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added comments, removed dead code

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git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@4779 221aa14e-8319-0410-a670-987f0aec2ac5
This commit is contained in:
matt
2007-03-20 01:02:25 +00:00
parent a67127dcd5
commit 403a009a8d
1 changed files with 6 additions and 10 deletions
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16
sdr_lib/cic_int_shifter.v
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@@ -20,25 +20,21 @@
//
// NOTE This only works for N=4, max interp rate of 128
// NOTE signal "rate" is ONE LESS THAN the actual rate
module cic_int_shifter(rate,signal_in,signal_out);
parameter bw = 16;
parameter N = 4;
parameter log2_of_max_rate = 7;
parameter maxbitgain = (N-1)*log2_of_max_rate;
parameter maxbitgain = 21;
input [7:0] rate;
input wire [bw+maxbitgain-1:0] signal_in;
output reg [bw-1:0] signal_out;
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
function [4:0] bitgain;
input [7:0] rate;
case(rate)
// Exact Cases
8'd4 : bitgain = 2*(N-1);
8'd8 : bitgain = 3*(N-1);
8'd16 : bitgain = 4*(N-1);
@@ -46,6 +42,7 @@ module cic_int_shifter(rate,signal_in,signal_out);
8'd64 : bitgain = 6*(N-1);
8'd128 : bitgain = 7*(N-1);
// Nearest without overflow
8'd5 : bitgain = 7;
8'd6 : bitgain = 8;
8'd7 : bitgain = 9;
@@ -90,7 +87,6 @@ module cic_int_shifter(rate,signal_in,signal_out);
5'd19 : signal_out = signal_in[19+bw-1:19];
5'd20 : signal_out = signal_in[20+bw-1:20];
default : signal_out = signal_in[21+bw-1:21];
endcase // case(shift)