양준성 교수

With the increasing integration of semiconductor design, many problems have emerged. Row-hammering is one of these problems. The row-hammering effect is a critical issue for reliable memory operation because it can cause some unexpected errors. Hence, it is necessary to address this problem. Mainly, there are two different methods to deal with the row-hammering problem. One is a counter based method, and the other is a probabilistic method. This paper proposes the improved version of the latter

Trace buffers are commonly used to capture data during in-system silicon debug. This paper exploits the fact that it is not necessary to capture error-free data in the trace buffer since that information is obtainable from simulation. The trace buffer need only capture data during clock cycles in which errors are present. A three pass methodology is proposed. During the first pass, the rough error rate is measured, in the second pass, a set of suspect clock cycles where errors may be present is

Internal signals of a circuit are observed to analyze, understand, and debug nonconforming chip behavior. The number of signals that can be observed is limited by bandwidth and storage requirements. This paper presents an automated procedure to select which signals to observe to facilitate early detection of circuit malfunction to help find the root cause of a bug. This paper exploits the nature of error propagation in sequential circuits by observing signals which are most often sensitized to p

This paper presents a novel test point insertion method for pseudorandom built-in self-test (BIST) to reduce the area overhead. The proposed method replaces dedicated flip-flops for driving control points by existing functional flip-flops. For each control point, candidate functional flip-flops are identified by using logic cone analysis that investigates the path inversion parity, logical distance, and reconvergence from each control point. Four types of new control point structures are introdu

This paper presents a novel technique for extending the capacity of trace buffers when capturing debug data during post-silicon debug. It exploits the fact that is it not necessary to capture error-free data in the trace buffer since that information can be obtained from simulation. A selective data capture method is proposed in this paper that only captures debug data during clock cycles in which errors are present. The proposed debug method requires only three debug sessions. The first session

Deep neural networks (DNNs) are deployed on hardware devices and are widely used in various fields to perform inference from inputs. Unfortunately, hardware devices can become unreliable by incidents such as unintended process, voltage and temperature variations, and this can introduce the occurrence of erroneous weights. Prior study reports that the erroneous weights can cause a significant accuracy degradation. In safety-critical applications such as autonomous driving, it can bring catastroph

Various studies have been carried out to improve the operational efficiency of the Deep Neural Networks (DNNs). However, the importance of the reliability in DNNs has generally been overlooked. As the underlying semiconductor technology decreases in reliability, the probability that some components of computing devices fail also increases, preventing high accuracy in DNN operations. To achieve high accuracy, ensuring operational reliability, even if faults occur, is necessary.

Nanoscale crossbar architectures have been proposed as viable alternatives for overcoming the fundamental physical limitations of CMOS technology. However due to the manufacturing processes for Nan fabrication and their smaller feature sizes, defect densities are higher. This paper presents an efficient function mapping method in the presence of high defect rates for nanoscale crossbar arrays. Given a function and a defect map that describes fault patterns in the crossbar architecture, the appro

A low-end embedded platform for Internet of Things (IoT) often suffers from a critical trade-off dilemma between security enhancement and computation overhead. We propose PUFSec, a new device fingerprint-based security architecture for IoT devices. By leveraging intrinsic hardware characteristics, we aim to design a computationally lightweight security software system architecture so that complex cryptography computation can dramatically be prohibited. We exploit the innovative idea of Public Ph

Scan-based debug methods give high observability of internal signals, however, they require halting the system to scan out responses from the circuit-under-debug (CUD). This is time consuming as many scan dumps may be required. In this paper, conventional scan chains that have non-destructive scan out capability are configured to operate as multiple MISRs during system operation. Information from the multiple MISRs is monitored periodically to identify erroneous behavior. A procedure for constru

In this paper, an <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -tolerant multiple-input signature register (MISR) compaction methodology that compacts output responses containing unknown <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> values is described. Each bit of the MISR signature is expressed as a linear combination in terms of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xli

This paper presents a novel method for reducing the area overhead introduced by test point insertion. Test point locations are calculated as usual using a commercial tool. However, the proposed method uses functional flip-flops to drive control test points instead of test-dedicated flip-flops. Logic cone analysis that considers the distance and path inversion parity from candidate functional flip-flops to each control point is used to select an appropriate functional flip-flop to drive the contr

In this paper, a technique is presented for selecting signals to observe during silicon debug. Internal signals are used to analyze, understand, and debug circuit misbehavior. An automated procedure to select which signals to observe is proposed to facilitate early detection of circuit malfunction and to enhance the utilization of hardware resources for storage. Signals that are most often sensitized to possible errors are observed in sequential circuits. Given a functional input vector set, an

An X-tolerant multiple-input signature register (MISR) compaction methodology that compacts output streams containing unknown (X) values was described in [Touba 07]. Unlike conventional approaches, it does not use X-masking logic at the input of the MISR. Instead it uses symbolic simulation to express each bit of the MISR signature as a linear equation in terms of the X's. Linearly dependent combinations of the signature bits are identified with Gaussian elimination and XORed together to cancel

Clock distribution is one of the key limiting factors in any high speed, sub-100nm VLSI design. Unwanted clock skews, caused by variation effects like manufacturing variations, power-ground noise etc., consume increasing proportion of the clock cycle. Thus, reducing the clock skew variations is one of the most important objectives of any high-speed clock distribution methodology. Inserting cross-links in a given clock tree is one way to reduce unwanted clock skew variations. However, most of the