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Configuration overview. |
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Data item configuration (begin). |
Configuration Overview
The tabs and available options in the Data Item dialog box depend upon your Type and Class selections in the New Data Item dialog box. This is the same as when you configure points.
The basic difference between configuring a data item and configuring a point, comes from the fact that the data item is a template for what could be several points (one per object) if several objects are created from the Class.
As a result
A value entered in the Data
Item dialog box may be:
A static value that applies to
all objects or
An expression that anticipates
the requirements of the several objects.
The following values are
omitted from data item configuration. This is because typically the
class developer will not know the devices or resources that are
configured for the objects in a project.
Instead, the object designer enters the following in the Object dialog box:
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Value |
Comes from the |
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Device ID |
$DEVICE_ID CIMPLICITY class attribute. |
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Resource ID |
$RESOURCE_ID CIMPLICITY class attribute. |
In addition, the object designer specifies:
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Alarm Routing |
The strategy is specified when the object is created. |
Data item configuration (begin)
Open the Data Item dialog box for a new or existing data item.
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1 |
The Data Item dialog box does not contain a Device ID field. The Point Properties dialog box does. |
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2 |
Expression tab is unique for data items. |
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3 |
You can create a data item that will behave like any other device point created in CIMPLICITY. Within class configuration, you can also create one of the following. |
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Just-in-time |
Data item point configuration is created by the Point Manager when an application requests it. When the application is done, the data item is removed from the Point Manager. It is not written to the point database. JIT Data Items can be used in:
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Delay load |
Point is not loaded into memory in the Point Manager or Devcom at project startup. Rather the point is loaded into memory only when it is demanded by an application. When the point ceases to be demanded it will be unloaded from memory in the Point Manager and Devcom. |
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Note: When one is checked the other is unavailable.
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Result: You can continue configuration, taking advantage of CIMPLICITY class attributes, string and numeric expressions, where appropriate.
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Step 4. Configure data items. |
