Troubleshooting
7-15
TI545/TI555 System Manual
Checking RS-485 (Twisted Pair) Cable Installation (continued)
Line-to-line
resistance that is below the minimum specified in T
able 7-3
may be caused by the following:
•
Incorrect termination resistors are installed.
•
More than two termination resistors are installed.
•
There is a short in the cable.
Line-to-shield resistance that is below the minimum specified in T
able 7-3
may be caused by the following:
•
One of the 9-pin connectors is connected to an RBC or CPU.
•
Cable line wires are shorted to the shield.
Line-to-line resistance that is above the maximum specified in T
able 7-3
may be caused by the following:
•
Incorrect termination resistors are installed.
•
Fewer than two termination resistors are installed.
•
The cable is open between the point of measurement and one or both of
the termination resistors.
Resistance Below
Minimum
Resistance Above
Maximum
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