Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual page 160

Commissioning
8.6 Commissioning PROFINET IO
Commissioning a PROFINET IO system via MPI/DP
Number
1
2
Commissioning a PROFINET IO system directly via PN interface
Number
1
2
8-36
Meaning
Use the PG cable to connect the PG to the integrated MPI/DP interface of the CPU.
Use the twisted-pair patch cable to interconnect the integrated PROFINET IO interface
of the CPU with the Industrial Ethernet (for example, connection to a switch).
1
PG/PC
Meaning
Use a twisted-pair patch cable to connect the PG/PC to a switch
In the same way, connect the switch to the integrated PROFINET interface of your CPU
2
1
2
Operating Instructions, Edition 08/2004, A5E00105492-05
S7-300, CPU 31xC and CPU 31x: Installation