掌握RAM扩充、8253计数器/定时器、8255并行口、8251串行口、8259中断控制器、D/A数模转换、A/D模数转换、DMA、LED显示等各个器件的性能和使用方法。-Master the RAM expansion, 8253 counter/timer, 8255 parallel port, serial port 8251, 8259 interrupt controller, D/A digital-analog conversion, A/D digital conversion, DMA, LED display and so on device performance and usage .