sfr P0 = 0x80;  		
sfr P1 = 0x90;  	
sfr P2 = 0xA0;  
void MSDelay(unsigned int);
void main(void)
  {
    while(1) 			
      { 
        P0=0x55;
        P1=0x55;
        P2=0x55;
        MSDelay(250);	
        P0=0xAA;
        P1=0xAA;
        P2=0xAA;
        MSDelay(250);
      }
  }
void MSDelay(unsigned int itime)
  {
    unsigned int i, j;
    for(i=0;i<itime;i++)
      for(j=0;j<1275;j++);
  }