Yes, but not AT89x5x. You might want to check out the Rx2's (e.g. AT89C51RD2/ED2, or P89V51RD2, or 'RC2 or 'RB2 for less FLASH).

Howewer, it's as slow as EEPROM would be, limited write time, need to erase before write etc.

However, that still might be good enough.

You might also want to reconsider serial EEPROMs - some of them have page write mode which considerably reduce the per-byte write time (with simultaneously buffered following page within the internal RAM - that's only a few bytes usually.) The nonvolatility would here come just as a bonus.

JW