Patent ID: 7894227

Claim:
A content addressable memory having a memory array divided in a plurality of entries each storing data to be retrieved, each of the entries being divided in sub-entries each having data storage cells and mask cells every predetermined number of bits, the number of mask cells in each sub-entry being smaller than the number of data storage cells, and the mask cell for storing information for masking data stored in the data storage cells, the content addressable memory comprising: entry selecting means for selecting a corresponding entry in the memory array in accordance with a given entry designation signal; pre-search means for generating an entry designation signal for designating a corresponding entry in the memory array in accordance with search data and supplying the entry designation signal to the entry selecting means; a sense amplifier circuit for detecting and amplifying data stored in an entry selected by the entry selecting means on the sub-entry unit basis; and a comparing/logic processing circuit for receiving the search data and output data having a predetermined bit width of the sense amplifier circuit, comparing the search data and the output data having a predetermined bit width of the sense amplifier circuit, and generating a signal indicative of a result of the comparison.