Chapter 3
Hardware Overview
©
National Instruments Corporation
3-9
PCI/PXI-1408 and NI-IMAQ for Win95/NT
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Acquisition window—After setting the pixel and line count, you
must program the active pixel region and active line region. The
active pixel region selects the starting pixel and number of pixels
to be acquired relative to the HSYNC signal. The active line region
selects the starting line and number of lines to be acquired relative
to the VSYNC signal.
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Region of interest—The 1408 device uses a second level of active
pixel and active line regions for selecting a region of interest. When
you disable the region-of-interest circuitry, the board stores the
entire acquisition window in system memory. However, when you
enable the region-of-interest circuitry, the board transfers only a
selected subset of the digitized frame to system memory.
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Scaling down—The scaling-down circuitry also controls the active
acquisition region. The 1408 device can scale down a frame by
reducing pixel, lines, or both. For active pixel selection, the
PCI/PXI-1408 can select every pixel, every other pixel, every
fourth pixel, or every eighth pixel. For active line selection, the
1408 device can select every line, every odd line, or multiples of
odd lines, for example, every other odd line or every fourth odd
line. You can use the scaling-down circuitry in conjunction with the
region-of-interest circuitry.
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Interlaced video—The 1408 device supports both interlaced and
noninterlaced video signals. In interlaced mode, the 1408 device
combines the odd and even field into one contiguous frame for
analysis. In noninterlaced mode, each field is treated as an
independent frame.