A fully computerized and distributed VME system for control and data acquisition on the tokamak ISTTOK

Abstract The ISTTOK operation and research programme require a very reliable control and data acquisition system due to the pulsed nature of the tokamak discharges. This system (SCAD) was designed in a distributed, modular, multivendor, integrated and transparent approach, taking advantage of recent improvements in networking, front-end processing and database management. This paper reports some of the most relevant aspects involved in the design of the SCAD current configuration. The computer system is based on personal computers (PCs) and Motorola 68 000 family microprocessors, linked by an ethernet local area network. Control is made by a vacuum controller unit as well as by VME digital I/O, timing and digital-to-analog converter modules. Data acquisition is provided by VME instrumentation as well as by PC based modules and by a digitizing oscilloscope. All VME modules were developed on site. The ISTTOK operation is controlled by a supervisory program. Data from the engineering and physics diagnostics is stored in a central database.