/////////////////////////////////////////////////////////////////////////                                                             ////////  JPEG Entropy Coding, Huffman Decoding                      ////////                                                             ////////  Decomposes incomming datastream into packets for the       ////////  Huffman tables.                                            ////////  See accompanying testbench how to use this code.           ////////                                                             ////////  Author: Richard Herveille                                  ////////          richard@asics.ws                                   ////////          www.asics.ws                                       ////////                                                             /////////////////////////////////////////////////////////////////////////////                                                             //////// Copyright (C) 2001 Richard Herveille                        ////////                    richard@asics.ws                         ////////                                                             //////// This source file may be used and distributed without        //////// restriction provided that this copyright statement is not   //////// removed from the file and that any derivative work contains //////// the original copyright notice and the associated disclaimer.////////                                                             ////////     THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     //////// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   //////// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   //////// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      //////// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         //////// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    //////// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   //////// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        //////// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  //////// LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  //////// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  //////// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         //////// POSSIBILITY OF SUCH DAMAGE.                                 ////////                                                             ///////////////////////////////////////////////////////////////////////////  CVS Log////  $Id: huffman_dec.v,v 1.2 2002/10/31 12:50:40 rherveille Exp $////  $Date: 2002/10/31 12:50:40 $//  $Revision: 1.2 $//  $Author: rherveille $//  $Locker:  $//  $State: Exp $//// synopsys translate_off`include "timescale.v"// synopsys translate_onmodule huffman_dec(clk, rst, tablesel, di, die, do, doe, busy);  input         clk;      // clock  input         rst;      // asynchronous active low reset  input  [ 1:0] tablesel; // huffman table select  input  [ 7:0] di;       // data input  input         die;      // data-in enable  output [ 7:0] do;       // category or Runlenght/Size codepair  output        doe;      // data-out enable  output        busy;     // busy. Do not assert die while busy asserted  reg [7:0] do;  reg       doe, busy;  wire [ 7:0] hdec_dc_lum, hdec_dc_chr;  wire [11:0] hdec_ac_lum, hdec_ac_chr;  reg  [ 4:0] codelen;  reg  [15:0] code;  reg [ 1:0] state;  reg [22:0] sreg;  reg [ 4:0] cnt;  `include "huffman_tables.v"  //  // hookup huffman tables  //  assign hdec_dc_lum = jpeg_dc_luminance_huffman_dec(code[15:7]);  assign hdec_dc_chr = jpeg_dc_chrominance_huffman_dec(code[15:5]);  assign hdec_ac_lum = jpeg_ac_luminance_huffman_dec(code);  assign hdec_ac_chr = jpeg_ac_chrominance_huffman_dec(code);  //  // split table data into category Run/Size and codelength  //  always @(posedge clk)    case (tablesel) // synopsys full_case parallel_case      2'b00: // DC Luminance        begin            codelen <= #1 hdec_dc_lum[ 7: 4] +4'h1;            do      <= #1 {4'h0, hdec_dc_lum[ 3: 0]};        end      2'b01: // DC Chrominance        begin            codelen <= #1 hdec_dc_chr[ 7: 4] +4'h1;            do      <= #1 {4'h0, hdec_dc_chr[ 3: 0]};        end      2'b10: // AC Luminance        begin            codelen <= #1 hdec_ac_lum[11:8] +4'h1;            do      <= #1 hdec_ac_lum[ 7:0];        end      2'b11: // AC Chrominance        begin            codelen <= #1 hdec_ac_chr[11:8] +4'h1;            do      <= #1 hdec_ac_chr[ 7:0];        end    endcase  //  // Hookup din statemachine  //  always @(posedge clk or negedge rst)    if(~rst)      begin          state <= #1 2'b00;          sreg  <= #1 24'h0;          cnt   <= #1 5'h0;          busy  <= #1 1'b0;		  doe   <= #1 1'b0;      end    else      begin          doe <= #1 1'b0;          case(state)            2'b00:                if(die)                  begin                      if( (cnt + 5'h8) > 15 ) // guaranteed valid code in sreg                        begin                            state <= #1 2'b01;                            busy  <= #1 1'b1;                        end                        sreg <= #1 ((sreg << 8) | di);                        cnt  <= #1 (cnt + 5'h8);                  end            2'b01:                begin                    state <= #1 2'b11; // wait for codelen (data from table)                    doe   <= #1 1'b1;                end            2'b11:                begin                    if( (cnt - codelen) > 15 ) // still valid codes in sreg                      state <= #1 2'b01;                    else                      begin                          state <= #1 2'b00;                          busy  <= #1 1'b0;                      end                    cnt  <= #1 (cnt - codelen);                end          endcase      end  always @(posedge clk)    if(die)      code <= #1 ((sreg << 8) | di) >> ((cnt + 5'h8) -5'h10);    else      code <= #1 sreg >> ((cnt - codelen) -5'h10);endmodule