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`timescale 1ns / 1ps

// ============================================================================

//      (C) 2007,2012  Robert Finch

//      All rights reserved.

//      robfinch<remove>@opencores.org

//

//      PSGMasterVolumeControl.v 

//              Controls the PSG's output volume.

//

// 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 3 of the License, or     

// (at your option) any later version.                                      

//                                                                          

// This source file is distributed in the hope that it will be useful,      

// but WITHOUT ANY WARRANTY; without even the implied warranty of           

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            

// GNU General Public License for more details.                             

//                                                                          

// You should have received a copy of the GNU General Public License        

// along with this program.  If not, see <http://www.gnu.org/licenses/>.    

//      

//============================================================================ */

module PSGMasterVolumeControl(rst_i, clk_i, i, volume, o);

input rst_i;

input clk_i;

input [15:0] i;

input [3:0] volume;

output [19:0] o;

reg [19:0] o;

// Multiply 16x4 bits

wire [19:0] v1 = volume[0] ? i : 20'd0;

wire [19:0] v2 = volume[1] ? {i,1'b0} + v1: v1;

wire [19:0] v3 = volume[2] ? {i,2'b0} + v2: v2;

wire [19:0] vo = volume[3] ? {i,3'b0} + v3: v3;

always @(posedge clk_i)

        if (rst_i)

                o <= 20'b0;              // Force the output volume to zero on reset

        else

                o <= vo;

endmodule