National Instruments NI-VXI

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.

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

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 2n -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.