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rehnmaak |
--
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-- USB 2.0 Packet-level logic.
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--
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-- This entity hides the details of the UTMI interface and handles
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-- computation and verificaton of CRCs.
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--
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-- The low-level interface signals are named PHY_xxx and may be
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-- connected to an UTMI compliant USB PHY, such as the SMSC GT3200.
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--
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-- The application interface signals are named P_xxx.
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-- The receiving side of the interface operates as follows:
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-- * At the start of an incoming packet, RXACT is set high.
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-- * When a new byte arrives, RXRDY is asserted and the byte is put
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-- on RXDAT. These signals are valid for only one clock cycle; the
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-- application must accept them immediately.
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-- * The first byte of a packet is the PID. Subsequent bytes contain
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-- data and CRC. This entity verifies the CRC, but does not
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-- discard it from the data stream.
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-- * Some time after correctly receiving the last byte of a packet,
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-- RXACT is deasserted; at the same time RXFIN is asserted for one cycle
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-- to confirm the packet.
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-- * If a corrupt packet is received, RXACT is deasserted without
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-- asserting RXFIN.
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--
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-- The transmission side of the interface operates as follows:
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-- * The application starts transmission by setting TXACT to 1 and setting
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-- TXDAT to the PID value (with correctly mirrored high order bits).
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-- * The entity asserts TXRDY when it needs the next payload byte.
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-- On the following clock cycle, the application must then provide the
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-- next payload byte on TXDAT, or deassert TXACT to indicate the end of
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-- the packet. The signal on TXDAT must be held stable until the next
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-- assertion of TXRDY.
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-- * CRC bytes should not be included in the payload; the entity will
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-- add them automatically.
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-- * As part of the high speed handshake, the application may request
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-- transmission of a continuous chirp K state by asserting CHIRPK.
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--
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-- Implementation note:
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-- Transmission timing is a bit tricky due to the following issues:
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-- * After the PHY asserts PHY_TXREADY, we must immediately provide
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-- new data or deassert PHY_TXVALID on the next clock cycle.
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-- * The PHY may assert PHY_TXREADY during subsequent clock cycles,
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-- even though the average byte period is more than 40 cycles.
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-- * We want to register PHY inputs and outputs to ensure valid timing.
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--
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-- To satisfy these requirements, we make the application run one byte
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-- ahead. While keeping the current byte in the output register PHY_DATAOUT,
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-- the application already provides the following data byte. That way, we
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-- can respond to PHY_TXREADY immediately in the next cycle, with the
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-- application following up in the clock cycle after that.
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--
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library ieee;
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use ieee.std_logic_1164.all, ieee.numeric_std.all;
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entity usb_packet is
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port (
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-- 60 MHz UTMI clock.
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CLK : in std_logic;
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-- Synchronous reset of this entity.
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RESET : in std_logic;
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-- High to force chirp K transmission.
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P_CHIRPK : in std_logic;
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-- High while receiving a packet.
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P_RXACT : out std_logic;
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-- Indicates next byte received; data must be read from RXDAT immediately.
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P_RXRDY : out std_logic;
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-- High for one cycle to indicate successful completion of packet.
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P_RXFIN : out std_logic;
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-- Received byte value. Valid if RXRDY is high.
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P_RXDAT : out std_logic_vector(7 downto 0);
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-- High while transmitting a packet.
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P_TXACT : in std_logic;
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-- Request for next data byte; application must change TXDAT on the next clock cycle.
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P_TXRDY : out std_logic;
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-- Data byte to transmit. Hold stable until next assertion of TXRDY.
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P_TXDAT : in std_logic_vector(7 downto 0);
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-- Connect to UTMI DataIn signal.
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PHY_DATAIN : in std_logic_vector(7 downto 0);
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-- Connect to UTMI DataOut signal.
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PHY_DATAOUT : out std_logic_vector(7 downto 0);
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-- Connect to UTMI TxValid signal.
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PHY_TXVALID : out std_logic;
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-- Connect to UTMI TxReady signal.
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PHY_TXREADY : in std_logic;
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-- Connect to UTMI RxActive signal.
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PHY_RXACTIVE : in std_logic;
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-- Connect to UTMI RxValid signal.
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PHY_RXVALID : in std_logic;
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-- Connect to UTMI RxError signal.
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PHY_RXERROR : in std_logic );
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end entity usb_packet;
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architecture usb_packet_arch of usb_packet is
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-- State machine
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type t_state is (
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ST_NONE, ST_CHIRPK,
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ST_RWAIT, ST_RTOKEN, ST_RDATA, ST_RSHAKE,
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ST_TSTART, ST_TDATA, ST_TCRC1, ST_TCRC2 );
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signal s_state : t_state := ST_NONE;
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signal s_txfirst : std_logic := '0';
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-- Registered inputs
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signal s_rxactive : std_logic;
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signal s_rxvalid : std_logic;
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signal s_rxerror : std_logic;
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signal s_datain : std_logic_vector(7 downto 0);
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signal s_txready : std_logic;
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-- Byte pending for transmission
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signal s_dataout : std_logic_vector(7 downto 0);
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-- True if an incoming packet would be valid if it ended now.
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signal s_rxgoodpacket : std_logic;
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-- CRC computation
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constant crc5_gen : std_logic_vector(4 downto 0) := "00101";
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constant crc5_res : std_logic_vector(4 downto 0) := "01100";
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constant crc16_gen : std_logic_vector(15 downto 0) := "1000000000000101";
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constant crc16_res : std_logic_vector(15 downto 0) := "1000000000001101";
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signal crc5_buf : std_logic_vector(4 downto 0);
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signal crc16_buf : std_logic_vector(15 downto 0);
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-- Update CRC 5 to account for a new byte
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function crc5_upd(
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c : in std_logic_vector(4 downto 0);
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b : in std_logic_vector(7 downto 0) )
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return std_logic_vector
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is
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variable t : std_logic_vector(4 downto 0);
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variable y : std_logic_vector(4 downto 0);
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begin
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t := (
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b(0) xor c(4),
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b(1) xor c(3),
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b(2) xor c(2),
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b(3) xor c(1),
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b(4) xor c(0) );
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y := (
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b(5) xor t(1) xor t(2),
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b(6) xor t(0) xor t(1) xor t(4),
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b(5) xor b(7) xor t(0) xor t(3) xor t(4),
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b(6) xor t(1) xor t(3) xor t(4),
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b(7) xor t(0) xor t(2) xor t(3) );
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return y;
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end function;
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-- Update CRC-16 to account for new byte
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function crc16_upd(
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c : in std_logic_vector(15 downto 0);
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b : in std_logic_vector(7 downto 0) )
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return std_logic_vector
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is
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variable t : std_logic_vector(7 downto 0);
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variable y : std_logic_vector(15 downto 0);
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begin
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t := (
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b(0) xor c(15),
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b(1) xor c(14),
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b(2) xor c(13),
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b(3) xor c(12),
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b(4) xor c(11),
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b(5) xor c(10),
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b(6) xor c(9),
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b(7) xor c(8) );
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y := (
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c(7) xor t(0) xor t(1) xor t(2) xor t(3) xor t(4) xor t(5) xor t(6) xor t(7),
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c(6), c(5), c(4), c(3), c(2),
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c(1) xor t(7),
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c(0) xor t(6) xor t(7),
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t(5) xor t(6),
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t(4) xor t(5),
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t(3) xor t(4),
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t(2) xor t(3),
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t(1) xor t(2),
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t(0) xor t(1),
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t(1) xor t(2) xor t(3) xor t(4) xor t(5) xor t(6) xor t(7),
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t(0) xor t(1) xor t(2) xor t(3) xor t(4) xor t(5) xor t(6) xor t(7) );
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return y;
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end function;
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begin
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-- Assign output signals
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P_RXACT <= s_rxactive;
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P_RXFIN <= (not s_rxactive) and (not s_rxerror) and s_rxgoodpacket;
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P_RXRDY <= s_rxactive and s_rxvalid;
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P_RXDAT <= s_datain;
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-- Assert P_TXRDY during ST_TSTART to acknowledge the PID byte,
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-- during the first cycle of ST_TDATA to acknowledge the first
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-- data byte, and whenever we need a new data byte during ST_TDATA.
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P_TXRDY <= '1' when (s_state = ST_TSTART)
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else (s_txfirst or s_txready) when (s_state = ST_TDATA)
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else '0';
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-- On every rising clock edge
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process is
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variable v_dataout : std_logic_vector(7 downto 0);
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variable v_txvalid : std_logic;
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variable v_crc_upd : std_logic;
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variable v_crc_data : std_logic_vector(7 downto 0);
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variable v_crc5_new : std_logic_vector(4 downto 0);
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variable v_crc16_new : std_logic_vector(15 downto 0);
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begin
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wait until rising_edge(CLK);
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-- Default assignment to temporary variables
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v_dataout := s_dataout;
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v_txvalid := '0';
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v_crc_upd := '0';
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v_crc_data := "00000000";
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v_crc5_new := "00000";
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v_crc16_new := "0000000000000000";
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-- Default assignment to s_txfirst
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s_txfirst <= '0';
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-- Register inputs
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s_rxactive <= PHY_RXACTIVE;
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s_rxvalid <= PHY_RXVALID;
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s_rxerror <= PHY_RXERROR;
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s_datain <= PHY_DATAIN;
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s_txready <= PHY_TXREADY;
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-- State machine
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if RESET = '1' then
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-- Reset entity
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s_state <= ST_NONE;
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s_rxgoodpacket <= '0';
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else
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case s_state is
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when ST_NONE =>
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-- Waiting for incoming or outgoing packet
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-- Initialize CRC buffers
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crc5_buf <= "11111";
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crc16_buf <= "1111111111111111";
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s_rxgoodpacket <= '0';
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if P_CHIRPK = '1' then
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-- Send continuous chirp K.
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s_state <= ST_CHIRPK;
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elsif s_rxactive = '1' then
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-- Receiver starting
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if s_rxerror = '1' then
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-- Receive error at PHY level
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s_state <= ST_RWAIT;
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elsif s_rxvalid = '1' then
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-- Got PID byte
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if s_datain(3 downto 0) = not s_datain(7 downto 4) then
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case s_datain(1 downto 0) is
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when "01" => -- token packet
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s_state <= ST_RTOKEN;
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when "11" => -- data packet
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s_state <= ST_RDATA;
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when "10" => -- handshake packet
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s_state <= ST_RSHAKE;
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s_rxgoodpacket <= '1';
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when others => -- PING token or special packet
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-- If this is a PING token, it will work out fine;
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-- otherwise it will be flagged as a bad packet
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-- either here or in usb_transact.
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s_state <= ST_RTOKEN;
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end case;
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else
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-- Corrupt PID byte
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s_state <= ST_RWAIT;
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end if;
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end if;
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elsif P_TXACT = '1' then
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-- Transmission starting; put data in output buffer
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v_txvalid := '1';
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v_dataout := P_TXDAT;
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s_state <= ST_TSTART;
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end if;
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when ST_CHIRPK =>
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-- Sending continuous chirp K.
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if P_CHIRPK = '0' then
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s_state <= ST_NONE;
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end if;
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when ST_RTOKEN =>
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-- Receiving a token packet
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if s_rxactive = '0' then
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-- End of packet
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s_rxgoodpacket <= '0';
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s_state <= ST_NONE;
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elsif s_rxerror = '1' then
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-- Error at PHY level
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s_rxgoodpacket <= '0';
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s_state <= ST_RWAIT;
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elsif s_rxvalid = '1' then
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-- Just received a byte; update CRC
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v_crc5_new := crc5_upd(crc5_buf, s_datain);
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crc5_buf <= v_crc5_new;
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if v_crc5_new = crc5_res then
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s_rxgoodpacket <= '1';
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else
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s_rxgoodpacket <= '0';
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end if;
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end if;
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when ST_RDATA =>
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-- Receiving a data packet
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if s_rxactive = '0' then
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-- End of packet
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s_rxgoodpacket <= '0';
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s_state <= ST_NONE;
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elsif s_rxerror = '1' then
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-- Error at PHY level
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s_rxgoodpacket <= '0';
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s_state <= ST_RWAIT;
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elsif s_rxvalid = '1' then
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342 |
|
|
-- Just received a byte; update CRC
|
343 |
|
|
v_crc_upd := '1';
|
344 |
|
|
v_crc_data := s_datain;
|
345 |
|
|
end if;
|
346 |
|
|
|
347 |
|
|
when ST_RWAIT =>
|
348 |
|
|
-- Wait until the end of the current packet
|
349 |
|
|
if s_rxactive = '0' then
|
350 |
|
|
s_state <= ST_NONE;
|
351 |
|
|
end if;
|
352 |
|
|
|
353 |
|
|
when ST_RSHAKE =>
|
354 |
|
|
-- Receiving a handshake packet
|
355 |
|
|
if s_rxactive = '0' then
|
356 |
|
|
-- Got good handshake
|
357 |
|
|
s_rxgoodpacket <= '0';
|
358 |
|
|
s_state <= ST_NONE;
|
359 |
|
|
elsif s_rxerror = '1' or s_rxvalid = '1' then
|
360 |
|
|
-- Error or unexpected data byte in handshake packet
|
361 |
|
|
s_rxgoodpacket <= '0';
|
362 |
|
|
s_state <= ST_RWAIT;
|
363 |
|
|
end if;
|
364 |
|
|
|
365 |
|
|
when ST_TSTART =>
|
366 |
|
|
-- Transmission starting;
|
367 |
|
|
-- PHY module sees our PHY_TXVALID signal;
|
368 |
|
|
-- PHY_TXREADY is undefined;
|
369 |
|
|
-- we assert P_TXRDY to acknowledge the PID byte
|
370 |
|
|
v_txvalid := '1';
|
371 |
|
|
-- Check packet type
|
372 |
|
|
case P_TXDAT(1 downto 0) is
|
373 |
|
|
when "11" => -- data packet
|
374 |
|
|
s_state <= ST_TDATA;
|
375 |
|
|
s_txfirst <= '1';
|
376 |
|
|
when "10" => -- handshake packet
|
377 |
|
|
s_state <= ST_RWAIT;
|
378 |
|
|
when others => -- should not happen
|
379 |
|
|
end case;
|
380 |
|
|
|
381 |
|
|
when ST_TDATA =>
|
382 |
|
|
-- Sending a data packet
|
383 |
|
|
v_txvalid := '1';
|
384 |
|
|
if (s_txready = '1') or (s_txfirst = '1') then
|
385 |
|
|
-- Need next byte
|
386 |
|
|
if P_TXACT = '0' then
|
387 |
|
|
-- No more data; send first CRC byte
|
388 |
|
|
for i in 0 to 7 loop
|
389 |
|
|
v_dataout(i) := not crc16_buf(15-i);
|
390 |
|
|
end loop;
|
391 |
|
|
s_state <= ST_TCRC1;
|
392 |
|
|
else
|
393 |
|
|
-- Put next byte in output buffer
|
394 |
|
|
v_dataout := P_TXDAT;
|
395 |
|
|
-- And update the CRC
|
396 |
|
|
v_crc_upd := '1';
|
397 |
|
|
v_crc_data := P_TXDAT;
|
398 |
|
|
end if;
|
399 |
|
|
end if;
|
400 |
|
|
|
401 |
|
|
when ST_TCRC1 =>
|
402 |
|
|
-- Sending the first CRC byte of a data packet
|
403 |
|
|
v_txvalid := '1';
|
404 |
|
|
if s_txready = '1' then
|
405 |
|
|
-- Just queued the first CRC byte; move to 2nd byte
|
406 |
|
|
for i in 0 to 7 loop
|
407 |
|
|
v_dataout(i) := not crc16_buf(7-i);
|
408 |
|
|
end loop;
|
409 |
|
|
s_state <= ST_TCRC2;
|
410 |
|
|
end if;
|
411 |
|
|
|
412 |
|
|
when ST_TCRC2 =>
|
413 |
|
|
-- Sending the second CRC byte of a data packet
|
414 |
|
|
if s_txready = '1' then
|
415 |
|
|
-- Just sent the 2nd CRC byte; end packet
|
416 |
|
|
s_state <= ST_RWAIT;
|
417 |
|
|
else
|
418 |
|
|
-- Last byte is still pending
|
419 |
|
|
v_txvalid := '1';
|
420 |
|
|
end if;
|
421 |
|
|
|
422 |
|
|
end case;
|
423 |
|
|
|
424 |
|
|
end if;
|
425 |
|
|
|
426 |
|
|
-- CRC-16 update
|
427 |
|
|
if v_crc_upd = '1' then
|
428 |
|
|
v_crc16_new := crc16_upd(crc16_buf, v_crc_data);
|
429 |
|
|
crc16_buf <= v_crc16_new;
|
430 |
|
|
if s_state = ST_RDATA and v_crc16_new = crc16_res then
|
431 |
|
|
-- If this is the last byte of the packet, it is a valid packet.
|
432 |
|
|
s_rxgoodpacket <= '1';
|
433 |
|
|
else
|
434 |
|
|
s_rxgoodpacket <= '0';
|
435 |
|
|
end if;
|
436 |
|
|
end if;
|
437 |
|
|
|
438 |
|
|
-- Drive data output to PHY
|
439 |
|
|
if RESET = '1' then
|
440 |
|
|
-- Reset.
|
441 |
|
|
PHY_TXVALID <= '0';
|
442 |
|
|
PHY_DATAOUT <= "00000000";
|
443 |
|
|
elsif s_state = ST_CHIRPK then
|
444 |
|
|
-- Continuous chirp-K.
|
445 |
|
|
PHY_TXVALID <= P_CHIRPK;
|
446 |
|
|
PHY_DATAOUT <= "00000000";
|
447 |
|
|
elsif (PHY_TXREADY = '1') or (s_state = ST_NONE and P_TXACT = '1') then
|
448 |
|
|
-- Move a data byte from the buffer to the output lines when the PHY
|
449 |
|
|
-- accepts the previous byte, and also at the start of a new packet.
|
450 |
|
|
PHY_TXVALID <= v_txvalid;
|
451 |
|
|
PHY_DATAOUT <= v_dataout;
|
452 |
|
|
end if;
|
453 |
|
|
|
454 |
|
|
-- Keep pending output byte in register.
|
455 |
|
|
s_dataout <= v_dataout;
|
456 |
|
|
|
457 |
|
|
end process;
|
458 |
|
|
|
459 |
|
|
end architecture usb_packet_arch;
|
460 |
|
|
|