The synthesis of electronic circuits on system level o ers the possibility to nd better locations of the A/D interfaces and to determine parameters like clock rates and bit widths. KANDIS, a tool for (K)construction of mixed ANalog/DIgital Systems, uses a structureoriented expert system for these tasks. The main idea is the succesive construction on functional and algorithmic blocks with di erent kinds of tools and the permanent exchange of resource limitations with constraint propagation.