A Computer-Aided Circuit Layout System Based on the Functional Structure and the Physical Structure of Circuits

Abstract

In this paper, there is reported a computer-aided circuit layout system which is based on a new design philosophy. For a circuit to be designed and laid out, two structures called the functional structure (FS) and the physical structure (PS) are defined. The former is concerned with the behavior of the circuit and is hierarchical, while the latter is dependent on the physical realization of the circuit. The FS has “blocks, ” “components, ” "connections, “terminals” and “external terminals” as its basic elements, whereas the PS has “modules, ” “nets, ” “pins” and “external pins” as its basic elements. A circuit description language to specify the FS is designed and its interpreter is computer programmed. In order to have access to specific basic elements, data reference formulae are defined. The realizations of the basic elements of the PS are displayed on a color CRT. Our circuit layout procedure consists of three steps : (1) inputting the FS by using the circuit description language, (2) assigning components and terminals to modules and pins respectively, and (3) layouting basic elements of the PS on the board by using layout and display commands which take data reference formulae as their operand. The last step is performed conversationally and the layout of the elements can easily be changed.