用VHDL语言编写一个八位数码管显示电路，每个数码管的八个段分别连在一起，八个数码管分别由八个选通信号选择。被选通的数码管显示数据，其余关闭-With the VHDL language to write a eight digital tube display circuit, each digital tube eight segments are connected together, the eight digital tube are respectively composed of