National Instruments DAQ M Series User Manual

Page 141

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Glossary

© National Instruments Corporation

G-7

NI 6236 User Manual

digital isolator

Provides voltage isolation between its input and output.

digital signal

A representation of information by a set of discrete values according to a
prescribed law. These values are represented by numbers.

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/
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.

DMA controller chip

Performs the transfers between memory and I/O devices independently of
the CPU.

driver

Software unique to the device or type of device, and includes the set of
commands the device accepts.

E

edge detection

A technique that locates an edge of an analog signal, such as the edge of a
square wave.

EEPROM

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.

encoder

A device that converts linear or rotary displacement into digital or pulse
signals. The most popular type of encoder is the optical encoder, which uses
a rotating disk with alternating opaque areas, a light source, and a
photodetector.

external trigger

A voltage pulse from an external source that causes a DAQ operation to
begin.

EXTREF

External reference signal.

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