I'm trying to get a Modicon 984-145 talking to a CEV 300 10 modbus to ethernet bridge to no avail. I have verified the plc modbus port is working with a straight modbus cable to my pc. Serial settings on both the bridge and plc are rtu, 9600, 8, E, 1 and the serial port on the bridge is configured to a slave device. The modbus port is assigned 1 on the plc and in the advanced modbus protocol configuration of the bridge I have tried it as both fixed to 1 and as modbus/tcp header. We have the exact same setup at another location in the plant and the bridge and cable I made work just fine there. I also successfully used the bridge and cable on a 984-265 at my workstation. However when I try it on the system where I need to install it, all I get is the serial transmit light on the bridge flashing furiously and very slow modbus flashes(like 10 secs between flashes) on the plc. Any help is appreciated.
One possible issue - the old 984 PLC need the correct linking of incoming DSR, or they won't talk. It just has to be high, not changing and not left floating.
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