This paper presents component-based and aspect-oriented methodology and tool for designing and developing Real-Time Embedded Control Systems (RTECS). This methodology defines a component model for describing modular and reusable software to cope with the increasing complexity of embedded systems. It proposes an aspect-oriented approach to address explicitly the extra-functional concerns of RTECS, to describe separately transversal real time and security constraints, and to support model properties analysis. The benefits of this methodology are shown via an example of Legway control software, a version of the Segway vehicle built with Lego Mindstorms NXT. Keywords-Model-based design, software component, aspect-oriented programming, embedded system design, embedded control software.