Siemens SINAMICS S120, Function Manual

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Communication
11.2 Communication via PROFIBUS DP
Drive functions
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Function Manual, 11/2017, 6SL3097-4AB00-0BP5
11.2.4 Slave-to-slave communication
For PROFIBUS DP, the master interrogates all of the slaves one after the other in a DP
cycle. In this case, the master transfers its output data (setpoints) to the particular slave and
receives as response the input data (actual values). Fast, distributed data transfer between
drives (slaves) is possible using the "slave-to-slave communication" function without direct
involvement from the master.
The following terms are used for the function described in this chapter:
● Slave-to-slave communication
● Data Exchange Broadcast (DXB.req)
● Slave-to-slave communication (is used in the following)
1) From the perspective of the Class 1 master
Figure 11-18 Slave-to-slave communication with the publisher-subscriber model
Publisher
With the "slave-to-slave communication" function, at least one slave must act as the
publisher.
The publisher is addressed by the master when the output data is transferred with a modified
layer 2 function code (DXB.req). The publisher then sends its input data for the master with a
broadcast telegram to all bus nodes.
Subscriber
The subscribers evaluate the broadcast telegrams, sent from the publishers, and use the
data which has been received as setpoints. These setpoints of the publisher are used, in
addition to the setpoints received from the master, corresponding to the configured telegram
structure (p0922).