[PDF] Automating with STEP 7 in LAD and FBD SIMATIC S7-300400 Programmable Controllers

The SIMATIC automation system unites all the subsystems of an automation solution under uniform system architecture into a homogeneous whole from the field level right up to process control. This Totally Integrated Automation (TIA) concept permits integrated configuring, programming, data management and communications within the complete automation
system. Fine-tuned communications mechanisms permit harmonious interaction between programmable controllers, visualization systems and distributed I/Os.

As the basic tool for SIMATIC, STEP 7 handles the parenthesis function for Totally Integrated Automation. STEP 7 is used to carry out the
configuration and programming of the SIMATIC S7, SIMATIC C7 and SIMATIC WinAC automation systems. Microsoft Windows has been selected as the operating system, thus opening up the world of standard PCs with
the user desktop widely used in the office environment.

For block programming STEP 7 provides programming languages that comply with DIN EN 6.1131-3: STL (statement list; an Assemblerlike language), LAD (ladder logic; a representation similar to relay logic diagrams), FBD (function block diagram) and the S7-SCL optional package (structured control language, a Pascal-like high-level language). Several
optional packages supplement these languages: S7-GRAPH (sequential control), S7-HiGraph (programming with state-transition diagrams)
and CFC (connecting blocks; similar to function block diagram). The various methods of representation allow every user to select the suitable control function description. This broad adaptability in representing the control
task to be solved significantly simplifies working with STEP 7.

This book describes the LAD and FBD programming languages for S7-300/400. As a valuable supplement to the language description, and following an introduction to the S7-300/400 automation system, it provides
valuable and practice-oriented information on the basic handling of STEP 7 for the configuration of SIMATIC PLCs, their networking and programming. The description of the “basic functions” of a binary control, such as e.g. logic
operations or storage functions, is particularly useful for beginners or those converting from contactor controls to STEP 7. The digital functions explain how digital values are combined; for example, basic calculations, comparisons or data type conversion.

The book shows how you can control the program processing (program flow) with LAD and FBD and design structured programs. In addition to the cyclically processed main program, you can also incorporate event-driven program sections as well as influence the behavior of the controller at startup and in the event of errors/ faults. The book concludes with a general overview of the system functions and the function set for LAD and FBD. The contents of this book describe Version 5.5 of the STEP 7 programming software.