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DM8148, what to do with DEVOSC_WAKE pin?

Brad Caldwell
Genius 12595 points

The DM8148 datasheet lists an input pin DEVOSC_WAKE, pin w6. However, there is no description of this pin other than saying oscillator wake-up. What is this pin used for and how are we to hook it up?

Thanks

  • 0
    TI__Expert 8260 points

    Brad,

    DEVOSC_WAKE is used to wake from DEEP SLEEP mode.

    ENTER DEEP SLEEP MODE

    To enter Deep Sleep, under s/w control the part is first placed in to Standby Mode.  The gated crystal oscillator mode is then enabled.  In this mode all active power is eliminated and all processor execution is halted.  The state of all modules in ALWAYS_ON power domain is retained.

    WAKE FROM DEEP SLEEP

    Centaurus wakes from deep sleep mode by use of the OSC_WAKE pin.

    Signal activity on the OSC_WAKE pin, disables the gated crystal oscillator mode.  The Cortex-A8 resumes execution.

    There is some descripion on P.319 in TRM (http://www.ti.com/lit/ug/sprugz8a/sprugz8a.pdf).

    I will get back to you on how to connnect this pin.

    Regards, Srirami.

  • 0 in reply to srirami
    TI__Expert 8260 points

    If DEEP SLEEP is not used, the DEVOSC_WAKE pin can be tied with PullDown or PullUp.

    Regards, Srirami.

  • 0 in reply to srirami
    TI__Guru 64500 points

    srirami said:

    Signal activity on the OSC_WAKE pin, disables the gated crystal oscillator mode.  The Cortex-A8 resumes execution.

    There is some descripion on P.319 in TRM (http://www.ti.com/lit/ug/sprugz8a/sprugz8a.pdf).

    This is a interesting comment regarding "signal activity".  Does this imply that one needs to toggle the DEVOSC_WAKE pin to get the device to wake up from the Deep Sleep state?  If so, how many times and with what minimum and maximum frequency?

  • 0 in reply to BrandonAzbell
    Prodigy 40 points

    According to SPRUGZ8a Page 319:

    NOTE: To enter deep sleep, the software must configure the desired sense of the wakeup (OSC_WAKE
    pin) and write to AUXOSC_CTRL.GZ in the control module to force a hardware mechanism to shut down
    DEVOSC. DEVOSC will be cleanly re-started upon a wakeup event (rising or falling edge on the
    OSC_WAKE pin depending on configured sense before going into deep sleep). Note that in case of
    external oscillator/vcxo, a clock can directly be connected to XI pin and oscillator will be put in bypass
    mode.