Test data compression is an enabling technology for low-cost test. Compression schemes however, require communication between the system under test and the automated test equipment. This communication, referred to in this paper as synchronization overhead, may hinder the effective deployment of this new test technology for core-based systems-on-chip. This paper analyzes the sources of synchronization overhead and discusses the different tradeoffs, such as area overhead, test time and automatic test equipment extensions. A novel scalable and programmable on-chip distribution architecture is proposed, which addresses the synchronization overhead problem and facilitates the use of low cost testers for manufacturing test. The design of the proposed architecture is introduced in a generic framework, and the implementation issues (including the test controller and test set preparation) have been considered for a particular case.

Driven by the industrial need for low-cost test methodologies, the academic community and the industry alike have put forth a number of efficient test data compression (TDC) methods. In addition, the need for core-based System-on-a-Chip (SoC) test led to considerable research in test access mechanism (TAM) design. While most previous work has considered TAM design and TDC independently, this work analyzes the interrelations between the two, outlining that a minimum test time solution obtained using TAM design will not necessarily correspond to a minimum test time solution when compression is applied. This is due to the dependency of some TDC methods on test bus width and care bit density, both of which are related to test time, and hence to TAM design. Therefore, this paper illustrates the importance of considering the characteristics of the compression method when performing TAM design, and it also shows how an existing TAM design method can be enhanced toward a compression-driven solution.

This paper presents a new compression method for embedded core-based system-on-a-chip test. In addition to the new compression method, this paper analyzes the three test data compression environment (TDCE) parameters: compression ratio, area overhead, and test application time, and explains the impact of the factors which influence these three parameters. The proposed method is based on a new variable-length input Huffman coding scheme, which proves to be the key element that determines all the factors that influence the TDCE parameters. Extensive experimental comparisons show that, when compared with three previous approaches, which reduce some test data compression environment's parameters at the expense of the others, the proposed method is capable of improving on all the three TDCE parameters simultaneously.

This paper analyzes the test memory requirements for core-based systems-on-a-chips and identifies useless test data as one of the contributors to the total amount of test data. The useless test data comprises the padding bits necessary to compensate for the difference between the lengths of different chains in multiple scan chain designs. Although useless test data does not represent any relevant test information, it is often unavoidable, and leads to the tradeoff between the test bus width and the volume of test data in multiple scan chain-based cores. Ultimately, this tradeoff influences the test access mechanism design algorithms leading to solutions that have either short test time or low volume of test data. Therefore, in this paper, a novel test methodology is proposed which, by dividing the wrapper scan chains (WSCs) into two or more partitions, and by exploiting automated test equipment memory management features, reduces the amount of useless test data. Extensive experimental results using ISCAS'89 and ITC'02 benchmark circuits are provided to analyze the implications of the number of WSCs in the partition, and the number of partitions on the proposed methodology.

Proposes a new test data compression/decompression method for systems-on-a-chip. The method is based on analyzing the factors that influence test parameters: compression ratio, area overhead and test application time. To improve compression ratio, the new method is based on a variable-length input Huffman coding (VIHC), which fully exploits the type and length of the patterns, as well as a novel mapping and reordering algorithm proposed in a pre-processing step. The new VIHC algorithm is combined with a novel parallel on-chip decoder that simultaneously leads to low test application time and low area overhead. It is shown that, unlike three previous approaches which reduce some test parameters at the expense of the others, the proposed method is capable of improving all the three parameters simultaneously. An experimental comparison on benchmark circuits validates the proposed method.

This paper discusses an integrated solution for reducing the volume of test data for deterministic system-on-a-chip testing. The proposed solution is based on a new test data decompression architecture which exploits the features of a core wrapper design algorithm targeting the elimination of useless test data. The compressed test data can be transferred from the automatic test equipment to the on-chip decompression architecture using only one test pin, thus providing an efficient reduced pin count test methodology for multiple scan chains-based embedded cores. In addition to reducing the volume of test data, the proposed solution decreases the control overhead, test application time and power dissipation during scan. Further, it also requires lower on-chip area when compared to the testing scenarios which employ decompression architectures for every scan chain and it eliminates the synchronization overhead between the automatic test equipment and the system-on-a-chip. Moreover, the proposed solution is scalable and programmable and, since it can be considered as an add-on to a test access mechanism of a given width, it provides seamless integration with any design flow. Thus, the proposed integrated solution is an efficient low-cost test methodology for systems-on-a-chip.

Unlike the existing research direction that focuses on useful test data reduction, this paper analyzes the useless test data memory requirements for system-on-a-chip test. The proposed solution to minimize the useless test memory is based on a new test methodology which combines a novel core wrapper design algorithm with a new test vector deployment procedure stored in the automatic test equipment (ATE). To reduce memory requirements, the proposed core wrapper design finds the minimum number of wrapper scan chain partitions such that the useless memory allocation is minimized in each partition, which facilitates efficient usage of ATE capabilities. Further the new test vector deployment procedure provides a seamless integration with the ATE. When compared to the previously proposed core wrapper design algorithms, the proposed test methodology reduces the memory requirements up to 45%, without any penalties in test area overhead.