MPC8280 datasheet(831/1386 Pages) FREESCALE

831 / 1386 page

Universal Serial Bus Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

27-15

27.5.5

Frame Number (FRAME_N)

This entry is used for frame number updates both in function mode and in host mode. In function mode it

is written by the USB controller; in host mode it is written by the application software and the USB

controller.

This entry is updated by the USB controller in function mode whenever a SOF (start of frame) token is

received—including the SOF token it transmitted in host mode. The entry contains 11 bits that represent

the frame number. An SOF interrupt is issued upon an update of this entry.

Table 27-6 describes FRAME_N fields.

In Host Mode, this entry must be updated by the application software between the transmission of one SOF

(start of frame) token and the next. See Section 27.5.1.2, “Transaction-Level Interface” for details. The

software should prepare the frame number and the CRC and place it in FRAME_N field.

Field

1 This bit is set if the SOF token was received error free.

—

FRAME NUMBER

Reset

—

R/W

Addr

USB base + 0x10

Figure 27-7. Frame Number (FRAME_N) in Function Mode—Updated by USB Controller

Table 27-6. FRAME_N Field Descriptions

Bits

Name

Description

The valid bit is set if the SOF token is received without error.

1–4

—

Reserved, should be cleared.

5–15

FRAME

NUMBER

The frame number is loaded with the value received in the SOF packet. Be sure the frame

number is cleared before beginning USB operation.

Field

CRC5

FRAME NUMBER

Reset

—

R/W

Addr

USB base + 0x10

Figure 27-8. Frame Number (FRAME_N) in Host Mode—Updated by Application

Software

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