module cordic(clock, reset, enable, xi, yi, zi, xo, yo, zo );
   parameter bitwidth = 16;
   parameter zwidth = 16;
   
   input clock;
   input reset;
   input enable;
   input [bitwidth-1:0] xi, yi;
   output [bitwidth-1:0] xo, yo;
   input [zwidth-1:0] zi;
   output [zwidth-1:0] zo;
   
   reg [bitwidth+1:0] 	 x0,y0;
   reg [zwidth-2:0] 	 z0;
   wire [bitwidth+1:0] 	 x1,x2,x3,x4,x5,x6,x7,x8,x9,x10,x11,x12;
   wire [bitwidth+1:0] 	 y1,y2,y3,y4,y5,y6,y7,y8,y9,y10,y11,y12;
   wire [zwidth-2:0] z1,z2,z3,z4,z5,z6,z7,z8,z9,z10,z11,z12;
   
   wire [bitwidth+1:0] xi_ext = {{2{xi[bitwidth-1]}},xi};
   wire [bitwidth+1:0] yi_ext = {{2{yi[bitwidth-1]}},yi};

   // Compute consts.  Would be easier if vlog had atan...
   // see gen_cordic_consts.py
   
   localparam 	       c00 = 15'd8192;
   localparam 	       c01 = 15'd4836;
   localparam 	       c02 = 15'd2555;
   localparam 	       c03 = 15'd1297;
   localparam 	       c04 = 15'd651;
   localparam 	       c05 = 15'd326;
   localparam 	       c06 = 15'd163;
   localparam 	       c07 = 15'd81;
   localparam 	       c08 = 15'd41;
   localparam 	       c09 = 15'd20;
   localparam 	       c10 = 15'd10;
   localparam 	       c11 = 15'd5;
   localparam 	       c12 = 15'd3;
   localparam 	       c13 = 15'd1;
   localparam 	       c14 = 15'd1;
   localparam 	       c15 = 15'd0;
   localparam 	       c16 = 15'd0;
   
   always @(posedge clock)
     if(reset)
       begin
	  x0   <= 0; y0   <= 0;  z0   <= 0;
       end
     else// if(enable)
       begin
	  z0 <= zi[zwidth-2:0];
	  case (zi[zwidth-1:zwidth-2])
	    2'b00, 2'b11 : 
	      begin
		 x0 <= xi_ext;
		 y0 <= yi_ext;
	      end
	    2'b01, 2'b10 :
	      begin
		 x0 <= -xi_ext;
		 y0 <= -yi_ext;
	      end
	  endcase // case(zi[zwidth-1:zwidth-2])
       end // else: !if(reset)
   
   // FIXME need to handle variable number of stages
   // FIXME should be able to narrow zwidth but quartus makes it bigger...
   // This would be easier if arrays worked better in vlog...
   cordic_stage #(bitwidth+2,zwidth-1,0) cordic_stage0 (clock,reset,enable,x0,y0,z0,c00,x1,y1,z1);
   cordic_stage #(bitwidth+2,zwidth-1,1) cordic_stage1 (clock,reset,enable,x1,y1,z1,c01,x2,y2,z2);
   cordic_stage #(bitwidth+2,zwidth-1,2) cordic_stage2 (clock,reset,enable,x2,y2,z2,c02,x3,y3,z3);
   cordic_stage #(bitwidth+2,zwidth-1,3) cordic_stage3 (clock,reset,enable,x3,y3,z3,c03,x4,y4,z4);
   cordic_stage #(bitwidth+2,zwidth-1,4) cordic_stage4 (clock,reset,enable,x4,y4,z4,c04,x5,y5,z5);
   cordic_stage #(bitwidth+2,zwidth-1,5) cordic_stage5 (clock,reset,enable,x5,y5,z5,c05,x6,y6,z6);
   cordic_stage #(bitwidth+2,zwidth-1,6) cordic_stage6 (clock,reset,enable,x6,y6,z6,c06,x7,y7,z7);
   cordic_stage #(bitwidth+2,zwidth-1,7) cordic_stage7 (clock,reset,enable,x7,y7,z7,c07,x8,y8,z8);
   cordic_stage #(bitwidth+2,zwidth-1,8) cordic_stage8 (clock,reset,enable,x8,y8,z8,c08,x9,y9,z9);
   cordic_stage #(bitwidth+2,zwidth-1,9) cordic_stage9 (clock,reset,enable,x9,y9,z9,c09,x10,y10,z10);
   cordic_stage #(bitwidth+2,zwidth-1,10) cordic_stage10 (clock,reset,enable,x10,y10,z10,c10,x11,y11,z11);
   cordic_stage #(bitwidth+2,zwidth-1,11) cordic_stage11 (clock,reset,enable,x11,y11,z11,c11,x12,y12,z12);

   assign xo = x12[bitwidth:1];  
   assign yo = y12[bitwidth:1];
   //assign xo = x12[bitwidth+1:2];  // CORDIC gain is ~1.6, plus gain from rotating vectors
   //assign yo = y12[bitwidth+1:2];
   assign zo = z12;		  

endmodule // cordic