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 disclosed technology relate to low power testing. A low power test circuit comprises a test stimulus source, a controller; and a grouping and selection unit. The grouping and selection unit has inputs coupled to the test stimulus source and the controller and has outputs coupled to a plurality of scan chains. The grouping and selection unit is configured to dynamically group scan chains in the plurality of scan chains into a plurality of scan chain groups and to selectively output either original test pattern values generated by the test stimulus source or a constant value to each scan chain group in the plurality of scan chain groups based on control signals received from the controller.

Abstract: Disclosed are representative embodiments of methods, apparatus, and systems for test scheduling and test access in a test compression environment. Clusters of test patterns for testing a plurality of cores in a circuit are formed based on test information that includes compressed test data, corresponding tester channel requirements and correlated cores. The formation of test pattern clusters is followed by tester channel allocation. A best-fit scheme or a balanced-fit scheme may be employed to generate channel allocation information. A test access circuit for dynamic channel allocation can be designed based on the channel allocation information.

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: 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: 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: Disclosed are representative embodiments of methods, apparatus, and systems for test scheduling for testing a plurality of cores in a system on circuit. Test data are encoded to derive compressed test patterns that require small numbers of core input channels. Core input/output channel requirement information for each of the compressed test patterns is determined accordingly. The compressed patterns are grouped into test pattern classes. The formation of the test pattern classes is followed by allocation circuit input and output channels and test application time slots that may comprise merging complementary test pattern classes into clusters that can work with a particular test access mechanism. The test access mechanism may be designed independent of the test data.

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: 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: Various aspects of the disclosed techniques relate to channel sharing techniques for testing circuits having non-identical cores. Compressed test patterns for a plurality of circuit blocks are generated for channel sharing. Each of the plurality of circuit blocks comprises a decompressor configured to decompress the compressed test patterns. Test data input channels are thus shared by the decompressors. Control data input channels are usually not shared by non-identical circuit blocks in the plurality of circuit blocks.

Abstract: Aspects of the invention relate to generating scan chain configurations for test-per-clock based on circuit topology. With various implementations of the invention, weight vectors between scan chains in a circuit are first determined. Based on the weight vectors, a scan chain configuration is generated by assigning some scan chains in the scan chains to a stimuli group and some other scan chains in the scan chains to a compacting group. Here, the stimuli group comprises scan chains to operate in a shifting-launching mode, and the compacting group comprises scan chains to operate in a capturing-compacting-shifting mode.

Abstract: Aspects of the invention relate to using fault-driven techniques to generate scan chain configurations for test-per-clock. A plurality of test cubes that detect a plurality of faults are first generated. Scan chains for loading specified bits of the test cubes are then assigned to a stimuli group. From the plurality of test cubes, a test cube that detects a large number of faults that do not propagate exclusively to scan chains in the stimuli group is selected. One or more scan chains that are not in the stimuli group and are needed for observing the large number of faults are assigned to a compacting group. The number of scan chains either in the compacting group or in both of the compacting group and the stimuli group may be limited to a predetermined number.

Abstract: Background scan cells are selected from scan cells in a circuit based on specified bit distribution information for a plurality of test cubes generated for testing the circuit. A main portion and a background portion are then determined for each test cube in the plurality of test cubes. The background portion corresponds to the background scan cells. Test cubes in the plurality of test cubes that have compatible main portions are merged into test cube groups. Each test cube group in the test cube groups comprises a main test cube and background test cubes. A main test cube, supplied by a tester or a decompressor, may be shifted into the scan chains. A background test cube may be shifted into background chains and be inserted into the main test cube in the scan chains based on control signals.

Abstract: Various aspects of the present invention relate to scan chain stitching techniques for test-per-clock. With various implementations of the invention, a plurality of scan cell partitions are generated based on combinational paths between scan cells. Scan cells may be assigned to one or more pairs of scan cell partitions based on combinational paths between the scan cells. Each pair of the scan cell partitions comprises one stimuli partition and one compacting partition. Using the plurality of scan cell partitions generated, scan chains are formed based on at least information of combinational paths between scan cell partitions in the plurality of scan cell partitions. The formed scan chains are to be dynamically divided into three groups during a test, which are configured to operate in a shifting-launching mode, a capturing-compacting-shifting mode and a mission mode, respectively.

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: Aspects of the invention relate to using fault-driven techniques to generate scan chain configurations for test-per-clock. A plurality of test cubes that detect a plurality of faults are first generated. Scan chains for loading specified bits of the test cubes are then assigned to a stimuli group. From the plurality of test cubes, a test cube that detects a large number of faults that do not propagate exclusively to scan chains in the stimuli group is selected. One or more scan chains that are not in the stimuli group and are needed for observing the large number of faults are assigned to a compacting group. The number of scan chains either in the compacting group or in both of the compacting group and the stimuli group may be limited to a predetermined number.

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 invention relate to generating scan chain configurations for test-per-clock based on circuit topology. With various implementations of the invention, weight vectors between scan chains in a circuit are first determined. Based on the weight vectors, a scan chain configuration is generated by assigning some scan chains in the scan chains to a stimuli group and some other scan chains in the scan chains to a compacting group. Here, the stimuli group comprises scan chains to operate in a shifting-launching mode, and the compacting group comprises scan chains to operate in a capturing-compacting-shifting mode.

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: 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.