Excellent info, so I can store the ID in the EEPROM or load it upon start up as a lookup table, either way OK? Another area which is unclear is the use of the built in chip ID code (4 bits I believe). Not much mention about its use by Microchip or users. Seems to be very restricted in what can be done with it? Thanks again, I'm going to start experimenting (breadboard) with a communications project.