Hello
I would be grateful if someone could help me with a problem of communication between plc s 1200 and a controller to regulate use an analog control valve refrigerant (Carel EVD Twin) in a cold room.(Carel EVD Twin)

I want to read a variable of this controller via RS485 communication using a communication module cm1241. I think I've typed the program correctly;  in OB start I have placed the block "Modbus comm load", and in the OB1 I have placed the block  "modbus master". I think that perhaps  I've got problem to know the parameter DATA_ADDR

But I can not read the value of the variable. The program does not tell me that there is error, I can also connect "online" without problem but  this value is always "0". My PLC is connected to HMI KP700 ( profinet ) too that it works good.

I'm very grateful

greetings

Hello,

Move the status word value in other memory location on error bit. Then only you can able to capture the error.

Once you get error then send the error code . Also test with Standard Modbus tester software  like modview  , which will act as Modbus Slave.

See the attached  Modbus Tester software