Area reduction after synthesis with scan

[viju]

Hi,

I have noticed that when I do synthesis with scan, the area is reduced. Can any one make me understand how it is possible? In face by scan logic we are adding some logic in front of flops, so how come area is reduced.

Please share your views/experience for it.

Thanks,
VJ

 

[qieda]

Hi,

If I understand you correct you did a synthesis with a library which has scan flops. So you did not do scan insertion???
Than I think the area is smaller because the synthesis tool is smart enough to use the 2:1 input mux of the scan FF for optimizing some of your logic.
Normally you did not use the scan flipflops for synthesis. After synthesis the scan insertion replaces all your flipflops with scan flops and adds the scan chain.

regards

 

[ebuddy]

That is what I was suspecting too. If it is indeed the case, then the area reduction is pretty small, 1-2% is my guess. OP, please confirm.