Subversion Repositories qaz_libs

//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2017 Authors and OPENCORES.ORG                 ////
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//// This source file may be used and distributed without         ////
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//// removed from the file and that any derivative work contains  ////
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//// 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   ////
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//// 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 ////
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//////////////////////////////////////////////////////////////////////


module
  axis_switch_allocator
  #(
    N, // data bus width in bytes
    I = 1, // TID width
    D = 1, // TDEST width
    U = 1, // TUSER width
    U_IS_EOP = -1, // set to -1 for tlast, else set to index of tuser
    SA, // select width
    SD = 2 ** SA
  )
  (
    axis_if axis_in,
    axis_if axis_out[SD-1:0],
    input   aclk,
    input   aresetn
  );

  // --------------------------------------------------------------------
  //
  wire eop_in;

  axis_eop_set #(U_IS_EOP)
    axis_eop_set_i
    (
      .axis_in(axis_in),
      .tready(axis_switch_in.tready),
      .tvalid(axis_in.tvalid),
      .axis_eop(eop_in),
      .*
    );


  // --------------------------------------------------------------------
  //
  wire eop_out_mux;
  reg [SA-1:0] select;

  axis_eop_mux #(.U_IS_EOP(U_IS_EOP), .MA(SA))
    axis_eop_mux_i
    (
      .axis_in(axis_out),
      .axis_eop(eop_out_mux),
      .*
    );


  // --------------------------------------------------------------------
  //
  axis_if #(.N(N), .I(I), .D(D), .U(U)) axis_switch_in(.*);

  axis_alias #(.CONNECT_TREADY(0), .CONNECT_TVALID(0))
    axis_alias_i(.axis_out(axis_switch_in), .*);


  // --------------------------------------------------------------------
  //  state machine binary definitions
  enum reg [3:0]
    {
      ALLOT   = 4'b0001,
      FLUSH   = 4'b0010,
      SWITCH  = 4'b0100,
      SETTLE  = 4'b1000
    } state, next_state;


  // --------------------------------------------------------------------
  //  state machine flop
  always_ff @(posedge aclk)
    if(~aresetn)
      state <= ALLOT;
    else
      state <= next_state;


  // --------------------------------------------------------------------
  //  state machine
  always_comb
    case(state)
      ALLOT:    if(eop_in)
                  next_state <= FLUSH;
                else
                  next_state <= ALLOT;

      FLUSH:    if(eop_out_mux)
                  next_state <= SWITCH;
                else
                  next_state <= FLUSH;

      SWITCH:   next_state <= SETTLE;
      
      SETTLE:   next_state <= ALLOT;  // let select propagate to the switches 

      default:  next_state <= ALLOT;
    endcase


  // --------------------------------------------------------------------
  //
  always_ff @(posedge aclk)
    if(~aresetn)
      select <= 0;
    else if(state == SWITCH)
      select <= select + 1;


  // --------------------------------------------------------------------
  //
  recursive_axis_switch #(.N(N), .I(I), .D(D), .U(U), .SA(SA))
    recursive_axis_switch_i(.axis_in(axis_switch_in), .*);


  // --------------------------------------------------------------------
  //
  assign axis_in.tready         = (state == ALLOT) & axis_switch_in.tready;
  assign axis_switch_in.tvalid  = (state == ALLOT) & axis_in.tvalid;


// --------------------------------------------------------------------
//
endmodule