unsigned char Data_Buffer[4]={1,2,3,4}; uchar
5e,0x79,0x71,0x76};
sbit P24=P2^4; sbit P25=P2^5; sbit P26=P2^6; sbit P27=P2^7;
bit flag=0;
bit DACconversion(unsigned char sla,unsigned char c, unsigned char Val); bit ISendByte(unsigned char sla,unsigned char c); unsigned char IRcvByte(unsigned char sla); /******************************/ void main(void) //主程序 {
unsigned int v;
unsigned char AD_CHANNEL=0; unsigned int D=255;
TMOD=0x11; TH0=THCO; TL0=TLCO; TR0=1; ET0=1; EA=1; while(1) {
if(flag==1) {flag=0;
code
Duan[17]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x
//四个数码管的位码口定义
//设置定时器0工作模式,16位计数模式
//启动定时器
//使能定时器中断
//开总中断
DACconversion(PCF8591,0x40, D); //DAC 数模转换 D=255-D;//输出方波
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}
Data_Buffer[1]=D/100; Data_Buffer[2]=D/10; } }
void timer0() interrupt 1 //定时器中断服务子程序 {
static unsigned int count=0;//软计时变量定义 static unsigned char Bit=0;
TH0=THCO; TL0=TLCO; Bit++;
//先关位码
if(Bit>=4)Bit=0; P2|=0xf0;
P0=Duan[Data_Buffer[Bit]]; //开段码 if(Bit==0)P0|=0x80; switch(Bit) {
case 0: P24=0;break; case 1: P25=0;break; case 2: P26=0;break; case 3: P27=0;break; }
count++;
if(count>=250) {
count=0;
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Data_Buffer[3]=D; }
//静态变量，退出程序后，值保留
//送位码
//半S时间到
flag=1; } }
六、思考题
利用单片机控制PDF8591 DA转换器输出三角波，用示波器观察PCF8591输出的方波。
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