Allen-Bradley 1756 ControlLogix User manual

User Manual
ControlNet Network Configuration
1756 ControlLogix, 1756 GuardLogix, 1769 CompactLogix,
1769 Compact GuardLogix, 1789 SoftLogix, Studio 5000 Logix Emulate

Important user information
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The examples and diagrams in this manual are included solely for illustrative purposes. Because of the many variables and requirements
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Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 3
Summary of Changes
This manual includes new and updated information. Use these reference
tables to locate changed information.
Grammatical and editorial style changes are not included in this summary.
Global changes
This table identifies changes that apply to all information about a subject in
the manual and the reason for the change. For example, the addition of new
supported hardware, a software design change, or additional reference
material would result in changes to all of the topics that deal with that
subject.
Subject Reason
Updated screen shots
throughout. The Studio 5000 Logix Designer® interface has been modified in versions 31 and later.
New or enhanced features
None in this release.

Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 5
Table of contents
Studio 5000 environment................................................................................ 7
Additional Resources...................................................................................... 8
Legal notices................................................................................................... 8
Chapter 1
Use ControlNet Communication Modules in a Control System................... 11
Bridge Across Networks............................................................................... 13
Exchange Information on a ControlNet Network......................................... 16
Network Update Time (NUT)................................................................ 17
Requested Packet Interval (RPI)............................................................ 18
Actual Packet Interval (API).................................................................. 18
Understand the Effect of the NUT on the API................................. 18
Schedule the Network ............................................................................ 19
Control of Scheduled I/O................................................................. 19
Understand the Network Keeper............................................................ 20
Default Parameters................................................................................. 21
ControlNet Network Capacity and Topology............................................... 22
Topology................................................................................................ 22
Number of Nodes................................................................................... 24
Lengths................................................................................................... 24
Chapter 2
Configure the ControlNet Communication Driver in RSLinx Classic
Software........................................................................................................ 28
Chapter 3
Use Logix Designer Application .................................................................. 31
Configure the I/O Configuration Tree in Your Project.......................... 31
Add and Configure a Local ControlNet Module.................................... 31
Add and Configure a Remote ControlNet Module ................................ 35
Communication Format................................................................... 36
Download the Project to the Logix 5000 Controller.............................. 38
Electronic Keying................................................................................... 40
Exact Match..................................................................................... 41
Compatible Keying.......................................................................... 42
Disabled Keying .............................................................................. 44
Use RSNetWorx for ControlNet Software ................................................... 46
Schedule a ControlNet Network for the First Time............................... 46
Schedule the Network Offline................................................................ 47
Schedule the Network Online ................................................................ 52
Reschedule a ControlNet Network that has Previously been Scheduled56
Preface
ControlNet Overview
Connect a Computer
to the ControlNet
Network
Configure a
ControlNet Module

Table of contents
6Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
Chapter 4
Set Up the Hardware..................................................................................... 60
Requested Packet Interval (RPI)................................................................... 60
Communication Format................................................................................ 60
Direct or Rack-optimized Connections.................................................. 62
Direct Connections for I/O Modules ............................................... 63
Rack-optimized Connections for I/O Modules................................ 64
Ownership .............................................................................................. 65
Choose the Type of Ownership for a Module.................................. 65
Add a Remote Adapter ................................................................................. 66
Add Distributed I/O...................................................................................... 67
Distributed I/O Communication Formats............................................... 68
Access Distributed I/O.................................................................................. 69
Validate Connections.................................................................................... 71
Chapter 5
Terminology ................................................................................................. 75
Set Up the Hardware..................................................................................... 76
Determine Connections for Produced and Consumed Tags......................... 77
Organize Tags for Produced or Consumed Data.......................................... 78
Adjust for Bandwidth Limitations................................................................ 79
Produce a Tag............................................................................................... 80
Consume a Tag............................................................................................. 83
Chapter 6
Set Up the Hardware..................................................................................... 87
Guidelines for MSG Instructions.................................................................. 88
Determine Connections for Messages .......................................................... 89
Guidelines for Caching Message Connections....................................... 90
Enter Message Logic .................................................................................... 90
Add the ControlNet Modules and Remote Devices to the Local
Controller’s I/O Configuration............................................................... 90
Enter a Message ..................................................................................... 91
Configure a Message Instruction.................................................................. 92
Stagger the Messages.................................................................................... 93
Chapter 7
Set Up the Hardware..................................................................................... 95
Determine Connections to PanelView Terminals......................................... 96
Add a PanelView Terminal........................................................................... 97
Organize Controller Data for a PanelView Terminal................................. 100
Control I/O
Produce and
Consume Tags
(interlock controllers)
Messaging
Communicate with
PanelView Terminals
Index

Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 7
Preface
This manual describes how you can use ControlNet communication modules
with your Logix 5000™ controller.
Use this manual if you program applications that use a ControlNet network
with one of these Logix 5000 controllers:
•CompactLogix controller
•ControlLogix controller
•PowerFlex 700S with DriveLogix controller
•SoftLogix5800 controller
Also be familiar with the following:
•Networking concepts
•Logix Designer software
•FactoryTalk® Linx™ or RSLinx Classic software
•RSNetWorx for ControlNet software
The Studio 5000 Automation Engineering & Design Environment®
combines engineering and design elements into a common environment. The
first element is the Studio 5000 Logix Designer® application. The Logix
Designer application is the rebranding of RSLogix 5000® software and will
continue to be the product to program Logix 5000™ controllers for discrete,
process, batch, motion, safety, and drive-based solutions.
The Studio 5000® environment is the foundation for the future of
Rockwell Automation® engineering design tools and capabilities. The Studio
5000 environment is the one place for design engineers to develop all
elements of their control system.
Studio 5000
environment

Preface
8Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
These documents contain additional information concerning related products
from Rockwell Automation.
Resource
Description
ControlNet Modules Installation
Instructions, publication CNET-IN005
Describes how to install 1756-CN2, 1756-
CN2R, 1756-CN2RXT, 1756-CNB, 1756-
CNBR, 1768-CNB, and 1768-CNBR
ControlNet modules.
Industrial Automation Wiring and
Grounding Guidelines, publication
1770-4.1
Provides general guidelines for installing a
Rockwell Automation industrial system.
Product Certifications website,
http://www.ab.com Provides declarations of conformity, certificates, and other certification details.
You can view or download publications at
http://www.rockwellautomation.com/literature. To order paper copies of
technical documentation, contact your local Rockwell Automation distributor
or sales representative.
Copyright notice
Copyright © 2018 Rockwell Automation Technologies, Inc. All Rights
Reserved. Printed in USA.
This document and any accompanying Rockwell Software products are
copyrighted by Rockwell Automation Technologies, Inc. Any reproduction
and/or distribution without prior written consent from Rockwell Automation
Technologies, Inc. is strictly prohibited. Please refer to the license agreement
for details.
End User License Agreement (EULA)
You can view the Rockwell Automation End-User License Agreement
("EULA") by opening the License.rtf file located in your product's install
folder on your hard drive.
Other Licenses
The software included in this product contains copyrighted software that is
licensed under one or more open source licenses. Copies of those licenses are
included with the software. Corresponding Source code for open source
packages included in this product can be located at their respective web
site(s).
You may alternately obtain complete Corresponding Source code by
contacting Rockwell Automation via our Contact form on the Rockwell
Automation website: http://www.rockwellautomation.com/global/about-
us/contact/contact.page.
Please include "Open Source" as part of the request text.
The following open source software is used in this product:
Additional
Resources
Legal notices

Preface
Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 9
Software Copyright License Name License Text
AngularJS Copyright 2010-2017 Google, Inc. MIT License AngularJS 1.5.9 License
Bootstrap Copyright 2011-2017 Twitter, Inc.
Copyright 2011-2017 The Bootstrap Authors MIT License Bootstrap 3.3.7 License
jQuery Copyright 2005, 2014 JS Foundation and
other contributors MIT License jQuery 2.1.1 License
OpenSans Copyright 2017 Google, Inc. Apache License,
Version 2.0 OpenSans License
Trademark Notices
Allen-Bradley, ControlBus, ControlFLASH, Compact GuardLogix, Compact
I/O, ControlLogix, CompactLogix, DCM, DH+, Data Highway Plus,
DriveLogix, DPI, DriveTools, Explorer, FactoryTalk, FactoryTalk
Administration Console, FactoryTalk Alarms and Events, FactoryTalk Batch,
FactoryTalk Directory, FactoryTalk Security, FactoryTalk Services Platform,
FactoryTalk View, FactoryTalk View SE, FLEX Ex, FlexLogix, FLEX I/O,
Guard I/O, High Performance Drive, Integrated Architecture, Kinetix,
Logix5000, Logix 5000, Logix5550, MicroLogix, DeviceNet, EtherNet/IP,
PLC-2, PLC-3, PLC-5, PanelBuilder, PowerFlex, PhaseManager, POINT
I/O, PowerFlex, Rockwell Automation, RSBizWare, Rockwell Software,
RSEmulate, Historian, RSFieldbus, RSLinx, RSLogix, RSNetWorx for
DeviceNet, RSNetWorx for EtherNet/IP, RSMACC, RSView, RSView32,
Rockwell Software Studio 5000 Automation Engineering & Design
Environment, Studio 5000 View Designer, SCANport, SLC, SoftLogix,
SMC Flex, Studio 5000, Ultra 100, Ultra 200, VersaView, WINtelligent,
XM, SequenceManager are trademarks of Rockwell Automation, Inc.
Any Rockwell Automation logo, software or hardware product not
mentioned herein is also a trademark, registered or otherwise, of Rockwell
Automation, Inc.
Other Trademarks
CmFAS Assistant, CmDongle, CodeMeter, CodeMeter Control Center, and
WIBU are trademarks of WIBU-SYSTEMS AG in the United States and/or
other countries. Microsoft is a registered trademark of Microsoft Corporation
in the United States and/or other countries. ControlNet is a trademark of
ControlNet International. DeviceNet is a trademark of the Open DeviceNet
Vendors Association (ODVA). Ethernet/IP is a trademark of ControlNet
International under license by ODVA.
All other trademarks are the property of their respective holders and are
hereby acknowledged.
Warranty
This product is warranted in accordance with the product license. The
product’s performance may be affected by system configuration, the
application being performed, operator control, maintenance, and other related

Preface
10 Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
factors. Rockwell Automation is not responsible for these intervening factors.
The instructions in this document do not cover all the details or variations in
the equipment, procedure, or process described, nor do they provide
directions for meeting every possible contingency during installation,
operation, or maintenance. This product’s implementation may vary among
users.
This document is current as of the time of release of the product; however,
the accompanying software may have changed since the release. Rockwell
Automation, Inc. reserves the right to change any information contained in
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responsibility to obtain the most current information available from Rockwell
when installing or using this product.
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Contact Rockwell Automation
Customer Support Telephone — 1.440.646.3434
Online Support — http://www.rockwellautomation.com/support/

Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 11
Chapter 1
ControlNet Overview
The ControlNet network provides high-speed transmission of time-critical
I/O and interlocking data and messaging data. This data transfer capability
enhances I/O performance and peer-to-peer communication in any system or
application.
The ControlNet network is highly deterministic and repeatable and remains
unaffected as devices are connected or disconnected from it. This ensures
dependable, synchronized, and coordinated real-time performance.
The ControlNet network is most often used in these ways:
•As the default network for the ControlLogix platform
•As a backbone to multiple distributed DeviceNet networks
•As a peer interlocking network
This chapter describes how you can use ControlNet modules in a network
control system.
Topic Page
Use ControlNet Communication Modules in a Control
System on page 11 9on page 11
Bridge Across Networks on page 13 11 on page 13
Exchange Information on a ControlNet Network on page 16 14 on page 16
ControlNet Network Capacity and Topology on page 22 21 on page 22
You can fit various ControlNet modules into your control system.
Figure 1 on page 10 shows the following:
•The controllers produce and consume tags among themselves.
•The controllers initiate MSG instructions that send/receive data or
configure devices.
•The computer uploads and downloads projects to the controllers.
•The computer configures devices on the ControlNet network and
configures the network itself.
Use ControlNet
Communication
Modules in a
Control System

Chapter 1
ControlNet Overview
12 Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
Figure 1 - ControlNet Modules and the Control System Overview
Item Description
1 Personal computer running SoftLogix5800 controller with 1784-PCICS card
2 1756-CNB module (as an adapter) with 1756 I/O modules
3 PowerFlex 700S drive
4 1794-ACN15 adapter with 1794 I/O modules
5 1734-ACNR adapter with 1734 I/O modules
6 PanelView terminal
7 CompactLogix 1769-L35CR controller with local 1769 I/O modules
8 ControlLogix controller with 1756-CN2, 1756-CN2R, 1756-CNB, or 1756-CNBR module as the scanner
Important: For an enhanced redundancy system, you must use a 1756-CNB,
1756-CNBR, 1756-CN2 series B, or 1756-CN2R series B communication module. The 1756-CN2 or 1756-
CN2R series A module does not support enhanced redundancy. For more information, refer to the
ControlLogix Enhanced Redundancy System User Manual, publication 1756-UM535.

ControlNet Overview
Chapter 1
Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 13
Some ControlNet modules support the ability to bridge or route
communication to and from different networks, depending on the capabilities
of the platform and communication devices.
Important: You can only bridge across networks to communicate with devices. You cannot bridge across networks to
control I/O, even though Logix Designer software can accept such a configuration in the I/O Configuration
folder. All I/O control must originate and end on the same physical network.
The following table describes how communication can bridge across
networks.
Table 1 - Bridging Across Networks
A device on this network Can communicate with a device on this network
EtherNet/IP
ControlNet
DeviceNet
RS-232(1)
EtherNet/IP Yes Yes Yes Yes
ControlNet Yes Yes Yes Yes
DeviceNet No No Yes No
RS-232 Yes Yes(2) Yes Yes
In Figure 2, a workstation configures a drive on the DeviceNet network. The
workstation bridges from the ControlNet network to the DeviceNet network
to reach the drive. The bridge is a ControLogix chassis with ControlNet and
DeviceNet modules.
Figure 2 - Drive Configuration on a DeviceNet Network
Item Description Item Description
Workstation Drive
Bridge Across
Networks

Chapter 1
ControlNet Overview
14 Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
Item Description Item Description
PanelView terminal DeviceNet network
Bridge ControlNet network
Important:
The performance of a CompactLogix controller on a ControlNet network degrades significantly if you use the
controller as a bridge. Target bridging over a CompactLogix controller on a ControlNet network toward
applications that are not real-time dependent, such as Logix Designer software program downloads.
In the example shown above, you can transfer messages from the DeviceNet
network through the Logix 5000 controller to an RSView32 operator
interface. With a CompactLogix controller as a bridge, you can map the data
into the DeviceNet I/O image and then use RSLinx OPC to send the data to
the Logix 5000 controller over the ControlNet network. This method
conserves the limited bridging resources of your CompactLogix controller.
The following example shows how a DeviceNet bridge links to an
EtherNet/IP network in RSLinx Classic software.
Figure 3 - EtherNet/IP Bridge Linking to a ControlNet Network
Item Description Item Description
EtherNet/IP network ControlNet Bridge in 1756 system
EtherNet/IP bridge in 1756
system ControlNet network
The following tables list the possible bridges between communication
networks. Note that you can bridge from a ControlNet network to an Ethernet
network and from an Ethernet network to a ControlNet via a SoftLogix
virtual chassis. However, the products and methods you must use to do so are
more detailed than can be effectively described in the following tables. For
more information on how to bridge from one network to another via a

ControlNet Overview
Chapter 1
Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 15
SoftLogix virtual chassis, see the SoftLogix5800 System User Manual,
publication 1789-UM002.
Table 2 - Bridges from a ControlNet Network
Destination
Network Modules for a 1768 CompactLogix System Modules for a 1769 CompactLogix System Modules for a ControlLogix Chassis
DeviceNet
•1768-L43 or 1768-L45 controller
•1768-CNB(R) module
•1769-SDN scanner
•1769-L32C or 1769-L35CR
controller
•1769-SDN scanner or 1788-
CN2DN module(1)
•1756-CN2 module
•1756-CN2R module
•1756-CNB module
•1756-CNBR module
•1756-DNB module
EtherNet/IP
•1768-L43 or 1768-L45 controller
•1768-CNB(R) module
•1768-ENBT module
Not applicable
•1756-CN2 module
•1756-CN2R module
•1756-CNB module
•1756-CNBR module
•1756-ENBT module
•1756-EN2T module
•1756-EN2TR module
•1756-EN3TR module
Table 3 - Bridges from an EtherNet/IP Network
Destination
Network Modules for a 1768 CompactLogix System Modules for a 1769 CompactLogix System Modules for a ControlLogix Chassis Modules for a 1769
CompactLogix
Packaged Controller
System
ControlNet
•1768-L43 or 1768-L45
controller
•1768-ENBT module
•1768-CNB(R) module
Not applicable
•1756-CN2 module
•1756-CN2R module
•1756-CNB module
•1756-CNBR module
•1756-ENBT module
•1756-EN2T module
•1756-EN2TR module
•1756-EN3TR module
Not applicable
DeviceNet
•1768-L43 or 1768-L45
controller
•1768-ENBT module
•1769-SDN scanner
•1769-L32E or 1769-
L35E controller
•1769-SDN scanner or
1788-
EN2DN module(1)
•1756-DNB module
•1756-ENBT module
•1756-EN2T module
•1756-EN2TR module
•1756-EN3TR module
•1769-L23E-QB1B
controller
•1769-L23E-QBFC1B
controller
•1769-L23-QBFC1B
controller
•1769-SDN scanner

Chapter 1
ControlNet Overview
16 Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
ControlNet communication modules use a message-based protocol that
implements a relative path to send a message from the producing module in a
system to the consuming modules. This protocol also lets you communicate
between devices on a ControlNet, DeviceNet, or EtherNet/IP network
without writing additional application code.
With unscheduled data, the device from which a message originates, such as
a Logix 5000 controller, contains the path information that makes sure the
message reaches its consumers.
For a full explanation of unscheduled and scheduled data, see Network
Update Time (NUT) on page 16 on page 17.
Because the producing module holds this information, other modules along
the path simply pass the information along and do not need to store it. The
significant benefits include the following:
•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 module.
Scheduled data in Logix-based systems use the producer/consumer
networking model instead of a source/destination (master/slave) model. The
producer/consumer model reduces network traffic and increases transmission
speed.
In traditional I/O systems, controllers poll input modules to obtain their input
status. In a Logix system, digital input modules are not polled by a controller.
Instead, they produce (multicast) their data either upon a change of state
(COS) 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
Logix backplane and the ControlNet network. This data exchange conforms
to the producer/consumer model.
A ControlNet network link’s most important function is to transport time-
critical control information, such as I/O data and control interlocking. Other
information that is not time-critical, such as program uploads and downloads,
is also transported but does not interfere with time-critical messages because
a ControlNet network can transmit scheduled and unscheduled data.
On a ControlNet network link, nodes transfer information by establishing
connections. Each message sent by a producer contains a Connection ID
(CID). Nodes that have been configured to recognize the CID consume the
message, becoming consumers themselves.
Exchange
Information on a
ControlNet Network

ControlNet Overview
Chapter 1
Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 17
Media access to the network is controlled by a time-slice access algorithm,
Concurrent Time Domain Multiple Access (CTDMA), which regulates a
node’s opportunity to transmit in each network update interval (NUI). You
configure how often the NUI repeats by selecting a network update time
(NUT) in milliseconds.
The network update time (NUT) is the shortest interval in which data can be
sent on a ControlNet network. It represents the fastest possible update rate
for scheduled data transfers on that network. For example, a network that
runs with a five ms NUT cannot send scheduled data at a rate faster than five
ms. It can, however, send data at a slower rate. The minimum NUT you can
specify is two ms. The NUT is divided into a three-part structure.
Table 4 - NUT Structure
Parts of NUT Functions
Scheduled On a sequential, rotating basis, every scheduled node can transmit data once per NUT.
Time-critical information is sent during this part of the interval.
Unscheduled
All nodes transmit on a sequential, rotating basis, the rotation repeating itself until the time allotted for
this portion is used up.
The number of scheduled transmissions determines the time available for unscheduled
transmissions. On a ControlNet network, at least one node can transmit unscheduled data every
NUT.
Information that can be delivered without time constraints is sent during this part of the interval.
Maintenance The node with the lowest address transmits information to keep the other nodes synchronized. This
time is automatically subtracted from your NUT. However, the time required for network maintenance
is brief (microseconds) when compared to that used for the scheduled and unscheduled portions of
the NUT.
Figure 4 - NUT Structure
Item Description
Boundary moves according to scheduled traffic load
Unscheduled traffic
Network maintenance
Network Update Time
(NUT)

Chapter 1
ControlNet Overview
18 Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
Item Description
Scheduled traffic. Each device transmits only once
Start
The RPI is the update rate specified for a particular piece of data on the
network. By using a rack-optimized connection, the RPI can specify the rate
for an entire rack of I/O. With a direct connection, the RPI can specify the
rate for a particular module or peer-to-peer data. When you add a module to
the I/O configuration of a controller, you must configure the RPI, specifying
how often to produce data for that module. For example, if you specify an
RPI of 50 ms, every 50 ms the I/O module sends its data to the controller or
the controller sends its data to the I/O module.
Set the RPI only as fast as needed by the application. The RPI also
determines the number of packets per second that the module will handle on
a connection. Each module has a limit of how many packets it can handle per
second. If you exceed this limit, the module cannot open any more
connections.
A faster RPI consumes more network bandwidth. So, to avoid wasting
network bandwidth, set the RPI only as fast as is necessary. For example, if
your application uses a thermocouple module that has data change every 100
ms, do not set the RPI for that node at 5 ms because the network bandwidth
is used to transmit mostly old data.
Important:
You cannot set the RPI to a rate faster than the NUT. The network cannot send data at a rate that is faster
than the NUT.
When you run RSNetWorx for ControlNet software, an Actual Packet
Interval (API) is calculated. The API is equal to or faster than the RPI.
The API is the actual update rate for a particular piece of data on the
network. A ControlNet network sets this rate equal to or faster than the RPI,
based on the binary multiple of the NUT, which is the next fastest rate at
which a module can send data. If this cannot be done, a ControlNet network
provides reports that it cannot support the configuration.
This example illustrates how the NUT affects the API. A module on the
network can produce data only at binary multiples of the NUT to a maximum
of the NUT multiplied by 128. These multiples are referred to as rates on a
ControlNet network. Therefore, with a NUT of 5 ms, the module can send
data at these rates.
Table 5 - NUT Example Data Rates
NUT Multiple Rate at Which Module Can Send Data
5 ms 1 5 ms
Requested Packet
Interval (RPI)
Actual Packet Interval
(API)
Understand the Effect of
the NUT on the API

ControlNet Overview
Chapter 1
Rockwell Automation Publication CNET-UM001F-EN-P - February 2018 19
NUT Multiple Rate at Which Module Can Send Data
2 10 ms
4 20 ms
8 40 ms
16 80 ms
32 160 ms
64 320 ms
128 640 ms
In this example, if you specify an RPI of 25 ms, then the network produces
an API of 20 ms, which is the next fastest rate at which the module can send
data. The module places the data on the network at every fourth network
update interval to produce the 20 ms API. Similarly, if you specify an RPI of
150 ms, the network produces an API of 80 ms.
Connections over a ControlNet network can be one of the following:
•Scheduled—Data transferred at specific times.
•Unscheduled—Data transferred when the network can accommodate
the transfer.
To use scheduled connections, you must schedule the ControlNet network
via RSNetWorx for ControlNet software. For more information on how to
schedule a ControlNet network with RSNetWorx for ControlNet software,
see the section Use RSNetWorx for ControlNet Software on page 46 on page
44 on page 46.
You must use RSNetWorx for ControlNet software to enable any connection
in a remote chassis. In addition, RSNetWorx software transfers configuration
information for the remote modules, verifies and saves NUT and other user-
specified network parameters, and establishes a schedule that is compliant
with the RPI and other connection options specified for each module.
Important: RSNetWorx for ControlNet software must be run whenever a scheduled connection is added to, removed
from, or changed in your system.
Scheduled connections let you send and receive data repeatedly at a
predetermined rate. You can use the 1756-CNB or the 1756-CN2 module to
control scheduled I/O when you use it in conjunction with a ControlLogix
controller. When you place the module in the I/O configuration list of a
ControlLogix controller and configure a second ControlLogix chassis with a
remote 1756-CNB or 1756-CN2 module on the same ControlNet network,
you can perform remote control operations on the I/O, or to a second
controller in the second chassis.
Schedule the Network
Control of Scheduled I/O

Chapter 1
ControlNet Overview
20 Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
In this case, the ControlLogix controller and the 1756-CN2 module in the
local chassis together act as a scanner, while the 1756-CN2 module in the
remote chassis with the I/O plays the role of an adapter.
Every ControlNet network requires at least one module to store programmed
parameters for the network and configures the network with those parameters
when the module is started. This module is called a keeper because it keeps
the network configuration. RSNetWorx for ControlNet software configures
the keeper.
To avoid a single point of failure, a ControlNet network supports multiple
redundant keepers. These ControlNet communication modules are keeper-
capable devices:
•1756-CN2 and 1756-CN2R modules
•1756-CNB and 1756-CNBR modules
•1768-CNB and 1768-CNBR modules
•1769-L32C and 1769-L35CR controllers
•1784-PCICS and 1784-PKTCS cards
•1788-CNxcards
•PLC-5C module
On a multi-keeper network, any keeper-capable module can keep the network
at any legal node address (01...99). The multi-keeper-capable node with the
lowest node address becomes the active keeper provided it is valid. It has
been configured by RSNetWorx for ControlNet software and that
configuration is the same as that of the first keeper that became active after
the network was formed or reconfigured by RSNetWorx software.
If the active keeper is taken off the network, a valid back-up keeper can take
over for it and continue to act as keeper. As long as at least one valid multi-
keeper device is present on the network, new scheduled connections can be
established.
To review the valid keeper devices on your network, follow this procedure in
RSNetWorx for ControlNet software.
Understand the
Network Keeper