ForceValue Tag Command

Introduction

The ForceValue Tag Command replaces the current value of a tag with a fixed constant value.

Parameters

Value : ANY_ELEMENTARY: The new, forced value of the tag.

Remarks

In some situations it may be appropriate to apply a force to a tag:

If there is a faulty sensor.
If there is a faulty connection to a sensor.

Forcing replaces the actual value read from the data source with a fixed value defined by the user. When forced, the actual value of the tag is still read, but is stored in these properties:

UnforcedValue
UnforcedQuality
UnforcedTimestamp
UnforcedColor

When the force is removed, using a RemoveForce Tag Command, the most recent actual value can be immediately restored.

The Value parameter is ANY_ELEMENTARY. ANY_ELEMENTARY is a generic data type, which allows any single value. For more information on ANY_ELEMENTARY and other generic data types see Generic Data Types.

The ForceValue Tag Command will try to convert the Value parameter to a type compatible with the host tag. To avoid errors you should ensure the Value parameter is compatible with the host tag. The type expected by the driver for a each tag type is shown in this table:

Icon	Tag Type	Expected Value Type
	Analog	LREAL
	Digital	BOOL
	Word	UINT
	Double Word	UDINT
	Long Word	ULINT
	String	WSTRING

You can execute ForceValue Tag Command from:

From an Operator Action using a TagForceValue Function.
From a Program Tag using a TagForceValueFB Function Block. See Example Program to learn more.
The Standard Tag Menu when used with one of the tags listed in the Applies To list.
The Java API. For an example see Executing a Tag Command from Java.

To use the ForceValue Tag Command, the user must have the Force User Right.

Requirements

Fernhill SCADA Version	Version 1.0
Required User Right	Force

Applies To

The ForceValue Tag Command can be used with these tag types: