Errata exists for this version of the document.

This VariableType defines the general characteristics of a DiscreteItem that can have two states. The TwoStateDiscreteType derives from the DiscreteItemType. It is formally defined in Table 4.

Table 4 – TwoStateDiscreteType definition

Attribute	Value
BrowseName	TwoStateDiscreteType
IsAbstract	False
ValueRank	−2 (−2 = ‘Any’)
DataType	Boolean
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the DiscreteItemType defined in 5.3.3; i.e the Properties of that type are inherited.
HasProperty	Variable	TrueState	LocalizedText	PropertyType	Mandatory
HasProperty	Variable	FalseState	LocalizedText	PropertyType	Mandatory

TrueState contains a string to be associated with this DataItem when it is TRUE. This is typically used for a contact when it is in the closed (non-zero) state.

for example: "RUN", "CLOSE", "ENABLE", "SAFE“, etc.

FalseState contains a string to be associated with this DataItem when it is FALSE. This is typically used for a contact when it is in the open (zero) state.

for example: "STOP", "OPEN", "DISABLE", "UNSAFE“, etc.

If the item contains an array, then the Properties will apply to all elements in the array.

The StatusCode SemanticsChanged bit shall be set if any of the FalseState or TrueState ( changes can cause misinterpretation by users or (scripting) programs) Properties are changed (see section 5.2 for additional information).