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From: urlichs@smurf.ira.uka.de (Matthias Urlichs)
Newsgroups: comp.sys.mac
Subject: Re: Pinouts and Cables for Mac II/SE mini-8 (DIN) Serial Ports
Message-ID: <822@smurf.ira.uka.de>
Date: 13 Feb 89 22:26:31 GMT
References: <1260@cascade.Stanford.EDU>
Reply-To: urlichs@smurf.ira.uka.de (Matthias Urlichs)
Organization: University of Karlsruhe, FRG
Lines: 47

In comp.sys.mac trewitt@cascade.ARPA (Glenn Trewitt) writes:
< 
< The signal assignments are:
< 	1	HSKo	Handshake out
< 	2	HSKi	Handshake in / external clock
< 	3	TxD-	Transmit data -
< 	4	GND	Signal ground
< 	5	RxD-	Receive data -
< 	6	TxD+	Transmit data +
< 	7	GPi	General purpose input
< 	8	RxD+	Receive data +
< On the modem port, GPi can be set to be a second external clock.
< 
< WARNING:
< I have seen DIN-8 to DIN-8 cables in two varieties.  One
< connects pin 1 to pin 1, 2 to 2, etc., and the other that
< exchanges (1,2), (3,5), and (6,8), making a null modem.  This
< is a deplorable situation, but itUs Apple's fault for not setting
< a standard.  I prefer to use the straight-through cables, since
< other devices, such as A-B printer switches, use the same scheme.
< Having a null modem appear out of nowhere is very confusing.

I disagree.
There _is_ a standard: Data go from pin 3/6 of the female into 3/6 of the
male side of the connection. Data go from pin 5/8 of the male into pin
5/8 of the female side. That's it.
And if you adhere to that convention on every DIN-8 connection there is,
you'll never have trouble no matter what you connect to whatever else.
If anyone manufacturers swap this, I'd be very angry with them if I were Apple.

On the DB-25 side, things are different. There one really has to look
carefully at the in/out side; I've seen lots of devices which act as DTE but
feature a DCE connector (or vice versa).
Or, since you can't hurt RS-232 signals no matter how wrong you connect them
to each other (well, almost), simply try it one way, and if that doesn't work,
try it the other way.
If that doesn't work either, set the correct baud rate and try again. :-)
< -- 
< Glenn Trewitt, Center for Integrated Systems, Stanford University
< 	{ucbvax,decvax}!decwrl!miasma.stanford.edu!trewitt	USENet
< 	trewitt@miasma.stanford.edu				Internet

Disclaimer:
If this is all wrong, it's not my fault: You were reading this upside down.
-- 
Matthias Urlichs -- Humboldtstrasse 7 -- 7500 Karlsruhe 1 -- FRG
urlichs@smurf.ira.uka.de -- ++49+721-621127@PTT