The paper introduces a method to model embedded dependability-critical systems as AND-composition of Guarded Statecharts which are special UMLstatecharts. With Guarded Statecharts we can model the reactive behavior of embedded systems so that their quantitative analysis can be performed. First, we present our motivation for using Guarded Statecharts to express the interaction between hardware and software components of embedded systems, and to model faults and errors as state perturbations. Then we discuss how these models are transformed into Stochastic Reward Nets amenable to a quantitative dependability analysis. Finally, our approach is illustrated by an example.