AR# 72121

How to report out detailed path on max skew for “actual value” calculation?

Description

How can I calculate the "actual value" in max skew analysis?

Solution

To report the detailed path on the Max Skew, you can use report_timing on the 2 pins involved in the Max Skew.

The difference between the arrival times will be the actual value of Max Skew.

Important note when calculating:

  • Timing should be reported in the same corner (Slow/Fast), but the 2 pins must be reported in Min/Max.   

For example: 0.607ns is the actual Max Skew value in the slow corner between PIPECLK and CORECLK (See the below screen capture)





Report timing on both PIPECLK and CORECLK using the following two commands:

report_timing -to $core -delay_type min_max -name core -nworst 10 -max 10
report_timing -to $pipe -delay_type min_max -name pipe -nworst 10 -max 10



Arrival time for CORECLK is 5.649ns calculated at the slow process corner in max, and arrival time forPIPECLK is 5.042ns calculated at the slow process corner in min.

The actual Max Skew value is: 5.649ns - 5.042ns = 0.607ns.


AR# 72121
Date 05/08/2019
Status Active
Type General Article
Devices
Tools