mulf2m.vhd

来自「椭圆曲线加密算法中的乘法器的生成」· VHDL 代码 · 共 72 行

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity mulf2m is
   generic(size:integer:=4);
      port(
           clk,rst,en:in std_logic;
           a,b:in std_logic_vector(size downto 0);
           fx:in std_logic_vector(size downto 0);
           done:buffer std_logic;
           c:buffer std_logic_vector(size downto 0));
end mulf2m;
architecture pipomul of mulf2m is
  type multistate is(idle,working);
      signal state:multistate;
      signal buff_a:std_logic_vector(size downto 0);
      signal buff_b:std_logic_vector(size downto 0);
      signal srlcount:integer range 0 to size;
      signal carry_bit:std_logic;
      signal present_a:std_logic;
   begin
     reg_shift:process(rst,clk)
       begin
         if rst='1' then
             state<=idle;
             done<='0';
             c<=(others=>'0');
        elsif(clk'event and clk='1')then
          case state is
             when idle=>
               if en='1' then
                 srlcount<=0;
                 buff_a<=a;
                 present_a<=a(0);
                 buff_b<=b;
                 carry_bit<=b(size-1);
                 done<='0';
                 c<=(others=>'0');
                 state<=working;
             end if;
   when working=>
         if carry_bit='0' then
           for i in size-2 downto 0 loop
               buff_b(i+1)<=buff_b(i);
              end loop;
           buff_b(0)<='0';
       else
          for i in size-2 downto 0 loop
              buff_b(i+1)<=buff_b(i) xor fx(i+1);
               end loop;
            buff_b(0)<=fx(0);
         end if;
      carry_bit<=buff_b(size-2);
      present_a<=buff_a(1);
        for j in 0 to size-2 loop
                buff_a(j)<=buff_a(j+1);
            end loop;
         buff_a(size-1)<='0';
          srlcount<=srlcount+1;
            if present_a='1' then
                 c<=c xor buff_b;
             end if;
        if srlcount=size-1 then
           done<='1';
           state<=idle;
            end if;
       when others=>
         state<=idle;
       end case;
     end if;
end process;
end pipomul;