Integrated Device Technology, Inc.

Netlogic Microsystems, Inc

Other

Kee W Park

Scott Yu-Fan Chu

Robert J Proebsting

Chuen-Der Lien

Michael J Miller

Chau-Chin Wu

Mark W Baumann

Kenneth Branth

Bertan Tezcan

Scott Chu

Thomas Diede

Jeff Vesey

Chuen Der Lien

Ting-Pwu Yen

Bruce Schwegler

An encoding scheme is disclosed that allows a CAM device to selectively store, within each cell of a row of the CAM device, either a single bit of a binary value or two bits of an encoded data word encoded from the binary value. By storing two bits of the encoded data word in each CAM cell, data may be stored more efficiently and CAM systems may consume less power. The encoded data words can be balanced data words that have equal number of logic high and logic low values.

Encoding data for storage in a content addressable memory

A method and apparatus are disclosed for improving reliability in a memory circuit. The method includes coupling a pull-down element to a word line, the pull-down element coupled distal to a word line driver. The method further includes, when the word line exhibits a defect causing a first portion of the word line to be electrically isolated from a second portion of the word line, holding the second portion of the word line at a logically low value using the pull-down element. A memory device is disclosed that includes a word line coupled to a memory cell, a word line driver coupled to one end of the word line, and a pull-down element coupled proximate the other end of the word line. The pull-down element is operable, when the word line exhibits a defect causing a first portion of the word line to be electrically isolated from a second portion of the word line, to hold the second portion of the word line at a logical low value.

System and method to improve reliability in memory word line

Approaches for an improved encoding scheme that allows a CAM device to selectively store, within each cell of a row of the CAM device, either a single bit of a binary value or two bits of an encoded data word encoded from the binary value. By storing two bits of the encoded data word in each CAM cell, data may be stored more efficiently and CAM systems may consume less power as compared to traditional binary CAMS when performing certain types of operations, such as exact matching and longest prefix matching. Encoded data words may be, but need not be, balanced data words which have equal number of logic high and logic low values.

A read operation and a search operation are performed during the same cycle within a CAM system including a CAM array by: (1) forcing a non-matching condition to exist in the row of the CAM array selected for the read operation, (2) comparing the read data value with the search data value outside of the CAM array to determine whether a match exists, and (3) prioritizing the results of the search operation performed within the CAM array and the results of the comparison performed outside of the CAM array to provide a final search result.

Content addressable memory (CAM) array capable of implementing read or write operations during search operations

A packaged integrated circuit device and a circuit board assembly are disclosed that include a semiconductor die and a package substrate that includes a first grid array of contact pads that are electrically coupled to corresponding contact pads on the semiconductor die. The first grid array of contact pads includes a first set of adjacent rows or columns of contact pads that are coupled to a first channel that extends within a ground plane of the package substrate. The first grid array of contact pads includes a second set of adjacent rows or columns of contact pads that are electrically coupled to a second channel that extends within a power plane of the package substrate. The contact pads in the first set of adjacent rows or columns of contact pads directly overlie a portion of the first channel and the contact pads in the second set of adjacent rows or columns of contact pads directly overlie a portion of the second channel. A circuit board assembly is disclosed that includes a first grid array of contact pads disposed on a top side of a circuit board. The circuit board includes a first channel that extends within a ground plane of the circuit board and a second channel that extends within a power plane of the circuit board. The circuit board assembly can include decoupling capacitors disposed on the top side of the circuit board and the packaged integrated circuit device can include decoupling capacitors attached to the top of the package substrate.

Circuit board assembly and packaged integrated circuit device with power and ground channels

A CAM system includes an integrated circuit chip having: logic & control circuitry, a CAM cell array, read/write access circuitry that performs read and write accesses to the CAM cell array, comparison access circuitry that performs comparison operations to the CAM cell array, a first voltage supply pad coupled to the read/write access circuitry; and a second voltage supply pad coupled to the comparison access circuitry. A first voltage supply, external to the integrated circuit chip, provides a first supply voltage to the first voltage supply pad, wherein the logic & control circuitry is powered by the first supply voltage. A second voltage supply, external to the integrated circuit chip, provides a second supply voltage to the second voltage supply pad, wherein at least a portion of the comparison access circuitry is powered by the second supply voltage, wherein the second supply voltage is less than the first supply voltage.

Separate CAM core power supply for power saving

Content addressable memory (CAM) devices use both hard and soft priority techniques to allocate entries of different priority therein. The priorities of multiple CAM array blocks within the CAM device may be programmed before or as entries are loaded therein and may be reprogrammed during operation as the allocation of entries within the CAM device changes. The allocation of entries may change in response to additions or deletions of entries or as entries are reprioritized. The CAM devices include preferred priority resolution circuits that can resolve competing soft and hard priorities between multiple hit signals that are generated in response to a search operation. Such hit signals may be active to reflect the presence of at least one matching entry within a CAM array block. The resolution of which active hit signal has the highest overall priority among many can be used to facilitate the identification of the location (e.g., array address and row address) of a highest priority matching entry within the entire CAM device. A priority resolution circuit may also resolve competing hard priorities between two or more active hit signals having equivalent soft priority. This aspect of the priority resolution circuit is provided so that an active hit signal having a highest overall priority can be resolved whenever multiple CAM array blocks having the same soft priority are detected as having matching entries therein during a search operation.

Content addressable memory (CAM) devices having soft priority resolution circuits therein and methods of operating same

A novel method for scanning bit parity in a memory array, and a circuit for implementing it, are disclosed. In a memory array that has one or more rows of memory cells, the method for checking data parity includes storing a plurality of data bits in the memory cells, scanning a row of memory cells independently of a memory read operation to ascertain the stored data bits; and determining parity for the row of memory cells by the results of the scanning. The method is accomplished by means of a dedicated parity scanning circuit.

Fast parity scan of memory arrays

A content addressable memory (CAM) system that includes a row of NAND-type CAM cells divided into a plurality of segments. Each segment includes a plurality of series-connected switching transistors, wherein each of the switching transistors is part of a corresponding NAND-type CAM cell. The series-connected switching transistors of each segment are coupled to the series-connected switching transistors in an adjacent segment by a repeater circuit, thereby forming a chain of series-connected switching transistors and repeater circuits. A match line driver circuit is coupled to one end of the chain, and a match line is connected to the other end of the chain. If a match condition exists for the entire row, then a signal driven by the match line driver is propagated to the match line, through the chain of series-connected switching transistors and repeater circuits.

Low power content addressable memory array (CAM) and method of operating same

A content addressable memory array includes a plurality of rows of active CAM cells electrically coupled to a corresponding plurality of active match lines and at least one row of dummy cells, which are configured to generate an always-match condition on a dummy match line when the CAM array is undergoing a search operation. A match line pull-up circuit is provided. This match line pull-up circuit is electrically coupled to the plurality of active match lines and the dummy match line. The pull-up circuit is responsive to a calibration control signal that sets a pull-up strength of the match line pull-up circuit when the CAM array is undergoing the search operation. A sense amplifier, which is coupled to the match lines, includes a control circuit configured to adjust the calibration control signal in response to evaluating a first voltage on the dummy match line relative to a reference voltage.

Content addressable memories (CAM) having low power dynamic match line sensing circuits therein

Search engine devices include a content addressable memory (CAM) core having a plurality of CAM array blocks therein and a control circuit. The control circuit, which is electrically coupled to the plurality of CAM array blocks, is configured to perform built-in self repair (BISR) of hard memory defects and/or compare logic defects in the plurality of CAM array blocks concurrently with operations to search entries in the plurality of CAM array blocks.

Content addressable memory (CAM) devices that support background BIST and BISR operations and methods of operating same

A CAM array has at least one row therein containing a plurality of memory cells with different susceptibilities to soft errors. The memory cells having reduced susceptibilities to soft errors include those used in check bit cells and/or CAM cells containing valid bit data and/or force no-hit data. Additional memory cells may also be provided with somewhat greater susceptibilities to soft errors and somewhat more aggressive design rules (e.g., smaller layout area). These additional memory cells may include those used in ternary CAM cells (e.g., XY CAM cells) within the row.

Content addressable memory (CAM) arrays having memory cells therein with different susceptibilities to soft errors

A CAM block includes a CAM array having a plurality of rows and columns of 4-bit NAND-type CAM cells therein. Each of a plurality of the NAND-type cells includes a respective ladder-type compare circuit having four two-transistor rungs. At least one of the plurality of rows includes a first 4-bit NAND-type CAM cell having a first ladder-type compare circuit with four two-transistor rungs and a second 4-bit NAND-type CAM cell having a second ladder-type compare circuit with four two-transistor rungs. A match line segment is also provided, which is connected to four source terminals of transistors in the first ladder-type compare circuit and four drain terminals of transistors in the second ladder-type compare circuit.

High speed NAND-type content addressable memory (CAM)

Content addressable memory (CAM) devices use both hard and soft priority techniques to allocate entries of different priority therein. The allocation of entries may change in response to additions or deletions of entries or as entries are reprioritized. The CAM devices include priority resolution circuits that can resolve competing soft and hard priorities between multiple hit signals that are generated in response to a search operation. Such hit signals may be active to reflect the presence of at least one matching entry within a CAM array block. The resolution of which active hit signal has the highest overall priority among many can be used to facilitate the identification of the location (e.g., array address and row address) of a highest priority matching entry within the entire CAM device. A priority resolution circuit may also resolve competing hard priorities between two or more active hit signals having equivalent soft priority.

Multi-bank content addressable memory (CAM) devices having staged segment-to-segment soft and hard priority resolution circuits therein and methods of operating same

Content addressable memory (CAM) devices include at least one CAM array having a plurality of columns of ternary CAM cells therein. A bit/data line driver circuit, which receives search words and write words, is electrically coupled to the CAM array. The bit/data line driver circuit is configured to save power by logically combining incoming search words with a global mask that designates locations of active ones of the plurality of columns having exclusively locally masked CAM cells at valid entries therein. The bit/data line driver circuit includes a global mask generator configured to receive write words to be added to the CAM array during respective write operations.

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San Jose, CA, United States of America

Kee W Park