Rockwell Automation Logix5000 Controllers Add-on Instructions Programming Manual - Manual (Page 11)

Preface
Term Definition
Passed by value
When an argument is passed to a parameter by value, the value is copied in or out of the parameter when the Add-On
Instruction executes. The value of the argument does not change from external code or HMI interaction outside of the Add-On
Instruction itself.
Module reference parameter
A module reference parameter is an InOut parameter of the MODULE data type that points to the Module Object of a hardware
module. You can use module reference parameters in both Add-on Instruction logic and program logic. Since the module
reference parameter is passed by reference, it can access and modify attributes in a hardware module from an Add-On
Instruction.
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