IEC programming languages

Powerful programming editors for efficient engineering


SIMATIC STEP 7 V11 provides powerful programming editors for programming the SIMATIC S7 controllers

  • Ladder logic (LAD) and function block diagram (FBD) languages are available for all controllers.

  • The structured text (SCL), statement list (STL) and step sequence programming (GRAPH, SFC) are additionally available for the controller series S7-300, S7-400 and WinAC.

Intuitive tools with functionalities such as drag & drop, project-wide cross-reference list, Intellisense, etc. are available to the user for all tasks. STEP 7 V11 thus enables users to efficiently create their user programs. Even complex technological functions such as controlling or positioning are quickly and graphically implemented in the engineering software

Programming editors and current Windows technologies adapted to the tasks and the processing are the basis of the intuitive operating concept of STEP 7 V11.
The embedding of the various editors in a common working environment ensures that all data is available to the user on a consistent basis and an overview of the project data is guaranteed at any time.
Program blocks can be saved at any time. Troubleshooting is made easier and quicker by means of several tools: a syntaxwindow lists all errors in the current block. This permits simple navigation between the errors and also has an indicator for faulty networks..

LAD and FBD – graphic programming languages

Graphic programming languages are experiencing a renaissance with STEP 7 V11. By means of powerful tools and the integrated functionality, such as indirect programming, programs can be generated at a speed that equals, if not surpasses that of the textual languages for the first time.

The user-friendly fully graphical LAD and FBD editors offer excellent clarity and fast navigation in the block editor by

  • opening and closing entire networks

  • showing and hiding symbols and addresses

  • direct zooming and saving of layouts

  • a host of keyboard shortcuts

  • lasso function, copying and pasting for individual commands and command structures

  • comments

  • new Compute Box permits the direct input of formulas for the S7-1200

SCL (Structured Control Language) – Programming of complex algorithms

The Structured Control Language (SCL) corresponds to the textual high-level language ST (Structured Text) defined in the standard IEC 61131-3 and fulfills base level and reusability level requirements according to PLC open. SCL is particularly suitable for the high-speed programming of complex algorithms and arithmetic functions or for data processing tasks. The SCL code is simpler, shorter and clearer to implement and handle.

S7-SCL Editor offers the following functionalities:

  • Complete areas of program code can be activated/deactivated with one click

  • Loops and multi-line comments can be expanded and collapsed

  • Bookmarks

  • The values of all tags are displayed clearly online

  • Breakpoints and step-by-step execution of the programcode

  • SCL blocks can be used in other STEP 7 languages

  • Perfect for user-defined function blocks for libraries

  • Considerable time savings compared to programming inLAD/FBD/STL

STL – Statement list

The statement list (STL) textual programming language enables the creation of hardware-level runtime and memory-optimized user programs.

It supports the user with a host of new user-friendly editing functions:

  • Intelligent selection of symbols from PLC tags, DBs, local tags

  • Clear presentation even of complex program code

  • Code can be activated/deactivated with one click

  • Option of adding display of absolute addresses

  • Clear online presentation

GRAPH (SFC) - Programming of sequencers

Sequential Function Chart (SFC) is used for describing procedures with alternative or parallel sequencers.

The sequencers are configured and programmed clearly and quickly in a standardized method of representation (according to IEC 61131-3,DIN EN 61131).

The process is described graphically, and divided into individual steps with an easily comprehensible scope of functions

Basic functions

  • Flexible sequencer structure:
    Simultaneous and alternative branches, jumps within the sequencers, step enabling and disabling.

  • Selective processing of steps.
    The processing time of a sequencer is thus independent of the number of steps.

  • Synchronizing of automatic and manual mode:
    The process is no longer synchronous if it was put into a different state manually. GRAPH supports the locating of synchronization points for restarting automatic operation. To do so, the relevant steps are marked. Transitions or interlocks can be defined as criteria.

  • Single-step presentation shows all details of a step at a glance

  • Considerable time savings compared to programming in LAD/FBD/STL

Test and diagnostics functions
The online functions can result in considerable time savings, particularly during the commissioning phase.

For example, it is possible to display

  • active steps,

  • the status of the interlocking, monitoring and step enabling conditions,

  • as well as past actions.