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11.4.3 Ethernet Address Recognition
The FEC filters the received frames based on the type of destination media access controller
address (hardware address). There are three destination address (DA) types:
• Individual (unicast)
• Group (multicast)
• Broadcast (all-ones group address).
The difference between an individual address and a group address is determined by the I/G
bit in the destination address field. A flowchart for address recognition on received frames
is illustrated in Figure 11-4 and summarized in Table 11-3, below.
.
Destination
Address Type
individual
The FEC compares the destination address field of the received frame with the 48-bit MAC address
programed into ADDR_LOW and ADDR_HIGH.
group
The FEC determines whether or not the group address is a broadcast address. If not broadcast, a
hash table lookup is performed using the 64-entry hash table defined in HASH_TABLE_LOW and
HASH_TABLE_HIGH.
broadcast
The frame is accepted unconditionally.
In promiscuous mode (PROM = 1 in R_CNTRL), the FEC receives all of the incoming
frames regardless of their address. In this mode, the destination address lookup is still
performed and RxBD[MISS] is set accordingly. If address recognition did not achieve a
match, the frame is received with RxBD[MISS] set. If address recognition achieves a
match, the frame is received without setting RxBD[MISS].
FEC Address Processing
Table 11-3. Ethernet Address Recognition
Chapter 11. Ethernet Module
FEC Frame Transmission
11-7
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