Siemens SENTRON VL Series System Manual page 12

Introduction and overview
1.2 Bus systems
Integration into automation systems
Integration and linking to current concepts in automation is similarly unproblematic since all
the large manufacturers offer PROFIBUS DP master modules for programmable logic
controllers (PLCs). And with high data transfer rates of up to 12 MBaud/s, the systems
operate almost in real time.
Master-master communication
The protocol used for PROFIBUS DP node communication ensures communication between
the complex automation devices with equal priority (masters). Each node completes its
communication tasks within a fixed time frame.
Master-slave communication (token-passing procedure)
Furthermore, simple cyclic data exchange is used for communication between a master and
the simple I/O devices (slaves) assigned to it. PROFIBUS DP uses a hybrid bus access
control for this comprising a central token-passing procedure between the active bus nodes
(masters) and a central master-slave procedure for data exchange between the active and
passive bus nodes.
System configuration
The following system configurations can be implemented with this bus access control:
● Pure master-slave system
● Pure master-master system with token passing
● A combination of both systems
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3WL/3VL circuit breakers with communication capability - PROFIBUS
System Manual, 03/2011, A5E01051353-02