The LEP OPAL Trigger and VME Based Data Collection

The LEP OPAL data collection process is based on a distributed architecture of the 16/32 bit MC 68000 microprocessors associated with a coherent use of the VME bus. This paper describes this system which collects data from each detector branch and delivers the information through a hierarchical tree structure to a VME matrix interface where individual events are assembled and filtered, ready for delivery to mass storage.