Real Time Clock(DS1307 with PIC18F4520)

#include<p18f4520.h>
#include<i2c.h>
#include<stdlib.h>
#include<stdio.h>
#include<delays.h>
#include<system4520.h>
 
#pragma config OSC = HS
#pragma config PWRT = OFF
#pragma config PBADEN = OFF   
#pragma config WDT = OFF
#pragma config LVP = OFF   
#pragma config DEBUG = OFF   
 
void i2c_init(void);
void rtc_init(void);
void write_rtc(unsigned char add, unsigned char data);
unsigned char read_rtc(unsigned char add);
unsigned char read_rtcn(unsigned char add);
unsigned char Read_I2C(void);
 
void main(void)
{
   int hr,mn,sc,dt,mon,yr,a,b;
   unsigned char sec,min,hour,day,date,month,year;
   lcd_init();
   i2c_init();
   rtc_init();   
 
   write_rtc(0x00, 0x80);
   write_rtc(0x01, 0x00);
   write_rtc(0x02, 0x19);
   write_rtc(0x03, 0x04);
   write_rtc(0x04, 0x03);
   write_rtc(0x05, 0x02);
   write_rtc(0x06, 0x12);
   write_rtc(0x00, 0x00);
 
   do {
      sec = read_rtc(0x00);
      min = read_rtc(0x01);
      hour = read_rtc(0x02);
      day = read_rtc(0x03);
      date = read_rtc(0x04);
      month = read_rtc(0x05);
      year = read_rtc(0x06);
 
      clear_screen();
      cursor_set(0,0);
       hr   =  ((hour & 0x03) >> 4)*10 + (hour & 0x0F);
      a = ((hr/10)+48);
      WriteC(a);
      b = ((hr%10)+48);
      WriteC(b);
      cursor_set(0,2);
      WriteC(0x3A);
      cursor_set(0,3);
      mn = (min& 0x0f) + ((min>> 4) * 10);
      a = ((mn/10)+48);
      WriteC(a);
      b = ((mn%10)+48);
      WriteC(b);
      cursor_set(0,5);
      WriteC(0x3A);
      cursor_set(0,6);
      sc   =  (sec & 0x0f) + (((sec >> 4) & 0x07) * 10);
      a = ((sc/10)+48);
      WriteC(a);
      b = ((sc%10)+48);
      WriteC(b);
 
 
      cursor_set(1,0);
       dt  =  (date & 0x0f) + (( date>> 4) * 10);
      a = ((dt/10)+48);
      WriteC(a);
      b = ((dt%10)+48);
      WriteC(b);
      cursor_set(1,2);
      WriteC(0x2f);
      cursor_set(1,3);
      mon = (month & 0x0f) + ((month >> 4) * 10);
      a = ((mon/10)+48);
      WriteC(a);
      b = ((mon%10)+48);
      WriteC(b);
      cursor_set(1,5);
      WriteC(0x2f);
      cursor_set(1,6);
      yr   =  (year & 0x0f) + ((year >> 4) * 10);
      a = ((yr/10)+48);
      WriteC(a);
      b = ((yr%10)+48);
      WriteC(b);
 
 
      Delay10KTCYx(20);
   } while(1);
 
}
 
void i2c_init(void)
{
   PORTCbits.RC3 = 1;
   PORTCbits.RC4 = 1;
   SSPADD = 0x09;
   SSPCON1 = 0x00;
   SSPCON2 = 0x00;
   SSPCON1 = 0x28;
}
 
void rtc_init(void)
{
   StartI2C();
   WriteI2C(0xD0);
   WriteI2C(0x00);
   WriteI2C(0x00);
   RestartI2C();
   WriteI2C(0xD0);
   WriteI2C(0x07);
   WriteI2C(0x80);
   StopI2C();
   IdleI2C();
}
 
void write_rtc(unsigned char add, unsigned char data)
{
 
   StartI2C();
   WriteI2C(0xD0);
   WriteI2C(add);
   WriteI2C(data);
   StopI2C();
 
}
 
unsigned char read_rtc(unsigned char add)
{
   unsigned char result;
   StartI2C();
   WriteI2C(0xD0);
   WriteI2C(add);
   RestartI2C();
   WriteI2C(0xD1);
   IdleI2C();
   result=ReadI2C();
   AckI2C();
   StopI2C();
   return result;
}
 
unsigned char read_rtcn(unsigned char add)
{
   unsigned char result;
   StartI2C();
   WriteI2C(0xD0);
   WriteI2C(add);
   RestartI2C();
   WriteI2C(0xD1);
   result=ReadI2C();
   NotAckI2C();
   StopI2C();
   return result;
}
 
unsigned char Read_I2C(void)
{
   SSPCON2bits.RCEN = 1;
   while(!SSPSTATbits.BF);
   return(SSPBUF);
}