Re: Caution on AP-64E EPROM Programmer

["Mark Cummings" <NOTfigjams@primus.com.au>]

"Glenn Jones" <rg.jones@rogers.com> wrote in message
news:_esja.40152$7Im.25940@news04.bloor.is.net.cable.rogers.com...
> "Mark Cummings" <NOTfigjams@primus.com.au> wrote in message
> 3e8d83a1_1@news.iprimus.com.au">news:3e8d83a1_1@news.iprimus.com.au...

<snip>

> To anyone else ....
>
> I have an eprom programmer that was developed by a local Toronto company
> called Exceltronix. It came with a photocopy of the listings for the
> Applesoft and Assembler burn routines.  It also came with a decent hand
> drawn schematic. Total 16 pages. It uses personality modules (2716, 2732,
> 2732A and 2764) and it may be possible to figure out new modules for
larger
> eproms.
>
> I had hoped to modify it to burn 27256 chips and have only gotten around
to
> downloading the data sheets for all the chips it can currently burn as
well
> as the 27128 and 27256.

just what I was thinking about for the AP-64e. some hardware and software
changes would be needed...

1. 27128 & 27256 & 27512 EPROMs use a programming voltage of ~12.5V instead
of the 21-25V Programming Voltage on most 2716, 2732 & 2764 EPROMs. This
would be fairly easily achievable on the TL497AC by switching in different
resistance in the voltage divider on pin 1.

2. The programming Pulse Width on the larger EPROMs is generally smaller
overall, and the algorythm is different. pulse width (or widths) is anywhere
from 0.5ms to over 50ms (total). this would require a change to the firmware
on the card.

3. Another potential problem is that the algorithm for burning some EPROMs
requires raising Vcc to 6V during programming. This is not that easy to
achieve on the existing card. I'm not sure it is necessary but at least
could cause a problem for some types.

I have started to hand disassemble some of the firmware on the AP64e, but
it's fairly slow going. If I do get anywhere with it, the first mods I'd
like to make is to be able to select 27128 and 27256 for reading, and remove
the 27128 mod to some extent making it more automatic. The extra unused pins
on the 6821 PIA could be used as address lines for the destination EPROM, or
possible to change the Programming Voltage via some switching circuitry.

Mark