Attention

IronPLC can only run very simple programs. The steps described are accurate but many language features are not yet supported.

Configuring Your Application¶

In the previous chapter, you wrote a program with inputs and outputs. But a program alone is not a complete IEC 61131-3 application — you need to tell the runtime how often to run it and on what hardware. That is the job of a configuration.

Add a Configuration Block¶

Open main.st and add the following below the existing END_PROGRAM:

Complete Application¶

PROGRAM main
   VAR
      Button AT %IX1: BOOL;
      Buzzer AT %QX1: BOOL;
   END_VAR

   Buzzer := NOT Button;

END_PROGRAM

CONFIGURATION config
   RESOURCE res ON PLC
      TASK plc_task(INTERVAL := T#100ms, PRIORITY := 1);
      PROGRAM plc_task_instance WITH plc_task : main;
   END_RESOURCE
END_CONFIGURATION

Save the file. The IronPLC extension should show no errors.

What the Configuration Does¶

The new block introduces three layers:

CONFIGURATION: The top-level container for your application. Every IEC 61131-3 application has exactly one configuration. Here it is named config.
RESOURCE: Represents a processing unit (a CPU or core). The resource named res runs ON PLC, where PLC is the name of the hardware target defined by the runtime environment.
TASK: Defines a scheduling policy. The task named plc_task runs every 100 milliseconds at priority level 1. This means the runtime will execute the sense-control-actuate cycle 10 times per second.

The line:

PROGRAM plc_task_instance WITH plc_task : main;

creates an instance of the main program, names it plc_task_instance, and binds it to plc_task. Every 100 ms, the runtime reads the inputs, runs main, and writes the outputs.

Tip

For a deeper look at how these layers fit together, see Program Organization.

You Now Have a Complete Application¶

Your main.st file now contains everything needed for a deployable IEC 61131-3 application:

A program that reads a button and controls a buzzer.
A configuration that runs the program every 100 ms.

In the next chapter, you will learn how to split this into multiple files as your project grows.

Continue to Working with Multiple Files.