LAN9303 datasheet(85/366 Pages) SMSC

85 / 366 page

Small Form Factor Three Port 10/100 Managed Ethernet Switch with Single MII/RMII/Turbo MII

Datasheet

SMSC LAN9303/LAN9303i

Revision 1.3 (08-27-09)

DATASHEET

For clarity, the following details the incoming un-tag instruction. As described in Section 6.4.4, "VLAN

Support," on page 74, the un-tag instruction is the three un-tag bits from the applicable entry in the

VLAN table. The entry in the VLAN table is either the VLAN from the received packet or the ingress

port’s default VID.

When a received packet is non-tagged, a new VLAN tag is added if two conditions are met. First,

the Insert Tag bit for the egress port in the Buffer Manager Egress Port Type Register

(BM_EGRSS_PORT_TYPE) must be set. Second, the un-tag bit, for the egress port, from the un-

tag instruction associated with the ingress port’s default VID, must be cleared. The VLAN tag that

is added will have a VID taken from either the ingress or egress port’s default VID. The priority of

the VLAN tag is either the priority calculated on ingress or the egress port’s default. The choice of

ingress or egress is determined by the egress port’s VID/Priority Select bit in the Buffer Manager

Egress Port Type Register (BM_EGRSS_PORT_TYPE).

When a received packet is priority-tagged, either the tag is removed or it is modified.

If the un-tag bit, for the egress port, from the un-tag instruction associated with the ingress port’s

default VID is set, then the tag is removed.

Otherwise, the tag is modified. The VID of the new VLAN tag is changed to either the ingress or

egress port’s default VID. If the Change Priority bit in the Buffer Manager Egress Port Type Register

(BM_EGRSS_PORT_TYPE) for the egress port is set, then the Priority field of the new VLAN tag

is also changed. The priority of the VLAN tag is either the priority calculated on ingress or the

egress port’s default. The choice of ingress or egress is determined by the egress port’s

VID/Priority Select bit.

When a received packet is normal-tagged, either the tag is removed, modified, or passed

unchanged.

If the un-tag bit, for the egress port, from the un-tag instruction associated with the VID in the

received packet is set, then the tag is removed.

Else, if the Change Tag bit in the Buffer Manager Egress Port Type Register

(BM_EGRSS_PORT_TYPE) for the egress port is clear, the packet passes untouched.

Else, if both the Change VLAN ID and the Change Priority bits in the Buffer Manager Egress Port

Type Register (BM_EGRSS_PORT_TYPE) for the egress port are clear, the packet passes

untouched.

Otherwise, the tag is modified. If the Change VLAN ID bit for the egress port is set, the VID of the

new VLAN tag is changed to either the ingress or egress port’s default VID. If the Change Priority

bit for the egress port is set, the Priority field of the new VLAN tag is changed to either the priority

calculated on ingress or the egress port’s default. The choice of ingress or egress is determined

by the egress port’s VID / Priority Select bit.

When a packet is received special-tagged from a CPU port, the special tag is removed.

LAN9303 Datasheet(PDF) 85 Page - SMSC Corporation