The OptionSetType VariableType is used to represent a bit mask. Each array element of the OptionSetValues Property contains either the human-readable representation for the corresponding bit used in the option set or an empty LocalizedText for a bit that has no specific meaning. The order of the bits of the bit mask maps to a position of the array, i.e. the first bit (least significant bit) maps to the first entry in the array, etc.

In addition to this VariableType, the DataType OptionSet can alternatively be used to represent a bit mask. As a guideline the DataType would be used when the bit mask is fixed and applies to several Variables. The VariableType would be used when the bit mask is specific for only that Variable.

The DataType of this VariableType shall be capable of representing a bit mask. It shall be either a numeric DataType representing a signed or unsigned integer, or a ByteString. For example, it can be the BitFieldMaskDataType.

The optional BitMask Property provides the bit mask in an array of Booleans. This allows subscribing to individual entries of the bit mask. The order of the bits of the bit mask points to a position of the array, i.e. the first bit points to the first entry in the array, etc. The VariableType is formally defined in Table 83.

Table 83 – OptionSetType definition

Attribute		Value
BrowseName		OptionSetType
IsAbstract		False
ValueRank		−1 (−1 = Scalar)
DataType		BaseDataType
References	NodeClass		Browse Name	DataType TypeDefinition	ModellingRule
Subtype of the BaseDataVariableType defined in 7.4
HasProperty	Variable		OptionSetValues	LocalizedText[] PropertyType	Mandatory
HasProperty	Variable		BitMask	Boolean[] PropertyType	Optional
Conformance Units
Base Info OptionSet