Diverging Scan Chains

Clock skew in the scan path could result in a scan pull-through or a diverging scan chain. In other words, during the scan shift phase, due to clock skew the same scan bit can be loaded into two successive scan cells. 

The set scan path command can be used to specify which scan chain the flops in a sub-design must be assigned to, depending on the clock skew on that branch. Further, this command can also be used to explicitly order scan cells within a scan chain. This command provides a means to arrange the scan-cells in the scan-chain in the order of reversed skew. 

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