Siemens SIMATIC PCS 7 Function Manual page 142

Advantages of fault-tolerant components
4.4 Distributed I/O
Basic procedure
1. Place one channel block in the CFC chart for each redundantly acquired signal.
2. For redundantly registered signals (e.g. input 1.1 and input 10.1), connect the symbol only
with the lowest value address (e.g. input 1.1).
3. Compile the user program when the configuration is completed.
The required driver blocks are automatically inserted, interconnected and configured during
compilation of the user program.
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Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA