Pic 16f887 interface ds18b20

//===============================================
// Written by: Luanktd
// DS18b20 with Pic 16F887, Display led 7 segments
////////////////////////////////////////////////////////////
#include <htc.h>
__CONFIG(FOSC_HS & WDTE_OFF & PWRTE_ON & MCLRE_ON & CP_OFF & BOREN_OFF
         & IESO_OFF & FCMEN_OFF & LVP_OFF & DEBUG_OFF); //1st config. Word
__CONFIG(BOR4V_BOR21V); //2st config.
#define _XTAL_FREQ 8000000
#define  uch unsigned char                     //
# define DQ RE2                                //define 18B20 data PORT
# define DQ_DIR TRISE2                         //define 18B20 D PORT direct register
# define DQ_HIGH() DQ_DIR =1                   //set data PORT INPUT
# define DQ_LOW() DQ = 0; DQ_DIR = 0           //set data PORT OUTPUT
 unsigned char  TLV=0 ;                        //temperature high byte
 unsigned char  THV=0;                         //temperature low byte
 unsigned char TZ=0;                           //temperature integer after convert
 unsigned char TX=0;                           //temperature decimal  after convert
 unsigned int  wd;                              //temperature BCD code  after convert
 unsigned char tram;
 unsigned char chuc;
 unsigned char donvi;
 unsigned char le;
 unsigned char table[10]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};
//the display code of 0-9
 //------------------------------------------------
//delay function
//display function
// each count take 12us;
 void delay (int uSeconds)
{
	int s;
	for (s=0; s<uSeconds; s++);
}
void display()
{

 TRISA=0X00;                     //set A PORT all OUTPUT
 PORTD=0xC6;                     //display degrees symbol
 PORTA=0x1f;
delay(250);
 PORTD=0x9C;                    //display "C" symbol
 PORTA=0x2f;
delay(250);
 PORTD=table[le];
 PORTA=0x37;
 delay(250);
 PORTD=table[donvi]&0x7F;
 PORTA=0x3b;
delay(250);
 PORTD=table[chuc];
 PORTA=0x3d;
delay(250);
PORTD=table[tram];
if(PORTD==0xC0) PORTA=0xFF; else PORTA=0x3e;
delay(250);
}

//------------------------------------------------
//system initialize function
void init()
{
  OPTION_REG  = 0x00;       // dung prescaler cho timer0 voi ti le la 1:2
  ANSEL  = 0;               // Configure AN pins as digital I/O
  ANSELH = 0;
  ADCON1=0X07;                                //set A PORT general data PORT
  TRISA=0X00;                                 //set A PORT direct OUTPUT
  TRISD=0X00;                                 //set D PORT direct OUTPUT
  TRISE=0x00;

}

//-----------------------------------------------
//reset DS18B20 function
reset(void)
{
  char presence=1;
  while(presence)
  {
    DQ_LOW() ;                                //MAIN MCU PULL LOW
   delay(41);                              //delay 503us
    DQ_HIGH();                                //release general line and wait for resistance pull high general line and keep 15~60us
   delay(5);                              //delay 70us
    if(DQ==1) presence=1;                     // not receive responsion signal,continue reset
    else presence=0;                          //receive responsion signal
   delay(40);                              //delay 430us
   }
  }

//-----------------------------------------------
//write 18b20 one byte function
void write_byte(uch val)
{
 uch i;
 uch temp;
 for(i=8;i>0;i--)
 {
   temp=val&0x01;                            //shift the lowest bit
   DQ_LOW();
   NOP();
   NOP();
   NOP();
   NOP();
   NOP();                                    //pull high to low,produce write time
   if(temp==1)  DQ_HIGH();                   //if write 1,pull high
   delay(5);                               //delay 63us
   DQ_HIGH();
   NOP();
   NOP();
   val=val>>1;                               //right shift a bit
  }
}

//------------------------------------------------
//18b20 read a byte function
uch read_byte(void)
{
 uch i;
 uch value=0;                                //read temperature
 static bit j;
 for(i=8;i>0;i--)
 {
   value>>=1;
   DQ_LOW();
   NOP();
   NOP();
   NOP();
   NOP();
   NOP();
   NOP();                                   //6us
   DQ_HIGH();                               // pull high
   NOP();
   NOP();
   NOP();
   NOP();
   NOP();                                  //4us
   j=DQ;
   if(j) value|=0x80;
  delay(5);                             //63us
  }
  return(value);
}

//-------------------------------------------------
//start temperature convert function
void get_temp()
{
int i;
DQ_HIGH();
reset();                                 //reset,wait for  18b20 responsion
write_byte(0XCC);                        //ignore ROM matching
write_byte(0X44);                        //send  temperature convert command
for(i=20;i>0;i--)
    {

     NOP();
	// display();                       //call some display function,insure the time of convert temperature
    }
reset();                                 //reset again,wait for 18b20 responsion
write_byte(0XCC);                        //ignore ROM matching
write_byte(0XBE);                        //send read temperature command
TLV=read_byte();                         //read temperature low byte
THV=read_byte();                         //read temperature high byte
DQ_HIGH();                               //release general line
TZ=((TLV>>4)|(THV<<4));// & 0X3f;               //temperature integer
TX=TLV<<4;                               //temperature decimal
// if(TZ>100) TZ/100;                       //not display hundred bit
donvi=TZ%10;                     //integer Entries bit
chuc=(TZ%100)/10;                      //integer ten bit
tram = TZ/100;
wd=0;
if (TX & 0x80) wd=wd+5000;
if (TX & 0x40) wd=wd+2500;
if (TX & 0x20) wd=wd+1250;
if (TX & 0x10) wd=wd+625;                //hereinbefore four instructions are turn  decimal into BCD code
le=wd/1000;                          //ten cent bit
NOP();
}

//--------------------------------------------------
//main function
void main()
{
   init();                              //call system initialize function

   while(1)
     {
       get_temp();                  //call temperature convert function
       display();                   //call display function

	}
}