MU9C8338A 10/100Mb Ethernet Filter Interface
General Description
GENERAL DESCRIPTION
The MU9C8338A, when configured with the MUSIC
Semiconductors MU9Cx480B family of LANCAMs
provides a high performance, large capacity Ethernet
address processing subsystem for use in Ethernet bridge,
switch, or remote access products. The device is designed
to work in single-port system supporting a 100Mb/s
Ethernet port at wire speed.
OPERATIONAL OVERVIEW
Because of the flexibility of the MU9C8338A, the best
way to approach the feature set of the device is to first
look at a typical 10/100Mb Ethernet application. The
MU9C8338A captures the Destination address (DA) and
the Source address (SA) of an incoming Ethernet frame on
the MII port. After checking for a frame error or collision,
the DA is processed and the result (associated data,
usually a port ID) is made available. The SA then is
checked, and either learned if new, or aged if already in the
list.
for the MII port to relay the Tag ID to the system for
systems that support Tag switching.
When the DA is processed, the MU9C8338A first checks
if the frame is Unicast, Multicast, or Broadcast. Unicast
frames destined for the same collision domain (visible on
the same switch port as it came in on) are rejected. If the
DA is found in the CAM database, the port ID associated
with it is stored in the Result register. Multicast and
Broadcast frames may also be processed by the system if
the MU9C8338A is configured to do so. When Multicast
is enabled, a default action is configured which causes
frames with unknown group addresses to be processed
correctly. Once processing completes, the Result register
is accessed through the Result port or Processor port.
Typical MU9C8338A Application
The MU9C8338A plays an integral role in the example of
an Ethernet bridge system, shown in Figure 1.
This system can handle up to 32,768 addresses on a
bidirectional 100Mb Ethernet port by utilizing the
MU9C8338A device and four LANCAMs connected as
shown in Figure 1. The MII bus is "tapped" to collect
packet data as it passes from the Ethernet PHY to the
MAC. That data is processed automatically by the
MU9C8338A/LANCAM combination. The MU9C8338A
transfers the DA and SA to the CAMs for comparison. The
results of MU9C8338A/LANCAM data processing are
available through the Result bus or through the Processor
bus. In addition to the Result bus, there is a serial Tag port
Provided the frame length is correct, and no errors are
detected, the SA is processed. If the SA exists in the CAM
database, the time stamp and Port ID are updated. If the
SA is not found in the CAM database, the address is
learned automatically, along with its Port ID and the
current time stamp information.
Address processing always has priority over management
routines, such as purging aged entries, inserting permanent
entries, deleting entries, or reading from the CAM
database.
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Rev. 0a
MUSIC [ MUSIC SEMICONDUCTORS ]
