National Instruments Data Acquisition Device NI USB-621x User Manual page 164

Glossary
DIFF
differential input
digital I/O
digital signal
digital trigger
DIO
DMA
DMA controller chip
driver
E
edge detection
EEPROM
NI USB-621x User Manual
Differential mode—An analog input mode consisting of two terminals,
both of which are isolated from computer ground, whose difference is
measured.
An input circuit that actively responds to the difference between two
terminals, rather than the difference between one terminal and ground.
Often associated with balanced input circuitry, but also may be used with
an unbalanced source.
The capability of an instrument to generate and acquire digital signals.
Static digital I/O refers to signals where the values are set and held, or
rarely change. Dynamic digital I/O refers to digital systems where the
signals are continuously changing, often at multi-MHz clock rates.
A representation of information by a set of discrete values according to a
prescribed law. These values are represented by numbers.
A TTL level signal having two discrete levels—A high and a low level.
Digital input/output.
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.
Performs the transfers between memory and I/O devices independently of
the CPU.
Software unique to the device or type of device, and includes the set of
commands the device accepts.
A technique that locates an edge of an analog signal, such as the edge of a
square wave.
Electrically Erasable Programmable Read-Only Memory—ROM that can
be erased with an electrical signal and reprogrammed. Some SCXI modules
contain an EEPROM to store measurement-correction coefficients.
G-6 ni.com