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Mismatch between RTL and synthesis result (CDFG-511)

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I experience a mismatch between behavior of RTL and the Ambit Synthesis Result; whereby Ambit displays the following WARNING:
--> WARNING: Possibly an 'X' or 'Z' value propagated to a control statement
that may cause simulation mismatches between the original and
synthesized designs (File ../RTL/com.v, Line 3957) .
What is CDFG-511?
Details:
The design is an FSM which has outputs dependent from the next_state, i.e. mealy outputs. In the synthesis result the next_state after the power on reset evaluates to 'x' although the next_state is in this case only dependent from the current state which is well defined by the reset. Ambit involves additional signals in the calculation of the next_state, which are not defined at this time. Ambit Version is v5.7-s133.


Originally posted in cdnusers.org by weidi1
Parents

  • Hi weidi1,
    I meant there might be some undriven signal propagated to the control statement like 'case', 'if'. Do you see any undriven net reported from 'check_netlist'?

    Seems like this is something specific to your design that triggers the warning. I don't think we can resolve it here in this forum. If you can send that piece of RTL to Cadence Support, we can investigate further.


    Originally posted in cdnusers.org by synthman
Reply

  • Hi weidi1,
    I meant there might be some undriven signal propagated to the control statement like 'case', 'if'. Do you see any undriven net reported from 'check_netlist'?

    Seems like this is something specific to your design that triggers the warning. I don't think we can resolve it here in this forum. If you can send that piece of RTL to Cadence Support, we can investigate further.


    Originally posted in cdnusers.org by synthman
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