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buffer cells vs delay cells in delay matching in placement

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nsreekanthbabu

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hi,
can any one suggest which one among buffer cells or delay cells is preferred in delay replacement in placement?
quote with reasons.
 

Could u be more precise...wt do u mean by the term "delay replacement??"

Which tool r u using?

Added after 9 minutes:

Buffers are use to boost the signal level and to minimise the skew...where as

Delay buffers are use to add or reduce the delay......In the case of setup violation u need to reduce the delay of the datapath by upsizing the buffers or gates which are present...........And if u want to increase the delay in the case of hold in the combi path to avoid hold time problems then we will add delay buffers...

Hope it is clear for u...If i am wrong then let me know.........

Reply me
 

Re: buffer cells vs delay cells in delay matching in placeme

In buffers itself has 2 different of cellsets..
1. Clock Buffers ---> These are designed in a such a way that it has equal rise & fall time.. So that there won't be any change in the clock signal.
2. Normal Buffers --> These are used to meet the timing.
 

Re: buffer cells vs delay cells in delay matching in placeme

hi,
thanks for your response. i will elaborate my question.

my question is buffers and delays are two diffrent cells available in libraries.
i heard that, for delay insertion/reduction, we generally prefer buffer cells than delay cells.
one reason i noted from library file is size diffrence.(buffer cell occupies less space than delay cells for same driving capacity.)
if i am wrong, let me know it.

quote me some other reasons.

thank you
sree
 

Re: buffer cells vs delay cells in delay matching in placeme

picking delay cell or buffer cell, really depends on the amount of delay you are trying to insert and the space you have available.

in fast fast corner, 1 delay cell can equal 10 buffers.

so one is not better than the other. really depends on the situation.

hope this helps.
 

Re: buffer cells vs delay cells in delay matching in placeme

thank you tony.
 

Re: buffer cells vs delay cells in delay matching in placeme

picking delay cell or buffer cell, really depends on the amount of delay you are trying to insert and the space you have available.

in fast fast corner, 1 delay cell can equal 10 buffers.

so one is not better than the other. really depends on the situation.

hope this helps.

Can u tell me Tony how buffers are used to add delay..since buffers cells restore the signal level so it will only improve the driving current..but how will it reduce the delay(or current)
 

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