Realtek RTL8169 Manual page 52

4 17
4 16
4 15:0
8 31:0
12 31:0
Normal (including IP, TCP, UDP Checksum Task Offloads) Tx Descriptor Format (before transmitting, OWN=1,
LGSEN=0, Tx command mode 1)
bit
31 30 29 28 27 26
O E F L L
W O S S G
N R S
= E
1 N
=
0
RSVD
TX_BUFFER_ADDRESS_LOW
TX_BUFFER_ADDRESS_HIGH
2002/03/27
TAGC
RSVD
VLAN_TAG
TxBuffL
TxBuffH
R R R R R R R R
S S S S S S S S
V V V V V V V V
D D D D D D D D
VLAN tag control bit: 1: Enable; 0: Disable.
1: Add TAG. 0x8100 (Ethernet encoded tag protocol ID, indicating
that this is a IEEE 802.1Q VLAN packet) is inserted after source
address, and 2 bytes are inserted after tag protocol ID from
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.
Reserved
The 2-byte VLAN_TAG contains information, from the upper layer, of
user priority, canonical format indication, and VLAN ID. Please refer to
IEEE 802.1Q for more VLAN tag information.
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.
Low 32-bit address of transmit buffer
High 32-bit address of transmit buffer
16 15
I U T
P D C Frame_Length
C P P
S C C
S S
T R
A S
VIDL
G V
C D
52
8 7 6 5 4 3 2
VLAN_TAG
PRIO C VIDH
FI
RTL8169
1 0
Offset 0
Offset 4
Offset 8
Offset 12
Rev.1.21