SMSC LAN9420 - Manual (Page 125)

Single-Chip Ethernet Controller with HP Auto-MDIX Support and PCI Interface
Datasheet
SMSC LAN9420/LAN9420i 125 Revision 1.22 (09-25-08)
DATASHEET
4.4.4 Multicast Hash Table High Register (HASHH)
The 64-bit Multicast table is used for group address filtering. For hash filtering, the contents of the
destination address in the incoming frame is used to index the contents of the Hash table. The most
significant bit determines the register to be used (Hi/Low), while the other five bits determine the bit
within the register. A value of 00000 selects Bit 0 of the Multicast Hash Table Lo register and a value
of 11111 selects the Bit 31 of the Multicast Hash Table Hi register.
If the corresponding bit is 1, then the multicast frame is accepted. Otherwise, it is rejected. If the “Pass All
Multicast” (MCPAS) bit is set (1), then all multicast frames are accepted regardless of the multicast hash
values.
The Multicast Hash Table Hi register contains the higher 32 bits of the hash table and the Multicast
Hash Table Low register contains the lower 32 bits of the hash table.
Offset: 008Ch Size: 32 bits
BITS DESCRIPTION TYPE DEFAULT
31-0 Upper 32 bits of the 64-bit Hash Table R/W 32‘h0