Communication Functions
8-13
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Note
Fault-tolerant connections occupy two connection resources on CP b1 for the
redundant connections. One connection resource each is assigned to CP a1 and
CP a2.
Fault-tolerant system a Standard system with fault-tolerant CPU
CPU
a1
CP
a1
CPU
b1
CPUb1
CPUa2
CPUa1
CPa1
CPa2
CPb1
Bus 1
Bus 2
Redundancy
block diagram
Fault-tolerant
system a
CP
b1
Standard system with fault-tolerant CPU
OLM
System bus as opti-
cal two-fiber ring
OLM OLM
Figure 8-6 Example of redundancy with fault-tolerant system and fault-tolerant CPU
Response to failure
Double faults in the fault–tolerant system (in other words, CPUa1 and CPa 2) and
a single fault in the standard system (CPb1) result in a complete failure of
communication between the systems involved (refer to Figure 8-6).
Fault-Tolerant S7 Connections
Interruptions of a partial connection result in a prolonging of the runtime for
ongoing communication jobs via fault-tolerant S7 connections.
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