A bus in computer systems means a collection of unbroken signal lines that interconnect computer modules; these connections are usually made by taps on the lines. Examples of parallel bus architectures and protocols include: IBM PC bus (IBM PC/XT/AT), the Intel iSBX bus, the MicroVAX Q-bus, the Intel Multibus (IEEE-796 bus), the IEEE-488 instrumentation bus (GPIB), among many others.
The IEEE-488 bus was developed by Hewlett Packard (HP) as standard 8-bit, bidirectional, asynchronous bus (HP-IB) to enable a number of HP-IB compatible instruments to communicate with a controlling computer and with one another. In addition to measured data being sent to the host computer for storage and processing, in particular GPIB compatible instruments, the computer can be used to set the instrument’s front panel controls and to control the measurements.
GPIB bus is special in the sense that it employs unique, stackable connectors on its cables as illustrated in the figure above. Several semiconductor manufacturers supply LSI IC interfaces for the GPIB. Examples include: the three Intel i829X series ICs (the i8291 talker/listener, the i8292 GPIB controller and the i2893 bus transceiver-drive), Signetics HEF4738, the Texas Instruments TMS9914 and so forth.
A number of manufacturers of interface cards for PCs and MACs supply IEEE-288.2 compatible cards and controlling software. For instance, the National Instrument’s NP-GPIB interface board for the Mac II has some of the modern IEEE-488.2 functions and can read and write data at a sustained 800 kB/s. The National Instrument’s LabVIEW 2 software for the Mac II is a robust, graphical programming language that allows the creation of virtual instruments on the monitor whose settings can be altered by mouse and sent to actual instrument by GPIB.
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