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CP3BT26
18.3.3 Main Event Register (MAEV)
The Main Event Register summarizes and reports the main
events of the USB transactions. This register provides read-
only access. The MAEV register is clear after reset.
WARN The Warning Event bit indicates whether one
of the unmasked bits in the FIFO Warning
Event (FWEV) register has been set. This bit
is cleared by reading the FWEV register.
0 – No warning event occurred.
1 – A warning event has occurred.
ALT The Alternate Event bit indicates whether one
of the unmasked ALTEV register bits has
been set. This bit is cleared by reading the AL-
TEV register.
0 – No alternate event has occurred.
1 – An alternate event has occurred.
TX_EV The Transmit Event bit indicates whether any
of the unmasked bits in the Transmit Event
(TXEV) register (TXFIFOn or TXUNDRNn) is
set. Therefore, it indicates that an IN transac-
tion has been completed. This bit is cleared
when all the TX_DONE bits and the TXUN-
DRN bits in each Transmit Status (TXSn) reg-
ister are cleared.
0 – No transmit event has occurred.
1 – A transmit event has occurred.
FRAME The Frame Event bit indicates whether the
frame counter has been updated with a new
value, due to receipt of a valid SOF packet on
the USB or to an artificial update if the frame
counter was unlocked or a frame was missed.
This bit is cleared when the register is read.
0 – The frame counter has not been updated.
1 – Frame counter has been updated.
NAK The Negative Acknowledge Event indicates
whether one of the unmasked NAK Event
(NAKEV) register bits has been set. This bit is
cleared when the NAKEV register is read.
0 – No unmasked NAK event has occurred.
1 – An unmasked NAK event has occurred.
UL The Unlocked/Locked Detected bit is set
when the frame timer has either entered un-
locked condition from a locked condition, or
has re-entered a locked condition from an un-
locked condition as determined by the UL bit
in the Frame Number (FNH or FNL) register.
This bit is cleared when the register is read.
0 – Frame timer has not entered an unlocked
condition from a locked condition or re-
entered a locked condition from an un-
locked condition.
1 – Frame timer has either entered an un-
locked condition from a locked condition
or re-entered a locked condition from an
unlocked condition.
RX_EV The Receive Event bit is set if any of the un-
masked bits in the Receive Event (RXEV) reg-
ister is set. It indicates that a SETUP or OUT
transaction has been completed. This bit is
cleared when all of the RX_LAST bits in each
Receive Status (RXSn) register and all RX-
OVRRN bits in the RXEV register are cleared.
0 – No receive event has occurred.
1 – A receive event has occurred.
INTR The Master Interrupt Enable bit is hardwired
to 0 in the Main Event (MAEV) register; bit 7
in the Main Mask (MAMSK) register is the
Master Interrupt Enable.
0 – USB interrupts disabled.
1 – USB interrupts enabled.
18.3.4 Main Mask Register (MAMSK)
The MAMSK register masks out events reported in the
MAEV registers. A set bit enables the interrupts for the re-
spective event in the MAEV register. If the corresponding bit
is clear, interrupt generation for this event is disabled. This
register provides read/write access. The MAMSK register is
clear after reset.
18.3.5 Alternate Event Register (ALTEV)
The ALTEV register summarizes and reports the further
events in the USB node. This register provides read-only ac-
cess. The ALTEV register is clear after reset.
DMA The DMA Event bit indicates that one of the
unmasked bits in the DMA Event (DMAEV)
register has been set. The DMA bit is read-
only and clear, when the DMAEV register is
cleared.
0 – No DMA event has occurred.
1 – A DMA event has occurred.
EOP The End of Packet bit indicates whether a val-
id EOP sequence has been detected on the
USB. It is used when this device has initiated a
Remote wake-up sequence to indicate that the
Resume sequence has been acknowledged
and completed by the host. This bit is cleared
when the register is read.
0 – No EOP sequence detected.
1 – EOP sequence detected.
7 6 5 4 3 2 1 0
INTR RX_EV ULD NAK FRAME TX_EV ALT WARN
7 6 5 4 3 2 1 0
INTR RX_EV ULD NAK FRAME TX_EV ALT WARN
7 6 5 4 3 2 1 0
RESUME RESET SD5 SD3 EOP DMA Reserved