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DS80PCI102: selecting Gen 3 with de-emphasis

David Mckinney
Expert 6860 points
Part Number: DS80PCI102


If we Float the RATE pin in SMBus mode (ENSMB = 1), do we need to write SMBUS registers 0x10 and 0x17, bit 6 to "0" to select GEN 3?

Is there anything else required to select Gen 3 with De-emphasis for both channels?  Are any writes or overrides required?

  • 0
    TI__Mastermind 43795 points

    Hi David,

    The RATE pin set to Float will automatically result in Gen3 with De-emphasis for PCIe 8 Gbps applications.  No other overrides are required.

    For datarates below 8 Gbps, the de-emphasis function will still be enabled and the output will operate in Gen1/2 mode.  

    Gen3 operation is a non-limiting mode output

    Gen1/2 operation is a limiting mode output

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    TI__Expert 6860 points

    Can you confirm that setting 0x10 and 0x17 from their default "1" settings of Gen 1/2 to "0" settings of GEN 3 are not required?

    In the datasheet, for the RATE pin, setting FLOAT = AUTO Rate Select of Gen1/2 and Gen3 with de-emphasis, so this is an "Auto" operation then. 

    Thank you in advance, but I want to be sure no additional setting are required for GEN 3 with de-emphasis in SMBUS mode, only to float the RATE pin and AUTO rate selection will occur.

  • 0 in reply to David Mckinney
    TI__Mastermind 43795 points

    Hi David,

    The RATE pin will take priority, even with ENSMB = 1.  In order to switch over to register control for this function an override register bit at Register 0x08[2] would also need to be programmed to a "1".

    Without register programming and RATE = Float the device will automatically select the correct output mode.

    Gen1/2 with de-emphasis  (PCIe_Gen1 or PCIe_Gen2)

    Gen3 with de-emphasis (PCIe _Gen3)

    Regards,

    Lee