xilinx ise synthesis timing summary

Discussion in 'VHDL' started by niyander, Jul 29, 2010.

  1. niyander

    niyander Guest

    hi,

    i have made a floating point multiplier and after synthesis i get the
    following result.
    does the "No path found" message means that my design is not
    synthesized properly?

    Minimum period: No path found
    Minimum input arrival time before clock: No path found
    Maximum output required time after clock: No path found
    Maximum combinational path delay: 18.621ns

    please help me.

    thanks
    niyander, Jul 29, 2010
    #1
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  2. niyander

    sridar

    Joined:
    Jun 5, 2007
    Messages:
    51
    Re:

    Looks like you didn't use any clock in your design. Since you use only combinational logic, the particular info " Maximum combinational path delay" is displayed.
    sridar, Jul 29, 2010
    #2
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  3. niyander

    vipin lal Guest

    On Jul 29, 8:43 am, niyander <> wrote:
    > hi,
    >
    > i have made a floating point multiplier and after synthesis i get the
    > following result.
    > does the "No path found" message means that my design is not
    > synthesized properly?
    >
    >    Minimum period: No path found
    >    Minimum input arrival time before clock: No path found
    >    Maximum output required time after clock: No path found
    >    Maximum combinational path delay: 18.621ns
    >
    > please help me.
    >
    > thanks


    No, "no path found" doesnt mean that your code is not synthesised
    properly. I found this answer from xilinx forum:

    "The PERIOD constraint only applies to internal signals which go from
    one flip-flop to another on the same clock."

    Your design doesnt use a clock,so no flip flops are generated. So the
    maximum operating frequency is not a function of internal timing and
    cannot be calculated during synthesis.

    Experts please verify this.

    --vipin
    vipin lal, Jul 29, 2010
    #3
  4. niyander

    backhus Guest

    On 29 Jul., 07:42, vipin lal <> wrote:
    > On Jul 29, 8:43 am, niyander <> wrote:
    >
    > > hi,

    >
    > > i have made a floating point multiplier and after synthesis i get the
    > > following result.
    > > does the "No path found" message means that my design is not
    > > synthesized properly?

    >
    > >    Minimum period: No path found
    > >    Minimum input arrival time before clock: No path found
    > >    Maximum output required time after clock: No path found
    > >    Maximum combinational path delay: 18.621ns

    >
    > > please help me.

    >
    > > thanks

    >
    > No, "no path found" doesnt mean that your code is not synthesised
    > properly. I found this answer from xilinx forum:
    >
    > "The PERIOD constraint only applies to internal signals which go from
    > one flip-flop to another on the same clock."
    >
    > Your design doesnt use a clock,so no flip flops are generated.  So the
    > maximum operating frequency is not a function of internal timing and
    > cannot be calculated during synthesis.
    >
    > Experts please verify this.
    >
    > --vipin


    Hi,
    vipins interpretation is correct.

    It may make one wonder that a FP-multiplier has no FFs at all, but if
    it's intended, why not.
    18 ns (including the slow I/O-buffers) allow operations up to 55 MHz.

    To be sure that everything went well you may check the amount of
    primitives (BELs) in the synthesis report, also check all the warnings
    and infos.
    A post translate/map/par simulation will show you quite fast wether
    the synthesized logic works as intended or not. Be prepared to see a
    lot of glitches. :)

    Have a nice synthesis
    Eilert
    backhus, Jul 29, 2010
    #4
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