Installing 
  5.3 Mounting modules onto the rail 
S7-300, CPU 31xC and CPU 31x: Installation 
Operating Instructions, Edition 08/2004, A5E00105492-05 
5-7 
5.3  Mounting modules onto the rail 
Requirements for module installation 
•  The configuration of the automation system is completed. 
•  The mounting rail is installed. 
Mounting order of the modules 
Hang the modules onto the rail, starting at the left and in the following order: 
1.  Power supply module 
2.  CPU 
3.  SMs, FMs, CPs, IMs 
 
 
 
Note 
Please check before you insert any SM 331 analog input modules whether you have to 
reposition the measuring range submodules at the side of the module. For further 
information, refer to chapter 4, "Analog Modules" in your 
Module Data
 Reference Manual.
 
 
 
 
Note 
When installing an S7-300 system with ungrounded reference potential, make the 
relevant settings on the CPU. You ideally do so before you mount any modules onto the 
rail.