In this paper we describe a complete design methodology for a globally asynchronous onchip communication network connecting both locally-synchronous and asynchronous modules. Synchronous modules are equipped with asynchronous wrappers which adapt their interfaces to the self-timed environment and prevent metastability. These wrappers are assembled from a concise library of predesigned technology-independent elements and provide high-speed data transfer. We confirmed the validity of our concept by successfully applying it to an ASIC design implementing the Safer crypto-algorithm.