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vhdlhuffman-codemodelsimdecoder
Cyan
Cyan

Reputation: 82

How to read a bit file in VHDL?

I am new to VHDL. I am doing a MP3 decoder using VHDL and i happen to come across with this huffman coding from a website. However, I have difficulty in figuring out which lines actually indicates the input bit file. Below is the source code:

use IEEE.std_logic_1164.all;
use IEEE.std_logic_unsigned.all;
use IEEE.std_logic_arith.all;
use work.all_types.all;         
use work.huffman_types.all;  -- this file contains all the tables of huffman decoders

entity huffman is
port( clk   : in  std_logic;      -- input clock signal
      rst   : in  std_logic;      -- reset signal ('1' = reset)
      start : in  std_logic;      -- start='1' means that this component is activated
      done  : out std_logic;      -- produce a done signal when process is finished
      gr    : in  std_logic;      -- granule ('0'=granule0, '1'=granule1)
      bin   : in  std_logic_vector(7 downto 0);    -- input main data for huffman
      addr  : out std_logic_vector(9 downto 0);    -- address for main data
      dout  :  out std_logic_vector(31 downto 0);   -- data to memory
      memc  : out mem_control_type;  -- memeory controll signal
      sco   : out scalefac_type;  -- output scale factors 
      frm   : in  frame_type      -- contains all header and side information for the current frame
  );
end;

architecture behavioral of huffman is
type state_type is 
(IDLE1,IDLE2,IDLE3,READ,READ1,READ2,READREADY,SCALE,HUFFMAN,HUFFBIGVALUE,TABLELOOKUP1,HUFFCOUNT1,TABLELOOKUP2,HUFFEND,DATAREADY,READY );
signal cs,ns:state_type;
type is_type is array (0 to 575) of integer;
signal isg : is_type;
signal addrcount1:std_logic_vector(9 downto 0);
signal valuebuffer : std_logic_vector(0 to 8191 );

begin

process(cs, frm, gr, start)

variable scalefac : integer;
variable count : integer ;
variable memaddrcount : std_logic_vector(9 downto 0);
variable scout : scalefac_type;
variable bitpos:std_logic_vector(12 downto 0);
variable region1start,region2start,bigvalues,count1s,start_bit1,start_bit2,start_bit,tempbit: integer;
variable line,line1,region,old_region : integer;
variable u,w,x,y,linbits:integer;
variable level,level1,value,temp,templevel:integer;
variable tindex:integer range 0 to 33;
variable tempvector : std_logic_vector(7 downto 0);
variable tempvector1 : std_logic_vector(3 downto 0);
variable slenval0,slenval1:integer;
variable tempval,tempdata,temphuff,temphuff1,temppos:integer;
variable tempcount1:std_logic;

begin

case cs is
  when IDLE1   =>  
                   addrcount1 <= (others =>'0');
           ns<=IDLE2;
  when IDLE2   =>  
                   done <= '0';
                   count :=0;
           line :=0;
           line1 :=0;
           bigvalues:=0;
           count1s:=0;
           start_bit:=0;
           linbits:=0;
           tempvector1:=(others =>'0');
           tempvector:=(others =>'0');
           tindex:=0;
           temp:=0;
           value:=0;
           isg<=(others=>0);   
               ns<=IDLE3;
  when IDLE3  => 
                 if (start = '1') then
             memaddrcount :=(others =>'0');
                 end if;
                 ns<=READ;
  when READ   => 

                 addr <= addrcount1;
                 ns<=READ1;

  when READ1=>
        ns<=READREADY;

  when READREADY => 
            valuebuffer(count to count+7 ) <= bin;
            count := count +8;
                addrcount1 <= addrcount1 +1;

                    if count=8192 then
                       if gr='0' then
              bitpos:=conv_std_logic_vector((conv_integer(frm.sideinfo.main_data)*8),13);
                   else
                  start_bit2:=conv_integer(bitpos);
                       end if;
                          ns<= SCALE;
                    else
                        ns<= READ;
                    end if;
                    .
                    .
                    .

As we can see, this line is the input main data 

bin   : in  std_logic_vector(7 downto 0);    -- input main data for huffman

Is this line indicates the bit file is fed into the buffer?

valuebuffer(count to count+7 ) <= bin;

I wonder why the read_mode method is not used. If read_mode is needed, where should it be inserted?

Upvotes: 1

Views: 1670

Answers (1)

Fisher
Fisher

Reputation: 422

Normally only read a file in testbench.

process
  variable status_input  : file_open_status;
begin
  -- Open files
  file_open(status_input, file_input, "../your_text_file.txt", read_mode); ...

After read the content of the file, you can feed the data to a module's I/O.

The code you posted is terrible. Lots of issues, I'll never reference it.

Upvotes: 2

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