User`s manual

Western Reserve Controls 1782-JDM User’s Manual

PUB 24.0

7 Troubleshooting

This section identifies some of the common problem observed when commissioning or operating

a DeviceNet and JDM.

Problem

JDM powers up, then the module status LED turns Red. JDM does not communicate over

the network.

Possible Solutions:

1. 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 Solutions:

1. 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 Red

Network Status LED is flashing Green or solid Green

Device will not perform serial I/O – does not return a poll response and ignores future

commands.

Possible Solutions:

1. 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.

2. The serial link baud rate does not match the Modbus device baud rate.

3. The communication parameters are not correct, including parity and number of data

bits.

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.