hex2ssd.vhd

This is a project about PWM. Application in motor speed control

----------------------------------------------------------------------------
-- hex2ssd: display hex on 7 segments display
-- blanks when not enable
-- pinout ssd: an3-0 dd abcdefg 
----------------------------------------------------------------------------

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity hex2ssd is
  port(
    clk: in std_logic;
    enable: in std_logic;
    hex: in std_logic_vector(15 downto 0);
    dot: in std_logic_vector(3 downto 0);
    ssd: out std_logic_vector(11 downto 0)
  );
end hex2ssd;

architecture behavioral of hex2ssd is
signal c: std_logic_vector(10 downto 0) := (others => '0');
signal nibble: std_logic_vector(3 downto 0); 

begin
  process
    begin
      wait until rising_edge(clk);
      case c(10 downto 9) is

        when "00" => 
          nibble <= hex(3 downto 0);
	  ssd(7) <= dot(0);
	  ssd(11 downto 8) <= "1110";

	when "01" => nibble <= hex(7 downto 4);
	  ssd(7) <= dot(1);
	  ssd(11 downto 8) <= "1101";

	when "10" => nibble <= hex(11 downto 8);
	  ssd(7) <= dot(2);
	  ssd(11 downto 8) <= "1011";

	when "11" => nibble <= hex(15 downto 12);
	  ssd(7) <= dot(3);
	  ssd(11 downto 8) <= "0111";

	when others => null;
      end case;

      case nibble is
        when "0000" => ssd(6 downto 0) <= "0000001"; -- 0
        when "0001" => ssd(6 downto 0) <= "1001111"; -- 1
        when "0010" => ssd(6 downto 0) <= "0010010"; -- 2
        when "0011" => ssd(6 downto 0) <= "0000110"; -- 3
        when "0100" => ssd(6 downto 0) <= "1001100"; -- 4
        when "0101" => ssd(6 downto 0) <= "0100100"; -- 5
        when "0110" => ssd(6 downto 0) <= "0100000"; -- 6
        when "0111" => ssd(6 downto 0) <= "0001111"; -- 7
        when "1000" => ssd(6 downto 0) <= "0000000"; -- 8
        when "1001" => ssd(6 downto 0) <= "0000100"; -- 9
        when "1010" => ssd(6 downto 0) <= "0001000"; -- A
        when "1011" => ssd(6 downto 0) <= "1100000"; -- b
        when "1100" => ssd(6 downto 0) <= "0110001"; -- C
        when "1101" => ssd(6 downto 0) <= "1000010"; -- d
        when "1110" => ssd(6 downto 0) <= "0110000"; -- E
        when "1111" => ssd(6 downto 0) <= "0111000"; -- F
	when others => null;
      end case;

      if (enable = '0') then
	ssd(6 downto 0) <= "1111111";
      end if;	   

      c <= c + '1';

    end process;
end behavioral;