DO Data Acquisition Design

The new generation of colliding beam experiments require new and more powerful systems for data acquisition. The DO experiment at Fermilab´s Tevatron-I employs a multi-level trigger system to reduce the primary interaction rate of 50 KHz. to an event recording rate of 1-2 Hz. We describe the DO acquisition system, focusing primarily on the second level, which is based on a large parallel array of MicroVAX-II´s. Data flows from the detector readout crates at a maximum rate of 320 Mbytes/sec into dual-port memories associated with one selected processor in which a VAXELN based program performs the filter analysis of a complete event.