National Instruments GPIB-PC - Manual (Page 50)

Section Three GPIB-PC Functions — Introduction
©National Instruments Corp. 3-7 GPIB-PC User Manual
IBTMO (bd,v)
IBTMO changes the time limit in which operations with the device must
complete.
IBONL (bd,v)
IBONL re-initializes the device and cancels any asynchronous I/O in
progress. All reconfigurable software parameters, such as the time limit
just discussed, are reset to their power-on values. See the discussion of
software configuration in Section Two for further information on
reconfigurable software parameters.
The last function in this group allows the computer to pass control to
another device capable of being the Controller.
IBPCT (bd)
IBPCT passes Controller-In-Charge authority to the specified device by
sending the Take Control (TCT) commands and appropriate addressing
commands.
Most GPIB-compatible instruments or other types of devices can be
programmed using the high-level functions of Groups I, II, or III. Not all
devices, however, are completely compatible with the IEEE-488
specification, nor are the combinations of bus management and/or I/O
operations contained in the high-level functions suitable for all
applications.
Some operations, such as interprocessor networks and peripheral
sharing, require additional capabilities and flexibility in controlling the
GPIB. This is achieved, in part, with low-level functions that perform
single GPIB activities, each with a limited scope or objective. Powerful
and versatile routines can be developed using these functions. Groups
IV, V, and VI consist mostly of low-level functions.