ABSTRACT
EtherCAT (Ethernet Control Automation Technology) is an open protocol based on Ethernet physical layer. It is standardized in IEC 61158. It has two variants: EtherCAT P and EtherCAT G.
EtherCAT is by far the fastest industrial Ethernet technology. It uses summation frame for data transfer with a synchronization accuracy in the range of nanosecond.
EtherCAT does not use hubs and switches. It can have line, tree, star topologies, or any combinations of them. EtherCAT has unique diagnostic and configuration capabilities, reducing downtime to a minimum. Any disturbance in the system can be detected down to the exact place of occurrence. EtherCAT can assign node addresses automatically and uses a flexible bus cycle—both short and long versions.
EtherCAT follows master-slave communication with the EtherCAT master sending datagram that passes through each node. Each node reads the data addressed to it on the fly and at the same time inserts its own data into the datagram. This way it proceeds until the datagram reaches the last device. The last node detects an open port and sends it back to the master by using Ethernet’s full duplex facility. This keeps the delay to a minimum ensuring real-time communication.
Redundancy and safety are the other two features associated with EtherCAT.
