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RTC in DM8148

Nanthan raj
Intellectual 270 points


Hi All,

        How RTC will work/implement in DM8148 processor?I couldn't see any RTC power pin/domain inside the processor on datasheet & TRM.Will it possible to implement RTC by processor or RTC can implement only by using power manager like TPS659113?

Regards,

Nanthan.

  • 0
    TI__Genius 15310 points

    Hi Nanthan,

    It is necessary to either use a PMIC with integrated battery backed RTC or to use an additional external battery backed RTC.

    The integrated RTC does not support battery backed operation.

    BR,

    Viet

  • 0 in reply to Viet Dinh
    Intellectual 270 points

    Thanks Viet.

    Regards,

    Nanthan.

  • 0 in reply to Nanthan raj
    Prodigy 140 points

    Hi  All

     

    if we don't need RTC function,

    Can I remove the crystal ??

     

    Max

  • 0 in reply to Max Chou14536
    Intellectual 700 points

    Yes.  We have actually done this on a custom board.

  • 0 in reply to Viet Dinh
    Prodigy 115 points

    hi Viet,

    In your post, you said that "The integrated RTC does not support battery backed operation". What does it mean? The integrated RTC of DM8148 can not keep calendar and time even with an additional external battery? In our design, we found that the RTC of DM8148 can work with a battery circuit. However, the RTC time is not accurate. There is about a deviation of 8 seconds per hour.  And then, we found that the RTC alos can not run accurately even without power-loss. This test was taken based on the Appro DM8127 reference design.

    BR,

    caijin

  • 0 in reply to Cai Jin
    Prodigy 80 points

    I have a related question.  We are seeing the RTC lose time and the scratch registers reset to zero on a reset.  Is the RTC supposed to retain the time and scratch register contents on a reset if power remains on?  Which power should I monitor to look for problems.

  • 0 in reply to John Rigby1
    TI__Guru**** 170625 points

    Hi John,

    DM8148 RTC doesnt have an independent voltage domain and power supply, thus to be able to use it the whole CORE domain must be switched ON. Lower power alternative is to use external RTC usually integrated in most PMICs.

    John Rigby1 said:
    Is the RTC supposed to retain the time and scratch register contents on a reset if power remains on?

    Yes, RTC on the DM814x EVM retain its registers content, see the below thread:

    http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/p/269019/940241.aspx

    For more information regarding DM8148 RTC, refer to the DM814x TRM, Datasheet and below e2e threads:

    http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/254522.aspx

    http://e2e.ti.com/support/power_management/pmu/f/43/t/152718.aspx

    http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/196693.aspx

    BR

    Pavel