This paper presents a novel efficient SAT-attack algorithm for logic encryption. The existing SAT-attack algorithm can decrypt almost all encrypted circuits proposed so far, however, there are cases that it takes a huge amount of CPU time. This is because the number of clauses being added during the decryption increases drastically in that case. To overcome that problem, a novel algorithm is developed, which considers the equivalence of clauses to be added. Experiments show that the proposed algorithm is much faster than the existing algorithm.

This paper describes two speed-up techniques for Boolean matching of LUT-based circuits. One is one-hot encoding technique for variables representing input assignments. Though it requires more variables than existing binary encoding technique, almost all added clauses using one-hot encoding are binary clauses, which are suitable for efficient Boolean constraint propagation. The other is CEGAR (counter example guided abstraction refinement) technique which reduces the CPU time significantly. With both techniques, we can solve Boolean matching problem with 9 input function in 20 milliseconds on average, which is faster than the existing algorithms more than one order of magnitude.

The index generation function is a multi-valued logic function which checks if the given input vector is a registered or not, and returns its index value if the vector is registered. If the latency of the operation is critical, dedicated hardware is used for implementing the index generation functions. This paper proposes a method implementing the index generation functions using parallel index generation units. A novel and efficient algorithm called `conflict free partitioning' is proposed to synthesis parallel index generation units. Experimental results show the proposed method outperforms other existing methods.

This paper presents a novel neutron-induced soft-error-rate (SER) estimation tool with a particle transport code: PHITS. The proposed tool can calculate the SER according to various data patterns and the layout of the memory cells in an SRAM. As layouts, two kinds of an NMOS-PMOS-NMOS 6T and an inside-out PMOS-NMOS-PMOS versions are considered. The proposed tool distinguishes a single-event-upset (SEU) SER, a horizontal multiple-cell-upset (MCU) SER, and a vertical MCU SER using an extracting function. The horizontal MCU SER in the inside-out version of the PMOS-NMOS-PMOS 6T SRAM cell layout was expected to be 26-41% less than that of the general NMOS-PMOS-NMOS 6T cell layout.

Analyzing logic masking effects in combinational circuits is an important key to evaluate soft error tolerance of circuits. Logic masking effects can be analyzed exactly with employing fault simulation. The computing complexity of a fault-simulation-based algorithm, however, is proportional to the square of circuit size, which might be unacceptable to achieve a scalable analyzer. On the other hand, a heuristic algorithm AnSER can analyze logic masking effects approximately in runtime proportional to circuit size. AnSER, however, is possible to analyze logic masking effects optimistically especially for circuits protected with spatial redundancy, which might not be suitable for soft error tolerant designs. This paper shows a robust algorithm to analyze logic masking effects pessimistically. Pessimistic analysis is guaranteed with employing the proposed algorithm, while the computing complexity of the proposed algorithm is proportional to circuit size. Experimental results show that the proposed algorithm runs about 91 times faster than a fault-simulation-based exact algorithm with 11.5% overestimate for average susceptibility to errors. For circuits partially protected with spatial redundancy, the proposed algorithm has estimated average susceptibility with 37.9% overestimates on average, while AnSER has estimated average susceptibility with 96% underestimates on average.

This paper presents a new 8T (8-transistor) SRAM cell layout mitigating multiple-bit upset (MBU) in a divided wordline structure. Because bitlines along unselected columns are not activated, the divided wordline structure eliminates a half-select problem and achieves low-power operation, which is often preferred for low-power / low-voltage applications. However, the conventional 8T SRAM with the divided wordline structure engenders MBUs because all bits in the same word are physically adjoining. Consequently, error correction coding (ECC) techniques are difficult to apply. This paper presents a new 8T cell layout pattern that separates internal latches in SRAM cells using both an n-well and a p-substrate. We investigated an SEU cross section of nMOS that is 3.5-4.5 times higher than that of pMOS. Using an iRoC TFIT simulator, we confirmed that the proposed 8T cell has better neutron-induced MBU tolerance. The MBU in the proposed 8T SRAM is improved by 90.70% and the MBU soft error rate (SER) is decreased to 3.46 FIT at 0.9 V when ECC is implemented. Additionally, we conducted Synopsys 3-D TCAD simulation, which indicates that the LET threshold (LETth) in single-event upset (SEU) is also improved by 66.47% in the proposed 8T SRAM by a common-mode effect.

Multi-operand adders usually consist of compression trees which reduce the number of operands per a bit to two, and a carry-propagate adder for the two operands in ASIC implementation. The former part is usually realized using full adders or (3;2) counters like Wallace-trees in ASIC, while adder trees or dedicated hardware are used in FPGA. In this paper, an approach to realize compression trees on FPGAs is proposed. In case of FPGA with m-input LUT, any counters with up to m inputs can be realized with one LUT per an output. Our approach utilizes generalized parallel counters (GPCs) with up to m inputs and synthesizes high-performance compression trees by setting some intermediate height limits in the compression process like Dadda's multipliers. Experimental results show its effectiveness against existing approaches at GPC level and on Altera's Stratix III.

Technology mapping for LUT-based FPGAs can be formulated as DAG covering problem that is to cover given Boolean network with a set of subgraphs called cones, which is known to be NP-hard. So far, no efficient algorithm exists to solve it exactly. Existing technology mappers employ cost flow which is a heuristic metric to indicate how good a cone is for total cost, i.e. area or power. The estimation of total cost based on cost flow might be inaccurate because it does not consider multiple fanouts adequately. This paper proposes a novel method to compute the lower bound for DAG covering problem by transforming a DAG into a tree graph. A novel mapping algorithm with weighted cost flow based on the lower bound is also presented. Weighted cost flow considers the effect of multiple fanouts accurately. Cone Resubstitution: an existing post-processing of technology mapping to reduce area/power by removing unnecessary node duplications is employed. The experimental results show that the proposed method generates networks whose average area is 7%, 7%, 10% smaller than that generated by DAOmap for K = 4, 5, 6 respectively. It is also shown that the proposed method works better than the combination of a mapper based on traditional cost flow and Cone Resubstitution. On the other hand, the proposed method generates LUT networks whose dynamic power is 10% smaller than that generated by Emap for K = 4 on average.

Recent technology mappers for LUT-based FPGAs employ cut enumeration. Although many cuts are often needed to find good network, enumerating all cuts with large size consumes run-time very much. The number of cuts exponentially increases with the size of cuts, which causes long run-time. Furthermore, an inefficiency of bottom-up merging in existing algorithms makes the run-time much longer. This paper presents a novel cut enumeration. The proposed algorithm is efficient because it enumerates cuts without bottom-up merging. Our algorithm has two modes; exhaustive enumeration and partial enumeration. Exhaustive enumeration enumerates all cuts. Partial enumeration enumerates partial cuts with a guarantee that a depth-minimum network can be constructed. The experimental results show that exhaustive enumeration runs about 3 times and 8 times faster than existing bottom-up algorithm [1] [2] for K=8, 9, respectively. The quality of network are the same. Furthermore, partial enumeration runs about 6 times and 18 times faster than bottom-up algorithm for K=8, 9, respectively. Area of network derived by the set of cuts enumerated by partial enumeration is only 4% larger than that derived by exhaustive enumeration on average, and the depth is the same.

This paper proposes a novel behavioral synthesis method that improves performance of synthesized circuits utilizing specialized functional units effectively. Specialized functional units (e.g. multiply-accumulator) are designed for specific operation patterns to achieve shorter delay and/or smaller area than cascaded basic functional units. Almost all conventional methods cannot use specialized functional units effectively under a total area constraint because of their less flexibility for resource sharing. The proposed method makes it possible to solve module selection, scheduling, and functional unit allocation problems utilizing specialized functional units in practical time with some heuristics, and to reduce the number of clock cycles under total area and clock cycle time constraints. Experimental results show that the proposed method has achieved up to 35% and on average 14% reduction of the number of cycles with specialized functional units in practical time.

In this paper we present the post-processing algorithm, Cut Substitution, for technology mapping for LUT-based FPGAs to minimize the area under depth minimum constraint. The problem to generate a LUT’s network whose area is minimum under depth minimum costraint seems to be as difficult as NP-Hard class problem. Cut Substitution is the process to generate a local optimum solution by eliminating redundant LUTs while the depth of network is maintained. The experiments shows that the proposed method derives the solutions whose area are 9% smaller than the solutions of a previous state-of-the-art, DAOmap on average.

This paper addresses parallel prefix adder synthesis which targets minimization of the total switching activities under bitwise timing constraints. This problem is treated as synthesis of prefix graphs which represent global structures of parallel prefix adders at technology-independent level. An approach for timing-driven area minimization has been proposed which first finds the exact minimum solution on a specific subset of prefix graphs by dynamic programming, then restructures the result for further reduction by removing restriction on the subset. This approach can be applied for switching cost minimization almost directly, though it is not so effective as area minimization in some cases. In this paper, a heuristic is proposed which estimates the effect of the restructuring phase and improve cost calculation for some specific cases. Through various kinds of experiments, conditions where this approach can be executed effectively is also discussed.

This paper addresses parallel prefix adder synthesis which targets area minimization under given timing constraints. This problem is treated as synthesis of prefix graphs which represent global structures of parallel prefix adders, and a two-folded robust heuristic is proposed. The first process is dynamic programming based area minimization (DPAM), where the search space is limited to a specific subset of the whole set of prefix graphs by imposing some restrictions on structure of prefix graphs, and an exact minimum prefix graph for the limited space can be found efficiently by dynamic programming. The second process is area reduction with re-structuring (ARRS),which removes imposed restrictions on structure, and restructures the result of DPAM for further area reduction. Experimental results show that the size of prefix graph can be reduced by about 10% compared to an existing approach, and area at gate level can also be reduced by more than 30% compared to a commercial tool in some case.

An ATPG tool is constructed by many functions. For evaluating new idea of only one subfunction accurately, it is necessary to develop all functions of the ATPG tool. Many of efficient techniques like static learning don't satisfy all evaluation standards of ATPG tools. Effectiveness of these efficient techniques is according to the structure of circuits. In FLEETS, practical and open EDA tools include ATPG tool have been developed for evaluating new ideas. The purpose of developing these EDA tools is to provide environment that facilitates evaluating new ideas. An ATPG tool which has flexible interfaces is developed as a part of environment for developing EDA tools

We propose a character size optimization technique to enhance the throughput of maskless lithography as well as photomask manufacture. The number of electron beam shots to draw the patterns of circuits is a dominant factor in the manufacture time and the cost for devices. Our technique is capable of drastically reducing them by optimizing the size of characters, which are the patterns to project and are placed on CP masks. Experimental results show that our technique reduced 72.0% of EB shots in the best case, comparing with the ad hoc character sizing

Pattern matching algorithm is simple and fast comparing to other matching algorithms such as Boolean matching. One major drawback of the pattern matching is that there is a case where a cell needs a lot of patterns representing its logic function. That is because patterns are decomposed into 2-AND/NOT patterns to match against decomposed subject graphs. Furthermore, the conventional technology mapper does not pay much attention to relations among patterns. Each pattern is tried to match independently. In this paper, a novel pattern matching algorithm that does not require patterns to be decomposed and couple of speeding up techniques utilizing inter-relations among cells are described. These methods are very effective for large cell libraries with complex cells. Experimental results show that our methods gain matching time up to 40 times faster. 1 Introduction Pattern matching algorithm is widely used for practical technology mapping programs[1, 2]. It is simple and fast comparing to...

This paper proposes a state reduction algorithm for incompletely specified FSMs. The algorithm is based on iterative improvements. When the number of compatibles is likely to be too large to handle explicitly, they are represented by a BDD. Experimental results are given to demonstrate that the algorithm described here is faster and obtains better solutions than conventional methods.

Article An efficient equivalence checker for combinational circuits Share on Author: Yusuke Matsunaga FUJITSU LABORATORIES LTD, Kawasaki 211-88, Japan FUJITSU LABORATORIES LTD, Kawasaki 211-88, JapanView Profile Authors Info & Claims DAC '96: Proceedings of the 33rd annual Design Automation ConferenceJune 1996 Pages 629–634https://doi.org/10.1145/240518.240637Online:01 June 1996Publication History 70citation315DownloadsMetricsTotal Citations70Total Downloads315Last 12 Months3Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

No abstract available.

Article On computing the transitive closure of a state transition relation Share on Authors: Yusuke Matsunaga View Profile , Patrick C. McGeer View Profile , Robert K. Brayton View Profile Authors Info & Claims DAC '93: Proceedings of the 30th international Design Automation ConferenceJuly 1993 Pages 260–265https://doi.org/10.1145/157485.164884Online:01 July 1993Publication History 26citation439DownloadsMetricsTotal Citations26Total Downloads439Last 12 Months28Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Ordered binary decision diagrams (OBDDs) use restricted decision trees with shared subgraphs. The ordering of variables is fixed throughout an OBDD diagram. However, the size of an OBDD is very sensitive to variable ordering, especially for large circuits. The results of experiments in variable ordering using an experimentally practical algorithm are presented. The algorithm is basically a depth-first traversal through a circuit from the output to the inputs. With this algorithm, circuits having more than 3000 gates and more than 100 inputs can be expressed in reasonable CPU time and with practical memory requirements.>

Article Free AccessA resynthesis approach for network optimization Authors: Kuang-Chien Chen Fujitsu America Inc. Fujitsu America Inc.View Profile , Yusuke Matsunaga Fujitsu Labs. Ltd., Japan Fujitsu Labs. Ltd., JapanView Profile , Saburo Muroga University of Illinois University of IllinoisView Profile , Masahiro Fujita Fujitsu Labs. Ltd., Japan Fujitsu Labs. Ltd., JapanView Profile Authors Info & Claims DAC '91: Proceedings of the 28th ACM/IEEE Design Automation ConferenceJune 1991Pages 458–463https://doi.org/10.1145/127601.127712Published:01 June 1991Publication History 11citation196DownloadsMetricsTotal Citations11Total Downloads196Last 12 Months13Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

The authors present a method for multilevel logic minimization which is particularly suitable for the minimization of look-up table type FPGAs (field programmable gate arrays). Given a set of nodes to be minimized, one first calculates sets of supports which are necessary to construct the functions for the given nodes by applying functional reduction. The functional reduction process guarantees that one can get the minimal support for each node. One then makes a covering table for the set of nodes to be minimized so that one can get the minimal supports to cover all the functions for the given set of nodes to be minimized. The authors present a preliminary implementation and its results for ISCAS combinational benchmark circuits combined with MIS2.1 standard script and a Boolean resubstitution minimizer, and show the effectiveness of the presented method.>

In this paper, we present a new Boolean resubstitution technique with permissible functions and ordered binary decision diagrams, abbreviated as OBDD[8]. Boolean resubstitution is one technique for multi-level logic optimization. Permissible functions are special don't care sets. We represent the data structure of permissible functions and logic functions at each node in Boolean networks in terms of OBDD. Therefore, logic functions can be flexibly manipulated and rapidly executed. We have previously reported a multi-level logic optimization technique called transduction methods[1] using OBDD in ICCAD'89[7]. We have improved the OBDD operation techniques, so that now OBDD operations can be executed faster than we reported before. We also applied Boolean resubstitution to our multi-level logic synthesis. We present results of experiments employing the improved OBDD operation techniques and applying Boolean resubstitution to our multi-level logic synthesis.

Automatic and semi-automatic verification methods for switch-level circuits are presented. Switch-level circuits with no delay (but with/without charge effects) are automatically verified using a formalism with binary decision diagrams (BDD) and temporal logic. Purely bidirectional transistors, such as those whose signal directions are dynamically determined in operations, are treated in the uniform way as nonbidirectional transistors. In the case of switch-level circuits with arbitrary delays, based on the work by M.E. Leeser (1989), the authors present a semi-automatic verification method which uses a propositional theorem prover using BDD. First some assignments of propositional variables to terms of temporal logic are manually given, and then the automatic theorem prover does verification.>

A method to minimize sequential circuits is presented. It uses permissible functions extended for sequential circuits, and can make use of don't cares derived from network topology. Also, an efficient binary decision diagram (BDD) implementation of the extended permissible functions is presented by introducing edge attributes that indicate time label to the BDD. Circuits including latches can be efficiently minimized with the proposed method.>

A Boolean technology mapping with permissible functions is presented. This technique makes use of complementary intermediate logic functions of circuits. Therefore, complementary outputs of ECL gates can be easily handled. High-quality synthesized ECL circuits and CMOS circuits free of logical redundancies are generated. Technology-independent networks are converted into technology-dependent virtual gates network. Virtual gates have an arbitrary number of fan-ins. CMOS virtual networks consist of only NOR and NAND gates, while ECL virtual networks consist of only OR gates (but each gate has complementary outputs). By considering logic function and the device restrictions these virtual gate networks are translated into cell networks using permissible functions.>

A multilevel logic optimizer, which is based on the transduction method, is introduced. The original transduction method is good for optimization, but its calculation time and storage area increase exponentially with the number of inputs because of the use of truth tables. To save CPU time and memory space, the authors implemented this algorithm using ordered binary decision diagrams (OBDD) as the data structure for representing logic functions. Since OBDD does not become as large as other representations, it can handle large circuits without partitioning.>

This paper presents a new parallel-processing architecture for hardware routers based on the Lee algorithm. Unlike the existing machines, which require N/sup 2/ processors to implement the Lee algorithm on an N x N grid plane, the proposed architecture requires only O(N) processors to find a path in O(N) time. A prototype machine with 64 processors has been developed to deal with a 128 x 128 grid plane. The architecture of the machine is discussed, together with its experimental performance data. Further, it is reported that the parallel-processed Lee algorithm is most useful and powerful when applied to interactive rip-up and reroute.