EN 61158-6-20:2012

SLOVENSKI STANDARD
01-september-2012
1DGRPHãþD
SIST EN 61158-6-20:2008
Industrijska komunikacijska omrežja - Specifikacije za procesno vodilo - 6-20. del:
Specifikacija protokola na aplikacijskem nivoju - Elementi tipa 20 (IEC 61158-6-
20:2010)
Industrial communication networks - Fieldbus specifications - Part 6-20: Application layer
protocol specification - Type 20 elements (IEC 61158-6-20:2010)
Industrielle Kommunikationsnetze - Feldbusse - Teil 6-20: Protokollspezifikation des
Application Layer (Anwendungsschicht) - Typ 20-Elemente (IEC 61158-6-20:2010)
Réseaux de communication industriels - Spécifications des bus de terrain - Partie 6-20:
Spécification des protocoles des couches d'application - Eléments de type 20 (CEI
61158-6-20:2010)
Ta slovenski standard je istoveten z: EN 61158-6-20:2012
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.100.70 Uporabniški sloj Application layer
35.110 Omreževanje Networking
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 61158-6-20
NORME EUROPÉENNE
June 2012
EUROPÄISCHE NORM
ICS 25.040.40; 35.100.70; 35.110 Supersedes EN 61158-6-20:2008

English version
Industrial communication networks -
Fieldbus specifications -
Part 6-20: Application layer protocol specification -
Type 20 elements
(IEC 61158-6-20:2010)
Réseaux de communication industriels -  Industrielle Kommunikationsnetze -
Spécifications des bus de terrain - Feldbusse -
Partie 6-20: Spécification des protocoles Teil 6-20: Protokollspezifikation des
des couches d'application - Application Layer (Anwendungsschicht) -
Eléments de type 20 Typ 20-Elemente
(CEI 61158-6-20:2010) (IEC 61158-6-20:2010)

This European Standard was approved by CENELEC on 2012-03-28. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the CEN-CENELEC Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland, Turkey and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2012 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61158-6-20:2012 E
Foreword
The text of document 65C/607/FDIS, future edition 2 of IEC 61158-6-20, prepared by SC 65C, "Industrial
networks", of IEC/TC 65, "Industrial-process measurement, control and automation" was submitted to the
IEC-CENELEC parallel vote and approved by CENELEC as EN 61158-6-20:2012.

The following dates are fixed:
(dop) 2012-12-28
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2015-03-28

standards conflicting with the
document have to be withdrawn
This document supersedes EN 61158-6-20:2008.
20:2008:
— revised Identify FAL PDU, see 5.3.2;
— revised Read device variables with status FAL PDU, see 5.3.9.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent
rights.
Endorsement notice
The text of the International Standard IEC 61158-6-20:2010 was approved by CENELEC as a European
Standard without any modification.

- 3 - EN 61158-6-20:2012
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

IEC 60559 - Binary floating-point arithmetic for HD 592 S1 -
microprocessor systems
IEC/TR 61158-1 2010 Industrial communication networks - CLC/TR 61158-1 2010
Fieldbus specifications -
Part 1: Overview and guidance for the IEC
61158 and IEC 61784 series
IEC 61158-5-20 - Industrial communication networks - EN 61158-5-20 -
Fieldbus specifications -
Part 5-20: Application layer service definition -
Type 20 elements
ISO/IEC 7498-1 - Information technology - Open Systems - -
Interconnection - Basic Reference Model:
The Basic Model
ISO/IEC 8824-1 - Information technology - Abstract Syntax - -
Notation One (ASN.1): Specification of basic
notation
ISO/IEC 8859-1 - Information technology - 8-bit single-byte - -
coded graphic character sets -
Part 1: Latin alphabet No.1
ISO/IEC 9545 - Information technology - Open Systems - -
Interconnection - Application Layer structure

IEC 61158-6-20 ®
Edition 2.0 2010-08
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 6-20: Application layer protocol specification – Type 20 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XA
ICS 25.04.40; 35.100.70; 35.110 ISBN 978-2-88912-134-2
– 2 – 61158-6-20 © IEC:2010(E)
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.8
1.1 General .8
1.2 Specifications.8
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 .10
3.2 IEC/TR 61158-1 terms.10
3.3 Type 20 fieldbus application-layer specific definitions.13
3.4 Abbreviations and symbols.15
3.5 Conventions .16
3.6 Conventions used in state machines .16
4 Abstract syntax.17
5 Transfer syntax .17
5.1 General .17
5.2 Common APDU structure .18
5.3 Service-specific APDU structures .20
5.4 Data coding rules .35
6 Structure of FAL protocol state machines .41
7 AP-context state machines .42
8 FAL service protocol machine (FSPM).42
8.1 General .42
8.2 FSPM state tables .43
8.3 Functions used by FSPM.48
8.4 Parameters of FSPM/ARPM primitives .48
9 Application relationship protocol machines (ARPMs) .49
9.1 AREP mapping to data link layer .49
9.2 Application relationship protocol machines (ARPMs) .50
9.3 AREP state machine primitive definitions .52
9.4 AREP state machine functions .52
10 DLL mapping protocol machine (DMPM).52
10.1 DMPM states.52
10.2 DMPM state machines.53
10.3 Primitives exchanged between data link layer and DMPM .53
10.4 Functions used by DMPM.54
Bibliography.55

Figure 1 – APDU format.18
Figure 2 – Normal response from slave to master .18
Figure 3 – Command error response from slave to master .19
Figure 4 – Communication error response from slave to master.20
Figure 5 – Coding without identification .36
Figure 6 – Coding of Integer type data .36

61158-6-20 © IEC:2010(E) – 3 –
Figure 7 – Coding of Integer16 type data .36
Figure 8 – Coding of Unsigned type data .36
Figure 9 – Coding of Unsigned16 type data .36
Figure 10 – Coding of single precision Floating Point type data .37
Figure 11 – Coding of double precision Floating Point type data .38
Figure 12 – Coding of Date type data.38
Figure 13 – Relationships among protocol machines and adjacent layers .42
Figure 14 – State transition diagram of FSPM.43
Figure 15 – State transition diagram of the client ARPM .50
Figure 16 – State transition diagram of the server ARPM .51
Figure 17 – State transition diagram of DMPM .53

Table 1 – Conventions used for state machines .16
Table 2 – Response code values .19
Table 3 – Device status values .19
Table 4 – Response code values .20
Table 5 – Communication error codes.20
Table 6 – Identify request APDU.21
Table 7 – Identify response value field.22
Table 8 – Identify command specific response codes.22
Table 9 – Read primary variable response value field .23
Table 10 – Read primary variable command specific response codes .23
Table 11 – Read loop current and percent of range value field.23
Table 12 – Read loop current and percent of range command specific response codes .24
Table 13 – Read dynamic variables and loop current value field .24
Table 14 – Read dynamic variables and loop current command specific response
codes.24
Table 15 – Write polling address value field.25
Table 16 – Loop current mode codes .25
Table 17 – Write polling address command specific response codes.25
Table 18 – Read loop configuration value field.26
Table 19 – Read loop configuration command specific response codes .26
Table 20 – Read dynamic variable families classifications value field.26
Table 21 – Read dynamic variable families classifications command specific response
codes.27
Table 22 – Read device variables with status request value field .27
Table 23 – Read device variables with status value field.27
Table 24 – Variable status values .29
Table 25 – Read device variables with status command specific response codes .29
Table 26 – Read message response value field .30
Table 27 – Read message command specific response codes .30
Table 28 – Read tag, descriptor, date response value field .30
Table 29 – Read tag, descriptor, date command specific response codes .30
Table 30 – Read primary variable transducer information response value field.31

– 4 – 61158-6-20 © IEC:2010(E)
Table 31 – Read primary variable transducer information command specific response
codes.31
Table 32 – Read device information response value field.32
Table 33 – Read device information command specific response codes.32
Table 34 – Read final assembly number response value field .32
Table 35 – Read final assembly number command specific response codes .33
Table 36 – Write message value field .33
Table 37 – Write message command specific response codes .33
Table 38 – Write tag, descriptor, date value field .33
Table 39 – Write tag, descriptor, date command specific response codes .34
Table 40 – Write final assembly number value field.34
Table 41 – Write final assembly number command specific response codes .34
Table 42 – Read long tag response value field.35
Table 43 – Read long tag command-specific response codes .35
Table 44 – Write long tag value field .35
Table 45 – Write long tag command specific Response codes .35
Table 46 – Coding for Date type .38
Table 47 – Coding for one octet Enumerated Type.39
Table 48 – One octet bit field .40
Table 49 – Packed ASCII character set.40
Table 50 – AccepTable subset of ISO Latin-1 characters .41
Table 51 – FSPM state Table – client transactions.43
Table 52 – FSPM state Table – server transactions .47
Table 53 – Function Command () .48
Table 54 – Function CommErr () .48
Table 55 – Function CommandErr () .48
Table 56 – Function Resp ().48
Table 57 – Function Device () .48
Table 58 – Parameters used with primitives exchanged between FSPM and ARPM .48
Table 59 – Client ARPM states .50
Table 60 – Client ARPM state table .51
Table 61 – Server ARPM states .51
Table 62 – Server ARPM state table .51
Table 63 – Primitives issued from ARPM to DMPM .52
Table 64 – Primitives issued by DMPM to ARPM .52
Table 65 – Parameters used with primitives exchanged between ARPM and DMPM .52
Table 66 – DMPM state descriptions.53
Table 67 – DMPM state Table – Client transactions .53
Table 68 – DMPM state Table – Server transactions.53
Table 69 – Primitives exchanged between data-link layer and DMPM .54

61158-6-20 © IEC:2010(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 6-20: Application layer protocol specification –
Type 20 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.
NOTE 1 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 profile parts. Use of the various protocol types in other
combinations may require permission from their respective intellectual-property-right holders.
International Standard IEC 61158-6-20 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This second edition cancels and replaces the first edition published in 2007. This edition
constitutes a technical revision.
The main changes with respect to the previous edition are listed below:
a) revised Identify FAL PDU, see 5 . 3. 2;

– 6 – 61158-6-20 © IEC:2010(E)
b) revised Read device variables with status FAL PDU, see 5. 3. 9;
The text of this standard is based on the following documents:
FDIS Report on voting
65C/607/FDIS 65C/621/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.
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 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.
NOTE 2 The revision of this standard will be synchronized with the other parts of the IEC 61158 series.

61158-6-20 © IEC:2010(E) – 7 –
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.

– 8 – 61158-6-20 © IEC:2010(E)
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 6-20: Application layer protocol specification –
Type 20 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 20 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
20 of the 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 define
a) the wire-representation of the service primitives defined in IEC 61158-5-20, and
b) the externally visible behavior associated with their transfer.
This standard specifies the protocol of the Type 20 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 61158-5-20.
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.

61158-6-20 © IEC:2010(E) – 9 –
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.
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 60559, Binary floating-point arithmetic for microprocessor systems
IEC/TR 61158-1:2010 , Industrial communication networks – Fieldbus specifications – Part 1:
Overview and guidance for the IEC 61158 and IEC 61784 series
IEC 61158-5-20, Industrial communication networks – Fieldbus specifications – Part 5-20:
Application layer service definition – Type 20 elements
ISO/IEC 7498-1, Information technology – Open Systems Interconnection – Basic Reference
Model: The Basic Model
ISO/IEC 8824-1, Information technology – Abstract Syntax Notation One (ASN.1):
Specification of basic notation
ISO/IEC 8859-1, Information technology – 8-bit single-byte coded graphic character sets –
Part 1: Latin alphabet No. 1
ISO/IEC 9545, Information technology – Open Systems Interconnection – Application Layer
structure
___________
To be published.
– 10 – 61158-6-20 © IEC:2010(E)
3 Terms, definitions, symbols, abbreviations and conventions
For the purposes of this document, the following definitions apply.
3.1 Terms and definitions from other ISO/IEC standards
3.1.1 Terms and definitions from ISO/IEC 7498-1
a) abstract syntax
b) application entity
c) application process
d) application protocol data unit
e) application service element
f) application entity invocation
g) application process invocation
h) application transaction
i) presentation context
j) real open system
k) transfer syntax
3.1.2 Terms and definitions from ISO/IEC 9545
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
3.1.3 Terms and definitions from ISO/IEC 8824-1
a) object identifier
b) type
c) value
d) simple type
e) structured type
f) component type
g) tag
i) true
j) false
k) integer type
m) octet string type
n) null type
o) sequence type
p) sequence of type
q) choice type
r) tagged type
s) any type
t) module
u) production
3.1.4 Terms and definitions from ISO/IEC 8825
a) encoding (of a data value)
b) data value
c) identifier octets (the singular form is used in this standard)
d) length octet(s) (both singular and plural forms are used in this standard)
e) contents octets
3.2 IEC/TR 61158-1 terms
The following IEC/TR 61158-1 terms apply.

61158-6-20 © IEC:2010(E) – 11 –
3.2.1
application
function or data structure for which data is consumed or produced
3.2.2
application layer interoperability
capability of application entities to perform coordinated and cooperative operations using the
services of the FAL
3.2.3
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.
3.2.4
application process
part of a distributed application on a network, which is located on one device and
unambiguously addressed
3.2.5
application process identifier
identifier that distinguishes among multiple application processes used in a device
3.2.6
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 (see
the definition for Application Process Object Class Definition). Application process object definitions may 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
3.2.7
application process object class
class of application process objects defined in terms of the set of their network-accessible
attributes and services
3.2.8
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 pre-
configuration activities
3.2.9
application relationship application service element
application-service-element that provides the exclusive means for establishing and
terminating all application relationships
3.2.10
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.
– 12 – 61158-6-20 © IEC:2010(E)
3.2.11
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.
3.2.12
behaviour
indication of how the object responds to particular events. Its description includes the
relationship between attribute values and services
3.2.13
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.
3.2.14
class attributes
attribute that is shared by all objects within the same class
3.2.15
class code
unique identifier assigned to each object class
3.2.16
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.
3.2.17
client
(a) an object which uses the services of another (server) object to perform a task
(b) an 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
3.2.18
conveyance path
unidirectional flow of APDUs across an application relationship
3.2.19
cyclic
term used to describe events which repeat in a regular and repetitive manner
3.2.20
dedicated AR
AR used directly by the FAL User. On Dedicated ARs, only the FAL Header and the user data
are transferred
3.2.21
device
physical hardware connection to the link. A device may contain more than one node

61158-6-20 © IEC:2010(E) – 13 –
3.2.22
device profile
collection of device dependent information and functionality providing consistency between
similar devices of the same device type
3.2.23
endpoint
one of the communicating entities involved in a connection
3.2.24
error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition
3.2.25
error code
identification of a specific type of error within an error class
3.2.26
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.
3.2.27
network
series of nodes connected by some type of communication medium
NOTE The connection paths between any pair of nodes can include repeaters, routers and gateways.
3.2.28
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.
3.2.29
pre-established AR endpoint
AR endpoint that is placed in an established state during configuration of the AEs that control
its endpoints
3.2.30
server
a) role of an AREP in which it returns a confirmed service response APDU to the client that
initiated the request
b) an object which provides services to another (client) object
3.2.31
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.
3.3 Type 20 fieldbus application-layer specific definitions
There are additional terms defined for this part.

– 14 – 61158-6-20 © IEC:2010(E)
3.3.1
analog channel
continuously varying electrical signal connecting a field device to the remainder of the data
acquisition or control system. Some field devices support multiple analog channels (input or
output)
NOTE Each analog channel transmits a single dynamic variable to or from the field device.
3.3.2
broadcast address
broadcast address is used by a master to send a command to all devices
NOTE The broadcast address is five octet long and has all zeros as the value.
3.3.3
busy
device is busy and cannot execute a command at the time; device indicates busy by returning
response code 32 when allowed by the command specification and the requested command is
not executed if a busy response is returned
3.3.4
device ID
serial number for a device
NOTE The manufacturer is required to assigned unique value for every device that has the identical values for
Manufacturer ID and Device Type.
3.3.5
device type
manufacturer’s type of a device, e.g. its product name
NOTE The value of this attribute is assigned by the manufacturer. Its value specifies the set of commands and
data objects supported by the device. The manufacturer is required to assigned unique value to each type of the
device.
3.3.6
device variable
uniquely defined data item within a Field Device that is always associated with cyclical
process information and a device variable's value varies in response to changes and
variations in the process to which the device is connected
3.3.7
dynamic variable
connection between a process and an analog channel
NOTE A device may contain primary, secondary, tertiary, and quaternary variables. These are collectively called
the dynamic variables.
3.3.8
long tag
32-character restricted ISO Latin-1 string used to identify a field device
3.3.9
loop current
value measured by a milli-ammeter in series with the field device
NOTE The loop current is a near DC analog 4-20 mA signal used to communicate a single value between the
control system and the field device. Voltage mode devices use "Volts DC" as their engineering units where "loop
current" values are used.
3.3.10
manufacturer ID
string identifying the manufacturer that produced a device

61158-6-20 © IEC:2010(E) – 15 –
NOTE A manufacturer is required to use the value assigned to it and is not permitted to use the value assigned to
another manufacturer.
3.3.11
master
device that initiates communication activity by sending request PDUs to other devices
3.3.12
polling address
integer used to identify a device
NOTE The polling address is used to construct a one-octet address.
3.3.13
slave
device that initiates communication activity only after it receives a request PDU from a master
device, and that is required to send a respons
...