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RTC Section clarification on AM389x

Roshan Dsouza
Intellectual 430 points
Other Parts Discussed in Thread: TPS65910

In AM389x1 reference manual section 9.2.1 Clock Source " The RTC has an internal oscillator buffer to support direct operation with a
crystal. The crystal is connected between pins RTC_XI and RTC_XO. RTC_XI is the input to the on-chip oscillator and RTC_XO is the output from the oscillator back to the crystal. For more information about the RTC crystal connection, see your device-specific data manual.An external 32.768-kHz clock source may be used instead of a crystal. In such a case, the clock source is connected to RTC_XI, and RTC_XO is left unconnected."

But i did not find any such pins in Am389x datasheet. Please can anyone help on this? Is there any specific user manual available for Am389x processor?

Regards,

Roshan D'souza

  • 0
    TI__Mastermind 25055 points

    Hello,

    Sorry for the confusion.  The information in the TRM is incorrect.  On the AM389x device the RTC is driven by SYSCLK18 (32.768 kHz) or an optional 32.768-kHz clock can be input on the CLKIN32 clock input pin for RTC reference.  We will correct the information in the TRM.

    Regards,
    Marc

  • 0 in reply to MarcPyne
    Intellectual 430 points

    Thanks Marc for the clarification.

    Also can you let me know how to backup RTC using external 3V coin battery when Main power is disconnected?
    Whether we need to use a external RTC controller using I2C or any other interface? Is there any reference design available regarding RTC implementation for AM389x?

    Thanks & Best Regards,

    Roshan D'souza

  • 0 in reply to Roshan Dsouza
    TI__Mastermind 25055 points

    Roshan,

    If a real-time-clock is needed even when the device is powered off then it has to be present outside of the AM389x.  The RTC module inside of the device does not support RTC operation when the device is powered down, so an external RTC module would be needed for this.

    Regards,
    Marc

  • 0 in reply to MarcPyne
    Prodigy 140 points

    Marc,

    I had a question on this topic.

    On the eval board (816x/389x EVM), is the real time clock function implemented using the PMIC TPS65910? Does the RTC function work even when the unit is powered down (I see a coin battery in the design) ?

    If that works, I want to use that design on ours.

    Please let me know

    Thx

    Vishy