IEC 61158-5-24:2023

IEC 61158-5-24 ®
Edition 2.0 2023-03
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 5-24: Application layer service definition – Type 24 elements

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IEC 61158-5-24 ®
Edition 2.0 2023-03
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –

Part 5-24: Application layer service definition – Type 24 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.100.70; 35.110 ISBN 978-2-8322-6580-2

– 2 – IEC 61158-5-24:2023 © IEC 2023
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
1.1 General . 8
1.2 Specifications . 9
1.3 Conformance . 9
2 Normative references . 9
3 Terms, definitions, symbols, abbreviated terms and conventions . 10
3.1 Referenced terms and definitions . 10
3.1.1 ISO/IEC 7498-1 terms . 10
3.1.2 ISO/IEC 9545 terms . 10
3.1.3 ISO/IEC 8824-1 terms . 10
3.1.4 Terms and definitions from ISO/IEC 10731 . 11
3.2 Additional terms and definitions . 11
3.3 Abbreviations and symbols . 16
3.4 Conventions . 17
3.4.1 Overview . 17
3.4.2 Conventions for class definitions . 18
3.4.3 Conventions for service definitions . 19
4 Concepts . 20
5 Data type ASE . 20
6 Communication model specifications . 20
6.1 Type specific concepts . 20
6.2 Overview. 21
6.3 FSM ASE . 23
6.3.1 Concepts . 23
6.3.2 FieldbusSystemManager class specifications . 24
6.4 FAL ASEs . 29
6.4.1 Field Device Control ASE . 29
6.4.2 Message ASE . 58
6.4.3 Event Management ASE . 71
6.5 FAL ARs . 75
6.5.1 AR model. 75
6.5.2 FDC AREP . 78
6.5.3 MSG AREP . 96
Bibliography . 102

Figure 1 – FAL ASE model of Type 24 . 23
Figure 2 – AR model for field device control service . 77
Figure 3 – AR model for message service . 77
Figure 4 – MSG ARs between each APs . 78

Table 1 – AP type definition . 22
Table 2 – Support list of service for each class of FSM ASE . 24
Table 3 – FSM-Reset . 26

Table 4 – FSM-GetStatus. 26
Table 5 – FSM-SetContext . 27
Table 6 – FSM-GetContext . 28
Table 7 – FSM-Start. 29
Table 8 – Support list of service for each class of FDC ASE . 29
Table 9 – FDC-Reset for master class . 33
Table 10 – FDC-Open for master class . 33
Table 11 – FDC-Enable for master class . 34
Table 12 – FDC-Connect for master class . 35
Table 13 – FDC-SyncSet for master class . 36
Table 14 – FDC-Disconnect for master class . 37
Table 15 – FDC-ResumeCycle for master class . 38
Table 16 – FDC-ComCycle for master class . 38
Table 17 – FDC-Command for master class . 39
Table 18 – FDC-DataExchange for master class . 40
Table 19 – FDC-Reset for slave class . 44
Table 20 – FDC-Open for slave class . 44
Table 21 – FDC-Enable for slave class . 45
Table 22 – FDC-Connect for slave class . 46
Table 23 – FDC-SyncSet for slave class . 47
Table 24 – FDC-Disconnect for slave class . 49
Table 25 – FDC-ResumeCycle for slave class . 50
Table 26 – FDC-ComCycle for slave class . 50
Table 27 – FDC-Command for slave class . 51
Table 28 – FDC-Command for slave class . 52
Table 29 – FDC-Reset for monitor class . 54
Table 30 – FDC-Open for monitor class . 55
Table 31 – FDC-Enable for monitor class . 55
Table 32 – FDC-GetCMD for monitor class . 56
Table 33 – FDC-GetRSP for monitor class . 57
Table 34 – Support list of service for each class of Message ASE. 58
Table 35 – MSG-Reset for requester class . 60
Table 36 – MSG-Open for requester class . 61
Table 37 – MSG-Enable for requester class . 61
Table 38 – MSG-UserMessage for requester class. 62
Table 39 – MSG-OnewayMessage for requester class . 64
Table 40 – MSG-AbortTransaction for requester class . 65
Table 41 – MSG-Reset for responder class . 67
Table 42 – MSG-Open for responder class . 68
Table 43 – MSG-Enable for responder class . 68
Table 44 – MSG-UserMessage for responder class . 69
Table 45 – MSG-OnewayMessage for responder class . 70
Table 46 – MSG-AbortTransaction for responder class . 71

– 4 – IEC 61158-5-24:2023 © IEC 2023
Table 47 – Support list of service for each class of Event Management ASE . 72
Table 48 – EVM-Reset . 73
Table 49 – EVM-Enable . 73
Table 50 – EVM-SyncEvent . 74
Table 51 – EVM-ReadNetClock . 74
Table 52 – Support list of service for each class of AR ASE . 75
Table 53 – AR-Reset for FDC Master AR class . 80
Table 54 – AR-Open for FDC Master AR class . 81
Table 55 – AR-Enable for FDC Master AR class . 81
Table 56 – AR-CycleEvent for FDC Master AR class . 82
Table 57 – AR-StartComCycle for FDC Master AR class . 82
Table 58 – AR-ResetCycle for FDC Master AR class . 83
Table 59 – AR-SendCommand for FDC Master AR class . 84
Table 60 – AR-Reset for FDC Slave AR class . 87
Table 61 – AR-Open for FDC Slave AR class . 87
Table 62 – AR-Enable for FDC Slave AR class . 88
Table 63 – AR-CycleEvent for FDC Slave AR class . 88
Table 64 – AR-StartComCycle for FDC Slave AR class . 89
Table 65 – AR-ResetCycle for FDC Slave AR class . 89
Table 66 – AR-SendCommand for FDC Slave AR class . 90
Table 67 – AR-Reset for FDC Monitor AR class . 92
Table 68 – AR-Open for FDC Monitor AR class . 93
Table 69 – AR-Enable for FDC Monitor AR class . 93
Table 70 – AR-GetCMD for FDC Monitor AR class . 94
Table 71 – AR-GetCMD for FDC Monitor AR class . 95
Table 72 – AR-Reset for Message AR class . 97
Table 73 – AR-Open for Message AR class . 98
Table 74 – AR-Enable for Message AR class . 98
Table 75 – AR-SendMessage for Message AR class . 99
Table 76 – AR-ReceiveMessage for Message AR class . 100
Table 77 – AR-AbortMessage for Message AR class. 101

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 5-24: Application layer service definition –
Type 24 elements
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
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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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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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
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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.
Attention is drawn to the fact that the use of the associated protocol type is restricted by its
intellectual-property-right holders. In all cases, the commitment to limited release of intellectual-
property-rights made by the holders of those rights permits a layer protocol type to be used with
other layer protocols of the same type, or in other type combinations explicitly
authorized by its intellectual-property-right holders.
NOTE Combinations of protocol types are specified in the IEC 61784-1 series and the IEC 61784-2 series.
IEC 61158-5-24 has been prepared by subcommittee 65C: Industrial networks, of IEC technical
committee 65: Industrial-process measurement, control and automation. It is an International
Standard.
This second edition cancels and replaces the first edition published in 2014. This edition
constitutes a technical revision.

– 6 – IEC 61158-5-24:2023 © IEC 2023
The main changes with respect to the previous edition are listed below:
a) modify to the AP type definition in Table 1;
b) modify to the Support list of service for each class of FDC ASE in Table 8.
The text of this International Standard is based on the following documents:
Draft Report on voting
65C/1203/FDIS 65C/1244/RVD
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 61158 series, published under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC web site.
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,
• replaced by a revised edition, or
• amended.
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 can
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 61158-5-24:2023 © IEC 2023
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 5-24: Application layer service definition –
Type 24 elements
1 Scope
1.1 General
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 document 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 24 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 document defines in an abstract way the externally visible service provided by the different
Types of fieldbus Application Layer in terms of
• an abstract model for defining application resources (objects) capable of being manipulated
by users via the use of the FAL service,
• the primitive actions and events of the service,
• the parameters associated with each primitive action and event, and the form which they
take, and
• the interrelationship between these actions and events, and their valid sequences.
The purpose of this International Standard is to define the services provided to
• the FAL user at the boundary between the user and the Application Layer of the Fieldbus
Reference Model, and
• 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 (ISO/IEC 7498-1) and the OSI Application
Layer Structure (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 the IEC 61158-6 series.
This document can 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
• the sizes and octet ordering of various multi-octet service parameters, and
• 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 do they 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 fulfil any given Type of application layer services as defined in this part of
IEC 61158.
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 the IEC 61784-1 series and the IEC 61784-2 series 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 61158-1:2023, Industrial communication networks – Fieldbus specifications – Part 1:
Overview and guidance for the IEC 61158 and IEC 61784 series
IEC 61158-4-24:2023, Industrial communication networks – Fieldbus specifications – Part 4-24:
Data link layer protocol specification – Type 24 elements
IEC 61158-6-24:2023, Industrial communication networks – Fieldbus specifications – Part 6-24:
Application layer protocol specification – Type 24 elements
ISO/IEC 7498-1, Information technology – Open Systems Interconnection – Basic Reference
Model – Part 1: The Basic Model

– 10 – IEC 61158-5-24:2023 © IEC 2023
ISO/IEC 8824-1, Information technology – Abstract Syntax Notation One (ASN.1) – Part 1:
Specification of basic notation
ISO/IEC 9545, Information technology – Open Systems Interconnection – Application Layer
structure
ISO/IEC 10731, Information technology – Open Systems Interconnection – Basic Reference
Model – Conventions for the definition of OSI services
3 Terms, definitions, symbols, abbreviated terms and conventions
For the purposes of this document, the following terms, definitions, symbols, abbreviated terms
and conventions apply.
ISO and IEC maintain terminological 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
3.1 Referenced terms and definitions
3.1.1 ISO/IEC 7498-1 terms
For the purposes of this document, the following terms as defined in ISO/IEC 7498-1 apply:
a) abstract syntax;
b) application-entity;
c) application process;
d) application protocol data unit;
e) application-process-invocation;
f) (N)-facility;
g) (N)-function;
h) correspondent-(N)-entities;
i) presentation context;
j) real system;
k) transfer syntax.
3.1.2 ISO/IEC 9545 terms
For the purposes of this document, the following terms as defined in ISO/IEC 9545 apply:
a) application-association;
b) application-context;
c) application-entity-invocation;
d) application-entity-type;
e) application-service-element.
3.1.3 ISO/IEC 8824-1 terms
For the purposes of this document, the following terms as defined in ISO/IEC 8824-1 apply:
a) object identifier.
3.1.4 Terms and definitions from ISO/IEC 10731
For the purposes of this document, the following terms as defined in ISO/IEC 10731 apply:
a) OSI-service-primitive; primitive;
b) OSI-service-provider; provider;
c) OSI-service-user; user.
3.2 Additional terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.2.1
alarm
field device status to tell that the device has detected a fatal problem to be solved and cannot
continue normal working, through the field device control (FDC) service of the type 24 fieldbus
Note 1 to entry: Any alarm statuses are latched and need some operation to be cleared.
Note 2 to entry: Alarms are classified into three groups; communication alarms, illegal-command-related ones, and
application specific ones. But concrete definitions are dependent on implementation of each field devices.
3.2.2
application process object
network representation of a specific aspect of an application process (AP), which is modelled
as a network accessible object contained within an AP or within another APO
Note 1 to entry: Refer IEC 61158-1, 9.3.4.
3.2.3
application process context
AP context
shared knowledge or a common set of rules, governing communication of FAL application
entities (AEs) and describing the permissible collective communications behavior between the
AEs that are party to a specific set of application relationships (ARs)
Note 1 to entry: Data within AP context can be specified by the user in advance, by the option selected while the
user uses a field bus management (FSM) service to read out the facility of peer AP, by the automatic negotiation
function that the FSM system handles, and so on. The method that is to be adopted depends on the specification of
each implementation.
3.2.4
application process type
AP type
description of a classification of application processes (APs) in terms of a set of capabilities for
FAL of the type 24 fieldbus
Note 1 to entry: AP types are classified into three ones, C1 master AP, C2 master AP and slave AP, by their
application roles in the fieldbus network. See 6.2.
3.2.5
async command
type of a command application protocol data unit (APDU) of the FDC service of the type 24 FAL,
which can be issued any time after the previous transaction without consideration of
synchronization with the communication cycle
Note 1 to entry: Definitions, which command should be async one or not, are dependent on an application. They
can be provided as a registered set of commands and responses or device profiles (see IEC 61158-6-24, 4.4 and
Annex A).
– 12 – IEC 61158-5-24:2023 © IEC 2023
3.2.6
asynchronous communication
state or a way of communication for the FDC service of the type 24 FAL, in which a command
can be issued any time after the previous transaction without consideration of synchronization
with the communication cycle
Note 1 to entry: In this state, sync commands cannot be issued, but async commands can.
3.2.7
attribute
information or parameter contained in variable portions of an object
Note 1 to entry: Typically, they provide status information or govern the operation of an object. Attributes also affect
the behavior of an object.
3.2.8
C1 master
AP type that has master facilities for the FDC service of the type 24 FAL, or the device
implementing that AP type
Note 1 to entry: Only one C1 master exists in a network of the type 24 fieldbus
3.2.9
C2 master
AP type that has only monitor facilities for the FDC service but requester facilities for message
(MSG) service of the type 24 FAL, or the device implementing that AP type
Note 1 to entry: Less than two C2 masters can exist in a network of the type 24 fieldbus
3.2.10
command
PDU issued by a requester or a master to make a responder or a slave execute some functions
3.2.11
communication
process to exchange information in a formal manner between two or more devices, users, APs
or entities
3.2.12
transfer
process to convey a PDU from a sender to a receiver
3.2.13
transmission
process to send out and propagate electrical signals or encoded data
3.2.14
communication cycle
period of repetitive activities synchronized with the transmission cycle while the connection
establishing for the FDC protocol of the type 24 FAL
Note 1 to entry: Communication cycle can synchronize with a cycle multiplying the transmission cycle by a specified
scaling factor.
3.2.15
connection
context or logical binding under specific conditions for the FDC protocol between a master
object and a slave object for the type 24 FAL

3.2.16
cyclic
repetitive in a regular manner
3.2.17
cyclic communication
transmission mode in which request PDUs and response PDUs are exchanged repetitively in
the scheduled time slots synchronized with a transmission cycle for the lower layer protocol of
the type 24 fieldbus
Note 1 to entry: In the AL, the communication cycle arises from the transmission cycle in this mode.
3.2.18
cycle scale counter
counter to generate a communication cycle by means of scaling a primary cycle or a
transmission cycle
3.2.19
device ID
part of "device information" to identify the device for a specific product type or model of the
type 24 fieldbus
3.2.20
device information
formatted and device-embedded information to characterize a device, which mainly consists of
data for device model identification and device-profile specific parameters for the type 24
fieldbus
3.2.21
device profile
collection of device model-common information and functionality providing consistency between
different device models among the same kind of devices
3.2.22
dual transfer
transfer mode for the FDC protocol of the type 24 FAL, in which a sender sends a same PDU
twice a transaction and a receiver uses them to detect and recover a communication error such
as data-corruption or data-loss in cyclic communication mode
3.2.23
event driven communication
transmission mode for the lower layer protocol of the type 24 fieldbus in which a transaction of
command-response-exchanging arises as user’s demands
Note 1 to entry: Both the transmission cycle and the communication cycle don’t arise in this mode.
3.2.24
error
abnormal condition or malfunction for communication or any other activities
3.2.25
field device control service
FDC service
time-critical communication service that handles a fixed length command data to control a field
device and the corresponding feedback response data in a severe restriction on delay or jitter
for the communication timing for the type 24 FAL

– 14 – IEC 61158-5-24:2023 © IEC 2023
3.2.26
field device control protocol
time-critical communication protocol that handles a fixed length command data to control a field
device and the corresponding feedback response data in a severe restriction on delay or jitter
for the communication timing for the type 24 FAL
3.2.27
master
class or its instance object of FDC application service element (ASE) who plays a role of a
command requester for the type 24 FAL
3.2.28
message service
MSG service
communication service that handles the variable length data and not required a severe
restriction on response time
3.2.29
monitor
class or its instance object of FDC ASE who plays a role of a watcher or subscriber of commands
and response between other communication nodes for the type 24 FAL
3.2.30
monitor slave
variant of slave AP type who has both slave class and monitor class for FDC ASE of the type 24
FAL
3.2.31
network clock
synchronized and periodically running counter that each node in a same network has, which
becomes an oscillation source of the transmission cycle
3.2.32
protocol machine
state machine that realizes the protocol as the main function of the entity in each layer
3.2.33
requester
class or its instance object of MSG ASE who plays a role of a command requester or sender for
the type 24 FAL
3.2.34
responder
class or its instance object of MSG ASE who plays a role of a command responder or receiver
for the type 24 FAL
3.2.35
response
PDU issued by a responder or a slave to inform a result or some status for the received
command to a requester or a master
3.2.36
service
operation or process that an object performs upon request from another object

3.2.37
single transfer
normal transfer mode for the FDC protocol of the type 24 FAL in which a sender sends a same
PDU once a transaction
3.2.38
slave AP
AP type that has slave facilities for the FDC service of the type 24 FAL, or the device
implementing that AP type
3.2.39
slave
FDC slave
class or its instance object of FDC ASE who plays a role of a responder for the type 24 FAL
3.2.40
state machine
logical automatic machine or automaton that has a finite number of states and handles state
transition fired by an event as a trigger
3.2.41
sync command
type of command or APDU of the FDC service of the type 24 FAL, which is issued at the
synchronized timing with every communication cycle
Note 1 to entry: Definitions which command should be sync one or not are dependent on an application. They can
be provided as a registered set of commands and responses or device profiles (see IEC 61158-6-24, 4.4 and
Annex A).
3.2.42
synchronous communication
state or a way of communication for the FDC service of the type 24 FAL, in which a command
is issued at the synchronized timing with every communication cycle
Note 1 to entry: In this state, both sync commands and async ones can be issued.
Note 2 to entry: In this state, an out-of-synchronization error of APs shall be detected by measures of the watchdog
counter.
3.2.43
transmission cycle
period of repetitive activities for the lower layers of the type 24 fieldbus, which of all the slave
devices are synchronized with that of a C1 master device by the lower layer protocol
3.2.44
transmission mode
state or a way of transmission for the lower layer protocol of the type 24 fieldbus; cyclic mode,
event driven mode
3.2.45
virtual memory space
large data block of APOs for the type 24 FAL which can be read and write with pseudo-memory-
addresses to provide consistency between different device models
Note 1 to entry: The virtual memory space includes the device information and other vender specific area. See
IEC 61158-6-24, Annex B.
– 16 – IEC 61158-5-24:2023 © IEC 2023
3.2.46
warning
field device status to tell that the device has detected a slight or passing problem but still
working normally through the field device control (FDC) service of the type 24 fieldbus
Note 1 to entry: Any warning statuses are latched and need to be operated to clear them.
Note 2 to entry: Warnings are classified into three groups, communication warnings, illegal-command-related ones,
and application specific ones. But concrete definitions are dependent on implementation of each field devices.
3.3 Abbreviations and symbols
For the purposes of this document, the following abbreviations and symbols apply.
AE Application Entity
AL Application Layer
A-, AL- Application layer (as a prefix)
AP Application Process
APDU Application Protocol Data Unit
API Application Process Invocation
APO Application Process Object
APC Application Process Context (as prefix of a protocol for type 24 fieldbus)
APC SM Application Process Context State Machine (for type 24 fieldbus)
AR Application Relationship
AR ASE Application Relationship Application Service Element
AREP Application Relationship End Point
ARPM Application Relationship Protocol Machine (for type 24 fieldbus)
ARPM-FDCM ARPM for Field Device Control service Master (for type 24 fieldbus)
ARPM-FDCMN ARPM for Field Device Control service Monitor (for type 24 fieldbus)
ARPM-FDCS ARPM for Filed Device Control service Slave (for type 24 fieldbus)
ARPM-MSG ARPM for Message service (for type 24 fieldbus)
ASCII American Standard code for Information Interchange
ASE Application Service Element
ASN.1 Abstract Syntax Notation One
Cnf Confirm primitive
DL Data-link-layer
DL- (as a prefix) Data Link-
...