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1-2 Micro PLC Programmer’s Guide – April 1994
GFK-0804B
Programming Basics
The most important ingredients in creating a successful PLC program are a thorough
understanding of the application itself, and a good measure of common sense.
The first step in creating a PLC application program is planning.
The desired sequence of program actions is determined.
All of the required inputs and outputs are identified and listed.
Each input and output is associated with a PLC memory location. For example:
Device Designation Memory Location
Start switch
Limit switch on conveyor line
Syrup tank #1, level detector
Syrup tank #2, level detector
Conveyor line optical sensor
Input 1
Input 2
Input 3
Input 4
Input 5
Discrete Input Table 1
”2
”3
”4
”5
Conveyor line motor starter
Operator warning light
Signal to bottle capper
Output 1
Output 2
Output 3
Discrete Output Table1
”2
”3
The program (like the short example program on the facing page) is created with a
programming device and transferred to the PLC.
Before the system begins full operation, the program is tested and any corrections
that are needed are made.
The final version of the program is transferred to the PLC, and the application is
ready to go.