ISP: no
IAP: yes

In-application programmable means, that the application
itself can program another code location.
But ist not so easy, since you can only program
bits of a byte from 1 to 0. To change from 0 to 1
you must erase a full page (4kByte).

I like more serial EEPROM (24C02 ... 24C512)
to store nonvolatile data. It need only 2 wire to the micro.


Peter