Tektronix 2714, Programmer'S Manual

Page: 277 / 308

2714 & 2715 Programmer Manual
B–1
Appendix B: GPIB System Concepts
The General Purpose Interface Bus (GPIB) is a digital control bus that allows
efficient communications between self-contained instruments or devices
connected in an instrumentation system. The GPIB is an interface system
independent of the stimulus or measurement functions incorporated in any
instrument.
Instruments or devices designed to operate on the GPIB digital control bus must
be developed according to the specifications contained in IEEE Std 488.1-1978,
IEEE Standard Digital Interface for Programmable Instrumentation. The
IEEE 488.1 digital interface is commonly known as the General Purpose
Interface Bus (GPIB). This section discusses the basic concepts of the GPIB. For
complete specifications, refer to the IEEE Std 488.1-1978 standard, published by
the Institute of Electrical and Electronics Engineers, Inc.
The GPIB has four elements: mechanical, electrical, functional, and operational.
Of these four, only the last is device-dependent. Operational elements state the
way in which each instrument reacts to a signal on the bus.
Mechanical Elements
The IEEE Std 488.1 defines the GPIB connector and cable assembly as the
mechanical elements of the instrumentation system. Standardizing the connector
and cable assembly ensures that GPIB-compatible instruments can be physically
linked together with complete pin compatibility. The connector has 24 pins:
sixteen active signal lines, seven interlaced grounds, and 1 shield connection.
Standard connector pin arrangement and nomenclature for the digital control
signals are illustrated in Figure B–1.
The cable that attaches to the GPIB connector must be no longer than 20 meters
with no more than fifteen peripheral devices (including a GPIB controller)
connected at one time. The interconnecting cable assembly, which is offered as
an optional accessory to the spectrum analyzer, is provided with a plug and
receptacle connector type at each end of the cable to allow either a star or linear
bus structure. Contact your local Tektronix Field Office or representative for
cable ordering information. Connectors may be rigidly stacked, using standard
counter-bored captive screws.