7-55
Register Descriptions
RxAddressFilteringCtrl Register
Address filtering, which is controlled by the R
X
A
DDRESS
F
ILTERING
C
TRL
register and
various address filtering memories, determines which frames are accepted by the
AIC-6915 and passed to the driver. The frame’s destination address is compared against
the following three criteria. If the address matches any of these criteria, the frame is
accepted.
1
Perfect Address Match: The destination address is compared against 16 pre-
programmed addresses in the Perfect Address Table. In standard perfect filtering
mode (P
ERFECT
F
ILTERING
M
ODE
= 01), the frame is accepted if the destination
address matches any of the pre-programmed addresses. If a Network Interface Card
(NIC) has only one destination address, all of the addresses can be programmed the
same. Other options include accepting all frames except those with a matching
programmed address. Refer to the P
ERFECT
F
ILTERING
M
ODE
field for more
information.
2
Hash Address Match: The internal CRC computation logic in the AIC-6915 is
executed on each byte of the destination address in sequence, producing a 32-bit
CRC. The upper 9-bits of that CRC are used as an index into the hash table. If
HashFilteringMode is enabled, and the bit in the Hash Address Bit Table at the given
index is a ‘1’, the frame is accepted. Refer to the H
ASH
F
ILTERING
M
ODE
field for more
information.
3
Multicast and Broadcast frames Explicitly Accepted: The destination address is
either a broadcast or multicast address. The P
ASS
M
ULTI
C
AST
bit causes the
AIC-6915 to accept all multicast frames including broadcast frames. The
PassBroadcast bit causes the AIC-6915 to accept all broadcast frames. The
P
ASS
M
ULTICAST
E
XCEPT
B
ROADCAST
bit causes the AIC-6915 to pass all multicast
frames except broadcast frames.
Type: R/W
Internal Registers Subgroup: Ethernet Functional Registers
Byte Address: F4h - F7h
Note: Writing to the status bits has no effect.
