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DS80PCI800 extended range values of SD_TH

Cedrick Beaulieu
Prodigy 215 points
Other Parts Discussed in Thread: DS80PCI800

Hello,


Bits 5 and 4 from register 0x28 of DS80PCI800, "Signal Detect / Status Control", allow usage of higher range for signal detect thresholds; however the values for this "higher range" are not defined in the datasheet. I woud expect that when enabled, this option offers values different than those specified in table 5 of the datasheet (160mV, 180mV, 190mV, 210mV).

We are currently experiencing false triggering caused by high crosstalk level on a specific channel while in compliance mode. Increasing the assert threshold by enabling the higher range for signal detect removes the false triggers. However, I would like to know which values are now in use.


Thank you very much,

Regards,

Cedrick

  • 0
    TI__Mastermind 43795 points

    Cedrick,

    I would not recommend using the high level signal detect setting for normal PCI 8.0 Gbps operation.  The threshold level increases  are enough to falsely mute the PCI800 outputs on lossy channels.  The actual levels are not specified, but they increase ~ 1.5x vs. the default range shown in Table 5.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Prodigy 215 points

    Hi Lee,

    Thank you for clarifying the impact of this setting. We do not plan to use it with standard applications; we were investigating false triggering on a specific RX lane, which was not connected to a downstream component during an electrical compliance test in a PCIe-over-cable application. Crosstalk occured inside the cable between a TX lane and an undriven RX lane, causing the false triggering issue seen at the RX endpoint.

    Regards,

    Cedrick