Please see our documentation: "ctrlX CORE Controls, Operating Manual --> Interfaces --> Interface description" "ctrlX DRIVE Drive Systems, Project Planning Manual --> Mounting and installation --> Electrical connection --> Control section connection points control section"
The top one is for engeneering. The third one for another Ethernet communication.
The second one can be used for Ethercat communication. At the moment no ring topology is possible and only one master is available.
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