7.2. Defining Variable Types

Cascade DataHub™ : Version 5.4
	Chapter 7. Connecting InTouch

We classify data into two main types when we are configuring a Windows client application. The first type is for read-write points that are used to display data both coming from and going to the Cascade DataHub. The second type is for read-only points that are only ever used to display data coming from the Cascade DataHub.

Read-Only Variables

Read-only variables used within an InTouch application may be defined as any type of variable within the InTouch internal database. The data point may be defined as memory real, memory integer, one among several group variables, etc. When the Cascade DataHub sends a new data value for one of these variables to InTouch, the InTouch database will accept the new value without question.

Only points sent from InTouch to the Cascade DataHub need to be defined as DDE type tags.

Read-Write Variables

Points to send from InTouch to Cascade DataHub must be defined as DDE type tags. DDE tags can be:

DDE Discrete
DDE Integer
DDE Real
DDE Message

Example DDE variable definition

To define a data point as a DDE tag within the InTouch internal database, follow these instructions:

In the InTouch WindowMaker program select Special, then Tagname Dictionary. The Dictionary - Tagname Definition window will appear:
Click the New button and enter the new tagname in the Tagname field. As an example we will define the variable output1 as a DDE Real tag that is to be written to the Cascade DataHub.
Click on the Type button and select DDE Real.
Ensure the definition of the point is set to Read Write.
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Click on the DDE Access Name: button and select datahub. This tells InTouch that this tag is associated with the Cascade DataHub DDE channel.
Make sure the Use Tagname as Item Name box at the lower left corner is checked.
Click Done when finished.