From 0df4b801a34697f2058b4a7b95e08d2a0576c9db Mon Sep 17 00:00:00 2001
From: Ben Hilburn <ben.hilburn@ettus.com>
Date: Thu, 10 Oct 2013 10:17:27 -0700
Subject: Squashed B200 FPGA Source. Code from Josh Blum, Ian Buckley, and Matt
 Ettus.

---
 fpga/usrp3/lib/dsp/cic_decim.v | 76 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 fpga/usrp3/lib/dsp/cic_decim.v

(limited to 'fpga/usrp3/lib/dsp/cic_decim.v')

diff --git a/fpga/usrp3/lib/dsp/cic_decim.v b/fpga/usrp3/lib/dsp/cic_decim.v
new file mode 100644
index 000000000..feb785de8
--- /dev/null
+++ b/fpga/usrp3/lib/dsp/cic_decim.v
@@ -0,0 +1,76 @@
+// -*- verilog -*-
+//
+//  USRP - Universal Software Radio Peripheral
+//
+//  Copyright (C) 2003 Matt Ettus
+//
+
+//
+
+
+module cic_decim
+  #(parameter bw = 16, parameter N = 4, parameter log2_of_max_rate = 7)
+    (input clock,
+     input reset,
+     input enable,
+     input [7:0] rate,
+     input strobe_in,
+     input strobe_out,
+     input [bw-1:0] signal_in,
+     output reg [bw-1:0] signal_out);
+
+   localparam 	     maxbitgain = N * log2_of_max_rate;
+   
+   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(~enable)
+       for(i=0;i<N;i=i+1)
+	 integrator[i] <= 0;
+     else if (strobe_in)
+       begin
+	  integrator[0] <= integrator[0] + signal_in_ext;
+	  for(i=1;i<N;i=i+1)
+	    integrator[i] <= integrator[i] + integrator[i-1];
+       end	
+   
+   always @(posedge clock)
+     if(~enable)
+       begin
+	  sampler <= 0;
+	  for(i=0;i<N;i=i+1)
+	    begin
+	       pipeline[i] <= 0;
+	       differentiator[i] <= 0;
+	    end
+       end
+     else if (strobe_out)
+       begin
+	  sampler <= integrator[N-1];
+	  differentiator[0] <= sampler;
+	  pipeline[0] <= sampler - differentiator[0];
+	  for(i=1;i<N;i=i+1)
+	    begin
+	       differentiator[i] <= pipeline[i-1];
+	       pipeline[i] <= pipeline[i-1] - differentiator[i];
+	    end
+       end // if (enable && strobe_out)
+   
+   wire [bw-1:0] signal_out_unreg;
+   
+   cic_dec_shifter #(bw)
+     cic_dec_shifter(rate,pipeline[N-1],signal_out_unreg);
+
+   always @(posedge clock)
+     signal_out <= signal_out_unreg;
+   
+endmodule // cic_decim
-- 
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