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CP3BT26
SD3 The Suspend Detect 3 ms bit is set after 3 ms
of IDLE have been detected on the upstream
port, indicating that the device should be sus-
pended. The suspend occurs under software
control by writing the suspend value to the
Node Functional State (NFSR) register. This
bit is cleared when the register is read.
0 – No 3 ms in IDLE has been detected.
1 – 3 ms in IDLE has been detected.
SD5 The Suspend Detect 5 ms bit is set after 5 ms
of IDLE have been detected on the upstream
port, indicating that this device is permitted to
perform a remote wake-up operation. The re-
sume may be initiated under software control
by writing the resume value to the NFSR reg-
ister. This bit is cleared when the register is
read.
0 – No 5 ms in IDLE has been detected.
1 – 5 ms in IDLE has been detected.
RESET The Reset bit is set when 2.5 µs of SEO have
been detected on the upstream port. In re-
sponse, the functional state should be reset
(NFS in the NFSR register is set to RESET),
where it must remain for at least 100 µs. The
functional state can then return to Operational
state. This bit is cleared when the register is
read.
0 – No 2.5 µs in SEO have been detected.
1 – 2.5 µs in SEO have been detected.
RESUME The Resume bit indicates whether resume
signalling has been detected on the USB
when the device is in Suspend state (NFS in
the NFSR register is set to SUSPEND), and a
non-IDLE signal is present on the USB, indi-
cating that this device should begin its wake-
up sequence and enter Operational state. Re-
sume signalling can only be detected when
the 48 MHz PLL clock is enabled to the USB
controller. This bit is cleared when the register
is read.
0 – No resume signalling detected.
1 – Resume signalling detected.
18.3.6 Alternate Mask Register (ALTMSK)
A set bit in the ALTMSK register enables automatic setting
of the ALT bit in the MAEV register when the respective
event in the ALTEV register occurs. Otherwise, setting
MAEV.ALT bit is disabled. The ALTMSK register is clear af-
ter reset. It provides read/write access from the CPU bus.
18.3.7 Transmit Event Register (TXEV)
The TXEV register reports the current status of the FIFOs,
used by the three Transmit Endpoints. The TXEV register is
clear after reset. It provides read-only access.
TXFIFO The Transmit FIFO n bits are copies of the
TX_DONE bits from the corresponding Trans-
mit Status registers (TXSn). A bit is set when
the IN transaction for the corresponding trans-
mit endpoint n has been completed. These
bits are cleared when the corresponding
TXSn register is read.
TXUDRRN The Transmit Underrun n bits are copies of the
respective TX_URUN bits from the corre-
sponding Transmit Status registers (TXSn).
Whenever any of the Transmit FIFOs under-
flows, the respective TXUDRRN bit is set.
These bits are cleared when the correspond-
ing Transmit Status register is read.
Note: Since Endpoint 0 implements a store
and forward principle, an underrun condition
for FIFO0 cannot occur. This results in the
TXUDRRN0 bit always being read as 0.
18.3.8 Transmit Mask Register (TXMSK)
The TXMSK register is used to select the bits of the TXEV
registers, which causes the TX_EV bit in the MAEV register
to be set. When a bit is set and the corresponding bit in the
TXEV register is set, the TX_EV bit in the MAEV register is
set. When clear, the corresponding bit in the TXEV register
does not cause TX_EV to be set. The TXMSK register pro-
vides read/write access. It is clear after reset.
7 6 5 4 3 2 1 0
RESUME RESET SD5 SD3 EOP DMA Reserved
7 4 3 0
TXUDRRN TXFIFO
7 4 3 0
TXUDRRN TXFIFO