Subversion Repositories sdram_controller

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-- Company: OPL Aerospatiale AG

-- Engineer: Owen Lynn <lynn0p@hotmail.com>

-- 

-- Create Date:    16:30:07 09/03/2009 

-- Design Name: 

-- Module Name:    sdram_reader - impl 

-- Project Name: 

-- Target Devices: 

-- Tool versions: 

-- Description: Logic to capture data from the chip after issuing a read command.

--

-- Dependencies: 

--

-- Revision: 

-- Revision 0.01 - File Created

-- Additional Comments: 

--  Copyright (c) 2009 Owen Lynn <lynn0p@hotmail.com>

--  Released under the GNU Lesser General Public License, Version 3

--

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library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.STD_LOGIC_ARITH.ALL;

use IEEE.STD_LOGIC_UNSIGNED.ALL;

---- Uncomment the following library declaration if instantiating

---- any Xilinx primitives in this code.

--library UNISIM;

--use UNISIM.VComponents.all;

-- I strongly suggest you run this in the post-PAR simulator first and then start making changes to it

--  after looking at what goes on at the post-PAR level. Don't say I didn't warn you. 

-- Why didn't I use the IDDR2 primitives? Map'nPack keeps bitching about how it won't fit into the IOBs

--  with the ODDR2 primitives. I decided the ODDR2s were more important to keep.

-- I'm just capturing the front side of the burst, and letting the back side of the burst fall on the

--  floor. If you want to support both sides of the 2 burst or bigger bursts, you'll need to rework this.

entity sdram_reader is

        port(

                clk000 : in std_logic;

                clk270 : in std_logic;

                rst    : in std_logic;

                dq     : in std_logic_vector(15 downto 0);

                data0  : out std_logic_vector(7 downto 0);

                data1  : out std_logic_vector(7 downto 0)

        );

end sdram_reader;

architecture impl of sdram_reader is

        type FSM0_STATES is ( FSM0_START, FSM0_WAIT0, FSM0_CAPTURE, FSM0_END );

        signal fsm0_state : FSM0_STATES;

        signal reg0 : std_logic_vector(7 downto 0);

        signal reg1 : std_logic_vector(7 downto 0);

begin

        data0 <= reg0;

        data1 <= reg1;

        process(clk270,rst)

        begin

                if (rst = '1') then

                        fsm0_state <= FSM0_START;

                elsif (rising_edge(clk270)) then

                        case fsm0_state is

                                when FSM0_START =>

                                        fsm0_state <= FSM0_WAIT0;

                                when FSM0_WAIT0 =>

                                        fsm0_state <= FSM0_CAPTURE;

                                when FSM0_CAPTURE =>

                                        reg0 <= dq(7 downto 0);

                                        reg1 <= dq(15 downto 8);

                                        fsm0_state <= FSM0_END;

                                when others =>

                                        fsm0_state <= fsm0_state;

                        end case;

                end if;

        end process;

end impl;