Can I write to the UICR registers with a Segger and JLink?

RE: Can I write to the UICR registers with a Segger and JLink?

Susheel Nuguru — Tue, 21 Jul 2015 08:55:16 GMT

Yes Eliot, you can write to a clean register but you cannot update an already written value without erasing it, UICR are speicial registers with same NVMC properties. That is once written to an address, you cannot update already written UICR register without erasing the whole chip. This decision was taken to remove the loopholes of security settings that lies in UICR (like CLENR0, RBPCONF), if something is set in these registers, it means that there is protection on code, and you cannot just write to this register, remove the security and read/modify the protected code.

RE: Can I write to the UICR registers with a Segger and JLink?

Eliot Stock — Tue, 21 Jul 2015 07:47:55 GMT

I haven't had a complete answer yet. Are you saying I need to read the whole page (1 KB) around the UICR registers, alter the bits I want to write to, then write the whole page back? How do I do that with a set of JLink commands?

RE: Can I write to the UICR registers with a Segger and JLink?

Susheel Nuguru — Tue, 21 Jul 2015 07:32:26 GMT

Can you please update/accept this thread Eliot.

RE: Can I write to the UICR registers with a Segger and JLink?

Susheel Nuguru — Tue, 26 May 2015 10:35:45 GMT

you cannot erase part of UICR registers, the only way is to erase the whole chip, devzone.nordicsemi.com/.../

in another words, you cannot update UICR register without erase the whole chip

RE: Can I write to the UICR registers with a Segger and JLink?

Eliot Stock — Fri, 22 May 2015 17:33:13 GMT

OK, let me restate the question: how do I clear the UICR registers before I write to them? See my edit above.

RE: Can I write to the UICR registers with a Segger and JLink?

Susheel Nuguru — Fri, 22 May 2015 16:15:29 GMT

ah, i thought 123 in your log was decimal. Read it again in decimal and see if it makes sense :)

RE: Can I write to the UICR registers with a Segger and JLink?

Eliot Stock — Fri, 22 May 2015 13:03:27 GMT

Very confused here. 0x0123 is not 01111011, it's 0000 0001 0010 0011.

RE: Can I write to the UICR registers with a Segger and JLink?

Susheel Nuguru — Wed, 20 May 2015 19:31:28 GMT

You cannot write to already written UICR register without erasing it. And to erase a register you need to erase everything if there is a softdevice. devzone.nordicsemi.com/.../

 if your old value is         0234(11101010'b), 
then writing                  0123(01111011'b)            to this value will make it 
                                  ------------------------------------------------------
                              0106(01101010'b)  -> could just toggle '1's to 0's

That is why your write was completed but verification failed. because you wanted to write 0123 but it actually wrote and read 0106 in our example.