本程序为美信公司单线式温度传感器DS18B20的温度读取和显示，

DS18B20采用外部供电方式，数据线接到单片机的P2.7口，一只

接入方式，不读取ROM直接跳过，温度数据将小数部分处理掉，

只要整数部分。显示器使用的是接在P0口的8段,4位共阴数码管

因专用板所以码值与一般常规不一样.温度传感器默认的12bits

的格式，并在数据上做了处理，将小数部分和负温度抛弃了.

增加了温度报警功能,可以设置最大值和最小值.

-This program is Maxim temperature sensor DS18B20 single temperature reading and display, DS18B20 using an external power supply, data cable to the MCU P2.7 port, an access way, do not skip reading ROM, fractional part of the temperature data will be disposed of, as long as the integer part. Display is connected using the P0 port 8, four common cathode tube because of dedicated board so the digital code value and general practices are no different. Temperature sensor default 12bits format, and made a deal with the data, the fractional part and negative temperature abandoned. an increase of temperature alarm function, you can set maximum and minimum values.