Recover the MBR

[mamrezo]

hello i have nRF51822 QFAAH1 and accidentally erased the chip and also MBR section with jlink, what should i do for bring MBR back.

[endnode]

Take lower 3 or 4kB (depending on version you have, see Soft Device release notes) of SD HEX file and flash it to the chip (if it is read/write protected then you are indeed out of luck and you need to erase entire NVM first).