User`s manual
Western Reserve Controls 1782-JDM User’s Manual
PUB 24.0 PRELIMINARY
24
7 Troubleshooting
This section identifies some of the common problem observed when commissioning or operating a
DeviceNet and JDM.
Problem: JDM powers up.
The module LED flashes green.
The network LED is OFF.
JDM does not communicate over the network.
Possible Solution:
The JDM is in Autobaud mode, and is waiting for a few messages to cross the network so it
may determine the baudrate setting. This should happen if any other devices send their Dup
Mac messages, or the scanner sends any messages over the network. If the JDM is the
only device on the network, it may be advisable to set the baudrate to a fixed speed. Check
Parameter 5 in Table 3-7
Problem: JDM powers up.
The network status LED flashes red.
JDM does not communicate over the network.
Possible Solution:
JDM has detected a duplicate MacID (DeviceNet address). Change the JDM’s MacID to an
unused address and cycle power.
Problem: Module Status LED is solid Green
Network Status LED is flashing Green
Device will not communicate on the network.
Possible Solution:
Network does not have a terminating resistor. Add a 121 ohm resistor across the CAN_H
and CAN_L signals at the first and last nodes.
Problem: Module Status LED is solid Green
Network Status LED is solid Green
Device will not perform serial I/O – does not return a poll response and ignores future
commands.
Possible Solution:
JDM received an unintelligible response from the Modbus device and the time-out is set to
0. Set the time-out value to a non-zero number greater than the longest message time
expected from the Modbus device.
Problem: JDM does not receive a response from the Modbus slave.
Possible Solutions:
1. The ASCII-RTU mode selection is not correct. Check Parameter 1 in Table 3-7.
2. The serial link baud rate does not match the Modbus device baud rate. Check
Parameter 4 in Table 3-7.
3. The communication Framing parameters are not correct. Check Parameter 11 in Table
3-7.
4. The Modbus address is not correct in the I/O command.
5. The Modbus device may not support the Modbus specific commands being issued.