コードの化石の断片

DrawCircle.v

module DrawCircle(
    input CLOCK,
    input nRESET,
    input START,
    input signed [11:0] X0,
    input signed [10:0] Y0,
    input signed [11:0] R,
    input FILL,
    output signed [11:0] X,
    output signed [10:0] Y,
    output OCLK,
    output BUSY
);

    reg signed [15:0] rD, rCX, rCY, rXX, rYY;
    reg [1:0] rQuadrant;
    reg [1:0] rSQ;
    reg signed [11:0] rX;
    reg signed [10:0] rY;
    reg rBUSY;

    always @( posedge CLOCK or negedge nRESET ) begin
        if ( ! nRESET ) begin
            rBUSY = 0;
            rSQ = 0;
            
        end else begin
            if ( START ) begin
                rSQ = 0;
                rD = 2 - 2 * R;
                rCX = 0;
                rCY = R;
                rXX = 0;
                rYY = R;
                rBUSY = 1;
                rQuadrant = 0;
                
            end else if ( rBUSY ) begin
                rSQ = rSQ + 1;
                if ( rSQ == 0 ) begin
                    rQuadrant = rQuadrant + 1;
                    if ( rQuadrant == 0 ) begin
                        rXX = rXX + 1;
                        if ( ! FILL || rXX > rCX ) begin
                            if ( rD > -rCY ) begin
                                rCY = rCY - 1;
                                rD = rD + 1 - 2 * rCY;
                            end
                            if ( rD <= rCX ) begin
                                rCX = rCX + 1;
                                rD = rD + 1 + 2 * rCX;
                            end
                            if ( ! FILL ) begin
                                rXX = rCX;
                            end else if ( rYY != rCY ) begin
                                rYY = rCY;
                                rXX = 0;
                            end
                        end
                    end
                    
                end else if ( rSQ == 3 ) begin
                    rX = X0 + ( ( rQuadrant == 1 || rQuadrant == 2 ) ? -rXX : rXX );
                    rY = Y0 + ( ( rQuadrant == 0 || rQuadrant == 1 ) ? rCY : -rCY );
                    if ( rQuadrant == 3 ) begin
                        rBUSY = ( rCY == 0 && rXX == rCX ) ? 0 : 1;
                    end
                    
                end
                
            end
        end
    end

    assign X = rX;
    assign Y = rY;
    assign OCLK = ( rSQ == 3 ) ? 1 : 0;
    assign BUSY = rBUSY;
endmodule