Decompilation of Flat CMOS Circuits in SPICE Format

 
Cheremisinov D.I., Cheremisinova L.D. (United Institute of Informatics Problems)
 
Abstract - This paper presents a computer program for automatically extracting the hierarchy of a large-scale digital CMOS circuit from its transistor-level netlist. By analogy with programming, the process of conversion of a flat CMOS circuit in SPICE format to a hierarchical circuit in the same format is referred as decompilation. Automatic recognition of a high-level structure from the transistor level netlist of a circuit is important for many tasks in VLSI circuit design. In the SPICE format, electrical circuits consist of elements that are connected to each other by nets, and the natural formal model for describing the circuit is a colored undirected bipartite graph. One part is made up of the terminals of the elements and the ports of the circuit, and the other is the connection between the terminals, i.e. nets. The decompilation is a factoring of flat netlist. If we don’t known how recognize a factor as subcircuit, then the decompilation problem is not tractable. Every group of tran-sistors can be refactored as subcircuit. We select as subcircuit the group of the transistorfor, which it is possible to define a logic function. Our program perform the following sequence of steps: 1) analyze the original SPICE description and construct a hash table for storing the bipartite color graph of the circuit, 2) divide the bipartite color graph into channel-connected-components (CCC), recognize the correct CCC, find their logical function in the form of an algebraic formula and con-struct a hash table for storing instances of CMOS gates, 3) generate a hierarchical SPICE description. Structural analysis of digital circuits was broadly covered by research in the past. For the recognition of subcircuit two classes of approaches exist: library based approaches and algorithmic approaches. Library based approaches use li-brary circuits as templates for recognition of subcircuits and their recognition ability is limited to subcircuits contained in the library. Algorithmic approaches recognize subcircuits for which haves the possibility for to compute the logic function of the gate. Our method allows us to recognize subcircuits with the same logic functions that are not isomorphic at the transistor level.

Keywords - VLSI design, transistor-level netlist, CMOS circuits redesign, SPICE format, subcircuit recognition, algebraic factorization of DNF, canonization of colored undirected graphs.

Декомпиляция КМОП схемы из транзисторов в формате SPICE

 
Черемисинов Д.И., Черемисинова Л.Д. (Объединенный институт проблем информатики НАН Белоруссии, г. Минск)
 
Аннотация - Рассматривается задача преобразования плоской КМОП схемы из транзисторов в формате SPICE иерархическую схему в том же формате. Задача возникает при верификации лейаута СБИС, а также при перепроектирования (reengineering) схем. Описывается метод распознавания подсхем, являющихся КМОП-вентилями. Метод реализован в виде программы на языке C++. Наш метод позволяет распознавать подсхемы с одинаковыми логическими функциями, но не изоморфные на уровне транзисторов, как различные. Это обеспечивает изоморфность исходной и декомпилированной схем.

Ключевые слова - проектирование СБИС, КМОП схемы из транзисторов, формат SPICE, поиск подсхем, КМОП-вентиль, алгебраическая факторизация ДНФ, канонизация цветных неориентированных графов