LAN9303MI-AKZE Datasheet, PDF (93/386 Pages) SMSC Corporation – Small Form Factor Three Port 10/100 Managed Ethernet Switch with Dual MII/RMII/Turbo MII

Small Form Factor Three Port 10/100 Managed Ethernet Switch with Dual MII/RMII/Turbo MII
Datasheet
For clarity, the following details the incoming un-tag instruction. As described in Section 6.4.4, "VLAN
Support," on page 82, 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.
SMSC LAN9303M/LAN9303Mi
93
DATASHEET
Revision 1.5 (07-08-11)