| Line 1... |
Line 1... |
`timescale 1ns / 1ps
|
`timescale 1ns / 1ps
|
// ============================================================================
|
// ============================================================================
|
// (C) 2007,2012 Robert Finch
|
// __
|
// All rights reserved.
|
// \\__/ o\ (C) 2007-2017 Robert Finch, Waterloo
|
// robfinch<remove>@opencores.org
|
// \ __ / All rights reserved.
|
|
// \/_// robfinch<remove>@finitron.ca
|
|
// ||
|
//
|
//
|
// PSGVolumeControl.v
|
// PSGVolumeControl.v
|
// Controls the PSG's output volume.
|
// Controls the PSG's output volume.
|
|
// The volume control is made non-linear with a ROM lookup table based on
|
|
// an increment similar to Fibonnaci series.
|
//
|
//
|
// This source file is free software: you can redistribute it and/or modify
|
// 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
|
// 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
|
// by the Free Software Foundation, either version 3 of the License, or
|
// (at your option) any later version.
|
// (at your option) any later version.
|
| Line 18... |
Line 22... |
// GNU General Public License for more details.
|
// GNU General Public License for more details.
|
//
|
//
|
// You should have received a copy of the GNU General Public License
|
// You should have received a copy of the GNU General Public License
|
// along with this program. If not, see <http://www.gnu.org/licenses/>.
|
// along with this program. If not, see <http://www.gnu.org/licenses/>.
|
//
|
//
|
//============================================================================ */
|
//=============================================================================
|
|
|
module PSGVolumeControl(rst_i, clk_i, i, volume, o);
|
module PSGVolumeControl(rst_i, clk_i, i, volume, o);
|
input rst_i;
|
input rst_i;
|
input clk_i;
|
input clk_i;
|
input [21:0] i;
|
input [21:0] i;
|
input [7:0] volume;
|
input [3:0] volume;
|
output [29:0] o;
|
output [29:0] o;
|
reg [29:0] o;
|
reg [29:0] o;
|
|
|
|
// This ROM lookup table to delinearize the volume control.
|
|
// Uses mangled Fibonnaci series.
|
|
reg [7:0] vol;
|
|
always @*
|
|
case(volume)
|
|
4'd00: vol = 8'd00;
|
|
4'd01: vol = 8'd01;
|
|
4'd03: vol = 8'd01;
|
|
4'd04: vol = 8'd02;
|
|
4'd05: vol = 8'd03;
|
|
4'd06: vol = 8'd05;
|
|
4'd07: vol = 8'd08;
|
|
4'd09: vol = 8'd13;
|
|
4'd10: vol = 8'd21;
|
|
4'd11: vol = 8'd34;
|
|
4'd12: vol = 8'd56;
|
|
4'd13: vol = 8'd90;
|
|
4'd14: vol = 8'd151;
|
|
4'd15: vol = 8'd255;
|
|
endcase
|
always @(posedge clk_i)
|
always @(posedge clk_i)
|
if (rst_i)
|
if (rst_i)
|
o <= 26'b0; // Force the output volume to zero on reset
|
o <= 26'b0; // Force the output volume to zero on reset
|
else
|
else
|
o <= i * volume;
|
o <= i * vol;
|
|
|
endmodule
|
endmodule
|
|
|
No newline at end of file
|
No newline at end of file
|
