Sequence Detector ( Moore Machine)

-- For the sequence 1010

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity seq_det is
    Port ( input_pin : in  STD_LOGIC;
           clock_pulse : in  STD_LOGIC;
           clear_pin : in  STD_LOGIC;
           output_pin : out  STD_LOGIC);
end seq_det;

architecture Behavioral of seq_det is
type state is (a,b,c,d,e);
signal present_state,next_state: state;
begin

clk_process: Process(clock_pulse)
begin
if clear_pin='0' then
present_state<=a;
else
if clock_pulse='1' and clock_pulse' event then
present_state<=next_state;
end if;
end if;
end process;

state_process: Process(present_state,input_pin)
begin
case present_state is
when a=>
if input_pin='1' then
next_state<=b;
else
next_state<=a;
end if;
when b=>
if input_pin='0' then
next_state<=c;
else
next_state<=b;
end if;
when c=>
if input_pin='1' then
next_state<=d;
else
next_state<=a;
end if;
when d=>
if input_pin='0' then
next_state<=e;
else
next_state<=b;
end if;
when e=>
if input_pin='0' then
next_state<=a;
else
next_state<=d;
end if;
end case;
end process;

output_process: Process(present_state)
begin
if present_state=e then
output_pin<='1';
else
output_pin<='0';
end if;
end process;

end Behavioral;