3B2 - HP7750A Woes
Tim J Ihde
tim at attdso.att.com
Thu Jan 19 08:41:12 AEST 1989
We're having a peculiar problem with some HP-7550A plotters connected
to our 3B2/400 (we actually have three of these plotters; each manifests
the problem). From what I can tell, it appears that the plotter is
unable to XOFF the computer when its buffer fills up.
The error manifests itself mainly when plotting a complex bar chart that
has some long filled bars in it. If the baud rate is high, say around
2400 - 4800, we get "Buffer Overrun" almost as soon as the bars are begun.
At lower speeds, down to 300 baud, it plots longer but still gets the error
eventually.
The really peculiar thing, which I still don't really believe, is that
it seems to work much better with paper than with transparencies. How
the plotter handles transparencies differently, and how it knows they are
there instead of paper in the first place, I don't understand. This seems
pretty consistent, though.
Anybody have any ideas?
Our plotter settings (from the panel) are:
Enhanced Serial
Handshaking = XON/XOFF Direct
Bypass = Off
Data Flow = Remote Standalone
Duplex = half
Parity = 8 Bits, none
Baud = 600 (works almost always for paper, occasionally for transp.)
The lp interface script we are using is:
stty 600 ixon ixoff -ixany -parity -tabs onlcr icanon clocal cread -inpck opost 0<&1
echo "\033.P1:" 2>&1 #set for xon/xoff
echo "\033.@;0:" 2>&1 #turn off hardware handshake mode
echo "\033.I250;;17:" 2>&1 # turn on XON handshake
echo "\033.N;19:" 2>&1 # set the XOFF character
shift; shift; shift; shift; shift
files="$*"
for file in $files
do
cat "$file" 2>&1
echo "AF;\000\c"
done
exit 0
I should point out that while I've used other plotters somewhat, and have
done lots of work with lpsched, I don't know a whole lot about this plotter
and I didn't write this interface (although I've been tweaking it lately :-)
--
Tim J Ihde INTERNET: tim at attdso.att.com
(201) 898-6687 UUCP: att!attdso!tim
"Blimey - this redistribution of wealth is more complicated than I'd thought!"
- Dennis Moore and various Presidents
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