Start conditions, Acquisition window control, Start conditions -5 acquisition window control -5 – National Instruments PCI-1428 User Manual
Page 24
Chapter 3
Hardware Overview
© National Instruments Corporation
3-5
Start Conditions
The PCI-1428 can start acquisitions in a variety of conditions:
•
Software control—The PCI-1428 supports software control of
acquisition start. You can configure the PCI-1428 to capture a fixed
number of 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—Use either software or triggers to start
acquisitions instantaneously or after skipping a specific period of time.
You can use delayed acquisition for posttrigger applications.
Acquisition Window Control
You can configure numerous parameters on the PCI-1428 to control the
video acquisition window. A brief description of each parameter follows:
•
Acquisition window—The PCI-1428 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-1428 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.
•
Scaling down—The scaling-down circuitry also controls the active
acquisition region. The PCI-1428 can scale down a frame by reducing
the number of pixels per line, the number of lines per frame, or both.
For active pixel selection, the PCI-1428 selects every pixel, every other
pixel, every fourth pixel, or every eighth pixel. For active line selection,
the PCI-1428 selects every line, every other line, every fourth line,
or every eighth line. You can use the scaling-down circuitry in
conjunction with the region-of-interest circuitry.