由于18B20时序要求严格，一般不建议采用niosii来实现对他的驱动。本人自己编写的基于NIOSII驱动函数，50MHz主频，保证可用，温度精确到0.0625度。-Due to stringent timing requirements 18B20 generally not recommended niosii to achieve his driver. I have written based on NIOSII driver function, 50MHz frequency, can be used to ensure the temperature is accurate to 0.0625 degrees.