说明：  ①在6个不带锁存器的数码管上，实现时钟的动态显示； ②当时钟显示不准时，实现时钟的实时校时功能； ③实现在数码管上、电脑上同步显示实时时钟信号
(① In the six non-digital pipe latches, dynamic display of the clock ② When the clock display are not allowed to achieve real-time clock when the function of the school ③ implemented in digital, the computer displays real-time clock synchronization)