Hello Adam.

> Is there any way I could use a pic 16f84 or something in the pic
> family to build a programmer for a 12c509.  Something standalone, and
> the code going to the 12c509 be on a eeprom.  Any help would be
> appreciated and links or reference would also be appreciated.

  Excellent idea!  In fact, most stand-alone programmers specially for
PICs use a PIC, generally a 17C42 as I understand it.  I've got one, a
PICSTART 16B2, but there is great suspicion that its firmware is
unstable so I'm not using it yet.

  The reason the 17C42 is used is mainly as it has plenty of I/O.  For
the 12C509 however you don't need much I/O anyway, so a 16F84 would be
perfect - well, with a few other bits.

  Firstly, you need a VPP (programming voltage) supply with switching.

  Actually, before I elaborate, may I presume you are using a parallel-
port programmer for the 16F84, or intend to do so?  In fact, the same
programmer will happily program 12C509s with an adapter.  Conversely,
you can program another 16F84 with your 16F84-based programmer etc.

  Anyway, whatever circuit controls the VPP for your current programmer
can be built into your stand-alone one.  You only have to connect the
programming lines to common port pins, and the serial EEPROM.  You'll
need a few control keys and some indicators.  Suggest a latch such as a
75HC595 to drive up to 8 LEDs as indicators.  Go for an 8K EEPROM so it
can hold a number of code images.

  Wild guess - is this to field-copy and "clone" parts, such as cable
decoders or Playstation picks?

  Cheers,
        Paul B.