利用实验箱上的8255A可编程并行接口芯片和矩阵键盘，编写程序，做到在键盘上每按一个数学键（0~F），用发光二极管将代码显示出来。

连线方法：将键盘RL10~RL17接8255A的PB0~PB7；KA10~KA12接8255A的PA0~PA2；PC0~PC7接发光二极管的L1~L8；8255A芯片的片选信号8255CS接CS0-The use of experimental box 8255A programmable parallel interface chip and matrix keyboard, programming, so each time you press a key mathematics (0 ~ F), with a light-emitting diode code displayed on the keypad. Connection Methods: 8255A keyboard RL10 ~ RL17 pick the PB0 ~ PB7　KA10 ~ KA12 pick 8255A of PA0 ~ PA2　PC0 ~ PC7 pick-emitting diodes L1 ~ L8　chip select signals CS0 8255CS 8255A chip connection