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

//

// Filename:    wbucompactlines.v

//

// Project:     XuLA2 board

//

// Purpose:     Removes 'end of line' characters placed at the end of every

//              deworded word, unless we're idle or the line is too long.

//      This helps to format the output nicely to fit in an 80-character

//      display, should you need to do so for debugging.

//

//

// 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

//

//

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

//

//

// When to apply a new line?

//      When no prior new line exists

//              or when prior line length exceeds (72)

//      Between codewords (need inserted newline)

//      When bus has become idle (~wb_cyc)&&(~busys)

//

// So, if every codeword ends in a newline, what we

// really need to do is to remove newlines.  Thus, if

// i_stb goes high while i_tx_busy, we skip the newline

// unless the line is empty.  ... But i_stb will always

// go high while i_tx_busy.  How about if the line

// length exceeds 72, we do nothing, but record the

// last word.  If the last word was a  <incomplete-thought>

//

//

module  wbucompactlines(i_clk, i_stb, i_nl_hexbits, o_stb, o_nl_hexbits,

                i_bus_busy, i_tx_busy, o_busy);

        input   i_clk, i_stb;

        input   [6:0]    i_nl_hexbits;

        output  reg     o_stb;

        output  reg     [6:0]    o_nl_hexbits;

        input                   i_bus_busy;

        input                   i_tx_busy;

        output  wire            o_busy;

        reg     last_out_nl, last_in_nl;

        initial last_out_nl = 1'b1;

        initial last_in_nl = 1'b1;

        always @(posedge i_clk)

                if ((~i_tx_busy)&&(o_stb))

                        last_out_nl <= (o_nl_hexbits[6]);

        always @(posedge i_clk)

                if ((i_stb)&&(~o_busy))

                        last_in_nl <= (i_nl_hexbits[6]);

        // Now, let's count how long our lines are

        reg     [6:0]    linelen;

        initial linelen = 7'h00;

        always @(posedge i_clk)

                if ((~i_tx_busy)&&(o_stb))

                begin

                        if (o_nl_hexbits[6])

                                linelen <= 0;

                        else

                                linelen <= linelen + 7'h1;

                end

        reg     full_line;

        initial full_line = 1'b0;

        always @(posedge i_clk)

                full_line <= (linelen > 7'd72);

        // Now that we know whether or not the last character was a newline,

        // and indeed how many characters we have in any given line, we can

        // selectively remove newlines from our output stream.

        initial o_stb = 1'b0;

        always @(posedge i_clk)

                if ((i_stb)&&(~o_busy))

                begin

                        o_stb <= (full_line)||(~i_nl_hexbits[6]);

                        o_nl_hexbits <= i_nl_hexbits;

                end else if (~o_busy)

                begin

                        o_stb <= (~i_tx_busy)&&(~i_bus_busy)&&(~last_out_nl)&&(last_in_nl);

                        o_nl_hexbits <= 7'h40;

                end else if (~i_tx_busy)

                        o_stb <= 1'b0;

        reg     r_busy;

        initial r_busy = 1'b0;

        always @(posedge i_clk)

                r_busy <= (o_stb);

        assign  o_busy = (r_busy)||(o_stb);

        /*

        output  wire    [27:0]  o_dbg;

        assign o_dbg = { o_stb, o_nl_hexbits, o_busy, r_busy, full_line,

                        i_bus_busy, linelen, i_tx_busy, i_stb, i_nl_hexbits };

        */

endmodule