Applies To:
  • CitectSCADA 7.xx
  • CitectHMI 7.xx
Summary:

DSPInfo function says it supports Type 4 (Raw Value) however in runtime the returned value is showing: "The specified Field is no longer supported"

The Help file for CitectSCADA v7.0 shows information for the function DspInfo() and shows that it supports Type 4 (Raw Value). When running the project we see that this function is no longer working and shows the following returned value message: "The specified Field is no longer supported".  

Solution:

In CitectSCADA v7.0, getting the raw value through DspInfo is no longer supported.

This is by design and the help documentation will be updated in the next release to reflect this change. The client process is no longer aware of the scales for a particular tag, as it has to subscribe to the data with the appropriate mode to get a value other than the engineering one. The TagSubscribe() function and the SubscriptionGetAttribute() function can now be used in conjunction as a workaround in CitectSCADA version 7.0 SPK-A as the TagSubscribe() function now has the capability to support this functionality loss. The workaround function to use is as follows. Reference to the Help Documentation for the TagSubscribe() function:

...
INT subsHandle = TagSubscribe ( "Conveyor1" , "Raw" );
...
// Get the Raw value
convRawValue = SubscriptionGetAttribute (subsHandle, "Value" );
...
// Unsubscribe the tag
TagUnsubscribe (subsHandle);
...
Return convRawValue;
...
End

 
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