what information does the nrfjprog.exe write to UICR(User Information Configuration Registers) register??
==========Tutorial of Flashing dfu bootloader to the nRF51 DK====== we need to make sure that nrfjprog.exe is configured as the tool for flash programming in project options. The default J-link target driver cannot correctly program the bootloader, this is because J-link can not write directly to the User Information Configuration Registers(UICR) from a hex file. The example project is preconfigured to use nrfjprog.exe, which is installed with the nRF51 MDK, and must be in the Windows system path.