IEC 61131-3 Scripts

Introduction

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:

Feature	Description
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:

Configure tags to represent plant and equipment.
Configure graphics and trends using simple mouse clicks.
Associate tags with graphics and trends using drag and drop.

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:

In an Operator Action. An operator action is run when:
- A user interacts with a Graphic Page, or
- A user clicks a button on the Operator Toolbar.
In a Data Binding to convert data before it is displayed on a Graphic Page.
In a calculation for a Text Report.
In a Program Tag, which could be used to:
- Run a batch control sequence.
- Define custom event driven scanning.
- Transfer data from a database to a PLC Device.
- Reflect data between any of the following:
  - PLC devices,
  - RTU devices,
  - IoT devices,
  - Databases,
  - OPC Servers,
  - SNMP Agents.
- Apply custom data transformations.
- Execute an SQL statement on the Fernhill SCADA database using a SQLCommand Data Object.
In a Calculated Data Tag.

Extensions to IEC 61131-3

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

Extension	Description
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:

The Graphic Editor Debug Tool.
The Toolbar Editor Debug Tool.

Further Information

Expressions

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

Program

To learn about declaring Programs.

Glossary

For the meaning of terms used in Fernhill SCADA.