Houston, we have a trunk.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@3122 221aa14e-8319-0410-a670-987f0aec2ac5

1 files changed, 106 insertions, 0 deletions

diff --git a/usrp/fpga/sdr_lib/cic_decim.v b/usrp/fpga/sdr_lib/cic_decim.v
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+// -*- verilog -*-
+//
+//  USRP - Universal Software Radio Peripheral
+//
+//  Copyright (C) 2003 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+//
+
+
+module cic_decim
+  ( clock,reset,enable,rate,strobe_in,strobe_out,signal_in,signal_out);
+   parameter bw = 16;
+   parameter N = 4;
+   parameter log2_of_max_rate = 8;
+   parameter maxbitgain = N * log2_of_max_rate;
+   
+   input clock;
+   input reset;
+   input enable;
+   input [7:0] rate;
+   input strobe_in,strobe_out;	
+   input [bw-1:0] signal_in;
+   output [bw-1:0] signal_out;
+   reg [bw-1:0] signal_out;
+
+   wire [bw+maxbitgain-1:0] signal_in_ext;
+   reg [bw+maxbitgain-1:0]  integrator [0:N-1];
+   reg [bw+maxbitgain-1:0] differentiator [0:N-1];
+   reg [bw+maxbitgain-1:0] pipeline [0:N-1];
+   reg [bw+maxbitgain-1:0] sampler;
+   
+   integer i;
+   
+   sign_extend #(bw,bw+maxbitgain) 
+      ext_input (.in(signal_in),.out(signal_in_ext));
+   
+   always @(posedge clock)
+     if(reset)
+       for(i=0;i<N;i=i+1)
+	 integrator[i] <= #1 0;
+     else if (enable && strobe_in)
+       begin
+	  integrator[0] <= #1 integrator[0] + signal_in_ext;
+	  for(i=1;i<N;i=i+1)
+	    integrator[i] <= #1 integrator[i] + integrator[i-1];
+       end	
+   
+   always @(posedge clock)
+     if(reset)
+       begin
+	  sampler <= #1 0;
+	  for(i=0;i<N;i=i+1)
+	    begin
+	       pipeline[i] <= #1 0;
+	       differentiator[i] <= #1 0;
+	    end
+       end
+     else if (enable && strobe_out)
+       begin
+	  sampler <= #1 integrator[N-1];
+	  differentiator[0] <= #1 sampler;
+	  pipeline[0] <= #1 sampler - differentiator[0];
+	  for(i=1;i<N;i=i+1)
+	    begin
+	       differentiator[i] <= #1 pipeline[i-1];
+	       pipeline[i] <= #1 pipeline[i-1] - differentiator[i];
+	    end
+       end // if (enable && strobe_out)
+      
+   wire [bw+maxbitgain-1:0] signal_out_unnorm = pipeline[N-1];
+
+   // Output Scaling to same width as input
+   function [2:0] log_ceil;
+      input [7:0] val;
+      log_ceil = val[6] ? 3'd7 : val[5] ? 3'd6 : val[4] ? 3'd5 :
+		 val[3] ? 3'd4 : val[2] ? 3'd3 : val[1] ? 3'd2 : 3'd1; 
+   endfunction // log_ceil
+   
+   wire [2:0] shift = log_ceil(rate);
+   
+   always @*
+     case(shift)
+       3'd2 : signal_out = signal_out_unnorm[2*N+bw-1:2*N]; //  Decim by 4
+       3'd3 : signal_out = signal_out_unnorm[3*N+bw-1:3*N];
+       3'd4 : signal_out = signal_out_unnorm[4*N+bw-1:4*N];
+       3'd5 : signal_out = signal_out_unnorm[5*N+bw-1:5*N];
+       3'd6 : signal_out = signal_out_unnorm[6*N+bw-1:6*N];
+       3'd7 : signal_out = signal_out_unnorm[7*N+bw-1:7*N];
+       default : signal_out = signal_out_unnorm[7*N+bw-1:7*N];
+     endcase // case(shift)
+   
+endmodule // cic_decim
+