I/O configuration variants   
6.5 Using single-channel switched I/O 
  CPU 410 Process Automation/CPU 410 SMART 
70  System Manual, 05/2017, A5E31622160-AC 
Single-channel switched I/O configuration at the PROFINET IO interface 
The installation with single-channel switched I/O is possible with the ET 200M and ET 200SP 
HA distributed I/O devices with active backplane bus and redundant PROFINET IO interface. 
 
Figure 6-8  Single-channel switched distributed I/O configuration at the PROFINET IO interface 
Each subsystem of the S7-400H is connected (over a PROFINET IO interface) to the 
PROFINET IO interface of the ET 200M or ET 200SP HA over one connection each. If the 
two PROFINET IO interfaces are located on one IM, this is known as an S2 configuration. 
The S stands for a single (single) IM and thus for only one PROFINET IO interface. If the