用单片机8051控制DS18B20温度传感器，包括温度上下限的设置（可以通过串口及时设置进DS18B20），读取及时温度，当温度超过上下限报警功能。-8051 using single-chip temperature sensor DS18B20 control, including the upper and lower limits of temperature settings (through the serial port settings into timely DS18B20),