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TMS320C6678 PCIe reference clock- spread spectrum requirements

Tom Saluzzo
Expert 1280 points
Other Parts Discussed in Thread: TMS320C6678

In section 3.5.6 of the sprabi2b.pdf (6/7/2013) it states that spread spectrum reference clocks are allowed for the PCIe and Hyperlink reference clocks. However, I’m am not able to find any specific spread spectrum requirements ( % spread, up, down or frequency). Can you help me out with this?

  • 0
    TI__Genius 13045 points

    Tom,

    According to the Data Sheet (SPRS691D/tms320c6678.pdf), sec 7.16 the electrical specifications for the interface are to be taken from the PCI Express Base Specification Revision 2.0 of PCI-SIG.  Do you have access to this document?

    The PCIe User Guide (SPRUGSC), sec 2.2 has some additional information on where in the Specification to look for clocking information.

     

    Regards.

  • 0 in reply to TommyG
    TI__Mastermind 46460 points

    The KeyStone Hardware Design Guide SPRABI2 also contains masks showing the random jitter tolerance when using a common clock such as when operating with a spread spectrum clock.  The frequency variations of spread spectrum clocking appears as low frequency random jitter.  The random jitter mask must be met.

    Tom