Rockwell Automation Logix5000 Program Parameters Programming Manual - Manual (Page 31)

Chapter 2
Directly accessing program parameters
This chapter provides an overview of direct access and an example procedure for
directly accessing program parameters when working within code editors.
Direct access lets you reference the program parameters from another program in
logic without configuring parameters in the local program. The syntax used for
direct access is \ProgramName.ParameterName. For example, assume Program_A
has an output parameter called Tank_Level. Without creating a corresponding
input parameter to connect to Program_A, Program_B can reference the
Tank_Level parameter in logic using the syntax \A.Tank_Level.
Program local tags cannot be accessed using direct access.
Behavior of direct access in logic
Input, Output, and Public parameters can all be directly accessed in logic.
• When direct access is implemented in Output parameters, values are
updated when the program that contains the Output parameter completes
execution.
• When direct access is implemented in Input and Public parameters, the
values of the referenced parameters are updated in real time. This means
that higher priority tasks are using parameter values that are up to date, thus
minimizing the risk of performing actions on stale data.
• Direct access to an Input parameter counts toward fan-in. You cannot have
both a connection and a direct access sourcing an Input parameter. You can
however still use direct access to read the value.
• Using direct access of Input parameters is a good way to circumvent the one
connection limit of Input parameters. If you create an Input parameter but
do not configure any connections for that Input parameter, you can directly
reference it from multiple programs.
Introduction
Direct access
Rockwell Automation Publication 1756-PM021A-EN-P - October 2014 31