数码管的初始显示值为00；当1s产生时，秒计数器加一；秒计数到60时清零，并从00，从新开始，如此周而复始进行。(The initial display value of the digital tube is 00; when 1s is generated, the second counter is incremented; when the second is counted to 60, it is cleared, and from 00, the new one is started, and so on.)