After powering up from cold, the whole aircraft is energized for 5 minutes for systems self-test, then many of the features de-power.
FADEC one of them, easily observed on the ECAM E/WD DU with amber crosses instead of the engine instruments after the time outs.
After ENG shut-down, assuming APU or EXT PWR is connected, the FADEC are left powered (EICAS showing what it should) for the same 5 minutes and then the indications go amber crossed again.