说明：  实现对DS18B20的读取,注意：单总线协议对延时要求比较严格，此程序中采用的是11.0592M的晶振，如果使用其他的晶振请跟据DS18B20的资料修改延时参数
(DS18B20 achieve the right read, attention : single bus protocol to delay more stringent requirements, This procedure is used in the M 11.0592 Crystal Oscillator, If you use other Oscillator please According to the information DS18B20 delay parameter changes)