Siemens SINAMICS S120 Series Function Manual page 82

Communication via PROFIBUS DP
4.1 General information about PROFIBUS
Master and slave
● Master and slave properties
● Master
The following classes are differentiated:
– Master class 1 (DPMC1):
– Master class 2 (DPMC2):
● Slaves
With respect to PROFIBUS, the SINAMICS drive unit is a slave.
Bus access method
PROFIBUS uses the token passing method, i.e. the active stations (masters) are arranged in
a logical ring in which the authorization to send is received within a defined time frame.
Within this time frame, the master with authorization to send can communicate with the
assigned slaves and/or with other masters in a master/slave procedure.
PROFIBUS telegram for cyclic data transmission and acyclic services
Each drive unit that supports cyclic process data exchange uses a telegram to send and
receive all the process data. A separate telegram is sent in order to perform all the acyclic
services (read/write parameters) under a single PROFIBUS address. The acyclic data is
transferred with a lower priority after cyclic data transmission.
The overall length of the telegram increases with the number of drive objects that are
involved in exchanging process data.
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Properties
As bus node
Send messages
Receive messages
Central automation stations that exchange data with the slaves in cyclic and acyclic
mode. Communication between the masters is also possible.
Examples: SIMATIC S7, SIMOTION
Devices for configuration, commissioning, operator control and monitoring during bus
operation. Devices that only exchange data with the slaves in acyclic mode.
Examples: Programming devices, human machine interfaces
Master
Active
Permitted without external
request
Possible without any re-
strictions
Function Manual, 12/2018, 6SL3097-5BD00-0BP0
Slave
Passive
Only possible on request by
master
Only receive and acknowledge
permitted
Communication