library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
  
entity RAM9X8_SerialBusMaster is	
	generic(		
		SB_DATA_LOWER : integer := 0;
		SB_DATA_UPPER : integer := 1;		
		SB_CMD_LOWER : integer := 2;
		SB_CMD_UPPER : integer := 3;		
		SB_CONTROL_LOWER : integer := 4;
		SB_CONTROL_UPPER : integer := 5;
		
		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;	
	
		sbclk : out std_logic := '0';
      sbdataout : out std_logic := '0';
      sbdatain : in std_logic
	);
end entity;

architecture behavorial of RAM9X8_SerialBusMaster is

signal dataBufIn : std_logic_vector(15 downto 0) := (others => '0');
signal dataBufOut : std_logic_vector(15 downto 0) := (others => '0');
signal cmdBuf : std_logic_vector(15 downto 0) := (others => '0');
signal controlBuf : std_logic_vector(15 downto 0) := (others => '0');

signal direction : std_logic := '0';
signal addressToTransmit : std_logic_vector(7 downto 0) := x"00";
signal dataToTransmit : std_logic_vector(15 downto 0) := x"0000";
signal dataFromDevices : std_logic_vector(15 downto 0) := x"0000";
    
type   CommunicationState_start  is (Waiting, TransmitAddress, TransmitData, TransmitCRC, TransmitCheck, ReceiveData, ReceiveCRC, ReceiveCheck, Timeout);  
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(31 downto 0) := x"00000000";                                                -- 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 = SB_DATA_UPPER or addr = SB_DATA_LOWER or addr = SB_CMD_UPPER or addr = SB_CMD_LOWER
				or addr = SB_CONTROL_UPPER or addr = SB_CONTROL_LOWER) then
				if (oe = '0' and we = '1') then  -- Если сигнал чтения активен, а записи нет	
					case addr is
						when SB_DATA_UPPER =>
							data <= dataBufOut(15 downto 8);
						when SB_DATA_LOWER =>
							data <= dataBufOut(7 downto 0);
						when SB_CMD_UPPER =>
							data <= cmdBuf(15 downto 8);
						when SB_CMD_LOWER =>
							data <= cmdBuf(7 downto 0);
						when SB_CONTROL_UPPER =>
							data <= controlBuf(15 downto 8);
							start <= '0';
						when SB_CONTROL_LOWER =>
							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 SB_DATA_UPPER =>
							dataBufIn(15 downto 8) <= data;
						when SB_DATA_LOWER =>
							dataBufIn(7 downto 0) <= data;
						when SB_CMD_UPPER =>
							cmdBuf(15 downto 8) <= data;							
							start <= '1';
						when SB_CMD_LOWER =>
							cmdBuf(7 downto 0) <= data;							
						when others =>
							data <= (others => 'Z');  -- Запретить запись на шину
					end case;
				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 halfPeriod : integer range 0 to 255 := 50;
		variable pause : integer range 0 to 255 := 200;
		variable state : integer range 0 to 1 := 1;
		variable bitCnt : integer range -1 to 31 := 0;
		variable latch : integer range 0 to 1 := 0;
	begin
		if(rising_edge (clk)) then
			case CommunicationState is
				when Waiting =>
					sbclk <= '0';
					bitCnt := 8;
					latch := 0;
					resetCRC <= '1';
					sbdataout <= '0';									
					state := 1;
					if start = '1' and  startPrev = '0' then                               
						direction <= cmdBuf(15);
                  dataCRC(24) <= cmdBuf(15);
                  addressToTransmit(7 downto 0) <= cmdBuf(7 downto 0);
                  dataCRC(23 downto 16) <= cmdBuf(7 downto 0);
                  dataToTransmit <= dataBufIn;
                  dataCRC(15 downto 0) <= dataBufIn;              
                  controlBuf(15 downto 2) <= (others => '0');
						controlBuf(1) <= '1';
						controlBuf(0) <= '0';
						if count < pause then
							CommunicationState <= Timeout;
							count := count + 1;
						else 	
							CommunicationState <= TransmitAddress;
							count:= 0;
						end if;	
					else 
						if count < pause then
							count := count + 1;
							controlBuf(1) <= '1';
						else 
							controlBuf(1) <= '0';	
						end if;	
               end if;
				when Timeout =>
					if count < pause then
						count := count + 1;
					else 	
						CommunicationState <= TransmitAddress;
						count:= 0;
					end if;
				when TransmitAddress =>	 
					if bitCnt = -1 then
						if direction = '1' then
							CommunicationState <= TransmitData;
							resetCRC <= '0';
						else
							CommunicationState <= ReceiveData;
						end if;
						bitCnt := 15;                      
					else 
						if count < halfPeriod and state = 1 then
							if count = 0 then
								if latch = 0 then 
									sbdataout <= direction;
								else 
									sbdataout <= addressToTransmit(bitCnt);
								end if;                           
								sbclk <= '0';
							end if;	
                     count := count + 1;
                  elsif count = halfPeriod and state = 1 then
							latch := 1;	                   
							count := 0;
							state := 0;	                   
						elsif count < halfPeriod and state = 0 then 
							if count = 0 then
								sbclk <= '1'; 
							end if;	
							count := count + 1;   
						elsif count = halfPeriod and state = 0 then  
							count := 0;
							state := 1;
							bitCnt := bitCnt - 1;
						end if; 
					end if;      
			   when TransmitData =>	
					if bitCnt = -1 then
						CommunicationState <= TransmitCRC;	                             
	               bitCnt := 3;
	            else 
						if count < halfPeriod and state = 1 then
							if count = 0 then
								sbdataout <= dataToTransmit(bitCnt);
								sbclk <= '0';
							end if;	
							count := count + 1;
						elsif count = halfPeriod and state = 1 then	                   
							count := 0;
							state := 0;	                   
						elsif count < halfPeriod and state = 0 then 
							if count = 0 then
								sbclk <= '1'; 
							end if;	
							count := count + 1;   
						elsif count = halfPeriod and state = 0 then  
							count := 0;
							state := 1;
							bitCnt := bitCnt - 1;
						end if; 
					end if;
				when TransmitCRC =>	
					if readyCRC = '1' then
						if bitCnt = -1 then
							CommunicationState <= TransmitCheck;
						else 
							if count < halfPeriod and state = 1 then
								if count = 0 then 
									sbdataout <= CRC(bitCnt);
									sbclk <= '0';
								end if;	
								count := count + 1;
							elsif count = halfPeriod and state = 1 then	                   
								count := 0;
								state := 0;	                   
							elsif count < halfPeriod and state = 0 then 
								if count = 0 then 
									sbclk <= '1'; 
								end if;	
								count := count + 1;   
							elsif count = halfPeriod and state = 0 then  
								count := 0;
								state := 1;
								bitCnt := bitCnt - 1;
							end if; 
						end if;    		
					else
						count := 0;	
						CommunicationState <= Waiting;
						controlBuf(15) <= '1';
					end if; 
			   when TransmitCheck =>
					if count < halfPeriod and state = 1 then
						if count = 0 then
							sbclk <= '0';
						end if;	
						count := count + 1;
					else	                   
						count := 0;
						state := 0;
						if sbdatain = '0' then                           
							controlBuf(0) <= '1';
						else
							controlBuf(14) <= '1';
						end if;
						CommunicationState <= Waiting;
					end if;    
			   when ReceiveData =>
					if bitCnt = -1 then
						CommunicationState <= ReceiveCRC;	                             
						bitCnt := 3;
					else 
						if count < halfPeriod and state = 1 then
							if count = 0 then
								sbclk <= '0';
							end if;	
							count := count + 1;
						elsif count = halfPeriod and state = 1 then
							dataFromDevices(bitCnt) <= sbdatain;	                   
							count := 0;
                     state := 0;	                   
                  elsif count < halfPeriod and state = 0 then 
							if count = 0 then
								sbclk <= '1'; 
							end if;	
							count := count + 1;   
						elsif count = halfPeriod and state = 0 then  
							count := 0;
							state := 1;
							bitCnt := bitCnt - 1;
						end if;
					end if;
				when ReceiveCRC =>
					if bitCnt = -1 then
						CommunicationState <= ReceiveCheck;
					else 
						if count < halfPeriod and state = 1 then
							if count = 0 then
								sbclk <= '0';	
							end if;	
							count := count + 1;
						elsif count = halfPeriod and state = 1 then
							bufCRC(BitCnt) <= sbdatain;	                   
							count := 0;
							state := 0;
							if bitCnt = 0 then
								dataCRC(24) <= direction;
								dataCRC(23 downto 16) <= addressToTransmit;
								dataCRC(15 downto 0) <= dataFromDevices(15 downto 0);
								resetCRC <= '0';
							end if;	                   
						elsif count < halfPeriod and state = 0 then 
							if count = 0 then 
								sbclk <= '1'; 
							end if;	
							count := count + 1;                                   
                  elsif count = halfPeriod and state = 0 then  
                     count := 0;
                     state := 1;
                     bitCnt := bitCnt - 1;
                  end if;
               end if;
				when ReceiveCheck =>
					if readyCRC = '1' then
						if bufCRC = CRC then
							dataBufOut <= dataFromDevices;
							controlBuf(0) <= '1';
						else
							controlBuf(13) <= '1';   
                  end if; 
					else 
						controlBuf(12) <= '1';    
					end if;
					count := 0;
					CommunicationState <= Waiting;     
				when others =>
					count := 0;
					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 24 := 0;
	begin
		if rising_edge(clk) then
			if resetCRC = '1' then
				bitCnt := 24; 
				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';
							--countreadyCRC <= countreadyCRC + 1;
						end if;
					end if;
				end if;
			end if;
		end if;
	end process;
	
end behavorial;