EN 61784-3:2016/A1:2017

SLOVENSKI STANDARD
01-februar-2018
Industrijska komunikacijska omrežja - Profili - 3. del: Funkcijska varnost procesnih
vodil - Splošna pravila in definicije profilov - Dopolnilo 1 (IEC 61784-
3:2016/A1:2017)
Industrial communication networks - Profiles - Part 3: Functional safety fieldbuses -
General rules and profile definitions (IEC 61784-3:2016/A1:2017)
Industrielle Kommunikationsnetze - Profile - Teil 3: Funktional sichere Übertragung bei
Feldbussen - Allgemeine Regeln und Festlegungen für Profile (IEC 61784-
3:2016/A1:2017)
Réseaux de communication industriels - Profils - Partie 3: Bus de terrain de sécurité
fonctionnelle - Règles générales et définitions de profils (IEC 61784-3:2016/A1:2017)
Ta slovenski standard je istoveten z: EN 61784-3:2016/A1:2017
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.100.05 9HþVORMQHXSRUDEQLãNH Multilayer applications
UHãLWYH
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 61784-3:2016/A1

NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2017
ICS 25.040.40; 35.100.05
English Version
Industrial communication networks - Profiles -
Part 3: Functional safety fieldbuses - General rules
and profile definitions
(IEC 61784-3:2016/A1:2017)
Réseaux de communication industriels - Profils -  Industrielle Kommunikationsnetze - Profile -
Partie 3: Bus de terrain de sécurité fonctionnelle - Règles Teil 3: Funktional sichere Übertragung bei Feldbussen -
générales et définitions de profils Allgemeine Regeln und Festlegungen für Profile
(IEC 61784-3:2016/A1:2017) (IEC 61784-3:2016/A1:2017)
This amendment A1 modifies the European Standard EN 61784-3:2016; it was approved by CENELEC on 2017-09-08. CENELEC
members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this amendment 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 amendment 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, 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: Avenue Marnix 17, B-1000 Brussels
© 2017 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 61784-3:2016/A1:2017 E

European foreword
The text of document 65C/879/FDIS, future IEC 61784-3:2016/A1, 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 61784-3:2016/A1:2017.

The following dates are fixed:
• latest date by which the document has to be (dop) 2018-06-08
implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2020-09-08
• latest date by which the national
standards conflicting with the
document have to be withdrawn
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 61784-3:2016/A1:2017 was approved by CENELEC as a
European Standard without any modification.
IEC 61784-3 ®
Edition 3.0 2017-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
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 978-2-8322-4585-9

– 2 – IEC 61784-3:2016/AMD1:2017
© IEC 2017
FOREWORD
This amendment has been prepared by subcommittee 65C: Industrial networks, of IEC
technical committee 65: Industrial-process measurement, control and automation.
The text of this amendment is based on the following documents:
FDIS Report on voting
65C/879/FDIS 65C/886/RVD
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC website 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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
_____________
IEC 61784-3:2016/AMD1:2017 – 3 –
© IEC 2017
INTRODUCTION
This Amendment 1 discusses the concepts of implicit data safety mechanisms for use in
functional safety communications protocols (FSCPs) as specified in IEC 61784-3:2016.
3 Terms, definitions, symbols, abbreviated terms and conventions
3.1 Terms and definitions
Add the following new terms and definitions 3.1.56 and 3.1.57:
3.1.56
explicit data
data that is transmitted
3.1.57
implicit data
additional data that is not transmitted but is known to the sender and receiver
[SOURCE: IEC 62280:2014, 3.1.25]
3.2 Symbols and abbreviated terms
Add two new Subclauses 3.2.1 and 3.2.2, as specified below.
3.2.1 Abbreviated terms
Move the existing list of symbols and abbreviated terms to this new Subclause 3.2.1.
Delete “Pe” and “RP” from the existing list of abbreviated terms. Add, in alphabetical order, in
the list of abbreviated terms the following new abbreviated terms:
A-code Authenticity code
T-code Timeliness code
3.2.2 Symbols
Add, in this new Subclause 3.2.2 the following list of symbols:
A Weight distribution of the code: number of valid
k
codewords having k bits set to “one”
e Bit length of explicit data
err Bitwise disjunction of impl and impl
impl S R
expl Explicit data
expl Explicit data in the receiver
R
expl Explicit data in the sender
S
FCS Frame check sequence calculated in the receiver
C
FCS Frame check sequence received
R
FCS Frame check sequence sent
S
i Bit length of implicit data
ID Incorrect delivery
impl Implicit data in the receiver
R
impl Implicit data in the sender
S
– 4 – IEC 61784-3:2016/AMD1:2017
© IEC 2017
n Bit length of SPDU
P Bit error probability
e
P Probability of incorrect delivery
ID
r Bit length of FCS (degree of generator polynomial)
RP Residual error probability
Add, after Annex F, the following new informative Annex G:

IEC 61784-3:2016/AMD1:2017 – 5 –
© IEC 2017
Annex G
(informative)
Implicit data safety mechanisms for IEC 61784­3 functional
safety communication profiles (FSCPs)
G.1 Overview
Annex G discusses the concepts of implicit data safety mechanisms for use in functional
safety communications protocols (FSCPs) as specified in this standard. Implicit data is that
which is not explicitly transmitted in a PDU. Instead, the implicit data values are known by
both the sender (source) and the receiver (sink). Implicit data values are validated by the
value of one or more transmitted frame check sequence(s) (FCS) which are calculated using
an overall data string comprised of the implicit data string appended with the explicit data
string. Because the implicit data is not transmitted, the load on the transmission media is
reduced.
Today, the FSCPs that use implicit data mechanisms do so in order to communicate complete
or partial timeliness codes (T-codes) and/or authenticity codes (A-codes), see Annex E.
These FSCPs also use cyclic redundancy check (CRC) algorithms for the frame check
sequence (FCS) exclusively. Therefore, Annex G is limited to the analysis of implicitly
transmitted T-codes and A-codes using CRC-algorithms.
According to Clause E.8, with regard to implicit data, "Due to the various possible approaches
generic formulae cannot be provided. It is up to the individual FSCP to prove sufficient
residual error probabilities." In the hope of advancing IEC 61784-3 for the next edition and
beyond, the subject of this new Annex G is to improve the understanding of formulating
models for the residual error probabilities of FSCPs using CRC-algorithms to implicitly
transmit T-codes and A-codes when a single FCS code is used by the protocol.
Presented in Annex G are two formulae examples, applicable for two special cases, and from
which a better understanding is promoted for the development of additional (specific and
general) formulae.
Also presented is a summation method generally applicable when conditional weight
distributions for implicit data error patterns are known and can be quantified in a way either
leading to a closed-form solution, or suitable for iterative summation with a reasonably
bounded execution time.
G.2 Basic principles
Calculations in Annex G also use the binary symmetric channel (BSC) model as specified in
Annex B.
NOTE 1 Although it does not take into account burst errors, the BSC model with a sufficiently conservative bit
error probability is so far the most practical known for use in probability calculations needed for the determination
of the FSCP residual error rate.
Figure G.1 shows the basic principle of an FSCP using single FCS protection mechanisms
involving implicit data. In the sender, a CRC-checksum over the implicit data impl
S
concatenated with the explicit data expl is generated, resulting in a frame check sequence
S
FCS . When multiple FCS codes are used in an FCSP format, the calculation shall be done
S
for each FCS code. While expl and FCS are explicitly transmitted over the black channel,
S S
impl is not transmitted, but impacts the value of the FCS . Therefore, it can only contain
S S
data whose value is already known to the receiver. Implicit data is used to detect e.g. SPDUs
which were misdirected in either space (“authentication error”) or time (“timeliness error”).
This is accomplished by deriving the implicit data from the A-code (e.g. connection identifier)
and/or the T-code (e.g. sequence number) of an SPDU.

– 6 – IEC 61784-3:2016/AMD1:2017
© IEC 2017
NOTE 2 Initialization details are addressed in F.12.1.
Sender Receiver
expl
S
impl
R
impl
S
CRC CRC
calculation calculation
impl expl
R R
impl expl
S S
?
FCS
C
ok
expl FCS
S S
expl FCS
R R
expl FCS
Black channel
SPDU
IEC
Key Symbols are specified in 3.2.2
Figure G.1 – FSCP with implicit transmission of authenticity
and/or timeliness codes
When the SPDU comprising expl and FCS is delivered to the FSCP-layer in the receiver, it
may contain transmission errors, i.e. the value delivered may differ from the value sent. For
discrimination, the symbols expl and FCS are used in the receiver.
R R
The expected value of the implicit data is called impl . In the error free case, this expectation
R
is identical to impl . In case of, for example, a misdirected SPDU, impl and impl may differ.
S R S
The receiver generates one or more frame check sequence(s) FCS by building a CRC-
C
checksum over the concatenation of impl and expl . When each FCS is identical to its
R R C
corresponding FCS , it is assumed that no error occurred. Otherwise an error has been
R
detected.
The lengths of the bitstrings for a single FCS are defined as follows:
r length of FCS (degree of generator-polynomial);
i length of implicit data (it is assumed that i ≥ r);
e length of explicit data;
n length of SPDU, with n = e + r.
G.3 Problem statement: constant values for implicit data
In FSCPs using implicit data, the CRC-check in the receiver is used for both the detection of
data integrity errors as well as the detection of mis-directed or mis-timed SPDUs. Therefore, it
may happen that the CRC-mechanism becomes “overburdened” by multiple simultaneous
errors, resulting in an increase of the overall residual error probability. This is exemplified in
the following scenario in Figure G.2.

IEC 61784-3:2016/AMD1:2017 – 7 –
© IEC 2017
A-code: 0x0001
R1
Authenticity error
S Router
SPDU
Data corruption
For receiver R1
A-code: 0x1156
R2
SPDU
Misdirected and corrupted content

IEC
Figure G.2 – Example of an incorrect transmission with
...