ACD80800 Datasheet, PDF (4/19 Pages) List of Unclassifed Manufacturers – Address Resolution Logic (8K MAC Addresses)

3. FUNCTIONAL DESCRIPTION
ACD80800 provides Address Resolution service for
ACD’s switch controller chip. ACD80800 provides a
glueless interface with ACD’s switch controller, and is
used to build an address table and provide address lookup
service to ACD’s switch controller. Figure 2 is a block
diagram of ACD80800.
Traffic Snooping
Learning Engine will first determine whether the frame
is a valid frame. For a valid frame, it will first try to find
the source address from the current address table. If
that address doesn’t exist, or if it does exist but the port
ID associated with the MAC address is not the ingress
port, the address will be learned into the address table.
After an address is learned by the address learning
engine, the CPU will be notified to read this newly learned
address so that it can add it into the CPU’s address
table.
All Ethernet frames received by ACD’s switch controller
have to be stored into memory buffer. As the frame
data are written into memory, the status of the data
shown on the data bus are displayed by ACD’s switch
controller through a state bus. ACD80800’s Switch Con-
troller Interface contains the signals of the data bus and
the state bus. By snooping the data bus and the state
bus of ACD’s switch controller, ACD80800 can detect
the occurrence of any destination MAC address and
source MAC address embedded inside each frame.
Address Learning
Address Aging
After each source address is learned into the address
table, it has to be refreshed at least once within each
address aging period. Refresh means it is caught again
from the switch interface. If it has not occurred for a
pre-set aging period, the address aging engine will re-
move the address from the address table. After an ad-
dress is removed by the address aging engine, the CPU
will be notified through interrupt request that it needs to
read this aged out address so that it can remove this
address from the CPU’s address table.
Each source address caught from the data bus, to- Address Lookup
gether with the ID of the ingress port, is passed to the
Address Learning Engine of ACD80800. The Address Each destination address is passed to the Address
Figure-2. ACD80800 Block Diagram
Switch Interface
CPU Interface
Address
Learning
Engine
Address
Aging
Engine
Address
Lookup
Engine
CPU Interface Engine
Address Table
(8K Entries)
4