8051单片机学习源码 包括定时器、键盘、液晶显示等，附有特定的proteus绘制电路图（89c52），和KEIL连接后可直接运行。-8051 study, including source timer, keyboard, liquid crystal display and so on, with a particular drawing proteus circuit (89c52), and can be directly run after being connected with K