Abstract: An improved compression technique can increase PRPG-based compression by modifying test generation so that justification of certain decision nodes, called xheadlines, is delayed and merged with PRPG seed computation. Xheadlines are defined by gate modification restrictions, dynamic value considerations, and fanout allowance. Before mapping, the xheadlines can be preprocessed. This preprocessing can include transforming XOR xheadlines having shared inputs, augmenting AND/OR xheadlines, and reducing AND/OR xheadlines with common inputs. Mapping can include determining which xheadlines are satisfied by a current seed, which xheadlines can be satisfied by a future seed, and which xheadlines can opportunistically be satisfied by the current seed.

Abstract: Scan testing and scan compression are key to realizing cost reduction and shipped quality. New defect types in ever more complex designs require increased compression. However, increased density of unknown (X) values reduces effective compression. A scan compression method can achieve very high compression and full coverage for any density of unknown values. The described techniques can be fully integrated in the design-for-test (DFT) and automatic test pattern generation (ATPG) flows. Results from using these techniques on industrial designs demonstrate consistent and predictable advantages over other methods.

Abstract: An improved compression technique can increase PRPG-based compression by modifying test generation so that justification of certain decision nodes, called xheadlines, is delayed and merged with PRPG seed computation. Xheadlines are defined by gate modification restrictions, dynamic value considerations, and fanout allowance. Before mapping, the xheadlines can be preprocessed. This preprocessing can include transforming XOR xheadlines having shared inputs, augmenting AND/OR xheadlines, and reducing AND/OR xheadlines with common inputs. Mapping can include determining which xheadlines are satisfied by a current seed, which xheadlines can be satisfied by a future seed, and which xheadlines can opportunistically be satisfied by the current seed.

Abstract: Scan testing and scan compression are key to realizing cost reduction and shipped quality. New defect types in ever more complex designs require increased compression. However, increased density of unknown (X) values reduces effective compression. A scan compression method can achieve very high compression and full coverage for any density of unknown values. The described techniques can be fully integrated in the design-for-test (DFT) and automatic test pattern generation (ATPG) flows. Results from using these techniques on industrial designs demonstrate consistent and predictable advantages over other methods.

Abstract: To increase scan compression during testing of an IC design, an X-chain method is provided. In this method, a subset of scan cells that are likely to capture an X are identified and then placed on separate X-chains. A configuration and observation modes for an unload selector and/or an unload compressor can be provided. The configuration and observation modes provide a first compression for non-X-chains that is greater than a second compression provided for X-chains. ATPG can be modified based on such configuration and observation modes. This X-chain method can be fully integrated in the design-for-test (DFT) flow, requires no additional user input, and has negligible impact on area and timing. Test generation results on industrial designs demonstrate significantly increased compression, with no loss of coverage, for designs with high X-densities.

Abstract: A method to perform launch-on-shift scanning for integrated circuits having multiple clock domains is presented. An integrated circuit includes both capture clock domains and non-capture clock domains. The portions of the test vectors for non-capture clock domains are shifted into the scan chains of the non-capture clock domains and allowed to settle prior to the last shift launch cycle and the capture cycle of the capture clock domains. Thus, the ambiguity of the timing between the non-capture domains and the capture domains caused by asynchronous clock signals is eliminated.

Abstract: An electronic device includes a scan-based circuit that includes a combinational decompressor, a combinational compressor, scan chains, and logic which typically includes a number of storage elements. Cycle time normally needed to shift data into or out of a scan cell to/from an external interface of the electronic device is reduced by use of one or more additional storage element(s) located between the external interface and one of the combinational elements (decompressor/compressor). The one or more additional storage element(s) form a pipeline that shifts compressed data in stages, across small portions of an otherwise long path between the external interface and one of the combinational elements. Staged shifting causes the limit on cycle time to drop to the longest time required to traverse a stage of the pipeline. The reduced cycle time in turn enables a corresponding increase in shift frequency.

Abstract: A scan-based circuit includes a selector that is implemented by multiple observation logics. Each observation logic is coupled to a scan chain to receive data to be supplied to a combinational compressor. Each observation logic is also coupled to a single input line in a corresponding group of input lines of the combinational compressor, to selectively supply data from the coupled scan chain. Each observation logic may be coupled to additional input lines (if present) in the corresponding group. The selector is operable on a per-shift basis in (a) transparent mode wherein data is supplied to all input lines and (b) several direct modes wherein data from only one scan chain is supplied at each compressor output without overlap.

Abstract: Scan testing and scan compression are key to realizing cost reduction and shipped quality. New defect types in ever more complex designs require increased compression. However, increased density of unknown (X) values reduces effective compression. A scan compression method can achieve very high compression and full coverage for any density of unknown values. The described techniques can be fully integrated in the design-for-test (DFT) and automatic test pattern generation (ATPG) flows. Results from using these techniques on industrial designs demonstrate consistent and predictable advantages over other methods.

Abstract: To increase scan compression during testing of an IC design, an X-chain method is provided. In this method, a subset of scan cells that are likely to capture an X are identified and then placed on separate X-chains. A configuration and observation modes for an unload selector and/or an unload compressor can be provided. The configuration and observation modes provide a first compression for non-X-chains that is greater than a second compression provided for X-chains. ATPG can be modified based on such configuration and observation modes. This X-chain method can be fully integrated in the design-for-test (DFT) flow, requires no additional user input, and has negligible impact on area and timing. Test generation results on industrial designs demonstrate significantly increased compression, with no loss of coverage, for designs with high X-densities.

Abstract: A method to perform launch-on-shift scanning for integrated circuits having multiple clock domains is presented. An integrated circuit includes both capture clock domains and non-capture clock domains. The portions of the test vectors for non-capture clock domains are shifted into the scan chains of the non-capture clock domains and allowed to settle prior to the last shift launch cycle and the capture cycle of the capture clock domains. Thus, the ambiguity of the timing between the non-capture domains and the capture domains caused by asynchronous clock signals is eliminated.

Abstract: A scan-based circuit includes a selector that is implemented by multiple observation logics. Each observation logic is coupled to a scan chain to receive data to be supplied to a combinational compressor. Each observation logic is also coupled to a single input line in a corresponding group of input lines of the combinational compressor, to selectively supply data from the coupled scan chain. Each observation logic may be coupled to additional input lines (if present) in the corresponding group. The selector is operable on a per-shift basis in (a) transparent mode wherein data is supplied to all input lines and (b) several direct modes wherein data from only one scan chain is supplied at each compressor output without overlap.

Abstract: An electronic device includes a scan-based circuit that includes a combinational decompressor, a combinational compressor, scan chains, and logic which typically includes a number of storage elements. Cycle time normally needed to shift data into or out of a scan cell to/from an external interface of the electronic device is reduced by use of one or more additional storage element(s) located between the external interface and one of the combinational elements (decompressor/compressor). The one or more additional storage element(s) form a pipeline that shifts compressed data in stages, across small portions of an otherwise long path between the external interface and one of the combinational elements. Staged shifting causes the limit on cycle time to drop to the longest time required to traverse a stage of the pipeline. The reduced cycle time in turn enables a corresponding increase in shift frequency.

Abstract: A BIST architecture that allows efficient compression and application of deterministic ATPG patterns while tolerating uncertain bits is provided. In accordance with one feature of the invention, a large number of short scan chains can be configured between a decompressor and an observe selector. The observe selector selectively presents values of specific scan chains or scan cells to an external tester, thereby significantly reducing test data and test cycles. Advantageously, the core of the tested device is not changed as would be the case in BIST architectures including MISRs. Moreover, test points or logic to block uncertain bits do not need to be inserted. Furthermore, the loaded care bits for the scan chains as well as the bits for controlling the observe selector can be deterministically controlled, thereby providing optimal testing flexibility.

Abstract: A filter for preventing uncertain bits output by test scan chains from being provided to a MISR is provided. The filter can include a gating structure for receiving a bit from a scan chain and control circuitry for providing a predetermined signal to the gating structure if the bit is an uncertain bit. In one embodiment, the gating structure can include a logic gate, such as an AND or an OR gate. The control circuitry can include components substantially similar to the pattern generator providing signals to the scan chain. For example, the control circuitry can include an LFSR and a PRPG shadow for loading the LFSR. In one embodiment, the control circuitry can further include a phase-shifter for receiving inputs from the LFSR and providing outputs to the gating structure.

Abstract: A method and system for constructing a structural model of a memory for use in ATPG (Automatic Test Pattern Generation). According to an embodiment of the present invention, behavioral models of memories of the simulation libraries are re-coded into simplified behavioral models using behavioral hardware description language (e.g., Verilog). Then, the simplified behavioral models are automatically converted into structural models that include ATPG memory primitives. The structural models are then stored for subsequent access during pattern generation. In one embodiment, for modeling random access memories (RAMs), the ATPG memory primitives include memory primitives, data bus primitives, address bus primitives, read-port primitives and macro output primitives. In another embodiment, for modeling content addressable memories (CAMs), the ATPG memory primitives include memory primitives, compare port primitives and macro output primitives.

Abstract: Deterministic ATPG test coverage is provided in a logic BIST architecture while reducing test application time and test data volume, as compared to deterministic ATPG patterns. The logic BIST architecture can include a PRPG shadow operatively coupled to a PRPG circuit. The PRPG shadow allows re-seeding of the PRPG circuit with zero cycle overhead. Two compressions can be provided. In a first compression, multiple tests for faults are compressed into one pattern. In a second compression, multiple deterministic ATPG patterns can be compressed into one seed. All patterns provided from the PRPG can be controlled by these seeds so that all care bits are properly set, while all other scan cells are set to pseudo-random values from the PRPG. In this manner, the PRPG can rapidly deliver highly pertinent data to the scan chains of the device under test.

Abstract: A system and method for time slicing deterministic patterns for reseeding in logic built-in self-test (BIST). The known properties of a linear feedback shift register (LFSR) and an associated set of channels are used in conjunction with a desired deterministic test pattern to create one or more seeds which can be used by the LFSR to generate the test pattern. The test pattern is divided into a number of segments, with each segment having a specific number of “care” bits. The number of shifts required to fill a segment using a particular seed is stored along with the seed as a seed lifetime. During testing, each deterministic test pattern is generated by loading a seed into the LFSR and cycling the LFSR in accordance with the lifetime of the seed. The seed lifetimes may have different values, and multiple seeds may be used in the generation of a single test pattern, or a single seed may be used to generate care bits of multiple test patterns.

Abstract: 42Method and system for constructing a structural model of a memory for use in ATPG (Automatic Test Pattern Generation). Behavioral models of memories of simulation libraries are re-coded into simplified behavioral models using behavioral hardware description language (e.g., Verilog). Simplified behavioral models are automatically converted into structural models that include ATPG memory primitives. Structural models are stored for subsequent access during pattern generation. In another embodiment for modeling random access memories (RAMs), the ATPG memory primitives include memory primitives, data bus primitives, address bus primitives, read-port primitives and macro output primitives. In another embodiment for modeling content addressable memories (CAMs), the ATPG memory primitives include memory primitives, compare port primitives and macro output primitives.

Abstract: A method for generating a test pattern for use in testing an integrated circuit device. The computer implemented steps of receiving and storing the netlist specification in a computer memory unit, and simulating the netlist using the computer implemented synthesis system. Using the netlist simulation, a set of circuit paths for each fault of the plurality of faults within the netlist specification is determined. From this set of paths, respective longest paths for each fault is determined. Using an ATPG (automatic test pattern generation) process, a test vector is determined for the first fault. Transition fault simulation is then performed on the first fault by applying the test vector to a first path through the first fault, wherein the first path is the longest path traversing through the first fault as determined by the ATPG process.