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Devices and Topology

Sample content. Replace with finalized descriptions and diagrams.

An EtherCAT network is made up of one master and one or more devices (historically called "slaves").

Master​

The master is the controller of the network. It:

  • Initializes and configures the devices.
  • Manages the network state machine.
  • Sends and receives the cyclic process data frames.

In our product, the master role is fulfilled by the Linux master software.

Devices​

Devices are the nodes attached to the network, such as I/O modules, drives, and sensors. Each device:

  • Processes the part of the frame addressed to it on the fly.
  • Exposes process data objects (PDOs) for cyclic real-time exchange.
  • Exposes service data objects (SDOs) for acyclic configuration.

Process data​

TermDescription
PDOProcess Data Object - cyclic, real-time data (inputs/outputs).
SDOService Data Object - acyclic configuration and parameters.
ESIEtherCAT Slave Information - XML describing a device's capabilities.

Topology​

EtherCAT supports flexible wiring topologies:

  • Line - the simplest layout; devices daisy-chained one after another.
  • Tree / Star - branches created using junction devices.
  • Ring - adds cable redundancy for fault tolerance.
Line:   M -- D1 -- D2 -- D3
Tree:   M -- D1 -- D2 -- D3
                    \-- D4 -- D5

Where M is the master and Dn are devices.