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 PKS retiming  

Last post Thu, Jan 28 2010 8:23 PM by grasshopper. 1 replies.
Started by comport 28 Jan 2010 06:08 PM. Topic has 1 replies.
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  • Thu, Jan 28 2010 6:08 PM

    • comport
    • Not Ranked
    • Joined on Mon, Sep 28 2009
    • Posts 1
    • Points 20
    PKS retiming Reply

    Hi

     I am trying to use the do_pipeline_check / do_pipeline_retime features in PKS, on a block with 4 layers of pipeline built-in. Since the combinatorial function is not easy to pipeline manually (not an arithmetic function but a decoder), I put it between 2 pipeline stages hoping for PKS to remap it through all the available stages by using do_pipeline_check / do_pipeline_retime.

    The check works but tells me that no register is retimable.

    Anybody knows what are the criteria for a register to be re-timable ?

    Thanks
    • Post Points: 20

  • Thu, Jan 28 2010 8:23 PM

    • grasshopper
    • Top 25 Contributor
    • Joined on Fri, Jul 18 2008
    • Chelmsford, MA
    • Posts 151
    • Points 2,095
    Re: PKS retiming Reply

    Hi comport,

    I have not used PKS in a while so its criteria may vary slightly. The general criteria for retiming is based on classes. For example a flop on CLKA will be on one class and one on CLKB will be on a different class so no retiming across different classes. The case of different clocks is quite an obvious one since moving flops across clock domains carries pretty evident dangers. Other class criterias are things like asynchronous signals feeding the flops, enable signals for stalling flops, etc. Regarding stalling flops an enable signals, not that the inference of clock gating can also have an impact on the ability of tools to apply retiming techniques. Last but not least I wonder why you are not using RTL Compiler instead of PKS. Synthesis technology is a substantial upgrade, not to mention support for CPF and linkage for Conformal and other tools. In the future, synthesis related questions are probably better suited for the Logic Design forum.

    hope this helps,

    gh-

    • Post Points: 5
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Started by comport at 28 Jan 2010 06:08 PM. Topic has 1 replies.