update JT12

rtl/sound/jt49/jt49_noise.v

@@ -0,0 +1,62 @@
+/*  This file is part of JT49.
+
+    JT49 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.
+
+    JT49 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 JT49.  If not, see <http://www.gnu.org/licenses/>.
+    
+    Author: Jose Tejada Gomez. Twitter: @topapate
+    Version: 1.0
+    Date: 10-Nov-2018
+    
+    Based on sqmusic, by the same author
+    
+    */
+
+
+module jt49_noise(
+  (* direct_enable *) input cen,
+    input       clk,
+    input       rst_n,
+    input [4:0] period,
+    output reg  noise
+);
+
+reg [5:0]count;
+reg [16:0]poly17;
+wire poly17_zero = poly17==17'b0;
+wire noise_en;
+reg last_en;
+
+wire noise_up = noise_en && !last_en;
+
+always @(posedge clk ) if(cen) begin
+    noise <= ~poly17[0];
+end
+
+always @( posedge clk, negedge rst_n )
+  if( !rst_n ) 
+    poly17 <= 17'd0;
+  else if( cen ) begin
+    last_en <= noise_en;
+    if( noise_up )
+        poly17 <= { poly17[0] ^ poly17[3] ^ poly17_zero, poly17[16:1] };
+  end
+
+jt49_div #(5) u_div( 
+  .clk    ( clk       ), 
+  .cen    ( cen       ),
+  .rst_n  ( rst_n     ), 
+  .period ( period    ), 
+  .div    ( noise_en  ) 
+);
+
+endmodule