IEC PAS 61158-5-22:2009

IEC/PAS 61158-5-22 ®
Edition 1.0 2009-08
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
Industrial communication networks – Fieldbus specifications –
Part 5-22: Application layer service definition – Type SNpTYPE elements

IEC/PAS 61158-5-22:2009(E)
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IEC/PAS 61158-5-22 ®
Edition 1.0 2009-08
PUBLICLY AVAILABLE
SPECIFICATION
PRE-STANDARD
Industrial communication networks – Fieldbus specifications –
Part 5-22: Application layer service definition – Type SNpTYPE elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XC
ICS 25.040.40; 35.100.70 ISBN 978-2-88910-796-4
– 2 – PAS 61158-5-22 © IEC:2009(E)

CONTENTS
FOREWORD.5

INTRODUCTION.7

1 Scope.8

1.1 Overview .8

1.2 Specifications.9

1.3 Conformance.9

2 Normative references .9
3 Terms, definitions, abbreviations, symbols and conventions .10
3.1 ISO/IEC 7498-1 terms .10
3.2 ISO/IEC 8822 terms .10
3.3 ISO/IEC 9545 terms .10
3.4 ISO/IEC 8824 terms .11
3.5 Fieldbus application-layer specific definitions .11
3.6 Abbreviations and symbols.14
3.7 Conventions .17
3.7.1 Overview .17
3.7.2 General conventions.17
3.7.3 Conventions for class definitions .17
3.7.4 Conventions for service definitions .19
4 Concepts .20
4.1 Common concepts.20
4.2 Type specific concepts .20
4.2.1 Operating principle .20
4.2.2 Communication model overview .20
4.2.3 Application layer element description.21
4.2.4 Producer-consumer interaction .21
4.2.5 Device reference models .22
5 Data type ASE.23
5.1 Overview .23
5.2 Formal definition of data type objects .23
5.3 FAL defined data types.23

5.3.1 Fixed length types .23
5.3.2 String types .30
5.3.3 Domain.31
6 Communication model specification.31
6.1 ASEs.31
6.1.1 CeS ASE .31
6.1.2 Standard Ethernet frame (SEF) communication ASE .64
6.1.3 Management ASE.66
6.2 ARs .75
6.2.1 Overview .75
6.2.2 Point-to-point network-scheduled unconfirmed producer-consumer
AREP .75
6.2.3 Point-to-multipoint network-scheduled unconfirmed producer-
consumer AREP .75

PAS 61158-5-22 © IEC:2009(E) – 3 –

6.2.4 Point-to-point network-scheduled confirmed client/server AREP .76

6.2.5 Point-to-point user-triggered confirmed client/server AREP .76

6.2.6 AR classes .76

6.2.7 FAL services by AREP class.78

6.2.8 Permitted FAL services by AREP role.78

Figure 1 – Producer-consumer interaction model .22

Figure 2 – RTFL device reference model .22

Figure 3 – RTFN device reference model.23

Figure 4 – Type SNpTYPE CeS device structure.32
Figure 5 – Successful SDO expedited download sequence .46
Figure 6 – Successful SDO normal download initialization sequence .46
Figure 7 – Successful SDO download sequence .47
Figure 8 – Successful SDO expedited upload sequence.47
Figure 9 – Successful SDO normal upload initialization sequence.47
Figure 10 – Successful SDO upload sequence.48
Figure 11 – Failed SDO expedited download initialization sequence .48
Figure 12 – Failed SDO download after initialization sequence .48
Figure 13 – Failed SDO download sequence.49
Figure 14 – Emergency sequence.49
Figure 15 – Heartbeat sequence .50
Figure 16 – Process data write sequence.50
Figure 17 – PDO mapping principle .51
Figure 18 – Process data object.51
Figure 19 – SEF service sequence.65

Table 1 – Object dictionary structure.33
Table 2 – Initiate SDO expedited download service.54
Table 3 – Initiate SDO normal download service .56
Table 4 – SDO download service .57
Table 5 – Initiate SDO expedited upload service .58
Table 6 – Initiate SDO normal upload service .59
Table 7 – SDO upload service .60
Table 8 – SDO abort service.61
Table 9 – Process data write service.62
Table 10 – Emergency service (EMCY).63
Table 11 – Heartbeat service .64
Table 12 – Send frame service .66
Table 13 – AL-Network verification service .68
Table 14 – AL-RTFL configuration service .69
Table 15 – AL-DelayMeasurement start service .70
Table 16 – AL-DelayMeasurement read service .71
Table 17 – PCS configuration service .71
Table 18 – MII read service .72

– 4 – PAS 61158-5-22 © IEC:2009(E)

Table 19 – MII write service .72

Table 20 – AL-RTFN scan network read service .73

Table 21 – Application layer management service.73

Table 22 – Start synchronization service.74

Table 23 – Stop synchronization service .75

Table 24 – PTPNSU AREP class .77

Table 25 – PTMNSU AREP class.77

Table 26 – PTPNSC AREP class .77

Table 27 – PTPUTC AREP class.77
Table 28 – FAL services by AREP class .78
Table 29 – FAL services by AREP role .79

PAS 61158-5-22 © IEC:2009(E) – 5 –

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
INDUSTRIAL COMMUNICATION NETWORKS –

FIELDBUS SPECIFICATIONS –
Part 5-22: Application layer service definition –

Type SNpTYPE 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
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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.

A PAS is a technical specification not fulfilling the requirements for a standard, but made
available to the public.
IEC-PAS 61158-5-22 has been processed by subcommittee 65C: Industrial networks, of IEC
technical committee 65: Industrial-process measurement, control and automation.
The text of this PAS is based on the This PAS was approved for
following document: publication by the P-members of the
committee concerned as indicated in
the following document
Draft PAS Report on voting
65C/530/PAS 65C/534/RVD
Following publication of this PAS, which is a pre-standard publication, the technical committee
or subcommittee concerned may transform it into an International Standard.

– 6 – PAS 61158-5-22 © IEC:2009(E)

This PAS shall remain valid for an initial maximum period of 3 years starting from the

publication date. The validity may be extended for a single 3-year period, following which it

shall be revised to become another type of normative document, or shall be withdrawn.

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.

PAS 61158-5-22 © IEC:2009(E) – 7 –

INTRODUCTION
This PAS contains an additional profile – SNpTYPE – which may be integrated into a future

new edition of the IEC 61158-5 series.

– 8 – PAS 61158-5-22 © IEC:2009(E)

INDUSTRIAL COMMUNICATION NETWORKS –

FIELDBUS SPECIFICATIONS –
Part 5-22: Application layer service definition –

Type SNpTYPE elements
1 Scope
1.1 Overview
The fieldbus application layer (FAL) provides user programs with a means to access the
fieldbus communication environment. In this respect, the FAL can be viewed as a “window
between corresponding application programs.”
This part of IEC 61158-5 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 SNpTYPE 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 part of IEC 61158-5 defines in an abstract way the externally visible service provided by
the fieldbus application layer in terms of
a) an abstract model for defining application resources (objects) capable of being
manipulated by users via the use of the FAL service;
b) the primitive actions and events of the service;
c) the parameters associated with each primitive action and event, and the form which they
take; and
d) the interrelationship between these actions and events, and their valid sequences.
The purpose of this part of IEC 61158-5 is to define the services provided to
1) the FAL user at the boundary between the user and the application layer of the fieldbus
reference model; and
2) Systems Management at the boundary between the application layer and Systems

Management of the fieldbus reference model.
This part of IEC 61158-5 specifies the structure and services of the fieldbus application layer,
in conformance with the OSI Basic Reference Model (ISO/IEC 7498) 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

PAS 61158-5-22 © IEC:2009(E) – 9 –

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 part of IEC 61158-5 to provide access to the FAL to control certain aspects of its

operation.
1.2 Specifications
The principal objective of this part of IEC 61158-5 is to specify the characteristics of

conceptual application layer services suitable for time-critical communications, and thus
supplement the OSI Basic Reference Model in guiding the development of application layer

protocols for time-critical communications.

A secondary objective is to provide migration paths from previously-existing industrial
communications protocols. It is this latter objective which gives rise to the diversity of services
standardized as the various Types of IEC 61158, and the corresponding protocols
standardized in subparts of IEC 61158-6.
This specification may be used as the basis for formal application programming interfaces.
Nevertheless, it is not a formal programming interface, and any such interface will need to
address implementation issues not covered by this specification, including:
a) the sizes and octet ordering of various multi-octet service parameters; and
b) the correlation of paired request and confirm, or indication and response, primitives.
1.3 Conformance
This part of IEC 61158-5 does not specify individual implementations or products, nor does it
constrain the implementations of application layer entities within industrial automation
systems.
There is no conformance of equipment to this application layer service definition standard.
Instead, conformance is achieved through implementation of conforming application layer
protocols that fulfill the application layer services as defined in this part of IEC 61158-5.
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 61131-3, Programmable controllers – Part 3: Programming languages
IEC 61158-4-22, Industrial communication networks – Fieldbus specifications –
Part 4-SNpTYPE: Data-link layer protocol specification – Type SNpTYPE elements
IEC 61158-6-22, Industrial communication networks - Fieldbus specifications - Part 6-
SNpTYPE: Application layer protocol specification - Type SNpTYPE 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: The Basic Model
– 10 – PAS 61158-5-22 © IEC:2009(E)

ISO/IEC 8802-3, Information technology – Telecommunications and information exchange

between systems – Local and metropolitan area networks – Specific requirements – Part 3:

Carrier sense multiple access with collision detection (CSMA/CD) access method and

physical layer specifications
ISO/IEC 8822, Information Technology – Open Systems Interconnection – Presentation

service definition
ISO/IEC 8824-1, Information Technology – Abstract Syntax Notation One (ASN.1):

Specification of basic notation

ISO/IEC 9545, Information Technology – Open Systems Interconnection – Application Layer
structure
ISO/IEC 10646, Information technology – Universal Multiple-Octet Coded Character Set
(UCS)
ISO/IEC 10731, Information technology – Open Systems Interconnection – Basic Reference
Model – Conventions for the definition of OSI services
IETF RFC 791, Internet Protocol
3 Terms, definitions, abbreviations, symbols and conventions
For the purposes of this document, the following terms as defined in these publications apply:
3.1 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
3.2 ISO/IEC 8822 terms
For the purposes of this document, the following terms as defined in ISO/IEC 8822 apply:
a) abstract syntax
b) presentation context
3.3 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 context name
d) application-entity-invocation
e) application-entity-type
PAS 61158-5-22 © IEC:2009(E) – 11 –

f) application-process-invocation

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

i) application control service element

3.4 ISO/IEC 8824 terms
For the purposes of this document, the following terms as defined in ISO/IEC 8824 apply:

a) object identifier
b) type
3.5 Fieldbus application-layer specific definitions
3.5.1
application
function for which data is exchanged
3.5.2
application object
representation of a particular component within a device
3.5.3
acyclic data
data which is transferred from time to time for dedicated purposes
3.5.4
bit
unit of information consisting of a 1 or a 0. This is the smallest data unit that can be
transmitted
3.5.5
cell
synonym for a single DL-segment which uses RTFL communication model
3.5.6
channel
path provided for conveying data
3.5.7
client
object which uses the services of a server by initiating a message to perform a task
3.5.8
communication cycle
fixed time period between which the root device issues empty frames for cyclic
communication initiation in which data is transmitted utilizing CDC and MSC
3.5.9
connection
logical binding between two application objects
3.5.10
cycle time
duration of a communication cycle

– 12 – PAS 61158-5-22 © IEC:2009(E)

3.5.11
cyclic
events which repeat in a regular and repetitive manner

3.5.12
cyclic communication
periodic exchange of telegrams

3.5.13
cyclic data
data which is transferred in a regular and repetitive manner for dedicated purposes

3.5.14
cyclic data channel (CDC)
part of one or more frames, which is reserved for cyclic data
3.5.15
data
generic term used to refer to any information carried over a fieldbus
3.5.16
device
physical entity connected to the fieldbus
3.5.17
error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition
3.5.18
error code
identification number of a specific type of error
3.5.19
gateway
device acting as a linking element between different protocols
3.5.20
index
position of an object within the object dictionary

3.5.21
inter-cell communication
communication between a RTFL device and a RTFN device or communication between a
RTFL device and another RTFL device in different cells linked by RTFN
3.5.22
interface
shared boundary between two functional units, defined by functional characteristics, signal
characteristic, or other characteristics as appropriate
3.5.23
intra-cell communication
communication between a RTFL device and another RTFL device in the same cell

PAS 61158-5-22 © IEC:2009(E) – 13 –

3.5.24
mapping parameters
set of values defining the correspondence between application objects and process data

objects
3.5.25
master clock
global time base for the PCS mechanism

3.5.26
message
ordered sequence of octets intended to convey data
3.5.27
message channel (MSC)
part of one or more frames, which is reserved for acyclic data
3.5.28
network
set of devices connected by some type of communication medium, including any intervening
repeaters, bridges, routers and lower-layer gateways
3.5.29
ordinary device (OD)
slave in the communication system, which utilizes RTFL for cyclic and acyclic data
interchange with other ODs in the same logical double line
3.5.30
precise clock synchronization (PCS)
mechanism to synchronize clocks of RTFL devices and maintain a global time base
3.5.31
process data
data designated to be transferred cyclically or acyclically for the purpose of processing
3.5.32
process data object
dedicated data object(s) designated to be transferred cyclically or acyclically for the purpose
of processing
3.5.33
protocol
convention about the data formats, time sequences, and error correction in the data exchange
of communication systems
3.5.34
root device (RD)
master in the communication system, which organises, initiates and controls the RTFL cyclic
and acyclic data interchange for one logical double line
3.5.35
real time frame line (RTFL)
communication model for communication with high real time requirements
3.5.36
real time frame network (RTFN)
communication model for communication with low real time requirements

– 14 – PAS 61158-5-22 © IEC:2009(E)

3.5.37
round trip time
transmission time needed by a DLPDU from the RD to the last OD in forward and backward

direction
3.5.38
sub-index
sub-position of an individual element of an object within the object dictionary

3.5.39
timing signal
time-based indication of the occurrence of an event, commonly as an interrupt signal, used for
DL-user synchronization
3.5.40
topology
physical network architecture with respect to the connection between the stations of the
communication system
3.6 Abbreviations and symbols
AE Application entity
AL Application layer
ALME Application layer management entity
AP Application process
APDU Application layer protocol data unit
APO Application process object
AR Application relationship
AREP Application relationship end point
ASE Application service element
CAN Controller area network
CDC Cyclic data channel
CDCL CDC line
CDCN CDC network
CeS CANopen expands Type SNpTYPE
CL Communication layer
Cnf Confirmation
DA Device address
PAS 61158-5-22 © IEC:2009(E) – 15 –

DHCP Dynamic Host Configuration Protocol

DL- Data-link layer (as a prefix)

DLL DL-layer
DLPDU DL-protocol data unit
EDS Electronic data sheet
EMCY Emergency
FAL Fieldbus application layer
GW Gateway
ID Identification
IETF Internet Engineering Task Force
Ind Indication
IP Internet protocol
IPv4 IP version 4
IPv6 IP version 6
IRQ Interrupt request
LME Layer management entity
MAC Medium access control
MC Master clock
MII Media independent interface

MSC Message channel
MSCL MSC line
MSCN MSC network
OD Ordinary device
OS Operating system
OSI Open systems interconnection
PCS Precise clock synchronization

– 16 – PAS 61158-5-22 © IEC:2009(E)

PDO Process data object
PHY Physical interface controller

PID Packet ID
PTMNSU Point-to-multipoint network-scheduled unconfirmed

PTPNSC Point-to-point network-scheduled confirmed

PTPNSU Point-to-point network-scheduled unconfirmed
PTPUTC Point-to-point user-triggered confirmed
RD Root device
Req Request
RFC Request for comments
Rsp Response
RTF Real time frame
RTFL Real time frame line
RTFN Real time frame network
RO Read only
RW Read and write access
Rx Receive direction
RxPDO Receive PDO
SDO Service data object
SEF Standard Ethernet frame
StdErr Standard error output
StdIn Standard input
StdOut Standard output
SYNC Synchronization
TCP Transmission control protocol
TT Transmission type
PAS 61158-5-22 © IEC:2009(E) – 17 –

Tx Transmit direction
TxPDO Transmit PDO
UDP User datagram protocol
WO Write only
3.7 Conventions
3.7.1 Overview
The FAL is defined as a set of object-oriented ASEs. Each ASE is specified in a separate sub-
clause. Each ASE specification is composed of two parts, its class specification, and its
service specification.
The class specification defines the attributes of the class. The attributes are accessible from
instances of the class using the Object Management ASE services specified in Clause 5 of
this part of IEC 61158-5. The service specification defines the services that are provided by
the ASE.
3.7.2 General conventions
This part of IEC 61158-5 uses the descriptive conventions given in ISO/IEC 10731.
3.7.3 Conventions for class definitions
Class definitions are described using templates. Each template consists of a list of attributes
for the class. The general form of the template is shown below:
FAL ASE: ASE Name
CLASS: Class name
CLASS ID: #
PARENT CLASS: Parent class name
ATTRIBUTES:
1 (o) Key Attribute: numeric identifier
2 (o) Key Attribute: name
3 (m) Attribute: attribute name(values)
4 (m) Attribute: attribute name(values)

4.1 (s) Attribute: attribute name(values)
4.2 (s) Attribute: attribute name(values)
4.3 (s) Attribute: attribute name(values)
5. (c) Constraint: constraint expression
5.1 (m) Attribute: attribute name(values)
5.2 (o) Attribute: attribute name(values)
6 (m) Attribute: attribute name(values)
6.1 (s) Attribute: attribute name(values)
6.2 (s) Attribute: attribute name(values)
SERVICES:
1 (o) OpsService: service name
2 (c) Constraint: constraint expression
2.1 (o) OpsService: service name

– 18 – PAS 61158-5-22 © IEC:2009(E)

3 (m) MgtService: service name

(1) The "FAL ASE:" entry is the name of the FAL ASE that provides the services for the

class being specified.
(2) The "CLASS:" entry is the name of the class being specified. All objects defined using

this template will be an instance of this class. The class may be specified by this part of

IEC 61158-5, or by a user of this part of IEC 61158-5.

(3) The "CLASS ID:" entry is a number that identifies the class being specified. This
number is unique within the FAL ASE that will provide the services for this class. When
qualified by the identity of its FAL ASE, it unambiguously identifies the class within the
scope of the FAL. The value "NULL" indicates that the class cannot be instantiated.
Class IDs between 1 and 255 are reserved by this part of IEC 61158-5 to identify
standardized classes. They have been assigned to maintain compatibility with existing
national standards. CLASS IDs between 256 and 2048 are allocated for identifying user
defined classes.
(4) The "PARENT CLASS:" entry is the name of the parent class for the class being
specified. All attributes defined for the parent class and inherited by it are inherited for
the class being defined, and therefore do not have to be redefined in the template for
this class.
NOTE The parent-class "TOP" indicates that the class being defined is an initial class definition. The parent
class TOP is used as a starting point from which all other classes are defined. The use of TOP is reserved for
classes defined by this part of IEC 61158-5.
(5) The "ATTRIBUTES" label indicate that the following entries are attributes defined for
the class.
a) Each of the attribute entries contains a line number in column 1, a mandatory (m) /
optional (o) / conditional (c) / selector (s) indicator in column 2, an attribute type
label in column 3, a name or a conditional expression in column 4, and optionally a
list of enumerated values in column 5. In the column following the list of values, the
default value for the attribute may be specified.
b) Objects are normally identified by a numeric identifier or by an object name, or by
both. In the class templates, these key attributes are defined under the key
attribute.
c) The line number defines the sequence and the level of nesting of the line. Each
nesting level is identified by period. Nesting is used to specify

i) fields of a structured attribute (4.1, 4.2, 4.3),
ii) attributes conditional on a constraint statement (5). Attributes may be
mandatory (5.1) or optional (5.2) if the constraint is true. Not all optional
attributes require constraint statements as does the attribute defined in (5.2).
iii) the selection fields of a choice type attribute (6.1 and 6.2).
(6) The "SERVICES" label indicates that the following entries are services defined for the
class.
a) An (m) in column 2 indicates that the service is mandatory for the class, while an
(o) indicates that it is optional. A (c) in this column indicates that the service is
conditional. When all services defined for a class are defined as optional, at least
one has to be selected when an instance of the class is defined.
b) The label "OpsService" designates an operational service (1).
c) The label "MgtService" designates an management service (2).
d) The line number defines the sequence and the level of nesting of the line. Each

PAS 61158-5-22 © IEC:2009(E) – 19 –

nesting level is identified by period. Nesting within the list of services is used to

specify services conditional on a constraint statement.

3.7.4 Conventions for service definitions

3.7.4.1 Overview
The service model, service primitives, and time-sequence diagrams used are entirely abstract

descriptions; they do not represent a specification for implementation.

3.7.4.2 Service parameters
Service primitives are used to represent service user/service provider interactions
(ISO/IEC 10731). They convey parameters which indicate information available in the
user/provider interaction. In any particular interface, not all parameters need be explicitly
stated.
The service specifications of this part of IEC 61158-5 use a tabular format to describe the
component parameters of the ASE service primitives. The parameters which apply to each
group of service primitives are set out in tables. Each table consists of up to five columns for
the:
1) parameter name;
2) request primitive;
3) indication primitive;
4) response primitive; and
5) confirm primitive.
One parameter (or component of it) is listed in each row of each table. Under the appropriate
service primitive columns, a code is used to specify the type of usage of the parameter on the
primitive specified in the column:
M parameter is mandatory for the primitive.
U parameter is a User option, and may or may not be provided depending on
dynamic usage of the service user. When not provided, a default value for
the parameter is assumed.
C parameter is conditional upon other parameters or upon the environment of
the service user.
(blank) parameter is never present.
S parameter is a selected item.
Some entries are further qualified by items in brackets. These may be
a) a parameter-specific constraint:
“(=)” indicates that the parameter is semantically equivalent to the parameter in the
service primitive to its immediate left in the table.
b) an indication that some note applies to the entry:
“(n)” indicates that the following note "n" contains additional information pertaining to the
parameter and its use.
3.7.4.3 Service procedures
The procedures are defined in terms of:

– 20 – PAS 61158-5-22 © IEC:2009(E)

• the interactions between application entities through the exchange of fieldbus Application

Protocol Data Units; and
• the interactions between an application layer service provider and an application layer

service user in the same system through the invocation of application layer service

primitives.
These procedures are applicable to instances of communication between systems which

support time-constrained communications services within the fieldbus application layer.

4 Concepts
4.1 Common concepts
All of IEC/TR 61158-1:2007, Clause 9 is incorporated by reference, except as specifically
overridden in 4.2.
4.2 Type specific concepts
4.2.1 Operating principle
Type SNpTYPE consists of two types of communication models: RTFL and RTFN. RTFL is
used to ensure synchronized cyclic real-time communication. RTFN is used in to network
several RTFL cells to an overall system providing data interchange between several RTFL
cells and between RTFL cells and RTFN devices.
In this context, a RTFL cell describes a DL-segment which uses RTFL for communication. An
RTFL cell consists of a root device (RD) and one or several ordinary devices (OD). The
central RTFL cell element is the root device which organizes and controls RTFL cell
sequences such as cyclic real-time frame sending. A RTFL RD has at least one connection to
RTFL, and can include a gateway (GW) which additionally has connection to RTFN. As each
OD in the RTFL cell can only have a RTFL connection, the RD incorporating a GW therefore
operates as a link between RTFL and RTFN. RTFN communication is not coordinated like
communication in RTFL, but utilized by a switched fully duplex standard Ethernet. Thus, no
determinism can be guaranteed for RTFN data transfer.
Communication of process and service data is accommodated by Type SNpTYPE networks
using different mechanisms (channels) in RTFL and RTFN. Cyclic data can be transferred
over the cyclic data channel (CDC).
...