说明：   EA = 1 //开总中断 ET0 = 1 //允许定时器0中断 TMOD = 1 //定时器工作方式选择 TL0 = 0x06 TH0 = 0xf8 //定时器赋予初值 TR0 = 1 //启动定时器
(EA = 1// open a total interruption of ET0 = 1// allow timer 0 interrupt TMOD = 1// Timer to choose working methods TL0 = 0x06 TH0 = 0xf8// timer initial value given TR0 = 1// start timer)