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////////////////////////////////////////////////////////////////////////////////

//

// Filename:    ifftmain.v

//

// Project:     A General Purpose Pipelined FFT Implementation

//

// Purpose:     This is the main module in the General Purpose FPGA FFT

//              implementation.  As such, all other modules are subordinate

//      to this one.  This module accomplish a fixed size Complex FFT on

//      2048 data points.

//      The FFT is fully pipelined, and accepts as inputs one complex two's

//      complement sample per clock.

//

// Parameters:

//      i_clk   The clock.  All operations are synchronous with this clock.

//      i_reset Synchronous reset, active high.  Setting this line will

//                      force the reset of all of the internals to this routine.

//                      Further, following a reset, the o_sync line will go

//                      high the same time the first output sample is valid.

//      i_ce    A clock enable line.  If this line is set, this module

//                      will accept one complex input value, and produce

//                      one (possibly empty) complex output value.

//      i_sample        The complex input sample.  This value is split

//                      into two two's complement numbers, 15 bits each, with

//                      the real portion in the high order bits, and the

//                      imaginary portion taking the bottom 15 bits.

//      o_result        The output result, of the same format as i_sample,

//                      only having 21 bits for each of the real and imaginary

//                      components, leading to 42 bits total.

//      o_sync  A one bit output indicating the first sample of the FFT frame.

//                      It also indicates the first valid sample out of the FFT

//                      on the first frame.

//

// Arguments:   This file was computer generated using the following command

//              line:

//

//              % ./fftgen -i -d ../rtl -f 2048 -1 -k 1 -p 0 -n 15 -a ../bench/cpp/ifftsize.h

//

//      This core will use hardware accelerated multiplies (DSPs)

//      for 0 of the 11 stages

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

////////////////////////////////////////////////////////////////////////////////

//

// Copyright (C) 2015-2018, Gisselquist Technology, LLC

//

// This file is part of the general purpose pipelined FFT project.

//

// The pipelined FFT project is free software (firmware): you can redistribute

// it and/or modify it under the terms of the GNU Lesser General Public License

// as published by the Free Software Foundation, either version 3 of the

// License, or (at your option) any later version.

//

// The pipelined FFT project is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTIBILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser

// General Public License for more details.

//

// You should have received a copy of the GNU Lesser General Public License

// along with this program.  (It's in the $(ROOT)/doc directory.  Run make

// with no target there if the PDF file isn't present.)  If not, see

// <http://www.gnu.org/licenses/> for a copy.

//

// License:     LGPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/lgpl.html

//

//

////////////////////////////////////////////////////////////////////////////////

//

//

`default_nettype        none

//

//

//

module ifftmain(i_clk, i_reset, i_ce,

                i_sample, o_result, o_sync);

        // The bit-width of the input, IWIDTH, output, OWIDTH, and the log

        // of the FFT size.  These are localparams, rather than parameters,

        // because once the core has been generated, they can no longer be

        // changed.  (These values can be adjusted by running the core

        // generator again.)  The reason is simply that these values have

        // been hardwired into the core at several places.

        localparam      IWIDTH=15, OWIDTH=21, LGWIDTH=11;

        //

        input   wire                            i_clk, i_reset, i_ce;

        //

        input   wire    [(2*IWIDTH-1):0] i_sample;

        output  reg     [(2*OWIDTH-1):0] o_result;

        output  reg                             o_sync;

        // Outputs of the FFT, ready for bit reversal.

        wire    [(2*OWIDTH-1):0] br_sample;

        wire            w_s2048;

        wire    [31:0]   w_d2048;

        fftstage        #(IWIDTH,IWIDTH+4,16,10,0,

                        0, 1, "icmem_2048.hex")

                stage_2048(i_clk, i_reset, i_ce,

                        (!i_reset), i_sample, w_d2048, w_s2048);

        wire            w_s1024;

        wire    [33:0]   w_d1024;

        fftstage        #(16,20,17,9,0,

                        0, 1, "icmem_1024.hex")

                stage_1024(i_clk, i_reset, i_ce,

                        w_s2048, w_d2048, w_d1024, w_s1024);

        wire            w_s512;

        wire    [33:0]   w_d512;

        fftstage        #(17,21,17,8,0,

                        0, 1, "icmem_512.hex")

                stage_512(i_clk, i_reset, i_ce,

                        w_s1024, w_d1024, w_d512, w_s512);

        wire            w_s256;

        wire    [35:0]   w_d256;

        fftstage        #(17,21,18,7,0,

                        0, 1, "icmem_256.hex")

                stage_256(i_clk, i_reset, i_ce,

                        w_s512, w_d512, w_d256, w_s256);

        wire            w_s128;

        wire    [35:0]   w_d128;

        fftstage        #(18,22,18,6,0,

                        0, 1, "icmem_128.hex")

                stage_128(i_clk, i_reset, i_ce,

                        w_s256, w_d256, w_d128, w_s128);

        wire            w_s64;

        wire    [37:0]   w_d64;

        fftstage        #(18,22,19,5,0,

                        0, 1, "icmem_64.hex")

                stage_64(i_clk, i_reset, i_ce,

                        w_s128, w_d128, w_d64, w_s64);

        wire            w_s32;

        wire    [37:0]   w_d32;

        fftstage        #(19,23,19,4,0,

                        0, 1, "icmem_32.hex")

                stage_32(i_clk, i_reset, i_ce,

                        w_s64, w_d64, w_d32, w_s32);

        wire            w_s16;

        wire    [39:0]   w_d16;

        fftstage        #(19,23,20,3,0,

                        0, 1, "icmem_16.hex")

                stage_16(i_clk, i_reset, i_ce,

                        w_s32, w_d32, w_d16, w_s16);

        wire            w_s8;

        wire    [39:0]   w_d8;

        fftstage        #(20,24,20,2,0,

                        0, 1, "icmem_8.hex")

                stage_8(i_clk, i_reset, i_ce,

                        w_s16, w_d16, w_d8, w_s8);

        wire            w_s4;

        wire    [41:0]   w_d4;

        qtrstage        #(20,21,11,1,0)  stage_4(i_clk, i_reset, i_ce,

                                                w_s8, w_d8, w_d4, w_s4);

        wire            w_s2;

        wire    [41:0]   w_d2;

        laststage       #(21,21,0)       stage_2(i_clk, i_reset, i_ce,

                                        w_s4, w_d4, w_d2, w_s2);

        // Prepare for a (potential) bit-reverse stage.

        assign  br_sample= w_d2;

        wire    br_start;

        reg     r_br_started;

        initial r_br_started = 1'b0;

        always @(posedge i_clk)

                if (i_reset)

                        r_br_started <= 1'b0;

                else if (i_ce)

                        r_br_started <= r_br_started || w_s2;

        assign  br_start = r_br_started || w_s2;

        // Now for the bit-reversal stage.

        wire    br_sync;

        wire    [(2*OWIDTH-1):0] br_o_result;

        bitreverse      #(11,21)

                revstage(i_clk, i_reset,

                        (i_ce & br_start), br_sample,

                        br_o_result, br_sync);

        // Last clock: Register our outputs, we're done.

        initial o_sync  = 1'b0;

        always @(posedge i_clk)

                if (i_reset)

                        o_sync  <= 1'b0;

                else if (i_ce)

                        o_sync  <= br_sync;

        always @(posedge i_clk)

                if (i_ce)

                        o_result  <= br_o_result;

endmodule