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02/2020 | ID 443025.06
9.2 Communication protocols
HTTP, FTP, etc.
CANopen
application
Process data
TCP UDP
IP
Ethernet
SDO
Object
directory
PDO
map-
ping
AT
MDT
EoE CoE CoE
Mailbox channel
Process data
channel
Ethernet slave controller
Physical layer
Fig.8: EtherCAT – Communication protocols
EtherCAT uses standard Ethernet frames containing EtherCAT payloads. Communication normally takes place over a
mailbox or process data channel.
Only data that is not time-critical, i.e. service data objects (SDO), are exchanged using the mailbox channel; time-critical
process data objects (PDO) are, like in CANopen, transferred using the process data channel.
Both the STOBER drive controllers of the 6th generation as well as the STOBER MC6 motion controller support the CoE and
EoE EtherCAT protocols.
9.2.1 CoE: CANopen over EtherCAT
EtherCAT, together with the CoE protocol, provides CANopen-compliant communication mechanisms, enabling the use of
the entire CANopen profile family over EtherCAT, thereby also allowing full use of the CiA 402 drive profile.
In terms of the respective state machines, CANopen and EtherCAT differ only in that the EtherCAT state machine (see the
chapter EtherCAT state machine [}56]) also has the Safe-Operational state.
9.2.2 EoE: Ethernet over EtherCAT
Using EoE, it is possible to transport any Ethernet data traffic between EoE-capable nodes in an EtherCAT network.
In this process, Ethernet frames are tunneled through the EtherCAT protocol, as is typical for Internet protocols. The
EtherCAT master is used as a gateway to the Ethernet network.
EoE is an acyclical protocol, meaning that the EtherCAT real-time properties (process data communication) remain
unaffected.
Acyclical frames can be exchanged starting in the Pre-Operational state of the EtherCAT state machine.
The IP address, subnet mask and gateway of the EoE-capable slaves are stored in the EtherCAT master.
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