[USRP-users] Cordic Algorithm quadrant selection

[imran qureshi via USRP-users]

Hi,
I want to learn the cordic implementation of the duc_chain, and want to
understand how the quadrant selection is done in the cordic_z.v code for
vector rotation.(fpga
<https://github.com/EttusResearch/fpga/tree/61cdf981dcfe8823b7941840c744b51c7994b79f>
/usrp3
<https://github.com/EttusResearch/fpga/tree/61cdf981dcfe8823b7941840c744b51c7994b79f/usrp3>
/lib
<https://github.com/EttusResearch/fpga/tree/61cdf981dcfe8823b7941840c744b51c7994b79f/usrp3/lib>
/dsp
<https://github.com/EttusResearch/fpga/tree/61cdf981dcfe8823b7941840c744b51c7994b79f/usrp3/lib/dsp>
/cordic_z24.v)
code snippet

  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])
Regards,
Immi

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