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Continuously Updating Analog Output Channels on One Module with a
Waveform
If you want to write a waveform to one or more analog output channels on one DT9850 Series
module, use software to perform a continuously paced analog output operation. This is also
known as streaming analog output data.
In a continuous analog output operation, you specify the analog output channels that you
want to update in the output channel list. For example, if you want to update all eight analog
output channels, specify the output channel list as follows: 0, 1, 2, 3, 4, 5, 6, 7.
You must also allocate one more buffers that contain the values to write to the selected analog
output channels. For example, if your output channel list contains analog output channels 0
and 1, specify your buffer as follows: first value for analog output channel 0, first value for
analog output channel 1, second value for analog output channel 0, second value for analog
output channel 1, and so on.
The module updates the specified analog output channels with the waveform that you
specified as soon as you start the continuous operation.
The values are output at the clock frequency that you specified (refer to
information on specifying the clock frequency). The operation repeats continuously until no
more buffers are on the subsystem queue or you stop the operation.
Note: Make sure that the host computer transfers data to the analog output channels fast
enough so that they do not empty completely; otherwise, an underrun error results.
To select continuously-paced analog output mode, use software to specify the following
parameters:
• Set the dataflow mode to Continuous.
• Set WrapSingleBuffer to True to use a single buffer or to False to use multiple buffers.
Refer to
page 58
• Set the trigger source to Software trigger.
Note: When in continuous mode, the DAC_Sync pin is not used.
• Set the clock frequency based on the number of channels that you specified in the output
channel list. Refer to
To stop a continuously paced analog output operation, you can stop sending data to the
module, letting the module stop when it runs out of data, or you can perform either an orderly
stop or an abrupt stop using software. In an orderly stop, the module finishes outputting the
data in the buffer, then stops; all subsequent triggers are ignored. In an abrupt stop, the
module stops outputting samples immediately; all subsequent triggers are ignored.
for more information on buffers.
page 54
for more information on clock frequency.
Principles of Operation
page 54
for more
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