How to use the Siemens structured text programming -

by:Coolmay     2020-06-23
With the continuous development of modern industrial control technology, which may be a lot of used PLC controller technicians have such a feeling: the traditional way of ladder diagram programming in the face of increasingly complex control requirements, has the co-action.

in fact, now many big brands of PLC is supported by the international electrotechnical commission IEC61131 standard of five kinds of programming language specification in mixed programming, namely the ladder diagram ( LD) , structured text ( 圣) And flow charts ( SFC) , instruction sheets ( IL) And the function block ( FB) 。 In the five kinds of programming languages, I think the ladder diagram + structured text is a good combination, written in ladder diagram logic control, written in structured text calculation, so that we can speed up the programming efficiency and make the program readability is greatly increased. The flow chart of programming is very suitable for some 'sequence control occasions. As for the instruction sheet and function block, then there are other applications.

Siemens S7 series PLC controller in the field of domestic industrial use is very wide, it Step7 programming software by default only supports the ladder diagram and instruction list programming, but by installing 'S7 - SCL package 'and' S7 - Graph 'package can realize structured text and flow chart of programming. The two installation package actually belongs to a separate charge, can also be found on the Internet.

but the latest Po road series, will the two language integrated in the software without the need for additional download the installation package and purchase authorization. But they are both methods used are generally consistent.

here, I will combine some of his own experience to introduce how to use structured text programming.


what is structured text programming structured text is a kind of similar to the way of computer programming in a high-level language, it's grammar specification close to

PASCAL language of computer. Specific rules of grammar you refer to the relevant manuals, Siemens in this don't do detailed introduction. Below the SCL in Step7 programming interface:

, S7-2 The installation of SCL packages

in Step7, structured text programming language called structured control ( 结构化的控制语言) , abbreviated as SCL. Step7 already included in the professional version of the software package S7 - SCL packages, when install Step7, whether you will be prompted to install S7 - SCL, the check box ticked, see below:

3, the use of SCL packages

SCL software package is used to write in the form of 'source' functions, function blocks. Steps are as follows:

the first step: when is correctly installed in Step7 SCL package, will have the following interface

step 2: enter the SCL programming interface, and select the category preparation program block

step 3: write a program and compile

FC compiled produced.

after the above four steps, completes a with SCL. Write the whole process of function block to FC1 source program, and stored in the 'Sources' folder, can open at any time.

4, SCL programming is used to implement 'indirect addressing'

Step7, PLC ladder diagram programming does not support the indirect addressing, although with instruction sheet can be realized, but steps and cumbersome procedure readability is poor, by contrast, use SCL is easy way to do many, specific methods are as follows: 1, addressing:

MX [ i, j] , I for byte address, j said byte of which, when I = 5; J = 0, said the M5. 0

2, bytes, characters, double word addressing

MB [ i] IW [ i] QB [ i] 医学博士( i]

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