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

///                                                               //// 

/// Wishbone arbiter, burst-compatible                            ////

///                                                               ////

/// Simple arbiter, single master, dual slave, primarily for      ////

/// processor instruction bus, providing access to one main       ////

/// memory server and one ROM                                     ////

///                                                               ////

/// Julius Baxter, julius@opencores.org                           ////

///                                                               ////

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

////                                                              ////

//// Copyright (C) 2009, 2010 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                     ////

////                                                              ////

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

`include "orpsoc-defines.v"

// One master, 2 slaves.

module arbiter_ibus

  (

   // instruction bus in

   // Wishbone Master interface

   wbm_adr_o,

   wbm_dat_o,

   wbm_sel_o,

   wbm_we_o,

   wbm_cyc_o,

   wbm_stb_o,

   wbm_cti_o,

   wbm_bte_o,

   wbm_dat_i,

   wbm_ack_i,

   wbm_err_i,

   wbm_rty_i,

   // Slave one

   // Wishbone Slave interface

   wbs0_adr_i,

   wbs0_dat_i,

   wbs0_sel_i,

   wbs0_we_i,

   wbs0_cyc_i,

   wbs0_stb_i,

   wbs0_cti_i,

   wbs0_bte_i,

   wbs0_dat_o,

   wbs0_ack_o,

   wbs0_err_o,

   wbs0_rty_o,

   // Slave two

   // Wishbone Slave interface

   wbs1_adr_i,

   wbs1_dat_i,

   wbs1_sel_i,

   wbs1_we_i,

   wbs1_cyc_i,

   wbs1_stb_i,

   wbs1_cti_i,

   wbs1_bte_i,

   wbs1_dat_o,

   wbs1_ack_o,

   wbs1_err_o,

   wbs1_rty_o,

   wb_clk,

   wb_rst

   );

   parameter wb_dat_width = 32;

   parameter wb_adr_width = 32;

   parameter wb_addr_match_width = 8;

   parameter slave0_adr = 8'hf0; // FLASH ROM

   parameter slave1_adr = 8'h00; // Main memory (SDRAM/FPGA SRAM)

`define WB_ARB_ADDR_MATCH_SEL wb_adr_width-1:wb_adr_width-wb_addr_match_width

   input wb_clk;

   input wb_rst;

   // WB Master

   input [wb_adr_width-1:0] wbm_adr_o;

   input [wb_dat_width-1:0] wbm_dat_o;

   input [3:0]               wbm_sel_o;

   input                    wbm_we_o;

   input                    wbm_cyc_o;

   input                    wbm_stb_o;

   input [2:0]               wbm_cti_o;

   input [1:0]               wbm_bte_o;

   output [wb_dat_width-1:0] wbm_dat_i;

   output                    wbm_ack_i;

   output                    wbm_err_i;

   output                    wbm_rty_i;

   // WB Slave 0

   output [wb_adr_width-1:0] wbs0_adr_i;

   output [wb_dat_width-1:0] wbs0_dat_i;

   output [3:0]       wbs0_sel_i;

   output                    wbs0_we_i;

   output                    wbs0_cyc_i;

   output                    wbs0_stb_i;

   output [2:0]       wbs0_cti_i;

   output [1:0]       wbs0_bte_i;

   input [wb_dat_width-1:0]  wbs0_dat_o;

   input                     wbs0_ack_o;

   input                     wbs0_err_o;

   input                     wbs0_rty_o;

   // WB Slave 1

   output [wb_adr_width-1:0] wbs1_adr_i;

   output [wb_dat_width-1:0] wbs1_dat_i;

   output [3:0]       wbs1_sel_i;

   output                    wbs1_we_i;

   output                    wbs1_cyc_i;

   output                    wbs1_stb_i;

   output [2:0]       wbs1_cti_i;

   output [1:0]       wbs1_bte_i;

   input [wb_dat_width-1:0]  wbs1_dat_o;

   input                     wbs1_ack_o;

   input                     wbs1_err_o;

   input                     wbs1_rty_o;

   wire [1:0]                 slave_sel; // One bit per slave

   reg                       watchdog_err;

`ifdef ARBITER_IBUS_WATCHDOG

   reg [`ARBITER_IBUS_WATCHDOG_TIMER_WIDTH:0]  watchdog_timer;

   reg                       wbm_stb_r; // Register strobe

   wire                      wbm_stb_edge; // Detect its edge

   reg                       wbm_stb_edge_r, wbm_ack_i_r; // Reg these, better timing

   always @(posedge wb_clk)

     wbm_stb_r <= wbm_stb_o;

   assign wbm_stb_edge = (wbm_stb_o & !wbm_stb_r);

   always @(posedge wb_clk)

     wbm_stb_edge_r <= wbm_stb_edge;

   always @(posedge wb_clk)

     wbm_ack_i_r <= wbm_ack_i;

   // Counter logic

   always @(posedge wb_clk)

     if (wb_rst) watchdog_timer <= 0;

     else if (wbm_ack_i_r) // When we see an ack, turn off timer

       watchdog_timer <= 0;

     else if (wbm_stb_edge_r) // New access means start timer again

       watchdog_timer <= 1;

     else if (|watchdog_timer) // Continue counting if counter > 0

       watchdog_timer <= watchdog_timer + 1;

   always @(posedge wb_clk)

     watchdog_err <= (&watchdog_timer);

`else // !`ifdef ARBITER_IBUS_WATCHDOG

   always @(posedge wb_clk)

     watchdog_err <= 0;

`endif // !`ifdef ARBITER_IBUS_WATCHDOG

`ifdef ARBITER_IBUS_REGISTERING

   // Master input registers

   reg [wb_adr_width-1:0]    wbm_adr_o_r;

   reg [wb_dat_width-1:0]    wbm_dat_o_r;

   reg [3:0]                  wbm_sel_o_r;

   reg                       wbm_we_o_r;

   reg                       wbm_cyc_o_r;

   reg                       wbm_stb_o_r;

   reg [2:0]                  wbm_cti_o_r;

   reg [1:0]                  wbm_bte_o_r;

   // Slave output registers

   reg [wb_dat_width-1:0]    wbs0_dat_o_r;

   reg                       wbs0_ack_o_r;

   reg                       wbs0_err_o_r;

   reg                       wbs0_rty_o_r;

   reg [wb_dat_width-1:0]    wbs1_dat_o_r;

   reg                       wbs1_ack_o_r;

   reg                       wbs1_err_o_r;

   reg                       wbs1_rty_o_r;

   wire                      wbm_ack_i_pre_reg;

   // Register master input signals

   always @(posedge wb_clk)

     begin

        wbm_adr_o_r <= wbm_adr_o;

        wbm_dat_o_r <= wbm_dat_o;

        wbm_sel_o_r <= wbm_sel_o;

        wbm_we_o_r <= wbm_we_o;

        wbm_cyc_o_r <= wbm_cyc_o;

        wbm_stb_o_r <= wbm_stb_o & !wbm_ack_i_pre_reg & !wbm_ack_i;//classic

        wbm_cti_o_r <= wbm_cti_o;

        wbm_bte_o_r <= wbm_bte_o;

        // Slave signals

        wbs0_dat_o_r <= wbs0_dat_o;

        wbs0_ack_o_r <= wbs0_ack_o;

        wbs0_err_o_r <= wbs0_err_o;

        wbs0_rty_o_r <= wbs0_rty_o;

        wbs1_dat_o_r <= wbs1_dat_o;

        wbs1_ack_o_r <= wbs1_ack_o;

        wbs1_err_o_r <= wbs1_err_o;

        wbs1_rty_o_r <= wbs1_rty_o;

     end // always @ (posedge wb_clk)

   // Slave select

   assign slave_sel[0] = wbm_adr_o_r[`WB_ARB_ADDR_MATCH_SEL] ==

                         slave0_adr;

   assign slave_sel[1] = wbm_adr_o_r[`WB_ARB_ADDR_MATCH_SEL] ==

                         slave1_adr;

   // Slave out assigns

   assign wbs0_adr_i = wbm_adr_o_r;

   assign wbs0_dat_i = wbm_dat_o_r;

   assign wbs0_we_i = wbm_dat_o_r;

   assign wbs0_sel_i = wbm_sel_o_r;

   assign wbs0_cti_i = wbm_cti_o_r;

   assign wbs0_bte_i = wbm_bte_o_r;

   assign wbs0_cyc_i = wbm_cyc_o_r & slave_sel[0];

   assign wbs0_stb_i = wbm_stb_o_r & slave_sel[0];

   assign wbs1_adr_i = wbm_adr_o_r;

   assign wbs1_dat_i = wbm_dat_o_r;

   assign wbs1_we_i = wbm_dat_o_r;

   assign wbs1_sel_i = wbm_sel_o_r;

   assign wbs1_cti_i = wbm_cti_o_r;

   assign wbs1_bte_i = wbm_bte_o_r;

   assign wbs1_cyc_i = wbm_cyc_o_r & slave_sel[1];

   assign wbs1_stb_i = wbm_stb_o_r & slave_sel[1];

   // Master out assigns

   // Don't care about none selected...

   assign wbm_dat_i = slave_sel[1] ? wbs1_dat_o_r :

                      wbs0_dat_o_r ;

   assign wbm_ack_i = (slave_sel[0] & wbs0_ack_o_r) |

                      (slave_sel[1] & wbs1_ack_o_r)

     ;

   assign wbm_err_i = (slave_sel[0] & wbs0_err_o_r) |

                      (slave_sel[1] & wbs1_err_o_r) |

                      watchdog_err;

   assign wbm_rty_i = (slave_sel[0] & wbs0_rty_o_r) |

                      (slave_sel[1] & wbs1_rty_o_r);

   // Non-registered ack

   assign wbm_ack_i_pre_reg = (slave_sel[0] & wbs0_ack_o) |

                              (slave_sel[1] & wbs1_ack_o);

`else // !`ifdef ARBITER_IBUS_REGISTERING

   // Slave select

   assign slave_sel[0] = wbm_adr_o[`WB_ARB_ADDR_MATCH_SEL] ==

                         slave0_adr;

   assign slave_sel[1] = wbm_adr_o[`WB_ARB_ADDR_MATCH_SEL] ==

                         slave1_adr;

   // Slave out assigns

   assign wbs0_adr_i = wbm_adr_o;

   assign wbs0_dat_i = wbm_dat_o;

   assign wbs0_we_i  = wbm_we_o;

   assign wbs0_sel_i = wbm_sel_o;

   assign wbs0_cti_i = wbm_cti_o;

   assign wbs0_bte_i = wbm_bte_o;

   assign wbs0_cyc_i = wbm_cyc_o & slave_sel[0];

   assign wbs0_stb_i = wbm_stb_o & slave_sel[0];

   assign wbs1_adr_i = wbm_adr_o;

   assign wbs1_dat_i = wbm_dat_o;

   assign wbs1_we_i  = wbm_we_o;

   assign wbs1_sel_i = wbm_sel_o;

   assign wbs1_cti_i = wbm_cti_o;

   assign wbs1_bte_i = wbm_bte_o;

   assign wbs1_cyc_i = wbm_cyc_o & slave_sel[1];

   assign wbs1_stb_i = wbm_stb_o & slave_sel[1];

   // Master out assigns

   // Don't care about none selected...

   assign wbm_dat_i = slave_sel[1] ? wbs1_dat_o :

                      wbs0_dat_o ;

   assign wbm_ack_i = (slave_sel[0] & wbs0_ack_o) |

                      (slave_sel[1] & wbs1_ack_o);

   assign wbm_err_i = (slave_sel[0] & wbs0_err_o) |

                      (slave_sel[1] & wbs1_err_o) |

                      watchdog_err;

   assign wbm_rty_i = (slave_sel[0] & wbs0_rty_o) |

                      (slave_sel[1] & wbs1_rty_o);

`endif

endmodule // arbiter_ibus