KS8995MA-EVAL Micrel Inc, KS8995MA-EVAL Datasheet - Page 32

• Manufacturer Part Number: KS8995MA-EVAL
• Description: BOARD EVAL EXPERIMENT KS8995MA
• Manufacturer: Micrel Inc

Specifications of KS8995MA-EVAL

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 576-1018

Semptember 2008
Learning state: only packets to and from the processor are forwarded. Learning is enabled.
Port setting: “transmit enable = 0, receive enable = 0, learning disable = 0.”
Software action: The processor should program the static MAC table with the entries that it needs to receive (e.g.,
BPDU packets). The “overriding” bit should be set so that the switch will forward those specific packets to the
processor. The processor may send packets to the port(s) in this state, see “Special Tagging Mode” section for
details. Address learning is enabled on the port in this state.
Forwarding state: packets are forwarded and received normally. Learning is enabled.
Port setting: “transmit enable = 1, receive enable = 1, learning disable = 0.”
Software action: The processor should program the static MAC table with the entries that it needs to receive (e.g.,
BPDU packets). The “overriding” bit should be set so that the switch will forward those specific packets to the
processor. The processor may send packets to the port(s) in this state, see “Special Tagging Mode” section for
details. Address learning is enabled on the port in this state.
Special Tagging Mode
The special tagging mode is designed for spanning tree protocol IGMP snooping and is flexible for use in other
applications. The special tagging mode, similar to 802.1q, requires software to change network drivers to
insert/modify/strip/interpret the special tag. This mode is enabled by setting both Register 11 bit 0 and Register 80 bit
2.
The STPID will only be seen and used on the port 5 interface, which should be connected to a processor. Packets
from the processor to the switch should be tagged with STPID and the port mask defined as below:
“0000” normal tag, will use the KS8995MA/FQ internal look-up result. Normal packets should use this setting. If
packets from the processors do not have a tag, the KS8995MA/FQ will treat them as normal packets and an internal
look-up will be performed.The KS8995MA/FQ uses a non-zero “port mask” to bypass the look-up result and override
any port setting, regardless of port states (blocking, disable, listening, learning). Table 5 shows the egress rules
when dealing with STPID.
802.1q Tag Format
TPID (tag protocol identifier, 0x8100) + TCI
“0001” packet to port 1 only
“0010” packet to port 2 only“0100” packet to port 3 only
“1000” packet to port 4 only
“0011” packet broadcast to port 1 and port 2
......
“1111” packet broadcast to port 1, 2, 3 and 4.
Table 4. Special Tagging Mode Format
Special Tag Format
STPID (special tag identifier, 0x8100) + TCI 0x810 + 4 bit for “port mask”) + TCI
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