Skew and delay

[iafo1]

Hi,I can’t understand the meaning of the skew and delay parameters on the timing reports. Reading the “constraint guide” I thought that the skew is the difference between the delays of all loads driven by the net. So why the report calculate a skew for each load? Why does it calculate a skew also for just one load!? Why the skew is not the difference between the delays? Maybe it accounts also the clock delay? If yes, which clock does it consider if the loads are clocked with different clocks? Please answer me!! Thank you.

[gszakacs]

Skew in the timing report is computed for each path.  A path is a combination of source and

destination.  Usually internal paths start on a clock edge at the source flip-flop and end at

a clock edge on the destination flip-flop.  The path delay is clock to Q for the source flip-flop

plus any routing delays and combinatorial delays to the D of the destination flip-flop plus the

setup time required by the destination flip-flop.  The skew is the difference in arrival of the

clock at the source flip-flop vs. the destination flip-flop.

HTH,

Gabor