--*********************************************************************
-- *********************************************************************
-- ** -----------------------------------------------------------------------------**
-- ** dct.v
-- **
-- ** 8x8 discrete Cosine Transform
-- **
-- **
-- **
-- **                  Author: Latha Pillai
-- **                  Senior Applications Engineer
-- **
-- **                  Video Applications
-- **                  Advanced Products Group
-- **                  Xilinx, Inc.
-- **
-- **                  Copyright (c) 2001 Xilinx, Inc.
-- **                  All rights reserved
-- **
-- **                  Date:   Feb. 10, 2002
-- **
-- **                  RESTRICTED RIGHTS LEGEND
-- **
-- **      This software has not been published by the author, and 
-- **      has been disclosed to others for the purpose of enhancing 
-- **      and promoting design productivity in Xilinx products.
-- **
-- **      Therefore use, duplication or disclosure, now and in the 
-- **      future should give consideration to the productivity 
-- **      enhancements afforded the user of this code by the author's 
-- **      efforts.  Thank you for using our products !
-- **
-- ** Disclaimer:  THESE DESIGNS ARE PROVIDED "AS IS" WITH NO WARRANTY 
-- **              WHATSOEVER AND XILINX SPECIFICALLY DISCLAIMS ANY 
-- **              IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
-- **              A PARTICULAR PURPOSE, OR AGAINST INFRINGEMENT.
-- ** Module: dct8x8 : 
-- ** A 1D-DCT is implemented on the input pixels first. The output of this
-- ** called  the intermediate value is stored in a RAM. The 2nd 1D-DCT operation 
-- ** is done on this stored value to give the final 2D-DCT ouput dct_2d. The 
-- ** inputs are 8 std_logics wide and the 2d-dct ouputs are 9 std_logics wide.
-- ** 1st 1D section
-- ** The input signals are taken one pixel at a time in the order x00 to x07,
-- ** x10 to x07 and so on upto x77. These inputs are fed into a 8 std_logic shift
-- ** register. The outputs of the 8 std_logic shift registers are registered by the 
-- ** div8clk which is the CLK signal divided by 8. This will enable us to 
-- ** register in 8 pixels (one row) at a time. The pixels are paired up in an 
-- ** adder subtractor in the order xk0,xk7:xk1,xk6:xk2,xk5:xk3,xk4. The adder 
-- ** subtractor is tied to CLK. For every clk, the adder/subtractor module 
-- ** alternaltley chooses addtion and subtraction. This selection is done by
-- ** the toggle flop. The ouput of the addsub is fed into a muliplier whose 
-- ** other input is connected to stored values in registers which act as 
-- ** memory. The ouput of the 4 mulipliers are added at every CLK in the 
-- ** final adder. The ouput of the  adder z_out is the 1D-DCT values given 
-- ** out in the order in which the inputs were read in.
-- ** It takes 8 clks to read in the first set of inputs, 1 clk to register 
-- ** inputs,1 clk to do add/sub, 1clk to get absolute value,
-- ** 1 clk for multiplication, 2 clk for the final adder. total = 14 clks to get 
-- ** the 1st z_out value. Every subsequent clk gives out the next z_out value.
-- ** So to get all the 64 values we need  11+63=74 clks.
-- ** Storage / RAM section
-- ** The ouputs z_out of the adder are stored in RAMs. Two RAMs are used so 
-- ** that data write can be continuous. The 1st valid input for the RAM1 is 
-- ** available at the 15th clk. So the RAM1 enable is active after 15 clks. 
-- ** After this the write operation continues for 64 clks . At the 65th clock, 
-- ** since z_out is continuous, we get the next valid z_out_00. This 2nd set of
-- ** valid 1D-DCT coefficients are written into RAM2 which is enabled at 15+64 
-- ** clks. So at 65th clk, RAM1 goes into read mode for the next 64 clks and 
-- ** RAM2 is in write mode. After this for every 64 clks, the read and write 
-- ** switches between the 2 RAMS.
-- ** 2nd 1D-DCT section
-- ** After the 1st 79th clk when RAM1 is full, the 2nd 1d calculations can 
-- ** start. The second 1D implementation is the same as the 1st 1D 
-- ** implementation with the inputs now coming from either RAM1 or RAM2. Also,
-- ** the inputs are read in one column at a time in the order z00 to z70, z10 to 
-- ** z70 upto z77. The oupts from the adder in the 2nd section are the 2D-DCT 
-- ** coeeficients.
-- **********************************************************************
library IEEE; 
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;
use IEEE.std_logic_unsigned.all;
use IEEE.numeric_std.all;
--library virtex; 
--use virtex.components.all; 
--library synplify; 
--use synplify.attributes.all; 
library unisims_ver; -- include this for modelsim simulation
                     -- when using mult18x18


ENTITY dct IS
   PORT (
      CLK                     : IN std_logic;   
      RST                     : IN std_logic;   
      xin                     : IN std_logic_vector(7 downto 0);   --  8 bit input.      
      dct_2d                  : OUT std_logic_vector(11 downto 0);   
      rdy_out                 : OUT std_logic);   
END dct;

ARCHITECTURE logic OF dct IS



-- The max value of a pixel after processing (to make their expected mean to 
-- zero). The max value of a pixel after processing (to make their expected 
-- mean to zero) is 127. If all the values in a row are 127, the max value of 
-- the product terms would be (127*8)*(23170/256) and that of z_out_int would 
-- be (127*8)*23170/65536. This value divided by 2raised to 16 is 
-- equivalent to ignoring the 16 lsb std_logics of the value 

   -- 1D section 

signal xa0_in, xa1_in, xa2_in, xa3_in, 
       xa4_in, xa5_in, xa6_in, xa7_in:           std_logic_vector(7 downto 0);
signal xa0_reg, xa1_reg, xa2_reg, xa3_reg, 
       xa4_reg, xa5_reg, xa6_reg, xa7_reg:       std_logic_vector (8 downto 0);
signal addsub1a_comp,addsub2a_comp,
       addsub3a_comp,addsub4a_comp :             std_logic_vector (7 downto 0);
signal add_sub1a,add_sub2a,add_sub3a,add_sub4a : std_logic_vector (9 downto 0);
signal save_sign1a,save_sign2a,
       save_sign3a,save_sign4a :                 std_logic;
signal xor1a,xor2a,xor3a,xor4a: std_logic;
signal p1a,p2a,p3a,p4a :                         std_logic_vector (18 downto 0);
signal p1a_all,p2a_all,p3a_all,p4a_all :         std_logic_vector (14 downto 0);   -- assign as 36 std_logic wide signal

signal i_wait                   :  std_logic_vector(1 downto 0);   
signal toggleA                  :  std_logic;   
signal z_out_int1               :  std_logic_vector(18 downto 0);   
signal z_out_int2               :  std_logic_vector(18 downto 0);   
signal z_out_int                :  std_logic_vector(18 downto 0);   
signal z_out_rnd                :  std_logic_vector(10 downto 0);   
signal z_out                    :  std_logic_vector(10 downto 0);   
signal indexi                   :  integer;   

   -- clks and counters 
signal cntr12                   :  std_logic_vector(3 downto 0);   
signal cntr8                    :  std_logic_vector(3 downto 0);   
signal cntr79                   :  std_logic_vector(6 downto 0);   
signal wr_cntr                  :  std_logic_vector(6 downto 0);   
signal rd_cntr                  :  std_logic_vector(6 downto 0);   
signal cntr92                   :  std_logic_vector(6 downto 0);  
 
-- memory section 
signal  memory1a, memory2a, memory3a, memory4a: std_logic_vector(7 downto 0);
signal data_out                 :  std_logic_vector(10 downto 0);   
signal en_ram1                  :  std_logic;   
signal en_dct2d                 :  std_logic;   
signal en_ram1reg               :  std_logic;   
signal en_dct2d_reg             :  std_logic;   

   
type ram1a_mem is array (0 to 63) of std_logic_vector(10 downto 0);
signal ram1_mem                 :  ram1a_mem;

   --  add the following to infer block RAM in synlpicity
   --    synthesis syn_ramstyle = "block_ram"  //shd be within /*..*/

   
type ram2a_mem is array (0 to 63) of std_logic_vector(10 downto 0);
signal ram2_mem                 :  ram2a_mem;

   --  add the following to infer block RAM in synlpicity
   --    synthesis syn_ramstyle = "block_ram"  //shd be within /*..*/


   -- 2D section 

signal data_out_final           :  std_logic_vector(10 downto 0);   
signal xb0_in, xb1_in, xb2_in, xb3_in, 
       xb4_in, xb5_in, xb6_in, xb7_in :       std_logic_vector(10 downto 0);
signal xb0_reg, xb1_reg, xb2_reg, xb3_reg, 
       xb4_reg, xb5_reg, xb6_reg, xb7_reg :   std_logic_vector(11 downto 0);
signal add_sub1b,add_sub2b,add_sub3b,add_sub4b: std_logic_vector(11 downto 0);
signal addsub1b_comp,addsub2b_comp,
       addsub3b_comp,addsub4b_comp :          std_logic_vector (10 downto 0);
signal save_sign1b,save_sign2b,save_sign3b,save_sign4b : std_logic;
signal xor1b,xor2b,xor3b,xor4b: std_logic;
signal p1b,p2b,p3b,p4b: std_logic_vector(19 downto 0);
signal p1b_all,p2b_all,p3b_all,p4b_all : std_logic_vector (17 downto 0);
                     -- assign as 36 std_logic wide signal if using mult18x18
signal toggleB                  :  std_logic;   
signal dct2d_int1               :  std_logic_vector(19 downto 0);   
signal dct2d_int2               :  std_logic_vector(19 downto 0);   
signal dct_2d_int               :  std_logic_vector(19 downto 0);   
signal dct_2d_rnd               :  std_logic_vector(11 downto 0);   
   -- rounding of the value

BEGIN

   --  1D-DCT BEGIN 
   -- store  1D-DCT constant coeeficient values for multipliers */
   
   PROCESS (RST, CLK)
   BEGIN
      IF (RST = '1') THEN
         memory1a <= "00000000";    
         memory2a <= "00000000";    
         memory3a <= "00000000";    
         memory4a <= "00000000";    
      ELSIF (CLK'EVENT AND CLK = '1') THEN
         CASE indexi IS
            WHEN 0 =>
                     memory1a <= "01011011";    
                     memory2a <= "01011011";    
                     memory3a <= "01011011";    
                     memory4a <= "01011011";    
            WHEN 1 =>
                     memory1a <= "01111110";    
                     memory2a <= "01101010";    
                     memory3a <= "01000111";    
                     memory4a <= "00011001";    
            WHEN 2 =>
                     memory1a <= "01110110";    
                     memory2a <= "00110001";    
                     memory3a <= "10110001";    -- -8'd49; 
                     memory4a <= "11110110";    --  end -8'd118;end
            WHEN 3 =>
                     memory1a <= "01101010";    
                     memory2a <= "10011001";    -- -8'd25;  
                     memory3a <= "11111110";    -- -8'd126; 
                     memory4a <= "11000111";    
            WHEN 4 =>
                     memory1a <= "01011011";    
                     memory2a<= "11011011";    -- -8'd91; 
                     memory3a <= "11011011";    -- -8'd91; 
                     memory4a <= "01011011";    
            WHEN 5 =>
                     memory1a <= "01000111";    
                     memory2a <= "11111110";    -- -8'd126; 
                     memory3a <= "00011001";    
                     memory4a <= "01101010";    
            WHEN 6 =>
                     memory1a <= "00110001";    
                     memory2a <= "11110110";    -- -8'd118; 
                     memory3a <= "01110110";    
                     memory4a <= "10110001";    
            WHEN 7 =>
                     memory1a <= "00011001";    
                     memory2a <= "11000111";    -- -8'd71; 
                     memory3a <= "01101010";    
                     memory4a <= "11111110";    
            WHEN OTHERS =>
                     NULL;
            
            ---8'd126;end
            
         END CASE;
      END IF;
   END PROCESS;

   -- 8-std_logic input shifted 8 times thru a shift register
   PROCESS (CLK, RST)
   BEGIN
      IF (RST = '1') THEN
         xa0_in <= "00000000";    xa1_in <= "00000000";    
         xa2_in <= "00000000";    xa3_in <= "00000000";    
         xa4_in <= "00000000";    xa5_in <= "00000000";    
         xa6_in <= "00000000";    xa7_in <= "00000000";    
      ELSIF (CLK'EVENT AND CLK = '1') THEN
         xa0_in <= xin;    xa1_in <= xa0_in;    
         xa2_in <= xa1_in;    xa3_in <= xa2_in;    
         xa4_in <= xa3_in;    xa5_in <= xa4_in;    
         xa6_in <= xa5_in;    xa7_in <= xa6_in;    
      END IF;
   END PROCESS;

   -- shifted inputs registered every 8th clk (using cntr8)
   PROCESS (CLK, RST)
   BEGIN
      IF (RST = '1') THEN
         cntr8 <= "0000";    
      ELSIF (CLK'EVENT AND CLK = '1') THEN
         IF (cntr8 < "1000") THEN
            cntr8 <= cntr8 + "0001";    
         ELSE
            cntr8 <= "0001";    
         END IF;
      END IF;
   END PROCESS;

   PROCESS (CLK, RST)
   BEGIN
      IF (RST = '1') THEN
         xa0_reg <= "000000000";    xa1_reg <= "000000000";    
         xa2_reg <= "000000000";    xa3_reg <= "000000000";    
         xa4_reg <= "000000000";    xa5_reg <= "000000000";    
         xa6_reg <= "000000000";    xa7_reg <= "000000000";    
      ELSIF (CLK'EVENT AND CLK = '1') THEN
         IF (cntr8 = "1000") THEN
            xa0_reg <= xa0_in(7) & xa0_in;    xa1_reg <= xa1_in(7) & xa1_in;    
            xa2_reg <= xa2_in(7) & xa2_in;    xa3_reg <= xa3_in(7) & xa3_in;    
            xa4_reg <= xa4_in(7) & xa4_in;    xa5_reg <= xa5_in(7) & xa5_in;    
            xa6_reg <= xa6_in(7) & xa6_in;    xa7_reg <= xa7_in(7) & xa7_in;    
         ELSE
            
         END IF;
      END IF;
   END PROCESS;

   PROCESS (CLK, RST)
   BEGIN
      IF (RST = '1') THEN
         toggleA <= '0';    
      ELSIF (CLK'EVENT AND CLK = '1') THEN
         toggleA <= NOT toggleA;    
      END IF;
   END PROCESS;

   -- adder / subtractor block 
   PROCESS (CLK, RST)