EN IEC 61784-3:2021

SLOVENSKI STANDARD
01-julij-2021
Nadomešča:
SIST EN 61784-3:2017
SIST EN 61784-3:2017/A1:2018
Industrijska komunikacijska omrežja - Profili - 3. del: Funkciijska varnost
procesnih vodil - Splošna pravila in definicije profilov (IEC 61784-3:2021)
Industrial communication networks - Profiles - Part 3: Functional safety fieldbuses -
General rules and profile definitions (IEC 61784-3:2021)
Industrielle Kommunikationsnetze - Profile - Teil 3: Funktional sichere Übertragung bei
Feldbussen - Allgemeine Regeln und Festlegungen für Profile (IEC 61784-3:2021)
Réseaux de communication industriels - Profils - Partie 3: Bus de terrain de sécurité
fonctionnelle - Règles générales et définitions de profils (IEC 61784-3:2021)
Ta slovenski standard je istoveten z: EN IEC 61784-3:2021
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.100.05 Večslojne uporabniške Multilayer applications
rešitve
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61784-3

NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2021
ICS 25.040.40; 35.100.05 Supersedes EN 61784-3:2016 and all of its amendments
and corrigenda (if any)
English Version
Industrial communication networks - Profiles - Part 3: Functional
safety fieldbuses - General rules and profile definitions
(IEC 61784-3:2021)
Réseaux de communication industriels - Profils - Partie 3: Industrielle Kommunikationsnetze - Profile - Teil 3:
Bus de terrain de sécurité fonctionnelle - Règles générales Funktional sichere Übertragung bei Feldbussen -
et définitions de profils Allgemeine Regeln und Festlegungen für Profile
(IEC 61784-3:2021) (IEC 61784-3:2021)
This European Standard was approved by CENELEC on 2021-03-23. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61784-3:2021 E

European foreword
The text of document 65C/1067/FDIS, future edition 4 of IEC 61784-3, prepared by SC 65C "Industrial
networks" of IEC/TC 65 "Industrial-process measurement, control and automation" was submitted to
the IEC-CENELEC parallel vote and approved by CENELEC as EN IEC 61784-3:2021.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2021-12-23
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2024-03-23
document have to be withdrawn
This document supersedes EN 61784-3:2016 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Endorsement notice
The text of the International Standard IEC 61784-3:2021 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 61000-1-2 NOTE Harmonized as EN 61000-1-2
IEC 61131-6 NOTE Harmonized as EN 61131-6
IEC 61158-2:2014 NOTE Harmonized as EN 61158-2:2014 (not modified)
IEC 61158-3-1 NOTE Harmonized as EN 61158-3-1
IEC 61158-3-2 NOTE Harmonized as EN 61158-3-2
IEC 61158-3-3 NOTE Harmonized as EN 61158-3-3
IEC 61158-3-8 NOTE Harmonized as EN 61158-3-8
IEC 61158-3-12 NOTE Harmonized as EN IEC 61158-3-12
IEC 61158-3-13 NOTE Harmonized as EN 61158-3-13
IEC 61158-3-14 NOTE Harmonized as EN 61158-3-14
IEC 61158-3-18 NOTE Harmonized as EN 61158-3-18
IEC 61158-3-19 NOTE Harmonized as EN IEC 61158-3-19
IEC 61158-3-21 NOTE Harmonized as EN IEC 61158-3-21
IEC 61158-3-22 NOTE Harmonized as EN 61158-3-22
IEC 61158-4-1 NOTE Harmonized as EN 61158-4-1
IEC 61158-4-2 NOTE Harmonized as EN IEC 61158-4-2
IEC 61158-4-3 NOTE Harmonized as EN IEC 61158-4-3
IEC 61158-4-8 NOTE Harmonized as EN 61158-4-8
IEC 61158-4-12 NOTE Harmonized as EN IEC 61158-4-12
IEC 61158-4-13 NOTE Harmonized as EN 61158-4-13
IEC 61158-4-14 NOTE Harmonized as EN 61158-4-14
IEC 61158-4-18 NOTE Harmonized as EN 61158-4-18
IEC 61158-4-19 NOTE Harmonized as EN IEC 61158-4-19
IEC 61158-4-21 NOTE Harmonized as EN IEC 61158-4-21
IEC 61158-4-22 NOTE Harmonized as EN 61158-4-22
IEC 61158-5-2 NOTE Harmonized as EN IEC 61158-5-2
IEC 61158-5-3 NOTE Harmonized as EN 61158-5-3
IEC 61158-5-5 NOTE Harmonized as EN 61158-5-5
IEC 61158-5-8 NOTE Harmonized as EN 61158-5-8
IEC 61158-5-9 NOTE Harmonized as EN 61158-5-9
IEC 61158-5-10 NOTE Harmonized as EN IEC 61158-5-10
IEC 61158-5-12 NOTE Harmonized as EN IEC 61158-5-12
IEC 61158-5-13 NOTE Harmonized as EN 61158-5-13
IEC 61158-5-14 NOTE Harmonized as EN 61158-5-14
IEC 61158-5-18 NOTE Harmonized as EN 61158-5-18
IEC 61158-5-19 NOTE Harmonized as EN IEC 61158-5-19
IEC 61158-5-21 NOTE Harmonized as EN IEC 61158-5-21
IEC 61158-5-22 NOTE Harmonized as EN 61158-5-22
IEC 61158-5-23 NOTE Harmonized as EN IEC 61158-5-23
IEC 61158-6-2 NOTE Harmonized as EN IEC 61158-6-2
IEC 61158-6-3 NOTE Harmonized as EN IEC 61158-6-3
IEC 61158-6-5 NOTE Harmonized as EN 61158-6-5
IEC 61158-6-8 NOTE Harmonized as EN 61158-6-8
IEC 61158-6-9 NOTE Harmonized as EN 61158-6-9
IEC 61158-6-10 NOTE Harmonized as EN IEC 61158-6-10
IEC 61158-6-12 NOTE Harmonized as EN IEC 61158-6-12
IEC 61158-6-13 NOTE Harmonized as EN 61158-6-13
IEC 61158-6-14 NOTE Harmonized as EN 61158-6-14
IEC 61158-6-18 NOTE Harmonized as EN 61158-6-18
IEC 61158-6-19 NOTE Harmonized as EN IEC 61158-6-19
IEC 61158-6-21 NOTE Harmonized as EN IEC 61158-6-21
IEC 61158-6-22 NOTE Harmonized as EN 61158-6-22
IEC 61158-6-23 NOTE Harmonized as EN IEC 61158-6-23
IEC 61496 (series) NOTE Harmonized as EN IEC 61496 (series)
IEC 61496-1 NOTE Harmonized as EN IEC 61496-1
IEC 61508-4:2010 NOTE Harmonized as EN 61508-4:2010 (not modified)
IEC 61508-5:2010 NOTE Harmonized as EN 61508-5:2010 (not modified)
IEC 61511 (series) NOTE Harmonized as EN 61511 (series)
IEC 61800-5-2 NOTE Harmonized as EN 61800-5-2
IEC 62061:2005 NOTE Harmonized as EN 62061:2005 (not modified)
IEC 62061:2005/A1:2012 NOTE Harmonized as EN 62061:2005/A1:2013 (not modified)
IEC 62061:2005/A2:2015 NOTE Harmonized as EN 62061:2005/A2:2015 (not modified)
ISO 10218-1 NOTE Harmonized as EN ISO 10218-1
ISO 13849 (series) NOTE Harmonized as EN ISO 13849 (series)
ISO 13849-1:2015 NOTE Harmonized as EN ISO 13849-1:2015 (not modified)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 61000-6-7 - Electromagnetic compatibility (EMC) - Part EN 61000-6-7 -
6-7: Generic standards - Immunity
requirements for equipment intended to
perform functions in a safety-related system
(functional safety) in industrial locations
IEC 61010-2-201 - Safety requirements for electrical equipment EN IEC 61010-2-201 -
for measurement, control, and laboratory
use - Part 2-201: Particular requirements for
control equipment
IEC 61158 series Industrial communication networks - EN IEC 61158 series
Fieldbus specifications
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 61326-3-2 - Electrical equipment for measurement, EN IEC 61326-3-2 -
control and laboratory use - EMC
requirements - Part 3-2: Immunity
requirements for safety-related systems and
for equipment intended to perform safety-
related functions (functional safety) -
Industrial applications with specified
electromagnetic environment
IEC 61508 series Functional safety of electrical EN 61508 series
/electronic/programmable electronic safety-
related systems
Publication Year Title EN/HD Year
IEC 61508-1 2010 Functional safety of electrical EN 61508-1 2010
/electronic/programmable electronic safety-
related systems - Part 1: General
requirements
IEC 61508-2 - Functional safety of electrical/ EN 61508-2 -
electronic/programmable electronic safety-
related systems - Part 2: Requirements for
electrical/electronic/programmable
electronic safety-related systems
IEC 61784-1 - Industrial communication networks - Profiles EN IEC 61784-1 -
Part 1: Fieldbus profiles
IEC 61784-2 - Industrial communication networks - Profiles EN IEC 61784-2 -
- Part 2: Additional fieldbus profiles for real-
time networks based on ISO/IEC/IEEE
8802-3
IEC 61784-3 series Industrial communication networks - Profiles - -
- Part 3: Functional safety fieldbuses
IEC 61784-3-1 - Industrial communication networks - Profiles EN 61784-3-1 -
- Part 3-1: Functional safety fieldbuses -
Additional specifications for CPF 1
IEC 61784-3-2 - Industrial communication networks - Profiles EN 61784-3-2 -
- Part 3-2: Functional safety fieldbuses -
Additional specifications for CPF 2
IEC 61784-3-3 - Industrial communication networks - Profiles EN 61784-3-3 -
- Part 3-3: Functional safety fieldbuses -
Additional specifications for CPF 3
IEC 61784-3-6 - Industrial communication networks - Profiles EN 61784-3-6 -
- Part 3-6: Functional safety fieldbuses -
Additional specifications for CPF 6
IEC 61784-3-8 - Industrial communication networks - Profiles EN 61784-3-8 -
- Part 3-8: Functional safety fieldbuses -
Additional specifications for CPF 8
IEC 61784-3-12 - Industrial communication networks - Profiles EN 61784-3-12 -
- Part 3-12: Functional safety fieldbuses -
Additional specifications for CPF 12
IEC 61784-3-13 - Industrial communication networks - Profiles EN 61784-3-13 -
- Part 3-13: Functional safety fieldbuses -
Additional specifications for CPF 13
IEC 61784-3-14 - Industrial communication networks - Profiles EN 61784-3-14 -
- Part 3-14: Functional safety fieldbuses -
Additional specifications for CPF 14
Publication Year Title EN/HD Year
IEC 61784-3-17 - Industrial communication networks - Profiles EN 61784-3-17 -
- Part 3-17: Functional safety fieldbuses -
Additional specifications for CPF 17
IEC 61784-3-18 - Industrial communication networks - Profiles EN 61784-3-18 -
- Part 3-18: Functional safety fieldbuses -
Additional specifications for CPF 18
IEC 61784-5 series Industrial communication networks - Profiles EN 61784-5 series
- Part 5: Installation of fieldbuses
IEC 61918 2018 Industrial communication networks - EN IEC 61918 2018
Installation of communication networks in
industrial premises
- - EN IEC 61918:2018 2019
/AC:2019-03
IEC 62443 series Security for industrial process measurement - -
and control - Network and system security

IEC 61784-3 ®
Edition 4.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial communication networks – Profiles –

Part 3: Functional safety fieldbuses – General rules and profile definitions

Réseaux de communication industriels – Profils –

Partie 3: Bus de terrain de sécurité fonctionnelle – Règles générales et

définitions de profils
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40; 35.100.05 ISBN 978-2-8322-9268-6

– 2 – IEC 61784-3:2021 © IEC 2021
CONTENTS
FOREWORD . 7
0 Introduction . 9
0.1 General . 9
0.2 Use of extended assessment methods in Edition 4 . 11
0.3 Patent declaration . 11
1 Scope . 12
2 Normative references . 12
3 Terms, definitions, symbols, abbreviated terms and conventions . 14
3.1 Terms and definitions . 14
3.2 Symbols and abbreviated terms . 21
3.2.1 Abbreviated terms . 21
3.2.2 Symbols . 22
4 Conformance . 22
5 Basics of safety-related fieldbus systems . 23
5.1 Safety function decomposition . 23
5.2 Communication system . 23
5.2.1 General . 23
5.2.2 IEC 61158 fieldbuses . 24
5.2.3 Communication channel types . 24
5.2.4 Safety function response time . 25
5.3 Communication errors . 25
5.3.1 General . 25
5.3.2 Corruption . 25
5.3.3 Unintended repetition . 26
5.3.4 Incorrect sequence . 26
5.3.5 Loss . 26
5.3.6 Unacceptable delay . 26
5.3.7 Insertion . 26
5.3.8 Masquerade. 26
5.3.9 Addressing . 26
5.4 Deterministic remedial measures . 27
5.4.1 General . 27
5.4.2 Sequence number. 27
5.4.3 Time stamp . 27
5.4.4 Time expectation . 27
5.4.5 Connection authentication . 27
5.4.6 Feedback message . 27
5.4.7 Data integrity assurance . 27
5.4.8 Redundancy with cross checking . 28
5.4.9 Different data integrity assurance systems . 28
5.5 Typical relationships between errors and safety measures . 28
5.6 Communication phases . 29
5.7 FSCP implementation aspects . 30
5.8 Models for estimation of the total residual error rate . 30
5.8.1 Applicability . 30
5.8.2 General models for black channel communications . 31

IEC 61784-3:2021 © IEC 2021 – 3 –
5.8.3 Identification of generic safety properties . 31
5.8.4 Assumptions for residual error rate calculations . 32
5.8.5 Residual error rates . 33
5.8.6 Data integrity . 35
5.8.7 Authenticity. 36
5.8.8 Timeliness . 38
5.8.9 Masquerade. 41
5.8.10 Calculation of the total residual error rates . 41
5.8.11 Total residual error rate and SIL . 43
5.8.12 Configuration and parameterization for an FSCP . 43
5.9 Relationship between functional safety and security . 45
5.10 Boundary conditions and constraints . 45
5.10.1 Electrical safety . 45
5.10.2 Electromagnetic compatibility (EMC) . 46
5.11 Installation guidelines . 46
5.12 Safety manual . 46
5.13 Safety policy . 46
6 Communication Profile Family 1 (FOUNDATION™ Fieldbus) – Profiles for functional
safety . 47
7 Communication Profile Family 2 (CIP™) and Family 16 (SERCOS®) – Profiles for
functional safety . 47
8 Communication Profile Family 3 (PROFIBUS™, PROFINET™) – Profiles for
functional safety . 48
9 Communication Profile Family 6 (INTERBUS®) – Profiles for functional safety . 48
10 Communication Profile Family 8 (CC-Link™) – Profiles for functional safety . 49
10.1 Functional Safety Communication Profile 8/1 . 49
10.2 Functional Safety Communication Profile 8/2 . 49
11 Communication Profile Family 12 (EtherCAT™) – Profiles for functional safety. 49
12 Communication Profile Family 13 (Ethernet POWERLINK™) – Profiles for

functional safety . 50
13 Communication Profile Family 14 (EPA®) – Profiles for functional safety . 50
14 Communication Profile Family 17 (RAPIEnet™) – Profiles for functional safety. 50
15 Communication Profile Family 18 (SafetyNET p™ Fieldbus) – Profiles for
functional safety . 51
Annex A (informative) Example functional safety communication models . 52
A.1 General . 52
A.2 Model A (single message, channel and FAL, redundant SCLs) . 52
A.3 Model B (full redundancy) . 52
A.4 Model C (redundant messages, FALs and SCLs, single channel) . 53
A.5 Model D (redundant messages and SCLs, single channel and FAL) . 53
Annex B (normative) Safety communication channel model using CRC-based error
checking . 55
B.1 Overview. 55
B.2 Channel model for calculations . 55
B.3 Bit error probability Pe . 56
B.4 Cyclic redundancy checking . 57
B.4.1 General . 57
B.4.2 Requirements for methods to calculate R . 57
CRC
Annex C (informative) Structure of technology-specific parts. 59

– 4 – IEC 61784-3:2021 © IEC 2021
Annex D (informative) Assessment guideline . 62
D.1 Overview. 62
D.2 Channel types . 62
D.2.1 General . 62
D.2.2 Black channel . 62
D.2.3 White channel . 62
D.3 Data integrity considerations for white channel approaches . 63
D.3.1 General . 63
D.3.2 Models B and C . 63
D.3.3 Models A and D . 64
D.4 Verification of safety measures . 64
D.4.1 General . 64
D.4.2 Implementation . 65
D.4.3 Default safety action . 65
D.4.4 Safe state . 65
D.4.5 Transmission errors . 65
D.4.6 Safety reaction and response times . 65
D.4.7 Combination of measures . 65
D.4.8 Absence of interference . 66
D.4.9 Additional fault causes (white channel) . 66
D.4.10 Reference test beds and operational conditions . 66
D.4.11 Conformance tester . 66
Annex E (informative) Examples of implicit vs. explicit FSCP safety measures. 67
E.1 General . 67
E.2 Example fieldbus message with safety PDUs . 67
E.3 Model with completely explicit safety measures . 67
E.4 Model with explicit A-code and implicit T-code safety measures . 68
E.5 Model with explicit T-code and implicit A-code safety measures . 68
E.6 Model with split explicit and implicit safety measures . 69
E.7 Model with completely implicit safety measures . 70
E.8 Addition to Annex B – impact of implicit codes on properness . 70
Annex F (informative) Legacy models for estimation of the total residual error rate . 71
F.1 General . 71
F.2 Calculation of the residual error rate . 71
F.3 Total residual error rate and SIL . 73
Annex G (informative) Implicit data safety mechanisms for IEC 61784-3 functional
safety communication profiles (FSCPs) . 74
G.1 Overview. 74
G.2 Basic principles . 74
G.3 Problem statement: constant values for implicit data . 75
G.4 RP for FSCPs with random, uniformly distributed err . 78
impl
G.4.1 General . 78
i
G.4.2 Uniform distribution within the interval [0;2 -1], i ≥ r . 79
r
G.4.3 Uniform distribution in the interval [1;2 -1], i = r . 81
G.5 General case . 83
G.6 Calculation of P . 83
ID
Annex H (informative) Residual error probability for example CRC codes (tables for
verification of calculation methods) . 85
H.1 Overview. 85

IEC 61784-3:2021 © IEC 2021 – 5 –
H.2 Example of a 32-bit CRC. 85
H.3 Example of a 16-bit CRC. 90
H.4 Conclusion . 94
Bibliography . 96

Figure 1 – Relationships of IEC 61784-3 with other standards (machinery) . 9
Figure 2 – Relationships of IEC 61784-3 with other standards (process) . 10
Figure 3 – Transitions from Ed. 2 to Ed. 4 and future Ed. 5 assessment methods . 11
Figure 4 – Safety communication as a part of a safety function . 23
Figure 5 – Example model of a functional safety communication system . 24
Figure 6 – Example of safety function response time components . 25
Figure 7 – Conceptual FSCP protocol model . 30
Figure 8 – FSCP implementation aspects. 30
Figure 9 – Black channel from an FSCP perspective . 31
Figure 10 – Model for authentication considerations . 36
Figure 11 – Fieldbus and internal address errors . 37
Figure 12 – Example of slowly increasing message latency . 39
Figure 13 – Example of an active network element failure . 40
Figure 14 – Example application 1 (m = 4) . 42
Figure 15 – Example application 2 (m = 2) . 42
Figure 16 – Example of configuration and parameterization procedures for FSCP . 44
Figure A.1 – Model A . 52
Figure A.2 – Model B . 53
Figure A.3 – Model C . 53
Figure A.4 – Model D . 54
Figure B.1 – Binary symmetric channel (BSC) . 55
Figure B.2 – Block codes for error detection . 56
Figure B.3 – Example of a block with a message part and a CRC signature . 57
Figure B.4 – Proper and improper CRC polynomials . 58
Figure D.1 – Basic Markov model . 64
Figure E.1 – Example safety PDUs embedded in a fieldbus message . 67
Figure E.2 – Model with completely explicit safety measures . 67
Figure E.3 – Model with explicit A-code and implicit T-code safety measures . 68
Figure E.4 – Model with explicit T-code and implicit A-code safety measures . 69
Figure E.5 – Model with split explicit and implicit safety measures . 69
Figure E.6 – Model with completely implicit safety measures . 70
Figure F.1 – Example application 1 (m = 4) . 72
Figure F.2 – Example application 2 (m = 2) . 73
Figure G.1 – FSCP with implicit transmission of authenticity and/or timeliness codes . 75
Figure G.2 – Example of an incorrect transmission with multiple error causes . 76
Figure G.3 – Impact of errors in implicit data on the residual error probability . 77
Figure H.1 – Residual error probabilities (example of a 32-bit CRC – result 1) . 87
Figure H.2 – Residual error probabilities (example of a 32-bit CRC – result 2) . 87

– 6 – IEC 61784-3:2021 © IEC 2021
Figure H.3 – Residual error probabilities (example of a 32-bit CRC – result 3) . 88
Figure H.4 – Residual error probabilities (example of a 32-bit CRC – result 4) . 88
Figure H.5 – Residual error probabilities (example of a 32-bit CRC – result 5) . 89
Figure H.6 – Residual error probabilities (example of a 32-bit CRC – result 6) . 89
Figure H.7 – Residual error probabilities (example of a 16-bit CRC – result 1) . 92
Figure H.8 – Residual error probabilities (example of a 16-bit CRC – result 2) . 92
Figure H.9 – Residual error probabilities (example of a 16-bit CRC – result 3) . 93
Figure H.10 – Residual error probabilities (example of a 16-bit CRC – result 4) . 93
Figure H.11 – Residual error probabilities (example of a 16-bit CRC – result 5) . 94
Figure H.12 – Example 1 of improper polynomial . 94
Figure H.13 – Example 2 of improper polynomial . 95

Table 1 – Overview of the effectiveness of the various measures on the possible errors . 29
Table 2 – Typical relationship of residual error rate to SIL . 43
Table 3 – Typical relationship of residual error on demand to SIL . 43
Table 4 – Overview of profile identifier usable for FSCP 6/7 . 48
Table B.1 – Example dependency d and block bit length n . 56
min
Table C.1 – Common subclause structure for technology-specific parts . 59
Table F.1 – Definition of items used for calculation of the residual error rates . 72
Table F.2 – Typical relationship of residual error rate to SIL . 73
Table F.3 – Typical relationship of residual error on demand to SIL . 73
Table H.1 – Residual error probabilities (R ) for example CRC32 polynomial . 86
CRC1
Table H.2 – Residual error probabilities (R ) for example CRC16 polynomial . 91
CRC2
IEC 61784-3:2021 © IEC 2021 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
PROFILES –
Part 3: Functional safety fieldbuses –
General rules and profile definitions

FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61784-3 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This fourth edition cancels and replaces the third edition, published in 2016 and its
Amendment 1, published in 2017. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
• Contents of previous Annex F were corrected based on feedback from peer review and
subsequent analysis (in particular deletion of RP for data integrity, reduction of the
U
Equation for RR , and clarifications on the values of RP and R ).
A I T
• Additional assumptions for residual error rate calculations, clarification of assumption a).

– 8 – IEC 61784-3:2021 © IEC 2021
• After correction, contents of previous Annex F were exchanged with the contents of
previous Subclause 5.8.
• Contents of Subclause 5.9 on security replaced by a simple reference to IEC 62443 in
accordance with Guide 120.
• Changes in Annex B: Dependency of this Annex B with the BSC model has been
highlighted. First two paragraphs and figure in Clause B.2 have been deleted because of
little relevance. The approximation Equation (B.4) has been deleted due to obsolescence,
based on the observations that the CRC shall be anyway explicitly calculated in order to
prove properness, and that it may produce optimistic results. Guidance for calculation of
R in B.4.2 has been reviewed.
CRC
• Changes in Annex D: Formula D.1 was changed from an approximation to a proper
Equation, with some adjustments, and contents of D.4.3 were clarified (default safety
action).
• New informative Annex H, providing additional guidance for the calculation of RCRC.
The text of this International Standard is based on the following documents:
FDIS Report on voting
65C/1067/FDIS 65C/1072/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 61784-3 series, published under the general title Industrial
communication networks – Profiles – Functional safety fieldbuses, can be found on the IEC
...