A CONTENT-ADDRESSABLE MEMORY FOR USE IN CEBAFS CLAS DETECTOR LEVEL-2 TRIGGERING SYSTEM

A collaboration of researchers from CEBAF, CNU and NASA is designing a 256 x 32 specialized Content Addressable Memory (CANI) for the level 2 triggering system in CEBAF's CLAS detector. These integrated circuit s will find tracks and the momentum and angle of each track. within 2 microseconds of an event. The custom CAM can operate as conventional m emory, performing read and write operations, and can additionally perf orm independent byte compare operations across all words simultaneousl y. It is this compare feature which makes these CAMs attractive for id entifying tracks passing through drift chambers by linking together se gment number triplets within the CAM. Simulations have indicated that less than 16k triplets need to be stored for each sector of the detect or. This implies the level 2 triggering can be performed with 64 CAM c hips per sector, or 384 total. Each data channel into a sector CAM arr ay is buffered in a FIFO and is designed to handle aggregate data rate s up to 750 Mbs for three channels (one channel/superlayer). The archi tecture of the level 2 trigger and details of the CAM chip design are discussed along with a performance report on our prototype CAMs.