Connections and Modbus

[richard 0]

All, I am trying to use a new item (MicroADM from CWT) that requires rs485 to rs232 connection to pc or whatever needs to communicate at that end(the unit has the converter connected inline). I am trying to connect the unit to a CJ1W-SCU21-V1. The programming that I am using is the the ModbusPM v5 that I downloaded here. I need to be able to read the coils(func 01) and registers(func 03). If i do a trace on the Protocol Macro Software I can see that I am sending the correct message but I get no return message or response. I am not sure is it is my cable pinout. If I connect my usb to rs232 to the 485 to 232 convertor I can get connected with Multiway( modbus) and send the same message but i get a response. My wiring for this is attached. any help will be much apreciated Thanks

[Jay Anthony 118]

Cabling: Be sure that you are using pin 9 as Signal Ground on the SCU21.

[richard 0]

Jay, thanks for reply. I am using pin 9 as signal ground. I have tried a few different configurations and still no reply.

[PdL 71]

Do you have pin 4/5 on PLC side wired? Try to jump them at PLC side.

[richard 0]

Do you have pin 4/5 on PLC side wired? Try to jump them at PLC side.

[PdL 71]

I asume you downloaded modified port settings into the SCU21, but did you also set the Port settings parameter to User settings instead of defaults? If not, even though you have changed baud rate, parity etc it will still use default settings. I've chased this ghost a few times myself.

[Jay Anthony 118]

Cable should be 2/3 3/2 9/5 for the Omron to Convertor cable.

[Fer 1]

Hi this a setup for a working program using modbus to talk to a drive. hope it helps

[banker 2]