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This paper presents an algorithm that allows one to create a static schedule of the Profinet IO IRT (Isochronous Real Time) communication, which is an industrial Ethernet protocol standardized in IEC 61158. This algorithm offers an alternative to the available commercial tool, providing comparable results with respect to the resulting schedule makespan. Furthermore, the problem is extended by useful temporal constraints (i.e., release dates, deadlines and end-to-end deadlines of the messages) providing a greater flexibility with respect to the individual messages. Due to this flexibility, it is possible to place the selected messages in various parts of the communication cycle (in order to increase the computational time available for the main-controller application, or to retransmit the synchronization message without holdup in the switch, or to add new messages into the original schedule). The solution is based on a formulation of the Profinet IO IRT scheduling problem in terms of the Resource Constrained Project Scheduling with Temporal Constraints.