Welcome to the OptoForums! What we call “modules” are not connected directly to the TCP/IP network. Instead, you’d plug them into a rack with an “I/O processor” (like a SNAP-PAC-EB1). Check out this handy configuration tool (click here).
All of our Ethernet “I/O processors” (brains and controllers) are Modbus slaves out of the box. More on that click here.
The communication between the brain (like a SNAP-PAC-EB1) and the Modbus master is described in detail in our Modbus/TCP Protocol Guide (form 1678, click here).
Our pre-sales engineers will also be happy to help you (it's FREE).