IEC 61158-6-15:2007

IEC 61158-6-15
Edition 1.0 2007-12
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 6-15: Application layer protocol specification – Type 15 elements

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IEC 61158-6-15
Edition 1.0 2007-12
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 6-15: Application layer protocol specification – Type 15 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XD
ICS 35.100.70; 25.040.40 ISBN 2-8318-9493-X

– 2 – 61158-6-15 © IEC:2007(E)

CONTENTS
FOREWORD.6

INTRODUCTION.8

1 Scope.9

1.1 General .9

1.2 Specifications.9

1.3 Conformance.9

2 Normative references .10

3 Terms and definitions, abbreviations, symbols and conventions .10
3.1 Terma and definitions.10
3.2 Abbreviations and symbols.17
3.3 Conventions .18
3.4 Conventions used in state machines .20
4 Abstract syntax for client/server .22
5 Transfer syntax for client/server .22
5.1 General .22
5.2 Common APDU structure .22
5.3 Service-specific APDU structures .26
5.4 Data representation ‘on the wire’ .50
6 Abstract syntax for publish/subscribe .50
7 Transfer syntax for publish/subscribe .51
7.1 General .51
7.2 APDU structure .51
7.3 Sub-message structure .52
7.4 APDU interpretation .54
7.5 Service specific APDU structures .56
7.6 Common data representation for publish/subscribe .77
8 Structure of FAL protocol state machines .82
9 AP-context state machines for client/server .84
10 FAL service protocol machine (FSPM) for client/server.84
10.1 General .84
10.2 FSPM state tables .84

10.3 Functions used by FSPM.90
10.4 Parameters of FSPM/ARPM primitives .90
10.5 Client/server server transactions .90
11 Application relationship protocol machines (ARPMs) for client/server .91
11.1 Application relationship protocol machines (ARPMs) .91
11.2 AREP state machine primitive definitions .93
11.3 AREP state machine functions .94
12 DLL mapping protocol machine (DMPM) for client/server.94
12.1 AREP mapping to data link layer .94
12.2 DMPM states.95
12.3 DMPM states.95
12.4 Primitives exchanged between data link layer and DMPM .95
12.5 Client/server on TCP/IP.96
13 AP-Context state machines for publish/subscribe .97

61158-6-15 © IEC:2007(E) – 3 –

14 Protocol machines for publish/subscribe.97

14.1 General .97

14.2 Publish/subscribe on UDP .99

Bibliography.100

Figure 1 – APDU Format.22

Figure 2 – Client to server confirmed service request.24

Figure 3 – Normal response from server to client.24

Figure 4 – Exception response from server to client.24

Figure 5 – Client to server unconfirmed service request.25
Figure 6 – Publish/subscribe APDU .51
Figure 7 – Relationships among protocol machines and adjacent layers .83
Figure 8 – State transition diagram of FSPM.84
Figure 9 – Client/server server transactions.91
Figure 10 – State transition diagram of the client ARPM .92
Figure 11 – State transition diagram of the server ARPM .92
Figure 12 – State transition diagram of DMPM .95
Figure 13 – APDU format.96
Figure 14 – TCP/IP PDU format .97
Figure 15 – Publish/subscribe receiver .98

Table 1 – Conventions used for state machines .21
Table 2 – Exception code.25
Table 3 – Read discretes request .26
Table 4 – Read discretes response.26
Table 5 – Read coils request .27
Table 6 – Read coils response.27
Table 7 – Write single coil request .28
Table 8 – Write single coil response .28
Table 9 – Write multiple coils request .29
Table 10 – Write multiple coils response.29
Table 11 – Broadcast write single coil request .30
Table 12 – Broadcast write multiple coils request.31
Table 13 – Read input registers request .31
Table 14 – Read input registers response.32
Table 15 – Read holding registers request.32
Table 16 – Read holding registers response .33
Table 17 – Write single holding register request .33
Table 18 – Write single holding register response.34
Table 19 – Write multiple holding registers request.34
Table 20 – Write multiple holding registers response .35
Table 21 – Mask write holding register request .36
Table 22 – Mask write holding register request .36

– 4 – 61158-6-15 © IEC:2007(E)

Table 23 – Read/Write multiple holding registers request.37

Table 24 – Read/Write multiple holding registers response .37

Table 25 – Read FIFO request.38

Table 26 – Read FIFO response .38

Table 27 – Broadcast write single holding register request.39

Table 28 – Broadcast write multiple holding registers request .40

Table 29 – Read file record request .41

Table 30 – Read file record response .42

Table 31 – Write file record request .43
Table 32 – Write file record response .45
Table 33 – Read device identification request.46
Table 34 – Device identification categories .47
Table 35 – Read device ID code .47
Table 36 – Read device identification response .48
Table 37 – Conformity level .49
Table 38 – Requested vs. returned known objects .50
Table 39 – APDU structure .52
Table 40 – Sub-message structure .53
Table 41 – Publish/subscribe service identifier encoding .53
Table 42 – Attributes changed modally and affecting APDUs interpretations .55
Table 43 – Issue request .56
Table 44 – Flags of issue request .57
Table 45 – Meaning of issue request flags .57
Table 46 – Interpretation of issue.58
Table 47 – Heartbeat request .59
Table 48 – Flags of heartbeat request.59
Table 49 – Meaning of heartbeat request flags .60
Table 50 – Interpretation of heartbeat .61
Table 51 – VAR request.62
Table 52 – Flags of VAR request .63
Table 53 – Meaning of VAR request flags .63

Table 54 – Interpretation of VAR.64
Table 55 – GAP request.65
Table 56 – Flags of GAP request .65
Table 57 – Meaning of GAP request flags .66
Table 58 – Interpretation of GAP.66
Table 59 – ACK request.67
Table 60 – Flags of ACK request .67
Table 61 – Meaning of ACK request flags .68
Table 62 – Interpretation of ACK.68
Table 63 – Header request .69
Table 64 – Change in state of the receiver.70
Table 65 – INFO_DST request.70

61158-6-15 © IEC:2007(E) – 5 –

Table 66 – Flags of INFO_DST request .71

Table 67 – Meaning of INFO_DST request flags .71

Table 68 – INFO_REPLY request .72

Table 69 – Flags of INFO_REPLY request .72

Table 70 – Meaning of INFO_REPLY request flags .72

Table 71 – INFO_SRC request .74

Table 72 – Flags of INFO_SRC request .74

Table 73 – Meaning of INFO_SRC request flags .74

Table 74 – INFO_TS request .75
Table 75 – Flags of INFO_TS request.76
Table 76 – Meaning of INFO_TS request flags.76
Table 77 – PAD request.77
Table 78 – Flags of PAD request .77
Table 79 – Meaning of PAD request flags .77
Table 80 – Semantics .78
Table 81 – FSPM state table – client transactions.85
Table 82 – FSPM state table – server transactions .90
Table 83 – Function MatchInvokeID().90
Table 84 – Function HighBit() .90
Table 85 – Parameters used with primitives exchanged between FSPM and ARPM .90
Table 86 – Client ARPM states .92
Table 87 – Client ARPM state table .92
Table 88 – Server ARPM states .92
Table 89 – Server ARPM state table .93
Table 90 – Primitives issued from ARPM to DMPM .93
Table 91 – Primitives issued by DMPM to ARPM .93
Table 92 – Parameters used with primitives exchanged between ARPM and DMPM .93
Table 93 – DMPM state descriptions.95
Table 94 – DMPM state table – client transactions.95
Table 95 – DMPM state table – server transactions .95
Table 96 – Primitives exchanged between data-link layer and DMPM .96

Table 97 – Encapsulation parameters for client/server on TCP/IP .96

– 6 – 61158-6-15 © IEC:2007(E)

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
INDUSTRIAL COMMUNICATION NETWORKS –

FIELDBUS SPECIFICATIONS –
Part 6-15: Application layer protocol specification – Type 15 elements

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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
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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.
NOTE  Use of some of the associated protocol types is restricted by their 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 particular data-link layer protocol type to be used with physical layer and application layer protocols in Type
combinations as specified explicitly in the IEC 61784 series. Use of the various protocol types in other
combinations may require permission from their respective intellectual-property-right holders.
International Standard IEC 61158-6-15 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This first edition and its companion parts of the IEC 61158-6 subseries cancel and replace
IEC 61158-6:2003. This edition of this part constitutes a technical addition. This part and its
Type 15 companion parts also cancel and replace IEC/PAS 62030, published in 2005.
This edition of IEC 61158-6 includes the following significant changes from the previous
edition:
61158-6-15 © IEC:2007(E) – 7 –

a) deletion of the former Type 6 fieldbus for lack of market relevance;

b) addition of new types of fieldbuses;

c) partition of part 6 of the third edition into multiple parts numbered -6-2, -6-3, …

The text of this standard is based on the following documents:

FDIS Report on voting
65C/476/FDIS 65C/487/RVD
Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.
This publication has been drafted in accordance with ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.
NOTE  The revision of this standard will be synchronized with the other parts of the IEC 61158 series.
The list of all the parts of the IEC 61158 series, under the general title Industrial
communication networks – Fieldbus specifications, can be found on the IEC web site.

– 8 – 61158-6-15 © IEC:2007(E)

INTRODUCTION
This part of IEC 61158 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/TR 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 standard

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 implementors 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 standard is concerned, in particular, with the communication and interworking of sensors,
effectors and other automation devices. By using this standard together with other standards
positioned within the OSI or fieldbus reference models, otherwise incompatible systems may
work together in any combination.

61158-6-15 © IEC:2007(E) – 9 –

INDUSTRIAL COMMUNICATION NETWORKS –

FIELDBUS SPECIFICATIONS –
Part 6-15: Application layer protocol specification – Type 15 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 standard 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 15 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 standard defines in an abstract way the externally visible behavior provided by the Type
15 fieldbus Application Layer in terms of
a) the abstract syntax defining the application layer protocol data units conveyed between
communicating application entities,
b) the transfer syntax defining the application layer protocol data units conveyed between
communicating application entities,
c) the application context state machine defining the application service behavior visible
between communicating application entities; and
d) the application relationship state machines defining the communication behavior visible
between communicating application entities; and.
The purpose of this standard is to define the protocol provided to
1) define the wire-representation of the service primitives defined in IEC 61158-5-15, and
2) define the externally visible behavior associated with their transfer.
This standard specify the protocol of the Type 15 IEC fieldbus Application Layer, in

conformance with the OSI Basic Reference Model (ISO/IEC 7498) and the OSI Application
Layer Structure (ISO/IEC 9545).
1.2 Specifications
The principal objective of this standard is to specify the syntax and behavior of the application
layer protocol that conveys the application layer services defined in IEC 61158-5-15.
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 IEC 61158-6.
1.3 Conformance
This standard does not specify individual implementations or products, nor does it constrain
the implementations of application layer entities within industrial automation systems.

– 10 – 61158-6-15 © IEC:2007(E)

Conformance is achieved through implementation of this application layer protocol

specification.
2 Normative references
The following referenced documents are indispensable for the application 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 61158-5-15, Industrial communication networks – Fieldbus specifications – Part 5-15:
Application layer service definition – Type 15 elements
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 8822, Information technology – Open Systems Interconnection – Presentation
service definition
ISO/IEC 8824, Information technology – Open Systems Interconnection – Specification of
Abstract Syntax Notation One (ASN.1)
3 Terms and definitions, abbreviations, symbols and conventions
3.1 Terma and definitions
For the purposes of this document, the following terms as defined in these publications apply:
3.1.1 ISO/IEC 7498-1 terms
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 ISO/IEC 8822 terms
a) abstract syntax
b) presentation context
3.1.3 ISO/IEC 9545 terms
a) application-association
b) application-context
c) application context name
d) application-entity-invocation
e) application-entity-type
61158-6-15 © IEC:2007(E) – 11 –

f) application-process-invocation

g) application-process-type
h) application-service-element

i) application control service element

3.1.4 ISO/IEC 8824 terms
a) object identifier
b) type
3.1.5 IEC/TR 61158-1 terms
The following IEC/TR 61158-1 terms apply.
3.1.5.1 application
function or data structure for which data is consumed or produced
3.1.5.2 application layer interoperability
capability of application entities to perform coordinated and cooperative operations using the
services of the FAL
3.1.5.3 application object
object class that manages and provides the run time exchange of messages across the
network and within the network device
NOTE Multiple types of application object classes may be defined.
3.1.5.4 application process
part of a distributed application on a network, which is located on one device and
unambiguously addressed
3.1.5.5 application process identifier
distinguishes multiple application processes used in a device
3.1.5.6 application process object
component of an application process that is identifiable and accessible through an FAL
application relationship
NOTE  Application process object definitions are composed of a set of values for the attributes of their class.
3.1.5.7 application process object class
class of application process objects defined in terms of the set of their network-accessible
attributes and services
3.1.5.8 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  This relationship is activated either by the exchange of application-protocol-data-units or as a result of
preconfiguration activities.
– 12 – 61158-6-15 © IEC:2007(E)

3.1.5.9 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  Each application process involved in the application relationship maintains its own application relationship

endpoint.
3.1.5.10 application service element

application-service-element that provides the exclusive means for establishing and

terminating all application relationships

3.1.5.11 attribute
description of an externally visible characteristic or feature of an object
NOTE  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 behaviour of an object.
Attributes are divided into class attributes and instance attributes.
3.1.5.12 behaviour
indication of how the object responds to particular events
NOTE  Its description includes the relationship between attribute values and services.
3.1.5.13 class
set of objects, all of which represent the same kind of system component
NOTE  A class is a generalisation of the object; a template for defining variables and methods. All objects in a
class are identical in form and behaviour, but usually contain different data in their attributes.
3.1.5.14 class attributes
attribute that is shared by all objects within the same class
3.1.5.15 class code
unique identifier assigned to each object class
3.1.5.16 class specific service
service defined by a particular object class to perform a required function which is not
performed by a common service
NOTE  A class specific object is unique to the object class which defines it.
3.1.5.17 Client
a) object which uses the services of another (server) object to perform a task
b) initiator of a message to which a server reacts, such as the role of an AR endpoint in which
it issues confirmed service request APDUs to a single AR endpoint acting as a server
3.1.5.18 conveyance path
unidirectional flow of APDUs across an application relationship
3.1.5.19 cyclic
term used to describe events which repeat in a regular and repetitive manner

61158-6-15 © IEC:2007(E) – 13 –

3.1.5.20 dedicated AR
AR used directly by the FAL user

NOTE  On Dedicated ARs, only the FAL Header and the user data are transferred.

3.1.5.21 device
physical hardware connection to the link

NOTE  A device may contain more than one node.

3.1.5.22 device profile
collection of device dependent information and functionality providing consistency between
similar devices of the same device type
3.1.5.23 dynamic AR
AR that requires the use of the AR establishment procedures to place it into an established
state
3.1.5.24 endpoint
one of the communicating entities involved in a connection
3.1.5.25 error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition
3.1.5.26 error class
general grouping for error definitions
NOTE  Error codes for specific errors are defined within an error class.
3.1.5.27 error code
identification of a specific type of error within an error class
3.1.5.28 FAL subnet
networks composed of one or more data link segments

NOTE  Subnets are permitted to contain bridges, but not routers. FAL subnets are identified by a subset of the
network address.
3.1.5.29 logical device
FAL class that abstracts a software component or a firmware component as an autonomous
self-contained facility of an automation device
3.1.5.30 management information
network-accessible information that supports managing the operation of the fieldbus system,
including the application layer
NOTE  Managing includes functions such as controlling, monitoring, and diagnosing.
3.1.5.31 network
series of nodes connected by some type of communication medium

– 14 – 61158-6-15 © IEC:2007(E)

NOTE  The connection paths between any pair of nodes can include repeaters, routers and gateways.

3.1.5.32 peer
role of an AR endpoint in which it is capable of acting as both client and server

3.1.5.33 pre-defined AR endpoint

AR endpoint that is defined locally within a device without use of the create service

NOTE  Pre-defined ARs that are not pre-established are established before being used.

3.1.5.34 pre-established AR endpoint

AR endpoint that is placed in an established state during configuration of the AEs that control
its endpoints
3.1.5.35 Publisher
role of an AR endpoint in which it transmits APDUs onto the fieldbus for consumption by one
or more subscribers
NOTE  The publisher may not be aware of the identity or the number of subscribers and it may publish its APDUs
using a dedicated AR. Two types of publishers are defined by this standard, Pull Publishers and Push Publishers,
each of which is defined separately.
3.1.5.36 server
a) role of an AREP in which it returns a confirmed service response APDU to the client that
initiated the request
b) object which provides services to another (client) object
3.1.5.37 service
operation or function than an object and/or object class performs upon request from another
object and/or object class
NOTE  A set of common services is defined and provisions for the definition of object-specific services are
provided. Object-specific services are those which are defined by a particular object class to perform a required
function which is not performed by a common service.
3.1.5.38 subscriber
role of an AREP in which it receives APDUs produced by a publisher
NOTE  Two types of subscribers are defined by this standard, pull subscribers and push subscribers, each of

which is defined separately.
3.1.6 Specific definitions for client/server
3.1.6.1
coils, discrete outputs
application process object, a set of coils, characterized by the address of a coil and a quantity
of coils
3.1.6.2
discrete, discrete input
application process object, addressed by an unsigned number and having a width of one bit,
representing a 1-bit encoded status value, read-only, with the value '1' encoding the status
ON and the value '0' encoding the status OFF

61158-6-15 © IEC:2007(E) – 15 –

3.1.6.3
discrete inputs, discretes
application process object, a set of discretes, characterized by the address of a discrete and

a quantity of discretes
3.1.6.4
coil, discrete output
application process object, addressed by an unsigned number and having a width of one bit,

representing a 1-bit encoded status value, read-write, with the value '1' encoding the status

ON and the value '0' encoding the status OFF

3.1.6.5
encapsulated interface
mechanism encapsulating a service for an interface, which is an application process object
characterized by an MEI type
3.1.6.6
exception
encoding used to signal a service request failure
3.1.6.7
exception code
encoding associated with an exception, detailing the reason of a service request failure
3.1.6.8
file
application process object, an organization of records, characterized by an unsigned number
3.1.6.9
function code
encoding of a service requested to a server
3.1.6.10
holding register,output register
application process object, addressed by an unsigned number and representing values with
16 bits, read-write
3.1.6.11
holding registers,output registers
application process object, a set of holding registers, characterized by the address of a
holding register and a quantity of holding registers

3.1.6.12
input register
application process object, addressed by an unsigned number and representing values with
16 bits, read-only
3.1.6.13
input registers
application process object, a set of input registers, characterized by the address of an input
register and a quantity of input registers
3.1.6.14
record
application process object, a set of contiguous registers of a specified type, characterized by
the address of th
...