Reachability

From: Fabio Somenzi (Fabio@colorado.edu)
Date: Wed Jun 06 2001 - 12:07:07 MDT

  • Next message: Mario Escobar: "edif2blif"

    >>>>> "vg" == vanessa goyal <vanessa_goyal@rediffmail.com> writes:

     vg> Sir
     vg> (1)For the FSM code below,taking "ald" as MSB, and bits
     vg> for moorestate as LSB's
     vg> [0,1,2,3,4,5,6,7] are the 8 states.

     vg> please tell me what are the
     vg> "reachable states set" and "unreachable states set".

    They are all reachable. If you run "rch," it will tell you that there
    are 8 reachable states. In general, however, vis does not report
    which states are reachable; only how many. For large designs, listing
    all reachable states is usually infeasible. For individual states,
    one can use EF properties to determine whether they are reachable.

     vg> (2)Please tell me the same for the counter code.

    Again, all states are reachable.

     vg> How does,skip of reachability analysis for proving the property
     vg> "AG(clatched=1->AX(q[20:0]=0))" saves time?

    For the counter, it doesn't.

     vg> Also how does this case differs from the case which
     vg> includes reachability analysis?

    For the general explanation, refer to

      http://vlsi.colorado.edu/~vis/vis-users/0139.html

    In this case, reachability takes a long time, but in the end all
    states are reachable. Hence, the effort put into reachability
    analysis is wasted.

    Fabio



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