Xref: utzoo comp.os.os9:286 comp.sys.m6809:970
Path: utzoo!utgpu!watmath!clyde!att!ihlpl!knudsen
From: knudsen@ihlpl.ATT.COM (Knudsen)
Newsgroups: comp.os.os9,comp.sys.m6809
Subject: Re: MIDI Interface driver for CoCo 3
Summary: COCO-MIDI address; blocking interrupts; religion
Keywords: OS-9, Driver, MIDI
Message-ID: <7943@ihlpl.ATT.COM>
Date: 1 Dec 88 17:14:58 GMT
References: <37148@clyde.ATT.COM> <24727@wlbr.EATON.COM>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 29

In article <24727@wlbr.EATON.COM>, pete@wlbr.EATON.COM (Pete Lyall) writes:

> Kent Meyers and I attempted to adapt an existing 6850 ACIA driver to 
> work with the COCO MIDI 2 pak (a 6850 UART - I forget the address, but
> *think* it's $FF60 or $FF66). It works, but *not* for steady stream

The correct address is $FF6E (contro/status) and $FF6F for data.
Intercomp Sound's interface pak also uses this address so as to
be compatible with all software, and I suggested to Ag that he
put his there also.  Unforch'ly he uses a 6551.

>[discussion of how/when OS9 system blocks interrupts]

Well, Pete, it looks like the only way we can record MIDI is
to block interrupts ourselves, solid for the duration of the recording,
and use our own timing loops to keep time.
Alternately, add a FIFO buffer and self-timing counter to the
interface a la MPU-401.  Burke & Burke are coming out with
a clone of this well-known interface and and adapter and driver
for it.

Funny, isn't it -- the more sophisticated your software (OS9),
the more hardware you need to do the same job.
(Or is it just overcoming some hardware (MPI, GIME) whose contribution
is sometimes negative....?)	--mike k
-- 
Mike Knudsen  Bell Labs(AT&T)   att!ihlpl!knudsen
"Lawyers are like nuclear bombs and PClones.  Nobody likes them,
but the other guy's got one, so I better get one too."