GPIB
4-2 370B User Manual
Review
The General Purpose Interface Bus, or GPIB, is a standardized digital interface
for interconnecting up to 15 self-contained instruments, controllers, and other
devices. The instruments may be units such as the 370B Curve Tracer, signal
generators, digital multimeters, or digital oscilloscopes. The ANSI
1
/ IEEE
2
488.1 - 198x standard defines two aspects of the interface: the hardware and a
basic communication protocol.
The hardware consists of a set of interface circuits in each device, along with
standard 24-conductor cabling for interconnecting the device in a system.
Sixteen of 24 wires are used for signaling: eight for addresses or data, three for
handshaking during data transfers, and five for interface management. Most data
is transferred as a series of eight-bit bytes over the eight data lines.
The basic communication protocol specifies a set of pre-defined interface
messages for system organization and housekeeping, but only indicates the basic
requirements for communicating other information such as setup commands and
measurement results. The protocol does not define the meaning or format of the
measurement results, which are termed device-dependent messages.
Meaningful messages for each instrument are specified by the instrument
manufacturer and are usually defined in the instrument manual. Tektronix has
standardized on a higher level protocol for all its GPIB instruments, called
Tektronix Codes and Formats.
A typical GPIB system will include a controller and one or more instruments,
such as the 370B Curve Tracer. Some instruments are talk-only or listen-only
devices while others can both talk and listen. The 370B does both. Linking a
controller to the 370B, and possibly other instruments, provides operation in four
major task areas:
Program development
System control
Data processing
Display and storage
These four task areas are discussed in the following paragraphs.
Program development. Program development includes writing, editing, and
debugging the programs needed to control the instruments in the system.
1
ANSI - American National Standards Institute
2
IEEE - Institute of Electric and Electronic Engineers. Inc.
Hardware
Communication Protocol
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