National Instruments GPIB-PC - Manual (Page 52)

Section Three GPIB-PC Functions — Introduction
©National Instruments Corp. 3-9 GPIB-PC User Manual
Group IV functions can be used under the following conditions:
• Messages are broadcast to more than one device at a time.
• Messages are sent directly from one device to another, without
passing through the Controller.
• GPIB lines, such as Attention (ATN), must be turned off or on
in a particular fashion to ensure proper operation of a device.
• Devices must be polled in parallel rather than in serial.
Purpose of Board Functions
The handler software can control or communicate over the GPIB only by
manipulating a GPIB-PC interface board. Remote devices are accessed
indirectly by programming the interface board to do specific things.
Device functions are selected sequences of some basic board functions.
Board functions provide the precise control of the GPIB that is needed
for special applications.
Multiboard Capability
The handler can control or manipulate more than one interface board.
This type of handler is commonly called a multiboard handler, as
opposed to a single board handler in which one copy of the handler can
control only one board.
Figure 3.1 shows a multiboard GPIB system with board GPIB0
connected to two devices, an oscilloscope and a digital voltmeter; and
with board
GPIB1 connected to two other devices, a printer and a
plotter.
Each board is called the access board for its attached devices because
the board is used automatically by the device functions to access those
devices. More information about board and device functions is provided
in More About Device and Board Functions at the end of this section.