出租车计价器VHDL程序与仿真

--文件名：taxi.hd。
--功能：出租车计价器。
--最后修改日期：2004.4.9。
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity taxi is
port ( clk_240  :in std_logic;                           --频率为240Hz的时钟                        
       start :in std_logic;                               --计价使能信号
       stop:in std_logic;                                --等待信号
       fin:in std_logic;                                 --公里脉冲信号
       cha3,cha2,cha1,cha0:out std_logic_vector(3 downto 0); --费用数据
       km1,km0:out std_logic_vector(3 downto 0);          --公里数据           
       min1,min0: out std_logic_vector(3 downto 0));       --等待时间  
end taxi;
architecture behav of taxi is
signal f_15,f_16,f_1:std_logic;                         --频率为15Hz，16Hz，1Hz的信号
signal q_15:integer range 0 to 15;                       --分频器
signal q_16:integer range 0 to 14;                       --分频器
signal q_1:integer range 0 to 239;                       --分频器
signal w:integer range 0 to 59;                         --秒计数器
signal c3,c2,c1,c0:std_logic_vector(3 downto 0);          --制费用计数器
signal k1,k0:std_logic_vector(3 downto 0);               --公里计数器
signal m1:std_logic_vector(2 downto 0);                 --分的十位计数器
signal m0:std_logic_vector(3 downto 0);                 --分的个位计数器
signal en1,en0,f:std_logic;                             --使能信号
begin

feipin:process(clk_240,start)
begin
  if clk_240'event and clk_240='1' then
     if start='0' then q_15<=0;q_16<=0;f_15<='0';f_16<='0';f_1<='0';f<='0';
     else
        if q_15=15 then q_15<=0;f_15<='1';          --此IF语句得到频率为15Hz的信号
        else q_15<=q_15+1;f_15<='0';
        end if;
        if q_16=14 then q_16<=0;f_16<='1';          --此IF语句得到频率为16Hz的信号
        else q_16<=q_16+1;f_16<='0';
        end if;
        if q_1=239 then q_1<=0;f_1<='1';            --此IF语句得到频率为1Hz的信号
        else q_1<=q_1+1;f_1<='0';
        end if;
        if en1='1' then f<=f_15;                    --此IF语句得到计费脉冲f
        elsif en0='1' then f<=f_16;
        else f<='0';
        end if;
     end if;
  end if;
end process;

process(f_1)
begin
  if f_1'event and f_1='1' then
     if start='0' then
w<=0;en1<='0';en0<='0';m1<="000";m0<="0000";k1<="0000";k0<="0000";
     elsif stop='1' then
        if w=59 then w<=0;                             --此IF语句完成等待计时
           if m0="1001" then m0<="0000";                --此IF语句完成分计数
              if m1<="101" then m1<="000";
              else m1<=m1+1;
              end if;
           else m0<=m0+1;
           end if;
           if m1&m0>"0000001"then en1<='1';             --此IF语句得到en1使能信号
           else en1<='0';
           end if;
        else w<=w+1;en1<='0';
        end if;
     elsif fin='1' then
        if k0="1001" then k0<="0000";                    --此IF语句完成公里脉冲计数
           if k1="1001" then k1<="0000";
           else k1<=k1+1;
           end if;
        else k0<=k0+1;
        end if;
        if k1&k0>"00000010" then en0<='1';               --此IF语句得到en0使能信号
        else en0<='0';
        end if;       
     else en1<='0';en0<='0';
     end if;
cha3<=c3;cha2<=c2;cha1<=c1;cha0<=c0;                   --费用数据输出
km1<=k1;km0<=k0;min1<='0'&m1;min0<=m0;              --公里数据、分钟数据输出
  end if;
end process;

process(f,start)
begin
  if start='0' then c3<="0000";c2<="0001";c1<="0000";c0<="0000";
  elsif f'event and f='1' then
     if c0="1001" then c0<="0000";                       --此IF语句完成对费用的计数
        if c1="1001" then c1<="0000";
           if c2="1001" then c2<="0000";
              if c3<="1001" then c3<="0000";
              else c3<=c3+1;
              end if;
           else c2<=c2+1;
           end if;
        else c1<=c1+1;
        end if;
     else c0<=c0+1;
     end if;
  end if;
end process;
end behav;