Intel PCI-X manual Transmit Descriptor Tdesc Layout Type = 0001b, Popts RSV STA Dcmd Dtyp Dtalen

Receive and Transmit Description

Table 3-17. Transmit Descriptor (TDESC) Layout – (Type = 0001b)

0

8

Address [63:0]

Special POPTS RSV STA DCMD DTYP DTALEN

0	63	48 47	40 39	36 35	32 31	24 23	20 19	0
Transmit Descriptor					Description
Address		Data buffer address
		Address of the data buffer in the host memory which contains a portion of the
		transmit packet.
		Data Length Field
		Total length of the data pointed to by this descriptor, in bytes.
DTALEN		For data descriptors not associated with a TCP Segmentation operation
		(TDESC.TSE not set), the descriptor lengths are subject to the same restrictions
		specified for legacy descriptors (the sum of the lengths of the data descriptors
		comprising a single packet must be at least 80 bytes less than the allocated size
		of the transmit FIFO.)
DTYP		Data Type
		Set to 0001b to identify this descriptor as a TCP/IP data descriptor.
DCMD		Descriptor Command Field
		Provides options that control some of the generic descriptor processing
		features. Refer to Section 3.3.7.1 for bit definitions of the DCMD field.
		TCP/IP Status field
STA		Provides transmit status indication.
		Section 3.3.7.2 provides the bit definition for the TDESC.STA field.
RSV		Reserved
		Set to 0b for future compatibility.
		Packet Option Field
POPTS		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.
		Section 3.3.7.3 provides the bit definition for the TDESC.POPTS field.
		Special field
Special		The Special field is used to provide 802.1q tagging information.
		This field is only valid in the last descriptor of the given packet (qualified by the
		EOP bit).

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