ram_ls.vhd

红绿灯的控制

-----------------------------------------------------------------------------
--
--      The following information has been generated by Exemplar Logic
--      and may be freely distributed and modified.
--
--      Design name : ram
--
--      Purpose : This design is a generic ram. Both the address and data 
--                have programmable widths. This ram can be used in place 
--                of technology specific rams.
--	-- download from: www.pld.com.cn & www.fpga.com.cn 
----------------------------------------------------------------------------
Library IEEE ;
use IEEE.std_logic_1164.all ;
use IEEE.std_logic_arith.all ;
use IEEE.std_logic_unsigned.all ;

entity ram is
   generic (data_width     : natural := 8 ;
            address_width  : natural := 8);
   port (
         data_in  : in  UNSIGNED(data_width - 1 downto 0) ;
         address  : in  UNSIGNED(address_width - 1 downto 0) ;
         we       : in  std_logic ;
         data_out : out UNSIGNED(data_width - 1 downto 0)
        );
end ram ;

architecture rtl of ram is
  type mem_type is array (2**address_width downto 0) of
                      UNSIGNED(data_width - 1 downto 0) ;
  signal mem : mem_type ;
  begin
    I0 : process (we,address,mem,data_in)
      begin
        if (we = '1') then
          mem(conv_integer(address)) <= data_in ;
        end if ;
        data_out <= mem(conv_integer(address)) ;
    end process ;
end RTL ;