Subversion Repositories spi_core_dsp_s3ean_kits

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

////                                                              ////

////  spi_shift_out.v                                                                                     ////

////                                                                          ////

////  WAS: spi_shift.v                                            ////

////                                                              ////

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

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

////                                                              ////

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

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

////      - William Gibb (williamgibb@gmail.com)                  ////

////                    Modified to be TX only                                                    ////

////                    Fixed Width of 24 Bits                            ////

////                                                              ////

////                                                              ////

////                                                              ////

////                                                              ////

////  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 "timescale.v"

`include "spi_defines.v"

module spi_shift_out (clk, rst, len, lsb, go, pos_edge, neg_edge, tx_negedge,

                  capture, tip, last, p_in, s_out);

        parameter Tp = 1;

        input                          clk;          // system clock

        input                          rst;          // reset

        input     [`SPI_CHAR_LEN_BITS-1:0] len;         // data len in bits (minus one)

        input                          lsb;          // lbs first on the line

        input                          go;           // start stansfer

        input                                                   capture;                // 

        input                          pos_edge;     // recognize posedge of sclk

        input                          neg_edge;     // recognize negedge of sclk

        input                          tx_negedge;   // s_out is driven on negative edge

        output                         tip;          // transfer in progress

        output                         last;         // last bit

        input                   [23:0] p_in;         // parallel in

        output                         s_out;        // serial out

        reg                            s_out;

        reg                            tip;

        reg             [`SPI_CHAR_LEN_BITS:0] cnt;          // data bit count

        reg                     [`SPI_MAX_CHAR-1:0] data;                // shift register

        wire             [`SPI_CHAR_LEN_BITS:0] tx_bit_pos;              // next bit position

        wire                           tx_clk;          // tx clock enable

        assign tx_bit_pos = lsb ? {!(|len), len} - cnt : cnt - {{`SPI_CHAR_LEN_BITS{1'b0}},1'b1};

        assign last = !(|cnt);

        assign tx_clk = (tx_negedge ? neg_edge : pos_edge) && !last;

        // Character bit counter

        always @(posedge clk or posedge rst)

        begin

                if(rst)

                        cnt <= #Tp {`SPI_CHAR_LEN_BITS+1{1'b0}};

                else

                begin

        if(tip)

                        cnt <= #Tp pos_edge ? (cnt - {{`SPI_CHAR_LEN_BITS{1'b0}}, 1'b1}) : cnt;

                else

                        cnt <= #Tp !(|len) ? {1'b1, {`SPI_CHAR_LEN_BITS{1'b0}}} : {1'b0, len};

                end

        end

        // Transfer in progress

        always @(posedge clk or posedge rst)

        begin

                if(rst)

                        tip <= #Tp 1'b0;

                else if(go && ~tip)

                        tip <= #Tp 1'b1;

                else if(tip && last && pos_edge)

                        tip <= #Tp 1'b0;

        end

         // Sending bits to the line

         always @(posedge clk or posedge rst)

         begin

                if (rst)

                        s_out   <= #Tp 1'b0;

                else

                        s_out <= #Tp (tx_clk || !tip) ? data[tx_bit_pos[`SPI_CHAR_LEN_BITS-1:0]] : s_out;

         end

         // Capture data from p_in to the 

         always @(posedge clk or posedge rst)

         begin

                 if (rst)

                      data   <= #Tp {24{1'b0}};

                 else if(!tip && capture)

                                data <= #Tp p_in;

         end

endmodule