用外部中断读取PS2键盘的数据 并在数码管上显示，此程序只处理数字键盘。其余按键功能用户可以自行扩展，为了程序简单便于阅读和学习，程序中没有使用奇偶校验，　　

校验程序请自行添加-External interrupt data read PS2 keyboard and display on the digital tube, this program only handles numeric keypad. Remaining keys function the user can expand their own, simple to program easy to read and learn, the program does not use parity,

Please add their own verification procedures