Negative Hold time

Hi, I was checking out some spec sheets and came aross a negative hold time. Does anyone know why there is a negative sign cause I can understand a positive hold time but negative??? Thanks Rohit

Asked By: rskurane
On: Feb 26, 2005 10:34:04 PM

Comments(6)

Hi all, Had great prologues and conversations even in holidays. ****Negative HOLD TIME is EXISTING particlarly in the case of CLOCK SKEW. ****** Consider two FFS with CLOCK SKEW i.e &nbspFF1 lags behind FF2 and suppose FF1's op is fed to FF2's ip thru some logic( or directly) then by the time FF1 is &nbspactive &nbspthe FF2 would have done its sampling the FF1's op there by no violation of hold time. This is -ve hold time similarly setup time can be there. ********* if thold2< t skew(2-1) then there is -ve hold time that is op can change even at 0 sec after the clock(for FF1 here ) Contemplate the above one since i could not exactly portray the scenario. Bye

Comment By: venkateshr
On: Feb 28, 2005 5:03:59 AM

So what you mean to say is that the data get latched,lets say a FF, before the clock arrives? and that is why it is negative. If so how does that FF work of it does not need a clock to latch the data. I am still confused about this. If you could explain with an example I would appreciate it. Thanks

Comment By: rskurane
On: Feb 27, 2005 1:32:55 PM

Hi, I am sorry, ya even i came across negative hold time. Hold time can be negative meaning that data can be changed even before clock edge and still previous value will be stored.Thanks for the info. Let me know if u need any additional details abt negative hold time. Pradeep

Comment By: gpradeep.rsv
On: Feb 27, 2005 11:47:28 AM

Comment By: gpradeep.rsv
On: Feb 27, 2005 11:36:57 AM

well thats what it says, negative hold time(-0.1ns) and thus a negative hold margin

Comment By: rskurane
On: Feb 27, 2005 2:43:48 AM

Hi, I never heard abt negative hold time.There can be negative setup time. The min hold time can be 0.So please check the spec sheet again and let me know too if there can be negative hold time Pradeep

Comment By: gpradeep.rsv
On: Feb 27, 2005 2:15:06 AM

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