# Understanding the Basics of Modicon Programming: Logic, Variables, Instructions, and Functions

Modicon programming is a type of industrial automation programming that allows users to control and automate various types of machines and processes. Modicon programming is widely used in industrial automation because of its ease of use and flexibility.

In this blog post, we will discuss the basics of Modicon programming, including logic, variables, instructions, and functions.

### Logic

Logic is the foundation of Modicon programming. Logic is used to create programs that control and automate machines and processes. Modicon programming uses boolean logic, which means that variables can only have two possible values: true or false.

The most common boolean operators used in Modicon programming are AND, OR, and NOT. These operators allow programmers to create complex conditions that control the behavior of machines and processes.

For example, let’s say we have a machine that needs to be turned on when a certain temperature is reached. We can use Modicon programming to create a program that checks the temperature sensor and turns on the machine when the temperature is reached.

To do this, we would use an IF statement, which is a common logic statement used in Modicon programming. The IF statement checks a condition and executes a certain set of instructions if the condition is true.

#### Here’s an example of an IF statement:

IF Temperature >= 100 THEN

Turn on Machine

END_IF

In this example, the IF statement checks if the temperature is greater than or equal to 100. If the temperature is greater than or equal to 100, the program turns on the machine.

Variables

Variables are used to store data in Modicon programming. Variables can store values such as numbers, strings, and boolean values. Variables can be used to store values that change over time, such as the temperature of a machine or the speed of a conveyor belt.

In Modicon programming, variables are declared at the beginning of a program. Here’s an example of how to declare a variable in Modicon programming:

VAR

Temperature : INT;

END_VAR

In this example, we are declaring a variable called Temperature that is an integer value. The INT data type is used to represent integer values.

Once a variable is declared, it can be used throughout the program. Here’s an example of how to use a variable in Modicon programming:

Temperature := 75;

In this example, we are assigning the value of 75 to the Temperature variable. The := operator is used to assign a value to a variable.

Instructions

Instructions are the building blocks of Modicon programming. Instructions are used to perform specific tasks, such as turning on a machine or moving a conveyor belt.

There are many different types of instructions in Modicon programming, including arithmetic instructions, comparison instructions, and communication instructions.

Arithmetic instructions are used to perform mathematical operations, such as addition, subtraction, multiplication, and division. Comparison instructions are used to compare two values and determine if they are equal, greater than, or less than each other. Communication instructions are used to communicate with other devices, such as sensors or other machines.

Here’s an example of how to use an arithmetic instruction in Modicon programming:

Speed := Speed + 5;

In this example, we are using the addition operator to add 5 to the value of the Speed variable. The new value of the Speed variable is then assigned to the Speed variable using the := operator.

Functions

Functions are pre-written blocks of code that can be used to perform specific tasks. Functions can be used to perform complex calculations or to control the behavior of machines and processes.

Modicon programming includes many built-in functions, such as mathematical functions, string functions, and time functions. There are also user-defined functions, which are functions that programmers create themselves.

Here’s an example of how to use a built-in function in Modicon programming:

Time := TON(Timer, 10);

In this example, we are using the TON function to create a timer. The Timer variable specifies the starting time of the timer, and the 10 specifies the duration of the timer in milliseconds. The value of the timer is then assigned to the Time variable using the := operator.

User-defined functions can be created using the FUNCTION block in Modicon programming. Here’s an example of how to create a user-defined function in Modicon programming:

FUNCTION

MyFunction : INT

VAR_INPUT

Input1 : INT;

Input2 : INT;

END_VAR

VAR_OUTPUT

Output : INT;

END_VAR

Output := Input1 + Input2;

END_FUNCTION

In this example, we are creating a function called MyFunction that takes two integer inputs and returns an integer output. The function adds the two inputs together and assigns the result to the Output variable using the := operator.

Modicon programming is a powerful tool for controlling and automating machines and processes. Logic, variables, instructions, and functions are the building blocks of Modicon programming. Understanding these basics is essential for creating effective Modicon programs.

In this blog post, we have discussed the basics of Modicon programming, including boolean logic, variables, instructions, and functions. By understanding these basics, you can start creating your own Modicon programs and controlling machines and processes with ease.