Chapter 2
Hardware Overview
2-4
ni.com
read and write cycles, both single and multiple. In slave mode, the NI 1411
is a medium-speed decoder that accepts both memory and configuration
cycles. The interface logic ensures that the NI 1411 can meet PCI loading,
driving, and timing requirements.
Board Configuration NVRAM
The NI 1411 contains onboard nonvolatile RAM (NVRAM) that
configures all registers on power-up.
Start Conditions
The NI 1411 can start acquisitions in a variety of conditions:
•
Software control
—The NI 1411 supports software control of
acquisition start. You can configure the NI 1411 to capture a fixed
number of fields or frames. Use this configuration for capturing a
single frame or a sequence of frames.
•
Trigger control
—You can start an acquisition by enabling the
external trigger line. This input can start a video acquisition on a rising
or falling edge.
•
Frame/field selection
—With an interlaced camera and the NI 1411 in
frame mode, you can program the NI 1411 to start an acquisition on
any odd or even field.
Acquisition Window Control
You can configure numerous parameters on the NI 1411 to control the
video acquisition window. A brief description of each parameter follows:
•
Acquisition window
—The NI 1411 allows you 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 NI 1411 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 into onboard or system memory. However, when
you enable the region-of-interest circuitry, the board acquires only a
selected subset of the image frame.
