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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., 51 Franklin Street, Boston, MA 02110-1301 USA
//
// DDC block
module ddc(input clock,
input reset,
input enable,
input [3:0] rate1,
input [3:0] rate2,
output strobe,
input [31:0] freq,
input [15:0] i_in,
input [15:0] q_in,
output [15:0] i_out,
output [15:0] q_out
);
parameter bw = 16;
parameter zw = 16;
wire [15:0] i_cordic_out, q_cordic_out;
wire [31:0] phase;
wire strobe1, strobe2;
reg [3:0] strobe_ctr1,strobe_ctr2;
always @(posedge clock)
if(reset | ~enable)
strobe_ctr2 <= #1 4'd0;
else if(strobe2)
strobe_ctr2 <= #1 4'd0;
else
strobe_ctr2 <= #1 strobe_ctr2 + 4'd1;
always @(posedge clock)
if(reset | ~enable)
strobe_ctr1 <= #1 4'd0;
else if(strobe1)
strobe_ctr1 <= #1 4'd0;
else if(strobe2)
strobe_ctr1 <= #1 strobe_ctr1 + 4'd1;
assign strobe2 = enable & ( strobe_ctr2 == rate2 );
assign strobe1 = strobe2 & ( strobe_ctr1 == rate1 );
assign strobe = strobe1;
function [2:0] log_ceil;
input [3:0] val;
log_ceil = val[3] ? 3'd4 : val[2] ? 3'd3 : val[1] ? 3'd2 : 3'd1;
endfunction
wire [2:0] shift1 = log_ceil(rate1);
wire [2:0] shift2 = log_ceil(rate2);
cordic #(.bitwidth(bw),.zwidth(zw),.stages(16))
cordic(.clock(clock), .reset(reset), .enable(enable),
.xi(i_in), .yi(q_in), .zi(phase[31:32-zw]),
.xo(i_cordic_out), .yo(q_cordic_out), .zo() );
cic_decim_2stage #(.bw(bw),.N(4))
decim_i(.clock(clock),.reset(reset),.enable(enable),
.strobe1(1'b1),.strobe2(strobe2),.strobe3(strobe1),.shift1(shift2),.shift2(shift1),
.signal_in(i_cordic_out),.signal_out(i_out));
cic_decim_2stage #(.bw(bw),.N(4))
decim_q(.clock(clock),.reset(reset),.enable(enable),
.strobe1(1'b1),.strobe2(strobe2),.strobe3(strobe1),.shift1(shift2),.shift2(shift1),
.signal_in(q_cordic_out),.signal_out(q_out));
phase_acc #(.resolution(32))
nco (.clk(clock),.reset(reset),.enable(enable),
.freq(freq),.phase(phase));
endmodule
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