Patent ID: 6477071
Filing Date: 2002-11-05
Classification: G11C

Abstract:
In a content addressable memory comprising at least one row of memory cells, each memory cell in said row for storing data and including a comparator for comparing the data in said memory cell with search data selectively coupled to the memory cell and a match line connected to the memory cell to indicate whether the search data matched the data stored-in the memory cell, a row compare circuit for generating a result output that indicates when the data in each memory cell in said row matches the search data coupled thereto, comprising:a plurality of comparison control units for partitioning the memory cells in said row into at least two segments of memory cells, each said comparison control unit for controlling the comparing of the data in the memory cells grouped in its associated segment of memory cells with search data coupled to the memory cells in said segment, each said memory cell in a given segment connected in common to a match line, said match line being caused to indicate whether the search data does not match the data stored in any of the memory cells in that segment, each said comparison control unit except the first comparison control unit operative to determine the result of a previous segment's compare operation, each said comparison control unit being prevented from executing a compare operation with respect to its segment of memory cells when a mismatch has been detected by a previous segment's compare operation in said row, and wherein the first comparison control unit in said row presets the match line connected to the memory cells in the first segment of memory cells to cause the memory cells in said first segment to be compared with search data coupled to the memory cells in said segment whenever a row comparison operation is initiated, said first segment match line being caused to indicate whether the search data does not match the data stored in any of the memory cells in said first segment, said subsequent match lines in said row being preset only if the combined result of the segment compare operations of the respective preceding segments is a match; and a match determination unit coupled to the match line of the last segment of memory cells in said row for generating said result output.