PUB00123R1_Common-Industrial_Protocol_and_Family_of_CIP_Networks

PUB00123R1_Common-Industrial_Protocol_and_Family_of_CIP_Networks
COMMON INDUSTRIAL
PROTOCOL (CIP™ )
AND THE FAMILY OF
CIP NETWORKS
PUB00123R1
FEBRUARY 2016
he Common Industrial Protocol (CIP™) and the Family of
T
CIP Networks
Publication Number: PUB00123R1
Copyright © 2006-2016 ODVA, Inc. All rights reserved. For permissions to reproduce excerpts of this material,
with appropriate attribution to the author(s), please contact ODVA at:
ODVA, Inc.
Ann Arbor, MI, USA
TEL 1-734-975-8840
FAX 1-734-922-0027
WEB www.odva.org
The right to make, use or sell product or system implementations described herein is granted only under separate license pursuant to a Terms of Usage Agreement or other agreement. Terms of Usage Agreements for
individual CIP Networks are available, at standard charges, over the Internet at www.odva.org:
Warranty Disclaimer Statement
The right to make, use, or sell product or system implementations based upon the Common Industrial Protocol
(CIP) is granted only under separate license pursuant to a Terms of Usage Agreement or other agreement. The
ODVA Terms of Usage Agreement is available, at standard charges, over the Internet at www.odva.org. NOTE:
Because the technologies described in the CIP Networks Library may be applied in many diverse situations and
in conjunction with products and systems from multiple vendors, the user and those responsible for specifying
these technologies must determine for themselves their suitability for the intended use. ALL INFORMATION
PROVIDED BY ODVA IS PROVIDED “AS IS” WITH NO WARRANTIES WHATSOEVER, WHETHER EXPRESS,
IMPLIED, STATUTORY, OR OTHERWISE, AND ODVA AND ITS MEMBERS, PARTICIPANTS, SPECIAL INTERESTS GROUPS, EXECUTIVE DIRECTOR AND BOARD OF DIRECTORS EXPRESSLY DISCLAIM ANY WARRANTY OF MERCHANTABILITY, NON-INFRINGEMENT, FITNESS FOR ANY PARTICULAR OR INTENDED
PURPOSE, OR ANY OTHER WARRANTY OTHERWISE ARISING OUT OF THE SPECIFICATIONS. ODVA AND
ITS MEMBERS, PARTICIPANTS, SPECIAL INTERESTS GROUPS, EXECUTIVE DIRECTOR AND BOARD OF
DIRECTORS DO NOT WARRANT THAT USE OF THE SPECIFICATIONS (INCLUDING, WITHOUT LIMITATION,
THE MANUFACTURE, DISTRIBUTION AND SALE OF PRODUCTS THAT COMPLY WITH THE SPECIFICATIONS) WILL BE ROYALTY-FREE. The user should always verify interconnection requirements to and from other
equipment, and confirm installation and maintenance requirements for their specific application. IN NO EVENT
SHALL ODVA, ITS OFFICERS, DIRECTORS, MEMBERS, AGENTS, LICENSORS, OR AFFILIATES BE LIABLE
TO YOU, ANY CUSTOMER, OR THIRD PARTY FOR ANY DAMAGES, DIRECT OR INDIRECT, INCLUDING BUT
NOT LIMITED TO LOST PROFITS, DEVELOPMENT EXPENSES, OR ANY OTHER DIRECT, INDIRECT, INCIDENTAL, SPECIAL, PUNITIVE OR CONSEQUENTIAL DAMAGES.
CIP, DeviceNet, EtherNet/IP ControlNet, CompoNet, ODVA CONFORMANT, CIP Safety, CIP Sync, CIP Motion,
CIP Energy, and OEU are trademarks of ODVA, Inc.
2
PUBLISHER:
ODVA, Inc.
AUTHOR:
Viktor Schiffer – on behalf of Rockwell Automation
EDITORS:
David J. VanGompel – Member of Technical Review Board, ODVA
Raymond A. Romito – Senior Project Engineer, Rockwell Automation
Katherine Voss – Executive Director, ODVA
ABOUT THE AUTHOR
Viktor Schiffer has over 25 years of experience in the field of manufacturing automation and industrial networks.
Mr. Schiffer graduated from RWTH Aachen in Germany with a degree of Diplom-Ingenieur in Electrical Engineering and earned a Master of Science degree in Electronic Instrumentation from the University College of Wales
in Swansea in the United Kingdom. He served as Engineering Manager for Rockwell Automation in Germany
where he was responsible for third party support of the open CIP Networking technologies DeviceNet, ControlNet and EtherNet/IP.
The author has been writing on the topic of industrial networks and has published a number of papers related
to the CIP Networking technologies, including specifically on the use of Electronic Data Sheets and on real-time
behavior of networks.
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The Common Industrial Protocol (CIP™) and the Family of CIP Networks
Contents
4
1.Introduction
7
2. Description of CIP 2.1. Object Modeling 2.2. Services 2.3. Messaging Protocol 2.4. Communication Objects 2.5. Object Library 2.6. Device Profiles 2.7. Configuration and Electronic Data Sheets 2.8. Bridging and Routing 2.9. Data Management 10
12
14
14
16
18
26
27
29
30
3. Network Adaptations of CIP 3.1. DeviceNet™ 3.2. ControlNet™ 3.3. EtherNet/IP™ 3.4. CompoNet™ 33
33
54
65
82
4. Benefits of The CIP Family 4.1. Benefits for the Manufacturer of Devices 4.2. Benefits for the Users of Devices and Systems 93
93
93
5. Application Layer Enhancements 5.1. CIP Sync™ and CIP Motion™ 5.2. CIP Safety™ 94
94
99
6. Conformance Testing 121
7. Endnotes 123
8. Bibliography 126
9. Related Publications 126
10. Abbreviations 127
11. Terminology 129
The Common Industrial Protocol (CIP™)
and the Family of CIP Networks
Preface
Founded in 1995, ODVA (www.odva.org) is a global association whose members comprise the world’s leading
automation companies. Combined with the support of its members, ODVA’s mission is to advance open,
interoperable information and communication technologies in industrial automation. The basis of the membership community is its primary common interest in developing standards and promoting adoption of the Common
Industrial Protocol (CIP™), ODVA’s media independent network protocol, and the network adaptations of CIP –
EtherNet/IP™, DeviceNet™, CompoNet™ and ControlNet™. ODVA manages these technologies, and develops
and distributes the specifications for these four networks in a common structure to help ensure consistency and
accuracy. The following diagram illustrates the organization of the library of four networks.
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Organization of the CIP Networks Specifications
This common structure presents CIP in one volume with a separate volume for each network adaptation of CIP.
The specifications for the CIP Networks are typically three-volume sets, structured as shown below and as of
April 2015.
The EtherNet/IP Specification consists of:
Volume 1: Common Industrial Protocol (CIP)
Volume 2: EtherNet/IP Adaptation of CIP
Volume 7: Integration of Modbus Devices into
the CIP Architecture
The ControlNet Specification consists of:
Volume 1: Common Industrial Protocol (CIP)
Volume 4: ControlNet Adaptation of CIP
Volume 7: Integration of Modbus Devices into the
CIP Architecture
The DeviceNet Specification consists of:
Volume 1: Common Industrial Protocol (CIP)
Volume 3: DeviceNet Adaptation of CIP
Volume 7: Integration of Modbus Devices into the
CIP Architecture
The CIP Safety™ Specification is distributed
in a single volume:
Volume 5: CIP Safety
The CompoNet Specification consists of:
Volume 1: Common Industrial Protocol (CIP)
Volume 6: CompoNet Adaptation of CIP
Volume 7: Integration of Modbus Devices into the
CIP Architecture
Chapters 2 of this book provides an overview of the Common Industrial Protocol (CIP). Chapter 3 analyzes
the network adaptations of CIP by network, and Chapters 4 and 5 detail the benefits of CIP and the powerful
extensions to it, including extensions for synchronization, motion, and functional safety. In conclusion. Chapter 6
outlines the ODVA Conformance Test process, and Chapters 7 through 11 of this book contain reference material (literature references, abbreviations and terminology).
Specification Enhancement Process
The specifications for CIP Networks are continually being
enhanced to meet the increasing needs of users for
features and functionality. ODVA uses a Specification Enhancement Process in order to ensure open and stable
specifications for all CIP Networks. This process is ongoing throughout the year for each CIP Network Specification as shown in the figure below. New editions of each
ODVA specification are published on a periodic basis.
In recent years, the CIP Networks Library subscriptions
have been updated twice annually.
6
New Specification Edition
Published
Conformance Tests
Updated
Members Develop Specification
Enhancements in Special Interest
Groups (SIGs)
Technical Review Board Reviews
and Approves Specification
Enhancements
Member Review and
Comment Period
Specification Enhancements
Integrated in New Revisions of
Publications
The Common Industrial Protocol (CIP™)
and the Family of CIP Networks
1 Introduction
Traditionally, networks used in manufacturing enterprises were optimized for performance in specific applications,
most commonly for control, information and safety. While well suited to the functionality for which they were designed, these networks were not developed with a single, coherent enterprise architecture in mind. Since efficiency, reliability and, ultimately, profitability are generally dependent on having more than one of these capabilities,
manufacturers were forced to implement several different networks, none of which communicated innately with
the other. As a result, over the course of time, most manufacturing enterprise network environments have been
characterized by numerous specialized – and generally incompatible – networks existing in one space.
Today, however, corporate expectations for the manufacturing automation network landscape are dramatically different, thanks to the rapid and ubiquitous adoption of Internet technology. Companies of all sizes, all over the world,
are trying to find the best ways to connect the entire enterprise. No longer is control of the manufacturing processes
enough: the new manufacturing mandate is to enable users throughout the company to access manufacturing data
from any location, at any time, and to integrate this data seamlessly with business information systems.
Due to this adoption and expansion of the use of Internet technologies, a rapidly increasing number of users worldwide have looked to “open” systems as a way to connect their disparate enterprise processes. However, the devices, programs and processes used at the various layers of the seven-layer Open Systems Interconnection (OSI)
model have different options, capabilities and standards (or lack of). In general, integrating these networks requires
extra resources and programming and even then, gaps between the systems often cannot be fully and seamlessly
bridged. Consequently, without a way to seamlessly integrate a network, users compromise their investments and
rarely achieve all of the productivity and quality benefits promised by open network technology.
Common application layers are the key to advanced communication and true network integration. ODVA’s
four best-in-class networks — EtherNet/IP™, DeviceNet™, ControlNet™ and CompoNet™ — all are linked
by one of industrial automation’s most versatile protocols: the Common Industrial Protocol, known as CIP™.
CIP encompasses a comprehensive suite of messages and services for the collection of industrial automation
applications — control, safety, energy, synchronization & motion, information and network management. CIP
allows users to integrate these applications with enterprise-level Ethernet networks and the Internet. Supported
by hundreds of vendors around the world and truly media-independent, CIP provides users with a unified communication architecture throughout the industrial enterprise. CIP allows users to benefit today from the many
advantages of open networks and protects their existing automation investments, while providing an extensible
and upgradable communication architecture.
With media independence comes choice — the ability to choose the CIP Network best suited for an application.
As a single, media-independent platform that is shared by a variety of networking technologies, CIP provides
the interoperability and interchangeability that is essential to open networks and open systems. Four network
adaptations of CIP are available.
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EtherNet/IP™: CIP on Ethernet Technology
EtherNet/IP provides users with the network tools to deploy standard Ethernet technology (IEEE 802.3 combined with the TCP/IP Suite) for industrial automation applications while enabling Internet and enterprise connectivity resulting in data anytime and anywhere. EtherNet/IP offers various topology options including a conventional star with standard Ethernet infrastructure devices, or Device Level Ring (DLR) with EtherNet/IP devices so
enabled. QuickConnect™ functionality allows devices to be reconnected quickly while the network is running by
using an abbreviated start-up procedure.
DeviceNet™: CIP on CAN Technology
DeviceNet provides users with a cost-effective network to distribute and manage simple devices throughout
their architecture. DeviceNet uses a trunkline/dropline topology and has DC power available on the network cable to simplify installations by providing a single connection point for network communications and device power
up to 24 Vdc, 8 Amps. QuickConnect functionality allows devices to be reconnected quickly while the network
is running by using an abbreviated start-up procedure.
ControlNet™: CIP on CTDMA Technology
ControlNet provides users with the tools to achieve deterministic, high-speed transport of time-critical I/O and
peer-to-peer interlocks. ControlNet offers a choice of topology options including trunkline/dropline, star or tree.
Hardware options are also offered for applications requiring intrinsically safe hardware. Redundant network communication is also available.
CompoNet™: CIP on TDMA Technology
CompoNet enables users to maximize network throughput for applications needing to transmit small packets
of data quickly between controllers, sensors and actuators. Its simple network connector and cabling scheme
reduces overall system cost and time.
In addition to these network implementations, ODVA has published extensions to CIP for critical applications.
Functional Safety
Safety application coverage in CIP provides the ability to mix safety devices and standard devices on the same
network or wire for seamless integration and increased flexibility. CIP Safety™ provides fail-safe communication
between nodes such as safety I/O blocks, safety interlock switches, safety light curtains and safety PLCs in
safety applications up to Safety Integrity Level (SIL) 3 according to IEC 61508 standards. CIP Safety has also
been adopted by Sercos International. A more detailed description of the CIP Safety extension is given in Section 5.2.
Synchronization
Synchronization services in CIP provide the increased control coordination needed for control applications
where absolute time synchronization is vital to achieve real-time synchronization between distributed intelligent
devices and systems. CIP Sync™ is compliant with IEEE-1588™ standard, and allows synchronization accuracy between two devices of better than 100 nanoseconds. Real-time synchronization can be achieved over
conventional 100Mbps, Ethernet systems with a switch-based architecture. A more detailed description of the
CIP Sync extension is given in Section 5.1.
Distributed Motion Control
Motion application coverage in CIP eliminates the need for a purpose-built motion-optimized network by
8
allowing high performance motion control and other devices to be combined on a single EtherNet/IP network.
This approach results in a modular and streamlined approach to system design and lowers overall system and
training cost. CIP Motion™ achieves real-time deterministic behavior of multiple axes through a common sense
of time, allowing for 100 axes to be coordinated with a 1 millisecond network update to all axes. Clock synchronization between axes of better than 100 nanoseconds can be readily achieved, meeting the needs of the most
demanding motion control applications.
Energy Optimization
Energy application coverage in CIP provides a family of objects and services for the optimization of energy
usage (OEU™) and allows scalability of implementation within the device from basic energy awareness to more
advanced functions for control of energy, aggregation and reporting of energy information or dynamic demand-response. Further, the CIP family of energy objects and services will allow systems to monitor energy usage and manage energy for efficient energy consumption through dynamic control of energy state and analysis
of energy information. Protocol-neutral energy attributes allow for flexibility in the propagation of energy information via multiple protocols to facilitate an e-business model such as capturing energy requirements as a line item
on production bills of material or to implement demand-response mechanisms for dynamic energy transactions.
The universal principles of CIP easily lend themselves to possible future implementations on new physical/data
link layers. The overall relationship between the four implementations of CIP is shown in Figure 1.
Figure 1 The Common
Industrial Protocol and
its network adaptations
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2 Description of the CIP Networks Library
CIP is a very versatile protocol designed with the automation industry in mind. However, due to its open nature, it
can be and has been applied to many more areas. The CIP Networks Library contains several volumes:
- Volume 1 deals with the common aspects of CIP that apply to all of the network adaptations. This volume
contains the common object library and the device profile library, along with a general description of the
communications model, device configuration and CIP data management. This volume also defines an
auxiliary power distribution system that is common to all adaptations of CIP.
- Volume 2 is the EtherNet/IP Adaptation of CIP, which describes how CIP is adapted to the Ethernet TCP/
IP and UDP/IP transportation layers. It also contains any extensions to the material in Volume 1 that are
necessary for EtherNet/IP, such as the optional industrial physical layer and connectors.
- Volume 3 is the DeviceNet Adaptation of CIP, which describes how CIP is adapted to the CAN data link
layer. It also contains any extensions to the material in Volume 1 that are necessary for DeviceNet.
- Volume 4 is the ControlNet Adaptation of CIP, which describes how CIP is adapted to the ControlNet
data link layer. It contains a complete description of the ControlNet data link layer and any extensions to
the material in Volume 1 that are necessary for ControlNet.
- Volume 5 is CIP Safety. It contains the information necessary to implement the CIP Safety protocol on
CIP Networks.
- Volume 6 is the CompoNet Adaptation of CIP, which describes how CIP is adapted to the CompoNet
data link layer. It contains a complete description of the CompoNet data link layer and any extensions to
the material in Volume 1 that are necessary for CompoNet.
- Volume 7 is the Integration of Modbus Devices into the CIP Architecture. This volume describes a standard for the integration of Modbus devices into the CIP world.
For brevity, this document will use the volume numbers above when referencing the different books in the CIP
Networks Library.
Specifications for the CIP Networks referenced above, and other documents discussing CIP, are available from
ODVA at www.odva.org. It is beyond the scope of this book to fully describe each and every detail of CIP, but
key features of the protocol and the auxiliary power distribution system will be discussed, including:
10
- Object modeling;
- Services;
- Messaging protocol;
- Communication objects;
- Object library;
- Device profiles;
- Configuration and electronic data sheets;
- Bridging and routing;
- Data management;
- Auxiliary power distribution system.
A few terms used throughout this section are described here to make sure they are well understood, further
terms are described in section 11:
- Client:
Within a client/server model, the client is the device that sends a request to a server. The client expects a response from the server.
- Server:
Within a client/server model, the server is the device that receives a request from a client. The server is expected
to give a response to the client.
- Producer:
Within the producer/consumer model, the producing device places a message on the network for consumption
by one or several consumers. Generally, the produced message is not directed to a specific consumer.
- Consumer:
Within the producer/consumer model, the consumer is one of potentially several consuming devices that picks
up a message placed on the network by a producing device.
- Producer/Consumer Model:
The producer/consumer model is inherently multicast. Nodes on the network determine if they should consume
the data in a message based on the connection ID in the packet. CIP uses the producer/consumer model, as
opposed to the traditional source/destination message addressing scheme (see Figure 2).
Source/Destination
src
dst
data
crc
data
crc
Producer/Consumer
identifier
Figure 2 Source/
Destination vs. Producer/
Consumer Model
- Explicit Message:
Explicit messages contain addressing and service information that directs the receiving device to perform a
certain service (action) on a specific part (e.g., an attribute of a given object) of a device.
- Implicit (I/O) Message:
Implicit messages do not carry address and/or service information; any consuming nodes already know what to
do with the data based on the connection ID that was assigned when the connection was established. Implicit
messages are so named because the meaning of the data is “implied” by the connection ID. In most cases they
are used to transport I/O data.
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Let’s have a look at the individual elements of CIP:
2.1. Object Modeling
CIP uses abstract object modeling to describe:
- The suite of available communication services;
- The externally visible behavior of a CIP node;
- A common means by which information within CIP products is accessed and exchanged.
Every CIP node is modeled as a collection of objects. An object provides an abstract representation of a particular component within a product. Anything not described in object form is not visible through CIP. CIP objects are
structured into classes, instances and attributes.
A class is a set of objects that all represent the same kind of system component. An object instance is the actual representation of a particular object within a class. Each instance of a class has the same attributes, but also
has its own particular set of attribute values. As Figure 3 illustrates, multiple object instances within a particular
class can reside within a CIP node.
CIP Node
A Class of
Objects
Object Instances
Figure 3 A Class of Objects
In addition to the instance attributes, an object class may also have class attributes. These are attributes that
describe properties of the whole object class, e.g., how many instances of this particular object exist. Furthermore, both object instances and the class itself exhibit a certain behavior and allow certain services to be
applied to the attributes, instances or to the whole class. All publicly defined objects that are implemented in
a device must follow at least the mandatory requirements defined in the various CIP Networks specifications.
Vendor-specific objects may also be defined with a set of instances, attributes and services according to the requirements of the vendor. However, they need to follow certain rules that are also set forth in the specifications.
The objects and their components are addressed by a uniform addressing scheme consisting of:
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- Node Address:
An integer identification value assigned to each node on a CIP Network. On DeviceNet, ControlNet and CompoNet, this is also called a MAC ID (Media Access Control Identifier) and is nothing more than the node number
of the device. On EtherNet/IP, the node address is the IP address.
- Class Identifier (Class ID):
An integer identification value assigned to each object class accessible from the network.
- Instance Identifier (Instance ID):
An integer identification value assigned to an object instance that identifies it among all instances of the same class.
- Attribute Identifier (Attribute ID):
An integer identification value assigned to a class or instance attribute.
- Service Code:
An integer identification value which denotes an action request that can be directed at a particular object instance or object attribute (see Section 2.2).
Object class identifiers are divided into two types of objects: publicly defined objects (ranging from 0x0000
– 0x0063 and 0x00F0 – 0x02FF) and vendor-specific objects (ranging from 0x0064 – 0x00C7 and 0x0300 –
0x04FF). All other class identifiers are reserved for future use. In some cases, e.g., within the assembly object
class, instance identifiers are divided into two types of instances: publicly defined (ranging from 0x0001 –
0x0063 and 0x00C8 – 0x02FF) and vendor-specific (ranging from 0x0064 – 0x00C7 and 0x0300 – 0x04FF). All
other instance identifiers are reserved for future use. Attribute identifiers are divided into two types of attributes:
publicly defined (ranging from 0x0000 – 0x0063, 0x0100 – 0x02FF and 0x0500 – 0x08FF) and vendor-specific (ranging from 0x0064 – 0x00C7, 0x0300 – 0x04FF and 0x0900 – 0x0CFF). All other attribute identifiers are
reserved for future use. While vendor-specific objects can be created with a great deal of flexibility, these objects
must adhere to certain rules specified for CIP, e.g., they can use whatever instance and attribute IDs the developer wishes, but their class attributes must follow guidelines detailed in Volume 1, Chapter 4 of the CIP Networks Library.
Addressing objects and their attributes can be performed with 8 bit, 16 bit or 32 bit addresses. In most cases,
class and instance addresses are 8 or 16 bit wide, and attribute addresses are only 8 bit wide. 32 bit addresses
are currently reserved for instance addressing only.
Figure 4 shows an example of this object addressing scheme.
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Node ID #1
Node ID #2
Node ID #4: Object Class
#5:
Instance #2:Attribute #2
CIP Link
Object Class #5
Object Class #5
Instance
#1
Object Class #7
Attribute #2
Instance
#1
Instance #2
Node ID #3
Instance
#1
Node ID #4
Figure 4 Object Addressing Example
2.2. Services
Service codes are used to define the action that is requested to take place when an object or parts of an object
are addressed through explicit messages using the addressing scheme described in Section 2.1. Apart from
simple read and write functions, a set of CIP services has been defined. These CIP services are common in
nature, meaning they may be used in all CIP Networks and they are useful for a variety of objects. Furthermore,
there are object-specific service codes that may have a different meaning for the same code, depending on the
class of object. Finally, defining vendor-specific services according to the requirements of the product developer
is possible. While this provides a lot of flexibility, the disadvantage of vendor-specific services is that they may
not be understood universally. Minimally, vendors provide a description of the public information that their customers will need access to in their literature.
2.3. Messaging Protocol
CIP is a connection-based protocol. A CIP connection provides a path between multiple application objects.
When a connection is established, the transmissions associated with that connection are assigned a connection
ID, or CID (see Figure 5). If the connection involves a bi-directional exchange, then two CID values are assigned.
Application
Object X
Obj.
Connection
ID = 1
Obj.
Obj.
Connection
Object
Device #1
Figure
5 Connections and Connection IDs
Data =
A message
Obj.
Connection
Object
Obj.
Application
Object X
Device #2
Obj.
The definition and format of the CID is network dependent. For example, the CID for CIP connections over DeviceNet is based on the CAN identifier field.
14
Since most messaging on a CIP Network is done through connections, a process has been defined to establish
such connections between devices that are not yet connected. This is done through the unconnected message
manager (UCMM) function, which is responsible for processing unconnected explicit requests and responses.
Establishing a CIP connection is generally accomplished by sending a UCMM Forward_Open service request message. The Forward_Open is required for all devices that support connections on ControlNet and
EtherNet/IP. CompoNet uses a different method described in Section 3.4.12. DeviceNet only uses the simplified
methods described in Sections 3.1.16 and 3.1.17.
A Forward_Open request contains all information required to create a connection between the originator and
the target device. The resulting data exchange may be unidirectional or bidirectional. In particular, the Forward_
Open request contains information on the following:
- Time-out information for this connection;
- Network CID for the connection from the originator to the target;
- Network CID for the connection from the target to the originator;
- Information about the identity of the originator (vendor ID and serial number);
- Maximum data sizes of the messages on this connection;
- Whether it will be unicast or multicast;
- Trigger mechanisms, e.g., cyclic, change of state (COS);
- Electronic key so the target node can verify that it is the proper type of node (optional);
- Connection path for the application object data in the node that will be produced and consumed;
- Data Segment containing configuration information for the node (optional);
- Routing information if the connection is to span more than one network (optional).
Some networks, like ControlNet, EtherNet/IP and CompoNet, also make use of unconnected explicit messaging. DeviceNet uses unconnected explicit messaging only to establish connections.
All connections on a CIP Network can be categorized as I/O connections or explicit messaging connections.
- I/O connections provide dedicated, special-purpose communication paths between a producing application and one or more consuming applications. Application-specific I/O data move through these ports, a
process that is often referred to as implicit messaging. These messages can be unicast or multicast. These
connections are also called “implicit” connections because the meaning of the data is implied by the connection ID.
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- Explicit messaging connections provide generic, multi-purpose communication paths between two devices. These connections often are referred to simply as messaging connections. Explicit messages provide
typical request/response-oriented network communications. These messages are point-to-point. They
are called “explicit” messages because the data in the request explicitly states what service and object is
being requested.
The actual data transmitted in CIP I/O messages are the I/O data in an appropriate format; e.g., the data may
be prefixed by a sequence count value. This sequence count value can be used to distinguish old data from
new, e.g., if a message has been re-sent as a heartbeat in a COS connection. The two states “Run” or “Idle”
can be indicated with an I/O message either by prefixing a real-time header, as is primarily used for ControlNet
and EtherNet/IP, or by sending I/O data (Run) or no I/O data (Idle), a process primarily used for DeviceNet. CompoNet uses a bit within the OUT frame or the TRG frame to indicate the states “Run” and “Idle”. “Run” is the
normal operational state of a device with the outputs under the control of the controlling application, while the
reaction to receiving an “Idle” event is vendor-specific and application-specific. Typically, this means bringing all
outputs of the device to a predefined, safe “Idle” state (which usually means “off”), i.e., de-energized.
Explicit messaging requests contain a service code with path information to the desired object within the target
device followed by data (if any). The associated responses repeat the service code followed by status fields
followed by data (if any). DeviceNet and CompoNet use a “condensed” format for explicit messages in most
cases, while ControlNet and EtherNet/IP only use the “full” format.
2.4. Communication Objects
CIP communication objects manage and provide the run-time exchange of messages. Communication objects
are unique in that they are the focal points for all CIP communication. It therefore makes sense to look at them in
more detail.
Each communication object contains a link producer part, a link consumer part or both. I/O connections may be
either producing or consuming or producing and consuming, while explicit messaging connections are always
producing and consuming.
Figure 6 and Figure 7 show the typical connection arrangement for CIP I/O messaging and CIP explicit messaging. The attribute values in the connection objects define a set of attributes that describe vital parameters of this
connection. Note that explicit messages are always directed to the message router object.
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I/O Connection
I/O
Producing
Application
Object
Producing
I/O
Connection
Consuming
I/O
Connection
Device #1
I/O
Consuming
Application
Object
Device #2
I/O Message
Consuming
I/O
Connection
I/O
Consuming
Application
Object
Device #3
Figure 6 CIP Multicast I/O Connection
The attribute values of a connection object specify whether it is an I/O connection or an explicit messaging connection, the maximum size of the data to be exchanged across this connection and the source and destination
of the data. Further attributes define the state and behavior of the connection. Particularly important behaviors
include how messages are triggered (from the application, through change of state (COS), i.e., when data has
changed, through cyclic events or by network events) and the timing of the connections (time-out associated
with this connection and predefined action if a time-out occurs). CIP allows multiple connections to coexist in a
device, although simple devices – e.g., simple DeviceNet or CompoNet slaves – typically will only have one or
two live connections at any time (only one connection on CompoNet).
Explicit Messaging Connection
Device #1
Request
Application
Object
Explicit
Messaging
Connection
Explicit
Messages
Explicit
Messaging
Connection
Response
Device #2
Request
Message
Router
Response
Obj.
Obj.
Figure 7 CIP Explicit Messaging Connection
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2.5. Object Library
The CIP family of protocols contains a large collection of commonly defined objects. The overall set of object
classes can be subdivided into three types:
- General use;
- Application specific;
- Network specific.
Objects defined in Volume 1 of the CIP Networks Library are available for use on all network adaptations of CIP.
Some of these objects may require specific changes or limitations when implemented on some of the network
adaptations. These exceptions are noted in the network-specific volume. Therefore, to see a complete picture of
a specific network implementation of an object, refer to Chapter 5 in both the Protocol Adaptation Volume and
Volume 1.
The following are general use objects (object IDs in brackets):
- Assembly (0x04)
- Acknowledge Handler (0x2B) - Connection (0x05) - Connection Configuration (0xF3) - Connection Manager (0x06) - File (0x37) - Identity (0x01) - Message Router (0x02)
- Originator Connection List (0x45)
- Parameter (0x0F)
- Parameter Group (0x10)
- Port (0xF4)
- Register (0x07)
- Selection (0x2E)
The following group of objects is application-specific (object IDs in brackets):
- AC/DC Drive (0x2A)
- Analog Group (0x22)
- Analog Input Group (0x20)
- Analog Input Point (0x0A)
- Analog Output Group (0x21)
- Analog Output Point (0x0B)
- Base Energy (0x4E)
- Block Sequencer (0x26)
- Command Block (0x27)
- Control Supervisor (0x29)
- Discrete Group (0x1F)
- Discrete Input Group (0x1D)
- Discrete Output Group (0x1E)
- Discrete Input Point (0x08)
- Discrete Output Point (0x09)
- Electrical Energy (0x4F)
- Event Log (0x41)
- Group (0x12)
18
- Motion Device Axis (0x42)
- Motor Data (0x28)
- Non-Electrical Energy (0x50)
- Overload (0x2C)
- Position Controller (0x25)
- Position Controller Supervisor (0x24)
- Position Sensor (0x23)
- Power Curtailment Object (0x5C)
- Power Management Object (0x53)
- Presence Sensing (0x0E)
- S-Analog Actuator (0x32)
- S-Analog Sensor (0x31)
- S-Device Supervisor (0x30)
- S-Gas Calibration (0x34)
- S-Partial Pressure (0x38)
- S-Sensor Calibration (0x40)
- S-Single Stage Controller (0x33)
- Safety Analog Input Group (0x4A)
- Safety Analog Input Point (0x49)
- Safety Dual Channel Feedback Object (0x59)
- Safety Feedback Object (0x5A)
- Safety Discrete Input Group (0x3E)
- Safety Discrete Input Point (0x3D)
- Safety Discrete Output Group (0x3C)
- Safety Discrete Output Point (0x3B)
- Safety Dual Channel Analog Input (0x4B)
- Safety Dual Channel Output (0x3F)
- Safety Limit Functions Object (0x5B
- Safety Stop Functions Object (0x5A)
- Safety Supervisor (0x39)
- Safety Validator (0x3A)
- Softstart (0x2D)
- Target Connection List (0x4D)
- Time Sync (0x43)
- Trip Point (0x35)
The last group of objects is network-specific (object IDs in brackets):
- Base Switch (0x51)
- CompoNet Link (0xF7)
- CompoNet Repeater (0xF8)
- ControlNet (0xF0)
- ControlNet Keeper (0xF1)
- ControlNet Scheduling (0xF2)
- Device Level Ring (DLR) (0x47)
- DeviceNet (0x03)
- Ethernet Link (0xF6)
- Modbus (0x44)
- Modbus Serial Link (0x46)
- Parallel Redundancy Protocol (0x56)
- Power Management (0x53)
- PRP Nodes Table (0x57)
- SERCOS III Link (0x4C)
- SNMP (0x52)
- QoS (0x48)
- RSTP Bridge (0x54)
- RSTP Port (0x55)
- TCP/IP Interface (0xF5)
The general use objects can be found in many different devices, while the application-specific objects are typically
found only in devices hosting such applications. New objects are added on an ongoing basis by the various ODVA
Special Interest Groups (SIGs). As mentioned earlier, there are many vendor-specific objects defined by developers
to satisfy needs that may not be met by the existing open objects contained in the published specifications.
Although this looks like a large number of object types, typical devices implement only a subset of these objects.
Figure 8 shows the object model of such a typical device.
Parameter
Application
Object(s )
Identity
Required
Objects
Message
Router
Assembly
Network
Specific*
Optional
Objects
I/O
Explicit
Msg
Connection(s)
*
D e v ic e N e t O b je c t
C o n t r o lN e t O b je c t
T C P / IP In t e r f a c e O b je c t
E t h e r n e t L in k O b je c t
C o m p o N e t L in k O b je c t
C o m p o N e t R e p e a t e r O b je c t
CIP Network
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Figure 8 Typical Device Object Model
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The objects required in a typical device are:
- Either a connection object or a connection manager object;
- An identity object;
- One or several network-specific link objects (depends on network);
- A Message router object (at least its function).
Further objects are added according to the functionality of the device. This enables scalability for each
implementation so that simple devices, such as proximity sensors, are not burdened with unnecessary
overhead. Developers typically use publicly defined objects (see above list), but can also create their own
objects in the vendor-specific areas, e.g., Class ID 100 – 199. However, they are strongly encouraged to
work with the Special Interest Groups (SIGs) of ODVA to create common definitions for additional objects
instead of inventing private ones.
Out of the general use objects, several are described in more detail below.
2.5.1. Identity Object (Class ID: 0x01)
The identity object is described in greater detail because, being a relatively simple object, it can serve to illustrate
the general principles of CIP objects. In addition, every device must have an identity object.
The vast majority of devices support only one instance of the identity object. Thus, typically there are no requirements for any class attributes that describe additional class details, e.g., how many instances exist in the
device. Only instance attributes are required in most cases. These are as follows:
Mandatory Attributes:
- Vendor ID
- Device Type
- Product Code
- Revision
- Status
- Serial Number
- Product Name
Optional or Conditional Attributes:
- State
- Configuration Consistency Value
- Heartbeat Interval
- Active Language
- Supported Language List
- International Product Name
20
- Semaphore
- Assigned_Name
- Assigned_Description
- Geographic_Location
- Modbus Identity Info
- Protection Mode
Let us have a look at these attributes in more detail:
- The Vendor ID attribute identifies the vendor that markets the device. This UINT (Unsigned Integer) value
(for Data Type descriptions see Section 2.9) is assigned to a specific vendor by ODVA. If a vendor intends
to build products for more than one CIP Network, the same Vendor ID will generally be assigned for all
networks, but they must be registered independently with ODVA prior to use.
- The Device Type, again a UINT value, specifies which profile has been used for this device. It must be
one of the vendor IDs listed in Volume 1, Chapter 6 of the CIP Networks Library or a vendor-specific type
(see Section 2.6).
- The Product Code is a UINT number defined by the vendor of the device. This code is used to distinguish multiple products of the same vendor ID from the same vendor. There is generally a loose association between a Catalog Number and aproduct code, but not necessarily.
- The Revision is split into two USINT (Unsigned Short Integer) values specifying a major revision and a minor revision. Any device change(s) that result in modifying the behavior of the device on the network must
be reflected in a change to the minor revision at minimum. Any changes in the device’s logical interface,
e.g., additional attributes, modified/additional I/O assemblies etc., require a change to the major revision
and this change must be reflected in a revised Electronic Data Sheet (EDS) (see Section 2.7). vendor ID,
vendor ID,product code and major revision provide an unambiguous identification of an EDS for this device.
- The Status attribute provides information on the status of the device, e.g., whether it is owned (controlled
by another device) or configured (to something different than the out-of-the-box default), and whether any
major or minor faults have occurred.
- The Serial Number is used to uniquely identify individual devices in conjunction with the vendor ID, i.e.,
no two CIP devices from one vendor may carry the same serial number. The 32 bits of the serial number
allow ample space for a subdivision into number ranges that can be used by different divisions of larger
companies.
- The Product Name attribute allows the vendor to give a meaningful ASCII name string (up to 32 characters) to the device.
- The State attribute describes the state of a device in a single UINT value. It is less detailed than the Status attribute.
- The Configuration Consistency Value allows a distinction between a device that has been configured
and one that has not, or between different configurations in a single device. This helps avoid unnecessary
configuration downloads.
- The Heartbeat Interval enables the Device Heartbeat Message. This is an unconnected change-of-state
message that has a settable background cyclic interval between one and 255 seconds. Currently, this
option is only defined for use on DeviceNet.
- The Supported Language List and International Product Name attributes can be used to describe
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the product in multiple languages and the Active Language attribute then specifies which of the supported languages is in use.
- The Semaphore attribute provides a semaphore for client access synchronization to the entire device.
- The Assigned_Name, Assigned_Description and Geographical_Location attributes can be used to
individualize products by the user of the product.
- The Modbus Identity Info attribute can provide identity information in Modbus format to the extent the
device supports it.
- The Protection Mode attribute is an indication of the present mode of protection for the device.
The services supported by the class and instance attributes are either Get_Attribute_Single (typically implemented in DeviceNet and CompoNet devices) or Get_Attributes_All (typically implemented in ControlNet and
EtherNet/IP devices). The only attributes that can be set are: the Heartbeat Interval, the Active Language, the
Semaphore, the Assigned_Name, Assigned_Description and Geographical_Location attributes. The only other
service that typically is supported by the identity object is the Reset service. This Reset service comes with three
different options that can let the device restart in three different ways.
The behavior of the identity object is described through a state transition diagram.
2.5.2. Parameter Object (Class ID: 0x0F)
This object is described in some detail since it is referred to in Section 2.7, Configuration and Electronic Data
Sheets. When used, the parameter object comes in two types: a complete object and an abbreviated version
(parameter object Stub). This abbreviated version is used primarily by DeviceNet and CompoNet devices that
have only small amounts of memory available. The parameter object stub, in conjunction with the Electronic
Data Sheet, has roughly the same functionality as the full object (see Section 2.7).
The purpose of the parameter object is to provide a general means of allowing access to many attributes of the
various objects in the device without requiring a tool (such as a handheld terminal) to have any knowledge about
specific objects in the device.
The class attributes of the parameter object contain information about how many instances exist in this
device and a Class Descriptor, indicating, among other properties, whether a full or a stub version is
supported. In addition, class attributes tell whether a configuration assembly is used and what language is
used in the parameter object.
22
The first six instance attributes are required for the object stub. These are:
Parameter Value
The actual parameter
Link Path Size
These two attributes describe the application object/ instance/
attribute from which the parameter value was retrieved.
Descriptor
This describes parameter properties, e.g., read-only, monitor
parameter, etc.
Data Type
This describes the data type (e.g., size, range) using a standard
mechanism defined by CIP
Data Size
Data size in bytes
These six attributes allow access, interpretation and modification of the parameter value, but the remaining attributes make it much easier to understand the meaning of the parameter:
- The next three attributes provide ASCII strings with the name of the parameter, its engineering units and
an associated help text;
- Another three attributes contain the minimum, maximum and default values of the parameter;
- Four more attributes can link the scaling of the parameter value so that the parameter can be displayed in
a more meaningful way, e.g., raw value in multiples of 10 mA, scaled value displayed in amps;
- Another four attributes can link the scaling values to other parameters. This feature allows variable scaling
of parameters, e.g., percentage scaling to a full range value that is set by another parameter;
- Attribute #21 defines how many decimal places are to be displayed if the parameter value is scaled;
- Finally, the last three attributes are an international language version of the parameter name, its engineering units and the associated help text.
2.5.3. Assembly Object (Class ID: 0x04)
Assembly objects provide the option of mapping data from attributes of different instances of various classes
into one single attribute (#3) of an assembly object. This mapping is generally used for I/O messages to maximize the efficiency of the control data exchange on the network. Assembly mapping makes the I/O data available in one block; thus, there are fewer connection object instances and fewer transmissions on the network.
The process data are normally combined from different application objects. An assembly object also can be
used to configure a device with a single data block, alleviating the need to set individual parameters.
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CIP makes a distinction between input and output assemblies. “input” and “output” in this context are viewed
from the perspective of the controlling element (e.g., a PLC/PAC). An input assembly in a device collects data
from the input application (e.g., field wiring terminal, proximity sensor, etc.) and produces it on the network,
where it is consumed by the controlling device and/or operator interface. An output assembly in a device
consumes data that the controlling element sends to the network and writes that data to the output application (e.g., field wiring terminals, motor speed control, etc.). This data mapping is very flexible; even mapping of
individual bits is permitted. Assemblies also can be used to transmit a complete set of configurable parameters
instead of accessing them individually. These assemblies are called configuration assemblies.
Figure 9 shows an example of assembly mapping. The data from application objects 100 and 101 are mapped in
two instances of the assembly object. Instance 1 is set up as an input assembly for the input data, and instance 2
as an output assembly for output data. The data block is always accessed via attribute 3 of the relevant assembly
instance. Attributes 1 and 2 contain mapping information.
I/O assembly mapping is specified for many Device Profiles in Chapter 6 of Volume 1. Device developers then
can choose which assemblies they support in their products. If none of the publicly defined assemblies fully represents the functionality of the product, a device vendor may implement additional vendor-specific assemblies
(Instance IDs 100 – 199).
CIP defines static and dynamic assembly objects. Whereas mapping for static assemblies is permanently programmed
in the device (ROM), dynamic assemblies can be modified and extended through dynamic mapping (RAM). Most
simple CIP devices support only static assembly objects. Dynamic assembly objects may be used in more complex
devices, but they are not very common.
24
Application Object #100
Application Object #101
Instance #1
Instance #2
Attribute #100
Attribute #100
Attribute #101
Attribute #101
Attribute #102
Attribute #102
Attribute #103
Attribute #103
Instance #1
Instance #2
Attribute #100
Attribute #100
Assembly Object #4
Instance #1
Attribute #3
(data structure)
Input Assembly
Instance #2
Attribute #3
(data structure)
Output Assembly
Connection Object
Producer
Consumer
Output Mapping
Class #100:Instance #1:Attribute #100
Input Mapping
Class #100:Instance #1:Attribute #102
Class #100:Instance #1Attribute #101
Class #100:Instance #2:Attribute #102
Class #100:Instance #1Attribute #103
Class #101:Instance #1:Attribute #100
Class #100:Instance #2Attribute #103
Class #101:Instance #2:Attribute #100
CIP Network
!Figure 9 Example of an Assembly Mapping in a Typical I/O Device
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2.6. Device Profiles
It would be possible to design products using only the definitions of communication networks and objects, but this
could easily result in similar products having quite different data structures and behavior. To overcome this situation
and to make the application of CIP devices much easier, devices of similar functionality have been grouped into vendor IDs with associated profiles. Such a CIP profile contains the full description of the object structure and behavior.
The following vendor IDs and associated profiles are defined in Volume 1 (profile numbers in parentheses):
- AC Drives (0x02)
- CIP Modbus Device (0x28)
- CIP Modbus Translator (0x29)
- CIP Motion Drive (0x25)
- CIP Motion Encoder (0x2F)
- CIP Motion I/O (0x31)
- CIP Motion Safety Drive Device (0x2D)
- Communications Adapter (0x0C)
- CompoNet Repeater (0x26)
- Contactor (0x15)
- ControlNet Physical Layer Component (0x32)
- DC Drives (0x13)
- DC Power Generator (0x1F)
- Embedded Component (0xC8)
- Encoder (0x22)
- Enhanced Mass Flow Controller (0x27)
- Fluid Flow Controller (0x24)
- General Purpose Discrete I/O (0x07)
- Generic Device, keyable (0x2B)
- Human Machine Interface (HMI) (0x18)
- Inductive Proximity Switch (0x05)
- Limit Switch (0x04)
- Managed Ethernet Switch (0x2C)
- Mass Flow Controller (0x1A)
- Mass Flow Controller, Enhanced (0x27)
- Motor Overload Device (0x03)
- Motor Starter (0x16)
- Photoelectric Sensor (0x06)
- Pneumatic Valve(s) (0x1B)
- Position Controller (0x10)
- Process Control Valve (0x1D)
- Programmable Logic Controller (0x0E)
- Residual Gas Analyzer (0x1E)
- Resolver (0x09)
- RF Power Generator (0x20)
- Safety Analog I/O Device (0x2A)
- Safety Drive Device (0x2E)
- Safety Discrete I/O Device (0x23)
- Softstart Starter (0x17)
- Turbomolecular Vacuum Pump (0x21)
- Vacuum/Pressure Gauge (0x1C)
Device developers must use a vendor ID to uniquely identify their product. Any device that does not fall
into the scope of one of the specialized Device Profiles must use the Generic Device profile (0x2B) or a
vendor-specific profile. What profile is used and which parts of it are implemented must be described in
the user’s device documentation.
Every profile consists of a set of objects – some required, some optional – and a behavior associated with that
particular type of device. Most profiles also define one or more I/O data formats (assemblies) that define the
makeup of the I/O data. In addition to the commonly-defined objects and I/O data assemblies, vendors can
add objects and assemblies of their own if their devices provide additional functionality. Furthermore, vendors
can create profiles within the vendor-specific profile range. They are then free to define whatever behavior and
objects are required for their device as long as they adhere to the general rules for profiles outlined in Chapter 6
of Volume 1 of the CIP Networks Library. Whenever additional functionality is needed by multiple vendors, ODVA
encourages coordinating these new features through Special Interest Groups (SIGs), which can then create new
profiles or additions to existing profiles for everybody’s use and for the benefit of the device users.
26
All open (ODVA defined) profiles carry numbers in the 0x00 through 0x63 or 0x0100 through 0x02FF ranges,
while vendor-specific profiles carry numbers in the 0x64 through 0xC7 or 0x0300 through 0x02FF ranges. All
other profile numbers are reserved by CIP.
2.7. Configuration and Electronic Data Sheets
CIP provides several options for configuring devices:
- A printed data sheet;
- Parameter objects and parameter object stubs;
- An Electronic Data Sheet (EDS);
- A combination of an EDS and parameter object stubs;
- A configuration assembly combined with any of the above methods.
When using configuration information collected on a printed data sheet, configuration tools can only provide prompts
for service, class, instance and attribute data and relay this information to a device. While this procedure can do the
job, it is the least desirable solution since it does not determine the context, content or format of the data.
Parameter objects, on the other hand, provide a full description of all configurable data for a device. Since
the device itself provides all the necessary information, a configuration tool can gain access to all parameters
and maintain a user-friendly interface. However, this method imposes a burden on a device with full parameter
information that may be excessive for a small device with limited internal resources. Therefore, an abbreviated
version of the parameter object, called a parameter object stub, may be used (see Section 2.5.2). This option
still allows access to the parameter data, but it does not describe any meaning to the data. parameter object
stubs in conjunction with a printed data sheet are usable, but certainly not optimal. On the other hand, an EDS
supplies all of the information that a full parameter object contains, in addition to I/O connection information, so
the EDS provides the full functionality and ease of use of the parameter object without imposing an excessive
burden on the individual device. In addition, an EDS provides a means for tools to perform offline configuration
and to download configuration data to the device at a later time.
An EDS is a simple ASCII text file that can be generated on any ASCII editor. Since the CIP Specification provides a set of rules for the overall design and syntax of an EDS, specialized EDS editing tools, such as ODVA’s
EZ-EDS, can simplify the creation of EDS files. The main purpose of the EDS is to give information on several
aspects of the device’s capabilities, the most important ones being the I/O connections it supports and what
parameters for display or configuration exist within the device. It is highly recommended that an EDS describe all
supported I/O connections, as this makes the application of a device in a control system much easier. When it
comes to parameters, EDS files should contain the attributes of application objects so that software can provide
user access for monitoring and/or configuration purposes.
Let’s look at some details of the EDS. First, an EDS is structured into sections, each of which starts with a section name in square brackets [ ]. The first two sections are mandatory for all EDS files.
- [File]: Describes the contents and revision of the file;
- [Device]: Is equivalent to the identity object information and is used to match an EDS to a device;
- [Device Classification]: Describes what network the device can be connected to. This section is optional
for DeviceNet, required for ControlNet, EtherNet/IP and CompoNet;
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- [ParamClass]: Describes configuration details in addition to class-level attributes of the parameter object;
- [Params]: Identifies all configuration parameters in the device, follows the parameter object definition. Further details below;
- [Groups]: Identifies all parameter groups in the device and lists group name and parameter numbers;
- [Assembly]: Describes the structure of data items;
- [Connection Manager]: Describes connections supported by the device. Typically used in ControlNet and
EtherNet/IP;
- [Connection ManagerN]: Same as the [Connection Manager] section, but only for connection entries that
do not apply to all CIP ports of the device;
- [Port]: Describes the various network ports a device may have;
- [Capacity]: Specifies the communication capacity of EtherNet/IP and ControlNet devices;
- [Connection Configuration]: This section defines the characteristics of the connection configuration object
implemented in this device, if a connection configuration object implementation exists. It is used for EDSbased I/O Scanner configuration;
- [Event Enumeration]: The Event Enumeration section associates specific event or status codes within a
device with an international string;
- [Symbolic Translation]: This section is used to publicize the translation between a Symbolic Segment or an
ANSI Extended Symbol Segment encoded EPATH specification to the equivalent ParamN or AssemN entry
keywords;
- [Internationalization]: This section allows the representation of all strings within an EDS in multiple languages;
- [Modular]: Describes modular structures inside a device;
- [IO_Info]: Describes I/O connection methods & I/O sizes. Allowed for DeviceNet only;
- [Variant_IO_Info]: Describes multiple IO_Info data sets. Allowed for DeviceNet only;
- [EnumPar]: Enumeration list of parameter choices to present to the user. This is an old enumeration method specified for DeviceNet only;
- [ControlNet Physical Layer]: Describes details of the ControlNet physical layer. Allowed for ControlNet only;
- [CompoNet_Device]: Describes the type of CompoNet device. Allowed for CompoNet only;
- [CompoNet_IO]: Describes the I/O connection details of CompoNet slaves. Allowed for CompoNet only;
28
- [Modbus Mapper]: Used to provide a description of individual Modbus items that correspond to a specific
CIP object attribute.
- Object class sections: These sections – one for every object class – can be used to describe all object
details, such as instances, attributes and supported services.
These sections allow a very detailed device description, although only a few of these details are described here.
Further reading is available in endnotes [41], [42].
A tool with a collection of EDS files will first use the [Device] section to try to match an EDS with each device it
finds on a network. Once this is done and a particular combination of device and EDS is chosen, the tool can then
display device properties and parameters and allow their modification if the user so chooses. A tool may also display what I/O connections a device allows and which of these are already in use. EDS-based tools are mainly used
for slave or I/O Adapter devices, as I/O Scanner devices typically are too complex to be configured through EDS
constructs alone. For those devices, the EDS is used primarily to identify the device and then guide the tool to call
a matching configuration applet.
A particular strength of the EDS approach lies in the methodology of parameter configuration. A configuration
tool typically takes all of the information that can be supplied by the parameter objects and an EDS and displays
it in a user-friendly manner. In many cases, this enables the user to configure a device without needing a detailed manual, as the tool presentation of the parameter information and the help text enables decision making
for a complete device configuration. This assumes the developer of the product and the EDS file has supplied all
required information and any optional information with completeness and accuracy.
A complete description of what can be done with EDS files goes well beyond the scope of this book. Available
materials on this topic provide greater detail [41], [42].
2.8. CIP Routing
CIP defines mechanisms that allow the transmission of messages across multiple networks, provided that the
intermediate devices (CIP routers) between the various networks are equipped with the objects and services
used in CIP routing. If this is the case, the message will be forwarded from CIP router to CIP router until it has
reached its destination node. Here is how it works:
For unconnected explicit messaging, the actual explicit message to be executed on the target device is
“wrapped up” inside of another explicit message service, the so-called Unconnected_Send service (Service
Code 0x52 of the connection manager object). This service message contains all the information about the
transport mechanism, such as the request time-out (which may be modified as the message moves through
each CIP router), the message request path information and the routing path information.
The first CIP router device that receives an Unconnected_Send message will take its contents and forward it to the
next CIP router, as specified within the Route Path section of the message. Before the message is actually sent, the
“used” part of the path is removed, but is remembered by the CIP router device for the return of the response. The CIP
router may subtract some time from the timeout value, thereby reducing the timeout value as it closes in on the destination. This process is executed for every CIP router the message goes through, until the final CIP router is reached.
The number of CIP routers an Unconnected_Send may pass through is theoretically limited by the message length.
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Once the Unconnected_Send message has arrived at the last CIP router, the Unconnected_Send “wrapper” is
removed and the “inner” explicit message is sent to the target device, which executes the requested service and
generates a response. That response, as received from the target device, is then transported back through all the
CIP routers it traversed during its forward journey until it reaches the originating node. It is important to note in this
context that the transport mechanism may have been successful in forwarding the message and returning the response, but the response still could contain an indication that the desired service could not be performed successfully in the target network/device. Through this mechanism, the CIP router devices do not need to know anything
about the message paths ahead of time so no pre-configuration of the CIP router devices is required. This is often
referred to as “seamless routing”.
When a connection (I/O or Explicit) is set up using the Forward_Open service (see Section 3.1.14), it may go to
a target device on another network. To enable the appropriate setup process, the Forward_Open message may
contain a field with path information describing a route to the target device. This is very similar to the Unconnected_Send service described above. The routing information is then used to create routed connections within the
CIP routing devices between the originator and the target of the message. Once set up, these connections automatically forward any incoming messages for this connection to the proper outgoing port. Again, this is repeated
through each CIP router until the message has reached the target node. As with routed unconnected explicit messages, the number of hops is generally limited only by the capabilities of the devices involved. In contrast to routed
unconnected messages, routed connected messages do not carry path information. Since connected messages
always use the same path for any given connection, the path information that was given to the routing devices
during connection setup is held there as long as the connection exists. Again, the CIP routing devices do not have
to be preprogrammed; they are self-configured during the connection establishment process.
2.9. Data Management
The Data Management part of the CIP Specification describes addressing models for CIP entities and the data
structures of the entities themselves.
Entity addressing is done by Segments, which allows flexible usage so that many different types of addressing
methods can be accommodated. Two uses of this addressing scheme (logical segments and data types) are
looked at in more detail below.
2.9.1. Logical Segments
Logical segments (first byte = 0x20 – 0x3F) are addressing Segments that can be used to address objects and their
attributes within a device. They are typically structured as follows: [class ID] [instance ID] [attribute ID, if required].
Each element of this structure allows various formats (1 byte, 2 byte and 4 byte). Figure 10 shows a typical
example of this addressing method.
30
20 04
24 10
Class 0x04
Class ID
1 byte format
30 03
Instance 0x10
Instance ID
1 byte format
Attribute 0x03
Attribute ID
1 byte format
Figure 10 Logical Segment Encoding Example
This type of addressing is commonly used to point to assemblies, Parameters and other addressable entities within a
device. It is used extensively in EDS files, but also within explicit messages, to name just a few application areas.
2.9.2. Data Types
Data types (first byte = 0xA0–0xDF) can be either structured (first byte = 0xA0–0xA3, 0xA8 or 0xB0) or elementary (first and only byte = 0xC1–0xDE). All other values are reserved. structured data types can be arrays of
elementary data types or a collection of arrays or elementary data types. Of particular importance in the context
of this book are elementary data types, which are used within EDS files to specify the data types of parameters
and other entities.
Here is a list of commonly used data types:
- 1-bit (encoded into 1 byte):
• Boolean, BOOL, Type Code 0xC1;
- 1-byte:
• Bit string, 8 bits, BYTE, Type Code 0xD1;
• Unsigned 8-bit integer, USINT, Type Code 0xC6;
• Signed 8-bit integer, SINT, Type Code 0xC2;
- 2-byte:
• Bit string, 16-bits, WORD, Type Code 0xD2;
• Unsigned 16-bit integer, UINT, Type Code 0xC7;
• Signed 16-bit integer, INT, Type Code 0xC3;
- 4-byte:
• Bit string, 32 bits, DWORD, Type Code 0xD3;
• Unsigned 32-bit integer, UDINT, Type Code 0xC8;
• Signed 32-bit integer, DINT, Type Code 0xC4.
The data types in CIP follow the requirements of IEC 61131-3 [17] [16] .
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2.10. Auxiliary Power Distribution System
The CIP application layer can be used on a variety of network technologies. Each CIP network specification
consists of two volumes. The physical layer behavior defined on a particular network is described in the appropriate CIP network adaptation volume.
Chapter 8 of Volume 1 of the CIP Networks Library defines an optional auxiliary power distribution system that is
separate and distinct from the physical layer requirements of any of the CIP networks.
Auxiliary power may be used to provide application power for such devices as input/output modules, Emergency Stop circuitry, and other application-specific needs. The cabling system provides 4-wire, two-circuit wiring
that supplies 24V switched and un-switched power. Depending on the cabling selected by the designer, the
maximum current ranges from 7 to 10 amperes. This standard specifies system topologies, cable and connector requirements and power supply requirements for auxiliary power distribution.
This system is not intended to provide redundant network power for already powered networks such as DeviceNet or CompoNet.
2.11. Maintenance and Further Development of the Specifications
ODVA has a set of working groups that maintain the specifications and create protocol extensions, e.g.,
new profiles or functional enhancements such as CIP Sync and CIP Safety. These groups are called Special Interest Groups (SIGs).
The results of these SIGs are written up and presented to the Technical Review Board (TRB) for approval and
then incorporated into the specifications. Only ODVA members can work within the SIGs. These participants
have the advantage of advance knowledge of technical changes coming to the specifications. Participation in
one or several SIGs is, therefore, highly recommended.
32
3. Network Adaptations of CIP
There are currently four public adaptations of CIP, each based on different data link layers and transport mechanisms, which maintain the common upper layers of CIP, as illustrated earlier in Figure 1.
3.1. DeviceNet
3.1.1. Introduction
DeviceNet was the first implementation of CIP. As mentioned in Section , DeviceNet is based on the Controller
Area Network (CAN). DeviceNet uses a subset of the CAN protocol (11-bit identifier only, no remote frames). The
DeviceNet adaptation of CIP accommodates the 8-byte packet size limitation of the CAN protocol and allows
the use of simple devices with minimal processing power. For a more detailed description of the CAN protocol
and some of its applications, see endnote [18].
3.1.2. Relationship to standards
Like other CIP Networks, DeviceNet follows the Open Systems Interconnection (OSI) model, an ISO standard for
network communications that is hierarchical in nature. Networks that follow this model define all necessary functions, from physical implementation up to the protocol and methodology to communicate control and information
data within and across networks.
Figure 11 shows the relationship between CIP and DeviceNet.
Figure 11 Relationship Between
CIP and DeviceNet
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The DeviceNet adaptation of CIP is described in Volume 3 of the CIP Networks Library [3]. All other features are
based on CIP. DeviceNet is also described in a number of national and international standards, e.g. [25], [30].
3.1.3. DeviceNet Features
DeviceNet is a communication system at the low end (sensors, actuators) of the industrial communication spectrum with the following features:
- Trunkline/dropline configuration;
- Support for up to 64 nodes;
- Node insertion or removal while the network is up and running;
- QuickConnect for devices that are frequently removed from and added to the network, e.g., robot tools;
- Simultaneous support for both network-powered devices, e.g., sensors, and separately-powered devices,
e.g., actuators;
- Use of sealed or open-style connectors;
- Protection from wiring errors;
- Selectable data rates of 125 kBaud, 250 kBaud and 500 kBaud;
- Adjustable power configuration to meet individual application needs;
- High current capability (up to 16 Amps per supply);
- Operation with off-the-shelf power supplies;
- Power taps that allow the connection of several power supplies from multiple vendors that comply with
DeviceNet standards;
- Built-in overload protection;
- Power available along the bus: both signal and power lines contained in the cable;
- Several cables that are suitable for a number of different applications.
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3.1.4. DeviceNet Physical Layer and Relationship to CAN
The physical layer of DeviceNet is an extension of the ISO 11898 standard [19]. This extension defines the following additional details:
- Improved transceiver characteristics that allow the support of up to 64 nodes per network;
- Additional circuitry for over-voltage and mis-wiring protection;
- Several types of cables for a variety of applications;
- Several types of connectors for open (IP 20) and sealed (IP 65/67) devices.
The cables described in the CIP Networks Library were designed specifically to meet minimum propagation
speed requirements to ensure that they can be used up to the maximum system length. Figure 12 shows examples of some of the key characteristics that can be achieved with some of the defined cable types in conjunction
with suitable transceiver circuits and proper termination resistors (121 Ω).
Trunk Distance
Data Rate
Thick Cable
125 kBaud
500 meters
250 kBaud
250 meters
500 kBaud
100 meters
Thin Cable
Drop Length
Flat Cable
Maximum
420 meters
100 meters
200 meters
75 meters
Cumulative
156 meter
6 meters
78 meters
39 meters
Figure 12 Data Rate vs. Trunk and Drop Length
ODVA has issued a guideline [8] that gives complete details of how to build the physical layer of a DeviceNet
Network, equivalent information can also be found in an IEC standard [27].
Developers of DeviceNet devices can create DeviceNet circuits with or without physical layer isolation (both
versions are fully specified). Furthermore, a device may take some or all of its power from the bus, thus avoiding
extra power lines for devices that can live on the power supplied through the DeviceNet cable.
All DeviceNet devices must be equipped with one of the connectors described in Volume 3, although hard wiring of a device is allowed, provided the node is removable without severing the trunk.
3.1.5. Frame Structure
DeviceNet uses standard CAN frames with an 11-bit identifier, for further details see [19], [20] and chapter 3.1.15 of
this publication.
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3.1.6. Protocol Adaptations
On the protocol side, there are basically two adaptations of CIP that have been made to better accommodate it
to the CAN data frame:
- Shortening CIP explicit messages to 8 bytes or less where possible, with the use of message fragmentation for longer messages;
- Definition of a master/slave communications option to minimize the connection establishment overhead
(see chapter 3.1.17).
These two features have been created to allow the use of simple and thus inexpensive microcontrollers. This is
particularly important for small, cost-sensitive devices like photoelectric or proximity sensors. As a result of this
adaptation, the DeviceNet protocol in its simplest form has been implemented in 8-bit microprocessors with as
little as 4 Kbytes of code memory and 175 bytes of RAM.
The message fragmentation mentioned previously comes in two varieties:
- For I/O messages the use of fragmentation is defined by the maximum length of the data to be transmitted through a connection. Any connection that has more than 8 bytes to transmit always uses the fragmentation protocol, even if the actual data to be transmitted is 8 bytes or less, e.g., an “Idle” Message.
- For explicit messaging, the use of the fragmentation protocol is indicated in the header of every message,
since the actual frame size can vary in length, depending on the content of the explicit message. The
actual fragmentation protocol is contained in one extra byte within the message that indicates whether the
fragment is a start fragment, a middle fragment or an end fragment. A modulo 64 rolling fragment counter
allows very long fragmented messages, and is limited in theory only by the maximum Produced or Consumed Connection sizes (65,535 bytes). In reality, the capabilities of the devices limit the message sizes.
3.1.7. Indicators and Switches
Indicators and switches are optional on DeviceNet. However, certain DeviceNet users not only require indicators
and switches, they also specify what type to use. Many factors must be considered before implementing these
devices, including packaging, accessibility and customer expectations.
Indicators allow the user to determine the state of the device and its network connection(s). Since indicators can
be very useful when troubleshooting the operation of a device, manufacturers are advised to incorporate some
or all of the indicators described in the DeviceNet specification. While devices may incorporate additional indicators with behavior not described in the specification, any indicators labeled per specification must also follow
their specified behavior.
Similarly, devices may be built with or without switches or other directly accessible means for configuration of
MAC ID and baud rate. If these switches are used, certain rules apply to how these values are used at power-up
and during the operation of the device.
36
3.1.8. Additional Objects
The DeviceNet Specification defines one additional object, the DeviceNet object.
3.1.8.1. DeviceNet Object (Class ID: 0x03)
A DeviceNet object is required for every DeviceNet port of the device. The instance attributes of this object
contain information on how this device uses the DeviceNet port, including the MAC ID of the device and the
(expected) baud rate of the DeviceNet network the device is attached to. Both attributes are always expected
to be non-volatile, i.e., after a power interruption, the device is expected to try to go online again with the same
values that were stored in these attributes before the power interruption. Devices that set these values through
switches typically override any stored values at power-up. The DeviceNet object may also contain information on
further aspects associated with its DeviceNet behavior, such as information related to the master/slave communications status, QuickConnect support (see chapter 3.1.17.7) and Active Node Table.
3.1.9. Network Access
DeviceNet uses the network access mechanisms described in the CAN specification, i.e., bitwise arbitration
through the CAN Identifier for every frame to be sent. This requires a system design that does not allow multiple
uses of any of these identifiers. Since the node number of every device is coded into the CAN Identifier (see
chapter 3.1.15), it is generally sufficient to make sure that none of the node numbers exists more than once on
any given network. This is guaranteed through the Network Access algorithm (see chapter 3.1.10).
3.1.10. Going Online
Any device that wants to communicate on DeviceNet must go through a network access algorithm before
any communication is allowed. The main purpose of this process is to avoid duplicate node IDs on the same
network, a secondary purpose is to announce a node’s presence on the link for nodes that maintain an Active
Node Table. Every device that is ready to go online sends a Duplicate MAC ID Check Message containing its
port number, vendor ID and serial number. If another device is already online with this MAC ID or is in the process of going online with this MAC ID, it responds with a Duplicate MAC ID Response Message that directs the
checking device to go offline and not communicate any further.
If two or more devices with the same MAC ID happen to transmit the Duplicate MAC ID Check Message at
exactly the same time, all of them will win arbitration at the same time and will proceed with their message.
However, since this message has different values (port number, vendor ID and serial number) in the data field,
the nodes will detect bit errors and will flag error frames that cause all nodes to discard the frame. This reaction
triggers a re-transmission of the message by the sending node. While this action may eventually result in a BusOff condition for the devices involved, a situation with duplicate node IDs is safely avoided.
3.1.11. Offline Connection Set
The Offline Connection Set is a set of messages created to communicate with devices that have failed to go
online (see Section 3.1.10), to allow a new MAC ID to be set. At any given point in time, only one offline device
and one tool can use the Offline Connection Set, therefore, the first step in its use is to determine if a tool has
ownership of the Offline Connection Set. Once a tool has successfully claimed ownership, it can check whether
there are any nodes on the network that are in the offline state. If such nodes exist, the tool can then determine
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their vendor ID(s) and serial number(s). Using this information, which is unique by definition, the tool can then address a specific device which responds by flashing an indicator. Once this identification is complete and the user
is certain communication is established with the intended device, the tool can then send a new MAC address to
the device. The target device then restarts the Duplicate MAC ID algorithm and tries to go online with the new
MAC Address. More information on this topic can be found in [3] and [18].
3.1.12. DeviceNet Status Indication Messages
There are two optional DeviceNet messages that indicate a status or a status transition of a device. One of
them is called “Device Heartbeat” and the other is called “Device Shutdown”. Both messages are transmitted
by a UCMM capable device as an unconnected response message (Message Group 3, Message ID 5) and by a
Group 2 Only Server as an unconnected response message (Message Group 2, Message ID 3). These messages are independent of any other communication relationship that may exist with other devices on the network.
The Device Heartbeat Message, sent at a heartbeat interval set in the ID object, provides a way for a device to
indicate its presence on the network and its current “health” condition. The Device Shutdown Message provides
a way for a device to indicate that it is in the process of shutting down and going to the offline state.
3.1.13. Explicit Messaging
All explicit messaging in DeviceNet is done via connections and the associated connection object instances.
However, these objects first must be set up in the device. This can be done by using the predefined master/
slave connection set to activate a static connection object already available in the device or by using the
UCMM (unconnected message manager) port of a device, to dynamically set up a connection object for
explicit messaging. The only messages sent to the UCMM are “Open” or “Close” requests that set up or
tear down an explicit messaging connection, while the only messages that can be sent to the master/slave
equivalent of the UCMM called the Group 2 Only Unconnected Port, are the “Allocate” or “Release” service
requests (see chapter 3.1.17). Explicit messages always pass via the message router object to the object that
is being addressed (refer to Figure 8).
As mentioned in Section 2.3, explicit messages on DeviceNet have a very compact structure to make them fit
into the 8-byte frame in most cases. Figure 13 shows a typical example of a request message using the 8/8
Message Body Format (“8/8” means 1 byte for Class ID, 1 byte for Instance ID).
Bit number
Byte
offset
7
6
0
Frag
[0]
XID
1
R/R [0]
5
4
3
2
MAC ID
38
0
Message
header
Service Code
2
Class ID
3
Instance ID
4
...
Service data
...
Figure 13 Non-Fragmented Explicit Request Message Format
1
Message
body
The consumer of this explicit message responds using the format shown in Figure 14. The consumer sets the
R/R (Request/Response) bit and repeats the Service Code of the request message. Any data transferred with
the response is entered in the service data field.
Bit number
Byte
offset
7
6
0
Frag
[0]
XID
1
R/R [1]
5
4
3
2
1
0
Message
header
MAC ID
Service Code
Message
body
Service data
...
(optional)
2
...
7
Figure 14 Non-Fragmented Explicit Response Message Format
Most messages will use the 8/8 format shown in Figure 13, since they only need to address Class and Instance
IDs up to 255. If there is a need to address any class/instance combinations above 255, then this is negotiated
between the two communication partners during the setup of the connection. Should an error occur, the receiver responds with the Error Response Message. The Service Code for an Error Response message is 0x14, and
two bytes of error code are included in the service data field to convey more information about the nature of the
error. See endnotes [3], [18] for further details of message encoding, including the use of fragmentation.
3.1.14. I/O Messaging
Since DeviceNet does not use a Real-Time Header or sequence count value like ControlNet and EtherNet/IP
do, I/O messages in DeviceNet have a very compact structure. For I/O data transfers up to 8 bytes long, the
data is sent in a non-fragmented message, which uses the entire CAN data field for I/O data. For I/O data
transfers longer than 8 bytes, a fragmentation protocol spreads the data over multiple frames. This fragmentation protocol uses one byte of the CAN data field to control the fragmentation of the data. See Figure 15
and Figure 16 for examples of fragmented and non-fragmented I/O messages. I/O messages without data
(i.e., with zero length data) indicate the “Idle” state of the producing application. Any producing device can do
this – master, slave or peer.
Bit number
Byte
offset
7
0
...
7
6
5
4
3
2
1
0
Process data
(0 – 8 bytes)
Figure 15 Non-Fragmented I/O Message Format
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Bit number
Byte
offset
7
6
5
4
3
2
0
Fragmentation protocol
1
...
7
Process data
(0 – 7 bytes)
1
0
Figure 16 Fragmented I/O Message Format
As mentioned, I/O messages are used to exchange high-priority application and process data via the network, and this communication is based on the producer/consumer model. The associated I/O data are always
transferred from one producing application object to one or more consuming application objects. This is accomplished using I/O messages via I/O messaging connection objects (Figure 17 shows two consuming applications) that have been pre-set in the device. This can be done in one of two ways by using:
- The predefined master/slave connection set to activate a static I/O connection object already available in
the device;
- An explicit messaging connection object already available in the device to dynamically create and set up
an appropriate I/O connection object.
Application
Object
(I/O Data)
Producing
I/O Messaging
Connection
Consuming
I/O Messaging
Connection
Node #1
Application
Object
(I/O Data)
Node #2
I/O Message
Figure 17 I/O Messaging Connections
Consuming
I/O Messaging
Connection
Application
Object
(I/O Data)
Node #3
I/O messages usually pass directly to the data of the assigned application object. The assembly object is the
most common application object used with I/O connections. Also refer to Figure 8.
3.1.15. Using the CAN Identifier
DeviceNet is based on the standard CAN protocol and therefore uses an 11-bit message identifier. A distinction
therefore can be made between 211 = 2048 messages. The 6-bit MAC ID field is sufficient to identify a device
40
because a DeviceNet Network is limited to a maximum of 64 participants.
The overall CAN Identifier range is divided into four Message Groups of varying sizes, as shown in Figure 18:
Connection ID = CAN Identifier (bits 10:0)
10
9
0
8
7
6
5
Message ID
4
3
2
1
0
Source MAC ID
1
0
MAC ID
1
1
Message ID
1
1
1
1
1
1
1
1
1
1
1
Used for
Message Group 1
Message ID
Message Group 2
Source MAC ID
Message Group 3
Message ID
Message Group 4
1
x
x
x
x
Invalid CAN Identifiers
Figure 18 Definition of the Message Groups
The bitwise arbitration mechanism of CAN determines the priority of messages on DeviceNet. When two nodes
transmit simultaneously, the numerically lower CAN Identifier value will win arbitration. The arbitration mechanism
is explained in the CAN specification [20]. A detailed description is beyond the scope of this document, but in
short, transmitted bits are shifted onto the wire most significant bit first, so a zero in the upper bit positions will
take precedence over a one. As is shown in Figure 18, Message Group 1 has a zero in bit 10, so it is the highest
priority group. Group 2 is the second highest priority group because of the zero in bit 9. Group 3 is the next
highest priority group, because the CAN IDs contain a one in bits 9 and 10. All valid Group 3 Message IDs are
lower numerically than the corresponding bits (8-6) in Group 4 and therefore Group 4 is the lowest priority of all.
In DeviceNet, the CAN Identifier is the connection ID. This comprises the Message Group ID, the Message
ID within this group and the device’s MAC ID, which can be the source or destination address. The definition
depends on the Message Group and the Message ID. The significance of the message within the system is
defined by the Message Group and Message ID.
The four Message Groups are used as follows:
Message Group 1 is assigned 1024 CAN Identifiers (0x0000 – 0x03FF), which is 50 % of all identifiers available. Up to 16 different Message IDs are available per device (node) within this group. The priority of a message
within this group is primarily determined by the Message ID (the significance of the message), and only after that
by the source MAC ID (the producing device). If two devices transmit a Message Group 1 message at the same
time, then the device with the lower Message ID will always win the arbitration. However, if two devices transmit
the same Message ID at the same time on the CAN bus, then the device with the lower MAC ID will win. The
messages of Group 1 are, therefore, well suited for the exchange of high-priority process data.
Message Group 2 is assigned 512 identifiers (0x0400 – 0x05FF). Most of the Message IDs in this group are
optionally defined for what is commonly referred to as the predefined master/slave connection set (see chapter 3.1.17). One Message ID is reserved for the Duplicate Node ID Check (see chapter 3.1.10). Priority within
Message Group 2 is determined primarily by the MAC ID and, only after that, by the Message ID. This message
group was designed so that a CAN controller with an 8-bit mask is able to filter out its Group 2 Messages based
on MAC ID. This makes it possible for very low cost, low functionality microcontrollers with integral CAN controllers to be suitable for use on DeviceNet.
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Message Group 3, with 448 CAN Identifiers (0x0600 – 0x07BF), has a similar structure to Message Group 1,
however, it is mainly used for low priority process data exchange due to the relative priority difference between
Groups 1 and 3. In addition, the main use of this group is setting up dynamic Explicit Connections. Seven Message IDs per device are possible, and two of these are reserved for what is commonly referred to as the UCMM
port (see chapter 3.1.16).
Message Group 4, with 48 CAN Identifiers (0x07C0 – 0x07EF), does not include any MAC IDs, only Message
IDs. The messages in this group are only used for network management. Four Message IDs are currently assigned for services of the Offline Connection Set.
The remaining 16 CAN Identifiers (0x07F0 – 0x07FF) are invalid CAN IDs and thus are not permitted for use in
DeviceNet systems.
With this allocation of CAN Identifiers, the unused CAN Identifiers cannot be used by other devices. Therefore,
each device has exactly 16 Message IDs in Group 1, eight Message IDs in Group 2 and seven Message IDs
in Group 3. One advantage of this system is that the CAN Identifiers used in the network can always be clearly assigned to a device. Devices are responsible for managing their own identifiers. This simplifies the design,
troubleshooting and diagnosis of DeviceNet systems, as a central tool that keeps a record of all CAN ID assignments on the network is not needed.
3.1.16. Connection Establishment
As described in chapters 3.1.12 and 3.1.14, messages on DeviceNet are always exchanged in a connection-based manner. Communication objects must be set up for this purpose. These are not initially available
when a device is powered on; they first have to be created. There are two ports by which a DeviceNet device
can be addressed when first powered on, the unconnected message manager port (UCMM port) or the Group
2 Only Unconnected Explicit Request port, which is defined by the predefined master/slave connection set. Picture these ports as doors to the device. Only one key will unlock each door. The appropriate key for each lock is
the connection ID – i.e., the CAN Identifier – of the selected port. Other doors in the device can be opened only
if and when the appropriate key is available and other instances of connection objects are set up.
The setting up of communication relationships (i.e., connections) via the UCMM port represents a general procedure that should be adhered to with all DeviceNet devices. Devices that feature the predefined master/slave
connection set and are UCMM capable are called Group 2 Servers. A Group 2 Server can be addressed by one
or more connections from one or more clients.
Since UCMM capable devices need a good amount of processing power to service multiple communication requests, a simplified communication establishment and I/O data exchange method has been created for low-end
devices. This is called the predefined master/slave connection set (see chapter 3.1.17). This covers as many
as five predefined connections that can be activated (assigned) when accessing the device. The predefined
master/slave connection set represents a subset of the general connection establishment method, and it is limited to pure master/slave relations. Slave devices that are not UCMM capable and only support this subset are
called Group 2 Only Servers. Only the master that allocates it can address a Group 2 Only Server. All messages
received by this device are defined in Message Group 2.
For more details of the connection establishment using UCMM and the master/slave connection set, refer to
endnotes [3], [18].
42
3.1.17. Predefined Master/Slave Connection Set
Establishing a connection via the UCMM port requires a relatively large number of steps that must be completed to allow data exchange via DeviceNet and the devices must provide resources to administer the dynamic
connections. Because every device can set up a connection with every other device, and the source MAC ID
of the devices is contained in the connection ID, the CAN Identifier (connection ID) may have to be filtered via
software. This depends on how many connections a device supports, and on the type and number of screeners
(hardware CAN ID filters) of the CAN chip used in the device’s implementation.
While this approach maximizes use of the multicast, peer-to-peer, and producer/consumer capabilities of CAN,
it requires a higher performance CPU and more RAM and ROM resources. These requirements eliminate an
entire class of low cost microcontrollers with internal CAN controllers from consideration, raising the cost of
implementation to levels that preclude cost effective solutions for low-end (e.g., low end-user cost) devices. The
predefined master/slave connection set was designed to minimize message processing and to take advantage
of the limited screening capabilities of many CAN controllers. The predefined master/slave connection set is the
way that the vast majority of devices communicate on DeviceNet.
The predefined master/slave connection set defines an alternate way to establish connections called the Group
2 Only Unconnected Explicit Request Port. This method allows a device to limit the messages received to only
those in Group 2 with its own MAC ID. This greatly reduces the amount of packets that a node must deal with.
A CAN controller with a single mask and match screener (a so called BasicCAN screener) can be used in this
type of device, which makes it possible to use the low cost microcontrollers and simple CAN controllers mentioned earlier. Devices that operate in this manner are referred to as Group 2 Only Servers, deriving their name
from the fact that they are only required to receive messages in Group 2.
The predefined master/slave connection set is also used in UCMM capable devices. Such devices are referred
to as Group 2 Servers, deriving their name from the fact that they respond to Group 2 messages but are not
limited to just Group 2 messages.
Many of the reasons for defining the predefined master/slave connection set were due to hardware limitations
prevalent when the protocol was first developed. Many of the cost considerations have changed as hardware
evolved over time. Today, most devices can be implemented with a UCMM port and still be cost effective. This is
the preferred type of device to develop today. For reasons that go beyond this scope of this document, devices that are not capable of UCMM place extra burden on other devices and tools. Except in extremely low cost
situations, UCMM should always be a design goal for DeviceNet products.
The predefined master/slave connection set provides an interface for a set of up to five pre-configured connection types in a node.
The basis of this model is a 1:n communication structure consisting of one control device and decentralized
I/O devices. The central portion of such a system is known as the “Master” and the decentralized devices
are known as “Slaves”. Multiple masters are allowed on the network, but a slave can only be allocated to one
master at any time.
The predefined connection objects occupy instances 1 to 5 in the connection object (Class ID 0x05, see Section 2.4):
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- Explicit Messaging Connection:
• Group 2 Explicit Request/Response Message (Instance ID 1);
- I/O Messaging Connections:
• Polled I/O connection (Instance ID 2);
• Bit-strobe I/O connection (Instance ID 3);
• Change of State or cyclic I/O connection (Instance ID 4);
• Multicast Polling I/O connection (Instance ID 5).
The messages to the slave are defined in Message Group 2, and some of the responses from the slave are contained in Message Group 1. The distribution of connection IDs for the predefined master/slave connection set is
defined as shown in Figure 19.
Connection ID = CAN Identifier (bits 10:0)
10
0
9
8
7
6
5
Group 1
Message ID
4
3
2
1
0
Used for
Source MAC ID
Group 1 Messages
0
1
1
0
0
Source MAC ID
Slave’s I/O Multicast Poll Response
0
1
1
0
1
Source MAC ID
Slave’s I/O Change of State or Cyclic Message
0
1
1
1
0
Source MAC ID
Slave’s I/O Bit-Strobe Response Message
0
1
1
1
1
Source MAC ID
Slave’s I/O Poll Response or COS/Cyclic Ack
Message
1
0
MAC ID
1
0
Source MAC ID
0
0
0 Master’s I/O Bit-Strobe Command Message
1
0
Source MAC ID
0
0
1 Master’s I/O Multicast Poll Group ID
1
0
Destination MAC ID
0
1
0 Master’s Change of State or Cyclic Ack Message
1
0
Source MAC ID
0
1
1 Slave’s Explicit/Unconnected Response Messages
1
0
Destination MAC ID
1
0
0 Master’s Explicit Request Messages
1
0
Destination MAC ID
1
0
1 Master’s I/O Poll Command/COS/Cyclic Message
Group 2
Message
ID
Group 2 Messages
Figure 19 Connection IDs of the Predefined Master/Slave Connection Set
Because the CAN ID of most of the messages the master produces contains the destination MAC ID of the
slave, it is imperative that only one master talks to any given slave. Therefore, before it can use this Predefined
Connection Set, the master must first allocate it with the device. The DeviceNet object manages this important
function in the slave device. It allows only one master to allocate its Predefined Connection Set, thereby preventing duplicate CAN IDs from appearing on the wire.
44
The two services used are called Allocate_Master/Slave_Connection_Set (Service Code 0x4B) and Release_
Group_2_Identifier_Set (Service Code 0x4C). These two services always access instance 1 of the DeviceNet
object (Class ID 0x03) (see Figure 20).
Bit number
Byte
offset
7
6
0
Frag [0]
XID
1
R/R [0]
5
4
3
2
1
0
Message
header
MAC ID
Service Code [0x4B]
Class ID [0x03]
2…5
Message
body
Instance ID [0x01]
Allocation Choice
Figure
20 Allocate_Master/Slave_Connect_Set request message
Figure 20 shows the Allocate Message with 8-bit Class ID and 8-bit Instance ID, a format that is always used
when it is sent as a Group 2 Only unconnected message. It also may be sent across an existing connection and
in a different format if a format other than 8/8 was agreed during the connection establishment.
The Allocation Choice Byte is used to determine which predefined connections are to be allocated (see Figure 21).
Bit number
7
6
5
4
3
2
1
0
Reserved
Ack
Suppression
Cyclic
Change of
State
Multicast
Polling
Bit-Strobe
Polled
Explicit
Message
Figure 21 Format of the Allocation Choice Byte
The associated connections are activated by setting the appropriate bits. Change of State and Cyclic are mutually exclusive choices. The Change of State/Cyclic Connection may be configured as not acknowledged using
the acknowledge suppression bit. The individual connection types are described in more detail below.
The allocator’s MAC ID contains the address of the node (master) that wants to assign the predefined master/slave
connection set. Byte 0 of this message differs from the allocator’s MAC ID if this service has been passed on to a
Group 2 Only Server via a Group 2 Only Client (what is commonly referred to as a “proxy function”).
The slave, if not already claimed, responds with a Success Message. The connections are now in the Configuring State. Setting the Expected_Packet_Rate EPR (Set_Attribute_Single service to attribute 9 in the appropriate
connection object instance, value in ms) starts the connection’s time-monitoring function. The connection then
changes into Established State, and I/O messages begin transferring via this connection.
The allocated connections can be released individually or collectively through the Release_ Master/Slave_Connection_Set service (Service Code 0x4C), using the same format as that in Figure 20, except that the last byte
(Allocator’s MAC ID) is omitted.
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The following is an explanation of the four I/O connection types in the predefined master/slave connection set.
3.1.17.1. Polled I/O Connection
A polled I/O connection is used to implement a classic master/slave relationship between a control unit
and a device. In this setup, a master can transfer data to a slave using the Poll Request and receive data
from the slave using the Poll Response. Figure 22 shows the exchange of data between one master and
three slaves in Polled I/O mode.
The amount of data transferred in a message between a master and a slave using the polled I/O connection
can be any length. If the length exceeds 8 bytes, the fragmentation protocol is automatically used. A polled I/O
connection is always a point-to-point connection between a master and a slave. The slave consumes the Poll
Message and sends back an appropriate response (normally, its input data).
Link
Producer
Object
Application
Object
Link
Consumer
Object
Link
Producer
Object
Link
Consumer
Object
Link
Producer
Object
Master
MAC ID = 0
Link
Consumer
Object
Figure 22 Polled I/O Connections
Poll Command
Message
CID = 0x041D
Poll Response
Message
CID = 0x03C3
Poll Command
Message
CID = 0x042D
Poll Response
Message
CID = 0x03C5
Poll Command
Message
CID = 0x0455
Poll Response
Message
CID = 0x03CA
CID = Connection ID
Link
Consumer
Object
Link
Producer
Object
Link
Consumer
Object
Link
Producer
Object
Application
Object
Slave
MAC ID = 3
Application
Object
Slave
MAC ID = 5
Link
Consumer
Object
Link
Producer
Object
Application
Object
Slave
MAC ID = 10
The Polled Connection is subject to a time-monitoring function, which can be adjusted, in the device. A Poll Command must have been received within this time (4 × EPR) or else the connection reverts to time-out mode. When
a connection times out, the node optionally may go to a preconfigured fault state as set up by the user. A master
usually polls all the slaves in a round-robin manner.
46
A slave’s response time to a poll command is not defined in The DeviceNet Specification. While this provides
flexibility for slave devices to be tailored to their primary application, it may also exclude the device from use in
higher-speed applications.
3.1.17.2. Bit-Strobe I/O Connection
The master’s transmission on this I/O connection is the bit-strobe command. Using this command, a master
multicasts one message to reach all its slaves allocated for the bit-strobe connection. The frame sent by the
master using a bit-strobe command is always 8 bytes or 0 bytes (if Idle). From these 8 bytes, each slave is assigned one bit (see Figure 23). Each slave can send back as many as 8 data bytes in its response.
7
Bit Numbers
Byte 0
MAC ID 7
0
7
Bit Numbers
0
Byte 1
MAC ID 0 MAC ID 15
7
•••
MAC ID 8
Bit Numbers
Byte 6
0
7
Bit Numbers
0
Byte 7
MAC ID 55 MAC ID 48 MAC ID 63 MAC ID 56
Figure 23 Data Format of the Bit-Strobe I/O Connection
A bit-strobe I/O connection represents a multicast connection between one master and any number of
strobe-allocated slaves (see Figure 24). Since all devices in a network receive the bit-strobe command at the
same time, they can be synchronized by this command. When the bit-strobe command is received, the slave
may consume its associated bit, and then send a response of up to 8 bytes.
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Link
Producer
Object
Application
Object
Link
Consumer
Object
Bit-Strobe
Command
Message
CID = 0x0400
Bit-Strobe
Response
Message
CID = 0x0383
Link
Consumer
Object
Link
Producer
Object
Application
Object
Slave
MAC ID = 3
Link
Consumer
Object
Link
Consumer
Object
Bit-Strobe
Response
Message
CID = 0x0385
Link
Producer
Object
Application
Object
Slave
MAC ID = 5
Link
Consumer
Object
Master
MAC ID = 0
Link
Consumer
Object
Bit-Strobe
Response
Message
CID = 0x038A
Link
Producer
Object
CID = Connection ID
Application
Object
Slave
MAC ID = 10
Figure 24 Bit-Strobe I/O Connections
Since this command uses the source MAC ID in the connection ID (see Figure 19), devices that support the
bit-strobe I/O connection and have a CAN chip with screening limited to only 8 bits of the CAN ID (11 bits) must
perform software screening of the CAN Identifier.
3.1.17.3. Change of State/Cyclic I/O Connection
The COS/cyclic I/O connection differs from the other types of I/O connections in that both endpoints produce
their data independently. This can be done in a change of state or cyclic manner. In the former case, the COS
I/O connection recognizes that the application object data indicated by the Produced_Connection_Path has
changed. In the latter case, a timer of the cyclic I/O connection expires and therefore triggers the message
transfer of the latest data from the application object.
A COS/cyclic I/O connection can be set up as acknowledged or unacknowledged. When acknowledged, the
consuming side of the connection must define a path to the acknowledge handler object to ensure proper handling of acknowledgments and management of any required retries.
Figure 25 shows the various COS/Cyclic I/O connection possibilities.
48
Master
COS/Cyclic
Message
Link
Producer
Object
Application
Object
CID = 0x041D
Slave
Acknowledge
Message
Link
Consumer
Object
CID = 0x03C3
Slave
COS/Cyclic
Message
Link
Consumer
Object
CID = 0x0345
Master
Acknowledge
Message
Link
Producer
Object
CID = 0x042A
Master
COS/Cyclic
Message
Link
Producer
Object
Master
MAC ID = 0
Link
Consumer
Object
CID = 0x0455
Slave
COS/Cyclic
Message
CID = 0x034A
CID = Connection ID
Link
Consumer
Object
Link
Producer
Object
Application
Object
Slave
MAC ID = 3
Link
Producer
Object
Application
Object
Link
Consumer
Object
Ack
Handler
Object
Slave
MAC ID = 5
Link
Consumer
Object
Application
Object
Link
Producer
Object
Application
Object
Slave
MAC ID = 10
Figure 25 COS/Cyclic I/O Connections
A COS/cyclic I/O connection can also originate from a master, making it appear to the slave like a polled I/O
connection. This can be seen in Figure 19 since the same connection ID is used for the master’s polled I/O
message as is used for the master’s COS/cyclic I/O message. COS Connections have two additional behaviors
not present in other connection types. The Expected Packet Rate (EPR) is used as a default production trigger
so that, if the connection data have not changed after the EPR timer has expired, it will be resent anyway. This
“heartbeat”, as it is sometimes called, is utilized so the consuming node can know the difference between a
node that has gone offline and one whose data have not changed. COS Connections also have a Production
Inhibit Timer feature that prevents a node from producing data too often, and thus using too much network
bandwidth. The production inhibit timer determines the amount of time the node must remain quiet after producing data to the network.
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3.1.17.4. Multicast Polled I/O Connection
This connection is similar to the regular I/O poll except that all of the slaves belonging to a multicast group
consume the same output data from the master. Each slave responds with its own reply data. A unique aspect
of this connection is that the master picks the CAN ID from one of the slaves in the multicast group and must
then set the consumed CAN ID in each of the other slaves to that same value. If, during runtime, that slave’s
connection times out, the master must either stop producing its multicast poll command or pick another slave in
the group and reset the command CAN ID in all the remaining slaves in the group to that value before sending
another Multicast Poll Command.
3.1.17.5. I/O Data Sharing
Due to the inherent broadcast nature of all CAN frames, applications can be set up to “listen” to the data
produced by other applications. Such a “listen only” mode is not described in the DeviceNet specification, but
some vendors have created products that do exactly that, e.g., “shared inputs” in Allen-Bradley I/O Scanners.
3.1.17.6. Typical Master/Slave Start Sequence
Typically, starting up a DeviceNet Network with an I/O Scanner and a set of slaves is executed as follows:
- All devices run their self-test sequence and then try to go online with the algorithm described in Section
3.1.10. Any device that uses an autobaud mechanism to detect the baud rate of a network has to wait
with its Duplicate Node ID Message until it has seen enough CAN frames to detect the correct baud rate;
- Once online, slave devices will remain silent, except to defend their MAC ID, until their master allocates
them;
- Once online, a master will try to allocate each slave configured into its scan list by running the following
sequence of messages:
• Try to open a connection to the slave using a UCMM Open Message;
• If successful, the master can then use this connection for further communication with the slave (the
device is a Group 2 Server);
• If not successful, the master will try again after a minimum wait time of one second;
• If unsuccessful again, the master will try to allocate the slave using the Group 2 Only Unconnected
Explicit Request Message (at least for explicit messaging) after a minimum wait time of one second;
• If successful, the master can then use this connection for further communication with the slave (the
device is a Group 2 Only Server);
• If not successful, the master will try again after a minimum wait time of one second;
• If unsuccessful again, the master will start over with the UCMM Message after a minimum wait time of
one second. This process will carry on indefinitely or until the master has allocated the slave.
50
- Once the master has allocated the slave, it may carry out some identity verification to see whether it is
safe to start I/O messaging with the slave. The master also may apply further configuration to the connections it has established, e.g., setting the explicit messaging connection to “Deferred Delete”;
- Setting the EPR value(s) brings the I/O connection(s) to the Established State so that I/O messaging can
commence.
3.1.17.7. QuickConnect Connection Establishment
DeviceNet also allows an optional method of connection establishment known as QuickConnect. This was designed
to provide the same level of protection against duplicate MAC IDs, but to do so in a much shorter time period, allowing
connections to be established in a fraction of the time they normally take. This method is useful in applications where
nodes are added to an operating network, and the time required for establishing connections directly impacts productivity. For example, in robotic applications, the end-of-arm electronics are often changed out when a new item enters its
workspace. These electronics need to be operational very quickly to avoid cycle time delays.
The QuickConnect process includes all the same steps as the typical startup process, but most of them are
done in parallel rather than in sequence. As a result, the device self-check and Duplicate MAC ID Check processes begin immediately, and the node goes online almost simultaneously. A failure of the device self-test or a
duplicate MAC ID indication causes the device to remove itself from the bus.
In order for applications to benefit fully from this method, QuickConnect must be implemented in both the
master and the slave. This feature is selectable through an EDS entry, and by default, is disabled in nodes
that support it.
3.1.17.8. Master/Slave Summary
Device manufacturers can easily support the predefined master/slave connection set by using simple BasicCAN
controllers. Software screening of the CAN Identifier generally is not necessary, which enables the use of lowcost, 8-bit controllers. This may represent an advantage as far as the devices are concerned but entails some
disadvantages for the system design.
Group 2 Only (i.e., UCMM incapable) devices permit only one explicit messaging connection between client
(master) and server (slave), whereas UCMM capable devices can maintain explicit messaging connections with
more than one client at the same time.
If a device wants to communicate with one of the allocated slaves that does not support UCMM, the master
recognizes this situation and sets up a communication relationship with the requestor instead. Any communication between the requestor is then automatically routed via the master. This is called the Proxy function. Since
this puts an additional burden on the master and on network bandwidth, it is recommended that slave devices
support UCMM.
Although not explicitly defined in The DeviceNet Specification, DeviceNet masters can, under certain conditions,
automatically configure their scan lists and/or the devices contained in their scan lists. This functionality simply
makes use of the explicit messaging capabilities of masters and slaves that allows the master to read from a
slave whatever information is required to start an I/O communication and to download any configurable param-
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eters that have been communicated to the master via EDS. This functionality facilitates the replacement of even
complex slave devices without the need for a tool, dramatically reducing system downtime.
3.1.18. Device Profiles
DeviceNet devices may utilize any of the device profiles described in the CIP Networks Library. As of the publication date of this book, no DeviceNet-specific profiles have been defined.
3.1.19. Configuration
DeviceNet devices typically come with Electronic Data Sheets (EDS) as described in chapter 2.7. EDS files for
DeviceNet devices can make full use of all EDS features, but they do not necessarily contain all sections. Typical
DeviceNet devices contain (apart from the mandatory sections) at least an IO_Info section.
This section specifies which types of master/slave connections are supported and which one(s) should be enabled as defaults. It also tells which I/O connections may be used simultaneously.
An EDS also may contain individual parameters and/or a configuration assembly with a complete description of
all parameters within this assembly. A full description of what can be done in DeviceNet EDS files would go well
beyond the scope of this book. For available materials on this topic that go into more detail see [41], [42].
3.1.20. Conformance Test
See chapter 6 of this publication for information on conformance testing.
3.1.21. Tools
Tools for DeviceNet networks can be divided into three groups:
- Physical layer tools are tools (hardware and/or software) that verify the integrity and conformance of the
physical layer or monitor the quality of the data transmission;
- Configuration tools are software tools capable of communicating with individual devices for data monitoring and configuration purposes. They can range from very basic software operating on handheld devices
to powerful PC-based software packages used to configure complete networks. Most configuration tools
are EDS-based; however, more complex devices like I/O Scanners tend to have their own configuration
applets that are only partially based on EDS files. Some of these tools support multiple access paths to
the network, e.g., via Ethernet and suitable routing devices, and thus allow remote access. High-level
tools also actively query the devices on the network to identify them and monitor their “health”;
- Monitoring tools typically are PC-based software packages that can capture and display CAN frames on
the network. A raw CAN frame display may be good enough for some experts, but using a tool that allows
both raw CAN display and DeviceNet interpretation of the frames is recommended.
For a typical installation, a configuration tool is all that is needed. However, to ensure that the network is
operating reliably, verification with a physical layer tool is highly recommended. Experience shows that the
52
overwhelming majority of DeviceNet network problems are caused by inappropriate physical layer installation.
Protocol monitoring tools are used primarily to investigate interoperability problems and to assist during the
development process. Turn to the ODVA Marketplace on the ODVA website to access a list of vendors that
provide tools for DeviceNet.
3.1.22. Advice for Developers
Before starting any DeviceNet product development, the following issues should be considered in detail:
- What functionality does the product require today and in future applications?
• Slave functionality;
• Group 2 Server vs. Group 2 Only Server.
• Master functionality;
• Combination of the above.
- What are the physical layer requirements? Is IP 65/67 required or is IP 20 good enough?
- What type of hardware should be chosen for this product?
- What kind of firmware should be used for this product? Will a commercially available communication stack
be used?
- Will the development of hardware and/or software be done internally or will it be designed by an outside
company?
- What are the configuration requirements?
- What design and verification tools should be used?
- What kind of configuration software should be used for this product? Will a commercially available software package be used, i.e., is an EDS adequate to describe the device or is custom software needed?
- When and where will the product be tested for conformance and interoperability?
- What is an absolute must before my products can be placed on the market (i.e., own the specification,
have the company’s own vendor ID, have the product conformance tested)?
A full discussion of these issues goes well beyond the scope of this publication, for more information see [43].
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3.1.23. DeviceNet Summary
Since its introduction in 1994, DeviceNet has been used successfully in tens of millions of nodes in many different applications. It is a de facto standard in many countries, which is reflected in several national and international standards [25], [29], [30]. Due to its universal communication characteristics, it is one of the most versatile
networks for low-end devices. While optimized for devices with small amounts of I/O, it can easily accommodate larger devices as well. Powerful EDS-based configuration tools allow easy commissioning and configuration of even complex devices without the need to consult manuals.
With the introduction of CIP Safety on DeviceNet, many machine-level applications that previously required a set
of dedicated networks today can be accommodated on a single DeviceNet network.
Finally, as a member of the CIP family of networks, DeviceNet can be combined into an overall CIP Network
structure that allows seamless communication among CIP Networks, as if they were only one network.
3.2. ControlNet
3.2.1. Introduction
Introduced in 1997, ControlNet is a deterministic digital communications network that provides high-speed
transport of time-critical I/O and explicit messaging data – including upload/download of programming and
configuration data and peer-to-peer messaging – on a single physical media link. Each device and/or controller
is a node on the network.
ControlNet is a producer/consumer network that supports multiple communication hierarchies and message
prioritization. ControlNet systems offer a single point of connection for configuration and control by supporting
both implicit (I/O) and explicit messaging. ControlNet’s time-based message scheduling mechanism provides
network devices with deterministic and predictable access to the network while preventing network collisions.
This scheduling mechanism allows time-critical data, which is required on a periodic, repeatable and predictable basis, to be produced on a predefined schedule without the loss of efficiency associated with continuously
requesting, or “polling”, for the required data.
3.2.2. Relationship to Standards
Like other CIP Networks, ControlNet follows the Open Systems Interconnection (OSI) model, an ISO standard
for network communications that is hierarchical in nature. Networks that follow this model define all necessary
functions, from physical implementation up to the protocol and methodology to communicate control and information data within and across networks.
54
Figure 26 shows the relationship between CIP and ControlNet.
Figure 26 Relationship Between
CIP and ControlNet
The ControlNet adaptation of CIP is described in Volume 4 of the CIP Networks Library [4]. All other features are
based on CIP. ControlNet is also described in international standards, e.g., [31].
3.2.3. ControlNet Features
ControlNet is a high-speed deterministic industrial communication system with the following features:
- Trunkline/dropline configuration (copper media), star configuration (optical media);
- Support for media redundancy;
- Support for up to 99 nodes;
- Node insertion or removal while the network is up and running;
- Use of sealed or open-style connectors;
- Fixed baudrate (5 Mbaud).
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3.2.4. ControlNet Physical Layer
The physical layer of ControlNet has been designed specifically for this network; it does not reuse any existing
open technology. The basis of the physical layer is a 75 Ω coaxial trunkline (typically of RG-6 type cable) terminated at both ends with 75 Ω terminating resistors. To reduce impedance mismatch, all ControlNet devices are connected to the network through special taps that consist of a coupling network and a specific length of dropline
(1 m). There is no minimum distance requirement between taps, but, since every tap introduces some signal
attenuation, each tap reduces the maximum length of the trunkline by 16.3 m. This results in a full length trunkline
of 1,000 m with only two taps at the ends while a fully populated physical network with 48 taps allows a trunkline
length of 250 m (see Figure 27).
maximum allowable segment length =
Segment length (m)
1000
1000 m – 16.3 m × [number of taps – 2]
750
500
250
2
32
16
2
Number of taps
48
Figure 27 Coax Medium Topology Limits
This physical layer limitation is addressed by including repeaters that can increase the network size without lowering the speed. Therefore, if a network is to be built with a higher number of nodes (up to 99 nodes are possible) or with a topology that goes beyond the single trunkline limitations, repeaters can be used to extend the
bus. It’s possible to create any type of topology: tree, star or linear bus. Even a ring topology is possible using a
special type of repeater. Repeaters for fiber optic media can be used either to further increase the system size or
to allow isolation of network segments in harsh EMC environments or for high voltage applications.
The number of repeaters between any two nodes was initially limited to five, but further technology developments now allow up to 20 repeaters in series. However, regardless of the media technology used, the overall
length of a ControlNet system (the distance between any two nodes on the network) is still limited by propagation delay. With currently available media, this translates into approximately 20 km.
To better accommodate industry requirements, ControlNet supports redundant media, allowing bumpless
transfer from primary to secondary media or vice versa if one of them should fail or deteriorate. Developers are
encouraged to support this redundant media feature in their designs. For cost-sensitive applications, less ex-
56
pensive device variants may then be created by populating one channel only.
Another feature often used in the process industry is the capability of running ControlNet systems into areas with an explosion hazard. ControlNet is fully approved to meet worldwide standards for intrinsic safety
(explosion protection).
Copper media uses BNC type connectors for IP 20 type applications and TNC type connectors for IP 67 protection. Devices also may implement a network access port (NAP). This feature takes advantage of the repeater
function of the ControlNet ASICs. It uses an additional connector (RJ-45) with RS 422-based signals that provides easy access to any node on the network for configuration devices.
The signal transmitted on the copper media is a 5-Mbit/s Manchester-encoded signal with an amplitude of up to
9.5 V (pk-pk) at the transmitter that can be attenuated down to 510 mV (pk-pk) at the receiving end. The specification provides reference transmitting and receiving circuits.
3.2.5. Frame Structure
Every frame transmitted on ControlNet has the format of the MAC frame shown in Figure 28.
MAC Frame
Preamble
Start
Delimiter
Source
MAC ID
Lpackets
CRC
End
Delimiter
16 bits
8 bits
8 bits
0…510 bytes
16 bits
8 bits
Lpacket
Lpacket
•••
Lpacket
Figure 28 MAC Frame Format
Within every MAC frame, a field of up to 510 bytes is available for transmitting data or messages. This field may
be populated with one or several Lpackets (link packets). These Lpackets carry the individual CIP messages (I/O
or Explicit). Specialized Lpackets are used for network management. Since all nodes always listen to all MAC
frames, they have no problem consuming any of the Lpackets in a frame that is unicast, multicast or broadcast
in nature. This feature allows fine-tuned multicasting of small amounts of data to different sets of consumers
without much overhead.
There are two types of Lpacket formats: fixed tag and generic tag. Fixed tag Lpackets are used for unconnected messaging and network administration packets, while the generic tag Lpackets are used for all connected
messaging (I/O and Explicit).
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Lpacket
Size
Control
Service
Destination MAC ID
Link data
1 byte
1 byte
1 byte
1 byte
3…506 bytes
Figure 29 Fixed Tag Lpacket Format
Figure 29 shows the format of a fixed tag Lpacket. By including the destination MAC ID, this format reflects the
fact that these Lpackets are always directed from the requesting device (sending the MAC frame) to the target
device (the destination MAC ID). The service byte within a fixed tag Lpacket does not represent the service of
an explicit message, but a service type on a different level, since the fixed tag Lpacket format can be used for a
variety of actions, such as network administration.
Lpacket
Size
Control
Connection ID
Link data
1 byte
1 byte
3 bytes
0…504 bytes
Figure 30 Generic Tag Lpacket Format
Figure 30 shows the format of a generic tag Lpacket. The size byte specifies the number of words within the
Lpacket, while the control byte gives information on what type of Lpacket this is. The 3-byte Connection Identifier specifies which connection this Lpacket belongs to. These three bytes are the three lower bytes of the 4-byte
connection ID specified in the Forward_Open message; the uppermost byte is always zero. For a device that
receives the MAC frame, the connection ID indicates whether to ignore the Lpacket (the device is not part of the
connection), to consume the data and forward it to the application (the device is an end point of this connection)
or to forward the data to another network (the device acts as a router in a routed connection).
3.2.6. Protocol Adaptation
ControlNet can use all features of CIP. The ControlNet frame is big enough that fragmentation is rarely required
and thus is only provided by application-specific services that might require it. Since ControlNet is not used in
very simple devices, no scaling is required.
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3.2.7. Indicators and Switches
ControlNet devices must be built with Device Status and Network Status indicators as described in the specification. Devices may have additional indicators which must not carry any of the names of those described in
the specification.
Devices may be built with or without switches or other directly accessible means for configuration. If switches
for the MAC ID exist, then certain rules apply regarding how these values must be used at power up and during
the operation of the device.
3.2.8. Additional Objects
Volume 4 defines three additional objects: the ControlNet object, the keeper object and the scheduling object.
3.2.8.1. ControlNet Object (Class ID: 0xF0)
The ControlNet object contains a host of information about the state of the device’s ControlNet interface, among
them diagnostic counters, data link and timing parameters and the MAC ID. A ControlNet object is required for
every physical layer attachment of the device. A redundant channel pair counts as one attachment.
3.2.8.2. Keeper Object (Class ID: 0xF1)
The keeper object (not required for every device) holds (for the network scheduling software) a copy of the
Connection Originator schedule data for all Connection Originator devices using the network. Every ControlNet Network with scheduled I/O traffic must have at least one device with a keeper object (typically, a PLC or
another Connection Originator). If there are multiple keeper objects on a network, they perform negotiations to
determine which Keeper is the Master Keeper and which Keeper(s) perform Backup Keeper responsibilities. The
Master Keeper is the Keeper actively distributing attributes to the nodes on the network. A Backup Keeper is
one that monitors Keeper-related network activity and can transition into the role of Master Keeper should the
original Master Keeper become inoperable.
3.2.8.3. Scheduling Object (Class ID: 0xF2)
The scheduling object is required in every device that can originate an I/O messaging connection. Whenever a network scheduling tool accesses a Connection Originator on a ControlNet Network, an instance of the
scheduling object is created and a set of object-specific services is used to interface with this object. Once the
instance is created, the network scheduling tool can then read and write connection data for all connections
that originate from this device. After having read the connection data from all Connection Originators, the network scheduling tool can calculate an overall schedule for the ControlNet Network and write this data back to all
Connection Originators. The scheduling session is ended by deleting the instance of the scheduling object.
3.2.9. Network Access
ControlNet’s bus access mechanism allows full determinism and repeatability while still maintaining sufficient
flexibility for various I/O message triggers and explicit messaging. This bus access mechanism is called Concurrent Time Domain Multiple Access (CTDMA); it is illustrated in Figure 31.
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Scheduled Service
Network Update Time (NUT)
Unscheduled Service
Network Maintenance Service the “Guardband”
Time
Figure 31 Media Access through CTDMA (Concurrent Time Domain Multiple Access)
The time axis is divided into equal intervals called Network Update Time (NUT). Each NUT is subdivided into the
Scheduled Service Time, the Unscheduled Service Time and the Guardband Time.
Time
SCHEDULED
UNSCHEDULED
GUARDBAND
1
2
1
2
3
n
1
3
3
n
n
SMAX
Maximum scheduled
network address
Max Scheduled Node is
user-selected
Each node is allowed to transmit
exactly once during each interval
(implied token from 1 to SMAX)
Nodes wait one slot-time for each missing
node (network address)
from 1 to SMAX
Example:
node #3 waits one slot time
because device #2 was
turned off
This boundary moves
depending on the utilization of
reserved/configured scheduled
bandwidth
Figure 32 Scheduled Service
Figure 32 shows the function of the Scheduled Service. Every node up to, and including, the SMAX node (maximum node number participating in the Scheduled Service) has a chance to send a message within the Scheduled Service. If a particular node has no data to send, it will send a short frame to indicate that it is still alive. If a
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node fails to send its frame, the next-higher node number will step in after a very short, predetermined waiting
time. This process ensures that a node failure will not lead to an interruption of the NUT cycle.
Figure 33 shows the function of the Unscheduled Service. Since this service is designed for non-time-critical
messages, only one node is guaranteed access to the bus during the Unscheduled Service Time. If there is time
left, the other nodes (with higher node numbers) will also get a chance to send. As with the Scheduled Service
Time, if a node fails to send during its turn, the next node will step in. The node number that is allowed to send
first within the Unscheduled Service Time is increased by one in each NUT. This guarantees an equal chance
to all nodes. When the node sequencing within a NUT reaches the maximum value, known as UMAX, it wraps
around to node 1, and the sequence resumes.
Time
SCHEDULED
UNSCHEDULED
GUARDBAND
8
9
9
10
10
1
11
10
11
12
Permission to transmit is passed
on a round-robin basis
(implied Token from 1 to UMAX)
Nodes wait one slot-time for each
missing node (network address)
from 1 to UMAX
Network address from
previous interval plus one gets
first opportunity to transmit in
interval plus one
2
3
Node number wraps to
“1”
UMAX
Maximum unscheduled
network address
Each node may
transmit many times
........or not at all
Figure
33 Unscheduled Service
These two service intervals, combined with the Guardband, guarantee determinism and repeatability while still
maintaining sufficient freedom to allow for unscheduled message transmissions, e.g., for parameterization.
3.2.10. Network Startup
After power-on, every ControlNet device goes through a process of accessing the ControlNet communication network and learning the current NUT and other timing requirements. This is a fairly complex process typically handled
by commercially available ControlNet ASICs. It is beyond the scope of this book to describe the details here.
3.2.11. Explicit Messaging
Explicit messages on ControlNet, unlike those on DeviceNet, can be sent either connected or unconnected;
both are transmitted within the unscheduled part of the NUT. Connected explicit messaging requires setting up
a connection (see chapter 3.2.13) before messages are exchanged. This means that all resources required for
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managing the connection are reserved for this purpose as long as the connection exists, which allows more
timely responses to message requests. This is very useful when the application requires periodic explicit requests. Most explicit messages also can be sent unconnected, but this mechanism makes use of generally
limited resources in nodes that sometimes can be highly utilized. For this reason, unconnected explicit messaging should be used only when the application requires very irregular and infrequent request intervals. Every
part of an explicit message (request, response, acknowledgements) is wrapped into an Lpacket using the fixed
tag Lpacket format for unconnected explicit messaging (see Figure 29) and the generic tag Lpacket format for
connected explicit messaging (see Figure 30). The service/class/instance/attribute fields (see chapter 2.3) of the
explicit message are contained in the link data field.
3.2.12. I/O Messaging
ControlNet I/O messaging is accomplished using connections, and always takes place in the scheduled part of
the NUT. Only one MAC frame may be transmitted by any device within its time slot, but this MAC frame may
contain multiple Lpackets so that data can be sent to multiple nodes in one NUT. The individual Lpackets may
be consumed by one node only or by multiple nodes if they are set up to consume the same data.
I/O messages use the generic tag Lpacket format (see Figure 30). The link data field contains the I/O data
prefixed with a 16-bit sequence count value for the packet. Run/Idle can be indicated within a prefixed Real-Time Header or by sending the data packet (Run) or no data packet (Idle). The method used is indicated in
the connection parameters of the Connection Manager section of the EDS. However, only the Real-Time Header
method has been used for ControlNet up to now.
3.2.13. Connection Establishment
All connections on ControlNet are established using a UCMM Forward_Open message (see Section 2.3).
3.2.14. Device Classes
Four classes of device functionality are built with CIP. While they are not explicitly defined in the specification,
they are useful for distinguishing among several classes of devices. The four classes are described here:
- The minimal device function is that of an explicit message Server, which is used for explicit messaging
applications only and acts as a target for Unconnected and (optionally) connected explicit messages, e.g.,
for program upload/download, data collection, status monitoring, etc.;
- The next device class is an I/O Server, which adds I/O messaging support to an explicit message Server device and acts as a target for both Explicit and I/O messages, e.g., simple I/O Devices, Pneumatic
Valves, AC Drives. These devices are also called I/O Adapters;
- Another device class is an explicit message client, which adds client support to explicit message Server
applications and acts as a target and as an originator for explicit messaging applications, e.g., computer
interface cards, HMI devices;
- The most powerful type of device is an I/O Scanner, which adds I/O message origination support to the
functionality of all the other device classes, and which acts as a target and as an originator for Explicit and
I/O messages, e.g., PLCs, I/O Scanners.
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3.2.15. Device Profiles
ControlNet devices may utilize any device profiles described in the CIP Networks Library. As of the publication
date of this book, no ControlNet-specific profiles have been defined.
3.2.16. Configuration
ControlNet devices typically come with Electronic Data Sheets (EDS) as described in Section 2.6. For EDSbased configuration tools, the EDS should contain a Connection Manager section to describe the details of the
connections that can be made into the device. This section basically mirrors the contents of the Forward_Open
message that a Connection Originator would send to the device. Multiple connections can be specified within
an EDS, then one or more can be chosen by the configuration tool.
An EDS may also contain individual parameters and/or a configuration assembly with a complete description
of all parameters within this assembly. In many applications, the configuration assembly is transmitted as an
attachment to the Forward_Open message.
3.2.17. Conformance Test
See chapter 6 of this publication for information on conformance testing.
3.2.18. Tools
Tools for ControlNet Networks can be divided into three groups:
- Physical layer tools are tools (hardware and/or software) that verify the integrity and conformance of the
physical layer or monitor the quality of the data transmission;
- Configuration tools are software tools capable of communicating with individual devices for data monitoring and configuration purposes. Most configuration tools are EDS-based; however, more complex devices
like I/O Scanners tend to have their own configuration applets that are only partially based on EDS files.
Some of these tools support multiple access paths to the network, e.g., via Ethernet and suitable routing
devices, and thus allow remote access. High-level tools also actively query the devices on the network to
identify them and monitor their health. Configuration tools also may be integrated into other packages like
PLC programming software;
- Monitoring tools typically are PC-based software packages that can capture and display the ControlNet
frames on the network. A raw ControlNet frame display may be good enough in some instances, but
using a tool that can display both raw ControlNet frames and interpreted frames is recommended.
For a typical installation, a configuration tool is all that is needed. However, to ensure the network is operating
reliably, testing with a physical layer tool is highly recommended. Experience shows that the overwhelming majority of ControlNet network problems are caused by inappropriate physical layer installation. Protocol monitoring
tools are mainly used to investigate interoperability problems and to assist during the development process.
Turn to the ODVA Marketplace on the ODVA website to access a list of vendors that provide tools for ControlNet.
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3.2.19. Advice for Developers
Before any development of a ControlNet product is started, the following issues should be considered in detail:
- What functionality (Device Classes, see chapter 3.2.14) does the product require today and in future applications?
• Explicit messaging server only;
• I/O Adapter functionality;
• Explicit messaging client;
• I/O scanner functionality.
- What are the physical layer requirements? Is IP 65/67 required or is IP 20 good enough?
- Will the development be based on commercially available hardware components and software packages
(recommended) or designed from scratch (possible but costly)?
- What are the configuration requirements?
- What design and verification tools should be used?
- When and where will the product be tested for conformance and interoperability?
- What is an absolute must before products can be placed on the market (own the specification, have the
company’s own vendor ID, have the product conformance tested)?
Rockwell Automation has published a comprehensive developer’s handbook that assists vendors in developing
products, see [44]. ControlNet chipsets and associated software packages are available from Rockwell Automation. Turn to the ODVA website for a list of companies that can support ControlNet developments.
3.2.20. ControlNet Summary
Since its introduction in 1997, ControlNet has been used successfully in millions of nodes in many different applications. It is the network of choice for many high speed I/O and PLC interlocking applications. Like DeviceNet, ControlNet
has become an international standard [31]. Due to its universal communication characteristics, it is one of the most
powerful controller-level networks available.
ControlNet’s greatest strengths are its media redundancy and its full determinism and repeatability. These
strengths make it ideally suited for many applications that require media redundancy and also for many highspeed applications, in which ControlNet maintains full explicit messaging capabilities without compromising its
real-time behavior.
Finally, as a member of the CIP family of networks, ControlNet can be combined into an overall CIP Network
structure that allows seamless communication among CIP Networks, just as if they were only one network.
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3.3. EtherNet/IP
3.3.1. Introduction
Introduced in 2000, EtherNet/IP is another member of the CIP Family. Using CIP as its upper-layer protocol,
EtherNet/IP extends the application of Ethernet TCP/IP to the plant floor. EtherNet/IP can coexist with any other
protocol running on top of the standard TCP/UDP Transport Layer, and with other CIP Networks. EtherNet/IP –
CIP plus Internet and Ethernet standards – provides a pure, unmodified, standards-based Ethernet solution for
interoperability among manufacturing enterprise networks, and it enables Internet and enterprise connectivity
anywhere, anytime utilizing commonly available switches. The “IP” in EtherNet/IP stands for the “Industrial Protocol” in CIP; this is not to be confused with “IP” in TCP/IP which stands for “Internet Protocol”.
Due to the length of Ethernet frames and the typical multi-master structure of Ethernet networks, there are no
particular limitations in the EtherNet/IP implementation of CIP. Basically, all that is required is a mechanism to
encode CIP messages into Ethernet frames.
3.3.2. Relationship to standards
Like other CIP Networks, EtherNet/IP follows the Open Systems Interconnection (OSI) model, an ISO standard
for network communications that is hierarchical in nature. Networks that follow this model define all necessary
functions, from physical implementation up to the protocol and methodology to communicate control and information data within and across networks.
Figure 34 shows the relationship between CIP and EtherNet/IP.
Figure 34 Relationship Between
CIP and EtherNet/IP
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The EtherNet/IP adaptation of CIP is described in Volume 2 of the CIP Networks Library. All other features are
based on CIP. This volume defines how CIP is adapted for use on Ethernet. An encapsulation mechanism (see
chapter 3.3.11) is defined for EtherNet/IP specifying how I/O and explicit messages are carried in Ethernet
frames. The well-known TCP/IP protocol is used for encapsulating explicit messages, while UDP/IP is used for
encapsulating I/O messages. Since the commonly implemented TCP/IP and UDP/IP protocol stacks are used
for encapsulation, many applications will not require extra middleware for this purpose.
Ethernet has its roots in the office computing environment, which is not traditionally concerned with determinism
like industrial applications are. However, with the proper selection and configuration of infrastructure devices
(see chapter 3.3.21) using fast data rates with full duplex communications there will be no collisions or lost
packets, giving Ethernet a level of determinism that is more than adequate for use in industrial control applications. Additionally, extensions to CIP like CIP Sync and CIP Motion (see Section 5.1) allow EtherNet/IP to be
used in highly synchronous and deterministic applications like coordinated drives and motion control.
EtherNet/IP is also described in international standards, i.e., the IEC fieldbus standards, see [27], [31].
3.3.3. EtherNet/IP Features
EtherNet/IP is a communication system built on standard, unmodified Ethernet with the following features:
- Built on and compliant with the relevant Ethernet standards, not just compatible with them;
- Fully independent of data rate: 10, 100, 1000 Mbit/s;
- Systems can be built with standard infrastructure;
- Virtually unlimited number of nodes in a network;
- Networks can be structured into subnets with IP routers;
- Full support of communication across subnets since EtherNet/IP uses IP addressing for all communication;
- Non-realtime communication and realtime communication can coexist in the same subnet;
- Support for coordinated drives and motion control;
- Support for Device Level Ring (DLR) which provides single fault tolerance through media redundancy;
- QuickConnect for devices that are frequently removed from and added to the network, e.g., robot tools;
- Coexistence with other upper-layer protocols, such as HTTP, FTP, VOIP etc.
3.3.4. EtherNet/IP Physical Layer
Since EtherNet/IP takes the Ethernet protocol to the factory floor, recommendations are made in Volume 2 [2]
regarding grounding, isolation and cable and connector construction that are designed to make EtherNet/IP
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successful in a typical factory automation environment. These changes do not affect the actual signaling or
interoperability with standard Ethernet products, but simply make devices more suitable for harsher industrial
environments. As a result, two levels of performance criteria are defined:
- The COTS (Commercial Off The Shelf) EtherNet/IP Level provides basic Ethernet connectivity. This level
includes the well-known RJ-45 type Ethernet connector but specifies topology constraints (e.g., up to 100
m) and cabling requirements through references to specific IEEE, ANSI/TIA/EIA standards. Such devices
are typically suited for IP 20 applications;
- The Industrial EtherNet/IP Level goes beyond the COTS Level by specifying minimum environmental, cabling and connector requirements that include IEC, ANSI/TIA/EIA standards. Connectors required for the
Industrial EtherNet/IP Level include an enhanced performance RJ-45 connector, a sealed RJ-45 connector as well as a more compact, D-coded M 12-4 connector. The sealed RJ-45 and M 12 connectors can
achieve an IP 67 rating.
Cat 5E or Cat 6 shielded or unshielded cables are recommended for EtherNet/IP. The use of shielded cables is
specifically recommended in applications where adjacent material, such as metal cable ducts, may have substantial influence on the characteristics of the cable. In accordance with IEEE 802.3, copper media may be used
only for distances up to 100 m. Fiber-optic media is recommended for longer distances. Fiber-optic media may
also be advisable for applications with very high electromagnetic disturbances or high-voltage potential differences between devices.
ODVA has published a guideline for the installation of Ethernet media, see [15]. This topic is also covered by the
international standard IEC 61784-5-2 [27].
3.3.5. Frame Structure
EtherNet/IP uses standard Ethernet TCP/IP and UDP/IP frames as defined by international standards [22], [47],
[48], [50]. Therefore, no further frame details are described here.
3.3.6. Protocol Adaptation
EtherNet/IP can use all features of CIP. The Ethernet frame is big enough that fragmentation is rarely required. If
it is required, fragmentation is automatically handled by IP fragmentation provided by TCP/IP and UDP/IP. Since
EtherNet/IP is not expected to be used in very simple devices, no further scaling is required.
3.3.7. Indicators and Switches
EtherNet/IP devices that need to conform to the Industrial EtherNet/IP Level must have the two indicators set
forth in the specification: Module Status and Network Status. Devices may have additional indicators which
must not carry any of the names of those described in the specification.
Devices may be built with or without switches or other manual means for configuration.
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3.3.8. Additional Objects
Volume 2 defines the following 11 additional objects that are found only on EtherNet/IP devices. Most of
these objects are only required when the feature they pertain to are implemented. Exceptions to this are
noted where appropriate.
3.3.8.1. TCP/IP Interface Object (Class ID: 0xF5)
The TCP/IP interface object provides a mechanism for configuring a device’s TCP/IP network interface. Examples of configurable items include the device’s IP address, network mask and gateway address. Every
EtherNet/IP must have at least one instance of this class.
3.3.8.2. Ethernet Link Object (Class ID: 0xF6)
The Ethernet Link object maintains configuration parameters, various error counters and status information for
the Ethernet IEEE 802.3 communications interface. Each device has exactly one instance of the Ethernet Link
object for each Ethernet IEEE 802.3 communications interface.
3.3.8.3. Device Level Ring (DLR) Object (Class ID: 0x47)
The DLR object manages all data and behavior associated with the DLR functionality of a device. For further
details on DLR see chapter 3.3.23.2 of this publication.
3.3.8.4. QoS Object (Class ID: 0x48)
The QoS object manages all data and behavior associated with the QoS (Quality of service) functionality of a
device. It includes the settings for DSCP in the IP header and the Frame Prioritization settings for the Ethernet
header. If the device supports DLR, then this class must be implemented, too.
3.3.8.5. Base Switch Object (Class ID: 0x51)
The base switch object provides the CIP application-level interface to basic status information for a Managed
Ethernet switch device. Devices shall implement no more than one instance of the base switch object.
3.3.8.6. Simple Network Management (SNMP) Object (Class ID: 0x52)
The SNMP object provides parameters used to configure aspects of the SNMP Agent in the device.
3.3.8.7. Power Management Object (Class ID: 0x53)
The power management object defines a Sleeping state and a Paused state. The method to trigger the transition from the Sleeping stat to the Paused state is network adaptation-specific.
3.3.8.8. RSTP Bridge Object (Class ID: 0x54)
The RSTP bridge object provides the configuration and diagnostic interface for the RSTP protocol at the bridge
level. For further details on the use of RSTP, see Section 3.3.24 of this publication
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3.3.8.9. RSTP Port Object (Class ID: 0x55)
The RSTP port object provides a configuration and diagnostic interface for the RSTP protocol at the port level.
For further details on the use of RSTP, see Section 3.3.24 of this publication.
3.3.8.10. Parallel Redundancy Protocol (PRP) Object (Class ID: 0x56)
The Parallel Redundancy Protocol (PRP) object provides a configuration and diagnostic interface for PRP parameters, if implemented in the product.
3.3.8.11. PRP Nodes Table Object (Class ID: 0x57)
The PRP node table object keeps the record of all PRP capable nodes that have been detected on the network.
3.3.9. IP Address Assignment
Since the initial development of TCP/IP, numerous methods for configuring a device’s IP address have evolved.
Not all of these methods are suitable for industrial control devices. In the office environment, for example, it is
common for a PC to obtain its IP address via DHCP (Dynamic Host Configuration Protocol), meaning that it can
potentially acquire a different address each time the PC reboots. This is acceptable because the PC is typically a
client device that only makes requests, so there is no impact if its IP address changes.
However, for an industrial control device that is a target of communication requests, the IP address cannot
change at each power up. A PLC, for example, must be at the same address each time it powers up.
In addition, the only interface common to all EtherNet/IP devices is an Ethernet communications port. Some devices may also have a serial port, a user interface display, hardware switches or other interfaces, but these are
not universally shared across all devices. Since Ethernet is the common interface, the initial IP address should at
least be configurable over Ethernet.
The EtherNet/IP Specification, via the TCP/IP interface object, defines a number of ways to configure a device’s
IP address. A device may obtain its IP address via BOOTP (Bootstrap Protocol), via DHCP or via an explicit
Set_Attribute_Single or Set_Attributes_All service. None of these methods is mandated however. As a result,
vendors could choose different methods for configuring IP addresses.
From the user’s perspective, it is desirable for vendors to support some common mechanism(s) for IP address
configuration. The current ODVA recommendations on this subject can be downloaded from the ODVA website [9].
3.3.10. Address Conflict Detection (ACD)
Since IP addresses are often assigned by human interaction or as a default private address by the device manufacturer (e.g., 192.168.1.1), it is not uncommon to find multiple devices on the same network with the same
IP address. This situation is undesirable; therefore, duplicate IP address detection and the subsequent address
conflict resolution has been defined for EtherNet/IP. The ACD mechanism deployed in EtherNet/IP conforms to
the IETF RFC 5227 [62]. Support for ACD is optional; however, any EtherNet/IP device that supports it, must
follow the method described in Volume 2, Appendix F of The EtherNet/IP Specification.
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3.3.11. EtherNet/IP Encapsulation
EtherNet/IP is based entirely on existing TCP/IP and UPD/IP technologies and uses them without any modification.
TCP/IP is mainly used for the transmission of explicit messages while UDP/IP is used mainly for I/O messaging.
The encapsulation protocol defines two reserved TCP/UDP port numbers. All EtherNet/IP devices accept at
least 2 TCP connections on TCP port number 0xAF12. This port is used for all TCP-based explicit messaging,
either connected or unconnected. It is also used for the encapsulation protocol commands that are employed
when setting up communications between nodes. Some encapsulation commands may also be sent to port
0xAF12 via UDP datagrams.
Port 0x08AE is used by any devices that support EtherNet/IP’s I/O messaging over UDP. These messages can
be sent either unicast or multicast by taking advantage of the multicast capabilities of IP. Multicast data flow
makes more efficient use of the available bandwidth and provides for better data consistency across the system.
Being connectionless, UDP is well suited to this purpose as connection management is handled by CIP.
3.3.11.1. General Use of the Ethernet frame
Since EtherNet/IP is completely based on Ethernet with TCP/IP and UDP/IP, all CIP-related messages sent on
an EtherNet/IP network are Ethernet frames with an IP header (see Figure 35).
Ethernet Frame
Ethernet
Header
IP
Header
TCP or UDP
Header
Encapsulation
Header
Encapsulation Data
Trailer
Described in EtherNet/IP
Specification
Figure
35 Relationship Between CIP and Ethernet Frames
The Ethernet header, the IP header and the TCP or UDP headers are described through international standards
(see chapter 3.3.5); therefore, details of these headers are mentioned only in The EtherNet/IP Specification when
it is necessary to understand how they are used to carry CIP.
The encapsulation header contains a command which determines the meaning of the encapsulation data. Many
commands specify the use of the so-called Common Packet Format. I/O messages sent in UDP frames do not
use the encapsulation header, but they still follow the Common Packet Format.
3.3.11.2. Encapsulation Header and Encapsulation Commands
The overall encapsulation packet has the structure described in Figure 36.
70
Encapsulation Packet
Encapsulation Header
Encapsulation Data
Command
Length
Session
Handle
Status
Sender
Context
Options
Command-specific
Data
2 bytes
2 bytes
4 bytes
4 bytes
8 bytes
4 bytes
0 to 65,511 bytes
Figure
36 Structure of the Encapsulation Packet
While the description of some of the encapsulation header details would go beyond the scope of this book, the
command field requires more attention here. However, only those commands that are needed to understand the
EtherNet/IP protocol are described, and their description only lists the main features.
3.3.11.2.1. ListIdentity Command
The ListIdentity command typically is sent as a broadcast UDP message to tell all EtherNet/IP devices to return
a data set with identity information. This command is used by software tools to browse a network.
3.3.11.2.2. RegisterSession/UnRegisterSession Commands
These two commands are used to open and close an Encapsulation Session between two devices. Once a Session is established, it is used to exchange more messages. Only one Session may exist between two devices.
The device receiving the RegisterSession request creates a Session Handle that it returns in the RegisterSession
reply. This value is used to identify messages sent between the two devices that use this Session.
3.3.11.2.3. SendRRData/SendUnitData Commands
The SendRRData Command is used for unconnected explicit messaging, and the SendUnitData Command is
used for connected explicit messaging. The device transmitting the SendRRData request creates a Sender Context value that is returned with the reply. The SendUnitData does not use the Sender Context field.
3.3.11.2.4. Common Packet Format
The Common Packet Format is a construct that provides a way to structure the Encapsulation Data field for those
Encapsulation commands that specify Encapsulation data. The Common Packet Format defines Items that represent different types of information to be exchanged between devices. If the command definition requires it, the
Common Packet Format allows packing of multiple Items into one encapsulation frame, as shown in Figure 37.
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Common Packet Format
Item Count
Address Item
Data Item
Optional Additional Items
2 bytes
Type ID
Length
2 bytes
2 bytes
Data
Type ID
Length
2 bytes
2 bytes
Data
Figure 37 Example of the Common Packet Format
3.3.12. Use of the Encapsulation Data
3.3.12.1. Explicit Messaging
Explicit messages on EtherNet/IP can be sent either connected or unconnected. Connected explicit messaging requires setting up a connection (see chapter 3.3.13) before messages are exchanged. This means that all
resources required for managing the connection are reserved for this purpose as long as the connection exists,
which allows for more timely responses to message requests. This is very useful in applications that require
periodic explicit requests. Explicit messages also can be sent unconnected, but this mechanism makes use of
generally limited resources in nodes that sometimes can be highly utilized. For this reason, unconnected explicit messaging should be used only when the application requires very irregular and infrequent request intervals. Explicit messages on EtherNet/IP are sent with a TCP/IP header and use the SendRRData Encapsulation
Command (unconnected) or the SendUnitData Encapsulation Command (connected). As an example, the full
encapsulation of a UCMM request is shown in Figure 38.
Command
[0x6F]
•••
Length
[bytes]
Session
Handle
72
Sender
Context
Options
[0]
•••
Interface Time- Item Address Address
Data
Data
Message
out
Handle
Count Type
Length
Type
Length Router Request
[0]
[2]
[0]
[0]
[0x00B2]
Packet
Figure 38 UCMM Request Encapsulation
Status
[0]
The Message Router Request Packet noted in the figure contains the CIP message request or response. This
part of the packet follows the general format of explicit messages – the Message Router Request/Response
Format – defined in Volume 1, Chapter 2 of the CIP Networks Library.
3.3.12.2. I/O Messaging
I/O messages on EtherNet/IP are sent with a UDP/IP header. No encapsulation header is required, but the message still follows the Common Packet Format. See Figure 39 for an example.
Item Address Type Address Conn. Sequence Data Type
Data
Count (Sequenced) Length
ID
Number (Connected) Length
[2]
[0x8002]
[8]
[0x00B1]
Sequence Real-Time
Count Value
Header
Data
I/O Data
Figure 39 I/O Message Encapsulation
The data field contains the I/O data prefixed with a 16-bit sequence count value for the packet. I/O data transmission
without the sequence count value is possible, but it is only used for CIP Safety connections. Run/Idle can be indicated
within a Real-Time Header or by sending the packet with I/O data (Run) or without I/O data (Idle). The method used is
indicated in the connection parameters of the Connection Manager section of the EDS. The Real-Time Header method
is recommended [10] for use on EtherNet/IP for interoperability reasons and this is what is shown in Figure 39.
I/O messages from the originator to the target are typically sent as UDP unicast frames, while those sent
from the target to the originator can be sent as UDP multicast or unicast frames. Multicast frames allow other
EtherNet/IP devices to listen to the input data. To avoid having these UDP multicast frames propagating too
widely over the network, the use of switches that support IGMP Snooping is highly recommended. IGMP (Internet Group Management Protocol [61]) is a protocol that allows the automatic creation of multicast groups. Using
this functionality, the switch will automatically create and maintain a multicast group consisting of the devices
that need to consume these multicast messages. Once the multicast groups have been established, the switch
will direct such messages only to those devices that have subscribed to the multicast group of that message.
3.3.13. Connection Establishment
All connections on EtherNet/IP are established using a UCMM Forward_Open message (see chapter 2.3).
3.3.14. QuickConnect Connection Establishment
While most applications can wait several seconds until a connection is established, there are certain applica-
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tion scenarios that require a device to be operational with only a very short delay after the application of power.
Typically, these are devices sitting on an exchangeable tool that a robot would pick up for certain manufacturing
steps. In comparison to DeviceNet, EtherNet/IP devices are more complex and larger and more complex parts
of the communication stack are typically implemented in software, so it will take more time to power up a device. The other additional complexity in EtherNet/IP is the TCP layer with a timeout behavior of its own. Furthermore, active infrastructure (switches) may take a long time to reboot. Under consideration of these conditions,
the following method was developed for a fast establishment of I/O connections:
- If more than one EtherNet/IP device is mounted onto the exchangeable tool, embedded infrastructure with
defined start-up behavior must be used;
- In preparation of a restart, every connection that participates in the QuickConnect application must be
shut down using the Forward_Close service before disconnecting the device;
- When the device has responded to the Forward_Close request, it closes the TCP connection with the I/O Scanner;
- At the restart of any QuickConnect device, the I/O Scanner receives notification of power reapplication
through a contact in the tool changer;
- The I/O Scanner then waits for a predetermined time (described in the EDS) before a connection is reestablished.
Using this methodology, startup times of less than 100 ms can be achieved with current technology; the first
products are available on the market,
The full description of the QuickConnect functionality can be found in Appendix E of The EtherNet/IP Specification.
3.3.15. Device Classes
Four classes of device functionality are built with CIP. While they are not explicitly defined in the specification,
they are useful for distinguishing among several classes of devices. The four classes are described here:
- The minimal device function is that of an explicit message server, which is used for explicit messaging
applications only and acts as a target for Unconnected and (optionally) connected explicit messages, e.g.,
for program upload/download, data collection, status monitoring, etc.;
- The next device class is an I/O Server, which adds I/O messaging support to an explicit message server device and acts as a target for both Explicit and I/O messages, e.g., simple I/O Devices, Pneumatic
Valves, AC Drives. These devices are also called I/O Adapters;
- Another device class is an explicit message client, which adds client support to explicit message server
applications and acts as a target and as an originator for explicit messaging applications, e.g., computer
interface cards, HMI devices;
- The most powerful type of device is an I/O Scanner, which adds I/O message origination support to the
functionality of all the other device classes, and which acts as a target and as an originator for Explicit and
I/O messages, e.g., PLCs, I/O Scanners.
74
3.3.16. Device Profiles
EtherNet/IP devices may utilize any of the device profiles described in the CIP Networks Library. As of the publication date of this book, no EtherNet/IP-specific device profiles have been defined.
3.3.17. Configuration
EtherNet/IP devices typically come with Electronic Data Sheets (EDS) as described in Section 2.7. For EDSbased configuration tools, the EDS should contain a Connection Manager section to describe the details of the
connections that can be made into the device. This section basically mirrors what is contained in the Forward_
Open message that a Connection Originator would send to the device. Multiple connections can be specified
within an EDS that can then be chosen by the configuration tool.
An EDS also may contain individual parameters and/or a configuration assembly with a complete description
of all parameters within this assembly. In many applications, the configuration assembly is transmitted as an
attachment to the Forward_Open message.
3.3.18. Conformance Test
See section 6 of this publication for information on conformance testing.
3.3.19. Requirements for TCP/IP Support
In addition to the various requirements set forth in The EtherNet/IP Specification, all EtherNet/IP hosts are required to have a functional TCP/IP protocol suite and transport mechanism. The minimum host requirements for
EtherNet/IP hosts are those covered in RFC 1122 [55], RFC 1123 [56], and RFC 1127 [57] and the subsequent
documents that may supersede them. Whenever a feature or protocol is implemented by an EtherNet/IP host,
that feature shall be implemented in accordance to the appropriate RFC (Request for Comment) documents,
regardless of whether the feature or protocol is considered required or optional by this specification. The Internet
and the RFCs are dynamic. There will be changes to the RFCs and to the requirements included in this section
as the Internet and The EtherNet/IP Specifications evolve.
All EtherNet/IP devices shall at a minimum support:
- Internet Protocol (IP version 4) (RFC 791 [48]);
- User Datagram Protocol (UDP) (RFC 768 [47]);
- Transmission Control Protocol (TCP) (RFC 793 [50]);
- Address Resolution Protocol (ARP) (RFC 826 [51]);
- Internet Control Messaging Protocol (ICMP) (RFC 792 [49]);
- Internet Group Management Protocol (IGMP) (RFC 1112 [54] & 2236 [61]);
- IEEE 802.3 (Ethernet) as defined in RFC 894 [52].
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Although the encapsulation protocol is suitable for use on other networks besides Ethernet that support TCP/
IP and products may be implemented on these other networks, conformance testing of EtherNet/IP products is
limited to those products on Ethernet. Other suitable networks include:
- Point to Point Protocol (PPP) (RFC 1171 [58]);
- ARCNET (RFC 1201 [59]);
- FDDI (RFC 1103 [53]).
3.3.20. Coexistence of EtherNet/IP and Other Ethernet-Based Protocols
EtherNet/IP devices are encouraged, but not required, to support other Ethernet-based protocols and applications not specified in The EtherNet/IP Specification. For example, they may support HTTP, Telnet, FTP, etc. The
EtherNet/IP protocol makes no requirements with regard to these protocols and applications.
Figure 40 shows the relationship between CIP and other typical Ethernet-based protocol stacks. Since
EtherNet/IP, like many other popular protocols, is based on TCP/IP and UDP/IP, coexistence with many other
services and protocols is not a problem, and CIP blends nicely into the set of already existing functions. This
means that anyone who is already using some or all of these popular Ethernet services can add CIP without undue burden; the existing services like HTTP or FTP may remain as before, and CIP will become another service
on the process layer.
Process
Layer
FTP
Host-to-Host
Layer
Internet
Layer
HTTP
DNS
TCP
OSPF
IGRP
ARP
Network Access
Layer
SNMP
BOOTP
DHCP
UDP
ICMP
IGMP
IP
RARP
Any IP-based Network, i.e. Ethernet
Figure 40 Relationship of CIP to Other Typical Ethernet Protocols
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CIP
3.3.21. Ethernet Infrastructure
3.3.21.1. Traditional approach
To apply EtherNet/IP successfully to the automation world, the issue of determinism has to be considered. The
inherent principle of the Ethernet bus access mechanism, whereby collisions are detected and nodes back off
and try again later, cannot guarantee determinism. While Ethernet in its present form cannot be made strictly
deterministic, there are ways to improve this situation.
First, the hubs typically used in many office environments must be replaced by more intelligent switches
that will forward only those Ethernet frames intended for nodes connected to these switches. By using
wire-speed switching fabric and full duplex switch technology, collisions are completely avoided; instead
of colliding, multiple messages sent to the same node at the same time are queued up inside the switch
and are then delivered one after another.
As already mentioned in Section 3.3.12.2, using switches that support IGMP Snooping is highly recommended.
If EtherNet/IP networks are to be connected to a general company network, this should always be done through
a router. The router keeps the UDP multicast messages from propagating into the company network and ensures that the broadcast or multicast office traffic does not congest the control network. Even though the router
separates the two worlds, it can be set up to allow the TCP/IP-based explicit messages to pass through so
that a configuration tool sitting in a PC in the office environment may be capable of monitoring and configuring
devices on the control network.
3.3.22. Devices with multiple Ethernet Ports
Chapter 6 of Volume 2 of the CIP Specifications describes a number of scenarios for devices with multiple Ethernet ports and how these scenarios are to be mapped in the object structure.
3.3.23. Ring and Linear Topologies
3.3.23.1. Linear Topology
Many end user applications benefit from connecting devices in a linear or ring topology. With such a topology,
end devices typically have two Ethernet ports (with an embedded switch), and are connected in sequence, one
device to the next.
With linear topology a failure of one node or a link between two nodes causes nodes on either side of the failure
to be unreachable. By using a ring protocol implemented in the end devices, these devices may be configured
in a ring topology so that a single-point failure does not prevent communication between the remainder of the
functioning devices.
Node 1
Node 2
Node 3
Figure
41 Linear Topology
Node 4
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3.3.23.2. Ring Topology with Device Level Ring (DLR)
3.3.23.2.1. DLR Overview
The EtherNet/IP specification includes the Device Level Ring (DLR) protocol, allowing multi-port devices to be
connected in a ring topology. DLR provides for fast network fault detection and reconfiguration in order to support the most demanding control applications. For example, a ring network of 50 nodes implementing the DLR
protocol has a worst case fault recovery time of less than 3ms.
The DLR protocol operates at Layer 2 (in the ISO OSI network model). The presence of the ring topology and
the operation of the DLR protocol are transparent to higher layer protocols, such as TCP/IP and CIP, with the
exception of a DLR object that provides a DLR configuration and diagnostic interface via CIP.
There are several classes of DLR implementation, as described below:
- Ring Supervisor:
This class of devices is capable of being a ring supervisor. These devices must implement the required
ring supervisor behaviors, including the ability to send and process Beacon frames at the default Beacon
interval of 400 microseconds and may be user-configured for as fast as 100 microseconds Beacon interval. Ring supervisors must also send Announce frames, for those devices that rely on the Announce frame
mechanism to detect a change in ring status;
- -
Ring Node, Beacon-based:
This class of devices implements the DLR protocol, but without the ring supervisor capability. The device
must be able to process and act on the Beacon frames sent by the ring supervisor. Beacon-based ring
nodes must support Beacon rates from 100 microseconds to 100 milliseconds;
Ring Node, Announce-based:
This class of devices implements the DLR protocol, but without the ring supervisor capability. These devices do not have the capacity to process Beacon frames, so they simply forward Beacon frames received
on one port to the other port and instead rely on Announce frames to indicate the ring state. Announce
frames are sent at a much slower rate than Beacon frames.
3.3.23.2.2. Normal DLR Operation
A DLR network includes at least one node configured to be a ring supervisor, and any number of normal
ring nodes. The ring supervisor sends special frames (“Beacon” and “Announce” frames) to detect ring
fault and ring restoration.
Figure 42 illustrates the normal operation of a DLR network. Each node has two Ethernet ports, has implemented an embedded switch and supports DLR. When a ring node receives a packet on one of its Ethernet ports, it determines whether the packet needs to be received by the ring node itself (e.g., the packet
has this node’s MAC address as the destination MAC address) or whether the packet should be sent out
the other Ethernet port.
78
Active Ring
Supervisor
Beacon
Announce
Ring
Node 1
Beacon
Announce
Ring
Node 2
Ring
Node 3
Ring
Node 4
Figure 42 Normal DLR Operation
The active ring supervisor blocks traffic on one of its ports with the exception of few special frames and does
not forward traffic from one port to other. This configuration avoids a network loop, so only one path exists between any two ring nodes during normal operation.
The active ring supervisor transmits a Beacon frame through both of its Ethernet ports once per beacon interval
(400 microseconds by default). The active ring supervisor also sends Announce frames once per second. The
Beacon and Announce frames serve several purposes:
- The presence of Beacon and Announce frames inform ring nodes to transition from linear topology mode
to ring topology mode;
- Loss of Beacon frames at the supervisor enables detection of certain types of ring faults. (Note that normal ring nodes are also able to detect and announce ring faults);
- The Beacon frames carry a precedence value, allowing selection of an active supervisor when multiple ring
supervisors are configured.
3.3.23.2.3. Ring Faults
Ring faults may include common link failures such as device power failure or media disconnection, or higher
level failures where the physical layer is active but the device has failed.
The ring supervisor detects a ring fault directly via a Link Status message from a ring node, or indirectly via loss
of Beacon frames. When a ring fault is detected, the active ring supervisor reconfigures the network by unblocking traffic on its previously blocked port and flushing its unicast MAC table. The supervisor immediately sends
Beacon and Announce frames with the ring state value indicating that the ring is now faulted.
Ring nodes also flush their unicast MAC tables upon detecting loss of the Beacon in one direction, or upon receipt of Beacon or Announce frames with the ring state value indicating the ring fault state. Flushing the unicast
MAC tables at both supervisor and ring nodes is necessary for network traffic to reach its intended destination
after the network reconfiguration.
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Figure 43 shows the network configuration after a link failure, with the active ring supervisor passing traffic
through both of its ports.
Active Ring
Supervisor
Ring
Node 1
Ring
Node 2
Ring
Node 3
Ring
Node 4
Figure 43 Network Reconfiguration after Link Failure
3.3.23.2.4. Further Information for Developers
Further details of the DLR protocol operation, including event tables, state diagrams, and other implementation
requirements are included in Chapter 9 of the EtherNet/IP specification.
3.3.24. Use of the Rapid Spanning Tree Protocol (RSTP)
In addition to the DLR protocol, the Rapid Spanning Tree Protocol (RSTP) has also been allowed for use in conjunction with EtherNet/IP.
The Rapid Spanning Tree Protocol (RSTP) was originally designed for networks based on a tree topology where
many devices are connected back to an Ethernet switch which in turn can be connected to other Ethernet
switches. RSTP is a mature and widely accepted approach to solve the Ethernet ring recovery issue when one
looks at the most current enhancements to the specification. The IEEE Standard 802.1D 2004 edition incorporated RSTP into that part of the standard. Changes were made by the IEEE Standards committee to RSTP that
make it a suitable recovery mechanism for a ring topology for some automation applications.
Chapter 9 of The EtherNet/IP specification describes the use of RSTP within EtherNet/IP.
3.3.25. Tools
Tools for EtherNet/IP Networks can be divided into four groups:
- Physical layer tools are tools (hardware and/or software) that verify the integrity and conformance of the
physical layer or monitor the quality of the data transmission;
- Commissioning tools: all EtherNet/IP devices need an IP address. In some cases, setting this address can be
obtained only through the Ethernet network (see Section 3.3.9). In these cases, a BOOTP/DHCP server tool,
such as the free BOOTP/DHCP routine downloadable from the Rockwell Automation website, is required;
80
- Configuration tools are software tools capable of communicating with individual devices for data monitoring and configuration purposes. Most configuration tools are EDS-based; however, more complex
devices like I/O Scanners tend to have their own configuration applets that are only partially based on EDS
files. Some of these tools support multiple access paths to the network, e.g., via suitable routing devices.
High-level tools also actively query the devices on the network to identify them and monitor their health.
Configuration tools also may be integrated into other packages like PLC programming software;
- Monitoring tools typically are PC-based software packages (e.g., traffic analyzers or “sniffers”) that can
capture and display the Ethernet frames on the network. A raw Ethernet frame display may be good
enough in some instances, but using a tool that can display both raw Ethernet frames and provide
multiple levels of frame interpretation (IP, TCP/UDP, EtherNet/IP header interpretation) is recommended.
Due to the popularity of Ethernet, a large number of these tools are available, but not all of them support
EtherNet/IP decoding.
In a typical installation, only a commissioning tool and a configuration tool are needed. Protocol monitoring tools
are used mainly to investigate interoperability problems and to assist during the development process.
Turn to the ODVA Marketplace on the ODVA website to access a list of vendors that provide tools for EtherNet/IP.
3.3.26. Advice for Developers
Before any development of an EtherNet/IP product is started, the following issues should be considered in detail:
- What functionality (Device Classes, see Section 3.2.13) does the product require today and in future applications?
• Explicit messaging server only;
• I/O adapter functionality;
• Explicit messaging client;
• I/O scanner functionality.
- What are the physical layer requirements? Is IP 65/67 required or is IP 20 good enough?
- Will the development be based on commercially available hardware components and software packages
(recommended) or designed from scratch (possible but costly)?
- What are the configuration requirements?
- What design and verification tools should be used?
- When and where will the product be tested for conformance and interoperability?
- What is an absolute must before products can be placed on the market (own the specification, have the
company’s own vendor ID, have the product conformance tested)?
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Ethernet chipsets and associated base software packages are available from many vendors. For support of the
EtherNet/IP part of development, refer to the ODVA website for a list of companies that can support EtherNet/IP
development. An extended description of the development process is available for download from the ODVA
website [14].
To help EtherNet/IP developers in creating their products, ODVA runs a series of so-called Implementor Roundtables for EtherNet/IP during which various aspects of EtherNet/IP are discussed. These workshops (with a
North American and a European series) have created a number of documents with functionality recommendations for EtherNet/IP devices, see [9], [10], [11], [12] and [13]. EtherNet/IP devices are then tested against these
recommendations during multi-vendor testing events, called Plugfests. Visit the ODVA web page to learn more
about upcoming EtherNet/IP Implementor Roundtables and Plugfests.
3.3.27. EtherNet/IP Summary
Since its introduction in 2000, EtherNet/IP has shown remarkable growth in many applications that previously
used traditional networks. This success (several million nodes installed to date) is largely attributed to the fact
that EtherNet/IP uses standard, unmodified Ethernet to introduce real-time behavior into the Ethernet domain
without sacrificing any of Ethernet’s most useful features, such as company-wide access with standard and
specialized tools through corporate networks.
A major strength of EtherNet/IP is the fact that it does not require a modified or highly segregated network: standard switches and routers used in the office world can be used for industrial applications without modification.
At the same time, all existing transport-level or TCP/UDP/IP-level protocols can continue to be used without any
need for special bridging devices. The substantially improved real-time behavior of CIP Sync and the introduction of CIP Safety also allow EtherNet/IP to be used in applications that currently require several dedicated
networks.
Finally, as a member of the CIP family of networks, EtherNet/IP Networks can be combined into an overall CIP
Network structure that allows seamless communication among CIP Networks, just as if they were only one
network.
3.4. CompoNet
3.4.1. Introduction
CompoNet is a low-level network that provides high-speed communication between higher-level devices such
as controllers and simple industrial devices such as sensors and actuators. IEC has published CompoNet as
IEC 62026-7 in 2010 [26].
3.4.2. Relationship to Standards
Like other CIP Networks, CompoNet follows the Open Systems Interconnection (OSI) model, an ISO standard
for network communications that is hierarchical in nature. Networks that follow this model define all necessary
functions, from physical implementation up to the protocol and methodology to communicate control and information data within and across networks.
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Figure 44 shows the relationship between CIP and CompoNet.
Figure 44 Relationship
Between CIP and CompoNet
The CompoNet adaptation of CIP is described in Volume 6 of the CIP Networks Library [6]. All other features are
based on CIP. CompoNet is also described in an international standard [26].
3.4.3. CompoNet Features
CompoNet supports both bit-level I/O slaves (BitIN and BitOUT slaves) and byte-level I/O slaves (WordIN and
WordOUT slaves) simultaneously in one network. It also supports intelligent repeaters to expand the network
flexibly and provide network diagnosis [37].
The main features of CompoNet are:
- Selectable data rates: 4 Mbps/3 Mbps/1.5 Mbps/93.75 kbps;
- Single master network with a large number of slave nodes: 384 slave devices maximum including WordIN:
64; WordOUT: 64; BitIN: 128; BitOUT: 128;
- Up to 64 repeaters per network to expand physical covering area and to adapt different cables;
- Up to 32 nodes (slaves and repeaters) per segment;
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- I/O capacity: 1280 input/1280 output points;
- Support for flat 4-wire, round 4-wire and 2-wire cables in bus and branch topologies;
- Maximum of 3 segment layers. This means up to 2 repeaters are allowed between any slave
and the master;
- 30/30/100/500 m maximum trunk cable distance with respect to data rates, 150/150/500/2500 m maximum distance between the most distant slaves with repeaters;
- Trunkline/dropline except for 4 Mbps;
- Efficient communication with multicast polling and Time Division Multiple Access (TDMA).
3.4.4. CompoNet Physical Layer
The physical layer of CompoNet has been designed specifically for this network; it does not reuse any existing
open technology.
CompoNet uses a transformer-coupled transmission method and a Manchester-encoded signal on the wire; the
principle circuit of the physical media attachment is shown in Figure 45.
Transceiver
Coupling
Network
Transformer
Network
Figure 45 Physical Media Attachment of CompoNet
Master ports and slave ports use the same physical media attachment with only minor differences in the coupling network. To help vendors design their CompoNet physical media attachment, ODVA has published recommended circuits for both masters and slaves in Chapter 8 of The CompoNet Specification [6]. Vendors can also
design their own circuits.
3.4.5. Frame Structure
A typical message frame is composed of the Preamble, Command Code, Command Code Dependent Block(s),
and CRC, as shown in Figure 46.
Preamble Command Code Command Code Dependent Block(s)
Checked by CRC
Figure 46 A General Frame
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CRC
All frames use the same Preamble. Two types of CRC generator polynomials, CRC8 (8-bit) and CRC16 (16-bit),
are used depending on which frame is used.
There are seven types of frames with varying lengths of command codes as shown in Figure 47:
Command Code
Meaning
B0
B1
B2
B3
B4
B5
B6
0
0
0
1
x
x
x
OUT
0
0
1
1
x
x
x
TRG
0
1
x
x
1
0
1
1
1
x
x
x
A_EVENT
1
1
0
x
x
x
B_EVENT
0
0
0
0
1
CN
IN
BEACON
Figure 47 Command Code in Frames
- OUT Frame: This is a frame from the Master to the Slaves/Repeaters, which delivers OUT data to OUT
slaves, specifies the group of slaves/repeaters that should report their status and synchronizes the slaves/
repeaters to start time domain timers of the CN and IN frames. Data is organized in 16-bit words and
transmitted, LSB first, word by word in ascending order;
- TRG Frame: This frame functions like the OUT frame except that it contains no output data; it is a trigger
frame sent by the master in place of the OUT frame when it has no outputs to send;
- CN Frame: This frame is used by slaves/repeaters to report their connection status to the master and
notify the master of a request to send an event;
- IN Frame: This is a frame from input slaves to the master with input data. Data is transmitted, LSB first,
word by word in ascending order, if the size is greater than 16 bits;
- A_EVENT Frame: Any node on the network can send A_EVENT frames, used for acyclic message communications. Data is in 16-bit words and transmitted, LSB first, word by word in ascending order;
- B_EVENT Frame This frame is always originated by a master who sets data link parameters or reads the
information as described in Chapter 3.4.9.2. Also, it is used to grant a slave/repeater permission to send
an A_EVENT request or response;
- BEACON Frame: This frame specifies the data rate and sends the initial communication parameters to
slaves/repeaters.
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3.4.6. Protocol Adaptation
CompoNet uses connection-based I/O messaging and unconnected explicit messaging. Thus every device
must have the UCMM (unconnected message manager) function.
3.4.7. Indicators and Switches
CompoNet does not require a product to have indicators. However, if a product includes indicators with any of
the legends in Chapter 9 of The CompoNet Specification, they must follow the behavior specified in that chapter.
Chapter 9 of The CompoNet Specification describes how switches are used to set the MAC address and baud
rate. The MAC address may also be set via explicit messaging.
3.4.8. Additional Objects
The CompoNet Specification defines two additional objects, the CompoNet link object and the CompoNet
repeater object.
3.4.8.1. CompoNet Link Object (Class ID: 0xF7)
The CompoNet link object manages all aspects associated with the CompoNet link, in particular node address
and baud rate as well as the switches associated with MAC address and baud rate. Furthermore, this object
contains information on the allocation of the I/O communication. Within a master device, this object may also
contain information on the slaves that are present on the network.
3.4.8.2. CompoNet Repeater Object (Class ID: 0xF8)
Every repeater device on CompoNet must support one instance of the CompoNet repeater object. Its main
purpose is to monitor the power supply voltage of the subnet it connects to.
3.4.9. Network Access
3.4.9.1. Network Schedule
In a CompoNet network, the master controls bus communications according to its configuration. A master
divides a communication cycle into several time domains or time slots.
CompoNet conducts arbitration under strict time supervision managed by the master. The communication cycle
is partitioned into time domains as shown in Figure 48. Each node obtains the right to send data to the network
within a specified time period after the completion of the OUT time domain.
86
Communication Cycle
OUT
CN
IN
EXTEND
Time Domain Time Domain Time Domain Time Domain
OUT
Time Domain
Figure 48 Time Domains
The first domain of each communication cycle is the OUT time domain. Subsequent domains are the CN time
domain, the IN time domain, and the EXTEND time domain:
- OUT Time Domain: The master sends an OUT frame or a TRG frame in this period;
- CN Time Domain: CN frames are sent in this period. The number of CN frames sent in this time domain
is determined by the master;
- IN Time Domain: IN frames are sent in this period consecutively by all input type devices;
- EXTEND Time Domain: The master executes message communications in this period. Event frames,
i.e., A_EVENT frames and B_EVENT frames, can be sent in this period. BEACON frames shall be sent
periodically. The master can send a BEACON before every OUT Time Domain starts or in an idle EXTEND
Time Domain.
Figure 49 shows the sequence of frames in a Communication Cycle. The master starts the cycle by sending
an OUT frame. The OUT frame is a broadcast message used to send output data to all OUT slaves. Each OUT
slave consumes its output data (up to 16 bits) from its offset in the OUT frame. The completion of the OUT
frame indicates the end of the OUT Time Domain and triggers slaves and repeaters to start the timers that allow
them to correctly participate in the CN Time Domain and the IN Time Domain.
In the CN Time Domain, the slaves or repeaters addressed by the "CN Request MAC ID Mask" field in the OUT
frame will transmit their CN frames at the pre-defined time sequence.
During the IN Time Domain IN frames are sent by any IN devices that are in the Participated State, at the
pre-defined time sequence (see Figure 49). During the IN Time Domain, nodes in the EventOnly Substate do not
transmit an IN frame.
During the EXTEND Time Domain, nodes may transmit an event command frame and possibly an immediate
acknowledge frame, depending on the event type. These can be sent by the master, slaves or repeaters. The
node designated in the event command frame’s Destination MAC ID field will send an event acknowledge frame,
if required by the specific event command. CIP explicit messaging is done during this domain.
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Master
event command
frame
OUT frame
Slave/Repeater
CN frame CN frame
IN frame
event ack. frame
IN frame
frame
The number of CN frames is set by the master.
Either the master or a slave/repeater may send
A_EVENT command frame.
Figure 49 A Typical Communication Cycle
3.4.9.2. Network Access
CompoNet has an algorithm that controls the network access of any of the slaves and repeaters. This is a combination of actions taken by the slave itself and commands from the master using STR (Status Read) and STW
(Status Write) operation.
Starting from power-up, all devices first need to detect the data rate of the network. Once a device has detected
the data rate from the BEACON frames sent by the master, it transitions to the “Non-participated” state. The
device will stay in this state as long as it receives valid frames within the timeout period (650 ms for 93.75 Kbit/s,
200 ms for the other data rates) and no other event occurs. When the master has determined that it is ok for
the slave to transition to the normal operating mode, i.e., no duplicate of the slave’s node number has been
detected, it sends an STW_Run command to the slave and the slave then transitions to the “Participated” state,
which is the normal operating state. The slave will leave this state and fall back to the “Non-participated” state
either when it has experienced a network timeout (no OUT or TRG frames within the timeout period) or when it
receives an STW_Standby command from the master.
The detection of duplicate node IDs is also a combination of master and slave action. The slave will go to the
Communication Fault state if told to do so by the master through an STW_Dup command or when its CN
Counter overflows due to communication errors caused by duplicate node IDs.
3.4.10. Explicit Messaging
CompoNet uses UCMM for explicit messaging; there is no connection-based explicit messaging. Explicit messages are encapsulated into A_EVENT frames as shown in Figure 50.
Preamble Command Destination
Code
MAC ID
Source
MAC ID
Length
Event
Data
Explicit Message
Figure 50 A_EVENT Frame Format
88
CRC
The format of an explicit message is defined to have 2 parts as shown in Figure 51 : Header and Service Data.
The Header is the CompoNet-specific part containing information for flow control, fragmentation protocol and
addresses in a word format. The Service Data part consists of the Request/Response Data as defined in the
Message Router Request/Response format in Volume 1, Chapter 2 of the CIP Networks Library.
Word
offset
B15
…
B00
0 to n
Header: Control Code, Destination MAC ID, Source MAC
ID, SID/Extended SID, Size, Service Code, Class ID,
Instance ID
n+1
to 21
Service Data
Figure 51 CompoNet Explicit Message Format
2 types of explicit message formats are defined:
- Compact - 1 Octet Class ID and Instance ID (required);
- Expanded – CIP EPATH (optional).
A fragmentation protocol is defined optionally for supporting long data transfers in explicit messages.
The SID/Extended SID field is used for reply matching. The client sets the value and the server echoes it back.
Values used are specific to whether the master or the slave is the client in the transaction.
Explicit messaging transactions are subject to timeouts. The default timeout values can be changed by explicit
messages.
3.4.11. I/O Messaging
I/O messages on CompoNet, like on any other CIP network, are always exchanged in a connection-based manner. Communication object s must be set up for this purpose. CompoNet uses a Predefined Allocation service
to establish I/O communication between the master and the slaves. Since these I/O connections are not initially
available when a device is powered on; they first have to be created. This is done by sending an Allocate Service
to the CompoNet link object of the slave that is to be allocated. When an I/O connection is no longer needed,
the slave(s) can be released by sending a Release Service to the slave’s CompoNet link object.
CompoNet uses OUT frames to deliver output data to consuming slaves and to trigger IN frame transmission,
IN frames to deliver produced data to the master and TRG frames to trigger IN frame transmission when the
master has no output data to send.
OUT/TRG frames are monitored by I/O slaves to restart a watchdog timer. If an I/O slave has not received any
OUT/TRG frames before the watchdog timer expires, it will produce a Timeout event. The timer value of the
watchdog is 4 times the Expected Packet Rate (EPR) attribute in the I/O connection instance. A watchdog time-
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out event transitions the connection instance to the “Timeout” state and the application will be notified.
An OUT frame with I/O-Refresh disabled or a TRG frame indicates “Idle”, and an OUT frame with I/O-Refresh
enabled indicates “Run”.
3.4.12. I/O Connection Establishment
As described in Section 3.4.11, I/O messages on CompoNet are always exchanged in a connection-based
manner. Similar to DeviceNet, a CompoNet slave is allocated by the master by sending an Allocate Service to
the CompoNet link object of the slave that is to be allocated.
When an I/O connection is no longer needed, a slave can be released by sending a Release Service to the
slave’s CompoNet link object.
In contrast to DeviceNet, which also uses a predefined master/slave connection set, CompoNet only has one
I/O data exchange mechanism (polled). Therefore, only one type of allocation may take place so there is only a
single Allocation Choice bit defined in the Allocate service.
3.4.13. Device Profiles
3.4.13.1. Bit slave or Word slave
All existing profiles must be realized by using the minimum amount of CompoNet communication. The following
rules apply to the adaptation of existing profiles:
- CompoNet frame rules must be observed;
- If an existing profile can be realized by a Bit Slave, it must be a Bit Slave;
- An existing profile must be realized with the minimal data length that is feasible.
3.4.13.2. Byte size differences
CompoNet uses the same definitions as other CIP network even though it has specific transmission frames. In
order to agree with the data size in bytes as used by CIP, CompoNet needs some rules to align a CompoNet I/O
frame (which counts I/O size in bits) with CIP objects (which typically count data length in bytes).
For bit-level slaves, the related I/O size shown in the connection object instance is rounded up to 1 byte. For example, A BitIN slave with 1 bit valid input data uses IN frames with 2 bits of data to deliver data on the wire, but
the “produced_connection_size” (attribute 7) of its connection instance shall be “1”, which means 1 byte in CIP.
For byte-level slaves, the same sizes shall be used as with other CIP networks. If the CIP byte size does not match
the CompoNet frame size, the size is rounded up to the next even number for the transmission. For example, a
device with 3 bytes of application data will have size 3 in its application object (e.g., the assembly object) and size of 3
for the “produced_connection_size” (attribute 7) of its connection instance, but the IN frames on the wire have 32 bits
of valid data.
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3.4.14. Configuration
CompoNet devices typically come with Electronic Data Sheets (EDS) as described in Section 2.7.
To support EDS-based configuration, several CompoNet-specific EDS keywords have been added. With these
new keywords and most CIP EDS keywords, CompoNet masters can be configured by a tool which can decode CompoNet EDS files. As a minimum (apart from the required sections), CompoNet EDSs should contain
the CompoNet-specific sections that describe the I/O connections available in the slave.
An EDS also may contain individual parameters and/or a configuration assembly with a complete description of all parameters within this assembly.
CompoNet can also be configured by FDT/DTM, which is beyond the scope of CIP [46].
3.4.15. Advice for Developers
Before starting any CompoNet product development, the following issues should be considered in detail:
- What functionality does the product require today and in future applications?
• Slave functionality;
• Master functionality.
- What are the physical layer requirements? Is IP 65/67 required or is IP 20 good enough?
- What type of hardware should be chosen for this product?
- What kind of firmware should be used for this product? Will a commercially available communication stack
be used?
- Will the development of hardware and/or software be done internally or will it be designed by an outside
company?
- What are the configuration requirements?
- What design and verification tools should be used?
- What kind of configuration software should be used for this product? Will a commercially available software package be used, i.e., is an EDS adequate to describe the device or is custom software needed?
- When and where will the product be tested for conformance and interoperability?
- What is an absolute must before my products can be placed on the market (i.e., own the specification,
have the company’s own vendor ID, have the product conformance tested)?
A full discussion of these issues goes well beyond the scope of this publication, see [38], [39] instead. ODVA
provides a developer’s toolkit including working source code for CompoNet slaves and repeaters.
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3.4.16. Conclusions
CompoNet is a well-adapted CIP network. It complies with the CIP object modeling, object addressing as
well as the CIP communication model and its configuration rules. It is easy to realize CIP network routing and
bridging. Combining with its advantages in aspects of data link and physical layer, CompoNet provides unique
solutions with existing CIP resources to vendors and users.
All the changes in automation require consideration of the next generations of networking. In view of these
trends and in view of technologies similar to those described above, it can be seen how much more successful a network can be if it is from the family of CIP Networks in all levels of hierarchy – instead of being patched
together as a result of selecting isolated independent networks specific to each level.
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4. Benefits of the CIP Family
CIP offers distinct benefits for two groups:
- Device manufacturers;
- Users of devices and systems.
4.1. Benefits for Device Manufacturers
For device manufacturers, a major benefit of using CIP is the fact that existing knowledge can be re-used from
one protocol to another, resulting in lower training costs for development, sales and support personnel. Manufacturers also can reduce development costs, since certain parts (e.g., parameters, profiles) of the embedded
firmware that are the same regardless of the network can be re-used from one network to the other. As long as
these parts are written in a high-level language, the adaptation is simply a matter of running the right compiler
for the new system.
Another important advantage for manufacturers is the easy routing of messages from one system to another.
Any routing device can be designed very easily since there is no need to invent a “translation” from one system
to another; both systems already speak the same language. Manufacturers also benefit from working with the
same organizations for support and conformance testing.
4.2. Benefits for the Users of Devices and Systems
For users of devices and systems, a major benefit of using CIP is the fact that existing knowledge can be
re-used from one protocol to another, e.g., through Device Profiles, and device behavior is identical from one
system to another, resulting in lower training costs. Technical personnel and users do not have to make great
changes to adapt an application from one type of CIP Network to another, and the system integrator can
choose the CIP Network that is best suited to his application without having to sacrifice functionality.
Another important CIP advantage is the ease of bridging and routing between CIP Networks. Moving information among incompatible networks is always difficult and cumbersome since there is seldom a direct translation
of all functionality on one network to another. This is where users can reap the full benefits of CIP. Forwarding
data and messages from top to bottom and back again is very easy to implement and uses very little system
overhead. There is no need to translate from one data structure to another – they are the same. Services and
status codes share the same benefit, as these, too, are identical over all CIP Networks. Finally, creating a message
that runs through multiple hops of CIP Networks is simply a matter of inserting the full path from the originating to
the target device. Not a single line of code or any other configuration is required in the routing devices, resulting in
fast and efficient services that are easy to create and maintain. Even though these networks may be used in different parts of the application, messaging from beginning to end really functions as if there is only one network.
Finally, the producer/consumer mechanisms used in all CIP Networks provide highly efficient use of transmission
bandwidth, resulting in system performance that often is much higher than that of other networks running at
higher raw baud rates. With CIP, only the truly important data is transmitted, rather than old data being repeated
over and over again.
Planned and future protocol extension will always be integrated in a manner that allows coexistence of “normal”
devices with “enhanced” devices like those supporting CIP Sync and/or CIP Safety. Therefore, no strict segmentation into “Standard”, CIP Sync and CIP Safety networks is required unless there is a compelling reason, e.g.,
unacceptably high response times due to high bus load.
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5. Application Layer Enhancements
5.1. CIP Sync and CIP Motion
5.1.1. General Considerations
While CIP Networks [1]-[4], [6] provide real-time behavior that is appropriate for many applications, a growing
number of applications require even tighter control of certain real-time parameters. Let us have a look at some
of these parameters:
- Real-Time:
This term is being used with a variety of meanings in various contexts. For further use in this section the following definition is used: A system exhibits real-time behavior when it can react to an external stimulus within a predetermined time. How short or how long this time is depends on the application. Demanding industrial control
applications require reactions in the millisecond range while, in some process control applications, a reaction
time of several seconds or more is sufficient;
- Determinism:
A deterministic system allows for a worst-case scenario (not a prediction or a probability) when deciding on
the timing of a specific action. Industrial communication systems may offer determinism to a greater or lesser
degree, depending on how they are implemented and used. Networks featuring message transmission at a predetermined point in time, such as ControlNet, Sercos Interface and Interbus-S, are often said to offer absolute
determinism. On the other hand, networks such as Ethernet may become non-deterministic under certain load
conditions; specifically, when it is deployed in half-duplex mode with hubs. However, when Ethernet is deployed
with full-duplex, high-speed switches, it operates in a highly deterministic manner (see Section 3.3.21);
- Reaction Time:
In an industrial control system, the overall system reaction time is what determines real-time behavior. The
communication system is only one of several factors contributing to the overall reaction time. In general, reaction
time is the time from an input stimulus to a related output action;
- Jitter:
This term defines the time deviation of a certain event from its average occurrence. Some communication systems rely on very little message jitter, while most applications require only that a certain jitter is not exceeded for
actions at the borders of the system, such as input sampling jitter and output action jitter;
- Synchronicity:
Distributed systems often require certain actions to occur in a coordinated fashion, i.e., the actions must take place
at a predetermined moment in time, independent of where the action is to take place. A typical application is coordinated motion or electronic gearing. Some of these applications require synchronicity in the microsecond range;
This is a system’s capability to process a certain amount of data within a specific time span. In communication systems,
protocol efficiency, the communication model (e.g., producer/consumer) and end point processing power are most
important, while the wire speed only sets the limit of how much raw data can be transmitted across the physical media.
CIP Sync is a communication principle that enables synchronous low jitter system reactions without the need
for low jitter data transmission. This is of great importance in systems that do not provide absolute deterministic
94
data transmission or where it is desirable for a variety of higher layer protocols to run in parallel with the application system protocol. The latter situation is characteristic of Ethernet. Most users of TCP/IP-based Ethernet
want to keep using it as before without the need to resort to a highly segregated network segment to run the
real-time protocol. The CIP Sync communication principle meets these requirements.
5.1.2. Using IEEE 1588 Clock Synchronization
The published IEEE standard 1588 – Standard for a Precision Clock Synchronization Protocol for Networked
Measurement and Control Systems [40] – lays the foundation for a precise synchronization of real-time clocks in
a distributed system.
An IEEE 1588 system consists of a Time Master that distributes its system time to Time Slaves in a tree-like
structure. The Time Master may be synchronized with another real-time clock further up in the hierarchy while
the Time Slaves may be Time Masters for other devices “below” them. A Time Slave that is Time Master to
another set of devices (typically, in another part of the system) is also called a Boundary Clock. The time distribution is done by multicasting a message with the actual time of the master clock. This message originates in a
relatively high layer of the communication stack and, therefore, the actual transmission takes place at a slightly
later point in time. Also, the stack processing time varies from one message to another. To compensate for this
delay and its jitter, the actual transmission time can be captured in a lower layer of the communication stack,
such as noting the “transmit complete” feedback from the communication chip. This update time capture is then
distributed in a follow-up message. The average transmission delay also is determined so that the time offset
between the master and slave clock can be compensated.
This protocol has been fully defined for Ethernet UDP/IP systems, and the protocol details for further industrial
communication systems will follow. The clock synchronization accuracy that can be achieved with this system
depends largely on the precision time capture of the master clock broadcast message. Hardware-assisted time
capture systems can reach a synchronization accuracy of 250 ns or less. Some Ethernet chip manufacturers
offer integrated IEEE 1588 hardware support.
5.1.3. Additional Object
CIP Sync requires the addition of a time synchronization object.
5.1.3.1. Time Sync Object, (Class ID: 0x43)
The time sync object manages the real-time clock inside a CIP Sync device and provides access to the IEEE
1588 timing information.
5.1.4. Fundamentals of CIP Sync Communication
Real-time clocks coordinated through the IEEE 1588 protocol do not, of their own accord, constitute a real-time
system yet. Additional details showing how time stamping is used for input sampling and for the coordination of
output actions need to be added. Some Device Profiles need to be extended as well to incorporate time information in their I/O assemblies.
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5.1.5. Message Prioritization
Combining these three elements (Sections 5.1.2, 5.1.3 and 5.1.4) in conjunction with a collision-free infrastructure
(see Section 3.3.21) is sufficient to build a real-time system. However, it is necessary to consider all traffic within the
system and to arrange all application messages containing time-critical data in such a way that they are guaranteed to arrive at all consumers in time. When other Ethernet protocols – such as HTTP or FTP, which may have
very long frames – need to coexist in the same system, careful configuration may be required. Ethernet frames with
up to 1,500 bytes of payload (approximately 122 µs long in a 100-Mbit/second system) can easily congest the
system and delay important messages by an undetermined amount of time, possibly too long for the system to
function correctly.
This is where message prioritization, known as Quality of Service (QoS) in the Ethernet world, becomes an important element. EtherNet/IP defines common usage for two standard QoS mechanisms: Differentiated Services
(Diffserv) and IEEE 802.1Q tagged frames. These schemes are supported by many switches available today. QoS
allows preferential treatment of Ethernet frames in such a way that those frames with the highest priority will jump
the message queues in a switch and will be transmitted first. Messages with high priority will be transmitted while
those with lower priority typically have to wait. Suitable priority assignments for all time-critical messages then guarantee their preferential treatment. Standard EtherNet/IP and other Ethernet messages will receive low or no priority
and thus have to wait until all higher-priority messages have passed. Once this prioritization scheme is implemented, one full-length frame can be accommodated within each communication cycle consisting of a set of prioritized
input (port A through port E) and output (port F) messages. Figure 52 illustrates this process.
Port A
Port B
Port C
Port D
Port E
1
6
3
9
5
7
4
8
2
CIP
frames with
priority
Port F
Ethernet frame
without priority
1 3 4 5
2
6 7 8 9
Result after
priorization in the
switch
The numbers inside the frames indicate their relative arrival time at the switch port
Figure 52 Ethernet Frame Prioritization
The overall approach to QoS for EtherNet/IP calls for devices to mark their packets with a priority value, using
Diffserv Code Points and/or 802.1D priority values. By explicitly marking packets with a priority value, switches
and routers are able to differentiate EtherNet/IP traffic from non-critical traffic, as well as differentiate specific
EtherNet/IP traffic streams (e.g., IEEE 1588 vs. I/O vs. explicit messaging).
96
The following list summarizes the QoS behavior for EtherNet/IP:
- For CIP transport class 0 and 1 connections (i.e., UDP-based), there is a defined mapping of CIP priorities
to 802.1D priorities and DiffServ Code Points;
- For UCMM and CIP transport class 3 connections (i.e., TCP-based), there is a single defined DiffServ
Code Point and 802.1D priority value;
- For PTP (IEEE 1588) messages, there are DiffServ Code Points and 802.1D priority values corresponding
to the two different types of PTP messages;
- When QoS is implemented, the default behavior is to mark packets with DSCP values. Devices may optionally support sending and receiving 801.1Q frames with the corresponding priority values. If supported,
sending tagged frames is disabled by default in order to prevent device interoperability problems. The end
user is responsible for enabling the tagged frame behavior and ensuring interoperability between devices;
- The QoS Object provides a means to configure DSCP values, and a means to enable/disable sending of
802.1Q tagged frames;
- There are no requirements for devices to mark traffic other than CIP or IEEE 1588, but devices are free to
do so.
5.1.6. Applications of CIP Sync
Typical applications for CIP Sync are time-stamping sensor inputs, distributed time-triggered outputs and distributed motion, such as electronic gearing or camming applications. For example, in motion applications, sensors
sample their actual positions at a predetermined time, i.e., in a highly synchronized way, and transmit them to the
application master that coordinates the motion. The application master then calculates the new reference values
and sends them to the motion drives. Using CIP Sync, the communication system is not required to have extremely low jitter; it is sufficient to transmit all time-critical messages, and their exact arrival time becomes irrelevant. The
assignment of suitable priorities to CIP Sync communication guarantees that all time-critical messages always
have the bandwidth they need, and all other traffic automatically is limited to the remaining bandwidth.
As a result of these measures, CIP Sync devices can coexist side by side with other EtherNet/IP devices
without any need for network segmentation or special hardware. Even non-EtherNet/IP devices – provided
they do not override any of the CIP Sync prioritizations – can be connected without any loss of performance in the CIP Sync application.
5.1.7. Expected Performance of CIP Sync Systems
As mentioned, CIP Sync systems can be built to maintain a synchronization accuracy of better than 250 ns, in
many cases without the use of Boundary Clocks. The communication cycle and thus the reaction delay to unexpected events is largely governed by the number of CIP Sync devices in a system. Allowing some bandwidth
(approx. 40%) for non-CIP Sync messages as described in Section 5.1.5, the theoretical limit (close to 100%
wire load) for the communication cycle of a CIP Sync system based on a 100-Mbit/s Ethernet network is around
500 µs for 30 coordinated motion axes, with 32 bytes of data each.
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5.1.8. CIP Sync Summary
CIP Sync is a natural extension of the EtherNet/IP system into the real-time domain. Unlike many other proposed or existing real-time extensions to other protocols, CIP Sync does not require any strict network segmentation between high-performance, real-time sections and other parts of the communication system. CIP Sync
provides the ability to mix parallel TCP/IP-based protocols with industrial communication architectures of any
size without compromising performance.
CIP Sync currently has been applied to EtherNet/IP, and an extension to other CIP implementations will follow.
5.1.9. CIP Sync and CIP Motion
CIP Motion utilizes CIP Sync to manage real-time motion control. As discussed previously, CIP Sync utilizes the
IEEE-1588 “Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control
Systems” [40] to synchronize devices to a very high degree of accuracy. CIP Sync encapsulates the IEEE-1588
services which measure network transmission latencies and correct for infrastructure delays. The result is the
ability to synchronize distributed clocks to within hundreds of nanoseconds of accuracy, or less.
Once all the devices in a control system share a synchronized, common, understanding of system time, real-time control can be accomplished by including time as a part of the motion information. Unlike the traditional
approaches to motion control, the CIP Motion solution doesn’t schedule the network to create determinism.
Instead, CIP Motion delivers the data and the timestamp for execution as a part of the packet on the network.
This allows motion devices to plan and follow positioning path information according to a pre-determined execution plan. Since the motion controller and the drives share a common understanding of time, the motion controller can tell the drive where to go – and what time to be there. This direct use of time in the data packet frees the
network from the constraint of a rigid data delivery schedule. If data delivery fluctuates slightly on the network
– the motion execution is unaffected.
There are many benefits to this approach. Since the network is not “scheduled” there is flexibility in the amount of
data that can be sent back from each device. During runtime, a drive can be re-configured to send more or less
data depending on the needs of the application. In addition, devices can be added or removed from the system
because specific time slots are not allocated from the network bandwidth. The motion data packets that move
between drives and controllers contain all the relevant information required for real-time motion execution; as long
as basic clock synchronization is maintained - time is used as the event for execution – not the data delivery itself.
5.1.10. CIP Motion
CIP Motion was added to the CIP Networks Library in 2006, with the addition of the CIP Motion Axis Object and
the CIP Motion Device Profile.
5.1.10.1. CIP Motion Profile
The CIP application profile used on EtherNet/IP provides a comprehensive set of services and device profiles
that provide a wide range of functionality and device support. CIP Motion extends the CIP capability by defining
extensions focused on drive control as listed below:
98
- Torque, velocity, or position control of servo and VFDs (Variable Frequency Drives)
- Servo drive and VFD configuration, status, and diagnostic parameters
- Support for feedback-only axes that can provide reference information for camming and lineshafting applications;
- Unicast control-to-drive communications;
- Multicast peer-to-peer communications (future).
The CIP Motion profile is designed to minimize the differences between servo drive and VFD handling. This
facilitates features like common configuration services, common status and diagnostic services, and common
application instruction support for servo drives and VFDs making them interchangeable at the application level.
The CIP Motion profile takes advantage of the latest advances in motion control technology to provide a comprehensive, state of the art profile. Extensive use of floating point data eliminates the complexity typically associated with integer math and scaling. The profile focuses on a simplified slave interface, making it easier for drive
vendors to develop products that connect to the EtherNet/IP network and utilize the CIP Motion extensions.
5.2. CIP Safety
Like other safety protocols based on industry standard networks, CIP Safety adds additional services to transport data with high integrity. Unlike other networks, CIP Safety presents a scalable, network-independent
approach to safety network design, one in which the safety services are described in a well-defined layer. Since
safety functionality is incorporated into each device – rather than in the network infrastructure – CIP Safety
allows both standard and safety devices to operate on the same open network. This capability gives users
a choice of network architectures – with or without a safety PLC – for their functional safety networks. This
approach also enables safety devices from multiple vendors to communicate seamlessly across standard CIP
Networks to other safety devices without requiring difficult-to-manage gateways.
A complete definition of all details of CIP Safety can be found in Volume 5 [5].
5.2.1. General Considerations
Hardwired safety systems employ safety relays that are interconnected to provide a safety function. Hardwired
systems are difficult to develop and maintain for all but the most basic applications. Furthermore, these systems
place significant restrictions on the distance between devices.
Because of these issues, as well as distance and cost considerations, implementing safety services on standard
communication networks is highly preferable. The key to developing safety networks is not to create a network
that cannot fail, but to create a system where failures in the network cause safety devices to go to a known
state. If the user knows which state the system will go to in the event of a failure, they can make their application
safe. But this means that significantly more checking and redundant coding information is required.
So, to determine the additional safety requirements, the German Safety Bus committee [32] implemented and
later extended an existing railway standard [33]. This committee provided design guidelines to safety network
developers to allow their networks and safety devices to be certified according to IEC 61508 [24]. The latest
version of this document has been published as GS-ET-26 [34].
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Based on these standards, CIP was extended for high-integrity safety services. The result is a scalable, routable,
network-independent safety layer that alleviates the need for dedicated safety gateways. Since all safety devices
execute the same protocol, independent of the media on which they reside, the user approach is consistent and
independent of media or network used.
CIP Safety is an extension to standard CIP that has been approved by TÜV Rheinland for use in IEC 61508 SIL
3 and EN 954-1 Category 4 applications, now ISO 13849-1, performance level e [35]. It extends the model by
adding CIP Safety application layer functionality, as shown in Figure 53. The additions include several safety-related objects and Safety Device Profiles with specific implementation details of CIP Safety as implemented on
DeviceNet, EtherNet/IP and Sercos.
Figure 53 CIP Communication
Layers Including Safety
Because the safety application layer extensions do not rely on the integrity (see Section 5.2.3) of the underlying
standard CIP as described in Section 2 and data link layers as described in Sections 3.1, 3.2 and 3.3, single
channel (non-redundant) hardware can be used for the data link communication interface. This same partitioning of
functionality allows the use of standard routers for safety data, as shown in Figure 54. Routing safety messages is
possible because the end device is responsible for ensuring the integrity of the data. If an error occurs during data
transmission or in the intermediate router, the end device will detect the failure and take appropriate action.
This routing capability allows the creation of safety cells on one network, e.g., DeviceNet, with quick reaction
times to be interconnected with other cells via a backbone network such as EtherNet/IP for interlocking, as
shown in Figure 55. Only the safety data that is needed is routed to the required cell, which reduces individual
bandwidth requirements. The combination of rapidly responding local safety cells and the inter-cell routing of
safety data allows users to create large safety applications with fast response times. Another benefit of this configuration is the ability to multicast safety messages across multiple networks.
100
CIP Safety
App. Objects
CIP Safety
App. Objects
CIP Safety
Connection
CIP Safety
Connection
CIP Routing
DeviceNet
Transport &
Data Link
Layer
DeviceNet
Transport &
Data Link
Layer
EtherNet/IP
Transport &
Data Link
Layer
DeviceNet
EtherNet/IP
Transport &
Data Link
Layer
EtherNet/IP
Figure 54 Routing of Safety Data
Safety
PLC
EtherNet/IP
Safety
Safety
PLC
Router
Router
DeviceNet
Safety 1
I
I
O
Safety
PLC
Router
DeviceNet
Safety 2
I
I
O
DeviceNet
Safety 3
Safety
PLC
I
O
Figure 55 Network Routing
5.2.2. Implementation of Safety
As indicated in Figure 53, all CIP Safety devices also have underlying standard CIP functionality. The extension
to the CIP Safety application layer is specified using a Safety validator object. This object is responsible for managing the CIP Safety Connections (standard CIP Connections are managed through communication objects)
and serves as the interface between the safety application objects and the link layer connections, as shown in
Figure 56. The safety validator ensures the integrity of the safety data transfers by applying the measures described in Section 5.2.3.
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Producing
Safety
Application
Data Connection
Safety
Validator
Client
Data
Producer
Data
Consumer
Safety
Validator
Server
Safety_Data
Production
Safety_Data
Reception
Safety_Ack
Reception
Safety_Ack
Production
Consuming
Safety
Application
Time Coordination
Connection
Data
Consumer
Data
Producer
Figure 56 Relationship of Safety Validators
Functions performed by the safety validator object:
- The producing safety application uses an instance of a Client Validator to produce safety data and ensure
time coordination;
- The client uses a link data producer to transmit the data and a link consumer to receive time coordination
messages;
- The consuming safety application uses a Server Validator to receive and check data;
- The server uses a link consumer to receive data and a link producer to transmit time coordination messages.
- The link producers and consumers have no knowledge of the safety packet and fulfill no safety function
The responsibility for high-integrity transfer and checking of safety data lies within the safety validators.
102
5.2.3. Ensuring Integrity
CIP Safety does not prevent communication errors from occurring; rather, it ensures transmission integrity by
detecting errors and allowing devices to take appropriate actions. The safety validator is responsible for detecting these communication errors. The nine communication errors which must be detected are shown in Figure
57, along with the five measures CIP Safety uses to detect these errors [33].
Measures to detect communication errors
Communication
Errors
Time Expectation
via time stamp
ID for send
and receive
Message Repetition
X
X
Message Loss
X
X
Message Insertion
X
Incorrect Sequence
X
Redundancy
with Cross
Checking
Diverse
measure
*
*
X
X
*
X
*
Message Corruption
Message Delay
Safety CRC
X
X
X
X
X
Coupling of safety
and safety data
X
Coupling of safety
and standard data
X
Increased age of data
in bridge
X
X
X
* The Safety CRC provides additional protection for communication errors in fragmented messages.
Figure
57 Error Detection Measures
5.2.3.1. Time Expectation via Time Stamp
All CIP Safety data are produced with a time stamp that allows Safety Consumers to determine the age of the
produced data. This detection measure is superior to the more conventional reception timers. Reception timers
can tell how much time has elapsed since a message was last received, but they do not convey any information
about the actual age of the data. A time stamp allows transmission, media access/arbitration, queuing, retry and
routing delays to be detected.
Time is coordinated between producers and consumers using ping requests and ping responses, as shown in
Figure 58. After a connection is established, the producer generates a ping request, which causes the consumer
to respond with its consumer time. The producer will note the time difference between the ping production and
the ping response and store this as an offset value. The producer will add this offset value to its producer time
for all subsequent data transmissions. This value is transmitted as the time stamp. When the consumer receives
a data message, it subtracts its internal clock from the time stamp to determine the data age. If the data age is
less than the maximum age allowed, the data are applied; otherwise, the connection goes to the safety state.
The device application is notified so that the connection safety state can be reflected accordingly.
The ping request-and-response sequence is repeated periodically to correct for any producer or consumer time
base drift.
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Producer
Consumer
Count
Count
0
89
Ping
1
90
2
91
2 92
3
e=9
m
i
t
r
4
93
ume
Cons
Offset = 92-5 = 87
5
94
6
95
7
96
Time Sta
Time Stamp = 87+8 = 95
8
97
mp = 95
Max. Age = 98-95 = 3
9
98
99
10
11
100
12
101
102
13
T
im
e Stamp
Time Stamp = 87+14 = 101 14
= 101 103
104 Max. Age = 104-101 = 3
15
105
16
106
17
Figure
58 Time Stamp
5.2.3.2. Production Identifier (PID)
A Production Identifier is encoded in all data produced by a Safety Connection to ensure that each received message
arrives at the correct consumer. The PID is derived from an electronic key, the device serial number and the CIP connection serial number. Any safety device inadvertently receiving a message with the incorrect PID will go to a safety
state. Any safety device that does not receive a message within the expected time interval with the correct PID will
also go to a safety state. This measure ensures that messages are routed correctly in multi-network applications.
5.2.3.3. Safety CRC (Cyclic Redundancy Code)
All safety transfers on CIP Safety use Safety CRCs to ensure the integrity of the transfer of information. The
Safety CRCs serve as the primary means of detecting possible corruption of transmitted data. They provide
detection up to a Hamming distance of four for each data transfer section, though the overall Hamming distance
coverage is greater for the complete transfer due to the protocol’s redundancy. The Safety CRCs are generated
in the Safety Producers and checked in the Safety Consumers. Intermediate routing devices do not examine
the Safety CRCs. Thus, by employing end-to-end Safety CRCs, the individual data link CRCs are not part of
the safety function. This eliminates certification requirements for intermediate devices and helps to ensure that
the safety protocol is independent of the network technology. The Safety CRC also provides a strong protection
mechanism that allows detection of underlying data link errors, such as bit stuffing or fragmentation.
104
While the individual link CRCs are not relied on for safety, they are still enabled. This provides an additional level
of protection and noise immunity by allowing data retransmission for transient errors at the local link.
5.2.3.4. Redundancy and Cross-check
Data and CRC redundancy with cross-checking provides an additional measure of protection by detecting
possible corruption of transmitted data. By effectively increasing the Hamming distance of the protocol, these
measures allow long safety data packets – up to 250 bytes – to be transmitted with high integrity. For short
packets of two bytes or less, data redundancy is not required; however, redundant CRCs are cross-checked
to ensure integrity.
5.2.3.5. Diverse Measures for Safety and Standard
The CIP Safety protocol is present only in safety devices, which prevents standard devices from masquerading
as safety devices.
5.2.4. Safety Connections
CIP Safety provides two types of Safety Connections:
- Unicast Connections;
- Multicast Connections.
A Unicast Connection, as shown in Figure 59, allows a safety validator client to be connected to a safety validator Server using two link-layer connections
Producing
Safety
Application
Data Connection
Safety
Validator
Client
Data
Producer
Data
Consumer
Safety
Validator
Server
Safety_Data
Production
Safety_Data
Reception
Safety_Ack
Reception
Safety_Ack
Production
Consuming
Safety
Application
Time Coordination
Connection
Data
Consumer
Data
Producer
Figure 59 Unicast Connection
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A Multicast Connection, as shown in Figure 60, allows up to 15 safety validator servers to consume safety
data from a safety validator client. When the first safety validator server establishes a connection with a safety
validator client, a pair of link layer connections are established, one for data-and-time correction and one for
time coordination. Each new safety validator server uses the existing data-and-time correction connection and
establishes a new time coordination connection with the safety validator client.
Producing
Safety
Application
Safety
Validator
Client
Safety_Data
Production
Safety_Ack
Reception
Consuming
Safety
Application
1
Data Connection 1
Data
Producer
Data
Consumer
Time Coordination
Connection 1
Data
Producer
Data
Consumer
Time
Correction
Production
Safety
Validator
Server 1
Safety_Data
Reception
Safety_Ack
Production
Time
Correction
Reception
Consuming
Safety
Application
2
Data Connection 2
Data
Producer
Data
Consumer
Time Coordination
Connection 2
Data
Producer
Data
Consumer
Safety
Validator
Server 2
Safety_Data
Reception
Safety_Ack
Production
Time
Correction
Reception
Figure
60 Multicast Connection
106
To optimize throughput on DeviceNet, each Multicast Connection uses three data link connections, as shown in
Figure 61.
Producing
Safety
Application
Consuming
Safety
Application
1
Data Connection 1
Data
Producer
Safety
Validator
Client
Safety_Data
Production
Safety_Ack
Reception
Data
Consumer
Time Coordination
Connection 1
Data
Producer
Time
Correction
Production
Data
Consumer
Time Correction
Connection 1
Data
Consumer
Safety
Validator
Server 1
Safety_Data
Reception
Safety_Ack
Production
Time
Correction
Reception
Data
Producer
Consuming
Safety
Application
2
Data Connection 2
Data
Producer
Data
Consumer
Time Coordination
Connection 2
Data
Producer
Data
Consumer
Time Correction
Connection 2
Data
Producer
Safety
Validator
Server 2
Safety_Data
Reception
Safety_Ack
Production
Time
Correction
Reception
Data
Consumer
Figure 61 Multicast Connection on DeviceNet
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CIP Safety implementations on other networks do not require this split. The data-and-time correction messages
are sent on separate connections. This allows short messages to be transmitted on DeviceNet within a single
CAN frame and reduces the overall bandwidth, since the time correction and time coordination messages are
sent at much slower periodic intervals.
When multicast messages are routed off-link, the router combines the data-and-time correction messages
from DeviceNet and separates them when messages reach DeviceNet. Since the safety message contents are
unchanged, the router provides no safety function.
5.2.5. Message Packet Sections
CIP Safety has four message sections:
- Data;
- Time-stamp;
- Time correction;
- Time coordination.
The description of these formats goes beyond the scope of this book. For available materials on this topic that
go into more detail see [5], [36].
5.2.6. Configuration
Before safety devices can be used in a safety system, they first must be configured and connections must be
established. The process of configuration requires placement of configuration data from a configuration tool in a
safety device. There are two possible sequences for configuration:
- Configuration tool directly to device;
- Via an intermediate device.
In the configuration tool-to-device case, as shown in Figure 62, the configuration tool writes directly to the device to be configured (1), (2).
(T (1)
oo D
l t ow
o
Or nlo
igi ad
na
tor
)
Originator
Device
(3) Download
(Originator to Target Download)
(4) SafetyOpen Configuration
Figure 62 Configuration Transfers
108
ad )
nlo get
ow Tar
)D o
(2 ol t
o
(T
Safety Network
Configuration Tool
Target
Device
In the case of intermediate device configuration, the tool first writes to an originator (1) and the originator writes
to the target using an Originator-to-Target Download (3) or a SafetyOpen service (4). The SafetyOpen service (4)
is unique in that it allows a safety connection to be established at the same time that a device is configured.
5.2.7. Connection Establishment
CIP provides a connection establishment mechanism, using a Forward_Open service that allows producer-to-consumer connections to be established locally or across multiple networks via intermediate routers. An
extension of the Forward_Open, called the SafetyOpen service, has been created to allow the same multi-network connections for safety.
There are two types of SafetyOpen requests:
- Type 1: With configuration;
- Type 2: Without configuration.
With the Type 1 SafetyOpen request, configuration and connections are established at the same time, allowing
rapid configuration of devices with simple and relatively small configuration data.
With the Type 2 SafetyOpen request, the safety device first must be configured and the SafetyOpen request
then establishes a Safety Connection. This separation of configuration and connection establishment allows the
configuration of devices with large and complex configuration data.
In both cases, the SafetyOpen request establishes all underlying link layer connections – across the local network as well as any intermediate networks and routers.
5.2.8. Configuration Implementation
CIP Safety provides the following protection measures to ensure configuration integrity:
- Safety Network Number;
- Password Protection;
- Configuration Ownership;
- Configuration Locking.
5.2.8.1. Safety Network Number
The Safety Network Number provides a unique network identifier for each network in the safety system. The Safety Network Number, combined with the local device address, allows any device in the safety system to be uniquely addressed.
5.2.8.2. Password Protection
All safety devices support the use of an optional password. The password mechanism provides an additional
protection measure, prohibiting the reconfiguration of a device without the correct password.
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5.2.8.3. Configuration Ownership
The owner of a CIP Safety device can be specified and enforced. Each safety device can specify that it be configured only by a selected originator, or that the configuration is accomplished by a configuration tool.
5.2.8.4. Configuration Locking
Configuration Locking provides the user with a mechanism to ensure that all devices have been verified and
tested prior to being used in a safety application.
5.2.9. Safety Devices
The relationship of the objects within a safety device is shown in Figure 63. Note that CIP Safety extends the
CIP object model, with the addition of Safety I/O assemblies, safety validator and Safety Supervisor Objects.
Application
Objects
Parameters
Other
Objects
Safety I/O
Assemblies
Standard I/O
Assemblies
Safety
Supervisor
Message
Router
Identity
Safety
Validator
Safety
I/O
Connections
Network
Figure 63 Safety
Device Objects
110
Explicit
msg
Network
Link*
*
-
DeviceNet
ControlNet
Ethernet
SERCOS
5.2.10. Additional Objects
CIP Safety requires two additional objects, the Safety Supervisor Object and the Safety validator object.
5.2.10.1. Safety Supervisor Object, (Class ID: 0x39)
The Safety Supervisor Object provides a common configuration interface for safety devices. The Safety Supervisor Object centralizes and coordinates application object state behavior and related status information,
exception status indications (alarms and warnings) and defines a behavior model which is assumed by objects
belonging to safety devices.
5.2.10.2. Safety Validatior Object, (Class ID: 0x3A)
The Safety validator object contains the information necessary to coordinate and maintain reliable safety connections between client and server safety applications. The primary role of the Safety validator object is to act as a
safety transport manager of multiple low-level CIP connections that together form a complete safety connection.
5.2.11. CIP Safety on Sercos
5.2.11.1. What is Sercos?
Sercos (SErial Realtime COmmunication System), the digital drive interface approved as international standard
IEC 61491 [28] in 1995, is optimized for high-speed deterministic motion control, where the exact synchronization of multiple drives is required. Sercos has become a globally accepted real-time networking standard for
demanding motion control applications over the last decade. Sercos has outstanding technical features like real
time capabilities, high performance, noise immunity, and a very large variety of products and suppliers. Sercos
not only defines the protocol structure, but also includes an ample variety of profile definitions (parameters and
functionalities), which are already successfully used in a large number of applications. Sercos is supported and
maintained by Sercos International [45].
The third generation Sercos (Sercos III) combines the proven mechanisms of Sercos interface with Ethernet's
physics and protocol. Typical Sercos III networks use a double ring structure which provides media redundancy
with fast switch-over. In addition to the ring structure, a linear structure is also possible, see Figure 64.
Ring structure
(Double ring)
Line structure
(Single ring)
Master
M1
Slave
1
Master
M2
Slave
2
M1
Slave
n
With hardware redundancy
Slave
1
M2
Slave
2
Slave
n
Without hardware redundancy
Figure 64 Sercos III Ring
and Line Topology
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A Sercos ring or line structure consists of one master and multiple slaves – drives, I/O, sensors. Multiple rings
can be used in a network to realize distributed and hierarchical network structures. The communication is based
on a time-slot protocol using fixed and distinct communication cycles. A communication cycle is divided into
two channels with a timing control.
In the real-time channel, collective Sercos III telegrams are transferred as broadcast data. This increases the
bandwidth and improves the protocol efficiency. The addressing of the Sercos III devices is achieved by pre-defined addresses or by addresses assigned by the master (remote addressing). Sercos III telegrams are processed on the fly to reduce delay times in a network.
In the non-real-time channel, any non-real-time Ethernet frames can be sent as individual telegrams to any device in the
network. The addressing for this is carried out directly via the MAC addresses allocated to the master and slave devices.
5.2.11.2. CIP Safety on Sercos
CIP Safety on Sercos extends the functionality of the Sercos III real-time communication system to support both
safety-relevant and non-safety relevant data transmission over one single network.
The CIP Safety Stack (CSS) is implemented corresponding to the CIP Safety specification without modifications.
Thus, CIP Safety on Sercos uses the safe message format and the CIP Safety objects and services of the CIP
Safety specification, as well as the same CRC polynomials and algorithms. For this reason, it is possible for the
CIP Safety Adaptation Layer (CSAL) as well as the Sercos III subordinate communication system, including the
Sercos Messaging Protocol (SMP), to be viewed as part of the non-safety-relevant transfer, see Figure 65.
Sercos
Safety
Profiles
CIP Safety
Profiles
Safety
relevant
CIP Safety Stack (CSS)
CIP Safety Adaptation Layer
(CSAL)
SMP
Non-safety
relevant
Sercos III
SMP: Sercos Messaging Protocol
Figure 65 CIP Safety on
Sercos - Structure
The main task of the CIP Safety Stack (CSS) in a CIP Safety Device is to create and process CIP Safety messages using cyclic process data, and to correspondingly specify communication errors with the help of the
112
different error recognition measures. A CIP Safety Device can be a tool, an originator or a target. In addition to
the process data, the CSS must also process configuration data.
Because Sercos III does not provide any transport connections, an adaptation layer is required in order to fill
the gaps between CIP Safety and Sercos III. An important task is assigned to the Sercos Messaging Protocol
(SMP), which is located above the cyclic Sercos III connections. It offers the CSAL services in order to send
messages, which can be of any length, from a producer to the consumers. In order to transport this data, the
SMP uses data containers with a fixed length in a cyclic connection. Messages that are larger than one data
container are split up into several fragments and transferred subsequently. Messages with a higher priority can
interrupt the transfer of long, fragmented messages with lower priority. This means that an effective multiplexing
of several logical communication channels in a single transport container is possible. The SMP is part of the
non-safety-relevant transfer. Mechanisms and measures for the data integrity of CIP Safety are not influenced.
With Sercos III and CIP Safety the implementation of a wide range of topologies is possible. The range stretches
from structures with a central safety control to completely decentralized solutions without any safety control.
With Sercos III and CIP Safety it is also possible to route safe data beyond the limits of a Sercos network, and
also beyond non-safety-relevant participants.
CIP Safety on Sercos has been integrated into the CIP Specification by extending Volume 5 (CIP Safety) and
through some minor adjustments to Volume 1 (CIP Common). Since the safety protocol was not changed at all,
the main parts of Volume 5 were only changed in those areas where modified wording was needed to accommodate the additional network. However, there is a new appendix in Volume 5 (Appendix G) that describes how
CIP Safety is being transported on the Sercos transport layer. Since the CIP Safety protocol as such remained
unchanged, most of the adaptation work was done on the Sercos side which is reflected in the CIP Safety on
Sercos specification available from Sercos International [45].
5.2.12. CIP Safety Summary
CIP Safety is a scalable, routable, network-independent safety protocol based on extensions to the CIP architecture. This concept can be used in solutions ranging from device-level networks such as DeviceNet to higher
level networks such as EtherNet/IP. Designing network independence into CIP Safety allows multi-network routing of Safety Connections. Functions such as multi-network routing and multicast messaging provide a strong
foundation that enables users to create the rapidly responding local cells and interconnect remote cells that are
required for today’s safety applications. CIP Safety’s design also enables expansion to future network technologies as they become available.
5.3. CIP Energy
The optimization of energy usage is a natural expansion of ODVA’s application coverage for industrial automation. The objects that support this functionality were added to Volume 1 of the CIP Networks Library in Edition
3.12. The management of energy usage methodology described in the specification defines a set of standard
attributes, services and behaviors that will facilitate the reporting of industrial devices’ use of operational energy,
and the control of industrial devices into and out of non-operational energy conserving states.
Four objects have been defined as of the publication of this text. A “Base Energy” application object standardizes access to the most basic data and services common to the various energy resources used in industry. The
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base energy object also provides the means to aggregate energy information at various levels of the enterprise
and present this data consistently at all levels: from the asset level at the bottom of the energy usage tree, up
through the machine and process level to the system level and ultimately to the production and enterprise domains. Two resource type application objects are defined. An electrical energy object provides electrical energy
data reporting capabilities and diagnostics for the electrical energy consumers and producers found within the
various levels of an industrial facility. A “non-electrical energy object” provides unified reporting of energy consumption and production of non-electrical energy data such as gas and steam. A “power management object”
provides standardized attributes and services to support the control of devices into and out of paused or sleep
states. An overview of these objects in the overall construct of CIP is shown in Figure 66.
Base Energy Object
Type,
Capabilities,
Accuracy, Path,
Attributes
Electrical
Energy Object
Energy
Odometer Attribute
(consumed,
generated, etc.)
CIP
Parameter
Object
CIP
Identity
Object
Explicit
Message
Router
Total Energy Odometer
Transfer Rate Metering
State, etc; Attributes
Non-Electrical
Energy Object
Power
Management
Object
Explicit
Messages
CIP Connection Object
Required
Optional
Conditional
Optional network-specific
“Wake from Deep Sleep” message
CIP Network
Figure 66 CIP Energy Objects
What follows is a brief introduction to the objects involved in CIP Energy. More information can be found in references [63], [64].
5.3.1. Additional Objects
4 additional objects have been defined for energy management so far, the base energy object, the electrical
energy object, the non-electrical energy object and the power management object.
5.3.1.1. Base Energy Object (Class ID: 0x4E)
The base energy object acts as an “Energy Supervisor” for energy implementations in CIP. It provides energy
mode services, and can provide aggregation services for aggregating energy values up through the various
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levels of an industrial facility. It also provides a standard format for reporting energy metering results. The object
is independent of the energy type and allows data and functionality specific to the energy type to be integrated
into an energy system in a standard way.
Multiple instances of the base energy object may exist in a device. For instance, an electric power monitor may
count metering pulse output transitions of a separate metering device. The count of such transitions, represented by a base energy object instance, would reflect the energy consumption measured by the separate device.
As another example, a device may act as a proxy for the energy consumed by a number of simple devices,
where each device is associated with a separate instance of the base energy object. An instance of the base
energy object may exist as a stand-alone instance, or it may exist in conjunction with an instance of either the
electrical energy object or the Non-electrical energy object. If an instance of either the electrical or non-electrical
energy object is implemented in a device, it must be associated with a base energy object instance in the device
(i.e., it is a child of the base energy object instance).
The object definition allows for creating five types of devices, Energy Measured, Energy Derived, Energy Proxy,
Energy Rate Fixed and Energy Aggregated devices.
- Energy Measured devices are devices such as a power monitor that measures voltage, current, phase
angle, etc., and calculates power and energy;
- Energy Derived devices are devices such as an overload relay that measures motor current, assumes a
value of motor voltage and then derives the value of power and energy;
- Energy Proxy devices such as a controller with discrete outputs that control external devices, each of
which has an associated user-provided energy transfer rate that the controller uses to calculate the energy
used based on the state of the output;
- Energy Rate Fixed devices are simple devices that report a nominal or user-defined energy value when
operating and zero when in a non-operating state:
- Energy Aggregated devices are devices that can collect energy usage of “child” devices and report them
together as an aggregate value.
Figure 67 illustrates these devices.
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!
!
!
!
!
!
!
!
!
!
!
!
Energy!
Source!
Energy!Measured!
Energy!Derived!
Power!monitor!
Line!or!
department!
Overload!relay!
Motor!amps!
(measured)!
Voltage!
(assumed)!
Energy!Proxy!
!
Controller!or!
Translator!
Energy!Aggregated!
Software!
application!
Generic!device!
Parent/child!relationship!!
Specified!using!EPATHs!
Energy!Rate!Fixed!
Power!supply!
300W!
!
Figure 67 Types of Energy-Related Devices
Energy Odometers are defined to report large amounts of energy usage in a manner similar to a car odometer or
a typical power meter on a residential home. The values are in multiples of kilowatt-hours as shown in Figure 68:
Array[4]
Array[3]
Array[2]
Array[1]
Array[0]
Terawatt-hours
(kWh x 109)
Gigawatt-hours
(kWh x 106)
Megawatt-hours
(kWh x 103)
Kilowatt-hours
(kWh)
Watt-hours
(kWh x 10-3)
Figure 68 Energy Odometer
The Base Energy object may contain information about Electrical and Non-Electrical Energy object instances
that it refers to or it may be a stand-alone instance with no children.
5.3.1.2. Electrical Energy Object (Class ID: 0x4F)
The electrical energy object provides unified electrical energy specific data reporting and diagnostics for the CIP
enabled devices and processes found within the various levels of an industrial facility. Energy management is typically
related to the measurement and reporting of a variety of metering results. This object provides for the consistent reporting of electrical energy data. Electrical energy is organized in a separate object to accommodate its alternating and
poly-phase characteristics, which result in a collection of attributes that are unique among energy sources.
Using the electrical energy object in association with an instance of the base energy object (via the associated
base energy object path, attribute 41) provides a comprehensive approach to reporting usage of electrical energy in a consistent and open fashion.
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5.3.2. Non-Electrical Energy Object (Class ID: 0x50)
The non-electrical energy object provides unified non-electrical energy specific data reporting and diagnostics for the CIP enabled devices and processes found within the various levels of an industrial facility. Energy
management is typically related to the measurement and reporting of a variety of metering results. This object
provides for the consistent reporting of non-electrical energy data, including, without limitation, natural gas, fuel
oil, steam, compressed air, hot water, chilled water, etc.
Using the non-electrical energy object in association with an instance of the base energy object (via the Associated base energy object Path, attribute 41) provides a comprehensive approach to reporting usage of non-electrical energy in a consistent and open fashion.
5.3.4. Power Management Object (Class ID: 0x53)
The power management object provides standardized attributes and services to support the control of devices
into and out of paused or sleeping states. A device supporting the power management object can transition
between various energy-related states. A Power Management service and optional adaptation specific sleep
mechanisms are used to control entry into and exit from energy saving states. Within the paused states, a device may have multiple internal energy saving modes, each with a different power consumption level.
There are six basic energy-related states for CIP Power Management capable devices:
1. Power Off;
2. Not Owned – Device is operational but no client “owns” the Power_Management service of the device;
3. Owned – The device is operational and a client “owns” the Power_Management service of the device;
4. Paused – Energy saving state; CIP communication continues;
5. Sleeping – Energy saving state; CIP communication is suspended.;
6. Resuming – Device is transitioning from Paused to Owned.
Within a particular power management state, a device’s operational capabilities and power levels may remain in
transition for a time until the agreed power usage level is attained.
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5.4. Integration of non-CIP Networks
5.4.1. Integration of Modbus into CIP
5.4.1.1. Overview
With the advent of the Modbus translator customers can take advantage of EtherNet/IP and Modbus capabilities in the same network. The simplicity of the Modbus protocol is combined with the unique values of
EtherNet/IP. The relationship is further strengthened because the Modbus/TCP protocol and EtherNet/IP are
both based on standard Ethernet technology. Both protocols can coexist in the same network because they
both operate over standard Ethernet. Migration of existing products is enabled with no custom hardware required.
By establishing the Modbus Integration SIG within ODVA, the seamless connection between the Modbus protocol and EtherNet/IP was enabled. Volume 7, Integration of Modbus Devices into CIP [7], was developed within
the SIG and later approved by the ODVA. Edition 1.0 of Volume 7 supports translation between EtherNet/IP
and Modbus/TCP. The Modbus Serial protocol support was added to Volume 7 in Edition 1.1 and approved by
the ODVA at the beginning of 2008. Clarifications and updates to Volume 7 are being considered to continually
improve the volume.
The Modbus protocol and the EtherNet/IP protocol make up the majority of the installed Ethernet-based device
level products to date. Both are widely accepted standards with strong international organizations behind them
and solid membership and participation from those organizations. Volume 7 links the two protocols together.
The Modbus Integration SIG was formed in May of 2007 with the purpose to create the Modbus translator. More
than 20 different companies belong to the Modbus Integration SIG. The diverse membership of the SIG insured
an unbiased specification was developed. The diversity of the SIG membership brought all perspectives into the
development of the specification from the Modbus target device developer to the Programmable Logic Controller (PLC) manufacturer to the EtherNet/IP target vendor to the CIP originator designer. All aspects of the CIP and
Modbus networks were and are represented.
The development of Volume 7 came with the requirement that the use of the Modbus translator would not force
changes to existing Modbus target devices or the EtherNet/IP target devices. Also a requirement for the development was to minimize the impact to CIP originators. These requirements were met. The impact to the CIP
originator was focused on the need to support both the Modbus/TCP and EtherNet/IP protocol on the same
physical Ethernet port should a customer desire to do so.
The Modbus translator can be implemented in the CIP originator or as a CIP router, i.e. the translator can be in
a PLC or as a standalone device. The Modbus translator effort and consequently Volume 7 of the CIP suite of
protocols was targeted at CIP originator developers, CIP router developers and Modbus vendors. The first two
audiences are obvious. The Modbus device vendor is targeted so that this vendor can better understand how
their device can be more easily integrated into the CIP to Modbus solution.
As the name states the Modbus translator translates CIP objects and services into Modbus messages and
function codes. A CIP originator communicates with and controls Modbus target devices through the Modbus
translator. To the CIP originator the Modbus target devices appear as CIP target devices. The Modbus target
devices believe they are being controlled by a Modbus client. The translation is transparent.
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The user would place a standalone Modbus translator in the user’s CIP-based network then connect
Modbus target devices to the Modbus side of the translator. The other side of the translator would be
connected to the CIP originator.
The user also has the option to use a Modbus translator as a module inside the CIP originator. In this case the
user would talk EtherNet/IP across the backplane to the translator. The Modbus target devices connect externally to the PLC-based translator.
A third approach places the Modbus translator and the Modbus/TCP target devices on the same network
as the EtherNet/IP target devices using the shared cabling. The EtherNet/IP traffic destined for the Modbus
target devices would be sent to the Modbus translator and the Modbus translator would send the Modbus/
TCP traffic over the same network to the Modbus/TCP target devices. The Modbus/TCP target devices would
reply to the Modbus translator then the translator will translate the Modbus traffic into EtherNet/IP traffic sent
to the CIP originator.
In all three cases, the CIP-to-Modbus translation allows communication using I/O connections as well as explicit
messaging. When explicit messaging is used, the translator may offer two types of access to the data in the
Modbus device, through publicly defined instances for Modbus data in the assembly object using Common
Services or through the Modbus Object using object-specific services.
Logically in the OSI model of the TCP/IP stack, the Modbus translation on Ethernet sits above Modbus/TCP
application in the application layer (Layer 7) and below the CIP application layers. The Modbus translator on
Ethernet is on the same level as the EtherNet/IP encapsulation. The lower layers of the stack are the standard
TCP/IP stack layering.
Changes to the CIP originator were limited. Port types were added for Modbus/TCP and Modbus Serial devices
with associated port names and numbering. The identity object was extended to include Modbus-specific information and a Modbus Object was developed and included in the CIP Object Library. Status codes were added
to identify errors and status items that are specific to Modbus. Other status codes were modified to better support Modbus and EtherNet/IP together.
All the capabilities of Modbus translator are detailed in Volume 7, “Integration of Modbus Devices into CIP” within the CIP suite of protocols. The updated Volume 1, Common Industrial Protocol (CIP) Specification, includes
support for the Modbus translation as does the updated Volume 2, EtherNet/IP Adaptation of CIP.
Customers now have greater opportunity to improve their automation networks by being able to incorporate
Modbus devices into their existing CIP networks seamlessly, especially in the case of EtherNet/IP and Modbus
TCP devices on the same physical network. Customers have a broader range of products available to them and
can mix and match features they need from a device without being restricted to a single protocol. Risk to the
buyer is reduced by the availability of greater choices to use devices based on EtherNet/IP and Modbus/TCP.
5.4.1.2. Object Extensions
The definition of the Modbus translation has resulted in extensions of existing objects as well as the creation of
new objects.
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5.4.1.2.1. Extension of Existing Objects
The main extension for the Modbus integration is within the identity object which has been enhanced with an attribute containing Modbus-specific identity information plus a translation definition for standard CIP ID information.
A set of assembly object and parameter object Instances has been defined that mirrors Modbus-specific data
tables (holding registers, input registers, coils, discrete inputs). These instance numbers are now represented by
32-bit numbers (UDINT) to accommodate the 4 data set ranges represented by 16-bit numbers each.
5.4.1.3. Additional Objects
Volume 7 defines two additional objects that are found only on Modbus devices, the Modbus object and the
Modbus serial link object.
5.4.1.3.1. Modbus Object (Class ID: 0x44)
The Modbus object provides an interface to Modbus data existing in a CIP device. Within a CIP to Modbus
translator the Modbus object provides an interface to the data and functions within a target Modbus device.
No instance attributes are defined for this object; instead, the Modbus object defines services that mirror Modbus Function Codes along with their associated address data.
5.4.1.3.2. Modbus Serial Link Object (Class ID: 0x46)
The Modbus serial link object is used for configuration of a Modbus serial data communication channel and
includes link-specific counters and status information for the port. Each instance of this object represents the
client portion of a Modbus serial channel, which allows the Modbus translator to read/write data with external
Modbus serial servers.
5.4.2. Integration of IO-Link into CIP
IO-Link, standardized as IEC 61131-9, is a communication standard that extends the 24 VDC I/O interface of
IEC 61131-2 to allow serial communication between I/O devices (IO-Link Masters) and sensors and actuators
(IO-Link Devices).
An ODVA SIG, established in fall 2012, is working on the definition of the integration of IO-Link masters and
devices into CIP as of the publication of this document. Check www.odva.org for updates on this work.
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6. Conformance Testing
Open specifications, such as those managed by ODVA, both provide vendors with the ability to build products
that will interoperate with products from other vendors, and allow users to choose products that will interoperate
in multi-vendor systems by ensuring a common network interface for given device types. In order to achieve
interoperability of devices from multiple vendors, product compliance with these open specifications is essential.
ODVA drives product compliance with the CIP Network Specifications primarily in two ways. First, each vendor
is required to sign a Terms of Usage Agreement for the ODVA technology or technologies, for which they intend
to make, have made, sell or have sold products. In signing this agreement, the vendor agrees to comply with
the network technology specification and meet a set of user responsibilities, including the conformance testing
of developed and/or sold products. A list of authorized vendors can be found on the ODVA web site.
Second, ODVA administers a vendor-independent conformance testing process. The goal of the ODVA conformance testing process is to help to ensure, to the greatest extent practicable, that products implementing ODVA
technologies and standards comply with the ODVA specifications and interoperate in multi-vendor systems.
A cornerstone of this process is the successful completion of the ODVA conformance test at an ODVA authorized test service provider (TSP). A full list of ODVA authorized TSPs can be found on the ODVA website. TSPs
perform conformance tests that are designed, developed and managed by ODVA and conduct the tests in
accordance with ODVA test requirements and procedures. ODVA TSPs must meet certain standards, including
vendor-independence, neutrality and technical competency in networks and testing practices. The ODVA conformance test is typically a composite test comprised of three parts:
- An automated software test that verifies the function of the network protocol. Depending on the complexity of the device, several thousand messages are transmitted to the device under test (DUT). To ensure
a test that is closely adapted to the characteristics of the DUT, the manufacturer must provide a formal
description of all relevant CIP features of the DUT;
- A hardware test that examines the characteristics of the physical layer for conformance. Physical layer tests vary by network and may include product labeling, indicator operation, isolation, connectors,
mis-wiring, voltage ranges, timing, etc.;
- An interoperability test that exercises the product using prescribed test scenarios designed to demonstrate the successful interoperability of the product in multi-vendor systems.
The automated conformance test software is a Windows®-based tool that uses a network interface card in
the PC to access the device under test. It is recommended that device developers run this test in their own lab
before taking devices to a test service provider. The hardware test (where appropriate) and the system interoperability test involve more complex test setups that typically are not available to device developers but are documented in the test plans or other ODVA publications. The vendor of the product may, at its option, observe the
test at the TSP.
Upon the product’s successful completion of the test, the TSP submits the test results to ODVA for review and
final approval. Contingent on passing results from the conformance tests and other requirements of ODVA,
ODVA issues a Declaration of Conformity for the product. Declarations of Conformity are posted on ODVA’s
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website at www.odva.org.
Adjunct tests are also available from the ODVA headquarters’ test service provider. These adjunct tests require that
the device submitted for additional testing passes the appropriate conformance test first. Adjunct tests include:
- DeviceNet Semiconductor Industry (test is in addition to DeviceNet Node test);
Passing adjunct test results are listed on the Declaration of Conformity for the device or device family.
Products that have received an official Declaration of Conformity from ODVA earn the right to use ODVA's
CONFORMANT certification marks as appropriate for the network connectivity of the product. (Refer to the
ODVA Identity Guidelines on the ODVA web site for more information on logo usage.) End users should check
the ODVA web site under “Product Compliance” for the list of ODVA issued Declarations of Conformity or look
the following conformance mark on a product:
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7. Endnotes
[1] CIP Networks Library, Volume 1, Common Industrial Protocol, Edition 3.18, April 2015, © 2001 through
2015 ODVA, Inc.
[2]CIP Networks Library, Volume 2, EtherNet/IP Adaptation of CIP, Edition 1.19, April 2015, © 1999 through
2015 ODVA, Inc.
[3] CIP Networks Library, Volume 3, DeviceNet Adaptation of CIP, Edition 1.14, November 2013, © 1994
through 2013 ODVA, Inc.
[4] CIP Networks Library, Volume 4, ControlNet Adaptation of CIP, Edition 1.8, April 2013, © 1997 through
2013 ODVA, Inc.
[5] CIP Networks Library, Volume 5, CIP Safety, Edition 2.11, April 2015, © 2005 through 2015 ODVA, Inc.
[6] CIP Networks Library, Volume 6, CompoNet Adaptation of CIP, Edition 1.7, April 2010, © 2006 through
2010 ODVA, Inc.
[7] CIP Networks Library, Volume 7, Integration of Modbus Devices into the CIP Architecture, Edition 1.7, April
2014, © 2007 through 2014 ODVA, Inc.
[8] Planning and Installation Manual, DeviceNet Cable System, Publication number PUB00027, downloadable
from ODVA website (http://www.odva.org/).
[9] Recommended IP Addressing Methods for EtherNet/IP Devices, Publication number PUB00028, downloadable from ODVA website (http://www.odva.org/).
[10] Recommended Functionality for EtherNet/IP Devices, Publication number PUB00070, downloadable from
ODVA website (http://www.odva.org/).
[11] EtherNet/IP Interoperability Test Procedures, Publication number PUB00095, downloadable from ODVA
website (http://www.odva.org/).
[12] Performance Test Terminology for EtherNet/IP Devices, Publication number PUB00080, downloadable from
ODVA website (http://www.odva.org/).
[13] Performance Test Methodology for EtherNet/IP Devices, Publication number PUB00081, downloadable
from ODVA website (http://www.odva.org/).
[14] EtherNet/IP Quick Start for Vendors Handbook – A Guide for EtherNet/IP Developers, Publication number
PUB00213, downloadable from ODVA website (http://www.odva.org/).
[15] EtherNet/IP Media Planning and Installation Manual, Publication number PUB00148, downloadable from
ODVA website (http://www.odva.org/).
[16] IEC 61131-2:2007 – Programmable controllers – Part 2: Equipment requirements and tests.
[17] IEC 61131-3:2013 – Programmable controllers – Part 3: Programming languages.
[18] Controller Area Network – Basics, Protocols, Chips and Application. IXXAT Automation, 2001. ISBN 3-00007376-0.
[19] ISO 11898:1993 – Road vehicles – Interchange of digital information – Controller area network (CAN) for
high-speed communication.
[20] CAN Specifications – Controller Area Network, Version 2.0, 1991, Robert Bosch GmbH. http://www.semiconductors.bosch.de/pdf/can2spec.pdf.
[21] IEEE 802.3:2000, ISO/IEC 8802-3:2000 – IEEE Standard for Information technology – Local and metropolitan area networks – Part 3: Carrier sense multiple access with collision detection (CSMA/CD) access
method and physical layer specification.
[22] IEEE 802.3:2002 – Information Technology – Telecommunication & Information Exchange Between Systems – LAN/MAN – Specific Requirements – Part 3: Carrier Sense Multiple Access with Collision Detection
(CSMA/CD) Access Method and Physical Layer Specifications 2002.
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[23] ISO/IEC 7498-1:1994 – ISO/IEC Standard – Information technology – Open Systems Interconnection – Basic Reference Model.
[24] IEC 61508:1998 – Functional safety of electrical/electronic/programmable electronic safety-related systems.
[25] IEC 62026-3:2014 – Low-voltage switchgear and controlgear – Controller-device interfaces (CDIs) – Part 3:
DeviceNet.
[26] IEC 62026-7:2010 – Low-voltage switchgear and controlgear – Controller-device interfaces (CDIs) – Part 7:
CompoNet.
[27] IEC 61784-5-2:2013 – Industrial communication networks – Profiles – Part 5-2: Installation of fieldbuses –
Installation profiles for CPF 2.
[28] IEC 61491:1995 – Electrical equipment of industrial machines – Serial data link for real-time communications between controls and drives.
[29] EN 62026-3:2015 – Low-voltage switchgear and controlgear – Controller-device interfaces (CDIs) – Part 3:
DeviceNet.
[30] Chinese national standard: GB/T 18858:2003 – Low-voltage Switchgear and Controlgear Controller-Device
Interface.
[31] IEC 61158:2014 – Digital data communications for measurement and control – Network for use in industrial
control systems.
[32] Draft proposal test and certification guideline, safety bus systems, BG Fachausschuß Elektrotechnik 28May-2000.
[33] EN 50159-1:2001 – Railway applications, communication, signaling and processing systems.
[34] GS-ET-26 – Grundsatz für die Prüfung und Zertifizierung von „Bussystemen für die Übertragung sicherheitsrelevanter Nachrichten“, Fachausschuss "Elektrotechnik" Prüf- und Zertifizierungsstelle im BG-PRÜFZERT,
downloadable from http://www.bgetf.de/bilder/pdf/gs-et-26_a05-2002.pdf.
[35] ISO 13849-1:2006 – Safety of machinery – Safety-related parts of control systems – Part 1: General principles for design.
[36] David A. Vasko, Suresh R. Nair: CIP Safety: Safety Networking for the Future; Proceedings of the 9th International CAN Conference, Munich, Germany. 2003. Downloadable from http://www.can-cia.org/
[37] Hideki Harada, "CompoNet: Innovations for High Performance Sensor-Actuator Applications", CIP Networks Conference & 12th Annual Meeting, Englewood, California. Presented Papers, 2007, downloadable
from ODVA website (http://www.odva.org/).
[38] Hedon Ri, Overview of CompoNet Developer’s Toolkit, Presented at the ODVA 2007 CIP Networks Conference & 12th Annual Meeting, 2007, Englewood, California. Downloadable from ODVA website (http://www.
odva.org/).
[39] Hedon Ri, Design Considerations for CompoNet Processors, Presented at the ODVA 2007 CIP Networks
Conference & 12th Annual Meeting, 2007, Englewood, California. Downloadable from ODVA website (http://
www.odva.org/).
[40] IEEE 1588-2008 – Standard for a Precision Clock Synchronization Protocol for Networked Measurement
and Control Systems.
[41] Viktor Schiffer: Modular EDSs and other EDS Enhancements for DeviceNet; Proceedings of the 9th International CAN Conference 2003.
[42] Viktor Schiffer: Device Configuration Using Electronic Data Sheets, ODVA 2003 Conference and 9th Annual
Meeting, Ann Arbor, Michigan.
[43] Viktor Schiffer, Ray Romito: DeviceNet Development Considerations, 2000.
[44] ControlNet Product Developer’s Guide, Rockwell Automation, Publication Number 9220-6.5.1, downloadable from http://literature.rockwellautomation.com.
[45] Sercos International, http://www.sercos.de/EUROPE-English.15.0.html.
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[46] FDT Group Homepage. http://www.fdtgroup.org/.
[47] RFC 768 – User Datagram Protocol, 1980.
[48] RFC 791 – Internet Protocol, 1981.
[49] RFC 792 – Internet Control Message Protocol, 1981.
[50] RFC 793 – Transmission Control Protocol, 1981.
[51] RFC 826 – Ethernet Address Resolution Protocol: Or converting network protocol addresses to 48.bit Ethernet address for transmission on Ethernet hardware, 1982.
[52] RFC 894 – Standard for the transmission of IP datagrams over Ethernet networks, 1984.
[53] RFC 1103 – Proposed standard for the transmission of IP datagrams over FDDI Networks, 1989.
[54] RFC 1112 – Host extensions for IP multicasting, 1989.
[55] RFC 1122 – Requirements for Internet Hosts – Communication Layers, 1989.
[56] RFC 1123 – Requirements for Internet Hosts – Application and Support, 1989.
[57] RFC 1127 – Perspective on the Host Requirements RFCs, 1989.
[58] RFC 1171 – Point-to-Point Protocol for the transmission of multi-protocol datagrams over Point-to-Point
links, 1990.
[59] RFC 1201 – Transmitting IP traffic over ARCNET networks, 1991.
[60] RFC 1392 – Internet Users' Glossary.
[61] RFC 2236 – Internet Group Management Protocol, Version 2, 1997.
[62] RFC 5227 – IPv4 Address Conflict Detection.
All RFCs are downloadable from http://www.faqs.org/rfcs/.
[63] ODVA Technology at a Glance, Technical Approach to Optimization of Energy Usage, Publication number
PUB00265, available through ODVA website (http://www.odva.org/).
[64] O
DVA white paper, Optimization of Energy Usage (OEU™): ODVA’s Vision of Energy Optimization for the
Industrial Consumer, Publication number PUB00246, downloadable from ODVA website
(http://www.odva.org/).
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8. Bibliography
CIP Networks Library, Volume 1, Common Industrial Protocol, Edition 3.18, April 2015, © 2001 through 2015
CIP Networks Library, Volume 2, EtherNet/IP Adaptation of CIP, Edition 1.19, April 2015, © 1999 through 2015
CIP Networks Library, Volume 3, DeviceNet Adaptation of CIP, Edition 1.14, November 2013, © 1994 through
2013
CIP Networks Library, Volume 4, ControlNet Adaptation of CIP, Edition 1.8, April 2013 © 1997 through 2013
CIP Networks Library, Volume 5, CIP Safety, Edition 2.11, April 2015, © 2015 ODVA.
9. Related Publications
Planning and Installation Manual, DeviceNet Cable System, Publication number PUB00027, downloadable from
ODVA website (http://www.odva.org/)
EtherNet/IP Planning and Installation Manual, Publication number PUB00148, downloadable from ODVA website (http://www.odva.org/)
Performance Test Terminology for EtherNet/IP Devices, Publication number PUB00080, downloadable from
ODVA website (http://www.odva.org/)
CAN Specifications – Controller Area Network, Version 2.0, 1991, Robert Bosch GmbH.
http://www.semiconductors.bosch.de/pdf/can2spec.pdf
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10. Abbreviations
For the purposes of this chapter, the following abbreviations apply:
Abbreviation
Meaning
ASCII
American Standard Code for Information Interchange
CIP
The Common Industrial Protocol defined by Volume 1 of the CIP Networks Library
CID
Connection Identifier
EPR
Expected Packet Rate
ISO
International Standards Organization
MAC ID
Media Access Control Identifier (another name for Network Address)
OSI
Open Systems Interconnection (see ISO 7498)
UCMM
Unconnected Message Manager
CRC
Cyclic Redundancy Check
LED
Light Emitting Diode
MAC
Media Access Control sublayer
NAP
Network Access Port
NUT
Network Update Time
RG-6
Standard for coaxial cable
SMAX
MAC ID of the maximum scheduled node
UMAX
MAC ID of the maximum unscheduled node
FTP
File Transfer Protocol. An internet application that uses TCP reliable packet transfer to move
files between different nodes.
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Abbreviation
Meaning
RFC
Request For Comments (RFC) – This document series, which was launched in 1969,
describes the Internet suite of protocols and related experiments. Not all (in fact, very few)
RFCs describe the Internet Standards, but all Internet Standards are written up as RFCs. The
RFC series is unusual in that the proposed protocols are forwarded by the Internet research
and development community, acting on their own behalf, as opposed to the formally reviewed and standardized protocols that are promoted by organizations such as CCITT and
ANSI. [Source: RFC 1392]
TCP
Transmission Control Protocol (TCP) – An Internet Standard transport layer protocol defined
in STD 7, RFC 793. It is connection-oriented and stream-oriented, as opposed to UDP. See
also: connection-oriented, stream-oriented, User Datagram Protocol. [Source: RFC1392]
UDP
User Datagram Protocol (UDP) – An Internet Standard transport layer protocol defined in
STD 6, RFC 768. It is a connectionless protocol which adds a level of reliability and multiplexing to IP. See also: connectionless, Transmission Control Protocol. [Source: RFC1392]
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11. Terminology
For the purposes of this document, the following definitions apply:
Term
Definition
allocate
In the DeviceNet context, this is the process of reserving resources of the predefined master/slave connection set in a DeviceNet node. It is associated with
services of a similar name, of the DeviceNet object class (Class ID 0x03).
Typically refers to the application layer of the ISO-OSI model. The application layer is the part of the product that performs application-specific functions. Typically,
application objects that provide the desired behavior are associated with the
application.
application
A description of an externally visible characteristic or feature of an object. The
attributes of an object contain information about variable portions of an object.
Typically, they provide status information or govern the operation of an object. Attributes also may affect the behavior of an object. Attributes are divided into class
attributes and instance attributes.
attribute
behavior
Indication of how the object responds to particular events. Its description includes the relationship between attribute values and services.
bit
A unit of information consisting of a 1 or a 0. This is the smallest data unit that
can be transmitted.
broadcast
A message that is sent to all nodes on a network. It also refers to the property
of a network where all nodes listen to all messages transmitted for purposes of
determining bus access/priority.
byte
A sequence of 8 bits that is treated as a single unit.
A set of objects, all of which represent a similar system component. A class is
a generalization of the object, a template for defining variables and methods. All
objects in a class are identical in form and behavior, but they may contain different attribute values.
class
object-specific service
client
A service defined by a particular object class to perform a required function that
is not performed by any common services. A class-specific service is unique to
the object class that defines it.
(1) An object that uses the services of another (server) object to perform a task.
(2) An initiator of a message to which a server reacts.
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Term
Definition
connection
A logical binding between two application objects. These application objects may
be the same or different devices.
Connection Identifier
Identifier assigned to a transmission that is associated with a particular connection between producers and consumers that identifies a specific piece of application information.
connection path
Is made up of a byte stream that defines the application object to which a connection instance applies.
consumer
A node that is receiving (i.e., consumes) data from a producer.
consuming application
The application that consumes data.
CRC error
Error that occurs when the cyclic redundancy check (CRC) value does not match
the value generated by the transmitter.
cyclic
Term used to describe events that repeat in a regular and repetitive manner.
datagram
A transmitted message.
device
A physical hardware connection to the link. A device may contain more than one
node.
Device Profile
A collection of device-dependent information and functionality providing consistency between similar devices of the same device type.
drop or dropline
The cable that connects one or more nodes to a trunk cable, usually accomplished using a tap.
encapsulation
The technique used by layered protocols in which a layer adds header information to the protocol data unit (PDU) from the layer above for purposes of carrying
one protocol within another.
Ethernet
A standard for LANs, initially developed by Xerox, and later refined by Digital, Intel
and Xerox (DIX). In its original form, all hosts are connected to a coaxial cable,
where they contend for network access using a Carrier Sense Multiple Access
with Collision Detection (CSMA/CD) paradigm. See also: IEEE 802.3, Local Area
Network. [Source: RFC1392]
Expected Packet Rate
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A misnomer, the Expected Packet Rate (EPR) is basic interval at which a connection transmits its data.
Term
fixed tag
Definition
A two-byte field in a ControlNet Lpacket that identifies unconnected or station
management services the node is expected to perform. The first byte is the
specific service code and the second byte contains the MAC ID of the destination
node.
frame
See MAC Frame.
generic tag
A three-byte field in a ControlNet Lpacket that serves as the Connection Identifier
(CID). It is associated with a specific piece of application information.
Guardband
It is the portion of ControlNet bandwidth that is allocated for the transmission of
the moderator frame.
instance
The actual physical presentation of an object within a class. Identifies one of
potentially many objects within the same object class.
Keeper
Object responsible for holding and distributing the Connection Originator schedule data for all Connection Originator devices on a ControlNet Network.
Link or Data Link
Refers to the Data Link layer of the ISO/OSI model.
Lpacket
On ControlNet, the Lpacket (or link packet) is a portion of the MAC Frame where
application information that contains a size, control byte, tag, and link data is
transmitted. There may be one or more Lpackets in a single MAC Frame.
MAC frame
A collection of MAC symbols transmitted on the network medium that contains
the required message formatting/framing necessary to pass a message to another node. For example, a ControlNet MAC Frame consists of a preamble, start
delimiter, source MAC ID, Lpackets, CRC, and end delimiter.
Message Router
The object within a node that distributes explicit message requests to the appropriate application objects.
multicast
A packet that is sent to multiple nodes on the network.
network
A series of nodes connected by some type of communication medium. The connection paths between any pair of nodes can include repeaters and bridges.
Network Access Port
On ControlNet, this is an alternate physical layer connection point on a permanent node that allows a temporary node to be connected to the link. The temporary node has its own network address, but simply shares the permanent node’s
physical layer connection to the network.
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Term
Definition
network address
An integer identification value assigned to each node on a CIP Network.
network status indicators
Indicators (i.e., LEDs) on a node indicating the status of the Physical and Data
Link Layers.
Network Update Time
Repetitive time interval on a ControlNet Network that is used to subdivide the
network bandwidth. It determines the fastest rate that real-time data can be
transferred on the network.
node
A connection to a link that requires a single MAC ID.
object
(1) An abstract representation of a particular component within a product. Objects can be composed of any or all of the following components:
a) data (information which changes with time); b) configuration (parameters for
behavior); c) methods (things that can be done using data and configuration). (2)
A collection of related data (in the form of variables) and methods (procedures) for
operating on that data that have clearly defined interface and behavior.
object-specific service
A service defined by a particular object class to perform a required function that
is not performed by one of the common services. An object-specific service is
unique to the object class that defines it.
originator
The client responsible for establishing a connection path to the target.
point-to-point
A one-to-one data exchange relationship between two, and only two nodes.
port
A CIP port is the abstraction for a physical network connection to a CIP device.
A CIP device has one port for each network connection. Within the EtherNet/IP
specific context, a TCP or UDP port is a transport layer de-multiplexing value.
Each application has a unique port number associated with it. [Source: RFC1392]
producer
A node that is responsible for transmitting data.
redundant media
A system using more than one medium to help prevent communication failures.
repeater
Two-port active Physical Layer device that reconstructs and retransmits all traffic
on one segment to another segment.
scheduled
On ControlNet these are data transfers that occur in a deterministic and repeatable manner, on preconfigured NUT-based intervals.
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Term
Definition
This term has two uses within CIP. With respect to cable topology, a segment is a
length of cable connected via taps with terminators at each end; a segment has
no active components and does not include repeaters. With respect to explicit
messaging, segments (logical segments, port segments, etc.) are used in explicit
messages to describe various addressing elements of devices such as: class IDs,
attribute IDs, ports, connection points, etc.
segment
serial number
A unique 32-bit integer assigned by each manufacturer to every device. The
number needs only be unique with respect to the manufacturer.
server
A device or object that provides services to another device (the client).
service
Operation or function that an object performs upon request from another object.
tap
Point of attachment on the trunk where one or more droplines are attached.
target
The end-node to which a connection is established.
terminator
A resistor placed at the physical extreme ends of trunk segments to prevent
transmission reflections from occurring.
transceiver
The physical component within a node that provides transmission and reception
of signals onto and off of the medium.
trunk or trunkline
The main bus or central part of a cable system, typically terminated at each end
by a termination resistor.
Unconnected Message
Manager
The function within a node that transmits and receives unconnected explicit
messages.
unscheduled
On ControlNet, this refers to data transfers that use the unscheduled portion of
the NUT.
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