Data Translation MACH Series, Руководство пользователя

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Principles of Operation
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Area-Scan Operations
For area-scan operations, the DT3152-LS board supports both
synchronous and asynchronous bitmap passthru mode.
In a synchronous operation, you cannot perform another operation
until the operation is stopped. In an asynchronous operation, the
operation starts but gives control to you immediately, allowing you to
perform other operations while data is displayed.
Area-scan bitmap passthru mode requires a frame buffer in device
memory in which the image is captured.
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 bitmap passthru operation continues until you stop it. You can stop
an asynchronous bitmap passthru operation using software. To stop a
synchronous bitmap passthru operation, click the mouse or press a
key.