Programming instructions

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LESSON 9 – PLC Instruction Types
To write a program for a PLC, it is necessary to be familiar with the instructions that
make up the PLC Instruction Set. An overview is provided here, with more detailed
information to follow in later lessons.
Lesson Objectives: At the conclusion of this lesson, you will be able to…
9 Describe the 3 different types of instructions.
Materials: FX-Series PLC Training Manual
All three of these instruction types can be found in great detail in the FX Programming
Manual for the appropriate model of PLC.
Part Number Series Of PLC Covered
JY992D48301 FX, FX0, FX0S, FX0N, FX2C
JY992D88101 FX1S, FX1N, FX2N, FX2NC
JY997D16601 FX3U
9.1 Basic Program Instructions
This category refers to the 4 basic bit devices (X, Y, M, and S), the timer device,
the counter device, and operation that pertain to these devices. This includes
SET, RESET, and the PULSE functions. These instructions will make up about
80 ~ 90 percent of a program.
9.2 Step Ladder Instructions
Step ladder instructions are used in Step Ladder Programming (STL). This
programming is similar to SFC programming in that it implements a flow chart,
but the flow chart is implied, and the code is actually created in ladder logic.
When programming in ladder logic, the STL contact is a common instruction
used to check if a state is active. S relays are used to indicate states.
STL Programming is not typically covered in this class. However, and excellent
explanation and examples can be found in Chapter 34.2 of the FX3U
Programming Manual.
9.3 Applied Instructions
These instructions are the ‘specialist’ instructions of the FX line. These
instructions allow the PLC to perform complex data manipulations, mathematical
operations, and communications. Most applied instructions work on the 16 bit or
32 bit word level.