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April, 2002
L84302 Quad 4-Port Ethernet Controller - Technical Manual
Copyright 1997-2002 by LSI Logic Corporation. All rights reserved.
3.5.2 Preamble and SFD Stripping
The receive MAC strips the preamble and SFD from all receive packets
before they are sent to the receive FIFO for storage.
3.5.3 CRC Stripping
The receive MAC normally strips the FCS from the receive packet. The
device can be programmed to not strip the FCS field by setting the
receive CRC enable bit in the Configuration 1 register. When this bit is
set, the last four bytes of the packet containing the CRC value are left
on the receive packet and are stored in the receive FIFO as part of the
packet.
3.5.4 Unicast Address Filter
Unicast packets are filtered by comparing the destination address of the
receive packet against the 48-bit value stored in the six Station Address
0-5 registers. When the destination address of a unicast packet matches
the value stored in these Station Address registers, the unicast packet is
deemed valid and passed to the receive FIFO; otherwise, the packet is
rejected. The correspondence between the bits in the Station Address
Registers and the incoming bits in the destination address of the receive
packet is defined in
Table 16
.
The device can be programmed to disable the unicast address filter
function and reject all unicast packets, regardless of their address, by
appropriately setting the receive address match select bits in the RX
Command register.
The device can also be programmed to ignore the last 4 bits of the
receive destination address when comparing the DA to the SA for unicast
packets. This mode can be enabled by setting the group address mode
enable bit in the Configuration 1 register.
The reception of MAC Control frames is unaffected by any of the unicast
packet address filtering functions and is controlled by other bits
described in the
Section 3.16, “MAC Control Frames,” page 52
.
3.5.5 Multicast Address Filter
Multicast packets can be filtered by processing the destination address
with the multicast address filter function. The multicast address filter