Hello ,we are in the production phase, I use us addess mac(If I bought unique MAC address from IEEE. ) so our factory asks for the registry that will be configured, so is it possible to modify the register FICR or is it UICR?
Yes, you should store the addresses in UICR, and read the address from there every time the chip power-up/re-boot. The purpose of UICR is to store user specific settings.
FICR is programmed in the production of the chip itself, and cannot be used to store custom addresses.
Thanks you ,its possible to do a write lock in the UICR ,to protect it (in erase )
The NVMC chapter in the product specification describes erase of UICR, I would recommend you to read it.