## STRUCTURAL TEST GENERATION WITH EMPLOYMENT OF MULTIPLE OBSERVATION TIME STRATEGY

**Vadim Skobtsov,**
Institute of Applied Mathematics and Mechanics of Ukrainian Academy of Sciences.

The test generation and logical simulation are important parts of digital devices (DD) CAD. They allow to improve quality and productivity of DD design, control and diagnosis. The test generation problem is one of the most difficult in DD CAD.

We propose structural automatic test pattern generation (ATPG) method for sinchronous sequential DD. It takes into account stuck-at faults. Iterative combinational circuit is used as model of considered
sequential DD.

We use the set of multivalued functions and universal 16-valued alphabet like basic mathematical model of proposed method.

The algorithm is based at the propagation of critical values D(D') through improved procedures of structural and logical local implication and application of multiple observation time strategy.

Improved logical local implication is based at the employment of multivalued functions. Multiple observation time strategy is as follows. During test generation process we take into account the output responses of given device at the all time frames. That is the output values of each iteration of iterative combinational model are taken into account. The main advantages of multiple observation time strategy are:

- the set of undetectable faults under multiple observation is contained in the set of undetectable faults under single observation and therefore more faults can be detected;
- test sequences under this strategy are shorter and therefore potentially easier to derive.

Thus
- the speed of test generation for offered ATPG method is essentially increased due to the employment of multivalued functions and universal 16-valued alphabet;
- amount of detectable faults is essentially increased due to the application of multiple observation time strategy.