A content-addressable memory cell with MNOS transistors

Describes a new associative memory cell in which MNOS transistors are used as storage elements. The memory can perform functions as a read-only memory and at the same time as a read-write memory. The cell can be read as a random-access memory or as a content-addressable memory. As a CAM certain bits can be masked out, i.e., not compared with the stored bits. The comparison can also be controlled from the memory by the stored words. Since the word length or combinations of normal words can be stored in one word of the memory, fewer memory cells are needed than in an ordinary memory. Searches for groups of words (prime implicands) can be performed. Memory cells with an area of 5000-m- have been built to demonstrate the feasibility of the MNOS-CAM.