control_unit.vhd

实现简单CPU功能的源码

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

ENTITY control_unit IS
  PORT
	(  clk	       :  in	std_logic;
       flag        :  in    std_logic; --ACC is 0 or not
       cs          :  in 	std_logic_vector(31 downto 0);
	   IR_out      :  in    std_logic_vector(7 downto 0); 
       address_out :  out   std_logic_vector(7 downto 0)
    );
END control_unit ;

ARCHITECTURE behave OF control_unit IS
BEGIN
 PROCESS (clk)
   variable address : std_logic_vector(7 downto 0);
   BEGIN										
     IF clk'event and clk = '1' THEN
        if cs(4)='1' then  --Increament car
			 address:=address+1; 
        elsif cs(5)='1' then  --reset car
               address:="00000000";
        elsif cs(6)='1' then  --load
           case IR_out is
              when "00000001"=>       --store
                 address:="00010000"; 
              when "00000010"=>       --load
                 address:="00010100"; 
              when "00000011"=>       --add
                 address:="00011001"; 
              when "00000100"=>       --sub
                 address:="00011110"; 
              when "00001010"=>       --and
                 address:="00000110";
              when "00001011"=>       --or
                 address:="00001000";
              when "00001100"=>       --not
                 address:="00111001";
              when "00001101"=>       --shiftr
                 address:="00111110";
              when "00001110"=>       --shilfl
                 address:="01000100";
              when "00001000"=>       --mpy
                 address:="00101001";
              when "00000101"=>       --jmpegz
                 if flag='0' then
                   address:="00100011";
                 else address:="00100101"; 
                 end if;
              when "00000111"=>       --halt
                 address:="00100111"; 
            when others=>null;      
           end case;
        end if;
        address_out<=address;
     END IF;
   END PROCESS;
 END behave;