internetsnd.vhd

设计ip协议的vhdl实现

				else
					-- latch all information about the datagram and set up first fragment
					nextState <= stSetHeader;
					rstCnt <= '1';
					newHeader <= '1';
					rstFragmentOffset <= '1';
					latchDatagramSize <= '1';
					latchIden <= '1';
					latchAddressOffset <= '1';
					latchDestinationIP <= '1';
					latchProtocol <= '1';
				end if;
			
			when stSetHeader =>
				-- write header into RAM				
				if cnt = x"14" then
					-- header has been fully written so go to data stage
					nextState <= stWrChksumHi;
					nextWrData <= checksum (15 downto 8);
				else
					nextState <= stWrHeader;
					newByte <= '1';			-- send byte to checksum calculator
					-- choose wrData and inByte values
					-- inByte is the data for the checksum signals
					case cnt(4 downto 0) is
						-- version and header length
						when '0' & x"0" =>
							nextWrData <= x"45";
							inByte <= x"45";
						-- total length high byte
						when '0' & x"2" =>
							nextWrData <= datagramLen (15 downto 8);
							inByte <= datagramLen (15 downto 8);
						-- total length low byte
						when '0' & x"3" =>
							nextWrData <= datagramLen (7 downto 0);
							inByte <= datagramLen (7 downto 0);			
						-- identification high byte
						when '0' & x"4" =>
							nextWrData <= idenLatch(15 downto 8);
							inByte <= idenLatch(15 downto 8);
						-- identification low byte
						when '0' & x"5" =>
							nextWrData <= idenLatch (7 downto 0);
							inByte <= idenLatch (7 downto 0);
						-- flags and fragmentOffset high bits
						when '0' & x"6" =>
							nextWrData <= "00" & moreFragments & fragmentOffset(5 downto 1);
							inByte <= "00" & moreFragments & fragmentOffset(5 downto 1);
						-- fragmentOffset low byte
						when '0' & x"7" =>
							nextWrData <= fragmentOffset(0) & "0000000";
							inByte <= fragmentOffset(0) & "0000000";
						-- time to live
						when '0' & x"8" =>
							nextWrData <= x"20";
							inByte <= x"20";
						-- protocol
						when '0' & x"9" =>
							nextWrData <= protocolLatch;
							inByte <= protocolLatch;					
						-- source IP for C, D, E, F
						when '0' & x"C" =>
							nextWrData <= DEVICE_IP(31 downto 24);
							inByte <= DEVICE_IP(31 downto 24);					
						when '0' & x"D" =>
							nextWrData <= DEVICE_IP(23 downto 16);
							inByte <= DEVICE_IP(23 downto 16);						
						when '0' & x"E" =>
							nextWrData <= DEVICE_IP(15 downto 8);
							inByte <= DEVICE_IP(15 downto 8);
						when '0' & x"F" =>
							nextWrData <= DEVICE_IP(7 downto 0);
							inByte <= DEVICE_IP(7 downto 0);				
						-- destination IP for 10, 11, 12, 13
						when '1' & x"0" =>
							nextWrData <= destinationIPLatch(31 downto 24);
							inByte <= destinationIPLatch(31 downto 24);
						when '1' & x"1" =>
							nextWrData <= destinationIPLatch(23 downto 16);
							inByte <= destinationIPLatch(23 downto 16);
						when '1' & x"2" =>
							nextWrData <= destinationIPLatch(15 downto 8);
							inByte <= destinationIPLatch(15 downto 8);					
						when '1' & x"3" =>
							nextWrData <= destinationIPLatch(7 downto 0);
							inByte <= destinationIPLatch(7 downto 0);						
						-- Service type and checksum which will be updated later
						when others =>
							nextWrData <= (others => '0');
							inByte <= (others => '0');
					end case;
				end if;
			
			when stWrHeader =>
				-- Write a byte to RAM
				if complete = '0' then
					-- Wait for RAM to acknowledge the write
					nextState <= stWrHeader;
					wrRAM <= '1';
					wrAddr <= "00000001" & Cnt;
				else
					-- When it does increment the counter and go to next header byte
					nextState <= stSetHeader;
					incCnt <= '1';
				end if;
			
			when stWrChksumHi =>
				-- Write high byte of the checksum to RAM
				if complete = '0' then
					-- Wait for RAM to acknowledge the write
					nextState <= stWrChksumHi;
					wrRAM <= '1';
					wrAddr <= "000" & x"080a";
				else
					-- When it does write the lower byte
					nextState <= stWrChksumLo;
					nextWrData <= checksum (7 downto 0);
				end if;
			
			when stWrChksumLo =>
				-- Write low byte of the checksum to RAM
				if complete = '0' then
					nextState <= stWrChksumLo;
					wrRAM <= '1';
					wrAddr <= "000" & x"080B";
				else
					-- When it does copy data from RAM to write location
					nextState <= stGetData;
				end if;

			when stGetData =>
				-- Read data from RAM if there is more left
				if cnt = datagramLen then
					-- If there is no more data left, wait until the frame completes sending
					if frameSent = '1' then
						nextState <= stMoreFragments;
					else
						-- otherwise tell the frame to send until it does finish sending
						nextState <= stGetData;
						sendFrame <= '1';
						frameSize <= datagramLen (10 downto 0);
					end if;
				else
					-- if there is more data then perform a read from RAM
					if complete = '0' then
						-- Wait for RAM to acknowledge read
						nextState <= stGetData;
						rdRAM <= '1';
						rdAddr <= (addressOffsetLatch & (fragmentOffset + cnt(10)) & cnt(9 downto 0)) - 20;
					else
						-- Then get ready to write the data
						nextState <= stWrData;
						latchRdData <= '1';
					end if;
				end if;

			when stWrData =>
				-- Write one data byte
				if complete = '0' then
					-- Wait for RAM to acknoledge the write
					nextState <= stWrData;
					wrRAM <= '1';
					wrAddr <= "00000001" & cnt;
				else
					-- When done, read another byte
					nextState <= stGetData;
					incCnt <= '1';
				end if;
				
			when stMoreFragments =>
				-- When the frame has finished transmitting
				if moreFragments = '1' then
					-- There are more fragments so set up data for the next fragment and generate it
					nextState <= stSetHeader;
					rstCnt <= '1';
					newHeader <= '1';
					incFragmentOffset <= '1';
				else
					-- There are no more fragments so wait for a new datagram to arrive
					nextState <= stIdle;
				end if;
			when others =>
		end case;
	end process;

	
	-- checksum calculator : see internet.vhd for comments
	checksumInt <= checksumLong(15 downto 0) + checksumLong(16);
	checksum <= NOT checksumInt;

	process (clk,rstn)
	begin
		if rstn = '0' then
			checkState <= stMSB;
			latchMSB <= (others => '0');
			checkSumLong <= (others => '0');
			valid <= '0';
			lastNewByte <= '0';
		elsif clk'event and clk = '1' then
			lastNewByte <= newByte;		
			case checkState is
				when stMSB =>
					if newHeader = '1' then
						checkState <= stMSB;
						checkSumLong <= (others => '0');
						valid <= '0';
					elsif newByte = '1' and lastNewByte = '0' then
						checkState <= stLSB;
						latchMSB <= inByte;
						valid <= '0';
					else
						checkState <= stMSB;
						valid <= '1';
					end if;
				when stLSB =>
					valid <= '0';		
					if newHeader = '1' then
						checkState <= stMSB;
						checkSumLong <= (others => '0');
					elsif newByte = '1' and lastnewByte = '0' then
						checkState <= stMSB;
						checkSumLong <= ('0' & checkSumInt) + ('0' & latchMSB & inByte);
					else
						checkState <= stLSB;
					end if;
				when others =>
					checkState <= stMSB;
					valid <= '0';
			end case;
		end if;
	end process;

end InternetSnd_arch;