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Posting-Version: version B 2.10.2 9/17/84 chuqui version 1.7 9/23/84; site daisy.UUCP
Path: utzoo!utcs!lsuc!pesnta!hplabs!nsc!daisy!david
From: david@daisy.UUCP (David Schachter)
Newsgroups: net.music.synth
Subject: Re: MIDI and RS232
Message-ID: <65@daisy.UUCP>
Date: Sun, 24-Feb-85 22:44:24 EST
Article-I.D.: daisy.65
Posted: Sun Feb 24 22:44:24 1985
Date-Received: Wed, 27-Feb-85 10:38:45 EST
References: <1854@pucc-h>
Reply-To: david@daisy.UUCP (David Schachter)
Organization: Daisy Systems Corp., Mountain View, Ca
Lines: 31
Summary: 


9600 Baud is not necessarily 9600 bits per second (bps).  Baud measures the
number of signal changes per second.  For example, a Vadic 1200 Baud modem
is actually a 1200 bps modem.  The Baud rate is 600 and Vadic puts two bits
(called a dibit) into each signal change (Baud).  9600 Baud modems are
actually 9600 bps modems, transmitting at a much lower baud rate.  (Typically,
they pack three or four bits into each signal change.)

Also, contrary to a previous writer, 9600 bps doesn't necessarily translate
into 960 bytes per second (Bps).  The formula Bps = bps/10 is correct if you
are transmitting 8 bit bytes on an asynchronous link with one start bit and
one stop bit.  On synchronous links, you don't need start and stop bits so
you can send more bytes down the line faster, ignoring certain overhead bits
(which can be noticable if you screw things up.)  Or you can use more stop
bits, thus slowing down the byte rate.  Or you can use statistical data
compression thus sending more useful bytes down the line.  So on and so forth.

In summary, "9600" is usually a bit rate, not baud rate.  The formula Bps =
bps/10 is frequently correct but not always.  It is the special cases caused
by the above words "usually" and "frequently" that cause data communications
to be considered a black art.  (You can make good money at it and you can get
to travel a lot.  To Fremont and Milpitas and Newark and Cleveland and....)
Please be careful in posting data communications related stuff unless you 
really know what you are talking about.  People can waste enormous amounts of
time really easily.  

[The above do not necessarily reflect the views or policy of Daisy Systems,
its employees, or its subsidiaries.  The contents of this posting are the
responsibility of the author who is generally capable of walking and chewing
gum in near-real time.] {Cry of anguish heard at the Programming Clinic an
hour before the project deadline: "But I only changed one card!"}