1、利用数/模转换器DAC0832分别构造2种波形：正弦波、方波、锯齿波，并通过示波器来观察波形情况。
2、软件编程提示：
方波：实验要求在DOUT端输出方波信号，方波信号的周期由延时时间常数确定。
根据Vout =-〔VREF×（输入数字量的十进制数）〕/256，当数字量的十进制数为256（FFH）时，由于VREF =－5V，Vout = +5V。当数字量的十进制数为0(00H) 时， 由于VREF = － 5V，Vout = 0V。因此，只要将上述数字量写入DAC0832端口地址时，模拟电压就从DOUT 端输出 。
#include<reg51.h> //包含单片机寄存器的头文件
#include<absacc.h> //包含对片外存储器地址进行操作的头文件 //参考文库
sbit CS=P2^7;
sbit WR12=P3^6;
sbit bu_sin=P1^0;
sbit bu_juchi=P1^1;
sbit bu_squa=P1^2;
//正弦波数组参考百度文库
unsigned char code sin[256]={0x80,0x83,0x86,0x89,0x8d,0x90,0x93,0x96,0x99,0x9c,0x9f,
0xa2,0xa5,0xa8,0xab,0xae,0xb1,0xb4,0xb7,0xba,0xbc,0xbf,0xc2,0xc5 ,
0xc7,0xca,0xcc,0xcf,0xd1,0xd4,0xd6,0xd8,0xda,0xdd,0xdf,0xe1,0xe3,
0xe5,0xe7,0xe9,0xea,0xec,0xee,0xef,0xf1,0xf2,0xf4,0xf5 ,0xf6,0xf7,
0xf8,0xf9,0xfa,0xfb,0xfc,0xfd,0xfd,0xfe,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xfe,0xfd ,0xfd,0xfc,0xfb,0xfa,
0xf9,0xf8,0xf7,0xf6,0xf5,0xf4,0xf2,0xf1,0xef,0xee,0xec,0xea,0xe9,
0xe7,0xe5,0xe3,0xe1,0xde,0xdd,0xda ,0xd8,0xd6,0xd4,0xd1,0xcf,0xcc,
0xca,0xc7,0xc5,0xc2,0xbf,0xbc,0xba,0xb7,0xb4,0xb1,0xae,0xab,0xa8,
0xa5,0xa2,0x9f,0x9c,0x99 ,0x96,0x93,0x90,0x8d,0x89,0x86,0x83,0x80,
0x80,0x7c,0x79,0x76,0x72,0x6f,0x6c,0x69,0x66,0x63,0x60,0x5d,0x5a,
0x57,0x55,0x51 ,0x4e,0x4c,0x48,0x45,0x43,0x40,0x3d,0x3a,0x38,0x35,
0x33,0x30,0x2e,0x2b,0x29,0x27,0x25,0x22,0x20,0x1e,0x1c,0x1a,0x18,
0x16 ,0x15,0x13,0x11,0x10,0x0e,0x0d,0x0b,0x0a,0x09,0x08,0x07,0x06,
0x05,0x04,0x03,0x02,0x02,0x01,0x00,0x00,0x00,0x00,0x00,0x00 ,0x00,
0x00,0x00,0x00,0x00,0x00,0x01,0x02 ,0x02,0x03,0x04,0x05,0x06,0x07,
0x08,0x09,0x0a,0x0b,0x0d,0x0e,0x10,0x11,0x13,0x15 ,0x16,0x18,0x1a,
0x1c,0x1e,0x20,0x22,0x25,0x27,0x29,0x2b,0x2e,0x30,0x33,0x35,0x38,
0x3a,0x3d,0x40,0x43,0x45,0x48,0x4c,0x4e ,0x51,0x55,0x57,0x5a,0x5d,
0x60,0x63,0x66 ,0x69,0x6c,0x6f,0x72,0x76,0x79,0x7c,0x80 };
void main(void)
{
unsigned char i,j;
CS=0; //输出低电平以选中DAC0832
WR12=0; //输出低电平以选中DAC0832
P1=0xff;
while(1)
{
if(bu_sin==0)
{
bu_sin=0;bu_juchi=1; bu_squa=1;
for(i=0;i<255;i++)
XBYTE[0x7fff]=sin[i]; }if(bu_juchi==0)
{
bu_sin=1;bu_juchi=0; bu_squa=1;
for(i=0;i<255;i++)
XBYTE[0x7fff]=i; }//将数据i送入片外地址07FFFH ，实际上就是通过P0口将数据送入DAC0832 ，直接赋值给P0端口会无输出
if(bu_squa==0)
{
bu_sin=1;bu_juchi=1; bu_squa=0;
XBYTE[0x7fff]=0xff;
for(j=0;j<150;j++);
XBYTE[0x7fff]=0x00;
for(j=0;j<148;j++);
}
}
}