Circuit layout

The problem of layout considered is a problem of placing box-like modules in a plane and connecting them by wires according to a given set of rules. A description is presented of examples which demonstrate the similarity among the layouts of different types of electrical circuits. The traditional division of layout into placement and routing is considered, and typical algorithms are described. The proper placement and selection of shapes appears to be a key in hierarchical design. It is pointed out that good placement is the key ingredient to a successful layout. Computer-aided design (CAD) methods for this operation are still under development. The algorithms for placement can be divided into two groups, related to constructive (initial) placement and interactive improvement of placement.