原创 11．00－59秒计时器（利用软件延时）

1．  实验任务<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

　　如下图所示，在AT89S51单片机的P0和P2端口分别接有两个共阴数码管，P0口驱动显示秒时间的十位，而P2口驱动显示秒时间的个位。

2．  实现程序

1．  汇编源程序

Second                 EQU 30H

                            ORG 0

START:               MOV Second,#00H

NEXT:                MOV A,Second

                           MOV B,#10

                            DIV AB

                            MOV DPTR,#TABLE

                           MOVC A,@A+DPTR

                            MOV P0,A

                            MOV A,B

                           MOVC A,@A+DPTR

                            MOV P2,A

                            LCALL DELY1S

                           INC Second

                            MOV A,Second

                            CJNE A,#60,NEXT

                           LJMP START

DELY1S:             MOV R5,#100

D2:                      MOV R6,#20

D1:                     MOV R7,#248

                            DJNZ R7,$

                            DJNZ R6,D1

                           DJNZ R5,D2

                            RET

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

                            END

2．  C语言源程序

#include <AT89X51.H>

unsigned char code table[]={0x3f,0x06,0x5b,0x4f,0x66,

                            0x6d,0x7d,0x07,0x7f,0x6f};

unsigned char Second;

void delay1s(void)

{

  unsigned char i,j,k;

  for(k=100;k>0;k--)

  for(i=20;i>0;i--)

  for(j=248;j>0;j--);

}

void main(void)

{

  Second=0;

  P0=table[Second/10];

  P2=table[Second%10];

  while(1)

    {

      delay1s();

      Second++;

      if(Second==60)

        {

          Second=0;

        }

      P0=table[Second/10];

      P2=table[Second%10];

    }

}

4、总结

     软件延时1秒钟并试用数码管显示