A fast programmable trigger for isolated cluster counting in the BELLE experiment

We have developed a fast programmable trigger processor board based on a fi eld programmable gate array and a complex programmable logic device for use in the BELLE experiment. The trigger board accommodates 144 ECL input sign als, 2 NIM input signals, 24 ECL output signals, and the VME bus specificat ion. An asynchronous trigger logic for counting isolated clusters is used. We have obtained a trigger latency of 50 ns with full access to input and o utput signals via a VME interface. The trigger logic can be modified at any time depending on the experimental conditions. (C) 2001 Elsevier Science B .V. All rights reserved.