The usage of formal description techniques (FDTs) has arisen as a promising way of dealing with the increasing complexity of embedded real-time systems. However, FDTs do not take into account non-functional aspects, such as the time requirements, that are especially important in the context of this kind of system. In this paper, we present how to integrate real-time analysis in the context of the specification and description language (SDL) FDT. In order to get this integration a real-time execution model for SDL is presented to allow us to express hard real-time constraints and solve SDL real-time anomalies as priority inversion and the access to shared resources. Based on this model, a schedulability analysis for systems specifed in SDL is proposed. Additionally, a set of SDL design techniques are proposed to redesign the system to meet the imposed deadlines in case the system does not meet them. To illustrate our proposals, an example of a computerized numerical control (CNC) machine is presented.