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Altera_Forum
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13 years ago

Demultiplexor Megafunction?

Hello, I am wondering if anybody created a custom megafunction that lets you make a demultiplexor. I am already aware that Altera provides a multiplexor megafunction, but it seems strange that they d...
Altera_Forum's avatar
Altera_Forum
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13 years ago

It's fairly easy to create your own demux using HDL.

Quartus has an option to create a symbol from an HDL module, which you can then use in your design.

Here a small example in VHDL 

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
entity demux1_4 is
port (
      out0 : out std_logic;   --output bit
      out1 : out std_logic;   --output bit
       out2 : out std_logic;   --output bit
      out3 : out std_logic;   --output bit
       sel : in std_logic_vector(1 downto 0);
       bitin : in std_logic   --input bit
     );
end demux1_4;
architecture Behavioral of demux1_4 is
begin
process(bitin,sel)
begin
out0 <= '0';
out1 <= '0';
out2 <= '0':
out3 <= '0';
case sel is
  when "00" => out0 <= bitin;
  when "01" => out1 <= bitin;
  when "10" => out2 <= bitin;
  when others => out3 <= bitin;
end case; 
end process;
end Behavioral;