A number of software routines comprising at least two software routines are created for an interface unit of a computer system having a first and a second interface processor for forwarding input data from a peripheral to a processor of the computer system on which software is programmed. A first subset of the software routines is assigned to a first category provided for task-synchronous data transfer, and a second subset of the software routines are assigned to a second category provided for continuous data transfer. The first interface processor is programmed with the first subset and the second interface processor with the second subset of software routines. During execution of the software, the first subset is cyclically executed by the first interface processor at a first cycle rate, and the second subset is cyclically executed by the second interface processor at a second cycle rate.