Abstract: A content addressable memory (CAM) device includes a CAM array and a configuration circuit. The CAM array has a plurality of rows of CAM cells, each row segmented into a plurality of row segments, each row segment including a plurality of CAM cells coupled to a corresponding match line segment, and a match line control circuit having an input coupled to the corresponding match line segment, an output coupled to the match line segment in a next row segment, and a control terminal to receive a corresponding enable signal. The configuration circuit has an input to receive configuration information indicative of a width and depth configuration of the CAM array and having outputs to generate the enable signals.

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: The present invention discloses a butterfly match-line structure and a search method implemented thereby, wherein the parallelism of the match lines is increased to shorten the search time, and a butterfly-type connection is used to reduce the power consumption and achieve the best energy efficiency. Via the butterfly-type connection, information can be reciprocally transmitted between the parallel match lines, which are independent originally. When a miss case occurs, more succeeding memory cells will not be compared but will be turned off. Thereby, the power consumption is reduced. Further, XOR-based conditional keepers are used to reduce the matching time and the power consumption. Besides, such a circuit is also used to shorten the delay time of the butterfly-type connection.

Abstract: The present invention is directed to reduce array area and power consumption in a content addressable memory. A comparator for performing a match determination and a size determination is provided commonly for plural entries each storing data to be retrieved. Each entry includes data storage cells for storing data and mask cells for storing mask bits. The number of mask cells is smaller than that of the data storage cells. Search data is transmitted to the comparator via a search data bus. One of the entries is selected according to a predetermined rule. The comparator decodes the mask bits, generates a mask instruction signal, and performs match comparison and size comparison between the search data and data to be retrieved which is stored in the selected entry.

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: An N-way mode CAM (content addressable memory) array includes M rows that each contain N subwords. Each of the N subwords has a respective mode cell. Additionally, a mode input bus is coupled to each mode cell of each of the N subwords, and a data input bus is coupled to each of the M rows. The mode input bus and the data input bus can uniquely identify as a match a single subword or a plurality of subwords in one of the M rows during a search operation. The N-way mode CAM further includes a row address encoder/generator coupled to each of the M rows, and an address output bus coupled to each of the row address encoder/generators. The mode input bus is also coupled to each of the row address encoder/generators. A uniquely identified single subword address may be outputted on the address output bus.

Abstract: In a method for detecting patterns, a plurality of data patterns is stored in a memory, and a data block from a stream of data is received. A first subset of the data block is compared in parallel to the plurality of data patterns. A second subset of the data block is compared in parallel to the plurality of data patterns, wherein the second subset partially overlaps the first subset. At least one signal is generated that indicates a detected data pattern in the data block.

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: Systems, devices, and methods, including executable instructions are provided for content addressable memory (CAM). One method includes defining the CAM into an array of data words having M rows and N columns, with each of N and M being greater than one. The data words of the CAM are arranged according to a 2-dimensional priority scheme. Data words outside a selected 1×M column are masked to be ignored in determining a match, and the CAM is searched. Each search includes N compare cycles and each compare cycle having a different 1×M column selected. A highest priority match per compare cycle is pipelined from a priority encoder with the pipelined matches arranged to communicate a priority order in a first dimension of the 2-dimensional priority scheme.

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: 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 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: A flash memory is managed by reserving one or more cells as flag cells to represent the number N of bits to store in the cells of a memory block, selecting the value of N from at least three candidates, and programming the flag cell(s) to represent the selected value. A flash memory is managed by selecting a value of the number N>2 of bits to store in the cells of a portion (e.g. a block or page) of the memory, reserving one other cell of the memory as a flag cell to represent how many bits actually are stored in each cell of the portion, and, as the cells of the portion are successively programmed with 1?n?N bits, programming the flag cell to represent n.

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: In a memory array structured of memory cells using a storage circuit STC and a comparator CP, either one electrode of a source electrode or a drain electrode of a transistor, whose gate electrode is connected to a search line, of a plurality of transistors structuring the comparator CP is connected to a match line HMLr precharged to a high voltage. Further, a match detector MDr is arranged on a match line LMLr precharged to a low voltage to discriminate a comparison signal voltage generated at the match line according to the comparison result of data. According to such memory array structure and operation, comparison operation can be performed at low power and at high speed while influence of search-line noise is avoided in a match line pair. Therefore, a low power content addressable memory which allows search operation at high speed can be realized.

Abstract: A tree-style AND-type match circuit device applied to the content addressable memory (CAM) is provided. In this tree-style AND-type match circuit device, a plurality of AND-type match circuit groups branchingly connect with each other by a first AND logic gate. The tree-style AND-type match circuit increases the parallelism of the evaluation of the entire match circuit so that it can efficiently reduce the searching period and the switching activity. Thus, the switching caused by the transformation activity is also shortened. As a result, the match circuit device will not increase the loading of the clock signal so the power consumption is reduced significantly.

Abstract: In the proposed stored don't-care hierarchical search-line scheme, a content-addressable memory (CAM) is divided into several blocks. Each block contains a plurality of local search-lines, a global search-line, a buffer and a memory memory cell. Data are stored in the blocks in order according to the length of the prefix. Data with the longest prefix is stored at the bottommost, and its don't-care state is used as the control signal of the buffer to control whether to transfer the data on the global search-line to the local search-line or not. The local search-line then transfer the value into the memory cell. There is no complex control circuit and extra storage device needed. Moreover, because the control signal directly comes from the don't-care state, power consumption on search-lines can be effectively reduced with no increase of search delay.

Abstract: Content addressable memory (CAM) in which search results such as an address code and an array match signal can be obtained for multiple search widths. The CAM includes a CAM array that can provide match signals and suppress signals for memory locations. Match combining circuitry combines the match signals for memory locations to obtain combined match signals; the combination depends on an indicated search width, which can be one of a set of multiples of the memory location width. A priority encoder provides a priority signal indicating a combined match signal that has priority and is asserted; the priority encoder can therefore be smaller than would be necessary to prioritize all the match signals. An address encoder obtains most significant bits of an address code in response to the priority signal. Select circuitry responds to the priority signal by selecting match signals and suppress signals for the combined match signal with priority.

Abstract: A content addressable memory (CAM) device having a multi-row write function. The CAM device includes a CAM array and an address circuit. The CAM array includes a plurality of CAM cells and word lines coupled to respective rows of the CAM cells. The address circuit is coupled to the CAM array and configured to activate a plurality of the word lines simultaneously to enable a write value to be stored within a selected plurality of the rows of CAM cells.

Abstract: 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.

Abstract: A non-volatile memory device and data comparison circuit are described that facilitate the comparison of data between two blocks of data, such as the I/O buffer or data cache of a memory and the sense amplifiers, that allow for simple and rapid comparison of data bits and results in a signal flag indicating a data match or a mis-match. This allows for a simple parallel data bit comparison capability that allows a fast initial comparison result without requiring a time-consuming individual bit-by-bit data comparison. In one embodiment, two data blocks to be compared are divided into a number of paired segments, wherein each pair of segments are compared in parallel by a data comparison circuit, such that a mis-match can be located to the affected data segments or the results logically combined to indicate a match or mis-match for the complete data blocks.

Abstract: A novel match/mismatch emulation scheme for an addressed location in a CAM system that includes a plurality of CAM blocks. 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. During debug mode, where the individual array cells do not participate in search, all the cells in the debug column behave the same way to emulate a match/mismatch on all words. The circuit provides a control input to include address evaluation of a debug cell in a row. The circuit also provides simultaneous switching noise analysis on an evaluating row. The resulting CAM cell provides a circuit to test individual rows for defects and noise analysis.

Abstract: A CAM (Content Addressable Memory) cell includes first and second data storage portions storing data, horizontal port write gates for storing data applied through a match line pair in the data storage portions in a data write through a horizontal port, and search/read gates for driving the match lines of the match line pair in accordance with the data stored in the data storage portions in a search operation and in a data read through the horizontal port. The match lines are used as horizontal bit line pair, or signal lines for accessing the horizontal port. As the first and second data storage portions are used, it becomes possible to store ternary data, and accordingly, a write mask function of inhibiting a data write at a destination of data transfer is realized. Further, as the CAM cell is used, an arithmetic/logic operation following a search process can be executed selectively, and high speed data writing/reading becomes possible.

Abstract: A segmented search line circuit device for content addressable memory is provided. This device includes a content addressable memory and a segmented unit, wherein the content addressable memory has a plurality of cells arranged in an array and a search line connected between each pair of adjacent cells. Moreover, a first segmented unit is connected between the cells to divide the cells into a plurality of segments to search and between a pair of the adjacent segments to cut off the search lines between the pair of the adjacent segments. Because the circuit of this device is divided into a plurality of segments to search, the circuit of the search line driver need not be modified. As a result, this circuit device can diminish the loading capacitance of the search line driver and reduce the power consumption with the segmented search method.

Abstract: A technique that provides width expansion of two CAMs of varying widths by combining match results from two CAMs by integrating the two CAMs. In one embodiment, a synchronizer circuit triggers the operation of an External Priority Encoder module which can be used to cascade two CAMs to form a wider CAM. When the External Priority Encoder module is used with the CAM, the External Priority Encoder module will receive MATCH signals and control signals from individual CAMs residing on either side, and will be triggered by the last arriving signal between two ports associated with two CAMs. In case one of the ports is disabled the External Priority Encoder module relies totally on the control signal from the other port for operation. The synchronizer circuit has the ability to handle mismatches between the CAMs as well as differentiating valid and invalid combinations between the CAMs.

Abstract: A novel match/mismatch emulation scheme for an addressed location in a CAM system that includes a plurality of CAM blocks. 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. During debug mode, where the individual array cells do not participate in search, all the cells in the debug column behave the same way to emulate a match/mismatch on all words. The circuit provides a control input to include address evaluation of a debug cell in a row. The circuit also provides simultaneous switching noise analysis on an evaluating row. The resulting CAM cell provides a circuit to test individual rows for defects and noise analysis.