EN 61508-7:2001

Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 7: Overview of techniques and measures

Provides information on the underlying concepts of risk and the relationship of risk to safety integrity (see annex A); a number of methods that will enable the safety integrity levels for the E/E/PE safety-related systems, other technology safety-related systems and external risk reduction facilities to be determined (see annexes, B, C, D and E) Intended for use by technical committees in the preparation of standards in accordance with the principles contained in IEC Guide 104 and ISO/IEC Guide 51. EN 61508 is also intended as a stand-alone standard.

Funktionale Sicherheit sicherheitsbezogener elektrischer/elektronischer/programmierbarer elektronischer Systeme - Teil 7: Anwendungshinweise über Verfahren und Maßnahmen

Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques programmables relatifs à la sécurité - Partie 7: Présentation de techniques et mesures

Fournit des informations sur les concepts sous-jacents à la notion de risque et les liens entre le risque et l'intégrité de sécurité (voir annexe A), des méthodes qui permettront d'assurer le niveau d'intégrité de sécurité des systèmes E/E/PE relatifs à la sécurité; des systèmes relatifs à la sécurité basés sur d'autres technologies et des dispositifs externes de réduction de risque (voir annexes, B, C, D et E). Destinées à être utilisées par tous les comités d'études pour la mise au point de leurs normes, conformément aux principes décrits dans le Guide CEI 104 et dans le Guide ISO/CEI 51. La EN 61508 est également prévue pour une utilisation en tant que norme autonome.

Funkcijska varnost električnih/elektronskih/programirljivih elektronskih varnostnih sistemov - 7. del: Pregled tehnik in ukrepanja (IEC 61508-7:2000)

General Information

• Status: Withdrawn
• Publication Date: 20-Dec-2001
• Withdrawal Date: 31-Jul-2004
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.240.50 - IT applications in industry
• Technical Committee: CLC/SR 65A - System aspects
• Drafting Committee: IEC/SC 65A - IEC_SC_65A
• Parallel Committee: IEC/SC 65A - IEC_SC_65A
• Current Stage: 9960 - Withdrawal effective - Withdrawal
• Start Date: 01-May-2013
• Completion Date: 01-May-2013
• Ref Project: SIST EN 61508-7:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 7: Overview of techniques and measures

Relations

• Replaced By: EN 61508-7:2010 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 7: Overview of techniques and measures
• Effective Date: 28-Jan-2023

Standards Content (Sample)

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EUROPEAN STANDARD EN 61508-7
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2001
ICS 25.040.40; 35.240.50
English version
Functional safety of electrical/electronic/programmable electronic
safety-related systems
Part 7: Overview of techniques and measures
(IEC 61508-7:2000)
Sécurité fonctionnelle des systèmes Funktionale Sicherheit
électriques/électroniques/électroniques sicherheitsbezogener elektrischer/
programmables relatifs à la sécurité elektronischer/programmierbarer
Partie 7: Présentation de techniques et elektronischer Systeme
mesures Teil 7: Anwendungshinweise über
(CEI 61508-7:2000) Verfahren und Maßnahmen
(IEC 61508-7:2000)
This European Standard was approved by CENELEC on 2001-07-03. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61508-7:2001 E
Foreword
The text of the International Standard IEC 61508-7:2000, prepared by SC 65A, System aspects, of
IEC TC 65, Industrial-process measurement and control, was submitted to the Unique Acceptance
Procedure and was approved by CENELEC as EN 61508-7 on 2001-07-03 without any modification.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2002-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-08-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A, B, C and D are informative.
Annex ZA has been added by CENELEC.
IEC 61508 is a basic safety publication covering the functional safety of electrical, electronic and
programmable electronic safety-related systems. The scope states:
"This International Standard covers those aspects to be considered when electrical/electronic/
programmable electronic systems (E/E/PESs) are used to carry out safety functions. A major objective
of this standard is to facilitate the development of application sector international standards by the
technical committees responsible for the application sector. This will allow all the relevant factors
associated with the application, to be fully taken into account and thereby meet the specific needs of
the application sector. A dual objective of this standard is to enable the development of
electrical/electronic/programmable electronic (E/E/PE) safety-related systems where application sector
international standards may not exist".
The CENELEC Report R0BT-004, ratified by 103 BT (March 2000) accepts that some IEC standards,
which today are either published or under development, are sector implementations of IEC 61508. For
example:
� IEC 61511, Functional safety - Safety instrumented systems for the process industry sector;
� IEC 62061, Safety of machinery – Functional safety of electrical, electronic and programmable
electronic control systems;
� IEC 61513, Nuclear power plants – Instrumentation and control for systems important to safety –
General requirements for systems.
The railways sector has also developed a set of European Standards (EN 50126; EN 50128 and
prEN 50129).
NOTE  EN 50126 and EN 50128 were based on earlier drafts of IEC 61508. prEN 50129 is based on the principles of the
latest version of IEC 61508.
This list does not preclude other sector implementations of IEC 61508 which could be currently under
development or published within IEC or CENELEC.
__________
- 3 - EN 61508-7:2001
Endorsement notice
The text of the International Standard IEC 61508-7:2000 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60068-1 NOTE  Harmonized as EN 60068-1:1994 (not modified).
IEC 60529 NOTE  Harmonized as EN 60523:1991 (not modified).
IEC 60812 NOTE  Harmonized as HD 485 S1:1987 (not modified).
IEC 61000-4-1 NOTE  Harmonized as EN 61000-4-1:1994 (not modified).
IEC 61000-4-5 NOTE  Harmonized as EN 61000-4-5:1995 (not modified).
IEC 61025 NOTE  Harmonized as HD 617 S1:1992 (not modified).
IEC 61069-5 NOTE  Harmonized as EN 61069-5:1995 (not modified).
IEC 61078 NOTE  Harmonized as EN 61078:1993 (not modified).
IEC 61131-3 NOTE  Harmonized as EN 61131-3:1993 (not modified).
IEC 61346-1 NOTE  Harmonized as EN 61346-1:1996 (not modified).
__________
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 61508-1 1998 Functional safety of EN 61508-1 2001
+ corr. May 1999 electrical/electronic/programmable
electronic safety-related systems
Part 1: General requirements
IEC 61508-2 2000 Part 2: Requirements for EN 61508-2 2001
electrical/electronic/programmable
electronic safety-related systems
IEC 61508-3 1998 Part 3: Software requirements EN 61508-3 2001
+ corr. April 1999
IEC 61508-4 1998 Part 4: Definitions and abbreviations EN 61508-4 2001
+ corr. April 1999
IEC 61508-5 1998 Part 5: Examples of methods for the EN 61508-5 2001
+ corr. April 1999 determination of safety integrity levels
IEC 61508-6 2000 Part 6: Guidelines on the application of EN 61508-6 2001
IEC 61508-2 and IEC 61508-3
IEC Guide 104 1997 The preparation of safety publications--
and the use of basic safety publications
and group safety publications
ISO/IEC Guide 51 1990 Guidelines for the inclusion of safety--
aspects in standards
INTERNATIONAL IEC
STANDARD
61508-7
First edition
2000-03
Functional safety of electrical/electronic/
programmable electronic safety-related systems –
Part 7:
Overview of techniques and measures
 IEC 2000 Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical,
including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail]  Web: www.iec.ch
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Commission Electrotechnique Internationale
International Electrotechnical Commission
Международная Электротехническая Комиссия
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61508-7 © IEC:2000 – 3 –
CONTENTS
Page
FOREWORD.15
INTRODUCTION.19
Clause
1 Scope.23
2 Normative references.27
3 Definitions and abbreviations .27
Annex A (informative) Overview of techniques and measures for E/E/PES: control of random
hardware failures (see IEC 61508-2).29
A.1 Electrical.29
A.1.1 Failure detection by on-line monitoring .29
A.1.2 Monitoring of relay contacts .29
A.1.3 Comparator.29
A.1.4 Majority voter .31
A.1.5 Idle current principle (de-energised to trip).31
A.2 Electronic .31
A.2.1 Tests by redundant hardware.31
A.2.2 Dynamic principles.33
A.2.3 Standard test access port and boundary-scan architecture .33
A.2.4 Fail-safe hardware .33
A.2.5 Monitored redundancy .35
A.2.6 Electrical/electronic components with automatic check.35
A.2.7 Analogue signal monitoring.35
A.2.8 De-rating .37
A.3 Processing units.37
A.3.1 Self-test by software: limited number of patterns (one-channel).37
A.3.2 Self-test by software: walking bit (one-channel) .37
A.3.3 Self-test supported by hardware (one-channel) .37
A.3.4 Coded processing (one-channel) .39
A.3.5 Reciprocal comparison by software .39
A.4 Invariable memory ranges .39
A.4.1 Word-saving multi-bit redundancy (for example ROM monitoring with
a modified Hamming code) .39
A.4.2 Modified checksum .41
A.4.3 Signature of one word (8-bit).41
A.4.4 Signature of a double word (16-bit) .41
A.4.5 Block replication (for example double ROM with hardware or
software comparison).43
A.5 Variable memory ranges .43
A.5.1 RAM test "checkerboard" or "march".43
A.5.2 RAM test "walkpath".45
A.5.3 RAM test "galpat" or "transparent galpat".45
A.5.4 RAM test "Abraham" .47
A.5.5 One-bit redundancy (for example RAM monitoring with a parity bit).47
A.5.6 RAM monitoring with a modified Hamming code, or detection of data failures
with error-detection-correction codes (EDC) .47
A.5.7 Double RAM with hardware or software comparison and read/write test .49

61508-7 © IEC:2000 – 5 –
Clause Page
A.6 I/O-units and interfaces (external communication) .49
A.6.1 Test pattern.49
A.6.2 Code protection.49
A.6.3 Multi-channel parallel output .51
A.6.4 Monitored outputs .
...