//參考程序:文件名:PHOT1.c  程序驅動固體繼電器
#include <c8051f020.h>                    
#include <intrins.h>
void PORT_Init (void);
void sleep_ms(unsigned int count);
void main (void) {
   /*無效看門狗*/
   WDTCN = 0xde;
   WDTCN = 0xad;
   PORT_Init ();
   P5=P5&0x0ff;		/*關SSR,SCR和步進電機*/
    while (1) 
   {            P5 = P5 & 0x7F;		//固體繼電器SSR
		        sleep_ms(1000);
P5 = P5 | 0x80;		//固體繼電器SSR
				sleep_ms(1000);
   }
}
void PORT_Init (void)
{
  P74OUT |= 0x08;     /*P5高4位為推挽輸出，其余口為開漏輸出*/
}
/*延時子程序*/
void sleep_ms(unsigned int count)
{
  unsigned int ii,jj;
  for(ii=0;ii<count;ii++)
    {
      for(jj=0;jj<250;jj++)
	  _nop_();			
    }
	
}