Data Translation DT3155, User Manual

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Principles of Operation
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In continuous-acquire passthru mode, data is stored in a circular
buffer in device memory. This mode also has a synchronization
mechanism using a WIN32 event object. Using this object, you can
synchronize your application with the DT3155 board to process data
as it becomes available.
A continuous-acquire passthru operation continues until you stop it
using software.
Source Origin
The source origin of an image is the upper left corner of the image.
Using software, you can change the source origin of an image to pan
and scroll the image during a passthru operation.
The source origin is a pixel position in the image. Values in the
horizontal direction range from 0 to 636 for 60 Hz, and 0 to 764 for
50 Hz (in increments of 4). Values in the vertical direction range from
0 to 476 for 60 Hz, and 0 to 572 for 50 Hz (in increments of 4).
When set, the pixel position becomes the upper left corner of the
window. The passthru image shifts to the new position.
Passthru Scaling
After the passthru image is transferred to system memory, you can
scale the passthru image up to 1/2 of the frame size in either
dimension using software. This feature allows a real-time display
window that takes less room on the Windows desktop. Images with
sharp (single-pixel) vertical or horizontal lines may have missing
information when acquired.
For the width, values are 320 or 640 pixels for 60 Hz, and 384 or 768
pixels for 50 Hz. For the height, values are 240 or 480 lines for 60 Hz,
and 288 or 576 lines for 50 Hz.