UPSD3422 datasheet(159/293 Pages) STMICROELECTRONICS

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uPSD34xx

USB interface

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USB Global Interrupt Flag Register (UIF0)

There are many different events that generate a USB interrupt requiring a number of

registers to indicate the cause of the interrupt. To more efficiently identify the cause of

the interrupt, the USB Global Interrupt Flag Register (see Table 76) indicates the type

of interrupt that occurred. Once the type of interrupt is identified, the associated

Interrupt Flag Register may be read to determine the exact cause of the interrupt.

Table 76.

USB global interrupt flag register (UIF0 0E8h, reset value 00h)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

GLF

INF

OUTF

NAKF

RSTF

SUSPENDF

EOPF

RESUMF

Bit

Symbol

R/W

Definition

7GLF

Global Interrupt flag

Logical OR of the RSTF, SUSPENDF, EOPF, and RESUMF

interrupt flags

6INF

IN FIFO Interrupt flag

Logical OR of the IN4F, IN3F, IN2F, IN1F, and IN0F interrupt

flags

5OUTF

OUT FIFO Interrupt flag

Logical OR of the OUT4F, OUT3F, OUT2F, OUT1F, and OUT0F

interrupt flags

NAKF

NAK FIFO Interrupt flag

Logical OR of the NAK4F, NAK3F, NAK2F, NAK1F, and NAK0F

interrupt flags

3RSTF

R/W

USB Reset flag

This bit is set when a USB Reset is detected on the D+ and D-

lines.

Note: A USB Reset does not reset the MCU nor the USB

module. Firmware should disable/enable the USB SIE using

the USEN bit in the UCTL register and initialize all USB related

registers as appropriate.

SUSPENDF

R/W

USB suspend mode flag

This bit is set when the SIE detects 3ms of no activity on the

bus and the clock to the SIE is also shut down to conserve

power. Clearing this bit turns the SIE clock on.

EOPF

R/W

End of Packet flag

This bit is set when a valid End of Packet sequence is detected

on the D+ and D– line.

RESUMEF

R/W

Resume flag

This bit is set when USB bus activity is detected while the

SUSPNDF Bit is set. When a Resume is detected, the

SUSPENDF bit must be cleared (if set) to turn the SIE clock on.

UPSD3422 Datasheet(PDF) 159 Page - STMicroelectronics

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