VT6516 datasheet(52/73 Pages) ETC

52 / 73 page

VIA Technologies, Inc.

Preliminary VT6516 Datarsheet

-52-

20H

spanning tree state for PORT 0

2’b00 – blocking state (default)

2’b01 – listening state

2’b10 - learning state

2’b11 – forwarding state

The forwarding operation in each Ethernet port is controlled by its

associated spanning tree state.

In blocking or listening state, the incoming packets will not trigger

any DMAC lookup operation and SMAC learning operation.

In learning state, the incoming packets will not trigger DMAC

lookup operation, but the SMAC learning operation will be

triggered for CRC-OK packets.

Only in forwarding state, an incoming packet will trigger DMAC

lookup operation while the first 24 bytes are received, and it will

trigger the SMAC learning operation while the whole packet is

received with good CRC.

For the 802.1d spanning tree algorithm, a blocked port for loop

avoidance should enter the blocking state so that any incoming

packets are filtered without forward. A normal port that does not

cause any loop should be in the forwarding state.

PORT0_STP_

STATE

[1:0]

R/W

21H

spanning tree state for PORT 1

PORT1_STP_

STATE

[1:0]

R/W

22H

spanning tree state for PORT 2

PORT2_STP_

STATE

[1:0]

R/W

23H

spanning tree state for PORT 3

PORT3_STP_

STATE

[1:0]

R/W

24H

spanning tree state for PORT 4

PORT4_STP_

STATE

[1:0]

R/W

25H

spanning tree state for PORT 5

PORT5_STP_

STATE

[1:0]

R/W

26H

spanning tree state for PORT 6

PORT6_STP_

STATE

[1:0]

R/W

27H

spanning tree state for PORT 7

PORT7_STP_

STATE

[1:0]

R/W

28H

spanning tree state for PORT 8

PORT8_STP_

STATE

[1:0]

R/W

29H

spanning tree state for PORT 9

PORT9_STP_

STATE

[1:0]

R/W

2AH

spanning tree state for PORT 10

PORT10_STP

_STATE

[1:0]

R/W

2BH

spanning tree state for PORT 11

PORT11_STP

_STATE

[1:0]

R/W

2CH

spanning tree state for PORT 12

PORT12_STP

_STATE

[1:0]

R/W

2DH

spanning tree state for PORT 13

PORT13_STP

_STATE

[1:0]

R/W

2EH

spanning tree state for PORT 14

PORT14_STP

_STATE

[1:0]

R/W

2FH

spanning tree state for PORT 15

PORT15_STP

_STATE

[1:0]

R/W

80H

port 0 VLAN ID

The VLAN feature is enabled only when all port VID's are

configured to a valid (non-zero) VID.

PORT0_VID

[5:0]

R/W

82H

port 1 VLAN ID

PORT1_VID [5:0]

R/W

84H

port 2 VLAN ID

PORT2_VID [5:0]

R/W

86H

port 3 VLAN ID

PORT3_VID [5:0]

R/W

88H

port 4 VLAN ID

PORT4_VID [5:0]

R/W

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