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//   ____  ____

//  /   /\/   /

// /___/  \  /    Vendor: Xilinx

// \   \   \/     Version: 3.0

//  \   \         Application: MIG

//  /   /         Filename: ddr2_phy_write.v

// /___/   /\     Date Last Modified: $Date: 2008/12/23 14:26:00 $

// \   \  /  \    Date Created: Thu Aug 24 2006

//  \___\/\___\

//

//Device: Virtex-5

//Design Name: DDR2

//Purpose:

//Reference:

//   Handles delaying various write control signals appropriately depending

//   on CAS latency, additive latency, etc. Also splits the data and mask in

//   rise and fall buses.

//Revision History:

//   Rev 1.1 - For Dual Rank parts support ODT logic corrected. PK. 08/05/08

//*****************************************************************************

`timescale 1ns/1ps

module ddr2_phy_write #

  (

   // Following parameters are for 72-bit RDIMM design (for ML561 Reference

   // board design). Actual values may be different. Actual parameters values

   // are passed from design top module ddr2_mig module. Please refer to

   // the ddr2_mig module for actual values.

   parameter DQ_WIDTH      = 72,

   parameter CS_NUM        = 1,

   parameter ADDITIVE_LAT  = 0,

   parameter CAS_LAT       = 5,

   parameter ECC_ENABLE    = 0,

   parameter ODT_TYPE      = 1,

   parameter REG_ENABLE    = 1,

   parameter DDR_TYPE      = 1

   )

  (

   input                       clk0,

   input                       clk90,

   input                       rst90,

   input [(2*DQ_WIDTH)-1:0]    wdf_data,

   input [(2*DQ_WIDTH/8)-1:0]  wdf_mask_data,

   input                       ctrl_wren,

   input                       phy_init_wren,

   input                       phy_init_data_sel,

   output reg                  dm_ce,

   output reg [1:0]            dq_oe_n,

   output reg                  dqs_oe_n ,

   output reg                  dqs_rst_n ,

   output                      wdf_rden,

   output reg [CS_NUM-1:0]     odt ,

   output [DQ_WIDTH-1:0]       wr_data_rise,

   output [DQ_WIDTH-1:0]       wr_data_fall,

   output [(DQ_WIDTH/8)-1:0]   mask_data_rise,

   output [(DQ_WIDTH/8)-1:0]   mask_data_fall

   );

  localparam   MASK_WIDTH               = DQ_WIDTH/8;

  localparam   DDR1                     = 0;

  localparam   DDR2                     = 1;

  localparam   DDR3                     = 2;

  // (MIN,MAX) value of WR_LATENCY for DDR1:

  //   REG_ENABLE   = (0,1)

  //   ECC_ENABLE   = (0,1)

  //   Write latency = 1

  //   Total: (1,3)

  // (MIN,MAX) value of WR_LATENCY for DDR2:

  //   REG_ENABLE   = (0,1)

  //   ECC_ENABLE   = (0,1)

  //   Write latency = ADDITIVE_CAS + CAS_LAT - 1 = (0,4) + (3,5) - 1 = (2,8)

  //     ADDITIVE_LAT = (0,4) (JEDEC79-2B)

  //     CAS_LAT      = (3,5) (JEDEC79-2B)

  //   Total: (2,10)

  localparam WR_LATENCY = (DDR_TYPE == DDR3) ?

             (ADDITIVE_LAT + (CAS_LAT) + REG_ENABLE ) :

             (DDR_TYPE == DDR2) ?

             (ADDITIVE_LAT + (CAS_LAT-1) + REG_ENABLE ) :

             (1 + REG_ENABLE );

  // NOTE that ODT timing does not need to be delayed for registered

  // DIMM case, since like other control/address signals, it gets

  // delayed by one clock cycle at the DIMM

  localparam ODT_WR_LATENCY = WR_LATENCY - REG_ENABLE;

  wire                     dm_ce_0;

  reg                      dm_ce_r;

  wire [1:0]               dq_oe_0;

  reg [1:0]                dq_oe_n_90_r1;

  reg [1:0]                dq_oe_270;

  wire                     dqs_oe_0;

  reg                      dqs_oe_270;

  reg                      dqs_oe_n_180_r1;

  wire                     dqs_rst_0;

  reg                      dqs_rst_n_180_r1;

  reg                      dqs_rst_270;

  reg                      ecc_dm_error_r;

  reg                      ecc_dm_error_r1;

  reg [(DQ_WIDTH-1):0]     init_data_f;

  reg [(DQ_WIDTH-1):0]     init_data_r;

  reg [3:0]                init_wdf_cnt_r;

  wire                     odt_0;

  reg                      rst90_r /* synthesis syn_maxfan = 10 */;

  reg [10:0]               wr_stages ;

  reg [(2*DQ_WIDTH)-1:0]   wdf_data_r;

  reg [(2*DQ_WIDTH/8)-1:0] wdf_mask_r;

  wire [(2*DQ_WIDTH/8)-1:0] wdf_ecc_mask;

  reg [(2*DQ_WIDTH/8)-1:0] wdf_mask_r1;

  wire                     wdf_rden_0;

  reg                      calib_rden_90_r;

  reg                      wdf_rden_90_r;

  reg                      wdf_rden_90_r1;

  reg                      wdf_rden_270;

  always @(posedge clk90)

      rst90_r <= rst90;

  //***************************************************************************

  // Analysis of additional pipeline delays:

  //   1. dq_oe (DQ 3-state): 1 CLK90 cyc in IOB 3-state FF

  //   2. dqs_oe (DQS 3-state): 1 CLK180 cyc in IOB 3-state FF

  //   3. dqs_rst (DQS output value reset): 1 CLK180 cyc in FF + 1 CLK180 cyc

  //      in IOB DDR

  //   4. odt (ODT control): 1 CLK0 cyc in IOB FF

  //   5. write data (output two cyc after wdf_rden - output of RAMB_FIFO w/

  //      output register enabled): 2 CLK90 cyc in OSERDES

  //***************************************************************************

  // DQS 3-state must be asserted one extra clock cycle due b/c of write

  // pre- and post-amble (extra half clock cycle for each)

  assign dqs_oe_0 = wr_stages[WR_LATENCY-1] | wr_stages[WR_LATENCY-2];

  // same goes for ODT, need to handle both pre- and post-amble (generate

  // ODT only for DDR2)

  // ODT generation for DDR2 based on write latency. The MIN write

  // latency is 2. Based on the write latency ODT is asserted.

  generate

    if ((DDR_TYPE != DDR1) && (ODT_TYPE > 0))begin: gen_odt_ddr2

       if(ODT_WR_LATENCY > 2)

         assign odt_0 =

                   wr_stages[ODT_WR_LATENCY-1] |

                   wr_stages[ODT_WR_LATENCY-2] |

                   wr_stages[ODT_WR_LATENCY-3] ;

       else

         assign odt_0 =

                  wr_stages[ODT_WR_LATENCY] |

                  wr_stages[ODT_WR_LATENCY-1] |

                  wr_stages[ODT_WR_LATENCY-2] ;

    end else

      assign odt_0 = 1'b0;

   endgenerate

  assign dq_oe_0[0]   = wr_stages[WR_LATENCY-1] | wr_stages[WR_LATENCY];

  assign dq_oe_0[1]   = wr_stages[WR_LATENCY-1] | wr_stages[WR_LATENCY-2];

  assign dqs_rst_0    = ~wr_stages[WR_LATENCY-2];

  assign dm_ce_0      = wr_stages[WR_LATENCY] | wr_stages[WR_LATENCY-1]

                        | wr_stages[WR_LATENCY-2];

  // write data fifo, read flag assertion

  generate

    if (DDR_TYPE != DDR1) begin: gen_wdf_ddr2

      if (WR_LATENCY > 2)

        assign wdf_rden_0 = wr_stages[WR_LATENCY-3];

      else

        assign wdf_rden_0 = wr_stages[WR_LATENCY-2];

    end else begin: gen_wdf_ddr1

      assign wdf_rden_0 = wr_stages[WR_LATENCY-2];

    end

  endgenerate

  // first stage isn't registered

  always @(*)

    wr_stages[0] = (phy_init_data_sel) ? ctrl_wren : phy_init_wren;

  always @(posedge clk0) begin

    wr_stages[1] <= wr_stages[0];

    wr_stages[2] <= wr_stages[1];

    wr_stages[3] <= wr_stages[2];

    wr_stages[4] <= wr_stages[3];

    wr_stages[5] <= wr_stages[4];

    wr_stages[6] <= wr_stages[5];

    wr_stages[7] <= wr_stages[6];

    wr_stages[8] <= wr_stages[7];

    wr_stages[9] <= wr_stages[8];

    wr_stages[10] <= wr_stages[9];

  end

  // intermediate synchronization to CLK270

  always @(negedge clk90) begin

    dq_oe_270         <= dq_oe_0;

    dqs_oe_270        <= dqs_oe_0;

    dqs_rst_270       <= dqs_rst_0;

    wdf_rden_270      <= wdf_rden_0;

  end

  // synchronize DQS signals to CLK180

  always @(negedge clk0) begin

    dqs_oe_n_180_r1  <= ~dqs_oe_270;

    dqs_rst_n_180_r1 <= ~dqs_rst_270;

  end

  // All write data-related signals synced to CLK90

  always @(posedge clk90) begin

    dq_oe_n_90_r1  <= ~dq_oe_270;

    wdf_rden_90_r  <= wdf_rden_270;

  end

  // generate for wdf_rden and calib rden. These signals

  // are asserted based on write latency. For write

  // latency of 2, the extra register stage is taken out.

  generate

   if (WR_LATENCY > 2) begin

     always @(posedge clk90) begin

        // assert wdf rden only for non calibration opertations

        wdf_rden_90_r1 <=  wdf_rden_90_r &

                           phy_init_data_sel;

        // rden for calibration

        calib_rden_90_r <= wdf_rden_90_r;

     end

   end else begin

     always @(*) begin

        wdf_rden_90_r1 = wdf_rden_90_r

                         & phy_init_data_sel;

        calib_rden_90_r = wdf_rden_90_r;

     end

  end // else: !if(WR_LATENCY > 2)

  endgenerate

  // dm CE signal to stop dm oscilation

  always @(negedge clk90)begin

    dm_ce_r <= dm_ce_0;

    dm_ce <= dm_ce_r;

  end

  // When in ECC mode the upper byte [71:64] will have the

  // ECC parity. Mapping the bytes which have valid data

  // to the upper byte in ecc mode. Also in ecc mode there

  // is an extra register stage to account for timing.

  genvar mask_i;

  generate

    if(ECC_ENABLE) begin

      for (mask_i  = 0; mask_i < (2*DQ_WIDTH)/72;

          mask_i = mask_i+1) begin: gen_mask

       assign wdf_ecc_mask[((mask_i*9)+9)-1:(mask_i*9)] =

                {&wdf_mask_data[(mask_i*8)+(7+mask_i):mask_i*9],

                wdf_mask_data[(mask_i*8)+(7+mask_i):mask_i*9]};

      end

    end

   endgenerate

  generate

    if (ECC_ENABLE) begin:gen_ecc_reg

       always @(posedge clk90)begin

          if(phy_init_data_sel)

               wdf_mask_r <= wdf_ecc_mask;

          else

             wdf_mask_r <= {(2*DQ_WIDTH/8){1'b0}};

      end

    end else begin

      always@(posedge clk90) begin

        if (phy_init_data_sel)

          wdf_mask_r <= wdf_mask_data;

        else

          wdf_mask_r <= {(2*DQ_WIDTH/8){1'b0}};

      end

    end

  endgenerate

   always @(posedge clk90) begin

      if(phy_init_data_sel)

          wdf_data_r <= wdf_data;

      else

          wdf_data_r <={init_data_f,init_data_r};

   end

  // Error generation block during simulation.

  // Error will be displayed when all the DM

  // bits are not zero. The error will be

  // displayed only during the start of the sequence

  // for errors that are continous over many cycles.

  generate

    if (ECC_ENABLE) begin: gen_ecc_error

      always @(posedge clk90) begin

        //synthesis translate_off

        wdf_mask_r1 <= wdf_mask_r;

        if(DQ_WIDTH > 72)

           ecc_dm_error_r

              <= (

              (~wdf_mask_r1[35] && (|wdf_mask_r1[34:27])) ||

              (~wdf_mask_r1[26] && (|wdf_mask_r1[25:18])) ||

              (~wdf_mask_r1[17] && (|wdf_mask_r1[16:9])) ||

              (~wdf_mask_r1[8] &&  (|wdf_mask_r1[7:0]))) && phy_init_data_sel;

         else

            ecc_dm_error_r

              <= ((~wdf_mask_r1[17] && (|wdf_mask_r1[16:9])) ||

              (~wdf_mask_r1[8] &&  (|wdf_mask_r1[7:0]))) && phy_init_data_sel;

        ecc_dm_error_r1 <= ecc_dm_error_r ;

        if (ecc_dm_error_r && ~ecc_dm_error_r1) // assert the error only once.

          $display ("ECC DM ERROR. ");

        //synthesis translate_on

      end

    end

  endgenerate

  //***************************************************************************

  // State logic to write calibration training patterns

  //***************************************************************************

  always @(posedge clk90) begin

    if (rst90_r) begin

      init_wdf_cnt_r  <= 4'd0;

      init_data_r <= {64{1'bx}};

      init_data_f <= {64{1'bx}};

    end else begin

      init_wdf_cnt_r  <= init_wdf_cnt_r + calib_rden_90_r;

      casex (init_wdf_cnt_r)

        // First stage calibration. Pattern (rise/fall) = 1(r)->0(f)

        // The rise data and fall data are already interleaved in the manner

        // required for data into the WDF write FIFO

        4'b00xx: begin

          init_data_r <= {DQ_WIDTH{1'b1}};

          init_data_f <= {DQ_WIDTH{1'b0}};

        end

        // Second stage calibration. Pattern = 1(r)->1(f)->0(r)->0(f)

        4'b01x0: begin

           init_data_r <= {DQ_WIDTH{1'b1}};

           init_data_f <= {DQ_WIDTH{1'b1}};

          end

        4'b01x1: begin

           init_data_r <= {DQ_WIDTH{1'b0}};

           init_data_f <= {DQ_WIDTH{1'b0}};

        end

        // MIG 2.1: Changed Stage 3/4 training pattern

        // Third and fourth stage calibration patern = 

        //   11(r)->ee(f)->ee(r)->11(f)-11(r)->ee(f)->ee(r)->11(f)

        4'b1000: begin

          init_data_r <= {DQ_WIDTH/4{4'h1}};

          init_data_f <= {DQ_WIDTH/4{4'hE}};

        end

        4'b1001: begin

          init_data_r <= {DQ_WIDTH/4{4'hE}};

          init_data_f <= {DQ_WIDTH/4{4'h1}};

          end

        4'b1010: begin

          init_data_r <= {(DQ_WIDTH/4){4'h1}};

          init_data_f <= {(DQ_WIDTH/4){4'hE}};

        end

        4'b1011: begin

          init_data_r <= {(DQ_WIDTH/4){4'hE}};

          init_data_f <= {(DQ_WIDTH/4){4'h1}};

         end

        default: begin

          init_data_f <= {(2*DQ_WIDTH){1'bx}};

          init_data_r <= {(2*DQ_WIDTH){1'bx}};

        end

      endcase

    end

  end

  //***************************************************************************

  always @(posedge clk90)

    dq_oe_n   <= dq_oe_n_90_r1;

  always @(negedge clk0)

    dqs_oe_n  <= dqs_oe_n_180_r1;

  always @(negedge clk0)

    dqs_rst_n <= dqs_rst_n_180_r1;

  // generate for odt. odt is asserted based on

  //  write latency. For write latency of 2

  //  the extra register stage is taken out.

  generate

    if (ODT_WR_LATENCY > 2) begin

      always @(posedge clk0) begin

        odt    <= 'b0;

        odt[0] <= odt_0;

      end

    end else begin

      always @ (*) begin

        odt = 'b0;

        odt[0] = odt_0;

      end

    end

  endgenerate

  assign wdf_rden  = wdf_rden_90_r1;

  //***************************************************************************

  // Format write data/mask: Data is in format: {fall, rise}

  //***************************************************************************

  assign wr_data_rise = wdf_data_r[DQ_WIDTH-1:0];

  assign wr_data_fall = wdf_data_r[(2*DQ_WIDTH)-1:DQ_WIDTH];

  assign mask_data_rise = wdf_mask_r[MASK_WIDTH-1:0];

  assign mask_data_fall = wdf_mask_r[(2*MASK_WIDTH)-1:MASK_WIDTH];

endmodule