IEC 61158-6-24:2023

IEC 61158-6-24 ®
Edition 2.0 2023-03
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 6-24: Application layer protocol specification – Type 24 elements

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IEC 61158-6-24 ®
Edition 2.0 2023-03
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –

Part 6-24: Application layer protocol specification – Type 24 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.040.40; 35.100.70; 35.110 ISBN 978-2-8322-6642-7

– 2 – IEC 61158-6-24:2023 © IEC 2023
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
1.1 General . 9
1.2 Specifications . 9
1.3 Conformance . 10
2 Normative references . 10
3 Terms, definitions, symbols, abbreviated terms, and conventions . 10
3.1 Referenced terms and definitions . 10
3.1.1 Terms and definitions from ISO/IEC 7498-1 . 11
3.1.2 Terms and definitions from ISO/IEC 9545 . 11
3.1.3 Terms and definitions from ISO/IEC 8824-1 . 11
3.1.4 Terms and definitions from ISO/IEC 10731 . 11
3.1.5 Terms and definitions from ISO/IEC 19501 . 12
3.2 Additional terms and definitions . 12
3.3 Abbreviations and symbols . 17
3.4 Conventions . 19
3.4.1 General conventions . 19
3.4.2 PDU data type conventions . 19
3.4.3 State machine conventions . 19
4 Abstract syntax . 22
4.1 Basic Data types . 22
4.2 FAL PDU types . 23
4.2.1 Top of APDU types: _APDU . 23
4.2.2 PDUs for field device control service . 24
4.2.3 PDUs for message service . 37
4.3 Detailed definitions of _FDCService-PDUs . 38
4.3.1 Short PDU type . 38
4.3.2 Long PDU type . 45
4.3.3 Enhanced PDU type . 48
4.3.4 SubCommand PDU type . 58
4.3.5 Short PDU type II. 59
4.4 Device profile . 66
5 Transfer syntax . 66
5.1 Concepts . 66
5.2 Encode rules . 66
5.2.1 INTEGER and its subtypes . 66
5.2.2 REAL type and its subtypes . 68
5.2.3 BIT STRING type . 69
5.2.4 OCTET STRING type and IA5String type . 70
5.2.5 NULL type . 71
5.2.6 Structure type and Array type . 71
6 Structure of FAL protocol state machine . 71
7 AP-context state machine (APC SM) . 73
7.1 Overview. 73
7.2 State descriptions . 74

7.3 Triggering events . 75
7.4 Action descriptions at state transitions . 75
8 FAL service protocol machines (FSPM) . 77
8.1 Overview. 77
8.2 Field Device Control Protocol Machine (FDC PM) . 77
8.2.1 Protocol overview . 77
8.2.2 Cyclic communication mode . 78
8.2.3 Event driven communication mode . 82
8.2.4 Master Protocol Machine (FDCPM-M) . 83
8.2.5 Slave Protocol Machine (FDCPM-S) . 92
8.2.6 Monitor Protocol Machine (FDCPM-MN) . 102
8.2.7 Error procedure summary . 104
8.3 Message Protocol Machine (MSGPM) . 106
8.3.1 Protocol overview . 106
8.3.2 Requester Protocol Machine (MSGPM-RQ) . 108
8.3.3 Responder Protocol Machine (MSGPM-RS) . 111
9 Application relationship protocol machine (ARPM) . 113
9.1 General . 113
9.2 ARPM for FDC ASE . 114
9.2.1 Overview . 114
9.2.2 ARPM for FDC Master (ARPM-FDCM) . 116
9.2.3 ARPM for FDC Slave (ARPM-FDCS) . 122
9.2.4 ARPM for FDC Monitor (ARPM-FDCMN). 129
9.3 ARPM for MSG ASE (ARPM-MSG) . 131
9.3.1 State descriptions . 131
9.3.2 Triggering events . 132
9.3.3 Action descriptions at state transitions . 133
10 DLL mapping protocol machine (DMPM) . 134
Annex A (informative) Device profile and FDC command sets . 135
Annex B (normative) Virtual memory space and Device Information . 137
B.1 Overview. 137
B.2 Device Information . 137
B.2.1 Device identifier area structure . 137
B.2.2 Detail specifications of device IDs . 138
Annex C (informative) Basic message function . 144
Bibliography . 145

Figure 1 – Tree structure of APDU types . 24
Figure 2 – Encode of Integer subtypes . 67
Figure 3 – Example of transfer of INTEGER value . 67
Figure 4 – Encode of Unsigned subtypes . 68
Figure 5 – Float type encode . 68
Figure 6 – Float type encode . 69
Figure 7 – Bit field definition example with named bits . 70
Figure 8 – Bit field definition example with field size . 70
Figure 9 – SEQUENCE type encode . 71

– 4 – IEC 61158-6-24:2023 © IEC 2023
Figure 10 – Structure of FAL protocol state machines . 73
Figure 11 – Statechart diagram of APCSM . 74
Figure 12 – Example communication cycle of FDC master AP . 79
Figure 13 – Example communication cycle of FDC slave AP . 79
Figure 14 – Synchronous command communication in sync state . 80
Figure 15 – Asynchronous command communication in sync state . 81
Figure 16 – Asynchronous command communication in async state . 82
Figure 17 – Event-driven communication . 83
Figure 18 – Statechart diagram of FDCPM-M . 84
Figure 19 – Statechart diagram of FDCPM-S . 93
Figure 20 – Statechart diagram of FDCPM-MN . 102
Figure 21 – PDU transmission flow for user message . 107
Figure 22 – PDU transmission flow for one-way message . 108
Figure 23 – Statechart diagram of MSGPM-RQ . 109
Figure 24 – Statechart diagram of MSGPM-RS . 111
Figure 25 – Example of single transfer process . 114
Figure 26 – Example of dual transfer process . 114
Figure 27 – Example of Synchronous command communication. 115
Figure 28 – Timing chart for individual communication cycle setting . 116
Figure 29 – Statechart diagram of ARPM-FDCM . 117
Figure 30 – Statechart diagram of ARPM-FDCS . 123
Figure 31 – Statechart diagram of ARPM-FDCMN . 129
Figure 32 – Statechart diagram of ARPM-MSG . 132
Figure B.1 – Memory map of virtual memory space . 137
Figure B.2 – Memory map of device ID area . 138

Table 1 – State transition descriptions . 20
Table 2 – Description of state machine elements . 20
Table 3 – Conventions used in state machines . 21
Table 4 – Mapping for Protocol State Machines . 72
Table 5 – State descriptions of APC SM . 74
Table 6 – Trigger event descriptions of APC SM . 75
Table 7 – Transitions of APC SM . 75
Table 8 – FDC protocol mode . 77
Table 9 – State descriptions of FDCPM-M. 84
Table 10 – Trigger event descriptions of FDCPM-M . 86
Table 11 – Transitions of main SM of FDCPM-M . 87
Table 12 – Transitions of submachine of FDCPM-M . 89
Table 13 – State descriptions of FDCPM-S . 93
Table 14 – Trigger event descriptions of FDCPM-S . 94
Table 15 – Transitions of main SM of FDCPM-S . 95
Table 16 – Transitions of submachine of FDCPM-S . 97
Table 17 – State descriptions of FDCPM-MN . 102

Table 18 – Trigger event descriptions of FDCPM-MN . 103
Table 19 – Transitions of main SM of FDCPM-MN . 103
Table 20 – Transitions of submachine of FDCPM-MN . 104
Table 21 – State descriptions of MSGPM-RQ . 109
Table 22 – Trigger event descriptions of MSGPM-RQ . 110
Table 23 – Transitions of MSGPM-RQ . 110
Table 24 – State descriptions of MSGPM-RS . 112
Table 25 – Trigger event descriptions of MSGPM-RS . 112
Table 26 – Transitions of MSGPM-RS . 113
Table 27 – State descriptions of ARPM-FDCM . 117
Table 28 – Trigger event descriptions of ARPM-FDCM . 119
Table 29 – Transitions of main SM of ARPM-FDCM . 120
Table 30 – Transitions of submachine of ARPM-FDCM . 121
Table 31 – State descriptions of ARPM-FDCS . 123
Table 32 – Trigger event descriptions of ARPM-FDCS . 125
Table 33 – Transitions of main SM of ARPM-FDCS . 126
Table 34 – Transitions of submachine of ARPM-FDCS . 127
Table 35 – State descriptions of ARPM-FDCMN . 129
Table 36 – Trigger event descriptions of ARPM-FDCMN . 130
Table 37 – Transitions of main SM of ARPM-FDCMN . 130
Table 38 – Transitions of submachine of ARPM-FDCMN . 131
Table 39 – State descriptions of ARPM-MSG . 132
Table 40 – Trigger event descriptions of ARPM-MSG . 133
Table 41 – Transitions of ARPM-MSG . 133
Table A.1 – Example of registered device profiles . 135
Table A.2 – Example command list of the profile ‘00'H . 136
Table B.1 – Specifications of device IDs . 138
Table C.1 – Example of message command set . 144

– 6 – IEC 61158-6-24:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 6-24: Application layer protocol specification –
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
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 61158-6-24 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.

The main changes with respect to the previous edition are listed below:
• addition of a new PDU type which called "Short PDU type II" in 4.2;
• update of Table 4;
• addition of examples of Synchronous Command communication in 9.2.1, Figure 27 and
Figure 28.
The text of this International Standard is based on the following documents:
Draft Report on voting
65C/1204/FDIS 65C/1245/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.
– 8 – IEC 61158-6-24:2023 © IEC 2023
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 protocol provides the application service by making use of the services
available from the data-link or other immediately lower layer. The primary aim of this document
is to provide a set of rules for communication expressed in terms of the procedures to be carried
out by peer application entities (AEs) at the time of communication. These rules for
communication are intended to provide a sound basis for development in order to serve a variety
of purposes:
• as a guide for implementers and designers;
• for use in the testing and procurement of equipment;
• as part of an agreement for the admittance of systems into the open systems environment;
• as a refinement to the understanding of time-critical communications within OSI.
This document is concerned, in particular, with the communication and interworking of sensors,
effectors and other automation devices. By using this document together with other standards
positioned within the OSI or fieldbus reference models, otherwise incompatible systems can
work together in any combination.

INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 6-24: Application layer protocol specification –
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 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 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 behavior provided by the Type
24 fieldbus application layer in terms of
• the abstract syntax defining the application layer protocol data units conveyed between
communicating application entities,
• the transfer syntax defining the application layer protocol data units conveyed between
communicating application entities,
• the application context state machines defining the application service behavior visibly
between communicating application entities, and
• the application relationship state machines defining the communication behavior visibly
between communicating application entities.
The purpose of this document is to define the protocol provided to
• define the representation-on-wire of the service primitives defined in IEC 61158-5-24, and
• define the externally visible behavior associated with their transfer.
This document specifies the protocol of the Type 24 fieldbus application layer, in conformance
with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI Application Layer Structure
(ISO/IEC 9545).
1.2 Specifications
The principal objective of this document is to specify the syntax and behavior of the application
layer protocol that conveys the application layer services defined in IEC 61158-5-24.
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 protocols
standardized in the IEC 61158-6 series.

– 10 – IEC 61158-6-24:2023 © IEC 2023
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.
Conformance is achieved through implementation of this application layer protocol specification.
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 61158-5-24:2023, Industrial communication networks – Fieldbus specifications –
Part 5-24: Application layer service definition – Type 24 elements
ISO/IEC 646, Information technology – ISO 7-bit coded character set for information
interchange
ISO/IEC 7498-1, Information technology – Open Systems Interconnection – Basic Reference
Model – Part 1: The Basic Model
ISO/IEC 9545, Information technology – Open Systems Interconnection – Application Layer
structure
ISO/IEC 9899, Information technology – Programming languages – C
ISO/IEC 10731, Information technology – Open Systems Interconnection – Basic Reference
Model – Conventions for the definition of OSI services
ISO/IEC 19501:2005, Information technology – Open Distributed Processing – Unified Modeling
Language (UML) Version 1.4.2
ISO/IEC/IEEE 60559:2020, Information technology – Microprocessor Systems – Floating-Point
arithmetic
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
For the purposes of this document, the following terms, definitions, symbols, abbreviations and
conventions apply.
3.1.1 Terms and definitions from ISO/IEC 7498-1
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) peer-(N)-entities;
i) presentation context;
j) real system;
k) transfer syntax.
3.1.2 Terms and definitions from ISO/IEC 9545
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 Terms and definitions from ISO/IEC 8824-1
For the purposes of this document, the following terms as defined in ISO/IEC 8824-1 apply:
a) simple type;
b) component;
c) component type;
d) integer type;
e) bitstring type;
f) octetstring type;
g) null type;
h) sequence type;
i) sequence of type;
j) choice type;
k) IA5String type;
l) encoding.
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.
– 12 – IEC 61158-6-24:2023 © IEC 2023
3.1.5 Terms and definitions from ISO/IEC 19501
For the purposes of this document, the following terms as defined in ISO/IEC 19501 apply:
a) event;
b) state;
c) state machine;
d) substate;
e) submachine;
f) transition.
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 operations 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 to 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, C1 master AP, C2 master AP and slave AP, by their application
roles in the fieldbus network.
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 4.4 and Annex A.

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 the transmission cycle multiplied 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

– 14 – IEC 61158-6-24:2023 © IEC 2023
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
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
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

3.2.26
field device protocol
FDC 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 nodes in a same network have, which
becomes an oscillation source of the transmission cycle
3.2.32
primary cycle
period of repetitive activities synchronized with the transmission cycle before the connection
establishing for the FDC protocol in Type 24 FAL
3.2.33
protocol machine
state machine that realizes a protocol as the main function of the entity in each layer
3.2.34
requester
class or its instance object of MSG ASE who plays a role of a command requester or sender for
the Type 24 FAL
3.2.35
responder
class or its instance object of MSG ASE who plays a role of a command responder or receiver
for the Type 24 FAL
3.2.36
response
PDU issued by a responder or a slave to inform a result or some status for the receive
...