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DS90UB953A-Q1: some questions about ub953

Jiawei Hu1
Expert 6495 points

Part Number: DS90UB953A-Q1

Hi team,

My customer use UB953+UB954 in their DVR project, and they found UB953+UB954 work normal when UB953 mode is Non-Sync and UB954 mode is Sync. Could you kindly tell me why this happen? Thanks!

B.R

Jiawei

  • 0
    TI__Mastermind 33120 points

    Hi Jiawei,

    The UB953 and UB954 should not be able to operate normally if they are in different modes. In the UB953, it uses an external reference clock to drive the Forward Channel (Serializer -> Deserializer). But it should not be able to communicate over the Back Channel (Deserializer -> Serializer). When you say that the UB953+UB954 project works normally, does that mean you are able to properly send video data from the 953 to the 954? And are you able to send any information over the Back Channel (Deserializer -> Serializer)?

     Also, could you double-check the register settings to see if the UB953 is Non-Sync and the UB954 is Sync. Look at register 0x03 in the UB953 and registers 0x58 and 0x6D in the UB954?

    Best,

    Justin Phan

  • 0 in reply to Justin Phan
    TI__Expert 6495 points

    Hi Phan,

    Thanks for your quickly reply. Let me tell you this issue more clearly.

    • Customer's topology is UB953-UB954-SoC-UB927-UB928-display.
    • UB954 mode set to CSI-2 Sync back channel
    • display can show video data from camera when UB953 sets to sync or non-sync
    • UB953 0x03 is 0x4A when set to non-sync without external clock, 0x03 is 0x48 when set to sync
    • UB954 0x58 and 0x6d are 0x1E and 0x7C

    From the register, there seems no problem in mode configuration. About communication over back channel, I don't understand your meaning, could you kindly tell me more clearly? And could you kindly tell me why above issue happen? Appreciate for your help!

    B.R

    Jiawei

  • 0 in reply to Jiawei Hu1
    TI__Mastermind 33120 points

    Hi Jiawei,

    The UB953 and UB954 can achieve about 4Gbps in Forward Channel transmission in either Synchronous Mode or Non-Synchronous Mode. But Back Channel transmission (Deserializer -> Serializer) is not possible, since the Synchronous Mode operates at a Back Channel frequency of 50Mbps and the Non-Synchronous Mode operates at a Back Channel frequency of 10Mbps. See Table 7-6. Clocking Modes in the 953 datasheet for more details.

    It might be possible to send video data from the 953 to the 954, even if they are both not in the same synchronous mode, but you shouldn't be able to send any Back Channel communication. You can verify this by trying to send a remote I2C message from the 954 side to the 953, while configured in the unmatched Non-Sync/Sync modes. It should not work. You can also try to verify this by configuring the GPIOs to send a signal from the 954 to the 953, since GPIOs can be sampled as part of the Back Channel frame. See 7.3.6.5 Back Channel GPIO in the 953 datasheet for more details. 

    Proper use of our devices involves using the same Mode on the Serializer and Deserializer side, such that Forward and Back Channel communication is possible.

    Best,

    Justin Phan

  • 0 in reply to Justin Phan
    TI__Expert 6495 points

    Hi Phan,

    When UB953 sets to non-sync mode and without external clock, is it possible to send video data from 953 to 954? UB953 don't have reference clock, how UB953 work? I am confused.

    And how to judge ub954 mode through register, sync or non-sync? 0x58 and 0x6d only can get fpd-link III mode, either CSI or RAW mode. 

    B.R

    Jiawei

  • 0 in reply to Jiawei Hu1
    TI__Mastermind 33120 points

    Hi Jiawei,

    The UB953 has an internal Always-On-Clock (AON). If you run in Non-Synchronous External Clock mode, the UB953 expects a reference clock at its CLKIN pin. But if no reference clock is detected, then it will use its internal AON clock. In Non-Synchronous Internal Clock mode, the UB953 does not look for an external reference clock and will immediately use the AON clock.

    On the UB954, the strap resistors at the MODE pin decide the mode by setting registers 0x58 and 0x6D at startup. In order to manually set Synchronous or Non-Synchronous mode, you need to select the proper Back Channel frequency and RX input mode. Register 0x58 determines the Back Channel frequency and register 0x6D determines the RX input mode. 

    1. For Synchronous mode, you need to select CSI mode in register 0x6D and set the Back Channel frequency to 50Mbps in register 0x58.
    2. For Non-Synchronous mode, you need to also select CSI mode in register 0x6D, but set the Back Channel frequency to 10Mbps in register 0x58.

    See Section 7.4.1 CSI-2 Mode in the datasheet for more information.

    Best,

    Justin Phan

  • 0 in reply to Justin Phan
    TI__Expert 6495 points

    Hi Phan,

    Understood. If no reference clock is detected, then UB953 will use its internal AON clock even though its default mode is non-sync external clock mode with HW configuration, right?

    Ok, I understood it. If I have more questions, I will let you know. Appreciate for your help!

    B.R

    Jiawei 

  • +1 in reply to Jiawei Hu1
    TI__Mastermind 33120 points

    Hi Jiawei,

    Okay, I will close this thread for now. Feel free to post here again for a related question. Or create a new post for a different topic.

    Best,

    Justin Phan