用Verilog语言和实验箱上的按键和灯，实现三层电梯简单的上下楼和开关门。-With buttons and lights Verilog language and experimental box, simple to implement Layer elevator downstairs and switch on the door.

简单地三层电梯程序，通过代码实现电梯上行下降及开关门(Simply three layers of elevator program, through the code to achieve the elevator down and open the door)