On Mon, 30 Dec 2002, Tony Duell wrote:
> > the addressing of the timers and registers into the Apple's memory bus or
>
> The 7473 is a flip-flop, and I can't see what it's needed for here.
Ok, then it inverts one of the Apple's clocks to make the timing work
properly with the 6522. This is what I remember from way back when.
> > I didn't design it. I just built it from plans :(
>
> Fat lot of use that course was, then...
It was a lot of use, actually, especially now that I really need the
knowledge I acquired to make this interface work. Unfortunately, I was
merely a good student. I passed all the tests and got a good grade but
didn't really learn as much as I would have liked. Electronics confused
me then.
> > I have a data sheet. I just haven't had a chance to study it yet.
>
> I guess it's easier to ask the rest of the world to make guesses about
> a card they've never seen than to actually look at the data for yourself...
Yes, it is. Thanks! ;)
> > > The keyboard also can't sent more than 128 different characters to the
> > > Apple (it's read in on a 7 bit port -- the 8th bit is the keyboard strobe
> > > line, indicating that a key has been pressed). If you really want to use
> > > the keyboard port for a reader input, then you're better off attacking it
> > > at this interface -- the cable between the keyboard assembly and the CPU
> > > board.
> >
> > Oh, well that's what I was considering doing. At that point it's a TTL
> > parallel input, correct?
>
> Correct. Look at the keyboard interface section in the Apple ][ reference
> manual. It gives a pinout of the connector and a description of the
> signals IIRC.
That's where I looked, and where I gleaned that it would be possible to
send the outputs of the reader into the keyboard connector.
(See, I do read once in a while.)
> > Yes, but for run of the mill cards it would work pretty well. The problem
>
> You will find punctuation characters on 'run of the mill' cards. I
Yes, but they are fairly standardized. The idea is to have at least a
modicum of knowledge about the cards being read. In this case, the cards
are printed with the data on the top, so I can tell it is using a FORTRAN
character set. A couple batches don't have any printing, so I'll have to
do some analysis of the data after it's been read and deduce the correct
character set.
> discovered this the hard way -- I have one of those manual card punches
> with 12 buttons, one for each row. There's a mechanical interlock to
> prevent more than one button in the 1-9 range being pressed at a time,
> there are other interlocks too. And when all buttons are released, the
> card steps on one column. Punching some quite common characters on that
> turned into a mental exercise of what keys to hold down, and which to
> press one after the other (as in : hold down 0, then press 3, release 3,
> press 8, release 8 and 0)
I have a Wrightline manual punch and it is far more accommodating than
yours. It allows the special 8-3 zone to be pressed along with whatever
other key.
Sellam Ismail Vintage Computer Festival
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Received on Tue Dec 31 2002 - 02:07:00 GMT