同时用两个定时器控制蜂鸣器发声，定时器0控制频率，定时器1控制同个频率持续的时间，间隔2s依次输出1，10，50,100，200,400,800,1k（hz）的方波? 设晶振频率为12MHz。(At the same time, with two timers to control buzzer sound, timer 0 control frequency, timer 1 control the same frequency of the duration of time, interv