这五个例程是51单片机中很重要的内容，包括数模转换、串口通信、IIC总线、四乘四矩阵键盘和单片机的中断系统。熟练运用单片机这些功能对将来从事嵌入式开发具有极大的帮助。-These five routines are very important in 51 single-chip microcontrollers, including digital-to-analog conversion, serial communication, IIC bus, quadruple quadruple