单片机硬件系统设计原则一个单片机应用系统的硬件电路设计包含两部分内容：一是系统扩展，即单片机内部的功能单元，如ROM、RAM、I/O、定时器/计数器、中断系统等不能满足应用系统的要求时，必须在片外进行扩展，选择适当的芯片，设计相应的电路。二是系统的配置，即按照系统功能要求配置外围设备，如键盘、显示器、打印机、A/D、D/A转换器等，要设计合适的接口电路。 -MCU hardware design principles of a system based application system hardware circuit design includes two parts : First, the expansion of internal microcontroller that is the function modules, such as ROM, RAM, I/O, timer/counter, interrupt system can not meet the application requirements, must chip in for expansion, the selection of appropriate chips, The circuit design accordingly. Second, the system configuration, according to the functional requirements of system configuration peripheral equipment, such as keyboards, monitors, printers, A/D, D/A converters, it is necessary to design appropriate interface circuit.