Date   : Thu, 23 Dec 2004 17:58:26 -0000
From   : "John & Helen Simpson" <john@...>
Subject: Re: Eprom programming problem - part 2

Hi there

After all the useful advice from this list, I went away to fix my Eprom
programmer and get some NMOS Eproms (Thanks Chris). Having implemented
all the specified changes, I now have a system which can read and write
without generating any errors.

However there is still a problem (as you have probably guessed by now!).
The problem is that the Eproms don't actually seem to get written to. I
have managed to program the first byte of one Eprom correctly (to &4C,
which is clearly right), but the rest are just &FF (which is blank as I
understand it).

When I follow the correct procedure which is (1) load buffer (2) program
Eprom from buffer (3) write eprom back to buffer (4) save buffer (5)
*dump the buffer file, I get a blank result, ie all FF.

In the case where I managed to program the first byte OK, I actually
made a mistake. What I did was to program the Eprom first, but then I
tried to compare it against the buffer without first putting the switch
back to "Read". It generated a comparison error at &8000. I realised my
mistake and set the switch to Read, then did a comparison again. This
time it failed at &8001 (sensible if the first byte was 4C). Not sure if
this is relevant. I have not tried to reproduce this, but I did try to
test whether I'd got Write and Read mixed up on the switch by
programming in Read mode and reading back in Write mode. This didn't
work and my Eprom is still blank.

Something must be wrong, any ideas?

john