International Business Machines Corporation

Robert E Busch

Kevin A Batson

Endre P Thoma

Reid A Wistort

Fred John Towler

Gary S Koch

Albert Manhee Chu

Geordie M Braceras

Theodore M Redman

Harold Pilo

George Maria Braceras

Garrett Stephen Koch

Ezra D B Hall

John Atkinson Fifield

Wayne Frederick Ellis

William Paul Hovis

Anthony Richard Bonaccio

Paul Christian Parries

Christopher P Miller

Frank Ray Keyser, Iii

Robert Maurice Houle

Frederick J Aichelmann, Jr

Jeffrey Scott Zimmerman

R Dean Adams

Daryl Michael Seitzer

Troy A Seman

Barton E Green

Bruce E Bachman

Kenneth Michael Zick

James A Yankosky

George E Rudgers

Jonathan B Ashbrook

Daryl M Seizter

A design structure for content addressable memory including a first array of memory cells, and a second array of memory cells. A search logic circuit is configured to prevent a discharge of the second array of memory cells when a search of the first array of memory cells finds certain data.

Design structure for content addressable memory

A content addressable memory including a first array of memory cells, and a second array of memory cells. A search logic circuit is configured to prevent a discharge of the second array of memory cells when a search of the first array of memory cells finds certain data.

Content addressable memory structure

A structure, apparatus and method for reducing the power requirement of CAM memories, where the memory cells of the memory array are divided into groups of rows of multiple memory segments. Each memory segment has its own search driver and is searched separately. The memory segments are also searched in a prescribed order. If the search data is found in a particular memory segment, the search is stopped, leaving subsequent memory segments unsearched. By searching memory segments only until the search data is found, match lines of the subsequent memory segments are not unnecessarily discharge and recharged thereby reducing the current demands placed upon the power supply by the CAM memory. A selectable option to do a full search of the CAM memory is also provided for when the power supply is able to meet such current demands.

An integrated circuit including: a set of bitlines; a set of data lines; means for coupling each respective data line to a first respective bitline or to a second respective bitline based on a steering signal, the second respective bitline being adjacent to the first respective bitline; and means for maintaining the first respective bitline at a desired potential after the data line is coupled to the second bitline.

Memory device with data line steering and bitline redundancy

An integrated circuit and a method of reconfiguring an integrated circuit in which multiple configuration sets, each including a plurality of register settings, are stored on the chip. Selection of at least a portion of a configuration set allows for quicker and easier retrieval and loading of register settings, and reduces the complexity and size of the higher level system control program. In an alternative embodiment, at least a portion of a configuration set that is stored on the chip can be directly loaded to at least one device to be controlled to eliminate the need for the set of registers.

Integrated circuit having register configuration sets

The present invention provides a memory architecture that allows memory checking and replacement of defective words by spare elements already provided on the chip that do not increase the chip size. The method of the invention uses a separate redundant array architecture to provide address translation, so that the redundant entries are represented as the correct entry index that they are replacing.

Redundant array architecture for word replacement in CAM

A method and structure for an array of content addressable memory (CAM) cells is disclosed. Each of the CAM cells has a search line and a bitline parallel to the search line. Across the array, search lines and bit lines of the CAM cells are interdigitated so that the search lines and bitlines alternate across the array. CAM cell macro's are inverted with respect to adjacent macros to balance parasitic capacitances across the array.

CAM cell with interdigitated search and bit lines

A method for combining a refresh operation with a parity validation for a DRAM-based content addressable memory (CAM) is disclosed. In an exemplary embodiment of the invention, the method includes implementing the memory refresh operation and examining a word included within the CAM. A determination is made as to whether data contained within the word constitutes valid data. If the data contained within the word does not constitute valid data, then the parity validation is bypassed. However, if the data contained within the word does constitute valid data, then the parity validation is implemented. The parity validation further includes reading the data contained within the word, generating a parity bit from the data contained within the word, and comparing the generated parity bit with a previously stored parity bit. If the parity validation is implemented and if the generated parity bit does not match the previously stored parity bit, then the data contained within the word is invalidated.

Method for combining refresh operation with parity validation in a DRAM-based content addressable memory (CAM)

A high-reliability content & addressable memory using a shadow content-addressable memory (CAM) array in parallel with a primary CAM array to increase the reliability of CAM searches. The reliability of CAM searches has been less than desired because of random environmental influences that corrupt data. The shadow CAM is written, read, and searched in parallel with the primary CAM. The search results from the parallel searches are compared and, if identical, are declared valid. If the search results are not equal, corrective action is initiated. The high-reliability content-addressable memory may be used with or without priority encoders.

High reliability content-addressable memory using shadow content-addressable memory

A high-reliability content-addressable memory using a shadow content-addressable memory (CAM) array in parallel with a primary CAM array to increase the reliability of CAM searches. The reliability of CAM searches has been less than desired because of random environmental influences that corrupt data. The shadow CAM is written, read, and searched in parallel with the primary CAM. The search results from the parallel searches are compared and, if identical, are declared valid. If the search results are not equal, corrective action is initiated. The high-reliability content-addressable memory may be used with or without priority encoders.

A fast DRAM memory uses ground-sensing as opposed to traditional Vdd/2 sensing. A selected DRAM cell connects to a bit-line true (BLT) or a bit-line complement (BLC). At the start of each cycle the BLT and BLC are restored to ground potential. A pair of alternating reference cells are provided for each bit-line. When a selected DRAM cell is connected either BLT or BLC the first reference cell in the pair is connected to the other bitline to provide a reference voltage to the other bitline which can be compared to the voltage provided by the selected DRAM cell. On a subsequent cycle using the same bitline the second reference cell in the pair is used. Thus it is not necessary to wait for the first reference cell to recharge prior to beginning the next cycle. Switching between the first and second reference cells in the pair alternates in this manner resulting in faster cycle time. The write-back of the reference cells can be hidden since an alternate cell is available for next cycle's reference bitline generation.

Alternating reference wordline scheme for fast DRAM

A method and structure for a content addressable memory (CAM) array having a plurality of memory cells. Each of the memory cells has capacitive storage devices, transistors connected to the storage devices, a wordline connected to and controlling the transistors, bitlines connected to the storage devices through the transistors, combined search and global bitlines connected to the capacitive storage devices. These cells are further arranged into columns, each containing multiplexers connected to the combined search and global bitlines, data-in lines connected to the multiplexers, and search-data lines connected to the multiplexers. Further, the multiplexers select between the data-in lines and the search-data lines to allow the combined search and global bitlines to be alternatively used as data lines and search lines. Also, in the invention each of the columns further has drivers between the multiplexers and the combined search and global bitlines. The drivers drive signals between the multiplexers and the combined search and global bitlines during search and write operations.

Use of search lines as global bitlines in a cam design

A system and method is disclosed for operating a content addressable memory (CAM) within an integrated circuit using search signals at search input voltages which are substantially independent from an operating voltage of the CAM. A method is disclosed in which search signals are input to CAM cells of the CAM at search input voltages which are substantially independent of an operating voltage of storage elements within the CAM cells. A match signal is output upon detecting a matching condition between the search signals and data stored in the storage elements. The search input voltage can be within about 0.2V above a threshold voltage of a search input device of the CAM memory cell. Search input devices can be selected to have a lower threshold voltage than other devices included within the CAM cell.

System and method for conserving power in a content addressable memory by providing an independent search line voltage

A Dynamic Content Addressable Memory (DCAM) cell topology that contains fewer that can perform a &ldquo;hidden&rdquo; refresh of stored data that does not delay nor interrupt the CAM search cycle, thereby providing SCAM-like performance. A non-destructive read operation, is performed such that the stored-data does not have to be written back because of a refresh-read operation. A reliable CAM search can be performed after a read operation and before or even while the refresh-data is being written back. Soft-error detection processes can be performed on each CAM entry during the pendency of the refresh cycle. The DCAM cell can be used in a digital system such as a digital computer and a Network Router.

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Essex Junction, VT, United States of America

Robert E Busch