EPROM emulator boards

[Andrew K. Mattei]

I just looked at the board a little closer, and have a couple of comments /
concerns that I'd like to present / discuss... (oh Jeez, here he goes...
;-D)

The basic premise of operation is very similar to the emulator I had in my
mind. It uses a serial port (with UART) instead of a parallel. However...

It also relies on the 4040-IC for address information. This is done with a
clock pulse causing an increment in the binary counter. I built an EPROM
programmer from a design using this technique (see
http://www.zws.com/products/epromr2/index.html ). I was rather disappointed
with the results. The problem with this design (which operated at a higher
speed than the 9600 baud unit), was that the clock would not run at a
consistent rate - so, I'd do five reads of an EPROM and they'd all be
different. Perhaps the 9600 baud unit, along with the fixed on board clock,
helps resolve this problem. Still, the unit does not provide any feedback
that your hardware and software are on the same address when programming the
emulator. I had put the low 4 address bits from my counter coming back
through the parallel port - so I'd at least know that my hardware and
software were in sync (remember, I did not build this thing, just designed
it in my brain...).

Steve's email just popped in to my box. "Edit while you drive" is a feature
we (as a group, I think) had hoped for. That is why I was thinking of a
dual-bank design - you have a flash on one side that contains code, and ram
on the other - and it would use this sort of design. Yes, you have to push a
button to reset the counter IC to 0, but you can let the motor keep
running... ;)

A PIC would still be the "best" design (could program via non-sequential
addresses (don't have to run up through the counters and press the reset
button at the end), could provide very accurate feedback, etc...)... Albeit
more expensive... Any thoughts?

-Andrew