Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbvax.ARPA Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!ardc.arpa!ekijak From: ekijak@ARDC.ARPA (Edmund S. Kijak, POINT) Newsgroups: net.micro.atari Subject: Re: 600xl disk simulation? Message-ID: <8509241721.AA07193@UCB-VAX.ARPA> Date: Tue, 24-Sep-85 13:13:35 EDT Article-I.D.: UCB-VAX.8509241721.AA07193 Posted: Tue Sep 24 13:13:35 1985 Date-Received: Thu, 26-Sep-85 07:38:50 EDT Sender: usenet@ucbvax.ARPA Organization: The ARPA Internet Lines: 11 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).