#pragma db code
#include<AT89X52.H>
#define uchar unsigned char
#define uint  unsigned int


;可以用示波器觀察輸出頻率和波形.

sbit K1=P2^4;
sbit K2=P2^5;

sbit out=P3^7;

void delay(uint a);

void main()
{
  TMOD=0x01;
  TR0=1;
  for(;;)
  {
    TH0=(65535-9200)/256;
	TL0=(65535-9200)%256;
	while(!TF0);
	
	  out=!out;
	  TF0=0;
	
  }
}