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Onboard Device Memory Underflow When Using DaqComponent Example Code for an NI-DAQmx Non-regenerative Continuous Digital Output Task in Measurement Studio Support for Visual Studio 2005

Primary Software: Driver Software>>NI-DAQmx
Primary Software Version: 8.6
Primary Software Fixed Version: N/A
Secondary Software: Measurement Studio>>Enterprise Edition (Full Development System), Measurement Studio>>Professional Edition (Base Package)
Hardware: Digital I/O (DIO)

Problem: When generating the user interface and source code for a DaqComponent that refers to a continuous digital output task with a Regeneration Mode set to "Do not allow regeneration," you may receive an error message when you run the task similar to: "Measurements: Onboard device memory underflow. Because of system and/or bus-bandwidth limitations, the driver could not write data to the device fast enough to keep up with the device output rate. Reduce your sample rate, or reduce the number of programs your computer is executing concurrently. Task Name: DigitalDisallow. Status Code: -200621." The generated example code only writes the data to the digital output channels once, but the non-regenerative output mode requires additional data to be written continuously. Because additional data is never written to the task, an onboard device memory underflow occurs.

Solution: First, modify the DaqComponent User.cs or User.vb partial class source code to allow access to the Task. The result will be similar to the DaqTask.User.cs or DaqTask.User.vb attachment. Second, modify the generated example code to continuously write asynchronous data, as shown in the Form1.cs or Form1.vb code attachment.

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Report Date: 06/26/2007
Last Updated: 08/27/2007
Document ID: 4AP9PRUP

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