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From: craig@x.UUCP (Craig Lund)
Newsgroups: net.micro.mac
Subject: Mac Serial Port pinout
Message-ID: <517@x.UUCP>
Date: Mon, 27-May-85 12:22:36 EDT
Article-I.D.: x.517
Posted: Mon May 27 12:22:36 1985
Date-Received: Thu, 30-May-85 03:39:17 EDT
Distribution: net
Organization: Charles River Data Systems, Framingham MA
Lines: 31

Somebody out there asked for the pinout of the serial port on
the back of a Macintosh.

The serial port is RS422, NOT RS-232 !  If you wire it right,
most RS-232 devices won't care.

Pinout:

1	Ground
2	+5
3	Ground
4	Transmit Data +
5	Transmit Data -
6	+12
7	Incoming handshake
8	Receive Data +
9	Receive Data -


I connected directly to my UNIX box using the following
three-wire connection:

MAC Pin		UNIX Pin
1		7
5		2
9		3

If this does not work for you, try switching pins 2 and 3 on the UNIX side.
Also, some RS-232 ports will require connecting ground and/or +5 to
some of the RS-232 control lines.  Consult the manual for your RS-232-based
computer or modem.