A content addressable memory with independent byte and partial match capability

A collaboration from Christopher Newport University (CNU), the Continuous Electron Beam Accelerator Facility (CEBAF) and NASA is designing a 256/spl times/32 specialized Content Addressable Memory (CAM). This 0.8 micron cmos device uses a combination of custom cells developed at CNU and CMOSX standard cells. The CAM is being developed to identify particle tracks at CEBAF for nuclear science experiments, although the design is of a general nature and can be used in other pattern matching applications. The CAM chip has several unique features. First, this four byte wide memory can perform independent byte matching. This means that each byte in the CAM internally stores a matched or unmatched status. This feature allows independent byte streams to be matched simultaneously in the CAM. Second, all byte matches are processed by a threshold circuit which allows for partial word matching to be performed. Depending on the state of external chip inputs the threshold logic can be set to indicate a word match on 1, 2, 3 or 4 byte matches. Small versions have been successfully designed and tested and the final design of the CAM is underway.