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library ieee;
use ieee.std_logic_1164.all;
entity fsm_4s is
port (clk : std_logic;
rst : std_logic;
d : std_logic;
done : out std_logic);
end fsm_4s;
architecture behav of fsm_4s is
type state_t is (S0_1, S1_0, S2_0, S3_1);
signal s : state_t;
begin
process (clk)
begin
if rising_edge(clk) then
if rst = '1' then
s <= S0_1;
done <= '0';
else
-- Reset by default
s <= S0_1;
done <= '0';
case s is
when S0_1 =>
if d = '1' then
s <= S1_0;
end if;
when S1_0 =>
if d = '0' then
s <= S2_0;
end if;
when S2_0 =>
if d = '0' then
s <= S3_1;
end if;
when S3_1 =>
if d = '1' then
done <= '1';
end if;
end case;
end if;
end if;
end process;
end behav;
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