LAN9353 Datasheet, PDF (208/523 Pages) Microchip Technology – Interfaces at up to 200Mbps via Turbo MII

LAN9353
Aging can be disabled by clearing the ALR Age Enable field of the Switch Engine ALR Configuration Register (SWE_AL-
R_CFG).
10.3.1.2 Static Entries
If a MAC address entry is manually added by the host CPU, it can be (and typically is) marked as Static. Static entries
are not subjected to the aging process. Static entries also cannot be changed by the learning process (including migra-
tion).
10.3.1.3 Multicast Pruning
The destination port that is returned as a result of a destination MAC address lookup may be a single port or any com-
bination of ports. The latter is used to setup multicast address groups. An entry with a multicast MAC address would be
entered manually by the host CPU with the appropriate destination port(s). Typically, the Static bit should also be set to
prevent automatic aging of the entry.
10.3.1.4 Broadcast Entries
If desired, the host CPU can manually add the broadcast address of 0xFFFFFFFFFFFF. This feature is enabled by set-
ting the Allow Broadcast Entries field of the Switch Engine ALR Configuration Register (SWE_ALR_CFG). Typically, the
Static bit should also be set in the ALR entry to prevent automatic aging of the entry.
10.3.1.5 Address Filtering
Filtering can be performed on a destination MAC address. Such an entry would be entered manually by the host CPU
with the Filter bit active. Typically, the Static bit should also be set to prevent automatic aging of the entry.
Note:
To meet the IEEE 802.1 Filtering Database requirements, the MAC addresses of 01-80-C2-00-00-01
through 01-80-C2-00-00-0F should be added into the ALR address table as filtering entries by either
EEPROM sequence or by software. The MAC address of 01-80-C2-00-00-00 is typically added as a for-
warding entry to direct BPDU frames to the host CPU.
10.3.1.6 Spanning Tree Port State Override
A special spanning tree port state override setting can be applied to MAC address entries. When the host CPU manually
adds an entry with both the Static and Age 1/Override bits set, packets with a matching destination address will bypass
the spanning tree port state (except the Disabled state) and will be forwarded. This feature is typically used to allow the
reception of the BPDU packets while a port is in the non-forwarding state. Refer to Section 10.3.5, "Spanning Tree Sup-
port," on page 214 for additional details.
10.3.1.7 MAC Destination Address Lookup Priority
If enabled, globally via the DA Highest Priority field in the Switch Engine Global Ingress Configuration Register (SWE_-
GLOBAL_INGRSS_CFG) along with the, per entry, Priority Enable bit, the transmit priority for MAC address entries is
taken from the associated data of that entry.
10.3.1.8 ALR Result Override
Results from the ALR Destination MAC lookup can be overridden on a per port basis. This feature is enabled by setting
the appropriate ALR Override Enable bit in the Switch Engine ALR Override Register (SWE_ALR_OVERRIDE). When
enabled, the destination port from the ALR Destination MAC Address lookup is replaced with the appropriate ALR Over-
ride Destination field in the Switch Engine ALR Override Register (SWE_ALR_OVERRIDE).
The ALR Spanning Tree Override, Static, Filter and Priority results for the Destination MAC Address are still used.
Note: Forwarding rules described in Section 10.3.2 are still followed.
10.3.1.9 Host Access
Note: Refer to Section 10.7.3.1, on page 286 through Section 10.7.3.6, on page 293 for detailed definitions of the
registers.
ADD, DELETE, AND MODIFY ENTRIES
The ALR contains a learning engine that is used by the host CPU to add, delete and modify the MAC Address Table.
This engine is accessed by using the Switch Engine ALR Command Register (SWE_ALR_CMD), the Switch Engine
ALR Command Status Register (SWE_ALR_CMD_STS), the Switch Engine ALR Write Data 0 Register (SWE_AL-
R_WR_DAT_0) and the Switch Engine ALR Write Data 1 Register (SWE_ALR_WR_DAT_1).
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