DAP and TAP register documentation

[janpieterderuit]

Hi,

I'm looking into unlocking a locked LPC5460x processor from PyOCD like the unlock command in the Segger J-link Commander does.

I followed pyOCD/security.md, and was able to access Access Point #2 over CMSIS-DAP with a locked processor.
However I can't find any information about the available registers in that Access Point (or about the registers from the default Access Point #0).

Where can I find this information, or information how to unlock the processor from a CMSIS-DAP debug probe?

Thanks in advance.

Jan Pieter de Ruiter

[Sebastian_Del_Rio]

Hi Jan Pieter, I hope you're doing well!

J-Link commander actually supports the "unlock" command for the LPC5460x:

To use this command, you can program the J-Link firmware to your LPC5460x using the "program_JLINK.cmd" script included in the LPCScrypt toolset, which can be downloaded from here.

After the debug probe is programmed with the J-Link firmware, J-Link commander can send the "unlock LPC5460x" command, and your LPC should unlock.

Please let me know if you continue to have issues with this.

Take care, best regards,

Sebastian

[janpieterderuit]

Hi Sebastian,

Thanks for your response.

I knew about the jlink software for the LPC boards, and it works fine indeed.

However, from the license of that software I get that you are only allowed to use it for the onboard processor, not for an external processor on our custom hardware.

I actually was able to monitor the SWD commands with a logicanalyzer, and found the needed registers that way.

But it would be nice if it was documented somehow, because now I have no idea what is actually going on.

Best regards,

Jan Pieter

[Sebastian_Del_Rio]

Hi Jan Pieter, 

Thank you for your feedback, we will take it into consideration!

Please let me know if you need any more information.

Take care, best regards,

Sebastian