Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 38)

Chapter
5
5Ć1
Fundamental Instruction Set
This chapter describes fundamental programming and editing techniques
common to the controller.
In this chapter you will read sections A through E concerning:
Programming Logic
Relay Type Instructions
Timer and Counter Instructions
Data Manipulation Instructions
Arithmetic
Instructions
NOTE: Refer to the operations section of this manual for example instructions
concerning chapters 5 and 6.
Section A
Programming Logic
In this section will you read about the instructions needed to write a program,
and how to define the needed conditions before the action takes place.
A program is a list of instructions that guides the controller. These instructions
can examine or change the status of bits in the memory of the controller. The
status of these bits determines the operation of your output devices.
When you write a program you specify the things you want done in your
application and the conditions that must be met before those things are done.
For example, if you want a solenoid energized when a limit switch is closed,
you would specify:
Condition: If limit switch is closed
Action: Energize solenoid
Programming logic differs from relay logic in an important way. Programming
logic is only concerned with whether or not conditions have been met. These
conditions may be open or closed input or output devices. We must have a
continuous or unbroken path of true logic conditions for an action to be taken.
The number of conditions is not important. There can be none, one, or many
conditions preceding an output action.
Programming Logic:
Objectives
Introduction