电话计费器程序/*信号定义：

clk： 时钟信号，本例中其频率值为1Hz；

decide： 电话局反馈回来的信号，代表话务种类，“01”表示市话，“10”表示

长话，“11”表示特话；

dispmoney： 用来显示卡内余额，其单位为角，这里假定能显示的最大数额为50 元

（500 角）；

disptime： 显示本次通话的时长；

write,read： 当write 信号下降沿到来时写卡，当话卡插入，read 信号变高时读卡；

warn： 余额过少时的告警信号。本例中，当打市话时，余额少于3 角，打长

话时，余额少于6 角，即会产生告警信号；

cut： 当告警时间过长时自动切断通话信号。 */-telephone billing for procedures / * signal definition : clk : clock signal, which in this case, their frequency of 1Hz; decide : Telephone Bureau feedback signal, then the Treasury representative types, "01" Urban said, "10" The point said, "11" expressed special words; dispmoney : to show the card balance, the unit of angle, Here are supposed to show the maximum amount of 50 billion yuan (500 angle); disptime : The calls show the length; write, read : When the write signal arrival of the down time to write cards, When the card insert, read signal change high Reader; warn : Fees balance of the alarm signal. In this example, when fighting City words, the balance is less than 30 cents, playing The point, the balance is less than 60 cents, would produce warning