Receive and Transmit Description

3.3.6.2TCP/UDP Offload Transmit Descriptor Status Field

Four bits are reserved to provide transmit status, although only one is currently assigned for this specific descriptor type. The status word is only written back to host memory in cases where the RS is set in the command.

Table 3-16. Transmit Status Layout

3

2

1

0

RSV

DD

TDESC.STA

Description

 

 

RSV

Reserved

Reserved for future use. Reads as 0b.

 

 

 

DD (bit 0)

Descriptor Done

Indicates that the descriptor is finished and is written back after the descriptor has

 

been processed.

 

 

3.3.7TCP/IP Data Descriptor Format

The TCP/IP data descriptor is the companion to the TCP/IP context transmit descriptor described in the previous section. This descriptor type provides similar functionality to the legacy mode descriptor but also integrates the checksum offloading and TCP Segmentation feature.

To select this descriptor format, bit 29 in the command field (TDESC.DEXT) must be set to 1b and TDESC.DTYP must be set to 0001b. In this case, the descriptor format is defined as shown in Table 3-17.

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Software Developer’s Manual

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Intel PCI 7 TCP/IP Data Descriptor Format, 6.2 TCP/UDP Offload Transmit Descriptor Status Field, Transmit Status Layout