Re: Info on this particular A2 EEPROM burner

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

> > Here's the weird part... The card didn't work when I booted into ProDOS
on
> > an enhanced IIe. However, when I just fire up the IIe without a disk,
and
> > hit the reset into Applesoft BASIC, then the card works. May be a tip
for
> > those who face the same problem. Why is that?
> > --- Bryan
> Found out the culprit after posting my original issue.
> The computer is an enhanced IIe w/extended 80-column card. Using a Unidisk
> 5.25 drive and matching Apple controller in slot 6, as well as the CFFA
card
> in slot 7. Nothing else in the machine. I popped the AP-64e into both
slots
> 2 and 1 during my troubleshooting.
> I was originally booting ProDOS 2.0.3 on the CFFA, then running
basic.system
> 1.5 to get to applesoft. Typed PR#x and it would immediately bounce me
into
> the monitor
> So I turned off the computer, pulled the CFFA card, took the CF module
out,
> then popped the CFFA card back in. Same result. Took the CFFA card, and
> booted off of the same exact ProDOS software, and now the AP-64e works.
> Earlier, I was just pulling the CFFA card out of the computer, then
booting
> without any disk, and doing a hard reset.

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.

Mark