Siemens SINAMICS S120, Function Manual

Page: 775 / 1094

Communication
11.2 Communication via PROFIBUS DP
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
775
Master and slave
● Master and slave properties
Properties Master Slave
As bus node Active Passive
Send messages Permitted without external
request
Only possible on request by
master
Receive messages Possible without any re-
strictions
Only receive and acknowledge
permitted
● Master
The following classes are differentiated:
–
Master class 1 (DPMC1):
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
– Master class 2 (DPMC2):
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
● 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.