IEC 61158-5-26:2019

IEC 61158-5-26 ®
Edition 1.0 2019-04
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 5-26: Application layer service definition – Type 26 elements

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IEC 61158-5-26 ®
Edition 1.0 2019-04
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –

Part 5-26: Application layer service definition – Type 26 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.100.70; 35.110 ISBN 978-2-8322-6768-4

– 2 – IEC 61158-5-26:2019 © IEC 2019
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
1.1 Overview . 8
1.2 Specifications . 9
1.3 Conformance . 9
2 Normative references . 9
3 Terms, definitions, symbols, abbreviations and conventions . 10
3.1 Terms and definitions from other ISO/IEC standards . 11
3.1.1 Terms and definitions from ISO/IEC 7498-1 . 11
3.1.2 Terms and definitions from ISO/IEC 8822 . 11
3.1.3 Terms and definitions from ISO/IEC 9545 . 11
3.1.4 Terms and definitions from ISO/IEC 8824-1 . 11
3.2 Fieldbus application layer Type 26-specific definitions . 12
3.3 Abbreviations and symbols . 18
3.4 Conventions . 20
3.4.1 Overview . 20
3.4.2 General conventions . 20
3.4.3 Conventions for class definitions . 20
3.4.4 Conventions for service definitions . 21
4 Concepts . 22
5 Data type ASE . 23
5.1 Overview . 23
5.2 Formal definition of data type objects . 23
5.2.1 Data type class definitions . 23
5.2.2 Attributes . 24
5.3 FAL defined data types . 25
5.3.1 Fixed length types . 25
5.3.2 String types . 29
5.4 Data type ASE service specification . 30
6 Communication model specification . 30
6.1 General . 30
6.2 Protocol stack for Type 26 fieldbus . 30
6.3 Overview of Type 26 communication model . 31
6.4 Cyclic data communication service with Common-memory . 32
6.4.1 Overview . 32
6.4.2 Common–memory: allocation to each node . 32
6.4.3 Data sharing among nodes with the CM . 33
6.4.4 CM data type . 35
6.5 ASEs . 35
6.5.1 Overview of Type 26 ASEs . 35
6.5.2 Type 26 specific conventions for FAL service common parameters . 36
6.5.3 Cyclic-data ASE. 37
6.5.4 Message data ASE . 42
6.5.5 Communication load measurement ASE . 69
6.5.6 Network management ASE . 74

6.5.7 General purpose command server ASE . 87
6.5.8 AR ASE . 90
6.5.9 FAL ASE summary . 101
Bibliography . 104

Figure 1 – Protocol stack for Type 26 fieldbus . 31
Figure 2 – Unconfirmed Push-Publisher/Subscriber type interaction . 32
Figure 3 – Unconfirmed/Confirmed Client/Server type interaction . 32
Figure 4 – Common memory allocation . 33
Figure 5 – Data sharing with the CM . 34
Figure 6 – Node #01 for reception only . 34
Figure 7 – Node #01 without the CM . 35
Figure 8 – The structure of ASEs for Type 26 FAL . 36
Figure 9 – Virtual-address-space for Byte block . 45
Figure 10 – Virtual-address-space for Word block . 48
Figure 11 – AR ASE internal architecture . 91
Figure 12 – Structure of IP address . 99

Table 1 – Write service parameters . 39
Table 2 – Send-CM service parameters . 40
Table 3 – Read service parameters. 40
Table 4 – Update memory service parameters . 41
Table 5 – Get- buffer service parameters . 42
Table 6 – Byte block read service parameters . 46
Table 7 – Byte block write service parameters . 47
Table 8 – Word block read service parameters . 48
Table 9 – Word block write service parameters . 49
Table 10 – Network parameter read service parameters . 50
Table 11 – Network parameter write service parameters . 51
Table 12 – Stop command service parameters . 52
Table 13 – Operation command service parameters. 53
Table 14 – profile read service parameters . 53
Table 15 – Transparent message service parameters . 56
Table 16 – Log data read service parameters . 57
Table 17 – Log data items. 57
Table 18 – Log data clear service parameters . 61
Table 19 – Message return service parameters . 62
Table 20 – Vendor specific message service parameters . 63
Table 21 – Set remote node configuration parameter service parameters . 64
Table 22 – Data elements and Node configuration parameters. 64
Table 23 – Service parameters of Read remote participating node management
information parameter service . 65
Table 24 – Participating node management information parameters . 66
Table 25 – Read remote node management information parameter service parameters . 67

– 4 – IEC 61158-5-26:2019 © IEC 2019
Table 26 – Node management information parameters . 67
Table 27 – Read remote node setting information parameter service parameters . 68
Table 28 –Node setting information parameters . 69
Table 29 – Start TK-holding-time measurement service parameters . 71
Table 30 – Terminate TK-holding-time measurement service parameters . 71
Table 31 – Token-holding-time measurement result . 72
Table 32 – Start GP_Comm sender log service parameters . 73
Table 33 – Terminate GP_Comm sender log service parameters . 73
Table 34 – GP_Comm sender log measurement result . 74
Table 35 – Service parameters for Set configuration parameter . 77
Table 36 – Configuration parameters . 78
Table 37 – Read node management information parameter service parameters . 78
Table 38 – Node management information parameters . 79
Table 39 – Service parameters for Read participating node mgt. information parameter . 80
Table 40 – Participating node management information parameters . 80
Table 41 – Service parameters for Read network management information parameter . 81
Table 42 – Network management information parameters . 81
Table 43 – Service parameters for Read message sequence number management
information. 82
Table 44 – Read message sequence number management information parameters . 82
Table 45 –Read node status service parameters . 83
Table 46 – Read node status parameters . 83
Table 47 – Upper layer operating condition matrix . 84
Table 48 –Reset node service parameters . 84
Table 49 – Set network address service parameters . 85
Table 50 – Register service parameters . 85
Table 51 – Event service parameters . 86
Table 52 – Activate/Deactivate measurement service parameters . 86
Table 53 – Get log data service parameters . 87
Table 54 – Send command service parameters . 90
Table 55 – CT send service parameters . 93
Table 56 – MT send service parameters . 95
Table 57 – CS send service parameters . 96
Table 58 – Notify state change service parameters . 97
Table 59 – Control measurement service parameters. 97
Table 60 – DLSAP assignments . 99
Table 61 – DLS Primitives and parameters . 100
Table 62 – Lower layer T-profile and the required standards . 101
Table 63 – Summary of FAL ASEs . 101

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 5-26: Application layer service definition –
Type 26 elements
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61158-5-26 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement and control.
The text of this International Standard is based on the following documents:
FDIS Report on voting
65C/947/FDIS 65C/950/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 publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – IEC 61158-5-26:2019 © IEC 2019
A list of all parts in the IEC 61158 series, published under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
A bilingual version of this publication may be issued at a later date.

INTRODUCTION
This document is one of a series produced to facilitate the interconnection of automation
system components. It is related to other standards in the set as defined by the “three-layer”
fieldbus reference model described in IEC 61158-1.
The application service is provided by the application protocol making use of the services
available from the data-link or other immediately lower layer. This document defines the
application service characteristics that fieldbus applications and/or system management may
exploit.
Throughout the set of fieldbus standards, the term “service” refers to the abstract capability
provided by one layer of the OSI Basic Reference Model to the layer immediately above. Thus,
the application layer service defined in this document is a conceptual architectural service,
independent of administrative and implementation divisions.

– 8 – IEC 61158-5-26:2019 © IEC 2019
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 5-26: Application layer service definition –
Type 26 elements
1 Scope
1.1 Overview
The Fieldbus Application Layer (FAL) provides user programs with a means to access the
Fieldbus communication environment. In this respect, the FAL can be viewed as a “window
between corresponding application programs.”
This part of IEC 61158 provides common elements for basic time-critical and non-time-critical
messaging communications between application programs in an automation environment and
material specific to Type 26 fieldbus. The term “time-critical” is used to represent the
presence of a time-window, within which one or more specified actions are required to be
completed with some defined level of certainty. Failure to complete specified actions within
the time window risks failure of the applications requesting the actions, with attendant risk to
equipment, plant and possibly human life.
This International Standard defines in an abstract way the externally visible service provided
by the different Types of fieldbus Application Layer in terms of
a) an abstract model for defining application resources (objects) capable of being
manipulated by users via the use of the FAL service;
b) the primitive actions and events of the service;
c) the parameters associated with each primitive action and event, and the form which they
take; and
d) the interrelationship between these actions and events, and their valid sequences.
The purpose of this document is to define the services provided to
a) the FAL user at the boundary between the user and the Application Layer of the Fieldbus
Reference Model, and
b) Systems Management at the boundary between the Application Layer and Systems
Management of the Fieldbus Reference Model.
This document specifies the structure and services of the IEC Fieldbus Application Layer, in
conformance with the OSI Basic Reference Model (see ISO/IEC 7498-1) and the OSI
Application Layer Structure (see ISO/IEC 9545).
FAL services and protocols are provided by FAL application-entities (AE) contained within the
application processes. The FAL AE is composed of a set of object-oriented Application
Service Elements (ASEs) and a Layer Management Entity (LME) that manages the AE. The
ASEs provide communication services that operate on a set of related application process
object (APO) classes. One of the FAL ASEs is a management ASE that provides a common
set of services for the management of the instances of FAL classes.
Although these services specify, from the perspective of applications, how request and
responses are issued and delivered, they do not include a specification of what the requesting
and responding applications are to do with them. That is, the behavioral aspects of the
applications are not specified; only a definition of what requests and responses they can

send/receive is specified. This permits greater flexibility to the FAL users in standardizing
such object behavior. In addition to these services, some supporting services are also defined
in this document to provide access to the FAL to control certain aspects of its operation.
1.2 Specifications
The principal objective of this document is to specify the characteristics of conceptual
application layer services suitable for time-critical communications, and thus supplement the
OSI Basic Reference Model in guiding the development of application layer protocols for time-
critical communications.
A secondary objective is to provide migration paths from previously-existing industrial
communications protocols. It is this latter objective which gives rise to the diversity of services
standardized as the various Types of IEC 61158, and the corresponding protocols
standardized in subparts of IEC 61158-6.
This specification may be used as the basis for formal Application Programming-Interfaces.
Nevertheless, it is not a formal programming interface, and any such interface will need to
address implementation issues not covered by this specification, including
a) the sizes and octet ordering of various multi-octet service parameters, and
b) the correlation of paired request and confirm, or indication and response, primitives.
1.3 Conformance
This document does not specify individual implementations or products, nor does it constrain
the implementations of application layer entities within industrial automation systems.
There is no conformance of equipment to this application layer service definition standard.
Instead, conformance is achieved through implementation of conforming application layer
protocols that fulfill any given Type of application layer services as defined in this document.
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.
NOTE All parts of the IEC 61158 series, as well as IEC 61784-1 and IEC 61784-2, are maintained simultaneously.
Cross-references to these documents within the text therefore refer to the editions as dated in this list of normative
references.
IEC 61131-3, Programmable controllers – Part 3: Programming languages
IEC 61158-1:2019, Industrial communication networks – Fieldbus specifications – Part 1:
Overview and guidance for the IEC 61158 and IEC 61784 series
IEC 61158-6-26:2019, Industrial communication networks – Fieldbus specifications –
Part 6-26: Application layer protocol specification – Type 26 elements
IEC 61784-2:2019, Industrial communication networks – Profiles – Part 2: Additional fieldbus
profiles for real-time networks based on ISO/IEC/IEEE 8802-3
ISO/IEC 646, Information technology – ISO 7-bit coded character set for information
interchange
– 10 – IEC 61158-5-26:2019 © IEC 2019
ISO/IEC 7498-1, Information technology – Open Systems Interconnection – Basic Reference
Model – Part 1: The Basic Model
ISO/IEC/IEEE 8802-3, Information technology – Telecommunications and information
exchange between systems – Local and metropolitan area networks – Specific requirements –
Part 3: Standard for Ethernet
ISO/IEC 8822, Information technology – Open Systems Interconnection – Presentation
service definition
ISO/IEC 8824-1, Information Technology – Abstract Syntax notation One (ASN-1):
Specification of basic notation
ISO/IEC 9545, Information technology – Open Systems Interconnection – Application Layer
structure
ISO/IEC 10646, Information technology – Universal Coded Character Set (UCS)
ISO/IEC 10731, Information technology – Open Systems Interconnection – Basic Reference
Model – Conventions for the definition of OSI services
ISO/IEC 60559, Information technology – Microprocessor Systems – Floating-Point arithmetic
IETF RFC 768, User Datagram Protocol, available at http://www.ietf.org [viewed 2018-09-20]
IETF RFC 791, Internet Protocol, available at http://www.ietf.org [viewed 2018-09-20]
IETF RFC 792, Internet Control Message Protocol, available at http://www.ietf.org [viewed
2018-09-20]
IETF RFC 793, Transmission Control Protocol, available at http://www.ietf.org [viewed 2018-
09-20]
IETF RFC 796, Address mappings, available at http://www.ietf.org [viewed 2018-09-20]
IETF RFC 826, An Ethernet Address Resolution Protocol, available at http://www.ietf.org
[viewed 2018-09-20]
IETF RFC 894, A Standard for the Transmission of IP Datagrams over Ethernet Networks,
[viewed 2018-09-20]
available at http://www.ietf.org
IETF RFC 919, Broadcasting Internet Datagrams, available at http://www.ietf.org [viewed
2018-09-20]
IETF RFC 922, Broadcasting Internet Datagrams in the presence of subnets, available at
http://www.ietf.org [viewed 2018-09-20]
IETF RFC 950, Internet Standard Subnetting Procedure, available at http://www.ietf.org
[viewed 2018-09-20]
3 Terms, definitions, symbols, abbreviations and conventions
For the purposes of this document, the following terms, definitions, symbols, abbreviations
and conventions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions from other ISO/IEC standards
3.1.1 Terms and definitions from ISO/IEC 7498-1
For the purposes of this document, the following terms and definitions given in
ISO/IEC 7498-1 apply.
a) application entity
b) application process
c) application protocol data unit
d) application service element
e) application entity invocation
f) application process invocation
g) application transaction
h) real open system
i) transfer syntax
3.1.2 Terms and definitions from ISO/IEC 8822
For the purposes of this document, the following terms and definitions given in ISO/IEC 8822
apply.
a) abstract syntax
b) presentation context
3.1.3 Terms and definitions from ISO/IEC 9545
For the purposes of this document, the following terms and definitions given in ISO/IEC 9545
apply.
a) application-association
b) application-context
c) application context name
d) application-entity-invocation
e) application-entity-type
f) application-process-invocation
g) application-process-type
h) application-service-element
i) application control service element
3.1.4 Terms and definitions from ISO/IEC 8824-1
For the purposes of this document, the following terms and definitions given in
ISO/IEC 8824-1 apply.
a) object identifier
b) type
c) value
– 12 – IEC 61158-5-26:2019 © IEC 2019
d) simple type
e) structured type
f) tag
g) Boolean type
h) true
i) false
j) integer type
k) bitstring type
l) octetstring type
3.2 Fieldbus application layer Type 26-specific definitions
For the purposes of this document, the following terms and definitions apply.
3.2.1
application
function or data structure for which data is consumed or produced
3.2.2
application objects
multiple object classes that manage and provide a run time exchange of messages across the
network and within the network device
3.2.3
application process object
component of an application process that is identifiable and accessible through an FAL
application relationship
Note 1 to entry: Application process object definitions are composed of a set of values for the attributes of their
class (see the definition for Application Process Object Class Definition). Application process objects can be
accessed remotely using the services of the FAL Object Management ASE. FAL Object Management services can
be used to load or update object definitions, to read object definitions, and to dynamically create and delete
application objects and their corresponding definitions.
3.2.4
application process object class
class of application process objects defined in terms of the set of their network-accessible
attributes and services
3.2.5
application relationship
cooperative association between two or more application-entity-invocations for the purpose of
exchange of information and coordination of their joint operation
Note 1 to entry: This relationship is activated either by the exchange of application-protocol-data-units or as a
result of preconfiguration activities.
3.2.6
application relationship ASE
ASE used for establishing and terminating application relationship
3.2.7
application relationship endpoint
context and behavior of an application relationship as seen and maintained by one of the
application processes involved in the application relationship
Note 1 to entry: Each application process involved in the application relationship maintains its own application
relationship endpoint.
3.2.8
attribute
description of an externally visible characteristic or feature of an object
Note 1 to entry: The attributes of an object contain information about variable portions of an object. Typically,
they provide status information or govern the operation of an object. Attributes may also affect the behavior of an
object. Attributes are divided into class attributes and instance attributes.
3.2.9
behavior
indication of how an object responds to particular events
3.2.10
channel
single physical or logical link of an input or output application object of a server to the process
3.2.11
class
set of objects, all of which represent the same kind of system component
Note 1 to entry: A class is a generalization of an object; a template for defining variables and methods. All objects
in a class are identical in form and behavior, but usually contain different data in their attributes.
3.2.12
class attributes
attribute that is shared by all objects within the same class
3.2.13
client
object which uses the services of another (server) object to perform a task
3.2.14
client
initiator of a message to which a server reacts
3.2.15
common-memory
virtual memory accessible with logically unique address used for the cyclic-data transmission
Note 1 to entry: It is composed of the memory-area-1 and -2 of the memory size 512 words and 8 192 words
respectively and is shared with the Type 26 nodes in a Type 26 fieldbus network.
3.2.16
connection
logical binding between application objects that are within the same or different devices
Note 1 to entry: Connections can be either point-to-point or multipoint.
3.2.17
consumer
node or sink that is receiving data from a producer
3.2.18
control commands
action invocations transferred from client to server to clear outputs, freeze inputs and/or
synchronize outputs
3.2.19
cyclic
repetitive in a regular manner

– 14 – IEC 61158-5-26:2019 © IEC 2019
3.2.20
cyclic-data frame
frame used for the Type 26 cyclic-data transmission
3.2.21
cyclic-data transmission
data transmission with which a Type 26 node sends out data on a pre-assigned area for the
node on the common-memory, in broadcasting to all other Type 26 nodes every time the node
obtains a token
3.2.22
dedicated AR
AR used directly by the FAL User
Note 1 to entry: On dedicated ARs, only the FAL Header and the user data are transferred.
3.2.23
device
physical hardware connected to the link
Note 1 to entry: A device can contain one or more than one node.
3.2.24
device profile
collection of device dependent information and functionality providing consistency between
similar devices of the same device type
3.2.25
end node
producing or consuming node
3.2.26
endpoint
one of the communicating entities involved in a connection
3.2.27
error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition
3.2.28
event
instance of a change of conditions
3.2.29
FA-link protocol
communication protocol for Type 26 fieldbus
Note 1 to entry: It defines the token management, the cyclic data transmission and the message data
transmission, with which each Type 26 node performs data transmission on an equal basis.
3.2.30
FAL subnet
subnetworks composed of one or more data link segments, identified by a subset of the
network address
3.2.31
frame
synonym for DLPDU
3.2.32
invocation
act of using a service or other resource of an application process
Note 1 to entry: Each invocation represents a separate thread of control that can be described by its context.
Once the service completes, or use of the resource is released, the invocation ceases to exist. For service
invocations, a service that has been initiated but not yet completed is referred to as an outstanding service
invocation.
3.2.33
index
address of an object within an application process
3.2.34
instance
actual physical occurrence of an object within a class that identifies one of many objects
within the same object class
EXAMPLE California is an instance of the object class state.
Note 1 to entry: The terms object, instance, and object instance are used to refer to a specific instance.
3.2.35
instance attributes
attribute that is unique to an object instance and not shared by the object class
3.2.36
instantiated
object that has been created in a device
3.2.37
logical device
FAL class that abstracts a software component or a firmware component as an autonomous
self-contained facility of an automation device
3.2.38
management information
network-accessible information that supports managing the operation of the fieldbus system,
including the application layer
Note 1 to entry: Managing includes functions such as controlling, monitoring, and diagnosing.
3.2.39
message-data frame
frame used for the Type 26 message-data transmission
3.2.40
message-data transmission
sporadic data transmission with which a Type 26 node sends out the message data of request,
response, information report, notification upon event happened at the node and so forth, to
other Type 26 nodes
3.2.41
method
synonym for an operational service which is provided by the server ASE and invoked by a
client
3.2.42
module
hardware or logical component of a physical device

– 16 – IEC 61158-5-26:2019 © IEC 2019
3.2.43
multipoint connection
connection from one node to many
Note 1 to entry: Multipoint connections allow messages from a single producer to be received by many consumer
nodes.
3.2.44
network
set of nodes connected by some type of communication medium, including any intervening
repeaters, bridges, routers and lower-layer gateways
3.2.45
network load measurement function
provision for monitoring and measurement of the communication load over a Type 26 fieldbus
with a Type 26 node
3.2.46
object
abstract representation of a particular component within a device, usually a collection of
related data (in the form of variables) and methods (procedures) for operating on that data
that have clearly defined interface and behavior
3.2.47
participation-request-frame
frame used for a Type 26 node notifying of its participation-request in a Type 26 fieldbus
network
3.2.48
peer
role of an AR endpoint in which it is capable of acting as both client and server
3.2.49
physical device
automation or other network device
3.2.50
point-to-point connection
connection that exists between exactly two application objects
3.2.51
property
general term for descriptive information about an object
3.2.52
protocol type
identification of communication protocol
3.2.53
publisher
role of an AR endpoint that transmits APDUs onto the fieldbus for consumption by one or
more subscribers
Note 1 to entry: A publisher may not be aware of the identity or the number of subscribers and it may publish its
APDUs using a dedicated AR.
3.2.54
pull publisher
type of publisher that publishes an object in response to a request received from its pull
publishing manager
3.2.55
pull publishing manager
type of publishing manager that requests that a specified object be published in a
corresponding response APDU
3.2.56
push publisher
type of publisher that publishes an object in an unconfirmed service request APDU
3.2.57
push publishing manager
type of publishing manager that requests that a specified object be published using an
unconfirmed service
3.2.58
push subscriber
type of subscriber that recognizes received unconfirmed service request APDUs as published
object data
3.2.59
resource
processing or information capability of a subsystem
3.2.60
sequence number
consecutive number used to determine whether a receiving message-data from other nodes
has been previously received and is redundant
Note 1 to entry: The sequence number of a node is set to 0 (zero) at the time of the network-startup, and it is
incremented by 1 (one) every time a message-data transmission is completed. The sequence nu
...