#include <REGX51.H>
unsigned int n;
void initTimer7(void)   //timer init
{ TMOD=0x1;
 TH0=0x15;
 TL0=0xa0;  
}
void timer07(void) interrupt 1   //timer0/counter0 interrupt
{ TH0=0x15;
 TL0=0xa0;
 if(n++>33)	 {  P0= ~P0;
    n=0; }
}
void ex7(void)   //the main fun
{	initTimer7();
	TR0=1;	ET0=1; 	n=0;  	EA=1;
    P2 |= 0x0f;//選通LED1~LED4工作
	while(1);
}