MU9C4485A datasheet(2/28 Pages) MUSIC

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WidePort LANCAM® Family

Rev. 2

OPERATIONAL OVERVIEW

The MU9C4485A/L, MU9C2485A/L, and MU9C1485A/L

WidePort LANCAMs are 64-bit wide content-addressable

memories (CAMs), featuring a 32-bit wide interface. This

interface doubles the available I/O bandwidth in many

applications while maintaining the same powerful enhanced

architecture and instruction set as the MU9C2480A/L.

Content-addressable memories, also known as associative

memories, operate in the converse way to random access

memories (RAM). In a RAM, the input to the device is an

address and the output is the data stored at that address. In a

CAM, the input is a data sample and the output is a flag to

indicate a match and the address of the matching data. As a

result, a CAM searches large databases for matching data in a

short, constant time period, no matter how many entries are in

the database. The ability to search data words up to 64 bits

wide allows large address spaces to be searched rapidly and

efficiently. A patented architecture links each CAM entry to

associated data and makes this data available for use after a

successful compare operation.

While the WidePort LANCAMs are optimized for LAN network

address filtering, they are also well suited for applications that

require high-speed data searching, such as virtual memories

and cache management, data compression and encryption,

database accelerators, and image processing.

Skip Bit

Empty Bit

Entry Type

Valid

Empty

Skip

RAM

Table 1: Entry Types vs. Validity Bits

Table 2: I/O Cycles

LOW

HIGH

/CM

LOW

HIGH

LOW

HIGH

Cycle Type

Command Write Cycle

Data Write Cycle

Command Read Cycle

Data Read Cycle

Pinout Diagram

GND

DQ 9

DQ 1 0

DQ 1 1

VCC

TE S T2

GND

DQ 1 2

DQ 1 3

GND

DQ 1 4

DQ 1 5

DQ 1 6

/FF

/MI

/MF

/MM

GND

/ R ES ET

VCC

TE S T1

DQ 3 1

DQ 3 0

GND

8 0 -P IN TQ FP

(Top V ie w )

GND

GENERAL DESCRIPTION

To use the WidePort LANCAM, the user loads the data into

the Comparand register, which is automatically compared to

all valid CAM locations. The device then indicates whether

or not one or more of the valid CAM locations contains data

that match the target data. The status of each CAM location

is determined by two validity bits at each memory location.

The two bits are encoded to render four validity conditions:

Valid, Skip, Empty, and Random Access, as shown in Table 1.

The memory can be partitioned into CAM and associated

RAM segments on 16-bit boundaries, but by using one of the

two available mask registers, the CAM/RAM partitioning can

be set at any arbitrary size between zero and 64 bits.

The WidePort LANCAM’s internal data path is 64 bits wide

for rapid internal comparison and data movement. A data

translation facility converts between IEEE 802.3 (CSMA/CD

“Ethernet”) and 802.5 (Token Ring) address formats. Vertical

cascading of additional WidePort LANCAMs in a daisy chain

fashion extends the CAM memory depth for large databases.

Cascading requires no external logic. Loading data to the

Control, Comparand, and mask registers automatically triggers

a compare. Compares may also be initiated by a command to

the device. Associated RAM data is available immediately

after a successful compare operation. The Status register reports

the results of compares including all flags and addresses. Two

mask registers are available and can be used in two different

ways: to mask comparisons or to mask data writes. The random

access validity type allows additional masks to be stored in

the CAM array where they may be retrieved rapidly.

A simple four-wire control interface and commands loaded

into the Instruction decoder control the device. A powerful

instruction set increases the control flexibility and minimizes

software overhead. Additionally, dedicated pins for match and

multiple-match flags enhance performance when the device is

controlled by a state machine. These and other features make

the WidePort LANCAM a powerful associative memory that

drastically reduces search delays.

80-Pin TQFP

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