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Glossary
DIO 6533 User Manual G-4
©
National Instruments Corporation
DLL dynamic link library—a software module in Microsoft Windows
containing executable code and data that can be called or used by
Windows applications or other DLLs. Functions and data in a DLL are
loaded and linked at run time when they are referenced by a Windows
application or other DLLs.
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.
DPULL data pullup/pulldown selection
drivers software that controls a specific hardware device such as a DAQ board
E
EEPROM electrically erasable programmable read-only memory–ROM that can
be erased with an electrical signal and reprogrammed
EISA extended industry standard architecture
event the condition or state of an analog or digital signal
external trigger a voltage pulse from an external source that triggers an event such as
A/D conversion
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.