MULTIPLE ENTRY MATCHING IN A CONTENT ADDRESSABLE MEMORY

摘要

A content addressable memory (CAM) permits a matching operation to be performed over multiple stored entries. The CAM includes a matrix of cells having (n+1) columns and m rows, wherein n and m are each integers greater than or equal to 1, and wherein each row of cells comprises: n data storage cells; a carry storage cell; word compare logic; and carry write logic. For each word of CAM storage, the data storage cells store bits representing one of a number of fractional parts of the data to be stored. The carry storage cell stores a signal that represents whether a previous row generated a catch in a preceding matching operation. By presenting fractional parts of a large comparand in sequence, a final compare operation generates an output that indicates whether the entire comparand (i.e., the fractional parts of the comparand considered together) matched a stored entry in the CAM.