System overview EtherCAT
The Beckhoff Embedded PCs can be ordered ex works with an optional interface, e.g. PROFIBUS, CANopen or RS232. Some of the optional interfaces can be delivered as master or slave.
The following Embedded PCs can be ordered with an optional interface:
- CX9020
- CX50x0
- CX51x0
- CX20x0
EtherCAT slave (B110)
The optional interface B110 is an EtherCAT slave and enables an Embedded PC to be used as subordinate decentral controller for configuring complex or modular systems.
The optional interface B110 offers the possibility to operate an Embedded PC as an EtherCAT slave device, which can then be integrated into an existing topology with further EtherCAT devices.
The EtherCAT slave receives external process data from the master and processes them or returns data from its own process periphery to the master after processing.
The optional EtherCAT slave interface is parameterized and configured in TwinCAT.
Further Information |
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EtherCAT system documentation |
EtherCAT Technology Group |
Further information about EtherCAT and features such as cable redundancy, distributed clocks or diagnostics can be found in the EtherCAT system documentation or on the website of the EtherCAT Technology Group.
Functioning
EtherCAT is the real-time Ethernet technology from Beckhoff, which makes the familiar Ethernet telegram real-time capable. In contrast to Ethernet, the telegram is no longer initially received and interpreted in each connection, before the process data are copied. Instead, each EtherCAT device picks up the data intended for it while the telegram passes through the device. In the same way, input data are dynamically added to the data stream.
The slave detects the commands intended for it and executes them accordingly. The process is hardware-implemented in the slave controller and is therefore independent of the protocol stack software run times or the processor power. The last EtherCAT slave returns the processed telegram, so that it is sent from the first slave to the controller as a response telegram.
Protocol
The EtherCAT protocol is optimized for process data and is either transported directly in the Ethernet frame or packed into UDP/IP datagrams. The UDP version is used in situations where EtherCAT segments in other subnets are addressed via routers. Ethernet frames may contain several EtherCAT telegrams, with each telegram serving a particular memory area of the logical process image with a size of up to 4 GB. The data sequence is independent of the physical order of the EtherCAT terminals in the network; addressing can be in any order. Broadcast, Multicast and communication between slaves are possible. The protocol can also handle parameter communication, which typically is acyclical.
Performance
EtherCAT reaches new dimensions in network performance. The update time for the data from 1.000 distributed inputs/outputs is only 30 µs - including terminal cycle time. Up to 1.486 bytes of process data can be exchanged with a single Ethernet frame - this is equivalent to almost 12.000 digital inputs and outputs. The transfer of this data quantity only takes 300 µs.
Topology
Line, tree or star: EtherCAT supports almost any topology. The bus or line structure known from the fieldbuses thus also becomes available for Ethernet. Particularly useful for system wiring is the combination of line and junctions or stubs. The required interfaces exist on the couplers; no additional switches are required. Naturally, the classic switch-based Ethernet star topology can also be used.