Siemens SIMATIC S7-400H - Communications via S7 Connections

Communication Functions
8-15
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
OLM
System bus as opti-
cal two-fiber ring
OLM OLM
2oo2 redundancy
CPU
a1
CP
a1
Fault-tolerant system a
WinCC
server
CP
1
PC
Redundancy
block diagram
Fault-tolerant
system a
CP
2
CPUa1
CPUa2
CPa1
CPa2
Bus 1
Bus 2
CP 1
CP 2
PC
OLM
Figure 8-8 Example of redundancy with a fault-tolerant system, redundant bus system
and CP redundancy in the PC
Response to failure
Double faults in the fault–tolerant system (in other words, CPUa1 and CPa 2) and
the failure of the PC result in a complete failure of communication between the
systems involved (refer to Figures 8-7and 8-8).
8.5 Communications via S7 Connections
Communications with standard systems
Fault-tolerant communications are not possible between fault-tolerant and standard
systems. The following examples illustrate the actual availability of the
communicating systems.
Configuration
Standard connections are configured with STEP 7.
Programming
If standard communications are used on a fault-tolerant system, all the
communication functions apart from “global data communications” can be used for
them.
The standard communication SFBs are used for programming communications
with STEP 7.