IEC 61784-3-19:2024

IEC 61784-3-19 ®
Edition 1.0 2024-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial communication networks – Profiles –
Part 3-19: Functional safety fieldbuses – Additional specifications for CPF 19

Réseaux de communication industriels – Profils –
Partie 3-19: Bus de terrain de sécurité fonctionnelle – Spécifications
supplémentaires pour CPF 19
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IEC 61784-3-19 ®
Edition 1.0 2024-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial communication networks – Profiles –

Part 3-19: Functional safety fieldbuses – Additional specifications for CPF 19

Réseaux de communication industriels – Profils –

Partie 3-19: Bus de terrain de sécurité fonctionnelle – Spécifications

supplémentaires pour CPF 19
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40, 35.100.05 ISBN 978-2-8322-9802-2

– 2 – IEC 61784-3-19:2024 © IEC 2024
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 10
2 Normative references . 10
3 Terms, definitions, symbols, abbreviated terms and conventions . 11
3.1 Terms and definitions . 11
3.1.1 Common terms and definitions . 11
3.1.2 CPF 19: Additional terms and definitions . 15
3.2 Symbols and abbreviated terms . 15
3.2.1 Common symbols and abbreviated terms . 15
3.2.2 CPF 19: Additional symbols and abbreviated terms . 16
3.3 Conventions . 16
4 Overview of FSCP 19 (MECHATROLINK Safety) . 16
5 General . 17
5.1 External documents providing specifications for the profile . 17
5.2 Safety functional requirements . 17
5.3 Safety measures . 17
5.3.1 General . 17
5.3.2 Sequence number. 18
5.3.3 Time expectation . 19
5.3.4 Connection ID . 21
5.3.5 CRC calculation . 21
5.3.6 Redundancy with cross checking . 22
5.4 Safety communication layer structure . 25
5.5 Relationships with FAL (and DLL, PhL) . 26
5.5.1 General . 26
5.5.2 Data types . 26
6 Safety communication layer services . 26
6.1 Service description . 26
6.1.1 S_CONNECT_START . 26
6.1.2 S_CONNECT_CONF . 28
6.1.3 S_PRM_SET . 31
6.1.4 S_PRM_APPLY . 33
6.1.5 S_SAFE_DATA . 34
6.1.6 S_DISCONNECT . 35
6.1.7 S_FAIL_SAFE . 36
6.1.8 S_NOP . 37
7 SCL protocol . 38
7.1 SPDU format . 38
7.1.1 SPDU structure . 38
7.1.2 Connection ID . 39
7.1.3 Sequence number. 39
7.1.4 Command . 39
7.1.5 State number . 40
7.1.6 CRC . 40
7.1.7 Redundant data . 40

7.2 Safety FAL service protocol machine . 40
7.2.1 State transition of safety master . 40
7.2.2 State transition of safety slave . 47
7.3 Behaviour description . 53
7.3.1 Connection establishment . 53
7.3.2 Safety data sending/receiving sequence . 60
7.3.3 Disconnect safety channel . 64
8 SCL management . 65
8.1 Parameter definitions . 65
8.1.1 General . 65
8.1.2 T_Watchdog . 65
8.1.3 T_Response . 65
8.1.4 Master_Connection_Key . 66
8.1.5 Slave_Connection_Key . 66
8.1.6 Connection_Id . 66
8.1.7 Master_Sequence_Number . 66
8.1.8 Extended_Master_Sequence_Number . 66
8.1.9 Slave_Sequence_Number. 66
8.1.10 Extended_Slave_Sequence_Number . 66
8.1.11 Node_Address . 66
8.1.12 Device_Info (structure) . 67
8.1.13 Output_Data_Length . 67
8.1.14 Input_Data_Length . 67
8.1.15 Output_User_Data_Length . 67
8.1.16 Input_User_Data_Length . 67
8.1.17 Stop_Safety_Loop . 67
8.1.18 Stop_Safety_Loop_Oth . 68
9 System requirements . 69
9.1 Indicators and switches . 69
9.1.1 General . 69
9.1.2 Safety connection LED . 70
9.2 Installation guidelines . 70
9.3 Safety function response time . 70
9.3.1 System response time . 70
9.3.2 FSCP 19 response time . 71
9.4 Duration of demands . 72
9.5 Constraints for calculation of system characteristics . 72
9.5.1 Number of stations . 72
9.5.2 Probability considerations . 72
9.6 Maintenance . 73
9.7 Safety manual . 73
10 Assessment . 73
Bibliography . 74

Figure 1 – Relationships of IEC 61784-3 with other standards (machinery) . 8
Figure 2 – Relationships of IEC 61784-3 with other standards (process) . 9
Figure 3 – Basic FSCP 19 system . 17
Figure 4 – Incrementing procedure of sequence number . 19

– 4 – IEC 61784-3-19:2024 © IEC 2024
Figure 5 – Time expectation with watchdog timer . 20
Figure 6 – Synchronization of transmission timing. 20
Figure 7 – Time expectation with response timer . 21
Figure 8 – Redundant data generation processing . 23
Figure 9 – Redundant data verification process . 25
Figure 10 – SCL structure . 26
Figure 11 – Safety PDU format . 38
Figure 12 – Safety master SCL – state transition diagram . 40
Figure 13 – Safety master safety connection − state transition diagram . 42
Figure 14 – Safety slave SCL − state transition diagram . 48
Figure 15 – Safety slave safety connection − state transition diagram . 49
Figure 16 – Node address and device information processing flow at start-up . 56
Figure 17 – S_CONNECT_START command reception processing flow . 56
Figure 18 – S_CONNECT_CONF command reception processing flow . 57
Figure 19 – Sequence example 1 from connection establishment to safety data
transmission/reception . 58
Figure 20 – Sequence example 2 from connection establishment to safety data

transmission/reception . 59
Figure 21 – S_SAFE_DATA command sequence . 60
Figure 22 – Loss of S_SAFE_DATA command from safety master . 61
Figure 23 – Delay of S_SAFE_DATA command from safety master . 61
Figure 24 – Loss of S_SAFE_DATA command from safety slave . 62
Figure 25 – Delay of S_SAFE_DATA command from safety slave . 62
Figure 26 – Insertion of message to safety slave . 63
Figure 27 – Insertion of message to safety master . 64
Figure 28 – Elements of safety function . 71
Figure 29 – Safety function of FSCP 19 system . 71
Figure 30 – Residual error rate . 73

Table 1 – Communication errors and safety measures . 18
Table 2 – Sequence number list . 18
Table 3 – CRC seed values . 22
Table 4 – S_CONNECT_START command data. 27
Table 5 – S_CONNECT_START command SPDU (1st SPDU) . 27
Table 6 – S_CONNECT_START command SPDU (2nd SPDU) . 28
Table 7 – S_CONNECT_CONF command data . 29
Table 8 – S_CONNECT_CONF command SPDU (1st SPDU) . 29
Table 9 – S_CONNECT_CONF command SPDU (2nd SPDU) . 30
Table 10 – S_CONNECT_CONF command SPDU (3rd SPDU) . 30
Table 11 – S_PRM_SET command data . 31
Table 12 – S_PRM_SET command SPDU (1st SPDU) . 32
Table 13 – S_PRM_SET command SPDU (2nd SPDU) . 32
Table 14 – S_PRM_SET command SPDU (3rd SPDU) . 33
Table 15 – S_PRM_APPLY command data . 33

Table 16 – S_PRM_APPLY command SPDU . 34
Table 17 – S_SAFE_DATA command SPDU . 34
Table 18 – S_DISCONNECT command SPDU . 35
Table 19 – Factor in S_DISCONNECT command . 36
Table 20 – S_FAIL_SAFE command SPDU . 37
Table 21 – S_NOP command SPDU . 37
Table 22 – List of commands . 39
Table 23 – Safety master SCL – state description . 40
Table 24 – Safety master SCL − state transition matrix . 41
Table 25 – Safety master safety connection − state description . 43
Table 26 – Safety master safety connection − state transition matrix . 43
Table 27 – Safety slave SCL − state description . 48
Table 28 – Safety slave SCL – state transition matrix . 48
Table 29 – Safety slave safety connection − state description . 49
Table 30 – Safety slave safety connection − state transition matrix . 50
Table 31 – Safety salve node and device variables . 55
Table 32 – List of parameter variables . 65
Table 33 – Specification of stop safety loop setting . 68
Table 34 – Specification of stop safety loop other setting . 69
Table 35 – LED specifications . 70
Table 36 – Safety connection LED specification . 70
Table 37 – Residual error rate . 72

– 6 – IEC 61784-3-19:2024 © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
PROFILES –
Part 3-19: Functional safety fieldbuses –
Additional specifications for CPF 19

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) IEC draws attention to the possibility that the implementation of this document may involve the use of a patent.
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held responsible for identifying any or all such patent rights.
IEC 61784-3-19 has been prepared by subcommittee 65C: Industrial networks, of IEC technical
committee 65: Industrial-process measurement, control and automation. It is an International
Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
65C/1276/CDV 65C/1298/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
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
website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
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.

– 8 – IEC 61784-3-19:2024 © IEC 2024
INTRODUCTION
The IEC 61158 fieldbus standard series together with its companion standards series
IEC 61784-1 and IEC 61784-2 defines a set of communication protocols that enable distributed
control of automation applications. Fieldbus technology is now considered well accepted and
well proven. Thus, fieldbus enhancements continue to emerge, addressing applications for
areas such as real time and safety-related applications.
The IEC 61784-3 series explains the relevant principles for functional safety communications
with reference to the IEC 61508 series and specifies several safety communication layers
(profiles and corresponding protocols) based on the communication profiles and protocol layers
of the IEC 61784-1, IEC 61784-2 and IEC 61158 series. It does not cover electrical safety and
intrinsic safety aspects. It also does not cover security aspects, nor does it provide any
requirements for security.
Figure 1 shows the relationships between the IEC 61784-3 series and relevant safety and
fieldbus standards in a machinery environment.

NOTE IEC 62061 specifies the relationship between PL (Category) and SIL.
Figure 1 – Relationships of IEC 61784-3 with other standards (machinery)
Figure 2 shows the relationships between the IEC 61784-3 series and relevant safety and
fieldbus standards in a process environment.

a
For specified electromagnetic environments; otherwise IEC 61326-3-1 or IEC 61000-6-7.
Figure 2 – Relationships of IEC 61784-3 with other standards (process)
Safety communication layers which are implemented as parts of safety-related systems
according to the IEC 61508 series provide the necessary confidence in the transportation of
messages (information) between two or more participants on a fieldbus in a safety-related
system, or sufficient confidence of safe behaviour in the event of fieldbus errors or failures.
Safety communication layers specified in the IEC 61784-3 series do this in such a way that a
fieldbus can be used for applications requiring functional safety up to the Safety Integrity Level
(SIL) specified by its corresponding functional safety communication profile.
The resulting SIL claim of a system depends on the implementation of the selected functional
safety communication profile (FSCP) within this system – implementation of a functional safety
communication profile in a standard device is not sufficient to qualify it as a safety device.
The IEC 61784-3 series describes:
• basic principles for implementing the requirements of the IEC 61508 series for safety-related
data communications, including possible transmission faults, remedial measures and
considerations affecting data integrity;
• functional safety communication profiles for several communication profile families in the
IEC 61784-1 and IEC 61784-2 series, including safety layer extensions to the
communication service and protocols sections of the IEC 61158 series.

– 10 – IEC 61784-3-19:2024 © IEC 2024
INDUSTRIAL COMMUNICATION NETWORKS –
PROFILES –
Part 3-19: Functional safety fieldbuses –
Additional specifications for CPF 19

1 Scope
This part of IEC 61784-3 specifies a safety communication layer (services and protocol) based
on IEC 61784-1-19, IEC 61784-2-19 and the IEC 61158 series (Type 24 and Type 27). It
identifies the principles for functional safety communications defined in IEC 61784-3 that are
relevant for this safety communication layer. This safety communication layer is intended for
implementation in safety devices only.
NOTE 1 It does not cover electrical safety and intrinsic safety aspects. Electrical safety relates to hazards such as
electrical shock. Intrinsic safety relates to hazards associated with potentially explosive atmospheres.
This document defines mechanisms for the transmission of safety-relevant messages among
participants within a distributed network using fieldbus technology in accordance with the
requirements of the IEC 61508 series for functional safety. These mechanisms can be used in
various industrial applications such as process control, manufacturing automation and
machinery.
This document provides guidelines for both developers and assessors of compliant devices and
systems.
NOTE 2 The resulting SIL claim of a system depends on the implementation of the selected functional safety
communication profile within this system – implementation of a functional safety communication profile according to
this document in a standard device is not sufficient to qualify it as a safety device.
2 Normative references
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.
IEC 61131-2, Industrial-process measurement and control – Programmable controllers – Part 2:
Equipment requirements and tests
IEC 61158 (all parts), Industrial communication networks – Fieldbus specifications
IEC 61158-6-24, Industrial communication networks – Fieldbus specifications – Part 6-24:
Application layer protocol specification – Type 24 elements
IEC 61158-6-27, Industrial communication networks – Fieldbus specifications – Part 6-27:
Application layer protocol specification – Type 27 elements
IEC 61326-3-1, Electrical equipment for measurement, 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
___________
In the following pages of this document, "IEC 61508" will be used for "the IEC 61508 series".

IEC 61326-3-2, Electrical equipment for measurement, 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 (all parts), Functional safety of electrical/electronic/programmable electronic safety-
related systems
IEC 61511 (all parts), Functional safety – Safety instrumented systems for the process industry
sector
IEC 61784-1-19:2023, Industrial networks – Profiles – Part 1-19: Fieldbus profiles –
Communication Profile Family 19
IEC 61784-2-19:2023, Industrial networks – Profiles – Part 2-19: Additional real-time fieldbus
profiles based on ISO/IEC/IEEE 8802-3 – CPF 19
IEC 61784-3, Industrial communication networks − Profiles − Part 3: Functional safety
fieldbuses − General rules and profile definitions
IEC 61784-5-19, Industrial networks – Profiles – Part 5: Installation of fieldbuses – Installation
profiles for CPF 19
IEC 62061, Safety of machinery – Functional safety of safety-related control systems
3 Terms, definitions, symbols, abbreviated terms and conventions
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61784-3 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
NOTE Italics are used in the definitions to highlight terms which are themselves defined in 3.1.
3.1.1 Common terms and definitions
NOTE These common terms and definitions are inherited from IEC 61784-3:2021.
3.1.1.1
communication channel
logical connection between two end-points within a communication system
3.1.1.2
communication system
arrangement of hardware, software and propagation media to allow the transfer of messages
(ISO/IEC 7498-1 application layer) from one application to another
3.1.1.3
connection
logical binding between two application objects within the same or different devices

– 12 – IEC 61784-3-19:2024 © IEC 2024
3.1.1.4
CRC
Cyclic Redundancy Check
redundant data derived from, and stored or transmitted together with, a block of data
in order to detect data corruption
3.1.1.5
CRC
Cyclic Redundancy Check
procedure used to calculate the redundant data
Note 1 to entry: Terms "CRC code" and "CRC signature", and labels such as CRC1, CRC2, can also be used in this
document to refer to the redundant data.
3.1.1.6
error
discrepancy between a computed, observed or measured value or condition and the true,
specified or theoretically correct value or condition
Note 1 to entry: Errors can be due to design mistakes within hardware/software and/or corrupted information due
to electromagnetic interference and/or other effects.
Note 2 to entry: Errors do not necessarily result in a failure or a fault.
[SOURCE: IEC 61508-4:2010, 3.6.11, modified – Notes to entry have been added.]
3.1.1.7
failure
termination of the ability of a functional unit to provide a required function or operation of a
functional unit in any way other than as required
Note 1 to entry: Failure can be due to an error (for example, problem with hardware/software design or message
disruption).
[SOURCE: IEC 61508-4:2010, 3.6.4, modified – Notes and figures have been replaced.]
3.1.1.8
fault
abnormal condition that may cause a reduction in, or loss of, the capability of a functional unit
to perform a required function
Note 1 to entry: IEC 60050-191:1990, 191-05-01 defines "fault" as a state characterized by the inability to perform
a required function, excluding the inability during preventive maintenance or other planned actions, or due to lack of
external resources.
[SOURCE: IEC 61508-4:2010, 3.6.1, modified – Figure reference has been deleted.]
3.1.1.9
frame
denigrated synonym for DLPDU
3.1.1.10
master
communication entity able to initiate and schedule communication activities by other stations
which may be masters or slaves

3.1.1.11
message
ordered sequence of characters (usually
octets) intended to convey information
[SOURCE: ISO/IEC 2382:2015, 2123205, modified – insertion of "(usually octets)", deletion of
notes and source]
3.1.1.12
redundancy
existence of more than one means for performing a required function or for representing
information
[SOURCE: IEC 61508-4:2010, 3.4.6, modified – Example and notes have been deleted.]
3.1.1.13
safety communication channel
SC
communication channel starting at the top of the SCL of the source and ending at the top of the
SCL of the sink
Note 1 to entry: It can be modeled as two SCLs connected by a black channel or a defined communication system,
or a defined channel.
3.1.1.14
safety communication layer
SCL
communication layer above the FAL that includes all necessary additional measures to ensure
safe transmission of data in accordance with the requirements of IEC 61508
3.1.1.15
safety connection
connection that utilizes the safety protocol for communications transactions
3.1.1.16
safety data
data transmitted across a safety network using a safety protocol
Note 1 to entry: The Safety Communication Layer does not ensure safety of the data itself, only that the data is
transmitted safely.
3.1.1.17
safety device
device designed in accordance with IEC 61508 and which implements the functional safety
communication profile
3.1.1.18
safety function
function to be implemented by an E/E/PE safety-related system or other risk reduction
measures, that is intended to achieve or maintain a safe state for the EUC, in respect of a
specific hazardous event
[SOURCE: IEC 61508-4:2010, 3.5.1, modified – References and example have been deleted.]

– 14 – IEC 61784-3-19:2024 © IEC 2024
3.1.1.19
safety function response time
worst case elapsed time following an actuation of a safety sensor connected to a fieldbus, until
the corresponding safe state of its safety actuator(s) is achieved in the presence of errors or
failures in the safety function
Note 1 to entry: This concept is introduced in IEC 61784-3:2021, 5.2.4 and addressed by the functional safety
communication profiles defined in this document.
3.1.1.20
safety integrity level
SIL
discrete level (one out of a possible four), corresponding to a range of safety integrity values,
where safety integrity level 4 has the highest level of safety integrity and safety integrity level 1
has the lowest
Note 1 to entry: The target failure measures (see IEC 61508-4:2010, 3.5.17) for the four safety integrity levels are
specified in IEC 61508-1:2010, Tables 2 and 3.
Note 2 to entry: Safety integrity levels are used for specifying the safety integrity requirements of the safety
functions to be allocated to the E/E/PE safety-related systems.
Note 3 to entry: A safety integrity level (SIL) is not a property of a system, subsystem, element or component. The
correct interpretation of the phrase "SILn safety-related system" (where n is 1, 2, 3 or 4) is that the system is
potentially capable of supporting safety functions with a safety integrity level up to n.
[SOURCE: IEC 61508-4:2010, 3.5.8]
3.1.1.21
safety measure
measure to control possible communication errors that is designed and implemented in
compliance with the requirements of IEC 61508
Note 1 to entry: In practice, several safety measures are combined to achieve the required safety integrity level.
Note 2 to entry: Communication errors and related safety measures are detailed in IEC 61784-3:2021, 5.3 and 5.4.
3.1.1.22
safety PDU
SPDU
PDU transferred through the safety communication channel
Note 1 to entry: The SPDU may include
...