HARTING Solutions for Industrial Ethernet User Manual
HARTING
04 2E
Solutions for Industrial Ethernet
HARTING was founded in 1945 by
the family that still owns the company.
Today, HARTING employs around
2,300 people worldwide, including
150 qualified engineers. The sales
team, including more than 100 sales
engineers is in daily contact with our
customers.
The company is one of the world’s
leading manufacturers of connectors,
and currently have 33 subsidiary
companies in Europe, the United States
and Asia. In several product ares,
HARTING is a market leader.
Great emphasis is placed on close links
with customers, including the provision
of a ‘Just-in-Time’-Service to ensure
rapid delivery to key customers.
HARTING products are designed and
manufactured using the latest
automated techniques, from CAD
systems in the research and
development department to automatic
production techniques on the assembly
lines.
Production and quality control is based
on a ‘zero-error’ philosophy which can
only be reached by the continuous
successful implementation of fully
automated production techniques.
The organisation and procedures for
quality assurance are based on the
EN ISO 9001 standard. A total of
60 engineers and other employees,
most of whom are trained and qualified
to standards laid down by the DGQ
(German Association of Quality) or the
SAQ (Swiss Association of Quality), are
employed solely on quality-assurance
activities.
Quality Connections
Worldwide
People | Power | Partnership
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Chapter
Directory
Solutions for Industrial Ethernet
Industrial Ethernet – General information 00
Connectors 02
Active and passive
network components
01
System cables 03
List of part numbers 10
Company addresses 20
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Solutions for Industrial Ethernet
General information
It is the user's responsibility to check
whether the components illustrated in
this catalogue comply with different
regulations from those stated in special
fields of application which we are unable
to foresee.
We reserve the right to modify designs
in order to improve quality, keep pace
with technological advancement or meet
particular requirements in production.
This catalogue must not be used in any
form or manner without our prior
approval in writing (Copyright Law,
Fair Trading Law, Civil Code).
We are bound by the German version
only.
General
information
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03
What is Ethernet?
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00.04
Ethernet principles
Classic Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00.04
Ethernet transmission media in common use . . . . . . . . . . . . . . . . . . . . . . 00.04
Fast Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00.05
Switched Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00.05
The Industrial Ethernet network
General requirements for Industrial Ethernet networks . . . . . . . . . . . . . . . 00.08
PROFInet
®
transmission system and wiring . . . . . . . . . . . . . . . . . . . . . . . 00.09
Glossary
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00.12
Industrial Ethernet – General information
Page
Directory chapter 00
General
information
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Industrial Ethernet – General information
What is Ethernet?
Ethernet is a well established specification for serial
data transmission, originally published by Xerox in
1975. In 1985 Ethernet was standardised in IEEE
802.3, since when it has been extended a number of
times. "Classic" Ethernet operates at a data transmission rate of 10 Mbit/s.
Since the 1990s, Ethernet has developed in the
following areas:
– Transmission media
– Data transmission rates
l
Fast Ethernet at 100 Mbit/s (1995)
l
Gigabit Ethernet at 1 Gbit/s (1999)
l
There are plans for Ethernet running at 10 gigabits
– Networked topologies
l
Switched Ethernet
– Industrial Ethernet
Nowadays Ethernet is the most widespread base
technology in the world in commercial DP systems,
and is also gaining importance in industrial automation. The use of Ethernet creates a homogenous
and standardised communication infrastructure,
extending seamlessly from the office environment to
the machine.
Classic Ethernet (Shared Ethernet)
All network users have the same rights under Ethernet.
Any user can exchange data of any size with another
user at any time.
Because Ethernet was conceived as a logical bus system, any network device that is transmitting is heard by
all other users. Each Ethernet user filters the data
packets that are intended for it out from the stream, ignoring all the others.Telegrams that are intended for all
devices are an exception to this rule.These are known
as broadcast or multicast telegrams.
The CSMA/CD network access procedure
In Classic Ethernet, also frequently called shared
Ethernet, all the network users share one collision
domain. In Ethernet, network access is controlled by
the CSMA/CD procedure (Carrier Sense Multiple
Access with Collision Detection).
If a network user wishes to transmit data, it first checks
whether the network is free (carrier sense). If so, it
starts to transmit data. At the same time it checks
whether other users have also begun to transmit
(collision detection). If that is the case, a collision
occurs. All the network users concerned now stop their
transmission, wait for a period of time determined
according to a randomising principle, and then start
transmission again.
The result of this is that the time required to transmit
data packets depends heavily on the network loading,
and cannot be determined in advance. The more
collisions occur, the "slower" the entire network
becomes. Shared Ethernet therefore only has limited
suitability for industrial automation.
The physical size of the network is also limited. It
depends on the data rate being used and on the
maximum permissible transmission time of data
packets.
Approaches to improved performance
A number of approaches have been tried to improve
performance:
Segmentation: -> subdividing the collision domains
Higher
bandwidths: -> Fast Ethernet, Gigabit Ethernet
Switching: -> Switched Ethernet
and combinations of these.
Only with the implementation of these approaches
does Ethernet become interesting and useful for
industrial automation. For this reason, only Switched
Ethernet and Fast Ethernet will be considered further
in the following chapters.
Ethernet installations are primarily characterised by
two parameters: the Category of the cable (Category)
and the Class of the channel (Class).
General
information
Ethernet transmission media in common use
Description Meaning Distance
10 Mbit/s system
10 Base T [FD] 2 conductor pairs, min. Category 3, UTP and STP >100 m
10 Base FX [FD] Fibre-optic cable Depends on fibre type
100 Mbit/s system (Fast Ethernet)
100 Base TX [FD] 2 conductor pairs, Category 5, UTP and STP 100 m
100 Base FX [FD] Fibre-optic cable Depends on fibre type
[FD] = Full-duplex operation possible
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Next = Near end crosstalk
Industrial Ethernet – General information
The cable is identified by its Category in accordance
with its electrical transmission and high-frequency
properties, as follows:
Category 1: not specified
Category 2: up to 1 MHz
Category 3: up to 16 MHz
Category 4: up to 20 MHz
Category 5: up to 100 MHz
Category 6: up to 250 MHz
Category 7: up to 600 MHz
The channel is the point-to-point part of the transmission process, and is specified as follows:
Class A: up to 100 kHz
Class B: up to 1 MHz
Class C: up to 16 MHz
Class D: up to 100 MHz
Class E: up to 250 MHz
Class F: up to 600 MHz
The higher the alphabetical sequence of the letter, the
tougher are the requirements on the transmission
channel, and therefore also on the cable. If, for
instance, only Category 5 components are used in a
system, the capacity of a Class D cable is required.
The same applies to Category 6 and Class E, as to
Category 7 and Class F.
General
information
TE = Terminal Equipment
Switched Ethernet
Definition
Switched Ethernet refers to a network in which each
Ethernet user is assigned a port in a switch.
Switches separate former collision domains into
individual point-to-point connections between the
network components and the relevant user equipment.
Preventing collisions makes the full network bandwidth
available to each point-to-point connection. The second
pair of conductors in the Ethernet cable, which otherwise is necessary for the detection of collisions, can
now be used as an additional transmission medium, so
providing a significant increase in data transfer rate.
The use of switches allows any desired network
configuration, such as star, ring, tree or linear, to be
implemented.
Switched Ethernet offers the following important
advantages:
l
The possibility of scaling the collision regions to
match the needs of the application, going as far as
fully collision-free networks in which only one user is
assigned to each port
l
Very fast packet transfer between the collision
regions
l
A considerable increase in data transfer rate through
"true" full duplex operation
l
Preventing collisions allows deterministic operation
Network size
There is no theoretical limit to the physical extent of a
Switched Ethernet network. The maximum length of
conductor between the ends of a point-to-point
connection is only determined by the physical
transmission properties and is, according to the
specification, 100 m. In practice, the connectors and
cables used have a decisive effect on the transmission
length that can actually be achieved.
Fast Ethernet
Fast Ethernet, according to IEEE 802.3, is not a new
standard, but an extension of Classic Ethernet to
include the following new properties:
l
A data rate of 100 Mbit/s
l
Switching
l
Full duplex operation
These form the basis of industrially useful Ethernet
networks. Autonegotiation provides compatibility with
Classic Ethernet in accordance with IEEE 802.3.
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Industrial Ethernet – General information
The switch – the central network
component in Switched Ethernet
Switches are active infrastructure components that
operate according to IEEE 801.3 on layer 2 of the OSI
reference model. Switches analyse all the data
packets as they arrive, directing them on to the port
where the corresponding user is located. Only multicast and broadcast telegrams are an exception to
this. They are passed on to all the active ports and
switches.
Each switch requires an address/port assignment
table in order to correctly redirect the telegrams. The
assignment of a destination address to a specific port
in the switch is stored in this table. The destination
address of an incoming data packet is analysed with
the aid of this table, and the data packet is passed on
immediately to the corresponding port. The
address/port assignment table is usually generated
and maintained automatically by the switch in a selflearning process. One switch can learn several
thousand addresses. This is necessary when more
than one item of user equipment is connected to one
or more ports. This allows a number of independent
subnets to be connected to one switch.
In this way, each of the ports in a switch generates its
own collision region. This prevents data collision with
users attached through other ports. In Switched
Ethernet, only one user is assigned to any port. In this
way collisions are avoided altogether. Guaranteed
freedom from collisions provides a significant
increase in the effective data transfer rate. Additional-
ly, full duplex operation is now possible, since one pair
of conductors in the Ethernet cable, otherwise
required to detect collisions, can be used as an
additional data transfer medium. With Fast Ethernet
operating in full duplex mode (100 Base TX), 100
Mbit/s can be transferred simultaneously in the two
directions.This corresponds to doubling the data rate.
Thanks to the switching technology it is possible to
construct Industrial Ethernet networks that satisfy the
requirements both for reliability and for real-time
performance.
Different types of switches
Switches are chiefly distinguished according to the
following features:
Modes of operation: Store and forward
Cut-through
Modified cut-through
Blocking: Blocking
Non-blocking
Management: Managed
Unmanaged
Principle of a switch
Incoming
telegrams
Outgoing
telegrams
Assignment table
General
information
Address
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07
Industrial Ethernet – General information
A comparison of the operating modes
Store and forward (Figure 1)
In this mode of operation, the switch temporarily
stores the entire data packet, checks it for errors and,
if it is free of errors, passes it on to the appropriate
port.
Cut-through / Modified cut-through (Figure 2)
In this mode of operation only enough bytes from the
data packet are placed into temporary storage as are
necessary for the evaluation in the address/port
assignment table.
Once this has been done, all the incoming bytes from
the data packet are passed on immediately to the
corresponding port without any intermediate storage.
In modified cut-through, the switch waits for precisely
64 bytes before making a decision according to the
address/port assignment table.
Blocking
A switch has a certain number of ports available to
it, and these are connected through the switch matrix.
If the switch matrix is capable of handling all
the connections without delay at full data rate
immediately, then it is called a non-blocking switch. If
the number of simultaneous connections at full data
rate is limited, the switch is said to be blocking.
Management
An unmanaged switch handles all the data traffic on
the basis of the address/port assignment table. The
user has no options for manipulating this.
A managed switch controls the data flow in
accordance with certain parameters or rules. The
basis for this activity is provided by the switch
management software. Modern switches support
SNMP management and web-based management.
These provide a variety of options for manipulation by
the user. The capabilities of the management
software differ from one switch to another.
Time behaviour
In Switched Ethernet, all the uncertainties of time
that result from Ethernet's collision management
algorithm (CSMA/CD) are eliminated. If correctly
dimensioned, Switched Ethernet thus becomes a
deterministic system. For the purposes of industrial
automation it is necessary to select the switches and
to dimension the network in such a way that the
switches operate within their deterministic range
under all operating conditions.
General
information
Figure 1
Figure 2
Address
Address
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Industrial Ethernet – General information
The Industrial Ethernet network
General requirements for Industrial Ethernet
networks
The international standard ISO/IEC 11801 and its
European equivalent, EN 50173, define an
application-neutral standard form of information
networking for a building complex. The contents of the
two standards are largely identical. Both standards
assume that the buildings are used in a way similar to
an office, and aim to be neutral towards particular
applications. The specific requirements for Ethernet
networks in industrial environments, such as
l
equipment-specific cabling
l
individually adapted levels of networking for each
machine/plant
l
linear network structures
l
robust, industrial cables and connectors meeting
special requirements for EMC, temperature,
humidity, dust and vibration
are not considered in either of these standards.
General
information
Office areas Production and other industrial areas
Installation
conditions
Transmission
capacity
Environmental
requirements
l
Fixed basic installation in the building
l
Cables laid in false floor
l
Devices connected at workstation vary
frequently
l
Prefabricated connecting cables
l
Largely standard work places
(desk with PC, …)
l
Tree network structures
l
Wiring depends heavily on the equipment
l
Equipment-specific cabling
l
Connection points are rarely modified
l
Device connections may be assembled on
site
l
Each machine/plant requires individual
levels of networking
l
Linear or (redundant) ring network
structures are common
l
Large data packets (e.g. images)
l
Medium network availability
l
Transmission time on the scale of
seconds
l
Predominantly acyclic transmission
l
No isochronism
l
Moderate temperatures
l
Low dust levels
l
No humidity
l
Little shock or vibration
l
Low EMI exposure
l
Low mechanical hazard
l
Low UV radiation
l
Very little chemical hazard
l
Small data packets (measurement data)
l
Very high network availability
l
Transmission time on the scale of
microseconds
l
High proportion of cyclic transmission
l
Isochronism
l
Extreme temperatures
l
High dust levels
l
Humidity possible
l
Vibrating machines
l
High EMI exposure
l
Risk of mechanical damage
l
UV exposure out of doors
l
Chemical hazard from oily or aggressive
atmospheres
Table: Differing requirements of office and industrial areas
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Industrial Ethernet – General information
Network topologies
The topologies of Industrial Ethernet networks are
oriented toward the requirements of the equipment
that must be connected. Star, linear, tree and ring
structures are amongst the most common. In practice,
a real installation often consists of a mixture of the
individual structures considered below.
Star
A star structure is characterised by a central signal
distributor (switch) with single connections to all the
network's end devices. Star network structures are
best applied to areas where the density of devices is
high and the physical distances between them is
small, such as small production cells or an individual
production machine.
Tree
A tree topology is formed when a number of stars are
combined into one network. It is used when a complex
installation is divided into smaller regions.
Linear
A linear structure can be implemented by a switch
close to the end device requiring connection, or by a
switch integrated into the end device. Linear
structures are most often used in installations that
are physically extensive, such as conveyor systems,
and for the connection of manufacturing cells.
General
information
Ring (redundancy)
If the ends of a line are closed by an additional
connection, a ring structure results. Ring topologies
are used to protect against line breaks or the failure
of one network component in installations with high
requirements for availability.
PROFInet®transmission system and wiring
The "PROFInet®transmission system and wiring"
guideline defines a method of cabling for Industrial
Ethernet, suitable for industrial application, on the
basis of the fundamental requirements of ISO/IEC
11801.
The PROFInet
®
guideline sets new standards,
because:
l
The component manufacturer is provided with
unambiguous interface specifications
l
The user is provided with simple rules for the
installation
l
He is therefore able to implement networks without
additional Ethernet-specific planning, as with a field
bus.
The PROFInet
®
guideline specifies cables and
connectors with which the user can create an
installation without special calculations relating to the
transmission routes.
Detailed information can be found on the internet
under www.profibus.com
SW = Switch
TE = Terminal Equipment
Star structure
SW = Switch
TE = Terminal
Equipment
Linear structure
ISO / IEC 11801
Structured building network
Structured
machine
network
Manufacturing plant
BD = Building Distributor
MD = Machine Distributor
InO = Industrial Outlet
TE = Terminal Equipment
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2 100 m
2 100 m
2 100 m
4 100 m
4 100 m
6 100 m
6 100 m
Industrial Ethernet – General information
Cabling
Cables in an industrial environment may be exposed
to extreme mechanical stresses. To ensure adequate
mechanical protection special industrialised cable
may be required, and this can have an effect on
the transmission properties, which may mean that
only relatively short transmission routes can be
implemented. Signal transmission along symmetric
copper cables (twisted pair) must be in accordance
with 100 BASE-TX at 100 Mbit/s (Fast Ethernet). The
transmission medium contains two pairs of twisted,
screened copper cables (twisted pair or star quad)
with a characteristic impedance of 100 Ohms. Only
screened cables and connectors are permitted. The
individual components must satisfy the requirements
for Category 5 in accordance with ISO/IEC 11801.
The entire transmission route must satisfy the
requirements for Class D in accordance with ISO/IEC
11801. Removable connections on the cable side are
made using either RJ 45 or M12 male connectors. On
the device connections are in the form of female
mating connectors. Connecting cables (device
connecting cables and routing cables) accordingly
have male connectors at both ends. Each device is
connected through an active network component.The
transmission cable therefore has identical connectors
at both ends which simplifies installation as the
connecting cable fulfils the function of a patch lead.
The maximum cable length is 100 metres.
As long as the cable and the connectors meet with the
above specifications a maximum cabling length of
100 m can be achieved with up to six connector pairs.
The combination of a male and female connector is
regarded as one pair.
General
information
Table: Transmission route lengths
Wiring example Number of Maximum
connector pairs cabling length
TE = Terminal
Equipment
PMD = PROFInet
®
Machine Distributor
Area
"inside"
Connector
Connector
coupling
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Industrial Ethernet – General information
Connectors
An important criterion for industrial applications is the
ease with which connection equipment can be
handled on site. Connectors for M12 and for RJ 45
are available for this purpose. They can easily be
assembled on site using standard tools.
In the control cabinet area, PROFInet
®
uses RJ45 in
an IP 20 implementation. It is compatible with office
connectors.
HARTING RJ Industrial®IP 20 Data
Connectors outside the control cabinet must be capable of withstanding the stresses of industrial applications. RJ 45 or M12 connectors with protection to
IP 65 or IP 67 are used in this environment.The RJ 45
in IP 65 / IP 67 implementation has a robust housing
with push pull locking. Special versions allow a level
of protection up to IP 68 to be achieved. The M12
connectors use the screened, D-coded, 4-pin version,
as included by DKE for Industrial Ethernet in the IEC
standard.
HARTING RJ Industrial
®
IP 67 Push Pull
and
HARAX
®
M12-L shielded
Hybrid connectors can be used where distributed field
devices require connection to both the data network
and to a low voltage power supply. A fully contactprotected connector allows the connectors to be
identical at both ends, since the integrated contact
protection means that it is not necessary to alternate
between male and female contact.An RJ 45 providing
IP 67 protection is used to connect twin-pair,
screened data lines for communication and four
electrical contacts provide connection to the power
supply.
HARTING RJ Industrial®IP 67 Hybrid
Connector
assignment
RJ 45
Signal Function
Conductor colour
Pin assignment
RJ 45 M12
TD+
Transmission
Data + Yellow 1 1
TD-
Transmission
Data - Orange 2 3
RD+ Receiver
Data + White 3 2
RD- Receiver
Data - Blue 6 4
Switches
Switches are devices located in the transmission path
between end devices, and which regenerate signals they
receive before passing them on to their destinations.
They are used to construct networks, and permit data
communication over long distances. Switches suitable
for PROFInet
®
are designed for Fast Ethernet (100
Mbit/s, IEEE 802.3u) and for full duplex transmission. In
full duplex operation, a switch simultaneously sends and
receives data at the same port. Collisions do not occur.
No bandwidth is therefore lost through the Ethernet
collision process. Network planning is made significantly
more straightforward, because it is not necessary to
examine route lengths within a collision domain.
Industrialised switches are used for applications in the
industrial environments. Switches designed for the office
environment can only be used under certain conditions.
One reason for this is that they are not suitable for harsh
industrial surroundings. Secondly, large numbers of
ports can become expensive.
Industrial Outlets
The interface between the structured building network in
accordance with ISO/IEC 11801 and the PROFInet
®
plant cabling is provided by the Industrial Outlet, or InO.
Its function corresponds to the socket outlet used in the
office environment. The InO is manufactured to meet
protection levels IP 65 / IP 67 and is suitable for the
harsh conditions found in the industrial environment.
Source:
PROFInet®Technologie und Anwendung
(PROFInet
®
Technology and Application),
November 2002
PROFInet®transmission system and wiring,
November 2002
General
information
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Industrial Ethernet – General information
Glossary
10 Base T
The standard for data transmission of 10 Mbit/s
Ethernet through unscreened twisted pair cables
(Category 3, 4 or 5). Each connection is made using
two pairs of wires, one pair being used for data
transmission and the other for data reception.
10 Base FX
The standard for data transmission of 10 Mbit/s
Ethernet through optical fibres. Each connection is
made using two fibres, one fibre being used for data
transmission and the other for data reception.
100 Base TX
The standard for data transmission of 100 Mbit/s
Ethernet through twisted pair cables (Category 5).
Each connection is made using two pairs of wires,
one pair being used for data transmission and the
other for data reception.
100 Base FX
The standard for data transmission of 100 Mbit/s
Ethernet through optical fibres. Each connection is
made using two fibres, one fibre being used for data
transmission and the other for data reception.
Autonegotiation
A procedure defined in Fast Ethernet in which the
devices agree a transmission mode with one another
before the actual data transmission begins (100
Mbit/s or 10 Mbit/s, full or half duplex).
Autocrossing (1:1 cable; cross-over cable)
This function makes it possible to cross the send and
receive lines of twisted pair interfaces automatically.
Devices such as switches that support this function
can be joined through a cable that is wired 1:1 instead
of a cross-over cable.
AWG (American Wire Gauge)
The AWG value describes a cable in terms of the wire
thickness and the permissible attenuation.
Depending on the structure of the cable:
AWG 22 corresponds to a conductor
wire gauge of 0.33 - 0.38 mm²
AWG 24 corresponds to a conductor
wire gauge of 0.21 - 0.25 mm²
AWG 26 corresponds to a conductor
wire gauge of 0.13 - 0.15 mm²
Broadcast telegram
A broadcast telegram is defined as a call to all
network devices ("one to all").
CSMA/CD procedure
Carrier Sense Multiple Access/Collision Detection
Access procedure in Ethernet according to IEEE
802.3. Before sending a message, each network user
first checks whether the transmission medium is free
(Carrier Sense). It then begins to transmit, checking at
the same time whether other devices (Multiple
Access) have also begun to transmit data. If two or
more devices transmit at the same time, a collision
takes place. The devices stop transmitting their data
(Collision Detection). After a randomly chosen time
the next attempt is made when the line is free. In the
CSMA/CD procedure the physical size of the network
is limited by the maximum permissible transmission
time of the data signals across the network, and this
depends on the data rate.
Ethernet
The name of a data network that has been
standardised in IEEE 802.3 since 1985. The term
"Ethernet" is often used as a general term, without
distinguishing between the different versions
(Ethernet, Fast Ethernet etc.).
Fast Ethernet
A fast data network specified in IEEE 802.3 in 1995.
Important parameters: transmission speed 100
Mbit/s, variable packet length 64 - 1522 bytes
(with optional 4 byte tag field).
FEXT (Far End Cross Talk)
A form of crosstalk in which the signals from devices
located at the opposite ends of a twisted pair cable
are superimposed on one another.
Full Duplex
A mode of operation in which one device can
simultaneously send and receive data.
General
information
00
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Industrial Ethernet – General information
Gigabit Ethernet
A fast data network specified in IEEE 802.3 in 1999.
Important parameters: transmission speed 1000
Mbit/s, variable packet length 64 – 1518 bytes.
Half Duplex
A mode of operation in which a device either sends or
receives data at any one time. Collision detection is
active in Ethernet for half duplex operation. The
physical size of the network is limited by the
transmission time delays in the devices and the
transmission media.
Hub
The central point in a star arrangement.
A hub – often also called a star coupler – can be used
to connect a number of devices in a star arrangement.
In this arrangement, data packets must take turns to
pass through the hub one after another. Data packets
received at one port are immediately transmitted
again on all the other ports.
Industrial Ethernet
A name for the form of Ethernet used in automation
engineering. Because of the conditions encountered
in industrial applications, the network components
must withstand greater ranges of temperature and
satisfy tougher requirements in terms of availability
and reliability of the network.
Collision Domain
The CSMA/CD access procedure restricts the
transmission time of a data packet from one network
device to another. In accordance with the data rate,
this yields a spatially limited network referred to as a
collision domain. The maximum size of a collision
domain is 4250 m at 10 Mbit/s (Ethernet) and 412 m
at 100 Mbit/s (Fast Ethernet).If a connection operates
in full duplex mode, the physical size can exceed
these limits, because collisions do not then occur.
This requires bridges or switches to be used.
LAN (Local Area Network)
A name for local networks extending up to 10 km.
Multicast Telegram
A multicast telegram is sent to a group of defined
receivers. This group can be reached through one
address (cf. Broadcast Telegram).
NEXT (Near End Cross Talk)
A form of crosstalk in which the signals from devices
located at the same end of a twisted pair cable are
superimposed on one another.
POF (Plastic Optical Fibre)
A name for an optical fibre whose core and sheath are
formed of plastic. POF fibres have a typical core
diameter of 0.98 mm.
PROFInet
®
A network concept that defines the communication
from the field level to the control level utilising Profibus and Ethernet, along with a model for the
network engineering of the entire plant. See also:
www.profibus.com
Queue / Queuing
Queue is a general term for a series of elements or
tasks awaiting sequential processing. In a data
transmission system, a queue is a number of
messages or data packets that are waiting for further
processing or to be transmitted elsewhere. They are
temporarily sorted, and are processed one after
another under the control of appropriate queueing
procedures.
Segmentation / Network Segmentation
Network segmentation is used to set limits to collision
domains, allowing Ethernet networks to achieve
higher performance. A network can be segmented
with the aid, for instance, of switches.
Switched Network
A name for an Ethernet network constructed using
switches.
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