1．实验任务
（1)．开机时，显示12：00：00的时间开始计时；
（2)．P0.0/AD0控制“秒”的调整，每按一次加1秒；
（3)．P0.1/AD1控制“分”的调整，每按一次加1分；
（4)．P0.2/AD2控制“时”的调整，每按一次加1个小时；
2．电路原理图

　　　　　　　　　　　　　　　　　　　　　　　　　　　图4.20.1
3．系统板上硬件连线
（1)．把“单片机系统”区域中的P1.0－P1.7端口用8芯排线连接到“动态数码显示”区域中的A－H端口上；
（2)．把“单片机系统：区域中的P3.0－P3.7端口用8芯排线连接到“动态数码显示”区域中的S1－S8端口上；
（3)．把“单片机系统”区域中的P0.0/AD0、P0.1/AD1、P0.2/AD2端口分别用导线连接到“独立式键盘”区域中的SP3、SP2、SP1端口上；
4．相关基本知识
（1)．动态数码显示的方法
（2)．独立式按键识别过程
（3)．“时”，“分”，“秒”数据送出显示处理方法
5．程序框图
6．汇编源程序
SECOND          EQU 30H
MINITE                     EQU 31H
HOUR            EQU 32H
HOURK          BIT P0.0
MINITEK         BIT P0.1
SECONDK        BIT P0.2
DISPBUF            EQU 40H
DISPBIT            EQU 48H
T2SCNTA            EQU 49H
T2SCNTB            EQU 4AH
TEMP               EQU 4BH
 
        ORG 00H
        LJMP START
        ORG 0BH
        LJMP INT_T0
START:  MOV SECOND,#00H
        MOV MINITE,#00H
        MOV HOUR,#12
        MOV DISPBIT,#00H
        MOV T2SCNTA,#00H
        MOV T2SCNTB,#00H
        MOV TEMP,#0FEH
        LCALL DISP
        MOV TMOD,#01H
        MOV TH0,#(65536-2000) / 256
        MOV TL0,#(65536-2000) MOD 256
        SETB TR0
        SETB ET0
        SETB EA
WT:     JB SECONDK,NK1
        LCALL DELY10MS
        JB SECONDK,NK1
        INC SECOND
        MOV A,SECOND
        CJNE A,#60,NS60
        MOV SECOND,#00H
NS60:   LCALL DISP
        JNB SECONDK,$
NK1:    JB MINITEK,NK2
        LCALL DELY10MS
        JB MINITEK,NK2
        INC MINITE
        MOV A,MINITE
        CJNE A,#60,NM60
        MOV MINITE,#00H
NM60:   LCALL DISP
        JNB MINITEK,$
NK2:    JB HOURK,NK3
        LCALL DELY10MS
        JB HOURK,NK3
        INC HOUR
        MOV A,HOUR
        CJNE A,#24,NH24
        MOV HOUR,#00H
NH24:   LCALL DISP
        JNB HOURK,$
NK3:    LJMP WT
DELY10MS:
        MOV R6,#10
D1:     MOV R7,#248
        DJNZ R7,$
        DJNZ R6,D1
        RET
DISP:  
        MOV A,#DISPBUF
        ADD A,#8
        DEC A
        MOV R1,A
        MOV A,HOUR
        MOV B,#10
        DIV AB
        MOV @R1,A
        DEC R1
        MOV A,B
        MOV @R1,A
        DEC R1
        MOV A,#10
       MOV @R1,A
        DEC R1
        MOV A,MINITE
        MOV B,#10
        DIV AB
        MOV @R1,A
        DEC R1
        MOV A,B
        MOV @R1,A
        DEC R1
        MOV A,#10
       MOV @R1,A
        DEC R1
        MOV A,SECOND
        MOV B,#10
        DIV AB
        MOV @R1,A
        DEC R1
        MOV A,B
        MOV @R1,A
        DEC R1
        RET
INT_T0:
        MOV TH0,#(65536-2000) / 256
        MOV TL0,#(65536-2000) MOD 256
        MOV A,#DISPBUF
        ADD A,DISPBIT
        MOV R0,A
        MOV A,@R0
        MOV DPTR,#TABLE
        MOVC A,@A+DPTR
        MOV P1,A
        MOV A,DISPBIT
        MOV DPTR,#TAB
        MOVC A,@A+DPTR
        MOV P3,A
        INC DISPBIT
        MOV A,DISPBIT
        CJNE A,#08H,KNA
        MOV DISPBIT,#00H
KNA:    INC T2SCNTA
        MOV A,T2SCNTA
        CJNE A,#100,DONE
        MOV T2SCNTA,#00H
        INC T2SCNTB
        MOV A,T2SCNTB
        CJNE A,#05H,DONE
        MOV T2SCNTB,#00H
        INC SECOND
        MOV A,SECOND
        CJNE A,#60,NEXT
        MOV SECOND,#00H
        INC MINITE
        MOV A,MINITE
        CJNE A,#60,NEXT
        MOV MINITE,#00H
        INC HOUR
        MOV A,HOUR
        CJNE A,#24,NEXT
        MOV HOUR,#00H
NEXT:   LCALL DISP
DONE:   RETI
TABLE:  DB 3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH,40H
TAB:    DB 0FEH,0FDH,0FBH,0F7H,0EFH,0DFH,0BFH,07FH
        END
7．C语言源程序
#include
unsigned char code dispcode[]={0x3f,0x06,0x5b,0x4f,
                               0x66,0x6d,0x7d,0x07,
                               0x7f,0x6f,0x77,0x7c,
                               0x39,0x5e,0x79,0x71,0x00};
unsigned char dispbitcode[]={0xfe,0xfd,0xfb,0xf7,
                             0xef,0xdf,0xbf,0x7f};
unsigned char dispbuf[8]={0,0,16,0,0,16,0,0};
unsigned char dispbitcnt;
unsigned char second;
unsigned char minite;
unsigned char hour;
unsigned int tcnt;
unsigned char mstcnt;
unsigned char i,j;
void main(void)
{
  TMOD=0x02;
  TH0=0x06;
  TL0=0x06;
  TR0=1;
  ET0=1;
  EA=1;
  while(1)
    {
      if(P0_0==0)
        {
          for(i=5;i>0;i--)
          for(j=248;j>0;j--);
          if(P0_0==0)
            {
              second++;
              if(second==60)
                {
                  second=0;
                }
              dispbuf[0]=second;
              dispbuf[1]=second/10;
              while(P0_0==0);
            }
        }
      if(P0_1==0)
        {
          for(i=5;i>0;i--)
          for(j=248;j>0;j--);
          if(P0_1==0)
            {
              minite++;
              if(minite==60)
                {
                  minite=0;
                }
              dispbuf[3]=minite;
              dispbuf[4]=minite/10;
              while(P0_1==0);
            }
        }
      if(P0_2==0)
        {
          for(i=5;i>0;i--)
          for(j=248;j>0;j--);
          if(P0_2==0)
            {
              hour++;
              if(hour==24)
                {
                  hour=0;
                }
              dispbuf[6]=hour;
              dispbuf[7]=hour/10;
              while(P0_2==0);
            }
        }
    }
}
void t0(void) interrupt 1 using 0
{
  mstcnt++;
  if(mstcnt==8)
    {
      mstcnt=0;
      P1=dispcode[dispbuf[dispbitcnt]];
      P3=dispbitcode[dispbitcnt];
      dispbitcnt++;
      if(dispbitcnt==8)
        {
          dispbitcnt=0;
        }
    }
  tcnt++;
  if(tcnt==4000)
    {
      tcnt=0;
      second++;
      if(second==60)
        {
          second=0;
          minite++;
          if(minite==60)
            {
              minite=0;
              hour++;
              if(hour==24)
                {
                  hour=0;
                }
            }
        }
      dispbuf[0]=second;
      dispbuf[1]=second/10;
      dispbuf[3]=minite;
      dispbuf[4]=minite/10;
      dispbuf[6]=hour;
      dispbuf[7]=hour/10;
    }
}