GPIB Bus

General Purpose Interface Bus
IEEE-488 Digital Interface for Programmable Instrumentation



[GPIB Description]
[GPIB Data Transfer Timing] [IEEE488 Interface ICs]
[HPIB Connector] [IEEE488 PinOut] [GPIB Cable Assemblies] [IEEE488 Standards] [GPIB Software]
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GPIB Description [IEEE488]

GPIB Interconnect Modules, Instrument Control Modules
GPIB System

Extracted from 'GPIB Interface Design Document'. 6-13-86, Leroy Davis





GPIB Connector Mechanical Dimensions

HPIB Connector Size, Mechanical Dimensions for HPIB Connector
GPIB Connector

IEEE-488 / ANSI Connector - Mechanical Drawing

Additional Military CID Mechanical Drawings, listed by CID number [Military Commercial Item Description].

{GPIB Index}


GPIB Bus Pin-Out Descriptions

IEEE-488 / ANSI Connector IEEE488 PinOut

24-Pin GPIB Bus PinOut [IEEE488 Pinout]
Pin # Signal Names Signal Description Pin # Signal Names Signal Description
1 DIO1 Data Input/Output Bit 1 13 DIO5 Data Input/Output Bit 5
2 DIO2 Data Input/Output Bit 2 14 DIO6 Data Input/Output Bit 6
3 DIO3 Data Input/Output Bit 3 15 DIO7 Data Input/Output Bit 7
4 DIO4 Data Input/Output Bit 4 16 DIO8 Data Input/Output Bit 8
5 EIO End-Or-Identify 17 REN Remote Enable
6 DAV Data Valid 18 Shield Ground (DAV)
7 NRFD Not Ready For Data 19 Shield Ground (NRFD)
8 NDAC Not Data Accepted 20 Shield Ground (NDAC)
9 IFC Interface Clear 21 Shield Ground (IFC)
10 SRQ Service Request 22 Shield Ground (SRQ)
11 ATN Attention 23 Shield Ground (ATN)
12 Shield Chassis Ground 24 Single GND Single Ground

{GPIB Index}


GPIB On-Line Standards and Specifications Information

ANSI/IEEE 488.1 [IEC 60625-1] IEEE Standard Digital Interface for Programmable Instrumentation
Defines the Physical and Electrical layer, and signaling protocol.

ANSI/IEEE 488.2 IEEE Codes, Formats, Protocols, and Common Commands, and Standard Commands for Programmable Instruments

IEC/IEEE 60488-2 defines communication protocols for devices connected via IEEE 488 buses and common commands and characteristics useful in a wide range of instrument applications. It includes message-handling protocols, status reporting structures, and system configuration and synchronization protocols.

HS488 High-Speed GPIB Handshake Protocol Hand shake protocol, increases bus transfers to 8MBytes/s with other HS488 devices. NDAC is not required to Handshake, The Talker outputs data with DAV, waits then outputs new data with DAV without NDAC occurring.

SCPI Standard Commands for Programmable Instruments Defines a programming language for Instruments

{HPIB Bus Index}


IEEE488 Bus Interface IC Manufacturers

Standard TTL levels (2.0v/0.8v) @ 5.2mA source / 48mA sink, Totem Pole, Open Collector and Tristate devices are used with IEEE488.
Open Collector: SRQ, NRFD, NDAC
Open Collector or Tristate: ATN, IFC, REN, EOI, DAV.





MC3446; Quadruple Bus Transceiver [IEEE Standard 488 Compliant], 16-pin DIP [Obsolete part].
MC3447; Bidirectional Instrumentation Bus [GPIB] Transceiver, 24-pin DIP [Obsolete part].

ines-Innovative Electronic Systems {CMOS GPIB interface ASIC ICs}

National Instruments {HS-488 Controller TNT4882-Controller NAT9914A, Talker/Listener}

National Semiconductor {IEEE-488 GPIB Transceiver ICs 75160 / 75162}

TI {Controller TMS9914A-Transceiver, 75xx160/161/162}

There is not much special about driving over a IEEE488 bus, the original interface ICs were just normal TTL devices.
The Octal Transceiver 74F588 was used in many applications.

Federal stock class designator: [DOD Drawing numbers]
5962-89680; Microcircuit Linear, Octal General Interface Bus Transceiver [GPIB]
5962-89681; Microcircuit Linear, Octal General Interface Bus Transceiver [GPIB], Generic number 55ALS161

IC Manufacturers Listing All other device types

IEEE-STD-488 I/O Characteristics
Single Type Digital Value
Input Voltage High: VIH = 3.4 volts typical, 2.4 volts minimum
Input Voltage Low: VIL = 0.22 volts typical, 0.4 volts maximum
Input Current High: IIH = 2.5mA maximum
Input Current Low: VIL = -3.2mA maximum
Output Voltage High: VOH = 3.4 volts typical, 2.5 volts minimum
Output Voltage Low: VOL = 0.22 volts typical, 0.5 volts maximum
Output Current High: IOH = -5.2mA maximum
Output Current Low: IOL = 48mA maximum

{GPIB Bus top}


IEEE488 Data Bus Transfer Timing


GPIB Bus Handshake Timing, and IEEE488 Data Bus Transfer Timing
GPIB Bus Handshake Timing

The IEEE488 bus operates at the speed of the slowest device, all devices have to be ready before operation begins.
Signals are active low. Data is transferred asynchronous, using the Handshake lines instead of a clock.
Only Parallel Polling does not use the Handshake, all other transfers use Hand-shaking.

HS488 High-Speed GPIB Handshake Protocol Hand shake protocol [not shown above], increases bus transfers to 8MBytes/s with other HS488 devices.
NDAC is not required to Handshake, the Talker outputs data with DAV, waits then outputs new data with DAV without NDAC occurring.

{HPIB Index}


GPIB Cable Assemblies

GPIB Connector Head and cable Assembly
GPIB Cable

Connector Type: (The connector pin-outs differ) ....
IEEE488/ANSI MC1.1; 24 pins, accepts a ribbon cable. ....
IEC 625-1, MIL-C-24308; 25 pins
Connectors are tested to MIL-STD-202E (Environmental).

IEEE488 has a Maximum cable length of 20 meters, or 2 meters per device - which ever is less.
IEEE488 devices may be connected in either a Star or Linear fashion [Device-to-Device].





GPIB Cable Manufacturers
Belden
Keithley {Single/Double shielded GPIB Cables, IEEE-488 to Centronics cable adapter}
INES Test and Measurement
Normal cable lengths; 0.5 meters, 1m, 2m, and 4 meters.

Metric threads are Black, English threads are Silver; the two will not mate together.

{IEEE488 Index}


GPIB Software


IEEE-728-1982 Recommended Practice for code and Format Conventions for IEEE Standard 488
IEC 625-2 ------
NOTE: The IEEE-488 is very easy to program, just send the device address, command, and function.
Example of HP BASIC used over IEEE-488 [programming example].

NOTE: The IEEE-488 is also know by a number of other names, which all mean the same thing.
GPI Bus; General Purpose Interface Bus
GPIB; General Purpose Interface Bus
HPIB; Hewlett-Packard Interface Bus
IEEE-488; Adopted by the Institute of Electrical and Electronic Engineers [US Standard]
IEC 60488; Adopted by the International Electrotechnical Commission [International Standard]
IEC 60625-1; Adopted by the International Electrotechnical Commission [International Standard], Old IEC version ?
Is there a difference between the US standards or names, NO; but there may be between the US and International Standard.
IEC 60625-2; No data
IEEE1174; may be an application of IEC 60625-2, which translates GPIB functionality to a serial RS232 line.

USB to GPIB translation; no defined standard.

Adlink Technology Inc. {IEEE-488 to USB GPIB Interface Controller Cable device}

Editor Note; The GPIB interface has been around for decades, my first design implementing a GPIB interface was back in 1986. However no matter how old the 488 interface is there are still thousands of fielded devices being used in industry which need to be accounted for. Many companies are not going to replace a device just because of its age, however a device would be replaced it it could no longer fulfill a function. Again power supplies, signal generators and many other types of lab equipment never really go obsolete [a BERT or Eye Scope sure will].


To be sure the IEEE488 interface is an old and dated method of commanding a piece of equipment. But again, if you only need to transfer an 8-bit command every few seconds the HPIB will continue to be found on lab gear; although not on all new gear. A quick check indicates that a high speed BERT does include a GPIB interface as an option. After all it is a cheap interface to add, and if it makes a sale.
The most common upgrade path is to use a USB to GPIB interface module. However much of the Programmable Instrumentation delivered over the last decade contained an Ethernet port instead of or in addition to the 488 bus.
The proper upgrade when buying new test equipment is to select an LXI bus [LAN eXtensions for Instrumentation], if one resides on the selected gear; otherwise there should be an Ethernet port.

So IEEE488 is a legacy interface, but easy to design a hardware interface to; but, even if you don't need communication speed, you my want processor speed ~ as the older HPIB may be claiming more processing power than a newer Ethernet interface. Than again, it all depends how the electrical portion of HPIB interacts with the cpu located in the device. By slowing down the processor, I'm referring to the cpu waiting on the slow transfer speed of the bus to finish talking to the interface.

All these comments only relate to tech labs that communicate to there devices over some interface. If you just use the front panel controls than none of this matters.

GPIB Search Trend

GPIB Search Trend History
2004 to 2011 Search History

The graph shows the declining interest in the IEEE488 interface bus over the last five years. Although no inference can be gain about the future of the bus, the graph makes clear the point that fewer people are searching for information regarding the GPIB interface.

The argument could be made that engineers are still searching for GPIB data, but not using Google, which has 70 percent of the search market. Even that as a mature subject every company already own the IEEE488 standard and does not need to look up any data. However, the GPIB standard does not give any insight into designing with the standard or the pitfalls that might be encountered.

Should the GPIB interface bus continue to be used, that would depend on the number of pieces of equipment all ready owned or being used in a particular lab. Of course usage also depends on the amount of code already written. Even though writing code for the GPIB is relatively straightforward, coding for the Ethernet bus may not be [even requiring a new software package].

A comparison could be made with the LXI bus, but the search trend for that term is basically a straight line at unity between the dates covered in the graph above [showing no useful data].

The Recommendation is to replace the GPIB interface. The connector is 4 times the size of an RJ [Ethernet] connector, and the GPIB cable is at least three times as thick as a LAN cable. Of course any interface transfers data faster than the GPIB.


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{General Purpose Interface Bus [GPIB] top}


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Modified 2/26/12
Copyright © 1998 - 2012 Al2 rights reserved Leroy Davis