Datasheet
KSZ8863MLL/FLL/RLL
DS00002335B-page 28 2017 Microchip Technology Inc.
Software action: The processor should program the static MAC table with the entries that it needs to receive (for exam-
ple, BPDU packets). The “overriding” bit should be set so that the switch forwards those specific packets to the proces-
sor. The processor may send packets to the port(s) in this state, see Section 3.7, "Tail Tagging Mode" for details.
Address learning is enabled on the port in this state.
Ports in Forwarding states fully participate in both data forwarding and MAC learning.
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 (for exam-
ple, BPDU packets). The “overriding” bit should be set so that the switch forwards those specific packets to the proces-
sor. The processor may send packets to the port(s) in this state, see Section 3.7, "Tail Tagging Mode" for details.
Address learning is enabled on the port in this state.
RSTP uses only one type of BPDU called RSTP BPDUs, which are similar to STP Configuration BPDUs with the excep-
tion of a type field set to “version 2” for RSTP and “version 0” for STP, and a flag field carrying additional information.
3.7 Tail Tagging Mode
The Tail Tag is only seen and used by the port 3 interface, which should be connected to a processor. It is an effective
way to retrieve the ingress port information for spanning tree protocol IGMP snooping and other applications. Bit 1 and
bit 0 in the one byte tail tagging is used to indicate the source or destination port in port 3. Bit 3 and bit 2 are used for
the priority setting of the ingress frame in port 3. Other bits are not used. The Tail Tag feature is enabled by setting reg-
ister 3 bit 6.
FIGURE 3-7: TAIL TAG FRAME FORMAT
TABLE 3-13: TAIL TAG RULES
Ingress to Port 3 (Host to KSZ8863)
Bit [1,0] Destination Port
0,0 Normal (address lookup)
0,1 Port 1
1,0 Port 2
1,1 Port 1 and 2
Bit [3,2] Frame Priority
0,0 Priority 0
0,1 Priority 1
1,0 Priority 2
1,1 Priority 3
Egress from Port 3 (KSZ8863 to Host)
Bit [0] Source Port
0Port 1
1Port 2
Preamble DA TCI
866 2
length LLC Data Tail Tag
2 46-1500 1
FCS
4
Bytes 2
SA VPID