用VHDL 语言设计实现一个10 秒倒计时电路，要求使用8×8 点阵显示计时结果。能在计时到0后开始播放乐曲，同时乐曲可以自由转换。-VHDL Language Design and Implementation with a 10 seconds countdown circuits require the use of 8 × 8 dot matrix display time results. To 0 in time to start playing after the music, and music are free to convert.