Schematic specification of datapath layout

A graphical assembly language for specifying custom VLSI datapaths is described. By applying certain restrictions to the format, hierarchical annotated schematics which specify the logical structure of a datapath can also be used to specify the physical layout. The close coupling of the logical and physical specifications allows more efficient implementations by highlighting the implications of architectural decisions for the layout. The format restrictions make it possible for the schematics to exactly specify the datapath physical interface on the top and the bottom of the layout, thereby enabling datapaths to be stacked with other separately assembled datapaths and submodules. This approach represents a good compromise between very high level compiled design and direct layout specification, and has been used successfully in six designs