用FPGA开发板的按键作为电子表的时间初值设置控制信号，数码管当前时间值输出。用按键选择分别输出：分、秒、1/10秒。(With FPGA development board button, as the time value of the electronic table, set the control signal, digital tube current time value output. Select output by buttons: minutes, seconds, and