Glossary
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National Instruments Corporation
G-5
G
group
A collection of one, two, or four ports and an associated timing controller.
All buffered operations must be performed on groups.
H
handshaking I/O
Data-transfer mode in which the 653
X
device engages in a two-way
communication with the peripheral device. The 653
X
asserts a signal, ACK,
when it is ready for a data transfer and the peripheral device asserts a
separate signal, REQ, when it is ready for a data transfer. Data is transferred
only when both the 653
X
and the peripheral device are ready.
I
interrupt
a computer signal indicating that the CPU should suspend its current task
to service a designated activity
I/O
Input/Output—a transfer of data to/from a computer system involving
communications channels, operator interface devices, and/or data
acquisition and control interfaces
K
k
Kilo—the standard metric prefix for 1,000, or 10
3
, used with units of
measure such as volts, hertz, and meters
L
line
Individual digital bit
LSB
Least significant bit
low/high
Refers to the active, or “on” state of handshaking I/O lines. For example, if
ACK is
active low
, the 653
X
device is ready when its ACK line asserts
(changes to) low.