MU9C4320L データシートの表示（PDF） - Music Semiconductors

部品番号

コンポーネント説明

メーカー

MU9C4320L

ATMCAM

Music Semiconductors 

Operational Overview

MU9C4320L ATMCAM

The VP Table contains 4K entries, corresponding to the 12

bits in the VPI field of the ATM header. In a multiple

device system, only the lowest-priority device holds the

VP Table. A hit in the VP Table takes lower priority than a

match in the CAM array where the VPI/VCI fields are

compared associatively. If there is a mismatch in the CAM

array, but a hit in the VP Table, the VPI value is driven

onto the Address Output bus. Flags indicate whether a

CAM match or VP Table hit has occurred.

The VP Table eliminates the need to do two sequential

compares, one on the full VPI/VCI fields, and the other on

the VPI fields. The test of both sets of fields is

accomplished by the ATMCAM in a single compare cycle.

The validity of a location in the CAM array is determined

by an extra bit called the Validity bit. This bit is set and

reset either with an address or an associative match.

Therefore, when a new VPI/VCI entry is written to the

CAM, its Validity bit is set valid.

When a connection is removed, the Validity bit for that

entry is reset, and the address of the location is driven onto

the Active Address bus. This simple mechanism allows

easy maintenance of the connection list in both the CAM

array and the external RAM.

The ATMCAM supports simple daisy chained vertical

cascading that serves to prioritize multiple devices and

provides system-level match and full indication. If the

slight timing overhead associated with the daisy chain is

unacceptable in the fastest systems, the ATMCAM is

designed to facilitate external prioritization across

multiple devices.

Rev. 3

3

Share Link: