Glossary
G-4
ni.com
dithering
the addition of Gaussian noise to an AI signal
DMA
direct memory access—a method by which data can be transferred to/from
computer memory from/to a device or memory on the bus while the
processor does something else. DMA is the fastest method of transferring
data to/from computer memory.
DNL
differential nonlinearity—a measure in least significant bit of the
worst-case deviation of code widths from their ideal value of 1 LSB
DO
digital output
DoC
Declaration of Conformity
DOC
Department of Communications
driver
software that controls a specific hardware device such as a DAQ device or
a GPIB interface board
E
EEPROM
electrically erasable programmable read-only memory—ROM that can be
erased with an electrical signal and reprogrammed
EXTSTROBE
external strobe signal
F
FCC
Federal Communications Commission
FIFO
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 AI 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.
