用定时器做
void timer0(void) interrupt 1 //using 2
{
static uchar click=0;中断次数计数器变量*/
TH0=T_TH0;恢复定时器初始值*/
TL0=T_TL0;
++click;
if (click>=100) click=0;
/*当小于占空比值时输出低电平,高于时是高电平,从而实现占空比的调整*/
if (click