A sequence control process can be divided into several stages, also called steps or states, and each state has different actions. When the transition conditions between two adjacent states are met, the transition will be realized, that is, the transition from the previous state to the next state will be executed.

We often use the state transition diagram (menu diagram) to describe this sequential control process. Record each state with state meter S, and X is the transition condition. If X1 is ON, the system changes from S20 state to S21 state.

Each step in the state transition diagram contains three contents: the content driven by this step, the transition conditions and the transition target of instructions.



Step drive Y0. When X1 is effectively ON, the system changes from S20 state to S21 state. X1 is the conversion condition, and the conversion target is S21 step.

3. Instructions for step command



1) STL contact is a normally open contact connected to the left bus. If a STL contact is connected, the corresponding state is dynamic step;



2) The contact connected with STL contact shall apply LD or LDI command and return to the left bus only after executing RET




3) STL contact can directly drive or drive the coil of Y, M, S, T and other components through other contacts;





4) Since PLC only executes the circuit block corresponding to the active step, double coil output is allowed when STL command is used (sequence control program can drive the same coil multiple times in different steps);





5) MC and MCR commands cannot be used in circuit blocks driven by STL contacts, but CJ commands can be used;



A function is a collection of functional code blocks. For example, we can calculate two numbers and write them into a function, so a function is a functional code block with a certain meaning. In our daily work, we habitually write the reused code block into a function, which is convenient for reading and understanding, and also simplifies the code amount.



Functions actually use scopes. Generally, functions can be used globally by default. We can also limit functions to only work in a fixed task or a module. This involves the scope of functions, which I will discuss with you in the next chapter.



All functions must have a function name. The function name and variable name have the same rules, that is, the arrangement and combination of letters and arrays. Of course, the first character must be a letter. We can't name functions too long or too short. I remember that there was an old professor in school who taught us the microcontroller, He likes to name programs with handwritten letters in Chinese Pinyin. For example, the name of the function "JQRDD" below is "machine machine human power off". You will find it very difficult to look at his programs, especially the functions without comments are a disaster. The funny thing is that the old man bought a number of "80C51" for his car. There is hardly anyone else. I suggest you name "Robot_Power_Off" this way, or you can directly name "RobotPowerOff" without underlining. Roast about that old man. The main advantage of the function is that it can be executed any number of times at the place where it is needed. If the code function cannot be written, our project will be written in the Main function, which will be a huge daily account. As a saying goes, it will take a while to rewrite the crematorium. Everyone should do what they want.



Another advantage of the function is that it is convenient for development, testing and maintenance. For example, if you add some functions to a function or modify a bug that was missed before, as long as the input and output of the function do not change and the logic is correct, the part of the previous program that calls the code will not be affected. Of course, you can add a "V2" or "New" after the name of the modified function. The problem is, how to name the modified function next time? "V3" or "New_New". I have seen many colleagues write this before, but later they found it wrong. They directly thanked "Year Month Day" after the function. At that time, I saw that just like Nezha, "eyes were in the sand".



Of course, if you are too lazy to follow the above principles, in order that you can still see the code you wrote in the past, you can make a note at the beginning of another function and write the following lines: When we write the first robot code in ABB RAPID, most people start from the Main function. "Mian" is the function name, that is, the function header of the function, followed by the function body, Our function.



If ABB RAPID has no returned function, it will write "PROC" and "ENDPROC" directly, and the style is similar to that of VB.



When we can add parameters to the function header, we can also let the function return results. "PROC" function is a function format that does not return results, and the function format that returns is "FUNC". I will share it with you later in this chapter. The discussion in the previous two sections is actually enough to deal with most of the situations, even 99% of the situations, in our work. However, there are always some situations that are difficult for us. For example, we have written a function to send data to the upper computer. Previously, it was sent through the serial port. Now, the customer wants to send data through the network cable, but my program framework has been written. Just modify the function to send data separately, As a result, the next customer requires both functions and can switch freely. This time, you may feel that you can write two programs and use them. But if you master the following programming skills, you will find that your life has changed. Your boss appreciates you, your colleagues respect you, and the aunt who cooks in the canteen will not shake her hand.



The following is our interesting programming syntax sugar, "Swith" keyword, optional parameters.



We still use the previous example, the addition of two data. Now we need to change it to the same function, which can achieve addition and also can calculate the subtraction of two data. Although subtraction is a special addition, we still need to tell the robot how to operate when programming. Without much to say, code directly:



6) The STL instruction cannot be used in interrupt programs and subprograms.



As a digital transformation expert in the field of global energy management and automation, Schneider Electric has always been paying attention to the growth and sound development of small and medium-sized enterprises, and opened the first quarter of the "Green Intelligent Manufacturing Win Plan" in 2020.英维思(3008, 3625, 3508E.3721, 3700A 4351B)
本特利(3500/42M， 3500/ 22M, 3500/ 95.3500/05)
黑马(F3330, F3236， F6217, F7126, F8621A)
福克斯波罗(FBM203, FBM204, FBM217, FMB231)
AB: (1746 1747 1756 1770 1771 1785触摸屏2711系列CPU PLC)
普罗索芙特PROSOFT MVI46/56/69, AB旗下，跟AB模块
瑞恩RELIANCE模块,卡件
飞利浦EPRO MMS6210/ 621…. PR6423/003-031
美尔托Meltal MT1102-02-00, MS3101-00-00, MS3102-01-00
横河YOKOGAWA AAI, ADV, ADI, ANB, AMM, SB, PW(型号开头),卡件模块(CPU,电源,输出，PLC)
摩尔MOORE Q开头, 3开头模块,像电视显示器
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