Glossary
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National Instruments Corporation
G-9
P
PCI
Peripheral Component Interconnect—a high-performance expansion bus
architecture originally developed by Intel to replace ISA and EISA; it is
achieving widespread acceptance as a standard for PCs and workstations
and offers a theoretical maximum transfer rate of 132 Mbytes/s
PCLK
pixel clock signal—times the sampling of pixels on a video line
picture aspect ratio
the ratio of the active pixel region to the active line region; for standard
video signals like RS-170 or CCIR, the full-size picture aspect ratio
normally is 4/3 (1.33)
pixel
picture element—the smallest division that makes up the video scan line;
for display on a computer monitor, a pixel’s optimum dimension is square
(aspect ratio of 1:1, or the width equal to the height)
pixel aspect ratio
the ratio between the physical horizontal size and the vertical size of the
region covered by the pixel; an acquired pixel should optimally be square,
thus the optimal value is 1.0, but typically it falls between 0.95 and 1.05,
depending on camera quality
pixel clock
divides the incoming horizontal video line into pixels
pixel count
the total number of pixels between two HYSNCs; the pixel count
determines the frequency of the pixel clock
protocol
the exact sequence of bits, characters, and control codes used to transfer
data between computers and peripherals through a communications
channel
pts
points
PXI
PCI eXtensions for Instrumentation. PXI is an open specification that
builds off the CompactPCI specification by adding
instrumentation-specific features.
R
RAM
random-access memory
real time
a property of an event or system in which data is processed as it is acquired
instead of being accumulated and processed at a later time
