The paper presents a sampling period dependent RST controller used in the context of control/scheduling co-design. This plant controller is implemented on a real-time operating system as a control task. A scheduling controller adapts control task periods to regulate the processor load. The link established between scheduling and plant control provides more flexibility and robustness w.r.t. the variation of the processor load. Parameterized RST and scheduling controller synthesis are presented and a co-design example illustrates the approach flexibility.