rshom Posted August 6, 2019 Report Share Posted August 6, 2019 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 Quote Link to comment Share on other sites More sharing options...
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