51 MCU interrupt and software simulation

12

From the structure diagram, we can see that the 51 MCU has 5 interrupts, namely external interrupt 0 (INT0), external interrupt 1 (INT1), timer interrupt 0 (T0), timer interrupt 1 (T1) and serial port interrupt (TX/RX). There are two priorities, and the priority order in an interrupt group from high to low is INT0, T0, INT1, T1, TX/RX.

Partial Interrupt Register 12

1. Interrupt Enable Control Register (IE) 

EX0: External interrupt 0 enable bit; 
ET0: Timer/Counter T0 interrupt enable bit; 
EX1: External interrupt 1 enable bit; 
ET1: Timer/Counter T1 interrupt enable bit; 
ES: Serial port interrupt enable bit; 
EA: CPU interrupt enable (always enable) bit. 
All of the above are enabled by 1 and disabled by 0. 
2. Timer/controller control register TCON 

IT0: External interrupt 0 trigger mode control bit 
When IT0=0, it is level trigger mode (low level is valid) 
When IT0=1, it is edge trigger mode (falling edge is valid) 
IE0: External interrupt 0 interrupt request flag bit (automatically completed by hardware) 
IT1: External interrupt 1 trigger mode control bit (same as IT0) 
IE1: External interrupt 1 interrupt request flag bit (same as IE1) 
TF0: Timer/counter T0 overflow interrupt request flag bit 
TF1: Timer/counter T1 overflow interrupt request flag bit 
3. Interrupt priority control register (IP) 

PX0: External interrupt 0 priority setting bit 
PT0: Timer/counter T0 priority setting bit 
PX1: External interrupt 0 priority setting bit 
PT1: Timer/counter T1 priority setting bit 
PS: Serial port priority setting bit All 
of the above are 1 for high priority and 0 for low priority. 
4. Timer/counter working mode register TMOD 

GATE-gate control bit. 
GATE=0, the start and stop of the timer/counter are only controlled by TRX (X=0,1) in the TCON register. 
GATE=1, the start and stop of the timer counter are controlled by the level status of TRX (X=0,1) in the TCON register and the external interrupt pin (INT0 or INT1). 
C/T—Timer and counter mode selection bit. 
C/T=1, counter mode; C/T=0, timer mode. 
M1M0—Working mode selection bit. 
 
Before using the interrupt, turn on the general interrupt, turn on the interrupt enable bit you use, set the interrupt trigger mode for the external interrupt, and configure the corresponding registers for other interrupts. If multiple interrupts are used, configure the interrupt priority.

The format of the interrupt service function: 
The writing method of the interrupt service program 
void function name () interrupt interrupt number [using workgroup] 
{ 
interrupt service program content 
}

These are basically the interrupts of 51 single-chip microcomputer. Here is an example. 

Use the falling edge to trigger INT0 (P3.2), and then let P1^0 output 0; 12

Main Program

include "intrins.h"include 

sbit LED = P1^0 ;void Int0 (void) interrupt 0{
    LED = 0 ;
}void Init_INT(void)
{
    EA = 1; // Enable general interrupt
    EX0 = 1; //Open external interrupt 0
    IT0 = 1; // Edge trigger}void main()
{
      Init_INT(); //Interrupt initialization

      while(1)
      {  

      }
}123456789101112131415161718192021222324252627

Simulation with signal function

signal void test(void)  
{  
    while(1)  
    {  
        port3 = 0xff ;
        swatch(0.02);

        port3 = 0xfB ;      
        swatch(0.1) ;

        port3 = 0xff ;
        swatch(0.02);

        _break_ = 1 ;

    }  
}1234567891011121314151617

The simulation waveform is as follows, the upper one is the external interrupt signal, and the lower one is the P1^0 output signal.