CP3BT26

18.3.3Main 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.

7

 

6

5

4

 

3

2

1

 

0

INTR

RX_EV

ULD

NAK

FRAME

TX_EV

ALT

WARN

 

 

 

 

 

 

 

 

 

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.

18.3.4Main 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.

7 6 5 4 3 2 1 0

INTR RX_EV ULD NAK FRAME TX_EV ALT WARN

18.3.5Alternate 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.

 

7

 

6

 

5

4

3

 

2

1

0

RESUME

RESET

SD5

SD3

EOP

DMA

Reserved

 

 

 

 

 

 

 

 

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.

 

 

 

www.national.com

96

Page 96
Image 96
National CP3BT26 manual Main Event Register Maev, Main Mask Register Mamsk, Alternate Event Register Altev