Can I modify ucir in my application?

[frank zhang]

Can I modify the value of ucir in my application? If yes, How to do it?

[endnode]

Yes you can, simply write to UICR->xxx address (must be 32-bit aligned and better not overwrite some significant registers;)

[Jørgen Holmefjord]

Your code is correct, I have tested it and get correct reading. Note that UICR registers are located in flash, and it can take up to 338 us to write one word. Try adding a short delay before reading back the value, to make sure it have enough time to be written to flash.