MU9C8338A datasheet(2/32 Pages) MUSIC

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MU9C8338A 10/100Mb Ethernet Filter Interface

General Description

2Rev. 0a

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.

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

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.

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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