8255方式0，由A口（B口、C口）输出数据，驱动四个LED，使其顺序显示 ‘0’～‘F’的二进制状态，每个状态保留1秒钟。-8255 mode 0, the A port (B port, C port) output data to drive four LED, so that the order of display ' 0' ~ ' F' binary state, each state retained a second.