一个单片机最小系统，包括串口下载、复位电路，采用外部小键盘输入数据，能够实现加法、乘法及一个科学计算，计算结果显示在四位一体的数码管上。-A single chip minimize system, including serial download and reset circuit, use external small keyboard input data, will be able to realize the addition, multiplication and a scient