实时时钟1302的源代码，应用PIC16f877显示时间，采用锂离子电池做备用电源，在系统掉电的情况下能够记录时间信息。-Real-time clock 1302 of the source code, application PIC16f877 display time, the use of lithium-ion battery backup power to do in case of power failure the system can record the time inform