I made always very good experience with serial EEPROM in opposition to using parallel EEPROM, since its very unlikely, that a crazy CPU can perform the special write cycle sequence. Only some never parallel EEPROM have included a software protection to need also a special sequence to enable the write cycle.

In any case the current write cycle was corrupted, if power was switched off.
To avoid this, you need an early power fail warning circuit.
Also some serial EEPROM have a write disable input, which can direct be connected to such a low power detection circuit.

Additional you must select the EEPROM for the same operating voltage as the microcontroller.
E.g. an EEPROM for 1.8V can easy catch some noise, if the 5V micro was already sleeping fast.


Peter