Architecture and development of the CDF hardware event builder

A hardware event builder (EVB) has been developed for use at the collider detector experiment at Fermi National Accelerator (CDF). The event builder presently consists of five FASTBUS modules and has the task of reading out the front-end scanners, reformatting the data into YBOS band structure, and transmitting the data to a level-3 (L3) trigger system which is composed of multiple VME processing nodes. The event builder receives its instructions from a VAX-based buffer manager program via a Unibus processor interface. The buffer manager instructs the event builder to read out one of the four CDF front end buffers. The event builder informs the buffer manager when the event has been formatted and is then instructed to push it up to the L3 trigger system. Once the event is in the L3 system, a decision is made as to whether to write the event to tape. The authors describe the EVB modules and discuss the flexibility of the EVB architecture, the measured system throughput, and the prototyping of the EVB