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🎨 Preface

The DD Language Enhancements are the first changes to the Device Description Language (DDL) after more than 10 years. All changes are backward compatible ensuring the existing investments in Device Description (DD) are protected. This version of the DD Language contains several new constructs and many significant enhancements. The DDL enhancements result from the efforts of the HCF DDL Working Group and many were jointly developed with the Fieldbus Foundation (FF) and the PROFIBUS Nutzerorganisation (PNO). These enhancements allow the increasingly more complex devices being developed for HART to be supported and adds many important capabilities to the DD Language. Some of the highlights of the enhancements made to this version include:

  • Addition of the FILE Construct;
  • Improved capabilities for the COLLECTION Construct;
  • Enhancements to MENU by supporting STYLEs;
  • Support for Value Arrays;
  • Data visualization support using Graphs and Charts;
  • Method enhancements; and
  • Many useful enhancements in the details of the language

The FILE construct allows data storage by the host on behalf of a device (Section 8.5) and allows recall of the stored data at a later time. The DD specifies the data to be stored with a similar syntax to COLLECTION. It defines the data to be stored for this device. Members may be VARIABLEs, ARRAYs, COLLECTIONs, or LISTs. The data is automatically stored by the host when written by the DD and the data last stored in the FILE is provided whenever the DD accesses it.

The MENUS construct has added a new attribute referred to as STYLE, which provides support for dialog boxes, windows, pages (tabs), group boxes and pull-down / popup menus (Section 14). COLLECTIONs are a general purpose group of DD items and can mix VARIABLEs, ARRAYs and Collections. Backward compatibility to previously defined Collections is given. Value Arrays require that only index declaration exist while the Reference Arrays require every array element to be explicitly defined in the DD.

The ability to allow devices to describe complex data sets as Graphs and Charts were added (Section 16). The GRAPH construct will specify WAVEFORMs determining how the data will be plotted, which can include emphasizing or highlighting specific data points using an attribute called KEY_POINTS. While the CHART construct will provide graphical information as it periodically updates. There are three (3) meter types and three (3) trending types supported for Charting Other valuable enhancements include as adding: the HELP attribute to MENU and EDIT_DISPLAY; bit-enum status clauses of INFO, WARNING, ERROR and IGNORE_IN_HOST; support for LIKE construct; and adding the DEFAULT_VALUE attribute to the VARIABLE construct.

Very significant enhancements were made for METHODS to include "Methods calling Methods" and "String manipulation builtins". DDL is the only technology supported by the HCF for the universal configuration of all HART compatible devices. The resolute commitment and support of DDL by the HCF, the HCF’s DDL Working Group, and cooperation with FF and PNO ensure the continued growth of the DDL. Enhancements demonstrate ongoing evolution and growing importance of DDL Technology.