MU9C8338 10/100Mb Ethernet Filter Interface
General Description
GENERAL DESCRIPTION
The MU9C8338, 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 MU9C8338, the best way
to approach the feature set of the device is to first look at a
typical 10/100Mb Ethernet application. The MU9C8338
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 MU9C8338 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 are not processed by the system. Instead
they are identified and their classification is stored in the
Result register. Once processing completes, the Result
register is accessed through the Result port or Processor
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.
Typical MU9C8338 Application
The MU9C8338 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
MU9C8338 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
MU9C8338/LANCAM combination. The MU9C8338
transfers the DA and SA to the CAMs for comparison. The
results of MU9C8338/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
2
Rev. 1a
MUSIC [ MUSIC SEMICONDUCTORS ]
