Update turbosound.

rtl/sound/jt12/jt12_eg_cnt.v

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+/*  This file is part of JT12.
+
+	JT12 is free software: 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.
+
+	JT12 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 JT12.  If not, see <http://www.gnu.org/licenses/>.
+
+	Author: Jose Tejada Gomez. Twitter: @topapate
+	Version: 1.0
+	Date: 29-10-2018
+
+	*/
+
+module jt12_eg_cnt(
+	input rst,
+	input clk,
+	input clk_en,
+	input zero,
+	output reg [14:0] eg_cnt
+);
+
+reg	[1:0] eg_cnt_base;
+
+always @(posedge clk) begin : envelope_counter
+	if( rst ) begin
+		eg_cnt_base	<= 2'd0;
+		eg_cnt		<=15'd0;
+	end
+	else begin
+		if( zero && clk_en ) begin
+			// envelope counter increases every 3 output samples,
+			// there is one sample every 24 clock ticks
+			if( eg_cnt_base == 2'd2 ) begin
+				eg_cnt 		<= eg_cnt + 1'b1;
+				eg_cnt_base	<= 2'd0;
+			end
+			else eg_cnt_base <= eg_cnt_base + 1'b1;
+		end
+	end
+end
+
+endmodule // jt12_eg_cnt