Lenze E94AYCET - Manual (Page 54)

7 Data transfer
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Lenze · E94AYCET communication module (EtherCAT®) · Communication Manual · DMS 9.0 EN · 02/2014 · TD17
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7 Data transfer
Compared with conventional Ethernet, the collision-free transfer of frames 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 frame sent by
the master passes through all EtherCAT slaves. The last slave of the communication chain sends the
frame back to the EtherCAT master. On the way back, the frame is directly sent to the master,
without being processed in the slaves.
EtherCAT transmits data in so-called "EtherCAT frames". The EtherCAT nodes only extract the data
intended for them while the EtherCAT 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 EtherCAT frame – the datagrams. Therefore it is not
necessary to receive the complete frame before it can be processed. Processing starts as soon as
possible.
EtherCAT transmits process data, parameter data, configuration data, and diagnostic data between
the EtherCAT master and the drives (slaves) that are part of the fieldbus. The data are transmitted
via corresponding communication channels depending on their time-critical behaviour (see Process
data transfer ( 59) / Parameter data transfer ( 68) ).