[SI-LIST] Re: Timing equations - help

  • From: <Alex_Messan@xxxxxxxx>
  • To: <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 31 Aug 2006 00:16:13 -0500

 Kranthi,
What is important in the equations is to realize that they are worst
case scenarios (minimal margin). In common clock environment, an early
clock edge reduces setup margin while a late clock edge reduces hold
margin.

Regards,
Alex

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of kranthi
Sent: Wednesday, August 30, 2006 11:50 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Timing equations - help

Hi,

I have a doubt in timing equations for calculating the setup and hold
margins.i referred few documents but, were very confusing and so I did
not have another option other than posting it on this group.

The cause of confusion is the clock skew parameter.some documents
subtract it for calculating the set up margin and add it for calculating
the hold margin while others do the opposite way.One point to be noted
is that the skew can be positive or negative.So, what is the exact way
in which the skew should be accounted.i have a general conception that,

If the clock skew is positive then Tclk_skew should be added in
setup_margin equation and subtracted in hold_margin equation, and when
the clock skew is negative it should be taken the opposite way.Is this
conception correct?

Please help me on the exact way of considering this parameter(clock
skew) in estimating the setup and hold margins.

Best regards,
Kranthi

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