Configuring the PN/PN Coupler in TIA Portal: Transfer Areas, IO Modules, and Transfer Mapping

The SIMATIC PN/PN Coupler is a Siemens gateway that links two physically separate PROFINET IO networks and exchanges process data between them. It is the standard device for IO controller-to-IO controller communication across plant subnets, machine cells, or safety zones. Although the device is mechanically simple (two RJ45 PROFINET interfaces, status LEDs, a 24 V power terminal), commissioning it inside TIA Portal frequently trips up engineers because the configuration is split across three locations: the hardware catalog, the device view, and the Transfer areas editor. This reference walks through the complete commissioning flow, explains the role of the dummy IO modules that the catalog exposes, and documents every parameter exposed in the Transfer mapping dialog.

1. PN/PN Coupler Functional Overview

The PN/PN Coupler is a PROFINET proxy: it appears as an IO device on the left PROFINET subnet and as an IO device on the right PROFINET subnet, with internal data buffers in between. Each side of the coupler runs an independent PROFINET stack with its own IP address, device name, and IO controller. The two stacks are galvanically isolated; process data is exchanged through up to 16 input transfer areas and 16 output transfer areas on each side.

Typical applications include:

• Coupling two S7-1500 controllers that must remain on independent PROFINET subnets for network load or administrative reasons.
• Bridging two machine cells where each cell is shipped with its own IO controller and must be commissioned as a stand-alone unit before integration.
• Exchanging a small number of flags/words between a higher-level line controller and a packaging machine.
• Safety-related communication between two F-CPUs (F-PN/PN coupler variant) using PROFIsafe slots.

The coupler itself is not a router, not a switch, and does not participate in IRT. It supports RT (real-time) PROFINET and standard TCP/IP services such as DCP, SNMP, and LLDP. Both PROFINET ports on the device are switched internally, so additional PROFINET devices may be daisy-chained to either side without an external switch, subject to the standard PROFINET cable-length and device-count limits.

2. Prerequisites

Verify the following before starting the TIA Portal configuration:

1. TIA Portal version. Use TIA Portal V14 or higher. The device description (GSDML-based HSP or HW catalog entry) ships with the portal installation; if a very new firmware was released, install the matching Hardware Support Package (HSP) from the Siemens support portal.
2. PN/PN Coupler firmware. The hardware manual entry ID 44319532 documents firmware versions and supported TIA Portal releases. Update the coupler's firmware to a version compatible with the TIA Portal release in use; otherwise the device view will not expose all transfer area parameters.
3. Both controllers available in the project. The project must contain two PROFINET IO controllers (typically two S7-1200, S7-1500, ET 200SP CPUs, or equivalent third-party controllers with PROFINET support). Each side of the coupler is assigned to one controller.
4. PROFINET topology and addresses planned. Decide the IP subnet, IP address, and PROFINET device name for each of the two coupler ports before opening the portal. PROFINET device names must be unique and conform to RFC 1123 (letters, digits, hyphens, no leading hyphen, max 240 characters).
5. Number of transfer areas and their data widths. Each transfer area can carry up to 256 bytes input and 256 bytes output. Up to 16 transfer areas per direction can be configured on each side. Slot 0 (the coupler itself) uses a small fixed input/output of typically 4 bytes for status/diagnostics.
6. 24 V power supply. The coupler requires a stable 24 V DC supply on its power terminal. Voltage dips below approximately 18 V will cause PROFINET faults on both sides.

3. Inserting the PN/PN Coupler into the Project

Open the project in TIA Portal and switch to the Project view. The configuration of each IO controller is independent, and the PN/PN Coupler must be inserted twice: once as a PROFINET IO device on the left controller, and once as a PROFINET IO device on the right controller. The two instances in the project are linked by their transfer-area configuration; the runtime instance is a single physical device.

3.1 Add the coupler to the first controller's PROFINET network

1. Open the Devices & networks editor.
2. Select the first IO controller (for example, PLC_1) and open the Device view.
3. Open the Hardware catalog on the right side of the window.
4. Navigate to Other field devices > PROFINET IO > Gateway > Siemens AG > PN/PN Coupler. The exact path depends on the HSP installed.
5. Drag the PN/PN Coupler from the catalog into the network view and connect its PROFINET port to the PROFINET subnet of the first controller.

3.2 Add the coupler to the second controller's PROFINET network

1. Add a second PN/PN Coupler instance in the same way under the second IO controller (for example, PLC_2).
2. Connect its PROFINET port to the second PROFINET subnet. In the network view you will see two subnets; the left subnet terminates at the first controller and the right subnet terminates at the second controller.

4. Inserting the IO Modules (Slot Filling)

This is the configuration step that most engineers hit first. After dragging the coupler into the network, the device view of the coupler instance initially shows only slot 0. The transfer data must be modeled by inserting submodules in slots 1, 2, 3, ... up to the slot limit of the device. These submodules are not real I/O modules; they are PROFINET placeholder modules that the hardware catalog exposes specifically for the PN/PN Coupler. The slot configuration defines the data width, IO type, and access mode of each transfer area.

4.1 Why the catalog may appear empty

If the hardware catalog pane does not show any submodules under the PN/PN Coupler entry, verify the following:

• The Hardware catalog filter is set to All and not filtered by another vendor.
• The TIA Portal installation includes the Siemens device family HSP that ships the PN/PN Coupler submodules.
• The right TIA Portal version is installed. STEP 7 Classic shows the modules because the hardware catalog there is independent of HSP delivery and contains legacy entries; TIA Portal V14+ requires the HSP to be present.

4.2 Procedure to insert the submodules

1. Double-click the PN/PN Coupler instance in the network view to open the Device view.
2. Look at the Device overview table at the top. Slot 0 contains the coupler itself (PN/PN Coupler interface module).
3. Open the hardware catalog and search for PN/PN Coupler. Under it, a list of transfer area submodules is shown, typically named Transfer area 1 byte I / 1 byte O, 2 byte I / 2 byte O, 4 byte I / 4 byte O, up to 256 byte I / 256 byte O.
4. Drag the submodule that matches the desired transfer area size into slot 1 of the device overview.
5. Continue dragging additional submodules into slots 2, 3, ... for every transfer area required (up to 16 areas per side).

Each inserted submodule becomes one entry in the device's slot list and corresponds to one transfer area on that side. The total number of configured input bytes summed across all inserted submodules on a side determines the data width the controller must reserve.

Insert the same set of submodules in mirror-image order on the second coupler's device view. The first subcontroller's output area becomes the second controller's input area and vice versa; the order and the number of areas must match between the two sides so that every byte the first controller writes into slot n output reaches the second controller in slot n input.

5. Transfer Areas Editor (Transfer Mapping)

With the submodules inserted, the configuration of data flow is performed in the Transfer areas editor. Open the device view of one coupler instance, then select Properties > Transfer areas from the inspector window. The editor shows a table where each row corresponds to one of the inserted submodules.

The Transfer areas editor is the location where the engineer decides which data crosses from the left PROFINET network to the right PROFINET network. The configuration is per submodule slot.

5.1 Columns and their meaning

The Type column determines whether the bytes flow from this side to the partner (output of this side) or from the partner to this side (input of this side). The Access column controls whether the partner controller can place data into any byte of the area (full) or only into restricted byte ranges (restricted); restricted access is used when the partner must be prevented from overwriting status or reserved bytes.

5.2 What the manual refers to as "Transfer Mapping"

The Siemens hardware manual (entry ID 44319532) describes the mapping of transfer areas in section 6.1.4.1, Configuring the PN/PN Coupler with STEP 7 in the TIA Portal. The terminology is the same as the editor: the mapping defines the data relationship between the two PROFINET subnets.

To complete the mapping:

1. Open the Transfer areas editor on the first coupler instance.
2. For each slot, set Type, I length, and Q length as required by the application.
3. Switch to the device view of the second coupler instance and repeat the configuration in the same slot order.
4. Verify in the network view that the slot configurations on both sides are mirrored.

6. I Address and Q Address Assignment

The I address (input address) and Q address (output address) shown in the device overview are PROFINET IO addresses in the IO controller's process image. They are not edited in the Transfer areas editor; they are assigned in the device overview or in the controller's I/O mapping table.

6.1 Address assignment procedure

1. Open the device view of the IO controller (for example, PLC_1).
2. Open the Device overview table. The PN/PN Coupler appears with its slot list and current I/Q addresses.
3. Click the I address or Q address cell of a slot. The cell becomes editable.
4. Enter a free input or output address in the controller's process image. S7-1500 controllers support byte-granular addresses, for example %IB100 (input byte 100) or %QB200 (output byte 200).
5. Repeat for each slot. Address ranges for different submodules must not overlap.

If the cell is greyed out, the most common cause is that the controller has not been fully compiled or that the I/O mapping table has been opened in a context that does not allow editing. Save and recompile the project, then retry.

6.2 Address alignment recommendation

For S7-1500 / S7-1200, addresses can be assigned at any byte boundary, but for cleanest code the recommendation is to align transfer areas to a word boundary (even byte address) and to start the next transfer area at the next word after the previous one ends. Example layout for the first controller's PROFINET side:

On the partner controller, the I and Q roles swap: what is an output on side A is an input on side B. Use the same numeric address range on side B if you want the application code to mirror, or use a different range if the partner project has its own addressing convention.

7. PROFINET Device Name and IP Address

Each side of the coupler requires:

• A unique PROFINET device name (max 240 chars, RFC 1123 compliant).
• An IP address, subnet mask, and (if used) router address.

Open the device view of the coupler instance, select the PROFINET port, and open Properties > Ethernet addresses. The PROFINET device name is set in the PROFINET tab; the IPv4 parameters are in the IP protocol section. The IP address is only assigned at PROFINET startup by the controller via DCP, but it must be configured in the project so that the controller pushes the correct value.

For two-port PROFINET devices, do not configure the same device name on both instances of the coupler in the project; each side of the physical device has its own identity. A typical convention is pn-pn-coupler-a and pn-pn-coupler-b.

8. Safety-Related Communication (F-PN/PN Coupler Variant)

When PROFIsafe data must cross between two F-CPUs through the PN/PN Coupler, the F-variant of the coupler is used. The configuration procedure is documented in the function manual at docs.tia.siemens.cloud - Configure safety-related IO controller-IO controller communication.

The key additional steps versus the standard variant are:

1. Use the F-PN/PN Coupler device variant in the hardware catalog (separate part number, requires TIA Portal safety option enabled).
2. Configure the transfer areas as described in the SIMATIC bus links PN/PN coupler manual, section Configuring the transfer areas for the output and input data.
3. Assign PROFIsafe addresses (F-source address and F-destination address) to the relevant slots, per the PROFIsafe profile V2.4 or V2.6.1, depending on firmware.
4. Check the F-monitoring time; for safety, the value must be smaller than the safety reaction time of the F-CPU divided by the number of F-devices on the bus.
5. Compile the safety program. TIA Portal performs a consistency check on F-source / F-destination addresses and will refuse a download if the F-addresses are swapped.

Standard PN/PN Coupler devices do not transport PROFIsafe data; inserting a PROFIsafe slot on a standard coupler will fail at compile time.

9. Project Compilation, Download, and Commissioning

1. Select Project > Compile all in TIA Portal. Watch the Info pane for warnings related to the coupler; the most common ones are Address overlap and Configuration mismatch between the two coupler instances.
2. Download the hardware configuration to the first controller. Use Online > Download to device. The controller assigns the IP address and PROFINET device name to the first port of the coupler during the next PROFINET start-up.
3. Repeat the download for the second controller.
4. Use Online & diagnostics > PROFINET topology to confirm that both sides of the coupler are visible and have an active connection to their respective controllers.
5. Open the Watch table of the first controller and toggle a bit at the output address of the coupler. Watch the corresponding input address of the second controller to confirm data flow.

10. Status LEDs and On-Site Diagnostics

The coupler has at least the following LEDs on its front face. Their behavior is documented in the hardware manual, entry ID 44319532.

11. Troubleshooting Matrix

12. Frequently Asked Questions