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genericsvhdl
Bomfly
Bomfly

Reputation: 11

VHDL DMUX with Generics (1:8 DMUX)

I wrote this entity but i don't know how to write the architecture.It has to be done by using generics and it needs to work for any DMUX (1:2,1:4,1:8,1:16 etc) if I change the Nr_sel (number of selection inputs). The data(input) is on 1 bit.

entity DMUX is
generic (
    Nr_sel: integer:= 3
);
port (
    Input: in std_logic;
    Sel: in std_logic_vector (Nr_sel - 1 downto 0);
    Outputs: out std_logic_vector(2**Nr_sel - 1 downto 0)
);  
end DMUX;

Upvotes: 0

Views: 583

Answers (2)

FRob
FRob

Reputation: 4041

It could be achieved the following way:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity DMUX is
    Generic (
        num_sel : positive := 1 -- or 2, 3, ... etc.
    );
    Port (
        SEL  : in   unsigned(num_sel - 1 downto 0);
        DIN  : in   std_logic;
        DOUT : out  std_logic_vector(2**num_sel - 1 downto 0)
    );
end entity DMUX;

architecture Behavioral of DMUX is
begin

output_p : process (
    SEL,
    DIN
    )
begin

    -- default assignment
    DOUT <= (others => '0');
    DOUT(to_integer(SEL)) <= DIN;

end process output_p;

end architecture Behavioral;

Depending on your needs, you could also have low-active logic, i.e. all ones (others => '1') and invert DIN.

Upvotes: 1

Eugene Sh.
Eugene Sh.

Reputation: 18299

I believe the right method would be to use generate, since we have a variable number of outputs, while all of them have to be assigned, and without any sequential logic:

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.NUMERIC_STD.ALL;

entity DMUX is
generic (
    Nr_sel: integer:= 3
);
port (
    Input: in std_logic;
    Sel: in std_logic_vector (Nr_sel - 1 downto 0);
    Outputs: out std_logic_vector(2**Nr_sel - 1 downto 0)
);  
end DMUX;

architecture Arch of DMUX is
begin
    GEN_OUT:
    for i in 0 to (2**Nr_sel - 1) generate
        Outputs(i) <= Input when (to_integer(Sel) = i) else '0';
    end generate GEN_OUT;
end Arch;

I haven't tested it's functionality, but it compiles and gives the idea.

Upvotes: 0

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