DM9302EP datasheet(51/64 Pages) DAVICOM

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DM9302

10/100Mbps Ethernet Fiber/Twisted Pair Media Converter with Local bus

Preliminary datasheet

DM9302-15-DS-P01

July 30, 2009

9.2.13 VLAN Support

9.2.13.1 Port-Based VLAN

The DM9302 supports port-based VLAN as

default, up to 16 groups. Each port has a default VID

called PVID (Port VID, see register 6Fh). The

DM9302 used LSB 4-bytes of PVID as index and

mapped to register B0h~BFh, to define the VLAN

groups.

9.2.13.2 802.1Q-Based VLAN

Regarding IEEE 802.1Q standard, Tag-based

VLAN uses an extra tag to identify the VLAN

membership

frame

across

VLAN-aware

switch/router. A tagged frame is four bytes longer

than an untagged frame and contains two bytes of

TPID (Tag Protocol Identifier) and two bytes of TCI

(Tag Control Information).

Dest.

Src.

Length/Type

Data

Dest.

Src.

TPID

Data

TCI

Length / Type

Priority

CFI

VID

Standard frame

Tagged frame

0x8100

2 bytes

3 bits

1 bits

12 bits

The DM9302 also supports 16 802.1Q-based

VLAN groups, as specified in bit 1 of register 53h. It’s

obvious that the tagged packets can be assigned to

several different VLANs which are determined

according to the VID inside the VLAN Tag. Therefore,

the operation is similar to port-based VLAN. The

DM9302 used LSB 4-bytes VID of received packet

with VLAN tag and VLAN Group Mapping Register

(B0h~BFh) to configure the VLAN partition. If the

destination port of received packet is not same VLAN

group with received port, it will be discarded.

9.2.13.3 Tag/Untag

User can define each port as Tag port or Un-tag

port by bit 7 of register 6Dh in 802.1Q-based VLAN

mode. The operation of Tag and Un-tag can explain

as below conditions:

(1). Receive untagged packet and forward to

Un-tag port.

Received packet will forward to destination port

without modification.

(2). Receive tagged packet and forward to Un-tag

port.

The DM9302 will remove the tag from the

packet and recalculate CRC before sending it out.

(3). Receive untagged packet and forward to Tag

port.

The DM9302 will insert the PVID tag when an

untagged packet enters the port, and recalculate

CRC before delivering it.

(4). Receive tagged packet and forward to Tag

port.

Received packet will forward to destination port

without modification.

9.2.14 Priority Support

The DM9302 supports Quality of Service (QoS)

mechanism for multimedia communication such as

VoIP and video conferencing.

The DM9302 provides three priority classifications:

Port-based, 802.1p-based and DiffServ-based priority.

See next section for more detail. The DM9302 offers

four level queues for transmit on per-port based.

The DM9302 provides two packet scheduling

algorithms: Weighted Round-Robin Queuing and

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