Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/12/84; site aero.ARPA Path: utzoo!linus!decvax!tektronix!hplabs!sdcrdcf!trwrb!trwrba!aero!sinclair From: sinclair@aero.ARPA (William S. Sinclair ) Newsgroups: net.music.synth,net.micro.atari Subject: MIDI on the Atart ST Message-ID: <363@aero.ARPA> Date: Thu, 15-Aug-85 14:42:23 EDT Article-I.D.: aero.363 Posted: Thu Aug 15 14:42:23 1985 Date-Received: Mon, 19-Aug-85 22:32:05 EDT Reply-To: sinclair@aero.UUCP (William S. Sinclair (5435)) Organization: The Aerospace Corp., El Segundo, CA Lines: 13 Xref: linus net.music.synth:408 net.micro.atari:962 I took a peek at the schematics provided by the Atari ST developers' kit. The MIDI interface is essentially a Motorola 6850 ACIA driven by a SHARP 900 opto-isolator. Output apperas to be standard open-collector logic. Ther are actually TWO 6850's in the box. The second goes to an output port directly. I don't know for what purpose. As far as I/O addresses, the chip select comes from the "glue" chip, so it's not obvious what they are. I couldn't find a refernce to the addresses in the ducumentation either. Perhaps the developers package contains a more detailed I/O memory map, but I haven't found it yet. Bill Sinclair 213/647-1753