nRF54LM20A: APPROTECT/SECUREAPPROTECT in UICR not taking effect after reset

[wenc]

Hi everyone,

I am currently facing an issue with the nRF54LM20A where the access port protection is not taking effect after programming SECUREAPPROTECT and APPROTECT into the UICR, even after a power-on reset.

I verified that the UICR address 0x00FFD000 has been written. However, the protection remains inactive. As shown in my test with nrfutil, running "device protection-set" changed the UICR value from FFFFFFFF to 50FA50FA, but "device protection-get" still shows "Debug access is enabled".

Currently, the only way I can enable the protection is by setting CONFIG_NRF_APPROTECT_LOCK=y in the firmware code. However, this enables protection regardless of the UICR configuration, which makes it impossible to distinguish between hardware-based and software-based protection in my production setup.

Could anyone provide some insights or point out if I am missing a step to properly use hardware-based UICR protection on the nRF54LM20A?

Any help would be greatly appreciated. Thank you!

[Maria Gilje]

Hello, 

By looking at your screenshots it looks like you are doing what you should to enable SECUREAPPROTECT and APPROTECT. I unfortunately don't have an nRF54LM20 DK with me today, so I'm not able to test this on my end. I will do so on Monday. 

In the mean time, could you please let me know which versions of nrfutil and nrfutil device you are using? 

Best regards,

Maria

[wenc]

Hi Maria,
Thanks for getting back to me.
Here are the version details you requested:

• nrfutil version: 8.1.1 (b6089d0 2025-08-21)
• nrfutil device version: 2.15.5

Looking forward to your test results on Monday. Let me know if you need any other information.
Best regards,
wenc

[Maria Gilje]

Hi wenc,

These are not the most recent versions. Please upgrade nRF Util with 'nrfutil self-upgrade' and nrfutil device with 'nrfutil upgrade device' and let me know if you see the same issue after. 

Best regards,

Maria