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顯示結果：
Library ieee;
use ieee.std_logic_1164.all;
entity zhuangt is
Port(f10MHz:in bit;
input,reset:in bit;
output:out integer range 0 to 4);
end;
architecture dd of zhuangt is
type state_Type is (s1,s0,s2,s3);
signal state :state_Type;
signal cnt:integer range 0 to 10000000;
signal clk:std_logic;
begin
process(f10MHz)
begin
if f10MHz'event and f10MHz='1' then
if cnt=4999999 then cnt<=0;clk<=not clk;
else cnt<=cnt+1;
end if;
end if;
end process;
Process(clk,reset)
begin
if reset='1' then state<=s0;
elsif clk'event and clk='1' then
case state is
when s0=> state <=s1;
when s1=>
if input='1' then state <=s2;
else state<=s1;
end if;
when s2=>
if input='0' then state <=s3;
else state<=s2;
end if;
when s3=>state<=s0;
end case;
end if;
end process;
process(state,input)
begin
case state is
when s0=>
if input='1' then output<=0;
else output<=4;
end if;
when s1=>
if input='1' then output<=1;
else output<=4;
end if;
when s2=>
if input='1' then output<=2;
else output<=4;
end if;
when s3=>
if input='1' then output<=3;
else output<=4;
end if;
end case;
end process;
end;
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