library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
  
entity RAM9X8_ParallelBusMaster is	
	generic(
		REG_ADDR_FIRST_FREE_UPPER_BYTE : integer := 6;
		REG_ADDR_FIRST_FREE_LOWER_BYTE : integer := 7;
		REG_ADDR_CMD_UPPER_BYTE : integer := 8;
		REG_ADDR_CMD_LOWER_BYTE : integer := 9;
		REG_ADDR_FILL_ADDRESS_SPACE_UPPER_BYTE : integer := 10;
		REG_ADDR_FILL_ADDRESS_SPACE_LOWER_BYTE : integer := 11;
		REG_ADDR_CONTROL_UPPER_BYTE : integer := 12;
		REG_ADDR_CONTROL_LOWER_BYTE : integer := 13;
		
		ARRAY_LENGTH : integer := 128;
		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;	
	
		pbclk : out std_logic := '1';
		pbce : out std_logic := '1';
		pbdir : out std_logic_vector(1 downto 0) := (others => '1');
      pbdata : inout std_logic_vector(15 downto 0) := (others => 'Z');
      pback : in std_logic
	);
end entity;

architecture behavorial of RAM9X8_ParallelBusMaster is

type mem is array (ARRAY_LENGTH - 1 downto 0) of std_logic_vector(7 downto 0);
signal memoryAddress : mem;
signal memoryData : mem; 

signal firstFreeBuf : std_logic_vector(15 downto 0) := (others => '0');
signal cmdBuf : std_logic_vector(15 downto 0) := (others => '0');
signal fasBuf : std_logic_vector(15 downto 0) := (others => '0');

signal controlBuf : std_logic_vector(7 downto 0) := (others => '0');
signal errorBuf : std_logic_vector(7 downto 0) := x"00";

signal addrTemp : std_logic_vector(7 downto 0) := x"00";
signal dataTemp : std_logic_vector(15 downto 0) := x"0000";
    
type CommunicationState_start is (Waiting, TransmiteAddress, TransmiteCheck, PreparingToReceiveData, ReceiveData, ReceiveCheck, Timeout, ReceiveCheckTimeout);  
signal CommunicationState : CommunicationState_start := Waiting ;

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;
		variable position : integer range 0 to ARRAY_LENGTH - 1 := 0;
	begin
		if (ce = '0') then  -- Если микросхема выбрана
			addr := conv_integer(address);
			if (addr = REG_ADDR_FIRST_FREE_UPPER_BYTE or addr = REG_ADDR_FIRST_FREE_LOWER_BYTE or addr = REG_ADDR_CMD_UPPER_BYTE or addr = REG_ADDR_CMD_LOWER_BYTE
				or addr = REG_ADDR_FILL_ADDRESS_SPACE_UPPER_BYTE or addr = REG_ADDR_FILL_ADDRESS_SPACE_LOWER_BYTE or addr = REG_ADDR_CONTROL_UPPER_BYTE or addr = REG_ADDR_CONTROL_LOWER_BYTE) then
				if (oe = '0' and we = '1') then  -- Если сигнал чтения активен, а записи нет	
					case addr is
						when REG_ADDR_FIRST_FREE_UPPER_BYTE =>
							data <= firstFreeBuf(15 downto 8);
						when REG_ADDR_FIRST_FREE_LOWER_BYTE =>
							data <= firstFreeBuf(7 downto 0);
						when REG_ADDR_CMD_UPPER_BYTE =>
							data <= cmdBuf(15 downto 8);
						when REG_ADDR_CMD_LOWER_BYTE =>
							data <= cmdBuf(7 downto 0);
						when REG_ADDR_FILL_ADDRESS_SPACE_UPPER_BYTE =>
							data <= fasBuf(15 downto 8);
						when REG_ADDR_FILL_ADDRESS_SPACE_LOWER_BYTE =>
							data <= fasBuf(7 downto 0);
						when REG_ADDR_CONTROL_UPPER_BYTE =>
							data <= errorBuf;
						when REG_ADDR_CONTROL_LOWER_BYTE =>
							data <= controlBuf(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 REG_ADDR_FIRST_FREE_UPPER_BYTE =>
							firstFreeBuf(15 downto 8) <= data;
						when REG_ADDR_FIRST_FREE_LOWER_BYTE =>
							firstFreeBuf(7 downto 0) <= data;
						when REG_ADDR_CMD_UPPER_BYTE =>
							cmdBuf(15 downto 8) <= data;
						when REG_ADDR_CMD_LOWER_BYTE =>
							cmdBuf(7 downto 0) <= data;
						when REG_ADDR_FILL_ADDRESS_SPACE_UPPER_BYTE =>
							fasBuf(15 downto 8) <= data;
						when REG_ADDR_FILL_ADDRESS_SPACE_LOWER_BYTE =>
							fasBuf(7 downto 0) <= data;
							position := conv_integer(data);
							memoryAddress(position) <= fasBuf(15 downto 8);
						when others =>
							data <= (others => 'Z');  -- Запретить запись на шину
					end case;
				else
					data <= (others => 'Z');  -- Запретить запись на шину
				end if;
			elsif (addr >= conv_integer(firstFreeBuf) and addr <= conv_integer(firstFreeBuf) + conv_integer(cmdBuf(7 downto 0))) then
				if (oe = '0') then  -- Если сигнал чтения активен	
					data <= memoryData(addr - conv_integer(firstFreeBuf));				
				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 255 := 0;
		variable countValue : integer range 0 to 255 := 63;
		variable errorCount : integer range 0 to 15 := 0;
		variable position : integer range 0 to ARRAY_LENGTH - 1 := 0;
	begin
		if(rising_edge (clk)) then
			if cmdBuf(15) = '1' then
				case CommunicationState is
					when Waiting =>
						if errorCount < conv_integer(cmdBuf(11 downto 8)) then
							addrTemp <= memoryAddress(position);	
							CommunicationState <= TransmiteAddress;							
						else
							errorBuf(7 downto 4) <= conv_std_logic_vector(errorCount, 4);
						end if;
						pbclk <= '1';
                  pbce <= '1';
                  pbdata <= (others =>'Z');
						pbdir <= b"11";
						countValue := 7;
						count := 0;	
					when TransmiteAddress =>	 
	               if count < countValue then
							if count = 0 then	
								pbdata(15 downto 8) <= addrTemp;
								pbdata(7 downto 0) <= not addrTemp;                          
							end if;
							count := count + 1;	
						else                      
							pbce <= '0';
	                  CommunicationState <= TransmiteCheck;
	                  count := 0;
							countValue := 15;
						end if;     
					when TransmiteCheck =>
						if pback = '0' then
							count := 0;
							countValue := 1;
							pbdata <= (others => 'Z');
							CommunicationState <= PreparingToReceiveData;
						else
							if count < countValue then
								count := count + 1;
							else         
								CommunicationState <= Waiting;
								errorBuf(0) <= '1';
							end if;	
						end if;						
					when PreparingToReceiveData =>	
						if count < countValue then
							count := count + 1;	
						else
							pbdir <= b"00";
	                  pbclk <= '0';
							count := 0;
							countValue := 15;
	                  CommunicationState <= ReceiveData;
						end if; 
					when ReceiveData =>
						if pback = '1' then
							pbclk <= '1';
							dataTemp <= pbdata;
							CommunicationState <= ReceiveCheck;
							count := 0;
							countValue := 15;
						else
							if count < countValue then							               
								count := count + 1;
							else         
								CommunicationState <= Waiting;	                             
								errorBuf(1) <= '1';
							end if;
						end if;						         
					when ReceiveCheck =>
						if pback = '0' then
							if pbdata = not dataTemp then 
								memoryData(position) <= dataTemp(15 downto 8);
								memoryData(position + 1) <= dataTemp(7 downto 0);
								controlBuf <= memoryAddress(position);
								CommunicationState <= Timeout;
								count := 0;
								pbce <= '1';
								countValue := 5;
								if position + 1 < conv_integer(cmdBuf(7 downto 0)) then
									position := position + 2;
								else
									position := 0;
								end if;	
							else
								CommunicationState <= Waiting;	                             
								errorBuf(2) <= '1';
							end if;	
						else
							if count < countValue then							               
								count := count + 1;
							else         
								CommunicationState <= Waiting;	                             
								errorBuf(3) <= '1';
							end if;
						end if; 
               when Timeout =>
						if count < countValue then							               
                     count := count + 1;
						else         
	                  CommunicationState <= Waiting;
						end if;                          
					when others => CommunicationState <= Waiting;
				end case;
			else
				pbclk <= '1';
				pbce <= '1';
				pbdata <= (others =>'Z');
				pbdir <= b"11";
				position := 0;
				errorCount := 0;
				errorBuf <= (others => '0');				
			end if;
		end if;
	end process;
	
end behavorial;