ST and SCL and STL PLC simple introduction - high-level programming language

The concept is clear, clear logical thinking, is to get all the essential condition of engineering technology. Engaged in industrial control, if your concept is fuzzy, or a little knowledge of, so, you will never be able to understand all kinds of knowledge, you will always be busy! ! Like many who say, how I learned the Siemens S7 - 200 smart, to learn the Siemens S7 - again 1200 as a brand, but also to learn? 吗? So, clear concepts, is a prerequisite for you to become a great god.

although a lot of ladder diagram of the fan and small make up for the seesaw battle rounds, but small make up, found that many but even confuse what ST language, including many and small make up, like ST language are also not too sure what is the ST language, today small make up you with your science.

ST, STRUCT is the abbreviation of the TEXT, is the IEC61131 - 3 standards programming language! ! From the literal understanding, it is structured text language! Obviously, it is born for structured programming. ! It is based on computer of Pascal language, for industrial control conducted a series of optimization and modification! ! Can also think it is according to the C language, but that is not too serious, because ST language is case-insensitive, and C strictly is case sensitive. These are based on the actual situation of industrial control.

, for example, Axis_Enable and Axis_Enable these two variables, in the ST language is no different, but in C, but not the same.

4 mentioned industry. 0, mention of industrial automation, Siemens is a round of candy! ! In a word, it is in the field of industrial automation, big dipper is mount taishan, shaolin wudang! Siemens is also very strong, it's new Po road software platform, is not fully comply with the IEC61131 - 3 standard, but a slightly modified, like wulin bosses own kung fu martial arts or modify the predecessors. Siemens launched its own programming language, SCL ( 结构化的控制语言) Language, that is, a structured control language, it actually and IEC standards set by the ST language is the same, just in individual syntax and function block ( FB） Call on a slightly different! ! Most in need of major such as

IF

statement;

END_IF;

in the SCL of Siemens, END_IF is to add a semicolon, in the standard of the ST language, is not.

so, ST and SCL is one thing! !

and STL, is the LANGUAGE of Siemens in STEP7 era, it is not a STRUCT TEXT LANGUAGE, so it has nothing to do with ST LANGUAGE completely. STL language is a kind of assembly language, is facing the machine at the bottom of the language, you can directly register operation, readability, and 80 c51 machine language is a plane. So, it is a low-level language, and ST, SCL is senior language.

the more high-level language, readability, the better, more focus on the variables and the algorithm, and is independent of the hardware, and the low-level language, more focus on the register address, and closely tied to the hardware, and can directly operate the hardware, but readability is poor, high execution efficiency. Now, Siemens's platform is main SCL.

so, STL and ST, SCL is not the same completely, cannot confuse STH with STH else, don't MOVE, seem are in English, is considered to be the same thing! ! This way of thinking, destined to you will be, the concept of chaos and the concept of chaos, is engaged in industrial control industry big fear! ! IL

there is a kind of language, is called instruction table, it is a description of the ladder diagram, can be mutual conversion and ladder diagram, is not a programming language, strictly speaking, it is just a form of ladder diagram.