Integrated Circuits and Systems Group

Date: Thursday, September 24, 2015

Time: 10:00 – 11:00 AM

Place: POB 2.402

Talk title: logic debugging by replacing internal gates with new functions

Talk abstract: Firs is a general QBF (Quantified Boolean Formula)-based formulation and its SAT-based solver which can be applied to partial logic synthesis.  It can deal with problems including logic debugging, test pattern generation for multiple functional faults and logic optimization. Then we show its application and extension for logic debugging by replacing internal gates with new appropriate functions.  We describe experiences on debugging industrial circuits, and based on them define different problems: replacing only functions of internal gates (no change in circuit topology), replacing internal gates with new functions of primary inputs, and replacing internal gates with new functions of internal signals.  The last one is the most general approach for logic debugging, but needs new formulations.  A new search method for good internal signals as inputs to the replacing functions, which is based on QBF formulation, is presented. This method is quite different from the previous ones in the sense that it searches for not only appropriate functions which replace the target gates, but also their inputs out of all internal signals.

Biography:

Masahiro Fujita received his Ph.D. in Information Engineering from the University of Tokyo in 1985 on his work on model checking of hardware designs by using logic programming languages. In 1985, he joined Fujitsu as a researcher and started to work on hardware automatic synthesis as well as formal verification methods and tools, including enhancements of BDD/SAT-based techniques. From 1993 to 2000, he was director at Fujitsu Laboratories of America and headed a hardware formal verification group developing a formal verifier for real-life designs having more than several million gates. The developed tool has been used in production internally at Fujitsu and externally as well. Since March 2000, he has been a professor at VLSI Design and Education Center of the University of Tokyo. He has done innovative work in the areas of hardware verification, synthesis, testing, and software verification-mostly targeting embedded software and web-based programs. He has been involved in a Japanese governmental research project for dependable system designs and has developed a formal verifier for C programs that could be used for both hardware and embedded software designs. The tool is now under evaluation jointly with industry under governmental support. He has authored and co-authored 10 books, and has more than 200 publications. He has been involved as program and steering committee member in many prestigious conferences on CAD, VLSI designs, software engineering, and more. His current research interests include synthesis and verification in SoC (System on Chip), hardware/software co-designs targeting embedded systems, digital/analog co-designs, and formal analysis, verification, and synthesis of web-based programs and embedded programs.