Text - KFUPM - King Fahd University of Petroleum and Minerals

analysis gives a reduced number of representative parallel scan chains if the
given parallel chains are compatible amongst themselves.
• The extent of compatibility achieved depends upon how many bits are specified
per scan vector. The lesser the specified bits, the lesser the conflicts, resulting
in greater compatibility between the set of parallel chains.
• The compatibility analysis can be applied to parallel scan chains of a single
vector or a set of vectors. Depending upon the extent of specified bits present,
the amount of conflict tends to increase the longer the chains (or columns) are.
The length of each column is determined by the number of bits per column
per vector multiplied by the total number of test vectors being considered for
the analysis.
• Compatibility analysis per vector gives the lower bound on achievable representative
parallel scan chains for a given test set for a specified number of
parallel scan chains per vector.
When the compatibility analysis is done per vector, the resulting number of
representative scan chains and the configuration of compatible groups may vary
among the different vectors in a test set depending upon the amount of specified bits
present and their relative positions in each vector. Even if most vectors individually
lend themselves favorably to compression using compatibility analysis, the gains
become less due to the increased conflicts when multiple vectors are considered
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