National Instruments NI PCI-1426 High-Speed Timing, Acquisition and Region of Interest (ROI)

Chapter 2 Hardware Overview

High-Speed Timing

Built from high-speed counters, the high-speed timing circuitry on the

NI1 426 can generate precise real-time control signals for your camera.

Map the output of this circuitry to a trigger line to provide accurate pulses

and pulse trains. Map these control signals to the camera control lines to

control exposure time and frame rate.

Note For your convenience, the external control for cameras that support the NI 1426 has

been preprogrammed into the camera file. You can use MAX to specify the frequency and

duration of these signals in easy-to-use units.

The NI 1426 also allows you to route the external trigger inputs 0–3 onto

the camera control lines 1–4. Use MAX to select the source for the camera

control lines. You have the option to choose either the default control signal

that is specified in the camera file or the external trigger input as the source

for the camera control lines.

Acquisition and Region of Interest (ROI)

The acquisition and ROI circuitry monitors incoming video signals and

routes the active pixels to the multiple-tap data formatter and SDRAM.

The NI 1426 can perform ROI acquisitions on all video lines and frames.

In an ROI acquisition, select an area within the acquisition window to

transfer across the PCI bus to system memory.

Configure the following parameters on the NI 1426 to control the video

acquisition window:

•Acquisition window—The NI 1426 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 NI 1426 uses a second level of active pixel

and active line regions for selecting a region of interest. Using the

region-of-interest circuitry, the device acquires only a selected subset

oft he acquisition window.

Note You can use MAX to set the acquisition window on the NI 1426.