Specification links Modbus with CIP

An ODVA product story

Edited by the Engineeringtalk editorial team Dec 3, 2007

Extension gives existing Modbus/TCP users a clear path to CIP network architectures while protecting their automation investments.

ODVA has published the specifications for the integration of Modbus devices into the Common Industrial Protocol (CIP) architecture.

This extension, which has been published in the CIP Networks Library of specifications, provides seamless access from CIP originator devices to Modbus target devices consistent with the existing CIP model, providing a standard translation of a subset of CIP functions into the appropriate Modbus functions.

First announced in April 2007, this concept was brought to fruition through the efforts of the 20 ODVA member companies participating on ODVA's Modbus Integration Joint Special Interest Group (JSIG).

Completion of this extension gives existing Modbus/TCP users a clear path to CIP network architectures while protecting their automation investments.

Users will benefit through significantly increased interoperability between the largest installed base of industrial Ethernet networks - EtherNet/IP and Modbus/TCP - as well as between automation products from a growing number of vendors.

Combined, these benefits will reduce cost, time and risk for users deploying and maintaining their network architectures.

This extension requires no change to existing Modbus/TCP target devices or EtherNet/IP target devices in order to take advantage of the seamless connectivity offered.

In addition, no changes are required for installed CIP-Modbus gateway devices.

"This new functionality can be implemented in a gateway device or in a CIP originator, and the translation function uses existing CIP Parameter and Assembly Objects", says Todd Snide, Chair of ODVA's Modbus Integration JSIG.

"This extension allows existing vendor-specific CIP-to-Modbus/TCP gateway products to work without change; however, those vendors and users who take advantage of this extension will see an automatic translation that is not similar to the traditional gateway approach: the enablement of a seamless virtual CIP router, allowing CIP messages to be directly sent to Modbus/TCP target devices".

"The integration of Modbus devices into the CIP architecture provides users with two key benefits: the ability to protect their investment in their existing automation installations and a seamless migration path for their next generation network architecture", says Katherine Voss, Executive Director of ODVA.

"Users who take advantage of the benefits of the integration of Modbus devices into the CIP architecture will be well positioned to reap increasing benefits from the return on investment provided by CIP and industrial Ethernet".

EtherNet/IP was introduced in 2001 and has more than 1.4 million installed nodes.

EtherNet/IP and Modbus/TCP are the two most popular industrial Ethernet protocols, representing over 50% worldwide market share, according to the most recent market study from ARC Advisory Group.

Products incorporating this new functionality are anticipated to be on the market in 2008.

In addition, the development allows for seamless CIP-to-Modbus serial line communication in a future revision of the specifications of the CIP Networks Library.