Understand the basics of etherCAT technology from following article
Can be any software and or hardware configured to assemble and receive EtherCAT datagrams Requires only standard ethernet physical layer components for communication Facilitates coordination between EtherCAT slaves,writing and receiving data from each slave in an EtherCAT frame. In motion control applications,the relevant data sent to the drives are profiling data. The data requested are position and input data.
Read and processes profiling data. Writes position input and drive status for return to the master Can be configured in for multiple modes of operation All slaves contain specific spaces in memory where data can be written These spaces are called objects,the entire memory space is called the object dictionary Each object has its own address,specified as an index /sub index