Software reset of 51 MCU

    Please look at the program at the bottom first.
      This is a program for Keil software, called "pure software" reset. The so-called "pure software" means that it does not directly operate hardware and registers.
      In fact, if you don't understand hardware and assembly, you can't have this C program. Anyway, let's take a look at its true face:
      We know that 51 microcontrollers 
      can put data in the program memory, that is, there is no essential difference between programs and data, they are all specific data. If we store a program in the form of array data in the program memory, can it be executed? The answer is yes.
       -Now
      back to the topic, let's take a look at the array data 0xe4, 0xc0, 0xe0, 0xc0, 0xe0, 0x22. From the assembly window of Keil, we can see that it is actually four assembly statements:
        CLR A; compiled as 0XE4
        PUSH ACC; compiled as 0XC0 0XE0
        PUSH ACC; compiled as 0XC0 0XE0
        RET; function return is compiled as 0X22. It can be seen that this is actually the assembly reset instruction of the 51 microcontroller.
      In fact, it's just that the C reset code is written in an ugly way. rst is a byte pointer pointing to the program memory. We convert it to a pointer to a function that returns void. The format of a function pointer that returns void is: void 
      (*)(). This expression is more complicated because of the operator priority relationship. Enclose it in parentheses and it becomes (void 
      (*)())rst. In this way, rst becomes a function pointer. Let's take a look at the general format of function pointer (*p)(). Replace p with (void 
      (*)())rst and enclose it in parentheses to become (*((void (*)())rst))(). This reveals the whole veil of this reset.
      The following is the test and verification program:
#include
main()
{
        unsigned char code rst[6]={0xe4,0xc0,0xe0,0xc0,0xe0,0x22}; //Define an array of code type, it must be of code type
        while(1) //Loop test
        {
                TMOD=5; //The test can be any language name
                TI=1;
                P1=0;
                P1=1;
                P2=2;
                P3=3;
                (*((void (*)())rst))(); //Reset
                SCON=0x50;
        }
}