Configure an S7 Connection Between Two S7-400 CPUs for GET/PUT Data Exchange

To transfer selected signals between two S7-400 CPUs, configure an S7 connection in the PCS 7 project and call the applicable GET or PUT function block with the connection ID and compatible source/destination areas. The Siemens configuration instruction documents creating an S7 connection and associating its connection number with the block ID. The exact CPU connection path and data layout depend on the hardware and program, so they must be taken from the applicable S7-400 documentation.

Configure the connection in the project

In the network configuration, insert a new connection, select an unspecified partner and choose S7 connection. Configure the partner endpoint and connection properties for the actual CPUs. The Siemens example identifies the connection number in the S7 connection properties; use the same identifier at the ID input of the GET or PUT function block. Since the cited instruction uses an S7-300 example for active connection establishment, confirm which S7-400 CPU must initiate the connection and which connection mode its manual supports.

Map the signals and call the transfer function

Decide how the five values are laid out in a data area on the source and destination CPUs. Match the data type, size, and offsets on both sides, then configure GET or PUT addresses to that layout as supported by the function block and CPU. Do not guess DB numbers or pointer syntax: the source ticket supplies no block interface, DB layout, CPU order number, firmware, or signal types.

Compile, download, and test

Compile the network configuration and program changes, then download the required configuration to both CPUs under the project's change procedure. Test first with known values in a non-production setup. Monitor the block's status and verify the destination values and update behavior for each signal.

Verification

Confirm that the configured S7 connection is online, both CPUs have the matching compiled connection data, the block reports successful transfer, and the receiving data area matches the source values and types. Test loss and restoration of the communication path only in a safe test environment.

Limitations and Operational Precautions

The original discussion was closed as a duplicate and contains no final configuration. Siemens technical instruction 17628518 provides a useful S7 connection example, but its active-connection detail is not an exact S7-400-to-S7-400 recipe. CPU model, firmware, topology, access protection, and memory layout must be checked before applying it. Protect production data and use site change control.

Technical References

Siemens, Technical Instructions on Configuring an S7 Connection, Item ID 17628518: https://support.industry.siemens.com/cs/attachments/17628518/S7_Connection_en.pdf
Siemens, Integration of S7-300 Package Units in PCS 7, S7-400 communication configuration example: https://support.industry.siemens.com/cs/attachments/50708061/50708061_application_pcs7_s7300_en.pdf

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Engineer FAQ

What identifies an S7 connection? The connection has a configured local connection ID; the user program passes the corresponding identifier to the GET or PUT function block.

How does the documented S7 connection setup begin? The Siemens S7 connection instruction describes creating a new connection with an unspecified partner and S7 connection type, then configuring its properties.

Which blocks are used to read data? The documented function blocks are SFB14 GET and SFB15 PUT; their roles and parameter mapping must follow the applicable CPU manual.

Does GET or PUT move data continuously? These are user-program communication functions; the program must invoke and monitor them according to the block interface and desired update behavior.

Can I read five individual signals directly? The required area and data layout depend on the partner DB and types; map the five signals into a defined compatible data area before configuring the read.

Do both CPUs need compatible connection settings? The connection endpoints, IDs, partner addressing, and CPU capabilities must agree; verify both sides and compile/download the required configuration.

Does this Siemens example exactly cover two S7-400 CPUs? The cited example's described active connection initiator is an S7-300, so apply only the generic configuration concepts and check the S7-400-specific manual.

What should be checked if data is not updating? Check connection status, local ID, partner endpoint, loaded connection descriptions, block execution and status outputs, and source/destination areas.

Can this be used across a safety boundary? No safety communication claim is made here; use the approved safety communication mechanisms and engineering validation if safety data is involved.

What details are needed for a concrete configuration? CPU order numbers, firmware, rack/slot or connection path, DB layout, five signal types/offsets, and which CPU initiates the connection are required.

Configure an S7 Connection Between Two S7-400 CPUs for GET/PUT Data Exchange