Data Translation DT3162, User Manual

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Principles of Operation
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Unlike single-pass synchronous mode, however, this
asynchronous operation starts and then returns control to you
immediately, allowing you to perform other operations while
data is acquired. Therefore, you can stop the operation before all
the ROIs have been acquired, if you wish, using software.
Specify SinglePassAsync in software to use this mode.
• Continuous asynchronous mode
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The DT3162 board
continuously acquires an unlimited number of fields or frames
and saves the corresponding ROIs to buffers in memory until you
stop the acquisition. You are responsible for managing the data in
the buffers so that it is retrieved before the buffer is overwritten.
Continuous mode is an asynchronous acquisition, where the
operation starts and then returns control to you immediately,
allowing you to perform other operations while data is acquired.
For example, assume that you specified the acquire type as
interlaced, the acquisition mode as continuous, and the number
of buffers as 3. When the acquisition operation is started, the
software allocates three buffers, acquires the first frame and
stores its ROI in buffer 1, acquires the second frame and stores its
ROI in buffer 2, then acquires the third frame and stores its ROI in
buffer 3. Then, the process repeats so that ROI 4 is stored in buffer
1 (overwriting any data previously stored there), ROI 5 is stored
in buffer 2 (overwriting any data previously stored there), ROI 6
is stored in buffer 3 (overwriting any data previously stored
there), and so on. The operation repeats until you stop it. You
must manage the buffers so that the data in buffers 1 through 3 is
read before the buffers are overwritten.
Specify ContinuousAsync in software to use this mode.
Note: During asynchronous acquisitions, your application program
is notified by Active-X events that various conditions (such as a
frame completed or the acquisition completed) have occurred.