91C100FDREVB Datasheet, PDF (34/68 Pages) SMSC Corporation – FEAST FAST ETHERNET CONTROLLER WITH FULL DUPLEX CAPABILITY

BANK3
OFFSET
0 THROUGH 7
NAME
MULTICAST TABLE
TYPE
READ/WRITE
SYMBOL
MT
LOW
BYTE
MULTICAST TABLE 0
0
0
0
0
0
0
0
0
HIGH
BYTE
MULTICAST TABLE 1
0
0
0
0
0
0
0
0
LOW
BYTE
MULTICAST TABLE 2
0
0
0
0
0
0
0
0
HIGH
BYTE
MULTICAST TABLE 3
0
0
0
0
0
0
0
0
LOW
BYTE
MULTICAST TABLE 4
0
0
0
0
0
0
0
0
HIGH
BYTE
MULTICAST TABLE 5
0
0
0
0
0
0
0
0
LOW
BYTE
MULTICAST TABLE 6
0
0
0
0
0
0
0
0
HIGH
BYTE
MULTICAST TABLE 7
0
0
0
0
0
0
0
0
The 64 bit multicast table is used for group address filtering. The hash value is defined as the six most significant bits of the
CRC of the destination addresses. The three msb's determine the register to be used (MT0-MT7), while the other three
determine the bit within the register.
If the appropriate bit in the table is set, the packet is received.
If the ALMUL bit in the RCR register is set, all multicast addresses are received regardless of the multicast table values.
Hashing is only a partial group addressing filtering scheme, but being the hash value available as part of the receive status
word, the receive routine can reduce the search time significantly. With the proper memory structure, the search is limited
to comparing only the multicast addresses that have the actual hash value in question.
SMSC DS – LAN91C100FD REV. B
Page 34
Rev. 05/31/2000