5
Fundamentals of EtherCAT
ID 441896.05
WE KEEP THINGS MOVING
Operation manual
18
5.1
How it functions
Ethernet transfers data within packets. With other real-time Ethernet systems
each packet is received by the stations, interpreted via a complicated software
system, and the process data then removed. After this a response packet is
generated.
With EtherCAT, the stations on the hardware interface (see ) pick out the data
intended for them from the data stream. Similarly the station's own response data
are added to the telegram. The master sends the telegram to the first station. This
station and all other stations receive the packet, change it as described, and send
it on to the next station.
Fig. 5-2 Data processing, EtherCAT stations
When the packet arrives at the last station, this station determines that no cable
is plugged into a next station. Using a "logical short circuit" it sends the data via
the other core pair through all stations back to the master (full duplex).
Fig. 5-3 Data processing, last EtherCAT station
EtherCAT uses the plug-in sequence together with full duplex technology to
create a logical ring.
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