National Instruments 653X - Manual (Page 131)

Glossary
© National Instruments Corporation G-5 653X User Manual
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 653X device engages in a two-way
communication with the peripheral device. The 653X 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 653X 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 653X device is ready when its ACK line asserts
(changes to) low.