--- /dev/null
+// -*- 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., 51 Franklin Street, Boston, MA 02110-1301 USA
+//
+
+
+// NOTE This only works for N=4, max decim rate of 128
+// NOTE signal "rate" is ONE LESS THAN the actual rate
+
+module cic_dec_shifter(rate,signal_in,signal_out);
+ parameter bw = 16;
+ parameter maxbitgain = 28;
+
+ input [7:0] rate;
+ input wire [bw+maxbitgain-1:0] signal_in;
+ output reg [bw-1:0] signal_out;
+
+ function [4:0] bitgain;
+ input [7:0] rate;
+ case(rate)
+ // Exact Cases -- N*log2(rate)
+ 8'd4 : bitgain = 8;
+ 8'd8 : bitgain = 12;
+ 8'd16 : bitgain = 16;
+ 8'd32 : bitgain = 20;
+ 8'd64 : bitgain = 24;
+ 8'd128 : bitgain = 28;
+
+ // Nearest without overflow -- ceil(N*log2(rate))
+ 8'd5 : bitgain = 10;
+ 8'd6 : bitgain = 11;
+ 8'd7 : bitgain = 12;
+ 8'd9 : bitgain = 13;
+ 8'd10,8'd11 : bitgain = 14;
+ 8'd12,8'd13 : bitgain = 15;
+ 8'd14,8'd15 : bitgain = 16;
+ 8'd17,8'd18,8'd19 : bitgain = 17;
+ 8'd20,8'd21,8'd22 : bitgain = 18;
+ 8'd23,8'd24,8'd25,8'd26 : bitgain = 19;
+ 8'd27,8'd28,8'd29,8'd30,8'd31 : bitgain = 20;
+ 8'd33,8'd34,8'd35,8'd36,8'd37,8'd38 : bitgain = 21;
+ 8'd39,8'd40,8'd41,8'd42,8'd43,8'd44,8'd45 : bitgain = 22;
+ 8'd46,8'd47,8'd48,8'd49,8'd50,8'd51,8'd52,8'd53 : bitgain = 23;
+ 8'd54,8'd55,8'd56,8'd57,8'd58,8'd59,8'd60,8'd61,8'd62,8'd63 : bitgain = 24;
+ 8'd65,8'd66,8'd67,8'd68,8'd69,8'd70,8'd71,8'd72,8'd73,8'd74,8'd75,8'd76 : bitgain = 25;
+ 8'd77,8'd78,8'd79,8'd80,8'd81,8'd82,8'd83,8'd84,8'd85,8'd86,8'd87,8'd88,8'd89,8'd90 : bitgain = 26;
+ 8'd91,8'd92,8'd93,8'd94,8'd95,8'd96,8'd97,8'd98,8'd99,8'd100,8'd101,8'd102,8'd103,8'd104,8'd105,8'd106,8'd107 : bitgain = 27;
+ default : bitgain = 28;
+ endcase // case(rate)
+ endfunction // bitgain
+
+ wire [4:0] shift = bitgain(rate+1);
+
+ // We should be able to do this, but can't ....
+ // assign signal_out = signal_in[shift+bw-1:shift];
+
+ always @*
+ case(shift)
+ 5'd8 : signal_out = signal_in[8+bw-1:8];
+ 5'd10 : signal_out = signal_in[10+bw-1:10];
+ 5'd11 : signal_out = signal_in[11+bw-1:11];
+ 5'd12 : signal_out = signal_in[12+bw-1:12];
+ 5'd13 : signal_out = signal_in[13+bw-1:13];
+ 5'd14 : signal_out = signal_in[14+bw-1:14];
+ 5'd15 : signal_out = signal_in[15+bw-1:15];
+ 5'd16 : signal_out = signal_in[16+bw-1:16];
+ 5'd17 : signal_out = signal_in[17+bw-1:17];
+ 5'd18 : signal_out = signal_in[18+bw-1:18];
+ 5'd19 : signal_out = signal_in[19+bw-1:19];
+ 5'd20 : signal_out = signal_in[20+bw-1:20];
+ 5'd21 : signal_out = signal_in[21+bw-1:21];
+ 5'd22 : signal_out = signal_in[22+bw-1:22];
+ 5'd23 : signal_out = signal_in[23+bw-1:23];
+ 5'd24 : signal_out = signal_in[24+bw-1:24];
+ 5'd25 : signal_out = signal_in[25+bw-1:25];
+ 5'd26 : signal_out = signal_in[26+bw-1:26];
+ 5'd27 : signal_out = signal_in[27+bw-1:27];
+ 5'd28 : signal_out = signal_in[28+bw-1:28];
+
+ default : signal_out = signal_in[28+bw-1:28];
+ endcase // case(shift)
+
+endmodule // cic_dec_shifter
+
projects / debian / gnuradio / blobdiff