LAN9211_12 Datasheet, PDF (29/147 Pages) SMSC Corporation – High-Performance Small Form Factor Single-Chip Ethernet Controller with HP Auto-MDIX Support

High-Performance Small Form Factor Single-Chip Ethernet Controller with HP Auto-MDIX Support
Datasheet
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:
p
DST
SRC
r
o
t
L3 Packet
F
C
S
0123
1DWORD
Calculate Checksum
Figure 3.3 Type II Ethernet Frame
DST
SRC
8
1
0
0
V
I
D
t
y
p
e
L3 Packet
F
C
S
01234
1DWORD
Calculate Checksum
Figure 3.4 Ethernet Frame with VLAN Tag
{DSAP, SSAP, CTRL, OUI[23:16]}
{OUI[15:0], PID[15:0]}
SS
LN N
F
DST SRC e A A
L3 Packet
C
nP P
S
01
012345
1DWORD
Calculate Checksum
Figure 3.5 Ethernet Frame with Length Field and SNAP Header
SMSC LAN9211
29
DATASHEET
Revision 2.9 (03-01-12)