CORDIC-based DDFS Architectures - Digital Design of Signal Processing Systems: A Practical Approach - page 499

R 1 R 2 R 3

R 0

k,k,k,k

cos θ dj = x Nj

N N N

0,0,0, 0

sin θ dj = y Nj

CE 0 CE 1 CE 2 CE 3

θ Nj 0

θ d3 , θ θ θ

d2, d1, d0

rst_n

tan 2 -4i

2

tan 2 -
(4i+1)

2

tan 2 -(4i+2) tan 2 -(4i+3)

counter [3:2]

Figure 12.13 Four-slow folded architecture by a folding factor of 4

reg signed [M - 1:0] x_o;
reg signed [M - 1:0] y_o;
reg signed [M-1:0] x_i;
reg signed [M-1:0] y_i;
reg signed [N-1:0] theta_i, theta_o;
reg signed [N-1:0] arcTan;
reg [LOGN-1:0] counter;
reg sel, valid;

integer i;
// Arctan table: radian values are represented in Q1.15 format
always@*
begin
case (counter)
4'b0000: arcTan = 16'h3B59;
4'b0001: arcTan = 16'h1F5B;
4'b0010: arcTan = 16'h0FEB;
4'b0011: arcTan = 16'h07FD;
4'b0100: arcTan = 16'h0400;
4'b0101: arcTan = 16'h0200;
4'b0110: arcTan = 16'h0100;
4'b0111: arcTan = 16'h0080;
4'b1000: arcTan = 16'h0040;
4'b1001: arcTan = 16'h0020;
4'b1010: arcTan = 16'h0010;
4'b1011: arcTan = 16'h0008;
4'b1100: arcTan = 16'h0004;