FFTIndexer_R2 | Codetter（こーどったー）

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//FFT Radix2 DIT 用Index生成module
//A-B交互にIndexを出力
/*
FFTIndexer_R2 #(.bw_fftp(bw_fftp),.bw_stage(bw_stage)) 
    indexer(.Clock(Clock),Reset(Reset),.Index(),Start(),.Busy(),.End());
*/
module FFTIndexer_R2 #(
    ////////////////////////////////////////////////////
    // Parameters
    parameter bw_fftp = 4,      //Bit width of output index
    parameter bw_stage = 2      //bw_fftpが収まるビット幅
)
(
    ////////////////////////////////////////////////////
    // Ports
    input Clock,Reset,Start,
    output [bw_stage-1:0] Stage,
    output reg [bw_fftp-1:0] Index,
    output reg Busy,End
);
    localparam bw_count = bw_fftp+bw_stage;
    
    ////////////////////////////////////////////////////
    // Registers
    reg rEnd;
    reg [bw_count-2:0] rCount;
    reg [bw_fftp-2:0] rMask;
    reg [bw_fftp-1:0] rMaskB;
    reg [bw_stage-1:0] rStage;
    reg rABSwitch;
    wire wCountEn = rABSwitch;
    reg rSW;
    ////////////////////////////////////////////////////
    // Net
    
    wire [bw_count-1:0] wCount      = rCount + 1'b1;
    wire [bw_fftp-1:0] Pre_IndexA   =
    (rCount[bw_fftp-2:0]&rMask)|({rCount[bw_fftp-2:0]&(~rMask),1'b0});
    
    wire [bw_fftp-1:0] Pre_IndexB   = Pre_IndexA | rMaskB;
    
    assign  Stage       = rCount[bw_count-2:bw_fftp-1];
    wire    wEnd        = (Stage == bw_fftp);
    
    always@(posedge Clock or posedge Reset) begin
        if(Reset) begin
            Busy        <= 1'b0;
            End     <= 1'b0;
            rEnd        <= 1'b0;
            rABSwitch   <= 1'b0;
            rStage      <= 1'b0;
            rCount      <= 1'b0;
            rMask       <= {(bw_fftp-1){1'b1}};
            rMaskB      <= 1'b1<<(bw_fftp-1);
            rSW     <= 1'b0;
            Index       <= 1'b0;
        end else begin
            if(Start)
                Busy    <= 1'b1;
            else if (rEnd)
                Busy    <= 1'b0;
                
            if(rEnd)
                rEnd        <= 1'b0;
            else if(wEnd)
                rEnd        <= 1'b1;
            
            if (End)
                End     <= 1'b0;
            else if(rEnd) begin
                End     <= 1'b1;
            end
                
            if(wEnd || rEnd)
                rCount  <= 0;
            else if((Busy||Start) && rSW) begin 
                rCount  <= wCount[bw_count-2:0];
            end
            
            if(Start)
                rSW         <= 1'b1;
            else if(Busy)
                rSW         <= ~rSW;
                    
            if(!rSW)
                Index   <= Pre_IndexA;
            else
                Index   <= Pre_IndexB;
                
            rStage  <= Stage;
            
            if(Start) begin
                rMaskB      <= 1'b1<<(bw_fftp-1);
                rMask       <= {(bw_fftp-1){1'b1}};
            end else if(Stage != rStage) begin
                rMask       <= rMask    >> 1;
                rMaskB      <= rMaskB   >> 1;
            end
                
        end
    end
endmodule
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