National Instruments Image Acquisition Software User Manual
Page 56
Glossary
©
National Instruments Corporation
G-5
dynamic range
the ratio of the largest signal level a circuit can handle to the smallest signal
level it can handle (usually taken to be the noise level), normally expressed
in decibels
E
EEPROM
electrically erasable programmable read-only memory—ROM that can be
erased with an electrical signal and reprogrammed
external trigger
a voltage pulse from an external source that triggers an event such as A/D
conversion
F
field
For an interlaced video signal, a field is half the number of horizontal lines
needed to represent a frame of video; the first field of a frame contains all
the odd-numbered lines, the second field contains all of the even-numbered
lines.
FIFO
first-in first-out memory buffer—the first data stored is the first data sent to
the acceptor; FIFOs are used on IMAQ devices to temporarily store
incoming data until that data can be retrieved. For example, an analog input
FIFO stores the results of A/D conversions until the data can be retrieved
into system memory, a process that requires the servicing of interrupts and
often the programming of the DMA controller. This process can take
several milliseconds in some cases. During this time, data accumulates in
the FIFO for future retrieval.
flash ADC
an ADC whose output code is determined in a single step by a bank of
comparators and encoding logic
frame
a complete image; in interlaced formats, a frame is composed of two fields
front porch
the area of a video signal between the start of the horizontal blank and the
start of the horizontal sync
ft
feet
UM.book Page 5 Monday, July 13, 1998 9:49 AM