说明：  l、设计用于竞赛的四人抢答器，功能如下： (1) 有多路抢答器，台数为四； (2) 具有抢答开始后20秒倒计时，20秒倒计时后无人抢答显示超时，并报警； (3) 能显示超前抢答台号并显示犯规警报； (4) 能显示各路得分，并具有加、减分功能； 2、系统复位后进入抢答状态，当有一路抢答键按下时，该路抢答信号将其余各路抢答封锁，同时铃声响，直至该路按键松开，显示牌显示该路抢答台号。 3、用VHDL语言设计符合上述功能要求的四人抢答器，并用层次设计方法设计该电路
(l, designed for Answer four contests, and features are as follows: (1) Answer the way how, and the number to four (2) Answer 20 seconds after the beginning of the countdown, countdown to 20 seconds after the Answer shows no overtime, and report to the police (3) can show in advance Answer Desk No. foul alarm and display (4) can display various scoring with Canada, by sub-function 2, the system reset after entering the Answer state, all the way when pressing the Answer key , the signals will be the rest of the way each Answer Answer blockade, ring tones at the same time, release the button until the road, the road signs showing the number Answer Desk. 3, using VHDL language design meets the functional requirements of the above Answer four devices, and design method-level design of the circuit)