Ethercat Introduction; Ethercat - Advantech PCIE-1203 User Manual

1.1

EtherCAT Introduction

EtherCAT (Ethernet Control Automation Technology) is a high-performance, Ether-
net-based fieldbus industrial network system. The protocol is standardized in IEC
61158 and applies to automation applications that need faster and more efficient
communications. Short data update times with precise synchronization make Ether-
CAT suitable for real-time requirements in automation technology.
1.1.1

EtherCAT

1.1.1.1 Functional Principle
EtherCAT is a real time, high speed and flexible Ethernet based protocol. In Ether-
CAT network, the master sends Ethernet frames through all of the slave nodes. Stan-
dard Ethernet packets or frames are no longer received, interpreted, and copied as
process data at every node. Instead, slave devices read the data addressed to them
and the input data are inserted at the same time while the telegram passes through
the device, processing data "on the fly". Typically the entire network can be
addressed with just one frame.In comparison to other Ethernet based communication
solutions EtherCAT utilizes the available full duplex bandwidth efficiently.
1.1.1.2 Protocol
Data exchange are cyclically updated between EtherCAT master and slaves. Data in
EtherCAT frames are transported directly within the standard IEEE 802.3 Ethernet
frame using Ethertype 0x88a4 and are processed by the EtherCAT Slave Controller
on the fly. Each EtherCAT datagram is a command that consists of a header, data
and a working counter. The datagram header indicates what type of access the mas-
ter device would like to execute:
Read, write, read-write

Access to a specified slave device through direct addressing

Access to multiple slave devices through logical addressing

Logical addressing is used for the cyclical exchange of process data. The header and
data are used to specify the operation that the slave must perform, and the working
counter is updated by the slave to let the master to know that a slave has processed
the command.
Every EtherCAT datagram ends with a 16 Bit Working Counter (WKC). The Working
Counter counts the number of devices that were successfully addressed by this Eth-
erCAT datagram.
PCIE-1203 User Manual
Figure 1.1 EtherCAT Function Principle
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