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about bufferTreeSynthesis ??

icmaple

if Net resetn connects RN port of many different SDFF ( X2 X4 ..) ,  when i use bufferTreeSynthesis cmd, Need I use its option: -leafPorts for thest different SDFF.?   bufferTreeSynthesis consider what type of Pin/Port as Leafport by default??   

  • BobD
    I'm curious why you're using bufferTreeSynthesis instead of allowing optDesign to automatically buffer these nets? Do you want the skew to be balanced between the flops the net drives?  Or does the net connect to an always-on power domain?  If not, bufferTreeSynthesis may not be the best option for dealing with these high fanout nets.

    bufferTreeSynthesis considers clock pins on instances (according to .lib and/or .lef markings) leafPorts by default, similarly as does CTS.  So, it's possible that you don't need to specify any leafPorts at all.

    That said, I did some testing and I see that the leafPort option appears to not handle wildcards:

    bufferTreeSynthesis -nets clk -bufList BUFX1 -leafPorts *FF*/CK
    **WARN: (SOCCK-664):    The LeafPort + *FF*/CK is an invalid name.
     
    bufferTreeSynthesis -nets clk -bufList BUFX1 -leafPorts {SDFFSHQX1/CK SEDFFX1/CK}
    ->This works

    Therefore, it appears that you need to specify each drive strength in your list of leafPorts.

    Hope this helps,
    Bob

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