Solid-state equipment has operational characteristics differing from those of electromechanical equipment. Safety
Guidelines for the Application, Installation and Maintenance of Solid State Controls (publication SGI-1.1
your local Rockwell Automation® sales office or online at http://www.rockwellautomation.com/literature/
important differences between solid-state equipment and hard-wired electromechanical devices. Because of this difference,
and also because of the wide variety of uses for solid-state equipment, all persons responsible for applying this equipment
must satisfy themselves that each intended application of this equipment is acceptable.
In no event will Rockwell Automation, Inc. be responsible or liable for indirect or consequential damages resulting from the
use or application of this equipment.
The examples and diagrams in this manual are included solely for illustrative purposes. Because of the many variables and
requirements associated with any particular installation, Rockwell Automation, Inc. cannot assume responsibility or
liability for actual use based on the examples and diagrams.
No patent liability is assumed by Rockwell Automation, Inc. with respect to use of information, circuits, equipment, or
software described in this manual.
Reproduction of the contents of this manual, in whole or in part, without written permission of Rockwell Automation,
Inc., is prohibited.
Throughout this manual, when necessary, we use notes to make you aware of safety considerations.
available from
) describes some
WARNING: Identifies information about practices or circumstances that can cause an explosion in a hazardous environment,
which may lead to personal injury or death, property damage, or economic loss.
ATTENTION: Identifies information about practices or circumstances that can lead to personal injury or death, property
damage, or economic loss. Attentions help you identify a hazard, avoid a hazard, and recognize the consequence.
SHOCK HAZARD: Labels may be on or inside the equipment, for example, a drive or motor, to alert people that dangerous
voltage may be present.
BURN HAZARD: Labels may be on or inside the equipment, for example, a drive or motor, to alert people that surfaces may
reach dangerous temperatures.
Identifies information that is critical for successful application and understanding of the product.
Allen-Bradley, Rockwell Software, Rockwell Automation, and TechConnect are trademarks of Rockwell Automation, Inc.
Trademarks not belonging to Rockwell Automation are property of their respective companies.
Summary of Changes
This manual contains new and updated information. Changes throughout this
revision are marked by change bars, as shown to the right of this paragraph.
New and Updated
Information
This table contains the changes made to this revision.
TopicPage
The Gross Rate for the Prover Function has been updated.48
The Configurable Output Behaviors section has been added.58
The Attention and Warning tables have been updated.61
Detailed filtering information has been added to the Configurable
Flowmeter Module Configuration Tags table.
The Configure Output Behavior with RSLogix 5000 Version 16 and Earlier
appendix has been added.
122 and 124
147
3Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
4 Summary of Changes
Notes:
4Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Table of Contents
Preface
What is the Configurable
Flowmeter Module?
Configurable Flowmeter
Operation in the ControlLogix
System
Who Should Use This Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Industrial Automation Wiring and Grounding
Guidelines, publication 1770-4.1
1756-UM001
1756-UM058
1756-UM009
Provides specifications for the
ControlLogix controllers, I/O modules,
specialty modules, chassis, power
supplies and accessories.
Detailed description of how to use your
ControlLogix operating system.
Detailed description of how to install and
use ControlLogix digital I/O Modules.
Detailed description of how to install and
use ControlLogix analog I/O Modules.
Detailed description of how to install and
use the ControlLogix High-speed Counter
Module.
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/
technical documentation, contact your local Allen-Bradley distributor or
Rockwell Automation sales representative.
9Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
. To order paper copies of
10 Preface
Notes:
10Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Chapter
1
What is the Configurable Flowmeter Module?
What this Chapter Contains
This chapter describes the ControlLogix Configurable Flowmeter (1756-CFM)
module. It also describes what you must know and do before using the
module.
TopicPage
Using a ControlLogix CFM Module12
Understanding Module Input Capabilities15
Understanding Module Output Capabilities15
Using Module Identification and Status
Information
The ControlLogix CFM module is an intelligent I/O module that performs
high-speed flowmetering for industrial applications. The CFM module is a
single-slot module that interfaces between a Logix controller and external I/O
devices.
The module interfaces with the following output types:
Magnetic Pickup
TTL
Preamps
16
11Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
12 What is the Configurable Flowmeter Module?
IMPORTANT
Using a ControlLogix
CFM Module
ControlLogix CFM modules mount in a ControlLogix chassis and use a
Removable Terminal Block (RTB) or a Bulletin 1492 Interface Module cable
that connects to an IFM to connect all field-side wiring.
Before you install and use your module you should have already:
installed and grounded a 1756 chassis and power supply. To install these
products, refer to the ControlLogix Chassis and Power Supplies
Installation Instructions, publication 1756-IN005
ordered and received an RTB or IFM and its components for your
application.
RTBs and IFMs are not included with your module.
.
Module Features
The following are some of the features available on the ControlLogix CFM
module that allow greater system applicability.
2 Configurable Flowmetering channels
Flowmeter inputs
Gate inputs
2 current-sourcing outputs
Removal and insertion under power
CE marked
UL listed
CSA certified for Class I Division 2 hazardous locations
For a complete listing and detailed explanation of all the features available on
the ControlLogix CFM module, see Configurable Flowmeter Module Features
and Operational Modes on page 25.
12Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Physical Features
Indicators
Locking tab
Removable Terminal Block
Slots for
keying the
RTB
Connector pins
Top and
bottom
guides
ControlLogix backplane
connector
METERING
DC I/O
O
K
F0Z0F1Z
1
O0O
1
40200-M
What is the Configurable Flowmeter Module? 13
ControlLogix backplane connector - The backplane connector interface for
the ControlLogix system connects the module to the ControlLogix backplane.
Connectors pins - Input/output, power and grounding connections are made
to the module through these pins with the use of an RTB or IFM.
Locking tab - The locking tab anchors the RTB or IFM cable on the module,
maintaining wiring connections.
Slots for keying - Mechanically keys the RTB to prevent inadvertently making
the wrong wire connections to your module.
Status indicators - Indicators display the status of communication, module
health and input/output devices. Use these indicators to help in
troubleshooting.
Top and bottom guides - Guides provide assistance in seating the RTB or
IFM cable onto the module.
13Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
14 What is the Configurable Flowmeter Module?
42731
CV
Pulse output
Fuel
Monitors fuel flow
and total gallons
Generator
Electricity
Shaft
encoder
Tur bi ne
Shaft speed
1756-CFM
Logix controller
The controller
monitors shaft
speed, performs
PID calculations
and adjusts valve
by a 1756-OF6VI
analog output
module.
1756-OF6VI
Typical Applications
You can use the CFM module in power management, automotive, food and
beverage, and oil and gas industries for various flow and/or turbine metering
applications.
This figure shows a CFM module in a turbine shaft speed monitoring
application. In this example, the 1756-CFM module is operating in high
resolution frequency mode. Other examples are shown in Chapter 3 to reflect
the various operational modes available on the 1756-CFM module.
For a detailed explanation of how the CFM module works with other portions
of a ControlLogix control system, see Chapter 2, Configurable Flowmeter
Operation in the ControlLogix System.
14Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
What is the Configurable Flowmeter Module? 15
IMPORTANT
Understanding Module
Input Capabilities
Understanding Module
Output Capabilities
The CFM module accepts input for up to two channels (mode dependent).
Each of the input channels can connect to:
You configure the CFM module’s two input channels for your specific
application(s). Each input channel has two input selections:
Flowmeter Input (F0 & F1) - Connect input device to this input.
Gate Input (Z0 & Z1) - Accepts 4-40V DC input pulses from open
collectors or external contact closures. These inputs are used in
Totalizer mode to:
– interface to a prover when a prover is enabled.
The CFM module has two assignable outputs. These outputs are designed for
applications that require fast response. The outputs:
are electrically fused/current limited to 4A; the total output
combination is limited to 7A.
can be assigned to any input channel with user-defined trigger parameter
(see Table 1
are current sourcing at 10-31.2V DC (1A maximum per output).
must be connected to an external power supply.
may be forced ON or OFF by the program.
).
You can assign both outputs to a given channel; however,
you cannot use the same output with two different
channels.
Table 1 - Assign the CFM Module’s Outputs
In this operational modeYou can assign outputs that are
configured to trigger
TotalizerFrequency (acceleration)
Prover status
Fill control
High-Resolution FrequencyFrequency
Frequency rate of change (acceleration)
15Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
16 What is the Configurable Flowmeter Module?
IMPORTANT
Using Module
Identification and Status
Information
Each ControlLogix CFM module maintains specific identification information
that separates it from all other modules. This information assists you in
tracking all the components of your system.
For example, you can track module identification information to be aware of
exactly what modules are located in any ControlLogix rack at any time. While
retrieving module identity, you can also retrieve the module’s status.
Each module maintains the following information:
Table 2 - Module Identification and Status Information
Module IdentificationDescription
Product TypeModule’s product type, such as Digital I/O or
Analog I/O module
Catalog CodeModule’s catalog number
Major RevisionModule’s major revision number
Minor RevisionModule’s minor revision number
StatusModule’s status. Returns the following information:
Controller ownership (if any)
Whether module has been configured
Device Specific Status, such as:
Self-Test
Flash update in progress
Communications fault
Not owned (outputs in program mode)
Internal fault (need flash update)
Run mode
Program mode (output mods only)
Minor recoverable fault
Minor unrecoverable fault
Major recoverable fault
Major unrecoverable fault
Vendor IDModule manufacturer vendor, for example Allen-Bradley
Serial NumberModule serial number
Length of ASCII Text StringNumber of characters in module’s text string
ASCII Text StringNumber of characters in module’s text string
You must perform a WHO service to retrieve this
information.
16Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Chapter
Configurable Flowmeter Operation in
the ControlLogix System
2
What This Chapter Contains
This chapter describes how the CFM module works within the ControlLogix
system.
In traditional industrial applications, controllers poll Flowmeter modules to
obtain their status. Controllers also send commands to the Flowmeter
modules. Retrieving Flowmeter status and sending commands occurs during
the normal I/O program scan.
ControlLogix CFM modules do not follow the traditional operational manner.
Instead, they use the Producer/Consumer Model
information) to produce data without having been polled by a controller first.
TopicPage
Ownership19
Using RSNetWorx and RSLogix 5000 Software19
Connections21
Configurable Flowmeter Modules in a Local Chassis23
Requested Packet Interval (RPI)23
Configurable Flowmeter Modules in a Remote Chassis24
Listen-Only Connections22
(see page 33 for more
17Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
18 Configurable Flowmeter Operation in the ControlLogix System
IMPORTANT
42732
Input
device
1
2
4
53
1756-CFMLogix controller
1756-CFM modules follow these basic operational steps, as shown in Figure 2.
1. The Logix controller establishes a connection to the CFM module and
downloads configuration via ladder logic and message instructions.
2. Flowmeters transmit input signals to the CFM module.
3. The 1756-CFM module calculates volume from accumulated pulse
counts as engineering units.
4. Rather than being scanned by an owner-controller, the 1756-CFM
module periodically multicasts its status to the controller. (see Requested
Packet Interval (RPI) on page 23.) The 1756-CFM module also
multicasts its status to controllers connected by a listen-only connection
(page 22
5. The Logix owner-controller processes the data it received from the
1756-CFM module and returns the appropriate data.
Figure 2 - 1756-CFM Basic Operational Steps
).
A 1756-CFM module’s communication, or multicasting,
behavior varies depending upon whether it operates in the
local chassis or in a remote chassis. The following sections
detail the differences in data transfers between these
set-ups.
18Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Configurable Flowmeter Operation in the ControlLogix System 19
IMPORTANT
Ownership
Using RSNetWorx and
RSLogix 5000 Software
Every CFM module in the ControlLogix system must be owned by a
Logix5550
Each CFM module continuously maintains communication with its owner
during normal operation. When connections are severed or compromised, the
CFM module performs as configured, either setting all outputs to reset (ON or
OFF) or continuous operations.
Other controllers may also listen to the CFM module (while another controller
owns the module) through a listen-only connection. For more information on
listen-only connections, see page 22
The I/O configuration portion of RSLogix™ 5000 software generates
configuration data structures and tags for that CFM module, whether the
module is located in a local or remote chassis. A remote chassis, also known as
networked, contains the CFM module but not the module’s owner-controller.
®
Controller. The owner-controller:
stores configuration data for every CFM module that it owns.
can be local or remote in regard to the I/O module’s position.
sends configuration data to the CFM module to define the module’s
behavior within the control system.
.
After creating the CFM module, you can write specific configuration in the
module’s data structures; you must access the module tags to change
information in the data structures. This process is explained in detail in
Chapter 5, Configuring the Configurable Flowmeter Module
Application-specific configuration data is transferred to the
controller during the program download and sent to the
CFM module during the initial power-up. After CFM
module operation has begun, you must use ladder logic and
message instructions to make configuration changes.
.
19Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
20 Configurable Flowmeter Operation in the ControlLogix System
IMPORTANT
CFM Modules in Local Chassis
CFM modules in the same chassis as the owner-controller are ready to run as
soon as the configuration data has been downloaded.
CFM Modules in Remote Chassis
You must run RSNetWorx™ software to enable CFM modules in the
networked chassis. Running RSNetWorx software transfers configuration data
to networked modules and establishes a Network Update Time (NUT) for
ControlNet. The NUT is compliant with the desired communications options
specified for each module during configuration.
Follow these general guidelines when configuring CFM modules:
1. Configure all CFM modules for a given controller using RSLogix 5000
software and download that information to the controller.
2. If the CFM configuration data references a module in a remote chassis,
run RSNetWorx software.
RSNetWorx software must be run whenever a new
module is added to a networked chassis. When a module is
permanently removed from a remote chassis, we
recommend that RSNetWorx software be run to optimize
the allocation of network bandwidth.
20Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Configurable Flowmeter Operation in the ControlLogix System 21
IMPORTANT
Connections
Logix controllers make connections to 1756-CFM modules to exchange data.
The controller can make either of the following connections to a 1756-CFM
module:
Direct Connections
CFM module.
Listen-Only Connections
connection to a CFM module simultaneously.
- Only one controller can make this connection to a
- Multiple controllers can make this
Direct Connections
A direct connection is a real-time data transfer link between the controller
and the device that occupies the slot that the configuration data references.
When module configuration data is downloaded to an owner-controller, the
controller attempts to establish a direct connection to each of the modules
referenced by the data. One of the following events occurs:
If the data is appropriate to the module found in the slot, a connection
is made and operation begins.
If the configuration data is not appropriate, the data is rejected and an
error message displays in the software. In this case, the configuration
data can be inappropriate for any of a number of reasons. For example, a
module’s configuration data may be appropriate except for a mismatch
in electronic keying that prevents normal operation.
The controller maintains and monitors its connection with a module. Any
break in the connection, such as removal of the module from the chassis while
under power, causes the controller to set fault status bits in the data area
associated with the module. The RSLogix 5000 software may monitor this data
area to announce the modules’ failures.
The typical Logix controller can make and maintain up to
250 connections. Each 1756-CFM module requires 1
connection.
21Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
22 Configurable Flowmeter Operation in the ControlLogix System
IMPORTANT
Listen-Only Connections
Any controller in the system can listen to the data from any CFM module
even if the controller does not own the module (in other words, it does not
have to hold the module’s configuration data to listen to the module).
During the CFM module creation process in RSLogix 5000 software, you can
specify the ‘Listen-Only’ Communication Format. For more information on
Communication Format, see page 82
Choosing ‘Listen-Only’ mode allows the controller and module to establish
communications without the controller sending any configuration data. In this
instance, another controller owns the CFM module.
.
Controllers using the Listen-Only mode continue to receive
data multicast from the CFM module as long as a
connection between an owner and CFM module is
maintained.
If the connection between all owners and the CFM module
is broken, the module stops multicasting data and
connections to all ‘Listening controllers’ are also broken.
22Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Configurable Flowmeter Operation in the ControlLogix System 23
IMPORTANT
On-Board Memory
Status Data
Flowmeter 0
Flowmeter 1
Ch 0
Ch 1
41361
Configurable Flowmeter
Modules in a Local Chassis
CFM modules multicast their data periodically. Multicast frequency depends
on the options chosen during configuration and where in the control system
the module physically resides. The data consumer (an owner-controller) is
responsible for knowing that the format of the new data is integers.
Requested Packet Interval (RPI)
This configurable parameter instructs the module to multicast its channel and
status data to the local chassis backplane at specific time intervals.
The RPI instructs the module to multicast the current contents of its
on-board memory when the RPI expires, (i.e. the module does not update its
channels prior to the multicast) as shown in this figure.
You set the RPI value during the initial module
configuration and can adjust it the controller is in Program
mode.
The minimum RPI is determined by channel usage. For
each channel using High Resolution Frequency mode, add
5 ms to the minimum RPI. For each channel using
Totalizer Mode, add 50 ms to the minimum RPI.
For example, if one channel uses High Resolution
Frequency mode and the other goes unused, the minimum
RPI = 5 ms. If one channel uses High Resolution
Frequency mode and the other uses Totalizer mode, the
minimum RPI = 55 ms.
23Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
24 Configurable Flowmeter Operation in the ControlLogix System
Configurable Flowmeter
Modules in a Remote
Chassis
If an CFM module resides in a networked chassis, the role of the RPI changes
slightly with respect to getting data to the owner.
The RPI not only defines when the module multicasts data within its own chassis (as described in the previous section), but also determines how often
the owner-controller will receive it over
the network.
When an RPI value is specified for an CFM module in a remote chassis, in
addition to instructing the module to multicast data within its own chassis, the
RPI also “reserves” a spot in the stream of data flowing across the ControlNet
network.
The timing of this “reserved” spot may or may not coincide with the exact
value of the RPI, but the control system guarantees that the owner controller
receives data at least as often as the specified RPI.
See Figure 2
for a better understanding of the data flow with a CFM module in
a remote chassis.
Figure 2 - CFM Module in Remote Chassis with RPI Reserving a Spot in Flow of
Data
24Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Chapter
3
Configurable Flowmeter Module Features
and Operational Modes
What this Chapter Contains
This chapter describes the ControlLogix Configurable Flowmeter module’s
features and operational modes.
TopicPage
Understanding General Module Features25
Electronic Keying27
Choosing an Operational Mode35
Operating in High Resolution Frequency Mode36
Operating in Totalizer Mode41
Using the Totalizer Mode Prover Function42
Using the Totalizer Mode Filler Function50
Configurable Output Behaviors58
This chapter only provides a general description of each feature, whether
general or operational mode-specific. For examples of how to use these
features in your module’s configuration, see Configuring the Configurable
Flowmeter Module 5 on page 77.
Understanding General
Module Features
25Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
The following general module features are available with the ControlLogix
CFM module.
Module FeaturePage
Removal and Insertion Under Power (RIUP)26
Module Fault Reporting26
Fully Software Configurable26
Producer/Consumer Model33
Module Status Information34
Configurable Flowmetering Channels34
Flowmeter Inputs34
Gate Inputs34
User-Defined Preset and Rollover Values35
Current-Sourcing Outputs35
26 Configurable Flowmeter Module Features and Operational Modes
Removal and Insertion Under Power (RIUP)
All ControlLogix CFM modules may be inserted and removed from the
chassis while power is applied. This feature allows greater availability of the
overall control system because, while the module is being removed or inserted,
there is no additional disruption to the rest of the controlled process.
Module Fault Reporting
ControlLogix CFM modules provide both hardware and software indication
when a module fault has occurred. Each module’s LED fault indicator and
RSLogix 5000 software will graphically display this fault and include a fault
message describing the nature of the fault.
This feature allows you to determine how your module has been affected and
what action should be taken to resume normal operation.
Fully Software Configurable
The RSLogix 5000 software uses a custom, easily understood interface to write
configuration. All module features are enabled or disabled through the I/O
configuration portion of the software.
You can also use the software to interrogate any module in the system to
retrieve:
serial number
revision information
catalog number
vendor identification
error/fault information
diagnostic counters.
By eliminating such tasks as setting hardware switches and jumpers, the
software makes module configuration easier and more reliable.
26Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Configurable Flowmeter Module Features and Operational Modes 27
Electronic Keying
The electronic keying feature automatically compares the expected module, as
shown in the RSLogix 5000 I/O Configuration tree, to the physical module
before I/O communication begins. You can use electronic keying to help
prevent communication to a module that does not match the type and revision
expected.
For each module in the I/O Configuration tree, the user-selected keying
option determines if, and how, an electronic keying check is performed.
Typically, three keying options are available:
Exact Match
Compatible Keying
Disable Keying
You must carefully consider the benefits and implications of each keying
option when selecting between them. For some specific module types, fewer
options are available.
Electronic keying is based on a set of attributes unique to each product
™
revision. When a Logix5000
controller begins communicating with a
module, this set of keying attributes is considered.
Table 3 - Keying Attributes
AttributeDescription
VendorThe manufacturer of the module, for example, Rockwell
Automation/Allen-Bradley.
Product TypeThe general type of the module, for example, communication
adapter, AC drive, or digital I/O.
Product CodeThe specific type of module, generally represented by its catalog
number, for example, 1756-IB16I.
Major RevisionA number that represents the functional capabilities and data
exchange formats of the module. Typically, although not always, a
later, that is higher, Major Revision supports at least all of the data
formats supported by an earlier, that is lower, Major Revision of the
same catalog number and, possibly, additional ones.
Minor RevisionA number that indicates the module’s specific firmware revision.
Minor Revisions typically do not impact data compatibility but may
indicate performance or behavior improvement.
You can find revision information on the General tab of a module’s Properties
dialog box.
27Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
28 Configurable Flowmeter Module Features and Operational Modes
IMPORTANT
Figure 3 - General Tab
Exact Match
Exact Match keying requires all keying attributes, that is, Vendor, Product
Type, Product Code (catalog number), Major Revision, and Minor Revision, of
the physical module and the module created in the software to match precisely
to establish communication. If any attribute does not match precisely, I/O
communication is not permitted with the module or with modules connected
through it, as in the case of a communication module.
Changing electronic keying selections online may cause the
I/O communication connection to the module to be
disrupted and may result in a loss of data.
Use Exact Match keying when you need the system to verify that the module
revisions in use are exactly as specified in the project, such as for use in
highly-regulated industries. Exact Match keying is also necessary to enable
Automatic Firmware Update for the module via the Firmware Supervisor
feature from a Logix5000 controller.
28Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
Configurable Flowmeter Module Features and Operational Modes 29
EXAMPLE
IMPORTANT
Module Configuration
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IB16D
Major Revision = 3
Minor Revision = 1
Physical Module
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IB16D
Major Revision = 3
Minor Revision = 2
Communication is prevented.
In this scenario, Exact Match keying prevents I/O
communication.
The module configuration is for a 1756-IB16D module with
module revision 3.1. The physical module is a 1756-IB16D
module with module revision 3.2. In this case,
communication is prevented because the Minor Revision of
the module does not match precisely.
Changing electronic keying selections online may cause the
I/O Communication connection to the module to be
disrupted and may result in a loss of data.
Compatible Keying
Compatible Keying indicates that the module determines whether to accept or
reject communication. Different module families, communication adapters,
and module types implement the compatibility check differently based on the
family capabilities and on prior knowledge of compatible products. Release
notes for individual modules indicate the specific compatibility details.
Compatible Keying is the default setting. Compatible Keying allows the
physical module to accept the key of the module configured in the software,
provided that the configured module is one the physical module is capable of
emulating. The exact level of emulation required is product and revision
specific.
29Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
30 Configurable Flowmeter Module Features and Operational Modes
EXAMPLE
Module Configuration
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IB16D
Major Revision = 3
Minor Revision = 3
Physical Module
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IB16D
Major Revision = 3
Communication is prevented.
With Compatible Keying, you can replace a module of a certain Major
Revision with one of the same catalog number and the same or later, that is
higher, Major Revision. In some cases, the selection makes it possible to use a
replacement that is a different catalog number than the original. For example,
you can replace a 1756-CNBR module with a 1756-CN2R module.
When a module is created, the module developers consider the module’s
development history to implement capabilities that emulate those of the
previous module. However, the developers cannot know future developments.
Because of this, when a system is configured, we recommend that you
configure your module using the earliest, that is, lowest, revision of the
physical module that you believe will be used in the system. By doing this, you
can avoid the case of a physical module rejecting the keying request because it
is an earlier revision than the one configured in the software.
In this scenario, Compatible Keying prevents I/O communication:
The module configuration is for a 1756-IB16D module with
module revision 3.3. The physical module is a 1756-IB16D
module with module revision 3.2. In this case,
communication is prevented because the minor revision of
the module is lower than expected and may not be
compatible with 3.3.
30Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
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