Causes for UO faults in ATPG

[ranger01]

Hello DFT experts,

UO faults are faults which are not observed at the POs. What could be the possible causes for this category of faults ? When I run analyze_faults on a UO fault in mentor, it is detected successfully, however I do not understand why it wasn't put under DI/DS bucket.

 

[rca]

you're PO always drive the same value?
or do you mean the PO is not connected to the internal scan chain and so the scan out does change?

 

[ranger01]

I just defined UO faults in my question. The issue is with the tool. I had to re-target only the UO faults to detect them with higher abort.