IEC PAS 62410:2005

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IEC
AVAILABLE
PAS 62410
SPECIFICATION
First edition
2005-08
Real-time Ethernet SERCOS III
Reference number
IEC/PAS 62410:2005(E)
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PUBLICLY
IEC
AVAILABLE
PAS 62410
SPECIFICATION
First edition
2005-08
Real-time Ethernet SERCOS III
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– 2 – PAS 62410 © IEC:2005(E)
CONTENTS
Foreword .3

Introduction .5

Section A – Update of IEC 61158-2 .7

Section B – Update of IEC 61158-3 .16
Section C – Update of IEC 61158-4.20
Section D – Update of IEC 61158-5.37
Section E – Update of IEC 61158-6 .54
Section F – Update of IEC 61784-2 .77

PAS 62410 © IEC:2005(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
Real-time Ethernet SERCOS III
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
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.

The International Electrotechnical Commission (IEC) draws attention to the fact that it is claimed that compliance
with this document may involve the use of a patent concerning SERCOS III.
The Interest Group SERCOS interface (IGS) has the patent applications listed below:
German Publication Number DE 102 37 097 A1.

IEC takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured the IEC that he is willing to negotiate licences under reasonable and non-
discriminatory terms and conditions with applicants throughout the world. In this respect, the statement of the holder
of this patent right is registered with IEC. Information may be obtained from:
Bosch Rexroth Electric Drives and Controls GmbH
Bürgem.-Dr.-Nebel-Str.2
97816 Lohr, 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.
A PAS is a technical specification not fulfilling the requirements for a standard but made
available to the public .
IEC-PAS 62410 has been processed by subcommittee 65C: Digital communications, of IEC
technical committee 65: Industrial-process measurement and control.

– 4 – PAS 62410 © IEC:2005(E)
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/358/NP 65C/374/RVN
Following publication of this PAS, the technical committee or subcommittee concerned will

transform it into an International Standard.

It is intended that the content of this PAS will be incorporated in the future new editions of the
various parts of the IEC 61158 series and IEC 61784 series according to the structure of
these series.
This PAS shall remain valid for an initial maximum period of three years starting from
2005-08. The validity may be extended for a single three-year period, following which it shall
be revised to become another type of normative document or shall be withdrawn.

PAS 62410 © IEC:2005(E) – 5 –
INTRODUCTION
This PAS relates to the integration of SERCOS III fieldbus specification in future editions of

IEC 61158 and IEC 61784 series.

It shows in various clauses what updates are required in each of these individual standards.

All definitions, abbreviations and symbols that relate to SERCOS III appear together in
Section F, which belongs to the updates of IEC 61784-2, as a temporary fix.

NOTE 1 Some sections of this PAS still refer to IEC 61491. As it has been decided to split this standard into

future IEC 61800 series, under consideration, (power drive systems) and IEC 61158/61784 series (communication)
according to 65C/365/RQ, references to these new standards will be incorporated later on, in accordance with the
relevant SC22G and SC65C working groups.
NOTE 2 For the reader who is unfamiliar with SERCOS interfaces, 17.3 of Section F can serve as a preface to the
specific details which follow in later clauses.
NOTE 3 A temporary "Type S" has been allocated for SERCOS III.
The SERCOS/CPF16 standard structure is described in the table below.
IEC 61784-1 Communication profiles CP16/1 and CP16/2.
(new edition)
CP16/1 fits to the existing SERCOS specification IEC
61491:2002 (fibre optic media, 2 and 4 Mbit/s). IEC 61491 (new
edition) shall not specify any communication and refer instead
to CP16/1 in IEC 61784-1 after release of its new edition
according to this structure proposal.
nd
CP16/2 fits to the 2 SERCOS generation (fibre optic media, 2,
4, 8 and 16 Mbit/s), which is downwards compatible to IEC
61491:2002 (CP16/1) while specifying additional features.
st
IEC 61784-2 (1 Communication profiles CP16/3.
edition)
CP16/3 fits to the newest, real-time Ethernet SERCOS Defined in the PAS.
generation, which is application compatible to IEC 61491:2002
(CP16/1) and CP16/2 while specifying additional
communication features.
IEC 61158-2 Physical layer specification for all CPF16 profiles (Type not yet known)
(new edition)
Type specifications for CP16/1 and CP16/2
Type specifications for CP16/3 Defined in the PAS

IEC 61158-3 Data Link layer service specification for all CPF16 profiles
(new edition) (Type not yet known)
Type specifications for CP16/1 and CP16/2
Type specifications for CP16/3 Defined in the PAS
IEC 61158-4 Data Link layer protocol specification for all CPF16 profiles
(new edition) (Type not yet known)
Type specifications for CP16/1 and CP16/2
Type specifications for CP16/3 Defined in the PAS

– 6 – PAS 62410 © IEC:2005(E)
IEC 61158-5 Application Link layer service specification for all CPF16 profiles

(new edition) (Type not yet known)

Type specifications for CP16/1 and CP16/2

Type specifications for CP16/3 Defined in the PAS

IEC 61158-6 Application Link layer protocol specification for all CPF16 profiles

(new edition) (Type not yet known)

Type specifications for CP16/1 and CP16/2
Type specifications for CP16/3 Defined in the PAS

PAS 62410 © IEC:2005(E) – 7 –
Section A – Update of IEC 61158-2

0 Introduction
0.5 Major Physical Layer variations specified in IEC 61158-2

0.5.1 Type S: optical media and twisted-pair wire

Type S specifies the following synchronous transmission:

a) optical fibre medium, at 2, 4, 8 and 16 Mbit/s;

b) twisted-pair wire medium, at 100 Mbit/s, according to ISO/IEC 8802-3 – 100Base-TX;
c) optical fibre medium, at 100 Mbit/s, according to ISO/IEC 8802-3 – 100Base-FX
2 Normative references
IEC 61491:2002, Electrical equipment of industrial machines – Serial data link for real-time
communication between controls and drives.
ISO/IEC 8802-3:2001, 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.
29 Type S: Medium Attachment Unit: Ethernet 100Base-TX and 100 Base-FX
29.1 Transfer medium part of physical layer
29.1.1 Basics
The physical layer of the SERCOS profile is according to ISO/IEC 8802-3. Therein the
transmission mode and the physical layer are specified. The transmission rate is 100 Mbit/s.
29.1.2 Topology
29.1.2.1 General
A SERCOS network uses slaves with integrated repeaters which have a constant delay time
(t , input Æ output). The topology consists of point-to-point transmission lines and
rep
participants. The master and the slaves are part of the network and are its participants. The
connection line between the participants is a shielded CAT5 (or better) cable.

Each participant has two communication ports (port 1 and port 2). Port 1 (P1) and port 2 (P2)
are interchangeable (see slave 3 in Figure 1 and Figure 2 for an example).
The topology can be either a ring structure or a line structure. A ring has two logical channels
(see Figure 1) and a line has only one logical channel (see Figure 2).
The difference between ring and line structure is that the ring has a built-in redundancy
against transmission media errors (e.g. cable break) and is therefore preferred.
A control unit may have one or more master interfaces depending on configuration. Each
master handles only one network on the physical layer.

– 8 – PAS 62410 © IEC:2005(E)
Slave interfaces are used to connect the devices to the network. At the physical layer, a slave
represents the connection of one or more devices to the network. Logically, one slave with

several devices acts the same as several slaves with each one device. The slaves are

connected to each other physically through the network. Communication takes place between

the master and the slaves; cross communication between the slaves is also supported.

The physical arrangement of slaves in the network is independent from the predefined device

address ADR for the slave, as well as from the sequence of the real-time data fields in the AT

and MDT. See 33.3.2 “Device address ADR” in IEC 61158-4, as well as 16.2 “Data transfer in

RT channel” in IEC 61158-5.
Any slave can recognize the topology at any time, since there is a distinction between primary
and secondary telegrams. This is important when a slave is added to the communication at a
later point in time (hot plug). When a slave receives telegrams with the same SERCOS type
on both ports (MDT0-P or MDT0-S) it recognizes a line. When it receives a MDT0-P on one
port and a MDT0-S on the other port, it recognizes a ring.
29.1.2.2 Ring structure
The ring structure consists of a primary and secondary channel. All slaves work in forwarding
mode (see Figure 1). Redundancy against cable break is achieved through this ring. It is also
possible to open the ring and insert/remove slaves during operation (hot plug).
TxD RxD
P1 = Port1
master
RxD
P2 = Port2 TxD
P1
P2
primary channel
master
P1 and P2 are interchangeable
secondary channel
processing
processing
P1
P2 P1 P2 P2 P1
slave
slave 1 slave 2
slave 3
Figure 1 – Ring structure
29.1.2.3 Line structure
The line structure consists of either a primary or secondary channel. The last physical slave
performs the loopback function. This is shown in Figure 2 with the loopback of slave 3. All
other slaves work in forwarding mode. No redundancy against cable break is achieved. It is
also possible to insert and remove slaves during operation (hot plug). This is restricted to the
last physical slave. The ports which are not used for SERCOS communication (e.g., master
port 2 and slave 3 port 1) can be used with IP communication. The master may communicate
with slaves using two lines.
PAS 62410 © IEC:2005(E) – 9 –
TxD
P1 = Port1
master
RxD
P2 = Port2
P1 P2
master
P1 and P2 are interchangeable
processing
processing
slave 1, 2
P2
P2 P1 P2 P1
P1
loopback
slave 2
slave 1 slave 3
processing
slave 3
Figure 2 – Line structure
29.1.2.4 Transmission media
29.1.2.4.1 Transmission medium 100Base-TX
The characteristics of the 100Base-TX network are specified in ISO/IEC 8802-3. To ensure
maximum noise immunity only shielded cables and connectors shall be used.
SERCOS devices shall use the MDI-X-ports with auto crossover function. The advantage is
that standard cables as well as crossover cables (TxD / RxD) can be used.
29.1.2.4.2 Transmission medium 100Base-FX
The characteristics of the 100Base-FX network are specified in ISO/IEC 8802-3.
29.2 Communication mechanisms
29.2.1 General
Master and slave have the same hardware properties. Each port is assigned to a processing
unit and a multiplexer (see Figure 3). The functions in the master and the slave depend on the
topology and on the time slot within the communication cycle (RT channel or IP channel).

– 10 – PAS 62410 © IEC:2005(E)

P1-->P2
processing
MUX
RxD
unit P1
TxD
P2
Loopback P1
Port 1
Port 2
Loopback P2
MUX
processing
TxD P1
RxD
unit P2
P1<--P2
Figure 3 – Block diagram of master and slave
29.2.2 Forwarding
In the slave, the data from RxD (P1) shall be passed on with or without change to TxD (P2).
The data from RxD (P2) shall be passed on with or without change to TxD (P1). See
“Forwarding P1 → P2” and “Forwarding P2 → P1” in Figure 4). While the RT channel is
active, the data shall be passed on, delayed by t . While the IP channel is active,
REP
forwarding shall always be active and data shall be passed on, either at once or later in time,
depending upon communication load.
In the master, forwarding shall always be switched off while the RT channel is active. While
the IP channel is active, forwarding shall be:
• switched off if the master is connected to a single line configuration (only P1 or P2 is
connected) or to an error-free ring configuration;
• activated if the master is connected to two independent lines or to a faulty ring
configuration. Depending on the master’s functionality, the telegrams may be passed on
either at once or later in time.
Forwarding: P1-->P2
processing
MUX
RxD
unit P1
TxD
P2
Port 1
Port 2
MUX
processing
P1
TxD
RxD
unit P2
Forwarding: P1<--P2
Figure 4 – Forwarding
PAS 62410 © IEC:2005(E) – 11 –

29.2.3 Loopback
In the slave, the data from RxD (P1 or P2) shall be passed on with or without change to TxD

(P1 and P2). Loopback may be activated either at P1 or P2 depending on the topology, but

not at both ports simultaneously. The states are called “loopback P1”, respectively “loopback

P2”. See Figure 5. While the IP channel is active, loopback shall never be active. While the
RT channel is active, the slave shall activate loopback in the following (and only in those)

cases:
• during CP0, as soon as an MDT0 has been received at a port (P1 or P2), but only as long

as no MDT0 has been received at the other port;

• when the slave is the last physical one in the line topology;

• when a cable fault is detected.
The master shall have no loopback functionality.
Forwarding: P1-->P2
processing
MUX
RxD
unit P1
TxD
P2
Port 1
Port 2
Loopback P1
MUX
processing
TxD P1
RxD
unit P2
Figure 5 – Loopback
29.2.4 Device behaviour by addresses 0 and 255
Slaves with device addresses 0 and 255 shall also behave as described in 29.2.2 and 29.2.3.
They shall also evaluate MDT0 in the same matter as the slaves with other addresses.
29.2.5 Redundancy of RT-Communication with ring topology

29.2.5.1 Ring topology without fault
Figure 6 shows an error free ring topology. The master shall send all telegrams with the same
content on the P channel and on the S channel. Each slave shall receive both telegrams, work
on the assigned data fields in P und S channel, and pass them on in their respective
channels. Likewise, the master shall receive the telegrams from the slaves twice and process
the data from the slave only once (either P or S channel).

– 12 – PAS 62410 © IEC:2005(E)

P1-->P2
processing
S-Channel
MUX
RxD unit P1
TxD
P2
Port 1
Master
Port 2
P-Channel MUX
processing
TxD P1
RxD
unit P2
P1<--P2
P1-->P2
P1-->P2
processing
processing
MUX
MUX
RxD unit P1
RxD unit P1
TxD
TxD
P2
P2
Slave 1
Slave 2
Port 1 Port 1
Port 2
Port 2
MUX
MUX
processing
processing
TxD P1
TxD P1
RxD
unit P2 unit P2 RxD
P1<--P2
P1<--P2
Figure 6 – Ring topology example with 2 slaves (example)
29.2.5.2 Cable faults between slaves
29.2.5.2.1 Case 1: Double channel interruption between two slaves
Figure 7 shows a first example of a faulty ring topology. Slave 1 shall detect an interruption at
RxD of port 2 and close loopback at port 1. Slave 2 shall detect an interruption at RxD of port
1 and close loopback at port 2. The master shall receive the telegrams from slave 1 at port 1
only, and those from slave 2 at port 2 only.
P1-->P2
processing
S-Channel
MUX
RxD
unit P1
TxD
P2
Port 1
Master
Port 2
P-Channel
MUX
processing
TxD P1
RxD
unit P2
P1<--P2
P1-->P2
P1-->P2
processing
processing
MUX
MUX
RxD unit P1 RxD
unit P1
TxD TxD
P2
P2
Slave 1
Slave 2
Loopback P1
Port 1 Port 2 Port 1
Port 2
Loopback P2
MUX
MUX
processing processing
TxD P1
RxD TxD P1
unit P2
unit P2 RxD
P1<--P2
P1<--P2
Figure 7 – Double channel interruption between two slaves (example)
29.2.5.2.2 Case 2: Single channel interruption between two slaves
Figure 8 shows another faulty ring topology example. Slave 1 shall detect an interruption at
RxD of port 1 and close loopback at port 2. The master shall receive the telegrams from all
slaves at port 1. At port 2, the master receives the telegrams from slave 2 in addition.

PAS 62410 © IEC:2005(E) – 13 –

P1-->P2
processing
S-Channel
MUX
RxD unit P1
TxD
P2
Port 1
Master
Port 2
P-Channel MUX
processing
TxD P1
RxD
unit P2
P1<--P2
P1-->P2
P1-->P2
processing
processing
MUX
MUX
RxD unit P1
RxD unit P1
TxD
TxD
P2
P2
Slave 1
Slave 2
Port 1 Port 1
Port 2
Port 2
Loopback P2
MUX
MUX
processing
processing
TxD P1
TxD P1
RxD
unit P2 unit P2 RxD
P1<--P2
P1<--P2
Figure 8 – Single channel interruption between two slaves (example)
29.2.5.3 Cable faults between master and slave
29.2.5.3.1 Case 1: Double channel interruption between master and slave
Figure 9 shows another faulty ring topology as an example. Slave 1 shall detect an
interruption at RxD of port 1 and close loopback at port 2. The master shall detect an
interruption at RxD of port 1. The master shall receive the telegrams from all slaves at port 2
only.
Fault detection
P1-->P2
S-Channel processing
MUX
RxD unit P1
TxD
P2
Port 1
Master
Port 2
P-Channel
MUX
processing
P1
TxD
RxD
unit P2
P1<--P2
P1-->P2
P1-->P2
processing
processing
MUX
MUX
RxD
unit P1 RxD unit P1
TxD TxD
P2 P2
Slave 1
Slave 2
Port 1
Port 1 Port 2
Port 2
Loopback P2
MUX
MUX
processing processing
TxD P1
RxD TxD P1
unit P2
unit P2 RxD
P1<--P2
P1<--P2
Figure 9 – Double channel interruption between the master and a slave (example)

– 14 – PAS 62410 © IEC:2005(E)

29.2.5.3.2 Case 2: Single channel interruption between master output and slave

Figure 10 shows another faulty ring topology example. Slave 1 shall detect an interruption at

RxD of port 1 and close loopback at port 2. The master shall receive the telegrams from all

slaves twice.
P1-->P2
processing
S-Channel
MUX
RxD
unit P1
TxD
P2
Port 1
Master
Port 2
P-Channel MUX
processing
TxD P1
RxD
unit P2
P1<--P2
P1-->P2
P1-->P2
processing
processing
MUX
MUX
RxD unit P1
RxD unit P1
TxD
TxD
P2
P2
Slave 1
Slave 2
Port 1 Port 1
Port 2
Port 2
Loopback P2
MUX
MUX
processing
processing
TxD P1
TxD P1
RxD
unit P2 unit P2 RxD
P1<--P2
P1<--P2
Figure 10 – Single channel interruption at master output (example)
29.2.5.3.3 Case 3: Single channel interruption between master input and slave
Figure 11 shows another faulty ring topology example. The master shall detect an interruption
at RxD of port 1. The master shall receive the telegrams from all slaves at port 2 only.
Fault detection
P1-->P2
processing
S-Channel
MUX
RxD
unit P1
TxD
P2
Port 1
Master
Port 2
P-Channel
MUX
processing
TxD P1
RxD
unit P2
P1<--P2
P1-->P2
P1-->P2
processing
processing
MUX
MUX
RxD unit P1 RxD
unit P1
TxD TxD
P2
P2
Slave 1
Slave 2
Port 1 Port 2 Port 1
Port 2
MUX
MUX
processing processing
TxD P1
RxD TxD P1
unit P2
unit P2 RxD
P1<--P2
P1<--P2
Figure 11 – Single channel interruption at master input (example)

PAS 62410 © IEC:2005(E) – 15 –

29.2.6 IP communication mechanisms

29.2.6.1 Slaves within a line or a ring

Should a slave receive a telegram while IP channel is active and as it is transmitting an IP
telegram, the currently transmitted IP telegram shall not be interrupted and the incoming

telegram shall be stored.
Slaves shall always send their own IP telegrams on both ports (P1 and P2). The following

conditions shall all be met before doing it:

• when it is forwarding a telegram, the slave shall wait that this telegram has been fully

forwarded;
• the remaining IP channel duration is long enough to fully transmit its own IP telegram;
• its memory has enough free capacity for storing at least one new incoming IP telegram
with maximum length.
Should a slave receive an MDT0 while it is sending an IP telegram, then it shall immediately
interrupt this sending and forward the MDT0.
29.2.6.2 Slave in the last position within a line
Although the last slave in a line has its loopback active, it shall check for any incoming IP
telegram on its other port. It shall forward IP telegrams when its IP channel is active, provided
that the remaining duration of this IP channel is long enough to fully transmit this IP telegram.
Otherwise, or if the IP channel is not active, the last slave shall store all incoming IP
telegrams. It shall forward one or several of them as soon as IP channel is active again,
provided that the remaining duration of this new IP channel is long enough.

– 16 – PAS 62410 © IEC:2005(E)

Section B – Update of IEC 61158-3

1 Scope and object
1.1 Overview
Type S — A DL-service which provides a superset of those services expected of OSI Data

Link Protocols as specified in ISO/IEC 8886.

2 Normative references
IEC 61491:2002, Electrical equipment of industrial machines - Serial data link for real-time
communication between controls and drives.
ISO/IEC 8802-3:2001, 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.
21 Type S: Data Link concepts, services and management
21.1 Data transfer and data link layer
21.1.1 General
In this subclause, the telegram structure (frame structure) is described. Telegrams are
according to the Ethernet standard ISO/IEC 8802-3.
SERCOS header specifies two sub types of SERCOS telegrams:
• Master data telegram (MDT): The MDTs transmit data from the master to the slaves;
• Device telegram (AT): The ATs transmit data from the slaves to the master.
Furthermore, ISO/IEC 8802-3 Ethernet protocols can be transported.
21.1.2 Real-time telegram types
21.1.2.1 General
Real-time telegrams are transmitted in the real-time part of the communication cycle time (RT
channel). They transport mainly command values and actual values. SERCOS defines two

types of real-time telegrams (MDT and AT).
21.1.2.2 Master data telegram (MDT)
SERCOS specifies 4 MDTs (MDT0 to MDT3). The MDTs are transmitted by the master and
received by each slave. The MDTs contain all information (e.g., synchronisation, command
values, digital outputs .) which is sent from the master to the slaves through the real-time
channel.
MDT0 is always transmitted. MDT1 through 3 are transmitted only if required and depend on
the total amount of data to be transmitted to the slaves. The master always sends the same
number of MDTs during each communication cycle.

PAS 62410 © IEC:2005(E) – 17 –

21.1.2.3 Device telegram (AT)
SERCOS specifies 4 ATs (AT0 to AT3). The ATs are transmitted by the master with empty

data fields. Each slave inserts its data into its allocated data field within the AT. The ATs

contain all information (e.g., feedback values, digital inputs .) which is sent from the slaves

to the master as well as between the slaves through the real-time channel.

AT0 is always transmitted. AT1 through 3 are transmitted only if required and depend on total

amount of data to be transmitted to the master. The master always sends the same number of
ATs during each communication cycle.

21.1.2.4 Cycle time
The following reference values have been determined for the communication cycle time,
t .
Scyc
t = 31,25µs, 62,5µs, 125µs, 250µs and integer multiples of 250 µs up to 65 000 µs.
Scyc
This cycle time is allowed to have some jitter. The jitter describes the deviations from the
t value in the distance between two MDT0. J shall belong to a class as in Table 1.
Scyc tscyc
Table 1 – Synchronisation classes
Synchronisation Jitter of MDT0 J
tscyc
high performance class
≤ +/- 1 µs
low performance class
≤ +/- 50 µs
Therefore, the actual time interval between the MDT0 and the following MDT0 has a minimum
value of:
j x t * 0,9999 – J (j = 1, 2, 3, .),
Scyc tscyc
and a maximum value of:
j x t * 1,0001 + J (j = 1, 2, 3, .).
Scyc tscyc
NOTE j is an arbitrary, strictly positive integer, and is not related to the abbreviations.
The factors 0,9999 or 1,0001 take into account the deviation of the communication cycle time
t , compared to the accuracy of the usual crystal oscillators (±100 ppm). Note that the jitter
Scyc
shall not accumulate over several periods (i.e., the average value shall be zero).

21.1.2.4.1 Telegram transmission times
During the initialization phase, the master inquires for time parameters from the slaves. See
subclause 14.2. “Communication phase 2 (CP2)” in IEC 61158-6. With this information, it is
possible to calculate a collision-free distribution of transmission time-slots of the telegrams
within the RT channel.
The master transmits to each slave the AT transmission starting time, t , as well as the
beginning and ending times of the IP channel, t respectively t . These starting times for the
6 7
transmitting time-slots for the telegrams are defined next.
Jitter has been incorporated in t :
– 18 – PAS 62410 © IEC:2005(E)

t AT transmission starting time: this is the nominal time interval between the beginning of
MDT0 and the beginning of the AT0. This parameter has been determined by the master

and is stored in the associated devices as an IDN.

J Jitter in t : this is the maximum deviation of the beginning of the AT0. It is the allowed
t1 1
deviation of the time interval t . The actual time interval between the beginning of MDT0

and the beginning of AT0 shall lie between t - J and t + J J shall have the same
1 t1 1 t1. t1
value as the jitter of MDT0, J . See Table 1.
tscyc
t t Time-slot of IP channel (t begin of IP channel, t end of IP channel). Within the IP
6, 7 6 7
channel there are no special time-slots. Every participant can send its IP telegrams during

this time-slot. The time parameters (t and t ) are set by the master in communication phase 2
6 7
(CP2).
Figure 4 “Access to the transfer medium” (subclause 33.2.2.2.1) in IEC 61158-4 shows the
timing of the transmission time-slots.
21.1.2.5 Timing parameters
The following time parameters are characteristics of the network.
t time by which the received signal is delayed by a forwarding slave (input to output).
rep
This parameter is saved as an IDN in the slave.
t time by which the transmitted signal is delayed by the cable (approx., 5 ns/m).
cable
t time between the transmitted and received signal at the master. The master measures
ring
the ring delay in CP0. The ring delay contains all forwarding and cable delays in the
network and is used for synchronisation purposes.
21.1.2.6 MDT partitioning
A service channel and a configurable real-time data field (RTD) are defined in the MDT for
each slave. S-0-1013 sets the offset for the service channel. S-0-1009 sets the offset for the
real-time data field. S-0-1010 contains the length of the MDT (see Figure 1). These
parameters are transmitted by the master to the slaves in CP2.
MDT
H M H F
SVC SVC SVC SVC RTD RTD RTD RTD
. . . . . . . . . . . .
D S O C
1 2 n N 1 2 k K
R T T S
S-0-1013
S-0-1009
S-0-1010
Figure 1 – Partitioning of MDT data fields
21.1.2.7 AT partitioning
A service channel and a configurable real-time data field are defined in the AT for every
device. S-0-1014 defines the offset for the service channel. S-0-1011 defines the offset for the

PAS 62410 © IEC:2005(E) – 19 –

real-time data field. S-0-1012 defines the length of the AT (see Figure 2). These parameters

are transmitted from the master to the slaves in CP2.

AT
H M H F
SVC SVC SVC SVC RTD RTD RTD RTD
. . . . . . . . . . . .
D S O C
1 2 n N 1 2 m M
R T T S
S-0-1014
S-0-1011
S-0-1012
Figure 2 – Partitioning of AT data fields
21.1.3 MDT and AT combinations
The allocations of the service channels (SVC) and the real-time data fields (RTD) in the MDT
as well as in the AT are configured with parameters (see Figure 1 and Figure 2). The RTD
lengths in the MDTs and the ATs depend on the configuration and may be different. The
number of MDTs and ATs may be different. This configuration shall meet the following
requirements:
1) All service channels shall be configured directly after the hot plug field.
2) All real-time data fields shall be configured directly after the last service channel.
3) All SVCs of a device shall be transmitted within one telegram (MDT and AT). The telegram
shall be filled up with SVCs as much as possible before using the next telegram.
4) All RTDs of a device shall be transmitted within one telegram (MDT and AT). The telegram
shall be filled up with RTDs as much as possible before using the next telegram.
Figure 3 shows examples of valid telegram combinations of MDTs and ATs.
MDT0 / AT0 MDT1 / AT1 MDT2 / AT2 MDT3 / AT3
Maximum SERCOS
data length
1. H SVC
RTD
2. H SVC R RTD
RTD
H R RTD R RTD
3. SVC
H R SVC RTD R RTD R
4. SVC RTD
NOTE H = Hot plug field, R = reserved
Figure 3 – Examples of valid telegram combinations

– 20 – PAS 62410 © IEC:2005(E)

Section C – Update of IEC 61158-4

1 Scope and object
1.1 Overview
Type S — A DL-protocol for the Type S DL-service. The maximum system size is 2 links of

255 nodes.
1.2 Specifications
1.2.1 Type S: Additional characteristics
This protocol provides a highly-optimized means of interchanging fixed-length real-time data
and variable-length segmented messages between a single master device and a set of slave
devices, or between slave devices directly, interconnected in a line or in a ring topology. The
ring topology provides for redundant communication paths, and in case of an error it
automatically switches to a set of two lines without disturbing the communication. The
exchange of real-time data is totally synchronous by configuration and is unaffected by the
messaging traffic.
The device addresses are set by the user, e.g., using a selector. Additional devices may be
added whenever required, even during operation, without affecting the already existing
address selections. The determination of the number, identity and characteristics of each
device may be configured or may be detected automatically at start-up.
This protocol provides in addition a standard Ethernet means of interchanging data and files
in non real-time way between standard devices such as personal computers and the
interconnected devices. This feature provides a way of addressing each individual device
even if the device addresses have not yet been set.
2 Normative references
IEC 61491:2002, Electrical equipment of industrial machines - Serial data link for real-time
communication between controls and drives.
ISO/IEC 8802-3:2001, 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.

5 DL-protocol elements common to multiple DL-protocol Types
5.1 Frame check sequences
Table 1 – FCS length, polynomials and constants by protocol Type
Protocol Item Value
Type S n-k 32
32 26 23 22 16 12 11 10 8 7 5 4 2
G(x) x + x + x + x + x + x + x + x + x + x + x + x + x + x + 1 (note 1)
NOTE 1: Refer to ISO/IEC 8802-3 for a thorough description of this polynomial.

PAS 62410 © IEC:2005(E) – 21 –

33 Type S: Data Link protocol definition

33.1 General
In this subclause, the telegram structure (frame structure) is described. Telegrams follow the

Ethernet standard ISO/IEC 8802-3.

SERCOS telegrams are indicated by the Ethernet type field number (0x88CD).

SERCOS header specifies two sub-types of SERCOS telegrams:

• Master data telegram (MDT): The MDTs transmit data from the master to the slaves;
• Device telegram (AT): The ATs transmit data from the slaves back to the master.
Furthermore ISO/IEC 8802-3 Ethernet protocols can be transported.
33.2 Data transfer and data link layer
33.2.1 Real-time telegram structure
33.2.1.1 General
Data transmission takes place in telegrams. The general structure of real-time telegrams has
been shown in Figure 1.
media layer
MAC layer
Data field are padded
IDLE SSD preamble SFD destination source type SERCOS SERCOS FCS ESD
address address 0x88CD header data field
7+1 bytes 6 bytes 6 bytes 2 bytes 6 bytes 40–1494 bytes 4 bytes 1 byte
≥11+1 bytes
SERCOS
checked against FCS data length
telegram length: 72 - 1526 bytes (overhead = 26+6=32 bytes)
telegram length: 84 - 1538 bytes (overhead = 38+6=44 bytes)

Figure 1 – General telegram structure
33.2.1.2 Telegram delimiters
To receive telegrams correctly the following telegram delimiters are needed:
• Inter Packet Gap (IPG ≥ 12 bytes, IDLE and SSD);
• Preamble (7 bytes);
• Start Frame Delimiter (SFD, 1 byte);
• End Stream Delimiter (ESD, 1 byte).
33.2.1.3 Destination address (DA)
Length: 6 bytes
– 22 – PAS 62410 © IEC:2005(E)

The master transmits MDTs and ATs to all slaves using the broadcast address

0xFFFFFFFFFFFF as destination address.

33.2.1.4 Source address (SA)
Length: 6 bytes
The source address in the real-time telegrams is always the MAC address of the master.

33.2.1.5 Type / length
Length: 2 bytes
The type / length contains the unique SERCOS Ethernet type field number (0x88CD).
33.2.1.6 Data field
Length: 46 bytes to 1500 bytes
All transmitted data is allowed to have arbitrary bit sequences, whereas the total number of
bytes follows the rules below.
The data field contains:
• SERCOS specific header (6 bytes) ;
• SERCOS data (40 bytes to1494 bytes);
• padding bytes shall be inserted whenever the SERCOS data is shorter than 40 bytes.
33.2.1.7 Frame check sequence (FCS)
Length: 4 bytes
A cyclic redundancy check (CRC) is used by the transmit and receive algorithms to generate
a CRC value for the FCS field. The frame check sequence (FCS) field contains a 4 byte (32-
bit) cyclic redundancy check (CRC) value. This value is computed as a function of the
contents of the destination address, source address, type, data and pad (in other words, all
MAC layer fields except the preamble, SFD and FCS fields). The FCS is generated by the
transmitter. The encoding is defined by the Type S generating polynomial of Table 1, section
5. 1.
33.2.2 Timing of the transmission (communication cycle)

33.2.2.1 General
The sequence of transmitting synchronisation, RT-data telegrams and IP telegrams is
repeated every communication cycle. The time slots for the RT channel and the IP channel
and the transmission time of the AT are transmitted during initialization and are therefore
known by each slave. Figure 2 shows two principle arrangements of RT channel and IP
channel. Both methods are possible and can be parameterized by the master (see Figure 4).
Within the IP channel there are no special time slots. Every participant may send its IP
telegrams during this time slot depending upon configuration.
A synchronous collision-free media access control is used in the RT channel. Telegrams are
exchanged in fixed communication cycles. The master starts the communication cycle strictly
equidistant with the communication cycle time t , by transmitting the MDT0. The next
Scyc
communication cycle starts with the transmitting of the next MDT0.

PAS 62410 © IEC:2005(E) – 23 –

The MDTs (MDT0 through MDT3) are transmitted as broadcast telegrams to all slaves. The

MDT0 contains the synchronisation information and the status of the communication in the

MDT MST field. The content of the MDT MST field remains constant during the same

communication phase.
The ATs (AT0 through AT3) are transmitted by the master with an empty data field. Each

slave inserts its data into its allocated data field within the ATs. The sequence of the device

data fields within the ATs is independent of the physical order of the topology as well as the

predefined device address. The master is the final recipient of the ATs. Slave units positioned

between the master and the transmitting slave transmit the telegrams by means of their
forwarding function.
MDT0 MDT1 MDT2 MDT3 AT0 AT1 AT2 AT3 MDT0
H M H M
H M H M H M H M H M H M H M
D S D S D S D S D S
D S D S D S D S
R T R T R T R T R T R T R T R T R T
RT channel
IP channel
method 1
communication cycle
MDT3
MDT0 MDT1 MDT2 AT0 AT1 AT2 AT3 MDT0
H M H M H M
H M H M H M H M H M H M
D S S D S D S D S D S D S D S D S
D
T R T R T
R T R R T R T R T R T R T
IP channel
RT channel RT channel
method 2
communication cycle
Figure 2 – Telegram sequence in CP3/CP4
33.2.2.2 Transfer medium access
33.2.2.2.1 General
Figure 4 shows the medium access d
...