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--------------------------------------------------------------------

-- Company       : XESS Corp.

-- Engineer      : Dave Vanden Bout

-- Creation Date : 05/17/2005

-- Copyright     : 2005, XESS Corp

-- Tool Versions : WebPACK 6.3.03i

--

-- Description:

--    Customizes the generic SDRAM controller module for the XSA Board.

--

-- Revision:

--    1.1.0

--

-- Additional Comments:

--    1.1.0:

--        Added CLK_DIV generic parameter to allow stepping-down the clock frequency.

--        Added MULTIPLE_ACTIVE_ROWS generic parameter to enable/disable keeping an active row in each bank.

--    1.0.0:

--        Initial release.

--

-- License:

--    This code can be freely distributed and modified as long as

--    this header is not removed.

--------------------------------------------------------------------

library IEEE, UNISIM;

use IEEE.std_logic_1164.all;

use IEEE.numeric_std.all;

use UNISIM.VComponents.all;

use WORK.common.all;

use WORK.sdram.all;

package XSASDRAM is

  component XSASDRAMCntl

    generic(

      FREQ                 :     natural := 50_000;  -- operating frequency in KHz

      CLK_DIV              :     real    := 1.0;  -- divisor for FREQ (can only be 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 8.0 or 16.0)

      PIPE_EN              :     boolean := true;  -- if true, enable pipelined read operations

      MAX_NOP              :     natural := 10000;  -- number of NOPs before entering self-refresh

      MULTIPLE_ACTIVE_ROWS :     boolean := true;  -- if true, allow an active row in each bank

      DATA_WIDTH           :     natural := 16;  -- host & SDRAM data width

      NROWS                :     natural := 4096;  -- number of rows in SDRAM array

      NCOLS                :     natural := 512;  -- number of columns in SDRAM array

      HADDR_WIDTH          :     natural := 23;  -- host-side address width

      SADDR_WIDTH          :     natural := 12  -- SDRAM-side address width

      );

    port(

      -- host side

      clk                  : in  std_logic;  -- master clock

      bufclk               : out std_logic;  -- buffered master clock

      clk1x                : out std_logic;  -- host clock sync'ed to master clock (and divided if CLK_DIV>1)

      clk2x                : out std_logic;  -- double-speed host clock

      lock                 : out std_logic;  -- true when host clock is locked to master clock

      rst                  : in  std_logic;  -- reset

      rd                   : in  std_logic;  -- initiate read operation

      wr                   : in  std_logic;  -- initiate write operation

      earlyOpBegun         : out std_logic;  -- read/write/self-refresh op begun     (async)

      opBegun              : out std_logic;  -- read/write/self-refresh op begun (clocked)

      rdPending            : out std_logic;  -- read operation(s) are still in the pipeline

      done                 : out std_logic;  -- read or write operation is done

      rdDone               : out std_logic;  -- read done and data is available

      hAddr                : in  std_logic_vector(HADDR_WIDTH-1 downto 0);  -- address from host

      hDIn                 : in  std_logic_vector(DATA_WIDTH-1 downto 0);  -- data from host

      hDOut                : out std_logic_vector(DATA_WIDTH-1 downto 0);  -- data to host

      status               : out std_logic_vector(3 downto 0);  -- diagnostic status of the FSM         

      -- SDRAM side

      sclkfb : in    std_logic;         -- clock from SDRAM after PCB delays

      sclk   : out   std_logic;         -- SDRAM clock sync'ed to master clock

      cke    : out   std_logic;         -- clock-enable to SDRAM

      cs_n   : out   std_logic;         -- chip-select to SDRAM

      ras_n  : out   std_logic;         -- SDRAM row address strobe

      cas_n  : out   std_logic;         -- SDRAM column address strobe

      we_n   : out   std_logic;         -- SDRAM write enable

      ba     : out   std_logic_vector(1 downto 0);  -- SDRAM bank address bits

      sAddr  : out   std_logic_vector(SADDR_WIDTH-1 downto 0);  -- SDRAM row/column address

      sData  : inout std_logic_vector(DATA_WIDTH-1 downto 0);  -- SDRAM in/out databus

      dqmh   : out   std_logic;         -- high databits I/O mask

      dqml   : out   std_logic          -- low databits I/O mask

      );

  end component;

end package XSASDRAM;

library IEEE, UNISIM;

use IEEE.std_logic_1164.all;

use IEEE.numeric_std.all;

use UNISIM.VComponents.all;

use WORK.common.all;

use WORK.sdram.all;

entity XSASDRAMCntl is

  generic(

    FREQ                 :     natural := 50_000;  -- operating frequency in KHz

    CLK_DIV              :     real    := 1.0;  -- divisor for FREQ (can only be 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 8.0 or 16.0)

    PIPE_EN              :     boolean := true;  -- if true, enable pipelined read operations

    MAX_NOP              :     natural := 10000;  -- number of NOPs before entering self-refresh

    MULTIPLE_ACTIVE_ROWS :     boolean := true;  -- if true, allow an active row in each bank

    DATA_WIDTH           :     natural := 16;  -- host & SDRAM data width

    NROWS                :     natural := 4096;  -- number of rows in SDRAM array

    NCOLS                :     natural := 512;  -- number of columns in SDRAM array

    HADDR_WIDTH          :     natural := 23;  -- host-side address width

    SADDR_WIDTH          :     natural := 12  -- SDRAM-side address width

    );

  port(

    -- host side

    clk                  : in  std_logic;  -- master clock

    bufclk               : out std_logic;  -- buffered master clock

    clk1x                : out std_logic;  -- host clock sync'ed to master clock (and divided if CLK_DIV>1)

    clk2x                : out std_logic;  -- double-speed host clock

    lock                 : out std_logic;  -- true when host clock is locked to master clock

    rst                  : in  std_logic;  -- reset

    rd                   : in  std_logic;  -- initiate read operation

    wr                   : in  std_logic;  -- initiate write operation

    earlyOpBegun         : out std_logic;  -- read/write/self-refresh op begun     (async)

    opBegun              : out std_logic;  -- read/write/self-refresh op begun (clocked)

    rdPending            : out std_logic;  -- read operation(s) are still in the pipeline

    done                 : out std_logic;  -- read or write operation is done

    rdDone               : out std_logic;  -- read done and data is available

    hAddr                : in  std_logic_vector(HADDR_WIDTH-1 downto 0);  -- address from host

    hDIn                 : in  std_logic_vector(DATA_WIDTH-1 downto 0);  -- data from host

    hDOut                : out std_logic_vector(DATA_WIDTH-1 downto 0);  -- data to host

    status               : out std_logic_vector(3 downto 0);  -- diagnostic status of the FSM         

    -- SDRAM side

    sclkfb : in    std_logic;           -- clock from SDRAM after PCB delays

    sclk   : out   std_logic;           -- SDRAM clock sync'ed to master clock

    cke    : out   std_logic;           -- clock-enable to SDRAM

    cs_n   : out   std_logic;           -- chip-select to SDRAM

    ras_n  : out   std_logic;           -- SDRAM row address strobe

    cas_n  : out   std_logic;           -- SDRAM column address strobe

    we_n   : out   std_logic;           -- SDRAM write enable

    ba     : out   std_logic_vector(1 downto 0);  -- SDRAM bank address bits

    sAddr  : out   std_logic_vector(SADDR_WIDTH-1 downto 0);  -- SDRAM row/column address

    sData  : inout std_logic_vector(DATA_WIDTH-1 downto 0);  -- SDRAM in/out databus

    dqmh   : out   std_logic;           -- high databits I/O mask

    dqml   : out   std_logic            -- low databits I/O mask

    );

end XSASDRAMCntl;

architecture arch of XSASDRAMCntl is

  -- The SDRAM controller and external SDRAM chip will clock on the same edge

  -- if the frequency and divided frequency are both greater than the minimum DLL lock frequency.

  -- Otherwise the DLLs cannot be used so the SDRAM controller and external SDRAM clock on opposite edges

  -- to try and mitigate the clock skew between the internal FPGA logic and the external SDRAM.

  constant MIN_LOCK_FREQ : real    := 25_000.0;

  constant IN_PHASE      : boolean := real(FREQ)/CLK_DIV >= MIN_LOCK_FREQ;

  -- Calculate the frequency of the clock for the SDRAM.

  constant SDRAM_FREQ    : natural := int_select(IN_PHASE, (FREQ*integer(2.0*CLK_DIV))/2, FREQ);

  -- Compute the CLKDV_DIVIDE generic paramter for the DLL modules.  It defaults to 2 when CLK_DIV=1

  -- because the DLL does not support a divisor of 1 on the CLKDV output.  We use the CLK0 output

  -- when CLK_DIV=1 so we don't care what is output on thr CLK_DIV output of the DLL.

  constant CLKDV_DIVIDE  : real    := real_select(CLK_DIV = 1.0, 2.0, CLK_DIV);

  signal int_clkin,                     -- signals for internal logic clock DLL

    int_clk1x, int_clk1x_b,

    int_clk2x, int_clk2x_b,

    int_clkdv, int_clkdv_b              : std_logic;

  signal ext_clkin, sclkfb_b, ext_clk1x : std_logic;  -- signals for external logic clock DLL

  signal dllext_rst, dllext_rst_n       : std_logic;  -- external DLL reset signal

  signal clk_i                          : std_logic;  -- clock for SDRAM controller logic

  signal int_lock, ext_lock, lock_i     : std_logic;  -- DLL lock signals

  -- bus for holding output data from SDRAM

  signal sDOut   : std_logic_vector(sData'range);

  signal sDOutEn : std_logic;

begin

  -----------------------------------------------------------

  -- setup the DLLs for clock generation 

  -----------------------------------------------------------

  -- master clock must come from a dedicated clock pin

  clkin : IBUFG port map (I => clk, O => int_clkin);

  -- The external DLL is driven from the same source as the internal DLL

  -- if the clock divisor is 1.  If CLK_DIV is greater than 1, then the external DLL 

  -- is driven by the divided clock from the internal DLL.  Otherwise, the SDRAM will be

  -- clocked on the opposite edge if the internal and external logic are not in-phase.

  ext_clkin <= int_clkin    when (IN_PHASE and (CLK_DIV = 1.0)) else

                int_clkdv_b when (IN_PHASE and (CLK_DIV/=1.0))  else

                not int_clkin;

  -- Generate the DLLs for sync'ing the clocks as long as the clocks

  -- have a frequency high enough for the DLLs to lock

  gen_dlls : if IN_PHASE generate

    -- generate an internal clock sync'ed to the master clock

    dllint : CLKDLL

      generic map(

        CLKDV_DIVIDE => CLKDV_DIVIDE

        )

      port map(

        CLKIN        => int_clkin,

        CLKFB        => int_clk1x_b,

        CLK0         => int_clk1x,

        RST          => ZERO,

        CLK90        => open,

        CLK180       => open,

        CLK270       => open,

        CLK2X        => int_clk2x,

        CLKDV        => int_clkdv,

        LOCKED       => int_lock

        );

    -- sync'ed single, doubled and divided clocks for use by internal logic

    int_clk1x_buf : BUFG port map(I => int_clk1x, O => int_clk1x_b);

    int_clk2x_buf : BUFG port map(I => int_clk2x, O => int_clk2x_b);

    int_clkdv_buf : BUFG port map(I => int_clkdv, O => int_clkdv_b);

    -- The external DLL is held in a reset state until the internal DLL locks.

    -- Then the external DLL reset is released after a delay set by this shift register.

    -- This keeps the external DLL from locking onto the internal DLL clock signal

    -- until it is stable.

    SRL16_inst : SRL16

      generic map (

        INIT => X"0000"

        )

      port map (

        CLK  => clk_i,

        A0   => '1',

        A1   => '1',

        A2   => '1',

        A3   => '1',

        D    => int_lock,

        Q    => dllext_rst_n

        );

    dllext_rst <= not dllext_rst when CLK_DIV/=1.0 else ZERO;

    -- generate an external SDRAM clock sync'ed to the master clock

    sclkfb_buf : IBUFG port map(I => sclkfb, O => sclkfb_b);  -- SDRAM clock with PCB delays

    dllext     : CLKDLL port map(

      CLKIN                       => ext_clkin,  -- this is either the master clock or the divided clock from the internal DLL

      CLKFB                       => sclkfb_b,

      CLK0                        => ext_clk1x,

      RST                         => dllext_rst,

      CLK90                       => open,

      CLK180                      => open,

      CLK270                      => open,

      CLK2X                       => open,

      CLKDV                       => open,

      LOCKED                      => ext_lock

      );

  end generate;

  -- The buffered clock is just a buffered version of the master clock.

  bufclk <= int_clkin;

  -- The host-side clock comes from the CLK0 output of the internal DLL if the clock divisor is 1.

  -- Otherwise it comes from the CLKDV output if the clock divisor is greater than 1.

  -- Otherwise it is just a copy of the master clock if the DLLs aren't being used.

  clk_i  <= int_clk1x_b when (IN_PHASE and (CLK_DIV = 1.0)) else

            int_clkdv_b when (IN_PHASE and (CLK_DIV/=1.0))  else

            int_clkin;

  clk1x  <= clk_i;                      -- This is the output of the host-side clock

  clk2x  <= int_clk2x_b when IN_PHASE                       else int_clkin;  -- this is the doubled master clock

  sclk   <= ext_clk1x   when IN_PHASE                       else ext_clkin;  -- this is the clock for the external SDRAM

  -- indicate the lock status of the internal and external DLL

  lock_i <= int_lock and ext_lock when IN_PHASE else YES;

  lock   <= lock_i;                     -- lock signal for the host logic

  -- SDRAM memory controller module

  u1 : sdramCntl

    generic map(

      FREQ                 => SDRAM_FREQ,

      IN_PHASE             => IN_PHASE,

      PIPE_EN              => PIPE_EN,

      MAX_NOP              => MAX_NOP,

      MULTIPLE_ACTIVE_ROWS => MULTIPLE_ACTIVE_ROWS,

      DATA_WIDTH           => DATA_WIDTH,

      NROWS                => NROWS,

      NCOLS                => NCOLS,

      HADDR_WIDTH          => HADDR_WIDTH,

      SADDR_WIDTH          => SADDR_WIDTH

      )

    port map(

      clk                  => clk_i,    -- master clock from external clock source (unbuffered)

      lock                 => lock_i,   -- valid synchronized clocks indicator

      rst                  => rst,      -- reset

      rd                   => rd,       -- host-side SDRAM read control from memory tester

      wr                   => wr,       -- host-side SDRAM write control from memory tester

      rdPending            => rdPending,

      opBegun              => opBegun,  -- SDRAM memory read/write done indicator

      earlyOpBegun         => earlyOpBegun,  -- SDRAM memory read/write done indicator

      rdDone               => rdDone,   -- SDRAM memory read/write done indicator

      done                 => done,

      hAddr                => hAddr,    -- host-side address from memory tester

      hDIn                 => hDIn,     -- test data pattern from memory tester

      hDOut                => hDOut,    -- SDRAM data output to memory tester

      status               => status,   -- SDRAM controller state (for diagnostics)

      cke                  => cke,      -- SDRAM clock enable

      ce_n                 => cs_n,     -- SDRAM chip-select

      ras_n                => ras_n,    -- SDRAM RAS

      cas_n                => cas_n,    -- SDRAM CAS

      we_n                 => we_n,     -- SDRAM write-enable

      ba                   => ba,       -- SDRAM bank address

      sAddr                => sAddr,    -- SDRAM address

      sDIn                 => sData,    -- input data from SDRAM

      sDOut                => sDOut,    -- output data to SDRAM

      sDOutEn              => sDOutEn,  -- enable drivers to send data to SDRAM

      dqmh                 => dqmh,     -- SDRAM DQMH

      dqml                 => dqml      -- SDRAM DQML

      );

  sData <= sDOut when sDOutEn = YES else (others => 'Z');

end arch;