For the purposes of the serial transfer of the configuration, the OP 3 is ideally connected to the PC's RS232 port via the cable which is supplied.
If you wish to create a connection cable yourself, the structure of the cable is shown below.
Connector on the OP3: 6-pin RJ12 connector (available, for example, from Conrad Electronic http://www.conrad.de under order no. 921529)
Connector on the PC: 9-pin Sub D-female
The power supply (DC 24V) must take place via the PS connection if the OP 3 is not connected to a SIMATIC S7.
If the OP 3 is connected to a SIMATIC S7 controller via the MPI interface, it is powered from the controller via the MPI interface.