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TSConf_MiST/rtl/sound/jt12/jt12_eg_pure.v
2020-05-11 23:43:24 +08:00

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Verilog

/* 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_pure(
input attack,
input step,
input [ 5:1] rate,
input [ 9:0] eg_in,
input ssg_en,
input sum_up,
output reg [9:0] eg_pure
);
reg [ 3:0] dr_sum;
reg [ 9:0] dr_adj;
reg [10:0] dr_result;
always @(*) begin : dr_calculation
case( rate[5:2] )
4'b1100: dr_sum = { 2'b0, step, ~step }; // 12
4'b1101: dr_sum = { 1'b0, step, ~step, 1'b0 }; // 13
4'b1110: dr_sum = { step, ~step, 2'b0 }; // 14
4'b1111: dr_sum = 4'd8;// 15
default: dr_sum = { 2'b0, step, 1'b0 };
endcase
// Decay rate attenuation is multiplied by 4 for SSG operation
dr_adj = ssg_en ? {4'd0, dr_sum, 2'd0} : {6'd0, dr_sum};
dr_result = dr_adj + eg_in;
end
reg [ 7:0] ar_sum0;
reg [ 8:0] ar_sum1;
reg [10:0] ar_result;
reg [ 9:0] ar_sum;
always @(*) begin : ar_calculation
casez( rate[5:2] )
default: ar_sum0 = {2'd0, eg_in[9:4]};
4'b1101: ar_sum0 = {1'd0, eg_in[9:3]};
4'b111?: ar_sum0 = eg_in[9:2];
endcase
ar_sum1 = ar_sum0+9'd1;
if( rate[5:4] == 2'b11 )
ar_sum = step ? { ar_sum1, 1'b0 } : { 1'b0, ar_sum1 };
else
ar_sum = step ? { 1'b0, ar_sum1 } : 10'd0;
ar_result = eg_in-ar_sum;
end
///////////////////////////////////////////////////////////
// rate not used below this point
reg [9:0] eg_pre_fastar; // pre fast attack rate
always @(*) begin
if(sum_up) begin
if( attack )
eg_pre_fastar = ar_result[10] ? 10'd0: ar_result[9:0];
else
eg_pre_fastar = dr_result[10] ? 10'h3FF : dr_result[9:0];
end
else eg_pre_fastar = eg_in;
eg_pure = (attack&rate[5:1]==5'h1F) ? 10'd0 : eg_pre_fastar;
end
endmodule // jt12_eg_pure