Realtek RTL8169 Manual page 53

Offset# Bit#
0 31
0 30
0 29
0 28
0 27
0 26:19
0 18
0 17
0 16
0 15:0
4 31:18
4 17
4 16
4 15:0
8 31:0
12 31:0
2002/03/27
Symbol
OWN
Ownership: This bit, when set, indicates that the descriptor is owned
by the NIC, and that the data relative to this descriptor is ready to be
transmitted. When cleared, it indicates that the descriptor is owned by
the host system. The NIC clears this bit when the relative buffer data is
transmitted. In this case, OWN=1.
EOR End of descriptor Ring: This bit, when set, indicates that this is the last
descriptor in the descriptor ring. When the NIC's internal transmit
pointer reaches here, the pointer will return to the first descriptor of the
descriptor ring after transmitting the data relative to this descriptor.
FS First segment descriptor: This bit, when set, indicates that this is the
first descriptor of a Tx packet, and that this descriptor is pointing to the
first segment of the packet.
LS Last segment descriptor: This bit, when set, indicates that this is the
last descriptor of a Tx packet, and that this descriptor is pointing to the
last segment of the packet.
LGSEN Large Send: A command bit; TCP/IP Large send operation enable.
Driver sets this bit to ask NIC to offload Large send operation. In this
case, LGSEN=0.
RSVD Reserved
IPCS
IP checksum offload: A command bit. The driver sets this bit to ask the
NIC to offload the IP checksum.
UDPCS UDP checksum offload: A command bit. The driver sets this bit to ask
the NIC to offload the UDP checksum.
TCPCS TCP checksum offload enable: A command bit; The driver sets this
bit to ask the NIC to offload the TCP checksum.
Frame_Length
Transmit frame length: This field indicates the length of the TX
buffer, in bytes, to be transmitted
RSVD Reserved
TAGC VLAN tag control bit: 1: Enable; 0: Disable.
RSVD
Reserved
VLAN_TAG VLAN Tag: The 2-byte VLAN_TAG contains information, from upper
layer, of user priority, canonical format indicator, and VLAN ID. Please
refer to IEEE 802.1Q for more VLAN tag information.
TxBuffL Low 32-bit address of transmit buffer
TxBuffH High 32-bit address of transmit buffer
1: Add TAG. 0x8100 (Ethernet encoded tag protocol ID, indicating
that this is an IEEE 802.1Q VLAN packet) is inserted after the
source address, and 2 bytes are inserted after tag protocol ID from
the VLAN_TAG field in transmit descriptor.
0: Packet remains unchanged when transmitting. I.e., the packet
transmitted is the same as it was passed down by upper layer.
VIDH: The high 4 bits of a 12-bit VLAN ID.
VIDL: The low 8 bits of a 12-bit VLAN ID.
PRIO: 3-bit 8-level priority.
CFI: Canonical Format Indicator.
53
Description
RTL8169
Rev.1.21