Receive and Transmit Description

TDESC.STA

Description

 

 

 

Late Collision

LC (bit2)

Indicates that late collision occurred while working in half-duplex mode.

It has no meaning while working in full-duplex mode.

 

Note that the collision window is speed dependent: 64 bytes for 10/100 Mb/s and

 

512 bytes for 1000 Mb/s operation.

 

 

 

Excess Collision

EC (bit 1)

Indicates that the packet has experienced more than the maximum excessive

collisions as defined by TCTL.CT control field and was not transmitted.

 

 

Is has no meaning while working in full-duplex mode.

 

 

 

Descriptor Done

DD (bit 0)

Indicates that the descriptor is done and is written back either after the descriptor

has been processed (with RS set), or for the 82554GC/EI only, after the packet has

 

 

been transmitted on the wire (with RPS set).

 

 

3.3.7.3TCP/IP Data Descriptor Option Field

The POPTS field provides a number of options which control the handling of this packet. This field is ignored except on the first data descriptor of a packet.

Table 3-20. Packet Options Field (TDESC.POPTS) Layout

7

6

5

4

3

2

1

0

RSV

RSV

RSV

RSV

RSV

RSV

TXSM IXSM

TDESC.POPTS

Description

 

 

RSV (bit 2-7)

Reserved

Should be written with 0b for future compatibility.

 

 

 

 

Insert TCP/UDP Checksum

 

Controls the insertion of the TCP/UDP checksum.

TXSM (bit1)

If not set, the value placed into the checksum field of the packet data is not modified,

and is placed on the wire. When set, TCP/UDP checksum field is modified by the

 

 

hardware.

 

Valid only in the first data descriptor for a given packet or TCP Segmentation context.

 

 

 

Insert IP Checksum

 

Controls the insertion of the IP checksum.

IXSM (bit 0)

If not set, the value placed into the checksum field of the packet data is not modified

and is placed on the wire. When set, the IP checksum field is modified by the

 

 

hardware.

 

Valid only in the first data descriptor for a given packet or TCP Segmentation context.

 

 

3.3.7.4TCP/IP Data Descriptor Special Field

The SPECIAL field is used to provide the 802.1q/802.3ac tagging information.

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Software Developer’s Manual

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Intel PCI-X manual 7.3 TCP/IP Data Descriptor Option Field, 7.4 TCP/IP Data Descriptor Special Field, RSV Txsm Ixsm