MPC8280 datasheet(846/1386 Pages) FREESCALE

846 / 1386 page

Universal Serial Bus Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

27-30

Freescale Semiconductor

Table 27-17 describes USB TrBD fields.

01234

567

OFFSET + 0x0

—

CNF LSP

PID

RXER NAK STAL

BOV

OFFSET + 0x2

DATA LENGTH

OFFSET + 0x4

DATA BUFFER POINTER

OFFSET + 0x6

OFFSET + 0x8

TOK

—

ISO

—

ENDP

ADDR

OFFSET + 0xA

Reserved

Figure 27-21. USB Transaction Buffer Descriptor (TrBD)1,2

1 Entries in boldface must be initialized by the user.

2 All fields should be prepared by the user before transmission.

Table 27-19. USB Host TrBD Fields

Offset

Bit

Name

Description

0x00

Ready

0 The data buffer associated with this BD is not ready for transmission. The user

is free to manipulate this BD or its associated data buffer. The CP clears this

bit after the buffer has been transmitted or after an error condition is

encountered.

1 The data buffer, which has been prepared for transmission by the user, has not

been transmitted or is currently being transmitted. No fields of this BD may be

written by the user once this bit is set.

—

Reserved, should be cleared.

Wrap (Final BD in Table)

0 This is not the last BD in the TrBD table.

1 This is the last BD in the TrBD table. After this buffer has been used, the CP

will send data using the first BD in the table (the BD pointed to by TBASE).

The number of TrBDs in this table is programmable, and is determined only

by the TrBD[W] and the overall space constraints of the dual-port RAM.

Interrupt

0 No interrupt is generated after this buffer has been serviced.

1The TXB bit in the event register is set when this buffer is serviced. TXB can

cause an interrupt if it is enabled.

Last

This bit should always be 1 since each TrBD represents an entire transaction.

Transmit CRC. Append CRC to transmitted data packet.

0 Transmit end-of-packet after the last data byte. This setting can be used for

testing purposes to send a bad CRC after the data.

1 Transmit the CRC sequence after the last data byte.

CNF

Transmit confirmation.

This bit should always be set to 1 to obtain confirmation for each transaction.

LSP

Low-speed transaction.

0 This transaction is with the host or a full-speed device.

1 This transaction is with a low-speed device. Transmit a PRE packet before

the token.

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