Troubleshooting/Service
328 UDC3500 Universal Digital Controller Product Manual 3/07
7.7.9 Procedure #9 – RS-485
Table 7-13 explains how to troubleshoot a RS 485 Communications failure.
Table 7-13 Troubleshooting a RS-485 Communications Failure
Step What to do How to do it
1
Check the Address Number,
ComState and Baud Rate
settings.
See Section
3.23.
2
Check if the controller is wired
correctly to the Network.
See Section 2.7 for wiring diagrams.
3
Determine if the
Communications board is faulty
by running a LOCAL
LOOPBACK TEST.
If the test fails, replace the
board. If the test passes, the
problem is most likely
elsewhere in the
communications network.
Disconnect the communications cable from the
rear terminals. Run the Local Loopback Test.
P
ress
Setup key until you see:
COM
Lower Display
SET UP
Upper Display
Press
Func-Loop 1/2 key until you see:
LOOPBACK
Lower Display
DISABLE
Upper Display
Press
or and you will see:
LOOPBACK
Lower Display
ENABLE
Upper Display
Press
Lower Display key and you will see:
LOOPBACK
Lower Display
START
Upper Display
Then you will see either PASS or FAIL in the
Upper Display. The test will run until the
operator disables it or until the unit is power-
cycled.
If you see FAIL, go to Step 4. If you see PASS,
then the problem is most likely not in the
instrument, but somewhere else in the
network. Reconnect the communications cable
and then go to Step 7.
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