keilc 使用8255可编程并行口芯片，设定为工作方式0， PA口做输入，PB口做输出，来检验八位拨动开关的状态，并控制八位发光二极管，使得八位发光二极管的亮灭变化与八位拨动开关的状态相一致。-keilc the use of 8255 programmable parallel port chip, set to work 0, PA I do enter, PB I do output, to verify the status of eight DIP switches and control eight light-emitting diodes, making eight LEDs light out of eight DIP switches and change the status line.