Chapter 11. Ethernet Module
11-7
FEC Frame Transmission
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.
.
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].
Destination
Address Type
FEC Address Processing
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.
Table 11-3. Ethernet Address Recognition
Содержание DigitalDNA ColdFire MCF5272
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