MPC8280 datasheet(845/1386 Pages) FREESCALE

845 / 1386 page

Universal Serial Bus Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

27-29

Data length (the second half word of a TxBD) is the number of octets the CP should send from this BD’s

data buffer. It is never modified by the CP.

Tx buffer pointer (the third and fourth half words of a TxBD) always points to the first location of the

buffer in internal or external memory. The pointer may be even or odd.

27.6.4

USB Transaction Buffer Descriptor (TrBD) for Host

The TrBD described in this section is used when the transaction-level interface is active. See

Section 27.5.1.2, “Transaction-Level Interface” for more information.

Data to be transmitted with the USB to the CP by is arranged in buffers referenced by the TrBD ring. The

first word of the TrBD contains status and control bits.

LSP

Low-speed transaction. Use for tokens only.

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

1 The following transaction is with a low-speed device. Required only for tokens.

Note that LSP should always be cleared in slave mode.

8–9

PID

Packet ID. This bit field is valid for the first BD of a packet; otherwise it is ignored.

0X Do not append PID to the data.

10 Transmit DATA0 PID before sending the data.

11 Transmit DATA1 PID before sending the data.

—

Reserved, should be cleared

NAK1

NAK received. Indicates that the endpoint has responded with a NAK handshake.

The packet was received error-free; however, the endpoint could not accept it.

STAL1

STALL received. Indicates that the endpoint has responded with a STALL

handshake. The endpoint needs attention through the control pipe.

TO1

Time out. Indicates that the endpoint failed to acknowledge the packet.

UN1

Underrun. Indicates that the USB encountered a transmitter underrun condition

while sending the buffer.

—

Reserved, should be cleared

0x02

0–15

Data length The data length is the number of octets that the CP should transmit from this BD’s

data buffer. It is never modified by the CP. This value should normally be greater than

zero.

0x04

0–31

Tx data

buffer

pointer

The transmit buffer pointer, which always points to the first location of the associated

data buffer, may be even or odd.The buffer may reside in either internal or external

memory.

1 Written by the USB controller after it finishes sending the associated data buffer.

Table 27-18. USB Host Tx BD Fields (continued)

Offset

Bit

Name

Description

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