Rockwell Automation 57C428 Toledo Scale Interface Module - Manual (Page 27)

5Ć1
5.0 DIAGNOSTICS AND
TROUBLESHOOTING
This section explains how to troubleshoot the module and field
connections. If you cannot determine the problem, the unit is not
userĆserviceable.
5.1 No Activity on Serial Line
Problem: No data is being received on the serial line. You can
confirm this by monitoring the values in register 14Ć18. If they do not
change regularly, no data is being received. The possible causes of
this error are a programming error or a malfunctioning module. It is
also possible that the transmitter is malfunctioning, or that the serial
line is not connected or is connected to the wrong transmitter. Use
the following procedure to isolate the problem:
Step 1.
Verify that the module has been configured correctly.
The LED on the module faceplate should be blank. If it is,
verify that the baud rate in register 21 is the same as the
baud rate of the transmitting device.
If the LED on the module faceplate displays the letter C,"
the module has not been configured correctly. Review
your rack configuration as well as the programming
statements to configure the module.
Step 2. Verify that the module is connected to the correct
transmitter.
Check the cabling between the module and the
transmitter. Make certain that the proper devices are
connected together, that all the connections are secure,
and that the proper signals are connected together. Refer
to Appendix C for DĆshell connections and to figure 4 for
the proper connector on the transmitting device.
Step 3. Verify that the serial link is working.
Connect an oscilloscope to the transmitter terminals on
the Toledo Scale digital indicator. The oscilloscope should
display a square wave with periods equal to the values in
figure 5.1 when the device is transmitting. If it does not
display a square wave, the transmitter is malfunctioning.
Volts ąąą1200 baud = 833 microseconds
ąąą2400 baud = 417 microseconds
ąąą4800 baud = 208 microseconds
ąąą9600 baud = 104 microseconds
ąąă19200 baud = ă52 microseconds
time
Figure 5.1Ć Pulse Time for Different Baud Rates