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//////////////////////////////////////////////////////////////////////

////                                                              ////

////  spi_top.v                                                   ////

////                                                              ////

////  This file is part of the SPI IP core project                ////

////  http://www.opencores.org/projects/spi/                      ////

////                                                              ////

////  Author(s):                                                  ////

////      - Simon Srot (simons@opencores.org)                     ////

////                                                              ////

////  All additional information is avaliable in the Readme.txt   ////

////  file.                                                       ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

////                                                              ////

//// Copyright (C) 2002 Authors                                   ////

////                                                              ////

//// This source file may be used and distributed without         ////

//// restriction provided that this copyright statement is not    ////

//// removed from the file and that any derivative work contains  ////

//// the original copyright notice and the associated disclaimer. ////

////                                                              ////

//// This source file is free software; you can redistribute it   ////

//// and/or modify it under the terms of the GNU Lesser General   ////

//// Public License as published by the Free Software Foundation; ////

//// either version 2.1 of the License, or (at your option) any   ////

//// later version.                                               ////

////                                                              ////

//// This source is distributed in the hope that it will be       ////

//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////

//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////

//// PURPOSE.  See the GNU Lesser General Public License for more ////

//// details.                                                     ////

////                                                              ////

//// You should have received a copy of the GNU Lesser General    ////

//// Public License along with this source; if not, download it   ////

//// from http://www.opencores.org/lgpl.shtml                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

`include "spi_defines.v"

`include "timescale.v"

module spi_flash_top

  (

   // Wishbone signals

   wb_clk_i, wb_rst_i, wb_adr_i, wb_dat_i, wb_dat_o, wb_sel_i,

   wb_we_i, wb_stb_i, wb_cyc_i, wb_ack_o,

   // SPI signals

   ss_pad_o, sclk_pad_o, mosi_pad_o, miso_pad_i

   );

   parameter divider_len = 2;

   parameter divider = 0;

   parameter Tp = 1;

   // Wishbone signals

   input                            wb_clk_i;         // master clock input

   input                            wb_rst_i;         // synchronous active high reset

   input [4:2]                      wb_adr_i;         // lower address bits

   input [31:0]              wb_dat_i;         // databus input

   output [31:0]                     wb_dat_o;         // databus output

   input [3:0]                       wb_sel_i;         // byte select inputs

   input                            wb_we_i;          // write enable input

   input                            wb_stb_i;         // stobe/core select signal

   input                            wb_cyc_i;         // valid bus cycle input

   output                           wb_ack_o;         // bus cycle acknowledge output

   // SPI signals                                     

   output [`SPI_SS_NB-1:0]           ss_pad_o;         // slave select

   output                           sclk_pad_o;       // serial clock

   output                           mosi_pad_o;       // master out slave in

   input                            miso_pad_i;       // master in slave out

   reg [31:0]                        wb_dat_o;

   reg                              wb_ack_o;

   // Internal signals

   //  reg       [`SPI_DIVIDER_LEN-1:0] divider;          // Divider register

   wire [`SPI_CTRL_BIT_NB-1:0]       ctrl;             // Control and status register

   reg [`SPI_SS_NB-1:0]      ss;               // Slave select register

   wire [`SPI_MAX_CHAR-1:0]          rx;               // Rx register

   wire [5:0]                        char_len;

   reg                              char_len_ctrl;    // char len

   reg                              go;               // go

   wire                             spi_ctrl_sel;     // ctrl register select

   wire                             spi_tx_sel;       // tx_l register select

   wire                             spi_ss_sel;       // ss register select

   wire                             tip;              // transfer in progress

   wire                             pos_edge;         // recognize posedge of sclk

   wire                             neg_edge;         // recognize negedge of sclk

   wire                             last_bit;         // marks last character bit

  wire                             rx_negedge;       // miso is sampled on negative edge

  wire                             tx_negedge;       // mosi is driven on negative edge

  wire                             lsb;              // lsb first on line

  wire                             ass;              // automatic slave select

   // Address decoder

   assign spi_ctrl_sel    = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_CTRL);

   assign spi_tx_sel      = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_TX_0);

   assign spi_ss_sel      = wb_cyc_i & wb_stb_i & (wb_adr_i[`SPI_OFS_BITS] == `SPI_SS);

   // Read from registers

   // Wb data out

   always @(posedge wb_clk_i or posedge wb_rst_i)

  begin

     if (wb_rst_i)

       wb_dat_o <= #Tp 32'b0;

     else

       case (wb_adr_i[`SPI_OFS_BITS])

         `SPI_RX_0:    wb_dat_o <= rx;

         `SPI_CTRL:    wb_dat_o <= {18'd0, ctrl};

         `SPI_DEVIDE:  wb_dat_o <= {{32-divider_len{1'b0}}, divider};

         `SPI_SS:      wb_dat_o <= {{32-`SPI_SS_NB{1'b0}}, ss};

        default:      wb_dat_o  <= rx;

       endcase

  end

   // Wb acknowledge

   always @(posedge wb_clk_i or posedge wb_rst_i)

     begin

        if (wb_rst_i)

          wb_ack_o <= #Tp 1'b0;

    else

      wb_ack_o <= #Tp wb_cyc_i & wb_stb_i & ~wb_ack_o;

     end

   // Ctrl register

   always @(posedge wb_clk_i or posedge wb_rst_i)

     begin

        if (wb_rst_i)

          {go,char_len_ctrl} <= #Tp 2'b01;

        else if(spi_ctrl_sel && wb_we_i && !tip)

          begin

             if (wb_sel_i[0])

               char_len_ctrl <= #Tp wb_dat_i[5];

             if (wb_sel_i[1])

               go <= #Tp wb_dat_i[8];

          end

        else if(tip && last_bit && pos_edge)

          go <= #Tp 1'b0;

     end

   assign char_len = char_len_ctrl ? 6'd32 : 6'd8;

`ifdef SPI_CTRL_ASS

   assign ass = 1'b1;

`else

   assign ass = 1'b0;

`endif

`ifdef SPI_CTRL_LSB

   assign lsb = 1'b1;

`else

   assign lsb = 1'b0;

`endif

`ifdef SPI_CTRL_RX_NEGEDGE

   assign rx_negedge = 1'b1;

`else

   assign rx_negedge = 1'b0;

`endif

`ifdef SPI_CTRL_TX_NEGEDGE

   assign tx_negedge = 1'b1;

`else

   assign tx_negedge = 1'b0;

`endif

   assign ctrl = {ass,1'b0,lsb,tx_negedge,rx_negedge,go,1'b0,1'b0,char_len};

   // Slave select register

   always @(posedge wb_clk_i or posedge wb_rst_i)

     if (wb_rst_i)

       ss <= #Tp {`SPI_SS_NB{1'b0}};

     else if(spi_ss_sel && wb_we_i && !tip)

       if (wb_sel_i[0])

         ss <= #Tp wb_dat_i[`SPI_SS_NB-1:0];

   assign ss_pad_o = ~((ss & {`SPI_SS_NB{tip & ass}}) | (ss & {`SPI_SS_NB{!ass}}));

   spi_flash_clgen

     #

     (

      .divider_len(divider_len),

      .divider(divider)

      )

     clgen

       (

        .clk_in(wb_clk_i),

        .rst(wb_rst_i),

        .go(go),

        .enable(tip),

        .last_clk(last_bit),

        .clk_out(sclk_pad_o),

        .pos_edge(pos_edge),

        .neg_edge(neg_edge)

        );

   spi_flash_shift  shift

     (

      .clk(wb_clk_i),

      .rst(wb_rst_i),

      .len(char_len[`SPI_CHAR_LEN_BITS-1:0]),

      .latch(spi_tx_sel & wb_we_i),

      .byte_sel(wb_sel_i),

      .go(go),

      .pos_edge(pos_edge),

      .neg_edge(neg_edge),

      .lsb(lsb),

      .rx_negedge(rx_negedge),

      .tx_negedge(tx_negedge),

      .tip(tip),

      .last(last_bit),

      .p_in(wb_dat_i),

      .p_out(rx),

      .s_clk(sclk_pad_o),

      .s_in(miso_pad_i),

      .s_out(mosi_pad_o)

      );

endmodule