Subversion Repositories xspi

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

////                                                              ////

////  xSPI Interface Module                                       ////

////                                                              ////

////  This file is part of the xspi project                       ////

////  https://opencores.org/projects/xspi                         ////

////                                                              ////

////  Description                                                 ////

////  xspi definitions.                                           ////

////                                                              ////

////  To Do:                                                      ////

////    nothing                                                   ////

////                                                              ////

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

////      - Dinesh Annayya, dinesha@opencores.org                 ////

////                                                              ////

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

////                                                              ////

//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////

////                                                              ////

//// 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                     ////

////                                                              ////

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

module xspi_if

          (

           clk,

           reset_n,

           // towards ctrl i/f

           sck_pe,

           sck_int,

           cs_int_n,

           byte_in,

           load_byte,

           byte_out,

           shift_out,

           shift_in,

           cfg_tgt_sel,

           sck,

           so,

           si,

           cs_n

           );

  input clk,reset_n;

  input sck_pe;

  input sck_int,cs_int_n;

  input       load_byte;

  input [1:0] cfg_tgt_sel;

  input [7:0] byte_out;

  input       shift_out,shift_in;

  output [7:0] byte_in;

  output       sck,so;

  output [3:0] cs_n;

  input        si;

  reg [7:0]    so_reg;

  reg [7:0]    si_reg;

  wire [7:0]   byte_out;

  wire         sck;

  reg          so;

  wire [3:0]   cs_n;

  //Output Shift Register

  always @(posedge clk or negedge reset_n) begin

     if(!reset_n) begin

        so_reg <= 8'h00;

        so <= 1'b0;

     end

     else begin

        if(load_byte) begin

           so_reg <= byte_out;

           if(shift_out) begin

              // Handling backto back case : 

              // Last Transfer bit + New Trasfer Load

              so <= so_reg[7];

           end

        end // if (load_byte)

        else begin

           if(shift_out) begin

              so <= so_reg[7];

              so_reg <= {so_reg[6:0],1'b0};

           end // if (shift_out)

        end // else: !if(load_byte)

     end // else: !if(!reset_n)

  end // always @ (posedge clk or negedge reset_n)

// Input shift register

  always @(posedge clk or negedge reset_n) begin

     if(!reset_n) begin

        si_reg <= 8'h0;

     end

     else begin

        if(sck_pe & shift_in) begin

           si_reg[7:0] <= {si_reg[6:0],si};

        end // if (sck_pe & shift_in)

     end // else: !if(!reset_n)

  end // always @ (posedge clk or negedge reset_n)

  assign byte_in[7:0] = si_reg[7:0];

  assign cs_n[0] = (cfg_tgt_sel[1:0] == 2'b00) ? cs_int_n : 1'b1;

  assign cs_n[1] = (cfg_tgt_sel[1:0] == 2'b01) ? cs_int_n : 1'b1;

  assign cs_n[2] = (cfg_tgt_sel[1:0] == 2'b10) ? cs_int_n : 1'b1;

  assign cs_n[3] = (cfg_tgt_sel[1:0] == 2'b11) ? cs_int_n : 1'b1;

  assign sck = sck_int;

endmodule