr 2026 15:40:37 GMT

Hello,

Please see the section on disabling Approtect. I have attached a script that you can use; it does the same thing as described in that section.

devzone.nordicsemi.com/.../eraseall.jlink

Kind Regards,

Abhijith