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From: cbradley@blackbox.lonestar.org (Chris Bradley)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Help!! Laser Writer II NTX behaves funny on serial port.
Summary: use DTR!
Keywords: printer, laser writer, serial port, problem
Message-ID: <1990Nov27.155741.23297@blackbox.lonestar.org>
Date: 27 Nov 90 15:57:41 GMT
References: <28411@usc>
Sender: news@blackbox.lonestar.org
Followup-To: comp.sys.mac.hardware
Organization: Businessland Advanced Systems
Lines: 27

In article <28411@usc> kamesh@bmsr7.usc.edu (Kamesh V. Kothuri) writes:
    >	I am having a problem with the serial port on Apple
    >Laser-Writer II NTX model printer when I try connecting a SUN Sparc
    >station or an IBM PC-AT on its serial port.
    >	The printer uses only TD,RD and GND on pins 2,3 and 7
    >respectively. I have tried both a null modem cable in which lines 2
    >and 3 are crossed and one which is straight. Neither worked.

The LaserWriter most definitely will use the DTR signal for "hardware
handshaking."  The poster does not mention what the asynchronous 
communications parameters settings are, but even the NTX cannot accept
a continuous input stream at 9600bps.

In this case, I would recommend adding support for DTR to the cable that
connects the NTX to the Sun, which is pin 20 on the normal EIA RS-232-C 
connector.

The LaserWriters can also be set to use XON-XOFF ("software") handshaking,
which doesn't require DTR.  This is supposed to be done with a short
PostScript program that gets downloaded to the printer, but I don't know
what that is.

-- 
Chris Bradley			| "I confess freely to you, I could never look 
Businessland Advanced Systems	| long upon a monkey, without very mortifying 
Dallas, Texas US		| reflections." 
cbradley@blackbox.lonestar.org	|		-- WILLIAM CONGREVE 1670-1729