SMSC LAN91C111 8.22Bank 3 - Multicast Table Registers, NAME, TYPE, OFFSET, SYMBOL, THROUG, READ/WRITE, MULTICAST TABLE

10/100 Non-PCI Ethernet Single Chip MAC + PHY

Datasheet

8.22Bank 3 - Multicast Table Registers

	OFFSET			NAME		TYPE		SYMBOL
0
	THROUG
	H 7		MULTICAST TABLE			READ/WRITE		MT
LOW					MULTICAST TABLE 0
BYTE
	0	0		0	0	0	0		0	0
HIGH					MULTICAST TABLE 1
BYTE
	0	0		0	0	0	0		0	0
LOW					MULTICAST TABLE 2
BYTE
	0	0		0	0	0	0		0	0
HIGH					MULTICAST TABLE 3
BYTE
	0	0		0	0	0	0		0	0
LOW					MULTICAST TABLE 4
BYTE
	0	0		0	0	0	0		0	0
HIGH					MULTICAST TABLE 5
BYTE
	0	0		0	0	0	0		0	0
LOW					MULTICAST TABLE 6
BYTE
	0	0		0	0	0	0		0	0
HIGH					MULTICAST TABLE 7
BYTE
	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.

Revision 1.91 (08-18-08) 66 SMSC LAN91C111 REV C

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