Data Translation DT9837A User Manual

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Data Translation DT9837A User Manual Manual pdf 78 page image

Chapter 578When it detects a software trigger, the host computer transfers the entire waveform pattern tothe 8 kByte output FIFO on the module, and the module starts writing output values to theanalog output channel at the specified clock rate. The module recycles the data, allowing youto output the same pattern continuously without any further CPU or USB bus activity.When it reaches the end of the FIFO, the module returns to the first location of the FIFO andcontinues outputting the data. This process continues indefinitely until you stop it.To select waveform generation mode, use software to specify the following parameters:• Specify the data flow as Continuous• Specify WrapSingleBuffer as True to use a single buffer• Specify the clock source as internal and specify the clock frequency. Refer to page 76 formore information about the clock source and frequency.• Specify a software trigger source, described in the next sectionNote: On the DT9837, an error will be reported if you specify a buffer with greater than 8192samples (the size of the output FIFO on the module).If you want to output data from the analog output channel on the DT9837 module whileacquiring analog input data, ensure that you set up and start the analog output operationbefore starting the analog input operation, or an error will be reported.The DT9837, DT9837A, and DT9837C modules support the ability to mute the output voltageto 0 V. Muting the output does not stop the analog output operation; instead, the analogoutput voltage is reduced to 0 V over 1020 samples. When desired, you can unmute the outputvoltage to its current level. Refer to your software documentation for more information onmuting and unmuting the output voltage.Continuous Analog Output OperationsContinuous analog output operations are supported on the DT9837A module only. Usecontinuously paced analog output mode to continuously output buffered values to the analogoutput channel at a specified clock frequency. The DT9837A and DT9837C support the abilityto start continuous analog output operations and continuous analog input operationssimultaneously.Use software to fill multiple output buffers with the values that you want to write to theanalog output channel. When it detects the specified trigger, the module starts writing thevalues from the output buffer to the analog output channel at the specified clock frequency.The operation repeats continuously until either all the data is output from the buffers or youstop the operation.Note: Make sure that the host computer transfers data to the output channel list fast enoughso that the list does not empty completely; otherwise, an underrun error results.