The 3B20D Processor & DMERT Operating System: DMERT Operating System

This article describes the design of the DMERT operating system nucleus. The reader should be familiar with the basic architecture of Duplex Multiple Environment Real Time (DMERT), which is described in a companion paper.1 The operating system nucleus is composed of: the kernel, which supports interprocess communication mechanisms, the system clock, and interrupts; the special processes, which perform memory management and scheduling; two supervisor processes, which handle process management and the UNIX* operating system environment; and three kernel processes that control communication with peripherals and the file system. In general, DMERT applications view the operating system nucleus * Trademark of Bell Laboratories. 303 as one entity rather than a set of cooperating processes. Thus, the interrelationships between these processes are hidden from them. This article describes the design of DMERT's nucleus from the user's perspective; that is, it is feature oriented rather than process oriented. After finishing this paper, however, the reader should be familiar with both the feature set and the internal design of the cooperating processes. In order for a process to use any of the operating system's features, it must interface to the operating system with Operating System Traps (OSTs) or Interprocess Communication (IPC) mechanisms. OSTs were discussed in Ref. 1, and Section II describes IPCs. Sections III, IV, and V define the image and life cycle of processes by describing how memory is handled, the scheduling options, and how processes are created and terminated.