Principle and implementation of PIC microcontroller controlling DS18B20 digital temperature sensor

#define uchar unsigned char
#define uint  unsigned int
#define DQ RC1
#define DQ_HIGH() TRISC1=1
#define DQ_LOW() TRISC1=0;DQ=0
__CONFIG(0x3B31);
const uchar table[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,
                        0x07,0x7f,0x6f};
const uchar table1[]={0xbf,0x86,0xdb,0xcf,0xe6,0xed,0xfd,
                        0x87,0xff,0xef};
uint temper;
uchar a1,a2,a3,a4;
void delay(uint x);
void delayus(uint,uchar);
void init();
void disp(uchar num1,uchar num2,uchar num3,uchar num4);
void write_byte(uchar date);
uchar read_byte();
void get_tem();
void main()
{
 init();
 while(1)
 {
/*  delayus(0,0);//20
  delayus(1,1);//30
  delayus(2,2);//45
  delayus(4,4);//70
  delayus(70,30);//750
  delayus(50,10);//500*/
 // uchar num;
  get_tem();
 // for(num=20;num>0;num--)
 //  disp(a1,a2,a3,a4);
 } 
}
void reset()
{
 uchar st=1;
 DQ_HIGH();
 NOP();NOP();
 while(st)
 {
  DQ_LOW();
  delayus(70,30);
  DQ_HIGH();
  delayus(4,4);
  if(DQ==1)
   st=1;
  else
   st=0;
  delayus(50,10);
 }
}
void write_byte(uchar date)
{
 uchar i,temp;
 DQ_HIGH();
 NOP();NOP();
 for(i=8;i>0;i--)
 {
  temp=date&0x01;//01010101
  DQ_LOW();
  delayus(0,0);
  if(temp==1)
   DQ_HIGH();
  delayus(2,2);
  DQ_HIGH();
  date=date>>1;//00101010
 }
}
uchar read_byte()
{
 uchar i,date;
 static bit j;
 for(i=8;i>0;i--)
 {
  date=date>>1;
  DQ_HIGH();
  NOP();NOP();
  DQ_LOW();
  NOP();NOP();NOP();NOP();NOP();NOP();
  DQ_HIGH();
  NOP();NOP();NOP();NOP();
  j=DQ;
  if(j==1)
   date=date|0x80;//1000 0000
  delayus(1,1);
 }
 return (date);
}

void get_tem()
{
 uchar tem1,tem2,num;
 float aaa;
 reset(); //Reset
 write_byte(0xCC); //Skip ROM
 write_byte(0x44); //Temperature conversion
 for(num=100;num>0 ;num--)
  disp(a1,a2,a3,a4);
 reset();
 write_byte(0xCC);
 write_byte(0xBE);
 tem1=read_byte();
 tem2=read_byte();
 aaa=(tem2*256+tem1 )*6.25;
 temper=(int)aaa;
 a1=temper/1000;
 a2=temper%1000/100;
 a3=temper%100/10;
 a4=temper%10;
}
void delayus(uint x,uchar y)
{
 uint i;
 uchar j;
 for(i=x;i>0;i--);
 for(j=y;j>0;j--);
}
void delay(uint x)
{
 uint a,b;
 for(a=x;a>0;a--)
  for(b=110;b> 0;b--);
}
void init()
{
 TRISD=0;
 TRISA=0;
 PORTD=0;
 PORTA=0;
}
void disp(uchar num1,uchar num2,uchar num3,uchar num4)
{
 PORTD=table[ num1]; //Display the first digital tube
 PORTA=0x20; //0010 0000
 delay(2);
 PORTD=table1[num2]; //Display the second digital tube
 PORTA=0x10; //0001 0000
 delay(2 );
 PORTD=table[num3]; //Display the third digital tube
 PORTA=0x08; //0000 1000
 delay(2);
 PORTD=table[num4];//Display the fourth digital tube
 PORTA=0x04;//0000 0100
 delay(2);
/* PORTD=table[num5];//Display the fifth digital tube
 PORTA=0x02;/ /0000 0010
 delay(2);
 PORTD=table[num6];//display the sixth digital tube
 PORTA=0x01;//0000 0001
 delay(2);*/
}