# Random Testing of Asynchronous VLSI Circuits

O. Petlin

### Abstract

Asynchronous VLSI designs are becoming an intensive area of research due to their advantages in comparison with synchronous circuits, such as the absence of the clock distribution problem, lower power consumption and higher performance. The work described in this thesis is an attempt to find possible ways to test asynchronous VLSI circuits using random (or, more accurately, pseudo-random) patterns. The main results have been obtained in the field of random testing of stuck-at faults in micropipelines.

An asynchronous random testing interface has been designed which includes an asynchronous pseudo-random pattern generator and an asynchronous parallel signature analyser. A program model of the universal pseudo-random pattern generator has been developed. The universal pseudo-random pattern generator can produce multi-bit pseudo-random sequences without an obvious shift operation and it can also produce weighted pseudo-random test patterns.

Mathematical expressions have been derived for predicting the test length for random pattern testing of logic blocks of micropipelines by applying equiprobable and weighted random patterns to the inputs.

The probabilistic properties of the n-input Muller-C element have been investigated. It is shown that the optimal random test procedure for the n-input Muller-C element is random testing using equiprobable input signals. Using the probabilistic properties of the Muller-C element and multiplexers incorporated into the circuit a certain class of asynchronous networks can be designed for random pattern testability. It is also shown how it is possible to produce pseudo-random patterns to detect all stuck-at faults in micropipelines.

Full text available by ftp in postscript or pdf form.