Kwang-Ting Cheng

Fast Human Detection Using a Cascade of Histograms of Oriented Gradients

We integrate the cascade-of-rejectors approach with the Histograms of Oriented Gradients (HoG) features to achieve a fast and accurate human detection system. The features used in our system are HoGs of variable-size blocks that capture salient features of humans automatically. Using AdaBoost for feature selection, we identify the appropriate set of blocks, from a large set of possible blocks. In our system, we use the integral image representation and a rejection cascade which significantly speed up the computation. For a 320 × 280 image, the system can process 5 to 30 frames per second depending on the density in which we scan the image, while maintaining an accuracy level similar to existing methods.

A partial scan method for sequential circuits with feedback

A method of partial scan design is presented in which the selection of scan flip-flops is aimed at breaking up the cyclic structure of the circuit. Experimental data are given to show that the test generation complexity may grow exponentially with the length of the cycles in the circuit. This complexity grows only linearly with the sequential depth. Graph-theoretic algorithms are presented to select a minimal set of flip-flops for eliminating cycles and reducing the sequential depth. Tests for the resulting circuit are generated by a sequential logic test generator. An independent control of the scan clock allows insertion of scan sequences within the vector sequence produced by the test generator. An independent control of the scan clock allows insertion of scan sequences within the vector sequences produced by the test generator. 98% fault coverage is obtained for a 5000-gate circuit by scanning just 5% of the flip-flops. >

Automatic Functional Test Generation Using The Extended Finite State Machine Model

We present a method of automatic generation of functional vectors for sequential circuits. A high-level description of the circuit, in VHDL or C, is assumed available. Our method automatically transforms the high-level description, in VHDL or C, of a circuit into an extended finite state machine (EFSM) model using which functional vectors are generated. The EFSM model is a generalization of the traditional state machine model. It can be considered as a compact representation of the machine that preserves many nice properties of a traditional state machine. Theoretical background of the EFSM model will be addressed. Our method guarantees that the generated vectors cover every statement in the high-level description at least once. Experimental results show that a set of comprehensive functional vectors for sequential circuits with more than a hundred flip-flops can be generated automatically in a few minutes of CPU time using our prototype system.

False-path-aware statistical timing analysis and efficient path selection for delay testing and timing validation

We propose a false-path-aware statistical timing analysis framework. In our framework, cell as well as interconnect delays are assumed to be correlated random variables. Our tool can characterize statistical circuit delay distribution for the entire circuit and produce a set of true critical paths.

Delay testing for non-robust untestable circuits

Recently published results have shown that, for many circuits, only a small percentage of path delay faults is robust testable. Among the robust untestable faults, a significant percentage of them is not non-robust testable either. In this paper, we take a closer look at the properties of these non-robust untestable faults with the goal of determining whether and how these faults should be tested.<<ETX>>

A BIST scheme for on-chip ADC and DAC testing

In this paper we present a BIST scheme for testing on-chip A/D and D/A converters. We discuss on-chip generation of linear ramps as test stimuli, and propose techniques for measuring the DNL and INL of the converters. We validate the scheme with software simulation-5% LSB (least significant bit) test accuracy can be achieved in the presence of reasonable analog imperfection.

Automatic generation of functional vectors using the extended finite state machine model

We present a method of automatic generation of functional vectors for sequential circuits. These vectors can be used for design verification, manufacturing testing, or power estimation. A high-level description of the circuit in VHDL or C is assumed available. Our method automatically transforms the high-level description of a circuit in VHDL or C into an extended finite state machine (EFSM) model that is used to generate functional vectors. The EFSM model is a generalization of the traditional state machine model. It is a compact representation of models with local data variables and preserves many nice properties of a traditional state machine model. The theoretical background of the EFSM model is addressed in this article. Our method guarantees that the generated vectors cover every statement in the high-level description at least once. Experimental results show that a set of comprehensive functional vectors for sequential circuits with more than a hundred flip-flops can be generated automatically in a few minutes of CPU time using our prototype system.

Fast statistical timing analysis by probabilistic event propagation

We propose a new statistical timing analysis algorithm, which produces arrival-time random variables for all internal signals and primary outputs for cell-based designs with all cell delays modeled as random variables. Our algorithm propagates probabilistic timing events through the circuit and obtains final probabilistic events (distributions) at all nodes. The new algorithm is deterministic and flexible in controlling run time and accuracy. However, the algorithm has exponential time complexity for circuits with reconvergent fanouts. In order to solve this problem, we further propose a fast approximate algorithm. Experiments show that this approximate algorithm speeds up the statistical timing analysis by at least an order of magnitude and produces results with small errors when compared with Monte Carlo methods.

Designing circuits with partial scan

In this scan design methodology, only selected faults are targeted for detection. These faults are those not detected by the designers functional vectors. The test generator decides exactly which flip-flops should be scanned using one of two methods. In the first method, all possible tests are generated for each target fault, and the set of tests requiring the fewest flip-flops is selected. In the second method, only one test is generated for each fault, and the use of flip-flops is avoided as much as possible during test generation. Examples of actual VLSI circuits show a savings of at least a 40% in full-scan overhead.<<ETX>>

A Circuit SAT Solver With Signal Correlation Guided Learning

Boolean Satisfiability has attracted tremendous research effort in recent years, resulting in the developments of various efficient SAT solver packages. Based upon their design architectures, researchers have tried to develop better heuristics to further improve its efficiency, by either speeding up the Boolean Constraint Propagation (BCP) procedure or finding a better decision ordering (or both). In this paper, we propose an entirely different SAT solver design concept that is circuit-based. Our solver is able to utilize circuit topological information and signal correlations to enforce a decision ordering that is more efficient for solving circuit-based SAT problem instances. In particular, for unsatisfiable circuit examples, our solver is able to achieve from 2x up to more than 75x speedup over a state-of-the-art SAT solver.