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shiftrotater.vhdl
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shiftrotater.vhdl
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library ieee;
use ieee.std_logic_1164.all;
entity shiftrotater is
port (
shift : in std_ulogic;
din : in std_ulogic_vector(3 downto 0);
desloc : in std_ulogic_vector(1 downto 0);
dout : out std_ulogic_vector(3 downto 0)
);
end entity;
architecture structural of shiftrotater is
signal sh1 : std_ulogic_vector(3 downto 0);
signal sh2 : std_ulogic_vector(2 downto 0);
begin
-- First level shifts by one
mux2_00: entity work.mux2(dataflow)
port map(din(0) => din(0), din(1) => din(3), sel => desloc(0), dout => sh1(0));
mux2_01: entity work.mux2(dataflow)
port map(din(0) => din(1), din(1) => din(0), sel => desloc(0), dout => sh1(1));
mux2_02: entity work.mux2(dataflow)
port map(din(0) => din(2), din(1) => din(1), sel => desloc(0), dout => sh1(2));
mux2_03: entity work.mux2(dataflow)
port map(din(0) => din(3), din(1) => din(2), sel => desloc(0), dout => sh1(3));
-- Second level shifts by two
mux2_10: entity work.mux2(dataflow)
port map(din(0) => sh1(0), din(1) => sh1(2), sel => desloc(1), dout => sh2(0));
mux2_11: entity work.mux2(dataflow)
port map(din(0) => sh1(1), din(1) => sh1(3), sel => desloc(1), dout => sh2(1));
mux2_12: entity work.mux2(dataflow)
port map(din(0) => sh1(2), din(1) => sh1(0), sel => desloc(1), dout => sh2(2));
mux2_13: entity work.mux2(dataflow)
port map(din(0) => sh1(3), din(1) => sh1(1), sel => desloc(1), dout => dout(3));
-- Finally change result to match operation
dout(0) <= sh2(0) and not (shift and (desloc(0) or desloc(1)));
dout(1) <= sh2(1) and not (shift and desloc(1));
dout(2) <= sh2(2) and not (shift and desloc(0) and desloc(1));
end architecture;