Communication and synchronization aspects of a mixed hardware control and data acquisition system

Aspects of the control and data acquisition system of the RFX nuclear fusion experiment are dealt with. The system is built around a local area network that connects programmable controllers, minicomputers with CAMAC front-end, and personal computes as operator consoles. These three types of nodes use compatible software that contains a set of low-level routines corresponding to levels one to four of the ISO OSI (Open Systems Interconnection) recommendations. A detailed description is provided of how the overall system synchronization is achieved. All subsystems (computer and programmable-controller based) follow the same state transition diagram (scheduler) and are coordinated by a supervisor system based on a programmable controller. The solution proposed for the precision timing and waveform generation and its integration with the overall system synchronization are described