说明：  DS1302 是DALLAS 公司推出的涓流充电时钟芯片，内含有一个实时时钟/日历和31 字节静态RAM，通过简单的串行接口与单片机进行通信。实时时钟/日历电路提供秒、分、时、日、日期、月、年的信息，每月的天数和闰年的天数可自动调整，时钟操作可通过AM/PM 指示决定采用24 或12 小时格式。DS1302 与单片机之间能简单地采用同步串行的方式进行通信，仅需用到三个口线：1 RES 复位；2 I/O 数据线；3 SCLK串行时钟。时钟/RAM 的读/写数据以一个字节或多达31 个字节的字符组方式通信。DS1302 工作时功耗很低。保持数据和时钟信息时功率小于1mW
(DS1302 is a trickle charge clock chip introduced by DALLAS, which contains a real-time clock / calendar and 31 bytes of static RAM, and communicates with the microcontroller through a simple serial interface. Real time clock / calendar circuit provides seconds, hours, day, date, month, year, days the number of days per month and leap year can automatically adjust the clock operation instructions through the AM/PM decided to use 24 or 12 hour format. DS1302 and SCM can simply use synchronous serial communication, only need to three lines: 1 RES reset; 2 I/O data line; 3 SCLK serial clock. The read / write data of the clock /RAM is communicated in groups of one byte or up to 31 bytes. The power consumption of the DS1302 is very low. When data and clock information is maintained, power is less than 1mW)