[net.music.synth] More on the ATari ST MIDI interface

sinclair@aero.ARPA (William S. Sinclair ) (08/16/85)

After poking around some more in the Atari developer's literature, I found
out some more stuff about MIDI. Apparently, the I/O is at $fffffc06. This is
the address of the 6850 ACIA chip. They do have a handler set up to send and
receive MIDI data, that can be called from C or assembly code. One thing I
found objectionable is the way they handle incoming MIDI stuff. Each byte
is time-stamped with 3 bytes of time info. That means that a key-press would
take 12 bytes of memory, and each note (key dn, key up) would require 24
bytes.
The time stamp is referenced to the 200 tick/sec system clock, not to
any user-definable clock. All of this means you would have to ignore the
input handler, and write your own.
Well, at least they wrote SOME software for the port.
                                  Bill Sinclair  213/647-1753