Extended Properties
The Extended Properties feature lets you define more information, such as limits, engineering units, or state identifiers for various components within your controller project.
Component | Extended Properties |
|---|---|
Tag | In the tag editor, add extended properties to a tag. |
User-defined data type | In the data type editor, add extended properties to data types. |
Add-On Instructions | In the properties that are associated with the Add-On Instruction definition, add extended properties to Add-On Instructions. |
Pass-through behavior is the ability to assign extended properties at a higher level of a structure or Add-On Instruction and have that extended property automatically available for all members. Pass-through behavior is available for descriptions, state identifiers, and engineering units and you can configure it.
Configure pass-through behavior on the Project tab of the Controller Properties dialog box. If you choose not to show pass-through properties, only extended properties that have been configured for a given component are displayed.
Pass-through behavior is not available for limits. When an instance of a tag is created, if limits are associated with the data type, the instance is copied.
Use the .@Min and .@Max syntax to define tags that have limits, as there is no indication in the tag browser that limit extended properties are defined for a tag. If you try to use extended properties that have not been defined for a tag, the editors show a visual indication and the routine does not verify. Visual indicators include the following:
- A rung error in Ladder Logic
- A verification error X in Function Block Diagrams
- The error underlined in Structured Text
You can access limit extended properties that .@Min and .@Max syntax defines. However, you cannot write to extended properties values in logic.
For more information on Extended Properties, see the Logix 5000 Controllers I/O and Tag Data Programming Manual, publication 1756-PM004.
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