Data Translation DT3130 Series, Руководство пользователя, Страница: 51 / 160

Principles of Operation
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Once the image is captured, functions in Windows perform bit copies
of the image data to display memory. Functions in Windows handle
obstructions to the passthru window by automatically clipping the
passthru image to the visible client window region. Therefore, even if
the window is obstructed in bitmap mode, the passthru can continue
unabated. Once an obstruction has been removed from the passthru
window client area, Windows automatically restores the correct
underlying image data.
A passthru operation continues until you stop it. You can stop an
asynchronous bitmap passthru operation using software.
Continuous-Acquire Passthru Mode
DT3130 Series boards support asynchronous, continuous-acquire
passthru mode. Since it is asynchronous, the operation starts but
gives control to you immediately, allowing you to perform other
operations while data is acquired and/or displayed.
Using software, you can set up the continuous-acquire passthru
operation so that data is continuously stored and displayed, or
continuously stored but not displayed.
If you want to display data in continuous-acquire passthru mode,
functions in Windows perform bit copies of the image data to display
memory. These functions also handle obstructions to the passthru
window by automatically clipping the passthru image to the visible
client window region. Therefore, even if the window is obstructed in
bitmap mode, the passthru can continue unabated. Once an
obstruction has been removed from the passthru window client area,
Windows automatically restores the correct underlying image data.
In continuous-acquire passthru mode, data is stored in a circular
buffer in device memory.