bjq.vhd

很多仪器都输出同步时钟

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity bjq is
port(                      ce,rd:in std_logic;
                              ea:in std_logic_vector(15 downto 0);
                              ed:inout std_logic_vector(15 downto 0);
   ren1,ren2,ren3,ren4,ren0,ren5:inout std_logic:='0'; 
                        dfftodsp0:in std_logic_vector(15 downto 0);
                        dfftodsp1:in std_logic_vector(15 downto 0);
                        dfftodsp2:in std_logic_vector(15 downto 0);
                        dfftodsp3:in std_logic_vector(15 downto 0);
                        dfftodsp4:in std_logic_vector(15 downto 0));
end bjq;
architecture bhv of bjq is
signal s:std_logic_vector(4 downto 0);
begin 
s<=ren4&ren3&ren2&ren1&ren0;
a: process(ea)
         begin
                 if(ce='0')then

                     if(rd='0')then
                         --case ea is
                         --   when "0100000000000000"=>ren0<='1';
                         --   when "0100000000000001"=>ren1<='1';
                         --  when "0100000000000010"=>ren2<='1';
                         --   when "0100000000000011"=>ren3<='1';
                         --   when "0100000000000100"=>ren4<='1';
                         --   when OTHERS=>ren5<='0';
                         --end case;
                           -- ed<="1010010110100101";
                         --   if(ren0='1')then
                         --      ed<=dfftodsp0;
                         --   elsif(ren0='1')then
                         --      ed<=dfftodsp1;
                         --   elsif(ren0='1')then
                         --      ed<=dfftodsp2;
                         --   elsif(ren0='1')then
                          --     ed<=dfftodsp3;
                         --   elsif(ren0='1')then
                         --     ed<=dfftodsp4;
                          --  else
                          --     ed<=(others=>'Z');
                          --  end if;
                        
                      if(ea="1000000000000000")then
                             ren0<='1';
                      elsif(ea="1000000000000001")then
                             ren1<='1';
                      elsif(ea="1000000000000010")then
                             ren2<='1';
                      elsif(ea="1000000000000011")then
                             ren3<='1';
                      elsif(ea="1000000000000100")then
                             ren4<='1';
                      else 
                             ren5<='0';
                      end if;
                         
                         case s is
                            when"00001"=>ed<=dfftodsp0;
                            when"00010"=>ed<=dfftodsp1;
                            when"00100"=>ed<=dfftodsp2;
                            when"01000"=>ed<=dfftodsp3;
                            when"10000"=>ed<=dfftodsp4;
                            when others=>ed<=(others=>'Z');
                          end case;
                      
                      end if;
                  end if;
               
end process;
 

end bhv;