An encoder is a digital circuit which performs the inverse of decoder.An encoder has 2^N input lines and N output lines.In encoder the output lines genrate the binary code corresponding to input value.The decimal to bcd encoder usually has 10 input lines and 4 ouput lines.The decoder decimal data as an input for decoder an encoded bcd ouput is available at 4 output lines.
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity Encoder8_3 is
port ( ENABLE : in STD_LOGIC;
D_IN: in STD_LOGIC_VECTOR(7 downto 0);
D_OUT: out STD_LOGIC_VECTOR(2 downto 0) );
end Encoder8_3;
architecture encoder_arch of encoder8_3 is
begin
process(ENABLE,D_IN)
begin
if ( ENABLE = '1') then
D_OUT <= "000";
Else
case D_IN is
when "00000001" => D_OUT <= "000";
when "00000010" => D_OUT <= "001";
when "00000100" => D_OUT <= "010";
when "00001000" => D_OUT <= "011";
when "00010000" => D_OUT <= "100";
when "00100000" => D_OUT <= "101";
when "01000000" => D_OUT <= "110";
when “10000000” => D_OUT <= "111";
when OTHERS => NULL";
end case;
end if;
end process;
end encoder_arch;
