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87 lines
2.6 KiB
Verilog
87 lines
2.6 KiB
Verilog
/* This file is part of JTOPL.
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JTOPL is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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JTOPL is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with JTOPL. If not, see <http://www.gnu.org/licenses/>.
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Author: Jose Tejada Gomez. Twitter: @topapate
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Version: 1.0
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Date: 17-6-2020
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*/
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module jtopl_eg_ctrl(
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input keyon_now,
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input keyoff_now,
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input [2:0] state_in,
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input [9:0] eg,
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// envelope configuration
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input en_sus, // enable sustain
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input [3:0] arate, // attack rate
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input [3:0] drate, // decay rate
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input [3:0] rrate,
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input [3:0] sl, // sustain level
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output reg [4:0] base_rate,
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output reg [2:0] state_next,
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output reg pg_rst
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);
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localparam ATTACK = 3'b001,
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DECAY = 3'b010,
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HOLD = 3'b100,
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RELEASE= 3'b000; // default state is release
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// wire is_decaying = state_in[1] | state_in[2];
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wire [4:0] sustain = { &sl, sl}; //93dB if sl==4'hF
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always @(*) begin
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pg_rst = keyon_now;
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end
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always @(*)
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casez ( { keyoff_now, keyon_now, state_in} )
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5'b01_???: begin // key on
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base_rate = {arate,1'b0};
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state_next = ATTACK;
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end
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{2'b00, ATTACK}:
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if( eg==10'd0 ) begin
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base_rate = {drate,1'b0};
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state_next = DECAY;
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end
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else begin
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base_rate = {arate,1'b0};
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state_next = ATTACK;
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end
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{2'b00, DECAY}: begin
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if( eg[9:5] >= sustain ) begin
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base_rate = en_sus ? 5'd0 : {rrate,1'b0};
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state_next = en_sus ? HOLD : RELEASE;
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end else begin
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base_rate = {drate,1'b0};
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state_next = DECAY;
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end
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end
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{2'b00, HOLD}: begin
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base_rate = 5'd0;
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state_next = HOLD;
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end
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default: begin // RELEASE, note that keyoff_now==1 will enter this state too
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base_rate = {rrate,1'b1};
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state_next = RELEASE; // release
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end
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endcase
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endmodule // jtopl_eg_ctrl
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