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DS90UB927Q-Q1: some questions about 927

Jiawei Hu1
Expert 5565 points
Part Number: DS90UB927Q-Q1

Hi team,

When the power is first turned on, the SoC has not output LVDS signal yet. Can SoC access the remote device through 927 and 928 by using I2C? How about 947 and 948? Thanks for your answer in advance!

Jiawei

  • 0
    TI__Guru** 108180 points

    Hello Jiawei,

    yes, your SoC can access the 927 registers and the paired 928 registers without having an active video. 

    Using the 947 and 948 is a bit different. You need first to make sure to change the LOCKing mode on the 948, by writing register 0x34[6] to 1, to have LOCK and access without active video. This register change can only be done locally on the 948 I2C bus.

    Generally, in both cases, you need to make sure you have I2C Passthrough is enabled. Also you need to make sure remote access is not disabled on the DES.

  • 0 in reply to Hamzeh Jaradat
    TI__Expert 5565 points

    Hi Hamzeh,

    Does 928 PDB need to be high if we want to access 928 register and remote slave? If need, does it violate 928 power up sequence? As I know, 948 PDB should be high after stable signal from 947.

    Jiawei

  • 0 in reply to Jiawei Hu1
    TI__Guru** 108180 points

    Hello Jiawei,

    Yes, 928 must be running and LOCKed to the SER.

    If the power-up sequence is violated, then you shall reset the 928 or 948 once they have stable signal from the SER.