A Hardware-Based Real-Time Operating System

The efficient use of multiprogrammed industrial control computers is largely a function of the relationship between hardware and software. A shift in this relationship is desirable, since multiprogrammed computers typically spend a large proportion of computing time in handling their own organization. This situation is compounded in many time-critical industrial process-control applications. This paper proposes that a possible solution lies in the adoption of a hardware-based real-time operating system. The system consists of a microcontroller working in close relationship with a conventional minicomputer. To retain a high degree offlexibility, the microcontroller makes use ofmicroprogrammable, bipolar, bit-slice microprocessor elements. In essense, the unit executes the principal functions of a real-time operating system, acts as a pre-processor for all incoming requests, and ensures a high rate of task switching. The system has been applied in a series of reals time experimental configurations. These were controlled successively by the conventional, software-implemented approach, and by the proposed system. The respective performances were evaluated. The new strategy is shown to result in a better and more economical industrial controller.

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