IEC 61131-3 Scripts

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The IEC 61131-3 standard describes a set of programming languages suitable for automation applications.

IEC 61131-3 Standard Language Elements

The IEC 61131-3 language standard defines:

Common Elements The common features used by the other language elements.
Structured Text (ST) A text based, high level, block structured, language similar to PASCAL.
Sequential Function Chart (SFC) A high level language that uses steps, transitions and actions to define a flow chart.
Function Block Diagram A graphical diagram that uses blocks and connections.
Ladder Diagram A graphical diagram that uses contacts, coils and rungs.
Instruction List (IL) A low level language similar to assembly language.

When to Use IEC 61131-3 in Fernhill SCADA

You can configure simple SCADA applications without any need to write scripts or code. For example the Configuration Tool allows you to do all of these actions without any scripts or code:

However, you may want to extend Fernhill SCADA beyond its core features. You can use IEC 61131-3 to do this.

Using IEC 61131-3 to Extend Fernhill SCADA

The areas where IEC 61131-3 can extend Fernhill SCADA include:

Extensions to IEC 61131-3

In addition to the core IEC 61131-3 language, Fernhill SCADA provides these extensions:

Data Objects Functions to manage complex data objects.
Operator Action Functions Functions to customize an Operator Action.
Tag Command Function Blocks Function blocks to send Tag Commands.

Debug Structured Text

You can use the IEC 61131-3 Debugger to step through and test IEC 61131-3 code.

You can start IEC 61131-3 Debugger sessions from:

Further Information


To learn about the expressions that can be used in calculated tags.


To learn about declaring Programs.


For the meaning of terms used in Fernhill SCADA.