定时器T1中断实验。 1、定时器中断实验。定时器产生10mS周期中断，通过计数让PB1电平产生周期变化。 2、内部1 M晶振。-Timer T1 interrupt the experiment. 1, the timer interruption experiments. 10ms cycle timer interrupt generated by count so that PB1-level changes have a cycle. 2, internal 1 M crystal.