traffic_fsm.vhd

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LIBRARY IEEE;   
USE IEEE.std_logic_1164.all;
USE IEEE.std_logic_arith.all;
USE IEEE.std_logic_unsigned.all;   
entity traffic_FSM is
  port(reset:in std_logic;
       clk:in std_logic;
       ena_scan:in std_logic;
       ena_1Hz:in std_logic;
       flash_1Hz:in std_logic;
       a_m:in std_logic;
       st_butt:in std_logic;
       next_state: in std_logic;
       recount: out std_logic;
       sign_state: out std_logic_vector(1 downto 0);
       red: out std_logic_vector(1 downto 0);
       green: out std_logic_vector(1 downto 0);
       yellow: out std_logic_vector(1 downto 0));
end;   
architecture BEHAVIOR of traffic_FSM is
type Sreg0_type is (r0g1, r0y1, g0r1, y0r1, y0y1, y0g1, g0y1, r0r1);
signal state: Sreg0_type;     
signal st_transfer: std_logic;
signal light: std_logic_vector(5 downto 0); -- r(10)y(10)g(10)
begin  
  rebounce:process (reset,clk,ena_scan,st_butt) 
  variable rebn_ff: std_logic_vector(5 downto 0);
  begin 
     if (st_butt='1' or reset='1') then
         rebn_ff := "111111"; 
         st_transfer <='0';
     elsif (clk'event and clk='1') then
       if (ena_scan='1') then 
          if (rebn_ff >= 3) then 
             rebn_ff := rebn_ff-1; 
             st_transfer<='0';
          elsif (rebn_ff=2) then       
             rebn_ff := rebn_ff-1; 
             st_transfer <='1';
          else
             rebn_ff := rebn_ff; 
             st_transfer <='0';
          end if;
       end if;
     end if;  
  end process;  
  FSM: process (clk,ena_1Hz,reset)
  begin
      if (reset='1') then    
          state<=r0g1; -- red=2'b01; green=2'b10; yellow=2'b00;
          sign_state<="01";
          recount<='1';    
      else
        if (clk'event and clk='1') then
          case STATE is
                when r0g1 =>  -- now state: red0 on green1 on  
                  if (a_m='1' and ena_1Hz='1') then
                    if (next_state = '1') then
                        recount<='1';
                        state<=r0y1;
                        sign_state <= "01";
                    else
                        recount<='0';
                        state<=r0g1; --red=2'b01; green=2'b10; yellow=2'b00;
                    end if; 
                  elsif (a_m='0' and ena_scan='1') then
                    if (st_transfer='0') then -- 0: unchange 1:transfer light state
                        recount<='1';
                        state<=r0g1;  
                    else 
                        recount<='1';
                        state<=r0y1;  
                        sign_state <= "01";  
                    end if;
                  end if;
                when r0y1 =>  -- now state: red0 on yellow1 flash       
                  if (a_m='1' and ena_1Hz='1') then
                    if (next_state = '1') then
                        recount<='1';
                        state<=g0r1;
                        sign_state <= "10";
                    else
                        recount<='0';
                        state<=r0y1; -- red=2'b01; green=2'b00; yellow=2'b10;
                    end if;
                  elsif (a_m='0' and ena_scan='1') then
                    if (st_transfer='0') then -- 0: unchange 1:transfer light state
                        recount<='1';
                        state<=r0y1; 
                    else
                        recount<='1';
                        state<=g0r1;  
                        sign_state <= "10";  
                    end if;
                  end if;
                when g0r1 =>  -- now state: green0 on red1 on 
                  if (a_m='1' and ena_1Hz='1') then
                    if (next_state = '1') then
                        recount<='1';
                        state<=y0r1;
                        sign_state <= "11";
                    else
                        recount<='0';
                        state<=g0r1; -- red=2'b10; green=2'b01; yellow=2'b00;
                    end if;    
                  elsif (a_m='0' and ena_scan='1') then
                    if (st_transfer='0') then -- 0: unchange 1:transfer light state
                        recount<='1';
                        state<=g0r1; 
                    else
                        recount<='1';
                        state<=y0r1;   
                        sign_state <= "11";  --
                    end if;
                  end if;
                when y0r1 =>  -- now state: green0 on red1 on
                  if (a_m='1' and ena_1Hz='1') then
                    if (next_state = '1') then
                        recount<='1';
                        state<=r0g1;
                        sign_state <= "00";
                    else
                        recount<='0';
                        state<=y0r1; -- red=2'b10; green=2'b00; yellow=2'b01;
                    end if;
                  elsif (a_m='0' and ena_scan='1') then
                    if (st_transfer='0') then -- 0: unchange 1:transfer light state
                        recount<='1';
                        state<=y0r1; 
                    else
                        recount<='1';
                        state<=r0g1;       
                        sign_state <= "00";  --
                    end if;
                  end if;
                when others =>
                    state<=r0g1;
                    recount<='0';
                    sign_state <= "00";
          end case; 
        end if;
      end if;   
  end process;  
  -- light: r(10)y(10)g(10)
  light <= "010010" when (state=r0g1) else
           "011000" when (state=r0y1) else
           "100001" when (state=g0r1) else
           "100100" when (state=y0r1) else
           "110000"; 
  red <= light(5 downto 4);
  yellow <= light(3 downto 2) and (flash_1Hz & flash_1Hz);
  green <= light(1 downto 0);
end BEHAVIOR;