----------------------------------------------------------------------------------
-- Company: 
-- Engineer: 
-- 
-- Create Date:    21:49:24 05/26/2008 
-- Design Name: 
-- Module Name:    top - Behavioral 
-- Project Name: 
-- Target Devices: 
-- Tool versions: 
-- Description: 
--
-- Dependencies: 
--
-- Revision: 
-- Revision 0.01 - File Created
-- Additional Comments: 
--
----------------------------------------------------------------------------------

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
library work;
use work.usefuls.all;

entity top is
  port (
      -- MCU(C8051F342) side
      sysclk : in std_logic;
      reset : in std_logic;      
      mcu_data : inout std_logic_vector(7 downto 0);
      mcu_dclk : in std_logic;
      mcu_req : in std_logic;
      mcu_ready : out std_logic;
      mcu_int_n : out std_logic;
      
      -- Camera side
      cam_extclk : out std_logic;
      cam_reset : out std_logic;
      cam_strobe : in std_logic;
      cam_dclk : in std_logic;
      cam_data : in std_logic_vector(7 downto 0);
      cam_hblk : in std_logic;
      cam_vblk : in std_logic;
      
      -- SDRAM side
      sdram_clk : out std_logic;
      sdram_cke : out std_logic;
      sdram_cs_n : out std_logic;
      sdram_we_n : out std_logic;
      sdram_cas_n : out std_logic;
      sdram_ras_n : out std_logic;
      sdram_dqm : out std_logic_vector(0 downto 0);
      sdram_bank_addr : out std_logic_vector(1 downto 0);
      sdram_addr : out std_logic_vector(11 downto 0);
      sdram_data : inout std_logic_vector(7 downto 0);
      
      -- Debug
      debug : out std_logic_vector(1 downto 0));
end top;

architecture Behavioral of top is

  signal cam_dclk_buf1 : std_logic;
  signal cam_dclk_buf2 : std_logic;
  signal cam_vblk_buf : std_logic;
  signal cam_hblk_buf : std_logic;
  constant cam_data_address_width : integer := min_bits(1280 * 2 * 1024); -- SXGA (color:16bits/pixel)
  signal cam_data_address : std_logic_vector(cam_data_address_width-1 downto 0) := (others => '0');
  
  signal mcu_dclk_buf : std_logic;
  signal mcu_data_address : std_logic_vector(cam_data_address_width-1 downto 0) := (others => '0');
  
  type state_type is (
      CAM_DATA_RXING,
      CAM_DATA_RXED,
      MCU_DATA_TXING,
      MCU_DATA_TXED);
  signal current_state : state_type;
  
  component SDRAM is
    generic (
        address_width : integer := 24;
        data_width : integer := 16;
        sdram_dqm_width : integer := 2;
        sdram_bank_addr_width : integer := 2;
        sdram_addr_width : integer := 12;
        sdram_data_width : integer := 16;
        clk_period : integer := 21; -- [ns] 48MHz
        sdram_refresh_cycle : integer := 15625;  -- [ns] 64 ms / 4096
        sdram_tRCD : integer := 18; -- [ns]
        sdram_tRFC : integer := 60; -- [ns]
        sdram_tRP : integer := 18; -- [ns]
        sdram_tWR : integer := 31; -- [ns]
        sdram_tMRD_clock : integer := 2;
        sdram_cas_latency : integer := 3);
    port (
        clk : in std_logic;
        
        -- Control side
        reset : in std_logic;
        cs : in std_logic;
        dir : in std_logic;   -- W => '1', R=> '0'
        done : out std_logic; -- complete write / data valid
        address : in std_logic_vector(
            address_width-1 downto 0);
        data_in : in std_logic_vector(
            data_width-1 downto 0);
        data_out : out std_logic_vector(
            data_width-1 downto 0);
        
        -- SDRAM side
        sdram_clk : out std_logic;
        sdram_cke : out std_logic;
        sdram_cs_n : out std_logic;
        sdram_we_n : out std_logic;
        sdram_cas_n : out std_logic;
        sdram_ras_n : out std_logic;
        sdram_dqm : out std_logic_vector(
            sdram_dqm_width-1 downto 0);
        sdram_bank_addr : out std_logic_vector(
            sdram_bank_addr_width-1 downto 0);
        sdram_addr : out std_logic_vector(
            sdram_addr_width-1 downto 0);
        sdram_data : inout std_logic_vector(
            sdram_data_width-1 downto 0));
  end component;
  
  constant sdram_data_width : integer := 8;
  
  signal sdram_if_cs : std_logic := '0';
  signal sdram_if_dir : std_logic;    -- W => '1', R=> '0'
  signal sdram_if_done : std_logic;   -- complete write / data valid
  constant sdram_if_addr_width : integer := 23; -- 2^23 = 8M
  signal sdram_if_addr : std_logic_vector(sdram_if_addr_width-1 downto 0);
  constant sdram_if_burst_length : integer := 4;
  constant sdram_if_burst_mask_length : integer := log2_ceil(sdram_if_burst_length);
  constant sdram_if_data_width : integer := 8 * sdram_if_burst_length;
  signal sdram_if_data_in : std_logic_vector(sdram_if_data_width-1 downto 0);
  signal sdram_if_data_out : std_logic_vector(sdram_if_data_width-1 downto 0);
  
  signal mcu_data_buf : std_logic_vector(sdram_if_data_width-1 downto 0);
  signal mcu_ready_buf : std_logic;
  
  signal is_burst_first_mcu_address : boolean;
  signal is_burst_last_cam_address : boolean;
  signal mcu_data_address_masked : std_logic_vector(cam_data_address_width-1 downto 0) := (others => '0');
  signal cam_data_address_masked : std_logic_vector(cam_data_address_width-1 downto 0) := (others => '0');
  signal sdram_if_data_in_shifted : std_logic_vector(sdram_if_data_width-1 downto 0);
  signal mcu_data_buf_shifted : std_logic_vector(sdram_if_data_width-1 downto 0);
  
  
  component DividerN is
    generic (
        divide_value : positive := 8);
    port (
        clk, reset : in std_logic;
        clk_out, tc : out std_logic);
  end component;
begin

  div1 : DividerN
      generic map (
          divide_value => 8)    -- 48MHz => 6MHz
      port map (
          clk => sysclk,
          reset => reset,
          clk_out => cam_extclk);

  sdram_if : SDRAM
      generic map (
          address_width => sdram_if_addr_width,
          data_width => sdram_if_data_width,
          sdram_dqm_width => 1,
          sdram_bank_addr_width => 2,
          sdram_addr_width => 12,
          sdram_data_width => sdram_data_width,
          clk_period => 21, -- [ns] 48MHz
          sdram_refresh_cycle => 15625, -- [ns]
          sdram_tRCD => 18, -- [ns]
          sdram_tRFC => 60, -- [ns]
          sdram_tRP => 18, -- [ns]
          sdram_tWR => 31, -- [ns]
          sdram_tMRD_clock => 2,
          sdram_cas_latency => 2)
      port map (
          clk => sysclk,
          
          -- Control side
          reset => reset,
          cs => sdram_if_cs,
          dir => sdram_if_dir,
          done => sdram_if_done, 
          address => sdram_if_addr,
          data_in => sdram_if_data_in,
          data_out => sdram_if_data_out,
          
          -- SDRAM side
          sdram_clk => sdram_clk, 
          sdram_cke => sdram_cke,
          sdram_cs_n => sdram_cs_n,
          sdram_we_n => sdram_we_n,
          sdram_cas_n => sdram_cas_n,
          sdram_ras_n => sdram_ras_n,
          sdram_dqm => sdram_dqm,
          sdram_bank_addr => sdram_bank_addr,
          sdram_addr => sdram_addr,
          sdram_data => sdram_data);
  
  cam_reset <= not reset;
  
  -- state machine
  process(sysclk, reset) begin
    if reset = '1' then
      current_state <= CAM_DATA_RXING;
    elsif sysclk'event and sysclk = '1' then
      case current_state is
      when CAM_DATA_RXING =>
        if cam_vblk_buf = '1' and cam_vblk = '0' then
          current_state <= CAM_DATA_RXED;
        else
          current_state <= CAM_DATA_RXING;
        end if;
      when CAM_DATA_RXED => 
        if mcu_req = '1' and sdram_if_cs = '0' then
          current_state <= MCU_DATA_TXING;
        elsif cam_vblk_buf = '0' and cam_vblk = '1' then
          current_state <= CAM_DATA_RXING;
        else
          current_state <= CAM_DATA_RXED;
        end if;
      when MCU_DATA_TXING => 
        if mcu_req = '0' then
          current_state <= MCU_DATA_TXED;
        else
          current_state <= MCU_DATA_TXING;
        end if;
      when MCU_DATA_TXED => 
        if cam_vblk_buf = '0' or cam_vblk = '0' then
          current_state <= CAM_DATA_RXING;
        else
          current_state <= MCU_DATA_TXED;
        end if;
      when others => null;
      end case;
    end if;
  end process;
  
  -- assign CAM inputs to SDRAM data inputs
  process(sysclk) begin
    if sysclk'event and sysclk = '1' then
      cam_dclk_buf1 <= cam_dclk;
      cam_dclk_buf2 <= cam_dclk_buf1;
      cam_vblk_buf <= cam_vblk;
      cam_hblk_buf <= cam_hblk;
      
      if current_state = MCU_DATA_TXING then
        cam_data_address <= cam_data_address;
      elsif current_state = MCU_DATA_TXED
          or (cam_vblk_buf = '0' and cam_vblk = '1') then
        cam_data_address <= (others => '0');
      elsif cam_hblk_buf = '1' and cam_dclk_buf1 = '1' and cam_dclk = '0' then
        cam_data_address <= cam_data_address + 1;
      else
        cam_data_address <= cam_data_address;
      end if;
      
      if cam_hblk = '1' and cam_dclk_buf1 = '0' and cam_dclk = '1' then
        sdram_if_data_in <= sdram_if_data_in_shifted;
      else
        sdram_if_data_in <= sdram_if_data_in;
      end if;
    end if;
  end process;
  
  -- assign SDRAM data outputs to MCU inputs
  process(sysclk) begin
    if sysclk'event and sysclk = '1' then
      mcu_dclk_buf <= mcu_dclk;
      
      if current_state = CAM_DATA_RXING or current_state = CAM_DATA_RXED then
        mcu_data_address <= (others => '0');
      elsif (mcu_data_address < cam_data_address) 
          and mcu_dclk_buf = '1' and mcu_dclk = '0' then
        mcu_data_address <= mcu_data_address + 1;
      else
        mcu_data_address <= mcu_data_address;
      end if;
    end if;
  end process;
  
  gen_with_burst : if sdram_if_burst_mask_length > 0 generate
    is_burst_first_mcu_address 
        <= true when mcu_data_address(sdram_if_burst_mask_length-1 downto 0)
                = conv_std_logic_vector(0, sdram_if_burst_mask_length)
            else false;
    is_burst_last_cam_address 
        <= true when cam_data_address(sdram_if_burst_mask_length-1 downto 0)
                = (not conv_std_logic_vector(0, sdram_if_burst_mask_length))
            else false;
    mcu_data_address_masked
        <= mcu_data_address(cam_data_address_width-1 downto sdram_if_burst_mask_length)
                & conv_std_logic_vector(0, sdram_if_burst_mask_length);
    cam_data_address_masked 
        <= cam_data_address(cam_data_address_width-1 downto sdram_if_burst_mask_length)
                & conv_std_logic_vector(0, sdram_if_burst_mask_length);
    sdram_if_data_in_shifted 
        <= cam_data & sdram_if_data_in(sdram_if_data_width-1 downto 8);
    mcu_data_buf_shifted 
        <= conv_std_logic_vector(0, 8) & mcu_data_buf(sdram_if_data_width-1 downto 8);
  end generate;
  
  gen_without_burst : if sdram_if_burst_mask_length = 0 generate
    is_burst_first_mcu_address <= true;
    is_burst_last_cam_address <= true;
    mcu_data_address_masked <= mcu_data_address;
    cam_data_address_masked <= cam_data_address;
    sdram_if_data_in_shifted 
        <= cam_data & conv_std_logic_vector(0, sdram_if_data_width-8);
    mcu_data_buf_shifted <= mcu_data_buf;
  end generate;
  
  process(sysclk, reset, mcu_dclk) begin
    if reset = '1' or mcu_dclk = '0' then
      mcu_ready_buf <= '0';
    elsif sysclk'event and sysclk = '1' then
      if (sdram_if_cs = '1' and sdram_if_done = '1')
          or (mcu_dclk_buf = '0' and mcu_dclk = '1' 
              and (not is_burst_first_mcu_address)) then
        mcu_ready_buf <= '1';
      else
        mcu_ready_buf <= mcu_ready_buf;
      end if;
      
      if sdram_if_cs = '1' and sdram_if_done = '1' then
        mcu_data_buf <= sdram_if_data_out;
      elsif mcu_dclk_buf = '0' and mcu_dclk = '1' 
          and (not is_burst_first_mcu_address) then
        mcu_data_buf <= mcu_data_buf_shifted;
      else
        mcu_data_buf <= mcu_data_buf;
      end if;
    end if;
  end process;
  mcu_data <= mcu_data_buf(7 downto 0);
  mcu_ready <= '1' when current_state = MCU_DATA_TXING
          and ((mcu_dclk = '0' and mcu_data_address < cam_data_address) 
              or (mcu_dclk = '1' and mcu_ready_buf = '1')) 
      else '0';
  
  -- push/pop SDRAM data
  process(sysclk, reset) begin
    if reset = '1' then
      sdram_if_cs <= '0';
    elsif sysclk'event and sysclk = '1' then
      if current_state = MCU_DATA_TXING or current_state = MCU_DATA_TXED then
        if mcu_dclk_buf = '0' and mcu_dclk = '1' 
            and is_burst_first_mcu_address then
          sdram_if_cs <= '1';
        elsif sdram_if_cs = '1' and sdram_if_done = '1' then
          sdram_if_cs <= '0';
        else
          sdram_if_cs <= sdram_if_cs;
        end if;
        sdram_if_dir <= '0';
        sdram_if_addr 
            <= conv_std_logic_vector(0, sdram_if_addr_width - cam_data_address_width) 
                & mcu_data_address_masked;
      else
        if sdram_if_cs = '0' and ((is_burst_last_cam_address
                and cam_dclk_buf2 = '0' and cam_dclk_buf1 = '1' and cam_hblk_buf = '1')
            or (cam_vblk_buf = '1' and cam_vblk = '0')) then
          sdram_if_cs <= '1';
        elsif sdram_if_cs = '1' and sdram_if_done = '1' then
          sdram_if_cs <= '0';
        else
          sdram_if_cs <= sdram_if_cs;
        end if;
        sdram_if_dir <= '1';
        sdram_if_addr 
            <= conv_std_logic_vector(0, sdram_if_addr_width - cam_data_address_width) 
                & cam_data_address_masked;
      end if;
    end if;
  end process;
  
  debug(0) <= sdram_if_cs;
  debug(1) <= cam_data_address(0);
end Behavioral;