VHDL利用四位拨盘输入数据，输入两个数，显示于数码管，另两个数码管显示其取反，四个数字再留个数码管上以一秒为周期左移-VHDL use four dial input data, input two numbers displayed on the digital control, the other two digital display its negation, then leave a four-digit digital tube left at one-second cycle