7 Data transfer
56 Lenze · E94AYCET communication module (EtherCAT®) · Communication Manual · DMS 10.2 EN · 11/2018 · TD06
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7 Data transfer
Compared with conventional Ethernet, the collision-free transfer of telegrams on the fieldbus
makes EtherCAT a real-time capable bus system.
Communication is always initiated by the EtherCAT master, e.g. a Lenze Controller. A telegram sent
by the master passes through all EtherCAT slaves. The last slave of the communication chain sends
the telegram back to the EtherCAT master. On the way back, the telegram is directly sent to the
master, without being processed in the slaves.
EtherCAT transmits data in standard Ethernet frames. The EtherCAT devices only extract the data
intended for them while the frame passes through the device. At the same time, output data are
inserted into the frame while it passes through the device. Read and write accesses are only
executed on a small section of the entire frame - the datagrams. Therefore, it is not necessary to
receive the complete frame before it is processed. Each datagram is forwarded with a minimum
delay.
EtherCAT transmits process data, parameter data, configuration data and diagnostic data between
the EtherCAT master and the inverters (slaves) that are part of the fieldbus. The data is transmitted
via corresponding communication channels depending on their time-critical behaviour (see Process
data transfer ( 61) / Parameter data transfer ( 67)).
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