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

//

// Filename:    wbuoutput.v

//

// Project:     XuLA2 board

//

// Purpose:     Converts 36-bit codewords into bytes to be placed on the serial

//              output port.  The codewords themselves are the results of bus

//      transactions, which are then (hopefully) compressed within here and

//      carefully arranged into "lines" for visual viewing (if necessary).

//

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

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

//

// Copyright (C) 2015, Gisselquist Technology, LLC

//

// This program is free software (firmware): you can redistribute it and/or

// modify it under the terms of  the GNU General Public License as published

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

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

//

//

module  wbuoutput(i_clk, i_rst, i_stb, i_codword,

                i_wb_cyc, i_int, i_bus_busy,

                o_stb, o_char, i_tx_busy, o_fifo_err);

        input                   i_clk, i_rst;

        input                   i_stb;

        input           [35:0]   i_codword;

        // Not Idle indicators

        input                   i_wb_cyc, i_int, i_bus_busy;

        // Outputs to our UART transmitter

        output  wire            o_stb;

        output  wire    [7:0]    o_char;

        // Miscellaneous I/O: UART transmitter busy, and fifo error

        input                   i_tx_busy;

        output  wire            o_fifo_err;

        wire            fifo_rd, dw_busy, fifo_empty_n, fifo_err;

        wire    [35:0]   fifo_codword;

        wire            cw_stb, cw_busy, cp_stb, dw_stb, ln_stb, ln_busy,

                        cp_busy, byte_busy;

        wire    [35:0]   cw_codword, cp_word;

        wire    [6:0]    dw_bits, ln_bits;

// `define      SKIP_FIFO

`ifdef  SKIP_FIFO

        assign  fifo_rd = i_stb;

        assign  fifo_codword = i_codword;

        assign  fifo_err = 1'b0;

`else

        assign  fifo_rd = (fifo_empty_n)&&(~cw_busy);

        wbufifo #(36,10) busoutfifo(i_clk, i_rst, i_stb, i_codword,

                                fifo_rd, fifo_codword, fifo_empty_n,

                                fifo_err);

`endif

        assign  o_fifo_err = fifo_err;

        wbuidleint      buildcw(i_clk, fifo_rd, fifo_codword,

                                i_wb_cyc, i_bus_busy, i_int,

                                cw_stb, cw_codword, cw_busy, cp_busy);

        // assign       o_dbg = dw_busy; // Always asserted ... ???

        // assign       o_dbg = { dw_busy, ln_busy, fifo_rd };

        // Stuck: dw_busy and ln_busy get stuck high after read attempt,

        //      fifo_rd is low

        // assign       o_dbg = { fifo_rd, cp_stb, cw_stb };

        // cw_stb and cp_stb get stuck high after one read

        //

        // cw_busy & cw_stb, not cp_stb, but dw_busy

        //

// `define      SKIP_COMPRESS

`ifdef  SKIP_COMPRESS

        assign  cp_stb = cw_stb;

        assign  cp_word = cw_codword;

        assign  cp_busy = dw_busy;

`else

        assign  cp_busy = cp_stb;

        wbucompress     packit(i_clk, cw_stb, cw_codword,

                                cp_stb, cp_word, dw_busy);

`endif

        wbudeword       deword(i_clk, cp_stb, cp_word, ln_busy,

                                        dw_stb, dw_bits, dw_busy);

        wbucompactlines linepacker(i_clk, dw_stb, dw_bits,

                        ln_stb, ln_bits,

                        (i_wb_cyc||i_bus_busy||fifo_empty_n||cw_busy),

                        byte_busy, ln_busy);

        wbusixchar      mkbytes(i_clk, ln_stb, ln_bits, o_stb, o_char, byte_busy, i_tx_busy);

endmodule