We reflect on the nature of digital telecommunication systems. We argue that these systems require, by nature, a heterogeneous specification and an implementation with heterogeneous architectural styles. CoWare is a hardware/software co-design environment based on a data model that allows to specify, simulate, and synthesize heterogeneous hardware/software architectures from a heterogeneous specification. CoWare is based on the principle of encapsulation of existing hardware and software compilers and special attention is paid to the interactive synthesis of hardware/software and hardware/hardware interfaces. The principles of CoWare are illustrated by the design process of a spread-spectrum receiver for a pager system.

A just-in-time (JIT) scheduling approach that incorporates register optimizations during scheduling is introduced. The technique is implemented in a hierarchical list scheduler, SMART, that is part of the Cathedral silicon compiler. Due to its computational complexity it can schedule hierarchical graphs containing a thousand or more operations. Experiments on relevant industrial examples show a gain in registers of more than 25% due to the proposed register optimization.>