Rockwell Automation 1747-PTxx Getting Started Guide for HHT - Manual (Page 18)

A–B
2 Chapter
Getting Started Guide
for HHT
2–1
Control Basics
This chapter introduces you to basic concepts essential for understanding
how the SLC 500 controller operates. It covers:
•
SLC 500 file concepts
•
How external I/O devices communicate with the processor
•
Addressing external I/O
•
External I/O addressing formats
•
Ladder logic concepts
The CPU, or processor, provides control through the use of a program you
create. This program contains files that break down into more manageable
sections. These sections are:
•
Program Files — provide storage and control of the main program and
subroutines.
•
Data Files — contain the status of inputs, outputs, the processor, timers,
counters, and so on.
Notes on terminology: The term program used in Hand–Held Terminal
(HHT) displays and documentation is equivalent to the term processor file
used in APS software displays and documentation. Both terms mean the
collective program files and data files created under a particular program or
processor file name.
Program
The HHT and each CPU can hold one program at a time. The program is
made up of program files (up to 256 per controller) and data files (up to 256
per controller).
Program
Data Files Program Files
A program is created in the offline mode using your HHT. It is then
downloaded to the processor for online operation.
SLC 500 File Concepts