Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!jarthur!bridge2!3comvax!tymix!tardis!jms
From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.dec.micro
Subject: Re: printing from within 20/20 spread sheet
Summary: XON/XOFF problems
Message-ID: <847@tardis.Tymnet.COM>
Date: 7 Dec 89 23:04:47 GMT
References: <8912032300.AA02025@LANAI.MCL.UNISYS.COM>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: BT Tymnet, San Jose, CA
Lines: 31

In article <8912032300.AA02025@LANAI.MCL.UNISYS.COM> perry@MCL.UNISYS.COM (Dennis Perry) writes:
>LA50.  The first page prints out fine, the second page print 
>after about 10-15 lines garbage.  A line will start out fine and
>then backward question marks will print out for the rest of the line
>and the CR will get lost, etc.  After about 10 lines of this the
>print stops, even if it is not complete.

This failure mode is very common with LA50 printers.  It indicates that the
printer tried to send Control-S (XOFF) to the computer, but the computer
kept sending.  Reverse question marks are an indication that the printer's
buffer overflowed.

The usual causes of this are:
  1) The computer is not configured to respond to XON/XOFF from the printer.
  2) The cable to the printer is defective, and not passing pin 2 back.
  3) The motherboard in the printer has gone defective and transmits garbage.

Case #3 is what I see a lot of.  It was determined by connecting a dumb
terminal (one that does not respond to escape sequences) to the LA50 with a
null modem and sending ESCape [ c to the printer.  It is supposed to respond
with ESCape [ ? 1 7 c which is the product identification.  (See page 40 of
the LA50 Programmer Reference Manual.)  When my printers went out, they
returned the right number of characters, but the wrong ASCII codes.  In this
state, the LA50 sends some random garbage character to the computer instead
of Control-S, leading to the buffer overflows.  They fixed it by swapping
out the entire control/logic board.
-- 
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@gemini.tymnet.com
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