E787 DATA-ACQUISITION SOFTWARE ARCHITECTURE

Brookhaven National Laboratory (BNL) Experiment 787's second generatio n Unix-based data aquisition system is comprised of several independen t programs, each of which controls a specific aspect of the experiment . These programs include packages for reading events from the hardware systems, analyzing and reducing the data, distributing the results to various data consumers, and logging the data to tape or disk. Most of these can be run in stand-alone mode, for ease of development and tes ting. There are also a number of daemon processes for writing special data records to the data streams, and several monitor programs for eva luating and controlling the progress of the whole. Coordination of the se processes is achieved through a combination of pipes, signals, shar ed memory, and FIFOs, overseen by the user through a Motif graphical u ser interface. The system runs on a Silicon Graphics 4D/320, interface d to a Fastbus system through the BNL Fastbus/VME interface (BBFC), an d runs under Irix and Motif/X-windows.