Hi Zhang Jinfu,

You make the mistake in your code.

The command byte is always input starting with the LSB (bit 0) so you have to use the RRC A instruction in SENDCLK and WRTCLK subroutines instead of the RLC A instruction.

Hope it helps you greatly.

Good luck to you,

Igor

P.S. By the way, I have full description of DS 1302 (1302.pdf, about 90 KB), if you are interesting in it.