Internal Digital Data Tag

Introduction

The Internal Digital Data Tag Digital Data Tag Icon stores a digital value with two states internally in the Fernhill SCADA Server.

The Internal Digital Data Tag is a license free tag. You can create any number of these tags without restriction.

Configuration Properties

The Internal Digital Data Tag supports the configuration properties of the Digital Data Tag plus these properties:

Property Type Version Description
ApplyInitialValue USINT 3.13 Specifies when the initial value should be applied to the tag.
Options are: 0 = Never, 1 = If no value written, 2 = On server restart.
InitialValue BOOL 3.13 The initial value of the tag.

ApplyInitialValue Property

The ApplyInitialValue property defines when the initial value is applied to the tag. The options are:

ApplyInitialValueDescription
Never The initial value is never applied to the tag. Changes to the InitialValue field have no effect.
New tags (including those created by copying an existing tag) will be initialized with a value of false (off) and bad quality.
If the Fernhill SCADA Server is restarted, the value of the tag is preserved.
If no value written The initial value is applied to the tag if no value has been written using the WriteValue or the WriteValueQuality tag commands. Changes to the InitialValue field will be reflected in the tag's value until the first WriteValue or WriteValueQuality tag command. After the first WriteValue or WriteValueQuality tag command, changes to the InitialValue field will have no effect.
New tags created by copying an existing tag will be initialized with the InitialValue and good quality.
If the Fernhill SCADA Server is restarted, the value of the tag is preserved.
On server start The initial value is applied to the tag if no value has been written using the WriteValue or the WriteValueQuality tag commands. Changes to the InitialValue field will be reflected in the tag's value until the first WriteValue or WriteValueQuality tag command. After the first WriteValue or WriteValueQuality tag command, changes to the InitialValue field will have no effect.
New tags created by copying an existing tag will be initialized with the InitialValue and good quality.
If the Fernhill SCADA Server is restarted, the initial value will be written to the tag.

Dynamic Properties

The Internal Digital Data Tag supports the dynamic properties of the Digital Data Tag.

Tag Commands

The Internal Digital Data Tag supports tag commands of the Digital Data Tag plus these tag commands:

Tag Command Version Description
WriteValue 1.0 Writes a new value to the internal analog tag.
WriteValueQuality1.2 Writes a new value and quality to the internal tag.

Relationships to Other Tag Types

The Internal Digital Data Tag builds on the features of these tag types:

Further Information

Digital Data Tag

To learn about properties common to all digital tags.

Core Data Driver

To learn about the Core Driver.

Glossary

For definitions of the terms used in Fernhill SCADA.