MPC8540 datasheet(1206/1302 Pages) FREESCALE

1206 / 1302 page

MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

21-66

Freescale Semiconductor

10/100 Fast Ethernet Controller

Offset + 0

Last in frame. Written by user.

0 The buffer is not the last in the transmit frame.

1 The buffer is the last in the transmit frame.

Offset + 0

Tx CRC. Written by user. (Valid only while it is set in first BD and TxBD[PAD/CRC]

is cleared and MACCFG2[PAD/CRC] is cleared and MACCFG2[CRC EN] is

cleared.) If MACCFG2[PAD/CRC] is set or MACCFG2[CRC EN] is set, this bit is

ignored.

0 End transmission immediately after the last data byte with no hardware

generated CRC appended, unless TxBD[PAD/CRC] is set.

1 Transmit the CRC sequence after the last data byte.

Offset + 0

DEF

Defer indication. Hardware updates this bit if an excessive defer condition occurs.

0 This frame was not deferred.

If HAFDUP[EXCESS_DEFER]=1, this frame did not have a collision before it

was sent but it was sent late because of deferring. If

HAFDUP[EXCESS_DEFER]=0, this frame was aborted and not sent.

Offset + 0

TO1

Transmit software ownership. This read/write bit may be utilized by software, as

necessary. Its state does not affect the hardware nor is it affected by the hardware.

Offset + 0

HFE/LC

Huge frame enable (written by user)/Late collision (written by the FEC)

Huge frame enable. Written by user. Valid only while it is set in first BD and the

MACCFG2[Huge Frame] is cleared. If MACCFG2[Huge Frame] is set, this bit is

ignored.

0 Truncate transmit frame if its length is greater than the MAC’s Maximum Frame

Length register.

1 Do not truncate the transmit frame.

Late collision. Written by the FEC.

0 No late collision.

1 A collision occurred after 64 bytes are sent. The FEC terminates the

transmission and updates LC.

Offset + 0

Retransmission Limit. Written by the FEC.

0 Transmission before maximum retry limit is hit.

1 The transmitter failed (maximum retry limit + 1) attempts to successfully send

a message due to repeated collisions. The FEC terminates the transmission

and updates RL.

Offset + 0

10–13

Retry Count. Written by the FEC.

0 The frame is sent correctly the first time or if RL is set then the retry limit has

been reached

x One or more attempts where needed to send the transmit frame. If this field is

15, then 15 or more retries were needed. The Ethernet controller updates RC

after sending the buffer.

Offset + 0

Underrun. Written by the FEC.

0 No underrun encountered (data was retrieved from external memory in time to

send a complete frame).

1 The Ethernet controller encountered a transmitter underrun condition while

sending the associated buffer. The FEC terminates the transmission and

updates UN.

Table 21-48. Transmit Data Buffer Descriptor (TxBD) Field

Descriptions (continued)

Offset

Bits

Name

Description

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