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 7.

Table 7 – 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

Conformance Units

Data Access TwoState

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 Properties are changed (see 5.2 for additional information).