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When is the good timing for adding the filler cell in Astro?

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hgby2209

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cghier

When is the good timing to add the core / pad filler, after routing or before routing?
 

astro well filler problem

Before routing. If you wait until after routing there won't be any room to add any spare cells.

Usually the number of spare cells you add depends only on placement utilization levels, and these are known after placement and before routing.
 

xofiller

So the good step for adding core filler is berfore routing and after placement.

But between placement and routing, there is CTS step.

Which is the good timing for adding filler cell before CTS or after CTS?
 

Re: When is the good timing for adding the filler cell in As

In principle, after CTS - you want to give CTS as much freedom as possible to place the clock distribution buffers in the optimal places to minimize skew.
 

Re: When is the good timing for adding the filler cell in As

I do add filler cell after CTS, and then routing ......
But error is happen.....

After CTS --> axgAddFillerCell --> aprPGConnect --> axgPrerouteStandardCells --> axgSetRouteOptions --> axgRouteGroup --> axgGlobalRoute --> astPostRouteOpt

in post rout opt. step the following message display, and frocess was terminated....
-----------------------------------------------------------------------
ERROR: Cannot place filler cell instance "xofiller!FILL64!1".
Please purge them or fix them first.
***************************************
* Overlap Removal(OV) Engine Terminated
***************************************
WARNING : Assert failed at pdsMain.c(2668)
WARNING : Assert failed at pdsMain.c(2065)
ERROR : pdsPushParams() failed --- parameter stack empty
CGHIER: +++ Checking for HCG and flat CG consistency ... +++
CGHIER: +++ Done with checking HCG and flat CG consistency. +++
CGHIER: Number of errors = 0
Fail to execute command
-----------------------------------------------------------------------
so I need to purge filler cell in this stage, and re-do add filler after detail route.

Could you please tell me how to avoid above problem ?
 

Re: When is the good timing for adding the filler cell in As

1. IO Filler : should be add after IO pads are placed.
2. Core Filler : Core filler is to fill up the void between standard cells, usually in acutal layout, it has power rail, diffusion, and N-well layer. Core filler should be fill up all the core space after CTS, IPO, DRV etc, but before final detailing routing.

In a simple term, core filler are added before detailing routing.
 

Re: When is the good timing for adding the filler cell in As

very good knowledge share and informative

_sree
 

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