用VHDL语言来实现一个电子时钟，可以调时间。小时，分，秒。可以下载到实验箱来运行验证。适用与大多数实验箱-use VHDL to achieve an electronic clock, the time can be set aside. Hours, minutes and seconds. Experiments can be downloaded to the box to run test. Apply with the majority of experimental boxes