lan9420 Standard Microsystems Corp., lan9420 Datasheet - Page 61

• Manufacturer Part Number: lan9420
• Description: Lan9420/lan9420i Single-chip Ethernet Controller With Hp Auto-mdix Support And Pci Interface
• Manufacturer: Standard Microsystems Corp.

Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface
Datasheet
SMSC LAN9420/LAN9420i
DST
In mode 1, the RXCOE supports VLAN tags and a SNAP header. In this mode the RXCOE calculates
the checksum at the start of L3 packet. The VLAN1 tag register is used by the RXCOE to indicate
what protocol type is to be used to indicate the existence of a VLAN tag. This value is typically 8100h.
Example frame configurations:
0
DST
0
1
SRC
DST
1
SRC
2
2
8
1
0
0
SRC
3
V
I
D
p
r
o
t
3
t
y
p
e
4
T
Y
P
E
Figure 3.21 Ethernet Frame with VLAN Tag
Figure 3.19 RXCOE Checksum Calculation
Figure 3.20 Type II Ethernet Frame
DATASHEET
Calculate Checksum
Calculate Checksum
Calculate Checksum
61
Frame Data
L3 Packet
L3 Packet
C
S
F
Revision 1.1 (03-31-08)
C
F
S
C
S
F