Emerson collaborates with standards groups to expand DDL technology

AUSTIN, TEXAS (January 22, 2004) — Emerson Process Management is collaborating with members of leading global standards groups to enhance Device Description Language (DDL) technology. After carefully considering user needs, Emerson believes enhanced DDL offers a better solution than a proposed alternative called Field Device Tool / Device Type Manager (FDT/DTM).

According to Emerson, efficiency in ownership of process automation requires that users be able to cost-effectively add, upgrade, and integrate instruments, equipment, and systems of choice. Open, interoperable, standards-based DDL is proven global technology meeting these needs in thousands of installations today.

DDL provides underlying technology for use by host suppliers to design robust Human-Machine Interface (HMI) and automation interfaces, and enhancements being developed will add to this functionality. DDL-based field devices from all suppliers will interface identically to the various hosts. When host operating system changes are needed, the host suppliers have complete ability to make all upgrades; field device descriptions are unaffected.

FDT/DTM technology development has recently been undertaken by the FDT Joint Interest Group (FDT JIG) as an alternative with goals described as similar to the DDL collaboration. While the goals are unarguable, Emerson’s review of the FDT/DTM concept prompted concerns about important shortcomings for users based on technical issues. In Emerson’s judgment, the proven DDL technology surpasses the FDT/DTM technology in meeting the following needs of end users:

  • Freedom of choice of instruments, equipment and systems
  • Clarity and ease of use of HMI design and displays
  • Streamlined integration of field devices
  • Efficient system upgrades

Emerson also noted that DDL technology is proven; it is employed in the millions of HART, Profibus DP and FOUNDATION fieldbus devices installed by users. DDL provides underlying technology for effective HMI interface to this large and rapidly growing installed base. FDT/DTM is missing provisions for these users.

Emerson is therefore focusing its resources on enhancement and standardization of DDL, and is collaborating with standards organization members to speed enhancement of the established technology toward the goal of an ever-strengthening HMI interface.

Enhancement of DDL Technology

Emerson is supporting members of the HART Communication Foundation, the Fieldbus Foundation, and Profibus International to expand visualization tools within DDL technology. Being developed within the context of the already-existing IEC 61804-2 DDL international standard¹, the enhancements streamline the ability of host suppliers to deliver a single, superior engineering interface capable of configuring, operating, and maintaining any smart field device, independent of vendor and communications protocol.

Emerson today offers HMIs as a single interface that supports HART, Modbus, DeviceNet, FOUNDATION fieldbus, Profibus DP, Profibus PA, and ASi Bus, as well as a wide variety of legacy communications. In participation with the collaborative DDL actions, Emerson continues its dedication to standards, and is strengthening FOUNDATION fieldbus while enhancing a single interface availability across the industry.

FDT/DTM Alternative to DDL

The FDT JIG has shaped a technology with a FDT that is a “software receptacle” into which a DTM is “inserted.” The FDT provides interfaces to the software architecture of the host system; it becomes an integral part of the host system. The FDT provides access to underlying services such as display, keyboard, database (if there is one), and other generic host features; it also provides access to any digital communication interfaces the host system might have.

The FDT specification requires implementation to be accomplished with a Microsoft Windows Operating System (OS) and is built on Microsoft’s Component Object Model (COM) and Distributed Component Object Model (DCOM) technology. Since COM/DCOM was not intended to communicate with process automation field devices, these technologies have been extended to accommodate this requirement.

The FDT is intended to provide interface to the HART, FOUNDATION fieldbus, and/or PROFIBUS communication drivers if they are present in the host system. At present, only HART and PROFIBUS are supported by the Joint Interest Group.

A DTM is software that is supplied by the field device manufacturer. It is installed as a component of the software architecture. A DTM is “plugged into” the FDT, and uses Microsoft Active X technologies to access the services provided by the FDT. Through the utilization of available FDT services, the DTM provides all access to the field device.

All of the information that the device manufacturer wishes to make available is programmed into the DTM. This includes all real-time data, alarms, events, configuration information, screen displays, multilingual help screens, device specific documentation, parameter validity check, generation of dependent variables, diagnostic functions, and the device calibration sequence. A DTM can support more than one field device; however, this increases its programming complexity.

HMI with FDT/DTM

In the proposed FDT/DTM technology, software for implementing HMI visualization is the responsibility of the field device suppliers. The HMI screen images served up with data from the devices have a different look and feel from each field device supplier. DDL insures a consistent look and feel on a given host system, because the host implements a single interpretation for all device description files, independent of vendor.

Upgrade Management and Revision Control with FDT/DTM

Whereas DDL is designed for interoperability, FDT/DTM requires custom drivers (i.e., DTMs) that tightly integrate the field device software with a host operating system. This executable software must be maintained by the field device manufacturer and integrated by the host system supplier.

FDT/DTM technology’s operating system dependence, and tight integration of software, lead to more challenging upgrades. For example, there are significant differences between Microsoft Win 95, 98, Me, NT, 2000, and XP. More significant changes are coming in the Microsoft Longhorn release that sports significant Graphical User Interface (GUI) changes. It is unlikely that the DTMs of all the vendors’ field devices would work correctly when upgraded with host system software, and that DTMs of all the vendors’ field devices would work correctly in the new Windows OS.

An existing DTM must be integrated in the host when new features or functionality are added, or when the OS is upgraded. It is not clear who is responsible for ensuring continued compatibility between the DTM and the host system FDT. It will likely be a combination of the device manufacturer, the host system supplier, and the end user. Their roles are interdependent and will require expensive, often time-consuming negotiation. A similar integration process for a new proprietary software driver must occur when a field device is revised or upgraded.

It is unlikely that installed DTMs can keep pace with enhancements, and even more unlikely that they can survive an upgrade. This will likely force host system suppliers to restrict the number of different vendors’ field devices. Otherwise, revision control would become unmanageable.

1. Draft International Standard IEC 61804-2 has been approved and will be circulated in January 2004 for a two month ballot as an international standard.

About Emerson Process Management

Emerson Process Management (www.emersonprocess.com), an Emerson business, is a leader in helping businesses automate their production, processing, and distribution in the chemical, oil and gas, refining, pulp and paper, power, food and beverage, pharmaceutical, and other industries. The company combines superior products and technology with industry specific engineering, consulting, project management, and maintenance services. Emerson brands include PlantWeb®, Fisher®, Micro Motion®, Rosemount®, DeltaV™, Ovation®, and AMS™ Suite.

About Emerson

St. Louis-based Emerson (www.gotoemerson.com) is a global leader in bringing technology and engineering together to provide innovative solutions to customers in process control; electronics and telecommunications; industrial automation; heating, ventilating and air conditioning; and appliance and tools. Sales in fiscal 2003 were $14 billion.

PlantWeb, Fisher, Micro Motion, Rosemount, DeltaV, Ovation, and AMS are property of Emerson Process Management. FOUNDATION is a mark of the Fieldbus Foundation. Other marks are property of their respective owners.