Fusion Engineering and Design 81 (2006) 1835–1840 Integration of MDSplus in real-time systems A. Luchetta, G. Manduchi * , C. Taliercio Consorzio RFX, Euratom-ENEA Association, corso Stati Uniti 4, 35127 Padova, Italy Available online 6 May 2006 Abstract RFX-mod makes extensive usage of real-time systems for feedback control and uses MDSplus to interface them to the main Data Acquisition system. For this purpose, the core of MDSplus has been ported to VxWorks, the operating system used for real-time control in RFX. Using this approach, it is possible to integrate real-time systems, but MDSplus is used only for non-real-time tasks, i.e. those tasks which are executed before and after the pulse and whose performance does not affect the system time constraints. More extensive use of MDSplus in real-time systems is foreseen, and a real-time layer for MDSplus is under development, which will provide access to memory-mapped pulse files, shared by the tasks running on the same CPU. Real-time communication will also be integrated in the MDSplus core to provide support for distributed memory-mapped pulse files. © 2006 Elsevier B.V. All rights reserved. Keywords: Real-time systems; Data acquisition; Distributed systems 1. Introduction The MDSplus data acquisition package is currently used in several nuclear fusion devices, such as RFX [1], CMOD [2], NSTX [3]. In these experiments MDSplus is used pervasively, i.e. for data acquisition, data access and presentation, graphical user interface and sequence coordination. Several other experiments employ cus- tom data acquisition systems, but use MDSplus for data presentation, i.e. to provide a MDSplus interface to stored experiment data so that data can be accessed by data analysis programs using a standard data access library. * Corresponding author. Tel.: +39 049 8295039; fax: +30 049 8700718. E-mail address: gabriele.manduchi@igi.cnr.it (G. Manduchi). The architecture of MDSplus is based on the con- cept of shot (or pulse) and therefore MDSplus han- dles pulsed experiments in which plasma discharge is achieved for a short period, during which the data acquisition system typically does not work, data being acquired by transient recorders which fill their local memory during the pulse. MDSplus comes in action before the shot, to download configuration parameters, and after the shot, to upload data stored in transient recorders and other devices and to store data into the pulse files. This organization fulfils the requirements for most current fusion devices, but cannot be used in the next generation of fusion devices, for which the plasma discharge is quasi-continuous. For such devices, it is not acceptable to restrict the usage of the data acquisition system to before and after the shot, and the system must carry out data acquisition and control 0920-3796/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2006.04.035