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Not-mapped help

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I got a unmapped point for golden when i am doing LEC (RTL vs netlist) in setup mode...
in the log file, it (DFF) is printed as NOT-Mapped...
but on the terminal, it (DFF) is displayed as Extra...
however, no NEQ is reported!
when i checked out the netlist, i found the DFF was removed for it was redudant ...
should I do some special treatment or just let it ignored?


Originally posted in cdnusers.org by yepp_hjs
Parents

  • This is normal. Mapping found that a DFF it could not map, but reachable, meaning that there is an unbroken connection from that flop to a primary output. i.e. that it looks like it does have an effect on the behaviour of the design.

    Compare came in and found that the flop cannot actually affect the behaviour of the design, even though it is not unreachable.

    The classical example: the Q of a flop feeds into the A pin of a AND gate, the Qbar of the same flop goes into the B pin of the AND gate. The connection to the flop doesn't matter: the output that AND gate will always be a constant zero.

    Synthesis will optimize the flop out of course.


    Originally posted in cdnusers.org by croy
Reply

  • This is normal. Mapping found that a DFF it could not map, but reachable, meaning that there is an unbroken connection from that flop to a primary output. i.e. that it looks like it does have an effect on the behaviour of the design.

    Compare came in and found that the flop cannot actually affect the behaviour of the design, even though it is not unreachable.

    The classical example: the Q of a flop feeds into the A pin of a AND gate, the Qbar of the same flop goes into the B pin of the AND gate. The connection to the flop doesn't matter: the output that AND gate will always be a constant zero.

    Synthesis will optimize the flop out of course.


    Originally posted in cdnusers.org by croy
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