Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!usc!skat.usc.edu!sutter
From: sutter@skat.usc.edu (Carl Sutter)
Newsgroups: comp.sys.next
Subject: Solution to Apple Laserwriter Plus Hookup
Keywords: Apple Laserwriter Plus Serial Wiring Diagram
Message-ID: <19278@usc.edu>
Date: 19 Aug 89 02:06:36 GMT
Sender: news@usc.edu
Reply-To: sutter@skat.usc.edu (Carl F. Sutter)
Distribution: usa
Organization: University of Southern California, Los Angeles, CA
Lines: 48

For the sake of the archives, and news readers (like me) out there...

The original question was how to get an Apple Laserwriter Plus to work
reliably as a serial port connected printer to the cube.

The solution was to scrap and re-load the network configuration, and since
that is taken care of by systems people here, I unfortunately can't explain
why it worked.  Maybe noone can :-)

Some of the images in the docs are in an Encapsulated PostScript format that
the printer will not handle. (ex. Ch. 3, p. 19 in the 0.9 system)

The interesting thing is that the cabling can be connected to either the 
DB25 or the DB9 connectors on the LaserWriter.  When the switch is set to
9600 baud, the DB25 is RS-232, and the DB9 is RS-422 (like the NeXT!).

The wiring is actually NOT a null-modem, and a possible confusing point is to
put two null-modems in line, since an off the shelf Mac-Modem cable is a
null-modem.

The important wires to connect for RS-232 are:

NeXT DIN 8                LaserWriter Plus DB25
   3  TxD-   -------------   TD    2
   4  GND    -------------   CGND  7
   5  RxD-   -------------   RD    3



An RS-422 is just a straight through connector:
(The LaserWriter Plus doesn't use hardware handshaking)

NeXT DIN 8                LaserWriter Plus DB9
   3  TxD-   -------------   TxD-  5
   4  GND    -------------   GND   3
   5  RxD-   -------------   RxD-  9
   6  TxD+   -------------   TxD+  4
   8  RxD+   -------------   RxD+  8


I know this is a little esoteric, since most laser printers are networked,
but it takes awhile to combine all the bits and pieces of information that
people have into a coherent picture.  I'm happy to answer questions about
the cabling.


Carl F. Sutter
sutter@skat.usc.edu