Allen-Bradley Logix5000 Series Owner's manual

Logix5000 Controllers I/O and Tag Data
Catalog Numbers 1756 ControlLogix, 1756 GuardLogix,
1768 Compact GuardLogix, 1769 CompactLogix, 1789 SoftLogix,
PowerFlex with DriveLogix
Programming Manual

Important User Information
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 available from your local Rockwell
Automation sales office or online at http://www.rockwellautomation.com/literature/) describes some 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.
Allen-Bradley, Rockwell Automation, RSLogix 5000, Logix5000, RSLinx Classic, RSLinx Enterprise, PanelView, PLC-2, PLC-5, SLC, CompactLogix, ControlLogix, GuardLogix, FlexLogix, DriveLogix, SoftLogix,
Rockwell Software, FactoryTalk Security, and TechConnect are trademarks of Rockwell Automation, Inc.
Trademarks not belonging to Rockwell Automation are property of their respective companies.
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.
IMPORTANT
Identifies information that is critical for successful application and understanding of the product.
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.

3Publication 1756-PM004C-EN-P - October 2009 3
Summary of Changes
Introduction
The release of this document contains new information.
New Information
New information is marked by change bars in the side column, as shown to
the right.
Section Changes
Chapter 1 New information and examples for electronic keying.
Chapter 4 Procedures and descriptions for the external access and
constant tag attributes that control access to
controller tags.

4Publication 1756-PM004C-EN-P - October 2009
Summary of Changes
Notes:

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Table of Contents
Preface Purpose of This Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Chapter 1
Communicate with I/O Modules
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Requested Packet Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Communication Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Direct or Rack-Optimized Connection . . . . . . . . . . . . . . . . . . . . . 11
Ownership . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Electronic Keying. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Address I/O Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Buffer I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Chapter 2
Organize Tags
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Tag Type. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Data Type. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Guidelines for Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Create a Tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Create an Array. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Configure an Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Create a User-defined Data Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Guidelines for User-defined Data Types . . . . . . . . . . . . . . . . . . . . 40
Create a User-defined Data Type . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Describe a User-defined Data Type . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Activate Pass-Through and Append Descriptions. . . . . . . . . . . . . 43
Paste a Pass-Through Description . . . . . . . . . . . . . . . . . . . . . . . . . 44
Address Tag Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Alias Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Display Alias Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Assign an Alias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Assign an Indirect Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Array Subscript Out of Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Tag Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Language Switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Chapter 3
Force I/O
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Enable Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Disable or Remove a Force. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Check Force Status. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
FORCE Status Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
GSV Instruction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
When to Use I/O Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

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Force an Input Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Force an Output Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Add an I/O Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Remove or Disable Forces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Remove an Individual Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Disable All I/O Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Remove All I/O Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Chapter 4
Data Access Control
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
External Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Configure External Access. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
External Access Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Configure External Access in the New Tag Dialog Box . . . . . . . . 66
Set Up External Access in the Tag Properties Dialog Box . . . . . . 68
View and Select External Access Status
on the Tag Editor Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
‘Go To’ Search Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
External Access Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
User-defined Type Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Add-On Instructions External Access Considerations . . . . . . . . . . . . 74
Tag Mapping Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Imported Tag Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Constant Value Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Configure Constant Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Set Up a Constant in the New Tag Dialog Box . . . . . . . . . . . . . . . 80
Configure a Constant in the Tag Properties Dialog Box . . . . . . . . 81
Designate a Constant in the Tag Editor . . . . . . . . . . . . . . . . . . . . . 82
Constant Checkbox Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Add-On Instructions Constant Value Considerations . . . . . . . . . . . . . 85
Index

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Preface
Purpose of This Manual
This manual shows how to access I/O and tag data in Logix5000 controllers.
This manual is one of a set of related manuals that show common procedures
for programming and operating Logix5000 controllers.
For a complete list of common procedures manuals, refer to the
Logix 5000 Controllers Common Procedures Programming Manual,
publication 1756-PM001.
The term Logix5000 controller refers to any controller that is based on the
Logix5000 operating system, such as:
•CompactLogix controllers.
•ControlLogix controllers.
•DriveLogix controllers.
•FlexLogix controllers.
•SoftLogix5800 controllers.

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Preface
Notes:

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Chapter 1
Communicate with I/O Modules
Introduction
To communicate with an I/O module in your system, you add the module to
the I/O Configuration folder of the controller.
When you add the module, you also define a specific configuration for the
module. While the configuration options vary from module to module, these
are some common options that you typically configure:
•Requested Packet Interval
•Communication Format
•Electronic Keying
Add I/O modules here.

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Chapter 1 Communicate with I/O Modules
Requested Packet Interval
The Logix5000 controller uses connections to transmit I/O data.
In Logix5000 controllers, I/O values update at a period that you configure via
the I/O configuration folder of the project. The values update asynchronous
to the execution of logic. At the specified interval, the controller updates a
value independently from the execution of logic.
•Programs within a task access input and output data directly from
controller-scoped memory.
•Logic within any task can modify controller-scoped data.
•Data and I/O values are asynchronous and can change during the
course of a task’s execution.
•An input value referenced at the beginning of a task’s execution can be
different when referenced later.
•To prevent an input value from changing during a scan, copy the value
to another tag and use the data from there (buffer the values).
Term Definition
Connection A communication link between two devices, such as between a controller and an I/O module, PanelView
terminal, or another controller.
Connections are allocations of resources that provide more reliable communications between devices than
unconnected messages. The number of connections that a single controller can have is limited.
You indirectly determine the number of connections the controller uses by configuring the controller to
communicate with other devices in the system. The following types of communication use connections:
•I/O modules
•produced and consumed tags
•certain types of Message (MSG) instructions (not all types use a connection)
Requested packet
interval (RPI) The RPI specifies the period at which data updates over a connection. For example, an input module sends data to a controller at the RPI that you assign to the module.
•Typically, you configure an RPI in milliseconds (ms). The range is 0.2 ms (200 microseconds)…750 ms.
•If a ControlNet network connects the devices, the RPI reserves a slot in the stream of data flowing across the
ControlNet network. The timing of this slot may not coincide with the exact value of the RPI, but the control
system guarantees that the data transfers at least as often as the RPI.
ATTENTION
Make sure that data memory contains the appropriate values
throughout a task’s execution. You can duplicate or buffer data
at the beginning of the scan to provide reference values for
your logic.

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Communicate with I/O Modules Chapter 1
Communication Format
The communication format that you choose determines the data structure for
the tags that are associated with the module. Many I/O modules support
different formats. Each format uses a different data structure. The
communication format that you choose also determines:
•Direct or Rack-Optimized Connection.
•Ownership.
Direct or Rack-Optimized Connection
The Logix5000 controller uses connections to transmit I/O data. These
connections can be direct connections or rack-optimized connections.
Term Definition
Direct connection A direct connection is a real-time, data transfer link between the controller and an I/O
module. The controller maintains and monitors the connection with the I/O module. Any
break in the connection, such as a module fault or the removal of a module while under
power, sets fault bits in the data area associated with the module.
Rack-optimized
connection For digital I/O modules, you can select rack-optimized communication. A rack-optimized connection consolidates connection usage between the controller and all the digital I/O
modules in the chassis (or DIN rail). Rather than having individual, direct connections for
each I/O module, there is one connection for the entire chassis (or DIN rail).
A direct connection is any
connection that does not
use the Rack Optimization
Comm Format.
Rack-Optimized Connection

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Chapter 1 Communicate with I/O Modules
Ownership
In a Logix5000 system, modules multicast data. This means that multiple
devices can receive the same data at the same time from a single device.
When you choose a communication format, you have to choose whether to
establish an owner or listen-only relationship with the module.
Owner controller The controller that creates the primary configuration and communication connection to a
module. The owner controller writes configuration data and can establish a connection to
the module.
Listen-only connection An I/O connection where another controller owns/provides the configuration data for the
I/O module. A controller using a listen-only connection only monitors the module. It does
not write configuration data and can only maintain a connection to the I/O module when
the owner controller is actively controlling the I/O module.
An owner connection is
any connection that does
not include Listen-Only
in its Comm Format.
Listen-only Connection

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Communicate with I/O Modules Chapter 1
Use the following table to choose the type of ownership for a module.
There is a noted difference in controlling input modules versus controlling
output modules.
Choose the Type of Ownership
If module is And another controller And you want to Then use this type of connection
Input module Does not own the module Owner (not listen-only)
Owns the module Maintain communication with the module
if it loses communication with the other
controller
Owner (not listen-only)
Use the same configuration as the other
owner controller.
Stop communication with the module if it
loses communication with the other
controller
Listen-only
Output module Does not own the module Owner (such as, not listen-only)
Owns the module Listen-only
Control Input and Output Modules
Controlling This Ownership Description
Input modules Owner An input module is configured by a controller that establishes a connection as an
owner. This configuring controller is the first controller to establish an
owner connection.
Once an input module has been configured (and owned by a controller), other
controllers can establish owner connections to that module. This lets additional owners
to continue to receive multicast data if the original owner controller breaks its
connection to the module. All other additional owners must have the identical
configuration data and identical communications format that the original owner
controller has, otherwise, the connection attempt is rejected.
Listen-only Once an input module has been configured (and owned by a controller), other
controllers can establish a listen-only connection to that module. These controllers can
receive multicast data while another controller owns the module. If all owner
controllers break their connections to the input module, all controllers with listen-only
connections no longer receive multicast data.
Output modules Owner An output module is configured by a controller that establishes a connection as an
owner. Only one-owner connection is allowed for an output module. If another
controller attempts to establish an owner connection, the connection attempt is
rejected.
Listen-only Once an output module has been configured (and owned by one controller), other
controllers can establish listen-only connections to that module. These controllers can
receive multicast data while another controller owns the module. If the owner
controller breaks its connection to the output module, all controllers with listen-only
connections no longer receive multicast data.

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Chapter 1 Communicate with I/O Modules
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.
You can find revision information on the General tab of a module’s Properties
dialog box.
General Tab
Keying Attributes
Attribute Description
Vendor The manufacturer of the module, for example, Rockwell
Automation/Allen-Bradley.
Product Type The general type of the module, for example, communication
adapter, AC drive, or digital I/O.
Product Code The specific type of module, generally represented by its catalog
number, for example, 1756-IB16I.
Major Revision A 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 Revision A number that indicates the module’s specific firmware revision.
Minor Revisions typically do not impact data compatibility but may
indicate performance or behavior improvement.

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Communicate with I/O Modules Chapter 1
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
in order 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.
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.
IMPORTANT
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.
EXAMPLE
In the following 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.
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

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Chapter 1 Communicate with I/O Modules
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.
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.
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.
Release notes for individual modules indicate the specific compatibility details.
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.
IMPORTANT
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.

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Communicate with I/O Modules Chapter 1
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.
EXAMPLE
In the following 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.
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
Minor Revision = 2
Communication is prevented

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Chapter 1 Communicate with I/O Modules
EXAMPLE
In the following scenario, Compatible Keying allows I/O
communication:
The module configuration is for a 1756-IB16D module with module
revision 2.1. The physical module is a 1756-IB16D module with
module revision 3.2. In this case, communication is allowed because
the major revision of the physical module is higher than expected and
the module determines that it is compatible with the prior major
revision.
IMPORTANT
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.
Module Configuration
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IB16D
Major Revision = 2
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 allowed

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Communicate with I/O Modules Chapter 1
Disabled Keying
Disabled Keying indicates the keying attributes are not considered when
attempting to communicate with a module. Other attributes, such as data size
and format, are considered and must be acceptable before I/O
communication is established. With Disabled Keying, I/O communication
may occur with a module other than the type specified in the I/O
Configuration tree with unpredictable results. We generally do not recommend
using Disabled Keying.
If you use Disabled Keying, you must take full responsibility for understanding
whether the module being used can fulfill the functional requirements of the
application.
ATTENTION
Be extremely cautious when using Disabled Keying; if used
incorrectly, this option can lead to personal injury or death,
property damage, or economic loss.
EXAMPLE
In the following scenario, Disable Keying prevents I/O
communication:
The module configuration is for a 1756-IA16 digital input module. The
physical module is a 1756-IF16 analog input module. In this case,
communication is prevented because the analog module
rejects the data formats that the digital module configuration
requests.
Module Configuration
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IA16
Major Revision = 3
Minor Revision = 1
Physical Module
Vendor = Allen-Bradley
Product Type = Analog Input
Module
Catalog Number = 1756-IF16
Major Revision = 3
Minor Revision = 2
Communication is prevented

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Chapter 1 Communicate with I/O Modules
EXAMPLE
In the following scenario, Disable Keying allows I/O
communication:
The module configuration is for a 1756-IA16 digital input module. The
physical module is a 1756-IB16 digital input module. In this case,
communication is allowed because the two digital modules share
common data formats.
IMPORTANT
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.
Module Configuration
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IA16
Major Revision = 2
Minor Revision = 1
Physical Module
Vendor = Allen-Bradley
Product Type = Digital Input
Module
Catalog Number = 1756-IB16
Major Revision = 3
Minor Revision = 2
Communication is allowed