我自己做的最小系統板 自己寫的代碼 所以有得地方不會和其他電路板兼容

但是ad0809是兼容的，你看一下

#include <reg52.h>
#include <intrins.h>

#define uchar unsigned char
#define uint unsigned int

uchar table[16] = {0x81,0xb7,0xc2,0x92,0xb4,0x98,0x88,0xb3,0x80,0x90,0xa0,0x8c,0xce,0x86,0xc8,0xe8};

sbit clk = p3^2; // 時鐘輸入端,最大為500khz
sbit oe = p3^3; // 輸出允許端 等于1時有效
sbit eoc = p3^4; // 轉化完成標志 高電平表示轉化結束.
sbit st = p3^5; // 地址鎖存信號.

// 控制每位數碼管顯示
sbit l0 = p0^0;
sbit l1 = p0^1;
sbit l2 = p0^2;
sbit l3 = p0^3;
sbit l4 = p0^4;
sbit l5 = p0^5;
sbit k1 = p0^6;

uchar a;
bit flag; // 輸出方式的標志位

void delay(uint m)
{
uint i,j;

for (i=0; i<m; i++)
for (j=0; j<150; j++);
}

//初始化串口,設置成工作方式0
void initport(void)
{
//; 不用設置,初始即為工作方式0
}

// 發送一個數據
void sendbyte(uchar dat)
{
sbuf = dat;
while (!ti);
ti = 0;
}

void initled(void)
{
l0 = 0;
l1 = 0;
l2 = 0;
l3 = 0;
l4 = 0;
l5 = 0;
}

void displayled(void)
{
uint value;

//unsigned long value;
//value = (a*500)/256;

if (a < 132)
value = (a*500)/256;
else
{
value = (a*500)/256;
value = value + 256;
}

if (!flag)
{
l0 = 0; l1 = 0; l2 = 1;
sendbyte(table[value/100]&0x7f);
delay(5);

l0 = 0; l1 = 1; l2 = 0;
sendbyte(table[(value/10)%10]);
delay(5);

l0 = 1; l1 = 0; l2 = 0;
sendbyte(table[value%10]);
delay(5);
}
else
{
l0 = 0; l1 = 0; l2 = 1;
sendbyte(table[a/100]);
delay(5);

l0 = 0; l1 = 1; l2 = 0;
sendbyte(table[(a/10)%10]);
delay(5);

l0 = 1; l1 = 0; l2 = 0;
sendbyte(table[a%10]);
delay(5);
}
}

void scankey(void)
{
if (k1 == 0)
{
flag = !flag;
while (!k1);
k1 = 1;
}
}

// 初始化ad0809
void initad0809(void)
{
st = 0;
oe = 0;
}

// 讀ad0809中的數據
uchar readad0809(void)
{
//eoc = 0;
oe = 0;
st = 0;
//_nop_();
st = 1; // 上升沿ad0809內部的寄存器清零
//_nop_();
st = 0; // 產生一個至少100ns的脈沖,在轉換期間st為低

while (!eoc)
{
displayled();
scankey();
}
oe = 1;
return p1;
}

main()
{
//uint i;
tmod = 0x01;
ea = 1;
tr0 = 1;
et0 = 1;
flag = 0;
k1 = 1;

initled();
initport();
initad0809();

/*for (i=0; i<16; i++)
{
sendbyte(table[i]);
delay(100);
}*/

while (1)
{
a = readad0809();
}
}

void timer0(void) interrupt 1 using 1
{
th0 = 0xff;
tl0 = 0x80;

clk = !clk;
}