Scan shift operation

[jaanki]

Assume a can chain of 5 bits.

Si->scan flops[1] …>scan_flop[5]->SO

Explain normal scan shift operation , what are the values shifted out scan ?
Assume if 3rd flop has setup violation, what are the values shifted out ?
Assume if 3rd flop has hold violation, what are the values shifted out from scan?

Please explain me with example , this question asked me one of the interview.

Thanks

 

[rca]

scan shift out data are the result of the previous captures.
if any timing violation occurs, the data capture could be wrong.
The scan is used to check the stuck, transition, bridge fault, not the setup/hold timing issue.

 

[jaanki]

Thanks for clarification
yes scan is used to check the faults , but what are the possible output of the scan chain if there is timing violation?

 

[rca]

certainly wrong output or unconsistant no repeatibility.