Abstract: Built-in self-test techniques for integrated circuits that address the issue of unknown states. Some implementations use a specialized scan chain selector coupled to a time compactor. The presence of the specialized scan chain selector increases the efficiency in masking X states. Also disclosed are: (1) an architecture of a selector that works with multiple scan chains and time compactors, (2) a method for determining and encoding per cycle scan chain selection masks used subsequently to suppress X states, and (3) a method to handle an over-masking phenomenon.

Abstract: A method for applying test patterns to scan chains in a circuit-under-test. The method includes providing a compressed test pattern of bits; decompressing the compressed test pattern into a decompressed test pattern of bits as the compressed test pattern is being provided; and applying the decompressed test pattern to scan chains of the circuit-under-test. The actions of providing the compressed test pattern, decompressing the compressed test pattern, and applying the decompressed pattern are performed synchronously at the same or different clock rates, depending on the way in which the decompressed bits are to be generated. A circuit that performs the decompression includes a decompressor such as a linear finite state machine adapted to receive a compressed test pattern of bits. The decompressor decompresses the test pattern into a decompressed test pattern of bits as the compressed test pattern is being received.

Abstract: Disclosed herein are exemplary embodiments of a so-called “X-press” test response compactor. Certain embodiments of the disclosed compactor comprise an overdrive section and scan chain selection logic. Certain embodiments of the disclosed technology offer compaction ratios on the order of 1000×. Exemplary embodiments of the disclosed compactor can maintain about the same coverage and about the same diagnostic resolution as that of conventional scan-based test scenarios. Some embodiments of a scan chain selection scheme can significantly reduce or entirely eliminate unknown states occurring in test responses that enter the compactor. Also disclosed herein are embodiments of on-chip comparator circuits and methods for generating control circuitry for masking selection circuits.

Abstract: Disclosed herein are exemplary methods, apparatus, and systems for performing timing-aware automatic test pattern generation (ATPG) that can be used, for example, to improve the quality of a test set generated for detecting delay defects or holding time defects. In certain embodiments, timing information derived from various sources (e.g. from Standard Delay Format (SDF) files) is integrated into an ATPG tool. The timing information can be used to guide the test generator to detect the faults through certain paths (e.g., paths having a selected length, or range of lengths, such as the longest or shortest paths). To avoid propagating the faults through similar paths repeatedly, a weighted random method can be used to improve the path coverage during test generation. Experimental results show that significant test quality improvement can be achieved when applying embodiments of timing-aware ATPG to industrial designs.

Abstract: Aspects of the invention relate to scan-based test architecture for interconnects in stacked designs. The disclosed scan-based test architecture comprises a scan chain. Scan cells on the scan chain are configured to receive data from, based on bits of a control signal, outputs of neighboring scan cells or outputs of mixing devices that combine data from through-silicon vias with data from the outputs of the neighboring scan cells. The scan-based test architecture can be used to identify single or multiple defective through-silicon vias.

Abstract: Aspects of the invention relate to a test-per-clock scheme based on dynamically-partitioned reconfigurable scan chains. Every clock cycle, scan chains configured by a control signal to operate in a shifting-launching mode shift in test stimuli one bit and immediately applies the newly formed test pattern to the circuit-under-test; and scan chains configured by the control signal to operate in a capturing-compacting-shifting mode shift out one bit of previously compacted test response data while compacting remaining bits of the previously compacted test response data with a currently-captured test response to form currently compacted test response data. A large number of scan chains may be configured by the control signal to work in a mission mode. After a predetermined number of clock cycles, a different control signal may be applied to reconfigure and partition the scan chains for applying different test stimuli.

Abstract: Aspects of the disclosed technology relate to techniques of test pattern generation based on the cell transition fault model. An assignment for two consecutive clock cycles at inputs of a complex cell in a circuit design is determined based on a gate-level representation of the circuit design. The assignment includes a first transition at one of the inputs which is sensitized by remaining part of the assignment to cause a second transition at an output of the complex cell. A test pattern that generates the assignment at the inputs and propagates a value at the output corresponding to the second clock cycle of the two consecutive clock cycles from the output to an observation point is then derived based on the gate-level representation.

Abstract: Various aspects of the disclosed technology relate to techniques of using control test points to enhance hardware security. The design-for-security circuitry reuses control test points, a part of design-for-test circuitry. The design-for-security circuitry comprises: identity verification circuitry; scrambler circuitry coupled; and test point circuitry. The test point circuitry comprises scan cells and logic gates The identify verification circuitry outputs an identity verification result to the scrambler circuitry to enable/disable control test points of the test point circuitry through the logic gates, and the scrambler circuitry outputs logic bits for loading the scan cells to activate/inactivate the control test points through the logic gates.

Abstract: Various aspects of the disclosed technology relate to techniques of creating test templates for test pattern generation. Residual test cubes for a plurality of faults are first generated based on a signal probability analysis of a circuit design. Test templates are then generated based on merging the residual test cubes. Finally, a plurality of test patterns and/or compressed test cubes are generated based on one of the test templates.

Abstract: Built-in self-test techniques for integrated circuits that address the issue of unknown states. Some implementations use a specialized scan chain selector coupled to a time compactor. The presence of the specialized scan chain selector increases the efficiency in masking X states. Also disclosed are: (1) an architecture of a selector that works with multiple scan chains and time compactors, (2) a method for determining and encoding per cycle scan chain selection masks used subsequently to suppress X states, and (3) a method to handle an over-masking phenomenon.

Abstract: The test circuitry according to various aspects of the presently disclosed techniques comprises: low-toggling pseudo-random test pattern generation circuitry, wherein the low-toggling pseudo-random test patterns generated by the low-toggling pseudo-random test pattern generation circuitry causing switching activity during scan shift cycles lower than pseudo-random test patterns generated by a pseudo-random pattern generator; scan chains configurable to shift in a low-toggling pseudo-random test pattern generated by the low-toggling pseudo-random test pattern generation circuitry; background chains configurable to shift in a background test pattern; and weight insertion circuitry configurable to modify a plurality of bits in the low-toggling pseudo-random test pattern based on bits in the background test pattern to form a weighted pseudo-random test pattern.

Abstract: Disclosed herein are exemplary embodiments of a so-called “X-press” test response compactor. Certain embodiments of the disclosed compactor comprise an overdrive section and scan chain selection logic. Certain embodiments of the disclosed technology offer compaction ratios on the order of 1000×. Exemplary embodiments of the disclosed compactor can maintain about the same coverage and about the same diagnostic resolution as that of conventional scan-based test scenarios. Some embodiments of a scan chain selection scheme can significantly reduce or entirely eliminate unknown states occurring in test responses that enter the compactor. Also disclosed herein are embodiments of on-chip comparator circuits and methods for generating control circuitry for masking selection circuits.

Abstract: Aspects of the invention relate to a test-per-clock scheme based on dynamically-partitioned reconfigurable scan chains. Every clock cycle, scan chains configured by a control signal to operate in a shifting-launching mode shift in test stimuli one bit and immediately applies the newly formed test pattern to the circuit-under-test; and scan chains configured by the control signal to operate in a capturing-compacting-shifting mode shift out one bit of previously compacted test response data while compacting remaining bits of the previously compacted test response data with a currently-captured test response to form currently compacted test response data. A large number of scan chains may be configured by the control signal to work in a mission mode. After a predetermined number of clock cycles, a different control signal may be applied to reconfigure and partition the scan chains for applying different test stimuli.

Abstract: Various aspects of the disclosed technology relate to deterministic built-in self-test. A deterministic built-in self-test system comprises: a decompressor configured at least to decompress one of compressed test patterns stored on chip for a predetermined number of times; and a controller configured at least to output a control signal that inverts outputs of the decompressor at one or more scan shift clock cycles based on control data stored on chip, enabling the system to output the predetermined number of test patterns based on the one of compressed test patterns, wherein the one or more scan shift clock cycles are different for each of the predetermined number of test patterns.

Abstract: Built-in self-test techniques for integrated circuits that address the issue of unknown states. Some implementations use a specialized scan chain selector coupled to a time compactor. The presence of the specialized scan chain selector increases the efficiency in masking X states. Also disclosed are: (1) an architecture of a selector that works with multiple scan chains and time compactors, (2) a method for determining and encoding per cycle scan chain selection masks used subsequently to suppress X states, and (3) a method to handle an over-masking phenomenon.

Abstract: Aspects of the invention relate to test generation techniques for test-per-clock. Test cubes may be generated by adding constraints to a conventional automatic test pattern generator. During a test cube merging process, a first test cube is merged with one or more test cubes that are compatible with the first test cube to generate a second test cube. The second test cube is shifted by one bit along a direction of scan chain shifting to generate a third test cube. The third test cube is then merged with one or more test cubes in the test cubes that are compatible with the third test cube to generate a fourth test cube. The shifting and merging operations may be repeated for a predetermined number of times.

Abstract: Various aspects of the disclosed techniques relate to using dynamic shift for test pattern compression. Scan chains are divided into segments. Non-shift clock cycles are added to one or more segments to make an uncompressible test pattern compressible. The one or more segments may be selected based on compressibility, the number of specified bits and/or the location on the scan chains. A dynamic shift controller may be employed to control the dynamic shift.

Abstract: Aspects of the invention relate to a test-per-clock scheme based on dynamically-partitioned reconfigurable scan chains. Every clock cycle, scan chains configured by a control signal to operate in a shifting-launching mode shift in test stimuli one bit and immediately applies the newly formed test pattern to the circuit-under-test; and scan chains configured by the control signal to operate in a capturing-compacting-shifting mode shift out one bit of previously compacted test response data while compacting remaining bits of the previously compacted test response data with a currently-captured test response to form currently compacted test response data. A large number of scan chains may be configured by the control signal to work in a mission mode. After a predetermined number of clock cycles, a different control signal may be applied to reconfigure and partition the scan chains for applying different test stimuli.

Abstract: Various aspects of the disclosed technology relate to conflict-reducing test point insertion techniques. Locations in a circuit design for inserting test points are determined based on internal signal conflicts caused by detecting multiple faults with a single test pattern. Test points are then inserted at the locations. The internal signal conflicts may comprise horizontal conflicts, vertical conflicts, or both. The test points may comprise control points, observation points, or both.

Abstract: Disclosed herein are exemplary embodiments of a so-called “X-press” test response compactor. Certain embodiments of the disclosed compactor comprise an overdrive section and scan chain selection logic. Certain embodiments of the disclosed technology offer compaction ratios on the order of 1000×. Exemplary embodiments of the disclosed compactor can maintain about the same coverage and about the same diagnostic resolution as that of conventional scan-based test scenarios. Some embodiments of a scan chain selection scheme can significantly reduce or entirely eliminate unknown states occurring in test responses that enter the compactor. Also disclosed herein are embodiments of on-chip comparator circuits and methods for generating control circuitry for masking selection circuits.