Glossary
G-6
ni.com
DIFF
Differential mode—An analog inp
u
t mode consisting of two terminals,
both of which are isolated from comp
u
ter gro
u
nd, whose difference is
meas
u
red.
differential inp
u
t
An inp
u
t circ
u
it that actively responds to the difference between two
terminals, rather than the difference between one terminal and gro
u
nd.
Often associated with balanced inp
u
t circ
u
itry, b
u
t also may be
u
sed with
an
u
nbalanced so
u
rce.
digital I/O
The capability of an instr
u
ment to generate and acq
u
ire digital signals.
Static digital I/O refers to signals where the val
u
es are set and held, or
rarely change. Dynamic digital I/O refers to digital systems where the
signals are contin
u
o
u
sly changing, often at m
u
lti-MHz clock rates.
digital signal
A representation of information by a set of discrete val
u
es according to a
prescribed law. These val
u
es are represented by n
u
mbers.
digital trigger
A TTL level signal having two discrete levels—A high and a low level.
DIO
Digital inp
u
t/o
u
tp
u
t.
DMA
Direct Memory Access—A method by which data can be transferred
to/from comp
u
ter memory from/to a device or memory on the b
u
s while the
processor does something else. DMA is the fastest method of transferring
data to/from comp
u
ter memory.
DMA controller chip
Performs the transfers between memory and I/O devices independently of
the CPU.
driver
Software
u
niq
u
e to the device or type of device, and incl
u
des the set of
commands the device accepts.
E
edge detection
A techniq
u
e that locates an edge of an analog signal, s
u
ch as the edge of a
sq
u
are wave.
EEPROM
Electrically Erasable Programmable Read-Only Memory—ROM that can
be erased with an electrical signal and reprogrammed. Some SCXI mod
u
les
contain an EEPROM to store meas
u
rement-correction coefficients.
