Modbus-IDA, CiA interface CANopen with Modbus/TCP Mapping

North Grafton, MA; Erlangen, Germany—Modbus-IDA and CAN in Automation e.V. (CiA) have formed a licensing agreement, and produced a specification, entitled CiA DSP 309-2: Interfacing CANopen with TCP/IP Part 2: Modbus/TCP Mapping.


North Grafton, MA; Erlangen, Germany— Modbus-IDA and CAN in Automation e.V. (CiA) have formed a licensing agreement, and produced a specification, entitled CiA DSP 309-2: Interfacing CANopen with TCP/IP Part 2: Modbus/TCP Mapping. The two organizations’ CiA DSP 309-2 provides a standardized mapping of CANopen data for transport on Modbus TCP networks.

In the specification, Modbus Function Code 43/13 is reserved for this purpose. The reservation of this function code exclusively for CANopen is simultaneously being submitted to the Modbus-IDA RFC standardization process.

CiA will maintain the specification, which will be available for CiA members on its website at and for Modbus-IDA members on request by sending an e-mail to: .

The specification defines mapping services so that CANopen devices can communicate over a Modbus TCP network via a gateway device or by incorporating a local Modbus TCP transport layer. Access to the entries of a CANopen object dictionary is supported on both a read and write basis, along with a variety of device control functions.

The two organizations report their specification increases the options for users communicating via Modbus TCP by standardizing the way Modbus communications will be used with CANopen. They add this also decreases the opportunity for multiple incompatible approaches proliferating.

“We’re delighted to see this extension of capability being promulgated by the CAN in Automation group, and believe the result will better serve suppliers and users,” says Ken Crater, Modbus-IDA’s president. “In keeping with the commitment to open, accessible protocols, our two organizations seek to harmonize our efforts with the publication of this specification, rather than attempting development along parallel incompatible paths.”

CiA is the international users’ and manufacturers’ organization that develops and supports CAN-based higher-layer protocols. CiA’s representatives actively support international standardization of CAN protocols and represent the members’ interest in national and international standardization committees, such as ISO and IEC. CiA members initiate and develop specifications that are then published as CiA standards. These specifications cover physical-layer definitions, as well as application layer and device profile descriptions.

Modbus-IDA is a group of independent users and suppliers of automation devices that seeks to drive the adoption of the Modbus communication protocol suite and the evolution to address architectures for distributed automation systems across multiple market segments.

Control Engineering Daily News Desk
Jim Montague, news editor

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