Siemens SIMATIC S7-400 Configuration And Use Manual page 99

Program and Data Storage
Projects are used to store the data and programs which are created when you put
together an automation solution. The data collected together in a project include:
• Configuration data on the hardware structure and parameters for modules
• Configuration data for communication in networks
• Programs for programmable modules
Data are stored in a project in object form. The objects in a project are arranged in
a tree structure (project hierarchy). The display of the hierarchy in the project
window is similar to that of the Windows Explorer.
Program Editor
The program editor enables you to program in conformity to the IEC 1131 standard
for the S7-400 automation system. You can use both symbolic and absolute
addressing of the operands when writing programs.
Programming Languages
• LAD (Ladder Logic) is a graphic programming language. Its syntax for the
instructions is similar to a circuit diagram. Ladder allows you to track the power
flow between power rails as it passes through various contacts, complex
elements, and output coils.
• STL (Statement List) is a textual programming language similar to machine
code. If a program is written in Statement List, the individual instructions
correspond to the steps with which the CPU executes the program. To make
programming easier, Statement List has been extended to include some
high-level language constructions (such as structured data access and block
parameters).
• FBD (Function Block Diagram) is a graphic programming language and uses
the logic boxes familiar from Boolean algebra to represent the logic. Complex
functions (for example, math functions) can be represented directly in
conjunction with the logic boxes.
• SCL (Structured Control Language) is a programming language resembling
Pascal used especially for programming complex algorithms and mathematical
functions or for task definitions from the area of data processing.
• CFC (Continuous Function Chart) enables you to accomplish technological
tasks in completed, executable automation programs with minimal effort. You
can insert the ready-to-use blocks from a library into a CFC chart using
drag-and-drop, graphically interconnect them and assign parameters to them.
In-depth programming knowledge is not needed.
Data Storage in the Programming Device
The programming device stores the data for all S7-400 components. This means
you only have to enter your data once and then it is available for configuration,
programming and for operator control and monitoring functions.
Automation System S7-400 Configuration and Use
A5E00442711-02
Programming the S7-400
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