Real time clock using 8051 timer and interrupt

#include "config.c"
#include "def_pinos.h"
#include <stdio.h>


unsigned int hora, min, seg;
unsigned int check;




//a period = (65535 - 50000) = 3CAF (0.05 s/pulse) */
/* 0.05 x 20 = 1 s/pulse */


void delay_ms(unsigned int tempo){

    for (;tempo;tempo--){
        TR0 = 0;
        TF0 = 0;
        TL0 = 0xAF;
        TH0 = 0x3C;
        TR0 = 1;                                                                                   
        while(TF0 == 0);
    }
}


void set_time (char Shora, char Smin, char Sseg)
{
    hora = Shora;
    min = Smin;
    seg = Sseg;
}


void print_time ()
{   
    char h1, h2, m1, m2, s1, s2;
    h1 = hora/10 + '0';
    h2 = hora%10 + '0';
    m1 = min/10 + '0';
    m2 = min%10 + '0';
    s1 = seg/10 + '0';
    s2 = seg%10 + '0';


    putchar (h1);
    putchar (h2);
    putchar (':');
    putchar (m1);
    putchar (m2);
    putchar (':');
    putchar (s1);
    putchar (s2);
}

  

void time_inc(void)    
{
   
    check++;                     

    if(check==1000)              
     { 
      check=0;                    
       seg++;


    if(seg>59)
     {  
       seg=0;
       min++;


   if(min>59)
     {  
       min=0;
       hora++;
  

   if (hora==24)
     {
      hora=0;
      }
  }
              }
        }

}

void incrementaTempo () __interrupt 5 //Interrupção a cada 1s
{
    seg++;
    if (seg<1)
    return;
    seg = 0;
    time_inc();
   
}   



void main () {
   
    Init_Device();

    SFRPAGE = LEGACY_PAGE;

    TCON=0x00;
    TMOD=0x01;
    IE=0x83;
    TL0 = 0x00;
    TH0 = 0xB7;
    TR1 = 1;
     EA=1;
     ET0=1;
    
    set_time (01,02,00);
   
     print_time ();
    time_inc();
    delay_ms(1000);


    }


void putchar (char c) {
   SBUF0=c;
   while(TI0==0);
   TI0=0;
}
void int_serial(void) __interrupt 4{
    unsigned char c;
    while(!RI0);                           // Wait until character received completely
    c=SBUF0;                       // Read the character from buffer reg
    RI0=0;  

}