Interaction semantics of a symbolic layout editor for parameterized modules

An interactive graphical editor for parameterized layout generators, based on symbolic layout, is discussed. One basic idea is to have built-in rules, corresponding to basic knowledge about elementary things in VLSI design, in order to make the tool behave as an experienced partner to the designer. It was found that the fundamental problem was not to implement but to select a proper set of rules to define the semantics of the tool. The problem was attacked by actually implementing various experimental versions and using them to create layout. These experiments and the conclusions are summarized. For example, the fundamental importance of proper mechanisms to explicitly express geometrical constraints, such as pitch-matching, is shown. It is also shown how parameterization can be introduced in a user-friendly and natural way through the graphical, symbolic layout view