能实现连续脉冲还手动脉冲计数，在实验板上实验过~！ 程序很简单，相应的注释就没加了，     library ieee;use ieee.std_logic_1164.all;use ieee.std_logic_unsigned.all;entity counter is port(rst,clk,clk1: in std_logic;   con : std_logic_vector(1 downto 0);   output : out std_logic_vector(7 downto 0));   end entity counter; architecture behave of counter is begin  process(rst,con,clk,clk1)  variable temp1 : std_logic_vector(7 downto 0);  begin  if rst = '1' then temp1 := (others => '0');  else   case con is   when "10" =>--手动顺记数    if clk'event and (clk='1') and (clk'last_value='0') then       if temp1 < 255 then temp1 := temp1 + 1;              else temp1 := (others => '0');              end if;    end if;   when "11"  =>--手动逆记数    if clk'event and (clk='1') and (clk'last_value='0') then          if temp1 > 0 then temp1 := temp1 - 1;          else temp1 := (others => '1');                      end if;     end if;   when "00" =>--连续顺记数    if clk1'event and (clk1='1') and (clk1'last_value='0') then       if temp1 < 255 then temp1 := temp1 + 1;              else temp1 := (others => '0');              end if;    end if;   when "01" =>--连续逆记数    if clk1'event and (clk1='1') and (clk1'last_value='0') then          if temp1 > 0 then temp1 := temp1 - 1;          else temp1 := (others => '1');                      end if;    end if;   end case;  end if; output <= temp1; end process;end architecture behave;

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