SIST EN 61508-2:2011

Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 2: Requirements for electrical/electronic/programmable electronic safety-related systems (IEC 61508-2:2010)

1.1 This part of the IEC 61508 series
a) is intended to be used only after a thorough understanding of IEC 61508-1, which provides the overall framework for the achievement of functional safety;
b) applies to any safety-related system, as defined by IEC 61508-1, that contains at least one electrical, electronic or programmable electronic element;
c) applies to all elements within an E/E/PE safety-related system (including sensors, actuators and the operator interface);
d) specifies how to refine the E/E/PE system safety requirements specification, developed in accordance with IEC 61508-1 (comprising the E/E/PE system safety functions requirements specification and the E/E/PE system safety integrity requirements specification), into the E/E/PE system design requirements specification;
e) specifies the requirements for activities that are to be applied during the design and manufacture of the E/E/PE safety-related systems (i.e. establishes the E/E/PE system safety lifecycle model) except software, which is dealt with in IEC 61508-3 (see Figures 2 to 4). These requirements include the application of techniques and measures that are graded against the safety integrity level, for the avoidance of, and control of, faults and failures;
f) specifies the information necessary for carrying out the installation, commissioning and final safety validation of the E/E/PE safety-related systems;
g) does not apply to the operation and maintenance phase of the E/E/PE safety-related systems – this is dealt with in IEC 61508-1 – however, IEC 61508-2 does provide requirements for the preparation of information and procedures needed by the user for the operation and maintenance of the E/E/PE safety-related systems;
h) specifies requirements to be met by the organisation carrying out any modification of the E/E/PE safety-related systems;
NOTE 1 This part of IEC 61508 is mainly directed at suppliers and/or in-company engineering departments, hence the inclusion of requirements for modification.
NOTE 2 The relationship between IEC 61508-2 and IEC 61508-3 is illustrated in Figure 4.
i) does not apply for medical equipment in compliance with the IEC 60601 series.
1.2 IEC 61508-1, IEC 61508-2, IEC 61508-3 and IEC 61508-4 are basic safety publications, although this status does not apply in the context of low complexity E/E/PE safety-related systems (see 3.4.3 of IEC 61508-4). As basic safety publications, they are 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. IEC 61508-1, IEC 61508-2, IEC 61508-3 and IEC 61508-4 are also intended for use as stand-alone standards. The horizontal safety function of this international standard does not apply to medical equipment in compliance with the IEC 60601 series.
1.3 One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety publications in the preparation of its publications. In this context, the requirements, test methods or test conditions of this basic safety publication will not apply unless specifically referred to or included in the publications prepared by those technical committees.
NOTE The functional safety of an E/E/PE safety-related system can only be achieved when all related requirements are met. Therefore, it is important that all related requirements are carefully considered and adequately referenced.

Funktionale Sicherheit sicherheitsbezogener elektrischer/elektronischer/programmierbarer elektronischer Systeme - Teil 2: Anforderungen an sicherheitsbezogene elektrische/elektronische/programmierbare elektronische Systeme (IEC 61508-2:2010)

Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques programmables relatifs à la sécurité - Partie 2: Prescriptions pour les systèmes électriques/électroniques/électroniques programmables relatifs à la sécurité (CEI 61508-2:2010)

La CEI 61508-2:2010 s'applique à tout système relatif à la sécurité tel que défini dans la CEI 61508-1, qui contient au moins:
- un composant à base électrique, électronique ou électronique programmable;
- s'applique à tous les éléments d'un système E/E/PE relatif à la sécurité;
- spécifie la manière d'affiner la spécification des exigences de sécurité des systèmes E/E/PE, développée conformément à la CEI 61508-1, dans le cadre de la spécification des exigences de conception des systèmes E/E/PE;
- spécifie les exigences pour des activités qui doivent être appliquées pendant la conception et la fabrication des systèmes E/E/PE relatifs à la sécurité, à l'exception du logiciel qui est traité dans la CEI 61508-3.
Ces exigences comprennent l'application de techniques et de mesures qui sont classées en fonction du:
- niveau d'intégrité de sécurité pour éviter et maîtriser les anomalies et défaillances;
- spécifie les informations nécessaires à l'installation, à la mise en service et à la validation finale de la sécurité des systèmes E/E/PE relatifs à la sécurité;
- fournit des exigences relatives à la préparation des informations et procédures nécessaires à l'utilisateur pour l'exploitation et la maintenance des systèmes E/E/PE relatifs à la sécurité;
- spécifie les exigences auxquelles doit satisfaire l'entité qui effectue une modification des systèmes E/E/PE relatifs à la sécurité.
Cette deuxième édition annule et remplace la première édition publiée en 1998 dont elle constitue une révision technique. Elle a fait l'objet d'une révision approfondie et intègre de nombreux commentaires reçus lors des différentes phases de révision. Elle a le statut d'une publication fondamentale de sécurité conformément au Guide CEI 104.

Funkcijska varnost električnih/elektronskih/programljivih elektronskih varnostnih sistemov - 2. del: Zahteve za električne/elektronske/programljive elektronske varnostne sisteme (IEC 61508-2:2010)

1.1 Ta del serije IEC 61508
a) je namenjen uporabi šele po temeljitem razumevanju IEC 61508-1, ki zagotavlja celovit okvir;
b) velja za vse varnostne sisteme, kot jih opredeljuje IEC 61508-1, ki vsebujejo vsaj en električni, elektronski ali programirljiv elektronski element;
d) velja za vse elemente v varnostnem sistemu E/E/PE (vključno s senzorji, aktuatorji in uporabniškim vmesnikom);
d) določa, kako izboljšati specifikacijo za varnostne zahteve sistema E/E/PE, razvito v skladu z IEC 61508-1 (vključno s specifikacijo za zahteve varnostnih funkcij sistema E/E/PE in specifikacijo za zahteve varnostne celovitosti sistema E/E/PE), v okviru specifikacije za zahteve projektiranja sistema E/E/PE;e) določa zahteve za aktivnosti, potrebne med projektiranjem in proizvodnjo varnostnih sistemov E/E/PE (tj. vzpostavlja model varnostnega cikla za sistem E/E/PE), razen programske opreme, ki jo obravnava IEC 61508-3 (glej slike 2 do 4). te zahteve vključujejo uporabo tehnik in ukrepov, razvrščenih glede na stopnjo varnostne celovitosti za preprečevanje in nadzor napak in okvar;
f) določa potrebne informacije za izvedbo namestitve, začetka obratovanja in končne varnostne validacije varnostnih sistemov E/E/PE;
g) ne velja za obratovalno in vzdrževalno fazo varnostnih sistemov E/E/PE – to obravnava IEC 61508-1 – vendar pa IEC 61508-2 zagotavlja zahteve za pripravo informacij in postopkov, ki jih potrebuje uporabnik za obratovanje in vzdrževanje varnostnih sistemov E/E/PE;
h) določa zahteve, ki jih mora izpolnjevati organizacija, ki kakor koli spreminja varnostne sisteme E/E/PE;
OPOMBA 1: Ta del IEC 61508 je v glavnem namenjen dobaviteljem in/ali notranjim inženirskim oddelkom, zato so vključene zahteve za spreminjanje.
OPOMBA 2: Razmerje med IEC 61508-2 in IEC 61508-3 prikazuje slika 4.
i) ne velja za medicinsko opremo v skladu s serijo IEC 60601.
1.2 IEC 61508-1, IEC 61508-2, IEC 61508-3 in IEC 61508-4 so osnovne varnostne objave, čeprav ta status ne velja v okviru nezapletenih varnostnih sistemov E/E/PE (glej točko 3.4.3 IEC 61508-4). Kot osnovne varnostne objave so namenjeni temu, da jih uporabljajo tehnični odbori pri pripravi standardov v skladu z načeli, opredeljenimi v Vodilu IEC 104 in Vodilu ISO/IEC 51. IEC 61508-1, IEC 61508-2, IEC 61508-3 in IEC 61508-4 so namenjeni tudi uporabi kot samostojni standardi. Horizontalno varnostno delovanje tega mednarodnega standarda ne velja za medicinsko opremo v skladu s serijo IEC 60601.
1.3 Ena od odgovornosti tehničnega odbora je, če je primerno, da uporabi temeljne varnostne objave pri pripravi svojih objav. V tem okviru zahteve, preskusne metode ali preskusni pogoji te temeljne varnostne objave ne veljajo, razen če se objave, ki so jih pripravili tehnični odbori, nanje izrecno sklicujejo ali jih vključujejo.
OPOMBA: Funkcijska varnost varnostnih sistemov E/E/PE se lahko doseže le, ko so izpolnjene vse povezane zahteve. Zato je pomembno, da se vse povezane zahteve natančno obravnavajo in so primerno navedene.

General Information

• Status: Published
• Publication Date: 11-Apr-2011
• ICS: 25.040.40 - Industrial process measurement and control
• Technical Committee: MOV - Measuring equipment for electromagnetic quantities
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 06-Apr-2011
• Due Date: 11-Jun-2011
• Completion Date: 12-Apr-2011
• Ref Project: EN 61508-2:2010 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 2: Requirements for electrical/electronic/programmable electronic safety-related systems

Relations

• Replaces: SIST EN 61508-2:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 2: Requirements for electrical/electronic/programmable electronic safety-related systems
• Effective Date: 01-May-2011
• Replaces: SIST EN 61508-2:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 2: Requirements for electrical/electronic/programmable electronic safety-related systems
• Effective Date: 28-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61508-2:2011
01-maj-2011
1DGRPHãþD
SIST EN 61508-2:2007
)XQNFLMVNDYDUQRVWHOHNWULþQLKHOHNWURQVNLKSURJUDPOMLYLKHOHNWURQVNLKYDUQRVWQLK
VLVWHPRYGHO=DKWHYH]DHOHNWULþQHHOHNWURQVNHSURJUDPOMLYHHOHNWURQVNH
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Functional safety of electrical/electronic/programmable electronic safety-related systems
- Part 2: Requirements for electrical/electronic/programmable electronic safety-related
systems (IEC 61508-2:2010)
Funktionale Sicherheit sicherheitsbezogener
elektrischer/elektronischer/programmierbarer elektronischer Systeme - Teil 2:
Anforderungen an sicherheitsbezogene elektrische/elektronische/programmierbare
elektronische Systeme (IEC 61508-2:2010)
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité - Partie 2: Prescriptions pour les systèmes
électriques/électroniques/électroniques programmables relatifs à la sécurité (CEI 61508-
2:2010)
Ta slovenski standard je istoveten z: EN 61508-2:2010
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
SIST EN 61508-2:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61508-2:2011

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SIST EN 61508-2:2011

EUROPEAN STANDARD
EN 61508-2

NORME EUROPÉENNE
May 2010
EUROPÄISCHE NORM

ICS 25.040.40 Supersedes EN 61508-2:2001


English version


Functional safety of electrical/electronic/programmable electronic
safety-related systems -
Part 2: Requirements for electrical/electronic/programmable electronic
safety-related systems
(IEC 61508-2:2010)


Sécurité fonctionnelle des systèmes Funktionale Sicherheit sicherheitsbezogener
électriques/électroniques/électroniques elektrischer/elektronischer/programmierbarer
programmables relatifs à la sécurité - elektronischer Systeme -
Partie 2: Exigences pour les systèmes Teil 2: Anforderungen
électriques/électroniques/électroniques an sicherheitsbezogene
programmables relatifs à la sécurité elektrische/elektronische/programmierbare
(CEI 61508-2:2010) elektronische Systeme
(IEC 61508-2:2010)




This European Standard was approved by CENELEC on 2010-05-01. 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, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels


© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61508-2:2010 E

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SIST EN 61508-2:2011
EN 61508-2:2010 - 2 -
Foreword
The text of document 65A/549/FDIS, future edition 2 of IEC 61508-2, prepared by SC 65A, System
aspects, of IEC TC 65, Industrial-process measurement, control and automation, was submitted to the
IEC-CENELEC parallel vote and was approved by CENELEC as EN 61508-2 on 2010-05-01.
This European Standard supersedes EN 61508-2:2001.
It has the status of a basic safety publication according to IEC Guide 104.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
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) 2011-02-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2013-05-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61508-2:2010 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:
[1] IEC 61511 series NOTE  Harmonized in EN 61511 series (not modified).
[2] IEC 62061 NOTE  Harmonized as EN 62061.
[3] IEC 61800-5-2 NOTE  Harmonized as EN 61800-5-2.
[4] IEC 61508-5:2010 NOTE  Harmonized as EN 61508-5:2010 (not modified).
[5] IEC 61508-6:2010 NOTE  Harmonized as EN 61508-6:2010 (not modified).
[6] IEC 60601 series NOTE  Harmonized in EN 60601 series (partially modified).
[7] IEC 61165 NOTE  Harmonized as EN 61165.
[8] IEC 61078 NOTE  Harmonized as EN 61078.
[9] IEC 61164 NOTE  Harmonized as EN 61164.
[10] IEC 62308 NOTE  Harmonized as EN 62308.
[11] IEC 61000-6-2 NOTE  Harmonized as EN 61000-6-2.
[12] ISO 14224 NOTE  Harmonized as EN ISO 14224.
[14] ISO 9000 NOTE  Harmonized as EN ISO 9000.
[15] IEC 60300-3-2 NOTE  Harmonized as EN 60300-3-2.
__________

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SIST EN 61508-2:2011
- 3 - EN 61508-2:2010
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.

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

- - Relays with forcibly guided (mechanically EN 50205 -
linked) contacts


IEC 60947-5-1 - Low-voltage switchgear and controlgear - EN 60947-5-1 -
Part 5-1: Control circuit devices
and switching elements - Electromechanical
control circuit devices


IEC/TS 61000-1-2 - Electromagnetic compatibility (EMC) - - -
Part 1-2: General - Methodology for the
achievement of functional safety of electrical
and electronic systems including equipment
with regard to electromagnetic phenomena


IEC 61326-3-1 - Electrical equipment for measurement, EN 61326-3-1 -
control and laboratory use - EMC
requirements -
Part 3-1: Immunity requirements for safety-
related systems and for equipment intended to
perform safety-related functions (functional
safety) - General industrial applications


IEC 61508-1 2010 Functional safety of EN 61508-1 2010
electrical/electronic/programmable electronic
safety-related systems -
Part 1: General requirements


IEC 61508-3 2010 Functional safety of EN 61508-3 2010
electrical/electronic/programmable electronic
safety-related systems -
Part 3: Software requirements


IEC 61508-4 2010 Functional safety of EN 61508-4 2010
electrical/electronic/programmable electronic
safety-related systems -
Part 4: Definitions and abbreviations


IEC 61508-7 2010 Functional safety of EN 61508-7 2010
electrical/electronic/programmable electronic
safety-related systems -
Part 7: Overview of techniques and measures


IEC 61784-3 - Industrial communication networks - EN 61784-3 -
Profiles -
Part 3: Functional safety fieldbuses - General
rules and profile definitions

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SIST EN 61508-2:2011
EN 61508-2:2010 - 4 -
Publication Year Title EN/HD Year

IEC 62280-1 - Railway applications - Communication, - -
signalling and processing systems -
Part 1: Safety-related communication in
closed transmission systems


IEC 62280-2 - Railway applications - Communication, - -
signalling and processing systems -
Part 2: Safety-related communication in open
transmission systems


IEC Guide 104 1997 The preparation of safety publications - -
and the use of basic safety publications and
group safety publications


ISO/IEC Guide 51 1999 Safety aspects - Guidelines - -
for their inclusion in standards

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SIST EN 61508-2:2011
IEC 61508-2
®
Edition 2.0 2010-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Functional safety of electrical/electronic/programmable electronic safety-related
systems –
Part 2: Requirements for electrical/electronic/programmable electronic safety-
related systems

Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 2: Exigences pour les systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XD
CODE PRIX
ICS 25.040.40 ISBN 978-2-88910-525-0
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 61508-2:2011
– 2 – 61508-2 © IEC:2010
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.9
2 Normative references .12
3 Definitions and abbreviations.12
4 Conformance to this standard.12
5 Documentation .13
6 Management of functional safety .13
7 E/E/PE system safety lifecycle requirements .13
7.1 General .13
7.1.1 Objectives and requirements – general.13
7.1.2 Objectives .13
7.1.3 Requirements .13
7.2 E/E/PE system design requirements specification .17
7.2.1 Objective .17
7.2.2 General .17
7.2.3 E/E/PE system design requirements specification.18
7.3 E/E/PE system safety validation planning .19
7.3.1 Objective .19
7.3.2 Requirements .19
7.4 E/E/PE system design and development.19
7.4.1 Objective .20
7.4.2 General requirements .20
7.4.3 Synthesis of elements to achieve the required systematic capability.22
7.4.4 Hardware safety integrity architectural constraints.23
7.4.5 Requirements for quantifying the effect of random hardware failures .32
7.4.6 Requirements for the avoidance of systematic faults .34
7.4.7 Requirements for the control of systematic faults.35
7.4.8 Requirements for system behaviour on detection of a fault .35
7.4.9 Requirements for E/E/PE system implementation .36
7.4.10 Requirements for proven in use elements .38
7.4.11 Additional requirements for data communications .39
7.5 E/E/PE system integration.40
7.5.1 Objective .40
7.5.2 Requirements .40
7.6 E/E/PE system operation and maintenance procedures .41
7.6.1 Objective .41
7.6.2 Requirements .41
7.7 E/E/PE system safety validation .42
7.7.1 Objective .42
7.7.2 Requirements .42
7.8 E/E/PE system modification.43
7.8.1 Objective .43
7.8.2 Requirements .43
7.9 E/E/PE system verification .44
7.9.1 Objective .44

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SIST EN 61508-2:2011
61508-2 © IEC:2010 – 3 –
7.9.2 Requirements .44
8 Functional safety assessment.46
Annex A (normative) Techniques and measures for E/E/PE safety-related systems –
control of failures during operation.47
Annex B (normative) Techniques and measures for E/E/PE safety-related systems –
avoidance of systematic failures during the different phases of the lifecycle .62
Annex C (normative) Diagnostic coverage and safe failure fraction.71
Annex D (normative) Safety manual for compliant items .74
Annex E (normative) Special architecture requirements for integrated circuits (ICs)
with on-chip redundancy .76
Annex F (informative) Techniques and measures for ASICs – avoidance of systematic
failures .81
Bibliography.89

Figure 1 – Overall framework of the IEC 61508 series .11
Figure 2 – E/E/PE system safety lifecycle (in realisation phase).14
Figure 3 – ASIC development lifecycle (the V-Model).15
Figure 4 – Relationship between and scope of IEC 61508-2 and IEC 61508-3 .15
Figure 5 – Determination of the maximum SIL for specified architecture (E/E/PE safety-
related subsystem comprising a number of series elements, see 7.4.4.2.3) .28
Figure 6 – Determination of the maximum SIL for specified architecture (E/E/PE safety-
related subsystem comprised of two subsystems X & Y, see 7.4.4.2.4).30
Figure 7 – Architectures for data communication.40

Table 1 – Overview – realisation phase of the E/E/PE system safety lifecycle.16
Table 2 – Maximum allowable safety integrity level for a safety function carried out by
a type A safety-related element or subsystem.26
Table 3 – Maximum allowable safety integrity level for a safety function carried out by
a type B safety-related element or subsystem.27
Table A.1 – Faults or failures to be assumed when quantifying the effect of random
hardware failures or to be taken into account in the derivation of safe failure fraction .49
Table A.2 – Electrical components .51
Table A.3 – Electronic components.51
Table A.4 – Processing units .52
Table A.5 – Invariable memory ranges.52
Table A.6 – Variable memory ranges .53
Table A.7 – I/O units and interface (external communication).53
Table A.8 – Data paths (internal communication) .54
Table A.9 – Power supply .54
Table A.10 – Program sequence (watch-dog).55
Table A.11 – Clock .55
Table A.12 – Communication and mass-storage .55
Table A.13 – Sensors .56
Table A.14 – Final elements (actuators).56
Table A.15 – Techniques and measures to control systematic failures caused by
hardware design .58

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SIST EN 61508-2:2011
– 4 – 61508-2 © IEC:2010
Table A.16 – Techniques and measures to control systematic failures caused by
environmental stress or influences.59
Table A.17 – Techniques and measures to control systematic operational failures.60
Table A.18 – Effectiveness of techniques and measures to control systematic failures .61
Table B.1 – Techniques and measures to avoid mistakes during specification of
E/E/PE system design requirements (see 7.2) .63
Table B.2 – Techniques and measures to avoid introducing faults during E/E/PE
system design and development (see 7.4) .64
Table B.3 – Techniques and measures to avoid faults during E/E/PE system
integration (see 7.5).65
Table B.4 – Techniques and measures to avoid faults and failures during E/E/PE
system operation and maintenance procedures (see 7.6).66
Table B.5 – Techniques and measures to avoid faults during E/E/PE system safety
validation (see 7.7) .67
Table B.6 – Effectiveness of techniques and measures to avoid systematic failures.68
Table E.1 – Techniques and measures that increase β .79
B-IC
Table E.2 – Techniques and measures that decrease β .80
B-IC
Table F.1 – Techniques and measures to avoid introducing faults during ASIC’s design
and development – full and semi-custom digital ASICs (see 7.4.6.7).83
Table F.2 – Techniques and measures to avoid introducing faults during ASIC design
and development: User programmable ICs (FPGA/PLD/CPLD) (see 7.4.6.7) .86

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SIST EN 61508-2:2011
61508-2 © IEC:2010 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/
PROGRAMMABLE ELECTRONIC SAFETY-RELATED SYSTEMS –

Part 2: Requirements for electrical/electronic/programmable
electronic safety-related systems


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
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agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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International Standard IEC 61508-2 has been prepared by subcommittee 65A: System
aspects, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This second edition cancels and replaces the first edition published in 2000. This edition
constitutes a technical revision.
This edition has been subject to a thorough review and incorporates many comments received
at the various revision stages.
It has the status of a basic safety publication according to IEC Guide 104.

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SIST EN 61508-2:2011
– 6 – 61508-2 © IEC:2010
The text of this standard is based on the following documents:
FDIS Report on voting
65A/549/FDIS 65A/573/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2
A list of all parts of the IEC 61508 series, published under the general title Functional safety
of electrical / electronic / programmable electronic safety-related systems, can be found on
the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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SIST EN 61508-2:2011
61508-2 © IEC:2010 – 7 –
INTRODUCTION
Systems comprised of electrical and/or electronic elements have been used for many years to
perform safety functions in most application sectors. Computer-based systems (generically
referred to as programmable electronic systems) are being used in all application sectors to
perform non-safety functions and, increasingly, to perform safety functions. If computer
system technology is to be effectively and safely exploited, it is essential that those
responsible for making decisions have sufficient guidance on the safety aspects on which to
make these decisions.
This International Standard sets out a generic approach for all safety lifecycle activities for
systems comprised of electrical and/or electronic and/or programmable electronic (E/E/PE)
elements that are used to perform safety functions. This unified approach has been adopted
in order that a rational and consistent technical policy be developed for all electrically-based
safety-related systems. A major objective is to facilitate the development of product and
application sector international standards based on the IEC 61508 series.
NOTE 1 Examples of product and application sector international standards based on the IEC 61508 series are
given in the Bibliography (see references [1], [2] and [3]).
In most situations, safety is achieved by a number of systems which rely on many
technologies (for example mechanical, hydraulic, pneumatic, electrical, electronic,
programmable electronic). Any safety strategy must therefore consider not only all the
elements within an individual system (for example sensors, controlling devices and actuators)
but also all the safety-related systems making up the total combination of safety-related
systems. Therefore, while this International Standard is concerned with E/E/PE safety-related
systems, it may also provide a framework within which safety-related systems based on other
technologies may be considered.
It is recognized that there is a great variety of applications using E/E/PE safety-related
systems in a variety of application sectors and covering a wide range of complexity, hazard
and risk potentials. In any particular application, the required safety measures will be
dependent on many factors specific to
...