SCM learning notes: interrupt learning

1. What is interruption , The principle of interruption

Interrupt is set to enable the single chip microcomputer to have real-time processing of external or internal random events , The existence of interrupt function , It greatly improves the ability of MCU to deal with external or internal events .

In order to make it easier for everyone to understand the concept of interruption , Let's start with a life example ： You turn on the fire , Boil a pot of water . Then go and do the laundry , In the process of washing clothes , Suddenly I heard the kettle send out the alarm of boiling The sound , At this time , You stop washing clothes , Turn off the fire immediately , Then pour boiling water into the thermos , Completion of irrigation After boiling water , You go back and continue washing clothes . There is actually an interruption in this process . For single chip microcomputer , Interruption means CPU Dealing with an event A when , Another incident happened B, request CPU Deal with quickly ( Interruption occurs );CPU Temporarily stop the current work ( Interrupt response ), turn and go Handling events B( Interruption of service ); stay CPU Put the event I After processing , Back to the original event A By Continue processing events where interrupted A( Interrupt return ), This process is called interruption .

With the application of computer technology , It has been found that interrupt technology not only solves the problems of fast host and slow host I/O Data transmission problem of equipment , It also has the following advantages ： ① Time sharing operation .CPU It can be divided into multiple I/O Equipment services , Improve the utilization of the computer ; ② Real time response .CPU Be able to handle random events of application system in time , The real-time performance of the system is greatly increased strong ;③ High reliability .CPU Have the ability to deal with emergencies such as equipment failure and power failure , So that the system Improved reliability .

2.STC89C5X Interrupt in series single chip microcomputer

STC89C5X Series MCU provides 8 An interrupt request source , They are ： External interrupt O(INTO)、 External interrupt 1(INT1)、 External interrupt 2(INT2)、 External interrupt 3(INT3)、 Timer 0 interrupt 、 Timer 1 interrupt 、 Timer 2 interrupt 、 A serial port (UART) interrupt .
Now let's 51 SCM must have 5 An interrupt to introduce , Its internal structure block diagram is as follows ：

（1）. Interrupt allow control

（2）. Interrupt request flag TCON

（3）. Interrupt priority

（4）. Interrupt number

（5）. Interrupt response condition

Code representation ：

EA=1;// Turn on the main interrupt switch 
EX0=1;// Open external interrupt 0
IT0=0/1;// Set the trigger mode of external interrupt 
void int() interrupt()  using 1
{
    
// Function code 
}

3. Button control is realized through external interrupt LED Turn off and on the lights

（1） Circuit design

External interrupt 0 Corresponding to MCU p3.2 mouth , External interrupt 1 Corresponding to MCU p3.3 mouth , So here we use p3.2 Connect button K1, And then d1 Connect to P2.0, As shown in the figure below ：

Code design ：

/**************************************************************************************  Experimental phenomena ： After downloading the program , operation K3 Press the key to make D1 State inversion   Wiring instructions ： ( The specific wiring diagram can be seen in the corresponding experiment of the development strategy “ Experimental phenomena ” chapter ) 1, Single chip microcomputer -->LED& Traffic light module  P20-->D1 2, Single chip microcomputer --> Independent key module  P32-->K3  matters needing attention ： ***************************************************************************************/

#include "reg52.h" // This file defines some special function registers of MCU 

typedef unsigned int u16;	  // Declare and define data types 
typedef unsigned char u8;

sbit k3=P3^2;  // Define keys K3
sbit led=P2^0;	 // Definition P20 The mouth is led

/******************************************************************************* *  Letter   Count   name  : delay *  The functionality  :  The time delay function ,i=1 when , About time delay 10us *******************************************************************************/
void delay(u16 i)
{
    
	while(i--);	
}

/******************************************************************************* *  Letter   Count   name  : Int1Init() *  The functionality  :  Set external interrupt 1 *  transport   Enter into  :  nothing  *  transport   Out  :  nothing  *******************************************************************************/
void Int0Init()
{
    
	// Set up INT0
	IT0=1;// Jump along the departure mode （ Falling edge ）
	EX0=1;// open INT0 The interrupt allows . 
	EA=1;// Open total interrupt  
}

/******************************************************************************* *  Letter   Count   name  : main *  The functionality  :  The main function  *  transport   Enter into  :  nothing  *  transport   Out  :  nothing  *******************************************************************************/
void main()
{
    	
	Int0Init();  //  Set external interrupt 0
	while(1);		
}

/******************************************************************************* *  Letter   Count   name  : Int0() interrupt 0 *  The functionality  :  External interrupt 0 The interrupt function of  *  transport   Enter into  :  nothing  *  transport   Out  :  nothing  *******************************************************************************/

void Int0()	interrupt 0		// External interrupt 0 The interrupt function of 
{
    
	delay(1000);	 // Delay chattering 
	if(k3==0)
	{
    
		led=~led;
	}
}

The effect is as follows ：