8255扫描键盘、显示程序

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 scanning keyboard, display program using 8255 parallel port programmable keyboard to do a scan experiment, the button input keys code, displayed in the control of the team respectively by 8279 digital tube. 8255PA I make the keyboard input line, PB mouth for scan line.