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/*****************************************************************************
Licensed to Accellera Systems Initiative Inc. (Accellera) under one or
more contributor license agreements. See the NOTICE file distributed
with this work for additional information regarding copyright ownership.
Accellera licenses this file to you under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with the
License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied. See the License for the specific language governing
permissions and limitations under the License.
*****************************************************************************/
/*****************************************************************************
fft.cpp - This is the implementation file for the synchronous process "fft".
Original Author: Rashmi Goswami, Synopsys, Inc.
*****************************************************************************/
/*****************************************************************************
MODIFICATION LOG - modifiers, enter your name, affiliation, date and
changes you are making here.
Name, Affiliation, Date:
Description of Modification:
*****************************************************************************/
/* This is the implementation file for the synchronous process "fft" */
#include "systemc.h"
#include "fft.h"
//Function for butterfly computation
void func_butterfly
( const sc_int<16>& w_real /* snps width 16 */,
const sc_int<16>& w_imag /* snps width 16 */,
const sc_int<16>& real1_in /* snps width 16 */,
const sc_int<16>& imag1_in /* snps width 16 */,
const sc_int<16>& real2_in /* snps width 16 */,
const sc_int<16>& imag2_in /* snps width 16 */,
sc_int<16>& real1_out /* snps width 16 */,
sc_int<16>& imag1_out /* snps width 16 */,
sc_int<16>& real2_out /* snps width 16 */,
sc_int<16>& imag2_out /* snps width 16 */
)
{
// Variable declarations
sc_int<17> tmp_real1;
sc_int<17> tmp_imag1;
sc_int<17> tmp_real2;
sc_int<17> tmp_imag2;
sc_int<34> tmp_real3;
sc_int<34> tmp_imag3;
// Begin Computation
tmp_real1 = real1_in + real2_in;
// <s,6,10> = <s,5,10> + <s,5,10>
tmp_imag1 = imag1_in + imag2_in;
// <s,6,10> = <s,5,10> - <s,5,10>
tmp_real2 = real1_in - real2_in;
// <s,6,10> = <s,5,10> - <s,5,10>
tmp_imag2 = imag1_in - imag2_in;
// <s,13,20> = <s,6,10>*<s,5,10> - <s,6,10>*<s,5,10>
tmp_real3 = tmp_real2*w_real - tmp_imag2*w_imag;
// <s,13,20> = <s,6,10>*<s,5,10> - <s,6,10>*<s,5,10>
tmp_imag3 = tmp_real2*w_imag + tmp_imag2*w_real;
// assign the sign-bit(MSB)
real1_out[15] = tmp_real1[16];
imag1_out[15] = tmp_imag1[16];
// assign the rest of the bits
real1_out.range(14,0) = tmp_real1.range(14,0);
imag1_out.range(14,0) = tmp_imag1.range(14,0);
// assign the sign-bit(MSB)
real2_out[15] = tmp_real3[33];
imag2_out[15] = tmp_imag3[33];
// assign the rest of the bits
real2_out.range(14,0) = tmp_real3.range(24,10);
imag2_out.range(14,0) = tmp_imag3.range(24,10);
} // end func_butterfly
void fft::entry()
{
// Variable Declarations
sc_int<16> real[16];
sc_int<16> imag[16];
sc_int<16> tmp_real;
sc_int<16> tmp_imag;
short index;
sc_int<6> N;
sc_int<4> M;
sc_int<6> len;
sc_int<16> W_real[7];
sc_int<16> W_imag[7];
sc_int<16> w_real;
sc_int<16> w_imag;
sc_int<16> w_rec_real;
sc_int<16> w_rec_imag;
sc_int<32> w_temp1;
sc_int<32> w_temp2;
sc_int<32> w_temp3;
sc_int<32> w_temp4;
sc_int<33> w_temp5;
sc_int<33> w_temp6;
sc_int<16> real1_in;
sc_int<16> imag1_in;
sc_int<16> real2_in;
sc_int<16> imag2_in;
sc_int<16> real1_out;
sc_int<16> imag1_out;
sc_int<16> real2_out;
sc_int<16> imag2_out;
sc_int<4> stage;
short i;
short j;
short index2;
short windex;
short incr;
while(true)
{ data_req.write(false);
data_ready.write(false);
index = 0;
wait();
//Read in the Sample values
cout << endl << "Reading in the samples..." << endl;
while( index < 16 )
{
data_req.write(true);
do { wait(); } while ( !(data_valid == true) );
tmp_real = in_real.read();
tmp_imag = in_imag.read();
real[index] = tmp_real;
imag[index] = tmp_imag;
index++;
data_req.write(false);
wait();
}
index = 0;
// Initialize
M = 4; N = 16;
len = N >> 1;
cout << "Computing..." << endl;
// Calculate the W-values recursively
// <'s'/'u',m,n>: is used in comments to denote a fixed point representation
// 's'- signed, 'u'- unsigned, m - no. of integer bits, n - no. of fractional bits
// theta = 8.0*atan(1.0)/N; theta = 22.5 degree
// w_real = cos(theta) = 0.92 (000000.1110101110) <s,5,10>
w_real = 942;
// w_imag = -sin(theta) = -0.38(111111.1001111010) <s,5,10>
w_imag = -389;
// w_rec_real = 1(0000001.0000000000)
w_rec_real = 1024;
// w_rec_real = 0(000000.0000000000)
w_rec_imag = 0;
unsigned short w_index;
w_index = 0;
while(w_index < 7)
{
// <s,11,20> = <s,5,10> * <s,5,10>
w_temp1 = w_rec_real*w_real;
w_temp2 = w_rec_imag*w_imag;
// <s,11,20> = <s,5,10> * <s,5,10>
w_temp3 = w_rec_real*w_imag;
w_temp4 = w_rec_imag*w_real;
// <s,6,10> = <s,5,10> - <s,5,10>
w_temp5 = w_temp1 - w_temp2;
// <s,6,10> = <s,5,10> + <s,5,10>
w_temp6 = w_temp3 + w_temp4;
// assign the sign-bit(MSB)
W_real[w_index][15] = w_temp5[32];
W_imag[w_index][15] = w_temp6[32];
// assign the rest of the bits
W_real[w_index].range(14,0) = w_temp5.range(24,10);
W_imag[w_index].range(14,0) = w_temp6.range(24,10);
// update w_rec.. values for the next iteration
w_rec_real = W_real[w_index];
w_rec_imag = W_imag[w_index];
w_index++;
}
//////////////////////////////////////////////////////////////////////////
/// Computation - 1D Complex DFT In-Place DIF Computation Algorithm ////
//////////////////////////////////////////////////////////////////////////
stage = 0;
len = N;
incr = 1;
while (stage < M)
{
len = len >> 1;
//First Iteration : Simple calculation, with no multiplies
i = 0;
while(i < (short)N)
{
index = i; index2 = i + (short)len;
tmp_real = real[index] + real[index2];
tmp_imag = imag[index] + imag[index2];
real[index2] = (real[index] - real[index2]);
imag[index2] = (imag[index] - imag[index2]);
real[index] = tmp_real;
imag[index] = tmp_imag;
i = (short)(i + (len << 1));
}
//Remaining Iterations: Use Stored W
j = 1; windex = incr - 1;
// This loop executes N/2 times at the first stage, N/2 times at the second.. once at last stage
while (j < (short)len)
{
i = j;
while (i < (short)N)
{
index = i;
index2 = i + (short)len;
// Read in the data and twiddle factors
w_real = W_real[windex];
w_imag = W_imag[windex];
real1_in = real[index];
imag1_in = imag[index];
real2_in = real[index2];
imag2_in = imag[index2];
// Call butterfly computation function
func_butterfly(w_real, w_imag, real1_in, imag1_in, real2_in, imag2_in, real1_out, imag1_out, real2_out, imag2_out);
// Store back the results
real[index] = real1_out;
imag[index] = imag1_out;
real[index2] = real2_out;
imag[index2] = imag2_out;
i = (short)(i + (len << 1));
}
windex = windex + incr;
j++;
}
stage++;
incr = incr << 1;
}
//////////////////////////////////////////////////////////////////////////
//Writing out the normalized transform values in bit reversed order
//////////////////////////////////////////////////////////////////////////
sc_uint<4> bits_i;
sc_uint<4> bits_index;
sc_int<16> real1;
sc_int<16> imag1;
bits_i = 0;
bits_index = 0;
i = 0;
cout << "Writing the transform values..." << endl;
while( i < 16)
{
bits_i = i;
bits_index[3]= bits_i[0];
bits_index[2]= bits_i[1];
bits_index[1]= bits_i[2];
bits_index[0]= bits_i[3];
index = (short)bits_index;
real1 = real[index];
imag1 = imag[index];
out_real.write(real1);
out_imag.write(imag1);
data_ready.write(true);
do { wait(); } while ( !(data_ack == true) );
data_ready.write(false);
i++;
wait();
}
index = 0;
cout << "Done..." << endl;
}
}// end entry() function
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