KSZ8895MLU_11 Datasheet, PDF (86/110 Pages) Micrel Semiconductor – Integrated 5-Port 10/100 Managed Switch

Micrel, Inc.
KSZ8895MLU
VLAN Table
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 fields includes FID (filter ID), Valid and VLAN
membership need initializtion, due to provide 4K spacing for the VLAN table, there is no VID filed bits, VID is used as
address index to input up to 4096 entries with bits [12:0] information.
Address
12
11  7
60
Name
Valid
Membership
FID
Description
1, the entry is valid.
0, entry is invalid.
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, port 4 and port 1.
Filter ID. KSZ8895MLU supports 128 active VLANs
represented by these seven bit fields. FID is the
mapped ID. If 802.1q VLAN is enabled, the look-up in
MAC table will be based on FID+DA and FID+SA.
Mode
R/W
R/W
R/W
Initial Value
suggestion
0
11111
0
Table 13. Format of Static VLAN Table (Support Max 4096 VLAN ID Entries and 128 Active VLANs)
If 802.1q VLAN mode is enabled, KSZ8895MLU assigns a VID to every ingress packet when 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 based on VID number. If
the entry is not valid in VLAN table, the packet is dropped and no address learning occurs. If the entry is valid, the FID is
retrieved. The FID+DA and FID+SA lookups in MAC tables are performed. The FID+DA look-up determines the
forwarding ports. If FID+DA fails for look-up in MAC table, the packet is broadcast to all the members or specified
members (excluding the ingress port) based on the VLAN table. If FID+SA fails, the FID+SA is learned. If want to
communicate between different active VLANs, set same FID, otherwise set different FID.
The VLAN table configuration is organized as 1024 VLAN sets, each VLAN set consists of 4 VLAN entries, to support up
to 4096 VLAN entries. Each VLAN set has 52 bits and should be read or written at the same time specified by the indirect
address.
The VLAN entries in the VLAN set is mapped to indirect data registers as follow:
Entry0[12:0] maps to the VLAN set bits[12  0] {register119[4:0], register120[7:0]}
Entry1[12:0] maps to the VLAN set bits[25  13]{register117[1:0], register118[7:0], register119[7:5]}
Entry2[12:0] maps to the VLAN set bits[38  26]{register116[6:0], register117[7:2]}
Entry3[12:0] maps to the VLAN set bits[51  39]{register114[3:0], register115[7:0], register116[7]}
October 2011
86
M9999-100311-1.1