What are the general guidelines for inserting buffers ?

[smith_kang]

buffers

hi
what are the general guidelines to insert buffers in the design.
buffers reduces wire delays and slack Ok but what are the general rule for that.
means say like I'm not able to meet the timing requirement then is buffer is the only solution to this or I can use them elsewhere.
Please tell some paper or site address so that I can get more information for this topic

 

[rajavel]

Re: buffers

Normally not always buffers are inserted...First determine the critical or timing violated path in your design.Rearrange the combinatinal blocks near to the capturing flops or launching flops.try to reduce the distance between the launching and capturing flops.
Usually go for combinational block optimisation like logic duplication, increasing drive strength of devices, rearrangement of blocks,pin swapping for slow arrival signals etc..
Buffers are usually perferred as a last option to meet the timing as it consumes extra area.

 

[arunragavan]

buffers

buffers can be generally used to amplify a signal.. when a signal is to travel through a distance in the chip.. the strength of the signal might reduce, might diminish or fade due to various factors depending on the signal integrity constraints. So i wud siggest using buffers when ever needed to amplify the signals.

with regards,

 

[xiongdh]

Re: buffers

1)when clock tree synthesis,buffer inserted to balance clock skew
2)to amply a signal for long path
to drive more load
3)to isolation macro module,buffer can be take as less load for that drive it and having much driven capacity for the module that it drive.
4) to fix hold violation
5) circuit connect like this
--------buffer1x----buffer2x----buff4x------
comparing to
----------buffer4x---------
maybe have less transition delay.
-----------------
I dont know more ,Maybe there are errors.

 

[silencer3]

buffers

basically to fix timing violations at the back-end buffers are inserted. using DC or PT also u can insert buffers but the best way to dfo is at back-end. determine timing viol;ations and recommend to back-end guys

 

[stephens_forest]

Re: buffers

buffer has two functions:

1) for fixing hold time, we add buffer before a dff's inputs to increase

data delay.

2) for fixing transition time violation, we add buffers to

increase drive ability. but in these case, buffer also

increase delay by itself, but if reduced delay is greater

than increased delay, our objective is achieved.


best regards

hi
what are the general guidelines to insert buffers in the design.
buffers reduces wire delays and slack Ok but what are the general rule for that.
means say like I'm not able to meet the timing requirement then is buffer is the only solution to this or I can use them elsewhere.
Please tell some paper or site address so that I can get more information for this topic

 

[tarkyss]

buffers

i think you can study some paper about the algorithm for buffer insert

 

[amaccormack]

Re: buffers

I would think that buffers are mainly used for trees for clock and reset and other global nets, for hold time fixing and for transition time fixing.

 

[quake]

buffers

most of the above advices are right. and these rules
can be found in "Digital Integrated Circuits - a design perspective" by Rabaey. There are detailed
info and theory in it.