51单片机驱动PCF8591AD转换

51单片机驱动PCF8591AD/DA转换，功能：仅进行AD转换， 数码管显示模拟量，显示范围0.0~5.0，使用了
 定时器1进行定时和I2C总线通信。
 #include<reg52.h> 
 #define uchar unsigned char
 sbit sda=P2^0;
 sbit scl=P2^1;    
 sbit dula=P2^6;
 sbit wela=P2^7;
 sbit rst=P2^4;
 uchar c;
 uchar a[2];
 bit ADflag;
 uchar code table[]=
{
0x3f,0x06,0x5b,0x4f,
0x66,0x6d,0x7d,0x07,
0x7f,0x6f,0x77,0x7c,
0x39,0x5e,0x79,0x71,
0x80,//最后为小数点
};
void init();
void start();
void stop();
void response();
uchar read_byte();
void write_byte(uchar data1);
uchar ADC(uchar ch);
void display();
void delay_100(int z)  ;
void main()

 {
  uchar tem;
rst=0;
init();
while(1)
{
if(ADflag)//ADflag由定时器1控制
{
ADflag=0;
tem=ADC(2);
   a[0]=tem/50;
a[1]=(tem%50)/10;
display();
}
}  
 }
 void init()
 {
  TMOD=0x10;
TH1=(65535-500)/256;
TL1=(65535-500)%256;
EA=1;
TR1=1;
ET1=1;
 }
 void timer1() interrupt 3
 {
  TH1=(65535-500)/256;
TL1=(65535-500)%256;
c++;