Specification of real time control systems by means of sequential function charts

Very many specification techniques have been proposed for real time control systems, each with its own advantages and disadvantages. This paper considers the use of one of these techniques-sequential function charts (SFCs). SFCs are not new-GRAFCET, a standard for such charts, was presented in 1982-but until recently they were not widely known. This has now changed and the technique has received considerable coverage in the technical literature. In addition, several control system manufacturers have adopted SFCs as a programming language. The paper begins with a brief survey of specification techniques for real time control systems; it moves on to trace the origins of SFCs and then describes them in some detail. Finally, the practical production of SFCs is discussed and the need for an SFC diagram editor is identified. Current options in this field are presented