Software-based self-test and diagnosis for processors and system-on-chips.

摘要

The rising cost of high-end testers and the need for systematic test generation methods capable of achieving high fault coverage drive the microprocessor industry's migration from functional test to structural test approaches such as scan testing. At the same time, the practice of at-speed functional test remains an irreplaceable part of microprocessor tests due to its unique benefits in testing speed defects, but cannot be continued in its present form due the associated high cost. To address this problem, we propose a new self-test paradigm, Software-Based Self-Test (SBST), for testing microprocessors and System-on-Chips (SoCs) containing embedded processors. To allow at-speed tests using low-cost testers, SBST enables processor self-test using a software tester embedded in the on-chip memory. The software tester consists of processor instructions and is generated using a divide-and-conquer approach that enables the systematic generation of instruction-level tests with high coverage on structural faults. We achieve this goal by (i) partitioning the processor-under-test into modules manageable by automatic test pattern generation (ATPG) algorithms, (ii) generating tests at the module level targeting at structural faults, and (iii) delivering tests to the module-under-test (MUT) using processor instructions. The use of instruction-imposed constraints bridges the gap between instruction-level test application and module-level test generation, while a novel simulation-based method is used to extract the constraints, requiring no architectural knowledge of the processor-under-test. We have automated the entire test generation process and successfully demonstrated it on two processors, including a commercial state-of-the-art embedded processor, the Xtensa™ processor from Tensilica Inc. In addition to detecting stuck-at faults within the processor, we extend the application of SBST in two directions. (i) We explore the fault diagnosis capability of SBST by systematically constructing a large number of diagnosis test programs capable of achieving a high diagnostic resolution on an overwhelming majority of faults in the processor. (ii) We extend SBST to test for crosstalk errors on system-level interconnects by utilizing the signal transitions occurring on the interconnects during the execution of instructions. The two extensions of SBST have been successfully demonstrated on a processor example and a processor-memory system.