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/*

 Asynchronous SDM NoC

 (C)2011 Wei Song

 Advanced Processor Technologies Group

 Computer Science, the Univ. of Manchester, UK

 Authors:

 Wei Song     wsong83@gmail.com

 License: LGPL 3.0 or later

 The output buffer for VC routers.

 History:

 04/04/2010  Initial version. <wsong83@gmail.com>

 12/05/2010  Use MPxP crossbars. <wsong83@gmail.com>

 08/05/2010  Remove unnecessary pipeline stages. <wsong83@gmail.com>

 02/06/2011  Clean up for opensource. <wsong83@gmail.com>

*/

module outpbuf (/*AUTOARG*/

   // Outputs

   dia, do0, do1, do2, do3, dot, dovc, afc, vca,

   // Inputs

   di0, di1, di2, di3, dit, doa, credit, vcr, rst_n

   );

   parameter DW = 32;           // data width

   parameter VCN = 4;           // VC number

   parameter FT = 3;            // flit type, now 3, HOF, BOF, EOF

   parameter FCPD = 3;          // the depth of the credit pipeline

   parameter SCN = DW/2;

   //data in

   input [SCN-1:0] di0, di1, di2, di3;

   input [FT-1:0]  dit;

   output          dia;

   // data out

   output [SCN-1:0] do0, do1, do2, do3;

   output [FT-1:0]  dot;

   output [VCN-1:0] dovc;

   input            doa;

   // credit

   input [VCN-1:0]  credit;

   output [VCN-1:0] afc;

   // vc requests in

   input [VCN-1:0]  vcr;

   output [VCN-1:0] vca;

   // active-low reset

   input            rst_n;

   //--------------------------------------------------------------

   wire [VCN-1:0]   vcro, vcg, vcgl, vcrm;

   wire [SCN-1:0]   doan, diad;

   wire             dian, diavc, diavcn, diat;

   genvar           i, gsub;

   // flow control controller

   fcctl #(.VCN(VCN), .PD(FCPD))

   FCU (

        .afc    ( afc    ),

        .ro     ( vcro   ),

        .credit ( credit ),

        .ri     ( vcr    ),

        .rst    ( ~rst_n  )

        );

   // VC arbiter

   mutex_arb #(.wd(VCN)) Sch (.req(vcro), .gnt(vcg));

   // the control logic for VC arbiter

   generate

      for(i=0; i<VCN; i++)begin:SCEN

         c2 C (.a0(vcg[i]), .a1(diavcn), .q(vcgl[i]));

      end

   endgenerate

   assign diavcn = (~diavc)&rst_n;

   // output data buffer

   generate

      for(gsub=0; gsub<SCN; gsub++) begin:SC

         pipe4 #(.DW(2))

         L0D (

              .ia ( diad[gsub]   ),

              .o0 ( do0[gsub]    ),

              .o1 ( do1[gsub]    ),

              .o2 ( do2[gsub]    ),

              .o3 ( do3[gsub]    ),

              .i0 ( di0[gsub]    ),

              .i1 ( di1[gsub]    ),

              .i2 ( di2[gsub]    ),

              .i3 ( di3[gsub]    ),

              .oa ( doan[gsub]   )

              );

         assign doan[gsub] = (~doa)&rst_n;

      end // block: SC

   endgenerate

   pipen #(.DW(FT))

   L0T (

        .d_in    ( dit     ),

        .d_in_a  ( diat    ),

        .d_out   ( dot     ),

        .d_out_a ( (~doa)&rst_n )

        );

   ctree #(.DW(SCN+2)) ACKT (.ci({diavc,diat, diad}), .co(dia));

   pipen #(.DW(VCN))

   LSV (

        .d_in    ( vcgl       ),

        .d_in_a  ( diavc      ),

        .d_out   ( dovc       ),

        .d_out_a ( (~doa)&rst_n )

        );

   assign vca = dovc;

endmodule // outpbuf