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668 lvd 1 
// ZX-Evo Base Configuration (c) NedoPC 2008,2009,2010,2011,2012,2013,2014
360 lvd 2 
//
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// integrates sound features: tapeout, beeper and covox
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668 lvd 5 
/*
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    This file is part of ZX-Evo Base Configuration firmware.
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    ZX-Evo Base Configuration firmware is free software:
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    you can redistribute it and/or modify it under the terms of
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    the GNU General Public License as published by
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    the Free Software Foundation, either version 3 of the License, or
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    (at your option) any later version.
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    ZX-Evo Base Configuration firmware is distributed in the hope that
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    it will be useful, but WITHOUT ANY WARRANTY; without even
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    the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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    See the GNU General Public License for more details.
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    You should have received a copy of the GNU General Public License
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    along with ZX-Evo Base Configuration firmware.
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    If not, see <http://www.gnu.org/licenses/>.
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*/
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`include "../include/tune.v"
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360 lvd 26 
module sound(
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        input  wire       clk,
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        input  wire [7:0] din,
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        input  wire       beeper_wr,
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        input  wire       covox_wr,
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        input  wire       beeper_mux, // output either tape_out or beeper
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        output wire       sound_bit
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);
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        reg [6:0] ctr;
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        reg [7:0] val;
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        reg mx_beep_n_covox;
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        reg beep_bit;
473 chrv 48 
        reg beep_bit_old;
360 lvd 49 
 
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        wire covox_bit;
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        always @(posedge clk)
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        begin
473 chrv 57 
/*              if( beeper_wr ) */
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                                if( beeper_wr && (beep_bit!=beep_bit_old) )
360 lvd 59 
                        mx_beep_n_covox <= 1'b1;
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                else if( covox_wr )
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                        mx_beep_n_covox <= 1'b0;
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        end
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473 chrv 64 
        always @(posedge clk) if( beeper_wr ) beep_bit_old <= beep_bit;
360 lvd 65 
 
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        always @(posedge clk)
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        if( beeper_wr )
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                beep_bit <= beeper_mux ? din[3] /*tapeout*/ : din[4] /*beeper*/;
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        always @(posedge clk)
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        if( covox_wr )
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                val <= din;
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        always @(negedge clk)
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                ctr <= ctr + 6'd1;
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        assign covox_bit = ( {ctr,clk} < val );
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        bothedge trigger
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        (
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                .clk( clk ),
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                .d( mx_beep_n_covox ? beep_bit : covox_bit ),
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                .q( sound_bit )
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        );
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endmodule
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// both-edge trigger emulator
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module bothedge(
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        input  wire clk,
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        input  wire d,
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        output wire q
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);
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        reg trgp, trgn;
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        assign q = trgp ^ trgn;
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        always @(posedge clk)
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        if( d!=q )
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                trgp <= ~trgp;
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        always @(negedge clk)
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        if( d!=q )
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                trgn <= ~trgn;
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endmodule
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