--- Du code de debutante, pour les debutant(e)s.
---
--- Je ne garantis ni un parfait respect des
--- normes, ni une parfaite elegance, et encore
--- moins le plein fonctionnement en toutes
--- situations, critiques ou pas, d'ailleurs.
---
--- (C) 2010 Laura Becognee, paru dans GNU/Linux magazine France.

library IEEE;
use ieee.std_logic_1164.all;

entity conv_BCD_7seg is
  port ( 
  -- signaux externes
  conv_in : in std_logic_vector (3 downto 0);
  SEG : out std_ulogic_vector (6 downto 0);
  OE : in std_logic
  );
end conv_BCD_7seg;

architecture plup of conv_BCD_7seg is

-- declaration des signaux (fils) internes

signal NOR_out : std_logic_vector (3 downto 0);
signal NAND_out : std_logic_vector (7 downto 0);
signal OE_out : std_logic;

begin

-- cablage des portes nor :

NOR_out(0) <= not (conv_in(2) and conv_in(1) );
NOR_out(1) <= conv_in(1) or not conv_in(2);
NOR_out(2) <= not (nor_out(3) and conv_in(3));
NOR_out(3) <= conv_in(2) or conv_in(1);

-- cablage de la porte nor de OE :

OE_out <= not (not NOR_out(2) or OE );

-- cablage des premieres portes nand :

NAND_out(0) <= not conv_in(3) and not NOR_out(3) and conv_in(0);
NAND_out(1) <= not (NOR_out(1) or conv_in(0));
NAND_out(2) <= not NOR_out(1) and conv_in(0);
NAND_out(3) <= not conv_in(0) and not conv_in(2) and conv_in(1);
NAND_out(4) <= not (conv_in(0) or NOR_out(0) );
NAND_out(5) <= not NOR_out(0) and conv_in(0);
NAND_out(6) <= conv_in(0) and conv_in(1);
NAND_out(7) <= not (conv_in(3) or NOR_out(3) );

-- cablage des secondes portes nand :

SEG(0) <= not (OE_out or NAND_out(0) or NAND_out(1) );
SEG(1) <= not (OE_out or NAND_out(2) or NAND_out(4) );
SEG(2) <= not (OE_out or NAND_out(3) );
SEG(3) <= not (OE_out or NAND_out(0) or NAND_out(1) or NAND_out(5) );
SEG(4) <= not (OE_out or NAND_out(1) or conv_in(0) );
SEG(5) <= not (OE_out or NAND_out(0) or NAND_out(3) or NAND_out(6) );
SEG(6) <= not (OE_out or NAND_out(5) or NAND_out(7) );

end plup;


architecture plop of conv_BCD_7seg is

begin

process (conv_in, OE)
begin

if OE = '1' then

case conv_in is

when "0000" => SEG <= "0111111";
when "0001" => SEG <= "0000110";
when "0010" => SEG <= "1011011";
when "0011" => SEG <= "0001111";
when "0100" => SEG <= "1100110";
when "0101" => SEG <= "1101101";
when "0110" => SEG <= "1111101";
when "0111" => SEG <= "0000111";
when "1000" => SEG <= "1111111";
when "1001" => SEG <= "1101111";

when others => SEG <= "0000000";

end case;

else SEG <= "0000000";

end if;

end process;

end plop;