IEEE-488 is a short-range digital communications
busIn computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
specification. It was created for use with automated test equipment in the late 1960s, and is still in use for that purpose. IEEE-488 was created as
HP-IB (
Hewlett-Packard Interface Bus), and is commonly called
GPIB (
General Purpose Interface Bus). It has been the subject of several standards.
Origins
In the late 1960s,
Hewlett-Packard (HP)Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...
was manufacturing various automated test and measurement instruments, such as digital
multimeterA multimeter or a multitester, also known as a VOM , is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter may include features such as the ability to measure voltage, current and resistance...
s and
logic analyzerA logic analyzer is an electronic instrument which displays signals in a digital circuit. A logic analyzer may convert the captured data into timing diagrams, protocol decodes, state machine traces, assembly language, or correlate assembly with source-level software.Presently, there are three...
s. They developed the
HP Interface Bus (HP-IB) to enable easier interconnection between instruments and controllers (computers and other instruments).
The bus was relatively easy to implement using the technology at the time, using a simple parallel
electrical busElectric bus is a bus powered by electric energy. "Electric bus" can also refer to:* Bus , used for connecting components of a computer or communication between computers* Busbars, thick conductors acting as nodes in electrical substations...
and several individual control lines. For example, the HP 59501 Power Supply Programmer and HP 59306A Relay Actuator were both relatively simple HP-IB peripherals implemented only in TTL logic, using no microprocessor.
Other manufacturers copied HP-IB, calling their implementation the General Purpose Interface Bus (GPIB), and it became a
de facto standardA de facto standard is a custom, convention, product, or system that has achieved a dominant position by public acceptance or market forces...
for automated and industrial instrument control. As GPIB became popular, it was formalized by various
standards organizationA standards organization, standards body, standards developing organization , or standards setting organization is any organization whose primary activities are developing, coordinating, promulgating, revising, amending, reissuing, interpreting, or otherwise producing technical standards that are...
s.
Standards
In 1975, the
IEEEThe Institute of Electrical and Electronics Engineers is a non-profit professional association headquartered in New York City that is dedicated to advancing technological innovation and excellence...
standardized the bus as
Standard Digital Interface for Programmable Instrumentation,
IEEE-488 (now IEEE-488.1). It formalized the mechanical, electrical, and basic protocol parameters of GPIB, but said nothing about the format of commands or data.
In 1987, IEEE introduced
Standard Codes, Formats, Protocols, and Common Commands,
IEEE-488.2, re-designating the previous specification as
IEEE-488.1. IEEE-488.2 provided for basic syntax and format conventions, as well as device-independent commands, data structures, error protocols, and the like. IEEE-488.2 built on -488.1 without superseding it; equipment can conform to -488.1 without following -488.2.
While IEEE-488.1 defined the hardware, and IEEE-488.2 defined the protocol, there was still no standard for instrument-specific commands. Commands to control the same class of instrument (e.g., multimeters) would vary between manufacturers and even models.
The US Air Force and later Hewlett-Packard recognized this problem. In 1989, HP developed their TML language which was the forerunner to SCPI
Standard Commands for Programmable InstrumentationThe Standard Commands for Programmable Instruments defines a standard for syntax and commands to use in controlling programmable test and measurement devices.- Overview :...
. SCPI was introduced as an industry standard in 1990. SCPI added standard generic commands, and a series of instrument classes with corresponding class-specific commands. SCPI mandated the IEEE-488.2 syntax, but allowed other (non-IEEE-488.1) physical transports.
The
IECThe International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
developed their own standards in parallel with the IEEE, with
IEC-60625-1 and
IEC-60625-2, later replaced by IEC-60488.
National InstrumentsNational Instruments Corporation, or NI , is an American company with over 5,000 employees and direct operations in 41 countries. Headquartered in Austin, Texas, it is a producer of automated test equipment and virtual instrumentation software...
introduced a backward-compatible extension to IEEE-488.1, originally known as
HS-488. It increased the maximum data rate to 8
MbyteThe megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
/s, although the rate decreases as more devices are connected to the bus. This was incorporated into the standard in 2003 (IEEE-488.1-2003), over HP's objections.
In 2004, the IEEE and IEC combined their respective standards into a "Dual Logo" IEEE/IEC standard
IEC-60488-1,
Standard for Higher Performance Protocol for the Standard Digital Interface for Programmable Instrumentation - Part 1: General, replaces IEEE-488.1/IEC-60625-1, and
IEC-60488-2,
Part 2: Codes, Formats, Protocols and Common Commands, replaces IEEE-488.2/IEC-60625-2.
Characteristics
IEEE-488 is an
8-bitThe first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...
, electrically parallel bus. The bus employs sixteen signal lines — eight used for bi-directional data transfer, three for handshake, and five for bus management — plus eight ground return lines.
Every device on the bus has a unique 5-bit primary
addressIn computing, a physical address, also real address, or binary address, is the memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a particular storage cell of main memory.In a computer with virtual memory, the...
, in the range from 0 to 30 (31 total possible addresses).
The standard allows up to 15 devices to share a single physical bus of up to 20 meters total cable length. The physical topology can be linear or star (forked). Active extenders allow longer buses, with up to 31 devices theoretically possible on a logical bus.
Control and data transfer functions are logically separated; a controller can address one device as a “talker” and one or more devices as “listeners” without having to participate in the data transfer. It is possible for multiple controllers to share the same bus; but only one can be the "Controller In Charge" at a time.
In the original protocol, transfers use an interlocked, three-wire
ready–valid–accepted handshakeIn information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins...
. The maximum data rate is about one Mbyte/s. The later HS-488 extension relaxes the handshake requirements, allowing up to 8 Mbyte/s. The slowest participating device determines the speed of the bus.
IEEE-488
IEEE-488 specifies a 24-pin
AmphenolAmphenol Corporation is a major producer of electronic and fiber optic connectors, cable and interconnect systems such as Coaxial cables. Amphenol is a portmanteau from the corporation's original name, American Phenolic Corp....
-designed
micro ribbonThe micro ribbon or miniature ribbon connector is a common type of electrical connector used particularly in computer and telecommunications applications. Popularly referred to as a Centronics connector due to the widely used Centronics parallel interface, it is also known as a Telco, Amphenol,...
connector. Micro ribbon connectors have a D-shaped metal shell, but are larger than
D-subminiatureThe D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smaller connectors used on computer systems....
connectors. They are sometimes called "Centronics connectors" after the 36-pin
micro ribbonThe micro ribbon or miniature ribbon connector is a common type of electrical connector used particularly in computer and telecommunications applications. Popularly referred to as a Centronics connector due to the widely used Centronics parallel interface, it is also known as a Telco, Amphenol,...
connector
CentronicsCentronics Data Computer Corporation was a pioneering American manufacturer of computer printers, now remembered primarily for the parallel interface that bears its name.-The beginning:Centronics began as a division of Wang Laboratories...
used for their printers.
One unusual feature of IEEE-488 connectors is they commonly use a "double-headed" design, with male on one side, and female on the other (at both ends of the cable). This allows stacking connectors for easy
daisy-chainingIn electrical and electronic engineering a daisy chain is a wiring scheme in which multiple devices are wired together in sequence or in a ring...
. Mechanical considerations limit the number of stacked connectors to four or fewer, although a possible workaround involving physically supporting the connectors can expand this.
They are held in place by screws, either
UTSThe Unified Thread Standard defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada...
(now largely obsolete) or
metricThe ISO metric screw threads are the world-wide most commonly used type of general-purpose screw thread. They were one of the first international standards agreed when the International Organization for Standardization was set up in 1947.-Basic profile:...
M3.5×0.6
threadA screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...
s. By convention, metric screws are colored black, as the two threads do not mate.
IEC-60625
The IEC-60625 standard prescribes the use of 25-pin
D-subminiatureThe D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smaller connectors used on computer systems....
connectors (the same as used for the
parallel portA parallel port is a type of interface found on computers for connecting various peripherals. In computing, a parallel port is a parallel communication physical interface. It is also known as a printer port or Centronics port...
on
IBM-PCIBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...
s). This connector did not gain significant market acceptance against the established 24-pin connector.
Capabilities
| Function | Abbreviation | Description / Example |
| Source Handshake |
SH |
SH1 - complete |
| Acceptor Handshake |
AH |
AH1 - complete |
| Basic Talker |
T |
T5 - responds to serial poll; untalks when listen address received; talk only capability
T6 - untalks when listen address received; no talk only
T7 - no serial poll; untalks when listen address received; talk only capability |
| Extended Talker |
TE |
TE0 - no extended talker |
| Basic Listener |
L |
L3 - Listen only mode; unlistens if talk address received
L4 - Unlistens if talk address received |
| Extended Listener |
LE |
LE0 - no extended listener |
| Service Request |
SR |
SR0 - no service request capability
SR1 - complete |
| Remote-Local |
RL |
RL0 - no local lockout
RL1 - complete |
| Parallel Poll |
PP |
PP0 - does not respond to Parallel Poll |
| Device Clear |
DC |
DC1 - complete |
| Device Trigger |
DT |
DT0 - no device trigger capability
DT1 - complete |
| Controller |
C |
C0 - no controller function |
| |
E |
E1 - open collector drive electronics
E2 - three state drivers |
More information see Tektronix.
Use as a computer interface
HP's designers did not specifically plan for IEEE-488 to be a peripheral interface for general-purpose computers; the focus was on instrumentation. But when HP's early
microcomputerA microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
s needed an interface for peripherals (disk drives,
tape driveA tape drive is a data storage device that reads and performs digital recording, writes data on a magnetic tape. Magnetic tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and long archival stability.A tape drive provides...
s,
printersIn computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...
,
plotterA plotter is a computer printing device for printing vector graphics. In the past, plotters were widely used in applications such as computer-aided design, though they have generally been replaced with wide-format conventional printers...
s, etc.), HP-IB was readily available and easily adapted to the purpose.
HP computer products which used HP-IB included the
HP series 80The Hewlett-Packard series 80 of small scientific desktop computers was introduced in 1980, beginning with the popular HP-85 targeted at engineering and control applications. They provided the capability of the HP 9800 series desktop computers in a smaller package including storage and printer, at...
, HP 9800 series, the
HP 2100The HP 2100 was a series of minicomputers produced by Hewlett-Packard from the mid-1960s to early 1990s. The 2100 was also a specific model in this series. The series was renamed HP 1000 by the 1970s and sold as real-time computers, complementing the more complex IT-oriented HP 3000, and would be...
series, and the
HP 3000The HP 3000 series is a family of minicomputers released by Hewlett-Packard in 1973. It was designed to be the first minicomputer delivered with a full featured operating system with time-sharing. The first models were withdrawn from the market until speed improvements could be made. It ultimately...
series. Some of HP's advanced pocket calculators of the 1980s, such as the
HP-41The HP-41C series are programmable, expandable, continuous memory handheld RPN calculators made by Hewlett-Packard from 1979 to 1990. The original model, HP-41C, was the first of its kind to offer alphanumeric display capabilities...
and
HP-71BThe HP-71B was a hand-held computer or calculator programmable in BASIC, made by Hewlett-Packard from 1984 to 1989.The HP-71B was known as the "supreme" hand-held calculator/computer of choice at the time for those seeking the ultimate in hand-held devices. It was particularly popular at The...
series, also had IEEE-488 capabilities, via an optional
HP-ILThe HP-IL , was a short-range interconnection bus or network introduced by Hewlett-Packard in the early 1980s. It enabled several devices such as printers, floppy disk drives, tape readers, etc...
/HP-IB interface module.
Other manufacturers adopted GPIB for their computers as well, such as with the
Tektronix 405xThe Tektronix 405x series was a series of graphics microcomputers produced by Tektronix in the late 1970s through the early 1980s. The display technology was similar to the Tektronix 4014 terminal, using a storage tube display to avoid the need for video RAM...
line.
The
Commodore PETThe Commodore PET was a home/personal computer produced from 1977 by Commodore International...
(introduced 1977) range of personal computers connected their peripherals using the IEEE-488 bus, but with a non-standard card edge connector. Commodore's following 8-bit machines, including the
VIC-20The VIC-20 is an 8-bit home computer which was sold by Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commodore's first personal computer, the PET...
,
C-64The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...
, and
C-128The Commodore 128 home/personal computer was the last 8-bit machine commercially released by Commodore Business Machines...
, utilized an unrelated, proprietary serial interface, using a round
DIN connectorA DIN connector is a connector that was originally standardized by the , the German national standards organization. There are DIN standards for a large number of different connectors, therefore the term "DIN connector" alone does not unambiguously identify any particular type of connector unless...
, for which they retained the IEEE-488 programming interface and terminology, however.
Eventually, faster, more complete standards such as
SCSISmall Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
superseded IEEE-488 for peripheral access.
Advantages
- Simple hardware interface
- Ease of connecting multiple device to a single host
- Allows mixing of slow and fast devices
- Well-established and mature, widely supported
- Rugged connectors, held in place by screws, means cables can't easily be accidentally removed as they can with Firewire and USB
Disadvantages
- Mechanically bulky connectors and cables
- Limited speed and expansion
- Lack of command protocol standards (before SCPI)
- Implementation options (e.g. end of transmission handling) can complicate interoperability in pre-IEEE-488.2 devices
- No mandatory galvanic isolation between bus and devices
- High cost (compared to RS-232/USB/Firewire/Ethernet)
- Limited availability (again compared to RS-232/USB/Firewire/Ethernet)
See also
- Standard Commands for Programmable Instruments (SCPI)
- LAN eXtensions for Instrumentation (LXI)
- Virtual Instrument Software Architecture
Virtual Instrument Software Architecture, commonly known as VISA, is a widely used I/O API in the test and measurement industry for communicating with instruments from a PC...
(VISA)
- HP series 80
The Hewlett-Packard series 80 of small scientific desktop computers was introduced in 1980, beginning with the popular HP-85 targeted at engineering and control applications. They provided the capability of the HP 9800 series desktop computers in a smaller package including storage and printer, at...
- Rocky Mountain BASIC
Rocky Mountain BASIC is a dialect of the BASIC programming language created by Hewlett-Packard. It was especially popular for control of automatic test equipment using GPIB...