National Instruments GPIB-PC - Manual (Page 255)

Glossary
©National Instruments Corp. G-7 GPIB-PC User Manual
SRQ or SERVICE REQUEST - The GPIB line that a device asserts to
notify the CIC that the device needs servicing.
STATUS BYTE - The data byte sent by a device when it is serially
polled.
STATUS WORD - Same as IBSTA.
SYSTEM CONTROLLER - The single designated controller that can
assert control (become CIC of the GPIB) by sending the Interface
Clear (IFC) message. Other devices can become CIC only by
having control passed to them.
T1 - A GPIB timing parameter primarily associated with the data
settling time, i.e., the time in which new bytes on the DIO lines are
allowed to settle before the DAV signal is asserted. T1 ranges from
350 nsec to above 2
µ
sec.
TAD or TALK ADDRESS - See MTA.
TALKER - A GPIB device that sends data messages to Listeners.
TCT or TAKE CONTROL - A GPIB command used to pass control of
the bus from the current Controller to an addressed Talker.
TIMEOUT - A feature of the GPIB-PC handler that prevents I/O
functions from hanging indefinitely when there is a problem on the
GPIB.
TLC - An integrated circuit that implements most of the GPIB Talker,
Listener, and Controller functions in hardware.
UNIT DESCRIPTOR - A number that is used by the handler to
temporarily identify a device or board that has been opened with the
IBFIND function. The descriptor is not related to the unit's GPIB
address.
UNL or UNLISTEN - A GPIB command that unaddresses any active
Listeners.
UNT or UNTALK - A GPIB command that unaddresses an active Talker.
WARM BOOT - See Boot.