Chapter 3
Hardware Overview
PCI/PXI-1408 and NI-IMAQ for Win95/NT
3-6
©
National Instruments Corporation
Video Acquisition
The 1408 device can acquire video signals in a variety of modes and
transfer the digitized fields or frames to PCI system memory.
Start/Stop Conditions
The 1408 device can start and stop acquisition on a variety of
conditions:
•
Software control—The 1408 device supports software control of
acquisition start and stop. In addition, you can configure the
PCI/PXI-1408 to capture a fixed number of frames. Use this
configuration to capture single frames or a sequence of frames.
•
Trigger control—You can also start and stop acquisition by
enabling external or RTSI bus trigger lines. Each of these 11 inputs
can start or stop video acquisition on a rising or falling edge. You
can use all four external triggers and up to two RTSI bus triggers
simultaneously.
•
Delayed acquisition—You can use either software or triggers to
start and stop acquisitions instantaneously or after capturing a
desired number of frames or fields. Use this feature for post-
or pre-trigger applications.
•
Frame/field selection—With an interlaced camera and the
PCI/PXI-1408 in frame mode, you can program the 1408 device
to start or stop acquisition on any odd field or any even field.
Acquisition Window Control
You can configure numerous parameters on the 1408 device to control
the video acquisition window. A brief description of each parameter
follows:
•
Horizontal sync—HSYNC is the synchronization pulse signal
produced at the beginning of each video scan line that keeps a video
monitor’s horizontal scan rate in sequence with the transmission of
each new line.
•
Vertical sync—VSYNC is the synchronization pulse generated at
the beginning of each video field that signals the video monitor
when to start a new field.
•
Pixel clock—PCLK times the sampling of pixels on a video line.
•
Composite sync—CSYNC is the signal consisting of combined
horizontal sync pulses and vertical sync pulses.