KSZ8893M Datasheet, PDF (46/116 Pages) Micrel Semiconductor – Integrated 3-Port 10/100 Managed Switch with PHYs

Micrel, Inc.
KSZ8893MQL/MBL
For packets from regular ports (port 1 & port 2) to port 3, the port mask is used to tell the processor which port the
packets were received on, defined as follows:
“0001”, packet from port 1
“0010”, packet from port 2
No port mask values, other than the previous two defined ones, should be received in this direction in Special
Tagging Mode. The switch to processor egress rules are defined as follows:
Ingress Packets
Tagged with 0x8100 + TCI
Not tagged.
Egress Action to Tag Field
- Modify TPID to 0x810 + “port mask”, which indicates source port.
- No change to TCI if VID is not null
- Replace null VID with ingress port VID
- Recalculate CRC
- Insert TPID to 0x810 + “port mask”, which indicates source port
- Insert TCI with ingress port VID
- Recalculate CRC
Table 12. STPID Egress Rules (Switch Port 3 to Processor)
IGMP Support
For Internet Group Management Protocol (IGMP) support in layer 2, the KSZ8893MQL/MBL provides two
components:
IGMP Snooping
The KSZ8893MQL/MBL traps IGMP packets and forwards them only to the processor (port 3). The IGMP packets
are identified as IP packets (either Ethernet IP packets, or IEEE 802.3 SNAP IP packets) with IP version = 0x4
and protocol version number = 0x2.
Multicast Address Insertion in the Static MAC Table
Once the multicast address is programmed in the Static MAC Table, the multicast session is trimmed to the
subscribed ports, instead of broadcasting to all ports.
To enable IGMP support, set register 5 bit [6] to ‘1’. Also, Special Tagging Mode needs to be enabled, so that the
processor knows which port the IGMP packet was received on. This is achieved by setting both register 11 bit [0]
and register 48 bit [2] to ‘1’.
IPv6 MLD Snooping
The KSZ8893MQL/MBL traps IPv6 Multicast Listener Discovery (MLD) packets and forwards them only to
processor (port 3). MLD snooping is controlled by register 5 bit 5 (MLD snooping enable) and register 5 bit 4
(MLD option).
With MLD snooping enabled, the KSZ8893MQL/MBL traps packets that meet all of the following conditions:
• IPv6 multicast packets
• Hop count limit = 1
• IPv6 next header = 1 or 58 (or = 0 with hop-by-hop next header = 1 or 58)
If the MLD option bit is set to “1”, the KSZ8893MQL/MBL traps packets with the following additional condition:
• IPv6 next header = 43, 44, 50, 51, or 60 (or = 0 with hop-by-hop next header = 43, 44, 50, 51, or
60)
For MLD snooping, Special Tagging Mode also needs to be enabled, so that the processor knows which port the
MLD packet was received on. This is achieved by setting both register 11 bit [0] and register 48 bit [2] to ‘1’.
February 2010
46
M9999-021110-1.6