Additional resources, Important terminology, Additional resources important terminology – Rockwell Automation Logix5000 Program Parameters Programming Manual User Manual
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Preface
These documents contain additional information concerning related Rockwell
Automation products.
Resource
Description
publicatio
Provides general guidelines for installing a Rockwell
Automation industrial system.
Product Certifications webpage, available at
Provides declarations of conformity, certificates, and other
certification details.
You can view or download publications at
der paper copies of
technical documentation, contact your local Rockwell Automation distributor or
sales representative.
This table defines the terms that are important to understanding the concepts
described in this manual.
Term
Definition
Argument
An argument is assigned to a parameter and contains the specification of the data used by an
instruction in a user program. An argument can contain the following:
•
A simple tag (for example, L101)
•
A literal value (for example, 5)
•
A tag structure reference (for example, Recipe.Temperature)
•
A direct array reference (for example, Buffer[1])
•
An indirect array reference (for example, Buffer[Index+1])
•
A combination (for example, Buffer[Index+1].Delay)
InOut parameter An InOut parameter is a special usage program parameter that represents a reference to data that can
be used both as input and output during the execution of a program. Because InOut parameters pass by
reference rather than by value, they are merely a pointer to the original data and closely resemble the
behavior of an alias tag. With that in mind, it is possible that the InOut parameter values could change
during the execution of a program. Depending on your task structure, this behavior may be necessary.
Input parameter An Input parameter is a parameter that defines the data that is passed by value into an executing
program. Since Input parameters are passed by value, their values cannot change from external sources
during the execution of the program. An Input parameter supports a maximum of one sourcing
connection.
Output
parameter
An Output parameter is a parameter that defines the data that is produced as a direct result of executing
a program. Since Output parameters are always passed by value, their values only change at the end of
the scan of a program when the copy of the parameters is executed.
Tip: If using direct access another program can be a source for an Output parameter.
Passed by
reference
When an argument is passed to a parameter by reference, the logic directly reads or writes the value
that the tag uses in controller memory. External code or HMI interaction that changes the argument’s
value can change the value during execution of a program.
Passed by value When an argument is passed to a parameter by value, the value is copied in or out of the parameter
during execution of a program. The value of the argument does not change from external code or HMI
interaction.
Public
parameter
A Public parameter is an encapsulated version of a controller scope tag, and typically it is used for large
data structures that need to be shared among programs.
Additional resources
Important terminology
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Rockwell Automation Publication 1756-PM021A-EN-P - October 2014