lan9312 Standard Microsystems Corp., lan9312 Datasheet - Page 114

• Manufacturer Part Number: lan9312
• Description: Lan9312 High Performance Two Port 10/100 Managed Ethernet Switch With 32-bit Non-pci Cpu Interface
• Manufacturer: Standard Microsystems Corp.

Revision 1.2 (04-08-08)
9.4
Preamble
Preamble
7 Bytes
7 Bytes
both are set to the same value, VLAN1 is given higher precedence and the maximum legal frame
length is set to 1522.
The Ethernet address fields of an Ethernet packet consist of two 6-byte fields: one for the destination
address and one for the source address. The first bit of the destination address signifies whether it is
a physical address or a multicast address.
The Host MAC address check logic filters the frame based on the Ethernet receive filter mode that has
been enabled. The various filter modes of the Host MAC are specified based on the state of the control
bits in the
14.3.1, "Host MAC Control Register (HMAC_CR)," on page 271
If the frame fails the filter, the Host MAC does not receive the packet. The host has the option of
accepting or ignoring the packet.
Note: This filtering function is performed after any switch fabric filtering functions. The user must
Address Filtering
1 Byte
1 Byte
SOF
SOF
ensure the switch filtering is setup properly to allow packets to be passed to the Host MAC for
further filtering.
Host MAC Control Register
Dest. Addr.
Dest. Addr.
6 Bytes
6 Bytes
2 Bytes
TPID
Source Addr.
Source Addr.
6 Bytes
6 Bytes
Standard Ethernet Frame (1518 Bytes)
High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Figure 9.1 VLAN Frame
Tag Control Information
Ethernet Frame with VLAN TAG (1522 Bytes)
DATASHEET
2 Bytes
2 Bytes
Type
TPID
(HMAC_CR), as shown in
User Priority
(TCI)
114
3 Bits
2 Bytes
Type
Tag Protocol ID: \x81-00
1 Bit
46-1500 Bytes
CFI
2 Bytes
Type
Indicates the frame’s priority
Data
VLAN ID
Canonical Address Format Indicator
12 Bits
Table
for more information on this register.
46-1500 Bytes
9.1. Please refer to the
Data
Defines the VLAN to
which the frame belongs
4 Bytes
FCS
SMSC LAN9312
4 Bytes
FCS
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