Abstract
Petri nets have been extensively applied for specification, design, verification, performance evaluation, and simulation of the DECS. A real-time Petri net is a further improvement over timed Petri net. It is aimed for both control and simulation of the system under study. This paper proposes to use a real-time Petri net to represent the stage programming of a programmable logic controller for a discrete-event control system. An illustrated example is used to explore the Petri net-based PLC stage programming methodology.