Subject: Re: Casette I/O
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From: Edward Berry <eaberry@lbl.gov>
Newsgroups: comp.sys.apple2
Date: Sun, 20 Aug 2000 01:28:32 -0700
Organization: Lawrence Berkeley Laboratory
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The apple connection to the cassette is actually digital, not analog
(TTL with pullup resistor if I remember correctly, maybe AC coupled 
through a capacitor). So there's no real reason to use the sound card 
on the PC, just use one bit of the parallel port (Some PC paralell
ports are supposedly write-only, but if you write $FF they can be
pulled down by the incoming signal. Or you could use a handshaking
input signal). 

I ported the Apple tape code to a C-64 (no big deal, since both are 6502),
but I never tried connecting directly- only through a tape recorder.

Since the PC's all have serial ports with software in BIOS, and Wozniac
early on published software for sending/receiving serial via the
game port, that would sound like a much easier route. I think that
only works up to ~9600 baud, considerably less than your 6kB/s, but still
much faster than the monitor LOAD and SAVE commands. Come to think of it,
the tape signal is more complex than the serial signal, so timing of
the 6502 probably limit it to even lower speeds.  If your idea was 
that the sound card has higher bandwidth than the serial port on the PC,
forget it- the limiting factor is going to be the 6502 for the tape
drive, and the UART on an apple serial card will be much faster.
-- 
Edward A. Berry, MailStop 3-250
Lawrence Berkeley National Laboratory
1 Cyclotron Road, Berkeley, CA 94720
Phone: +1-510-486-4335
Fax: +1-510-486-6059
Jfax +1-530-323-9836 (you send fax, I receive email)
e-mail: EABerry@lbl.gov