EtherCAT
The protocol is standardized in IEC 61158 and is suitable for both hard and soft real-time computing requirements in automation technology.
The goal during development of EtherCAT was to apply Ethernet for automation applications requiring short data update times (also called cycle times; ≤ 100 μs) with low communication jitter (for precise synchronization purposes; ≤ 1 μs) and reduced hardware costs.
[1] With EtherCAT, the standard Ethernet packet or frame (according to IEEE 802.3) is no longer received, interpreted, and copied as process data at every node.
[2] ISO/OSI Reference Model The EtherCAT protocol is optimized for process data and is transported directly within the standard IEEE 802.3 Ethernet frame using Ethertype 0x88a4.
Typical network update rates are 1–30 kHz, but EtherCAT can be used with slower cycle times, too, if the DMA load is too high[citation needed].
Due to these features EtherCAT enables a multitude of network topologies, including line, tree, ring, star, or any combination thereof.
Thus the combination of the topology variations and different network architectures, e.g. sub-ordinated or neighboring control systems with consistent synchronization, enables numerous possibilities.
Therefore, EtherCAT does not require special hardware in the master device and can be implemented in software on any standard Ethernet MAC, even without dedicated communication coprocessor.
The typical process of establishing a distributed clock is initiated by the master by sending a broadcast to all slaves to a certain address.
The automated analysis of the according error counters enables the exact localization of critical network segments.
The protocol as well as the implementation are certified by TÜV and meet the requirements of the Safety Integrity Level 3 according to IEC 61508.
By using gateways, existing networks such as CANopen, DeviceNet, or Profibus, can be integrated into the EtherCAT environment seamlessly.
Furthermore, gateways provide a trip-free migration path from a traditional fieldbus to EtherCAT, reducing further investment costs.
Thanks to the performance of EtherCAT, communication with external fieldbus masters is as fast as with traditional cards connected via PCI or other backbone buses.
Since decentralized fieldbus interfaces lead to shorter extensions, they can be operated with even higher baud rates than would have been possible with the traditional architecture.
In order to operate a network, the EtherCAT master requires the cyclic process data structure as well as boot-up commands for each slave device.
Due to the advanced protocol features of EtherCAT, efficient synchronous data throughput is assured.
The EtherCAT Technology Group (ETG) was established in 2003, and is the industrial Ethernet user organization with the most members in the world today.
[6][7] A wide range of industrial controls vendors, OEMs, machine builders, and technology organizations from around the world constitute the ETG member roster.
The ETG offers its members implementation support and training, organizes interoperability tests (often called "Plug Fests"[8]), and promotes the development and distribution of the technology, supported by its members and the teams working in offices in Germany, China, Japan, Korea, and North America.
[9] System partners give qualified feedback for the simple integration of hardware and software modules in all required equipment classes.
In IEC 61800-7, EtherCAT is a standardized communication technology for the SERCOS and CANopen drive profiles (also known as CiA 402).
Furthermore, SEMI has added EtherCAT to its standards portfolio (E54.20)[17] and approved the technology for usage in semiconductor and flat panel display manufacturing equipment.
