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Glossary
653X User Manual G-4 ni.com
default setting A default parameter value recorded in the driver. In many cases, the default
input of a control is a certain value (often 0) that means use the current
default setting.
device
A plug-in data acquisition board, card, or pad that can contain multiple
channels and conversion devices. Plug-in boards, PCMCIA cards, and
devices that connects to your computer parallel port, are all examples of
DAQ devices.
DGND
digital ground
digital trigger a TTL-level signal having two discrete levels—a high and a low level
DIO
Digital Input/Output
DMA Direct Memory Access—a method by which data can be transferred to or
from computer memory from or to a device or memory on the bus while the
processor does something else. DMA is the fastest method of transferring
data to or from computer memory.
DPULL A user-configurable 100 kΩ internal resistor for data lines. You can connect
the line to +5 VDC (pull up) or connect the line to ground (pull down).
F
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 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.
function a set of software instructions executed by a single line of code that may
have input and/or output parameters and returns a value when executed