High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface

Datasheet

Table 9.1 Address Filtering Modes

MCPAS

PRMS

INVFILT

HO

HPFILT

DESCRIPTION

 

 

 

 

 

 

0

0

0

0

0

MAC address perfect filtering only

 

 

 

 

 

for all addresses.

 

 

 

 

 

 

0

0

0

0

1

MAC address perfect filtering for

 

 

 

 

 

physical address and hash filtering

 

 

 

 

 

for multicast addresses

 

 

 

 

 

 

0

0

0

1

1

Hash Filtering for physical and

 

 

 

 

 

multicast addresses

 

 

 

 

 

 

0

0

1

0

0

Inverse Filtering

 

 

 

 

 

 

X

1

0

X

X

Promiscuous

 

 

 

 

 

 

1

0

0

0

X

Pass all multicast frames. Frames

 

 

 

 

 

with physical addresses are

 

 

 

 

 

perfect-filtered

 

 

 

 

 

 

1

0

0

1

1

Pass all multicast frames. Frames

 

 

 

 

 

with physical addresses are hash-

 

 

 

 

 

filtered

 

 

 

 

 

 

9.4.1Perfect Filtering

This filtering mode passes only incoming frames whose destination address field exactly matches the value programmed into the Host MAC Address High Register (HMAC_ADDRH) and the Host MAC Address Low Register (HMAC_ADDRL). The MAC address is formed by the concatenation of these two registers.

9.4.2Hash Only Filtering

This type of filtering checks for incoming receive packets (from switch Port 0) with either multicast or physical destination addresses, and executes an imperfect address filtering against the hash table. The hash table is formed by merging the values in the Host MAC Multicast Hash Table High Register (HMAC_HASHH) and the Host MAC Multicast Hash Table Low Register (HMAC_HASHL) to form a 64-bit hash table.

During imperfect hash filtering, the upper 6-bits of the destination address of the incoming frame are used to index the contents of the hash table. The most significant bit of the destination address determines the register to be used (HMAC_HASHH or HMAC_HASHL), while the other five bits determine the bit within the register. A value of 00000 selects Bit 0 of the HMAC_HASHL register and a value of 11111 selects Bit 31 of the HMAC_HASHH register.

9.4.3Hash Perfect Filtering

In hash perfect filtering, if the received frame is a physical address, the Host MAC packet filter will perfect-filter the incoming frame’s destination field with the value programmed into the Host MAC Address High Register (HMAC_ADDRH) and the Host MAC Address Low Register (HMAC_ADDRL). However, if the incoming frame is a multicast frame, the Host MAC packet filter function performs an imperfect address filtering against the hash table.

The imperfect filtering against the hash table is the same imperfect filtering process described in Section 9.4.2, "Hash Only Filtering".

SMSC LAN9312

115

Revision 1.4 (08-19-08)

 

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