Taxi meter VHDL program

    Programming and simulation.
1. Taxi meter VHDL program
-- File name: taxi.hd 
-- Function: Taxi meter 
library IEEE;
use IEEE.STD_LOG IC _1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity taxi is
port ( clk_240 :in std_logic; --Clock start with a frequency of 240Hz                        
       :in std_logic; --Pricing enable signal
      stop:in std_logic; --Waiting signal
      fin:in std_logic; --Kilometer pulse signal
      cha3,cha2,cha1,cha0:out std_logic_vector(3 downto 0); --Fee data
      km1,km0:out std_logic_vector(3 downto 0); --Kilometer data            
      min1,min0: out std_logic_vector(3 downto 0)); --Waiting time  
 end taxi;
architecture behav of taxi is
signal f_15,f_16,f_1:std_logic; --Frequency signal of 15Hz, 16Hz, 1Hz
signal q_15:integer range 0 to 15; --Frequency divider
signal q_16:integer range 0 to 14; --Frequency divider signal q_1:integer range 0 to 239; --Frequency divider signal w:integer range 0 to 59; --Second counter  signal c3,c2,c1,c0:std_logic_vector(3 downto 0); --Toll counter signal k1,k0:std_logic_vector(3 downto 0); --Kilometer counter signal m1:std_logic_vector(2 downto 0); --Tens counter  signal m0:std_logic_vector(3 downto 0); --Units counter signal en1,en0,f:std_logic; -- Enable signal  begin fei PIN : 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'; --This statement gets a signal with a frequency of 15Hzelse       q_15<=q_15+1;f_15<='0';       end if;       if q_16=14 then q_16<=0;f_16<='1'; --This statement gets a signal with a frequency of 16Hzelse       q_16<=q_16+1;f_16<='0';        end if;       if q_1=239 then q_1<=0;f_1<='1'; --This statement gets a signal with a frequency of 1Hz       else q_1<=q_1+1;f_1<='0';       end if;       if en1='1' then f<=f_15; --This statement gets the billing pulse 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; --This statement completes the waiting timingif
        m0="1001" then m0<="0000"; --This statement completes the minute countingif 
          m1<="101" then m1<="000";
          else m1<=m1+1;
          end if;
        else m0<=m0+1;
        end if;
        if m1&m0>"0000001"then en1<='1'; --This statement gets the en1 enable signalelse
        en1<='0';
        end if;
      else w<=w+1;en1<='0';
      end if;
    elsif fin='1' then 
      if k0="1001" then k0<="0000"; --This statement completes the kilometer pulse countingif
        k1="1001" then k1<="0000";
        else k1<=k1+1;
        end if;
      else k0<=k0+1;
      end if;
      if k1&k0>"00000010" then en0<='1'; --This statement gets the en0 enable signal
      else en0<='0';
      end if;        
    else en1<='0';en0<='0';
    end if;
cha3<=c3;cha2<=c2;cha1<=c1;cha0<=c0; --Cost data output
km1<=k1;km0<=k0;min1<='0'&m1;min0<=m0; --Kilometer data, minute data output
  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"; --This statement completes the cost counting
      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; 

    2. Program simulation diagram

    Note: 1. The relationship between seconds and minutes in the simulation diagram is ternary, that is, when w is 2, it returns to 0;

    2. The taxi traveled a total of 5 kilometers, the cumulative waiting time was 4 minutes, and the total fare was 16.2 yuan.

    
Figure 8.22.3 Taxi meter program simulation full picture