Origin of the following was extracted from the draft of AG10193 FDI Technology Version Migration Guide, therefore it is subject to change in the final version. 

3.8    Change/Addition to behavior to support color banding on CHARTs




Legacy behavior:          HCF_SPEC-500 14.0 E, Section A.7.1

FDI behavior:                61804-4 Ed 2.0, Section 4.8

Version Implemented

FDI Technology Version 1.2

Communication Profiles: CS, GPE, PB, PN, FF, HART
Description of Change

Only the legacy HART profile supported a mechanism for adding color banding to charts. Starting with FDI version 1.2, color banding is supported by all of the communication profiles.


For HART, starting with FDI version 1.2, the rendering of background colored regions on a chart has been enhanced to allow limit lines to either define the lower boundary (for HIGH and HIGH_HIGH types) or the upper boundary (for LOW_LOW types) of a region. The legacy HART specification stated that it is always the upper boundary of the region that is determined by the value of the limit line. It was not possible to specify a lower boundary of the region with the legacy specification.


This change in behavior was made to support additional use-cases for presenting useful visual cues on charts to end users. Previously, the only way to specify a banded region at the top end of the axis on the gauge, was to define another “dummy” region at the lower end of the axis.   With the updated specification, it is now possible to specify only a region at the top end of the axis if it is desired.


Compatibility Considerations

DD developers should be aware that HART DDs developed to render color banding on meter charts (charts of type GAUGE) according to the legacy HART DD specification are specified differently from how they are specified for FDI applications. Developers should test the rendering of HART meter charts in both a non FDI application and an FDI application. Specifying all limit types of “LOW” may render a chart that is similar in applications designed to the old legacy HART specification and those designed to the FDI specification. If both LOW and HIGH limit line types are used to generate a specific color banding appearance, then the appearance will not be as intended when used with non-FDI applications. DD developers should include a pre-processor conditional around the LINE_TYPE declaration in the DD because non-FDI applications would not support this behavior of color bands.


For developers of non-HART DDs, be aware that any application designed prior to FDI v1.2 may not support any type of color banding on a chart. Developers should not count on the color banding alone to convey the information that is necessary for their end users to view.