EtherCAT interface
Leuze electronic
AMS 338
i
51
TNT
35/7-2
4
V
9
EtherCAT interface
9.1
General information on EtherCAT
EtherCAT is an Ethernet-based fieldbus initialized by Beckhoff. The EtherCAT Technology
Group (ETG) is the official standardization partner of the IEC working groups.
EtherCAT has been an IEC standard since 2005.
• IEC 61158: protocols and services
• IEC 61784-2: communication profiles for the specific device classes
All EtherCAT-specific communication mechanisms are explained in detail in the standards
mentioned. The technical description of the AMS 338
i
will describe parts of the
IEC standard, if this serves basic understanding.
9.2
EtherCAT topology
EtherCAT permits a wide range of topologies such as line, tree, ring, star and their combi-
nations. The bus or line structure known from the fieldbuses is thus also available for
EtherCAT.
Telegrams are transmitted on one line pair in the "processing direction" from the master to
the slave. The EtherCAT device processes the frames only in this direction and sends them
to the subsequent device until the telegram has passed through all devices. The last device
returns the telegram on the second line pair in the cable in "forward direction" back to the
master. Here, EtherCAT always forms a logical ring structure independent of the topology
installed.
From the Ethernet perspective, an EtherCAT bus segment is nothing but a single, large
Ethernet participant which receives and transmits Ethernet telegrams. However, there are
many EtherCAT slaves within the "participant", not just a single Ethernet controller.
Figure 9.1:
Topology example