Circuit and method for increasing scan cell observability of response compactors
US8006150B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 24, 2009 |
| Grant date | Aug 23, 2011 |
| Priority date | — |
| Expiry date | Nov 6, 2029 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R31/318547
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The circuit and method for increasing the scan cell observability of response compactors is based on manipulation of x distribution in responses prior to taking them through a compactor. An x-align block is capable of delaying scan chains by judiciously computed values, and thus aligning x's within the same slices. The x-alignment is effected in the insertion of proper control data to the generic x-align hardware. As a result, fewer scan cells are masked due to response x's into other cells, reflecting into enhanced test quality. An ILP formulation can be used to identify the delay assignment that leads to the maximum number of observable scan cells. Alternatively, a computationally efficient greedy heuristic can be used to attain near-optimal results in reasonable run-time. Thus, the x-align block enhances the effectiveness of response compactors and reaps high test quality, even in the dense presence of response x's.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.