Intel PCI-X manual 7.2 TCP/IP Data Descriptor Status Field, Transmit Status Layout, Reserved

Receive and Transmit Description

TDESC.DCMD	Description
TSE (bit 2)	TCP Segmentation Enable
	TSE indicates that this descriptor is part of the current TCP Segmentation context. If
	this bit is not set, the descriptor is part of the “normal” context.
	Insert IFCS
IFCS (Bit 1)	Controls the insertion of the FCS/CRC field in normal Ethernet packets.
	IFCS is only valid in the last descriptor of the given packet (qualified by the EOP bit).
	End Of Packet
	The EOP bit indicates that the buffer associated with this descriptor contains the last
EOP (Bit 0)	data for the packet or for the given TCP Segmentation context. In the case of a TCP
	Segmentation context, the DTALEN length of this descriptor should match the
	amount remaining of the original PAYLEN. If it does not, the TCP Segmentation
	context is terminated but the end of packet processing may be incorrectly performed.
	These abnormal termination events are counted in the TSCTFC statistics register.

Note: The VLE, IFCS, and VLAN fields are only valid in certain descriptors. If TSE is enabled, the VLE, IFCS, and VLAN fields are only valid in the first data descriptor of the TCP segmentation context. If TSE is not enabled, then these fields are only valid in the last descriptor of the given packet (qualified by the EOP bit).

3.3.7.2TCP/IP Data Descriptor Status Field

Four bits are reserved to provide transmit status, although only the DD is valid1. The status word is only written back to host memory in cases where the RS bit is set in the command field. The DD bit indicates that the descriptor is finished and is written back after the descriptor has been processed.

Table 3-19. Transmit Status Layout

3 2 1 0

RSV

TUa

LC

EC

DD

a.82544GC/EI only.

TDESC.STA	Description
Reserved	Reserved

1. Unless the RPS bit is set in the descriptor (82544GC/EI only).

Software Developer’s Manual 49