微机8255并行口硬件实验 8255A的A口作为输入口，与逻辑电平开关相连。8255A的B口作为输出口，与发光二极管相连。编写程序，使得逻辑电平开关的变化在发光二极管上显示出来。-8255 microcomputer parallel port hardware experiment 8255A mouth of A as input port, and logic-level switch connected. B-I as the 8255A output connected wit