IEC 61158-3-22:2010

IEC 61158-3-22 ®
Edition 1.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial communication networks – Fieldbus specifications –
Part 3-22: Data-link layer service definition – Type 22 elements

Réseaux de communication industriels – Spécifications des bus de terrain –
Partie 3-22: Définition des services de couche liaison de données – Eléments
de Type 22
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IEC 61158-3-22 ®
Edition 1.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Industrial communication networks – Fieldbus specifications –

Part 3-22: Data-link layer service definition – Type 22 elements

Réseaux de communication industriels – Spécifications des bus de terrain –

Partie 3-22: Définition des services de couche liaison de données – Eléments

de Type 22
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
V
CODE PRIX
ICS 25.040.40; 35.100.20; 35.110 ISBN 978-2-88912-857-0

– 2 – 61158-3-22  IEC:2010
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
1.1 Overview . 7
1.2 Specifications . 7
1.3 Conformance . 7
2 Normative References . 8
3 Terms, definitions, symbols, abbreviations and conventions . 8
3.1 Reference model terms and definitions . 8
3.2 Service convention terms and definitions . 10
3.3 Data-link service terms and definitions . 11
3.4 Symbols and abbreviations . 13
3.5 Common conventions . 15
4 Data-link layer services and concepts . 16
4.1 Operating principle . 16
4.2 Communication models . 16
4.3 Topology . 18
4.4 Addressing . 19
4.5 Gateway . 20
4.6 Interaction models . 20
4.7 Synchronization concept . 20
5 Communication services . 21
5.1 Overview . 21
5.2 Communication management services . 23
5.3 Cyclic data channel service (CDC) . 27
5.4 Message channel services (MSC) . 28
5.5 Time synchronization . 29
5.6 Media independent interface (MII) management services . 32
Bibliography . 34

Figure 1 – RTFL device reference model . 17
Figure 2 – RTFN device reference model . 18
Figure 3 – Logical double line in a physical tree topology. 18
Figure 4 – Logical double line in a physical line topology . 19
Figure 5 – Addressing modes . 19
Figure 6 – Time sequence diagram for time SYNC_START service . 21
Figure 7 – Synchronized timing signals without offset . 21
Figure 8 – Synchronized timing signals with offset . 21

Table 1 – Summary of DL-services and primitives . 22
Table 2 – DL-Network verification service (NV) . 23
Table 3 – DL-RTFN scan network read service (RTFNSNR) . 23
Table 4 – DL-RTFN connection establishment DLL service (RTFNCE) . 24

61158-3-22  IEC:2010 – 3 –
Table 5 – DL-RTFN connection release service (RTFNCR) . 24
Table 6 – DL-RTFL control service (RTFLCTL) . 25
Table 7 – DL-RTFL configuration service (RTFLCFG) . 25
Table 8 – DL-Read configuration data service (RDCD) . 26
Table 9 – CDC send service (CDCS) . 28
Table 10 – MSC send service (MSCS) . 28
Table 11 – MSC send broadcast service (MSCSB) . 29
Table 12 – MSC read service (MSCR) . 29
Table 13 – DL-DelayMeasurement start service (DMS) . 30
Table 14 – DL-DelayMeasurement read service (DMR) . 30
Table 15 – DL-PCS configuration service (PCSC) . 30
Table 16 – DL-Sync master configuration service (SYNC_MC) . 31
Table 17 – DL-Sync start service (SYNC_START) . 31
Table 18 – DL-Sync stop service (SYNC_STOP). 32
Table 19 – DL-MII read service (MIIR) . 32
Table 20 – DL-MII write service (MIIW) . 33

– 4 – 61158-3-22  IEC:2010
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 3-22: Data-link layer service definition –
Type 22 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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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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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 of their respective intellectual-property-right holders.
International Standard IEC 61158-3-22 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial process measurement, control and
automation.
This standard cancels and replaces IEC/PAS 61158-3-22 published in 2009. This first edition
constitutes a technical revision.

61158-3-22  IEC:2010 – 5 –
This bilingual version published in 2012-01 corresponds to the English version published in
2010-08.
The text of this standard is based on the following documents:
FDIS Report on voting
65C/604/FDIS 65C/618/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
The French version has not been voted upon.
This publication has been drafted in accordance with the 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 The revision of this standard will be synchronized with the other parts of the IEC 61158 series.

– 6 – 61158-3-22  IEC:2010
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.
Throughout the set of fieldbus standards, the term “service” refers to the abstract capability
provided by one layer of the OSI Basic Reference Model to the layer immediately above.
Thus, the data-link layer service defined in this standard is a conceptual architectural service,
independent of administrative and implementation divisions.

61158-3-22  IEC:2010 – 7 –
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 3-22: Data-link layer service definition –
Type 22 elements
1 Scope
1.1 Overview
This part of IEC 61158 provides common elements for basic time-critical messaging
communications between devices in an automation environment. 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 service provided by the Type
22 fieldbus data-link layer in terms of:
a) the primitive actions and events of the service;
b) the parameters associated with each primitive action and event, and the form which they
take; and
c) the interrelationship between these actions and events, and their valid sequences.
The purpose of this standard is to define the services provided to:
• the Type 22 fieldbus application layer at the boundary between the application and data-
link layers of the fieldbus reference model; and
• systems management at the boundary between the data-link layer and systems
management of the fieldbus reference model.
1.2 Specifications
The principal objective of this standard is to specify the characteristics of conceptual data-link
layer services suitable for time-critical communications, and thus supplement the OSI Basic
Reference Model in guiding the development of data-link protocols for time-critical
communications. A secondary objective is to provide migration paths from previously-existing
industrial communications protocols.
This specification may be used as the basis for formal DL-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 standard does not specify individual implementations or products, nor do they constrain
the implementations of data-link entities within industrial automation systems.
There is no conformance of equipment to this data-link layer service definition standard.
Instead, conformance is achieved through implementation of the corresponding data-link
protocol that fulfils the Type 22 data-link layer services defined in this standard.

– 8 – 61158-3-22  IEC:2010
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.
ISO/IEC 7498-1, Information technology – Open Systems Interconnection – Basic Reference
Model: The Basic Model
ISO/IEC 7498-3, Information technology – Open Systems Interconnection – Basic Reference
Model: Naming and addressing
ISO/IEC 10731, Information technology – Open Systems Interconnection – Basic Reference
Model – Conventions for the definition of OSI services
ISO/IEC 8802-3:2000, 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.
3 Terms, definitions, symbols, abbreviations and conventions
For the purposes of this document, the following terms, definitions, symbols, abbreviations
and conventions apply.
3.1 Reference model terms and definitions
This standard is based in part on the concepts developed in ISO/IEC 7498-1 and
ISO/IEC 7498-3, and makes use of the following terms defined therein:
DL-address [ISO/IEC 7498-3]
called-DL-address [ISO/IEC 7498-3]
calling-DL-address [ISO/IEC 7498-3]
DL-connection [ISO/IEC 7498-1]
DL-connection-end-point [ISO/IEC 7498-1]
DL-connection-end-point-identifier [ISO/IEC 7498-1]
DL-connection-mode transmission [ISO/IEC 7498-1]
DL-connectionless-mode transmission [ISO/IEC 7498-1]
correspondent (N)-entities [ISO/IEC 7498-1]
correspondent DL-entities (N=2)
correspondent Ph-entities (N=1)
decentralized multi-end-point-connection [ISO/IEC 7498-1]
DL-duplex-transmission [ISO/IEC 7498-1]

61158-3-22  IEC:2010 – 9 –
(N)-entity [ISO/IEC 7498-1]
DL-entity (N=2)
Ph-entity (N=1)
DL-facility [ISO/IEC 7498-1]
flow control [ISO/IEC 7498-1]
(N)-layer [ISO/IEC 7498-1]
DL-layer (N=2)
Ph-layer (N=1)
layer-management [ISO/IEC 7498-1]
DL-local-view [ISO/IEC 7498-3]
multi-endpoint-connection [ISO/IEC 7498-1]
DL-name [ISO/IEC 7498-3]
naming-(addressing)-domain [ISO/IEC 7498-3]
peer-entities [ISO/IEC 7498-1]
primitive name [ISO/IEC 7498-3]
DL-protocol [ISO/IEC 7498-1]
DL-protocol-connection-identifier [ISO/IEC 7498-1]
DL-protocol-data-unit [ISO/IEC 7498-1]
DL-relay [ISO/IEC 7498-1]
reassembling [ISO/IEC 7498-1]
reset [ISO/IEC 7498-1]
responding-DL-address [ISO/IEC 7498-3]
routing [ISO/IEC 7498-1]
segmenting [ISO/IEC 7498-1]
(N)-service [ISO/IEC 7498-1]
DL-service (N=2)
Ph-service (N=1)
(N)-service-access-point [ISO/IEC 7498-1]
DL-service-access-point (N=2)
Ph-service-access-point (N=1)
DL-service-access-point-address [ISO/IEC 7498-3]

– 10 – 61158-3-22  IEC:2010
DL-service-connection-identifier [ISO/IEC 7498-1]
DL-service-data-unit [ISO/IEC 7498-1]
DL-simplex-transmission [ISO/IEC 7498-1]
DL-subsystem [ISO/IEC 7498-1]
systems-management [ISO/IEC 7498-1]
DL-user-data [ISO/IEC 7498-1]
3.2 Service convention terms and definitions
This standard also makes use of the following terms defined in ISO/IEC 10731 as they apply
to the data-link layer:
acceptor
asymmetrical service
confirm (primitive);
requestor.deliver (primitive)
deliver (primitive)
DL-confirmed-facility
DL-facility
DL-local-view
DL-mandatory-facility
DL-non-confirmed-facility
DL-provider-initiated-facility
DL-provider-optional-facility
DL-service-primitive;
primitive
DL-service-provider
DL-service-user
DL-user-optional-facility
indication (primitive);
acceptor.deliver (primitive)
multi-peer
request (primitive);
requestor.submit (primitive)
requestor
response (primitive);
acceptor.submit (primitive)
submit (primitive)
symmetrical service
61158-3-22  IEC:2010 – 11 –
3.3 Data-link service terms and definitions
3.3.1
acyclic data
data which is transferred from time to time for dedicated purposes
3.3.2
cell
synonym for a single DL-segment which uses RTFL communication model
3.3.3
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
3.3.4
cycle time
duration of a communication cycle
3.3.5
cyclic
events which repeat in a regular and repetitive manner
3.3.6
cyclic communication
periodic exchange of frames
3.3.7
cyclic data
data which is transferred in a regular and repetitive manner for dedicated purposes
3.3.8
cyclic data channel (CDC)
one or more frames, which are reserved for cyclic data
3.3.9
data
generic term used to refer to any information carried over a fieldbus
3.3.10
device
physical entity connected to the fieldbus
3.3.11
DL-segment
single DL-subnetwork in which any of the connected DLEs may communicate directly, without
any intervening DL-relaying, whenever all of those DLEs that are participating in an instance
of communication are simultaneously attentive to the DL-subnetwork during the period(s) of
attempted communication
3.3.12
error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition

– 12 – 61158-3-22  IEC:2010
3.3.13
extended link
DL-subnetwork, consisting of the maximal set of links interconnected by DL-relays, sharing a
single DL-name (DL-address) space, in which any of the connected DL-entities may
communicate, one with another, either directly or with the assistance of one or more of those
intervening DL-relay entities
NOTE An extended link may be composed of just a single link.
3.3.14
frame
denigrated synonym for DLPDU
3.3.15
gateway
device acting as a linking element between different protocols
3.3.16
interface
shared boundary between two functional units, defined by functional characteristics, signal
characteristics, or other characteristics as appropriate
3.3.17
link
synonym for DL-segment
3.3.18
logical double line
sequence of root device and all ordinary devices processing the communication frame in
forward and backward direction
3.3.19
master clock
global time base for the PCS mechanism
3.3.20
message
ordered sequence of octets intended to convey data
3.3.21
message channel
MSC
one or more DPUs (frames), which are reserved for acyclic data
3.3.22
network
set of devices connected by some type of communication medium, including any intervening
repeaters, bridges, routers and lower-layer gateways
3.3.23
open network
any network based on IEC 8802.3 with no further restrictions
3.3.24
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

61158-3-22  IEC:2010 – 13 –
3.3.25
precise clock synchronization
PCS
mechanism to synchronize clocks of RTFL devices and maintain a global time base
3.3.26
process data
data designated to be transferred cyclically or acyclically for the purpose of processing
3.3.27
protocol
convention about the data formats, time sequences, and error correction in the data exchange
of communication systems
3.3.28
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
3.3.29
real time frame line
RTFL
communication model communicating in a logical double line
3.3.30
real time frame network
RTFN
communication model communicating in a switched network
3.3.31
switch
MAC bridge as defined in IEEE 802.1D
3.3.32
timing signal
time-based indication of the occurrence of an event, commonly as an interrupt signal, used for
DL-user synchronization
3.3.33
topology
physical network architecture with respect to the connection between the stations of the
communication system
3.4 Symbols and abbreviations
CDC Cyclic data channel
CDCS Cyclic data channel send
DA Device address
DL- Data-link layer (as a prefix)
DLL DL-layer
DLS DL-service
– 14 – 61158-3-22  IEC:2010
DMR DL-DelayMeasurement read
DMS DL-DelayMeasurement send
ID Identification
IP Internet protocol
IRQ Interrupt request
MAC Medium access control
MII Media independent interface
MIIR DL-Media independent interface read
MIIW DL-Media independent interface write
MSC Message channel
MSCDN Message channel data notification
MSCR Message channel read
MSCS Message channel send
MSCSB Message channel send broadcast
NV DL-Network verification
OD Ordinary device
OSI Open systems interconnection
PID Packet ID
PCS Precise clock synchronization
PCSC DL-PCS configuration
RD Root device
RDCD DL-Read configuration data
RTF Real time frame
RTFL Real time frame line
RTFLCFG DL-RTFL configuration
RTFLCTL DL-RTFL control
61158-3-22  IEC:2010 – 15 –
RTFN Real time frame network
RTFNCE DL-RTFN connection establishment
RTFNCR DL-RTFN connection release
RTFNSNR DL-RTFN Scan network read
SYNC Synchronization
SYNC_MC DL-Sync master configuration
SYNC_START DL-Sync start
SYNC_STOP DL-Sync stop
3.5 Common conventions
This standard uses the descriptive conventions given in ISO/IEC 10731.
The service model, service primitives, and time-sequence diagrams used are entirely abstract
descriptions; they do not represent a specification for implementation.
Service primitives, used to represent service user/service provider interactions (see
ISO/IEC 10731), convey parameters that indicate information available in the user/provider
interaction.
This standard uses a tabular format to describe the component parameters of the DLS
primitives. The parameters that apply to each group of DLS primitives are set out in tables
throughout the remainder of this standard. Each table consists of up to six columns,
containing the name of the service parameter, and a column each for those primitives and
parameter-transfer directions used by the DLS:
• the request primitive’s input parameters;
• the request primitive’s output parameters;
• the indication primitive’s output parameters;
• the response primitive’s input parameters; and
• the confirm primitive’s output parameters.
NOTE The request, indication, response and confirm primitives are also known as requestor.submit,
acceptor.deliver, acceptor.submit, and requestor.deliver primitives, respectively (see ISO/IEC 10731).
One parameter (or part 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 and parameter direction 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
the dynamic usage of the DLS-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 DLS-user.
– 16 – 61158-3-22  IEC:2010
(blank) parameter is never present.
Some entries are further qualified by items in brackets. These may be 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.
In any particular interface, not all parameters need be explicitly stated. Some may be
implicitly associated with the primitive.
In the diagrams which illustrate these interfaces, dashed lines indicate cause-and-effect or
time-sequence relationships, and wavy lines indicate that events are roughly
contemporaneous.
4 Data-link layer services and concepts
4.1 Operating principle
Type 22 of this series of international standards describes a technology for ISO/IEC 8802-3
based networks which was developed to meet the requirements of automation technology.
For the purpose of fast intra-machine communication Type 22 describes a communication
model (RTFL) for fast real-time communication. Furthermore, networking of several parts of
an automation system into an overall system is supported by the specification of a second
communication model (RTFN). Type 22 is designed as a multi-master bus system to enable
networking of individual control systems in a distributed automation solution.
A Type 22 network utilizes standard ISO/IEC 8802-3 DPUs (frames) for both communication
models.
4.2 Communication models
4.2.1 Overview
Type 22 technology essentially specifies two communication models. RTFL communication is
intended for fast machine communication while RTFN provides for the networking of individual
machines or cells.
For RTFL communication model, communication follows a line topology. RTFL communication
is based on cyclic data transfer in an ISO/IEC 8802-3 DLPDU . This basic cyclic data transfer
is provided by a special device, the root device (RD). Root devices act as communication
master to cyclically initiate communication. The DLPDUs originated by the root device are
passed to the Type 22 ordinary devices (OD). Each ordinary device receives the frame, writes
its data and passes the frame on. A RTFL network requires exactly one root device. The last
ordinary device of a RTFL network sends the processed frame back. The frame is transferred
back in reverse device order to the root device so that it is returned by the first ordinary
device to the root device as response frame. In backward direction, the ordinary devices read
their relevant data from the frame.
For RTFN communication model, communication is based on individual point to point
connections between participating devices.
4.2.2 RTFL device reference model
Type 22 services are described using the principles, methodology and model of
ISO/IEC 7498-1 (OSI). The OSI model provides a layered approach to communications
standards, whereby the layers can be developed and modified independently. The Type 22
specification defines functionality from top to bottom of a full OSI model. Functions of the

61158-3-22  IEC:2010 – 17 –
intermediate OSI layers, layers 3 to 6, are consolidated into either the Type 22 data-link layer
or the DL-user. The device reference model for a Type 22 RTFL device is shown in Figure 1.
Layer
management
DL-user
Message Cyclic
channel data
Clock
channel
synchronization
DLL
DLL configuration
RTF processor
Communication
MAC
management
Physical layer
Figure 1 – RTFL device reference model
4.2.3 RTFN device reference model
Type 22 services are described using the principles, methodology and model of
ISO/IEC 7498-1 (OSI). The OSI model provides a layered approach to communications
standards, whereby the layers can be developed and modified independently. The Type 22
specification defines functionality from top to bottom of a full OSI model. Functions of the
intermediate OSI layers, layers 3 to 6, are consolidated into either the Type 22 data-link layer
or the DL-user. The device reference model for a Type 22 RTFN device is shown in Figure 2.

– 18 – 61158-3-22  IEC:2010
Layer
management
DL-user
Cyclic Message Clock
data channel synchronization
channel
DLL
UDP/IP
Communication
MAC
management
Physical layer
Figure 2 – RTFN device reference model
4.3 Topology
4.3.1 RTFL topology
A Type 22 network utilizing the RTFL communication model uses a logical double line
topology. A logical double line is represented by the arrangement of all ordinary devices and
the root device and the DLPDU processing in forward and backward direction. Data transfer is
handled by DLPDU transfer from one device to the next device along the logical double line.
The last ordinary device returns the frame back to the root device along all participating
ordinary devices
A logical double line is able to allow different network topologies. In a switch operated tree
structure each ordinary device has a predecessor and a successor device although they are
not physically located in a sequence. This is shown in Figure 3.
Logical double line
Root Ordinary Ordinary Ordinary Ordinary
device device device device device

Switch
Figure 3 – Logical double line in a physical tree topology
The ordinary devices for the RTFL communication model should provide two ISO/IEC 8802.3
based communication interfaces. This allows set-up of a physical line structure as shown in

61158-3-22  IEC:2010 – 19 –
Figure 4. If the ordinary devices are arranged in a physical line DLPDUs shall be directly
forwarded from one interface to the next interface and processed on-the-fly (cut-through).
Logical double line
Root Ordinary Ordinary
Ordinary Ordinary
device device device
device device
Figure 4 – Logical double line in a physical line topology
For a Type 22 network utilizing the RTFL communication model the frame pump concept is
specified. This concept shall be applied by the root device within a RTFL network to cyclically
initiate communication. Frame pumping depicts the generation of an RTFL DLDPU into the
RTFL network to be processed by all participating ordinary devices for communication
purposes.
4.3.2 RTFN topology
A Type 22 network utilizing the RTFN communication model shall support all commonly used
topologies like star, tree and line.
4.4 Addressing
4.4.1 Overview
Different addressing modes are supported for Type 22 devices, as noted in Figure 5. A
general differentiation exists for RTFL devices and RTFN devices.
RTFL device addressing RTFN device addressing
MAC Device MAC IP
address address address address

Figure 5 – Addressing modes
4.4.2 RTFL device addressing
MAC addresses as defined in ISO/IEC 8802.3 shall be used to address each device via its
MAC address within the logical double line.
Device addresses shall be used to address devices via a configured device address assigned
by the root device during the start-up phase. Device addresses shall be used for addressing
devices within DL-user communication relationships.
4.4.3 RTFN device addressing
IP addresses as defined in RFC 791 shall be used to address devices within a RTFN network
for cyclic or acyclic communication based on UDP DLPDUs (frames).

– 20 – 61158-3-22  IEC:2010
MAC addresses shall be used to address devices within a RTFN network for cyclic
communication based on MAC DLPDUs.
4.5 Gateway
The gateway acts as linking element between RTFL and RTFN networks. In addition, it is a
gateway between Type 22 networks and the open network. A device incorporating a gateway
can be an ordinary device or can also include the root device. Address translation between
the different addressing modes for RTFL and RTFN shall be performed by the gateway.
4.6 Interaction models
4.6.1 Overview
Depending on the specified communication models RTFL and RTFN Type 22 networks utilize
different interaction models for cyclic data exchange.
4.6.2 Producer-consumer
Communication model RTFL uses the producer-consumer interaction model. It involves a
single producer and a group of zero or more consumer(s). The model is characterized by an
unconfirmed service requested by the producer to distribute its cyclic data and a correlated
service indication in all available consumers.
4.6.3 Publisher-subscriber
Communication model RTFN utilizes the publisher-subscriber push interaction model for
cyclic data exchange. Publisher-subscriber interactions involve a single publisher and a group
of one or more subscribers. Two services are used, one confirmed and one unconfirmed. The
confirmed service is used by the subscriber to request to join the publishing. The response to
this request is returned to the subscriber. The unconfirmed service is used by the publisher to
distribute its cyclic data to subscribers.
4.7 Synchronization concept
Clock synchronization within Type 22 networks is based on synchronization protocols. For DL-
users, synchronization is achieved by using a set of DL-services.
Synchronization protocols enable all Type 22 devices to have the same system time. This
system time is synchronized with a dedicated master clock. Based on this time, the concept of
synchronized timing signals (IRQs) that can be generated independent of the communication
cycle for DL-users is provided. Each timing signal is unambiguously identifiable within a Type
22 network and assigned to a dedicated synchronization master (SYNC master). The
synchronization master shall maintain all required configuration information. DL-users which
act as synchronization slaves (SYNC slave) shall request this information for configuration
and activation purpose using a DL-service. The main properties of synchronized timing
signals are:
• cycle time;
• time offset; and
• start time.
DL-users which act as synchronization master (SYNC master) shall use a local configuration
service for the configuration.
Figure 6 illustrates the interactions between a SYNC slave and a SYNC master for
configuration data exchange utilizing a time-sequence diagram.

61158-3-22  IEC:2010 – 21 –
SYNC master
SYNC slave
SYNC start.request
SYNC start.indication
SYNC start.confirm
SYNC start.response
Figure 6 – Time sequence diagram for time SYNC_START service
Figure 7 illustrates the generation of synchronized timing signals (IRQs) for one SYNC slave
and its corresponding SYNC master after successful slave configuration. Independent from
the communication system synchronized timing signals (IRQs) are generated in both devices
to the DL-user.
SYNC master
SYNC slave
… …
SYNC IRQ SYNC IRQ
Cycle time
…
…
Figure 7 – Synchronized timing signals without offset
Figure 8 illustrates the generation of synchronized timing signals (IRQs) for one SYNC slave
and its corresponding SYNC master after successful slave configuration. Independent from
the communication system synchronized timing signals (IRQs) are generated in both devices
to the DL-user. For the SYNC slave, a time offset relating to the SYNC master timing signal is
configured.
SYNC master
SYNC slave
…
…
SYNC IRQ
Offset
SYNC IRQ
Cycle tim
...