Are fieldbus wars heating up again?

By Walt Boyes, Editor in Chief

Recent developments in the digital fieldbus space have us wondering if the “Great Fieldbus Wars” of the 1990s are going to flame up again. Emerson’s Martin Zielinski has been touring media hotspots with the latest on the EDDL standards. The HART Communications Foundation is piggybacking a new user-focused associate membership on the revitalization of the use of HART enabled instruments for asset management and calibration documentation requirements. ModbusTCP has received IEC acceptance as a standard. The Siemens folks are the fount of a new public relations campaign to introduce Profinet as “the one and only fieldbus you will ever need.”

EDDL vs. FDT-DTM
The recent decision of Siemens to adopt the EDDL standard instead of the rival FDT-DTM standard for electronic device descriptions means that the majority of the large automation manufacturers have decided that EDDL is superior to FDT. Zielinski made the point that the most significant superiority issue is that FDT-DTM is operating system and software program dependent, while EDDL requires much less overhead to produce the same quality of API. (A copy of Zielinski’s white paper on EDDL is posted on ControlGlobal.com.) An FDT spokesperson, quoted in Andrew Bond’s Industrial Automation Insider, said that counting out FDT/DTM is premature, saying, “For your information, there will be a few other big names backing FDT in the coming months, so please do not believe all the ‘spin’ at the moment.”

Work-in-Progress
Profinet is being rolled out, according to Siemens, over the next few years, with machine control being the first of its functionalities to be offered. Process control with Profinet will await final refinement, and, says Siemens, is not going to be available until early in 2006. The Siemens tactical marketing team CONTROL met with in November insist that Profinet for process control is not vaporware, it’s just not ready yet. Eventually, Profinet will absorb all other Profibus offshoots.

The HART Communications Foundation, previously a vendors-only club, has opened its doors to end users and others interested in furthering the use of HART in process automation. HART appears to be the little protocol that could, and has survived far longer with much more utility than its creators could ever have dreamed. Economically, with the large installed base of HART enabled instruments already wired for 4–20 mADC communications, it is difficult to argue with those, like the HART Plant of the Year, who are connecting their HART instruments to their control and asset management systems digitally, as well as communicating via analog channels. The relative differential in cost between so equipping a brownfield plant and tearing out existing instruments to install a “more modern” fieldbus system makes it economically unsound to do so. More Fieldbus Wars? Stay tuned.

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