Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 768

SCC Ethernet Mode
Broadcast
True
Enabled
Receive Frame
Ignore REJECT
In group address recognition, the controller determines whether the group address is a broadcast address.
If broadcast addresses are enabled, the frame is accepted, but if the group address is not a broadcast
address, address recognition can be performed on multiple group addresses using the GADDRn hash table.
In promiscuous mode, the controller receives all incoming frames regardless of their address.
27.11 Hash Table Algorithm
Individual and group hash filtering operate using certain processes. The ethernet controller maps any
48-bit address into one of 64 bins, each represented by a bit stored in GADDRx or IADDRx. When a
command is executed, the ethernet controller maps the selected 48-bit address into one
GROUP ADDRESS
of the 64 bits by passing the 48-bit address through the on-chip 32-bit CRC generator and selecting 6 bits
27-12
Broadcast
True False
Address
?
Hash Search
False
Use Group
?
Match
False
PROMISC
Discard Frame
Figure 27-4. Ethernet Address Recognition Flowchart
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Check Address
G
I/G Address
?
Multiple Individual
Addresses
Table
True True
?
False
Receive Frame
Ignore REJECT
True
?
Start Receive
Discard Frame if REJECT
is Asserted
I
True
Multiple IND
?
False
Hash_Search
Use Indicated
Table
Single
Address
Match
?
False
False
Match
?
True
Receive Frame
Ignore REJECT
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