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 how to identify unique nets connected to preset/clear pins of all FFs in a scope 

Last post Thu, Feb 27 2014 11:01 AM by grasshopper. 1 replies.
Started by Sporadic Crash 07 Jan 2014 12:07 PM. Topic has 1 replies and 4935 views
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  • Tue, Jan 7 2014 12:07 PM

    • Sporadic Crash
    • Not Ranked
    • Joined on Mon, Sep 8 2008
    • Hamburg, Hamburg
    • Posts 7
    • Points 110
    how to identify unique nets connected to preset/clear pins of all FFs in a scope Reply

    I have not been able to find an attribute that shows whether a net in a scope is connected to a preset/clear of FF. 

    The only way I have found:

    foreach FF in a scope {
     foreach pin of this FF {
      if { libpin of this pin is a {async_clear} } { set an async_clear net }
      if { libpin of this pin is a {async_preset} } { set an async_preset net }
      if { libpin of this pin is a {sync_clear} } { set a sync_clear net }
      if { libpin of this pin is a {sync_preset} } { set a sync_preset net }
    }
    }

    This is quite complicated, because in a certain block there can be several FFs each of which can be resetted in a different way, thus HW designer might need to create a TCL associative array to identify unique nets.

    Is there an easier way to do this?

    • Post Points: 20
  • Thu, Feb 27 2014 11:01 AM

    • grasshopper
    • Top 25 Contributor
    • Joined on Fri, Jul 18 2008
    • Chelmsford, MA
    • Posts 242
    • Points 3,205
    Re: how to identify unique nets connected to preset/clear pins of all FFs in a scope Reply

     Hi Sporadic Crash,

     logical nets have 'driver' and 'loads' attributes

     instances have a libcell attribute 

     libcell have attributes async_clear, async_preset, sync_clear, sync_preset

     That should provide all the pieces of needed solution

    gh-

    • Post Points: 5
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Started by Sporadic Crash at 07 Jan 2014 12:07 PM. Topic has 1 replies.