28 Oct
2001
28 Oct
'01
1:28 p.m.
I don't know what data rate you're after, but with a couple of parallel I/O
bits, you can build a very seriously reliable audio cassette interface,
requiring only that you ditially time the transitions on the serial link. If
you use Manchester encoding which has timing information embedded in every bit,
you can operate the cassette interface at the highest rate at which the
head/media combination is capable, without any particular hardship. You just
need to low-pass filter the output and AC-couple the input with a couple or
three passives for each, you're done. If your cassette is capable of 10 kHz
then you need simply approximate the I/O rate to match, since a string of either
1's or 0's will have that frequency, and the transitions between them will never
have less than a +180-degree phase shift.
Dick
----- Original Message -----
From: "Ben Franchuk" <bfranchuk(a)jetnet.ab.ca>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, October 28, 2001 11:58 AM
Subject: Almost on topic - Cassette I/O
I am building a FPGA ( Field programmable gate array )
computer
in the style of the early computers that had a front panel and
TTY for I/O. While I don't have have a front panel working the
Hardware serial bootstrap does work on my prototype. Since I
have a few LOGIC cells left in my FPGA to play with I was
thinking adding a cassette interface. Does anybody know of
schematics on the web that I can get ideas from.
Ben Franchuk.
--
Standard Disclaimer : 97% speculation 2% bad grammar 1% facts.
"Pre-historic Cpu's" http://www.jetnet.ab.ca/users/bfranchuk
Now with schematics.