Re: Info on this particular A2 EEPROM burner

["Bryan Villados" <news003@macgeek.org>]

"Mark Cummings" <NOTfigjams@primus.com.au> wrote in message
3ef8435c_1@news.iprimus.com.au">news:3ef8435c_1@news.iprimus.com.au...
> > > Here's the weird part... The card didn't work when I booted into
ProDOS
> hi Bryan,
>
> not sure if you have read the back of the manual, but I found the AP64e to
> be incompatable with certain hardware such as Apple's AHS card, and also
it
> doesn't work in 80col mode. this could be your problem. also it might not
> work in 40col if the 80column firmware is running. I havn't tried, but
this
> is a high possibility due to the way the card uses the screen to store the
> address counter. As I only just got a CFFA card a few days ago, havn't
tried
> that yet either for compatability.
>
> If anyone can narrow down any hardware/software incompatabilities, I can
add
> that to the next version of the book in the troubleshooting section. and
> maybe that will help in making an improved firmware version.
>
> Laine and I are working on an upgrade for this card to support larger
> EPROMs. So far I have drawn up changes to the hardware and Laine has done
a
> lot toward newer firmware. Eventually I hope to be able to support 2716
> through 27256 read and write. Laine and I have discovered a lot of baggage
> in the original firmware which slowed me down on the upgrade, but it is
> starting to become clear now.
>
> A couple of snags I have run into so far is that the -OE pin is not
> controlled by the 6821 on the PIA, and it may have to be routed through
one
> of the spare Inverters for the larger EPROMs. the other problem is whether
> 6V is really required to write to certain EPROMs as is indicated in their
> data sheets.
>
> Anyway I have also put a reverse engineered circuit diagram on my home
page
> at:
>
> http://home.iprimus.com.au/figjams/apple2/AP64Ecct.pdf
>
> don't bother with the 27128 mod at the moment because I hope to have an
even
> better one later on that is controlled by software (after a different
> hardware mod).
>
> I just discovered that the Zener marked on the diagram as ZD2, which
someone
> told me was a 21V zener, may in fact be something else. On my card it is
> just a 1N4148 signal diode. Can anyone who has one of these cards please
let
> me know what the part is at D2 in the lower left corner of the card.

Woah! This is a really cool project!

--- Bryan