The standard design of control systems is based on the periodic sampling. Every period the data is read from the input, the control law is computed, and the output is written to the actuators. However the periodicity of the sampling instants is a constraint that arises from the ease of implementation and it is not strictly necessary in the control system. In this paper we present an execution model that samples the input “when needed”. This model saves a considerable amount of computational resources. We show the schedulability analysis for a set of control-driven tasks using both Fixed Priority (FP) and Earliest Deadline First (EDF).