#include <REGX52.H>

void disp(unsigned char *x,db);
void delay(unsigned int c);
void timerint ()  ;

sbit D1=P2^0;
sbit D2=P2^1;
sbit D3=P2^2;
sbit D4=P2^3;
sbit DP=P1^7;

#define  DT  P1

unsigned char code  dis[13]={
							
		0X3F,/*0*/
        0X06,/*1*/
        0X5B,/*2*/
        0X4F,/*3*/
        0X66,/*4*/
        0X6D,/*5*/
        0X7D,/*6*/
        0X07,/*7*/
        0X7F,/*8*/
        0X6F,/*9*/
        0X40,/*-*/
        0XBF,/*0.*/
		0X00,/*NULL*/
			};

signed int sign,Num=-20;
int count=0;

	



void main(void)
{

unsigned char DB,X[4]="0000";
    DB=4;
	
	EA    = 1;
	ET0   = 1;
	TR0   = 1;
	TMOD = 0x01;
	TH0 = 0x03C;
	TL0 = 0x0B0;


	while(1)
	{
	DB=P3&3;
	if(Num>9999)Num=-50;  
	if(Num<0)
		{
			*X=10;
			sign=-Num;
			*(X+1)=(sign/100)%10;
			*(X+2)=(sign/10)%10;
			*(X+3)=sign%10;
		}	
	 else
	 	{
	
		*X=(Num/1000)%10;
		*(X+1)=(Num/100)%10;
		*(X+2)=(Num/10)%10;
		*(X+3)=Num%10;
		}
	if(*X==0&&DB<4)*X=12;
	if(*(X+1)==0&&DB<3)*(X+1)=12;
	if(*(X+2)==0&&DB<2)*(X+1)=12;
	disp(X,DB);

	}
}


void delay(unsigned int c)
{
	unsigned int i,j;
	for(i=0;i<c;i++)
	for(j=0;j<100;j++);
	
}


void disp(unsigned char *x,db)
{
    DT=dis[*x];
	D1=1;
	if(db==4)DP=1;
	delay(10);
	D1=0;

	DT=dis[*(x+1)];
	D2=1;
	if(db==3)DP=1;
	delay(10);
	D2=0;

	DT=dis[*(x+2)];
	D3=1;
	if(db==2)DP=1;
	delay(10);
	D3=0;

	DT=dis[*(x+3)];
	D4=1;
	if(db==1)DP=1;
	delay(10);
	D4=0;
	
}




void timerint () interrupt 1 
{
	count++;
	
	if(count==5){	count=0;  Num++;	}	

	TF0 = 0;
	TH1=(65536-64000)/256;
	TL1=(65536-64000)%256;
	TR0 = 1;
      
}