CLS200 Series User’s Guide
Chapter 8: Troubleshooting and Reconfiguring
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• You can also connect an oscilloscope to the transmit or receive line to see whether data is
being sent or received. If the serial port does not appear to be working, the software setup
may need to be modified or the hardware may need to be repaired or replaced.
Communications
Most communications problems are due to incorrect wiring or incorrectly set communications
parameters. Therefore, when there is a problem, check the wiring and communications settings first.
Verify the following:
•
Communications port:
Software must be configured to use the communications port to
which the controller is connected.
•
Software protocol:
Set the correct protocol for the software MOD for Modbus
®
or ANA
for Anafaze.
•
Controller address:
Configure software to look for the controller at the correct address. In a
multiple-controller installation, each controller must have a unique address.
•
Baud rate:
Software and controller must be set the same.
•
Error checking (ANA protocol only):
Software and controller must be set the same
(CRC or BCC).
•
Hardware protocol:
PC and controller must use the same protocol, or a converter must be
used. The controller is typically configured for EIA/TIA-232 when it is shipped. See
on to change between EIA/TIA-232 and EIA/TIA-485. To
communicate with more than one controller, or when more than 50 feet of cable is required,
use EIA/ TIA-485. Even for a single controller, you may use EIA/TIA-485 and an optically
isolating converter to eliminate ground loops.
•
Converter:
Make sure that the EIA/TIA-232-to-485 converter is powered, configured and
wired correctly.
•
Cables:
Check continuity by placing a resistor across each pair of wires and measuring the
resistance with an ohmmeter at the other end.
Ground Loops
Many PC communications ports have their common wires connected to chassis ground. Once
connected to the controller, this can provide a path to ground for current from the process that can
enter the controller through a sensor (such as a thermocouple). This creates a ground loop that
can affect communications and other controller functions. To eliminate a ground loop, either use an
optically isolated communications adapter or take measures to ensure that sensors and all other
connections to the controller are isolated and not conducting current into the unit.
Software Problems
If the controller and serial communications connections seem to be working correctly, but you are
still not getting the result you expect, consult the resources you have available for the software
program you are using.
