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DS90UB941AS-Q1: Technical Query for DS941/948

Haiwen Huang
Intellectual 2360 points

Part Number: DS90UB941AS-Q1

Dears:

customer has below quesiton need BU help check:

1. In DE (Data Enable) Mode, do the Ser (941) and Des (948) detect HSync/VSync polarity? Does the polarity configuration affect the SerDes link?
 
2. Under the default configuration of the DS948, what is the default polarity for HSync and VSync (High or Low)? Is there a specific register to modify these polarities?
 
3. If the DS941 is configured for DE Mode with HSync/VSync set to "Low," while the DS948 remains at its default configuration, would this scenario cause display abnormalities? What is the probability of such an occurrence?



  • 0
    TI__Mastermind 23185 points

    Hi Haiwen,

    Haiwen Huang said:
    1. In DE (Data Enable) Mode, do the Ser (941) and Des (948) detect HSync/VSync polarity? Does the polarity configuration affect the SerDes link?

    Yes, even during the incoming information being DE mode only, the FPD-Link devices still attempts to parse "HS" and "VS". DE can be configured for a different polarity.

    DSI HS and VS polarity can be flipped through DSI Control registers on the 941AS.

    DE, HS, and VS polarity can be flipped in 948 through FRC register.

    Haiwen Huang said:
    2. Under the default configuration of the DS948, what is the default polarity for HSync and VSync (High or Low)? Is there a specific register to modify these polarities?

    The default is active high, the FRC_CONTROL register is the specific register to change polarities.

    What is the anticipation of changing the polarities? Is the incoming data expected to be active low?

    Haiwen Huang said:
    3. If the DS941 is configured for DE Mode with HSync/VSync set to "Low," while the DS948 remains at its default configuration, would this scenario cause display abnormalities? What is the probability of such an occurrence?

    I think this would cause some abnormality, as 941AS does not have a native DE mode and always expects HS and VS incoming to the DSI receiver, at least HSS and VSS packets.

    Please let me know if there are any additional questions.

    Best,

    Miguel

  • 0 in reply to Miguel Bolante
    TI__Intellectual 2360 points

    Miguel:

    Thanks for the reply.

    Attachment is the test waveform.

    Could you please re-confirm whether modifying the polarity in register 0x29 definitely takes effect in normal mode, or is it only supported in FRC mode?

    941.docx

  • 0 in reply to Haiwen Huang
    TI__Mastermind 23185 points

    Hi Haiwen,

    Thanks for providing this detailed analysis, I will get back to you with the confirmation soon.

    Best,

    Miguel

  • 0 in reply to Miguel Bolante
    TI__Mastermind 23185 points

    Hiawen,

    Haiwen Huang said:
    Could you please re-confirm whether modifying the polarity in register 0x29 definitely takes effect in normal mode, or is it only supported in FRC mode?

    This effect only takes place in FRC mode, and additionally;

    Miguel Bolante said:
    Yes, even during the incoming information being DE mode only, the FPD-Link devices still attempts to parse "HS" and "VS". DE can be configured for a different polarity.

    For further clarification, if the SER side is receiving DE only signal, it will simply pass this along to the DES - it will be up to the sink / display to extract this signal and interpret the signals from there.

    Please let me know if you have any further questions!

    Best,

    Miguel