THE USE OF CONTENT-ADDRESSABLE MEMORIES IN THE LEVEL-2 TRIGGER FOR THE CLAS DETECTOR AT CEBAF

The LEVEL 2 trigger in the CLAS detector will find tracks and associat e a momentum and angle with each track within 2 mu s after the event. This is done through a hierarchical track finding design in which trac k segments are found in each drift chamber axial superlayer. An array of 384 custom content addressable (or associative) memories (CAMs) use s independent subfield matching to link these track segments into road s. The track parameters corresponding to each found road are then look ed up in a separate memory. We present the overall architecture of the LEVEL 2 trigger, the details of how the CAM chip links tracks segment s to find roads, and report on the performance of our prototype CAM ch ips.