vhdl.txt

高质量的VHDL代码乒乓处理FIFO缓存

 library ieee;
      use ieee.std_logic_1164.all;
      entity fifo is
       generic( w: integer :=8; k: integer :=8 );
       port (clk,reset,wr,rd :in std_logic;
              din :in std_logic_vector( k-1 downto 0);
             dout :out std_logic_vector( k-1 downto 0);
             full,empty :out std_logic);
      end fifo;
      architecture fifo_arch of fifo is
        type memory is array (0 to w-1) of std_logic_vector( k-1 downto 0);
        signal ram:memory;
        signal wp,rp: integer range 0 to w-1;
        signal in_full,in_empty:std_logic;
      begin
      process(clk)
        begin
        if rising_edge(clk) then
           if (wr='0' and in_full='0') then
               ram(wp)<=din;
           end if;
        end if;
      end process;
      process(clk,reset)
        begin
        if (reset='1') then
           wp<=0;
        elsif rising_edge(clk) then
           if (wr='0' and in_full='0') then
               if(wp=w-1) then
                  wp<=0;
                 else wp<=wp+1;
                end if;
           end if;
         end if;
      end process;
      process(clk,reset)
        begin
        if (reset='1') then
           rp<=w-1;
        elsif rising_edge(clk) then
           if (rd='0' and in_empty='0') then
               if(rp=w-1) then
                  rp<=0;
                 else rp<=rp+1;
                end if;
           end if;
         end if;
      end process;
      process(clk,reset)
        begin
        if (reset='1') then
           in_empty<='1';
          elsif rising_edge(clk) then
           if ((rp=wp-2 or (rp=w-1 and wp=1) or (rp=w-2 and wp=0)) and (rd='0' 
      and wr='1'))then
                 in_empty<='1';
             elsif (in_empty='1' and wr='0') then
                 in_empty<='0';
           end if;
         end if;
      end process;
      process(clk,reset)
        begin
         if (reset='1') then
            in_full<='0';
          elsif rising_edge(clk) then
            if (rp=wp and wr='0' and rd='1') then
               in_full<='1';
             elsif (in_full='1' and rd='0') then
               in_full<='0'; 
             end if;
          end if;
      end process;
      full<=in_full;
      empty<=in_empty;
      dout<=ram(rp) when rd='0' ;
      end fifo_arch;