Abstract: A content addressable memory (CAM) device can include a number of match lines, each coupled to a plurality of CAM cells. The CAM device also includes one or more one precharge circuits. Such a precharge circuit can have a first precharge path that couples a match line to a precharge voltage node in response the activation of a first control signal, and a second precharge path that couples the match line to the precharge voltage node in response to the activation of a second control signal. Prior to a compare operation leakage current through the CAM cells can prevented by disabling the precharge paths and isolating the CAM cells from a reference voltage (e.g., ground). The second control signal can be activated after the first control signal in a compare operation.

Abstract: A memory cell includes an access transistor, first and second pull-up transistors, first and second pull-down transistors, and a first search transistor. The access transistor is connected to a first word line and connected between a first bit line and a first data node. The first pull-up transistor is connected to a first power supply point and the first data node, and the second pull-up transistor is connected to the first power supply point and the second data node. The first pull-down transistor is connected to a second power supply point and the first data node, and the second pull-down transistor is connected to the second power supply point and the second data node. The first search transistor is connected to the second data node and includes a source terminal connected to a third power supply point comprising a voltage less than the voltage at the second power supply point.

Abstract: A content addressable memory (CAM) device includes a comparand register, a CAM array, and partition logic. The comparand register has inputs to receive a search key, and outputs coupled to the CAM array, which includes a plurality of individually selectable sub-arrays. Each sub-array includes a number of rows of CAM cells and a control circuit, wherein each row of CAM cells is coupled to a match line, and wherein the control circuit has an input to receive a corresponding sub-array enable signal. The partition logic has an input to receive a partition select signal, and is configured to generate the sub-array enable signals in response to the partition select signal. The control circuits selectively propagate the search key through the sub-arrays in response to the sub-array enable signals.

Abstract: A content addressable memory (CAM) device includes an array of memory cells arranged in rows in a word line direction and columns arranged in a bit line direction, and compare circuitry configured to compare data presented to the array with data stored in each row and column of the array, and simultaneously indicate match results on each row and column of the array, thereby resulting in a two-dimensional, matrix-based data comparison operation.

Abstract: Method and apparatus for writing data to a storage array, such as but not limited to an STRAM or RRAM memory array, using a read-mask-write operation. In accordance with various embodiments, a first bit pattern stored in a plurality of memory cells is read. A second bit pattern is stored to the plurality of memory cells by applying a mask to selectively write only those cells of said plurality corresponding to different bit values between the first and second bit patterns.

Abstract: A content addressable memory (CAM) device includes a plurality of CAM rows, a number of sequencing logic circuits, and a programmable interconnect structure. Each CAM row includes a number of CAM cells to generate a match signal on a match line and includes an enable input. Each sequencing logic circuit includes an input and an output, and is configured to count sequences of match signals from the CAM rows. The programmable interconnect structure selectively connects the match line of any CAM row to the input of any sequencing logic circuit, and selectively connects the output of any sequencing logic circuit to the enable input of any CAM row.

Abstract: A pre-decoded address is generated at a high speed in a semiconductor memory device. The device comprises a pre-decoder (210) for generating a first pre-decoded address (PDA1) by pre-decoding the input address (ADD), a CAM circuit (220) for activating the match signal (MT) by responding to the indication of a defective memory cell by the input address (ADD), a ROM circuit (230) for outputting a second pre-decoded address (PDA2) and an enable signal (ES) in response to the activation of the match signal (MT), and a multiplexer (240) for selecting either the first or second pre-decoded address (PDA1 or PDA2) on the basis of the enable signal (ES). According to the present invention, there is no need to use a circuit with numerous stages as there is in substituted logic; accordingly, pre-decoded addresses can be generated at a high speed.

Abstract: A column of ternary content addressable memory (TCAM) cells includes a bit line pair that is twisted at a location at or near the center of the column. Data is written to (and read from) TCAM cells located above the twist location with a first bit line polarity. Data is written to (and read from) TCAM cells located below the twist location with a second bit line polarity, opposite the first bit line polarity. As a result, read leakage currents introduced by TCAM cells storing ‘Don't Care’ values are reduced.

Abstract: A content addressable memory device with a plurality of memory cells storing data words. Each data bit in the data words is set to one of three values of a first binary value, a second binary value, and a don't care value. An aspect of the content addressable memory device is the use of a single memory element and an access device in the memory cells. The memory cells are arranged such that each memory cell is electrically coupled to a single bit line, a single match line, and a single word line. The memory elements in the memory cells store low resistance states if the data bit value is the first binary value, high resistance states if the data bit value is the second binary value, and very high resistance states if the data bit value is the don't care value.

Abstract: A content addressable memory (CAM) device can include a plurality of CAM cells arranged in rows and columns to form multi-byte words. Each CAM cell can include a comparator circuit and one or more data storing circuits. Each comparator circuit can have one or more charge transfer paths arranged between a match line and a first voltage source node. Each data storing circuit can include a write circuit that provides a controllable impedance path between one or more charge transfer paths and a data storage node of the data storing circuit.

Abstract: A segmented ternary content addressable memory (TCAM) search architecture is disclosed. In one embodiment, a TCAM device with a row of TCAM cells includes a first segment of the TCAM cells for determining a match of corresponding search bits of a search string with a first portion of a stored string in the first segment of the TCAM cells, an evaluation module for generating a search enable signal if the match of the corresponding search bits with the first portion of the stored string is determined, and a second segment of the TCAM cells for determining a match of remaining search bits of the search string with a remaining portion of the stored string in response to the search enable signal.

Abstract: An integrated circuit device can include a plurality of compare cell circuits that selectively provide charge transfer path between a result line and a reference node according to a comparison between a stored data value and an applied compare data value during a compare time period. A first precharge circuit can have a controllable impedance path coupled between the result line and a precharge voltage node. A control circuit can place the first precharge circuit into a low impedance state during a first portion of the compare time period, and into a high impedance state during a second portion of the compare time period.

Abstract: A CAM column structure includes an interface that drives search data to a plurality of CAM cells via a search line pair. The CAM cells are divided into sections, each section including: a set of CAM cells, a bit line pair coupled to the set of CAM cells, a sense amplifier coupled to the bit line pair, a tri-state read buffer configured to drive read data from the sense amplifier to the search line pair, and a pair of tri-state write buffers configured to drive write data from the search line pair to the bit line pair. In one embodiment, the pair of tri-state write buffers is replaced by a pair of switches that couple the search line pair to the sense amplifier. The search line pair may be segmented by tri-state buffers, which are controlled to drive the search, read and write data along the search line pair.

Abstract: 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.

Abstract: A content addressable memory device with a plurality of memory cells storing ternary data values of high, low, and don't care. An aspect of the content addressable memory device is the use of first memory elements and second memory elements in the memory cells. The first and second memory elements are electrically coupled in parallel circuit to a match-line. The first memory elements are coupled to first word-lines and the second memory elements are coupled to second word-lines. The first memory elements are configured to store low resistance states if the ternary data value is low and high resistance states if the ternary data value is either high or don't care. The second memory elements are configured to store the low resistance states if the ternary data value is high and the high resistance states if the ternary data value is either low or don't care.

Abstract: A mechanism is provided for transparent multi-hit correction in associative memories. A content associative memory (CAM) device is provided that transparently and independently executes a precise corrective action in the case of a multiple hit being detected. The wordlines of a CAM array are modified to include a valid bit storage circuit element that indicates whether or not the corresponding wordline is valid or not. In operation, if multiple hits are detected, the multiple hit is signaled to the host system and the particular entries in the CAM array corresponding to the multiple hits are invalidated by setting their associated valid bit storage circuit elements to an invalid value or clearing the value in the associated valid bit storage circuit element. Any data returned to the host system as a result of the multiple hits is invalidated in the host system in response to the signaling of the multiple hits.

Abstract: Mechanisms for multiple hit (multi-hit) detection in associative memories, such as a content addressable memory (CAM), are provided. The illustrative embodiments include a hit bitline that discharges as RAM side entries of the associative memory are accessed. The hit bitline is precharged high and pulled low by a series of devices that are activated as each RAM side row is accessed. As more RAM side rows are accessed, the hit bitline drops lower in voltage. The hit bitline drives an inverter with a threshold set such that any voltage equal to or lower than the threshold indicates a multi-hit situation. Any voltage higher than the threshold indicates a single hit or “no-hit” situation. Thus, from the voltage of the hit bitline, the presence of a multi-hit condition may be detected.

Abstract: A content addressable memory using encoded data words and search words, and techniques for operating such device. In one embodiment, the data word is transformed into a code word guaranteeing a mismatch of at least two code word bits of different binary values during the memory search operation when the data word does not match a search word. In another embodiment, the search word is transformed into a search code such that the Hamming distance between the code word and the search code is greater than a given threshold when there is a mismatch of at least one bit between the data word and the search word.

Abstract: An integrated circuit device can include a plurality of configuration storage locations each comprising at least one encoding field. Each encoding field can selectively enable at least one received data value to be encoded into an encoded data value prior to being applied to a corresponding block of the integrated circuit device. Each block can comprise a plurality of content addressable memory (CAM) cells.

Abstract: A content addressable memory array storing stored words in memory elements. Each memory element stores one of at least two complementary binary bits as one of at least two complementary resistances. Each memory element is electrically coupled to an access device. An aspect of the content addressable memory array is the use of a biasing circuit to bias the access devices during a search operation. During the search operation, a search word containing a bit string is received. Each access device is biased to a complementary resistance value of a corresponding search bit in the search word. A match between the search word and stored word is indicated if the bits stored in the memory elements are complementary to the bits represented by the resistances in the access devices.

Abstract: A method and apparatus for multiple string searching using a ternary content addressable memory. For one embodiment, the method includes selecting character groups from an input text string in a temporal sequence, each character group having more than one character. A first character group of the character groups is compared with a plurality of character fields and a current state of a state machine is compared with a plurality of states of the state machine that correspond to the plurality of character fields to identify information indicative of a subsequent state of the state machine. Comparison of the first character group with the plurality of sets of character fields is repeated if the information indicative of the subsequent state of the state machine indicates that a terminal number of characters of a desired character pattern has been located and that the terminal number of characters is fewer than the number of characters in the first character group.

Abstract: An offset removal circuit (10) includes a removal circuit (1) and a removal circuit (2). The removal circuit (1) digitally removes offset voltage from an input voltage Vin. The removal circuit (2) removes offset voltage, in an analog manner, from the voltage subjected to offset voltage removal by the removal circuit (1). Then, the removal circuit (2) outputs the voltage subjected to the offset voltage removal to a non-inverting input terminal of a differential amplifier (20).

Abstract: A semiconductor device is provided to have two groups of nonvolatile memory cells, two groups of data registers and a compare circuit. Each of the two groups of the nonvolatile memory cells stores a set of predetermined data and a set of complementary data respectively. The two groups of data registers are respectively connected to the two groups of the nonvolatile memory cells. The compare circuit is connected to the two groups of the data registers, for performing a comparison to generate a compare result.

Abstract: Static-based comparators and methods for comparing data are disclosed. The static-based comparator is configured to selectively switch at least one comparator output in response to a comparison of corresponding data with compare data, and a validity indicator for the data. If the validity indicator indicates valid data, the static-based comparator switches to drive the comparator output indicating either a match or mismatch between corresponding compared data. If the validity indicator indicates invalid data, the static-based comparator provides a mismatch on the comparator output without switching the static-based comparator regardless of whether or not the data matches the compare data. In this manner, the static-based comparator does not dissipate power switching the comparator output for data marked invalid. The static-based comparator can be employed in content addressable memories (CAMs) for comparing one or more bits of tag data to corresponding bit(s) of compare data.

Abstract: For receiving an input data, a pattern data and a data clock signal and outputting a hit signal and an address signal, a content addressable memory is disclosed to include a plurality of content addressable memory units connected in series, each content addressable memory unit being adapted to receive the input data and the data clock signal and to output a comparison result signal, and an encoder coupled to the comparison result signal of each content addressable memory unit and adapted for outputting a hit signal and a memory address signal subject to the comparison result signal received.

Abstract: Systems, devices, and methods, including executable instructions are provided for resolving content addressable memory (CAM) match address priority. One method includes retaining a first match address as the best match address. Subsequent match addresses are compared to the retained best match address, each match address being associated with a compare cycle during which a selected columnar portion of each CAM entry is compared to a corresponding portion of a search term. The best match address is updated as a result of the comparison.

Abstract: A device includes a first semiconductor die. Nonvolatile memory stores information associated with a second semiconductor die. Cache memory caches a portion of the information. A cache controller controls the cache memory. A device interface communicates the information to the second semiconductor die. On the second semiconductor die, a semiconductor circuit processes the information stored on the first semiconductor die.

Abstract: A design structure for designing, manufacturing, or testing a content addressable memory (CAM) device. The CAM device includes a plurality of CAM cells, match-lines (MLs), search lines, and ML sense amplifiers. The ML sense amplifiers are capable of self-calibration to their respective thresholds to reduce effects of random device variation between adjacent sense amplifiers.

Abstract: A novel schematic for executing search, write and valid bit clear operations in one cycle in a CAM system that includes a plurality of CAM blocks is disclosed. In one embodiment, the plurality of CAM blocks are organized into at least one rectangular array having rows each having a plurality of CAM blocks, a group of CAM cells and associated read/write bit lines connecting the group of CAM cells to an addressed search circuit. The write operation depends on the output of the search operation, wherein the same data is written in to the CAM when the search operation results in a miss in a given cycle. Further, during the same cycle a valid bit clear operation is also performed. The resulting CAM cell provides a high speed three port operation.

Abstract: Content addressable memory device utilizing phase change devices. An aspect of the content addressable memory device is the use of a comparatively lower power search-line access element and a comparatively higher power word-line access element. The word-line access element is only utilized during write operations and the search-line access element is only utilized during search operations. The word-line access element being electrically coupled to a second end of a phase change memory element and a word-line. The search-line access element also being electrically coupled to the second end of the phase change memory element and a search-line. The search-line being electrically coupled to a match-line. A bit-line is electrically coupled to a first end of the phase change memory element. Additionally, a complementary set of access elements, a complementary phase change memory element, a complementary search-line, and a complementary bit-line are also included in the content addressable memory device.

Abstract: An associative memory device includes a magnetically responsive layer adapted to store a representation of a pattern, the magnetically responsive layer includes magnetic nanoparticles as a magnetically active component. The magnetic nanoparticles of the associative memory device are dispersed in a solvent with variable viscosity, and the magnetically responsive layer is a layer of ferrofluid.

Abstract: An entry including multiple bits of unit cells each storing data bit is coupled to a match line. The match line is supplied with a charging current having a restricted current value smaller than a match line current flowing in a one-bit miss state in one entry, but larger than a match line current flowing in an all-bit match state in one entry. A precharge voltage level of a match line is restricted to a voltage level of half a power supply voltage or smaller. Power consumption in a search cycle of a content addressable memory can be reduced, and a search operation speed can be increased.

Abstract: A segmented ternary content addressable memory (TCAM) search architecture is disclosed. In one embodiment, a TCAM device with a row of TCAM cells includes a first segment of the TCAM cells for determining a match of corresponding search bits of a search string with a first portion of a stored string in the first segment of the TCAM cells, an evaluation module for generating a search enable signal if the match of the corresponding search bits with the first portion of the stored string is determined, and a second segment of the TCAM cells for determining a match of remaining search bits of the search string with a remaining portion of the stored string in response to the search enable signal.

Abstract: An amplifier circuit according to the present invention includes a plurality of input nodes receiving a plurality of input voltages (VI1 to VIR), a plurality of differential amplifiers provided corresponding to the plurality of input nodes, each having one input which receives a voltage of the corresponding input node, and a control circuit generating a control voltage (CONTROL) that follows a minimum voltage or a maximum voltage of the plurality of input voltages (VI1 to VIR) from outputs of the plurality of differential amplifiers and supplying the generated control voltage (CONTROL) as a common value to the other inputs of the plurality of differential amplifiers.

Abstract: A disclosed embodiment is a range checking CAM array comprising a plurality of words, where each of the plurality of words comprises a plurality of bound check cells. Each of the plurality of bound check cells outputs a corresponding plurality of match signals and a corresponding plurality of bound check signals. The corresponding plurality of match signals and corresponding plurality of bound check signals are combined to produce a range check output indicating whether data on a data input bus is within a target range. The plurality of bound check cells may be coupled to form at least one cascade of bound check cells, where each cascade of bound check cells may be terminated at a ripple logic. The CAM array produces a final range check output based on the corresponding plurality of match signals and the corresponding plurality of bound check signals.

Abstract: In order to realize high speed carbon nanotube memory, bit line is multi-divided into short lines for reducing parasitic capacitance. For reading, a small local sense amp is composed of a local pre amplifier and a local main amplifier with high gain, and a simple global sense amp is composed of an inverter as amplifying circuit for receiving an output of the local sense amp through a global bit line. By the sense amps, time domain sensing scheme is realized such that a voltage difference in the bit line is converted to a time difference as an output of the global sense amp, for differentiating high data and low data. In this manner, fast read operation is realized with fast sensing circuit. And alternative circuits are described. Particularly, field-effect alignment process is realized for aligning the carbon nanotubes on exact location of the memory cell, when forming the memory cell.

Abstract: A leakage current cut-off device for a ternary content addressable memory is provided. The storage cell of a ternary content addressable memory may be in the active mode, data-retention mode and cut-off mode. This invention applies a multi-mode data retention power gating device to the storage cell of the ternary content addressable memory to reduce the leakage current through the storage cell in the data-retention mode and the cut-off mode, and support the full speed operation in the active mode.

Abstract: In one embodiment, a method includes receiving a portion of a hash key vector. The hash key vector can be defined based on a range value and based on at least a portion of an address value from a data packet queued within a multi-stage switch. The method also includes defining, based on the hash key vector, a hash value associated with a location in a hash table when the portion of the hash key vector matches a bit vector stored in a tag table.

Abstract: An apparatus, circuit, and method are provided herein for locating and extracting a plurality of matching entries from one or more databases stored within a Content Addressable Memory (CAM) device. The apparatus, circuit, and method may locate the plurality of matching entries by comparing variations of a single search key to the entire database of entries. In other words, a number of bits may be stored within each of the database entries as a descriptor field. When searching for a particular entry or entries, a corresponding descriptor field included within (or appended to) the search key may be modified, after at least one matching entry is found, for locating and extracting additional entries matching the original search key. Use of the descriptor field, therefore, enables the circuit and method to locate and extract a potentially unlimited number of entries matching the original search key.

Abstract: The present invention discloses a read and match circuit for a low-voltage content addressable memory, wherein the write circuit inputs the signals needing storing into the memory cells, and the read circuit retrieves the stored signals from the memory cells, and the match circuit compares the data stored in the memory cell with the data searched by the match circuit. As the circuits for writing, reading and matching are separated from each other and exempt from mutual interference, the present invention can achieve high reliability and low power consumption under a low-voltage operation environment without using a special fabrication process. In the present invention, the circuit is optimized to meet different requirements. The present invention enables the user to determine whether to have high speed or to have low power consumption. Further, the present invention can overcome the problems of current leakage and noise allowance in a low-voltage environment.

Abstract: A differential non-volatile content addressable memory array has a differential non-volatile content addressable memory cell which uses a pair of non-volatile storage elements. Each of the non-volatile storage elements can be a split-gate floating gate transistor or a stack gate floating gate transistor having a first terminal, a second terminal, a channel therebetween and a floating gate over at least a portion of the channel to control the conduction of electrons in the channel, and a control gate. The floating gate storage transistor can be in one of two states: a first state, such as erase, in which current can flow between the first terminal and the second terminal, and a second state, such as programmed, in which substantially no current flows between the first terminal and the second terminal. A pair of differential compare data lines connects to the control gate of each of the pair of non-volatile floating gate transistors.

Abstract: A semiconductor device that includes a memory cell having a junction field effect transistor (JFET) used to form a content addressable memory (CAM) cell is disclosed. The JFET may include a data storage region disposed between a first and second insulating region. The data storage region provides a first threshold voltage to the JFET when storing a first data value and provides a second threshold voltage to the JFET when storing a second data value. The memory cell is a dynamic random access memory (DRAM) cell and can be used to form a CAM cell. The CAM cell may be a ternary CAM cell formed with as few as two JFETs.

Abstract: A content addressable memory (CAM) device and process for searching a CAM. The CAM device includes a plurality of CAM cells, match-lines (MLs), search lines, and ML sense amplifiers. The ML sense amplifiers are capable of self-calibration to their respective thresholds to reduce effects of random device variation between adjacent sense amplifiers.

Abstract: A content addressable memory includes a first plurality of search lines, a second plurality of search lines, a first match line, and a storage location. Each search line of the first plurality of search lines receives a corresponding high voltage level or low voltage level during a match detect operation, and each search line of the second plurality of search lines to receive a corresponding high voltage level or low voltage level during the match detect operation. The storage location of the content addressable memory includes a plurality of CAM cells, each CAM cell a first thyristor and second thyristor.

Abstract: A method for writing a magnetic random access memory-based ternary content addressable memory cell comprising a first magnetic tunnel junction being formed from a storage layer, a sense layer having a magnetization direction adjustable relative to the magnetization of the storage layer, and an insulating layer between the storage and sense layers; a sense line coupled with the storage layer; a first field line and a second field line, and the first field line being orthogonal to the second field line; comprising: providing a first write data to said storage layer via the second field line to store a first stored data with a high or low logic state; characterized in that, the method further comprises providing the first write data to said storage layer via the first field line to store the first stored data with a masked logic state.

Abstract: In accordance with a specific embodiment of the present disclosure, a content addressable memory (CAM) of a data processing device can operate in a normal mode or a test mode. In the normal mode, the CAM provides a match value in response to determining that a received data value matches one of a plurality of values stored at memory locations of the CAM. In a test mode of operation, a plurality of test signals are applied to the CAM, and the CAM provides a match value in response to assertion of one of the test signals. The match value is applied to a functional module associated with the CAM to determine a test result. Accordingly, the test signals applied to the CAM provide a flexible way to generate match values and apply those values to the functional module during testing of the data processing device.

Abstract: A processing system includes a network processor and a CAM device having a re-entrant processor coupled to a CAM array. The re-entrant processor is configured to selectively modify an initial search key provided by the network processor by replacing portions of the initial search key with portions of one or more previous search keys and/or one or more previous results. The re-entrant processor is also configured to initiate a series of subsequent compare operations between new search keys and data stored in the CAM array without receiving additional instructions or search keys from the network processor.

Abstract: This patent describes a method for switching search-lines in a Content Addressable Memory (CAM) asynchronously to improve CAM speed and reduce CAM noise without affecting its power performance. This is accomplished by resetting the match-lines prior to initiating a search and then applying a search word to the search-lines. A reference match-line is provided to generate the timing for the search operation and provide the timing for the asynchronous application of the search data on the SLs. Additional noise reduction is achieved through the staggering of the search data application on the SLs through programmable delay elements.

Abstract: A CAM includes first and second memory units. The first memory unit includes: a first data memory cell for storing a first data bit; a first comparison circuit for comparing a first search bit with the first data bit to determine if there is a match, and outputting a first comparison result; and a first CMOS logic circuit for performing a logic operation on the first comparison result and outputting a first matching result. The second memory unit includes: a second data memory cell for storing a second data bit; a second comparison circuit for comparing a second search bit with the second data bit to determine if there is a match, and outputting a second comparison result; and a second static CMOS logic circuit for performing a logic operation on the first matching result and the second comparison result, and outputting an output matching result.

Abstract: A CAM array including volatile or non-volatile ternary CAM cells that discharge their associated match line through a special discharge line (e.g., a low match line), instead of through the bit line, is disclosed. Each ternary CAM cell includes a pair of storage elements that are used to store a data bit value, a comparison element that is used to compare the stored value with an applied data value, and a discharge element that is coupled between the discharge line and the match line. During operation, when the applied data value matches the stored value, the discharge element de-couples the discharge line from the match line (i.e., a high voltage on the match line remains high). Conversely, when the applied data value does not match the stored value, the discharge elements couple the discharge line to the match line, thereby discharging the match line to the discharge line.