关于单片机DAC0832输出一路三角形方波程序中的0xfeff是什么意思，如图，给的初始地址是这个

这里是采用访问外设的方式来与DAC0832进行数据交换；

这种方式用到 P0、P2口，P2口输出地址高8位，P0口输出地址低8位以及数据；

因此，从时序看，搜悔当访问DAC0832时，先输出地址，即 0xfeff，其中 P2=0xfe，P0=0xff，

然后 P0输出波形数据（时序中 P2=0xfe 保持不变）；

而世衫对于DAC0832，其片选信号Cs 连接到P2.0，所以，P2.0=Cs=0 时，使能0832，在WR信号的配合下，接收P0输世返正出波形数据；

#include<reg51.h>

/*位定义*/

sbit wr=P3^6

sbit rd=P3^2

sbit k0=P1^0

sbit k1=P1^1

sbit k2=P1^2

sbit k3=P1^3

sbit k4=P1^4

unsigned char flag//当拆斗flag为0、1、2、3、4时分别产生正弦碰御桥笑猛波、方波、三角波、梯形波、锯齿波

unsigned char const code sin_code[256]={

0x80,0x83,0x86,0x89,0x8c,0x8f,0x92,0x95,0x98,0x9c,0x9f,0xa2,

0xa5,0xa8,0xab,0xae,0xb0,0xb3,0xb6,0xb9,0xbc,0xbf,0xc1,0xc4,

0xc7,0xc9,0xcc,0xce,0xd1,0xd3,0xd5,0xd8,0xda,0xdc,0xde,0xe0,

0xe2,0xe4,0xe6,0xe8,0xea,0xec,0xed,0xef,0xf0,0xf2,0xf3,0xf4,

0xf6,0xf7,0xf8,0xf9,0xfa,0xfb,0xfc,0xfc,0xfd,0xfe,0xfe,0xff,

0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xfe,0xfe,

0xfd,0xfc,0xfc,0xfb,0xfa,0xf9,0xf8,0xf7,0xf6,0xf5,0xf3,0xf2,

0xf0,0xef,0xed,0xec,0xea,0xe8,0xe6,0xe4,0xe3,0xe1,0xde,0xdc,

0xda,0xd8,0xd6,0xd3,0xd1,0xce,0xcc,0xc9,0xc7,0xc4,0xc1,0xbf,

0xbc,0xb9,0xb6,0xb4,0xb1,0xae,0xab,0xa8,0xa5,0xa2,0x9f,0x9c,

0x99,0x96,0x92,0x8f,0x8c,0x89,0x86,0x83,0x80,0x7d,0x79,0x76,

0x73,0x70,0x6d,0x6a,0x67,0x64,0x61,0x5e,0x5b,0x58,0x55,0x52,

0x4f,0x4c,0x49,0x46,0x43,0x41,0x3e,0x3b,0x39,0x36,0x33,0x31,

0x2e,0x2c,0x2a,0x27,0x25,0x23,0x21,0x1f,0x1d,0x1b,0x19,0x17,

0x15,0x14,0x12,0x10,0xf,0xd,0xc,0xb,0x9,0x8,0x7,0x6,0x5,0x4,

0x3,0x3,0x2,0x1,0x1,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,

0x0,0x1,0x1,0x2,0x3,0x3,0x4,0x5,0x6,0x7,0x8,0x9,0xa,0xc,0xd,

0xe,0x10,0x12,0x13,0x15,0x17,0x18,0x1a,0x1c,0x1e,0x20,0x23,

0x25,0x27,0x29,0x2c,0x2e,0x30,0x33,0x35,0x38,0x3b,0x3d,0x40,

0x43,0x46,0x48,0x4b,0x4e,0x51,0x54,0x57,0x5a,0x5d,0x60,0x63,

0x66,0x69,0x6c,0x6f,0x73,0x76,0x79,0x7c

}//用于生成正弦

unsigned char kscan() //键盘扫描函数

{

unsigned char kscannum,t

P1=0xff

t=P1

if(~(t&0xff))

{

if(k0==0)

{

kscannum=1

}

else if(k1==0)

{

kscannum=2

}

else if(k2==0)

{

kscannum=3

}

else if(k3==0)

{

kscannum=4

}

else if(k4==0)

{

kscannum=5

}

else

{

kscannum=0

}

return kscannum

}

}

void init_DA0832()//DA0832初始化

{

rd=0

wr=0

}

void fangbo()//产生方波函数

{

EA=1 //开总中断

ET0=1//计时器T0工作

TMOD=1

TR0=1//开启T0

TH0=0xff //装入初值

TL0=0x83

}

void sin()//产生正弦波函数

{

unsigned int i

do{

P2=sin_code[i]

i=i+1

}while(i<256)

}

void juchibo()//产生锯齿波函数

{

P2=0x00

do{

P2=P2+1

}while(P2<=0xff)

}

void sanjiaobo()//产生三角波函数

{

P2=0x00

do{

P2=P2+1

}while(P2<0xff)

P2=0xff

do{

P2=P2-1

}while(P2>0x00)

P2=0x00

}

void tixingbo()//产生梯形波函数

{

unsigned char i

P2=0x00

do{

P2=P2+1

}while(P2<0xff)

P2=0xff

for(i=255i>0i--)

{

P2=0xff

}

do{

P2=P2-1

}while(P2>0x00)

P2=0x00

}

void timer0(void) interrupt 1//中断函数

{

P2=~P2 //取反

TH0=0xff //重新装入初值

TL0=0x83

TR0=1

}

/*主函数*/

void main()

{

init_DA0832()//初始化

do

{

flag=kscan()

}while(!flag)//等待按键按下

while(1)

{

switch(flag)

{

case 1:

do{

flag=kscan()

sin()

}while(flag==1)//产生正弦波

break

case 2:

fangbo()

do{

flag=kscan()

}while(flag==2)//产生方波

TR0=0

break

case 3:

do{

flag=kscan()

sanjiaobo()

}while(flag==3)//产生三角波

break

case 4:

do{

flag=kscan()

tixingbo()

}while(flag==4)//产生梯形波

break

case 5:

do{

flag=kscan()

juchibo()

}while(flag==5)//产生锯齿波

break

default:

flag=kscan()

break

}

}

}

#include<reg52.h>

#define  uchar unsigned char

#define  uint  unsigned int

#define DAdata  P0//DA数据端口

可以产生弦波、方波、三角波、三角波、梯形波及其他任意波形,波形的频率（最大790HZ）和幅度在一定范围内可任意改变。波形和频率的改变通过软件控制,幅度的改变通过硬件实现。

正弦波是频率成分最为单一的一种信号，因这种信号的波形是数学上的正弦曲线而得名。任何复杂信号——例如音乐毕乱胡信号，都可以看成由许许多多频率不同、大小不等的正弦波复合手拦而成。陪尘振荡电路是电子技术的一个重要组成部分，正弦波振荡器广泛应用于广播、电视、通讯，工业自动控制，测量表计， 以及高频加热，超声波探伤等等方面。

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