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.

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

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

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

Understand EtherCAT masters and EtherCAT slaves
ICS protocols for factories

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