ds18b20编程的问题（急！！！！！）

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温度大于32度之后，数码管显示正常，小于32度只显示0或者8



#include
#include"intrins.h"
#define uchar unsigned char
unsigned char code table[]={
      0x3f,0x06,0x5b,0x4f,
      0x66,0x6d,0x7d,0x07,
      0x7f,0x6f,0x77,0x7c,
      0x39,0x5e,0x79,0x71
     };


***it rs=P2^2;
***it duan=P2^6;
***it wei=P2^7;

delay(t)
{
int i,j;
for(i=0;i  for(j=0;j<10;j++);


}

display(t)
{
int ge,shi,bai;



   ge=t%10;
   shi=t%100/10;
   bai=t/100;
wei=1;
P0=0xdf;
wei=0;

duan=1;
P0=table[ge];
duan=0;
delay(20);

wei=1;
P0=0xef;
wei=0;

duan=1;
P0=table[shi]+0x80;
duan=0;
delay(20);

  wei=1;
P0=0xf7;
wei=0;

duan=1;
P0=table[bai];
duan=0;
delay(20);


wei=1;
P0=0xff;
wei=0;
delay(50);


}











bitread()
{bit tembit;
int i;
rs=1;
rs=0;

i++;

rs=1;
i++;i++;
  tembit=rs;
i=15;while(i--);

  return(tembit);
 
}

byteread()
{ int i;
unsigned char tembyte,j;
tembyte=0;
  for(i=0;i<8;i++)
  {
  j=bitread();

   tembyte=(j<<7)|(tembyte>>1);

}
return tembyte;
}


bytewrite(char com)
{
  int i,k;
  bit j;
 
  for(i=0;i<8;i++)
  {rs=1;
  j=com&0x01;
  com=com>>1;
    if(!j)
    {
     rs=0;
    k=8;while(k--);
     rs=1;
    k=2;while(k--);
    
    }
    else{
       rs=0;
       k++;k++;
       rs=1;
      k=8;while(k--);
      }
  }
}



reset()
{
rs=1;
rs=0;
delay(5);
rs=1;
delay(1);
}


change()
{
reset();
delay(20);
bytewrite(0xcc);
bytewrite(0x44);
}


temp()
{char a,b;
float tt;
int tem;
  reset();
  delay(20);
  bytewrite(0xcc);
bytewrite(0xbe);
  a=byteread();
 
b=byteread();P1=a;

    tem=b;
tem<<=8;             //two byte  compose a int variable
tem=tem|a;
tt=tem*0.0625;
tem=tt*10+0.5;
return tem;


}

void main()


{
int i;
change();
P0=0xff;
duan=1;
duan=0;
P0=0xff;
wei=1;
wei=0;
while(1){

change();
delay(20);
for(i=0;i<8;i++){

display( temp());

}
}

}

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