Path: utzoo!utdoe!generic!pnet91!sb
From: sb@pnet91.cts.com (Stephen Brown)
Newsgroups: comp.sys.apple2
Subject: Re: Apple II+ 80-col card wire
Message-ID: <580@generic.UUCP>
Date: 19 Mar 91 06:30:09 GMT
Sender: root@generic.UUCP
Organization: People-Net [pnet91], Etobicoke, ON
Lines: 56

umsmit72@ccu.umanitoba.ca (Kenneth G. Smith) writes:
>
>I previously posted an article (Apple II+ 80-col card wire) and was
>asked to identify my card somewhat in order to assist those who are
>willing to help.  The only problem here is that the card has
>no markings.  Two things that I found rather distinctive about it
>were:  1) has rather large (~42 pins) chip #HD6845SP 
>       2) has three white (?) Mitsubishi chips;  2 - #MB8516, 1 - #MBM2716

The HD6845 is a Hitachi 6845 CRT controller. I think the Videx card works
better with the Hitachi part than it does with the Motorola part.
The three white chips sound like the EPROMs (eraseable, programmable, ROMs) --
these contain the firmware (the one by itself), and the bit maps for the
characters (the two at the top). One of these character generators contains
the "normal" characters; the other contains the "alternate" (graphic, dim,
inverse, or foreign) character set. They're either 2708's or 2716's. The
latter were commonly used because they were cheaper.

>Also, I found it rather odd that the RCA-type video jack points
>toward the front of the computer rather than the back (although I don't
>really know whether or not this is actually peculiar since I have
>never actually seen another one of these beasts).  This small red
>wire in question connects to the card right below the jack.  Does
>this ring a bell with anyone, yet?

Some cards had a built-in softswitch to make it easy to switch between 40 and
80 columns. I'd have to see the card, as there were so many different 80
column cards in the golden days of the II.

>As for the question asked about turning the card off for graphics
>mode or otherwise;  it seems to deactivate (via pr#0) alright, but
>I haven't ran any graphics as of lately (I'll have to try some).
>You see, most of my DOS 3.3 stuff doesn't seem to load quite right
>since I blew up my video trying to hook up this damn wire (granted
>that's a whole different problem, though!), and that is what most of
>my current graphics stuff is written under.  Actually, I find it rather
>odd that the DOS 3.3 "HELLO" programs seem to bomb on "TEXT" cmd
>(possibly related to the card or it's wire?).
>

Pr#3 will turn the card on. Pr#0 doesn't properly turn it off, unless you do a
in#0 as well. (In deferred mode, these are DOS commands, and must be preceded
by a chr$(4) or control-D). If you have the latest version of the firmware,
then I think these control codes will be helpful:

control-Z followed by 0 -- home cursor and clear screen
   "          "     " 1 -- turn off 80 column card completely
   "          "     " 2 -- select standard character set (right one)
   "          "     " 3 -- select alternate character set (left one)
control-A                  shift lock for computers without the shiftkey mod.


Stephen Brown, Toronto, CANADA

UUCP: lsuc!graham!pnet91!sb
INET: sb@pnet91.cts.com