说明：  接口与通讯实验报告(内有代码) 1、8253定时/计数器实验 2、8255并行接口实验 3、数字式时钟（电子钟） 4、D/A（数/模）转换实验 5、A/D（模/数）转换实验
(Interface and communication lab report (which contains code) 1,8253 timer/counter experiment 2,8255 Parallel Interface Experiment 3, digital clock (clock) 4, D/A (D/A) conversion experiments 5, A/D ( analog/digital) conversion experiments)