Time-shared communications software for real-time digital controllers

The paper describes a software package designed to provide operator communication with a realtime digital controller. The structure of the program gives priority to the execution of the control algorithm, while the communication routines run in a time shared manner as a background task. The communication package can be used by the control algorithm itself to signal faults or error conditions to the operator, and provides an automatic method of fault logging. Operator intervention can be initiated from a keyboard or from a special-purpose operator console. The system has been designed and built round a Texas Instruments TI9900 microprocessor-based controller, although the package could be adapted for use with other processors. The total memory requirement of the present implementation is under 2K words