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TDP142: Boot on display issue with SNOOPENZ for DP++ application

Edward Lee
Intellectual 1655 points
Part Number: TDP142

Hi Expert,

     My customers are using TDP142 for supporting DP++ in their application.

     They found a boot on display issue that is some kind related to the function of SNOOPENZ.

     When the device is connected to DP fixed monitor, it can display the BIOS screen during boot on and entering OS.

     When the device is connected to a multiple-inputs monitor (auto-scan), it can not display the BIOS screen but can normally display after entering os.

      

     They try to disconnect the circuit between SNOOPENZ and CONFIG1 pin on DisplayPort receptacle and make aux snoop function disabled (keep it at logic high).

      After the adjustment, the device can display BIOS screen with any multiple-inputs monitor.

      is this related to the longer detection time which comes from the auto-scan of monitor and the snoop time from the TDP142?

       We just saw a description in the datasheet of TDP142 below.

"The TDP142 snoops native AUX writes to DisplayPort sink’s DPCD registers 0x00101
(LANE_COUNT_SET) and 0x00600 (SET_POWER_STATE). TDP142 disables/enables lanes based on value
written to LANE_COUNT_SET. The TDP142 disables all lanes when SET_POWER_STATE is in the D3.
Otherwise active lanes will be based on value of LANE_COUNT_SET."

       Does this mean TDP142 may disable lanes during AUX snooping and that cause failed to display during boot on?

       If we just disable the snoop function for DP++ application. will there be any side effect?

Thanks

Sincerely,

Edward

  • 0
    TI__Guru**** 176281 points

    Edward

    On the multi-inputs monitors, are you able to see the BIOS screen if you disabled the auto-scan function?

    There is no functional side effect with the SNOOP function being disabled. The impact is the power consumption since all 4 DP lanes will be active when the SNOOP function is disabled.

    Thanks

    David