Basics; Basic Function Principles Of Ethercat Junctions; Fig. 20 Ethercat Line Topology; Fig. 21 Line Topology With Extensions - Beckhoff EK15 Series Documentation

Basics

4 Basics
4.1

Basic function principles of EtherCAT junctions

Some Beckhoff EtherCAT devices can be used for junctions in the EtherCAT segment. These include
EK1122, EK1521, EP1122 or also CU1128. In the following examples only the EK1122 is used. The
technical and system characteristics of the other devices are similar. test
EtherCAT handling in the slaves
With EtherCAT as fieldbus protocol a wide range of bus topologies can be used: line, star and tree topology,
with redundancy support even ring topology. The simplest topology is the line topology, in which each
EtherCAT slave passes the data on to the only next slave; see following Fig. "EtherCAT line topology".
Fig. 20: EtherCAT line topology
When using, for example, EK1100 EtherCAT Couplers, a junction and thus a type of tree topology is
possible; see following Fig. "Line topology with extensions".
Fig. 21: Line topology with extensions
The basic principle is that internally the Ethernet frame(s) with the EtherCAT protocol data continue to be
transported in a logical ring:
• the EtherCAT master sends the frame on the two outgoing lines of the Ethernet cable
• this frame passes each slave once,
• is reversed by the last slave in the logical sequence
28 Version: 3.4 EK1122, EK15xx