Programming instructions

Glossary
DAQ Hardware Overview Guide G-6 www.ni.com
F
FIFO A first-in first-out memory buffer; the first data stored is the first data sent
to the acceptor. FIFOs are often used on DAQ devices to temporarily store
incoming or outgoing data until that data can be retrieved or output. 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. With a larger FIFO,
longer latencies can be tolerated. In the case of analog output, a FIFO
permits faster update rates, because the waveform data can be stored on the
FIFO ahead of time. This again reduces the effect of latencies associated
with getting the data from system memory to the DAQ device.
FOUT frequency out
G
gain The factor by which a signal is amplified, sometimes expressed in decibels.
gate A signal used for gating the data acquisition.
group A collection of digital ports, combined to form a larger entity for digital
input and/or output.
H
hold mode when a circuit stores an analog voltage on a capacitor for a short period of
time
hysteresis the lag time between making a change and the effect of the change
Hz hertz
I
IBM International Business Machines
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