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SN65HVDA100-Q1: About communication mode setting

Kenji Ohno1
Genius 5095 points
Part Number: SN65HVDA100-Q1

Hi team,

Our customer have problem about SN65HVDA100-Q1.

Please answer the question below.

1.Is there a problem with LIN IC and CPU only by connecting TX / RX / EN?

2.I want to know how the CPU detects mode,is there a way to do it?

3.Is there a fail-safe to avoid communication failure?

 (Is there any restoration method other than turning off the power?)

4.In which case can the LIN IC not be able to communicatez?

5.What will happen if the LIN signal enters within the standard time of tmode_change when EN enters Low or High?

 (When EN is changed within max 5 us)

6.Does inconvenience or trouble occur when the EN terminal is always operated at high?

Best Regard,

Kenji

  • 0
    TI__Guru 60112 points
    Kenji-san,

    Thanks for bringing this opportunity and the questions to our attention. Is there any way you can share what the application for this project is?

    1. There is no inherent problem with this approach, but you're limited on what you can control and detect from the LIN transceiver.

    2. The best way to detect the modes of the device is to monitor the INH pin, and control the signal going to the EN pin. Without knowing the state of INH, it will be difficult to determine if you are in Sleep vs. Standby mode. You could also monitor the state of the RXD pin, as it changes from mode to mode as well. In Sleep mode the RXD pin is floating, in Standby mode the RXD pin is low, and in Normal mode the RXD acts as it normally should: following the bus traffic.

    3. There are several fault detection circuits on this device (undervoltage, overtemperature, and loss-of-ground protection). When these happens, the devices switches itself off, and will come back up once the fault condition is gone. The device is indeed powering on and off, but automatically, and not something manual that the user has to do.

    4. Any of the conditions I mentioned in 3., undervoltage, overtemperature, and loss-of-ground, as these will all cause the device to shutdown. The device will also not be able to communicate in either Sleep or Standby mode; however, in Sleep mode, the device is in a low power monitoring state that allows for it to respond to a LIN Wake up request on the LIN bus. This is further explained in the datasheet on page 10, but please let me know if you would like for it explained in more detail.

    5. If you are going from low EN to high EN, the LIN bus may be ignored because you'd be transitioning from Sleep/Standby to Normal, and the bits that happen for tmode_change has passed won't be recognized by the transceiver because the circuits will still be in the low-power/sleep modes. If this occurs while going from high EN to low EN, the same might occur, and you could also inadvertently cause a LIN wake up to trigger depending on the timing of the message and the pattern on the LIN bus.

    6. There is no problem with holding the EN pin high at all times if the user requires the device to be in Normal mode at all times. However, if the user wants to go to Sleep and/or Standby mode, holding the EN pin high at all times will not allow this.

    Let me know if you have any more questions or issues, I'm happy to help.

    Regards,
  • 0 in reply to Eric Hackett
    Genius 5095 points
    Dear Eric,

    Thank you for answering.
    The application is an in-vehicle clock.
    Does that mean that even if EN is changed from High to Low to High in a shorter time than the tmode_change standard, will it become Normalmode?
    The problem does not occur, is it?

    Best Regards,

    Kenji
  • 0 in reply to Kenji Ohno1
    TI__Guru 60112 points
    Kenji-san,

    If you toggle EN from high to low to high in less than 5us, you should see no mode change on the device. I'm not certain, but I think there is a deglitch filter so that when short glitches on the EN pin happen, the mode doesn't unintentionally change. It also protects against any noise that might toggle the EN pin.

    Regards,