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Chapter 3: Client, Host, and MDIO Interfaces
Address Filtering
The address filtering block accepts or rejects frames by examining the destination address
of an incoming frame. This block includes:
•
•
•
•
•
The Address Filter (AF) protects the client from extraneous traffic. With this technique, the
hardware matches the Destination Address (DA) field of the Ethernet MAC frame. This
relieves the task from the bus and software.
The AF is programmed in software through the host interface. Typically this includes
unicast and multicast addresses. Pause-frame addresses and broadcast address are
hardwired; they do not need to be programmed. The AF can be enabled and disabled
under software control, using an enable bit in the control register. See
Registers," page 80
When the function is enabled, Ethernet frames are passed to the client interface only if they
pass the filter. When the AF function is disabled, all incoming RX frames are passed to the
client interface.
For system monitoring, the event of a frame failing the filter is signaled. Equally, when a
frame passes the filter, a match is indicated to the client by using the output pins
EMAC#CLIENTRXDVLD and EMAC#CLIENTRXFRAMEDROP together.
shows the values of the two signals for possible outcomes of an incoming RX frame when
the AF is enabled.
promiscuous mode).
When the AF is enabled, it is impossible to determine if there is an incoming RX frame or
if the AF has rejected incoming RX frames (using only EMAC#CLIENTRXDVLD) because
in both cases, the EMAC#CLIENTRXDVLD is deasserted. See
the EMAC#CLIENTRXFRAMEDROP signal, the nature of an incoming RX frame can be
distinguished for system monitoring.
Table 3-2:
EMAC#CLIENTRXDVLD and EMAC#CLIENTRXFRAMEDROP Values When AF is Enabled
EMAC#CLIENTRXDVLD
0
0
1
1
Table 3-3: EMAC#CLIENTRXDVLD and EMAC#CLIENTRXFRAMEDROP Values When AF is Disabled
EMAC#CLIENTRXDVLD
0
0
1
1
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58
Programmable unicast destination address matching
Four programmable multicast address matching
Broadcast address recognition (0xFFFF_FFFF_FFFF)
Optional pass-through mode with address filter disabled (promiscuous mode)
Pause control frame address recognition (0x0100_00C2_8001)
for the control register.
Table 3-3
shows the two signal values when the AF is disabled (in
EMAC#CLIENTRXFRAMEDROP
0
1
0
1
EMAC#CLIENTRXFRAMEDROP
0
1
0
1
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Table
Result of an Incoming RX Frame
No incoming RX frame
AF rejects RX frame
AF passes RX frame
N/A
Result of an Incoming RX Frame
No incoming RX frame
N/A
AF passes RX frame
AF rejects RX frame
Embedded Tri-Mode Ethernet MAC User Guide
UG074 (v2.2) February 22, 2010
R
"Address Filter
Table 3-2
3-2. However, using
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