slack values using encounter

[vlsi_student]

Dear all

I am working for the first time on timing closure probs. I have a very strange values generated . i am using a freq of 1.25 ns .
and wen i see the slack report post placed it shows me a +ve slack of 2+ i am confused abt this values. the slack valus is more then the freq. i am using.

please through some light on this.

Thank you

vlsi student

 

[chandooo]

Positive slack is no harm!! Slack is the arrival time of data before clock edge.

 

[iwpia50s]

It could also be the slack of a multicycle path as well, or the slack of an async path which has a max_delay set.

 

[venkatesankalidass]

this the formula for find slack
slack = required time - arrivel time
if get the positive value of slack means no error ( time is meet )
if it is nagetive value time is not meet
thanks

 

[lakshman.ar]

i do agree by the reply posted by "iwpia50s" ..... thts the only possibility !!

btw do u have ne MCPs in ur design ???
go thru timing report in detail ..

do let us kno if u hv more doubts

WBR
Lakshman

 

[sizzlers]

hi
there is no problem with +slack
if u got -ve slack greater than clock period it means u missed some false path

thanks