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DS90UB954-Q1: how long should I wait for sending I2C command after PDB is high?

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Replies: 9

Views: 97

Part Number: DS90UB954-Q1

hello, please tell me how long should I wait for sending I2C command after PDB is high? I found it for 953 but not sure about 954. 

Also please tell me what could happen if this requirement is not met. 

ito

  • Hello Ito,

    similar to the 953, it needs to be >2ms.

    If this is not met, the first few I2C transactions may be not excuted!

    Regards,

    Hamzeh

    ------------------------------------------------------------------------------------------------------------------------------------------------

    Training on FPD-Link Serializer Deserializer devices and system: https://training.ti.com/fpd-link-learning-center

    More information on IVI or ADAS FPD-Link products: http://www.ti.com/interface/fpd-link-serdes/overview.html

  • In reply to Hamzeh Jaradat:

    Hi Hamzeh,  

    thanks. let me clarify. 

    The first I2C before 2ms could cause device's unknown state, or it might be just ignored? 

    ito 

  • In reply to Takuma Ito:

    You are right! This may cause unknown state!

    Regards,

    Hamzeh

    ------------------------------------------------------------------------------------------------------------------------------------------------

    Training on FPD-Link Serializer Deserializer devices and system: https://training.ti.com/fpd-link-learning-center

    More information on IVI or ADAS FPD-Link products: http://www.ti.com/interface/fpd-link-serdes/overview.html

  • In reply to Hamzeh Jaradat:

    hi Hamzeh

    after device enters unknow state, the device may not work properly, correct? did you actually have such issue? 

    My customer's system may not be able to avoid this because the master polls 954's I2C from before PDB is pulled high. Do you have any good idea to avoid thsi?

  • In reply to Takuma Ito:

    Hello Ito,

    which kind of issue do they see exactly? The 954 is not responding any more to I2C or what?

    They may digital reset the 954 and restart the initialization again!

    Regards,

    Hamzeh

    ------------------------------------------------------------------------------------------------------------------------------------------------

    Training on FPD-Link Serializer Deserializer devices and system: https://training.ti.com/fpd-link-learning-center

    More information on IVI or ADAS FPD-Link products: http://www.ti.com/interface/fpd-link-serdes/overview.html

  • In reply to Hamzeh Jaradat:

    hi Hamzeh

    The issue is that they are not able to avoid sending command before 2ms from PDB. They have not seen any actual issue such as not responding to I2C. 

    If the device enters unknown state, does the device still accept digital reset command? 

    ito 

  • In reply to Takuma Ito:

    Hello Ito,

    2ms after PDB, just digital reset the device using reg 0x01[1] to resets the entire digital block including registers, and then restart the initialization from the beginning.

    Regards,

    Hamzeh

    ------------------------------------------------------------------------------------------------------------------------------------------------

    Training on FPD-Link Serializer Deserializer devices and system: https://training.ti.com/fpd-link-learning-center

    More information on IVI or ADAS FPD-Link products: http://www.ti.com/interface/fpd-link-serdes/overview.html

  • In reply to Hamzeh Jaradat:

    hi Hamzeh,  

    let me check my understanding, the I2C command could be sent before 2ms, as you mentioned the device may enter unknow state by this command. If so, does the device still accept the digital reset command? 

    also, customer sees the I2C command 0.3ms after PDB, and in this case was NACK. Is this just NACK of device may in unknown stat? 

  • In reply to Takuma Ito:

    Hello Ito-san,

    If the customer issues a command before 2ms, then we do not know the possible effects. This means that the device may not function correctly in general which is the case for any violation of the power sequence requirements. Please make sure this is corrected in the system design and keep in mind that this is condition for which we do not have any data to show possible behavior. 

    Best Regards,

    Casey