Rockwell Automation Publication 1756-PM004D-EN-P - September 2012
23
Chapter
2
Organizing Tags
Introduction
With a Logix5000controller, you use a tag (alphanumeric name) to address data
(variables).
The controller uses the tag name internally and does not need to cross-reference a
physical address.
·
In conventional programmable controllers, a physical address identifies
each item of data.
–
Addresses follow a fixed, numeric format that depends on the type of
data, such as N7:8, F8:3.
–
Symbols are required to make logic easier to interpret.
·
In Logix5000 controllers, there is no fixed, numeric format. The tag name
itself identifies the data. This lets you:
–
organize your data to mirror your machinery.
–
document (through tag names) your application as you develop it.
Term
Definition
Tag
A text-based name for an area of the controller’s memory where data is stored.
·
Tags are the basic mechanism for allocating memory, referencing data from logic, and
monitoring data.
·
The minimum memory allocation for a tag is four bytes.
·
When you create a tag that stores data that requires less than four bytes, the controller
allocates four bytes, but the data only fills the part it needs.
Summary of Contents for 1756-L65 ControlLogix 5565
Page 4: ...2 Rockwell Automation Publication 1756 PM004D EN P September 2012 Summary of Changes Notes...
Page 8: ...6 Rockwell Automation Publication 1756 PM004D EN P September 2012 Preface Notes...
Page 66: ...64 Rockwell Automation Publication 1756 PM004D EN P September 2012 Chapter 3 Force I O Notes...
Page 88: ...86 Rockwell Automation Publication 1756 PM004D EN P September 2012 Index...
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