EtherCAT Communication

EtherCAT stands for Ethernet for Control Automation Technology. The XMC is an EtherCAT master device.

  • EtherCAT is a high-performance industrial network system which uses Real-Time Ethernet.

  • EtherCAT provides short communication cycle time between the master and slaves by transmitting Ethernet frames at a high speed.

  • EtherCAT communication uses one frame to all slaves without transmitting data to each slave node in the network.

  • Each slave reads and writes data to its own area in the frame when a communication frame passes through.

  • The communication frame goes through the last slave and returns to the master through all the slaves.

The XMC communicates with slaves using the CANopen over EtherCAT (CoE) protocol. A CoE slave’s parameter and data information is stored in an object dictionary. The object dictionary contains information used in the configuration of the device and communication to the device.

  • A Process Data Object (PDO) is used for synchronous transmission of data between the master and slave nodes.

  • The motion controller performs synchronous process data communication to handle input/output signals and to control the position of EtherCAT servo drives.

  • A Service Data Object (SDO) is used for asynchronous transmission of data between the master and slave nodes.

  • The motion controller performs asynchronous service data communication for error information in the slave and parameter reading/writing.

  • CiA 402 is an application profile used to standardize the control of VFDs and servo drives.

  • CiA 402 describes all functional behavior including the FSA and all process data and configuration parameters.

Type Communication Time Content of Communication
Process Data Communication (PDO) Synchronous with main task period Servo drive position control data, input/output data, etc.
Service Data Communication (SDO) Asynchronous only when requested Servo parameter reading/writing, servo error information reading/acknowledgement, etc.

Communication between master and slave begins in the Init state.

  • Master configures the synchronous communication and proceeds to the Pre-operational state.

  • Master configures slave parameters to enter the Safe-Operational state.

  • Master starts sending valid outputs and the system enters Operational state.

The synchronous data communication in EtherCAT communication of the motion controller occurs through process data object (PDO).

  • TxPDO is configured for data that is transmitted from the slave to the motion controller.

  • RxPDO is configured for data that is transmitted from the motion controller to the slave.

  • The manufacturer of the slave node will have an EtherCAT Slave Information (ESI) file which contains the PDO data that the slave supports.

  • This file must be imported into XG5000 for the XMC to be able to control the slave device.

Example Configuration of RxPDO and TxPDO:

Item Specification
Communication Protocol EtherCAT using CANopen over EtherCAT (CoE)
Physical Layer 100BASE-TX
Communication Speed 100 Mbps
Topology Daisy Chain.Ring Topology is supported with a Junction Slave module.
Maximum number of Slaves

  • XMC-E08A & XMC-E08A/DC: 16 total EtherCAT slaves, 8 maximum motion axes.

  • XMC-E16A & XMC-E16A/DC: 32 total EtherCAT slaves, 16 maximum motion axes.
Communication Period 0.5 ms / 1 ms / 2 ms / 4 ms
Synchronous Jitter between slaves 0.5 ms / 1 ms / 2 ms / 4 ms
Synchronous Communication PDO (Process Data Object) mapping through CoE.
Asynchronous Communication SDO (Service Data Object) communication through CoE.

The XMC supports daisy chain and ring connection topologies. Branches and ring connection can be added using a junction slave. Only one junction slave may be used in the EtherCAT network.

Daisy Chain Topology with No Branches

Daisy Chain Topology using Branches

Ring Topology

Note: When using ring topology, do not use the open ports on the junction slave.

 

 

 

 

 

 

 

 

 

 

 

 

 

LM400