MPC8280 datasheet(836/1386 Pages) FREESCALE

836 / 1386 page

Universal Serial Bus Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

27-20

Freescale Semiconductor

27.5.7.4

USB Command Register (USCOM)

USCOM is used to start the USB transmit operation.

Table 27-12 describes USCOM fields.

27.5.7.5

USB Event Register (USBER)

The USBER reports events recognized by the USB channel and generates interrupts. Upon recognition of

an event, the USB sets its corresponding bit in the USBER. Interrupts generated by this register may be

masked in the USB mask register.

The USBER may be read at any time. A bit is cleared by writing a one (writing a zero does not affect a

bit’s value). More than one bit may be cleared at a time. All unmasked bits must be cleared before the CP

will clear the internal interrupt request. This register is cleared at reset.

234

567

Field

STR

FLUSH

ISFT

DSFT

—

Reset

0000_0000

R/W

Addr

0x11B62

Figure 27-13. USB Command Register (USCOM)

Table 27-12. USCOM Fields

Bits

Name

Description

STR

Start FIFO fill. Setting the STR bit to one causes the USB controller to start the filling the

corresponding end point transmit FIFO with data. Transmission will begin once the IN token

for this end-point is received. The STR bit is read always as a zero.

FLUSH

Flush FIFO. Setting the FLUSH bit to one causes the USB controller to flush the

corresponding end point transmit FIFO. Before flushing the FIFO, the user should issue the

Stop_Tx command. After flushing the FIFO the user should issue the Restart_Tx command

(Refer to Section 27.7, “USB CP Commands.”). FLUSH is always read as a zero.

ISFT

Increment Start-of-Frame Time. Setting the ISFT bit increments the start-of-frame time by

one. This bit could be used to synchronize the USB frames to an external timing source.

DSFT

Decrement Start-of-Frame Time. Setting the DSFT bit decrements the start-of-frame time

by one. This bit could be used to synchronize the USB frames to an external timing source.

4–5

—

Reserved, should be cleared.

6–7

End point. Selects one of the four supported end points.

012

Field

—

SFT

RESET IDLE TXE4 TXE3 TXE2 TXE1 SOF

BSY

TXB

RXB

Reset

0000_0000_0000_0000

R/W

Addr

0x11B70

Figure 27-14. USB Event Register (USBER)

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