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what's the differnt between fanout and fanout load?

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rickyice

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fanout load

what's the differnt between fanout and fanout load?
 

fanout_load

Hi Rickyice,

I don't know the different between fanout and fanout load. I think they are the same. However, I am aware of the different between fanout and load.

In engineering term, total fan-out is the count of the number of input pins an output is driving. For example, a net with fanout of 3 means there are three input (some maybe bi-direction) in the net.

However, .lib defination of fan-out is different. In the .lib, an input pin can have a fanout value of anything (e.g. 1.2321). Then, in DC, fanout is the sum of these fanout value.

Load, is the capacitance load. It is the sum of all input cap and wireload cap.

Regards,
Eng Han
www.eda-utilities.com
 

load vs fanout

ok, i see
thanks
 

fanout load

Hi,
It depends on the context in which you are using. Fanout implies how many loads (read nets) are connected to the output pin. Fanout load refers to the capacitance in suitable units. This depends on the context in which the terms are used
EDA BOY
 

fanout load

I believe that there is a difference between fanout and fanout load.

Fanout is the ability of the gate's output to drive no of input of other gates.

Fanout load comes in the form of a context. i.e theoritically you can say that infinite no of wires can go from the o/p of one gate, but reality is that the gate can't drive such a big "LOAD".

Is that OK ?
 

fanout load wiki

from DC's view,

fanout means the connected cell count on cell output; while fanout load means the output load capacitance (including the parastic cap, which is estimated by wireload model)

however, there is no linear relation between fanout and fanout load, and fanout load would be more accurate.
 

count the fanout of the gate forum

Hi Jackson,

I believe DC does not support "fanout" according to your defination.

If you refer to the .lib for the standard cell, for input pin there is a "fanout", and it is not necessary equal to 1.

When I worked with Magam tool, there is another command to get the engineering defination of fanout (the one you use). (I cannot remember the command as I don't use Magma tool for more than a year).


Regards,
Eng Han
 

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