The Fieldbus wars have plagued device manufacturers for years. Complying with HART, Profibus or Foundation Fieldbus meant writing various device descriptions, as each had its own slant on how it communicated the characteristics of an intelligent device back to the control system.

But about two years ago there was a truce. The HART Communication Foundation, the Fieldbus Foundation and the Profibus Nutzerorganisation banded together, each providing its own individual electronic device description language (EDDL) specification. Those various specs were to be unified within the International Electrotechnical Commission IEC 61804-2 standard. This collaboration was a huge moment in field device history, as it promised to remove from device makers the cumbersome task of writing multiple device drivers for each fieldbus protocol. For device developers, having a common language would lower engineering cost. For end users, it would mean a visually appealing interface that is uniform across different vendors' devices and digital control systems (DCS).

"It was a noble idea, and the miracle of all miracles is that they did it," says Dick Caro, CEO of CMC Associates (Acton, MA). IEC took device description attributes from HART, Foundation Fieldbus and Profibus, mixed and matched them and developed a single common language that is currently in draft form to become an international standard by the first quarter of 2006.

The three groups, along with the OPC Foundation, have agreed not only to comply with the standard, but to cooperate and contribute technology that allows the text-based file to be converted to easy-to-see graphics and charts that can be displayed on a screen by the process-oriented DCS. This aspect of the standard is referred to as "enhanced EDDL."

Major consortium-contributing DCS vendors including Emerson Process Management (St. Louis, MO), Siemens Energy & Automation Inc. (Alpharetta, GA) and Honeywell Process Solutions (Phoenix, AZ) are all planning to roll out enhanced EDDL-enabled asset management products over the next few months.

But does IEC 61804-2 signify peace and an end to the fieldbus wars? Not yet.

In the background looms another device description technology: Field Device Tools and Device Tool Management (FDT/DTM), introduced several years before the EDDL agreement. The idea -- which was spearheaded by ABB Ltd. (Zurich, Switzerland) -- was to develop a single set of attribute names that could be used independent of whatever communication bus was actually being employed, providing portability at the user layer. So, like EDDL, it offered device independence. And vendors like Rockwell Automation (Milwaukee, WI), Invensys Process Systems (Foxboro, MA) and Omron Corp. (Kyoto, Japan) lined up behind FDT/DTM, as did device manufacturers Endress+Hauser Group (Reinach, Switzerland), Pepperl+Fuchs GmbH (Mannheim, Germany) and SICK AG (Waldkirch, Germany).

Today, despite the fact that protocol-independent device interfaces exist, there are still two from which developers must choose. Big FDT/DTM backers, including ABB and Invensys, say the two technologies are complementary, but that doesn't negate the need for DCS and device vendors to choose to support one or the other or both.

So indeed, there's still a war, just not the fieldbus wars of past. Rather, it's a device description language battle that's brewing.

"It's the EDDL and FDT wars now," says Mike Bryant, executive director of the Profibus Trade Organization (PTO) in Scottsdale, AZ.