With the increasing complexity of semiconductor devices, the problem of hardware testing and diagnosis becomes one of the major bottlenecks in computer industry. As a result of a high density of components and limited numbers of input/output pins, controllabilities and observabilities of internal interconnections and gates are going down, which makes testing more and more costly. There are good reasons to believe that this trend will continue in the future (269).

The conventional approach to testing is to identify a subset of input vectors (the test set) such that correct behavior of the device-under-test for these input vectors ensures correct behavior of the device relative to the selected class of faults. The device is tested off-line by applying input test vectors and verifying test responses.

Testing of sequential devices is performed by breaking feedback loops in the testing mode and testing separately combinational part and memories (269).

In this chapter, we will present several approaches based on the Walsh transform and its generalizations for testing and diagnosis of combinational networks, Random-Access Memories (RAMs), Read-Only Memories (ROMs), and software computing numerical functions.

As we will see in the next few sections, spectral techniques provide in many cases for simple and analytical solutions of testing and diagnostic problems.

Approaches to testing and diagnosis of computer hardware can be classified ...

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