Allen-Bradley ControlLogix User manual

User Manual
ControlLogix
ControlNet Interface
Module
(Cat. No. 1756-CNB, -CNBR)
Allen-Bradley

Important User Information Because of the variety of uses for the products described in this publication,
those responsible for the application and use of this control equipment must
satisfy themselves that all necessary steps have been taken to assure that
each application and use meets all performance and safety requirements,
including any applicable laws, regulations, codes and standards.
The illustrations, charts, sample programs and layout examples shown in
this guide are intended solely for purposesof example. Since there are many
variables and requirements associated with any particular installation,
Allen-Bradley does not assume responsibility or liability (to include
intellectual property liability) for actual use based upon theexamples shown
in this publication.
Allen-Bradley publication SGI-1.1, Safety Guidelines for the Application,
Installation and Maintenance of Solid-State Control (available from your
local Allen-Bradley office), describes some important differences between
solid-state equipment and electromechanical devices that should be taken
into consideration when applying products such as those described in this
publication.
Reproduction of the contents of this copyrighted publication, in whole or
part, without written permission of Rockwell Automation, is prohibited.
Throughout this manual we use notes to make you aware of safety
considerations:
Attention statements help you to:
•identify a hazard
•avoid a hazard
•recognize the consequences
Important:Identifies information that is critical for successful application
and understanding of the product.
ControlLogix and PLC-5 are trademarks of Rockwell Automation.
ControlNet is a trademark of ControlNet International, Ltd.
RSLogix5, RSLogix5000, and RSNetWorx are trademarks of Rockwell Software, Inc.
Windows 95 and Windows NT are trademarks of Microsoft Corporation.
!
ATTENTION: Identifies information about practices or
circumstances that can lead to personal injury or death,
property damage or economic loss

European Communities (EC)
Directive Compliance
If this product has the CE mark, it is approved for installation within the
European Union and EEA regions and has been designed and tested to meet
the following directives.
EMC Directive
This product is tested to meet the Council Directive 89/336/EC
Electromagnetic Compatibility (EMC) by applying the following standards,
in whole or in part, documented in a technical construction file:
•EN 50081-2 EMC — Generic Emission Standard, Part 2 — Industrial
Environment
•EN 50082-2 EMC — Generic Immunity Standard, Part 2 — Industrial
Environment
This product is intended for use in an industrial environment.
Low Voltage Directive
This product is tested to meet Council Directive 73/23/EEC Low Voltage,
by applying the safety requirements of EN 61131-2 Programmable
Controllers, Part 2 - Equipment Requirements and Tests. For specific
information required by EN 61131-2, see the appropriate sections in this
publication, as well as the Allen-Bradley publication Industrial Automation
Wiring and Grounding Guidelines For Noise Immunity, publication
1770-4.1.
This equipment is classified as open equipment and must be mounted in an
enclosure during operation to provide safety protection.

1756-6.5.3 - December 1999
Preface
Using This Manual
What the Preface Contains This manual describes how to use the 1756-CNB or 1756-CNBR
ControlNet interface modules(1) to communicate over a ControlNet
network. This preface explains how to use this manual most effectively.
Who Should Use This Manual Use this manual if you are knowledgeable about ControlLogix products, but
need information about integrating them into a ControlNet network. You
should:
•be familiarwith Microsoft® Windows® NT and with terms that describe
what you should be doing when working in Windows NT, e.g., double
click, dialog box, radio button.
•understand basic networking concepts.
•be familiar with Logix5550 and PLC-5C controllers and ladder logic
programming using RSLogix5 and RSLogix5000 software.
If you are not familiar with these products and concepts or would like
additional information, refer to the documentation listed on page P-5 or
contact your Rockwell Automation representative for information about
available training.
How To Use This Manual Chapter 1 of this manual provides an overview of ControlNet
communications. Chapter 2 describes how to install the ControlLogix and
PLC-5C modules and connect them to the network. Chapter 12 provides
information on troubleshooting the 1756-CNB module. The remainder of
this manual (chapters 3 through 11) presents example applications of
scheduled and unscheduled communications among Logix5550 controllers
and PLC-5C controllers, and between a local Logix5550 controller and
remote I/O.
(1) Unless noted otherwise, for the rest of this manual 1756-CNB refers to both of these modules.
For information about See page
Who Should Use This Manual P-1
How To Use This Manual P-1
About the Example Applications P-2
System Components P-3
Common Techniques Used in This Manual P-4
Where to Find More Information P-5
Rockwell Automation Support P-5

1756-6.5.3 - December 1999
P-2
The example applications are intended to provide you with enough
information to get your own network up and running. We recommend that
you set up and run the example applications and use them as a guide for
setting up your own system.
About the Example
Applications
The example applications presented in this manual are as follows:
•Logix5550 controller to Logix5550 controller:
–unscheduled messaging (chapter 3)
–scheduled communications (chapter 4)
•Logix5550 controller to PLC-5C:
–unscheduled messaging (chapter 5)
–scheduled communications (chapter 6)
•PLC-5C to Logix5550 controller:
–unscheduled messaging (chapter 7)
–scheduled communications (chapter 8)
•Bridging unscheduled messages from a PLC-5C on one ControlNet
network to a PLC-5C on another ControlNet network (chapter 9)
•Controlling I/O (chapter 10)
•Adding I/O to an existing network (chapter 11)
Here’s an example of one type of system you’ll be creating:
ControlNet Network
Logix5550 1756-CNB
(Node 1)
1756-CNB
(Node 6)
Local
Chassis Remote
Chassis
PC with
1784-KTCX15
Interface
Message
Slot 0 1 Slot 1 2 3
1756-IB16
Digital Input
1756-OB16I
Digital Output
Controller

1756-6.5.3 - December 1999
P-3
System Components We used the following main components to set up the example applications:
Quantity Product Name Catalog Number Series Firmware
Revision
Hardware
3 ControlLogix chassis 1756-A4, (or -A7, -A13, -A13,
-A17)
A-
3 ControlLogix power supply 1756-PA72, -PB72 A -
3 ControlLogix ControlNet Interface Module 1756-CNB, (or -CNBR) B(1) 2.10
2 Logix5550 controller 1756-L1 A 4.41
2 PLC-5 processor, ControlNet version 1785 -L40C15 D C
1 ControlNet Communication Interface Card 1784-KTCX15 - -
1 Analog Output Module 1756-OF6VI A 1.5
1 Digital Input Module 1756-IB16 A 2.4
1 Digital Output Module 1756-0B16I A 1.5
1 personal computer that supports RSLogix software any appropriate model running
Windows 95/98 or NT 4.0
--
associated wiring and cabling as needed
Software Version
1 RSLinx 9355-WAB, -WABOEM, -WABC
(Windows 95/98, NT 4.0)
-2.10
1 RSLogix5 programming software 9324-RL5300ENE
(Windows 95/98, NT 4.0)
-3.21
1 RSLogix5000 programming software 9324-RLD300ENE
(Windows 95/98, NT 4.0)
-2.25(2)
1 RSNetWorx for ControlNet software 9357-CNETL3
(Windows 95/98, NT 4.0)
-1.80
(1) To receive a free firmware upgrade from series A to series B, contact Rockwell Technical Support. See page P-5.
(2) Version 2.10 may also be used. See Appendix D.

1756-6.5.3 - December 1999
P-4
Common Techniques Used
in This Manual
The following conventions are used throughout this manual:
•Numbered lists provide sequential steps.
•Bulleted lists provide information, not procedural steps.
•Text in bold font indicates words or phrases you should type,
programming windows, and menu selections.
•Pictures of keys and/or screens and windows represent the actual keys
you press or the screens and windows you use (see the following figure).
We use this symbol to call attention to helpful information.

1756-6.5.3 - December 1999
P-5
Where to Find More
Information
Refer to the following publications as needed for additional help when
setting up and using your ControlNet network:
Rockwell Automation Support Rockwell Automation offers support services worldwide, with over 75
sales/support offices, 512 authorized distributors, and 260 authorized
systems integrators located throughout the United States alone, plus
Rockwell Automation representatives in every major country in the world.
Local Product Support
Contact your local Rockwell Automation representative for:
•sales and order support
•product technical training
•warranty support
•support service agreements
0RUH
For information about See this publication Publication number
network cabling and wiring ControlNet Cable Planning and Installation Guide 1786-6.2.1
the ControlLogix ControlNet Interface Module ControlLogix ControlNet Bridge Installation Instructions 1756-5.71
the ControlLogix Chassis ControlLogix Chassis Installation instructions 1756-5.2
ControlLogix power supplies ControlLogix Power Supplies Installation Instructions 1756-5.1
Logix5550 programmable controllers Logix5550 Controller User Manual 1756-6.5.12
PLC-5 programmable controllers Enhanced PLC-5 Programmable Controller Quick Start 1785-10.4
ControlNet PLC-5 Programmable Controller Quick Start 1785-10.7
ControlNet PLC-5 Programmable Controller User Manual 1785-6.5.22
ControlLogix Analog I/O modules ControlLogix Analog I/O Users Manual 1756-6.5.9
ControlLogix Digital I/O modules ControlLogix Digital I/O Users Manual 1756-6.5.8
PC communication interface cards 1784-KTX15 Communication Interface Card User Manual 1784-6.5.22
RSLogix5 programming software Getting Results with RSLogix5 9399-RL53GR
RSLogix5000 programming software Getting Results with RSLogix5000 9399-RLD300GR
RSNetWorx for ControlNet software Getting Results with RSLogix with RSNetWorx for ControlNet 9399-RWCNTGR
RSLinx Lite software RSLinx Lite User’s Guide 9399-WAB32LUG
current Allen-Bradley documentation,
including ordering instructions
Allen-Bradley Publication Index SD499
terms and definitions Allen-Bradley Industrial Automation Glossary AG-7.1
Many of these manuals are available online from the Automation
Bookstore, http://www.theautomationbookstore.com.
For more information on Rockwell Software products, visit the Rockwell
Software internet site, http://www.software.rockwell.com.

1756-6.5.3 - December 1999
P-6
Technical Product Assistance
If you need to contact Rockwell Automation for technical assistance, call
your local Rockwell Automation representative.
Your Questions or Comments about This Manual
If you find a problem with this manual, please notify us of it on the enclosed
Publication Problem Report (at the back of this manual).
If you have any suggestions about how we can make this manual more
useful to you, please contact us at the following address:
Rockwell Automation, Allen-Bradley Company, Inc.
Control and Information Group
Technical Communication
1 Allen-Bradley Drive
Mayfield Heights, OH 44124-6118
Telephone Number: 1 440 646-6800

1756-6.5.3 - December 1999
Table of Contents
Chapter 1
ControlNet
Communication Basics
What This Chapter Contains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Module Versions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Before you go any further . . .. . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Module Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
Support for up to 64 Bidirectional Connections. . . . . . . . . . . 1-2
Bridging Unscheduled Data . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Understanding the Producer/Consumer Model . . . . . . . . . . . . . . 1-4
Processing Produced and Consumed Tags. . . . . . . . . . . . . . . 1-5
Control of Scheduled I/O Communications . . . . . . . . . . . . . . 1-6
Understanding the Control and Information Protocol . . . . . . . . . 1-6
Understanding the Network Keeper . . . . . . . . . . . . . . . . . . . . . . . 1-7
Network Update Time (NUT) . . . . . . . . . . . . . . . . . . . . . . . . 1-7
Requested Packet Interval (RPI). . . . . . . . . . . . . . . . . . . . . . . 1-7
Actual Packet Interval (API) . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
Rack Optimized and Direct Connections . . . . . . . . . . . . . . . . 1-8
Default Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
Chapter 2
Installing the
ControlNet Network
What this Chapter Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Installing the 1784-KTCX15 Communication Interface Card . . . 2-2
Configuring the 1784-KTCX15 Card. . . . . . . . . . . . . . . . . . . 2-3
Installing the ControlLogix Modules . . . . . . . . . . . . . . . . . . . . . . 2-5
Connecting the ControlNet Network . . . . . . . . . . . . . . . . . . . . . . 2-7
Installing the PLC-5C Controllers . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Required Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10
Chapter 3
Logix5550 to Logix5550
Controller: Unscheduled
Messaging
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Set Up the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Create the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Create the Controller Tags for the Write Message Program . 3-3
Create the Write Message Ladder Program . . . . . . . . . . . . . . 3-4
Download and Run the Program . . . . . . . . . . . . . . . . . . . . . . 3-6
Test the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Create the Controller Tags for the Test Program . . . . . . . . . . 3-7
Download the Test Program. . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
Test the Communications. . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
Chapter 4
Logix5550 to Logix5550
Controller: Scheduled
Communication
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Set Up the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Create the Producer Application. . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Create the Producer Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Create the Producer Ladder Program . . . . . . . . . . . . . . . . . . . 4-5
Download to the Producer . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

1756-6.5.3 - December 1999
ii
Chapter 4 (continued)
Configure the Consumer Logix5550 Controller. . . . . . . . . . . . . . 4-6
Add the Producer to the I/O Configuration of the Consumer. 4-6
Create the Consumer Tags . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Download to the Consumer. . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
Schedule the Network Using RSNetWorx for ControlNet. . . . . 4-16
Verify the Network Properties . . . . . . . . . . . . . . . . . . . . . . . 4-17
Test the Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
Chapter 5
Logix5550 Controller to PLC-5C:
Unscheduled Messaging
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
Set Up the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
Create the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
Create the Controller Tags for the Write Message Program. . 5-3
Create the Write Message Ladder Program . . . . . . . . . . . . . . 5-4
Download the Write Message Program . . . . . . . . . . . . . . . . . 5-6
Test the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Chapter 6
Logix5550 Controller to PLC-5C:
Scheduled Communications
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Set Up the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
Create the Logix5550 Producer Application . . . . . . . . . . . . . . . . 6-2
Create the Producer Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
Create the Producer Ladder Program . . . . . . . . . . . . . . . . . . . 6-5
Download and Run the Program. . . . . . . . . . . . . . . . . . . . . . . 6-6
Schedule the Network Using RSNetWorx for ControlNet. . . . . . 6-7
Verify the Network Properties . . . . . . . . . . . . . . . . . . . . . . . . 6-9
Survey the Network for Connected Devices. . . . . . . . . . . . . 6-10
Configure the PLC-5C to Receive Scheduled Messages . . . 6-11
Test the Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
Chapter 7
PLC-5C to Logix5550 Controller:
Unscheduled Messaging
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
Set Up the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
Create the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
Create the PLC-5C Program. . . . . . . . . . . . . . . . . . . . . . . . . . 7-3
Download the PLC-5C Program. . . . . . . . . . . . . . . . . . . . . . . 7-5
Test the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
Create the Controller Tags for the Logix5550 Controller. . . . 7-8
Download the Logix5550 Program. . . . . . . . . . . . . . . . . . . . 7-10
Verify the Message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11
Chapter 8
PLC-5C to Logix5550 Controller:
Scheduled Communications
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1
Set Up the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 8-1
Configure the Network Using RSNetWorx for ControlNet . . . . . 8-2
Verify the Network Properties . . . . . . . . . . . . . . . . . . . . . . . . 8-4

1756-6.5.3 - December 1999
iii
Chapter 8 (continued)
Survey the Network for Connected Devices . . . . . . . . . . . . . 8-5
Configure the PLC-5C Processor . . . . . . . . . . . . . . . . . . . . . . 8-6
Configure the Consumer Logix5550 Controller. . . . . . . . . . . . . . 8-9
Add the Producer to the I/O Configuration . . . . . . . . . . . . . 8-10
Create the Consumer Tags . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13
Download the Logix5550 Program . . . . . . . . . . . . . . . . . . . 8-17
Create the Producer Application. . . . . . . . . . . . . . . . . . . . . . . . . 8-18
Create the PLC-5C Program. . . . . . . . . . . . . . . . . . . . . . . . . 8-19
Download the PLC-5C Program. . . . . . . . . . . . . . . . . . . . . . 8-19
Schedule the Network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-22
Verify the Message. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23
Chapter 9
PLC-5C to PLC-5C Unscheduled
Messaging Over Two
ControlNet Networks
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1
Set Up the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . 9-1
Create the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 9-2
Create the Ladder Program. . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3
Download the Program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-5
Test the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6
Chapter 10
Controlling I/O Over a
ControlNet Network
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . 10-1
Set Up the Example Application . . . . . . . . . . . . . . . . . . . . . . . . 10-2
Create the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . 10-2
Add the Local CNB Module to the I/O Configuration. . . . . 10-3
Add the Remote CNB Module to the I/O Configuration . . . 10-4
Add the Remote I/O Modules to the I/O Configuration. . . . 10-7
Edit the Controller Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-11
Create the Ladder Logic Program . . . . . . . . . . . . . . . . . . . 10-12
Download the Program. . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12
Schedule the Network Using RSNetWorx for ControlNet. . . . 10-13
Verify the Network Properties . . . . . . . . . . . . . . . . . . . . . . 10-15
Survey the Network for Connected Devices . . . . . . . . . . . 10-16
Schedule the Network and Save the Configuration . . . . . . 10-17
Test the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . 10-18
Chapter 11
Adding an I/O Chassis to an
Existing ControlNet Network
About the Example Application . . . . . . . . . . . . . . . . . . . . . . . . . 11-1
Set Up the Example Application . . . . . . . . . . . . . . . . . . . . . . . . 11-2
Create the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . 11-2
Add the Second Remote 1756-CNB Module
to the I/O Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-3
Add the Remote Analog I/O Module
to the I/O Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5
Edit the Controller Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-9
Modify the Ladder Program . . . . . . . . . . . . . . . . . . . . . . . . 11-10

1756-6.5.3 - December 1999
iv
Chapter 11 (continued)
Download the Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-10
Schedule the Network Using RSNetWorx for ControlNet. . . . 11-11
Verify the Network Properties . . . . . . . . . . . . . . . . . . . . . . 11-13
Survey the Network for Connected Devices. . . . . . . . . . . . 11-14
Schedule the Network and Save the Configuration . . . . . . 11-15
Test the Example Application. . . . . . . . . . . . . . . . . . . . . . . . . . 11-16
Adding 1756-CNB Modules to Expand the Network. . . . . . . . 11-17
Chapter 12
Troubleshooting Module Status Indicator and Display . . . . . . . . . . . . . . . . . . 12-1
ControlNet Network Status Indicators . . . . . . . . . . . . . . . . . 12-3
Appendix A
Allocating Communication
Connections
What This Appendix Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
How the ControlLogix System Uses Connections . . . . . . . . . . . . A-1
Determining Connections for I/O Modules . . . . . . . . . . . . . . . . . A-2
Direct connections for I/O modules . . . . . . . . . . . . . . . . . . . . A-2
Rack optimized connections for I/O modules. . . . . . . . . . . . . A-3
Combining direct and rack optimized connections. . . . . . . . . A-5
Determining Connections for Produced and Consumed Tags . . . A-6
Connections for produced tags . . . . . . . . . . . . . . . . . . . . . . . . A-6
Optimizing produced tags. . . . . . . . . . . . . . . . . . . . . . . . . . . . A-7
Connections for consumed tags . . . . . . . . . . . . . . . . . . . . . . . A-7
Determining Connections for Messaging . . . . . . . . . . . . . . . . . . . A-8
Determining Total Connection Requirements . . . . . . . . . . . . . . . A-9
Appendix B
Creating Produced and
Consumed Tags
What This Appendix Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
Produced Tags. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
Consumed Tags. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-3
Producing a tag from a Logix5550 Controller
to a ControlNet PLC-5 Processor . . . . . . . . . . . . . . . . . . . . . . . . . B-5
Consuming a tag from a ControlNet PLC-5 Processor
to a Logix5550 Controller. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-5
Appendix C
Electronic Keying Specifying Electronic Keying. . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1
Appendix D
Setting Paths for Downloads in
RSLogix5000, Version 2.10
Communications Path. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1
Index

1756-6.5.3 - December 1999
Chapter 1
ControlNet Communication Basics
What This Chapter Contains This chapter provides an overview of the primary features and requirements
of ControlNet communication using the 1756-CNB module.
Module Versions The ControlLogix ControlNet interface module is available in redundant
(1756-CNBR) and non-redundant (1756-CNB) configurations. Either
versionmay be used in the example applications, but for simplicity, we refer
to both as the 1756-CNB module.
Before you go any further . . .
The example applications use series B (firmware version 2.10) 1756-CNB
modules. If you currently have series A modules, you can obtain free
firmware upgrades to series B by contacting Rockwell Technical Support.
See page P-6.
For information about See page
Module Versions 1-1
Support for up to 64 Bidirectional Connections 1-2
Bridging Unscheduled Data 1-3
Understanding the Producer/Consumer Model 1-4
Processing Produced and Consumed Tags 1-5
Control of Scheduled I/O Communications 1-6
Understanding the Control and Information Protocol 1-6
Understanding the Network Keeper 1-7
Network Update Time (NUT) 1-7
Requested Packet Interval (RPI) 1-7
Actual Packet Interval (API) 1-8
Rack Optimized and Direct Connections 1-8
Default Parameters 1-10
For further information on the differences between using the redundant and
non-redundant versions of the 1756-CNB module in your network, refer to
the ControlNet Cable Planning and Installation Manual, publication
1786-6.2.1.

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1-2 ControlNet Communication Basics
Module Features The 1756-CNB module performs two primary tasks:
1. control of I/O data in conjunction with a Logix5550 controller
(scheduled data)
2. support of messaging data for configuration and programming
information (unscheduled data)
The 1756-CNB module has these primary features:
•support for a maximum of 64 bidirectional connections with other
ControlNet devices
•support of up to 20 buffers for unconnected messages
•bridging of unscheduled data (messaging and programming information)
•control of scheduled I/O and scheduled data (in conjunction with a
Logix5550 controller)
Support for up to 64 Bidirectional Connections
A connection is an open communication path between the data producer and
the data consumer on the network. The connection includes information
about the location of the consumer that significantly decreases the data
overhead. By contrast, an unconnected message is a traditional message that
uses the network address of the target device and the data address within the
target.
The 1756-CNB module supports a maximum of 64 bidirectional
connections. These connections can be any mix of unscheduled and
scheduled connections. If your application requires more connections, you
can place additional 1756-CNB modules in the same chassis and on the
same network as the first module to provide additional connections.
Important:The number of connections that can actually be supported on a
network is dependent upon the network configuration. For
example, only 10 to 12 connections can be supported at an RPI
(requested packet interval) of 5ms, and only 4 at an RPI of 2ms.
Important:If you choose to use additional modules to provide additional
connections, be sure to partition your application so that it best
uses the additional modules. See page 11-17 for an example
network.

1756-6.5.3 - December 1999
ControlNet Communication Basics 1-3
Bridging Unscheduled Data
Unscheduled messaging is data transfer or communication between
controllers that is triggered by the program (i.e., the message instruction)
and uses one or more of the communication protocols, including
ControlNet. Unscheduled messaging allow you to send and receive data
when needed.
ControlLogix bridges transfer unscheduled data from one network protocol
(ControlNet, DeviceNet, Ethernet) to the ControlLogix backplane and vise
versa. The 1756-CNB module bridges unscheduled data, such as messaging
and programming information, between its ControlLogix backplane and the
ControlNet network.
To properly route the messages that it receives, the 1756-CNB must be
supplied with the correct path information.To route an unscheduled
message through the ControlLogix backplane, a path segment of “1 ss” is
first required, where ss is the slot number of the module the message is
being sent to. To route the message through the ControlNet network, a path
segment of “2 nn” is required, where nn is the node number of the module
the message is being sent to.
For example, to route an unscheduled message through a 1756-CNB
module in chassis slot 3 through another 1756-CNB module at ControlNet
node 6 in a different chassis, the path would be:
The next device in the path could be a controller, an I/O device, a bridge to
another communication protocol such as DeviceNet, etc.
2 nn
1ss
Side of Module
Backplane = 1
ControlNet “wire” = 2
Redundant media connector
(1756-CNBR module only)
to backplane
to backplane slot 3 onto ControlNet wire
to ControlNet node 6
1, 3, 2, 6, . .

1756-6.5.3 - December 1999
1-4 ControlNet Communication Basics
With the RSLogix5000 programming software the path is configured using
the Communication tab in the Message Configuration window. See page
3-5 for an example.
Understanding the
Producer/Consumer Model
In traditional I/O systems, controllers poll input modules to obtain their
input status. Digital input modules in the ControlLogix system are not
polled by a controller. Instead, the modules produce (“multicast”) their data
either upon a change of state or periodically. The frequency of update
depends upon the options chosen during configuration and where on the
network the input module resides. The input module, therefore, is a
producer of input data and the controller is a consumer of the data.
The controller can also produce data for other controllers to consume. The
produced and consumed data is accessible by multiple controllers over the
ControlBus backplane and over the ControlNet network. This data
exchange conforms to the producer/consumer model.
This manual provides examples of the producer/consumer model as it
applies to ControlLogix and PLC-5C controllers.
Note that PLC-5 terminology differs slightly from that used by
ControlLogix. A PLC-5C “send scheduled message” is functionally
equivalent to a ControlLogix “produced tag.” A PLC5 “receive scheduled
message” is functionally equivalent to a ControlLogix “consumed tag.”
Important:
ControlLogix
Tag Type
Description Specify Using RSLogix5000 Software
Produced(1) Tags that the controller produced for other
nodes to consume. •Enabled for producing •Number of consumers allowed
Consumed(1) Tags whose values are produced by
another controller. •Name of controller that owns the tag the local controller wants
to consume
•Tag name or instance that the local controller wants to
consume
•Data type of the tag to consume
•Update interval of how often the local controller consumes the
tag data
PLC-5C
Message Type
Description Specify Using the Map Editing Tool (MET)
in RSNetWorx for ControlNet
Send Scheduled Scheduled data that the PLC-5C produces
for other nodes to consume. •Message number
•Message Size
Receive
Scheduled
Scheduled data produced by another
controller. •Node number sending the message onto ControlNet
•Slot number of the controller that owns the tag the PLC-5C
wants to receive
•Tag name or instance that the PLC-5C wants to receive
•Requested Packet Interval
•Message Size
(1) Produced and consumed tags must be controller-scoped tags of DINT or REAL data type, or in an array or structure.

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ControlNet Communication Basics 1-5
See the chapters on scheduled communications for examples of creating
produced/consumed tags and send/receive scheduled messages.
Processing Produced and Consumed Tags
In the producer/consumer model, the consumer is the connection originator
(it opens the connection). When several consumers are trying to open the
connection to the same tag, the connection will be opened to transfer data at
the rate of the consumer with the smallest API (see Actual Packet Interval
on page 1-8).
The producer and consumer must be configured correctly for the specified
data to be shared. To produce for several consumers, the producer must be
configured for this using the RSLogix5000 software for the Logix5550
controller. For the PLC-5C send and receive scheduled messages are
configured using the Map Editing Tool in RSNetWorx for ControlNet.
For ControlLogix controllers, a consumed tag in the consumer must be
specified exactly the same as a produced tag in the producer. In the
following example, consumer_2 does not have the correct tags.
When consumer_2 tries to obtain the shared tags, the connections fail. Even
though three of the tags are specified correctly (B, C, and D), the
connections fail for all the consumed tags because one was incorrect (E).
The other consumers (consumer_1 and consumer_3) can still obtain the
shared tags from the network, as long as their tags are specified correctly.
One consumer failing to obtain shared data does not affect other consumers
accessing the same data.
A
B
C
D
Produced tag names
producer consumer_1
consumer_2
consumer_3
E
B
C
D
Consumed tag names
B
C
D
Consumed tag names
A
B
D
Consumed tag names

1756-6.5.3 - December 1999
1-6 ControlNet Communication Basics
Control of Scheduled I/O Communications
Scheduled connections allow you to send and to receive data repeatedly at a
predetermined rate. You can use the 1756-CNB module to control
scheduled I/O when you use it in conjunction with a Logix5550 controller.
When you place the module in the I/O configuration list of a Logix5550
controller and attach a second ControlLogix chassis to the same ControlNet
network, you can perform remote control operations on the I/O in the
second chassis.
In this situation, the 1756-CNB module in the local chassis with the
Logix5550 controller acts as a scanner while the 1756-CNB module in the
remote chassis with the I/O plays the role of an adapter.
Using RSNetWorx for ControlNet Software
You must use RSNetWorx for ControlNet to enable any connection in a
remote chassis. In addition, RSNetWorx transfers configuration data to the
remote modules and establishes a network update time (NUT) that is
compliant with the desired communications options specified for each
module during configuration.
Important:RSNetWorx must be run whenever a scheduled connection is
added to, removed from, or changed in your system.
Understanding the Control and
Information Protocol
ControlLogix routing uses the Control and Information Protocol (CIP). CIP
isamessage-basedprotocolthatimplementsarelativepathtosendamessage
from the producing device in a system to theconsuming devices. In this way,
the producing device in a networked system contains the path information
that steers the message along the proper route to reach its consumers. Since
the producing device holds this information, other devices along the path
simply pass this information; they do not need to store it. This has two
significant benefits:
•You do not need to configure routing tables in the bridging module,
which greatly simplifies maintenance and module replacement.
•You maintain full control over the route taken by each message, which
enables you to select alternative paths for the same end device.
See Appendices A and B for more information on connections and on
produced and consumed tags.
I/O I/O
C
N
B
L
5
5
5
0
C
N
B
Scanner
Adaptor
ControlNet Network
You can learn more about RSNetWorx for ControlNet and other Rockwell
Software products by visiting the Rockwell Software internet site,
http://www.software.rockwell.com.