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

The paper deals with some specific aspects of the control and data acquisition system of the RFX nuclear fusion experiment, at present under construction in Padova, Italy. This system is built around a local area network which connects programmable controllers, minicomputers with CAMAC front-end, and personal computers as operator consoles. These three types of nodes use compatible software which contain a set of low level routines according to levels one to four of the IS0 OS1 recommendations. The paper describes in detail how the overall system synchronization is achieved. All subsystems (computer and programmable controller based) follow the same state transition diagram ('scheduler'). All subsystems are co-ordinated by a programmable controller based supervisor system which communicates with the operator via the main machine console (physically a personal computer). Stand-alone operation of the subsystems is also possible for commissioning and trouble-shooting situations. Another aspect described in the paper is the proposed solution for the precision timing and waveform generation (which uses commercial CAMAC hardware) and its integration with the overall system synchronization.