I'm new to PLC operations, and I was hoping I could get some help getting started with MODBUS communications.
I have a PLC/HMI running UniLogic and Festo CMMO which I am trying to run over MODBUS TCP. I have added the remote slave, and downloaded the program onto the PLC. However, I haven't been able to get any proof of the connection. I have added registers (3 and 17) based on reads to tags (INT16), but they all display as 0. I have also tried displaying the value of slave.sessions, but it also shows 0 which leads me to believe it has not even tried to start the connection yet.
I feel like I'm missing some critical first step or debugging process?
I would appreciate any help or point in the right direction. I'm using the controller linked below and trying to follow the MODBUS instructions starting on pg 27.
UniLogic Festo CMMO modbus operation
in UniLogic Software
Posted
Hi
I'm new to PLC operations, and I was hoping I could get some help getting started with MODBUS communications.
I have a PLC/HMI running UniLogic and Festo CMMO which I am trying to run over MODBUS TCP. I have added the remote slave, and downloaded the program onto the PLC. However, I haven't been able to get any proof of the connection. I have added registers (3 and 17) based on reads to tags (INT16), but they all display as 0. I have also tried displaying the value of slave.sessions, but it also shows 0 which leads me to believe it has not even tried to start the connection yet.
I feel like I'm missing some critical first step or debugging process?
I would appreciate any help or point in the right direction. I'm using the controller linked below and trying to follow the MODBUS instructions starting on pg 27.
https://www.festo.com/net/SupportPortal/Files/425129/CMMO-ST-LK-SY_2015-07a_8043621g1.pdf
Cheers
Russ