Mid-term exam stopwatch timer

Making a stopwatch timer, the recording time of 0-15 seconds. It requires accurate and controllable.

Claim:

• Start the stopwatch can be controlled with a key
• Button can be controlled by stopping the stopwatch
• Button can be used to control the clock to zero
• Time using the timer control precision is required.
• Using a plurality of digital control and implement the functions keys.

1. First, a circuit diagram of the request plus two buttons, as shown in the FIG.

 

 The write code requirements, the following reference code is

#include<reg52.h>
#define LED P0
unsigned int i = 0;
unsigned int j =0;
sbit KEY1 = P1 ^ 0; // Pause, Start button
sbit KEY2 = P1 ^ 2; // reset button
unsigned char NUM[]= {0xC0,0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,\
                    0x80,0x90,0x88,0x83,0xA7,0xA1,0x86,0x8E}; 
void INT_T0(void)
{
    TMOD = 0X01; // open timer 0, timer 1 mode using
    TH0 = 0XFC;
    TL0 = 0X18; // Initial value
    EA = 1; // Turn on the main switch
    ET0 = 1; // Open the interrupt switch T0
}
void main(void)
{    
    INT_T0();
    TR0 = 0; // close timing function
    LED = NUM[0];
    while(1)
    {            
        if(KEY1 == 0)
        {
            TR0 = 1; // determination button is pressed, the timing of the opened chronograph
        }
        else
        {
            TR0 = 0; // Analyzing key release, timed disconnect feature
        }
        if(KEY2 == 0)
        {
             break; // out of the loop, time to zero
        }    
    }
}
 
void time0(void) interrupt 1 
{
    TH0 = 0XFC;
    TL0 = 0X18; // Initial value
    if(i < 1000)
    {
        i++;
    }
    else
    {
         LED NUM = [j];
        if(j < 16)
        {
         j++;
        }
        else
        {
             j=0;
        }
        i = 0;
    }
    
}

Press 1 to start counting, stop release, press 2 Reset