User guide

Chapter 3
Understanding File Organization
3–2
Program
A program is the collective program files and data files of a particular user
program. It contains all the instructions, data, and configuration information
pertaining to that user program. The HHT allows only numbers and certain
letters available on the keyboard to be entered for a program name.
The program is a transferable unit. It can be located in the Hand-Held
Terminal (or in the APS programming terminal); it can be transferred to/from
an SLC 500, 5/01, or 5/02 processor, or to/from a memory module located in
the processor.
Program 01 Program 02 Program 03
HHT SLC 500 Processor Memory Module
HHT SLC 500 Processor
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Download
The HHT and each CPU hold one program at a time. A program is created
in the offline mode using your HHT. You first configure your controller,
then create your user program. When you have completed and saved your
program, you download it to the processor RAM memory for online
operation. (See page 3–3 for more information on downloading.) You may
also keep a back–up of your program in the EEPROM memory module
located in the processor.
Program Files
Program files contain controller information, the main control program, and
any subroutine programs. The first three program files are required for each
program. These are:
• System Program (file 0)–This file is always included and contains
various system related information and user-programmed information
such as processor type, I/O configuration, program name and password.
• Reserved (file 1)– This file is always included and is reserved for internal
controller use.
• Main Ladder Program (file 2)–This file is always included and contains
user-programmed instructions defining how the controller is to operate.
• Subroutine Ladder Program (files 3 – 255)–These are user-created and
activated according to subroutine instructions residing in the main ladder
program file.