IEEE-488

Infobox connector
name=IEEE-488 / HP-IB / GPIB
type=General purpose data bus


logo=
caption=IEEE-488 stacking connectors
designer=Hewlett-Packard
design_date=late 1960s standardized in 1975
manufacturer=Hewlett-Packard
production_date=1960s to present
external=yes
hotplug=
length=
width=
height=
data_signal=Parallel data bus with handshaking
data_bit_width=8 bits
data_bandwidth=1 Mbyte/s
(later extended to 8 Mbyte/s)
data_devices=15
data_style=Parallel
physical_connector=24-pin Amphenol-designed micro ribbon
cable=20 meters max
num_pins=24 (8 data, 5 bus management, 3 handshake, 8 ground)
pinout_

pinout_caption=A female IEEE-488 connector
pin1=Data input/output bit.
pin1_name=DIO1
pin2=Data input/output bit.
pin2_name=DIO2
pin3=Data input/output bit.
pin3_name=DIO3
pin4=Data input/output bit.
pin4_name=DIO4
pin5=End-or-identify.
pin5_name=EOI
pin6=Data valid.
pin6_name=DAV
pin7=Not ready for data.
pin7_name=NRFD
pin8=Not data accepted.
pin8_name=NDAC
pin9=Interface clear.
pin9_name=IFC
pin10=Service request.
pin10_name=SRQ
pin11=Attention.
pin11_name=ATN
pin12=
pin12_name=SHIELD
pin13=Data input/output bit.
pin13_name=DIO5
pin14=Data input/output bit.
pin14_name=DIO6
pin15=Data input/output bit.
pin15_name=DIO7
pin16=Data input/output bit.
pin16_name=DIO8
pin17=Remote enable.
pin17_name=REN
pin18=(wire twisted with DAV)
pin18_name=GND
pin19=(wire twisted with NRFD)
pin19_name=GND
pin20=(wire twisted with NDAC)
pin20_name=GND
pin21=(wire twisted with IFC)
pin21_name=GND
pin22=(wire twisted with SRQ)
pin22_name=GND
pin23=(wire twisted with ATN)
pin23_name=GND
pin24=
pin24_name=Logic ground
pinout_notes=

IEEE-488 is a short-range, digital communications bus specification that has been in use for over 30 years. Originally created for use with automated test equipment, the standard is still in wide use for that purpose. IEEE-488 is also commonly known as HP-IB (Hewlett-Packard Instrument Bus) and GPIB (General Purpose Interface Bus).

IEEE-488 allows up to 15 devices to share a single 8-bit parallel electrical bus by daisy chaining connections. The slowest device participates in control and data transfer handshakes to determine the speed of the transaction. The maximum data rate is about one Mbyte/s in the original standard, and about 8 Mbyte/s with later extensions.

The IEEE-488 connector has 24 pins. The bus employs 16 signal lines — eight bi-directional used for data transfer, three for handshake, and five for bus management — plus eight ground return lines.

History

In the late 1960s, Hewlett-Packard (HP), a manufacturer of test and measurement instruments [This portion of the company was later spun-off as Agilent Technologies] , such as digital multimeters and logic analyzers, developed the "HP Interface Bus (HP-IB)" to enable easier interconnection between instruments and controllers such as computers. Early HP 9800 series [ [http://www.hpmuseum.net/display_item.php?hw=463 HP 9815 98135A HP-IB Interface] ] desktop computers used HP-IB to connect peripherals (printers, plotters, disk drives etc.).

The bus was relatively easy to implement using the technology at the time, using a simple parallel electrical bus and several individual control lines; the interface functions could be implemented in simple TTL logic [Examples: HP 59501 Power Supply Programmer, HP 59306A Relay Actuator]

Other manufacturers copied HP-IB, calling their implementation the General Purpose Interface Bus (GPIB).

In 1975 the bus was standardized by the Institute of Electrical and Electronics Engineers as the IEEE Standard Digital Interface for Programmable Instrumentation, IEEE-488-1975 (now 488.1). IEEE-488.1 formalized the mechanical, electrical, and basic protocol parameters of GPIB, but said nothing about the format of commands or data. The IEEE-488.2 standard, Codes, Formats, Protocols, and Common Commands for IEEE-488.1 (June 1987), 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 syntax, 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. A standard for device commands, SCPI, was introduced in the 1990s. Due to the late introduction, it has not been universally implemented.

National Instruments introduced a backwards-compatible extension to IEEE-488.1, originally known as HS-488. It increased the maximum data rate to 8 Mbyte/s, although the rate decreases as more devices are connected to the bus. This was incorporated into the standard in 2003, as IEEE-488.1-2003.

In addition to the IEEE, several other standards committees have adopted HP-IB. The American National Standards Institute's corresponding standard is known as ANSI Standard MC 1.1, and the International Electrotechnical Commission has its IEC Publication 625-1.

Applications

At the outset, HP-IB's designers did not specifically plan for IEEE-488 to be a standard peripheral interface for general-purpose computers. By 1977 the Commodore PET/CBM range of educational/home/personal computers connected their disk drives, printers, modems, etc, by IEEE-488 bus. All of Commodore's post-PET/CBM 8-bit machines, from the VIC-20 to the C128, utilized a proprietary 'serial IEEE-488' for peripherals, with round DIN connectors instead of the heavy-duty HP-IB plugs or a card-edge connector plugging into the motherboard (for PET computers).

Hewlett-Packard and Tektronix also used IEEE-488 as a peripheral interface to connect disk drives, tape drives, printers, plotters etc. to their workstation products and HP's HP 2100 [ [http://www.hpmuseum.net/display_item.php?hw=522 HP 2100 59310A HP-IB Interface] ] and HP 3000 [ [http://www.hpmuseum.net/display_item.php?hw=786 HP 3000 27113A CIO HP-IB Interface] ] minicomputers. While the bus speed was increased to 10 MB/s for such applications, the lack of command protocol standards limited third-party offerings and interoperability, and later, faster, open standards such as SCSI eventually superseded IEEE-488 for peripheral access.

Additionally, some of HP's advanced pocket calculators/computers of the 1980s, such as the HP-41 and HP-71B series, could work with various instrumentation via an optional HP-IB interface. The interface would connect to the calculator via an optional HP-IL module.

ignals

Signals are in TTL negative logic.

Connectors

IEEE-488

IEEE-488 uses 24-pin Amphenol-designed micro ribbon connectors (often incorrectly termed Centronics-type), most commonly in a stackable male/female combination that allows for easy daisy-chaining by stacking cables. Mechanical considerations limit the number of stacked connectors to four or less. They are held in place by screws, which come in UTS (now largely obsolete) or metric (M3.5×0.6) threads. By convention, metric screws are colored black, as the two threads do not mate. Total cable length is limited to 20 metres, although non-standard "bus extender" devices are available.

IEC-625

The IEC-625 standard prescribes the use of 25-pin D-subminiature connectors (the same are used for parallel ports on PCs). This standard did not gain significant market acceptance against the established 24-pin connector.

ee also

* LXI, the intended replacement for GPIB
* HP series 80
* Rocky Mountain BASIC

References

* IEEE Standards
** [http://standards.ieee.org/reading/ieee/std_public/description/im/488.1-1987_desc.html IEEE-488.1: Standard Digital Interface for Programmable Instrumentation]
** [http://standards.ieee.org/reading/ieee/std_public/description/im/488.2-1992_desc.html IEEE-488.2: Standard Codes, Formats, Protocols, and Common Commands for Use With IEEE-488.1]
** [http://standards.ieee.org/announcements/pr_4881upgrade.html Press release on IEEE 488.1-2003, which allows for higher speeds]

External links

* [http://www.htbasic.com/support/tutorials/hardware/gpib.html A GPIB tutorial] ( [http://www.techsoft.de/htbasic/tutgpib.htm mirror] ) from TransEra Corporation
* [http://www.l-com.com/multimedia/tips/tip_connector_stacking.pdf Explanation of connector stacking GPIB (<1Mb PDF)] from L-com Connectivity Products
* [http://www.icselect.com/ab_note.html#anchor338658 Tutorials, application notes, and sample programs] from ICS Electronics (index is HTML; content is PDF)
* [http://sourceforge.net/projects/linux-gpib/ Linux GPIB drivers and libraries]
* [http://www.ke5fx.com/gpib/readme.htm KE5FX GPIB Toolkit] , several freeware GPIB applications for Windows
* From http://www.bitsavers.org:
** [http://www.bitsavers.org/pdf/hp/hpib/TutorialDescrOfHPIB.pdf Tutorial description of HP-IB (5Mb PDF)]
** [http://www.bitsavers.org/pdf/hp/disc/09134-90032-Aug-1983.pdf Amigo documentation in Appendix A (13Mb PDF)]
** [http://www.bitsavers.org/pdf/hp/disc/5955-3442_cs80-is-pm.pdf CS/80 (5Mb PDF)]
** [http://www.bitsavers.org/pdf/hp/disc/5958-4129_SS80_Nov-1985.pdf Subset/80 (SS/80) (8Mb PDF)]
* [http://epccs.org/indexes/Software/PyWinGPIB/ Python Wrapper for NI GPIB]
* [http://gpib-tcl.sourceforge.net/ Tcl Extension for NI GPIB]
* [http://www.adlinktech.com/solution/tech_forum.php?file=measure/20071121.htm GPIB: Challenges and Potentials from ADLINK]
* [http://www.adlinktech.com/GPIB/intro.html What's ADLINK GPIB?]