Compacting circuit responses
First Claim
Patent Images
1. A method comprising:
- forming a compactor matrix for a response compactor circuit; and
for each scan chain that produces an unknown logic value at the same time as another scan chain produces an unknown value, adding at least two columns to said matrix.
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Abstract
A compactor has a reduced number of outputs and the ability to handle a higher number of errors and unknown logic values. The procedure for designing the matrix and the resulting compactor involves determining the number of unknown logic values that may be encountered and adding columns to the compactor matrix based on the number of errors. Basically, the number of possible combinations of scan in lines is determined. Then, additional columns are added for each possible combination of scan in lines. The number of columns that are added for each combination of scan in lines is equal to the number of errors plus one in one embodiment.
19 Citations
15 Claims
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1. A method comprising:
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forming a compactor matrix for a response compactor circuit; and for each scan chain that produces an unknown logic value at the same time as another scan chain produces an unknown value, adding at least two columns to said matrix. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A response compactor formed by a process including the steps of:
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obtaining a number of circuit outputs from scan chains that can produce unknown logic values at the same time; and for each scan chain that produces an unknown logic value at the same time as another scan chain produces an unknown value, adding at least two columns to a compactor matrix. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A response compactor comprising:
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a plurality of coupled exclusive OR gates to handle any number of scan chains with unknown logic values; and a control, coupled to said gates, to add two columns to a compactor matrix for each scan chain that produces an unknown value at an unknown logic value at the same time as another scan chain produces an unknown logic value.
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Specification