Technology mapping apparatus for a combination circuit for use in automatically synthesizing an LSI logic circuit

摘要

A graph converter converts functionally descriptive information expressing a combination circuit into a graph expression having only NOR and inversion circuits. A multiple input NOR converter detects from the above graph expression a circuit element having a NOR circuit and an inversion circuit alternately connected in series and converts the circuit element to a graph expression where a multiple input NOR circuit replaces the circuit element. A cell mapper detects from the above graph expression a circuit element having NOR circuits connected together in series, maps the circuit element to gate cells with or without a composite cell, and outputs the mapping result with the least number of gates as the mapping output for the circuit element. A circuit element having a NOR circuit and an inversion circuit alternately connected in series is substituted by a unique multiple input NOR circuit. A circuit element mapped to a composite cell is efficiently determined just by detecting a circuit element where "nor" circuits are connected together in series. It is possible to replace NOR circuits by NAND circuits.