repo2/eclaireXL_ITX/hdmi/encoder.vhd @ 1475
| 479 | markw | -------------------------------------------------------------------[01.11.2014]
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-- Encoder
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-------------------------------------------------------------------------------
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-- V1.0 03.08.2014 Initial release
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-- V2.0 01.11.2014 Added AUX
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library IEEE;
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use IEEE.STD_LOGIC_1164.ALL;
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use IEEE.STD_LOGIC_UNSIGNED.ALL;
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| 483 | markw | entity encoder is
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| 479 | markw | port (
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CLK : in STD_LOGIC;
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DATA : in STD_LOGIC_VECTOR (7 downto 0);
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C : in STD_LOGIC_VECTOR (1 downto 0);
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VDE : in STD_LOGIC; -- Video Data Enable (VDE)
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| 483 | markw | ADE : in STD_LOGIC := '0'; -- Audio/auxiliary Data Enable (ADE)
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AUX : in STD_LOGIC_VECTOR (3 downto 0) := "0000";
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| 479 | markw | ENCODED : out STD_LOGIC_VECTOR (9 downto 0));
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| 483 | markw | end encoder;
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| 479 | markw | ||
| 483 | markw | architecture rtl of encoder is
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| 479 | markw | signal xored : STD_LOGIC_VECTOR (8 downto 0);
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signal xnored : STD_LOGIC_VECTOR (8 downto 0);
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signal ones : STD_LOGIC_VECTOR (3 downto 0);
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signal data_word : STD_LOGIC_VECTOR (8 downto 0);
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signal data_word_inv : STD_LOGIC_VECTOR (8 downto 0);
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signal data_word_disparity : STD_LOGIC_VECTOR (3 downto 0);
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signal dc_bias : STD_LOGIC_VECTOR (3 downto 0) := (others => '0');
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begin
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-- Work our the two different encodings for the byte
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xored(0) <= DATA(0);
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xored(1) <= DATA(1) xor xored(0);
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xored(2) <= DATA(2) xor xored(1);
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xored(3) <= DATA(3) xor xored(2);
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xored(4) <= DATA(4) xor xored(3);
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xored(5) <= DATA(5) xor xored(4);
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xored(6) <= DATA(6) xor xored(5);
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xored(7) <= DATA(7) xor xored(6);
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xored(8) <= '1';
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xnored(0) <= DATA(0);
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xnored(1) <= DATA(1) xnor xnored(0);
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xnored(2) <= DATA(2) xnor xnored(1);
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xnored(3) <= DATA(3) xnor xnored(2);
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xnored(4) <= DATA(4) xnor xnored(3);
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xnored(5) <= DATA(5) xnor xnored(4);
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xnored(6) <= DATA(6) xnor xnored(5);
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xnored(7) <= DATA(7) xnor xnored(6);
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xnored(8) <= '0';
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-- Count how many ones are set in data
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ones <= "0000" + DATA(0) + DATA(1) + DATA(2) + DATA(3) + DATA(4) + DATA(5) + DATA(6) + DATA(7);
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-- Decide which encoding to use
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process (ones, DATA(0), xnored, xored)
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begin
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if ones > 4 or (ones = 4 and DATA(0) = '0') then
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data_word <= xnored;
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data_word_inv <= NOT(xnored);
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else
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data_word <= xored;
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data_word_inv <= NOT(xored);
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end if;
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end process;
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-- Work out the DC bias of the dataword;
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data_word_disparity <= "1100" + data_word(0) + data_word(1) + data_word(2) + data_word(3) + data_word(4) + data_word(5) + data_word(6) + data_word(7);
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-- Now work out what the output should be
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process(CLK)
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begin
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if (CLK'event and CLK = '1') then
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-- Video Data Coding
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if VDE = '1' then
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if dc_bias = "00000" or data_word_disparity = 0 then
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-- dataword has no disparity
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if data_word(8) = '1' then
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ENCODED <= "01" & data_word(7 downto 0);
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dc_bias <= dc_bias + data_word_disparity;
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else
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ENCODED <= "10" & data_word_inv(7 downto 0);
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dc_bias <= dc_bias - data_word_disparity;
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end if;
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elsif (dc_bias(3) = '0' and data_word_disparity(3) = '0') or
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(dc_bias(3) = '1' and data_word_disparity(3) = '1') then
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ENCODED <= '1' & data_word(8) & data_word_inv(7 downto 0);
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dc_bias <= dc_bias + data_word(8) - data_word_disparity;
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else
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ENCODED <= '0' & data_word;
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dc_bias <= dc_bias - data_word_inv(8) + data_word_disparity;
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end if;
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-- TERC4 Coding
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elsif ADE = '1' then
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case AUX is
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when "0000" => ENCODED <= "1010011100";
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when "0001" => ENCODED <= "1001100011";
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when "0010" => ENCODED <= "1011100100";
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when "0011" => ENCODED <= "1011100010";
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when "0100" => ENCODED <= "0101110001";
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when "0101" => ENCODED <= "0100011110";
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when "0110" => ENCODED <= "0110001110";
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when "0111" => ENCODED <= "0100111100";
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when "1000" => ENCODED <= "1011001100";
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when "1001" => ENCODED <= "0100111001";
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when "1010" => ENCODED <= "0110011100";
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when "1011" => ENCODED <= "1011000110";
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when "1100" => ENCODED <= "1010001110";
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when "1101" => ENCODED <= "1001110001";
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when "1110" => ENCODED <= "0101100011";
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when others => ENCODED <= "1011000011";
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end case;
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else
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-- In the control periods, all values have and have balanced bit count
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case C is
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when "00" => ENCODED <= "1101010100";
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when "01" => ENCODED <= "0010101011";
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when "10" => ENCODED <= "0101010100";
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when others => ENCODED <= "1010101011";
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end case;
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dc_bias <= (others => '0');
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end if;
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end if;
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end process;
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end rtl;
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--
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-- process(CLK)
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-- begin
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-- if (CLK'event and CLK = '1') then
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-- case encoding is
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-- when "00"
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