insert scan chain problem

[ls000rhb]

As a dc beginner ,i have a problem to ask for help!After i insert a complete scan chain, i run the report_test -scan_path command ,a scan path is shown .but when i implement another compile -inc and report_test -scan_path again，the report tell me that there is no scan_path information,that is no scan path shown .why?what should i do?

 

[seanwu]

I'd rather insert scan chain after all cells be placed.

 

[wkong_zhu]

after insert_scan you should not compile again.
you should "compile -scan -inc" after compile.
That's my point.

 

[luancao]

YES. the above answers are right. The insert scan in Test Complier is in fact a scan replace, changing your DFF to the scannable conterpart and connect them togather. Therefore, you'd better not optimize your design after the scan chain is inserted.

From functional point of view, without the scanchain, the function is still the same as expected. So after you optimize your design after scan insertion, the scan chains of course are optimized. No scan chains anymore, and the DFFs are return to the non-scanable ones. You could see the result in GTL. ( I did not try it before )