Subversion Repositories wb4pb

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

// This sourcecode is released under BSD license.

// Please see http://www.opensource.org/licenses/bsd-license.php for details!

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

//

// Copyright (c) 2010, Stefan Fischer <Ste.Fis@OpenCores.org>

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without 

// modification, are permitted provided that the following conditions are met:

//

//  * Redistributions of source code must retain the above copyright notice, 

//    this list of conditions and the following disclaimer.

//  * Redistributions in binary form must reproduce the above copyright notice,

//    this list of conditions and the following disclaimer in the documentation

//    and/or other materials provided with the distribution. 

//  * Neither the name of the author nor the names of his contributors may be 

//    used to endorse or promote products derived from this software without 

//    specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 

// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 

// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 

// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 

// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 

// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 

// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 

// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 

// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 

// POSSIBILITY OF SUCH DAMAGE.

//

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

// filename: wbm_picoblaze.v

// description: synthesizable wishbone master adapter for PicoBlaze (TM),

//              working together with "wb_wr" and "wb_rd" assembler subroutines

// todo4user: module should not be changed!

// version: 0.0.0

// changelog: - 0.0.0, initial release

//            - ...

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

module wbm_picoblaze (

  rst,

  clk,

  wbm_cyc_o,

  wbm_stb_o,

  wbm_we_o,

  wbm_adr_o,

  wbm_dat_m2s_o,

  wbm_dat_s2m_i,

  wbm_ack_i,

  pb_port_id_i,

  pb_write_strobe_i,

  pb_out_port_i,

  pb_read_strobe_i,

  pb_in_port_o

);

  input rst;

  wire  rst;

  input clk;

  wire  clk;

  output wbm_cyc_o;

  wire   wbm_cyc_o;

  output wbm_stb_o;

  reg    wbm_stb_o;

  output wbm_we_o;

  reg    wbm_we_o;

  output[7:0] wbm_adr_o;

  reg   [7:0] wbm_adr_o;

  output[7:0] wbm_dat_m2s_o;

  reg   [7:0] wbm_dat_m2s_o;

  input[7:0] wbm_dat_s2m_i;

  wire [7:0] wbm_dat_s2m_i;

  input wbm_ack_i;

  wire  wbm_ack_i;

  input[7:0] pb_port_id_i;

  wire [7:0] pb_port_id_i;

  input pb_write_strobe_i;

  wire  pb_write_strobe_i;

  input[7:0] pb_out_port_i;

  wire [7:0] pb_out_port_i;

  input pb_read_strobe_i;

  wire  pb_read_strobe_i;

  output[7:0] pb_in_port_o;

  reg   [7:0] pb_in_port_o;

  reg[7:0] wb_buffer;

  parameter[7:0] WB_ACK_FLAG = 8'h01;

  parameter[1:0]

    S_IDLE = 2'b00,

    S_WAIT_ON_WB_ACK = 2'b01,

    S_SOFTWARE_HANDSHAKE = 2'b10,

    S_SOFTWARE_READ = 2'b11

  ;

  reg[1:0] state;

  assign wbm_cyc_o = wbm_stb_o;

  always@(posedge clk) begin

    case(state)

      S_IDLE:

        // setting up wishbone address, data and control signals from 

        // PicoBlaze (TM) signals

        if (pb_write_strobe_i) begin

          wbm_stb_o <= 1'b1;

          wbm_we_o <= 1'b1;

          wbm_adr_o <= pb_port_id_i;

          wbm_dat_m2s_o <= pb_out_port_i;

          state <= S_WAIT_ON_WB_ACK;

        end else if (pb_read_strobe_i) begin

          wbm_stb_o <= 1'b1;

          wbm_we_o <= 1'b0;

          wbm_adr_o <= pb_port_id_i;

          state <= S_WAIT_ON_WB_ACK;

        end

      S_WAIT_ON_WB_ACK:

        // waiting on slave peripheral to complete wishbone transfer cycle

        if (wbm_ack_i) begin

          wbm_stb_o <= 1'b0;

          wb_buffer <= wbm_dat_s2m_i;

          pb_in_port_o <= WB_ACK_FLAG;

          state <= S_SOFTWARE_HANDSHAKE;

        end

      S_SOFTWARE_HANDSHAKE:

        // software recognition of wishbone handshake

        if (pb_read_strobe_i)

          // transfer complete for a write access

          if (wbm_we_o) begin

            pb_in_port_o <= 8'h00;

            state <= S_IDLE;

          // presenting valid wishbone data to PicoBlaze (TM) port in read 

          // access

          end else begin

            pb_in_port_o <= wb_buffer;

            state <= S_SOFTWARE_READ;

          end

      S_SOFTWARE_READ:

        // transfer complete for a read access after software recognition of

        // wishbone data

        if (pb_read_strobe_i) begin

          pb_in_port_o <= 8'h00;

          state <= S_IDLE;

        end

      default: ;

    endcase

    if (rst) begin

      wbm_stb_o <= 1'b0;

      pb_in_port_o <= 8'h00;

      state <= S_IDLE;

    end

  end

endmodule