Parallel Port eprom programmers - suggestions

[Andrew K. Mattei]

Todd Israels wrote:
> 
>
>         What was the design you found on the net and its address?  I am
> considering such a project but am at this stage just checking options and
> would like to learn from your experince and possibly try your completed
> curcuit if it is completely abandoned.
>         Your design sounds interesting but I think I would like more flexibility
> in chips I can read and Write than you currently have.

I built this one:

http://zws.com/products/epromr2/index.html

It's actually a pretty cool setup. "Supposed to" program EPROMs from
small (16's) to big (1M+). He uses a 32 pin socket. In my testing, the
device worked, but I could not get the same binary file twice out of the
thing. I'd plug in a chip, read it, then read it again, and read it
again, and all 3 files would be different. I found that using 74HC4040
counter IC's worked better than plain CMOS 4040's, but it still wasn't
good enough. I had a ribbon cable about a foot long (not too much RF
noise there), and a decent 5V power supply, checked/rechecked/rechecked
my wiring, and compared data files, and "concluded" ;) that the clocking
of the 4040's was throwing things off. And, I was seeing strange data
errors. I attribute the data errors to the bidirectional port, and the
clock runout was uncontrolled. Even if I used the "slow down" option in
the software, it wouldn't provide repeatable results. So, I started
thinking about designing my own - based on similar principles, but with
feedback for the clock (basically, checking the lowest clock bit for an
odd or even number - so, if the clock ran fast, the software would catch
it), and ditching the bidirectional port in lieu of the true inputs and
outputs of the parallel port. Means the use of multiplexing the bits,
which complicates the software slightly, but "should" provide my desired
accuracy.

The design I'm working on could do the 1M+ 32 pin EPROMs - but right
now, I don't need them ;) The extended addresses are no problem (just
let the clock keep going), and the programming pins would just require
the creative use of dip switches (as demonstrated in the design I
referenced at the above web page). However, my needs are for 64, 128,
and 256 right away, and probably 512 in the future. Who knows... Maybe
I'll just adapt the board I've already done and put my "new" parts on
it. And leave it at 32 pins... ;)

Have fun. :) That's what it's all about anyway...

-Andrew