ATPG generates the pattern for particular fault model.So it totally depends on the fault which can be detected.So as per my opinion,Not possible to generate test patterns with lots of dont cares.
If u targeted the stuck at fault model thn Tetramax generates the pattern w.r.t Stuck at faults.So pattern generation is totally depends on fault models so we can not generate test patterns with lots of don't care.
Thank you for your reply. I thought don't care bits are specified for pattern compression. Most commercial tools would do the pattern compression automatically to ensure a min pattern set, I don't quite sure whether TetraMAX allow users to generate a less compact pattern set.
ATPG tool find the pattern for targeted faults thn from one pattern how much fault coverage is achieved and thereafter TetraMAX find the pattern for remaining faults for specific fault model...so TetraMAX automatically try to find maximum faults with use of minimum pattern counts.