IEEE 488

The IEEE 488 is an 8-bit parallel multi-master interface bus specification for digital communication at short distances. IEEE 488 is made as HP-IB (Hewlett-Packard Interface Bus) and is commonly referred to as GPIB (General Purpose Interface Bus). This is the subject of different standards.

Although it was made in the late 1960s for the connection of automated testing equipment, it was also successful in the 1970s and 1980s as a peripheral bus for early microcomputers, including Commodore PET. Recent criteria replaced the IEEE 488 for computer use, but it is still useful in the field of testing equipment.


In the late 1960’s, Hewlett-Packard (HP) [1] produced a large number of automatic tests and measuring instruments, such as digital multimeters and logic analyzer. They created the HP Interface Bus (HP-IB) to provide a simpler connection between devices and controllers (computer and other instruments).

The bus is relatively easy to implement in the technology of that time, a simple parallel bus and different individual lines of control. For example, the HP 59501 Power Scheduler and the HP 59306A relay actuator are relatively simple HP-IB devices that are implemented only in TTL mode without a microprocessor.

HP is licensed by HP-IB patents at a competitive price with other manufacturers. Known as the General Purpose Bus (GPIB), it has become a de facto standard for automated and industrial control of the device. As popular GPIB, it is formally produced by various body standardization.


In 1975, IEEE described the bus as a standard digital interface for programmable instrumentation, IEEE 488; It was revised in 1978 (production of IEEE 488-1978). The standard was amended in 1987 and replaced IEEE 488.1 (IEEE 488.1-1987). These standards formally formally formalize GPIBs of mechanical, electrical and protocol parameters, but are not about the format of orders or data.

In 1987 IEEE introduced the standard, general code, format, protocol and IEEE 488.2 order. It changed in 1992. IEEE 488.2 contains a convention base and convention format as well as instructions, data structures, error logs, etc. IEEE 488.2, based on IEEE 488.1, is not replaced; The device may comply with IEEE 488.1 without regard to the IEEE 488.2 standard.

Although IEEE 488.1 and IEEE 488.2 are specified in the hardware record, there is no standard for specific device orders. Control the ingredients to run the same type of instrument, for example B. Multiple meters, depending on the manufacturer and even the model.

Then the US Air Force and Hewlett-Packard identified this problem. In 1989, HP developed its TML language, a precursor to the standard control of the programming instrument (SCPI). SCPI was introduced in 1990 as industry standard. General standard orders and certain types of instruments with associated class-specific orders are added to the SCPI. SCPI applied the IEEE 488.2 syntax, but allowed other physical behaviors (not IEEE 488.1).

The IEC was developed in parallel to the standard IEEE standards themselves of IEC 60.625-1 and IEC 60.625-2 (IEC 625), subsequently replaced by IEC 60488

National Instruments provided a compatible west extension to IEEE 488.1, originally known as HS-488. The maximum data rate was increased to 8 MB / s. However, this rate decreases because more devices are connected to the bus. This was included in the standard (IEEE 488.1-2003) despite objections from HP 2003.

In 2004, IEEE and IEC combined their respective standards in the IEEE / IEC 60488-1 “Double Logo” standard, High Performance Protocol Standard for the Digital Standard Interface for Registrable Devices – Part 1 General 60625-1 and IEC 60488-2, Part 2: Combining Codes, Formats, Protocols, and Orders for IEEE 488.2 / IEC 60625-2.


The IEEE 488 is an electrically parallel 8-bit bus. The bus uses sixteen lines of signals – eight for bi-directional data transfer, three for handshake and five for bus management – and eight return lines to the ground.

Each bus device has a unique primary address of 5 bits, between 0 and 30 (31 possible total addresses).

The standard allows up to 15 devices to share a physical bus with a total cable length of up to 20 meters. Physical topology can be linear or star-shaped. [15] Active extensions are possible longer buses, with the highest 31 devices possible on a logical bus.

The controls and functions of data transfer are logically separated. A controller can address a device as a “speaker” and one or more devices as a “listener” without participating in data transfer. It is possible that some controllers share the same bus. However, it can only be one of the “controllers”.

In the original protocol, transmissions are accepted, accepted, valid, accepted and three-wire arrangements. The maximum data rate is approximately one megabyte per second. The latest HS-488 extension simplifies the required structural requirements up to 8 MB / s. The slowest holding device refers to the speed of the bus.


The IEEE 488 standard refers to a 24-pin micro-pin connector developed by Amphenol. Microstrip connectors have D-shaped metal shells, but larger than D-subminiature connectors. These are sometimes referred to as “Centronics connectors” and are named after the 36-pin Centronics micro-pin connector for their printers.

IEEE 488
Pin out
Female IEEE 488 connector
Pin 1 DIO1 Data input/output bit.
Pin 2 DIO2 Data input/output bit.
Pin 3 DIO3 Data input/output bit.
Pin 4 DIO4 Data input/output bit.
Pin 5 EOI End-or-identify.
Pin 6 DAV Data valid.
Pin 7 NRFD Not ready for data.
Pin 8 NDAC Not data accepted.
Pin 9 IFC Interface clear.
Pin 10 SRQ Service request.
Pin 11 ATN Attention.
Pin 13 DIO5 Data input/output bit.
Pin 14 DIO6 Data input/output bit.
Pin 15 DIO7 Data input/output bit.
Pin 16 DIO8 Data input/output bit.
Pin 17 REN Remote enable.
Pin 18 GND (wire twisted with DAV)
Pin 19 GND (wire twisted with NRFD)
Pin 20 GND (wire twisted with NDAC)
Pin 21 GND (wire twisted with IFC)
Pin 22 GND (wire twisted with SRQ)
Pin 23 GND (wire twisted with ATN)
Pin 24 Logic ground

An unusual feature of the IEEE 488 connector is that they typically use a “two-head” design, with one plug in one side and one plug in the other. This makes it possible to stack connectors to facilitate daisy-chaining. Mechanical considerations limit the number of connectors stacked four or less, although a solution requiring physical media from connectors can help solve this problem.

These are held by screws, with UTS (now more obsolete) or with M3.5 × 0.6 metric thread. Previous versions of the standard proposed metric gauge for blackening to avoid confusion with unmatched UTS threads. In the 1987 revision, however, it is no longer considered necessary due to the spread of network measures

IEC 60625 standard recommends the use of 25-pin D-subminiature connectors (similar to connectors used in IBM computers for parallel interfaces). This connector is not widely accepted by the market compared to the established 24-pin connector.


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

Used as a computer interface

The developers of HP IEEE 488 have not explicitly confirmed that it is a peripheral interface for multifunction computers. focused on instrumentation. However, when HP’s first microcomputers (hard disk drives, tape drives, printers, designers, etc.) needed peripheral reactors, HP-IB was easily accessible and easily customizable for that purpose.

HP products for HP IB computers were the HP Series 80, HP 9800 Series, HP 2100 Series, and HP 3000 Series. HP computer peripherals did not use the RS-232 communication interface, which often used HP-IB, including hard disk systems such as the HP 7935. Some of the high-end calculators were 80 HP as the IEEE HP-41 series and HP-71B , An optional interface is also available through the HP-IL / HP-IB interface module.

Other manufacturers have also used GPIB on their computers, such as the Tektronix 405x line.

Commodore PET (introduced in 1977), a selection of PCs connected to peripherals over the IEEE 488 bus, but with a non-standard board connector. The 8-bit Commodore machines used a serial interface based on the IEEE 488 protocol and sold the IEEE 488 cassette with VIC-20 and Commodore 64. A C64 cassette with an IEEE 488 interface on the board, like the PET series.

After all, the standards are faster and more complete, as is the replacement of 488 peripherals with SCSI.

Comparison with other interface standards

From electrical side, IEEE 488 uses a hardware interface that can be applied to a discrete logic or a micro-controller. The hardware interface allows devices from different manufacturers to communicate with hosts only. As each device generates the required asynchronous linked signal for the bus protocol, slow and fast devices can be built into a bus. Because data transmission is relatively slow, line-serving problems such as matching barriers and circular lines are ignored. There is no need for calibration calibration between bus and equipment, which can create ground loops to create additional noise and data.

The IEEE 488 connections and cables are powerful and held screws. Even with strong and strong connectors in industrial or laboratory environments, their size and cost are handicapped for applications such as PCs.

While electrical and physical interfaces are well defined, there is no advance introduction. Devices from different manufacturers can use different controls for the same function. [28] Some aspects of the control protocol standards were standardized only in 1990 (Standard Registrable Instrument Orders (SCPI)). Implementation options (such as processing at the end of switching) can make interoperability of devices with older devices than IEEE 488.2 difficult.

Recent criteria, such as USB, FireWire and Ethernet, utilize the reduced cost of electronics on the interface to apply more complex and higher bandwidth standards. Multilateral data ports (parallel) and protected cables are more expensive than ports and cables that are compatible with serial standards such as RS-232, RS-485, USB, FireWire or Ethernet. There are several computers or peripherals (eg printers or scanners) used by IEEE 488 in the mass market.