THE EQUIPMENT ACCESS SOFTWARE FOR A DISTRIBUTED UNIX-BASED ACCELERATOR CONTROL-SYSTEM

This paper presents a generic equipment access software package for a distributed control system using computers with UNIX or UNIX-like oper ating systems. The package consists of three main components, an appli cation Equipment Access Library, Message Handler and Equipment Data Ba se. An application task, which may run in any computer in the network, sends requests to access equipment through Equipment Library calls. T he basic request is in the form Equipment-Action-Data and is routed vi a a remote procedure call to the computer to which the given equipment is connected. In this computer the request is received by the Message Handler. According to the type of the equipment connection, the Messa ge Handler either passes the request to the specific process software in the same computer or forwards it to a lower level network of equipm ent controllers using MIL2553B, GPIB, RS232 or BITBUS communication. T he answer is then returned to the calling application, Descriptive inf ormation required for request routing and processing is stored in the real-time Equipment Data Base. The package has been written to be port able and is currently available on DEC Ultrix, LynxOS, HPUX, XENIX, OS -9 and Apollo domain.