1．  實驗任務 

用AT89S51單片機的P0.0/AD0－P0.7/AD7端口接數碼管的a－h端，8位數碼管的S1－S8通過74LS138譯碼器的Y0－Y7來控制選通每個數碼管的位選端。AT89S51單片機的P1.0－P1.2控制74LS138的A，B，C端子。在8位數碼管上從右向左循環(huán)顯示“12345678”。能夠比較平滑地看到拉幕的效果。

2． 電路原理圖

3． 系統(tǒng)板上硬件連線

（1．       把“單片機系統(tǒng)”區(qū)域中的P0.0/AD0－P0.7/AD7用8芯排線連接到“動態(tài)數碼顯示”區(qū)域中的a－h端口上；

（2．       把“三八譯碼模塊”區(qū)域中的Y0－Y7用8芯排線連接到“動態(tài)數碼顯示”區(qū)域中的S1－S8端口上；

（3．       把“單片機系統(tǒng)”區(qū)域中的P1.0－P1.2端口用3根導線連接到“三八譯碼模塊”區(qū)域中的A、B、C“端口上；

4． 程序設計方法

動態(tài)數碼顯示技術：如何進行動態(tài)掃描，由于一次只能讓一個數碼管顯示，因此，要顯示8位的數據，必須經過讓數碼管一個一個輪流顯示才可以，同時每個數碼管顯示的時間大約在1ms到4ms之間，所以為了保證正確顯示，我必須每隔1ms，就得刷新一個數碼管。而這刷新時間我們采用單片機的定時/計數器T0來控制，每定時1ms對數碼管刷新一次，T0采用方式2。在進行數碼顯示的時候，要對顯示單元開辟8個顯示緩沖區(qū)，每個顯示緩沖區(qū)裝有顯示的不同數據即可。

5． 程序框圖

 主程序框圖

中斷服務程序

6． 匯編源程序

DISPBUF         EQU 30H

DISPCNT         EQU 38H

DISPBIT         EQU 39H

T1CNTA          EQU 3AH

T1CNTB          EQU 3BH

CNT             EQU 3CH

                ORG 00H

              LJMP START

                ORG 0BH

                LJMP INT_T0

START:          MOV DISPCNT,#8

                MOV A,#10

                MOV R1,#DISPBUF

LP:             MOV @R1,A

                INC R1

                DJNZ DISPCNT,LP

                MOV DISPBIT,#00H

                MOV T1CNTA,#00H

                MOV T1CNTB,#00H

                MOV CNT,#00H

                MOV TMOD,#01H

                MOV TH0,#(65536-1000) / 256

                MOV TL0,#(65536-1000) MOD 256

                SETB TR0

                SETB ET0

                SETB EA

                SJMP $

INT_T0:

                MOV TH0,#(65536-1000) / 256

                MOV TL0,#(65536-1000) MOD 256

                MOV A,DISPBIT

                ADD A,#DISPBUF

                MOV R0,A

                MOV A,@R0

                MOV DPTR,#TABLE

                MOVC A,@A+DPTR

                MOV P0,A

                MOV A,P1

                ANL A,#0F8H

                ADD A,DISPBIT

                MOV P1,A                

                INC DISPBIT

                MOV A,DISPBIT

                CJNE A,#08H,NEXT

                MOV DISPBIT,#00H

NEXT:           INC T1CNTA

                MOV A,T1CNTA

                CJNE A,#50,LL1

                MOV T1CNTA,#00H

                INC T1CNTB

                MOV A,T1CNTB

                CJNE A,#8,LL1

                MOV T1CNTB,#00H

                INC CNT

                MOV A,CNT

                CJNE A,#9,LLX

                MOV CNT,#00H

                MOV A,CNT

LLX:            CJNE A,#01H,NEX1

                MOV 30H,#8

LL1:            LJMP DONE

NEX1:           CJNE A,#02H,NEX2

                MOV 31H,#8

                MOV 30H,#8

                LJMP DONE

NEX2:           CJNE A,#03H,NEX3

                MOV 32H,#8

                MOV 31H,#8

                MOV 30H,#8

                LJMP DONE

NEX3:           CJNE A,#04H,NEX4

                MOV 33H,#8

                MOV 32H,#8

                MOV 31H,#8

                MOV 30H,#8

                LJMP DONE

NEX4:           CJNE A,#05H,NEX5

                MOV 34H,#8

                MOV 33H,#8

                MOV 32H,#8

                MOV 31H,#8

                MOV 30H,#8

                LJMP DONE

NEX5:           CJNE A,#06H,NEX6

                MOV 35H,#8

                MOV 34H,#8

                MOV 33H,#8

                MOV 32H,#8

                MOV 31H,#8

                MOV 30H,#8

                LJMP DONE

NEX6:           CJNE A,#07H,NEX7

                MOV 36H,#8

                MOV 35H,#8

                MOV 34H,#8

                MOV 33H,#8

                MOV 32H,#8

                MOV 31H,#8

                MOV 30H,#8

                LJMP DONE

NEX7:           CJNE A,#08H,NEX8

                MOV 37H,#8

                MOV 36H,#8

                MOV 35H,#8

                MOV 34H,#8

                MOV 33H,#8

                MOV 32H,#8

                MOV 31H,#8

                MOV 30H,#8

                LJMP DONE

NEX8:           CJNE A,#00H,DONE

                MOV 37H,#10

                MOV 36H,#10

                MOV 35H,#10

                MOV 34H,#10

                MOV 33H,#10

                MOV 32H,#10

                MOV 31H,#10

                MOV 30H,#10

LL:             LJMP DONE

DONE:           RETI

TABLE:          DB 3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH,00H

                END

7． C語言源程序

#include <AT89X51.H>

unsigned char code dispcode[]={0x3f,0x06,0x5b,0x4f,

                               0x66,0x6d,0x7d,0x07,

                               0x7f,0x6f,0x77,0x7c,

                               0x39,0x5e,0x79,0x71,0x00};

unsigned char dispbitcode[]={0xf8,0xf9,0xfa,0xfb,

                             0xfc,0xfd,0xfe,0xff};

unsigned char dispbuf[8]={16,16,16,16,16,16,16,16};

unsigned char dispbitcnt;

unsigned int t02scnt;

unsigned char t5mscnt;

unsigned char u;

unsigned char i;

void main(void)

{

  TMOD=0x02;

  TH0=0x06;

  TL0=0x06;

  TR0=1;

  ET0=1;

  EA=1;

  while(1);

}

void t0(void) interrupt 1 using 0

{

  t5mscnt++;

  if(t5mscnt==4)

    {

      t5mscnt=0;

      P0=dispcode[dispbuf[dispbitcnt]];

      P1=dispbitcode[dispbitcnt];

      dispbitcnt++;

      if(dispbitcnt==8)

        {

          dispbitcnt=0;

        }

    }

  t02scnt++;

  if(t02scnt==1600)

    {

      t02scnt=0;

      u++;

      if(u==9)

        {

          u=0;

        }

      for(i=0;i<8;i++)

        {

          dispbuf[i]=16;

        }

      for(i=0;i<u;i++)

        {

          dispbuf[i]=8;

        }

    }

}