sem6/dig/m4/ex2.vhdl


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-- TEST_START{"inputs": ["sw0"], "outputs": ["o,3,0"], "clk": "bt0", "testin": "000111001001"}TEST_STOP
library ieee;
use ieee.std_logic_1164.all;

entity ex2 is
    port (
        sw0: in std_logic;
        bt0: in std_logic;
        o: out std_logic_vector(3 downto 0)
    );
end ex2;

architecture impl of ex2 is
    signal state: std_logic_vector(3 downto 0) := "0000";
    signal next_state: std_logic_vector(3 downto 0) := "0000";
begin
    -- Implement shifting
    next_state(3 downto 1) <= state(2 downto 0);
    next_state(0) <= sw0;
    o <= state;

    process (bt0)
    begin
        if (bt0'event and bt0 = '1') then
            state <= next_state;
        end if;
    end process;
end impl;