TECHNOLOGY OVERVIEW SERIESCIP on CTDMA Technology

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MARCH 2016

ControlNet™ CIP on CTDMA Technology

ControlNet offers several unique advantages for manufacturing
automation applications:• omprehensive producer-consumer services let youCsimultaneously control, configure and collect datafrom intelligent devices over a single network;•eterministic, repeatable performance for bothD
discrete and process applications;•lexible topology options, including trunklineF
dropline, ring, star, tree and combinations there ofusing repeaters;•

 bility to remove and replace nodes under power atA
any point on the network;•Intrinsically safe options available that meet various
EU, CENELEC, UL and FM certifications for use inpotentially explosive atmospheres;•

Duplicate Node ID detection;•

ultiple media types, including coaxial andMfiber, including RG-6 quad shield cable, which is
inexpensive and used widely in the cable TV industry;•

 ptional media redundancy that transparently allows
O
higher system availability; and• upport for up to 99 nodes, and a bus speed of 5S
Mbits per second.

Here’s a more in-depth look at the technology behind every
ControlNet-compliant product.

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CIP Motion™
ProfilesMotor Control
ProfilesTransducer
ProfilesOther
ProfilesI/O
ProfilesSemiconductor CIP Safety™
ProfilesProfilesObject Library(Communications, Applications, Time Synchronization)

SafetyObject Library

Data Management Services
Explicit and I/O Messages

Safety Services
and Messages

Originator Services
for Modbus® Device
Integration

Connecting Management, Routing

TCP/UDPInternet Protocol

CompoNet
ControlNet
DeviceNet
Network and Transport Network and Transport Network and Transport

Ethernet
CSMA/CD

CompoNet
Time Slot

ControlNet
CTDMA

CAN
CSMA/NBA

Ethernet
Physical Layer

CompoNet
Physical Layer

ControlNet
Physical Layer

DeviceNet
Physical Layer

EtherNet/IP™

CompoNet™

ControlNet™

DeviceNet™

Network Adaptations of CIP

With media independence comes the ability to choose the CIP
Network best suited for each application. One of these possible
choices is ControlNet, which adapts CIP to Concurrent
Time Domain, Multiple Access (CTDMA) Technology. Why
adapt CIP to CTDMA? CTDMA allows for users to achieve
deterministic, high-speed transport of I/O and peer-to-peer
interlocks in applications that are time-critical.

ControlNet, like other CIP Networks, follows the Open Systems
Interconnection (OSI) model, which defines a framework for
implementing network protocols in seven layers: physical, datalink, network, transport, session, presentation and application.
Networks that follow this model define a suite of network
functionality from the physical implementation through theapplication or user interface layer. As with all CIP Networks,
ControlNet implements CIP at the Session layer and above
while adapting CIP to the ControlNet technology at the Transportlayer and below. This network architecture is shown in Figure 1.
Common Industrial Protocol (CIP™)

ControlNet™ is a serial communication system forcommunication between devices that wish to exchange
time-critical application information in a deterministic andpredictable manner. ControlNet is a member of a familyof networks that implements the Common Industrial
Protocol (CIP™) at its upper layers. CIP encompasses acomprehensive suite of messages and services for a variety
of manufacturing automation applications, including control,
safety, synchronization, motion, configuration and information.
As a truly media-independent protocol that is supported byhundreds of vendors around the world, CIP provides users
with a unified communication architecture throughout the
manufacturing enterprise.

What is ControlNet?

Figure 1: ControlNet as Part of the CIP OSI Model

ControlNet is a digital network that provides high-speedtransport of time-critical I/O and messaging data - including
upload/download of programming and configuration dataand peer-to-peer messaging - on a physical media link.
Each device and/or controller is a node on the network. The
ControlNet network infrastructure is passive, making nodefunctionality independent of physical location and the network
inherently tolerant to node connections.
To further decrease complexity, ControlNet systems require a
point of connection for both configuration and control. This isbecause ControlNet supports I/O (or implicit) messages—thosethat typically contain time-critical control data—and explicit
messages—those in which the data field carries both protocol
information and specific service requests. As a producer-consumer
network that supports multiple communication hierarchies andmessage prioritization, ControlNet provides efficient use of
bandwidth than a device network based on a source-destination
model. ControlNet systems can be configured to operate either ina centralized or distributed control architecture using peer-to-peer
communication. ControlNet’s time-based message schedulingmechanism provides 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 associatedwith continuously requesting, or “polling,” for the required data.

The Physical Layer
ControlNet offers users a choice of network topologies andphysical media. The variants in topology are shown in Figure 2.
Multiple topologies and media types can be mixed within one
system. End-to-end network length varies based on the numberof nodes, type of media and use of repeaters, as shown in Table 1.
Media

2 Nodes

32 Nodes48 Nodes49-99 Nodes

Coax

1000 m (3280 ft)

500 m (1520 ft)

250 m (820 ft)

requiresrepeaters

Fiber

Depends on repeater capability, fiber and termination quality

Coax or Fiberwith Repeater

Depends on number of repeaters, repeater capability, fiber andtermination quality

Maximum Drop
Length

1m

1m

1m

1m

(3.3 ft)(3.3 ft)(3.3 ft)(3.3 ft)

Table 1: End-to-end network distance based on cable media

When a coax cable media is chosen, ControlNet uses RG-6
quad shield coax cable, the same standard cable that is usedin the cable TV industry. This coax cable is inexpensive,
readily available and has high noise immunity. Several typesof outer jackets are available (plenum, high flex, armor) tomeet any application or environmental requirement.
Connectors are standard BNC-type for IP20 applications andTNC-type for IP67 applications where dust, dirt and/or liquids
are present. Two 75-W termination resistors are required:
one on each end of the cable to limit the reflections fromtransmitted signals on the trunkline.

Redundant cable media is a ControlNet option that allows
all messages to be transmitted simultaneously on both cable
paths. Each node evaluates signal quality, and the best quality
signal is chosen dynamically.
In addition to its ControlNet port for control and information,
each ControlNet node has a network access port that makes
it possible for a computer or other support tool to plug into
the network and communicate with any other device on the
network. The network access port uses a standard 8-pin, RJ45 connector.
Repeaters may be used to increase end-to-end network lengths
and the number of nodes per segment. They may also be used
to connect coax to fiber cables for increased noise immunity
or greater distance. For a given system, the maximum numberof repeaters will be limited by the propagation delay introducedby the repeater. When determining the maximum numberof repeaters and/or the maximum distance capabilities of thesystem, the individual propagation delays (media, taps andrepeaters) must total less than 120 microseconds between thetwo furthest points on the network.
Intrinsically safe options are available through vendor
implementations of ControlNet products that meet various
EU, CENELEC, UL and FM certifications for use in potentiallyexplosive atmospheres.

A passive tap is required for every permanent node on the
network. Custom taps for ControlNet can be rail-mounted
and easily connected to the ControlNet trunk cable. Taps
are available in different styles, including straight, rightangle and “Y.” Although the taps must be installed while the
network is powered-down, they allow devices to be added or
removed while the network is powered. Taps may be installed
anywhere along the ControlNet trunk cable, with no minimum
separation distance. A 1m drop line from the tap to the device
is standard. Transformer coupling is utilized in each node toprovide electrical isolation.
When a fiber optic media is chosen, ControlNet incorporates
a full-duplex, point-to-point fiber link using a transmitter andreceiver at each end of a pair of fibers. The fiber characteristics
are shown in Table 2.
Specification

Short Range (300 m)

Medium Range (3000 m)

Fiber Technology

Step index, hard clad silica(HCS)

Graded index, multi-mode

Core/Cladding

200/230 um

62.5/125 um

Numerical Aperture

0.5

0.275

Figure 2: ControlNet Topology Options

Table 2: Fiber characteristics

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The Data Link Layer
ControlNet uses a Concurrent Time Domain, Multiple Access(CTDMA) algorithm to ensure the precise time for message
delivery. This protocol is based on a fixed, repetitive time cycle
called a Network Update Time (NUT), as shown in Figure 3.

The Network andTransport Layers
ControlNet uses two forms of messaging:•Unconnected messaging is used in the connection
establishment process and for infrequent, lowpriority
messages.
Unconnected
messages
always use the unscheduled bandwidth, and theunconnected resources in a device are referred toas the Unconnected Message Manager, or UCMM.
To receive a Declaration of Conformity, ControlNet
products are required to implement a UCMM toreceive requests from other devices.

• onnected messaging on ControlNet utilizes
C
resources within each node that are dedicated inadvance to a particular purpose, such as frequent
explicit message transactions or real-time I/O datatransfers. Connection resources are reserved andconfigured using communications services available
via the UCMM.

Figure 3: The CMDT algorithm´s NUT ensures precise
time for message delivery.

The NUT can be configured for a duration ranging from
2 to 100 milliseconds. Each node contains its own timer
synchronized to the NUT for the local link. Media access isdetermined by local subdivision of the NUT into access slots
based on node number. Each NUT is divided into three majorparts: scheduled, unscheduled and guardband, and thissequence is repeated in every NUT.
Users select NUT parameters with a network configuration
tool. These parameters are distributed to all nodes via themoderator, which is the node with the lowest MAC ID on
the link. The network parameters are broadcast during theguardband portion of the bandwidth. ControlNet’s network
synchronization method assures that no node will transmit
on the medium with parameters that do not agree with thosecurrently in use. Different links (joined by bridges) may havedifferent NUT durations and network parameters, and will
have their own moderators.

The process of opening a connection is called Connection
Origination, and the node that initiates the connection
establishment request is called a Connection Originator, orjust an Originator. Conversely, the node that responds to theestablishment request is called a Connection Target, or aTarget.
ControlNet has two types of messaging connections: explicit
and implicit (I/O data). Explicit messaging connections arepoint-to-point relationships that are established to facilitate
request-response transactions between two nodes. These
connections are general purpose in nature and can be used toreach any network-accessible items within a device. Explicit
messaging connections utilize unscheduled services onControlNet.
Implicit connections, on the other hand, are established tomove application-specific I/O data at regular intervals. These
connections are multicast in nature, and often are set up as
one-to-many relationships in order to take full advantageof the producer/consumer model. Implicit connections
utilize scheduled services on ControlNet, providing highly
deterministic transfer of data.
ControlNet supports three device classes based on network
communication capabilities: Messaging Class, Adapter
Class and Scanner Class. Each class supports a basic setof communications services, but may provide other optional
services too.
Messaging Class products support unscheduled explicit
messaging (connected or unconnected) that is sent or
received from all other classes of products. Messaging Class
products are the targets of explicit message connection
requests, and may also be an originator of these requests,
but they cannot send or receive scheduled, real-time I/O data.

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Examples of products in this class include:• omputer interface cards for program upload andCdownload to HMI products, robots and 			
PLCs;

•

 omputer interface cards or other hardware thatC
supports HMI applications that gather data fromcontrol systems (i.e., MIS);• oftware applications that do not require real-time
S
I/O response; and•Network configuration and diagnostic tools.

Adapter Class products are the targets of scheduled I/Odata connection requests from Scanner Class products. They
cannot send or receive scheduled real-time I/O data unlessthey are requested to do so by a scanner, and they do notstore or originate the data transmit schedule. Adapter Class
products receive unscheduled explicit message requests(connected or unconnected) from all other classes of products.
They may also exchange (peer) data using unscheduled
messages with any class of device, but they cannot originate
such relationships.
Examples of products in this class include:•I/O rack adapters producing and consuming
scheduled real-time data;• eigh scales, welders, drives and robots sendingW
and receiving real time scheduled data at the requestof PLCs and other controllers;• eigh scales, welders, drives and robots sendingW
and receiving unscheduled message data to andfrom computer interface cards, PLCs and each other;and HMI products sending and receiving scheduled
and unscheduled data to PLCs.

Scanner Class products are the originators of scheduled
I/O data connection requests to Adapter Class products,
as well as to other Scanner Class products (i.e., scheduled
peer-to-peer). These products may also be the originators or
targets of unscheduled explicit connection requests to andfrom other classes of products, and they can also send or
receive unscheduled messages to or from all other classes
of products.
Examples of products in this class include:• LCs, controllers and robots sending and receiving
Preal time scheduled data to I/O rack adapters, PLCs,
robots, weigh scales, welders and MMI products;•

 LCs, controllers and robots sending and receiving
P
unscheduled message data to other PLCs, robots,weigh scales, computer cards, welders and MMI
products; and•Computer interface cards used for PC-based control.

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The Upper Layers
ControlNet uses the Common Industrial Protocol (CIP), a
strictly object-oriented protocol, at the upper layers. Each
CIP object has attributes (data), services (commands) andbehaviors (reactions to events). CIP’s producer-consumer
communication model provides more efficient use of network
resources than a source-destination model by allowing theexchange of application information between a sending device(e.g., the producer) and many receiving devices (e.g., theconsumers) without requiring data to be transmitted multiple
times by a single source to multiple destinations. In producerconsumer networks, a message is identified by its connection
ID, not its destination address (as is the case with sourcedestination networks). CIP’s message structure makes it
possible for multiple nodes to consume data produced by asingle source based solely on the connection ID to which themessage refers. Thus, the producer-consumer model provides
a clear advantage for users of CIP Networks by making efficientuse of network resources in the following ways:•If a node wants to receive data, it only needs to ask
for it once to consume the data each 			time it is produced.

•If a second (third, fourth, etc.) node wants the samedata, all it needs to know is the connection ID toreceive the same data simultaneously with all othernodes.

CIP also includes “device types” for which there are “device
profiles.” For a given device type, the device profile will specify
the set of CIP objects that must be implemented, configuration
options and I/O data formats. This consistency in object
implementation for a given device type provides another clear
advantage for users of CIP Networks by promoting a common
application interface for a given device type and interoperability
in networks comprised of devices from multiple vendors. For
applications where unique functionality is required, it is also
possible for a ControlNet vendor to define additional vendorspecific objects in a ControlNet-compliant product in order tosupport the functional requirements of particular applications.
Seamless bridging and routing is perhaps the most significant
advantage for users of CIP Networks for it is this mechanismthat most protects the user’s investment for the future. The
ability to originate a message on one CIP Network, such as
DeviceNet, and then pass it to another CIP Network, suchas ControlNet, with no presentation at the Application Layer,means that users can incorporate incremental application
improvements to existing installations and/or integrate
automation systems with diagnostic, prognostic and/or IT
applications. Seamless bridging and routing between bothhomogeneous and heterogeneous CIP Networks is enabled
by a set of objects that defines routing mechanisms for a device
to use when forwarding the contents of a message producedon one network port to another. This mechanism does notalter the contents of a message during the routing process.
When using this mechanism, the user’s only responsibility is
to describe the path that a given message must follow. CIP
ensures that the message is handled correctly, independentof the CIP Networks involved.

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Management of theControlNet Technology
ControlNet is managed by ODVA, an international associationof the world’s leading automation companies. ODVA’s
ControlNet management responsibilities include:•

Publishing The ControlNet Specification;•verseeing the process to incorporate newOenhancements to The ControlNet Specification;•

 icensing the ControlNet Technology to companies
Ldesiring to make and/or sell ControlNet-compliant
products;•

 romoting industry awareness of ControlNet and its
P
benefits; and• elping to ensure compliance of ControlNet productsHwith the specification through conformance testing
and conformity reporting.

For more information about ControlNet, CIP or ODVA, visit
ODVA at www.odva.org..

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About ODVAFounded in 1995, ODVA is a global association whose members
comprise the world’s leading automation companies. ODVA’s mission
is to advance open, interoperable information and communication
technologies in industrial automation. ODVA recognizes its media
independent network protocol, the Common Industrial Protocol or “CIP” –and the network adaptations of CIP – EtherNet/IP, DeviceNet, CompoNet
and ControlNet – as its core technology and the primary common interestof its membership. ODVA’s vision is to contribute to the sustainability
and prosperity of the global community by transforming the model for
information and communication technology in the industrial ecosystem.
For future interoperability of production systems and the integration of the
production systems with other systems, ODVA embraces the adoptionof commercial-off-the-shelf (COTS) and standard, unmodified Internet
and Ethernet technologies as a guiding principle wherever possible. This
principle is exemplified by EtherNet/IP – the world’s number one industrial
Ethernet network. For more information about ODVA, visit odva.org.

ODVA

Ann Arbor, Michigan, USA
TEL: +1 734-975-8840
FAX: +1 734-922-0027
WEB: www.odva.org
PUB00200R1©1999-2016 ODVA, Inc.

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