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// -*- verilog -*-
//
// USRP - Universal Software Radio Peripheral
//
// Copyright (C) 2003 Matt Ettus
//
//
module cic_interp
#(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);
integer i;
localparam maxbitgain = (N-1)*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];
sign_extend #(bw,bw+maxbitgain)
ext_input (.in(signal_in),.out(signal_in_ext));
//FIXME Note that this section has pipe and diff reversed
// It still works, but is confusing
always @(posedge clock)
if(reset | ~enable)
for(i=0;i<N;i=i+1)
integrator[i] <= 0;
else if (enable & strobe_out)
begin
if(strobe_in)
integrator[0] <= integrator[0] + pipeline[N-1];
for(i=1;i<N;i=i+1)
integrator[i] <= integrator[i] + integrator[i-1];
end
always @(posedge clock)
if(reset | ~enable)
begin
for(i=0;i<N;i=i+1)
begin
differentiator[i] <= 0;
pipeline[i] <= 0;
end
end
else if (enable && strobe_in)
begin
differentiator[0] <= signal_in_ext;
pipeline[0] <= signal_in_ext - 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
wire [bw-1:0] signal_out_unreg;
cic_int_shifter #(bw)
cic_int_shifter(rate,integrator[N-1],signal_out_unreg);
always @(posedge clock)
signal_out <= signal_out_unreg;
endmodule // cic_interp
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