1、定時顯示

  開辟一顯示緩沖區，顯示中斷程序定時讀取緩沖區顯示各燈位，每燈位顯示2.5ms，顯示4只燈需要10ms,也就是顯示的刷新頻率是100Hz，亮度為25%。這樣既保證亮度又不閃爍，同時CPU還有足夠時間做其他事情。

2、鍵盤中斷掃描

  利用鍵盤中斷掃描程序，讀出按鍵的鍵碼，存入鍵盤緩沖區，供主程序讀區。

3、計算器的主程序讀取鍵盤緩沖區的鍵碼，驅動計算器的運行，計算器的運行過程要清晰明了；

4、計算中需要十進制與十六進制（或二進制）轉化。

#define LED_seg      XBYTE[0x6000]     //段碼地址

#define LED_light    XBYTE[0x8000]      //燈位地址

#include "reg51.h"

#include "absacc.h"

unsigned char read_key(unsigned char);

unsigned char display(unsigned char,unsigned char);

void delay(unsigned int);

unsigned char light[4]={0xfe,0xfd,0xfb,0xf7};   //掃描值 燈位碼

unsigned char seg[16]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,

0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71}; //段碼

unsigned char disp_buffer[5]={1,0,0,0,0};            //當前燈位、 顯示區

unsigned char key_buffer[2]={0,0xff};           //緩沖區滿標志、鍵碼

void main()

{

 Unsigned char temp[5];

 unsigned char i;

 unsigned char operator=0;

 unsigned int tempa,tempb;

 bit first=1;

 TMOD=0x01;       //置T0為方式1

 TL0=0x0;          //延時2.5mS的定時器初始值

 TH0=0xf7;          //賦初值

 PT0=1;             //定時中斷0優先設置

TR0=1;           //啟動定時

 ET0=1;           //允許定時

 IT1=0;        //電平觸發低電平有效

 EX1=1;       //允許外中斷

 PX1=1;       // 外部中斷1優先級設定

 EA=1;        //中斷總允許

 while(1)

      {

       P1=0xf0;                           //掃描

       if (key_buffer[0])

                {

                    switch(key_buffer[1])              //緩沖區滿

                      {

                          case 0:

                          case 1:

                          case 2:

                          case 3:

                          case 4:

                          case 5:

                          case 6:

                          case 7:

                          case 8:

                          case 9: if (first)  for(i=1;i<=4;i++)   //保存數據，等待另一個數據輸入

                                             {

                                                                temp[i]=disp_buffer[i];

                                                                disp_buffer[i]=0;                                           

                                                                }

                   first=0;

                                      for(i=1;i<=3;i++)  disp_buffer[i]=disp_buffer[i+1];

                                      disp_buffer[4]=key_buffer[1];

                                break;

                          case 10:

                          case 11:

                          case 12:

                          case 13:

                          case 14: first=1;

tempa=1000*disp_buffer[1]+100*disp_buffer[2]+10*disp_buffer[3]+disp_buffer[4];

                     tempb=1000*temp[1]+100*temp[2]+10*temp[3]+temp[4];

                     switch(operator)

                          {

                           case 10:tempa+=tempb;

                                   break;

                           case 11:tempa=tempb-tempa;

                                   break;

                           case 12:tempa*=tempb;

                                   break;

                           case 13:tempa=tempb/tempa;

                           }

                     tempa%=10000;

                     disp_buffer[1]=tempa/1000;

                     tempa%=1000;

                     disp_buffer[2]=tempa/100;

                     tempa%=100;

                     disp_buffer[3]=tempa/10;

                     disp_buffer[4]=tempa%10;

                                  operator=key_buffer[1];

                                        break;

                          case 15: for(i=1;i<=4;i++)  disp_buffer[i]=temp[i]=0;

                           first=1;

                                          operator=0;

                          }

                    key_buffer[0]=0;                     //緩沖區空

                    }          

       }

 }

void disp_LED() interrupt 1

{

 TL0=0x0;         //延時2.5mS的定時器初始值

 TH0=0xf7;

 if (disp_buffer[0]==5)  disp_buffer[0]=1;

 display(disp_buffer[disp_buffer[0]],disp_buffer[0]);

 disp_buffer[0]++;

 }

void get_keypad_code() interrupt 2

{

 unsigned char i,key;

 EA=0;

 for (i=0;i<=3;i++)

      {

       key=read_key(light[i]);    //讀鍵碼

       if (key!=0xff) delay(10);                //延時5-10ms,去抖動

       if (read_key(light[i])!=key) key=0xff;    //讀鍵碼比較

       if (key!=0xff)

                {

                    key_buffer[0]=1;                //緩沖區滿

                    key_buffer[1]=key;      //鍵碼

                    }                     

       }

 EA=1;

 }

unsigned char read_key(unsigned char scan)

{

 P1=scan;       //掃描

 switch(P1)     //返回掃描碼->鍵碼

    {

     case 0x77:return(0x7);

     case 0xb7:return(0x8);

     case 0xd7:return(0x9);

     case 0xe7:return(0xd);

     case 0x7b:return(0x4);

     case 0xbb:return(0x5);

     case 0xdb:return(0x6);

     case 0xeb:return(0xc);

     case 0x7d:return(0x1);

     case 0xbd:return(0x2);

     case 0xdd:return(0x3);

     case 0xed:return(0xb);

     case 0x7e:return(0xf);

     case 0xbe:return(0x0);

     case 0xde:return(0xe);

     case 0xee:return(0xa);

     default:  return(0xff);

     }

 }

unsigned char display(unsigned char disp_key,unsigned char n) //disp_key 顯示字符,n 燈位

{

 if ((n<=4)&&(n>=1)) LED_light=light[n-1];

 else  LED_light=0xff;

 if ((disp_key>=0)&&(disp_key<=16)) LED_seg=seg[disp_key];

 else  LED_seg=0x00;

 return light[n-1];

 }

void delay(unsigned int k)     //延時k*1ms

{

unsigned int i,j;

 for (j=0;j<=k;j++)

    for(i=0;i<=1085;i++);

}

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