Selective per-cycle masking of scan chains for system level test
First Claim
1. One or more non-transitory machine-readable storage media storing computer-readable instructions that when executed by a computer, cause the computer to perform a method, the instructions comprising:
- instructions for generating mask data indicating patterns of unknown states for which to mask test responses received from scan cells in an integrated circuit;
instructions for storing the mask data in a memory of the integrated circuit;
instructions for 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
instructions for providing a test response compactor configured to receive the masked test responses.
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Accused Products
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.
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Citations
15 Claims
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1. One or more non-transitory machine-readable storage media storing computer-readable instructions that when executed by a computer, cause the computer to perform a method, the instructions comprising:
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instructions for generating mask data indicating patterns of unknown states for which to mask test responses received from scan cells in an integrated circuit; instructions for storing the mask data in a memory of the integrated circuit; instructions for 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 instructions for providing a test response compactor configured to receive the masked test responses. - View Dependent Claims (2, 3)
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4. One or more non-transitory machine-readable storage media storing computer-readable instructions that when executed by a computer, cause the computer to perform a method, the instructions comprising:
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instructions for generating mask data indicating patterns of unknown states for which to mask test responses received from scan cells in an integrated circuit; instructions for causing the mask data to be stored in a memory of the integrated circuit; instructions for configuring a selector to mask test responses produced by the scan cells based on the stored mask data, thereby producing masked test responses, the selector comprising; a shadow register configured to capture and save one or more outputs of a ring generator for more than one clock cycle, and logic for determining whether to load the shadow register with the outputs of the ring generator based on control information merged with the stored mask data; and instructions for configuring a test response compactor to receive the masked test responses. - View Dependent Claims (5, 6, 7, 8)
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9. One or more non-transitory machine-readable storage media storing computer-readable instructions that when executed by a computer, cause the computer to perform a method, the instructions comprising:
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instructions for 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; instructions for providing a selector configured to mask the produced test responses responsive to per-cycle mask data, producing the masked test responses, the selector comprising; a ring generator, and a shadow register configured to capture and save one or more outputs of the ring generator for more than one clock cycle, the shadow register being operable independently of the ring generator; and instructions for generating the per-cycle mask data, the per-cycle mask data indicating scan cell locations to mask in the produced test responses by masking patterns of unknown states. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification