The PN/PN coupler provides the output data of the writing CPU as input data to the receiving CPUs within a PN cycle. Both fail-safe data (via F_SendDP/F_ReceiveDP of a SIMATIC F-CPU only) and standard data can be transmitted.

• Transfer to the opposite side of the network:
  In a PN cycle, the writing CPU provides its output data as input data at the same time as up to four CPUs connected to the other side of the network. The network separation between the two network sides remains completely intact.
• Transfer to the same side of the network:
  In a PN cycle, the writing CPU provides its output data as input data at the same time as up to three other CPUs connected to its own side of the network.

Two basically different methods are available for data transmission:

• Data exchange via virtual I/O modules (coupling modules):
  The local CPU reads the values that the CPU of the other subnet writes over the configured outputs of the coupling partner through the configured inputs of a slot. The local CPU writes values via the configured outputs of a slot. These values are received by the CPU of the other subnet via the configured inputs of the coupling partner.
• Data record transfer:
  Publisher and Storage modules types are used. These consist of read and write combinations. The module types address the data record order by module addresses during data record transfer.

The PN/PN coupler provides extensive diagnostic information about LEDs, interrupts and status bytes. In this way, errors can be quickly located and commissioning and downtimes minimized.

The PN/PN coupler supports a variety of SIMATIC BusAdapters for flexible connection to PROFINET.