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IVI Error BFFA0016: "Attribute Already Has a Value Waiting to be Updated."

Primary Software: Instrument Drivers/IVI>>IVI Specific Driver
Primary Software Version: N/A
Primary Software Fixed Version: N/A
Secondary Software: Instrument Drivers/IVI>>IVI Compliance Package, Instrument Drivers/IVI>>IVI Class Driver

Problem: While using an IVI driver, I sometimes get the IVI error message "Attribute already has a value waiting to be updated." (Error number BFFA0016). This error occurs intermittently. What exactly does this mean and what can I do to the instrument driver or in the code that communicates with the instrument driver to handle this type of error?

Solution: This type of error can occur if you call the SetAttribute function before an earlier function call that has the same Attribute ID finishes successfully. The earlier function call can fail for three reasons:
  1. Our IVI Specific driver is not implementing the Defer Update attribute correctly. Check whether our IVI Specific driver uses this attribute at all.

  2. You enable the Defer Update attribute, which is not allowed. See the help file: 
    Constant:  IVI_ATTR_DEFER_UPDATE
    Data Type:  ViBoolean
    Description:  This attribute specifies whether to defer the actual updating 
    of the physical instrument when you call an Ivi_SetAttribute function.  The 
    IVI engine performs all the deferred updates for the session when you call 
    Ivi_Update.
        Typically, it is not necessary to defer updates.  Deferring updates can 
    be useful when the overhead of initiating instrument I/O is very high.  By 
    deferring updates, you can buffer multiple instrument commands into one I/O 
    action.
        Generally, only instrument driver developers use this attribute, and 
    they do so on a temporary basis around a sequence of calls to 
    Ivi_SetAttribute functions.  Instrument driver functions that the end-user 
    calls must never return with IVI_ATTR_DEFER_UPDATE in the enabled state.
        The default value is VI_FALSE.
  3. In the interactive mode, you terminate execution in the WriteCallback and then try to set the same attribute again in the same session (either by calling Configure or SetAttribute).


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Report Date: 02/28/2001
Last Updated: 03/19/2008
Document ID: 26RCMUV8

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