Section Three GPIB-PC Functions — Introduction©National Instruments Corp. 3-9 GPIB-PC User ManualGroup 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, withoutpassing through the Controller.• GPIB lines, such as Attention (ATN), must be turned off or onin a particular fashion to ensure proper operation of a device.• Devices must be polled in parallel rather than in serial.Purpose of Board FunctionsThe handler software can control or communicate over the GPIB only bymanipulating a GPIB-PC interface board. Remote devices are accessedindirectly 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 neededfor special applications.Multiboard CapabilityThe handler can control or manipulate more than one interface board.This type of handler is commonly called a multiboard handler, asopposed to a single board handler in which one copy of the handler cancontrol only one board.Figure 3.1 shows a multiboard GPIB system with board GPIB0connected to two devices, an oscilloscope and a digital voltmeter; andwith board GPIB1 connected to two other devices, a printer and aplotter.Each board is called the access board for its attached devices becausethe board is used automatically by the device functions to access thosedevices. More information about board and device functions is providedin More About Device and Board Functions at the end of this section.
