31 Dec
2002
31 Dec
'02
2:07 a.m.
On Mon, 30 Dec 2002, Tony Duell wrote:
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.
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.
Yes, it is. Thanks! ;)
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 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.
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. I didn't
design it. I just built it from plans :(
Fat lot of use that course was, 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... 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? 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 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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