Texas Instruments Corporation

Nisha Padattil Kuliyampattil

Krishnan Santhana Rengarajan

Rashmi Sachan

Bryan David Sheffield

Santhosh Narayanaswamy

Abdul M J Muthalif

Rengarajan S Krishnan

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.

Match mismatch emulation scheme for an addressed location in a CAM

A Content Addressable Memory (CAM) device with an improved match sensing circuit is provided. The CAM is provided with a dummy cell and a respective dummy match line, as well as a reference dummy match line. The dummy match line is designed to be evaluated after all other cell match lines. The reference dummy match line triggers a dummy sensing block to initiate a time window for sensing the dummy match line. By this time, all other array match lines will have been stabilized and have reached their respective sensing blocks, to then allow the data to be latched. The match sensing circuit provided may be applied to a variety of arrangements including BCAMs and TCAMs.

Match sensing circuit for a content addressable memory device

A technique that provides highly scalable width expansion architecture for cascading CAMs to facilitate searching of increased wordlengths. In one example embodiment, this is achieved by combining a plurality of CAM devices in a serial cascade arrangement. Each CAM device of the serial cascade arrangement receives a portion of the search word. Each of the CAM devices in the serial cascade arrangement includes a CAM, a plurality of GMAT lines, a dummy match line, and a GMAT interface circuitry. The GMAT interface circuitry facilitates driving the match signals from a substantially previous CAM to a substantially adjacent CAM. The last CAM device is coupled to a match latch and a priority encoder. The first CAM device provides a single mismatch signal on an associated dummy match line for coordinating match signals associated with the plurality of GMAT lines of each of the plurality of CAM devices and to transfer the match signals from the last CAM device to the match latch circuit and the priority encoder and to output a combined search result.

High performance and scalable width expansion architecture for fully parallel CAMs

A tracking circuit in a memory unit which generates sense enable signals at optimal time instances. The tracking circuit includes a scalable driver block containing a number of dummy cells, each having a drive strength identical to the drive strength of a cell in a memory array. The dummy cells are turned on and drive a column as would the memory cells in the memory array. As a result, the scalable driver block approximates the delay caused by (a number of rows in) a column at least when the number of rows is large. An inverse control logic emulates the delay in case of a smaller number of rows, and one of the inverse control logic and the scalable driver blocks provides a pulse, which is used to trigger a sense operation.

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Karnataka, India

Nisha Padattil Kuliyampattil