31.1.17.3 Power-on Reset

A Power-on Reset (POR) causes immediate termination of any FCW operation. A POR is a full and hard reset of all states of the FCW and therefore no error flags originating from a prior operation survive the reset.

Several SFR bits get reset by POR so they survive a BOR or user resets (WDT Reset, RESET pin, etc). Doing so allows many NVM operations to complete and the ones that don’t can report errors. Also, they prevent values like address from changing in the middle of an operation.