mh1020 Music Semiconductors, Inc., mh1020 Datasheet - Page 2

• Manufacturer Part Number: mh1020
• Description: Hla Packaged Asynchronous Data Recognition And Recall Processor
• Manufacturer: Music Semiconductors, Inc.

GENERAL DESCRIPTION
The MH1020 is a 2048x64-bit Content Addressable
Memory (CAM), with a 16-bit wide interface.
CAMs, also known as associative memories, operate in the
converse way to random access memories (RAM). In
RAM, the input to the device is an address and the output
is the data stored at that address. In 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, 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
OPERATIONAL OVERVIEW
To use the MH, 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
matches 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, Empty, Skip, and RAM, shown in Status
Register Bits on page 25 (bits 29:28). 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 MH’s internal data path is 64 bits wide for rapid
internal comparison and data movement. Vertical
cascading of additional MHs 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
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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.
The MUSIC MHs are ideal for address filtering and
translation applications in LAN switches and routers. The
MHs are also well suited to encryption, database
accelerators, and image processing.
triggers a compare. Compares also may 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 RAM 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 MH a
powerful associative memory that drastically reduces
search delays.
Rev. 1