Deployment; Basics Ethercat; General - YASKAWA SLIO Manual

System SLIO
4

Deployment

4.1 Basics EtherCAT

4.1.1 General

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EtherCAT
Transfer medium
Communication principle
EtherCAT State Machine
Object dictionary (SDOs)
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Field buses were established for many years in the automation technology. Since higher
speeds are required but the technical limits of this technology have already been
reached, new solutions needed to be found.
At least in theory, the Ethernet, which is familiar to all of us from the office world, is fast
with its 100Mbit/s speed, which is available everywhere today. However, these networks
do not offer real-time capability due to the kind of cabling that they use and the rules gov-
erning access rights. This effect was corrected with EtherCAT
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For EtherCAT is valid: EtherCAT
n
nology, licensed by Beckhoff Automation GmbH, Germany.
n EtherCAT means Ethernet for Controller and Automation Technology. It was originally
developed by Beckhoff Automation GmbH and is now supported and further devel-
oped by the EtherCAT Technology Group (ETG). ETG is the word biggest interna-
tional user and producer connection for industrial Ethernet
n EtherCAT is an open Ethernet based field bus system, which is standardized at the
IEC.
n As open field bus system EtherCAT matches the user profile for the part of industrial
real-time systems.
n In opposition to the normal Ethernet communication at EtherCAT the data exchange
of I/O data takes place during the frame passes the coupler with 100Mbit/s in full-
duplex. Since in this way a frame to send and receive direction reaches the data of
many stations, EtherCAT has a rate of user data of over 90%.
n The EtherCAT protocol, which is optimized for process data, is directly transported
with the Ethernet frame. This again can consist of several sub-frames, which serve for
a storage area of the process image.
EtherCAT uses Ethernet as transfer medium Standard CAT5 cables are used. Here dis-
tances of about 100m between 2 stations are possible.
Only EtherCAT components may be used in an EtherCAT network. For topologies, which
depart from the line structure, the corresponding EtherCAT components are necessary.
Hubs may not be used.
At EtherCAT the master sends a telegram to the first station. The station takes its data
from the current data stream, inserts its answer data and sends the frame to the suc-
ceeding station. Here the frame is handled with the same way.
When the frame has reached the last station this recognizes that no further is connected
and sends the frame back to the master. Here the telegram is sent through every station
via the other pair of leads (full-duplex). Due to the plug sequence and the use of the full-
duplex technology EtherCAT represents a logical ring.
Via the EtherCAT State Machine the state of the EtherCAT members is controlled.
In the object directory the parameter, diagnostics, interrupt or other data are listed, which
may be written or read via EtherCAT. The object directory may be accessed by the SDO
information service. Additionally the object directory may be found in the device master
file.
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is a registered trademark and patented tech-
Deployment
Basics EtherCAT > General
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