Re: 600xl disk simulation?

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1 total messages Started by Edmund S. Kijak, POINT Tue, 24 Sep 1985 17:13

#1089

Author: Edmund S. Kijak, POINT
Date: Tue, 24 Sep 1985 17:13

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Regarding the casette interface, I don't see how it can be done entirely in
software.  The casette output is an analog voltage whose magnitude depends
on the volume control setting - you would need some hardware simply to convert
it to a standard voltage level, say TTL.
	The interface converts FSK (frequency shift keyed) audio tones to 
digital bits.  The bits are asynchronous serial with a start bit, data bits,
and a stop bit.  Baud rate is 600, a ZERO is a 3995 Hz tone, a ONE is a
5327 Hz tone, the tone durations are equal.  The output of the casette needs
to be converted to TTL levels (0 or 5 volts for logic ONE or logic ZERO)
before feeding to computer. (I may have the ONEs and ZEROes swapped, and
may be off a few Hz, but the info is basically correct).

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