RTL8169
2002/03/27
Rev.1.21
51
Large-Send Task Offload Tx Descriptor Format (before transmitting, OWN=1, LGSEN=1, Tx command mode 0)
bit
31 30 29 28 27 26
16 15
8 7 6 5 4 3 2 1 0
O
W
N
=
1
E
O
R
F
S
L
S
L
G
S
E
N
=
1
Large-Send MSS value
(11 bits)
Frame_Length
Offset 0
VLAN_TAG
RSVD
T
A
G
C
R
S
V
D
VIDL PRIO
C
FI
VIDH
Offset 4
TX_BUFFER_ADDRESS_LOW
Offset 8
TX_BUFFER_ADDRESS_HIGH
Offset 12
Offset#
Bit#
Symbol
Description
0 31
OWN
Ownership:
This bit, when set, indicates that the descriptor is owned
by THE NIC, and the data relative to this descriptor is ready to be
transmitted. When cleared, it indicates that the descriptor is owned by
host system. The NIC clears this bit when the relative buffer data is
transmitted. In this case, OWN=1.
0 30
EOR
End of Descriptor Ring:
This bit, when set, indicates that this is the
last descriptor in 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.
0 29
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.
0 28
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.
0 27
LGSEN
Large Send:
A command bit; TCP/IP Large send operation enable. The
driver sets this bit to ask the NIC to offload the Large send operation. In
this case, LGSEN=1.
0 26:16
MSS
Maximum Segmentation Size:
An 11-bit long command field, the
driver passes large send MSS to the NIC through this field.
0 15:0 Frame_Length
Transmit Drame Length:
This field indicates the length in TX buffer,
in byte, to be transmitted
4 31:18
RSVD
Reserved
cont...