This VariableTypedefines the general characteristics of a DiscreteItemthat can have more than two states and where the state values (the enumeration) does not consist of consecutive numeric values (may have gaps) or where the enumeration is not zero-based. The MultiStateValueDiscreteTypederives from the DiscreteItemType. It is formally defined in Table 6.
Table 6– MultiStateValueDiscreteType definition
Attribute |
Value |
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BrowseName |
MultiStateValueDiscreteType |
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IsAbstract |
False |
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ValueRank |
Scalar |
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DataType |
Number |
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References |
NodeClass |
BrowseName |
DataType TypeDefinition |
ModellingRule |
|
Subtype of the DiscreteItemTypedefined in 5.3.3; i.e the Propertiesof that type are inherited. |
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HasProperty |
Variable |
EnumValues |
See OPC 10000-3 |
Mandatory |
|
HasProperty |
Variable |
ValueAsText |
See OPC 10000-3 |
Mandatory |
EnumValuesis an array of EnumValueType. Each entry of the array represents one enumeration value with its integer notation, a human-readable representation, and help information. This represents enumerations with integers that are not zero-based or have gaps (e.g. 1, 2, 4, 8, 16). See OPC 10000-3for the definition of this type. MultiStateValueDiscrete Variablesexpose the current integer notation in their Value Attribute. Clientswill often read the EnumValues Propertyin advance and cache it to lookup a name or help whenever they receive the numeric representation.
MultiStateValueDiscrete Variablescan have any numeric Data Type; this includes signed and unsigned integers from 8 to 64 Bit length.
The numeric representation of the current enumeration value is provided via the Value Attributeof the MultiStateValueDiscrete Variable. The ValueAsText Propertyprovides the localized text representation of the enumeration value. It can be used by Clientsonly interested in displaying the text to subscribe to the Propertyinstead of the Value Attribute.