Why not use a PIC12CE518?
You can put the ID in eeprom using a one switch procedure.

Leo van Loon
SBB simpeltronics
Netherlands
tel +31 (0481) 450034
fax+31 (0481) 450051
mail sbb.simpeltron@tip.nl
url http://www.sbb-simpeltronics.nl
SBB simpeltronics ontwikkelt technische projecten voor basisschool en
basisvorming.
SBB simpeltronics develops technical projects for children in primary and
secondary education.

-----Oorspronkelijk bericht-----
Van: Shahid Sheikh <sheikh@EROLS.COM>
Aan: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Datum: zondag 28 juni 1998 7:20
Onderwerp: Assisgning an ID to a PIC using as few input pins as possible


>Greetings everyone,
>
>I'm working on a hobby project using a 12C508 to turn on and off the lights
>on a model train locomotive. The locomotive has an ID ( 1 ~ 80 ) on the
>track. The decoder circuit based around the 12C508 needs to have ID
>selection switches by which I can assign the decoder an ID.
>
>I can use a bigger chip and waste 4 pins just to hardwire the ID with DIP
>switches or jumpers which seems a waste for such trivial thing. I was
>looking at the AN512 Ohmmeter/Temperature sensor application note where I
>could use a variable resistor to select the ID or the other thought was to
>have a simple flasher circuit to clock the T0CK pin and then read the TMR0
>register after a fixed amount of time to get the locomotives ID. Have a
>variable to vary the pulsing rate of the flasher circuit.
>
>Am I wasting my time with the 12C508 chip here and should just use a 16F84?
>Does anyone know when the 12CE518 chip would be available? With that (and
>also with the 16F84) I could write a routine to actually program and store
>the decoders ID in the EEPROM by using a key sequence on the central
>control unit.
>
>I've got a few 12C508 around right now but I dont have any 16x84's which is
>why I was just trying to use the 12C508 chip. If anyone has any ideas on
>implementing a way to assign the 12C508 chip an ID (1 ~ 80) through
>external circuitry which the chip can pick up during its program
>initialization stage, I would like to hear it.
>
>Thanks!
>
>Shahid
>
>