Datasheet

Micrel, Inc. KS8995MA/FQ
October 2011 68 M9999-102611-3.0
VLAN Address
The VLAN table is used for VLAN table look-up. If 802.1q VLAN mode is enabled (Register 5 Bit 7 = 1), this table is used
to retrieve VLAN information that is associated with the ingress packet. The information includes FID (filter ID), VID (VLAN
ID), and VLAN membership described below:
Address Name Description Mode Default
Format of Static VLAN Table (16 entries)
21 Valid
1, the entry is valid.
0, entry is invalid.
R/W 1
20 − 16
Membership
Specify which ports are members of the VLAN.
If a DA look-up fails (no match in both static and dynamic tables), the packet
associated with this VLAN will be forwarded to ports specified in this field.
E.g., 11001 means port 5, 4, and 1 are in this VLAN.
R/W 11111
15 − 12
FID
Filter ID. KS8995MA/FQ supports 16 active VLANs represented by these four
bit fields. FID is the mapped
ID. If 802.1q VLAN is enabled, the look-up will be based on FID+DA and
FID+SA.
R/W 0
11 − 0
VID IEEE 802.1q 12 bit VLAN ID. R/W 1
If 802.1q VLAN mode is enabled, KS8995MA/FQ assigns a VID to every ingress packet. If the packet is untagged or
tagged with a null VID, the packet is assigned with the default port VID of the ingress port. If the packet is tagged with
non-null VID, the VID in the tag is used. The look-up process starts from the VLAN table look-up. If the VID is not valid,
the packet is dropped and no address learning occurs. If the VID is valid, the FID is retrieved. The FID+DA and FID+SA
lookups are performed. The FID+DA look-up determines the forwarding ports. If FID+DA fails, the packet is broadcast to
all the members (excluding the ingress port) of the VLAN. If FID+SA fails, the FID+SA is learned.
VLAN Table Read Example
(1) VLAN Table Read (read the 3rd entry)
Write to Register 110 with 0x14 (read VLAN table selected)
Write to Register 111 with 0x2 (trigger the read operation)
Then,
Read Register 118 (VLAN table bits 21-16)
Read Register 119 (VLAN table bits 15-8)
Read Register 120 (VLAN table bits 7-0)
VLAN Table Write Example
(2) VLAN Table Write (write the 7th entry)
Write to Register 118 (VLAN table bits 21-16)
Write to Register 119 (VLAN table bits 15-8)
Write to Register 120 (VLAN table bits 7-0)
Write to Register 110 with 0x04 (write VLAN table selected)
Write to Register 111 with 0x6 (trigger the write operation)
Note:
The sequence of the writing entries should start from entry 0. Improper sequence of the VLAN entries could cause the VLAN to be non-functional.