I am trying to connect TM172DCL (Display for M172) but I keep getting Modbus Comm error.
1. I am using RS485-2 as a Modbus Master on M172.
2. Created a Generic Modbus Device for TM172DCL.
3. Since they both have the same power source, I left ground disconnected.
4. Installed 120 ohm to TM172DCL. Maybe I need to install 120 ohm on M172 as well?
Can you tell me what I am doing wrong? I need to be able to exchange variables between them but It seems that RS485-2 link on M172 is dead.
Thank you for your help!
Solved! Go to Solution.
Hi @jyoon ,
When I work with the M172D I usually use it as a master in the communication because for me is much simpler to exchange the information between the devices.
Take a look on this presentation of how to connect both devices (M172 plc as slave):
In your case if something is not working you should try to check:
1) The connection from the M172 RS-485 2 to the display (you can check the connection in my presentation but with RS 485-1).
2) The Actual values on the modbus configuration on the M172D and the PLC (They must match).
3) Verify the registers that you want to read from the M172D.
I hope this helps you 👍
Thank you very much for your help. I followed it and everything is working fine now.
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