Chapter 3
Hardware Overview
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National Instruments Corporation
3-5
Video Acquisition
The PCI/PXI-1422 can acquire digital video in a variety of modes and store
the images in the onboard SDRAM memory or transfer the images directly
to PCI system memory.
Start Conditions
The PCI/PXI-1422 can start acquisitions in a variety of conditions:
•
Software control—The PCI/PXI-1422 supports software control
of acquisition start. You can configure the PCI/PXI-1422 to capture
a fixed number of fields or frames. This configuration is useful for
capturing a single frame or a sequence of frames.
•
Trigger control—You can start an acquisition by enabling external
or RTSI bus trigger lines. Each of these 11 inputs can start a video
acquisition on a rising or falling edge. You can use all four external
triggers and up to four RTSI bus triggers simultaneously.
•
Delayed acquisition—You can use either software or triggers to start
acquisitions instantaneously or after skipping a specific number of
images.
•
Frame/field selection—With an interlaced camera and the
PCI/PXI-1422 in frame mode, you can program the PCI/PXI-1422
to start an acquisition on any odd or even field.
Acquisition Window Control
You can configure numerous parameters on the PCI/PXI-1422 to control
the video acquisition window. A brief description of each parameter
follows:
•
Acquisition window—The PCI/PXI-1422 allows the user to specify a
particular region of active pixels and active lines within the incoming
video data. The active pixel region selects the starting pixel and
number of pixels to be acquired relative to the assertion edge of the
horizontal (or line) enable signal from the camera. The active line
region selects the starting line and number of lines to be acquired
relative to the assertion edge of the vertical (or frame) enable signal.
•
Region of interest
—
The PCI/PXI-1422 uses a second level of active
pixel and active line regions for selecting a region of interest. Using the
region-of-interest circuitry, the board acquires only a selected subset of
the acquisition window.
