Siemens SIMATIC PCS 7 Function Manual page 45

Overview of the redundant and fault-tolerant bus systems
In PCS 7 systems, you can configure fully redundant bus systems with redundant components
for the following bus systems:
● Redundant, fault-tolerant terminal bus (Page 53)
● Redundant, fault-tolerant plant bus (Page 63)
● Redundant PROFIBUS DP (Page 68)
Bus systems set up as a ring are fault-tolerant. In ring structures, the signal path remains intact
even if there is a disconnection on the transmission cable at any point in the ring (for example
due to a wire break). The availability is ensured by ring redundancy.
This fault-tolerance is used in the following bus systems:
● Fault-tolerant terminal bus (Page 51)
● Fault-tolerant plant bus (Page 61)
● Fault-tolerant PROFIBUS PA (Page 74)
● Fault-tolerant FOUNDATION Fieldbus (Page 80)
● Fault-tolerant PROFINET bus (Page 70)
The following sections describe the basics of these communications solutions.
Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA
Fault-tolerant Solutions in PCS 7
3.3 Solutions for communication
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