原创 6．报警产生器

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

用P1.0输出1KHz和500Hz的音频信号驱动扬声器，作报警信号，要求1KHz信号响100ms，500Hz信号响200ms,交替进行，P1.7接一开关进行控制，当开关接低电平响报警信号，当开关断开告警信号停止，编出程序。

2． 电路原理图

3、实现程序

1． 汇编源程序

FLAG                           BIT 00H

                                      ORG 00H

START:                        JB P1.7,START

                                      JNB FLAG,NEXT

                                      MOV R2,#200

DV:                               CPL P1.0

                                      LCALL DELY500

                                      LCALL DELY500

                                      DJNZ R2,DV

                                      CPL FLAG

NEXT:                         MOV R2,#200

DV1:                   CPL P1.0

                                      LCALL DELY500

                                      DJNZ R2,DV1

                                      CPL FLAG

                                      SJMP START

DELY500:           MOV R7,#250

<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />LOOP:                         NOP

                                      DJNZ R7,LOOP

                                      RET

                                      END

2． C语言源程序

#include <AT89X51.H>

unsigned char count;

void dely500(void)
{
  unsigned char i;
  for(i=250;i>0;i--);
}

void main(void)
{
  while(1)
    {
      if(P1_7==0)
        {
          for(count=200;count>0;count--)
            {
              P1_0=~P1_0;
              dely500();            //每间隔500usP1.0取反一次，周期就是1ms，频率LKHZ
            }
          for(count=200;count>0;count--)
            {
              P1_0=~P1_0;
              dely500();
              dely500();          //每间隔1000usP1.0取反一次，周期是2ms，频率500HZ
            }
        }
    }
}