利用并行接口8255作为键盘接口，设计一个具有2个八度音阶的键盘乐器，音阶键不少于16个，采用扫描方式管理键盘，音域范围自行定义-8255 parallel interface to use as a keyboard interface, the design of a two octave keyboard scale, scale of not less than 16 keys, the keyboard scanning management, self-definition of t