IEC 61158-4-22:2010

IEC 61158-4-22 ®
Edition 1.0 2010-08
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 4-22: Data-link layer protocol specification – Type 22 elements

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IEC 61158-4-22 ®
Edition 1.0 2010-08
INTERNATIONAL
STANDARD
Industrial communication networks – Fieldbus specifications –
Part 4-22: Data-link layer protocol specification – Type 22 elements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 25.04.40; 35.100.20; 35.110 ISBN 978-2-88912-093-2
– 2 – 61158-4-22 © IEC:2010(E)
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.9
1.1 General .9
1.2 Specifications.9
1.3 Procedures.9
1.4 Applicability.9
1.5 Conformance.10
2 Normative references .10
3 Terms, definitions, symbols, abbreviations and conventions .10
3.1 Reference model terms and definitions.10
3.2 Service convention terms and definitions.12
3.3 Common terms and definitions .13
3.4 Additional Type 22 definitions.14
3.5 Common symbols and abbreviations .17
3.6 Additional Type 22 symbols and abbreviations .18
3.7 Conventions .20
4 Overview of the DL-protocol .21
4.1 Operating principle .21
4.2 Communication model .21
4.3 Topology .22
4.4 DLPDU processing .22
4.5 General communication mechanisms .23
4.6 Gateway.24
4.7 Interaction models.24
5 DLPDU structure .24
5.1 Overview .24
5.2 Data types and encoding rules .25
5.3 DLPDU identification .26
5.4 General DLPDU structure.27
5.5 Communication management DLPDUs .29
5.6 Cyclic data channel (CDC) DLPDUs .34
5.7 Cyclic data channel (CDC) DLPDU data .35
5.8 Message channel (MSC) DLPDUs .36
5.9 Message channel DLPDU data - MSC message transfer protocol (MSC-MTP).37
5.10 Time synchronization .41
6 Telegram timing and DLPDU handling .42
6.1 Communication mechanism.42
6.2 Device synchronization.44
7 Type 22 protocol machines.45
7.1 RTFL device protocol machines.45
7.2 RTFN device protocol machines .57
7.3 Message channel - message transfer protocol (MSC-MTP) .59
Bibliography.63

61158-4-22 © IEC:2010(E) – 3 –
Figure 1 – DLPDU sequence.43
Figure 2 – Communication relationship RTFN device .44
Figure 3 – Overview RTFL device protocol machines.45
Figure 4 – Protocol machine send DLPDU procedure.46
Figure 5 – Protocol machine receive DLPDU procedure.47
Figure 6 – CDCL send cyclic data sequence .48
Figure 7 – CDCL receive cyclic data sequence .49
Figure 8 – MSCL send sequence .50
Figure 9 – MSCL receive sequence .51
Figure 10 – Network management protocol machine .52
Figure 11 – Net management sequence at system boot up .53
Figure 12 – Initialization sequence ordinary device .54
Figure 13 – PCS configuration sequence .55
Figure 14 – Delay measurement principle .56
Figure 15 – Overview RTFN device protocol machines .57
Figure 16 – CDCN connection setup and release .58
Figure 17 – CDCN unpulish data.59
Figure 18 – Segmentation sequence .60
Figure 19 – Expedited transfer sequence.60
Figure 20 – Toggling from expedited transfer to segmented transfer .61
Figure 21 – Segmentation sequence for broad- or multicast message without
Acknowledgement.62

Table 1 – DLPDU element definition .20
Table 2 – Conventions for protocol machine description .21
Table 3 – Transfer syntax for bit sequences.25
Table 4 – Transfer syntax for data type Unsignedn .26
Table 5 – Transfer syntax for data type Signedn .26
Table 6 – Type 22 DLPDU inside an ISO/IEC 8802-3.27
Table 7 – Type 22 DLPDU inside a VLAN tagged ISO/IEC 8802-3 DLPDU.27
Table 8 – Type 22 DLPDU inside an UDP DLPDU.28
Table 9 – General structure of a Type 22 DLPDU .28
Table 10 – DLPDU header structure .29
Table 11 – Network verification prepare DLPDU .29
Table 12 – Network verification environment DLPDU .29
Table 13 – Network verification information DLPDU .29
Table 14 – Network verification acknowledgement DLPDU.30
Table 15 – RTFN scan network read request DLPDU.30
Table 16 – RTFN scan network read response DLPDU .30
Table 17 – Identification data.30
Table 18 – PhyLinkPortX .31
Table 19 – RTF support .31
Table 20 – UseDHCP.32

– 4 – 61158-4-22 © IEC:2010(E)
Table 21 – DeviceRole.32
Table 22 – RTFN connection management DLPDU .33
Table 23 – CDCN connection still alive DLPDU.33
Table 24 – ID data .33
Table 25 – RTFL control DLPDU.33
Table 26 – RTFL configuration DLPDU .34
Table 27 – RTFL configuration acknowledgement DLPDU .34
Table 28 – CDCL DLPDU.35
Table 29 – CDCN DLPDU .35
Table 30 – CDC DLPDU data arrangement .35
Table 31 – CDC DLPDU data.36
Table 32 – MSCL DLPDU .36
Table 33 – MSCL control .37
Table 34 – MSCN DLPDU .37
Table 35 – MSC-MTP frame structure .38
Table 36 – Address type .38
Table 37 – MSC-MTP Init structure .39
Table 38 – MSC-MTP Init_Fast structure .39
Table 39 – MSC-MTP Send structure.39
Table 40 – MSC-MTP Acknowledgement structure.40
Table 41 – MSC-MTP Abort structure.40
Table 42 – Data structure of a message.40
Table 43 – DelayMeasurement start encoding.41
Table 44 – DelayMeasurement read encoding.41
Table 45 – PCS configuration encoding .41
Table 46 – Time synchronization service request.41
Table 47 – Time synchronization service response .42

61158-4-22 © IEC:2010(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 4-22: Data-link layer protocol specification –
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
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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.
International Standard IEC 61158-4-22 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 61158-4-22 published in 2009. This first edition
constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
65C/605/FDIS 65C/619/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.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – 61158-4-22 © IEC:2010(E)
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.

61158-4-22 © 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 data-link protocol provides the data-link service by making use of the services available
from the physical 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 data-link
entities (DLEs) 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:
a) as a guide for implementers and designers;
b) for use in the testing and procurement of equipment;
c) as part of an agreement for the admittance of systems into the open systems environment;
d) 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.
NOTE Use of some of the associated protocol types is restricted by their intellectual-property-right holders. In all
cases, the commitment to limited release of intellectual-property-rights made by the holders of those rights permits
a particular data-link layer protocol type to be used with physical layer and application layer protocols in Type
combinations as specified explicitly in the profile parts. Use of the various protocol types in other combinations
may require permission from their respective intellectual-property-right holders.
The International Electrotechnical Commission (IEC) draws attention to the fact that it is
claimed that compliance with this document may involve the use of patents concerning
Type 22 elements and possibly other types:
WO-2006/069691-A1 [PI] Control system with a plurality of spatially distributed stations
and method for transmitting data in said control system
DE - 10 2004 063 213 [PI] Steuerungssystem mit einer Vielzahl von räumlich verteilten
- B4 Stationen sowie Verfahren zum Übertragen von Daten in einem
solchen Steuerungssystem
IEC takes no position concerning the evidence, validity and scope of these patent rights.
The holder of these patent rights has assured the IEC that he/she is willing to negotiate
licences either free of charge or under reasonable and non-discriminatory terms and
conditions with applicants throughout the world. In this respect, the statement of the holder of
these patent rights is registered with IEC. Information may be obtained from:
Information may be obtained from:
[PI] Pilz GmbH & Co. KG
Felix-Wankel-Str. 2
73760 Ostfildern
Germany
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights other than those identified above. IEC shall not be held responsible for
identifying any or all such patent rights.

– 8 – 61158-4-22 © IEC:2010(E)
ISO (www.iso.org/patents) and IEC (http://www.iec.ch/tctools/patent_decl.htm) maintain on-
line data bases of patents relevant to their standards. Users are encouraged to consult the
data bases for the most up to date information concerning patents.

61158-4-22 © IEC:2010(E) – 9 –
INDUSTRIAL COMMUNICATION NETWORKS –
FIELDBUS SPECIFICATIONS –
Part 4-22: Data-link layer protocol specification –
Type 22 elements
1 Scope
1.1 General
The data-link layer provides basic time-critical messaging communications between devices in
an automation environment.
This protocol provides communication opportunities to all participating data-link entities
a) in a synchronously-starting cyclic manner, according to a pre-established schedule, and
b) in a cyclic or acyclic asynchronous manner, as requested each cycle by each of those
data-link entities.
Thus this protocol can be characterized as one which provides cyclic and acyclic access
asynchronously but with a synchronous restart of each cycle.
1.2 Specifications
This standard specifies:
a) procedures for the timely transfer of data and control information from one data-link user
entity to a peer user entity, and among the data-link entities forming the distributed data-
link service provider;
b) the structure of the fieldbus DLPDUs used for the transfer of data and control information
by the protocol of this standard, and their representation as physical interface data units.
1.3 Procedures
The procedures are defined in terms of:
a) the interactions between peer DL-entities (DLEs) through the exchange of fieldbus
DLPDUs;
b) the interactions between a DL-service (DLS) provider and a DLS-user in the same system
through the exchange of DLS primitives;
c) the interactions between a DLS-provider and a Ph-service provider in the same system
through the exchange of Ph-service primitives.
1.4 Applicability
These procedures are applicable to instances of communication between systems which
support time-critical communications services within the data-link layer of the OSI or fieldbus
reference models, and which require the ability to interconnect in an open systems
interconnection environment.
Profiles provide a simple multi-attribute means of summarizing an implementation’s
capabilities, and thus its applicability to various time-critical communications needs.

– 10 – 61158-4-22 © IEC:2010(E)
1.5 Conformance
This standard also specifies conformance requirements for systems implementing these
procedures.
This part of IEC 61158 does not contain tests to demonstrate compliance with such
requirements.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 61158-3-22:2010 , Industrial communication networks – Fieldbus specifications – Part 3-
22: Data-link layer service definition – Type 22 elements
IEC 61588:2009, Precision clock synchronization protocol for networked measurement and
control system
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 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
ISO/IEC 10731, Information technology – Open Systems Interconnection – Basic Reference
Model – Conventions for the definition of OSI services
IETF RFC 768, User Datagram Protocol; available at
IETF RFC 791, Internet Protocol; available at
IEEE 802.1Q, IEEE Standard for Local and metropolitan area networks – Virtual Bridged
Local Area Networks; available at
3 Terms, definitions, symbols, abbreviations and conventions
For the purposes of this document, the following terms, definitions, symbols and abbreviations
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.
—————————
To be published.
61158-4-22 © IEC:2010(E) – 11 –
3.1.1 acknowledgement [ISO/IEC 7498-1]
3.1.2 DL-address [ISO/IEC 7498-3]
3.1.3 DL-address-mapping [ISO/IEC 7498-1]
3.1.4 called-DL-address [ISO/IEC 7498-3]
3.1.5 calling-DL-address [ISO/IEC 7498-3]
3.1.6 DL-connection [ISO/IEC 7498-1]
3.1.7 DL-connection-end-point [ISO/IEC 7498-1]
3.1.8 DL-connection-end-point-identifier [ISO/IEC 7498-1]
3.1.9 DL-connection-mode transmission [ISO/IEC 7498-1]
3.1.10 DL-connectionless-mode transmission [ISO/IEC 7498-1]
3.1.11 decentralized multi-end-point-connection [ISO/IEC 7498-1]
3.1.12 DL-duplex-transmission [ISO/IEC 7498-1]
3.1.13 (N)-entity [ISO/IEC 7498-1]
DL-entity (N=2)
Ph-entity (N=1)
3.1.14 flow control [ISO/IEC 7498-1]
3.1.15 (N)-layer [ISO/IEC 7498-1]
DL-layer (N=2)
Ph-layer (N=1)
3.1.16 layer-management [ISO/IEC 7498-1]
3.1.17 DL-local-view [ISO/IEC 7498-3]
3.1.18 multi-endpoint-connection [ISO/IEC 7498-1]
3.1.19 DL-name [ISO/IEC 7498-3]
3.1.20 naming-(addressing)-domain [ISO/IEC 7498-3]
3.1.21 peer-entities [ISO/IEC 7498-1]
3.1.22 primitive name [ISO/IEC 7498-3]
3.1.23 DL-protocol [ISO/IEC 7498-1]
3.1.24 DL-protocol-connection-identifier [ISO/IEC 7498-1]
3.1.25 DL-protocol-control information [ISO/IEC 7498-1]

– 12 – 61158-4-22 © IEC:2010(E)
3.1.26 DL-protocol-data-unit [ISO/IEC 7498-1]
3.1.27 DL-protocol-version-identifier [ISO/IEC 7498-1]
3.1.28 DL-relay [ISO/IEC 7498-1]
3.1.29 reassembling [ISO/IEC 7498-1]
3.1.30 reset [ISO/IEC 7498-1]
3.1.31 responding-DL-address [ISO/IEC 7498-3]
3.1.32 routing [ISO/IEC 7498-1]
3.1.33 segmenting [ISO/IEC 7498-1]
3.1.34 sequencing [ISO/IEC 7498-1]
3.1.35 (N)-service [ISO/IEC 7498-1]
DL-service (N=2)
Ph-service (N=1)
3.1.36 (N)-service-access-point [ISO/IEC 7498-1]
DL-service-access-point (N=2)
Ph-service-access-point (N=1)
3.1.37 DL-service-access-point-address [ISO/IEC 7498-3]
3.1.38 DL-service-connection-identifier [ISO/IEC 7498-1]
3.1.39 DL-service-data-unit [ISO/IEC 7498-1]
3.1.40 DL-simplex-transmission [ISO/IEC 7498-1]
3.1.41 DL-subsystem [ISO/IEC 7498-1]
3.1.42 systems-management [ISO/IEC 7498-1]
3.1.43 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:
3.2.1 acceptor
3.2.2 asymmetrical service
3.2.3 confirm (primitive);
requestor.deliver (primitive)
3.2.4 deliver (primitive)
3.2.5 DL-confirmed-facility
61158-4-22 © IEC:2010(E) – 13 –
3.2.6 DL-facility
3.2.7 DL-local-view
3.2.8 DL-mandatory-facility
3.2.9 DL-non-confirmed-facility
3.2.10 DL-provider-initiated-facility
3.2.11 DL-provider-optional-facility
3.2.12 DL-service-primitive;
primitive
3.2.13 DL-service-provider
3.2.14 DL-service-user
3.2.15 DL-user-optional-facility
3.2.16 indication (primitive);
acceptor.deliver (primitive)
3.2.17 multi-peer
3.2.18 request (primitive);
requestor.submit (primitive)
3.2.19 requestor
3.2.20 response (primitive);
acceptor.submit (primitive)
3.2.21 submit (primitive)
3.2.22 symmetrical service
3.3 Common terms and definitions
NOTE Many definitions are common to more than one protocol Type; they are not necessarily used by all protocol
Types.
3.3.1
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
3.3.2
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.

– 14 – 61158-4-22 © IEC:2010(E)
3.3.3
frame
denigrated synonym for DLPDU
3.3.4
receiving DLS-user
DL-service user that acts as a recipient of DL-user-data
NOTE A DL-service user can be concurrently both a sending and receiving DLS-user.
3.3.5
sending DLS-user
DL-service user that acts as a source of DL-user-data
3.4 Additional Type 22 definitions
3.4.1
acyclic data
data which is transferred from time to time for dedicated purposes
3.4.2
bit
unit of information consisting of a 1 or a 0. This is the smallest data unit that can be
transmitted
3.4.3
cell
synonym for a single DL-segment which uses RTFL communication model
3.4.4
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
3.4.5
cycle time
duration of a communication cycle
3.4.6
cyclic
events which repeat in a regular and repetitive manner
3.4.7
cyclic communication
periodic exchange of frames
3.4.8
cyclic data
data which is transferred in a regular and repetitive manner for dedicated purposes
3.4.9
cyclic data channel
CDC
part of one or more frames, which is reserved for cyclic data
3.4.10
data
generic term used to refer to any information carried over a fieldbus

61158-4-22 © IEC:2010(E) – 15 –
3.4.11
device
physical entity connected to the fieldbus
3.4.12
error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition
3.4.13
gateway
device acting as a linking element between different protocols
3.4.14
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
3.4.15
interface
shared boundary between two functional units, defined by functional characteristics, signal
characteristic, or other characteristics as appropriate
3.4.16
intra-cell communication
communication between a RTFL device and another RTFL device in the same cell
3.4.17
link
synonym for DL-segment
3.4.18
logical double line
sequence of root device and all ordinary devices processing the communication frame in
forward and backward direction
3.4.19
ma st er c lo ck
global time base for the PCS mechanism
3.4.20
message
ordered sequence of octets intended to convey data
3.4.21
message channel
MSC
part of one or more frames, which is reserved for acyclic data
3.4.22
network
set of devices connected by some type of communication medium, including any intervening
repeaters, bridges, routers and lower-layer gateways
3.4.23
open network
any ISO/IEC 8802-3 -based network with no further restrictions

– 16 – 61158-4-22 © IEC:2010(E)
3.4.24
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
3.4.25
precise clock synchronization
PCS
mechanism to synchronize clocks of RTFL devices and maintain a global time base
3.4.26
process data
data designated to be transferred cyclically or acyclically for the purpose of processing
3.4.27
process data object
dedicated data object(s) designated to be transferred cyclically or acyclically for the purpose
of processing
3.4.28
protocol
convention about the data formats, time sequences, and error correction in the data exchange
of communication systems
3.4.29
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
3.4.30
real time frame line
RTFL
communication model communicating in a logical double line
3.4.31
real time frame network
RTFN
communication model communicating in a switched network
3.4.32
switch
MAC bridge as defined in IEEE 802.1D
3.4.33
round trip time
transmission time needed by a DLPDU from the RD to the last OD in forward and backward
direction
3.4.34
timing signal
time-based indication of the occurrence of an event, commonly as an interrupt signal, used for
DL-user synchronization
61158-4-22 © IEC:2010(E) – 17 –
3.4.35
topology
physical network architecture with respect to the connection between the stations of the
communication system
3.5 Common symbols and abbreviations
NOTE Many symbols and abbreviations are common to more than one protocol Type; they are not necessarily
used by all protocol Types.
CIDR Classless Inter-Domain Routing
DHCP Dynamic Host Configuration Protocol
DL- Data-link layer (as a prefix)
DLC DL-connection
DLCEP DL-connection-end-point
DLE DL-entity
DLL DL-layer
DLPCI DL-protocol-control-information
DLPDU DL-protocol-data-unit
DLM DL-management
DLME DL-management entity
DLMS DL-management service
DLPDU DL-protocol-data-unit
DLS DL-service
DLSAP DL-service-access-point
DLSDU DL-service-data-unit
DNS Domain name server
FCS Frame check sequence
FIFO First-in first-out
IANA Internet Assigned Numbers Authority
IEEE Institute of Electrical and Electronics Engineers
IETF Internet Engineering Task Force

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OSI Open systems interconnection
Ph- Physical layer (as a prefix)
PhE Ph-entity
PhL Ph-layer
QoS Quality of service
RFC Request for comments
UTF Unicode transformation format
3.6 Additional Type 22 symbols and abbreviations
ACK Acknowledgement
ADL ACK data length
CDC Cyclic data channel
CDCL CDC line
CDCLPM CDCL protocol machine
CDCN CDC network
CDCNPM CDCN protocol machine
CDCS CDC send
CL Communication layer
CMD Command
DA Device address or destination address
DMR Delay measurement read
DMS Delay measurement send
FHPM Frame handling protocol machine
ID Identification
IP Internet protocol
IPv4 IP version 4
IPv6 IP version 6
IRQ Interrupt request
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MAC Medium access control
MC Master clock
MSC-MTP Message channel message transfer protocol
MSC Message channel
MSCL MSC line
MSCLPM MSCL protocol machine
MSCN MSC network
MSCNPM MSCN protocol machine
MSCR MSC read
MSCS MSC send
MSS Maximum segment size
NMPM Net management protocol machine
NV Network verification
OD Ordinary device
PD Previous device
PID Packet ID
PCS Precise clock synchronization
PCSC PCS configuration
PM Protocol machine
RD Root device
RTF Real time frame
RTFL Real time frame line
RTFLCFG RTFL configuration
RTFLCTL RTFL control
RTFN Real time frame network
RTFNCS RTFN connection setup
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RTFNCR RTFN connection release
RTFNSNR RTFN Scan network read
RX Receive direction
SA Source address
SYNC Synchronization
SYNC_START SYNC start
SYNC_STOP SYNC stop
TCP Transmission control protocol
TSU Time stamping unit
TX Transmit direction
UDP User datagram protocol
3.7 Conventions
3.7.1 Abstract syntax conventions
The DL syntax elements related to DLPDU structure are described as shown in Table 1.
• Fra
me part denotes the element that will be replaced by this reproduction.
• Data field is the name of the elements.
• Data Type denotes the type of the terminal symbol.
• Value/Description contains the constant value or the meaning of the parameter.
Table 1 – DLPDU element definition
Frame part Data field Data type Value/description

3.7.2 Protocol machine description conventions
The protocol sequences are described by means of protocol machines. For the specification
of protocol machines within this part of this standard, the following graphical description
language is used. Table 2 specifies the graphical elements of this description language and
their meanings.
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Table 2 – Conventions for protocol machine description
Graphical element Description
Each state of a protocol machine is uniquely identified using a
Name descriptive name
/Action
An action, if required, is performed by the protocol machine in this
particular state
A transition between different states of a protocol machine is
caused by an event or a particular condition
Name of Event
Conditions describing the state of a part of or of the whole system
[Conditions]
can be stated which have to be fulfilled to perform a certain
/Actions
transition
Additionally actions which are performed when performing a certain
transition can be stated
The initial state of a protocol machine is labeled using this symbol

4 Overview of the DL-protocol
4.1 Operating principle
Type 22 of this series of international standards describes a real-time communication
technology based on ISO/IEC 8802-3 for the requirements of automation technology. For the
purpose of fast intra-machine communication Type 22 describes a communication model and
protocol (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 and protocol (RTFN). Type 22 is designed as a multi-master bus
system.
Type 22 networks utilize ISO/IEC 8802-3 communication DLPDUs for both communication
models.
4.2 Communication model
4.2.1 Overview
Type 22 technology essentially specifies two communication models with corresponding
protocols. RTFL communication is intended for fast machine communication while RTFN
provides for the networking of individual machines or cells. The corresponding protocols aim
to offer an equal set of services for cyclic process data exchange as well as for acyclic
message data communication.
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 DLPDU,
writes its data and passes the DLPDU on. A RTFL network requires exactly one root device.
The last ordinary device of a RTFL network sends the processed DLPDU back. The DLPDU
is transferred back along exactly the same way to the root device so that it is returned by the
first ordinary device to the root device as response DLPDU. In backward direction, the
ordinary devices read their relevant data from the DLPDU.
For RTFN communication model, communication is based on point to point connections
between participating devices.

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Networking of different RTFL parts or cells of an automation system into an overall
automation system is supported by the usage of RTFN communication and corresponding
gateways.
4.2.2 RTFL device reference model
Type 22 services are described using the principles, methodology and model of
ISO/IEC 7498-
...