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Abstract: This standard defines the VHSIC Hardware Description Language (VHDL). VHDL is a formal notation intended for use in all phases of the creation of electronic systems. Because it is both machine readable and human readable, it supports the development, verification, synthesis , and testing of hardware designs; the communication of hardware design data; and the maintenance, modification, and procurement of hardware. Its primary audience are the implementers of tools supporting the language and the advanced users of the language.
Keywords: Computer, computer languages, electronic systems, hardware, hardware design, VHDL
The Institute of Electrical and Electronics Engineers, Inc.
Copyright © 1994 by
The Institute of Electrical and Electronics Engineers, Inc.
Printed in the United States of America
ISBN 1-55937-376-8
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(This introduction is not a part of IEEE Std 1076-1993, IEEE Standard VHDL Language Reference Manual.)
The VHSIC Hardware Description Language (VHDL) is a formal notation intended for use in all phases of the creation of electronic systems. Because it is both machine readable and human readable, it supports the development, verification, synthesis, and testing of hardware designs; the communication of hardware design data; and the maintenance, modification, and procurement of hardware.
This document specifies IEEE Std 1076-1993, which is a revision of IEEE Std 1076-1987. The VHDL Analysis and Standardization Group (VASG) of the Computer Society of the IEEE started the development of IEEE Std 1076-1993 in June 1990. The VASG commissioned a Standardization Steering Committee to drive the standardization effort. The Steering Committee created standardization chapters in North America, Europe, and Asia-Pacific; administered the standardization guidelines of the IEEE; and staffed the volunteer positions in the various standardization chapters.
New capabilities in this version of the language include groups, shared variables, hierarchical pathnames, and a facility to include foreign models in a VHDL description. Some of the existing capabilities were extended or modified to facilitate initial and incremental creation of a design hierarchy. New shift/rotate operators were added to the language. The delay model of the language was modified to support pulse rejection. The syntactic consistency of the language was enhanced. Finally, resolutions of ambiguities and inconsistencies addressed by the Issue Screening and Analysis Committee (ISAC) of the VASG were incorporated into this revision of the language.
The VHDL 92 standardization effort consisted of five major phases: definition of VHDL 92 requirements, language design, language documentation, design validation, and balloting. The following working documents were developed during each phase of the standardization effort:
Requirements Definition: VHDL 92 Requirements
VHDL 92 Design Objectives Document
Language Design: Language Change Specifications
Language Documentation: Draft and Final Language Reference Manuals
Design Validation: Validation Reports
Ballot Response Document: Balloting
Numerous volunteers in North America, Europe, and Asia-Pacific contributed to development of VHDL 92. The Standardization Steering Committee consisted of the following:
Moe Shahdad Steering Committee Chair
Stan Krolikoski VASG Chair
Victor Berman North-American Chapter Chair
Jean Mermet European Chapter Chair
Kazuyuki Hirakawa Asia-Pacific Chapter Chair
Jacques Rouillard
Ron Waxman
John Hillawi
Andreas Hohl
The following volunteers led the various working groups of the standardization effort:
Requirements Definition Jacques Rouillard
Language Design Doug Dunlop
Language Documentation Paul Menchini
Design Validation Alex Zamfirescu
Ballot Comment Resolution Clive Charlwood
In addition, the following volunteers in the North America, European, and Asia-Pacific standardization chapters contributed to the VHDL 92 standardization effort by participating in the requirements gathering, requirements analysis, design review, documentation review, design validation, and balloting:
Mart Altmäe Eric Gutt Zainalabedin Navabi
Stephen A. Bailey Andrew Guyler Wolfgang Nebel
Daniel Barclay William A. Hanna Mary Lynne Nielsen
Jean-Michel Bergé John Hines Bill Paulsen
David Bernstein Masaharu Imai Hitomi Sato
Bill Billowitch Kenichi Kanehara Ken Scott
Dominique Borrione Krishna Kumar Sunder Singhani
Mark Brown Oz Levia Chuck Swart
Tedd Corman Serge Maginot Atushi Takahara
Alain Fonkoua Erich Marschner Cary Ussery
Rita Glover Gabe Moretti Eugenio Villar
IEEE Std 1076 is being maintained by the VASG. This group has been established to resolve issues that may arise with the language and to develop its future versions. The working documents of the VASG are available from the Computer Society Standards Secretariat, Computer Society of the IEEE, 1730 Massachusetts Ave. N.W., Washington, DC 20036, 1-202-371-0101, and also from the IEEE Standards Department, 445 Hoes Lane, Piscataway, NJ 08855, 1-800-678-IEEE. The working documents are not formally approved documents; however, they do reflect current status of the working group's direction.
As a result of the standardization activity leading to the development of IEEE Std 1076-1993, a number of working groups were formed to address areas that could not be adequately address within the scope of standardization:
Working Group Project Authorization Request (PAR) Number
Shared Variables 1076.a
Analog Extensions 1076.1
Math Package 1076.2
Synthesis Package 1076.3
Timing Methodology 1076.4
Interested parties should contact the Chair of the Design Automation Standards Committee (DASC) to participate in these activities. Development of IEEE Standard VHDL 1076-1987 IEEE Standard VHDL was developed through the work of the VASG, a working group within the Design Automation Standards Subcommittee (DASS) of the Design Automation Technical Committee (DATC) of the Computer Society of the IEEE. The work of the VASG was jointly sponsored by the DATC and by the Automatic Test Program Generation (ATPG) subcommittee of IEEE Standards Coordinating Committee 20 (SCC20). Larry Saunders was the Chair of the VASG; Ron Waxman was Chair of the DASS; Al Lowenstein was the Chair of the ATPG subcommittee. In the foreword to IEEE Std 1076-1987, Ronald Waxman (then Chair of DASS) and Larry Saunders (then Chair of VASG) acknowledged the efforts of Erich Marschner and Moe Shahdad as the principal designers of VHDL. They felt that the hard work and professionalism of the designers contributed significantly to the final result, and they wished the dedication of Marschner and Shahdad to be recognized. The creation of IEEE Std 1076-1987 began in February 1986 with the adoption of VHDL version 7.2 as the baseline language. In order to assist the voluntary standardization process of the IEEE, the Air Force Wright Aeronautical Laboratories contracted with CAD Language Systems Inc. (CLSI) to support the IEEE in the analysis of VHDL language issues, extension of the baseline language, and preparation of the draft and final definitions of the IEEE Std 1076-1987. This work was performed under contracts F33615-82-C-1716 and F33615-86-C-1050. The CLSI Project Manager for the IEEE standardization effort was Moe Shahdad, and the CLSI Technical Lead was Erich Marschner. The Air Force point of contact was John Hines, and Ron Waxman, Chair of the DASS, was the IEEE coordinator. Many individuals from many different organizations participated in the development of IEEE Std 1076-1987. In particular, the following people attended meetings of the VASG:
Dean Anderson Ching Hsiao Thomas Panfil
Kevin Anderson Paul Hubbard Steve Piatz
Larry Anderson Youm Huh Signe Post
Jim Armstrong John Jensen Jean Pouilly
Lisa Asher Bob Johnson Bob Powell
James Aylor Susan Johnston Kim Rawlinson
Jwahar Bammi George Konstantino Joel Rodriguez
Peter Barck Stan Krolikoski Cary Sandvig
Daniel Barclay Rick Lazansky Larry Saunders
Dave Barton Jean Lester Lowell Savage
Bill Beck Roger Lipsett Tim Saxe
Victor Berman Shin-ming Liu Dick Schlotfeldt
Ken Caron Al Lowenstein Peggy Schmidt
Hal Carter Bruce Lundeby Ken Scott
Marc Casad Mark Macke Moe Shahdad
Moon Jung Chung Robert Mackey Arina Shainski
Patti Cochran Erich Marschner Alec Stanculescu
Dave Coelho Paul Menchini Stephen Sutherland
Doug Dunlop Lynn Meredith Tom Tempero
Cathy Edwards Jean Mermet Jacques Tete
Thomas Elliot Ellen Mickanin Tim Thorp
Mike Endrizzi Kieu Mien Le Tuan Tran
Dave Evans Dwight Miller Stan Wagner
Deborah Frauenfelder Kent Moffat Rich Wallace
Mark Glewwe Bob Morris Karen Watkins
Prabhu Goel Jim Morris Ron Waxman
William Guzek Dan Nash Isaiah White
Jeff Haeffele John Newkirk Greg Winter
Charlie Haynes Tim Noble Craig Winton
John Hines Ghulam Nurie Dan Youngbauer
Mike Hirasuna Leslie Orlidge
Ray Hookway Ed Ott
1993 Development Record
The following persons were members of the balloting group that approved this standard for submission to the IEEE Standards Board:
William J. Abboud Akira Hasegawa William R. Paulsen
Mostapha Aboulhamid Greg Haynes Joseph Pick
David Ackley Frank Heile Robert Piloty
Guy Adam John I. Hillawi Jean Pouilly
Gordon Adshead Robert Hillman Jan Pukite
David G. Agnew John Hines Sai V. Ramamoorthy
Gus Anderson Atsunobu Hiraiwa Edward P. Ratazzi
Kenneth R. Anderson Kazuyuki Hirakawa William E. Reeves
Walter Anheier Charles Homes John P. Ries
James R. Armstrong Paul W. Horstmann Jean-Paul Rigault
Stephen A. Bailey Tamio Hoshino Fred Rose
Pete Bakowski Andy Huang Charles W. Rosenthal
Peter E. Barck Stephen C. Hughes Jacques Rouillard
Daniel S. Barclay Robert Stephen Hurley Paul Rowbottom
Graham J. Barker Monique Hyvernaud Susan Runowicz-Smith
John K. Bartholomew Kazuhiko Iijima William E. Russell, Jr.
Jean-Michel Berge Masaharu Imai Michael Ryba
Victor Berman Nagisa Ishiura Ashraf M. Salem
David B. Bernstein Michel Israel Hitomi Sato
Dinesh Bettadapur David Jakopac Larry F. Saunders
William D. Billowitch Curtis Jensen Paul Scheidt
Martin J. Bolton John E. Jensen Paul W. Schlie
Thomas H. Borgstrom Susan M. Johnston Kenneth E. Scott
Dominique Borrione Hilary J. Kahn Jorge Seidel
Mark Brown Masaru Kakimoto Francesco Sforza
Patrick K. Bryant Takashi Kambe Moe Shahdad
Walter H. Burkhardt Osamu Karatsu Ravi Shankar
Rosamaria Carbonell Jake Karrfalt Takao Shinsha
Steven Carlson Steve Kelum Isao Shirakawa
Todd P. Carpenter Khozema Khambati Lee A. Shombert
Harold W. Carter Choon B. Kim Supreet Singh
Shir-Shen Chang Eskil Kjelkerud Sunder Singhani
Clive R. Charlwood Paul Knese John Sissler
Luc Claesen Tokinori Kozawa Djahida Smati
Carl Cleaver Albert J. Kreutzer J. W. Smith
David A. Clough Stanley J. Krolikoski Dennis Soderberg
David Coelho Howard K. Lane Jay R. Southard
John Colley Kin Sing Lau Joseph J. Stanco
Frank Conforti Oz Levia Alec G. Stanculescu
Tedd Corman Paul A. Lewis Balsha R. Stanisic
Robert A. Cottrell Stephen Lim Charles Swart
Michael Crastes Alfred Lowenstein Atsushi Takahara
Brian A. Dalio Martin J. Lynch Kiyotaka Teranishi
Joseph P. Damore Don MacMillen Jacques Tete
Carlos Dangelo Serge Maginot Jose A. Torres
Mark Davoren Leon I. Maissel Carl W. Traber
Joanne DeGroat Erich Marschner S. Tracey
Antonie deJager Peter Marwedel Andy S. Tsay
Allen Dewey Gayle Matysek Jean Pierre Tual
Joseph P. Dorocak Pankaj Mayor Cary Ussery
Glenn E. Dukes George A. Mazoko Radha Vaidyanathan
Dr. Michael Dukes Robert L. McGarvey Sai K. Vedantam
Douglas D. Dunlop Sean McGoogan Kerry Veenstra
Nikil D. Dutt William S. McKinney James H. Vellenga
Thomas D. Eberle Paul J. Menchini Ranganadha R. Vemuri
Rodney Farrow Jean Mermet Venkat V. Venkataraman
Saverio Fazzari Dwight L. Miller Eugenio Villar
Jacques P. Flandrois John T. Montague Malcolm Wallace
Alain Fonkoua Gabe Moretti Xinning Wang
Barbara Fredrick David S. Morris Karen E. Watkins
Edmond Fumo Wolfgang Mueller Ronald Waxman
Benoit A. Gennart Pradipto Mukherjee J. Richard Weger
Vassilios Gerousis Jack Mullins Ron Werner
Alfred S. Gilman Shinichi Murai Gregory Whitcomb
Rita Glover Satish Nagarajan Francis Wiest
Yogesh Goel Jayant L. Nagda Paul S. Williams
Rich Goldman Hiroshi Nakamura John C. Willis
Kenji Gotoh Michael P. Nassif G. Winter
James Graves Zainalabedin Navabi James L. Wong
Arnold Greenspan Sivaram Nayudu Akihiko Yamada
Brent L. Gregory Dr. Wolfgang H. Nebel Hiroto Yasuura
Brian Griffin Richard E. Neese Ping Yeung
Paul-Marie Grojean Gordon Newell Joseph M. Youmans
Steve Grout Meyer Elias Nigri Will W. Young
Laurence T. Groves Ryo Nomura Simon Young
Andrew Guyler Nancy Nugent Tonny Yu
Jeffrey J. Haeffele John W. O'Leary Tetsuo Yutani
Claes L. Hammar Tetsuya Okabe Alex Zamfirescu
William A. Hanna Vincent Olive Guoqing Zhang
James P. Hanna Yoichi Onishi Reinhard Zippelius
John W. Harris Catherine Ozenfant
Damon C. Hart Curtis Parks
When the IEEE Standards Board approved this standard on September 15, 1993, it had the following membership:
Wallace S. Read, Chair Donald C. Loughry, Vice Chair
Andrew G. Salem, Secretary
Gilles A. Baril Jim Isaak Don T. Michael*
José A. Berrios de la Paz Ben C. Johnson Marco W. Migliaro
Clyde R. Camp Walter J. Karplus L. John Rankine
Donald C. Fleckenstein Lorraine C. Kevra Arthur K. Reilly
Jay Forster* E. G. "Al" Kiener Ronald H. Reimer
David F. Franklin Ivor N. Knight Gary S. Robinson
Ramiro Garcia Joseph L. Koepfinger* Leonard L. Tripp
Donald N. Heirman D. N. "Jim" Logothetis Donald W. Zipse
*Member Emeritus
Also included are the following nonvoting IEEE Standards Board liaisons:
Satish K. Aggarwal
James Beall
Richard B. Engelman
David E. Soffrin
Stanley I. Warshaw
Mary Lynne Nielsen
IEEE Standards Project Editor
This standard has been adopted for Federal Government use.
Details concerning its use within the Federal Government are contained in Federal Information Processing Standards Publication 172-1, VHSIC Hardware Description Language (VHDL). For a complete list of publications available in the Federal Information Processing Standards series, write to the Standards Processing Coordinator, Computer Systems Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899.