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BHG_jt49.v
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BHG_jt49.v
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/* This file is part of JT49.
*******************************************************************
*** Modified by BrianHG providing a volumetric attenuation db, ***
*** and variable/higher resolution DAC. ***
*** + Patched Modelsim initialization bug when using DC filter. ***
*******************************************************************
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 BHG_jt49 #(
parameter DAC_BITS = 8 // The number of DAC bits for each channel of the YM2149 PSG. Supports 8 thru 14.
// 10 bits almost perfectly replicates the YM2149 DA converter's Normalized voltage.
// With 8 bits, the lowest volumes settings will be slightly louder than normal.
// With 12 bits, the lowest volume settings will be too quiet.
)( // note that input ports are not multiplexed
input rst_n,
input clk, // signal on positive edge
input clk_en /* synthesis direct_enable = 1 */,
input [3:0] addr,
input cs_n,
input wr_n, // write
input [7:0] din,
input sel, // if sel is low, the clock is divided by 2
output reg [7:0] dout,
output reg [DAC_BITS+1:0] sound, // combined channel output
output reg [DAC_BITS-1:0] A, // linearised channel output
output reg [DAC_BITS-1:0] B,
output reg [DAC_BITS-1:0] C,
output sample,
input [7:0] IOA_in,
output [7:0] IOA_out,
input [7:0] IOB_in,
output [7:0] IOB_out
);
localparam CLKDIV=3;
reg [7:0] regarray[15:0];
wire [7:0] port_A, port_B;
wire [4:0] envelope;
wire bitA, bitB, bitC;
wire noise;
reg Amix = 0, Bmix = 0, Cmix = 0;
wire cen16, cen256;
assign IOA_out = regarray[14];
assign IOB_out = regarray[15];
assign port_A = !regarray[7][6] ? IOA_in : IOA_out;
assign port_B = !regarray[7][7] ? IOB_in : IOB_out;
assign sample = cen16;
jt49_cen #(.CLKDIV(CLKDIV)) u_cen(
.clk ( clk ),
.rst_n ( rst_n ),
.cen ( clk_en ),
.sel ( sel ),
.cen16 ( cen16 ),
.cen256 ( cen256 )
);
// internal modules operate at clk/16
jt49_div #(12) u_chA(
.clk ( clk ),
.rst_n ( rst_n ),
.cen ( cen16 ),
.period ( {regarray[1][3:0], regarray[0][7:0] } ),
.div ( bitA )
);
jt49_div #(12) u_chB(
.clk ( clk ),
.rst_n ( rst_n ),
.cen ( cen16 ),
.period ( {regarray[3][3:0], regarray[2][7:0] } ),
.div ( bitB )
);
jt49_div #(12) u_chC(
.clk ( clk ),
.rst_n ( rst_n ),
.cen ( cen16 ),
.period ( {regarray[5][3:0], regarray[4][7:0] } ),
.div ( bitC )
);
jt49_noise u_ng(
.clk ( clk ),
.cen ( cen16 ),
.rst_n ( rst_n ),
.period ( regarray[6][4:0] ),
.noise ( noise )
);
// envelope generator
wire eg_step;
wire [15:0] eg_period = {regarray[4'hc],regarray[4'hb]};
wire null_period = eg_period == 16'h0;
jt49_div #(16) u_envdiv(
.clk ( clk ),
.cen ( cen256 ),
.rst_n ( rst_n ),
.period ( eg_period ),
.div ( eg_step )
);
reg eg_restart;
jt49_eg u_env(
.clk ( clk ),
.cen ( cen256 ),
.step ( eg_step ),
.rst_n ( rst_n ),
.restart ( eg_restart ),
.null_period( null_period ),
.ctrl ( regarray[4'hD][3:0] ),
.env ( envelope )
);
reg [4:0] logA = 5'd0, logB = 5'd0, logC = 5'd0, log = 5'd0;
wire [DAC_BITS-1:0] lin;
BHG_jt49_exp #(
.DAC_BITS ( DAC_BITS )
) u_exp (
.clk ( clk ),
// .comp ( comp ), *** no longer used.
.din ( log ),
.dout ( lin )
);
wire [4:0] volA = { regarray[ 8][3:0], regarray[ 8][3] };
wire [4:0] volB = { regarray[ 9][3:0], regarray[ 9][3] };
wire [4:0] volC = { regarray[10][3:0], regarray[10][3] };
wire use_envA = regarray[ 8][4];
wire use_envB = regarray[ 9][4];
wire use_envC = regarray[10][4];
wire use_noA = regarray[ 7][3];
wire use_noB = regarray[ 7][4];
wire use_noC = regarray[ 7][5];
reg [3:0] acc_st;
always @(posedge clk) if( clk_en ) begin
Amix <= (noise|use_noA) & (bitA|regarray[7][0]);
Bmix <= (noise|use_noB) & (bitB|regarray[7][1]);
Cmix <= (noise|use_noC) & (bitC|regarray[7][2]);
logA <= !Amix ? 5'd0 : (use_envA ? envelope : volA );
logB <= !Bmix ? 5'd0 : (use_envB ? envelope : volB );
logC <= !Cmix ? 5'd0 : (use_envC ? envelope : volC );
end
reg [DAC_BITS+1:0] acc;
always @(posedge clk, negedge rst_n) begin
if( !rst_n ) begin
acc_st <= 4'b1;
acc <= (DAC_BITS+2)'(0) ;
A <= (DAC_BITS)'(0) ;
B <= (DAC_BITS)'(0) ;
C <= (DAC_BITS)'(0) ;
sound <= (DAC_BITS+2)'(0) ;
end else if(clk_en) begin
acc_st <= { acc_st[2:0], acc_st[3] };
acc <= acc + {2'b0,lin};
case( acc_st )
4'b0001: begin
log <= logA;
acc <= (DAC_BITS+2)'(0) ;
sound <= acc;
end
4'b0010: begin
A <= lin;
log <= logB;
end
4'b0100: begin
B <= lin;
log <= logC;
end
4'b1000: begin // last sum
C <= lin;
end
default:;
endcase
end
end
reg [7:0] read_mask;
always @(*)
case(addr)
4'h0,4'h2,4'h4,4'h7,4'hb,4'hc,4'he,4'hf:
read_mask = 8'hff;
4'h1,4'h3,4'h5,4'hd:
read_mask = 8'h0f;
4'h6,4'h8,4'h9,4'ha:
read_mask = 8'h1f;
endcase // addr
// register array
wire write;
reg last_write;
wire wr_edge = write & ~last_write;
assign write = !wr_n && !cs_n;
always @(posedge clk, negedge rst_n) begin
if( !rst_n ) begin
dout <= 8'd0;
last_write <= 0;
eg_restart <= 0;
regarray[0]<=8'd0; regarray[4]<=8'd0; regarray[ 8]<=8'd0; regarray[12]<=8'd0;
regarray[1]<=8'd0; regarray[5]<=8'd0; regarray[ 9]<=8'd0; regarray[13]<=8'd0;
regarray[2]<=8'd0; regarray[6]<=8'd0; regarray[10]<=8'd0; regarray[14]<=8'd0;
regarray[3]<=8'd0; regarray[7]<=8'd0; regarray[11]<=8'd0; regarray[15]<=8'd0;
end else begin
last_write <= write;
// Data read
case( addr )
4'he: dout <= port_A;
4'hf: dout <= port_B;
default: dout <= regarray[ addr ] & read_mask;
endcase
// Data write
if( write ) begin
regarray[addr] <= din;
if ( addr == 4'hD && wr_edge ) eg_restart <= 1;
end else begin
eg_restart <= 0;
end
end
end
endmodule