Understand EtherCat technology.Difference between ethernet and ethercat

EtherCAT (Ethernet for Control Automation Technology)

Invented by Beckhoff automation in 2003. Ethernet based fieldbus,optimized for industrial automation control Based on CANOpen,a device profile for embedded system used in automation Standards defined and maintained by the EtherCAT technology group

Difference between EtherNet and EtherCAT

EtherNET - Designed to move large amounts of data through many different nodes Able to route data to and from billions of separate address allowing communication across vast networks. Large overhead involved in encapsulating routing and formatting data. Software handles extractions and processing of data.

EtherCAT- Use standard ethernet hardware,CAT5 cabling and network interface card (NIC) Streamline ethernet communication at the hardware level Data processing on slave devices is handled “on the fly” via FPGA or ASIC minimizing latency Initial setup and Configuration required

An EtherNet Fram Contains - 1.EtherNet Header Destination address - 6 bytes Source Address - 6 bytes EtherType - 2 bytes,0x0800 specifies IPv4

2.Ethernet data Payload 46-1500 bytes

3.CRC Checksum - 4 bytes

An EtherCAT frame is very similar to an ethernet frame-

1.EtherNet header

EtherType 0x08A4 specifies EtherCAT

2.EtherCAT header

Data length - 11 bits Reserved - 1 bit Protocol type - 4 bits (0x01 indicates COE,CAN over etherCAT)

3.EtherCAT data

46-1496 bytes

4.Working counter - 2 bytes

5.CRC Checksum - 4 bytes

EtherCAT communication

Each drive on the network has a unique address,set by the hardware Master/Slave configuration with EtherCAT Master sending and request data from Slave Data not addressed to a particular slave are forwarded along to the network Minimal processing time can provide cycle update rates of up to 32 khz Network layout size is limited only by the allowable length of CAT5 ethernet cable upto 100m Increased noise immunity due to reliance on Ethernet physical components

EtherCAT operation modes

1.Profile Position - Master sends position commands to slave,slave handles profiling parameter 2.Profile Velocity - Master sends velocity commands to the slave,slave handles profiling parameter 3.Profile Torque - Master sends torque commands to the slave,slave handles profiling parameter 4.Cyclic position - Position is continuously updated by the master,master handles profiling parameter 5.Cyclic velocity - Speed is continuously updated by the master,master handles profiling parameters 6.Cyclic torque - Torque is continuously updated by the master,master handles profiling parameters