tim@attdso.att.com (Tim J Ihde) (01/19/89)
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@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