Time-triggered architectures (TTAs) are strong candi- date platforms for safety-critical real-time applications. A typical time-triggered architecture is constituted by one or more clusters. Each cluster consists of nodes communicat- ing with one another via a time-triggered communication protocol. Designing applications to run on such a platform is a challenging task. We address this problem by construct- ing a UML-based design framework which exposes the es- sential features of the time-triggered platforms at the UML- level and allows applications to be developed at a more ab- stract level before full implementation. To support prelim- inary functional validation, we have constructed a transla- tor by which SystemC code can be automatically generated from UML designs. Our framework enables fast prototyping of time-triggered applications and early design validation. It also supports key design principles of TTAs, such as tem- poral firewalls and composability.