Different Methods to Exchange PLC Data

Data Exchange between ControlLogix and Siemens S7 PLCs.

Exchanging register information between a Siemens PLC and a ControlLogix PLC, which is typically an Allen-Bradley product, can be challenging due to the differences in the communication protocols and programming environments used by each manufacturer. However, it is possible to achieve this through various methods. Here are some common ways to exchange register information between these two PLC systems:

1 - OPC (OLE for Process Control): OPC is a standard protocol used for communication between different industrial automation devices. You can set up OPC servers and clients on both the Siemens and ControlLogix PLCs to exchange data. The OPC server on one PLC can read or write data to the OPC client on the other PLC.

2 - Modbus TCP/IP: If both PLCs support Modbus TCP/IP, you can use this protocol to exchange data. One PLC can act as a Modbus server, and the other as a Modbus client. You would configure data exchange using Modbus registers or coils.

3 - Ethernet/IP: ControlLogix PLCs use the Ethernet/IP protocol for communication. Siemens PLCs can also be configured to communicate over Ethernet/IP, but it might require additional hardware or communication modules. You can set up Ethernet/IP communication between the two PLCs to exchange data.

4 - Custom Communication Protocols: Depending on the specific models and capabilities of the Siemens and ControlLogix PLCs, you may need to develop custom communication protocols. This could involve using the manufacturer's proprietary libraries or communication modules.

5 - Gateway Devices: Consider using third-party gateway devices that can translate the communication protocol of one PLC into a format that the other PLC can understand. These devices act as intermediaries between the two systems and facilitate data exchange.

 

6 - Data Exchange through SCADA Systems: If you have a supervisory control and data acquisition (SCADA) system in place, you can route data through the SCADA system, which can communicate with both PLCs and manage data exchange.

7 - PLC Data Exchange Program: Boxx Engineering has develop a Windows program to manage the exchange of data between Siemens PLCs and Rockwell’s ControlLogix PLCs.  The program’s main feature is the exchange of Real Array Register Data for numbers and a Double Integer Register for discrete bit exchange.  The Big Endian and Little Endian difference between Siemens and Rockwell PLCs is handled by the program so that the bits stay in the same position in each PLC.

The specific method you choose depends on the capabilities of your PLCs, your networking infrastructure, and your project requirements. Keep in mind that you may need to consult the documentation and support resources provided by Siemens and Rockwell Automation (Allen-Bradley) for your particular PLC models to ensure compatibility and successful data exchange. Additionally, it's important to follow best practices for industrial network security when setting up communication between PLCs from different vendors to protect your automation systems.