Which registers in the UICR of the nRF5340 are reserved for user access?

[Palmer Huang]

As far as I know, UICR->OTP should be similar to the UICR->CUSTOM register in the nRF52 series. However, I have learned that the nRF Secure Immutable Bootloader (NSIB) writes some parameters to the OTP registers. So, I would like to know which registers are reserved for user access?

[Naeem Maroof]

Hi Gray,

Thank you for clarifying that you are using NSIB.

NSIB implements ROT (root of trust) for secure boot chain, and using NSIB the public key hashes are written to the device (called provisioning)

On nrf5340, provisioned data is held in the OTP region instead of the internal flash memory, so that is why only some of the registers are available for user.

I could confirm that 640 bytes from the otp are used for provision. 

I was not able to find anything to release OTP from being used for provisioning using NSIB. 

Regards,
Naeem