Selective per-cycle masking of scan chains for system level test
AssigneeMentor Graphics Corporation
InventorsJanusz Rajski, Dariusz Czysz, Grzegorz Mrugalski, Nilanjan Mukherjee, Jerzy Tyszer
Life of this patent
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Abstract
Built-in self-test techniques for integrated circuits that address the issue of unknown states. Some implementations use a specialized scan chain selector coupled to a time compactor. The presence of the specialized scan chain selector increases the efficiency in masking X states. Also disclosed are: (1) an architecture of a selector that works with multiple scan chains and time compactors, (2) a method for determining and encoding per cycle scan chain selection masks used subsequently to suppress X states, and (3) a method to handle an over-masking phenomenon.
Claims20
1-14. (canceled)
A method, comprising:
- generating mask data indicating patterns of unknown states for which to mask test responses received from scan cells in an integrated circuit;
- storing the mask data in a memory of the integrated circuit;
- providing a selector configured to mask test responses produced by the scan cells based on the stored mask data, thereby producing masked test responses;
- and
- providing a test response compactor configured to receive the masked test responses.
An integrated circuit, comprising:
- a circuit-under-test comprising one or more scan cells;
- a memory storing mask data, the mask data indicating one or more of the scan cells to mask in scan cell test responses by masking patterns of unknown states in the test responses;
- a selector configured to mask the received test responses responsive to the mask data, producing masked test responses;
- and
- a compactor operable to receive the masked test responses.
A method, comprising:
- providing a test response compactor configured to receive masked test responses masking one or more unknown states in test responses produced by error-capturing scan cells;
- providing a selector configured to mask the produced test responses responsive to mask data, producing the masked test responses;
- and
- generating the mask data, the mask data indicating scan cell locations to mask in the produced test responses by masking patterns of unknown states.
Dependencies are inferred from the claim text.