Tri-state buffers : multiple processes

Modeling tri-state buffers from several processes using if statement

library IEEE;

use IEEE.std_logic_1164.all;

entity tri_state_1 is

    port (a,b,c,d: in std_logic; ea,eb,ec,ed: in std_logic; x: in std_logic);

end tri_state_1;

architecture several_processes of tri_state_1 is

begin

    A: process (a,ea)

    begin

      if (ea='1') then

        x <= a;

      else

        x <= 'Z';

      end if;

    end process A;

    -- process B

    -- process C

    D: process (d,ed)

    begin

      if (ed='1') then

        x <= d;

      else

        x <= 'Z';

      end if;

    end process D;

end several_processes;