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-- -- SpaceWire core with character-stream interface. -- -- This entity provides a SpaceWire core with a character-stream interface. -- The interface provides means for connection initiation, sending and -- receiving of N-Chars and TimeCodes, and error reporting. -- -- This entity instantiates spwlink, spwrecv, spwxmit and one of the -- spwrecvfront implementations. It also implements a receive FIFO and -- a transmit FIFO. -- -- The SpaceWire standard requires that each transceiver use an initial -- signalling rate of 10 Mbit/s. This implies that the system clock frequency -- must be a multiple of 10 MHz. See the manual for further details on -- bitrates and clocking. -- library ieee; use ieee.std_logic_1164.all; use ieee.numeric_std.all; use work.spwpkg.all; entity spwstream is generic ( -- System clock frequency in Hz. -- This must be set to the frequency of "clk". It is used to setup -- counters for reset timing, disconnect timeout and to transmit -- at 10 Mbit/s during the link handshake. sysfreq: real; -- Transmit clock frequency in Hz (only if tximpl = impl_fast). -- This must be set to the frequency of "txclk". It is used to -- transmit at 10 Mbit/s during the link handshake. txclkfreq: real := 0.0; -- Selection of a receiver front-end implementation. rximpl: spw_implementation_type := impl_generic; -- Maximum number of bits received per system clock -- (must be 1 in case of impl_generic). rxchunk: integer range 1 to 4 := 1; -- Selection of a transmitter implementation. tximpl: spw_implementation_type := impl_generic; -- Size of the receive FIFO as the 2-logarithm of the number of bytes. -- Must be at least 6 (64 bytes). rxfifosize_bits: integer range 6 to 14 := 11; -- Size of the transmit FIFO as the 2-logarithm of the number of bytes. txfifosize_bits: integer range 2 to 14 := 11 ); port ( -- System clock. clk: in std_logic; -- Receiver sample clock (only for impl_fast) rxclk: in std_logic; -- Transmit clock (only for impl_fast) txclk: in std_logic; -- Synchronous reset (active-high). rst: in std_logic; -- Enables automatic link start on receipt of a NULL character. autostart: in std_logic; -- Enables link start once the Ready state is reached. -- Without autostart or linkstart, the link remains in state Ready. linkstart: in std_logic; -- Do not start link (overrides linkstart and autostart) and/or -- disconnect a running link. linkdis: in std_logic; -- Scaling factor minus 1, used to scale the transmit base clock into -- the transmission bit rate. The system clock (for impl_generic) or -- the txclk (for impl_fast) is divided by (unsigned(txdivcnt) + 1). -- Changing this signal will immediately change the transmission rate. -- During link setup, the transmission rate is always 10 Mbit/s. txdivcnt: in std_logic_vector(7 downto 0); -- High for one clock cycle to request transmission of a TimeCode. -- The request is registered inside the entity until it can be processed. tick_in: in std_logic; -- Control bits of the TimeCode to be sent. Must be valid while tick_in is high. ctrl_in: in std_logic_vector(1 downto 0); -- Counter value of the TimeCode to be sent. Must be valid while tick_in is high. time_in: in std_logic_vector(5 downto 0); -- Pulled high by the application to write an N-Char to the transmit -- queue. If "txwrite" and "txrdy" are both high on the rising edge -- of "clk", a character is added to the transmit queue. -- This signal has no effect if "txrdy" is low. txwrite: in std_logic; -- Control flag to be sent with the next N_Char. -- Must be valid while txwrite is high. txflag: in std_logic; -- Byte to be sent, or "00000000" for EOP or "00000001" for EEP. -- Must be valid while txwrite is high. txdata: in std_logic_vector(7 downto 0); -- High if the entity is ready to accept an N-Char for transmission. txrdy: out std_logic; -- High if the transmission queue is at least half full. txhalff: out std_logic; -- High for one clock cycle if a TimeCode was just received. tick_out: out std_logic; -- Control bits of the last received TimeCode. ctrl_out: out std_logic_vector(1 downto 0); -- Counter value of the last received TimeCode. time_out: out std_logic_vector(5 downto 0); -- High if "rxflag" and "rxdata" contain valid data. -- This signal is high unless the receive FIFO is empty. rxvalid: out std_logic; -- High if the receive FIFO is at least half full. rxhalff: out std_logic; -- High if the received character is EOP or EEP; low if the received -- character is a data byte. Valid if "rxvalid" is high. rxflag: out std_logic; -- Received byte, or "00000000" for EOP or "00000001" for EEP. -- Valid if "rxvalid" is high. rxdata: out std_logic_vector(7 downto 0); -- Pulled high by the application to accept a received character. -- If "rxvalid" and "rxread" are both high on the rising edge of "clk", -- a character is removed from the receive FIFO and "rxvalid", "rxflag" -- and "rxdata" are updated. -- This signal has no effect if "rxvalid" is low. rxread: in std_logic; -- High if the link state machine is currently in the Started state. started: out std_logic; -- High if the link state machine is currently in the Connecting state. connecting: out std_logic; -- High if the link state machine is currently in the Run state, indicating -- that the link is fully operational. If none of started, connecting or running -- is high, the link is in an initial state and the transmitter is not yet enabled. running: out std_logic; -- Disconnect detected in state Run. Triggers a reset and reconnect of the link. -- This indication is auto-clearing. errdisc: out std_logic; -- Parity error detected in state Run. Triggers a reset and reconnect of the link. -- This indication is auto-clearing. errpar: out std_logic; -- Invalid escape sequence detected in state Run. Triggers a reset and reconnect of -- the link. This indication is auto-clearing. erresc: out std_logic; -- Credit error detected. Triggers a reset and reconnect of the link. -- This indication is auto-clearing. errcred: out std_logic; -- Data In signal from SpaceWire bus. spw_di: in std_logic; -- Strobe In signal from SpaceWire bus. spw_si: in std_logic; -- Data Out signal to SpaceWire bus. spw_do: out std_logic; -- Strobe Out signal to SpaceWire bus. spw_so: out std_logic ); end entity spwstream; architecture spwstream_arch of spwstream is -- Convert boolean to std_logic. type bool_to_logic_type is array(boolean) of std_ulogic; constant bool_to_logic: bool_to_logic_type := (false => '0', true => '1'); -- Reset time (6.4 us) in system clocks constant reset_time: integer := integer(sysfreq * 6.4e-6); -- Disconnect time (850 ns) in system clocks constant disconnect_time: integer := integer(sysfreq * 850.0e-9); -- Initial tx clock scaler (10 Mbit). type impl_to_real_type is array(spw_implementation_type) of real; constant tximpl_to_txclk_freq: impl_to_real_type := (impl_generic => sysfreq, impl_fast => txclkfreq); constant effective_txclk_freq: real := tximpl_to_txclk_freq(tximpl); constant default_divcnt: std_logic_vector(7 downto 0) := std_logic_vector(to_unsigned(integer(effective_txclk_freq / 10.0e6 - 1.0), 8)); -- Registers. type regs_type is record -- packet state rxpacket: std_logic; -- '1' when receiving a packet rxeep: std_logic; -- '1' when rx EEP character pending txpacket: std_logic; -- '1' when transmitting a packet txdiscard: std_logic; -- '1' when discarding a tx packet -- FIFO pointers rxfifo_raddr: std_logic_vector(rxfifosize_bits-1 downto 0); rxfifo_waddr: std_logic_vector(rxfifosize_bits-1 downto 0); txfifo_raddr: std_logic_vector(txfifosize_bits-1 downto 0); txfifo_waddr: std_logic_vector(txfifosize_bits-1 downto 0); -- FIFO state rxfifo_rvalid: std_logic; -- '1' if s_rxfifo_rdata is valid txfifo_rvalid: std_logic; -- '1' if s_txfifo_rdata is valid rxfull: std_logic; -- '1' if RX fifo is full rxhalff: std_logic; -- '1' if RX fifo is at least half full txfull: std_logic; -- '1' if TX fifo is full txhalff: std_logic; -- '1' if TX fifo is at least half full rxroom: std_logic_vector(5 downto 0); end record; constant regs_reset: regs_type := ( rxpacket => '0', rxeep => '0', txpacket => '0', txdiscard => '0', rxfifo_raddr => (others => '0'), rxfifo_waddr => (others => '0'), txfifo_raddr => (others => '0'), txfifo_waddr => (others => '0'), rxfifo_rvalid => '0', txfifo_rvalid => '0', rxfull => '0', rxhalff => '0', txfull => '0', txhalff => '0', rxroom => (others => '0') ); signal r: regs_type := regs_reset; signal rin: regs_type; -- Interface signals to components. signal recv_rxen: std_logic; signal recvo: spw_recv_out_type; signal recv_inact: std_logic; signal recv_inbvalid: std_logic; signal recv_inbits: std_logic_vector(rxchunk-1 downto 0); signal xmiti: spw_xmit_in_type; signal xmito: spw_xmit_out_type; signal xmit_divcnt: std_logic_vector(7 downto 0); signal linki: spw_link_in_type; signal linko: spw_link_out_type; -- Memory interface signals. signal s_rxfifo_raddr: std_logic_vector(rxfifosize_bits-1 downto 0); signal s_rxfifo_rdata: std_logic_vector(8 downto 0); signal s_rxfifo_wen: std_logic; signal s_rxfifo_waddr: std_logic_vector(rxfifosize_bits-1 downto 0); signal s_rxfifo_wdata: std_logic_vector(8 downto 0); signal s_txfifo_raddr: std_logic_vector(txfifosize_bits-1 downto 0); signal s_txfifo_rdata: std_logic_vector(8 downto 0); signal s_txfifo_wen: std_logic; signal s_txfifo_waddr: std_logic_vector(txfifosize_bits-1 downto 0); signal s_txfifo_wdata: std_logic_vector(8 downto 0); begin -- Instantiate link controller. link_inst: spwlink generic map ( reset_time => reset_time ) port map ( clk => clk, rst => rst, linki => linki, linko => linko, rxen => recv_rxen, recvo => recvo, xmiti => xmiti, xmito => xmito ); -- Instantiate receiver. recv_inst: spwrecv generic map( disconnect_time => disconnect_time, rxchunk => rxchunk ) port map ( clk => clk, rxen => recv_rxen, recvo => recvo, inact => recv_inact, inbvalid => recv_inbvalid, inbits => recv_inbits ); -- Instantiate transmitter. xmit_sel0: if tximpl = impl_generic generate xmit_inst: spwxmit port map ( clk => clk, rst => rst, divcnt => xmit_divcnt, xmiti => xmiti, xmito => xmito, spw_do => spw_do, spw_so => spw_so ); end generate; xmit_sel1: if tximpl = impl_fast generate xmit_fast_inst: spwxmit_fast port map ( clk => clk, txclk => txclk, rst => rst, divcnt => xmit_divcnt, xmiti => xmiti, xmito => xmito, spw_do => spw_do, spw_so => spw_so ); end generate; -- Instantiate receiver front-end. recvfront_sel0: if rximpl = impl_generic generate recvfront_generic_inst: spwrecvfront_generic port map ( clk => clk, rxen => recv_rxen, inact => recv_inact, inbvalid => recv_inbvalid, inbits => recv_inbits, spw_di => spw_di, spw_si => spw_si ); end generate; recvfront_sel1: if rximpl = impl_fast generate recvfront_fast_inst: spwrecvfront_fast generic map ( rxchunk => rxchunk ) port map ( clk => clk, rxclk => rxclk, rxen => recv_rxen, inact => recv_inact, inbvalid => recv_inbvalid, inbits => recv_inbits, spw_di => spw_di, spw_si => spw_si ); end generate; -- Instantiate RX memory. rxmem: spwram generic map ( abits => rxfifosize_bits, dbits => 9 ) port map ( rclk => clk, wclk => clk, ren => '1', raddr => s_rxfifo_raddr, rdata => s_rxfifo_rdata, wen => s_rxfifo_wen, waddr => s_rxfifo_waddr, wdata => s_rxfifo_wdata ); -- Instantiate TX memory. txmem: spwram generic map ( abits => txfifosize_bits, dbits => 9 ) port map ( rclk => clk, wclk => clk, ren => '1', raddr => s_txfifo_raddr, rdata => s_txfifo_rdata, wen => s_txfifo_wen, waddr => s_txfifo_waddr, wdata => s_txfifo_wdata ); -- Combinatorial process process (r, linko, s_rxfifo_rdata, s_txfifo_rdata, rst, autostart, linkstart, linkdis, txdivcnt, tick_in, ctrl_in, time_in, txwrite, txflag, txdata, rxread) is variable v: regs_type; variable v_tmprxroom: unsigned(rxfifosize_bits-1 downto 0); variable v_tmptxroom: unsigned(txfifosize_bits-1 downto 0); begin v := r; v_tmprxroom := to_unsigned(0, v_tmprxroom'length); v_tmptxroom := to_unsigned(0, v_tmptxroom'length); -- Keep track of whether we are sending and/or receiving a packet. if linko.rxchar = '1' then -- got character v.rxpacket := not linko.rxflag; end if; if linko.txack = '1' then -- send character v.txpacket := not s_txfifo_rdata(8); end if; -- Update RX fifo pointers. if (rxread = '1') and (r.rxfifo_rvalid = '1') then -- read from fifo v.rxfifo_raddr := std_logic_vector(unsigned(r.rxfifo_raddr) + 1); end if; if r.rxfull = '0' then if (linko.rxchar = '1') or (r.rxeep = '1') then -- write to fifo (received char or pending EEP) v.rxfifo_waddr := std_logic_vector(unsigned(r.rxfifo_waddr) + 1); end if; v.rxeep := '0'; end if; -- Keep track of whether the RX fifo contains valid data. -- (use new value of rxfifo_raddr) v.rxfifo_rvalid := bool_to_logic(v.rxfifo_raddr /= r.rxfifo_waddr); -- Update room in RX fifo (use new value of rxfifo_waddr). v_tmprxroom := unsigned(r.rxfifo_raddr) - unsigned(v.rxfifo_waddr) - 1; v.rxfull := bool_to_logic(v_tmprxroom = 0); v.rxhalff := not v_tmprxroom(v_tmprxroom'high); if v_tmprxroom > 63 then v.rxroom := (others => '1'); else v.rxroom := std_logic_vector(v_tmprxroom(5 downto 0)); end if; -- Update TX fifo pointers. if (r.txfifo_rvalid = '1') and ((linko.txack = '1') or (r.txdiscard = '1')) then -- read from fifo v.txfifo_raddr := std_logic_vector(unsigned(r.txfifo_raddr) + 1); if s_txfifo_rdata(8) = '1' then v.txdiscard := '0'; -- got EOP/EEP, stop discarding data end if; end if; if (r.txfull = '0') and (txwrite = '1') then -- write to fifo v.txfifo_waddr := std_logic_vector(unsigned(r.txfifo_waddr) + 1); end if; -- Keep track of whether the TX fifo contains valid data. -- (use new value of txfifo_raddr) v.txfifo_rvalid := bool_to_logic(v.txfifo_raddr /= r.txfifo_waddr); -- Update room in TX fifo (use new value of txfifo_waddr). v_tmptxroom := unsigned(r.txfifo_raddr) - unsigned(v.txfifo_waddr) - 1; v.txfull := bool_to_logic(v_tmptxroom = 0); v.txhalff := not v_tmptxroom(v_tmptxroom'high); -- If the link is lost, set a flag to discard the current packet. if linko.running = '0' then v.rxeep := v.rxeep or v.rxpacket; -- use new value of rxpacket v.txdiscard := v.txdiscard or v.txpacket; -- use new value of txpacket v.rxpacket := '0'; v.txpacket := '0'; end if; -- Clear the discard flag when the link is explicitly disabled. if linkdis = '1' then v.txdiscard := '0'; end if; -- Drive control signals to RX fifo. s_rxfifo_raddr <= v.rxfifo_raddr; -- using new value of rxfifo_raddr s_rxfifo_wen <= (not r.rxfull) and (linko.rxchar or r.rxeep); s_rxfifo_waddr <= r.rxfifo_waddr; if r.rxeep = '1' then s_rxfifo_wdata <= "100000001"; else s_rxfifo_wdata <= linko.rxflag & linko.rxdata; end if; -- Drive control signals to TX fifo. s_txfifo_raddr <= v.txfifo_raddr; -- using new value of txfifo_raddr s_txfifo_wen <= (not r.txfull) and txwrite; s_txfifo_waddr <= r.txfifo_waddr; s_txfifo_wdata <= txflag & txdata; -- Drive inputs to spwlink. linki.autostart <= autostart; linki.linkstart <= linkstart; linki.linkdis <= linkdis; linki.rxroom <= r.rxroom; linki.tick_in <= tick_in; linki.ctrl_in <= ctrl_in; linki.time_in <= time_in; linki.txwrite <= r.txfifo_rvalid and not r.txdiscard; linki.txflag <= s_txfifo_rdata(8); linki.txdata <= s_txfifo_rdata(7 downto 0); -- Drive divcnt input to spwxmit. if linko.running = '1' then xmit_divcnt <= txdivcnt; else xmit_divcnt <= default_divcnt; end if; -- Drive outputs. txrdy <= not r.txfull; txhalff <= r.txhalff; tick_out <= linko.tick_out; ctrl_out <= linko.ctrl_out; time_out <= linko.time_out; rxvalid <= r.rxfifo_rvalid; rxhalff <= r.rxhalff; rxflag <= s_rxfifo_rdata(8); rxdata <= s_rxfifo_rdata(7 downto 0); started <= linko.started; connecting <= linko.connecting; running <= linko.running; errdisc <= linko.errdisc; errpar <= linko.errpar; erresc <= linko.erresc; errcred <= linko.errcred; -- Reset. if rst = '1' then v.rxpacket := '0'; v.rxeep := '0'; v.txpacket := '0'; v.txdiscard := '0'; v.rxfifo_raddr := (others => '0'); v.rxfifo_waddr := (others => '0'); v.txfifo_raddr := (others => '0'); v.txfifo_waddr := (others => '0'); v.rxfifo_rvalid := '0'; v.txfifo_rvalid := '0'; end if; -- Update registers. rin <= v; end process; -- Update registers. process (clk) is begin if rising_edge(clk) then r <= rin; end if; end process; end architecture spwstream_arch;