clewis@eci386.uucp (Chris Lewis) (05/17/89)
Some time ago I posted a question about Xenix 2.3.1 hanging with Computone
boards/VPIX with Wyse 60's. Just in case this helps anyone else ...
The problem turned out to be that several of the handshaking wires were
misconnected. Eg: outputs driving outputs etc. I didn't bother to keep
a description of what I found. My eventual conclusion was that any
time that the wyse hardware-flow-controlled or powered off the computone
firmware/driver got confused and locked Xenix into some sort of high-cpu
interrupt overhead/loop. (This isn't the only trouble we've had with
the guys who installed the cable - we didn't hire 'em)
Anyhow, if you start having hanging problems, particularly if they seem
related to a specific line, get your volt-ohm-meter out and find out
whether the wires are connected the way you think they're supposed to be.
System has been working perfectly ever since.
A number of people made remarks about cable length. Yes, I know that
the RS232 specs specify 50 feet max. However, I've worked on and installed
systems with 100's of feet (perhaps as much as 700') in their RS232 connections
and have never had problems at 9600 baud. In particular: hundreds of drops
combined together in 25 pair and 100 pair Bell cable (not even twisted) run
through BIX/punch/RJ11 blocks etc. Another example: AT&T PDS wiring systems.
If AT&T trusts it, it's good enough for me.
In general, provided that the wires aren't in an electrically noisy
environments (Eg: an Aluminum smelter or wrapped around fluorescent
ballasts ;-) you can usually rely on several hundred feet at 9600.
Any Comms port that can't drive several hundred feet of reasonably good
quality cable at 9600 baud in a reasonably quiet environment is broken.
Eg: non-standard RS232 driver/receivers, or doesn't use +/- 12 volts for
driver supply.
Be that as it may, the cable in question was shorter than 50 feet anyhow.
--
Chris Lewis, R.H. Lathwell & Associates: Elegant Communications Inc.
UUCP: {uunet!mnetor, utcsri!utzoo}!lsuc!gate!eci386!clewis
Phone: (416)-595-5425