Rockwell Automation Logix5000 Program Parameters Programming Manual - Manual (Page 7)

Chapter 1
Connecting program parameters
This chapter provides an overview of program parameters and then further defines
each type of program parameter. Explanations are provided on when to use each
type of program parameter and the general rules to follow, and example procedures
are provided for connecting each type of program parameter.
A program parameter is an argument that is exposed for external access by a
program. Unlike local tags, all program parameters are publicly accessible outside
of the program. Additionally, HMI external access can be specified for each
parameter. Data sharing between programs can be achieved either through
pre-defined connections between parameters or directly accessed through a special
notation.
There are four types of program parameters.
• Input
• Output
• InOut
• Public
Among other benefits, program parameters allow you to clearly define the inputs
to the routines in a program, and the outputs from those routines. Input and
Output parameters also automatically buffer data, so that you do not need to
create separate tags to buffer IO data (although if desired, you can still buffer data
using the Synchronous Copy File [CPS] instruction).
Introduction
Program parameters
Rockwell Automation Publication 1756-PM021A-EN-P - October 2014 7