89S52 RESET Automatically...

#include<reg51.h>
#include<stdio.h>
sbit row0=P0^4;	//assigning PORT-0 to read rows
sbit row1=P0^5;	//assigning PORT-0 to read rows
sbit row2=P0^6;	//assigning PORT-0 to read rows
sbit row3=P0^7;	//assigning PORT-0 to read rows
sfr COL=0xA0;	//assigning PORT-2 to read colomns
sfr ldata=0x90;	//assigning PORT-1 for LCD data
sbit rs=P0^0;
sbit rw=P0^1;
sbit en=P3^0;
sbit busy=P1^7;

sbit batind = P0^3;
sbit syslock=P3^7;
sbit buzzer=P3^1;
sbit stepup=P0^2;
sbit dc0=P3^4;
sbit dc1=P3^5;
sbit l293d=P3^6;

void timer(unsigned int msec);
void lcdcmd(unsigned char value) ;
void lcddata(unsigned char value);
void lcdready(void)	   ;
void printstring(unsigned char ch[]) ;
void lcdclear(void);
void msdelay(unsigned int value)  ;
int keypad();

void door_open();
void lock();
void door_close();
void setpassprog();
void newpassword();
void newpasswordlong();
void userpassprog();
void counting();
void systemlock();

unsigned char userid[5]={"0000"};
unsigned char password[5]={"0000"};
unsigned char chanuser[5]={"0000"};
unsigned char chanpass[5]={"0000"};
unsigned char syspass[17]={"0000000000000000"};
unsigned char sysupt[17]= {"0000000000000000"};
unsigned char x;
unsigned char cancel[2]={"0"};
unsigned char count[2]={"0"};
unsigned char fig[2]={"3"};

unsigned char ex0_isr_counter = 0; // interrupt 

void ex0_isr (void) interrupt  0
{
	 ex0_isr_counter++;
	 
}

 void timer(unsigned int msec)     // Function for timer
{
unsigned int i;
for(i=0;i<msec;i++)
{
TMOD=0x20;         // Mode2
TH1=0xD1;
TL1=0xFF;

TR1=1;
while(TF1==0);
TF1=0;
TR1=0;
}
}

void lcdcmd(unsigned char value)		//LCD command
{
 lcdready();
 ldata=value;
 rs=0;
 rw=0;
 en=1;
 msdelay(10);
 en=0;
 }
 /* sending commnad to LCD to display characters*/
void lcddata(unsigned char value)			 // LCD data
{
 lcdready();
 ldata=value;
 rs=1;
 rw=0;
 en=1;
 msdelay(20);
 en=0;
 }
 /* checking LCD buffer for free */
void lcdready(void)					// LCD ready
{
 busy=1;
 rs=0;
 rw=1;
 if(busy==1)
  {
   en=0;
   msdelay(1);
   en=1;
   }
}

void printstring(unsigned char ch[])		// Print to LCD
{
 unsigned int i;
 for(i=0;ch[i]!='\0';i++)
 lcddata(ch[i]);
 }
/* generating delay*/
void msdelay(unsigned int value)			// Delay
{
 unsigned int i,j;
 for(i=0;i<value;i++)
 for(j=0;j<100;j++);
 }

void LCDclear(void)
 {
  lcdcmd(0x01);
  }
int keypad() 
 {
   unsigned char dat[4][4]={'1','2','3','A',	 // assigning key matrix
                            '4','5','6','B',
						    '7','8','9','-',
						    'C','0','=','+',
						   };
 unsigned char colloc,rowloc;
 COL=0xFF;
 row0=0;
 row1=0;
 row2=0;
 row3=0;
 rs=0;
 rw=0;
 en=0;
 busy=0;
  /* setting LCD screen*/ 
 ldata=0x00;
 lcdcmd(0x38);
 lcdcmd(0x0E);
 lcdcmd(0x06);

 while(1)
 {
/* reading character from keyboard */
   do
   {
    row0=0;
 	row1=0;
 	row2=0;
 	row3=0;
   	colloc=COL;
	colloc&=0x0F;
	}while(colloc!=0x0F);
	do
	{
	 do
	 {
	  msdelay(10);
	  colloc=COL;
	  colloc&=0x0F;
	  }while(colloc==0x0F);
	  msdelay(10);
	  colloc=COL;
	  colloc&=0x0F;
	  }while(colloc==0x0F);
    while(1)
	{
	 row0=0;
 	 row1=1;
     row2=1;
     row3=1;
	 msdelay(5);
	 colloc=COL;
	 colloc&=0x0F;
	 if(colloc!=0x0F)
	 { 
	  rowloc=0;
	  break;
	  }
	  row0=1;
 	  row1=0;
      row2=1;
      row3=1;
	  msdelay(5);
	  colloc=COL;
	  colloc&=0x0F;
	   if(colloc!=0x0F)
	   {
	    rowloc=1;
		break;
		}
	  row0=1;
      row1=1;
      row2=0;
      row3=1;
      msdelay(5);
	  colloc=COL;
	  colloc&=0x0F;
	   if(colloc!=0x0F)
	   {
	    rowloc=2;
		break;
		}
	  row0=1;
 	  row1=1;
 	  row2=1;
 	  row3=0;
	  msdelay(5);
	  colloc=COL;
	  colloc&=0x0F;
	if(colloc!=0x0F)
	  {  
	      rowloc=3;
	      break;
	    }
	   }
   if(colloc==0x0E)
   return(dat[rowloc][0]);
   else if(colloc==0x0D)
   return(dat[rowloc][1]);
   else if(colloc==0x0B)
   return(dat[rowloc][2]);
   else
    return(dat[rowloc][3]);
	}
	}

void main(void)
{
   unsigned int i;
	 lcdcmd(0x38);
     lcdcmd(0x0F);
     lcdcmd(0x06);
     lcdcmd(0x01);
	 while(1)
	 {
	 batind=1;
	 syslock=1;
	 stepup=1;
	 l293d=1;
	 IT0=0;
	 EX0 = 1;
	 EA = 1;
	 PCON |= 0x01; 
	 lcdcmd(0x80);
	 printstring("ENTER NEW 4 DIGIT");
	 lcdcmd(0xC0);
	 printstring("USER-ID:");
	 do
	  {	
	    userid[i]=keypad();
		if
		(userid[i]=='A')
		  {
		    return;
		  }
		lcddata(userid[i]);
		i++;
      }
	  while(i!=4);
      i=0;
	  msdelay(1000);
	  userpassprog();
	 }
}

void userpassprog()		// User Pass Prog
{
   unsigned int i;
     lcdcmd(0x38);
     lcdcmd(0x0F);
     lcdcmd(0x06);
     lcdcmd(0x01);
	 while(1)
	 {
	 batind=1;
	 syslock=1;
	 stepup=1;
	 l293d=1;
	 IT0=0;
	 EX0 = 1;
	 EA = 1;
	 PCON |= 0x01; 
	 lcdcmd(0x80);
	 printstring("USER ID:");
	 do
	 {
		chanuser[i]=keypad();
		if
	    (chanuser[i]=='C')
	      {
	         userpassprog();
	      }
	    if
		(chanuser[i]=='A')
		 {
		   lcdclear();
		   userpassprog();
		 }
		 lcddata(chanuser[i]);
		 i++;
	 }
		while(i!=4);
		i=0;
		if(chanuser[0]==userid[0] && chanuser[1]==userid[1] && chanuser[2]==userid[2] && chanuser[3]==userid[3] )
		{
		 printstring("PASSWORD");
		}
	 }
}