用DS12C887来进行时钟控制，提供RTC日历，定时闹钟，三个可屏蔽的中断和一个中断的输出-With DS12C887 to carry out clock control, provide RTC calendar, timer alarm clock, three can shield the interrupt and a interrupt output

一个关于DS12C887的时钟程序，很实用(A DS12C887 clock program, very practical)