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// -*- verilog -*-
//
// USRP - Universal Software Radio Peripheral
//
// Copyright (C) 2003, 2007 Matt Ettus
//
// This program 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 2 of the License, or
// (at your option) any later version.
//
// This program 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 this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Boston, MA 02110-1301 USA
//
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
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