Merge FPGA repository back into UHD repository

The FPGA codebase was removed from the UHD repository in 2014 to reduce
the size of the repository. However, over the last half-decade, the
split between the repositories has proven more burdensome than it has
been helpful. By merging the FPGA code back, it will be possible to
create atomic commits that touch both FPGA and UHD codebases. Continuous
integration testing is also simplified by merging the repositories,
because it was previously difficult to automatically derive the correct
UHD branch when testing a feature branch on the FPGA repository.

This commit also updates the license files and paths therein.

We are therefore merging the repositories again. Future development for
FPGA code will happen in the same repository as the UHD host code and
MPM code.

== Original Codebase and Rebasing ==

The original FPGA repository will be hosted for the foreseeable future
at its original local location: https://github.com/EttusResearch/fpga/

It can be used for bisecting, reference, and a more detailed history.

The final commit from said repository to be merged here is
05003794e2da61cabf64dd278c45685a7abad7ec. This commit is tagged as
v4.0.0.0-pre-uhd-merge.

If you have changes in the FPGA repository that you want to rebase onto
the UHD repository, simply run the following commands:

- Create a directory to store patches (this should be an empty
  directory):

    mkdir ~/patches

- Now make sure that your FPGA codebase is based on the same state as
  the code that was merged:

    cd src/fpga # Or wherever your FPGA code is stored
    git rebase v4.0.0.0-pre-uhd-merge

  Note: The rebase command may look slightly different depending on what
  exactly you're trying to rebase.

- Create a patch set for your changes versus v4.0.0.0-pre-uhd-merge:

    git format-patch v4.0.0.0-pre-uhd-merge -o ~/patches

  Note: Make sure that only patches are stored in your output directory.
  It should otherwise be empty. Make sure that you picked the correct
  range of commits, and only commits you wanted to rebase were exported
  as patch files.

- Go to the UHD repository and apply the patches:

    cd src/uhd # Or wherever your UHD repository is stored
    git am --directory fpga ~/patches/*
    rm -rf ~/patches # This is for cleanup

== Contributors ==

The following people have contributed mainly to these files (this list
is not complete):

Co-authored-by: Alex Williams <alex.williams@ni.com>
Co-authored-by: Andrej Rode <andrej.rode@ettus.com>
Co-authored-by: Ashish Chaudhari <ashish@ettus.com>
Co-authored-by: Ben Hilburn <ben.hilburn@ettus.com>
Co-authored-by: Ciro Nishiguchi <ciro.nishiguchi@ni.com>
Co-authored-by: Daniel Jepson <daniel.jepson@ni.com>
Co-authored-by: Derek Kozel <derek.kozel@ettus.com>
Co-authored-by: EJ Kreinar <ej@he360.com>
Co-authored-by: Humberto Jimenez <humberto.jimenez@ni.com>
Co-authored-by: Ian Buckley <ian.buckley@gmail.com>
Co-authored-by: Jörg Hofrichter <joerg.hofrichter@ni.com>
Co-authored-by: Jon Kiser <jon.kiser@ni.com>
Co-authored-by: Josh Blum <josh@joshknows.com>
Co-authored-by: Jonathon Pendlum <jonathan.pendlum@ettus.com>
Co-authored-by: Martin Braun <martin.braun@ettus.com>
Co-authored-by: Matt Ettus <matt@ettus.com>
Co-authored-by: Michael West <michael.west@ettus.com>
Co-authored-by: Moritz Fischer <moritz.fischer@ettus.com>
Co-authored-by: Nick Foster <nick@ettus.com>
Co-authored-by: Nicolas Cuervo <nicolas.cuervo@ettus.com>
Co-authored-by: Paul Butler <paul.butler@ni.com>
Co-authored-by: Paul David <paul.david@ettus.com>
Co-authored-by: Ryan Marlow <ryan.marlow@ettus.com>
Co-authored-by: Sugandha Gupta <sugandha.gupta@ettus.com>
Co-authored-by: Sylvain Munaut <tnt@246tNt.com>
Co-authored-by: Trung Tran <trung.tran@ettus.com>
Co-authored-by: Vidush Vishwanath <vidush.vishwanath@ettus.com>
Co-authored-by: Wade Fife <wade.fife@ettus.com>

1 files changed, 375 insertions, 0 deletions

diff --git a/fpga/usrp3/lib/dsp/ddc_chain.v b/fpga/usrp3/lib/dsp/ddc_chain.v
new file mode 100644
index 000000000..9c25d8e43
--- /dev/null
+++ b/fpga/usrp3/lib/dsp/ddc_chain.v
@@ -0,0 +1,375 @@
+//
+// Copyright 2011-2013 Ettus Research LLC
+// Copyright 2018 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: LGPL-3.0-or-later
+//
+
+
+//! The USRP digital down-conversion chain
+
+module ddc_chain
+  #(
+    parameter BASE = 0,
+    parameter DSPNO = 0,
+    parameter WIDTH = 24,
+    parameter NEW_HB_DECIM = 0,
+    parameter DEVICE = "SPARTAN6"
+  )
+  (input clk, input rst, input clr,
+   input 	     set_stb, input [7:0] set_addr, input [31:0] set_data,
+
+   // From RX frontend
+   input [WIDTH-1:0] rx_fe_i,
+   input [WIDTH-1:0] rx_fe_q,
+
+   // To RX control
+   output [31:0] sample,
+   input 	     run,
+   output 	     strobe,
+   output [31:0]     debug
+   );
+
+   localparam  cwidth = 25;
+   localparam  zwidth = 24;
+
+   wire [31:0] phase_inc;
+   reg [31:0]  phase;
+
+   wire [17:0] scale_factor;
+   wire [cwidth-1:0] to_cordic_i, to_cordic_q;
+   wire [cwidth-1:0] i_cordic, q_cordic;
+   reg  [WIDTH-1:0] i_cordic_pipe, q_cordic_pipe;
+   wire [WIDTH-1:0] i_cic, q_cic;
+
+
+   wire        strobe_cic, strobe_hb1, strobe_hb2;
+   wire        enable_hb1, enable_hb2;
+   wire [7:0]  cic_decim_rate;
+
+   reg [WIDTH-1:0]  rx_fe_i_mux, rx_fe_q_mux;
+   wire        realmode;
+   wire        swap_iq;
+   wire        invert_i;
+   wire        invert_q;
+
+   setting_reg #(.my_addr(BASE+0)) sr_0
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(phase_inc),.changed());
+
+   setting_reg #(.my_addr(BASE+1), .width(18)) sr_1
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(scale_factor),.changed());
+
+   setting_reg #(.my_addr(BASE+2), .width(10)) sr_2
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out({enable_hb1, enable_hb2, cic_decim_rate}),.changed());
+
+   setting_reg #(.my_addr(BASE+3), .width(4)) sr_3
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out({invert_i,invert_q,realmode,swap_iq}),.changed());
+
+
+   // MUX so we can do realmode signals on either input
+
+   always @(posedge clk)
+     if(swap_iq)
+       begin
+          rx_fe_i_mux <= invert_i ? ~rx_fe_q : rx_fe_q;
+          rx_fe_q_mux <= realmode ? {WIDTH{1'b0}} : invert_q ? ~rx_fe_i : rx_fe_i;
+       end
+     else
+       begin
+	  rx_fe_i_mux <= invert_i ? ~rx_fe_i : rx_fe_i;
+          rx_fe_q_mux <= realmode ? {WIDTH{1'b0}} : invert_q ? ~rx_fe_q : rx_fe_q;
+       end
+
+   // NCO
+   always @(posedge clk)
+     if(rst)
+       phase <= 0;
+     else if(~run)
+       phase <= 0;
+     else
+       phase <= phase + phase_inc;
+
+   // CORDIC  24-bit I/O
+   // (Algorithmic gain through CORDIC => 1.647 * 0.5 = 0.8235)
+   // (Worst case gain through rotation => SQRT(2) = 1.4142)
+   // Total worst case gain => 0.8235 * 1.4142 = 1.1646
+   // So add an extra MSB bit for word growth.
+
+   sign_extend #(.bits_in(WIDTH), .bits_out(cwidth)) sign_extend_cordic_i (.in(rx_fe_i_mux), .out(to_cordic_i));
+   sign_extend #(.bits_in(WIDTH), .bits_out(cwidth)) sign_extend_cordic_q (.in(rx_fe_q_mux), .out(to_cordic_q));
+
+   cordic_z24 #(.bitwidth(cwidth))
+   cordic(.clock(clk), .reset(rst), .enable(run),
+	  .xi(to_cordic_i),. yi(to_cordic_q), .zi(phase[31:32-zwidth]),
+	  .xo(i_cordic),.yo(q_cordic),.zo() );
+
+   always @(posedge clk) begin
+      i_cordic_pipe[23:0] <= i_cordic[24:1];
+      q_cordic_pipe[23:0] <= q_cordic[24:1];
+   end
+
+
+   // CIC decimator  24 bit I/O
+   // Applies crude 1/(2^N) right shift gain compensation internally to prevent excesive downstream word growth.
+   // Output gain is = algo_gain/(POW(2,CEIL(LOG2(algo_gain))) where algo_gain is = cic_decim_rate^4
+   // Thus output gain is <= 1.0 and no word growth occurs.
+   cic_strober cic_strober(.clock(clk),.reset(rst),.enable(run),.rate(cic_decim_rate),
+			   .strobe_fast(1'b1),.strobe_slow(strobe_cic) );
+
+   cic_decim #(.bw(WIDTH))
+     decim_i (.clock(clk),.reset(rst),.enable(run),
+	      .rate(cic_decim_rate),.strobe_in(1'b1),.strobe_out(strobe_cic),
+	      .signal_in(i_cordic_pipe),.signal_out(i_cic));
+
+   cic_decim #(.bw(WIDTH))
+     decim_q (.clock(clk),.reset(rst),.enable(run),
+	      .rate(cic_decim_rate),.strobe_in(1'b1),.strobe_out(strobe_cic),
+	      .signal_in(q_cordic_pipe),.signal_out(q_cic));
+
+   //////////////////////////////////////////////////////////////////////////
+   //
+   // Conditional compilation of either:
+   // 1) New X300 style decimation filters, or
+   // 2) Traditional N210 style decimation filters.
+   //
+   //////////////////////////////////////////////////////////////////////////
+   generate
+      if (NEW_HB_DECIM == 1) begin: new_hb
+
+	 wire        reload_go, reload_we1, reload_we2,  reload_ld1, reload_ld2;
+	 wire [17:0] coef_din;
+
+	 setting_reg #(.my_addr(BASE+4), .width(22)) sr_4
+	   (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+	    .in(set_data),.out({reload_ld2,reload_we2,reload_ld1,reload_we1,coef_din[17:0]}),.changed(reload_go));
+
+	 // Halfbands
+	 wire 	     nd1, nd2, nd3;
+	 wire 	     rfd1, rfd2, rfd3;
+	 wire 	     rdy1, rdy2, rdy3;
+	 wire 	     data_valid1, data_valid2, data_valid3;
+	 wire [46:0] i_hb1, q_hb1;
+	 wire [46:0] i_hb2, q_hb2;
+	 localparam HB1_SCALE = 18;
+	 localparam HB2_SCALE = 18;
+
+
+	 assign strobe_hb1 = data_valid1;
+	 assign strobe_hb2 = data_valid2;
+
+	 assign nd1 = strobe_cic;
+	 assign nd2 = strobe_hb1;
+
+	 // Default Coeffs have gain of ~1.0
+	 hbdec1 hbdec1
+	   (.clk(clk), // input clk
+	    .sclr(rst), // input sclr
+	    .ce(enable_hb1), // input ce
+	    .coef_ld(reload_go & reload_ld1), // input coef_ld
+	    .coef_we(reload_go & reload_we1), // input coef_we
+	    .coef_din(coef_din), // input [17 : 0] coef_din
+	    .rfd(rfd1), // output rfd
+	    .nd(nd1), // input nd
+	    .din_1(i_cic), // input [23 : 0] din_1
+	    .din_2(q_cic), // input [23 : 0] din_2
+	    .rdy(rdy1), // output rdy
+	    .data_valid(data_valid1), // output data_valid
+	    .dout_1(i_hb1), // output [46 : 0] dout_1
+	    .dout_2(q_hb1)); // output [46 : 0] dout_2
+
+	 // Default Coeffs have gain of ~1.0
+	 hbdec2 hbdec2
+	   (.clk(clk), // input clk
+	    .sclr(rst), // input sclr
+	    .ce(enable_hb2), // input ce
+	    .coef_ld(reload_go & reload_ld2), // input coef_ld
+	    .coef_we(reload_go & reload_we2), // input coef_we
+	    .coef_din(coef_din), // input [17 : 0] coef_din
+	    .rfd(rfd2), // output rfd
+	    .nd(nd2), // input nd
+	    .din_1(i_hb1[23+HB1_SCALE:HB1_SCALE]), // input [23 : 0] din_1
+	    .din_2(q_hb1[23+HB1_SCALE:HB1_SCALE]), // input [23 : 0] din_2
+	    .rdy(rdy2), // output rdy
+	    .data_valid(data_valid2), // output data_valid
+	    .dout_1(i_hb2), // output [46 : 0] dout_1
+	    .dout_2(q_hb2)); // output [46 : 0] dout_2
+
+
+
+	 reg [18:0]  i_unscaled, q_unscaled;
+	 reg 	     strobe_unscaled;
+
+	 always @(posedge clk)
+	   case({enable_hb1,enable_hb2})
+	     // No Halfbands enabled, no decimation.
+	     2'd0 :
+	       begin
+		  strobe_unscaled <= strobe_cic;
+		  i_unscaled <= i_cic[23:5];
+		  q_unscaled <= q_cic[23:5];
+	       end
+	     // ILLEGAL. Only half sample rate half band enabled.
+	     2'd1 :
+	       begin
+		  strobe_unscaled <= strobe_cic;
+		  i_unscaled <= i_cic[23:5];
+		  q_unscaled <= q_cic[23:5];
+	       end
+	     // One Halfband enabled, decimate by 2.
+	     2'd2 :
+	       begin
+		  strobe_unscaled <= strobe_hb1;
+		  i_unscaled <= i_hb1[23+HB1_SCALE:5+HB1_SCALE];
+		  q_unscaled <= q_hb1[23+HB1_SCALE:5+HB1_SCALE];
+	       end
+	     // Both Halfbands enabled, decimate by 4.
+	     2'd3 :
+	       begin
+		  strobe_unscaled <= strobe_hb2;
+		  i_unscaled <= i_hb2[23+HB2_SCALE:5+HB2_SCALE];
+		  q_unscaled <= q_hb2[23+HB2_SCALE:5+HB2_SCALE];
+	     end
+	   endcase // case (hb_rate)
+
+	 // Need to clip 1 bit here or we loose small signal performance out the truncated LSB's for worst case CIC gain cases.
+	 // NOTE: We can only clip here with CORDIC rotating, CIC in it's highest gain configurations and an input signal thats
+	 // saturated.
+	 wire strobe_unscaled_clip;
+	 wire [17:0] i_unscaled_clip, q_unscaled_clip;
+
+	 clip_reg #(.bits_in(19), .bits_out(18), .STROBED(1)) unscaled_clip_i
+	   (.clk(clk), .in(i_unscaled[18:0]), .strobe_in(strobe_unscaled), .out(i_unscaled_clip[17:0]), .strobe_out(strobe_unscaled_clip));
+	 clip_reg #(.bits_in(19), .bits_out(18), .STROBED(1)) unscaled_clip_q
+	   (.clk(clk), .in(q_unscaled[18:0]), .strobe_in(strobe_unscaled), .out(q_unscaled_clip[17:0]), .strobe_out());
+
+	 // Apply scaling gain to compensate for CORDIC and CIC gain adjustments so that signal swing over network transport has
+	 // optimal dynamic range.
+	 wire [35:0] 	  prod_i, prod_q;
+
+	 MULT_MACRO #(.DEVICE(DEVICE),  // Target Device: "VIRTEX5", "VIRTEX6", "SPARTAN6","7SERIES"
+		      .LATENCY(1),         // Desired clock cycle latency, 0-4
+		      .WIDTH_A(18),        // Multiplier A-input bus width, 1-25
+		      .WIDTH_B(18))        // Multiplier B-input bus width, 1-18
+	 mult_i (.P(prod_i),             // Multiplier output bus, width determined by WIDTH_P parameter
+		.A(i_unscaled_clip),         // Multiplier input A bus, width determined by WIDTH_A parameter
+		.B(scale_factor),       // Multiplier input B bus, width determined by WIDTH_B parameter
+		.CE(strobe_unscaled_clip),   // 1-bit active high input clock enable
+		.CLK(clk),              // 1-bit positive edge clock input
+		.RST(rst));             // 1-bit input active high reset
+
+	 MULT_MACRO #(.DEVICE(DEVICE),  // Target Device: "VIRTEX5", "VIRTEX6", "SPARTAN6","7SERIES"
+		      .LATENCY(1),         // Desired clock cycle latency, 0-4
+		      .WIDTH_A(18),        // Multiplier A-input bus width, 1-25
+		      .WIDTH_B(18))        // Multiplier B-input bus width, 1-18
+	 mult_q (.P(prod_q),             // Multiplier output bus, width determined by WIDTH_P parameter
+		.A(q_unscaled_clip),         // Multiplier input A bus, width determined by WIDTH_A parameter
+		.B(scale_factor),       // Multiplier input B bus, width determined by WIDTH_B parameter
+		.CE(strobe_unscaled_clip),   // 1-bit active high input clock enable
+		.CLK(clk),              // 1-bit positive edge clock input
+		.RST(rst));             // 1-bit input active high reset
+
+	 reg 		  strobe_scaled;
+	 wire 		  strobe_clip;
+	 wire [32:0] 	  i_clip, q_clip;
+
+	 always @(posedge clk)  strobe_scaled <= strobe_unscaled_clip;
+
+	 clip_reg #(.bits_in(36), .bits_out(33), .STROBED(1)) clip_i
+	   (.clk(clk), .in(prod_i[35:0]), .strobe_in(strobe_scaled), .out(i_clip), .strobe_out(strobe_clip));
+	 clip_reg #(.bits_in(36), .bits_out(33), .STROBED(1)) clip_q
+	   (.clk(clk), .in(prod_q[35:0]), .strobe_in(strobe_scaled), .out(q_clip), .strobe_out());
+
+	 round_sd #(.WIDTH_IN(33), .WIDTH_OUT(16)) round_i
+	   (.clk(clk), .reset(rst), .in(i_clip), .strobe_in(strobe_clip), .out(sample[31:16]), .strobe_out(strobe));
+	 round_sd #(.WIDTH_IN(33), .WIDTH_OUT(16)) round_q
+	   (.clk(clk), .reset(rst), .in(q_clip), .strobe_in(strobe_clip), .out(sample[15:0]), .strobe_out());
+
+      end else begin: old_hb // block: new_hb
+	 ///////////////////////////////////////////////
+	 //
+	 // Legacy Decimation Filters from USRP2
+	 //
+	 ///////////////////////////////////////////////
+	 wire [WIDTH-1:0] i_hb1, q_hb1;
+	 wire [WIDTH-1:0] i_hb2, q_hb2;
+	 // First (small) halfband  24 bit I/O
+	 small_hb_dec #(.WIDTH(WIDTH),.DEVICE(DEVICE)) small_hb_i
+	   (.clk(clk),.rst(rst),.bypass(~enable_hb1),.run(run),
+	    .stb_in(strobe_cic),.data_in(i_cic),.stb_out(strobe_hb1),.data_out(i_hb1));
+
+	 small_hb_dec #(.WIDTH(WIDTH),.DEVICE(DEVICE)) small_hb_q
+	   (.clk(clk),.rst(rst),.bypass(~enable_hb1),.run(run),
+	    .stb_in(strobe_cic),.data_in(q_cic),.stb_out(),.data_out(q_hb1));
+
+	 // Second (large) halfband  24 bit I/O
+	 wire [8:0] 	  cpi_hb = enable_hb1 ? {cic_decim_rate,1'b0} : {1'b0,cic_decim_rate};
+	 hb_dec #(.WIDTH(WIDTH),.DEVICE(DEVICE)) hb_i
+	   (.clk(clk),.rst(rst),.bypass(~enable_hb2),.run(run),.cpi(cpi_hb),
+	    .stb_in(strobe_hb1),.data_in(i_hb1),.stb_out(strobe_hb2),.data_out(i_hb2));
+
+	 hb_dec #(.WIDTH(WIDTH),.DEVICE(DEVICE)) hb_q
+	   (.clk(clk),.rst(rst),.bypass(~enable_hb2),.run(run),.cpi(cpi_hb),
+	    .stb_in(strobe_hb1),.data_in(q_hb1),.stb_out(),.data_out(q_hb2));
+
+	 // Need to clip 1 bit here or we loose small signal performance out the truncated LSB's for worst case CIC gain cases.
+	 wire strobe_unscaled_clip;
+	 wire [17:0] i_unscaled_clip, q_unscaled_clip;
+
+	 clip_reg #(.bits_in(19), .bits_out(18), .STROBED(1)) unscaled_clip_i
+	   (.clk(clk), .in(i_hb2[WIDTH-1:WIDTH-19]), .strobe_in(strobe_hb2), .out(i_unscaled_clip[17:0]), .strobe_out(strobe_unscaled_clip));
+	 clip_reg #(.bits_in(19), .bits_out(18), .STROBED(1)) unscaled_clip_q
+	   (.clk(clk), .in(q_hb2[WIDTH-1:WIDTH-19]), .strobe_in(strobe_hb2), .out(q_unscaled_clip[17:0]), .strobe_out());
+
+	 //scalar operation (gain of 6 bits)
+	 wire [35:0] 	  prod_i, prod_q;
+
+	 MULT_MACRO #(.DEVICE(DEVICE),  // Target Device: "VIRTEX5", "VIRTEX6", "SPARTAN6","7SERIES"
+		      .LATENCY(1),         // Desired clock cycle latency, 0-4
+		      .WIDTH_A(18),        // Multiplier A-input bus width, 1-25
+		      .WIDTH_B(18))        // Multiplier B-input bus width, 1-18
+	 mult_i (.P(prod_i),             // Multiplier output bus, width determined by WIDTH_P parameter
+		.A(i_unscaled_clip),// Multiplier input A bus, width determined by WIDTH_A parameter
+		.B(scale_factor),       // Multiplier input B bus, width determined by WIDTH_B parameter
+		.CE(strobe_unscaled_clip),        // 1-bit active high input clock enable
+		.CLK(clk),              // 1-bit positive edge clock input
+		.RST(rst));             // 1-bit input active high reset
+
+	 MULT_MACRO #(.DEVICE(DEVICE),  // Target Device: "VIRTEX5", "VIRTEX6", "SPARTAN6","7SERIES"
+		      .LATENCY(1),         // Desired clock cycle latency, 0-4
+		      .WIDTH_A(18),        // Multiplier A-input bus width, 1-25
+		      .WIDTH_B(18))        // Multiplier B-input bus width, 1-18
+	 mult_q (.P(prod_q),             // Multiplier output bus, width determined by WIDTH_P parameter
+		.A(q_unscaled_clip),// Multiplier input A bus, width determined by WIDTH_A parameter
+		.B(scale_factor),       // Multiplier input B bus, width determined by WIDTH_B parameter
+		.CE(strobe_unscaled_clip),        // 1-bit active high input clock enable
+		.CLK(clk),              // 1-bit positive edge clock input
+		.RST(rst));             // 1-bit input active high reset
+
+	 reg 		  strobe_scaled;
+	 wire 		  strobe_clip;
+	 wire [32:0] 	  i_clip, q_clip;
+
+	 always @(posedge clk)  strobe_scaled <= strobe_unscaled_clip;
+
+	 clip_reg #(.bits_in(36), .bits_out(33), .STROBED(1)) clip_i
+	   (.clk(clk), .in(prod_i[35:0]), .strobe_in(strobe_scaled), .out(i_clip), .strobe_out(strobe_clip));
+	 clip_reg #(.bits_in(36), .bits_out(33), .STROBED(1)) clip_q
+	   (.clk(clk), .in(prod_q[35:0]), .strobe_in(strobe_scaled), .out(q_clip), .strobe_out());
+
+	 round_sd #(.WIDTH_IN(33), .WIDTH_OUT(16)) round_i
+	   (.clk(clk), .reset(rst), .in(i_clip), .strobe_in(strobe_clip), .out(sample[31:16]), .strobe_out(strobe));
+	 round_sd #(.WIDTH_IN(33), .WIDTH_OUT(16)) round_q
+	   (.clk(clk), .reset(rst), .in(q_clip), .strobe_in(strobe_clip), .out(sample[15:0]), .strobe_out());
+
+      end // block: old_hb
+   endgenerate
+
+
+
+   assign debug = {enable_hb1, enable_hb2, run, strobe, strobe_cic, strobe_hb1, strobe_hb2};
+
+endmodule // ddc_chain