Automatic test pattern generation: Difference between revisions

Revision as of 08:32, 8 September 2017

Revision as of 02:31, 10 January 2018

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== Sequential ATPG ==

Sequential-circuit ATPG searches for a sequence of [[Testtest vector|test vectors]]s to detect a particular fault through the [[State space|space of all possible test vector sequences]]. Various search strategies and heuristics have been devised to find a shorter sequence, or to find a sequence faster. However, according to reported results, no single strategy or heuristic out-performs others for all applications or circuits. This observation implies that a test generator should include a comprehensive set of heuristics.

Even a simple stuck-at fault requires a sequence of vectors for detection in a sequential circuit. Also, due to the presence of memory elements, the [[controllability]] and [[observability]] of the internal signals in a [[sequential circuit]] are in general much more difficult than those in a [[combinational logic]] circuit. These factors make the complexity of sequential ATPG much higher than that of combinational ATPG, where a scan-chain (i.e. switchable, for-test-only signal chain) is added to allow simple access to the individual nodes.

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== Algorithmic methods ==

Testing [[very-large-scale integration|very-large-scale integrated]] circuits with a high [[fault coverage]] is a difficult task because of complexity.

Therefore, many different ATPG methods have been developed to address [[Combinational logic|combinational]] and [[Sequential logic|sequential]] circuits.

* Early test generation algorithms such as [[boolean difference]] and [[literal proposition]] were not practical to implement on a computer.

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* [[Design For Test]] (DFT)

* [[Fault model]]

* [[Built-in_selfin self-test|Built-In Self-Test]] (BIST)

* [[JTAG]]

* [[Boundary Scan]] (BSCAN)