Path: utzoo!attcan!uunet!mailrus!usenet.ins.cwru.edu!mephisto!ncsuvx!news
From: mark@ccvr1.ncsu.edu (Mark Boyd)
Newsgroups: comp.sys.atari.st
Subject: Re: Running MIDI at 500KHz -- conclusions??
Keywords: midi keyboard
Message-ID: <1990Mar23.174740.18830@ncsuvx.ncsu.edu>
Date: 23 Mar 90 17:47:40 GMT
References: <1990Mar9.215613.17075@wam.umd.edu> <1436@uvm-gen.UUCP> <11493@stag.math.lsa.umich.edu> <1990Mar23.150337.15770@ncsuvx.ncsu.edu>
Reply-To: mark@ccvr1.ncsu.edu (Mark Boyd)
Organization: Univ. of North Carolina - Asheville
Lines: 17

Ops - rn put my message in the Keywords line, highly truncated. I'll
try again.

The midi port and the keyboard port of the ST both use the same 500
KHz clock, but it is simple to make the UARTs clock inputs independent.
All it requires is cutting one trace on the PC board. I did this to
change the baud rate for the midi port. It is documented in deckeybd
which is archived in comp.{sources|binaries}.atari.st.

On the other hand, you cannout run a UART asynchronously with its baud
rate equal to its clock rate. That, with or without the optical
isolators, doomed Howard's ( I think it was .. ) experiment. You need
to use a 16X clock. I don't remember the max clock input on the ST's
UART, but I don't think it is nearly fast enough for AppleTalk speed.

	Mark
	mark@ccvr1.ncsu.edu