eda 实验考试答案 石化学院

2

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_unsigned.all;

entity twelvecounter is

port (cp: in std_logic;

LD,R:in std_logic;

A:in std_logic_vector (4 downto 0);

Q:buffer std_logic_vector(4 downto 0);

co:out std_logic);

end twelvecounter ;

architecture one of twelvecounter is

begin

co<='1' when(Q="10001") else'0'; process(cp,R)

begin

if R='0' then

Q<="00000";

elsif(cp'event and cp='1') then

if LD='0' then Q<=A;

elsif Q="10001" then Q <= "00000" ;

else Q <= Q + 1;

end if;

end if;

end process;

end one;