|Again for each EPROM the position, voltage, and algorithm are different for
|each part. The great thing about PICs are their consistency. All 12 bit parts
|program the same, all 14 bit parts program the same, all 16 bit parts program
|the same. It really simplifies things.

Actually, there's a lot of consistency among the 27xx EPROMs.  The
VPP is always in the same place (though not always the same voltage)
relative to the bottom of the chip, as is almost everything else.
The only somewhat tricky bits are [1] Having a programmable VPP, and
[2] having address drivers that can supply a good strong +5 at pins
26 and 30 of a 32-pin device, since on 24- and 28-pin devices those
will be the VDD supply.

As for PIC's, there are two methods for 12-bit parts (16C5x vs 12Cxx)
and two for 16-bit parts (the 17C42 requires parallel programming [why
the #$@$?] while the 17C56 allows for serial as well).

|I had some thoughts along that line. Create a base unit that housed the
|intelligence (a PIC of course) and the PC interface. Then instead of having
|the complexity of trying to fit all possible chips into a single socket, and
|trying to shove all the programming code for a host of chips to program, go
|the route of modularizing via an expansion card. The card would contain three
|things:

|1) The socket to program the part.
|2) Any extension circuitry required to program the part.
|3) A serial EEPROM that contains the programming algorithm.

This sounds somewhat like the "personality modules" a lot of programmers
used to use; I'd go with a somewhat simpler design than yours, though:
use a pair of dual-row (0.1" spacing) 40-pin sockets, with one of them
tied pin-for-pin to a 40-pin ZIF and the other one wired to...

  24-bits of bidirectional shift registers [wired as a group of 16 and a
    group of 8].
  a programmable VDD [which also powers the shifters]
  the programmer's [unswitched] VDD
  8 or so PIC port pins.
  a programmable VPP pin [high-current VPP, VDD, and Vss, or floating]
  feedback control for VPP
  ground

Setting the device up to program different devices would simply require
connecting together two 40-pin dual-row headers in an appropriate con-
figuration and giving the PIC suitable instructions for what it should
do.

The base unit would be more complicated than the one you described, but
would avoid redundancy in the personality modules [since they wouldn't
need to include actual circuitry in most cases, nor would they have to
include a ZIF socket].

How does that sound for a design?


Attachment converted: wonderland:WINMAIL.DAT (????/----) (0002C6B6)