MDS212 Datasheet, PDF (54/111 Pages) Zarlink Semiconductor Inc – 12-Port 10/100Mbps Ethernet Switch

MDS212
Data Sheet
Note: P0 to P11 are used to identify the ports on the first chip, while P12 to P23 are used to identify the ports on the
second chip.
14.2.4.2 VLAN MAC Table
The size of this table is defined by VLMS subfield in BIT[8:7] of VTBP register. The base address of this table is
specified by VMACB subfield in BIT[15:9] of VTBP register. The VLAN MAC Table contains all associated VLANs
for each MAC Address learned by MDS212, and is used by the software to keep track of every MAC and its
associated VLANs. The contents of this table are set up by the Search Engine at the reception of incoming frames,
if the Search Engine is not fully occupied. When the Search Engine is too busy handling frame forwarding
decisions, microcode in the HISC engine will be assigned the setup new MAC to VLAN associations. Rows in this
table can be cleared up by microcode through a CPU software command during VLAN deletion or port link down. A
row in this table will be cleared and a new bit set up by the MDS212’s microcode, when the port change of a MAC
address is detected.
There are a total of 2K entries in this table, one entry per MAC. Each entry may consist of 256, 128 or 64 bits, one
bit per VLAN. The total size of the VLAN Table may be 64, 32, or 16KB. This table must be located at the boundary
of its own table size.
MAC
Handle
0 1 2 3...............................................
100
0
1
2
3
.
.
.
.
.
.
.
.
.
.
2K
256
VLAN
ID
Figure 20 - VLAN MAC Table
14.2.4.3 VLAN Port Mapping Table (VMAP)
The VLAN Port Mapping Table (VMAP) is an internal table within the MDS212. It contains 256 entries, one for each
VLAN, identified by an internal VLAN Index. This table can be accessed by CPU software through CPUIRCMD and
CPUIRDAT registers. The contents of this table are set up and maintained by CPU software during VLAN creation,
54
Zarlink Semiconductor Inc.