SYSTEM SOFTWARE

REAL-TIME ETHERNET

EtherCAT

Using the original collision detection media access method CSMA/CD, the Ethernet based networking systems offer a very poor real-time performance. On the other hand, because of its wide market acceptance and price performance ratio, Ethernet based networking systems are a preferred candidate to be used also for factory automation. In order to achieve this goal, substantial changes and enhancements of the way how data are transmitted and processed within the network must be made. Meanwhile, there are more than 25 implementations of the so called "Real-Time Ethernet" for factory automation on the market. EUROS supports the Real-Time Ethernet solution of the company Beckhoff, which is known under the name EtherCAT (Ethernet for Control Automation Technology), and claims to be the fastest Real-Time Ethernet solution on the market. The EtherCAT technology achieves the real-time performance by introducing a special EtherType used for the transportation of the EtherCAT protocol itself. Thus, Ethernet packets are no longer processed in the conventional way by receiving, then interpreting, processing and copying the data for the receiving node. In contrast, the data addressed to the EtherCAT slave devices is read by them on the fly while the frame passes through it. In the same fashion, input data is inserted while the telegram passes through the device node. The inevitably accrued delay in the magnitude of a very few nanoseconds is negligible.