Interfacing the DS1302 with a microprocessor is simplified by using synchronous serial communication. Only three wires are required to communicate with the clock/RAM: CE, I/O (data line), and SCLK (serial clock). Data can be transferred to and from the clock/RAM 1 byte at a time or in a burst of up to 31 bytes. The DS1302 is designed to operate on very low power and retain data and clock information on less than 1μW.

我是第一次看这个，我看了下手册，感觉上面是有用的。第一：采用同步串行通信，高达31个字节。这31一个字节你就可以包括了seconds, minutes, hours, day, date, month, and year information的信息，一次行发给他。

看了这个寄存器后就明白了是读写都可以的，我没怎么仔细看手册，就抓重点看的，难免有错误。和串口数据联系起来，这里的低位应该是seconds，依次类推。你可以去实验下，看看读取的结果是多少。