Omron CJ1W- ECT21, Руководство по эксплуатации

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1 Features and System Configuration
1 - 2 CJ-series EtherCAT Slave Units Operation Manual (W541)
1-1 Introduction to EtherCAT
EtherCAT (Ethernet Control Automation Technology) is a high-performance industrial network system
that enables faster and more efficient communications based on Ethernet.
Each node achieves a short communications cycle time by transmitting Ethernet frames at high speed.
Although EtherCAT is a unique communications protocol, standard Ethernet technology is used for the
physical layer, which means you can use Ethernet cables for wider application.
The effectiveness of EtherCAT can be fully utilized not only in large control systems that require high
processing speeds and system integrity, but also in small and medium control systems.
With EtherCAT, Ethernet frames pass through all of the slave nodes.
When a frame passes through a slave node, the slave node reads and writes the data in the area that is
allocated to it in the frame in a few nanoseconds.
The Ethernet frames that are transmitted by the EtherCAT master pass through all EtherCAT slaves
without stopping. The last slave returns all of the frames, which again pass through all of the slaves
before returning to the EtherCAT master.
This mechanism ensures high speed and realtime data transmission.
The data exchanges that are cyclically performed between the EtherCAT master and EtherCAT slaves
use EtherCAT datagrams that are stored directly in the Ethernet frames.
Each EtherCAT datagram consists of a header (including the data length and one or more slave
addresses), data, and a working counter (i.e., check bits).
If you think of an Ethernet frame as a train, the EtherCAT datagrams would be the cars of the train.
1-1-1 How EtherCAT Works
Slave
• Output data addressed to the local node is read.
• Input data is written.
Ethernet frames
EtherCAT master
Slave
data
Slave
IN OUT