National CP3BT26 - Manual (Page 104)

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CP3BT26
FLUSH Writing a 1 to the Flush FIFO bit flushes all
data from the control endpoint FIFOs, resets
the endpoint to Idle state, clears the FIFO
read and write pointer, and then clears itself.
If the endpoint is currently using the FIFO0 to
transfer data on USB, flushing is delayed until
after the transfer is complete. The FLUSH bit
is cleared on reset. It is equivalent to the
FLUSH bit in the RXC0 register.
0 – Writing 0 has no effect.
1 – Writing 1 flushed the FIFOs.
IGN_IN When the Ignore IN Tokens bit is set, the end-
point will ignore any IN tokens directed to its
configured address.
0 – Do not ignore IN tokens.
1 – Ignore IN tokens.
18.3.27 Transmit Data 0 Register (TXD0)
Data written to the TXD0 register is copied into the FIFO of
Endpoint 0 at the current location of the transmit write point-
er. The register allows write-only access from the CPU bus.
TXFD The Transmit FIFO Data Byte is used to load
the transmit FIFO. Software is expected to
write only the packet payload data. The PID
and CRC16 are created automatically.
18.3.28 Receive Status 0 Register (RXS0)
The RXS0 register indicates status conditions for the bidi-
rectional Control Endpoint 0. To receive a SETUP packet af-
ter receiving a zero length OUT/SETUP packet, there are
two copies of this register in hardware. One holds the re-
ceive status of a zero length packet, and another holds the
status of the next SETUP packet with data. If a zero length
packet is followed by a SETUP packet, the first read of this
register indicates the status of the zero length packet (with
RX_LAST set and RCOUNT clear), and the second read in-
dicates the status of the SETUP packet. This register pro-
vides read-only access from the CPU bus. After reset it is
clear.
RCOUNT The Receive Count field reports the number of
bytes presently in the RX FIFO. This number
is never larger than 8 for Endpoint 0.
RX_LAST The Receive Last Bytes bit indicates that an
ACK was sent on completion of a successful
receive operation. This bit is unchanged for
zero-length packets. It is cleared when this
register is read.
0 – No ACK was sent.
1 – An ACK was sent.
TOGGLE The Toggle bit reports the PID used when re-
ceiving the packet. When clear, this bit indi-
cates that the last successfully received
packet had a DATA0 PID. When set, this bit in-
dicates that the packet had a DATA1 PID. This
bit is unchanged for zero-length packets. It is
cleared when this register is read.
0 – DATA0 PID was used.
1 – DATA1 PID was used.
SETUP The Setup bit indicates that the setup packet
has been received. This bit is unchanged for
zero-length packets. It is cleared when this
register is read.
0 – Setup packet has not been received.
1 – Setup packet has been received.
18.3.29 Receive Command 0 Register (RXC0)
The RXC0 register controls the mandatory Endpoint 0 when
used in receive direction. This register provides read/write
access from the CPU bus. It is clear after reset.
RX_EN The Receive Enable bit enables receiving
packets. OUT packet reception is disabled af-
ter every data packet is received, or when a
STALL handshake is returned in response to
an OUT token. The RX_EN bit must be set to
re-enable data reception. Reception of SET-
UP packets is always enabled. In the case of
back-to-back SETUP packets (for a given
endpoint) where a valid SETUP packet is re-
ceived with no other intervening non-SETUP
tokens, the Endpoint Controller discards the
new SETUP packet and returns an ACK hand-
shake. If any other reasons prevent the End-
point Controller from accepting the SETUP
packet, it must not generate a handshake.
This allows recovery from a condition where
the ACK of the first SETUP token was lost by
the host.
0 – Receive disabled.
1 – Receive enabled.
IGN_OUT The Ignore OUT Tokens bit controls whether
OUT tokens are ignored. When this bit is set,
the endpoint ignores any OUT tokens directed
to its configured address.
0 – Do not ignore OUT tokens.
1 – Ignore OUT tokens.
IGN_SETUP The Ignore SETUP Tokens bit controls wheth-
er SETUP tokens are ignored. When this bit is
set, the endpoint ignores any SETUP tokens
directed to its configured address.
0 – Do not ignore SETUP tokens.
1 – Ignore SETUP tokens.
7 0
TXFD
7 6 5 4 3 0
Res. SETUP TOGGLE RX_LAST RCOUNT
7 4 3 2 1 0
Reserved FLUSH IGN_SETUP IGN_OUT RX_EN