8255A的A口作为输出功能，连接8盏LED灯。

8255A的B口作为输入功能，连接8个按钮。

当B口的某一按钮按下，对应的LED灯就点亮同时。同时，数码管上显示对应的按键号。如B口按钮1按下，1号LED灯就点亮，8段数码管显示1.-8255A A-port as output, connect 8 LED lights. 8255A, B port as input, connecting eight buttons. When the B port of a button is pressed, the corresponding LED lights will light up simultaneously. Meanwhile, the digital tube display the corresponding key number. If port B button 1 Press, the 1st LED lights will illuminate and an 8-segment LED display.