library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
  
entity RAM9X8_OpticalBusMaster is	
	generic(
		OB_BASE_ADDRESS : integer := 56;
		
		DATA_BUS_WIDTH : integer := 8;
		ADDRESS_BUS_WIDTH : integer := 9
	);
	
	port(
		clk : in std_logic;
		
		data : inout std_logic_vector(DATA_BUS_WIDTH - 1 downto 0);
		address : in std_logic_vector(ADDRESS_BUS_WIDTH - 1 downto 0);
		we : in std_logic;
		oe : in std_logic;
		ce : in std_logic;	
	
		obclk : out std_logic := '1';
      obdata : out std_logic := '1'
	);
end entity;

architecture behavorial of RAM9X8_OpticalBusMaster is

signal OB_CMD_LOWER : integer := OB_BASE_ADDRESS;
signal OB_CMD_UPPER : integer := OB_BASE_ADDRESS + 1;
signal OB_WORD_8_LOWER : integer := OB_BASE_ADDRESS + 2;
signal OB_WORD_8_UPPER : integer := OB_BASE_ADDRESS + 3;
signal OB_WORD_7_LOWER : integer := OB_BASE_ADDRESS + 4;
signal OB_WORD_7_UPPER : integer := OB_BASE_ADDRESS + 5;
signal OB_WORD_6_LOWER : integer := OB_BASE_ADDRESS + 6;
signal OB_WORD_6_UPPER : integer := OB_BASE_ADDRESS + 7;
signal OB_WORD_5_LOWER : integer := OB_BASE_ADDRESS + 8;
signal OB_WORD_5_UPPER : integer := OB_BASE_ADDRESS + 9;
signal OB_WORD_4_LOWER : integer := OB_BASE_ADDRESS + 10;
signal OB_WORD_4_UPPER : integer := OB_BASE_ADDRESS + 11;
signal OB_WORD_3_LOWER : integer := OB_BASE_ADDRESS + 12;
signal OB_WORD_3_UPPER : integer := OB_BASE_ADDRESS + 13;
signal OB_WORD_2_LOWER : integer := OB_BASE_ADDRESS + 14;
signal OB_WORD_2_UPPER : integer := OB_BASE_ADDRESS + 15;
signal OB_WORD_1_LOWER : integer := OB_BASE_ADDRESS + 16;
signal OB_WORD_1_UPPER : integer := OB_BASE_ADDRESS + 17;

signal dataBuf : std_logic_vector(127 downto 0) := (others => '0');
signal dataToSend : std_logic_vector(127 downto 0) := (others => '0');
signal cmdBuf : std_logic_vector(15 downto 0) := x"0004";
    
type   CommunicationState_start  is (Waiting, DataSending, CRCSending);  
signal CommunicationState  : CommunicationState_start := Waiting ;
	
signal resetCRC : std_logic := '1';
signal CRC : std_logic_vector(3 downto 0) := x"0";
signal bufCRC : std_logic_vector(3 downto 0) := x"0";
signal dataCRC : std_logic_vector(127 downto 0) := (others => '0');                                                -- переключает 
signal readyCRC : std_logic := '0';                                                -- готовность контрольной суммы
	
signal lineBusy : std_logic := '1';
signal start : std_logic := '0';
signal startPrev : std_logic := '0';

begin	

	process (we, oe, ce)
		variable addr : integer range 0 to 2**ADDRESS_BUS_WIDTH - 1 := 0;
	begin
		if (ce = '0') then  -- Если микросхема выбрана
			addr := conv_integer(address);
			if (addr = OB_CMD_UPPER or addr = OB_CMD_LOWER
				or addr = OB_WORD_8_UPPER or addr = OB_WORD_8_LOWER
				or addr = OB_WORD_7_UPPER or addr = OB_WORD_7_LOWER
				or addr = OB_WORD_6_UPPER or addr = OB_WORD_6_LOWER
				or addr = OB_WORD_5_UPPER or addr = OB_WORD_5_LOWER
				or addr = OB_WORD_4_UPPER or addr = OB_WORD_4_LOWER
				or addr = OB_WORD_3_UPPER or addr = OB_WORD_3_LOWER
				or addr = OB_WORD_2_UPPER or addr = OB_WORD_2_LOWER
				or addr = OB_WORD_1_UPPER or addr = OB_WORD_1_LOWER) then
				if (oe = '0' and we = '1') then  -- Если сигнал чтения активен, а записи нет	
					case addr is
						when OB_CMD_UPPER =>
							data <= cmdBuf(15 downto 8);
						when OB_CMD_LOWER =>
							data <= cmdBuf(7 downto 0);
						when OB_WORD_8_UPPER =>
							data <= dataBuf(127 downto 120);
						when OB_WORD_8_LOWER =>
							data <= dataBuf(119 downto 112);
						when OB_WORD_7_UPPER =>
							data <= dataBuf(111 downto 104);
						when OB_WORD_7_LOWER =>
							data <= dataBuf(103 downto 96);
						when OB_WORD_6_UPPER =>
							data <= dataBuf(95 downto 88);
						when OB_WORD_6_LOWER =>
							data <= dataBuf(87 downto 80);
						when OB_WORD_5_UPPER =>
							data <= dataBuf(79 downto 72);
						when OB_WORD_5_LOWER =>
							data <= dataBuf(71 downto 64);
						when OB_WORD_4_UPPER =>
							data <= dataBuf(63 downto 56);
						when OB_WORD_4_LOWER =>
							data <= dataBuf(55 downto 48);
						when OB_WORD_3_UPPER =>
							data <= dataBuf(47 downto 40);
						when OB_WORD_3_LOWER =>
							data <= dataBuf(39 downto 32);
						when OB_WORD_2_UPPER =>
							data <= dataBuf(31 downto 24);
						when OB_WORD_2_LOWER =>
							data <= dataBuf(23 downto 16);
						when OB_WORD_1_UPPER =>
							data <= dataBuf(15 downto 8);
						when OB_WORD_1_LOWER =>
							data <= dataBuf(7 downto 0);							
						when others => 
							data <= (others => 'Z');  -- Запретить запись на шину
					end case;				
				elsif (oe = '1' and we = '0') then  -- Если сигнал записи активен, а чтения нет
					case addr is
						when OB_CMD_UPPER =>
							cmdBuf(15 downto 8) <= data;
						when OB_CMD_LOWER =>
							cmdBuf(7 downto 0) <= data;
						when OB_WORD_8_UPPER =>
							dataBuf(127 downto 120) <= data;
						when OB_WORD_8_LOWER =>
							dataBuf(119 downto 112) <= data;
						when OB_WORD_7_UPPER =>
							dataBuf(111 downto 104) <= data;
						when OB_WORD_7_LOWER =>
							dataBuf(103 downto 96) <= data;
						when OB_WORD_6_UPPER =>
							dataBuf(95 downto 88) <= data;
						when OB_WORD_6_LOWER =>
							dataBuf(87 downto 80) <= data;
						when OB_WORD_5_UPPER =>
							dataBuf(79 downto 72) <= data;
						when OB_WORD_5_LOWER =>
							dataBuf(71 downto 64) <= data;
						when OB_WORD_4_UPPER =>
							dataBuf(63 downto 56) <= data;
						when OB_WORD_4_LOWER =>
							dataBuf(55 downto 48) <= data;
						when OB_WORD_3_UPPER =>
							dataBuf(47 downto 40) <= data;
						when OB_WORD_3_LOWER =>
							dataBuf(39 downto 32) <= data;
						when OB_WORD_2_UPPER =>
							dataBuf(31 downto 24) <= data;
						when OB_WORD_2_LOWER =>
							dataBuf(23 downto 16) <= data;
						when OB_WORD_1_UPPER =>
							dataBuf(15 downto 8) <= data;
						when OB_WORD_1_LOWER =>
							dataBuf(7 downto 0) <= data;						
						when others =>
							data <= (others => 'Z');  -- Запретить запись на шину
					end case;
					if (addr = OB_WORD_1_UPPER) then
						start <= '1';
					else
						start <= '0';
					end if;	
				else
					data <= (others => 'Z');  -- Запретить запись на шину
				end if;
			else 
				data <= (others => 'Z');  -- Запретить запись на шину
			end if;	
		else
			data <= (others => 'Z');  -- Запретить запись на шину
		end if;
	end process;
	
	process(clk) is
		variable count : integer range 0 to 31 := 0;
		variable countValue : integer range 0 to 31 := 25;
		variable state : integer range 0 to 1 := 0;
		variable bitCnt : integer range 0 to 127 := 0;
	begin
		if(rising_edge (clk)) then
			case CommunicationState is
				when Waiting =>
					obclk <= '1';
					obdata <= '1';
					resetCRC <= '1';					
					count := 0;
					state := 0;
					if start = '1' and  startPrev = '0' then                               
						dataToSend <= dataBuf;
						dataCRC <= dataBuf;
						if conv_integer(cmdBuf(3 downto 0)) < 9 and conv_integer(cmdBuf(3 downto 0)) > 0 then 
							bitCnt := (conv_integer(cmdBuf(3 downto 0)) * 16) - 1;
						else 
							bitCnt := 63;
						end if;	
                  CommunicationState <= DataSending;
						resetCRC <= '0';						
               end if;
				when DataSending =>	 
					if count < countValue and state = 0 then
						if count = 0 then
							obdata <= dataToSend(bitCnt);
						end if;
						count := count + 1;
					elsif count = countValue and state = 0 then
						obclk <= '0';
						count := 0;
						state := 1;
					elsif count < countValue and state = 1 then
						count := count + 1;
					elsif count = countValue and state = 1 then
						obclk <= '1';
						count := 0;
						state := 0;
						if bitCnt > 0 then
							bitCnt := bitCnt - 1;
						else
							bitCnt := 3;
							CommunicationState <= CRCSending;
						end if;
					end if;
				when CRCSending =>	
					if count < countValue and state = 0 then
						if count = 0 then
							obdata <= CRC(bitCnt);
						end if;
						count := count + 1;
					elsif count = countValue and state = 0 then
						obclk <= '0';
						count := 0;
						state := 1;
					elsif count < countValue and state = 1 then
						count := count + 1;
					elsif count = countValue and state = 1 then
						obclk <= '1';
						count := 0;
						state := 0;
						if bitCnt > 0 then
							bitCnt := bitCnt - 1;
						else
							CommunicationState <= Waiting;
						end if;
					end if;			        
				when others =>
					CommunicationState <= Waiting;
			end case;
      startPrev <= start;
		end if;
	end process;
	
	process(clk)  
		variable lacth : integer range 0 to 1 := 0;
		variable bitCnt : integer range -1 to 127 := 0;
	begin
		if rising_edge(clk) then
			if resetCRC = '1' then
				if conv_integer(cmdBuf(3 downto 0)) < 9 and conv_integer(cmdBuf(3 downto 0)) > 0 then  
					bitCnt := (conv_integer(cmdBuf(3 downto 0)) * 16) - 1;
				else 
					bitCnt := 63;
				end if; 
				CRC <= x"0";
				lacth := 0;
				readyCRC <= '0';
			else
				if readyCRC = '0' then
					if lacth = 0 then
						if bitCnt /= -1  then
							CRC(3) <= CRC(2) xor CRC(3);
							CRC(2) <= CRC(1) xor CRC(0);	
							CRC(1) <= CRC(0);
							CRC(0) <=  dataCRC(bitCnt) xor CRC(1);											
							bitCnt := bitCnt - 1;
						else
							bitCnt := 3;
							lacth := 1;
						end if;   
					else
						if bitCnt /= -1  then
							CRC(3) <= CRC(2) xor CRC(3);
							CRC(2) <= CRC(1) xor CRC(0);	
							CRC(1) <= CRC(0);	
							CRC(0) <= '1' xor CRC(1);	
							bitCnt := bitCnt - 1;	 
						else
							readyCRC <= '1';
						end if;
					end if;
				end if;
			end if;
		end if;
	end process;
	
end behavorial;