Experimental Physics and
Industrial Control System

[email protected] (Jeff Hill) · Fri, 10 Dec 1999 15:37:51 -0700

> Why does that work better? My thought was that the problem 
> was actually with the 
> transceiver on iocB, but a different one did the same thing. 
> Cable? All the data still goes 
> through it, the "T" just isn't connected to anything any more? 
> Bad "T"? Possible, but not 
> likely since the other legs of it are fine and, keep in mind, the 
> sniffer never did see any 
> problems with the network. Bad cables tend to show up pretty readily.
> 

Double check that your thin wire network is following the proper
wiring procedures. Wiring problems can result in certain devices working 
perfectly while others at periodic intervals on the cable may not!

1) Make certain that your thinwire network does not have any "T"s
in it that are not directly connected to a transceiver (or disconnected). 
"T"s with three bits of coax connected are invalid. "T"s with two bits of 
coax connected are ok.

2) Both ends of the coax cable need to have terminations unless the
ends are connected to devices with internal terminations. 

3) Certain types of coax cable used for analog electronics have the
wrong characteristic impedance for use in thin wire installations.

4) There are also maximum and minimum length requirements for this wire.

5) I have observed some in house designed invalid transceiver wiring 
here which resulted in poor performance of CA, but otherwise allowed 
the IOC to boot slowly and run.

Jeff

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System