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Glossary
NI-VXI User Manual G-14 © National Instruments Corporation
System Controller A functional module that has arbiter, daisy-chain driver, and MXIbus
cycle timeout responsibility. Always the first device in the MXIbus
daisy-chain.
system hierarchy The tree structure of the Commander/Servant relationships of all
devices in the system at a given time. In the VXIbus structure, each
Servant has a Commander. A Commander can in turn be a Servant to
another Commander.
T
TIC Trigger Interface Chip; a proprietary National Instruments ASIC used
for direct access to the VXI trigger lines. The TIC contains a 16-bit
counter, a dual 5-bit tick timer, and a full crosspoint switch.
tick The smallest unit of time as measured by an operating system.
trigger Either TTL or ECL lines used for intermodule communication.
tristated Defines logic that can have one of three states: low, high, and
high-impedance.
TTL Transistor-Transistor Logic
U
unasserted A signal in its inactive false state.
UINT8 An 8-bit unsigned integer; may also be called an unsigned char.
UINT16 A 16-bit unsigned integer; may also be called an unsigned short or
word.
UINT32 A 32-bit unsigned integer; may also be called an unsigned long or
longword.
unsigned integer n bit pattern interpreted such that the range is from 0 to 2
n
-1.
UnSupCom Unsupported Command; a type of Word Serial Protocol error. If a
Commander sends a command or query to a Servant which the Servant
does not know how to interpret, an Unsupported Command protocol
error is generated.