The current RFX-mod machine control system relies upon proprietary products for control (PLCs) and supervision (SCADA). To improve the software versatility and to overcome increasing difficulties with legacy products, a major overhaul is being implemented. The new architecture retains the modularity of the current one, but Javais used to program most of the control tasks and the graphical user interfaces, moving the control functions to a new PC-based layer. The physical layer of the communication employs Industrial Ethernet technology for the local area network; data exchange is based on TCP/IP and OPC communication protocols, and on MDS plus technology. The master scheduler talks to non-PLC subsystems using TCP/IP and exchanges data with the tasks on the PLCs through the MDS plus transport layer and OPC. One Windows PC hosts the OPC and MDS plus servers; other PCs execute the control functions and provide the graphical user interface.

This paper describes and analyses the current architecture of the RFX-mod machine control system and the renewed one, which is under development. The first encouraging tests, concerning mainly the communication performance, are reported.