Process news from across the pond

ODVA will bring the Modbus community under its umbrella by integrating Modbus connectivity into the CIP architecture in a way that will require no changes to the existing Modbus slave devices. This will be achieved by extending the definition of Ethernet/IP “originators” to include the optional ability to communicate with Modbus/TCP slaves. The integration will also be backwards-compatible with the existing CIP standard, ensuring that both existing Modbus/TCP and Ethernet/IP devices will be covered. ODVA says that the next release of the EtherNet/IP specification, which will include Modbus support, will be available before the end of the year, while Schneider says that it expects to have products based on the new protocol available in 2008.

Critical Mass
The development has major significance at a number of levels. DeviceNet and its related networks have been the dominant force in factory automation in North America, but have had much less impact in the rest of the world, where Profibus can justifiably claim market leadership. However adding Modbus/TCP—and the Schneider user base—gives ODVA the critical mass and global coverage it has previously lacked and puts it on a comparable footing with ProfiNet.

There could also be a knock-on effect in the process automation market, given that, as a ‘Producer-Consumer’ protocol, CIP has more in common with Foundation fieldbus than with Profibus PA, the process automation implementation of Profibus.

As a result vendors and end users might be tempted to reassess their choice of network for ‘non-process’ applications in process industry environments, an area where Profibus and ProfiNet have traditionally been strong.

By no means the least significant potential consequence is the impact on the PLC market. As ARC’s Harry Forbes points out in an “Insight” document discussing Schneider’s strategy, ODVA’s principal members, which include Omron as well as Rockwell and Schneider, between them now account for 36% of the global PLC market, and that share is pretty evenly distributed across North America, Asia and Europe. If Schneider’s closer involvement in ODVA were to lead to closer cooperation between it and Rockwell on a broader front, perhaps giving the latter a broader platform from which to address European and Asian markets, then the combination could pose a significant challenge to Siemens’ current position as the global automation market leader.

Forbes is in no doubt about the significance of the development. “It is unusual to see several automation majors joining in such close collaboration, especially in a strategic area such as industrial Ethernet, and it adds to the value of ODVA and its CIP Network technologies in the automation industry. Automation users of Modbus/TCP can now look forward to benefiting from CIP Networks. Schneider Electric products will also benefit from the many capabilities of CIP, but end users will be the real winners here, because future CIP Networks will offer them a broader range of choices.”

Other Networks
Schneider says that its decision in no way diminishes its commitment to its other core networks, SERCOS and CANopen, but that it now sees Ethernet/IP as the foundation of its network strategy. “Our customers want the level of interoperability and seamless automation of factory floor equipment that only networks using standard, unmodified Ethernet can provide,” said senior vice president of innovation for automation business Adrien Scolé. “They also want a single network that they can use for control, information, configuration, safety, synchronization and motion. Ethernet/IP is the answer to meeting these needs, since it provides compatibility with existing Modbus/TCP products, as well as access to the complete suite of services provided by CIP. We believe that our strengthened relationship with ODVA will make Ethernet/IP the most widely used industrial network.”

That view was echoed by ODVA’s Katherine Voss, who described Schneider as “a leader in driving the adoption of standard, unmodified Ethernet technologies on the factory floor and throughout the enterprise. We look forward to leveraging the vast experience of Schneider Electric in automation, as well as its expertise with Ethernet and the Internet, to continue to expand the capabilities and benefits of ODVA technologies.”

Unmodified Ethernet
According to Forbes, that word “unmodified” is a key element in the Schneider strategy, which is aimed at reducing the “fragmentation of industrial Ethernet protocols, which they believe is throttling market growth,” he says. “They object to Ethernet automation systems that require custom protocol stacks (or in some cases ASICs) supplied by a controlled set of certified providers.”

Not everyone is entirely bowled over by the development, however. PTO’s Carl Henning, in his blog at http://us.profibus.com/community/blogs, isn’t impressed by the plan to encapsulate Modbus packets within CIP so they can be handled on the CIP network. “To me encapsulation is less than ideal,” he writes. “It introduces one more step in the process which adds to the response time. And encapsulating it in TCP/IP or UDP/IP adds to the uncertainty of the delivery time.” Henning quotes data from the University of Michigan which suggest that performance will be inferior to that of ProfiNet. More dismissively he adds that “The press release says products will be available in 2008. But there is no reason to wait; ProfiNet can communicate to Modbus today through a proxy … without encapsulation.”

One can’t help feeling that Henning is, perhaps deliberately, missing the point. Reducing the number of alternative Industrial Ethernet protocols must in long term be to the advantage of users even if in the shorter term it may not make choosing between them any easier. Now, isn’t it time Profibus started talking seriously to the Fieldbus Foundation?