Key Information Resources
EtherCAT (Ethernet for Control Automation Technology) is an International Standard, part of IEC-61158 and IEC-61784-2, for a high-speed industrial fieldbus based on Ethernet. EtherCAT was developed to dramatically increase the bandwidth utilization of a fieldbus using Ethernet. This is accomplished by “processing on the fly” (see How EtherCAT Works, below).
Watch this short video demonstrating EtherCAT…
The CTC EtherCAT Master
EtherCAT is supported in the CTC 5300 Series of control systems in the form of an EtherCAT Master module (model M3-41A), offering high-performance control of networked servos, stepping motors and I/O devices. This Master module can coexist in the same system with Modbus®, DeviceNet® and BACnet® interfaces, allowing for multi-vendor configurations with the CTC system acting as a protocol bridge as well as a control system.
Unlike other implementations, CTC has fully integrated EtherCAT support into our programming environment, by pre-engineering support for the most popular EtherCAT slave devices. Through auto-discovery, the system will automatically determine what specific devices are on the EtherCAT network and automatically configure the master to talk to them. This eliminates a time-consuming and potentially error-prone step of having to use a configurator to manually set up your network.
Further, EtherCAT-based drives and I/O points then appear in the programming environment along with any other drives and I/O in your system, and are programmed just as though they were local devices. This means you can freely and transparently intermix local and remote servos and I/O, or change a device from local to remote without extensive programming changes.
A Multi-Vendor EtherCAT Demonstration…
How EtherCAT Works
Most protocols require processing time at each node connected to the system, which can decrease the efficiency of the network. A communications packet must be received by a slave system, parsed by software routines which determine its content and what local action must be taken, and then a response packet is assembled and transmitted back onto the network.
Using EtherCAT, however, an Ethernet frame is processed on the fly at each slave device — an FMMU (Fieldbus Memory Management Unit) reads the data as it passes through the system. A portion of each frame is dedicated to the slave device; the FMMU identifies this portion and substitutes new locally-generated data as the packet goes through the system. The actual delays caused by this substitution are tiny — only a few nanoseconds — compared with the tens or hundreds of milliseconds typically required to process a communications packet.
The resultant update time for 1000 distributed I/O points can be as low as 30 µs, with control of nearly 12,000 I/O points possible with a single frame. EtherCAT supports various topologies, including line, star, and ring topologies and there is no limitation on the number of nodes you can connect.
EtherCAT also supports synchronization, by making use of high-resolution distributed clocks to greatly improve the accuracy of velocity calculations.
The EtherCAT Technology Group (ETG), a nonprofit organization, launched in November 2003, supports the protocol with the standards bodies and gives developers and users access to the protocol and educational materials. The ETG is headquartered in Nurnberg, Germany, and has offices in Japan, China, Korea, and the USA. Membership in the organization is free.
EtherCAT® is a registered trademark and patented technology, licensed by Beckhoff Automation GmbH, Germany.