利用8255可编程并行口做一个扫描键盘实验，把按键输入的键码，显示在由8279控制的七段数码管上。8255PA口做键盘输入线，PB口作扫描线-8255 programmable parallel port using a scanning keyboard to do the experiment, the button input keys code, displayed in the control of the team respectively by 8279 digital tube.