The NA48 trigger supervisor

The aim of the NA48 experiment at CERN SPS is to measure the direct CP violation in the neutral kaon system with an accuracy of 2/spl times/10/sup -4/. This demanding sensitivity requires both very high statistics and detailed control of systematics. High performances of the trigger and acquisition systems are necessary. This paper describes the NA48 Trigger Supervisor, a 40 MHz pipelined hardware system which represents the Level 2 central decision system. It merges and processes the trigger informations coming from the local trigger sources, dedicated devices optimized to recognize charged and neutral two-pions decays. The final trigger packet includes the timestamp information, used in a pipeline read-out framework to retrieve detector data from the front-end memories. A description of the Trigger Supervisor design and of its functionality is given below.