Jerzy Tyszer

Embedded deterministic test

This paper presents a novel test-data volume-compression methodology called the embedded deterministic test (EDT), which reduces manufacturing test cost by providing one to two orders of magnitude reduction in scan test data volume and scan test time. The presented scheme is widely applicable and easy to deploy because it is based on the standard scan/ATPG methodology and adopts a very simple flow. It is nonintrusive as it does not require any modifications to the core logic such as the insertion of test points or logic bounding unknown states. The EDT scheme consists of logic embedded on a chip and a new deterministic test-pattern generation technique. The main contributions of the paper are test-stimuli compression schemes that allow us to deliver test data to the on-chip continuous-flow decompressor. In particular, it can be done by repeating certain patterns at the rates, which are adjusted to the requirements of the test cubes. Experimental results show that for industrial circuits with test cubes with very low fill rates, ranging from 3% to 0.2%, these schemes result in compression ratios of 30 to 500 times. A comprehensive analysis of the encoding efficiency of the proposed compression schemes is also provided.

Embedded deterministic test for low cost manufacturing test

This paper introduces embedded deterministic test (EDT) technology, which reduces manufacturing test cost by providing one to two orders of magnitude reduction in scan test data volume and scan test time. The EDT architecture, the compression algorithm, design flow, experimental results, and silicon implementation are presented.

Convolutional compaction of test responses

This paper introduces a finite memory compactor called convolutional compactor that provides compaction ratios of test responses in excess of 100x even for a very small number of outputs. This is combined with the capability to detect multiple errors, handling of unknown states, and the ability to diagnose failing scan cells directly from compacted responses. A convolutional compactor can be easily configured into a MISR that preserves most of these properties. Experimental results demonstrate the efficiency of compaction for several industrial circuits.

Decompression of test data using variable-length seed LFSRs

This paper presents a new and efficient scheme to decompress a set of deterministic test vectors for circuits with scan. The scheme is based on the reseeding of a Multiple Polynomial Linear Feedback Shift Register (MP-LFSR) but uses variable-length seeds to improve the encoding efficiency of test vectors with a wide variation in their number of specified bits. The paper analyzes the effectiveness of this novel approach both theoretically and through extensive experiments. A modular design of the decompression hardware re-uses the same LFSR used for pseudo-random vector generation and scan registers to minimize the area overhead.

Test responses compaction in accumulators with rotate carry adders

An accumulator-based compaction (ABC) scheme for parallel compaction of test responses is presented. In this scheme an accumulator with an n-bit binary adder is slightly modified such that the quality of compaction defined by the asymptotic coverage drop is similar to that offered by shift registers with irreducible polynomials of cellular automata. A Markov-chain model is used to analyze both the asymptotic coverage drop introduced by this scheme, and its transient behavior. It is shown that the asymptotic coverage drop depends both on the size of the accumulator and the probability of a fault injection. The upper bound of the coverage drop during the transition phrase is also provided. The proposed scheme is compatible with the width of the data path, and the test can be applied at the normal mode speed. The minimal hardware overhead involves only one-bit register to implement the feedback between the carry-out and carry-in lines. >

Ring generators - new devices for embedded test applications

This paper presents a novel methodology of designing generators and compactors of test data. The essence of the proposed approach is to use a set of transformations, which alters the structure of the conventional linear feedback shift registers (LFSRs) while preserving the transition function of the original circuits. It is shown that after applying the transition function preserving transformations in a certain order, the resultant circuits feature a significantly reduced the number of levels of XOR logic, minimized internal fanouts, and simplified circuit layout and routing, as compared to previous schemes based on external feedback LFSRs, internal feedback LFSRs, and cellular automata, all implementing the same characteristic polynomial. Consequently, the proposed devices can operate at higher speeds than those of conventional solutions and become highly modular structures.

Accumulator-based compaction of test responses

An accumulator-based compaction (ABC) scheme for parallel compaction of test responses is introduced. The asymptotic and transient coverage drop introduced by accumulators with binary and 1s complement adders is studied using Markov chain models. It is proven that the asymptotic coverage drop in ABC with binary adders is 2/sup -k/, where k is the number of bits in the adder that the fault can reach. In ABC with 1s complement adders, the asymptotic coverage drop for a fairly general class of faults is (2n-1)/sup -1/, where n is the total number of bits. The analysis of transient behavior relates the coverage drop with the probability of fault injection, the size of the accumulator, and the length of the test experiment. The process is characterized by damping factors derived for various values of these parameters. >

Diagnosis of scan cells in BIST environment

The paper presents a new fault diagnosis technique for scan-based designs with BIST. It can be used for nonadaptive identification of the scan cells that are driven by erroneous signals. The proposed scheme employs a pseudorandom scan cell selection routine which, in conjunction with a conventional signature analysis and simple reasoning procedure, allows flexible trade-offs between the test application time and the diagnostic resolution.

Finite memory test response compactors for embedded test applications

This paper introduces a new class of finite memory compaction schemes called convolutional compactors (CCs). They provide compaction ratios of test responses in excess of 100/spl times/, even for a very small number of outputs. This is combined with the capability to detect multiple errors, handling of unknown states, and the ability to diagnose failing scan cells directly from compacted responses. The CCs can also be used to significantly enhance conventional multiple input signature registers. Experimental results presented in the paper demonstrate the efficiency of convolutional compaction for several industrial circuits.

Automated synthesis of phase shifters for built-in self-test applications

This paper presents novel systematic design techniques for the automated register transfer level synthesis of phase shifters-circuits used to remove effects of structural dependencies featured by pseudorandom test pattern generators driving parallel scan chains. Using a concept of linear feedback shift register (LFSR) duality this paper relates the logical states of LFSRs and circuits spacing their inputs to each of the output channels. Consequently, the method generates a phase-shifter network satisfying criteria of channel separation and circuit complexity by taking advantage of simple logic simulation of the LFSRs. It is shown that it is possible to synthesize in a time-efficient manner very large and fast phase shifters for built-in self-test applications with guaranteed minimum phaseshifts between scan chains, and very low delay and area of virtually one two-way XOR gate/channel.