KS8995MAL Micrel Inc, KS8995MAL Datasheet - Page 30

• Manufacturer Part Number: KS8995MAL
• Description: IC SWITCH 10/100 5PORT 128PQFP
• Manufacturer: Micrel Inc

Specifications of KS8995MAL

• Applications: *
• Mounting Type: Surface Mount
• Package / Case: 128-MQFP, 128-PQFP
• For Use With: 576-1017 - BOARD EVAL EXPERIMENT KS8995M
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

KS8995MA
M9999-051305
For packets from regular ports (port 1 - port 4) to port 5, the port mask is used to tell the processor which port the packet was
received on, defined as:
No values other than the previous four defined should be received in this direction in the special mode. Table 6 shows the egress
rule for this direction.
IGMP Support
There are two parts involved to support IGMP in Layer 2. The first part is “IGMP” snooping. The switch will trap IGMP packets
and forward them only to the processor port. The IGMP packets are identified as IP packets (either Ethernet IP packets or IEEE
802.3 SNAP IP packets) AND IP version = 0x4 AND protocol number = 0x2. The second part is “multicast address insertion”
in the static MAC table. Once the multicast address is programmed in the static MAC table, the multicast session will be trimmed
to the subscribed ports, instead of broadcasting to all ports. To enable this feature, set Register 5 bit 6 to 1. Also “special tag
mode” needs to be enabled, so that the processor knows which port the IGMP packet was received on. Enable “special tag
mode” by setting both Register 11 bit 0 and Register 80 bit 2.
Ingress Tag Field
(0x810+ port mask)
(0x810+ port mask)
(0x810+ port mask)
(0x810+ port mask)
Not tagged
Ingress Packets
Tagged with 0x8100 + TCI
Not tagged
“0001” from port 1,
“0010” from port 2,
“0100” from port 3,
“1000” from port 4
“Tag Insertion”
Table 5. STPID Egress Rules (Processor to Switch Port 5)
Don’t care
Tx Port
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 6. STPID Egress Rules (Switch to Processor)
0
0
1
1
“Tag Removal”
Don’t care
Tx Port
0
1
0
1
30
Egress Action to Tag Field
• Modify tag field to 0x8100.
• Recalculate CRC.
• No change to TCI if not null VID.
• Replace VID with ingress (port 5) port VID if null VID.
• (STPID + TCI) will be removed.
• Padding to 64 bytes if necessary.
• Recalculate CRC.
• Modify tag field to 0x8100.
• Recalculate CRC.
• No change to TCI if not null VID.
• Replace VID with ingress (port 5) port VID if null VID.
• Modify tag field to 0x8100.
• Recalculate CRC.
• No change to TCI if not null VID.
• Replace VID with ingress (port 5) port VID if null VID.
Determined by the dynamic MAC address table.
Micrel, Inc.
May 2005