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Does negative slack mean negative hold time?

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kris2552

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negative slack

What happens to respective setup and hold times .....with positive and negative slacks? reeally confused between negative setup,hold snd slacks......Please somebody explain?
 

negative slack time

hai dude,

Hope u know what is slack . it is diffrence between requried time and Arrival time.

Slack =RT-AT =set up
slack = AT-RT = hold

If RT is greater than AT leads tp setup

If AT is greater than RT leads to Hold.


Means slack or setup occurs of the signal reaches earlier than the requried time before the clk has reached. it is similar to setup violation

also slack or hold occurs if the signal reaches later than the requried time after the clk has reached. it si similar to hold violations

one more slack should be always positive.

hope u understood else shoot me a question

phutane
 

what is negative slack

Hi Phutane,

Thank you for ur prompt reply.
So according to the eaquations provided here, does it mean either of the slack would negative? i.e., either slack(setup) or slack(hold) will be definitely negative?

I googled the definiton for slack, but evrywhere it was explained that "slack is defined as the differnece between arrival time and required time".
And its also the terminology that confuses me a lot......

negative slack means .....is it -ve slack means -ve setup or -ve hold ?

Please refer me some good material regarding this and some problems so that I could be able make myself clear.....

Thank you in advance.....
 

how to solve negative slack

Nothing confusion

set up or hold violation occurs depending on the value we get

That is for SET UP= RT-AT and Hold is AT-RT

we should always have a positive value.

just c to get a negative value in set up AT must be more

similarly for Hold RT must be more.

but we design to keep slack value as positive depending on which violation u get.
 

positive and negative slack

hey,

"negative slack means .....is it -ve slack means -ve setup or -ve hold ? "

negative slack cn occur both for setup and hold !

When u perform setup analysis, if your arrival time ( Tcq + Tcombi) is greater than required time ( Clock Period- Tsu), then u get a "-ve slack" for setup !

similarly if u r doin a hold analysis, u wil get a "-ve slack", if ur arrival time(Tcq + Tcombi) is lesser than the required time ( Th of the flip flop)

clear ?

phutanesv has explained it verr clealy in both of his replies.
 

what is a negative slack

Thank you very much guys!!
Its clear now....I was totally confused......

Thanks and regards.
 

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