Introduction

The sequence language SFC (Sequential Function Chart), which conforms to IEC 61131-3, is described in this section.

IEC conformity restrictions can be lifted through explicit enable procedures. Features such as multi token, multiple initial steps, jumps to and from parallel strings etc. are then possible.

Representation

Representation of an SFC section:

Objects

An SFC section provides the following objects for creating a program:

• Steps

• Macro steps (embedded sub-step sequences)

• Transitions (transition conditions)

• Transition sections

• Action sections

• Jumps

• Links

• Alternative sequences

• Parallel sequences

• Text objects to comment on the logic

Properties

The SFC editor has a background grid that divides the section into 200 rows and 64 columns.

The program can be entered using the mouse or the keyboard.

Input Aids

The SFC editor offers the following input aids:

• Toolbars for quick and easy access to the desired objects

• Automatic step numbering

• Direct access to actions and transition conditions

• Syntax and semantics are checked as the program is being written.

  • Incorrect objects are displayed in blue

  • Unknown words (e.g. undeclared variables) or unsuitable data types are marked with a red wavy line

  • Brief description of errors in the Quickinfo (Tooltip)

• Information for variables and for transitions can be displayed in a Quickinfo (Tooltip)

  • type, name, address and comment of a variable/expression

  • type, name and comment of transitions

• Different zoom factors

• Show/hide the allocated actions

• Tracking of links

• Optimization of link routes

Step Properties

Step properties:

The step properties are defined using a dialog box that offers the following features:

• Definition of initial steps

• Definition of diagnostics times

• Step comments

• Allocation of actions and their qualifiers