Siemens SIMATIC PCS 7 Function Manual page 35

Configuration
A switched I/O can be set up in PCS 7 with the following distributed I/O devices:
● ET 200M
For this setup, you require an ET 200M with active backplane bus modules and a redundant
IM 153-2 interface module.
● ET 200iSP
For this setup, you require an ET 200iSP and a redundant IM 152-1 interface module.
Each subsystem of the S7-400H is connected to one of the two PROFIBUS DP interfaces of
the interface module via a DP master interface.
The following figure illustrates this configuration for the ET 200M.
Availability
The block diagram shows the availability of the configuration illustrated above. When both
systems are operating without fault, the block diagram appears as follows:
The following figure shows how one component may fail without this affecting the operation of
the complete system.
Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA
Fault-tolerant Solutions in PCS 7
3.1 Solutions for the I/O
35