Which cell delay to use when calculating data arrival time?

[hfooo1]

AND (A , B , .Y(n1));
DFF (.D(n1) , CK , Q );
when we calculate data arriving time,
whick cell delay should we use , path delay from A to Y or B to Y?
how does tool think about it ?

 

[Nandy]

cell delay

Tool would think there are two paths here, A->Y and B->Y, considering wire delay is zero.

www.nandigits.com
Netlist debug/ECO in GUI mode

 

[crtled]

Re: cell delay

Tool will use the worst path to caculate the cell delay.

 

[atena]

Re: cell delay

Tool would think there are two paths here, A->Y and B->Y, considering wire delay is zero.

www.nandigits.com
Netlist debug/ECO in GUI mode

I think it will consider wire delay zero if and only if you have specified the ideal case, and the proper wire load model. Otherwise it still can take in count the wire delay.

 

[silencer3]

cell delay

tool will use the worst delay of a->y & b->y.

In the cell both a->y and b->y may be same. So the worst path will be the one which has more load and worst transition. so, your input (a, b) characteristics will determine which is the worst path.